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排序方式: 共有443条查询结果,搜索用时 343 毫秒
91.
M. Naftaly A. P. Foulds R. E. Miles A. G. Davies 《International Journal of Infrared and Millimeter Waves》2005,26(1):55-64
Terahertz time-domain spectroscopy is used to study properties of non-polar materials. Terahertz absorption spectra and refractive indices are measured in a number of glasses, lubricating oils, and types of paper. The results are correlated with material properties. 相似文献
92.
Attenuation of ultrasound in post rigor bovine skeletal muscle 总被引:4,自引:0,他引:4
A pulse transmission method for measuring the attenuation of 1-7 MHz ultrasound in bovine skeletal muscle is described. Measurements of the attenuation coefficient at -20, 0, 20 and 40 degrees C conformed to the relation alpha = Afn, where A and n are temperature-dependent coefficients and f is the frequency. alpha/f varied slowly with frequency, and at 4 MHz and 20 degrees C mean values were 1.3 dB cm-1 MHz-1 along the fibres and 0.55 dB cm-1 MHz-1 across the fibres. These data are lower than most previous measurements of skeletal muscle, but comparable with recent measurements of canine heart muscle. 相似文献
93.
94.
Rayleigh and Raman scattering have not been widely used for flow field and combustion imaging because of their very low scattering cross-sections and because of interference from strong background light. With the use of sharp cut-off, atomic and molecular filters this background can be rejected while high throughput is maintained. The sharp cut-off edge of the filters provides for the possibility of using them for high-resolution spectral discrimination. Consequently, Rayleigh and Raman imaging are now becoming feasible and have the promise of providing quantitative images of temperature, velocity, pressure, density, species, and nonequilibrium phenomena. Because Rayleigh and Raman scattering arise from all molecules and are not affected by quenching, quantitative images can be taken of all dominant molecular species as well as thermodynamic and transport properties of complex flows, weakly ionized plasmas, and combusting fields. 相似文献
95.
M. van Kooten S. de Haan J.C. Lodder A. Lyberatos R.W. Chantrell J.J. Miles 《Journal of magnetism and magnetic materials》1993,120(1-3):145-148
Micromagnetic simulations of the magnetization reversal of clusters of 9 and 25 magnetostatically coupled Co-Cr particles are presented. The magnetostatic interaction between neighbouring particles facilitates reversal. The non-uniform magnetization configuration plays an important role in this effect. 相似文献
96.
A. K. Dinnis B. K. Middleton J. J. Miles 《Journal of magnetism and magnetic materials》1993,120(1-3):149-153
A theory of the digital magnetic recording process has been produced which facilitates the prediction of the recording properties of thick particulate and other media. It allows studies to be made of recorded patterns through the depths of media and the influence of these on overall recording properties. The theory is capable of dealing with particulate, thin-film and multilayer media. 相似文献
97.
John Miles 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1985,36(4):609-615
Summary The free oscillations of a slightly detuned spherical pendulum, for which the difference between the natural frequencies in two transverse planes of symmetry is small, are determined by retaining fourth-order (in the angular displacement), but neglecting sixth-order, terms in the Lagrangian, positing slowly modulated sinusoids for the displacements, and integrating the resulting Hamiltonian system.
Zusammenfassung Es werden die kleinen Schwingungen eines schwach verstimmten sphärischen Pendels untersucht, für den die Frequenzdifferenz in zwei Symmetrie-Ebenen klein ist. Die Lagrange-Funktion wird unter Berücksichtigung von Termen vierter Ordnung (mit Vernachlässigung der sechsten Ordnung) in den Winkeln berechnet. Langsame periodische Variation der Variabeln wird angesetzt, und das so erhaltene Hamilton'sche System wird integriert.相似文献
98.
Enantioselective Synthesis of N,S‐Acetals by an Oxidative Pummerer‐Type Transformation using Phase‐Transfer Catalysis
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Dr. Souvagya Biswas Dr. Koji Kubota Dr. Manuel Orlandi Mathias Turberg Dr. Dillon H. Miles Prof. Dr. Matthew S. Sigman Prof. Dr. F. Dean Toste 《Angewandte Chemie (International ed. in English)》2018,57(2):589-593
Reported is the first enantioselective oxidative Pummerer‐type transformation using phase‐transfer catalysis to deliver enantioenriched sulfur‐bearing heterocycles. This reaction includes the direct oxidation of sulfides to a thionium intermediate, followed by an asymmetric intramolecular nucleophilic addition to form chiral cyclic N,S‐acetals with moderate to high enantioselectivites. Deuterium‐labelling experiments were performed to identify the stereodiscrimination step of this process. Further analysis of the reaction transition states, by means of multidimensional correlations and DFT calculations, highlight the existence of a set of weak noncovalent interactions between the catalyst and substrate that govern the enantioselectivity of the reaction. 相似文献
99.
Melanie A. Short J. Miles Blackburn Prof. Dr. Jennifer L. Roizen 《Angewandte Chemie (International ed. in English)》2018,57(1):296-299
Masked alcohols are particularly appealing as directing groups because of the ubiquity of hydroxy groups in organic small molecules. Herein, we disclose a general strategy for aliphatic γ‐C(sp3)?H functionalization guided by a masked alcohol. Specifically, we determine that sulfamate ester derived nitrogen‐centered radicals mediate 1,6‐hydrogen‐atom transfer (HAT) processes to guide γ‐C(sp3)?H chlorination. This reaction proceeds through a light‐initiated radical chain‐propagation process and is capable of installing chlorine atoms at primary, secondary, and tertiary centers. 相似文献
100.
Chaykovski MM Bae LC Cheng MC Murray JH Tortolani KE Zhang R Seshadri K Findlay JH Hsieh SY Kalverda AP Homans SW Brown JM 《Journal of the American Chemical Society》2003,125(51):15767-15771
13C relaxation studies on side-chain methyl groups in proteins typically involve measurements on (13)CHD(2) isotopomers, where the (13)C relaxation mechanism is particularly straightforward in the presence of a single proton. While such isotopomers can be obtained in proteins overexpressed in bacteria by use of (13)C enriched and fractionally deuterated media, invariably all possible (2)H isotopomers are obtained. This results in a loss of both resolution and sensitivity, which becomes particularly severe for larger proteins. We describe an approach that overcomes this problem by chemical synthesis of amino acids containing a pure (13)CHD(2) isotopomer. We illustrate the benefits of this approach in (13)C side-chain relaxation measurements on the mouse major urinary protein selectively enriched with [gamma(1),gamma(2)-(13)C(2),alpha,beta,gamma(1),gamma(1),gamma(2),gamma(2)-(2)H(6)] valine. Relaxation measurements in the absence and presence of pyrazine-derived ligands suggest that valine side-chain dynamics do not contribute significantly to binding entropy. 相似文献