Abstract. The James Webb Space Telescope (JWST) is a large (6.6 m), cold (<50 K), infrared (IR)-optimized space observatory that will be launched early in the next decade into orbit around the second Earth-Sun Lagrange point. The observatory will have four instruments: a near-IR camera, a near-IR multiobject spectrograph, and a tunable filter imager will cover the wavelength range, 0.6 < λ < 5.0 μm, while the mid-IR instrument will do both imaging and spectroscopy from 5.0 < λ < 29 μm.The JWST science goals are divided into four themes. The key objective of The End of the Dark Ages: First Light and Reionization theme is to identify the first luminous sources to form and to determine the ionization history of the early universe. The key objective of The Assembly of Galaxies theme is to determine how galaxies and the dark matter, gas, stars, metals, morphological structures, Space Science Reviews (2006) and active nuclei within them evolved from the epoch of reionization to the present day. The key objective of The Birth of Stars and Protoplanetary Systems theme is to unravel the birth and early evolution of stars, from infall on to dust-enshrouded protostars to the genesis of planetary systems. The key objective of the Planetary Systems and the Origins of Life theme is to determine the physical and chemical properties of planetary systems including our own, and investigate the potential for the origins of life in those systems. Within these themes and objectives, we have derived representative astronomical observations. To enable these observations, JWST consists of a telescope, an instrument package, a spacecraft, and a sunshield. The telescope consists of 18 beryllium segments, some of which are deployed. The segments will be brought into optical alignment on-orbit through a process of periodic wavefront sensing and control. The instrument package contains the four science instruments and a fine guidance sensor. The spacecraft provides pointing, orbit maintenance, and communications. The sunshield provides passive thermal control. The JWST operations plan is based on that used for previous space observatories, and the majority of JWST observing time will be allocated to the international astronomical community through annual peer-reviewed proposal opportunities.

Two procedures, the jackknife and the bootstrap, are discussed as methods for estimating the number of species by the sampling of quadrats. Explicit formulas for both procedures are presented and evaluated under a model with a random distribution of individuals. The jackknife and bootstrap are shown to reduce the bias although they underestimate the actual number of species if there is a large number of rare species and the number of quadrats sampled is small. When a small number of quadrats is sampled, the jackknife is shown to give better estimates. When the number of quadrats is large, the jackknife tends to overestimate the number of species and the bootstrap performs better.

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We examined and summarized existing knowledge regarding the distribution and status of selfsustaining populations of brook trout Salvelinus fontinalis at the subwatershed scale (mean subwatershed area ¼ 8,972 ha) across their native range in the eastern USA. This region represents approximately 25% of the species' entire native range and 70% of the U.S. portion of the native range. This assessment resulted in an updated and detailed range map of historical and current brook trout distribution in the study area. Based on known and predicted brook trout status, each subwatershed was classified according to the percentage of historical brook trout habitat that still maintained self-sustaining populations. We identified 1,660 subwatersheds (31%) in which over 50% of brook trout habitat was intact; 1,859 subwatersheds (35%) in which less than 50% of brook trout habitat was intact; 1,482 subwatersheds (28%) from which self-sustaining populations were extirpated; and 278 subwatersheds (5%) where brook trout were absent but the explanation for the absence was unknown (i.e., either extirpation from or a lack of historical occurrence in those subwatersheds). A classification and regression tree using five core subwatershed metrics (percent total forest, sulfate and nitrate deposition, percent mixed forest in the water corridor, percent agriculture, and road density) was a useful predictor of brook trout distribution and status, producing an overall correct classification rate of 71%. Among the intact subwatersheds, 94% had forested lands encompassing over 68% of the land base. Continued habitat loss from land use practices and the presence of naturalized exotic fishes threaten the remaining brook trout populations. The distribution of brook trout subwatershed status and related threshold metrics can be used for risk assessment and prioritization of conservation efforts.

SUMMARYTo assess water quality standards, measurements of water quality under the Clean Water Act are collected on a regular basis over a period of time. The data are analyzed to evaluate the percentage of samples exceeding the standard. One problem is that current data are limited by the time range and consequently the sample size is inadequate to provide necessary precision in parameter estimation. To address this issue, we present a Bayesian approach using a power prior to incorporate historical data and/or the data collected at adjacent stations. We develop a modified power prior approach and discuss its properties under the normal mean model. Several sets of water quality data are studied to illustrate the implementation of the power prior approach and its differences from alternative methods.

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Bias refers to the accuracy of a particular estimator. We evaluate bias, using analytic and simulation technics, for six measures of overlap: the likelihood ratio measure, the chi—square measure, the measure based on the Freeman—Tukey statistic, Morisita's adjusted index, Morista's original index, and Horn's information index. We present an exact formula for a seventh, the percentage similarity measure. We consider bias due to resource a sample size, total number of different resources, and evenness of resource distribution. Results indicate that of the seven measures, changes in evenness of resource of distribution produce significant bias only in the percentage similarity measure and Morista's adjusted index. All measures show increasing bias with increasing number of resources. For estimating unbiased overlap, Morisita's original measure of overlap gives the most accurate results, especially when using small sample sizes. The percentage similarity measure, one of the most commonly used measures among ecologists, is also one of the most biased and for this reason is not preferred.

Measures of niche breadth are discussed in relation to the distance between the resource use distribution and the resource availability distribution. Methods are developed for comparing breadth measures, testing a breadth measure equal to a given value, and for estimating confidence intervals. A new breadth measure is presented which has good statistical properties and is related to some commonly used niche overlap measures.