Structure and Properties of the Gypsum Mortar with Silica Sand Under Temperature Load

International Journal of Thermophysics - The electrospray (ES) cooling technique, which is a combination of spray cooling and high-voltage electrostatic technology, has attracted considerable...     

Catalytic decomposition of nitric oxide by perovskites

Catalytic decomposition of nitric oxide has been studied for nearly a century, using materials ranging from noble metals to alkaline earth metal oxides, without much success. Only since about last fifteen years some progress in finding promising materials has been made. Of the numerous catalyst systems studied, very few show tangible decomposition rates : copper substituted zeolites, silver-cobalt mixed oxides, some perovskites, and supported noble metals. Although at 773 K the rates of decomposition over zeolites are two to three orders higher than those over remaining systems, these materials have very low thermal stability, above 773 K. In this respect, perovskites have much higher potential, although so far no composition exhibiting practical decomposition rates has been found. Systematic study of the effect of composition on the performance should help to advance the complete understanding of this important reaction. In this paper a current state of art is outlined, and some latest preliminary results for new specially formulated perovskites are presented.     

Assay of Citrus Flavonoids, Troxerutin, and Ascorbic Acid in Food Supplements and Pharmaceuticals by Capillary Zone Electrophoresis

Capillary electrophoretic method suitable for the assay of citrus flavonoids (hesperidin, diosmin, and rutin), troxerutin, and ascorbic acid in food supplements and pharmaceutical formulations was devised and validated. The separation was carried out at 25 kV in uncoated fused-silica capillary (50 μm i.d.; total length, 32 cm (21 cm to detector); and spectrophotometric detection at 280 nm) maintained at 25 °C with 40 mM sodium tetraborate buffer of pH 9.5 containing 25 % (v/v) of methanol as the background electrolyte. The samples were injected hydrodynamically (50 mbar, 6 s). The calibration curves were linear (correlation coefficients r?=?0.9994–0.9998) for 0.05–0.50 mg/mL of hesperidin, diosmin, rutin, and troxerutin and 0.10–1.00 mg/mL of ascorbic acid when using cinnamic acid (0.05 mg/mL) as internal standard (IS). The LOQ values (S/N?=?10) ranged between 0.02 and 0.04 mg/mL of an analyte. The intra- and interday repeatability of migration times and corrected peak areas was characterized by RSD?≤?3.6 %. Single CE analysis of a standard mixture containing all five analytes and the IS took less than 11 min. Accuracy of the method was evaluated by the added/found analyte recovery experiments (recoveries, 95.5–99.8 %). The method was applied to the analysis of five commercially available food supplements and pharmaceuticals.     

Lucifensin, a novel insect defensin of medicinal maggots: synthesis and structural study

Recently, we identified a new insect defensin, named lucifensin that is secreted/excreted by the blowfly Lucilia sericata larvae into a wound as a disinfectant during the medicinal process known as maggot therapy. Here, we report the total chemical synthesis of this peptide of 40 amino acid residues and three intramolecular disulfide bridges by using three different protocols. Oxidative folding of linear peptide yielded a peptide with a pattern of disulfide bridges identical to that of native lucifensin. The synthetic lucifensin was active against Gram-positive bacteria and was not hemolytic. We synthesized three lucifensin analogues that are cyclized through one native disulfide bridge in different positions and having the remaining four cysteines substituted by alanine. Only the analogue cyclized through a Cys16-Cys36 disulfide bridge showed weak antimicrobial activity. Truncating lucifensin at the N-terminal by ten amino acid residues resulted in a drop in antimicrobial activity. Linear lucifensin having all six cysteine residues alkylated was inactive. Circular dichroism spectra measured in the presence of α-helix-promoting compounds showed different patterns for lucifensin and its analogues. Transmission electron microscopy revealed that Bacillus subtilis treatment with lucifensin induced significant changes in its envelope.     

A Wavelet-Based Approach to Filter Out Symmetric Macroeconomic Shocks

We propose a novel method for econometric time series analysis. This method acts as the comovement-selective filter and is useful to filter out the cycles that are caused by an global event present in the reference time series. We demonstrate its applicability on removing symmetric macroeconomic shock caused by recent financial crisis from the business cycle of the euro area according to the comovement with the United States. The application allowing to identify the country specific business cycles in the Visegrad countries data using the comovement with Germany is also presented. The method is based on the continuous wavelet transform, its inverse and the comovement measurement in the time-frequency domain. Its application also enables to uncover detailed development of the business cycle synchronization in time.     

Microstructures and mechanical properties of Mg–Zn–Y alloy consolidated from gas-atomized powders using high-pressure torsion

In this paper, rapid solidified Mg₉₅Zn_4.3Y_0.7 (at.%) alloy powders produced by an inert gas atomizer were consolidated using a severe plastic deformation technique of high pressure torsion (HPT) at room temperature and 373 K. The behavior of powder consolidation, matrix microstructural evolution, and mechanical properties of the powders and compacts were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, microhardness, and tensile testing. As the HPT processing temperature increases, the powders are more plastically deformed due to decreased deformation resistance, grain boundaries are more in equilibrium, powder bonding is enhanced due to increased interparticle diffusion, hence, tensile ductility and strength increases. On the other hand, hardness decreases with the increased processing temperature, due to less dislocation density.