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排序方式: 共有149条查询结果,搜索用时 15 毫秒
61.
D. Bertrand G. Bertrand-Coremans R. Blaes F.W. Bullock M. Dewit B. Escoubes E. Fett A. Haatuft A. Halsteinslid T.W. Jones J.G. Morfin K. Myklebost J.M. Olsen P. Petitjean M. Pohl F. Rahimi P.N. Ratoff J. Sacton L.C. Welch 《Physics letters. [Part B]》1979,84(3):354-356
Candidates for the purely leptonic process have been searched for in the bubble chamber Gargamelle exposed to the CERN-SPS antineutrino wide-band beam. No single e?, of energy greater than 1 GeV, was found in a total of 230 000 pictures, corresponding to 7400 charged current events. This leads to an upper limit for the observed cross section of cm2 (90% C.L.). Interpretation of this value in terms of the standard W Weinberg-Salam model yields an upper limit to the mixing parameter sin2θW < 0.39 at 90% C.L. 相似文献
62.
In this paper we discuss the recovery of derivatives and thecomputation of rigorous and useful upper bounds for the pointwiseerror in the recovered derivatives, for finite element approximationsof the Laplace equation with Neumann boundary conditions, especiallyat points close to or on a smooth, curved boundary. We analyzethe dipole image technique for the case of curved boundaries,and show how to compute reliable recovered derivatives and errorbounds even in the limiting case of points lying on the curvedboundary. Numerical experiments show reasonably tight errorbounds for points both close to and away from a curved boundary. 相似文献
63.
The 1H and 13C NMR spectra of the heterobimetallic compound (CO)4Fe(μ-AsMe2)Mo(CO)2(C5H5) reveal three different fluxional processes. 相似文献
64.
Angela F. Danil de Namor Jaime D. Crdenas Joseph I. Bullock Angel Alvarez Garcia Jose L. Brians Jordi Rius Claire R. Whitaker 《Polyhedron》1997,16(24):4323-4330
Complexes of ethylenediamine-N,N,N′,N′-tetraacetanilide (edtan, C34H36N6O14) with cobalt(II), nickel(II) and copper(II) in the solid state and in solution are reported for the first time. Thermodynamic data (stability constant, and derived Gibbs energy, enthalpy and entropy changes)for the 1 : 1 complexation of edtan with the metal ions at 298.15 K in water-saturated butan-1-ol gave the selectivity sequence log10Ks; Ni2+, 4.56±0.02; Cu2+, 4.41±0.01; Co2+, 4.18±0.04 as found from microcalorimetric titration studies. The entropies suggested that the structure of the 1 : 1 complex with copper(II) contains fewer chelate rings than those for nickel(II) and cobalt(II) (δcS0 : Cu-21.4, Co 5.7, Ni 3.9 J mol−1K−1). Solid complexes of the metal ions with edtan and perchlorate as the counter anion were prepared. For each, a complex with a 1 : 1 metal: edtan stoichiometry with non-coordinated perchlorate was isolated. The X-ray structure of [Cu(edtan)(H2O)][ClO4]2·1.5H2O (1) revealed a six-coordinate Cu centre with edtan acting as pentadentate ligand (2N, 3O) with the coordination sphere completed by an oxygen atom from water. In striking contrast to the Cu complex, the Co centre in [Co(edtan)(H2O)][ClO4]2·H2O·0.5C2H5OH (2) is seven-coordinate with hexadentate edtan (2N, 4O) and one coordinated water molecule. There is thus an excellent confirmation of the results obtained from the microcalometric study in that edtan forms four chelate rings to Cu but five to Co in the solid state. The ability of the ligand to extract metal ions from water to the water-saturated butan-1-ol phase was assessed from distribution data as a function of the aqueous phase hydrogen ion concentration and of the ligand concentration in the organic phase. The data showed that Cu2+ is selectively extracted over a wide range of aqeous phase hydrogen ion concentrations. 相似文献
65.
H. Cobbaert P. R. Hobson R. Arnold J. L. Bailly J. F. Balland M. Barth J. H. Bartley M. Boratav F. W. Bullock M. Callichio M. Coupland H. Drevermann B. G. Duff O. Erriquez M. J. Esten D. Geiregat K. Geissler F. Grard V. P. Henri A. Herve F. F. Heymann J. Hrubec D. C. Imrie E. Johannsson J. Kesteman P. Lecoq G. J. Lush G. Maurer M. t. Muciaccia S. Natali S. Nuzzo G. Neuhofer P. Olivier R. Roosen F. Ruggieri A. Taurok S. P. K. Tavernier M. C. Touboul A. M. Touchard O. R. Williams 《Zeitschrift fur Physik C Particles and Fields》1987,36(4):577-591
In the first holographic bubble chamber experiment — the HOBC experiment — we have accumulated a total of 40000 holograms with particle interactions. We have determined the total charm pair cross section inpN collisions to be 23.3 ?7.7 +10 μb and 3.6 ?1.7 +2.3 μb for 360 and 200 GeV/c incident protons respectively. We have assumed a linear dependence of the cross section on the atomic number of the target. This experiment has demonstrated the feasibility of holographic recording in small bubble chambers. Assuming that the charm cross section can be described by the standard QCD factorized expression with gluon fusion and quark-antiquark annihilation, we have used our measured charm cross sections with other measurements to determine the effective charmed quark mass to be 1.8 ?0.35 +0.25 GeV/c2. TheK factor, which describes the importance of the higher order corrections, is calculated to be 9.8 ?6.9 +12.5 (See noted added in proof.) 相似文献
66.
Bullock JP Carter E Johnson R Kennedy AT Key SE Kraft BJ Saxon D Underwood P 《Inorganic chemistry》2008,47(17):7880-7887
The oxidative electrochemistry of luminescent rhenium (I) complexes of the type Re(CO) 3(LL)Cl, 1, and Re(CO) 3(LL)Br, 2, where LL is an alpha-diimine, was re-examined in acetonitrile. These compounds undergo metal-based one-electron oxidations, the products of which undergo rapid chemical reaction. Cyclic voltammetry results imply that the electrogenerated rhenium (II) species 1 ( + ) and 2 ( + ) disproportionate, yielding [Re(CO) 3(LL)(CH 3CN)] (+), 7, and additional products. Double potential step chronocoulometry experiments confirm that 1 ( + ) and 2 ( + ) react via second-order processes and, furthermore, indicate that the rate of disproportionation is influenced by the basicity and steric requirements of the alpha-diimine ligands. The simultaneous generation of rhenium (I) and (III) carbonyl products was detected upon the bulk oxidation of 1 using infrared spectroelectrochemistry. The rhenium (III) products are assigned as [Re(CO) 3(LL)Cl 2] (+), 5; an inner-sphere electron-transfer mechanism of the disproportionation is proposed on the basis of the apparent chloride transfer. Chemically irreversible two-electron reduction of 5 yields 1 and Cl (-). No direct spectroscopic evidence was obtained for the generation of rhenium (III) tricarbonyl bromide disproportionation products, [Re(CO) 3(LL)Br 2] (+), 6; this is attributed to their relatively rapid decomposition to 7 and dibromine. In addition, the 17-electron radical cations, 7 ( + ), were successfully characterized using infrared spectroelectrochemistry. 相似文献
67.
Doug Bullock 《Proceedings of the American Mathematical Society》1997,125(6):1835-1839
We introduce a new technique for estimating the number of generators of the Kauffman bracket skein module of a three manifold; one which requires the construction of linear functionals on a simpler version of the module. Of particular interest is the use of representations of the fundamental group into to generate the functionals.
68.
G. T. Jones R. W. L. Jones B. W. Kennedy S. W. O'Neale O. Villalobos-Baillie H. Klein D. R. O. Morrison P. Schmid H. Wachsmuth D. B. Miller M. M. Mobayyen S. Wainstein M. Aderholz D. Hantke U. F. Katz J. Kern N. Schmitz W. Wittek H. P. Borner G. Myatt D. Radojicic F. W. Bullock S. Burke 《Zeitschrift fur Physik C Particles and Fields》1993,57(2):197-209
The production of the neutral strange particlesK
0, and
invp and
charged current interactions is studied in an experiment with the Big European Bubble Chamber. Mean multiplicities are measured as a function of the event variablesE
v,W
2 andQ
2 and of the hadron variablesx
F,z andp
T
2
.K
*± (892) and
*± (1385) signals are observed, whereas there is no evidence for
*- (1385) production invp scattering. Forward, backward and total mean multiplicities are found to compare well with the predictions of an empirical model for deep-inelastic reactions in the case of the strange mesonsK
0 andK
*± (892) but less so for the strange baryons ,
and
*± (1385). The strange baryon multiplicities are used to obtain the decuplet to octet baryon production ratio and to assess the probabilities of auu orud system to break up. 相似文献
69.
G. Gerbier D. Bertrand J. Guy P. Marage M. Aderholz N. Armenise J. H. Bartley J. P. Baton V. Brisson R. Belusevic D. Brou F. W. Bullock M. Calicchio E. F. Clayton T. Coghen A. M. Cooper-Sarkar O. Erriquez P. J. Fitch P. O. Hulth G. T. Jones P. Kasper H. Klein C. Kochowski M. Lagraa S. Leighton-Davis R. Middleton D. B. Miller M. M. Mobayyen D. R. O. Morrison M. Neveu S. Nuzzo S. O'Neale M. A. Parker P. Petiau J. Sacton R. A. Sansum N. Schmitz E. Simopoulou M. Talebzadeh K. Varvell C. Vallee A. Vayaki W. Venus H. Wachsmuth J. Wells W. Wittek E. Zevgolatakos BEBC WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1985,29(1):15-28
A sample of over 25,000 fully measured neutrino and antineutrino charged current interactions in BEBC includes 192 dilepton candidates. The prompt signal after subtraction of background is 41 ±7µ+ e -, 35±7µ+µ- events from \(\bar v\) interactions, and 32±7µ-µ+ events from ν interactions. There are 2 trileptons, µ-µ- e + and µ-µ-µ+. Results are compared with other experimental data and with the standard model. Limits to prompt like sign µ+ e +, µ+µ+ and µ-µ- signals are given and compared with other experiments and with theoretical calculations. 相似文献
70.