224 research outputs found
Union Threat Effects and Nonunion Industry Wage Differentials
We investigate the impact of union strength on changes in nonunion wages and employment. The prevailing model in this area is the threat model, which predicts that increases in union strength cause increases in nonunion wages and decreases in nonunion employment. In testing the threat model, we are also testing two alternatives, the crowding and complements models. In contrast to the prediction of the threat model, decreases in the percent organized (reflecting a declining union threat) are associated with increases in the nonunion wage. Furthermore, increases in union wages appear to decrease, rather than to increase, nonunion wages. Evidence on the determinants of intra-industry variation in nonunion wage premia is somewhat more consistent with the crowding model and is strikingly consistent with the complements model of union and nonunion wage determination. Further evidence on the determinants of intra-industry variation in nonunion employment is consistent with the complements model and the threat model; movements in nonunion industry employment are negatively related to changes in proxies for union strength. Thus, the combined evidence supports the complements model, but neither the threat model nor the crowding model.
A Mid-Infrared Counterpart to the Magnetar 1E 2259+586
We report the discovery of a 4.5 um counterpart to the anomalous X-ray pulsar
(magnetar) 1E 2259+586 with the Spitzer Space Telescope. The mid-infrared flux
density is 6.3+/-1.0 uJy at 4.5 um and <20 uJy (at 95% confidence) at 8 um, or
0.02% of the 2-10 keV X-ray flux (corrected for extinction). Combining our
Spitzer measurements with previously published near-infrared data, we show that
the overall infrared emission from 1E 2259+586 is qualitatively similar to that
from the magnetar 4U 0142+61. Therefore the passive X-ray-heated dust disk
model originally developed for 4U 0142+61 might also apply to 1E 2259+586.
However, the IR data from this source can also be fitted by a simple power-law
spectrum as might be expected from magnetospheric emission.Comment: Accepted for publication in ApJ. 6 pages, 4 figures, uses emulateap
An inexpensive device to treat postpartum hemorrhage: a preliminary proof of concept study of health provider opinion and training in Nepal
BACKGROUND: Obstetric hemorrhage remains the leading cause of maternal mortality in resource limited areas. An inexpensive pneumatic anti-shock garment was devised of bicycle tubes and tailored cloth which can be prepared from local materials in resource-limited settings. The main purposes of this study were: 1) to determine acceptability of the device by nurses and midwives and obtain suggestions for making the device more suitable for use in their particular work environments, 2) to determine whether a three hour training course provided adequate instruction in the use of this device for the application of circumferential abdominal pelvic pressure, and 3) determine production capability and cost in a resource-limited country. METHODS: Fifty-eight nurse and midwife participants took part in three sessions over eight months in Nepal. Correct device placement was assessed on non-pregnant participants using ultrasound measurement of distal aortic flow before and after device inflation, and analyzed using confidence intervals. Participants were surveyed to determine acceptability of the device, obtain suggestions for improvement, and to collect data on clinical use. RESULTS: Device placement achieved flow decreases with a mean of 39% (95% CI 25%-53%, p < 0.001) in the first session, 28% (95% CI 21%-33%, P < 0.001) after four months and 29% (95% CI 24%-34%, p < 0.001) at 8 months. All nurses and midwives thought the device would be acceptable for use in obstetric hemorrhage and that they could make, clean, and apply it. They quickly learned to apply the device, remembered how to apply it, and were willing and able to use the device clinically. Ten providers used the device, each on one patient, to treat obstetric hemorrhage after routine measures had failed; bleeding stopped promptly in all ten, two of whom were transported to the hospital. Production of devices in Kathmandu using local tailors and supplies cost approximately $40 per device, in a limited production setting. CONCLUSIONS: Preliminary data suggest that an inexpensive, easily-made device is potentially an appropriate addition to current obstetric hemorrhage treatment in resource-limited areas and that further study is warranted
Modeling Multi-Wavelength Stellar Astrometry. I. SIM Lite Observations of Interacting Binaries
Interacting binaries consist of a secondary star which fills or is very close
to filling its Roche lobe, resulting in accretion onto the primary star, which
is often, but not always, a compact object. In many cases, the primary star,
secondary star, and the accretion disk can all be significant sources of
luminosity. SIM Lite will only measure the photocenter of an astrometric
target, and thus determining the true astrometric orbits of such systems will
be difficult. We have modified the Eclipsing Light Curve code (Orosz &
Hauschildt 2000) to allow us to model the flux-weighted reflex motions of
interacting binaries, in a code we call REFLUX. This code gives us sufficient
flexibility to investigate nearly every configuration of interacting binary. We
find that SIM Lite will be able to determine astrometric orbits for all
sufficiently bright interacting binaries where the primary or secondary star
dominates the luminosity. For systems where there are multiple components that
comprise the spectrum in the optical bandpass accessible to SIM Lite, we find
it is possible to obtain absolute masses for both components, although
multi-wavelength photometry will be required to disentangle the multiple
components. In all cases, SIM Lite will at least yield accurate inclinations,
and provide valuable information that will allow us to begin to understand the
complex evolution of mass-transferring binaries. It is critical that SIM Lite
maintains a multi-wavelength capability to allow for the proper deconvolution
of the astrometric orbits in multi-component systems.Comment: 12 pages, 6 figures, 6 tables. Accepted for publication in the
Astrophysical Journa
Radio and IR interferometry of SiO maser stars
Radio and infrared interferometry of SiO maser stars provide complementary
information on the atmosphere and circumstellar environment at comparable
spatial resolution. Here, we present the latest results on the atmospheric
structure and the dust condensation region of AGB stars based on our recent
infrared spectro-interferometric observations, which represent the environment
of SiO masers. We discuss, as an example, new results from simultaneous VLTI
and VLBA observations of the Mira variable AGB star R Cnc, including VLTI near-
and mid-infrared interferometry, as well as VLBA observations of the SiO maser
emission toward this source. We present preliminary results from a monitoring
campaign of high-frequency SiO maser emission toward evolved stars obtained
with the APEX telescope, which also serves as a precursor of ALMA images of the
SiO emitting region. We speculate that large-scale long-period chaotic motion
in the extended molecular atmosphere may be the physical reason for observed
deviations from point symmetry of atmospheric molecular layers, and for the
observed erratic variability of high-frequency SiO maser emissionComment: 8 pages, 4 figures, submitted to Proc. IAU Symp. 287 "Cosmic masers -
from OH to H_0", R.S. Booth, E.M.L. Humphreys, W.H.T. Vlemmings (eds.),
invited pape
Synthesising interprocedural bit-precise termination proofs
Proving program termination is key to guaranteeing absence of undesirable behaviour, such as hanging programs and even security vulnerabilities such as denial-of-service attacks. To make termination checks scale to large systems, interprocedural termination analysis seems essential, which is a largely unexplored area of research in termination analysis, where most effort has focussed on difficult single-procedure problems. We present a modular termination analysis for C programs using template-based interprocedural summarisation. Our analysis combines a context-sensitive, over-approximating forward analysis with the inference of under-approximating preconditions for termination. Bit-precise termination arguments are synthesised over lexicographic linear ranking function templates. Our experimental results show that our tool 2LS outperforms state-of-the-art alternatives, and demonstrate the clear advantage of interprocedural reasoning over monolithic analysis in terms of efficiency, while retaining comparable precision
Spitzer Observations of Var Her 04: Possible Detection of Dust Formation in a Super-Outbursting TOAD
We present four MIPS (24 \micron) and two IRAC (3.6, 4.5, 5.8, and 8.0
\micron) Spitzer observations of the newly discovered Tremendous Outburst
Amplitude Dwarf nova (TOAD) Var Her 04 during decline from super-outburst. The
four MIPS observations span 271 days and the two IRAC observations span 211
days. Along the line-of-sight to Var Her 04, there is a foreground M-star
within 1\arcsec of the variable; as a result, all of the Spitzer photometry
presented in this paper is a blend of the foreground M-star and Var Her 04. We
estimate the quiescent level of the TOAD to be magnitudes below
that of the M-star. Based upon the spectral energy distribution and the 2MASS
colors, we find the M-star to be an M3.5V dwarf at a distance of 80-130 pc.
Based upon its outburst amplitude and quiescent apparent magnitude, we estimate
the distance to Var Her 04 to be 200-400 pc, suggesting that the line-of-sight
foreground star is physically unrelated to the cataclysmic variable. All of the
Spitzer photometry is consistent with the photospheric emission of the
line-of-sight M3.5V star, except for one 24 \micron observation obtained after
the variable re-brightened. This 24 \micron flux density is 75 Jy
() above the preceding and following MIPS observations. We tentatively
suggest that the mid-infrared brightening of 75 Jy may be associated with
a dust formation event in the super-outburst ejecta. Assuming a dust
temperature of 100-400 K, we have estimated the amount of dust required. We
find M of dust is needed, consistent with amounts
of mass ejection in TOADs expected during super-outburst, and possibly making
TOADs important contributors to the recycling of the interstellar medium.Comment: Accepted for publication in The Astronomical Journa
Dynamics and transport properties of heavy fermions: theory
The paramagnetic phase of heavy fermion systems is investigated, using a
non-perturbative local moment approach to the asymmetric periodic Anderson
model within the framework of dynamical mean field theory. The natural focus is
on the strong coupling Kondo-lattice regime wherein single-particle spectra,
scattering rates, dc transport and optics are found to exhibit w/w_L,T/w_L
scaling in terms of a single underlying low-energy coherence scale w_L.
Dynamics/transport on all relevant (w,T)-scales are encompassed, from the
low-energy behaviour characteristic of the lattice coherent Fermi liquid,
through incoherent effective single-impurity physics likewise found to arise in
the universal scaling regime, to non-universal high-energy scales; and which
description in turn enables viable quantitative comparison to experiment.Comment: 27 pages, 12 figure
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