506 research outputs found
The Mountain Pass Rare-Earth Deposits
Rare-earth minerals were discovered near Mountain Pass in northeastern San Bernardino County, Calif., in April 1949, and in the following year the Sulphide Queen carbonate body was found. This body is the world's greatest known concentration of rare-earth metals with a tonnage larger than the total of all rare earths used in the world prior to 1950. The rare earths in the Mountain Pass district are chiefly cerium, lanthanum, and neodymium.
These elements occur principally in bastnaesite, a rare-earth fluocarbonate, heretofore reported from only about 10 localities in the world.
The bastnaesite was discovered in samples from Mountain Pass obtained by H. E. Woodward and Clarence Watkins of Goodsprings, Nev., and its identity was established in laboratory studies by E . T. Schenk of the U. S. Bureau of Mines and D. F. Hewett of the U. S. Geological Survey. Subsequent prospecting by individuals and geologic investigations by the U. S. Geological Survey resulted in the discovery of bastnaesite in the Sulphide Queen carbonate body and numerous other deposits in a belt 6 miles long.
Investigations by the U. S. Geological Survey since 1949 (Olson et al., in preparation) include detailed mapping of the site of the initial discovery-the Birthday claims-by L. C. Pray and W. N. Sharp; geologic mapping of the district by J. C. Olson; detailed mapping of the Sulphide Queen carbonate body and several smaller deposits by D. R. Shawe and W. N. Sharp; and laboratory mineralogic investigations by H. W. Jaffe
Stability Properties of the Time Domain Electric Field Integral Equation Using a Separable Approximation for the Convolution with the Retarded Potential
The state of art of time domain integral equation (TDIE) solvers has grown by
leaps and bounds over the past decade. During this time, advances have been
made in (i) the development of accelerators that can be retrofitted with these
solvers and (ii) understanding the stability properties of the electric field
integral equation. As is well known, time domain electric field integral
equation solvers have been notoriously difficult to stabilize. Research into
methods for understanding and prescribing remedies have been on the uptick. The
most recent of these efforts are (i) Lubich quadrature and (ii) exact
integration. In this paper, we re-examine the solution to this equation using
(i) the undifferentiated form of the TD-EFIE and (ii) a separable approximation
to the spatio-temporal convolution. The proposed scheme can be constructed such
that the spatial integrand over the source and observer domains is smooth and
integrable. As several numerical results will demonstrate, the proposed scheme
yields stable results for long simulation times and a variety of targets, both
of which have proven extremely challenging in the past.Comment: 9 pages, 13 figures. To be published in IEEE Transactions on Antennas
and Propagatio
The Mountain Pass Rare-Earth Deposits
Rare-earth minerals were discovered near Mountain Pass in northeastern San Bernardino County, Calif., in April 1949, and in the following year the Sulphide Queen carbonate body was found. This body is the world's greatest known concentration of rare-earth metals with a tonnage larger than the total of all rare earths used in the world prior to 1950. The rare earths in the Mountain Pass district are chiefly cerium, lanthanum, and neodymium.
These elements occur principally in bastnaesite, a rare-earth fluocarbonate, heretofore reported from only about 10 localities in the world.
The bastnaesite was discovered in samples from Mountain Pass obtained by H. E. Woodward and Clarence Watkins of Goodsprings, Nev., and its identity was established in laboratory studies by E . T. Schenk of the U. S. Bureau of Mines and D. F. Hewett of the U. S. Geological Survey. Subsequent prospecting by individuals and geologic investigations by the U. S. Geological Survey resulted in the discovery of bastnaesite in the Sulphide Queen carbonate body and numerous other deposits in a belt 6 miles long.
Investigations by the U. S. Geological Survey since 1949 (Olson et al., in preparation) include detailed mapping of the site of the initial discovery-the Birthday claims-by L. C. Pray and W. N. Sharp; geologic mapping of the district by J. C. Olson; detailed mapping of the Sulphide Queen carbonate body and several smaller deposits by D. R. Shawe and W. N. Sharp; and laboratory mineralogic investigations by H. W. Jaffe
An in vitro anatomic model of the human cerebral arteries with saccular arterial aneurysms
Summary: Anin vitro model of the main human cerebral arteries with or without saccular arterial aneurysms is presented. A cast of the cerebral arteries was obtained in a human specimen. Three aneurysms were simulated and added to the cast. Wax copies of the cast were produced, and embedded with liquid resin solidifying into solid blocks. After evacuation of the wax, a model consisting of a hollow reproduction of the cast within the resin block was obtained. The model is reproducible and anatomically accurate. Since it is transparent to visible light, and compatible with x-ray, magnetic resonance and transcranial doppler techniques, it should prove useful for a wide range of haemodynamic and radiologic investigations. The reported technique may be adapted to any structure with a hollow configuration, allowing for the preparation of arterial and venous models from other vascular areas, as well as models from other anatomic systems, such as the biliary or urinary tract
The binary near-Earth asteroid (175706) 1996 FG3 - An observational constraint on its orbital evolution
Using our photometric observations taken between 1996 and 2013 and other
published data, we derived properties of the binary near-Earth asteroid
(175706) 1996 FG3 including new measurements constraining evolution of the
mutual orbit with potential consequences for the entire binary asteroid
population. We also refined previously determined values of parameters of both
components, making 1996 FG3 one of the most well understood binary asteroid
systems. We determined the orbital vector with a substantially greater accuracy
than before and we also placed constraints on a stability of the orbit.
Specifically, the ecliptic longitude and latitude of the orbital pole are
266{\deg} and -83{\deg}, respectively, with the mean radius of the uncertainty
area of 4{\deg}, and the orbital period is 16.1508 +/- 0.0002 h (all quoted
uncertainties correspond to 3sigma). We looked for a quadratic drift of the
mean anomaly of the satellite and obtained a value of 0.04 +/- 0.20 deg/yr^2,
i.e., consistent with zero. The drift is substantially lower than predicted by
the pure binary YORP (BYORP) theory of McMahon and Scheeres (McMahon, J.,
Scheeres, D. [2010]. Icarus 209, 494-509) and it is consistent with the theory
of an equilibrium between BYORP and tidal torques for synchronous binary
asteroids as proposed by Jacobson and Scheeres (Jacobson, S.A., Scheeres, D.
[2011]. ApJ Letters, 736, L19). Based on the assumption of equilibrium, we
derived a ratio of the quality factor and tidal Love number of Q/k = 2.4 x 10^5
uncertain by a factor of five. We also derived a product of the rigidity and
quality factor of mu Q = 1.3 x 10^7 Pa using the theory that assumes an elastic
response of the asteroid material to the tidal forces. This very low value
indicates that the primary of 1996 FG3 is a 'rubble pile', and it also calls
for a re-thinking of the tidal energy dissipation in close asteroid binary
systems.Comment: Many changes based on referees comment
Policy recommendations from the 13th ICABR conference on the emerging bioeconomy
The International Consortium on Agricultural Biotechnology Research held its 13th annual conference in Ravello, Italy in June 2009. The theme of the conference was the bioeconomy,and this topic was addressed through research presentations from academia, government, and industry. Numerous presentations from developing countries highlighted the benefits of agricultural biotechnology in these nations. The broad range of presentations provided a wealth of insights, resulting in three policy recommendations regarding future funding, international regulation, and technology transfer.global food crisis, biofuels, food safety, innovation
GPS Tracking of Free-Ranging Pigs to Evaluate Ring Strategies for the Control of Cysticercosis/Taeniasis in Peru
Background Taenia solium, a parasitic cestode that affects humans and pigs, is the leading cause of preventable epilepsy in the developing world. T. solium eggs are released into the environment through the stool of humans infected with an adult intestinal tapeworm (a condition called taeniasis), and cause cysticercosis when ingested by pigs or other humans. A control strategy to intervene within high-risk foci in endemic communities has been proposed as an alternative to mass antihelminthic treatment. In this ring strategy, antihelminthic treatment is targeted to humans and pigs residing within a 100 meter radius of a pig heavily-infected with cysticercosis. Our aim was to describe the roaming ranges of pigs in this region, and to evaluate whether the 100 meter radius rings encompass areas where risk factors for T. solium transmission, such as open human defecation and dense pig activity, are concentrated. Methodology/Principal Findings In this study, we used Global Positioning System (GPS) devices to track pig roaming ranges in two rural villages of northern Peru. We selected 41 pigs from two villages to participate in a 48-hour tracking period. Additionally, we surveyed all households to record the locations of open human defecation areas. We found that pigs spent a median of 82.8% (IQR: 73.5, 94.4) of their time roaming within 100 meters of their homes. The size of home ranges varied significantly by pig age, and 93% of the total time spent interacting with open human defecation areas occurred within 100 meters of pig residences. Conclusions/Significance These results indicate that 100 meter radius rings around heavily-infected pigs adequately capture the average pig’s roaming area (i.e., home range) and represent an area where the great majority of exposure to human feces occurs
Why Agricultural Technological Transfers to Developing Countries Should be Deregulated
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