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151.
Let R(t)=P(t)/Q(t) be a quotient of real polynomials. We show that ∫exp(iR(t)) dt/t has a uniform bound with a bound depending only on the degrees of P and Q and not on their coefficients. Also
LP estimates are obtained for certain associated singular integral operators. 相似文献
152.
Imaginary powers of Laplace operators 总被引:1,自引:0,他引:1
We show that if is a second-order uniformly elliptic operator in divergence form on , then . We also prove that the upper bounds remain true for any operator with the finite speed propagation property.
153.
We report the development of the four wave mixing vibrational analog to 2D NMR and demonstrate its spectral selectivity, sensitivity to the interactions causing mode coupling, and ability to spectrally resolve isotopic mixtures. The method discriminates against uncoupled vibrational modes and isolates the features that are associated with intra- or intermolecular interactions. 相似文献
154.
We show that the time-dependent nonlinear Schrodinger equation of mean-field theory has limited utility for a one-dimensional condensate of impenetrable bosons. Mean-field theory with its associated order parameter predicts interference between split condensates that are recombined, whereas an exact many-body treatment shows minimal interference. 相似文献
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We develop a parallel computational algorithm for simulating models of gel dynamics where the gel is described by two phases, a networked polymer and a fluid solvent. The models consist of transport equations for the two phases, two coupled momentum equations, and a volume‐averaged incompressibility constraint. Multigrid with Vanka‐type box‐relaxation scheme is used as preconditioner for the Krylov subspace solver (GMRES) to solve the momentum and incompressibility equations. Through numerical experiments of a model problem, the efficiency, robustness and scalability of the algorithm are illustrated. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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EPR, microwave absorption, and dc magnetization measurements were made on single crystals of the form R2CuO4, which are the host compounds for the newly discovered series of electron cuprate superconductors. These measurements reveal two characteristic transition temperatures associated with a novel complex magnetic behavior, including weak ferromagnetism, two sharp peaks in the low field DC magnetization, an unusual anisotropy in the EPR resonance field for R = Gd, and two additional anisotropic microwave absorption modes. The higher characteristic transition temperature, at ≈270K, is attributed to AF ordering of the Cu moments, and the lower, at ≤20K, to a spontaneous canted spin reorientation. An understanding of this magnetic behavior is important in order to ascertain its relationship to possible mechanisms of high temperature superconductivity. 相似文献
160.
Alexander Alex Sophie Harvey Teresa Parsons Frank S. Pullen Patricia Wright Jo‐Anne Riley 《Rapid communications in mass spectrometry : RCM》2009,23(17):2619-2627
Prediction of tandem mass spectrometric (MS/MS) fragmentation for non‐peptidic molecules based on structure is of immense interest to the mass spectrometrist. If a reliable approach to MS/MS prediction could be achieved its impact within the pharmaceutical industry could be immense. Many publications have stressed that the fragmentation of a molecular ion or protonated molecule is a complex process that depends on many parameters, making prediction difficult. Commercial prediction software relies on a collection of general heuristic rules of fragmentation, which involve cleaving every bond in the structure to produce a list of ‘expected’ masses which can be compared with the experimental data. These approaches do not take into account the thermodynamic or molecular orbital effects that impact on the molecule at the point of protonation which could influence the potential sites of bond cleavage based on the structural motif. A series of compounds have been studied by examining the experimentally derived high‐resolution MS/MS data and comparing it with the in silico modelling of the neutral and protonated structures. The effect that protonation at specific sites can have on the bond lengths has also been determined. We have calculated the thermodynamically most stable protonated species and have observed how that information can help predict the cleavage site for that ion. The data have shown that this use of in silico techniques could be a possible way to predict MS/MS spectra. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献