Mechanical properties, biodegradation, and biocompatibility of ultrafine grained magnesium alloy WE43

In this work, the effect of an ultrafine-grained (UFG) structure obtained by multiaxial deformation (MAD) on the mechanical properties, fatigue strength, biodegradation, and biocompatibility in vivo of the magnesium alloy WE43 was studie

CASE-tools for database design: overview and brief description

The article deals with the automation of database design; an overview of existing CASE-tools on the market.Given their brief description and a comparative analysis with emphasis on non-commercial CASE-tools that implement the model method of design automationВ статье рассмотрены средства автоматизации проектирования баз данных; сделан обзор существующих CASE-средств, представленных на рынке. Дана их краткая характеристика и проведен сравнительный анализ с акцентом на некоммерческих CASE-средствах, реализующих модельный метод автоматизации проектировани

Academic stress and its effect on medical students’ mental health status

This review aimed to analyze the data on features of a medical students’ mental status and its dynamics in the course of study. The analysis was applied to the scientific publications (mainly over the past 5 years) on the issue of academic stress and medical students’ mental status in different countries from computer databases: PubMed, Medical-Science, eLibrary, Web of Science, and Scopu

The Role of Outer Membrane Vesicles of Agents of Particularly Dangerous Infections in the Pathogenesis and Immunogenesis of Infectious Process

The literature review is devoted to the modern concepts of the vesiculation phenomenon and its biological role in pathogenic bacteria – causative agents of particularly dangerous human infections. Data on the production, structure, composition, and functions of the outer membrane vesicles (OMV) of bacteria have been summarized. In recent years, the interest of researchers in the formation of spherical structures (so called bubbles or vesicles) from outer membrane of gram-negative bacteria has significantly increased. Such structures are surrounded by the double layer of a phospholipid membrane, the outer layer of which is enriched with lipopolysaccharide molecules. The inner space of vesicles could include various antigens, receptors, adhesins, toxins, enzymes, porins, etc. The formation of vesicles by the outer membranes of bacteria is recognized as a normal physiological manifestation of bacterial activity aimed at adaptation to environmental conditions. The investigation of the biological role of OMV showed their connection with the pathogenesis and immunogenesis of bacterial diseases. The review provides information on the peculiarity of induction, OMV composition and their participation in the processes of patho- and immunogenesis of severe infections caused by groups I–II PBA – the gram-negative causative agents of plague, tularemia, brucellosis, glanders, melioidosis, cholera, and formation of extracellular vesicles in a gram-positive anthrax pathogen. The particular attention is paid to the issue of developing safe and effective next-generation vaccine preparations based on bacterial vesicles

Students' individual work on studying the discipline «Mathematics Teaching Methodology» by using distance technologies

© 2017. revistaESPACIOS.com. The urgency of the problem set in the article is stipulated by the fact that over the recent years the role of information technologies in organizing students' individual work has strengthened. In this context, it is necessary to provide the educational process with electronic educational resources. The aim of the article is to organize individual work of students and to estimate its efficiency when mastering the discipline "Mathematics Teaching Methodology" by using distance technologies. The leading methods in researching this problem include the method of design aimed at selecting and structuring the content of the electronic resource, as well as testing according to the estimation of the performed work efficiency. The developed resources include all required components for organizing and carrying out the students' individual work: study, control, and correction. The experiment made by teachers of the Elabuga Institute of the Kazan (Volga Region) Federal University and related to implementing the developed electronic resources in the educational process showed the importance and efficiency of applying distance technologies in organizing individual work of students

The effect of equal-channel angular pressing on microstructure, mechanical properties, and biodegradation behavior of magnesium alloyed with silver and gadolinium

The effect of equal channel angular pressing (ECAP) on the microstructure, texture, mechanical properties, and corrosion resistance of the alloys Mg-6.0%Ag and Mg-10.0%Gd was studied. It was shown that ECAP leads to grain refinement of the alloys down to the average grain size of 2–3 μm and 1–2 μm, respectively. In addition, in both alloys the precipitation of fine particles of phases Mg$_{54}$Ag$_{17}$ and Mg$_{5}$Gd with sizes of ~500–600 and ~400–500 nm and a volume fraction of ~9% and ~8.6%, respectively, was observed. In the case of the alloy Mg-6.0%Ag, despite a significant grain refinement, a drop in the strength characteristics and a nearly twofold increase in ductility (up to ~30%) was found. This behavior is associated with the formation of a sharp inclined basal texture. For alloy Mg-10.0%Gd, both ductility and strength were enhanced, which can be associated with the combined effect of significant grain refinement and an increased probability of prismatic and basal glide. ECAP was also shown to cause a substantial rise of the biodegradation rate of both alloys and an increase in pitting corrosion. The latter effect is attributed to an increase in the dislocation density induced by ECAP and the occurrence of micro-galvanic corrosion at the matrix/particle interfaces

Complex analysis of flax seeds composition for breeding programs

Single plant selection using complex of seed quality traits requires development and optimization of the methods, which allow qualitative and quantitative analysis applying minimum quantity of seeds. The proposed evaluation scheme of seed composition enables optimal use of seed material for individual plant analysis: oil percentage (Rushkovsky’s extraction method), fatty acid composition (vaporliquid chromatography), protein and ash content (dynamic thermogravimetry), elemental composition (electron probe X-ray fluorescence method). Reproducibility of analytical methods used was assessed by the coefficient of variation, the reproducibility index (ARI) and the convergence of data on seasonal cultivation

Кистозные изменения фильтрационной подушки после применения цитостатиков при антиглаукоматозной операции. Экспериментальные исследования

PURPOSE: Experimental comparative analysis of hystomorphology associated with different ways of fibrosis prevention in the bleb zone after glaucoma surgery. METHODS: Experiments were conducted on rabbits with approximate weight up to 2.5 kg both male and female (12 animals, 12 eyes). In the first group the rabbits underwent penetrating deep sclerectomy (PDS) with subsequent application of mitomycin C (5 rabbits, 5 eyes). In the second group PDS was performed with Xenoplast (Transkontakt, Moscow, Russia) collagen drainage implantation under the scleral flap (5 rabbits, 5 eyes). The third or control group included 2 rabbits (4 eyes) that underwent PDS with no modifications. Follow-up period lasted for 2 months in all groups. RESULTS: Early postoperative period was characterized by the formation of high filtration blebs in all groups. Filtration surgery with mitomycin C application resulted in high thin-walled avascular bleb formation. In all rabbits of group 1 after 2 months the filtration area gradually decreased in size and lost bleb appearance, replaced by a cystoid formation corresponding with the area of previous mitomycin C application. According to histological examination, the blebs in the comparison group were filled with loose, porous tissue with a minimal amount of connective tissue cellular elements. A formation of separate vessels was noted, which was indicative of their low functional consistency. The sclera located under the filtration bleb consisted of well-defined collagen fibers, more structured than the sclera in the comparison groups, which can be attributed to the impact of drainage on the collagen fibers that constitute the mechanical basis of the scleral tissue. CONCLUSION: Cytostatics, while inhibiting the regeneration, apparently do not affect the remodulation processes. The implantation of collagen drainage containing collagen type I prevents scarring of the operation site and at the same time prolong the effect of glaucoma surgery by helping neutralize the process of eye tunic remodulation associated with the formation of thin-walled capsules impermeable to fluid.ЦЕЛЬ. Сравнительная оценка гистоморфологической картины при различных способах профилактики фиброза в зоне фильтрующей антиглаукоматозной операции в эксперименте. МЕТОДЫ. Экспериментальные исследования проводили на кроликах массой до 2,5 кг обоего пола (12 животных, 12 глаз). В 1-й опытной группе проводили глубокую склерэктомию с последующей аппликацией митомицина С (5 кроликов - 5 глаз). Во 2-й группе после аналогичной операции имплантировали под глубокий склеральный лоскут коллагеновый дренаж ДКА Ксенопласт (производства ООО «Трансконтакт», Москва) (5 кроликов - 5 глаз). В 3-й группе 2 кролика (4 глаза) составили группу сравнения. В этой группе производили глубокую склерэктомию (ГСЭ) без дополнительных мер. Срок наблюдения составил 2 месяца. РЕЗУЛЬТАТЫ. Ранний послеоперационный период характеризовался формированием высокой фильтрационной подушечки (ФП) во всех группах. В результате проведения фистулизирующей операции с аппликацией митомицином формировались высокие аваскулярные тонкостенные ФП. В 1-й группе через 2 месяца во всех случаях сформированные зоны фильтрации постепенно уменьшались в размерах и теряли вид подушки. На их месте образовывались кистовидные образования, по размерам соответствующие области, в которой осуществлялась аппликация митомицина. В группе сравнения на гистологическом срезе в области ФП можно видеть, что весь ее объем заполнен рыхлой, пористой тканью с минимальным количеством клеточных элементов соединительной ткани. Отмечается формирование отдельных сосудов, что свидетельствует об их малой функциональной состоятельности. Склера, расположенная под фильтрационной подушкой, состоит из хорошо определяющихся коллагеновых волокон, более структурированных, чем склера в препаратах группы сравнения. Это можно отнести на счет воздействия дренажа на коллагеновые волокна, составляющие механическую основу склеральной оболочки. ВЫВОДЫ. Цитостатики, угнетая регенерацию, по-видимому, не влияют на процессы ремодуляции. Имплантация коллагенового дренажа, включающего коллаген I типа, препятствует рубцеванию зоны операции и одновременно позволяет нейтрализовать процессы ремодуляции оболочек глаза с образованием тонкостенной непроницаемой для влаги капсулы, что продлевает фильтрующий эффект антиглаукоматозной операции

Selective Constraints on Amino Acids Estimated by a Mechanistic Codon Substitution Model with Multiple Nucleotide Changes

Empirical substitution matrices represent the average tendencies of substitutions over various protein families by sacrificing gene-level resolution. We develop a codon-based model, in which mutational tendencies of codon, a genetic code, and the strength of selective constraints against amino acid replacements can be tailored to a given gene. First, selective constraints averaged over proteins are estimated by maximizing the likelihood of each 1-PAM matrix of empirical amino acid (JTT, WAG, and LG) and codon (KHG) substitution matrices. Then, selective constraints specific to given proteins are approximated as a linear function of those estimated from the empirical substitution matrices. Akaike information criterion (AIC) values indicate that a model allowing multiple nucleotide changes fits the empirical substitution matrices significantly better. Also, the ML estimates of transition-transversion bias obtained from these empirical matrices are not so large as previously estimated. The selective constraints are characteristic of proteins rather than species. However, their relative strengths among amino acid pairs can be approximated not to depend very much on protein families but amino acid pairs, because the present model, in which selective constraints are approximated to be a linear function of those estimated from the JTT/WAG/LG/KHG matrices, can provide a good fit to other empirical substitution matrices including cpREV for chloroplast proteins and mtREV for vertebrate mitochondrial proteins. The present codon-based model with the ML estimates of selective constraints and with adjustable mutation rates of nucleotide would be useful as a simple substitution model in ML and Bayesian inferences of molecular phylogenetic trees, and enables us to obtain biologically meaningful information at both nucleotide and amino acid levels from codon and protein sequences.Comment: Table 9 in this article includes corrections for errata in the Table 9 published in 10.1371/journal.pone.0017244. Supporting information is attached at the end of the article, and a computer-readable dataset of the ML estimates of selective constraints is available from 10.1371/journal.pone.001724

Опыт создания личного кабинета студента – личной электронной библиотеки в РГАУ-МСХА им. К. А. Тимирязева

The article is devoted to the currently topical topic of using the electronic library system by means of creating a student's personal account – a personal electronic library. The problem of using information technologies to provide students with high-quality educational information is currently coming to the fore due to the emergence of a large flow of information and the lack of criteria for its selection among students. The purpose of the publication is to acquaint readers with the results of work on the development of a personal electronic library of a university student, to provide students with educational materials in full, as well as with the results of a study of the effectiveness of using a personal account in the process of teaching students. To achieve this goal, the authors carried out experimental work, consisting of three modules: basic, theoretical and intellectual, as well as experimental work to establish the influence of the developed personal electronic library on the level of educational motivation of students, as well as its relationship with academic performance. The results of the study show that the use of a personal electronic library increases the educational motivation of students to study the subject, and also positively affects the academic performance of students, improving the quality of education. The practical significance of the work lies in the creation of a student's personal electronic library based on the electronic library system of the RSAU-Moscow Agricultural Academy named after K. A. Timiryazeva, which can be used in teaching university students.Статья посвящена использованию электронно-библиотечной системы с помощью личного кабинета студента – личной электронной библиотеки. В связи с появлением большого потока информации и отсутствием у студентов критериев её отбора проблема использования информационных технологий для обеспечения обучающихся качественной учебной информацией выходит на первый план. Статья знакоимт с результатами разработки личной электронной библиотеки, обеспечивающей студентов учебным материалом в полном объёме, а также с исследованием эффективности использования личного кабинета в процессе обучения. Авторы провели экспериментальную работу, состоящую из трёх модулей: базового, теоретического и интеллектуального, а также установили влияние личной электронной библиотеки на уровень учебной мотивации студентов и успеваемости. Результаты исследования показали, что личная электронная библиотека повышает учебную мотивацию студентов, положительно влияет на их успеваемость, повышая качество образования. Практическая значимость работы заключается в создании личной электронной библиотеки студента на базе электронно-библиотечной системы РГАУ-МСХА им. К. А. Тимирязева. Библиотека студента может использоваться при обучении студентов вуза