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71.
72.
Organometallic compounds of general formula (RAsO)α are associated as trimers (R = C2H5, C3H7, C4H9) or even as a tetramer (R = CH3). Their physicochemical properties show them to be cyclic, the oxygen atoms being located in the bridging position. A “limited” electron delocalization may occur in these rings. 相似文献
73.
74.
Marcel Brelot 《Journal d'Analyse Mathématique》1960,8(1):273-288
Sans résumé
Ces recherches ont fait l'objet d'exposés, d'abord au Séminaire de théorie du potential (Paris, javier 1960). 相似文献
75.
Quantum systems with quadratic Hamiltonians are considered. Some results about the time evolution of homogeneous polynomials and of quantum correlation functions are given. The image of arbitrary orbit of Weyl–Heisenberg group under this time evolution is shown to be again an orbit of this group. For quantum free particle it is shown that its time evolution intersects arbitrary such orbit at most once. A result about existence of more orbits having the same dispersion of some quantum position is presented.PACS: 02.20.Qs, 02.30.Sa 相似文献
76.
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
77.
We present a single curve that describes the decay in average growth velocity for microtubules in response to a mechanical force. Curves obtained at two new and one previously studied tubulin concentrations coalesce when normalized with the growth velocity at zero load. This scaling provides direct evidence for a force-independent molecular off rate, in agreement with Brownian ratchet models. In addition, microtubule length changes were measured with a precision up to 10 nm, revealing that microtubules under load abruptly switch between different growth velocities. 相似文献
78.
The facile and efficient conversion of a tert-butyl protecting group to an acetyl protecting group for thiols by catalytic amounts of bromine in acetyl chloride and the presence of acetic acid has been developed. The fairly mild reaction conditions are of particular interest for new protecting group strategies for sulfur functionalised target structures. 相似文献
79.
Summary. We prove that a standard second order finite difference uniform space discretization of the semilinear wave equation with periodic boundary conditions, analytic nonlinearity, and analytic initial data conserves momentum up to an error which is exponentially small in the stepsize. Our estimates are valid for as long as the trajectories of the full semilinear wave equation remain real analytic. The method of proof is that of backward error analysis, whereby we construct a modified equation which is itself Lagrangian and translation invariant, and therefore also conserves momentum. This modified equation interpolates the semidiscrete system for all time, and we prove that it remains exponentially close to the trigonometric interpolation of the semidiscrete system. These properties directly imply approximate momentum conservation for the semidiscrete system. We also consider discretizations that are not variational as well as discretizations on non-uniform grids. Through numerical example as well as arguments from geometric mechanics and perturbation theory we show that such methods generically do not approximately preserve momentum.Mathematics Subject Classification (2000): 65M20, 58J70, 70H33 相似文献
80.
Marcel?DreefEmail author Peter?Borm Ben van der?Genugten 《Mathematical Methods of Operations Research》2004,59(3):375-391
An aspect of casino games that in general leads to discussions among both participants and spectators, is the relative extent to which a player can positively influence his results by making appropriate strategic choices. This question is closely related to the issue of how to distinguish between games of skill and games of chance. This is an issue that is interesting from a juridical point of view too, since in many countries the legitimacy of exploiting a specific game depends on the category to which it belongs. This paper summarizes recent developments concerning the measurement of skill in games. It points out the elements in the definitions that need closer attention, it illustrates the analysis with examples and it discusses further possibilities. 相似文献