A Large, Uniform Sample of X-ray Emitting AGN: Selection Approach and an Initial Catalog from the ROSAT All-Sky and Sloan Digital Sky Surveys

Many open questions in X-ray astronomy are limited by the relatively small number of objects in uniform optically-identified samples, especially when rare subclasses are considered, or subsets isolated to search for evolution or correlations between wavebands. We describe initial results of a program aimed to ultimately yield 10^4 X-ray source identifications--a sample about an order of magnitude larger than earlier efforts. The technique employs X-ray data from the ROSAT All-Sky Survey (RASS), and optical imaging and spectroscopic followup from the Sloan Digital Sky Survey (SDSS). Optical objects in the SDSS catalogs are automatically cross-correlated with RASS X-ray source positions; then priorities for follow-on SDSS optical spectra of candidate counterparts are automatically assigned using an algorithm based on the known fx/fopt ratios for various classes of X-ray emitters. SDSS parameters for optical morphology, magnitude, colors, plus FIRST radio data, serve as proxies for object class. Initial application of this approach to 1400 deg^2 of sky provides a catalog of 1200 spectroscopically confirmed quasars/AGN that are probable RASS identifications. Most of the IDs are new, and only a few percent of the AGN are likely to be random superpositions. The magnitude and redshift ranges of the counterparts extend over 15<m<21 and 0.03<z<3.6. Although most IDs are quasars and Sy 1s, a variety of other AGN subclasses are also sampled. Substantial numbers of rare AGN are found, including more than 130 narrow-line Seyfert 1s and 45 BL Lac candidates. These results already provide a sizeable set of new IDs, show utility of the sample in multi-waveband studies, and demonstrate the capability of the RASS/SDSS approach to efficiently proceed towards the largest homogeneously selected/observed sample of X-ray emitting AGN. Abridged AbstractComment: 39 pages, 11 bitmapped figs (PDF view or print OK). Version accepted by AJ: slightly expanded sample, 1 new fig, minor modification

Model for RNA Binding and the Catalytic Site of the RNase Kid of the Bacterial parD Toxin–Antitoxin System

The toxin Kid and antitoxin Kis are encoded by the parD operon of Escherichia coli plasmid R1. Kid and its chromosomal homologues MazF and ChpBK have been shown to inhibit protein synthesis in cell extracts and to act as ribosome-independent endoribonucleases in vitro. Kid cleaves RNA preferentially at the 50 side of the A residue in the nucleotide sequence 50-UA(A/C)-30 of single-stranded regions. Here, we show that RNA cleavage by Kid yields two fragments with a 20:30-cyclic phosphate group and a free 50-OH group, respectively. The cleavage mechanism is similar to that of RNases A and T1, involving the uracil 20-OH group. Via NMR titration studies with an uncleavable RNA mimic, we demonstrate that residues of both monomers of the Kid dimer together form a concatenated RNA-binding surface. Docking calculations based on the NMR chemical shifts, the cleavage mechanism and previously reported mutagenesis data provide a detailed picture of the position of the AUACA fragment within the binding pocket. We propose that residues D75, R73 and H17 form the active site of the Kid toxin, where D75 and R73 are the catalytic base and acid, respectively. The RNA sequence specificity is defined by residues T46, S47, A55, F57, T69, V71 and R73. Our data show the importance of these residues for Kid function, and the implications of our results for related toxins, such as MazF, CcdB and RelE, are discussed

Near infrared spectroscopy for enforcement of European legislation concerning the use of animal by-products in animal feeds

The paper summarises the work done in the framework of two R&D projects aimed to demonstrate the contribution of Near Infrared Spectroscopy (NIRS) to help the enforcement of the European legislation governing the use of animal by-products in animal feeds. Three different types of animal feed products were studied: compound feeds (CFs), animal protein byproducts meals (APBPs) and animal fats by-products (AFBPs). The quantitative and qualitative chemometric models produced with a large collection of compound feed samples (n = 1005 ground and 523 unground) have demonstrated, that NIRS can be used for the detection and quantification of the meat and bone meal (MBM) added to compound feeds. Discriminant models produced with unground samples produced 100% of correctly classified samples in two cloned instruments placed in two different locations. The results also show that two dimensions NIR spectra of Animal By-Products (ABP, animal meals and fats) may contain information about the animal species or group of species from which the ABPs were produced. However, further work is needed to enlarge the sample bank and the spectral libraries with well authenticated samples in order to increase the robustness of the quantitative and qualitative NIRS models. The paper opens expectations for using NIRS for the enforcement of legislation concerning the use of ABPs in animal feeds. More research and demonstration efforts have to be done in order to obtain more definitive and robust predictive models and for optimising its implementation either at-line, on-line and in-line in feed factories and inspection laboratories

Prostaglandin F-2 alpha-induced Prostate Transmembrane Protein, Androgen Induced 1 mediates ovarian cancer progression increasing epithelial plasticity

Cellular mechanisms in basic and clinical gastroenterology and hepatolog