4,673 research outputs found
A new genus and species of tyrannosauroid from the Late Cretaceous (Middle Campanian) Demopolis Formation of Alabama
American Woodcock Conservation Plan: A Summary of and Recommendations for Woodcock Conservation in North America
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
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 1.5Ć
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
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
Attitude-referenced radiometer study. Volume 2 - Precision radiometric system
Attitude reference radiometer study for earth orbiting spacecraf
Alkali-rich replacement zones in evolved NYF pegmatites: metasomatic fluids or immiscible melts?
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 ācleavelanditeā RZ is assessed from textural, mineralogical, chemical and melt inclusion studies of evolved, Proterozoic Niobium-Yttrium-Fluorine (NYF) rare metal pegmatites from EvjeāIveland, 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 ācleavelanditeā document high H2O contents of up to18 wt.% of the F-rich silicate melt from which the RZ crystallized. In addition, from mineral compositions (ācleavelanditeā, āamazoniteā, 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. āAmazoniteā 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 publisherās version if you wish to cite from it
A randomised trial comparing three Delphi feedback strategies found no evidence of a difference in a setting with high initial agreement
Peer reviewedPostprintPostprintPostprintPostprintPostprintPostprintPostprintPostprintPostprintPostprintPostprin
Trichophycins BāF, Chlorovinylidene-Containing Polyketides Isolated from a Cyanobacterial Bloom
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
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
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 electrons and 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 -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 and tight-binding methods.Comment: 10 pages, 8 figure
MEPicides: Potent antimalarial prodrugs targeting isoprenoid biosynthesis
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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