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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Closed Cycle Magnetohydrodynamic Nuclear Space Power Generation Using Helium/Xenon Working Plasma

A multimegawatt-class nuclear fission powered closed cycle magnetohydrodynamic space power plant using a helium/xenon working gas has been studied, to include a comprehensive system analysis. Total plant efficiency was expected to be 55.2 percent including pre-ionization power. The effects of compressor stage number, regenerator efficiency, and radiation cooler temperature on plant efficiency were investigated. The specific mass of the power generation plant was also examined. System specific mass was estimated to be 3 kg/kWe for a net electrical output power of 1 MWe, 2-3 kg/kWe at 2 MWe, and approx.2 kg/KWe at >3 MWe. Three phases of research and development plan were proposed: (1) Phase I-proof of principle, (2) Phase II-demonstration of power generation, and (3) Phase III-prototypical closed loop test.

Litchford, R. J.↗
NASA NTRS2017

Structure in the 3D Galaxy Distribution. III. Fourier Transforming the Universe: Phase and Power Spectra

We demonstrate the effectiveness of a relatively straightforward analysis of the complex 3D Fourier transform of galaxy coordinates derived from redshift surveys. Numerical demonstrations of this approach are carried out on a volume-limited sample of the Sloan Digital Sky Survey redshift survey. The direct unbinned transform yields a complex 3D data cube quite similar to that from the Fast Fourier Transform of finely binned galaxy positions. In both cases, deconvolution of the sampling window function yields estimates of the true transform. Simple power spectrum estimates from these transforms are roughly consistent with those using more elaborate methods. The complex Fourier transform characterizes spatial distributional properties beyond the power spectrum in a manner different from (and we argue is more easily interpreted than) the conventional multipoint hierarchy. We identify some threads of modern large-scale inference methodology that will presumably yield detections in new wider and deeper surveys.

Galaxies↗
NASA NTRS2017

Structure in the 3D Galaxy Distribution: III. Fourier Transforming the Universe: Phase and Power Spectra

We demonstrate the effectiveness of a relatively straightforward analysis of the complex 3D Fourier transform of galaxy coordinates derived from redshift surveys. Numerical demonstrations of this approach are carried out on a volume-limited sample of the Sloan Digital Sky Survey redshift survey. The direct unbinned transform yields a complex 3D data cube quite similar to that from the Fast Fourier Transform (FFT) of finely binned galaxy positions. In both cases deconvolution of the sampling window function yields estimates of the true transform. Simple power spectrum estimates from these transforms are roughly consistent with those using more elaborate methods. The complex Fourier transform characterizes spatial distributional properties beyond the power spectrum in a manner different from (and we argue is more easily interpreted than) the conventional multi-point hierarchy. We identify some threads of modern large scale inference methodology that will presumably yield detections in new wider and deeper surveys.

Galactic clusters↗
NASA NTRS2021

Nanostructure and compositional segregation of soft magnetic FeNi-based nanocomposites with multiple nanocrystalline phases

Soft magnetic metal amorphous nanocomposite alloys are produced through rapid solidification and thermal annealing yielding nanocrystals embedded within an amorphous precursor. Similar free energies in Co-rich and FeNi-based alloy systems result in multiple nanocrystalline phases being formed during devitrification. Studies of multi-phase crystallization processes have been reported for Co-rich alloys but relatively few have investigated FeNi-based systems. A detailed characterization of compositional partitioning and microstructure of an optimally annealed FeNi-based MANC (Fe70Ni30)80Nb4Si2B14 alloy is presented through complementary high-resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT). HRTEM demonstrates orientation relationships between FCC and BCC nanocrystals, suggesting heterogeneous nucleation of nanocrystals in the amorphous matrix or a cooperative mechanism of nucleation between BCC and FCC nanocrystallites. APT results show evidence for (i) the segregation of Fe and Ni between nanocrystals of different phases, (ii) B partitioning to the amorphous phase, and (iii) an Nb-enriched shell surrounding nanocrystals.

soft magnetic materials↗
DOE OSTI2018

Exploiting Knowledge of Technetium in the Subsurface to Develop Remediation Strategies – 18223

Technetium-99 (Tc) contamination remains a major environmental problem at legacy nuclear reprocessing sites, such as the Hanford Site in south-central Washington state, where the total inventory of released Tc is estimated at 700 Ci. The environmental risk associated with Tc is due to its long half-life (213,000 years) and the high mobility of the oxidized anionic pertechnetate species (Tc(VII)O4-). Thus, there is a critical need to resolve scientific and technical issues underpinning the ability to safely, cost-effectively, and efficiently remediate Tc-contaminated vadose zone sediments and groundwater. Developing enhanced attenuation strategies for released Tc that reduce contaminant migration, while mitigating risk to human health and the environment, requires characterization of any retardation processes and mass flux. The current conceptual model for Tc transport in the vadose zone assumes that Tc is predominantly present in its oxidized form as TcO4-, which is highly soluble and mobile. However, under certain conditions, Tc can become entrained in solid phases. Characterization of Tc-containing mineral phases from sediment cores extracted from various Hanford waste disposal sites were analyzed to determine Tc present in vadose zone sediments as (i) TcO4- that remains in water films associated with fine-grained sediments; (ii) Tc co-precipitated with other lanthanides in phosphate mineral phases; and (iii) Tc present as TcO2•nH2O in localized reducing zones. These results will be used to develop improved long-term Tc remediation strategies that are most likely to succeed during field application, through stimulation of conditions that enhance Tc attenuation.

Pearce, Carolyn I.↗
DOE OSTI2018

Exploiting Knowledge of Technetium in the Subsurface to Develop Remediation Strategies - 18223

Technetium-99 (Tc) contamination remains a major environmental problem at legacy nuclear reprocessing sites, such as the Hanford Site in south-central Washington State, where the total inventory of released Tc is estimated at 700 curies (Ci). The environmental risk associated with Tc is due to its long half-life (213,000 years) and the high mobility of the oxidized anionic pertechnetate species (Tc(VII)O{sub 4}{sup -}). Thus, there is a critical need to resolve scientific and technical issues underpinning the ability to safely, cost-effectively, and efficiently remediate Tc-contaminated vadose zone sediments and groundwater. Developing enhanced attenuation strategies for released Tc that reduce contaminant migration, while mitigating risk to human health and the environment, requires characterization of any retardation processes and Tc mass flux. The current conceptual model for Tc transport in the vadose zone assumes that Tc is predominantly present in its oxidized form as TcO{sub 4}{sup -}, which is highly soluble and mobile. However, under certain conditions, Tc can become entrained in solid phases. Tc-containing mineral phases from sediment cores extracted from various Hanford waste disposal sites were characterized to determine Tc present in vadose zone sediments as (i) TcO{sub 4} - that remains in water films associated with fine-grained sediments; (ii) Tc co-precipitated with other lanthanides in phosphate mineral phases; and (iii) Tc present as TcO{sub 2}.nH{sub 2}O in localized reducing zones. These results will be used to develop improved long-term Tc remediation strategies that are most likely to succeed during field application, through stimulation of conditions that enhance Tc attenuation. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Adjuvant Intensity Modulated Whole-Abdominal Radiation Therapy for High-Risk Patients With Ovarian Cancer (International Federation of Gynecology and Obstetrics Stage III): First Results of a Prospective Phase 2 Study

Purpose: To assess treatment tolerance and toxicity rates of consolidative whole-abdominal radiation therapy (WART) following cytoreductive surgery and carboplatin/paclitaxel chemotherapy in high-risk patients with advanced ovarian cancer (International Federation of Gynecology and Obstetrics stage III) using intensity modulated radiation therapy. Methods and Materials: The OVAR-IMRT-02 study is a multicenter, single-arm, phase 2 trial. Twenty patients with optimally debulked ovarian cancer (International Federation of Gynecology and Obstetrics stage III) with complete remission after chemotherapy were treated with intensity modulated WART as a consolidation therapy. A total dose of 30 Gy in 20 fractions of 1.5 Gy was applied to the entire peritoneal cavity. The primary endpoint was treatment tolerability, defined as lack of any Common Terminology Criteria for Adverse Events grade 4 toxicity within 10 weeks after start of treatment; secondary objectives were acute and chronic toxicity, quality of life, rates of therapy disruption and abortion, and progression-free and overall survival. Results: Intensity modulated WART resulted in excellent coverage of the whole peritoneal cavity, with effective sparing of all organs at risk. The primary analysis included all 20 enrolled patients, of whom 19 did not experience Common Terminology Criteria for Adverse Events grade 4 toxicity. Only 1 patient experienced acute grade 4 hematologic toxicity. Thus, the tolerability rate of intensity modulated WART was significantly higher than 70%. No gastrointestinal acute toxicities higher than grade 2 have been observed. During WART, mean global health status decreased by 18.1 points (95% confidence interval 7.1, 29.0). Six weeks after WART, global health status had already increased, with a mean score difference of 4.6 (95% confidence interval −11.1, 20.4) compared with baseline. Similar characteristics were observed for all function scale scores. Conclusion: Intensity modulated WART after aggressive surgery and carboplatin/paclitaxel chemotherapy is associated with an acceptable risk of acute toxicity and a treatment tolerability rate significantly higher than 70%. Together with our knowledge about clinical feasibility, meaning excellent coverage of the planning target volume and effective sparing of organs at risk, intensity modulated WART could offer a new therapeutic option for consolidation treatment of patients with advanced ovarian cancer.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2025

Toward extracting scattering phase shift from integrated correlation functions. III. Coupled channels

The formalism developed in the preceding papers that connects integrated correlation function of a trapped two-particle system to infinite volume scattering phase shift is further extended to coupled-channel systems in the present work. Using a trapped nonrelativistic two-channel system as an example, a new relation is derived that retains the same structure as in the single channel, and has explicit dependence on the phase shifts in both channels but not on the inelasticity. The relation is illustrated by a exactly solvable coupled-channel quantum mechanical model with contact interactions. It is further validated by path integral Monte Carlo simulation of a quasi-one-dimensional model that can admit general interaction potentials. In all cases, we found rapid convergence to the infinite volume limit as the trap size is increased, even at short times, making it potentially a good candidate to overcome signal-to-noise issues in Monte Carlo applications. Published by the American Physical Society 2025

Guo, Peng (ORCID:0000000265660881)↗
DOE OSTI2018

GaLnAsP Solar Cells Grown by Hydride Vapor Phase Epitaxy for One-Sun & Low-Concentration III-V/Si Photovoltaics

Dynamic hydride vapor phase epitaxy (D-HVPE) has recently reemerged as a low-cost alternative to metalorganic chemical vapor deposition (MOCVD) for the growth of highefficiency III-V solar cells. Quaternary GaInAsP solar cells in the bandgap range of ~1.6-1.8 eV are promising top-cell candidates for III-V/Si tandem solar cells. In this work, we report on the development of lattice-matched GaInAsP (Eg~1.66 eV) solar cells grown via low-cost HVPE at very high growth rates of ~0.7 um/min (~42 um/h). We demonstrate for the first time HVPE grown passivated GaInAsP homojunction solar cells that show substantial improvement in the short-wavelength photoresponse attributed to the incorporation of a GaInP window layer. The heterointerfaces in these multilayer devices were characterized by transmission electron microscopy. The best device achieved a certified one-sun efficiency of 18.7% under AM1.5G, demonstrating the viability of HVPE to grow multilayered structures comprising ternary and quaternary alloys. This work represents a promising step towards low-cost III-V/Si tandem photovoltaics with one-sun efficiencies exceeding 30%.

14 SOLAR ENERGY↗
DOE OSTI2017

Protein extraction into the bicontinuous microemulsion phase of a Water/SDS/pentanol/dodecane winsor-III system: Effect on nanostructure and protein conformation

Bicontinuous microemulsions (BμEs), consisting of water and oil nanodomains separated by surfactant monolayers of near-zero curvature, are potentially valuable systems for purification and delivery of biomolecules, for hosting multiphasic biochemical reactions, and as templating media for preparing nanomaterials. We formed Winsor-III systems by mixing aqueous protein and sodium dodecyl sulfate (SDS) solutions with dodecane and 1-pentanol (cosurfactant) to efficiently extract proteins into the middle (BμE) phase. Bovine serum albumin (BSA) and cytochrome c partitioned to the BμE phase at 64% and 81% efficiency, respectively, producing highly concentrated protein solutions (32 and 44 g L –1 , respectively), through release of water and oil from the BμEs. Circular dichroism spectroscopic analysis demonstrated that BSA underwent minor secondary structural changes upon incorporation into BμEs, while the secondary structure of cytochrome c and pepsin underwent major changes. Small-angle x-ray scattering (SAXS) results show that proteins promoted an increase of the interfacial fluidity and surface area per volume for the BμE surfactant monolayers, and that each protein uniquely altered self-assembly in the Winsor-III systems. Cytochrome c partitioned via electrostatic attractions between SDS and the protein’s positively-charged groups, residing near the surfactant head groups of BμE monolayers, where it decreased surfactant packing efficiency. BSA partitioned through formation of SDS-BSA complexes via hydrophobic and electrostatic attractive interactions. As the BSA-SDS ratio increased, complexes’ partitioning favored BμEs over the oil excess phase due to the increased hydrophilicity of the complexes. In conclusion, this study demonstrates the potential utility of BμEs to purify proteins and prepare nanostructured fluids possessing high protein concentration.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Six-junction III–V solar cells with 47.1% conversion efficiency under 143 Suns concentration

Single-junction flat-plate terrestrial solar cells are fundamentally limited to about 30% solar-to-electricity conversion efficiency, but multiple junctions and concentrated light make much higher efficiencies practically achievable. Until now, four-junction III–V concentrator solar cells have demonstrated the highest solar conversion efficiencies. Here, we demonstrate 47.1% solar conversion efficiency using a monolithic, series-connected, six-junction inverted metamorphic structure operated under the direct spectrum at 143 Suns concentration. Furthermore, when tuned to the global spectrum, a variation of this structure achieves a 1-Sun global efficiency of 39.2%. Nearly optimal bandgaps for six junctions were fabricated using alloys of III–V semiconductors. To develop these junctions, it was necessary to minimize threading dislocations in lattice-mismatched III–V alloys, prevent phase segregation in metastable quaternary III–V alloys and understand dopant diffusion in complex structures. Further reduction of the series resistance within this structure could realistically enable efficiencies over 50%.

14 SOLAR ENERGY↗