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51.
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G. T. Jones R. W. L. Jones B. W. Kennedy D. R. O. Morrison M. M. Mobayyen S. Wainstein M. Aderholz D. Hantke E. Hoffmann U. F. Katz J. Kern N. Schmitz W. Wittek H. P. Borner G. Myatt D. Radojicic S. Burke 《Zeitschrift fur Physik C Particles and Fields》1991,51(2):205-208
Using data obtained with the bubble chamber BEBC at CERN, the inclusivef 2 (1270) meson production invp and \(\bar vp\) charged current reactions is studied. It is found thatf 2 production occurs mainly in events with a hadronic invariant massW?7 GeV. In these events, the averagef 2 multiplicity is about half the average ρO multiplicity, and thex F andp T 2 distributions of thef 2 agree in shape with those of the ρO. The predictions of a semi-empirical model (Wells model) are in accord with the measured multiplicities atW>7 GeV, whereas at lowerW the model predicts too largef 2 multiplicities. 相似文献
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A normal-phase LC method has been developed to analyze high-molecular-mass grape phenolic compounds. Samples are prepared by first isolating phenolics using C18-SPE. The analytical method uses a silica column and gradient elution with mobile phases of methylene chloride, methanol, formic acid and heptanesulfonic acid. This separation enables the analysis of these compounds from grape and wine samples in the presence of anthocyanins without extensive purification. Based on the elution order of proanthocyanidins and anthocyanins, phenolics elute in order of increasing molecular mass. Currently, it is not possible to identify all of the components separated in the chromatogram. 相似文献
56.
Affinity probe capillary isoelectric focusing (CIEF) with laser-induced fluorescence was explored for detection of Ras-like G proteins. In the assay, a fluorescent BODIPY FL GTP analogue (BGTPgammaS) and G protein were incubated resulting in formation of BGTPgammaS-G protein complex. Excess BGTPgammaS was separated from BGTPgammaS-G protein complex by CIEF using a 3-10 pH gradient and detected in whole-column imaging mode. In other cases, a single point detector was used to detect zones during the focusing step of CIEF using a 2.5-5 pH gradient. In this case, analyte peaks passed the detector in approximately 5 min at an electric field of 350 V/cm. Detection during focusing allowed for more reproducible assays at shorter times but with a sacrifice in sensitivity compared to detection during mobilization. Resolution was adequate to separate BGTPgammaS-Ras and BGTPgammaS-Rab3A complexes. Formation of specific complexes was confirmed by adding GTPgammaS to samples containing BGTPgammaS-G protein. GTPgammaS competed with BGTPgammaS for G protein binding sites resulting in decreased BGTPgammaS-G protein peak heights. The concentrating effect of CIEF enabled detection limits of 30 pM. 相似文献
57.
N. G. Thame R. D. Lundberg J. P. Kennedy 《Journal of polymer science. Part A, Polymer chemistry》1972,10(9):2507-2525
Cationically polymerizable olefins can be efficiently grafted onto poly(vinyl chloride) in the presence of alkylaluminum compounds. The substitution of labile chlorines in PVC by various branches yields a product of improved thermal stability as compared with unmodified PVC. Thus the grafting of a few per cent of polyisobutylene or poly-butadiene onto PVC gives graft copolymers superior in thermal stability to the PVC backbone, as determined by thermogravimetric and differential thermal analyses as well as color development of molded films. At advanced stages of thermal degradation the thermal stability of poly(vinyl chloride)-g-isobutylene) (PVC-g-PIB is some 40°C superior to the unmodified PVC. In addition to grafting of polymer chains onto the PVC backbone, other methods are also available to achieve improved thermal stability. In pentane suspension, alkylaluminum compounds efficiently alkylate labile chlorines in PVC, and the product exhibits improved thermal stability. Alternatively, PVC carbonium ions can alkylate aromatic compounds, and these products also exhibit high heat stability. Based on the assumption that certain alkylaluminums quantitatively react with labile chlorines in PVC, it was estimated that 2–3% of the chlorines present in suspension-grade PVC are labile. 相似文献
58.
Franken A Kilner CA Thornton-Pett M Kennedy JD 《Chemical communications (Cambridge, England)》2002,(18):2048-2049
Reaction of the [1-Ph-closo-1-CB9H(4)-6,7,8,9,10-I5]- anion with 4-MeC6H4MgBr in the presence of [PdCl2(PPh3)2] gives the [Pd2I2(P(C6H(4)-4-Me)3)4]2+ salt of the [1-Ph-closo-1-CB9H(4)-10-I-6,7,8,9-(C6H(4)-4-Me)4]- anion, which exhibits an unusual neutral supramolecular assembly in the solid state, in which the dipalladium dication is encapsulated by two four-armed 'tetrapus' anionic units; the anion also has potentialities for four-fold dendrimer construction. 相似文献
59.
Abstract The effect of anion concentration on the apparent rate constant of polymerization kA p of isobutylene (IB) induced by the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl4 initiating system using the CH2Cl2/nC6H14 (60/40 v/v) solvent system at ?40 and ?80°C was studied by the use of nBu4NCl. Computer simulation has shown that kA p decreases several orders of magnitude upon the addition of even a very small amount of common anion TiCl?- 5 to the charge. The rate of change is reduced in the concentration range of experimental interest. It was concluded that the decrease of kA p with increasing TiCl ?- 5 concentration is mainly due to the decreasing contribution of propagation by free ions. The contribution (%) of propagation by free ions to the apparent rate of propagation was calculated. 相似文献
60.
Abstract The preparation and characterization of multiblock copolymers consisting of polyiso-butylene (PIB) soft segments connected to dimethyl terephthalate (DMT) plus 1,4-butane diol (BD) hard segments (PIB-b-PBT)n are described. Syntheses involved solution poly-condensation of DMT + BD + hydroxyl ditelechelic PIB (HO-PIB-OH). The overall block composition, and the lengths of the soft segments were varied in the Mn,PIB=1,400–10,000 g/mol range. The presence of PIB in the multiblocks was demonstrated. The solubility in THF and other solvents, and extractability of the polymers with n-hexane were studied. Efforts to determine solution viscosity remained unsuccessful due to the insolubility of the polar and nonpolar segments in a common solvent. Mechanical testing gave unacceptable results, however, the multiblocks showed good thermal stability (up to 367°C in air) and melt processibility appears to be feasible. 相似文献