Technology of ceramic material siliconborating impact on the properties of protective covering

Досліджено процес послідовного насичення реакційноспеченої кераміки на основі карбіду кремнію і дисиліциду молібдену та властивості захисного шару. Встановлено, що дифузійне насичення кремнієм і бором забезпечує повне відновлення диоксиду кремнію та отримання захисного покриття на поверхні матеріалу. Дослідження властивостей жаростійкого покриття показало, що гексаборид кремнію підвищує в 2–4 рази стабільність кераміки під час високотемпературного відпалу і призупиняє небажані дифузійні процеси на межі розподілу покриття – основа та покриття – середовище.The process of successive saturation of the carbide silicon and disilicide molybdenum reaction-sintered ceramics and properties of protective covering have been investigated. Silicon and boron diffusion saturation was found to provide complete recovery of dioxide silicon and obtaining the protective covering on the material surface. It was found that the silicon saturation can reduce more than twice the content of harmful admixtures in ceramics, silicon dioxide in particular. The saturation of carbide silicon and disilicide molybdenum by silicon reduces the content of harmful admixtures and thereby improves their properties. The main disadvantage of the silicon carbide and disilicide molybdenum products is their low resistance to high temperature oxidization. The method of combination of harmful admixtures under high-temperature treatment and chemical reactions was investigated. The process of carbide silicon and disilicide molybdenum saturation by the non-metallic materials has testified the heaters technological parameters to be improved. The investigation of the heat-resistant covering properties testified, that the hexaboride silicon increases in 2-4 times the ceramics stability under high-temperature sintering and retards undesirable diffusion processes on the covering distribution edge - basis and covering – environment. Carried out investigations make possible to conclude that creation of the protective covering on the surface of the reaction – sintered ceramics materials retards undesirable diffusion process, which occur on the edge basis – silicon-borid covering, and to increase the operating life of the protective layer. Carbide silicon and disilicide molybdenum silicon-boride covering provides complete recovery of the dioxide silicon and creation of the sufficient thickness hexaboride silicon heat-resistant layer on the material surface. The hexaboride silicon layer improves in 2 times the ceramics stability under vacuum annealing and in 4 times in the inert environment, the argon in particular. Creation of the triple phase on the edge covering – environment under siliconborating increases the heat-resistance covering stability and retards the undesirable processes, which occur on the edge hexaboride silicon-ceramics

Деятельность НОРАД: модель военно-политического сотрудничества в региональной системе международных отношений

У статті розглядається діяльність Об’єднаного командування протиповітряної оборони як цілісної системи та унікальної моделі військово-технічного співробітництва. Зроблено спробу виявити особливості формування та еволюції, цілі та завдання, а також можливості пристосування такої моделі до нових умов сучасного світу.This article considers the activity of North American Aerospace Defense Command as an all-in-one system and unique model of military-technical cooperation. It was done an attempt to detect features of formation and evolution, purposes and tasks, and also the possibility to adapt of this model to new conditions of modern world.В статье рассматривается деятельность Объединенного командования противовоздушной обороны как целостной системы и уникальной модели военно-технического сотрудничества. Сделано попытку выявить особенности формирования и эволюции, цели и задания, а также возможности приспособления такой модели к новым условиям современного мира

Technological characteristics of forming silicide coating on silicon carbide and disilicide molybdenum

Описано процес силіціювання карбідокремнієвої та дисиліцид молібденової кераміки. Подальше підвищення робочих температур і жорсткіші умови експлуатації нагрівачів вимагають покращення їх фізико-механічних і хімічних властивостей. Одним із напрямів підвищення характеристик електронагрівачів є вдосконалення технології. Встановлено, що насичення кремнієм дозволяє зменшити у понад двічі вміст у неметалевих матеріалах диоксиду кремнію. Силіціювання карбідокремнієвої та дисиліцид молібденової кераміки зменшує у них вміст шкідливих домішок і тим самим покращує їх експлуатаційні характеристики.The process of carbide silicon and disilicide molybdenum ceramics saturation is described in the article. The subsequent increase of operating temperatures and more severe conditions of heaters operation require the improvement of their physical-mechanical and chemical properties. One of the directions of improving the electric heaters characteristics is the improvement of technology. It was found that the silicon saturation can reduce more than twice the content of non-metallic materials of silicon dioxide. The saturation of silicon, carbide silicon and disilicide of molybdenum ceramics reduces the content of harmful admixtures and thereby improves their performance. The main disadvantage of the silicon carbide and disilicide molybdenum products is their low resistance to high temperature oxidization. To our mind, the promissing method is a method of combination of admixtures in different compounds under chemical-thermal treatment. Thus, the process of silicon-carbide and disilicide molybdenum based non-metal materials saturation with the purpose of disilicide molybdenum recovering, which makes worse the operating parameters of heaters, has been investigated in the paper. Studying of the influence of exposure time on the rate of the silicon saturation of non-metallic materials testified that with the increase of saturation duration from 2 to 12 hours the specific gain of silicon carbide specimens sharply increases, while in the molybdenum disilicide specimens only a slight increase is observed. The saturation of silicon carbide and molybdenum disilicide during more than 12 hours leads to sintering of mixtures, which greatly complicates the removal of specimens. X-ray analysis of silicon carbide and molybdenum disilicide saturation showed that the amount of silicon dioxide in non-metallic materials is reduced by more than 50%. Thus, we consider the diffusive saturation to be the effective way to remove silicon dioxide from the silicon carbide and molybdenum disilicide

Method for processing reaction sintered products based on silicon carbide and molibdenum disilicide

Описано основні способи обробки керамічних матеріалів на основі реакційно-спеченого карбіду кремнію та дисиліциду молібдену. Досліджено та проаналізовано технологічні умови обробки неметалевих керамічних матеріалів залежно від складу силіцидоксидної композиції в порошковій суміші. Встановлено, що підвищити ресурс експлуатації керамічних матеріалів на основі карбіду кремнію та дисиліциду молібдену можна шляхом введення оксиду цирконію, оксиду ітрію та оксиду гафнію. На основі проведених досліджень запропоновано оптимальні умови вибору концентрації даних добавок, які забезпечують високу швидкість насичення й покращують експлуатаційні параметри виробів. Також встановлено, що для інтенсифікації процесу обробки керамічних матеріалів на основі реакційно-спечених керамічних матеріалів у насичувальне середовище можна вводити різні склади силіцидоксидної композиції. Дифузійне насичення керамічних матеріалів із використанням гідриду титану забезпечує високу швидкість насичення та добру якість оброблюваної поверхні. Дослідження кінетики взаємодії силікоборидної фази з карборундовою та дисиліцидмолібденовою основою показало, що зі збільшенням тривалості нагрівання товщина дифузійного покриття зменшується. Завершальною операцією способу обробки реакційно-спечених керамічних матеріалів є нанесення на силікоборовану поверхню карбідокремнієвих і дисиліцидмолібденових зразків шару суспензії силіцидоксидної композиції, яка містить дисиліцидмолібдену, цирконієво-ітрієву кераміку і алюмінат натрію. Запропонований спосіб обробки реакційно-спечених керамічних матеріалів підвищує в 2 і 1,5 раза ресурс роботи зразків на основі карбіду кремнію та дисиліциду молібдену. Результати проведених досліджень показали, що запропонований спосіб може бути рекомендований для обробки виробів на основі реакційно-спечених карбідокремнієвих і дисиліцидмолібденових матеріалів, які використовуються для виготовлення електронагрівачів і різного типу конструкційних елементів високотемпературного обладнання.The main methods for processing ceramic materials based on reaction-sintered silicon carbide and molybdenum disilicide are described. The technological conditions of nonmetallic ceramic materials processing depending on the oxide silicide composition in the powder mixture are studied and analyzed. It is determined that the increase in the lifetime of ceramic materials based on silicon carbide and molybdenum disilicide can be achieved by introduction of zirconium oxide, yttrium oxide and hafnium oxide. Based on the carried out investigations, optimal conditions for selecting the concentration of these additives, which ensure high saturation speed and improve the operational parameters of the products are proposed. It is also determined that in order to intensify the processing of ceramic materials based on reaction-sintered ceramic materials, various compositions of the silicide oxide composition can be introduced into the saturation medium. Diffusion saturation of ceramic materials with titanium hydride provides high saturation speed and good quality of the surface to be treated. The study of the kinetics of the interaction of silicoboride phase with the carborundum and disilicide with molybdenum base showed that, with increasing heating duration, the thickness of the diffusion coating decreases. The final operation of the process for processing reaction-sintered ceramic materials is to apply silicon-based surface of carbide-silicate and disilicide molybdenum samples of the suspension layer of silicide oxide composition containing molybdenum disilicide, zirconium-yttrium ceramics, and sodium aluminate. The proposed method of processing reaction-sintered ceramic materials increases in 2 and 1.5 times the lifetime of samples based on silicon carbide and molybdenum disilicide. The results of the carried out research show that the proposed method can be recommended for the processing of products based on reaction – sintered carbide silicic acid and disilicide molybdenum materials used for the manufacturing the electric heaters and various types of structural elements of high-temperature equipment

PROTO-HORMONES LEVELS OF ADIPOSE TISSUE, INTERLEUKIN-6 AND INDICATORS OF DETOXIFYING FUNCTION OF THE LIVER IN PATIENTS WITH HYPERTENSION AND OBESITY COMBINED WITH NON-ALCOHOLIC FATTY LIVER DISEASE

The research estimates the state of liver detoxifying function and analyzes the changes in the levels of leptin, adiponectin and interleukin-6 in patients with arterial hypertension in combination with obesity and non-alcoholic fatty liver disease. Aim. The aim of the study is to evaluate levels of proto-hormones adipose tissue, interleukin-6 and indicators of detoxifying function of the liver in patients with hypertension and obesity combined with non-alcoholic fatty liver disease (NAFLD). Materials and methods. The study involved patients with arterial hypertension combined with obesity and NAFLD. All patients underwent anthropometric, general clinical, laboratory (blood lipid profile) and instrumental diagnostics (electrocardiography, echocardiography, ultrasonography, 13C-metacetin breath test, ELISA (adiponectin, leptin, IL-6). The patients’ height and weight were measured, the body mass index was calculated according to standard formulas. Results. Patients with arterial hypertension combined with obesity and NAFLD at the stage of steatohepatitis showed an increase in the levels of leptin and IL-6 and a decrease in the level of adiponectin. This group also revealed a moderate decrease in liver detoxifying function, as indicated by the results of 13C- MBT due to a 46.7 % decrease in the metabolic rate and a decrease in cumulative doses of CUM40 by 40 % and CUM120 by 46.8 %, respectively. Conclusions. The elevated levels of leptin and IL-6 and lowered adiponectin levels can be used to determine the degree of activity of non-alcoholic steatohepatitis and predict the course of NAFLD in combination with hypertension and obesity. An increased level of leptin and IL-6 and a low level of adiponectin in patients with such a comorbid pathology lead to an increase in the left ventricular myocardial mass index and aggravate the course of arterial hypertension

Identification of genes induced by BRCA1 in breast cancer cells

Cataloged from PDF version of article.Inherited mutations of the BRCA1 gene predispose to breast, ovarian, and other cancers. The role of the BRCA1 gene in the maintenance of chromosomal integrity is linked to a number of biological properties of its protein product, including transcriptional regulation. In the present study, we have used suppression subtractive hybridisation (SSH) to identify genes induced by BRCA1 by comparing control MCF7 breast carcinoma cells (driver) with MCF7 cells ectopically expressing BRCA1 (tester) and generated a forward subtracted cDNA library. We screened 500 putative positive clones from this library. Two hundred and ten of these clones were positive by differential screening with forward and reverse subtracted probes and the 65 cDNA clones which showed more than fivefold increase were selected for sequencing analysis. We clustered 46 different genes that share high homology with sequences in the GenBank/EMBL databases. Among these, 30 were genes whose function had been previously identified while the remaining 16 clones were genes with,unknown functions. Of particular interest, BRCA1 gene induces the expression of genes encoding DNA repair proteins RAD21 and MSH2, ERBB2/HER2 interacting protein ERBIN, meningioma-associated protein MAC30, and a candidate ovarian tumour-suppressor OVCA1. Northern and Western blot analyses confirmed that the expression of these five genes are up-regulated following BRCA1 overexpression in MCF7 and UBR60-bcl2 cells. This is the first study reporting a set of BRCA1-induced genes in breast carcinoma cells by the SSH technique. We suggest that some known genes identified in this study may provide new insights into the tumour-suppressor function of BRCA1. (C) 2002 Elsevier Science (USA). All rights reserved

Designing flexible learning for adults: Dialogue between University Lifelong Learning and professional contexts Engineering Example

Engineers are the professionals that have intense and continuous lifelong learning (LLL) activities regulated by professional organizations, by employers and by official agencies. That is due to the obsolescence of competences and the need face new challenges. The dialogue between with LLL providers and users of the required continuing professional development (CPD) training is not structured in most of the cases. An analysis of the CPD policy of the federation of engineering professional organizations (FEANI) is made in terms of foreseeing methods and approaches to improve the communications between the LLL providers and engineering CPD consumers. In the first place, the FEANI policy affirms that there is an on-going need for CPD of engineers in Europe. CPD is considered the acquisition of knowledge, experience and skills and the development of personal qualities. It embraces both the acquisition of new capabilities to broaden competence and the enhancement of existing capabilities to keep abreast of evolving technology and its application. CPD is essential for the maintenance of high professional standards and enhances the employability and mobility of individual engineers. It assists career progression and strengthens professional satisfaction. CPD benefits society and is of crucial importance in sustaining the competitiveness of European industry in the global market. CPD is the individual's responsibility and requires the cooperation, encouragement and support of employers and professional and academic institutions as CPD providers. Some countries professional engineering organizations require mandatory periodic CPD to keep the status as engineers. Therefore, engineering CPD, to be most effective, has to be planned and related to specific objectives. A personal development plan in terms of competences needs to be periodically updated. The CPD plan can include a variety of forms, including mentoring and the sharing of knowledge and expertise. This is one of the areas where LLL providers can cooperate with professional engineering organizations to provide guidelines for engineers. These guidelines could address inclusion of promotion of CPD as an important element of the engineering mission and establishment of a CPD policy highlighting the key role of qualified professional engineers for the development of the economy and society. The cooperation between the LLL providers and professional engineering organizations could address encouraging all stakeholders to invest in CPD for engineers, define quality standards in CPD as well as innovative practises in learning. Other topics are the support of individual engineers in their personal CPD definition, publicizing good practices in CPD and include initiatives on competence recognition, mobility, employability and accreditation of education. A second aspect of possible cooperation between engineering professional bodies and LLL providers could address the identification of training needs resulting from innovation developments among academic institutions in cooperation with engineering companies. Relevant innovations result from industry requests and respective training to implement those developments could then be defined and planned jointly as LLL provisions. A third aspect could be the recording and accreditation by academic institutions of CPD achievements by engineers in terms of the professional personal development plan