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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Selling Demand Response Using Options

Wholesale electricity markets in many jurisdictions use a two-settlement structure: a day-ahead market for bulk power transactions and a real-time market for fine-grain supply-demand balancing. This paper explores trading demand response assets within this two-settlement market structure. Here, we consider two approaches for trading demand response assets: (a) an intermediate spot market with contingent pricing, and (b) an over-the-counter options contract. In the first case, we characterize the competitive equilibrium of the spot market, and show that it is socially optimal. Economic orthodoxy advocates spot markets, but these require expensive infrastructure and regulatory blessing. In the second case, we characterize competitive equilibria and compare its efficiency with the idealized spot market. Options contract are private bilateral over-the-counter transactions and do not require regulatory approval. We show that the optimal social welfare is, in general, not supported. We then design optimal option prices that minimize the social welfare gap. This optimal design serves to approximate the ideal spot market for demand response using options with modest loss of efficiency. Our results are validated through numerical simulations.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2020

Biological evaluation of Keggin‐type polyoxometalates on tyrosinase: Kinetics and molecular modeling

Abstract Abnormal overexpression of tyrosinase activity can lead to the production of hyperpigmentation in human skin and enzymatic browning in fruits and vegetables. Herein, the inhibition and mechanism of the H 3 PMo 12 O 40 and two transition metal‐substituted Keggin‐type polyoxometalates (Na 7 PMo 11 CoO 40 and Na 7 PMo 11 ZnO 40 ) on tyrosinase were studied by kinetics and molecular modeling. Kinetic studies indicated that all compounds had more potent inhibitory activities than standard arbutin, and H 3 PMo 12 O 40 (IC 50 = 0.443 ± 0.006 m m ) is ~15‐fold stronger inhibition than arbutin. Additionally, all compounds inhibited tyrosinase in a reversible competitive manner. Intriguingly, molecular modeling elucidated that three compounds competitively bind to tyrosinase mainly through more interactions with Cu 2+ ions and the amino acid residue capable of forming cation‐π and hydrogen bonding, forming a reversible non‐covalent complex. Molecular simulation study correlated well with the biological activity of three compounds in vitro. This work provided new insights into design and synthesis of polyoxometalates as tyrosinase inhibitors in the field of medicine, cosmetic, and food.

Chi, Guoxiang↗
DOE OSTI2020

Phosphorus alleviation of nitrogen‐suppressed methane sink in global grasslands

Abstract Grassland ecosystems account for more than 10% of the global CH 4 sink in soils. A 4‐year field experiment found that addition of P alone did not affect CH 4 uptake and experimental addition of N alone significantly suppressed CH 4 uptake, whereas concurrent N and P additions suppressed CH 4 uptake to a lesser degree. A meta‐analysis including 382 data points in global grasslands corroborated these findings. Global extrapolation with an empirical modelling approach estimated that contemporary N addition suppresses CH 4 sink in global grassland by 11.4% and concurrent N and P deposition alleviates this suppression to 5.8%. The P alleviation of N‐suppressed CH 4 sink is primarily attributed to substrate competition, defined as the competition between ammonium and CH 4 for the methane mono‐oxygenase enzyme. The N and P impacts on CH 4 uptake indicate that projected increases in N and P depositions might substantially affect CH 4 uptake and alter the global CH 4 cycle.

Zhang, Lihua↗
DOE OSTI2023

Leaf angle as a leaf and canopy trait: Rejuvenating its role in ecology with new technology

Abstract Life on Earth depends on the conversion of solar energy to chemical energy by plants through photosynthesis. A fundamental challenge in optimizing photosynthesis is to adjust leaf angles to efficiently use the intercepted sunlight under the constraints of heat stress, water loss and competition. Despite the importance of leaf angle, until recently, we have lacked data and frameworks to describe and predict leaf angle dynamics and their impacts on leaves to the globe. We review the role of leaf angle in studies of ecophysiology, ecosystem ecology and earth system science, and highlight the essential yet understudied role of leaf angle as an ecological strategy to regulate plant carbon–water–energy nexus and to bridge leaf, canopy and earth system processes. Using two models, we show that leaf angle variations have significant impacts on not only canopy‐scale photosynthesis, energy balance and water use efficiency but also light competition within the forest canopy. New techniques to measure leaf angles are emerging, opening opportunities to understand the rarely‐measured intraspecific, interspecific, seasonal and interannual variations of leaf angles and their implications to plant biology and earth system science. We conclude by proposing three directions for future research.

Yang, Xi↗
DOE OSTI2024

Body size and early marine conditions drive changes in Chinook salmon productivity across northern latitude ecosystems

Disentangling the influences of climate change from other stressors affecting the population dynamics of aquatic species is particularly pressing for northern latitude ecosystems, where climate‐driven warming is occurring faster than the global average. Chinook salmon (Oncorhynchus tshawytscha) in the Yukon‐Kuskokwim (YK) region occupy the northern extent of their species' range and are experiencing prolonged declines in abundance resulting in fisheries closures and impacts to the well‐being of Indigenous people and local communities. These declines have been associated with physical (e.g., temperature, streamflow) and biological (e.g., body size, competition) conditions, but uncertainty remains about the relative influence of these drivers on productivity across populations and how salmon–environment relationships vary across watersheds. To fill these knowledge gaps, we estimated the effects of marine and freshwater environmental indicators, body size, and indices of competition, on the productivity (adult returns‐per‐spawner) of 26 Chinook salmon populations in the YK region using a Bayesian hierarchical stock‐recruitment model. Across most populations, productivity declined with smaller spawner body size and sea surface temperatures that were colder in the winter and warmer in the summer during the first year at sea. Decreased productivity was also associated with above average fall maximum daily streamflow, increased sea ice cover prior to juvenile outmigration, and abundance of marine competitors, but the strength of these effects varied among populations. Maximum daily stream temperature during spawning migration had a nonlinear relationship with productivity, with reduced productivity in years when temperatures exceeded thresholds in main stem rivers. These results demonstrate for the first time that well‐documented declines in body size of YK Chinook salmon were associated with declining population productivity, while taking climate into account.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Techno‐economic feasibility analysis of engineered energycane‐based biorefinery co‐producing biodiesel and ethanol

Abstract High feedstock cost and low oil yields per unit of land from temperate oilseed crops limit the growth of commercial‐scale biodiesel production. Recently, highly productive crops, such as sugarcane and energycane, have been engineered to accumulate triacylglycerides (TAGs) that allow the production of far more industrial vegetable oil than previously possible. A proof‐of‐concept suggests that biodiesel production from engineered energycane will be possible. However, before making efforts for scale‐up, it is critical to understand the commercial feasibility and economic competitiveness of this process. This study performs techno‐economic analysis of a unique biorefinery processing energycane to co‐produce biodiesel and ethanol. Comprehensive process simulation models were developed for two scenarios: (i) biodiesel from TAGs and ethanol from fermentation of sugars in juice and (ii) biodiesel from TAGs and ethanol from fermentation of sugars in juice and hydrolysis of carbohydrates in bagasse. Based on the target levels, the analysis was performed for energycane containing 0%, 5%, and 7.7% TAGs (d.b.). The biodiesel from engineered energycane was found economically viable and competitive to soybean biodiesel. Although the capital investment is higher compared to the soybean biodiesel plant, the biodiesel production costs ($0.66–$0.9/L) were lower than soybean biodiesel ($0.91/L). Biorefinery‐scenario‐1 processing energycane containing 7.7% TAG produces biodiesel with profitability (IRR 7.84) slightly lower than soybean biodiesel (IRR 8.3), but yields five times of biodiesel per unit land and is self‐sustainable for energy requirements. The surplus electricity can displace fossil electricity and provide environmental benefits. Monte Carlo simulation indicated that biorefinery is profitable with a 29%–65% probability (NPV > 0) which is largely controlled by feedstock composition and biodiesel market price. It is important to note that energycane can be grown on the marginal rainfed lands in S.E. USA, where soybean would not be viable. Biodiesel from engineered energycane would therefore be complementary to soydiesel in the United States.

09 BIOMASS FUELS↗
DOE OSTI2020

Anti‐adhesive effects of sialic acid and Lactobacillus plantarum on Staphylococcus aureus in vitro

Abstract Staphylococcus aureus (S. aureus) is a common food‐borne pathogen that causes severe diseases after adhesion to epithelial cells. Lactobacillus inhibits pathogenic bacterial adhesion and infection. In addition, sialic acid (SA) is widely known for its beneficial biological functions. A new way of reducing the occurrence of diseases and curbing the overuse of antibiotics is ingesting prebiotics and probiotics that regulate the intestinal flora. In this study, we first evaluated the anti‐adhesive effects of several strains of Lactobacillus on S. aureus . The study revealed that the S. aureus adhesion was inhibited by all the strains of Lactobacillus . Besides, the rate of inhibition by L. plantarum Z‐4 was significantly higher than other Lactobacillus species . We then investigated the effects of different SA concentrations (40, 100, 150, 200, and 260 μg/ml) on the growth and adhesion characteristics of L. plantarum and S. aureus . The results showed that SA influences bacterial adhesion by regulating the bacteria's growth characteristics. Finally, the effects of SA combined with Lactobacillus on the adhesion of S. aureus were assessed by competition, exclusion and displacement methods. SA with a concentration of 260 μg/mL combined with L. plantarum had the highest inhibition effect on the competition assays. In addition, the expression of S. aureus adhesion‐related genes was reduced. This provides a new perspective on the application of SA and/or L. plantarum and its potential to resist adhesion of S. aureus .

Lu, Yingying↗
DOE OSTI2024

Transcriptomics reveal a mechanism of niche defense: two beneficial root endophytes deploy an antimicrobial GH18-CBM5 chitinase to protect their hosts

Effector secretion is crucial for root endophytes to establish and protect their ecological niche. We used time-resolved transcriptomics to monitor effector gene expression dynamics in two closely related Sebacinales, Serendipita indica and Serendipita vermifera, during symbiosis with three plant species, competition with the phytopathogenic fungus Bipolaris sorokiniana, and cooperation with root-associated bacteria. We observed increased effector gene expression in response to biotic interactions, particularly with plants, indicating their importance in host colonization. Some effectors responded to both plants and microbes, suggesting dual roles in intermicrobial competition and plant–microbe interactions. A subset of putative antimicrobial effectors, including a GH18-CBM5 chitinase, was induced exclusively by microbes. Functional analyses of this chitinase revealed its antimicrobial and plant-protective properties. We conclude that dynamic effector gene expression underpins the ability of Sebacinales to thrive in diverse ecological niches with a single fungal chitinase contributing substantially to niche defense.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

Contrasting effects of glutamate and branched-chain amino acid metabolism on acid tolerance in a Castellaniella isolate from acidic groundwater

Groundwater acidification co-occurring with nitrate pollution is a common, global environmental health hazard. Denitrifying bacteria have been leveraged for the in situ removal of nitrate in groundwater. However, co-existing stressors—such as low pH—reduce the efficacy of biological removal processes. Castellaniella sp. str. MT123 is a complete denitrifier that was isolated from acidic, nitrate-contaminated groundwater. The strain grows robustly by nitrate respiration at pH < 6.0, completely reducing nitrate to dinitrogen gas. Genomic analyses of MT123 revealed few previously characterized acid tolerance genes. Thus, we utilized a combination of proteomics, metabolomics, and competitive mutant fitness to characterize the genetic mechanisms of MT123 acclimation to growth under mildly acidic conditions. We found that glutamate accumulation is critical in the acid acclimation of MT123, possibly through consumption of intracellular protons via glutamate decarboxylation to GABA. This is despite the fact that MT123 lacks the canonical glutamate decarboxylase-glutamate/GABA antiporter system implicated in acid tolerance in other bacteria. In contrast, branched-chain amino acid (BCAA) accumulation was detrimental to cell growth at lower pHs, possibly through indirect mechanisms impacting the cellular glutamate pool. Genetic analysis previously linked MT123 to a population of Castellaniella that bloomed—concurrent to nitrate removal—during a biostimulation effort to reduce groundwater nitrate concentrations at MT123’s location of origin. Thus, our analyses provide novel insight into mechanisms of acclimation to acidic conditions in a strain with significant potential for nitrate bioremediation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Variable Inhibition of Nitrous Oxide Reduction in Denitrifying Bacteria by Different Forms of Methanobactin

Aerobic methanotrophic activity is highly dependent on copper availability, and methanotrophs have developed multiple strategies to collect copper. Specifically, when copper is limiting (ambient concentrations < 1 μM), some methanotrophs produce and secret a small modified peptide (< 1,300 Da) termed methanobactin (MB) that binds copper with high affinity. As MB is secreted into the environment, other microbes that require copper for their metabolism may be inhibited as MB may make copper unavailable; e.g., inhibition of denitrifiers as complete conversion nitrate to dinitrogen involves multiple enzymes, some of which are copper-dependent. Of key concern is inhibition of the copper-dependent nitrous oxide reductase (NosZ), the only known enzyme capable of converting nitrous oxide (N 2 O) to dinitrogen. Herein, we show that different forms of MB differentially affect copper uptake and N2O reduction by Pseudomonas stutzeri strain DCP-Ps1 (that expresses clade I NosZ) and Dechloromonas aromatica strain RCB (that expresses clade II NosZ). Specifically, in the presence of MB from Methylocystis sp. strain SB2 (SB2-MB), copper uptake and nosZ expression were more significantly reduced than in the presence of MB from Methylosinus trichosporium OB3b (OB3b-MB). Further, N2O accumulation increased more significantly for both P. stutzeri strain DCP-Ps1 and D. aromatica strain RCB in the presence of SB2-MB versus OB3b-MB. These data illustrate that copper competition between methanotrophs and denitrifying bacteria can be significant and that the extent of such competition is dependent on the form of MB that methanotrophs produce.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Investigating the Unique Ability of Trichodesmium To Fix Carbon and Nitrogen Simultaneously Using MiMoSA

The open ocean is an extremely competitive environment, partially due to the dearth of nutrients. Trichodesmium erythraeum, a marine diazotrophic cyanobacterium, is a keystone species in the ocean due to its ability to fix nitrogen and leak 30 to 50% into the surrounding environment, providing a valuable source of a necessary macronutrient to other species. While there are other diazotrophic cyanobacteria that play an important role in the marine nitrogen cycle, Trichodesmium is unique in its ability to fix both carbon and nitrogen simultaneously during the day without the use of specialized cells called heterocysts to protect nitrogenase from oxygen. Here, we use the advanced modeling framework called multiscale multiobjective systems analysis (MiMoSA) to investigate how Trichodesmium erythraeum can reduce dimolecular nitrogen to ammonium in the presence of oxygen. Our simulations indicate that nitrogenase inhibition is best modeled as Michealis-Menten competitive inhibition and that cells along the filament maintain microaerobia using high flux through Mehler reactions in order to protect nitrogenase from oxygen. We also examined the effect of location on metabolic flux and found that cells at the end of filaments operate in distinctly different metabolic modes than internal cells despite both operating in a photoautotrophic mode. These results give us important insight into how this species is able to operate photosynthesis and nitrogen fixation simultaneously, giving it a distinct advantage over other diazotrophic cyanobacteria because they can harvest light directly to fuel the energy demand of nitrogen fixation.

09 BIOMASS FUELS↗
DOE OSTI2021

Sulfur Metabolites Play Key System-Level Roles in Modulating Denitrification

Competition between nitrate-reducing bacteria (NRB) and sulfate-reducing bacteria (SRB) for resources in anoxic environments is generally thought to be governed largely by thermodynamics. It is now recognized that intermediates of nitrogen and sulfur cycling (e.g., hydrogen sulfide, nitrite, etc.) can also directly impact NRB and SRB activities in freshwater, wastewater, and sediment and therefore may play important roles in competitive interactions. Here, through comparative transcriptomic and metabolomic analyses, we have uncovered mechanisms of hydrogen sulfide- and cysteine-mediated inhibition of nitrate respiratory growth for the NRB Intrasporangium calvum C5. Specifically, the systems analysis predicted that cysteine and hydrogen sulfide inhibit growth of I. calvum C5 by disrupting distinct steps across multiple pathways, including branched-chain amino acid (BCAA) biosynthesis, utilization of specific carbon sources, and cofactor metabolism. Here, we have validated these predictions by demonstrating that complementation with BCAAs and specific carbon sources relieves the growth inhibitory effects of cysteine and hydrogen sulfide. We discuss how these mechanistic insights give new context to the interplay and stratification of NRB and SRB in diverse environments.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Lipo-Chitooligosaccharides Induce Specialized Fungal Metabolite Profiles That Modulate Bacterial Growth

Lipo-chitooligosaccharides (LCOs) are historically known for their role as microbial-derived signaling molecules that shape plant symbiosis with beneficial rhizobia or mycorrhizal fungi. Recent studies showing that LCOs are widespread across the fungal kingdom have raised questions about the ecological function of these compounds in organisms that do not form symbiotic relationships with plants. To elucidate the ecological function of these compounds, we investigate the metabolomic response of the ubiquitous human pathogen Aspergillus fumigatus to LCOs. Our metabolomics data revealed that exogenous application of various types of LCOs to A. fumigatus resulted in significant shifts in the fungal metabolic profile, with marked changes in the production of specialized metabolites known to mediate ecological interactions. Using network analyses, we identify specific types of LCOs with the most significant effect on the abundance of known metabolites. Extracts of several LCO-induced metabolic profiles significantly impact the growth rates of diverse bacterial species. These findings suggest that LCOs may play an important role in the competitive dynamics of non-plant-symbiotic fungi and bacteria. This study identifies specific metabolomic profiles induced by these ubiquitously produced chemicals and creates a foundation for future studies into the potential roles of LCOs as modulators of interkingdom competition.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Excited state electron transfer in A 2 and A 2 B 2 functionalized zinc porphyrins carrying rigid and flexible β -pyrrole π-extended substituents

Optical absorption and emission, electrochemical, and photochemical properties of peripherally functionalized with flexible and rigid π-extended substituents on A 2 and A 2 B 2 type zinc porphyrins is investigated. The significance of rigid π-substituents over flexible ones in governing the spectral properties is unraveled. Flexible π-substituents on the porphyrin ring caused appreciable spectral broadening compared to porphyrin carrying rigid π-substituents. Further, supramolecular dyads are formed by coordinating phenyl imidazole functionalized fullerene, C 60 Im. Here, the calculated binding constants for the 1:1 complexes is in the order of 2–7 × 10 5 M −1 suggesting stable complex formation. Free-energy calculations performed according to the Rehm–Weller approach suggested possibility of excited state electron transfer in these dyads. Femtosecond transient absorption studies of the dyads performed in o-dichlorobenzene showed evidence of occurrence of electron transfer from the singlet-excited state that was in competition with the intersystem crossing process to populate the triplet-excited state of porphyrins.

A2 and A2B2 functionalized zinc↗
DOE OSTI2021

10 Years Later: Cloud Computing is Closing the Performance Gap

Can cloud computing infrastructures provide HPC-competitive performance for scientific applications broadly? Despite prolific related literature, this question remains open. Answers are crucial for designing future systems and democratizing high-performance computing. We present a multi-level approach to investigate the performance gap between HPC and cloud computing, isolating different variables that contribute to this gap. Our experiments are divided into (i) hardware and system microbenchmarks and (ii) user application proxies. The results show that today’s high-end cloud computing can deliver HPC-competitive performance not only for computationally intensive applications, but also for memory- and communication-intensive applications – at least at modest scales – thanks to the high-speed memory systems and interconnects and dedicated batch scheduling now available on some cloud platforms.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Single-node Partitioned-Memory for Huge Graph Analytics: Cost and Performance Trade-offs

Nonvolatile memory NVDIMMs, available as Intel Optane, are less expensive than DRAM and bring large byte-addressable storage within reach to many applications. Evaluations on graph analytics have shown promising performance only when DRAM is used as a hardware cache (Memory mode). An open question is whether graph applications can exploit Optane and DRAM directly (AppDirect mode) and achieving better-than-DRAM average bandwidth and run times. We evaluate Optane as a volatile pool on two large-scale graph applications with very different computational patterns, Grappolo and Ripples. We show that AppDirect mode can deliver better-than-DRAM performance, by allocating data structures to Optane and DRAM according to their access characteristics, resulting in higher average memory bandwidth and lower average latency. Memory mode provides DRAM-competitive performance with capacity equal to persistent memory. We demonstrate occasional 4x improvement using the latest AppDirect option and frequently observe competitive performance between Optane AppDirect Memory modes and DRAM.

Ghosh, Sayan↗
DOE OSTI2022

Dictionary Learning with Accumulator Neurons

The Locally Competitive Algorithm (LCA) uses local competition between non-spiking leaky integrator neurons to infer sparse representations, allowing for potentially real-time execution on massively parallel neuromorphic architectures such as Intel's Loihi processor. Here, we focus on the problem of inferring sparse representations from streaming video using dictionaries of spatiotemporal features optimized in an unsupervised manner for sparse reconstruction. Non-spiking LCA has previously been used to achieve unsupervised learning of spatiotemporal dictionaries composed of convolutional kernels from raw, unlabeled video. We demonstrate how unsupervised dictionary learning with spiking LCA (\hbox{S-LCA}) can be efficiently implemented using accumulator neurons, which combine a conventional leaky-integrate-and-fire (\hbox{LIF}) spike generator with an additional state variable that is used to minimize the difference between the integrated input and the spiking output. We demonstrate dictionary learning across a wide range of dynamical regimes, from graded to intermittent spiking, for inferring sparse representations of both static images drawn from the CIFAR database as well as video frames captured from a DVS camera. On a classification task that requires identification of the suite from a deck of cards being rapidly flipped through as viewed by a DVS camera, we find essentially no degradation in performance as the LCA model used to infer sparse spatiotemporal representations migrates from graded to spiking. We conclude that accumulator neurons are likely to provide a powerful enabling component of future neuromorphic hardware for implementing online unsupervised learning of spatiotemporal dictionaries optimized for sparse reconstruction of streaming video from event based DVS cameras.

artificial intelligence↗
DOE OSTI2020

EMIS-CompetitiveEquilibrium.jl [SWR-19-56]

The Electricity Markets Investment Suite - Competitive Equilibrium (EMIS-CE) model is an optimization-based power system investment model developed at NREL. It attempts to approximate a market-driven investment equilibrium outcome under the assumption of idealized or perfect competition (e.g. no participants are able to exert market power or leverage exclusive cost advantages) and uncertain future conditions.

Stephen, Gord [National Renewable Energy Lab. (NRE↗