7 research outputs found
Information entropy and nucleon correlations in nuclei
The information entropies in coordinate and momentum spaces and their sum
(, , ) are evaluated for many nuclei using "experimental"
densities or/and momentum distributions. The results are compared with the
harmonic oscillator model and with the short-range correlated distributions. It
is found that depends strongly on and does not depend very much
on the model. The behaviour of is opposite. The various cases we consider
can be classified according to either the quantity of the experimental data we
use or by the values of , i.e., the increase of the quality of the density
and of the momentum distributions leads to an increase of the values of . In
all cases, apart from the linear relation , the linear relation
also holds. V is the mean volume of the nucleus. If is
considered as an ensemble entropy, a relation between or and the
ensemble volume can be found. Finally, comparing different electron scattering
experiments for the same nucleus, it is found that the larger the momentum
transfer ranges, the larger the information entropy is. It is concluded that
could be used to compare different experiments for the same nucleus and to
choose the most reliable one.Comment: 14 pages, 4 figures, 2 table
Nuclear symmetry energy effects on neutron stars properties
We construct a class of nuclear equations of state based on a schematic
potential model, that originates from the work of Prakash et. al.
\cite{Prakash-88}, which reproduce the results of most microscopic
calculations. The equations of state are used as input for solving the
Tolman-Oppenheimer-Volkov equations for corresponding neutron stars. The
potential part contribution of the symmetry energy to the total energy is
parameterized in a generalized form both for low and high values of the baryon
density. Special attention is devoted to the construction of the symmetry
energy in order to reproduce the results of most microscopic calculations of
dense nuclear matter. The obtained nuclear equations of state are applied for
the systematic study of the global properties of a neutron star (masses, radii
and composition). The calculated masses and radii of the neutron stars are
plotted as a function of the potential part parameters of the symmetry energy.
A linear relation between these parameters, the radius and the maximum mass of
the neutron star is obtained. In addition, a linear relation between the radius
and the derivative of the symmetry energy near the saturation density is found.
We also address on the problem of the existence of correlation between the
pressure near the saturation density and the radius.Comment: 17 pages, 25 figure
Spatial and temporal heterogeneity in human mobility patterns in Holocene Southwest Asia and the East Mediterranean
We present a spatiotemporal picture of human genetic diversity in Anatolia, Iran, Levant, South Caucasus, and the Aegean, a broad region that experienced the earliest Neolithic transition and the emergence of complex hierarchical societies. Combining 35 new ancient shotgun genomes with 382 ancient and 23 present-day published genomes, we found that genetic diversity within each region steadily increased through the Holocene. We further observed that the inferred sources of gene flow shifted in time. In the first half of the Holocene, Southwest Asian and the East Mediterranean populations homogenized among themselves. Starting with the Bronze Age, however, regional populations diverged from each other, most likely driven by gene flow from external sources, which we term “the expanding mobility model.” Interestingly, this increase in inter-regional divergence can be captured by outgroup-f-based genetic distances, but not by the commonly used F statistic, due to the sensitivity of F, but not outgroup-f, to within-population diversity. Finally, we report a temporal trend of increasing male bias in admixture events through the Holocene
Phylogeography of Aegean green toads (Bufo viridis subgroup): continental hybrid swarm vs. insular diversification with discovery of a new island endemic
BACKGROUND: Debated aspects in speciation research concern the amount of gene flow between incipient species under secondary contact and the modes by which post-zygotic isolation accumulates. Secondary contact zones of allopatric lineages, involving varying levels of divergence, provide natural settings for comparative studies, for which the Aegean (Eastern Mediterranean) geography offers unique scenarios. In Palearctic green toads (Bufo viridis subgroup or Bufotes), Plio-Pleistocene (~ 2.6 Mya) diverged species show a sharp transition without contemporary gene flow, while younger lineages, diverged in the Lower-Pleistocene (~ 1.9 Mya), admix over tens of kilometers. Here, we conducted a fine-scale multilocus phylogeographic analysis of continental and insular green toads from the Aegean, where a third pair of taxa, involving Mid-Pleistocene diverged (~ 1.5 Mya) mitochondrial lineages, earlier tentatively named viridis and variabilis, (co-)occurs. RESULTS: We discovered a new lineage, endemic to Naxos (Central Cyclades), while coastal islands and Crete feature weak genetic differentiation from the continent. In continental Greece, both lineages, viridis and variabilis, form a hybrid swarm, involving massive mitochondrial and nuclear admixture over hundreds of kilometers, without obvious selection against hybrids. CONCLUSIONS: The genetic signatures of insular Aegean toads appear governed by bathymetry and Quaternary sea level changes, resulting in long-term isolation (Central Cyclades: Naxos) and recent land-bridges (coastal islands). Conversely, Crete has been isolated since the end of the Messinian salinity crisis (5.3 My) and Cretan populations thus likely result from human-mediated colonization, at least since Antiquity, from Peloponnese and Anatolia. Comparisons of green toad hybrid zones support the idea that post-zygotic hybrid incompatibilities accumulate gradually over the genome. In this radiation, only one million years of divergence separate a scenario of complete reproductive isolation, from a secondary contact resulting in near panmixia
Resolving complex phylogeographic patterns in the Balkan Peninsula using closely related wall-lizard species as a model system
The Balkan Peninsula constitutes a biodiversity hotspot with high levels of species richness and endemism. The complex geological history of the Balkans in conjunction with the climate evolution are hypothesized as the main drivers generating this biodiversity. We investigated the phylogeography, historical demography, and population structure of closely related wall-lizard species from the Balkan Peninsula and southeastern Europe to better understand diversification processes of species with limited dispersal ability, from Late Miocene to the Holocene. We used several analytical methods integrating genome-wide SNPs (ddRADseq), microsatellites, mitochondrial and nuclear DNA data, as well as species distribution modelling. Phylogenomic analysis resulted in a completely resolved species level phylogeny, population level analyses confirmed the existence of at least two cryptic evolutionary lineages and extensive within species genetic structuring. Divergence time estimations indicated that the Messinian Salinity Crisis played a key role in shaping patterns of species divergence, whereas intraspecific genetic structuring was mainly driven by Pliocene tectonic events and Quaternary climatic oscillations. The present work highlights the effectiveness of utilizing multiple methods and data types coupled with extensive geographic sampling to uncover the evolutionary processes that shaped the species over space and time. © 2018 Elsevier Inc
Spatial and temporal heterogeneity in human mobility patterns in Holocene Southwest Asia and the East Mediterranean
We preŞent a spatiotemporal picture of human genetic diversity in Anatolia, Iran, Levant, South Caucasus, and the Aegean, a broad region that experienced the earliest Neolithic transition and the emergence of com-plex hierarchical societies. Combining 35 new ancient shotgun genomes with 382 ancient and 23 preŞent-day published genomes, we found that genetic diversity within each region steadily increased through the Holo-cene. We further observed that the inferred sources of gene flow shifted in time. In the first half of the Holo-cene, Southwest Asian and the East Mediterranean populations homogenized among themselves. Starting with the Bronze Age, however, regional populations diverged from each other, most likely driven by gene flow from external sources, which we term the expanding mobility model.Interestingly, this increase in in-ter-regional divergence can be captured by outgroup-f3-based genetic distances, but not by the commonly used FST statistic, due to the Şensitivity of FST, but not outgroup-f3, to within-population diversity. Finally, we report a temporal trend of increasing male bias in admixture events through the Holocene.Wenner-Gren Foundation Dissertation Fieldwork grant; H2020 ERC Consolidator grant; EMBO Scientific Exchange grant [9573]; H2020-WIDESPREAD-05-2020 TWINNING grant [772390 NEOGENE]; TUBITAK of Turkey [8883]; Klaus-Tschira Foundation [952317 NEOMATRIX]; German Research Foundation (DFG) [117Z229]; National Genomics Infrastructure in Stockholm - Science for Life Laboratory; Knut and Alice Wallenberg Foundation [SCHA 889/4-4]; Swedish Research Council; SNIC/Uppsala Multidisciplinary Center for Advanced Computational (UPPMAX) projects; operational programme Competitiveness, Entrepreneurship and Innovation (NSRF 2014-2020); European Union (European Regional Development Fund) [uppstore20180102, SNIC 2018/8-293, SNIC 2018/8-88, SNIC 2021-2-17]; Hacettepe University Scientific Research Projects Coordination Unit [MIS 5002735, MIS 5002478]; [16769]; [14528]We thank Orhan Efe Yavuz, Anna-Sapfo Malaspinas, Flora Jay, Ayshin Ghali-chi, Yesxim Ayd?n Son, Can Alkan, HamitIzgi, Asl?han Ilgaz, Maja Krzewinska, and all colleagues at the METU CompEvo, Hacettepe Human_G and Center for Palaeogenetics (CPG) for their support, suggestions, and/or comments. We also thank three anonymous reviewers for their constructive criticism. The authors acknowledge support from Wenner-Gren Foundation Dissertation Fieldwork grant (no. 9573 to D. Koptekin); H2020 ERC Consolidator grant (no. 772390 NEOGENE to M.S.); EMBO Scientific Exchange grant (no. 8883 to D. Koptekin); H2020-WIDESPREAD-05-2020 TWINNING grant (no. 952317 NEOMATRIX to M.S.); TUBITAK of Turkey (no. 117Z229 to M.S.); Klaus-Tschira Foundation; German Research Foundation (DFG, grant no. SCHA 889/4-4 to A. Schachner); the National Genomics Infrastructure in Stockholm funded by Science for Life Laboratory, the Knut and Alice Wallenberg Foundation, and the Swedish Research Council; SNIC/Uppsala Multidisciplinary Center for Advanced Computational (UPPMAX) projects uppstore20180102, SNIC 2018/8-293, SNIC 2018/8-88, and SNIC 2021-2-17; the projects HELLAS-CH (MIS 5002735), implemented under Action for Strengthening Research and Innovation Infrastructures, and POLITEIA-II (MIS 5002478), implemented under Action for the Strategic Development on the Research and Technological Sector, both funded by the operational programme Competitiveness, Entrepreneurship and Innovation (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund); and Hacettepe University Scientific Research Projects Coordination Unit (nos. 16769 and 14528 to A.M.B.). Computations were performed at NEOGENE (Middle East Technical University) and UPPMAX resources