3,168 research outputs found

    The racist bodily imaginary: the image of the body-in-pieces in (post)apartheid culture

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    This paper outlines a reoccurring motif within the racist imaginary of (post)apartheid culture: the black body-in-pieces. This disturbing visual idiom is approached from three conceptual perspectives. By linking ideas prevalent in Frantz Fanon’s description of colonial racism with psychoanalytic concepts such as Lacan’s notion of the corps morcelĂ©, the paper offers, firstly, an account of the black body-in-pieces as fantasmatic preoccupation of the (post)apartheid imaginary. The role of such images is approached, secondly, through the lens of affect theory which eschews a representational ‘reading’ of such images in favour of attention to their asignifying intensities and the role they play in effectively constituting such bodies. Lastly, Judith Butler’s discussion of war photography and the conditions of grievability introduces an ethical dimension to the discussion and helps draw attention to the unsavory relations of enjoyment occasioned by such images

    The Second APM UKST Colour Survey for z>4 Quasars

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    We present the spectra, positions, and finding charts for 31 bright (R4.5. The majority are in the southern sky (dec 2.5) colours from UK or POSSII Schmidt Plates scanned at the Automated Plate Measuring facility in Cambridge. Low resolution (~> 10A) 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 Lyman-alpha absorption system at z = 4.46. This is currently the highest redshift damped Lyman-alpha 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 UKST survey we have now surveyed a total of ~8000 squ deg of sky i.e. 40% of the high galactic latitude (|b|>30 deg) sky, resulting in 59 optically selected quasars in the redshift range 3.85 to 4.78; 49 of which have z>=4.00

    A framework for the prospective analysis of super-diversity coming from high levels of immigration

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    Background Pressures to keep immigration rates at relatively high levels are likely to persist in most developed countries. At the same time, immigrant cohorts are becoming more and more diverse, leading host societies to become increasingly heterogeneous across multiple dimensions. For scholars who study demographic or socio-economic behaviours, the need to account for ethnocultural “super-diversity” brings new challenges and complications. Objective The main objective of this paper is to present a framework for the prospective analysis of super-diversity in several high immigration countries. Methods We developed microsimulation models that simultaneously project several population-dimensions for Canada, the United States and countries of the European Union, with the aim of studying the consequences of alternate future population and migration trends. Results The paper presents the projected progression of three indicators of diversity for Canada, the USA and the EU28: percentage of foreign-born population, percentage of the population using a non-official language at home and percentage of non-Christians under the reference scenario. Results from alternative scenarios show the potential impact of modifying the composition of migrant cohorts. The paper also examines the projected changes in the labour force for each region by education level and language. Finally, the paper proposes a new longitudinal indicator that counts the number of years lived as active and inactive over the life course for foreign- and native-born cohorts. Contribution The microsimulation models provide much more informative results than more traditional cohort-component or multi-state models to study the future effects of ethnocultural super-diversity on high immigration countries

    A survey for high-redshift radio-loud quasars: optical spectroscopy of S > 0.2 Jy, flat-spectrum radio sources

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    We present optical spectroscopic data for a complete sample of 161 S_5GHz >= 0.2 Jy, flat-spectrum radio sources. The sources were observed as part of a survey for high redshift, radio-loud quasars, and were selected for spectroscopic follow-up based on criteria of red optical colour and unresolved optical counterpart, as measured from APM scans of POSS-I plates. 13 objects from the spectroscopic sample were found to be radio-loud quasars with z > 3, of which two were previously known. We give positions, E (red) magnitudes, O-E colours, 5GHz radio fluxes, radio spectral indices, optical spectra and redshifts where possible for the spectroscopic sample. We also give finding charts for the z > 3 QSOs. The highest redshift object found is a QSO with z = 4.30 (GB1508+5714, the subject of an earlier Letter). The sample also contains a z = 3.05 QSO, GB1759+7539, which is optically very luminous (E=16.1). In addition, spectra are given for 18 S_5GHz >= 0.2 Jy, flat-spectrum radio sources that do not form part of the complete sample.Comment: 14 pages including tables and figures, except Figs. 3 and 4 (spectra) which are available from http://panisse.lbl.gov/public/isobelpage/ . To appear in MNRA

    Radio Properties of z>4 Optically-Selected Quasars

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    We report on two programs to address differential evolution between the radio-loud and radio-quiet quasar populations at high (z>4) redshift. Both programs entail studying the radio properties of optically-selected quasars. First, we have observed 32 optically-selected, high-redshift (z>4) quasars with the VLA at 6 cm (5 GHz). These sources comprise a statistically complete and well-understood sample. We detect four quasars above our 3-sigma limit of ~0.15 mJy, which is sufficiently sensitive to detect all radio-loud quasars at the probed redshift range. Second, we have correlated 134 z>4 quasars, comprising all such sources that we are aware of as of mid-1999, with FIRST and NVSS. These two recent 1.4 GHz VLA sky surveys reach 3-sigma limits of approximately 0.6 mJy and 1.4 mJy respectively. We identify a total of 15 z>4 quasars, of which six were not previously known to be radio-loud. The depth of these surveys does not reach the radio-loud/radio-quiet demarcation luminosity density (L(1.4 GHz) = 10^32.5 h(50)^(-2) ergs/s/Hz) at the redshift range considered; this correlation therefore only provides a lower limit to the radio-loud fraction of quasars at high-redshift. The two programs together identify eight new radio-loud quasars at z>4, a significant increase over the seven currently in the published literature. We find no evidence for radio-loud fraction depending on optical luminosity for -25 > M_B > -28 at z~2, or for -26>M_B>-28 at z>4. Our results also show no evolution in the radio-loud fraction between z~2 and z>4 (-26>M_B>-28).Comment: 19 pages, 7 figures; to appear in The Astronomical Journal (April 2000

    The Gemini Deep Deep Survey: II. Metals in Star-Forming Galaxies at Redshift 1.3<z<2

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    The goal of the Gemini Deep Deep Survey (GDDS) is to study an unbiased sample of K<20.6 galaxies in the redshift range 0.8<z<2.0. Here we determine the statistical properties of the heavy element enrichment in the interstellar medium (ISM) of a subsample of 13 galaxies with 1.34<z<1.97 and UV absolute magnitude M_2000 < -19.65. The sample contains 38% of the total number of identified galaxies in the first two fields of the survey with z>1.3. The selected objects have colors typical of irregular and Sbc galaxies. Strong [OII] emission indicates high star formation activity in the HII regions (SFR~13-106 M_sun/yr). The high S/N composite spectrum shows strong ISM MgII and FeII absorption, together with weak MnII and MgI lines. The FeII column density, derived using the curve of growth analysis, is logN_FeII = 15.54^{+0.23}_{-0.13}. This is considerably larger than typical values found in damped Ly-alpha systems (DLAs) along QSO sight lines, where only 10 out of 87 (~11%) have logN_FeII > 15.2. High FeII column densities are observed in the z=2.72 Lyman break galaxy cB58 (logN_FeII ~ 15.25) and in gamma-ray burst host galaxies (logN_FeII ~ 14.8-15.9). Given our measured FeII column density and assuming a moderate iron dust depletion (delta_Fe ~ 1 dex), we derive an optical dust extinction A_V ~ 0.6. If the HI column density is log N(HI)<21.7 (as in 98% of DLAs), then the mean metallicity is Z/Z_sun > 0.2. The high completeness of the GDDS sample implies that these results are typical of star-forming galaxies in the 1<z<2 redshift range, an epoch which has heretofore been particularly challenging for observational programs.Comment: ApJ in press, corrected HI column density estimat

    Magnetodielectric coupling in Mn3O4

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    We have investigated the dielectric anomalies associated with spin ordering transitions in the tetragonal spinel Mn3_3O4_4, using thermodynamic, magnetic, and dielectric measurements. We find that two of the three magnetic ordering transitions in Mn3_3O4_4 lead to decreases in the temperature dependent dielectric constant at zero applied field. Applying a magnetic field to the polycrystalline sample leaves these two dielectric anomalies practically unchanged, but leads to an increase in the dielectric constant at the intermediate spin-ordering transition. We discuss possible origins for this magnetodielectric behavior in terms of spin-phonon coupling. Band structure calculations suggest that in its ferrimagnetic state, Mn3_3O4_4 corresponds to a semiconductor with no orbital degeneracy due to strong Jahn-Teller distortion.Comment: 6 pages, 7 figure

    Twenty-Five Years of Landsat Thermal Band Calibration

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    Landsat-7 Enhanced Thematic Mapper+ (ETM+), launched in April 1999, and Landsat-5 Thematic Mapper (TM), launched in 1984, both have a single thermal band. Both instruments thermal band calibrations have been updated previously: ETM+ in 2001 for a pre-launch calibration error and TM in 2007 for data acquired since the current era of vicarious calibration has been in place (1999). Vicarious calibration teams at Rochester Institute of Technology (RIT) and NASA/Jet Propulsion Laboratory (JPL) have been working to validate the instrument calibration since 1999. Recent developments in their techniques and sites have expanded the temperature and temporal range of the validation. The new data indicate that the calibration of both instruments had errors: the ETM+ calibration contained a gain error of 5.8% since launch; the TM calibration contained a gain error of 5% and an additional offset error between 1997 and 1999. Both instruments required adjustments in their thermal calibration coefficients in order to correct for the errors. The new coefficients were calculated and added to the Landsat operational processing system in early 2010. With the corrections, both instruments are calibrated to within +/-0.7K

    Red Parkes-Quasars: Evidence for Soft X-ray Absorption

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    The Parkes Half-Jansky Flat Spectrum Sample contains a large number of sources with unusually red optical-to-near-infrared continua. If this is to be interpreted as extinction by dust in the line-of-sight, then associated material might also give rise to absorption in the soft X-ray regime. This hypothesis is tested using broadband (0.1-2.4 keV) data from the {\it ROSAT} All-Sky Survey provided by Siebert et al. (1998). Significant (>3σ>3\sigma confidence level) correlations between optical (and near-infrared)--to--soft X-ray continuum slope and optical extinction are found in the data, consistent with absorption by material with metallicity and a range in gas-to-dust ratio as observed in the local ISM. Under this simple model, the soft X-rays are absorbed at a level consistent with the range of extinctions (0<AV<60< A_{V}< 6 magnitudes) implied by the observed optical reddening. Excess X-ray absorption by warm (ionised) gas, (ie. a `warm absorber') is not required.Comment: 23 pages of text, 3 figures, to appear in Jan 10 (1999) issue of The Astrophysical Journa
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