510 research outputs found
The survivors
Missing pages 204, 208, and 287. Thesis (M.A.)--Boston Universit
Frictional Heating and Neutron Star Thermal Evolution
Differential rotation between the neutron star crust and a more rapidly
rotating interior superfluid leads to frictional heating that affects the
star's long-term thermal evolution and resulting surface emission. Here we
present the results of thermal evolution simulations based on two models of the
vortex pinning forces that bracket a range of plausible pinning strengths. We
include the effects of superfluidity, magnetic fields, and temperature
gradients. As representative standard and accelerated neutrino emission
processes taking place in the core, we consider the modified Urca process in
normal baryonic matter, and the much faster quark Urca process. Comparison of
our results with neutron star surface temperature data, including the recent
temperature measurement of the Geminga pulsar, shows that stars with soft
equations of state and modest frictional heating are in closest agreement with
the data; stars with stronger frictional heating have temperatures inconsistent
with the upper limit of PSR 1929+10. Stiffer stars undergoing standard cooling
generally have temperatures lying above the Vela detection, a situation
worsened by the inclusion of frictional heating. Stars undergoing accelerated
cooling without frictional heating have temperatures that fall far below most
temperature measurements; the Vela and Geminga detections being the most
compelling examples. Only in stiff stars, which have thick crusts, can the
inclusion of strong frictional heating raise the temperature at late stages in
the evolution to a level consistent with the data. However, such a large amount
of heating leads to a temperature at yr in excess of the Crab upper
limit. Suppression of accelerated neutrino emission processes, perhaps by
superfluid pairing in the core, may yield acceptable cooling models.Comment: AASTeX, 24 pages, 7 figures (Substantial Changes
Comment on ``Signal of Quark Deconfinement in the Timing Structure of Pulsar Spin-Down''
This is a comment on a paper by Glendenning, Pei, and Weber (Phys. Rev.
Lett., 79, 1603, 1997), where the authors gave an incorrect estimate of the
event rate and neglected the important gravitational energy release. Previous
work on the same subject is reviewed, and a new suggestion is made to link
quark-hadron phase transitions with soft gamma-ray repeaters.Comment: 4 pages; to appear in Phys. Rev. Let
Planning For and Applying Military Force: An Examination of Terms
The author briefly examines current and in some cases still evolving definitions in joint doctrine--especially as regards strategy, center of gravity, decisive point, and commander\u27s intent. He discusses the heritage of those concepts and terms, most of which derived from the writings of Clausewitz and Sun Tzu, and finds that current joint planning definitions and concepts tend to confuse more than they inform.https://press.armywarcollege.edu/monographs/1368/thumbnail.jp
University Band Symphonic Band Symphonic Winds
Center for the Performing Arts Sunday Afternoon November 13, 2005 3:00p.m
ROSAT HRI Observations of the Crab Pulsar: An Improved Temperature upper limit for PSR 0531+21
ROSAT HRI observations have been used to determine an upper limit of the Crab
pulsar surface temperature from the off-pulse count rate. For a neutron star
mass of 1.4 \Mo and a radius of 10 km as well as the standard distance and
interstellar column density, the redshifted temperature upper limit is\/
K . This is the lowest temperature
upper limit obtained for the Crab pulsar so far. Slightly different values for
are computed for the various neutron star models available in the
literature, reflecting the difference in the equation of state.Comment: 5 pages, uuencoded postscript, to be published in the Proceedings of
the NATO Advanced Study Insitute on "Lives of the Neutron Stars", ed. A.
Alpar, U. Kiziloglu and J. van Paradijs ( Kluwer, Dordrecht, 1995 )
WATER-VAPOR PRESSURE IN NESTS OF THE SAN MIGUEL ISLAND SONG SPARROW'
Abstract. The water-vapor pressure (Pd in nests of the San Miguel Island race of Song Sparrows (Melospiza melodia micronyx) averaged 16 torr, but varied considerably between nests and within individual nests during successive days of incubation. Large daily fluctuations occurred throughout the incubation period and did not parallel concurrent changes in ambient vapor pressure (P,). Daily rates of water loss from nest eggs (hjl~~o) averaged 28 mg day-' , but also varied considerably within and between nests and did not correlate with changes in P!. I~H,o increased 6-33% after the third day of incubation. P, was significantly higher and MH~O significantly lower in nests located in sheltered gullies than in nests from a windswept slope. These data suggest that Song Sparrows do not regulate P, to achieve hatching success
Landbird Migration in the American West: Recent Progress and Future Research Directions
Our knowledge of avian behaviors during the non-breeding period still lags behind that of the breeding season, but the last decade has witnessed a proliferation in research that has yielded significant progress in understanding migration patterns of North American birds. And, although the great majority of migration research has historically been conducted in the eastern half of the continent, there has been much recent progress on aspects of avian migration in the West. In particular, expanded use of techniques such as radar, plasma metabolites, mist-netting, count surveys, stable isotopes, genetic data, and animal tracking, coupled with an increase in multi-investigator collaborations, have all contributed to this growth of knowledge. There is increasing recognition that migration is likely the most limiting time of year for migratory birds, and this places increasing importance on continuing to decipher patterns of stopover ecology, identifying critical stopover habitats, and documenting migration routes in the diverse and changing landscapes of the American West. Here, we review and briefly synthesize the latest avian migration findings and advances and consider research needs to guide future research on migration in the West
General Relativistic Effects in the Core Collapse Supernova Mechanism
We apply our recently developed code for spherically symmetric, fully general
relativistic (GR) Lagrangian hydrodynamics and multigroup flux-limited
diffusion neutrino transport to examine the effects of GR on the hydrodynamics
and transport during collapse, bounce, and the critical shock reheating phase
of core collapse supernovae. Comparisons of models computed with GR versus
Newtonian hydrodynamics show that collapse to bounce takes slightly less time
in the GR limit, and that the shock propagates slightly farther out in radius
before receding. After a secondary quasistatic rise in the shock radius, the
shock radius declines considerably more rapidly in the GR simulations than in
the corresponding Newtonian simulations. During the shock reheating phase, core
collapse computed with GR hydrodynamics results in a substantially more compact
structure from the center out to the stagnated shock. The inflow speed of
material behind the shock is also increased. Comparisons also show that the
luminosity and rms energy of any neutrino flavor during the shock reheating
phase increases when switching from Newtonian to GR hydrodynamics, and
decreases when switching from Newtonian to GR transport. This latter decrease
in neutrino luminosities and rms energies is less in magnitude than the
increase that arise when switching from Newtonian to GR hydrodynamics, with the
result that a fully GR simulation gives higher neutrino luminosities and harder
neutrino spectra than a fully Newtonian simulation of the same precollapse
model.Comment: 35 pages, 23 figure
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