1,346 research outputs found

    Forward-Backward Multiplicity Correlations in Au+Au Collisions at sNN\sqrt{s_{NN}} = 200 Gev

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    The study of correlations among particles produced in different rapidity regions may provide understanding of the mechanisms of particle production. Correlations that extend over a longer range are observed in hadron-hadron interactions only at higher energies. Results for short and long-range multiplicity correlations (Forward-Backward) are presented for Au+Au collisions at sNN\sqrt{s_{NN}} = 200 GeV. The growth of long range correlations are observed as a function of the pseudorapidity gap in central Au+Au collisions. The Dual Parton model and Color Glass Condensate phenomenology have been explored to understand the origin of long range correlations.Comment: 8 pages, 4 figures, IWCF06, Hangzhou, China, Nov. 21-24, 200

    Two new Lower Cretaceous hymenopterous insects (Insecta: Hymenoptera) from Sierra del Montsec, Spain

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    Two new hymenoterans are described from the Lower Barremian lithographic limestones of Sierra del Montsec (Lleida, Spain), Leridatoma pulcherrimapulcherima n.gen., n.sp. (Xyelotomidae RASNITSYN, 1968) that combines the most and the least advanced character states in the family (in structure of antenna and fore wing RS, respectively), and Cretephialtites pedrerae n.gen., n.sp. (Ephialtitidae HANDLIRSCH, 1906)

    Identity of Prosepididontus calpterys Handlirsch 1920 (Insecta: Grylloblattida: Geinitziidae)

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    Prosepididontus calopteryx HANDLIRSCH 1920, from the upper Lower Jurassic of Germ a ny, is transferred from Trichoptera to Grylloblattida: Geinitziidae. The anal loop like structure of Prosepididontus calopteryx is built of the concave CuP and two anal veins. Prosepididontidae HANDLIRSCH, 1920 is synonymised under Geinitziidae HANDLIRSCH, 1906.Prosepididontus calopteryx HANDLIRSCH 1920, from the upper Lower Jurassic of Germ a ny, is transferred from Trichoptera to Grylloblattida: Geinitziidae. The anal loop like structure of Prosepididontus calopteryx is built of the concave CuP and two anal veins. Prosepididontidae HANDLIRSCH, 1920 is synonymised under Geinitziidae HANDLIRSCH, 1906

    The Conrad Rise as an obstruction to the Antarctic Circumpolar Current

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    The Antarctic Circumpolar Current (ACC) carries water freely around the whole continent of Antarctica, but not without obstructions. Some, such as the Drake Passage, constrict its path, while others, such as mid-ocean ridges, may induce meandering in the current's cores and may cause the genesis of mesoscale turbulence. It has recently been demonstrated that some regions that are only relatively shallow may also have a major effect on the flow patterns of the ACC. This is here shown to be particularly true for the Conrad Rise. Using the trajectories of surface drifters, altimetry and the simulated velocities from a numerical model, we show that the ACC bifurcates at the western side of this Rise. In this process it forms two intense jets at the two meridional extremities of the Rise with a relatively stagnant water body over the Rise itself. Preliminary results from a recent cruise provide compelling support for this portrayal

    Studying the impact of ocean eddies on the ecosystem of the Prince Edward Islands: DEIMEC ll

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    The Dynamics of Eddy Impacts on Marion’s Ecosystem Study (DEIMEC) programme was begun in 2002 with the aim of understanding the importance of the oceanic, upstream environment to the ecosystem of the Prince Edward Islands. This island group consists of two small volcanic islands and provides many opportunities for studying ecological and evolutionary processes, for monitoring ecological changes in relation to global climate change and for conserving a unique component of the planet’s biological diversity

    Prince Edward Islands' offshore oceanographic study: report of research cruise April-May 1997

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    preprintFocuses on the preliminary results of the second cruise of the Marion Island Oceanographic Study designed to provide oceanological observations off Prince Edward Islands from April 25 to May 28, 1997. Physical and chemical oceanographic results; Surface seawater temperature; Total chlorophyll-a distribution

    Energy Scaling of Minimum-Bias Tunes

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    We propose that the flexibility offered by modern event-generator tuning tools allows for more than just obtaining "best fits" to a collection of data. In particular, we argue that the universality of the underlying physics model can be tested by performing several, mutually independent, optimizations of the generator parameters in different physical regions. For regions in which these optimizations return similar and self-consistent parameter values, the model can be considered universal. Deviations from this behavior can be associated with a breakdown of the modeling, with the nature of the deviations giving clues as to the nature of the breakdown. We apply this procedure to study the energy scaling of a class of minimum-bias models based on multiple parton interactions (MPI) and pT-ordered showers, implemented in the Pythia 6.4 generator. We find that a parameter controlling the strength of color reconnections in the final state is the most important source of non-universality in this model.Comment: 17 pages, 3 figures, 4 table

    Decadal-scale thermohaline variability in the Atlantic sector of the Southern Ocean

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    An enhanced Altimetry Gravest Empirical Mode (AGEM), including both adiabatic and diabatic trends, is developed for the Antarctic Circumpolar Current (ACC) south of Africa using updated hydrographic CTD sections, Argo data, and satellite altimetry. This AGEM has improved accuracy compared to traditional climatologies and other proxy methods. The AGEM for the Atlantic Southern Ocean offers an ideal technique to investigate the thermohaline variability over the past two decades in a key region for water mass exchanges and transformation. In order to assess and attribute changes in the hydrography of the region, we separate the changes into adiabatic and diabatic components. Integrated over the upper 2000 dbar of the ACC south of Africa, results show mean adiabatic changes of 0.16 ± 0.11°C decade−1 and 0.006 ± 0.014 decade−1, and diabatic differences of −0.044 ± 0.13°C decade−1 and −0.01 ± 0.017 decade−1 for temperature and salinity, respectively. The trends of the resultant AGEM, that include both adiabatic and diabatic variability (termed AD-AGEM), show a significant increase in the heat content of the upper 2000 dbar of the ACC with a mean warming of 0.12 ± 0.087°C decade−1. This study focuses on the Antarctic Intermediate Water (AAIW) mass where negative diabatic trends dominate positive adiabatic differences in the Subantarctic Zone (SAZ), with results indicating a cooling (−0.17°C decade−1) and freshening (−0.032 decade−1) of AAIW in this area, whereas south of the SAZ positive adiabatic and diabatic trends together create a cumulative warming (0.31°C decade−1) and salinification (0.014 decade−1) of AAIW

    Horizontally transmitted symbiont populations in deep-sea mussels are genetically isolated

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    Eukaryotes are habitats for bacterial organisms where the host colonization and dispersal among individual hosts have consequences for the bacterial ecology and evolution. Vertical symbiont transmission leads to geographic isolation of the microbial population and consequently to genetic isolation of microbiotas from individual hosts. In contrast, the extent of geographic and genetic isolation of horizontally transmitted microbiota is poorly characterized. Here we show that chemosynthetic symbionts of individual Bathymodiolus brooksi mussels constitute genetically isolated subpopulations. The reconstruction of core genome-wide strains from high-resolution metagenomes revealed distinct phylogenetic clades. Nucleotide diversity and strain composition vary along the mussel life span and individual hosts show a high degree of genetic isolation. Our results suggest that the uptake of environmental bacteria is a restricted process in B. brooksi, where self-infection of the gill tissue results in serial founder effects during symbiont evolution. We conclude that bacterial colonization dynamics over the host life cycle is thus an important determinant of population structure and genome evolution of horizontally transmitted symbionts
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