19,760 research outputs found
Cluster Winds Blow along Supercluster Axes
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 .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)
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)
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
Sea-surface circulation, sediment transport, and marine mammal distribution, Alaska continental shelf
There are no author-identified significant results in this report
Identifying invertebrate invasions using morphological and molecular analyses: North American Daphnia ‘pulex’ in New Zealand fresh waters
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
Let be an odd prime, an abelian totally real number field,
its cyclotomic -extension,
We give an explicit description of the equivariant characteristic ideal of
over for all odd 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 -invariant of
$F_\infty/F.
The momentum distribution of J/psi in B decays
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
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
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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