Topological constraints on spiral wave dynamics in spherical geometries with inhomogeneous excitability

We analyze the way topological constraints and inhomogeneity in the excitability influence the dynamics of spiral waves on spheres and punctured spheres of excitable media. We generalize the definition of an index such that it characterizes not only each spiral but also each hole in punctured, oriented, compact, two-dimensional differentiable manifolds and show that the sum of the indices is conserved and zero. We also show that heterogeneity and geometry are responsible for the formation of various spiral wave attractors, in particular, pairs of spirals in which one spiral acts as a source and a second as a sink -- the latter similar to an antispiral. The results provide a basis for the analysis of the propagation of waves in heterogeneous excitable media in physical and biological systems.Comment: 5 pages, 6 Figures, major revisions, accepted for publication in Phys. Rev.

Analysis of the English Language Needs of Students at the Russian Technological University

The article looks into the English language needs of engineering students and young graduates at one of the leading technological universities in Russia - NUST MISiS. The authors used a mixed methodology approach to explore how often and in what real-life situations current and former students use the English language. 107 paper questionnaires were completed by master’s degree students in class and the answers were counted; 123 responses were received online from 2015 and 2016 graduates and processed statistically; 17 structured interviews with college administrators and subject professors were recorded and then coded for the main categories. The results demonstrate that despite dramatic changes at NUST MISiS under The Competitiveness Enhancement Program 5-100, good English competence is not a priority, with the majority of young graduates being ‘unsure’ about its benefits for their career and some administrators calling it ‘the least required competence’. However, the English language needs vary across subject departments. Thus, students majoring in new materials and programming use English on a regular basis, while economists and metallurgists might not really need it in both studies and future job. Overall, the most required skill is reading, and the least used ones are oral communication and academic writing in English. The authors discuss how orientation on potential rather than actual needs can affect the ESP/EAP course design in the context of engineering education in Russia

Ab initio calculation of the NMR spin-lattice relaxation time and the diffusion coefficient of 21Ne in liquid and supercritical states

Molecular dynamics simulations are performed with ab initio calculated potentials and electric field gradient curves on different levels of approximation, to study their influence on the relaxation time and diffusion coefficient of fluid 21Ne. Additional properties, such as quadrupole couplings, effective electric field gradient correlation times, and diffusion correlation times, are studied to get a better understanding of the underlying mechanisms. Semi-quantitative models for the total, self and cross correlation functions of the electric field gradient are developed

On the Cauchy Problem for the Korteweg-de Vries Equation with Steplike Finite-Gap Initial Data I. Schwartz-Type Perturbations

We solve the Cauchy problem for the Korteweg-de Vries equation with initial conditions which are steplike Schwartz-type perturbations of finite-gap potentials under the assumption that the respective spectral bands either coincide or are disjoint.Comment: 29 page

Microstructure of Complex Silicon-containing Modifier

Various research methods show that the microstructure of the complex siliconcontaining modifier ”Insteel 7” consists of six phases: TiFeSi2, Ca1

ACTIVE DYNAMICS OF THE ENZYMES OF THE ANTIRADICAL PROTECTION AND THE GENERAL ANTIOXIDATIVE ACTIVITY BY THE DEVELOPMENT OF THE EXPERIMENTAL ISCHEMIC REPERFUSION OF LIVER

The purpose of the study: to research the active changes in several enzymes of the antioxidative protection within the dynamical development of the liver reperfusion in rats. Materials and methods: the study has been performed on 95 white non-lineal male rats with the mass of 240-280 g divided into groups, the biological material of which has been sampled within 5-20 minutes of the ischemic period and 5-20 minutes of the reperfusion period with the interval of 5 minutes. To evaluate the changes of the antioxidative system the activity of the superoxide dismutase, the erythrocyte catalase and the liver homogenate as well as the general antioxidative activity have been determined. Results: the performed study has demonstrated the imbalance development for the relation between the activity of catalase and superoxide dismutase by the development of the ischemic reperfusion syndrome with the change of this relation to the prevalence of the catalase activity on the systemic level and the superoxide dismutase activity on the organic level after the circulatory restoration. Besides the increase in activity of the studied enzymes from the erythrocyte, meal by 2 times in comparison with the control group has been determined especially at the ischemic period as well as the tendencies to the progressive activity decrease of the same enzymes in the liver tissue. The general antioxidative activity in the period of ischemic reperfusion has been decreasing to the fifth minute of ischemia by 2 times and has lasted on the same level (0.04-0.05 mg/l of vitamin C in terms of 1 gram of homogenate protein) during the entire experiment. Conclusion: the received results have demonstrated the possibility for the evaluation of the functional state for the system of oxidative restorative homeostasis in an animal by ischemic reperfusion of the liver against the background of the lowered general antioxidative activity. It was marked also the necessity of the metabolic support of this link within the system of non-specific resistance for the correction of the developing disorders

Gender differences in the pharmacological actions of pegylated glucagon-Like peptide-1 on endothelial progenitor cells and angiogenic precursor cells in a combination of metabolic disorders and lung emphysema

In clinical practice, the metabolic syndrome (MetS) is often associated with chronic obstructive pulmonary disease (COPD). Although gender differences in MetS are well documented, little is known about sex-specific differences in the pathogenesis of COPD, especially when combined with MetS. Consequently, it is not clear whether the same treatment regime has comparable efficacy in men and women diagnosed with MetS and COPD. In the present study, using sodium glutamate, lipopolysaccharide, and cigarette smoke extract, we simulated lipid metabolism disorders, obesity, hyperglycemia, and pulmonary emphysema (comorbidity) in male and female C57BL/6 mice. We assessed the gender-specific impact of lipid metabolism disorders and pulmonary emphysema on angiogenic precursor cells (endothelial progenitor cells (EPC), pericytes, vascular smooth muscle cells, cells of the lumen of the nascent vessel), as well as the biological effects of pegylated glucagon-like peptide 1 (pegGLP-1) in this experimental paradigm. Simulation of MetS/COPD comorbidity caused an accumulation of EPC (CD45−CD31+CD34+), pericytes, and vascular smooth muscle cells in the lungs of female mice. In contrast, the number of cells involved in the angiogenesis decreased in the lungs of male animals. PegGLP-1 had a positive effect on lipids and area under the curve (AUC), obesity, and prevented the development of pulmonary emphysema. The severity of these effects was stronger in males than in females. Furthermore, PegGLP-1 stimulated regeneration of pulmonary endothelium. At the same time, PegGLP-1 administration caused a mobilization of EPC (CD45−CD31+CD34+) into the bloodstream in females and migration of precursors of angiogenesis and vascular smooth muscle cells to the lungs in male animals. Gender differences in stimulatory action of pegGLP-1 on CD31+ endothelial lung cells in vitro were not observed. Based on these findings, we postulated that the cellular mechanism of in vivo regeneration of lung epithelium was at least partly gender-specific. Thus, we concluded that a pegGLP-1-based treatment regime for metabolic disorder and COPD should be further developed primarily for male patients

The Role of the Pyruvate Dehydrogenase Complex in the Development of Ischemic-Reperfusion Syndrome

Background. One of the key components of energy metabolism is the pyruvate dehydrogenase complex (PDC), the activity of which can be targeted by some cytoprotectors. However, their role remains unclear. It is known that the activation of the PDC in tumor cells leads to an inversion of anaerobic glycolysis with an increase in the generation of free radicals in the respiratory chain and a decrease in viability. At the same time, there is evidence of increased resistance of normal cells to hypoxia and reperfusion.Objectives. Analysis of current information on the role of PDC in the development of pathologic biochemical changes in ischemic reperfusion syndrome and methods of metabolic correction using agents for regulating the activity of the considered multienzyme complex. Methods. The bibliographical search was carried out across the eLIBRARY and PubMed databases with a selection of articles published over the past 10 years in the English and Russian languages, as well as some parts of fundamental works in the selected field, published more than 10 years. To be selected for bibliographical review, the article can be of any design, reflecting the ideas about the role of PDC in the development of pathologic biochemical changes in ischemic-reperfusion lesions of various organs and tissues.Results. The bibliographical analysis indicates a decrease in the activity of PDC in myocardial tissue during a heart attack or heart failure, the activity of the enzyme in skeletal muscles decreases against the background of acute hypoxia. PDC activity also decreases under chronic stress and extensive muscular exercise. At the same time, the PDC activity remains at the normal level in the ischemic period, and the transition to the reperfusion period is accompanied by a sharp decrease in the activity of the multienzyme complex. The PDC inactivation occurring under these conditions can result from a damage by reactive oxygen species, as well as by regulatory control changes through phosphorylation/dephosphorylation. Assuming the key role of PDC in the development of energy exchange disorders against the ischemic-reperfusion injuries 2 main strategies might be offered for metabolic correction: 1) an increase in the activity of PDC (activator — sodium dichloroacetate) or compensation for its lack with substrates of the tricarboxylic acids (acetylcarnitine, β-ydroxybutyrate); 2) protection of PDC from damage (antioxidants).Conclusion. The basis of energy exchange disorders in the reperfusion period is a decrease in PDC activity, and modification of its activity is a promising direction for metabolic prevention or correction of ischemic-reperfusion injures

ЭКСТРАКЦИОННО-ФЛУОРИМЕТРИЧЕСКОЕ ОПРЕДЕЛЕНИЕ ХЛОРОФИЛЛА «А» В ПРИРОДНЫХ ВОДАХ

The assessment methods of chlorophyll «а» in the natural waters have been analyzed. This pigment of phytoplankton is the main indicator of the primary bioproductivity and trophicity of the reservoir.  The key spectrometric methods of determination were compared, and their advantages and disadvantages were discussed.  The application features of different types of spectrometric determination of the analyte from classical spectrophotometric methods to remote sensing of water bodies were considered.  The preference was shown for the determination of chlorophyll by the fluorescent methods, which were used in different implementation variations.  The method of extraction-fluorescent determination of chlorophyll «а» was substantiated and implemented after the chlorophyll extraction from the water with chloroform and measuring the fluorescence intensity at λexc = 418 nm and λlum = 675 nm.  The results of the chlorophyll «а» determination were compared using the standardized spectrophotometric and the developed techniques for the model and real water samples.  It was educed that in the area of low concentrations of chlorophyll «а» (0.05 μg of analyte in 1000 cm3 of water) the analytical signal was recorded only by the fluorimetric method, while in the area of higher concentrations (0.2 μg of analyte in 1000 cm3 of water) the standardized spectrophotometric method produced the overestimated results.  The developed method for the extraction-fluorimetric determination of chlorophyll «а» in the natural waters (both fresh and marine) was metrologically certified and put into the register of the Federal Information Fund for ensuring the uniformity of measurements.Key words: chlorophyll «а» , extraction - fluorimetric determination, trophicity of the reservoirDOI: http://dx.doi.org/10.15826/analitika.2019.23.3.001(Russian)Z. A. Temerdasheva1, L. F. Pavlenko2, Ya. S. Ermakova1,2, I. G. Korpakova1,             B. D. Eletskii1 1Department of Chemistry and High Technology, Kuban State University, Krasnodar, 350040, Russian Federation2Azov-Black Sea branch of VNIRO (“AzNIIRKH”), Rostov-on-Don, 344002, Russian FederationВ статье проводится анализ методов определения хлорофилла «а» в природных водах – основного пигмента фитопланктона, являющегося индикатором первичной биопродуктивности и трофности водоема. Приводится сравнительная характеристика спектрометрических методов определения, их достоинства и недостатки. Обсуждаются особенности применения различных видов спектрометрического определения аналита: от классических спектрофотометрических до методов дистанционного зондирования водоемов. Показана предпочтительность определения хлорофилла флуоресцентными методами, которые используются в различных вариантах реализации. Обоснована и реализована методика экстракционно-флуоресцентного определения хлорофилла «а» после экстракции его из воды хлороформом и измерении интенсивности флуоресценции при λвозб = 418 нм и λлюм = 675 нм. Проведено сравнение результатов определения хлорофилла «а» стандартизированной спектрофотометрической и разработанной методиками на модельных и реальных пробах воды.  Показано, что в области низких концентраций хлорофилла «а» (0,05 мкг аналита в 1000 см3 воды) аналитический сигнал регистрируется только флуориметрическим методом, а в области более высоких концентраций (0.2 мкг аналита в 1000 см3 воды) спектрофотометрическая стандартизированная методика дает завышенные результаты. Разработанная методика экстракционно-флуориметрического определения хлорофилла «а» в природных водах (пресных и морских) метрологически аттестована и внесена в реестр Федерального информационного фонда по обеспечению единства измерений.Ключевые слова. Хлорофилл «а» , экстракционно-флуориметрическое определение, трофность водоемов.DOI: http://dx.doi.org/10.15826/analitika.2019.23.3.00