Modeling the long term dynamics of pre-vaccination pertussis

The dynamics of strongly immunizing childhood infections is still not well understood. Although reports of successful modeling of several incidence data records can be found in the literature, the key determinants of the observed temporal patterns have not been clearly identified. In particular, different models of immunity waning and degree of protection applied to disease and vaccine induced immunity have been debated in the literature on pertussis. Here we study the effect of disease acquired immunity on the long term patterns of pertussis prevalence. We compare five minimal models, all of which are stochastic, seasonally forced, well-mixed models of infection based on susceptible-infective-recovered dynamics in a closed population. These models reflect different assumptions about the immune response of naive hosts, namely total permanent immunity, immunity waning, immunity waning together with immunity boosting, reinfection of recovered, and repeat infection after partial immunity waning. The power spectra of the output prevalence time series characterize the long term dynamics of the models. For epidemiological parameters consistent with published data for pertussis, the power spectra show quantitative and even qualitative differences that can be used to test their assumptions by comparison with ensembles of several decades long pre-vaccination data records. We illustrate this strategy on two publicly available historical data sets.Comment: paper (31 pages, 11 figures, 1 table) and supplementary material (19 pages, 5 figures, 2 tables

Stochastic oscillations in models of epidemics on a network of cities

We carry out an analytic investigation of stochastic oscillations in a susceptible-infected-recovered model of disease spread on a network of $n$ cities. In the model a fraction $f_{jk}$ of individuals from city $k$ commute to city $j$, where they may infect, or be infected by, others. Starting from a continuous time Markov description of the model the deterministic equations, which are valid in the limit when the population of each city is infinite, are recovered. The stochastic fluctuations about the fixed point of these equations are derived by use of the van Kampen system-size expansion. The fixed point structure of the deterministic equations is remarkably simple: a unique non-trivial fixed point always exists and has the feature that the fraction of susceptible, infected and recovered individuals is the same for each city irrespective of its size. We find that the stochastic fluctuations have an analogously simple dynamics: all oscillations have a single frequency, equal to that found in the one city case. We interpret this phenomenon in terms of the properties of the spectrum of the matrix of the linear approximation of the deterministic equations at the fixed point.Comment: 13 pages, 7 figure

Fluctuations and oscillations in a simple epidemic model

We show that the simplest stochastic epidemiological models with spatial correlations exhibit two types of oscillatory behaviour in the endemic phase. In a large parameter range, the oscillations are due to resonant amplification of stochastic fluctuations, a general mechanism first reported for predator-prey dynamics. In a narrow range of parameters that includes many infectious diseases which confer long lasting immunity the oscillations persist for infinite populations. This effect is apparent in simulations of the stochastic process in systems of variable size, and can be understood from the phase diagram of the deterministic pair approximation equations. The two mechanisms combined play a central role in explaining the ubiquity of oscillatory behaviour in real data and in simulation results of epidemic and other related models.Comment: acknowledgments added; a typo in the discussion that follows Eq. (3) is corrected

Deviant behavior of youth in the context of psychology and pedagogy

The article notes that Analysis of psychological and pedagogical literature allowed us to identify the following factors influencing formation and development of various deviant behavior forms: socio-economic, sociocultural, biological, psychological, pedagogical, subcultural. Most researchers consider the violation of social norms and norms of behavior as the main criterion for deviations and consider this phenomenon in term of “adaptation (socialization) - disadaptation (de-socialization)

Phase lag in epidemics on a network of cities

We study the synchronisation and phase-lag of fluctuations in the number of infected individuals in a network of cities between which individuals commute. The frequency and amplitude of these oscillations is known to be very well captured by the van Kampen system-size expansion, and we use this approximation to compute the complex coherence function that describes their correlation. We find that, if the infection rate differs from city to city and the coupling between them is not too strong, these oscillations are synchronised with a well defined phase lag between cities. The analytic description of the effect is shown to be in good agreement with the results of stochastic simulations for realistic population sizes.Comment: 10 pages, 6 figure

Cluster approximations for infection dynamics on random networks

In this paper, we consider a simple stochastic epidemic model on large regular random graphs and the stochastic process that corresponds to this dynamics in the standard pair approximation. Using the fact that the nodes of a pair are unlikely to share neighbors, we derive the master equation for this process and obtain from the system size expansion the power spectrum of the fluctuations in the quasi-stationary state. We show that whenever the pair approximation deterministic equations give an accurate description of the behavior of the system in the thermodynamic limit, the power spectrum of the fluctuations measured in long simulations is well approximated by the analytical power spectrum. If this assumption breaks down, then the cluster approximation must be carried out beyond the level of pairs. We construct an uncorrelated triplet approximation that captures the behavior of the system in a region of parameter space where the pair approximation fails to give a good quantitative or even qualitative agreement. For these parameter values, the power spectrum of the fluctuations in finite systems can be computed analytically from the master equation of the corresponding stochastic process.Comment: the notation has been changed; Ref. [26] and a new paragraph in Section IV have been adde

Search and evaluation of pharmacodynamic and pharmacokinetic parameters of selective blocker of TRPA₁ ion channels from the group of substituted pyrazinopyrimidinones

Search considerations evaluation of pharmacodynamic and pharmacokinetic parameters of selective blocker of TRPA₁ ion channels from the group of substituted pyrazinopyrimidinone

СРАВНИТЕЛЬНАЯ ХАРАКТЕРИСТИКА МАТЕРИАЛОВ, ПРИМЕНЯЕМЫХ В СТОМАТОЛОГИЧЕСКОЙ ИМПЛАНТАЦИИ

The objective of the research is a review of some characteristics of dental implants’ products and an analysis of prospects of using them in modern medicine.Dental implantation as a high-technology method of restoring the natural anatomical structure has no competitors at present. The advantages of dental implants consist in their high operational dependability, a longer life time, a higher functionality and a lesser rate of complications as compared to the use of complete or bridge prostheses.The materials used in dental implantation for this purpose are rather diverse. Doctors using them rely on extensive clinical experience, a developed industry of accessory materials, instruments, that is everything that ensures comfortable work and conveniences for the patient.At the same time, the data mentioned in the article testify to the effect that ceramic implants as compared to titanium alloy implants have comparable or better indices. This is guaranteed, for example, by the requirements of the new international standard ISO6474-2:2012: first-rate strength and wear resistance; thermal stability and corrosion resistance; ceramics’ four point bending strength over 750 MPa.The result of the conducted analysis is a review of using various materials in dental implantation. The author compares the aesthetic indices and durability of titanium or metal alloy implants to those of ceramic ones. The comparison shows that, under the current level of ceramic materials’ structural property, it is actual for dentistry to develop its own methodological approaches in relation to a wide use of ceramic implants and creation of various ceramic mono-implants with the purpose of improving the results of treatment of patients, suffering from secondary partial or complete adentia accompanied by bone tissue deficiency, by applying the methods of dental implantation.Целью работы является обзор некоторых характеристик материалов стоматологических имплантатов и анализ перспектив их использования в современной медицине.Стоматологическая имплантация как высокотехнологичный способ восстановления естественной анатомической структуры в настоящее время не имеет конкурентов. Преимущество дентальных имплантатов заключается в высокой надежности в эксплуатации, более длительном сроке службы, большей функциональности и меньшей частоте осложнений, чем при использовании съемных или мостовидных протезов.Материалы, применяемые в стоматологической имплантации, весьма разнообразны. Врачи, пользуясь ими, основываются на большом клиническом опыте, развитой индустрии вспомогательных материалов, инструментов, т.е. всего того, что обеспечивает комфортную работу и удобство для пациента.В то же время данные, приведенные в статье, свидетельствуют о том, что керамические имплантаты, по сравнению с имплантатами из сплавов титана, имеют сравнимые или лучшие показатели. Превосходная прочность и износостойкость, термическая и коррозионная стойкость, прочность керамики при четырехточечном изгибе более 750 МПа гарантируются, например, требованиями нового международного стандарта ISO 6474-2:2012.Результатом проведенного анализа является обзор применения различных материалов в стоматологической имплантации. Сравнение эстетических показателей и долговечности имплантатов из титана или металлических сплавов с керамическими аналогами показало, что при современном уровне структурного состояния керамических материалов для стоматологии актуально совершенствование собственных методологических подходов в сторону широкого использования керамических имплантатов и создание различных керамических моноимплантатов для улучшения результатов лечения больных с вторичной частичной или полной адентией с сопутствующим дефицитом костной ткани методами стоматологической имплантации

Genetic and biochemical characterization of staphylococci occurring in Novosibirsk, Russia

Staphylococci are capable of penetrating many human tissues and organs, causing superficial and deep purulent infections, respiratory and urinary tract infections, food poisoning and intoxication. Last years, coagulase­negative staphylococci were the cause of infection in many cases. Infectious agents, namely Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus hominis, were detected more often as nosocomial infections. A particular danger of these infections is a high virulence and  pathogenicity of bacterial strains and their resistance to various anti ­ biotics. Methicillin­resistant staphylococci are especially difficult to treat. The correct identification of staphylococci and their sensitivity to antibiotics are important for clinical diagnosis and appointment of adequate drug therapy. Rapid and accurate identification of Staphylococcus species and detection of their sensitivity to antibiotics is quite important. The aim of this study was to study staphylococci isolated in Novosibirsk from human, animal and environmental samples. A collection of 100 staphylococcus strains was analyzed. Staphylococcus species were identified by sequencing the 16S rRNA gene. Eleven staphylococcus species were identified. Among the strains obtained from hospitalized patients, Staphylococcus aure us dominated (79.1 %), Staphylococcus  epidermidis amounted to about 12.5 %. However, S. aureus and S. epi dermidis strains were isolated in an approximately equal proportion from community­associated samples. Identification of coagulase positive strains was performed using a standard biochemical method and by real­time PCR of the coa gene. 100 % coincidence between the presence of the gene and coagulase activity for S. aureus strains was recorded, which suggests that detection of the coa gene can be used as a correct method for S. aure us identification. A high coincidence rate (99 %) was reveal ed between the phenotypic resistance to oxacillin and the presence of the staphylococcal mecA gene. The study of staphylococci for the presence of the mecA gene can be considered as an alternative to the phenotypical method for identification of methicillin­resistant strains of staphylococci