28,771 research outputs found

    Rotorcraft convertible engine study

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    The objective of the Rotorcraft Convertible Engine Study was to define future research and technology effort required for commercial development by 1988 of convertible fan/shaft gas turbine engines for unconventional rotorcraft transports. Two rotorcraft and their respective missions were defined: a Fold Tilt Rotor aircraft and an Advancing Blade Concept (ABC) rotorcraft. Sensitivity studies were conducted with these rotorcraft to determine parametrically the influence of propulsion characteristics on aircraft size, mission fuel requirements, and direct operating costs (DOC). The two rotorcraft were flown with conventional propulsion systems (separate lift/cruise engines) and with convertible propulsion systems to determine the benefits to be derived from convertible engines. Trade-off studies were conducted to determine the optimum engine cycle and staging arrangement for a convertible engine. Advanced technology options applicable to convertible engines were studied. Research and technology programs were identified which would ensure technology readiness for commercial development of convertible engines by 1988

    Is the transition redshift a new cosmological number?

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    Observations from Supernovae Type Ia (SNe Ia) provided strong evidence for an expanding accelerating Universe at intermediate redshifts. This means that the Universe underwent a transition from deceleration to acceleration phases at a transition redshift ztz_t of the order unity whose value in principle depends on the cosmology as well as on the assumed gravitational theory. Since cosmological accelerating models endowed with a transition redshift are extremely degenerated, in principle, it is interesting to know whether the value of ztz_t itself can be observationally used as a new cosmic discriminator. After a brief discussion of the potential dynamic role played by the transition redshift, it is argued that future observations combining SNe Ia, the line-of-sight (or "radial") baryon acoustic oscillations, the differential age of galaxies, as well as the redshift drift of the spectral lines may tightly constrain ztz_t, thereby helping to narrow the parameter space for the most realistic models describing the accelerating Universe.Comment: 12 pages, 5 figures. Some discussions about how to estimate the transition redshift have been added. New data by Planck and H(z) data have been mentioned. New references have been adde

    Estimation of Parameters in DNA Mixture Analysis

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    In Cowell et al. (2007), a Bayesian network for analysis of mixed traces of DNA was presented using gamma distributions for modelling peak sizes in the electropherogram. It was demonstrated that the analysis was sensitive to the choice of a variance factor and hence this should be adapted to any new trace analysed. In the present paper we discuss how the variance parameter can be estimated by maximum likelihood to achieve this. The unknown proportions of DNA from each contributor can similarly be estimated by maximum likelihood jointly with the variance parameter. Furthermore we discuss how to incorporate prior knowledge about the parameters in a Bayesian analysis. The proposed estimation methods are illustrated through a few examples of applications for calculating evidential value in casework and for mixture deconvolution

    Postcard: I\u27m on the Hike to the Barbecue at Carlton, Kansas

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    This black and white printed postcard features an illustration of a man walking along railroad tracks towards a town. Text is printed on the top right of the card. Handwriting is on the bottom and back of the card.https://scholars.fhsu.edu/tj_postcards/1543/thumbnail.jp

    Ground state of two electrons on concentric spheres

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    We extend our analysis of two electrons on a sphere [Phys. Rev. A {\bf 79}, 062517 (2009); Phys. Rev. Lett. {\bf 103}, 123008 (2009)] to electrons on concentric spheres with different radii. The strengths and weaknesses of several electronic structure models are analyzed, ranging from the mean-field approximation (restricted and unrestricted Hartree-Fock solutions) to configuration interaction expansion, leading to near-exact wave functions and energies. The M{\o}ller-Plesset energy corrections (up to third-order) and the asymptotic expansion for the large-spheres regime are also considered. We also study the position intracules derived from approximate and exact wave functions. We find evidence for the existence of a long-range Coulomb hole in the large-spheres regime, and infer that unrestricted Hartree-Fock theory over-localizes the electrons.Comment: 10 pages, 10 figure

    Connecting species’ geographical distributions to environmental variables: range maps versus observed points of occurrence

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    Connecting the geographical occurrence of a species with underlying environmental variables is fundamental for many analyses of life history evolution and for modeling species distributions for both basic and practical ends. However, raw distributional information comes principally in two forms: points of occurrence (specific geographical coordinates where a species has been observed), and expert-prepared range maps. Each form has potential short-comings: range maps tend to overestimate the true occurrence of a species, whereas occurrence points (because of their frequent non-random spatial distribution) tend to underestimate it. Whereas previous comparisons of the two forms have focused on how they may differ when estimating species richness, less attention has been paid to the extent to which the two forms actually differ in their representation of a species’ environmental associations. We assess such differences using the globally distributed avian order Galliformes (294 species). For each species we overlaid range maps obtained from IUCN and point-of-occurrence data obtained from GBIF on global maps of four climate variables and elevation. Over all species, the median difference in distribution centroids was 234 km, and median values of all five environmental variables were highly correlated, although there were a few species outliers for each variable. We also acquired species’ elevational distribution mid-points (mid-point between minimum and maximum elevational extent) from the literature; median elevations from point occurrences and ranges were consistently lower (median −420 m) than mid-points. We concluded that in most cases occurrence points were likely to produce better estimates of underlying environmental variables than range maps, although differences were often slight. We also concluded that elevational range mid-points were biased high, and that elevation distributions based on either points or range maps provided better estimates

    Effects of diabetes family history and exercise training on the expression of adiponectin and leptin and their receptors

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    The daughters of patients with diabetes have reduced insulin sensitivity index (ISI) scores compared with women with no family history of diabetes, but their ISI increase more in response to exercise training(1). The present study aimed to determine whether differences between these groups in exercise-induced changes in circulating adiponectin and leptin concentrations and expression of their genes and receptors in subcutaneous adipose tissue (SAT), could explain differences in the exercise-induced changes in ISI between women with and without a family history of diabetes

    Cell Junction Remodeling in Gingival Tissue Exposed to a Microbial Toxin

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    The gingival epithelium plays a key role in protecting the supporting structures of the teeth from bacteria and their products. In ex vivo experiments, we recently showed that the cytolethal distending toxin (Cdt) from the periodontal pathogen Aggregatibacter actinomycetemcomitans causes extensive damage to gingival tissue. Morphological changes included detachment of the keratinized outer layer, distention of spinous and basal cells in the oral epithelium, disruption of rete pegs, and apparent dissolution of cell junctions. Adherens junctions (zonula adherens) are essential for maintaining barrier function and integrity of gingival epithelium. Therefore, immunohistochemical and RT-PCR analyses of human gingival explants (HGX) and human gingival epithelial cells (HGEC) were utilized for a closer examination of the effects of the Cdt on E-cadherin, the key membrane component of adherens junctions. Although there was some variability among tissue donors, exposure of gingival tissue or isolated epithelial cells to the toxin generally resulted in a pronounced increase in the expression and cytosolic distribution of E-cadherin, accompanied by an increase in levels of the intracellular scaffolding proteins β-catenin and β-actin. These results indicate that the Cdt induced substantial remodeling of adherens junctions, with a potential impact on the barrier function of gingival epithelium. Abbreviations: cytolethal distending toxin (Cdt), 4′,6-diamidino-2-phenylindole (DAPI), human gingival epithelial cells (HGEC), human gingival explants (HGX), human gingival fibroblasts (HGF), transepithelial resistance (TER)

    Optimal full estimation of qubit mixed states

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    We obtain the optimal scheme for estimating unknown qubit mixed states when an arbitrary number N of identically prepared copies is available. We discuss the case of states in the whole Bloch sphere as well as the restricted situation where these states are known to lie on the equatorial plane. For the former case we obtain that the optimal measurement does not depend on the prior probability distribution provided it is isotropic. Although the equatorial-plane case does not have this property for arbitrary N, we give a prior-independent scheme which becomes optimal in the asymptotic limit of large N. We compute the maximum mean fidelity in this asymptotic regime for the two cases. We show that within the pointwise estimation approach these limits can be obtained in a rather easy and rapid way. This derivation is based on heuristic arguments that are made rigorous by using van Trees inequalities. The interrelation between the estimation of the purity and the direction of the state is also discussed. In the general case we show that they correspond to independent estimations whereas for the equatorial-plane states this is only true asymptotically.Comment: 19 pages, no figure
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