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131.
We show that in the standard model the parametrically leading (by a factor 1/α(s)) contribution to the inclusive CP asymmetry in B→X(s,d)γ decays arises from a long-distance effect in the interference of the electromagnetic dipole amplitude with the amplitude for an up-quark penguin transition accompanied by soft gluon emission. Using model estimates for the associated hadronic parameter Λ(17)(u), we predict a value in the range -0.6% < A(X(s)γ)(SM) < 2.8%. In view of current experimental data, a future precision measurement of the flavor-averaged CP asymmetry would signal the presence of new physics only if a value below -2% was found. A cleaner probe of new physics is offered by the difference of the CP asymmetries in charged versus neutral B→X(s,d)γ decays. 相似文献
132.
Whereas periodic gratings enable us to couple light into a surface plasmon polariton only at a specific angle and wavelength, we show here that quasiperiodic gratings enable the coupling of light at multiple wavelengths and angles. The quasiperiodic grating can be designed in a systematic manner using the dual-grid method, thereby enabling us to control the coupling strength and grating dimensions. We verified the method experimentally by efficiently coupling light into a surface plasmon from several different illumination angles using a single quasiperiodic grating. 相似文献
133.
The generalized Marcum functions appear in problems of technical and scientific areas such as, for example, radar detection and communications. In mathematical statistics and probability theory these functions are called the noncentral gamma or the noncentral chi‐squared cumulative distribution functions. In this paper, we describe a new asymptotic method for inverting the generalized Marcum Q‐function and for the complementary Marcum P‐function. Also, we show how monotonicity and convexity properties of these functions can be used to find initial values for reliable Newton or secant methods to invert the function. We present details of numerical computations that show the reliability of the asymptotic approximations. 相似文献
134.
F. J. Gil Llambías N. Escalona C. Pfaff C. Scott J. Goldwasser 《Reaction Kinetics and Catalysis Letters》1999,66(2):225-229
Apparent surface coverage (ASC) of a series of tungsten-alumina catalysts was determined by the electrophoretic migration
method (EM). A linear increase in W coverage with increasing W loading (up to 13.1 wt.% W) was observed. The results were
in close agreement with those obtained previously by ion scattering spectroscopy (ISS) and low temperature CO adsorption. 相似文献
135.
Gil Garrote Herminia Domínguez Juan C. Parajó 《Applied biochemistry and biotechnology》2001,95(3):195-207
Milled corncob samples were mixed with water and heated to obtain a liquid phase containing oligosaccharides, sugars, and
acetic acid as main reaction products (autohydrolysis reaction). To hydrolyze the sugar oligomers to the correspondent monomers,
sulfuric acid was added to the autohydrolysis liquors to reach 0.5–2 wt% of solution, and the reaction media were heated at
101.5–135°C. With this operational procedure, sugar solutions suitable as fermentation media (containing xylose as the major
component) were obtained. The kinetics of the posthydrolysis step was characterized on the basis of experimental data concerning
the time courses of the concentrations of xylooligosaccharides, xylose, furfural, and acetic acid. The concentrations of other
reaction byproducts (glucose or arabinose) were also measured. 相似文献
136.
Mónica S. Estevão Filipe J.S. Duarte Eduarda Fernandes A. Gil Santos M. Manuel B. Marques 《Tetrahedron letters》2012,53(16):2132-2136
Several trifluoromethylated compounds were reacted with indole sodium salt, leading to monofluorinated compounds. The unexpected products formation was rationalized by DFT calculations. 相似文献
137.
138.
139.
Preparation and characterization of some unusually transparent poly(dimethylsiloxane) nanocomposites
Guru S. Rajan Gil S. Sur James E. Mark Dale W. Schaefer Gregory Beaucage 《Journal of Polymer Science.Polymer Physics》2003,41(16):1897-1901
A technique was developed for preparing poly(dimethylsiloxane) nanocomposites having unusually high transparencies as quantitatively judged by ultraviolet–visible spectroscopy. The method was the in situ generation of silica particles by a two‐step sol–gel procedure in which the required water of hydrolysis was simply absorbed from the air, and the catalyst was generated in situ from a tin salt. Electron microscopy showed that the phase‐separated silica domains were very small (30–50 nm in diameter) and well dispersed, as expected from the transparency of the composites. Stress‐strain measurements in tension indicated that the particles provide very good reinforcement. Ultra‐small‐angle X‐ray scattering data showed that the domain morphology depends strongly on catalyst, but weakly on loading level. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1897–1901, 2003 相似文献
140.
Mauricio Gomes Constantino Valdemar Lacerda Júnior Gil Valdo Jos Da Silva 《Journal of heterocyclic chemistry》2003,40(2):369-371
A new and efficient 2‐step synthesis of 3‐hydroxychromone is described. Commercially available chromone is converted to the corresponding epoxide which is rearranged with niobium pentachloride to 3‐hydroxychromone in 61% overall yield. 相似文献