3,875 research outputs found

    Seasonal Movements, Migratory Behavior, and Site Fidelity of West Indian Manatees along the Atlantic Coast of the United States as Determined by Radio-telemetry

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    The study area encompassed the eastern coasts of Florida, Georgia, and South Carolina, including inland waterways such as the St. Johns River (Fig. 1). Manatees inhabited the relatively narrow band of water that lies between the barrier beaches and the mainland, occasionally venturing into the ocean close to shore. Between Miami and Fernandina Beach, Florida, 19 inlets provided manatees with corridors between the intracoastal waters and the Atlantic Ocean; the distance between adjacent inlets averaged 32 km(SD = 24 km) and varied from 3 to 88 km. Habitats used by manatees along this 900-km stretch ofcoastline varied widely and included estuaries, lagoons, rivers and creeks, shallow bays and sounds, and ocean inlets. Salinities in most areas were brackish, but ranged from completely fresh to completely marine. The predominant communities of aquatic vegetation also varied geographically and with salinity: seagrass meadows and mangrove swamps in brackish and marine waters along the southern half of peninsular Florida; salt marshes in northeastern Florida and Georgia; benthic macroalgae in estuarine and marine habitats; and a variety of submerged, floating, and emergent vegetation in freshwater rivers, canals, and streams throughout the region. Radio-telemetry has been used successfully to track manatees in other regions ofFlorida (Bengtson 1981, Powell and Rathbun 1984, Lefebvre and Frohlich 1986, Rathbun et al. 1990) and Georgia (Zoodsma 1991), but these early studies relied primarily on conventional VHF (very high frequency) transmitters and were limited in their spatial and temporal scope (see O'Shea and Kochman 1990 for overview). Typically, manatees were tagged at a thermal refuge in the winter and then tracked until the tag detached, usually sometime between the spring and fall of the same year. Our study differs from previous research on manatee movements in several important respects. First, we relied heavily on data from satellite-monitored transmitters using the Argos system, which yielded a substantially greater number of locations and more systematic collection of data compared to previous VHF tracking studies (Deutsch et al. 1998). Second, our tagging and tracking efforts encompassed the entire range of manatees along the Atlantic coast, from the Florida Keys to South Carolina, so inferences were not limited to a small geographic area. Third, we often used freshwater to lure manatees to capture sites, which allowed tagging in all months of the year; this provided more information about summer movement patterns than had previous studies which emphasized capture and tracking at winter aggregations. Finally, the study spanned a decade, and success in retagging animals and in replacing transmitters allowed long-term tracking ofmany individuals. This provided the opportunity to investigate variation in seasonal movements, migratory behavior, and site fidelity across years for individual manatees. (254 page document.

    Resonance Zones and Lobe Volumes for Volume-Preserving Maps

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    We study exact, volume-preserving diffeomorphisms that have heteroclinic connections between a pair of normally hyperbolic invariant manifolds. We develop a general theory of lobes, showing that the lobe volume is given by an integral of a generating form over the primary intersection, a subset of the heteroclinic orbits. Our definition reproduces the classical action formula in the planar, twist map case. For perturbations from a heteroclinic connection, the lobe volume is shown to reduce, to lowest order, to a suitable integral of a Melnikov function.Comment: ams laTeX, 8 figure

    MMP-13 Selective α-sulfone Hydroxamates: a Survey of P1\u27 Heterocyclic Amide Isosteres

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    Seeking compounds preferentially potent and selective for MMP-13, we reported in the preceding Letter on a series of hydroxamic acids with a flexible benzamide tail groups.(1a) Here, we replace the amide moiety with non-hydrolyzable heterocycles in an effort to improve half-life. We identify a hydroxamate tetrazole 4e that spares MMP-1 and -14, shows \u3e400-fold selectivity versus MMP-8 and \u3e600-fold selectivity versus MMP-2, and has a 4.8 h half-life in rats. X-ray data (1.9 Å) for tetrazole 4c is presented

    Heteroclinic intersections between Invariant Circles of Volume-Preserving Maps

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    We develop a Melnikov method for volume-preserving maps with codimension one invariant manifolds. The Melnikov function is shown to be related to the flux of the perturbation through the unperturbed invariant surface. As an example, we compute the Melnikov function for a perturbation of a three-dimensional map that has a heteroclinic connection between a pair of invariant circles. The intersection curves of the manifolds are shown to undergo bifurcations in homologyComment: LaTex with 10 eps figure

    The Influence of the effect of solute on the thermodynamic driving force on grain refinement of Al alloys

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    Grain refinement is known to be strongly affected by the solute in cast alloys. Addition of some solute can reduce grain size considerably while others have a limited effect. This is usually attributed to the constitutional supercooling which is quantified by the growth restriction factor, Q. However, one factor that has not been considered is whether different solutes have differing effects on the thermodynamic driving force for solidification. This paper reveals that addition of solute reduces the driving force for solidification for a given undercooling, and that for a particular Q value, it is reduced more substantially when adding eutectic-forming solutes than peritectic-forming elements. Therefore, compared with the eutectic-forming solutes, addition of peritectic-forming solutes into Al alloys not only possesses a higher initial nucleation rate resulted from the larger thermodynamic driving force for solidification, but also promotes nucleation within the constitutionally supercooled zone during growth. As subsequent nucleation can occur at smaller constitutional supercoolings for peritectic-forming elements, a smaller grain size is thus produced. The very small constitutional supercooling required to trigger subsequent nucleation in alloys containing Ti is considered as a major contributor to its extraordinary grain refining efficiency in cast Al alloys even without the deliberate addition of inoculants.The Australian Research Council (ARC DP10955737)

    Politiewerking in multiculturele buurten: de beeldvorming bij burgers en agenten over de gemeenschapsgerichte politiezorg

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    In deze bijdrage wordt een antwoord geformuleerd op de vraag hoe politiemensen omgaan met etnisch-culturele minderheden op basis van data verzameld in het kader van een 34 maand durend beleidsgericht onderzoek naar de toepassing van de gemeenschapsgerichte politiezorg in multiculturele buurten (in opdracht van Federaal Wetenschapsbeleid). Daarbij werden in vijf Belgische politiezones observaties uitgevoerd bij wijk- en interventieagenten die in multiculturele buurten werkzaam zijn. Het onderzoek beoogt inzicht te verwerven in de manier waarop interacties tussen politie en etnisch-culturele minderheden verlopen en de elementen die deze interacties beïnvloeden. Percepties, betekenisverlening en verwachtingen werden in kaart gebracht. Concreet zal de bijdrage ingaan op de beeldvorming over etnische culturele minderheden bij wijk- en interventieagenten met aandacht voor de inhoud ervan, de totstandkoming en de factoren die erop van invloed zijn. Vervolgens wordt de vraag beantwoord in welke mate en op welke manier beelden en attitudes ook het gedrag van de politiemensen op het terrein beïnvloeden met aandacht voor de situationele, contextuele, persoonlijke en organisatorische factoren die daarop van invloed zijn

    Restoration of spermatogenesis and male fertility using an androgen receptor transgene

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    Androgens signal through the androgen receptor (AR) to regulate male secondary sexual characteristics, reproductive tract development, prostate function, sperm production, bone and muscle mass as well as body hair growth among other functions. We developed a transgenic mouse model in which endogenous AR expression was replaced by a functionally modified AR transgene. A bacterial artificial chromosome (BAC) was constructed containing all AR exons and introns plus 40 kb each of 5' and 3' regulatory sequence. Insertion of an internal ribosome entry site and the EGFP gene 3' to AR allowed co-expression of AR and EGFP. Pronuclear injection of the BAC resulted in six founder mice that displayed EGFP production in appropriate AR expressing tissues. The six founder mice were mated into a Sertoli cell specific AR knockout (SCARKO) background in which spermatogenesis is blocked at the meiosis stage of germ cell development. The AR-EGFP transgene was expressed in a cyclical manner similar to that of endogenous AR in Sertoli cells and fertility was restored as offspring were produced in the absence of Sertoli cell AR. Thus, the AREGFP transgene under the control of AR regulatory elements is capable of rescuing AR function in a cell selective, AR-null background. These initial studies provide proof of principle that a strategy employing the AR-EGFP transgene can be used to understand AR functions. Transgenic mice expressing selective modifications of the AR-EGFP transgene may provide crucial information needed to elicit the molecular mechanisms by which AR acts in the testis and other androgen responsive tissues

    'A light in a very dark place' : The role of a voluntary organisation providing support for those affected by encephalitis

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    Voluntary organisations are seen as contributing to the ‘democratisation’ of health and social care. Little, however, is written about their role and this paper, by focusing on the work of The Encephalitis Society, provides insights into the challenges facing voluntary organisations as they manage twin roles as service providers and advocates, of people with neurological disorders. Two studies are presented: a review conducted by the Society, focusing on patient’s experiences of neurological services; and an external evaluation of the Society’s current provision. The first, based on a postal survey of its members affected by encephalitis (n = 339), illustrates the Society’s advocacy role. The survey provided support for the Association of British Neurologists’ recommendation for nationally agreed standards of care. The second study, a postal survey of recent contacts (n = 76) and in-depth telephone interviews (n = 22), illustrates the Society’s value role as a service provider and supports its role in helping rehabilitate affected individuals and their families. These studies provided the Society with information for policy and service development. Importantly, providing the basis of informed action and partnership with stakeholders and informing the organisation’s sense of purpose, in the changing context of welfare provision in the UK

    Physicochemical analysis of rotavirus segment 11 supports a 'modified panhandle' structure and not the predicted alternative tRNA-like structure (TRLS)

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    .Rotaviruses are a major cause of acute gastroenteritis, which is often fatal in infants. The viral genome consists of 11 double-stranded RNA segments, but little is known about their cis-acting sequences and structural elements. Covariation studies and phylogenetic analysis exploring the potential structure of RNA11 of rotaviruses suggested that, besides the previously predicted "modified panhandle" structure, the 5' and 3' termini of one of the isoforms of the bovine rotavirus UKtc strain may interact to form a tRNA-like structure (TRLS). Such TRLSs have been identified in RNAs of plant viruses, where they are important for enhancing replication and packaging. However, using tRNA mimicry assays (in vitro aminoacylation and 3'- adenylation), we found no biochemical evidence for tRNA-like functions of RNA11. Capping, synthetic 3' adenylation and manipulation of divalent cation concentrations did not change this finding. NMR studies on a 5'- and 3'-deletion construct of RNA11 containing the putative intra-strand complementary sequences supported a predominant panhandle structure and did not conform to a cloverleaf fold despite the strong evidence for a predicted structure in this conserved region of the viral RNA. Additional viral or cellular factors may be needed to stabilise it into a form with tRNA-like properties
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