4,442 research outputs found

    A Completion Report of The Alaska Cooperative Wildlife Research Unit

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    Field data and observational records emphasized three themes for research: a) behavior of individual animals (by sex and age) and groups of caribou (by size and composition) in the vicinity of man-made obstructions, b) reactions of caribou presented with deflection or choice situations, that is, when in proximity to an alternate method of passage over or under the pipelines, and c) reaction of maternal cows and calves when confronting similar structures. The responses of animals on subsequent encounters with the pipelines were studied for insights on the learning ability of caribou to pass beneath or over obstacles.Submitted to: Alyeska Pipeline Service Company, British Petroleum Alaska Inc., and The U.S. Bureau of Sport Fisheries and WildlifeIntroduction -- Historical and Contemporary Importance of the Prudhoe Bay Area to Arctic Caribou Populations -- Study Facilities -- Research Objectives -- Field Procedures -- Results and Discussions -- Summary -- Recommendations -- References Cited -- Appendix A: I. Test of Independence of Two Properties Using the G-test; II. Testing for the Equality of Two Percentages and Independence of Two Properties -- Appendix B -- Appendix

    Aerodynamic configuration development of the highly maneuverable aircraft technology remotely piloted research vehicle

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    The aerodynamic development of the highly maneuverable aircraft technology remotely piloted research vehicle (HiMAT/RPRV) from the conceptual design to the final configuration is presented. The design integrates several advanced concepts to achieve a high degree of transonic maneuverability, and was keyed to sustained maneuverability goals while other fighter typical performance characteristics were maintained. When tests of the baseline configuration indicated deficiencies in the technology integration and design techniques, the vehicle was reconfigured to satisfy the subcritical and supersonic requirements. Drag-due-to-lift levels only 5 percent higher than the optimum were obtained for the wind tunnel model at a lift coefficient of 1 for Mach numbers of up to 0.8. The transonic drag rise was progressively lowered with the application of nonlinear potential flow analyses coupled with experimental data

    Bifurcation in Rotational Spectra of Nonlinear AB2_2 Molecules

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    A classical microscopic theory of rovibrational motion at high angular momenta in symmetrical non-linear molecules AB2_2 is derived within the framework of small oscillations near the stationary states of a rotating molecule. The full-dimensional analysis including stretching vibrations has confirmed the existence of the bifurcation predicted previously by means of the rigid-bender model. The formation of fourfold energy clusters has already been experimentally verified for H2_2Se and it has been demonstrated in fully-dimensional quantum mechanical calculations using the MORBID computer program. We show in the present work that apart from the level clustering, the bifurcation produces physically important effects including molecular symmetry-breaking and a transition from the normal mode to the local mode limit for the stretching vibrations due to rovibrational interaction. The application of the present theory with realistic molecular potentials to the H2_2Te, H2_2Se and H2_2S hydrides results in predictions of the bifurcation points very close to those calculated previously. However for the lighter H2_2O molecule we find that the bifurcation occurs at higher values of the total angular momentum than obtained in previous estimations. The present work shows it to be very unlikely that the bifurcation in H2_2O will lead to clustering of energy levels. This result is in agreement with recent variational calculations.Comment: latex, 19 pages including 2 figures provided as *.uu fil

    Letter to Philander Chase

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    S.N. Child thanks Philander Chase for his donation of $15.00 and requests five more to pay off debts until he can earn an income form his new school.https://digital.kenyon.edu/chase_letters/2340/thumbnail.jp

    Statistical Mechanics for Unstable States in Gel'fand Triplets and Investigations of Parabolic Potential Barriers

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    Free energies and other thermodynamical quantities are investigated in canonical and grand canonical ensembles of statistical mechanics involving unstable states which are described by the generalized eigenstates with complex energy eigenvalues in the conjugate space of Gel'fand triplet. The theory is applied to the systems containing parabolic potential barriers (PPB's). The entropy and energy productions from PPB systems are studied. An equilibrium for a chemical process described by reactions A+CB⇄AC+BA+CB\rightleftarrows AC+B is also discussed.Comment: 14 pages, AmS-LaTeX, no figur

    Landau-Zener-St\"uckelberg interferometry in pair production from counterpropagating lasers

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    The rate of electron-positron pair production in linearly polarized counter-propagating lasers is evaluated from a recently discovered solution of the time-dependent Dirac equation. The latter is solved in momentum space where it is formally equivalent to the Schr\"odinger equation describing a strongly driven two-level system. The solution is found from a simple transformation of the Dirac equation and is given in compact form in terms of the doubly-confluent Heun's function. By using the analogy with the two-level system, it is shown that for high-intensity lasers, pair production occurs through periodic non-adiabatic transitions when the adiabatic energy gap is minimal. These transitions give rise to an intricate interference pattern in the pair spectrum, reminiscent of the Landau-Zener-St\"uckelberg phenomenon in molecular physics: the accumulated phase result in constructive or destructive interference. The adiabatic-impulse model is used to study this phenomenon and shows an excellent agreement with the exact result.Comment: 22 pages, 7 figure

    Wave Mechanics of a Two Wire Atomic Beamsplitter

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    We consider the problem of an atomic beam propagating quantum mechanically through an atom beam splitter. Casting the problem in an adiabatic representation (in the spirit of the Born-Oppenheimer approximation in molecular physics) sheds light on explicit effects due to non-adiabatic passage of the atoms through the splitter region. We are thus able to probe the fully three dimensional structure of the beam splitter, gathering quantitative information about mode-mixing, splitting ratios,and reflection and transmission probabilities

    State-to-state rotational transitions in H2_2+H2_2 collisions at low temperatures

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    We present quantum mechanical close-coupling calculations of collisions between two hydrogen molecules over a wide range of energies, extending from the ultracold limit to the super-thermal region. The two most recently published potential energy surfaces for the H2_2-H2_2 complex, the so-called DJ (Diep and Johnson, 2000) and BMKP (Boothroyd et al., 2002) surfaces, are quantitatively evaluated and compared through the investigation of rotational transitions in H2_2+H2_2 collisions within rigid rotor approximation. The BMKP surface is expected to be an improvement, approaching chemical accuracy, over all conformations of the potential energy surface compared to previous calculations of H2_2-H2_2 interaction. We found significant differences in rotational excitation/de-excitation cross sections computed on the two surfaces in collisions between two para-H2_2 molecules. The discrepancy persists over a large range of energies from the ultracold regime to thermal energies and occurs for several low-lying initial rotational levels. Good agreement is found with experiment (Mat\'e et al., 2005) for the lowest rotational excitation process, but only with the use of the DJ potential. Rate coefficients computed with the BMKP potential are an order of magnitude smaller.Comment: Accepted by J. Chem. Phy

    The quality of different types of child care at 10 and 18 months. A comparison between types and factors related to quality.

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    The quality of care offered in four different types of non-parental child care to 307 infants at 10 months old and 331 infants at 18 months old was compared and factors associated with higher quality were identified. Observed quality was lowest in nurseries at each age point, except that at 18 months they offered more learning activities. There were few differences in the observed quality of care by child-minders, grandparents and nannies, although grandparents had somewhat lower safety and health scores and offered children fewer activities. Cost was largely unrelated to quality of care except in child-minding, where higher cost was associated with higher quality. Observed ratios of children to adults had a significant impact on quality of nursery care; the more infants or toddlers each adult had to care for, the lower the quality of the care she gave them. Mothers' overall satisfaction with their child's care was positively associated with its quality for home-based care but not for nursery settings
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