[01-15] grown 6H SiC bulk crystals investigated by high energy triple axis x-ray diffraction - Hock, Rainer; et al. (2005)
A structural characterisation of the first [01-15] grown 6H SiC crystals is presented. They show a different micro domain structure outside the facetted region as compared to conventionally [0001] grown crystals. It is imposed by the reduced rotational symmetry for this direction which favours the activation of a low number of glide systems.
Keywords: [01-15] growth; crystal growth; defects; x-ray diffraction

1550 nm ErAs:In(Al)GaAs large area photoconductive emitters - Preu, Sascha; Mittendorff, M.; Lu, H.; Weber, Heiko B.; Winnerl, Stefan; Gossard, Art (Applied Physics Letters, 2012)
We report on high power terahertz (THz) emission from ErAs-enhanced In0.52Al0.48As-In0.53Ga0.47As superlattices for operation at 1550 nm. ErAs clusters act as efficient recombination centers. The optical power is distributed among a large, microstructured area in order to reduce the local optical intensity. A THz field strength of 0.7 V/cm (1 V/cm peak-to-peak) at 100 mW average optical power has been obtained, with emission up to about 4 THz in air, limited by the detection crystal used in the system. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4750244]

1D Chains of Diruthenium Tetracarbonyl Sawhorse Complexes - Fritsch, Nico; Wick, Christian; Waidmann, Thomas; Pflock, Stephan; Dral, Pavlo; Tucher, Johannes; Steiner, Christian; Shubina, Tatyana; Maier, Sabine; Clark, Timothy; Burzlaff, Nicolai (European Journal of Inorganic Chemistry, 2018)
The syntheses of five 1D coordination polymers containing the sawhorse-type unit [Ru-2(mu-OAc)(2)(CO)(4)] linked by various bridging N,N-donor ligands are reported. Various pi-conjugated linkers, such as trans-[1,2-bis(N-methyl)imidazol-2-yl]ethylene (trans-bie), pyrazine (pyz), 4,4-bipyridine (4,4-bipy) and 1,2-bis(4-pyridyl)ethylene (bpe) as well as the aliphatic linker 1,4-diazabicyclo[2.2.2]octane (DABCO), were applied in the syntheses. The formation of 1D coordination polymers was proven by crystal structure determinations of two of the polymeric materials. The geometries and electronic structures of all polymers were analysed further by CASSCF/CASPT2 and DFT calculations based on monomeric model compounds. Finally, first attempts regarding deposition of the 1D chain, the sawhorse fragment and/or the ligands on a highly ordered pyrolytic graphite surface, analysed by STM measurements, are also reported.
Keywords: Coordination polymers; Chain structures; Bridging ligands; N ligands; Ruthenium

23Na MRI of human skeletal muscle using long inversion recovery pulses - Wilferth, Tobias; Gast, Lena; Stobbe, Robert W.; Beaulieu, Christian; Hensel, Bernhard; Uder, Michael; Nagel, Armin Michael (Magnetic Resonance Imaging, 2019)
23Na inversion recovery (IR) imaging allows for a weighting toward intracellular sodium in the human calf muscle and thus enables an improved analysis of pathophysiological changes of the muscular ion homeostasis. However, sodium signal-to-noise ratio (SNR) is low, especially when using IR sequences. 23Na has a nuclear spin of 3/2 and therefore experiences a strong electrical quadrupolar interaction. This results in very short relaxation times as well as in possible residual quadrupolar splitting. Consequently, relaxation effects during a radiofrequency pulse can no longer be neglected and even allow for increasing SNR as has previously been shown for human brain and knee. The aim of this work was to increase the SNR in 23Na IR imaging of the human calf muscle by using long inversion pulses instead of the usually applied short pulses. First, the influence of the inversion pulse length (1 to 20 ms) on the SNR as well as on image contrast was simulated for different model environments and verified by phantom measurements. Depending on the model environment (agarose 4% and 8%, xanthan 2% and 3%), SNR values increased by a factor of 1.15 up to 1.35, while NaCl solution was successfully suppressed. Thus, image contrast between the non-suppressed model compartments changes with IR pulse length. Finally, in vivo measurements of the human calf muscle of ten healthy volunteers were conducted at 3 Tesla. On average, a 1.4-fold increase in SNR could be achieved by increasing the inversion pulse length from 1 ms to 20 ms, leaving all other parameters – including the scan time – constant. This enables 23Na IR MRI with improved spatial resolution or reduced acquisition time.
CRIS-Team Scopus Importer:2019-10-22
Keywords: B; Human skeletal muscle; Intracellular weighting; Inversion recovery; Long inversion pulses; Sodium (

2D conjugated polymers: exploiting topological properties for the rational design of metal-free photocatalysts - Jing, Yu; Zhu, Xinyue; Maier, Sabine; Heine, Thomas (Trends in Chemistry, 2022)
Solar-to-hydrogen conversion is one of the most promising avenues to provide emission-free fuels and long-term chemical energy storage. Wide-range application crucially requires high-performance photocatalysts that are environmentally benign and free of precious metals. With high robustness, controllable composition, tunable electronic structure, and high porosity, 2D conjugated polymers (2DCPs) are among the most appealing candidates. We provide rational design principles for 2DCPs that are suitable for water splitting, highlight progress and open challenges in synthesis, and review the recent theory-based investigations on 2DCPs for photocatalysis. The role of theory as an indispensable tool is highlighted, as it promotes the understanding of the inner relationship between geometry, electronic structure, and photocatalytic performance of 2DCPs and, therefore, enables rational design of new photocatalysts.
CRIS-Team Scopus Importer:2022-07-22
Keywords: 2D polymers; 2D topology; conjugation; on-surface synthesis; photocatalysis; water splitting

2-PHOTON PHOTOEMISSION - Fauster, Thomas (Progress in Surface Science, 1994)
The current state of the spectroscopy of image states by two-photon photoemission is reviewed. The high resolution permits the detection of several members of the Rydberg series and the determination of the intrinsic linewidth of these states. Recent results for metal overlayers show that the concept of the local work function can be applied and that two-photon photoemission is a sensitive probe for the potential at the surface.

2-PI-STAR-DERIVED STATES FOR CO ON NI(111) STUDIED BY UV BREMSSTRAHLUNG SPECTROSCOPY - Fauster, Thomas; et al. (Physical Review B, 1983)

3D-Delta PDF from electron diffraction data - Schmidt, E. M.; Krysiak, Yasar; Klar, Paul Benjamin; Palatinus, Lukas; Neder, Reinhard; Goodwin, Andrew L. (ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES, 2021)
CRIS-Team WoS Importer:2022-04-01

3-DIMENSIONAL ENERGY-BAND IN GRAPHITE AND LITHIUM-INTERCALATED GRAPHITE - Fauster, Thomas; et al. (Physical Review Letters, 1983)

3-DIMENSIONAL LOCALIZATION OF ELECTRONS ON AG ISLANDS - Fauster, Thomas; et al. (Physical Review B, 1993)
Image states on Pd(111) with various coverages of Ag were investigated by two-photon photoemission spectroscopy for temperatures between 90 and 1300 K. The formation of three-dimensional islands, smooth layers, and surface alloys is identified. The transition from one-dimensional localization in front of the surface to, three-dimensional localization on top of Ag islands with diameters between 10 and 100 Angstrom is observed. The high-resolution spectroscopy of image states provides a new tool to study the growth mode, morphology, and island size distribution of ultrathin metal films.

3D Traction Forces in Cancer Cell Invasion - Koch, Thorsten; Münster, Stefan; Bonakdar, Navid; Butler, James P.; Fabry, Ben (PLoS ONE, 2012)

Ab initio calculations of edge-functionalized armchair graphene nanoribbons: Structural, electronic, and vibrational effects - Rosenkranz, Nils; Till, Christian; Thomsen, Christian; Maultzsch, Janina (Physical Review B, 2011)
We present a theoretical study on narrow armchair graphene nanoribbons (AGNRs) with hydroxyl functionalized edges. Although this kind of passivation strongly affects the structure of the ribbon, a high degree of edge functionalization, i.e., a high ratio of edge atoms being hydroxylized, proves to be particularly stable. An important consequence of the geometric deviations is a severe reduction of the band gap of the investigated 7-AGNR. This shift follows a linear dependence on the number of added hydroxyl groups per unit cell and thus offers the prospect of a tunable band gap by edge functionalization. We furthermore cover the behavior of characteristic phonons for the ribbon itself as well as fingerprint modes of the hydroxyl groups. A large downshift of prominent Raman active modes allows the experimental determination of the degree of edge functionalization.

Ablation-cooled material removal with ultrafast bursts of pulses - Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Çetin, Barbaros; Kesim, Denizhan K.; Akçaalan, Önder; Yavaş, Seydi; Aşık, Mehmet D.; Öktem, Bülent; Hoogland, Heinar; Holzwarth, Ronald; Ilday, Fatih Ömer (Nature, 2016)
The use of femtosecond laser pulses allows precise and thermal damage -free removal of material (ablation) with wide-ranging scientificl(1,5), medical(6-11) and industrial applications(12). However, its potential is limited by the low speeds at which material can be removed(1,9-11,13) and the complexity of the associated laser technology. The complexity of the laser design arises from the need to overcome the high pulse energy threshold for efficient ablation. However, the use of more powerful lasers to increase the ablation rate results in unwanted effects such as shielding, saturation and collateral damage from heat accumulation at higher laser powers(6,13,14). Here we circumvent this limitation by exploiting ablation cooling, in analogy to a technique routinely used in aerospace engineering(13,16). We apply ultrafast successions (bursts) of laser pulses to ablate the target material before the residual heat deposited by previous pulses diffuses away from the processing region. Proof-of-principle experiments on various substrates demonstrate that extremely high repetition rates, which make ablation cooling possible, reduce the laser pulse energies needed for ablation and increase the efficiency of the removal process by an order of magnitude over previously used laser parameters(17,18). We also demonstrate the removal of brain tissue at two cubic millimetres per minute and dentine at three cubic millimetres per minute without any thermal damage to the bulk(9,11).

A Blind Spot in Confocal Reflection Microscopy: The Dependence of Fiber Brightness on Fiber Orientation in Imaging Biopolymer Networks - Jawerth, Louise M.; Münster, Stefan; Vader, David A.; Fabry, Ben; Weitz, David A. (Journal of Biophysics, 2009)

Abnormal strong burn-in degradation of highly efficient polymer solar cells caused by spinodal donor-acceptor demixing - Li, Ning; Perea, José Darío; Kassar, Thaer; Richter, Moses; Heumüller, Thomas; Matt, Gebhard; Hou, Yi; Güldal, Nusret Sena; Chen, Haiwei; Chen, Shi; Langner, Stefan; Berlinghof, Marvin; et al. (Nature Communications, 2017)
The performance of organic solar cells is determined by the delicate, meticulously optimized bulk-heterojunction microstructure, which consists of finely mixed and relatively separated donor/acceptor regions. Here we demonstrate an abnormal strong burn-in degradation in highly efficient polymer solar cells caused by spinodal demixing of the donor and acceptor phases, which dramatically reduces charge generation and can be attributed to the inherently low miscibility of both materials. Even though the microstructure can be kinetically tuned for achieving high-performance, the inherently low miscibility of donor and acceptor leads to spontaneous phase separation in the solid state, even at room temperature and in the dark. A theoretical calculation of the molecular parameters and construction of the spinodal phase diagrams highlight molecular incompatibilities between the donor and acceptor as a dominant mechanism for burn-in degradation, which is to date the major short-time loss reducing the performance and stability of organic solar cells.

ABSOLUTE DETERMINATION OF EMPTY BAND DISPERSION IN COPPER BY MOMENTUM RESOLVED BREMSSTRAHLUNG ISOCHROMAT SPECTROSCOPY - Fauster, Thomas; et al. (Solid State Communications, 1985)

Accelerated silent echo-planar imaging - Liebig, Patrick; Heidemann, Robin M.; Hensel, Bernhard; Porter, David A. (Magnetic Resonance Imaging, 2019)
Purpose: The standard approach to Echo-Planar Imaging (EPI) is to use trapezoidal readout (RO) gradients with blipped phase-encoding (PE) gradients. Sinusoidal RO gradients with constant PE gradients can reduce acoustic noise. However, this sequence, originally introduced by Mansfield et al., constitutes major challenges for Cartesian parallel imaging techniques. In this study two alternatives to reconstruct a non-blipped EPI are proposed and evaluated. Theory and methods: The first method separates the acquired k-space data into odd and even echoes and applies Cartesian GRAPPA separately to each partial data set. Afterwards, the resulting reconstructed data sets for each echo are summed in image space. In the second method, an iterative parallel-imaging algorithm is used to reconstruct images from the highly non-Cartesian data samples. Results: Compared to blipped-EPI, the first method reduces image SNR depending on the acceleration factor between 11% and 60%. For an acceleration factor of 3 folding artefacts appear. The second method produces slight fold-over artefacts although image SNR is on the same level as the blipped approach. Conclusion: In this study, we have introduced two new approaches to EPI that allow the use of Cartesian parallel imaging in conjunction with continuous data sampling. In addition to providing a reduction in acoustic noise compared to the standard blipped PE EPI sequence, the proposed techniques improve sampling efficiency, resulting in a reduction of the echo-spacing. Of the two methods, the second approach, based on an iterative image reconstruction, provides higher SNR, but requires a longer reconstruction time.
CRIS-Team Scopus Importer:2019-06-18
Keywords: Acoustic noise; EPI; Interlaced FT; Iterative reconstruction; Non-Cartesian; Parallel imaging

Acceleration of sub-relativistic electrons with an evanescent optical wave at a planar interface - Kozak, Martin; Beck, Paul; Deng, H.; McNeur, Joshua; Schönenberger, Norbert; Gaida, C.; Stutzki, F.; Gebhardt, M.; Limpert, Jens; Ruehl, A.; Hartl, I.; Solgaard, O.; et al. (Optics Express, 2017)
We report on a theoretical and experimental study of the energy transfer between an optical evanescent wave, propagating in vacuum along the planar boundary of a dielectric material, and a beam of sub-relativistic electrons. The evanescent wave is excited via total internal reflection in the dielectric by an infrared (λ = 2 μm) femtosecond laser pulse. By matching the electron propagation velocity to the phase velocity of the evanescent wave, energy modulation of the electron beam is achieved. A maximum energy gain of 800 eV is observed, corresponding to the absorption of more than 1000 photons by one electron. The maximum observed acceleration gradient is 19 ± 2 MeV/m. The striking advantage of this scheme is that a structuring of the acceleration element’s surface is not required, enabling the use of materials with high laser damage thresholds that are difficult to nano-structure, such as SiC, Al2O3 or CaF2.
Keywords: Particles; Ultrafast phenomena; Scattering; particles; Surface waves

Accurate screened exchange band structures for the transition metal monoxides MnO, FeO, CoO and NiO - Gillen, Roland; Robertson, John (Journal of Physics: Condensed Matter, 2013)

A Chemical Reaction Network to Generate Random, Power-Law-Distributed Time Intervals - Krauß, Patrick; Schulze, Holger; Metzner, Claus (Artificial Life, 2017)
In Lévy walks (LWs), particles move with a fixed speed along straight line segments and turn in new directions after random time intervals that are distributed according to a power law. Such LWs are thought to be an advantageous foraging and search strategy for organisms. While complex nervous systems are certainly capable of producing such behavior, it is not clear at present how single-cell organisms can generate the long-term correlated control signals required for a LW. Here, we construct a biochemical reaction system that generates long-time correlated concentration fluctuations of a signaling substance, with a tunable fractional exponent of the autocorrelation function. The network is based on well-known modules, and its basic function is highly robust with respect to the parameter settings.
EVALuna2:33191

A Combined SAXS/SANS Study for the in Situ Characterization of Ligand Shells on Small Nanoparticles: The Case of ZnO - Schindler, Torben; Schmiele, Martin; Schmutzler, Tilo; Kassar, Thaer; Segets, Doris; Peukert, Wolfgang; Radulescu, Aurel; Kriele, Armin; Gilles, Ralph; Unruh, Tobias (Langmuir, 2015)
ZnO nanoparticles (NPs) have great potential for their use in, e.g., thin film solar cells due to their electro-optical properties adjustable on the nanoscale. Therefore, the production of well-defined NPs is of major interest. For a targeted production process, the knowledge of the stabilization layer of the NPs during and after their formation is of particular importance. For the study of the stabilizer layer of ZnO NPs prepared in a wet chemical synthesis from zinc acetate, only ex situ studies have been performed so far. An acetate layer bound to the surface of the dried NPs was found; however, an in situ study which addresses the stabilizing layer surrounding the NPs in a native dispersion was missing. By the combination of small angle scattering with neutrons and X-rays (SANS and SAXS) for the same sample, we are now able to observe the acetate shell in situ for the first time. In addition, the changes of this shell could be followed during the ripening process for different temperatures. With increasing size of the ZnO core (dcore) the surrounding shell (dshell) becomes larger, and the acetate concentration within the shell is reduced. For all samples, the shell thickness was found to be larger than the maximum extension of an acetate molecule with acetate concentrations within the shell below 50 vol %. Thus, there is not a monolayer of acetate molecules that covers the NPs but rather a swollen shell of acetate ions. This shell is assumed to hinder the growth of the NPs to larger macrostructures. In addition, we found that the partition coefficient μ between acetate in the shell surrounding the NPs and the total amount of acetate in the solution is about 10% which is in good agreement with ex situ data determined by thermogravimetric analysis.
Keywords: nanoparticle; solar; cell; electroptical; property

A COMPACT 3-AXIS CRYOGENIC ULTRAHIGH-VACUUM MANIPULATOR - Fauster, Thomas; et al. (Journal of Vacuum Science & Technology A, 1990)

A comparative analysis of a-C:H by infrared spectroscopy and mass selected thermal effusion - Ristein, Jürgen; Ley, Lothar; et al. (Journal of Applied Physics, 1998)
A comparative analysis of quantitative infrared absorption spectra and mass selected thermal effusion transients measured for a large number of hydrogenated amorphous carbon (a-C:H) films is presented in order to establish reliable IR absorption cross sections for the different hydrogen bonding configurations in the material. The structural character of the material and the hydrogen concentration were varied over a wide range from soft and wide band gap polymerlike a-C:H, via so-called diamondlike carbon, to the tetrahedral form of a-C:H deposited from a plasma beam source. The results show that the IR absorption cross sections from molecular hydrocarbons can well be transferred to the solid state as long as the material is of polymeric character, but that this procedure fails as soon as the material converts into a three-dimensional cross-linked and mechanically hard structure. For the latter material an empirical average IR absorption cross section for the C-H stretch band can nevertheless be determined from a comparison between hydrogen effusion and IR spectra. © 1998 American Institute of Physics.
UnivIS-Import:2015-04-14:Pub.1998.nat.dphy.IAP.exphys.acompa

A comprehensive study on the mechanism behind formation and depletion of Cu2ZnSnS4 (CZTS) phases - Ahmad, Rameez; Brandl, Marco; Distaso, Monica; Herre, Patrick; Spiecker, Erdmann; Hock, Rainer; Peukert, Wolfgang (Crystengcomm, 2015)
High efficiency kesterite based solar cells have vigorously raised the research interests in this material. The challenge lies in understanding the formation and co-existence of more than 10 possible by-products during and after the synthesis of Cu2ZnSnS4 (CZTS) and their various different structural and electronic defects. The present contribution shows an in-depth study on the stages of formation and depletion of nanoparticulate CZTS. Employing a hot injection synthesis method, we give direct experimental evidence of the co-existence of cubic, tetragonal and defected CZTS structures and different by-products as a function of time and temperature. SEM, (HR) TEM, XRD, EDX, ICP-OES, Raman spectroscopy and UV-Vis-NIR spectroscopy have been used in order to better evaluate and interpret data for crystal structures and compositions. The obtained understanding on the formation of different phases suggests 250 degrees C as the most favourable synthesis temperature. Based on our study, general strategies can be developed for controlling the amount of formed phases, the by-products and the defects in kesterite and other similar multicomponent nanoparticles as well as in bulk systems.

Acquisition of paclitaxel resistance is associated with a more aggressive and invasive phenotype in prostate cancer - Kim, John J.; Yin, Bo; Christudass, Christhunesa S.; Terada, Naoki; Rajagopalan, Krithika; Fabry, Ben; Lee, Danielle Y.; Shiraishi, Takumi; Getzenberger, Robert H.; Veltri, Robert W.; An, Steven S.; Mooney, Steven M. (Journal of Cellular Biochemistry, 2013)

A Critical Comparison of Biomembrane Force Fields: Structure and Dynamics of Model DMPC, POPC, and POPE Bilayers. - Pluhackova, Kristyna; Kirsch, Sonja; Han, Jing; Sun, Liping; Jiang, Zhenyan; Unruh, Tobias; Böckmann, Rainer (Journal of Physical Chemistry B, 2016)
Atomistic molecular dynamics simulations have become an important source of information for the structure and dynamics of biomembranes at molecular detail difficult to access in experiments. A number of force fields for lipid membrane simulations have been derived in the past; the choice of the most suitable force field is, however, frequently hampered by the availability of parameters for specific lipids. Additionally, the comparison of different quantities among force fields is often aggravated by varying simulation parameters. Here, we compare four atomistic lipid force fields, namely, the united-atom GROMOS54a7 and the all-atom force fields CHARMM36, Slipids, and Lipid14, for a broad range of structural and dynamical properties of saturated and monounsaturated phosphatidylcholine bilayers (DMPC and POPC) as well as for monounsaturated phosphatidylethanolamine bilayers (POPE). Additionally, the ability of the different force fields to describe the gel-liquid crystalline phase transition is compared and their computational efficiency estimated. Moreover, membrane properties like the water flux across the lipid bilayer and lipid acyl chain protrusion probabilities are compared.

A crystallographic description of experimentally identified formation reactions of Cu(In,Ga)Se-2 - Hock, Rainer; et al. (Journal of Solid State Chemistry, 2006)
This work describes solid-state reactions for the formation of the chalcopyrite compounds CuInSe2, CuGaSe2 and Cu(In,Ga)Se-2 on atomic scale. The most important chalcopyrite formation reactions which were identified by the authors by real-time in situ X-ray diffraction in preceding experiments are (A) CuSe + InSe -> CuInSe2, (B) Cu2Se + 2 InSe + Se -> 2 CuInSe2 and (C) Cu2Se + In2Se3 -> 2 CuInSe2. During the selenistaion of a metallic precursor containing gallium a separate fourth reaction occurs: (D) Cu2Se + Ga2Se3 -> 2 CuGaSe2. The quaternary compound is finally formed by interdiffusion of CuInSe2 with CuGaSe2 (E). These five reactions differ in their activation energy and reaction speed. We explain these differences qualitatively by analysing the involved crystal structures for each reaction. It turns out that all reactions involved in the formation of Cu(In,Ga)Se-2 are promoted by epitaxial relations, which facilitates the formation of polycrystalline thin films at temperatures much below those necessary for single crystal growth. Recommendations for the growth of larger grains of Cu(In,Ga)Se-2 containing fewer defects are given. (c) 2006 Elsevier Inc. All rights reserved.
Keywords: chalcogenide; crystal growth; epitaxial growth; semiconducting materials; solid state synthesis; ternary compounds; thin films

Activation and regulation of endogenous retroviral genes in the human pituitary gland and related endocrine tumours - Buslei, R.; Strissel, Pamela; Henke, Christine; Schey, Regina; Lang, Nadine; Ruebner, M.; Stolt, Claus; Fabry, Ben; Buchfelder, Michael; Strick, Reiner (Neuropathology and Applied Neurobiology, 2015)
Adenohypophysis (AH) hormone-producing cells represent the origin of diverse groups of pituitary adenomas (PA). Deregulation of hypothalamic hormone receptors, growth factors and cAMP signalling have been implicated in the aetiology of PA. Endogenous retroviruses (ERVs) are derived from past exogenous retroviral infections and represent more than 8% of the human genome. Some ERV genes encode open reading frames and produce functional proteins, for example, the ERVW-1 envelope gene Syncytin-1, essential for placentogenesis, but also deregulated in human tumours. Data concerning ERV expression in the AH and related endocrine tumours are missing.Syncytin-1 protein was analysed in normal AH (n = 15) and compared with five PA subtypes (n = 117) by immunohistochemistry. Absolute gene expression of 20 ERV functional envelope genes and ERVW-5 gag was measured. PA tissues were examined for Syncytin-1 and the cAMP signalling marker phospho-CREB-Ser133 using immunohistochemistry. Isolated primary human PA cells were treated with different hormones. Murine embryonic and adult pituitary gland ERV expressions were compared with human AH.Syncytin-1 protein colocalized with corticotropic cells of AH. In contrast, all PA demonstrated significant Syncytin-1 protein overexpression, supporting deregulation. All other ERV genes showed significant up-regulations in different PA subtypes. Phospho-CREB-Ser133 and Syncytin-1 colocalized in PA cells. Cultivated primary PA cells with ACTH or CRH induced their respective receptors and ERV genes. Syncytin-A/-B, murine orthologues to human Syncytin-1/-2, localized to embryonic and adult pituitary glands demonstrating functional mammalian conservation.Deregulated ERV genes may contribute to PA development via cAMP signalling.
EVALuna2:4955

Active soft glassy rheology of adherent cells - Kollmannsberger, Philip; Fabry, Ben (Soft Matter, 2009)

Adaptive stochastic resonance for unknown and variable input signals - Krauß, Patrick; Metzner, Claus; Schilling, Achim; Schütz, Christian; Tziridis, Konstantin; Fabry, Ben; Schulze, Holger (Scientific Reports, 2017)

ADDED-ROW GROWTH OF THE (2X1)O-CU(110) RECONSTRUCTION - Fauster, Thomas; et al. (Physical Review B, 1991)
By impact-collision ion-scattering spectroscopy we show that the growth of the (2 x 1)O reconstruction on Cu(110) proceeds via added Cu-O rows in the [001] direction on top of flat terraces. The observed small creation energy for copper adatoms provides a solution of the mass-transport problem in surface reconstruction. The Cu-O rows are formed by a condensation of adsorbed oxygen atoms and copper adatoms diffusing across the surface.

[Added work of breathing, respiratory pattern and determination of ventilator weaning readiness in inspiratory pressure support and and automatic tube compensation] - Stocker, R.; Fabry, Ben; et al. (Unfallchirurg, 1996)

Additional inspiratory work of breathing imposed by tracheostomy tubes and non-ideal ventilator properties in critically ill patients - Haberthür, Christoph; Fabry, Ben; Stocker, R.; Ritz, Beate; Guttmann, Josef (Intensive Care Medicine, 1999)

Adiabaticity parameters for the categorization of light-matter interaction: From weak to strong driving - Heide, Christian; Boolakee, Tobias; Higuchi, Takuya; Hommelhoff, Peter (Physical Review A, 2021)
We investigate theoretically and numerically the light-matter interaction in a two-band system (TBS) as a model system for excitation in a solid-state band structure. We identify five clearly distinct excitation regimes, categorized with well-known adiabaticity parameters: (1) the perturbative multiphoton absorption regime for small driving field strengths, and four light-field-driven regimes, where intraband motion becomes important (2) the impulsive Landau-Zener (LZ) regime, (3) the nonimpulsive LZ regime, (4) the adiabatic regime, and (5) the adiabatic-impulsive regime for large electric field strengths. This categorization is tremendously helpful to understand the highly complex excitation dynamics in solids, in particular, when the driving field strength varies, and this categorization naturally connects Rabi physics with Landau-Zener physics. In addition, we find an insightful analytical expression for the photon orders connecting the perturbative multiphoton regime with the light-field-driven regimes. Moreover, in the adiabatic-impulsive regime, adiabatic motion and impulsive LZ transitions are equally important, leading to a broken symmetry of the TBS and a residual current when applying few-cycle laser pulses of broken temporal symmetry. This categorization allows a deep understanding of strong-field excitation in solids, including current and high-harmonic generation in a large variety of settings, and will help to find optimal driving parameters for a given purpos
Keywords: light-matter interaction; two-band system; adiabaticity parameter; Rabi physics; Landau-Zener physics

A DISORDERED SUPERSPACE APPROACH TO UNDERSTAND HIGHLY STRUCTURED DIFFUSE SCATTERING - Schmidt, Ella; Neder, Reinhard (ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES, 2019)
CRIS-Team WoS Importer:2020-08-07

Adsoption of water - Maier, Sabine; Salmeron, Miquel (Surface and Interface Science, 2016)

Adsorbed water-molecule hexagons with unexpected rotations in islands on Ru(0001) and Pd(111) - Maier, Sabine; Stass, Ingeborg; Mitsui, Toshiyuki; Feibelman, Peter J.; Thürmer, Konrad; Salmeron, Miquel (Physical Review B, 2012)
High-resolution scanning tunneling microscopy (STM) reveals that the first layer of water on Ru(0001) and also on Pd(111) consists of hexagonal molecular domains of two types, rotated by 30 degrees relative to one another. Pentagon and heptagon clusters bridge the two types of hexagons. One of the orientations is in registry with the substrate. Its molecules lie flat and their O atoms form strong bonds to the metal atoms lying directly below. In the other domain the molecules have dangling H bonds. They are weakly bound to the substrate and lie correspondingly higher. This bonding motif, though nonperiodic, is of similar nature to the periodic wetting structure recently reported on Pt(111), and very different from the conventional "ice-like" bilayer. First-principles density functional theory (DFT) simulations of the STM images support these conclusions.

Adsorption and Activation of CO on Co3O4(111) Thin Films - Ferstl, Pascal; Mehl, Sascha; Arman, M. A.; Schuler, Marina; Toghan, A.; Laszlo, B.; Lykhach, Yaroslava; Brummel, Olaf; Lundgren, Edvin; Knudsen, J.; Hammer, Lutz; Schneider, M. Alexander; et al. (Journal of Physical Chemistry C, 2015)
To explore the catalytic properties of cobalt oxide at the atomic level, we have studied the interaction of CO and O2 with well-ordered Co3O4(111) thin films using scanning tunneling microscopy (STM), high-resolution X-ray photoelectron spectroscopy (HR-XPS), infrared reflection absorption spectroscopy (IRAS), and temperature-programmed desorption spectroscopy (TPD) under ultrahigh vacuum (UHV) conditions. At low coverage and temperature, CO binds to surface Co2+ ions on the (111) facets. At larger exposure, a compressed phase is formed in which additional CO is located at sites in between the Co2+ ions. In addition, a bridging carbonate species forms that is associated with defects such as step edges of Co3O4(111) terraces or the side facets of the (111) oriented grains. Preadsorbed oxygen neither affects CO adsorption at low coverage nor the formation of the surface carbonate, but it blocks formation of the high coverage CO phase. Desorption of the molecularly bound CO occurs up to 180 K, whereas the surface carbonate decomposes in a broad temperature range up to 400 K under the release of CO and, to a lesser extent, of CO2. Upon strong loss of crystalline oxygen, the Co3O4 grains eventually switch to the CoO rocksalt structure.

Adsorption and Intermolecular Interaction of Cobalt Phthalocyanine on CoO(111) Ultrathin Films: An STM and DFT Study - Schmitt, Tobias; Ferstl, Pascal; Hammer, Lutz; Schneider, M. Alexander; Redinger, Josef (Journal of Physical Chemistry C, 2017)
We investigate the adsorption of cobalt phthalocyanine (CoPc) molecules on a thin layer of cobalt oxide grown on Ir(100). To that end we compare the results of low-temperature scanning tunneling microscopy (STM) with those of ab initio density functional theory (DFT) calculations and reveal the adsorption geometry. We find that the CoPc molecules lie flat on the surface and that their central cobalt atom forms a chemical bond to a substrate oxygen ion. However, this bond contributes only modestly to the adsorption energy, while van der Waals forces dominate the potential landscape and determine to a large extent the geometry as well as the distortion of substrate and molecule. Furthermore, they lead to attractive molecule-molecule interactions at higher molecular coverages. The DFT calculations predict energetic positions of the molecular orbitals, which are compared to scanning tunneling spectroscopy (STS) measurements.

Adsorption and self-assembly of a mono-cyano Zn-tetraphenylporphyrin derivative on KBr(001) and MgO(001) - Ammon, Maximilian Michael; Devarajulu, Mirunalini; LIU, YI; Gurrath, Martin; Lungerich, Dominik; Jux, Norbert; Meyer, Bernd; Maier, Sabine (Surface Science, 2022)
The adsorption and self-assembly of a Zn-tetraphenylporphyrin derivative (Zn-pCNTPP) with a cyano group was investigated on KBr(001) and MgO(001) using low-temperature non-contact atomic force microscopy (nc-AFM) combined with dispersion-corrected density-functional theory (DFT). The deposition of Zn-pCNTPP at submonolayer coverage leads on both surfaces to self-assembled networks, in which the porphyrin assumes a planar adsorption configuration with the macrocycle parallel to the surface. DFT calculations confirm the planar adsorption geometry and reveal important differences in the adsorption on KBr vs. MgO. While a global minimum structure is found on KBr due to a strong CN⋯K interaction, multiple and energetically nearly equivalent adsorption sites occur on MgO. Therefore, commensurate adsorption on KBr is suggested, while optimizing the molecule–molecule over molecule–surface interactions is more important on MgO, which is experimentally both evidenced by the nc-AFM data. The expected Zn adsorption site ontop of the anion is the energetically most favored configuration only on KBr, while on MgO, it is above the surface cation.
CRIS-Team Scopus Importer:2022-06-10
Keywords: Adsorption geometry; Dispersion-corrected density-functional theory; Molecular self-assembly; Non-contact atomic force microscopy; Porphyrins

Adsorption and self-assembly of porphyrins on ultrathin CoO films on Ir(100) - Xiang, Feifei; Schmitt, Tobias; Raschmann, Marco; Schneider, M. Alexander (Beilstein Journal of Nanotechnology, 2020)
Porphyrins represent a versatile class of molecules, the adsorption behavior of which on solid surfaces is of fundamental interest due to a variety of potential applications. We investigate here the molecule-molecule and molecule-substrate interaction of Co-5,15-diphenylporphyrin (Co-DPP) and 2H-tetrakis(p-cyanophenyl)porphyrin (2H-TCNP) on one bilayer (1BL) and two bilayer (2BL) thick cobalt oxide films on Ir(100) by scanning tunneling microscopy (STM) and density functional theory (DFT). The two substrates differ greatly with respect to their structural and potential-energy landscape corrugation with immediate consequences for adsorption and self-assembly of the molecules studied. On both films, an effective electronic decoupling from the metal substrate is achieved. However, on the 1BL film, Co-DPP molecules are sufficiently mobile at 300 K and coalesce to self-assembled molecular islands when cooled to 80 K despite their rather weak intermolecular interaction. In contrast, on the 2BL film, due to the rather flat potential landscape, molecular rotation is thermally activated, which effectively prevents self-assembly. The situation is different for 2H-TCNPP, which, due to the additional functional anchoring groups, does not self-assemble on the 1BL film but forms self-assembled compact islands on the 2BL film. The findings demonstrate the guiding effect of the cobalt oxide films of different thickness and the effect of functional surface anchoring.
CRIS-Team WoS Importer:2020-10-23

Adsorption Behavior of 4-Methoxypyridine on Gold Nanoparticles - Lange, Holger; Maultzsch, Janina; Meng, Weizhe; Mollenhauer, Doreen; Paulus, Beate; Peica, Niculina; Schlecht, Sabine; Thomsen, Christian (Langmuir, 2011)
We demonstrate a phase transfer method to create stable colloidal solutions of Au nanoparticles with 4-methoxypyridine ligands. We then investigate the adsorption behavior of 4-methoxypyridine onto gold surfaces by Raman spectroscopy, DFT calculations, and H-1 NMR. In contrast to unsubstituted pyridine and the frequently used (N,N-dimethylamino)pyridine (DMAP), a flat adsorption of 4-methoxypyridine on gold was found.

Adsorption Behavior of a Cyano-Functionalized Porphyrin on Cu(111) and Ag(111): From Molecular Wires to Ordered Supramolecular Two-Dimensional Aggregates - Lepper, Michael; Schmitt, Tobias; Gurrath, Martin; Raschmann, Marco; Zhang, Liang; Stark, Michael Werner; Hölzel, Helen; Jux, Norbert; Meyer, Bernd; Schneider, M. Alexander; Steinrück, Hans-Peter; Marbach, Hubertus (Journal of Physical Chemistry C, 2017)
We investigate the impact of peripheral cyano functionalization of the previously well-studied 2H-tetraphenylporphyrin (2HTPP) by scanning tunneling microscopy (STM) and density functional theory (DFT). The adsorption behavior of 2H-tetralds(p-cyano)-phenylporphyrin (2HTCNPP) is studied at room temperature and at 80 K on Cu(111) and Ag(111). Interestingly, the cyano-functionalized porphyrins tend to form isolated ID chains on Cu(111), in particular after mild annealing at 350 K. The individual 2HTCNPPs as well as the formed chains are oriented along the main crystallographic directions of the Cu(111) substrate due to a strongly attractive and site-specific interaction between the iminic nitrogens of the 2HTCNPP and Cu substrate atoms. The linking within the 1D molecular chains is realized by Cu adatoms as evidenced by comparison of STM and DFT. In contrast, on Ag(111) the molecules assemble into 2D supramolecular layers with long-range order and a square unit cell, stabilized by molecule-molecule interactions. The orientation of the molecules with respect to the unit cell lattice vectors leads to organizational chirality. By codeposition of cobalt, the porphyrin molecules are metalated at room temperature. We did not observe any evidence for metal-organic network formation on Ag(111), even after varying the deposition parameters or the order of metal and porphyrin deposition. Our study shows that cyano functionalization of porphyrins can give rise to novel and unique self-assembled structures like 1D molecular chains without any cross-connections via adatom linking.

Adsorption of cobalt (II) octaethyIporphyrin and 2H-octaethylporphyrin on Ag(111): New insight into the surface coordinative bond - Bai, Yun; Buchner, Florian; Kellner, Ina; Schmid, Martin; Vollnhals, Florian; Steinrück, Hans-Peter; Marbach, Hubertus; Gottfried, Michael (New Journal of Physics, 2009)
The adsorption of cobalt (II) octaethylporphyrin (CoOEP) and 2H-octaethylporphyrin (2HOEP) on Ag(111) was investigated with scanning tunneling microscopy (STM) and photoelectron spectroscopy (XPS/UPS), in order to achieve a detailed mechanistic understanding of the surface chemical bond of coordinated metal ions. Previous studies of related systems, especially cobalt (II) tetraphenylporphyrin (CoTPP) on Ag(111), have revealed adsorptioninduced changes of the oxidation state of the Co ion and the appearance of a new valence state. These effects were attributed to a covalent interaction of the Co ion with the silver substrate. However, recent studies show that the porphyrin ligand of adsorbed CoTPP undergoes a pronounced saddle-shape distortion, which could alter the electronic structure and thus provide an alternative explanation for the new valence state previously attributed to the formation of a surface coordinative bond. With the octaethylporphyrins investigated here, which were found to adsorb in a flat, undistorted conformation on Ag(111), the effects of geometric distortion can be separated from those of the electronic interaction with the substrate. The CoOEP monolayer gives rise to an adsorption-induced shift of the Co 2p signal (-1.9 eV relative to the multilayer), a new valence state at 0.6 eV below the Fermi energy, and a work-function shift of -0.84eV (2HOEP: -0.44eV) relative to the clean surface. Comparison with data for the distorted CoTPP confirms the existence of a covalent ion-surface interaction that is insensitive to the conformation of the ligand. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Adsorption of hydrogen on stable and metastable Ir(100) surfaces - Arman, Mohammad Alif; Klein, Andreas; Ferstl, Pascal; Valookaran, Abhilash; Gustafson, Johan; Schulte, Karina; Lundgren, Edvin; Heinz, Klaus; Schneider, M. Alexander; Mittendorfer, Florian; Hammer, Lutz; Knudsen, Jan (Surface Science, 2017)
Using the combination of high resolution core level spectroscopy and density functional theory we present a detailed spectroscopic study for all clean and hydrogen covered phases of Ir(100). The results are complemented by an investigation of the hydrogen desorption process from various phases using temperature programmed desorption spectroscopy and scanning tunneling microscopy. In total, all experimentally determined core level shifts match very well with those predicted by density functional theory based on established structural models. In particular, we find for the (bridge site) adsorption on the unreconstructed 1×1 phase that the initial core level shift of surface Ir atoms is altered by +0.17 eV for each Ir–H bond formed. In the submonolayer regime we find evidence for island formation at low temperatures. For the H-induced deconstructed 5×1-H phase we identify four different surface core level shifts with two of them being degenerate. Finally, for the reconstructed 5×1-hex phase also four surface components are identified, which undergo a rather rigid core level shift of +0.15 eV upon hydrogen adsorption suggesting a similarly homogeneous charge transfer to all Ir surface atoms. Thermodesorption experiments for the 5×1-H phase reveal two different binding states for hydrogen independent of the total coverage. We conclude that the surface always separates into patches of fully covered deconstructed and uncovered reconstructed phases. We could also show by tunneling microscopy that with the desorption of the last hydrogen atom from the deconstructed unit cell the surface instantaneously reverts into the reconstructed state. Eventually, we could determine the saturation coverage upon molecular adsorption for all phases to be θ =1.0ML, θ =0.8ML, and θ ≥1.0ML.
Keywords: Density functional theory; High resolution core level photoemission spectroscopy; Hydrogen; Ir(100); Temperature programmed desorption

Adsorption, Ordering, and Metalation of Porphyrins on MgO Nanocube Surfaces: The Directional Role of Carboxylic Anchoring Groups - Schneider, Johannes; Kollhoff, Fabian; Schindler, Torben; Bichlmaier, Stephan; Bernardi, Johannes; Unruh, Tobias; Libuda, Jörg; Berger, Thomas; Diwald, Oliver (Journal of Physical Chemistry C, 2016)
The understanding of porphyrin adsorption on oxide nanoparticles including knowledge about coverages and adsorbate geometries is a prerequisite for the improvement and optimization of hybrid materials. The combination of molecular spectroscopies with small-angle X-ray scattering provides molecular insights into porphyrin adsorption on MgO nanocube dispersions in organic solvents. In particular, we address the influence of terminal carboxyl groups on the adsorption of free base porphyrins, on their chemical binding, on the metalation reaction as well as on the coverage and orientation of adsorbate molecules. We compare the free base form 5,10,15,20-tetraphenyl-21,23H-porphyrin (2HTPP) with the carboxyl-functionalized 5,10,15,20-tetrakis(4-carboxyphenyl)-21,23H-porphyrin (2HTCPP) and show that without carboxylic anchoring groups the free base form metalates on the nanocube surface and adopts a flat-lying adsorbate geometry. The saturation limit for flat-lying adsorption on nanocubes with an average edge length of 6 nm corresponds to 90 14 molecules per particle. This limit is surpassed when 2HTCPP molecules attach via their terminal carboxyl groups to the surface. The resulting upright adsorption geometry suppresses self-metalation, on the one hand, and allows for much higher porphyrin coverages, on the other (at porphyrin concentrations in the stock solution of 2 X 10(-2) mol.L-1). UV-vis diffuse reflectance results are perfectly consistent with conclusions from SAXS data analysis. The experiments reveal concentration dependent 2HTCPP coverages in the range between 0.4 to 1.9 molecules nm(-2) which correspond to the formation of a shell of upright standing porphyrin molecules around the MgO nanocubes. In contrast, after adsorption and metalation of nonfunctionalized 2HTPP the resulting porphyrin shells are in the range of a tenth of a nanometer and thus too thin to be captured by SAXS measurements. Related insights advance our opportunities to prepare well-defined nanohybrids containing highly organized porphyrin films.

Adsorption, self-assembly and self-metalation of tetra-cyanophenyl porphyrins on semiconducting CoO(100) films - Ammon, Maximilian; Raabgrund, Andreas; Schneider, M. Alexander (Surface Science, 2022)
The adsorption properties of free base 5,10,15,20-tetrakis(p-cyanophenyl)porphyrin (2H-TCNPP) on thin films of rock salt (rs) CoO(100) on Au(111) was studied in ultra-high vacuum (UHV) by a combination of low-temperature scanning tunneling microscopy and spectroscopy (STM/STS) and density functional theory (DFT). Films of rs-CoO(100) on Au(111) are prepared with excellent quality in a suitable thickness range. Particularly, we found that films of only 1 nm thickness show a semiconducting energy gap of Eg=(2.5±0.2)eV. Upon deposition at 300 K, 2H-TCNPP adsorbs flat-lying and self-assembles in a long-range ordered superstructure that is stable at 80 K. The adsorption geometry of the molecules on the surface and within the self-assembly is analyzed by DFT. We find that the self-assemblies are stabilized by hydrogen bridge bonding via the functional cyano groups. Our STS data shows molecular states within the fundamental gap of the CoO. By comparison with the calculated DOS we determine the energetic positions of the frontier orbitals and find that the first three LUMO states 2H-TCNPP are located within the band gap, whereas the HOMO is shifted 1 eV below the CoO conduction band edge. Upon annealing to 420 K the molecules change their appearance in STM images and a new prominent electronic state located at the center of the molecule is formed. We interpret this changed configuration as Co-TCNPP created by self-metalation on the oxide surface.
CRIS-Team Scopus Importer:2022-02-25
Keywords: Cobalt oxide; Electronic states; Pophyrin; Scanning tunneling microscopy; Self-assembly; Self-metalation

Advances in understanding of transparent conducting oxides - Robertson, John; Gillen, Roland; Clark, Steward (Thin Solid Films, 2012)
Keywords: ZnO; SnO2; In2O3; CuAlO2; CuGaO2; CuInO2; CuCrO2; InGaZnO4; Defossalite; Amorphous semiconducting oxides; Field effect transistor; Extended states; Mobility; Localised states

A finite element model of cell deformation during magnetic bead twisting - Mijailovich, Srboljub M; Kojic, Milos; Zivkovic, Miroslav; Fabry, Ben; Fredberg, Jeffrey (JPN J PHYSIOL, 2002)

A Gold Needle Tip Array Ultrafast Electron Source with High Beam Quality - Brückner, Leon; Nauk, Constantin; Dienstbier, Philip; Gerner, Constanze; Löhrl, Bastian; Paschen, Timo; Hommelhoff, Peter (Nano Letters, 2024)
Electron sources are crucial elements in diverse applications such as electron microscopes, synchrotrons, and free-electron lasers. Nanometer-sharp needle tips are electron emitters with the highest beam quality, yet for a single needle the current is limited. Combining the emission of multiple needles promises large current yields while preserving the individual emitters’ favorable properties. We present an ultrafast electron source consisting of a lithographically fabricated array of sharp gold tips illuminated with 25 fs laser pulses. The source provides up to 2000 electrons per pulse for moderate laser peak intensities of 1011 W/cm2 and a narrow energy width of 0.5 ± 0.05 eV at low current. The electron beam has a well-behaved Gaussian profile and is highly collimated, yielding a small normalized emittance on the order of nm·rad. These properties are well suited for applications requiring both high current and spatial resolution, such as free-electron light sources and chip-based particle accelerators.<br
Keywords: nano-optics; ultrafast electron emission; field enhancement; lasers; electron sources

Agonistic autoantibodies against ß2-adrenergic receptor influence retinal microcirculation in glaucoma suspects and patients - Hohberger, Bettina; Hosari, Sami; Wallukat, Gerd; Kunze, Rudolf; Krebs, Johann Ferdinand; Müller, Magdalena; Hennig, Till; Lämmer, Robert; Horn, Folkert; Garcia Munoz, Luis Enrique; Herrmann, Martin; Mardin, Christian (PLoS ONE, 2021)
PURPOSE: Agonistic β2-adrenergic receptor autoantibodies (β2-agAAb) have been observed in sera of patients with ocular hypertension and open-angle glaucoma (OAG). They target the β2-receptors on trabecular meshwork, ciliary body and pericytes (Junemann et al. 2018; Hohberger et al. 2019). In addition to their influence on the intraocular pressure, an association to retinal microcirculation is discussed. This study aimed to investigate foveal avascular zone (FAZ) characteristics by en face OCT angiography (OCT-A) in glaucoma suspects and its relationship to β2-agAAb status in patients with OAG. MATERIAL AND METHODS: Thirty-four patients (28 OAG, 6 glaucoma suspects) underwent standardized, clinical examination including sensory testing as white-on-white perimetry (Octopus G1, mean defect, MD) and structural measures as retinal nerve fibre layer (RNFL) thickness, neuroretinal rim width (BMO-MRW), retinal ganglion cell layer (RGCL) thickness, and inner nuclear layer (INL) thickness with high-resolution OCT. FAZ characteristics were measured by OCT-A scans of superficial vascular plexus (SVP), intermediate capillary plexus (ICP), and deep capillary plexus (DCP). FAZ-R was calculated (area FAZ (SVP)/area FAZ (ICP)). Using cardiomyocyte bioassays we analysed serum samples for the presence of β2-agAAb. RESULTS: (I) Total mean FAZ area [mm2]: 0.34±0.16 (SVP), 0.24±0.12 (ICP), and 0.49±0.24 (DCP); mean FAZ-R 1.58±0.94. No correlation was seen for FAZ-R with MD, RNFL, BMO-MRW, RGCL thickness and INL thickness (p>0.05). (II) ß2-agAAb have been observed in 91% patients and showed no correlation with MD, RNFL, BMO-MRW, RGCL thickness and INL thickness (p>0.05). (III) FAZ-R correlated significantly with the β2-agAAb-induced increase of the beat rate of cardiomyocyte (p = 0.028). CONCLUSION: FAZ characteristics did not correlate with any glaucoma associated functional and morphometric follow-up parameter in the present cohort. However, level of β2-agAAb showed a significantly correlation with FAZ-ratio. We conclude that β2-agAAb might be a novel biomarker in glaucoma pathogenesis showing association to FAZ-ratio with OCT-A.
CRIS-Team Scopus Importer:2021-05-21

A high-energy triple-axis X-ray diffractometer for the study of the structure of bulk crystals - Hock, Rainer; et al. (Journal of Applied Crystallography, 2004)
A triple-axis diffractometer for high-energy X-ray diffraction is described. A 450 kV/4.5 kW stationary tungsten X-ray tube serves as the X-ray source. Normally, 220 reflections of thermally annealed Czochralski Si are employed for the monochromator and analyser. Their integrated reflectivity is about ten times higher than the ideal crystal value. With the same material as the sample, and working with the W Kalpha line at 60 keV in symmetric Laue geometry for all axes, the full width at half-maximum (FWHM) values for the longitudinal and transversal resolution are 2.5 x 10(-3) and 1.1 x 10(-4) for DeltaQ/Q, respectively, and the peak intensity for a non-dispersive setting is 3000 counts s(-1). In particular, for a double-axis mode, an energy well above 100 keV from the Bremsstrahlung spectrum can be used readily. High-energy X-rays are distinguished by a high penetration power and materials of several centimetre thickness can be analysed. The feasibility of performing experiments with massive sample environments is demonstrated.

A high temperature high pressure cell for quasielastic neutron scattering - Yang, Fan; Kaplonski, Joseph; Unruh, Tobias; Mamontov, Eugene; Meyer, Andreas (Review of Scientific Instruments, 2011)
We present our recent development of a high temperature high pressure cell for neutron scattering. Combining a water cooled Nb1Zr pressure cell body with an internal heating furnace, the sample environment can reach temperatures of up to 1500 K at a pressure of up to 200 MPa at the sample position, with an available sample volume of about 700 mm(3). The cell material Nb1Zr is specifically chosen due to its reasonable mechanical strength at elevated temperatures and fairly small neutron absorption and incoherent scattering cross sections. With this design, an acceptable signal-to-noise ratio of about 10:1 can be achieved. This opens new possibilities for quasielastic neutron scattering studies on different types of neutron spectrometers under high temperature high pressure conditions, which is particularly interesting for geological research on, e.g., water dynamics in silicate melts. (C) 2011 American Institute of Physics. [doi:10.1063/1.3623796]

A hybrid density functional view of native vacancies in gallium nitride - Gillen, Roland; Robertson, John (Journal of Physics: Condensed Matter, 2013)

Airway Hyperresponsiveness, Remodeling, and Smooth Muscle Mass: Right Answer, Wrong Reason? - Oliver, Madavi; Fabry, Ben; Marinkovic, Aleksandar; Mijailovich, Srboljub M; Butler, James P.; Fredberg, Jeffrey (American Journal of Respiratory Cell and Molecular Biology, 2007)

Airway smooth muscle dynamics: a common pathway of airway obstruction in asthma - Seow, Chun Y.; An, Steven S.; Bai, T. R.; Bates, JHT; Black, J. L.; Brown, R.H.; Brusasco, Vito; Chitano, Pasquale; Deng, L.; Dowell, M.; Eidelman, D.H.; Fabry, Ben; et al. (European Respiratory Journal, 2007)

AKAP6 orchestrates the nuclear envelope microtubule-organizing center by linking golgi and nucleus via AKAP9 - Vergarajauregui, Silvia; Becker, Robert; Steffen, Ulrike; Sharkova, Maria; Esser, Tilman; Petzold, Jana; Billing, Florian; Kapiloff, Michael S.; Schett, Georg; Thievessen, Ingo; Engel, Felix (eLife, 2020)
The switch from centrosomal microtubule-organizing centers (MTOCs) to noncentrosomal MTOCs during differentiation is poorly understood. Here, we identify AKAP6 as key component of the nuclear envelope MTOC. In rat cardiomyocytes, AKAP6 anchors centrosomal proteins to the nuclear envelope through its spectrin repeats, acting as an adaptor between nesprin-1 alpha and Pcnt or AKAP9. In addition, AKAP6 and AKAP9 form a protein platform tethering the Golgi to the nucleus. Both Golgi and nuclear envelope exhibit MTOC activity utilizing either AKAP9, or Pcnt-AKAP9, respectively. AKAP6 is also required for formation and activity of the nuclear envelope MTOC in human osteoclasts. Moreover, ectopic expression of AKAP6 in epithelial cells is sufficient to recruit endogenous centrosomal proteins. Finally, AKAP6 is required for cardiomyocyte hypertrophy and osteoclast bone resorption activity. Collectively, we decipher the MTOC at the nuclear envelope as a bi-layered structure generating two pools of microtubules with AKAP6 as a key organizer.
CRIS-Team WoS Importer:2021-01-01

Akt and p53 are potential mediators of reduced mammary tumor growth by Chloroquine and the mTOR inhibitor RAD001 - Löhberg, Christian; Strissel, Pamela; Dittrich, Ralf; Strick, Reiner; Dittmer, Jürgen; Dittmer, Angela; Fabry, Ben; Kalender, Willi Alfred; Koch, Thorsten; Wachter, David; Groh, Nicole; Polier, Astrid; et al. (Biochemical Pharmacology, 2012)

Alginate-based hydrogels with improved adhesive properties for cell encapsulation - Sarker, Bapi; Rompf, Julia; Silva, Raquel; Lang, Nadine; Detsch, Rainer; Kaschta, Joachim; Fabry, Ben; Boccaccini, Aldo R. (International Journal of Biological Macromolecules, 2015)
Hydrogel-based biomaterials are ideal scaffolding matrices for microencapsulation, but they need to be modified to resemble the mechanical, structural and chemical properties of the native extracellular matrix. Here, we compare the mechanical properties and the degradation behavior of unmodified and modified alginate hydrogels in which cell adhesive functionality is conferred either by blending or covalently cross-linking with gelatin. Furthermore, we measure the spreading and proliferation of encapsulated osteoblast-like MG-63 cells. Alginate hydrogels covalently crosslinked with gelatin show the highest degree of cell adhesion, spreading, migration, and proliferation, as well as a faster degradation rate, and are therefore a particularly suitable material for microencapsulation.
Keywords: Alginate; Cell encapsulation; Hydrogel

Alkali-Metal-Templated Self-Assembly of Nickel(II) [12-MC-3] Metallacoronates Based on Bis(pyrazol-1-yl)acetato Ligands - Beyer, Andreas; von Gernler, Marc; Pflock, Stephan; Türkoglu, Gazi; Müller, Lisa; Zahl, Achim; Gieb, Klaus; Müller, Paul; Drewello, Thomas; Burzlaff, Nicolai (Chemistry - A European Journal, 2018)
Keywords: Metallacrowns; Nickel; Acetyl acetonate; Template synthesis; Tripodal ligands

Alloying of thin Ag and Au films on Pd(111) studied by high-resolution photoelectron spectroscopy of surface states - Fauster, Thomas; et al. (Surface Review and Letters, 1996)
Alloy formation by annealing of thin Ag and Au films on Pd(111) is studied by high-resolution ultraviolet and two-photon photoelectron spectroscopy of surface states. Changes in the composition of the top layer of the surface alloys are reflected in the energy of the surface states. Above an annealing temperature of 500 K on both systems, the crystal-induced surface state shifts continuously from the occupied state of the adsorbate to the unoccupied state of the substrate. The continuous shift reflects the variable composition of the alloys in the surface region which depends on the initial coverage and the annealing temperature. The spectroscopy of the unoccupied image states permits the investigation of growth and morphology of deposited metal layers. Three-dimensional island growth, layer-by-layer growth, and surface alloy formation with metastable surface configurations and diffusion of the overlayer material into the bulk are identified.

All-PM coherent 2.05 µm Thulium/Holmium fiber frequency comb source at 100 MHz with up to 0.5 W average power and pulse duration down to 135 fs - Hoogland, Heinar; Thai, Alexandre; Sanchez, Daniel; Cousin, Seth L.; Hemmer, Michael; Engelbrecht, Martin; Biegert, Jens; Holzwarth, Ronald (Optics Express, 2013)
We report on a dual output all-PM fiber laser system running at 100 MHz repetition rate offering coherent broadband and narrowband pulses centered at 2.05 µm with a spectral FWHM bandwidth of 60 nm and 1.5 nm at up to 360 mW and 500 mW, respectively. The broadband pulses are compressed down to 135 fs. The multi-stage double-clad amplifier based on Tm/Ho codoping is seeded by a supercontinuum light source, spanning from around 1 µm up to 2.4 µm.
Keywords: Fiber optics amplifiers and oscillators; Ultrafast lasers

All polarization-maintaining fiber laser architecture for robust femtosecond pulse generation - Hänsel, Wolfgang; Hoogland, Heinar; Giunta, Michele; Schmid, Sebastian; Steinmetz, Tilo; Doubek, Ralf; Mayer, Peter; Dobner, Sven; Cleff, Carsten; Fischer, Marc; Holzwarth, Ronald (Applied Physics B-Lasers and Optics, 2017)
We report on a novel architecture for robust mode-locked femtosecond fiber lasers using a nonlinear optical loop mirror with all polarization-maintaining fibers. Due to a nonreciprocal phase shift, the loop mirror can be operated in a compact and efficient reflection mode, offering the possibility to reach high repetition rates and easy implementation of tuning elements. In particular, longitudinal mode spacing and carrier-envelope offset frequency may be controlled in order to operate the laser as an optical frequency comb. We demonstrate femtosecond pulse generation at three different wavelengths (1030, 1565, and 2050 nm) using Ytterbium, Erbium, and co-doped Thulium-Holmium as gain media, respectively. Robust operation is achieved for a wide range of parameters, including repetition rates from 10 to 250 MH

A low-cost uniaxial cell stretcher for six parallel wells - Kah, Delf-Thorge Eric; Winterl, Alexander; Přechová, Magdalena; Schöler, Ulrike; Schneider, Werner; Friedrich, Oliver; Gregor, Martin; Fabry, Ben (HardwareX, 2021)
Cells in the lungs, the heart, and numerous other organs, are constantly exposed to dynamic forces and deformations. To mimic these dynamic mechanical loading conditions and to study the resulting cellular responses such as morphological changes or the activation of biochemical signaling pathways, cells are typically seeded on flexible 2D substrates that are uniaxially or biaxially stretched. Here, we present an open-source cell stretcher built from parts of an Anet A8 3D printer. The cell stretcher is controlled by a fully programmable open-source software using GCode and Python. Up to six flexible optically clear substrates can be stretched simultaneously, allowing for comparative multi-batch biological studies including microscopic image analysis. The cell yield from the cell culture area of 4 cm2 per substrate is sufficient for Western-blot protein analysis. As a proof-of-concept, we study the activation of the Yes-associated protein (YAP) mechanotransduction pathway in response to increased cytoskeletal tension induced by uniaxial stretching of epithelial cells. Our data support the previously observed activation of the YAP transcription pathway by stretch-induced increase in cytoskeletal tension and demonstrate the suitability of the cell stretcher to study complex mechano-biological processes.
CRIS-Team Scopus Importer:2021-01-01
Keywords: 3D printer; Cell Mechanics; Cell stretcher; Mechanosensing; Uniaxial stretch; YAP

Alterations in the electronic structure upon hierarchical growth of 2D networks - Maier, Sabine (Elsevier, 2018)
Surface-supported one-dimensional and two-dimensional polymers fabricated via on-surface synthesis are promising materials for future applications in nanoelectronics. However, the fabrication of extended crystalline 2D polymers in a bottom-up approach directly on a metal surface still presents a challenge in ultra-high vacuum surface science. The irreversible nature of the C-C coupling reaction results in a lack of structural control and in the formation of equilibrium disordered structures featuring a range of different polygons. A multistep, hierarchical synthesis seems promising to improve the network’s quality and further allows for measuring the evolution of the electronic properties across different dimensions. The narrowing of the electronic band gap when going from the monomer to 1D and 2D structures gives a direct measure of the effective conjugation in these polymeric materials.
CRIS-Team Scopus Importer:2022-04-14
Keywords: Band structure; Conjugation; Hierarchical growth; Network formation; On-surface synthesis; Polymer; Surface reaction; Ullmann-type coupling; π-conjugated

Alternating-Phase Focusing for Dielectric-Laser Acceleration - Niedermayer, Uwe; Egenolf, Thilo; Boine-Frankenheim, Oliver; Hommelhoff, Peter (Physical Review Letters, 2018)
The concept of dielectric-laser acceleration provides the highest gradients among breakdown-limited (nonplasma) particle accelerators. However, stable beam transport and staging have not been shown experimentally yet. We present a scheme that confines the beam longitudinally and in one transverse direction. Confinement in the other direction is obtained by a single conventional quadrupole magnet. Within the small aperture of 420 nm we find the matched distributions, which allow an optimized injection into pure transport, bunching, and accelerating structures. The combination of these resembles the photonics analogue of the radio frequency quadrupole, but since our setup is entirely two dimensional, it can be manufactured on a microchip by lithographic techniques. This is a crucial step towards relativistic electrons in the MeV range from low-cost, handheld devices and connects the two fields of attosecond physics and accelerator physics.
Keywords: dielectric-laser acceleration; Alternating-Phase Focusing; relativistic electrons; accelerator physics

Aluminum acceptor activation and charge compensation in implanted p-type 4H-SiC - Weiße, Julietta; Hauck, Martin; Krieger, Michael; Bauer, Anton; Erlbacher, Tobias (AIP Advances, 2019)
In 4H silicon carbide, aluminum implantation causes unusual high compensation ratios as obtained from Hall effect investigations by fitting the neutrality equation with a single acceptor. We show that this approach cannot fully describe the experimental data, in particular in case of moderate doping and at high measurement temperatures above 450 K. We develop two extended models by adding an additional acceptor- or donor-like defect to the equation. Both approaches describe the data well. However, it turns out that an additional aluminum-correlated acceptor is the more reasonable choice. In this case, the compensation ratio stays almost independent of the implantation dose between 30 % and 40 %. The deep acceptor is located at EV + (280...400) me
Keywords: silicon carbide; SiC; aluminum implantation; charge compensation

A miniaturized electron source based on dielectric laser accelerator operation at higher spatial harmonics and a nanotip photoemitter - McNeur, Joshua; Kozak, Martin; Ehberger, Dominik; Schönenberger, Norbert; Tafel, Alexander; Li, Ang; Hommelhoff, Peter (Journal of Physics B-Atomic Molecular and Optical Physics, 2016)
Here we propose a miniaturized electron source driven by recent experimental results of laser-triggered electron emission from tungsten nanotips and dielectric laser acceleration of sub relativistic electrons with velocities as low as 5.7 x 10(7)m s(-1) or energies as low as 9.6 keV, less than 20% of the speed of light. The recently observed laser-triggered emission of coherent low-emittance electron pulses from tungsten nanotips naturally lends itself towards incorporation with subrelativistic dielectric laser accelerators (DLAs). These structures have previously been shown to accelerate 28 keV electrons and here we report on the utilization of the 4th and 5th spatial harmonics of near fields in the single grating DLA to achieve acceleration of electrons with kinetic energies of 15.2 and 9.6 keV. We then propose the combination of needle tip emitters with subrelativistic accelerators to form a mm-scale device capable of producing electrons with arbitrary energies.
Keywords: laser-driven electron emission; laser-driven electron acceleration; non-relativistic electron beam; inverse Smith-Purcell effect

A mixed waveform protocol for reduction of the cardiac motion artifact in black-blood diffusion-weighted imaging of the liver - Rauh, Susanne S.; Riexinger, Andreas; Ohlmeyer, Sabine; Hammon, Matthias; Saake, Marc; Stemmer, Alto; Uder, Michael; Hensel, Bernhard; Laun, Frederik Bernd (Magnetic Resonance Imaging, 2020)
Objective: Diffusion-weighted imaging (DWI) in the liver suffers from signal loss due to the cardiac motion artifact, especially in the left liver lobe. The purpose of this work was to improve the image quality of liver DWI in terms of cardiac motion artifact reduction and achievement of black-blood images in low b-value images. Material and methods: Ten healthy volunteers (age 20–31 years) underwent MRI examinations at 1.5 T with a prototype DWI sequence provided by the vendor. Two diffusion encodings (i.e. waveforms), monopolar and flow-compensated, and the b-values 0, 20, 50, 100, 150, 600 and 800 s/mm2 were used. Two Likert scales describing the severity of the pulsation artifact and the quality of the black-blood state were defined and evaluated by two experienced radiologists. Regions of interest (ROIs) were manually drawn in the right and left liver lobe in each slice and combined to a volume of interest (VOI). The mean and coefficient of variation were calculated for each normalized VOI-averaged signal to assess the severity of the cardiac motion artifact. The ADC was calculated using two b-values once for the monopolar data and once with mixed data, using the monopolar data for the small and the flow-compensated data for the high b-value. A Wilcoxon rank sum test was used to compare the Likert scores obtained for monopolar and flow-compensated data. Results: At b-values from 20 to 150 s/mm2, unlike the flow-compensated diffusion encoding, the monopolar encoding yielded black blood in all images with a negligible signal loss due to the cardiac motion artifact. At the b-values 600 and 800 s/mm2, the flow-compensated encoding resulted in a significantly reduced cardiac motion artifact, especially in the left liver lobe, and in a black-blood state. The ADC calculated with monopolar data was significantly higher in the left than in the right liver lobe. Conclusion: It is recommendable to use the following mixed waveform protocol: Monopolar diffusion encodings at small b-values and flow-compensated diffusion encodings at high b-values.
CRIS-Team Scopus Importer:2020-01-21

An adapted method for analyzing 4H silicon carbide metal-oxide-semiconductor field-effect transistors - Hauck, Martin; Lehmeyer, Johannes; Pobegen, Gregor; Weber, Heiko B.; Krieger, Michael (Communications Physics, 2019)
Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) are key devices for next-generation power electronics. However, accurate determination of device parameters from 3-terminal characteristics is hampered by the presence of interface traps. Here we present a method that, in contrast to previous evaluation schemes, explicitly considers those defects. A well-tractable parametrization of the SiC/SiO2-specific interface trap spectrum is introduced that reflects the body of known data. With this ingredient, we develop an analysis that targets for an accurate determination of device parameters from simple 3-terminal characteristics. For its validation, we investigate MOSFETs with significantly different defect densities. The resulting parameters – charge carrier density, mobility and threshold voltage – are in excellent agreement with Hall effect investigations on the very same devices, avoiding systematic errors inherent to conventional evaluation techniques. With this adapted scheme, 4H-SiC power MOSFETs, even packaged, can be meaningfully characterized, speeding up innovation cycles in energy-saving power electronics.<br
Keywords: silicon carbide; SiC; power electronic transistors; interface defects

Analysis and visualization of sleep stages based on deep neural networks - Krauß, Patrick; Metzner, Claus; Joshi, Nidhi; Schulze, Holger; Traxdorf, Maximilian; Maier, Andreas; Schilling, Achim (Neurobiology of Sleep and Circadian Rhythms, 2021)
Automatic sleep stage scoring based on deep neural networks has come into focus of sleep researchers and physicians, as a reliable method able to objectively classify sleep stages would save human resources and simplify clinical routines. Due to novel open-source software libraries for machine learning, in combination with enormous recent progress in hardware development, a paradigm shift in the field of sleep research towards automatic diagnostics might be imminent. We argue that modern machine learning techniques are not just a tool to perform automatic sleep stage classification, but are also a creative approach to find hidden properties of sleep physiology. We have already developed and established algorithms to visualize and cluster EEG data, facilitating first assessments on sleep health in terms of sleep-apnea and consequently reduced daytime vigilance. In the following study, we further analyze cortical activity during sleep by determining the probabilities of momentary sleep stages, represented as hypnodensity graphs and then computing vectorial cross-correlations of different EEG channels. We can show that this measure serves to estimate the period length of sleep cycles and thus can help to find disturbances due to pathological conditions.
CRIS-Team Scopus Importer:2021-03-19
Keywords: Artificial neural networks; Deep learning; Electroencephalography (EEG); Hypnodensity graphs; Multidimensional scaling (MDS); Polysomnography (PSG); Sleep cycle analysis; Sleep stage scoring

Analysis of cell mechanics in single vinculin-deficient cells using a magnetic tweezer - Alenghat, Francis J.; Fabry, Ben; Tsai, Kenneth; Goldmann, Wolfgang; Goldmann, Wolfgang; Ingber, Donald E. (Biochemical and Biophysical Research Communications, 2000)

Analysis of chemical short range order using single crystal diffuse scattering - Schmidt, Ella; Neder, Reinhard (ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES, 2018)
CRIS-Team WoS Importer:2019-07-19

Analysis of Compensation Effects in Aluminum-Implanted 4H-SiC Devices - Weiße, Julietta; Hauck, Martin; Sledziewski, Tomasz; Tschiesche, Mattias; Krieger, Michael; Bauer, Anton; Mitlehner, Heinz; Frey, Lothar; Erlbacher, Tobias (Materials Science Forum, 2018)
In this work, we analyze compensating defects which are formed after implantation of aluminum (Al) into n-type 4H-SiC epitaxial layers and subsequent thermal annealing. These defects reduce the expected free charge carrier density by 84% for a low doped layer with [Al]impl ≈ 9·1016 cm-3 and by 27 % for a high doped layer with [Al]impl ≈ 2·1019 cm-3. Furthermore, an electrical activation ratio of implanted aluminum ions of 100 % is calculated. The ionization energy of implanted aluminum as measured by Hall effect and admittance spectroscopy ranges from 101 meV to 305 meV depending on the doping concentratio
Keywords: Activation; Admittance Spectroscopy; Aluminium Implantation; Compensation; Hall Effect; Ionization Energy; Secondary Ion Mass Spectrometry (SIMS)

Analysis of continuous neuronal activity evoked by natural speech with computational corpus linguistics methods - Schilling, Achim; Tomasello, Rosario; Henningsen-Schomers, Malte R.; Zankl, Alexandra; Surendra, Kishore; Haller, Martin; Karl, Valerie; Uhrig, Peter; Maier, Andreas; Krauß, Patrick (Language, Cognition and Neuroscience, 2020)
In the field of neurobiology of language, neuroimaging studies are generally based on stimulation paradigms consisting of at least two different conditions. Designing those paradigms can be very time-consuming and this traditional approach is necessarily data-limited. In contrast, in computational and corpus linguistics, analyses are often based on large text corpora, which allow a vast variety of hypotheses to be tested by repeatedly re-evaluating the data set. Furthermore, text corpora also allow exploratory data analysis in order to generate new hypotheses. By drawing on the advantages of both fields, neuroimaging and computational corpus linguistics, we here present a unified approach combining continuous natural speech and MEG to generate a corpus of speech-evoked neuronal activity.
CRIS-Team Scopus Importer:2020-08-21
Keywords: computational corpus linguistics; MEG/EEG; natural language processing (NLP); naturalistic continuous speech stimuli; neurobiology of language

Analysis of interface trap parameters from double-peak conductance spectra taken on N-implanted 3C-SiC MOS capacitors - Krieger, Michael; Beljakowa, Svetlana; Trapaidze, Lia; Frank, Thomas; Weber, Heiko B.; Pensl, Gerhard; Hatta, N.; Abe, M.; Nagasawa, H.; Schöner, Adolf (physica status solidi (b), 2008)
3C-SiC/SiO2 capacitors are fabricated by over-oxidation of an implanted Gaussian nitrogen (N) profile and investigated by conductance spectroscopy. An unexpected double peak structure is observed in the conductance spectra indicating two types of independent traps at different energy positions in the bandgap, which change their charge state with identical time constant. A theoretical model is developed assuming two independent distributions of interface traps in the bandgap of 3C-SiC with different trap parameters. The experimental G/ω-V and C-V spectra are simulated and the trap parameters are determined on the basis of this model. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
UnivIS-Import:2015-04-14:Pub.2008.nat.dphy.IAP.LAP.analys

Analysis of Multichannel EEG Patterns During Human Sleep: A Novel Approach - Krauß, Patrick; Schilling, Achim; Bauer, Judith; Tziridis, Konstantin; Metzner, Claus; Schulze, Holger; Traxdorf, Maximilian (Frontiers in Human Neuroscience, 2018)
Classic visual sleep stage scoring is based on electroencephalogram (EEG) frequency band analysis of 30 s epochs and is commonly performed by highly trained medical sleep specialists using additional information from submental EMG and eye movements electrooculogram (EOG). In this study, we provide the proof-of-principle in 40 subjects that sleep stages can be consistently differentiated solely on the basis of spatial 3-channel EEG patterns based on root-mean-square (RMS) amplitudes. The polysomnographic 3-channel EEG data are pre-processed by RMS averaging over intervals of 30 s leading to spatial cortical activity patterns represented by 3-dimensional vectors. These patterns are visualized using multidimensional scaling (MDS), allowing a comparison of the spatial cortical activity patterns with the conventional visual sleep scoring system according to the American Academy of Sleep Medicine (AASM). Spatial cortical activity patterns based on RMS amplitudes naturally divide into different clusters that correspond to visually scored sleep stages. Furthermore, these clusters are reproducible between different subjects. Especially the cluster associated with the REM sleep stage seems to be very different from the one associated with the wake state. This study provides a proof-of-principle that it is possible to separate sleep stages solely by analyzing spatially distributed EEG RMS amplitudes reflecting cortical activity and without classical EEG feature extractions like power spectrum analysis.
EVALuna2:35750

Analysis of Random telegraph noise in large-area amorphous double-barrier structures - Hundhausen, Martin; Ley, Lothar; et al. (Physical Review B, 1993)
We have measured the temporal behavior of the perpendicular current through large-area (0.25 mm2) double-barrier structures fabricated from n+-type a-Si:H and quasistoichiometric a-SiNx:H. The current switches randomly between distinct values with an amplitude between 0.5% and 10% of the total current. This behavior is reminiscent of random telegraph noise (RTN) observed in small-area (<1 μm2) devices. The power spectra of the RTN can be fitted by a superposition of Lorentzians from which effective switching rates can be deduced. They are thermally activated and exhibit a dependence on the voltage applied to the sample. The RTN switching can be influenced optically by illuminating the sample surface with a He-Ne laser. While scanning the device area with the focused laser the RTN is influenced at one well-defined spot only. We associate this spot with a filament of less than 1 μm2 in size that carries a large fraction of the current through the device and argue that the current is controlled by the charging and discharging of a single defect in proximity to this filament via Coulomb blocking resulting in the observed RTN. In different samples distributions of switching times for capture and emission of electrons at a single defect are measured as a function of applied voltage and temperature. Based on these data different configurations of the defect located in the nitride barrier are discussed within a model of an acceptorlike trap with a strong electron-lattice coupling which exchanges charge with the adjacent n+-type a-Si:H layers. © 1993 The American Physical Society.
UnivIS-Import:2015-03-05:Pub.1993.nat.dphy.IAP.exphys.analys

Analysis of short range phenomena in novel materials using the PDF-method - Hans, Philipp; Neder, Reinhard; Hradil, Klaudia (ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES, 2018)
CRIS-Team WoS Importer:2019-07-19

Analysis of Structure and Dynamics in Three-Neuron Motifs - Krauß, Patrick; Zankl, Alexandra; Schilling, Achim; Schulze, Holger; Metzner, Claus (Frontiers in Computational Neuroscience, 2019)
Recurrent neural networks can produce ongoing state-to-state transitions without any driving inputs, and the dynamical properties of these transitions are determined by the neuronal connection strengths. Due to non-linearity, it is not clear how strongly the system dynamics is affected by discrete local changes in the connection structure, such as the removal, addition, or sign-switching of individual connections. Moreover, there are no suitable metrics to quantify structural and dynamical differences between two given networks with arbitrarily indexed neurons. In this work, we present such permutation-invariant metrics and apply them to motifs of three binary neurons with discrete ternary connection strengths, an important class of building blocks in biological networks. Using multidimensional scaling, we then study the similarity relations between all 3,411 topologically distinct motifs with regard to structure and dynamics, revealing a strong clustering and various symmetries. As expected, the structural and dynamical distance between pairs of motifs show a significant positive correlation. Strikingly, however, the key parameter controlling motif dynamics turns out to be the ratio of excitatory to inhibitory connections.
CRIS-Team WoS Importer:2019-02-27

Analysis of the moving photocarrier grating technique for semiconductors of high defect density - Hundhausen, Martin; Ley, Lothar; et al. (Physical Review B, 2001)
The moving photocarrier grating (MPG) technique allows us to determine the carrier drift mobilities and the recombination lifetime of semiconductors. This technique utilizes a spatially and temporally modulated light intensity for the generation of photocarriers, which leads to a modulation of the carrier densities. The different mobilities of electrons and holes introduce a phase shift between the charge distributions. The resulting internal electric field produces a short circuit current which depends on the modulation frequency. The theoretical calculation of that short circuit current includes the diffusion and drift currents, and the generation and recombination processes. In the original treatment of the MPG method recombination between electrons and holes was assumed to proceed only through band-to-band transitions. We analyze here the MPG method by explicitly considering recombination through dangling bond states. We simulate short circuit current curves and compare them with measurements. The inclusion of recombination through dangling bonds allows us to explain an apparent contradiction in the evolution of the recombination lifetime as a function of light-induced degradation.

Analysis of the moving-photocarrier-grating technique for the determination of the mobility and lifetime of photocarriers in semiconductors - Hundhausen, Martin; Ley, Lothar; et al. (Physical Review B, 1995)
We describe a technique for the determination of the carrier lifetime (τ) and the carrier mobilities (μn,μp) in semiconductors, namely the moving-photocarrier-grating method. This technique utilizes a moving intensity grating that is generated by the superposition of frequency shifted laser beams for the illumination of the sample. This results in a spatial and temporal modulation of the generation rate of photoelectrons and holes and, as a consequence, in a modulation of the photocarrier densities. The amplitudes and phases of the resulting carrier densities, space charges, and electric fields are calculated by solving the continuity and Poisson equations in the small signal approach. Their dependence on grating velocity and grating period are analyzed in the lifetime and the relaxation-time regimes. It is shown that a dc short circuit current jsc results from the action of space charge induced fields on the photogenerated electrons and holes that can be measured in an external circuit. The validity of this analysis is demonstrated by comparing the expression for jsc with data obtained for two a-Si:H samples that realize the lifetime and the relaxation-time regimes, respectively. Good fits are obtained over a wide range of grating periods and grating velocities for material parameters μn, μp, and τ that compare favorably with values obtained from other measurements. © 1995 The American Physical Society.
UnivIS-Import:2015-03-05:Pub.1995.nat.dphy.IAP.exphys.analys

Analysis of the structure of nanocomposites of triglyceride platelets and DNA - Schmiele, Martin; Knittel, Charlotte; Unruh, Tobias; Busch, Sebastian; Morhenn, Humphrey; Boesecke, Peter; Funari, Sergio S.; Schweins, Ralf; Lindner, Peter; Westermann, Martin; Steiniger, Frank (Physical Chemistry Chemical Physics, 2015)
DNA-complexes with platelet-like, cationically modified lipid nanoparticles (cLNPs) are studied with regard to the formation of nanocomposite structures with a sandwich-like arrangement of the DNA and platelets. For this purpose suspensions of platelet-like triglyceride nanocrystals, stabilized by a mixture of two nonionic (lecithin plus polysorbate 80 or poloxamer 188) and one cationic stabilizer dimethyldioctadecylammonium (DODAB), are used. The structure of the platelets in the native suspensions and their DNA-complexes, ranging from the sub-nano to the micron scale, is investigated with small- and wide-angle scattering (SAXS, SANS, WAXS), calorimetry, photon correlation spectroscopy, transmission electron microscopy and computer simulations. The appearance of strong, lamellarly ordered peaks in the SAXS patterns of the DNA-complexes suggests a stacked arrangement of the nanocrystals, with the DNA being partially condensed between the platelets. This finding is supported with computer simulated small-angle scattering patterns of nanocrystal stacks, which can reproduce the measured small-angle scattering patterns on an absolute scale. The influence of the choice of the nonionic stabilizers and the amount of the cationic stabilizer DODAB on the structure of the native suspensions and the inner structure of their DNA-complexes is studied, too. Using high amounts of DODAB, lecithins with saturated acyl chains and polysorbate 80 instead of poloxamer 188 produces thinner nanocrystals, and thus decreases their repeat distances in the nanocomposites. Such nanocomposites could be of interest as DNA carriers, where the triglyceride platelets protect the sandwiched DNA from degradation.

An analysis of desynchronization between the spontaneously breathing patient and ventilator during inspiratory pressure support - Fabry, Ben; Guttmann, Josef; Eberhard, Luc; Bauer, Tilman; Haberthür, Christoph; Wolff, Gunther (Chest, 1995)

A nanoscale vacuum-tube diode triggered by few-cycle laser pulses - Higuchi, Takuya; Hommelhoff, Peter (Optics InfoBase Conference Papers, 2014)
We propose and demonstrate a nanoscale vacuum-tube diode consisting of two metal nano-tips as an ultrafast electronic device employing pulsed electrons emitted by few- cycle photoemission. © 2014 OSA.
CRIS-Team Scopus Importer:2023-03-07

A nanoscale vacuum-tube diode triggered by few-cycle laser pulses - Higuchi, Takuya; Maisenbacher, Lothar; Liehl, Andreas; Dombi, Peter; Hommelhoff, Peter (Applied Physics Letters, 2015)
We propose and demonstrate a nanoscale vacuum-tube diode triggered by few-cycle near-infrared laser pulses. It represents an ultrafast electronic device based on light fields, exploiting near-field optical enhancement at surfaces of two metal nanotips. The sharper of the two tips displays a stronger field-enhancement, resulting in larger photoemission yields at its surface. One laser pulse with a peak intensity of 4.7 × 1011W/cm2 triggers photoemission of ∼16 electrons from the sharper cathode tip, while emission from the blunter anode tip is suppressed by 19 dB to ∼0.2 electrons per pulse. Thus, the laser-triggered current between two tips exhibit a rectifying behavior, in analogy to classical vacuum-tube diodes. According to the kinetic energy of the emitted electrons and the distance between the tips, the total operation time of this laser-triggered nanoscale diode is estimated to be below 1 ps.
UnivIS-Import:2015-04-14:Pub.2015.nat.dphy.IAP.exphys.ananos

An atomic-scale view of cyclocarbon synthesis - Maier, Sabine (Science, 2019)
CRIS-Team Scopus Importer:2019-09-27

Anchorage of vinculin to lipid membranes influences cell mechanical properties - Diez, Gerold; Kollmannsberger, Philip; Mierke, Claudia; Koch, Thorsten; Vali, Hojatollah; Fabry, Ben; Goldmann, Wolfgang (Journal of Biophysics, 2009)

An efficient Terahertz rectifier on the graphene/SiC materials platform - Schlecht, Maria-Theresa; Malzer, Stefan; Preu, Sascha; Weber, Heiko B. (Scientific Reports, 2019)
We present an efficient Schottky-diode detection scheme for Terahertz (THz) radiation, implemented on the material system epitaxial graphene on silicon carbide (SiC). It employs SiC as semiconductor and graphene as metal, with an epitaxially defined interface. For first prototypes, we report on broadband operation up to 580 GHz, limited only by the RC circuitry, with a responsivity of 1.1 A/W. Remarkably, the voltage dependence of the THz responsivity displays no deviations from DC responsivity, which encourages using this transparent device for exploring the high frequency limits of Schottky rectification in the optical regime. The performance of the detector is demonstrated by resolving sharp spectroscopic features of ethanol and acetone in a THz transmission experiment.<br
Keywords: Terahertz; Halbleiter-Bauelement

An electrical analogy to Mie scattering - Caridad, Jose M.; Connaughton, Stephen; Ott, Christian; Weber, Heiko B.; Krstic, Vojislav (Nature Communications, 2016)
Keywords: Mie scattering is an optical phenomenon that appears when electromagnetic waves; in particular light; are elastically scattered at a spherical or cylindrical object. A transfer of this phenomenon onto electron states in ballistic graphene has been proposed theoretically; assuming a well-defined incident wave scattered by a perfectly cylindrical nanometer scaled potential; but experimental fingerprints are lacking. We present an experimental demonstration of an electrical analogue to Mie scattering by using graphene as a conductor; and circular potentials arranged in a square two-dimensional array. The tabletop experiment is carried out under seemingly unfavourable conditions of diffusive transport at roomtemperature. Nonetheless; when a canted arrangement of the array with respect to the incident current is chosen; cascaded Mie scattering results robustly in a transverse voltage. Its response on electrostatic gating and variation of potentials convincingly underscores Mie scattering as underlying mechanism. The findings presented here encourage the design of functional electronic metamaterials.

An electrostatic gate for mechanically controlled single-molecule junctions - Ballmann, Stefan Dieter; Weber, Heiko B. (New Journal of Physics, 2012)
We present a fabrication scheme for a tunable single-molecule transistor that allows for controlling the electrode separation and provides an electrostatic gate. The experimental approach is based on the mechanically controlled break junction technique but integrates an additional bottom gate electrode and an uninterrupted high-kappa gate dielectric. The device performance is demonstrated for a single-molecule junction showing Coulomb blockade characteristics.

A new approach to accelerate readout segmented EPI with compressed sensing - Liebig, Patrick; Heidemann, Robin Martin; Hensel, Bernhard; Porter, David Andrew (Magnetic Resonance in Medicine, 2019)
Purpose High resolution diffusion-weighted imaging is limited by susceptibility-induced distortions and relaxation-induced blurring. Segmented acquisition techniques can address these limitations at the expense of a prolonged scan time. If segmentation is performed along the readout direction, e.g., in RESOLVE (readout segmentation of long and variable echo-trains), scan time can be reduced by readout (RO) partial Fourier methods, or simultaneous multi-slice (SMS) methods. In this paper, we present a new approach to additionally accelerate the image acquisition called variable segment (VASE) RESOLVE. Methods To avoid discontinuities at the boundaries of the segments, the phase evolution and therefore the effective echo-spacing needs to be adjusted. To achieve this, we use higher undersampling factors in the outer parts of k-space. Simultaneously we increase the width of the outer segments resulting in an increase of the echo-spacing. Because of this variation, we introduce a kind of randomization to the sampling scheme. This enables the use of compressed sensing reconstruction techniques, which results in improved image quality compared to standard parallel imaging methods. Results The RMS errors for the VASE RESOLVE acquisitions were lower compared to the standard reconstructions. The VASE RESOLVE in vivo images show a higher apparent signal to noise ratio. Conclusion VASE RESOLVE is a new approach to further decrease the acquisition time of RO segmented acquisitions. Compared to RESOLVE with SMS, VASE RESOLVE additionally reduces the acquisition time by a factor of 2.
CRIS-Team WoS Importer:2020-01-07

A New Class of Task-Specific Imidazolium Salts and Ionic Liquids and Their Corresponding Transition-Metal Complexes for Immobilization on Electrochemically Active Surfaces - Seidl, Vera; Romero Cordero, Angel Heriberto; Heinemann, Frank Wilhelm; Scheurer, Andreas; Vogel, Carola; Unruh, Tobias; Wasserscheid, Peter; Meyer, Karsten (Chemistry - A European Journal, 2022)
Adding to the versatile class of ionic liquids, we report the detailed structure and property analysis of a new class of asymmetrically substituted imidazolium salts, offering interesting thermal characteristics, such as liquid crystalline behavior, polymorphism or glass transitions. A scalable general synthetic procedure for N-polyaryl-N’-alkyl-functionalized imidazolium salts with para-substituted linker (L) moieties at the aryl chain, namely [LPhmImHR]+ (L=Br, CN, SMe, CO2Et, OH; m=2, 3; R=C12, PEGn; n=2, 3, 4), was developed. These imidazolium salts were studied by single-crystal X-ray diffraction (SC-XRD), NMR spectroscopy and thermochemical methods (DSC, TGA). Furthermore, these imidazolium salts were used as N-heterocyclic carbene (NHC) ligand precursors for mononuclear, first-row transition metal complexes (MnII, FeII, CoII, NiII, ZnII, CuI, AgI, AuI) and for the dinuclear Ti-supported Fe-NHC complex [(OPy)2Ti(OPh2ImC12)2(FeI2)] (OPy=pyridin-2-ylmethanolate). The complexes were studied concerning their structural and magnetic behavior via multi-nuclear NMR spectroscopy, SC-XRD analyses, variable temperature and field-dependent (VT-VF) SQUID magnetization methods, X-band EPR spectroscopy and, where appropriate, zero-field 57Fe Mössbauer spectroscopy.
CRIS-Team Scopus Importer:2022-03-25
Keywords: carbene ligands; electronic structure; ionic liquids; solid-state structure; thermal properties

A new printable alginate / hyaluronic acid / gelatin hydrogel suitable for biofabrication of in vitro and in vivo metastatic melanoma models - Schmid, Rafael; Schmidt, Sonja; Detsch, Rainer; Horder, Hannes; Blunk, Torsten; Schrüfer, Stefan; Schubert, Dirk W.; Fischer, Lena; Thievessen, Ingo; Heltmann-Meyer, Stefanie; Steiner, Dominik; Schneidereit, Dominik; et al. (Advanced Functional Materials, 2021)
Two-dimensional (2D) cancer models have been the standard for drug development over the past few years, but they frequently do not resemble in vivo properties adequately. 3D models are superior in many aspects and are, therefore, more similar to human pathophysiology. Over the past years, the emerging field of biofabrication has made significant advances, resulting in even more sophisticated 3D models. With this study, a hydrogel is created for biofabrication that is suitable for mimicking the tumor microenvironment in vitro and is further tested as a new vascularized melanoma model in vivo. The alginate/hyaluronic acid/gelatin bioink shows good shape-fidelity, high cell survival rates, and enables successful cultivation of melanoma cells and adipose-derived stem cells as well as cell differentiation in vitro. In vivo, in the arteriovenous loop model, it proves to be a unique method to study melanoma progression, tumor vascularization, and ultimately and reliably metastases in an isolated and controlled environment. These results show that this 3D model is very application-oriented for molecular research and therapy developmen

A New Printable Alginate/Hyaluronic Acid/Gelatin Hydrogel Suitable for Biofabrication of In Vitro and In Vivo Metastatic Melanoma Models - Schmid, Rafael; Schmidt, Sonja; Detsch, Rainer; Horder, Hannes; Blunk, Torsten; Schrüfer, Stefan; Schubert, Dirk W.; Fischer, Lena; Thievessen, Ingo; Heltmann-Meyer, Stefanie; Steiner, Dominik; Schneidereit, Dominik; et al. (Advanced Functional Materials, 2021)
Two-dimensional (2D) cancer models have been the standard for drug development over the past few years, but they frequently do not resemble in vivo properties adequately. 3D models are superior in many aspects and are, therefore, more similar to human pathophysiology. Over the past years, the emerging field of biofabrication has made significant advances, resulting in even more sophisticated 3D models. With this study, a hydrogel is created for biofabrication that is suitable for mimicking the tumor microenvironment in vitro and is further tested as a new vascularized melanoma model in vivo. The alginate/hyaluronic acid/gelatin bioink shows good shape-fidelity, high cell survival rates, and enables successful cultivation of melanoma cells and adipose-derived stem cells as well as cell differentiation in vitro. In vivo, in the arteriovenous loop model, it proves to be a unique method to study melanoma progression, tumor vascularization, and ultimately and reliably metastases in an isolated and controlled environment. These results show that this 3D model is very application-oriented for molecular research and therapy development.
CRIS-Team Scopus Importer:2021-10-22
Keywords: bioinks; metastasis; stem cells; tissue engineering; tumors

A new printable alginate / hyaluronic acid / gelatin hydrogel suitable for biofabrication of in vitro and in vivo metastatic melanoma models - Schmid, Rafael; Schmidt, Sonja; Detsch, Rainer; Horder, Hannes; Blunk, Torsten; Schrüfer, Stefan; Schubert, Dirk W.; Fischer, Lena; Thievessen, Ingo; Heltmann-Meyer, Stefanie; Steiner, Dominik; Schneidereit, Dominik; et al. (Advanced Functional Materials, 2022)

A New Statistical Approach for the Evaluation of Gap-prepulse Inhibition of the Acoustic Startle Reflex (GPIAS) for Tinnitus Assessment - Schilling, Achim; Krauß, Patrick; Gerum, Richard; Metzner, Claus; Tziridis, Konstantin; Schulze, Holger (Frontiers in Behavioral Neuroscience, 2017)
Background: An increasingly used behavioral paradigm for the objective assessment of a possible tinnitus percept in animal models has been proposed by Turner and coworkers in 2006. It is based on gap-prepulse inhibition (PPI) of the acoustic startle reflex (ASR) and usually referred to as GPIAS. As it does not require conditioning it became the method of choice to study neuroplastic phenomena associated with the development of tinnitus.Objective:It is still controversial if GPIAS is really appropriate for tinnitus screening, as the hypothesis that a tinnitus percept impairs the gap detection ability ("filling-in interpretation" is still questioned. Furthermore, a wide range of criteria for positive tinnitus detection in GPIAS have been used across different laboratories and there still is no consensus on a best practice for statistical evaluation of GPIAS results. Current approaches are often based on simple averaging of measured PPI values and comparisons on a population level without the possibility to perform valid statistics on the level of the single animal.Methods:A total number of 32 animals were measured using the standard GPIAS paradigm with varying number of measurement repetitions. Based on this data further statistical considerations were performed.Results:We here present a new statistical approach to overcome the methodological limitations of GPIAS. In a first step we show that ASR amplitudes are not normally distributed. Next we estimate the distribution of the measured PPI values by exploiting the full combinatorial power of all measured ASR amplitudes. We demonstrate that the amplitude ratios (1-PPI) are approximately lognormally distributed, allowing for parametrical testing of the logarithmized values and present a new statistical approach allowing for a valid and reliable statistical assessment of PPI changes in GPIAS.Conclusion:Based on our statistical approach we recommend using a constant criterion, which does not systematically depend on the number of measurement repetitions, in order to divide animals into a tinnitus and a non-tinnitus group. In particular, we recommend using a constant threshold based on the effect size as criterion, as the effect size, in contrast to thep-value, does not systematically depend on the number of measurement repetitions.
EVALuna2:33208

ANGULAR-DISTRIBUTION OF THE INVERSE PHOTOEMISSION FROM CU(100) - Fauster, Thomas; et al. (Physical Review B, 1989)

ANGULAR-DISTRIBUTIONS OF VUV PHOTOELECTRONS FROM CU(001) - Fauster, Thomas; et al. (Surface Science, 1995)
He resonance lamp and synchrotron radiation in the energy range from 15 to 60 eV were used to excite the valence band electrons on Cu(001) surfaces. The complete angular intensity distributions of the photoelectrons within 45 degrees away from the surface normal were recorded with a two-dimensional display-type analyzer. The symmetry of the observed patterns permits an easy identification of the different character of the initial states as a function of energy. Additional information is obtained by exploiting the tunability and the polarization of the synchrotron radiation.
Keywords: ANGLE RESOLVED PHOTOEMISSION; COPPER; LOW INDEX SINGLE CRYSTAL SURFACES; VISIBLE AND ULTRAVIOLET PHOTOELECTRON SPECTROSCOPY

An Innovative Arteriovenous (AV) Loop Breast Cancer Model Tailored for Cancer Research - An, Ran; Strissel, Pamela; Al-Abboodi, Majida; Robering, Jan Willem; Reakasame, Supachai; Eckstein, Markus; Peddi, Ajay; Hauck, Theresa; Bäuerle, Tobias; Boccaccini, Aldo R.; Youssef, Almoatazbellah; Sun, Jiaming; et al. (Bioengineering, 2022)
Animal models are important tools to investigate the pathogenesis and develop treatment strategies for breast cancer in humans. In this study, we developed a new three-dimensional in vivo arteriovenous loop model of human breast cancer with the aid of biodegradable materials, including fibrin, alginate, and polycaprolactone. We examined the in vivo effects of various matrices on the growth of breast cancer cells by imaging and immunohistochemistry evaluation. Our findings clearly demonstrate that vascularized breast cancer microtissues could be engineered and recapitulate the in vivo situation and tumor-stromal interaction within an isolated environment in an in vivo organism. Alginate–fibrin hybrid matrices were considered as a highly powerful material for breast tumor engineering based on its stability and biocompatibility. We propose that the novel tumor model may not only serve as an invaluable platform for analyzing and understanding the molecular mechanisms and pattern of oncologic diseases, but also be tailored for individual therapy via transplantation of breast cancer patient-derived tumors.
CRIS-Team Scopus Importer:2022-07-15
Keywords: animal model; arteriovenous loop; breast cancer

Anisotropic nitriding behavior upon formation of expanded hcp in Co-Cr alloys - Akhlaghi, Maryam; Martin, Stefan; Dallmann, Johannes; Hock, Rainer; Körner, Carolin; Leineweber, Andreas (Scripta Materialia, 2021)
The transformation from hexagonal close packed (hcp) to face-centered cubic (fcc) crystal structure upon gaseous nitriding of Co-Cr alloy with initial hcp crystal structure was investigated. During early stages of low-temperature nitriding at 400°C, new reflections on the low-angle side of the hcp-substrate reflections in X-ray diffraction patterns can be attributed to the formation of hcp phase with an expanded lattice on the surface. Prolonged nitriding treatment and nitriding at higher temperatures result in transformation of this expanded hcp into an expanded fcc. An anisotropic progress of mentioned transformation on differently-oriented hcp crystallites is observed. The transformation is slower in hcp orientations with the highest Schmid factor of the basal slip mode with respect to the nitriding direction. This is discussed in a view of developed macrostress in early stages of nitriding and its influence on plastic anisotropic deformation of hcp variant
Keywords: Nitriding; Phase transformations; Residual stresses; Metal and alloys; Expanded phase

Annealing of Pt-H Defects in High-Voltage Si p+/n− Diodes - Rasinger, Fabian; Prohinig, Jennifer; Schulze, Holger; Schulze, Hans Joachim; Pobegen, Gregor (physica status solidi (a), 2019)
A sophisticated way to adjust the minority carrier lifetime and, therefore, the reverse recovery charge in silicon (Si) power diodes is doping with platinum (Pt), as deep levels within the silicon bandgap are created. However, additional deep levels are introduced by hydrogen-incorporating processes during the fabrication of these diodes, which are caused by platinum–hydrogen (Pt–H) defects. Herein, the focus is on how Pt–H defects influence the p+/n− diode characteristics at reverse biasing and verify that annealing at temperatures higher than 300 K decreases the concentration of these defects to a minimum. The dissociation energy of this annealing process is obtained by assuming a first-order reaction. Furthermore, depth profiles of the Pt–H defect are calculated via current–voltage (IV) characteristics. Not only the impact of the Pt–H defect on the device performance is in a reverse direction but also its controllability via thermal annealing in a conventional furnace is presented.
CRIS-Team Scopus Importer:2019-07-16
Keywords: annealing study; capacitance–voltage; current–voltage characteristics; deep-level transient spectroscopy; high voltage p+/n− diode; platinum–hydrogen defects

Annular long Josephson junctions in a magnetic field: Engineering and probing the fluxon potential - Wallraff, Andreas; Koval, Yury; Levitchev, M.; Fistul, Mikhail; Ustinov, Alexey (2000)
UnivIS-Import:2015-03-09:Pub.2000.nat.dphy.IAP.pephys.annula

Anodic mesoporous TiO(2) layer on Ti for enhanced formation of biomimetic hydroxyapatite - Dey, Tuli; Roy, Poulumi; Fabry, Ben; Schmuki, Patrik (Acta Biomaterialia, 2010)
Ti surfaces can be very efficiently coated by a robust ( extgreekmm thick) mesoporous titania layer (MTL). These coatings are produced by anodization of Ti at elevated temperature in a glycerol/K2HPO4 electrolyte, followed by an appropriate etching process. In the present work we examine these layers with regard to their ability to form hydroxyapatite. Immersion tests in two types of simulated body fluids (Kokubo SBF and Bohner and Lemaitre SBF) combined with scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy investigations show that these MTL layers lead to a significant enhancement of HAp formation and anchoring in the structure compared with non-coated or even nanotubular Ti surface coatings (these were recently reported to be the most efficient in terms of HAp formation).

Anodic Titanium Dioxide Nanotubes for Magnetically Guided Therapeutic Delivery - Hasanzadeh Kafshgari, Morteza; Kah, Delf-Thorge Eric; Mazare, Anca Valentina; Nguyen, Nhat Truong; Distaso, Monica; Peukert, Wolfgang; Goldmann, Wolfgang; Schmuki, Patrik; Fabry, Ben (Scientific Reports, 2019)
Hollow titanium dioxide (TiO2) nanotubes offer substantially higher drug loading capacity and slower drug release kinetics compared to solid drug nanocarriers of comparable size. In this report, we load TiO2 nanotubes with iron oxide nanoparticles to facilitate site-specific magnetic guidance and drug delivery. We generate magnetic TiO2 nanotubes (TiO2NTs) by incorporating a ferrofluid containing Ø ≈ 10 nm iron oxide nanoparticles in planar sheets of weakly connected TiO2 nanotubes. After thermal annealing, the magnetic tubular arrays are loaded with therapeutic drugs and then sonicated to separate the nanotubes. We demonstrate that magnetic TiO2NTs are non-toxic for HeLa cells at therapeutic concentrations (≤200 µg/mL). Adhesion and endocytosis of magnetic nanotubes to a layer of HeLa cells are increased in the presence of a magnetic gradient field. As a proof-of-concept, we load the nanotubes with the topoisomerase inhibitor camptothecin and achieve a 90% killing efficiency. We also load the nanotubes with oligonucleotides for cell transfection and achieve 100% cellular uptake efficiency. Our results demonstrate the potential of magnetic TiO2NTs for a wide range of biomedical applications, including site-specific delivery of therapeutic drugs.
CRIS-Team Scopus Importer:2019-09-27

Anomalous Dirac point transport due to extended defects in bilayer graphene - Shallcross, Sam; Sharma, Sangeeta; Weber, Heiko B. (Nature Communications, 2017)
Charge transport at the Dirac point in bilayer graphene exhibits two dramatically different transport states, insulating and metallic, that occur in apparently otherwise indistinguishable experimental samples. We demonstrate that the existence of these two transport states has its origin in an interplay between evanescent modes, that dominate charge transport near the Dirac point, and disordered configurations of extended defects in the form of partial dislocations. In a large ensemble of bilayer systems with randomly positioned partial dislocations, the distribution of conductivities is found to be strongly peaked at both the insulating and metallic limits. We argue that this distribution form, that occurs only at the Dirac point, lies at the heart of the observation of both metallic and insulating states in bilayer graphene.

ANOMALOUS DYNAMIC BEHAVIOR OF THE CU(110) SURFACE - Fauster, Thomas; et al. (Physical Review B, 1991)
The thermal vibrations of surface atoms on Cu(110) have been studied as a function of temperature with ion-scattering spectroscopy in the impact-collision mode. By comparing the experimental data to Monte Carlo simulations of the scattering process, mean-square displacements of surface atoms are obtained that agree well with the results of helium diffraction and inverse photoemission experiments. Below 550 K the atom vibrations can be described quite well by a Debye temperature of 224 K obtained from phonon slab calculations. Above 550 K strong anharmonic vibrations are observed. In this temperature region we find thermally activated adatoms to be produced with an activation energy of 0.27 +/- 0.07 eV. Both effects lead above 1000 K to structural changes of the surface that can be described in terms of a rough surface or a quasiliquid layer on the surface.

A Non-Oxidative Approach Towards Hybrid Silicon Nanowire- Based Solar Cell Heterojunctions - Bashouti, Muhammad; Ristein, Jürgen; Haick, Hossam; Christiansen, Silke. H. (Hybrid Materials, 2013)
UnivIS-Import:2015-03-09:Pub.2013.nat.dphy.IAP.exphys.anonox

An optimized b-value distribution for triexponential intravoxel incoherent motion (IVIM) in the liver - Riexinger, Andreas; Martin, Jan; Wetscherek, Andreas; Kuder, Tristan Anselm; Uder, Michael; Hensel, Bernhard; Laun, Frederik Bernd (Magnetic Resonance in Medicine, 2020)
Purpose: To find an optimized b-value distribution for reproducible triexponential intravoxel incoherent motion (IVIM) exams in the liver. Methods: A numeric optimization of b-value distributions was performed using the triexponential IVIM equation and 27 different IVIM parameter sets. Starting with an initially optimized distribution of 6 b-values, the number of b-values was increased stepwise. Each new b-value was chosen from a set of 64 predefined b-values based on the computed summed relative mean error of the fitted triexponential IVIM parameters. This process was repeated for up to 100 b-values. In simulations and in vivo measurements, optimized b-value distributions were compared to 4 representative distributions found in literature. Results: The first 16 optimized b-values were 0, 0.3, 0.3, 70, 200, 800, 70, 1, 3.5, 5, 70, 1.2, 6, 45, 1.5, and 60 in units of s/mm2. Low b-values were much more frequent than high b-values. The optimized b-value distribution resulted in a higher fit stability compared to distributions used in literature in both, simulation and in vivo measurements. Using more than 6 b-values, ideally 16 or more, increased the fit stability considerably. Conclusion: Using optimized b-values, the fit uncertainty in triexponential IVIM can be largely reduced. Ideally, 16 or more b-values should be acquired.
CRIS-Team Scopus Importer:2020-12-04
Keywords: diffusion; intravoxel incoherent motion; liver; MRI; optimization; triexponential

A novel experimental approach for nanostructure analysis: simultaneous small-angle X-ray and neutron scattering - Metwalli, Ezzeldin; Götz, Klaus; Lages, Sebastian; Bär, Christian; Zech, Tobias; Noll, Dennis; Schuldes, Isabel; Schindler, Torben; Prihoda, Annemarie; Lang, Herbert; Grasser, Jürgen; Jacques, Mark; et al. (Journal of Applied Crystallography, 2020)
Exploiting small-angle X-ray and neutron scattering (SAXS/SANS) on the same sample volume at the same time provides complementary nanoscale structural information in two different contrast situations. Unlike an independent experimental approach, the truly combined SAXS/SANS experimental approach ensures the exactness of the probed samples, particularly for in situ studies. Here, an advanced portable SAXS system that is dimensionally suitable for installation in the D22 zone of ILL is introduced. The SAXS apparatus is based on a Rigaku switchable copper/molybdenum microfocus rotating-anode X-ray generator and a DECTRIS detector with a changeable sample-to-detector distance of up to 1.6 m in a vacuum chamber. A case study is presented to demonstrate the uniqueness of the newly established method. Temporal structural rearrangements of both the organic stabilizing agent and organically capped gold colloidal particles during gold nanoparticle growth are simultaneously probed, enabling the immediate acquisition of correlated structural information. The new nano-analytical method will open the way for real-time investigations of a wide range of innovative nanomaterials and will enable comprehensive in situ studies on biological systems. The potential development of a fully automated SAXS/SANS system with a common control environment and additional sample environments, permitting a continual and efficient operation of the system by ILL users, is also introduced.
CRIS-Team WoS Importer:2020-06-19

Antibacterial activity and biocompatibility of zein scaffolds containing silver-doped bioactive glass - El-Rashidy, Aiah A.; Waly, Gihan; Gad, Ahmed; Roether, Judith; Hum, Jasmin; Yang, Yuyun; Detsch, Rainer; Hashem, Azza A.; Sami, Inas; Goldmann, Wolfgang; Boccaccini, Aldo R. (Biomedical Materials, 2018)
Keywords: zein scaffolds; silver; in vitro biocompatibility; bioactive glass; antibacterial

Anti-Stokes Photoluminescence of Monolayer WS2 - Pierret, Aurelie; Tornatzky, Hans; Maultzsch, Janina (physica status solidi (b), 2019)
Anti-Stokes photoluminescence excitation of a WS2 monolayer flake between 10 and 300 K is reported herein. Even with continuous-wave lasers at low power, the emission of the exciton at excitation 100 meV below its emission energy at room temperature is observed. A mechanism which involves the trions as the intermediate state is proposed, leading to an efficient up-conversion process. In addition, it is demonstrated that phonons are the source of the additional energy needed by the system. Overall, the results provide evidence that anti-Stokes luminescence in transition metal dichalcogenides is very efficient.
CRIS-Team WoS Importer:2019-10-22

An ultra-stable setup for measuring electrical and thermoelectrical properties of nanojunctions - Popp, Matthias Albert; Weber, Heiko B. (Applied Physics Letters, 2019)
We present a setup that is excellently suited to measure the electrical and thermoelectrical transport across single-molecule junctions at both room temperature and low temperatures. It employs a sandwich configuration of two silicon carbide chips each equipped with metallic electrodes. Upon compression with an external piezo/spring mechanism, fine-tuned displacement control is achieved such that ultrastable atomically thin nanojunctions can be established. As a consequence of its stability, the setup gives access to point-by-point comparisons of electrical and thermoelectrical transport across single-molecule contacts. As a first demonstration of the capabilities of our setup, we present experiments with gold-molecule-gold contacts. Investigating a large ensemble of nanojunctions, each fully characterized by current-voltage characteristics and thermovoltage, correlations between these quantities are uncovered which can be rationalized within the Landauer transport picture. When including characteristics with resonant features, the Seebeck coefficient adds the decisive parameter to fully describe datasets within a resonant tunneling model. The setup provides further potential of controlling additional parameters as it is optically fully transparent. It also allows for nearly arbitrary material combinations for electrode-nanoobject object-electrode nanojunction

A One-Pot Universal Approach to Fabricate Lubricant-Infused Slippery Surfaces on Solid Substrates - Tesler, Alexander; Prado, Lucia; Khusniyarov, Marat; Thievessen, Ingo; Mazare, Anca Valentina; Fischer, Lena; Virtanen, Sannakaisa; Goldmann, Wolfgang; Schmuki, Patrik (Advanced Functional Materials, 2021)
Wetting is a surface phenomenon that commonly occurs in nature and has an enormous influence on human life. Slippery liquid-infused porous surfaces have recently been developed to support the growing demand for anti-fouling coatings. While short-chain fluorinated compounds, commonly used to reduce the surface energy of substrates, are banned due to environmental toxicity, silane-based compounds are expensive and barely scalable. In this sense, silicone-based chemistry may match the gap as a real alternative. However, the grafting approaches demonstrated so far suffered from either slow binding kinetics or are applied under harsh conditions. Here, it is demonstrated that polydimethylsiloxanes graft to virtually any substrate when illuminated by UV light serving simultaneously as a reducing surface energy agent and infusing lubricant. This procedure is applied on metals, metal oxides, and ceramics of various surface morphologies. The proposed approach is simple, fast, scalable, environmentally friendly, and of low-cost, yet forms stable lubricant-infused slippery surfaces by a one-pot process. Due to the biocompatibility of silicone-based compounds, the process is examined on plain medically applicable substrates such as scalpel blades and glass lenses that display enhanced corrosion resistance, reduced friction through incision, and repel blood staining and bacterial adhesion without deteriorating their mechanical and optical characteristics.
CRIS-Team Scopus Importer:2021-05-14
Keywords: anti-biofouling; blood-repellent coating; corrosion resistance; lubricant-infused slippery surfaces; polydimethylsiloxane

A Path Loss and Fading Model for RSSI-based Localization in Forested Areas - Nowak, Thorsten; Hartmann, Markus; Zech, Tobias; Thielecke, Jörn (IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (IEEE-APWC 2016), 2016)
Location-awareness is a prerequisite for many applications, today. Demanding applications, e.g. wildlife monitoring, rely on precise location information. A prospective approach tracking tiny lightweight animals is to capture field-strength measurements utilizing a wireless sensor network. Apriori knowledge of propagation channel characteristics is essential for precise localization. Hence, in this paper a channel model for forested areas is proposed. Therefore, a reference set of field-strength measurements has been evaluated and a channel model has been derived from these measurements. Besides path loss and fading, also cross fading between two directional antennas has been characterized. Cross-fading between these antennas is crucial for RSSI-based direction finding by directional antennas. Furthermore, the impact of incorrect modeling measurement uncertainties on the position estimation error is assessed.

A Peltier cooled single pass amplifier for Titanium:Sapphire laser pulses - Ozawa, A.; Schneider, W.; Najafi, F.; Haensch, T. W.; Udem, Th.; Hommelhoff, Peter (Laser Physics, 2010)
We report on a Peltier cooled single pass amplifier for high repetition rate Titanium:sapphire laser pulses. Pumped with 14 W and seeded with around 400 mW, the output reaches 1.1 W with good beam quality. This amplifier is very user-friendly, easy to maintain and set up and thus represents a device situated between more complicated liquid-nitrogen cooled amplifiers that can operate at higher pump power, and very simple near to room temperature amplifiers that can only be pumped with less power. In addition, we show the results of a finite element simulation on the temperature distribution in a liquid nitrogen cooled amplifier setup designed for highest output powers. © Pleiades Publishing, Ltd., 2010.
UnivIS-Import:2015-03-09:Pub.2010.nat.dphy.IAP.exphys.apelti

A point-like thermal light source as a probe for sensing light-matter interaction - Korn, Sascha; Popp, Matthias Albert; Weber, Heiko B. (Scientific Reports, 2022)
Historically, thermal radiation is related to 3D cavities. In practice, however, it is known that almost any hot surface radiates according to Planck’s law. This approximate universality roots in the smooth electromagnetic mode structure of free space, into which the radiation is emitted. Here, we study the effect for a strongly patterned mode structure and use quasi-transparent point-like thermal light emitters as a probe. As such, we choose current-driven graphene nanojunctions for which the emission into free space obeys Planck’s law. Placed in front of a mirror, however, this process is highly sensitive to a node/antinode pattern of light modes. By varying the distance, we can sample the latter with atomic precision, and observe a deep imprint on the observed spectrum. The experiment allows an unprecedented view on thermal radiation in a spatially/spectrally patterned electromagnetic environment.<br

Applications of integrated magnetic microtraps - Reichel, Jakob; Hänsel, Wolfgang; Hommelhoff, Peter; Hänsch, Theodor (Applied Physics B-Lasers and Optics, 2001)
Lithographically fabricated circuit patterns can provide magnetic guides and microtraps for cold neutral atoms. By combining several such structures on the same ceramic substrate, we have realized the first 'atom chips' that permit complex manipulations of ultracold trapped atoms or de Broglie wave packets. We show how to design magnetic potentials from simple conductor patterns and we describe an efficient trap-loading procedure in detail. Applying the design guide, we describe some new microtrap potentials, including a trap which reaches the Lamb-Dicke regime for rubidium atoms in all three dimensions, and a rotatable Ioffe-Pritchard trap, which we also demonstrate experimentally. Finally, we demonstrate a device allowing independent linear positioning of two atomic clouds which are very tightly confined laterally. This device is well suited for the study of one-dimensional collisions.
UnivIS-Import:2015-03-09:Pub.2001.nat.dphy.IAP.exphys.applic

Area-Selective Growth of HfS(2)Thin Films via Atomic Layer Deposition at Low Temperature - Cao, Yuanyuan; Wähler, Tobias; Park, Hyoungwon; Will, Johannes; Prihoda, Annemarie; Moses Badlyan, Narine; Fromm, Lukas; Yokosawa, Tadahiro; Wang, Bingzhe; Guldi, Dirk Michael; Görling, Andreas; Maultzsch, Janina; et al. (Advanced Materials Interfaces, 2020)
The transition-metal dichalcogenide HfS(2)is a promising alternative semiconductor with adequate band gap and high carrier mobility. However, a controllable growth of continuous HfS(2)films with selectivity for specific surfaces at a low temperature on a large scale has not been demonstrated yet. Herein, HfS(2)films are grown at 100 degrees C by atomic layer deposition (ALD) based on the precursors tetrakis(dimethylamido)hafnium and H2S. In situ vibrational spectroscopy allows for the definition of the temperature range over which (Me2N)(4)Hf chemisorbs as one monolayer. In that range, sequential exposures of the solid surface with (Me2N)(4)Hf and H2S result in self-limiting reactions that yield alternating surface termination with dimethylamide and thiol. Repeating the cycle grows smooth, continuous, stoichiometric films of thicknesses adjustable from angstroms to >100 nm, as demonstrated by spectroscopic ellipsometry, XRR, AFM, UV-vis and Raman spectroscopy, XPS, and TEM. The well-defined surface chemistry enables one to deposit HfS(2)selectively using, for example, patterns generated in molecular self-assembled monolayers. This novel ALD reaction combines several attractive features necessary for integrating HfS(2)into devices.
Keywords: 2D materials; atomic layer deposition; dichalcogenides; hafnium disulfide; thin films

Area-Selective Growth of HfS(2)Thin Films via Atomic Layer Deposition at Low Temperature - Cao, Yuanyuan; Wähler, Tobias; Park, Hyoungwon; Will, Johannes; Prihoda, Annemarie; Moses Badlyan, Narine; Fromm, Lukas; Yokosawa, Tadahiro; Wang, Bingzhe; Guldi, Dirk Michael; Görling, Andreas; Maultzsch, Janina; et al. (Advanced Materials Interfaces, 2020)
The transition-metal dichalcogenide HfS(2)is a promising alternative semiconductor with adequate band gap and high carrier mobility. However, a controllable growth of continuous HfS(2)films with selectivity for specific surfaces at a low temperature on a large scale has not been demonstrated yet. Herein, HfS(2)films are grown at 100 degrees C by atomic layer deposition (ALD) based on the precursors tetrakis(dimethylamido)hafnium and H2S. In situ vibrational spectroscopy allows for the definition of the temperature range over which (Me2N)(4)Hf chemisorbs as one monolayer. In that range, sequential exposures of the solid surface with (Me2N)(4)Hf and H2S result in self-limiting reactions that yield alternating surface termination with dimethylamide and thiol. Repeating the cycle grows smooth, continuous, stoichiometric films of thicknesses adjustable from angstroms to >100 nm, as demonstrated by spectroscopic ellipsometry, XRR, AFM, UV-vis and Raman spectroscopy, XPS, and TEM. The well-defined surface chemistry enables one to deposit HfS(2)selectively using, for example, patterns generated in molecular self-assembled monolayers. This novel ALD reaction combines several attractive features necessary for integrating HfS(2)into devices.
CRIS-Team Scopus Importer:2020-10-23
Keywords: 2D materials; atomic layer deposition; dichalcogenides; hafnium disulfide; thin films

Are environmental factors responsible for changed breeding behaviour in emperor penguins? - Paranhos Zitterbart, Daniel; Richter, Sebastian; Spiekermann, Georg; Behrens, Lisa K.; Regnery, Julia; Fontes, Renè P.; Hänssler, Thedda; König-Langlo, Gert; Weller, Rolf; Fabry, Ben (Antarctic Science, 2014)

A remote-controlled observatory for behavioural and ecological research: A case study on emperor penguins - Richter, Sebastian; Gerum, Richard; Schneider, Werner; Fabry, Ben; Le Bohec, Céline; Paranhos Zitterbart, Daniel (Methods in Ecology and Evolution, 2018)

A robust comparison of dynamical scenarios in a glass-forming liquid - Vispa, Alessandro; Busch, Sebastian; Tamarit, Josep Lluis; Unruh, Tobias; Fernandez-Alonso, Felix; Pardo, Luis Carlos (Physical Chemistry Chemical Physics, 2016)
We use Bayesian inference methods to provide fresh insights into the sub-nanosecond dynamics of glycerol, a prototypical glass-forming liquid. To this end, quasielastic neutron scattering data as a function of temperature have been analyzed using a minimal set of underlying physical assumptions. On the basis of this analysis, we establish the unambiguous presence of three distinct dynamical processes in glycerol, namely, translational diffusion of the molecular centre of mass and two additional localized and temperature-independent modes. The neutron data also provide access to the characteristic length scales associated with these motions in a model-independent manner, from which we conclude that the faster (slower) localized motions probe longer (shorter) length scales. Careful Bayesian analysis of the entire scattering law favors a heterogeneous scenario for the microscopic dynamics of glycerol, where molecules undergo either the faster and longer or the slower and shorter localized motions.

A route to continuous ultra-thin cerium oxide films on Cu(111) - Staudt, T.; Lykhach, Yaroslava; Hammer, Lutz; Schneider, M. Alexander; Matolin, Vladimir; Libuda, Jörg (Surface Science, 2009)
The growth and morphology of ultra-thin CeO(2) (1 1 1) films on a Cu(1 1 1) substrate were investigated by means of low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The films were grown by physical vapor deposition of cerium in an oxygen atmosphere at different sample temperatures. The preparation procedure is based on a modification of a previous method suggested by Matolin and co-workers [1], involving growth at elevated temperature (520 K). Here, LEED shows good long range ordering with a "(1.5 x 1.5)" superstructure, but STM reveals a three-dimensional growth mode (Vollmer-Weber) with formation of a closed film only at larger thickness. Using a kinetically limited growth process by reactive deposition at low sample temperatures (100 K) and subsequent annealing, we show that closed layers of ceria with atomically flat terraces can be prepared even in the regime of ultra-thin films (1.5 ML). Closed and atomically flat ceria films of larger thickness (3 ML) are obtained by applying a multistep preparation procedure, in which successive ceria layers are homoepitaxially grown on this initial film. The resulting overlayers show strong similarities with the morphology of CeO(2)(1 1 1) single crystal surfaces, suggesting the possibility to model bulk ceria by thin film systems. (C) 2009 Elsevier B.V. All rights reserved.
Keywords: Ceria; Ultra-thin oxide films; Scanning tunneling microscopy; Low energy electron diffraction; Model catalysts

Arrayed free space continuous-wave terahertz photomixers - Bauerschmidt, Sebastian; Döhler, Gottfried; Lu, Hong; Gossard, Art; Malzer, Stefan; Preu, Sascha (Optics Letters, 2013)
We present free space coherent arrays of continuous-wave terahertz (THz) photomixers and compare the results to on-chip arrays. By altering the relative phases of the exciting laser signals, the relative THz phase between the array elements can be tuned, allowing for beam steering. In addition, the constructive interference of the emission of N elements leads to an increase of the focal intensity by a factor of N2 while reducing the beam width by ∼N-1, below the diffraction limit of a single source. Such array architectures strongly improve the THz power distribution for stand-off spectroscopy and imaging systems while providing a huge bandwidth at the same time. We demonstrate this by beam profiles generated by a 2 × 2 and a 4 × 1 array for a transmission distance of 4.2 m. Spectra between 70 GHz and 1.1 THz have been recorded with these arrays. © 2013 Optical Society of America.
Keywords: Terahertz emitter array; beam steering

Arrayed telecom-wavelength compatible THz n-i-pn-i-p superlattice photomixers for spectroscopy applications - Preu, Sascha; Bauerschmidt, Sebastian; Malzer, Stefan; Döhler, Gottfried; Lu, Hong; Gossard, Art; Wang, Lijun (Terahertz and Midinfrared Radiation, 2011)
We report on the progress of room-temperature operating, continuous-wave, tunable n-i-pn-i-p superlattice THz photomixers, compatible with 1.55μm telecom laser systems. An output power of 0.65μW at 1THz has been achieved at a photocurrent of 9.5mA, using a broadband antenna. The spectral power is at a level where high resolution spectroscopy becomes attractive. This is demonstrated by measuring the absorption spectrum of water vapor between 0.4 and 1.6THz. We constructed an array of 4 mutually coherent photomixers for higher output power and spatial resolution. The interference of the four individual beams was measured in the target plane at a stand-off distance of 4.2m. We report on both a small THz spot diameter along the array axis of<1cm for ν>0.3THz and a high intensity of the central interference peak, in excellent agreement with numerical simulations. These features are very attractive for stand-off imaging and spectroscopy. © 2011 Springer Science+Business Media B.V.

Arrays and new antenna topologies for increasing THz power generation using photomixers - Rivera-Lavado, Alejandro; Garcia-Munoz, Enrique; Döhler, Gottfried; Malzer, Stefan; Preu, Sascha; Bauerschmidt, Sebastian; Montero-De-Paz, J.; Ugarte-Munoz, E.; Andres-Garcia, Belen; Izquierdo-Bermudez, V.; Segovia-Vargas, Daniel (Journal of Infrared, Millimeter, and Terahertz Waves, 2013)
Power limitations in CW THz generation imposed by conventional photomixers ("antenna emitters", AEs) are the major drawbacks on THz generation. From the antenna point of view, two different strategies are proposed to increase the generated power: optimized arrays and lenses arrangements and the use of new dielectric horn antennas. Then, using multiple small lenses, one per each single element, instead of a large one, bigger than the array, makes the generated power much higher. In addition, horn antennas etched in the substrate are considered in order to reduce the energy distribution scattering. Finally, some manufacturing issues are discussed. © 2013 Springer Science+Business Media New York.
UnivIS-Import:2015-03-09:Pub.2013.nat.dphy.IAP.LAP.arrays

A Self‐Ordered Nanostructured Transparent Electrode of High Structural Quality and Corresponding Functional Performance - Döhler, Dirk; Triana Merlo, Andres Dario; Büttner, Pascal; Scheler, Florian; Görlitzer, Eric; Harrer, Johannes; Vasileva, Anna A.; Ali, Ezzeldin; Gruber, Wolfgang; Unruh, Tobias; Manshina, Alina A.; Vogel, Nicolas; et al. (Small, 2021)
The preparation of a highly ordered nanostructured transparent electrode based on a combination of nanosphere lithography and anodization is presented. The size of perfectly ordered pore domains is improved by an order of magnitude with respect to the state of the art. The concomitantly reduced density of defect pores increases the fraction of pores that are in good electrical contact with the underlying transparent conductive substrate. This improvement in structural quality translates directly and linearly into an improved performance of energy conversion devices built from such electrodes in a linear manne
Keywords: nanosphere lithography; anodic alumina; antimony sulfide

A SIMPLE METHOD FOR THE DETERMINATION OF THE ANGLE OF INCIDENCE FOR LOW-ENERGY ELECTRONS - Fauster, Thomas; et al. (Journal of Vacuum Science & Technology A, 1990)

A simplified implementation of the bubble analysis of biopolymer network pores - Münster, Stefan; Fabry, Ben (Biophysical Journal, 2013)

A single-molecular diode - Elbing, Mark; Ochs, Rolf; Koentopp, Max; Fischer, Matthias; von Hänisch, Carsten; Weigend, Florian; Evers, Ferdinand; Weber, Heiko B.; Mayor, Marcel (Proceedings of the National Academy of Sciences of the United States of America, 2005)
UnivIS-Import:2018-09-05:Pub.2005.nat.dphy.IAP.LAP.asingl

A single-molecule diode - Elbing, Mark; Ochs, Rolf; Koentopp, Max; Fischer, Matthias; von Hänisch, Carsten; Weigend, Florian; Evers, Ferdinand; Weber, Heiko B.; Mayor, Marcel (Proceedings of the National Academy of Sciences of the United States of America, 2005)
We have designed and synthesized a molecular rod that consists of two weakly coupled electronic pi-systems with mutually shifted energy levels. The asymmetry thus implied manifests itself in a current-voltage characteristic with pronounced dependence on the sign of the bias voltage, which makes the molecule a prototype for a molecular diode. The individual molecules were immobilized by sulfur-gold bonds between both electrodes of a mechanically controlled break junction, and their electronic transport properties have been investigated. The results indeed show diode-like current-voltage characteristics. In contrast to that, control experiments with symmetric molecular rods consisting of two identical pi-systems did not show significant asymmetries in the transport properties. To investigate the underlying transport mechanism, phenomenological arguments are combined with calculations based on density functional theory. The theoretical analysis suggests that the bias dependence of the polarizability of the molecule feeds back into the current leading to an asymmetric shape of the current-voltage characteristics, similar to the phenomena in a semiconductor diode.
Keywords: molecular electronics; rectification; single-molecule studies

A spatially and temporally localized sub-laser cycle electron source - Hommelhoff, Peter; Kealhofer, Catherine; Kasevich, Mark A. (Ultrafast Phenomena XV, 2007)
We simulate electron emission from a sharp tungsten tip induced by sub-8fs laser pulses and compare DC field and laser power dependence of the emission with experimental results. The simulation shows that with the correct choice of carrier-envelope phase of the exciting laser pulse, a single 700 attosecond electron pulse can be generated. We also discuss the applicability of such a system as a carrier-envelope phase detector. © 2007 Springer-Verlag.
UnivIS-Import:2015-04-16:Pub.2007.nat.dphy.IAP.exphys.aspati

A Spectroscopic Investigation of Magnetic Exchange Between Highly Anisotropic Spin Centers - Boeer, Angelika B.; Barra, Anne-Laure; Chibotaru, Liviu F.; Collison, David; McInnes, Eric; Mole, Richard A.; Simeoni, Giovanna G.; Timco, Grigore A.; Ungur, Liviu; Unruh, Tobias; Winpenny, Richard E. P. (Angewandte Chemie International Edition, 2011)
Keywords: cluster compounds; cobalt; EPR spectroscopy; inelastic neutron scattering; magnetic properties

Assembly Kinetics of Vimentin Tetramers to Unit-Length Filaments: A Stopped-Flow Study - Muecke, Norbert; Kaemmerer, Lara; Winheim, Stefan; Kirmse, Robert; Krieger, Jan; Mildenberger, Maria; Bassler, Jochen; Hurt, Ed; Goldmann, Wolfgang; Aebi, Ueli; Toth, Katalin; Langowski, Joerg; et al. (Biophysical Journal, 2018)
Intermediate filaments (IFs) are principal components of the cytoskeleton, a dynamic integrated system of structural proteins that provides the functional architecture of metazoan cells. They are major contributors to the elasticity of cells and tissues due to their high mechanical stability and intrinsic flexibility. The basic building block for the assembly of IFs is a rod-like, 60-nm-long tetrameric complex made from two antiparallel, half-staggered coiled coils. In low ionic strength, tetramers form stable complexes that rapidly assemble into filaments upon raising the ionic strength. The first assembly products, "frozen" by instantaneous chemical fixation and viewed by electron microscopy, are 60-nm-long "unit-length" filaments (ULFs) that apparently form by lateral in-register association of tetramers. ULFs are the active elements of IF growth, undergoing longitudinal end-to-end annealing with one another and with growing filaments. Originally, we have employed quantitative time-lapse atomic force and electron microscopy to analyze the kinetics of vimentin-filament assembly starting from a few seconds to several hours. To obtain detailed quantitative insight into the productive reactions that drive ULF formation, we now introduce a "stopped-flow" approach in combination with static light-scattering measurements. Thereby, we determine the basic rate constants for lateral assembly of tetramers to ULFs. Processing of the recorded data by a global fitting procedure enables us to describe the hierarchical steps of IF formation. Specifically, we propose that tetramers are consumed within milliseconds to yield octamers that are obligatory intermediates toward ULF formation. Although the interaction of tetramers is diffusion controlled, it is strongly driven by their geometry to mediate effective subunit targeting. Importantly, our model conclusively reflects the previously described occurrence of polymorphic ULF and mature filaments in terms of their number of tetramers per cross section.
EVALuna2:34589

Assessing Temperature Dependence of Drift Mobility in Methylammonium Lead Iodide Perovskite Single Crystals - Shrestha, Shreetu; Matt, Gebhard; Osvet, Andres; Niesner, Daniel; Hock, Rainer; Brabec, Christoph (Journal of Physical Chemistry C, 2018)
Hybrid organic-inorganic perovskites have emerged as cost-effective and high-performance semiconductors for optoelectronic applications. Precise knowledge of charge carrier mobility and especially the temperature dependence of mobility is therefore of utmost relevance for advancing high-performance materials. Here, the charge carrier mobility in methylammonium lead iodide single crystals is investigated with time of flight technique from 290 to 100 K. A nondispersive transport with an electron mobility of 135 (+/- 20) cm(2)/V s and a hole mobility of 90 (+/- 20) cm(2)/V s is obtained at room temperature. A power-law temperature dependence of mobility, mu alpha T-m, with an exponent m = -2.8 and -2.0, is measured for electrons and holes in the tetragonal phase. The highest electron and hole mobilities measured are 635 (+/- 70) and 415 (+/- 20) cm(2)/V s, respectively. Our results indicate that the scattering of charge carriers with phonons is the limiting factor for carrier mobilities at room temperature.

Assessing the Severity of Congestive Heart Failure by New Parameters of Circadian variation - Rockstroh, Christian; Kirchner, Jens; Krämer, Thomas; Hensel, Bernhard (Biomedizinische Technik. Biomedical engineering, vol. 56, iss. s1, 2011)
Introduction Circadian variation reflects the overall activity of a patient and thus promises to particularly indicate changes in cardiac function in patients with congestive heart failure (CHF). A model that allows reconstructing parameters of the day-night rhythm with a minimal set of presuppositions is provided by the non-stationary Langevin equation. The clinical applicability of these parameters was evaluated. Methods We analyzed 24-h RR-interval time series, which are publicly available at PhysioNet.org. The study populations included patients with normal sinus rhythm as well as with mild to medium CHF. From the Langevin model, parameters were derived that correspond to heart rates typical for day and night phases, respectively, to the difference between these values and to sleeping duration. Additionally, standard parameters of heart rate variability in time domain were computed, which serve as gold standard for cardiologic time series analysis. In order to estimate the impact of measurement artifacts on the method, analysis was performed both on raw and filtered signals. Results The Langevin parameters discriminate between patients with normal sinus rhythm and those suffering from mild CHF as well as the standard HRV parameters. When applied to patient groups with mild and medium CHF, respectively, the new approach performs even better than the gold standard. Hence, both the onset and worsening of heart failure are indicated by the new parameters. In contrast to the standard HRV parameters, these results remain unaltered if the raw instead of the filtered signal is used. These results indicate that the parameters from circadian variation are robust against measurement artifacts. Sensitivity to clinical cofounders is unlikely, due to tests with medium CHF patients from different databases showing no significant differences. Conclusion The Langevin approach to circadian variation provides robust markers for changes in cardiac condition, which are hence suitable for clinical use.

A statistical method for analyzing and comparing spatiotemporal cortical activation patterns - Krauß, Patrick; Metzner, Claus; Schilling, Achim; Tziridis, Konstantin; Traxdorf, Maximilian; Wollbrink, Andreas; Rampp, Stefan; Pantev, Christo; Schulze, Holger (Scientific Reports, 2018)
Information in the cortex is encoded in spatiotemporal patterns of neuronal activity, but the exact nature of that code still remains elusive. While onset responses to simple stimuli are associated with specific loci in cortical sensory maps, it is completely unclear how the information about a sustained stimulus is encoded that is perceived for minutes or even longer, when discharge rates have decayed back to spontaneous levels. Using a newly developed statistical approach (multidimensional cluster statistics (MCS)) that allows for a comparison of clusters of data points in n-dimensional space, we here demonstrate that the information about long-lasting stimuli is encoded in the ongoing spatiotemporal activity patterns in sensory cortex. We successfully apply MCS to multichannel local field potential recordings in different rodent models and sensory modalities, as well as to human MEG and EEG data, demonstrating its universal applicability. MCS thus indicates novel ways for the development of powerful read-out algorithms of spatiotemporal brain activity that may be implemented in innovative brain-computer interfaces (BCI).
EVALuna2:35749

A study of kesterite Cu2ZnSn(Se,S)(4) formation from sputtered Cu-Zn-Sn metal precursors by rapid thermal processing sulfo-selenization of the metal thin films - Wibowo, Rachmat Adhi; Yoo, Hye Sun; Hölzing, Astrid; Lechner, R.; Jost, S.; Palm, J.; Gowtham, M.; Louis, B.; Hock, Rainer (ELSEVIER SCIENCE SA, 2013)
Cu-Zn-Sn intermetallic thin films were sputtered on Mo-coated soda-lime glass substrates from elemental targets. Samples representing a wide range of compositions around the 2:1:1 kesterite ratio of the Cu-Zn-Sn material system have been investigated. Crystalline phase content and chemical composition of the metal precursors were characterized by X-ray phase analysis and X-ray fluorescence. The metal precursor films were then processed into metal chalcogenides by rapid thermal processing in sulfur ambient with a maximum process temperature around 500 degrees C. Thin films were investigated by X-ray powder diffraction, X-ray fluorescence and Raman spectroscopy to identify their phase contents as a function of precursor composition and initial intermetallic crystalline phase content. Compositional regions of kesterite crystallization as well as remaining secondary chalcogenide phases were identified. Consequences of the obtained results for the thin film crystallization of Kesterite absorbers for solar cell fabrication by rapid thermal processing of metallic precursors will be discussed. (C) 2012 Elsevier B.V. All rights reserved.
Keywords: Kesterite; Sulfo-selenization; X-ray diffraction; Intermetallic compounds

A switch for epitaxial graphene electronics: Utilizing the silicon carbide substrate as transistor channel - Krach, Florian; Hertel, Stefan; Waldmann, Daniel; Jobst, Johannes; Krieger, Michael; Reshanov, S.; Schoner, A.; Weber, Heiko B. (Applied Physics Letters, 2012)
Due to the lack of graphene transistors with large on/off ratio, we propose a concept employing both epitaxial graphene and its underlying substrate silicon carbide (SiC) as electronic materials. We demonstrate a simple, robust, and scalable transistor, in which graphene serves as electrodes and SiC as a semiconducting channel. The common interface has to be chosen such that it provides favorable charge injection. The insulator and gate functionality is realized by an ionic liquid gate for convenience but could be taken over by a solid gate stack. On/off ratios exceeding 44000 at room temperature are found. © 2012 American Institute of Physics.
UnivIS-Import:2015-04-14:Pub.2012.nat.dphy.IAP.LAP.aswitc

Asymmetry in the reciprocal epitaxy of NaCl and KBr - Maier, Sabine; Pfeiffer, Oliver; Glatzel, Thilo; Meyer, Ernst; Filleter, Tobin; Bennewitz, Roland (Physical Review B, 2007)
Ultrathin well-ordered films of KBr on NaCl (100) and of NaCl on KBr (100) have been grown. The films were imaged by means of noncontact atomic force microscopy with atomic resolution under ultrahigh vacuum conditions. An extreme asymmetry in the structure of the interface was found for the two systems. The first layer of KBr on NaCl (100) grows with the lattice constant of bulk KBr, while the first layer of NaCl on KBr (100) stretches to the bulk lattice constant of KBr. The KBr films exhibit a superstructure with the periodicity of the least common multiple of the NaCl and KBr lattice constants, while the stretched NaCl films grow flat. We discuss the anharmonicity of the ionic bond as origin of the dependence of the interface structure on the growth sequence.

A thermodynamical approach to the formation reactions of sodium-doped Cu(In,Ga)Se-2 - Hock, Rainer; et al. (ELSEVIER SCIENCE SA, 2006)
This work describes the influence of sodium doping on the formation reactions of the semiconductor material Cu(In,Ga)Se-2. Assuming the sodium dopant to act as a surface catalyst by formation of sodium polyselenides, we estimate the shift in the reaction enthalpies for the formation of binary selenides. Since the release of selenium from sodium polyselenides is an endothermic process, five of six possible reactions resulting in copper selenides are energetically suppressed whereas all indium and gallium selenides can still be formed exothermically. Furthermore, we have applied the effective heat of formation model on the ternary Cu-In-Se system to predict the first compound being formed during the selenisation of the metallic precursor. Our model predicts that sodium doping does not influence which selenide compound will be formed at first, but that influences consecutive reactions by shifting their reaction enthalpies. (c) 2005 Elsevier B.V. All rights reserved.
Keywords: chalcogenides; thin films; crystal growth; X-ray diffraction; thermodynamic properties

Atomically accurate Si grating with 5.73 nm period - Fauster, Thomas; et al. (Applied Physics Letters, 2001)
A vicinal surface of silicon is found that exhibits an atomically accurate step pattern with a period of 5.73 nm, corresponding to 17 atomic rows per (111) terrace. It can be viewed as reconstructed Si(557) surface, where a triple step is combined with a single Si(111)7x7 unit. The driving forces for establishing regular step patterns are discussed. (C) 2001 American Institute of Physics.

Atomically-defined model catalysts in ultrahigh vacuum and in liquid electrolytes: particle size-dependent CO adsorption on Pt nanoparticles on ordered Co3O4(111) films - Faisal, Firas; Stumm, Corinna; Bertram, Manon; Wähler, Tobias; Schuster, Ralf; Xiang, Feifei; Lytken, Ole; Katsounaros, Ioannis; Mayrhofer, Karl; Schneider, M. Alexander; Brummel, Olaf; Libuda, Jörg (Physical Chemistry Chemical Physics, 2018)
We have studied particle size effects on atomically-defined model catalysts both in ultrahigh vacuum (UHV) and under electrochemical (EC) conditions in liquid electrolytes. The model catalysts were prepared in UHV by physical vapour deposition (PVD) of Pt onto an ordered Co3O4(111) film on Ir(100), yielding nanoparticles (NPs) with an average size from 10 to 500 atoms per particle (0.8 to 3 nm). The model systems were characterized in UHV using surface science methods including scanning tunnelling microscopy (STM), before transferring them out of the UHV and into the electrolyte without contact to ambient conditions. By X-ray photoelectron spectroscopy (XPS) we show that the model surfaces are stable in the EC environment under the applied conditions (0.1 to 1 M phosphate buffer, pH 10, 0.33 to 1.03 V-RHE). As a reference, we study Pt(111) under identical conditions. In UHV, we also investigated the adsorption of CO using infrared reflection absorption spectroscopy (IRRAS). Under EC conditions, we performed equivalent experiments using EC infrared reflection absorption spectroscopy (EC-IRRAS) in combination with cyclic voltammetry (CV). Characteristic differences were observed between the IR spectra under EC conditions and in UHV. Besides the red-shift induced by the interfacial electric field (Stark effect), the EC IR bands of CO on Pt(111) show a larger width (by a factor of 2) as a result of local variations in the CO environment and coupling to the electrolyte. The CO IR bands of the Pt NPs are even broader (by a factor of 5), which is attributed to local variations of the interfacial electric field at the NP surface. Further pronounced differences are observed between the spectra taken in UHV and in the electrolyte regarding the site occupation and its dependence on particle size. In UHV, adsorption at on-top sites is preferred on Pt(111) at low coverage and similar adsorption ratios of on-top and bridge-bonded CO are formed at saturation coverage. In sharp contrast, on-top adsorption of CO on Pt(111) is partially suppressed under EC conditions. This effect is attributed to the competitive adsorption of anions from the electrolyte and leads to a clear preference for bridge sites at higher potentials (>0.5 V-RHE). For the Pt NPs, the situation is different and an increasing fraction of on-top CO is observed with decreasing particle size, both under EC conditions and in UHV. For the smallest particles (10-20 atoms) we do not detect any bridge-bonded CO. This change in site preference as a function of particle size is attributed to stronger on-top adsorption on low-coordinated Pt atoms of small Pt NPs. The effect leads to a clear preference for on-top adsorption in the electrolyte even at low CO coverage and over the full potential range studied.

Atomic and electronic structure of few-layer graphene on SiC(0001) studied with scanning tunneling microscopy and spectroscopy - Lauffer, Peter; Emtsev, Konstantin; Graupner, Ralf; Ley, Lothar; Seyller, Thomas; Reshanov, Sergey; Weber, Heiko B. (Physical Review B, 2008)
Epitaxial growth of graphene on SiC surfaces by solid state graphitization is a promising route for future development of graphene based electronics. In the present work, we have studied the morphology, atomic scale structure, and electronic structure of thin films of few-layer graphene (FLG) on SiC(0001) by scanning tunneling microscopy and spectroscopy (STS). We show that a quantitative evaluation of the roughness induced by the interface is a tool for determining the layer thickness of FLG. We present and interpret thickness dependent tunneling spectra, which can serve as an additional fingerprint for the determination of the layer thickness. By performing spatially resolved STS, we find evidence that the charge distribution in bilayer graphene is inhomogeneous. © 2008 The American Physical Society.
UnivIS-Import:2015-04-14:Pub.2008.nat.dphy.IAP.LAP.atomic

Atomic diffusion in liquid gallium and gallium-nickel alloys probed by quasielastic neutron scattering and molecular dynamic simulations - Shahzad, Anjum; Yang, Fan; Steffen, Julien; Neiß, Christian; Panchenko, Artem; Götz, Klaus; Vogel, Carola; Weißer, Matthias; Embs, Jan Peter; Petry, Winfried; Lohstroh, Wiebke; Görling, Andreas; et al. (Journal of Physics: Condensed Matter, 2024)
The atomic mobility in liquid pure gallium and a gallium-nickel alloy with 2 at% of nickel is studied experimentally by incoherent quasielastic neutron scattering. The integral diffusion coefficients for all-atom diffusion are derived from the experimental data at different temperatures. DFT-based ab-initio molecular dynamics (MD) is used to find numerically the diffusion coefficient of liquid gallium at different temperatures, and numerical theory results well agree with the experimental findings at temperatures below 500 K. Machine learning force fields derived from ab-initio molecular dynamics (AIMD) overestimate within a small 6% error the diffusion coefficient of pure gallium within the genuine AIMD. However, they better agree with experiment for pure gallium and enable the numerical finding of the diffusion coefficient of nickel in the considered melted alloy along with the diffusion coefficient of gallium and integral diffusion coefficient, that agrees with the corresponding experimental values within the error bars. The temperature dependence of the gallium diffusion coefficient D Ga ( T ) follows the Arrhenius law experimentally for all studied temperatures and below 500 K also in the numerical simulations. However, D Ga ( T ) can be well described alternatively by an Einstein-Stokes dependence with the metallic liquid viscosity following the Arrhenius law, especially for the MD simulation results at all studied temperatures. Moreover, a novel variant of the excess entropy scaling theory rationalized our findings for gallium diffusion. Obtained values of the Arrhenius activation energies are profoundly different in the competing theoretical descriptions, which is explained by different temperature-dependent prefactors in the corresponding theories. The diffusion coefficient of gallium is significantly reduced (at the same temperature) in a melted alloy with natural nickel, even at a tiny 2 at% concentration of nickel, as compared with its pure gallium value. This highly surprising behavior contradicts the existing excess entropy scaling theories and opens a venue for further research.
CRIS-Team Scopus Importer:2024-02-16
Keywords: ab-initio molecular dynamics; DFT-based machine learning force fields; gallium-nickel alloy; liquid gallium; quasielastic neutron scattering; self-diffusion

Atomic diffusion mechanisms in a binary metallic melt - Voigtmann, Thomas; Meyer, Andreas; Holland-Moritz, Dirk; Stüber, Sebastian; Hansen, Thomas; Unruh, Tobias (EPL - Europhysics Letters, 2008)
The relation between static structure and dynamics as measured through the diffusion coefficients in viscous multicomponent metallic melts is elucidated by the example of the binary alloy Zr(64)Ni(36), by a combination of neutron-scattering experiments and mode-coupling theory of the glass transition. Comparison with a hard-sphere mixture shows that the relation between the different self diffusion coefficients strongly depends on chemical short-range ordering. For the Zr-Ni example, the theory predicts both diffusivities to be practically identical. The kinetics of concentration fluctuations is dramatically slower than that of self-diffusion, but the overall interdiffusion coefficient is equally large or larger due to a purely thermodynamic prefactor. This result is a general feature for non-demixing dense melts, irrespective of chemical short-range order. Copyright (C) EPLA, 2008.

Atomic Friction Investigations on Ordered Superstructures - Pascal, Steiner; Gnecco, Enrico; Filleter, Tobin; Gosvami, Nitya Nand; Maier, Sabine; Meyer, Ernst; Bennewitz, Roland (Tribology Letters, 2010)
We review recent friction measurements on ordered superstructures performed by atomic force microscopy. In particular, we consider ultrathin KBr films on NaCl(001) and Cu(001) surfaces, single and bilayer graphene on SiC(0001), and the herringbone reconstruction of Au(111). Atomically resolved friction images of these systems show periodic features spanning across several unit cells. Although the physical mechanisms responsible for the formation of these superstructures are quite different, the experimental results can be interpreted within the same phenomenological framework. A comparison between experiments and modeling shows that, in the cases of KBr films on NaCl(001) and of graphene films, the tip-surface interaction is well described by a potential with the periodicity of the substrate which is modulated or, respectively, superimposed with a potential with the symmetry of the superstructure.
Keywords: Nanotribology; Friction mechanisms; Stick-slip; AFM

Atomic layer deposited aluminum oxide films on graphite and graphene studied by XPS and AFM - Speck, Florian; Ostler, Markus; Röhrl, Jonas; Emtsev, Konstantin; Hundhausen, Martin; Ley, Lothar; Seyller, Thomas (Physica Status Solidi (C) Current Topics in Solid State Physics, 2010)
Epitaxial graphene (EG) grown by solid-state decomposition of SiC is a promising material for future graphenebased electronics. On EG, the fabrication of a field-effect device requires the deposition of suitable gate insulator. Atomic layer deposition (ALD) of aluminum oxide might be useful for this purpose. Therefore, we investigated the growth of ALD-Al 2O 3 on highly oriented pyrolytic graphite (HOPG) and EG by atomic force microscopy (AFM), photoelectron spectroscopy (XPS) and Raman spectroscopy. Water as oxidant in the ALD process leads to inhomogeneous nucleation, whereas ozone leads to the formation of closed oxide layers. However, significant degradation of the EG takes place at higher temperatures and ozone exposure as witnessed by XPS and Raman spectroscopy. Careful adjustment of the process parameters allows reducing the damage to a level undetectable in XPS while providing enough nucleation centers for the formation of a closed Al 2O 3 film potentially suitable as a gate insulator. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
UnivIS-Import:2015-03-09:Pub.2010.nat.dphy.IAP.exphys.atomic

Atomic-level structural correlations across the morphotropic phase boundary of a ferroelectric solid solution: XBiMg1/2Ti1/2O3-(1-x)PbTiO3 - Datta, Kaustuv; Neder, Reinhard; Chen, Jun; Neuefeind, Joerg C.; Mihailova, Boriana (Scientific Reports, 2017)
Revelation of unequivocal structural information at the atomic level for complex systems is uniquely important for deeper and generic understanding of the structure property connections and a key challenge in materials science. Here we report an experimental study of the local structure by applying total elastic scattering and Raman scattering analyses to an important non-relaxor ferroelectric solid solution exhibiting the so-called composition-induced morphotropic phase boundary (MPB), where concomitant enhancement of physical properties have been detected. The powerful combination of static and dynamic structural probes enabled us to derive direct correspondence between the atomic-level structural correlations and reported properties. The atomic pair distribution functions obtained from the neutron total scattering experiments were analysed through big-box atom-modelling implementing reverse Monte Carlo method, from which distributions of magnitudes and directions of off-centred cationic displacements were extracted. We found that an enhanced randomness of the displacement-directions for all ferroelectrically active cations combined with a strong dynamical coupling between the A- A nd B-site cations of the perovskite structure, can explain the abrupt amplification of piezoelectric response of the system near MPB. Altogether this provides a more fundamental basis in inferring structure-property connections in similar systems including important implications in designing novel and bespoke material

Atomic real-space perspective of light-field-driven currents in graphene - Morimoto, Yuya; Shinohara, Yasushi; Ishikawa, Kenichi L.; Hommelhoff, Peter (New Journal of Physics, 2022)
When graphene is exposed to a strong few-cycle optical field, a directional electric current can be induced depending on the carrier-envelope phase of the field. This phenomenon has successfully been explained by the charge dynamics in reciprocal space, namely an asymmetry in the conduction band population left after the laser excitation. However, the corresponding real-space perspective has not been explored so far although it could yield knowledge about the atomic origin of the macroscopic currents. In this work, by adapting the nearest-neighbor tight-binding model including overlap integrals and the semiconductor Bloch equation, we reveal the spatial distributions of the light-field-driven currents on the atomic scale and show how they are related to the light-induced changes of charge densities. The atomic-scale currents flow dominantly through the network of the π bonds and are the strongest at the bonds parallel to the field polarization, where an increase of the charge density is observed. The real-space maps of the currents and changes in charge densities are elucidated using simple symmetries connecting real and reciprocal space. We also discuss the strong-field-driven Rabi oscillations appearing in the atomic-scale charge densities. This work highlights the importance of real-space measurements and stimulates future time-resolved atomic-scale experimental studies with high-energy electrons or x-rays, for example

Atomic-scale control of friction by actuation of nanometer-sized contacts - Socoliuc, Anisoara; Gnecco, Enrico; Maier, Sabine; Pfeiffer, Oliver; Baratoff, Alexis; Bennewitz, Roland; Meyer, Ernst (Science, 2006)
Stiction and wear are demanding problems in nanoelectromechanical devices, because of their large surface-to-volume ratios and the inapplicability of traditional liquid lubricants. An efficient way to switch friction on and off at the atomic scale is achieved by exciting the mechanical resonances of the sliding system perpendicular to the contact plane. The resulting variations of the interaction energy reduce friction below 10 piconewtons in a finite range of excitation and load, without any noticeable wear. Without actuation, atomic stick-slip motion, which leads to dissipation, is observed in the same range. Even if the normal oscillations require energy to actuate, our technique represents a valuable way to minimize energy dissipation in nanocontacts.

Atomic-scale friction measurements in ultra-high vacuum - Maier, Sabine; Gnecco, Enrico; Meyer, Ernst (Springer Verlag, 2015)
This chapter reviews friction force microscopy experiments that reveal atomic-scale processes in single asperity contacts during sliding. Different regimes of atomic friction will be discussed including smooth sliding with low dissipation and the dissipative atomic stick-slip motion, where the tip jumps from one lattice site to the next. Furthermore, effects owing to finite temperatures, varying scan velocity and the influence of surface structures on the atomic friction are presented. Finally, the empirical Prandtl-Tomlinson model is introduced, which explains well the main observations in atomic-scale friction force microscopy experiments.
CRIS-Team Scopus Importer:2023-03-17

Atomic scale structure and optical emission of Alx Ga1-x As GaAs quantum wells - Ropers, Claus; Wenderoth, Martin; Lars, Winking; Thilo, Reusch; Erdmann, Matthias; Ulbrich, Rainer G.; Grochol, M.; Grosse, F.; Zimmermann, R.; Malzer, Stefan; Döhler, Gottfried (Physical Review B, 2007)
A combined study of the optical and structural properties of AlGaAs GaAs quantum wells is presented. Microphotoluminescence experiments, magnetomicrophotoluminescence, and atomically resolved cross-sectional scanning tunneling microscopy were performed on the same quantum well sample. Constant-current topographs with aluminum and/or gallium sensitivity are used to directly extract disorder potentials. Using these potentials, exciton absorption spectra, microphotoluminescence spectra, and diamagnetic shifts of individual exciton states are calculated in an envelope function approximation. Very good agreement between the theoretical and experimental results is found. © 2007 The American Physical Society.

Atomic-scale yield and dislocation nucleation in KBr - Filleter, Tobin; Maier, Sabine; Bennewitz, Roland (Physical Review B, 2006)
Atomic-scale plastic deformation on a KBr(100) surface has been produced and characterized by use of atomic force microscopy (AFM) in ultrahigh vacuum. The structure of displaced material was imaged using noncontact mode AFM after first implementing the sharp silicon tip as an indenter. After indentation the KBr(100) surface is found to exhibit monatomic terraces which are formed via dislocation nucleation and glide. Discontinuities in the force-distance curves recorded during indentation are correlated to the creation of dislocation loops in the crystal. Incipient dislocation nucleation has been characterized as the abrupt monatomic layer displacement of the tip into the sample and the corresponding creation of monatomic terraces. The indenter radius has been found to significantly influence the lateral extent of the dislocation structure and the distribution of force discontinuities during indentation. The shear stress at the yield point was experimentally determined to be 2.5 GPa which is consistent with recent theoretical predictions for the ideal shear stress of KBr.

Atomistic origin of huge response functions at the morphotropic phase boundary of (1-x)Na0.5Bi0.5TiO3-xBaTiO(3) - Datta, Kaustuv; Richter, Andreas; Göbbels, Matthias; Neder, Reinhard; Mihailova, B. (Physical Review B, 2014)
The ferroelectric solid solution (1 - x)Na0.5Bi0.5TiO3-BaTiO3 (NBT-xBT) is a promising material to substitute for the environmentally undesired Pb-based ferroelectrics. The strong enhancement of the dielectric permittivity and piezoelectric coefficients near the morphotropic phase boundary (MPB) in ferroelectric ABO(3)-type solid solutions is commonly related to the existence of a single or several long-range-ordered phases resulting in a complex nanodomain pattern. Here, NBT-xBT is studied by Raman scattering and complementary synchrotron x-ray total elastic scattering to follow the temperature evolution of the mesoscopic-scale structural transformations for x below, at, and slightly above x(MPB). The most remarkable result is that at x similar to x(MPB) the phonon mode involving vibrations of both off-centered A-site Bi and B-site Ti experiences strong softening and damping near the triple-point temperature in the phase diagram, in strong contrast to the compounds with x < x(MPB) or x > x(MPB). The chemically enhanced coupling between the Bi and Ti subsystems at x(MPB) is facilitated by the subtle disturbance of the coupling processes within the Bi subsystem induced by Ba at x(MPB). These mesoscopic-scale structural and dynamic phenomena seem to be significant for the enhanced response functions at the MPB in NBT-xBT.

A tool to automatically analyze electromagnetic tracking data from high dose rate brachytherapy of breast cancer patients - Goetz, Th. I.; Lahmer, Godehard; Strnad, Vratislav; Bert, Christoph; Hensel, Bernhard; Tome, A. M.; Lang, E. W. (PLoS ONE, 2017)
During High Dose Rate Brachytherapy (HDR-BT) the spatial position of the radiation source inside catheters implanted into a female breast is determined via electromagnetic tracking (EMT). Dwell positions and dwell times of the radiation source are established, relative to the patient's anatomy, from an initial X-ray-CT-image. During the irradiation treatment, catheter displacements can occur due to patient movements. The current study develops an automatic analysis tool of EMT data sets recorded with a solenoid sensor to assure concordance of the source movement with the treatment plan. The tool combines machine learning techniques such as multi-dimensional scaling (MDS), ensemble empirical mode decomposition (EEMD), singular spectrum analysis (SSA) and particle filter (PF) to precisely detect and quantify any mismatch between the treatment plan and actual EMT measurements. We demonstrate that movement artifacts as well as technical signal distortions can be removed automatically and reliably, resulting in artifact-free reconstructed signals. This is a prerequisite for a highly accurate determination of any deviations of dwell positions from the treatment plan.
EVALuna2:33034

A top-down strategy identifying molecular phase stabilizers to overcome microstructure instabilities in organic solar cells - Zhang, Chaohong; Heumüller, Thomas; Leon, Salvador; Gruber, Wolfgang; Burlafinger, Klaus; Tang, Xiaofeng; Perea, Jose Dario; Wabra, Isabell; Hirsch, Andreas; Unruh, Tobias; Li, Ning; Brabec, Christoph (Energy and Environmental Science, 2019)
The operational stability of organic solar cells (OSCs) is the essential barrier to commercialization. Compared to thermally-induced degradation, photo-stability of OSCs is far away from being resolved. Here, we demonstrate that the thermal- and photo-degradation of metastable bulk-heterojunction OSCs are governed by the same mechanism. Understanding the fundamental principles behind this mechanism is of significant importance to fully address the instability issues. Structural incompatibilities between the donor and acceptor molecules are identified as the main origin of the instability. Further, we introduce a top-down approach mainly based on their melting temperature and interaction parameters to rationally screen molecular phase stabilizers from a database with more than 10000 small molecules. Eventually, five chemicals were selected to validate our concept and tested in unstable organic solar cells. 1,4-Piperazine, which possesses a high melting point, good miscibility with polymers and the capability of forming inter-molecular hydrogen bonding, can indeed stabilize the mixed amorphous phases, leading to significantly improved stability of otherwise metastable OSCs.<br

A trans-platinum(II) complex as a single-molecule insulator - Mayor, Marcel; von Hänisch, Carsten; Weber, Heiko B.; Reichert, Joachim; Beckmann, Detlef (Angewandte Chemie International Edition, 2002)
Keywords: electron transport; insulators; molecular electronics; platinum; single-molecule studies

Attosecond control of electrons emitted from a nanoscale metal tip - Krüger, Michael; Schenk, Markus; Hommelhoff, Peter (Nature, 2011)
Attosecond science is based on steering electrons with the electric field of well controlled femtosecond laser pulses. It has led to the generation of extreme-ultraviolet pulses with a duration of less than 100-attoseconds (ref. 3; 1-as = 10 18 's), to the measurement of intramolecular dynamics (by diffraction of an electron taken from the molecule under scrutiny) and to ultrafast electron holography. All these effects have been observed with atoms or molecules in the gas phase. Electrons liberated from solids by few-cycle laser pulses are also predicted to show a strong light-phase sensitivity, but only very small effects have been observed. Here we report that the spectra of electrons undergoing photoemission from a nanometre-scale tungsten tip show a dependence on the carrier-envelope phase of the laser, with a current modulation of up to 100 per cent. Depending on the carrier-envelope phase, electrons are emitted either from a single sub-500-attosecond interval of the 6-femtosecond laser pulse, or from two such intervals; the latter case leads to spectral interference. We also show that coherent elastic re-scattering of liberated electrons takes place at the metal surface. Owing to field enhancement at the tip, a simple laser oscillator reaches the peak electric field strengths required for attosecond experiments at 100-megahertz repetition rates, rendering complex amplified laser systems dispensable. Practically, this work represents a simple, extremely sensitive carrier-envelope phase sensor, which could be shrunk in volume to about one cubic centimetre. Our results indicate that the attosecond techniques developed with (and for) atoms and molecules can also be used with solids. In particular, we foresee subfemtosecond, subnanometre probing of collective electron dynamics (such as plasmon polaritons) in solid-state systems ranging in scale from mesoscopic solids to clusters and to single protruding atoms. © 2011 Macmillan Publishers Limited. All rights reserve
UnivIS-Import:2015-04-14:Pub.2011.nat.dphy.IAP.exphys.attose

Attosecond Electron Response in Nanoscale Interfaces - Higuchi, Takuya; Hommelhoff, Peter (Optics InfoBase Conference Papers, 2015)
A subcycle of intense laser light can force an electron to travel over nanometer lengthscales. We employ this ultrafast control of attosecond electron dynamics as key ingredient of nanoscale devices potentially operating at optical bandwidth.
CRIS-Team Scopus Importer:2023-03-07

Attosecond emission dynamics in nonlinear photoemission from metal tips - Krüger, Michael; Schenk, M.; Hommelhoff, Peter (European Quantum Electronics Conference, EQEC 2011, 2011)

Attosecond-fast internal photoemission - Heide, Christian; Hauck, Martin; Higuchi, Takuya; Ristein, Jürgen; Ley, Lothar; Weber, Heiko B.; Hommelhoff, Peter (Nature Photonics, 2020)
The photoelectric effect has a sister process relevant in optoelectronics called internal photoemission1,2,3. Here an electron is photoemitted from a metal into a semiconductor4,<a title="Di Bartolomeo, A. Graphene Schottky diodes: an experimental review of the rectifying graphene/semiconductor heterojunction. Phys. Rep. 606, 1–58 (2016)." href="https://www.nature.com/articles/s41566-019-0580-6#ref-CR5">5. While the photoelectric effect takes place within less than 100 attoseconds (1 as = 10−18 seconds)6,7, the attosecond timescale has so far not been measured for internal photoemission. Based on the new method CHArge transfer time MEasurement via Laser pulse duration-dependent saturation fluEnce determinatiON—CHAMELEON—we show that the atomically thin semimetal graphene coupled to bulk silicon carbide, forming a Schottky junction, allows charge transfer times as fast as (300 ± 200) as. These results are supported by a simple quantum mechanical model simulation. With the obtained cut-off bandwidth of 3.3 PHz (1 PHz = 1015 Hz) for the charge transfer rate, this semimetal/semiconductor interface represents a functional solid-state interface offering the speed and design space required for future light-wave signal processing.<br
Keywords: Nonlinear optics; Optical properties and devices; Optoelectronic devices and components; Ultrafast photonics

Attosecond Nanophysics: From Basic Science to Applications - Hommelhoff, Peter; Kling, Matthias Friedrich (2015)
UnivIS-Import:2015-10-26:Pub.2015.nat.dphy.IAP.exphys.attose

Attosecond nanoscale near-field sampling - Förg, Benjamin; Schoetz, Johannes; Süßmann, Frederik; Förster, Michael; Krüger, Michael; Ahn, B; Okell, William A.; Wintersperger, Karen; Zherebtsov, Sergey; Guggenmos, Alexander; Pervak, Vladimir; Kessel, Alexander; et al. (Nature Communications, 2016)
The promise of ultrafast light-field-driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite for advancing this new area is the ability to characterize optical near fields from light interaction with nanostructures, with sub-cycle resolution. Here we experimentally demonstrate attosecond near-field retrieval for a tapered gold nanowire. By comparison of the results to those obtained from noble gas experiments and trajectory simulations, the spectral response of the nanotaper near field arising from laser excitation can be extracte

Attosecond physics at the nanoscale - Ciappina, Marcelo F.; Perez-Hernandez, J. A.; Landsman, Alexandra; Okell, William A.; Zherebtsov, Sergey; Förg, Benjamin; Schoetz, Johannes; Seiffert, Lennart; Fennel, Thomas; Shaaran, Tahir; Zimmermann, T; Chacón, Alexis; et al. (Reports on Progress in Physics, 2017)
Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto- and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds (1 attosecond = 1 as = 10 s), which is comparable with the optical field. For comparison, the revolution of an electron on a 1s orbital of a hydrogen atom is ∼152 as. On the other hand, the second branch involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the merger with intense laser physics is relatively recent. In this report on progress we present a comprehensive experimental and theoretical overview of physics that takes place when short and intense laser pulses interact with nanosystems, such as metallic and dielectric nanostructures. In particular we elucidate how the spatially inhomogeneous laser induced fields at a nanometer scale modify the laser-driven electron dynamics. Consequently, this has important impact on pivotal processes such as above-threshold ionization and high-order harmonic generation. The deep understanding of the coupled dynamics between these spatially inhomogeneous fields and matter configures a promising way to new avenues of research and applications. Thanks to the maturity that attosecond physics has reached, together with the tremendous advance in material engineering and manipulation techniques, the age of atto-nanophysics has begun, but it is in the initial stage. We present thus some of the open questions, challenges and prospects for experimental confirmation of theoretical predictions, as well as experiments aimed at characterizing the induced fields and the unique electron dynamics initiated by them with high temporal and spatial resolutio
Keywords: attosecond physics; plasmonic fields; strong field physics

Attosecond physics in photoemission from a metal nanotip - Krueger, M.; Schenk, M.; Foerster, M.; Hommelhoff, Peter (Journal of Physics B-Atomic Molecular and Optical Physics, 2012)
Nanometre-scale metal tips irradiated by femtosecond laser pulses represent ultrafast electron sources. The combination of the laser pulse and the tip offers the possibility of extending attosecond science from atomic or molecular gases to surfaces of solid nanoemitters. We first review this emerging research field focusing on electron rescattering at sharp metal tips. In particular, we investigate the carrier-envelope phase effects that reveal attosecond emission dynamics. Furthermore, we present detailed theory models that support this interpretation. © 2012 IOP Publishing Ltd.
UnivIS-Import:2015-04-14:Pub.2012.nat.dphy.IAP.exphys.attose

Attosecond physics phenomena at nanometric tips - Krüger, Michael; Lemell, Christoph; Wachter, Georg; Burgdörfer, Joachim; Hommelhoff, Peter (Journal of the Physics B: Atomic and Molecular Physics, 2018)
Attosecond science is based on electron dynamics driven by a strong optical electric field and has evolved beyond its original scope in gas-phase atomic and molecular physics to solid-state targets. In this review, we discuss a nanoscale attosecond physics laboratory that has enabled the first observations of strong-field-driven photoemission and recollision at a solid surface: laser-triggered metallic nanotips. In addition to the research questions of rather fundamental nature, femtosecond electron sources with outstanding beam qualities have resulted from this research, which has prompted follow-up application in the sensing of electric fields and lightwave electronics, ultrafast microscopy and diffraction, and fundamental matter-wave quantum optics. We review the theoretical and experimental concepts underlying near-field enhancement, photoemission regimes and electron acceleration mechanisms. Nanotips add new degrees of freedom to well known strong-field phenomena from atomic physics. For example, they enable the realization of a true sub-optical-cycle acceleration regime where recollision is suppressed. We also discuss the possibility of high-harmonic generation due to laser irradiation of metallic nanostructure

Author Correction: Isolated Rh atoms in dehydrogenation catalysis (Scientific Reports, (2023), 13, 1, (4458), 10.1038/s41598-023-31157-y) - Wittkämper, Haiko; Hock, Rainer; Weißer, Matthias; Dallmann, Johannes; Vogel, Carola; Raman, Narayanan; Taccardi, Nicola; Haumann, Marco; Wasserscheid, Peter; Hsieh, Tzung En; Maisel, Sven; Moritz, Michael; et al. (Scientific Reports, 2023)
Correction to: Scientific Reports, published online 17 March 2023 The original version of this Article contained an error in the spelling of the author Nicola Taccardi, which was incorrectly given as Nicola Tacardi. The original Article has been corrected.
CRIS-Team Scopus Importer:2023-06-30

Automatic quantification of angiogenesis in 2D sections: a precise and timesaving approach - Weis, Christian; Covi, J. M.; Hilgert, Johannes; Leibig, N.; Arkudas, Andreas; Horch, Raymund E.; Kneser, U.; Schmidt, V. J. (Journal of Microscopy, 2015)
The standardized characterization of angiogenesis is crucial in the field of tissue engineering as sufficient blood supply is the limiting factor of mass transfer. However, reliable algorithms that provide a straight forward and observer-independent assessment of new vessel formation are still lacking. We propose an automatic observer-independent quantitative method (including downloadable source code) to analyze vascularization using two-dimensional microscopic images of histological cross-sections and advanced postprocessing, based on a 'positive- and negative-experts' model and a (corrected) nearest neighbour classification, in a vascularized tissue engineering model.An established angioinductive rat arteriovenous loop model was used to compare the new automatic analysis with a common 2D method and a ?CT algorithm. Angiogenesis was observed at three different time points (5, 10 and 15 days).In line with previous results, formation of functional new vessels that arose from the venous graft was evident within the three-dimensional construct and a significant (p < 0.05) increase in vessel count and area was observed over time. The proposed automatic analysis obtained precise values for vessel count and vessel area that were similar to the manually gained data. The algorithm further provided vectorized parameterization of the newly formed vessels for advanced statistical analysis. Compared to the ?CT-based three-dimensional analyses, the presented two-dimensional algorithm was superior in terms of small vessel detection as well as cost and time efficiency.The quantitative evaluation method, using microscopic images of stained histological sections, 'positive- and negative-experts'-based vessel segmentation, and nearest neighbour classification, provides a user-independent and precise but also time- and cost-effective tool for the analysis of vascularized constructs. Our algorithm, which is freely available to the public, outperforms previous approaches especially in terms of unambiguous vessel classification and statistical analyses.
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A versatile high resolution scanning tunneling potentiometry implementation - Druga, Thomas; Wenderoth, Martin; Homoth, Jan; Schneider, M. Alexander; Ulbrich, Rainer G. (Review of Scientific Instruments, 2010)
We have developed a new scanning tunneling potentiometry technique which can-with only minor changes of the electronic setup-be easily added to any standard scanning tunneling microscope (STM). This extension can be combined with common STM techniques such as constant current imaging or scanning tunneling spectroscopy. It is capable of performing measurements of the electrochemical potential with microvolt resolution. Two examples demonstrate the versatile application. First of all, we have determined local variations of the electrochemical potential due to charge transport of biased samples down to angstrom length scales. Second, with tip and sample at different temperatures we investigated the locally varying thermovoltage occurring at the tunneling junction. Aside from its use in determining the chemical identity of substances at the sample surface our method provides a controlled way to eliminate the influence of laterally varying thermovoltages on low-bias constant current topographies. (C) 2010 American Institute of Physics. [doi:10.1063/1.3469809]

Axisymmetric and Asymmetric Naphthalene-Bisthienothiophene Based Nonfullerene Acceptors: On Constitutional Isomerization and Photovoltaic Performance - Hu, Wei; Du, Xiaoyan; Zhuang, Wenliu; Su, Wenyan; Cao, Jiamin; Pourrahimi, Amir Masoud; Li, Ning; Shen, Xingxing; Zhang, Maojie; Yu, Donghong; Gruber, Wolfgang; Unruh, Tobias; et al. (ACS Applied Energy Materials, 2020)
Two pairs of constitutional isomers of fused-octacyclic nonfullerene acceptors (NFAs) based on a naphthalene-bisthienothiophene core with or without fluorination at the ending groups have been developed. Compared with the axisymmetric NFAs N66-IC and N66-2FIC with two six-member-ring bridges, their asymmetric constitutional isomers N65-IC and N65-2FIC both with one six-member-ring bridge and one five-member-ring bridge exhibit remarkable red-shifted absorption, higher crystallinity, and slightly down-shifted LUMO energy levels. Organic solar cells based on PBDB-T-2F:N65-2FIC achieved a promising power conversion efficiency of 10.19%, which is three times higher than that of its counterpart PBDB-T-2F:N66-2FIC cell (3.46%). While being blended with PBDB-T as the donor material, the asymmetric acceptor analogue N65-IC based solar cell pronounces a PCE of 9.03%, being significantly improved from that of 5.45% for the PBDB-T:N66-IC based cell, which is in consistency with the results from those cells from their both fluorinated donor and acceptor counterparts. Design rules on either both fluorinated, both nonfluorinated, or cross-combined donor/acceptors for device fabrication has been explored. In addition, PBDB-T-2F:N65-2FIC possesses very promising device stability with 85% of its initial PCE after an exposure time of 1500 h under one sun illumination, which is meaningful for their future commercial devices.<br
Keywords: asymmetry; axisymmetry; isomerization

Background removal in scanning tunneling spectroscopy of single atoms and molecules on metal surfaces - Wahl, Peter; Diekhöner, Lars; Schneider, M. Alexander; Kern, Klaus (Review of Scientific Instruments, 2008)
Scanning tunneling spectroscopy has developed into a powerful spectroscopic technique that has found wide application in the atomic scale characterization of the electronic properties of clean surfaces as well as adsorbates and defects at surfaces. However, it still lacks the standard methods for data treatment and removal of artifacts in spectra as they are, e.g., common in photoemission spectroscopy. The properties of the atomic scale tip apex-the probe of the instrument-tend to introduce spurious background signals into tunneling spectra. We present and discuss two methods which permit to extract tip-independent information from low temperature tunneling spectra acquired on single atoms and molecules on single crystal surfaces by background subtraction. The methods rely on a characterization of the tip on the clean metal surface. The performance of both methods is demonstrated and compared for simulated and experimental tunneling spectra. (C) 2008 American Institute of Physics.

Band diagrams of intrinsic and p-tye diamond with hydrogenated surfaces - Ristein, Jürgen; Ley, Lothar; et al. (physica status solidi (a), 2003)
UnivIS-Import:2015-03-09:Pub.2003.nat.dphy.IAP.exphys.banddi

Band structure calculations of CuAlO2, CuGaO2, CuInO2, and CuCrO2 by screened exchange - Gillen, Roland; Robertson, John (Physical Review B - Condensed Matter and Materials Physics, 2011)

Basal plane dislocation conversion enhancement in 4H-SiC homoepitaxial layers by ion implantation into the wafer - Heidorn, Christian; Esteve, Romain; Höchbauer, Tobias; Krieger, Michael; Weber, Heiko B.; Rupp, Roland (Materials Science Forum, 2019)
We studied the impact of ion implantation into the wafer substrate prior to the epitaxy process on the basal plane dislocation conversion behavior during epitaxial layer growth. Defect density measurements show an enhancing effect of the ion implantation on the basal plane dislocation to threading edge dislocation conversion. Analysis of the lateral conversion distribution, the stress field in the material as well as the wafer topography at the onset of epitaxial growth lead us to believe that stresses in the epitaxy layer cause the enhanced basal plane dislocation conversion.
CRIS-Team Scopus Importer:2019-09-17
Keywords: 4H-SiC; Basal Plane Dislocation (BPD) conversion; Ion implantation

Bayesian inference of time varying parameters in autoregressive processes - Mark, Christoph; Metzner, Claus; Fabry, Ben (arXiv, 2014)

Bayesian model selection for complex dynamic systems - Mark, Christoph; Metzner, Claus; Lautscham, Lena; Strissel, Pamela; Strick, Reiner; Fabry, Ben (Nature Communications, 2018)
Time series generated by complex systems like financial markets and the earth's atmosphere often represent superstatistical random walks: on short time scales, the data follow a simple low-level model, but the model parameters are not constant and can fluctuate on longer time scales according to a high-level model. While the low-level model is often dictated by the type of the data, the high-level model, which describes how the parameters change, is unknown in most cases. Here we present a computationally efficient method to infer the time course of the parameter variations from time-series with short-range correlations. Importantly, this method evaluates the model evidence to objectively select between competing high-level models. We apply this method to detect anomalous price movements in financial markets, characterize cancer cell invasiveness, identify historical policies relevant for working safety in coal mines, and compare different climate change scenarios to forecast global warming.
EVALuna2:210064

Beam splitting of low-energy guided electrons with a two-sided microwave chip - Zimmermann, Robert; Weber, Philipp; Seidling, Michael; Hommelhoff, Peter (Applied Physics Letters, 2019)
We present a two-layer design and experimental demonstration of a chip-based electron beam splitter working for electron energies up to 200 eV. Beam splitting arises from smoothly transforming the transverse microwave guiding potential from a single-well into a double-well, thereby generating two separated output beams. We discuss future structures for coherent electron beam splitting, which would pave the way for an electron interferometer on a chi
Keywords: chip based electron splitter; quantum microscope; electron microscopy

Behavior of encapsulated MG-63 cells in RGD and gelatine-modified alginate hydrogels - Grigore, Alexandra; Sarker, Bapi; Fabry, Ben; Boccaccini, Aldo R.; Detsch, Rainer (Tissue Engineering - Part A, 2014)
Achieving cell spreading and proliferation inside hydrogels that are compatible with microencapsulation technology represents a major challenge for tissue engineering scaffolding and for the development of three-dimensional cell culture models. In this study, microcapsules of 650-900μm in diameter were fabricated from oxidized alginate covalently cross-linked with gelatine (AlGel). Schiff's base bond formed in AlGel, detected by Fourier transform infrared spectroscopy, which confirmed the cross-linking of oxidized alginate with gelatine. Biological properties of alginate based hydrogels were studied by comparing the viability and morphology of MG-63 osteosarcoma cells encapsulated in gelatine and RGD-modified alginate. We hypothesized that the presence of gelatine and RGD will support cell adhesion and spreading inside the microcapsules and finally, also vascular endothelial growth factor (VEGF) secretion. After 4 days of incubation, cells formed extensive cortical protrusions and after 2 weeks they proliferated, migrated, and formed cellular networks through the AlGel material. In contrast, cells encapsulated in pure alginate and in RGD-modified alginate formed spherical aggregates with limited cell mobility and VEGF secretion. Metabolic activity was doubled after 5 days of incubation, making AlGel a promising material for cell encapsulation. © Mary Ann Liebert, Inc.

Beyond double-resonant Raman scattering: Ultraviolet Raman spectroscopy on graphene, graphite, and carbon nanotubes - Tyborski, Christoph; Herziger, Felix; Gillen, Roland; Maultzsch, Janina (Physical Review B, 2015)
We present an analysis of deep-UV Raman measurements of graphite, graphene, and carbon nanotubes. For excitation energies above the strong optical absorption peak at the M point in the Brillouin zone (approximate to 4.7 eV), we partially suppress double-resonant scattering processes and observe the two-phonon density of states of carbon nanomaterials. The measured peaks are assigned to contributions from LO, TO, and LA phonon branches, supported by calculations of the phonon dispersion. Moreover, we gain access to the infrared-active E-1u mode in graphite. By lowering the excitation energy and thus allowing double-resonant scattering processes, we demonstrate the rise of the 2D mode in graphite with ultrashort phonon wave vector

BICHROMATIC 2-PHOTON PHOTOEMISSION SPECTROSCOPY OF IMAGE POTENTIAL STATES ON AG(100) - Fauster, Thomas; et al. (Applied Physics A-Materials Science & Processing, 1990)

BILAYER GROWTH IN A METALLIC SYSTEM - FE ON CU(100) - Fauster, Thomas; et al. (Surface Science, 1991)
During epitaxial growth of Fe on Cu(100) the normalized Auger signal of Fe was taken as a function of evaporation time. This curve shows evidence for a layer-by-layer growth mode and clearly rules out other possible growth modes. Rutherford backscattering spectrometry was used to determine thicknesses of a one- and two-layer film quantitatively with an accuracy of +/- 0.3 ML. These data together with the Auger analysis unveil a bilayer-by-bilayer growth mode for the first two bilayers.

Binary supramolecular networks of bridged triphenylamines with different substituents and identical scaffolds - Steiner, Christian; Yang, Zechao; Gliemann, Bettina; Meinhardt, Ute; Gurrath, Martin; Ammon, Maximilian Michael; Meyer, Bernd; Kivala, Milan; Maier, Sabine (Chemical Communications, 2018)
Based on scanning tunneling microscopy experiments combined with density functional theory, we report the formation and the electronic structure of porous binary supramolecular networks on Au(111). The two triphenylamine derivatives with identical scaffolds intermix due to a maximization of the overall number of H-bonds instead of an optimization of the H-bond strength in the bonding motif. The HOMO-LUMO gap is defined by both molecules, which is typical for electron donor-acceptor networks.

Biologging of emperor penguins-Attachment techniques and associated deployment performance - Houstin, Aymeric; Paranhos Zitterbart, Daniel; Winterl, Alexander; Richter, Sebastian; Planas-Bielsa, Víctor; Chevallier, Damien; Ancel, André; Fournier, Jérôme; Fabry, Ben; Le Bohec, Céline (PLoS ONE, 2022)
An increasing number of marine animals are equipped with biologgers, to study their physiology, behaviour and ecology, often for conservation purposes. To minimise the impacts of biologgers on the animals' welfare, the Refinement principle from the Three Rs framework (Replacement, Reduction, Refinement) urges to continuously test and evaluate new and updated biologging protocols. Here, we propose alternative and promising techniques for emperor penguin (Aptenodytes forsteri) capture and on-site logger deployment that aim to mitigate the potential negative impacts of logger deployment on these birds. We equipped adult emperor penguins for short-term (GPS, Time-Depth Recorder (TDR)) and long-term (i.e. planned for one year) deployments (ARGOS platforms, TDR), as well as juvenile emperor penguins for long-term deployments (ARGOS platforms) in the Weddell Sea area where they had not yet been studied. We describe and qualitatively evaluate our protocols for the attachment of biologgers on-site at the colony, the capture of the animals and the recovery of the devices after deployment. We report unprecedented recaptures of long-term equipped adult emperor penguins (50% of equipped individuals recaptured after 290 days). Our data demonstrate that the traditional technique of long-term attachment by gluing the biologgers directly to the back feathers causes excessive feather breakage and the loss of the devices after a few months. We therefore propose an alternative method of attachment for back-mounted devices. This technique led to successful year-round deployments on 37.5% of the equipped juveniles. Finally, we also disclose the first deployments of leg-bracelet mounted TDRs on emperor penguins. Our findings highlight the importance of monitoring potential impacts of biologger deployments on the animals and the need to continue to improve methods to minimize disturbance and enhance performance and results.
CRIS-Team Scopus Importer:2022-08-12

Biomechanical characterization of a desminopathy in primary human myoblasts - Bonakdar, Navid; Luczak, Justyna; Lautscham, Lena; Czonstke, Maja; Koch, Thorsten M.; Mainka, Astrid; Jungbauer, Tajana; Goldmann, Wolfgang H.; Schroeder, Rolf; Fabry, Ben (Biochemical and Biophysical Research Communications, 2012)

Biomechanical characterization of myofibrillar myopathies - Winter, Lilli; Goldmann, Wolfgang (Cell Biology International, 2015)
Myofibrillar myopathies (MFMs) are a group of sporadic and hereditary skeletal muscle diseases, which lead to severe physical disability and premature death. Most MFMs are caused by mutations in genes encoding desmin, plectin, VCP, filamin C, BAG3, FHL-1, ?B-crystallin, DNAJB6, myotilin, and ZASP. Biomechanical studies on primary human myoblasts carrying desmin and plectin mutations showed increased stiffness and reduced mechanical stress tolerance i.e., higher mechanical vulnerability compared to control cells. Higher stiffness of mutant cells may lead to higher intracellular stress at physiologic stretch and shear deformation, which in turn could trigger muscle fiber degeneration.
EVALuna2:7269

Biomembrane-mimicking lipid bilayer system as a mechanically tunable cell substrate - Lautscham, Lena; Lin, Corey Y.; Auernheimer, Vera; Naumann, Christoph A.; Goldmann, Wolfgang; Fabry, Ben (Biomaterials, 2014)

Bioprinting and Differentiation of Adipose-Derived Stromal Cell Spheroids for a 3D Breast Cancer-Adipose Tissue Model - Horder, Hannes; Lasheras, Mar Guaza; Grummel, Nadine; Nadernezhad, Ali; Herbig, Johannes; Erguen, Sueleyman; Tessmar, Joerg; Groll, Juergen; Fabry, Ben; Bauer-Kreisel, Petra; Blunk, Torsten (Cells, 2021)
Biofabrication, including printing technologies, has emerged as a powerful approach to the design of disease models, such as in cancer research. In breast cancer, adipose tissue has been acknowledged as an important part of the tumor microenvironment favoring tumor progression. Therefore, in this study, a 3D-printed breast cancer model for facilitating investigations into cancer cell-adipocyte interaction was developed. First, we focused on the printability of human adipose-derived stromal cell (ASC) spheroids in an extrusion-based bioprinting setup and the adipogenic differentiation within printed spheroids into adipose microtissues. The printing process was optimized in terms of spheroid viability and homogeneous spheroid distribution in a hyaluronic acid-based bioink. Adipogenic differentiation after printing was demonstrated by lipid accumulation, expression of adipogenic marker genes, and an adipogenic ECM profile. Subsequently, a breast cancer cell (MDA-MB-231) compartment was printed onto the adipose tissue constructs. After nine days of co-culture, we observed a cancer cell-induced reduction of the lipid content and a remodeling of the ECM within the adipose tissues, with increased fibronectin, collagen I and collagen VI expression. Together, our data demonstrate that 3D-printed breast cancer-adipose tissue models can recapitulate important aspects of the complex cell-cell and cell-matrix interplay within the tumor-stroma microenvironment.
CRIS-Team WoS Importer:2021-05-14

Biosensitive and antibacterial coatings on metallic material for medical applications - Goldmann, Wolfgang (Cell Biology International, 2021)
Metallic materials are commonly used for load-bearing implants and as internal fixation devices. It is customary to use austenitic stainless steel, especially surgical grade type 316L SS as temporary and Ti alloys as permanent implants. However, long-term, poor bonding with bone, corrosion, and release of metal ions, such as chromium and nickel occur. These ions are powerful allergens and carcinogens and their uncontrolled leaching may be avoided by surface coatings. Therefore, bioactive glasses (BGs) became a vital biomedical material, which can form a biologically active phase of hydroxycarbonate apatite on their surface when in contact with physiological fluids. To reduce the high coefficient of friction and the brittle nature of BGs, polymers are normally incorporated to avoid the high-temperature sintering/densification of ceramic-only coatings. For medical application, electrophoretic deposition (EPD) is now used for polymer (organic) and ceramic (inorganic) components at room temperature due to its simplicity, control of coating thickness and uniformity, low cost of equipment, ability to coat substrates of intricate shape and to supply thick films in composite form, high purity of deposits as well as no phase transformation during coating. Although extensive research has been conducted on polymer/inorganic composite coatings, only some studies have reported multifunctional properties, such as biological antibacterial activity, enhanced cell adhesion, controlled drug release ability, and mechanical properties. This review will focus on biodegradable coatings, including zien, chitosan, gelatin, cellulose loaded with antibacterial drugs/metallic ions/natural herbs on biostable substrates (PEEK/PMMA/PCL/PLLA layers), which have the potential of multifunctional coating for metallic implants.
CRIS-Team Scopus Importer:2021-05-07
Keywords: bioceramics; biocomposites; biomaterials; biopolymers; bone and teeth implants

Biphasic response of cell invasion to matrix stiffness in three-dimensional biopolymer networks - Lange, Nadine; Skodzek, Kai; Hurst, Sebastian; Mainka, Astrid; Steinwachs, Julian; Schneider, Julia; Aifantis, Katerina E.; Fabry, Ben (Acta Biomaterialia, 2015)

Bipolar treatment of the electrically detected transient grating technique - Hundhausen, Martin; Ley, Lothar (Applied Physics Letters, 1995)
UnivIS-Import:2015-03-05:Pub.1995.nat.dphy.IAP.exphys.bipola

Bonding of Ammonia and Its Dehydrogenated Fragments on Ru(0001) - Maier, Sabine; Stass, Ingeborg; Cerda, Jorge I.; Salmeron, Miquel (Journal of Physical Chemistry C, 2012)
The adsorption and dissociation of ammonia on Ru(0001) was studied by scanning tunneling microscopy (STM), density functional theory (DFT), and STM contrast simulations. Various NHx (with x = 0-2) species were formed by controlled STM tip manipulation. Each species shows a characteristic imaging contrast in STM measurements, changing from a protrusion for NH3 and NH2, to a depression for NH and N. The adsorption sites of each species determined from the STM images and their contrast agree well with DFT calculations and STM image simulations. Ammonia was found to interact with hydrogen atoms present on the surface, leading to the formation of triangular-shaped NH3 + 3H complexes. At submonolayer coverage, ammonia dimers were also identified and their formation and dissociation were observed upon tip manipulation.

Boosting the Efficiency of Smith-Purcell Radiators Using Nanophotonic Inverse Design - Haeusler, Urs; Seidling, Michael; Yousefi, Peyman; Hommelhoff, Peter (ACS Photonics, 2022)
The generation of radiation from free electrons passing a grating, known as Smith-Purcell radiation, finds various applications, including nondestructive beam diagnostics and tunable light sources, ranging from terahertz toward X-rays. So far, the gratings used for this purpose have been designed manually, based on human intuition and simple geometric shapes. Here we apply the computer-based technique of nanophotonic inverse design to build a 1400 nm Smith-Purcell radiator for subrelativistic 30 keV electrons. We demonstrate that the resulting silicon nanostructure radiates with a 3X higher efficiency and 2.2X higher overall power than previously used rectangular gratings. With better fabrication accuracy and for the same electron-structure distance, simulations suggest a superiority by a factor of 96 in peak efficiency. While increasing the efficiency is a key step needed for practical applications of free-electron radiators, inverse design also allows to shape the spectral and spatial emission in ways inaccessible with the human mind.
CRIS-Team WoS Importer:2022-02-04

Boron-containing MFI-type zeolites with a hierarchical nanosheet assembly for lipase immobilization - Marthala, Venkata; Urmoneit, Lynn; Zhou, Zhou; Machoke, Albert; Schmiele, Martin; Unruh, Tobias; Schwieger, Wilhelm; Hartmann, Martin (Dalton Transactions, 2017)
Hierarchical nanosheet assemblies of boron-containing MFI-type zeolites were successfully synthesized using bifunctional surfactant molecules under static conditions. With the optimized Si/B = 50 in the synthesis gel, a material with high specific surface area (483 m2 g(-1)) and a maximum pore size of 6.5 nm suitable for lipase encapsulation was obtained.

BoseEinstein condensation on a microelectronic chip - Hänsel, Wolfgang; Hommelhoff, Peter; Hänsch, Theodor; Reichel, Jakob (Nature, 2001)
Although Bose-Einstein condensates of ultracold atoms have been experimentally realizable for several years, their formation and manipulation still impose considerable technical challenges. An all-optical technique that enables faster production of Bose-Einstein condensates was recently reported. Here we demonstrate that the formation of a condensate can be greatly simplified using a microscopic magnetic trap on a chip. We achieve Bose-Einstein condensation inside the single vapour cell of a magneto-optical trap in as little as 700 ms - more than a factor of ten faster than typical experiments, and a factor of three faster than the all-optical technique. A coherent matter wave is emitted normal to the chip surface when the trapped atoms are released into free fall; alternatively, we couple the condensate into an 'atomic conveyor belt', which is used to transport the condensed cloud non-destructively over a macroscopic distance parallel to the chip surface. The possibility of manipulating laser-like coherent matter waves with such an integrated atom-optical system holds promise for applications in interferometry, holography, microscopy, atom lithography and quantum information processing.
UnivIS-Import:2015-03-09:Pub.2001.nat.dphy.IAP.exphys.boseei

Bottom-gated epitaxial graphene - Waldmann, Daniel; Jobst, Johannes; Speck, Florian; Seyller, Thomas; Krieger, Michael; Weber, Heiko B. (Nature Materials, 2011)
High-quality epitaxial graphene on silicon carbide (SiC) is today available in wafer size. Similar to exfoliated graphene, its charge carriers are governed by the Dirac-Weyl Hamiltonian and it shows excellent mobilities. For many experiments with graphene, in particular for surface science, a bottom gate is desirable. Commonly, exfoliated graphene flakes are placed on an oxidized silicon wafer that readily provides a bottom gate. However, this cannot be applied to epitaxial graphene as the SiC provides the source material out of which graphene grows. Here, we present a reliable scheme for the fabrication of bottom-gated epitaxial graphene devices, which is based on nitrogen (N) implantation into a SiC wafer and subsequent graphene growth. We demonstrate working devices in a broad temperature range from 6 to 300-K. Two gating regimes can be addressed, which opens a wide engineering space for tailored devices by controlling the doping of the gate structure. © 2011 Macmillan Publishers Limited. All rights reserved.
UnivIS-Import:2015-04-14:Pub.2011.nat.dphy.IAP.LAP.bottom

Bottom-up fabrication of atomically precise molecular nanostructures through on-surface reactions - Maier, Sabine (ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 2019)
CRIS-Team WoS Importer:2019-08-23

Breakdown of the Endothelial Barrier Function in Tumor Cell Transmigration - Mierke, Claudia; Paranhos Zitterbart, Daniel; Kollmannsberger, Philip; Raupach, Carina; Schlötzer-Schrehardt, Ursula; Goecke, Tamme W.; Behrens, Jürgen; Fabry, Ben (Biophysical Journal, 2007)
UnivIS-Import:2015-04-14:Pub.2007.nat.dphy.IAP.lpmt.breakd
Keywords: transendothelial migration; invasion; metastasis; endothelium; CXCR2; Gro-â; IL-8; cell mechanics