A study of the effects of minor additives to Pb-Bi eutectic: Designing novel Pb-Bi-X liquid alloys for heat transfer applications
Not Available
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
SEARCH · Engineering Papers
Results for “MINORITY”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Effect of Band Mismatch on Minority Carrier Transport in Heterojunction Solar Cells
Abstract not provided
14 SOLAR ENERGY↗
The high risk HPV16 L2 minor capsid protein has multiple transport signals that mediate its nucleocytoplasmic traffic
In this study we examined the transport signals contributing to HPV16 L2 nucleocytoplasmic traffic using confocal microscopy analysis of enhanced green fluorescent protein-L2 (EGFP-L2) fusions expressed in HeLa cells. We confirmed that both nuclear localization signals (NLSs), the nNLS (1MRHKRSAKRTKR12) and cNLS (456RKRRKR461), previously characterized in vitro (Darshan et al., 2004), function independently in vivo. We discovered that a middle region rich in arginine residues (296SRRTGIRYSRIGNKQTLRTRS316) functions as a nuclear retention sequence (NRS), as mutagenesis of critical arginine residues within this NRS reduced the fraction of L2 in the nucleus despite the presence of both NLSs. Significantly, the infectivity of HPV16 pseudoviruses containing either RR297AA or RR297EE within the L2 NRS was strongly reduced both in HaCaT cells and in a murine challenge model. Experiments using Ratjadone A nuclear export inhibitor and mutation-localization analysis lead to the discovery of a leucine-rich nuclear export signal ({sub 462}LPYFFSDVSL) mediating 16L2 nuclear export. These data indicate that HPV16 L2 nucleocytoplasmic traffic is dependent on multiple functional transport signals.
60 APPLIED LIFE SCIENCES↗
Thermodynamic estimation of minor element distribution between immiscible liquids in Fe-Cu-based metal phase generated in melting treatment of municipal solid wastes
Graphical abstract: Display Omitted Highlights: Black-Right-Pointing-Pointer Two liquids separation of metal occurs in the melting of municipal solid waste. Black-Right-Pointing-Pointer The distribution of PGMs etc. between two liquid metal phases is studied. Black-Right-Pointing-Pointer Quite simple thermodynamic model is applied to predict the distribution ratio. Black-Right-Pointing-Pointer Au and Ag originated from WEEE are found to be concentrated into Cu-rich phase. - Abstract: Waste electrical and electronic equipment (WEEE) has become an important target in managing material cycles from the viewpoint of not only waste management and control of environmental pollution but also resource conservation. This study investigated the distribution tendency of trace elements in municipal solid waste (MSW) or incinerator ash, including valuable non-ferrous metals (Ni, Co, Cr, Mn, Mo, Ti, V, W, Zr), precious group metals (PGMs) originated from WEEE (Ag, Au, Pd, Pt), and others (Al, B, Pb, Si), between Fe-rich and Cu-rich metal phases by means of simple thermodynamic calculations. Most of the typical alloying elements for steel (Co, Cr, Mo, Nb, Ni, Si, Ti, V, and W) and Rh were preferentially distributed into the Fe-rich phase. PGMs, such as Au, Ag, and Pd, were enriched in the Cu-rich phase, whereas Pt was almost equally distributed into both phases. Since the primary metallurgical processing of Cu is followed by an electrolysis for refining, and since PGMs in crude copper have been industrially recovered from the resulting anode slime, our results indicated that Ag, Au, and Pd could be effectively recovered from MSW if the Cu-rich phase could be selectively collected.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Minor Impact of Ligand Shell Steric Profile on Colloidal Nanocarbon Catalysis
The catalytic activity of a colloidal nanoparticle is typically inhibited by the very capping agents that are required to maintain colloidal stability and catalyst dispersion. Yet, the relative importance of steric contributions to the observed attenuation in catalytic activity is poorly understood. In this work, we prepare colloidal graphitic carbon nanoparticles featuring covalent amide linkages to aliphatic surface capping agents of varying length. Using aerobic benzylamine oxidation as a test reaction, we find that the steric profile of the ligand shell plays a negligible role in suppressing catalytic activity relative to chemisorption interactions that alter the surface chemistry of the catalyst. The work indicates that heterostructured nanoparticles that provide distinct surface sites for ligand binding and substrate activation should allow for high colloidal stability and robust catalytic activity.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Critical role of the sorting polymer in carbon nanotube-based minority carrier devices
A prerequisite for carbon nanotube-based optoelectronic devices is the ability to sort them into a pure semiconductor phase. One of the most common sorting routes is enabled through using specific wrapping polymers. Here we show that subtle changes in the polymer structure can have a dramatic influence on the figures of merit of a carbon nanotube-based photovoltaic device. By comparing two commonly used polyfluorenes (PFO and PFO-BPy) for wrapping (7,5) and (6,5) chirality SWCNTs, we demonstrate that they have contrasting effects on the device efficiency. We attribute this to the differences in their ability to efficiently transfer charge. Although PFO may act as an efficient interfacial layer at the anode, PFO-BPy, having the additional pyridine side groups, forms a high resistance layer degrading the device efficiency. By comparing PFO|C 60 and C 60 -only devices, we found that presence of a PFO layer at low optical densities resulted in the increase of all three solar cell parameters, giving nearly an order of magnitude higher efficiency over that of C 60 -only devices. In addition, with a relatively higher contribution to photocurrent from the PFO-C 60 interface, an open circuit voltage of 0.55 V was obtained for PFO-(7,5)-C 60 devices. On the other hand, PFO-BPy does not affect the open circuit voltage but drastically reduces the short circuit current density. Lastly, these results indicate that the charge transport properties and energy levels of the sorting polymers have to be taken into account to fully understand their effect on carbon nanotube-based solar cells.
14 SOLAR ENERGY↗
Development of a Fluorescence-Activated Cell Sorting Method Coupled with Whole Genome Amplification To Analyze Minority and Trace Dehalococcoides Genomes in Microbial Communities
Dehalococcoides mccartyi are functionally important bacteria that catalyze the reductive dechlorination of chlorinated ethenes. However, these anaerobic bacteria are fastidious to isolate, making downstream genomic characterization challenging. In order to facilitate genomic analysis, a fluorescence-activated cell sorting (FACS) method was developed in this study to separate D. mccartyi cells from a microbial community, and the DNA of the isolated cells was processed by whole genome amplification (WGA) and hybridized onto a D. mccartyi microarray for comparative genomics against four sequenced strains. First, FACS was successfully applied to a D. mccartyi isolate as positive control, and then microarray results verified that WGA from 10 6 cells or ∼1 ng of genomic DNA yielded high-quality coverage detecting nearly all genes across the genome. As expected, some inter- and intrasample variability in WGA was observed, but these biases were minimized by performing multiple parallel amplifications. Subsequent application of the FACS and WGA protocols to two enrichment cultures containing ∼10% and ∼1% D. mccartyi cells successfully enabled genomic analysis. As proof of concept, this study demonstrates that coupling FACS with WGA and microarrays is a promising tool to expedite genomic characterization of target strains in environmental communities where the relative concentrations are low.
59 BASIC BIOLOGICAL SCIENCES↗
Folding and Assembly of Short α, β, γ -Hybrid Peptides: Minor Variations in Sequence and Drastic Differences in Higher-Level Structures
Multilevel protein structures typically involve polypeptides of sufficient lengths. Here we report the folding and assembly of seven short tetrapeptides sharing the same types of α-, β-, and aromatic γ-amino acid residues. These are two sets of hybrid peptides, with three members in one set and four in the other, having complementary hydrogen-bonding sequences that were hypothesized to pair into linear H-bonded duplexes. However, instead of undergoing the anticipated pairing, the initially examined three oligomers, 1 and 2a or 2b, differing only in their central αβ hybrid dipeptide sequence, do not associate with each other and exhibit distinctly different folding behavior. Experiments based on NMR and mass spectrometry, along with computational studies and systematic inference, reveal that oligomer 1 folds into an expanded β-turn containing an unusual hybrid α/β-amino acid sequence composed of glycine and β-alanine, two α- and β-amino acid residues that are conformationally most flexible, and peptides 2a and 2b adopt a noncanonical, extended helical conformation and dimerize into double helices undergoing rapid conformational exchange or helix inversion. The different central dipeptide sequences, αβ vs βα, result in drastically different intramolecular H-bonding patterns that are responsible for the observed folding behavior of 1 and 2. The revealed turn and double helix have few natural or synthetic counterparts, and provide novel and unique folding prototypes based on which chiral α- and β-amino acids are incorporated. The resultant derivatives 1a, 1b, 2c, and 2d follow the same folding and assembling behavior and demonstrate the generality of this system with the formation of expanded β-turns and double helices with enhanced folding stabilities, hampered helix inversion, as well as defined and dominant helical sense. This work has demonstrated the unique capability of synthetic foldamers in generating structures with fascinating folding and assembling behavior. As a result, the revealed systems offer ample opportunity for further structural optimization and applications.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Unraveling the role of tungsten as a minor alloying element in the oxidation NiCr alloys
Ni-based superalloys offer a unique combination of mechanical properties, corrosion resistance and high temperature performance. Near ambient pressure X-ray photoelectron spectroscopy was used to study in operando the initial steps of oxidation for Ni-5Cr, Ni-15Cr, Ni-30Cr and Ni-15Cr-6W at 500 °C, p(O 2 )=10 -6 mbar. The comparison of oxide evolution for these alloys quantifies the outsized impact of W in promoting chromia formation. For the binary alloys an increase in chromia due to Cr-surface enrichment is followed by NiO nucleation and growth thus seeding a dual-layer structure. The addition of W (Ni-15Cr-6W) shifts the reaction pathways towards chromia thus enhancing oxide quality. Density functional theory calculations confirm that W atoms adjacent to Cr create highly favorable oxygen adsorption sites. The addition of W supercharges the reactivity of Cr with oxygen essentially funneling oxygen atoms into Cr sites. The experimental results are discussed in the context of surface composition, chemistry, reactant fluxes, and microstructure.
36 MATERIALS SCIENCE↗
Closing the Nuclear Fuel Cycle with a Simplified Minor Actinide Lanthanide Separation Process (ALSEP) and Additive Manufacturing
Expanded low-carbon baseload power production through the use of nuclear fission can be enabled by recycling long-lived actinide isotopes within the nuclear fuel cycle. This approach provides the benefits of (a) more completely utilizing the energy potential of mined uranium, (b) reducing the footprint of nuclear geological repositories, and (c) reducing the time required for the radiotoxicity of the disposed waste to decrease to the level of uranium ore from one hundred thousand years to a few hundred years. A key step in achieving this goal is the separation of long-lived isotopes of americium (Am) and curium (Cm) for recycle into fast reactors. To achieve this goal, a novel process was successfully demonstrated on a laboratory scale using a bank of 1.25-cm centrifugal contactors, fabricated by additive manufacturing, and a simulant containing the major fission product elements. Americium and Cm were separated from the lanthanides with over 99.9% completion. The sum of the impurities of the Am/Cm product stream using the simulated raffinate was found to be 3.2 × 10 –3 g/L. The process performance was validated using a genuine high burnup used nuclear fuel raffinate in a batch regime. Separation factors of nearly 100 for 154 Eu over 241 Am were achieved. All these results indicate the process scalability to an engineering scale.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Electrochemical CO 2 reduction on Au surfaces: mechanistic aspects regarding the formation of major and minor products
In the future, industrial CO 2 electroreduction using renewable energy sources could be a sustainable means to convert CO 2 and water into commodity chemicals at room temperature and atmospheric pressure. This study focuses on the electrocatalytic reduction of CO 2 on polycrystalline Au surfaces, which have high activity and selectivity for CO evolution. Here, we explore the catalytic behavior of polycrystalline Au surfaces by coupling potentiostatic CO 2 electrolysis experiments in an aqueous bicarbonate solution with high sensitivity product detection methods. We observed the production of methanol, in addition to detecting the known products of CO 2 electroreduction on Au: CO, H 2 and formate. We suggest a mechanism that explains Au's evolution of methanol. Specifically, the Au surface does not favor C-O scission, and thus is more selective towards methanol than methane. These insights could aid in the design of electrocatalysts that are selective for CO 2 electroreduction to oxygenates over hydrocarbons.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗