A symmetric problem of elasticity is formulated to analyze the plastic zone at the corner point of the interface between two isotropic media. The piecewise-homogeneous isotropic body with an interface in the form of angle sides consists of different elastic parts joined by a thin elastoplastic layer. The plastic zone is modeled by discontinuity lines of tangential displacement, which are located at the interface. The exact solution of the problem is found using the Wiener-Hopf method and is then used to determine the length of the plastic zone. The stress at the corner point is analyzed Keywords: plastic zone, corner point, interface, displacement discontinuity line, Wiener-Hopf method Introduction. There are a great variety of recent publications on plastic and other fracture process zones at cracks tips in anisotropic and piecewise-homogeneous bodies [1,[10][11][12][14][15][16][17][18]. Of current importance are problems related to fracture process zones at corner points of such bodies. For example, of considerable interest for the fracture mechanics of adhesive joints is analysis of the stress-strain state at singular points of piecewise-homogeneous bodies composed of different elastic parts bonded with each other by a thin elastoplastic layer. Here we will perform such an analysis for a corner point of the interface between media.This stress-strain analysis is reduced to problems of elasticity for piecewise-homogeneous wedge-shaped bodies. The information on the singularities of the stresses at corner points obtained by solving these problems can be used in developing numerical methods for stress-strain analysis of compound piecewise-homogeneous bodies with corner points.1. Problem Formulation. Assuming plane strain, we will formulate a symmetric problem of elasticity for a piecewise-homogeneous isotropic body. It has an interface in the form of angle sides and consists of different elastic parts bonded to each other by a thin elastoplastic layer.As the external load increases, a plastic zone develops at the corner point, which is a peaked stress concentrator. The zone has the form of two narrow bands emerging from the point and located in the interface. We will study only the initial stage of development of the plastic zone and consider that the external load is weak for the zone to be much less than the body.The task is to determine the length of the plastic zone and to analyze the stress state at the corner point.Since the bonding material is elastoplastic, primarily shear deformation occurs in the fracture process zone. Therefore, we will model the zone by a discontinuity line of tangential displacement on which the tangential stress is equal to the shear yield stress of the bonding material t s .Thus, we arrive at a static symmetric plane problem of elasticity for a piecewise-homogeneous isotropic plane having an interface in the form of angle sides and cuts of finite length emerging from the corner point and located in the interface (Fig. 1). At infinity, the solution of this problem is the solution of ...
The relevance of the research topic. On the recent methods of biotechnology are increasingly used in plant breeding and seed production. Herbaceous plants such as strawberries, potatoes, a vegetable, some medicinal and others are capable of vegetative propagation the traditional methods of culture, successfully introduced in both in vitro and can achieve a high rate of reproduction. Modern plant biotechnology – the sum of the technologies developed in molecular and cell biology of plants – a new stage in the development of the technology of plant breeding. With these improved characteristics may occur at the level of individual genes and individual genes that determine a specific trait, can be identified. They may be the final selection, they can be isolated, insert, delete, or modify the genotype or variety. Goal. Identify the features of the manifestation of economically valuable features and decorative properties of Callistephus chinensis and the inclusion of the best varieties in the biotech link, their adaptation to the conditions of the Forest-Steppe of Ukraine and their further use in landscaping. Methods. Laboratory – determination of seed germination; mathematical and statistical - for processing the reliability of the obtained research results. Results. The nutrient medium for growing plant tissues and cells, by analogy with the medium for culturing animal tissues, should contain all that the tissues in the plant organism receive from xylem and phloem currents of substances. However, in practice it has been found that vegetable juices cannot serve as a complete nutrient medium for growing isolated tissues and cells. This manifests the specificity of the receipt, transportation and especially the redistribution of nutrients in the plant. Based on the analysis, research was conducted to study the possibility of mass off-season vegetative propagation of plants of Callistephus chinensis in vitro. Practical recommendations on the selection of sterilizer, sterilization, nutrient medium and for the adaptation period of the best genotypes of this culture have been developed. As a result of the conducted researches the methods of selection of the initial plant material of Callistephus chinensis (Callistephus Chinensis (L.) NEES) and its surface sterilization, modification of existing aseptic culture methods have been studied and mastered. The morphogenetic potential of explants from different plant organs was investigated and selection of nutrient medium and study of the influence of plant growth regulators and physical parameters on the process of morphogenesis was carried out. The features of regeneration of isolated explants depending on the composition of the nutrient medium and selection of conditions for obtaining self-clones of Callistephus chinensis (Callistephus Chinensis (L.) NEES) were studied. Key words: in vitro, plant biotechnology, Callistephus Chinensis, nutrient medium, rhizogenesis.
Introduction: Alcohol addiction is one of major public health concerns because rich assortment of alcohol drinks, alcohol advertising may hasten the initiation of alcohol drinking and increase consumption among children and adolescents nowadays. Cytotoxic effect of alcohol is among the leading causes of oral mucosa malignant degeneration, therefore alcohol drinkers are at risk of cancerous diseases. This should be taken into consideration by dentists during routing check-ups. The assessment of oral status in alcohol abusers is essential for making up a treatment plan and prophylaxis, and the investigation of oral manifestations in alcohol drinkers is of great clinical significance. The aim: To determine the peculiarities of oral status in underage drinkers. Materials and methods: The study involved 135 inpatients aged 14-17, who took the course of treatment at the Narcological Department, Poltava Regional Clinical Psychiatric Hospital. We assessed the condition of periodontal tissues and oral mucosa. Results: There was a tendency towards an increase in precancerous diseases depending on the age of patients and the length of alcohol addiction. The prevalence rate of the diseases in the first group of patients who had being abused alcohol for 2 years was 10,91% of cases; and in the second group of patients who had being abused alcohol for 3 years it made up 16,80%. This may be explained by adverse effect of ethanol on the oral mucosa and by no regular dental check-ups. Conclusions: Based on the results obtained, it is appropriate to recommend mandatory oral check-ups for adolescents with alcohol abuse.
Санкт-Петербургский государственный педиатрический медицинский университет, Санкт-Петербург, Российская Федерация Скрининговые медицинские осмотры детского населения представляют собой мощный инструмент мониторинга здоровья подрастающего поколения, другими словами-это активный метод динамического наблюдения за состоянием здоровья детей. Цель скрининга-раннее выявление отклонений от нормы с дальнейшей постановкой на учет, диспансерным наблюдением и комплексным лечением больных. На сегодняшний день в Российской Федерации действует регламентирующий документ по проведению профилактических периодических и предварительных осмотров (Приказ МЗ РФ № 1346). Проблема заключается в нехватке времени и ресурсов, что приводит к формальному подходу к этому необходимому разделу профилактической работы. В статье предлагаются выходы из сложившейся ситуации, которые бы удовлетворили и руководителей, и самих участковых педиатров.
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