12,656 research outputs found

    Proton and neutron electromagnetic form factors and uncertainties

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    We determine the nucleon electromagnetic form factors and their uncertainties from world electron scattering data. The analysis incorporates two-photon exchange corrections, constraints on the low-Q2 and high-Q2 behavior, and additional uncertainties to account for tensions between different data sets and uncertainties in radiative corrections.Comment: 9 pages, 7 figures. Published on Phys. Lett.

    Substructure in clusters containing wide-angle tailed radio galaxies. I. New redshifts

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    We present new redshifts and positions for 635 galaxies in nine rich clusters containing Wide-Angle Tailed (WAT) radio galaxies. Combined with existing data, we now have a sample of 18 WAT-containing clusters with more than 10 redshifts. This sample contains a substantial portion of the WAT clusters in the VLA 20 cm survey of Abell clusters, including 75% of WAT clusters in the complete survey (z0.09. It is a representative sample which should not contain biases other than selection by radio morphology. We graphically present the new data using histograms and sky maps. A semi-automated procedure is used to search for emission lines in the spectra in order to add and verify galaxy redshifts. We find that the average apparent fraction of emission line galaxies is about 9% in both the clusters and the field. We investigate the magnitude completeness of our redshift surveys with CCD data for a test case, Abell 690. This case indicates that our galaxy target lists are deeper than the detection limit of a typical MX exposure, and they are 82% complete down to R=19.0. The importance of the uniformity of the placement of fibers on targets is posited, and we evaluate this in our datasets. We find some cases of non-uniformities which may influence dynamical analyses. A second paper will use this database to look for correlations between the WAT radio morphology and the cluster's dynamical state.Comment: 15 pages, 5 figures, 7 tables. To appear in the Astronomical Journa

    Layered Model for Radiation-Induced Chemical Evolution of Icy Surface Composition on Kuiper Belt and Oort Cloud Bodies

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    The diversity of albedos and surface colors on observed Kuiper Belt and Inner Oort Cloud objects remains to be explained in terms of competition between primordial intrinsic versus exogenic drivers of surface and near-surface evolution. Earlier models have attempted without success to attribute this diversity to the relations between surface radiolysis from cosmic ray irradiation and gardening by meteoritic impacts. A more flexible approach considers the different depth-dependent radiation profiles produced by low-energy plasma, suprathermal, and maximally penetrating charged particles of the heliospheric and local interstellar radiation environments. Generally red objects of the dynamically cold (low inclination, circular orbit) Classical Kuiper Belt might be accounted for from erosive effects of plasma ions and reddening effects of high energy cosmic ray ions, while suprathermal keV-MeV ions could alternatively produce more color neutral surfaces. The deepest layer of more pristine ice can be brought to the surface from meter to kilometer depths by larger impact events and potentially by cryovolcanic activity. The bright surfaces of some larger objects, e.g. Eris, suggest ongoing resurfacing activity. Interactions of surface irradiation, resultant chemical oxidation, and near-surface cryogenic fluid reservoirs have been proposed to account for Enceladus cryovolcanism and may have further applications to other icy irradiated bodies. The diversity of causative processes must be understood to account for observationally apparent diversities of the object surfaces

    Environmental Geology of Lake and Porter Counties, Indiana - An Aid to Planning

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    Indiana Geological Survey Special Report 11; Indiana Geological Survey Environmental Study 8Lake and Porter Counties are subdivided into three physiographically and geologically distinct regions: (1) the Calumet Lacustrine Plain, (2) the ValparaisoMorainal Area, and (3) the Kankakee Outwash and Lacustrine Plain. The surficial deposits of these regions, which range in thickness from 40 feet near the Kankakee River to more than 250 feet near Valparaiso, Ind,. Are the products, either directly or indirectly, of the Wisconsinan Age of glaciation. The Calumet lake plain is characterized by low-lying complexly intermixed clay, sand, and silt deposits, mostly of glacial Lake Chicago origin , The Valparaiso Moraine forms high ground in the two counties and is composed of clay-rich to fine sandy till. Sand and fine gravel deposits constitute the bulk of the Kankakee Outwash and Lacustrine Plain, this area being the low-lying outwash and flood plain for the glacially derived rivers as well as for the present Kankakee River. The two-county area has an abundance of geologic and geologically related resources; some of the most important are: (1) groundwater of the Kankakee Outwash and Lacustrine Plain and Valparaiso Morainal Area, (2) sand deposits of glacial Lake Chicago and of recent origin, (3) rich soils developed on the Valparaiso Moraine and Kankakee outwash plain, and (4) surface water in the form of streams, rivers, and small lakes. Some of these resources have already been damaged during the course of man’s habitation and use, but all can, with proper understanding of the problems and the willingness to act, be saved from further unnecessary degradation. Certain kinds of land use, which are partly dependent on the local geology, are potential sources of difficulty. These include (1) siting and use of sanitary landfills, (2) placement of septic systems, sewage lagoons, and industrial holding ponds, (3) management of flood plains, (4) development of the Lake Michigan shoreline, (5) construction of all kinds in areas where little is known about the engineering and hydrologic properties of the materials, (6) disposal of industrial wastes by deep well injection methods, and (7) development of groundwater supplies without sufficient hydrologic and geologic data. The environmental problems of Lake and Porter Counties, are related to geology, are as varied and complex as the materials themselves. Specific questions related to a given problem are best answered by the competent consultant equipped to do so. This report, though intended to supply valuable geologic information on a variety of land use related subjects, should not replace onsite evaluation of the salient parameters involved with each problem that potentially arises whenever man uses earth materials or otherwise disturbs or rearranges the natural earth condition.Indiana Department of Natural Resource

    The Dynamics of Abell 2125

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    We present 371 galaxy velocities in the field of the very rich cluster Abell 2125 (z~0.25). These were determined using optical spectroscopy collected over several years from both the WIYN 3.5m telescope and NOAO Mayall 4m telescope. Prior studies at a variety of wavelengths (radio, optical, and X-ray) have indicated that A2125 is a likely cluster-cluster merger, a scenario which we are able to test using our large velocity database. We identified 224 cluster galaxies, which were subjected to a broad range of statistical tests using both positional and velocity information to evaluate the cluster dynamics and substructure. The tests confirmed the presence of substructures within the Abell 2125 system at high significance, demonstrating that A2125 is a complex dynamical system. Comparison of the test results with existing simulations strengthens the merger hypothesis, and provides clues about the merger geometry and stage. The merger model for the system can reconcile A2125's low X-ray temperature and luminosity with its apparently high richness, and might also explain A2125's high fraction of active galaxies identified in prior radio and optical studies.Comment: 34 pages, including tables and 3 color figures; to appear in Ap

    Increasing Usage of ESL Instructional Practices in a Rural County Elementary School

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    The study setting is one elementary school located in a remote rural county school district in a mountain western state. Implementing a specific set of procedures, ESL Instructional Improvement Process, educators examined and increased use of research-based ESL instructional practices in the education of English learners (ELs). A key feature of the piloted process is educator self-assessment of instructional practices, resulting in the development of workshop sessions and action items, and completion of classroom observations. Researchers found that the process proved effective in increasing rural educators’ knowledge and application of ESL best practices. Self-assessment was highly effective in helping educators examine existing instructional practices, leading to relevant workshop sessions and classroom implementation of ESL action items. Numerous examples of the use of research-based ESL instructional practices as a result of this project are provided, along with suggestions for further research to improve the education of ELs in rural county schools

    A Search for the Damped Ly-alpha Absorber at z=1.86 toward QSO 1244+3443 with NICMOS

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    We have carried out a high-resolution imaging search for the galaxy associated with the damped Lyman-alpha (DLA) absorber at z=1.859 toward the z_{em}=2.48 quasar QSO 1244+3443, using the HST and the NICMOS. Images were obtained in the broad filter F160W and the narrow filter F187N with camera 2 on NICMOS with the goal of detecting the rest-frame optical continuum and the H-alpha line emission from the DLA. After PSF subtraction, two weak features are seen at projected separations of 0.16-0.24" from the quasar. Parts of these features may be associated with the DLA absorber, although we cannot completely rule out that they could be artifacts of the point spread function (PSF). If associated with the DLA, the objects would be ~1-2 h_{70}^{-1} kpc in size with integrated flux densities of 2.5 and 3.3 mu Jy in the F160W filter, implying luminosities at lambda_{central}=5600 A in the DLA rest frame of 4.4-5.9 x 10^{9} h_{70}^{-2} L_{solar} at z=1.86, for q0=0.5. However, no significant H-alpha line emission is seen from these objects, suggesting low star formation rates (SFRs). Our 3 sigma upper limit on the SFR in the DLA is 1.3 h_{70}^{-2} M_{solar}/yr for q0 = 0.5 (2.4 h_{70}^{-2} M_{solar} yr^{-1} for q0 = 0.1). This together with our earlier result for LBQS 1210+1731 mark a significant improvement over previous constraints on the star formation rates of DLAs. A combination of low SFR and some dust extinction is likely to be responsible for the lack of H-alpha emission. Alternatively, the objects, may be associated with the quasar host galaxy. In any case, our observations suggest that the DLA is not a large bright proto-disk, but a compact object or a low-surface brightness galaxy. If the two features are PSF artifacts then the constraints on DLA properties are even more severe.Comment: 28 pages, 9 figures. Accepted for publication in The Astrophysical Journal. Figures are given at a slightly lower resolution here, to decrease file sizes. The higher resolution versions can be found in the Ap
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