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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Melting point of group IV and V transition metal diborides

The environmental conical nozzle levitator system enables cooling trace experiments above 4000 K. These cooling trace experiments were used to determine the melting points through observation of thermal arrest of group IV and V transition metal diborides (TiB 2 , T m = 3313 ± 33 K; ZrB 2 , T m = 3404 ± 38 K; HfB 2 , T m = 3529 ± 33 K; and TaB 2 , T m = 3284 ± 10 K; note: mean ± 2 standard error). Temperature measurements were conducted utilizing dual single-color pyrometers at wavelengths of 0.9 and 0.65 µm. This system utilizes aerodynamic levitation and dual laser heating to achieve temperatures approaching 4000 K. The samples were synthesized from commercial powders using ceramic gel-casting to produce high-density spherical components. The measurements obtained were compared to previously reported melting temperature values and were generally found to be in agreement with most of the published values.

Materials science↗
NASA NTRS1972

Broadening of the infrared absorption lines at reduced temperatures. II - Carbon monoxide in an atmosphere of carbon dioxide.

The strengths of the rotational lines in the R branch of the CO fundamental have been determined at temperatures of 298, 202, and 132 K by means of a high-resolution spectrograph. The results can be used to determine line strengths at other temperatures by means of the Herman-Wallis relation or by considerations of the populations of the rotational levels in the ground vibrational state. Parameters describing the self-broadening and carbon dioxide broadening of CO lines have been determined at 298 and 202 K. The results are compared with other recent experimental and theoretical studies.

Tubbs, L. D.↗
DOE OSTI2024

Local probe investigation of the spin dynamics in the kagome and interlayers of orthorhombic barlowite $\mathrm{Cu4(OD)_6FBr; ^{79}Br}$ and $\mathrm{^{63}Cu}$ NQR study

Here we report 79 Br and 63 Cu nuclear quadrupole resonance (NQR) in the paramagnetic state above T N =15 K of the antiferromagnetic orthorhombic phase of barlowite Cu 4 (OD) 6 FBr consisting of a layered kagome structure. The divergent behavior of the longitudinal 79 (1/T 1 ) and transverse 79 (1/T 2 ) relaxation rates observed at 79Br sites evidences that critical slowing down of Cu spin fluctuations sets in below ~20 K. This means that one or more Cu sites, most likely at the interlayer Cu(3,4,5) sites between the kagome planes, undergo the antiferromagnetic phase transition in a fairly conventional way. On the other hand, the 63 Cu NQR signal intensity is gradually wiped out below ~30 K, pointing toward gradual spin freezing of the kagome layers instead. These contrasting findings suggest significant roles played by magnetic frustration effects within the kagome layers.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Compression behavior of lithium fluoride up to 80 GPa and 2300 K

Here, the high-temperature compression behavior of lithium fluoride (LiF) has been determined to ∼80 GPa and 2300 K by means of high-resolution synchrotron-based x-ray diffraction in a laser-heated diamond-anvil cell. The room-temperature Vinet equation of state (EOS) for LiF yields an isothermal room-temperature, ambient-pressure lattice parameter a 0 = 4.028 (±0.003) Å, volume V 0 = 65.35 (±0.03) Å 3 , bulk modulus K 0 = 67.57 (±0.34) GPa, and its pressure derivative K 0 ’ = 4.64 (±0.03). This expanded experimental dataset is in good agreement with the LiF thermal equation of state by Myint et al. (2019) up to ∼2300 K and 25 GPa. At higher pressures and temperatures our data shows reduced thermal expansion compared to the prediction and may be particularly important for experiments at more extreme conditions.

High-pressure behavior↗
NASA NTRS1978

Multistation refrigeration system

A closed cycle refrigeration (CCR) system is disclosed for providing cooling at different parts of a maser. The CCR includes a first station for cooling the maser's parts, except the amplifier portion, to 4.5 K. The CCR further includes means with a 3.0 K station for cooling the maser's amplifier to 3.0 K and, thereby, increases the maser's gain and/or bandwith by a significant factor. The means which provide the 3.0 K cooling include a pressure regulator, heat exchangers, an expansion valve, and a vacuum pump, which coact to cause helium, provided from a compressor, to liquefy and thereafter expand so as to vaporize. The heat of vaporization for the helium is provided by the maser amplifier, which is thereby cooled to 3.0 K.

Wiebe, E. R.↗
DOE OSTI2026

$K^{*}(892)^0$ production and the time between freeze-outs in $^{40}$Ar+$^{45}$Sc collisions by NA61/SHINE at the CERN SPS

The analysis of the production of strange $K^{*}(892)^0$ resonances allows us to better understand the temporal evolution of high-energy nucleus--nucleus collisions. In particular, the ratio of $K^{*}(892)^0$ to charged kaon yields is used to determine the time interval between chemical and kinetic freeze-outs. In this paper, the first measurements of $K^{*}(892)^0$ production in central $^{40}$Ar+$^{45}$Sc collisions at the CERN Super Proton Synchrotron are reported. They were performed by NA61/SHINE at collision center-of-mass energies per nucleon pair $\sqrt{s_\mathrm{NN}}$ = 8.8, 11.9, 16.8 GeV. The obtained $\langle K^{*}(892)^0 \rangle/\langle K^{+} \rangle $ and $\langle K^{*}(892)^0 \rangle/\langle K^{-} \rangle$ mean multiplicity ratios are compared with corresponding results in $p$+$p$ collisions, allowing for an estimate of the time interval between chemical and thermal freeze-outs in the $^{40}$Ar+$^{45}$Sc system. These are the first such results reported for $^{40}$Ar+$^{45}$Sc collisions.

Adrich, P. [NCBJ, Warsaw] (ORCID:0000000270195451)↗
NASA NTRS1980

The H I Lyman continuum in solar prominences and its interpretation in the presence of inhomogeneities

Observations of the H I Lyman continuum are presented for nine hedgerow prominences observed at the limb with the Harvard EUV spectrometer on Skylab. Methods of analysis for both the continuum emission and absorption are developed for two contrasting models for the prominence fine structure, namely multiple resolved slabs, and multiple unresolved cylindrical threads. The absorption data set a lower limit on the total optical thickness at 912 A and on the number of structures in the line of sight. The emission data yield a mean electron temperature of 7524 + or - 739 K and a mean brightness temperature of 6316 + or - 75 K. Taken together the emission and absorption data set firm constraints on the ionization, density, and fractional volume.

Orrall, F. Q.↗
NASA NTRS1994

The future of large format HgCdTe arrays for astronomy

Rockwell has developed the 256 x 256 Near Infrared Camera and Multi-Object Spectrometer 3 (NICMOS3) FPA for the Hubble Space Telescope under funding from NASA through the University of Arizona. Since 1989, dozens of science grade devices have been delivered to astronomers throughout the world for ground based infrared observations. These devices have excellent sensitivity at 77 K with mean dark currents of 0.1 e(-)/s, noise of 25 e(-), and quantum efficiency of 55-70%. Pixel yields as high as 99.9% have been achieved. Our present plans are to develop a 1024 x 1024 focal plane array (FPA) with 2.5 micron cutoff and make it available to astronomers. Such large arrays are made possible by the advances in detector material size (3 in. diameter producible alternative to CdTe for epitaxy (PACE-I) wafers), multiplexer advances (ability to verify the design in detail and availability of advanced foundries), and novel hybridization and reliability approaches.

Vural, K.↗
DOE OSTI2025

Magnetic properties of a staggered S = 1 chain with an alternating single-ion anisotropy direction

Materials composed of spin-1 antiferromagnetic (AFM) chains are known to adopt complex ground states that are sensitive to the single-ion-anisotropy (SIA) energy ( D ), and intrachain ( J 0 ) and interchain ( J 1 , 2 ′ ) exchange energy scales. While theoretical and experimental studies have extended this model to include various other energy scales, the effect of the lack of a common SIA axis is not well explored. Here we investigate the magnetic properties of Ni ( pyrimidine ) ( H 2 O ) 2 ( NO 3 ) 2 , a chain compound where the tilting of Ni octahedra leads to a twofold alternation of the easy-axis directions along the chain. Muon-spin relaxation measurements indicate a transition to long-range order at T N = 2.3 K and the magnetic structure is initially determined to be antiferromagnetic and collinear using elastic neutron diffraction experiments. Inelastic neutron scattering measurements were used to find J 0 = 5.107 ( 7 ) K , D = 2.79 ( 1 ) K , J 1 ′ = 0.00 ( 5 ) K , J 2 ′ = 0.18 ( 3 ) K , and a rhombic anisotropy energy E = 0.19 ( 9 ) K . Mean-field modeling reveals that the ground state structure hosts spin canting of ϕ ≈ 6 . 5 ∘ , which is not detectable above the noise floor of the elastic neutron diffraction data. Monte Carlo simulation of the powder-averaged magnetization, M ( H ) , is then used to confirm these Hamiltonian parameters, while single-crystal M ( H ) simulations provide insight into features observed in the data. Published by the American Physical Society 2025

Vaidya, S. (ORCID:000000033975497X)↗
DOE OSTI2024

Using Knowledge-Guided Machine Learning To Assess Patterns of Areal Change in Waterbodies across the Contiguous United States

Lake and reservoir surface areas are an important proxy for freshwater availability. Advancements in machine learning (ML) techniques and increased accessibility of remote sensing data products have enabled the analysis of waterbody surface area dynamics on broad spatial scales. However, interpreting the ML results remains a challenge. While ML provides important tools for identifying patterns, the resultant models do not include mechanisms. Thus, the “black-box” nature of ML techniques often lacks ecological meaning. Using ML, we characterized temporal patterns in lake and reservoir surface area change from 1984 to 2016 for 103,930 waterbodies in the contiguous United States. We then employed knowledge-guided machine learning (KGML) to classify all waterbodies into seven ecologically interpretable groups representing distinct patterns of surface area change over time. Many waterbodies were classified as having “no change” (43%), whereas the remaining 57% of waterbodies fell into other groups representing both linear and nonlinear patterns. This analysis demonstrates the potential of KGML not only for identifying ecologically relevant patterns of change across time but also for unraveling complex processes that underpin those changes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Using Knowledge-Guided Machine Learning To Assess Patterns of Areal Change in Waterbodies across the Contiguous United States

Lake and reservoir surface areas are an important proxy for freshwater availability. Advancements in machine learning (ML) techniques and increased accessibility of remote sensing data products have enabled the analysis of waterbody surface area dynamics on broad spatial scales. However, interpreting the ML results remains a challenge. While ML provides important tools for identifying patterns, the resultant models do not include mechanisms. Thus, the “black-box” nature of ML techniques often lacks ecological meaning. Using ML, we characterized temporal patterns in lake and reservoir surface area change from 1984 to 2016 for 103,930 waterbodies in the contiguous United States. We then employed knowledge-guided machine learning (KGML) to classify all waterbodies into seven ecologically interpretable groups representing distinct patterns of surface area change over time. Many waterbodies were classified as having “no change” (43%), whereas the remaining 57% of waterbodies fell into other groups representing both linear and nonlinear patterns. This analysis demonstrates the potential of KGML not only for identifying ecologically relevant patterns of change across time but also for unraveling complex processes that underpin those changes.

58 GEOSCIENCES↗
DOE OSTI2020

Planck 2018 results XI. Polarized dust foregrounds

The study of polarized dust emission has become entwined with the analysis of the cosmic microwave background (CMB) polarization in the quest for the curl-like B-mode polarization from primordial gravitational waves and the low-multipole E-mode polarization associated with the reionization of the Universe. We used the new Planck PR3 maps to characterize Galactic dust emission at high latitudes as a foreground to the CMB polarization and use end-to-end simulations to compute uncertainties and assess the statistical significance of our measurements. We present Planck EE, BB, and TE power spectra of dust polarization at 353 GHz for a set of six nested high-Galactic-latitude sky regions covering from 24 to 71% of the sky. We present power-law fits to the angular power spectra, yielding evidence for statistically significant variations of the exponents over sky regions and a difference between the values for the EE and BB spectra, which for the largest sky region are α EE = -2.42 ± 0.02 and α BB = -2.54 ± 0.02, respectively. The spectra show that the TE correlation and E/B power asymmetry discovered by Planck extend to low multipoles that were not included in earlier Planck polarization papers due to residual data systematics. We also report evidence for a positive TB dust signal. Combining data from Planck and WMAP, we have determined the amplitudes and spectral energy distributions (SEDs) of polarized foregrounds, including the correlation between dust and synchrotron polarized emission, for the six sky regions as a function of multipole. This quantifies the challenge of the component-separation procedure that is required for measuring the low-ℓ reionization CMB E-mode signal and detecting the reionization and recombination peaks of primordial CMB B modes. The SED of polarized dust emission is fit well by a single-temperature modified black-body emission law from 353 GHz to below 70 GHz. For a dust temperature of 19.6 K, the mean dust spectral index for dust polarization is β d P = 1.53±0.02. The difference between indices for polarization and total intensity is β d P -β d I = 0.05±0.03. By fitting multi-frequency cross-spectra between Planck data at 100, 143, 217, and 353 GHz, we examine the correlation of the dust polarization maps across frequency. We find no evidence for a loss of correlation and provide lower limits to the correlation ratio that are tighter than values we derive from the correlation of the 217- and 353 GHz maps alone. If the Planck limit on decorrelation for the largest sky region applies to the smaller sky regions observed by sub-orbital experiments, then frequency decorrelation of dust polarization might not be a problem for CMB experiments aiming at a primordial B-mode detection limit on the tensor-to-scalar ratio r ≃ 0.01 at the recombination peak. However, the Planck sensitivity precludes identifying how difficult the component-separation problem will be for more ambitious experiments targeting lower limits on r.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Correlative piezoresponse and micro-Raman imaging of CuInP 2 S 6 –In 4/3 P 2 S 6 flakes unravels phase-specific phononic fingerprint via unsupervised learning

Characterizing the novel properties of layered van der Waals materials is key for their application in functional devices. A better understanding of this type of material requires correlative imaging of diverse nanoscale material properties. Within this class of materials, CuInP 2 S 6 (CIPS) has received a significant degree of interest due to its ionically mediated room temperature ferroelectricity. Moreover, it is possible to form stable self-assembled heterostructures of ferroelectric CuInP 2 S 6 (CIPS) and non-ferroelectric (i.e., lacking Cu) In 4/3 P 2 S 6 (IPS) phases, by controlling the targeted composition and kinetics of synthesis. In this work, we present a correlative nanometric imaging study of the phononic modes and piezoelectricity of the phase-separated thin heteroepitaxial CIPS/IPS flakes. Here, we show that it is possible to isolate the different phononic modes of the two phases by spatially correlating them with their distinct ferroelectric behavior. The coupling of our experimental data with unsupervised learning statistical methods enables unraveling specific Raman peaks that are characteristic of each chemical phase (CIPS and IPS) present in the composite sample, discarding the less significant ones.

correlative microscopy↗
DOE OSTI2021

Genomic patterns of structural variation among diverse genotypes of Sorghum bicolor and a potential role for deletions in local adaptation

Genomic structural mutations, especially deletions, are an important source of variation in many species and can play key roles in phenotypic diversification and evolution. Previous work in many plant species has identified multiple instances of structural variations (SVs) occurring in or near genes related to stress response and disease resistance, suggesting a possible role for SVs in local adaptation. Sorghum [Sorghum bicolor (L.) Moench] is one of the most widely grown cereal crops in the world. It has been adapted to an array of different climates as well as bred for multiple purposes, resulting in a striking phenotypic diversity. In this study, we identified genome-wide SVs in the Biomass Association Panel, a collection of 347 diverse sorghum genotypes collected from multiple countries and continents. Using Illumina-based, short-read whole-genome resequencing data from every genotype, we found a total of 24,648 SVs, including 22,359 deletions. The global site frequency spectrum of deletions and other types of SVs fit a model of neutral evolution, suggesting that the majority of these mutations were not under any types of selection. Clustering results based on single nucleotide polymorphisms separated the genotypes into eight clusters which largely corresponded with geographic origins, with many of the large deletions we uncovered being unique to a single cluster. Even though most deletions appeared to be neutral, a handful of cluster-specific deletions were found in genes related to biotic and abiotic stress responses, supporting the possibility that at least some of these deletions contribute to local adaptation in sorghum.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Visualizing superconductivity in a doped Weyl semimetal with broken inversion symmetry

The Weyl semimetal Mo Te 2 offers a rare opportunity to study the interplay between Weyl physics and superconductivity. Recent studies have found that Se substitution can boost the superconductivity up to 1.5 K, but suppresses the T d structure phase that is essential for the emergence of the Weyl state. A microscopic understanding of the possible coexistence of enhanced superconductivity and the T d phase has not been established so far. Here, we use scanning tunneling microscopy to study an optimally doped superconductor Mo Te 1.85 Se 0.15 with bulk T c ~ 1.5 K . By means of quasiparticle interference imaging, we identify the existence of a low-temperature T d phase with broken inversion symmetry where superconductivity globally coexists. Furthermore, we find that the superconducting coherence length, extracted from both the upper critical field and the decay of density of states near a vortex, is much larger than the characteristic length scale of the existing chemical disorder. Overall, our findings of robust superconductivity arising from a Weyl semimetal normal phase in Mo Te 1.85 Se 0.15 make it a promising candidate for realizing topological superconductivity.

36 MATERIALS SCIENCE↗
NASA NTRS1971

High resolution Fouier transform spectrometer Serial No. 091002: Instruction manual

A description of the spectrometer and procedures for its operation, maintenance, alignments, adjustments, and control functions are presented. The interferometer spectrometer is a modified Model 296 capable of 0.5/cm resolution over the spectral region of 5 to 15 microns configured for operation with the optical head at a temperature of approximately 80 K. Details are given on the optical system and the electronic circuits. The detector used with the optical head is mercury doped germanium kept at a temperature of about 4 K by means of liquid helium. Electronic schematics, and instruction manuals for handling the liquid helium dewars, tape recorder for analog outputs, and playback console are included.

Source record↗