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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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Electro-kinetic Separation of Rare Earth Elements Using a Redox-Active Ligand
Not provided.
From Isolated Ions to Multilayer Functional Materials Using Ion Soft Landing
The ability to deposit intact polyatomic ions with well-defined composition, charge state, and kinetic energy onto surfaces makes preparative mass spectrometry, also called ion soft-landing, particularly attractive for preparing uniform molecular and ionic layers. Early studies characterized structures, charge states, and reactivity of sparsely distributed soft-landed species. Recent development of high-flux ionization sources has opened up new opportunities for the precisely-controlled preparation of both two-dimensional assemblies and three-dimensional multilayer architectures using ion soft-landing. Previously unknown phenomena have been uncovered following deposition of large numbers of ions onto supports thereby opening several exciting research directions in this field. Furthermore, faster ion deposition has enabled fabrication of novel functional devices. This review discusses important phenomena and highlights key developments pertaining to preparation of well-defined interfaces for studies in energy storage, catalysis, soft materials, and biology.
Photoenzymatic Hydrogenation of Heteroaromatic Olefins Using 'Ene'-Reductases with Photoredox Catalysts
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Rates of Ligand Exchange around the Bis-Oxalato Complex [NpO 2 (C 2 O 4 ) 2 ] 3- Measured by Using Multinuclear NMR Spectroscopy under Neutral to Semi-Alkaline Conditions [Rates of ligand exchange around the bis-oxalato complex NpO2(C2O4)23- measured using multinuclear NMR at neutral to semi-alkaline conditions]
The kinetics of ligand exchange between the free oxalate ion, C 2 O 4 2- , and the bis-oxalato Np V complex, [NpO 2 (C 2 O 4 ) 2 ] 3- , in aqueous solution are reported by using 13 C and 17 O NMR spectroscopy methods. Rates of exchange were measured in the pH regime of 6.5–9.0, at which speciation is shown to be suitably simple. Because the neptunium(V) complex is paramagnetic, the rates of ligand exchange were estimated by following the width of the 13 C and 17 O signals assigned to the free oxalate ion in solution and by applying the Swift–Connick method for measuring rates of exchange. A set of experiments were conducted in which pH and total oxalate concentration were varied, and the linear dependence of the rate on these parameters was demonstrated. Variable-temperature NMR spectroscopy was also performed to measure activation parameters of complexation. Finally, at pH<8.0, ΔH ≠ =16.9 ±4.9 kJ mol -1 and ΔS≠=-116.3 ±17.1kJ mol -1 K -1 , whereas at pH>8.0 there is almost no dependence on temperature, which is interpreted to indicate that hydrolysis is coupled to ligand exchange under these conditions.
Modeling Magneto‐Photoabsorption Using Time‐Dependent Complex Generalized Hartree‐Fock
Abstract Magneto‐optical spectroscopy provides a glimpse into the hidden electronic structure of molecules and materials that normally cannot be resolved with regular optical absorption spectroscopy. The magneto‐optical signal is difficult to simulate computationally due to the necessity of modeling perturbations from both uniform magnetic and oscillating electric fields. In this work, we introduce a time‐dependent complex generalized Hartree‐Fock framework for calculating electronic magneto‐optical spectra of atomic and molecular systems. Complex‐valued gauge including atomic orbitals are used in a non‐perturbative treatment of the uniform magnetic field. The magneto‐photoabsorption spectra of atomic alkalis and aromatic systems are investigated with a focus on understanding how spectroscopic signals change in the presence of a uniform magnetic field.
One-Pot Process for Hydrodeoxygenation of Lignin to Alkanes Using Ru-Based Bimetallic and Bifunctional Catalysts Supported on Zeolite Y
The synthesis of high-efficiency and low-cost multifunctional catalysts for hydrodeoxygenation (HDO) of waste lignin into advanced biofuels is crucial for enhancing current biorefinery processes. Inexpensive transition metals, including Fe, Ni, Cu, Zn, were severally co-loaded with Ru on HY zeolite to form bimetallic and bifunctional catalysts. These catalysts were subsequently tested for HDO conversion of softwood lignin and several lignin model compounds. Results indicated that the inexpensive earth abundant metals could modulate the hydrogenolysis activity of Ru and decrease the yield of low molecular weight gaseous side-products. Among all the prepared catalysts, Ru-Cu/HY showed the best HDO performance, giving the highest selectivity to hydrocarbon products. The improved catalytic performance of Ru-Cu/HY was probably due to the following three factors: (1) high total and strong acid sites, (2) good dispersion of metal species and limited segregation, (3) high adsorption capacity for polar fractions, including hydroxyl groups and ether bonds. Moreover, all the bifunctional catalysts were proven to be superior over the combination catalysts of Ru/Al2O3 and HY zeolite, and this could be attributed to the “intimacy criterion”. The practical use of the designed catalysts would be promising in lignin valorization.
Incorporating variability in simulations of seasonally forced phenology using integral projection models
Phenology models are becoming increasingly important tools to accurately predict how climate change will impact the life histories of organisms. We propose a class of integral projection phenology models derived from stochastic individual-based models of insect development and demography. Our derivation, which is based on the rate-summation concept, produces integral projection models that capture the effect of phenotypic rate variability on insect phenology, but which are typically more computationally frugal than equivalent individual-based phenology models. We demonstrate our approach using a temperature-dependent model of the demography of the mountain pine beetle (Dendroctonus ponderosae Hopkins), an insect that kills mature pine trees. This work illustrates how a wide range of stochastic phenology models can be reformulated as integral projection models. Due to their computational efficiency, these integral projection models are suitable for deployment in large-scale simulations, such as studies of altered pest distributions under climate change.
Using phenology to unravel differential soil water use and productivity in a semiarid savanna
Savannas are water-limited ecosystems characterized by two dominant plant types: trees and an understory primarily made up grass. Different phenology and root structures of these plant types complicate how savanna primary productivity responds to changes in water availability. We tested the hypothesis that productivity in savannas is controlled by the temporal and vertical distribution of soil water content (SWC) and differences in growing season length of understory and tree plant functional types. To quantify the relationship between tree, understory, and savanna-wide phenology and productivity, we used PhenoCam and satellite observations surrounding an eddy covariance tower at a semiarid savanna site in Arizona, USA. We distinguished between SWC across two different depth intervals (shallow, <0–30 cm and deep, >30–100 cm). We found that tree greenness increased with SWC at both depths, while understory greenness was only sensitive to the shallower SWC measurements. Onset of ecosystem dormancy, estimated from satellite observations close to the eddy covariance tower, explained more variability in annual gross primary productivity (GPP) than in other phenometrics. Higher SWC led to an extended growing season, caused by delayed dormancy in trees, but the understory showed no evidence of delayed dormancy in wetter periods. We infer that the timing of ecosystem scale dormancy, driven by trees, is important in understanding changes in a savanna's GPP. These findings highlight the important effects of rainfall during the winter. These findings suggest that savanna GPP is conditional on different responses to moisture availability in each of the dominant vegetation components.
The use of tetragnathid spiders as bioindicators of metal exposure at a coal ASH spill site
Abstract On 22 December 2008, a dike containing coal fly ash from the Tennessee Valley Authority Kingston Fossil Fuel Plant (TN, USA) failed, resulting in the largest coal ash spill in US history. The present study was designed to determine sediment metal concentrations at multiple site locations and to determine whether site-specific bioaccumulation of metals existed in tetragnathid spiders. Selenium and nickel were the only 2 metals to exceed the US Environmental Protection Agency sediment screening levels. Selenium concentrations in spiders were significantly higher at ash-affected sites than in those from reference sites. The ratio of methylmercury to total mercury in spiders was found to be similar to that in other organisms (65–75%), which highlights the potential use of tetragnathid spiders as an indicator species for tracing contaminant transfer between the aquatic and terrestrial ecosystems. Environ Toxicol Chem 2013;32:2065–2068. © 2013 SETAC
A simple route to prepare supramolecular block copolymers using telechelic polystyrene/polydimethyls
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Reaction Routes for the Synthesis of CuInSe2 Using Bilayer Compound Precursors
Abstract not provided
Depyrogenation using plasmas: A novel approach for endotoxin deactivation using a dielectric barrier discharge at atmospheric pressure
Developing a low-cost depyrogenation process is vital in extending the medical applicability of polymers that can be used in medicine. We present an overview of the plasma-based depyrogenation literature and address the need to develop a nonthermal plasma-based depyrogenation process for delicate materials such as chitosan. We present a low-cost plasma apparatus to treat chitosan powder in hermetically sealed bags. We decouple the experiments into two parts: depyrogenation experiments for dried standard endotoxin on glass slides and analysis of chitosan modifications through Fourier-transform infrared spectroscopy. We demonstrate depyrogenation efficacy with up to a 4-log reduction in endotoxin levels and discuss minor changes observed in plasma-treated chitosan.