3,252 research outputs found

    Shorebirds Breed in Unusually High Densities in the Teshekpuk Lake Special Area, Alaska

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    On the Arctic Coastal Plain of the National Petroleum Reserve-Alaska (NPR-A), the Teshekpuk Lake Special Area (TLSA) was recognized to protect outstanding wildlife values. Although information has accumulated on the TLSA’s value to caribou and waterfowl, its importance to breeding shorebirds remains largely unquantified. Therefore, we undertook a broad-scale ground study to estimate the population size and density of shorebirds breeding in the TLSA. From a series of plot surveys conducted from 2006 to 2008, we estimated a detection-adjusted total breeding population of more than 573 000 shorebirds and an overall density of 126 shorebirds/km2. Most shorebird species had their greatest densities on the Outer Coastal Plain or had approximately equal densities on Outer and Inner Coastal Plains; only two species had their greatest densities on the Inner Coastal Plain. The greatest densities of breeding shorebirds occurred immediately around Teshekpuk Lake. The TLSA supported more than 10% of the biogeographic populations of black-bellied plover (Pluvialis squatarola), semipalmated sandpiper (Calidris pusilla), and dunlin (C. alpina). Breeding shorebird density in the TLSA is one of the highest in the NPR-A, on Alaska’s North Slope, and throughout the circumpolar Arctic. Our results, coupled with previous information on waterfowl and caribou, indicate that the area around Teshekpuk Lake and the recognized goose molting area northeast of the lake should be protected from oil and gas development.Sur la plaine côtière arctique de la réserve pétrolière nationale-Alaska (NPRA), la région spéciale du lac Teshekpuk (TLSA) a été créée dans le but de protéger les valeurs exceptionnelles de la faune. Même s’il existe beaucoup d’information sur la valeur du caribou et de la sauvagine de la TLSA, l’importance qu’elle revêt en matière d’oiseaux de rivage nicheurs demeure peu quantifiée. Nous avons par conséquent entrepris de faire une étude sur le terrain à grande échelle pour estimer la taille et la densité de la population d’oiseaux de rivage nichant dans la TLSA. À partir d’une série d’enquêtes réalisées de 2006 à 2008, nous avons estimé que le total redressé en fonction de la détection de la population nicheuse s’établissait à plus de 573 000 oiseaux de rivage, et que la densité générale s’élevait à 126 oiseaux de rivage/km2. Les plus grandes densités de la plupart des espèces d’oiseaux de rivage se trouvaient sur la plaine côtière extérieure ou encore, les densités étaient environ égales entre les plaines côtières intérieure et extérieure. Seulement deux espèces avaient leurs plus fortes densités sur la plaine côtière intérieure. Les plus grandes densités d’oiseaux de rivage se manifestaient immédiatement autour du lac Teshekpuk. La TLSA accueillait plus de 10 % des populations biogéographiques de pluviers argentés (Pluvialis squatarola), de bécasseaux semipalmés (Calidris pusilla) et de bécasseaux variables (C. alpina). La densité d’oiseaux nicheurs dans la TLSA est l’une des plus élevées de la NPR-A, sur le versant nord de l’Alaska et à l’échelle de l’Arctique circumpolaire. Nos résultats, jumelés à l’information obtenue antérieurement au sujet de la sauvagine et du caribou, indiquent que la région autour du lac Teshekpuk et la région reconnue pour la mue des oies au nord-est du lac devraient être protégées contre la mise en valeur pétrolière et gazière

    The Role of Gas in the Merging of Massive Black Holes in Galactic Nuclei. I. Black Hole Merging in a Spherical Gas Cloud

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    Using high-resolution SPH numerical simulations, we investigate the effects of gas on the inspiral and merger of a massive black hole binary. This study is motivated by both observational and theoretical work that indicate the presence of large amounts of gas in the central regions of merging galaxies. N-body simulations have shown that the coalescence of a massive black hole binary eventually stalls in a stellar background. However, our simulations suggest that the massive black hole binary will finally merge if it is embedded in a gaseous background. Here we present results in which the gas is assumed to be initially spherical with a relatively smooth distribution. In the early evolution of the binary, the separation dimishes due to the gravitational drag exerted by the background gas. In the later stages, when the binary dominates the gravitational potential in its vicinity, the medium responds by forming an ellipsoidal density enhancement whose axis lags behind the binary axis, and this offset produces a torque on the binary that causes continuing loss of angular momentum and is able to reduce the binary separation to distances where gravitational radiation is efficient. Assuming typical parameters from observations of Ultra Luminous Infrared Galaxies, we predict that a black hole binary will merge within 10710^{7}yrs; therefore these results imply that in a merger of gas-rich galaxies, any massive central black holes will coalescence soon after the galaxies merge. Our work thus supports scenarios of massive black hole evolution and growth where hierarchical merging plays an important role. The final coalescence of the black holes leads to gravitational radiation emission that would be detectable up to high redshift by LISA. We show that similar physical effects are important for the formation of close binary stars.Comment: 38 pages, 14 figures, submitted to Ap

    Distribution of Breeding Shorebirds on the Arctic Coastal Plain of Alaska

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    Available information on the distribution of breeding shorebirds across the Arctic Coastal Plain of Alaska is dated, fragmented, and limited in scope. Herein, we describe the distribution of 19 shorebird species from data gathered at 407 study plots between 1998 and 2004. This information was collected using a single-visit rapid area search technique during territory establishment and early incubation periods, a time when social displays and vocalizations make the birds highly detectable. We describe the presence or absence of each species, as well as overall numbers of species, providing a regional perspective on shorebird distribution. We compare and contrast our shorebird distribution maps to those of prior studies and describe prominent patterns of shorebird distribution. Our examination of how shorebird distribution and numbers of species varied both latitudinally and longitudinally across the Arctic Coastal Plain of Alaska indicated that most shorebird species occur more frequently in the Beaufort Coastal Plain ecoregion (i.e., closer to the coast) than in the Brooks Foothills ecoregion (i.e., farther inland). Furthermore, the occurrence of several species indicated substantial longitudinal directionality. Species richness at surveyed sites was highest in the western portion of the Beaufort Coastal Plain ecoregion. The broad-scale distribution information we present here is valuable for evaluating potential effects of human development and climate change on Arctic-breeding shorebird populations.Les renseignements qui existent en matière de répartition des oiseaux de rivage en reproduction sur la plaine côtière de l’Arctique en Alaska sont anciens, fragmentés et restreints. Ici, nous décrivons la répartition de 19 espèces d’oiseaux de rivage à partir de données recueillies à 407 lieux de recherche entre 1998 et 2004. Cette information a été recueillie grâce à une technique de recherche consistant en une seule visite rapide durant les périodes d’établissement du territoire et de début d’incubation, périodes pendant lesquelles les comportements sociaux et les vocalisations permettent de bien repérer les oiseaux. Nous décrivons la présence ou l’absence de chaque espèce, de même que le nombre général d’espèces, ce qui procure une perspective régionale de la répartition des oiseaux de rivage. Nous comparons et contrastons nos cartes de répartition des oiseaux de rivage à celles d’études antérieures, en plus de décrire les tendances les plus marquées en matière de répartition des oiseaux de rivage. Notre examen de la variation latitudinale et longitudinale en matière de répartition et de nombre d’espèces d’oiseaux de rivage à l’échelle de la plaine côtière arctique de l’Alaska nous a permis de constater que la plupart des espèces d’oiseaux de rivage se manifestaient plus souvent dans la région écologique de la plaine côtière de Beaufort (c’est-à-dire plus proche de la côte) que dans la région écologique des contreforts de Brooks (c’est-à-dire plus à l’intérieur des terres). Par ailleurs, l’occurrence de plusieurs espèces indiquait une directionalité longitudinale substantielle. La richesse des espèces aux sites à l’étude était à son meilleur dans la partie ouest de la région écologique de la plaine côtière de Beaufort. Les renseignements sur la répartition à grande échelle que nous présentons ici jouent un rôle dans l’évaluation des effets éventuels des travaux de mise en valeur par l’être humain et du changement climatique sur les populations d’oiseaux de rivage en reproduction de l’Arctique

    From Capillary Condensation to Interface Localization Transitions in Colloid Polymer Mixtures Confined in Thin Film Geometry

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    Monte Carlo simulations of the Asakura-Oosawa (AO) model for colloid-polymer mixtures confined between two parallel repulsive structureless walls are presented and analyzed in the light of current theories on capillary condensation and interface localization transitions. Choosing a polymer to colloid size ratio of q=0.8 and studying ultrathin films in the range of D=3 to D=10 colloid diameters thickness, grand canonical Monte Carlo methods are used; phase transitions are analyzed via finite size scaling, as in previous work on bulk systems and under confinement between identical types of walls. Unlike the latter work, inequivalent walls are used here: while the left wall has a hard-core repulsion for both polymers and colloids, at the right wall an additional square-well repulsion of variable strength acting only on the colloids is present. We study how the phase separation into colloid-rich and colloid-poor phases occurring already in the bulk is modified by such a confinement. When the asymmetry of the wall-colloid interaction increases, the character of the transition smoothly changes from capillary condensation-type to interface localization-type. The critical behavior of these transitions is discussed, as well as the colloid and polymer density profiles across the film in the various phases, and the correlation of interfacial fluctuations in the direction parallel to the confining walls. The experimental observability of these phenomena also is briefly discussed.Comment: 36 pages, 15 figure

    Examples of risk tools for pests in Peanut (Arachis hypogaea) developed for five countries using Microsoft Excel

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    Suppressing pest populations below economically-damaging levels is an important element of sustainable peanut (Arachis hypogaea L.) production. Peanut farmers and their advisors often approach pest management with similar goals regardless of where they are located. Anticipating pest outbreaks using field history and monitoring pest populations are fundamental to protecting yield and financial investment. Microsoft Excel was used to develop individual risk indices for pests, a composite assessment of risk, and costs of risk mitigation practices for peanut in Argentina, Ghana, India, Malawi, and North Carolina (NC) in the United States (US). Depending on pests and resources available to manage pests, risk tools vary considerably, especially in the context of other crops that are grown in sequence with peanut, cultivars, and chemical inputs. In Argentina, India, and the US where more tools (e.g., mechanization and pesticides) are available, risk indices for a wide array of economically important pests were developed with the assumption that reducing risk to those pests likely will impact peanut yield in a positive manner. In Ghana and Malawi where fewer management tools are available, risks to yield and aflatoxin contamination are presented without risk indices for individual pests. The Microsoft Excel platform can be updated as new and additional information on effectiveness of management practices becomes apparent. Tools can be developed using this platform that are appropriate for their geography, environment, cropping systems, and pest complexes and management inputs that are available. In this article we present examples for the risk tool for each country.Fil: Jordan, David L.. University of Georgia; Estados Unidos. North Carolina State University; Estados UnidosFil: Buol, Greg S.. North Carolina State University; Estados UnidosFil: Brandenburg, Rick L.. North Carolina State University; Estados UnidosFil: Reisig, Dominic. North Carolina State University; Estados UnidosFil: Nboyine, Jerry. Council for Scientific and Industrial Research Savanna Agricultural Research Institute; GhanaFil: Abudulai, Mumuni. Council for Scientific and Industrial Research Savanna Agricultural Research Institute; GhanaFil: Oteng Frimpong, Richard. Council for Scientific and Industrial Research Savanna Agricultural Research Institute; GhanaFil: Mochiah, Moses Brandford. Council for Scientific and Industrial Research Crops Research Institute; GhanaFil: Asibuo, James Y.. Council for Scientific and Industrial Research Crops Research Institute; GhanaFil: Arthur, Stephen. Council for Scientific and Industrial Research Crops Research Institute; GhanaFil: Akromah, Richard. Kwame Nkrumah University Of Science And Technology; GhanaFil: Mhango, Wezi. Lilongwe University Of Agriculture And Natural Resources; MalauiFil: Chintu, Justus. Chitedze Agricultural Research Service, Lilongwe; MalauiFil: Morichetti, Sergio. Aceitera General Deheza; ArgentinaFil: Paredes, Juan Andres. Instituto Nacional de TecnologĂ­a Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de PatologĂ­a Vegetal; Argentina. Instituto Nacional de TecnologĂ­a Agropecuaria. Centro de Investigaciones Agropecuarias. Unidad de FitopatologĂ­a y ModelizaciĂłn AgrĂ­cola - Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - CĂłrdoba. Unidad de FitopatologĂ­a y ModelizaciĂłn AgrĂ­cola; ArgentinaFil: Monguillot, JoaquĂ­n Humberto. Instituto Nacional de TecnologĂ­a Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de PatologĂ­a Vegetal; Argentina. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas; ArgentinaFil: Singh Jadon, Kuldeep. Central Arid Zone Research Institute, Jodhpur; IndiaFil: Shew, Barbara B.. North Carolina State University; Estados UnidosFil: Jasrotia, Poonam. Indian Institute Of Wheat And Barley Research, Karnal; IndiaFil: Thirumalaisamy, P. P.. India Council of Agricultural Research, National Bureau of Plant Genetic Resources; IndiaFil: Harish, G.. Directorate Of Groundnut Research, Junagadh; IndiaFil: Holajjer, Prasanna. National Bureau Of Plant Genetic Resources, New Delhi; IndiaFil: Maheshala, Nataraja. Directorate Of Groundnut Research, Junagadh; IndiaFil: MacDonald, Greg. University of Florida; Estados UnidosFil: Hoisington, David. University of Georgia; Estados UnidosFil: Rhoads, James. University of Georgia; Estados Unido

    Effect of educational outreach on general practice prescribing of antibiotics and antidepressants: a two-year randomised controlled trial

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    Objective. Prescribing of broad spectrum antibiotics and antidepressants in general practice often does not accord with guidelines. The aim was to determine the effectiveness of educational outreach in improving the prescribing of selected antibiotics and antidepressants, and whether the effect is sustained for two years. Design. Single blind randomized trial. Setting. Twenty-eight general practices in Leicestershire, England. Intervention. Educational outreach visits were undertaken, tailored to barriers to change, 14 practices receiving visits for reducing selected antibiotics and 14 for improving antidepressant prescribing. Main outcome measures. Number of items prescribed per 1000 registered patients for amoxicillin with clavulanic acid (co-amoxiclav) and quinolone antibiotics, and average daily quantities per 1000 patients for lofepramine and fluoxetine antidepressants, measured at the practice level for six-month periods over two years. Results. There was no effect on the prescribing of co-amoxiclav, quinolones, or fluoxetine, but prescribing of lofepramine increased in accordance with the guidelines. The increase persisted throughout two years of follow-up. Conclusion. A simple, group-level educational outreach intervention, designed to take account of identified barriers to change, can have a modest but sustained effect on prescribing levels. However, outreach is not always effective. The context in which change in prescribing practice is being sought, the views of prescribers concerning the value of the drug, or other unrecognised barriers to change may influence the effectiveness of outreach
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