1,998 research outputs found

    GrameneMart: the BioMart data portal for the Gramene project

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    Gramene is a well-established resource for plant comparative genome analysis. Data are generated through automated and curated analyses and made available through web interfaces such as GrameneMart. The Gramene project was an early adopter of the BioMart software, which remains an integral and well-used component of the Gramene website. BioMart accessible data sets include plant gene annotations, plant variation catalogues, genetic markers, physical mapping entities, public DNA/mRNA sequences of various types and curated quantitative trait loci for various species. Database URL: http://www.gramene.org/biomart/martview

    New Distributional Records of the Ohio Shrimp, Macrobrachium ohione Smith (Decapoda: Palaemonidae) in Arkansas

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    The Ohio shrimp (Macrobrachium ohione) is a migratory (amphidromous) river shrimp that occurs in some Arkansas rivers. It is known from the Upper Missouri River from its mouth downstream to the Gulf of Mexico, but shrimp abundance has declined, particularly upstream of Louisiana. Ohio Shrimp has also been collected in the lower reach of the Missouri River not far from the confluence of the Mississippi River in St. Louis County. Dams and alterations in channel flow are hypothesized to have impacted upriver migrations of shrimp. Current range, abundance, and life history of Ohio shrimp is relatively unknown in the Mississippi River basin in reaches distant from sea water. Here, we report recent collections of Ohio shrimp in Arkansas rivers that were notably greater than 800 km from the Gulf of Mexico

    Measurement of the quenching factor of Na recoils in NaI(Tl)

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    Measurements of the quenching factor for sodium recoils in a 5 cm diameter NaI(Tl) crystal at room temperature have been made at a dedicated neutron facility at the University of Sheffield. The crystal has been exposed to 2.45 MeV mono-energetic neutrons generated by a Sodern GENIE 16 neutron generator, yielding nuclear recoils of energies between 10 and 100 keVnr. A cylindrical BC501A detector has been used to tag neutrons that scatter off sodium nuclei in the crystal. Cuts on pulse shape and time of flight have been performed on pulses recorded by an Acqiris DC265 digitiser with a 2 ns sampling time. Measured quenching factors of Na nuclei range from 19% to 26% in good agreement with other experiments, and a value of 25.2 \pm 6.4% has been determined for 10 keV sodium recoils. From pulse shape analysis, the mean times of pulses from electron and nuclear recoils have been compared down to 2 keVee. The experimental results are compared to those predicted by Lindhard theory, simulated by the SRIM Monte Carlo code, and a preliminary curve calculated by Prof. Akira Hitachi.Comment: 21 pages, 13 figure

    Cosmic Acceleration, Dark Energy and Fundamental Physics

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    A web of interlocking observations has established that the expansion of the Universe is speeding up and not slowing, revealing the presence of some form of repulsive gravity. Within the context of general relativity the cause of cosmic acceleration is a highly elastic (p\sim -rho), very smooth form of energy called ``dark energy'' accounting for about 75% of the Universe. The ``simplest'' explanation for dark energy is the zero-point energy density associated with the quantum vacuum; however, all estimates for its value are many orders-of-magnitude too large. Other ideas for dark energy include a very light scalar field or a tangled network of topological defects. An alternate explanation invokes gravitational physics beyond general relativity. Observations and experiments underway and more precise cosmological measurements and laboratory experiments planned for the next decade will test whether or not dark energy is the quantum energy of the vacuum or something more exotic, and whether or not general relativity can self consistently explain cosmic acceleration. Dark energy is the most conspicuous example of physics beyond the standard model and perhaps the most profound mystery in all of science.Comment: 10 pages, 8 figures, invited review for Journal of the Physical Society of Japan, in pres
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