Processing,Microstructure, and Mechanical Properties of B4C ― TiB2 Particulate Sintered Composites. Part I. Pressureless Sintering and Microstructure Evolution

Pressureless sintering of boron carbide ceramics containing 0-25 vol. % TiB₂ phase, produced via an in-situ chemical reaction between B₄C, TiO₂, and elemental carbon, was studied in the isothermal and constant-heating-rate regimes. The presence of TiB₂ results in a decrease in activation energy for sintering from 717 kJ/mol at 0 vol. % TiB₂ to 266 kJ/mol at 25 vol. % TiB₂. Ceramic bodies of B₄C TiB₂ particulate composites with relative densities of up to 99% were sintered without pressure at temperatures of 2050-2100°C. Grain boundary diffusion is the primary mechanism of TiB₂ particle coarsening. TiB₂ particle size is bimodal depending on whether the particle is confined within a B₄C grain or located on the grain boundary. Densification behavior of the B₄C TiB₂ system is identical at different heating rates in the temperature range of 1800-2150°C.     

Calibration-free method to determine the size and hemoglobin concentration of individual red blood cells from light scattering

At present, hemoglobin concentration and the volume of an erythrocyte can be determined from the intensities of light scattered by an individual cell at fixed angular intervals. This method is used in modern hemoglobin analyzers, but it requires calibration of optical and electronic units by certified particles of known size and refractive index. We describe a method that is based on the parametric solution of an inverse light-scattering problem and does not require a calibration procedure. The method is based on the use of parameters of the entire angular light-scattering pattern, called an indicatrix here. These parameters do not depend on the absolute intensity of light scattering. The indicatrix parameters form approximating equations that relate these parameters to the size and the phase-shift parameters of the particle. The applicability of the method is demonstrated by measurement of the indicatrices of individual sphered erythrocytes. The indicatrices of the individual erythrocytes were measured with a scanning flow cytometer at an angular range of from 15 to 55 deg. The volume and the hemoglobin concentration have been calculated by use of the developed method and by fitting of the experimental indicatrices to the indicatrices calculated from the Mie theory.     

Sum-Frequency Generation of Femtosecond Pulses in CsLiB(6)O(10) Down to 175 nm

Using a 150-mum-thick CsLiB(6)O(10) crystal, we produced 100-fs, >200-nJ light pulses tunable between 175 and 180 nm by sum-frequency generation at a 1-kHz repetition rate with an all-solid-state laser system mixing the fourth harmonic of a femtosecond Ti:sapphire regenerative amplifier and the idler pulse from a traveling-wave optical parametric amplifier.     

Organization of monitoring the safety of hydraulic structures of the Volga-Lenin hydroelectric station

Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 1, pp. 23–25, January, 1994.     

Concept of acceptable risk in space flight medical support system

The concept of acceptable risk is considered in the context of the system of medical support to space missions. Risk is defined as probability of cosmonaut's health and life deterioration as a result of spaceflight impacts on the human body. Mathematical formulas giving the general characteristic of the relations among risk components, total risk, and human survivability in flight and after its end. The earlier published quantitative recommendations for these parameters are inserted as illustration.     

Reverse adaptation studied by recording short-latency auditory evoked potentials

Difficulties of diagnosis of pleural neoplasms in biopsies are discussed. The short history of serous tumors as entity, their classification, methodological approaches to their morphological diagnosis are outlined. It is concluded that the problem of neoplastic pleural diseases verification can be solved by clinical and morphological correlations. Histochemistry, immunomorphology, and electron microscopy should be combined with conventional morphologic methods used in biopsy investigations.