DRYING KINETICS DERIVED FROM DIFFUSION EQUATION WITH FLUX-TYPE BOUNDARY CONDITIONS

A novel approach to drying of both hygroscopic and non-hygroscopic capillary - porous materials is presented. The equations for drying kinetics are obtained, based on the analytical solution of the differential equation of diffusion with a boundary condition in the form of the flux. Theoretical drying curves generated form the model solution compare well with experimental literature data for drying of materials with different sorption properties exemplified by wool bobbins, brick slabs and corn kernels.     

Description of Manufacture of a Chemisorption Fibre from Polycaproamide Graft Copolymers

A study of the kinetics of hydrazidation of PCA—PGMA graft copolymers showed that the reaction takes place with a high rate and practically ends in 10-15 min. Equations with the corresponding coefficients were obtained for describing the kinetics of the macromolecular reaction of hydrazidation of the graft polymer based on a mathematical model for solving a diffusion equation with a boundary condition in the form of flow. This approach can be used for creating principles for regulation of processes in chemical engineering of polymer systems.     

New polyamide chemisorption fibres containing aromatic and heterocyclic compounds units

Analytical equations describing production of polymide chemisorption fibres with functionally active units of aryl(hetaryl)carboxylic acid hydrazides were obtained by mathematical modeling. The high activity of the fibre chemisorbents in sorption of copper ions is demonstrated.Translated from Khimicheskie Volokna, No. 5, pp. 34–37, September–October, 2004.     

AICAR Protects Vascular Endothelial Cells from Oxidative Injury Induced by the Long-Term Palmitate Excess

Hyperlipidemia manifested by high blood levels of free fatty acids (FFA) and lipoprotein triglycerides is critical for the progression of type 2 diabetes (T2D) and its cardiovascular complications via vascular endothelial dysfunction. However, attempts to assess high FFA effects in endothelial culture often result in early cell apoptosis that poorly recapitulates a much slower pace of vascular deterioration in vivo and does not provide for the longer-term studies of endothelial lipotoxicity in vitro. Here, we report that palmitate (PA), a typical FFA, does not impair, by itself, endothelial barrier and insulin signaling in human umbilical vein endothelial cells (HUVEC), but increases NO release, reactive oxygen species (ROS) generation, and protein labeling by malondialdehyde (MDA) hallmarking oxidative stress and increased lipid peroxidation. This PA-induced stress eventually resulted in the loss of cell viability coincident with loss of insulin signaling. Supplementation with 5-aminoimidazole-4-carboxamide-riboside (AICAR) increased endothelial AMP-activated protein kinase (AMPK) activity, supported insulin signaling, and prevented the PA-induced increases in NO, ROS, and MDA, thus allowing to maintain HUVEC viability and barrier, and providing the means to study the long-term effects of high FFA levels in endothelial cultures. An upgraded cell-based model reproduces FFA-induced insulin resistance by demonstrating decreased NO production by vascular endothelium.     

Electronic structure of UO<Subscript>2.12</Subscript> calculated in the coherent potential approximation taking into account strong electron correlations and spin-orbit coupling

Based on the coherent potential approximation, the method of calculating the electronic structure of nonstoichiometric and hyperstoichiometric compounds with strong electron correlations and spin-orbit coupling has been developed. This method can be used to study both substitutional and interstitial impurities, which is demonstrated based on the example of the hyperstoichiometric UO_2.12 compound. The influence of the coherent potential on the electronic structure of compounds has been shown for the nonstoichiometric UO_1.87 containing vacancies in the oxygen sublattice as substitutional impurities, for stoichiometric UO₂ containing vacancies in the oxygen sublattice and oxygen as an interstitial impurity, and for hyperstoichiometric UO_2.12 with excess oxygen also as interstitial impurity. In the model of the uniform distribution of impurities, which forms the basis of the coherent potential approximation, the energy spectrum of UO_2.12 has a metal-like character.     

Dynamic “Molecular Portraits” of Biomembranes Drawn by Their Lateral Nanoscale Inhomogeneities

To date, it has been reliably shown that the lipid bilayer/water interface can be thoroughly characterized by a sophisticated so-called “dynamic molecular portrait”. The latter reflects a combination of time-dependent surface distributions of various physicochemical properties, inherent in both model lipid bilayers and natural multi-component cell membranes. One of the most important features of biomembranes is their mosaicity, which is expressed in the constant presence of lateral inhomogeneities, the sizes and lifetimes of which vary in a wide range—from 1 to 10³ nm and from 0.1 ns to milliseconds. In addition to the relatively well-studied macroscopic domains (so-called “rafts”), the analysis of micro- and nanoclusters (or domains) that form an instantaneous picture of the distribution of structural, dynamic, hydrophobic, electrical, etc., properties at the membrane-water interface is attracting increasing interest. This is because such nanodomains (NDs) have been proven to be crucial for the proper membrane functioning in cells. Therefore, an understanding with atomistic details the phenomena associated with NDs is required. The present mini-review describes the recent results of experimental and in silico studies of spontaneously formed NDs in lipid membranes. The main attention is paid to the methods of ND detection, characterization of their spatiotemporal parameters, the elucidation of the molecular mechanisms of their formation. Biological role of NDs in cell membranes is briefly discussed. Understanding such effects creates the basis for rational design of new prospective drugs, therapeutic approaches, and artificial membrane materials with specified properties.     

Analysis of the parameters of sorption-desorption isotherms for highly hygroscopic fibres

Equations for describing the desorption isotherms for fibres with high hygroscopicity and curves for finding the points of inflection, the boundary between solvation and volume sorption segments are proposed and can be used for qualitatively and quantitatively evaluating the hygroscopic characteristics of fibres in a wide range of changes in the relative humidity and temperature. Equations for the equilibrium moisture content suitable for use in calculations of the kinetics of drying and other finishing processes for fibres and textile materials based on them and in processing sorption—desorption isotherms for fibres of other types are obtained. Moscow State Textile Academy. Translated fromKhimicheskie Volokna, No. 3, pp. 45–49, May–June, 1999.     

Nutritional pattern of the "Komsomolskaya Pravda" Arctic expedition]

Data on the chemical composition, nutritional value and caloricity of food ration used by the "Komsomolskaya Pravda" expedition during ski marches in the Arctics are reported. The rations consisted chiefly of dehydrated products and weighed 800-1000 g. The daily caloricity of the rations amounted to 3400 and 4400 great calories.     

Effect of gas mixing ratio on etch behaviors of Ba2Ti9O20 (BTO) and Pt thin films in Cl2/Ar inductively coupled plasma

An investigation of the Ba₂Ti₉O₂₀ (BTO) and Pt thin films etch mechanism in the Cl₂/Ar inductively coupled plasma was carried out. It was found that an increase in Ar mixing ratio at fixed gas pressure and input power causes a fast decrease in the BTO etch rate (26.9-1.2 nm/min for 0-100% Ar) while the Pt etch rate increases slightly from 17.4-23.0 nm/min. Langmuir probe diagnostics and zero-dimensional plasma modeling provided the data on plasma parameters, steady-state composition and fluxes of active species on the etched surface. From the model-based analysis of etch kinetics, it was shown that the behavior of the BTO etch rate corresponds to the reaction-rate-limited etch regime, where the etch rate is limited neither by physical sputtering of the main material nor by the ion-stimulated desorption of low-volatile reaction products. The etch process of Pt appears in the transitional regime and is controlled by the neutral and ion fluxes together.     

Features of the Kinetics of Bulk and Heterogeneous Processes in CHF3 + Ar and C4F8 + Ar Plasma Mixtures

Russian Microelectronics - We carry out a comparative study of the kinetics of plasma-chemical processes and plasma composition in CHF3 + Ar and C4F8 + Ar mixtures under the conditions of a...