Enantiocomplementary inverting sec-alkylsulfatase activity in cyano- and thio-bacteria Synechococcus and Paracoccus spp.: selectivity enhancement by medium engineering

Whole resting cells of cyano- and thio-bacteria Synechococcus and Paracoccus spp. were shown to possess inverting alkylsulfatase activity for a broad spectrum of sec-alkylsulfate esters, which furnished either (R)- or (S)-sec-alcohols from the corresponding rac-sulfate esters in an enantiocomplementary fashion. Low enantioselectivities (E-values 1–4) could be dramatically improved by the addition of lower alcohols (e.g., t-BuOH) or by using a biphasic medium containing t-BuOMe (E >200).     

Simulation of the speckle pattern rotation in an absorbing optical fiber under the change of sign of the circular polarization of propagating light

The effect of rotation of a speckle pattern of circularly polarized light outgoing from a few-mode absorbing optical fiber under the change of sign of the circulation is numerically simulated on the basis of the wave approach. The theoretically predicted parabolic dependence of the value of the angle of rotation of the speckle pattern on the fiber length is discussed. Optical fibers with power-law refractive index profiles are considered.     

Chains anisotropy in PDMS networks due to friction on gold surfaces

In this article, we describe an experimental friction study of poly(dimethyl siloxane) (PDMS) networks on metallic substrates such as gold-coated slides, and under different conditions. The friction generates a transfer of a thin layer of PDMS and a preferential orientation of the polymer chains at the interface. However, the characterization of this layer is complicated, given the small amount of matter and the contact with a metallic surface. The polarization-modulation infrared reflexion-absorption spectroscopy (PM-IRRAS), which is an excellent tool for anisotropy and orientation studies, was used to characterize the PDMS transferred layer. Our results showed an induced anisotropy due to the friction, and in which PDMS chains are lying parallel to the gold substrate surface. Our spectroscopic analyzes allowed us to imagine a scheme of PDMS transfer on the gold surface. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2348–2353, 2004     

Controlled quantum interference of Mössbauer radiation in resonant scattering

Previously, our group described a quantum-interference effect (“valve effect”) to be expected in the resonant scattering of Mössbauer photons in the NMR mode. In the present study, it is shown that similar effects also occur in resonant-scattering spectra at the point of anticrossing of nuclear sublevels. Dynamical level anticrossing is also examined in this context.     

Derivation of the system of evolution equations in optical filaments

A system of differential evolution equations for numerical modeling of the radiation propagation process is obtained for the amplitude of the field of an optical filament taking into account coupling coefficients. It is shown that, in optical filaments consisting of single-mode light guiding elements, the field amplitude in the transverse cross section of the filament satisfies a parabolic equation (the paraxial wave equation). The “diffusion” coefficient is defined by the distance between the centers of light guiding cores and the overlapping integral of interacting modes (the value of cross noise). In the case of few-mode and multimode light guiding channels, the system of equations can be solved using the method of splitting in physical processes.     

One-loop corrections to the Drell–Yan process in SANC: the charged current case

Radiative corrections to the charged current Drell–Yan processes are revisited. Complete one-loop electroweak corrections are calculated within the automatic SANC system. Electroweak scheme dependence and the choice of the factorization scale are discussed. Comparisons with earlier calculations are presented. PACS 13.85.Qk, 12.15.Lk     

Resonance fluorescence of gamma radiation under conditions of coherent mixing of Mössbauer sublevels

A method is proposed for calculating the resonance fluorescence spectrum of coherent gamma radiation with a finite linewidth under conditions when the sublevels of the ground nuclear state are coupled through a strong field. The spectrum line shape is substantially affected by both the coherent effects induced in the system by a strong field and the finite gamma-radiation width. The results obtained earlier and in this work give impetus to experimental investigations into the coherence of a quantum system and quantum interference of Mössbauer gamma transitions through the excitation of coherent magnetization dynamics or an optical subsystem in solids.     

Interpretation of Isotope Exchange Data “without Time”: Nonisothermal Exchange of Dioxygen with Oxides1

As a result of transformation of isotope-exchange rate equations (isotope-kinetic equations), a relationship was derived that does not contain time and universally relates the variables of isotope composition (an isotope-mechanistic equation). With the use of this relationship, mechanistic parameters that characterize atomic rearrangements can be determined from experimental data even in cases when the rate of exchange varied in the course of a process, for example, under nonisothermal conditions. The use of the proposed approach for the treatment of the results of dynamic thermal isotope exchange in the O₂–YBa₂Cu₃O _y and O₂–Pt/CeZrO systems demonstrated that the experimental data were excellently described by the theoretical equation derived in this work     

The generation,propagation, and extinction of multiphases in the KdV zero‐dispersion limit

We study the multiphases in the KdV zero‐dispersion limit. These phases are governed by the Whitham equations, which are 2g + 1 quasi‐linear hyperbolic equations where g is the number of phases. We are interested in both the interaction of two single phases and the breaking of a single phase for general initial data. We analyze in detail how a double phase is generated from the interaction or breaking, how it propagates in space‐time, and how it collapses to a single phase in a finite time. The Whitham equations are known to be integrable via a hodograph transform. The crucial step in our approach is to formulate the hodograph transform in terms of the Euler‐Poisson‐Darboux solutions. Under our scheme, the zeros of the Jacobian of the transform are given by the zeros of the Euler‐Poisson‐Darboux solution. Hence, the problem of inverting the hodograph transform to give the Whitham solution reduces to that of counting the zeros of the Euler‐Poisson‐Darboux solution. © 2002 Wiley Periodicals, Inc.