Numerical modeling of spalling brittle fracture along the (0001) plane in HCP-single crystals under shock loading

Numerical modeling of spalling brittle fracture along the (0001) plane in a zinc single crystal under shock loading by an aluminum projectile was performed in the work. Numerical modeling was carried out by the finite element method in a three-dimensional statement. The mathematical model allows to take into account the anisotropy of bulk compressibility in a single crystal of zinc, auxeticity, anisotropy of the propagation velocities of elastic longitudinal and volume waves. Stresses are determined on the basis of a comparison of velocity profiles of the rear surfaces of targets from zinc single crystal in mutually perpendicular directions when it is destroyed along the (0001) plane in natural experiments and numerical simulation

Numerical simulation of the fractures of anisotropic materials characterized by the high degree of anisotropy of elongation at break

The failure criteria of anisotropic materials, the criteria being expressed via deformations, are rarely applied in practice, and are usually used for low-ductility materials. Another situation involves the simulation of failures in materials with the high anisotropy of mechanical properties and that suffer elastic-brittle fracture. For such materials the failure criteria are formulated using ultimate strains and strain tensor invariants. For simulating the fractures of materials that are characterized by the anisotropy of strength properties, the failure criteria are applied with the critical values of stresses and strains, as well as their intensities. Using the value of cumulative plastic strain as a failure criterion does reflect the anisotropy of elastic and plastic properties of a material, but it does not reflect that of the strength properties. The application of this method allows accounting the total plastic strain induced by tension and compression in the conditions of the wave strain of targets during their impact loading

Limits on the Majorana neutrino mass in the 0.1 eV range

The Heidelberg-Moscow experiment gives the most stringent limit on the Majorana neutrino mass. After 24 kg yr of data with pulse shape measurements, we set a lower limit on the half-life of the neutrinoless double beta decay in 76Ge of T_1/2 > 5.7 * 10^{25} yr at 90% C.L., thus excluding an effective Majorana neutrino mass greater than 0.2 eV. This allows to set strong constraints on degenerate neutrino mass models.Comment: 6 pages (latex) including 3 postscript figures and 2 table

Direct Search for Dark Matter - Striking the Balance - and the Future

Weakly Interacting Massive Particles (WIMPs) are among the main candidates for the relic dark matter (DM). The idea of the direct DM detection relies on elastic spin-dependent (SD) and spin-independent (SI) interaction of WIMPs with target nuclei. In this review paper the relevant formulae for WIMP event rate calculations are collected. For estimations of the WIMP-proton and WIMP-neutron SD and SI cross sections the effective low-energy minimal supersymmetric standard model is used. The traditional one-coupling-dominance approach for evaluation of the exclusion curves is described. Further, the mixed spin-scalar coupling approach is discussed. It is demonstrated, taking the high-spin Ge-73 dark matter experiment HDMS as an example, how one can drastically improve the sensitivity of the exclusion curves within the mixed spin-scalar coupling approach, as well as due to a new procedure of background subtraction from the measured spectrum. A general discussion on the information obtained from exclusion curves is given. The necessity of clear WIMP direct detection signatures for a solution of the dark matter problem, is pointed out.Comment: LaTeX, 49 pages, 14 figures, 185 reference

Identification of the Farm Animals Immune to Pathogens of Zoonotic Infectious Diseases in the Republic of Guinea

The most common anthropozoonoses on the African continent are coxiellosis and Rift Valley fever. It is known that detection of specific IgG antibodies in the blood sera of farm animals is one of the indicators of the pathogen circulation in a certain territory. The aim of the work was to identify specific IgG antibodies in the blood sera of farm animals collected on the territory of the Republic of Guinea to pathogens of zoonotic infectious diseases: coxiellosis, brucellosis, glanders, CCHF, West Nile and Rift Valley fevers, using enzyme immunoassay (ELISA). Materials and methods. A panel of 970 samples of blood sera from farm animals inhabiting all landscape-geographical zones of Guinea was compiled for the work. Identification of specific antibodies was carried out using enzyme immunoassay with preparations recommended for veterinary studies. Results and discussion. Specific antibodies to zoonoses were detected in 700 out of 1074 samples (65.2 % of the total), including: to Coxiella burnetii – in 172 (16.0 %); to Brucella spp. – in 212 (19.7 %); viruses of Rift Valley fever – 85 (7.9 %); CCHF – in 139 (12.9 %) and West Nile fever – in 92 (8.6 %). Antibodies to Burkholderia mallei were not found in the tested material. Positive samples were registered in all landscape-geographical zones. Thus, an urgent task is to continue studying the circulation of pathogens of zoonoses and anthropozoonoses in the territory of the Republic of Guinea and to organize regular monitoring over the spread of zoonotic infectious diseases in collaboration with veterinary services, which will allow timely forecasting and coordinating prophylactic (anti-epidemic) measures to prevent cases of diseases

Dark Energy from Mass Varying Neutrinos

We show that mass varying neutrinos (MaVaNs) can behave as a negative pressure fluid which could be the origin of the cosmic acceleration. We derive a model independent relation between the neutrino mass and the equation of state parameter of the neutrino dark energy, which is applicable for general theories of mass varying particles. The neutrino mass depends on the local neutrino density and the observed neutrino mass can exceed the cosmological bound on a constant neutrino mass. We discuss microscopic realizations of the MaVaN acceleration scenario, which involve a sterile neutrino. We consider naturalness constraints for mass varying particles, and find that both ev cutoffs and ev mass particles are needed to avoid fine-tuning. These considerations give a (current) mass of order an eV for the sterile neutrino in microscopic realizations, which could be detectable at MiniBooNE. Because the sterile neutrino was much heavier at earlier times, constraints from big bang nucleosynthesis on additional states are not problematic. We consider regions of high neutrino density and find that the most likely place today to find neutrino masses which are significantly different from the neutrino masses in our solar system is in a supernova. The possibility of different neutrino mass in different regions of the galaxy and the local group could be significant for Z-burst models of ultra-high energy cosmic rays. We also consider the cosmology of and the constraints on the ``acceleron'', the scalar field which is responsible for the varying neutrino mass, and briefly discuss neutrino density dependent variations in other constants, such as the fine structure constant.Comment: 26 pages, 3 figures, refs added, typos corrected, comment added about possible matter effect

Обнаружение и генотипирование Anaplasma phagocytophilum в клещах I. persulcatus и D. reticulatus , собранных в г. Томске в 2015–2016 гг.

Introduction. The detection of the first cases of tick-borne human granulocytic anaplasmosis in Russia, discovery of genetic markers for Anaplasma spp. in ixodid ticks and reporting of a significant number of cases of tick-borne infections in the southern part of Western Siberia give reason to suppose that causative agents of tick-borne anaplasmosis may be transmitted in Tomsk and its suburbs. Objective. To study the distribution and species biodiversity of A. phagocytophilum in ixodid ticks in Tomsk Region. Materials and methods. The analysis of 690 individual ixodid ticks (larvae and adults) was carried out for Ixodes persulcatus (n = 530) and Dermacentor reticulatus (n = 160) ticks collected in 2015–2016 on the territory of urban and suburban biotopes of Tomsk. Primary screening of ticks for the presence of genetic material of A. phagocytophilum was conducted using two-round PCR with species-specific primers for the 16S rRNA gene. The amplification (1,220 kB) of the groESL fragment of the heat shock protein operon was performed for positive isolates with subsequent determination of the nucleotide sequence in the gene fragment for phylogenetic analysis. Results. The number of A. phagocytophilum positive samples for I. persulcatus (larvae) was 1.2 ± 0.6%, I. persulcatus (adult) was 1.8 ± 0.7%; and D. reticulatus (adult) was 0.6 ± 0.3%. Analysis of the nucleotide sequence of the gene fragments in groESL operon for nine isolates confirmed that the genetic material of the granulocytic anaplasmosis was detected. Phylogenetic analysis showed that all the isolates belonged to the first group of the “new cluster” of A. phagocytophilum. Conclusion. The causative agent of human granulocytic anaplasmosis has been newly detected in I. persulcatus ticks collected in urban and suburban biotopes of Tomsk and in D. reticulatus from urban foci.Введение. Выявление первых случаев заболевания клещевым гранулоцитарным анаплазмозом человека в Российской Федерации, обнаружение генетических маркеров анаплазмозов в иксодовых клещах, регистрация значительного количества случаев различных клещевых инфекций на юге Западной Сибири ставят вопрос о возможной циркуляции возбудителя анаплазмоза в г. Томске и его пригородах. Цель исследования. Изучение распространения и видового разнообразия A. phagocytophilum в иксодовых клещах на территории Томской области. Материалы и методы. Проведен анализ 690 индивидуальных образцов личинок и имаго иксодовых клещей видов Ixodes persulcatus (n = 530) и Dermacentor reticulatus (n = 160), собранных в 2015–2016 гг. на территории городских и пригородных биотопов г. Томска. Первичный скрининг клещей на наличие генетического материала A. phagocytophilum проводили с помощью двухраундовой полимеразной цепной реакции в присутствии родоспецифичных праймеров из области гена 16S рРНК. Для положительных изолятов осуществлялось амплифицирование фрагмента (1 220 пар нуклеотидов) groESL-оперона белков теплового шока с последующим определением нуклеотидной последовательности фрагмента гена и проведением филогенетического анализа. Результаты. Уровень инфицированности A. phagocytophilum у личинок I. persulcatus составил (1,2 ± 0,6)%; у половозрелых особей I. persulcatus – (1,8 ± 0,7)%; у половозрелых особей D. reticulatus–(0,6 ± 0,3)%. Анализ нуклеотидной последовательности фрагмента groESL-оперона для девяти изолятов подтвердил обнаружение генетического материала возбудителя гранулоцитарного анаплазмоза. Филогенетический анализ показал, что все изоляты относятся к первой группе «нового» кластера A. phagocytophilum. Вывод. Возбудитель гранулоцитарного анаплазмоза человека впервые обнаружен в клещах I. рersulcatus, собранных в городских и пригородных биотопах г. Томска, и D. reticulatus из городского биотопа

Морфофункциональные свойства стромальных стволовых клеток при культивировании in vitro в динамических условиях

The culture of stromal stem cells was incubated under constant and dynamic conditions. The incubation period was lasting 48 h. Intracellular enzyme activity of stromal stem cells were carried out with cytochemical methods. Alkaline phosphatase activity was increased under dynamic conditions, differentiation of stromal stem cells being accelerated comparatively steady-state conditions.Проведено культивирование стромальных клеток в динамических и стационарных условиях в течение 24-48 ч. Исследована их внутриклеточная ферментативная активность с помощью цитохимических методов - окраски на щелочную фосфатазу и неспецифическую эстеразу. В условиях динамического культивирования активность щелочной фосфатазы была выше по сравнению со стационарными условиями, что свидетельствует об ускорении дифференцировки и созревания стромальных клеток человека

Mathematical simulation of elastoplastic deformation in cubic materials with an account of anisotropic bulk compressibility

It was shown for the first time that when modelling the deformation of materials with cubic symmetry (at full stress), the rotation of the computational axes leads to the identification of anisotropic volumetric compressibility. Loading of the materials with cubic symmetry of properties in the directions not coincided with the main directions (for example, 011) allows one to detect 75% cases of the auxetic single crystals (i.e. with negative Poisson’s ratio). In these cases, the negative volumetric compressibility has anisotropy, in contrast to the volumetric compressibility calculated along the crystallographic axes for cubic material