Optical Astronomy from Orbiting Observatories

Atmospheric extinction, seeing, and light pollution £re the most significant factors affecting the quality of observations obtained from ground-based optical telescopes, degrading resolution and limiting reach. In addition, the earth\u27s atmosphere is opaque to radiation shorter than 0.3 microns preventing the ultraviolet from being observed in detail from the ground. The solution to these problems has been to move astronomical telescopes into earth orbit. Initially these orbiting observatories carried instruments sensitive to ultraviolet and higher energy radiation since it was otherwise unobservable. The success of the first series of these orbiting observatories, the Orbiting Astronomical Observatories (OAO), established these satellites as one of a new generation of tools for exploring the universe. Another orbiting observatory, the International Ultraviolet Explorer (IUE), is unique among the current orbiting observatories in that it is in a geosynchronous orbit and provides a guest observer facility serving the international community. IUE has had a significant impact on observational astronomy. Nearly 10 percent of all observational papers published JLi the Astrophysical Journal in 1980 reported or used observations made by IUE. The figure for all astronomical satellites is about 3 times higher and continues to rise. With the orbiting of the Space Telescope in the mid 1980s by the Space Shuttle, observational astronomy will enter a new era. For the first time, astronomers will have access to a large (2.4 meter) high-resolution telescope unhindered by the earth f s atmosphere. With the potential such an instrument offers, there is little doubt that the near future will see a large fraction of observational astronomy performed from orbiting observatories

Direct Evidence for the Source of Reported Magnetic Behavior in "CoTe"

In order to unambiguously identify the source of magnetism reported in recent studies of the Co-Te system, two sets of high-quality, epitaxial CoTe$_x$ films (thickness $\simeq$ 300 nm) were prepared by pulse laser deposition (PLD). X-ray diffraction (XRD) shows that all of the films are epitaxial along the [001] direction and have the hexagonal NiAs structure. There is no indication of any second phase metallic Co peaks (either $fcc$ or $hcp$) in the XRD patterns. The two sets of CoTe$_x$ films were grown on various substrates with PLD targets having Co:Te in the atomic ratio of 50:50 and 35:65. From the measured lattice parameters $c = 5.396 \AA$ for the former and $c = 5.402\AA$ for the latter, the compositions CoTe$_{1.71}$ (63.1% Te) and CoTe$_{1.76}$ (63.8% Te), respectively, are assigned to the principal phase. Although XRD shows no trace of metallic Co second phase, the magnetic measurements do show a ferromagnetic contribution for both sets of films with the saturation magnetization values for the CoTe$_{1.71}$ films being approximately four times the values for the CoTe$_{1.76}$ films. $^{59}$Co spin-echo nuclear magnetic resonance (NMR) clearly shows the existence of metallic Co inclusions in the films. The source of weak ferromagnetism reported in several recent studies is due to the presence of metallic Co, since the stoichiometric composition "CoTe" does not exist.Comment: 19 pages, 7 figure

A Trap for Use on Tidal Weirs and Streams

Over 100,000 ha of Louisiana coastal marsh have been semi-impounded by weir construction. This paper describes a trap designed specifically for use at weirs to study certain aspects of the juvenile life history of aquatic species. The trap could be modified easily for use in other situations

Supporting data - Recycling of nitrate and organic matter by plants in the vadose zone of a saturated riparian buffer

Data from the analysis of nitrate as nitrogen in the soil and soil pore water within the vadose zone of a saturated riparian buffer (SRB). Additional properties measured include: Organic matter (as %), bulk density, moisture content, and porosity. Soil samples were collected pre-growing season (n=57) and post-growing season from two plots (n=29): vegetated plots and barren plots. Statistical comparison of among the treatments, Pre-growing season, plot with plants, and barren plot, and among the different depths, 30 cm, 60 cm, and 90 cm identified significantly different soil NO3--N concentrations. Plots with plants experienced a reduction in nitrate from the soil and vadose waters. Plants withdrew nitrate from the vadose zone, generating organic matter. Nitrate concentrations in the soils underlying the barren plot were high because there was no uptake and the residual plants materials decomposed, returning nitrogen to the vadose. Soil pore water samples were collected using a lysimeter from the barren plots (n=64) and the vegetated plots (n=35)

Interventions to Promote More Effective Balance-Recovery Reactions in Industrial Settings: New Perspectives on Footwear and Handrails

“Change-in-support” balance-recovery reactions that involve rapid stepping or reaching movements play a critical role in preventing falls. Recent geriatrics studies have led to new interventions to improve ability to execute these reactions effectively. Some of these interventions have the potential to reduce fall risk for younger persons working in industrial settings. In this paper, we review research pertaining to two such interventions: 1) balance-enhancing footwear insoles designed to improve stepping reactions, and 2) proximity-triggered handrail cueing systems designed to improve reach-to-grasp reactions. The insole has a raised ridge around the perimeter that is intended to improve balance control by providing increased stimulation of sensory receptors on the footsole in situations where loss of balance may be imminent. The cueing system uses flashing lights and/or verbal prompts to attract attention to the handrail and ensure that the brain registers its location, thereby facilitating more rapid and accurate grasping of the rail if and when sudden loss of balance occurs. Results to date support the efficacy of both interventions in geriatric populations. There is also some evidence that these interventions may improve balance control in younger persons; however, further research is needed to confirm their efficacy in preventing falls in industrial settings

Phenomenology for the decay of energy-containing eddies in homogeneous MHD turbulence

We evaluate a number of simple, one‐point phenomenological models for the decay of energy‐containing eddies in magnetohydrodynamic(MHD) and hydrodynamicturbulence. The MHDmodels include effects of cross helicity and Alfvénic couplings associated with a constant mean magnetic field, based on physical effects well‐described in the literature. The analytic structure of three separate MHDmodels is discussed. The single hydrodynamic model and several MHDmodels are compared against results from spectral‐method simulations. The hydrodynamic model phenomenology has been previously verified against experiments in wind tunnels, and certain experimentally determined parameters in the model are satisfactorily reproduced by the present simulation. This agreement supports the suitability of our numerical calculations for examining MHDturbulence, where practical difficulties make it more difficult to study physical examples. When the triple‐decorrelation time and effects of spectral anisotropy are properly taken into account, particular MHDmodels give decay rates that remain correct to within a factor of 2 for several energy‐halving times. A simple model of this type is likely to be useful in a number of applications in space physics, astrophysics, and laboratory plasma physics where the approximate effects of turbulence need to be included

The Antiferromagnetic Band Structure of La2CuO4 Revisited

Using the Becke-3-LYP functional, we have performed band structure calculations on the high temperature superconductor parent compound, La2CuO4. Under the restricted spin formalism (rho(alpha) equal to rho(beta)), the R-B3LYP band structure agrees well with the standard LDA band structure. It is metallic with a single Cu x2-y2/O p(sigma) band crossing the Fermi level. Under the unrestricted spin formalism (rho(alpha) not equal to rho(beta)), the UB3LYP band structure has a spin polarized antiferromagnetic solution with a band gap of 2.0 eV, agreeing well with experiment. This state is 1.0 eV (per formula unit) lower than that calculated from the R-B3LYP. The apparent high energy of the spin restricted state is attributed to an overestimate of on-site Coulomb repulsion which is corrected in the unrestricted spin calculations. The stabilization of the total energy with spin polarization arises primarily from the stabilization of the x2-y2 band, such that the character of the eigenstates at the top of the valence band in the antiferromagnetic state becomes a strong mixture of Cu x2-y2/O p(sigma) and Cu z2/O' p(z). Since the Hohenberg-Kohn theorem requires the spin restricted and spin unrestricted calculations give exactly the same ground state energy and total density for the exact functionals, this large disparity in energy reflects the inadequacy of current functionals for describing the cuprates. This calls into question the use of band structures based on current restricted spin density functionals (including LDA) as a basis for single band theories of superconductivity in these materials.Comment: 13 pages, 8 figures, to appear in Phys. Rev. B, for more information see http://www.firstprinciples.co

Aeroservoelastic wind-tunnel investigations using the Active Flexible Wing Model: Status and recent accomplishments

The status of the joint NASA/Rockwell Active Flexible Wing Wind-Tunnel Test Program is described. The objectives are to develop and validate the analysis, design, and test methodologies required to apply multifunction active control technology for improving aircraft performance and stability. Major tasks include designing digital multi-input/multi-output flutter-suppression and rolling-maneuver-load alleviation concepts for a flexible full-span wind-tunnel model, obtaining an experimental data base for the basic model and each control concept and providing comparisons between experimental and analytical results to validate the methodologies. The opportunity is provided to improve real-time simulation techniques and to gain practical experience with digital control law implementation procedures

Fertilizer Recommendations for the Rio Grande Plain.

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