1,652 research outputs found
X-ray and optical variability of Seyfert 1 galaxies as observed with XMM-Newton
We have examined simultaneous X-ray and optical light curves of a sample of
eight nearby Seyfert 1 galaxies observed using the EPIC X-ray cameras and
Optical Monitor on board XMM. The observations span ~1 day and revealed optical
variability in four of the eight objects studied. In all cases, the X-ray
variability amplitude exceeded that of the optical both in fractional and
absolute luminosity terms. No clearly significant correlations were detected
between wavebands using cross correlation analysis. We conclude that, in three
of the four objects in which optical variability was detected, reprocessing
mechanisms between wavebands do not dominate either the optical or X-ray
variability on the time-scales probed.Comment: 9 pages, 2 figures, accepted for publication in MNRA
Development and Validity of a Workplace Health Promotion Best Practices Assessment
Objective:
To explore the factor structure of the HERO Health and Well-being Best Practices Scorecard in Collaboration with Mercer (HERO Scorecard) to develop a reduced version and examine the reliability and validity of that version. Methods:
A reduced version of the HERO Scorecard was developed through formal statistical analyses on data collected from 845 organizations that completed the original HERO Scorecard. Results:
The final factors in the reduced Scorecard represented content pertaining to organizational and leadership support, program comprehensiveness, program integration, and incentives. All four implemented practices were found to have a strong, statistically significant effect on perceived effectiveness. Organizational and leadership support had the strongest effect (β = 0.56), followed by incentives (β = 0.23). Conclusion:
The condensed version of the HERO Scorecard has the potential to be a promising tool for future research on the extent to which employers are adopting best practices in their health and well-being (HWB) initiatives
FUSE Observations of Molecular Hydrogen in Translucent Interstellar Clouds: The Line of Sight Toward HD 73882
We report the results of initial FUSE observations of molecular hydrogen (H2)
in translucent clouds. These clouds have greater optical depth than any of the
diffuse clouds previously observed for far-UV H2 absorption, and provide new
insights into the physics and chemistry of such regions. Our initial results
involve observations of HD 73882, a well-studied southern hemisphere star lying
behind substantial interstellar material (E(B-V) = 0.72; A_V = 2.44). We find a
total H2 column density, N(H2) = 1.2 x 10^{21} cm^{-2}, about three times
larger than the values for diffuse clouds previously measured in the far-UV.
The gas kinetic temperature indicated by the ratio N(J=1)/N(J=0) is 58 +/- 10
K. With the aid of ground-based data to calculate an appropriate
multi-component curve of growth, we have determined column densities for all
rotational levels up to J = 7. The J >= 2 states can be reasonably fitted with
a rotational excitation temperature of 307 +/- 23 K. Both the kinetic and
rotational temperatures are similar to those found in previous investigations
of diffuse clouds. The ratios of carbonaceous molecules to hydrogen molecules
are also similar to ratios in diffuse clouds, suggesting a similar chemistry
for this line of sight.Comment: 7 pages, 3 figures, to appear in ApJ Letters (FUSE first-results
issue
Uptake, outcomes, and costs of implementing non-invasive prenatal testing for Down's syndrome into NHS maternity care: prospective cohort study in eight diverse maternity units.
OBJECTIVE: To investigate the benefits and costs of implementing non-invasive prenatal testing (NIPT) for Down's syndrome into the NHS maternity care pathway. DESIGN: Prospective cohort study. SETTING: Eight maternity units across the United Kingdom between 1 November 2013 and 28 February 2015. PARTICIPANTS: All pregnant women with a current Down's syndrome risk on screening of at least 1/1000. MAIN OUTCOME MEASURES: Outcomes were uptake of NIPT, number of cases of Down's syndrome detected, invasive tests performed, and miscarriages avoided. Pregnancy outcomes and costs associated with implementation of NIPT, compared with current screening, were determined using study data on NIPT uptake and invasive testing in combination with national datasets. RESULTS: NIPT was prospectively offered to 3175 pregnant women. In 934 women with a Down's syndrome risk greater than 1/150, 695 (74.4%) chose NIPT, 166 (17.8%) chose invasive testing, and 73 (7.8%) declined further testing. Of 2241 women with risks between 1/151 and 1/1000, 1799 (80.3%) chose NIPT. Of 71 pregnancies with a confirmed diagnosis of Down's syndrome, 13/42 (31%) with the diagnosis after NIPT and 2/29 (7%) after direct invasive testing continued, resulting in 12 live births. In an annual screening population of 698 500, offering NIPT as a contingent test to women with a Down's syndrome screening risk of at least 1/150 would increase detection by 195 (95% uncertainty interval -34 to 480) cases with 3368 (2279 to 4027) fewer invasive tests and 17 (7 to 30) fewer procedure related miscarriages, for a non-significant difference in total costs (£-46 000, £-1 802 000 to £2 661 000). The marginal cost of NIPT testing strategies versus current screening is very sensitive to NIPT costs; at a screening threshold of 1/150, NIPT would be cheaper than current screening if it cost less than £256. Lowering the risk threshold increases the number of Down's syndrome cases detected and overall costs, while maintaining the reduction in invasive tests and procedure related miscarriages. CONCLUSIONS: Implementation of NIPT as a contingent test within a public sector Down's syndrome screening programme can improve quality of care, choices for women, and overall performance within the current budget. As some women use NIPT for information only, the Down's syndrome live birth rate may not change significantly. Future research should consider NIPT uptake and informed decision making outside of a research setting
Customer Deviance: A Framework, Prevention Strategies, and Opportunities for Future Research
The phrase the “customer is always right” assumes that customers provide universal benefits for
firms. However, in recent years, customer deviance is on the rise and the academic literature has
provided little insight into the drivers of deviance, the actual behaviors, and strategies for how
managers can better manage a customer base that cannot be classified as universally benign. This
article addresses customer deviance ranging from classic examples like shoplifting to engaging
in hostile to anti-brand behaviors on social media or even breaking established norms such as
trespassing in stores after closing hours. In an effort to spur new research into customer
deviance, we propose a customer deviance framework encompassing the triggers, behaviors, and
consequences of customer deviance with attention given to differentiating firms, employees, and
other customers as the possible targets of deviant behaviors. We outline prevention strategies that
comprise social, design, and technological-oriented factors, which in turn can help firms better
manage deviant behavior. In doing so, we identify gaps in the literature and close with an
actionable agenda for future research that can help firms curtail these negative customer
behaviors
Novae Ejecta as Colliding Shells
Following on our initial absorption-line analysis of fifteen novae spectra we
present additional evidence for the existence of two distinct components of
novae ejecta having different origins. As argued in Paper I one component is
the rapidly expanding gas ejected from the outer layers of the white dwarf by
the outburst. The second component is pre-existing outer, more slowly expanding
circumbinary gas that represents ejecta from the secondary star or accretion
disk. We present measurements of the emission-line widths that show them to be
significantly narrower than the broad P Cygni profiles that immediately precede
them. The emission profiles of novae in the nebular phase are distinctly
rectangular, i.e., strongly suggestive of emission from a relatively thin,
roughly spherical shell. We thus interpret novae spectral evolution in terms of
the collision between the two components of ejecta, which converts the early
absorption spectrum to an emission-line spectrum within weeks of the outburst.
The narrow emission widths require the outer circumbinary gas to be much more
massive than the white dwarf ejecta, thereby slowing the latter's expansion
upon collision. The presence of a large reservoir of circumbinary gas at the
time of outburst is suggestive that novae outbursts may sometime be triggered
by collapse of gas onto the white dwarf, as occurs for dwarf novae, rather than
steady mass transfer through the inner Lagrangian point.Comment: 12 pages, 3 figures; Revised manuscript; Accepted for publication in
Astrophysics & Space Scienc
Diffusion of impurities in a granular gas
Diffusion of impurities in a granular gas undergoing homogeneous cooling
state is studied. The results are obtained by solving the Boltzmann--Lorentz
equation by means of the Chapman--Enskog method. In the first order in the
density gradient of impurities, the diffusion coefficient is determined as
the solution of a linear integral equation which is approximately solved by
making an expansion in Sonine polynomials. In this paper, we evaluate up to
the second order in the Sonine expansion and get explicit expressions for
in terms of the restitution coefficients for the impurity--gas and gas--gas
collisions as well as the ratios of mass and particle sizes. To check the
reliability of the Sonine polynomial solution, analytical results are compared
with those obtained from numerical solutions of the Boltzmann equation by means
of the direct simulation Monte Carlo (DSMC) method. In the simulations, the
diffusion coefficient is measured via the mean square displacement of
impurities. The comparison between theory and simulation shows in general an
excellent agreement, except for the cases in which the gas particles are much
heavier and/or much larger than impurities. In theses cases, the second Sonine
approximation to improves significantly the qualitative predictions made
from the first Sonine approximation. A discussion on the convergence of the
Sonine polynomial expansion is also carried out.Comment: 9 figures. to appear in Phys. Rev.
"We're worth what we are paid": Unravelling the 'paradox of the contented female worker'
Pay satisfaction research has suggested that women are more satisfied with their pay than men, even though, in general, women earn less. This paper argues that this body of research has misconceptualised this phenomenon as an issue of women only. It also argues that previous explanations for this gender pay paradox have not adequately explained these patterns of satisfaction. A social constructionist approach to pay satisfaction is proposed which situates satisfaction within the context of structural inequality. This draws upon the scholarly work of feminist scholars and the conceptual ideas of Pierre Bourdieu. This theoretical approach is explored with data from qualitative interviews with support staff at universities in the United Kingdom. This evidence suggests that their pay satisfaction is influenced by beliefs about the ‘value’ of different occupations
Deciphering Museums, Politics and Impact
This paper makes a contribution towards deciphering the relationship between museums, politics and impact. I suggest that this is akin to that between three languages in the early nineteenth century: Greek, Demotic and Hieroglyphs. I argue that museums should be taken much more seriously by the discipline of politics and international relations. This paper begins with an analysis of the REF 2014 Impact Case Studies submitted under the Politics and International Studies Unit of Assessment. Thereafter, it looks at how museums have been examined in the field of politics and international relations. Finally, it outlines some of the benefits and opportunities of scholars in the field engaging with museums in terms of their research, as potential collaborators, and as partners for knowledge transfer and impactful activities – within and outwith the strictures of the UK Research Excellence Framework (REF)
UV and EUV Instruments
We describe telescopes and instruments that were developed and used for
astronomical research in the ultraviolet (UV) and extreme ultraviolet (EUV)
regions of the electromagnetic spectrum. The wavelength ranges covered by these
bands are not uniquely defined. We use the following convention here: The EUV
and UV span the regions ~100-912 and 912-3000 Angstroem respectively. The
limitation between both ranges is a natural choice, because the hydrogen Lyman
absorption edge is located at 912 Angstroem. At smaller wavelengths,
astronomical sources are strongly absorbed by the interstellar medium. It also
marks a technical limit, because telescopes and instruments are of different
design. In the EUV range, the technology is strongly related to that utilized
in X-ray astronomy, while in the UV range the instruments in many cases have
their roots in optical astronomy. We will, therefore, describe the UV and EUV
instruments in appropriate conciseness and refer to the respective chapters of
this volume for more technical details.Comment: To appear in: Landolt-Boernstein, New Series VI/4A, Astronomy,
Astrophysics, and Cosmology; Instruments and Methods, ed. J.E. Truemper,
Springer-Verlag, Berlin, 201
- …