The synthesis of thermally expandable residual graphite nitrate in the system HNO<Subscript>3</Subscript>-CH<Subscript>3</Subscript>COOH-H<Subscript>2</Subscript>O

Effect exerted by the synthesis conditions of residual graphite nitrate in the system concentrated nitric acid-glacial acetic acid-water on the properties of the final product was studied in wide consumption range of the reagents. The optimal ratio of the reagents was determined. The dependence of expansion coefficient on the loss of mass by the expanded product was determined.     

Dependence of Separation Characteristics of Pervaporation on Parameters of Membranes Composed of Cellulose Myristinate and Polyphenylene Oxide

Experimental data on evaporation of binary mixtures composed of ethanol and water, ethyl acetate and acetic acid, water and acetic acid, and ethyl acetate and water in a wide range of concentrations, across film membranes composed of cellulose myristinate and polyphenylene oxide are presented.     

Impact of Deuterium Plasma Flux on Fusion Reactor Materials: Radiation Damage,Surface Modification,Erosion

Physics of Atomic Nuclei - Results of the complex experimental research of plasma impact on fusion reactor materials are presented. The near-wall plasma of a tokamak reactor is simulated on the...     

Deep desalination of water by evaporation through polymeric membranes

Transport properties and structural features of a number of already known and new types of polymeric membranes in desalination of aqueous salt solutions by membrane distillation and pervaporation were studied. The possibility of obtaining distilled water in a single stage by pervaporation from dilute or concentrated aqueous salt solutions was examined for the example of membranes fabricated from celluloses of varied origin (wood, cotton, bacterial).     

Comparison of electrochemical characteristics of acetylcellulose microfiltration membranes and a model system

The electrokinetic properties of commercial acetylcellulose microfiltration membranes are compared to a model system, i.e., an acetylcellulose film applied to a plane-parallel capillary made of quartz glass. It is shown that the absolute magnitudes of the electrokinetic potentials of the model system are higher than those of the examined microfilters, seemingly because the latter are modified to increase their mechanical strength and elasticity. The dissociation constants of carboxyl groups and the adsorption potentials of potential-determining ions are found from the electrokinetic data on the model system.     

Formation of a composite based on selenium nanoparticles stabilized with poly-<Emphasis Type="Italic">N,N,N,N</Emphasis>-trimethylmethacryloyloxyethylammonium methyl sulfate and on Acetobacter xylinum cellulose gel films

Formation of a composite based on selenium nanoparticles stabilized with poly-N,N,N,N-trimethylmethacryloyloxyethylammonium methyl sulfate and on Acetobacter xylinum cellulose gel films was studied. Optimal sorption parameters at which the amorphous form of selenium is preserved in the composite film were suggested.     

Study of the gel films of Acetobacter Xylinum cellulose and its modified samples by 1H NMR cryoporometry and small-angle X-ray scattering

Gel films of Acetobacter Xylinum cellulose and its modified samples have been investigated by 1H nuclear magnetic resonance (NMR) cryoporometry and small-angle X-ray scattering. The joint use of these two methods made it possible to characterize the sizes of aqueous pores in gel films and estimate the sizes of structural inhomogeneities before and after the sorption of polyvinylpyrrolidone and Se₀ nanoparticles (stabilized by polyvinylpyrrolidone) into the films. According to small-angle X-ray scattering data, the sizes of inhomogeneities in a gel film change only slightly upon the sorption of polyvinylpyrrolidone and nanoparticles. The impregnated material is sorbed into water-filled cavities that are present in the gel film. ¹H NMR cryoporometry allowed us to reveal the details of changes in the sizes of small aqueous pores during modifications.     

Instrumental broadening of spectral line profiles due to discrete representation of a continuous physical quantity

It is the usual situation in spectroscopy that a continuous physical quantity, which plays the role of a spectral function argument (i.e. the abscissa of a spectrum), is sampled electronically as discrete point clouds or channels. Each channel corresponds to the midpoint of a small interval of the continuous argument. The experimentally registered value of intensity in the channel describes the averaged spectral intensity in this interval. However, an approximation of spectra by a continuous theoretical model function often assumes that the interval is small enough, and tabulation of the theoretical model function may be used without appreciable disadvantages for the fitting results. At this point, a new type of approximation error appears, such as the error of midpoint approximation to a definite integral in the rectangle method of numeric integration. This paper aims at quantitative estimation of this error in the cases of a pure Lorentz lineshape and a generalized Voigt contour. It is shown that discrete representation of continuous spectral data leads to some non-physical broadening in comparison with the tabulated model function. As a first approximation it is normal broadening. We show that even in the case of a Lorentz true lineshape we must use the tabulated Voigt function measured in channels fixed Gauss linewidth rather than a tabulated Lorentzian. Application of the results of this paper is demonstrated on Mössbauer spectra.     

Composite hydrogels based on polyacrylamide and cellulose: Synthesis and functional properties

Biocompatible composite hydrogels based on polyacrylamide and reinforced with bacterial or vegetable cellulose were synthesized. In the mechanical characteristics and water content, these hydrogels are similar to knee joint cartilages with average rigidity level. The structure and chemical composition of the hydrogels after their residence for 45 days in laboratory animal joints were studied by scanning electron microscopy and energydispersive X-ray microanalysis. Prolonged contact of the hydrogels with bones results in formation of calcium phosphate spherulites similar in composition to hydroxyapatite.