The propagation of in-plane P-SV waves in a layered elastic plate with periodic interface cracks: exact versus spring boundary conditions

The propagation of in-plane (P-SV) waves in a symmetrically three-layered thick plate with a periodic array of interface cracks is investigated. The exact dispersion relation is derived based on an integral equation approach and Floquet's theorem. The interface cracks can be a model for interface damage, but a much simpler model is a recently developed spring boundary condition. This boundary condition is used for the thick plate and also in the derivation of plate equations with the help of power series expansions in the thickness coordinate. For low frequencies (cracks small compared to the wavelength) the three approaches give more or less coinciding dispersion curves, and this is a confirmation that the spring boundary condition is a reasonable approximation at low frequencies

Analysis of typical communicative situations arising in the process of teaching foreign students in Russian as a foreign language

The article discusses the concept of speech action: the results of studies of speech impact in business communication are presented; analyzes typical communicative situations in intercultural communication between a teacher and foreign students of Russian universities

Global survey of star clusters in the Milky Way: III. 139 new open clusters at high Galactic latitudes

Context. An earlier analysis of the Milky Way Star Cluster (MWSC) catalogue revealed an apparent lack of old (t � 1 Gyr) open clusters in the solar neighbourhood (d � 1 kpc). Aims. To fill this gap we undertook a search for hitherto unknown star clusters, assuming that the missing old clusters reside at high Galactic latitudes | b | > 20°. Methods. We were looking for stellar density enhancements using a star count algorithm on the 2MASS point source catalogue. To increase the contrast between potential clusters and the field, we applied filters in colour-magnitude space according to typical colour-magnitude diagrams of nearby old open clusters. The subsequent comparison with lists of known objects allowed us to select thus far unknown cluster candidates. For verification they were processed with the standard pipeline used within the MWSC survey for computing cluster membership probabilities and for determining structural, kinematic, and astrophysical parameters. Results. In total we discovered 782 density enhancements, 524 of which were classified as real objects. Among them 139 are new open clusters with ages 8.3 < log (t [yr]) < 9.7, distances d< 3 kpc, and distances from the Galactic plane 0.3 <Z< 1 kpc. This new sample has increased the total number of known high latitude open clusters by about 150%. Nevertheless, we still observe a lack of older nearby clusters up to 1 kpc from the Sun. This volume is expected to still contain about 60 unknown clusters that probably escaped our detection algorithm, which fails to detect sparse overdensities with large angular size

Deformation Behavior under Static and Cyclic Tension of Polymer Grafts without and after Modification by RGD Peptides

The structure, mechanical properties, and deformation behavior under static and cyclic tension of biofunctionalized biodegradable vascular grafts based on polyhydroxybutyrate/valerate and polycaprolactone were studied. It is shown that the modification gives rise to an almost twofold decrease of the elongation at break as well as the ultimate strength. It is shown that under cyclic loading the modification of grafts results in decreasing cyclic durability by more than twice. In doing so, the level of deforming stress decreases to a much lesser extent and is practically inferior to that for unmodified material. The analysis of principal strain [epsilon]1 and [epsilon]2 component distribution patterns in grafts of both types is carried out while the reason for the observed changes is discussed

In Search of Possible Associations between Planetary Nebulae and Open Clusters

We consider the possibility of cluster membership for 13 planetary nebulae that are located in close proximity to open clusters lying in their lines of sight. The short lifetimes and low sample size of intermediate-mass planetary nebulae with respect to nearby open clusters conspire to reduce the probability of observing a true association. Not surprisingly, line of sight coincidences almost certainly exist for 7 of the 13 cases considered. Additional studies are advocated, however, for 6 planetary nebula/open cluster coincidences in which a physical association is not excluded by the available evidence, namely M 1-80/Berkeley 57, NGC 2438/NGC 2437, NGC 2452/NGC 2453, VBRC 2 & NGC 2899/IC 2488, and HeFa 1/NGC 6067. A number of additional potential associations between planetary nebulae and open clusters is tabulated for reference purposes. It is noteworthy that the strongest cases involve planetary nebulae lying in cluster coronae, a feature also found for short-period cluster Cepheids, which are themselves potential progenitors of planetary nebulae.Comment: Accepted for publication in PASP (December 2007

СТРЕПТОКОККОВАЯ (ГРУППЫА) ИНФЕКЦИЯ ВРОССИИ: СОСТОЯНИЕ ПРОБЛЕМЫ И ТЕНДЕНЦИИ РАЗВИТИЯ

Aim. To assess the current situation on streptococcal (group A) infection in Russia, to study the molecular properties and antimicrobial susceptibility of group A streptococcus isolated from patients with soft tissue infection.Materials and methods. We performed a descriptive epidemiological study using official statistics. A total of 97 cases of soft tissue infection caused by group A streptococci were investigated for emm-types, the presence of genes of bacteriophage toxins and integrases by PCR and sequencing. We tested 91 strains for antimicrobial susceptibility by the micro dilution methods.Results. From 2009 through 2017, 2.8 million cases (563 thousand primary cases) of group A streptococcal disease were reported. There was a decrease in the incidence of scarlet fever in Russia (31.5 per 100 000 population). In 2009–2017 the incidence of rheumatic fever and rheumatic heart diseases increase slightly but the prevalence of this forms group A streptococcal disease are decrease. Annually 2600 people die from the rheumatic fever and rheumatic heart diseases. Of the 97 cultures of group A streptococci, 33 were associated with invasive infection. We identified 33 different emm-type. All cultures contained speB gene. Some strains contained speA, and others speC genes. We did not find any correlation between the presence of bacteriophage toxin genes and the invasive properties of streptococci. Tetracycline and macrolides are ineffective in patients with of soft tissue infectionConclusion. Streptococcal (group A) infection continues to be of significant social and economic importance for Russia. The streptococcus cultures isolated from patients with invasive forms were heterogeneous in molecular and biological properties and remained sensitive to penicillin antibiotics.Цель: оценить современную ситуацию по стрептококковой (группы А) инфекции в России, изучить молекулярно-биологические свойства и чувствительность к антибактериальным препаратам культур стрептококка группы А, выделенных от больных с инфекцией мягких тканей.Материалы и методы. Описательное исследование проведено на основании данных официаль-ой статистической отчетности. 97 культур стрептококка группы А, выделенных от больных с инфекцией мягких тканей, были исследованы на принадлежность к emm-типам, наличие генов бактериофаговых токсинов и интеграз с помощью ПЦР и секвенирования. Из них 91 штамм был исследован на чувствительность к антибиотикам методом микроразведений. Результаты. В целом за 2009–2017 гг. в России, по данным официальной регистрации, было выявлено около 2,8 млн случаев заболеваний, непосредственно связанных со стрептококком группы А, из которых 563 тысячи были выявлены впервые. Заболеваемость скарлатиной в России за исследуемый период снижалась (31,5 на 100 тысяч населения). За 2009–2017 гг. отмечается некоторое увеличение заболеваемости ревматической лихорадкой и ревматическими болезнями сердца при снижении распространенности. Смертность, связанная с ревматической лихорадкой и ревматическими болезнями сердца, также снижается (ежегодно в среднем умирает 2,6 тысячи человек).Из 97 выделенных культур стрептококков группы А 33 были связаны с инвазивной инфекцией. Всего установлено 33 различных emm-типа воз-будителя. Ген speB был выявлен у всех культур. Гены остальных исследуемых токсинов (speA, speC) встречались у ряда штаммов. Корреляции между наличием генов бактериофаговых токсинов и агрессивностью стрептококков обнаружено не было. Использование тетрациклина и макролидов для лечения инфекции мягких тканей неэффективно.Заключение. Стрептококковая (группы А) инфекция продолжает представлять значительную социальную и экономическую значимость для России. Выделенные от больных с инвазивными формами культуры стрептококка были гетерогенны по молекулярно-биологическим свойствам и сохраняли чувствительность к антибиотикам пенициллинового ряда