3,198 research outputs found

    A Simple Model for Deglacial Meltwater Pulses

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    Evidence from radiocarbon dating and complex ice sheet modeling suggests that the fastest rate of sea level rise in Earth's recent history coincided with collapse of the ice saddle between the Laurentide and Cordilleran ice sheets during the last deglaciation. In this study, we derive a simple, two‐equation model of two ice sheets intersecting in an ice saddle. We show that two conditions are necessary for producing the acceleration in ice sheet melt associated with meltwater pulses: the positive height‐mass balance feedback and an ice saddle geometry. The amplitude and timing of meltwater pulses is sensitively dependent on the rate of climate warming during deglaciation and the relative size of ice sheets undergoing deglaciation. We discuss how simulations of meltwater pulses can be improved and the prospect for meltwater pulses under continued climate warming

    Self-citation and corruption: cross-sectional, cross-country study

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    # Background Self-citation appears to be widely prevalent. However, the structural drivers of self-citation are poorly understood. # Methods Data for this study were obtained from a recently published study of Scopus data aggregated across all authors with \>5 publications, across all scientific fields, which yielded aggregate, country-level data on the mean co-author self-citation rate for the period 1960-2018. These data were merged with 2018 data from Transparency International on corruption, and additional data extracted from the World Development Indicators. The country-level association between the self-citation rate and the corruption index was estimated using multivariable linear regression. # Results Across 178 countries, the correlation between the mean self-citation rate and the corruption index was -0.52, 95% confidence interval, CI=-0.62 to -0.41. Among the 49 countries in the lowest quartile of the corruption index, the mean self-citation rate was 0.24 (standard deviation, SD=0.06). Among the 44 countries in the highest quartile of the corruption index, the mean self-citation rate was 0.21 (SD=0.05). In a weighted linear regression model with robust estimates of variance, the corruption index had a statistically significant association with the mean self-citation rate (2nd quartile compared with 1st quartile: *b*=-0.08 (95% CI=-0.17 to -0.01); 3rd quartile: *b*=-0.11 (95% CI=-0.19 to -0.02); 4th quartile: *b*=-0.10 (95% CI=-0.19 to -0.01; N=165). The implied effect size was large in magnitude and robust to potential confounding by unmeasured covariates. # Conclusions In this cross-sectional, cross-country analysis, there was a strong correlation between a country’s overall level of corruption and the mean self-citation rate. The estimated association was statistically significant, large in magnitude, and unlikely to be explained away by unmeasured confounding. Better understanding of how corruption norms evolve is likely to be critical in addressing the problem of extreme self-citation and other forms of citation manipulation

    Is Food Insecurity Associated with HIV Risk? Cross-Sectional Evidence from Sexually Active Women in Brazil

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    Alexander Tsai and colleagues show that in sexually active women in Brazil severe food insecurity with hunger was positively associated with symptoms potentially indicative of sexually transmitted infection and with reduced odds of condom use

    Quantifying Bias in Measuring Insecticide-treated Bednet Use: Meta-analysis of Self-reported vs Objectively Measured Adherence

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    Background Insecticide-treated bednets (ITNs) are recommended for use by 3.4 billion people at risk of malaria world-wide. Policy makers rely on measurements of ITN use to optimize malaria prevention efforts. Self-reports are the most common means of assessing ITN use, but self-reports may be biased in a way that reduces their reliability as a proxy for ITN adherence. This meta-analysis compared self-reported and two methods which are more objective measures of ITN use to explore whether self-reports overestimate actual ITN adherence. Methods A comprehensive search of electronic databases and hand searching reference lists resulted in screening 2885 records and 202 articles were read in full. Sixteen articles with comparable data were chosen for the meta-analysis. Comparable data was defined as self-reported and objectively measured ITN use (observation of a mounted ITN or surprise visits confirming use) at the same unit of analysis, covering the same time period and same population. A random effects model was used to determine a weighted average risk difference between self-reported and objectively measured ITN use. Additional stratified analyses were conducted to explore study heterogeneity. Results Self-reported ITN use is 8 percentage points (95% confidence interval CI: 3 to 13) higher than objectively measured ITN use, representing a 13.6% overestimation relative to the proportion measured as adherent to ITN use by objective measures. Wide variations in the discrepancies between self-reports and objective measures were unable to be explained using stratified analyses of variables including location, year of publication, seasonality and others. Conclusions Self-reports overestimate ITN adherence relative to objectively measured ITN use by 13.6% and do so in an unpredictable manner that raises questions about the reliability of using self-reported ITN use alone as a surveillance tool and a guide for making policy decisions

    Tidal modulation of ice shelf buttressing stresses

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    Ocean tides influence the flow of marine-terminating glaciers. Observations indicate that the large fortnightly variations in ice flow at Rutford Ice Stream in West Antarctica originate in the floating ice shelf. We show that nonlinear variations in ice shelf buttressing driven by tides can produce such fortnightly variations in ice flow. These nonlinearities in the tidal modulation of buttressing stresses can be caused by asymmetries in the contact stress from migration of the grounding line and bathymetric pinning points beneath the ice shelf. Using a simple viscoelastic model, we demonstrate that a combination of buttressing and hydrostatic stress variations can explain a diverse range of tidal variations in ice shelf flow, including the period, phase and amplitude of flow variations observed at Rutford and Bindschadler Ice Streams

    Mental health spillovers and the millennium development goals : the case of perinatal depression in Khayelitsha, South Africa

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    CITATION: Tsai, A. C. & Tomlinson, M. 2012. Mental health spillovers and the millennium development goals : the case of perinatal depression in Khayelitsha, South Africa. Journal of Global Health, 2(1):010302, doi: 10.7189/jogh.02.010302.The original publication is available at http://www.jogh.orgMental illness currently ranks among the top ten causes of burden of disease in low-income countries [1]. In the African region specifically, neuropsychiatric disorders account for approximately 5% of disability-adjusted life years lost, with nearly one quarter of this burden attributable to unipolar depressive disorders .http://www.jogh.org/issue201201.htmPublisher's versio

    A Simple Model for Deglacial Meltwater Pulses

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    Evidence from radiocarbon dating and complex ice sheet modeling suggests that the fastest rate of sea level rise in Earth's recent history coincided with collapse of the ice saddle between the Laurentide and Cordilleran ice sheets during the last deglaciation. In this study, we derive a simple, two‐equation model of two ice sheets intersecting in an ice saddle. We show that two conditions are necessary for producing the acceleration in ice sheet melt associated with meltwater pulses: the positive height‐mass balance feedback and an ice saddle geometry. The amplitude and timing of meltwater pulses is sensitively dependent on the rate of climate warming during deglaciation and the relative size of ice sheets undergoing deglaciation. We discuss how simulations of meltwater pulses can be improved and the prospect for meltwater pulses under continued climate warming
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