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Search Results: 1 - 10 of 3437 matches for " Owen Hill "
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A relaxation of Steinberg's Conjecture
Owen Hill,Gexin Yu
Mathematics , 2012,
Abstract: A graph is $(c_1, c_2, ..., c_k)$-colorable if the vertex set can be partitioned into $k$ sets $V_1,V_2, ..., V_k$, such that for every $i: 1\leq i\leq k$ the subgraph $G[V_i]$ has maximum degree at most $c_i$. We show that every planar graph without 4- and 5-cycles is $(1, 1, 0)$-colorable and $(3,0,0)$-colorable. This is a relaxation of the Steinberg Conjecture that every planar graph without 4- and 5-cycles are properly 3-colorable (i.e., $(0,0,0)$-colorable).
A Comprehensive Radio and Optical Study of Abell 2256: Activity from an Infalling Group
Neal Miller,Frazer Owen,John Hill
Physics , 2003, DOI: 10.1086/374628
Abstract: Abell 2256 is a nearby (z~0.06), rich cluster of galaxies with fascinating observed properties across a range of wavelengths. Long believed to represent a cluster merger, recent X-ray and optical results have suggested that in addition to the primary cluster and subcluster there is evidence for a third, poorer system. We present wide-field, high sensitivity 1.4 GHz VLA radio observations of Abell 2256 in conjunction with optical imaging and additional spectroscopy. Over 40 cluster radio galaxies are identified, with optical spectroscopy indicating the emission source (star formation or AGN) for most of them. While the overall fraction of galaxies exhibiting radio emission is consistent with a large sample of other nearby clusters, we find an increase in the activity level of galaxies belonging to the third system (hereafter, the ``Group''). Specifically, the Group has relatively more star formation than both the primary cluster and main subcluster. The position of the Group is also coincident with the observed cluster radio relic. We suggest that the Group recently (~0.3 Gyr) merged with the primary cluster and that this merger, not the ongoing merger of the primary and the main subcluster, might be responsible for many of the unusual radio properties of Abell 2256. Furthermore, the greater star formation activity of the Group suggests that the infall of groups is an important driver of galaxy evolution in clusters.
Improving prostate cancer detection in veterans through the development of a clinical decision rule for prostate biopsy
Owen T Hill, Thomas J Mason, Skai W Schwartz, Philip R Foulis
BMC Urology , 2013, DOI: 10.1186/1471-2490-13-6
Abstract: This case–control study evaluated men from the Tampa, Florida, James A. Haley (JH) Veteran’s Administration (VA) (N = 1,378), from January 1, 1998, through April 15, 2005. To assess the PBCDR we did all of the following: 1) Identified biomarkers that are related to PC and have the capability of improving the efficiency of PC screening; 2) Developed statistical models to determine which can best predict the probability of PC; 3) Compared each potential model to PSA alone using Receiver Operator Characteristic (ROC) curves, to evaluate for improved overall effectiveness in PC detection and reduction in (negative) biopsies; and 4) Evaluated dose–response relationships between specified lab biomarkers (surrogates for extra-prostatic disease development) and PC progression.The following biomarkers were related to PC: hemoglobin (HGB) (OR = 1.42 95% CI 1.27, 1.59); red blood cell (RBC) count (OR = 2.52 95% CI 1.67, 3.78); PSA (OR = 1.04 95% CI 1.03, 1.05); and, creatinine (OR = 1.55 95% CI 1.12, 2.15). Comparing all PC stages versus non-cancerous conditions, the ROC curve area under the curve (AUC) enlarged (increasing the probability of correctly classifying PC): PSA (alone) 0.59 (95% CI 0.55, 0.61); PBCDR model 0.68 (95% CI 0.65, 0.71), and the positive predictive value (PPV) increased: PSA 44.7%; PBCDR model 61.8%. Comparing PC (stages II, III, IV) vs. other, the ROC AUC increased: PSA (alone) 0.63 (95% CI 0.58, 0.66); PBCDR model 0.72 (95% CI 0.68, 0.75), and the PPV increased: 20.6% (PSA); PBCDR model 55.3%.These results suggest evaluating certain common biomarkers in conjunction with PSA may improve PC prediction prior to biopsy. Moreover, these biomarkers may be more helpful in detecting clinically relevant PC. Follow-up studies should begin with replicating the study on different U.S. VA patients involving multiple practices.The number of men who undergo prostate biopsies to rule out prostate cancer (PC) increases annually (estimated at over one million per year)
The Cluster of Galaxies Surrounding Cygnus A
Frazer N. Owen,Michael J. Ledlow,Glenn E. Morrison,John M. Hill
Physics , 1997, DOI: 10.1086/310908
Abstract: We report optical imaging and spectroscopy of 41 galaxies in a 22 arcmin square region surrounding Cygnus A. The results show that there is an extensive rich cluster associated with Cygnus A of Abell richness at least 1 and possibly as high as 4. The velocity histogram has two peaks, one centered on Cygnus A, and a more significant peak redshifted by about 2060 km/s from the velocity of Cygnus A. The dynamical centroid of the spatial distribution is also shifted somewhat to the NW. However, statistical tests show only weak evidence that there are two distinct clusters. The entire system has a velocity dispersion of 1581 km/s which is slightly larger than other, well studied, examples of rich clusters.
Redshifts for a Sample of Radio-Selected Poor Clusters
Neal A. Miller,Michael J. Ledlow,Frazer N. Owen,John M. Hill
Physics , 2002, DOI: 10.1086/340694
Abstract: Multifiber optical spectroscopy has been performed on galaxies in the vicinity of strong, nearby radio galaxies. These radio galaxies were selected from the 3CR and B2 catalogs based on their exclusion from the Abell catalog, which is puzzling given the hypothesis that an external medium is required to confine the radio plasma of such galaxies. Velocities derived from the spectra were used to confirm the existence of groups and poor clusters in the fields of most of the radio galaxies. We find that all radio galaxies with classical FR I morphologies prove to reside in clusters, whereas the other radio galaxies often appear to be recent galaxy-galaxy mergers in regions of low galaxy density. These findings confirm the earlier result that the existence of extended X-ray emission combined with a statistical excess of neighboring galaxies can be used to identify poor clusters associated with radio galaxies.
A Large-Scale Jet and FR I Radio Source in a Spiral Galaxy: The Host Properties and External Environment
Michael J. Ledlow,Frazer N. Owen,Min S. Yun,John M. Hill
Physics , 2000, DOI: 10.1086/320458
Abstract: We have identified a large (~200 kpc), powerful double radio source whose host galaxy is clearly a disk and most likely a spiral. This FR I radio galaxy is located very near the center of the RC 0 cluster Abell 428. The existence of such an object violates a fundamental paradigm for radio loud AGN. In paper I, we showed that this object was most likely a spiral host with optical line ratios and colors consistent with an AGN. In this paper, we present new, higher resolution radio imaging, a radio/mm continuum spectrum for the nucleus, a detection of HI absorption against the bright radio core, an upper-limit to CO and the gas mass, and 70 optical redshifts. We confirm the existence of a radio jet at 20cm extending 42 kpc into the southern lobe. At 3.6cm, we also detect a nuclear jet similar in length to that in M87 but 10 times weaker. We believe that this is the first detection of a radio jet on these scales in a disk or spiral host galaxy. The nuclear radio spectrum is similar to many blazar or QSO like objects, suggesting that the galaxy harbors an imbedded and obscured AGN. We model a turnover in the spectrum at low frequencies as Free-Free absorption. We detect very strong and narrow HI absorption with nearly the entire 20 cm core continuum absorbed, implying an unusually large optical depth (tau~1). We suggest that the nucleus is seen through a disk-like distribution of ISM gas, possibly through a spiral arm or a warp to account for the high column density. From the radial velocities, we find that A428 is in fact made up of at least 2 clumps of galaxies separated by 3300 km/s, which are imbedded in a nearly continuous distribution of galaxies over 13000 km/s in velocity. Thus, the environment resembles a poor group within a filament viewed end-on.
Radio-selected Galaxies in Very Rich Clusters at z < 0.25: I. Multi-wavelength Observations and Data Reduction Techniques
G. E. Morrison,F. N. Owen,M. J. Ledlow,W. C. Keel,J. M. Hill,W. Voges,T. Herter
Physics , 2002, DOI: 10.1086/368014
Abstract: Radio observations were used to detect the `active' galaxy population within rich clusters of galaxies in a non-biased manner that is not plagued by dust extinction or the K-correction. We present wide-field radio, optical (imaging and spectroscopy), and ROSAT All-Sky Survey (RASS) X-ray data for a sample of 30 very rich Abell (R > 2) cluster with z < 0.25. The VLA radio data samples the ultra-faint radio (L(1.4 GHz) > 2E22 W/Hz) galaxy population within these extremely rich clusters for galaxies with M_R < -21. This is the largest sample of low luminosity 20 cm radio galaxies within rich Abell clusters collected to date. The radio-selected galaxy sample represents the starburst (Star formation rate > 5 M_sun/yr) and active galactic nuclei (AGN) populations contained within each cluster. Archival and newly acquired redshifts were used to verify cluster membership for most (~95%) of the optical identifications. Thus we can identify all the starbursting galaxies within these clusters, regardless of the level of dust obscuration that would affect these galaxies being identified from their optical signature. Cluster sample selection, observations, and data reduction techniques for all wavelengths are discussed.
Cardiometabolic Risk Markers in Indian Children: Comparison with UK Indian and White European Children
Claire M. Nightingale, Ghattu V. Krishnaveni, Alicja R. Rudnicka, Christopher G. Owen, Sargoor R. Veena, Jacqueline C. Hill, Derek G. Cook, Caroline H. D. Fall, Peter H. Whincup
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0036236
Abstract: Objective UK Indian adults have higher risks of coronary heart disease and type 2 diabetes than Indian and UK European adults. With growing evidence that these diseases originate in early life, we compared cardiometabolic risk markers in Indian, UK Indian and white European children. Methods Comparisons were based on the Mysore Parthenon Birth Cohort Study (MPBCS), India and the Child Heart Health Study in England (CHASE), which studied 9–10 year-old children (538 Indian, 483 UK Indian, 1375 white European) using similar methods. Analyses adjusted for study differences in age and sex. Results Compared with Mysore Indians, UK Indians had markedly higher BMI (% difference 21%, 95%CI 18 to 24%), skinfold thickness (% difference 34%, 95%CI 26 to 42%), LDL-cholesterol (mean difference 0.48, 95%CI 0.38 to 0.57 mmol/L), systolic BP (mean difference 10.3, 95% CI 8.9 to 11.8 mmHg) and fasting insulin (% difference 145%, 95%CI 124 to 168%). These differences (similar in both sexes and little affected by adiposity adjustment) were larger than those between UK Indians and white Europeans. Compared with white Europeans, UK Indians had higher skinfold thickness (% difference 6.0%, 95%CI 1.5 to 10.7%), fasting insulin (% difference 31%, 95%CI 22 to 40%), triglyceride (% difference 13%, 95%CI 8 to 18%) and LDL-cholesterol (mean difference 0.12 mmol/L, 95%CI 0.04 to 0.19 mmol/L). Conclusions UK Indian children have an adverse cardiometabolic risk profile, especially compared to Indian children. These differences, not simply reflecting greater adiposity, emphasize the need for prevention strategies starting in childhood or earlier.
Corporate Character Formation and CSR: The Function of Habit and Practice in the Mining Industry  [PDF]
John R. Owen, Deanna Kemp
American Journal of Industrial and Business Management (AJIBM) , 2014, DOI: 10.4236/ajibm.2014.45030
Abstract:

The mining industry provides a rich context through which to engage the practical and ethical limits of Corporate Social Responsibility (CSR). Recent debates in organizational ethics have drawn attention to institutional constraints which inhibit awareness raising and ethical practice within corporate settings. During the last decade, the mining industry has come under increasing pressure to improve its environmental, social and ethical performance. In an effort to respond to these more ethically-orientated external expectations, the mining industry has developed a range of internal regulatory mechanisms and process, which can be applied individually or in conjunction with other companies and organizations. This combination of internal and external drivers indicates a growing imperative for mining companies to ground CSR principles in their day-to-day operating practices. The challenge is to avoid organizational rules and procedures for CSR that lack depth and meaning and which fail to result in the wise and courageous use of personal agency. Instead mining companies must work to establish appropriate mechanisms that will see ethical norms adopted as organizational principles that guide, and result in, improved corporate conduct. Using the Aristotelean notion of “character formation”, the authors offer practical considerations for how this might occur in the mining industry.

Selection for prolificacy in the Cambridge sheep
JB Owen
Genetics Selection Evolution , 1982, DOI: 10.1186/1297-9686-14-4-579c
Abstract:
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