35,031 research outputs found

    Slavery\u27s Legacy: Georgetown Faces Its Past

    Get PDF

    Methodological Frontiers in Environmental Epidemiology

    Full text link
    Environmental epidemiology comprises the epidemiologic study of those environmental factors that are outside the immediate control of the individual. Exposures of interest to environmental epidemiologists include air pollution, water pollution, occupational exposure to physical and chemical agents, as well as psychosocial elements of environmental concern. The main methodologic problem in environmental epidemiology is exposure assessment, a problem that extends through all of epidemiologic research but looms as a towering obstacle in environmental epidemiology. One of the most promising developments in improving exposure assessment in environmental epidemiology is to find exposure biomarkers, which could serve as built-in dosimeters that reflect the biologic footprint left behind by environmental exposures. Beyond exposure assessment, epidemiologists studying environmental exposures face the difficulty of studying small effects that may be distorted by confounding that eludes easy control. This challenge may prompt reliance on new study designs, such as two-stage designs in which exposure and disease information are collected in the first stage, and covariate information is collected on a subset of subjects in state two. While the analytic methods already available for environmental epidemiology are powerful, analytic methods for ecologic studies need further development. This workshop outlines the range of methodologic issues that environmental epidemiologists must address so that their work meets the goals set by scientists and society at large

    Rush to Judgment: Teacher Evaluation in Public Education

    Get PDF
    The troubled state of teacher evaluation is a glaring and largely neglected problem in public education. Co-director Thomas Toch and Robert Rothman of the Annenberg Institute for School Reform examine the causes and consequences of the crisis in teacher evaluation, as well as its implications for the current debate about performance pay

    A Comparison of Water Vapor Line Parameters for Modeling the Venus Deep Atmosphere

    Full text link
    The discovery of the near infrared windows into the Venus deep atmosphere has enabled the use of remote sensing techniques to study the composition of the Venus atmosphere below the clouds. In particular, water vapor absorption lines can be observed in a number of the near-infrared windows allowing measurement of the H2O abundance at several different levels in the lower atmosphere. Accurate determination of the abundance requires a good database of spectral line parameters for the H2O absorption lines at the high temperatures (up to ~700 K) encountered in the Venus deep atmosphere. This paper presents a comparison of a number of H2O line lists that have been, or that could potentially be used, to analyze Venus deep atmosphere water abundances and shows that there are substantial discrepancies between them. For example, the early high-temperature list used by Meadows and Crisp (1996) had large systematic errors in line intensities. When these are corrected for using the more recent high-temperature BT2 list of Barber et al. (2006) their value of 45+/-10 ppm for the water vapor mixing ratio reduces to 27+/-6 ppm. The HITRAN and GEISA lists used for most other studies of Venus are deficient in "hot" lines that become important in the Venus deep atmosphere and also show evidence of systematic errors in line intensities, particularly for the 8000 to 9500 cm-1 region that includes the 1.18 um window. Water vapor mixing ratios derived from these lists may also be somewhat overestimated. The BT2 line list is recommended as being the most complete and accurate current representation of the H2O spectrum at Venus temperatures.Comment: 42 pages, 11 figures, Accepted by Icaru
    corecore