Some features of spinning cuprammonium fibres into precipitation baths containing calcium salts

Conclusions On the basis of data on precipitating power and the rate of dehydration of cuprammonium solutions of cellulose, the fundamental possibility has been demonstrated of spinning fibres from such solutions into precipitation baths containing calcium salts, using the technological scheme for viscose fibre manufacture.The dependence of the basic characteristics of the freshly-spun fibre on calcium salt content and temperature of the precipitation bath has been found.Moscow Textile Institute. Translated from Khimicheskie Volokna, No. 1, pp. 11–13, January–February, 1987.     

Influence of pitch composition and surface properties of petroleum coke on their interaction during the preparation of carbon/carbon composites

The influence of pitch composition and surface properties of petroleum coke on the interaction of pitch and coke in the composite is studied. The adsorption results and EPR data indicate that recombination of paramagnetic centers and interaction of oxygen functional groups occur during the preparation of the composite. As a result of interaction between petroleum coke and pitch, polar compounds are concentrated in the adsorption layer. The baking criterion is used for the characterization of the baking ability of the pitches obtained as a result of different oxidation treatments of commercial coal tar pitch. It is determined that physico-chemical properties of the obtained pitches influence the value of the “baking criterion”. The kind of thermo-oxidation treatment of the parent pitch should be chosen hence achieving the maximum value of the baking criterion. For this purpose, the maximal part of the pitch has to take part in the adsorption layer.     

Kinetics of redox processes in manganese oxides

The redox processes in ceramic and powder samples of α-Mn₂O₃ (kurnakite) and β-Mn₃O₄ (hausmannite) have been studied in the temperature range 20–1000°C. The results demonstrate that the conversion of α-Mn₂O₃ to β-Mn₃O₄ in the binary system Mn-O is essentially irreversible, even if there are nucleation centers in the form of the higher oxide α-Mn₂O₃ during the oxidation of hausmannite. It is shown that the high reactivity of hausmannite ground in a WC mill is not due to a mechanochemical effect. Grinding-induced contamination has a significant effect on the oxidation behavior of the system: the impurities incorporated into the sample during grinding in a mill favor complete (WC contamination) or partial (Fe contamination) conversion of hausmannite to kurnakite. Hausmannite contaminated with tungsten carbide oxidizes by a catalytic mechanism. In the case of Fe impurities, oxidation follows a solid-state mechanism, through the formation of restricted Fe_xMn_2?x O₃ solid solutions.     

Accurate measurement of total attenuation coefficient of thin tissue with optical coherence tomography

Noninvasive accurate measurements of tissue optical properties are needed for many diagnostic and therapeutic applications. Optical coherence tomography (OCT) recently proposed for high-resolution imaging in tissue can potentially be applied for accurate, noninvasive, and high-resolution measurement of tissue total attenuation coefficient. However, confocal function (dependence of OCT sensitivity on the distance of probed site from the focal plane of the objective lens) and multiple scattering substantially limit the accuracy of the measurement with the OCT technique. We studied the influence of the confocal function and multiple scattering on the accuracy of the measurement and proposed methods that provide measurement of the total attenuation coefficient with a significantly reduced systematic error. Experiments were performed in tissue phantoms and porcine and human skin in vitro and in vivo. Our data indicate that the tissue total attenuation coefficient can noninvasively be measured in vivo with the accuracy of 5%-10% in the range from 0.5 to 17 mm/sup -1/ and about 20% in the range up to 40 mm/sup -1/. These results suggest that the proper correction of the OCT-based measurement for the confocal function and multiple scattering provides absolute values of tissue total attenuation coefficient with high accuracy and resolution that may not be achievable by other optical techniques in vivo.     

用于激光起爆的新型光敏炸药——过氯酰胺(英)

介绍了过氯酰胺盐的一些性质,指出过氯酰胺盐是激光起爆阈值低的光敏炸药。用１０％光学透明的聚合物分别５０ｍｇ／ｃｍ＾２的过氯酰胺钾和过氯酰胺钡制１ｃｍ＾２的光敏炸药薄板并进行了实验。Ⅱ的起爆阈值经久０．１Ｊ／ｃｍ＾２,Ⅳ的起爆阈值为５－７ｍＪ／ｃｍ＾２,皆低于压装的叠氮化铅药柱,全都实现了平面起爆。     

The effect of annealing on the properties of Ga2O3 anodic films

The effect of annealing and oxygen plasma on the electrical characteristics of gallium oxide films has been investigated. Ga₂O₃ films with thicknesses of 200–300 nm were formed by the anodic oxidation of n-GaAs wafers with the donor concentration N _d = (1–2) × 10¹⁶ cm⁻³. It is shown that, after annealing at 900°C for 30 min, the gallium arsenide films contain only the β Ga₂O₃ phase. The effect of the duration of oxygen plasma treatment prior to annealing on the nucleation of β-phase crystallites with different orientations has been studied. It has been established that the electrical conductivity of the Ga₂O₃ films can be managed by annealing and variation in the duration of oxygen plasma treatment. It is shown that the response of the V/Ni-GaAs-Ga₂O₃-V/Ni structure to a mixture exhaled by a person depends on the value and sign of the potential on the control electrode.     

Investigation of Chemical Constituents of Eranthis longistipitata (Ranunculaceae): Coumarins and Furochromones

Aqueous-ethanol extracts (70%) from the leaves of Eranthis longistipitata Regel. (Ranunculaceae Juss.)—collected from natural populations of Kyrgyzstan—were studied by liquid chromatography with high-resolution mass spectrometry (LC-HRMS). There was no variation of the metabolic profiles among plants that were collected from different populations. More than 160 compounds were found in the leaves, of which 72 were identified to the class level and 58 to the individual-compound level. The class of flavonoids proved to be the most widely represented (19 compounds), including six aglycones [quercetin, kaempferol, aromadendrin, 6-methoxytaxifolin, phloretin, and (+)-catechin] and mono- and diglycosides (the other 13 compounds). In the analyzed samples of E. longistipitata, 14 fatty acid–related compounds were identified, but coumarins and furochromones that were found in E. longistipitata were the most interesting result; furochromones khelloside, khellin, visnagin, and cimifugin were found in E. longistipitata for the first time. Coumarins 5,7-dihydroxy-4-methylcoumarin, scoparone, fraxetin, and luvangetin and furochromones methoxsalen, 5-O-methylvisammioside, and visamminol-3′-O-glucoside were detected for the first time in the genus Eranthis Salisb. For all the above compounds, the structural formulas are given. Furthermore, detailed information (with structural formulas) is provided on the diversity of chromones and furochromones in other representatives of Eranthis. The presence of chromones in plants of the genus Eranthis confirms its closeness to the genus Actaea L. because chromones are synthesized by normal physiological processes only in these members of the Ranunculaceae family.