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At least 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Use of Atomic Oxygen for Increased Water Contact Angles of Various Polymers for Biomedical Applications

The purpose of this study was to determine the effect of atomic oxygen (AO) exposure on the hydrophilicity of nine different polymers for biomedical applications. Atomic oxygen treatment can alter the chemistry and morphology of polymer surfaces, which may increase the adhesion and spreading of cells on Petri dishes and enhance implant growth. Therefore, nine different polymers were exposed to atomic oxygen and water-contact angle, or hydrophilicity, was measured after exposure. To determine whether hydrophilicity remains static after initial atomic oxygen exposure, or changes with higher fluence exposures, the contact angles between the polymer and water droplet placed on the polymer s surface were measured versus AO fluence. The polymers were exposed to atomic oxygen in a 100-W, 13.56-MHz radio frequency (RF) plasma asher, and the treatment was found to significantly alter the hydrophilicity of non-fluorinated polymers. Pristine samples were compared with samples that had been exposed to AO at various fluence levels. Minimum and maximum fluences for the ashing trials were set based on the effective AO erosion of a Kapton witness coupon in the asher. The time intervals for ashing were determined by finding the logarithmic values of the minimum and maximum fluences. The difference of these two values was divided by the desired number of intervals (ideally 10). The initial desired fluence was then multiplied by this result (2.37), as was each subsequent desired fluence. The flux in the asher was determined to be approximately 3.0 x 10(exp 15) atoms/sq cm/sec, and each polymer was exposed to a maximum fluence of 5.16 x 10(exp 20) atoms/sq cm.

deGroh, Kim↗
NASA NTRS2005

Atomic Oxygen Treatment and Its Effect on a Variety of Artist's Media

Atomic oxygen treatment has been investigated as an unconventional option for art restoration where conventional methods have not been effective. Exposure of surfaces to atomic oxygen was first performed to investigate the durability of materials in the low Earth orbit environment of space. The use of the ground based environmental simulation chambers, developed for atomic oxygen exposure testing, has been investigated in collaboration with conservators at a variety of institutions, as a method to clean the surfaces of works of art. The atomic oxygen treatment technique has been evaluated as a method to remove soot and char from the surface of oil paint (both varnished and unvarnished), watercolors, acrylic paint, and fabric as well as the removal of graffiti and other marks from surfaces which are too porous to lend themselves to conventional solvent removal techniques. This paper will discuss the treatment of these surfaces giving an example of each and a discussion of the treatment results.

Miller, Sharon K. R.↗
NASA NTRS2010

Analyzing the Effect of Intraseasonal Meteorological Variability and Land Cover on Aerosol-Cloud Interactions During the Amazonian Biomass Burning Season

High resolution aerosol, cloud, water vapor, and atmospheric profile data from the Moderate Resolution Imaging Spectroradiometer (MODIS) are utilized to examine the impact of aerosols on clouds during the Amazonian biomass burning season in Rondnia, Brazil. It is found that increasing background column water vapor (CWV) throughout this transition season between the Amazon dry and wet seasons exerts a strong effect on cloud properties. As a result, aerosol-cloud correlations should be stratified by column water vapor to achieve a more accurate assessment of the effect of aerosols on clouds. Previous studies ignored the systematic changes to meteorological factors during the transition season, leading to possible misinterpretation of their results. Cloud fraction is shown generally to increase with aerosol optical depth (AOD) for both low and high values of column water vapor, whereas the relationship between cloud optical depth (COD) and AOD exhibits a different relationship. COD increases with AOD until AOD approx. 0.25 due to the first indirect (microphysical) effect. At higher values of AOD, COD is found to decrease with increasing AOD, which may be due to: (1) the inhibition of cloud development by absorbing aerosols (radiative effect) and/or (2) a retrieval artifact in which the measured reflectance in the visible is less than expected from a cloud top either from the darkening of clouds through the addition of carbonaceous biomass burning aerosols or subpixel dark surface contamination in the measured cloud reflectance. If (1) is a contributing mechanism, as we suspect, then a linear relationship between the indirect effect and increasing AOD, assumed in a majority of GCMs, is inaccurate since these models do not include treatment of aerosol absorption in and around clouds. The effect of aerosols on both column water vapor and clouds over varying land surface types is also analyzed. The study finds that the difference in column water vapor between forest and pasture is not correlated with aerosol loading, supporting the assumption that temporal variation of column water vapor is primarily a function of the larger-scale meteorology. However, a difference in the response of cloud fraction to increasing AOD is observed between forest and pasture. This suggests that dissimilarities between other meteorological factors, such as atmospheric stability, are likely to have an impact on aerosol-cloud correlations between different land-cover types.

TenHoeve, J. E.↗
NASA NTRS1975

Design and the parametric testing of the space station prototype integrated vapor compression distillation water recovery module

Potable water for the Space Station Prototype life support system is generated by the vapor compression technique of vacuum distillation. A description of a complete three-man modular vapor compression water renovation loop that was built and tested is presented; included are all of the pumps, tankage, chemical post-treatment, instrumentation, and controls necessary to make the loop representative of an automatic, self-monitoring, null gravity system. The design rationale is given and the evolved configuration is described. Presented next are the results of an extensive parametric test during which distilled water was generated from urine and urinal flush water with concentration of solids in the evaporating liquid increasing progressively to 60 percent. Water quality, quantity and production rate are shown together with measured energy consumption rate in terms of watt-hours per kilogram of distilled water produced.

Reveley, W. F.↗
DOE OSTI2023

Impact of Thermal Scattering Law on Similarity Assessment in Light-Water or Polyethylene-Moderated Systems

A collaborative effort between Pacific Northwest National Laboratory (PNNL) and Oak Ridge National Laboratory (ORNL) is underway to provide a technical basis and methodology for the criticality safety community to use the sum of fractions (SoF) method for generating limits for mixtures of “selected actinide nuclides” included in the ANSI/ANS 8.15 standard. The PNNL scope in this project is to define a range of mixtures of 233 U, 235 U, and 239 Pu moderated with either light water or polyethylene and to examine the critical masses for these mixtures. The ORNL scope is primarily to provide validation support for these studies. More complete discussion of the project and its validation aspects will be presented at the upcoming International Conference on Nuclear Criticality Safety (ICNC) this Fall in Sendai, Japan. Clear differences in benchmark similarity to application systems as assessed by the integral parameter ck are noted in the validation studies performed as part of this project as a function of moderator. The c k value is a correlation coefficient that represents that amount of shared uncertainty in k eff due to cross sections between two systems. Individual nuclide-reaction contributions between the two systems can be simply summed to arrive at the total c k value. Specifically, the c k values for light-water–moderated solution experiments are higher for a water-moderated application than for a polyethylene-moderated application. This result is neither totally unexpected nor surprising, but the magnitude of the difference was difficult to anticipate. The TSUNAMI sequence, in the SCALE 6.2.4 code package developed by ORNL, was used to generate eigenvalues and reactivity effects with perturbation-theory based approach through sensitivity coefficients for all nuclides in the system with all reactions and energy groups. The TSUNAMI-Indices and Parameters (IP) sequence then uses the sensitivity data generated through TSUNAMI to generate relational parameters (i.e., c k ) to determine the degree of similarity between systems. One detail of the SCALE material and data implementation must be discussed at this point. Several thermal scattering laws (TSLs) are available for 1 H. SCALE uses a different nuclide ID number for each TSL; essentially, each version of 1 H is treated as a unique nuclide. For example, 1 H bound in water ( 1 H-H2O) is assigned the nuclide ID 1001, whereas 1 H bound in polyethylene (h-poly) is assigned the nuclide ID 9001001. The same cross section data are used for all reactions in 1 H, regardless of TSL, except for scattering below the TSL cutoff energy. TSUNAMI-IP treats different nuclide IDs as different nuclides; thus, no uncertainty is shared between 1 H-H2O and h-poly, despite much of the same data, including covariance data, being used for both nuclides. This presents a question: how much of the difference in assessed similarity between water- and polyethylene-moderated systems is due to the moderators, and how much is caused by the treatment of 1 H-H2O and h poly with cross section and covariance data. The extended edits generated by TSUANMI-IP allow for an investigation of this issue specifically, as well as a demonstration of the general techniques available within TSUNAMI to understand the results of the similarity assessment. This paper presents and analyzes the similarity assessment of both water- and polyethylene-moderated systems for a single benchmark: PST-002-001.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Divergent species-specific impacts of whole ecosystem warming and elevated CO 2 on vegetation water relations in an ombrotrophic peatland

Boreal peatland forests have relatively low species diversity and thus impacts of climate change on one or more dominant species could shift ecosystem function. Despite abundant soil water availability, shallowly rooted vascular plants within peatlands may not be able to meet foliar demand for water under drought or heat events that increase vapor pressure deficits while reducing near surface water availability, although concurrent increases in atmospheric CO 2 could buffer resultant hydraulic stress. We assessed plant water relations of co-occurring shrub (primarily Rhododendron groenlandicum and Chamaedaphne calyculata) and tree (Picea mariana and Larix laricina) species prior to, and in response to whole ecosystem warming (0 to +9°C) and elevated CO 2 using 12.8-m diameter open-top enclosures installed within an ombrotrophic bog. Water relations (water potential [Ψ], turgor loss point, foliar and root hydraulic conductivity) were assessed prior to treatment initiation, then Ψ and peak sap flow (trees only) assessed after 1 or 2 years of treatments. Under the higher temperature treatments, L. laricina Ψ exceeded its turgor loss point, increased its peak sap flow, and was not able to recover Ψ overnight. In contrast, P. mariana operated below its turgor loss point and maintained constant Ψ and sap flow across warming treatments. Similarly, C. calyculata Ψ stress increased with temperature while R. groenlandicum Ψ remained at pretreatment levels. The more anisohydric behavior of L. laricina and C. calyculata may provide greater net C uptake with warming, while the more conservative P. mariana and R. groenlandicum maintained greater hydraulic safety. These latter species also responded to elevated CO 2 by reduced Ψ stress, which may also help limit hydraulic failure during periods of extreme drought or heat in the future. Along with Sphagnum moss, the species-specific responses of peatland vascular communities to drier or hotter conditions will shape boreal peatland composition and function in the future.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Differential effects of redox conditions on the decomposition of litter and soil organic matter

Soil redox conditions exert substantial influence on biogeochemical processes in terrestrial ecosystems. Humid tropical forests are often characterized by fluctuating redox dynamics, yet how redox fluctuations affect patterns in soil versus litter decomposition and associated CO2 fluxes are not well understood in these ecosystems. We used a 13C-labeled litter addition to explicitly follow the decomposition of litter-derived vs. native soil-derived organic matter in response to four different soil redox regimes—static oxic or anoxic, and two oscillating treatments—in soil from the Luquillo Experimental Forest, Puerto Rico. We coupled this incubation experiment with high-resolution mass spectrometry analysis to characterize the preferential decomposition of specific classes of organic molecules. CO2 production from litter and soil organic matter (SOM) showed distinctly different responses to redox manipulation. The cumulative production of SOM-derived CO2 was positively correlated with the length of soil exposure to an oxic headspace (r = 0.89, n = 20), whereas cumulative 13C-litter-derived CO2 production was not linked to oxygen availability. The CO2 production rate from litter was highest under static anoxic conditions in the first half of the incubation period, and later dropped to the lowest among all redox treatments. In the consistently anoxic soils, we observed the depletion of more oxidized water-extractable organic matter (especially amino sugars, carbohydrates, and proteins) over time, suggesting that under anaerobic conditions, microbes preferentially used more oxidized litter-derived compounds during the early stages of decomposition. Results from kinetic modeling showed that more frequent anoxic exposure limited the decomposition of a slow-cycling C pool, but not a fast-cycling pool. Overall, our results demonstrate that substrate source—freshly added litter vs. native organic matter—plays an important role in the redox sensitivity of organic matter decomposition. In soil environments that regularly experience redox fluctuations, anaerobic heterotrophs can be surprisingly effective in degrading fresh plant litter.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Dietary uptake of geosmin in rainbow trout ( Oncorhynchus mykiss )

Geosmin is a primary source of muddy/earthy ‘off-flavors’ in farmed fish, which may render their organoleptic quality unacceptable to consumers. Model systems of geosmin uptake typically comprise exposure to waterborne geosmin that is absorbed via the gills. The present research demonstrates dietary exposure as an alternative route of geosmin uptake in Rainbow Trout (Oncorhynchus mykiss) fillets. Trout (average initial weight of 355 g) were stocked in quadruplicate compartmentalized raceways (N = 4 compartments per treatment, n = 50 fish per compartment) supplied with first-use, flow-through water (4.5 complete turnovers per hour). Fish were fed diets containing 0 (control dose), 0.005 (low dose), 0.05 (medium dose), or 0.5 (high dose) mg geosmin/kg feed at 1% body weight/day for four weeks. Fillets (12 fillets/diet/week plus 12 pre-trial fillet samples) and weekly feed and water samples were analyzed via GC–MS to determine geosmin concentrations. Feeding behavior was documented daily according to a four-point scale. ANOVA with post-hoc Tukey tests and polynomial contrast, regression, correlation, and chi-squared statistical analyses were applied to data (α = 0.05 significance level). Palatability of feed did not hinder consumption of the geosmin-spiked feeds: although fish responded positively to all feeds, the most aggressive feeding behavior was observed among those fed medium and high dose feed. Geosmin was effectively imparted into fillets after one week, and no significant temporal effect was found after four weeks. Mean geosmin concentrations significantly increased in fillets from low (mean of 26 ng/kg geosmin) to medium (202 ng/kg) to high (441 ng/kg) dose feed groups during the trial. Polynomial contrasts and regression modeling validated this significant positive effect of dose on geosmin uptake, with an estimated 166 ng/kg rise in fillet-geosmin for every log 10 increase in feed concentration. Waterborne geosmin levels immediately post-feeding were conditionally independent of concentrations in feed and fillets, therefore dietary uptake was affirmed as the predominant mechanism of absorption in the present experimental system. Finally, based on these findings, geosmin-spiked feeds may be used to induce predictable, repeatable levels of this off-flavor compound in fillets and serve as a model system for further investigation of sensory quality and off-flavor mitigation strategies for farm-raised fish.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Water-Assisted Lift-Off Process for Flexible CdTe Solar Cells

In recent years, various lift-off methods have been developed to fabricate lightweight and flexible cadmium telluride (CdTe)-based solar cells. In this work, we report flexible cadmium sulfide (CdS)/CdTe solar cells using a water-assisted lift-off approach. Here we demonstrate that an additional cadmium chloride treatment for the CdS film is critical to improve the grain size of CdS and the post-deposited CdTe film and the electron conductivity of the CdS film. As a result, the quality of the CdS/CdTe front junction is significantly improved with reduced nonradiative recombination. Finally, our lightweight and flexible polycrystalline CdTe solar cells demonstrate a champion power conversion efficiency of 12.6%.

14 SOLAR ENERGY↗
DOE OSTI2021

Impact of Lateral Flow on Surface Water and Energy Budgets over the Southern Great Plains – A Modeling Study

As we see the horizontal grid spacing decrease, treatment of hydrologic processes in land surface models, such as the lateral flow of surface and subsurface flow, need to be explicitly represented. Unlike previous studies that mainly focused on the mountainous regions, in this study the offline WRF-Hydro model is employed to study the impact of lateral flow on soil moisture and energy fluxes over the relatively flat southern Great Plains (SGP). The vast amount of measurements over the SGP provide an unique opportunity to assess the model behavior. In addition, newly developed land surface properties and input forcing are ingested into the model, in an attempt to reduce uncertainties associated with the initial and boundary forcing and help to identify model deficiencies. Our results show that the more realistic inputs (parameters, soil types, forcing) lead to larger underestimation of latent heat flux and dry bias, indicating the existence of model structural uncertainty (embedded errors) in WRF-Hydro that need to be characterized to inform future model development efforts. Including lateral flow processes partly mitigates the model deficiencies in representing hydrologic processes and alleviates the dry bias. In particular, both surface and subsurface lateral flow increase soil moisture mainly over the lower elevations, except that subsurface flow also affects soil moisture over steeper terrains. Additional simulations are performed to assess the effect of routing resolution on model results. When LSM resolution is high, noticeable differences in soil moisture are produced between different routing resolutions especially over steep terrain. Whereas when LSM resolution is coarse, differences between routing resolutions become negligible, especially over flat terrain.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Fungal and bacterial growth variation due to drought and nitrogen addition experimental treatments. Loma Ridge Experimental Project. 2010-2012

Terrestrial ecosystem models assume that microbial communities respond instantaneously, or are immediately resilient, to environmental change. Here we tested this assumption by quantifying the resilience of a leaf litter community to changes in precipitation or nitrogen availability. By manipulating composition within a global change experiment, we decoupled the legacies of abiotic parameters versus that of the microbial community itself. After one rainy season, more variation in fungal composition could be explained by the original microbial inoculum than the litterbag environment (18% versus 5.5% of total variation). This compositional legacy persisted for 3 years, when 6% of the variability in fungal composition was still explained by the microbial origin. In contrast, bacterial composition was generally more resilient than fungal composition. Microbial functioning (measured as decomposition rate) was not immediately resilient to the global change manipulations; decomposition depended on both the contemporary environment and rainfall the year prior. Finally, using metagenomic sequencing, we showed that changes in precipitation, but not nitrogen availability, altered the potential for bacterial carbohydrate degradation, suggesting why the functional consequences of the two experiments may have differed. Predictions of how terrestrial ecosystem processes respond to environmental change may thus be improved by considering the legacies of microbial communities. This data package includes ten csv files (five data files and their corresponding data dictionaries) and one file-level metadata excel file. Data files contains information about which plots were exposed to treatments related to drought and nitrogen, information about litter bags reciprocal transplants manipulation for water input and nitrogen, detail information about water addition, precipitation records, and litter variables collected. Data dictionary files include detail explanation for each column in the data files. The file-level metadata file describes each file mentioned above. All the analyses were done using the R software.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Energy Efficient Waste Heat Coupled Forward Osmosis for Effluent Water Management at Coal-Fired Power Plants

This project sought to evaluate the technical and economic viability of the Aquapod©, a transformational low energy (<200 kJ/kg water) waste heat coupled forward osmosis (FO) technology, to manage effluents, meet cooling water demands, and achieve water conservation in a coal-fired power plant environment. The Aquapod© process is innovative because it is heat-driven, avoids the evaporation of water, and uses no toxic chemicals such as ammonia or amines. The Aquapod© process accomplishes this using an aqueous two-phase system (ATPS) coupled FO process. The evaluation revealed that the Aquapod© process offers a pathway to exploit waste heat resources within a power plant to achieve flue-gas desulfurization (FGD) wastewater volume reduction and water recovery with minimal pretreatment. Water recovery of 80% from FGD wastewater was achieved with minimal pretreatment, exceeding the project target of 50%. The estimated electrical energy of 2.16 kWh/m 3 of water produced for the Aquapod© process met the project target of < 3.6 kWh/m 3 . The heat required for the process operation was approximately 186 kJ/kg of produced water, which was slightly lower than the project target of 200 kJ/kg. The estimated treatment cost for installing and operating the Aquapod© process in conjunction with a spray dryer evaporator to achieve zero-liquid discharge (ZLD) of the 100 gpm FGD wastewater was $13.24/m 3 over a 30-year lifetime. As a point of reference, this study’s host power plant currently incurs a cost of $3.70/m 3 – $8.87/m3 on a discharged volume basis to discharge its wastewater into the publicly owned treatment works (POTW) after physical-chemical treatment. Therefore, the Illinois power plant would incur an incremental cost increase of $4.37/m 3 – 9.54/m 3 to achieve ZLD using the Aquapod© and spray dryer combination. Ample opportunities exist to further lower the ZLD capital and operating costs in the next design iteration to attain pipe parity at the higher end of the site treatment costs.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2022

Regulatory Treatment of Non-Core Sources of Radioactivity for Advanced Reactor Designs

The recent resurgence in advance (non-light water) reactor development has been paralleled by the development of risk-informed performance-based (RIPB) licensing pathways. Specifically, the creation of the RIPB Licensing Modernization Project (LMP) approach and subsequent endorsement by the U.S. Nuclear Regulatory Commission (NRC) now provides advanced reactor vendors with a defined RIPB method to develop an affirmative safety case for licensing. In addition, the Technology Inclusive Content of Applications Project (TICAP) has published guidance on developing a license application based on the LMP approach. To support the utilization of risk information as part of advanced reactor design and licensing efforts, the American Society of Mechanical Engineers (ASME)/American Nuclear Society (ANS) Joint Committee on Nuclear Risk Management (JCNRM) has developed a probabilistic risk assessment (PRA) standard for advanced reactors. The standard, which was formerly approved by the American National Standards Institute (ANSI) in 2021 and recently endorsed by the NRC in trial use Regulatory Guide (RG) 1.247, is an integral standard, covering from initiating events to offsite consequence. A major feature of the standard is that it permits the inclusion of any source of radioactivity material at the site within the plant PRA. Therefore, non-core sources of radioactivity, such as fuel storage, fuel processing, and purification systems, can be included within a single comprehensive plant PRA. For those advanced reactor vendors utilizing a RIPB licensing approach, there is an opportunity to include the non-core sources of radioactivity within the RIPB framework for licensing decision-making, such as the categorization of events, classification of structures, systems, and components (SSCs), and evaluation of the adequacy of defense-in-depth (DID). For advanced reactor designs that contain multiple non-core sources of radioactivity, or for monolithic plant sites that include associated fuel facilities, this approach could potentially simplify licensing applications through the use of a single, uniform, and consistent decision-making framework across all radioactive sources at the site. In addition, a RIPB approach could provide additional insights regarding plant behavior, flexibility regarding licensing decision-making, and potentially allow the use of risk information as part of the plant oversight process. Risk-informing these aspects of advanced reactor licensing would also be consistent with the NRC’s risk policy statement. However, there is diverse regulation and guidance regarding the licensing of non-core sources of radioactivity and generally limited experience using RIPB approaches for the evaluation as part of licensing.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2022

Enhancing organic matter removal, product recovery, and hydrogen generation from fermentation wastewater

Existing ethanol biorefineries produce billions of gallons of wastewater (stillage) that must be treated extensively prior to discharge or concentrated in an energy intense evaporation step to produce animal feed as a value-added bioproduct. Yeasts and filamentous fungi were screened for growth and reduction of soluble organic compounds, carbohydrates, and protein from stillage to identify species capable of rapidly concentrating organic compounds into readily separable biomass in an attempt to concentrate the product using a much more efficient centrifugation step. Yeasts amenable to production of biomass derived products including bio-oils (Yarrowia lipolytica and Rhodotorula pallida), chitosan (Aspergillus niger) and animal feed (Cyberlindnera jadinii) were identified as well as microbes capable of efficient production of small organic acids with applications as bioderived polymers including 3-hydroxypropionic acid (engineered A. niger) and lactic acid using a co-culture of Debaryomyces udenii and Lactobacillus pentosus. The filamentous fungus A. niger eliminated all specifically measured soluble organics (glycerol, acetate, lactate, ethanol, and citrate) in under 48 hours and reduced total soluble protein content by 46% and total carbohydrate content by 83% within 96 hours, the greatest reduction in organic content observed. During this process an A. niger strain engineered to produce 3-hydroxypropionic acid achieved a yield of 0.35 C-mol 3HP / C-mol non-protein organics consumed at an overall rate of 0.09 g/Lh in unmodified stillage without pH control. Stillage treated by the fodder yeast C. jadinii as well as stillage containing acetic or lactic acid was found to be most suitable for growth by electrogenic bacteria with applications in production of electricity or hydrogen from wastewater. This work establishes fungal and bacterial strains appropriate for biological treatment of stillage to produce biomass derived products, soluble commodity chemicals, energy, and treated water to reduce the energy intensity and improve the economics of ethanol biorefineries.

09 BIOMASS FUELS↗
NASA NTRS1978

Treatment of cloudiness in regional scale - Numerical weather prediction models

A numerical weather prediction model is considered in which cloud water and precipitation are explicitly predicted as functions of three space dimensions and time. Approximations in the thermodynamic and continuity equations are discussed in detail, as well as the cumulus parameterization and the cloud microphysics parameterization. An example of a real-data forecast indicates that very accurate quantitative precipitation and cloud cover forecasts are possible using initial observations from only the relatively sparse rawinsonde network in the U.S.

Kreitzberg, C. W.↗
NASA NTRS1989

C-band scatterometer measurements of a tallgrass prairie

C-band (4.75 GHz) scatterometer measurements were made of a tallgrass prairie in an attempt to determine the relationship between (1) the backscattering coefficient and different expressions of soil moisture and (2) the backscattering coefficient and various canopy parameters. A moderately strong correlation and partial correlation between the backscattering coefficient and leaf water potential indicates the capability of C-band measurements to detect extremes in the water status of prairie vegetation under shallow soil conditions. Site differences due to burn treatments appeared to be sufficient to cause significant differences in the sensitivity of the backscattering coefficient to soil moisture. The site differences could not be removed by any known expression of soil moisture.

Martin, Robert D., Jr.↗
NASA NTRS1999

Absence of Change in Total Daily Energy Expenditure (EE(sub TD)) in Young and Mature Rats During 14 Days of Hypergravity

Effect of age on the response of EE(sub TD) to an increase in gravity was assessed in young (Y; 1.5 month old) and mature (M; 8 month old) Sprague-Dawley rats. Rats were implanted with transmitters to monitor activity, and metabolism was determined by the double labeled water technique. Daily food intake was measured. For each age, rats (n=8 per treatment) were exposed to centrifugation at 2G, or remained at 1G. There was a difference in EE(sub TD) between age groups, 182 plus or minus 11 and 143 plus or minus 5 kcal/kg/day in Y and M, respectively. This difference was attributed in part to a lower activity level in M animals, 48% of Y rats. After day 6 there was no effect on EE(sub TD) of exposure to 2G, or on food intake per 100g BW. Prior studies show a 20% increase in resting EE with hypergravity. In our study the level of activity was reduced to 41% of 1G in both age groups during 2G. For Y at 1G resting EE accounted for 78% of the EE(sub TD) and activity 22%, while at 2G resting EE was 96% of EE(sub TD) and activity 4%. M rats had similar changes. Independent of age, with exposure to hypergravity EE(sub TD) is maintained by behavioral changes.

Wade, C. E.↗