723 research outputs found
Plans for a 10-m Submillimeter-wave Telescope at the South Pole
A 10 meter diameter submillimeter-wave telescope has been proposed for the
NSF Amundsen-Scott South Pole Station. Current evidence indicates that the
South Pole is the best submillimeter-wave telescope site among all existing or
proposed ground-based observatories. Proposed scientific programs place
stringent requirements on the optical quality of the telescope design. In
particular, reduction of the thermal background and offsets requires an
off-axis, unblocked aperture, and the large field of view needed for survey
observations requires shaped optics. This mix of design elements is well-suited
for large scale (square degree) mapping of line and continuum radiation from
submillimeter-wave sources at moderate spatial resolutions (4 to 60 arcsecond
beam size) and high sensitivity (milliJansky flux density levels). the
telescope will make arcminute angular scale, high frequency Cosmic Microwave
Background measurements from the best possible ground-based site, using an
aperture which is larger than is currently possible on orbital or airborne
platforms. Effective use of this telescope will require development of large
(1000 element) arrays of submillimeter detectors which are background-limited
when illuminated by antenna temperatures near 50 K.Comment: 12 pages, 3 figure
Remote sensing and geologic studies of the orientale basin region
Both visual and near-infrared spectral observations are combined with multispectral imaging to study the Orientale interior and exterior, the Cruger region, Grimaldi Region, the Schiller-Schickard Region, and the Humorum Region of the Moon. It was concluded that anorthosites occur in the Inner Rook Mountains of Orientale, the inner ring of Grimaldi, and the main ring of Humorum. Imaging spectroscopy shows that the entire eastern Inner Rook Mountains are composed of anorthosites. Orientale ejecta are strikingly like the surface materials in the region where Apollo 16 landed. This similarity indicates similar mineralogy, i.e., noritic anorthosite. Thus, Orientile ejecta is more mafic than the Inner Rook Mountains. This situation is also true for the Nectaris, Humorum, and Gramaldi basins. Isolated areas of the Orientale region show the presence of gabbroic rocks, but, in general, Orientale ejecta are noritic anorthosites, which contain much more low-Ca pyroxene than high-Ca pyroxene. Ancient (pre-Orientale) mare volcanism apparently occurred in several areas of the western limb
Extrahepatic tissue concentrations of vitamin K are lower in rats fed a high vitamin E diet
BACKGROUND: An adverse hematological interaction between vitamins E and K has been reported, primarily in patients on anticoagulants. However, little is known regarding circulating levels or tissue concentrations of vitamin K in response to vitamin E supplementation. The purpose of this study was to examine the effect of different levels of dietary α-tocopherol on phylloquinone and menaquinone-4 concentrations, while maintaining a constant intake of phylloquinone, in rat tissues. METHODS: Male 4-wk old Fischer 344 rats (n = 33) were fed one of 3 diets for 12 wk: control (n = 13) with 30 mg all-rac-α-tocopherol acetate/kg diet; vitamin E-supplemented (n = 10) with 100 mg all-rac-α-tocopherol acetate/kg diet; and vitamin E-restricted (n = 10) with <10 mg total tocopherols/kg diet. All 3 diets contained 470 ± 80 μg phylloquinone/kg diet. RESULTS: Phylloquinone concentrations were lower (P ≤ 0.05) in the vitamin E-supplemented compared to the vitamin E-restricted group (mean ± SD spleen: 531 ± 58 vs.735 ± 77; kidney: 20 ± 17 vs. 94 ± 31, brain: 53 ± 19 vs.136 ± 97 pmol/g protein respectively); no statistically significant differences between groups were found in plasma, liver or testis. Similar results were noted with menaquinone-4 concentrations in response to vitamin E supplementation. CONCLUSION: There appears to be a tissue-specific interaction between vitamins E and K when vitamin E is supplemented in rat diets. Future research is required to elucidate the mechanism for this nutrient-nutrient interaction
Developmental Morphology Of Tropical Sorghum And Sorghum X Sudangrass
Tropical sorghum and sorghum x sudangrass are known to be efficient scavengers of soil nitrogen and are important forage crops in the U.S. Nitrate contamination of groundwater due to disposal of organic wastes and excessive fertilization is a major concern in the Central Great Plains. A common disposal method of municipal wastes is application to fallow cropland. Quantification of the developmental morphology of tropical sorghum and sorghum x sudangrass is important to developing management strategies that allow multiple applications of organic wastes to optimize nitrogen removal and dry matter production. The objective of this study was to quantify the developmental morphology of tropical sorghum and sorghum x sudangrass irrigated at levels approximating transpiration and evaporative demand. Tropical sorghum mean stage by count (MSC) was 33% lower than MSC for sorghum x sudangrass in September. Leaf-to-stem ratio was greater for tropical sorghum than sorghum x sudangrass throughout most of the growing season. Dry matter per plant was as much as 30% greater for sorghum x sudangrass, although values were nearly equal at the end of the growing season
Developmental Morphology Of Tropical Sorghum And Sorghum X Sudangrass
Tropical sorghum and sorghum x sudangrass are known to be efficient scavengers of soil nitrogen and are important forage crops in the U.S. Nitrate contamination of groundwater due to disposal of organic wastes and excessive fertilization is a major concern in the Central Great Plains. A common disposal method of municipal wastes is application to fallow cropland. Quantification of the developmental morphology of tropical sorghum and sorghum x sudangrass is important to developing management strategies that allow multiple applications of organic wastes to optimize nitrogen removal and dry matter production. The objective of this study was to quantify the developmental morphology of tropical sorghum and sorghum x sudangrass irrigated at levels approximating transpiration and evaporative demand. Tropical sorghum mean stage by count (MSC) was 33% lower than MSC for sorghum x sudangrass in September. Leaf-to-stem ratio was greater for tropical sorghum than sorghum x sudangrass throughout most of the growing season. Dry matter per plant was as much as 30% greater for sorghum x sudangrass, although values were nearly equal at the end of the growing season
High-resolution diffraction reveals magnetoelastic coupling and coherent phase separation in tetragonal CuMnAs
Tetragonal CuMnAs was the first antiferromagnet where reorientation of the
N\'eel vector was reported to occur by an inverse spin galvanic effect. A
complicating factor in the formation of phase-pure tetragonal CuMnAs is the
formation of an orthorhombic phase with nearly the same stoichiometry.
Pure-phase tetragonal CuMnAs has been reported to require an excess of Cu to
maintain a single phase in traditional solid state synthesis reactions. Here we
show that subtle differences in diffraction patterns signal pervasive
inhomogeneity and phase separation, even in Cu-rich CuMnAs.
From calorimetry and magnetometry measurements, we identify two transitions
corresponding to the N\'eel temperature (T) and an antiferromagnet to weak
ferromagnet transition in CuMnAs and
CuMnAs. These transitions have clear crystallographic
signatures, directly observable in the lattice parameters upon in-situ heating
and cooling. The immiscibility and phase separation could arise from a
spinoidal decomposition that occurs at high temperatures, and the presence of a
ferromagnetic transition near room temperature warrants further investigation
of its effect on the electrical switching behavior.Comment: 10 pages, 9 figures, added author middle initia
Electrical conductivity of dispersions: from dry foams to dilute suspensions
We present new data for the electrical conductivity of foams in which the
liquid fraction ranges from two to eighty percent. We compare with a
comprehensive collection of prior data, and we model all results with simple
empirical formul\ae. We achieve a unified description that applies equally to
dry foams and emulsions, where the droplets are highly compressed, as well as
to dilute suspensions of spherical particles, where the particle separation is
large. In the former limit, Lemlich's result is recovered; in the latter limit,
Maxwell's result is recovered
NGC 5548 in a Low-Luminosity State: Implications for the Broad-Line Region
We describe results from a new ground-based monitoring campaign on NGC 5548,
the best studied reverberation-mapped AGN. We find that it was in the lowest
luminosity state yet recorded during a monitoring program, namely L(5100) = 4.7
x 10^42 ergs s^-1. We determine a rest-frame time lag between flux variations
in the continuum and the Hbeta line of 6.3 (+2.6/-2.3) days. Combining our
measurements with those of previous campaigns, we determine a weighted black
hole mass of M_BH = 6.54 (+0.26/-0.25) x 10^7 M_sun based on all broad emission
lines with suitable variability data. We confirm the previously-discovered
virial relationship between the time lag of emission lines relative to the
continuum and the width of the emission lines in NGC 5548, which is the
expected signature of a gravity-dominated broad-line region. Using this lowest
luminosity state, we extend the range of the relationship between the
luminosity and the time lag in NGC 5548 and measure a slope that is consistent
with alpha = 0.5, the naive expectation for the broad line region for an
assumed form of r ~ L^alpha. This value is also consistent with the slope
recently determined by Bentz et al. for the population of reverberation-mapped
AGNs as a whole.Comment: 24 pages, 3 tables, 7 figures, accepted for publication in Ap
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