Interaction of Oxide Melt with External-Trap Zirconium Dioxide Refractories

The results of an investigation of the interaction of zirconium dioxide refractories – ceramic and concrete with iron oxides – are presented. The investigations showed that starting at 1600 K in an argon atmosphere contact of a mixture of iron oxides with refractories gives rise to erosion of the latter. Under isothermal conditions (2270 K), ceramic with 16% porosity completely absorbs a melt with mass 1/7 of the ceramic mass. The concrete confines the same melt mass with a lower temperature 1870 K and, in the process, unlike the ceramic, it loses strength.The results obtained and the published data were used to analyze the operation of a refractory protective layer of an EPR trap.     

Phosphatidylinositol 3-kinase-gamma activates Bruton's tyrosine kinase in concert with Src family kinases

Bruton's tyrosine kinase (Btk) is essential for normal B lymphocyte development and function. The activity of Btk is partially regulated by transphosphorylation within its kinase domain by Src family kinases at residue Tyr-551 and subsequent autophosphorylation at Tyr-223. Activation correlates with Btk association with cellular membranes. Based on specific loss of function mutations, the Btk pleckstrin homology (PH) domain plays an essential role in this activation process. The Btk PH domain can bind in vitro to several lipid end products of the phosphatidylinositol 3-kinase (PI 3-kinase) family including phosphatidylinositol 3,4,5-trisphosphate. Activation of Btk as monitored by elevation of phosphotyrosine content and a cellular transformation response was dramatically enhanced by coexpressing a weakly activated allele of Src (E378G) and the two subunits of PI 3-kinase-gamma. This activation correlates with new sites of phosphorylation on Btk identified by two-dimensional phosphopeptide mapping. Activation of Btk was dependent on the catalytic activity of all three enzymes and an intact Btk PH domain and Src transphosphorylation site. These combined data define Btk as a downstream target of PI 3-kinase-gamma and Src family kinases.     

Ceramics based on partly stabilized zirconium dioxide: technology,structure, properties,and behavior under dynamic action

Technology is described for manufacturing dense ceramic from very fine powder based on zirconium dioxide partly stabilized with yttrium oxide. Some engineering properties of the manufactured ceramic are defined. Its microstructure and phase composition are studied. Ceramic properties with impact-wave loading are studied, and values of dynamic elastic limit and spalling strength are obtained.     

Chitosan—Cellulose Films Fabricated from Mixtures of Polysaccharides in N-methylmorpholine N-oxide

The possibility of fabricating composite chitosan—cellulose films from mixed solutions of polysaccharides in MMO was demonstrated. Unoriented films of inhomogeneous phase composition exhibit elevated swelling in aqueous media (500-600%) and could be of great interest as separating membranes or film dressings.     

Optical Properties and Structure of Highly Concentrated Solutions of Cellulose in N-Methylmorpholine N-Oxide

The nature of the anisotropy of highly concentrated solutions of cellulose in MMO was investigated. The temperature-concentration intervals of the existence of nonequilibrium and thermodynamically equilibrium anisotropic states of cellulose in solutions of MMO were detected and determined. The proposed explanation of the specific features of the reaction of cellulose with MMO, which results in the formation of a mesophase, does not exhaust the group of problems of the mechanism of ordering of highly concentrated cellulose solutions and the structural characteristics of the liquid-crystalline phase formed. An examination of these questions requires conducting further detailed studies.     

Shock-induced phase transitions of C70 fullerite

Shock-induced phase transitions of C₇₀ fullerite were studied at the pressure range up to 52 GPa with use of recovery assemblies of planar geometry. The starting material consists of two crystalline phases: phase with hexagonal close-packed (HCP) and phase with rhombohedral structure. We have found that C₇₀ fullerite undergoes a series of polymorphic phase transitions in conditions of step-like shock-wave compression. In the specimens, recovered from 9, 14 and 19 GPa, a dominant phase was fullerite C₇₀ with cubic structure. Also, some amount of C₇₀ with HCP structure was observed. The quantity of HCP phase was decreasing with increasing of intensity of shock loading. With further growth of shock pressure, destruction of C₇₀ molecules occurs. In the samples, recovered after shock loading, the main phase was graphite with a low degree of three-dimensional regularity.     

Thermal Denaturation in Fish Muscle Proteins During Gelling: Effect of Spawning Condition

We studied thermal denaturation of myofibrillar proteins from pre-and post-spawning hake by differential scanning calorimetry (DSC), and evaluated denaturation kinetics under both conditions. The denaturation enthalpies of all pre-spawning fish muscle extracts were less than those from post-spawning. The area under the DSC thermogram corresponding to myosin denaturation was smaller in myofibrillar extracts from pre-spawning than from post-spawning hake, while the areas corresponding to denaturation of actin were similar. Between 40 and 55°C the myosin denaturation rates were greater for post-spawning than for pre-spawning hake. Both entalphies and kinetic data indicated proteins of fish in a better biological condition (post-spawned) denature more rapidly and completely.     

0412-1961

TAN Yanchang; HE Bin; ZHAO Yuhua (Northeast Institute of Technology, Shenyang)