Wear Resistance Improvement of Linear Block-Polyurethanes Under Conditions of Liquid Friction

A significant disadvantage of parts made of linear block polyurethanes under conditions of friction contact in the presence of an aqueous medium is the intensification of hydrolysis processes and decrease in volume strength. It was proposed to slow down the hydrolysis of polyurethanes in three ways: by directed changes in chemical structure, by electromagnetic radiation of different intensities and by creation of composite materials, based on the principle of additional intermolecular crosslinking at the manufacturing and hot processing stages. The conditions for the formation of a smooth wear-resistant surface that protects the material from rapid destruction are revealed.

Three Stages of Composite Specimen Destruction in Static Failure

The paper presents the results of standard specimen fracture made of anisotropic carbon fiber plastic with an epoxy matrix. Static stepwise loading of the specimen was carried out on an Instron 8801 testing machine to determine the characteristics of ductile fracture G1C in the first mode in accordance with ASTM D5528. During loading, the parameters of acoustic emission (AE) signals, such as AE impulse amplitudes and their energy were synchronously recorded. At the same time, the magnitude of the opening and the growth of the crack initiated by the artificial cut at the end of the specimen were recorded. According to the analysis of the acoustic emission signals, three zones with different G1C behaviour were identified: initial crack propagation, its stationary growth and accelerated fracture of the specimen. The zonal character of the change in the acoustic emission signals made it possible to determine the energy of the acoustic emission signals as diagnostic evidence for the onset of rapid destruction of the specimen. The amplitude of the AE-signals in the zones, however, remained constant. Online monitoring of changes in the energy of acoustic emission signals will prevent the onset of rapid destruction of an object in places of its deformations. The paper does not aim at defining G1C as usual. It presents the investigation of the fracture stages for a composite material using an acoustic emission method.

Gram stain microscopy in septic arthritis

Septic arthritis is a serious condition that can lead to rapid destruction of joint if it is not rapidly diagnosed and treated appropriately. The reported annual incidence is 10 in 100 000 although this increases to 70 in 100 000 in those with risk factors for developing septic arthritis mainly rheumatoid arthritis and immune-compromised patients. The aim of this study is to examine the sensitivity and specificity, and thus the clinical usefulness, of gram stain results. This was a single centre, retrospective case series. All joint aspirates over a three year period from May 2015 to April 2018 were reviewed. The gram stain and final culture results noted. 830 samples were included from both native and replaced joints. Native joints accounted for a total of 701 cases (84%) of the aspirates, whilst those obtained from prosthetic joints 129 (16%). In 74 (9%) cases there was a discrepancy between the gram stain and culture results. The sensitivity of the gram stain in this case series is 22% and the specificity of the test is 99.6%. The clinician should have a low threshold for overlooking a negative gram stain result and place greater emphases on the clinical findings in conjunction with biochemical markers.

Evaluation and Management of Septic Arthritis in Emergency Department “Narrative Review”

Septic arthritis (SA) is a secondary infective disease due to joints inflammation. It often appears with mono- or oligoarticular acute arthritis that frequently leads to an emergency department (ED) visit with need for prolonged hospitalization. SA is an orthopedic emergency that can threaten both life and limb due to its potential rapid destruction of the joint with fulminant sepsis, causing significant disability within hours to days. Delayed or poor treatment of septic arthritis can lead to irreversible joint damage with consequent disability in addition there to significant mortality rate. Management includes early detection and treatment with antibiotics, joint aspiration, and consultation for orthopedic surgery as potential operative management. This review aims to summarize current evidence regarding evaluation and management of septic arthritis in emergency department, and to highlight the difficulties of diagnosing and managing SA that face the healthcare providers to help overcome those difficulties and to recommend further studies to be done regarding those problems and their solutions.

Design of New-type Impactor Based on Combined Effect by Air-pressure and Electromagnetism

Analysis ofrock-breaking mechanism of cyclical impact loading under high and low impact on the basis of impact stress wave theory holds that microcrack occurs in the rock due to high energy impact and the following medium and low impact can cause rapid destruction of the rock. Intermittent impact method of variable impact energy is hence suggested. Electromagnetically-propelled device is added to the traditional air hammer by means of intermittent intervention by electromagnetic impact.Combined impact by gas and power and interval pneumatic impact is applied to design new-type impactor based on the combined effect by air-pressure and electromagnetism, which is supposed to provide a new solution for improvement of impactor work efficiency.

Cognitive Modeling Concepts of Sustainable Development of Society

In the context of rapid scientific and technological progress, which is the result of the development of science and technology and the process of accumulation and creation of new knowledge, fundamental and applied scientific research, information and technological changes are taking place. As a result, scientific-technological progress arose new forms and methods of organization of production, introduced a new technology, automated production processes, accelerating rate digitalization of all spheres of society, etc. The information society cre-ates prerequisites for the diversification of the structure of production and consumption, thereby changing the needs of society, encouraging the producer to create more and more new goods and services. However, along with the development of advanced technologies, there is the rapid destruction of nature and environmental pollution caused by the consequences of human industrial activity. The article substantiates the socio-ecological aspects of sustainable development on the basis of cognitive modeling, as well as suggests specific measures that contribute to the implementation of certain goals of the International strategy for sustainable development 2030. It is proved that the functioning of the technogenic system leads to the emergence of technogenic risks, the existence of which confirms the presence of a causal relationship between the technogenic load on the envi-ronment and the state of public health. The necessity of diagnostics of ecological and safe development of the population, which is designed to identify the selected parameters of the technogenic danger in the changing socio-economic reality, is justified.

Comparison of Long-term Prognosis in Siblings with Dentinogenesis Imperfecta depending on the Timing of the Treatment Intervention : Case Reports

Dentinogenesis imperfecta (DI) is a hereditary disorder of dentinal defect. It is generally inherited as a single autosomal dominant trait. DI usually affects both the primary and permanent dentition. Affected teeth have various types of discolorations, rapid destruction of the dentin, and severe attrition. In radiologic view, the affected teeth have bulbous crowns, short roots and narrow or closed pulp chambers. The treatment objective is to prevent additional attrition and recover the vertical dimension of occlusion.The aim of this report was to present the long-term prognosis in 15 years in a pair of siblings. Both the patients had DI with tooth attrition and discoloration. Different treatment procedures were used, depending on the difference in the timing of intervention. The first patient saved most of his teeth. The second patient had all of her teeth extracted. This report could be helpful for early diagnosis and overall treatment of DI.

Implementation of the "environmental imperative" in the framework of educational work at the university

Стремительное разрушение экологии в XXI веке стало одной из наиболее опасных тенденций, обсуждаемых на уровне мирового сообщества. Изменение климата и вызванные этим фактором наводнения, засухи и иные природные катаклизмы, истощение почв, дефицит воды, угроза голода – всё это говорит о том, что естественная среда обитания человека стремительно разрушается. Неблагоприятные условия, связанные с деформацией естественной эко-системы, загрязнением природной среды и истощением ресурсов, становятся фактором выживания человека и осложняют условия его жизнедеятельности. Статья посвящена проблеме экологического воспитания студентов вуза как неотъемлемой составляющей их профессиональной подготовки. Представлены результаты шестилетней работы автора по экологическому воспитанию в рамках проекта «Зелёный университет», реализуемого в Московском гуманитарном университете. Показаны дидактические принципы этой работы - социальности, научности, субъектности, диалогичности, проблемности, единства существования, познания, действия, обязательности, комплексности, равнозначности, - отражаемые в соответствующем содержании и организационных формах; определены методологические основания данной работы, изложенные в педагогических концепциях, теориях и подходах; выделены и содержательно представлены ее уровни - организационный, образовательный, воспитательный, социальный, научный, просветительский; показано влияние на экологическое воспитание эколого-ориентированной образовательной среды вуза, выделены ее элементы: научно-педагогические традиции вуза, его профессорско-преподавательский состав, инфраструктура. The rapid destruction of the environment in the XXI century has become one of the most dangerous trends discussed at the level of the world community. Climate change and the floods, droughts and other natural disasters caused by this factor, soil depletion, water scarcity, and the threat of famine-all this suggests that the natural habitat of man is rapidly being destroyed. Unfavorable conditions associated with the deformation of the natural eco-system, pollution of the natural environment and depletion of resources become a factor of human survival and complicate the conditions of his life. The article is devoted to the problem of environmental education of university students as an integral part of their professional training. The results of the author's six-year work on environmental education in the framework of the project "Green University", implemented at the Moscow University for the Humanities, are presented. The didactic principles of this work - sociality, scientific character, subjectivity, dialogicality, problemativeness, unity of existence, cognition, action, obligation, complexity, equivalence-are shown, which are reflected in the corresponding content and organizational forms; the methodological foundations of this work, set out in pedagogical concepts, theories and approaches, are determined; its levels - organizational, educational, educational, social, scientific, educational-are highlighted and presented in a meaningful way; the influence of the eco-oriented educational environment of the university on environmental education is shown, its elements are highlighted: the scientific and pedagogical traditions of the university, its teaching staff, infrastructure.

Rapid destruction of planetary debris around white dwarfs through aeolian erosion

ABSTRACT The discovery of numerous debris discs around white dwarfs (WDs) gave rise to extensive study of such discs and their role in polluting WDs, but the formation and evolution of these discs is not yet well understood. Here, we study the role of aeolian (wind) erosion in the evolution of solids in WD debris discs. Aeolian erosion is a destructive process that plays a key role in shaping the properties and size distribution of planetesimals, boulders, and pebbles in gaseous protoplanetary discs. Our analysis of aeolian erosion in WD debris discs shows that it can also play an important role in these environments. We study the effects of aeolian erosion under different conditions of the disc and its erosive effect on planetesimals and boulders of different sizes. We find that solid bodies smaller than $\sim \! 5 \, \rm {km}$ will be eroded within the short disc lifetime. We compare the role of aeolian erosion in respect to other destructive processes such as collisional fragmentation and thermal ablation. We find that aeolian erosion is the dominant destructive process for objects with radius $\lesssim \! 10^3 \, \rm {cm}$ and at distances $\lesssim \! 0.6 \, \mathrm{R}_\odot$ from the WD. Thereby, aeolian erosion constitutes the main destructive pathway linking fragmentational collisions operating on large objects with sublimation of the smallest objects and Poynting–Robertson drag, which leads to the accretion of the smallest particles on to the photosphere of WDs, and the production of polluted WDs.