50,927 research outputs found
Detector panels-micrometeoroid impact Patent
Development of large area micrometeoroid impact detector panel
Polarization and Extent of Maser Emission from Late-Type Stars: Support for a Plasma Turbulence Model of Maser Production
The integrated spectrum of OH emission from late-type stars is often
circularly polarized, by as much as 50% in some cases. While the spectra are
partially polarized, the individual maser components revealed by VLBI are much
more so. Using VLBI observations of late-type stars from the literature, we
show that the difference in circular polarization between main lines correlates
with a difference in angular extent for a given object. This is a natural
result if turbulent magnetic fields are causing the masers to be polarized via
the Cook mechanism, and might serve as a good diagnostic for determining which
objects should be investigated in the search for magnetic fields around evolved
stars.Comment: 5 pages, 2 figs ApJL, accepte
Alaska mining and water quality
The Institute of Water Resources has sought financial assistance
for some time in an attempt to initiate research relative to the impact
of mining on water quality. Attempts were made as early as 1971 by Dr.
Timothy Tilsworth and later by Dr. Donald Cook and Dr. Sage Murphy.
These investigators anticipated growth in placer gold mining and the
development of natural resources in Alaska during a period of national
and environmental concern. The subsequent energy "crisis," the major
increase in the price of gold on the world market, and dwindling nonrenewable
resource supplies have resulted in large-scale mineral
exploration in Alaska. This exploration, coupled with development of
the trans-Alaska oil pipeline, has attracted considerable capital for
potential investment and development in Alaska. Expected industrial
growth has already started and major new projects are "just around the
corner."
Yet, as of 1976, no major research effort has occurred to determine
the extent of or potential for water quality impacts from mining operations
in Alaska. Recently a series of interdisciplinary research projects
have been completed in Canada; however, the application of Canadian data
to Alaskan problems is uncertain. Although, state and federal government
agencies have been advised and are aware of this potential problem
and lack of baseline data they have not sought out new information or
rational solutions. Even now, with deadlines of Public Law 92-500 at
hand, some regulatory agencies give the impression of attempting to
ignore the situation. Interim limitations are proposed and permits
are issued with no discernible rationale or basis. Data have not been
obtained relative to the Alaskan mining operations and thus are not
available for use in seeking solutions compatible with mining and environmental protection. Numbers appear to have been arbitrarily
assigned to permits and water quality standards. When permits are
issued, self-monitoring requirements are negligible or nonexistent.
Nor have regulatory agencies demonstrated the ability or inclination
to monitor mining operations or enforce permits and water quality
standards.
It was hoped that the project would bring together miners, environmentalists, and regulators in a cooperative effort to identify the
problems and seek solutions. The investigators recognized the political
sensitivity of the subject matter but proceeded optimistically.
Relatively good cooperation, though not total, occurred early in the
project. In April 1976, a symposium was held to exchange ideas and
determine the state-of-the-art. Although the symposium had good
attendance and an exchange of information occurred, the symposium
itself was somewhat of a disappointment. With few exceptions, the
participants aligned on one side or the other in preconceived fixed
positions. Some even chose not to attend and were therefore able to
avoid the issues. Little hard data was presented.
Optimistically, some of the miners, environmentalists, and
regulators are prepared to resolve their differences. This report,
hopefully, will be of benefit to them. It is our experience that
miners and environmentalists share a love of the land that is uniquely
Alaska. We feel that technology is available for application to this
problem for those who care about doing the job right in the "last
frontier." Whether or not it will be effectively applied to protect
Alaska's water resources is a question which remains unanswered.The work upon which this report is based was supported in part by
funds provided by the United States Department of the Interior, Office
of Water Resources Research Act of 1964, Public Law 88-379, as amended
(Project A-055-ALAS)
Quasi-circular Orbits for Spinning Binary Black Holes
Using an effective potential method we examine binary black holes where the
individual holes carry spin. We trace out sequences of quasi-circular orbits
and locate the innermost stable circular orbit as a function of spin. At large
separations, the sequences of quasi-circular orbits match well with
post-Newtonian expansions, although a clear signature of the simplifying
assumption of conformal flatness is seen. The position of the ISCO is found to
be strongly dependent on the magnitude of the spin on each black hole. At close
separations of the holes, the effective potential method breaks down. In all
cases where an ISCO could be determined, we found that an apparent horizon
encompassing both holes forms for separations well inside the ISCO.
Nevertheless, we argue that the formation of a common horizon is still
associated with the breakdown of the effective potential method.Comment: 13 pages, 10 figures, submitted to PR
Exotic Meson Decay Widths using Lattice QCD
A decay width calculation for a hybrid exotic meson h, with JPC=1-+, is
presented for the channel h->pi+a1. This quenched lattice QCD simulation
employs Luescher's finite box method. Operators coupling to the h and pi+a1
states are used at various levels of smearing and fuzzing, and at four quark
masses. Eigenvalues of the corresponding correlation matrices yield energy
spectra that determine scattering phase shifts for a discrete set of relative
pi+a1 momenta. Although the phase shift data is sparse, fits to a Breit-Wigner
model are attempted, resulting in a decay width of about 60 MeV when averaged
over two lattice sizes.Comment: 9 pages, 8 figures, RevTex4, minor change to Fig.
Formation of molecular oxygen in ultracold O + OH reaction
We discuss the formation of molecular oxygen in ultracold collisions between
hydroxyl radicals and atomic oxygen. A time-independent quantum formalism based
on hyperspherical coordinates is employed for the calculations. Elastic,
inelastic and reactive cross sections as well as the vibrational and rotational
populations of the product O2 molecules are reported. A J-shifting
approximation is used to compute the rate coefficients. At temperatures T = 10
- 100 mK for which the OH molecules have been cooled and trapped
experimentally, the elastic and reactive rate coefficients are of comparable
magnitude, while at colder temperatures, T < 1 mK, the formation of molecular
oxygen becomes the dominant pathway. The validity of a classical capture model
to describe cold collisions of OH and O is also discussed. While very good
agreement is found between classical and quantum results at T=0.3 K, at higher
temperatures, the quantum calculations predict a larger rate coefficient than
the classical model, in agreement with experimental data for the O + OH
reaction. The zero-temperature limiting value of the rate coefficient is
predicted to be about 6.10^{-12} cm^3 molecule^{-1} s^{-1}, a value comparable
to that of barrierless alkali-metal atom - dimer systems and about a factor of
five larger than that of the tunneling dominated F + H2 reaction.Comment: 9 pages, 8 figure
Design and development of a water vapor electrolysis unit
Design and development of water vapor electrolysis unit for oxygen productio
Collisions of boosted black holes: perturbation theory prediction of gravitational radiation
We consider general relativistic Cauchy data representing two nonspinning,
equal-mass black holes boosted toward each other. When the black holes are
close enough to each other and their momentum is sufficiently high, an
encompassing apparent horizon is present so the system can be viewed as a
single, perturbed black hole. We employ gauge-invariant perturbation theory,
and integrate the Zerilli equation to analyze these time-asymmetric data sets
and compute gravitational wave forms and emitted energies. When coupled with a
simple Newtonian analysis of the infall trajectory, we find striking agreement
between the perturbation calculation of emitted energies and the results of
fully general relativistic numerical simulations of time-symmetric initial
data.Comment: 5 pages (RevTex 3.0 with 3 uuencoded figures), CRSR-107
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