Electromagnetohydrodynamics

Interaction of plasma flow with a magnetic obstacle is a frequent process in many laser-plasma experiments in the laboratory, and is an important event in many astrophysical objects such as X-ray pulsars, AGN, GRB etc. As a result of plasma penetration through the magnetic wall we could expect a formation of magnetohydrodynamic (MHD) shock waves, as well as of electromagnetic (EM) ones. To study these processes we need equations following from hydrodynamic and Maxwell equations, which in the limiting situations describe MHD and EM waves, and are valid for the general case, when both phenomena are present. Here we derive a set of equations following from hydrodynamic and Maxwell equations, without neglecting a displacement current, needed for a formation of EM waves. We find a dispersion equation describing a propagation of a weak linear wave in a magnetized plasma along the $x$ axis, perpendicular to the magnetic field $H_y(x)$, which contains MHD, hydrodynamic and EM waves in the limiting cases, and some new types of behaviour in a general situation. We consider a plasma with zero viscosity and heat conductivity, but with a finite electric conductivity with a scalar coefficient.Comment: 8 papers, 8 figures, 1 table, to be submitted in PR

Multi-agent simulation of the processing shop

Multi-agent model is applied for the transformation of resources used for research companies or parts of companies in the presence of high load or idle assets in production, realized by means of the metallurgical enterprise information system. The following solution has been found as a result of experiments. There are needs in increase the number of heat-treatment furnaces and reduction the number of staff.Мультиагентная модель процесса преобразования ресурсов применяется для исследования предприятий или частей предприятий на наличие простоев или высокой загруженности средств в производстве, реализованной при помощи автоматизированной системы выпуска металлургической продукции. На основании построенной модели проведены эксперименты и представлены рекомендации по изменению анализируемых процессов: необходимо увеличить количество термических печей и снизить количество персонала цеха

Neutron star composition in strong magnetic fields

We study the problem of neutron star composition in the presence of a strong magnetic field. The effects of the anomalous magnetic moments of both nucleons and electrons are investigated in relativistic mean field calculations for a $\beta$-equilibrium system. Since neutrons are fully spin polarized in a large field, generally speaking, the proton fraction can never exceed the field free case. An extremely strong magnetic field may lead to a pure neutron matter instead of a proton-rich matter.Comment: 12 pages, 3 postscript files include

Characterization of extrasolar terrestrial planets from diurnal photometric variability

The detection of massive planets orbiting nearby stars has become almost routine, but current techniques are as yet unable to detect terrestrial planets with masses comparable to the Earth's. Future space-based observatories to detect Earth-like planets are being planned. Terrestrial planets orbiting in the habitable zones of stars-where planetary surface conditions are compatible with the presence of liquid water-are of enormous interest because they might have global environments similar to Earth's and even harbor life. The light scattered by such a planet will vary in intensity and colour as the planet rotates; the resulting light curve will contain information about the planet's properties. Here we report a model that predicts features that should be discernible in light curves obtained by low-precision photometry. For extrasolar planets similar to Earth we expect daily flux variations up to hundreds of percent, depending sensitively on ice and cloud cover. Qualitative changes in surface or climate generate significant changes in the predicted light curves. This work suggests that the meteorological variability and the rotation period of an Earth-like planet could be derived from photometric observations. Other properties such as the composition of the surface (e.g., ocean versus land fraction), climate indicators (for example ice and cloud cover), and perhaps even signatures of Earth-like plant life could be constrained or possibly, with further study, even uniquely determined.Comment: Published in Nature. 9 pages including 3 figure

Basic Operator Method in 3D and Heat Transfer Modelling in Neutron Star Crust

Basic operator method has proven itself well in numerical simulations of various two-dimensional astrophysical problems. In this work this method was extended to a 3D case. Grid analogues of continuous vector operators are obtained using the cell-node approximation. 3D Poisson equation for the Newtonian gravitational potential was solved as a test problem. Method is applied to anisotropic heat transfer simulation in a neutron star crust.Метод опорных операторов хорошо проявил себя при численном моделировании различных двумерных астрофизических задач. В данной работе этот метод был расширен на трехмерный случай. Трехмерные сеточные аналоги непрерывных векторных операторов получены с использованием ячеечно-узловой аппроксимации. Трехмерное уравнение Пуассона для гравитационного потенциала решено в качестве тестовой задачи. Метод применен к моделированию анизатропной теплопроводности в коре нейтронной звезды

Оценка риска желудочно-кишечного кровотечения у пациентов с повреждением головного мозга

The aim of the study was to develop a risk model for upper gastrointestinal tract (GIT) bleeding in patients with brain injury of various etiologies.Material and methods. Case histories of 33 patients were included into a retrospective descriptive study: 22 patients had severe brain injury of various etiologies, and 11 patients after elective surgery for cerebral aneurisms with uneventful postop period were taken for comparison. The patients were grouped in two arms: Group 1 included patients with obvious signs of GIT bleeding (N=11) and Group 2 had no obvious signs of bleeding (N=22). Complaints, life and medical history, comorbidities, specialists’ exams data, results of laboratory and instrumental examinations, therapeutic regimens were analyzed. Presence of disproportionate pathologic sympathetic overreaction to acute brain injury, i.e., paroxysmal sympathetic hyperactivity (PSH), was assessed on admission and on Days 1, 3 and 5 after brain injury. Results. A model for upper GIT bleeding risk assessment was designed using logistic regression. The resulting model gains high quality rating: χ²=33,78, 3; p<0,001; OR=315. The risk of upper GIT bleeding exceeded 95% in patients having combination of 4 symptoms in their medical history (presence of PSH on Day 1 after acute brain injury; Karnofsky performance scale index 75; lack of neurovegetative stabilization in the acute period of brain injury; gastric and/or duodenal ulcer).Conclusion. Determining the risk factors thresholds enables stratification of patients by the risk for upper GIT bleeding. Modification of the identified four risk factors (presence of PSH on Day 1after acute brain injury; Karnofsky performance scale index 75; lack of neurovegetative stabilization in the acute period of brain injury; gastric and/or duodenal ulcer) will probably reduce the occurrence of upper GIT bleeding in patients with acute brane injury of various etiology.Цель исследования — построение модели риска развития желудочно-кишечного кровотечения из желудка и двенадцатиперстной кишки у пациентов с повреждением головного мозга различной этиологии. Материал и методы. В ретроспективное описательное исследование включили истории болезни 33-х пациентов: 22 пациентов — с тяжелым повреждением головного мозга различной этиологии и, для сравнения, 11 пациентов — с аневризматической болезнью сосудов головного мозга с неосложненным течением послеоперационного периода после плановых нейрохирургических вмешательств. Всех пациентов разделили на 2 группы: с явными признаками кровотечения из ЖКТ (n=11) и без явных признаков кровотечения (n=22). Проанализировали жалобы, анамнез заболевания и жизни, сопутствующие заболевания, данные осмотров специалистов, результаты лабораторных и инструментальных исследований, особенности терапии. Функции вегетативной нервной системы оценивали по проявлениям пароксизмальной симпатической гиперактивности (ПСГА) при поступлении в стационар, на 1-е, 3-и и 5-е сут после повреждения ГМ. Результаты. Средствами логистической регрессии построили модель оценки риска развития явного кровотечения из верхних отделов желудочно-кишечного тракта. Полученная модель обладает высокой оценкой качества: χ²=33,78, 3; p<0,001; OR=315. При сочетании в анамнезе 4-х признаков (повышение ПСГА в 1-е сут после повреждения головного мозга; индекс Карновского менее 75; отсутствие нейровегетативной стабилизации в остром периоде повреждения головного мозга; язвенная болезнь желудка и двенадцатиперстной кишки (ДПК)) риск развития явного кровотечения из верхних отделов желудочно-кишечного тракта превышал 95%.Заключение. Выделение пороговых значений факторов риска позволяет разделить пациентов на группы риска развития кровотечений из верхних отделов ЖКТ. Воздействие на выявленные 4 фактора риска (проявления ПСГА в 1-е сут после повреждения головного мозга; индекс Карновского менее 75; отсутствие нейровегетативной стабилизации в остром периоде повреждения головного мозга; язвенная болезнь желудка и ДПК) позволит, вероятно, снизить частоту ЖКК из верхних отделов ЖКТ у пациентов с повреждением ГМ различной этиологии.