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51.
We study a vector-dominance model which predicts quite a large number of currently interesting decay amplitudes of the types S-->gammagamma, V-->Sgamma, and S-->Vgamma, where S and V denote scalar and vector mesons, in terms of three parameters. As an application, the model makes it easy to study in detail a recent proposal to boost the ratio Gamma(phi-->f(0)gamma)/Gamma(phi-->a(0)(0)gamma) by including the isospin violating a(0)(0)-f(0) mixing. However, we find that this effect is actually small in our model. 相似文献
52.
R.J. Peterson S. de Barros H. Schechter S.G. Mashnik A.G. daSilva J.C. Suita 《The European Physical Journal A - Hadrons and Nuclei》2001,10(1):69-71
Cross-sections for the π+-induced fission of 209Bi and 235U have been measured in small steps across the 3-3 resonance to search for any mechanisms that might signal a change in the
reaction mechanism across a region where strong coupling of available energy into nuclear excitation can be expected. The
bismuth data are found to be in good agreement with a statistical calculation not including new mechanisms.
Received: 15 August 2000 / Accepted: 23 January 2001 相似文献
53.
54.
Guanwei Chen Martin Schechter 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2016,67(3):72
In this paper, we study a class of non-periodic discrete Schrödinger equations with superlinear non-linearities at infinity. Under conditions weaker than those previously assumed, we obtain the existence of ground state solutions, i.e., non-trivial solutions with least possible energy. In addition, an example is given to illustrate our results. 相似文献
55.
A local interaction simulation approach (LISA) for the wave propagation in inhomogeneous 2D media is presented. The method is designed to take full advantage of massively parallel computing, such as provided by the Connection Machine. Crosspoints at the intersection of orthogonal interfaces separating media of different physical properties are treated in the framework of a sharp interface model. A comparison with finite difference techniques shows that the proposed method avoids the ambiguities due to the smoothing of the physical quantities, which is necessary in order to transform differential equations into finite difference equations. The smoothing procedure may cause severe numerical errors, when the variations of the physical properties across the interfaces are large.
In order to demonstrate the efficiency and reliability of the approach several examples of simulation of pulse propagation in different media are reported. 相似文献
56.
Dr. Maurice Schechter 《Monatshefte für Mathematik》1911,22(1):224-234
Ohne Zusammenfassung 相似文献
57.
Murray Schechter 《Journal of Mathematical Analysis and Applications》1979,71(1):251-262
A duality theorem of P. Wolfe for nonlinear differential programming has been extended by the author to the non-differentiable case by replacing gradients by subgradients. In this paper this extended result is improved by allowing additional types of constraints. Also a converse duality theorem is proved. 相似文献
58.
The carbon-supported cobalt(III) complex of β-pyrrole-brominated 5,10,15-tris(pentafluorophenyl)corrole [Co(tpfc)Br(8)/C] is introduced as a nonplatinum alternative for electrocatalytic oxygen reduction in aqueous solutions. Through systematic work, the basic kinetic parameters of this reaction were studied, using rotating ring disk electrode electrochemical methods in the pH range of 0-11. Pronounced catalytic activity was detected in acid solutions along with shifts of the Co(II)/Co(III) and O(2) redox couples to more positive values (onset of 0.56 V at pH 0). A series of independent measurements have been used to prove that the dominant mechanism for oxygen reduction by Co(tpfc)Br(8)/C catalysis is the direct four-electron pathway to water. 相似文献
59.
Fourier transform-based spectroscopic imaging was used for direct, time-resolved, analysis of UV-irradiated anthracene crystallites. Well-resolved fluorescence spectra were obtained at a spatial resolution of 1 microm. The appearance of such photochemical by-products as dianthracene and anthraquinone was monitored throughout the irradiation experiments. Under deaerated conditions, photolysis of anthracene was accompanied by formation of dianthracene. When performed under aerated conditions, however, the spectral data indicated formation of both dianthracene and anthraquinone. Spectral features obtained for the directly monitored photolysis of anthracene are discussed in respect to the structural and compositional modifications in such crystallites. Capabilities of the spectral imaging device for the quantification of the photochemical products of anthracene are discussed. 相似文献
60.
The objective of this preliminary investigation of a number of water‐soluble carrier‐bound platinum(II) complexes for potential use in cancer chemotherapy was to assess the toxicological behavior of representative platinum coordination compounds anchored to, or incorporated into, polymeric carriers via polymer‐attached amine ligands. The conjugates included linear polyaspartamides (1–4, 6, 7), each composed of a major fraction of subunits featuring side‐chain‐attached tertiary amino groups as water‐solubilizing entities, and a minor fraction of subunits comprising the anchored platinum complexes, again as side‐chain components. Whereas in 1–4 the platinum atom was polymer‐bound through a single amino group, both 6 and 7 contained polymer‐attached cis‐diamine‐chelating ligands coordinating to the metal center. Also included in this study was a linear polyamidoamine (5), which contained a poly(ethylene oxide) segment in the backbone in addition to intrachain ethylenediamine segments acting as cis‐diamine chelating ligands for coordination to the platinum center. The compounds were injected as aqueous (phosphate‐buffered saline) solutions into the tail veins of CD‐1 mice (four to eight mice per conjugate), and the maximally tolerated dose was determined for each compound. For polyaspartamides 1–4 the dose levels ranged from about 25 mg Pt (kg body weight−1) (in conjugate 4) to 500 mg Pt kg−1 (in compound 1), the latter conjugate proving some 100‐fold less toxic than cisplatin (3–4 mg Pt kg−1), which was included in this study for comparison. Low toxicity (tolerated dose 160 mg Pt kg−1) was also observed for the intrachain cis‐diamineplatinum complex polymer (5). The polyaspartamide conjugates 6 and 7, on the other hand, both characterized by a cis‐diamineplatinum complex system in the side chain, were toxic even below the dose level of 20–25 mg Pt kg−1. The preliminary findings of this study, while providing a basis for more extensive and broad‐based toxicological studies, will serve to direct and optimize structural conjugate designs in forthcoming synthetic programs. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献