The elastic,electronic, and optical properties of PtSi and PtGe compounds

The structural, mechanical, electronic and optical properties of orthorhombic PtSi and PtGe were investigated using norm-conserving pseudopotentials within the local density approximation in the frame of density functional theory. The calculated lattice parameters and bulk modulus for PtSi and PtGe have been compared with the experimental and theoretical values. The second-order elastic constants were calculated, and the other related quantities such as the Young's modulus, shear modulus, Poisson's ratio, anisotropy factor, sound velocities and Debye temperature have also been estimated. The linear photon-energy dependent dielectric functions and some optical properties such as the energy-loss function, the effective number of valance electrons and the effective optical dielectric constant were calculated. Our structural estimation and some other results are in agreement with the available experimental and theoretical data.     

Analytical evaluation of cylindrical exponential integrals arising in radiative transfer

New analytical results are presented performing to cylindrical exponential integral (CEI) functions for integer and noninteger values of parameter n. These integrals are often employed of two-dimensional radiative transfer in an absorbing-emitting medium and determination of the radiative flux in cylindrical media. The simple and efficient algorithm for the calculation of these functions is developed. The series expansion relations established in this work are accurate enough in the whole range of parameters.     

Calculation of two-center overlap integral in molecular coordinate system over Slater type orbital using Löwdin α-radial and Guseinov rotation–angular functions

By use of Löwdin and Guseinov relations for the radial and angular part of two-center overlap integrals, respectively, the computer calculations of overlap integrals over Slater type orbitals (STOs) in molecular coordinate system are performed. The results of calculations are valid for arbitrary principal quantum numbers, screening constants and location of STOs. Excellent agreement with benchmark results and stability of the technique are demonstrated.     

Three-component condensation of diethyl isophthaloyldiacetate, aromatic aldehyde, and urea as a new method for the synthesis of 1,3-bis(2-oxo-1,2,3,4-tetrahydropyrimidin-6-yl)benzenes

Condensation of diethyl isophthaloyldiacetate, aromatic aldehyde, and urea in the presence of Me₃SiCl proceeds efficiently and faster than in the absence of the latter to form 1,3-bis(2-oxo-1,2,3,4-tetrahydropyrimidin-6-yl)benzene derivatives capable to give inclusion complexes with DMF. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1233–1239, June, 2008.     

Synthesis of 5-[bromo(aryl)methyl]-2,2-dimethyl-1,3-oxazolidin-4-ones

A Darzens condensation of α-chloroacetamide with aromatic aldehydes furnished a series of 3-aryl-2,3-epoxypropionamides, which were further converted to 5-[bromo(aryl)methyl]-2,2-dimethyl-1,3-oxazolidin-2-ones.     

Comparative study of the water oxidizing reactions and the millisecond delayed chlorophyll fluorescence in photosystem II at different pH

Water splitting activity, the multiline EPR signal associated with S(2)-state of the CaMn(4)-cluster and the fast and slow phases of the induction curve of the millisecond delayed chlorophyll fluorescence from photosystem II (PSII) in the pH range of 4.5-8.5 were studied in the thylakoid membranes and purified PSII particles. It has been found that O(2) evolution and the multiline EPR signal were inhibited at acidic (pK approximately 5.3) and alkaline (pK approximately 8.1) pH values, and were maximal at pH 6.0-7.0. Our results indicate that the loss of O(2) evolution and the S(2)-state multiline EPR signal associated with the decrease of the millisecond delayed chlorophyll fluorescence only in alkaline region (pH 7.0-8.5). Possible correlations of the millisecond delayed chlorophyll fluorescence components with the donor side reactions in PSII are discussed.     

Spectroscopic studies of sorbing fibers using combined elements with multiple attenuated total internal reflection

Spectroscopic studies of sorbing devices on the basis of silica capillaries coated by sorbing polymer films are carried out by methods of spectroscopy of multiple attenuated total internal reflection with the use of combined elements of internal reflection. A technique for inspecting and improving the technological process of manufacture of sorbing devices for solid-phase microextraction and subsequent chromatographic analysis of organic compounds is developed.     

Heat source optimization in a multisection heater for the growth of bismuth germanate crystals by the low-gradient Czochralski method

The growth of bismuth germanate crystals with uniform heater control has been simulated within the time-dependent approach. To optimize the multisection heater control, the global heat transfer optimization problem in a crystallization setup was considered. A new control algorithm, based on the solution of the optimization problem, is proposed.     

Control of temperature field and residual stresses in growing basal-plane-faceted sapphire ribbons

The influence of different heat shielding constructions on the distribution of temperature and thermoelastic and residual stresses in growing basal-plane-faceted sapphire ribbons (Al₂O₃) is studied. It is shown that inclined shields decrease thermoelastic stresses owing to the redistribution of heat fluxes from a heater to a ribbon, which allows growing block-free basal-plane-faceted sapphire ribbons.