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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Long life nickel electrodes for a nickel-hydrogen cell. I Initial performance

In order to develop a long life nickel electrode for a Ni/H2 cell, an investigation was begun to study the effects of sinter structure and active material loading level on the long life performance of nickel electrodes. This paper is a report on the initial performance of these electrodes as a part of an accelerated life test program. Seven different types of nickel plaques were made which included three levels of both their mechanical strength and median pore size. These plaques were impregnated with three levels of active material loading. The resultant electrodes were tested by a 200-cycle stress test which was conducted in flooded electrolyte, and also for initial performance in a Ni/H2 boiler plate cell. An interesting and unexpected observation was that an increased initial utilization of the active material was due more to its complete discharge to the lower average oxidation state than its increased charge acceptance in the charged state.

Lim, H. S.↗
NASA NTRS1990

Electrochemical impregnation and cycle life of lightweight nickel electrodes for nickel-hydrogen cells

Development of a high specific energy nickel electrode is the main goal of the lightweight nickel electrode program at NASA-Lewis. The approach was to improve the nickel electrode by continuing combined in-house and contract efforts to develop a more efficient and lighter weight electrode for the nickel-hydrogen cell. Lightweight plaques are used as conductive supports for the nickel hydroxide active material. These plaques are commercial products that are fabricated into nickel electrodes by electrochemically impregnating them with active material. The electrodes are life cycle tested in a low Earth orbit regime at 40 and 80 percent depths-of-discharge.

Britton, Doris L.↗
NASA NTRS1992

Progress in the development of lightweight nickel electrode for aerospace applications

The NASA Lewis Research Center is currently developing nickel electrodes for nickel-hydrogen (Ni-H2) cells and batteries. These electrodes are lighter in weight and have higher specific energy than the heavy sintered state of the art nickel electrodes. In the present approach, lightweight materials or plaques are used as conductive supports for the nickel hydroxide active material. These plaques (fiber, felt, and nickel plated plastic) are fabricated into nickel electrodes by electrochemically impregnating them with active material. Initial performance tests include capacity measurements at five discharge levels, C/2, 1.0C, 1.37C, 2.0C, and 2.74C. The electrodes that pass the initial tests are life cycle tested at 40 and 80 percent depths of discharge (DOD). Different formulations of nickel fiber materials obtained from several manufacturers are currently being tested as possible candidates for nickel electrodes. Over 7,000 cycles of life cycle testing have been accumulated at 40 percent DOD, using the lightweight fiber electrode in a boiler plate Ni-H2 cell with stable voltage.

Britton, Doris L.↗
NASA NTRS1990

Electrochemical impregnation and cycle life of lightweight nickel electrodes for nickel-hydrogen cells

Development of a high specific energy nickel electrode is the main goal of the lightweight nickel electrode program at NASA-Lewis. The approach was to improve the nickel electrode by continuing combined in-house and contract efforts to develop a more efficient and lighter weight electrode for the nickel-hydrogen cell. Lightweight plaques are used as conductive supports for the nickel hydroxide active material. These plaques are commercial products that are fabricated into nickel electrodes by electrochemically impregnating them with active material. The electrodes are life cycle tested in a low earth orbit regime at 40 and 80 percent depths-of-discharge.

Britton, Doris L.↗
NASA NTRS1993

Lightweight nickel electrodes for nickel/hydrogen cells

Thick nickel electrodes with lightweight substrate material have been prepared and tested in Ni/H2 boilerplate cells containing 26 percent KOH electrolyte. Lightweight substrates used were either 85 or 90 percent in porosity and either 0.8 or 2 mm in thickness, respectively, compared with 80 to 82 percent porosity and 0.75 to 0.8 mm thickness of the state-of-the-art sintered plaque substrate. All of these thick electrodes had substantially improved theoretical (or chemical) capacity over that of state-of-the-art sintered nickel plaque electrodes. However, utilization of the active material was low (65 to 80 percent) compared with that of the state-of-the-art electrodes (approximately 90 percent) in 26 percent KOH. Due to this low utilization, the electrodes using 85 percent porous substrates did not show any advantage over the state-of-the-art ones. The electrodes using a 90 percent porous substrate, however, showed 17 percent higher usable specific capacity (about 0.13 Ah/g in 26 percent KOH) than that of the state-of-the-art nickel electrodes despite the low utilization. These electrodes achieved up to 4860 cycles at 40 percent depth-of-discharge with neither capacity loss nor any significant changes of rate capability and charging efficiency with cycling.

Lim, Hong S.↗
NASA NTRS1995

Development of a micro-fiber nickel electrode for nickel-hydrogen cell

Development of a high specific energy nickel electrode is the main goal of the lightweight nickel electrode program at the NASA Lewis Research Center. The approach has been to improve the nickel electrode by continuing combined in-house and contract efforts to develop a more efficient and lighter weight electrode for the nickel-hydrogen cell. Small fiber diameter nickel plaques are used as conductive supports for the nickel hydroxide active material. These plaques are commercial products and have an advantage of increased surface area available for the deposition of active material. Initial tests include activation and capacity measurements at different discharge levels followed by half-cell cycle testing at 80 percent depth-of-discharge in a low-Earth-orbit regime. The electrodes that pass the initial tests are life cycle-tested in a boiler plate nickel-hydrogen cell before flightweight designs are built and tested.

Britton, Doris L.↗
NASA NTRS1996

SeaWiFs Technical Report Series. Volume 34: The Third SeaWiFS Intercalibration Round-Robin Experiment (SIRREX-3), 19-30 September 1994

This report presents results of the third Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Intercalibration Round- Robin Experiment (SIRREX-3), which was held at the San Diego State University (SDSU) Center for Hydro-Optics and Remote Sensing (CHORS) on 19-30 September 1994. Spectral irradiances of FEL lamps belonging to each participant were intercompared by reference to the National Institute of Standards and Technology (NIST) scale of spectral irradiance using secondary standard lamps F268, F269, and F182, with a Type A uncertainty between 1.1-1.5%. This level of uncertainty was achieved despite difficulties with lamp F269. The average spectral irradiances of FEL lamps, compared in both SIRREX-2 and SIRREX-3, differed between the two experiments by 1.5%, which probably indicates that the values assigned to the secondary standard lamp at the time of SIRREX-2 were in error. With two exceptions, spectral radiance values of integrating sphere sources were measured during SIRREX-3 with uncertainties in temporal stability of less than 0.3% and absolute uncertainties of 1.5-2.0%. This is a significant improvement over similar intercomparisons in SIRREX- I and SIRREX-2. Plaque reflectances were intercompared with an uncertainty of about 1-2%, but the absolute uncertainty is undefined. Although this is an improvement over results of previous SIRREXS, the sources and magnitude of uncertainty associated with transfers of spectral radiance using plaques requires further evaluation in future experiments.

Hooker, Stanford B.↗
NASA NTRS1996

Development of a Micro-Fiber Nickel Electrode for Nickel-Hydrogen Cell

The development of a high specific energy battery is one of the objectives of the lightweight nickel-hydrogen (NiH2) program at the NASA Lewis Research Center. The approach has been to improve the nickel electrode by continuing combined in-house and contract efforts to develop a more efficient and lighter weight electrode for the nickel-hydrogen fuel cell. Small fiber diameter nickel plaques are used as conductive supports for the nickel hydroxide active material. These plaques are commercial products and have an advantage of increased surface area available for the deposition of active materials. Initial tests include activation and capacity measurements at different discharge levels followed by half-cell cycle testing at 80 percent depth-of-discharge in a low Earth orbit regime. The electrodes that pass the initial tests are life cycle tested in a boiler plate nickel-hydrogen cell before flightweight designs are built and tested.

Britton, Doris L.↗
NASA NTRS1999

Progress in the Development of Lightweight Nickel Electrode for Nickel-Hydrogen Cell

Development of a high specific energy battery is one of the objectives of the lightweight nickel-hydrogen (Ni-H2) program at the NASA Glenn Research Center. The approach has been to improve the nickel electrode by continuing combined in-house and contract efforts to develop a lighter weight electrode for the nickel-hydrogen cell. Small fiber diameter nickel plaques are used as conductive supports for the nickel hydroxide active material. These plaques are commercial products and have an advantage of increased surface area available for the deposition of active material. Initial tests include activation and capacity measurements at five different discharge levels, C/2, 1.0 C, 1.37 C, 2.0 C, and 2.74 C. The electrodes are life cycle tested using a half-cell configuration at 40 and 80% depths-of-discharge (DOD) in a low-Earth-orbit regime. The electrodes that pass the initial tests are life cycle-tested in a boiler plate nickel-hydrogen cell before flight weight design are built and tested.

Britton, Doris L.↗
NASA NTRS2000

Long Life Nickel Electrodes for Nickel-Hydrogen Cells: Fiber Substrates Nickel Electrodes

Samples of nickel fiber mat electrodes were investigated over a wide range of fiber diameters, electrode thickness, porosity and active material loading levels. Thickness' were 0.040, 0.060 and 0.080 inches for the plaque: fiber diameters were primarily 2, 4, and 8 micron and porosity was 85, 90, and 95%. Capacities of 3.5 in. diameter electrodes were determined in the flooded condition with both 26 and 31% potassium hydroxide solution. These capacity tests indicated that the highest capacities per unit weight were obtained at the 90% porosity level with a 4 micron diameter fiber plaque. It appeared that the thinner electrodes had somewhat better performance, consistent with sintered electrode history. Limited testing with two-positive-electrode boiler plate cells was also carried out. Considerable difficulty with constructing the cells was encountered with short circuits the major problem. Nevertheless, four cells were tested. The cell with 95% porosity electrodes failed during conditioning cycling due to high voltage during charge. Discharge showed that this cell had lost nearly all of its capacity. The other three cells after 20 conditioning cycles showed capacities consistent with the flooded capacities of the electrodes. Positive electrodes made from fiber substrates may well show a weight advantage of standard sintered electrodes, but need considerably more work to prove this statement. A major problem to be investigated is the lower strength of the substrate compared to standard sintered electrodes. Problems with welding of leads were significant and implications that the electrodes would expand more than sintered electrodes need to be investigated. Loading levels were lower than had been expected based on sintered electrode experiences and the lower loading led to lower capacity values. However, lower loading causes less expansion and contraction during cycling so that stress on the substrate is reduced.

Rogers, Howard H.↗
NASA NTRS2002

The Seventh SeaWiFS Intercalibration Round-Robin Experiment (SIRREX-7), March 1999

This report documents the scientific activities during the seventh SeaWiFS Intercalibration Round-Robin Experiment (SIRREX-7) held at Satlantic, Inc. (Halifax, Canada). The overall objective of SIRREX-7 was to determine the uncertainties of radiometric calibrations and measurements at a single calibration facility. Specifically, this involved the estimation of the uncertainties in a) lamp standards, b) plaque standards (including the uncertainties associated with plaque illumination non-uniformity), c) radiance calibrations, and d) irradiance calibrations. The investigation of the uncertainties in lamp standards included a comparison between a calibration of a new FEL by the National Institute of Standards and Technology (NIST) and Optronic Laboratories, Inc. In addition, the rotation and polarization sensitivity of radiometers were determined, and a procedure for transferring an absolute calibration to portable light sources was defined and executed.

Hooker, Stanford B.↗
NASA NTRS2000

Vascular mechanics of the coronary artery

This paper describes our research into the vascular mechanics of the coronary artery and plaque. The three sections describe the determination of arterial mechanical properties using intravascular ultrasound (IVUS), a constitutive relation for the arterial wall, and finite element method (FEM) models of the arterial wall and atheroma. METHODS: Inflation testing of porcine left anterior descending coronary arteries was conducted. The changes in the vessel geometry were monitored using IVUS, and intracoronary pressure was recorded using a pressure transducer. The creep and quasistatic stress/strain responses were determined. A Standard Linear Solid (SLS) was modified to reproduce the non-linear elastic behavior of the arterial wall. This Standard Non-linear Solid (SNS) was implemented into an axisymetric thick-walled cylinder numerical model. Finite element analysis models were created for five age groups and four levels of stenosis using the Pathobiological Determinants of Atherosclerosis Youth (PDAY) database. RESULTS: The arteries exhibited non-linear elastic behavior. The total tissue creep strain was epsilon creep = 0.082 +/- 0.018 mm/mm. The numerical model could reproduce both the non-linearity of the porcine data and time dependent behavior of the arterial wall found in the literature with a correlation coefficient of 0.985. Increasing age had a strong positive correlation with the shoulder stress level, (r = 0.95). The 30% stenosis had the highest shoulder stress due to the combination of a fully formed lipid pool and a thin cap. CONCLUSIONS: Studying the solid mechanics of the arterial wall and the atheroma provide important insights into the mechanisms involved in plaque rupture.

NASA Program Biomedical Research and Countermeasur↗
NASA NTRS1999

Adenovirus-mediated gene delivery to hypothalamic magnocellular neurons in mice

Vasopressin is synthesized by magnocellular neurons in supraoptic (SON) and paraventricular (PVN) hypothalamic nuclei and released by their axon terminals in the neurohypophysis (NH). With its actions as an antidiuretic hormone and vasoactive agent, vasopressin plays a pivotal role in the control of body fluids and cardiovascular homeostasis. Because of its well-defined neurobiology and functional importance, the SON/PVN-NH system is ideal to establish methods for gene transfer of genetic material into specific pathways in the mouse central nervous system. In these studies, we compared the efficiency of transferring the gene lacZ, encoding for beta-galactosidase (beta-gal), versus a gene encoding for green fluorescent protein by using replication-deficient adenovirus (Ad) vectors in adult mice. Transfection with viral concentrations up to 2 x 10(7) plaque-forming units per coverslip of NH, PVN, and SON in dissociated, cultured cells caused efficient transfection without cytotoxicity. However, over an extended period of time, higher levels (50% to 75% of the cells) of beta-gal expression were detected in comparison with green fluorescent protein (5% to 50% of the cells). With the use of a stereotaxic approach, the pituitary glands of mice were injected with Ad (4 x 10(6) plaque-forming units). In material from these animals, we were able to visualize the expression of the beta-gal gene in the NH and in magnocellular neurons of both the PVN and SON. The results of these experiments indicate that Ad-Rous sarcoma virus promoter-beta-gal is taken up by nerve terminals at the injection site (NH) and retrogradely transported to the soma of the neurons projecting to the NH. We conclude that the application of these experimental approaches will provide powerful tools for physiological studies and potential approaches to deliver therapeutic genes to treat diseases.

Non-NASA Center↗
DOE OSTI2023

The catalytic domains of Streptococcus mutans glucosyltransferases: a structural analysis

Streptococcus mutans, found in the human oral cavity, is a significant contributor to the pathogenesis of dental caries. This bacterium expresses three genetically distinct types of glucosyltransferases named GtfB (GTF-I), GtfC (GTF-SI) and GtfD (GTF-S) that play critical roles in the development of dental plaque. The catalytic domains of GtfB, GtfC and GtfD contain conserved active-site residues for the overall enzymatic activity that relate to hydrolytic glycosidic cleavage of sucrose to glucose and fructose, release of fructose and generation of a glycosyl-enzyme intermediate in the reducing end. In a subsequent transglycosylation step, the glucosyl moiety is transferred to the nonreducing end of an acceptor to form a growing glucan polymer chain made up of glucose molecules. It has been proposed that both sucrose breakdown and glucan synthesis occur in the same active site of the catalytic domain, although the active site does not appear to be large enough to accommodate both functions. These three enzymes belong to glycoside hydrolase family 70 (GH70), which shows homology to glycoside hydrolase family 13 (GH13). GtfC synthesizes both soluble and insoluble glucans (α-1,3 and α-1,6 glycosidic linkages), while GtfB and GtfD synthesize only insoluble or soluble glucans, respectively. Here, crystal structures of the catalytic domains of GtfB and GtfD are reported. These structures are compared with previously determined structures of the catalytic domain of GtfC. With this work, apo structures and inhibitor-complex structures with acarbose are now available for the catalytic domains of GtfC and GtfB. The structure of GtfC with maltose allows further identification and comparison of active-site residues. A model of sucrose binding to GtfB is also included. The new structure of the catalytic domain of GtfD affords a structural comparison of the three S. mutans glycosyltransferases. Unfortunately, the catalytic domain of GtfD is not complete since crystallization resulted in the structure of a truncated protein lacking approximately 200 N-terminal residues of domain IV.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Area-Preserving Mapping of 3D Carotid Ultrasound Images Using Density-Equalizing Reference Map

Carotid atherosclerosis is a focal disease at the bifurcations of the carotid artery. To quantitatively monitor the local changes in the vessel-wall-plus-plaque thickness (VWT) and compare the VWT distributions for different patients or for the same patients at different ultrasound scanning sessions, a mapping technique is required to adjust for the geometric variability of different carotid artery models. In this work, we propose a novel method called density-equalizing reference map (DERM) for mapping 3D carotid surfaces to a standardized 2D carotid template, with an emphasis on preserving the local geometry of the carotid surface by minimizing the local area distortion. The initial map was generated by a previously described arc-length scaling (ALS) mapping method, which projects a 3D carotid surface onto a 2D non-convex L-shaped domain. A smooth and area-preserving flattened map was subsequently constructed by deforming the ALS map using the proposed algorithm that combines the density-equalizing map and the reference map techniques. This combination allows, for the first time, one-to-one mapping from a 3D surface to a standardized non-convex planar domain in an area-preserving manner. Evaluations using 20 carotid surface models show that the proposed method reduced the area distortion of the flattening maps by over 80% as compared to the ALS mapping method.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Candidatus Nanopusillus

The genus Candidatus Nanopusillus is comprised of small coccoid cells (~100–400 nm) that live epibiotically on the surface of archaeal hosts. The first described species, Candidatus Nanopusillus acidilobi, is an anaerobic, hyperthermophilic acidophile whose best growth is observed at 82°C, pH 3.6, cultivated from a hot spring in Yellowstone National Park. Ca. Nanopusillus acidilobi cells associate with the Crenarchaeota host organism Acidilobus sp. 7A. Archaeal flagella (archaella) have been predicted from the genome sequence and shown to be expressed in the proteome. Additionally, a second putative species, Candidatus Nanopusillus massiliensis, was recently reported from human dental plaque and associates with the methanogen Methanobrevibacter oralis. The genome consists of a single scaffold which is highly fragmented by spans of ambiguous nucleotides, with 16S rRNA gene fragments from Bacteria. Both species have small genomes (~0.6 Mb) encoding few biosynthetic genes and no apparent ATP synthase complex genes, suggesting that the nanoarchaeotes rely on their host for the production of major cellular precursors.

acidophile↗
DOE OSTI2022

A Hybrid Structural Method for Investigating Low Molecular Weight Oligomeric Structures of Amyloid Beta

Spurred in part by the failure of recent therapeutics targeting amyloid β plaques in Alzheimer's Disease (AD), attention is increasingly turning to the oligomeric forms of this peptide that form early in the aggregation process. However, while numerous amyloid β fibril structures have been characterized, primarily by NMR spectroscopy and cryo-EM, obtaining structural information on the low molecular weight forms of amyloid β that presumably precede and/or seed fibril formation has proved challenging. Furthermore, these transient forms are heterogeneous, and depend heavily on experimental conditions such as buffer, temperature, concentration, and degree of quiescence during measurement. Here, we present the concept for a new approach to delineating structural features of early-stage low molecular weight amyloid β oligomers, using a solvent accessibility assay in conjunction with simultaneous fluorescence measurements.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Seaweed-derived fucoidans and rhamnan sulfates serve as potent anti-SARS-CoV-2 agents with potential for prophylaxis

Seaweeds represent a rich source of sulfated polysaccharides with similarity to heparan sulfate, a facilitator of myriad virus host cell attachment. For this reason, attention has been drawn to their antiviral activity, including the potential for anti-SARS-CoV-2 activity. We have identified and structurally characterized several fucoidan extracts, including those from different species of brown macroalga, and a rhamnan sulfate from a green macroalga species. A high molecular weight fucoidan extracted from Saccharina japonica (FSjRPI-27), and a rhamnan sulfate extracted from Monostroma nitidum (RSMn), showed potent competitive inhibition of spike glycoprotein receptor binding to a heparin-coated SPR chip. This inhibition was also observed in cell-based assays using hACE2 HEK-293 T cells infected by pseudotyped SARS-CoV-2 virus with IC50 values <1 μg/mL. Effectiveness was demonstrated in vivo using hACE2–transgenic mice. Intranasal administration of FSjRPI-27 showed protection when dosed 6 h prior to and at infection, and then every 2 days post-infection, with 100 % survival and no toxicity at 104 plaque-forming units per mouse vs. buffer control. At 5-fold higher virus dose, FSjRPI-27 reduced mortality and yielded reduced viral titers in bronchioalveolar fluid and lung homogenates vs. buffer control. Furthermore, these findings suggest the potential application of seaweed-based sulfated polysaccharides as promising anti-SARS-CoV-2 prophylactics.

60 APPLIED LIFE SCIENCES↗