2,288 research outputs found
Long-Term Performance of Zero-Valent Iron Permeable Reactive Barriers: A Critical Review
Permeable reactive barriers (PRBs) have shown great promise as an alternative to pump and treat for the remediation of groundwater containing a wide array of contaminants including organics, metals, and radionuclides. Analyses to date have focused on individual case studies, rather than considering broad performance issues. In response to this need, this study analyzed data from field installations of in situ zero-valent iron (ZVI) PRBs to determine what parameters contribute to PRB failure. Although emphasis has been placed on losses of reactivity and permeability, imperfect hydraulic characterization was the most common cause of the few PRB failures reported in the literature. Graphical and statistical analyses suggested that internal EH, influent pH, and influent concentrations of alkalinity, NO3 − and Cl− are likely to be the strongest predictors of PRBs that could be at risk for diminished performance. Parameters often cited in the literature such as saturation indices, dissolved oxygen, and total dissolved solids did not seem to have much predictive capability. Because of the relationship between the predictive parameters and corrosion inhibition, it appears that reactivity of the ZVI, rather than the reduction in permeability, is more likely the factor that limits PRB longevity in the field. Due to the sparseness of field monitoring of parameters such as EH, the data available for these analyses were limited. Consequently, these results need to be corroborated as additional measurements become available.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63236/1/ees.2006.0071.pd
Subprime Mortgage Pricing: The Impact of Race, Ethnicity, and Gender on the Cost of Borrowing
The Galaxy Luminosity Function and Luminosity Density at Redshift z=0.1
Using a catalog of 147,986 galaxy redshifts and fluxes from the Sloan Digital Sky Survey (SDSS), we measure the galaxy luminosity density at z = 0.1 in five optical bandpasses corresponding to the SDSS bandpasses shifted to match their rest-frame shape at z = 0.1. We denote the bands (0.1)u, (0.1)g, (0.1)r, (0.1)i, (0.1)z with lambda(eff) = (3216; 4240; 5595; 6792; 8111 Angstrom), respectively. To estimate the luminosity function, we use a maximum likelihood method that allows for a general form for the shape of the luminosity function,fits for simple luminosity and number evolution, incorporates the flux uncertainties, and accounts for the flux limits of the survey. We find luminosity densities at z = 0.1 expressed in absolute AB magnitudes in a Mpc(3) to be (-14.10 +/- 0.15, -15.18 +/- 0.03, - 15.90 +/- 0.03, -16.24 +/- 0.03, -16.56 +/- 0.02) in ((0.1)u, (0.1)g, (0.1)r, (0.1)i, (0.1)z), respectively, for a cosmological model with Omega(0) = 0.3, Omega(Lambda) = 0.7, and h = 1 and using SDSS Petrosian magnitudes. Similar results are obtained using Sersic model magnitudes, suggesting that flux from outside the Petrosian apertures is not a major correction. In the (0.1)r band, the best-fit Schechter function to our results has phi* = (1.49 +/- 0.04) x 10(-2) h(3) Mpc(-3), M-* - 5 log(10) h = - 20.44 +/- 0.01, and alpha = - 1.05 +/- 0.01. In solar luminosities, the luminosity density in (0.1)r is (1.84 +/- 0.04) x 10(8) h L-0.1r,L-. Mpc(-3). Our results in the (0.1)g band are consistent with other estimates of the luminosity density, from the Two-Degree Field Galaxy Redshift Survey and the Millennium Galaxy Catalog. They represent a substantial change ( similar to 0.5 mag) from earlier SDSS luminosity density results based on commissioning data, almost entirely because of the inclusion of evolution in the luminosity function model
KL Estimation of the Power Spectrum Parameters from the Angular Distribution of Galaxies in Early SDSS Data
We present measurements of parameters of the 3-dimensional power spectrum of
galaxy clustering from 222 square degrees of early imaging data in the Sloan
Digital Sky Survey. The projected galaxy distribution on the sky is expanded
over a set of Karhunen-Loeve eigenfunctions, which optimize the signal-to-noise
ratio in our analysis. A maximum likelihood analysis is used to estimate
parameters that set the shape and amplitude of the 3-dimensional power
spectrum. Our best estimates are Gamma=0.188 +/- 0.04 and sigma_8L = 0.915 +/-
0.06 (statistical errors only), for a flat Universe with a cosmological
constant. We demonstrate that our measurements contain signal from scales at or
beyond the peak of the 3D power spectrum. We discuss how the results scale with
systematic uncertainties, like the radial selection function. We find that the
central values satisfy the analytically estimated scaling relation. We have
also explored the effects of evolutionary corrections, various truncations of
the KL basis, seeing, sample size and limiting magnitude. We find that the
impact of most of these uncertainties stay within the 2-sigma uncertainties of
our fiducial result.Comment: Fig 1 postscript problem correcte
Measuring the matter density using baryon oscillations in the SDSS
We measure the cosmological matter density by observing the positions of
baryon acoustic oscillations in the clustering of galaxies in the Sloan Digital
Sky Survey (SDSS). We jointly analyse the main galaxies and LRGs in the SDSS
DR5 sample, using over half a million galaxies in total. The oscillations are
detected with 99.74% confidence (3.0sigma assuming Gaussianity) compared to a
smooth power spectrum. When combined with the observed scale of the peaks
within the CMB, we find a best-fit value of Omega_m=0.256+0.029-0.024 (68%
confidence interval), for a flat Lambda cosmology when marginalising over the
Hubble parameter and the baryon density. This value of the matter density is
derived from the locations of the baryon oscillations in the galaxy power
spectrum and in the CMB, and does not include any information from the overall
shape of the power spectra. This is an extremely clean cosmological measurement
as the physics of the baryon acoustic oscillation production is well
understood, and the positions of the oscillations are expected to be
independent of systematics such as galaxy bias.Comment: 5 pages, 3 figures, updated to match version accepted by Ap
The First Hour of Extra-galactic Data of the Sloan Digital Sky Survey Spectroscopic Commissioning: The Coma Cluster
On 26 May 1999, one of the Sloan Digital Sky Survey (SDSS) fiber-fed
spectrographs saw astronomical first light. This was followed by the first
spectroscopic commissioning run during the dark period of June 1999. We present
here the first hour of extra-galactic spectroscopy taken during these early
commissioning stages: an observation of the Coma cluster of galaxies. Our data
samples the Southern part of this cluster, out to a radius of 1.5degrees and
thus fully covers the NGC 4839 group. We outline in this paper the main
characteristics of the SDSS spectroscopic systems and provide redshifts and
spectral classifications for 196 Coma galaxies, of which 45 redshifts are new.
For the 151 galaxies in common with the literature, we find excellent agreement
between our redshift determinations and the published values. As part of our
analysis, we have investigated four different spectral classification
algorithms: spectral line strengths, a principal component decomposition, a
wavelet analysis and the fitting of spectral synthesis models to the data. We
find that a significant fraction (25%) of our observed Coma galaxies show signs
of recent star-formation activity and that the velocity dispersion of these
active galaxies (emission-line and post-starburst galaxies) is 30% larger than
the absorption-line galaxies. We also find no active galaxies within the
central (projected) 200 h-1 Kpc of the cluster. The spatial distribution of our
Coma active galaxies is consistent with that found at higher redshift for the
CNOC1 cluster survey. Beyond the core region, the fraction of bright active
galaxies appears to rise slowly out to the virial radius and are randomly
distributed within the cluster with no apparent correlation with the potential
merger of the NGC 4839 group. [ABRIDGED]Comment: Accepted in AJ, 65 pages, 20 figures, 5 table
Characterization of lethal inhalational infection with Francisella tularensis in the common marmoset (Callithrix jacchus)
The intracellular Gram-negative pathogen Francisella tularensis is the causative agent of tularaemia and is prevalent in many countries in the northern hemisphere. To determine whether the common marmoset (Callithrix jacchus) would be a suitable non-human primate model of inhalational tularaemia, a pathophysiology study was undertaken. Ten animals were challenged with ∼102 c.f.u. F. tularensis strain SCHU S4 (F. tularensis subsp. tularensis). To look for trends in the infection, pairs of animals were sacrificed at 24 h intervals between 0 and 96 h post-challenge and blood and organs were assessed for bacteriology, pathology and haematological and immunological parameters. The first indication of infection was a raised core temperature at 3 days post-challenge. This coincided with a number of other factors: a rapid increase in the number of bacteria isolated from all organs, more pronounced gross pathology and histopathology, and an increase in the immunological response. As the disease progressed, higher bacterial and cytokine levels were detected. More extensive pathology was observed, with multifocal lesions seen in the lungs, liver and spleen. Disease progression in the common marmoset appears to be consistent with human clinical and pathological features of tularaemia, indicating that this may be a suitable animal model for the investigation of novel medical interventions such as vaccines or therapeutics
Single-Nucleotide Polymorphisms in Nucleotide Excision Repair Genes, Cigarette Smoking, and the Risk of Head and Neck Cancer
Cigarette smoking is associated with increased head and neck cancer (HNC) risk. Tobacco-related carcinogens are known to cause bulky DNA adducts. Nucleotide excision repair (NER) genes encode enzymes that remove adducts and may be independently associated with HNC, as well as modifiers of the association between smoking and HNC
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