2,682 research outputs found
Ideal black hole gas
The concept of a primordial blackhole fluid with intrinsic spin density is examined along with its consequence for supercluster-sized, i.e., large scale voids, and the missing mass question
Effects of environmental changes on marsh vegetation with special reference to salinity
A literature survey primarily concerned with brackish and salt marshes located along the eastern coast of North America and the Gulf Coast was presented. The review concentrated upon the vegetation of the marshes, particularly in regard to distribution, composition, succession, and productivity. Special efforts were made to include major works concerned with the Louisiana and Mississipi coastal marshes. It appears that spring to early summer (weeks 18-34 of the year; April - mid-July) is the best period of time to categorize the communities. It is during this time of the year that the communities appear most stable in regard to species composition. This allows a strong correlation to be drawn between the salinity of the region and the dominant species of the community. As such, this would seem to be best period in which to sample the marsh via air or land for differences in vegetation and salinity
Eclipsing binaries in open clusters
Accurate physical parameters have been determined for two early-type detached
eclipsing binaries in the open cluster h Persei (NGC 869). Masses accurate to
1.5% are derived from high-resolution spectroscopy and radii accurate to 4--6%
have been obtained from fitting the existing light curves. The four stars are
placed in the mass radius plane and compared to the theoretical stellar models
of the Granada Group. The best-fitting models have a low metallicity of
approximately Z=0.01 and a high helium abundance of Y=0.34. This is the first
determination of the bulk metallicity of the Perseus Double Cluster. Recent
studies have assumed a solar metallicity so their results should be reviewed.Comment: 4 pages, 5 figures. To appear in Spectroscopically and Spatially
Resolving the Components of Close Binary Stars, ASP Conf. Series, 200
The Hunter Elite: Manly Sport, Hunting Narratives, and American Conservation, 1880-1925
Review of: "The Hunter Elite: Manly Sport, Hunting Narratives, and American Conservation, 1880-1925" by Tara Kathleen Kell
Small, high-speed bearing technology for cryogenic turbo-pumps
The design of 20-mm bore ball bearings is described for cryogenic turbo-machinery applications, operating up to speeds of 120,000 rpm. A special section is included on the design of hybrid bearings. Each hybrid bearing is composed of a ball bearing in series with a conventional pressurized fluid-film journal bearing. Full details are presented on the design of a test vehicle which possesses the capability of testing the above named bearings within the given speed range under externally applied radial and axial loads
Inflation in Einstein-Cartan theory with energy-momentum tensor with spin
Generalized, or power-law, inflation is shown to necessarily exist for a simple, anisotropic (Bianchi Type I) cosmology in the Einstein-Cartan gravitational theory with the Ray-Smalley (RS) improved energy-momentum tensor with spin. Formal solution of the EC field equations with the fluid equations of motion explicitly shows inflation caused by the RS spin angular kinetic energy density
The mass and radius of the M-dwarf in the short period eclipsing binary RR Caeli
We present new photometry and spectroscopy of the eclipsing white dwarf -
M-dwarf binary star RR Cae. We use timings of the primary eclipse from
white-light photo-electric photometry to derive a new ephemeris for the
eclipses. We find no evidence for any period change greater than Pdot/P ~ 5E-12
over a timescale of 10 years. We have measured the effective temperature of the
white dwarf, T_WD, from an analysis of two high resolution spectra of RR Cae
and find T_WD = (7540 +- 175)K. We estimate a spectral type of M4 for the
companion from the same spectra. We have combined new spectroscopic orbits for
the white dwarf and M-dwarf with an analysis of the primary eclipse and cooling
models for helium white dwarfs to measure the mass and radius of the M-dwarf.
The mass of the M-dwarf is (0.182 - 0.183) +- 0.013 Msun and the radius is
(0.203 - 0.215) +- 0.013 Rsun, where the ranges quoted for these values reflect
the range of white dwarf models used. In contrast to previous studies, which
lacked a spectroscopic orbit for the white dwarf, we find that the mass and
radius of the M-dwarf are normal for an M4 dwarf. The mass of the white dwarf
is (0.440 +-0.022) Msun. With these revised masses and radii we find that RR
Cae will become a cataclysmic variable star when the orbital period is reduced
from its current value of 7.3 hours to 121 minutes by magnetic braking in 9-20
Gyr. We note that there is night-to-night variability of a few seconds in the
timing of primary eclipse caused by changes to the shape of the primary
eclipse. We speculate as to the possible causes of this phenomenon. (Abridged)Comment: Accepted for publication in MNRAS. The paper contains 10 figures and
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