5,238 research outputs found

    Mollusca of the Illinois River, Arkansas

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    The Illinois River is in the Ozark region of northwestern Arkansas and eastern Oklahoma. A survey of the Illinois River in Arkansas produced nine species and one morphological subspecies of gastropods, three species of sphaeriid clams, and 23 species of unionid mussels. Museum records resulted in another two species and an ecophenotype of the Unionidae. This represents the first published survey of molluscan species from the Illinois River in Arkansas

    Research Notes : United States : Evaluation of soybean germplasm for stress tolerance biological efficiency : To evaluate soybean germplasm and cultivars for stress tolerance toward : Pests

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    Soybean maturity groups V, VI, VII, and VIII have been screened systematically and accessions possessing potential source of natural resistance to Mexican Bean Beetle (MBB) have been identified along with several highly suscep-tible accessions for future studies. About 75% of the germplasm of maturity groups III and IV has been screened initially in 1985. A detailed copy of the screened germplasm can be obtained from scientists at Virginia State Univesit

    Application of superconducting coils to the NASA prototype magnetic balance

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    Application of superconducting coils to a general purpose magnetic balance was studied. The most suitable currently available superconducting cable for coils appears to be a bundle of many fine wires which are transposed and are mechanically confined. Sample coils were tested at central fields up to .5 Tesla, slewing rates up to 53 Tesla/ sec and frequencies up to 30 Hz. The ac losses were measured from helium boil-off and were approximately 20% higher than those calculated. Losses were dominated by hysteresis and a model for loss calculation which appears suitable for design purposes is presented along with computer listings. Combinations of two coils were also tested and interaction losses are reported. Two feasible geometries are also presented for prototype magnetic balance using superconductors

    Direct Measurement of the X-ray Time-Delay Transfer Function in Active Galactic Nuclei

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    The origin of the observed time lags, in nearby active galactic nuclei (AGN), between hard and soft X-ray photons is investigated using new XMM-Newton data for the narrow-line Seyfert I galaxy Ark 564 and existing data for 1H0707-495 and NGC 4051. These AGN have highly variable X-ray light curves that contain frequent, high peaks of emission. The averaged light curve of the peaks is directly measured from the time series, and it is shown that (i) peaks occur at the same time, within the measurement uncertainties, at all X-ray energies, and (ii) there exists a substantial tail of excess emission at hard X-ray energies, which is delayed with respect to the time of the main peak, and is particularly prominent in Ark 564. Observation (i) rules out that the observed lags are caused by Comptonization time delays and disfavors a simple model of propagating fluctuations on the accretion disk. Observation (ii) is consistent with time lags caused by Compton-scattering reverberation from material a few thousand light-seconds from the primary X-ray source. The power spectral density and the frequency-dependent phase lags of the peak light curves are consistent with those of the full time series. There is evidence for non-stationarity in the Ark 564 time series in both the Fourier and peaks analyses. A sharp `negative' lag (variations at hard photon energies lead soft photon energies) observed in Ark 564 appears to be generated by the shape of the hard-band transfer function and does not arise from soft-band reflection of X-rays. These results reinforce the evidence for the existence of X-ray reverberation in type I AGN, which requires that these AGN are significantly affected by scattering from circumnuclear material a few tens or hundreds of gravitational radii in extent.Comment: Accepted for publication in Ap

    Investigation of beauty production and parton shower effects at LHC

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    We present hadron-level predictions from the Monte Carlo generator Cascade and parton level calculations of open b quark, b-flavored hadron and inclusive b-jet production in the framework of the kt-factorization QCD approach for the LHC energies. The unintegrated gluon densities in a proton are determined using the CCFM evolution equation and the Kimber-Martin-Ryskin (KMR) prescription. Our predictions are compared with the first data taken by the CMS and LHCb collaborations at 7 TeV. We study the theoretical uncertainties of our calculations and investigate the effects coming from parton showers in initial and final states. The special role of initial gluon transverse momenta in description of the data is pointed out.Comment: 19 pages, 11 figures. arXiv admin note: substantial text overlap with arXiv:1105.507

    `St\"uckelberg interferometry' with ultracold molecules

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    We report on the realization of a time-domain `St\"uckelberg interferometer', which is based on the internal state structure of ultracold Feshbach molecules. Two subsequent passages through a weak avoided crossing between two different orbital angular momentum states in combination with a variable hold time lead to high-contrast population oscillations. This allows for a precise determination of the energy difference between the two molecular states. We demonstrate a high degree of control over the interferometer dynamics. The interferometric scheme provides new possibilities for precision measurements with ultracold molecules.Comment: 4 pages, 5 figure
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