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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Neutral rhenium( i ) tricarbonyl complexes with sulfur-donor ligands: anti-proliferative activity and cellular localization

Rhenium(I) tricarbonyl complexes are widely studied for their cell imaging properties and anti-cancer and anti-microbial activities, but the complexes with S-donor ligands remain relatively unexplored. A series of six fac-[Re(NN)(CO) 3 (SR)] complexes, where (NN) is 2,2'-bipyridyl (bipy) or 1,10-phenanthroline (phen), and RSH is a series of thiocarboxylic acid methyl esters, have been synthesized and characterized. Cellular uptake and anti-proliferative activities of these complexes in human breast cancer cell lines (MDA-MB-231 and MCF-7) were generally lower than those of the previously described fac-[Re(NN)(CO) 3 (OH 2 )]+ complexes; however, one of the complexes, fac-[Re(CO) 3 (phen)(SC(Ph)CH 2 C(O)OMe)] (3b), was active (IC 50 ~ 10 μM at 72 h treatment) in thiol-depleted MDA-MB-231 cells. Moreover, unlike fac-[Re(CO) 3 (phen)(OH 2 )]+, this complex did not lose activity in the presence of extracellular glutathione. Taken together these properties show promise for further development of 3b and its analogues as potential anti-cancer drugs for co-treatment with thiol-depleting agents. Conversely, the stable and non-toxic complex, fac-[Re(bipy)(CO) 3 (SC(Me)C(O)OMe)] (1a), predominantly localized in the lysosomes of MDA-MB-231 cells, as shown by live cell confocal microscopy (λ ex = 405 nm, λ em = 470–570 nm). It is strongly localized in a subset of lysosomes (25 μM Re, 4 h treatment), as shown by co-localization with a Lysotracker dye. Longer treatment times with 1a (25 μM Re for 48 h) resulted in partial migration of the probe into the mitochondria, as shown by co-localization with a Mitotracker dye. These properties make complex 1a an attractive target for further development as an organelle probe for multimodal imaging, including phosphorescence, carbonyl tag for vibrational spectroscopy, and Re tag for X-ray fluorescence microscopy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Theoretical study of the ammonia nitridation rate on an Fe (100) surface: A combined density functional theory and kinetic Monte Carlo study

Ammonia (NH{sub 3}) nitridation on an Fe surface was studied by combining density functional theory (DFT) and kinetic Monte Carlo (kMC) calculations. A DFT calculation was performed to obtain the energy barriers (E{sub b}) of the relevant elementary processes. The full mechanism of the exact reaction path was divided into five steps (adsorption, dissociation, surface migration, penetration, and diffusion) on an Fe (100) surface pre-covered with nitrogen. The energy barrier (E{sub b}) depended on the N surface coverage. The DFT results were subsequently employed as a database for the kMC simulations. We then evaluated the NH{sub 3} nitridation rate on the N pre-covered Fe surface. To determine the conditions necessary for a rapid NH{sub 3} nitridation rate, the eight reaction events were considered in the kMC simulations: adsorption, desorption, dissociation, reverse dissociation, surface migration, penetration, reverse penetration, and diffusion. This study provides a real-time-scale simulation of NH{sub 3} nitridation influenced by nitrogen surface coverage that allowed us to theoretically determine a nitrogen coverage (0.56 ML) suitable for rapid NH{sub 3} nitridation. In this way, we were able to reveal the coverage dependence of the nitridation reaction using the combined DFT and kMC simulations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Modeling Time to Failure in Potential-Induced Degradation of Silicon Solar Modules based on Quantitative Sodium Kinetics

We present a physics-based simulation environment for the prediction of potential-induced-degradation (PID) failure time in silicon solar modules. Our model is based on experimental sodium migration kinetics obtained from our recently developed trap-corrected bias-stress-temperature method and from secondary ion mass spectrometry measurements. Furthermore, we model sodium migration to stacking faults and subsequent formation of conductive pathways through the p-n junction, which causes a decrease of the shunt resistance and loss of efficiency.

42 ENGINEERING↗
DOE OSTI2024

Neutral rhenium(i) tricarbonyl complexes with sulfur-donor ligands: anti-proliferative activity and cellular localization

Rhenium(I) tricarbonyl complexes are widely studied for their cell imaging properties and anticancer and anti-microbial activities, but the complexes with S-donor ligands remain relatively unexplored. A series of six fac-[Re(NN)(CO) 3 (SR)] complexes, where (NN) is 2,2'-bipyridyl (bipy) or 1,10-phenanthroline (phen), and RSH is a series of thiocarboxylic acid methyl esters, have been synthesized and characterized. Cellular uptake and anti-proliferative activities of these complexes in human breast cancer cell lines (MDA-MB-231 and MCF-7) were generally lower than those of the previously described fac-[Re(NN)(CO) 3 (OH 2 )] + complexes; however, one of the complexes, fac-[Re(CO) 3 (phen)(SC(Ph)CH 2 C(O)OMe))] (3b), was active (IC 50 ~ 10 μM at 72 h treatment) in thiol-depleted MDA-MB-231 cells. Moreover, unlike fac- [Re(CO) 3 (phen)(OH 2 )] + , this complex did not lose activity in the presence of extracellular glutathione. Taken together these properties show promise for further development of 3b and its analogues as potential anti-cancer drugs for co-treatment with thiol-depleting agents. Conversely, the stable and non-toxic complex, fac-[Re(bipy)(CO) 3 (SC(Me)C(O)OMe)] (1a), predominantly localized in the lysosomes of MDA-MB-231 cells, as shown by live cell confocal microscopy (λ ex = 405 nm, λ em = 470-570 nm). It is strongly localized in a subset of lysosomes (25 μM Re, 4 h treatment), as shown by co-localization with a Lysotracker dye. Longer treatment times with 1a (25 μM Re for 48 h) resulted in partial migration of the probe into the mitochondria, as shown by co-localization with a Mitotracker dye. These properties make complex 1a an attractive target for further development as an organelle probe for multimodal imaging, including phosphorescence, carbonyl tag for vibrational spectroscopy, and Re tag for X-ray fluorescence microscopy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Dynamic Deformation in Nuclear Graphite and Underlying Mechanisms

Time-dependent deformation in nuclear graphite is influenced by the creation and migration of radiation-induced defects in the reactor environment. This study investigates the role of pre-existing defects such as point defect clusters and Mrozowski cracks in nuclear graphite IG-110. Separate specimens were irradiated with a 2.8 MeV Au 2+ beam with a fluence of 4.38 × 10 14 cm −2 and an 8 MeV C 2+ beam with a fluence of 1.24 × 10 16 cm −2 . Microscopic specimens were either mechanically loaded inside a transmission electron microscope (TEM) or subjected to ex situ indentation-based creep loading. In situ TEM tests showed significant plasticity in regions highly localized around the Mrozowski cracks, resembling slip or ripplocation bands. Slip bands were also seen near regions without pre-existing defects but at very high stresses. Ex situ self-ion irradiation embrittled the specimens and decreased the creep displacement and rate, while heavy ion irradiation resulted in the opposite behavior. We hypothesize that the large-sized gold ions (compared to the carbon atoms) induced interplanar swelling as well as cross-plane channels for increased defect mobility. These findings illustrate the role of pre-existing defects in the dynamic relaxation of stresses during irradiation and the need for more studies into the radiation environment’s impact on the mechanical response of nuclear graphite.

creep deformation↗
NASA NTRS1976

The effects of space flight on polymorphonuclear leukocyte response experiment MA-032

In a series of studies performed at intervals from 30 day before flight to 30 days after recovery, blood samples were obtained from the three astronauts of the Apollo Soyuz Test Project and from eight control subjects. To determine the effects of space flight on polymorphonuclear leukocytes, tests were performed on blood samples obtained as quickly as possible after splashdown and on the day following recovery. The astronauts' inhalation of propellant gases and the inception of corticosteroid therapy 1 day after recovery provided an additional opportunity to investigate the possible effects of these factors on leukocyte function. Data were obtained during each time period on the total leukocyte count, differential count, leukocyte adhesion, leukocyte migration and chemotaxis, phagocytosis, and histochemical staining for leukocyte acid and alkaline phosphatase. These observations present a variety of in vitro correlates to white blood cell function within the body. Taken together, they serve as a reasonable approximation of the effects of space flight on leukocyte function.

Martin, R. R.↗
NASA NTRS1992

Unsteady Thermocapillary Migration of Isolated Drops in Creeping Flow

The problem of an isolated immiscible drop that slowly migrates due to unsteady thermocapillary stresses is considered. All physical properties except for interfacial tension are assumed constant for the two Newtonian fluids. Explicit expressions are found for the migration rate and stream functions in the Laplace domain. The resulting microgravity theory is useful, e.g., in predicting the distance a drop will migrate due to an impulsive interfacial temperature gradient as well as the time required to attain steady flow conditions from an initially resting state.

Dill, Loren H.↗
NASA NTRS1992

Multiperiodicities in the photometric variability of RS CVn binaries - What we know after 15 years

An overview of the behavior of the RS CVn binaries is presented. It is argued that chromospherically active stars vary in brightness on a variety of different time scales, each involving very different physics. Some of them are literally periodic, some are quasi-periodic or cyclical, and some can be described only in terms of a time scale. Connections between some of the different periods, cycles, and time scales are explained. Attention is given to orbital period, rotation period, migration, spot lifetimes, magnetic cycles and flares.

Hall, Douglas S.↗
NASA NTRS1993

Averaging techniques for steady and unsteady calculations of a transonic fan stage

It is often desirable to characterize a turbomachinery flow field with a few lumped parameters such as total pressure ratio or stage efficiency. Various averaging schemes may be used to compute these parameters. Here three averaging schemes, the momentum, energy, and area averaging schemes, are described and compared for two computed solutions of the midspan section of a transonic fan stage: a steady averaging-plane solution in which average rotor outflow conditions were used as stator inflow conditions and an unsteady rotor-stator interaction solution. The unsteady solution is described, some unsteady flow phenomena are discussed and the steady pressure distributions are compared. Despite large unsteady pressure fluctuations on the stator surface, the steady pressure distribution matched the average unsteady distribution almost exactly. Stator wake profiles, stator loss coefficient, and stage efficiency were computed for the two solutions with the three averaging schemes and are compared. In general the energy averaging scheme gave good agreement between the averaging-plane solution and the time-averaged unsteady solution, even though certain phenomena due to unsteady wake migration were neglected.

Wyss, M. L.↗
NASA NTRS1993

Averaging techniques for steady and unsteady calculations of a transonic fan stage

It is often desirable to characterize a turbomachinery flow field with a few lumped parameters such as total pressure ratio or stage efficiency. Various averaging schemes may be used to compute these parameters. The momentum, energy, and area averaging schemes are described and compared. The schemes were compared for two computed solutions of the midspan section of a transonic fan stage: a steady averaging-plane solution in which average rotor outflow conditions were used as stator inflow conditions, and an unsteady rotor-stator interaction solution. The solutions were computed on identical grids using similar Navier-Stokes codes and an algebraic turbulence model. The unsteady solution is described, some unsteady flow phenomena are discussed, and the steady pressure distributions are compared. Despite large unsteady pressure fluctuations on the stator surface, the steady pressure distribution matched the average unsteady distribution almost exactly. Stator wake profiles, stator loss coefficient, and stage efficiency were computed for the two solutions with the three averaging schemes and are compared. In general, the energy averaging scheme gave good agreement between the averaging-plane solution and the time-averaged unsteady solution, even though certain phenomena due to unsteady wake migration were neglected.

Wyss, M. L.↗
NASA NTRS1996

Fish Scale Evidence for Rapid Post Glacial Colonization of an Atlantic Coastal Pond

Fish scales from the sediment of Allamuchy Pond, New Jersey, USA, indicate that fishes were present in the pond within 400 years of the time of the first deposition of organic material, at approximately 12,600 yrs BP. The earliest of the scales, from a white sucker, Catostomus commersoni, appears in sediment dated 12,260 +/- 220 yrs BP. Presence of scales in sediment deposited before I 0,000 yrs BP indicates that Atlantic salmon, Salmo salar, sunfish, Lepomis sp., and yellow perch, Perca flavescens, also were early inhabitants of the pond. The timing of the arrival of each of these fishes suggests that they migrated out from Atlantic coastal refugia. A minnow scale, referred to Phoxininae, was also retrieved; it could not be matched to any cyprinid currently found in northeastern North America. The species present historically in this pond are from five families found currently in ponds throughout the Northeast and sugoest that the lentic palaeo-enviromnent was similar to present mid-elevation or high-latitude lentic systems.

Daniels, R. A.↗
NASA NTRS2002

Studies of Islands on Freely Suspended Bubbles of Smectic Liquid Crystal

We have constructed an optical system for observing the internal structure of freely suspended smectic liquid crystal bubbles using a reflected light microscope. Liquid crystal bubbles can have thicker circular regions (islands) which can easily be generated by shrinking the bubble diameter. The diameter of these islands is approximately 10 microns and they are typically up to five times thicker than the surrounding liquid crystal film (500 angstroms). In the Laboratory, the location of the islands is strongly influenced by gravity, which causes the majority of islands to migrate to the bottom half of the bubble. We will describe the size and thickness distributions of islands and their time evolution, and also discuss two-dimensional hydrodynamics and turbulence of smectic bubbles, the shapes of islands and holes affected by bubble vibrations, and the interactions between islands, which we have probed using optical tweezers.

Pattanaporkratana, A.↗
DOE OSTI2017

Production of Macrophage Inhibitory Factor (MIF) by Primary Sertoli Cells; Its Possible Involvement in Migration of Spermatogonial Cells

Macrophage migration inhibitory factor (MIF) is a multifunctional molecule. MIF was originally identified as a T‐cell‐derived factor responsible for the inhibition of macrophage migration. In testicular tissue of adult rats, MIF is constitutively expressed by Leydig cells under physiological conditions. The aim of this study was to examine MIF levels in testicular homogenates from different aged mice, and the capacity of Sertoli cells to produce it. We also examined MIF involvement in spermatogonial cell migration. Similar levels of MIF protein were detected in testicular homogenates of mice of different ages (1–8‐week‐old). However, the RNA expression levels of MIF were high in 1‐week‐old mice and significantly decreased with age compared to 1‐week‐old mice. MIF was stained in Sertoli, Leydig cells, and developed germ cells in the seminiferous tubules. Isolated Sertoli cells from 1‐week‐old mice stained to MIF. Cultures of Sertoli cells from 1‐week‐old mice produced and expressed high levels of MIF which significantly decreased with age. MIF was localized in the cytoplasm and nucleus of Sertoli cell cultures isolated from 1‐week‐old mice; however, it was localized only in the cytoplasm and branches of cultures isolated from 8‐week‐old mice. MIFR was detected in GFRα1 and Sertoli cells. MIF could induce migration of spermatogonial cells, and this effect was synergistic with glial cell‐line neurotrophic factor. Our results show, for the first time, the capacity of Sertoli cells to produce MIF under normal conditions and that MIFR expressed in GFRα1 and Sertoli cells. We also showed that MIF induced spermatogonial cell migration. J. Cell. Physiol. 232: 2869–2877, 2017. © 2016 Wiley Periodicals, Inc.

Huleihel, Mahmoud↗
DOE OSTI2022

Turning points in the age–metallicity relations – created by late satellite infall and enhanced by radial migration

ABSTRACT The present-day age–metallicity relation (AMR) is a record of the star formation history of galaxies, as this traces the chemical enrichment of the gas over time. We use a zoomed-in cosmological simulation that reproduces key signatures of the Milky Way (MW), g2.79e12 from the NIHAO-UHD project, to examine how stellar migration and satellite infall shape the AMR across the disc. We find in the simulation, similar to the MW, the AMR in small spatial regions (R, z) shows turning points that connect changes in the direction of the relations. The turning points in the AMR in the simulation are a signature of late satellite infall. This satellite infall has a mass radio similar as that of the Sagittarius dwarf to the MW (∼0.001). Stars in the apex of the turning points are young and have nearly not migrated. The late satellite infall creates the turning points via depositing metal-poor gas in the disc, triggering star formation of stars in a narrow metallicity range compared to the overall AMR. The main effect of radial migration on the AMR turning points is to widen the metallicity range of the apex. This can happen when radial migration brings stars born from the infallen gas in other spatial bins, with slightly different metallicities, into the spatial bin of interest. These results indicate that it is possible that the passage of the Sagittarius dwarf galaxy played a role in creating the turning points that we see in the AMR in the Milky Way.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Dynamics of Transformation from Platinum Icosahedral Nanoparticles to Larger FCC Crystal at Millisecond Time Resolution

Atomic motion at grain boundaries is essential to microstructure development, growth and stability of catalysts and other nanostructured materials. However, boundary atomic motion is often too fast to observe in a conventional transmission electron microscope (TEM) and too slow for ultrafast electron microscopy. Here, we report on the entire transformation process of strained Pt icosahedral nanoparticles (ICNPs) into larger FCC crystals, captured at 2.5 ms time resolution using a fast electron camera. Results show slow diffusive dislocation motion at nm/s inside ICNPs and fast surface transformation at μm/s. By characterizing nanoparticle strain, we show that the fast transformation is driven by inhomogeneous surface stress. And interaction with pre-existing defects led to the slowdown of the transformation front inside the nanoparticles. Particle coalescence, assisted by oxygen-induced surface migration at T ≥ 300°C, also played a critical role. Furthermore by studying transformation in the Pt ICNPs at high time and spatial resolution, we obtain critical insights into the transformation mechanisms in strained Pt nanoparticles.

36 MATERIALS SCIENCE↗
DOE OSTI2019

From Grain to Floodplain: Evaluating heterogeneity of floodplain hydrostatigraphy using sedimentology, geophysics, and remote sensing

Stratigraphy is a fundamental component of floodplain heterogeneity and hydraulic conductivity and connectivity of alluvial aquifers, which affect hydrologic processes such as groundwater flow and hyporheic exchange. Watershed–scale hydrological models commonly simplify the sedimentology and stratigraphy of floodplains, neglecting natural floodplain heterogeneity and anisotropy. This study, conducted in the upper reach of the East River in the East River Basin, Colorado, USA, combines point–, meander–, and floodplain–scale data to determine key features of alluvial aquifers important for estimating hydrologic processes. We compare stratigraphy of two meanders with disparate geometries to explore floodplain heterogeneity and connectivity controls on flow and transport. Meander shape, orientation, and internal stratigraphy affected residence time estimates of laterally exchanged hyporheic water. Although the two meanders share a sediment source, vegetation, and climate, their divergent river migration histories resulted in contrasting meander hydrofacies. In turn, the extent and orientation of these elements controlled the effective hydraulic conductivity and, ultimately, estimates of groundwater transport and hyporheic residence times. Additionally, the meanders’ orientation relative to the valley gradient impacted the hydraulic gradient across the meanders—a key control of groundwater velocity. In conclusion, we combine our field data with remotely sensed data and introduce a potential approach to estimate key hydrostratigraphic packages across floodplains. Prospective applications include contaminant transport studies, hyporheic models, and watershed models.

58 GEOSCIENCES↗
DOE OSTI2017

Triple junction drag effects during topological changes in the evolution of polycrystalline microstructures

Experiments, theory and atomistic simulations show that finite triple junction mobility results in non-equilibrium triple junction angles in evolving polycrystalline systems. These angles have been predicted and verified for cases where grain boundary migration is steady-state. Yet, steady-state never occurs during the evolution of polycrystalline microstructures as a result of changing grain size and topological events (e.g., grain face/edge switching - “T 1 ” process, or grain disappearance “T 2 ” or “T 3 ” processes). We examine the non-steady evolution of the triple junction angle in the vicinity of topological events and show that large deviations from equilibrium and/or steady-state angles occur. We analyze $\tau$ the characteristic relaxation time of triple junction angles τ by consideration of a pair of topological events, beginning from steady-state migration. Using numerical results and theoretical analysis we predict how the triple junction angle varies with time and how τ varies with triple junction mobility. We argue that it is precisely those cases where grain boundaries are moving quickly (e.g., topological process in nanocrystalline materials), that the classical steady-state prediction of the triple junction angle about finite triple junction mobility is inapplicable and may only be applied qualitatively.

36 MATERIALS SCIENCE↗