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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 1,585 records · Page 88
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Theory of long-lived nuclear spin states in methyl groups and quantum-rotor induced polarisation

Long-lived nuclear spin states have a relaxation time much longer than the longitudinal relaxation time T{sub 1}. Long-lived states extend significantly the time scales that may be probed with magnetic resonance, with possible applications to transport and binding studies, and to hyperpolarised imaging. Rapidly rotating methyl groups in solution may support a long-lived state, consisting of a population imbalance between states of different spin exchange symmetries. Here, we expand the formalism for describing the behaviour of long-lived nuclear spin states in methyl groups, with special attention to the hyperpolarisation effects observed in {sup 13}CH{sub 3} groups upon rapidly converting a material with low-barrier methyl rotation from the cryogenic solid state to a room-temperature solution [M. Icker and S. Berger, J. Magn. Reson. 219, 1 (2012)]. We analyse the relaxation properties of methyl long-lived states using semi-classical relaxation theory. Numerical simulations are supplemented with a spherical-tensor analysis, which captures the essential properties of methyl long-lived states.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Synthesis and characterization of neopenthyl glycol diolete as a biolubricant base

Neopenthyl glycol is a polyol that is potential to be a good base for biolubricant via esterification process with oleic acid. In this study, esterification reaction between NPG and oleic acid has been carried out in the presence of 2% w/w sulphuric acid (based on weight of FA) as a catalyst to produce NPG dioleate. The temperature for this reaction was 130°C and the molar ration of oleic acid: NPG was 2:1. The time for the reaction was 4 hours. The presence of the ester in the product was confirmed through Fourier Transform Infrared (FTIR) and followed by NPG diolete composition determination via Gas Chromatography (GC-FID). The structure of NPG diolete was confirmed using both proton and carbon Nuclear Magnetic Resonance ({sup 1}H-NMR and {sup 13}C-NMR) analysis. 100% NPG diolete were obtained in this study. The viscosity index of the product is 227, flash point 200°C, pour point −44°C and oxidative stability 177°C.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Multimodality Imaging for the Assessment of Pericardial Diseases

Purpose of Review: The diagnosis of pericardial syndromes, while occasionally straightforward, includes a wide range of pathologies and is often a well-recognized clinical challenge. The aim of this review is to highlight the key role of the various imaging modalities for the diagnosis and management of the spectrum of pericardial diseases. Recent Findings: Cardiac imaging has become an integral part of the diagnostic process often beginning with echocardiography and supported by advanced imaging modalities including computed tomography, magnetic resonance imaging, and positive emission tomography. These modalities go beyond the simple identification of the pericardium, to identifying increased pericardial thickness, active pericardial edema and inflammation, and its effect on cardiac hemodynamics. Summary: Multimodality imaging has significantly facilitated the diagnosis and long-term management of patients with pericardial diseases. The role of these imaging modalities in overall prognosis and prevention remains to be investigated.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2010

Solution NMR characterization of Sgf73(1-104) indicates that Zn ion is required to stabilize zinc finger motif

Zinc finger motif contains a zinc ion coordinated by several conserved amino acid residues. Yeast Sgf73 protein was identified as a component of SAGA (Spt/Ada/Gcn5 acetyltransferase) multi-subunit complex and Sgf73 protein was known to contain two zinc finger motifs. Sgf73(1-104), containing the first zinc finger motif, was necessary to modulate the deubiquitinase activity of SAGA complex. Here, Sgf73(1-104) was over-expressed using bacterial expression system and purified for solution NMR (nuclear magnetic resonance) structural studies. Secondary structure and site-specific relaxation analysis of Sgf73(1-104) were achieved after solution NMR backbone assignment. Solution NMR and circular dichroism analysis of Sgf73(1-104) after zinc ion removal using chelation reagent EDTA (ethylene-diamine-tetraacetic acid) demonstrated that zinc ion was required to maintain stable conformation of the zinc finger motif.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Anneal-induced enhancement of refractive index and hardness of silicophosphate glasses containing six-fold coordinated silicon

A considerable number of optical devices have significantly benefited from the development of phosphate glasses as substrate materials. Introducing silica into sodium phosphate is an effective method to enhance its mechanical and optical properties. Through annealing treatment, the tetrahedral silicon oxide network structure (Si{sup (4)}) can be transformed into an octahedral structure (Si{sup (6)}) with more constraints. Here, we use high-temperature Raman and Nuclear Magnetic Resonance to reveal the mechanism of transformation between the Si{sup (4)} and Si{sup (6)} silicon oxide structures. The increase of the Si{sup (6)} content results in the phosphate glasses having higher refractive index and hardness. Based on this, the refractive index contribution of SiO{sub 6} is obtained.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Silicate species of water glass and insights for alkali-activated green cement

Despite that sodium silicate solutions of high pH are commonly used in industrial applications, most investigations are focused on low to medium values of pH. Therefore we have investigated such solutions in a broad modulus range and up to high pH values (∼14) by use of infrared (IR) spectroscopy and silicon nuclear magnetic resonance ({sup 29}Si-NMR). The results show that the modulus dependent pH value leads to more or less charged species, which affects the configurations of the silicate units. This in turn, influences the alkali-activation process of low CO{sub 2} footprint cements, i.e. materials based on industrial waste or by-products.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Plug-and-Play Methods for Integrating Physical and Learned Models in Computational Imaging: Theory, algorithms, and applications

Plug-and-play (PnP) priors constitute one of the most widely used frameworks for solving computational imaging problems through the integration of physical models and learned models. PnP leverages high-fidelity physical sensor models and powerful machine learning methods for prior modeling of data to provide state-of-the-art reconstruction algorithms. PnP algorithms alternate between minimizing a data fidelity term to promote data consistency and imposing a learned regularizer in the form of an image denoiser. Recent highly successful applications of PnP algorithms include biomicroscopy, computerized tomography (CT), magnetic resonance imaging (MRI), and joint ptychotomography. This article presents a unified and principled review of PnP by tracing its roots, describing its major variations, summarizing main results, and discussing applications in computational imaging. Additionally, we also point the way toward further developments by discussing recent results on equilibrium equations that formulate the problem associated with PnP algorithms.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2010

Metabonomics for detection of nuclear materials processing.

Tracking nuclear materials production and processing, particularly covert operations, is a key national security concern, given that nuclear materials processing can be a signature of nuclear weapons activities by US adversaries. Covert trafficking can also result in homeland security threats, most notably allowing terrorists to assemble devices such as dirty bombs. Existing methods depend on isotope analysis and do not necessarily detect chronic low-level exposure. In this project, indigenous organisms such as plants, small mammals, and bacteria are utilized as living sensors for the presence of chemicals used in nuclear materials processing. Such 'metabolic fingerprinting' (or 'metabonomics') employs nuclear magnetic resonance (NMR) spectroscopy to assess alterations in organismal metabolism provoked by the environmental presence of nuclear materials processing, for example the tributyl phosphate employed in the processing of spent reactor fuel rods to extract and purify uranium and plutonium for weaponization.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2010

Structural insights into mouse anti-apoptotic Bcl-xl reveal affinity for Beclin 1 and gossypol

This study reports the crystal structures of Bcl-xl wild type and three Bcl-xl mutants (Y101A, F105A, and R139A) with amino acid substitutions in the hydrophobic groove of the Bcl-xl BH3 domain. An additional 12 ordered residues were observed in a highly flexible loop between the {alpha}1 and {alpha}2 helices, and were recognized as an important deamidation site for the regulation of apoptosis. The autophagy-effector protein, Beclin 1, contains a novel BH3 domain (residues 101-125), which binds to the surface cleft of Bcl-xl, as confirmed by nuclear magnetic resonance (NMR) spectroscopy and analytical gel-filtration results. Gossypol, a potent inhibitor of Bcl-xl, had a K{sub d} value of 0.9 {mu}M. In addition, the structural and biochemical analysis of five Bcl-xl substitution mutants will provide structural insights into the design and development of anti-cancer drugs.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Bias voltage dependence of the electron spin depolarization in quantum wires in the quantum Hall regime detected by the resistively detected NMR

We performed the resistively-detected nuclear magnetic resonance (RDNMR) to study the electron spin polarization in the non-equilibrium quantum Hall regime. By measuring the Knight shift, we derive source-drain bias voltage dependence of the electron spin polarization in quantum wires. The electron spin polarization shows minimum value around the threshold voltage of the dynamic nuclear polarization.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Proton conduction in biopolymer exopolysaccharide succinoglycan

Protonic currents play a vital role in electrical signalling in living systems. It has been suggested that succinoglycan plays a specific role in alfalfa root nodule development, presumably acting as the signaling molecules. In this regard, charge transport and proton dynamics in the biopolymer exopolysaccharide succinoglycan have been studied by means of electrical measurements and nuclear magnetic resonance (NMR) spectroscopy. In particular, a dielectric dispersion in the system has revealed that the electrical conduction is protonic rather electronic. Besides, our laboratory- and rotating-frame {sup 1}H NMR measurements have elucidated the nature of the protonic conduction, activation of the protonic motion being associated with a glass transition.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2010

The Structure of the Bacterial Oxidoreductase Enzyme DsbA in Complex with a Peptide Reveals a Basis for Substrate Specificity in the Catalytic Cycle of DsbA Enzymes

Oxidative protein folding in Gram-negative bacteria results in the formation of disulfide bonds between pairs of cysteine residues. This is a multistep process in which the dithiol-disulfide oxidoreductase enzyme, DsbA, plays a central role. The structure of DsbA comprises an all helical domain of unknown function and a thioredoxin domain, where active site cysteines shuttle between an oxidized, substrate-bound, reduced form and a DsbB-bound form, where DsbB is a membrane protein that reoxidizes DsbA. Most DsbA enzymes interact with a wide variety of reduced substrates and show little specificity. However, a number of DsbA enzymes have now been identified that have narrow substrate repertoires and appear to interact specifically with a smaller number of substrates. The transient nature of the DsbA-substrate complex has hampered our understanding of the factors that govern the interaction of DsbA enzymes with their substrates. Here we report the crystal structure of a complex between Escherichia coli DsbA and a peptide with a sequence derived from a substrate. The binding site identified in the DsbA-peptide complex was distinct from that observed for DsbB in the DsbA-DsbB complex. The structure revealed details of the DsbA-peptide interaction and suggested a mechanism by which DsbA can simultaneously show broad specificity for substrates yet exhibit specificity for DsbB. This mode of binding was supported by solution nuclear magnetic resonance data as well as functional data, which demonstrated that the substrate specificity of DsbA could be modified via changes at the binding interface identified in the structure of the complex.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Identifying Low pH Active and Lactate-Utilizing Taxa within Oral Microbiome Communities from Healthy Children Using Stable Isotope Probing Techniques

Many human microbial infectious diseases including dental caries are polymicrobial in nature and how these complex multi-species communities evolve from a healthy to a diseased state is not well understood. Although many health- or disease-associated oral microbes have been characterized in vitro, their physiology in vivo in the presence of the complex oral microbiome is difficult to determine with current approaches. In addition, about half of these oral species remain uncultivated to date and little is known except their 16S rRNA sequence. Lacking culture-based physiological analyses, the functional roles of uncultivated microorganisms will remain enigmatic despite their apparent disease correlation. To start addressing these knowledge gaps, we applied a novel combination of in vivo Magnetic Resonance Spectroscopy (MRS) with RNA and DNA based Stable Isotope Probing (SIP) to oral plaque communities from healthy children for temporal monitoring of carbohydrate utilization, organic acid production and identification of metabolically active and inactive bacterial species.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

Historical Material Analysis of DC745U Pressure Pads

As part of the Enhance Surveillance mission, it is the goal to provide suitable lifetime assessment of stockpile materials. This report is an accumulation of historical publication on the DC745U material and their findings. It is the intention that the B61 LEP program uses this collection of data to further develop their understanding and potential areas of study. DC745U is a commercially available silicone elastomer consisting of dimethyl, methyl-phenyl, and methyl-vinyl siloxane repeat units. Originally, this material was manufactured by Dow Corning as Silastic® DC745U at their manufacturing facility in Kendallville, IN. Recently, Dow Corning shifted this material to the Xiameter® brand product line. Currently, DC745U is available through Xiameter® or Dow Corning's distributor R. D. Abbott Company. DC745U is cured using 0.5 wt% vinyl-specific peroxide curing agent known as Luperox 101 or Varox DBPH-50. This silicone elastomer is used in numerous parts, including two major components (outer pressure pads and aft cap support) in the W80 and as pressure pads on the B61. DC745U is a proprietary formulation, thus Dow Corning provides limited information on its composition and properties. Based on past experience with Dow Corning, DC745U is at risk of formulation changes without notification to the costumer. A formulation change for DC745U may have a significant impact because the network structure is a key variable in determining material properties. The purpose of this report is to provide an overview of historical DC745U studies and identify gaps that need to be addressed in future work. Some of the previous studies include the following: 1. Spectroscopic characterization of raw gum stock. 2. Spectroscopic, thermal, and mechanical studies on cured DC745U. 3. Nuclear Magnetic Resonance (NMR) and solvent swelling studies on DC745U with different crosslink densities. 4. NMR, solvent swelling, thermal, and mechanical studies on thermally aged DC745U. 5. NMR, solvent swelling, thermal, and mechanical studies on radiolytically aged DC745U. Each area is reviewed and further work is suggested to improve our understanding of DC745U for systems engineering, surveillance, aging assessments, and lifetime assessment.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Optimal control of the signal-to-noise ratio per unit time of a spin 1/2 particle: The crusher gradient and the radiation damping cases

We show to which extent the signal to noise ratio per unit time of a spin 1/2 particle can be maximized. We consider a cyclic repetition of experiments made of a measurement followed by a radio-frequency magnetic field excitation of the system, in the case of unbounded amplitude. In the periodic regime, the objective of the control problem is to design the initial state of the system and the pulse sequence which leads to the best signal to noise performance. We focus on two specific issues relevant in nuclear magnetic resonance, the crusher gradient and the radiation damping cases. Optimal control techniques are used to solve this non-standard control problem. We discuss the optimality of the Ernst angle solution, which is commonly applied in spectroscopic and medical imaging applications. In the radiation damping situation, we show that in some cases, the optimal solution differs from the Ernst one.

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

Atomic resolution structure of the E. coli YajR transporter YAM domain

Highlights: • We report the crystal structure of the YAM domain of YajR transporter at 1.07 Å. • The YAM dimerization is related to the halogen-dependent high thermal stability. • A belt of poly-pentagonal water molecules was observed in the dimer interface. - Abstract: YajR is an Escherichia coli transporter that belongs to the major facilitator superfamily. Unlike most MFS transporters, YajR contains a carboxyl terminal, cytosolic domain of 67 amino acid residues termed YAM domain. Although it is speculated that the function of this small soluble domain is to regulate the conformational change of the 12-helix transmembrane domain, its precise regulatory role remains unclear. Here, we report the crystal structure of the YAM domain at 1.07-Å resolution, along with its structure determined using nuclear magnetic resonance. Detailed analysis of the high resolution structure revealed a symmetrical dimer in which a belt of well-ordered poly-pentagonal water molecules is embedded. A mutagenesis experiment and a thermal stability assay were used to analyze the putative role of this dimerization in response to changes in halogen concentration.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

NMR relaxation in the spin-1 Heisenberg chain

For this research, we consider the isotropic S = 1 Heisenberg chain with a finite Haldane gap Δ and use state-of-the-art numerical techniques to investigate its dynamical properties at finite temperature, focusing on the nuclear spin-lattice relaxation rate 1/ T 1 measured in nuclear magnetic resonance (NMR) experiments, for instance. In particular, we analyze the contributions from modes with momenta close to q ≈ 0 and q ≈ π as a function of temperature. At higherature we observe spin diffusion, while at lowerature we argue that a simple activated behavior 1/ T 1 exp (-Δ/ T ) can be observed only at temperatures much smaller than the gap Δ.

1-dimensional spin chains↗
DOE OSTI2019

Production of deuterated biomass by cultivation of Lemna minor (duckweed) in D 2 O

The small aquatic plant duckweed, particularly the genus Lemna , widely used for toxicity testing, has been proposed as a potential source of biomass for conversion into biofuels as well as a platform for production of pharmaceuticals and specialty chemicals. Ability to produce deuterium-substituted duckweed can potentially extend the range of useful products as well as assist process improvement. Cultivation of these plants under deuterating conditions was previously been reported to require addition of kinetin to induce growth and was hampered by anomalies in cellular morphology and protein metabolism. Here, we report the production of biomass with 50–60% deuterium incorporation by long-term photoheterotrophic growth of common duckweed Lemna minor in 50% D 2 O with 0.5% glucose. L. minor grown in 50% D 2 O without addition of kinetin exhibited a lag phase twice that of H 2 O-grown controls, before start of log phase growth at 40% of control rates. Compared to continuous white fluorescent light, growth rates increased fivefold for H 2 O and twofold for 50% D 2 O when plants were illuminated at higher intensity with a metal halide lamp and a diurnal cycle of 12-h light/12-h dark. Deuterium incorporation was determined by a combination of 1 H and 2 H nuclear magnetic resonance (NMR) to be 40–60%. The cellulose from the deuterated plants had an average-number degree of polymerization (DP n ) and polydispersity index (PDI) close to that of H 2 O-grown controls, while Klason lignin content was reduced. Furthermore, the only major gross morphological change noted was root inhibition.

59 BASIC BIOLOGICAL SCIENCES↗