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排序方式: 共有327条查询结果,搜索用时 390 毫秒
91.
A. Breakstone C. D. Buchanan R. Campanini H. B. Crawley G. M. Dallavalle M. M. Deninno K. Doroba D. Drijard F. Fabbri A. Firestone H. G. Fischer H. Frehse W. Geist G. Giacomelli R. Gokieli M. Gorbics P. Hanke M. Heiden W. Herr P. G. Innocenti E. E. Kluge J. W. Lamsa T. Lohse W. T. Meyer G. Mornacchi T. Nakada M. Panter A. Putzer K. Rauschnabel F. Rimondi R. Sosnowski J. Spahn M. Szczekowski O. Ullaland D. Wegener 《Zeitschrift fur Physik C Particles and Fields》1984,23(1):9-18
The density of charged particles near a single highp T trigger particle in proton-proton collisions has been studied with the SFM detector at the CERN-ISR. It is shown that:—the secondaries cluster in a jet-like manner about the trigger particle; —the momentum distributions in this trigger jet can be unambiguously separated from the spectator background distributions;—the momentum distributions in this trigger jet can be unambiguously separated from the spectator background distributions;—the momentum component transverse to the jet direction is exponentially damped;—the width of the transverse distributions increases with the momentum component along the jet;—the fractional longitudinal momentum density depends strongly on the trigger transverse momentum and scales with \(x_T = {{2p_T } \mathord{\left/ {\vphantom {{2p_T } {\sqrt s }}} \right. \kern-0em} {\sqrt s }}\) . All these findings support the hard constituent scattering origin of highp T hadrons. 相似文献
92.
The high vacuum distillation technique for the analysis of photolysis products has highlighted both the extreme difficulty of removing residual solvent and the slow diffusion of photodegradation products from thin cast poly(vinyl ester) films, even at temperatures 130°C above Tg. Very long product collection periods at temperatures just below the onset of thermal degradation were used in order to obtain reliable quantitative data. The distributions of liquid-nitrogen condensable products indicated that a closer relationship exists between the photodegradation of poly(vinyl esters) and the photolysis of low molecular mass esters than previous results had suggested. 相似文献
93.
T R Battersby D N Ang P Burgstaller S C Jurczyk M T Bowser D D Buchanan R T Kennedy S A Benner 《Journal of the American Chemical Society》1999,121(42):9781-9789
5-(3"-Aminopropynyl)-2'-deoxyuridine (dJ), a modified nucleoside with a side chain carrying a cationic functional group, was incorporated into an oligonucleotide library, which was amplified using the Vent DNA polymerase in a polymerase chain reaction (PCR). When coupled to an in vitro selection procedure, PCR amplification generated receptors that bind ATP. This is the first example of an in vitro selection generating oligonucleotide receptors where the oligonucleotide library has incorporated a cationic nucleotide functionality. The selection yielded functionalized receptors having sequences differing from a motif known to arise in a standard selection experiment using only natural nucleotides. Surprisingly, both the natural and the functionalized motifs convergently evolved to bind not one, but two ATP molecules cooperatively. Likewise, the affinity of the receptors for ATP had converged; in both cases, the receptors are half saturated at the 3 mM concentrations of ATP presented during the selection. The convergence of phenotype suggests that the outcome of this selection experiment was determined by features of the environment during which selection occurs, in particular, a highly loaded affinity resin used in the selection step. Further, the convergence of phenotype suggests that the optimal molecular phenotype has been achieved by both selections for the selection conditions. This interplay between environmental conditions demanding a function of a biopolymer and the ability of the biopolymer to deliver that function is strictly analogous to that observed during natural selection, illustrating the nature of life as a self-sustaining chemical system capable of Darwinian evolution. 相似文献
94.
The methane negative ion chemical ionization (NICI) mass spectra of polycyclic aromatic hydrocarbons are usually dominated by molecular, M? ˙ or M ? H? ions; however, ions resulting from additions to M have also been reported. Some of these ions have been observed at [M + 14]? ˙, [M + 15]?, [M + 30]? and [M + 32]?˙ and have been attributed to reactions with either oxygen-containing impurities in the buffer gas or alkyl radical species generated by ionization of a hydrocarbon buffer gas. In this study, the NICI spectra of fluorene, anthracene and fluoranthene were studied in detail using quadrupole and Fourier transform mass spectrometers. Spectra were acquired when reactive species such as oxygen, water, nitrous oxide and carbon dioxide were added to the nitrogen buffer gas. Experiments with deuterated methane were also carried out. These studies indicated that buffer gas impurities affect the NICI spectra; however, gas-phase ion-molecule reactions were not responsible for all of the observed products. In addition to electron- and ion-molecule reactions, ions were observed that resulted from wall-catalyzed oxidation reactions followed by electron capture. These reactions were enhanced by the addition of oxygen and elevated ion source temperatures. Depending upon the parent PAH structure, oxidation products such as ketones, quinones and anhydrides were formed. 相似文献
95.
β-(2-Oxocyclopentyl)ethylaryl ketones are transformed under acid conditions via a 2-aryl-bicyclo[3.2.1]oct-2-en-8-one intermediate into a mixture of arylcycloheptene carboxylic acids. The scope and the mechanism of the reaction are both discussed. 相似文献
96.
T W Archibald C S Buchanan K I M McKinnon L C Thomas 《The Journal of the Operational Research Society》1999,50(5):468-479
This paper presents a computational comparison of nested Benders decomposition and dynamic programming (DP) for stochastic optimisation problems arising from the optimisation of hydro-electric generation from hydraulically linked reservoirs. The examples considered have between 3 and 17 reservoirs, two weather states, three runoff patterns and five periods. The examples are solved exactly by the simplex method and nested Benders decomposition and solved approximately by discrete dynamic programming (DP). A full version of DP is used for examples with 3 and 4 reservoirs, and a decomposition method is used for all examples. The full DP results are within 1% of optimal and the DP decomposition results are within 3.2% of optimal. Timings are given for serial and parallel versions of the algorithms. An analysis is given of how the different methods scale with the number of periods, reservoirs, weather states and runoff patterns, and also how applicable they are to more general problems. 相似文献
97.
OK Yoon WG Hwang JC Choe MS Kim 《Rapid communications in mass spectrometry : RCM》1999,13(14):1515-1521
A technique to investigate photodissociation kinetics on a nanosecond time scale has been devised for molecular ions generated by multiphoton ionization (MPI) using mass-analyzed ion kinetic energy spectrometry. The branching ratio or rate constant has been determined for the photodissociation of the n-butylbenzene, bromobenzene, iodobenzene, and aniline molecular ions generated by MPI at 266 nm. The ion internal energies have been estimated by comparing the measured kinetic data with the previous energy dependence data. The analysis has shown that only those molecular ions generated by two-photon ionization contribute to the photodissociation signals. Around half of the available energy has been found to remain as molecular ion internal energy in the two-photon ionization process. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
98.
Nonlinear Dynamics - Port Knocking is a method for authenticating clients through a closed stance firewall, and authorising their requested actions, enabling severs to offer services to... 相似文献
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