排序方式: 共有67条查询结果,搜索用时 15 毫秒
41.
Zeller GP McFarland KS Adams T Alton A Avvakumov S de Barbaro L de Barbaro P Bernstein RH Bodek A Bolton T Brau J Buchholz D Budd H Bugel L Conrad J Drucker RB Fleming BT Frey R Formaggio JA Goldman J Goncharov M Harris DA Johnson RA Kim JH Koutsoliotas S Lamm MJ Marsh W Mason D McDonald J McNulty C Naples D Nienaber P Romosan A Sakumoto WK Schellman H Shaevitz MH Spentzouris P Stern EG Suwonjandee N Tzanov M Vakili M Vaitaitis A Yang UK Yu J Zimmerman ED 《Physical review letters》2002,88(9):091802
The NuTeV Collaboration has extracted the electroweak parameter sin(2)theta(W) from the measurement of the ratios of neutral current to charged current nu and (-)nu cross sections. Our value, sin(2)theta((on-shell))(W) = 0.2277 +/- 0.0013(stat) +/- 0.0009(syst), is 3 standard deviations above the standard model prediction. We also present a model independent analysis of the same data in terms of neutral-current quark couplings. 相似文献
42.
The one‐pot synthesis of a series of 1,2,4‐triazines from the reactions of semicarbazide or thiosemi‐carbazide with various α,β‐dicarbonyl compounds under reflux conditions in a EtOH‐H2O (9:1) mixture as solvent and catalyzed by nano‐sized silica supported FeCl3 (FeCl3@SiO2) was investigat‐ed. The FeCl3 content of the catalyst was measured by atomic absorption to get the adsorption ca‐pacity. The reactions gave high yields of the product and the catalyst was easily separated and re‐used for successive reaction runs without significant loss of activity. 相似文献
43.
Mason D Brau J Drucker RB Frey R Spentzouris P Conrad J Fleming BT Formaggio J Kim JH Koutsoliotas S McNulty C Romosan A Shaevitz MH Stern EG Vaitaitis A Zimmerman ED Johnson RA Suwonjandee N Vakili M Bernstein RH Bugel L Lamm MJ Marsh W Nienaber P Tobien N Yu J Adams T Alton A Bolton T Goldman J Goncharov M de Barbaro L Buchholz D Schellman H Zeller GP Boyd S McDonald J Naples D Radescu V Tzanov M Avvakumov S de Barbaro P Bodek A Budd H Harris DA McFarland KS Sakumoto WK Yang UK 《Physical review letters》2007,99(19):192001
44.
Poul Erik Hansen Mohammad Vakili Fadhil S. Kamounah Jens Spanget-Larsen 《Molecules (Basel, Switzerland)》2021,26(24)
The vibrational NH stretching transitions in secondary amines with intramolecular NH···O hydrogen bonds were investigated by experimental and theoretical methods, considering a large number of compounds and covering a wide range of stretching wavenumbers. The assignment of the NH stretching transitions in the experimental IR spectra was, in several instances, supported by measurement of the corresponding ND wavenumbers and by correlation with the observed NH proton chemical shifts. The observed wavenumbers were correlated with theoretical wavenumbers predicted with B3LYP density functional theory, using the basis sets 6-311++G(d,p) and 6-31G(d) and considering the harmonic as well as the anharmonic VPT2 approximation. Excellent correlations were established between observed wavenumbers and calculated harmonic values. However, the correlations were non-linear, in contrast to the results of previous investigations of the corresponding OH···O systems. The anharmonic VPT2 wavenumbers were found to be linearly related to the corresponding harmonic values. The results provide correlation equations for the prediction of NH stretching bands on the basis of standard B3LYP/6-311++G(d,p) and B3LYP/6-31G(d) harmonic analyses, with standard deviations close to 38 cm−1. This is significant because the full anharmonic VPT2 analysis tends to be impractical for large molecules, requiring orders of magnitude more computing time than the harmonic analysis. 相似文献
45.
46.
In this paper we propose a photonic crystal Mach-Zehnder interferometer (MZI) based on a new coupled-cavity waveguide, where its advantage over the previous type of photonic crystal coupled-cavity waveguide is discussed. A heterostructure Y-junction is comprised of square and hexagonal lattices of the new coupled-cavity waveguide. It is designed by applying the temporal coupled-mode theory and is optimized, where an overall throughput efficiency of more than 90% is achieved at the wavelength of 1.55 μm. The design of the Y-junction is performed using finite-difference time-domain method. The designed heterostructure Y-junction is used in the structure of a MZI, where its arms are approximately as short as 24 μm. Finally, the transient response of the proposed optical switch is investigated. 相似文献
47.
An efficient method has been developed for the synthesis of a novel series of unsymmetrically 3,3‐disubstituted oxindoles in good‐to‐high yields by a one‐pot three‐component condensation reaction of 2‐hydroxynaphthalene‐1,4‐dione, an isatin, and a barbituric acid derivative, in H2O, and with p‐toluenesulfonic acid as a catalyst, at 90°. The effects of solvent, temperature, and the amount of catalyst on the yield of the reaction have been investigated. Additionally, the influence of hydrophilicity and hydrophobicity of the reactants on the selectivity of products has been examined. 相似文献
48.
Babak Vakili 《International Journal of Theoretical Physics》2012,51(1):133-145
We study the canonical formalism of a spherically symmetric space-time. In the context of the 3+1 decomposition with respect
to the radial coordinate r, we set up an effective Lagrangian in which a couple of metric functions play the role of independent variables. We show
that the resulting r-Hamiltonian yields the correct classical solutions which can be identified with the space-time of a Schwarzschild black hole.
The Noether symmetry of the model is then investigated by utilizing the behavior of the corresponding Lagrangian under the
infinitesimal generators of the desired symmetry. According to the Noether symmetry approach, we also quantize the model and
show that the existence of a Noether symmetry yields a general solution to the Wheeler-DeWitt equation which exhibits a good
correlation with the classical regime. We use the resulting wave function in order to (qualitatively) investigate the possibility
of the avoidance of classical singularities. 相似文献
49.
Quantum chemical calculations are performed to study the cooperativity effects between chalcogen bond and halogen bond interactions in F2S···NCX···NCY complexes, where X = F, Cl, Br, I and Y = H, F, OH. These effects are investigated in terms of geometric and energetic features of the complexes, which are computed by second-order Møller–Plesset perturbation theory (MP2). For each F2S···NCX···NCY complex studied, the effect of cooperativity on the chalcogen bond is dependent on the strength of halogen bond. The results indicate that the interaction energies of chalcogen and halogen bonds in the triads are more negative relative to the respective dyads. The interaction energy of chalcogen bond is increased by 31%–49%, whereas that of halogen bond by 28%–62%. The energy decomposition analysis reveals that electrostatic force plays a main role in the cooperativity effects between the chalcogen bond and halogen bond interactions. The topological analysis, based on the quantum theory of atoms in molecules, is used to characterise the interactions and analyse their enhancement with varying electron density at bond critical points. 相似文献
50.
In planning and managing production systems, manufacturers have two main strategies for responding to uncertainty: they build inventory to hedge against periods in which the production capacity is not sufficient to satisfy demand, or they temporarily increase the production capacity by “purchasing” extra capacity. We consider the problem of minimizing the long-run average cost of holding inventory and/or purchasing extra capacity for a single facility producing a single part-type and assume that the driving uncertainty is demand fluctuation. We show that the optimal production policy is of a hedging point policy type where two hedging levels are associated with each discrete state of the system: a positive hedging level (inventory target) and a negative one (backlog level below which extra capacity should be purchased). We establish some ordering of the hedging levels, derive equations satisfied by the steady-state probability distribution of the inventory/backlog, and give a more detailed analysis of the optimal control policy in a two state (high and low demand rate) model. 相似文献