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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Targeted curation of the gut microbial gene content modulating human cardiovascular disease

Despite the promise of the gut microbiome to predict human health, few studies expose the molecular-scale processes underpinning such forecasts. We mined over 200,000 gut-derived genomes from cultivated and uncultivated microbial lineages to inventory the gut microorganisms and their gene content that control trimethylamine-induced cardiovascular disease. We assigned an atherosclerotic profile to the 6,341 microbial genomes that encoded metabolisms associated with heart disease, creating the Methylated Amine Gene Inventory of Catabolism database (MAGICdb). From microbiome gene expression data sets, we demonstrate that MAGICdb enhanced the recovery of disease-relevant genes and identified the most active microorganisms, unveiling future therapeutic targets. From the feces of healthy and diseased subjects, we show that MAGICdb predicted cardiovascular disease status as effectively as traditional lipid blood tests. This functional microbiome catalog is a public, exploitable resource, designed to enable a new era of microbiota-based therapeutics and diagnostics

metatranscriptomics↗
DOE OSTI2016

Antibody Binding Alters the Characteristics and Contents of Extracellular Vesicles Released by Histoplasma capsulatum

ABSTRACT Histoplasma capsulatum produces extracellular vesicles containing virulence-associated molecules capable of modulating host machinery, benefiting the pathogen. Treatment of H. capsulatum cells with monoclonal antibodies (MAbs) can change the outcome of infection in mice. We evaluated the sizes, enzymatic contents, and proteomic profiles of the vesicles released by fungal cells treated with either protective MAb 6B7 (IgG1) or nonprotective MAb 7B6 (IgG2b), both of which bind H. capsulatum heat shock protein 60 (Hsp60). Our results showed that treatment with either MAb was associated with changes in size and vesicle loading. MAb treatments reduced vesicle phosphatase and catalase activities compared to those of vesicles from untreated controls. We identified 1,125 proteins in vesicles, and 250 of these manifested differences in abundance relative to that of proteins in vesicles isolated from yeast cells exposed to Hsp60-binding MAbs, indicating that surface binding of fungal cells by MAbs modified protein loading in the vesicles. The abundance of upregulated proteins in vesicles upon MAb 7B6 treatment was 44.8% of the protein quantities in vesicles from fungal cells treated with MAb 6B7. Analysis of orthologous proteins previously identified in vesicles from other fungi showed that different ascomycete fungi have similar proteins in their extracellular milieu, many of which are associated with virulence. Our results demonstrate that antibody binding can modulate fungal cell responses, resulting in differential loading of vesicles, which could alter fungal cell susceptibility to host defenses. This finding provides additional evidence that antibody binding modulates microbial physiology and suggests a new function for specific immunoglobulins through alterations of fungal secretion. IMPORTANCE Diverse fungal species release extracellular vesicles, indicating that this is a common pathway for the delivery of molecules to the extracellular space. However, there has been no study reporting the impact of antibody binding to the fungal cell on extracellular vesicle release. In the present work, we observed that treatment of H. capsulatum cells with Hsp60-binding MAbs significantly changed the size and cargo of extracellular vesicles, as well as the enzymatic activity of certain virulence factors, such as laccase and phosphatase. Furthermore, this finding demonstrates that antibody binding can directly impact protein loading in vesicles and fungal metabolism. Hence, this work presents a new role for antibodies in the modification of fungal physiology.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2011

Structural and electrical properties of metamorphic nanoheterostructures with a high InAs content (37-100%) grown on GaAs and InP substrates

A complex study of the structural and electrical properties of nanoheterostructures containing a metamorphic barrier with a high InAs content (37-100%) in the active region have been performed by the Van der Pauw and X-ray diffraction methods. All peaks observed in the rocking curves for the samples studied (throughout the entire structure) have been revealed and identified. It is shown that, having properly chosen the design of the metamorphic buffer and the compositional gradient in it, one can obtain mobilities and concentrations of the 2D electron gas in the In{sub x}Ga{sub 1-x}As quantum well in the heterostructures formed on GaAs substrates that are comparable with the corresponding values for the nanoheterostructures grown on InP substrates. It is established that the mobility and concentration of 2D electron gas depend both on the metamorphic barrier design and on the structural quality of heterostructure as a whole.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

A setup for active neutron analysis of the fissile material content in fuel assemblies of nuclear reactors

An active neutron method for measuring the residual mass of {sup 235}U in spent fuel assemblies (FAs) of the IRT MEPhI research reactor is presented. The special measuring stand design and uniform irradiation of the fuel with neutrons along the entire length of the active part of the FA provide high accuracy of determination of the residual {sup 235}U content. AmLi neutron sources yield a higher effect/background ratio than other types of sources and do not induce the fission of {sup 238}U. The proposed method of transfer of the isotope source in accordance with a given algorithm may be used in experiments where the studied object needs to be irradiated with a uniform fluence.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Measurements and monitoring of the hydrogen and deuterium contents in the plasma of the L-2M stellarator

The program of experiments on ITER includes a sequential change of the plasma isotopic composition from pure hydrogen plasma in the initial stage of research to deuterium and, then, deuterium-tritium plasma with a gradual increase in the tritium content. In this context, the influence of the plasma isotopic composition on the processes of plasma heating and confinement are being actively studied on the existing tokamaks and stellarators. The plasma isotopic composition also depends on the composition of the gas desorbed from the vacuum chamber wall in the course of recycling. Therefore, the rate of change of the plasma isotopic composition after altering the injected gas also depends on the rate of change of the isotopic composition of the gas absorbed in the wall. These effects were studied in the experiments carried out on the L-2M stellarator in which the working gas was changed from hydrogen to deuterium. Spectral measurements of the intensity ratio between the H{sub {alpha}} and D{sub {alpha}} lines made it possible to monitor the isotopic composition of the plasma in the course of cleaning of the chamber wall from earlier absorbed hydrogen and its replacement with deuterium. After returning to hydrogen, the rate of cleaning of the wall from deuterium was also determined. The results of these experiments show that the plasma isotopic composition varies exponentially with the number N of shots after transition to another isotope, {approx}exp(-N/47). Hence, the isotopic composition can be changed almost completely over 2 to 3 working days. This allows one to study the influence of the plasma isotopic composition on plasma confinement during the same experimental session.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Interrelation of the construction of the metamorphic InAlAs/InGaAs nanoheterostructures with the InAs content in the active layer of 76-100% with their surface morphology and electrical properties

The influence of the construction of a metamorphic buffer on the surface morphology and electrical properties of InAlAs/InGaAs/InAlAs nanoheterostructures with InAs content in the active layer from 76 to 100% with the use of the GaAs and InP substrates is studied. It is shown that such parameters as the electron mobility and the concentration, as well as the root-mean-square surface roughness, substantially depend on the construction of the metamorphic buffer. It is established experimentally that these parameters largely depend on the maximal local gradient of the lattice constant of the metamorphic buffer in the growth direction of the layers rather than on its average value. It is shown that, with selection of the construction of the metamorphic buffer, it is possible to form nanostructured surfaces with a large-periodic profile.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Effect of the Cu content and ZnS treatment on the characteristics of synthesized ZnS:(Cu, Cl) electroluminescent phosphors

The effect of the pretreatment of ZnS via different methods on the characteristics of synthesized ZnS:(Cu, Cl) electroluminescent phosphors with varying concentrations of the activator dopant (Cu) is studied. As a result of the pretreatment of ZnS with accelerated electrons and in nitrogen plasma, an increase in the emission brightness of the synthesized phosphor and a shift of the luminescence spectrum to longer wavelengths are observed. These effects are attributed with increase in content of the activator in the phosphor matrix because of the formation of extra defects in the ZnS structure during treatment. In the case of shockwave treatment of ZnS, the generation of defects is not compensated by heat treatment during synthesis of the phosphor, and a positive enhanced-brightness effect is not attained.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Optical properties of silicon with a high content of boron

After exposure of silicon with a high content of boron and oxygen to light with the spectrum close to that of solar radiation and with the intensity 70-80 mW cm{sup -2}, a new defect corresponding to the absorption band observed at liquid-helium temperature at the frequency 1026.7 cm{sup -1} is detected in the material. It is shown that the components of the defect are boron and oxygen atoms. The defect is formed at a considerable concentration of free charge carriers induced by exposure of the sample to light or by heat treatments at a low current flow through the sample. It is thought that the defect can be formed due to the direct interaction between the components as well as via the precursors of the stable form of the defect. It is shown that doping of silicon with germanium reduces the efficiency of the formation of the defect corresponding to the detected absorption band.

36 MATERIALS SCIENCE↗
DOE OSTI2015

On the shift of the electroluminescence spectra of In{sub x}Ga{sub 1−x}N/GaN structures with various indium contents and various substrate materials caused by the stark effect and mechanical stresses

The shift between the maxima of the electroluminescence spectra of In{sub x}Ga{sub 1−x}N/GaN structures is measured at forward and reverse bias depending on the indium content x in the quantum well and on the substrate material (SiC, AuSn/Si, and Al{sub 2}O{sub 3}). It is established that this shift increases as the indium concentration in the In{sub x}Ga{sub 1−x}N layer and mechanical stresses from the substrate increase.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Photoluminescence of heterostructures containing an In{sub x}Ga{sub 1–x}As quantum well with a high in content at different excitation powers

The results of studies of the photoluminescence spectra of heterostructures containing an In{sub x}Ga{sub 1–x}As quantum well with a high In content x at different laser-radiation powers are reported. It is found that, as the radiation power density is increased, the luminescence spectrum of In{sub 0.70}Al{sub 0.30}As/In{sub 0.76}Ga{sub 0.24}As quantum-well heterostructures exhibits a decrease in the half-width and a shift of the peak to higher energies. It is shown that, for Al{sub 0.27}Ga{sub 0.73}As/In{sub 0.20}Ga{sub 0.80}As quantum-well heterostructures, no shift of the peak and no change in the shape of the spectrum is observed. It is established that the integrated photoluminescence intensity is related to the laser-radiation power density by a power law with the exponent α ≈ 1.3 for heterostructures with x ≈ 0.76, suggesting the predominantly excitonic character of the radiative recombination of charge carriers.

36 MATERIALS SCIENCE↗
DOE OSTI2019

The Optoelectronic Two-Wave Method for Remote Monitoring of the Content of Methane in Atmosphere

Abstracts: The optoelectronic two-wave method has been developed and a block scheme of the corresponding optoelectronic device has been proposed for remote monitoring of the content of methane in atmosphere. The optoelectronic device employs light-emitting diodes (LEDs) based on GaAlAsSb/GaInAsSb/GaAlAsSb (3.12 μm) and GaAlAsSb/GaInAsSb/GaAlAsSb (3.39 μm) structures as the sources of reference and probing radiation, respectively.

42 ENGINEERING↗
DOE OSTI2020

Direct measurement of the muonic content of extensive air showers between 2 $\times$ 10 17 and 2 $\times$ 10 18 eV at the Pierre Auger Observatory

The hybrid design of the Pierre Auger Observatory allows for the measurement of the properties of extensive air showers initiated by ultra-high energy cosmic rays with unprecedented precision. By using an array of prototype underground muon detectors, we have performed the first direct measurement, by the Auger Collaboration, of the muon content of air showers between 2 $\times$ 10 17 and 2 $\times$ 10 18 eV. We have studied the energy evolution of the attenuation-corrected muon density, and compared it to predictions from air shower simulations. The observed densities are found to be larger than those predicted by models. We quantify this discrepancy by combining the measurements from the muon detector with those from the Auger fluorescence detector at 10 17.5 eV and 10 18 eV. We find that, for the models to explain the data, an increase in the muon density of 38% $±$4%(12%) $±^{21\%}_{18\%}$ for EPOS-LHC, and of 50%(53%) $±$4%(13%) $±^{23\%}_{20\%}$ for QGSJETII-04, is respectively needed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Determining Water Content and Distribution in PEMFCs to Predict Aging While in Storage

Proton membrane exchange fuel cells (PEMFCs) have the potential to be long term backup power sources with a startup time on the order of seconds. Water management is the key issue in being able to successfully store PEMFCs for extended periods of time. In this work custom made PEMFCs were humidified at various relative humidities (%RH) and subsequently stored for different lengths of time. The fuel cell’s water content was then imaged at the National Institute of Standards and Technology (NIST) neutron imaging facility. In conclusion, the cells’ startup performances were measured simulating quick startup conditions to define the effect of different water distributions.

25 ENERGY STORAGE↗
DOE OSTI2022

High-Platinum-Content Catalysts on Atomically Dispersed and Nitrogen Coordinated Single Manganese Site Carbons for Heavy-Duty Fuel Cells

Fuel cells for heavy-duty vehicles (HDVs) have attracted considerable attention because of their unique scalability, better fuel economy, the less demand for hydrogen refilling infrastructure. However, the potential application requires more stringent fuel cell durability up to 25,000 h. Membrane electrode assemblies (MEAs) made from platinum group metal (PGM) catalyst with relatively high loading 0.3 mgPt cm –2 play a crucial role in ensuring high-power and long-term durability. Integrating fine PGM nanoparticles and robust carbon support with strengthened interactions is critical for improving MEA performance and durability. Herein, a unique atomically dispersed and nitrogen coordinated single Mn site-rich carbon (M–N–C) support was developed for high content (40 wt%) platinum catalysts for the oxygen reduction reaction (ORR) cathode with reduced thickness. Compared with two controls studied in this work (e.g., a porous graphitic carbon-supported Pt and a commercial TKK Pt/C catalysts), the Pt (40 wt%)/Mn–N–C catalyst exhibited much enhanced catalytic activity and stability for the ORR in both aqueous acidic electrolyte and polymer electrolyte-based MEA. Here, we carefully elucidated the—role of the Mn–N–C support in promoting Pt catalyst concerning its high surface area, partially graphitic structure, and nitrogen dopants, providing better Pt nanoparticle dispersion, and strengthened interactions between Pt and carbon. Consequently, the MEA from the Pt (40 wt%)/Mn–N–C catalyst generated a 1.61 A cm –2 at 0.7 V based on HDV conditions (0.2 mgPt cm –2 and 250 kPa air). More importantly, the MEA is highly durable and can retain 1.31 A cm –2 at 0.7 V after 30,000 voltage cycles (~19% loss), surpassing the commercial Pt/C catalyst (loss of ~56%). Therefore, the Mn–N–C carbon-supported Pt catalyst holds a great promise to meet the challenging DOE target (1.07 A cm –2 at 0.7 V after 150,000 cycles) for HDVs.

25 ENERGY STORAGE↗
DOE OSTI2022

Perspective—Potential Benefit of Li-Rich Cathode Materials: Reduction of Co and Ni Content Rather than Achievement of Ultra-High Capacities

In the conventional cycling protocol for lithium and manganese rich NMC layered oxides (LMRNMC), the upper cutoff voltage V cut is extended to ~ 4.8, to achieve capacities of similar to 250 mAh g -1 . With this mode of operation, structural rearrangements result in voltage fade upon cycling. Herein, a strategy is proposed to avoid these structural rearrangements based on (a) restricting V cut to values < ~ 4.6 to shut down the bulk instabilities, and (b) application of a (preferably) semi-coherent coating that protects the surface oxygen. The potential benefit of this strategy would be to minimize Co and Ni content, compared to Ni-rich NMC.

25 ENERGY STORAGE↗
DOE OSTI2016

Characterization of Electronic and Ionic Transport in Li 1- x Ni 0.33 Mn 0.33 Co 0.33 O 2 (NMC 333 ) and Li 1- x Ni 0.50 Mn 0.20 Co 0.30 O 2 (NMC 523 ) as a Function of Li Content

Despite the extensive commercial use of Li 1-x Ni 1-y-z Mn z Co y O 2 (NMC) as the positive electrode in Li-ion batteries, and its long research history, its fundamental transport properties are poorly understood. These properties are crucial for designing high energy density and high power Li-ion batteries. Here, the transport properties of NMC 333 and NMC 523 are investigated using impedance spectroscopy and DC polarization and depolarization techniques. The electronic conductivity is found to increase with decreasing Li-content (increasing state-of-charge) from ~10 –7 Scm –1 to ~10 –2 Scm –1 over Li concentrations x = 0.00 to 0.75, corresponding to an upper charge voltage of 4.8 V with respect to Li/Li + . The lithium ion diffusivity is at least one order of magnitude lower, and decreases with increasing x to at x = ~0.5. As a result, the ionic conductivity and diffusivity obtained from the two measurements techniques (EIS and DC) are in good agreement, and chemical diffusion is limited by lithium transport over a wide state-of-charge range.

25 ENERGY STORAGE↗
DOE OSTI2017

Mixed polyanion glass cathodes: Effect of polyanion content

Mixed polyanion glass cathodes in lithium-ion batteries have very high capacities (200-500 mAh/g), but currently these materials have fundamental problems with 1 st -cycle irreversible loss, cycling efficiency, and capacity fade. It is well established that polyanion substitutions into glasses can dramatically affect their physical properties, but the effect of polyanion content on the electrochemical performance has not been previously established. The proper amount of lithium and borate substitution in copper phosphate/vanadate glasses was shown to nearly eliminate 1 st -cycle irreversible loss and improve cycling efficiency. As a result, Raman and IR spectroscopy were used to identify polyanions that correlated with electrochemical performance changes.

25 ENERGY STORAGE↗
DOE OSTI2014

Thermal Analysis of ZPPR High Pu Content Stored Fuel

The Zero Power Physics Reactor (ZPPR) operated from April 18, 1969, until 1990. ZPPR operated at low power for testing nuclear reactor designs. This paper examines the temperature of Pu content ZPPR fuel while it is in storage. Heat is generated in the fuel due to Pu and Am decay and is a concern for possible cladding damage. Damage to the cladding could lead to fuel hydriding and oxidizing. A series of computer simulations were made to determine the range of temperatures potentially occuring in the ZPPR fuel. The maximum calculated fuel temperature is 292°C (558°F). Conservative assumptions in the model intentionally overestimate temperatures. The stored fuel temperatures are dependent on the distribution of fuel in the surrounding storage compartments, the heat generation rate of the fuel, and the orientation of fuel. Direct fuel temperatures could not be measured but storage bin doors, storage sleeve doors, and storage canister temperatures were measured. Comparison of these three temperatures to the calculations indicates that the temperatures calculated with conservative assumptions are, as expected, higher than the actual temperatures. The maximum calculated fuel temperature with the most conservative assumptions is significantly below the fuel failure criterion of 600°C (1,112°F).

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗