97 research outputs found

    Regime variance testing - a quantile approach

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    This paper is devoted to testing time series that exhibit behavior related to two or more regimes with different statistical properties. Motivation of our study are two real data sets from plasma physics with observable two-regimes structure. In this paper we develop estimation procedure for critical point of division the structure change of a time series. Moreover we propose three tests for recognition such specific behavior. The presented methodology is based on the empirical second moment and its main advantage is lack of the distribution assumption. Moreover, the examined statistical properties we express in the language of empirical quantiles of the squared data therefore the methodology is an extension of the approach known from the literature. The theoretical results we confirm by simulations and analysis of real data of turbulent laboratory plasma

    Tempered relaxation equation and related generalized stable processes

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    Fractional relaxation equations, as well as relaxation functions time-changed by independent stochastic processes have been widely studied (see, for example, \cite{MAI}, \cite{STAW} and \cite{GAR}). We start here by proving that the upper-incomplete Gamma function satisfies the tempered-relaxation equation (of index ρ(0,1)\rho \in (0,1)); thanks to this explicit form of the solution, we can then derive its spectral distribution, which extends the stable law. Accordingly, we define a new class of selfsimilar processes (by means of the nn-times Laplace transform of its density) which is indexed by the parameter ρ\rho : in the special case where ρ=1\rho =1, it reduces to the stable subordinator. Therefore the parameter ρ\rho can be seen as a measure of the local deviation from the temporal dependence structure displayed in the standard stable case.Comment: 20 page

    Longevity and cardiovascular mortality of Polish elite football players

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    Background: Despite wide popularity of football, there is a paucity of scientific evidence explaining the relationship between being a competitive footballer and life expectancy. Aim: The study analyses and compares cause-specific mortality of Polish male elite footballers and the general Polish male population. Methods: Data regarding of 455 elite footballers who died between 1990 and 2015 were retrospectively analysed. The cause of death was established based on the official data from the Polish Central Statistical Office. The control group consisted of men from the general male population in Poland who died in the sampled period at the age of 25 years or more. Results: The mean age at death turned out to be higher for footballers than controls (70.2 vs. 67.4 years). Cardiovascular diseases were a more common cause of death among footballers than in the general male population, both in the subgroup of subjects who died under the age of 65 years and in those who were at least 65 years old at the time of death (46.9% vs. 32.3% and 61.3% vs. 53.3%, respectively). A detailed analysis of cause-specific cardiovascular mortality revealed that acute myocardial infarction caused more deaths (odds ratio [OR] 1.31; 95% confidence interval [CI] 1.02–1.68) and hypertensive disease caused less deaths (OR 0.20; 95% CI 0.05–0.79) among athletes than in the general male population. A trend analysis has shown that the level of cardiovascular mortality among footballers is falling. Conclusions: The study results indicate excess cardiovascular mortality among Polish elite footballers

    MODOMICS: a database of RNA modification pathways

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    MODOMICS is the first comprehensive database resource for systems biology of RNA modification. It integrates information about the chemical structure of modified nucleosides, their localization in RNA sequences, pathways of their biosynthesis and enzymes that carry out the respective reactions. MODOMICS also provides literature information, and links to other databases, including the available protein sequence and structure data. The current list of modifications and pathways is comprehensive, while the dataset of enzymes is limited to Escherichia coli and Saccharomyces cerevisiae and sequence alignments are presented only for tRNAs from these organisms. RNAs and enzymes from other organisms will be included in the near future. MODOMICS can be queried by the type of nucleoside (e.g. A, G, C, U, I, m(1)A, nm(5)s(2)U, etc.), type of RNA, position of a particular nucleoside, type of reaction (e.g. methylation, thiolation, deamination, etc.) and name or sequence of an enzyme of interest. Options for data presentation include graphs of pathways involving the query nucleoside, multiple sequence alignments of RNA sequences and tabular forms with enzyme and literature data. The contents of MODOMICS can be accessed through the World Wide Web at
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