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Search Results: 1 - 10 of 138877 matches for " K. Borne "
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Integral Field Spectroscopy of Mrk 273: Mapping 10^3 km/s Gas Flows and an Off-Nucleus Seyfert 2 Nebula
L. Colina,S. Arribas,K. Borne
Physics , 1999, DOI: 10.1086/312389
Abstract: Integral field optical spectroscopy with the INTEGRAL fiber-based systemis used to map the extended ionized regions and gas flows in Mrk 273, one of the closest Ultraluminous Infrared galaxies (ULIRGs). The Hbeta and [OIII]5007 maps show the presence of two distinct regions separated by 4'' (3.1 kpc) along position angle (PA) 240. The northeastern region coincides with the optical nucleus of the galaxy and shows the spectral characteristics of LINERs. The southwestern region is dominated by [OIII] emission and is classified as a Seyfert 2. Therefore, in the optical, Mrk 273 is an ultraluminous infrared galaxy with a LINER nucleus and an extended off-nucleus Seyfert 2 nebula. The kinematics of the [OIII] ionized gas shows (i) the presence of highly disturbed gas in the regions around the LINER nucleus, (ii) a high-velocity gas flow with a peak-to-peak amplitude of 2.4 x 10^3 km/s, and (iii) quiescent gas in the outer regions (at 3 kpc). We hypothesize that the high-velocity flow is the starburst-driven superwind generated in an optically obscured nuclear starburst, and that the quiescent gas is directly ionized by a nuclear source, like the ionization cones typically seen in Seyfert galaxies.
Evidence for Multiple Mergers among Ultraluminous IR Galaxies (ULIRGs): Remnants of Compact Groups?
K. D. Borne,H. Bushouse,R. A. Lucas,L. Colina
Physics , 1999, DOI: 10.1086/312461
Abstract: In a large sample of ULIRGs imaged with HST, we have identified a significant subsample that shows evidence for multiple mergers. The evidence is seen among two classes of ULIRGs: (1) those with multiple remnant nuclei in their core, sometimes accompanied by a complex system of tidal tails; and (2) those that are in fact dense groupings of interacting (soon-to-merge) galaxies. We conservatively estimate that, in the redshift range 0.05
HST Observations of the Serendipitous X-ray Companion to Mrk 273: Cluster at z=0.46?
K. D. Borne,L. Colina,H. Bushouse,R. A. Lucas
Physics , 1999, DOI: 10.1086/308132
Abstract: We have used HST I-band images to identify Mrk 273X, the very unusual high-redshift X-ray-luminous Seyfert 2 galaxy found by ROSAT in the same field-of-view as Mrk 273. We have measured the photometric properties of Mrk 273X and have also analyzed the luminosity distribution of the faint galaxy population seen in the HST image. The luminosity of the galaxy and the properties of the surrounding environment suggest that Mrk 273X is the brightest galaxy in a relatively poor cluster at a redshift near 0.46. Its off-center location in the cluster and the presence of other galaxy groupings in the HST image may indicate that this is a dynamically young cluster on the verge of merging with its neighboring clusters. We find that Mrk 273X is a bright featureless elliptical galaxy with no evidence for a disk. It follows the de Vaucouleurs (r^{1/4}) surface brightness law very well over a range of 8 magnitudes. Though the surface brightness profile does not appear to be dominated by the AGN, the galaxy has very blue colors that do appear to be produced by the AGN. Mrk 273X is most similar to the IC 5063 class of active galaxies --- a hybrid Sy 2 / powerful radio galaxy.
Scientific Data Mining in Astronomy
Kirk Borne
Physics , 2009,
Abstract: We describe the application of data mining algorithms to research problems in astronomy. We posit that data mining has always been fundamental to astronomical research, since data mining is the basis of evidence-based discovery, including classification, clustering, and novelty discovery. These algorithms represent a major set of computational tools for discovery in large databases, which will be increasingly essential in the era of data-intensive astronomy. Historical examples of data mining in astronomy are reviewed, followed by a discussion of one of the largest data-producing projects anticipated for the coming decade: the Large Synoptic Survey Telescope (LSST). To facilitate data-driven discoveries in astronomy, we envision a new data-oriented research paradigm for astronomy and astrophysics -- astroinformatics. Astroinformatics is described as both a research approach and an educational imperative for modern data-intensive astronomy. An important application area for large time-domain sky surveys (such as LSST) is the rapid identification, characterization, and classification of real-time sky events (including moving objects, photometrically variable objects, and the appearance of transients). We describe one possible implementation of a classification broker for such events, which incorporates several astroinformatics techniques: user annotation, semantic tagging, metadata markup, heterogeneous data integration, and distributed data mining. Examples of these types of collaborative classification and discovery approaches within other science disciplines are presented.
Fibrés paraboliques et champ des racines
Niels Borne
Mathematics , 2006,
Abstract: Following ideas of Nori, Biswas, ..., we show that given an integer r>0, a noetherian scheme X, and an effective Cartier divisor D on it, the parabolic vector bundles on (X,D) with weights multiples of 1/r (in the sense of Maruyama-Yokogawa) are equivalent to ordinary vector bundles on an orbifold, the stack of r-th roots associated to (X,D) (a twisted scheme in the sense of Abramovich-Vistoli). We use this fact to get some information on the finite parabolic bundles on the (pointed) projective line.
A relative Shafarevich theorem
Niels Borne
Mathematics , 2002,
Abstract: Suppose given a Galois etale cover Y -> X of proper non-singular curves over an algebraically closed field k of prime characteristic p. Let H be its Galois group, and G any finite extension of H by a p-group P. We give necessary and sufficient conditions on G to be the Galois group of an etale cover of X dominating Y -> X.
Cohomology of G-sheaves in positive characteristic
Niels Borne
Mathematics , 2002,
Abstract: Let X be a noetherian scheme defined over an algebraically closed field of positive characteristic p, and G be a finite group, of order divisible by p, acting on X. We introduce a refinement of the equivariant K-theory of X to take into account the information related to modular representation theory. As an application, in the 1-dimensional case, we generalize a modular Riemann-Roch theorem given by S.Nakajima, extending the link between Galois modules and wild ramification.
Sur les représentations du groupe fondamental d'une variété privée d'un diviseur à croisements normaux simples
Niels Borne
Mathematics , 2007,
Abstract: Given a projective variety X over an algebraically closed field of characteristic zero, we show that finite parabolic bundles along a fixed simple normal crossings divisor D are in one to one correspondence with representations of the \'etale fundamental group of X-D.
Stigma of People with HIV/AIDS in Sub-Saharan Africa: A Literature Review
Ngozi C. Mbonu,Bart van den Borne,Nanne K. De Vries
Journal of Tropical Medicine , 2009, DOI: 10.1155/2009/145891
Abstract: The aim of this literature review is to elucidate what is known about HIV/AIDS and stigma in Sub-Saharan Africa. Literature about HIV/AIDS and stigma in Sub-Saharan Africa was systematically searched in Pubmed, Medscape, and Psycinfo up to March 31, 2009. No starting date limit was specified. The material was analyzed using Gilmore and Somerville's (1994) four processes of stigmatizing responses: the definition of the problem HIV/AIDS, identification of people living with HIV/AIDS (PLWHA), linking HIV/AIDS to immorality and other negative characteristics, and finally behavioural consequences of stigma (distancing, isolation, discrimination in care). It was found that the cultural construction of HIV/AIDS, based on beliefs about contamination, sexuality, and religion, plays a crucial role and contributes to the strength of distancing reactions and discrimination in society. Stigma prevents the delivery of effective social and medical care (including taking antiretroviral therapy) and also enhances the number of HIV infections. More qualitative studies on HIV/AIDS stigma including stigma in health care institutions in Sub-Saharan Africa are recommended.
Gender-related power differences, beliefs and reactions towards people living with HIV/AIDS: an urban study in Nigeria
Ngozi C Mbonu, Bart Van den Borne, Nanne K De Vries
BMC Public Health , 2010, DOI: 10.1186/1471-2458-10-334
Abstract: We conducted in-depth semi-structured interviews, lasting 60 to 90 minutes, with 100 persons (40 members of the general public, 40 HCPs and 20 PLWHA) in Port Harcourt, Nigeria. The interviews were tape-recorded and transcribed verbatim. The Nvivo 7 computer package was used to analyze the data.There are similarities and differences between the general public and HCPs towards PLWHA in gender-related beliefs and reactions. For instance, although association with promiscuity and power differences were commonly acknowledged in the different groups, there are differences in how these reactions are shown; such as HCPs asking the female PLWHA to inform their partners to ensure payment of hospital bills. Women with HIV/AIDS in particular are therefore in a disadvantaged position with regard to the care they receive.Despite the fact that men and women with HIV/AIDS suffer the same illness, clear disparities are apparent in the negative reaction women and men living with HIV/AIDS experience in society. We show that women's generally low status in society contributes to the extreme negative reactions to which female PLWHA are subject. The government should create policies aimed at reducing the power differences in family, society and health care systems, which would be important to decrease the gender-related differences in stigma experienced by PLWHA. Interventions should be directed at the prevailing societal norms through appropriate legislation and advocacy at grassroots level with the support of men to counter laws that put women in a disadvantaged position. Furthermore, development of a policy that encourages equality in access to health care for all patients with HIV/AIDS by applying the same conditions to both men and women in health care institutions is recommended. There is a need to protect women's rights through implementing support policies, including paying attention to gender in the training of HCPs.Women and girls continue to be affected disproportionately by H
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