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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

The EPED pedestal model and edge localized mode-suppressed regimes: Studies of quiescent H-mode and development of a model for edge localized mode suppression via resonant magnetic perturbations

The EPED model predicts the H-mode pedestal height and width based upon two fundamental and calculable constraints: (1) onset of non-local peeling-ballooning modes at low to intermediate mode number, (2) onset of nearly local kinetic ballooning modes at high mode number. We present detailed tests of the EPED model in discharges with edge localized modes (ELMs), employing new high resolution measurements, and finding good quantitative agreement across a range of parameters. The EPED model is then applied for the first time to quiescent H-mode (QH), finding a similar level of agreement between predicted and observed pedestal height and width, and suggesting that the model can be used to predict the critical density for QH-mode operation. Finally, the model is applied toward understanding the suppression of ELMs with 3D resonant magnetic perturbations (RMP). Combining EPED with plasma response physics, a new working model for RMP ELM suppression is developed. We propose that ELMs are suppressed when a 'wall' associated with the RMP blocks the inward penetration of the edge transport barrier. A calculation of the required location of this 'wall' with EPED is consistent with observed profile changes during RMP ELM suppression and offers an explanation for the observed dependence on safety factor (q{sub 95}).

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Using Low-Field Nuclear Magnetic Resonance and X-Ray Computed Microtomography Imaging to Explore Potential of Microbially-Induced Calcium Carbonate Precipitation Treatment to Seal Shale Fractures

Microbially-induced calcium carbonate precipitation (MICP) is a biological process in which microbially produced urease enzymes convert urea and calcium into solid calcium carbonate (CaCO 3 ) deposits. Studies have shown that MICP can be used to seal fractures in shale, raising the possibility of applying this technology to restimulate fracking wells by plugging underperforming fractures. For this and other applications to become a reality, non-invasive tools are needed to determine how effectively MICP seals shale fractures under subsurface conditions. In this study, a 2.54 cm wide and 5.08 cm long Marcellus shale core with a single, ~1 mm wide fracture held open by sand "proppant" underwent MICP-treatment at 60°C until reaching three orders of magnitude permeability reduction. Low-field nuclear magnetic resonance (LF-NMR) and X-Ray computed microtomography (μ-CT) techniques were used to assess the extent of biomineralization within the fracture. These tools revealed that while CaCO 3 precipitation occurred throughout the fracture, there was preferential precipitation around proppant, and the core sealed at the effluent end before filling most of the fracture. Both tools were able to independently calculate of the amount of solid biomineral formed inside the fracture. Furthermore, this study found that the distribution of proppant within the shale fracture was an important parameter controlling the degree of biomineralization.

clastic rock↗
DOE OSTI2015

Understanding Aqueous Electrolyte Stability through Combined Computational and Magnetic Resonance Spectroscopy: A Case Study on Vanadium Redox Flow Battery Electrolytes

Redox flow battery (RFB) is a promising candidate for energy storage component in designing resilient grid scale power supply due to the advantage of the separation of power and energy. However, poorly understood chemical and thermal stability issues of electrolytes currently limit the performance of RFB. Designing of high performance stable electrolytes requires comprehensive knowledge about the molecular level solvation structure and dynamics of their redox active species. The molecular level understanding of detrimental V2O5 precipitation process led to successful designing of mixed acid based electrolytes for vanadium redox flow batteries (VRFB). The higher stability of mixed acid based electrolytes is attributed to the choice of hydrochloric acid as optimal co-solvent, which provides chloride anions for ligand exchange process in vanadium solvation structure. The role of chloride counter anion on solvation structure and dynamics of vanadium species were studied using combined magnetic resonance spectroscopy and DFT based theoretical methods. Finally, the solvation phenomenon of multiple vanadium species and their impact on VRFB electrolyte chemical stability were discussed.

Comprehensive Solvation Chemistry↗
DOE OSTI2022

Characterization of Heparin’s Conformational Ensemble by Molecular Dynamics Simulations and Nuclear Magnetic Resonance Spectroscopy

Heparin is a highly charged, polysulfated polysaccharide and serves as an anticoagulant. Heparin binds to multiple proteins throughout the body, suggesting a large range of potential therapeutic applications. Although its function has been characterized in multiple physiological contexts, heparin’s solution conformational dynamics and structure–function relationships are not fully understood. Molecular dynamics (MD) simulations facilitate the analysis of a molecule’s underlying conformational ensemble, which then provides important information necessary for understanding structure–function relationships. However, for MD simulations to afford meaningful results, they must both provide adequate sampling and accurately represent the energy properties of a molecule. The aim of this study is to compare heparin’s conformational ensemble using two well-developed force fields for carbohydrates, known as GLYCAM06 and CHARMM36, using replica exchange molecular dynamics (REMD) simulations, and to validate these results with NMR experiments. In this work, the anticoagulant sequence, an ultra-low-molecular-weight heparin, known as Arixtra (fondaparinux, sodium), was simulated with both parameter sets. The results suggest that GLYCAM06 matches experimental nuclear magnetic resonance three-bond J-coupling values measured for Arixtra better than CHARMM36. In addition, NOESY and ROESY experiments suggest that Arixtra is very flexible in the sub-millisecond time scale and does not adopt a unique structure at 25 C. Moreover, GLYCAM06 affords a much more dynamic conformational ensemble for Arixtra than CHARMM36.

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

Interactions of clathrate hydrate promoters sodium dodecyl sulfate and tetrahydrofuran investigated using 1H diffusion nuclear magnetic resonance at hydrate-forming conditions

Thermodynamic hydrate promoters and kinetic hydrate promoters can be used to reduce the P–T conditions for clathrate hydrate synthesis to decrease the nucleation induction time while increasing growth rates. Two commonly used promoters for hydrate research are tetrahydrofuran (THF) and sodium dodecyl sulfate (SDS), which can increase the overall hydrate promotion when used in tandem as compared to individually. There are several molecular theories regarding how SDS promotes hydrate growth. This study explores the micellular theory, for which hydrate formation depends on surfactant aggregates (micelles) at a critical micelle concentration (CMC) to increase the interfacial surface area. The micellular theory is the most investigated and criticized surfactant hydrate promotion theory. To address questions related to micellar behavior, this study investigates the intermolecular behavior between SDS and THF for the identification of micelles at hydrate-forming conditions. The systems explored contained THF at 3 and 5 wt. % with varying concentrations of SDS below and above the CMC. Several methods including a qualitative visual method, conductivity, interfacial tensiometry, 13C Liquid-state Nuclear Magnetic Resonance (NMR) spectroscopy, and 1H diffusion NMR spectroscopy were evaluated at temperatures below the Krafft point of SDS and above 0 °C. The presence of THF at low concentrations decreased the critical temperature for the formation of SDS micelles, where SDS is solubilized in THF/water solution at hydrate-forming temperatures without precipitation. The CMC of SDS was decreased significantly even at hydrate-forming conditions. Mixed surfactant–cosolvent micellular behavior of SDS in the presence of low concentrations of THF was confirmed at hydrate-forming conditions above 0 °C.

Chemistry↗
DOE OSTI2016

Reduction process of nitroxyl spin probes used in Overhauser-enhanced magnetic resonance imaging: An ESR study

The Electron spin resonance studies on the reduction process of nitroxyl spin probes were carried out for 1mM {sup 14}N- labeled nitroxyl radicals in pure water and 1 mM concentration of ascorbic acid as a function of time. The electron spin resonance parameters, such as line width, hyperfine coupling constant, g-factor, signal intensity ratio and rotational correlation time were estimated. The 3-carbamoyl-PROXYL radical has narrowest line width and fast tumbling motion compared with 3-carboxy-PROXYL, 4-methoxy-TEMPO, and 4-acetamido-TEMPO radicals. The half life time and decay rate were estimated for 1mM concentration of {sup 14}N- labeled nitroxyl radicals in 1 mM concentration of ascorbic acid. From the results, the 3-carbamoyl-PROXYL has long half life time and high stability compared with 3-carboxy-PROXYL, 4-methoxy-TEMPO and 4-acetamido-TEMPO radicals. Therefore, this study reveals that the 3-carbamoyl-PROXYL radical can act as a good redox sensitive spin probe for Overhauser-enhanced Magnetic Resonance Imaging.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Scalable subsurface inverse modeling of huge data sets with an application to tracer concentration breakthrough data from magnetic resonance imaging

When characterizing subsurface properties is crucial for reliable and cost-effective groundwater supply management and contaminant remediation. With recent advances in sensor technology, large volumes of hydro-geophysical and geochemical data can be obtained to achieve high-resolution images of subsurface properties. However, characterization with such a large amount of information requires prohibitive computational costs associated with “big data” processing and numerous large-scale numerical simulations. To tackle such difficulties, the Principal Component Geostatistical Approach (PCGA) has been proposed as a “Jacobian-free” inversion method that requires much smaller forward simulation runs for each iteration than the number of unknown parameters and measurements needed in the traditional inversion methods. PCGA can be conveniently linked to any multi-physics simulation software with independent parallel executions. In our paper, we extend PCGA to handle a large number of measurements (e.g. 106 or more) by constructing a fast preconditioner whose computational cost scales linearly with the data size. For illustration, we characterize the heterogeneous hydraulic conductivity (K) distribution in a laboratory-scale 3-D sand box using about 6 million transient tracer concentration measurements obtained using magnetic resonance imaging. Since each individual observation has little information on the K distribution, the data was compressed by the zero-th temporal moment of breakthrough curves, which is equivalent to the mean travel time under the experimental setting. Moreover, only about 2,000 forward simulations in total were required to obtain the best estimate with corresponding estimation uncertainty, and the estimated K field captured key patterns of the original packing design, showing the efficiency and effectiveness of the proposed method. This article is protected by copyright. All rights reserved.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Connection between plasma response and resonant magnetic perturbation (RMP) edge localized mode (ELM) suppression in DIII-D [Connection between plasma response and RMP ELM suppression in DIII-D]

Calculations of the plasma response to applied non-axisymmetric fields in several DIII-D discharges show that predicted displacements depend strongly on the edge current density. This result is found using both a linear two-fluid-MHD model (M3D-C1) and a nonlinear ideal-MHD model (VMEC). Furthermore, it is observed that the probability of a discharge being edge localized mode (ELM)-suppressed is most closely related to the edge current density, as opposed to the pressure gradient. It is found that discharges with a stronger kink response are closer to the peeling–ballooning stability limit in ELITE simulations and eventually cross into the unstable region, causing ELMs to reappear. Thus for effective ELM suppression, the RMP has to prevent the plasma from generating a large kink response, associated with ELM instability. Experimental observations are in agreement with the finding; discharges which have a strong kink response in the MHD simulations show ELMs or ELM mitigation during the RMP phase of the experiment, while discharges with a small kink response in the MHD simulations are fully ELM suppressed in the experiment by the applied resonant magnetic perturbation. The results are cross-checked against modeled 3D ideal MHD equilibria using the VMEC code. The procedure of constructing optimal 3D equilibria for diverted H-mode discharges using VMEC is presented. As a result, kink displacements in VMEC are found to scale with the edge current density, similar to M3D-C1, but the displacements are smaller. A direct correlation in the flux surface displacements to the bootstrap current is shown.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Comparison of Magnetic Resonance Imaging and Computed Tomography for Breast Target Volume Delineation in Prone and Supine Positions

Purpose: To determine whether T2-weighted MRI improves seroma cavity (SC) and whole breast (WB) interobserver conformity for radiation therapy purposes, compared with the gold standard of CT, both in the prone and supine positions. Methods and Materials: Eleven observers (2 radiologists and 9 radiation oncologists) delineated SC and WB clinical target volumes (CTVs) on T2-weighted MRI and CT supine and prone scans (4 scans per patient) for 33 patient datasets. Individual observer's volumes were compared using the Dice similarity coefficient, volume overlap index, center of mass shift, and Hausdorff distances. An average cavity visualization score was also determined. Results: Imaging modality did not affect interobserver variation for WB CTVs. Prone WB CTVs were larger in volume and more conformal than supine CTVs (on both MRI and CT). Seroma cavity volumes were larger on CT than on MRI. Seroma cavity volumes proved to be comparable in interobserver conformity in both modalities (volume overlap index of 0.57 (95% Confidence Interval (CI) 0.54-0.60) for CT supine and 0.52 (95% CI 0.48-0.56) for MRI supine, 0.56 (95% CI 0.53-0.59) for CT prone and 0.55 (95% CI 0.51-0.59) for MRI prone); however, after registering modalities together the intermodality variation (Dice similarity coefficient of 0.41 (95% CI 0.36-0.46) for supine and 0.38 (0.34-0.42) for prone) was larger than the interobserver variability for SC, despite the location typically remaining constant. Conclusions: Magnetic resonance imaging interobserver variation was comparable to CT for the WB CTV and SC delineation, in both prone and supine positions. Although the cavity visualization score and interobserver concordance was not significantly higher for MRI than for CT, the SCs were smaller on MRI, potentially owing to clearer SC definition, especially on T2-weighted MR images.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Emission anomalous optical magnetic resonances in a mixture of even neon isotopes

Unusual resonances have been detected in the dependence of the discharge glow in neon on the longitudinal magnetic field. The resonances appear in fairly high magnetic fields and are observed only at low gas pressures and exclusively in a mixture of {sup 20}Ne and {sup 22}Ne isotopes. This phenomenon is an evidence of collective resonant radiation processes involving atoms of different neon isotopes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

The hydration of reactive cement-in-polymer dispersions studied by nuclear magnetic resonance

The behaviour of two novel cement-in-polymer (c/p) dispersions, namely cement-in-poly(vinyl acetate) and cement-in-poly(vinyl alcohol) upon exposure to water at room temperature was investigated by a combination of various NMR methods. The swelling, cracking, and the water ingress were monitored non-destructively using {sup 1}H single point imaging. The hydration of the cement matrix was investigated using {sup 29}Si NMR whilst {sup 13}C CPMAS NMR spectra allowed the quantification of the kinetics of the hydrolysis reaction of poly(vinyl acetate) into poly(vinyl alcohol). The polymer controls the rate of water ingress and swelling which in turn determines the behaviour of the c/p dispersions upon exposure to water. For the cement-in-poly(vinyl alcohol), the rates of water ingress and swelling are much faster than the hydration of the clinker whilst for the cement-in-poly(vinyl acetate) the slow rates of the two processes allow the formation of a cementious matrix which assures the stability of the sample.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Observation of narrow isotopic optical magnetic resonances in individual emission spectral lines of neon

Narrow resonances are observed in the course of recording the individual emission lines of the glow discharge in the mixture of isotopes {sup 20}Ne and {sup 22}Ne, depending on the strength of the longitudinal magnetic field. The position of resonances in the magnetic scale corresponds to the compensation of the isotopic shift for certain spectral lines due to the Zeeman effect. It is found that the contrast of the resonances is higher for the transitions between the highly excited energy levels, and the resonances themselves are formed in the zone of longitudinal spatial nonuniformity of the magnetic field. (laser applications and other topics in quantum electronics)

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2014

A finite elements method to solve the Bloch–Torrey equation applied to diffusion magnetic resonance imaging

The complex transverse water proton magnetization subject to diffusion-encoding magnetic field gradient pulses in a heterogeneous medium can be modeled by the multiple compartment Bloch–Torrey partial differential equation (PDE). In addition, steady-state Laplace PDEs can be formulated to produce the homogenized diffusion tensor that describes the diffusion characteristics of the medium in the long time limit. In spatial domains that model biological tissues at the cellular level, these two types of PDEs have to be completed with permeability conditions on the cellular interfaces. To solve these PDEs, we implemented a finite elements method that allows jumps in the solution at the cell interfaces by using double nodes. Using a transformation of the Bloch–Torrey PDE we reduced oscillations in the searched-for solution and simplified the implementation of the boundary conditions. The spatial discretization was then coupled to the adaptive explicit Runge–Kutta–Chebyshev time-stepping method. Our proposed method is second order accurate in space and second order accurate in time. We implemented this method on the FEniCS C++ platform and show time and spatial convergence results. Finally, this method is applied to study some relevant questions in diffusion MRI.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Charge-magnetic interference resonant scattering studies of ferromagnetic crystals and thin films

The element- and site-specificity of X-ray resonant magnetic scattering (XRMS) makes it an ideal tool for furthering our understanding of complex magnetic systems. In the hard X-rays, XRMS is readily applied to most antiferromagnets where the relatively weak resonant magnetic scattering (10 -2 –10 -6 I c ) is separated in reciprocal space from the stronger, Bragg charge scattered intensity, I c . In ferro(ferri)magnetic materials, however, such separation does not occur and measurements of resonant magnetic scattering in the presence of strong charge scattering are quite challenging. We discuss the use of charge-magnetic interference resonant scattering for studies of ferromagnetic (FM) crystals and layered films. We review the challenges and opportunities afforded by this approach, particularly when using circularly polarized X-rays. Here we illustrate current capabilities at the Advanced Photon Source with studies aimed at probing site-specific magnetism in ferromagnetic crystals, and interfacial magnetism in films.

36 MATERIALS SCIENCE↗