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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Range gate dependence of specular echoes

Some controversy has surrounded the interpretation of the enhancement of VHF radar echoes at vertical incidence (also known as partial reflections, specular reflections and Fresnel scattering) since they were reported by the Sunset and the SOUSY radars. There is little doubt as to the observational fact of this enhancement since it was observed by experimenters using at least eleven MST or ST radars. In addition to the Sunset and SOUSY radars, this result was obtained in the lower atmosphere at the Platteville, Poker Flat, Jicamarca Arecibo radars as well as the three radars of the ALPEX experiments. In the upper atmosphere, specular or partial reflections were observed. These vertical enhancements were associated with increases in the static stability of the atmosphere, with a temperature gradient in the stratosphere, were used to monitor the height of the tropopause, and were associated with the passage of fronts.

Green, J. L.↗
DOE OSTI2025

Towards Full ‘Galilei General Relativity’: Gravitational Kinematics in Bargmann Spacetimes

Because of the strict separation of mass and energy in Galilei physics, a Galilei-invariant tensor formalism is most at home in a 5-dimensional extended spacetime associated with the Bargmann-Galilei (traditionally ‘Bargmann’) group, a central extension of the Galilei group that explicitly exhibits the transformation properties of kinetic energy. While not necessary for a tensor formalism fully embodying Poincaré physics, a similar central extension of the Poincaré group to the Bargmann-Poincaré group may illuminate a path towards a strong-field ‘Galilei general relativity’. Here the Bargmann metric is generalized to curved spacetime by extending the usual 1+3 (traditionally ‘3+1’) formalism of general relativity on 4-dimensional spacetime to a 1+3+1 formalism, whose spacetime kinematics is shown to be consistent with that of the usual 1+3 formalism. On Bargmann spacetime, tensor laws governing the motion of an elementary classical material particle and the dynamics of a simple fluid reference the foliation of spacetime in a manner that partially reverts the Einstein perspective (accelerated fiducial observers, and geodesic material particles and fluid elements) to a Newton-like perspective (geodesic fiducial observers, and accelerated material particles and fluid elements subject to a gravitational force).

Cardall, Christian [ORNL] (ORCID:000000020086105X)↗
DOE OSTI2020

Mechanisms of mechanochemical synthesis of cesium lead halides: pathways toward stabilization of α-CsPbI 3

Cesium lead iodide with cubic perovskite structure (α-CsPbI 3 ) is gaining significant interest in photovoltaic applications due to its excellent absorbance of the visible solar light and other attractive optoelectronic properties. However, the synthesis of stable α-CsPbI 3 poses a significant challenge. Mechanochemical synthesis is emerging as a suitable method for the preparation of cesium lead halides. This work investigates the ball milling-induced synthesis of cesium lead halides perovskite phase using halide mixing or doping approaches. The synthesis in the CsI + PbI 2 , CsBr + PbBr 2 , CsBr + PbI 2 , and CsI + PbI 2 + NdI 3 mixtures and halide exchange reactions in the CsPbBr 3 + 3KI and CsBr + PbBr 2 + 3KI systems are investigated to elucidate the mechanism of this process. Then, CsPb(I 1–x Br x ) 3 and CsPb( 1–y )Nd y I 3 materials with different x and y ratios are prepared, and their stability is probed in the air using light absorption spectroscopy. These results suggest that Nd doping is more efficient in the stabilization of the perovskite structure than partial replacement of iodine with bromine. Microstructure observations reveal the existence of two different product formation mechanisms depending on the mechanical properties of reactants. The results reveal that the milling temperature has a significant impact on the reaction kinetics. Here, the produced particles nucleate and grow at the reactant interface and retard the synthesis reaction by creating a diffusion barrier. Extended milling reduces the product particle size and creates fresh contact between reactants, thus facilitating reaction completion.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Computer Model Calibration Based on Image Warping Metrics: An Application for Sea Ice Deformation

Arctic sea ice plays an important role in the global climate. Sea ice models governed by physical equations have been used to simulate the state of the ice including characteristics such as ice thickness, concentration, and motion. More recent models also attempt to capture features such as fractures or leads in the ice. These simulated features can be partially misaligned or misshapen when compared to observational data, whether due to numerical approximation or incomplete physics. In order to make realistic forecasts and improve understanding of the underlying processes, it is necessary to calibrate the numerical model to field data. Traditional calibration methods based on generalized least-square metrics are flawed for linear features such as sea ice cracks. We develop a statistical emulation and calibration framework that accounts for feature misalignment and misshapenness, which involves optimally aligning model output with observed features using cutting-edge image registration techniques. Here, this work can also have application to other physical models which produce coherent structures.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Acceleration of bone development and regeneration through the Wnt/β-catenin signaling pathway in mice heterozygously deficient for GSK-3β

Highlights: •The Wnt/β-catenin signaling pathway was activated in GSK-3β{sup +/−} mice. •The cortical and trabecular bone volumes were increased in GSK-3β{sup +/−} mice. •Regeneration of a partial bone defect was accelerated in GSK-3β{sup +/−} mice. -- Abstract: Glycogen synthase kinase (GSK)-3β plays an important role in osteoblastogenesis by regulating the Wnt/β-catenin signaling pathway. Therefore, we investigated whether GSK-3β deficiency affects bone development and regeneration using mice heterozygously deficient for GSK-3β (GSK-3β{sup +/−}). The amounts of β-catenin, c-Myc, cyclin D1, and runt-related transcription factor-2 (Runx2) in the bone marrow cells of GSK-3β{sup +/−} mice were significantly increased compared with those of wild-type mice, indicating that Wnt/β-catenin signals were enhanced in GSK-3β{sup +/−} mice. Microcomputed tomography of the distal femoral metaphyses demonstrated that the volumes of both the cortical and trabecular bones were increased in GSK-3β{sup +/−} mice compared with those in wild-type mice. Subsequently, to investigate the effect of GSK-3β deficiency on bone regeneration, we established a partial bone defect in the femur and observed new bone at 14 days after surgery. The volume and mineral density of the new bone were significantly higher in GSK-3β{sup +/−} mice than those in wild-type mice. These results suggest that bone formation and regeneration in vivo are accelerated by inhibition of GSK-3β, probably through activation of the Wnt/β-catenin signaling pathway.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Palliative Short-Course Radiation Therapy in Rectal Cancer: A Phase 2 Study

Purpose: The management of patients with symptomatic rectal cancer not amenable to curative treatment may be challenging. The aim of this phase 2 study was to evaluate the efficacy of short-course radiation therapy in patients with obstructing rectal cancer. Methods and Materials: Patients who were not candidates for surgical resection because of synchronous metastases, age, and/or comorbidities were considered eligible. The sample size was calculated based on the 2-stage design of Simon. Short-course radiation therapy was delivered with an isocentric 4-field box technique (total, 25 Gy; 5 fractions in 5 days). Chemotherapy was suspended during radiation treatment. Clinical outcome measures were symptomatic response rate, toxicity, colostomy-free survival, and overall survival. Results: From October 2003 to November 2012, 18 patients (median age, 77.5 years) were enrolled. The median follow-up was 11.5 months (range, 3-36 months). Four weeks after treatment, a complete response (ie, complete symptom resolution) was observed in 38.9% of patients and a partial response in 50.0% cases, whereas 11.1% had no response. The rates of reduction or resolution of pain and bleeding were 87.5% and 100%, respectively. The 1-, 2-, and 3-year colostomy-free survival rates were 100%, 71.4%, and 47.6%, respectively (median, 30 months). The 1-, 2-, and 3-year cumulative overall survival rates were 85.2%, 53%, and 39.8%, respectively (median, 25 months). No patients stopped treatment because of gastrointestinal or genitourinary toxicities: 38.9% of patients had grade 1 to 2 toxicity, and 16.7% had grade 3 toxicity. Only 1 patient had hematologic grade 2 toxicity, and 2 patients had grade 2 skin toxicity. Conclusions: Short-course radiation therapy may represent a safe and effective alternative treatment option in patients with obstructing rectal cancer not eligible for curative treatment, allowing colostomy to be avoided in a substantial proportion of patients.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Thermal stability and phase transformation in fully indium oxide (InO{sub 1.5}) stabilized zirconia

Indium oxide (InO{sub 1.5}) stabilized zirconia (InSZ) is an attractive material as electrolyte, or electrode, in solid oxide fuel cells (SOFCs), and as corrosion resistant top coat in thermal barrier coatings. However, little is known about the phase stability of cubic InSZ at temperatures that simulate the conditions in an operating SOFC or turbine. This article provides an investigation of the phase stability and phase transformations in cubic InSZ after heat treatments at 800, 1000, and 1200 °C for periods up to 2000 h. The results revealed that cubic InSZ is not stable during annealing at 1000 and 1200 °C, owing to a fast destabilization of the initial cubic phase to tetragonal, and eventually to monoclinic (c → t → m). The c → t → m transition in InSZ is intimately associated with the indium volatilization. On the other hand, cubic InSZ remained stable for 2000 h at 800 °C, although the partial formation of the tetragonal phase was observed along with a 0.25% contraction in the unit cell volume of the cubic phase, caused by short-range ordering. These results demonstrate that technological applications of cubic InSZ are restricted to temperatures at which the volatilization of the InO{sub 1.5} stabilizer does not occur. - Highlights: •Phase stability of fully InO{sub 1.5} stabilized zirconia (cubic InSZ) was evaluated. •Cubic InSZ is instable at temperatures ≥ 1000 °C, owing to the cubic-to-tetragonal-to-monoclinic destabilization. •Cubic InSZ undergoes the cubic-to-tetragonal transformation at ~ 800 °C. •Owing to the low phase stability, applications of cubic InSZ in TBCs or SOFCs are restricted.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Cryo-EM Structures of Human Drosha and DGCR8 in Complex with Primary MicroRNA

Metazoan microRNAs require specificmaturation steps initiated by Microprocessor, comprising Drosha and DGCR8. Lack of structural information for the assembled complex has hindered an understanding of how Microprocessor recognizes primary microRNA transcripts (pri-miRNAs). In this paper we present a cryoelectron microscopy structure of human Microprocessor with a pri-miRNA docked in the active site, poised for cleavage. The basal junction is recognized by a four-way intramolecular junction in Drosha, triggered by the Belt and Wedge regions that clamp over the ssRNA. The belt is important for efficiency and accuracy of pri-miRNA processing. TwodsRBDs form a molecular ruler tomeasure the stem length between the twodsRNA-ssRNAjunctions. The specific organization of thedsRBDs near the apical junction is independent of Drosha core domains, as observed in a second structure in the partially docked state. Collectively, we derive a molecular model to explain how Microprocessor recognizes a pri-miRNA and accurately identifies the cleavage site.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Quantifying uncertainties in α -nucleus reaction dynamics informed from first principles

The ab initio symmetry-adapted no-core shell model is a microscopic many-body method which naturally describes challenging collective and clustering features of atomic nuclei. Wave functions and observables computed with realistic nucleon-nucleon forces in this framework are tied to first principles, and are hence well-suited for rigorous uncertainty quantification. We discuss α-deuteron and α- 12 C cluster potentials informed by symmetry-adapted calculations, and propagate uncertainties in the effective binary cluster method as well as those in the nuclear interaction to reaction observables, namely scattering phase shifts, cross sections, partial widths and resonance energies. Here, we find that the overall uncertainties are dominated by those originating in the underlying nuclear force, speaking to the need for tighter constraints on realistic nucleon-nucleon interactions.

Ab initio↗
DOE OSTI2022

Seasonal Fluctuations in Iron Cycling in Thawing Permafrost Peatlands

In permafrost peatlands, up to 20% of total organic carbon (OC) is bound to reactive iron (Fe) minerals in the active layer overlying intact permafrost, potentially protecting OC from microbial degradation and transformation into greenhouse gases (GHG) such as CO 2 and CH 4 . During the summer, shifts in runoff and soil moisture influence redox conditions and therefore the balance of Fe oxidation and reduction. Whether reactive iron minerals could act as a stable sink for carbon or whether they are continuously dissolved and reprecipitated during redox shifts remains unknown. We deployed bags of synthetic ferrihydrite (FH)-coated sand in the active layer along a permafrost thaw gradient in Stordalen mire (Abisko, Sweden) over the summer (June to September) to capture changes in redox conditions and quantify the formation and dissolution of reactive Fe(III) (oxyhydr)oxides. We found that the bags accumulated Fe(III) under constant oxic conditions in areas overlying intact permafrost over the full summer season. In contrast, in fully thawed areas, conditions were continuously anoxic, and by late summer, 50.4 ± 12.8% of the original Fe(III) (oxyhydr)oxides were lost via dissolution. Periodic redox shifts (from 0 to +300 mV) were observed over the summer season in the partially thawed areas. This resulted in the dissolution and loss of 47.2 ± 20.3% of initial Fe(III) (oxyhydr)oxides when conditions are wetter and more reduced, and new formation of Fe(III) minerals (33.7 ± 8.6% gain in comparison to initial Fe) in the late summer under more dry and oxic conditions, which also led to the sequestration of Fe-bound organic carbon. Our data suggest that there is seasonal turnover of iron minerals in partially thawed permafrost peatlands, but that a fraction of the Fe pool remains stable even under continuously anoxic conditions.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Identification of Possible Pathways for C–C Bond Formation during Electrochemical Reduction of CO 2 : New Theoretical Insights from an Improved Electrochemical Model

Here, we have carried out a periodic Kohn-Sham density functional theory investigation of the pathways by which carbon-carbon bonds could be formed during the electrochemical reduction of CO 2 on Cu(100) using a model that includes the effects of the electrochemical potential, solvent, and electrolyte. The electrochemical potential was set by relating the applied potential to the Fermi energy and then calculating the number of electrons required by the simulation cell for that specific Fermi energy. The solvent was included as a continuum dielectric, and the electrolyte was described using a linearized Poisson-Boltzmann model. The calculated potential of zero charge for a variety of surfaces agrees with experiment to within a mean average error of 0.09 V, thereby validating the assumptions of the model. Analysis of the mechanism for C–C bond formation revealed that at low-applied potential, C–C bond formation occurs through a CO dimer. However, at high applied potentials, a large activation barrier blocks this pathway; therefore, C–C bond formation occurs through reaction of adsorbed CHO and CO. Rate parameters determined from our calculations were used to simulate the kinetics of ethene formation during the electrochemical reduction of CO over a Cu(100) surface. An excellent match was observed between previously reported measurements of the partial current for ethene formation as a function of applied voltage and the variation in the partial current for C–C bond formation predicted by our microkinetic model. The electrochemical model reported here is simple, fairly easy to implement, and involves only a small increase in computational cost over calculations neglecting the effects of the electrolyte and the applied field. Therefore, it can be used to study the effects of applied potential and electrolyte composition on the energetics of surface reactions for a wide variety of electrochemical reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Stochasticity of Pores Interconnectivity in Li–O 2 Batteries and its Impact on the Variations in Electrochemical Performance

While large dispersions in electrochemical performance have been reported for lithium oxygen batteries in the literature, they have not been investigated in any depth. The variability in the results is often assumed to arise from differences in cell design, electrode structure, handling and cell preparation at different times. An accurate theoretical framework turns out to be needed to get a better insight into the mechanisms underneath and to interpreting experimental results. Here, we develop and use a pore network model to simulate the electrochemical performance of three-dimensionally resolved lithium-oxygen cathode mesostructures obtained from TXM nano-computed tomography images. Here, we apply this model to the 3D reconstructed object of a Super P carbon electrode and calculate discharge curves, using identical conditions, for four different zones in the electrode and their reversed configurations. The resulting galvanostatic discharge curves show some dispersion, (both in terms of capacity and overpotential) which we attribute to the way pores are connected with each other. Based on these results, we propose that the stochastic nature of pores interconnectivity and the microscopic arrangement of pores can lead, at least partially, to the variations in electrochemical results observed experimentally.

25 ENERGY STORAGE↗
DOE OSTI2025

Revisiting the Effects of Seed Liquid Water Content on Isoprene Secondary Organic Aerosol Growth

Aerosol liquid water content (LWC) has been shown to enhance partitioning of water-soluble oxygenated organic vapors into the aerosol particles and facilitate aqueous chemistry, impact SOA formation, composition, and physicochemical properties. Here, this study examines the effect of aerosol liquid water content (LWC) on isoprene SOA formation using effloresced and deliquesced ammonium sulfate ((NH 4 ) 2 SO 4 ) and sodium chloride (NaCl) seed particles in an environmental chamber with photo-oxidation extending over hours under moderate relative humidity (50%-60%). Our findings indicate that isoprene SOA mass yield is not significantly influenced (p value >> 0.05) by the phase state or the chemical identity of the seed particles within a 3–4-hour reaction time scale. Detailed molecular analysis using advanced high resolution mass spectrometry indicates that while both effloresced and deliquesced seed types produced similar molecular formula distributions, deliquesced (NH 4 ) 2 SO 4 slightly favored the production of less volatile compounds. Depth-profiling analysis by single particle mass spectrometry confirmed that isoprene SOA predominantly located on the surfaces of particles with core-shell morphologies, with partial dissolution of the effloresced inorganic salt observed even below the deliquescence relative humidity (DRH) of salt. This finding suggests that assuming dry salt core particles do not interact with SOA coatings, based on salt deliquescence points, may overlook important aqueous chemistry. These results emphasize the critical role of reaction time scale and mixing state on SOA formation and call for further research to understand LWC effects on SOA from different precursors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Spatio‐temporally Resolved Methane Fluxes From the Los Angeles Megacity

Abstract We combine sustained observations from a network of atmospheric monitoring stations with inverse modeling to uniquely obtain spatiotemporal (3‐km, 4‐day) estimates of methane emissions from the Los Angeles megacity and the broader South Coast Air Basin for 2015–2016. Our inversions use customized and validated high‐fidelity meteorological output from Weather Research Forecasting and Stochastic Time‐Inverted Lagrangian model for South Coast Air Basin and innovatively employ a model resolution matrix‐based metric to disentangle the spatiotemporal information content of observations as manifested through estimated fluxes. We partially track and constrain fluxes from the Aliso Canyon natural gas leak and detect closure of the Puente Hills landfill, with no prior information. Our annually aggregated fluxes and their uncertainty excluding the Aliso Canyon leak period lie within the uncertainty bounds of the fluxes reported by the previous studies. Spatially, major sources of CH 4 emissions in the basin were correlated with CH 4 ‐emitting infrastructure. Temporally, our findings show large seasonal variations in CH 4 fluxes with significantly higher fluxes in winter in comparison to summer months, which is consistent with natural gas demand and anticorrelated with air temperature. Overall, this is the first study that utilizes inversions to detect both enhancement (Aliso Canyon leak) and reduction (Puente Hills) in CH 4 fluxes due to the unintended events and policy decisions and thereby demonstrates the utility of inverse modeling for identifying variations in fluxes at fine spatiotemporal resolution.

Yadav, Vineet↗
DOE OSTI2016

Charge retention of soft-landed phosphotungstate Keggin anions on self-assembled monolayers

Soft landing of mass-selected ions onto surfaces often results in partial loss of charge that may affect the structure and reactivity of deposited species. In this study, Keggin phosphotungstate anions in two selected charge states, PW12O403- (WPOM3-) and PW12O402- (WPOM2-), were soft-landed onto different self-assembled monolayer (SAM) surfaces and examined using in situ infrared reflection absorption spectroscopy (IRRAS) and density functional theory (DFT) calculations. Partial retention of the 3- charge was observed when WPOM3- was soft-landed onto the fluorinated SAM (FSAM), while the charge state distribution was dominated by the 2- charge after both WPOM3- and WPOM2- were deposited onto a hydrophilic alkylthiol SAM terminated with cationic NH3+ functional groups (NH3+SAM). We found that during the course of the soft landing of WPOM3-, the relative abundance of WPOM3- on FSAM decreased while that of WPOM2- increased. We propose that the higher stability of immobilized WPOM2- in comparison with WPOM3- makes it the preferred charge state of WPOM on both the FSAM and NH3+SAM. We also observe weaker binding of WPOM anions to SAMs in comparison with phosphomolybdate ions (MoPOM) reported previously (J. Phys. Chem. C 2014, 118, 27611–27622). The weaker binding of WPOM to SAMs is attributed to the lower reactivity of WPOM reported in the literature. This study demonstrates that both the charge retention and the reactivity of deposited anionic POM clusters on surfaces are determined by the type of addenda metal atoms in the cluster.

charge reduction↗
DOE OSTI2013

A comparative study on shock compression of nanocrystalline Al and Cu: Shock profiles and microscopic views of plasticity

Shock compressions of nanocrystalline (nc) metals Al and Cu with the same grain size and texture are studied by using molecular dynamics simulations. Results have revealed that the shock front of both Al and Cu can be divided into three stages: elastic, grain-boundary-mediated, and dislocation-mediated plastic deformation. The transition planes among these three stages are proven to be non-planar by two-dimensional shock response analysis, including local stress, shear, temperature, and atom configuration. The difference between shocked Al and Cu is that the rise rate of the elastic stage of Cu is slightly higher than that of Al, and that the shock-front width of Al is wider than Cu at the same loading conditions. For the plastic stage, the dislocation density of shocked Al is lower than Cu, and the contribution of grain-boundary-mediated plasticity to shock front and strain for nc Al is more pronounced than for nc Cu. These results are explained through intrinsic material properties and atomistic analysis of the plastic process. In the case of the shocked Al sample, partial dislocations, perfect dislocations, and twins are observed, but few evidence of perfect dislocations and twins are observed in the shocked Cu.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Quantitative and high spatial resolution d{sub 33} measurement of piezoelectric bulk and thin films

A single beam laser interferometer based on a modified Mirau detection scheme with a vertical resolution of ∼5 pm was developed for localized d{sub 33} measurements on patterned piezoelectric films. The tool provides high spatial resolution (∼2 μm), essential for understanding scaling and processing effects in piezoelectric materials. This approach enables quantitative information on d{sub 33}, currently difficult in local measurement techniques such as piezoresponse force microscopy. The interferometer is built in a custom microscope and employs a phase lock-in technique in order to detect sub-Angstrom displacements. d{sub 33} measurements on single crystal 0.67PbMg{sub 0.33}Nb{sub 0.67}O{sub 3}-0.33PbTiO{sub 3} and bulk PbZrTiO{sub 3}-5A ceramics demonstrated agreement within <3% with measurements using a double beam laser interferometer. Substrate bending contributions to out-of-plane strain, observed in thin continuous PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} films grown on Si substrates is reduced for electrode diameters smaller than 100 μm. Direct scanning across room temperature and 150 °C poled 5 μm and 10 μm features etched in 0.5 μm thick PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} films doped with 1% Nb confirmed minimal substrate contributions to the effective d{sub 33,f}. Furthermore, enhanced d{sub 33,f} values were observed along the feature edges due to partial declamping from the substrate, thus validating the application of single beam interferometry on finely patterned electrodes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗