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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Modeling ocean, rail, and truck transportation flows to support policy analysis

Freight transportation represents about 9.5% of GDP in the U.S., it is responsible for about 8% of greenhouse gas emissions, and supports the import and export of about 3.6 trillion in international trade. It is therefore important that the national freight transportation system is designed and operated efficiently. Hence, this paper develops a mathematical model to estimate international and domestic freight flows across ocean, rail, and truck modes, which can be used to study the impacts of changes in our infrastructure, as well as the imposition of new user fees and changes in operating policies. The model integrates a user equilibrium-based logit argument for path selection with a system optimal argument for rail network operations. This leads to the development of a unique solution procedure that is demonstrated in a large-scale analysis focused on all intercity freight and U.S export/import containerized freight. The model results are compared with the reported flow volumes. Here, the model is applied to two case studies: a disruption of the seaports of Los Angeles and Long Beach (LA and LB) similar to the impacts that would be felt in an earthquake; and implementation of new user fees at the California ports.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2014

Integrated testing of the Thales LPT9510 pulse tube cooler and the iris LCCE electronics

The Jet Propulsion Laboratory (JPL) has identified the Thales LPT9510 pulse tube cryocooler as a candidate low cost cryocooler to provide active cooling on future cost-capped scientific missions. The commercially available cooler can provide refrigeration in excess of 2 W at 100K for 60W of power. JPL purchased the LPT9510 cooler for thermal and dynamic performance characterization, and has initiated the flight qualification of the existing cooler design to satisfy near-term JPL needs for this cooler. The LPT9510 has been thermally tested over the heat reject temperature range of 0C to +40C during characterization testing. The cooler was placed on a force dynamometer to measure the selfgenerated vibration of the cooler. Iris Technology has provided JPL with a brass board version of the Low Cost Cryocooler Electronics (LCCE) to drive the Thales cooler during characterization testing. The LCCE provides precision closed-loop temperature control and embodies extensive protection circuitry for handling and operational robustness; other features such as exported vibration mitigation and low frequency input current filtering are envisioned as options that future flight versions may or may not include based upon the mission requirements. JPL has also chosen to partner with Iris Technology for the development of electronics suitable for future flight applications. Iris Technology is building a set of radiation-hard, flight-design electronics to deliver to the Air Force Research Laboratory (AFRL). Test results of the thermal, dynamic and EMC testing of the integrated Thales LPT9510 cooler and Iris LCCE electronics is presented here.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Accuracy of an infrared marker-based patient positioning system (ExacTrac®) for stereotactic body radiotherapy in localizing the planned isocenter using fiducial markers

Stereotactic Body Radiation Therapy (SBRT) requires a controlled immobilization and position monitoring of patient and target. The purpose of this work is to analyze the performance of the imaging system ExacTrac® (ETX) using infrared and fiducial markers. Materials and methods: In order to assure the accuracy of isocenter localization, a Quality Assurance procedure was applied using an infrared marker-based positioning system. Scans were acquired of an inhouse-agar gel and solid water phantom with infrared spheres. In the inner part of the phantom, three reference markers were delineated as reference and one pellet was place internally; which was assigned as the isocenter. The iPlan® RT Dose treatment planning system. Images were exported to the ETX console. Images were acquired with the ETX to check the correctness of the isocenter placement. Adjustments were made in 6D the reference markers were used to fuse the images. Couch shifts were registered. The procedure was repeated for verification purposes. Results: The data recorded of the verifications in translational and rotational movements showed averaged 3D spatial uncertainties of 0.31 ± 0.42 mm respectively 0.82° ± 0.46° in the phantom and the first correction of these uncertainties were of 1.51 ± 1.14 mm respectively and 1.37° ± 0.61°. Conclusions: This study shows a high accuracy and repeatability in positioning the selected isocenter. The ETX-system for verifying the treatment isocenter position has the ability to monitor the tracing position of interest, making it possible to be used for SBRT positioning within uncertainty ≤1mm.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

A new compact self-coherent high power microwave source based on dual beams

In this paper, a compact self-coherent high power microwave source based on dual beams is presented. It consists of a two-cavity triaxial klystron amplifier (TKA) (noted as the outer sub-source below) and a multiwave Cerenkov generators (noted as the inner sub-source) inserted in the TKA's inner conductor. These two sub-sources share a common cathode and the magnetic field. The injected signals to the outer sub-source are leakage microwaves from the inner sub-source through the anode-cathode gap (A-K gap). Particle-in-cell simulation shows that when the diode voltage is 687 kV and the axial magnetic field is 0.8 T, two microwaves with power of 1.02 GW and 2.65 GW and the same frequency of 9.72 GHz are generated in the inner and the outer sub-source, respectively; the corresponding power efficiencies are 24% and 31%. Two sub-sources reach the phase locking at 23 ns with a phase difference fluctuation within ±3°. The fast and stable phase locking in the voltage ranging from 665 kV to 709 kV further suggests that the proposed source is promising for coherent power combination and to export a higher power of combined microwaves.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

B2, B7 or B10: Which palm-based blend mandate wise to be chosen in Malaysia?

The diminishing fossil energy resources, coupled with heightened interest in the abatement of greenhouse gas emissions and concerns about energy security have motivated Malaysia to produce palm-based biodiesel and it has been started to be exported since 2006. In line with this issue, the government in Malaysia launched the palm-based biodiesel blending mandate of five percent (B5) in the federal administration of Putrajaya on 1{sup st} June 2011. This was then followed by four states: Malacca on July 11, Negeri Sembilan on August 1, Kuala Lumpur on September 1 and Selangor on October 1 of the same year but it is yet to be implemented nationwide. However what is the wise blend mandate to be chosen? Thus, this paper seeks to examine the possible impact of various blend mandates implementation (B2, B7 and B10) on the palm oil industry market variables (stock and price) since the main aim of biodiesel industry in Malaysia is to reduce domestic palm oil stock to below one million tones and provide a floor price to support Crude Palm Oil (CPO) prices at RM2,000 per tonne. A structural econometric model consisting of nine structural equations and three identities was proposed in this study. The model has been estimated by two stage least squares (2SLS) method using annual data for the period 1976-2013. The study indicates that counterfactual simulation of a decrease from B5 to B2 predicts a decrease (11.2 per cent) in CPO domestic consumption for biodiesel usage, 731.02 per cent reduction in CPO stock and an increase of 27.41 percent in domestic price of CPO. However the increase in the blend mandate from B5 to B7 and B10 suggest that domestic consumption of CPO for biodiesel purpose increase 7.40 and 18.55 percent respectively. The interesting findings in this study suggest that no matter whether Malaysian government increase or decrease the blend mandate the increase in the price of CPO are the same with an increase of is 27.41 percent. Hence, this study suggests that the lower blend mandate is the most favourable on.+-e compared to increasing it in this short period due to high production cost of CPO prices. However, future study on economic feasibility of palm-based biodiesel has to be conducted to support this study.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2016

Upgrading of data acquisition software for centralized radiation monitoring system in Malaysian Nuclear Agency

With the growth of technology, many devices and equipments can be connected to the network and internet to enable online data acquisition for real-time data monitoring and control from monitoring devices located at remote sites. Centralized radiation monitoring system (CRMS) is a system that enables area radiation level at various locations in Malaysian Nuclear Agency (Nuklear Malaysia) to be monitored centrally by using a web browser. The Local Area Network (LAN) in Nuclear Malaysia is utilized in CRMS as a communication media for data acquisition of the area radiation levels from radiation detectors. The development of the system involves device configuration, wiring, network and hardware installation, software and web development. This paper describes the software upgrading on the system server that is responsible to acquire and record the area radiation readings from the detectors. The recorded readings are called in a web programming to be displayed on a website. Besides the main feature which is acquiring the area radiation levels in Nuclear Malaysia centrally, the upgrading involves new features such as uniform time interval for data recording and exporting, warning system and dose triggering.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Charged particle tracking through electrostatic wire meshes using the finite element method

Wire meshes are used across many disciplines to accelerate and focus charged particles, however, analytical solutions are non-exact and few codes exist which simulate the exact fields around a mesh with physical sizes. A tracking code based in Matlab-Simulink using field maps generated using finite element software has been developed which tracks electrons or ions through electrostatic wire meshes. The fields around such a geometry are presented as an analytical expression using several basic assumptions, however, it is apparent that computational calculations are required to obtain realistic values of electric potential and fields, particularly when multiple wire meshes are deployed. The tracking code is flexible in that any quantitatively describable particle distribution can be used for both electrons and ions as well as other benefits such as ease of export to other programs for analysis. The code is made freely available and physical examples are highlighted where this code could be beneficial for different applications.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Multi-timescale operations of nuclear-renewable hybrid energy systems for reserve and thermal product provision

In this paper, an optimal operation strategy of a nuclear-renewable hybrid energy system (N-R HES), in conjunction with a district heating network, is developed within a comprehensive multi-timescale electricity market framework. The grid-connected N-R HES is simulated to explore the capabilities and benefits of N-R HES of providing energy products, different reserve products, and thermal products. An N-R HES optimization and control strategy is formulated to exploit the benefits from the hybrid energy system in terms of both energy and ancillary services. A case study is performed on the customized NREL-118 bus test system with high renewable penetrations, based on a multi-timescale (i.e., three-cycle) production cost model. Both day-ahead and real-time market clearing prices are determined from the market model simulation. In conclusion, the results show that the N-R HES can contribute to the reserve requirements and also meet the thermal load, thereby increasing the economic efficiency of N-R HES (with increased revenue ranging from 1.55% to 35.25% at certain cases) compared to the baseline case where reserve and thermal power exports are not optimized.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2016

Mechanism of a cytosolic O -glycosyltransferase essential for the synthesis of a bacterial adhesion protein

O-glycosylation of Ser and Thr residues is an important process in all organisms, which is only poorly understood. Such modification is required for the export and function of adhesin proteins that mediate the attachment of pathogenic Gram-positive bacteria to host cells. Here, we have analyzed the mechanism by which the cytosolic O-glycosyltransferase GtfA/B of Streptococcus gordonii modifies the Ser/Thr-rich repeats of adhesin. The enzyme is a tetramer containing two molecules each of GtfA and GtfB. The two subunits have the same fold, but only GtfA contains an active site, whereas GtfB provides the primary binding site for adhesin. During a first phase of glycosylation, the conformation of GtfB is restrained by GtfA to bind substrate with unmodified Ser/Thr residues. In a slow second phase, GtfB recognizes residues that are already modified with N-acetylglucosamine, likely by converting into a relaxed conformation in which one interface with GtfA is broken. Here, these results explain how the glycosyltransferase modifies a progressively changing substrate molecule.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Reply to Levermann et al.: Linear scaling for monsoons based on well-verified balance between adiabatic cooling and latent heat release

We demonstrated (1) that an analytical model of monsoons reflects no abrupt response to forcing changes when one assumes, consistent with observations (2), that monsoon circulations export energy away from their ascending branch. We claimed that a previous model (3) incorrectly produced an abrupt response because it neglected the adiabatic cooling of rising air in a stably stratified troposphere. Levermann et al. argue (4) that the abrupt response is preserved in the ref. 3 model as long as adiabatic cooling does not balance the latent heat released during precipitation formation, and that neither theory nor observations support the idea that “most of the energy from the rain’s latent heat release is consumed by adiabatic cooling.”

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Clues to the mechanism of cholesterol transfer from the structure of NPC1 middle lumenal domain bound to NPC2

Export of LDL-derived cholesterol from lysosomes requires the cooperation of the integral membrane protein Niemann–Pick C1 (NPC1) and a soluble protein, Niemann–Pick C2 (NPC2). Mutations in the genes encoding these proteins lead to Niemann–Pick disease type C (NPC). NPC2 binds to NPC1’s second (middle), lumenally oriented domain (MLD) and transfers cholesterol to NPC1’s N-terminal domain (NTD). Here, we report the 2.4-Å resolution crystal structure of a complex of human NPC1–MLD and NPC2 bearing bound cholesterol-3-O-sulfate. NPC1–MLD uses two protruding loops to bind NPC2, analogous to its interaction with the primed Ebola virus glycoprotein. Here, docking of the NPC1–NPC2 complex onto the full-length NPC1 structure reveals a direct cholesterol transfer tunnel between NPC2 and NTD cholesterol binding pockets, supporting the “hydrophobic hand-off” cholesterol transfer model.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Crystal structure of an orthomyxovirus matrix protein reveals mechanisms for self-polymerization and membrane association

Many enveloped viruses encode a matrix protein. In the influenza A virus, the matrix protein M1 polymerizes into a rigid protein layer underneath the viral envelope to help enforce the shape and structural integrity of intact viruses. The influenza virus M1 is also known to mediate virus budding as well as the nuclear export of the viral nucleocapsids and their subsequent packaging into nascent viral particles. Despite extensive studies on the influenza A virus M1 (FLUA-M1), only crystal structures of its N-terminal domain are available. Here we report the crystal structure of the full-length M1 from another orthomyxovirus that infects fish, the infectious salmon anemia virus (ISAV). The structure of ISAV-M1 assumes the shape of an elbow, with its N domain closely resembling that of the FLUA-M1. The C domain, which is connected to the N domain through a flexible linker, is made of four α-helices packed as a tight bundle. In the crystal, ISAV-M1 monomers form infinite 2D arrays with a network of interactions involving both the N and C domains. Results from liposome flotation assays indicated that ISAV-M1 binds membrane via electrostatic interactions that are primarily mediated by a positively charged surface loop from the N domain. Furthemore, cryoelectron tomography reconstruction of intact ISA virions identified a matrix protein layer adjacent to the inner leaflet of the viral membrane. The physical dimensions of the virion-associated matrix layer are consistent with the 2D ISAV-M1 crystal lattice, suggesting that the crystal lattice is a valid model for studying M1–M1, M1–membrane, and M1–RNP interactions in the virion.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

ATP compartmentation in plastids and cytosol of Arabidopsis thaliana revealed by fluorescent protein sensing

Matching ATP:NADPH provision and consumption in the chloroplast is a prerequisite for efficient photosynthesis. In terms of ATP:NADPH ratio, the amount of ATP generated from the linear electron flow does not meet the demand of the Calvin–Benson–Bassham (CBB) cycle. Several different mechanisms to increase ATP availability have evolved, including cyclic electron flow in higher plants and the direct import of mitochondrial-derived ATP in diatoms. By imaging a fluorescent ATP sensor protein expressed in living Arabidopsis thaliana seedlings, we found that MgATP 2- concentrations were lower in the stroma of mature chloroplasts than in the cytosol, and exogenous ATP was able to enter chloroplasts isolated from 4- and 5-day-old seedlings, but not chloroplasts isolated from 10- or 20-day-old photosynthetic tissues. This observation is in line with the previous finding that the expression of chloroplast nucleotide transporters (NTTs) in Arabidopsis mesophyll is limited to very young seedlings. Employing a combination of photosynthetic and respiratory inhibitors with compartment-specific imaging of ATP, we corroborate the dependency of stromal ATP production on mitochondrial dissipation of photosynthetic reductant. Our data suggest that, during illumination, the provision and consumption of ATP:NADPH in chloroplasts can be balanced by exporting excess reductants rather than importing ATP from the cytosol.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

3.3 Å structure of Niemann–Pick C1 protein reveals insights into the function of the C-terminal luminal domain in cholesterol transport

Niemann–Pick C1 (NPC1) and NPC2 proteins are indispensable for the export of LDL-derived cholesterol from late endosomes. Mutations in these proteins result in Niemann–Pick type C disease, a lysosomal storage disease. Despite recent reports of the NPC1 structure depicting its overall architecture, the function of its C-terminal luminal domain (CTD) remains poorly understood even though 45% of NPC disease-causing mutations are in this domain. Here, we report a crystal structure at 3.3 Å resolution of NPC1* (residues 314–1,278), which—in contrast to previous lower resolution structures—features the entire CTD well resolved. Here, all eight cysteines of the CTD form four disulfide bonds, one of which (C909–C914) enforces a specific loop that in turn mediates an interaction with a loop of the N-terminal domain (NTD). Importantly, this loop and its interaction with the NTD were not observed in any previous structures due to the lower resolution. Our mutagenesis experiments highlight the physiological relevance of the CTD–NTD interaction, which might function to keep the NTD in the proper orientation for receiving cholesterol from NPC2. Additionally, this structure allows us to more precisely map all of the disease-causing mutations, allowing future molecular insights into the pathogenesis of NPC disease.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods

Changes in bioavailable dust-borne iron (Fe) supply to the iron-limited Southern Ocean may influence climate by modulating phytoplankton growth and CO 2 fixation into organic matter that is exported to the deep ocean. The chemical form (speciation) of Fe impacts its bioavailability, and glacial weathering produces highly labile and bioavailable Fe minerals in modern dust sources. However, the speciation of dust-borne Fe reaching the iron-limited Southern Ocean on glacial–interglacial timescales is unknown, and its impact on the bioavailable iron supply over geologic time has not been quantified. Here we use X-ray absorption spectroscopy on subantarctic South Atlantic and South Pacific marine sediments to reconstruct dust-borne Fe speciation over the last glacial cycle, and determine the impact of glacial activity and glaciogenic dust sources on bioavailable Fe supply. We show that the Fe(II) content, as a percentage of total dust-borne Fe, increases from ~5 to 10% in interglacial periods to ~25 to 45% in glacial periods. Consequently, the highly bioavailable Fe(II) flux increases by a factor of ~15 to 20 in glacial periods compared with the current interglacial, whereas the total Fe flux increases only by a factor of ~3 to 5. The change in Fe speciation is dominated by primary Fe(II) silicates characteristic of glaciogenic dust. Furthermore, our results suggest that glacial physical weathering increases the proportion of highly bioavailable Fe(II) in dust that reaches the subantarctic Southern Ocean in glacial periods, which represents a positive feedback between glacial activity and cold glacial temperatures.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

A cryptic oxidoreductase safeguards oxidative protein folding in Corynebacterium diphtheriae

In many gram-positive Actinobacteria, including Actinomyces oris and Corynebacterium matruchotii , the conserved thiol-disulfide oxidoreductase MdbA that catalyzes oxidative folding of exported proteins is essential for bacterial viability by an unidentified mechanism. Intriguingly, in Corynebacterium diphtheriae , the deletion of mdbA blocks cell growth only at 37 °C but not at 30 °C, suggesting the presence of alternative oxidoreductase enzyme(s). By isolating spontaneous thermotolerant revertants of the mdbA mutant at 37 °C, we obtained genetic suppressors, all mapped to a single T-to-G mutation within the promoter region of tsdA , causing its elevated expression. Strikingly, increased expression of tsdA —via suppressor mutations or a constitutive promoter—rescues the pilus assembly and toxin production defects of this mutant, hence compensating for the loss of mdbA . Structural, genetic, and biochemical analyses demonstrated TsdA is a membrane-tethered thiol-disulfide oxidoreductase with a conserved CxxC motif that can substitute for MdbA in mediating oxidative folding of pilin and toxin substrates. Together with our observation that tsdA expression is upregulated at nonpermissive temperature (40 °C) in wild-type cells, we posit that TsdA has evolved as a compensatory thiol-disulfide oxidoreductase that safeguards oxidative protein folding in C. diphtheriae against thermal stress.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Energetic and structural control of polyspecificity in a multidrug transporter

Multidrug efflux pumps are dynamic molecular machines that drive antibiotic resistance by harnessing ion gradients to export chemically diverse substrates. Despite their clinical importance, the molecular principles underlying multidrug promiscuity and energy efficiency remain poorly understood. Using multiparametric deep mutational scanning across eight substrates and two energy conditions, we deconvolute the contributions of substrate recognition, energetic coupling, and protein stability, providing an integrated, high-resolution view of multidrug transport. We find that substrate specificity arises from a distributed network of residues extending beyond the binding site, with mutations that reshape binding, coupling, conformational flexibility, and membrane interactions. Further, we apply a pH-based selection scheme to measure the effect of mutation on pH-dependent transport efficiency. By integrating these data, we reveal a fundamental relationship between efficiency and promiscuity: Highly efficient variants exhibit broad substrate profiles, while inefficient variants are narrower. In conclusion, these findings establish a direct link between energy coupling and polyspecificity, uncovering the biochemical logic underlying multidrug transport.

Biological Sciences↗
DOE OSTI2020

The bacterial copper resistance protein CopG contains a cysteine-bridged tetranuclear copper cluster

CopG is an uncharacterized protein ubiquitous in Gram-negative bacteria whose gene frequently occurs in clusters of copper resistance genes and can be recognized by the presence of a conserved CxCC motif. To investigate its contribution to copper resistance, here we undertook a structural and biochemical characterization of the CopG protein from Pseudomonas aeruginosa . Results from biochemical analyses of CopG purified under aerobic conditions indicate that it is a green copper-binding protein that displays absorbance maxima near 411, 581, and 721 nm and is monomeric in solution. Determination of the three-dimensional structure by X-ray crystallography revealed that CopG consists of a thioredoxin domain with a C-terminal extension that contributes to metal binding. We noted that adjacent to the CxCC motif is a cluster of four copper ions bridged by cysteine sulfur atoms. Structures of CopG in two oxidation states support the assignment of this protein as an oxidoreductase. On the basis of these structural and spectroscopic findings and also genetic evidence, we propose that CopG has a role in interconverting Cu(I) and Cu(II) to minimize toxic effects and facilitate export by the Cus RND transporter efflux system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗