The PSCz catalogue

We present the catalogue, mask, redshift data and selection function for the PSC z survey of 15 411 IRAS galaxies across 84 per cent of the sky. Most of the IRAS data are taken from the Point Source Catalog, but this has been supplemented and corrected in various ways to improve the completeness and uniformity. We quantify the known imperfections in the catalogue, and we assess the overall uniformity, completeness and data quality. We find that overall the catalogue is complete and uniform to within a few per cent at high latitudes and 10 per cent at low latitudes. Ancillary information, access details, guidelines and caveats for using the catalogue are given.     

The Second APM UKST Colour Survey for z > 4 quasars

We present the spectra, positions, and finding charts for 31 bright ( R <19.3) colour-selected quasars covering the redshift range z =3.85–4.78, with four having redshifts z >4.5. The majority are in the southern sky ( δ <−25°). The quasar candidates were selected for their red ( B _J− R ≳2.5) colours from UK or POSSII Schmidt Plates scanned at the Automated Plate Measuring (APM) facility in Cambridge. Low-resolution (≳ 10 Å) spectra were obtained to identify the quasars, primarily at the Las Campanas Observatory. The highest redshift quasar in our survey is at z ≈4.8 ( R =18.7) and its spectrum shows a damped Ly α absorption system at z =4.46. This is currently the highest redshift damped Ly α absorber detected. Five of these quasars exhibit intrinsic broad absorption line features. Combined with the previously published results from the first part of the APM United Kingdom Schmidt Telescope (UKST) survey we have now surveyed a total of ∼8000 deg² of sky i.e. 40 per cent of the high galactic latitude (| b |>30°) sky, resulting in 59 optically selected quasars in the redshift range 3.85 to 4.78; 49 of which have z ≥4.00.     

Identification of a c-Ki-ras oncogene in a neoplasm isolated from winter flounder

It has been shown that a high incidence of hepatomas are present in winter flounder (Pseudopleuronectes americanus) obtained from Boston Harbor. It has been suggested that this may be a consequence of locally high levels of polycyclic aromatic hydrocarbons found in the sediment. The purpose of this study was to determine whether transforming DNA sequences (oncogenes) could be identified in liver neoplasms isolated from feral fish and to study their relationship to their corresponding proto-oncogenes. The ultimate aim of this study is to characterize novel mutations in oncogenes derived from these hepatomas to correlate these genetic changes with chemical exposure history. Genomic DNA was isolated from liver neoplasms and transfected into NIH3T3 mouse fibroblasts to assay for the formation of transformed foci. DNA was prepared from transformed foci and analyzed by Southern blot hybridization to viral DNA probes specific for c-Ki-ras and c-Ha-ras DNA sequences. A c-Ki-ras oncogene was identified in a transformant derived from one of the two tumors assayed. Comparison of c-Ki-ras DNA sequences of tumor and tumor-derived transformants indicate that the activated oncogene in the transformant is of flounder origin. We are currently analyzing the flounder oncogene for activating point mutations by primer-directed enzymatic amplification and direct sequence analysis.     

Fraction of young water as an indicator of aquifer vulnerability along two regional flow paths in the Mississippi embayment aquifer system,southeastern USA

Wells along two regional flow paths were sampled to characterize changes in water quality and the vulnerability to contamination of the Memphis aquifer across a range of hydrologic and land-use conditions in the southeastern United States. The flow paths begin in the aquifer outcrop area and end at public supply wells in the confined parts of the aquifer at Memphis, Tennessee. Age-date tracer (e.g. SF₆, ³H, ¹⁴C) data indicate that a component of young water is present in the aquifer at most locations along both flow paths, which is consistent with previous studies at Memphis that documented leakage of shallow water into the Memphis aquifer locally where the overlying confining unit is thin or absent. Mixtures of young and old water were most prevalent where long-term pumping for public supply has lowered groundwater levels and induced downward movement of young water. The occurrence of nitrate, chloride and synthetic organic compounds was correlated to the fraction of young water along the flow paths. Oxic conditions persisted for 10 km or more down dip of the confining unit, and the presence of young water in confined parts of the aquifer suggest that contaminants such as nitrate-N have the potential for transport. Long-term monitoring data for one of the flow-path wells screened in the confined part of the aquifer suggest that the vulnerability of the aquifer as indicated by the fraction of young water is increasing over time.     

Infrared observations of gravitational lensing in Abell 2219 with CIRSI

We present the first detection of a gravitational depletion signal at near-infrared wavelengths, based on deep panoramic images of the cluster Abell 2219 ( z =0.22) taken with the Cambridge Infrared Survey Instrument (CIRSI) at the prime focus of the 4.2-m William Herschel Telescope. Infrared studies of gravitational depletion offer a number of advantages over similar techniques applied at optical wavelengths, and can provide reliable total masses for intermediate-redshift clusters. Using the maximum-likelihood technique developed by Schneider, King & Erben, we detect the gravitational depletion at the 3 confidence level. By modelling the mass distribution as a singular isothermal sphere and ignoring the uncertainty in the unlensed number counts, we find an Einstein radius of (66 per cent confidence limit). This corresponds to a projected velocity dispersion of _v 800 km s¹, in agreement with constraints from strongly lensed features. For a Navarro, Frenk & White mass model, the radial dependence observed indicates a best-fitting halo scalelength of 125 h ¹ kpc. We investigate the uncertainties arising from the observed fluctuations in the unlensed number counts, and show that clustering is the dominant source of error. We extend the maximum-likelihood method to include the effect of incompleteness, and discuss the prospects of further systematic studies of lensing in the near-infrared band.     

Assessing the Relative Bioavailability of DOC in Regional Groundwater Systems

It has been hypothesized that the degree to which a hyperbolic relationship exists between concentrations of dissolved organic carbon (DOC) and dissolved oxygen (DO) in groundwater may indicate the relative bioavailability of DOC. This hypothesis was examined for 73 different regional aquifers of the United States using 7745 analyses of groundwater compiled by the National Water Assessment (NAWQA) program of the U.S. Geological Survey. The relative reaction quotient (RRQ), a measure of the curvature of DOC concentrations plotted versus DO concentrations and regressed to a decaying hyperbolic equation, was used to assess the relative bioavailability of DOC. For the basalt aquifer of Oahu, Hawaii, RRQ values were low (0.0013 mM^?2), reflecting a nearly random relationship between DOC and DO concentrations. In contrast, on the island of Maui, treated sewage effluent injected into a portion of the basalt aquifer resulted in pronounced hyperbolic DOC‐DO behavior and a higher RRQ (142 mM^?2). RRQ values for the 73 aquifers correlated positively with mean concentrations of ammonia, dissolved iron, and manganese, and correlated negatively with mean pH. This indicates that greater RRQ values are associated with greater concentrations of the final products of microbial reduction reactions. RRQ values and DOC concentrations were negatively correlated with the thickness of the unsaturated zone (UNST) and depth to the top of the screened interval. Finally, RRQ values were positively correlated with mean annual precipitation (MAP), and the highest observed RRQ values were associated with aquifers receiving MAP rates ranging between 900 and 1300 mm/year. These results are uniformly consistent with the hypothesis that the hyperbolic behavior of DOC‐DO plots, as quantified by the RRQ metric, can be an indicator of relative DOC bioavailability in groundwater systems.