24,637 research outputs found
A revised HRD for individual components of binary systems from BaSeL BVRI synthetic photometry. Influence of interstellar extinction and stellar rotation
Johnson BVRI photometric data for individual components of binary systems
have been provided by ten Brummelaar et al. (2000). This is essential because
such binaries could play a critical role in calibrating the single-star stellar
evolution theory. While they derived the effective temperature from their
estimated spectral type, we infer metallicity-dependent Teffs from a minimizing
method fitting the B-V, V-R and V-I colours. For this purpose, a grid of
621,600 flux distributions were computed from the Basel Stellar Library (BaSeL
2.2) of model-atmosphere spectra, and their theoretical colours compared with
the observed photometry. As a matter of fact, the BaSeL colours show a very
good agreement with the BVRI metallicity-dependent empirical calibrations of
Alonso et al. (1996), temperatures being different by 3+-3 % in the range
4000-8000 K for dwarf stars. Before deriving the metallicity-dependent Teff
from the BaSeL models, we paid particular attention to the influence of
reddening and stellar rotation. A comparison between the MExcess code and
neutral hydrogen column density data shows a good agreement for the sample but
we point out a few directions where the MExcess model overestimates the E(B-V)
colour excess. Influence of stellar rotation on the BVRI colours can be
neglected except for 5 stars with large vsini, the maximum effect on
temperature being less than 5%. Our final results are in good agreement with
previous spectroscopic determinations available for a few primary components,
and with ten Brummelaar et al. below ~10,000 K. Nevertheless, we obtain an
increasing disagreement with their Teffs beyond 10,000 K. Finally, we provide a
revised Hertzsprung-Russell diagram for the systems with the more accurately
determined temperatures. (Abridged)Comment: 11 pages, accepted for publication in A&
Numerical solution of open string field theory in Schnabl gauge
Using traditional Virasoro level-truncation computations, we evaluate
the open bosonic string field theory action up to level . Extremizing
this level-truncated potential, we construct a numerical solution for tachyon
condensation in Schnabl gauge. We find that the energy associated to the
numerical solution overshoots the expected value at level .
Extrapolating the level-truncation data for to estimate the vacuum
energies for , we predict that the energy reaches a minimum value at , and then turns back to approach asymptotically as . Furthermore, we analyze the tachyon vacuum expectation value (vev),
for which by extrapolating its corresponding level-truncation data, we predict
that the tachyon vev reaches a minimum value at , and then turns
back to approach the expected analytical result as .Comment: 37 pages, 9 figures, some typos correcte
Learning-by-Doing, Learning-by-Exporting, and Productivity: Evidence from Colombia
The empirical evidence on whether participation in export markets increases plant-level productivity has been inconclusive so far. We explain this inconclusiveness by drawing on Arrow's (1962) characterization of learning-by-doing, which suggests focusing on young plants and using measures of export experience rather than export participation. We find strong evidence of learning-by-exporting for young Colombian manufacturing plants between 1981 and 1991: total factor productivity increases 4%-5% for each additional year a plant has exported, after controlling for the effect of current exports on total factor productivity. Learning-by-exporting is more important for young than for old plants and in industries that deliver a larger percentage of their exports to high-income countries.learning, trade, total factor productivity, exports, export-led growth
Learning-by-doing, learning-by-exporting, and productivity : evidence from Colombia
The empirical evidence on whether participation in export markets increases plant-level productivity has been inconclusive so far. The authors explain this inconclusiveness by drawing on Arrow's (1962) characterization of learning-by-doing, which suggests focusing on young plants and using measures of export experience rather than export participation. They find strong evidence of learning-by-exporting for young Colombian manufacturing plants between 1981 and 1991: total factor productivity increases 4-5 percent for each additional year a plant has exported, after controlling for the effect of current exports on total factor productivity. Learning-by-exporting is more important for young than for old plants and in industries that deliver a larger percentage of their exports to high-income countries.Economic Theory&Research,Environmental Economics&Policies,Banks&Banking Reform,Educational Sciences,Scientific Research&Science Parks
Urinary incontinence: A vibration alert system for detecting pad overflow
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2011 RESNA.A sensor and electronics system is described that monitors the leakage of urine from continence pads into surrounding underwear. Urinary incontinence is involuntary loss of urine and occurs when the bladder muscles contract without warning or the sphincter muscles surrounding the urethra are too weak to prevent leakage. The system comprises a wetness sensor and electronics unit. The sensor is stitched into the underwear and detects overspills of urine from the pad. The electronics unit is attached to the underwear and responds by vibrating, signaling to the wearer that pad has failed. This system has application for individuals who use continence pads in the community, but it could also be used in care homes
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