45,740 research outputs found
A representative sample of Be Stars I: Sample Selection, Spectral Classification and Rotational Velocities
We present a sample of 58 Be stars containing objects of spectral types O9 to
B8.5 and luminosity classes III to V. We have obtained 3670 - 5070 Angstrom
spectra of the sample which are used to derive spectral types and rotational
velocities. We discuss the distribution of spectral types and rotational
velocities obtained and conclude that there are no significant selection
effects in our sample.Comment: 10 Pages, 9 Figures, Accepted for publication in A&A
Time, geodesy, and astrometry: Results from radio interferometry
The results from a total of a dozen transcontinental and intercontinental VLBI experiments are discussed. Particular emphasis is placed on: (1) the inferred behavior of the frequency standards, usually hydrogen masers, on time scales from 10 to 100,000 seconds; (2) the estimated celestial positions of the observed radio sources; (3) the determinations of the vector baselines; and (4) the inferred values of polar motion and UT.1
Ionisation-induced star formation II: External irradiation of a turbulent molecular cloud
In this paper, we examine numerically the difference between triggered and
revealed star formation. We present Smoothed Particle Hydrodynamics (SPH)
simulations of the impact on a turbulent 10^4 solar-mass molecular cloud of
irradiation by an external source of ionising photons. In particular, using a
control model, we investigate the triggering of star formation within the
cloud. We find that, although feedback has a dramatic effect on the morphology
of our model cloud, its impact on star formation is relatively minor. We show
that external irradiation has both positive and negative effects, accelerating
the formation of some objects, delaying the formation of others, and inducing
the formation of some that would not otherwise have formed. Overall, the
calculation in which feedback is included forms nearly twice as many objects
over a period of \sim0.5 freefall times (\sim2.4 Myr), resulting in a
star--formation efficiency approximately one third higher (\sim4% as opposed to
\sim3% at this epoch) as in the control run in which feedback is absent.
Unfortunately, there appear to be no observable characteristics which could be
used to differentiate objects whose formation was triggered from those which
were forming anyway and which were simply revealed by the effects of radiation,
although this could be an effect of poor statistics.Comment: 12 pages, 9 figures, accepted by MNRA
Gaining Access to Housing in Germany: The Foreign Minority Experience
Housing is a critical component of household well being and the extent to which minority households have achieved parity with Germans is a measure of the extent to which this population is integrated into the larger German society. Specifically we examine whether the housing conditions for immigrants2 has improved between 1985 and 1998 despite the greater barriers to upward mobility for low skill workers arising from industrial restructuring. We use regression models to determine the degree to which socioeconomic differences between the two populations account for variations in the average quality of their housing. Finally, given the low number of vacancies in the German housing market and the disadvantaged position of minorities within it, we are interested in measuring the magnitude of the improvements persons of foreign origin are able to make through residential mobility. Our descriptive analyses reveal that although housing conditions for minorities have improved in absolute terms across a wide array of indicators, only in a few instances has the housing quality gap between Germans and persons of foreign origin narrowed. Further, we find that the housing conditions of minorities remained poorer even after controlling for variables thought to be strong predictors of housing quality (income, age, family size etc..) Finally, persons of foreign origin are becoming increasingly likely to move into the large, often geographically and socially isolated apartment complexes built in the post World War II era.
High mass X-ray binaries in the NIRorbital solutions of two highly obscured systems
The maximum mass of a neutron star (NS) is poorly defined. Theoretical
attempts to define this mass have thus far been unsuccessful. Observational
results currently provide the only means of narrowing this mass range down.
Eclipsing X-ray binary (XRB) pulsar systems are the only interacting binaries
in which the mass of the NS may be measured directly. Only 10 such systems are
known to exist, 6 of which have yielded NS masses in the range 1.06 - 1.86
M.We present the first orbital solutions of two further eclipsing
systems, OAO 1657-415 and EXO 1722-363, whose donor stars have only recently
been identified. Using observations obtained using the VLT/ISAAC NIR
spectrograph, our initial work was concerned with providing an accurate
spectral classification of the two counterpart stars, leading to a consistent
explanation of the mechanism for spin period evolution of OAO 1657-415.
Calculating radial velocities allowed orbital solutions for both systems to be
computed. These are the first accurate determinations of the NS and counterpart
masses in XRB pulsar systems to be made employing NIR spectroscopy.Comment: 5 pages, 3 figures, contribution to the proceedings of "The
multi-wavelength view of hot, massive stars", 39th Li`ege Int. Astroph.
Coll., 12-16 July 201
Disc loss and renewal in A0535+26
This paper presents observations of the Be/X-ray binary system A0535+26
revealing the first observed loss of its circumstellar disc, demonstrated by
the loss of its JHK infrared excess and optical/IR line emission. However
optical/IR spectroscopy reveals the formation of a new inner disc with
significant density and emission strength at small radii; the disc has proven
to be stable over 5 months in this intermediate state.Comment: 4 pages, 4 figures, accepted by MNRAS, uses mn.st
Phase transitions, entanglement and quantum noise interferometry in cold atoms
We show that entanglement monotones can characterize the pronounced
enhancement of entanglement at a quantum phase transition if they are sensitive
to long-range high order correlations. These monotones are found to develop a
sharp peak at the critical point and to exhibit universal scaling. We
demonstrate that similar features are shared by noise correlations and verify
that these experimentally accessible quantities indeed encode entanglement
information and probe separability.Comment: 4 pages 4 figure
Healthcare assistants: distributional losses as a consequence of NHS modernisation?
This paper examines the labour process of Healthcare Assistants (HCAs) at a National Health Service (NHS) hospital trust (TUH) in the context of the NHS modernisation agenda. It determines whether application of the modernisation agenda is formalised at TUH and considers how HCAs are affected. The paper is based upon 60 interviews with HCAs, structured questionnaires completed by all interview respondents, observation of HCAs and interviews with non-clinical managers. The findings show that elements of the modernisation agenda are informally implemented at TUH to the detriment of HCAs. HCAs experience distributional losses in the form of intensification as nurses deflect duties to HCAs and insulate themselves from adverse effects. HCAs resist, using selective absence when pressures mount. They ameliorate losses by re-internalising their work as a job with caring elements not a genuine caring role. They rationalise their altered behaviour towards patients by blaming the regime's treatment of them as a subordinated group
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Managing health care assistants? The frontier of control in NHS modernization and skill-mix strategies?
NHS modernization aims to make hospitals more flexible, modern and private sector like for patients by cheapening the costs of nursing care and re-allocating these distributive gains internally at the workplace. Based on sixty interviews and structured questionnaires completed by in one NHS Trust this study asks three research questions. First, how do HCAâs experience modernization where the frontier of control has moved decisively in favour of management? Second, how do locally contingent approaches to HCAâs and equally contingent resistance strategies provide organizational context to workplace control regimes? Third, are absence and job satisfaction understood as resistance strategies which structure antagonism within NHS modernization? Absence appears as a form of resistance to work intensification and associated management demands but is tolerated because it does not formally threaten the managerial prerogative. HCAâs retain intrinsic job satisfaction by marginalizing aspects of their role particularly hands-off patient care and secure distributive gains by imposing this loss on those they seek to help. At the macro level HCAâs retain intrinsic job satisfaction in a contractual approach where they dissociate use of absence from its effects on patients and colleagues
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