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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Synthesis and Characterization of Hydrophobic Fe{sub 3}O{sub 4} Magnetic Nanoparticles with High Saturation Magnetization

A simple one-step solvothermal method is proposed to prepare hydrophobic Fe{sub 3}O{sub 4} nanoparticles (MNPs) using iron acetylacetonate (Fe(acac){sub 3}), oleylamine (OAm), and ethylene glycol (EG). X-ray powder diffraction, scanning electron microscope, infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectrometry, and vibrating sample magnetometer are used to characterize the structure, morphology, and properties of products. The testing results indicate that the as-synthesized products are spherical-like hydrophobic MNPs, superparamagnetic at room temperature, with a saturation magnetization up to 76.8 emu/g. The good hydrophobic property of MNPs is attributed to the coverage of oleylamine, without causing a remarkable loss of magnetic property. In addition, the influences of material ratio, aging time, oleic acid, and stearic acid used as additives are studied in our research.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Passively Q-switched erbium-doped fiber laser using quantum dots CdSe embedded in polymer film as saturable absorber

We demonstrate a passively Q-switched erbium doped fiber laser (EDFL) based on quantum dots (QD) CdSe as a saturable absorber (SA). The synthesized CdSe powder was embedded into a poly(methyl methacrylate) (PMMA) using emulsion polymerization process. The film is sandwiched between two fiber connector via an adapter to form a fiber-compatible SA device. By integrating the SA device into the EDFL ring cavity, the stable Q-switched operation is achieved at 1559.35 nm as the pump power is varied within 30–118 mW. The laser has a pump threshold of 20.4 mW. The pulse repetition rate shows an increasing trend from 33.2 to 68.45 kHz, whereas the pulse width exhibits a decreasing trend from 10.04 to 4.30 μs as the pump power is increased from 30 to 118 mW. The highest pulse energy of 11.83 nJ is obtained at a pump power of 118 mW. These results indicate that QD CdSe is a promising SA for Q-switching laser operation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Enzymatic esterification of saturated fatty acids with aliphatic alcohols as an alternative method of a low-temperature synthesis of esters

low-temperature synthesis of saturated fatty acid esters with aliphatic alcohols by enzymatic esterification in the presence of heterogeneous biоcatalysts was suggested. The biоcatalysts were prepared by immobilization of recombinant rPichia/lip lipase on mesoporous silica. A comparison of the reaction rates was used to make up a matrix of biоcatalyst activities and determine a pair of acid/alcohol substrates, for which a maximum esterification rate was observed. A high activity of biоcatalysts was observed in the esterification of fatty acids with seven or more carbon atoms in the molecule. The rate of esterification of fatty acids with primary alcohols (n-C{sub 3}—C{sub 16} or iso-С{sub 5}) was two orders of magnitude higher than that with secondary alcohols (sec-С{sub 3}—С{sub 4}). The silica-immobilized rPichia/lip lipase possessed a high operational stability; the biocatalyst operated without loss of activity for hun-dreds of hours at 18—22 °С in a non-traditional for enzymes medium of organic solvents.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2011

Transport of Explosive Residue Surrogates in Saturated Porous Media

Department of Defense operational ranges may become contaminated by particles of explosives residues (ER) as a result of low-order detonations of munitions. The goal of this study was to determine the extent to which particles of ER could migrate through columns of sandy sediment, representing model aquifer materials. Transport experiments were conducted in saturated columns (2×20 cm) packed with different grain sizes of clean sand or glass beads. Fine particles (approximately 2 to 50 μm) of 2,6- dinitrotoluene (DNT) were used as a surrogate for ER. DNT particles were applied to the top 1 cm of sand or beads in the columns, and the columns were subsequently leached with artificial groundwater solutions. DNT migration occurred as both dissolved and particulate phases. Concentration differences between unfiltered and filtered samples indicate that particulate DNT accounted for up to 41% of the mass recovered in effluent samples. Proportionally, more particulate than dissolved DNT was recovered in effluent solutions from columns with larger grain sizes, while total concentrations of DNT in effluent were inversely related to grain size. Of the total DNT mass applied to the uppermost layer of the column, <3% was recovered in the effluent with the bulk remaining in the top 2 cm of the column. Our results suggest there is some potential for subsurface migration of ER particles and that most of the particles will be retained over relatively short transport distances.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Robust H{sub ∞} control for singular time-delay systems with saturating actuators via static output feedback

The problem of H{sub ∞} robust exponential stability and static output feedback stabilization of uncertain singular time-delay systems with saturating actuators are investigated. First, the delay-dependent condition is given to guarantee that the singular time-delay systems are not only exponential admissible, but also satisfies H{sub ∞} performance γ. Moreover, the estimation of stability region and the design method of H{sub ∞} static output feedback controller are given by solving a convex optimization problem. Some simulation examples are provided to demonstrate the merit of the proposed design methods.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

H{sub ∞} memory feedback control for uncertain singular Markov jump systems with time-varying delay and input saturation

This paper concerns with the H{sub ∞} robust exponential stability and memory state feedback stabilization of singular Markov jump systems with time-delay and input saturation. Linear matrix inequality conditions are given to guarantee regularity, impulse-freeness and exponential stability for the singular Markov jump system. Moreover, sufficient conditions are presented to ensure the H{sub ∞} disturbance attenuation level, and the design method of memory feedback controller is developed by solving linear matrix inequalities optimization problem without any decompositions of system matrices and equivalent transformation. Furthermore, the function in the proof procedure belongs to multiple Lyapunov-like functions whose advantage lies in their flexibility. Finally, numerical examples are employed to verify the effectiveness of the proposed methods and to illustrate the significant improvement on the conservativeness of some reported results in the literature.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2013

Saturated fatty acid palmitate induces extracellular release of histone H3: A possible mechanistic basis for high-fat diet-induced inflammation and thrombosis

Highlights: •High-fat diet feeding and palmitate induces the release of nuclear protein histone H3. •ROS production and JNK signaling mediates the release of histone H3. •Extracellular histones induces proinflammatory and procoagulant response. -- Abstract: Chronic low-grade inflammation is a key contributor to high-fat diet (HFD)-related diseases, such as type 2 diabetes, non-alcoholic steatohepatitis, and atherosclerosis. The inflammation is characterized by infiltration of inflammatory cells, particularly macrophages, into obese adipose tissue. However, the molecular mechanisms by which a HFD induces low-grade inflammation are poorly understood. Here, we show that histone H3, a major protein component of chromatin, is released into the extracellular space when mice are fed a HFD or macrophages are stimulated with the saturated fatty acid palmitate. In a murine macrophage cell line, RAW 264.7, palmitate activated reactive oxygen species (ROS) production and JNK signaling. Inhibitors of these pathways dampened palmitate-induced histone H3 release, suggesting that the extracellular release of histone H3 was mediated, in part, through ROS and JNK signaling. Extracellular histone activated endothelial cells toexpress the adhesion molecules ICAM-1 and VCAM-1 and the procoagulant molecule tissue factor, which are known to contribute to inflammatory cell recruitment and thrombosis. These results suggest the possible contribution of extracellular histone to the pathogenesis of HFD-induced inflammation and thrombosis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Saturated fatty acids-induced miR-424–5p aggravates insulin resistance via targeting insulin receptor in hepatocytes

Highlights: • miR-424–5p expression is upregulated by SFA or HFD-induced obesity in hepatocytes. • Mechanistically, miR-424–5p targets 3′UTR of INSR directly, thereby downregulating INSR at the post-transcriptional step. • The ectopic expression of miR-424–5p impairs insulin signaling and insulin-induced glycogen synthesis in hepatocytes. • This study highlights the potential role of miR-424–5p in the insulin signaling pathway through the repression of INSR. The excessive intake of saturated fatty acids (SFA) causes obesity and liver steatosis, which are major risk factors for insulin resistance and type 2 diabetes. Although the expression of certain microRNAs (miRNAs) targeting the insulin signaling molecules are regulated aberrantly in SFA-induced obesity, their implications on hepatic insulin resistance are largely unknown. This study examined the associations of miR-424–5p, which is induced by SFA, with the development of insulin resistance. SFA palmitate (PA)-treated HepG2 cells and high fat diet (HFD)-induced obese mouse livers showed an impairment of insulin signaling due to a significant decrease in INSR and IRS-1 expression. Based on expression profiling and qRT-PCR analysis, miR-424–5p, which presumably targets the 3′UTR of INSR, was upregulated in both PA-treated HepG2 cells and the liver of HFD-fed mice. miR-424–5p was found to target the 3′UTR of INSR directly and downregulated INSR expression at the post-transcriptional step. Furthermore, the overexpression of miR-424–5p suppressed INSR expression significantly, leading to impaired insulin signaling and glycogen synthesis in hepatocytes. A novel mechanism for how SFA-induced miR-424–5p impairs insulin signaling through the targeting of INSR is reported. In addition, the crucial role and underlying mechanism of miR-424–5p in the obesity-induced hepatic insulin resistance is explained.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Effects of saturated lightweight sand content on key characteristics of ultra-high-performance concrete

In this study, 0 to 75% volume of river sand was replaced by an equivalent amount of pre-saturated lightweight sand (LWS) to enhance mechanical properties and reduce autogenous shrinkage of ultra-high-performance concrete (UHPC). The use of LWS is demonstrated to effectively decelerate and reduce the drop in internal relative humidity and autogenous shrinkage of UHPC. Isothermal calorimetry and thermal gravimetry results showed that the use of LWS promoted cement hydration degree after 28 d of hydration. Mercury intrusion porosimetry and scanning electron microscope analyses revealed that the porosity was decreased and interface properties between sand and cement matrix is enhanced by use of LWS up to 25%. The optimum replacement ratio of LWS to river sand was found to be 25%, which resulted in the highest compressive strength (168 MPa at 91 d), flexural strength (24 MPa at 28 d), and autogenous shrinkage limited to 365 μm/m at 28 d.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Hygro-thermo-mechanical modeling of partially saturated air-entrained concrete containing dissolved salt and exposed to freeze-thaw cycles

Highlights: • A model for cyclic freezing of air-entrained concrete containing salt is proposed. • The freeze-thaw hysteresis, also including the effect of dissolved salt, is modeled. • The diffusive and convective flux of salt is coupled to the freeze-thaw processes. • The freeze-thaw response of air-entrained concrete containing salt is reproduced. • Liquid absorption from reservoirs increases with an increased concentration of salt. In cold regions, understanding the freeze-thaw behavior of air-entrained concrete is important for designing durable structures and assessing the remaining service life of existing structures. This study presents a hygro-thermo-mechanical multiphase model that describes the cyclic freeze-thaw behavior of partially saturated air-entrained concrete containing dissolved salt. An equilibrium and a non-equilibrium approach are adopted to model the ice formation, including the freeze-thaw hysteresis, inside the porous network. The model also considers the diffusive and convective transport of the dissolved salt coupled to the freeze-thaw processes. Two examples are presented to verify and highlight the capabilities of the model. The first example shows that the model is capable of reproducing the experimentally observed mechanical response of specimens containing NaC1-solutions of different concentrations. In the second example, a larger absorption of liquid from an external reservoir is obtained with an increasing salt concentration in the reservoir, which is consistent with experimental observations.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Transport of fluorescently labeled hydroxyapatite nanoparticles in saturated granular media at environmentally relevant concentrations of surfactants

Hydroxyapatite nanoparticle (nHAP) is being used to remediate soils and aquifers contaminated with metals and radionuclides; however, the mobility of nHAP is still poorly understood in subsurface granular environments. In this study, transport and retention kinetics of alizarin red S (ARS)-labeled nHAP were investigated in water-saturated quartz sand at low concentrations of surfactants: sodium dodecyl benzene sulfonate (SDBS, an anionic surfactant, 0–50 mg L–1) and cetyltrimethylammonium bromide (CTAB, a cationic surfactant, 0–5 mg L–1). Both surfactants were found to have a marked effect on the electrokinetic properties of ARS-nHAP and, consequently, on their transport and retention behaviors. Transport of nanoparticles (NPs) increased significantly with increasing SDBS concentration, largely because of enhanced colloidal stability and reduced aggregate size arising from enhanced electrostatic, osmotic, and elastic-steric repulsions between ARS-nHAP and sand grains. Conversely, transport decreased significantly in the presence of increasing CTAB concentrations due to reduced surface charge and consequential enhanced aggregation of the NPs. Osmotic and elastic-steric repulsions played only a minor role in enhancing the colloidal stability of ARS-nHAP in the presence of CTAB. Retention profiles of ARS-nHAP exhibited hyperexponential-shapes (decreasing rates of retention with increasing distance) for all conditions tested, and became more pronounced as CTAB concentration increased. The phenomenon was attributed to the aggregation and ripening of ARS-nHAP in the presence of surfactants, particularly CTAB. Overall, the present study suggests that surfactants at environmentally relevant concentrations may be an important consideration in employing nHAP for engineered in-situ remediation of certain metals and radionuclides in contaminated soils and aquifers.

Wang, Dengjun↗
DOE OSTI2013

Clay hydration/dehydration in dry to water-saturated supercritical CO2: Implications for caprock integrity

Injection of supercritical CO2 (scCO2) for the geologic storage of carbon dioxide will displace formation water, and the pore space adjacent to overlying caprocks could eventually be dominated by dry to water-saturated scCO2. Wet scCO2 is highly reactive and capable of carbonating and hydrating certain minerals, whereas anhydrous scCO2 can dehydrate water-containing minerals. Because these geochemical processes affect solid volume and thus porosity and permeability, they have the potential to affect the long-term integrity of the caprock seal. In this study, we investigate the swelling and shrinkage of an expandable clay found in caprock formations, montmorillonite (Ca-STx-1), when exposed to variable water-content scCO2 at 50 °C and 90 bar using a combination of in situ probes, including X-ray diffraction (XRD), in situ magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), and in situ attenuated total reflection infrared spectroscopy (ATR-IR). We show that the extent of montmorillonite clay swelling/shrinkage is dependent not only on water hydration/dehydration, but also on CO2 intercalation reactions. Our results also suggest a competition between water and CO2 for interlayer residency where increasing concentrations of intercalated water lead to decreasing concentrations of intercalated CO2. Overall, this paper demonstrates the types of measurements required to develop fundamental knowledge that will enhance modeling efforts and reduce risks associated with subsurface storage of CO2.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2018

Effect of HCO 3 - on electrochemical kinetics of carbon steel corrosion in CO 2 -saturated brines

The effect of HCO 3 – (aq) on CO 2 corrosion of carbon steel was investigated in deaerated 3.5 wt% NaCl solutions at 30 °C from pH 3.96 to 7.15. In the CO 2 -saturated solutions, the pH was adjusted with different HCO 3 – (aq) concentrations, c[HCO 3 – (aq)]. The corrosion rate decreased by a factor of 2 as the pH and c[HCO 3 – (aq)] increased. The cathodic current density during polarization increased at higher pH with higher c[HCO 3 – (aq)], indicating that HCO 3 – (aq) acted as an additional hydrogen source for the hydrogen evolution reaction. As the pH increased, the active dissolution regions displayed similar anodic Tafel slopes and suggested a modified Bockris mechanism for the Fe oxidation reaction. The exchange current densities for the half reactions were calculated to study kinetics of the anodic and cathodic half reactions independently. The anodic exchange current density ( j 0,a ) increased by one order of magnitude in the presence of CO 2 , indicating the involvement of CO 2 (aq) in the Fe oxidation reaction. As the pH and c[HCO 3 – (aq)] increased, the cathodic exchange current density ( j 0,c ) decreased by a factor of 50 because the increase in j 0,c [HCO 3 – (aq)] was not high enough to compensate the decline from the other hydrogen sources, especially j 0,c [H + (aq)]; and j 0,a decreased by a factor of 2.4 because HCO 3 – (aq) may have competed with CO 2 (aq) for the surface coverage and the increase in j 0,a [CO 2 (aq)] could not compensate the decrease in j 0,a [CO 2 (aq)]. It suggests that the reaction rate constant of HCO 3 – (aq) was smaller than CO 2 (aq) for the anodic half reaction and was smaller than H + (aq) for the cathodic half reaction. The XPS results verified that the corrosion products transitioned from iron carbonate to hydroxide as the pH increased while iron carbonate remained the major product. As the pH increased with HCO 3 – (aq), a second time constant was observed at lower frequencies of the electrochemical impedance spectroscopy (EIS) results.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Geochemical reactions and alteration of pore architecture in saturated shale after injection of stimulation fluid

Pore architecture regulates fluid flow between unconventional shale reservoir and hydraulically-induced fractures. Imbibition of stimulation fluid may change this architecture and alter hydrocarbon flow. Hydrothermal experiments were conducted at reservoir conditions (125 °C, 45 MPa) to test two hypotheses: 1) Shale, not stimulation fluid, dominates the geochemistry of an unconventional reservoir containing formation water; and 2) Mineral dissolution and precipitation induced by stimulation fluid is transient and manifests across micro-, meso-, and macro-scales of pore architecture. Experiments replicated a shut-in well in the Cretaceous Baxter Shale, Green River Basin, Wyoming USA. Stimulation fluid was injected into one experiment after formation water (I = 0.35 mol/kg, pH = 6.4) and core reacted for 48 days. This novel approach equilibrated rock and formation water and saturated pores with formation water before introducing stimulation fluid. The second experiment served as a control. Trends of aqueous calcium, silica and aluminum in the injection experiment suggest transient dissolution of calcite and feldspar and/or quartz as well as clay and barite precipitation; mineralogic evidence was limited to calcite dissolution and barite precipitation. The rock maintained reducing conditions (Eh = +0.08 to -0.16 V) despite injection of oxidizing stimulation fluid (Eh = 1.1 V). pH of the stimulation fluid-formation water mixture evolved from 2.3 to pre-injection values (~6) within 24 h. The results indicate that mineral dissolution and precipitation manifest in macropores with barely detectable alteration to micro- and mesopores. Formation water or organic matter in pores may have inhibited access of stimulation fluid to micro- and mesopores

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Reaction of Water-Saturated Supercritical CO2 with Forsterite: Evidence for Magnesite Formation at Low Temperatures

The nature of the reaction products that form on the surfaces of nanometer-sized forsterite particles during reaction with H2O saturated supercritical CO2 (scCO2) at 35 C and 50 C were examined under in situ conditions and ex situ following reaction. The in situ analysis was conducted by X-ray diffraction (XRD). Ex situ analysis consisted of scanning electron microscopy (SEM) examination of the surface phases and chemical characterization of precipitates using a combination of confocal Raman spectroscopy, 13C and 29Si NMR spectroscopy, and energy-dispersive X-ray Spectroscopy (EDS). The results show that the forsterite surface is highly reactive with the primary reaction products being a mixture of nesquehonite (MgCO3.3H2O) and magnesite (MgCO3) at short reaction times ({approx}3-4 days) and then magnesite (MgCO3) and a highly porous amorphous silica phase at longer reaction times (14 days). After 14 days of reaction most of the original forsterite transformed to reaction products. Importantly, the formation of magnesite was observed at temperatures much lower (35 C) than previously thought needed to overcome its well known sluggish precipitation kinetics. The conversion of nesquehonite to magnesite liberates H2O which can potentially facilitate further metal carbonation, as postulated by previous investigators, based upon studies at higher temperature (80 C). The observation that magnesite can form at lower temperatures implies that water recycling may also be important in determining the rate and extent of mineral carbonation in a wide range of potential CO2 storage reservoirs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Change in T2-Fat Saturation MRI Correlates With Outcome in Cervical Cancer Patients

Purpose: To compare pretreatment and midtreatment tumor intensity as measured by T2 fat-saturation (T2-FS) MRI and its association with treatment response in cervical cancer patients. Methods and Materials: Weekly MRI scans were performed for brachytherapy planning on 23 consecutive patients with clinical Stage IB1 to IIIB cervical cancer treated with definitive chemoradiotherapy. These scans were performed on a 1.5-T clinical scanner using a specialized pelvic coil. Mean signal intensity from T2-FS imaging was calculated for each tumor voxel. Average tumor intensity and tumor volume were recorded pre- and midtreatment (at Weeks 0 and 4). All patients subsequently underwent routine follow-up, including periodic clinical examinations and fluorodeoxyglucose-positron emission tomography imaging. Results: Mean follow-up for surviving patients was 14.5 months. Mean tumor volume at presentation was 49.6 cc, and mean midtreatment tumor volume was 16.0 cc. There was no correlation between initial tumor volume and pretreatment signal intensity (r = 0.44), nor was there a correlation between pre- or midtreatment tumor volume with disease-free survival (p = 0.18, p = 0.08 respectively.) However, having at least a 30% drop in signal intensity from pretreatment to midtreatment was correlated with having disease resolution on posttreatment fluorodeoxyglucose-positron emission tomography imaging (p = 0.05) and with disease-free survival (p = 0.03.) Estimated disease-free survival at 22 months was 100% for patients with at least a 30% drop in tumor signal intensity compared with 33% for patients above this selected threshold (p = 0.004). Conclusions: Longitudinal changes in T2-FS tumor intensity during chemoradiation correlated with disease-free survival in cervical cancer patients. Persistently high midtreatment tumor intensities correlated with a high risk of treatment failure, whereas large decreases in tumor intensity correlated with a favorable outcome.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

Simulation of dilatancy-controlled gas migration processes in saturated bentonite using a coupled multiphase flow and elastoplastic H 2 M model

Dilatancy-controlled gas flow in preferential pathways plays a key role in the safety analysis of radioactive waste repositories. This is particularly the case for bentonite, an often-preferred barrier material. Gas flow in preferential pathways is characterized by localization and spontaneous behavior, which is challenging to simulate in numerical models due to strong hydro-mechanical coupling. To analyze a laboratory experiment in the framework of the DECOVALEX-2023 project, this study introduced a new approach of combining continuous modelling methods with spatial material properties derived from material heterogeneities and experimental observations. The proposed model utilized hydro-mechanical spatial distributions, namely Young's modulus and gas entry pressure, and elastoplasticity combined with a linear swelling model. A conceptual strain-dependent permeability approach simulated dilatancy-controlled gas flow based on hydro-mechanical coupling. To test the effectiveness of the presented approach, a gas injection test in a compacted, saturated bentonite sample was simulated using the open-source code OpenGeoSys 5.8 and compared with experimental observations. The presented methodology is capable of simulating localized gas flow in preferential pathways. The spatial distributions of Young's modulus and gas entry pressure affect the swelling pressure, relative permeability and, in combination with the strain-dependent permeability model, also the intrinsic permeability.

42 ENGINEERING↗