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Search Results: 1 - 10 of 18533 matches for " U. Diebold "
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Nucleic acids and endosomal pattern recognition: how to tell friend from foe?
Eva Brencicova,Sandra S. Diebold
Frontiers in Cellular and Infection Microbiology , 2013, DOI: 10.3389/fcimb.2013.00037
Abstract: The innate immune system has evolved endosomal and cytoplasmic receptors for the detection of viral nucleic acids as sensors for virus infection. Some of these pattern recognition receptors (PRR) detect features of viral nucleic acids that are not found in the host such as long stretches of double-stranded RNA (dsRNA) and uncapped single-stranded RNA (ssRNA) in case of Toll-like receptor (TLR) 3 and RIG-I, respectively. In contrast, TLR7/8 and TLR9 are unable to distinguish between viral and self-nucleic acids on the grounds of distinct molecular patterns. The ability of these endosomal TLR to act as PRR for viral nucleic acids seems to rely solely on the mode of access to the endolysosomal compartment in which recognition takes place. The current dogma states that self-nucleic acids do not enter the TLR-sensing compartment under normal physiological conditions. However, it is still poorly understood how dendritic cells (DC) evade activation by self-nucleic acids, in particular with regard to specific DC subsets, which are specialized in taking up material from dying cells for cross-presentation of cell-associated antigens. In this review we discuss the current understanding of how the immune system distinguishes between foreign and self-nucleic acids and point out some of the key aspects that still require further research and clarification.
Electron-phonon interaction effects on the direct gap transitions of nanoscale Si films
Vimal K Kamineni,Alain C Diebold
Physics , 2011, DOI: 10.1063/1.3650470
Abstract: This study shows that the dielectric function of crystalline Si quantum wells (c-Si QW) is influenced by both carrier confinement and electron-phonon interactions. The energy shifts and lifetime broadening of the excitonic E1 direct gap transition of c-Si QWs from 2 to 10 nm are found to have a significant dimensional and temperature dependence that can be traced to changes in the phonon dispersion of nanoscale films. The influence of electron-phonon interactions on the dielectric function was verified by altering the phonon dispersion using different dielectric layers above a 5 nm c-Si QW.
Tailoring the nature and strength of electron-phonon interactions in the SrTiO$_3$(001) two-dimensional electron liquid
Z. Wang,S. McKeown Walker,A. Tamai,Z. Ristic,F. Y. Bruno,A. de la Torre,S. Riccò,N. C. Plumb,M. Shi,P. Hlawenka,J. Sánchez-Barriga,A. Varykhalov,T. K. Kim,M. Hoesch,P. D. C. King,W. Meevasana,U. Diebold,J. Mesot,M. Radovic,F. Baumberger
Physics , 2015,
Abstract: Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO$_3$(001) surface to reveal a remarkably complex evolution of electron-phonon coupling with the tunable carrier density of this system. At low density, where superconductivity is found in the analogous 2DEL at the LaAlO$_3$/SrTiO$_3$ interface, our angle-resolved photoemission data show replica bands separated by 100\,meV from the main bands. This is a hallmark of a coherent polaronic liquid and implies strong long-range coupling to a single longitudinal optical phonon mode. In the overdoped regime the preferential coupling to this mode decreases and the 2DEL undergoes a crossover to a more conventional metallic state with weaker short-range electron-phonon interaction. These results place constraints on the theoretical description of superconductivity and allow for a unified understanding of the transport properties in SrTiO$_3$-based 2DELs.
Intoxication volontaire fatale à la metformine Fatal intoxication from metformin
Tournoud Christine,Diebold Lara,Kara Fady,Moulsma Mustapha
Annales de Toxicologie Analytique , 2012, DOI: 10.1051/ata/2011135
Abstract:
Observation and destruction of an elusive adsorbate with STM: O$_2$/TiO$_2$
Philipp Scheiber,Alexander Riss,Michael Schmid,Peter Varga,Ulrike Diebold
Physics , 2010, DOI: 10.1103/PhysRevLett.105.216101
Abstract: When a slightly defective rutile TiO$_2$(110) surface is exposed to O$_2$ at elevated temperatures, the molecule dissociates at defects, filling O vacancies (\ov) and creating O adatoms (\oad) on {\tifc} rows. The adsorption of molecular O$_2$ at low temperatures has remained controversial. Low-Temperature Scanning Tunneling Microscopy (LT-STM) of O$_2$, dosed on TiO$_2$(110) at a sample temperature of $\approx$ 100 K and imaged at 17 K, shows a molecular precursor at \ov as a faint change in contrast. The adsorbed O$_2$ easily dissociates during the STM measurements, and formation of \oad's at both sides of the original \ov is observed.
Coexistence of trapped and free excess electrons in SrTiO3
Xianfeng Hao,Zhiming Wang,Michael Schmid,Ulrike Diebold,Cesare Franchini
Physics , 2014, DOI: 10.1103/PhysRevB.91.085204
Abstract: The question whether excess electrons in SrTiO3 form free or trapped carriers is a crucial aspect for the electronic properties of this important material. This fundamental ambiguity prevents a consistent interpretation of the puzzling experimental situation, where results support one or the other scenario depending on the type of experiment that is conducted. Using density functional theory corrected with an on-site Coulomb interaction U, it is established that excess electrons form small polarons if the electron density is higher than ~ 1%. For densities below this critical value, the electrons stay delocalized or become large polarons. Our modeling of oxygen deficient SrTiO3 provides an alternative picture with respect to previous theoretical studies endowing firm evidence for the observed, temperature-driven metal-insulator transition in samples with homogeneously distributed oxygen vacancies. Small polarons confined to Ti(3+) sites are immobile at low temperature but can be thermally activated into a conductive state.
FlashCam: a fully-digital camera for the medium-sized telescopes of the Cherenkov Telescope Array
G. Pühlhofer,C. Bauer,S. Bernhard,M. Capasso,S. Diebold,F. Eisenkolb,D. Florin,C. F？hr,S. Funk,A. Gadola,F. Garrecht,G. Hermann,I. Jung,O. Kalekin,C. Kalkuhl,J. Kasperek,T. Kihm,R. Lahmann,A. Manalaysay,A. Marszalek,M. Pfeifer,P. J. Rajda,O. Reimer,A. Santangelo,T. Schanz,T. Schwab,S. Steiner,U. Straumann,C. Tenzer,A. Vollhardt,Q. Weitzel,F. Werner,D. Wolf,K. Zietara,for the CTA consortium
Physics , 2015,
Abstract: The FlashCam group is currently preparing photomultiplier-tube based cameras proposed for the medium-sized telescopes (MST) of the Cherenkov Telescope Array (CTA). The cameras are designed around the FlashCam readout concept which is the first fully-digital readout system for Cherenkov cameras, based on commercial FADCs and FPGAs as key components for the front-end electronics modules and a high performance camera server as back-end. This contribution describes the progress of the full-scale FlashCam camera prototype currently under construction, as well as performance results also obtained with earlier demonstrator setups. Plans towards the production and implementation of FlashCams on site are also briefly presented.
Ordered Array of Single Adatoms with Remarkable Thermal Stability: Au/Fe3O4(001)
Zbyněk Novotny,Giacomo Argentero,Zhiming Wang,Michael Schmid,Ulrike Diebold,Gareth S. Parkinson
Physics , 2012, DOI: 10.1103/PhysRevLett.108.216103
Abstract: Gold deposited on the Fe$_3$O$_4$(001) surface at room temperature was studied using Scanning Tunneling Microscopy (STM) and X-ray photoelectron spectroscopy (XPS). This surface forms a ($\sqrt2 \times \sqrt2$)R45$^{\circ}$ reconstruction, where pairs of Fe and neighboring O ions are slightly displaced laterally producing undulating rows with `narrow' and `wide' hollow sites. At low coverages, single Au adatoms adsorb exclusively at the narrow sites, with no significant sintering up to annealing temperatures of 400 $^{\circ}$C. We propose the strong site preference to be related to charge and orbital ordering within the first subsurface layer of Fe$_3$O$_4$(001)-($\sqrt2 \times \sqrt2$)R45$^{\circ}$. Due to its high thermal stability, this could prove an ideal model system for probing the chemical reactivity of single atomic species.
Ordered Array of Single Au Adatoms with Remarkable Thermal Stability: Au/Fe3O4(001)
Zbyněk Novotny,Giacomo Argentero,Zhiming Wang,Michael Schmid,Ulrike Diebold,Gareth S. Parkinson
Physics , 2012, DOI: 10.1103/PhysRevLett.108.216103
Abstract: We present a Scanning Tunneling Microscopy (STM) investigation of gold deposited at the magnetite Fe3O4(001) surface at room temperature. This surface forms a reconstruction with (\surd2\times\surd2)R45{\deg} symmetry, where pairs of Fe and neighboring O ions are slightly displaced laterally, forming undulating rows with 'narrow' and 'wide' adsorption sites. At fractional monolayer coverages, single Au adatoms adsorb exclusively at the narrow sites, with no significant sintering up to annealing temperatures of 400 {\deg}C. The strong preference for this site is possibly related to charge and orbital ordering within the first subsurface layer of the reconstructed Fe3O4(001) surface. Because of their high thermal stability, the ordered Au atoms at Fe3O4(001)- (\surd2\times\surd2)R45{\deg} could provide useful for probing the chemical reactivity of single atomic species.
Soft Proton Scattering Efficiency Measurements on X-Ray Mirror Shells
S. Diebold,C. Tenzer,E. Perinati,A. Santangelo,M. Freyberg,P. Friedrich,J. Jochum
Physics , 2015, DOI: 10.1007/s10686-015-9451-4
Abstract: In-orbit experience has shown that soft protons are funneled more efficiently through focusing Wolter-type optics of X-ray observatories than simulations predicted. These protons can degrade the performance of solid-state X-ray detectors and contribute to the instrumental background. Since laboratory measurements of the scattering process are rare, an experiment for grazing angles has been set up at the accelerator facility of the University of T\"ubingen. Systematic measurements at incidence angles ranging from 0.3{\deg} to 1.2{\deg} with proton energies around 250 keV, 500 keV, and 1 MeV have been carried out. Parts of spare mirror shells of the eROSITA (extended ROentgen Survey with an Imaging Telescope Array) instrument have been used as scattering targets. This publication comprises a detailed description of the setup, the calibration and normalization methods, and the scattering efficiency and energy loss results. A comparison of the results with a theoretical scattering description and with simulations is included as well.
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