19,760 research outputs found

    Cluster Winds Blow along Supercluster Axes

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    Within Abell galaxy clusters containing wide-angle tailed radio sources, there is evidence of a ``prevailing wind'' which directs the WAT jets. We study the alignment of WAT jets and nearby clusters to test the idea that this wind may be a fossil of drainage along large-scale supercluster axes. We also test this idea with a study of the alignment of WAT jets and supercluster axes. Statistical test neighbours indicate no alignment of WAT jets towards nearest clusters, but do indicate approximately 98% confidence in alignment with the long axis of the supercluster in which the cluster lies. We find a preferred scale for such superclusters of order 25 Mpc h1h^{-1}.Comment: Latex, 5 pages, with 5 postscript figures. To be published in MNRAS. Slight revisions to coincide with journal text. Linked to color image at http://kusmos.phsx.ukans.edu/~melott/images/A2634SUW.jp

    The 2^-+ assignment for the X(3872)

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    Very recently the BaBar collaboration has put forward a claim that the X(3872) is not a 1^++ resonance, as most of the phenomenological work on the subject was relying on, but rather a 2^-+ one. We examine the consequences of this quantum number assignment for the solution of the X(3872) puzzle. The molecular interpretation appears less likely, and the conventional charmonium interpretation should be reconsidered. There are several well-known difficulties with this interpretation, to which we add a new one: the production cross section at CDF is predicted to be much smaller than that observed. We also confirm, using a relativistic string model, the conclusion from potential models that the mass of the state is not consistent with expectations. In the tetraquark interpretation the 2^-+ assignment implies a rich spectrum of partner states, although the X(3872) may be among the few which are narrow enough to be observable.Comment: 18 pages, 6 figures, 4 tables; minor style corrections. Version to appear in PR

    Nuptial gift chemistry reveals convergent evolution correlated with antagonism in mating systems of harvestmen (Arachnida, Opiliones)

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    Nuptial gifts are material donations given from male to female before or during copulation and are subject to sexual selection in a wide variety of taxa. The harvestman genus Leiobunum has emerged as a model system for understanding the evolution of reproductive morphology and behavior, as transitions between solicitous and antagonistic modes of courtship have occurred multiple times within the lineage and are correlated with convergence in genital morphology. We analyzed the free amino acid content of nuptial gift secretions from five species of Leiobunum using gas chromatography–mass spectrometry. Multivariate analysis of the free amino acid profiles revealed that, rather than clustering based on phylogenetic relationships, nuptial gift chemical composition was better predicted by genital morphology and behavior, suggesting that convergent evolution has acted on the chemical composition of the nuptial gift. In addition, we found that, species with solicitous courtship produce gifts consisting of a 19% larger proportion of essential amino acids as compared to those with more antagonistic courtship interactions. This work represents the first comparative study of nuptial gift chemistry within a phylogenetic framework in any animal group and as such contributes to our understanding of the evolution of reproductive diversity and the participant role of nuptial gift chemistry in mating system transitions

    Identifying invertebrate invasions using morphological and molecular analyses: North American Daphnia ‘pulex’ in New Zealand fresh waters

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    We used a DNA barcoding approach to identify specimens of the Daphnia pulex complex occurring in New Zealand lakes, documenting the establishment of non-indigenous North American Daphnia 'pulex'. Morphological delineation of species in this complex is problematic due to a lack of good morphological traits to distinguish the species, as there is a relatively high degree of morphological stasis within the group through evolutionary time. Accordingly, genetic analyses were used to determine the specific identity and likely geographic origin of this species. Morphologically, individuals most closely resembled Daphnia pulicaria or Daphnia pulex sensu lato, which cannot be separated morphologically. Furthermore, each of these taxa comprises separate species in North America and Europe, despite carrying the same names. We identified individuals using a 658 bp nucleotide portion of the mitochondrial cytochrome c oxidase subunit 1 gene (COI) as North American Daphnia 'pulex', being distinct from European Daphnia pulex sensu stricto and D. pulicaria from Europe or North America. Cellulose allozyme electrophoresis was used to confirm that individuals were not hybrids with D. pulicaria. North American Daphnia 'pulex' in New Zealand were first recorded in New Zealand from South Island lakes that are popular for overseas recreational fishers, indicating a possible source of introduction for this species (e.g. on/in fishing gear). Our study provides an additional example of how genetic techniques can be used for the accurate identification of non-indigenous taxa, particularly when morphological species determination is not possible. The growth of global databases such as GenBank and Barcode of Life Datasystems (BOLD) will further enhance this identification capacity

    On equivariant characteristic ideals of real classes

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    Let pp be an odd prime, F/QF/{\Bbb Q} an abelian totally real number field, F/FF_\infty/F its cyclotomic Zp{\Bbb Z}_p-extension, G=Gal(F/Q),G_\infty = Gal (F_\infty / {\Bbb Q}), A=Zp[[G]].{\Bbb A} = {\Bbb Z}_p [[G_\infty]]. We give an explicit description of the equivariant characteristic ideal of HIw2(F,Zp(m))H^2_{Iw} (F_\infty, {\Bbb Z}_p(m)) over A{\Bbb A} for all odd mZm \in {\Bbb Z} by applying M. Witte's formulation of an equivariant main conjecture (or "limit theorem") due to Burns and Greither. This could shed some light on Greenberg's conjecture on the vanishing of the λ\lambda-invariant of $F_\infty/F.

    The momentum distribution of J/psi in B decays

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    The discrepancy between theory and data in the momentum distribution of slow J/psi in B decays has been several times addressed as a puzzle. Using the most recent results on exclusive B decays into J/psi and heavy kaons or exotic mesons and reconsidering the non-relativistic-QCD calculation of the color octet fragmentation component, we show that an improvement in the comparison between data and theory can be obtained. There is still room for a better fit to data and this may imply that new exotic mesons of the XYZ kind have yet to be discovered.Comment: 4 pages, 2 figures, 2 tables. To appear in Physical Review

    The space station: Human factors and productivity

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    Human factor researchers and engineers are making inputs into the early stages of the design of the Space Station to improve both the quality of life and work on-orbit. Effective integration of the human factors information related to various Intravehicular Activity (IVA), Extravehicular Activity (EVA), and teletobotics systems during the Space Station design will result in increased productivity, increased flexibility of the Space Stations systems, lower cost of operations, improved reliability, and increased safety for the crew onboard the Space Station. The major features of productivity examined include the cognitive and physical effort involved in work, the accuracy of worker output and ability to maintain performance at a high level of accuracy, the speed and temporal efficiency with which a worker performs, crewmember satisfaction with their work environment, and the relation between performance and cost

    Challenges & Rewards with an Institutional Repository

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    UVM Libraries launched ScholarWorks @ UVM in 2013 to collect, preserve and disseminate scholarly works of faculty, students as well as make collections, reports and other materials more discoverable and available.This institutional repository has grown to over twenty collections, comprising of student dissertations and theses, public health projects, historic botanical research, Vermont history, faculty publications and more.Challenges include varied participation across campus, impacting work flow in library positions, and adding another library service.Author’s works enjoy increased discoverability from all over the world, from low income countries to individuals that seek information without the benefit of library resources. IRs support libraries’ intellectual mission
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