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841.
Hoehne F Lu J Stegner AR Stutzmann M Brandt MS Rohrmüller M Schmidt WG Gerstmann U 《Physical review letters》2011,106(19):196101
We show that the electrical detection of electron-spin-echo envelope modulation (ESEEM) is a highly sensitive tool to study interfaces. Taking the Si/SiO2 interface defects in phosphorus-doped crystalline silicon as an example, we find that the main features of the observed echo modulation pattern allow us to develop a microscopic model for the dangling-bond-like P(b0) center by comparison with the results of ab initio calculations. The ESEEM spectrum is found to be far more sensitive to the defect characteristics than the spectrally resolved hyperfine splitting itself. 相似文献
842.
Andre Zavalin Junhai Yang Richard Caprioli 《Journal of the American Society for Mass Spectrometry》2013,24(7):1153-1156
We describe an easy and inexpensive way to provide a highly defined Gaussian shaped laser spot on target of 5 μm diameter for imaging mass spectrometry using a commercial MALDI TOF instrument that is designed to produce a 20 μm diameter laser beam on target at its lowest setting. A 25 μm pinhole filter on a swivel arm was installed in the laser beam optics outside the vacuum ion source chamber so it is easily flipped into or out of the beam as desired by the operator. The resulting ion images at 5 μm spatial resolution are sharp since the satellite secondary laser beam maxima have been removed by the filter. Ion images are shown to demonstrate the performance and are compared with the method of oversampling to achieve higher spatial resolution when only a larger laser beam spot on target is available. Figure
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843.
Sabine Kraml Suchita Kulkarni Ursula Laa Andre Lessa Wolfgang Magerl Doris Proschofsky-Spindler Wolfgang Waltenberger 《The European Physical Journal C - Particles and Fields》2014,74(5):1-23
We present a general procedure to decompose Beyond the Standard Model (BSM) collider signatures presenting a $\mathbb {Z}_2$ symmetry into Simplified Model Spectrum (SMS) topologies. Our method provides a way to cast BSM predictions for the LHC in a model independent framework, which can be directly confronted with the relevant experimental constraints. Our concrete implementation currently focusses on supersymmetry searches with missing energy, for which a large variety of SMS results from ATLAS and CMS are available. As show-case examples we apply our procedure to two scans of the minimal supersymmetric standard model. We discuss how the SMS limits constrain various particle masses and which regions of parameter space remain unchallenged by the current SMS interpretations of the LHC results. 相似文献
844.
845.
Leroux YR Fave C Zigah D Trippe-Allard G Lacroix JC 《Journal of the American Chemical Society》2008,130(40):13465-13470
Atomic contacts are nanoscience devices proposed for applications such as single-atom switches in nanoelectronic circuits or one-molecule sensing devices. The conductance of such contacts varies in a stepwise fashion with a tendency to quantize near integer multiples of the conductance quantum (G0) but can also deviate significantly from integer values upon molecular adsorption. However, for sensing applications it is first necessary to coat the contact permanently to avoid nonspecific adsorption. Here, we show that marked differences are observed between atomic contacts generated in water, and in water/beta-CD. In this latter medium, atomic contacts with unusual properties can be generated. They have below 1 G0 conductance, low conductance fluctuation with time, and appear to be protected or partially protected from salicylate external molecular probes. Such contacts are not obtained in water, in water/glucose, or when beta-CD is added after 1 G0 contacts have been generated in water. These results indicate specific adsorption of beta-cyclodextrin on the atomic contacts and are compatible with the formation of encapsulated atomic contacts. However, direct independent structural evidence is still needed to confirm or infirm this interpretation. 相似文献
846.
Sheo B. Singh Kithsiri Herath Nathan X. Yu Andre A. Walker Neal Connors 《Tetrahedron letters》2008,49(43):6265-6268
Nocathiacin-I is one of the newest members of thiazolyl peptide class of antibiotics. It is a potent inhibitor of bacterial protein synthesis and showed potent in vitro and in vivo Gram-positive antibacterial activity. Understanding of the biosynthesis of natural products is important for improvement of titer and precursor directed biosynthesis for new compounds. Biosynthesis of nocathiacin-I in Amycolatopsis fastidiosa using stable isotope precursor incorporation is described. 相似文献
847.
Photonic nanostructures for advanced light trapping in silicon solar cells: the impact of etching on the material electronic quality 下载免费PDF全文
Christos Trompoukis Andre Stesmans Eddy Simoen Valérie Depauw Ounsi El Daif Kidong Lee Ivan Gordon Robert Mertens Jef Poortmans 《固体物理学:研究快报》2016,10(2):158-163
Dry plasma etching, commonly used by the Photonics community as the etching technique for the fabrication of photonic nanostructures, could be a source of device performance limitations when used in the frame of silicon photovoltaics. So far, the lack of silicon solar cells with state‐of‐the‐art efficiencies utilizing nanophotonic concepts shows how challenging their integration is, owing to the trade‐off between optical and electrical properties. In this study we show that dry plasma etching results in the degradation of the silicon material quality due to (i) a high density of dangling bonds and (ii) the presence of sub‐surface defects, resulting in high surface recombination velocities and low minority carrier lifetimes. On the contrary, wet chemical anisotropic etching used as an alternative, leads to the formation of inverted nanopyramids that result in low surface recombination velocity and low density of dangling bonds. The proposed inverted nanopyramids could enable high efficiency photonic assisted solar cells by offering the potential to achieve higher short‐circuit current without degrading the open circuit voltage. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
848.
Andre Reznikov 《Journal of the American Mathematical Society》2008,21(2):439-477
We use the uniqueness of various invariant functionals on irreducible unitary representations of in order to deduce the classical Rankin-Selberg identity for the sum of Fourier coefficients of Maass cusp forms and its new anisotropic analog. We deduce from these formulas non-trivial bounds for the corresponding unipotent and spherical Fourier coefficients of Maass forms. As an application we obtain a subconvexity bound for certain -functions. Our main tool is the notion of a Gelfand pair from representation theory.
849.
Bonhomme C Gervais C Folliet N Pourpoint F Diogo CC Lao J Jallot E Lacroix J Nedelec JM Iuga D Hanna JV Smith ME Xiang Y Du J Laurencin D 《Journal of the American Chemical Society》2012,134(30):12611-12628
Strontium is an element of fundamental importance in biomedical science. Indeed, it has been demonstrated that Sr(2+) ions can promote bone growth and inhibit bone resorption. Thus, the oral administration of Sr-containing medications has been used clinically to prevent osteoporosis, and Sr-containing biomaterials have been developed for implant and tissue engineering applications. The bioavailability of strontium metal cations in the body and their kinetics of release from materials will depend on their local environment. It is thus crucial to be able to characterize, in detail, strontium environments in disordered phases such as bioactive glasses, to understand their structure and rationalize their properties. In this paper, we demonstrate that (87)Sr NMR spectroscopy can serve as a valuable tool of investigation. First, the implementation of high-sensitivity (87)Sr solid-state NMR experiments is presented using (87)Sr-labeled strontium malonate (with DFS (double field sweep), QCPMG (quadrupolar Carr-Purcell-Meiboom-Gill), and WURST (wideband, uniform rate, and smooth truncation) excitation). Then, it is shown that GIPAW DFT (gauge including projector augmented wave density functional theory) calculations can accurately compute (87)Sr NMR parameters. Last and most importantly, (87)Sr NMR is used for the study of a (Ca,Sr)-silicate bioactive glass of limited Sr content (only ~9 wt %). The spectrum is interpreted using structural models of the glass, which are generated through molecular dynamics (MD) simulations and relaxed by DFT, before performing GIPAW calculations of (87)Sr NMR parameters. Finally, changes in the (87)Sr NMR spectrum after immersion of the glass in simulated body fluid (SBF) are reported and discussed. 相似文献
850.
Multislice simulations in the transmission electron microscope (TEM) were used to examine changes in annular-dark-field scanning TEM (ADF-STEM) images, conventional bright-field TEM (BF-CTEM) images, and selected-area electron diffraction (SAED) patterns as atomically thin hexagonal boron nitride (h-BN) samples are tilted up to 500 mrad off of the [0001] zone axis. For monolayer h-BN the contrast of ADF-STEM images and SAED patterns does not change with tilt in this range, while the contrast of BF-CTEM images does change; h-BN multilayer contrast varies strongly with tilt for ADF-STEM imaging, BF-CTEM imaging, and SAED. These results indicate that tilt series analysis in ADF-STEM image mode or SAED mode should permit identification of h-BN monolayers from raw TEM data as well as from quantitative post-processing. 相似文献