4,673 research outputs found

    American Woodcock Conservation Plan: A Summary of and Recommendations for Woodcock Conservation in North America

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    Table of Contents Introduction ....................1 Bird Conservation Region Action Plans 11 Prairie Potholes ....................17James Kelley 12 Boreal Hardwood Transition ....................25Dan Dessecker 13 Lower Great Lakes/St. Lawrence Plain ....................32 Tim Post 14 Atlantic Northern Forest.................... 45 Dan McAuley 21 Oaks and Prairies ....................59David Haukos, James Kelley 22 Eastern Tallgrass Prairie ....................67 James Kelley 23 Prairie Hardwood Transition ....................75 James Kelley 24 Central Hardwoods ....................83 David Krementz, Nick Myatt 25 West Gulf Coastal Plain/Ouachita ....................92 David Krementz, Nick Myatt 26 Mississippi Alluvial Valley ....................99 David Krementz, Nick Myatt 27 Southeastern Coastal Plain ....................108 Scot Williamson 28 Appalachian Mountains.................... 116 Mark Banker 29 Piedmont ....................128 William Palmer 30 New England/Mid-Atlantic Coast ....................138 Scot Williamson 31 Peninsular Florida ....................148 Scot Williamson 37 Gulf Coastal Prairie ....................151 James Kelley Appendix I 155 Appendix II 157 Bibliography 15

    Sialic Acid Mutarotation Is Catalyzed by the Escherichia coli Ī²-Propeller Protein YjhT

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    The acquisition of host-derived sialic acid is an important virulence factor for some bacterial pathogens, but in vivo this sugar acid is sequestered in sialoconjugates as the {alpha}-anomer. In solution, however, sialic acid is present mainly as the Ī²-anomer, formed by a slow spontaneous mutarotation. We studied the Escherichia coli protein YjhT as a member of a family of uncharacterized proteins present in many sialic acid-utilizing pathogens. This protein is able to accelerate the equilibration of the {alpha}- and Ī²-anomers of the sialic acid N-acetylneuraminic acid, thus describing a novel sialic acid mutarotase activity. The structure of this periplasmic protein, solved to 1.5ƅ resolution, reveals a dimeric 6-bladed unclosed Ī²-propeller, the first of a bacterial Kelch domain protein. Mutagenesis of conserved residues in YjhT demonstrated an important role for Glu-209 and Arg-215 in mutarotase activity. We also present data suggesting that the ability to utilize {alpha}-N-acetylneuraminic acid released from complex sialoconjugates in vivo provides a physiological advantage to bacteria containing YjhT

    American Woodcock Conservation Plan: A Summary of and Recommendations for Woodcock Conservation in North America

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    Table of Contents Introduction ....................1 Bird Conservation Region Action Plans 11 Prairie Potholes ....................17James Kelley 12 Boreal Hardwood Transition ....................25Dan Dessecker 13 Lower Great Lakes/St. Lawrence Plain ....................32 Tim Post 14 Atlantic Northern Forest.................... 45 Dan McAuley 21 Oaks and Prairies ....................59David Haukos, James Kelley 22 Eastern Tallgrass Prairie ....................67 James Kelley 23 Prairie Hardwood Transition ....................75 James Kelley 24 Central Hardwoods ....................83 David Krementz, Nick Myatt 25 West Gulf Coastal Plain/Ouachita ....................92 David Krementz, Nick Myatt 26 Mississippi Alluvial Valley ....................99 David Krementz, Nick Myatt 27 Southeastern Coastal Plain ....................108 Scot Williamson 28 Appalachian Mountains.................... 116 Mark Banker 29 Piedmont ....................128 William Palmer 30 New England/Mid-Atlantic Coast ....................138 Scot Williamson 31 Peninsular Florida ....................148 Scot Williamson 37 Gulf Coastal Prairie ....................151 James Kelley Appendix I 155 Appendix II 157 Bibliography 15

    Alkali-rich replacement zones in evolved NYF pegmatites: metasomatic fluids or immiscible melts?

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    IMA2018 Abstract submission Pegmatite mineralogy, geochemistry, classification and origins IMA2018-1337 Alkali-rich replacement zones in evolved NYF pegmatites: metasomatic fluids or immiscible melts? Axel Muller* 1, John Spratt2, Rainer Thomas3, Ben J. Williamson4, Reimar Seltmann2 1Natural History Museum, University of Oslo, Oslo, Norway, 2Department of Earth Sciences, Natural History Museum, London, United Kingdom, 3Chemistry and Physics of Earth Materials, German Research Centre for Geoscience GFZ, Potsdam, Germany, 4Camborne School of Mines, University of Exeter, Penryn, United Kingdom What is your preferred presentation method?: Oral or poster presentation : Replacement zones (RZ), which are a common feature of evolved granitic pegmatites, are irregular, commonly alkali-rich zones superimposing, cross-cutting and replacing the primary zonation in almost all consolidated pegmatite bodies. RZ are widely considered to result from late-stage metasomatism even though little is known about the melts and/or fluids involved in their formation. However, the observed textures and mineral paragenesis of RZ cannot be explained by metasomatism in a strict sense. In this study, the nature of the late stage silicate melt forming ā€œcleavelanditeā€ RZ is assessed from textural, mineralogical, chemical and melt inclusion studies of evolved, Proterozoic Niobium-Yttrium-Fluorine (NYF) rare metal pegmatites from Evjeā€“Iveland, southern Norway. These were studied as they are mineralogically simple, compared with RZ in evolved Lithium-Caesium-Tantalum (LCT) pegmatites. Silicate melt inclusions in RZ-forming topaz and ā€œcleavelanditeā€ document high H2O contents of up to18 wt.% of the F-rich silicate melt from which the RZ crystallized. In addition, from mineral compositions (ā€œcleavelanditeā€, ā€œamazoniteā€, white mica, garnet, columbite group minerals, topaz, fluorite, and beryl), they must have also been strongly alkaline (Na-dominated) with enrichments in F (at least 4 wt.%), Cs, Rb, Ta, Nb, Mn, Ge, Bi, As, and in some cases also Li compared with host pegmatites. These elements are concentrated in a few RZ-forming minerals resulting in very distinctive mineral-trace element signatures. ā€œAmazoniteā€ is strongly enriched in Cs and Rb and often white mica and beryl in Li and Cs. To acquire these mineral compositions, the overall Li-Cs-Ta-poor Evje-Iveland original pegmatite melt must have undergone extreme internal chemical differentiation resulting in melt/melt immiscibility aiding rheology contrasts and resulting in RZ formation. The resulting RZ-forming H2O-F-rich silicate melt would have shown large differences in viscosity and density, and therefore physical flow/transport properties, to the host pegmatite melt resulting in discordant contacts. The mineralogy and melt inclusion data from the Evje-Iveland pegmatites document a gradient of crystallization temperatures within the investigated pegmatite bodies with highest temperatures at the pegmatite margin (during initial emplacement, ~680Ā°C) and lowest temperatures within the RZ (<500Ā°C). Considering the temperature and pressure conditions of the host rocks gneisses and amphibolites (~650Ā°C, up to 5 kbar) at the time of pegmatite emplacement and the crystallization conditions of the RZ, the Evje- Iveland pegmatites and RZ likely formed over a period of 2.2 million years, assuming an exhumation rate of 1.5 mm per million years and a geothermal gradient of 45Ā°C km-1. Such a long crystallization time contradicts the classical view that pegmatites represent strongly undercooled melts which crystallize relatively fast.The attached document is the authorsā€™ submitted version of the oral presentation. You are advised to consult the publisherā€™s version if you wish to cite from it

    Trichophycins Bā€“F, Chlorovinylidene-Containing Polyketides Isolated from a Cyanobacterial Bloom

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    NMR-guided isolation (based on 1D 1H and 13C NMR resonances consistent with a chlorovinylidene moiety) resulted in the characterization of five new highly functionalized polyketides, trichophycins B-F (1-5) and one non-chlorinated metabolite tricholactone (6) from a collection of Trichodesmium bloom material from the Gulf of Mexico. The planar structures of 1-6 were determined using 1D and 2D NMR spectroscopy, mass spectrometry and complementary spectroscopic procedures. Absolute configuration analysis of 1 and 2 were carried out by 1H NMR analysis of diastereomeric Mosher esters in addition to ECD spectroscopy, J-based configuration analysis and DFT calculations. The absolute configurations of 3-6 were proposed based on comparative analysis of 13C NMR chemical shifts, relative configurations, and optical rotation values to compounds 1 and 2. Compounds 1-5 represent new additions to the trichophycin family and are hallmarked by a chlorovinylidene moiety. These new trichophycins and tricholactone (1-6) feature intriguing variations with respect to putative biosynthetic starting units, halogenation, and terminations and trichophycin E (4) features a rare alkynyl bromide functionality. The phenyl-containing trichophycins showed low cytotoxicity to neuro-2A cells, while the alkyne-containing trichophycins showed no toxicity

    Multiband theory of multi-exciton complexes in self-assembled quantum dots

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    We report on a multiband microscopic theory of many-exciton complexes in self-assembled quantum dots. The single particle states are obtained by three methods: single-band effective-mass approximation, the multiband kā‹…pk\cdot p method, and the tight-binding method. The electronic structure calculations are coupled with strain calculations via Bir-Pikus Hamiltonian. The many-body wave functions of NN electrons and NN valence holes are expanded in the basis of Slater determinants. The Coulomb matrix elements are evaluated using statically screened interaction for the three different sets of single particle states and the correlated NN-exciton states are obtained by the configuration interaction method. The theory is applied to the excitonic recombination spectrum in InAs/GaAs self-assembled quantum dots. The results of the single-band effective-mass approximation are successfully compared with those obtained by using the of kā‹…pk\cdot p and tight-binding methods.Comment: 10 pages, 8 figure

    MEPicides: Potent antimalarial prodrugs targeting isoprenoid biosynthesis

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    AbstractThe emergence of Plasmodium falciparum resistant to frontline therapeutics has prompted efforts to identify and validate agents with novel mechanisms of action. MEPicides represent a new class of antimalarials that inhibit enzymes of the methylerythritol phosphate (MEP) pathway of isoprenoid biosynthesis, including the clinically validated target, deoxyxylulose phosphate reductoisomerase (Dxr). Here we describe RCB-185, a lipophilic prodrug with nanomolar activity against asexual parasites. Growth of P. falciparum treated with RCB-185 was rescued by isoprenoid precursor supplementation, and treatment substantially reduced metabolite levels downstream of the Dxr enzyme. In addition, parasites that produced higher levels of the Dxr substrate were resistant to RCB-185. Notably, environmental isolates resistant to current therapies remained sensitive to RCB-185, the compound effectively treated sexually-committed parasites, and was both safe and efficacious in malaria-infected mice. Collectively, our data demonstrate that RCB-185 potently and selectively inhibits Dxr in P. falciparum, and represents a promising lead compound for further drug development.</jats:p
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