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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

The Petrogenetic significance of Plagioclase megacrysts in Archean rocks

The petrogenetic significance of plagioclase megacryst-bearing Archean rocks was considered. It was suggested that these developed in mid-to upper-crustal magma chambers that were repeatedly replenished. Crystallization of megacrysts from a primitive liquid that evolves to an Fe-rich tholeiite (with LREE enrichment) is nearly isothermal and is an equilibrium process. Cumulates probably form near the margins of the chambers and liquids with megacrysts are periodically extracted and can appear as volcanics. Some flows and intrusives are found in arc-like settings in greenstone belts. Megacrystic dikes represent large volumes of melt and dike swarms such as the Metachawan swarm of Ontario suggest multiple sources of similar compositions. A complex series of melt ponding and migration are probable and involve large amounts of liquid.

Morrison, D. A.↗
NASA NTRS1989

Trace gas emissions from chaparral and boreal forest fires

Using smoke samples collected during low-level helicopter flights, the mixing ratios of CO2, CO, CH4, total nonmethane hydrocarbons, H2, and N2O over burning chaparral in southern California and over a burning boreal forest site in northern Ontario, Canada, were determined. Carbon dioxide-normalized emission ratios were determined for each trace gas for conditions of flaming, mixed, and smoldering combustion. The emission ratios for these trace gases were found to be highest for the smoldering combustion, generally thought to be the least efficient combustion stage. However, high emission ratios for these gases could be also produced during very vigorous flaming combustion.

Cofer, Wesley R., III↗
NASA NTRS1989

Observation of organized structure in turbulent flow within and above a forest canopy

Data obtained with seven triaxial sonic anemometer/thermometers and three Lyman-alpha hygrometers at an experimental site in Ontario, Canada reveal the coherent occurrence of ramp patterns of temperature and humidity at several levels within and above the deciduous forest considered. The ramps appear most clearly in the middle and upper portion of the forest, and near the top of the forest they are composed of a weak ejecting motion transporting warm and/or moist air out of the forest, followed by strong sweeps of cool and/or dry air penetrating into the canopy. In the middle and upper parts of the canopy, the sweeps are found to conduct a large proportion of the overall transfer between the forest and the lower atmosphere, with a lesser contribution from ejections.

Gao, W.↗
NASA NTRS1989

Spatial characterization of acid rain stress in Canadian Shield Lakes

The lake acidification in Northern Ontario was investigated using LANDSAT TM to sense lake volume reflectance and also to provide important vegetation and terrain characteristics. The purpose of this project was to determine the ability of LANDSAT to assess water quality characteristics associated with lake acidification. Results demonstrate that a remote sensor can discriminate lake clarity based upon reflection. The basic hypothesis is that seasonal and multi-year changes in lake optical transparency are indicative of sensitivity to acidic deposition. In many acid-sensitive lakes optical transparency is controlled by the amount of dissolved organic carbon present. Seasonal changes in the optical transparency of lakes can potentially provide an indication of the stress due to acid deposition and loading.

Tanis, F. J.↗
NASA NTRS1990

Partition coefficients for calcic plagioclase - Implications for Archean anorthosites

In most Archean cratons, cumulates of equant plagioclase megacrysts form anorthositic complexes, including those at Bad Vermilion Lake (Ontario). In this paper, partition coefficients (Ds) of REEs between natural high-Ca plagioclase megacrysts and their basaltic matrices were determined, using a multiple aliquot techique, and megacrystic plagioclases occurring in anorthosites were analyzed for the same components which, in conjunction with their Ds, were applied to calculations of melts in equilibrium with anorthosites. The REE's Ds were found to agree well with experimentally determined values and to predict equilibrium melts for Archean anorthosites that agree well with coeval basaltic flows and dikes. The Ds also appear to be valid for both the tholeiitic and alkali basalts over a wide range of mg numbers and REE concentrations. It is suggested that the moderately Fe-rich tholeiites that are hosts to plagioclase megacrysts in greenstone belts form the parental melts for megacrysts which make up the Bad Vermilion Lake Archean anorthositic complex.

Phinney, W. C.↗
NASA NTRS1990

Gaseous emissions from Canadian boreal forest fires

CO2-normalized emission ratios for carbon monoxide (CO), hydrogen (H2), methane (CH4), total nonmethane hydrocarbons (TNMHC), and nitrous oxide (N2O) were determined from smoke samples collected during low-altitude helicopter flights over two prescribed fires in northern Ontario, Canada. The emission ratios determined from these prescribed boreal forest fires are compared to emission ratios determined over two graminoid (grass) wetlands fires in central Florida and are found to be substantially higher (elevated levels of reduced gas production relative to CO2) during all stages of combustion. These results argue strongly for the need to characterize biomass burning emissions from the major global vegetation/ecosystems in order to couple combustion emissions to their vegetation/ecosystem type.

Cofer, Wesley R., III↗
NASA NTRS1991

Three-dimensional time domain model of lightning including corona effects

A new 3-D lightning model that incorporates the effect of corona is described for the first time. The new model is based on a Thin Wire Time Domain Lightning (TWTDL) Code developed previously. The TWTDL Code was verified during the 1985 and 1986 lightning seasons by the measurements conducted at the 553 m CN Tower in Toronto, Ontario. The inclusion of corona in the TWTDL code allowed study of the corona effects on the lightning current parameters and the associated electric field parameters.

Podgorski, Andrew S.↗
NASA NTRS1990

Recent technical advances in general purpose mobile Satcom aviation terminals

A second general aviation amplitude companded single sideband (ACSSB) aeronautical terminal was developed for use with the Ontario Air Ambulance Service (OAAS). This terminal is designed to have automatic call set up and take down and to interface with the Public Service Telephone Network (PSTN) through a ground earth station hub controller. The terminal has integrated RF and microprocessor hardware which allows such functions as beam steering and automatic frequency control to be software controlled. The terminal uses a conformal patch array system to provide almost full azimuthal coverage. Antenna beam steering is executed without relying on aircraft supplied orientation information.

Sydor, John T.↗
NASA NTRS1992

Lidar measurements using large liquid mirror telescopes

It is a well accepted practice in the discussion of lidars to compare systems by a performance factor given by the product of the transmitter power and receiver aperture. This form of the performance factor reflects the two key parameters that determine the amount of photons recorded from a given range bin; the amount of transmitted photons and the probability of collecting a scattered photon. We are interested in studying the propagation and breaking of gravity waves typically generated in the lower atmosphere. To study these waves requires high temporal and spatial resolution, as they have frequencies as high as 500 mHz and generate turbulent structures with vertical scales of less than 25 m. In the 80 - 100 km region of the atmosphere these measurements are most efficiently obtained by using resonance scattering from sodium atoms deposited by meteors. However, in the 30 - 80 km region, the most efficient scattering arises from molecules (Rayleigh scattering). Since the atmospheric scale height is nominally 7 km, this scattering becomes extremely weak above 60 km. Furthermore, present laser technology limits the power available for Rayleigh-scattering experiments to about 0.5 - 50 W. The transmitter for the lidar system under development at the University of Western Ontario uses a two-beam transmitter to simultaneously measure density perturbations and temperature from both Rayleigh and resonance scattering.

Sica, R. J.↗
NASA NTRS1991

Shock wave equation of state of muscovite

Shock wave data were obtained between 20 and 140 GPa for natural muscovite obtained from Methuen Township (Ontario), in order to provide a shock-wave equation of state for this crustal hydrous mineral. The shock equation of state data could be fit by a linear shock velocity (Us) versus particle velocity (Up) relation Us = 4.62 + 1.27 Up (km/s). Third-order Birch-Murnaghan equation of state parameters were found to be K(OS) = 52 +/-4 GPa and K-prime(OS) = 3.2 +/-0.3 GPa. These parameters are comparable to those of other hydrous minerals such as brucite, serpentine, and tremolite.

Sekine, Toshimori↗
NASA NTRS1992

The Sudbury Structure as a terrestrial mare basin

A review is presented of the origin, development, and current status of the hypothesis that the Sudbury Structure of Ontario, Canada, is a deformed Precambrian impact crater analogous to the circular lunar maria. Impact and isotopic modeling studies have shown that the Sudbury igneous complex may be largely impact melt rather than internally generated magma. The analogy between lunar maria and the Sudbury Structure, though petrologically wrong, is valid to the extent that both classes of structure were initially formed by impact.

Lowman, Paul D., Jr.↗
NASA NTRS1992

Shocked zircons in the Onaping Formation: Further proof of impact origin

The Onaping Formation fills the structural basin at Sudbury, Ontario, Canada. This formation is composed of three members: a basal, coarse, mainly quartzitic breccia (Basal Member); a light-colored, heavily included, polymict middle unit (Gray Member); and a similar but dark-colored upper unit (Black Member). Two different origins were proposed for the Onaping: (1) volcanic ash-flow sheet; and (2) impact fall-back ejecta. These origins are critically discussed in a review paper coauthored by proponents of each view.

Bohor, B. F.↗
NASA NTRS1992

The pseudotachylites from the Vredefort structure and the Witwatersrand basin

Pseudotachylite (PT) from both the Sudbury structure in Ontario and the Vredefort Dome in South Africa have been widely cited as the result of shock (impact)-induced brecciation. In the scientific and popular literature PT has been described as shock melt or even as impact melt rock. In contrast, others have for years requested that a clarification of the definitions for PT and impact melt rock be pursued. We have suggested that, until that time when well-defined criteria for genetically different melt rock types (e.g., generated by impact or tectonic processes) will have been established, the term PT should only be used as a descriptive one and that, wherever genetic implications are discussed, other terms, such as impact melt (rock) or friction melt, should be applied. It is obvious that these suggestions are not only of value for the discussion of terrestrial melt rocks of controversial origin, but also apply to the characterization of melt veins in extraterrestrial materials. Important observations on Vredefort and Witwatersrand pseudotachylite are summarized.

Reimold, W. U.↗
NASA NTRS1992

Floor-fractured crater models of the Sudbury structure, Canada

The Sudbury structure in Ontario, Canada, is one of the oldest and largest impact structures recognized in the geological record. It is also one of the most extensively deformed and volcanically modified impact structures on Earth. Although few other terrestrial craters are recognized as volcanically modified, numerous impact craters on the Moon have been volcanically and tectonically modified and provide possible analogs for the observed pattern of modification at Sudbury. We correlate the pattern of early deformation at Sudbury to fracture patterns in two alternative lunar analogs and then use these analogs both to estimate the initial size of the Sudbury structure and to model the nature of early crater modification at Sudbury.

Wichman, R. W.↗
NASA NTRS1992

Factors controlling fluxes of volatile sulfur compounds in Sphagnum peatlands

Exchange of DMS and OCS between the surface of Sphagnum peatlands and the atmosphere were measured with dynamic (S-free sweep air) and static enclosures. DMS emission rates determined by both methods were comparable. The dynamic method provided positive OCS flux rates (emission) for measurements performed at sites containing Sphagnum. Conversely, data from the static method indicated that OCS was consumed from the atmosphere. Short and long-term impacts of increased S deposition on fluxes of volatile S compounds (VSC's) from Sphagnum peatlands were investigated in a poor fen (Mire 239) at the Experimental Lakes Area, Ontario, Canada. Additional experiments were conducted in a poor fen (Sallie's Fen in Barrington, NH, USA). At Mire 239, emissions of VSC's were monitored, before and after acidification, at control and experimental sections within two major physiographic areas of the mire (oligotrophic and minerotrophic). DMS was the predominant VSC released from Mire 239 and varied largely with time and space. Sulfur addition did not affect DMS emissions in a period of hours to a few days. DMS emissions in the experimental oligotrophic area of the mire was approximately 3-fold greater than in the control oligotrophic area, and approximately 10-fold greater than in the minerotrophic zones. These differences could be due to a combination of differences in types of vegetation, nutritional status, and S input. At Sallie's Fen, DMS fluxes were not significantly affected by sulfate amendments, while DMS and MSH concentrations increased greatly with time in the top 10 cm of the peat column. The major environmental factors controlling fluxes of DMS in a Sphagnum-dominated peatland were investigated in Sallie's Fen, NH. DMS emissions from the surface of the peatland varied greatly over 24 hours and seasonally. Temperature seemed to be the major environmental factor controlling these variabilities. Concentrations of dissolved VSC's varied with time and space throughout the fen. Dissolved DMS, MSH, and OCS in the surface of the water table were supersaturated with respect to their concentrations in the atmosphere. Sphagnum mosses did not appear to be a direct source of VSC's, however they increase transport of DMS from the peat surface to the atmosphere.

Demello, William Zamboni↗
NASA NTRS1992

Effects of inorganic sulfur addition on fluxes of volatile sulfur compounds in Sphagnum peatlands

Short and long-term impacts of increased S deposition on fluxes of volatile S compounds (VSC's) from Sphagnum peatlands were investigated in an artificially acidified (sulfuric and nitric acids) poor fen (Mire 239) at the Experimental Lakes Area (ELA), Ontario, Canada. Additional experiments were conducted in a poor fen (Sallie's Fen) in Barrington, NH, USA. At Mire 239, emissions of VSC's were monitored, before and after acidification, at control (unacidified) and experimental sections within two major physiographic zones of the mire (oligotrophic and minerotrophic). The experimental segments of the mire received S amendments since 1983, in amounts equivalent to the annual S deposition in the highest polluted areas of Canada and U.S. Dimethyl sulfide (DMS) was the predominant VSC released from the mire and varied largely with time and space (i.e., from 2.5 to 127 nmol/m(sup -2)h(sup -1)). Sulfur addition did not affect DMS emissions in a period of hours to a few days, although it stimulated production of DMS and MSH in the anoxic surficial regions of the peat. DMS emissions in the experimental oligotrophic segment of the mire was approximately 3-fold greater than in the control oligotrophic segment, and approximately 10-fold greater than in the minerotrophic zones. These differences could be due to a combination of differences in types of vegetation, nutritional status, and S input. At Sallie's Fen, DMS fluxes were approximately 8 times higher from a Sphagnum site than from a bare peat site. Fluxes of VSC's were not significantly affected by sulfate amendments at both sites, while DMS and MSH concentrations increases greatly with time in the top 10 cm of the peat column. Our data indicated that although Sphagnum is not the direct source of DMS released from Sphagnum peatlands, it might play a role in regulating DMS emissions to the atmosphere.

Demello, William Zamboni↗
NASA NTRS1992

The effects of acid deposition on sulfate reduction and methane production in peatlands

Peatlands, as fens and bods, make up a large percentage of northern latitude terrestrial environments. They are organic rich and support an active community of anaerobic bacteria, such as methanogenic and sulfate-reducing bacteria. The end products of these microbial activities, methane and hydrogen sulfide, are important components in the global biogeochemical cycles of carbon and sulfur. Since these two bacterial groups compete for nutritional substrates, increases in sulfate deposition due to acid rain potentially can disrupt the balance between these processes leading to a decrease in methane production and emission. This is significant because methane is a potent greenhouse gas that effects the global heat balance. A section of Mire 239 in the Experimental Lakes Area, in Northwestern Ontario, was artificially acidified and rates of sulfate reduction and methane production were measured with depth. Preliminary results suggested that methane production was not affected immediately after acidification. However, concentrations of dissolved methane decreased and dissolved sulfide increased greatly after acidification and both took several days to recover. The exact mechanism for the decrease in methane was not determined. Analyses are under way which will be used to determine rates of sulfate reduction. These results will be available by Spring and will be discussed.

Murray, Georgia L.↗
NASA NTRS1992

DMS emissions from Sphagnum-dominated wetlands

The role of terrestrial sources of biogenic S and their effect on atmospheric chemistry remain as major unanswered questions in our understanding of the natural S cycle. The role of northern wetlands as sources and sinks of gaseous S was investigated by measuring rates of S gas exchange as a function of season, hydrologic conditions, and gradients in trophic status. Experiments were conducted in wetlands in New Hampshire (NH), and in Mire 239, a poor fen at the Experimental Lakes Area (ELA) in Ontario. Emissions were determined using Teflon enclosures, gas cryotrapping methods, and GC with flame photometric detection. Emissions of DMS dominated fluxes. In NH, DMS fluxes were greater than 1.6 micromol/m(sup -2)d(sup -1) in early summer, 1989 when temperatures were warm and the water table was approximately 5 cm below the surface. These rates are several-fold faster than average oceanic rates of DMS emission. A rapid drop in the water table resulted in a 6-fold decrease in DMS emissions in late July. In 1990, a new beaver dam kept water levels above the surface and S emissions were much lower than during 1989. The elimination of the beaver and a drop in the water table in August produced a rapid increase in S gas emissions. Emissions of DMS were highest in the most oligotrophic areas. Mire 239 (ELA) was irrigated with sulfuric and nitric acids to simulate acid rain. S emissions were determined before and after an acidification event in control and experimental areas in both minerotrophic and oligotrophic regions. Emissions of DMS were higher in the acidified areas compared to unacidified controls. Emissions were also much higher in the oligotrophic regions compared to the minerotrophic ones. Despite the wide differences in S gas fluxes (20-fold), it was difficult to determine whether acidification or variations in trophic status was not responsible for differences in S gas emissions. DMS emitted into the atmosphere was not derived from the water table but originated in peat in the unsaturated zone.

Hines, Mark E.↗