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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

CHANDRA X-RAY AND HUBBLE SPACE TELESCOPE IMAGING OF OPTICALLY SELECTED KILOPARSEC-SCALE BINARY ACTIVE GALACTIC NUCLEI. I. NATURE OF THE NUCLEAR IONIZING SOURCES

Kiloparsec-scale binary active galactic nuclei (AGNs) signal active supermassive black hole (SMBH) pairs in merging galaxies. Despite their significance, unambiguously confirmed cases remain scarce and most have been discovered serendipitously. In a previous systematic search, we optically identified four kpc-scale binary AGNs from candidates selected with double-peaked narrow emission lines at z = 0.1-0.2. Here, we present Chandra and Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging of these four systems. We critically examine and confirm the binary-AGN scenario for two of the four targets, by combining high angular resolution X-ray imaging spectroscopy with Chandra ACIS-S, better nuclear position constraints from WFC3 F105W imaging, and direct starburst estimates from WFC3 F336W imaging; for the other two targets, the existing data are still consistent with the binary-AGN scenario, but we cannot rule out the possibility of only one AGN ionizing gas in both merging galaxies. We find tentative evidence for a systematically smaller X-ray-to-[O III] luminosity ratio and/or higher Compton-thick fraction in optically selected kpc-scale binary AGNs than in single AGNs, possibly caused by a higher nuclear gas column due to mergers and/or a viewing angle bias related to the double-peak narrow-line selection. While our result lends some further support to the general approach of optically identifying kpc-scale binary AGNs, it also highlights the challenge and ambiguity of X-ray confirmation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Resonance ionization laser ion sources for on-line isotope separators (invited)

A Resonance Ionization Laser Ion Source (RILIS) is today considered an essential component of the majority of Isotope Separator On Line (ISOL) facilities; there are seven laser ion sources currently operational at ISOL facilities worldwide and several more are under development. The ionization mechanism is a highly element selective multi-step resonance photo-absorption process that requires a specifically tailored laser configuration for each chemical element. For some isotopes, isomer selective ionization may even be achieved by exploiting the differences in hyperfine structures of an atomic transition for different nuclear spin states. For many radioactive ion beam experiments, laser resonance ionization is the only means of achieving an acceptable level of beam purity without compromising isotope yield. Furthermore, by performing element selection at the location of the ion source, the propagation of unwanted radioactivity downstream of the target assembly is reduced. Whilst advances in laser technology have improved the performance and reliability of laser ion sources and broadened the range of suitable commercially available laser systems, many recent developments have focused rather on the laser/atom interaction region in the quest for increased selectivity and/or improved spectral resolution. Much of the progress in this area has been achieved by decoupling the laser ionization from competing ionization processes through the use of a laser/atom interaction region that is physically separated from the target chamber. A new application of gas catcher laser ion source technology promises to expand the capabilities of projectile fragmentation facilities through the conversion of otherwise discarded reaction fragments into high-purity low-energy ion beams. A summary of recent RILIS developments and the current status of laser ion sources worldwide is presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Infrared spectroscopy of the methanol cation and its methylene-oxonium isomer

The carbenium ion with nominal formula [C,H{sub 4},O]{sup +} is produced from methanol or ethylene glycol in a pulsed-discharge supersonic expansion source. The ion is mass selected, and its infrared spectrum is measured from 2000 to 4000 cm{sup −1} using laser photodissociation spectroscopy and the method of rare gas atom tagging. Computational chemistry predicts two isomers, the methanol and methylene-oxonium cations. Predicted vibrational spectra based on scaled harmonic and reduced dimensional treatments are compared to the experimental spectra. The methanol cation is the only isomer produced when methanol is used as a precursor. When ethylene glycol is used as the precursor, methylene-oxonium is produced in addition to the methanol cation. Theoretical results at the CCSD(T)/cc-pVTZ level show that methylene-oxonium is lower in energy than methanol cation by 6.4 kcal/mol, and is in fact the global minimum isomer on the [C,H{sub 4},O]{sup +} potential surface. Methanol cation is trapped behind an isomerization barrier in our source, providing a convenient method to produce and characterize this transient species. Analysis of the spectrum of the methanol cation provides evidence for strong CH stretch vibration/torsion coupling in this molecular ion.

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

Transportation Hub Infrastructure Expansion: Decision Support Under Uncertainty

The Athena project (www.athena-mobility.org) has worked to investigate the relationship between the Dallas-Fort Worth Airport (DFW) and the greater Dallas area in order to better understand and therefore better inform future decision-making regarding the critical infrastructure that influence mobility between the airport and the city. Through this work, infrastructure related to curbside pickup and drop-off, parking, public transit, and the road network congestion were identified as critical to the operation of the DFW transportation hub. The infrastructure analysis and expansion aspect of the Athena project is focused on the restructuring of the CTA curb as a hierarchical curb and the building or repurposing of parking infrastructure as the interplay between these two areas. Many sources of uncertainty exist that may impact future airport and transportation hub operations, such as passenger volume growth, population demographic changes over time, electric vehicle (EV) adoption rates, and autonomous vehicle (AV) adoption rates. Due to these sources of uncertainty, we have selected for our research a modeling framework that can capture various types of uncertainty and hedge against those uncertainties in the optimization process. We analyze road network and curb congestion, the rise of transportation networking companies, trends in parking usage, existing policies around this infrastructure, airport revenue streams, and other contributing factors to enable infrastructure decision making with less uncertainty. To accomplish this wholistic analysis, we have developed a novel multi-stage, multi-period stochastic optimization model which considers the airport's decisions from 2025-2045 under different possible future macro trajectories and day-to-day variations in operational conditions captured as "annual representation of operations" scenarios with respective probabilities. This model has also been designed to leverage the outputs of various efforts under the Athena project to create a combined decision framework for infrastructure decisions. These various efforts include the route optimization model, the ASPIRES simulation, the mode choice model, and the SUMO traffic simulation. Our computational experiments of this system at scale have resulted in a working version of our infrastructure model which enables the explicit representation and consideration of various sources of uncertainty in the decision process to enable robust, flexible decision-making. This model has been effectively run on NREL's HPC system, Eagle, with large numbers of stochastic scenarios and shows promise as a scalable tool for robust consideration of uncertainties in airport planning. We have tested our model using 30,240 operational circumstances in total, resulting in a problem with more 200 million variables. This model was solved in several different configurations, and a workflow to simulate the performance of the infrastructure model results was developed and deployed. In general, our results indicate that a combination of remote parking, remote curb infrastructure, and dynamic pricing can generate revenue, reduce emissions, accommodate emerging technologies such as AVs and EVs, and manage airport passenger growth over time. We note the success of the proposed strategy depends on the data collection and forecasting abilities of DFW. We have also seen that the AV adoption by TNCs might necessitate larger amounts of remote curb. The results of this work inform strategies for airport infrastructure decision making, as well as demonstrate the value of an adaptable model, but also indicate that there are avenues remaining where further research would be of value.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2018

The development of methods for primary mast cells in vitro and ex vivo: An historical review

Highlights: • Mast cells form a first-line defense of immune system against various challenges. • Over the past few decades, technologies for acquiring mast cells have been continually optimized. • The advantages and applicability of diverse mast cell models evaluated. • It is important to choose a proper cell source for mast cell-related experiments. Mast cells (MCs) are tissue-based stationary effector cells that form the immune system's first-line defense against various challenges. They are developed from the bone marrow-derived progenitors to complete their differentiation and maturation in the tissues where they eventually establish residence. MCs have been implicated in many diseases, such as allergy, parasitic infection, and neoplastic disorders. Immortalized MC lines, such as RBL-2H3, HMC-1, and LAD-2, are useful for investigating the biological functions of MC only to some extents due to the restriction of degranulation evaluation, in vivo injection and other factors. Over the past few decades, technologies for acquiring primarily MCs have been continually optimized, and novel protocols have been proposed. However, no relevant publications have analyzed and summarized these techniques. In this review, the classical approaches for extracting MCs are generalized, and new methods with potential values are introduced. We also evaluate the advantages and applicability of diverse MC models. Since MCs exhibit substantial plasticity and functional diversity due to different origins, it is both necessary and urgent to select a reliable and suitable source of MCs for a particular study.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Constant Rate Production: DOE Approach to Meeting NASA Needs for RPS for Nuclear-Enabled Launches.

The use of radioisotope power systems (RPS) for nuclear-enabled NASA missions is a long-standing arrangement between DOE and NASA. The requirements for the power system come from NASA, while DOE performs the procurement, fueling, testing and delivery. Recent examples include Mars Science Laboratory and New Horizons. A challenge has been interplay between the schedule for RPS availability from DOE versus the schedule NASA has for competitively selected missions. By mutual agreement, the actual operations to procure an RPS and prepare it for fueling, has always waited until the final selection of a mission. This timeline for a New Frontiers class mission leaves approximately 5-6 years from the time of final mission selection to the actual launch date. The number of RPS used for a Frontier class mission can be 1 to 3 units, i.e., the recent New Frontiers-2025 announcement of opportunity published in December 2016. If 1 or 2 units are needed for a specific mission, the timeline from the decision point to the launch date is a challenge, but doable. The activities taking place in this timeframe would include manufacturing the power system, producing the fuel, and performing the assembly/testing and delivery operations. If the mission selected requires 3 RPS the logistics of accomplishing all activities during the 5-6 years is problematic. The challenge involves appropriate resourcing for plutonium production, heat source production and assembly/testing operations. Typically, the time between RPS-enabled missions involve staffing attrition and reduction at the heat source production and the assembly/testing facilities that can be down to 60-75 percent of peak staffing levels to reduce costs. The duration for increasing staffing in these areas, which includes hiring, nuclear workforce training and obtaining the appropriate security clearance is 2 years. Taking account for this 2 years and the 6 months prior to launch arrival of the RPS at Kennedy Space Center erodes too much of the 5-6 years to comfortably support the use of 3 RPS on a mission and doesn't leave much schedule margin for a 2 RPS unit mission. To provide better support for NASA nuclear-enabled missions a different approach was devised, constant rate production. This involves a higher level of base capability at Los Alamos National Laboratory (LANL), Idaho National Laboratory (INL) and Oak Ridge National Laboratory (ORNL) to provide a stabilized work force. This will enable 10-15 heat sources to be produced annually at LANL, and subsequently shipped to the INL to be placed into a stable intermediate form that enables storage for up to several years that leads to quick production of general purpose heat source modules when a mission is selected. The up-front production of Pu-238 at ORNL is maintained so that there is material constantly in the pipeline. Production of key specialized components at ORNL is also maintained using this model. This allows for a reduction of risk to the nuclear-enabled missions, yet always having quantities of hardware available “on the shelf” to support production of RPS for NASA.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2020

Validation of selection function, sample contamination and mass calibration in galaxy cluster samples

ABSTRACT We construct and validate the selection function of the MARD-Y3 galaxy cluster sample. This sample was selected through optical follow-up of the 2nd ROSAT faint source catalogue with Dark Energy Survey year 3 data. The selection function is modelled by combining an empirically constructed X-ray selection function with an incompleteness model for the optical follow-up. We validate the joint selection function by testing the consistency of the constraints on the X-ray flux–mass and richness–mass scaling relation parameters derived from different sources of mass information: (1) cross-calibration using South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) clusters, (2) calibration using number counts in X-ray, in optical and in both X-ray and optical while marginalizing over cosmological parameters, and (3) other published analyses. We find that the constraints on the scaling relation from the number counts and SPT-SZ cross-calibration agree, indicating that our modelling of the selection function is adequate. Furthermore, we apply a largely cosmology independent method to validate selection functions via the computation of the probability of finding each cluster in the SPT-SZ sample in the MARD-Y3 sample and vice versa. This test reveals no clear evidence for MARD-Y3 contamination, SPT-SZ incompleteness or outlier fraction. Finally, we discuss the prospects of the techniques presented here to limit systematic selection effects in future cluster cosmological studies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Complex Sources and Impacts on Remediation and Monitoring Approaches

Remedy selection, implementation, and coordination with tank farm activities for adjacent waste sites need to be facilitated by a technically defensible description of sources and their relative strength and temporal contributions to groundwater contamination. Detailed data describing contaminant source releases are typically not available, so source locations are highly uncertain. Furthermore, data on sources and model parameters are not readily available through direct measurements. Instead, source data are often derived by extrapolation from a few direct and/or indirect measurements, while model parameters are commonly estimated using inverse modeling or calibration methods. Because the conceptual model of sources will influence the mass and timing of the flux of contaminants to groundwater, uncertainty in the source terms should be considered. Even though a best-fit model can often be identified, it may not be the best representation of the sources given the sparse, uncertain nature of the data used for estimating source terms. To support future feasibility studies, a systematic approach is needed for identifying remediation and monitoring activities appropriate under conditions of uncertainty. In this study, an integrated assessment of alternative conceptual model elements has been examined using the B-Complex site in the Hanford Central Plateau to demonstrate how multiple sources in a waste management complex can be described to identify their relative contributions to groundwater. The heterogeneous structure of the system is modeled based on available field information on the lithological data for both the vadose zone and aquifer. The approach includes a simulation assessment and linkages to site data, with an uncertainty analysis applied to evaluate the effects of source term uncertainty on contaminant mass flux to groundwater. An integrated assessment of alternative conceptual model elements was evaluated to identify how parameter uncertainty impacts both temporal and spatial uncertainties associated with vadose zone source terms. Modeling scenarios identify important characteristics of remediation target zones to provide context for how surface barriers, in situ remedies, and water-table treatment zones can be designed to account for source dynamics. Ramifications for remediation and monitoring are discussed within the context of the source term uncertainty. The described approach facilitates systematically addressing alternative conceptual model questions in relation to remediation and monitoring and supports the remedial investigation/ feasibility study process and the remediation strategy development for the Hanford Central Plateau.

Rockhold, Mark L.↗
DOE OSTI2025

Polyethylene Upcycling to Liquid Alkanes in Molten Salts under Neat and External Hydrogen Source-Free Conditions

Development of facile approaches to convert plastic waste into liquid fuels under neat conditions is highly desired but challenging, particularly without noble metal catalysts and an external hydrogen source. Herein, highly efficient and selective polyethylene-to-gasoline oil (branched C 6 –C 12 alkanes) conversion was achieved under mild conditions (<170 °C) using commercially available AlCl 3 -containing molten salts as reaction media and to provide catalytic sites (no extra solvents, additives, or hydrogen feeding). The high catalytic efficiency and selectivity was ensured by the abundant active Al sites with strong Lewis acidity (comparable to the Al type in acidic zeolite) and highly ionic nature of the molten salts to stabilize the carbenium intermediates. Dynamic genesis of the Al sites was elucidated via time-resolved Al K-edge soft X-ray and 27 Al NMR, confirming the tricoordinated Al 3+ as active sites and its coordination with the as-generated alkene/aromatic intermediates. Further, the carbenium formation and polyethylene chain variation was illustrated by inelastic neutron scattering (INS) and an isotope-labeling experiment. Theoretical simulations further demonstrated the successive hydride abstraction, β-scission, isomerization, and internal hydrogen transfer reaction pathway with AlCl 3 as active sites. This facile catalytic system can further achieve the conversion of robust, densely assembled, and high molecular weight plastic model compounds to liquid alkane products in the diesel range.

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

X-ray source considerations in operation of digital detector arrays

Digital Detector Arrays (DDA) are increasingly replacing film in radiography applications. Standards exist for characterizing the performance of these detectors, and for using them in specific inspections. We have observed that the selection of the x-ray source to use with these detectors can also have a significant influence on the performance. We look at differences between standard, and micro-focus x-ray tubes, and end-window vs. side-window micro-focus tubes. We find that for best results, one must calibrate the DDA for the source settings used during an inspection. This is particularly true for variable-focus sources.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Constant Rate Production: DOE Approach to Meeting NASA Needs for Radioisotope Power Systems for Nuclear-Enabled Launches

The use of radioisotope power systems (RPSs) for nuclear-enabled National Aeronautics and Space Administration (NASA) missions is made possible through a long-standing arrangement between the Department of Energy (DOE) and NASA. The requirements for the power system come from NASA, but DOE performs the procurement, fueling, testing, and delivery. A challenge has been interplay between the schedule for RPS availability from DOE versus the schedule for competitively selected missions. By mutual agreement, the actual operations to procure an RPS and prepare it for fueling have always been delayed until the final selection of a mission. The timeline for a New Frontiers–class mission leaves approximately 5 to 6 years from the time of final mission selection to the actual launch date. The number of RPSs used for a New Frontiers–class mission can be one to three units. If one or two units are needed, the timeline from the decision point to the launch date is a challenge, but it is achievable. The activities taking place include manufacturing the power system, producing the fuel, and performing the assembly/testing and delivery operations. If the mission selected requires three RPSs, the logistics of accomplishing all activities during the 5–6 years is problematic. The challenge involves obtaining the necessary resources for plutonium production, heat source production, and assembly/testing operations. Typically, the time between RPS-enabled missions requires staffing reduction down to 65%–75% of peak staffing levels to reduce costs. Coupling the ~2 year duration needed for hiring, training, and obtaining the appropriate security clearances for the required staff with the requirement for the RPS to arrive at Kennedy Space Center 6 months before the launch erodes much of the 5–6 years available to comfortably support the use of three RPSs. To provide better support for NASA RPS missions, a different approach for the production of heat sources was devised—constant rate production. This involves a higher level of base capability at DOE national laboratories to provide a stabilized workforce. This will enable 10–15 heat sources to be produced annually and placed into a stable intermediate form to enable storage for up to several years leading to quick production of general purpose heat source modules when a mission is selected. The upfront production of 238 Pu is maintained so material is constantly in the pipeline. Production of key specialized components is also maintained using this model.

42 ENGINEERING↗
DOE OSTI2017

Ceramic Proppant Design for In-situ Microbially Enhanced Methane Recovery

This project designed a new type of multi-functional lightweight proppant. The proppant is utilized as the conventional lightweight proppant but also transports microorganisms to coalbed reservoirs. The proppant is coated with a polymer which protects the methanogenic microorganisms and serves as a time-release delivery for methane generation. To produce the multifunctional proppant, we assigned five tasks: 1) culturing methanogenic microbes from natural carbon sources; 2) identifying optimized growth and methanogenesis conditions for the microbial consortia; 3) synthesizing the lightweight ceramic proppant; 4) encapsulating the consortia and proppant; and 5) demonstrating lab scale simulated performance by monitoring in-situ methane generation and hydraulic conductivity. Task 1) To evaluate the feasibility of ex-situ cultivation, natural microbial populations were collected from various hydrocarbon-rich environments and locations characterized by natural methanogenesis. Different rank coals, complex hydrocarbon sources, hydrocarbon seeps, and natural biogenic environments were incorporated in the sampling. Three levels of screening allowed selection of microbial populations, favorable nutrient amendments, sources of the microbial community, and quantification of methane produced from various coal types. Incubation periods of up to 24 weeks were evaluated at 23°C. Headspace concentrations of CH 4 and CO 2 were analyzed by gas chromatography. After a two-week incubation period of the most promising microbes, generated headspace gas concentrations reached 873,400 ppm for methane and 176,370 ppm for carbon dioxide. Task 2) A central composite design (CCD) was used to explore a broad range of operational conditions, examine the effects of the important environmental factors, such as temperature, pH and salt concentration, and query a feasible region of operation to maximize methane production from coal. Coal biogasification was optimal for this consortium at an initial pH value of 5.5, at 30 °C, and at a NaCl concentration 3.7 mg/cm 3 (i.e., 145,165 ppm). Task 3) To create the lightweight ceramic proppant, the kaolinite and iron oxide (Fe 2 O 3 ) mixture were sintered under reducing atmosphere varying partial pressures of oxygen from 1.7×10 -13 atm to 1.8×10-11 atm. The Fe 2 O 3 reduces to FeO and reacts with kaolinite decomposed to mullite to form Fe 2 SiO 4 , FeSiO 3 , and FeAl 2 O 4 . As a result the proppant develops large pores (~100 µm), giving it a low bulk density (1.43 g/cm 3 ), and high porosity (45.2 vol%) at P_(O_2 )of 1.8×10 -11 atm. The proppant sintered at P_(O_2 )of 1.7×10 -13 atm is characterized by smaller pores (26 µm), higher density (1.72 g/cm3) and lower porosity (37.5 vol%). Crush resistance testing at 9,000 psi yields 6.8 wt% fine particles increasing to 17.7 wt% in porous samples. Acid solubility varies from 5.5 wt% loss increasing to 12.9 wt% in porous samples. Task 4 and 5) The microbial consortia obtained from the optimized condition and lightweight proppant were encapsulated by calcium-alginate polymer. The encapsulation system, including microbes and a proppant, was stored at 20°C and 36°C. The sample stored at 36°C generated 7.1×[10] 3 ppm of methane at 670 h, whereas the sample incubated at 20°C generated 1.1×[10] 3 ppm of methane. Benchtop lab-scale bioreactors were constructed and showed with real-time measurements that, as the microbes produced methane, the pH decreased, and hydrogen and carbon dioxide gases were consumed. A calcium ion-selective sensor revealed the release mechanism of the microbes from encapsulation. The calcium ions interconnecting the alginate monomers were disassociated by counter cations such as protons and potassium ions. The counter cations bound to the carboxyl group on the alginate monomer, which thus lost its ionic interactions with the calcium ions, resulting in decomposition of the hydrogel structure. Furthermore, the conductivity was increased to ~700 mD-ft from ~530 mD-ft once the encapsulated sample was applied to the coal pack. The particle size of coal was reduced when the encapsulated sample was added to the coal. The reduced coal size implied that the microbes would consume the hydrocarbon in coal.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2017

Clustering of quasars in SDSS-IV eBOSS: study of potential systematics and bias determination

Here, we study the first year of the eBOSS quasar sample in the redshift range 0.9 Q = 2.45 ± 0.05 at $\bar{z}$=1.55, together with its evolution with redshift. We use this information to determine the minimum mass of the halo hosting the quasars and the characteristic halo mass, which we find to be both independent of redshift within statistical error. Using a recently-measured quasar-luminosity-function we also determine the quasar duty cycle. Lastly, the size of this first year sample is insufficient to detect any luminosity dependence to quasar clustering and this issue should be further studied with the final ~500,000 eBOSS quasar sample.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Layer-by-layer modification of aliphatic polyamide anion-exchange membranes to increase Cl - /SO 4 2- selectivity

Development of anion-exchange membranes (AEMs) with selectivities among anions may expand the applications of these membranes in salt separations. This work shows that layer-by-layer coating of aliphatic polyamide AEMs with poly(4-styrenesulfonate) (PSS)/protonated poly(allylamine) (PAH) films enhances Cl - /SO 4 2- dialysis selectivities, and the extent of this enhancement depends on the source-phase salt concentrations. For a source phase containing 0.01 M NaCl and 0.01 M Na 2 SO 4 and a receiving phase of 0.01 M Na 2 CO 3 , a (PSS/PAH) 5 PSS coating (5 PSS/PAH “bilayers” capped with a layer of PSS) increases the Cl - /SO 4 2- selectivity from 1.7 to 5.3 in diffusion dialysis and from 1.3 to 7.4 in electrodialysis. Remarkably, the diffusion dialysis selectivity of a coated membrane increases to 140 when the salt concentrations in the source phase are 0.1 M. Even with bare membranes, selectivity increases to 13 with 0.1 M source-phase salt concentrations. Moreover, AEMs coated only on the receiving side show much higher selectivities but lower fluxes than those coated only on the source side. In conclusion, partitioning experiments and modelling suggest that the increased Cl - /SO 4 2- selectivities at high source-phase salt concentrations stem from enhanced Cl - partitioning and electromigration that disproportionately decreases SO 4 2- flux in the AEM.

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

Identifying TeV Source Candidates among Fermi -LAT Unclassified Blazars

Blazars, in particular the subclass of high synchrotron peaked active galactic nuclei are among the main targets for the present generation of Imaging Atmospheric Cerenkov Telescopes (IACTs), and they will remain of great importance for very high-energy γ-ray science in the era of the Cerenkov Telescope Array (CTA). Observations by IACTs, which have relatively small fields of view (~few degrees), are limited by viewing conditions; therefore, it is important to select the most promising targets to increase the number of detections. The aim of this paper is to search for unclassified blazars among known γ-ray sources from the Fermi Large Area Telescope (LAT) third source catalog that are likely detectable with IACTs or CTA. We use an artificial neural network algorithm and updated analysis of Fermi-LAT data. We found 80 γ-ray source candidates, and for the highest-confidence candidates, we calculate their potential detectability with IACTs and CTA based on an extrapolation of their energy spectra. Follow-up observations of our source candidates could significantly increase the current TeV source population sample and ultimately confirm the efficiency of our algorithm to select TeV sources.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Glucose assimilation rate determines the partition of flux at pyruvate between lactic acid and ethanol in Saccharomyces cerevisiae

Engineered Saccharomyces cerevisiae expressing a lactic acid dehydrogenase can metab- olize pyruvate into lactic acid. However, three pyruvate decarboxylase (PDC) isozymes drive most carbon flux toward ethanol rather than lactic acid. Deletion of endoge- nous PDCs will eliminate ethanol production, but the resulting strain suffers from C 2 auxotrophy and struggles to complete a fermentation. Engineered yeast assimilating xylose or cellobiose produce lactic acid rather than ethanol as a major product with- out the deletion of any PDC genes. We report here that sugar flux, but not sensing, contributes to the partition of flux at the pyruvate branch point in S. cerevisiae express- ing the Rhizopus oryzae lactic acid dehydrogenase (LdhA). While the membrane glucose sensors Snf3 and Rgt2 did not play any direct role in the option of predominant product, the sugar assimilation rate was strongly correlated to the partition of flux at pyruvate: fast sugar assimilation favors ethanol production while slow sugar assimilation favors lactic acid. Applying this knowledge, we created an engineered yeast capable of simultaneously converting glucose and xylose into lactic acid, increasing lactic acid production to approximately 17 g L –1 from the 12 g L –1 observed during sequential consumption of sugars. This work elucidates the carbon source-dependent effects on product selection in engineered yeast.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Integration of a SMES–Battery-Based Hybrid Energy Storage System into Microgrids

The future trends of the industry require major renovations in the infrastructure of transmission, distribution, and storing of generated energy. With the increased use of renewable energy across the globe, energy storage (ES) systems have started to play a prominent role in shaping the future of the ES market. However, because of the uneven distribution of the renewable energy throughout the world, more emphasis must be made to the integration of power grids with the ES devices to utilize the excess power more effectively. In this paper, a study is performed regarding the integration of a hybrid system, consisting of a lithium-ion battery (LIB) and superconducting magnetic energy storage (SMES), into an interconnected microgrid operation. The structure of a microgrid is explained by analyzing the selected battery (LIB) and voltage source converter (VSC)-based SMES unit via MATLAB & Simulink. Finally, the voltage waveforms are compared and discussed in detail.

24 POWER TRANSMISSION AND DISTRIBUTION↗