Radiofrequency mössbauer forward scattering spectra in magnetic materials

Radiofrequency (RF) Mössbauer spectra in experiments on forward scattering by thick samples of iron borate (FeBO₃) below the Neel temperature are measured. The spectra have satellites spaced by doubled RF-field frequency. A semiclassical model of Mössbauer transmission through a magnetic absorber exposed to RF reversals of a hyperfine field on nuclei is proposed. The model reproduces all features of the measured spectra. Experiments and modeling calculations indicate additional possibilities for studying soft magnetic materials using this measurement scheme.     

QED bremsstrahlung in decays of electroweak bosons

Isolated lepton momenta, in particular their directions are the most precisely measured quantities in pp collisions at LHC. This offers opportunities for multitude of precision measurements. It is of practical importance to verify if precision measurements with leptons in the final state require all theoretical effects evaluated simultaneously or if QED bremsstrahlung in the final state can be separated without unwanted precision loss. Results for final-state bremsstrahlung in the decays of narrow resonances are obtained from the Feynman rules of QED in an unambiguous way and can be controlled with a very high precision. Also for resonances of non-negligible width, if calculations are appropriately performed, such separation from the remaining electroweak effects can be expected. Our paper is devoted to validation that final-state QED bremsstrahlung can indeed be separated from the rest of QCD and electroweak effects, in the production and decay of Z and W bosons, and to estimation of the resulting systematic error. The quantitative discussion is based on Monte Carlo programs PHOTOS and SANC, as well as on KKMC which is used for benchmark results. We show that for a large class of W and Z boson observables as used at LHC, the theoretical error on photonic bremsstrahlung is 0.1 or 0.2 %, depending on the program options used. An overall theoretical error on the QED final-state radiation, i.e. taking into account missing corrections due to pair emission and interference with initial state radiation is estimated respectively at 0.2 % or 0.3 % again depending on the program option used.     

Twistability of Spin Particle Trajectories

Using the geometric optics approximation, we establish the existence of the additional twisting effect for trajectories of spin particles, i.e., the analogue of the Magnus optical effect. The effect is determined by the polarization (chirality) and the curvature of the particle trajectory. We investigate the proton scattering in the Coulomb field of a nucleus and the mirror reflection law breaking for ultracold neutrons.     

Additional Curvature of Spinning-Particle Trajectories Proportional to the Trajectory Torsion

In the geometric optics approximation, we predict the effect of an additional curvature of the trajectories of particles (an analogue of the inverse Magnus optical effect). The effect is determined by the polarization (chirality) and torsion of particle trajectories. We find that the considered effect is linked to the Berry phase. The effect is a consequence of the conservation law for the angular momentum of the particles. We show that the effect must result in ultracold neutrons deviating from the mirror reflection law.__________Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 144, No. 3, pp. 555–563, September, 2005.     

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.