Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Hydromechanical modelling to evaluate impact of fault structure on CO 2 migration in stacked storage system

Faulting processes produce a complex fault damage zone (FDZ) having permeability variations over several orders of magnitude within a very short distance. In this study we use an example normal fault system from a depleted oil field in southern Louisiana with multiple stacked sand beds along the fault structure. Geostatistical techniques are used to introduce heterogeneities of several orders of magnitude over very short distances that honor the across- and along-fault architecture of the system. A total of 15 cases are simulated to account for the impact of a fragmented core, an intact core and a naturally fractured core on inter-sand leakage rates. The presented results show the complex nature of CO 2 migration within the fault structure, where an interplay between overcoming the fault core’s high capillary entry pressure and stress propagation in the vertical direction dictates the leakage direction and rates. It is observed that hydromechanical evolution of fracture flow properties may result in significant leakage from the storage zone. In one case with small caprock thickness, a loss of 18% of the total injected mass is observed. The results presented highlight some unique features of representative fault related leakage in stacked sand systems and thus will be beneficial for storage integrity analysis in these systems.

58 GEOSCIENCES↗
DOE OSTI2020

Tracking natural CO 2 migration through a sandstone aquifer using Sr, U and C isotopes: Chimayó, New Mexico, USA

The geochemical and isotopic characteristics of groundwaters in Chimayó, New Mexico, reflect processes that affect water quality in the Tesuque Aquifer, which overlies a leaking natural CO 2 source in a structurally complex region. In this study, select isotopes (δ 13 C, 87 Sr/ 86 Sr, 234 U/ 238 U) are applied to groundwaters to better understand CO 2 transport mechanisms and related water-rock interactions that impact Chimayó groundwater. Carbon stable isotope ratios of dissolved inorganic carbon (DIC; δ 13 CDIC = -15.10‰ to 4.50‰) identify a distinct source of upward-migrating CO 2 that interacts with the groundwater. Additionally, groundwater 87 Sr/ 86 Sr compositions (0.7098 to 0.7154) reflect intrusion of varying amounts of saline water associated with the high CO 2 source, while 234 U/ 238 U ratios corroborate presence of deep groundwater and suggest impacts from distinctive natural uranium sources are affecting groundwater. Previous work proposed two CO 2 transport mechanisms at the site: (1) dissolved in deep brine that underlies the aquifer and (2) in the gas phase; this study uses isotope mixing models to identify wells that are affected by these CO 2 transport mechanisms and demonstrates that both transport mechanisms are associated with impaired groundwaters. Overall, this study demonstrates that applying multiple isotope systems (δ 13 CDIC, 87 Sr/ 86 Sr, 234 U/ 238 U) is a dynamic tool for identifying and measuring the impact of CO 2 leakage from a sequestration site.

58 GEOSCIENCES↗
DOE OSTI2016

Formation, migration, and clustering energies of interstitial He in α-quartz and β-cristobalite

Precipitation of implanted helium (He) is detrimental to many nuclear materials. A solid in which implanted He does not precipitate, but rather remains in solution and diffuses readily is potentially of interest for applications requiring resistance to He-induced damage. Here we use density functional theory (DFT) calculations to examine He interstitial formation, migration, and clustering energies in two SiO 2 polymorphs: α-quartz and β-cristobalite. Our findings show greater He solubility and mobility in the latter than in the former. This difference appears to be due primarily to the unlike atomic-level structures of α-quartz and β-cristobalite, rather than their differing densities. Our findings also suggest that He is unlikely to cluster in either material. The behavior of He in α-quartz and β-cristobalite, and similar forms of silica make them promising materials for further investigation for potential use in applications requiring resistance to He-induced damage.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Plutonium migration and phase evolution in irradiated U-Pu-Zr metallic fuels: An integrated EPMA-SEM-TEM study

Constituent redistribution is a defining feature of irradiated U-Pu-Zr metallic fuels, yet its mechanisms and effects on fuel performance are not sufficiently resolved to guide model development. Although decades of irradiation testing have established broad trends, a true mechanistic understanding of constituent redistribution has not been achieved. Here, in this study, we use electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and transmission electron microscopy-based (TEM) selective area electron diffraction (SAED) on a EBR-II irradiated U-19 wt.% Pu-6 wt.% Zr fuel pin cross-section to correlate the composition, porosity, and crystallographic phases formed after irradiation. Constituent redistribution is thought to consist of three distinct zones, in which uranium and zirconium migrate while plutonium remains relatively unchanged. Our EPMA results resolve eight distinct compositional regions, and more importantly, show that plutonium redistributes alongside zirconium, contrary to historical assumptions. The distribution of fission products was highly asymmetric with a few large lanthanide precipitates observed at isolated sites on the pin periphery instead of a uniform distribution of smaller precipitates around the periphery. Using thermodynamic data from TAF-ID and the measured EPMA compositions, matrix phase fractions were predicted across the fuel radius. Phase predictions based on composition did not match TEM/SAED results, which revealed a much higher fraction of α−U phase than would be expected if phases were retained from reactor temperatures. These findings highlight the need for expanded SAED phase identification to capture post-irradiation and storage effects, as well as rigorous uncertainty quantification in fuel performance and phase diagram modeling to better constrain predictions from compositional data.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

Bi{sub 1−x}Nb{sub x}O{sub 1.5+x} (x=0.0625, 0.12) fast ion conductors: Structures, stability and oxide ion migration pathways

A combined experimental and computational study of Bi{sub 1−x}Nb{sub x}O{sub 1.5+x} (x=0.0625 and 0.12) has been carried out using laboratory X-ray, neutron and electron diffraction, impedance measurements and ab-initio molecular dynamics. We demonstrate that Bi{sub 0.9375}Nb{sub 0.0625}O{sub 1.5625}, previously reported to adopt a cubic fluorite-type superstructure, can form two different polymorphs depending on the synthetic method: a metastable cubic phase is produced by quenching; while slower cooling yields a stable material with a tetragonal √2×√2×1 superstructure, which undergoes a reversible phase transition into the cubic form at ~680 °C on subsequent reheating. Neutron diffraction reveals that the tetragonal superstructure arises mainly from ordering in the oxygen sublattice, with Bi and Nb remaining disordered, although structured diffuse scattering observed in the electron diffraction patterns suggests a degree of short-range ordering. Both materials are oxide ion conductors. On thermal cycling, Bi{sub 0.88}Nb{sub 0.12}O{sub 1.62} exhibits a decrease in conductivity of approximately an order of magnitude due to partial transformation into the tetragonal phase, but still exhibits conductivity comparable to yttria-stabilised zirconia (YSZ). Ab-initio molecular dynamics simulations performed on Bi{sub 0.9375}Nb{sub 0.0625}O{sub 1.5625} show that oxide ion diffusion occurs by O{sup 2−} jumps between edge- and corner-sharing OM{sub 4} groups (M=Bi, Nb) via tetrahedral □M{sub 4} and octahedral □M{sub 6} vacancies. - Graphical abstract: Oxide ion migration in tetragonal Bi{sub 0.9375}Nb{sub 0.0625}O{sub 1.5625} occurs by O{sup 2−} jumps between edge- and corner-sharing OM{sub 4} groups (M=Bi, Nb) via tetrahedral M{sub 4} and octahedral M{sub 6} vacancies. - Highlights: • Bi{sub 0.9375}Nb{sub 0.0625}O{sub 1.5625} adopts a tetragonal √2×√2×1 fluorite superstructure. • Superstructure is due to ordering in the O-sublattice, with Bi/Nb disordered. • Bi{sub 0.9375}Nb{sub 0.0625}O{sub 1.5625} is a good oxide ion conductor. • O{sup 2−} jump between OM{sub 4} groups (M=Bi, Nb) via tetrahedral and octahedral vacancies.

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

The GdF3 phosphors with enhanced multicolor luminescence via multi-channel excitation and energy migration procedure

Highlights: • Core-shell structured GdF{sub 3} phosphors were synthesized by hydrothermal method. • SiO{sub 2} coating layers prevent aggregation and sintering during thermal annealing. • The annealed CSS nanophosphors were highly dispersible. • The inserted PMA significantly enhances multicolor luminescence. • The annealed CSS phosphors exhibit enhanced multicolor luminescence properties. - Abstract: A collection of GdF{sub 3} core-shell structured (CSS) phosphors were synthesized by hydrothermal method. The as-prepared (AP) phosphors were coated with SiO{sub 2} layers to avoid aggregation and sintering during thermal annealing at 800 °C, after which the SiO{sub 2} layers were etched off and the annealed phosphors became highly dispersible. The annealed CSS phosphor aGdF{sub 3}:Eu{sup 3+}@GdF{sub 3}:Ce{sup 3+},Dy{sup 3+} shows excellent multicolor luminescence performance with the aid of dual-channel excitation and energy migration (EM) procedure of Gd{sup 3+} ions. By inserting pyromellitic acid (PMA) organic ligands into the interfaces between annealed core and AP shell layer regions, the so-called antenna effect of organic ligands of PMA forms a new excitation channel, which makes the CSS phosphor aGdF{sub 3}:Eu{sup 3+}@PMA@GdF{sub 3}:Ce{sup 3+},Dy{sup 3+} exhibit significantly enhanced multicolor luminescence via multi-channel excitation and EM process. The prepared CSS phosphors in this work are excellent candidates for applications in solid-state lighting.

36 MATERIALS SCIENCE↗
DOE OSTI2014

MiR-18a regulates the proliferation, migration and invasion of human glioblastoma cell by targeting neogenin

MiR-17-92 cluster has recently been reported as an oncogene in some tumors. However, the association of miR-18a, an important member of this cluster, with glioblastoma remains unknown. Therefore, this study aims to investigate the expression of miR-18a in glioblastoma and its role in biological behavior of U87 and U251 human glioblastoma cell lines. Quantitative RT-PCR results showed that miR-18a was highly expressed in glioblastoma tissues and U87 and U251 cell lines compared with that in human brain tissues and primary normal human astrocytes, and the expression levels were increased along with the rising pathological grades of glioblastoma. Neogenin was identified as the target gene of miR-18a by dual-luciferase reporter assays. RT-PCR and western blot results showed that its expression levels were decreased along with the rising pathological grades of glioblastoma. Inhibition of miR-18a expression was established by transfecting exogenous miR-18a inhibitor into U87 and U251 cells, and its effects on the biological behavior of glioblastoma cells were studied using CCK-8 assay, transwell assay and flow cytometry. Inhibition of miR-18a expression in U87 and U251 cells significantly up-regulated neogenin, and dramatically suppressed the abilities of cell proliferation, migration and invasion, induced cell cycle arrest and promoted cellular apoptosis. Collectively, these results suggest that miR-18a may regulate biological behavior of human glioblastoma cells by targeting neogenin, and miR-18a can serve as a potential target in the treatment of glioblastoma. - Highlights: • MiR-18a was highly expressed in glioblastoma tissues and U87 and U251 cell lines. • Neogenin was identified as the target gene of miR-18a. • Neogenin expressions were decreased along with the rising pathological grades of glioblastoma. • Inhibition of miR-18a suppressed biological behavior of glioma cells by up-regulating neogenin.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

The translational blocking of α5 and α6 integrin subunits affects migration and invasion, and increases sensitivity to carboplatin of SKOV-3 ovarian cancer cell line

Epithelial ovarian cancer is the most lethal gynecologic malignancy. Integrins, overexpressed in cancer, are involved in various processes that favor the development of the disease. This study focused on determining the degree of involvement of α5, α6 and β3 integrin subunits in the establishment/development of epithelial ovarian cancer (EOC), such as proliferation, migration, invasion, and response to carboplatin. The translation of the α5, α6 and β3 integrins was blocked using morpholines, generating morphant cells for these proteins, which were corroborated by immunofluorescence assays. WST-1 proliferation assay showed that silencing of α5, α6, and β3 integrins does not affect the survival of morphants. Wound healing and transwell chamber assays showed that blocking α5 and α6 integrins decrease, in lesser and greater level respectively, the migratory and the invasive capacity of SKOV-3 cells. Finally, blocking α5 and α6 integrins partially sensitized the cells response to carboplatin, while blocking integrin β3 generated resistance to this drug. Statistical analyses were performed with the GraphPad Prism 5.0 software employing one way and two-way ANOVA tests; data are shown as average±SD. Results suggest that α5 and α6 integrins could become good candidates for chemotherapy targets in EOC.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

SIPA1 promotes invasion and migration in human oral squamous cell carcinoma by ITGB1 and MMP7

Signal-induced proliferation-associated protein 1 (SIPA1) is known to be a GTPase activating protein. Overexpressed SIPA1 is related to metastatic progression in breast and prostate cancers; however, the relevance of SIPA1 in oral squamous cell carcinoma (OSCC) is still unknown. The aim of this study was to examine SIPA1 expression and its functional mechanisms in OSCC. SIPA1 mRNA and protein expressions were analyzed by quantitative reverse transcriptase-polymerase chain reaction, Western blot analysis, and immunohistochemistry. The expressions of SIPA1 were up-regulated significantly in vitro and in vivo. Moreover, SIPA1 expression was correlated with regional lymph node metastasis. We next assessed the cellular functions associated with tumoral metastasis using SIPA1 knockdown (shSIPA1) cells and analyzed the downstream molecules of SIPA1, i.e., bromodomain containing protein 4(BRD4), integrin beta1 (ITGB1), and matrix metalloproteinase 7 (MMP7). The shSIPA1 cells showed decreased invasiveness and migratory activities, however cellular adhesion ability was maintained at a high level. In addition, ITGB1 expression was greater in shSIPA1 cells, whereas MMP7 expression was lower than in control cells. This research is the first to establish that SIPA1 promotes cancer metastasis by regulating the ITGB1 and MMP7. Therefore, SIPA1 might be a novel therapeutic target for patients with lymph node metastasis of OSCC. - Highlights: • SIPA1 expression was up-regulated in oral squamous cell carcinoma (OSCC). • SIPA1-positive OSCCs were correlated with regional lymph node metastasis. • SIPA1 controlled BRD4 and influenced transcription of ITGB1and MMP7. • SIPA1 induced cellular invasion and migration and decreased cellular adhesion. • SIPA1 might be a potential biomarker of cancer metastasis for OSCC.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

DLX1, a binding protein of beta-catenin, promoted the growth and migration of prostate cancer cells

Several studies have indicated the involvement of DLX1 in the progression of prostate cancer. However, the functions of DLX1 in the prostate cancer and the underlying molecular mechanism remains largely unknown. In this study, we have shown that DLX1 was up-regulated in the prostate clinical samples. DLX1 promoted the growth, migration and colony formation of prostate cancer cells by activating beta-catenin/TCF signaling. DLX1 interacted with beta-catenin and enhanced the interaction between beta-catenin and TCF4. Taken together, this study demonstrated that DLX1 exerted the oncogenic roles on the prostate cancer by activating beta-catenin/TCF signaling.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Nicotine induces oral dysplastic keratinocyte migration via fatty acid synthase-dependent epidermal growth factor receptor activation

Despite advances in diagnostic and therapeutic management, oral squamous cell carcinoma (OSCC) patient survival rates have remained relatively unchanged. Thus, identifying early triggers of malignant progression is critical to prevent OSCC development. Traditionally, OSCC initiation is elicited by the frequent and direct exposure to multiple tobacco-derived carcinogens, and not by the nicotine contained in tobacco products. However, other nicotine-containing products, especially the increasingly popular electronic cigarettes (e-cigs), have unknown effects on the progression of undiagnosed tobacco-induced oral premalignant lesions, specifically in regard to the effects of nicotine. Overexpression of fatty acid synthase (FASN), a key hepatic de novo lipogenic enzyme, is linked to poor OSCC patient survival. Nicotine upregulates hepatic FASN, but whether this response occurs in oral dysplastic keratinocytes is unknown. We hypothesized that in oral dysplastic keratinocytes, nicotine triggers a migratory phenotype through FASN-dependent epidermal growth factor receptor (EGFR) activation, a common pro-oncogenic event supporting oral carcinogenesis. We report that in oral dysplastic cells, nicotine markedly upregulates FASN leading to FASN-dependent EGFR activation and increased cell migration. These results raise potential concerns about e-cig safety, especially when used by former tobacco smokers with occult oral premalignant lesions where nicotine could trigger oncogenic signals commonly associated with malignant progression.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

First-Principles Modeling of Mn(II) Migration above and Dissolution from Li x Mn 2 O 4 (001) Surfaces

The density functional theory and ab initio molecular dynamics simulations are applied to investigate the migration of Mn(II) ions to above-surface sites on spinel Li x Mn 2 O 4 (001) surfaces, the subsequent Mn dissolution into the organic liquid electrolyte, and the detrimental effects on graphite anode solid electrolyte interphase (SEI) passivating films after Mn(II) ions diffuse through the separator. The dissolution mechanism proves complex; the much-quoted Hunter disproportionation of Mn(III) to form Mn(II) is far from sufficient. Key steps that facilitate Mn(II) loss include concerted liquid/solid-state motions; proton-induced weakening of Mn–O bonds forming mobile OH – surface groups; and chemical reactions of adsorbed decomposed organic fragments. Mn(II) lodged between the inorganic Li 2 CO 3 and organic lithium ethylene dicarbonate (LEDC) anode SEI components facilitate electrochemical reduction and decomposition of LEDC. Our findings help inform future design of protective coatings, electrolytes, additives, and interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Impact of natural organic matter on plutonium vadose zone migration from an NH4Pu(V)O2CO3(s) source

Large amounts of plutonium produced at the Savannah River Site (SRS) in the latter half of the last century led to the release of plutonium to the subsurface. Low-level waste containing plutonium has also been disposed of in the SRS vadose zone. The mobility and risk posed by these plutonium sources is not well understood, in part, because of unknown interactions of the various mobile plutonium species with natural organic matter (NOM). This study investigated the influence of NOM on the behavior of plutonium(V) in the vadose zone through a combination of field lysimeter and laboratory studies. Well-defined solid sources of NH4PuVO2CO3(s) placed in 5-L lysimeters containing vadose zone soils NOM-amended or unamended were exposed to natural SRS meteorological conditions for three years. These lysimeters were removed from the field and analyzed using wet chemistry methods and X-ray absorption spectroscopy (XAS). Plutonium desorption from soils recovered from the lysimeters and laboratory batch sorption experiments using Pu-free soils both indicated that surface mediated reduction of Pu(V) to Pu(IV) was influencing Pu sorption behavior. For both lysimeters (amended and unamended with NOM), Pu migrated slowly through the lysimeter core, with > 95% of the Pu remaining within 2 cm of the source. However, without the NOM amendments, Pu was transported significantly farther than in the presence of NOM. Thus, the presence of NOM appeared to decrease the mobility. Working hypotheses to explain this behavior are that 1) formation of ternary surface-NOM-Pu complexes enhanced Pu sorption affinity causing less mobility and/or 2) formation of these ternary surface-NOM-Pu complexes prevented reoxidaiton of Pu(IV) to more mobile Pu(V) in the pore water.

plutonium, organic matter↗
DOE OSTI2016

Segregation and Migration of the Oxygen Vacancies in the 3 (111) Tilt Grain Boundaries of Ceria

In nanocrystalline materials, defect-grain boundary (GB) interaction plays a key role in determining the structure stability, as well as size-dependent ionic, electronic, magnetic and chemical properties. In this study, we systematically investigated using density functional theory segregation and migration of oxygen vacancies at the Σ3 [110] / (111) grain boundary of ceria. Three oxygen layers near the GB are predicted to be segregation sites for oxygen vacancies. Moreover, the presence of oxygen vacancies stabilizes this tilt GB at a low Fermi level and/or oxygen poor conditions. An atomic strain model was proposed to rationalize layer dependency of the relaxation energy for +2 charged oxygen vacancy. The structural origin of large relaxation energies at layers 1 and 2 was determined to be free-volume space that induces ion relaxation towards the GB. Our results not only pave the way for improving the oxygen transport near GBs of ceria, but also provide important insights into engineering the GB structure for better ionic, magnetic and chemical properties of nanocrystalline ceria.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Non-Faradaic Li + Migration and Chemical Coordination across Solid-State Battery Interfaces

Efficient and reversible charge transfer is essential to realizing high-performance solid-state batteries. Efforts to enhance charge transfer at critical electrode–electrolyte interfaces have proven successful, yet interfacial chemistry and its impact on cell function remains poorly understood. Using X-ray photoelectron spectroscopy combined with electrochemical techniques, we elucidate chemical coordination near the LiCoO 2 –LIPON interface, providing experimental validation of space-charge separation. Space-charge layers, defined by local enrichment and depletion of charges, have previously been theorized and modeled, but the unique chemistry of solid-state battery interfaces is now revealed. Here we highlight the non-Faradaic migration of Li+ ions from the electrode to the electrolyte, which reduces reversible cathodic capacity by ~15%. Inserting a thin, ion-conducting LiNbO 3 interlayer between the electrode and electrolyte, however, can reduce space-charge separation, mitigate the loss of Li+ from LiCoO 2 , and return cathodic capacity to its theoretical value. This work illustrates the importance of interfacial chemistry in understanding and improving solid-state batteries.

Gittleson, Forrest S.↗
DOE OSTI2025

In Situ Observation of Ion Migration in a Ferroelectric Ionic Conductor Rb-KTP during Thermal Annealing

Ion exchange in Rb-doped KTiOPO 4 has facilitated significant advancements in ferroelectric domain engineering, yet understanding the underlying mechanisms remains in its infancy. We perform time-of-flight secondary ion mass spectrometry analysis on multiple periodically ion-exchanged and periodically poled Rb-doped KTiOPO 4 samples under different temperatures and annealing durations. The results are compared between annealing in air, which involved ex situ annealing before periodic poling, and vacuum annealing conducted in situ after periodic poling. The Rb + diffusion profile after periodic ion exchange forms a tooth-shaped pattern. We show that in situ annealing causes a surface pinning effect on the nonpolar face, limiting Rb + migration along the polar axis at the surface. Once the pinned layer is removed through milling, the underlying Rb + diffusion is distinctively different from the surface. Additionally, the rate of Rb + diffusion during in situ annealing is linear, while the periodic domain structures remain stable after annealing. These results contribute to understanding the ionic diffusion process in a ferroelectric ionic conductor and using ion exchange to tailor the linear and nonlinear properties of KTiOPO 4 .

36 MATERIALS SCIENCE↗