Dental status of persons engaged in sports swimming

To date, information on the problem is contradictory and ambiguous. It is difficult to trace cause – effect relationships between the condition of hard dental tissues, oral fluid, the dental status of swimmers, and the characteristics of the water environment of training pools. The article presents an analysis and systematization of literature on the dental condition in swimming athletes, as well as formulates modern ideas on the subject and highlights topics for further research

Spin-fluctuation theory beyond Gaussian approximation

A characteristic feature of the Gaussian approximation in the functional-integral approach to the spin-fluctuation theory is the jump phase transition to the paramagnetic state. We eliminate the jump and obtain a continuous second-order phase transition by taking into account high-order terms in the expansion of the free energy in powers of the fluctuating exchange field. The third-order term of the free energy renormalizes the mean field, and fourth-order term, responsible for the interaction of the fluctuations, renormalizes the spin susceptibility. The extended theory is applied to the calculation of magnetic properties of Fe-Ni Invar.Comment: 20 pages, 4 figure

Пространственно-временная неоднородность снежной толщи по данным пенетрометра SnowMicroPen

Te paper presents the results of studies aimed at investigation of the spatial and temporal variability of snow coverstructure on the basis of strength values and its variations obtained by means of the high-resolution penetrometer SnowMicroPen. Te possibilities of fast and independent from the observer identifcation of layers (including identifcation of weakened, potentially avalanche-dangerous layers) were estimated under the climatic conditions of Moscow and the Khibiny mountains. Horizontal areas with homogeneous underlying surface and vegetation were selected for the stratigraphic studies that made it possible to avoid a possible influence of slope relief and exposure from the obtained data on the spatial and temporal variability of the snow depth structure. Te analysis of the information obtained in winter seasons 2014/15 and 2016/17 allowed constructing detailed schemes of the snow cover evolution at the Moscow site as well as assessing the inter-annual and intra-seasonal variability of its structure. Afer the SnowMicroPen data were recorded in the course of the feld works carried out in winter 2015/16 on the Khibiny educational and scientifc base of the Lomonosov Moscow State University (city of Kirovsk), the 10-meter trench on the same profle was described in details, and direct data on the snow cover structure were obtained. Te strength values resulted from the above studies characterize the layers composed of crystals of various shapes and sizes, and they are considered as the frst step to methodology of operational defnition of the spatially-inhomogeneous stratigraphy and stability of snowpack without snowpit observations. Te data analysis showed high spatial and temporal variability of the structure and properties of snow cover even at a homogeneous area, usually described by a single snowpit.Представлены результаты исследований снежной толщи, полученные на двух полигонах в Москве и Хибинах. Исследована пространственная неоднородность снежной толщи и её изменения в течение зимнего сезона. Прочность снега определяли с помощью пенетрометра высокого разрешения SnowMicroPen. Построены и проанализированы схемы развития снежной толщи и её пространственная изменчивость

Testing a Short Nuclear Marker for Inferring Staphylinid Beetle Diversity in an African Tropical Rain Forest

The use of DNA based methods for assessing biodiversity has become increasingly common during the last years. Especially in speciose biomes as tropical rain forests and/or in hyperdiverse or understudied taxa they may efficiently complement morphological approaches. The most successful molecular approach in this field is DNA barcoding based on cytochrome c oxidase I (COI) marker, but other markers are used as well. Whereas most studies aim at identifying or describing species, there are only few attempts to use DNA markers for inventorying all animal species found in environmental samples to describe variations of biodiversity patterns.In this study, an analysis of the nuclear D3 region of the 28S rRNA gene to delimit species-like units is compared to results based on distinction of morphospecies. Data derived from both approaches are used to assess diversity and composition of staphylinid beetle communities of a Guineo-Congolian rain forest in Kenya. Beetles were collected with a standardized sampling design across six transects in primary and secondary forests using pitfall traps. Sequences could be obtained of 99% of all individuals. In total, 76 molecular operational taxonomic units (MOTUs) were found in contrast to 70 discernible morphospecies. Despite this difference both approaches revealed highly similar biodiversity patterns, with species richness being equal in primary and secondary forests, but with divergent species communities in different habitats. The D3-MOTU approach proved to be an efficient tool for biodiversity analyses.Our data illustrate that the use of MOTUs as a proxy for species can provide an alternative to morphospecies identification for the analysis of changes in community structure of hyperdiverse insect taxa. The efficient amplification of the D3-marker and the ability of the D3-MOTUs to reveal similar biodiversity patterns as analyses of morphospecies recommend its use in future molecular studies on biodiversity

RESONANT PHOTOEMISSION OF INTERMETALLIC COMPOUNDS RMn2Si2

The compounds RMn2Si2 (R = La, Sm, Tb) with tetragonal ThCr2Si2 – type structure were studied. Experiments on resonant photoemission were performed and the partial densities of La 5d, 4f, Sm 4f, Tb 4f, and Mn 3d states, which form a valence band in the RMn2Si2, were found.Работа выполнена при финансовой поддержке Российского фонда фундаментальных исследований (проект 20-02-00541 А)

The Lake Krasnoe obsidian source in Chukotka (Northeastern Siberia): geological and geochemical frameworks for provenance studies in Beringia

Basic data on the geology and geochemistry of obsidian from the Lake Krasnoe source in Chukotka (Northeastern Siberia) are reported for the first time. The data are based on 2009 fieldwork and analytical studies of igneous rock samples. The lake shore and surrounding parts of the Rarytkin Range were thoroughly examined. Two geochemical types of rhyolitic obsidian were recognized for the first time: (1) metaluminous obsidian related to the fine-grained crystalline rocks and (2) peralkaline obsidian corresponding to ignimbrite ash-flows or lapilli-tuffs composition. Both types are related to the final phase of acidic volcanism in the Western Kamchatkan-Koryak Volcanic Belt. Based on the results obtained, we conclude that accumulation of obsidian pebbles in the lake’s modern beach deposits is related to silicic melts that erupted during the late Eocene-early Oligocene in the form of extrusive domes or pyroclastic flows, which are now either covered by Quaternary sediments or located below the water level. The Lake Krasnoe obsidian was intensively used by the ancient populations of Chukotka as a raw material for making stone tools. It was also occasionally transported to Alaska across the Bering Strait in later prehistory. The distances between source and utilization sites are up to 700– 1100 km. Geochemical data for Lake Krasnoe obsidian, based on neutron activation analysis and X-ray fluorescence that are presented here, can now be used for provenance studies in the Northeastern Siberia and adjacent regions of northern North America

The Lake Krasnoe obsidian source in Chukotka (Northeastern Siberia): geological and geochemical frameworks for provenance studies in Beringia

Basic data on the geology and geochemistry of obsidian from the Lake Krasnoe source in Chukotka (Northeastern Siberia) are reported for the first time. The data are based on 2009 fieldwork and analytical studies of igneous rock samples. The lake shore and surrounding parts of the Rarytkin Range were thoroughly examined. Two geochemical types of rhyolitic obsidian were recognized for the first time: (1) metaluminous obsidian related to the fine-grained crystalline rocks and (2) peralkaline obsidian corresponding to ignimbrite ash-flows or lapilli-tuffs composition. Both types are related to the final phase of acidic volcanism in the Western Kamchatkan-Koryak Volcanic Belt. Based on the results obtained, we conclude that accumulation of obsidian pebbles in the lake’s modern beach deposits is related to silicic melts that erupted during the late Eocene-early Oligocene in the form of extrusive domes or pyroclastic flows, which are now either covered by Quaternary sediments or located below the water level. The Lake Krasnoe obsidian was intensively used by the ancient populations of Chukotka as a raw material for making stone tools. It was also occasionally transported to Alaska across the Bering Strait in later prehistory. The distances between source and utilization sites are up to 700– 1100 km. Geochemical data for Lake Krasnoe obsidian, based on neutron activation analysis and X-ray fluorescence that are presented here, can now be used for provenance studies in the Northeastern Siberia and adjacent regions of northern North America

Gate Driver Integrated Circuit with Breakdown Protection for Switch-mode Power Amplifiers

This paper proposes a gate driver integrated circuit to prevent breakdown of switching power amplifiers. The proposed circuit consists of a dead-time generator, level shifters, and a breakdown blocker. The dead-time generator makes non-overlapped input signals and the breakdown blocker detects instantaneous turned-on input signals and resets them to the off-state before the switching power cells are damaged. The circuit is designed using TowerJazz\u27s 0.18 um BCD process for a tightly coupled wireless power transfer system. The protecting operation is verified using circuit simulation including layout-dependent characteristics.U ovom radu prikazan je pobudni sklop za sprječavanje kvarnog stanja pojačala snage. Predloženi krug sastoji se od generatora mrtvog vremena, translator razine i sklopa za sprječavanje kvarnog stanja. Generator mrtvog vremena tvori nepreklopljene ulazne signale, a sklop za sprječavanje kvarnog stanja prepoznaje trenutno paljenje ulaznog signala i resetira ih prije nego su ćelije pojačala snage oštećene. Krug je dizajniran koristeći TowerJazz\u27s 0.18 um BCD postupak za povezani sustav bežičnog prijenosa snage. Zaštita je verificirana koristeći simulaciju kruga uključujući karakteristike povezane s izgledom