Heat Transfer Through the Interface and Flow Regimes in Liquid Bridge Subjected to Co-Axial Gas Flow

We present results of an extensive numerical study on the thermocapillary (Marangoni) convection and a heat transfer through the interface in a liquid bridge of Pr?=?68. The geometry of the physical problem is a cylindrical and non-deformable liquid bridge concentrically surrounded by an annular gas channel under conditions of zero gravity. The gas flow is co- or counter-directed with respect to the Marangoni flow. The forced gas flow along the interface provides two actions: via shear stresses and heat exchange. Usually the cooling of the interface enhances the flow while the heating slows down. This general trend may not hold when shear and thermocapillary stresses are comparable. The results show that when gas enters from the cold side the heat transfer through the interface is considerably larger than that when gas enters from the hot side.     

A new high-brightness stepped-crystal diffractor for X-ray microanalysis

An electron-probe X-ray microanalyzers, the characteristic X-ray radiation is generated within a small volume of sample and the emitting surface area is on the order of 1 μm². For a distance to analyzer of approximately 0.5 m, this small emitting area can be considered as a point source. Practical implementations of the electron-probe X-ray microanalysis (EPMA) require a high spectral resolution and sufficient intensity.     

Microstructure effect on the properties of electrostrictive Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics

We have studied the effect of the mechanical activation of the starting oxide mixture on the particle size of the resulting powders and the microstructure of electrostrictive lead magnesium niobate-lead titanate ceramics. The results demonstrate that reducing the grain size of the ceramics reduces their dielectric permittivity in both weak and strong electric fields, reduces their electrostrictive coefficient M ₁₁, shifts the processes related to polarization saturation to higher electric fields, and increases the dielectric and electromechanical hystereses.     

Conjugates of Methylene Blue with Cycloalkaneindoles as New Multifunctional Agents for Potential Treatment of Neurodegenerative Disease

The development of multi-target-directed ligands (MTDLs) would provide effective therapy of neurodegenerative diseases (ND) with complex and nonclear pathogenesis. A promising method to create such potential drugs is combining neuroactive pharmacophoric groups acting on different biotargets involved in the pathogenesis of ND. We developed a synthetic algorithm for the conjugation of indole derivatives and methylene blue (MB), which are pharmacophoric ligands that act on the key stages of pathogenesis. We synthesized hybrid structures and performed a comprehensive screening for a specific set of biotargets participating in the pathogenesis of ND (i.e., cholinesterases, NMDA receptor, mitochondria, and microtubules assembly). The results of the screening study enabled us to find two lead compounds (4h and 4i) which effectively inhibited cholinesterases and bound to the AChE PAS, possessed antioxidant activity, and stimulated the assembly of microtubules. One of them (4i) exhibited activity as a ligand for the ifenprodil-specific site of the NMDA receptor. In addition, this lead compound was able to bypass the inhibition of complex I and prevent calcium-induced mitochondrial depolarization, suggesting a neuroprotective property that was confirmed using a cellular calcium overload model of neurodegeneration. Thus, these new MB-cycloalkaneindole conjugates constitute a promising class of compounds for the development of multitarget neuroprotective drugs which simultaneously act on several targets, thereby providing cognitive stimulating, neuroprotective, and disease-modifying effects.     

Correlation between the phase composition of composite YBa2Cu3O7−δ+xMeO superconductors and their strength characteristics

Experimental results on the doping of YBa₂Cu₃O_7−δ superconducting ceramic with various metals (Ti, Zr, Ag, Hf, Ta, and W) are summarized. Some conclusions are drawn on the degree of chemical interaction between the metals and the main phase of the composite responsible for the superconducting properties of the material as a whole. An assessment is also made if the influence of doping on the strength characteristics, which vary in the composite as a result of different effects examined in this study. Pis’ma Zh. Tekh. Fiz. 23, 32–37 (February 12, 1997)     

An experimental study of immunity to hepatitis A in monkeys

In this work the experimental model of hepatitis A on monkeys, adequate to human hepatitis A, was used. Ten monkeys (6 Macaca mulatta and 4 Cercopithecus aethiops) were reinfected with different doses of hepatitis A virus (HAV) a year after recovery from spontaneous and experimental hepatitis A. The monkeys were completely resistant to the inoculation of the virus in moderate doses (10(3) ID50). The inoculation of HAV in large doses (10(4)-10(5) ID50) induced a mild form of this infection in the animals with a transient rise in the level of serum alanin aminotransferase and HAV shedding in feces, but in the absence of morphological changes in the liver. It should be specially pointed out that after the reinfection of monkeys virus shedding in feces was observed, which may be of great epidemiological importance. After reinfection the absence of IgM and a pronounced rise in the titers of IgC antibodies were observed.     

Optimization of Taylor Dispersion Technique for Measurement of Mutual Diffusion in Benchmark Mixtures

The Taylor dispersion technique has been used for measuring binary mutual diffusion coefficients for mixtures of 1,2,3,4-tetrahydronaphthalene (THN), isobutylbenzene (IBB) and dodecane (C₁₂ H ₂₆) at 0.5:0.5 mass fraction symmetric points, and for 0.9:0.1 mass fraction in IBB- C₁₂ H ₂₆. From the Stokes–Einstein equation and our experimental results, the limiting diffusion coefficients, D ⁰, and the equivalent solvated radii, R _s, have been estimated at infinitesimal concentration of these species (TNH, IBB and C₁₂ H ₂₆). The measured diffusion coefficients are used to estimate activity coefficients of the components in the mixture, contributing to a better understanding of the structure of such systems and of their thermodynamic behaviour at different concentrations. We have also investigated the diffusion properties for a ternary system containing equal mass fractions of all the components (0.33THN: 0.33IBB: 0.33C₁₂ H ₂₆) and at 298.15 K.     

Giant vortex structures in mesoscopic spherical type-II superconducting samples

Giant vortex states which can occur in type-II mesoscopic spherical superconducting samples embedded in different materials have been studied within the framework of the nonlinear Ginzburg–Landau theory. The proposed method, which is based on presentation of the superconducting order parameter in a form of the spherical functions expansion gives the possibility to take into account different types of boundary condition.     

Structure clusterization preceding concentration phase transitions

The formation and development of bulk crystallochemical defects—mesoscopic clusters representing the nuclei of new phases—was studied in systems exhibiting concentration phase transitions. When a solid solution approaches a morphotropic region, the clusters exhibit a stepwise evolution involving several stages manifested by corresponding changes in macroscopic properties. The role of clusters in the development of the extreme electrophysical properties of the objects studied is discussed.