Spatially explicit identification of changes in ecological conditions over large areas is key to targeting and prioritizing areas for environmental protection and restoration by managers at watershed, basin, and regional scales. A critical limitation to this point has been the development of methods to conduct such broad-scale assessments. Field-based methods have proven to be too costly and too inconsistent in their application to make estimates of ecological conditions over large areas. New spatial data derived from satellite imagery and other sources, the development of statistical models relating landscape composition and pattern to ecological endpoints, and geographic information systems (GIS) make it possible to evaluate ecological conditions at multiple scales over broad geographic regions. In this study, we demonstrate the application of spatially distributed models for bird habitat quality and nitrogen yield to streams to assess the consequences of landcover change across the midAtlantic region between the 1970s and 1990s. Moreover, we present a way to evaluate spatial concordance between models related to different environmental endpoints. Results of this study should help environmental managers in the mid-Atlantic region target those areas in need of conservation and protection.
Measured values of the relative intensities of several K-fluorescent x rays are reported for 28 elements ranging from calcium through plutonium.Solid-state Si(I i) and Ge(Li) spectrometers and a Bragg-diffraction spectrometer were used in making the measurements.Fluorescence was excited in thin samples by higher-energy x rays. Corrections were made to the measured relative intensities for sample absorption, air absorption, and spectrometer efficiency. The accuracy of most of the measurements is +2 to 5%. The results are compared with those of other experimenters and with the Scofield calculations. 1NTRODUCTION Several recent experimental determinations of relative intensities of K emission lines have been reported. ' Most of these papers describe measurements made for a relatively small number of characteristic x rays or for relatively few elements.The purpose of the present work is to provide experimental measurements of the intensities of several K emission lines relative to the Ko'& intensity for a large number of elements from Z = 20 through 2= 94. Thin samples were used as fluorescers so that corrections for x-ray absorption would be minimized. Three spectrometers were used in these measurements.A Bragg-diffraction spectrometer with high-resolution Soller slits was used to measure K&2-to-K&& ratios for x-ray energies less than 50 keV; a Si(Li) spectrometer was used to measure Kp-to-Kn ratios for x-ray energies less than 20 keV; and a Ge(Li} spectrometer was used to make all of the higher-energy measurements.Peak
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