A simple mathematical model of gradual Darwinian evolution: Emergence of a Gaussian trait distribution in adaptation along a fitness gradient

We consider a simple mathematical model of gradual Darwinian evolution in continuous time and continuous trait space, due to intraspecific competition for common resource in an asexually reproducing population in constant environment, while far from evolutionary stable equilibrium. The model admits exact analytical solution. In particular, Gaussian distribution of the trait emerges from generic initial conditions.Comment: 21 pages, 2 figures, as accepted to J Math Biol 2013/03/1

Changes in somatosensory evoked potentials in rats following transient cerebral ischemia

Background. Cerebral ischemia induced by transient middle cerebral artery occlusion is one of the most popular ischemic stroke models used to evaluate drug candidates with neuroprotective properties. The possibilities of combining this model with neurophysiological techniques (e.g., electroencephalography, electrocorticography, evoked potential registration, etc.) to assess the effectiveness of novel pharmacotherapeutic strategies appear to be of great interest to current biomedical research.The aim. Identifying specific changes in somatosensory evoked potentials occurring after cerebral ischemia induced by middle cerebral artery occlusion in rats.Materials and methods. A total number of 18 white outbred male rats were randomized into 3 groups by 6 animals in each: 1) control (presumably healthy animals); 2) ischemia-30 (30-minute middle cerebral artery occlusion); 3) ischemia-45 (45-minute occlusion). At post-surgery day 7, cortical responses to sequential electrical stimulation of left and right n. ischiadicus were registered. N1, P2, N2, P3, and N3 peak latencies and amplitudes, peak-to-peak interval durations and amplitudes were calculated. Spearman’s rank correlation coefficients were used to assess the relationship between ischemia duration and evoked potential parameters, and the Chaddock scale was used to qualitatively evaluate the strength of correlations.Results. The rats subjected to cerebral ischemia demonstrated a decrease in some of the peak amplitudes of the ipsi- and contralateral somatosensory potentials evoked by n. ischiadicus stimulation. In the injured hemisphere, decreased P2 and N3 peak and P3–N3 interval amplitudes were registered ipsilaterally, and decreased P3 peak amplitudes and N2–P3 interval durations were observed contralaterally.Conclusions. The obtained data suggest that somatosensory evoked potential registration and analysis can be used to evaluate the functional state of central nerve tracts in rats subjected to cerebral ischemia

Межклеточные взаимоотношения и их роль в фиброгенезе при хроническом гепатите С

Introduction. The development of life-threatening complications in chronic hepatitis C (CHC) is based on progressive fibrogenesis. The developing of liver fibrosis is provided by intercellular interactions, first of all, of lymphocytes, macrophages and stellate cells (SC), the patterns of mutual influences of which have not been sufficiently studied at the moment.The objective was to study the features of intercellular interplay of nonparenchymal liver cells at different histological activity, at different stages of CHC fibrosis, and at different genotypes of the hepatitis C virus (HCV).Methods and materials. The object of the study was 64 liver biopsies of adult patients with natural course of CHC. Нistological, immunohistochemical and immunohistomorphometric methods were used.Results. The increasing histological activity is accompanied by an increase in the number and size (area) of CD68 + macrophages and SMA-alfa + SC. Correlation relationships of intercellular interactions at low and moderate histological activity had significant differences. In mild fibrosis, a relationship was found between the number of CD8 + lymphocytes, the number and area of CD68 + macrophages and SMA-alfa + SC. HCV genotype 1 is characterized by a predominance of the interactions between the number of CD8 + lymphocytes, the number and area of CD68 + macrophages in the liver, for genotype 3 – between the number of CD8 + lymphocytes, the number and area of SMA + SC.Conclusions. The maximum activation of SC and macrophages occurs even with moderate histological activity and persists with an increase. The consolidation of the immunopathological nature of the intercellular interplay between lymphocytes, macrophages and SC occurs at the stage of mild fibrosis. Intercellular interactions have significant differences depending on the HCV genotype, which can determine a poor prognosis of the disease.Введение. В основе формирования жизнеугрожающих осложнений при хроническом гепатите С (ХГС) лежит прогрессирующий фиброгенез. Процесс формирования фиброза печени обеспечивается межклеточными взаимодействиями, прежде всего, лимфоцитов, макрофагов и звездчатых клеток (ЗК), закономерности взаимных влияний которых на данный момент изучены недостаточно.Цель – изучить особенности межклеточных взаимосвязей непаренхиматозных клеток печени при различной гистологической активности, на разных стадиях фиброза ХГС и при разных генотипах вируса гепатита С (ВГС).Методы и материалы. Объект исследования – 64 биоптата печени взрослых пациентов с естественным течением ХГС. Использовали гистологический, иммуногистохимический и иммуногистоморфометрический методы.Результаты. Возрастание гистологической активности сопровождается увеличением количества и размеров (площади) CD68+-макрофагов и SMA-alfa+ ЗК. Корреляционные взаимосвязи межклеточных взаимодействий при низкой и умеренной гистологической активности имели значимые отличия. При слабо выраженном фиброзе выявлялась взаимосвязь между количеством CD8+-лимфоцитов, количеством и площадью CD68+-макрофагов и SMA-alfa+ ЗК. Для 1-го генотипа ВГС характерно преобладание взаимосвязи между содержанием CD8+-лимфоцитов, количеством и площадью CD68+-макрофагов в печени, для 3-го генотипа – между содержанием CD8+-лимфоцитов, количеством и площадью SMA+ ЗК.Заключение. Максимальная активация ЗК и макрофагов происходит уже при умеренной гистологической активности и сохраняется при ее увеличении. Закрепление иммунопатологического характера межклеточных взаимосвязей между лимфоцитами, макрофагами и ЗК происходит на стадии слабо выраженного фиброза. Межклеточные взаимосвязи имеют существенные различия в зависимости от генотипа ВГС, что может определять неблагоприятный прогноз заболевания

ВИРУСНЫЕ ПЛАЦЕНТИТЫ: МОРФОЛОГИЧЕСКИЕ ОСОБЕННОСТИ И ВОЗМОЖНОСТИ ВЕРИФИКАЦИИ

This article describes the results of own observations of viral placentitis caused by parvovirus, human immunodeficiency virus, respiratory syncytial virus and Herpesviridae family viruses – herpes simplex virus types 1 and 2, cytomegalovirus and Epstein–Barr virus), describing the morphological features of typical changes and immunohistochemical verification their etiology.В данной статье описаны результаты собственных наблюдений вирусных плацентитов, вызванных парвовирусом, вирусом иммунодефицита человека, респираторно-синцитиальным вирусом и вирусами семейства Herpesviridae – вирусами простого герпеса 1 и 2 типов, цитомегаловирусом и вирусом Эпштейна – Барр) с описанием морфологических особенностей типичных изменений и иммуногистохимической верификацией их этиологии

The peculiarities of perspective students selection mechanism by the future employers-enterprise

© 2015, Canadian Center of Science and Education. All rights reserved. The search of qualified staff is an up-to-date problem for all enterprises. In this regard the aim of the research is the development of perspective students selection mechanism by the future employers. One of the sub-stages of the algorithm is the formation of the resource and reserve groups of students by the enterprise representatives and by tutors of the faculty of professional educational institutions. The formation of the resource and reserve groups of students with flexible system of transition from one group into another according to the results of their progress, according to participation extracurricular life of the institute, participation at the international, All-Russian scientific and practical conferences, allow to intensify the process of their self-preparation by means of creation of the natural competitive environment in educational institution of professional education. It also helps to do the selection by employers and to distribute perspective students taking into account their potential opportunities and professional interests

Tensor compaction of porous rocks: theory and experimental verification

Compaction in sedimentary basins has been traditionally regarded as a one-dimensional process that ignores inelastic deformation in directions orthogonal to the active load. This study presents new experiments with sandstone demonstrating the role of three-dimensional inelastic compaction in cyclic true triaxial compression. The experiments were carried out on the basis of a triaxial independent loading test system in the Laboratory of Geomechanics of the Ishlinsky Institute for Problems in Mechanics of the Russian Academy of Science. The elastic moduli of the material were estimated from the stress-strain curves and the elastic deformations of the sample in each of the three directions were determined. Subtracting the elastic component from the total deformation allowed to show that inelastic compaction of the sandstone is observed in the direction of active loading, whereas in the orthogonal directions there is a expansion of the material. To describe the three-dimensional nature of the compaction, a generalization of Athy law to the tensor case is proposed, taking into account the role of the stress deviator. The compaction tensor and the kinetic equation to describe the evolution of inelastic deformation, starting from the moment of the load application are introduced. On the basis of experiments on cyclic multiaxial compression of sandstone, the identification and verification of the constructed model of tensor compaction were carried out. The possibility of not only qualitative, but also quantitative description of changes in inelastic deformation under complex cyclic triaxial compression is shown

Molecular and Cellular Mechanisms of M. tuberculosis and SARS-CoV-2 Infections-Unexpected Similarities of Pathogenesis and What to Expect from Co-Infection

Tuberculosis is still an important medical and social problem. In recent years, great strides have been made in the fight against M. tuberculosis, especially in the Russian Federation. However, the emergence of a new coronavirus infection (COVID-19) has led to the long-term isolation of the population on the one hand and to the relevance of using personal protective equipment on the other. Our knowledge regarding SARS-CoV-2-induced inflammation and tissue destruction is rapidly expanding, while our understanding of the pathology of human pulmonary tuberculosis gained through more the 100 years of research is still limited. This paper reviews the main molecular and cellular differences and similarities caused by M. tuberculosis and SARS-CoV-2 infections, as well as their critical immunological and pathomorphological features. Immune suppression caused by the SARS-CoV-2 virus may result in certain difficulties in the diagnosis and treatment of tuberculosis. Furthermore, long-term lymphopenia, hyperinflammation, lung tissue injury and imbalance in CD4+ T cell subsets associated with COVID-19 could propagate M. tuberculosis infection and disease progression

Measurement of event-by-event transverse momentum and multiplicity fluctuations using strongly intensive measures Δ[PT,N]\Delta[P_T, N] and Σ[PT,N]\Sigma[P_T, N] in nucleus-nucleus collisions at the CERN Super Proton Synchrotron

Results from the NA49 experiment at the CERN SPS are presented on event-by-event transverse momentum and multiplicity fluctuations of charged particles, produced at forward rapidities in central Pb+Pb interactions at beam momenta 20$A$, 30$A$, 40$A$, 80$A$, and 158$A$ GeV/c, as well as in systems of different size ($p+p$, C+C, Si+Si, and Pb+Pb) at 158$A$ GeV/c. This publication extends the previous NA49 measurements of the strongly intensive measure $\Phi_{p_T}$ by a study of the recently proposed strongly intensive measures of fluctuations $\Delta[P_T, N]$ and $\Sigma[P_T, N]$. In the explored kinematic region transverse momentum and multiplicity fluctuations show no significant energy dependence in the SPS energy range. However, a remarkable system size dependence is observed for both $\Delta[P_T, N]$ and $\Sigma[P_T, N]$, with the largest values measured in peripheral Pb+Pb interactions. The results are compared with NA61/SHINE measurements in $p+p$ collisions, as well as with predictions of the UrQMD and EPOS models.Comment: 12 pages, 14 figures, to be submitted to PR

Phase-space dependence of particle-ratio fluctuations in Pb+Pb collisions from 20A to 158A GeV beam energy

A novel approach, the identity method, was used for particle identification and the study of fluctuations of particle yield ratios in Pb+Pb collisions at the CERN Super Proton Synchrotron (SPS). This procedure allows to unfold the moments of the unknown multiplicity distributions of protons (p), kaons (K), pions ($\pi$) and electrons (e). Using these moments the excitation function of the fluctuation measure $\nu_{\text{\text{dyn}}}$[A,B] was measured, with A and B denoting different particle types. The obtained energy dependence of $\nu_{\text{dyn}}$ agrees with previously published NA49 results on the related measure $\sigma_{\text{dyn}}$. Moreover, $\nu_{\text{dyn}}$ was found to depend on the phase space coverage for [K,p] and [K,$\pi$] pairs. This feature most likely explains the reported differences between measurements of NA49 and those of STAR in central Au+Au collisions

Production of deuterium, tritium, and 3^3He in central Pb+Pb collisions at 20A, 30A, 40A, 80A, and 158A GeV at the CERN SPS

Production of $d$, $t$, and $^3$He nuclei in central Pb+Pb interactions was studied at five collision energies ($\sqrt{s_{NN}}=$ 6.3, 7.6, 8.8, 12.3, and 17.3 GeV) with the NA49 detector at the CERN SPS. Transverse momentum spectra, rapidity distributions, and particle ratios were measured. Yields are compared to predictions of statistical models. Phase-space distributions of light nuclei are discussed and compared to those of protons in the context of a coalescence approach. The coalescence parameters $B_2$ and $B_3$, as well as coalescence radii for $d$ and $^3$He were determined as a function of transverse mass at all energies.Comment: 22 pages, 29 figures, 8 tables, for submission to Phys. Rev.