Vitamin D and calcium metabolism in relation to different levels of vitamins B6 and D]

The influence of vitamin B6 deficiency on some vitamin D-dependent processes was studied in animals. The following parameters changing in relation to the level of vitamin D providing were investigated: activity of alkaline phosphatase in the serum and small intestine mucosa, the levels of Ca, P and parathormone, concentration of vitamin D metabolites and enzyme activity; and only 25-hydroxyvitamin D (25-OVD) concentration in the blood serum, under conditions of combined vitamin B6 and D deficiency was significantly lower as compared to cases with vitamin D deficiency alone. In the presence of vitamin B6 deficiency recovery of 25-OVD level in the blood serum, after vitamin D administration to the animals, had a tendency to delay as compared to that in the animals provided with vitamin B6. Vitamin B6 deficiency produced similar effect on 25-OVD 1-hydroxylase activity. The data obtained have evidenced a possibility of vitamin B6 influence on vitamin D metabolism.     

Effect of technological parameters on the mutual penetration of copper and iron in laser cladding of steel with a copper–nickel alloy

A copper–nickel alloy was deposited on steel using a powerful fibre laser. Beads of different height and width were produced by varying the process parameters. The results of metallographic examination show that at optimum cladding conditions there are areas of unmelted steel. In areas where the steel is melted the penetration depth, the width of the transition zone from steel to copper, the depth of penetration of the cracks caused by the Rehbinder effect and the content of the iron phase in the copper layer are lower than in other conditions.     

Organic polymers as pore-regulating agents in TiO2–Al2O3 mixed oxide catalytic supports

The synthesis of TiO2–Al2O3 mixed oxide catalytic supports with a TiO2/(TiO2+Al2O3) molar ratio equal to 0.5, was made by the co-precipitation of the corresponding metallic isopropoxides using different organic polymers as pore-regulating agents. The influence of the preparation parameters (type of polymeric additive, its amount, molecular weight and method of additive incorporation into the hydroxide precipitate) on the surface area and pore structure of the final solid were studied. It was found that organic polymers added during the hydrolysis step, in general, resulted in a significant increase in surface area and total pore volume. In all cases the pore-size distribution becomes clearly bimodal with two maxima in the pore-size distribution curve around 3 and 30–50 nm. In order to investigate the action mechanism of the polymeric additives, characterizations by Fourier transform-infrared, thermogravimetric/differential thermogravimetry and differential thermal analysis, as well as a TEM study of the hydroxide precipitates before calcination, were carried out. The results from these characterizations indicate that the textural changes induced by the polymeric additives can be rationalized in terms of a filler effect in the case where the additive is incorporated during the filtration step, and that when the additive is added during the hydrolysis step it is the chemistry of the polymer functional groups which determines the final texture of the solid. © 1998 Chapman & Hall     

Ni and Mo interaction with Al-containing MCM-41 support and its effect on the catalytic behavior in DBT hydrodesulfurization

A series of Mo and NiMo catalysts supported on Al-containing MCM-41 was prepared and characterized by N₂ physisorption, XRD, ammonia TPD, temperature programmed reduction (TPR), UV-Vis diffuse reflectance spectroscopy (DRS) and ²⁷Al MAS-NMR. It was shown that the incorporation of Al atoms into the siliceous MCM-41 framework causes a deterioration of the textural characteristics and some loss in the periodicity of the MCM-41 pore structure. However, the acidity of the Al-containing MCM-41 is substantially higher. The dispersion of Mo and Ni oxidic species increases with the incorporation of aluminum in the MCM-41 support due to the strong interaction of Mo and Ni oxidic species with aluminum atoms of the support. However, the strong interaction of metal species with the Al-containing MCM-41 supports, up to the formation of Al₂(MoO₄)₃ in the case of unpromoted Mo catalysts, produces an increase in the proportion of Ni and Mo species difficult to reduce. When Ni and Mo are impregnated simultaneously the formation of Al₂(MoO₄)₃ is prevented because of the competitive interaction of both, Ni and Mo species, with Al atoms of the support. For both, Mo and NiMo catalysts, maximum catalytic activity in dibenzothiophene (DBT) hydrodesulfurization is observed for the catalysts supported on Al-MCM-41 with SiO₂/Al₂O₃ molar ratio of 30. When Al-containing MCM-41 is used as a support for NiMo catalyst, some cracking of the main reaction products (biphenyl (BiP), cyclohexylbenzene (CHB) and dicyclohexyl (DCH)) is observed.     

Microwave synthesis of nanosized particles of a complex oxide system with a garnet structure

The possibility of applying the method of microwave synthesis for the fabrication of nanosized particles of complex oxides has been demonstrated. The effect of fabrication conditions on the size of nanoparticles with a garnet structure has been established on the example of the Gd–Ga–Al–O system. The concentration of the organic solvent for obtaining particles of an average size of 50 nm has been determined experimentally. The phase composition of thermally treated samples has been investigated. The optimal conditions of producing nanosized powders of garnets, Gd₃(Ga,Al)₅O₁₂, have been determined.     

Numerical simulation and experimental investigations of hydrodynamics and heat transfer for radial gas flow in an apparatus with ball packing

Results of numerical simulation and experimental data on hydrodynamics and heat transfer during radial gas flow in a bed of ball elements are presented.     

Investigation of the saturated vapor pressure of the Cu2Se and CuInSe2 compounds

The saturated vapor pressure of the Cu₂Se and CuInSe₂ compounds is investigated using the gravimetric method in the temperature ranges 1282–1450 and 1173–1423 K, respectively. It is demonstrated that, in the case of congruent vaporization, the temperature dependences of the saturated vapor pressure of the Cu₂Se and CuInSe₂ compounds in the temperature ranges under investigation are adequately described by the equation logP = ?A/T + B. The enthalpy and entropy of vaporization are estimated for both compounds.     

Flow Properties of Majolica Slip with a Thinning Additive Based on Sodium Polyacrylate

The effect of a new thinning agent, namely 40% sodium polyacrylate (SPA), on flow properties of majolica slip and the effect of hardness of water on changes in suspension moisture are considered. The use of 40% SPA makes it possible to reduce its content in slip by nearly half, compared to sodium silicate solution, to improve the slip flow properties, and to insignificantly decrease its moisture. An optimum content of 40% SPA in thinning a polymineral clay slip from the Gzhel'skoe deposit and a majolica mixture is determined.     

Mesenchymal Stem Cells Can Both Enhance and Inhibit the Cellular Response to DNA Immunization by Genes of Nonstructural Proteins of the Hepatitis C Virus

Despite extensive research, there is still no vaccine against the hepatitis C virus (HCV). The aim of this study was to investigate whether MSCs can exhibit adjuvant properties during DNA vaccination against hepatitis C. We used the pcNS3-NS5B plasmid encoding five nonstructural HCV proteins and MSCs derived from mice bone marrow. Five groups of DBA mice were immunized with the plasmid and/or MSCs in a different order. Group 1 was injected with the plasmid twice at intervals of 3 weeks; Group 2 with the plasmid, and after 24 h with MSCs; Group 3 with MSCs followed by the plasmid the next day; Group 4 with only MSCs; and Group 5 with saline. When the MSCs were injected prior to DNA immunization, the cell immune response to HCV proteins assessed by the level of IFN-γ synthesis was markedly increased compared to DNA alone. In contrast, MSCs injected after DNA suppressed the immune response. Apparently, the high level of proinflammatory cytokines detected after DNA injection promotes the conversion of MSCs introduced later into the immunosuppressive MSC2. The low level of cytokines in mice before MSC administration promotes the high immunostimulatory activity of MSC1 in response to a DNA vaccine. Thus, when administered before DNA, MSCs are capable of exhibiting promising adjuvant properties.