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A recent paper by Tewari and Yadav on the dielectric function at low electronic densities is discussed. 相似文献
204.
S. Roman A.K. Basak J.B.A. England J.M. Nelson N.E. Sanderson F.D. Santos A.M. Eiró 《Nuclear Physics A》1977,289(2):269-274
The tensor analysing power of the 27Al(d, 3He)26Mg reaction has been measured at Ed = 12.4 MeV. The results are reproduced by predictions of the DWBA including D-state components in the 3He wave function. The magnitude of the tensor analysing power provides information on the asymptotic D-state to S-state ratio in the 3He wave function. The value obtained for 3He is in agreement with the corresponding value for 3H. 相似文献
205.
Statistical properties of resonance fluorescence of a three-level atom, interacting with a monochromatic, strong laser field are examined. Analytical formulas, describing first- and second-order correlation functions are presented. The effect of antibunching is predicted and the nontrivial difference between the statistical properties of differently polarized fluorescence is discussed. 相似文献
206.
Constituents of Osmanthus Absolute, Ist communication:2,5-Epoxy-megastigma-6,8-dienes Besides some further ionone derivatives we identified two new bicyclic oxacompounds ( 1a / 1b ) of the megastigmane type in the Osmanthus absolute. Isolation, special features of their spectral datas and synthesis starting from ethyl α-safranate are described. The synthetic pathway choosen allowed the additional identification of four substances occurring in the same natural substrate, because some synthetic by-products formed int he reaction sequence exhibited corresponding spectra and GLC. retention as the hitherto unknown components of the Osmanthus absolute. 相似文献
207.
Boundary conditions and perturbation theory are combined to create a set of equations which, when solved, yield the reflected and transmitted wave forms in the case of a thin layer of material that is perfectly bonded between two isotropic half-spaces. The set of perturbed boundary conditions is created by first using the fully bonded boundary conditions at each of the two interfaces between the thin layer and the half-spaces. Then, by restricting the layer's thickness to be much smaller than an acoustic wavelength, perturbation theory can be used on these two sets of boundary equations, producing a set of equations which effectively treat the thin layer as a single interface via a perturbation term. With this set of equations, the full range of incident and polar angles can be considered, with results general enough to use with a layer that is anisotropic, nonlinear, or both anisotropic and nonlinear. Finally the validity of these equations is discussed, comparing the computer simulation results of this theory to results from standard methods, and looking at cases where the results (or various properties of the results) are known or can be predicted. 相似文献
208.
We present a stable regime of asymmetric bound states for spiral pairs in a generic numerical model of a homogeneous excitable medium. In this regime, one spiral tip (slave) rotates around the other (master). Master-slave dynamics occur for both same-chirality and opposite-chirality spiral pairs in a range of parameters and initial conditions. We study the dependency of master-slave characteristics on the medium's excitation threshold and present a phenomenological model that accounts for the qualitative properties of master-slave dynamics. 相似文献
209.
We study the asymptotic behavior of scroll wave turbulence in large three-dimensional excitable media modeled by FitzHugh-Nagumo equations. The focus is on the type of turbulence caused by negative tension of scroll wave filaments, which is considered to be one of the mechanisms of cardiac fibrillation. We discovered that the initial increase in turbulence complexity can be followed by intermittent self-organization, when complex filament tangles are replaced by a small number of relatively stable triple filament strands. The intermittency is the result of a competition between the destabilizing effect of negative tension and mutual attraction of filaments with similar orientation. 相似文献
210.
Kosinsky YA Volynsky PE Lagant P Vergoten G Suzuki E Arseniev AS Efremov RG 《Journal of computational chemistry》2004,25(11):1313-1321
Phosphorylation of histidine-containing proteins is a key step in the mechanism of many phosphate transfer enzymes (kinases, phosphatases) and is the first stage in a wide variety of signal transduction cascades in bacteria, yeast, higher plants, and mammals. Studies of structural and dynamical aspects of such enzymes in the phosphorylated intermediate states are important for understanding the intimate molecular mechanisms of their functioning. Such information may be obtained via molecular dynamics and/or docking simulations, but in this case appropriate force field parameters for phosphohistidine should be explicitly defined. In the present article we describe development of the GROMOS96 force field parameters for phosphoimidazole molecule--a realistic model of the phosphohistidine side chain. The parameterization is based on the results of ab initio quantum chemical calculations with subsequent refinement and testing using molecular mechanics and molecular dynamics simulations. The set of force constants and equilibrium geometry is employed to derive force field for the phosphohistidine moiety. Resulting parameters and topology are incorporated into the molecular modeling package GROMACS and used in molecular dynamics simulations of a phosphohistidine-containing protein in explicit solvent. 相似文献