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1.
Foda Omar Leclerc Bernard Okado Masato Thibon Jean-Yves Welsh Trevor A. 《Letters in Mathematical Physics》1998,43(1):31-42
A special family of partitions occurs in two apparently unrelated contexts: the evaluation of one-dimensional configuration sums of certain RSOS models, and the modular representation theory of symmetric groups or their Hecke algebras Hm. We provide an explanation of this coincidence by showing how the irreducible Hm-modules which remain irreducible under restriction to Hm_1 (Jantzen–Seitz modules) can be determined from the decomposition of a tensor product of representations sln. 相似文献
2.
Leclerc E Buchmann W Taphanel MH Morizur JP 《Rapid communications in mass spectrometry : RCM》2002,16(7):686-695
Ion/molecule reactions between O=P(OCH(3))(2)(+) phosphonium ions and six aromatic hydrocarbons (benzene, toluene, 1,2,4-trimethylbenzene, naphthalene, acenaphthylene and fluorene) were performed in a quadrupole ion trap mass spectrometer. The O=P(OCH(3))(2)(+) phosphonium ions, formed by electron impact from neutral trimethyl phosphite, were found to react with aromatic hydrocarbons (ArHs) to give (i) an adduct [ArH, O=P(OCH(3))(2)](+) and (ii) for ArHs which have an ionization energy below or equal to 8.14 eV, a radical cation ArH(+ *) by charge transfer reaction. Collision-induced dissociation experiments, which produce fragment ions other than the O=P(OCH(3))(2)(+) ions, indicate that the adduct ions are covalent species. Isotope-labeled ArHs were used to elucidate fragmentation mechanisms. The charge transfer reactions were investigated using density functional theory at the B3LYP/6-311 + G(3df,2p)//B3LYP/6-31G(d,p) level of theory. The potential energy surface obtained from B3LYP/6-31G(d,p) calculations for the reaction between O=P(OCH(3))(2)(+) and benzene is described. 相似文献
3.
The molecular energy of the complex (η5-C5H5)2TiCl2 has been calculated for experimental geometry and for several hypothetical forms by a semi-empirical CNDO/2 approach. The energy difference between experimental (quasi-tetrahedral) geometry and a planar geometry is ca. 20 kcal mol?1. This difference is sufficiently high to explain the difficulty of the inversion process. 相似文献
4.
Edwige Jeanneau-Nicolle Claude Bosso Martine Benoit-Guyod Grard Leclerc 《Journal of mass spectrometry : JMS》1993,28(1):37-41
The electron impact mass spectra of two series of 5-oxo-tetrahydro-5H-thiazolo [3,2-a]pyrimidine-6-ethylcarboxylates and 7-oxo-tetrahydro-7H-thiazolo [3,2-a]pyrimidine-6-ethylcarboxylates were measured and fragmentation patterns examined. Structures were assigned from analysis of oxo molecular ion fragmentations. Compounds of the 5-oxo series gave an [M – CO2C2H5]+ fragmentation whereas compounds of the 7-oxo series gave three characteristic cleavages. This decomposition was confirmed for one pair of isomers by high-resolution mass spectrometry and unimolecular mass-analysed ion kinetic energy spectrometry. Electron impact mass spectrometry is a convenient method for assigning structures of 5- and 7-oxo regioisomers of tetrahydrothiazolo[3,2-a]pyrimidine-6-carboxylates. 相似文献
5.
An essential element of implicit solvent models, such as the generalized Born method, is a knowledge of the volume associated with the individual atoms of the solute. Two approaches for determining atomic volumes for the generalized Born model are described; one is based on Voronoi polyhedra and the other, on minimizing the fluctuations in the overall volume of the solute. Volumes to be used with various parameter sets for protein and nucleic acids in the CHARMM force field are determined from a large set of known structures. The volumes resulting from the two different approaches are compared with respect to various parameters, including the size and solvent accessibility of the structures from which they are determined. The question of whether to include hydrogens in the atomic representation of the solute volume is examined. Copyright 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1857-1879, 2001 相似文献
6.
K Gluchoff-Fiasson B Fenet J C Leclerc J Reynaud M Lussignol M Jay 《Chemical & pharmaceutical bulletin》2001,49(6):768-770
Three new flavonol malonylrhamnosides, 3-O-(4"-O-malonyl)-alpha-L-rhamnopyranosides of mearnsetin, myricetin and quercetin respectively, together with the corresponding mearnsitrin, myricitrin, quercitrin and the 4-O-methyl phloracetophenone 2-O-beta-D-glucopyranoside, were isolated from the leaves of Ribes alpinum and fully characterized by spectrocopic methods including 2D NMR. 相似文献
7.
A theoretical and experimental treatment of axial dispersion in coiled tubes is presented. The dispersion, δ, is related to the theoretical plate height divided by four times the radius of the tube (H/4r). This parameter, when plotted against the product of the Reynolds number and the Schmidt number (ReSc), accurately predicts maxima in dispersion curves. Variations in the boundary layer thickness and the velocity profile cause the dispersion to pass through a maximum at a constant value of log (De2Sc1·14) equal to 6.13 for unretained solutes (De is the Dean number). A new measure of dispersion is proposed; the reduced dispersion, ? = 256/(Re0.667Sc), is derived from the experimental behavior of dispersion at values of log (De2Sc1·14) smaller than 6.13. The logarithm of ? is found to be approximately zero for 2.2 < log (De2Sc1·14) < 6.1 and to decrease linearly with log (De2Sc1·14) at higher values. Experiments with four solutes that have a wide range of molecular diffusivities are reported. Results agree with theory. 相似文献
8.
Systematic approach to the determination of cephalosporins in biological fluids by reversed-phase liquid chromatography 总被引:1,自引:0,他引:1
The chromatographic behaviour of some cephalosporins as a function of pH and ionic strength of the mobile phase was studied on 10-microns LiChrosorb RP-18. Acidic cephalosporins were retained longest in their neutral form with an acidic eluent. Amphoteric cephalosporins were retained longest in their protonated form with an acidic eluent of low ionic strength. Cefotiam was retained longer with an alkaline mobile phase. LiChrosorb RP-18, Nucleosil C18 and muBondapak C18 gave rise to different selectivities when an acidic eluent, methanol-water (25:75) containing 0.2% of 1.8 M H2SO4 was used. This may be related to interactions with residual silanol groups. The studied cephalosporins (with the exception of cefotiam and cefsulodin) were separated from compounds present in biological fluids on 5-microns LiChrosorb RP-18 using the mobile phase 0.2% of 1.8 M H2SO4 in a mixture of methanol and water with various methanol contents. The determination of cefotiam in biological fluids was performed with an alkaline mobile phase. The preparation of the sample was simple and rapid: precipitation of plasma proteins or dilution of urine. The method was applied to the determination of ceftizoxime in human plasma and urine. Concentrations down to 0.2 micrograms/ml of plasma and 25 micrograms/ml of urine could be determined with good reproducibility and accuracy. 相似文献
9.
Jean-Claude Leclerc 《International journal of quantum chemistry》1976,10(5):781-789
Introduction of noninteger powers of r (or the elliptical coordinate ξ) in the definition of the 1s AO is shown to give better approximate wave-functions for the ground states of H2 and He than other functions of comparable complexity. This trend is examined for various definitions of hybrid Slater–Gaussian orbitals using a limited CI . The best optimized single-term expansion energy is only 0.000160 a.u. above the “SCF limit” for H2 at R = 1.4 a.u. and 0.000382 a.u. for He at R = 1.3 a.u. 相似文献
10.