Measurement of the polarization bremsstrahlung of relativistic electrons in polycrystalline targets

The spectra of the collimated polarization bremsstrahlung of 7-MeV electrons intersecting Al, Cu, and Ni polycrystalline films have been measured. Detailed quantitative comparison of the experimental data with theoretical predictions has been performed. It has been shown that the model of a polycrystal as an ensemble of randomly oriented single crystals adequately describes the experimental results. This makes it possible to expect the development of a new method of diagnostics of the atomic structure of partially ordered solids.     

On one possibility of determining the atom position in the crystal unit cell

The possibility of the determination of the position of an atom incorporated in the crystal unit cell by measuring the yield of characteristic radiation of this atom, excited by an X-ray wave nonuniform over the cell cross section, is shown. Such a wave can appear, in particular, in the mode of dynamical diffraction of an ordinary plane wave.     

X-ray diagnostics of grain shapes in nanomaterials

It is demonstrated that an efficient method can be created and used to determine the shape of grains in nanomaterials. This method relies on the discovered correlations between the amplitudes of different Bragg peaks for wideband X rays scattered in the sample on the grain shape.     

The Kinetics of Nematic Phase Separation on Cooling the Isotropic Phase of Mesogenic Siloxane-Azomethine Polyether

The kinetics of nematic phase droplet growth as an isotropic melt of mesogenic siloxane-azomethine polyether was cooled was studied by polarizing microscopy. The results were processed statistically and described using the thermodynamics of irreversible processes. An analysis of the time dependences of statistical distribution parameters revealed the occurrence of two regimes of phase separation, (1) the formation of droplets and their growth and (2) coalescence of droplets. Both regimes were quantitatively described by the universal law of the growth of clusters.     

Computational methods and software in computer-aided combinatorial library design

Recent trends in the computer-aided design of diverse and focussed combinatorial libraries are surveyed. First, chemical data input, storage and retrieval including chemical database management and virtual chemical structure enumeration are outlined as background. Then, the optimization of ADMET parameters, diversity maximization, molecular similarity search, QSAR-based virtual screening, pharmacophore search and molecular docking are discussed.     

Dynamics of radiation scattering by particles of condensed phase in quasicontinuous laser irradiation of metals

Radiation scattering by particles of condensed phase in an ablation plasma plume has been experimentally studied during quasicontinuous laser irradiation (λ = 1.06 μm, q = 0.1–9 MW/cm², τ ∼ 1.5 msec) of duraluminum D16T, aluminum A99, and bismuth. The particle size distribution and the nature of their dispersal during irradiation was studied in scattered light (λ = 0.69 μm) from individual particles that could be visually observed on photographs. It was found that under the pressure developed in the plume, large particles ejected from the irradiated zone can move backward and return to the target (D16T). The plume (Bi) becomes brighter due to ablation of particles in the path of the laser beam. The directional scattering coefficients for scattering from the local zone on the axis of the plume, measured during the laser pulse, were used to study the relationship between the dynamics of entry of condensed phase into the plume, shielding of the target by the particles, and brightening of the plume under the action of the incident laser radiation. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 210–219, March–April, 2006.