Numerical simulation of helical-vortex effects in Rayleigh-Bénard convection

International audienceA numerical approach is substantiated for searching for the large-scale alpha-like instability in thermoconvective turbulence. The main idea of the search strategy is the application of a forcing function which can have a physical interpretation. The forcing simulates the influence of small-scale helical turbulence generated in a rotating fluid with internal heat sources and is applied to naturally induced fully developed convective flows. The strategy is tested using the Rayleigh-Bénard convection in an extended horizontal layer of incompressible fluid heated from below. The most important finding is an enlargement of the typical horizontal scale of the forming helical convective structures accompanied by a cells merging, an essential increase in the kinetic energy of flows and intensification of heat transfer. The results of modeling allow explaining how the helical feedback can work providing the non-zero mean helicity generation and the mutual intensification of horizontal and vertical circulation, and demonstrate how the energy of the additional helical source can be effectively converted into the energy of intensive large-scale vortex flow

ИЗУЧЕНИЕ МИГРАЦИЙ СЕЙСМИЧЕСКОЙ АКТИВНОСТИ С ПОМОЩЬЮ ПОСТРОЕНИЯ ПРОСТРАНСТВЕННО-ВРЕМЕННЫХ ДИАГРАММ

Seismicity migration is studied by a new method based on space-time diagrams and a combination of cluster and regression analyses. Data from the global and Baikal regional earthquake catalogues are analysed with the application of the specially designed geographic information system (GIS) in order to establish parameters and mechanisms of seismicity migration in space and time. We study the migration of seismic events in the following geostructural systems: the Baikal rift zone (BRZ), the area between BRZ and the Indo-Eurasian interplate collision zone, the area between BRZ and the West-Pacific seismic foci Benoiff zone, and two segments of the Middle Atlantic ridge.As evidenced by the obtained results, studying regimes of seismic migration provides for analyses of space-time distribution of seismic energy in the fault-block structure of the lithosphere and facilitates more detailed studies of the origin of deformation waves and mechanisms of the seismotectonic regime of the Earth. Forward (from the equator) and backward (towards the equator) migration of seismic events are established in all the regions under study. It is assumed that this phenomenon may result from regular changes of the polar compression of the Earth due to variations of its rotation regime. Besides, it is revealed that energy clusters of migration are regularly generated, and the regularity may be related to the 11-year cycle of the solar activity which impacts the seismic regime. We discuss the need to study the interference of wave deformations in the lithosphere which are initiated by several external energy sources. It is proposed to consider the regimes of planetary seismicity migration as a reflection of redistribution of endogenic (primarily heat) energy of the Earth during the destruction of its lithospheric shell under the impacts of cosmogenic factors via triggering mechansms. With reference to our positive experiences of applying the proposed concept to BRZ, we consider possibilities of using the seismicity migration data for prediction of earthquakes in the planetary and regional scales.Изучение процессов сейсмомиграции проводилось новым методом построения пространственно-временных диаграмм и посредством сочетания кластерного и регрессионного анализа. С помощью разработанной геоинформационной системы (ГИС) и с использованием всемирного и байкальского регионального каталогов землетрясений решались задачи по выяснению параметров и механизмов пространственно-временной миграции сейсмической активности. Сейсмомиграционные явления изучались в следующих геоструктурных системах: в пределах Байкальской рифтовой зоны (БРЗ), между БРЗ и областью Индо-Евразийской межплитной коллизии, между БРЗ и Западно-Тихоокеанской сейсмофокальной зоной Беньофа, а также в двух сегментах Срединно-Атлантического хребта.На основе анализа полученных результатов показано, что изучение режимов сейсмомиграций позволяет анализировать пространственно-временное перераспределение сейсмической энергии в разломно-блоковой структуре литосферы и, соответственно, более углубленно изучать деформационно-волновую природу и механизмы формирования сейсмотектонического режима Земли. Установлено проявление прямых (от экватора) и обратных (к экватору) сейсмомиграций для всех рассмотренных районов. Предполагается, что такое явление может быть объяснено периодическим изменением полярного сжатия Земли за счет вариаций ее ротационного режима. Выявлена также периодичность в режиме генерации энергетических кластеров миграции, что может быть связано с влиянием на сейсмический режим 11-летнего цикла солнечной активности. Обсуждается необходимость изучения интерференции волновых деформаций в литосфере, возбужденных несколькими внешними энергетическими источниками. С этих позиций режимы планетарной сейсмомиграции предлагается рассматривать как отражение перераспределения эндогенной, преимущественно тепловой, энергии нашей планеты в ходе деструкции ее литосферной оболочки под воздействием космогенных факторов через триггерные механизмы. На основе положительного опыта для БРЗ обсуждаются возможности применения полученных сведений о сейсмомиграции для прогноза землетрясений в планетарном и региональном масштабе

Phase formation processes and synthesis of solid solutions in Ca-R-Nb-M-O systems

During the study of the phase formation process in Ca-R-Nb-M-O systems (R=La, Bi, M=Mo, W), an attempt was made to obtain single-phase compounds of CaRNbMO8 composition by the standard ceramic technique. In addition, samples based on LaNbO4, CaWO4, BiNbO4 were also synthesized by the standard ceramic technique. The phase composition of the samples was studied by XRD analysis. The electrical conductivity of the obtained solid solutions and potential composite materials was investigated by impedance spectroscopy

QUALITY OF ECONOMIC SPACE: MEASUREMENT PROBLEMS AT THE MESO-LEVEL

The research of theoretical and methodological issues of assessing the quality of the economic space of Russian regions has been conducted. The concepts of economic space and its quality, institutional environment of economic space have been substantiated. In order to determine the integral indicator of the standard of living and the quality of the economic space, the method of a systematic approach has been applied, which allowed the authors to justify and identify the system-forming indicators of the quality of the ec onomic space and the features of the relationship between them. The developed method of assessing the quality of economic space at the meso-level allows you to form a rating of investment attractiveness of the subjects of the Federation and determine the integral indicator of the quality of life of the population of the regions. The results of the study can be used in the development of investment rating and typology of Russian regions, implementation of social policy and state regulation of spatial development

HIV-care access among people with incarceration experience in St. Petersburg, Russia

Background: Little is known about the clinical care experiences of HIV-infected persons in St. Petersburg who have experience with incarceration. To address this question, we conducted a capture-recapture study to identify individuals who had been diagnosed with HIV infection while incarcerated and who subsequently presented for medical care in St. Petersburg, Russia following release from prison. Methods: We matched 292 HIV-positive prisoners tested by the prison system in 2010 to the medical records at the St. Petersburg AIDS Center in the following 4 years. Results: The data analysis shows that as many as half of HIV+ prisoners fail to seek treatment in the community upon release. Of those who had sought care post-release, only 36% were receiving HAART. Of the 109 individuals for whom tuberculosis testing was indicated post-release, 36.7% were found to be reactive. Conclusion: Despite the limitations of the data, this study is the first of its kind to review records documenting HIV care among prisoners in Russia post-incarceration. In addition to providing important descriptive information about this marginalized population, the findings from this study highlight areas where HIV control efforts could be improved in order to address the HIV epidemic in the Russian Federation

Educational Migration Bridge: From Metaphor to Project

The purpose of the article is to analyze the topical problem of educational migration and ways to solve it. The article identifies factors preventing from successful adaptation and socialization of foreign students in recipient country as legal, pedagogical, psychological, lingvo-communicative are identified. Minimization of negative factors actualized the integrated strategy of educational migration «bridge construction» development aimed at solving tasks of migrants’ integration in Russian labour market, providing them with all-round support in getting education, improving professional qualification, adaptation and socialization. The term «bridge» is metaphorically used as an artificial, virtual «construction» functioning as a means for educational migration support of citizens.The experience of the Orenburg State University in development and realization of the longterm integrated strategy of educational migration «bridge construction» presented within the Strategic Academic Leadership Program «Priority 2030» is studied. Regarding the potential of the University and Orenburg region the ways of educational migration «bridge construction» are determined: introduction of educational migration interactions into mission and policy of the university; development of open university migration interactions network structures; implementation of educational migration interaction based on norms, values and ideals of person’s lingvo-communicative culture. The practical steps for the strategy realization within the project «Educational migration bridge» are described: formation of the united scientific, educational and cultural environment based on mutual activity in international scientific and educational community; arrangement of universities regional consortium for informing applicants from Asian countries, for training and living in universities campuses; establishment of the Faculty of foreign students’ education and digital educational platform ensuring logistics and student educational improvement management; development and realization of module network programs for foreign students; realization of additional educational programs in OSU Linguistic center. The authors analyze the main indicators of the project effectiveness: quantitative and qualitative results of the Faculty of foreign students’ education activity in training Russian and culture; establishment of the Orenburg branch of Foreign Students Association, students’ involvement in various interaction forms and special career guidance events; scientific and methodological support for teachers. Realization of the strategy implies creation in OSU in the nearest future a specific environment including social infrastructure for foreigners

Avalanches in self-organized critical neural networks: A minimal model for the neural SOC universality class

The brain keeps its overall dynamics in a corridor of intermediate activity and it has been a long standing question what possible mechanism could achieve this task. Mechanisms from the field of statistical physics have long been suggesting that this homeostasis of brain activity could occur even without a central regulator, via self-organization on the level of neurons and their interactions, alone. Such physical mechanisms from the class of self-organized criticality exhibit characteristic dynamical signatures, similar to seismic activity related to earthquakes. Measurements of cortex rest activity showed first signs of dynamical signatures potentially pointing to self-organized critical dynamics in the brain. Indeed, recent more accurate measurements allowed for a detailed comparison with scaling theory of non-equilibrium critical phenomena, proving the existence of criticality in cortex dynamics. We here compare this new evaluation of cortex activity data to the predictions of the earliest physics spin model of self-organized critical neural networks. We find that the model matches with the recent experimental data and its interpretation in terms of dynamical signatures for criticality in the brain. The combination of signatures for criticality, power law distributions of avalanche sizes and durations, as well as a specific scaling relationship between anomalous exponents, defines a universality class characteristic of the particular critical phenomenon observed in the neural experiments. The spin model is a candidate for a minimal model of a self-organized critical adaptive network for the universality class of neural criticality. As a prototype model, it provides the background for models that include more biological details, yet share the same universality class characteristic of the homeostasis of activity in the brain.Comment: 17 pages, 5 figure

Analysis of the results of intraoperative neurophysiological monitoring in the Center of Neurosurgery of Railway Clinical Hospital at the Irkutsk-Passazhirskiy Railway Station of Russian Railways Ltd

The reduction of postoperative complication rate is a significant trend in modern surgery. One of the most important methods of intraoperative diagnostics is intraoperative neurophysiological monitoring (IONM). The aim of the research was to assess capabilities of intraoperative neurophysiological monitoring in neurosurgical practice considering literature data and experience of IONM application in the Center of Neurosurgery Railway Clinical Hospital at the Irkutsk-Passazhirskiy Railway Station of Russian Railways Ltd. We conducted 17 surgeries using IONM. We described the procedure, analyzed data of monitoring and patients' condition in early postoperative period. No deviations requiring modifications in surgical manipulations were found during neuromonitoring. No iatrogenic neurological disorders were registered in postoperative period. Intraoperative neurophysiological monitoring is an additional effective method which allows reducing the risk of postoperative complications and indirectly improving the results of surgical manipulations

Self-organization without conservation: Are neuronal avalanches generically critical?

Recent experiments on cortical neural networks have revealed the existence of well-defined avalanches of electrical activity. Such avalanches have been claimed to be generically scale-invariant -- i.e. power-law distributed -- with many exciting implications in Neuroscience. Recently, a self-organized model has been proposed by Levina, Herrmann and Geisel to justify such an empirical finding. Given that (i) neural dynamics is dissipative and (ii) there is a loading mechanism "charging" progressively the background synaptic strength, this model/dynamics is very similar in spirit to forest-fire and earthquake models, archetypical examples of non-conserving self-organization, which have been recently shown to lack true criticality. Here we show that cortical neural networks obeying (i) and (ii) are not generically critical; unless parameters are fine tuned, their dynamics is either sub- or super-critical, even if the pseudo-critical region is relatively broad. This conclusion seems to be in agreement with the most recent experimental observations. The main implication of our work is that, if future experimental research on cortical networks were to support that truly critical avalanches are the norm and not the exception, then one should look for more elaborate (adaptive/evolutionary) explanations, beyond simple self-organization, to account for this.Comment: 28 pages, 11 figures, regular pape