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

Condition of hard tissues of teeth and oral fluid in athletes-swimmers

Objective: to determine the state of dental hard tissues and saliva parameters changing in competitive swimmers, before and after a 2­hour training session in the chlorinated water swimming pool.Materials and methods: saliva parameters of competitive swimmers trained in the sport club “Grifon”, city of St. Petersburg, Russia (n = 21), age of participants 18.1 ± 3.5 years, qualifications (1 category­Master of Sports) and track and field athletes of the sports schools “Nevsky district” and “Orlyonok”, city of St. Petersburg, Russia (n = 18), age of participants 18.80 ± 4.54 years, qualifications (1 category — Master of Sports), have been analyzed by various tests include a study of calcium (Ca), phosphorus (P), fluorine (F) levels, and pH before and after training sessions. All athletes in the experimental and control groups have passed an examination by dentist, including: examination of the oral cavity with the determination of the KPU index (the sum of carious, filled and removed permanent teeth in the subject), examination of the most common places of occurrence of dental enamel erosion (medical binoculars) and filling out specially designed questionnaires.Results: there was a tendency to decrease of the average saliva pH in competitive swimmers’ group after a training session, varying from 6.9 ± 0.1 (before training) to 6.5 ± 0.1 (after training) (p > 0.05). In track and field athletes, saliva pH did not change significantly (7.1 ± 0.2 before training and 7.0 ± 0.1 after training) (p < 0.05). The competitive swimmers showed a statistically significant increase in Calcium (Ca) levels (1.25 ± 0.15 mmol/L before exercise and 1.56 ± 0.11 mmol/L after exercise) and Fluorine (F) (0.0010 ± 0.0003 mmol / L before exercise and 0.0090 ± 0.0004 mmol / L after training session) in saliva. The Phosphorus (P) level in saliva was significantly reduced after the training session (from 6.09 ± 0.39 to 3.89 ± 0.46 mmol / L) (p > 0.05). In track and field athletes, there were no significant changes in Ca, F and P levels before and after a training session. As a result of the dentist’s examination, competitive swimmers were found to have 3 athletes (14.3 %) with lesions of the teeth enamel, corresponding to dental erosion and caused by localized demineralization. In the control group of athletes, no such pathologies were revealed.Conclusion: discovered saliva parameters changing in competitive swimmers (decrease in free salivation, pH level, and increase in the level of Ca and F in saliva) can contribute to the demineralization of tooth enamel. Timely and controlled use of fluorides (as part of mouth rinses, application gels, fluoride varnishes), regular preventive dental examinations, in order to prevent the loss of mineral composition of the teeth when swimming in chlorinated pools, will minimize the risk of staining and dental enamel erosions

Asymmetrical current generator operating modes in battery charging

This paper presents the investigation of the different operating modes of the asymmetrical quasi-sinusoidal output current inductive-switch generator. The purpose of investigation is to find the most effective operation mode where an acceptable output current quality is combined with relatively small dynamic losses in switches. Depending on the algorithm of the generator switches, there are four operating modes. The calculations describing the generator operating principle were obtained for each operating mode

Structure and content of e-learning information environment based on geo-information technologies

© 2017 Authors. The urgency of the paper is determined by the continuous information development of all spheres of education: integration of new knowledge, accessibility of information technologies and computer facility aids, professionalization and computerization of educational activities. The purpose of the research is to develop the structure and content of learning information environment in a higher education institute on the basis of geo-information technologies. The authors show the possibilities of using geo-information technologies in teaching outside the scope of their typical application (geographic, geodetic, geological education). The principles of designing the information environment for training on the basis of geo-information technologies are developed, which is built into the general information environment of higher education institute. The peculiarities of using geo-information technologies in non-core training are revealed, and the structure of learning environment modules based on geo-information technologies is developed and their content is described. The authors adapted the system of criteria evaluating the the effectiveness of training information environment, carried out an empirical study of the quality of education information environment in a higher education institute on the basis of geo-information technologies. The paper is intended for teachers, specialists in the field of information as means of education

Ranking of acidic soils by priority of liming in the Russian Federation

Excessively acidic soils account for one third of arable land in the Russian Federation (35.1 million ha). Over the post-reform period (1990–2019), the relative share of acidic soils increased by 2%, due to a sharp decrease in the area of liming, and thus restoration of acidic properties of genetically acidic soils previously limed, as well as the involvement in agricultural use of some abandoned fields and fallows covered by acidic soils. This paper demonstrates a new approach to prioritize areas for liming by the example of the Vladimir region. The study makes use of newly established database “Soils of agricultural lands in the Russian Federation” which includes 10,000 soil quality typological unites and 57,678 soil quality mapping units (SQMU). National “Grain equivalent model” calculates the standard yields for grain crops by each SQMU. The GIS analysis allows joining spatial distribution of soil acidity and standard yields of grains in order to determine the priority areas for lime application. Acidic soils with the highest grains standard yield are proposed to be considered as high-priority ones for liming. Application of the given method in two districts of the Vladimir region showed significant reduction in the payback period of liming

Modelling Stochastic and Deterministic Behaviours in Virus Infection Dynamics

Many human infections with viruses such as human immunodeficiency virus type 1 (HIV--1) are characterized by low numbers of founder viruses for which the random effects and discrete nature of populations have a strong effect on the dynamics, e.g., extinction versus spread. It remains to be established whether HIV transmission is a stochastic process on the whole. In this study, we consider the simplest (so-called, 'consensus') virus dynamics model and develop a computational methodology for building an equivalent stochastic model based on Markov Chain accounting for random interactions between the components. The model is used to study the evolution of the probability densities for the virus and target cell populations. It predicts the probability of infection spread as a function of the number of the transmitted viruses. A hybrid algorithm is suggested to compute efficiently the dynamics in state space domain characterized by a mix of small and large species densities

MAGNETO-OPTICAL STUDY OF THE TOPOLOGICAL INSULATOR Bi1.1Sb0.9Te2S

We study the electronic properties of the Bi1.1Sb0.9Te2S topological insulator by the magneto-optical spectroscopy. Reflection and transmission spectra were obtained in magnetic fields from 0 to 11 T. A strong influence of the magnetic field on the electronic structure and optical spectra is shown.Работа выполнена в рамках государственного задания МИНОБРНАУКИ России (тема «Спин», № 122021000036-3) при частичной поддержке РФФИ (проект № 19-29-12061)

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

(Im)material Culture : Towards an Archaeology of Cybercrime

Cybercrime is ubiquitous. People now inhabit a digital environment comprising permanent risk, exponential threats, and multiple virtual/physical harms, forming a global community of malefactors and the criminally exploited. The purpose of this paper is two-fold. First, through an archaeological lens, to characterize the new materiality of cybercrime (including its artefacts and architecture alongside digital/virtual manifestations). And second, to explore the potential for new perspectives on cybercrime borne out of this archaeological approach. In short: what is the archaeology of cybercrime and can new understandings emerge from an archaeological perspective? In undertaking this research we also challenge the long-held presumption that non-physical traces cannot be studied archaeologically. It is our contention that they can