Experimental Stand for Investigations of Insulator Degradation and Electrode Erosion in High-current Breaker

An experimental stand for studies of electric arc, electrode erosion and insulator degradation processes in high-current circuit breakers and some preliminary experimental data is described. The setup includes a discharge chamber, a capacitive energy storage with capacitance of 0.11 F, voltage up to 10 kV, and all necessary diagnostic techniques. The stand is designed for modeling current pulse with amplitude of 3–150 kA and duration of the first half period of 1.0–3.0  ms during the process of disconnecting the ring and the pin contacts. The arc is cooled by transverse gas blowing at pressure in the chamber of 0.5–3 MPa. Acquired experimental data can be used for verification of the modelling results of the heat transfer processes in the discharge chamber. At the stand, advanced composite materials based on carbon and iron-copper pseudoalloy are studied

The Key Criteria in Deciding to Tender for Construction Projects

Planning for a construction project is a formidable task which involves a huge investment with multiple stakeholders such as clients, consultants, and contractors. A tender is a submission of a technical, administrative, and contractual material made by a potential contractor in response to an invitation to tender by the project client. Established contractors normally realise the importance of doing initial research before committing themselves to enter the tender. Normally, tender pre-qualification is a strict process. A low-quality tender submitted due to problems such as insufficient time and incomplete tender documents normally lead to tender rejection by the client. Thus, this research aimed to provide a strategy to help the contractors in deciding whether they should or should not submit a tender at the initial tendering decision phase. The literature review was focused on the key factors identified in influencing the decision-making process and in the final part, the initial conceptual model was establishe

The origin of large molecules in primordial autocatalytic reaction networks

Large molecules such as proteins and nucleic acids are crucial for life, yet their primordial origin remains a major puzzle. The production of large molecules, as we know it today, requires good catalysts, and the only good catalysts we know that can accomplish this task consist of large molecules. Thus the origin of large molecules is a chicken and egg problem in chemistry. Here we present a mechanism, based on autocatalytic sets (ACSs), that is a possible solution to this problem. We discuss a mathematical model describing the population dynamics of molecules in a stylized but prebiotically plausible chemistry. Large molecules can be produced in this chemistry by the coalescing of smaller ones, with the smallest molecules, the `food set', being buffered. Some of the reactions can be catalyzed by molecules within the chemistry with varying catalytic strengths. Normally the concentrations of large molecules in such a scenario are very small, diminishing exponentially with their size. ACSs, if present in the catalytic network, can focus the resources of the system into a sparse set of molecules. ACSs can produce a bistability in the population dynamics and, in particular, steady states wherein the ACS molecules dominate the population. However to reach these steady states from initial conditions that contain only the food set typically requires very large catalytic strengths, growing exponentially with the size of the catalyst molecule. We present a solution to this problem by studying `nested ACSs', a structure in which a small ACS is connected to a larger one and reinforces it. We show that when the network contains a cascade of nested ACSs with the catalytic strengths of molecules increasing gradually with their size (e.g., as a power law), a sparse subset of molecules including some very large molecules can come to dominate the system.Comment: 49 pages, 17 figures including supporting informatio

ТЕПЛОВЫДЕЛЯЮЩИХ СБОРОК ОТ АКТИНИДНЫХ ЗАГРЯЗНИТЕЛЕЙ МЕТОДОМ ИНДУКЦИОННО-ШЛАКОВОЙ ПЕРЕПЛАВКИ В ХОЛОДНОМ ТИГЛЕ

«New atomic energy technologies» federal program is being realized in Russia. This program includes experimental energy complex development and building, which contains: - a natural safety lead coolant fast reactor «BREST-300»; - a spent fuel recycle facility including fuel fabrication and re-fabrication, radioactive waste immobilization and discarding in accordance with radioactively-equivalent state. The current recycle facility preliminary design involves dry operation of spent fuel elements disassembly using steel shell dissolution by liquid zinc. Fuel element shells are made of special radiation-proof steel «EP-823» containing the following amounts of elements (%): C - 0.2; Мn - 0.8; Si - 1; S - 0.01; Р - 0.015; Сr - 12; Ni - 0.5; Мо - 0.9; V - 0.2; N - 0.05; Fe - 84.325. After dissolution zinc liquid containing steel elements is distilled. Still zinc is sent back to shells dissolution. The bottom product is destructurized particulate with the composition corresponding to original steel. Actinides steel shell and bottom product contamination was predicted using computer modeling. In accordance with the project technical specification actinide content in the disposable materials must be under 0.0001%. Thus, the bottoms product should be purified. Oxidative slag cold crucible induction melting purification was chosen and tested in laboratory scale. The following slag types were investigated: Al2O3-SiO2, B2O3-SiO2, Al2O3 - CaO. It was found that the most appropriate slag is B2O3-SiO2, and the optimal process temperature is about 1600°C.В настоящий момент в России реализуется федеральная целевая программа «Ядерные энерготехнологии нового поколения» Программа подразумевает разработку и создание опытно-демонстрационного энергокомплекса, включающего: - реактор на быстрых нейтронах со свинцовым теплоносителем, обеспечивающий естественную безопасность, «БРЕСТ-300»; - пристанционный модуль переработки, включающий фабрикацию и рефабрикацию топлива, иммобилизацию и удаление РАО в радиационно-эквивалентном состоянии. В настоящее время эскизный проект модуля переработки включает операцию сухого растворения оболочек ТВЭЛ жидким цинком. ТВЭЛы изготовлены из специальной радиацинно-стойкой стали марки ЭП-823, состоящей из следующих элементов (%): C - 0.2; Мn - 0.8; Si - 1; S - 0.01; Р - 0.015; Сr - 12; Ni - 0.5; Мо - 0.9; V - 0.2; N - 0.05; Fe - 84.325. После растворения цинк подвергают дистилляции и направляют обратно в процесс растворения оболочек ТВЭЛ. Кубовый остаток дистилляции представляет собой крупку, химический состав которой соответствует исходной стали. Как показали результаты компьютерного моделирования, материал оболочек ТВЭЛ и, соответственно, кубовый остаток будут загрязнены актинидами. В соответствии с техническим заданием проекта содержание актинидов в утилизируемых материалах не должно превышать 0.0001% масс., в связи с чем кубовый остаток должен быть очищен. Для очистки был выбран и опробован в лабораторном масштабе метод окислительной индукционно-шлаковой переплавки в холодном тигле. Опробованы следующие типы флюсов: Al2O3-SiO2, B2O3-SiO2, Al2O3 - CaO. Как показали эксперименты, наиболее эффективным оказался флюс на основе боросиликатного стекла B2O3-SiO2 при температуре процесса около 1600°C

Promotion of protocell self-assembly from mixed amphiphiles at the origin of life

Vesicles formed from single-chain amphiphiles (SCAs) such as fatty acids probably played an important role in the origin of life. A major criticism of the hypothesis that life arose in an early ocean hydrothermal environment is that hot temperatures, large pH gradients, high salinity and abundant divalent cations should preclude vesicle formation. However, these arguments are based on model vesicles using 1–3 SCAs, even though Fischer–Tropsch-type synthesis under hydrothermal conditions produces a wide array of fatty acids and 1-alkanols, including abundant C10–C15 compounds. Here, we show that mixtures of these C10–C15 SCAs form vesicles in aqueous solutions between pH ~6.5 and >12 at modern seawater concentrations of NaCl, Mg2+ and Ca2+. Adding C10 isoprenoids improves vesicle stability even further. Vesicles form most readily at temperatures of ~70 °C and require salinity and strongly alkaline conditions to self-assemble. Thus, alkaline hydrothermal conditions not only permit protocell formation at the origin of life but actively favour it

Improving Newborn Survival in Low-Income Countries: Community-Based Approaches and Lessons from South Asia

David Osrin and colleagues discuss the critical importance of reducing global neonatal mortality in developing countries and how community-based approaches can help

Genetic research: the role of citizens, public health and international stakeholders

Background: Genetic research has become an indispensable instrument for medical research, and the subjects involved have both divergent and convergent interests. Objective: The possibility of having more detailed genetic information undoubtedly offers benefits for the health of the subject, but could also pose risks and make the subject vulnerable to discrimination. Methods: The scientific community has viewed very favorably the public health utility of family history, in which data from a family whose members suffer from chronic pathologies is collected and filed, in order to develop a sort of “stratification of family risk.” Even though in the last decade the scientific and juridical literature has contributed greatly to the topic of biobanks, the perplexities that continue to surround this theme give the idea that current ethical protocols on research are inadequate. Results: Researchers, citizens, International stakeholders, mass media, Public Health and Governments play a key role in genetic research. It is obvious that the methods used for genetic research do not present intrinsic risks; they are much less dangerous than other activities of diagnosis and research. Before authorizing a research project, it is important to reflect on the responsibility and transparency of the studies to be conducted, and on the impact they may have on the interests of public health. Conclusion: We believe that the highest priority need is to develop a common language on the theme, as is the case in the sphere of clinical experimentation where rules of good clinical practice, albeit at times conflicting, have led to uniform convergences in the scientific world on the points to be actuated