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Results for “time migration”

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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

MicroRNAs let-7b/i suppress human glioma cell invasion and migration by targeting IKBKE directly

We demonstrated that IKBKE is overexpressed in human gliomas and that the downregulation of IKBKE markedly inhibits the proliferative and invasive abilities of glioma cells, which is consistent with the results reported by several different research groups. Therefore, IKBKE represents a promising therapeutic target for the treatment of glioma. In the present study, we verified that the microRNAs let-7b and let-7i target IKBKE through luciferase assays and found that let-7b/i mimics can knock down IKBKE and upregulate E-cadherin through western blot analysis. Moreover, the expression levels of let-7b/i were significantly lower in glioma cell lines than that in normal brain tissues, as determined by quantitative real-time PCR. Furthermore, let-7b/i inhibit the invasion and migration of glioma cells, as determined through wound healing and Transwell assays. The above-mentioned data suggest that let-7b/i inhibit the invasive ability of glioma cells by directly downregulating IKBKE and indirectly upregulating E-cadherin. - Highlights: • Let-7b and let-7i are downregulated in glioma cell lines. • IKBKE is a target gene of let-7b/i. • Let-7b/i inhibit the invasion and migration of glioma cells. • Let-7b/i upregulate E-cadherin by downregulating IKBKE.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

HD 285507b: An eccentric hot Jupiter in the hyades open cluster

We report the discovery of the first hot Jupiter in the Hyades open cluster. HD 285507b orbits a V = 10.47 K4.5V dwarf (M {sub *} = 0.734 M {sub ☉}; R {sub *} = 0.656 R {sub ☉}) in a slightly eccentric (e=0.086{sub −0.019}{sup +0.018}) orbit with a period of 6.0881{sub −0.0018}{sup +0.0019} days. The induced stellar radial velocity corresponds to a minimum companion mass of M {sub P}sin i = 0.917 ± 0.033 M {sub Jup}. Line bisector spans and stellar activity measures show no correlation with orbital phase, and the radial velocity amplitude is independent of wavelength, supporting the conclusion that the variations are caused by a planetary companion. Follow-up photometry indicates with high confidence that the planet does not transit. HD 285507b joins a small but growing list of planets in open clusters, and its existence lends support to a planet formation scenario in which a high stellar space density does not inhibit giant planet formation and migration. We calculate the circularization timescale for HD 285507b to be larger than the age of the Hyades, which may indicate that this planet's non-zero eccentricity is the result of migration via interactions with a third body. We also demonstrate a significant difference between the eccentricity distributions of hot Jupiters that have had time to tidally circularize and those that have not, which we interpret as evidence against Type II migration in the final stages of hot Jupiter formation. Finally, the dependence of the circularization timescale on the planetary tidal quality factor, Q {sub P}, allows us to constrain the average value for hot Jupiters to be logQ{sub P}=6.14{sub −0.25}{sup +0.41}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Enhanced diffusion bonding of alloy 617 using electric field-assisted sintering

The development of compact heat exchangers (CHXs) has gained increasing interest in many industries owing to their high thermal efficiency and reduced size. Diffusion bonding (DB) is an advantageous technique for fabricating CHXs. Alloy 617 is a candidate for manufacturing CHXs for high-temperature advanced nuclear reactors due to its elevated-temperature properties. Previous endeavors in DB of Alloy 617 were conducted by hot pressing (HP), which reported precipitates at the diffusion-bond interface, limited grain boundary (GB) migration, and significantly reduced high-temperature mechanical properties. To overcome these challenges, this study investigated DB of Alloy 617 using electric field-assisted sintering (EFAS). Stacks composed of three sheets were bonded with EFAS using different temperatures, pressures, and hold times. DB using HP as the zero-current analog of EFAS was also performed for comparison. The result shows that Cr- and Mo-rich precipitates were formed at the interface of the hot-pressed samples. The electric current and temperature in EFAS play a significant role in precipitation and GB migration. The electric current coupled with correct temperatures can effectively prevent precipitate formation at the interface and achieve excellent GB migration. Nanoscale Al-rich oxide was formed at the interface of the samples made by both HP and EFAS, but grain boundaries can ignore the nanoscale Al-oxide and migrate across the interface. The temperature, pressure, and hold time also affected diffusion. The temperature is a prerequisite for a successful GB migration, and GB migration can be enhanced by increasing pressure and hold time.

36 MATERIALS SCIENCE↗
NASA NTRS1994

Time-series photometric spot modeling. 2: Fifteen years of photometry of the bright RS CVn binary HR 7275

We present a time-dependent spot modeling analysis of 15 consecutive years of V-band photometry of the long-period (P(sub orb) = 28.6 days) RS CVn binary HR 7275. This baseline in time is one of the longest, uninterrupted intervals a spotted star has been observed. The spot modeling analysis yields a total of 20 different spots throughout the time span of our observations. The distribution of the observed spot migration rates is consistent with solar-type differential rotation and suggests a lower limit of the differential-rotation coefficient of 0.022 +/-0.004. The observed, maximum lifetime of a single spot (or spot group) is 4.5 years, the minimum lifetime is approximately one year, but an average spot lives for 2.2 years. If we assume that the mechanical shear by differential rotation sets the upper limit to the spot lifetime, the observed maximum lifetime in turn sets an upper limit to the differential-rotation coefficient, namely 0.04 +/- 0.01. This would be differential rotation just 5 to 8 times less than the solar value and one of the strongest among active binaries. We found no conclusive evidence for the existence of a periodic phenomenon that could be attributed to a stellar magnetic cycle.

Strassmeier, K. G.↗
DOE OSTI2013

Raddeanin A induces human gastric cancer cells apoptosis and inhibits their invasion in vitro

Highlights: •Raddeanin A is a triterpenoid saponin in herb medicine Anemone raddeana Regel. •Raddeanin A can inhibit 3 kinds of gastric cancer cells’ proliferation and invasion. •Caspase-cascades’ activation indicates apoptosis induced by Raddeanin A. •MMPs, RECK, Rhoc and E-cad are involved in Raddeanin A-induced invasion inhibition. -- Abstract: Raddeanin A is one of the triterpenoid saponins in herbal medicine Anemone raddeana Regel which was reported to suppress the growth of liver and lung cancer cells. However, little was known about its effect on gastric cancer (GC) cells. This study aimed to investigate its inhibitory effect on three kinds of different differentiation stage GC cells (BGC-823, SGC-7901 and MKN-28) in vitro and the possible mechanisms. Proliferation assay and flow cytometry demonstrated Raddeanin A’s dose-dependent inhibitory effect and determined its induction of cells apoptosis, respectively. Transwell assay, wounding heal assay and cell matrix adhesion assay showed that Raddeanin A significantly inhibited the abilities of the invasion, migration and adhesion of the BGC-823 cells. Moreover, quantitative real time PCR and Western blot analysis found that Raddeanin A increased Bax expression while reduced Bcl-2, Bcl-xL and Survivin expressions and significantly activated caspase-3, caspase-8, caspase-9 and poly-ADP ribose polymerase (PARP). Besides, Raddeanin A could also up-regulate the expression of reversion inducing cysteine rich protein with Kazal motifs (RECK), E-cadherin (E-cad) and down-regulate the expression of matrix metalloproteinases-2 (MMP-2), MMP-9, MMP-14 and Rhoc. In conclusion, Raddeanin A inhibits proliferation of human GC cells, induces their apoptosis and inhibits the abilities of invasion, migration and adhesion, exhibiting potential to become antitumor drug.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

A probabilistic assessment of geomechanical reservoir integrity during CO 2 sequestration in flood basalt formations

Recent field experiments in Iceland and Washington State (USA) show that basalt formations may be favorable targets for carbon capture and sequestration (CCS) because CO 2 mineralization reactions proceed rapidly. These results imply that there is tremendous opportunity for implementing CCS in large igneous provinces. However, the magnitude of this opportunity comprises commensurate levels of uncertainty because basalt reservoirs are characterized by highly heterogeneous, fracture-controlled hydraulic properties. This geologic uncertainty is propagated as parametric uncertainty in quantitative risk models, thus limiting the efficacy of models to predict CCS performance attributes, such as reservoir integrity and storage potential. To overcome these limitations, here we present a stochastic approach for quantifying the geomechanical performance attributes of CCS operations in a highly heterogeneous basalt reservoir. We utilize geostatistical reservoir characterization to develop an ensemble of equally probable permeability distributions in a flood basalt reservoir with characteristics of the Wallula Basalt Pilot Project. We then simulate industrial-scale CO 2 injections within the ensemble and calculate the mean and variance of fluid pressure over a 1-year injection period. These calculations are combined with the state of stress in southeast Washington State to constrain the spatial extent at which shear failure, fracture initiation, and borehole breakdown may occur. Results from this study show that (i) permeability uncertainty alone causes injection pressure to vary over 25 MPa, (ii) shear failure is likely to occur at 7 times greater distances from the injection than the CO 2 migrates, and (iii) joint initiation pressures are localized within the volume comprising the CO 2 plume.

03 NATURAL GAS↗
DOE OSTI2013

Granulocyte colony-stimulating factor induces in vitro lymphangiogenesis

Highlights: •G-CSF induces tube formation, migration and proliferation of lymphatic cells. •G-CSF increases phosphorylation of MAPK and Akt in lymphatic endothelial cells. •MAPK and Akt pathways are linked to G-CSF-induced in vitro lymphangiogenesis. •G-CSF increases sprouting of a lymphatic ring. •G-CSF produces peritoneal lymphangiogenesis. -- Abstract: Granulocyte-colony stimulating factor (G-CSF) is reported to induce differentiation in cells of the monocyte lineage and angiogenesis in vascular endothelial cells, but its effects on lymphangiogenesis is uncertain. Here we examined the effects and the mechanisms of G-CSF-induced lymphangiogenesis using human lymphatic endothelial cells (hLECs). Our results showed that G-CSF induced capillary-like tube formation, migration and proliferation of hLECs in a dose- and time-dependent manner and enhanced sprouting of thoracic duct. G-CSF increased phosphorylation of Akt and ERK1/2 in hLECs. Supporting the observations, specific inhibitors of phosphatidylinositol 3′-kinase and MAPK suppressed the G-CSF-induced in vitro lymphangiogenesis and sprouting. Intraperitoneal administration of G-CSF to mice also stimulated peritoneal lymphangiogenesis. These findings suggest that G-CSF is a lymphangiogenic factor.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Ion transport through single-walled carbon nanotubes: Effects of electric field and fixed surface charge

The ion permeation trends for an aqueous sodium chloride solution through negatively charged carbon nanotubes under the simultaneous effects of a concentration gradient and an electric field using Molecular Dynamics simulations is investigated. A two-stage ion transport process was observed that resulted in a tunable effective ion flux toward the low concentration reservoir wherein the first stage resembled an electric-field assisted counter-ion (sodium) migration to the downstream reservoir for a short period of time followed by a second stage consisting of diffusion-driven electrolyte transport governed by the strength of the Donnan potential formed by the fixed charge on the nanotube.

Chemistry↗
DOE OSTI2020

CO 2 plume evolution in a depleted natural gas reservoir: Modeling of conformance uncertainty reduction over time

Uncertainty in the long-term fate of CO 2 injected for geologic carbon sequestration (GCS) is a significant barrier to the adoption of GCS as a greenhouse-gas emission-mitigation for industry and regulatory agencies alike. Here, we present a modeling study that demonstrates that the uncertainty in forecasts of GCS site performance decreases over time as monitoring data are used to update operational models. We consider a case study of GCS in a depleted natural gas reservoir, with CO 2 injection occurring over 20 years, with a 50-year post-injection site care period. We constructed a detailed model to generate the actual model output, which is considered synthetic observation data. A series of simpler operational models based on limited data and assumptions about how an operator would model such a site are then run and compared against actual model output at specific monitoring points after one year, two years, etc. The operational model is updated and improved using the synthetic observation data from the actual model at the same time intervals. Model parameter values and model features needed to be updated over time to improve matches to the actual model. These kinds of model adjustments would be a normal part of reservoir engineering and site management at GCS sites. Uncertainty in two key measures related to site performance decreases with time: extent of the CO 2 plume up-dip migration, and radial extent of the pressure pulse. This conclusion should help allay the concerns of industry and regulators about uncertainty in long-term fate of CO 2 at GCS sites.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Joint impedance and facies inversion of time-lapse seismic data for improving monitoring of CO 2 incidentally stored from CO 2 EOR

Time-lapse seismic monitoring is an effective and proven technology for mapping the distribution of CO 2 in a subsurface reservoir. When injected CO 2 displaces other reservoir fluids, porous-medium properties are changed and thus the seismic impedance changes, causing time-lapse seismic amplitude differences in the injection zones. The analysis and interpretation of images created from these amplitude differences can provide information about reservoir architecture and the CO 2 migration within the reservoir. Incorporating seismic inversion and rock physics into the interpretation of time-lapse seismic data can considerably improve the modeling and monitoring to detect and assess the location of CO 2 over time. The joint inversion method presented in this paper has an integral representation of the geology in the inversion algorithm using elastic facies, which provides information about the spatial distribution of the geologic heterogeneities controlling the movement of fluids in the reservoir. The method was successfully applied to time-lapse seismic data from a mature oil field undergoing CO 2 enhanced oil recovery. The estimated seismic acoustic impedances and facies reflect the characteristics of individual geologic facies and fluid conditions of the reservoir subject to CO 2 injection. Finally, the probabilities estimated by the joint impedance and facies inversion for the reservoir's litho-fluid facies can be used for forecasting CO 2 saturation and pressure changes within the target reservoir.

4D seismic↗
DOE OSTI2018

Life history variation is maintained by fitness trade-offs and negative frequency-dependent selection

Significance Many populations and species have different strategies for maximizing reproductive success in changing environments. For example, some species of plants reproduce only once in their lifetime (annuals), whereas others can reproduce over multiple years (perennials). Such variation can also occur in fishes, and we examine how this variation in life history strategies is maintained in a Pacific salmonid species ( Oncorhynchus mykiss ). We find that fish that successfully migrate between the ocean and their freshwater spawning grounds multiple times (repeat spawners) have more than twice the lifetime reproductive success of fish that only spawn once (single spawners). We also find a striking pattern of negative frequency-dependent selection in which older, larger females have higher lifetime fitness when they are less abundant.

Christie, Mark R.↗
DOE OSTI2015

Genetic Identification of Chinook Salmon: Stock-Specific Distributions of Juveniles along the Washington and Oregon Coasts

Abstract We used microsatellite DNA data and genetic stock identification methods to delineate the temporal and spatial distributions of juvenile Chinook Salmon Oncorhynchus tshawytscha occupying coastal habitats extending from central Oregon to northern Washington. Juveniles were collected in trawl surveys conducted during spring, summer, and autumn over 15 years. Distributions (mean latitude and distance from shore) differed between yearling and subyearling life history types and between stocks; many of these differences were consistent across years. Yearlings were nearly all (98%) from Columbia River sources, and only 6% were naturally produced. In late May, yearlings from the lower Columbia and Willamette rivers were farther north than other yearlings, likely due to the early spring timing of their releases from hatcheries and subsequent out-migration from the Columbia River. However, yearling distributions in late June reflected known migration behaviors. Yearlings from interior Columbia and Snake River sources were farthest north by June, whereas yearlings from other stocks were more spread out in latitude. Subyearlings sampled in early summer were also largely from the Columbia River (98%), but greater percentages of subyearlings from coastal rivers were present during the fall (24%). In contrast to yearlings, natural production accounted for nearly one-third of subyearlings. Subyearlings of most stocks tended to remain relatively near their point of sea entry throughout the summer. Subyearlings from the Snake River fall-run stock and upper Columbia River summer–fall-run stock exhibited diverse distributions that included both southward and northward dispersal. Overall, distributions of Chinook Salmon stocks and life history types reflected differences in migration behavior but also reflected the influence of environmental factors and hatchery practices. Received November 13, 2014; accepted April 15, 2015

Teel, David J.↗
DOE OSTI2019

Nonvolatile Ionic Modification of the Dzyaloshinskii-Moriya Interaction

The possibility of tuning the Dzyaloshinskii-Moriya interaction (DMI) by electric (E)-field gating in ultrathin magnetic materials has opened up new perspectives in terms of controlling the stabilization of chiral spin structures. The most recent efforts have used voltage-induced charge redistribution at the interface between a metal and an oxide to modulate the DMI. This approach is attractive for active devices but tends to be volatile, making it energy-demanding, and it is limited by Coulomb screening in the metal. Here we demonstrate nonvolatile E-field manipulation of the DMI by ionic-liquid gating of Pt/Co/Hf ⁢O 2 ultrathin films. The E-field effect on the DMI scales with the E-field exposure time, and we propose that it is linked to the migration of oxygen species from the Hf⁢ O 2 layer into the Co and Pt layers and subsequent anchoring. Here, this effect permanently changes the properties of the material, showing that E fields can be used not only for local gating in devices but also as a highly scalable materials design tool for postgrowth tuning of the DMI.

Domain walls↗
NASA NTRS1980

Radiation damage in lithium-counterdoped n/p silicon solar cells

Lithium counterdoped n+/p silicon solar cells were irradiated with 1 MV electrons and their post irradiation performance and low temperature annealing properties were compared to that of the 0.35 ohm cm control cells. Cells fabricated from float zone and Czochralski grown silicon were investigated. It was found that the float zone cells exhibited superior radiation resistance compared to the control cells, while no improvement was noted for the Czochralski grown cells. Room temperature and 60 C annealing studies were conducted. The annealing was found to be a combination of first and second order kinetics for short times. It was suggested that the principal annealing mechanism was migration of lithium to a radiation induced defect with subsequent neutralization of the defect by combination with lithium. The effects of base lithium gradient were investigated. It was found that cells with negative base lithium gradients exhibited poor radiation resistance and performance compared to those with positive or no lithium gradients; the latter being preferred for overall performance and radiation resistance.

Hermann, A. M.↗
NASA NTRS1991

Lower-mantle viscosity constrained by seismicity around deglaciated regions

It is shown here that seismicity around the margins of deglaciated areas provides a constraint on the viscosity of the lower mantle. Calculations using a spherical, viscoelastic earth model show that the present-day magnitude of the stress fields induced in the lithosphere beneath the Laurentide and Fennoscandian ice sheets is very sensitive to the value of the lower-mantle viscosity. Stress of about 100 bar, sufficient to cause seismicity, can still remain in the lithosphere for lower-mantle viscosities greater than about 10 to the 22nd Pa-s; for lower-mantle viscosities of about 10 to the 21st Pa-s, only a few tens of bars of stress persist in the lithosphere today. This influence of lower-mantle viscosity on the state of stress in the lithosphere also has implications for the migration of stress from earthquakes, and hence for earthquake recurrence times.

Spada, G.↗
DOE OSTI2017

Macrophage conditioned medium induced cellular network formation in MCF-7 cells through enhanced tunneling nanotube formation and tunneling nanotube mediated release of viable cytoplasmic fragments

Infiltrating macrophages in tumor microenvironment, through their secreted cytokines and growth factors, regulate several processes of cancer progression such as cancer cell survival, proliferation, invasion, metastasis and angiogenesis. Recently, intercellular cytoplasmic bridges between cancer cells referred as tunneling nanotubes (TNTs) have been recognized as novel mode of intercellular communication between cancer cells. In this study, we investigated the effect of inflammatory mediators present in conditioned medium derived from macrophages on the formation of TNTs in breast adenocarcinoma cells MCF-7. Results show that treatment with macrophage conditioned medium (MφCM) not only enhanced TNT formation between cells but also stimulated the release of independently migrating viable cytoplasmic fragments, referred to as microplasts, from MCF-7 cells. Time lapse microscopy revealed that microplasts were released from parent cancer cells in extracellular space through formation of TNT-like structures. Mitochondria, vesicles and cytoplasm could be transferred from parent cell body to microplasts through connecting TNTs. The microplasts could also be resorbed into the parent cell body by retraction of the connecting TNTs. Microplast formation inhibited in presence cell migration inhibitor, cytochalasin-B. Notably by utilizing migratory machinery within microplasts, distantly located MCF-7 cells formed several TNT based intercellular connections, leading to formation of physically connected network of cells. Together, these results demonstrate novel role of TNTs in microplast formation, novel modes of TNT formation mediated by microplasts and stimulatory effect of MφCM on cellular network formation in MCF-7 cells mediated through enhanced TNT and microplast formation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Grain growth of nanocrystalline aluminum under tensile deformation: A combined in situ TEM and atomistic study

Nanocrystalline Al thin films have been strained in situ in a transmission electron microscope using two separate nanomechanical techniques involving a push-to-pull device and a microelectromechanical system (MEMS) device. Deformation-induced grain growth was observed to occur via stress-assisted grain boundary migration with extensive grain growth occurring in the necked region, indicating that the increase in local stress drives the boundary migration. Under applied tensile stresses close to the ultimate tensile strength of 450 MPa for a nanocrystalline Al specimen, measured boundary migration speeds are 0.2 – 0.7 nm s -1 for grains outside necked region and increases to 2.5 nm s -1 for grains within the necked region where the local estimated tensile stresses are elevated to around 630 MPa. By tracking grain boundary motion over time, molecular dynamics simulations showed qualitative agreement in terms of pronounced grain boundary migration with the experimental observations. The combined in situ observation and molecular dynamics simulation results underscore the important role of stress-driven grain growth in plastically deforming nanocrystalline metals, leading to intergranular fracture through predominant grain boundary sliding in regions with large localized deformation.

36 MATERIALS SCIENCE↗
DOE OSTI2016

The effects of cation–anion clustering on defect migration in MgAl 2 O 4

Magnesium aluminate spinel (MgAl 2 O 4 ), like many other ceramic materials, offers a range of technological applications, from nuclear reactor materials to military body armor. For many of these applications, it is critical to understand both the formation and evolution of lattice defects throughout the lifetime of the material. We use the Speculatively Parallel Temperature Accelerated Dynamics (SpecTAD) method to investigate the effects of di-vacancy and di-interstitial formation on the mobility of the component defects. From long-time trajectories of the state-to-state dynamics, we characterize the migration pathways of defect clusters, and calculate their self-diffusion constants across a range of temperatures. We find that the clustering of Al and O vacancies drastically reduces the mobility of both defects, while the clustering of Mg and O vacancies completely immobilizes them. For interstitials, we find that the clustering of Mg and O defects greatly reduces O interstitial mobility, but has only a weak effect on Mg. Lastly, these findings illuminate important new details regarding defect kinetics relevant to the application of MgAl 2 O 4 in extreme environments.

36 MATERIALS SCIENCE↗