265 research outputs found

    Dynamic Evolution of Pairs of Trans-Neptunian Objects: the Case of Binary and Single Objects in Pair

    Full text link
    We performed a search for pairs of trans-Neptunian objects in close orbits with semi-ma jor axes of more than 30 AU. Distances in the space of Keplerian orbits were estimated using the Kholshevnikov metrics. Found 21 pairs of trans-Neptunian objects in which one of the components is binary, for Kholshevnikov metrics in five-dimensional space of Keplerian orbits less than 0.121 AU1/2. All pairs belong to cold Classical Kuiper belt objects. Based on nominal orbits, the dynamic evolution of pairs of trans-Neptunian objects in the past 10 Myr has been studied numerically. We searched for low relativevelocity close encounters between trans-Neptunian objects in pairs as well as the minima of the Kholshevnikov metrics and the convergence of the lines of nodes and apses, to estimate the age of the pairs. © 2021. All Rights Reserved.This work has been supported by the Russian Ministry of Science and Higher Education via the State Assignment Project FEUZ-2020-0038

    The geography of recent genetic ancestry across Europe

    Get PDF
    The recent genealogical history of human populations is a complex mosaic formed by individual migration, large-scale population movements, and other demographic events. Population genomics datasets can provide a window into this recent history, as rare traces of recent shared genetic ancestry are detectable due to long segments of shared genomic material. We make use of genomic data for 2,257 Europeans (the POPRES dataset) to conduct one of the first surveys of recent genealogical ancestry over the past three thousand years at a continental scale. We detected 1.9 million shared genomic segments, and used the lengths of these to infer the distribution of shared ancestors across time and geography. We find that a pair of modern Europeans living in neighboring populations share around 10-50 genetic common ancestors from the last 1500 years, and upwards of 500 genetic ancestors from the previous 1000 years. These numbers drop off exponentially with geographic distance, but since genetic ancestry is rare, individuals from opposite ends of Europe are still expected to share millions of common genealogical ancestors over the last 1000 years. There is substantial regional variation in the number of shared genetic ancestors: especially high numbers of common ancestors between many eastern populations likely date to the Slavic and/or Hunnic expansions, while much lower levels of common ancestry in the Italian and Iberian peninsulas may indicate weaker demographic effects of Germanic expansions into these areas and/or more stably structured populations. Recent shared ancestry in modern Europeans is ubiquitous, and clearly shows the impact of both small-scale migration and large historical events. Population genomic datasets have considerable power to uncover recent demographic history, and will allow a much fuller picture of the close genealogical kinship of individuals across the world.Comment: Full size figures available from http://www.eve.ucdavis.edu/~plralph/research.html; or html version at http://ralphlab.usc.edu/ibd/ibd-paper/ibd-writeup.xhtm

    Adiabatic description of nonspherical quantum dot models

    Full text link
    Within the effective mass approximation an adiabatic description of spheroidal and dumbbell quantum dot models in the regime of strong dimensional quantization is presented using the expansion of the wave function in appropriate sets of single-parameter basis functions. The comparison is given and the peculiarities are considered for spectral and optical characteristics of the models with axially symmetric confining potentials depending on their geometric size making use of the total sets of exact and adiabatic quantum numbers in appropriate analytic approximations

    Issues associated with energy efficiency programs implementation at the housing and utility enterprises

    Full text link
    Energy saving potential is quite huge in the most sectors of the national economy, particularly in housing and utilities and industry. Due to this, energy efficiency increase at the enterprises of housing and utilities and industry through the energy efficiency programs implementation, is one of the priorities in the modern economy of Russia and its regions, and requires radical measures to improve the effectiveness of its implementation. The purpose of the authors is the scientific and practical study of the main problems of energy efficiency programs implementation at the enterprises of housing and utilities services and industry in modern conditions. To achieve this purpose the authors solved the following problems: the current state of the housing and utilities sector and industry, the relevance and the need for energy saving policy at the enterprises of housing and utilities services and industry are studied; the main problems impeding to implement the energy-saving program effectively at the enterprises of housing and utilities services and industry are determined; the possible ways of solving the problems identified in the energy efficiency programs implementation at the enterprises of housing and industry are offered. The team of authors focuses in this study on the problems of the energy audit using in practice as a basic tool for the energy saving programs development at the enterprises of housing and utilities services, industry and their subsequent implementation. The subject of author's researches is the factors that determine the energy efficiency programs implementation at the enterprises of housing and utilities services and industry at the level of individual region and the whole country, and the object is the enterprises of housing and utilities services and industry. Methodologically the scientific and practical research is based on the complex approach using the methods of comparative, statistical and logical analysis

    Single-Tissue and Cross-Tissue Heritability of Gene Expression Via Identity-by-Descent in Related or Unrelated Individuals

    Get PDF
    Family studies of individual tissues have shown that gene expression traits are genetically heritable. Here, we investigate cis and trans components of heritability both within and across tissues by applying variance-components methods to 722 Icelanders from family cohorts, using identity-by-descent (IBD) estimates from long-range phased genome-wide SNP data and gene expression measurements for ∼19,000 genes in blood and adipose tissue. We estimate the proportion of gene expression heritability attributable to cis regulation as 37% in blood and 24% in adipose tissue. Our results indicate that the correlation in gene expression measurements across these tissues is primarily due to heritability at cis loci, whereas there is little sharing of trans regulation across tissues. One implication of this finding is that heritability in tissues composed of heterogeneous cell types is expected to be more dominated by cis regulation than in tissues composed of more homogeneous cell types, consistent with our blood versus adipose results as well as results of previous studies in lymphoblastoid cell lines. Finally, we obtained similar estimates of the cis components of heritability using IBD between unrelated individuals, indicating that transgenerational epigenetic inheritance does not contribute substantially to the “missing heritability” of gene expression in these tissue types
    corecore