Formation of medium-range order in fluoride glasses

A possible solution to the problem of determining the medium-range order in fluoride glasses is proposed. The model of the formation of the glass network is advanced on the basis of the complex-cluster model for salt melts and the percolation hypothesis. The determination of the glass network topology reduces to the experimental determination of the percolation point and the geometric estimation of the second coordination number of a glass-former. It is shown that the functionalities of glass-formers as determined from both the percolation point and the crystal chemical constraints turn out to be identical.     

Properties of composites containing biologically active substances and the polymeric materials prepared from them

The effect of the structure of polysaccharides containing ionogenic groups on the properties of proteolytic enzymes included in the structure of polyelectrolyte complexes was investigated. A correlation was established between the composition of the polymer composites containing the proteolytic enzyme, the antimicrobial, and the modifying additives and the properties of the fibre and film materials prepared from them. Moscow State Textile Academy. Translated fromKhimicheskie Volokna, No. 4, pp. 32–38, July–August, 1999.     

Noncanonical conformation of nucleic acids: structure with slipped-loops, occurring in DNA oligonucleotides

A HPLC method was developed and validated for the quantitation of 9-cis-retinoic acid (ALRT1057) and its major metabolite, 4-oxo-9-cis-retinoic acid (LG100182) in human plasma. Samples were buffered and extracted with methyl-tert-butyl-ether. The analytes and an I.S. were separated on a C18 HPLC column using a shallow gradient of 70-89% organic solvent. The analytes were quantitated by UV detection at 348 nm. Selectivity against endogenous compounds and potential metabolites (retinol, all trans-, 13-cis-, and 4-hydroxy-9-cis-retinoic acid) was demonstrated. The run time was 29 min. The standard curve was linear from 2.5 to 450 ng ml-1. Interassay precision for both analytes in quality control samples was less than 5.0% RSD. Accuracy was within 11.0% RE for both compounds. Analyte stability during sample storage, extraction processing, and chromatography was established. Method ruggedness was tested by two analysts and on two HPLC systems. This method has been applied to the quantitation of clinical samples.     

Dependence of the processing characteristics of a copper powder and its dendrite structure on electrolysis conditions at a constant overvoltage

Translated from Poroshkovaya Metallurgiya, No. 2(326), pp. 1–8, February, 1990.     

Total external x-ray reflection and infrared spectroscopy study of porous silicon and its aging

Study of p-type porous silicon has been carried out by x-ray reflectometry for the first time. Its critical total-external-reflection angle and its reflection coefficient in the subcritical angle range are much smaller than for c-Si, which was grown by the Czochralski method. The critical angle decreases with increase of the porosity. The critical angle and the reflection coefficient increase with aging. These results are attributable to the much smaller electron density of porous silicon in comparison with c-Si, to the microgeometry of its surface, and to changes in both of these factors attendant to aging due to an increase in the concentration of atmospheric constituents observed in the infrared absorption spectra. As the porosity increases, the concentration of atmosmopheric impurities also increases, and in high-porosity material in addition to chemically adsorbed oxygen, carbon and water seem to contribute appreciably. Fiz. Tekh. Poluprovodn. 31, 957–960 (August 1997)     

A Method for the Hermetic Connection of High-Pressure Tubing to a High-Pressure Apparatus

A method for the hermetic connection of small-diameter high-pressure tubing to a high-pressure apparatus without soldering is described.     

Application of the Luikov Approximate Solutions to Mathematical Description of the Process of Self-Freezing of Materials by Decreasing Pressure

A mathematical model for the process of self-freezing of moist materials in a continuously increasing vacuum which is developed on the basis of the approximate solutions obtained by A. V. Luikov for drying of capillary-porous media is presented. Results of experimental investigations into the self-freezing of a moist cloth are given, from which the temperature of supercooling of the surface material layer, the temperature coefficient, and the velocity of deepening of the freezing surface are determined; all of these parameters are used in mathematical simulation of the above process.     

Determination of the composition of copolyester based on glycolide and dℓ-lactide by chromatography

Conclusions A procedure has been developed for determining the composition of copolyesters based of glycolide and dl-lactide.The procedure has reasonable analytical accuracy and can be used for operative analytical control in copolymer synthesis.Translated from Khimicheskie Volokhna, No. 4, pp. 59–61, July–August, 1989.     

Quantitative estimates of gas maldistribution and methods for their localization in absorption columns

In the present work, we carry out evaluation of gas flow maldistribution in different types of gas distributing devices (GDD) and packings by using experimental data for the output velocity profiles for both the absorption pilot column and industrial column. Two GDD construction types—with circular and with local tube gas feed, together with their modifications—are investigated. Two pilot columns—with random packing RSRM 1.5″ and with structured ceramic Honey-comb packing, and one industrial contact economizer with Honey-comb and inclined rings—have been studied. Six types of quantitative estimations of GDD and packings maldistribution are determined by the help of MATHCAD. Then, their sensitivity toward several factors, such as the type of GDD and packing, the initial gas flow velocity, the number and dimension of measuring cells on the column cross-section, the measurement error, and so on, is investigated. It is found that only two of the quantitative maldistribution estimations take into account the formation of maldistribution clusters, which deteriorates the uniform gas distribution. A novel method for quantitative determination of these clusters and also for identification of the zones at column cross-section, in which they appeared, has been developed. It is established that the measurement error and the dimension of measuring cell deeply influence the number, the area, and spatial distribution of these zones on the cross-section, as well as the values of maldistribution estimates.