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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Single-epoch black hole mass estimators for broad-line active galactic nuclei: recalibrating Hβ with a new approach

Based on an updated Hβ reverberation mapping (RM) sample of 44 nearby active galactic nuclei (AGNs), we propose a novel approach for black hole (BH) mass estimation using two filtered luminosities computed from single-epoch (SE) AGN spectra around the Hβ region. We found that the two optimal-filter luminosities extract virial information (size and virial velocity of the broad-line region, BLR) from the spectra, justifying their usage in this empirical BH mass estimator. The major advantages of this new recipe over traditional SE BH mass estimators utilizing continuum luminosity and broad-line width are (1) it has a smaller intrinsic scatter of 0.28 dex calibrated against RM masses, (2) it is extremely simple to use in practice, without any need to decompose the spectrum, and (3) it produces unambiguous and highly repeatable results even with low signal-to-noise spectra. The combination of the two luminosities can also cancel out, to some extent, systematic luminosity errors potentially introduced by uncertainties in distance or flux calibration. In addition, we recalibrated the traditional SE mass estimators using broad Hβ FWHM and monochromatic continuum luminosity at 5100 Å (L {sub 5100}). We found that using the best-fit slopes on FWHM and L {sub 5100} (derived from fitting the BLR radius-luminosity relation and the correlation between rms line dispersion and SE FWHM, respectively) rather than simple assumptions (e.g., 0.5 for L {sub 5100} and 2 for FWHM) leads to more precise SE mass estimates, improving the intrinsic scatter from 0.41 dex to 0.36 dex with respect to the RM masses. We compared different estimators and discussed their applications to the Sloan Digital Sky Survey quasar sample. Due to the limitations of the current RM sample, application of any SE recipe calibrated against RM masses to distant quasars should be treated with caution.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Evaluation of SR/ TEVA/ TRU triple stack for separation of activation products

A rapid method to separate Ta, Po, Au, Pt, and W from a sample containing mixed fission and activation products was developed using three commercially available extraction chromatography resins stacked in series. When the separation was tested using all the target activation products, even those with short half-lives were measurable. Finally, combining multiple extraction chromatography resin cartridges in tandem allows for multiple short-lived activation products to be separated from one sample addition without the complication of multiple steps.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2019

Heavy Metal Atmospheric Deposition Study in Moscow Region, Russia

The air quality in north-eastern part of Moscow region was evaluated by trace metals atmospheric deposition using moss Pleurozium schreberi as bioindicator. Thirty six elements were determined in analyzed samples by Neutron activation analysis and Atomic absorption spectrometry. Principal component analysis was used to identify and characterize different pollution sources. Maps showing the geographical distribution of the factor scores were built using ArcGis software. Median values of the elements studied were compared with data obtained for other regions in Russia. The present survey showed that industrial activity, thermal power plants and transport still have the largest anthropogenic impact on air pollution in studied region.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Liquid Scintillation Counting of Environmental Radioisotopes: A Review of the Impact of Background Reduction

Liquid scintillation counting (LSC) is a versatile and commonplace method for radiometric measurement of charged particle emitting radionuclides. The LSC method provides utility in a range of environmental science applications including hydrological studies of water transport, anthropogenic releases of radionuclides into the environment, and vertical mixing rates within oceans. Instrumental measurement background is one limiting factor of radiometric measurement sensitivity. As part of the development of a custom low background LSC system located in a shallow underground laboratory at Pacific Northwest National Laboratory, a number of measurement applications of LSC have been considered and are summarized here. The focus is on determining which aspects of such measurements would gain the greatest benefit from the reduction of LSC backgrounds by a factor of 10-100 relative to values reported in the literature. Examples of benefits include lowering the minimum detectable activity, reducing the sample size required, and shortening the elapsed timeline of the processing and analysis sequence. In particular tritium, strontium, and actinium isotopes are examined as these isotopes cover a range of requirements related to the LSC measurement method (e.g., 3H: low energy; Sr: spectral deconvolution; Ac: alpha/beta discrimination).

actinium↗
DOE OSTI2017

Aqueous phase hydrogenation of phenol catalyzed by Pd and PdAg on ZrO 2

The impact of particle size of ZrO 2 -supported Pd and of alloying with Ag was explored for hydrogenation of phenol in aqueous phase. Kinetic assessments were performed in a batch reactor, on monometallic Pd/ZrO 2 samples with different Pd loadings (0.5%, 1% and 2%), as well as on a 1% PdAg/ZrO 2 sample. The catalytic activity normalized to accessible Pd (turnover frequency, TOF) increased with the particle size of Pd. Reaction orders in phenol and H 2 and lower activation energies suggest that smaller particles bind the reacting substrates more strongly, leading to higher surface coverages by phenol. But, surprisingly, smaller Pd particles exhibited lower TOFs. The lower activity of the small Pd particles is attributed to lower activation entropies for the strongly bound species. Furthermore, the presence of Ag increased the catalyst activity by decreasing the apparent energy of activation and increasing the coverages of phenol and H 2 , without negatively affecting the activation entropy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

{sup 1}H NMR-based spectroscopy detects metabolic alterations in serum of patients with early-stage ulcerative colitis

Highlights: •Twenty ulcerative colitis patients and nineteen healthy controls were enrolled. •Increased 3-hydroxybutyrate, glucose, phenylalanine, and decreased lipid were found. •We report early stage diagnosis of ulcerative colitis using NMR-based metabolomics. -- Abstract: Ulcerative colitis (UC) has seriously impaired the health of citizens. Accurate diagnosis of UC at an early stage is crucial to improve the efficiency of treatment and prognosis. In this study, proton nuclear magnetic resonance ({sup 1}H NMR)-based metabolomic analysis was performed on serum samples collected from active UC patients (n = 20) and healthy controls (n = 19), respectively. The obtained spectral profiles were subjected to multivariate data analysis. Our results showed that consistent metabolic alterations were present between the two groups. Compared to healthy controls, UC patients displayed increased 3-hydroxybutyrate, β-glucose, α-glucose, and phenylalanine, but decreased lipid in serum. These findings highlight the possibilities of NMR-based metabolomics as a non-invasive diagnostic tool for UC.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Photocatalytic NO{sub x} abatement by calcium aluminate cements modified with TiO{sub 2}: Improved NO{sub 2} conversion

Photocatalytic activity of TiO{sub 2} was studied in two types of calcium aluminate cement (CAC) under two different curing regimes. The effect of the TiO{sub 2} addition on the setting time, consistency and mechanical properties of the CACs was evaluated. The abatement of gaseous pollutants (NO{sub x}) under UV irradiation was also assessed. These cementitious matrices were found to successfully retain NO{sub 2}: more abundant presence of aluminates in white cement (w-CAC, iron-lean) helped to better adsorb NO{sub 2}, thus improving the conversion performance of the catalyst resulting in a larger NO{sub x} removal under UV irradiation. As evidenced by XRD, SEM, EDAX and zeta potential analyses, the presence of ferrite in dark cement (d-CAC, iron-reach) induced a certain chemical interaction with TiO{sub 2}. The experimental findings suggest the formation of new iron titanate phases, namely pseudobrookite. The reduced band-gap energy of these compounds compared with that of TiO{sub 2} accounts for the photocatalytic activity of these samples.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Solvothermal synthesis of vanadium phosphates in the form of xerogels, aerogels and mesostructures

Regularities and peculiarities of physicochemical changes, first of all phase transformations, during solvothermal treatment (with conventional and microwave heating) of the vanadium pentoxide and orthophosphoric acid mixture in organic solvents in the presence of reducing agents have been studied. Hemihydrate of vanadium hydrophosphate - the precursor of vanadium pyrophosphate, the active phase for n-butane to maleic anhydride oxidation, and ion exchanger with variable physicochemical characteristics, i.e. crystal structure, specific surface area, crystallite size and acidic properties - has been synthesized in the temperature range 170-200 {sup o}C. The obtained phases were examined using XRD, DTA-TG, SEM, FTIR spectroscopy, nitrogen adsorption as well as gas chromatographic determination of acidity through organic bases adsorption. The catalytic activity of prepared samples for n-butane oxidation has been investigated.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Highly uniform YF{sub 3}:Ln{sup 3+} (Ln = Ce{sup 3+}, Tb{sup 3+}) walnut-like microcrystals: Hydrothermal synthesis and luminescent properties

Graphical abstract: The emission spectra of Y{sub 0.98−x}F{sub 3}:0.02Ce{sup 3+}, xTb{sup 3+} microcrystals with different Tb{sup 3+} concentrations demonstrated that energy transfer from the Ce{sup 3+} and Tb{sup 3+} ions is highly efficient. The concentration quenching phenomenon occurs when the x = 0.13. We have discussed it in detail based on experiments and quantitative calculations. Highlights: ► YF{sub 3}:Ce{sup 3+}, Tb{sup 3+} walnut-like microcrystals were prepared by a hydrothermal synthesis. ► The optical properties of YF{sub 3}:Ce{sup 3+}, Tb{sup 3+} phosphors have been investigated in detail. ► The energy transfer distance and efficiency from Ce{sup 3+} to Tb{sup 3+} ions were calculated. ► The dipole–dipole interaction should be the dominant mechanism for energy transfer. - Abstract: Uniform and well-crystallized YF{sub 3} walnut-like microcrystals were prepared by a facile one-step hydrothermal synthesis. The crystalline phase, size, morphology, and luminescence properties were characterized using powder X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL) and photoluminescent excitation spectra (PLE). The results revealed that the existence of Ce{sup 3+} (sensitizer) can dramatically enhance green emission centered at 545 nm of Tb{sup 3+} (activator) in codoped samples due to an efficient energy transfer from Ce{sup 3+} to Tb{sup 3+}. The critical energy transfer distance between Ce{sup 3+} and Tb{sup 3+} was also calculated by methods of concentration quenching and spectral overlapping. Experimental analysis and theoretical calculations indicated that the dipole–dipole interaction should be the dominant mechanism for the Ce{sup 3+}–Tb{sup 3+} energy transfer.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Reinforcement of double-exchange ferromagnetic coupling by Ru in La{sub 1.24}Sr{sub 1.76}Mn{sub 2-y}Ru{sub y}O{sub 7} manganite system

Highlights: • Effect of Mn-site doping by Ru has been studied in La{sub 1.24}Sr{sub 1.76}Mn{sub 2-y}Ru{sub y}O{sub 7}. • Electrical resistance, magnetoresistance and magnetic properties were measured. • Ru substitution enhances the ferromagnetism and metallicity. • Results were interpreted by the ferromagnetically coupled Ru with Mn ions in Mn–O–Ru network. - Abstract: The effect of Mn-site doping on magnetic and transport properties in the bilayer manganites La{sub 1.24}Sr{sub 1.76}Mn{sub 2-y}Ru{sub y}O{sub 7} (y = 0.0, 0.04, 0.08 and 0.15) has been studied. The undoped compound La{sub 1.24}Sr{sub 1.76}Mn{sub 2}O{sub 7} exhibits a ferromagnetic metal to paramagnetic insulator transition at T{sub C} = 130 K and the substitution of Ru shifts the transition temperatures to higher temperature values. The increased metal–insulator transition by Ru substitution, obtained from temperature dependence of resistivity measurements, indicates that the Ru substitution enhances the metallic state at low temperature regime and favours the Mn–Ru pairs in the Ru doped samples. Moreover, the activation energy values calculated from the temperature dependence of resistivity curves suggest that the Ru substitution weakens the formation of polarons. The increased magnetoresistance ratio from 108% to 136% by Ru substitution, measured at 5 K, points out that the Ru substitution also enhances the inter-grain tunneling magnetoresistance. Thus, the ferromagnetic order and metallic state in La{sub 1.24}Sr{sub 1.76}Mn{sub 2}O{sub 7} system have been enhanced by the presence of Ru in the Mn-site. These reinforcements of ferromagnetic metallic state and magnetoresistance have been interpreted by the ferromagnetically coupled high spin states of Ru with Mn ions in the Mn–O–Ru network.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Silica supported TiO{sub 2} nanostructures for highly efficient photocatalytic application under visible light irradiation

Highlights: • Synthesis of silica–titania nanocomposite by simple and facile chemical route and characterization of the materials. • Excellent catalytic activity on organic pollutant methylene blue under the visible light irradiation. • Photocatalytic rate is much higher than commercial P25 TiO{sub 2} catalyst powder. • The higher activity is attributed to the special structure and synergistic effect of the materials which has immense application potential. - Abstract: Titanium dioxide decorated silica nanospheres have been synthesized by a simple wet chemical approach. X-ray diffraction, electron microscopy and energy dispersive X-ray analysis revealed that anatase phase of TiO{sub 2} nanostructures, with exposed {0 0 1} and {1 0 1} facets, are anchored onto the amorphous silica spheres of ∼60 nm diameter. The photocatalytic activity of the sample under visible light irradiation was examined. It is found that photocatalytic efficiency of the material is better than commercial P25 TiO{sub 2} photocatalyst and the result is attributed to the unique synergistic effect of SiO{sub 2}–TiO{sub 2} nanocomposite structure resulting enhanced charge separation and charge transfer.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Recyclable magnetic Fe3O4@SiO2/β-NaYF4:Yb3+,Tm3+/TiO2 composites with NIR enhanced photocatalytic activity

Highlights: • Fe{sub 3}O{sub 4}@SiO{sub 2}/β-NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+}/TiO{sub 2} composites have been successfully fabricated. • The upconversion of energy transfer from β-NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+} to TiO{sub 2} was confirmed. • Fe{sub 3}O{sub 4}@SiO{sub 2}/β-NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+}/TiO{sub 2} composites exhibit photocatalytic activity in NIR. • The composites can be easily magnetic separated from water after application. • The composites show good stability indicated from four recycled tests. - Abstract: To extend the activities of TiO{sub 2} to the near infrared (NIR) region and to separate and recycle photocatalysts easily is vital for the high harvest of solar energy for sustainable society. The magnetic NIR activated Fe{sub 3}O{sub 4}@SiO{sub 2}/β-NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+}/TiO{sub 2} (FS/UC/T) composites have been synthesized by using the solvothermal method by adding Fe{sub 3}O{sub 4}@SiO{sub 2} and Degussa P25 into the mixed solution of NaOH, ethanol, oleic acid, Re(NO{sub 3}){sub 3} and NH{sub 4}F. Moreover, the obtained composites were explored for photocatalytic applications. It was found that FS/UC/T emit UV–vis light under irradiation of 980 nm laser and efficient energy transfer from β-NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+} to TiO{sub 2} was verified. The photodegradation experiments for treating methylene blue (MB), rhodamine B (RhB), methyl orange (MO) and colorless phenol were carried out to evaluate the photocatalytic activities of the samples. The photodegradation rates reach 76.62%, 68.48%, 30.05% and 27.16% for MB, RhB, MO and phenol under irradiation of 980 nm laser, respectively, which suggested magnetic FS/UC/T composite is an advanced NIR-driven photocatalyst. Moreover, the magnetic photocatalyst showed easy separation and good stability in the recycled tests. It suggested a promising system to utilize the NIR energy for photocatalysis based on TiO{sub 2} and to utilize the magnetic for separation of photocatalysts, which will contribute to practical environmental remediation in the future.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Impact of composition modification induced by ion beam Coulomb-drag effects on the nanoindentation hardness of HT9

Accelerator-based ion irradiation is commonly used to simulate neutron damage, in lieu of neutron irradiation due to limited availability of fast flux facilities and little to no activation of the samples. Neutron atypical effects, however, must be recognized and their impact minimized in order to achieve the most accurate microstructural evolution under ion bombardment. Mechanical property changes, which arise from the synergy of numerous radiation-induced changes, are especially susceptible to these neutron atypical effects. Of these effects, a recently studied neutron atypical effect, arising from Coulomb-drag of vacuum contaminants and subsequent compositional alteration, was shown to substantially suppress swelling. Through the use of an ion beam filtering system, the resulting void swelling was shown to closely match neutron irradiation data. In this study, the impact of compositional modification via Coulomb-drag on the mechanical property changes is examined through the use of nanoindentation on a ferritic/martensitic alloy, HT9, irradiated with and without the use of the ion beam filtering system.

36 MATERIALS SCIENCE↗
DOE OSTI2019

High definition large area mapping of geological samples using a Maia detector array in the Nuclear Microprobe

A Maia detector array has been utilized and installed on the CSIRO-MARC Nuclear Microprobe. Maia uses an annular array of 384 silicon detectors to provide a solid-angle of 1.3 sr to improve the collection of X-rays induced by Particle Induced X-ray Emission (PIXE) using a micron focussed MeV proton beam. It features event-by-event data acquisition with dead-time correction and pileup rejection and a total count-rate capacity above 10 M/s, versatile stage and beam scanning modes (coupled to the DAQ-36 system described previously) to cater for a variety of sample configuration and experimental needs, precise measurement of transit time and integration of beam fluence per pixel, and spectral deconvolution of event data in real-time using the Dynamic Analysis method to provide element images during data collection. In this work we demonstrate the system on thin sections made from geological samples extracted from active seafloor hydrothermal vents in the PACMANUS hydrothermal field in Papua New Guinea.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Effect of warming on the degradation and production of low-molecular-weight labile organic carbon in an Arctic tundra soil

The fate of soil organic carbon (SOC) stored in the Arctic permafrost is a key concern as temperatures continue to rise in the northern hemisphere. Studies and conceptual models suggest that SOC degradation is affected by the composition of SOC, but it is unclear exactly what portions of SOC are vulnerable to rapid breakdown and what mechanisms may be controlling SOC degradation upon permafrost thaw. Here, we examine the dynamic consumption and production of labile SOC in an anoxic incubation experiment using soil samples from the active layer at the Barrow Environmental Observatory, Barrow, Alaska, USA. Free-reducing sugars, alcohols, and low-molecular-weight (LMW) organic acids were analyzed during incubation at either –2 or 8 °C for up to 240 days. Results show that simple sugar and alcohol SOC largely account for the initial rapid release of CO 2 and CH 4 through anaerobic fermentation, whereas the fermentation products, acetate and formate, are subsequently utilized as primary substrates for methanogenesis. Iron(III) reduction is correlated to acetate production and methanogenesis, suggesting its important role as an electron acceptor in tundra SOC respiration. These observations are further supported in a glucose addition experiment, in which rapid CO 2 and CH 4 production occurred concurrently with rapid production and consumption of labile organics such as acetate. However, addition of tannic acid, as a more complex organic substrate, showed little influence on the overall production of CO 2 and CH 4 and organic acids. Together our study shows that LMW labile organics in SOC control the initial rapid release of green-house gases upon warming. We thus present a conceptual framework for the labile SOC transformations and their relations to fermentation, iron reduction and methanogenesis, thereby providing the basis for improved model prediction of climate feedbacks in the Arctic.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Plutonium Isotopes in the Terrestrial Environment at the Savannah River Site, USA. A Long-Term Study

This work presents the findings of a long term plutonium study at Savannah River Site (SRS) conducted between 2003 and 2013. Terrestrial environmental samples were obtained at Savannah River National Laboratory (SRNL) in A-area. Plutonium content and isotopic abundances were measured over this time period by alpha spectrometry and three stage thermal ionization mass spectrometry (3STIMS). Here we detail the complete sample collection, radiochemical separation, and measurement procedure specifically targeted to trace plutonium in bulk environmental samples. Total plutonium activities were determined to be not significantly above atmospheric global fallout. However, the 238 Pu/ 239+240 Pu activity ratios attributed to SRS are above atmospheric global fallout ranges. The 240 Pu/ 239 Pu atom ratios are reasonably consistent from year to year and are lower than fallout, while the 242 Pu/ 239 Pu atom ratios are higher than fallout values. Overall, the plutonium signatures obtained in this study reflect a mixture of weapons-grade, higher burn-up, and fallout material. This study provides a blue print for long term low level monitoring of plutonium in the environment.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Isochronal annealing study of X-ray induced defects in single- and double-walled carbon nanotubes

X-ray induced defects in single-walled (SWCNTs) and double-walled carbon nanotubes (DWCNTs) were characterized by Raman scattering spectroscopy. Frenkel defects, interstitial-vacancy pairs, were revealed to form in both SWCNTs and DWCNTs after X-ray irradiation because these defects were entirely healed by thermal annealing. In order to clarify the structure of the X-ray induced defect in SWCNT and DWCNT, isochronal-annealing experiments were performed on the irradiated samples and the activation energy for defect healing was estimated. The intensity of D band (defect induced band) on Raman spectra was used as a measure of the density of X-ray induced defects. The experimental results were in good agreement with the simulated values using second order reaction model, which indicated that the defect healing was determined by the migration energy of interstitials on the carbon layer. We also found that the activation energy for defect healing of SWCNT and DWCNT were around 0.5 eV and 0.32 eV, respectively. The X-ray induced defects in SWCNTs were more stable than those in DWCNTs. Compared these estimated activation energies to previous theoretical reports, we concluded that bridge and/or dumbbell interstitials are formed in both SWCNT and DWCNT by X-ray irradiation.

36 MATERIALS SCIENCE↗