267 research outputs found

    Influence of Patagonian glaciers on Antarctic dust deposition during the last glacial period

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    Dust in the atmosphere plays a role in the transparency of the atmosphere1, the mineral nourishment of the oceans and can be used to constrain global circulation models today and in the past. Antarctic ice cores provide an 800,000 year record of changes in dust flux thought to reflect changes in the vigour of global atmospheric circulation and environmental conditions in source areas. Here for the first time we link the source of Last Glacial dust peaks in Antarctica to the gravel outwash plains of Patagonian glaciers in the Magellan area of southernmost South America. We find that there is an on-off switch in that the peaks coincide with episodes when glaciers discharge sediment directly onto outwash plains but not when they terminate in lakes. This finding helps solve several long-standing puzzles, namely: why both dust and fresh water diatom concentrations during glacial maxima are so much higher (x ~20) than at the present day; why dust peaks occur only below a certain temperature threshold; and why the decline in dust concentrations at the end of glacial cycles precedes the main phase of warming, the rise in sea level, and the reduction in southern hemisphere sea ice extent

    Lithium fluoride injection layers can form quasi-Ohmic contacts for both holes and electrons

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    Thin LiF interlayers are typically used in organic light-emitting diodes to enhance the electron injection. Here, we show that the effective work function of a contact with a LiF interlayer can be either raised or lowered depending on the history of the applied bias. Formation of quasi-Ohmic contacts for both electrons and holes is demonstrated by electroluminescence from symmetric LiF/polymer/LiF diodes in both bias polarities. The origin of the dynamic switching is charging of electrically induced Frenkel defects. The current density-electroluminescence-voltage characteristics can qualitatively be explained. The interpretation is corroborated by unipolar memristive switching and by bias dependent reflection measurements. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License

    Opto-electronic characterization of electron traps upon forming polymer oxide memory diodes

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    Metal-insulator-polymer diodes where the insulator is a thin oxide (Al2O3) layer are electroformed by applying a high bias. The initial stage is reversible and involves trapping of electrons near the oxide/polymer interface. The rate of charge trapping is limited by electron transport through the polymer. Detrapping of charge stored can be accomplished by illuminating with light under short-circuit conditions. The amount of stored charge is determined from the optically induced discharging current transient as a function of applied voltage and oxide thickness. When the charge density exceeds 8 1017/m2, an irreversible soft breakdown transition occurs to a non-volatile memory diode

    New constraints on elemental and Pb and Nd isotope compositions of South American and Southern African aerosol sources to the South Atlantic Ocean

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    Improving the geochemical database available for characterising potential natural and anthropogenic aerosol sources from South America and Southern Africa is a critical precondition for studies aimed at understanding trace metal controls on the marine biogeochemical cycles of the South Atlantic Ocean. We here present new elemental and isotopic data for a wide range of sample types from South America and Southern Africa that are potentially important aerosol sources. This includes road dust from Buenos Aires and lichen samples from Johannesburg, soil dust from Patagonia, volcanic ash from the Andean volcanic belt, and aerosol samples from São Paulo. All samples were investigated for major (Al, Ca, Fe, Mg, Na, K, Mn) and trace element (Cd, Co, Cr, Cu, Ni, Pb, REE, Sc, Th, Y, V, Zn) concentrations and Nd and Pb isotopic compositions. We show that diagrams of 208Pb/207Pb vs. εNd, 208Pb/207Pb vs. Pb/Al, 1/[Pb], Zn/Al, Cd/Al, Cu/Al, and εNd vs. Pb/Al, and 1/[Nd] are best suited to separate South American and South African source regions as well as natural and anthropogenic sources. A subset of samples from Patagonia and the Andes was additionally subjected to separation of a fine (<5 μm) fraction and compared to the composition of the bulk sample. We show that differences in the geochemical signature of bulk samples between individual regions and source types are significantly larger than between grain sizes. Jointly, these findings present an important step forward towards a quantitative assessment of aeolian trace metal inputs to the South Atlantic Ocean

    Introductory clifford analysis

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    In this chapter an introduction is given to Clifford analysis and the underlying Clifford algebras. The functions under consideration are defined on Euclidean space and take values in the universal real or complex Clifford algebra, the structure and properties of which are also recalled in detail. The function theory is centered around the notion of a monogenic function, which is a null solution of a generalized Cauchy–Riemann operator, which is rotation invariant and factorizes the Laplace operator. In this way, Clifford analysis may be considered as both a generalization to higher dimension of the theory of holomorphic functions in the complex plane and a refinement of classical harmonic analysis. A notion of monogenicity may also be associated with the vectorial part of the Cauchy–Riemann operator, which is called the Dirac operator; some attention is paid to the intimate relation between both notions. Since a product of monogenic functions is, in general, no longer monogenic, it is crucial to possess some tools for generating monogenic functions: such tools are provided by Fueter’s theorem on one hand and the Cauchy–Kovalevskaya extension theorem on the other hand. A corner stone in this function theory is the Cauchy integral formula for representation of a monogenic function in the interior of its domain of monogenicity. Starting from this representation formula and related integral formulae, it is possible to consider integral transforms such as Cauchy, Hilbert, and Radon transforms, which are important both within the theoretical framework and in view of possible applications

    Invisible medicine sellers and their use of antibiotics: a qualitative study in Cambodia.

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    BACKGROUND: Global attention to antimicrobial resistance has increased interest in tackling the widespread inappropriate dispensing of antibiotics by informal, for-profit healthcare providers (HCPs). We provide new evidence on an understudied group of informal HCPs: invisible medicine sellers (IMS) who operate without any marked facility. We investigated factors that influence community decisions on which HCPs to purchase medicines from, focusing on reasons for using IMS, and compared different HCPs' knowledge of antibiotic use. METHODS: We conducted community focus group discussions (FGDs) in seven purposively selected villages representing high and low informal HCPs use in two peri-urban districts in Phnom Penh, Cambodia. Using information from the FGDs to identify HCPs that sell medicines, we interviewed 35 participants: 21 HCPs (including five IMS) and 14 key informants, including government HCPs and village leaders. We adopted an interpretative approach and conducted a thematic analysis. RESULTS: Community members typically knew of several formal and informal HCPs selling medicines nearby, and IMS were common, as were doctors that sell medicines covertly. Two factors were most salient in influencing the choice of HCP for medicine purchasing. The first was trust in the effectiveness of medicines provided, judged by the speed of symptomatic relief. This pushed HCPs to provide several medicines, including antibiotics, at the first consultation. The second was the convenience offered by IMS and other informal HCPs: supplying medicines when other facilities are closed, accepting delayed payments, providing incomplete courses of medication and selling human antibiotics for animal use. CONCLUSION: This first study focusing on IMS indicates that it is important, but challenging, for public health agencies to engage with them to reduce inappropriate use of antibiotics. Although public health facilities must fill some gaps that informal HCPs are currently addressing, such as access to medicines at night, reducing demand for unnecessary antibiotics is also critical

    Interferon and Biologic Signatures in Dermatomyositis Skin: Specificity and Heterogeneity across Diseases

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    BACKGROUND: Dermatomyositis (DM) is an autoimmune disease that mainly affects the skin, muscle, and lung. The pathogenesis of skin inflammation in DM is not well understood. METHODOLOGY AND FINDINGS: We analyzed genome-wide expression data in DM skin and compared them to those from healthy controls. We observed a robust upregulation of interferon (IFN)-inducible genes in DM skin, as well as several other gene modules pertaining to inflammation, complement activation, and epidermal activation and differentiation. The interferon (IFN)-inducible genes within the DM signature were present not only in DM and lupus, but also cutaneous herpes simplex-2 infection and to a lesser degree, psoriasis. This IFN signature was absent or weakly present in atopic dermatitis, allergic contact dermatitis, acne vulgaris, systemic sclerosis, and localized scleroderma/morphea. We observed that the IFN signature in DM skin appears to be more closely related to type I than type II IFN based on in vitro IFN stimulation expression signatures. However, quantitation of IFN mRNAs in DM skin shows that the majority of known type I IFNs, as well as IFN g, are overexpressed in DM skin. In addition, both IFN-beta and IFN-gamma (but not other type I IFN) transcript levels were highly correlated with the degree of the in vivo IFN transcriptional response in DM skin. CONCLUSIONS AND SIGNIFICANCE: As in the blood and muscle, DM skin is characterized by an overwhelming presence of an IFN signature, although it is difficult to conclusively define this response as type I or type II. Understanding the significance of the IFN signature in this wide array of inflammatory diseases will be furthered by identification of the nature of the cells that both produce and respond to IFN, as well as which IFN subtype is biologically active in each diseased tissue

    Developmenrt of EST-SSR and genomic-SSR markers to assess genetic diversity in Jatropha Curcas L.

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    <p>Abstract</p> <p>Background</p> <p><it>Jatropha curcas L. </it>has attracted a great deal of attention worldwide, regarding its potential as a new biodiesel crop. However, the understanding of this crop remains very limited and little genomic research has been done. We used simple sequence repeat (SSR) markers that could be transferred from <it>Manihot esculenta </it>(cassava) to analyze the genetic relationships among 45 accessions of <it>J. curcas </it>from our germplasm collection.</p> <p>Results</p> <p>In total, 187 out of 419 expressed sequence tag (EST)-SSR and 54 out of 182 genomic (G)-SSR markers from cassava were polymorphic among the <it>J. curcas </it>accessions. The EST-SSR markers comprised 26.20% dinucleotide repeats, 57.75% trinucleotide repeats, 7.49% tetranucleotide repeats, and 8.56% pentanucleotide repeats, whereas the majority of the G-SSR markers were dinucleotide repeats (62.96%). The 187 EST-SSRs resided in genes that are involved mainly in biological and metabolic processes. Thirty-six EST-SSRs and 20 G-SSRs were chosen to analyze the genetic diversity among 45 <it>J. curcas </it>accessions. A total of 183 polymorphic alleles were detected. On the basis of the distribution of these polymorphic alleles, the 45 accessions were classified into six groups, in which the genotype showed a correlation with geographic origin. The estimated mean genetic diversity index was 0.5572, which suggests that our <it>J. curcas </it>germplasm collection has a high level of genetic diversity. This should facilitate subsequent studies on genetic mapping and molecular breeding.</p> <p>Conclusion</p> <p>We identified 241 novel EST-SSR and G-SSR markers in <it>J. curcas</it>, which should be useful for genetic mapping and quantitative trait loci analysis of important agronomic traits. By using these markers, we found that the intergroup gene diversity of <it>J. curcas </it>was greater than the intragroup diversity, and that the domestication of the species probably occurred partly in America and partly in Hainan, China.</p
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