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F. W. Froben I. Rabin M. Ritz W. Schulze 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1996,38(4):335-338
Silver clusters Agn prepared either by the gas aggregation technique (GAT) or by matrix aggregation of Ag were embedded in CO and CO/Ar-matrices. The vibrational CO stretch frequency at the monolayer coverage, which is found on bulk silver at 2110 cm-1, preserves its value with decreasing particle size, Agn n≥300. For smaller clusters a decrease of this frequency with decreasing size was observed. For the smallest investigated clusters Agn, n~30, a value of 2080 cm-1 was obtained. The weakening of the CO bond is an indication of a charge transfer from the cluster to the CO monolayer. This result is in accordance with the surface plasmon absorption measurements of Ag-clusters isolated in CO matrices. 相似文献
35.
Herbert Rabin 《辐射效应与固体损伤》2013,168(1):167-172
Abstract The condition for the generation of second harmonics in the dipole approximation is that the nonlinear crystal medium lack a center of inversion. Conversely, a center of inversion precludes optical second harmonic generation. It is well known, however, that lattice defects introduced into a crystal may alter the local point symmetry in the medium, and in fact may convert local inversion symmetry to that which corresponds to a noncentrosymmetric point group. It is thus clear that selected defects in nonlinear media may be of interest for studying nonlinear optical processes which depend on the square of the electric field strength. The specific case of second harmonic generation employing spatially ordered FA-centers in alkali halide crystals is considered. 相似文献
36.
We present a theoretical study of binding of DNA-bending proteins to circular DNA, using computer simulations of the wormlike chain model of DNA. We find that the binding affinity is affected by the bending elasticity and the conformational entropy of the polymer and that while protein adsorption is identical on open and closed long DNA molecules, there is significant enhancement of binding on DNA minicircles, compared to their linear counterparts. We also find that the ratio of the radii of gyration of open and closed chains depends on protein concentration for short DNA molecules. Experimental tests of our predictions are proposed. 相似文献
37.
Dietz G Ketelsen T Hoss M Simon O Wintermann C Wolff T Rabin I Hahn O 《Analytical and bioanalytical chemistry》2012,402(4):1505-1515
The aim of the research project “Typology of Dutch Drawing” was to establish an interdisciplinary approach for investigating
heterogeneous drawing collections. To define a type common to a group of drawings, we determine elements that are common to
them based on style and the use of identical materials. To that end, we investigated about 750 Dutch drawings from the sixteenth
century at the Dresden Kupferstich-Kabinett using art historical and scientific methods. In this work, we present a detailed
analysis of 30 drawings ascribed to the Egmont Master. 相似文献
38.
A. S. Hoover M. K. Bacrania N. J. Hoteling P. J. Karpius M. W. Rabin C. R. Rudy D. T. Vo J. A. Beall D. A. Bennett W. B. Doriese G. C. Hilton R. D. Horansky K. D. Irwin J. N. Ullom L. R. Vale 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(1):227-232
Microcalorimeter detectors provide superior energy resolution for the detection of X-rays and gamma-rays. The technology utilizes a cryogenic transition-edge sensor (TES) coupled to a tin bulk absorber. We are working on fabrication methods for the production of arrays with many sensors. In this paper, we present data collected with an array of microcalorimeters using as many as 26 sensor elements simultaneously. Advances in sensor design have extended the useful dynamic range to photon energies up to ~200 keV, while providing resolution performance in the 80–90 eV FWHM range, significantly better than planar high-purity germanium. These sensor arrays have applications in the measurement of nuclear materials. We present data collected from 153Gd, a highly-enriched uranium sample, and a plutonium isotopic standard source. We also demonstrate clean separation of the 235U 185.715 keV peak from the ubiquitous 226Ra 186.211 keV background peak interference. 相似文献
39.
The first microwave assisted Wittig reactions of β-chloroacroleins with a stabilized ylide are described here. A combination of sodium ethoxide and toluene was found to be optimum and using this reaction condition a number of alkenyl-substituted benzopyran/benzo[b]oxepine/2-chromenone derivatives were prepared within few minutes. The microwave mediated process was found to be comparable with the conventional Wittig reaction in terms of product yields. All the products isolated were found to have E-geometry around the CC bond. 相似文献
40.
The low strain-rate viscosity of glass-forming cryoprotective agents (CPAs) in the vicinity of the glass transition is studied
experimentally. Data on the mechanical behavior in this regime is necessary to the long-term goal of developing planning tools
for cryopreservation via vitrification (vitreous means glassy in Latin); such tools will provide guidelines for reducing thermal
stress with its devastating effects. While the flow behavior of some glass-forming CPAs is well documented in the literature
for the upper part of the cryogenic temperature range (where the CPA has a comparatively low viscosity), it is the flow behavior
near the glass transition temperature (where the CPA behaves as nearly a solid with an extremely high viscosity) which is
critical to the analysis of stress that develops in the cryopreserved material. If the elevated viscosity limits the material’s
ability to flow—in order to accommodate the thermal strain resulting from large temperature gradients, especially at the high
cooling rates necessary to form glass—structural damage may follow. Information on the behavior of the CPA in the lower part
of the cryogenic temperature range is largely unavailable. A new measurement device is presented in this study, in which a
solid rod is pulled from a long narrow cup containing a CPA, producing an essentially one-dimensional and isothermal field
of flow. The viscosity and relaxation time of the CPA is inferred from measurements of the resulting load on the rod when
extracted at a constant velocity. The current study reports on experimental data near glass transition of 7.05 M DMSO, a reference
CPA solution, and the CPA cocktails VS55 and DP6. 相似文献