Structure and Certain Properties of Hot-Pressed Boron Carbide-Based Ceramic with Calcium-Silicon Additive

The influence which the composition of powder mixtures, the treatment conditions which the mixtures are subjected to, and the conditions under which the hot-pressed composite materials B₄C – (5-10 mass%) calcium-silicon are fabricated exert on the structure, nature of failure, and mechanical properties of these materials is investigated. Optimum properties are possessed by material containing 10 mass% of addition. It is shown that the structure, morphology, and dispersivity, as well as the nature of the distribution of the components that are added to the composite material (secondary phase) vary as the temperature of hot pressing changes. Maximal mechanical characteristics of the composite material (σ_bend = 560 MPa, K _1c = 4.7 MPa·m^1/2, HV = 37 GPa) are attained at hot-pressing temperatures in the range 2000-2100°C.     

Molecular Mechanisms of the Deregulation of Muscle Contraction Induced by the R90P Mutation in Tpm3.12 and the Weakening of This Effect by BDM and W7

Point mutations in the genes encoding the skeletal muscle isoforms of tropomyosin can cause a range of muscle diseases. The amino acid substitution of Arg for Pro residue in the 90th position (R90P) in γ-tropomyosin (Tpm3.12) is associated with congenital fiber type disproportion and muscle weakness. The molecular mechanisms underlying muscle dysfunction in this disease remain unclear. Here, we observed that this mutation causes an abnormally high Ca²⁺-sensitivity of myofilaments in vitro and in muscle fibers. To determine the critical conformational changes that myosin, actin, and tropomyosin undergo during the ATPase cycle and the alterations in these changes caused by R90P replacement in Tpm3.12, we used polarized fluorimetry. It was shown that the R90P mutation inhibits the ability of tropomyosin to shift towards the outer domains of actin, which is accompanied by the almost complete depression of troponin’s ability to switch actin monomers off and to reduce the amount of the myosin heads weakly bound to F-actin at a low Ca²⁺. These changes in the behavior of tropomyosin and the troponin–tropomyosin complex, as well as in the balance of strongly and weakly bound myosin heads in the ATPase cycle may underlie the occurrence of both abnormally high Ca²⁺-sensitivity and muscle weakness. BDM, an inhibitor of myosin ATPase activity, and W7, a troponin C antagonist, restore the ability of tropomyosin for Ca²⁺-dependent movement and the ability of the troponin–tropomyosin complex to switch actin monomers off, demonstrating a weakening of the damaging effect of the R90P mutation on muscle contractility.     

Hydrotreating processes for catalytic abatement of water pollutants

Opportunities and problems in application of catalytic hydrotreating processes, which are presented a viable approach in the abatement of water pollutants, are discussed. Analysis of the hydrodechlorination (HDC) and hydrodenitrification (HDN) using Pd-based catalysts supported on various materials like granulated activated carbon (GAC), fibrous activated carbon cloths (ACCs) or glass fiber cloths (GFCs) studied recently in our laboratory suggests the following perspectives:

Exhaustive regeneration of Pd/GAC saturated with p-chlorophenol can be achieved in a two-step approach, incorporating gas-phase HDC by hydrogen followed by oxidation by air.

Pd/ACC catalysts are good candidates for the liquid-phase HDC showing activity higher than that of Pd/GAC or Pd/GFC; the high adsorption capacity of Pd/ACC lead suggesting its use in a technology with periodic adsorption and HDC, in similarity to adsorption with regeneration of GAC.

Pd/GFC and Pd–Cu/GFC are promising catalyst for removal of nitrites and nitrates, showing activity and selectivity that compares favorably with those of powdered catalysts.

Oxidation of methane in a wide range of pressures and effect of inert gases

The analysis of methane oxidation in a wide range of pressures (0.05–10 atm) demonstrates that the efficiency of CH₃ radicals recombination is of great importance for high selectivity of C₂ hydrocarbons formation. The relative efficiency of different “colliders” assisting the stabilization of exited C₂H*₆ molecules increases in the series: solid surface> Ar> He. The increase of the overall reaction rate upon increasing pressure of the inert gases in the case of catalysts having a higher surface area and more developed pore structure is likely due to the contribution of the surface-induced chain reaction in the volume of pores.     

Synthesis,Structure, Spectral-Luminescent Properties,and Biological Activity of Chlorine-Substituted N-[2-(Phenyliminomethyl)phenyl]-4-methylbenzenesulfamide and Their Zinc(II) Complexes

New azomethine compounds of 2-(N-tosylamino)benzaldehyde or 5-chloro-2-(N-tosylamino)benzaldehyde and the corresponding chlorine-substituted anilines, zinc(II) complexes based on them have been synthesized. The structures of azomethines and their complexes were determined by elemental analysis, IR, ¹H NMR, X-ray spectroscopy, and X-ray diffraction. It is found that all ZnL₂ complexes have a tetrahedral structure according to XAFS and X-ray diffraction data. The photoluminescent properties of azomethines and zinc complexes in methylene chloride solution and in solid form have been studied. It is shown that the photoluminescence quantum yields of solid samples of the complexes are an order of magnitude higher compared to the solutions and range from 11.34% to 48.3%. The thermal properties of Zn(II) complexes were determined by thermal gravimetric analysis (TGA) and differential scanning calorimetry. The TGA curves of all the compounds suggest their high thermal stability up to temperatures higher than 290 °C. The electrochemical properties of all complexes were investigated by the cyclic voltammetry method. The multilayered devices ITO/PEDOT:PSS/NPD/Zn complex/ TPBI/LiF/Al with wide electroluminescence (EL) color range spanning the range from bluish-green (494 nm) to green (533 nm) and the high values of brightness, current and power efficiency were fabricated. The biological activity of azomethines and zinc complexes has been studied. In the case of complexes, the protistocidal activity of the zinc complex with azomethine of 5-chloro-2-(N-tosylamino)benzaldehyde with 4-chloroaniline was two times higher than the activity of the reference drug toltrazuril.     

Synthesis and characterization of {Fe2CuO} clusters as precursors for nanosized catalytic system for Biginelli reaction

The novel μ₃-oxo-bridged heterotrinuclear iron(III)-copper(II) trichloroacetates of the composition [Fe₂CuO(CCl₃COO)₆(THF)₃] (1a) and [Fe₂CuO(CCl₃COO)₆(4-DMAP)₃] (1b) have been synthesized and characterized by X-ray crystallography, IR and Mossbauer spectroscopy. These clusters were used as precursors for the synthesis of the nanosized catalytic system (～5–6 nm of γ-Fe₂O₃/CuO), which works as an efficient organic phase catalyst (～0.02 mol%) in a one-pot three component Biginelli synthesis.     

Phase Equilibria in the Nd ― Re ― B System

Powder Metallurgy and Metal Ceramics - XRD has been applied to component interaction in the Nd ― Re ― B system. Isothermal sections have been constructed for the phase diagram at...     

Sintered Antifriction Materials for Use at Elevated Temperatures

The mechanical and antifriction properties of three types of new materials were investigated. These were based on powder scrap of steel R6M5, nickel, and the powder metallurgy nickel alloy ÉP975. The metallographic structures of the new materials were studied. It was shown that the developed materials can be successfully used in friction units operating at 500, 700, and 900°C, respectively.