Raman characterization and UV optical absorption studies of surface plasmon resonance in multishell nanographite

Nanographite (NG) particles were produced by annealing of superpurified detonation nanodiamonds (grain size ~ 5 nm) at 1600 °C. The aim of this research was to provide Raman characterization of nanographites obtained and to investigate characteristic features of UV optical absorption in NG suspensions caused by the excitation of surface plasmon resonance (SPR) and its dependence on disorder and defectiveness of graphene shells during their transformation. The 1-st and 2-nd order Raman spectra of the NG samples excited at 514 nm were analyzed. Two different approaches applied for evaluation of the in-plane NG crystallite sizes by using the D- and G-band intensities ratio gave quite different results (~ 3.5 nm and ~ 5.5 nm) reflecting, most likely, a complicated NG structure. The changes in both intensity and position of SPR absorption peak for water suspension of NG particles may originate in structural imperfections and/or changes in aggregation of NG particles.     

Changes in the Number of Double-Strand DNA Breaks in Chinese Hamster V79 Cells Exposed to γ-Radiation with Different Dose Rates

A comparative investigation of the induction of double-strand DNA breaks (DSBs) in the Chinese hamster V79 cells by γ-radiation at dose rates of 1, 10 and 400 mGy/min (doses ranged from 0.36 to 4.32 Gy) was performed. The acute radiation exposure at a dose rate of 400 mGy/min resulted in the linear dose-dependent increase of the γ-H2AX foci formation. The dose-response curve for the acute exposure was well described by a linear function y = 1.22 + 19.7x, where “y” is an average number of γ-H2AX foci per a cell and “x” is the absorbed dose (Gy). The dose rate reduction down to 10 mGy/min lead to a decreased number of γ-H2AX foci, as well as to a change of the dose-response relationship. Thus, the foci number up to 1.44 Gy increased and reached the “plateau” area between 1.44 and 4.32 Gy. There was only a slight increase of the γ-H2AX foci number (up to 7) in cells after the protracted exposure (up to 72 h) to ionizing radiation at a dose rate of 1 mGy/min. Similar effects of the varying dose rates were obtained when DNA damage was assessed using the comet assay. In general, our results show that the reduction of the radiation dose rate resulted in a significant decrease of DSBs per cell per an absorbed dose.     

Mass Action Law in Two-Temperature Reacting Systems

Within the framework of linear nonequilibrium thermodynamics, a generalization of the mass action law to the case of two-temperature reacting gases is performed. Concrete calculations are performed for the dissociation of diatomic molecules and ionization of atoms under conditions when the translational temperature of heavy particles differs from the vibrational temperature of molecules and from the temperature of electrons.     

A choice of trailing edge diameter of gas turbine blades

A possibility of increasing the efficiency and profitability of gas-turbine installations by optimization of the geometry of trailing parts of the blades profiles is considered. This is done on the basis of actual data on characteristics of the blades of gas turbines manufactured by Western companies.     

Density of clay minerals

Variation in the density of clay minerals with a crystal lattice that swells during hydration is examined. It is demonstrated that greatest intracrystal swelling is attained at the maximum hygroscopic moisture content, involving a reduction to 49% in the density of the solid component. The concept of intracrystal ultramicroporosity n _s is introduced. The values of n _s, which must be considered for solution of practical problems, is analyzed.     

Assessment of turbine blade lifetime used with a power unit during normalized primary frequency regulation

Full-size steam turbine blades were tested using the method of simulation modeling of the operational load on a servo hydraulic test system. Comparative evaluation of the turbine unit’s different operational modes influencing the lifetime of blades is represented, including participation of the power unit in the normalized primary frequency regulation.     

Group-III-nitride-based light-emitting diode on silicon substrate with epitaxial nanolayer of silicon carbide

A light-emitting diode (LED) structure based on group III nitride has been grown for the first time on Si(111) substrate with SiC buffer nanolayer (50- to 200-nm-thick) obtained by solid-phase epitaxy. This LED structure is characterized by record low (<10⁸ cm⁻²) density of lattice misfit dislocations at a total dislocation density of ∼8 × 10⁸ cm⁻². The photo- and electroluminescence spectra of obtained structures have been measured.     

Reduced gravitropism in hypocotyls of starch-deficient mutants of Arabidopsis

Gravitropism was examined in dark- and light-grown hypocotyls of wild-type (WT), two reduced starch mutants (ACG 20 and ACG 27), and a starchless mutant (ACG 21) of Arabidopsis. In addition, the starch content of these four strains was studied with light and electron microscopy. Based on time course of curvature and orientation studies, the graviresponse in hypocotyls is proportional to the amount of starch in a genotype. Furthermore, starch mutations seem to primarily affect gravitropism rather than differential growth since both phototropic curvature and growth rates among the four genotypes are approximately equal. Our results suggest that gravity perception may require a greater plastid mass in hypocotyls compared to roots. The kinetics of gravitropic curvature also was compared following reorientation at 45 degrees, 90 degrees, and 135 degrees. As has been reported for other plant species, the optimal angle of reorientation is 135 degrees for WT Arabidopsis and the two reduced starch mutants, but the magnitude of curvature of the starchless mutant appears to be independent of the initial angle of displacement. Taken together, the results of the present study and our previous experiments with roots of the same four genotypes [Kiss et al. (1996) Physiol. Plant. 97: 237] support a plastid-based hypothesis for gravity perception in plants.     

Nanopowders of orthophosphate LaPO4-YPO4-H2O system and ceramics based on them

Nanopowders of orthophosphate LaPO₄-YPO₄-H₂O system have been synthesized via the solgel method, and the limits of the mutual solubility of components have been specified through the calculation of the parameters of the unit cell. The dense ceramics were prepared based on the La_{1 ? x} Y _x PO₄ · nH₂O nan-opowders at 1000 and 1200°C. The porosity, microhardness, and bending strength of the ceramics were determined, and the dependence of the microhardness on the calcination time was established. The thermal behavior of the samples was studied by dilatometric method and the thermal coefficient of linear expansion of the ceramics was estimated.     

Assessing the condition of reinforcement in concrete using the gamma-absorption method

Basic concepts of an algorithm for assessing the condition of reinforcement in concrete are discussed. Analytical expressions for estimating the errors in the parameter characterizing the damage to steel reinforcement components have been obtained. A formula for calculating the efficiency of the testing procedure has been derived.