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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Novel Biocide Based on Cationic Derivative of Psyllium: Surface Modification and Antibacterial Activity

To circumvent the problems (such as volatilization, photolytic decomposition, chemical instability, easy permeability through the skin) associated with low molecular weight antimicrobial agents, our strategy employed graft copolymerization of cationic monomer with the polymeric substrate viz. psyllium husk. The surface graft concentration of quaternary ammonium ion on psyllium was optimized by measuring the extent of grafting in the microwave-induced process. The surface modification of graft copolymers was evident by different physico–chemical techniques like {sup 13}C nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffractometer (XRD), differential scanning calorimetry (DSC), Thermo gravimeteric analysis (TGA), and viscometric study. The synthesized water soluble product resulted good antibacterial activity against Gram positive Staphylococcus aureus and Bacillus anthracis but failed to produce any antibacterial activity against Gram negative Salmonella typhi and Escherichia coli. The reason to failure has been explained on the basis of differences in the electrokinetic property between Gram-positive and Gram-negative bacteria. Optimum minimum inhibitory concentration (MIC) for the polymeric grade which showed good biocidal effect evaluated by both zone of inhibition and absorbance is found at 1000 µg/ml.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Pore-size resolved water vapor adsorption kinetics of white cement mortars as viewed from proton NMR relaxation

The dynamic pore structure of partially saturated cement-based material is rather essential to quantify its mass transport and many other properties. To clarify the influence of water removal and re-entry, the low-field nuclear magnetic resonance technique is employed to characterize the pore structure of two white cement mortars during isopropanol exchange and water vapor adsorption kinetics. It is found that, after isopropanol replacement the pore structures of mortars become remarkably coarsen due to the significant collapse of C-S-H interlayer pores, which are only partly reversible at water re-saturation. Consistently, water vapor adsorption is not a simple progressively filling process from finer to coarser pores, but accompanied by continuous expansion of C-S-H gel adsorbing water in priority. Furthermore, the irrecoverable contraction of C-S-H gel is the physical root of irreversible shrinkage. The smaller BET surface area using nitrogen than water is also attributed to the collapse of interlayer pores after drying.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Study of the ferroelastic phase transition in the tetraethylammonium compound [N(C{sub 2}H{sub 5}){sub 4}]{sub 2}ZnBr{sub 4} by magic-angle spinning and static NMR

The ferroelastic phase transition of tetraethylammonium compound [N(C{sub 2}H{sub 5}){sub 4}]{sub 2}ZnBr{sub 4} at the phase transition temperature (T{sub C}) = 283 K was characterized by magic-angle spinning (MAS) and static nuclear magnetic resonance (NMR), and confirmed by optical polarizing spectroscopy. The structural geometry near T{sub C} was studied in terms of the chemical shifts and the spin-lattice relaxation times T{sub 1ρ} in the rotating frame for {sup 1}H MAS NMR and {sup 13}C cross-polarization (CP)/MAS NMR. The two inequivalent ethyl groups were distinguishable in the {sup 13}C NMR spectrum, and the T{sub 1ρ} results indicate that they undergo tumbling motion above T{sub C} in a coupled manner. From the {sup 14}N NMR results, the two nitrogen nuclei in the N(C{sub 2}H{sub 5}){sub 4}{sup +} ions were distinguishable above T{sub C}, and the splitting in the spectra below T{sub C} was related to the ferroelastic domains with different orientations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Prospects of biomolecule sequencing with the techniques of translocation through nanopores: A review

The interest in the functional properties of biomolecules in native solutions (in particular, their interaction with membranes) constantly increases with accumulation of data on the macromolecular structure, obtained by X-ray diffraction (with synchrotron radiation sources), nuclear magnetic resonance, and mass spectrometry; this interest is closely related to the development of new technologies of sequencing (i.e., determining the sequence of nucleotides in DNA biomolecule). One of the most promising 'physical' approaches to sequencing is the application of methods based on the use of nanochannels or nanopores, through which biomolecules pass in ionic solutions under an electric field applied. A nanopore provides spatial localization of molecules and makes it possible to detect a signal (electric, fluorescent, etc.) from an individual nucleotide. In view of the development of new high-intensity pulsed X-ray sources, the popularity of fluorescence analysis constantly increases. The existing methods for simulating the motion of biomolecules and interpreting their structure, sequencing techniques, and the prospects of further development of investigations in this field are discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Development and validation of a quantitative proton NMR method for the analysis of pregnenolone

Pregnenolone (PREG) is an endogenous steroid frequently sold as an over-the-counter dietary supplement touted to promote neurological and immunological health. While the PREG dietary supplement is added to the diet for health benefits, there are no FDA approved PREG drugs. However, compounded PREG drug products are available to U.S. patients. The FDA works with state regulatory authorities on the oversight of compounding activities, including developing 503A and 503B lists of bulk substances that compounders are permitted to use. PREG is one of the substances publicly nominated to be included on the 503B list. Compounded hormone therapies such as those using PREG are of interest given the lack of standardization in compounded drug products which may increase the possibility of underdosing, overdosing, or contamination. However, no USP monograph currently exists to evaluate the quality of PREG drug substance or product. To address knowledge gaps and assist in quality control, a simple and rapid quantitative proton nuclear magnetic resonance spectroscopy (qNMR) method for the identification and assay of PREG in different types of PREG products was developed and validated. PREG samples were characterized using 1D 1 H and 2D 1 H– 13 C HSQC NMR spectra. The qNMR assay method (taking approximately 10 min per NMR spectrum) was validated for precision, accuracy, specificity, robustness and linearity per ICH Q2(R1) guidance. The method was validated in a range from 0.032 to 3.2 mg/mL. As a proof of concept, seven PREG bulk substance samples, three tablet and two capsule PREG dietary supplements were assessed by the qNMR analytical procedure. NMR data from all tested samples met the expected criteria for identification and assay. The results demonstrate the potential of qNMR for the quality assessment of different types of PREG samples.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2026

Structuring, stochastic behavior, and charge storage capacity of redox-active microemulsions formulated with mixtures of toluene and ionic liquid as oil phase

Oil/water microemulsions (µEs) are promising electrolytes for redox flow batteries (RFBs) as they simultaneously improve charge capacity and ionic conductivity. Here, we report the successful formulation of bicontinuous µEs where the oil phase is a solution of trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide ionic liquid in toluene with redox-active ferrocene. We examined the effect of supporting electrolyte anion (NO 3 – , Cl – , ClO 4 – ) on the structure, reactivity, transport, and electrolytic performance of redox-active µEs. Neutron scattering and nuclear magnetic resonance showed that the domain size increased as Cl – > NO 3 – > ClO 4 – while the ferrocene diffusion coefficient increased as NO 3 – > Cl – > ClO 4 – . Scanning electrochemical microscopy indicated anion-dependent current fluctuations during electrolysis, with ClO 4 – exhibiting the least high-frequency oscillations, which correlate to the highest charge and discharge capacity and reversibility. All ionic liquid containing systems improved the performance of toluene-based µEs, highlighting new design principles for these electrolytes.

diffusion↗
DOE OSTI2014

The investigation of order–disorder transition process of ZSM-5 induced by spark plasma sintering

Based on the amorphization of zeolites, an order–disorder transition method was used to prepare silica glass via Spark Plasma Sintering (SPS). In order to get a better understanding about the mechanism of amorphization induced by SPS, the intermediate products in this process were prepared and characterized by different characterization techniques. X-ray diffraction and High-energy synchrotron X-ray scattering show a gradual transformation from ordered crystal to glass. Local structural changes in glass network including Si–O bond length, O–Si–O bond angle, size of rings, coordination were detected by Infrared spectroscopy and {sup 29}Si magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. Topologically ordered, amorphous material with a different intermediate-range structure can be obtained by precise control of intermediate process which can be expected to optimize and design material. - Graphical abstract: Low-density, ordered zeolites collapse to the rigid amorphous glass through spark plasma sintering. The intermediate-range structure formed in the process of order–disorder transition may give rise to specific property. - Highlights: • Order–disorder transition process of ZSM-5 induced by spark plasma sintering was investigated using several methods including XRD, High-energy synchrotron X-ray scattering, SAXS, IR, NMR, ect. • Order–disorder transition induced by SPS was compared with TIA and PIA. • Three stages has been divided during the whole process. • The collapse temperature range which may give rise to intermediate-range structure has been located.

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

Improving the efficiency of branch-and-bound complete-search NMR assignment using the symmetry of molecules and spectra

Nuclear magnetic resonance (NMR) assignment of small molecules is presented as a typical example of a combinatorial optimization problem in chemical physics. Three strategies that help improve the efficiency of solution search by the branch and bound method are presented: 1. reduction of the size of the solution space by resort to a condensed structure formula, wherein symmetric nuclei are grouped together; 2. partitioning of the solution space based on symmetry, that becomes the basis for an efficient branching procedure; and 3. a criterion of selection of input restrictions that leads to increased gaps between branches and thus faster pruning of non-viable solutions. Although the examples chosen to illustrate this work focus on small-molecule NMR assignment, the results are generic and might help solving other combinatorial optimization problems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Gel nanostructure in alkali-activated binders based on slag and fly ash, and effects of accelerated carbonation

Binders formed through alkali-activation of slags and fly ashes, including ‘fly ash geopolymers’, provide appealing properties as binders for low-emissions concrete production. However, the changes in pH and pore solution chemistry induced during accelerated carbonation testing provide unrealistically low predictions of in-service carbonation resistance. The aluminosilicate gel remaining in an alkali-activated slag system after accelerated carbonation is highly polymerised, consistent with a decalcification mechanism, while fly ash-based binders mainly carbonate through precipitation of alkali salts (bicarbonates at elevated CO{sub 2} concentrations, or carbonates under natural exposure) from the pore solution, with little change in the binder gel identifiable by nuclear magnetic resonance spectroscopy. In activated fly ash/slag blends, two distinct gels (C–A–S–H and N–A–S–H) are formed; under accelerated carbonation, the N–A–S–H gel behaves comparably to fly ash-based systems, while the C–A–S–H gel is decalcified similarly to alkali-activated slag. This provides new scope for durability optimisation, and for developing appropriate testing methodologies. -- Highlights: •C-A-S-H gel in alkali-activated slag decalcifies during accelerated carbonation. •Alkali-activated fly ash gel changes much less under CO{sub 2} exposure. •Blended slag-fly ash binder contains two coexisting gel types. •These two gels respond differently to carbonation. •Understanding of carbonation mechanisms is essential in developing test methods.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Dissipative particle dynamics of diffusion-NMR requires high Schmidt-numbers

We present an efficient mesoscale model to simulate the diffusion measurement with nuclear magnetic resonance (NMR). On the level of mesoscopic thermal motion of fluid particles, we couple the Bloch equations with dissipative particle dynamics (DPD). Thereby we establish a physically consistent scaling relation between the diffusion constant measured for DPD-particles and the diffusion constant of a real fluid. The latter is based on a splitting into a centre-of-mass contribution represented by DPD, and an internal contribution which is not resolved in the DPD-level of description. As a consequence, simulating the centre-of-mass contribution with DPD requires high Schmidt numbers. After a verification for fundamental pulse sequences, we apply the NMR-DPD method to NMR diffusion measurements of anisotropic fluids, and of fluids restricted by walls of microfluidic channels. For the latter, the free diffusion and the localisation regime are considered.

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

A Comprehensive Characterization of Pyrolysis Oil from Softwood Barks

Pyrolysis of raw pine bark, pine, and Douglas-Fir bark was examined. The pyrolysis oil yields of raw pine bark, pine, and Douglas-Fir bark at 500 °C were 29.18%, 26.67%, and 26.65%, respectively. Both energy densification ratios (1.32–1.56) and energy yields (48.40–54.31%) of char are higher than pyrolysis oils (energy densification ratios: 1.13–1.19, energy yields: 30.16–34.42%). The pyrolysis oils have higher heating values (~25 MJ/kg) than bio-oils (~20 MJ/kg) from wood and agricultural residues, and the higher heating values of char (~31 MJ/kg) are comparable to that of many commercial coals. The elemental analysis indicated that the lower O/C value and higher H/C value represent a more valuable source of energy for pyrolysis oils than biomass. The nuclear magnetic resonance results demonstrated that the most abundant hydroxyl groups of pyrolysis oil are aliphatic OH groups, catechol, guaiacol, and p-hydroxy-phenyl OH groups. The aliphatic OH groups are mainly derived from the cleavage of cellulose glycosidic bonds, while the catechol, guaiacol, and p-hydroxy-phenyl OH groups are mostly attributed to the cleavage of the lignin β–O-4 bond. Significant amount of aromatic carbon (~40%) in pyrolysis oils is obtained from tannin and lignin components and the aromatic C–O bonds may be formed by a radical reaction between the aromatic and aliphatic hydroxyl groups. In this study, a comprehensive analytical method was developed to fully understand and evaluate the pyrolysis products produced from softwood barks, which could offer valuable information on the pyrolysis mechanism of biomass and promote better utilization of pyrolysis products.

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

Crystal structure of the PDZ domain of mouse Dishevelled 1 and its interaction with CXXC5

Dishevelled (Dvl) plays a crucial role in Wnt signaling by interacting with membrane-bound receptors and downstream molecules through its PDZ domain. CXXC5 is one of the key molecules that interacts with Dvl and negatively regulates the Wnt/β-catenin pathway in osteoblast differentiation. Recently, the Dvl-CXXC5 interaction has been identified as an excellent target for osteoporosis treatment. Therefore, it is desirable to have detailed structural information for the Dvl-CXXC5 interaction. Although solution structures of the Dvl1 PDZ domain have been reported, a high-resolution crystal structure would provide detailed sidechain information that is essential for drug development. Here, we determined the first crystal structure of the Dvl-1 PDZ domain at a resolution of 1.76 Å, and compared it with its previously reported solution structure. The Dvl1 PDZ domain crystal belonged to the space group H32 with unit-cell parameters a = b = 72.837, c = 120.616, α = β = 90.00, γ = 120.00. The crystal structure of Dvl1 PDZ shared its topology with the previously reported structure determined by nuclear magnetic resonance (NMR); however, the crystal structure was quite different from the solution structure in both the secondary structural region and the ligand-binding pocket. Molecular modeling based on NMR and X-ray crystallographic data yielded detailed information about the Dvl1/CXXC5 interaction, which will be useful for designing inhibitors. - Highlights: • Crystal structure of PDZ domain of Dvl1 has been determined at 1.76 Å resolution. • NMR and X-ray crystal structure of PDZ domain is quite different in both the secondary structure and ligand binding pocket. • Molecular model of the Dvl1 PDZ and DBM peptide complex provides a detailed interaction between Dvl1 and CXXC5. • Dynamics data shows that the peptide binding pocket of the Dvl1 PDZ is stabilized upon CXXC5 binding.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Recalcitrance and structural analysis by water-only flowthrough pretreatment of 13 C enriched corn stover stem

This article presents high temperature water-only continuous flowthrough pretreatment coupled with nuclear magnetic resonance (NMR) as a promising analytical tool to examine the plant cell wall, to understand its recalcitrance (i.e., cell wall resistance to deconstruction), and to probe the chemistry occurring during batch pretreatment of biomass. 13 C-enriched corn stover stems were pretreated at 170 °C for 60 minutes with a hot-water flow rate of 20 mL/min to control fractionation of the cell wall. This approach helped elucidate the nature of plant cell wall chemical recalcitrance and biomass pretreatment chemistry by tracking cell wall fragmentation as a function of time. Fractions of the reactor effluent were collected in a time-resolved fashion and characterized by various NMR techniques to determine the degree and sequence of fragments released, as well as, the chemical composition, molecular structure, and relative molecular weight of those released fragments.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Effect of MHEC on evaporation and hydration characteristics of glue mortar

The influence of methylhydroxyethylcellulose (MHEC) on both moisture distribution and hydration characteristics of glue mortar using nuclear magnetic resonance imaging (NMR) is investigated. MHEC is added to glue mortar in order to control the drying rate by increasing the open time. Besides drying, MHEC might influence hydration characteristics of mortar. In this study, we therefore examined the effect of MHEC on the hydration characteristics of unsealed mortar. Without MHEC, the evaporation time is faster than hydration time and the water distribution is homogeneous in the mortar, resulting in poor hydration. Addition of MHEC > 1.3 wt.% exhibits an evaporation time comparable to the hydration time of mortar. However, in that case, inhomogeneous distribution of water causes differences in the degree of hydration throughout the mortar sample, i.e. the top surface shows poor hydration and the bottom surface shows good hydration, as confirmed by MIP and T{sub 2} relaxation analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Development and validation of time‐domain 1 H‐NMR relaxometry correlation for high‐throughput phenotyping method for lipid contents of lignocellulosic feedstocks

Abstract The bioenergy crops such as energycane, miscanthus, and sorghum are being genetically modified using state of the art synthetic biotechnology techniques to accumulate energy‐rich molecules such as triacylglycerides (TAGs) in their vegetative cells to enhance their utility for biofuel production. During the initial genetic developmental phase, many hundreds of transgenic phenotypes are produced. The efficiency of the production pipeline requires early and minimally destructive determination of oil content in individuals. Current screening methods require time‐intensive sample preparation and extraction with chemical solvents for each plant tissue. A rapid screen will also be needed for developing industrial extraction as these crops become available. In the present study, we have devised a proton relaxation nuclear magnetic resonance ( 1 H‐NMR) method for single‐step, non‐invasive, and chemical‐free characterization of in‐situ lipids in untreated and pretreated lignocellulosic biomass. The systematic evaluation of NMR relaxation time distribution provided insight into the proton environment associated with the lipids in the biomass. It resolved two distinct lipid‐associated subpopulations of proton nuclei that characterize total in‐situ lipids into bound and free oil based on their “molecular tumbling” rate. The T1T2 correlation spectra also facilitated the resolution of the influence of various pretreatment procedures on the chemical composition of molecular and local 1 H population in each sample. Furthermore, we show that hydrothermally pretreated biomass is suitable for direct NMR analysis unlike dilute acid and alkaline pretreated biomass which needs an additional step for neutralization.

pretreatment↗
DOE OSTI2014

Characterization of the fluorescence correlation spectroscopy (FCS) standard Rhodamine 6G and calibration of its diffusion coefficient in aqueous solutions

Precise diffusion measurements of rhodamine 6G (Rh6G) dissolved in D{sub 2}O at concentrations between 50 and 200 μM were carried out in the temperature range from 280 to 320 K using pulsed field gradient nuclear magnetic resonance (PFG-NMR). The obtained diffusion coefficients can be used as a calibration reference in fluorescence correlation spectroscopy (FCS). Besides measuring the diffusivity of Rh6G, the diffusion coefficient of the solvent in the same system could be determined in parallel by PFG-NMR as the resonances of water and Rh6G are well separated in the {sup 1}H NMR spectrum. To analyze the differences due to the isotope effect of the solvent (D{sub 2}O vs. H{sub 2}O), the correlation time τ{sub D} of Rh6G was measured by FCS in both D{sub 2}O and H{sub 2}O. The obtained isotopic correction factor, τ{sub D}(D{sub 2}O)/τ{sub D}(H{sub 2}O) = 1.24, reflects the isotope effect of the solvent´s self-diffusion coefficients as determined previously by PFG-NMR.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Pregnancy is accompanied by larger high density lipoprotein particles and compositionally distinct subspecies

Pregnancy is accompanied by significant physiological changes, which can impact the health and development of the fetus and mother. Pregnancy-induced changes in plasma lipoproteins are well documented, with modest to no impact observed on the generic measure of high density lipoprotein (HDL) cholesterol. However, the impact of pregnancy on the concentration and composition of HDL subspecies has not been examined in depth. In this prospective study, we collected plasma from 24 nonpregnant and 19 pregnant women in their second trimester. Using nuclear magnetic resonance (NMR), we quantified 11 different lipoprotein subspecies from plasma by size, including three in the HDL class. We observed an increase in the number of larger HDL particles in pregnant women, which were confirmed by tracking phospholipids across lipoproteins using high-resolution gel-filtration chromatography. Using liquid chromatography-mass spectrometry (LC-MS), we identified 87 lipid-associated proteins across size-speciated fractions. We report drastic shifts in multiple protein clusters across different HDL size fractions in pregnant females compared with nonpregnant controls that have major implications on HDL function. These findings significantly elevate our understanding of how changes in lipoprotein metabolism during pregnancy could impact the health of both the fetus and the mother.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2013

EXPLORING THE POTENTIAL FORMATION OF ORGANIC SOLIDS IN CHONDRITES AND COMETS THROUGH POLYMERIZATION OF INTERSTELLAR FORMALDEHYDE

Polymerization of interstellar formaldehyde, first through the formose reaction and then through subsequent condensation reactions, provides a plausible explanation for how abundant and highly chemically complex organic solids may have come to exist in primitive solar system objects. In order to gain better insight on the reaction, a systematic study of the relationship of synthesis temperature with resultant molecular structure was performed. In addition, the effect of the presence of ammonia on the reaction rate and molecular structure of the product was studied. The synthesized formaldehyde polymer is directly compared to chondritic insoluble organic matter (IOM) isolated from primitive meteorites using solid-state {sup 13}C nuclear magnetic resonance, Fourier transform infrared, and X-ray absorption near edge structure spectroscopy. The molecular structure of the formaldehyde polymer is shown to exhibit considerable similarity at the functional group level with primitive chondritic IOM. The addition of ammonia to the solution enhances the rate of polymerization reaction at lower temperatures and results in substantial incorporation of nitrogen into the polymer. Morphologically, the formaldehyde polymer exists as submicron to micron-sized spheroidal particles and spheroidal particle aggregates that bare considerable similarity to the organic nanoglobules commonly observed in chondritic IOM. These spectroscopic and morphological data support the hypothesis that IOM in chondrites and refractory organic carbon in comets may have formed through the polymerization of interstellar formaldehyde after planetesimal accretion, in the presence of liquid water, early in the history of the solar system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗