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NASA NTRS1996

Sulfur, Chlorine and Fluorine Degassing and Atmospheric Loading by the Roza eruption, Columbia River Basalt Group, Washington

In this study we attempt to quantify the amount of S, Cl and F released by the 1300 cu km Roza member (approximately 14.7 Ma) of the Columbia River Basalt Group, which was produced by a moderate-size flood basalt eruption in the mid-Miocene. Our results are the first indication of the potential atmospheric SO2 yield from a flood basalt eruption, and indicate the mechanism by which flood basalt eruptions may have seriously affected the environment. Glass inclusions in phenocrysts and quenched glass in products from various stages of the eruption were analyzed for concentrations of S, Cl and F and major elements. Glass inclusions contain 1965 +/- 110 ppm S, 295 +/- 65 ppm Cl and 1310 +/- 110 ppm F. Groundmass glass of Roza dike selvages contains considerably lower concentrations: 1110 +/- 90 ppm S, 245 +/- 30 ppm Cl and 1020 +/- 25 ppm F. Scoria clasts from near vent deposits contain 665 +/- 75 ppm S, 175 +/- 5 ppm Cl and 950 +/- 20 ppm F, and the groundmass glass of lava selvages contains 520 +/- 30 ppm S, 190 +/- 30 ppm Cl and 890 +/- 55 ppm F. In crystalline lava, the concentrations are 195 ppm S, 100 ppm Cl and 830 ppm F. Volatile element concentrations in these samples represent the progress of degassing through the eruption and can be used to estimate the potential amount of the volatiles S, Cl and F released by the magma into the atmosphere, as well as to evaluate the amount liberated by various phases of the eruption. The total amount of volatiles released by the Roza eruption is estimated to have been approximately 12,420 MtSO2, approximately 710 MtHCI and approximately 1780 MtHF. The Roza magma liberated approximately 9620 MtSO, (77% of the total volatile mass released), approximately 400 MtHCI (56%) and approximately 1450 MtHF (81%) at the vents and lofted by the eruption columns to altitudes of 7-13 km. Degassing of the lava is estimated to have released an additional approximately 2810 MtSO2, approximately 310 MtHCI and approximately 330 MtHF. The Roza eruption is likely to have lasted for approximately 10 years, indicating an annual H2SO4-mass loading of approximately 1800 Mt. Thus, the atmospheric perturbations associated with the Roza eruption may have been of the magnitude predicted for a severe "nuclear" or "volcanic" winter, but lasting up to a decade or more.

Thordarson, Th.↗

NASA NTRS1982

A theory of electrophoresis of emulsion drops in aqueous two-phase polymer systems

An electrophoresis study has been carried out in an emulsion formed from an electrically neutral aqueous mixture of dextran and polyethylene glycol equilibrated at sufficient concentrations in the presence of electrolytes. Electrophoresis of a drop of one phase suspended in the other is observed, and the direction of the drop's motion is reversed when the disperse phase and the continuous phase are interchanged. In the presence of sulfate, phosphate, or citrate ions, an electrostatic potential difference of the order of a few mV exists between the two phases. The potential implied by the direction of the electrophoretic motion is opposite to the Donnan potential observed between the two phases. The mobility of an emulsion drop increases with the drop radius and depends on ion concentration. These results are explained in terms of a model postulating an electric dipole layer associated with a mixture of oriented polymer molecules at the surface of a drop, with a potential difference between the interiors of the two phases resulting from the unequal ion distribution.

Levine, S.↗

NASA NTRS1995

An update on SCARLET hardware development and flight programs

Solar Concentrator Array with Refractive Linear Element Technology (SCARLET) is one of the first practical photovoltaic concentrator array technologies that offers a number of benefits for space applications (i.e. high array efficiency, protection from space radiation effects, a relatively light weight system, minimized plasma interactions, etc.) The line-focus concentrator concept, however, also offers two very important advantages: (1) low-cost mass production potential of the lens material; and (2) relaxation of precise array tracking requirements to only a single axis. These benefits offer unique capabilities to both commercial and government spacecraft users, specifically those interested in high radiation missions, such as MEO orbits, and electric-powered propulsion LEO-to-GEO orbit raising applications. SCARLET is an aggressive hardware development and flight validation program sponsored by the Ballistic Missile Defense Organization (BMDO) and NASA Lewis Research Center. Its intent is to bring technology to the level of performance and validation necessary for use by various government and commercial programs. The first phase of the SCARLET program culminated with the design, development and fabrication of a small concentrator array for flight on the METEOR satellite. This hardware will be the first in-space demonstration of concentrator technology at the 'array level' and will provide valuable in-orbit performance measurements. The METEOR satellite is currently planned for a September/October 1995 launch. The next phase of the program is the development of large array for use by one of the NASA New Millenium Program missions. This hardware will incorporate a number of the significant improvements over the basic METEOR design. This presentation will address the basic SCARLET technology, examine its benefits to users, and describe the expected improvements for future missions.

Jones, P. Alan↗

NASA NTRS2006

Siderophilic Cyanobacteria: Implications for Early Earth.

Of all extant environs, iron-depositing hot springs (IDHS) may exhibit the greatest similarity to late Precambrian shallow warm oceans in regards to temperature, O2 gradients and dissolved iron and H2S concentrations. Despite the insights into the ecology, evolutionary biology, paleogeobiochemistry, and astrobiology examination of IDHS could potentially provide, very few studies dedicated to the physiology and diversity of cyanobacteria (CB) inhabiting IDHS have been conducted. Results. Here we describe the phylogeny, physiology, ultrastructure and biogeochemical activity of several recent CB isolates from two different greater Yellowstone area IDHS, LaDuke and Chocolate Pots. Phylogenetic analysis of 16S rRNA genes indicated that 6 of 12 new isolates examined couldn't be placed within established CB genera. Some of the isolates exhibited pronounced requirements for elevated iron concentrations, with maximum growth rates observed when 0.4-1 mM Fe(3+) was present in the media. In light of "typical" CB iron requirements, our results indicate that elevated iron likely represents a salient factor selecting for "siderophilicM CB species in IDHS. A universal feature of our new isolates is their ability to produce thick EPS layers in which iron accumulates resulting in the generation of well preserved signatures. In parallel, siderophilic CB show enhanced ability to etch the analogs of iron-rich lunar regolith minerals and impact glasses. Despite that iron deposition by CB is not well understood mechanistically, we recently obtained evidence that the PS I:PS II ratio is higher in one of our isolates than for other CB. Although still preliminary, this finding is in direct support of the Y. Cohen hypothesis that PSI can directly oxidize Fe(2+). Conclusion. Our results may have implications for factors driving CB evolutionary relationships and biogeochemical processes on early Earth and probably Mars.

Brown, I. I.↗

NASA NTRS1989

Reconstruction of the constituent distribution and trends in the Antarctic polar vortex from ER-2 flight observations

The measurements of ozone, ClO, and N2O concentrations in the south polar region taken aboard the ER-2 aircraft during the Airborne Antarctic Ozone Experiment are analyzed using conservative coordinate transformations to potential temperature-N2O and potential temperature-potential vorticity space. The latter transformation is equivalent to interpreting trace species observations within the modified Lagrangian mean (MLM) coordinate system. The results show that the MLM transformed ozone concentration decreases at about 0.06 ppmv per day between 20- and 16-km altitude inside the polar vortex during the mid-August to mid-September period. These ozone changes are collocated with the region of high ClO concentration. Outside the chemically perturbed region, at the highest aircraft altitudes, ozone concentration systematically increases, suggesting a diabatic cooling of the order 0.3-0.6 K/day.

Schoeberl, Mark R.↗

NASA NTRS1994

Seasonal Patterns and Remote Spectral Estimation of Canopy Chemistry Across the Oregon Transect

We examined seasonal changes in canopy chemical concentrations and content in conifer forests growing along a climate gradient in western Oregon, as part of the Oregon Transect Ecosystem Research (OTTER) study. The chemical variables were related to seasonal patterns of growth and production. Statistical comparisons of chemical variables with data collected from two different airborne remote-sensing platforms were also carried out. Total nitrogen (N) concentrations in foliage varied significantly both seasonally and among sites; when expressed as content in the forest canopy, nitrogen varied to a much greater extent and was significantly related to aboveground net primary production (r = 0.99). Chlorophyll and free amino acid concentrations varied more strongly than did total N and may have reflected changes in physiological demands for N. Large variations in starch concentrations were measured from pre- to post-budbreak in all conifer sites. Examination of remote-sensing data from two different airborne instruments suggests the potential for remote measurement of some canopy chemicals. Multivariate analysis of high-resolution spectral data in the near infrared region indicated significant correlations between spectral signals and N concentration and canopy N content; the correlation with canopy N content was stronger and was probably associated in part with water absorption features of the forest canopy. The spectral bands that were significantly correlated with lignin concentration and content were similar to bands selected in the other laboratory and airborne studies; starch concentrations were not significantly related to spectral reflectance data. Strong relationships between the spectral position of specific reflectance features in the visible region and chlorophyll were also found.

Matson, Pamela↗

NASA NTRS1981

Calibration of a turbidity meter for making estimates of total suspended solids concentrations and beam attenuation coefficients in field experiments

Management of water resources such as a reservoir requires using analytical models which describe such parameters as the suspended sediment field. To select or develop an appropriate model requires making many measurements to describe the distribution of this parameter in the water column. One potential method for making those measurements expeditiously is to measure light transmission or turbidity and relate that parameter to total suspended solids concentrations. An instrument which may be used for this purpose was calibrated by generating curves of transmission measurements plotted against measured values of total suspended solids concentrations and beam attenuation coefficients. Results of these experiments indicate that field measurements made with this instrument using curves generated in this study should correlate with total suspended solids concentrations and beam attenuation coefficients in the water column within 20 percent.

Usry, J. W.↗

NASA NTRS2012

Impact of Aerosols on Convective Clouds and Precipitation

Aerosols are a critical.factor in the atmospheric hydrological cycle and radiation budget. As a major agent for clouds to form and a significant attenuator of solar radiation, aerosols affect climate in several ways. Current research suggests that aerosols have a major impact on the dynamics, microphysics, and electrification properties of continental mixed-phase convective clouds. In addition, high aerosol concentrations in urban environments could affect precipitation variability by providing a significant source of cloud condensation nuclei (CCN). Such pollution . effects on precipitation potentially have enormous climatic consequences both in terms of feedbacks involving the land surface via rainfall as well as the surface energy budget and changes in latent heat input to the atmosphere. Basically, aerosol concentrations can influence cloud droplet size distributions, the warm-rain process, the cold-rain process, cloud-top heights, the depth of the mixed-phase region, and the occurrence of lightning. Recently, many cloud resolution models (CRMs) have been used to examine the role of aerosols on mixed-phase convective clouds. These modeling studies have many differences in terms of model configuration (two- or three-dimensional), domain size, grid spacing (150-3000 m), microphysics (two-moment bulk, simple or sophisticated spectral-bin), turbulence (1st or 1.5 order turbulent kinetic energy (TKE)), radiation, lateral boundary conditions (i.e., closed, radiative open or cyclic), cases (isolated convection, tropical or midlatitude squall lines) and model integration time (e.g., 2.5 to 48 hours). Among these modeling studies, the most striking difference is that cumulative precipitation can either increase or decrease in response to higher concentrations of CCN. In this presentation, we review past efforts and summarize our current understanding of the effect of aerosols on convective precipitation processes. Specifically, this paper addresses the following topics: observational evidence of the effect of aerosols on precipitation processes, and results from (CRM) simulations. Note that this presentation is mainly based on a recent paper published in Geophy. Rev. (Tao et al. 2012).

Tao, Wei-Kuo↗

NASA NTRS2014

Synthesis and Properties of Cross-Linked Polyamide Aerogels

We report our ongoing research on polyamide aerogels made by step growth polymerization using a combination of terephthaloyl chloride, isophthaloyl chloride and m-phenylenediamine. Crosslinking of the amine capped polymer chains with 1,3,5-benzenetricarbonyl trichloride causes gelation in as little as two to five minutes. Removing the reaction solvent is accomplished through solvent exchange, followed by drying using supercritical CO2 extraction to give colorless aerogels with densities ranging from 0.07 to 0.33 grams per cubic centimeter and surface areas as high as 440 square meters per gram. Statistical experimental design methodology has been utilized to investigate dependence of properties of these aerogels, such as density, compressive modulus, and surface area, on changes in fabrication parameters including formulated number of amide oligomer repeat units (n-value), acid chloride (meta, para or combination), and solids concentration of solution used for gelation. For example, the density of these materials was found to be dependent on the acid chloride type and the solids concentration, but n was not a significant variable. However, surface area was significantly influenced by all three parameters. The polyamide aerogels represent a potential cost savings over previously reported polyimide aerogels, since monomers are all inexpensive and commercially available. Surface area and density were both highest when 100 terephthaloyl chloride was used but a combination of 5 solid concentration, 100 terephthaloyl chloride and n of 20 gave the best combination of properties.

cross-linked↗

NASA NTRS1990

Biophysical basis of growth promotion in primary leaves of Phaseolus vulgaris L. by hormones versus light: solute accumulation and the growth potential

Rapid cell enlargement in primary leaves of bean is induced by bright white light (WL), gibberellic acid (GA3) or the cytokinin N6-benzyladenine (BA). In previous studies it has been show that all three agents cause an increase in wall extensibility, although by different mechanisms. Here we examine the effects of the three growth promoters on the osmotic potential difference (delta Psi), the accumulation of solutes (delta TSC), the wall yield threshold (Y) and the growth potential (delta Psi -Y). With GA3 and BA, but not WL, there was a rapid decline in delta Psi as measured by the osmotic concentration of expressed sap. Unlike WL, neither GA3 nor BA promoted the accumulation of osmotic solutes. The decline in delta Psi, however, was apparently counteracted by a decline in Y since the growth potential, as measured by the external-osmoticum method, remained unchanged. It is concluded that WL, GA3 and BA all promote cell enlargement of bean leaves by increasing one cellular growth parameter, wall extensibility. Only WL, however, promotes osmotic adjustment during growth.

Non-NASA Center↗

NASA NTRS2001

An Assessment of the Ability of Potential Spaceborne Instruments to Resolve Spatial and Temporal Variability of Atmospheric Carbon Dioxide

Mounting concern regarding the possibility that increasing carbon dioxide concentrations will initiate climate change has stimulated interest in the feasibility of measuring CO2 mixing ratios from satellites. Currently, the most comprehensive set of atmospheric CO2 data is from the NOAA CMDL cooperative air sampling network, consisting of more than 40 sites where flasks of air are collected approximately weekly. Sporadic observations in the troposphere and stratosphere from airborne in situ and flask samplers are also available. Although the surface network is extensive, there is a dearth of data in the Southern Hemisphere and most of the stations were intentionally placed in remote areas, far from major sources. Sufficiently precise satellite observations with adequate spatial and temporal resolution would substantially increase our knowledge of the atmospheric CO2 distribution and would undoubtedly lead to improved understanding of the global carbon budget. We use a 3-D chemical transport model to investigate the ability of potential satellite instruments with a variety of orbits, horizontal resolution and vertical weighting functions to capture the variation in the modeled CO2 fields. The model is driven by analyzed winds from the Goddard Data Assimilation Office. Simulated CO2 fields are compared with existing surface and aircraft data, and the effects of the model convection scheme and representation of the planetary boundary layer are considered.

Andrews, Arlyn E.↗

NASA NTRS1973

Application of Papkovich-Neuber potentials to a crack problem.

The problem of an elastic solid containing a semi-infinite plane crack subjected to concentrated shears parallel to the edge of the crack is considered in this paper. A closed form solution using four harmonic functions is found to satisfy the finite displacement and inverse square root stress singularity at the edge of the crack. Explicit expressions in terms of elementary functions are given for the distribution of stress and displacement in the solid. These are obtained by employing Fourier and Kontorovich-Lebedev integral transforms and certain singular solutions of Laplace equations in three dimensions. The variations of the intensity of the local stress field along the crack border are shown graphically.

Kassir, M. K.↗

NASA NTRS1974

In situ measurements of the spectral characteristics of F region ionospheric irregularities

The retarding potential analyzer aboard Ogo 6 has provided high-resolution observations of the ion concentration along the satellite path. Changes in ion concentration as small as 0.03% and at times as small as 0.01% could be measured. Spatial resolution varied from 35 to 380 m. Samples of data have been analyzed to determine the spectral properties of the F region irregularities observed. The most common frequency spectrum observed suggests that the responsible irregularities result from the turbulent dissipation of larger irregularities. At the equator, the larger irregularities are probably produced by convective electric fields. At high latitudes, electric fields may also be involved, but other factors such as precipitating particles may contribute to, or be primarily responsible for, the production of large irregularities. Examples of other types of spectra associated with wavelike irregularities and with 'ground glass' (high-frequency noise) irregularities are also shown.

Dyson, P. L.↗

NASA NTRS1981

Study of the effects of gaseous environmental on the hot corrosion of superalloy materials

Studies have been conducted to examine the effect of low concentrations of NaCl(g) on the high temperature oxidation behavior of complex superalloys and potential coating formulations modified by silicon and reactive element (i.e., yttrium and hafnium) additions. Depending on alloy composition, a variety of effects were thermogravimetrically produced. Aluminum free alloys such as MAR-M509 and Hastelloy X with molybdenum and tungsten in solid solution showed accelerated (or breakaway) kinetics similar to that observed for Ni-Cr alloys. For IN-792, an alloy high in chromium and low in aluminum, molybdenum and tungsten present in solid solution does not adversely affect oxidation kinetics in the presence of NaCl(g). On the other hand, nickel-base alloys high in aluminum and molybdenum are catastrophically attacked by NaCl-bearing atmospheres. Silicon additions were, in general, observed to slightly improve the oxidation resistance of Ni, Ni-40Cr and CoCrAlY compositions in NaCl(g)-bearing atmospheres. To the degree that processes responsible for Al2O3 whisker formation deleteriously affect protective scale adherence, the addition of yttrium or hafnium can inhibit such whisker growth.

Smeggil, J. G.↗

NASA NTRS1989

Electrocatalysts for oxygen electrodes in fuel cells and water electrolyzers for space applications

In most instances separate electrocatalysts are needed to promote the reduction of O2 in the fuel cell mode and to generate O2 in the energy storage-water electrolysis mode in aqueous electrochemical systems operating at low and moderate temperatures (T greater than or equal to 200 C). Interesting exceptions are the lead and bismuth ruthenate pyrochlores in alkaline electrolytes. These catalysts on high area carbon supports have high catalytic activity for both O2 reduction and generation (1,2). Rotating ring-disk electrode measurements provide evidence that the O2 reduction proceeds by a parallel four-electron pathway. The ruthenates can also be used as self-supported catalysts to avoid the problems associated with carbon oxidation, but the electrode performance so far achieved in the research at Case Western Reserve University (CWRU) is considerably less. At the potentials involved in the anodic mode the ruthenate pyrochlores have substantial equilibrium solubility in concentrated alkaline electrolyte. This results in the loss of catalyst into the bulk solution and a decline in catalytic activity. Furthermore, the hydrogen generation counter electrode may become contaminated with reduction products from the pyrochlores (lead, ruthenium). A possible approach to this problem is to immobilize the pyrochlore catalyst within an ionic-conducting solid polymer, which would replace the fluid electrolyte within the porous gas diffusion O2 electrode. For bulk alkaline electrolyte, an anion-exchange polymer is needed with a transference number close to unity for the Oh(-) ion. Preliminary short-term measurements with lead ruthenates using a commercially available partially-fluorinated anion-exchange membrane as an overlayer on the porous gas-fed electrode indicate lower anodic polarization and virtually unchanged cathodic polarization.

Prakash, Jai↗

NASA NTRS1989

Ionospheric dynamo theory for production of far ultraviolet emissions on Uranus

A model is presented to explain diffuse FUV emissions from the outer planets, specifically Uranus, in excess of those diffuse emissions that are currently explainable by scattering of sunlight and/or excitation by photoelectrons. These electroglow emissions in H Ly-alpha and H2 bands, which occur in the sunlit hemisphere slightly above the homopause, appear to require particle excitation in the 10- to 50-eV range. An in situ mechanism for accelerating photoelectrons (and ions is proposed, involving neutral wind dynamo generation of field-aligned currents analogous to what occurs in the earth's equatorial E and F regions. Sufficiently strong field-aligned currents are found in the model calculation for Uranus to produce a potential drop of about 100 eV or greater between the F peak and homopause, concentrated at lower altitudes, and capable in principle of accelerating photoelectrons (and ions) to the 10- to 50-eV energies required to explain the observed emissions. The fact that the excitation and ionization cross sections are larger than elastic scattering cross sections in an H2 atmosphere at these energies makes in situ acceleration feasible for the production of UV on the outer planets.

Hudson, M. K.↗

NASA NTRS1989

Electrocatalysis for oxygen electrodes in fuel cells and water electrolyzers for space applications

Prakash, Jai↗

NASA NTRS1990

HgZnTe-based detectors for LWIR NASA applications

The initial goal was to grow and characterize HgZnTe and determine if it indeed had the advantageous properties that were predicted. Researchers grew both bulk and liquid phase epitaxial HgZnTe. It was determined that HgZnTe had the following properties: (1) microhardness at least 50 percent greater than HgCdTe of equivalent bandgap; (2) Hg annealing rates of at least 2 to 4 times longer than HgCdTe; and (3) higher Hg vacancy formation energies. This early work did not focus on one specific composition (x-value) of HgZnTe since NASA was interested in HgZnTe's potential for a variety of applications. Since the beginning of 1989, researchers have been concentrating, however, on the liquid phase growth of very long wavelength infrared (VLWIR) HgZnTe (cutoff approx. equals 17 microns at 65K) to address the requirements of the Earth Observing System (EOS). Since there are no device models to predict the advantages in reliability one can gain with increased microhardness, surface stability, etc., one must fabricate HgZnTe detectors and assess their relative bake stability (accelerated life test behavior) compared with HgCdTe devices fabricated in the same manner. Researchers chose to fabricate HIT detectors as a development vehicle for this program because high performance in the VLWIR has been demonstrated with HgCdTe HIT detectors and the HgCdTe HIT process should be applicable to HgZnTe. HIT detectors have a significant advantage for satellite applications since these devices dissipate much less power than conventional photoconductors to achieve the same responsivity.

Patten, Elizabeth A.↗