J/ψ核吸收新截面难以改变吸收机制的局面

将新发表的J/ψ核吸收截面输入强子和弦级联模型JPCIAE,计算了200AGeV/c的P-A,O-U,S-U和Pb-Pb最小偏畸碰撞中J/ψ压低因子并与实验作比较.结果表明:增大的新截面难以改变核吸收机制不易解释Pb-Pb碰撞J/ψ反常压低局面.     

General Formulations of Finite-field Method Classified by Symmetry for Molecular Linear and Nonlinear Polarizabilities

1 INTRODUCTIONWith the invention of lasers[1] and the observation of second-harmonic generation in quartz[2], nonlinear optics(NLO), as a cornerstone of photonics, has been booming since 1960's. And intense interest has been aroused to search materials exhibiting appropriate nonlinear optical properties suitable for the construction of practical optical devices for the important techniques such as frequency converting, signal processing and optical computing[3～6]. In order to determine …     

Net Charge Fluctuation and String Fragmentation

We present the simulation results of the net charge fluctuation in Au Au collisions at √Snn=130 GeV from a dynamic model, JPCIAE, and its revisions. The simulations are done for the quark-gluon matter, the directly produced pions, the pion matter, and the hadron matter. The simulated net charge fluctuation of the quark-gluon matter is close to the thermal model prediction for the quark-gluon gas. However, the discrepancy exists comparing the simulated net charge fluctuation for directly produced pions and the pion matter with the thermal model prediction for pion gas and the resonance pion gas, respectively. The net charge fluctuation of hadron matter from default JPCIAE simulations is nearly 3.5 times larger than quark-gluon matter. A discussion is given for the net charge fluctuation as an evidence of QGP phase transition.     

The Synthesis And Chemical Properties Of N-D-Pentopyranosylamines,Derivatives Of Tryptamine And Tyramine.

Abstract

The synthesis and structure of N-D-pentopyranosylamines derived from the amines tiyptamine tyramine and the pentoses D-xylose, D-arabinose and D-lyxose are presented. NMR spectroscopy and mass spectrometry were used to verify the proposed α,β-D-pentopyranosylamine structures.     

Rational functions over finite fields having continued fraction expansions with linear partial quotients

Let F be a finite field with q elements and let g be a polynomial in F[X] with positive degree less than or equal to q/2. We prove that there exists a polynomial f∈F[X], coprime to g and of degree less than g, such that all of the partial quotients in the continued fraction of g/f have degree 1. This result, bounding the size of the partial quotients, is related to a function field equivalent of Zaremba's conjecture and improves on a result of Blackburn [S.R. Blackburn, Orthogonal sequences of polynomials over arbitrary fields, J. Number Theory 6 (1998) 99-111]. If we further require g to be irreducible then we can loosen the degree restriction on g to deg(g)?q.     

C-2-side chain modification of 2-methyl-3-alkylindoles via 3-methylthioindolenines: a new approach to pyrrolo[1,2-a]indoles

A strategy for side chain alkylation of 2-methyl-3-alkylindoles, involving deprotonation of 3-methylthioindolenines, derived from 2-methyl-3-alkylindoles by reaction with methane sulfenyl chloride, reaction with carbon electrophiles and reduction, is outlined and applied to the synthesis of pyrrolo[1,2-a] indoles.     

The mass spectrometry of polychlorinated dibenzo-p-dioxins

The negative ion chemical ionization mass spectra of polychlorinated dibenzo-p-dioxins using oxygen, methane and methane/oxygen are reported together with their methane positive ion chemical ionization mass spectra and conventional electron impact spectra. The methane/oxygen negative ion chemical ionization mass spectra proved to be the most useful of the negative ion spectra for structure determination.     

The preparation of primary poly-hexafluoropropylene oxide halides (poly-HFPO-CF2X where X = I, Br, Cl and F)

Perfluorinated polyethers (PFPEs) are an important class of chemicals in industry due to their outstanding thermal stability, chemical inertness, and low vapor pressure. Since the first report on the polymerization of hexafluoropropylene oxide, there have been many papers on functionalized PFPEs. We have found that the reaction of poly-hexafluoropropylene oxide (HFPO) acid fluoride with LiI leads, to first the secondary and subsequently, to the primary poly-HFPO iodide. The primary poly-HFPO iodide, like perfluoroalkyl iodide, should provide the starting point for many new products. In this paper, from the primary poly-HFPO iodide we have prepared the family of primary poly-HFPO halides (X = I, Br, Cl and F). Their spectral data are discussed.     

Synthesis and diels-alder reactions of 5,5-dicyanocyclopentadiene: regioselective synthesis of 1,5-disubstituted-1,3-cyclohexadienes

5,5-Dicyanocyclopentadiene, readily prepared in three steps from commercially available cis-1,4-dichloro-2-butene, undergoes Diels-Alder reactions with a number of dienophiles to give 5-substituted 7,7-dicyanobicyclo[2.2.1]hept-2-enes with high endo-selectivity. The adduct produced with methyl acrylate undergoes base-induced retro-Michael reactions to give 1-carbomethoxy-5-dicyanomethyl-1,3-cyclohexadiene.     

PHOTOREACTIVITY OF 5-GERANOXYPSORALEN AND LACK OF PHOTOREACTION WITH DNA

5-Geranoxypsoralen, commonly called bergamottin, a major furocoumarin contained in bergamot oil, is reported in vitro as a highly photoreactive psoralen. In ethanol, it exhibits quite a high triplet state quantum yield (approximately 0.37). The triplet state is involved in subsequent photochemistry which depends on the initial concentration and on the presence of oxygen. In contrast to most psoralens, absorption and fluorescence data suggest that 5-geranoxypsoralen does not interact with DNA in the dark. No UVA-induced interstrand cross-links in DNA were shown.