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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 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Simultaneous oxygen and boron trifluoride functionalization of hexagonal boron nitride: a designer cathode material for energy storage

Covalent functionalization is a way to tune the electrochemical properties of hexagonal boron nitride (h-BN) monolayers. The wide bandgap insulator h-BN may become metallic conductor upon functionalization with strong oxidants, such as (fluorosulfonyl)oxy radicals (·OSO 2 F), as known since 1978 ( Bartlett et al in J Chem Soc Chem Commun 5:200, 1978), with electrical conductivity of 1.5 S/cm (Shen et al in J Solid State Chem 147:74, 1999) that greatly surpasses commercial cathode material Li x CoO 2 while retaining excellent ionic conductivity. Functionalized boron nitrides (FBN-s) have great potential for cathode applications in energy storage devices, for example, in solid-state batteries. While (fluorosulfonyl)oxy functionalization is unlikely to result in rechargeable cathodes, similarly to graphene fluoride (CF x ), some other FBN-s discussed here may do. In the present work, fluorene, oxygen and combined oxygen and boron trifluoride functionalizations are studied, on the basis of band structure calculations. Due to the open surfaces of FBN-s, fast ionic diffusion with Li, Na and Mg ions is possible, enabling batteries with voltages of 2.1–5.6 V, theoretical energy densities of 800–1200 Wh/kg and fast charge and discharge.

Chemistry↗
DOE OSTI2026

QTL Mapping of Seed Fatty Acid Contents in Camelina sativa Under Heat Stress

Heat stress alters oil quality in oilseed crops, yet its genetic underpinnings in Camelina sativa remain unclear. This study investigated the genetic basis of heat-induced changes in seed fatty acids using a recombinant inbred line (RIL) population derived from a cross between two camelina varieties, Suneson and Pryzeth. Exposure to high temperature during reproductive growth led to increased proportions of saturated (C16:0, C18:0) and monounsaturated (C18:1) fatty acids, whereas polyunsaturated C18:3, total unsaturated fatty acids (UFA) and the PUFA/MUFA ratio were decreased, suggesting an inhibition of the C18:1 → C18:2 → C18:3 desaturation pathway. A high-density linkage map (4981 bins across 20 chromosomes) was built, and 25 QTLs for fatty acids were detected, with hotspots on chromosomes 1, 9, 12, 13, 16, and 20. A major QTL on chromosome 1 (~ 80 cM) explained the largest variance component for PUFA/MUFA under heat. Three desaturase genes (FAD2, FAD7, FAD8) were located within key QTL intervals, nominating them as candidates for modulating unsaturation under elevated temperature. These results provide a genetic basis for fine mapping and functional validation, supporting future molecular and breeding efforts to stabilize oil quality under warming conditions.

Camelina↗
DOE OSTI2019

On the relationship between the energy characteristics of the isodesmic reactions of polychlorinated dioxins and their toxicity

Thermodynamic functions (ΔG{sub f} and ΔH{sub f}) of clorinated dibenzo-p-dioxins (Cl{sub n}DD) with n = 0–8 were calculated at the DFT level of theory using the B3LYP functional and extended 6–31** basis sets and used to analyze possible relationship of the structures and energy characteristics of these compounds with their toxicity. A new sequence of successive isodesmic reactions, which makes it possible to calculate chemical potentials μ{sub G} and μ{sub H} from the ΔG{sub f} and ΔH{sub f} values, has been proposed. In the framework of this approach, satisfactory linear correlations between the chemical potentials μ and the logarithms of toxicity of the corresponding polychlorodioxins were obtained for the first time.

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

The string of variable density: Further results

We analyze the problem of calculating the solutions and the spectrum of a string with arbitrary density and fixed ends. We build a perturbative scheme which uses a basis of WKB-type functions and obtain explicit expressions for the eigenvalues and eigenfunctions of the string. Using this approach we show that it is possible to derive the asymptotic (high energy) behavior of the string, obtaining explicit expressions for the first three coefficients (the first two can also be obtained with the WKB method). Finally, using an iterative approach we also obtain analytical expressions for the low energy behavior of the eigenvalues and eigenfunctions of a string with rapidly oscillating density, recovering (in a simpler way) results in the literature. - Highlights: > We devise a perturbative approach to finding the modes of a string with arbitrary density. > We obtain explicitly the first three coefficients of the asymptotic high energy expansion. > We apply our findings to a series of examples, obtaining both analytical and numerical results.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Sinomenine alleviates high glucose-induced renal glomerular endothelial hyperpermeability by inhibiting the activation of RhoA/ROCK signaling pathway

As an early sign of diabetic cardiovascular disease, endothelial dysfunction may contribute to progressive diabetic nephropathy (DN). Endothelial hyperpermeability induced by hyperglycemia (HG) is a central pathogenesis for DN. Sinomenine (SIN) has strong anti-inflammatory and renal protective effects, following an unknown protective mechanism against HG-induced hyperpermeability. We herein explored the role of SIN in vitro in an HG-induced barrier dysfunction model in human renal glomerular endothelial cells (HRGECs). The cells were exposed to SIN and/or HG for 24 h, the permeability of which was significantly increased by HG. Moreover, junction protein occludin in the cell-cell junction area and its total expression in HRGECs were significantly decreased by HG. However, the dysfunction of tight junction and hyperpermeability of HRGECs were significantly reversed by SIN. Furthermore, SIN prevented HG-increased reactive oxygen species (ROS) by activating nuclear factor-E2-related factor 2 (Nrf2). Interestingly, activation of RhoA/ROCK induced by HG was reversed by SIN or ROCK inhibitor. HG-induced hyperpermeability was prevented by SIN. High ROS level, tight junction dysfunction and RhoA/ROCK activation were significantly attenuated with knockdown of Nrf2. Mediated by activation of Nrf2, SIN managed to significantly prevent HG-disrupted renal endothelial barrier function by suppressing the RhoA/ROCK signaling pathway through reducing ROS. We successfully identified a novel pathway via which SIN exerted antioxidative and renal protective functions, and provided a molecular basis for potential SIN applications in treating DN vascular disorders.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Identification and characterization of a novel calmodulin binding site in Drosophila TRP C-terminus

Highlights: • Drosophila TRP 783–862 is a novel calmodulin binding site. • The shortest Ca{sup 2+}-CaM interaction region and core CaM binding sequences in TRP 783–862 were dissected. • Ca{sup 2+}-CaM binding induces helical structure formation of Drosophila TRP 783–862. Transient receptor potential (TRP) channels are a group of essential cation channels involved in many important sensory signal transduction processes, such as light, temperature, tastes and pressure sensing. Drosophila TRP channel is the first discovered family member and plays important roles in photo-transduction in Drosophila. Calmodulin (CaM), an important downstream effector of Ca{sup 2+} signal, was considered as a vital regulator of TRP activities. In this study, we discovered a novel Ca{sup 2+} dependent CaM binding site (TRP 783–862) in between the previously reported two calmodulin binding sites (CBSs). The isothermal titration calorimetry (ITC) and the size exclusion chromatography coupled with multi-angle static light scattering (SEC-MALS) results showed that the dissociation constant (Kd) between TRP 783–862 and Ca{sup 2+}-CaM is 0.10 ± 0.04 μM and their binding stoichiometry is 1:1. In addition, the shortest Ca{sup 2+}-CaM interaction region and core CaM binding sequences in TRP 783–862 were dissected by the boundary mapping and mutagenesis experiments. More interestingly, by comparing the circular dichroism (CD) spectra before and after Ca{sup 2+}-CaM binding, the TRP 783–862 fragment showed Ca{sup 2+}-CaM binding dependent secondary structure changes, indicating that the interaction between CaM and Drosophila TRP channel may have a conformational impact on TRP structure. In summary, by identifying and characterizing a novel CaM binding site in TRP C-terminus, our findings provided a biochemical and structural basis for further in vivo functional studies of Ca{sup 2+}-mediated TRP channel regulation through CaM/TRP interaction.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Investigation of methane and ethane pyrolysis with highly active and durable iron-alumina catalyst to produce hydrogen and valuable nano carbons: Continuous fluidized bed tests and reaction rate analysis

The goal of this research work was to evaluate a novel iron-alumina catalyst for methane and ethane pyrolysis with high conversion rates to H 2 with a long life time to address two major issues reported with previous catalysts. Fluidized bed tests demonstrated continuous hydrogen production while collecting carbon containing fines. During the 230 h fluid bed test the methane conversion rate to hydrogen at 700 °C remained above 80% for 160 h while creating valuable nano carbons. Similarly high catalyst lifetimes with high methane conversions have not been reported before. Ethane was more active than methane for pyrolysis with 100% conversion to H 2 . Transmission electron microscopy and Raman analysis of the carbon showed single and multiwall nanotubes and conglomerate nano-fibers. Ethane did not impact the allotrope of carbon formed. TGA was used to create a data array that was used for kinetic analysis and reaction model parametric regressions. Ethane had a higher rate of pyrolysis that was 2.3–2.8 times that of methane. Ethane pyrolysis was found to be more sensitive to temperature with a higher activation energy of 62 kJ/mol as compared to methane at 43 kJ/mol. The frequency factor, A i , was significantly higher for ethane at 0.73 [[kmol/m 3 -sec]/[N/m2] n ] compared to 0.03 for methane on the same basis. Both gases had a functional partial pressure order dependence of ~0.6 based on the regression analysis.

08 HYDROGEN↗
DOE OSTI2018

Multi-level spectral deferred corrections scheme for the shallow water equations on the rotating sphere

Efficient time integration schemes are necessary to capture the complex processes involved in atmospheric flows over long periods of time. We propose a high-order, implicit–explicit numerical scheme that combines Multi-Level Spectral Deferred Corrections (MLSDC) and the Spherical Harmonics (SH) transform to solve the wave-propagation problems arising from the shallow-water equations on the rotating sphere. The iterative temporal integration is based on a sequence of corrections distributed on coupled space–time levels to perform a significant portion of the calculations on a coarse representation of the problem and hence to reduce the time-to-solution while preserving accuracy. In our scheme, referred to as MLSDC-SH, the spatial discretization plays a key role in the efficiency of MLSDC, since the SH basis allows for consistent transfer functions between space–time levels that preserve important physical properties of the solution. We study the performance of the MLSDC-SH scheme with shallow-water test cases commonly used in numerical atmospheric modeling. We use this suite of test cases, which gradually adds more complexity to the nonlinear system of governing partial differential equations, to perform a detailed analysis of the accuracy of MLSDC-SH upon refinement in time. We illustrate the stability properties of MLSDC-SH and show that the proposed scheme achieves up to eighth-order convergence in time. Finally, we study the conditions in which MLSDC-SH achieves its theoretical speedup, and we show that it can significantly reduce the computational cost compared to single-level Spectral Deferred Corrections (SDC).

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2016

Electronic structure, thermodynamic properties and hydrogenation of LaPtIn and CePtIn compounds by ab-initio methods

The electronic structures and thermodynamic properties of LaPtIn and CePtIn are studied by means of ab-initio full-relativistic full-potential local orbital basis (FPLO) method within densities functional (DFT) methodologies. We have also examined the influence of hydrogen on the electronic structure and stability of CePtInH and LaPtInH systems. The positions of the hydrogen atoms have been found from the minimum of the total energy. Our calculations have shown that band structure and topology of the Fermi surfaces changed significantly during the hydrogenation. The thermodynamic properties (bulk modulus, Debye temperatures, constant pressure heat capacity) calculated in quasi-harmonic Debye-Grüneisen model are in a good agreement with the experimental data. We have applied different methods of the calculation of the equation of states (EOS) (Murnaghan, Birch-Murnaghan, Poirier–Tarantola, Vinet). The thermodynamic properties are presented for the pressure 0<P<9 GPa and the temperature range 0<T<300 K. - Highlights: • Full relativistic band structure of LaPtIn and CePtIn. • Fermi surface of LaPtIn, LaPtInH, CePtIn, CePtInH. • Effect of hydrogenation on the electronic structure of LaPtIn and CePtIn. • Thermodynamic properties in the quasi-harmonic Debye-Grüneisen model.

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

A Molecular Mechanism for Nonphotochemical Quenching in Cyanobacteria

The cyanobacterial orange carotenoid protein (OCP) protects photosynthetic cyanobacteria from photodamage by dissipating excess excitation energy collected by phycobilisomes (PBS) as heat. Dissociation of the PBS–OCP complex in vivo is facilitated by another protein known as the fluorescence recovery protein (FRP), which primarily exists as a dimeric complex. In this work, we used various mass spectrometry (MS)-based techniques to investigate the molecular mechanism of this FRP-mediated process. FRP in the dimeric state (dFRP) retains its high affinity for the C-terminal domain (CTD) of OCP in the red state (OCP r ). Site-directed mutagenesis and native MS suggest the head region on FRP is a candidate to bind OCP. After attachment to the CTD, the conformational changes of dFRP allow it to bridge the two domains, facilitating the reversion of OCPr into the orange state (OCP o ) accompanied by a structural rearrangement of dFRP. Interestingly, we found a mutual response between FRP and OCP; that is, FRP and OCP r destabilize each other, whereas FRP and OCP o stabilize each other. A detailed mechanism of FRP function is proposed on the basis of the experimental results.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Computation of Auger Electron Spectra in Organic Molecules with Multiconfiguration Pair-Density Functional Theory

Efficient and accurate computation of molecular Auger electron spectra for larger systems is limited by the rapid increase in the number of doubly ionized final states as the system size grows. Here, in this work, we benchmark the application of multiconfiguration pair-density functional theory with a restricted active space (RAS) reference wave function for computing the carbon K-edge decay spectra of 20 organic molecules. Decay rates are computed within the one-center approximation. We evaluate the performance of different basis sets and on-top functionals and find that multiconfiguration pair-density functional theory achieves accuracy comparable to RAS followed by second-order perturbation theory, but at significantly lower computational cost.

Fouda, Adam E. A. [Argonne National Laboratory (AN↗
DOE OSTI2016

Photoactive Excited States in Explosive Fe(II) Tetrazine Complexes: A Time-Dependent Density Functional Theory Study

Time-dependent density functional theory was used to investigate optical absorption of novel Fe(II) coordination complexes with tetrazine ligands. These octahedral compounds absorb near-infrared (NIR) light and can be applied as secondary explosives with low laser-initiation thresholds compared to pentaerythritol tetranitrate. Here in this paper, numerous ligand architectures are studied to determine relationships between molecular structure and optical absorption in order to tune the low-energy charge transfer (CT) band. Geometrical structures and vertical excitation energies calculated with the TPSSh density functional and 6-311G basis set are in excellent agreement with experiment, with a maximum deviation from UV–vis spectra of 0.10 eV. By altering molecular substituents of the ligand scaffold, the CT band can be tuned between 500 and 1100 nm. Additional conjugation in the ligand scaffold pushes the CT band into the NIR region of the spectrum. Triazolo-tetrazine ligands shift the CT band by approximately 0.70 eV relative to that of Fe(II) coordinated with bipyridine ligands. Oxygenated analogues of several compounds are also studied in order to predict optical response, while improving explosive performance. A natural population analysis suggests that the high nitrogen content of the ligand scaffolds in these energetic compounds lessens their metal-to-ligand charge transfer character compared to that of Fe(II) coordinated with bipyridine ligands. The proposed model quantum chemistry is used to establish structure–property relationships for optical properties in this class of materials in order to make optical initiation with conventional lasers a more feasible approach.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Binding of Li + to Negatively Charged and Neutral Ligands in Polymer Electrolytes

Conceptually, single-ion polymer electrolytes (SIPE) with the anion bound to the polymer could solve major issues in Li-ion batteries, but their conductivity is too low. Experimentally, weakly interacting anionic groups have the best conductivity. To provide a theoretical basis for this result, density functional theory calculations of the optimized geometries and energies are performed for charged ligands used in SIPE. Comparison is made to neutral ligands found in dual-ion conductors, which demonstrate higher conductivity. Further, the free energy differences between adding and subtracting a ligand are small enough for the neutral ligands to have the conductivity seen experimentally. However, charged ligands have large barriers, implying that lithium transport will coincide with the slow polymer diffusion, as observed in experiments. Overall, SIPE will require additional solvent to achieve a sufficiently high conductivity. Additionally, the binding of mono- and bidentate geometries varies, providing a simple and clear reason that polarizable force fields are required for detailed interactions.

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

Understanding Rubredoxin Redox Sites by Density Functional Theory Studies of Analogues

Determining the redox energetics of redox site analogues of metalloproteins is essential in unraveling the various contributions to electron transfer properties of these proteins. Since studies of the [4Fe-4S] analogues show that the energies are dependent on the ligand dihedral angles, broken symmetry density functional theory (BS-DFT) with the B3LYP functional and double-ζ basis sets calculations of optimized geometries and electron detachment energies of [1Fe] rubredoxin analogues are compared to crystal structures and gas-phase photoelectron spectroscopy data, respectively, for [Fe(SCH3)4]0/1-/2-, [Fe(S2-o-xyl)2]0/1-/2-, and Na+[Fe(S2-oxyl) 2]1-/2- in different conformations. In particular, the study of Na+[Fe(S2-o-xyl)2]1-/2- is the only direct comparison of calculated and experimental gas phase detachment energies for the 1-/2- couple found in the rubredoxins. These results show that variations in the inner sphere energetics by up to ~0.4 eV can be caused by differences in the ligand dihedral angles in either or both redox states. Moreover, these results indicate that the protein stabilizes the conformation that favors reduction. In addition, the free energies and reorganization energies of oxidation and reduction as well as electrostatic potential charges are calculated, which can be used as estimates in continuum electrostatic calculations of electron transfer properties of [1Fe] proteins.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2018

Bacterial microcompartments

We report that bacterial microcompartments (BMCs) are self-assembling organelles that consist of an enzymatic core that is encapsulated by a selectively permeable protein shell. The potential to form BMCs is widespread and found across the kingdom Bacteria. BMCs have crucial roles in carbon dioxide fixation in autotrophs and the catabolism of organic substrates in heterotrophs. They contribute to the metabolic versatility of bacteria, providing a competitive advantage in specific environmental niches. Although BMCs were first visualized more than 60 years ago, it is mainly in the past decade that progress has been made in understanding their metabolic diversity and the structural basis of their assembly and function. This progress has not only heightened our understanding of their role in microbial metabolism but is also beginning to enable their use in a variety of applications in synthetic biology. In this work, we focus on recent insights into the structure, assembly, diversity and function of BMCs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Structural basis for influenza virus NS1 protein block of mRNA nuclear export

Influenza viruses antagonize key immune defence mechanisms via the virulence factor non-structural protein 1 (NS1). A key mechanism of virulence by NS1 is blocking nuclear export of host messenger RNAs, including those encoding immune factors; however, the direct cellular target of NS1 and the mechanism of host mRNA export inhibition are not known. Here, we identify the target of NS1 as the mRNA export receptor complex, nuclear RNA export factor 1–nuclear transport factor 2-related export protein 1 (NXF1–NXT1), which is the principal receptor mediating docking and translocation of mRNAs through the nuclear pore complex via interactions with nucleoporins. We determined the crystal structure of NS1 in complex with NXF1–NXT1 at 3.8 Å resolution. The structure reveals that NS1 prevents binding of NXF1–NXT1 to nucleoporins, thereby inhibiting mRNA export through the nuclear pore complex into the cytoplasm for translation. We demonstrate that a mutant influenza virus deficient in binding NXF1–NXT1 does not block host mRNA export and is attenuated. Here, this attenuation is marked by the release of mRNAs encoding immune factors from the nucleus. In sum, our study uncovers the molecular basis of a major nuclear function of influenza NS1 protein that causes potent blockage of host gene expression and contributes to inhibition of host immunity.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Synergistic enzymatic and microbial lignin conversion

We represent the utilization of lignin for fungible fuels and chemicals and it's one of the most imminent challenges in modern biorefineries. However, bioconversion of lignin is highly challenging due to its recalcitrant nature as a phenolic heteropolymer. This study addressed the challenges by revealing the chemical and biological mechanisms for synergistic lignin degradation by a bacterial and enzymatic system, which significantly improved lignin consumption, cell growth and lipid yield. The Rhodococcus opacus cell growth increased exponentially in response to the level of laccase treatment, indicating the synergy between laccase and bacterial cells in lignin degradation. Other treatments like iron and hydrogen peroxide showed limited impact on cell growth. Chemical analysis of lignin under various treatments further confirmed the synergy between laccase and cells at the chemical level. 31 P nuclear magnetic resonance (NMR) suggested that laccase, R. opacus cell and Fenton reaction reagents promoted the degradation of different types of lignin functional groups, elucidating the chemical basis for the synergistic effects. 31 P NMR further revealed that laccase treatment had the most significant impact for degrading the abundant chemical groups. The results were further confirmed by the molecular weight analysis and lignin quantification by the Prussian blue assay. The cell–laccase fermentation led to a 17-fold increase of lipid production. Overall, the study indicated that laccase and R. opacus can synergize to degrade lignin efficiently, likely through rapid utilization of monomers generated by laccase to promote the reaction toward depolymerization. The study provided a potential path for more efficient lignin conversion and development of consolidated lignin conversion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗