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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

NEW NEUTRON-CAPTURE MEASUREMENTS IN 23 OPEN CLUSTERS. I. THE r -PROCESS

Neutron-capture elements, those with Z > 35, are the least well understood in terms of nucleosynthesis and formation environments. The rapid neutron-capture, or r -process, elements are formed in the environments and/or remnants of massive stars, while the slow neutron-capture, or s -process, elements are primarily formed in low-mass AGB stars. These elements can provide much information about Galactic star formation and enrichment, but observational data are limited. We have assembled a sample of 68 stars in 23 open clusters that we use to probe abundance trends for six neutron-capture elements (Eu, Gd, Dy, Mo, Pr, and Nd) with cluster age and location in the disk of the Galaxy. In order to keep our analysis as homogeneous as possible, we use an automated synthesis fitting program, which also enables us to measure multiple (3–10) lines for each element. We find that the pure r -process elements (Eu, Gd, and Dy) have positive trends with increasing cluster age, while the mixed r - and s -process elements (Mo, Pr, and Nd) have insignificant trends consistent with zero. Pr, Nd, Eu, Gd, and Dy have similar, slight (although mostly statistically significant) gradients of ∼0.04 dex kpc{sup −1}. The mixed elements also appear to have nonlinear relationships with R {sub GC}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

A Synthesis of Findings from an Integrated Hatchery Program after Three Generations of Spawning in the Natural Environment

Abstract The Cle Elum Supplementation and Research Facility in the Yakima River basin, Washington, is an integrated spring Chinook Salmon Oncorhynchus tshawytscha hatchery program designed to test whether artificial propagation can increase natural production and harvest opportunities while keeping ecological and genetic impacts within acceptable limits. Only natural-origin (naturally spawned) fish are used for hatchery broodstock. Spawning, incubation, and early rearing occur at a central facility; presmolts are transferred for final rearing, acclimation, and volitional release at sites adjacent to natural spawning areas, where returning adults can spawn with natural-origin fish. The first wild broodstock were collected in 1997, and age-4 adults have returned to the Yakima River since 2001. An unsupplemented population in the adjacent Naches River watershed provides a reference for evaluating environmental influences. The program has been comprehensively monitored from its inception. A synthesis of findings, many already published, is as follows: supplementation increased the harvest, redd counts, and spatial distribution of spawners; natural-origin returns were maintained; straying to nontarget systems was negligible; natural-origin females had slightly higher breeding success (production of surviving fry) in an artificial spawning channel, while the behavior and breeding success of natural- and hatchery-origin males were similar; hatchery-origin fish showed differences in morphometric and life history traits; high rates of hatchery age-2 (minijack) production were reported, but the observed proportions of out-migrating juvenile and adult (ages 4 and 5) returning males were comparable for hatchery- and natural-origin fish; hatchery smolts did not affect the levels of pathogens in natural smolts; and the ecological interactions attributed to the program were within adopted guidelines. Continued study is required to assess the long-term impacts on natural production and productivity.

Fast, David E.↗
DOE OSTI2018

A superstructure optimization approach for process synthesis under complex reaction networks

Here in this work, we present mixed integer linear programming methods for the synthesis of processes that involve complex reaction networks. Specifically, we consider the modeling of reactors and interconnecting streams in systems where the composition of the reactor inlet streams can vary substantially, thereby making the determination of the limiting component as well as the calculation of the stream heating/cooling and power requirements challenging. First, towards the modeling of reactors, we develop an extent-based method which detects the limiting reactant of each reaction occurring in parallel with others, based on the inlet flows of the reactants. Second, we develop a computationally tractable method for the calculation of the work and heating/cooling duty needed to condition any stream of a process based on simple calculations that can be performed offline. Finally, we present how the two aforementioned components can be integrated in an optimization model generated based on a process superstructure. We demonstrate the application of the developed methods for the synthesis of a biorefinery.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

FORTÉ Machine Learning

Of the non-corrupted data collected by the Orbiting Experiment (forté) satellite’s Photo-Diode Detector during the year 2001, I estimate that 7.9% of 914 894 signals are noise. My result differs dramatically from Guillen’s estimate of 96%. To arrive at this estimate, I used Gaussian mixture model (GMM) clustering–unsupervised machine learning–to aggregate the wave forms into groups based on the absolute value of the lowest 25 positive frequency discrete Fourier transform coefficients. Then, I marked several of the groups as noise by inspecting a random sampling of wave forms from each group. Marking groups as either noise or non-noise is a supervised binary classification operation. After removing the signals in noise groups from further consideration, I clustered the remaining signals into families. Again, I used a GMM, but for the familial clustering I used a Non-Negative Matrix Factorization feature vector transform. The result was 9 distinct families of lightning signals, as well as a second stage of noise filtering. To efficiently represent the entirety of the signal space, I broke each family into deciles based on their distance from the family mean. In this case, distance means the log-likelihood based on the GMM. Signals in lower deciles are more similar in shape and amplitude to their family average. I took the top 200 samples from each decile of each group, resulting in 18 000 signals. These signal approximately represent the entirety of the forté observations. To represent outliers, I also kept a zoo of the 1000 signals furthest from any family’s average. All told, the resulting data set represents the forté data with a reduction of about 51:1. To allow synthesis of an arbitrarily large number of test signals, I also captured each family’s average signal and the time-sample covariance matrix over the signals in each family. Using these two pieces of information, I can synthesize new waveforms by using a Gaussian random realization from the family average and covariance matrix. I wrote a program to test the synthesis quality. The program shows me two signals on the screen, one synthesized and one randomly drawn from the data. I attempted to identify the synthesized signal. Although the synthesis is imperfect, in an A/B comparison I only correctly chose the synthesized signal 36% of the time.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Fabricating Single Crystal Quantum Dot Solids

The central goal of this research program was to establish fundamental synthesis and processing principles to enable the fabrication of single crystal quantum dot solids (QDS) with programmable structure (i.e., hexagonal and square) and composition. Our approach towards that goal leveraged access to and experience with unique in-situ, multi-probe characterization techniques to understand and ultimately control the fundamental relationship between processing conditions and nucleation and growth of QDS. The program integrated synthesis and fabrication (Hanrath) with in-situ TEM analysis (Kourkoutis) and computational modeling (Clancy) to gain atomic-level insights into the underlying physical phenomena governing assembly and attachment and to guide the development of optimized processing methods. We have established a foundational understanding of physicochemical interactions of self-assembly at a fluid interface, superlattice structure transformation pathways, the critical role of disorder during the initial dimerization of colloidal quantum dot monomers, and the residual strain distribution within the inter-dot epitaxial bridge which hampers the formation of novel electronics states of the quantum dot solids. Collectively, these insights have contributed towards advancing the mechanistic understanding of the complex choreography of assembly and attachment as well as understanding what currently limits further advances in high-fidelity quantum dot solids and tiles.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Modular cell-free expression plasmids to accelerate biological design in cells

Industrial biotechnology aims to produce high-value products from renewable resources. This can be challenging because model microorganisms—organisms that are easy to use like Escherichia coli—often lack the machinery required to utilize desired feedstocks like lignocellulosic biomass or syngas. Non-model organisms, such as Clostridium, are industrially proven and have desirable metabolic features but have several hurdles to mainstream use. Namely, these species grow more slowly than conventional laboratory microbes, and genetic tools for engineering them are far less prevalent. To address these hurdles for accelerating cellular design, cell-free synthetic biology has matured as an approach for characterizing non-model organisms and rapidly testing metabolic pathways in vitro. Unfortunately, cell-free systems can require specialized DNA architectures with minimal regulation that are not compatible with cellular expression. In this work, we develop a modular vector system that allows for T7 expression of desired enzymes for cell-free expression and direct Golden Gate assembly into Clostridium expression vectors. Utilizing the Joint Genome Institute’s DNA Synthesis Community Science Program, we designed and synthesized these plasmids and genes required for our projects allowing us to shuttle DNA easily between our in vitro and in vivo experiments. We next validated that these vectors were sufficient for cell-free expression of functional enzymes, performing on par with the previous state-of-the-art. Lastly, we demonstrated automated six-part DNA assemblies for Clostridium autoethanogenum expression with efficiencies ranging from 68% to 90%. We anticipate this system of plasmids will enable a framework for facile testing of biosynthetic pathways in vitro and in vivo by shortening development cycles.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

An Optimization-Based Approach for Simultaneous Chemical Process and Heat Exchanger Network Synthesis

We propose a mixed-integer nonlinear programming (MINLP) model for simultaneous chemical process and heat exchanger network synthesis. The model allows process stream inlet/outlet temperatures and flow rates to vary and can be extended to handle unclassified streams, thereby facilitating integration with a process synthesis model. The proposed model is based on a generalized transshipment approach in which the heat cascade is built upon a “dynamic” temperature grid. Both hot and cold streams can cascade heat so that exchanger inlet and outlet temperature, heat duty, and area can be calculated at each temperature interval. Here, we develop mixed-integer constraints to model the number of heat exchangers in the network. Finally, we present several solution strategies tailored to improve the computation performance of the proposed models.

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

Utilizing Diselenide Precursors toward Rationally Controlled Synthesis of Metastable CuInSe 2 Nanocrystals

We present that within the past decade, there has been an emergence of reports regarding the synthetic isolation of multinary metal chalcogenide nano-crystals that persist under ambient conditions with metastable crystal structures; however, many of the direct syntheses remain largely serendipitous with respect to the conditions needed to achieve the metastable product. Towards the development of more rational design principles that enable the predictable isolation of metastable nanocrystals, we demonstrate a molecular programming approach for the synthesis of CuInSe 2 nanocrystals utilizing diorganyl diselenide precursors of the structure R-Se-Se-R. Specifically, we show that the kinetics of diselenide precursor conversion are dependent upon C–Se and Se–Se bond dissociation energies, and that the strength of the C–Se bond is the phase-directing variable. When employing dibenzyl and dimethyl selenide precursors with relatively weaker C–Se bonds, the resulting nanocrystals form in the thermodynamically stable chalcopyrite phase of CuInSe 2 . However, precursors like diphenyl diselenide that possess stronger C–Se bonds alter the reaction kinetics so as to steer the reaction towards formation of the metastable wurtzite-like phase. These two phases form via distinct copper selenide intermediates, with chalcopyrite forming through Cu 2-x Se and the wurtzite-like phase forming through Cu 3 Se 2 intermediates, and it was found that the ultimate wurtzite-like phase displays remarkable resistance to relaxation to the chalcopyrite phase. Lastly, this molecular programming approach should be applicable towards the isolation of other metastable phases of metal chalcogenide nanocrystals.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Systems Based Approaches for Conversion of Biomass to Bioenergy and Bioproducts

The research provided data on applicability of agricultural energy crops and forest biomass production and logistics models. While much of the overall research effort was focused on lignocellulosic feedstocks, the research also recognized that there are important opportunities for the production and use of starch-based agricultural crops to serve as alternative regionally-appropriate biofuel feedstocks. Also, the research identified fractionation techniques that can be used to separate biomass feedstocks into their basic chemical constituents and then streamline the biorefining industry by developing commodity products for cellulose, hemicellulose, and lignin. Finally, models and techniques were developed to determine economically feasible technologies for production of biomass-derived synthesis gases that can be used for clean, renewable power generation and for production of liquid transportation fuels through Fischer-Tropsch Synthesis. Moreover, this research program educated the next generation of engineers and scientists needed to implement these technologies.

09 BIOMASS FUELS↗
DOE OSTI2018

Simultaneous Process and Heat Exchanger Network Synthesis Using a Discrete Temperature Grid

We present mixed-integer linear programming models for utility targeting and heat exchanger network synthesis that account for variable stream temperatures and flow rates as well as unclassified streams and thus can be combined with process synthesis optimization models. By projecting temperature information onto a fixed discrete temperature grid, the model remains linear even under variable temperatures and flow rates, leading to a more tractable optimization model. The proposed model is well suited to address problems in the area of process intensification where the close interaction between different phenomena naturally leads to process synthesis problems with unclassified process streams. Several extensions are presented, including nonisothermal mixing as well as phase changes. Moreover, we show how a nonuniform grid can be adopted to reduce the complexity of the model for medium and large-size problems.

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

UCLA Translational Biomarker Development Program (UTBD)

The proposed UTBD program integrates the sciences of diagnostic nuclear medicine and (radio)chemistry with tumor biology and drug development. UTBD aims to translate new PET biomarkers for personalized medicine and to provide examples for the use of PET to determine pharmacokinetic (PK) and pharmacodynamic (PD) drug properties. The program builds on an existing partnership between the Ahmanson Translational Imaging Division (ATID) and the Crump Institute of Molecular Imaging (CIMI), the UCLA Department of Chemistry and the Division of Surgical Oncology. ATID provides the nuclear medicine training program, clinical and preclinical PET/CT scanners, biochemistry and biology labs for probe and drug development, radiochemistry labs, and two cyclotrons. CIMI provides DOE and NIH-funded training programs for radio-synthesis (START) and molecular imaging (SOMI). Other participating entities at UCLA are the Department of Chemistry and Biochemistry and the Division of Surgical Oncology. The first UTBD project focuses on deoxycytidine kinase, a rate-limiting enzyme in nucleotide metabolism, which is expressed in many cancers. Deoxycytidine kinase (dCK) positive tumors can be targeted uniquely by two distinct therapies: 1) nucleoside analog prodrugs such as gemcitabine (GEM) are activated by dCK to cytotoxic antimetabolites; 2) recently developed small molecule dCK inhibitors kill tumor cells by starving them of nucleotides required for DNA replication and repair. Since dCK-specific PET probes are now available, PET imaging of tumor dCK activity could improve the use of two different classes of drugs in a wide variety of cancers.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2024

CEERP SM3 Research, Monitoring, and Evaluation Workshop: Summary Report

The Columbia Estuary Ecosystem Restoration Program (CEERP) workshop, “CEERP Synthesis Memorandum (SM3): Research, Monitoring, and Evaluation,” was held in Portland, Oregon on June 24–25 2024. A diverse group of 26 domain experts with demonstrated knowledge and experience working in the Lower Columbia River Estuary (LCRE) participated. The workshop supported development of the forthcoming third Synthesis Memorandum for CEERP. The workshop furthered the collaborative understanding of the state of the science regarding the LCRE, helped to identify remaining knowledge gaps and uncertainties, and assisted in the prioritization of future restoration research and monitoring.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Rotating Detonation Combustion for Gas Turbines – Modeling and System Synthesis to Exceed 65% Efficiency Goal

Program description to date for the program. Objective: To advance combustion turbine technologies for combined cycle applications ... by integrating a Rotating Detonation Engine (RDE), pressure gain combustion system with an air-breathing power-generating turbine system to achieve a combined cycle efficiency equal to or greater than 65%.

rotating detonation, pressure gain combustion, rot↗
DOE OSTI2015

Asymmetric Hybrid Nanoparticles

Hybrid Nanoparticles (AHNs) are rationally-designed multifunctional nanostructures and novel building blocks for the next generation of advanced materials and devices. Nanoscale materials attract considerable interest because of their unusual properties and potential for practical applications. Most of the activity in this field is focused on the synthesis of homogeneous nanoparticles from metals, metal oxides, semiconductors, and polymers. It is well recognized that properties of nanoparticles can be further enhanced if they are made as hybrid structures. This program is concerned with the synthesis, characterization, and application of such hybrid structures termed AHNs. AHNs are composed of a homogeneous core and several caps of different materials deposited on its surface (Fig. 1). Combined properties of the core and the caps as well as new properties that arise from core-cap and cap-cap interactions render AHNs multifunctional. In addition, specific chemical reactivity of the caps enables directional self-assembly of AHNs into complex architectures that are not possible with only spherical nanoparticles.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Carbon-Based Quantum Information Science with Symmetry Protected Topological States (Final Report, DOE-BES award DE-SC0023105)

This research program established the scientific foundation for the rational, bottom-up design, synthesis, isolation, and investigation of symmetry-protected topological (SPT) electron spin qubits embedded in graphene nanoribbons (GNRs). The work focused on integrating atomically precise low-dimensional carbon nanostructures with emerging quantum logic architectures, providing a pathway toward scalable quantum materials for next-generation computing and sensing technologies. A central component of the program was the elucidation of fundamental relationships between real-space molecular architecture, local spin density distributions, electronic band dispersion, and energy level alignment in atomically precise GNR systems. These correlations define key operational parameters of SPT qubits and were systematically investigated to establish quantitative benchmarks against established molecular and solid-state spin qubit platforms. Attention was given to properties critical for quantum device performance, e.g. decoherence times, spectral sharpness of energy transitions, and tunable exchange interactions between spin states. The research demonstrated that these parameters can be engineered with atomic precision through scalable bottom-up synthetic strategies. Theory-guided design played a central role in identifying candidate structures hosting topologically protected spin states. Experimental validation was performed using both ensemble measurements and single-molecule characterization. In addition to advances in quantum materials synthesis, the program developed and applied spin-sensitive scanning probe microscopy techniques capable of directly probing quantum states and dynamic processes with atomic-scale spatial resolution. These capabilities enabled direct observation and characterization of quantum structures at the single-atom level. While the research activities were primarily hypothesis-driven fundamental investigations, the program adopted a comprehensive materials-by-design framework aimed at translating scientific discoveries into technological concepts compatible with scalable and intelligent manufacturing approaches.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Challenges and Prospects for Reducing Coupled Climate Model SST Biases in the Eastern Tropical Atlantic and Pacific Oceans: The U.S. CLIVAR Eastern Tropical Oceans Synthesis Working Group

Well-known problems trouble coupled general circulation models of the eastern Atlantic and Pacific Ocean basins. Model climates are significantly more symmetric about the equator than is observed. Model sea surface temperatures are biased warm south and southeast of the equator, and the atmosphere is too rainy within a band south of the equator. Near-coastal eastern equatorial SSTs are too warm, producing a zonal SST gradient in the Atlantic opposite in sign to that observed. The U.S. Climate Variability and Predictability Program (CLIVAR) Eastern Tropical Ocean Synthesis Working Group (WG) has pursued here an updated assessment of coupled model SST biases, focusing on the surface energy balance components, on regional error sources from clouds, deep convection, winds, and ocean eddies; on the sensitivity to model resolution; and on remote impacts. Motivated by the assessment, the WG makes the following recommendations: 1) encourage identification of the specific parameterizations contributing to the biases in individual models, as these can be model dependent; 2) restrict multimodel intercomparisons to specific processes; 3) encourage development of high-resolution coupled models with a concurrent emphasis on parameterization development of finer-scale ocean and atmosphere features, including low clouds; 4) encourage further availability of all surface flux components from buoys, for longer continuous time periods, in persistently cloudy regions; and 5) focus on the eastern basin coastal oceanic upwelling regions, where further opportunities for observational–modeling synergism exist.

58 GEOSCIENCES↗