High pressure sintering of TiB2 ceramics at different temperatures

In this paper the effect of high-pressure sintering (HPS) temperature on the microstructure, physical and mechanical properties of TiB2 ceramics has been investigated. Initial TiB2 powder with the average particle size of 5 μm was sintered in a modifi ed high-pressure anvil-type apparatus under static pressure of 4 GPa in the temperature range of 1400–1800°C. It is shown that HPS allows preparing full-dense TiB2 ceramics with fi ne-grained structure. The density of samples rises with increasing the sintering temperature up to 1800°C while the maximal microhardness is observed on samples prepared in the temperature range of 1500–1600°C. XRD analysis has shown that this fact is connected with an increase of the level of internal stresses in these samples

On the mechanism of structure formation of dead-hard carbon phase in the nanocomposite system of Fe - C for woodworking tools

In the article hypothesized that the formation of particulate gray superhardness carbon phase occurs through a stage of transition nanocarbon component of the mixture into a liquid state under highsintering method of consolidation

Effect of compacting pressure, powder degassing and thermobaric treatment on densification and properties of nanocrystalline titanium nitride

The effects of compacting pressure, powder degassing and high pressure sintering temperature and time on the densification and properties of nanocrystalline titanium nitride have been investigated. For this reason, TiN powder with a mean particle size of 55 nm was pressed in the range of compacting pressure from 0.2 to 1.0 GPa and sintered under static pressure of 3.5 GPa in the temperature range of 900–1600°C for 45–120 s. Some of green bodies were degassed in vacuum before sintering. It was shown that samples compacted in the pressure range of 0.2–0.6 GPa have the highest density after the thermobaric treatment. The maximum density (about 97.3 %TD) was obtained with degassed samples. Microhardness and microstructure investigations have shown that recrystallization of the TiN nanopowder begins at the sintering temperatures of 1100–1200°C and sintering time less than one minute. The maximum microhardness obtained was 23.2±1.0 GPa and themaximum Young modulus was 370 GPa

Determination of the quantitative content of chlorophylls in leaves by reflection spectra using the random forest algorithm

Determining the quantitative content of chlorophylls in plant leaves by their reflection spectra is an important task both in monitoring the state of natural and industrial phytocenoses, and in laboratory studies of normal and pathological processes during plant growth. The use of machine learning methods for these purposes is promising, since these methods allow inferring the relationships between input and output variables (prediction model), and in order to improve the quality of the prediction, a researcher may modify predictors and selects a set of method parameters. Here, we present the results of the implementation and evaluation of the random forest algorithm for predicting the total concentration of chlorophylls a and b from the ref lection spectra of plant leaves in the visible and infrared wavelengths. We used the ref lection spectra for 276 leaf samples from 39 plant species obtained from open sources. 181 samples were from the sycamore maple (Acer pseudoplatanus L.). The ref lection spectrum represented wavelengths from 400 to 2500 nm with a step of 1 nm. The training set consisted of the 85 % of A. pseudoplatanus L. samples, and the performance was evaluated on the remaining 15 % samples of this species (validation sample). Six models based on the random forest algorithm with different predictors were evaluated. The selection of control parameters was performed by cross-checking on five partitions. For the f irst model, the intensity of the ref lection spectra without any transformation was used. Based on the analysis of this model, the optimal ranges of wavelengths for the remaining f ive models were selected. The best results were obtained by models that used a two-point estimation of the derivative of the ref lection spectrum in the visible wavelength range as input data. We compared one of these models (the two-point estimation of the derivative of the ref lection spectrum in the range of 400–800 nm with a step of 1 nm) with the model by other authors (which is based on the functional dependence between two unknown parameters selected by the least squares method and two ref lection coeff icients, the choice of which is described in the article). The comparison of the results of predictions of the model based on the random forest algorithm with the model of other authors was carried out both on the validation sample of maple and on the sample from other plant species. In the f irst case, the predictions of the method based on a random forest had a lower estimate of the standard deviation. In the second case, the predictions of this method had a large error for small values of chlorophyll, while the third-party method had acceptable predictions. The article provides the analysis of the results, as well as recommendations for using this machine learning method to assess the quantitative content of chlorophylls in leaves

FEATURES MODIFYING VARIOUS TYPES OF IRON-CARBON ALLOYS

The article describes the features of the modification of cast iron, high chrome cast iron and steel. It is shown that the modification of cast iron complex modifier should be based on the thickness of the walls of castings, and for steel and high chrome cast iron, it is beneficial to the macro and microstructure. The data confirming the removal of transcrystallization and size reduction microand macrostructure of castings in various types of iron-carbon alloys. Experimentally proved that in the transition from columnar to equiaxed structure observed increase in the number of eutectic cells, which confirms the position that transcrystallization terminated as a result of nucleation and growth of equiaxed crystalsin the area of concentration supercoolin

ZYMOGRAPHIC ANALYSIS OF WATER-SOLUBLE PROTEASES OF VIBRIO CHOLERAE O1 AND О139 SEROGROUPS

Aim. Zymographic analysis of water-soluble proteases of Vibrio cholerae O1 и О139 serogroups. Materials and methods. Bacteria cultivated on a casein-yeast agar (рН 7,6) at 37 ° with during one twenty-four hours and washed off physiological solution. Bacterial mass (by the concentration of 109 cell./ml) was treatment by sterile solution of urea in an eventual concentration 4,5 М. After day's display and determination of sterility of got lysate insoluble in urea material (cell walls) was deleted by high-speed centrifugation. Supernatant liquid was exposed to the dialysis, released from insoluble in water sediment centrifugation and freeze dried out. Protease activity was determined in diffusion test in 1 % agarose gel, containing 0,5 % gelatin or 0,5% casein. The spectrum of proteases was analysed by a substrate electrophoresis in the blocks of 8% polyacrylamide gel, impregnated in the process of polymerization gelatin or casein (in an eventual concentration 0,1 %), in presence the dodecylsulphate of sodium. Results. After differential centrifugation of ureal lysate of cells and dialysis there are mainly intracellular water-soluble proteases in the investigated extracts. Diffusion tests showed that all preparations of the investigated strains of Vibrio cholerae possessed protease activity of different intensity. Changing of substrate in diffusion test from gelatin to the casein resulted in the general diminishing of the registered areas of hydrolysis, specifying that a casein fissions less actively by comparison to gelatin. Substrate electrophoresis showed that proteins, making the spectrum of water-soluble pro teases of Vibrio cholerae are extracted by urea, possessed molecular mass, varying within from less than 30 кйа to more than 120 кDа. Strains distinctions are marked in quantitative and high-quality description of spectrums of soluble proteases. Dependence of description of type of water-soluble proteases is educed on used substrate. At the estimation of spectrums of proteases clear confirmation is got, that on gels are impregnated by gelatin electrophoretic mobility of proteases is higher, than in gels, containing a casein. Conclusion. Substrate electrophoresis of preparations of cell-free lysates of Vibrio cholerae showed the presence of a few water-soluble proteases, quantitative and high-quality interstrain distinctions, dependence of spectrum of active proteases from of used substrate

Proteolytic cleavage of immunoglobulins G by subcellular fractions of Vibrio Cholerae O1 and O139 serougroups

With the use of diffusion test in substrate agarose gel in sterile subcellular fractions of Vibrio cholerae 01 and 0139 serogroups, got from by the lysis urea of living microbial cells, found out a ability for the proteolysis of rabbit and human immunoglobulins of class G. Substrate electrophoresis detected polypeptides with IgG-protease activity both in water-soluble and membrane fractions of the strains with different molecular masses. Differences in IgG-protease activity of subcellular fractions of V. cholerae ompT+ and ompT-strains were determined

Zymographic analysis of lipolytical enzymes of subcellular Vibrio cholerae fractions of O1 and O139 serogroups

Zymographic analysis showed that all subcellular fractions of the serogroups possessed different degree of lipolytical activity. Maximal hydrolysis in the radial enzyme-diffusion reaction in agarose gel was observed in Tween-20, Tween-80, Triton Х-305 and Triton Х-405. Total hydrolase activity of urea extracts in Tween-20, Tween-80, Triton Х-405, Span-85 excelled those in the preparations of outer membranes. Maximal lipolytical activity in regard to the Tweens was shown by the preparations of urea extracts prepared from the nontoxigenic strains of O1 serogroups, while in relation to the Tritons - preparations of urea extracts from the toxigenic strains (p < 0,05)

MLVA-TYPINGIN THE ANALYSIS of THE POPULATION STRUCTURE of VIBRIO CHOLERAE, CIRCULATING IN PRIMORSKY KRAI TERRITORY, DURING EPIDEMIOLOGICAL WELFARE

In order to study the population structure of Vibrio cholerae, circulating in the waters of Primorsky Region territory during epidemiological welfare, was carried out a retrospective MLVA-typing of 50 V.cholerae strains isolated since 1976 up to 2011 years. There was revealed non-toxigenic V. cholerae strains heterogeneity, consisting in the variability of structure of these tandem repeat loci. The waters circulation of Primorsky Region territory during epidemiological welfare V.cholerae, submitted by no less than 30 unique genotypes and 8 clusters is represented. There is a high discriminatory power of the MLVA. The Hunter Gaston index of isolates studied is 0.988. In some cases, was revealed relationship between genotype (identical and closely related allelic profiles) with time and place of V.cholerae strains isolation

Влияние электроэрозионной обработки поверхности твердосплавных пластин на их фазовый состав и пайку режущих элементов из нитридной керамики

The effect of electroerosive treatment of the surface of carbide plates from superhard nitride ceramics on their phase composition and vacuum soldering of cutting elements is studied. Studies of the surface quality and elemental composition have been carried out. The surface of the plates for soldering is processed by the method of electroerosive cutting with brass wire in water, as well as by the method of electroerosive direct burn-through using copper and graphite electrodes in kerosene. The microstructure and elemental composition of the surfaces of hard-alloy plates were investigated by scanning electron microscopy and energy-dispersive X-ray spectroscopy before and after their processing. The analysis of the obtained data indicates that the best results at electro-erosion treatment of the hard-alloyed plate and the strongest bonding of brazed materials are achieved using a copper electrode and brass wire, since this ensures maximum wetting of the plate surface with solder based on Cu–Ti–Sn and the absence of pores. The hard-alloy cutter plate and ceramic cutting element were joined by high-temperature brazing in vacuum. Tests of hard-alloy plates with brazed cutting elements showed that the roughness of the machined surface of workpieces made of ХВГ steel with hardness of HRC 47–62 and ШХ15 steel with hardness of HRC 57–58 corresponded to 6–8 purity class at cutting speed of 155–170 m/min. The wear of the cutter along the trailing edge of 0.4 mm served as a criterion for evaluation of the cutting properties of superhard materials according to the results of durability tests.Изучено влияние электроэрозионной обработки поверхности твердосплавных пластин на их фазовый состав и вакуумную пайку режущих элементов из сверхтвердой нитридной керамики. Проведены исследования качества поверхности и элементного состава твердосплавных пластин для пайки режущих элементов из сверхтвердых материалов. Поверхность пластин для напайки обработана методом электроэрозионной резки латунной проволокой в воде, а также методом электроэрозионного прямого прожога с использованием медного и графитового электродов в керосине. Микроструктура и элементный состав поверхностей твердосплавных пластин были исследованы методами электронной микроскопии и энергодисперсионной рентгеновской спектроскопии до и после их обработки. Анализ полученных данных свидетельствует, что наилучшие результаты при электроэрозионной обработке твердосплавной пластины и наиболее прочное сцепление спаиваемых материалов достигаются при использовании медного электрода и латунной проволоки, так как при этом обеспечиваются максимальное смачивание поверхности пластины припоем на основе Cu–Ti–Sn и отсутствие пор. Соединение твердосплавной резцовой пластины и керамического режущего элемента производилось методом высокотемпературной пайки в вакууме. Испытания пластин с напайными режущими элементами показали, что шероховатость обработанной поверхности заготовок из стали ХВГ с твердостью HRC 47–62 и из стали ШХ15 с твердостью HRC 57–58 соответствовала 6–8-му классам чистоты при скорости резания 155–170 м/мин. Критерием для оценки режущих свойств сверхтвердых материалов по результатам стойкостных испытаний служил износ резца по задней грани 0,4 мм