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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Roles of Sensory Nerves in the Regulation of Radiation-Induced Structural and Functional Changes in the Heart

Purpose: Radiation-induced heart disease (RIHD) is a chronic severe side effect of radiation therapy of intrathoracic and chest wall tumors. The heart contains a dense network of sensory neurons that not only are involved in monitoring of cardiac events such as ischemia and reperfusion but also play a role in cardiac tissue homeostasis, preconditioning, and repair. The purpose of this study was to examine the role of sensory nerves in RIHD. Methods and Materials: Male Sprague-Dawley rats were administered capsaicin to permanently ablate sensory nerves, 2 weeks before local image-guided heart x-ray irradiation with a single dose of 21 Gy. During the 6 months of follow-up, heart function was assessed with high-resolution echocardiography. At 6 months after irradiation, cardiac structural and molecular changes were examined with histology, immunohistochemistry, and Western blot analysis. Results: Capsaicin pretreatment blunted the effects of radiation on myocardial fibrosis and mast cell infiltration and activity. By contrast, capsaicin pretreatment caused a small but significant reduction in cardiac output 6 months after irradiation. Capsaicin did not alter the effects of radiation on cardiac macrophage number or indicators of autophagy and apoptosis. Conclusions: These results suggest that sensory nerves, although they play a predominantly protective role in radiation-induced cardiac function changes, may eventually enhance radiation-induced myocardial fibrosis and mast cell activity.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2024

Comparative life cycle analysis on ethylene production from electrocatalytic reduction of carbon dioxide

Ethylene is one of the largest greenhouse gas emitters and the most diversly used commodity chemicals globally. Electrocatalytic reduction of CO 2 to ethylene received great attention from the research society to decarbonize the ethylene production. Here, in this study, a life-cycle analysis is conducted using the Greenhouse Gases, Regulated Emissions, and Energy use in Technologies (GREET) model on the three electrocatalytic CO 2 -reduction pathways (or “e-ethylene” pathways): i) cascade conversion via carbon monoxide intermediate; ii) single-step conversion in membrane electrode assembly (MEA); and iii) single-step conversion in alkaline flow cell. The results showed that the electricity consumption is the lowest for the cascade pathway (164 MJ/kg), thus resulting in the lowest cradle-to-gate carbon intensity [18 kgCO 2 e/kg with United States (US) average grid)] among the three pathways followed by the single-step MEA (32 kgCO 2 e/kg) and then by the single-step alkaline (56 kgCO 2 e/kg). However, all three e-ethylene pathways were significantly more carbon-intensive than their fossil-based counterpart (1.1 kgCO 2 e/kg) due to their excessive energy consumption with the current state of technology. With renewable electricity, all three pathways yielded negative carbon intensity: from -3.1 kgCO 2 e/kg to -1.6 kgCO 2 e/kg depending on the source of CO 2 . The threshold carbon intensity of electricity (TCIE), defined as the upper bound of the carbon intensity of electricity to achieve lower carbon intensity for e-ethylene compared to fossil-based ethylene, is calculated for both current and future state of e-ethylene technologies. The cascade pathway had the highest TCIE out of the three e-ethylene pathways for both current (92 gCO 2 e/kWh) and future (124 gCO 2 e/kWh) state of technologies. However, the carbon intensity of average US grid (i.e., 467 and 303 gCO 2 e/kWh for current and future projections) were higher than the TCIEs of the corresponding timeline. Thus, reducing electricity requirement for e-ethylene pathways and bringing low-carbon generation mix in the United States (US) grid faster than the current projection are both essential to decarbonize ethylene and its downstream chemicals/polymers.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2011

Structural characterization and novel optical properties of defect chalcopyrite ZnGa{sub 2}Te{sub 4} thin films

Highlights: {yields} Preparation and characterization of ZnGa{sub 2}Te{sub 4} in powder and thin film forms. {yields} Structure properties such as XRD and EDX. {yields} Optical constant of the as-deposited ZnGa{sub 2}Te{sub 4} for the first time. {yields} Extraction of the optical parameters of the studied films. -- Abstract: Stoichiometric thin film samples of the ternary ZnGa{sub 2}Te{sub 4} defect chalcopyrite compound were prepared and characterized by X-ray diffraction technique. The elemental chemical composition of the prepared bulk material as well as of the as-deposited film was determined by energy-dispersive X-ray spectrometry. ZnGa{sub 2}Te{sub 4} thin films were deposited, by conventional thermal evaporation technique onto highly cleaned glass substrates. The X-ray and electron diffraction studies revealed that the as-deposited and the annealed ZnGa{sub 2}Te{sub 4} films at annealing temperature t{sub a} {<=} 548 K are amorphous, while those annealed at t{sub a} {>=} 573 K (for 1 h), are polycrystalline. The optical properties of the as-deposited films have been investigated for the first time at normal incidence in the spectral range from 500 to 2500 nm. The refractive index dispersion in the transmission and low absorption region is adequately described by the Wemple-DiDomenico single oscillator model, whereby, the values of the oscillator parameters have been calculated. The analysis of the optical absorption coefficient revealed an in-direct optical transition with energy of 1.33 eV for the as-deposited sample. This work suggested that ZnGa{sub 2}Te{sub 4} is a good candidate in solar cell devices as an absorbing layer.

36 MATERIALS SCIENCE↗
DOE OSTI2024

High-throughput single-cell transcriptomics of bacteria using combinatorial barcoding

Microbial split-pool ligation transcriptomics (microSPLiT) is a high-throughput single-cell RNA sequencing method for bacteria. With four combinatorial barcoding rounds, microSPLiT can profile transcriptional states in hundreds of thousands of Gram-negative and Gram-positive bacteria in a single experiment without specialized equipment. As bacterial samples are fixed and permeabilized before barcoding, they can be collected and stored ahead of time. During the first barcoding round, the fixed and permeabilized bacteria are distributed into a 96-well plate, where their transcripts are reverse transcribed into cDNA and labeled with the first well-specific barcode inside the cells. The cells are mixed and redistributed two more times into new 96-well plates, where the second and third barcodes are appended to the cDNA via in-cell ligation reactions. Finally, the cells are mixed and divided into aliquot sub-libraries, which can be stored until future use or prepared for sequencing with the addition of a fourth barcode. It takes 4 days to generate sequencing-ready libraries, including 1 day for collection and overnight fixation of samples. Here, the standard plate setup enables single-cell transcriptional profiling of up to 1 million bacterial cells and up to 96 samples in a single barcoding experiment, with the possibility of expansion by adding barcoding rounds. The protocol requires experience in basic molecular biology techniques, handling of bacterial samples and preparation of DNA libraries for next-generation sequencing. It can be performed by experienced undergraduate or graduate students. Data analysis requires access to computing resources, familiarity with Unix command line and basic experience with Python or R.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Revealing the transcriptomic complexity of switchgrass by PacBio long-read sequencing

Switchgrass ( Panicum virgatum L.) is an important bioenergy crop widely used for lignocellulosic research. While extensive transcriptomic analyses have been conducted on this species using short read-based sequencing techniques, very little has been reliably derived regarding alternatively spliced (AS) transcripts. Here, we present an analysis of transcriptomes of six switchgrass tissue types pooled together, sequenced using Pacific Biosciences (PacBio) single-molecular long-read technology. Our analysis identified 105,419 unique transcripts covering 43,570 known genes and 8795 previously unknown genes. 45,168 are novel transcripts of known genes. A total of 60,096 AS transcripts are identified, 45,628 being novel. We have also predicted 1549 transcripts of genes involved in cell wall construction and remodeling, 639 being novel transcripts of known cell wall genes. Most of the predicted transcripts are validated against Illumina-based short reads. Specifically, 96% of the splice junction sites in all the unique transcripts are validated by at least five Illumina reads. Comparisons between genes derived from our identified transcripts and the current genome annotation revealed that among the gene set predicted by both analyses, 16,640 have different exon-intron structures. Overall, substantial amount of new information is derived from the PacBio RNA data regarding both the transcriptome and the genome of switchgrass.

09 BIOMASS FUELS↗
NASA NTRS1985

Thermal stress cycling of GaAs solar cells

A thermal cycling experiment was performed on GaAs solar cells to establish the electrical and structural integrity of these cells under the temperature conditions of a simulated low-Earth orbit of 3-year duration. Thirty single junction GaAs cells were obtained and tests were performed to establish the beginning-of-life characteristics of these cells. The tests consisted of cell I-V power output curves, from which were obtained short-circuit current, open circuit voltage, fill factor, and cell efficiency, and optical micrographs, spectral response, and ion microprobe mass analysis (IMMA) depth profiles on both the front surfaces and the front metallic contacts of the cells. Following 5,000 thermal cycles, the performance of the cells was reexamined in addition to any factors which might contribute to performance degradation. It is established that, after 5,000 thermal cycles, the cells retain their power output with no loss of structural integrity or change in physical appearance.

Janousek, B. K.↗
NASA NTRS1997

Mechanical continuity and reversible chromosome disassembly within intact genomes removed from living cells

Chromatin is thought to be structurally discontinuous because it is packaged into morphologically distinct chromosomes that appear physically isolated from one another in metaphase preparations used for cytogenetic studies. However, analysis of chromosome positioning and movement suggest that different chromosomes often behave as if they were physically connected in interphase as well as mitosis. To address this paradox directly, we used a microsurgical technique to physically remove nucleoplasm or chromosomes from living cells under isotonic conditions. Using this approach, we found that pulling a single nucleolus or chromosome out from interphase or mitotic cells resulted in sequential removal of the remaining nucleoli and chromosomes, interconnected by a continuous elastic thread. Enzymatic treatments of interphase nucleoplasm and chromosome chains held under tension revealed that mechanical continuity within the chromatin was mediated by elements sensitive to DNase or micrococcal nuclease, but not RNases, formamide at high temperature, or proteases. In contrast, mechanical coupling between mitotic chromosomes and the surrounding cytoplasm appeared to be mediated by gelsolin-sensitive microfilaments. Furthermore, when ion concentrations were raised and lowered, both the chromosomes and the interconnecting strands underwent multiple rounds of decondensation and recondensation. As a result of these dynamic structural alterations, the mitotic chains also became sensitive to disruption by restriction enzymes. Ion-induced chromosome decondensation could be blocked by treatment with DNA binding dyes, agents that reduce protein disulfide linkages within nuclear matrix, or an antibody directed against histones. Fully decondensed chromatin strands also could be induced to recondense into chromosomes with pre-existing size, shape, number, and position by adding anti-histone antibodies. Conversely, removal of histones by proteolysis or heparin treatment produced chromosome decondensation which could be reversed by addition of histone H1, but not histones H2b or H3. These data suggest that DNA, its associated protein scaffolds, and surrounding cytoskeletal networks function as a structurally-unified system. Mechanical coupling within the nucleoplasm may coordinate dynamic alterations in chromatin structure, guide chromosome movement, and ensure fidelity of mitosis.

NASA Discipline Cell Biology↗
NASA NTRS2008

Fuel Cell Thermal Management Through Conductive Cooling Plates

An analysis was performed to evaluate the concept of utilizing conductive cooling plates to remove heat from a fuel cell stack, as opposed to a conventional internal cooling loop. The potential advantages of this type of cooling system are reduced stack complexity and weight and increased reliability through the reduction of the number of internal fluid seals. The conductive cooling plates would extract heat from the stack transferring it to an external coolant loop. The analysis was performed to determine the required thickness of these plates. The analysis was based on an energy balance between the thermal energy produced within the stack and the heat removal from the cooling plates. To accomplish the energy balance, the heat flow into and along the plates to the cooling fluid was modeled. Results were generated for various numbers of cells being cooled by a single cooling plate. The results provided cooling plate thickness, mass, and operating temperature of the plates. It was determined that utilizing high-conductivity pyrolitic graphite cooling plates can provide a specific cooling capacity (W/kg) equivalent to or potentially greater than a conventional internal cooling loop system.

Colozza, Anthony J.↗
DOE OSTI2023

Commissioning of Dedicated Furnace for Nb3Sn Coatings of 2.6 GHz Single Cell Cavities

We present the results of commissioning a dedicated furnace for Nb3Sn coatings of 2.6 GHz single cell cavities. Nb3Sn is a desired coating due to its high critical temperature and smaller surface resistance compared to bulk Nb. Usage of Nb3Sn coated cavities will greatly reduce operating costs due to decreased dependance on cryo cooling. Tin is deposited by use of a tin chloride nucleation agent and tin vapor diffusion. Analysis of the resultant coating was performed using SEM/EDS to verify successful formation of Nb3Sn. Witness samples in line of sight of the source were used in order to understand the coating efficacy.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Rational Enzyme Design for Controlled Functionalization of Acetylated Xylan for Cell-Free Polymer Biosynthesis

Xylan O-acetyltransferase 1 (XOAT1) is involved in O-acetylating the backbone of hemicellulose xylan. Recent structural analysis of XOAT1 showed two unequal lobes forming a cleft that is predicted to accommodate and position xylan acceptors into proximity with the catalytic triad. Here, we used docking and molecular dynamics simulations to investigate the optimal orientation of xylan in the binding cleft of XOAT1 and identify putative key residues (Gln445 and Arg444 on Minor lobe & Asn312, Met311 and Asp403 on Major lobe) involved in substrate interactions. Site-directed mutagenesis coupled with biochemical analyses revealed the major lobe of XOAT1 is important for xylan binding. Mutation of single key residues yielded XOAT1 variants with various enzymatic efficiencies that are applicable to one-pot synthesis of xylan polymers with different degrees of O-acetylation. Taken together, our results demonstrate the effectiveness of computational modeling in guiding enzyme engineering aimed at modulating xylan and redesigning plant cell walls.

93 SC - Biological and Environmental Research (BER↗
DOE OSTI2023

Electrolyzer energy dominates separation costs in state-of-the-art CO 2 electrolyzers: Implications for single-pass CO 2 utilization

In low-temperature CO 2 electrolysis, a fundamental trade-off exists between maximizing electrolyzer performance and minimizing downstream CO 2 recovery. Here, by coupling a down-the-gas-channel electrolyzer model with a techno-economic analysis, we find that the optimal single-pass CO 2 conversion for ethylene production is typically low—on the order of 5%–10%—although larger optima are found if the H 2 faradic efficiency is very low. Similarly, strategies for eliminating carbonate crossover require more energy than downstream gas separation if they increase the cell potential by ~0.2 V; however, when CAPEX are accounted for, this “break-even” voltage increases to ~ 0.4 to 0.8 V for electricity prices varying from 6c/kWh to 1.5c/kWh. These findings are a consequence of the low energy requirements of industrial gas separation relative to electrochemical CO 2 reduction. Under most circumstances, maintaining near-optimal electrolyzer performance is more important than reducing or eliminating downstream gas separations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Spatial symmetry breaking in single-frequency CCP discharge with transverse magnetic field

An independent control of the flux and energy of ions impacting on an object immersed in a plasma is often desirable for many industrial processes such as microelectronics manufacturing. We demonstrate that a simultaneous control of these quantities is possible by a suitable choice of a static magnetic field applied parallel to the plane electrodes in a standard single frequency capacitively coupled plasma device. Our particle-in-cell simulations show a 60% reduction in the sheath width (that improves control of ion energy) and a fourfold increase in the ion flux at the electrode as a consequence of the altered ion and electron dynamics due to the ambient magnetic field. A detailed analysis of the particle dynamics is presented, and the optimized operating parameters of the device are discussed. In conclusion, the present technique offers a simple and attractive alternative to conventional dual frequency based devices that often suffer from undesirable limitations arising from frequency coupling and electromagnetic effects.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Spectra and characteristics of somatic mutations induced by ionizing radiation in hematopoietic stem cells

Spectra and frequencies of spontaneous and X-ray-induced somatic mutations were revealed with mouse long-term hematopoietic stem cells (LT-HSCs) by whole-genome sequencing of clonal cell populations propagated in vitro from single isolated LT-HSCs. SNVs and small indels were the most common types of somatic mutations, and increased up to twofold to threefold by whole-body X-irradiation. Base substitution patterns in the SNVs suggested a role of reactive oxygen species in radiation mutagenesis, and signature analysis of single base substitutions (SBS) revealed a dose-dependent increase of SBS40. Most of spontaneous small deletions were shrinkage of tandem repeats, and X-irradiation specifically induced small deletions out of tandem repeats (non-repeat deletions). Presence of microhomology sequences in non-repeat deletions suggested involvement of microhomology mediated end-joining repair mechanisms as well as nonhomologous end-joining in radiation-induced DNA damages. We also identified multisite mutations and structural variants (SV), i.e., large indels, inversions, reciprocal translocations, and complex variants. The radiation-specificity of each mutation type was evaluated from the spontaneous mutation rate and the per-Gy mutation rate estimated by linear regression, and was highest with non-repeat deletions without microhomology, followed by those with microhomology, SV except retroelement insertions, and multisite mutations; these types were thus revealed as mutational signatures of ionizing radiation. Further analysis of somatic mutations in multiple LT-HSCs indicated that large fractions of postirradiation LT-HSCs originated from single LT-HSCs that survived the irradiation and then expanded in vivo to confer marked clonality to the entire hematopoietic system, with varying clonal expansion and dynamics depending on radiation dose and fractionation.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2021

X-ray microscopy enables multiscale high-resolution 3D imaging of plant cells, tissues, and organs

Capturing complete internal anatomies of plant organs and tissues within their relevant morphological context remains a key challenge in plant science. While plant growth and development are inherently multiscale, conventional light, fluorescence, and electron microscopy platforms are typically limited to imaging of plant microstructure from small flat samples that lack a direct spatial context to, and represent only a small portion of, the relevant plant macrostructures. We demonstrate technical advances with a lab-based X-ray microscope (XRM) that bridge the imaging gap by providing multiscale high-resolution three-dimensional (3D) volumes of intact plant samples from the cell to the whole plant level. Serial imaging of a single sample is shown to provide sub-micron 3D volumes co-registered with lower magnification scans for explicit contextual reference. High-quality 3D volume data from our enhanced methods facilitate sophisticated and effective computational segmentation. Advances in sample preparation make multimodal correlative imaging workflows possible, where a single resin-embedded plant sample is scanned via XRM to generate a 3D cell-level map, and then used to identify and zoom in on sub-cellular regions of interest for high-resolution scanning electron microscopy. In total, we present the methodologies for use of XRM in the multiscale and multimodal analysis of 3D plant features using numerous economically and scientifically important plant systems.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2010

NASA Tech Briefs, April 2010

Topics covered include: Active and Passive Hybrid Sensor; Quick-Response Thermal Actuator for Use as a Heat Switch; System for Hydrogen Sensing; Method for Detecting Perlite Compaction in Large Cryogenic Tanks; Using Thin-Film Thermometers as Heaters in Thermal Control Applications; Directional Spherical Cherenkov Detector; AlGaN Ultraviolet Detectors for Dual-Band UV Detection; K-Band Traveling-Wave Tube Amplifier; Simplified Load-Following Control for a Fuel Cell System; Modified Phase-meter for a Heterodyne Laser Interferometer; Loosely Coupled GPS-Aided Inertial Navigation System for Range Safety; Sideband-Separating, Millimeter-Wave Heterodyne Receiver; Coaxial Propellant Injectors With Faceplate Annulus Control; Adaptable Diffraction Gratings With Wavefront Transformation; Optimizing a Laser Process for Making Carbon Nanotubes; Thermogravimetric Analysis of Single-Wall Carbon Nanotubes; Robotic Arm Comprising Two Bending Segments; Magnetostrictive Brake; Low-Friction, Low-Profile, High-Moment Two-Axis Joint; Foil Gas Thrust Bearings for High-Speed Turbomachinery; Miniature Multi-Axis Mechanism for Hand Controllers; Digitally Enhanced Heterodyne Interferometry; Focusing Light Beams To Improve Atomic-Vapor Optical Buffers; Landmark Detection in Orbital Images Using Salience Histograms; Efficient Bit-to-Symbol Likelihood Mappings; Capacity Maximizing Constellations; Natural-Language Parser for PBEM; Policy Process Editor for P(sup 3)BM Software; A Quality System Database; Trajectory Optimization: OTIS 4; and Computer Software Configuration Item-Specific Flight Software Image Transfer Script Generator.

Source record↗
DOE OSTI2016

Reactor Physics Analysis of Transitioning to a Thorium Fuel Cycle with Molten Salt Reactors

Commercial power reactors operating in the United States are light-water reactors (LWRs) fueled with low-enriched uranium (LEU) in a once-through fuel cycle; the important fissile isotopes are {sup 235}U, {sup 239}Pu, and {sup 241}Pu. In a thorium fuel cycle, the fertile isotope {sup 232}Th is converted into {sup 233}U, a fissile isotope that is not naturally occurring. In transitioning from the once-through fuel cycle to the thorium fuel cycle, the availability of man-made {sup 233}U presents a challenge: without it, the initial fissile material fueling the first reactors built in this transition is not the fissile isotope that the reactor is breeding. The transition requires an alternate fissile material until enough surplus {sup 233}U is available to start up additional reactors. In liquid-fueled molten salt reactors (MSRs), the fuel is dissolved into molten salt, which is continuously circulated through the core, simultaneously undergoing irradiation, chemical treatments and separations, and feeds. MSRs are an attractive technology in which the thorium fuel cycle can be deployed, as the {sup 233}U bred from {sup 232}Th is continuously being recycled back through the core. The bred fissile material is immediately available to fuel the core without processing or fuel fabrication. After start-up, only a fertile {sup 232}Th feed is necessary to sustain criticality in the MSR. But, in single-fluid MSRs, the initial fissile and fertile materials are mixed into the same molten fuel salt, complicating separations of initial and bred fissile materials. In solid-fuel systems, these materials are often separate. This analysis herein builds on previous work modeling thorium-fueled MSR start-up. It is based on unit cell representations of the graphite-moderated, 2250 MWt Oak Ridge National Laboratory (ORNL) Molten Salt Breeder Reactor (MSBR). This paper discusses the start-up of the first MSR in the transition to a thorium fuel cycle and identifies challenges and limitations of fuel cycle deployment with this reactor technology. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗