8,127 research outputs found

    The Oxford Handbook of Ecocriticism edited by Greg Garrard

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    Camilla Nelson reviews The Oxford Handbook of Ecocriticism, edited by Greg Garrar

    Self-diffusion in a monatomic glassforming liquid embedded in the hyperbolic plane

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    We study by Molecular Dynamics simulation the slowing down of particle motion in a two-dimensional monatomic model: a Lennard-Jones liquid on the hyperbolic plane. The negative curvature of the embedding space frustrates the long-range extension of the local hexagonal order. As a result, the liquid avoids crystallization and forms a glass. We show that, as temperature decreases, the single particle motion displays the canonical features seen in real glassforming liquids: the emergence of a "plateau" at intermediate times in the mean square displacement and a decoupling between the local relaxation time and the (hyperbolic) diffusion constant.Comment: Article for the "11th International Workshop on Complex Systems

    Stressful Experiences in Children and Adolescents: Initial Report from the PSEI-NCPV Honolulu Study

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    As part of a federal study of the biology of stress and resilience, a comprehensive, structured stress-history interview (PSEI-NCPV) was administered to 307 participants recruited in Honolulu. A moderate correlation between childhood stress and current depression was found. A relatively high rate of "severe bullying/hazing," and a high mean stress-intensity reating for "blood-drawing induced anxiety" call for further research

    Does Wheat Cultivar Choice Affect Crop Quality and Soil Microbial Communities in Cropping Systems?

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    Wheat (Triticum aestivum L.) cultivars may have differential effects on soil microbial communities and the breadmaking quality of harvested grain. We compared six Canadian spring wheat cultivars under organic and conventional management systems for yield, breadmaking quality and soil phospholipid fatty acid analysis (PLFA) profile. Yields were lower, but protein levels were higher in the organic system. Cultivars differed for quality traits, but all cultivars had acceptable levels for processing. There were small differences in PLFA profiles for cultivars in the conventional system, but none in the organic system. More significant correlations between grain quality and PLFA measures were present in the organic system. Protein levels and breadmaking quality at least equal to conventional systems can be achieved in organic systems. Wheat cultivars differed for grain quality in both organic and conventional systems, and culivars altered the soil microbial profile in conventional systems. Microbes may play a greater role in determining crop quality in organic systems than in conventional systems

    Isolation and characterization of the full-length cDNA encoding a member of a novel cytochrome p450 family (CYP320A1) from the tropical freshwater snail, Biomphalaria glabrata, intermediate host for Schistosoma mansoni

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    Cytochrome p450s (cyp450s) are a family of structurally related proteins, with diverse functions, including steroid synthesis and breakdown of toxins. This paper reports the full-length sequence of a novel cyp450 gene, the first to be isolated from the tropical freshwater snail Biomphalaria glabrata, an important intermediate host of Schistosoma mansoni. The nucleotide sequence is 2291 bp with a predicted amino acid sequence of 584aa. The sequence demonstrates conserved cyp450 structural motifs, but is sufficiently different from previously reported cyp450 sequences to be given a new classification, CYP320A1. Initially identified as down-regulated in partially resistant snails in response to S. mansoni infection, amplification of this gene using RT-PCR in both totally resistant or susceptible snail lines when exposed to infection, and all tissues examined, suggests ubiquitous expression. Characterization of the first cyp450 from B. glabrata is significant in understanding the evolution of these metabolically important proteins

    How Obstacles Perturb Population Fronts and Alter Their Genetic Structure

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    This is the final version of the article. Available from Public Library of Science via the DOI in this record.As populations spread into new territory, environmental heterogeneities can shape the population front and genetic composition. We focus here on the effects of an important building block of heterogeneous environments, isolated obstacles. With a combination of experiments, theory, and simulation, we show how isolated obstacles both create long-lived distortions of the front shape and amplify the effect of genetic drift. A system of bacteriophage T7 spreading on a spatially heterogeneous Escherichia coli lawn serves as an experimental model system to study population expansions. Using an inkjet printer, we create well-defined replicates of the lawn and quantitatively study the population expansion of phage T7. The transient perturbations of the population front found in the experiments are well described by a model in which the front moves with constant speed. Independent of the precise details of the expansion, we show that obstacles create a kink in the front that persists over large distances and is insensitive to the details of the obstacle’s shape. The small deviations between experimental findings and the predictions of the constant speed model can be understood with a more general reaction-diffusion model, which reduces to the constant speed model when the obstacle size is large compared to the front width. Using this framework, we demonstrate that frontier genotypes just grazing the side of an isolated obstacle increase in abundance, a phenomenon we call ‘geometry-enhanced genetic drift’, complementary to the founder effect associated with spatial bottlenecks. Bacterial range expansions around nutrient-poor barriers and stochastic simulations confirm this prediction. The effect of the obstacle on the genealogy of individuals at the front is characterized by simulations and rationalized using the constant speed model. Lastly, we consider the effect of two obstacles on front shape and genetic composition of the population illuminating the effects expected from complex environments with many obstacles.Support for this work was provided by the National Institute of General Medical Sciences Grant P50GM068763 of the National Centers for Systems Biology (www.nih.gov, awarded to AWM), by the National Science Foundation through grant DMR1306367 and through the Harvard Materials Research and Engineering Center through Grant DMR-1420570 (www.nsf.gov/div/index.jsp?div=DMR, awarded to DRN). WM was supported by the Leopoldina Postdoc Scholarship LPDS 2009-51 (www.leopoldina.org) and by grants from the National Philanthropic Trust Grant RFP-12-15 (www.templeton.org, awarded to AWM), and from the Human Frontiers Science Program Grant RGP0041/2014 (www.hfsp.org, awarded to AWM). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

    A semi-Markov model for stroke with piecewise-constant hazards in the presence of left, right and interval censoring.

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    This paper presents a parametric method of fitting semi-Markov models with piecewise-constant hazards in the presence of left, right and interval censoring. We investigate transition intensities in a three-state illness-death model with no recovery. We relax the Markov assumption by adjusting the intensity for the transition from state 2 (illness) to state 3 (death) for the time spent in state 2 through a time-varying covariate. This involves the exact time of the transition from state 1 (healthy) to state 2. When the data are subject to left or interval censoring, this time is unknown. In the estimation of the likelihood, we take into account interval censoring by integrating out all possible times for the transition from state 1 to state 2. For left censoring, we use an Expectation-Maximisation inspired algorithm. A simulation study reflects the performance of the method. The proposed combination of statistical procedures provides great flexibility. We illustrate the method in an application by using data on stroke onset for the older population from the UK Medical Research Council Cognitive Function and Ageing Study

    Can science writing collectives overcome barriers to more democratic communication and collaboration? Lessons from environmental communication praxis in southern Appalachia

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    Despite compelling reasons to involve nonscientists in the production of ecological knowledge, cultural and institutional factors often dis-incentivize engagement between scientists and nonscientists. This paper details our efforts to develop a biweekly newspaper column to increase communication between ecological scientists, social scientists, and the communities within which they work. Addressing community-generated topics and written by a collective of social and natural scientists, the column is meant to foster public dialog about socio-environmental issues and to lay the groundwork for the coproduction of environmental knowledge. Our collective approach to writing addresses some major barriers to public engagement by scientists, but the need to insert ourselves as intermediaries limits these gains. Overall, our efforts at environmental communication praxis have not generated significant public debate, but they have supported future coproduction by making scientists a more visible presence in the community and providing easy pathways for them to begin engaging the public. Finally, this research highlights an underappreciated barrier to public engagement: scientists are not merely disconnected from the public, but also connected in ways that may be functional for their research. Many field scientists, for example, seek out neutral and narrowly defined connections that permit research access but are largely incompatible with efforts to address controversial issues of environmental governance
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