We discuss the optical and radio properties of ∼30,000 FIRST (radio, 20 cm, sensitive to 1 mJy) sources positionally associated within 1.5 arcsec with an SDSS (optical, sensitive to r * ∼22.2) source in 1230 deg 2 of sky. The matched sample represents ∼30% of the 108,000 FIRST sources and 0.1% of the 2.5 × 10 7 SDSS sources in the studied region. SDSS spectra are available for 4,300 galaxies and 1,154 quasars from the matched sample, and for a control sample of 140,000 galaxies and 20,000 quasars in 1030 deg 2 of sky. This large and unbiased catalog of optical identifications provides much firmer statistical footing for existing results and allows several new findings.The majority (83%) of the FIRST sources identified with an SDSS source brighter than r * =21 are optically resolved; the fraction of resolved objects among the matched sources is a function of the radio flux, increasing from ∼50% at the bright end to ∼90% at the FIRST faint limit. Nearly all optically unresolved radio sources have non-stellar colors indicative of quasars. We estimate an upper limit of ∼5% for the fraction of quasars with broad-band optical colors indistinguishable from those of stars. The distribution of quasars in the radio flux -optical flux plane supports the existence of the "quasar radio-dichotomy"; 8±1% of all quasars with i * <18.5 are radio-loud and this fraction seems independent of redshift and optical luminosity. The radio-loud quasars have a redder median color by 0.08±0.02 mag, and show a 3 times larger fraction of objects with extremely red colors.FIRST galaxies represent 5% of all SDSS galaxies with r * <17.5, and 1% for r * <20, and are dominated by red (u * − r * >2.22) galaxies, especially those with r * >17.5. Magnitude and redshift limited samples show that radio galaxies have a different optical luminosity distribution than non-radio galaxies selected by the same criteria; when galaxies are further separated by their colors, this result remains valid for both blue and red galaxies. For a given optical luminosity and redshift, the observed optical colors of radio-galaxies are indistinguishable from those of all SDSS galaxies selected by identical criteria. The distributions of radio-to-optical flux ratio are similar for blue and red galaxies in redshift-limited samples; this similarity implies that the difference in their luminosity functions, and resulting selection effects, are the dominant cause for the preponderance of red radio galaxies in flux-limited samples. The fraction of radio galaxies whose emission line ratios indicate an AGN (30%) rather than a starburst origin is 6 times larger than the corresponding fraction for all SDSS galaxies (r * <17.5). We confirm that the AGN-to-starburst galaxy number ratio increases with radio flux, and find that radio emission from AGNs is more concentrated than radio emission from starburst galaxies.

We investigate the overall continuum and emission-line properties of quasars as a function of their optical/ UV spectral energy distributions. Our sample consists of 4576 quasars from the Sloan Digital Sky Survey (SDSS) that were chosen using homogeneous selection criteria. Expanding on our previous work, which demonstrated that the optical/UV color distribution of quasars is roughly Gaussian but with a red tail, here we distinguish between (1) quasars that have intrinsically blue (optically flat) power-law continua, (2) quasars that have intrinsically red (optically steep) power-law continua, and (3) quasars whose colors are inconsistent with a single power-law continuum. We find that 273 (6.0%) of the quasars in our sample fall into the latter category and appear to be redder because of SMC-like dust extinction and reddening rather than because of synchrotron emission. Even though the SDSS quasar survey is optically selected and flux-limited, we demonstrate that it is sensitive to dust reddened quasars with E(BÀV ) d 0.5, assuming a classical SMC extinction curve. The color distribution of our SDSS quasar sample suggests that the population of moderately dust reddened, but otherwise normal (i.e., type 1) quasars is smaller than the population of unobscured quasars: we estimate that a further 10% of the quasar population with M i < À25.61 is missing from the SDSS sample because of extinction, bringing the total fraction of dust-reddened quasars to 15% of broad-line quasars. We also investigate the emission-and absorption-line properties of these quasars as a function of color and comment on how some of these results relate to Boroson-Green-type eigenvectors. Quasars with intrinsically red (optically steep) powerlaw continua tend to have narrower Balmer lines and weaker C iv, C iii], He ii, and 3000 Å bump emission as compared with bluer (optically flatter) quasars. The change in strength of the 3000 Å bump appears to be dominated by the Balmer continuum and not by Fe ii emission. The dust-reddened quasars have even narrower Balmer lines and weaker 3000 Å bumps, in addition to having considerably larger equivalent widths of [O ii] and [O iii] emission. The fraction of broad absorption line quasars (BALQSOs) increases from $3.4% for the bluest quasars to perhaps as large as 20% for the dust-reddened quasars, but the intrinsic color distribution will be much bluer if all BALQSOs are affected by dust reddening.

Carcinoma does arise in the midst of the anorectal fistulas and abscesses of Crohn's disease. Carcinoma arising in a Crohn's disease fistula can be very difficult to diagnose. Examination may be limited by pain, stricture, or induration of the perianal and perineal tissues. Examination under anesthesia can also overlook the lesion. Diagnostic examination under anesthesia yields increases with biopsies or curettage of the fistulous tracts.

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We demonstrate that the design of the Sloan Digital Sky Survey (SDSS) filter system and the quality of the SDSS imaging data are sufficient for determining accurate and precise photometric redshifts (``photo-z''s) of quasars. Using a sample of 2625 quasars, we show that photo-z determination is even possible for z<=2.2 despite the lack of a strong continuum break that robust photo-z techniques normally require. We find that, using our empirical method on our sample of objects known to be quasars, approximately 70% of the photometric redshifts are correct to within delta z = 0.2; the fraction of correct photometric redshifts is even better for z>3. The accuracy of quasar photometric redshifts does not appear to be dependent upon magnitude to nearly 21st magnitude in i'. Careful calibration of the color-redshift relation to 21st magnitude may allow for the discovery of on the order of 10^6 quasars candidates in addition to the 10^5 quasars that the SDSS will confirm spectroscopically. We discuss the efficient selection of quasar candidates from imaging data for use with the photometric redshift technique and the potential scientific uses of a large sample of quasar candidates with photometric redshifts.Comment: 29 pages, 8 figures, submitted to A

We present a catalog of 100,563 unresolved, UV-excess (UVX) quasar candidates to g = 21 from 2099 deg 2 of the Sloan Digital Sky Survey (SDSS) Data Release One (DR1) imaging data. Existing spectra of 22,737 sources reveals that 22,191 (97.6%) are quasars; accounting for the magnitude dependence of this efficiency, we estimate that 95,502 (95.0%) of the objects in the catalog are quasars.-2 -Such a high efficiency is unprecedented in broad-band surveys of quasars. This "proof-of-concept" sample is designed to be maximally efficient, but still has 94.7% completeness to unresolved, g 19.5, UVX quasars from the DR1 quasar catalog. This efficient and complete selection is the result of our application of a probability density type analysis to training sets that describe the 4-D color distribution of stars and spectroscopically confirmed quasars in the SDSS. Specifically, we use a non-parametric Bayesian classification, based on kernel density estimation, to parameterize the color distribution of astronomical sources -allowing for fast and robust classification. We further supplement the catalog by providing photometric redshifts and matches to FIRST/VLA, ROSAT, and USNO-B sources. Future work needed to extend the this selection algorithm to larger redshifts, fainter magnitudes, and resolved sources is discussed. Finally, we examine some science applications of the catalog, particularly a tentative quasar number counts distribution covering the largest range in magnitude (14.2 < g < 21.0) ever made within the framework of a single quasar survey.

For the past 20 years, internal anal sphincterotomy has generally been considered to be the standard operation for an anal fissure. We sought an alternative form of treatment because of the wound complications inherent in this operation. Anal dilatation, precisely performed with a Parks' retractor opened to 4.8 cm or with a 40-mm rectosigmoid balloon, has been found to cure successfully the fissure in 93 percent and 94 percent, respectively, of each group and to be associated with fewer complications.

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