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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Low rotational barriers for the most dynamically active methyl groups in the proposed antiviral drugs for treatment of SARS-CoV-2, apilimod and tetrandrine

A recent screening study highlighted a molecular compound, apilimod, for its efficacy against the SARS-CoV-2 virus, while another compound, tetrandrine, demonstrated a remarkable synergy with the benchmark antiviral drug, remdesivir. In this work, we find that because of significantly reduced potential energy barriers, which also give rise to pronounced quantum effects, the rotational dynamics of the most dynamically active methyl groups in apilimod and tetrandrine are much faster than those in remdesivir. Because dynamics of methyl groups are essential for biochemical activity, screening studies based on the computed potential energy profiles may help identify promising candidates within a given class of drugs.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

A European Sustainable Tourism Labels proposal using a composite indicator

The tourism sector in Europe faces important challenges which it must deal with to promote its future development. In this context, the European Commission considers that two key issues must be addressed. On the one hand, a better base of socio-economic knowledge about tourism and its relationship with the environment is needed, and, on the other hand, it is necessary to improve the image of European areas as quality sustainable tourism destinations. In this paper we present analytical tools that cover these needs. Specifically, we define a system of sustainable tourism indicators and we obtain a composite indicator incorporating weights quantified using a panel of experts. Employing the values of this global indicator as a basis, we define a Sustainable Tourism Country-Brand Ranking which assesses the perception of each country-brand depending on its degree of sustainability, and a system of sustainable tourism labels which reward the management carried out. - Highlights: • We define a system of indicators to improve the knowledge about sustainable tourism. • We obtain composite indicators based on expert knowledge. • The Sustainable Tourism Country-Brand Ranking would improve the image of destinations. • We define a Sustainable Tourism Labels System to assess country-brands. • The conclusions of the empirical analysis can be extrapolated to other tourist areas.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Reassessing the proposed “CY chondrites”: Evidence for multiple meteorite types and parent bodies from Cr-Ti-H-C-N isotopes and bulk elemental compositions

Here, we report a coordinated bulk Cr-Ti-H-C-N isotopic and compositional study of six carbonaceous chondrites from Antarctica that are often considered to be related and termed Yamato-like carbonaceous (CY) chondrites. These meteorites are known to have undergone extensive aqueous alteration followed by different degrees of thermal alteration, to be similar to one another in regard to mineralogy, and share affinities with both the Ivuna-like carbonaceous (CI) and Mighei-like carbonaceous (CM) chondrites. While mineralogically similar, a key difference among these samples is that chondrules have been found in some of these samples, but not in others. The aim of this study is to evaluate the relationship of these meteorites to one another, and investigate how they relate to the CI and CM chondrite groups. We find that with the addition of the isotopic compositions of these ‘CY’ chondrites, there is now a continuum of isotopic compositions among the carbonaceous chondrites. The CI chondrites are no longer separate in O isotopic compositions from the other carbonaceous chondrite groups in plots of Cr-O and Ti-O. We also find that the ‘CY’ chondrites represent two distinct populations, which correlate with their heating stage. However, the peak temperatures experienced by each population can only explain the differences in H and C isotopes and abundances and N abundances between samples, and cannot have caused the differences in N, Cr, and Ti isotopes, or all the volatile element depletions of the sample’s bulk compositions. Instead, we conclude that the compositional and isotopic data of these two populations correlate with their known chondrule abundances, indicating distinct precursors for each population. We find it most likely that these samples originate from two distinct asteroids, implying that among the six samples studied here, there are not five related samples to constitute a new meteorite group. The chondrule-free heating Stage III samples are most likely heated CI chondrites, while the chondrule-bearing heating Stage IV samples could be heated CM chondrites.

58 GEOSCIENCES↗
DOE OSTI2021

Optical vibrational spectra and proposed crystal structure of ε-UO 3

ε-UO 3 is an exotic polymorph in the uranium trioxide system with an undetermined crystal structure and limited optical vibrational spectroscopic data. To improve understanding of this compound, we synthesize and investigate the crystal structure and optical vibrational spectra of ε-UO 3 . Infrared spectra collected for ε-UO 3 are in good agreement with previously published results, and our studies extend the available data into the low-energy (600–100 cm –1 ) regime. For the first time, Raman spectra are presented for ε-UO 3 using both 785 and 532 nm excitation wavelengths. Previous reports suggest an impurity phase may be present in ε-UO 3 produced by calcination of U 3 O 8 ; however, spectral center-of-mass calculations, principal component analyses, and Raman spectroscopic mapping employed to investigate this possibility indicate that the product of U 3 O 8 calcined in O 3 (g) in this work is likely phase-pure. A possible novel structure solution for ε-UO 3 is determined via Rietveld refinement of powder X-ray diffraction data and is triclinic, P-1, with a = 4.01 Å, b = 3.85 Å, c = 4.18 Å, and α = 98.26°, β = 90.41°, γ = 120.46° (R wp = 8.30%). The asymmetric unit of ε-UO 3 consists of U(VI) in hexagonal bipyramidal coordination with displaced equatorial oxygen. Further analysis reveals that the structure of ε-UO3 is best described by a 2 × 1 × 2 supercell structure in P-1 with a = 8.03 Å, b = 3.86 Å, c = 8.37 Å with α = 98.26°, β = 90.41°, and γ = 120.46°, although a higher-symmetry structure is possible. Optical vibrational spectroscopic and structural measurements of ε-UO 3 presented here furthers our understanding of this complex uranium oxide and clarifies the origin of reported structural similarity to U 3 O 8 .

-UO3↗
DOE OSTI2016

A photochemical proposal for the preparation of ZnAl{sub 2}O{sub 4} and MgAl{sub 2}O{sub 4} thin films from β-diketonate complex precursors

Highlights: • ZnAl{sub 2}O{sub 4} and MgAl{sub 2}O{sub 4} thin films were prepared by photo-chemical method. • The Zn(II), Mg(II) and Al(III) β-diketonate complexes were used as precursors. • The photochemical reaction was monitored by UV–vis and FT-IR spectroscopy. • The results reveal spinel oxide formation and the generation of intermediate products. - Abstract: ZnAl{sub 2}O{sub 4} and MgAl{sub 2}O{sub 4} thin films were grown on Si(100) and quartz plate substrates using a photochemical method in the solid phase with thin films of β-diketonate complexes as the precursors. The films were deposited by spin-coating and subsequently photolyzed at room temperature using 254 nm UV light. The photolysis of these films results in the deposition of metal oxide thin films and fragmentation of the ligands from the coordination sphere of the complexes. The obtained samples were post-annealed at different temperatures (350–1100 °C) for 2 h and characterized by FT-Infrared spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force miscroscopy (AFM), and UV–vis spectroscopy. The results indicate the formation of spinel-type structures and other phases. These characteristics determined the quality of the films, which were obtained from the photodeposition of ternary metal oxides.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Proposed new accelerator design for homeland security x-ray applications

Two goals for security scanning of cargo and freight are the ability to determine the type of material that is being imaged, and to do so at low radiation dose. One commonly used technique to determine the effective Z of the cargo is dual-energy imaging, i.e. imaging with different x-ray energy spectra. Another technique uses the fact that the transmitted x-ray spectrum itself also depends on the effective Z. Spectroscopy is difficult because the energy of individual x rays needs to be measured in a very high count-rate environment. Typical accelerators for security applications offer large but short bursts of x-rays, suitable for current-mode integrated imaging. In order to perform x-ray spectroscopy, a new accelerator design is desired that has the following features: 1) increased duty factor in order to spread out the arrival of x-rays at the detector array over time; 2) x-ray intensity modulation from one delivered pulse to the next by adjusting the accelerator electron beam instantaneous current so as to deliver adequate signal without saturating the spectroscopic detector; and 3) the capability to direct the (forward peaked) x-ray intensity towards high-attenuation areas in the cargo (“fan-beam-steering”). Current sources are capable of 0.1% duty factor, although usually they are operated at significantly lower duty factors (~0.04%), but duty factors in the range 0.4-1.0% are desired. The higher duty factor can be accomplished, e.g., by moving from 300 pulses per second (pps) to 1000 pps and/or increasing the pulse duration from a typical 4 μs to 10 μs. This paper describes initial R&D to examine cost effective modifications that could be performed on a typical accelerator for these purposes, as well as R&D for fan-beam steering.

43 PARTICLE ACCELERATORS↗