1,219 research outputs found
Cloning of terminal transferase cDNA by antibody screening
A cDNA library was prepared from a terminal deoxynucleotidyltransferase-containing thymoma in the phage vector λgt11. By screening plaques with anti-terminal transferase antibody, positive clones were identified of which some had β-galactosidase-cDNA fusion proteins identifiable after electrophoretic fractionation by immunoblotting with anti-terminal transferase antibody. The predominant class of cross-hybridizing clones was determined to represent cDNA for terminal transferase by showing that one representative clone hybridized to a 2200-nucleotide mRNA in close-matched enzyme-positive but not to enzyme-negative cells and that the cDNA selected a mRNA that translated to give a protein of the size and antigenic characteristics of terminal transferase. Only a small amount of genomic DNA hybridized to the longest available clone, indicating that the sequence is virtually unique in the mouse genome
Multi-wavelength modeling of the spatially resolved debris disk of HD 107146
(abridged) We aim to constrain the location, composition, and dynamical state
of planetesimal populations and dust around the young, sun-like (G2V) star HD
107146}. We consider coronagraphic observations obtained with the Advanced
Camera for Surveys (HST/ACS) onboard the HST in broad V and broad I filters, a
resolved 1.3mm map obtained with the Combined Array for Research in
Millimeter-Wave Astronomy (CARMA), Spitzer/IRS low resolution spectra, and the
spectral energy distribution (SED) of the object at wavelengths ranging from
3.5micron to 3.1mm. We complement these data with new coronagraphic high
resolution observations of the debris disk using the Near Infrared Camera and
Multi-Object Spectrometer (HST/NICMOS) aboard the HST in the F110W filter. The
SED and images of the disk in scattered light as well as in thermal reemission
are combined in our modeling using a parameterized model for the disk density
distribution and optical properties of the dust. A detailed analytical model of
the debris disk around HD 107146 is presented that allows us to reproduce the
almost entire set of spatially resolved and unresolved multi-wavelength
observations. Considering the variety of complementary observational data, we
are able to break the degeneracies produced by modeling SED data alone. We find
the disk to be an extended ring with a peak surface density at 131AU.
Furthermore, we find evidence for an additional, inner disk probably composed
of small grains released at the inner edge of the outer disk and moving inwards
due to Poynting-Robertson drag. A birth ring scenario (i.e., a more or less
broad ring of planetesimals creating the dust disk trough collisions) is found
to be the most likely explanation of the ringlike shape of the disk.Comment: 15 pages, 9 figures, accepted for publication in A&
The Formation and Evolution of Planetary Systems: Description of the Spitzer Legacy Science Database
We present the science database produced by the Formation and Evolution of
Planetary Systems (FEPS) Spitzer Legacy program. Data reduction and validation
procedures for the IRAC, MIPS, and IRS instruments are described in detail. We
also derive stellar properties for the FEPS sample from available broad-band
photometry and spectral types, and present an algorithm to normalize Kurucz
synthetic spectra to optical and near-infrared photometry. The final FEPS data
products include IRAC and MIPS photometry for each star in the FEPS sample and
calibrated IRS spectra.Comment: 64 pages, 12 figures, 5 tables; accepted for publication in ApJ
The Circumstellar Disk of HD 141569 Imaged with NICMOS
Coronagraphic imaging with the Near Infrared Camera and Multi Object
Spectrometer on the Hubble Space Telescope reveals a large, ~400 AU (4'')
radius, circumstellar disk around the Herbig Ae/Be star HD 141569. A reflected
light image at 1.1 micron shows the disk oriented at a position angle of 356
+/- 5 deg and inclined to our line of sight by 51 +/- 3 deg; the intrinsic
scattering function of the dust in the disk makes the side inclined toward us,
the eastern side, brighter. The disk flux density peaks 185 AU (1.''85) from
the star and falls off to both larger and smaller radii. A region of depleted
material, or a gap, in the disk is centered 250 AU from the star. The dynamical
effect of one or more planets may be necessary to explain this morphology.Comment: 4 pages, LaTeX with emulateapj.sty and epsfig.sty, 4 postscript
figures, Accepted to ApJ Letter
Resummation of the Divergent Perturbation Series for a Hydrogen Atom in an Electric Field
We consider the resummation of the perturbation series describing the energy
displacement of a hydrogenic bound state in an electric field (known as the
Stark effect or the LoSurdo-Stark effect), which constitutes a divergent formal
power series in the electric field strength. The perturbation series exhibits a
rich singularity structure in the Borel plane. Resummation methods are
presented which appear to lead to consistent results even in problematic cases
where isolated singularities or branch cuts are present on the positive and
negative real axis in the Borel plane. Two resummation prescriptions are
compared: (i) a variant of the Borel-Pade resummation method, with an
additional improvement due to utilization of the leading renormalon poles (for
a comprehensive discussion of renormalons see [M. Beneke, Phys. Rep. vol. 317,
p. 1 (1999)]), and (ii) a contour-improved combination of the Borel method with
an analytic continuation by conformal mapping, and Pade approximations in the
conformal variable. The singularity structure in the case of the LoSurdo-Stark
effect in the complex Borel plane is shown to be similar to (divergent)
perturbative expansions in quantum chromodynamics.Comment: 14 pages, RevTeX, 3 tables, 1 figure; numerical accuracy of results
enhanced; one section and one appendix added and some minor changes and
additions; to appear in phys. rev.
Structure and Composition of Two Transitional Circumstellar Disks in Corona Australis
The late stages of evolution of the primordial circumstellar disks
surrounding young stars are poorly understood, yet vital to constrain theories
of planet formation. We consider basic structural models for the disks around
two ~10 Myr-old members of the nearby RCrA association, RX J1842.9-3532 and RX
J1852.3-3700. We present new arcsecond-resolution maps of their 230 GHz
continuum emission from the Submillimeter Array and unresolved CO(3-2) spectra
from the Atacama Submillimeter Telescope Experiment. By combining these data
with broadband fluxes from the literature and infrared fluxes and spectra from
the catalog of the Formation and Evolution of Planetary Systems (FEPS) Legacy
program on the Spitzer Space Telescope, we assemble a multiwavelength data set
probing the gas and dust disks. Using the Monte Carlo radiative transfer code
RADMC to model simultaneously the SED and millimeter continuum visibilities, we
derive basic dust disk properties and identify an inner cavity of radius 16 AU
in the disk around RX J1852.3-3700. We also identify an optically thin 5 AU
cavity in the disk around RX J1842.9-3532, with a small amount of optically
thick material close to the star. The molecular line observations suggest an
intermediate disk inclination in RX J1842.9-3532, consistent with the continuum
emission. In combination with the dust models, the molecular data allow us to
derive a lower CO content than expected, suggesting that the process of gas
clearing is likely underway in both systems, perhaps simultaneously with planet
formation.Comment: 11 pages, 5 figures, accepted for publication in A
Media Witnessing: Exploring the Audience of Distant Suffering
This article aims at demonstrating the relevance of the concept of ‘media witnessing’ as an analytical lens for the study of audience engagement with media reports of distant suffering. Drawing upon existing theoretical work on the concept, the article approaches media witnessing as a distinct modality of audience experience and constructs an analytical framework for its study. Applying this framework on an empirical study of Greek audiences, the article provides a typology of witnessing, consisting of four different types of audience engagement with media stories of human suffering. This typology illustrates the complexities inherent in the practice of watching suffering on television, as well as the limitations of mediated cosmopolitan imagination
"Ordinary, the same as anywhere else": notes on the management of spoiled identity in 'marginal' middle class neighbourhoods
Urban sociologists are becoming increasingly interested in neighbourhood as a source of middle-class identity. Particular emphasis is currently being given to two types of middle-class neighbourhood; gentrified urban neighbourhoods of ‘distinction’ and inconspicuous ‘suburban landscapes of privilege’. However, there has been a dearth of work on ‘marginal’ middle-class neighbourhoods that are similarly ‘inconspicuous’ rather than distinctive, but less exclusive, thus containing sources of ‘spoiled identity’. This article draws on data gathered from two ‘marginal’ middleclass neighbourhoods that contained a particular source of ‘spoiled identity’: social renters. Urban sociological analyses of neighbour responses to these situations highlight a process of dis-identification with the maligned object, which exacerbates neighbour differences. Our analysis of data from the ‘marginal’ middle-class neighbourhoods suggests something entirely different and Goffmanesque. This entailed the management of spoiled identity, which emphasized similarities rather than differences between neighbours.</p
'Moving life stories tell us just why politics matters’: personal narratives in tabloid anti-austerity campaigns
This article examines the use of personal narratives in two tabloid newspaper campaigns against a controversial welfare reform popularly known as the ‘bedroom tax’. It aims firstly to evaluate whether the personal narratives operate as political testimony to challenge government accounts of welfare reform and dominant stereotypes of benefits claimants, and secondly to assess the potential for and limits to progressive advocacy in popular journalism. The study uses content analysis of 473 articles over the course of a year in the Daily Mirror and Sunday People newspapers, and qualitative analysis of a sub-set of 113 articles to analyse the extent to which the campaign articles extrapolated from the personal to the general, and the role of ‘victim-witnesses’ in articulating their own subjectivity and political agency. The analysis indicates that both newspapers allowed affected individuals to express their own subjectivity to challenge stereotypes, but it was civil society organisations and opinion columnists who most explicitly extrapolated from the personal to the political. Collectively organised benefits claimants were rarely quoted, and there was some evidence of ventriloquization of the editorial voice in the political criticisms of victim-witnesses. However, a campaigning columnist in the Mirror more actively empowered some of those affected to speak directly to politicians. This indicates the value of campaigning journalism when it is truly engaged in solidarity with those affected, rather than instrumentalising victim-witnesses to further the newspapers’ campaign goals
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