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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 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

In situ measurement of low-Z material coating thickness on high Z substrate for tokamaks

Rutherford backscattering of energetic particles can be used to determine the thickness of a coating of a low-Z material over a heavier substrate. Simulations indicate that 5 MeV alpha particles from an {sup 241}Am source can be used to measure the thickness of a Li coating on Mo tiles between 0.5 and 15 μm thick. Using a 0.1 mCi source, a thickness measurement can be accomplished in 2 h of counting. This technique could be used to measure any thin, low-Z material coating (up to 1 mg/cm{sup 2} thick) on a high-Z substrate, such as Be on W, B on Mo, or Li on Mo. By inserting a source and detector on a moveable probe, this technique could be used to provide an in situ measurement of the thickness of Li coating on NSTX-U Mo tiles. A test stand with an alpha source and an annular solid-state detector was used to investigate the measurable range of low-Z material thicknesses on Mo tiles.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

DETECTION OF POWERFUL MID-IR H{sub 2} EMISSION IN THE BRIDGE BETWEEN THE TAFFY GALAXIES

We report the detection of strong, resolved emission from warm H{sub 2} in the Taffy galaxies and bridge. Relative to the continuum and faint polyclic aromatic hydrocarbon (PAH) emission, the H{sub 2} emission is the strongest in the connecting bridge, approaching L(H{sub 2})/L(PAH 8 {mu}m) = 0.1 between the two galaxies, where the purely rotational lines of H{sub 2} dominate the mid-infrared spectrum in a way very reminiscent of the group-wide shock in the interacting group Stephan's Quintet (SQ). The surface brightness in the 0-0 S(0) and S(1) H{sub 2} lines in the bridge is more than twice that observed at the center of the SQ shock. We observe a warm H{sub 2} mass of 4.2 Multiplication-Sign 10{sup 8} M{sub Sun} in the bridge, but taking into account the unobserved bridge area, the total warm mass is likely to be twice this value. We use excitation diagrams to characterize the warm molecular gas, finding an average surface mass of {approx}5 Multiplication-Sign 10{sup 6} M{sub Sun} kpc{sup -2} and typical excitation temperatures of 150-175 K. H{sub 2} emission is also seen in the galaxy disks, although there the emission is more consistent with normal star-forming galaxies. We investigate several possible heating mechanisms for the bridge gas but favor the conversion of kinetic energy from the head-on collision via turbulence and shocks as the main heating source. Since the cooling time for the warm H{sub 2} is short ({approx}5000 yr), shocks must be permeating the molecular gas in the bridge region in order to continue heating the H{sub 2}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

A New Sample of Gamma-Ray Emitting Jetted Active Galactic Nuclei—Preliminary Results

We are compiling a new list of gamma-ray jetted active galactic nuclei (AGN), starting from the fourth catalog of point sources of the Fermi Large Area Telescope (LAT). Our aim is to prepare a list of jetted AGN with known redshifts and classifications to be used to calibrate jet power. We searched in the available literature for all the published optical spectra and multiwavelength studies useful to characterize the sources. We found new, missed, or even forgotten information leading to a substantial change in the redshift values and classification of many sources. We present here the preliminary results of this analysis and some statistics based on the gamma-ray sources with right ascension within the interval 0 h --12 h (J2000). Although flat-spectrum radio quasars and BL Lac objects are still the dominant populations, there is a significant increase in the number of other objects, such as misaligned AGN, narrow-line Seyfert 1 galaxies, and Seyfert galaxies. We also introduced two new classes of objects: changing-look AGN and ambiguous sources. About one third of the sources remain unclassified.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Microwave Annealing for Fast and Effective Hydrogen Activation in Polycrystalline Silicon Passivating Contacts

Hydrogenation is a crucial step in the fabrication of high-efficiency silicon solar cells. In this study, the effectiveness of hydrogen activation is demonstrated via microwave annealing of hydrogen-rich dielectrics coated on poly-Si passivating contacts. This method is compared with conventional hydrogenation techniques, such as annealing in N2 in the presence of a hydrogen-rich source (such as hydrogenated aluminum oxide (AlOx:H), hydrogenated silicon nitride (SiNy:H), or a AlOx:H/SiNy:H stack). Key improvements observed include a reduction in J0 from 30 to <5 fA cm-2, an increase in iVoc from 690 to >730 mV, and an enhancement in effective lifetime (teff) from 0.6 to ~3.5 milliseconds on phosphorus-doped poly-Si/SiO2 passivating contact samples. With a very short annealing time of ~1-2 min, the samples passivated by AlOx:H, SiNy:H, or the stack show similar performance to samples subjected to 30 min of nitrogen annealing. Photoluminescence (PL) spectra corroborate the findings regarding the hydrogenation of the poly-Si layer and the c-Si substrate, with an increase in PL intensity after microwave annealing. Ultimately, this work suggests that microwave annealing could be a promising addition, offering flexibility to traditional firing hydrogenation processes.

hydrogenation↗
DOE OSTI2025

Feedstock-efficient conversion through hydrogen and formate-driven metabolism in Escherichia coli

Product yields for biomanufacturing processes are often constrained by the tight coupling of cellular energy generation and carbon metabolism in sugar-based fermentation systems. To overcome this limitation, we engineered Escherichia coli to utilize hydrogen gas (H 2 ) and formate (HCOO - ) as alternative sources of energy and reducing equivalents, thereby decoupling energy generation from carbon metabolism. This approach enabled precise suppression of decarboxylative oxidation during acetate growth, with 86.6 ± 1.6 % of electrons from hydrogen gas (via soluble hydrogenase from Cupriavidus necator H16) and 98.4 ± 3.6 % of electrons from formate (via formate dehydrogenase from Pseudomonas sp. 101) offsetting acetate oxidation. Hydrogen gas supplementation led to a titratable and stoichiometric reduction in CO 2 evolution in acetate-fed cultures. Metabolomic analysis suggests that this metabolic decoupling redirects carbon flux through the glyoxylate shunt, partially bypassing two decarboxylative steps in the TCA cycle. Here, we demonstrated the utility of this strategy by applying it to mevalonate biosynthesis, where formate supplementation during glucose fermentation increased titers by 57.6 % in our best-performing strain. Flux balance analysis further estimated that 99.0 ± 2.8 % of electrons from formate were used to enhance mevalonate production. These findings highlight a broadly applicable strategy for enhancing biomanufacturing efficiency by leveraging external reducing power to optimize feedstock and energy use.

Biomanufacturing↗
DOE OSTI2018

Release of Electron Donors during Thermal Treatment of Soils

Thermal treatment of soil and groundwater may provide an in situ source of soluble organic compounds and hydrogen (H 2 ) that could stimulate microbial reductive dechlorination (MRD) at sites impacted by chlorinated solvents. The objectives of this study were to identify and quantify the release of electron donors and fermentable precursors during soil heating and to estimate availability of these compounds following thermal treatment. Fourteen solid materials containing <0.01 to 63.81 wt % organic carbon (OC) were incubated at 30, 60, or 90 °C for up to 180 d, leading to the release of direct electron donors (i.e., H 2 and acetate) and fermentable volatile fatty acids (VFAs). Total VFA release ranged from 5 ± 0 × 10 –9 carbon per gram solid (mol C/gs) during 30 °C incubation of quartz sand to 820 ± 50 × 10 –6 mol C/gs during 90 °C incubation of humic acid, and was positively impacted by incubation time, temperature, and solid-phase OC content. H 2 gas was detected at a maximum of 180 ± 50 × 10 –9 mol H 2 /g s , accounting for less than 0.3% of reducing equivalents associated with VFAs released under the same conditions. These findings will allow for more reliable prediction of substrate release during thermal treatment, supporting the implementation of coupled thermal and biological remediation strategies.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Low Temperature Chlorine-Initiated Oxidation of Small-Chain Methyl Esters: Quantification of Chain-Terminating HO 2 -Elimination Channels

In this paper, Cl-initiated oxidation reactions of three small-chain methyl esters, methyl propanoate (CH 3 CH 2 COOCH 3 ; MP), methyl butanoate (CH 3 CH 2 CH 2 COOCH 3 ; MB), and methyl valerate (CH 3 CH 2 CH 2 CH 2 COOCH 3 ; MV), are studied at 1 or 8 Torr and 550 and 650 K. Products are monitored as a function of mass, time, and photoionization energy using multiplexed photoionization mass spectrometry coupled to tunable synchrotron photoionization radiation. Pulsed photolysis of molecular chlorine is the source of Cl radicals, which remove an H atom from the ester, forming a free radical. In each case, after addition of O 2 to the initial radicals, chain-terminating HO 2 -elimination reactions are observed to be important. Branching ratios among competing HO 2 -elimination channels are determined via absolute photoionization spectra of the unsaturated methyl ester coproducts. At 550 K, HO 2 -elimination is observed to be selective, resulting in nearly exclusive production of the conjugated methyl ester coproducts, methyl propenoate, methyl-2-butenoate, and methyl-2-pentenoate, respectively. However, in MV, upon raising the temperature to 650 K, other HO 2 -elimination pathways are observed that yield methyl-3-pentenoate and methyl-4-pentenoate. In each methyl ester oxidation reaction, a peak is observed at a mass consistent with cyclic ether formation, indicating chain-propagating OH loss/ring formation pathways via QOOH intermediates. Evidence is observed for the participation of resonance-stabilized QOOH in the most prominent cyclic ether pathways. Finally, stationary point energies for HO 2 -elimination pathways and select cyclic ether formation channels are calculated at the CBS-QB3 level of theory and assist in the assignment of reaction pathways and final products.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Mechanism of the Delithiation/Lithiation Process in LiFe 0.4 Mn 0.6 PO 4 : in Situ and ex Situ Investigations on Long-Range and Local Structures

LiFe 0.4 Mn 0.6 PO 4 olivine was prepared by a sol–gel route, using citric acid as a chelating agent and NH 4 H 2 PO 4 as a phosphorus source. Sucrose was used as the source for the carbon-coating of the particles. The correlation between the physicochemical and the electrochemical properties of this positive electrode material was explored. The electrochemical tests showed an initial discharge capacity of 121 mAh/g at a C/20 rate with a good reversibility of the lithiation/delithiation reactions. In situ XRD on LiFe 0.4 Mn 0.6 PO 4 reveals the occurrence of new phases upon cycling, which disappeared again at the end of discharge. The single phase observed after one complete cycle is identical to the pristine one. In situ XAS spectroscopy in combination with 57 Fe Mössbauer and 7 Li NMR spectroscopy were used to investigate the changes in the local structure and the oxidation states of the transition metals and thus to complete the overall characterization of the lithiation/delithiation mechanism. All findings reveal a high reversibility of the reactions in this electrode material.

36 MATERIALS SCIENCE↗
DOE OSTI2010

INFRARED PERIOD-LUMINOSITY RELATIONS OF EVOLVED VARIABLE STARS IN THE LARGE MAGELLANIC CLOUD

We combine variability information from the MAssive Compact Halo Objects survey of the Large Magellanic Cloud with infrared photometry from the Spitzer Space Telescope Surveying the Agents of a Galaxy's Evolution survey to create a data set of {approx}30,000 variable red sources. We photometrically classify these sources as being on the first ascent of the red giant branch, or as being in one of three stages along the asymptotic giant branch (AGB): oxygen-rich, carbon-rich, or highly reddened with indeterminate chemistry ('extreme' AGB candidates). We present linear period-luminosity (P-L) relationships for these sources using eight separate infrared bands (J, H, K{sub s}, 3.6, 4.5, 5.8, 8.0, and 24 {mu}m) as proxies for the luminosity. We find that the wavelength dependence of the slope of the P-L relationship is different for different photometrically determined classes of AGB stars. Stars photometrically classified as O-rich show the least variation of slope with wavelength, while dust enshrouded extreme AGB stars show a pronounced trend toward steeper slopes with increasing wavelength. We find that O-rich AGB stars pulsating in the fundamental mode obey a period-magnitude relation with a slope of -3.41 {+-} 0.04 when magnitude is measured in the 3.6 {mu}m band, in contrast to C-rich AGB stars, which obey a relation of slope -3.77 {+-} 0.05.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

CONSTRAINTS ON THE ASSEMBLY AND DYNAMICS OF GALAXIES. II. PROPERTIES OF KILOPARSEC-SCALE CLUMPS IN REST-FRAME OPTICAL EMISSION OF z {approx} 2 STAR-FORMING GALAXIES

We study the properties of luminous stellar 'clumps' identified in deep, high-resolution Hubble Space Telescope NIC2/F160W imaging at 1.6 {mu}m of six z {approx} 2 star-forming galaxies with existing near-infrared integral field spectroscopy from SINFONI at the Very Large Telescope. Individual clumps contribute {approx}0.5%-15% of the galaxy-integrated rest-frame {approx}5000 A emission, with median of {approx}2%; the total contribution of clump light ranges from 10% to 25%. The median intrinsic clump size and stellar mass are {approx}1 kpc and {approx}10{sup 9} M{sub sun}, in the ranges for clumps identified in rest-UV or line emission in other studies. The clump sizes and masses in the subset of disks are broadly consistent with expectations for clump formation through gravitational instabilities in gas-rich, turbulent disks given the host galaxies' global properties. By combining the NIC2 data with Advanced Camera for Surveys (ACS)/F814W imaging available for one source, and adaptive-optics-assisted SINFONI H{alpha} data for another, we infer modest color, M/L, and stellar age variations within each galaxy. In these two objects, sets of clumps identified at different wavelengths do not fully overlap; NIC2-identified clumps tend to be redder/older than ACS- or H{alpha}-identified clumps without rest-frame optical counterparts. There is evidence for a systematic trend of older ages at smaller galactocentric radii among the clumps, consistent with scenarios where inward migration of clumps transports material toward the central regions. From constraints on a bulge-like component at radii {approx}< 1-3 kpc, none of the five disks in our sample appears to contain a compact massive stellar core, and we do not discern a trend of bulge stellar mass fraction with stellar age of the galaxy. Further observations are necessary to probe the buildup of stellar bulges and the role of clumps in this process.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

COMPUTING INTRINSIC LY{alpha} FLUXES OF F5 V TO M5 V STARS

The Ly{alpha} emission line dominates the far-ultraviolet spectra of late-type stars and is a major source for photodissociation of important molecules including H{sub 2}O, CH{sub 4}, and CO{sub 2} in exoplanet atmospheres. The incident flux in this line illuminating an exoplanet's atmosphere cannot be measured directly as neutral hydrogen in the interstellar medium (ISM) attenuates most of the flux reaching the Earth. Reconstruction of the intrinsic Ly{alpha} line has been accomplished for a limited number of nearby stars, but is not feasible for distant or faint host stars. We identify correlations connecting the intrinsic Ly{alpha} flux with the flux in other emission lines formed in the stellar chromosphere, and find that these correlations depend only gradually on the flux in the other lines. These correlations, which are based on Hubble Space Telescope spectra, reconstructed Ly{alpha} line fluxes, and irradiance spectra of the quiet and active Sun, are required for photochemical models of exoplanet atmospheres when intrinsic Ly{alpha} fluxes are not available. We find a tight correlation of the intrinsic Ly{alpha} flux with stellar X-ray flux for F5 V to K5 V stars, but much larger dispersion for M stars. We also show that knowledge of the stellar effective temperature and rotation rate can provide reasonably accurate estimates of the Ly{alpha} flux for G and K stars, and less accurate estimates for cooler stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

SOLAR RADIATION PRESSURE AND LOCAL INTERSTELLAR MEDIUM FLOW PARAMETERS FROM INTERSTELLAR BOUNDARY EXPLORER LOW ENERGY HYDROGEN MEASUREMENTS

Neutral hydrogen atoms that travel into the heliosphere from the local interstellar medium (LISM) experience strong effects due to charge exchange and radiation pressure from resonant absorption and re-emission of Lyα. The radiation pressure roughly compensates for the solar gravity. As a result, interstellar hydrogen atoms move along trajectories that are quite different than those of heavier interstellar species such as helium and oxygen, which experience relatively weak radiation pressure. Charge exchange leads to the loss of primary neutrals from the LISM and the addition of new secondary neutrals from the heliosheath. IBEX observations show clear effects of radiation pressure in a large longitudinal shift in the peak of interstellar hydrogen compared with that of interstellar helium. Here, we compare results from the Lee et al. interstellar neutral model with IBEX-Lo hydrogen observations to describe the distribution of hydrogen near 1 AU and provide new estimates of the solar radiation pressure. We find over the period analyzed from 2009 to 2011 that radiation pressure divided by the gravitational force (μ) has increased slightly from μ = 0.94 ± 0.04 in 2009 to μ = 1.01 ± 0.05 in 2011. We have also derived the speed, temperature, source longitude, and latitude of the neutral H atoms and find that these parameters are roughly consistent with those of interstellar He, particularly when considering the filtration effects that act on H in the outer heliosheath. Thus, our analysis shows that over the period from 2009 to 2011, we observe signatures of neutral H consistent with the primary distribution of atoms from the LISM and a radiation pressure that increases in the early rise of solar activity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

THE PROTOCLUSTER G18.67+0.03: A TEST CASE FOR CLASS I CH{sub 3}OH MASERS AS EVOLUTIONARY INDICATORS FOR MASSIVE STAR FORMATION

We present high angular resolution Submillimeter Array and Karl G. Jansky Very Large Array observations of the massive protocluster G18.67+0.03. Previously targeted in maser surveys of GLIMPSE Extended Green Objects (EGOs), this cluster contains three Class I CH{sub 3}OH maser sources, providing a unique opportunity to test the proposed role of Class I masers as evolutionary indicators for massive star formation. The millimeter observations reveal bipolar molecular outflows, traced by {sup 13}CO(2-1) emission, associated with all three Class I maser sources. Two of these sources (including the EGO) are also associated with 6.7 GHz Class II CH{sub 3}OH masers; the Class II masers are coincident with millimeter continuum cores that exhibit hot core line emission and drive active outflows, as indicated by the detection of SiO(5-4). In these cases, the Class I masers are coincident with outflow lobes, and appear as clear cases of excitation by active outflows. In contrast, the third Class I source is associated with an ultracompact (UC) H II region, and not with Class II masers. The lack of SiO emission suggests that the {sup 13}CO outflow is a relic, consistent with its longer dynamical timescale. Our data show that massive young stellar objects (MYSOs) associated only with Class I masers are not necessarily young and provide the first unambiguous evidence that Class I masers may be excited by both young (hot core) and older (UC H II) MYSOs within the same protocluster.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Protocluster discovery in tomographic Ly α forest flux maps

Here, we present a new method of finding protoclusters using tomographic maps of Ly α forest flux. We review our method of creating tomographic flux maps and discuss our new highperformance implementation, which makes large reconstructions computationally feasible. Using a large N-body simulation, we illustrate how protoclusters create large-scale flux decrements, roughly 10 h -1 Mpc across, and how we can use this signal to find them in flux maps. We test the performance of our protocluster finding method by running it on the ideal, noiseless map and tomographic reconstructions from mock surveys, and comparing to the halo catalogue. Using the noiseless map, we find protocluster candidates with about 90 per cent purity, and recover about 75 per cent of the protoclusters that form massive clusters (>3 × 10 14 h -1 M ⊙ ). We construct mock surveys similar to the ongoing COSMOS Lyman-Alpha Mapping And Tomography Observations survey. While the existing data have an average sightline separation of 2.3 h -1 Mpc, we test separations of 2-6 h -1 Mpc to see what can be tolerated for our application. Using reconstructed maps from small separation mock surveys, the protocluster candidate purity and completeness are very close to what was found in the noiseless case. As the sightline separation increases, the purity and completeness decrease, although they remain much higher than we initially expected. We extended our test cases to mock surveys with an average separation of 15 h -1 Mpc, meant to reproduce high source density areas of the Baryon Oscillation Spectroscopic Survey. Finally, we find that even with such a large sightline separation, the method can still be used to find some of the largest protoclusters.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Anaerobic Microbial Metabolism of Dichloroacetate

Dichloroacetate (DCA) commonly occurs in the environment due to natural production and anthropogenic releases, but its fate under anoxic conditions is uncertain. Mixed culture RM comprising “Candidatus Dichloromethanomonas elyunquensis” strain RM utilizes DCA as an energy source, and the transient formation of formate, H 2 , and carbon monoxide (CO) was observed during growth. Only about half of the DCA was recovered as acetate, suggesting a fermentative catabolic route rather than a reductive dechlorination pathway. Sequencing of 16S rRNA gene amplicons and 16S rRNA gene-targeted quantitative real-time PCR (qPCR) implicated “Candidatus Dichloromethanomonas elyunquensis” strain RM in DCA degradation. An (S)-2-haloacid dehalogenase (HAD) encoded on the genome of strain RM was heterologously expressed, and the purified HAD demonstrated the cofactor-independent stoichiometric conversion of DCA to glyoxylate at a rate of 90 ± 4.6 nkat mg -1 protein. Differential protein expression analysis identified enzymes catalyzing the conversion of DCA to acetyl coenzyme A (acetyl-CoA) via glyoxylate as well as enzymes of the Wood-Ljungdahl pathway. Glyoxylate carboligase, which catalyzes the condensation of two molecules of glyoxylate to form tartronate semialdehyde, was highly abundant in DCA-grown cells. The physiological, biochemical, and proteogenomic data demonstrate the involvement of an HAD and the Wood-Ljungdahl pathway in the anaerobic fermentation of DCA, which has implications for DCA turnover in natural and engineered environments, as well as the metabolism of the cancer drug DCA by gut microbiota.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Metabolic engineering of Escherichia coli for the production of butyric acid at high titer and productivity

Background: Several anaerobic bacteria produce butyric acid, a commodity chemical with use in chemical, pharmaceutical, food and feed industries, using complex media with acetate as a co-product. Butyrate titer of various recombinant Escherichia coli did not exceed 10 g l -1 in batch fermentations in any of the media tested. Results: A recombinant E. coli (strain LW393) that produced butyrate as the major fermentation product was constructed with genes from E. coli, Clostridium acetobutylicum and Treponema denticola. Strain LW393 produced 323±6 mM (28.4±0.4 g l -1 ) butyric acid in batch fermentations in mineral salt medium with glucose as C source at a yield of 0.37±0.01 g (g glucose consumed) -1 . Butyrate accounted for 90% of the total products produced by the culture. Supplementing this medium with yeast extract further increased butyric acid titer to 375±4 mM. Average volumetric productivity of butyrate with xylose as C source was 0.89±0.07 g l -1 h -1 . Conclusions: The butyrate titer reported in this study is about 2.5–3-times higher than the values reported for other recombinant E. coli and this is achieved in mineral salt medium with an expectation of lower purifcation and production cost of butyrate.

09 BIOMASS FUELS↗
DOE OSTI2014

Multifunctional optical correlator for picosecond ultraviolet laser pulse measurement

A compact optical correlator system that measures both the autocorrelation between two infrared (IR) lights and the cross-correlation between an IR and an ultraviolet (UV) light using a single nonlinear optical crystal has been designed and experimentally demonstrated. The rapid scanning of optical delay line, switching between auto and cross-correlations, crystal angle tuning, and data acquisition and processing are all computer controlled. Pulse widths of an IR light from a mode-locked laser are measured by the correlator and the results are compared with a direct measurement using a high-speed photodetector system. The correlator has been used to study the parameter dependence of the pulse width of a macropulse UV laser designed for laser-assisted hydrogen ion (H-) beam stripping for the Spallation Neutron Source at Oak Ridge National Laboratory.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗