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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

DISCOVR strain pipeline screening – Part II: Winter and summer season areal productivities and biomass compositional shifts in climate-simulation photobioreactor cultures

Assessing the seasonal biomass productivity and compositional shift dynamics under simulated outdoor culture conditions of the top 22 algae strains selected during Tier I flask screening is an important step in the further prioritization of strains with regard to outdoor pond cultivation. These top 22 strains were subjected to Tier II testing in the PNNL Laboratory Environmental Algae Pond Simulator (LEAPS) photobioreactors, simulating light and temperature conditions of 20 cm deep outdoor ponds during the Arizona winter and summer season. All strains were grown in two consecutive nutrient-replete batch culture experiments at their particular optimal medium salinity to quantify their respective seasonal linear-phase areal biomass productivities. To determine biomass compositional shifts in response to nutrient-depletion, the LEAPS cultures were allowed to enter a 9-day nutrient depletion phase at the end of the second batch run. The following strains were evaluated in winter-season climate-simulated cultures and are listed in the order from highest (7.9 g m -2 day -1 ) to lowest (2.3 g m -2 day -1 ) areal N-replete biomass productivity: Monoraphidium minutum 26B-AM, Tetraselmis striata LANL1001, Chlorella vulgaris LRB AZ-1201, Micractinium reisseri NREL14-F2, Monoraphidium sp. MONOR1, Chlorella vulgaris NREL4-C12, Scenedesmus obliquus UTEX393, Scenedesmus acutus LRB-AP-0401, Nannochloropsis oceanica CCAP849/10, and Stichococcus minutus CCALA727. The following strains were evaluated in summer-season climate-simulated cultures and are listed in the order from highest (31.8 g m -2 day -1 ) to lowest (14.2 g m -2 day -1 ) areal N-replete biomass productivity: Picochlorum renovo NREL39-A8, Scenedesmus obliquus UTEX393, Porphyridium cruentum CCMP675, Picochlorum celeri TG2-WT-CSM/EMRE, Chlorella sorokiniana DOE1116, Stichococcus minor CCMP819, Picochlorum oklahomensis CCMP2329, Chlorella sorokiniana DOE1412 (UTEXB3016), Scenedesmus rubescens NREL46B-D3, Picochlorum soloecismus DOE101, Tetraselmis striata LANL1001, Scenedesmus obliquus DOE 0152.z, and Agmenellum quadruplicatum UTEX2268. All LEAPS cultures experienced a significant reduction in areal biomass productivity in response to nutrient-depletion, from 7-16% in the winter season simulation and up to 1-60% in the summer season simulation. Finally, for 10 of the strains tested, the carbohydrate content more than doubled upon nutrient depletion, and for 9 strains, the lipid content increased by over 50% of the initial content.

09 BIOMASS FUELS↗
DOE OSTI2015

NMR relaxation and exchange in metal-organic frameworks for surface area screening

We describe a robust screening technique that correlates the surface area of metal organic frameworks to the proton T-2 relaxation behavior of imbibed solvent at low field (13 MHz). In frameworks with small pore sizes (<1 nm) or strong solvent-framework interactions, diffusional exchange between the pore-confined and inter-particle solvent populations remains slow compared to the T-2 of the pore-confined solvent, allowing for a direct porosity analysis of the T-2 spectrum obtained from Laplace inversions. Increases in framework pore-size (>1 nm) lead to corresponding increases in the rate of solvent exchange, as confirmed by T-2 relaxation exchange (REXSY) experiments; increases in the pore size also increases the T-2 of the pore-confined solvent. The combination of these two effects results in comparable rates of relaxation and exchange, which precludes the direct analysis of Laplace inversions. Thus, two- and three-site kinetics models were applied to extract porosity from relaxation decays, thereby improving the utility of the porosity screening tool. (C) 2014 Elsevier Inc. All rights reserved.

Chen, JJ↗
DOE OSTI2012

Large-Scale Computational Screening of Zeolites for Ethane/Ethene Separation

Large-scale computational screening of thirty thousand zeolite structures was conducted to find optimal structures for seperation of ethane/ethene mixtures. Efficient grand canonical Monte Carlo (GCMC) simulations were performed with graphics processing units (GPUs) to obtain pure component adsorption isotherms for both ethane and ethene. We have utilized the ideal adsorbed solution theory (LAST) to obtain the mixture isotherms, which were used to evaluate the performance of each zeolite structure based on its working capacity and selectivity. In our analysis, we have determined that specific arrangements of zeolite framework atoms create sites for the preferential adsorption of ethane over ethene. The majority of optimum separation materials can be identified by utilizing this knowledge and screening structures for the presence of this feature will enable the efficient selection of promising candidate materials for ethane/ethene separation prior to performing molecular simulations.

Kim, J↗
DOE OSTI2012

Computational screening of dopants for photocatalytic two-electron reduction of CO 2 on anatase (101) surfaces

We have carried out first-principles calculations to explore reaction mechanisms of the 2e reduction of CO 2 to HCOOH or CO in photochemical reactions catalyzed by anatase (101) surface. Two energetically competitive reaction pathways to HCOOH were identified, which involve initial 1e (via bidentate) and 2e (via monodentate) reduction steps, respectively. The pathways of producing CO were also explored. From the electronic structure analysis, we have shown the role of the anatase surface in facilitating electron and proton transfer in CO 2 reduction. Based on the determined rate-limiting step, we have carried out screening of substitutional surface cation doping and found metallic elements that could substantially lower the reaction barriers. Finally, a simple model describing the relationship between the activation barriers and the binding energies of CO 2 - to the dopant surface site is proposed.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2013

Measurement of transmission efficiency for 400 MeV proton beam through collimator at Fermilab MuCool Test Area using Chromox-6 scintillation screen

The MuCool Test Area (MTA) at Fermilab is a facility to develop the technology required for ionization cooling for a future Muon Collider and/or Neutrino Factory. As part of this research program, feasibility studies of various types of RF cavities in a high magnetic field environment are in progress. As a unique approach, we have tested a RF cavity filled with a high pressure hydrogen gas with a 400 MeV proton beam in an external magnetic field (B = 3 T). Quantitative information about the number of protons passing through this cavity is an essential requirement of the beam test. The MTA is a flammable gas (hydrogen) hazard zone. Due to safety reasons, no active (energized) beam diagnostic instrument can be used. Moreover, when the magnetic field is on, current transformers (toroids) used for beam intensity measurements do not work due to the saturation of the ferrite material of the transformer. Based on these requirements, we have developed a passive beam diagnostic instrumentation using a combination of a Chromox-6 scintillation screen and CCD camera. This paper describes details of the beam profile and position obtained from the CCD image with B = 0 T and B = 3 T, and for high and low intensity proton beams. A comparison is made with beam size obtained from multi-wires detector. Beam transmission efficiency through a collimator with a 4 mm diameter hole is measured by the toroids and CCD image of the scintillation screen. Results show that the transmission efficiency estimated from the CCD image is consistent with the toroid measurement, which enables us to monitor the beam transmission efficiency even in a high magnetic field environment.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

High throughput nanostructure-initiator mass spectrometry screening of microbial growth conditions for maximal β-glucosidase production

Production of biofuels via enzymatic hydrolysis of complex plant polysaccharides is a subject of intense global interest. Microbial communities are known to express a wide range of enzymes necessary for the saccharification of lignocellulosic feedstocks and serve as a powerful reservoir for enzyme discovery. However, the growth temperature and conditions that yield high cellulase activity vary widely, and the throughput to identify optimal conditions has been limited by the slow handling and conventional analysis. A rapid method that uses small volumes of isolate culture to resolve specific enzyme activity is needed. In this work, a high throughput nanostructure-initiator mass spectrometry (NIMS)-based approach was developed for screening a thermophilic cellulolytic actinomycete, Thermobispora bispora , for β-glucosidase production under various growth conditions. Media that produced high β-glucosidase activity were found to be I/S + glucose or microcrystalline cellulose (MCC), Medium 84 + rolled oats, and M9TE + MCC at 45°C. Supernatants of cell cultures grown in M9TE + 1% MCC cleaved 2.5 times more substrate at 45°C than at all other temperatures. While T. bispora is reported to grow optimally at 60°C in Medium 84 + rolled oats and M9TE + 1% MCC, approximately 40% more conversion was observed at 45°C. This high throughput NIMS approach may provide an important tool in discovery and characterization of enzymes from environmental microbes for industrial and biofuel applications.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Dielectric Screening Modulates Semiconductor Nanoplatelet Excitons

The influence of external dielectric environments is well understood for 2D semiconductor materials but overlooked for colloidally grown II–VI nanoplatelets (NPLs). In this work, we synthesize MX (M = Cd, Hg; X = Se, Te) NPLs of varying thicknesses and apply the Elliott model to extract exciton binding energies—reporting values in good agreement with prior methods and extending to less studied cadmium telluride and mercury chalcogenide NPLs. Here, we find that the exciton binding energy is modulated both by the relative effect of internal vs external dielectric and by the thickness of the semiconductor material. An analytical model shows dielectric screening increases the exciton binding energy relative to the bulk by distorting the Coulombic potential across the NPL surface. We further confirm this effect by decreasing and recovering the exciton binding energy of HgTe NPLs through washing in polarizable solvents. Our results illustrate NPLs are colloidal analogues of van der Waals 2D semiconductors and point to surface modification as an approach to control photophysics and device properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Parallelized Screening of Characterized and DFT-Modeled Bimetallic Colloidal Cocatalysts for Photocatalytic Hydrogen Evolution

Using a newly designed and developed parallelized photoreactor and colorimetric detection method, a large sampling of bimetallic co-catalysts (Pd/Sn, Pd/Mo, Pd/Ru, Pd/Pb, Pd/Ni, Ni/Sn, Mo/Sn and Pt/Sn) for photocatalytic water reduction have been tested in this work. Of these co-catalysts, the combination of palladium and tin showed the highest synergistic behavior and peak hydrogen gas production at a low relative fraction of palladium. The resulting Pd/Sn bimetallic co-catalysts were characterized using high-angle annular dark-field (HAADF) and scanning transmission electron microscopy energy dispersive X-ray spectroscopy (STEM-EDS), and specifically, investigation of the palladium/tin mixture indicated that palladium and tin elements reside within the same particle. The experimental catalytic activity for the palladium/tin mixture was compared to density functional theory-derived energy values associated with the adsorption of hydrogen onto a surface. This comparison demonstrated that the typical peak found in electrochemical Sabatier volcano plots at ΔG H* = ~0 eV was replicated in the experimental photocatalytic system with a peak activity observed at ΔG H* = -0.036 eV. Computational confirmation of the results expressed here demonstrates the efficacy of colorimetric detection of hydrogen in parallel and presents a model for increasingly rapid catalyst screening.

08 HYDROGEN↗
DOE OSTI2014

Fragment-based screening of the bromodomain of ATAD2

Cellular and genetic evidence suggest that inhibition of ATAD2 could be a useful strategy to treat several types of cancer. To discover small-molecule inhibitors of the bromodomain of ATAD2, we used a fragment-based approach. As a result, fragment hits were identified using NMR spectroscopy, and ATAD2 was crystallized with three of the hits identified in the fragment screen.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Conservation laws, vertex corrections, and screening in Raman spectroscopy

We present a microscopic theory for the Raman response of a clean multiband superconductor, with emphasis on the effects of vertex corrections and long-range Coulomb interaction. The measured Raman intensity, R⁡(Ω), is proportional to the imaginary part of the fully renormalized particle-hole correlator with Raman form factors γ⁡( ⃗ k). In a BCS superconductor, a bare Raman bubble is nonzero for any γ⁡( ⃗ k) and diverges at Ω = 2⁢Δ max , where Δ max is the largest gap along the Fermi surface. However, for γ( ⃗ k) = constant, the full R⁡(Ω) is expected to vanish due to particle number conservation. It was sometimes stated that this vanishing is due to the singular screening by long-range Coulomb interaction. In our general approach, we show diagrammatically that this vanishing actually holds due to vertex corrections from the same short-range interaction that gives rise to superconductivity. We further argue that long-range Coulomb interaction does not affect the Raman signal for any γ( ⃗ k). We argue that vertex corrections eliminate the divergence at 2⁢Δ max . Here, we also argue that vertex corrections give rise to sharp peaks in R(Ω) at Ω < 2⁢Δ min (the minimum gap along the Fermi surface), when Ω coincides with the frequency of one of the collective modes in a superconductor, e.g., Leggett and Bardasis-Schrieffer modes in the particle-particle channel, and an excitonic mode in the particle-hole channel.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Lattice polarization effects on the screened Coulomb interaction W of the G W approximation

In polar insulators where longitudinal and transverse optical phonon modes differ substantially, the electron-phonon coupling affects the energy-band structure primarily through the long-range Fröhlich contribution to the Fan term. This diagram has the same structure as the GW self-energy where W originates from the electron part of the screened Coulomb interaction. The two can be conveniently combined by combining electron and lattice contributions to the polarizability. Both contributions are nonanalytic at the origin, and diverge as 1/q 2 so that the predominant contribution comes from a small region around q=0. In this work, we adopt a simple estimate forthe Fröhlich contribution by assuming that the entire phonon part can be attributed to a small volume of q near q=0. We estimate the magnitude for q→0 from a generalized Lyddane-Sachs-Teller relation, and the radiusfrom the inverse of the polaron length scale. The gap correction is shown to agree with Fröhlich’s simple estimate -α P ω LO /2 of the polaron effect with α P the polaron coupling factor.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗