Некоторые особенности создания подшипниковых узлов прецизионных электрошпинделей на основе пар трения скольжения

In mechanical engineering, various types of bearing units are used in moving connections and sliding pairs (sliding bearings, guides, bushings) are sufficiently widely used. This allows increasing the stiffness of the units, reducing their dimensions, improving heat dissipation, etc. But there are higher friction losses, probability in the increases of situations in which there is a jamming of friction surfaces for application of sliding friction pairs compared to the rolling bearings. These problems are even more important for application of sliding bearings in precision equipment, which typically operates under temperature and humidity stabilized conditions. The aim of the work is the development of methodological approaches to the creation and rational design and manufacture of sliding friction pairs based on the composite antifriction materials’ coatings for the application in vertical precision program-controlled electrospindles for high-speed machining. Questions of development and manufacturing of friction units for precision electrospindles with high rigidity on the basis of composite materials are considered. It is shown that acceptable cutting speed (750 m/min or more) for the quality standpoint of processing with a diamond-like tool can be achieved by placing the cutting edge of the tool on diameter of 200 mm. As a result, two tasks solved: the rigidity of the electrospindle for ultra-high accuracy of mechanical blade processing is achieved; high smoothness of work is provided, which allows achieving nanometric surface roughness with a decrease of deviations to 1 µm from the middle surface line. It is extremely important for a number of special applications.В машиностроении в подвижных соединениях используются различные типы подшипниковых узлов, причем достаточно широко – пары скольжения (подшипники скольжения, направляющие, втулки). Это позволяет повысить жесткость узлов, уменьшить их габаритные размеры, улучшить теплоотвод и обеспечить снижение шума и вибраций. Однако в ряде случаев при использовании пар трения скольжения возникают более высокие по сравнению с подшипниками качения потери на трение, повышается вероятность возникновения ситуаций, когда происходит заедание трущихся поверхностей. Большое значение эти проблемы имеют при применении подшипников скольжения в прецизионном оборудовании, которое, как правило, функционирует при стабилизированных по температуре и влажности внешних условиях. Поэтому целью исследований являлась разработка методических подходов к созданию и рациональному конструированию и изготовлению пар трения скольжения на основе применения покрытий из композиционных антифрикционных материалов, используемых в вертикальных прецизионных программно-управляемых электрошпинделях для скоростной механической обработки. Рассмотрены вопросы разработки и создания подшипниковых узлов прецизионных электрошпинделей повышенной жесткости с парами пар трения скольжения на основе композиционных материалов. Диаметры подшипников скольжения могут быть достаточно большими, что позволяет достигнуть требуемой сверхвысокой точности механической обработки и нанометрической шероховатости обрабатываемой поверхности. Приемлемые с позиций качества обработки алмазоподобным инструментом скорости резания (750 м/мин и более) могут быть достигнуты при размещении режущей кромки инструмента на диаметре 200 мм, что позволяет использовать в конструкции шпинделя смазываемые подшипники скольжения. Вследствие этого комплексно решаются две задачи: достигается необходимая для сверхвысокой точности механической лезвийной обработки жесткость электрошпинделя; обеспечивается высокая плавность работы, позволяющая достичь нанометрической шероховатости поверхности при снижении макроотклонений до 1 мкм от средней линии поверхности, что в совокупности чрезвычайно важно для ряда специальных применений

Expression of Foxm1 Transcription Factor in Cardiomyocytes Is Required for Myocardial Development

Forkhead Box M1 (Foxm1) is a transcription factor essential for organ morphogenesis and development of various cancers. Although complete deletion of Foxm1 in Foxm1−/− mice caused embryonic lethality due to severe abnormalities in multiple organ systems, requirements for Foxm1 in cardiomyocytes remain to be determined. This study was designed to elucidate the cardiomyocyte-autonomous role of Foxm1 signaling in heart development. We generated a new mouse model in which Foxm1 was specifically deleted from cardiomyocytes (Nkx2.5-Cre/Foxm1fl/f mice). Deletion of Foxm1 from cardiomyocytes was sufficient to disrupt heart morphogenesis and induce embryonic lethality in late gestation. Nkx2.5-Cre/Foxm1fl/fl hearts were dilated with thinning of the ventricular walls and interventricular septum, as well as disorganization of the myocardium which culminated in cardiac fibrosis and decreased capillary density. Cardiomyocyte proliferation was diminished in Nkx2.5-Cre/Foxm1fl/fl hearts owing to altered expression of multiple cell cycle regulatory genes, such as Cdc25B, Cyclin B1, Plk-1, nMyc and p21cip1. In addition, Foxm1 deficient hearts displayed reduced expression of CaMKIIδ, Hey2 and myocardin, which are critical mediators of cardiac function and myocardial growth. Our results indicate that Foxm1 expression in cardiomyocytes is critical for proper heart development and required for cardiomyocyte proliferation and myocardial growth

Исследование биоэквивалентности лекарственных средств Флутриксан и Нексавар

А replicate designed open-label, randomized, crossover single-dose bioequivalence study using three periods and three sequences was conducted to assess the comparative bioavailability of the sorafenib-containing medicinal products Flutrixan (200 mg tablet, Institute of Bioorganic Chemistry of NAS of Belarus, Belarus) and Nexavar (200 mg tablet, Bayer Pharma AG, Germany), in healthy volunteers under fasting conditions. It was shown that all criteria used to assess the bioequivalence of compared medicinal products were fulfilled. The Test/Reference geometric mean ratios obtained for the pharmacokinetic parameters Cmax and AUC0-72 and the corresponding 90 % confidence intervals were within the acceptance range of 80.0-125.0 %. Both sorafenib products were well tolerated and had a favorable safety profile. Therefore, it can be concluded that the generic medicinal product Flutrixan is bioequivalent to the reference medicinal product Nexavar.Открытое рандомизированное перекрестное с репликативным дизайном (3 периода, 3 последовательности) биоэквивалентное исследование было проведено с целью оценки сравнительной биодоступности сорафенибсо-держащих лекарственных средств Флутриксан (таблетки, покрытые пленочной оболочкой, 200 мг, производство Института биоорганической химии НАН Беларуси, Республика Беларусь) и Нексавар (таблетки, покрытые пленочной оболочкой, 200 мг, производство Bayer Pharma AG, Германия) в условиях однократного приема дозы натощак у здоровых добровольцев. Показано, что для сравниваемых лекарственных средств выполняются все критерии, использованные для установления их биоэквивалентности. Отношения геометрических средних исследуемых фармакокинетических параметров AUC0-72,T / AUC0-72,R и Cmax,T / Cmax,R и соответствующие 90 %-ные доверительные интервалы укладываются в допустимые границы интервала приемлемости (80,0-125,0 %). Оба лекарственных средства хорошо переносятся и имеют приемлемый профиль безопасности. С учетом этих данных можно заключить, что воспроизведенное лекарственное средство Флутриксан биоэквивалентно оригинальному лекарственному средству Нексавар

Conserved genes and pathways in primary human fibroblast strains undergoing replicative and radiation induced senescence

Additional file 3: Figure S3. Regulation of genes of Arrhythmogenic right ventricular cardiomyopathy pathway during senescence induction in HFF strains Genes of the “Arrhythmogenic right ventricular cardiomyopathy” pathway which are significantly up- (green) and down- (red) regulated (log2 fold change >1) during irradiation induced senescence (120 h after 20 Gy irradiation) in HFF strains. Orange color signifies genes which are commonly up-regulated during both, irradiation induced and replicative senescence

Analysis of modern composite materials used in the manufacture of model kits for small-scale foundry production, obtained using bonding technology

The article presents modern data on the materials used to create model kits, the method of their installation for use on any foundries, specializing in the repair and creation of castings by experimental or small-scale batches. The analysis of the used materials, adhesive compositions for their fastening, as well as economic indicators of the costs necessary for their production was made. The properties of glued joints used for manufacturing components of model kits from plastics and its combinations with metal parts are shown

Modern Methods of Creating Casting Model Kits

The article presents some information about creation of model kits and core equipment for the manufacture of molds and rods of cold-hardening sand-clay mixtures in the individual, serial and mass production of castings of ferrous and non-ferrous metals. There was analyzed their constituent materials and investigated a number of mechanical properties of the binding components for their attachment. Was shown the analysis of adhesive compositions of the world’s leading manufacturers, used for the manufacture of high-strength model sets by 3D milling methods

Некоторые особенности создания подшипниковых узлов прецизионных электрошпинделей на основе пар трения скольжения

Various types of bearing units are used for movable connections in mechanical engineering, and sliding pairs (sliding bearings, guides, bushings) are rather widely applied for this purpose. This allows increasing stiffness of units to reduce their dimensions, to improve heat dissipation and ensure reduction in noise and vibration. However in some cases while using a sliding friction pair higher friction losses occur in comparison with ball bearings and probability is increasing for situations when there is a jamming of friction surfaces. These problems have great significance for application of sliding bearings in precision equipment, which typically operates under stabilized temperature and humidity conditions. So an aim of the investigations is to develop methodological approaches for creation and rational design and manufacture of sliding friction pairs based on application of coatings formed of composite antifriction materials which are used in vertical precision program-controlled electro-spindles for high-speed machining. The paper considers issues pertaining to development and creation of friction units for precision electro-spindles of high rigidity with sliding friction pairs on the basis of composite materials. Diameters of sliding bearings can be rather large that makes it possible to obtain the required super-high accuracy in mechanical processing and nanometric roughness of the machined surface. A cutting speed (750 m/min or more) which is acceptable with regard to quality of machining by a diamond-like tool can be achieved by placing a cutting edge of the tool on diameter of 200 mm. Such approach permits to use lubricated sliding bearings in the spindle design. As a result, two tasks can be solved in an integrated manner. They include the required rigidity of an electrospindle for ultra-high accuracy of mechanical blade processing and high smoothness of the machined surface providing nanometric surface roughness with a decrease of macrodeviations up to 1 μm from a middle surface line. It is worth to note that this is extremely important for a number of special application

Dynamic integration of classifiers in the space of principal components

Recent research has shown the integration of multiple classifiers to be one of the most important directions in machine learning and data mining. It was shown that, for an ensemble to be successful, it should consist of accurate and diverse base classifiers. However, it is also important that the integration procedure in the ensemble should properly utilize the ensemble diversity. In this paper, we present an algorithm for the dynamic integration of classifiers in the space of extracted features (FEDIC). It is based on the technique of dynamic integration, in which local accuracy estimates are calculated for each base classifier of an ensemble, in the neighborhood of a new instance to be processed. Generally, the whole space of original features is used to find the neighborhood of a new instance for local accuracy estimates in dynamic integration. In this paper, we propose to use feature extraction in order to cope with the curse of dimensionality in the dynamic integration of classifiers. We consider classical principal component analysis and two eigenvector-based supervised feature extraction methods that take into account class information. Experimental results show that, on some data sets, the use of FEDIC leads to significantly higher ensemble accuracies than the use of plain dynamic integration in the space of original features. As a rule, FEDIC outperforms plain dynamic integration on data sets, on which both dynamic integration works (it outperforms static integration), and considered feature extraction techniques are able to successfully extract relevant features

Modulation of bacterial metabolism by the microenvironment controls MAIT cell stimulation article

Mucosal-associated invariant T (MAIT) cells are abundant innate-like T lymphocytes in mucosal tissues and recognize a variety of riboflavin-related metabolites produced by the microbial flora. Relevant issues are whether MAIT cells are heterogeneous in the colon, and whether the local environment influences microbial metabolism thereby shaping MAIT cell phenotypes and responses. We found discrete MAIT cell populations in human colon, characterized by the diverse expression of transcription factors, cytokines and surface markers, indicative of activated and precisely controlled lymphocyte populations. Similar phenotypes were rare among circulating MAIT cells and appeared when circulating MAIT cells were stimulated with the synthetic antigens 5-(2-oxoethylideneamino)-6-d-ribitylaminouracil, and 5-(2-oxopropylideneamino)-6-d-ribitylaminouracil. Furthermore, bacteria grown in colon-resembling conditions with low oxygen tension and harvested at stationary growth phase, potently activated human MAIT cells. The increased activation correlated with accumulation of the above antigenic metabolites as indicated by mass spectrometry. Thus, the colon environment contributes to mucosal immunity by directly affecting bacterial metabolism, and indirectly controlling the stimulation and differentiation of MAIT cells