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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Prediction of Stable and Active (Oxy-Hydro) Oxide Nanoislands on Noble-Metal Supports for Electrochemical Oxygen Reduction Reaction

Developing cost-effective oxygen electrocatalysts with high activity and stability is key to their commercialization. However, economical earth-abundant catalysts based on first-row transition-metal oxides suffer from low electrochemical stability, which is difficult to improve without compromising their activity. In this paper, using density functional theory calculations, we demonstrate that noble-metal supports lead to bifunctional enhancement of both the stability and the oxygen reduction reaction (ORR) activity of metal (oxy-hydro) oxide nanoislands. We observe a significant stabilization of supported nanoislands beyond the intrinsic stability limits of bulk phases, which originates from a favorable lattice mismatch and reductive charge transfer from oxophilic supports. Additionally, we discover that interfacial active sites (located between the nanoisland and the support) reinforce the binding strength of reaction intermediates, hence boosting ORR activity. Considering that both stability and activity lead to discovery of CoOOH|Pt, NiOOH|Ag, and FeO 2 |Ag as viable systems for alkaline ORR, we then use a multivariant linear regression method to identify elementary descriptors for efficient screening of promising cost-effective nanoisland|support catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Evaluating the effectiveness of a camera-based detection system to support informed curtailment and minimize eagle fatalities at wind energy facilities

The American Wind Wildlife Institute (AWWI – now Renewable Energy Wildlife Institute, REWI) – was appointed prime awardee of DOE award number DE-EE0007880 to lead a team of scientists, wind developers, and technology manufacturers in a collaborative evaluation of the effectiveness of a technology intended to help reduce eagle collisions with wind turbines. IdentiFlight, developed by Renewable Energy Systems (RES) in collaboration with Boulder Imaging, is an autonomous aerial monitoring and detection system. REWI partnered with ecological consultants, Western Ecosystems Technology, Inc. (WEST), to independently evaluate the performance of IdentiFlight reducing eagle collision risk under a suite of environmental conditions relative to the performance of a Biomonitor (human observer-based) Program. The project objectives were to 1) evaluate how IdentiFlight compared to biomonitors in detecting and identifying eagles under a suite of environmental conditions and 2) use the observation data to model how IdentiFlight and biomonitors reduced the eagle fatality prediction through informed curtailment. Field testing was to take place at two geographically distinct wind farms over two field seasons at each wind farm with a study design appropriate for meta-analyses across sites and years.

17 WIND ENERGY↗
NASA NTRS2003

Root phototropism: how light and gravity interact in shaping plant form

The interactions among tropisms can be critical in determining the final growth form of plants and plant organs. We have studied tropistic responses in roots as an example of these type of interactions. While gravitropism is the predominant tropistic response in roots, phototropism also plays a role in the oriented growth in this organ in flowering plants. In blue or white light, roots exhibit negative phototropism, but red light induces positive phototropism. In the flowering plant Arabidopsis, the photosensitive pigments phytochrome A (phyA) and phytochrome B (phyB) mediate this positive red-light-based photoresponse in roots since single mutants (and the double phyAB mutant) were severely impaired in this response. While blue-light-based negative phototropism is primarily mediated by the phototropin family of photoreceptors, the phyA and phyAB mutants (but not phyB) were inhibited in this response relative to the WT. The differences observed in phototropic responses were not due to growth limitations since the growth rates among all the mutants tested were not significantly different from that of the WT. Thus, our study shows that the blue-light and red-light systems interact in plants and that phytochrome plays a key role in integrating multiple environmental stimuli.

Non-NASA Center↗
NASA NTRS2002

Cellular and molecular responses to increased skeletal muscle loading after irradiation

Irradiation of rat skeletal muscles before increased loading has been shown to prevent compensatory hypertrophy for periods of up to 4 wk, possibly by preventing satellite cells from proliferating and providing new myonuclei. Recent work suggested that stem cell populations exist that might allow irradiated muscles to eventually hypertrophy over time. We report that irradiation essentially prevented hypertrophy in rat muscles subjected to 3 mo of functional overload (OL-Ir). The time course and magnitude of changes in cellular and molecular markers of anabolic and myogenic responses were similar in the OL-Ir and the contralateral nonirradiated, overloaded (OL) muscles for the first 3-7 days. These markers then returned to control levels in OL-Ir muscles while remaining elevated in OL muscles. The number of myonuclei and amount of DNA were increased markedly in OL but not OL-Ir muscles. Thus it appears that stem cells were not added to the irradiated muscles in this time period. These data are consistent with the theory that the addition of new myonuclei may be required for compensatory hypertrophy in the rat.

Non-NASA Center↗
NASA NTRS2004

Heavy particle irradiation, neurochemistry and behavior: thresholds, dose-response curves and recovery of function

Exposure to heavy particles can affect the functioning of the central nervous system (CNS), particularly the dopaminergic system. In turn, the radiation-induced disruption of dopaminergic function affects a variety of behaviors that are dependent upon the integrity of this system, including motor behavior (upper body strength), amphetamine (dopamine)-mediated taste aversion learning, and operant conditioning (fixed-ratio bar pressing). Although the relationships between heavy particle irradiation and the effects of exposure depend, to some extent, upon the specific behavioral or neurochemical endpoint under consideration, a review of the available research leads to the hypothesis that the endpoints mediated by the CNS have certain characteristics in common. These include: (1) a threshold, below which there is no apparent effect; (2) the lack of a dose-response relationship, or an extremely steep dose-response curve, depending on the particular endpoint; and (3) the absence of recovery of function, such that the heavy particle-induced behavioral and neural changes are present when tested up to one year following exposure. The current report reviews the data relevant to the degree to which these characteristics are common to neurochemical and behavioral endpoints that are mediated by the effects of exposure to heavy particles on CNS activity. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

Review↗
NASA NTRS2001

The radioresistance to killing of A1-5 cells derives from activation of the Chk1 pathway

Checkpoints respond to DNA damage by arresting the cell cycle to provide time for facilitating repair. In mammalian cells, the G(2) checkpoint prevents the Cdc25C phosphatase from removing inhibitory phosphate groups from the mitosis-promoting kinase Cdc2. Both Chk1 and Chk2, the checkpoint kinases, can phosphorylate Cdc25C and inactivate its in vitro phosphatase activity. Therefore, both Chk1 and Chk2 are thought to regulate the activation of the G(2) checkpoint. Here we report that A1-5, a transformed rat embryo fibroblast cell line, shows much more radioresistance associated with a much stronger G(2) arrest response when compared with its counterpart, B4, although A1-5 and B4 cells have a similar capacity for nonhomologous end-joining DNA repair. These phenotypes of A1-5 cells are accompanied by a higher Chk1 expression and a higher phosphorylation of Cdc2. On the other hand, Chk2 expression increases slightly following radiation; however, it has no difference between A1-5 and B4 cells. Caffeine or UCN-01 abolishes the extreme radioresistance with the strong G(2) arrest and at the same time reduces the phosphorylation of Cdc2 in A1-5 cells. In addition, Chk1 but not Chk2 antisense oligonucleotide sensitizes A1-5 cells to radiation-induced killing and reduces the G(2) arrest of the cells. Taken together these results suggest that the Chk1/Cdc25C/Cdc2 pathway is the major player for the radioresistance with G(2) arrest in A1-5 cells.

NASA Discipline Radiation Health↗
NASA NTRS2004

A Study to Compare the Failure Rates of Current Space Shuttle Ground Support Equipment with the New Pathfinder Equipment and Investigate the Effect that the Proposed GSE Infrastructure Upgrade Might Have to Reduce GSE Infrastructure Failures

The purposes of this study are to compare the current Space Shuttle Ground Support Equipment (GSE) infrastructure with the proposed GSE infrastructure upgrade modification. The methodology will include analyzing the first prototype installation equipment at Launch PAD B called the "Pathfinder". This study will begin by comparing the failure rate of the current components associated with the "Hardware interface module (HIM)" at the Kennedy Space Center to the failure rate of the neW Pathfinder components. Quantitative data will be gathered specifically on HIM components and the PAD B Hypergolic Fuel facility and Hypergolic Oxidizer facility areas which has the upgraded pathfinder equipment installed. The proposed upgrades include utilizing industrial controlled modules, software, and a fiber optic network. The results of this study provide evidence that there is a significant difference in the failure rates of the two studied infrastructure equipment components. There is also evidence that the support staff for each infrastructure system is not equal. A recommendation to continue with future upgrades is based on a significant reduction of failures in the new' installed ground system components.

Kennedy, Barbara J.↗
DOE OSTI2024

Pathways to formulate lightweight and ultra-lightweight 3D printable cementitious composites

Here, this paper studies the pathways to formulate lightweight and ultra-lightweight 3D printable cementitious composites. A hybrid approach was proposed by combining the advantages of traditional chemical-induced foaming (foaming approach) and lightweight particulate inclusions (synthetic foam approach). A comprehensive experimental program was conducted to evaluate the effects of foaming agents and fly ash cenosphere (FAC) on the printability, microstructure, mechanical and thermal properties of 3D printed samples. The results showed that the hybrid approach could produce a mixture with a density as low as 470 kg/m 3 while ensuring good flowability and buildability owing to the lubricating effect of foaming and supporting skeleton formed by FAC. In addition, a three-step homogenization procedure was also developed to predict the effective elastic modulus and thermal conductivity of 3D printable cementitious composites and cementitious foam. The findings of the study highlighted the effectiveness of the hybrid approach in formulating 3D printable ultra-lightweight cementitious composites in thermal insulation and acoustic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Effects of Surgery and Proton Therapy on Cerebral White Matter of Craniopharyngioma Patients

Purpose: The purpose of this study was to determine radiation dose effect on the structural integrity of cerebral white matter in craniopharyngioma patients receiving surgery and proton therapy. Methods and Materials: Fifty-one patients (2.1-19.3 years of age) with craniopharyngioma underwent surgery and proton therapy in a prospective therapeutic trial. Anatomical magnetic resonance images acquired after surgery but before proton therapy were inspected to identify white matter structures intersected by surgical corridors and catheter tracks. Longitudinal diffusion tensor imaging (DTI) was performed to measure microstructural integrity changes in cerebral white matter. Fractional anisotropy (FA) derived from DTI was statistically analyzed for 51 atlas-based white matter structures of the brain to determine radiation dose effect. FA in surgery-affected regions in the corpus callosum was compared to that in its intact counterpart to determine whether surgical defects affect radiation dose effect. Results: Surgical defects were seen most frequently in the corpus callosum because of transcallosal resection of tumors and insertion of ventricular or cyst catheters. Longitudinal DTI data indicated reductions in FA 3 months after therapy, which was followed by a recovery in most white matter structures. A greater FA reduction was correlated with a higher radiation dose in 20 white matter structures, indicating a radiation dose effect. The average FA in the surgery-affected regions before proton therapy was smaller (P=.0001) than that in their non–surgery-affected counterparts with more intensified subsequent reduction of FA (P=.0083) after therapy, suggesting that surgery accentuated the radiation dose effect. Conclusions: DTI data suggest that mild radiation dose effects occur in patients with craniopharyngioma receiving surgery and proton therapy. Surgical defects present at the time of proton therapy appear to accentuate the radiation dose effect longitudinally. This study supports consideration of pre-existing surgical defects and their locations in proton therapy planning and studies of treatment effect.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

Size-Dependent Adsorption and Adhesion Energetics of Ag Nanoparticles on Graphene Films on Ni(111) by Calorimetry

Interest in the use of carbon supports for late transition metal nanoparticle catalysts has expanded rapidly due to the increasing importance of electrocatalysts for clean energy and environmental technologies and the use and storage of renewable electricity. Compared to oxide supports, almost nothing is known about the effect of metal nanoparticle size on the energies of the metal atoms within carbon-supported nanoparticles, yet these energies are crucial for understanding their surface reactivity and sintering kinetics. Here, the growth morphology and adsorption energetics of vapor-deposited Ag onto clean graphene/Ni(111) surfaces have been studied using a combination of single-crystal adsorption calorimetry (SCAC) and He + low-energy ion scattering (LEIS). The differential heat of Ag adsorption is 207 kJ/mol for making ~30 atom Ag particles on graphene terraces at 100 K and 16 kJ/mol higher for making ~9 atom Ag clusters at defect sites at the same temperature. The heat of adsorption increases rapidly with Ag coverage as 3D Ag nanoparticles nucleate and grow in size, asymptotically reaching within 5 kJ/mol of the bulk Ag sublimation enthalpy (285 kJ/mol) by 2 ML. The heats of adsorption and Ag nanoparticle densities from LEIS (~10 16 /m 2 ) were combined to provide the Ag/graphene adhesion energy (E adh = 1.8 J/m 2 in the large-particle limit) and the Ag chemical potential (μ) versus effective particle diameter (D). The Ag chemical potential was well-fitted by μ(D) = (3γ v /M – E adh )(1 + (1.5 nm)/D)(2V m /D), where γ v /M is the surface energy of bulk Ag and V m is its molar volume. The same equation is known to fit similar data for late transition metals on clean surfaces of metal oxide single crystals. The adhesion energy of Ag measured here on graphene falls within the wide range measured for Ag on those oxide surfaces and is almost as large as on the oxide that binds Ag particles most strongly, namely CeO 2 (111), which is well-known to be very effective at resisting catalyst deactivation by metal sintering. Furthermore, these results imply that carbon supports will be effective at resisting sintering and that Ag particles smaller than 6 nm on graphene will bind small adsorbed reaction intermediates more weakly than supports with weaker adhesion to Ag, like MgO(100).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1988

Biomedical support of man in space

In its broadest sense, biomedical support of man in space must not be limited to assisting spacecraft crew during the mission; such support should also ensure that flight personnel be able to perform properly during landing and after leaving the craft. Man has developed mechanisms that allow him to cope with specific stresses in his normal habitat; there is indisputable evidence that, in some cases, the space environment, by relieving these stresses, has also allowed the adaptive mechanisms to lapse, causing serious problems after re-entry. Inflight biomedical support must therefore include means to simulate some of the normal stresses of the Earth environment. In the area of cardiovascular performance, we have come to rely heavily on complex feedback mechanisms to cope with two stresses, often combined: postural changes, which alter the body axis along which gravitational acceleration acts, and physical exercise, which increases the total load on the system. Unless the appropriate responses are reinforced continuously during flight, crew members may be incapacitated upon return. The first step in the support process must be a study of the way in which changes in g, even of short duration, affect these responses. In particular we should learn more about effects of g on the "on" and "off" dynamics, using a variety of approaches: increased acceleration on one hand at recumbency, immersion, lower body positive pressure, and other means of simulating some of the effects of low g, on the other. Once we understand this, we will have to determine the minimal exposure dose required to maintain the response mechanisms. Finally, we shall have to design stresses that simulate Earth environment and can be imposed in the space vehicle. Some of the information is already at hand; we know that several aspects of the response to exercise are affected by posture. Results from a current series of studies on the kinetics of tilt and on the dynamics of readjustment to exercise in different postures will be presented and discussed.

NASA Discipline Cardiopulmonary↗
DOE OSTI2017

Two-Stage Fracturing Wastewater Management in Shale Gas Development

Here, management of shale gas wastewater treatment, disposal, and reuse has become a significant environmental challenge, driven by an ongoing boom in development of U.S. shale gas reservoirs. Systems-analysis based decision support is helpful for effective management of wastewater, and provision of cost-effective decision alternatives from a whole-system perspective. Uncertainties are inherent in many modeling parameters, affecting the generated decisions. In order to effectively deal with the recourse issue in decision making, in this work a two-stage stochastic fracturing wastewater management model, named TSWM, is developed to provide decision support for wastewater management planning in shale plays. Using the TSWM model, probabilistic and nonprobabilistic uncertainties are effectively handled. The TSWM model provides flexibility in generating shale gas wastewater management strategies, in which the first-stage decision predefined by decision makers before uncertainties are unfolded is corrected in the second stage to achieve the whole-system’s optimality. Application of the TSWM model to a comprehensive synthetic example demonstrates its practical applicability and feasibility. Optimal results are generated for allowable wastewater quantities, excess wastewater, and capacity expansions of hazardous wastewater treatment plants to achieve the minimized total system cost. The obtained interval solutions encompass both optimistic and conservative decisions. Trade-offs between economic and environmental objectives are made depending on decision makers’ knowledge and judgment, as well as site-specific information. In conclusion, the proposed model is helpful in forming informed decisions for wastewater management associated with shale gas development.

04 OIL SHALES AND TAR SANDS↗
NASA NTRS1990

Applicability and evaluation of an implicit self-starting unconditionally stable methodology for the dynamics of structures

The applicability and evaluation of a new self-starting, unconditionally stable, implicit methodology of computation for the dynamics of structures is described. The methodology offers different perspectives and architecture for structural dynamics compared with the traditional (widely advocated and commonly used) time integration methods. It is based on velocity representations and architecture and uses finite elements as the principal analysis tool for structural dynamic modeling/analysis. In particular, the dynamics of beam-type flexural models are considered, and comparative results validate and support the proposed use of the self-starting methodology of computation for the dynamics of linear/nonlinear structures. The overall effectiveness and elegance strongly support its use in most existing commercial codes.

Tamma, Kumar K.↗
NASA NTRS2002

Spatial separation of light perception and growth response in maize root phototropism

Although the effects of gravity on root growth are well known and interactions between light and gravity have been reported, details of root phototropic responses are less documented. We used high-resolution image analysis to study phototropism in primary roots of Zea mays L. Similar to the location of perception in gravitropism, the perception of light was localized in the root cap. Phototropic curvature away from the light, on the other hand, developed in the central elongation zone, more basal than the site of initiation of gravitropic curvature. The phototropic curvature saturated at approximately 10 micromoles m-2 s-1 blue light with a peak curvature of 29 +/- 4 degrees, in part due to induction of positive gravitropism following displacement of the root tip from vertical during negative phototropism. However, at higher fluence rates, development of phototropic curvature is arrested even if gravitropism is avoided by maintaining the root cap vertically using a rotating feedback system. Thus continuous illumination can cause adaptation in the signalling pathway of the phototropic response in roots.

NASA Discipline Plant Biology↗
NASA NTRS2002

Interactions between gravitropism and phototropism in plants

To receive adequate light and nutrients for survival, plants orient stems and stem-like organs toward light and away from the gravity vector and, conversely, orient roots into the soil, away from light toward the direction of gravity. Therefore, both gravity and light can influence the differential growth of plant organs. To add to the complexity of the interactions between gravity and light, each stimulus can enhance or reduce the effectiveness of the other. On earth, the constant presence of gravity makes it difficult to determine whether plant growth and development is influenced by gravity or light alone or the combination of the two stimuli. In the past decade, our understanding of the gravity and light transduction pathways has advanced through the use of mutants in either gravitropic or phototropic responses and the use of innovative techniques that reduce the effects of one stimulus on the other. Thus, both unique and common elements in the transduction pathways of the gravitropic and phototropic responses have been isolated. This article is focused on the interactions between the light- and gravity-transduction pathways and describes methods used to separate the influences of these two environmental stimuli.

NASA Discipline Plant Biology↗
NASA NTRS2001

Light differentially regulates cell division and the mRNA abundance of pea nucleolin during de-etiolation

The abundance of plant nucleolin mRNA is regulated during de-etiolation by phytochrome. A close correlation between the mRNA abundance of nucleolin and mitosis has also been previously reported. These results raised the question of whether the effects of light on nucleolin mRNA expression were a consequence of light effects on mitosis. To test this we compared the kinetics of light-mediated increases in cell proliferation with that of light-mediated changes in the abundance of nucleolin mRNA using plumules of dark-grown pea (Pisum sativum) seedlings. These experiments show that S-phase increases 9 h after a red light pulse, followed by M-phase increases in the plumule leaves at 12 h post-irradiation, a time course consistent with separately measured kinetics of red light-induced increases in the expression of cell cycle-regulated genes. These increases in cell cycle-regulated genes are photoreversible, implying that the light-induced increases in cell proliferation are, like nucleolin mRNA expression, regulated via phytochrome. Red light stimulates increases in the mRNA for nucleolin at 6 h post-irradiation, prior to any cell proliferation changes and concurrent with the reported timing of phytochrome-mediated increases of rRNA abundance. After a green light pulse, nucleolin mRNA levels increase without increasing S-phase or M-phase. Studies in animals and yeast indicate that nucleolin plays a significant role in ribosome biosynthesis. Consistent with this function, pea nucleolin can rescue nucleolin deletion mutants of yeast that are defective in rRNA synthesis. Our data show that during de-etiolation, the increased expression of nucleolin mRNA is more directly regulated by light than by mitosis.

NASA Program Fundamental Space Biology↗
DOE OSTI2020

Unraveling the individual influences of supports and ionic liquid coatings on the catalytic properties of supported iridium complexes and iridium clusters

In this work, supported iridium complexes were synthesized by the reaction of Ir(CO) 2 (acac) (acac = acetylacetonato) with SiO 2 , γ-Al 2 O 3 , and MgO. Extended X-ray absorption fine structure (EXAFS) and infrared (IR) spectra demonstrate that the iridium was present as atomically dispersed species anchored to each support. The samples were treated in flowing H 2 at 673 K to form supported iridium clusters. EXAFS spectra and high-angle annular dark-field scanning transmission electron microscopy images demonstrate that the average diameter of the iridium clusters on each support was approximately 1.2 nm. Furthermore, the catalysts before and after cluster formation were coated with each of a family of 1,3-dialkylimidazolium ionic liquids (ILs) having varying electron-donor tendencies probed by their υ(C2H) frequencies determined by IR spectroscopy. The coated and uncoated samples were tested as catalysts for partial hydrogenation of 1,3-butadiene in a flow reactor at 333 K, with turnover frequencies determined from differential conversions. The individual influences of the IL coatings and supports on the catalyst performance were found to depend strongly on whether the iridium was site-isolated complexes or present in clusters. The IL coatings as ligands exerted dominant effects on the clusters as catalysts, whereas the supports exerted dominant effects on the isolated iridium atoms. The results indicate how to tune the effects of metal nuclearity, IL coatings, and supports on the electronic environments and catalytic properties of the metals.

1,3-Butadiene hydrogenation↗