2,712 research outputs found

    What to Pay for Feeder Steers

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    What to Pay for Feeder Pigs

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    Risk Allocation

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    Integrating paleoecology and genetics of bird populations in two sky island archipelagos

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    <p>Abstract</p> <p>Background</p> <p>Genetic tests of paleoecological hypotheses have been rare, partly because recent genetic divergence is difficult to detect and time. According to fossil plant data, continuous woodland in the southwestern USA and northern Mexico became fragmented during the last 10,000 years, as warming caused cool-adapted species to retreat to high elevations. Most genetic studies of resulting 'sky islands' have either failed to detect recent divergence or have found discordant evidence for ancient divergence. We test this paleoecological hypothesis for the region with intraspecific mitochondrial DNA and microsatellite data from sky-island populations of a sedentary bird, the Mexican jay (<it>Aphelocoma ultramarina</it>). We predicted that populations on different sky islands would share common, ancestral alleles that existed during the last glaciation, but that populations on each sky island, owing to their isolation, would contain unique variants of postglacial origin. We also predicted that divergence times estimated from corrected genetic distance and a coalescence model would post-date the last glacial maximum.</p> <p>Results</p> <p>Our results provide multiple independent lines of support for postglacial divergence, with the predicted pattern of shared and unique mitochondrial DNA haplotypes appearing in two independent sky-island archipelagos, and most estimates of divergence time based on corrected genetic distance post-dating the last glacial maximum. Likewise, an isolation model based on multilocus gene coalescence indicated postglacial divergence of five pairs of sky islands. In contrast to their similar recent histories, the two archipelagos had dissimilar historical patterns in that sky islands in Arizona showed evidence for older divergence, suggesting different responses to the last glaciation.</p> <p>Conclusion</p> <p>This study is one of the first to provide explicit support from genetic data for a postglacial divergence scenario predicted by one of the best paleoecological records in the world. Our results demonstrate that sky islands act as generators of genetic diversity at both recent and historical timescales and underscore the importance of thorough sampling and the use of loci with fast mutation rates to studies that test hypotheses concerning recent genetic divergence.</p

    VĪ“2+ T cell response to malaria correlates with protection from infection but is attenuated with repeated exposure.

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    VĪ“2+ Ī³Ī“ T cells are semi-innate T cells that expand markedly following P. falciparum (Pf) infection in naĆÆve adults, but are lost and become dysfunctional among children repeatedly exposed to malaria. The role of these cells in mediating clinical immunity (i.e. protection against symptoms) to malaria remains unclear. We measured VĪ“2+ T cell absolute counts at acute and convalescent malaria timepoints (nā€‰=ā€‰43), and VĪ“2+ counts, cellular phenotype, and cytokine production following in vitro stimulation at asymptomatic visits (nā€‰=ā€‰377), among children aged 6 months to 10 years living in Uganda. Increasing age was associated with diminished in vivo expansion following malaria, and lower VĪ“2 absolute counts overall, among children living in a high transmission setting. Microscopic parasitemia and expression of the immunoregulatory markers Tim-3 and CD57 were associated with diminished VĪ“2+ T cell pro-inflammatory cytokine production. Higher VĪ“2 pro-inflammatory cytokine production was associated with protection from subsequent Pf infection, but also with an increased odds of symptoms once infected. VĪ“2+ T cells may play a role in preventing malaria infection in children living in endemic settings; progressive loss and dysfunction of these cells may represent a disease tolerance mechanism that contributes to the development of clinical immunity to malaria

    Developing Performance Indicators to Evaluate the Management Effectiveness of the Massachusetts Ocean Management Plan

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    In June 2009, the Massachusetts Executive Office of Energy and Environmental Affairs (EEA) released its draft Massachusetts Ocean Management Plan (draft plan) for public comment. The plan is required by the Oceans Act of 2008 to, among other things, be adaptive to evolving knowledge and understanding of the ocean environment. The planā€™s Science Framework establishes a blueprint for future research and data acquisition and ensuring that the plan evolves and its management measures adapt to this new and enhanced information. As stated in Chapter 5 of the draft plan, an important part of the science framework is the development and implementation of a performance evaluation system with a series of indicators to help EEA and stakeholders evaluate the implementation of the Massachusetts Ocean Management Plan, identify the environmental and socio-economic impacts of plan management decisions, and identify new or emerging issues. Volume 2 of the draft plan contains a section entitled Development of Evaluation Measures for the Massachusetts Ocean Management Plan. This section outlines a proposed process ā€œto identify measures of success or indicators that can be used to measure performance of management strategies in achieving desired outcomes.ā€ As the development of indicators is a high priority of the draft plan, the Massachusetts Ocean Partnership (MOP) in consultation with EEA contracted with the Urban Harbors Institute (UHI) of the University of Massachusetts Boston (UMass Boston). The project team1 and other professionals from organizations and agencies experienced with the selection and use of indicators conducted the process outlined in Volume 2 of the draft plan to identify and select a set of environmental, socio-economic, and governmental indicators to evaluate the effectiveness of the Massachusetts Ocean Management Plan. The work described in this report also contributes to a broader interest and goal of the Massachusetts Ocean Partnership which is to coordinate indicator initiatives to inform ocean management and to advance the development and use of indicators of the oceanā€™s ability to provide ecosystem services. Currently, there are a number of initiatives, focusing on the coastal and ocean areas of the Northwest Atlantic/Gulf of Maine region, to develop indicators for various purposes and audiences. The process and products of this work in support of the Massachusetts Ocean Management Plan (e.g., the list of indicators and associated data) will be useful in collaborative efforts to integrate and coordinate these regional efforts

    Understanding the peculiarities of the piezoelectric effect in macro-porous BaTiO<sub>3</sub>

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    This work demonstrates the potential of porous BaTiO3 for piezoelectric sensor and energy-harvesting applications by manufacture of materials, detailed characterisation and application of new models. Ferroelectric macro-porous BaTiO3 ceramics for piezoelectric applications are manufactured for a range of relative densities, Ī±ā€‰=ā€‰0.30ā€“0.95, using the burned out polymer spheres method. The piezoelectric activity and relevant parameters for specific applications are interpreted by developing two models: a model of a 3ā€“0 composite and a ā€˜composite in compositeā€™ model. The appropriate ranges of relative density for the application of these models to accurately predict piezoelectric properties are examined. The two models are extended to take into account the effect of 90Ā° domain-wall mobility within ceramic grains on the piezoelectric coefficients d3jāˆ— d_{3j}^{\ast} . It is shown that porous ferroelectrics provide a novel route to form materials with large piezoelectric anisotropy (d33āˆ—/d33āˆ—āˆ£d31āˆ—āˆ£āˆ£d31āˆ—āˆ£>>1) \left( {{{d_{33}^{\ast} } \mathord{\left/ {\vphantom {{d_{33}^{\ast} } {\left| {d_{31}^{\ast} } \right|}}} \right. \kern-0pt} {\left| {d_{31}^{\ast} } \right|}} > > 1} \right) at 0.20 ā‰¤ Ī± ā‰¤ 0.45 and achieve a high squared figure of merit d33āˆ— d_{33}^{\ast} g33āˆ— g_{33}^{\ast} . The modelling approach allows a detailed analysis of the relationships between the properties of the monolithic and porous materials for the design of porous structures with optimum properties

    Polynomial diffeomorphisms of C^2, IV: The measure of maximal entropy and laminar currents

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    This paper concerns the dynamics of polynomial automorphisms of C2{\bf C}^2. One can associate to such an automorphism two currents Ī¼Ā±\mu^\pm and the equilibrium measure Ī¼=Ī¼+āˆ§Ī¼āˆ’\mu=\mu^+\wedge\mu^-. In this paper we study some geometric and dynamical properties of these objects. First, we characterize Ī¼\mu as the unique measure of maximal entropy. Then we show that the measure Ī¼\mu has a local product structure and that the currents Ī¼Ā±\mu^\pm have a laminar structure. This allows us to deduce information about periodic points and heteroclinic intersections. For example, we prove that the support of Ī¼\mu coincides with the closure of the set of saddle points. The methods used combine the pluripotential theory with the theory of non-uniformly hyperbolic dynamical systems
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