72 research outputs found

    Elastic stress coupling between supraglacial lakes

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    Supraglacial lakes have been observed to drain within hours of each other, leading to the hypothesis that stress transmission following one drainage may be sufficient to induce hydro-fracture-driven drainages of other nearby lakes. However, available observations characterizing drainage-induced stress perturbations have been insufficient to evaluate this hypothesis. Here, we use ice-sheet surface displacement observations from a dense global positioning system array deployed in the Greenland Ice Sheet ablation zone to investigate elastic stress transmission between three neighboring supraglacial lake basins. We find that drainage of a central lake can place neighboring basins in either tensional or compressional stress relative to their hydro-fracture scarp orientations, either promoting or inhibiting hydro-fracture initiation beneath those lakes. For two lakes located within our array that drain close in time, we identify tensional surface stresses caused by ice-sheet uplift due to basal-cavity opening as the physical explanation for these lakes’ temporally clustered, hydro-fracture-driven drainages and frequent triggering behavior. However, lake-drainage-induced stresses in the up-flowline direction remain low beyond the margins of the drained lakes. This short stress-coupling length scale is consistent with idealized lake-drainage scenarios for a range of lake volumes and ice-sheet thicknesses. Thus, on elastic timescales, our observations and idealized-model results support a stress-transmission hypothesis for inducing hydro-fracture-driven drainage of lakes located within the region of basal cavity opening produced by the initial drainage, but refute this hypothesis for distal lakes

    Assessing the adoption of high iron bean varieties and their impact on iron intakes and other livelihood outcomes in Rwanda: Listing Exercise Report

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    An impact assessment (IA) study was conducted in Rwanda in 2015 Season B in order to establish the adoption rates of HIB varieties among rural bean producing and to generate useful information on delivery and breeding efforts by analyzing the facilitating/hindering factors to adoption and diffusion of HIB varieties. A nationally representative listing exercise preceded the main household survey for the impact assessment. The listing exercise was conducted across 120 rural villages in 29 provinces of Rwanda and was administered to a total of 19,575 households. The aims of the listing exercise were to determine the adoption rate of High Iron Beans (HIBs) and to inform second-stage sampling for the main impact assessment survey that was to follow. This report presents results from the listing exercise

    Selective Enhancement of Donor Hematopoietic Cell Engraftment by the CXCR4 Antagonist AMD3100 in a Mouse Transplantation Model

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    The interaction between stromal cell-derived factor-1 (SDF-1) with CXCR4 chemokine receptors plays an important role in hematopoiesis following hematopoietic stem cell transplantation. We examined the efficacy of post transplant administration of a specific CXCR4 antagonist (AMD3100) in improving animal survival and in enhancing donor hematopoietic cell engraftment using a congeneic mouse transplantation model. AMD3100 was administered subcutaneously at 5 mg/kg body weight 3 times a week beginning at day +2 post-transplant. Post-transplant administration of AMD3100 significantly improves animal survival. AMD3100 reduces pro-inflammatory cytokine/chemokine production. Furthermore, post transplant administration of AMD3100 selectively enhances donor cell engraftment and promotes recovery of all donor cell lineages (myeloid cells, T and B lymphocytes, erythrocytes and platelets). This enhancement results from a combined effect of increased marrow niche availability and greater cell division induced by AMD3100. Our studies shed new lights into the biological roles of SDF-1/CXCR4 interaction in hematopoietic stem cell engraftment following transplantation and in transplant-related mortality. Our results indicate that AMD3100 provides a novel approach for enhancing hematological recovery following transplantation, and will likely benefit patients undergoing transplantation

    Explaining Marketing Strategies among Bolivian Potato Farmers

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    Improving market access and promoting participation in more lucrative markets among semi-subsistence farming households is crucial for poverty alleviation. This paper analyzes joint decisions about market participation and market choices among Bolivian potato farmers. First, stochastic dominance analysis is used to identify market choices that have high pay-off and limited risk; these are referred to as optimal marketing strategies. Second, a system of equations is estimated to identify factors contributing or restricting market entry, volume sold, and adoption of optimal market-ing strategies. Proportional and fixed transaction costs reduce income-generating opportunities associated with markets for all three dimensions considered in this study. Our analysis also suggests the possible existence of poverty traps since fetching higher price requires liquidity and high volume, while land and farm equipment are needed to achieve necessary volumes of production
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