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81.
Specific heat measurements on TmxY1?xAl2 have been performed to determine the crystalline electric field parameters in TmxY1?xAl2. We find for the ground state the Γ(1)5 triplet and for the Lea, Leask and Wolf parameters X = (0.47 ± 0.03) and W = (0.034 ± 0.013) meV. 相似文献
82.
Highlights? Recycling of genetic material is important for the origins of life ? Simulation studies show recycling leads to the selection of genotypes from a pool ? Recycling can lead to the sudden emergence of a high-fitness RNA genotype ? Experimental studies with the Azoarcus ribozyme show fragment recycling 相似文献
83.
Abstract In the Corey1 synthesis of prostaglandins and in our recently published modifications2,3 a synthon containing carbon atoms 14 to 20θ is first added to a bicyclic intermediate (C-6 to C-13) and completion of the prostaglandin skeleton by addition of a second synthon containing carbon atoms 1 to 5 forms a subsequent step. In a modification4,5 of the Corey synthesis1 PGF1α and PGE1 were made by reversing the order in which these two synthons were added to the cyclopentane ring (C-6 to C-13). The major limitation of this modified route4,5 is that it is restricted to the preparation of prostaglandins of the 1-series,? because hydrogenolysis of the benzyl group of the intermediate ester (1) reduces the C-5, C-6 double bond to form the saturated alcohol (2), which cannot be converted into prostaglandins of the 2-series?. 相似文献
84.
D. Greig M. J. Hall C. Hammond B. J. Hickey H. P. Ho M. A. Howson M. J. Walker N. Wiser D. G. Wright 《Journal of magnetism and magnetic materials》1992,110(3):L239-L246
We report the first observation of a giant magnetoresistance (MR) in Co/Cu superlattices grown by MBE. The maximum value of the MR is - 26% and this is found in a specimen for which the copper layers are about 7 Å thick and which includes a thin 10 Å layer of gold in the buffer region between the substrate and the superlattice. From RHEED and X-ray diffraction it is shown that the metallic layers in the specimens grown in this way are extremely flat and that the orientation of the copper is (111). 相似文献
85.
Spin relaxation resonances due to the spin-axis interaction in dense rubidium and cesium vapor 总被引:2,自引:0,他引:2
Erickson CJ Levron D Happer W Kadlecek S Chann B Anderson LW Walker TG 《Physical review letters》2000,85(20):4237-4240
Resonances in the magnetic decoupling curves for the spin relaxation of dense alkali-metal vapors prove that much of the relaxation is due to the spin-axis interaction in triplet dimers. Initial estimates of the spin-axis coupling coefficients for the dimers (likely accurate to a factor of 2) are |lambda|/h = 290 MHz for Rb; 2500 MHz for Cs. 相似文献
86.
87.
R. Atkinson W.R. Hendren I.W. Salter M.J. Walker 《Journal of magnetism and magnetic materials》1994,130(1-3):442-450
The optical and magneto-optical properties of Co/Au multilayers, grown by molecular beam epitaxy (MBE), have been examined in the wavelength range 300 to 900 nm using ellipsometry and normal incidence Kerr polarimetry. The dispersion of fundamental optical and magneto-optical constants and the complex Kerr rotation are discussed in terms of the interaction of electromagnetic radiation with a multilayered structure. This is done on the basis of a single equivalent layer approach for dealing with multilayered media using values for the optical constants of cobalt and gold measured on single films of these materials grown by MBE. It is suggested that a restriction of the mean free path of the conduction electrons in the gold layers, of the order of the individual sub-layer thickness, accounts for some aspects of the observed optical spectra. 相似文献
88.
Dejian Fu Keeyoon Sung Chris D. Boone Kaley A. Walker Peter F. Bernath 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(12-13):2219-2243
Carbon cycle science by Fourier transform spectroscopy (CC-FTS) is an advanced study for a future satellite mission. The goal of the mission is to obtain a better understanding of the carbon cycle in the Earth's atmosphere by monitoring total and partial columns of CO2, CH4, N2O, and CO in the near infrared. CO2, CH4, and N2O are important greenhouse gases, and CO is produced by incomplete combustion. The molecular O2 column is also needed to obtain the effective optical path of the reflected sunlight and is used to normalize the column densities of the other gases. As part of this advanced study, ground-based Fourier transform spectra are used to evaluate the spectral region and resolution needed. Spectra in the 3950–7140 cm?1 region with a spectral resolution of 0.0042 cm?1 recorded at Kiruna (67.84°N, 20.41°E, and 419 m above sea level), Sweden, on 1 April 1998, were degraded to the resolutions of 0.01, 0.1, and 0.3 cm?1. The effect of spectral resolution on the retrievals has been investigated with these four Kiruna spectra. To obtain further information on the spectral resolution, optical components and spectroscopic parameters required by the future mission, high-resolution solar absorption spectra between 2000 and 15000 cm?1 were recorded using Fourier transform spectrometers at Kitt Peak (31.9°N, 111.6°W, and 2.1 km above sea level), Arizona, on 25 July 2005 and Waterloo (43.5°N, 80.6°W, and 0.3 km above sea level), Ontario, on 22 November 2006 with spectral resolutions of 0.01 and 0.1 cm?1, respectively. Dry air volume mixing ratios (VMRs) of CO2 and CH4 were retrieved from these ground-based observations. The HITRAN 2004 spectroscopic parameters are used with the SFIT2 package for the spectral analysis. The measurement precisions for CO2 and CH4 total columns are better than 1.07% and 1.13%, respectively, for our observations. Based on these results, a Fourier transform spectrometer (maximum spectral resolution of 0.1 cm?1 or 5 cm maximum optical path difference (MOPD)) operating between 2000 and 15000 cm?1 is suggested as the primary instrument for the mission. Further progress in improving the atmospheric retrievals for CO2, CH4, and O2 requires new laboratory measurements of the spectroscopic line parameters. 相似文献
89.
A preliminary LEED theory experiment comparison for the InP(110) surface has been performed using experimental I(V) data recorded in the authors' laboratory from a clean, UHV-cleaved, single crystal specimen. A range of model surface geometries including both lateral and vertical displacements of the top layer In and P atoms have been examined. The results clearly demonstrate that the structure of this surface is substantially different from a simple termination of the bulk lattice and that the disturbance extends more than one layer into the real crystal. The possibility of extending the analysis to include second layer distortions is considered. 相似文献
90.
M. Leins J. Kopecki S. Gaiser A. Schulz M. Walker U. Schumacher U. Stroth T. Hirth 《等离子体物理论文集》2014,54(1):14-26
Microwave plasmas at atmospheric pressure are used for surface treatments like for example cleaning, sterilization or decontamination purposes, for a pre‐treatment to increase the adhesion of lacquer, paint, or glue, and for the deposition of different kind of layers and coatings. Micro plasma jets can also be applied for biomedical applications and for treatment of small and complex geometries like for example the inside of capillaries. Larger plasma torches which exhibit higher gas temperatures can also be used for chemical syntheses like waste gas decomposition, methane pyrolysis, or carbon dioxide dissociation and for plasma spraying purposes. In the present publication an overview on the development and the investigation of the operating principle of two atmospheric pressure microwave plasma torches at frequencies of 2.45 GHz and 915 MHz will be presented. The plasma sources are based on a cylindrical resonator combined with coaxial structures. To explain how these plasma sources work, simulations of the electric field distribution will be discussed. Furthermore, some physical characteristics of an air and an Ar/H2 atmospheric plasma like gas temperatures, excitation temperatures and densities as well as the heating of the plasma by the microwave will be investigated. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献