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in creator/contributor: "United States. National Aeronautics and Space Administration."

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Study of ICRF wave propagation and plasma coupling efficiency in a linear magnetic mirror device

Ion Cyclotron Range of Frequency (ICRF) wave propagation in an inhomogeneous axial magnetic field in a cylindrical plasma-vacuum system has historically been inadequately modelled. Previous works either sacrifice the cylindrical geometry in favor of a simpler slab geometry, concentrate on the resonance region, use a single mode to represent the entire field structure, or examine only radial propagation. This thesis performs both analytical and computational studies to model the ICRF wave-plasma… more

Date: July 1, 1991

Creator: Peng, S.Y.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Radioactivities of Long Duration Exposure Facility (LDEF) materials: Baggage and bonanzas

Radioactivities in materials onboard the returned Long Duration Exposure Facility (LDEF) satellite have been studied by a variety of techniques. Among the most powerful is low-background Ge-semiconductor detector gamma-ray spectrometry, illustrated here by results obtained at the Lawrence Berkeley Laboratory's (LBL) Low Bakground Facilities, in a multi-laboratory collaboration coordinated by Dr. Thomas Parnell's team at the Marshall Spacecraft Center, Huntsville, Alabama.

Date: August 1, 1991

Creator: Smith, A. R. & Hurley, D. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Future aircraft and potential effects on stratospheric ozone and climate

The purpose of this study is to extend the recent research examining the global environmental effects from potential fleets of subsonic and supersonic commercial aircraft. Initial studies with LLNL models of global atmospheric chemical, radiative, and transport processes have indicated that substantial decreases in stratospheric ozone concentrations could result from emissions of NO{sub x} from aircraft flying in the stratosphere, depending on fleet size and magnitude of the engine emissions. T… more

Date: October 1, 1991

Creator: Kinnison, D.E. & Wuebbles, D.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Cosmology and the weak interaction

The weak interaction plays a critical role in modern Big Bang cosmology. This review will emphasize two of its most publicized cosmological connections: Big Bang nucleosynthesis and Dark Matter. The first of these is connected to the cosmological prediction of Neutrino Flavours, N{sub {nu}} {approximately} 3 which is now being confirmed at SLC and LEP. The second is interrelated to the whole problem of galaxy and structure formation in the universe. This review will demonstrate the role of the … more

Date: December 1, 1989

Creator: Schramm, D. N.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The carbon isotopic composition of atmospheric methane and its sources and trends; distribution of source fluxes and their contribution to the increasing concentration

The goal of isotopic studies of atmospheric methane is the determination of the relative fluxes of the various sources of different isotopic composition. Because of the large number of generic anthropogenic source types it is not possible to determine their relative strengths based on carbon-13 data alone. However, by combining sources of similar isotopic composition (as well as similar origin), and utilizing results from other studies it is possible to calculate some important features of the … more

Date: January 1, 1991

Creator: Stevens, C.M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Quantitative analysis of bidirectional electron fluxes within coronal mass ejections at 1 AU

The solar wind electron heat flux is carried primarily by suprathermal halo'' electrons beamed antisunward along the interplanetary magnetic field (IMF), indicating magnetic connection to the Sun only in one direction. However, electron observations at 1 AU show that counterstreaming halo beams, suggesting closed magnetic structures, prevail within coronal mass ejections (CMEs). These structures might be magnetic tongues'', tied to the Sun at both ends, magnetically detached plasmoids, or compl… more

Date: January 1, 1991

Creator: Phillips, J.L.; Gosling, J.T.; McComas, D.J.; Bame, S.J. & Feldman, W.C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Development of ultra pure germanium epi layers for blocked impurity band far infrared detectors

The main goals of this paper are: (1) To develop a low-pressure CVD (LPCVD) process that allows epitaxial growth at lower temperatures. Lower temperatures will allow the achievement of a sharp dopant profile at the substrate/epi-layer interface. Less out-diffusion from the substrate would allow the use of thinner epitaxial layers, which would lead to a larger depletion width in the photoactive region. LPCVD also avoids, to a great extent, gas-phase nucleation, which would cause Ge particulates … more

Date: May 1, 1991

Creator: Lutz, M.P.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Quark matter and cosmology

The possible implications of the quark-hadron transition for cosmology are explored. Possible surviving signatures are discussed. In particular, the possibility of generating a dark matter candidate such as strange nuggets or planetary mass black holes is noted. Much discussion is devoted to the possible role of the transition for cosmological nucleosynthesis. It is emphasized that even an optimized first order phase transition will not significantly alter the nucleosynthesis constraints on the… more

Date: January 1, 1992

Creator: Schramm, D.N. (Chicago Univ., IL (United States) Fermi National Accelerator Lab., Batavia, IL (United States)); Fields, B. & Thomas, D. (Chicago Univ., IL (United States))

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Relating space radiation environments to risk estimates

This lecture will provide a bridge from the physical energy or LET spectra as might be calculated in an organ to the risk of carcinogenesis, a particular concern for extended missions to the moon or beyond to Mars. Topics covered will include (1) LET spectra expected from galactic cosmic rays, (2) probabilities that individual cell nuclei in the body will be hit by heavy galactic cosmic ray particles, (3) the conventional methods of calculating risks from a mixed environment of high and low LET… more

Date: October 1, 1991

Creator: Curtis, S.B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The many aspects of neutrino physics

In mid-November, over seventy physicists gathered at Fermilab for an informal workshop on the Many Aspects of Neutrino Physics, which dovetailed with and also helped lay the groundwork for the succeeding more narrowly focused conference on Long Baseline Neutrino Oscillations. The workshop indeed covered many of the interrelated aspects of neutrino physics: 17 keV neutrinos (experiments, theoretical models, and astrophysical constraints), neutrino properties (double beta decay experiments, neutr… more

Date: January 1, 1992

Creator: Frieman, J.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Resonant enhancement of flavor-changing neutrino interactions

The resonant amplification of neutrino oscillations in the presence of flavor-changing neutrino interactions with matter is analyzed. It is shown that a significant {mu}-flavor conversion can take place even in the absence of neutrino mixing in vacuum. To account for the solar neutrino deficit, the strength of the new interactions should be {approximately} 10{sup {minus}2}G{sub F} and the resulting neutrino suppression and spectrum is similar to that in the ordinary MSW effect. I discuss some e… more

Date: October 1, 1991

Creator: Roulet, E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Solar neutrinos: theory vs experiment

I review the standard solar model, the disparities between its predictions and the solar neutrino flux measurements of the Homestake and Kamioka II collaborations, and possible particle physics resolutions of this puzzle. The effects of matter, including density fluctuations and turbulence, on solar neutrino oscillations are reviewed, including possibilities for generating time variations in the solar neutrino flux. Finally, I consider possible outcomes and implications of the SAGE/GALLEX galli… more

Date: January 1, 1991

Creator: Haxton, W. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electrochemical energy storage using PEM systems

This paper gives the results of an engineering assessment for future, long-lived space power systems for extraterrestrial applications. Solar-based, regenerative fuel cell power plants formed from either alkaline or PEM components are the focus. Test results on advanced PEM fuel cell stack components are presented. 7 refs., 4 figs., 1 tab.

Date: January 1, 1991

Creator: Vanderborgh, N. E.; Hedstrom, J. C. & Huff, J. R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Capillary surfaces in exotic containers

A survey is presented of results to date for capillary surfaces in exotic'' containers. These containers have the property that each one admits a continuum of distinct equilibrium free surfaces, all bounding with the container walls the same volume of fluid, making the same contact angle at the trip interface curve, and having identical mechanical energies. The containers can be so designed that they are themselves axially symmetric but that the fluid configurations of minimizing energy cannot … more

Date: July 1, 1991

Creator: Concus, P. (Lawrence Berkeley Lab., CA (United States)) & Finn, R. (Stanford Univ., CA (United States). Dept. of Mathematics)

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Comparison of synchrotron x-ray microanalysis with electron and proton microscopy for individual particle analysis

This paper is concerned with the evaluation of the use of synchrotron/radiation induced x-ray fluorescences ({mu}-SRXRF) as implemented at two existing X-ray microprobes for the analysis of individual particles. As representative environmental particulates, National Institutes of Science and Technology (NIST) K227, K309, K441 and K961 glass microspheres were analyzed using two types of X-ray micro probes: the white light microprobe at beamline X26A of the monochromatic (15 keV) X-ray microprobe… more

Date: January 1, 1991

Creator: Janssens, K. H.; van Langevelde, F.; Adams, F. C.; Vis, R. D.; Sutton, S. R.; Rivers, M. L. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Dark matter and cosmology

The cosmological dark matter problem is reviewed. The Big Bang Nucleosynthesis constraints on the baryon density are compared with the densities implied by visible matter, dark halos, dynamics of clusters, gravitational lenses, large-scale velocity flows, and the {Omega} = 1 flatness/inflation argument. It is shown that (1) the majority of baryons are dark; and (2) non-baryonic dark matter is probably required on large scales. It is also noted that halo dark matter could be either baryonic or n… more

Date: March 1, 1992

Creator: Schramm, D. N.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Booster Applications Facility report, Phase 2

This report summarizes studies and planning performed by Brookhaven National Laboratory (BNL) personnel at the request of NASA for the design, construction and operation of experimental areas and facilities for utilization of ion beams from the BNL Booster synchrotron particle accelerator. These facilities would be primarily utilized to simulate space radiation for radiobiological research, shielding studies and detector calibrations. The feasibility of such a project has been established, prel… more

Date: June 1, 1991

Creator: Thieberger, P. (ed.)

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Status of the Advanced Stirling Conversion System Project for 25 kW dish Stirling applications

Under the Department of Energy's (DOE) Solar Thermal Technology Program, Sandia National Laboratories is evaluating heat engines for terrestrial Solar Heat Receivers. The Stirling engine has been identified by Sandia as one of the most promising heat engines for terrestrial applications. The Stirling engine also has the potential to meet DOE's performance and cost goals. The NASA Lewis Research Center is conducting technology development for Stirling convertors directed toward a dynamic power s… more

Date: January 1, 1991

Creator: Shaltens, R.K. & Schreiber, J.G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Status of Rankine-cycle technology for space nuclear power applications

A substantial effort on the development of the liquid metal Rankine cycle space nuclear power system was carried out in programs jointly sponsored by the National Aeronautics and Space Administration (NASA) and the Atomic Energy Commission (AEC) during the period of 1960--1972. Component tests were conducted which have established a considerable technology base for the concept. The development effort and technology status of each component are presented. The key technology issues remaining for … more

Date: January 1, 1991

Creator: Holcomb, R.S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Neon Novae, Recurrent Novae, and Type I Supernovae

Over the past few years, we have been investigating the effects of accretion onto massive white dwarfs and its implications for their growth in mass toward the Chandrasekhar limit, in attempts to identify a possible relationship between SN I and novae. In our studies we have considered accretion at various mass accretion rates onto a variety of different white dwarf masses. We have found that there is a critical white dwarf mass above which a significant fraction of the accreted mass can remain… more

Date: January 1, 1989

Creator: Starrfield, Sumner; Sparks, Warren M.; Truran, James W.; Shaviv, Giora; Illinois University, Urbana & Technion-Israel Institute of Technology, Haifa (Israel)

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Constraints on fermion mixing with exotics

We analyze the constraints on the mixing angles of the standard fermions with new heavy particles with exotic SU(2) {times} U(1) quantum number assignments (left-handed singlets or right-handed doublets), that appear in many extensions of the electroweak theory. The updated Charged Current and Neutral Current experimental data, including also the recent Z-peak measurements, are considered. The results of the global analysis of all these data are then presented.

Date: November 1, 1991

Creator: Nardi, E. (Michigan Univ., Ann Arbor, MI (United States). Randall Lab. of Physics); Roulet, E. (Fermi National Accelerator Lab., Batavia, IL (United States)) & Tommasini, D. (Valencia Univ. (Spain). Dept. de Fisica Teorica)

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

0-G experiments with advanced ceramic fabric wick structures

Both Air Force and NASA future spacecraft thermal management needs span the temperature range from cryogenic to liquid metals. Many of these needs are changing and not well defined and will remain so until goals, technology, and missions converge. Nevertheless, it is certain that high-temperature (> 800 K) and medium-temperature (about 450 K) radiator systems will have to be developed that offer significant improvements over current designs. This paper discusses experiments performed in the low… more

Date: July 1991

Creator: Antoniak, Z. I.; Webb, B. J.; Bates, J. M.; Cooper, M. F. & Pauley, K. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Measurements of induced radioactivity in some LDEF samples

Twenty-six stainless steel trunnion samples, five aluminum end support retainer plate samples, two aluminum keel plate samples, and two titanium clips were analyzed. The shielded high-purity germanium detectors used had efficiencies of 33%, 54%, and 80% at 1332 keV. Detector efficiencies as a function of energy and corrections for self-absorption in the samples were determined with calibrated sources and unactivated control samples. Several measurements were made on most samples. In the trunnio… more

Date: January 1, 1991

Creator: Moss, C. E. & Reedy, R. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A U.S. Carbon Cycle Science Plan

Report assessing the carbon cycle and providing guidance for U.S. researchers. It includes background on the history and context of the carbon cycle and previous science plan as well as chapters describing relevant fundamental science questions, science plan goals, the plan elements, interdisciplinary and international collaboration and cooperation, implementation and funding of the plan, and references with supplementary appendix information.

Date: August 2011

Creator: Michalak, Anna M.; Jackson, Robert B.; Marland, Gregg & Sabine, Christopher L.

Item Type: Report

Partner: UNT Libraries