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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 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

A Virtual Reality Visualization Tool for Neuron Tracing

Tracing neurons in large-scale microscopy data is crucial to establishing a wiring diagram of the brain, which is needed to understand how neural circuits in the brain process information and generate behavior. Automatic techniques often fail for large and complex datasets, and connectomics researchers may spend weeks or months manually tracing neurons using 2D image stacks. We present a design study of a new virtual reality (VR) system, developed in collaboration with trained neuroanatomists, to trace neurons in microscope scans of the visual cortex of primates. We hypothesize that using consumer-grade VR technology to interact with neurons directly in 3D will help neuroscientists better resolve complex cases and enable them to trace neurons faster and with less physical and mental strain. We discuss both the design process and technical challenges in developing an interactive system to navigate and manipulate terabyte-sized image volumes in VR. Using a number of different datasets, we demonstrate that, compared to widely used commercial software, consumer-grade VR presents a promising alternative for scientists.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

Enhancements to VTK enabling Scientific Visualization in Immersive Environments

Modern scientific, engineering and medical computational sim- ulations, as well as experimental and observational data sens- ing/measuring devices, produce enormous amounts of data. While statistical analysis provides insight into this data, scientific vi- sualization is tactically important for scientific discovery, prod- uct design and data analysis. These benefits are impeded, how- ever, when scientific visualization algorithms are implemented from scratch—a time-consuming and redundant process in im- mersive application development. This process can greatly ben- efit from leveraging the state-of-the-art open-source Visualization Toolkit (VTK) and its community. Over the past two (almost three) decades, integrating VTK with a virtual reality (VR) environment has only been attempted to varying degrees of success. In this pa- per, we demonstrate two new approaches to simplify this amalga- mation of an immersive interface with visualization rendering from VTK. In addition, we cover several enhancements to VTK that pro- vide near real-time updates and efficient interaction. Finally, we demonstrate the combination of VTK with both Vrui and OpenVR immersive environments in example applications.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Energy Conservation Through Cloned Execution Of Simulations

High-performance computing facilities used for scientific computing draw enormous energy, some of them consuming many megawatt-hours. Saving the energy consumption of computations on such facilities can dramatically reduce the total cost of their operation and help reduce environmental effects. Here, we focus on a way to reduce energy consumption in many ensembles of simulations. Using the method of simulation cloning to exploit parallelism while also significantly conserving the computational and memory requirements, we perform a detailed empirical study of energy consumed on a large supercomputer consisting of hardware accelerator cards (graphical processing units, GPUs). We build on previous insights from mathematical analysis and implementation of cloned simulations that result in computational and memory savings by several orders-of-magnitude. Using instrumentation to track the power drawn by thousands of accelerator cards, we report significant aggregate energy savings from cloned simulations.

Yoginath, Srikanth↗
DOE OSTI2019

Multi-omic analyses of exogenous nutrient bag decomposition by the black morel Morchella importuna reveal sustained carbon acquisition and transferring

The black morel (Morchella importuna Kuo, O'Donnell and Volk) was once an uncultivable wild mushroom, until the development of exogenous nutrient bag (ENB), making its agricultural production quite feasible and stable. To date, how the nutritional acquisition of the morel mycelium is fulfilled to trigger its fruiting remains unknown. To investigate the mechanisms involved in ENB decomposition, the genome of a cultivable morel strain (M. importuna SCYDJ1-A1) was sequenced and the genes coding for the decay apparatus were identified. Expression of the encoded carbohydrate-active enzymes (CAZymes) was then analyzed by metatranscriptomics and metaproteomics in combination with biochemical assays. The results show that a diverse set of hydrolytic and redox CAZymes secreted by the morel mycelium is the main force driving the substrate decomposition. Plant polysaccharides such as starch and cellulose present in ENB substrate (wheat grains plus rice husks) were rapidly degraded, whereas triglycerides were accumulated initially and consumed later. ENB decomposition led to a rapid increase in the organic carbon content in the surface soil of the mushroom bed, which was thereafter consumed during morel fruiting. In contrast to the high carbon consumption, no significant acquisition of nitrogen was observed. Finally, our findings contribute to an increasingly detailed portrait of molecular features triggering morel fruiting.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

Contributions of the [NiFe]- and [FeFe]-hydrogenase to H2 production in Shewanella oneidensis MR-1 as revealed by isotope ratio analysis of evolved H2

Shewanella oneidensis MR-1 encodes both a [NiFe]- and an [FeFe]-hydrogenase. While the output of these proteins has been characterized in mutant strains expressing only one of the enzymes, the contribution of each to H2 synthesis in the wild-type organism is not clear. Here we use stable isotope analysis of H2 in the culture headspace, along with transcription data and measurements of the concentrations of gases in the headspace, to characterize H2 production in the wild-type strain. After most of the O2 in the headspace had been consumed, H2 was produced and then consumed by the bidirectional [NiFe]-hydrogenase. Once the cultures were completely anaerobic, a new burst of H2 synthesis catalyzed by both enzymes took place. Our data is consistent with the hypothesis that at this point in the culture cycle, a pool of electrons is shunted toward both hydrogenases in the wild-type organism, but that in the absence of one of the hydrogenases, the flux is redirected to the available enzyme. To our knowledge, this is the first use of stable isotope analysis of a metabolic product to elucidate substrate flux through two alternative enzymes in the same cellular system.

stable isotope, bacteria, metabolism, anaerobic, e↗
DOE OSTI2014

The fungus gardens of leaf-cutter ants undergo a distinct physiological transition during biomass degradation

Leaf-cutter ants are dominant herbivores in ecosystems throughout the Neotropics. Rather than directly consuming the fresh foliar biomass they harvest, these ants use it to cultivate specialized fungus gardens. Although recent investigations have shed light on how plant biomass is degraded in fungus gardens, the cycling of nutrients that takes place in these specialized microbial ecosystems is still not well understood. Here, using metametabolomics and metaproteomics techniques, we examine the dynamics of nutrient turnover and biosynthesis in these gardens. Our results reveal that numerous free amino acids and sugars are depleted throughout the process of biomass degradation, indicating that easily accessible nutrients from plant material are readily consumed by microbes in these ecosystems. Accumulation of cellobiose and lignin derivatives near the end of the degradation process is consistent with previous findings of cellulases and laccases produced by Leucoagaricus gongylophorus, the fungus cultivated by leaf-cutter ants. Our results also suggest that ureides may be an important source of nitrogen in fungus gardens, especially during nitrogen-limiting conditions. No free arginine was detected in our metametabolomics experiments despite evidence that the host ants cannot produce this amino acid, suggesting that biosynthesis of this metabolite may be tightly regulated in the fungus garden. These results provide new insights into the dynamics of nutrient cycling that underlie this important ant-fungus symbiosis.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2020

Experimental nitrogen and phosphorus enrichment stimulates multiple trophic levels of algal and detrital-based food webs: a global meta-analysis from streams and rivers

Anthropogenic increases in nitrogen (N) and phosphorus (P) concentrations can strongly influence the structure and function of ecosystems. Even though lotic ecosystems receive cumulative inputs of nutrients applied to and deposited on land, no comprehensive assessment has quantified nutrient-enrichment effects within streams and rivers. We conducted a meta-analysis of published studies that experimentally increased concentrations of N and/or P in streams and rivers to examine how enrichment alters ecosystem structure (state: primary producer and consumer biomass and abundance) and function (rate: primary production, leaf breakdown rates, metabolism) at multiple trophic levels (primary producer, microbial heterotroph, primary and secondary consumers, and integrated ecosystem). Our synthesis included 184 studies, 885 experiments, and 3497 biotic responses to nutrient enrichment. We documented widespread increases in organismal biomass and abundance (mean response = +48%) and rates of ecosystem processes (+54%) to enrichment across multiple trophic levels, with no large differences in responses among trophic levels or between autotrophic or heterotrophic food-web pathways. Responses to nutrient enrichment varied with the nutrient added (N, P, or both) depending on rate versus state variable and experiment type, and were greater in flume and whole-stream experiments than in experiments using nutrient-diffusing substrata. Generally, nutrient-enrichment effects also increased with water temperature and light, and decreased under elevated ambient concentrations of inorganic N and/or P. Overall, increased concentrations of N and/or P altered multiple food-web pathways and trophic levels in lotic ecosystems. Finally, our results indicate that preservation or restoration of biodiversity and ecosystem functions of streams and rivers requires management of nutrient inputs and consideration of multiple trophic pathways.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Tigers at a crossroads: Shedding light on the role of Bangladesh in the illegal trade of this iconic big cat

Abstract Unsustainable wildlife trade is a major threat to many species, but quantifying trade remains challenging, as seizure data provides an incomplete understanding. For this reason, integrating multiple types of information, including interviews with actors involved in trade, is crucial if we are to understand the problem better. Hence, in this study, we digitized Bangladesh Forest Department tiger seizure records to identify trade routes and interviewed 163 individuals involved in trafficking tigers through Bangladesh's air, sea and land ports, including poachers, smugglers, and traders. We identified six ports used to import tigers, 14 ports used for tiger export and three ports showing bi‐directional trade. Elite Bangladeshis were the most important consumer group, and tigers were sourced from populations in NE India, Myanmar and Bangladesh Sundarbans to supply domestic demand. Tiger products were exported to 14 countries, including seven G20 nations, with Bangladeshi expatriates as the consumer group in three countries (United Kingdom, Germany and Qatar). Rising economic development in Bangladesh over the last decade, combined with deep‐rooted cultural ties to tiger consumption, has led to a rise in domestic demand. Additionally, rapid growth in international transport links has increased smuggling and connected local traders with global markets, increasing the complexity of global trade. These findings suggest Bangladesh is poised to play a pivotal role in tiger conservation over the next decade, requiring strong national strategies to reduce trade opportunities, disrupt networks and weaken demand.

Uddin, Nasir↗
DOE OSTI2016

Nitrogen processing by grazers in a headwater stream: riparian connections

Primary consumers play important roles in the cycling of nutrients in headwater streams, storing assimilated nutrients in growing tissue and recycling them through excretion. Though environmental conditions in most headwater streams and their surrounding terrestrial ecosystems vary considerably over the course of a year, relatively little is known about the effects of seasonality on consumer nutrient recycling these streams. Here, we measured nitrogen accumulated through growth and excreted by the grazing snail Elimia clavaeformis (Pleuroceridae) over the course of 12 months in Walker Branch, identifying close connections between in-stream nitrogen processing and seasonal changes in the surrounding forest.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Understanding variation in salamander ionomes: A nutrient balance approach

1. Ecological stoichiometry uses information on a few key biological elements (C, N and P) to explain complex ecological patterns. Although factors driving variation in these elements are well established, expanding stoichiometric principles to explore dynamics of the many other essential elements comprising biological tissues (i.e. the ionome) is needed to determine their metabolic relationships and better understand biological control of elemental flows through ecosystems. 2. Here in this paper, we report observations of ionomic variation in two species of salamander (Ambystoma opacum and A. talpoideum) across ontogenic stages using specimens from biological collections of two wetlands sampled over a 30-year period. This unique data set allowed us to explore the extent of ionomic variation between species, among ontogenic stages, between sites and through time. 3. We found species- and, to a lesser extent, site-specific differences in C, N and P along with 13 other elements forming salamander ionomes but saw no evidence of temporal changes. Salamander ionomic composition was most strongly related to ontogeny with relatively higher concentrations of many elements in adult males (i.e. Ca, P, S, Mg, Zn and Cu) compared to metamorphic juveniles, which had greater amounts of C, Fe and Mn. 4. In addition to patterns of individual elements, covariance among elements was used to construct multi-elemental nutrient balances, which revealed differences in salamander elemental composition between species and sites and changes in elemental proportions across ontogenic development. These multi-elemental balances distinguished among species-site-ontogenic stage groups better than using only C, N and P. 5. Overall, this study highlights the responsiveness of consumer ionomes to life-history and environmental variation while reflecting underlying relationships among elements tied to biological function. As such, ionomic studies can provide important insights into factors shaping consumer elemental composition and for predicting how these changes might affect higher-order ecological processes.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Traits drive global wood decomposition rates more than climate

Wood decomposition is a major component of the global carbon cycle. Decomposition rates vary across climate gradients, which is thought to reflect the effects of temperature and moisture on the metabolic kinetics of decomposers. However, decomposition rates also vary with wood traits, which may reflect the influence of stoichiometry on decomposer metabolism as well as geometry relating the surface areas that decomposers colonize with the volumes they consume. In this paper, we combined metabolic and geometric scaling theories to formalize hypotheses regarding the drivers of wood decomposition rates, and assessed these hypotheses using a global compilation of data on climate, wood traits, and wood decomposition rates. Our results are consistent with predictions from both metabolic and geometric scaling theories. Approximately half of the global variation in decomposition rates was explained by wood traits (nitrogen content and diameter), whereas only a fifth was explained by climate variables (air temperature, precipitation, and relative humidity). These results indicate that global variation in wood decomposition rates is best explained by stoichiometric and geometric wood traits. Our findings suggest that inclusion of wood traits in global carbon cycle models can improve predictions of carbon fluxes from wood decomposition.

Hu, Zhenhong↗
DOE OSTI2017

Thermal properties of simulated Hanford waste glasses

Abstract The Hanford Tank Waste Treatment and Immobilization Plant will vitrify the mixed hazardous wastes generated from 45 years of plutonium production at the Hanford Site in Washington State. The molten glasses will be poured into stainless steel containers or canisters and subsequently cooled for storage and disposal. For appropriate facility design and operations to handle such highly energy‐consuming processes, knowledge of the material properties is required. The thermal properties (heat capacity, thermal diffusivity, and thermal conductivity) of representative high‐level and low‐activity waste glasses were studied as functions of temperature in the range of 200°C‐800°C (relevant to the cooling process). Simultaneous differential scanning calorimetry‐thermal gravimetry (DSC‐TGA), Xe‐flash diffusivity, pycnometry, and dilatometry were implemented. The study showed that simultaneous DSC‐TGA would be a reliable method for obtaining the heat capacity of various glasses in the temperature range of interest. Accurate thermal properties from this study were shown to provide a more realistic guideline for capacity and time constraints of the heat removal process when compared to the original conservative design‐basis engineering estimates. The estimates, though useful for design in the absence of measured physical properties, can now be supplanted and the measured thermal properties can be used in design verification activities.

Rodriguez, Carmen P.↗
DOE OSTI2023

The role of photorespiration in preventing feedback regulation via ATP synthase in Nicotiana tabacum

Abstract Photorespiration consumes substantial amounts of energy in the forms of adenosine triphosphate (ATP) and reductant making the pathway an important component in leaf energetics. Because of this high reductant demand, photorespiration is proposed to act as a photoprotective electron sink. However, photorespiration consumes more ATP relative to reductant than the C3 cycle meaning increased flux disproportionally increases ATP demand relative to reductant. Here we explore how energetic consumption from photorespiration impacts the flexibility of the light reactions in nicotiana tabacum . Specifically, we demonstrate that decreased photosynthetic efficiency (ϕ II ) at low photorespiratory flux was related to feedback regulation at the chloroplast ATP synthase. Additionally, decreased ϕ II at high photorespiratory flux resulted in the accumulation of photoinhibition at photosystem II centers. These results are contrary to the proposed role of photorespiration as a photoprotective electron sink. Instead, our results suggest a novel role of ATP consumption from photorespiration in maintaining ATP synthase activity, with implications for maintaining energy balance and preventing photodamage that will be critical for plant engineering strategies.

Plant Sciences↗
DOE OSTI2012

Thermodynamics and Transport Phenomena in High Temperature Steam Electrolysis Cells

Hydrogen can be produced from water splitting with relatively high efficiency using high temperature electrolysis. This technology makes use of solid-oxide cells, running in the electrolysis mode to produce hydrogen from steam, while consuming electricity and high temperature process heat. The overall thermal-to-hydrogen efficiency for high temperature electrolysis can be as high as 50%, which is about double the overall efficiency of conventional low-temperature electrolysis. Current large-scale hydrogen production is based almost exclusively on steam reforming of methane, a method that consumes a precious fossil fuel while emitting carbon dioxide to the atmosphere. An overview of high temperature electrolysis technology will be presented, including basic thermodynamics, experimental methods, heat and mass transfer phenomena, and computational fluid dynamics modeling.

03 NATURAL GAS↗
DOE OSTI2022

Network Uncertainty Quantification for Analysis of Multi-Component Systems

To impact physical mechanical system design decisions and realize the full promise of high-fidelity computational tools, simulation results must be integrated at the earliest stages of the design process. This is particularly challenging when dealing with uncertainty and optimizing for system-level performance metrics, as full-system models (often notoriously expensive and time-consuming to develop) are generally required to propagate uncertainties to system-level quantities of interest. Methods for propagating parameter and boundary condition uncertainty in networks of interconnected components hold promise for enabling design under uncertainty in real-world applications. These methods avoid the need for time consuming mesh generation of full-system geometries when changes are made to components or subassemblies. Additionally, they explicitly tie full-system model predictions to component/subassembly validation data which is valuable for qualification. These methods work by leveraging the fact that many engineered systems are inherently modular, being comprised of a hierarchy of components and subassemblies that are individually modified or replaced to define new system designs. By doing so, these methods enable rapid model development and the incorporation of uncertainty quantification earlier in the design process. The resulting formulation of the uncertainty propagation problem is iterative. We express the system model as a network of interconnected component models, which exchange solution information at component boundaries. We present a pair of approaches for propagating uncertainty in this type of decomposed system and provide implementations in the form of an open-source software library. We demonstrate these tools on a variety of applications and demonstrate the impact of problem-specific details on the performance and accuracy of the resulting UQ analysis. This work represents the most comprehensive investigation of these network uncertainty propagation methods to date.

42 ENGINEERING↗
DOE OSTI2023

Radius of Contact During Friction Surfacing of Stainless Steel 304L: Effect of Spindle Speed and Rod Diameter

Abstract The “radius of contact” or the “real-rotational contact plane,” has been increasingly mentioned terminology in friction surfacing. However, the fundamental understanding of the flow dynamics behind this phenomenon is still very limited. The goal of this study was to understand the influence of spindle speed and consumable rod diameter on the flow dynamics and the radius of contact during friction surfacing of 304L stainless steel over a substrate of the same material. Friction surfacing was performed using consumable rods with diameters of 4.76 mm, 9.52 mm, and 12.7 mm while using spindle speeds from 1500 rpm to 20,000 rpm. The impact of spindle speed on deposition morphology, including the radius of contact, was studied. The radius of contact was calculated empirically and was found to be inversely proportional to the tangential velocity of the rod. The coupling between flow stresses and localized forces is hypothesized to be the key factor behind the variation of the radius of contact with processing conditions.

Engineering↗
DOE OSTI2015

TiN coated aluminum electrodes for DC high voltage electron guns

Preparing electrodes made of metals like stainless steel, for use inside DC high voltage electron guns, is a labor-intensive and time-consuming process. In this paper, the authors report the exceptional high voltage performance of aluminum electrodes coated with hard titanium nitride (TiN). The aluminum electrodes were comparatively easy to manufacture and required only hours of mechanical polishing using silicon carbide paper, prior to coating with TiN by a commercial vendor. The high voltage performance of three TiN-coated aluminum electrodes, before and after gas conditioning with helium, was compared to that of bare aluminum electrodes, and electrodes manufactured from titanium alloy (Ti-6Al-4V). Following gas conditioning, each TiN-coated aluminum electrode reached −225 kV bias voltage while generating less than 100 pA of field emission (<10 pA) using a 40 mm cathode/anode gap, corresponding to field strength of 13.7 MV/m. Smaller gaps were studied to evaluate electrode performance at higher field strength with the best performing TiN-coated aluminum electrode reaching ∼22.5 MV/m with field emission less than 100 pA. These results were comparable to those obtained from our best-performing electrodes manufactured from stainless steel, titanium alloy and niobium, as reported in references cited below. The TiN coating provided a very smooth surface and with mechanical properties of the coating (hardness and modulus) superior to those of stainless steel, titanium-alloy, and niobium electrodes. These features likely contributed to the improved high voltage performance of the TiN-coated aluminum electrodes.

36 MATERIALS SCIENCE↗