Wet-oxidation waste management system for CELSS

NASA Technical Reports Server (NTRS)

Takahashi, Y.; Ohya, H.

1986-01-01

A wet oxidation system will be useful in the Closed Ecological Life Support System (CELSS) as a facility to treat organic wastes and to redistribute inorganic compounds and elements. However at rather higher temperatures needed in this reaction, for instance, at 260 deg C, only 80% of organic in a raw material can be oxidized, and 20% of it will remain in the liquid mainly as acetic acid, which is virtually noncombustible. Furthermore, nitrogen is transformed to ammonium ions which normally cannot be absorbed by plants. To resolve these problems, it becomes necessary to use catalysts. Noble metals such as Ru, Rh and so on have proved to be partially effective as these catalysts. That is, oxidation does not occur completely, and the unexpected denitrification, instead of the expected nitrification, occurs. So, it is essential to develop the catalysts which are able to realize the complete oxidation and the nitrification.

Metagenomic Evidence for the Presence of Comammox Nitrospira-Like Bacteria in a Drinking Water System.

PubMed

Pinto, Ameet J; Marcus, Daniel N; Ijaz, Umer Zeeshan; Bautista-de Lose Santos, Quyen Melina; Dick, Gregory J; Raskin, Lutgarde

2016-01-01

We report metagenomic evidence for the presence of a Nitrospira-like organism with the metabolic potential to perform the complete oxidation of ammonia to nitrate (i.e., it is a complete ammonia oxidizer [comammox]) in a drinking water system. This metagenome bin was discovered through shotgun DNA sequencing of samples from biologically active filters at the drinking water treatment plant in Ann Arbor, MI. Ribosomal proteins, 16S rRNA, and nxrA gene analyses confirmed that this genome is related to Nitrospira-like nitrite-oxidizing bacteria. The presence of the full suite of ammonia oxidation genes, including ammonia monooxygenase and hydroxylamine dehydrogenase, on a single ungapped scaffold within this metagenome bin suggests the presence of recently discovered comammox potential. Evaluations based on coverage and k-mer frequency distribution, use of two different genome-binning approaches, and nucleic acid and protein similarity analyses support the presence of this scaffold within the Nitrospira metagenome bin. The amoA gene found in this metagenome bin is divergent from those of canonical ammonia and methane oxidizers and clusters closely with the unusual amoA gene of comammox Nitrospira. This finding suggests that previously reported imbalances in abundances of nitrite- and ammonia-oxidizing bacteria/archaea may likely be explained by the capacity of Nitrospira-like organisms to completely oxidize ammonia. This finding might have significant implications for our understanding of microbially mediated nitrogen transformations in engineered and natural systems. IMPORTANCE Nitrification plays an important role in regulating the concentrations of inorganic nitrogen species in a range of environments, from drinking water and wastewater treatment plants to the oceans. Until recently, aerobic nitrification was considered to be a two-step process involving ammonia-oxidizing bacteria or archaea and nitrite-oxidizing bacteria. This process requires close cooperation between these two functional guilds for complete conversion of ammonia to nitrate, without the accumulation of nitrite or other intermediates, such as nitrous oxide, a potent greenhouse gas. The discovery of a single organism with the potential to oxidize both ammonia and nitrite adds a new dimension to the current understanding of aerobic nitrification, while presenting opportunities to rethink nitrogen management in engineered systems.

Calculating the balance between atmospheric CO2 drawdown and organic carbon oxidation in subglacial hydrochemical systems

NASA Astrophysics Data System (ADS)

Graly, Joseph A.; Drever, James I.; Humphrey, Neil F.

2017-04-01

In order to constrain CO2 fluxes from biogeochemical processes in subglacial environments, we model the evolution of pH and alkalinity over a range of subglacial weathering conditions. We show that subglacial waters reach or exceed atmospheric pCO2 levels when atmospheric gases are able to partially access the subglacial environment. Subsequently, closed system oxidation of sulfides is capable of producing pCO2 levels well in excess of atmosphere levels without any input from the decay of organic matter. We compared this model to published pH and alkalinity measurements from 21 glaciers and ice sheets. Most subglacial waters are near atmospheric pCO2 values. The assumption of an initial period of open system weathering requires substantial organic carbon oxidation in only 4 of the 21 analyzed ice bodies. If the subglacial environment is assumed to be closed from any input of atmospheric gas, large organic carbon inputs are required in nearly all cases. These closed system assumptions imply that order of 10 g m-2 y-1 of organic carbon are removed from a typical subglacial environment—a rate too high to represent soil carbon built up over previous interglacial periods and far in excess of fluxes of surface deposited organic carbon. Partial open system input of atmospheric gases is therefore likely in most subglacial environments. The decay of organic carbon is still important to subglacial inorganic chemistry where substantial reserves of ancient organic carbon are found in bedrock. In glaciers and ice sheets on silicate bedrock, substantial long-term drawdown of atmospheric CO2 occurs.

Recovery and biological oxidation of dissolved methane in effluent from UASB treatment of municipal sewage using a two-stage closed downflow hanging sponge system.

PubMed

Matsuura, Norihisa; Hatamoto, Masashi; Sumino, Haruhiko; Syutsubo, Kazuaki; Yamaguchi, Takashi; Ohashi, Akiyoshi

2015-03-15

A two-stage closed downflow hanging sponge (DHS) reactor was used as a post-treatment to prevent methane being emitted from upflow anaerobic sludge blanket (UASB) effluents containing unrecovered dissolved methane. The performance of the closed DHS reactor was evaluated using real municipal sewage at ambient temperatures (10-28 °C) for one year. The first stage of the closed DHS reactor was intended to recover dissolved methane from the UASB effluent and produce a burnable gas with a methane concentration greater than 30%, and its recovery efficiency was 57-88%, although the amount of dissolved methane in the UASB effluent fluctuated in the range of 46-68 % of methane production greatly depending on the temperature. The residual methane was oxidized and the remaining organic carbon was removed in the second closed DHS reactor, and this reactor performed very well, removing more than 99% of the dissolved methane during the experimental period. The rate at which air was supplied to the DHS reactor was found to be one of the most important operating parameters. Microbial community analysis revealed that seasonal changes in the methane-oxidizing bacteria were key to preventing methane emissions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Ammonia- and nitrite-oxidizing bacterial communities in a pilot-scale chloraminated drinking water distribution system.

PubMed

Regan, John M; Harrington, Gregory W; Noguera, Daniel R

2002-01-01

Nitrification in drinking water distribution systems is a common operational problem for many utilities that use chloramines for secondary disinfection. The diversity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in the distribution systems of a pilot-scale chloraminated drinking water treatment system was characterized using terminal restriction fragment length polymorphism (T-RFLP) analysis and 16S rRNA gene (ribosomal DNA [rDNA]) cloning and sequencing. For ammonia oxidizers, 16S rDNA-targeted T-RFLP indicated the presence of Nitrosomonas in each of the distribution systems, with a considerably smaller peak attributable to Nitrosospira-like AOB. Sequences of AOB amplification products aligned within the Nitrosomonas oligotropha cluster and were closely related to N. oligotropha and Nitrosomonas ureae. The nitrite-oxidizing communities were comprised primarily of Nitrospira, although Nitrobacter was detected in some samples. These results suggest a possible selection of AOB related to N. oligotropha and N. ureae in chloraminated systems and demonstrate the presence of NOB, indicating a biological mechanism for nitrite loss that contributes to a reduction in nitrite-associated chloramine decay.

Ammonia- and Nitrite-Oxidizing Bacterial Communities in a Pilot-Scale Chloraminated Drinking Water Distribution System

PubMed Central

Regan, John M.; Harrington, Gregory W.; Noguera, Daniel R.

2002-01-01

Nitrification in drinking water distribution systems is a common operational problem for many utilities that use chloramines for secondary disinfection. The diversity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in the distribution systems of a pilot-scale chloraminated drinking water treatment system was characterized using terminal restriction fragment length polymorphism (T-RFLP) analysis and 16S rRNA gene (ribosomal DNA [rDNA]) cloning and sequencing. For ammonia oxidizers, 16S rDNA-targeted T-RFLP indicated the presence of Nitrosomonas in each of the distribution systems, with a considerably smaller peak attributable to Nitrosospira-like AOB. Sequences of AOB amplification products aligned within the Nitrosomonas oligotropha cluster and were closely related to N. oligotropha and Nitrosomonas ureae. The nitrite-oxidizing communities were comprised primarily of Nitrospira, although Nitrobacter was detected in some samples. These results suggest a possible selection of AOB related to N. oligotropha and N. ureae in chloraminated systems and demonstrate the presence of NOB, indicating a biological mechanism for nitrite loss that contributes to a reduction in nitrite-associated chloramine decay. PMID:11772611

TEST REPORT OF MOBILE SOURCE EMISSIONS CONTROL DEVICES DONALDSON COMPANY INC.SERIES 6100 DIESEL OXIDATION CATALYST MUFFLER AND SPIRACLE CLOSED CRANKCASE FILTRATION SYSTEM

EPA Science Inventory

This report is on an environmental verification of the emissions characteristics of a Donaldson Corp. catalytic muffler and catalyic crankcase emissions control. It was found the systems reduced emissions.

Effects of interventions on oxidative stress and inflammation of cardiovascular diseases

PubMed Central

Lee, Sewon; Park, Yoonjung; Zuidema, Mozow Yusof; Hannink, Mark; Zhang, Cuihua

2011-01-01

Excessive oxidative stress and low-grade chronic inflammation are major pathophysiological factors contributing to the development of cardiovascular diseases (CVD) such as hypertension, diabetes and atherosclerosis. Accumulating evidence suggests that a compromised anti-oxidant system can lead to excessive oxidative stress in cardiovascular related organs, resulting in cell damage and death. In addition, increased circulating levels of pro-inflammatory cytokines, such as tumor necrosis factor α, interleukin-6 and C-reactive protein, are closely related to morbidity and mortality of cardiovascular complications. Emerging evidence suggests that interventions including nutrition, pharmacology and exercise may activate expression of cellular anti-oxidant systems via the nuclear factor erythroid 2-related factor 2-Kelch-like ECH-associated protein 1 signaling pathway and play a role in preventing inflammatory processes in CVD. The focus of the present review is to summarize recent evidence showing the role of these anti-oxidant and anti-inflammatory interventions in cardiovascular disease. We believe that these findings may prompt new effective pathogenesis-oriented interventions, based on the exercise-induced protection from disease in the cardiovascular system, aimed at targeting oxidant stress and inflammation. PMID:21286214

Observations on gas exchange and element recycle within a gas-closed algal-mouse system

NASA Technical Reports Server (NTRS)

Smernoff, D. T.; Wharton, R. A., Jr.; Averner, M. M.

1986-01-01

Life support systems based on bioregeneration rely on the control and manipulation of organisms. Algae are potentially useful for a variety of Closed Ecological Life Support System (CELSS) functions including the revitalization of atmospheres, production of food and for nitrogen fixation. The results of experiments conducted with a gas-closed algal-mouse system designed to investigate gas exchange phenomena under varying algal environmental conditions, and the ability of algae to utilize oxidized mouse solid waste are reported. Inherent instabilities exist between the uptake and release of carbon dioxide (CO2) and oxygen (O2) by the mouse and algae in a gas-closed system. Variations in light intensity and cell density alter the photosynthetic rate of the algae and enable short-term steady-state concentrations of atmospheric CO2 and O2. Different nitrogen sources (urea and nitrate) result in different algal assimilatory quotients (AQ). Combinations of photosynthetic rate and AQ ratio manipulations were examined for their potential in stabilizing atmospheric gas concentrations in the gas-closed algal-mouse system.

Assessment of anti-oxidant activity of plant extracts using microbial test systems.

PubMed

Oktyabrsky, O; Vysochina, G; Muzyka, N; Samoilova, Z; Kukushkina, T; Smirnova, G

2009-04-01

To evaluate the anti-oxidant properties of extracts from 20 medicinal herbs growing in western Siberia using microbial test systems and different in vitro methods. In vivo anti-oxidant activity of extracts was evaluated for their capacity to protect bacteria, Escherichia coli, against bacteriostatic and bactericidal effects of H(2)O(2) and menadione, and action on anti-oxidant gene expression. In vitro anti-oxidant activity has been examined by a number of methods including: the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH(*))-scavenging assay, chelating activity and capacity to protect plasmid DNA against oxidative damage. In addition, total polyphenol content was determined. The extracts of Fragaria vesca, Rosa majalis, Pentaphylloides fruticosa, Alchemilla vulgaris and Pulmonaria mollis possessed the highest levels of anti-oxidant activity in vivo and in vitro. The protective properties were more closely related to the DPPH(*) radical-scavenging activity, tannin content and action on anti-oxidant gene expression than to other parameters. The extracts of medicinal plants may have anti-oxidant effects on bacteria simultaneously through several different pathways, including direct inhibition of reactive oxygen species, iron chelation and anti-oxidant genes induction. Using microbial test systems, we revealed herbs that may be used as potential sources of natural anti-oxidants.

Ultrasound assisted, thermally activated persulfate oxidation of coal tar DNAPLs.

PubMed

Peng, Libin; Wang, Li; Hu, Xingting; Wu, Peihui; Wang, Xueqing; Huang, Chumei; Wang, Xiangyang; Deng, Dayi

2016-11-15

The feasibility of ultrasound assisted, thermally activated persulfate for effective oxidation of twenty 2-6 ringed coal tar PAHs in a biphasic tar/water system and a triphasic tar/soil/water system were investigated and established. The results indicate that ultrasonic assistance, persulfate and elevated reaction temperature are all required to achieve effective oxidation of coal tar PAHs, while the heating needed can be provided by ultrasonic induced heating as well. Further kinetic analysis reveals that the oxidation of individual PAH in the biphasic tar/water system follows the first-order kinetics, and individual PAH oxidation rate is primary determined by the mass transfer coefficients, tar/water interfacial areas, the aqueous solubility of individual PAH and its concentration in coal tar. Based on the kinetic analysis and experimental results, the contributions of ultrasound, persulfate and elevated reaction temperature to PAHs oxidation were characterized, and the effects of ultrasonic intensity and oxidant dosage on PAHs oxidation efficiency were investigated. In addition, the results indicate that individual PAH degradability is closely related to its reactivity as well, and the high reactivity of 4-6 ringed PAHs substantially improves their degradability. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of Layer-Graded Bond Coats on Edge Stress Concentration and Oxidation Behavior of Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Ghosn, Louis J.; Miller, Robert A.

1998-01-01

Thermal barrier coating (TBC) durability is closely related to design, processing and microstructure of the coating Z, tn systems. Two important issues that must be considered during the design of a thermal barrier coating are thermal expansion and modulus mismatch between the substrate and the ceramic layer, and substrate oxidation. In many cases, both of these issues may be best addressed through the selection of an appropriate bond coat system. In this study, a low thermal expansion and layer-graded bond coat system, that consists of plasma-sprayed FeCoNiCrAl and FeCrAlY coatings, and a high velocity oxyfuel (HVOF) sprayed FeCrAlY coating, is developed to minimize the thermal stresses and provide oxidation resistance. The thermal expansion and oxidation behavior of the coating system are also characterized, and the strain isolation effect of the bond coat system is analyzed using the finite element method (FEM). Experiments and finite element results show that the layer-graded bond coat system possesses lower interfacial stresses. better strain isolation and excellent oxidation resistance. thus significantly improving the coating performance and durability.

Atmosphere stabilization and element recycle in an experimental mouse-algal system

NASA Technical Reports Server (NTRS)

Smernoff, David T.

1986-01-01

Life support systems based on bioregeneration rely on the control and manipulation of organisms. Experiments conducted with a gas-closed mouse-algal system designed to investigate principles of photosynthetic gas exchange focus primarily on observing gas exchange phenomena under varying algal environmental conditions and secondarily on studying element cycling through compartments of the experimental system. Inherent instabilities exit between the uptake and release of carbon dioxide CO2 and oxygen O2 by the mouse and algae. Variations in light intensity and cell density alter the photosynthetic rate of the algae and enable maintenance of physiologic concentrations of CO2 and O2. Different nitrogen sources (urea and nitrate) result in different algal assimilatory quotients (AQ). Combinations of photosynthetic rate and AQ ratio manipulations have been examined for their potential in stabilizing atmospheric gas concentrations in the gas-closed algal-mouse system. Elemental mass balances through the experimental systems compartments are being studied with the concurrent development of a mathematical simulation model. Element cycling experiments include quantification of elemental flows through system compartments and wet oxidation of system waste materials for use as an algal nutrient source. Oxidized waste products demonstrate inhibitory properties although dilution has been shown to allow normal growth.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, B.D.; Apel, W.A.; Walton, M.R.

Conceptually, biofilters are vapor phase bioreactors that rely on microorganisms in the bed medium to oxidize contaminants in off-gases flowing through the bed to less hazardous compounds. In the most studied and utilized systems reduced compounds such as fuel hydrocarbons are enzymatically oxidized to compounds such as carbon dioxide and water. In these types of reactions the microorganisms in the bed oxidize the contaminant and transfer the electrons to oxygen which is the terminal electron acceptor in the process. In essence the contaminant is the carbon and energy source for the microorganisms in the bed medium and through this catabolicmore » process oxygen is reduced to water. An example of this oxidation process can be seen during the degradation of benzene and similar aromatic compounds. Aromatics are initially attacked by a dioxygenase enzyme which oxidizes the compounds to a labile dihydrodiole which is spontaneously converted to a catechol. The dihydroxylated aromatic rings is then opened by oxidative {open_quotes}ortho{close_quotes} or {open_quotes}meta{close_quotes} cleavage yielding cis, cis-muconic acid or 2-hydroxy-cis, cis-muconic semialdehyde, respectively. These organic compounds are further oxidized to carbon dioxide or are assimilated for cellular material. This paper describes the conversion of carbon tetrachloride using methanol as the primary carbon and energy source.« less

Development of a selective oxidation CO removal reactor for methanol reformate gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okada, Shunji; Takatani, Yoshiaki; Terada, Seijo

1996-12-31

This report forms part of a joint study on a PEFC propulsion system for surface ships, summarized in a presentation to this Seminar, entitled {open_quotes}Study on a Polymer Electrolyte Fuel Cell (PEFC) Propulsion System for Surface Ships{close_quotes}, and which envisages application to a 1,500 DWT cargo vessel. The aspect treated here concerns laboratory-scale tests aimed at reducing by selective oxidation to a level below 10 ppm the carbon monoxide (CO) contained to a concentration of around 1% in reformate gas.

Metal Oxide/Graphene Composites for Supercapacitive Electrode Materials.

PubMed

Jeong, Gyoung Hwa; Baek, Seungmin; Lee, Seungyeol; Kim, Sang-Wook

2016-04-05

Graphene composites with metal or metal oxide nanoparticles have been extensively investigated owing to their potential applications in the fields of fuel cells, batteries, sensing, solar cells, and catalysis. Among them, much research has focused on supercapacitor applications and have come close to realization. Composites include monometal oxides of cobalt, nickel, manganese, and iron, as well as their binary and ternary oxides. In addition, their morphological control and hybrid systems of carbon nanotubes have also been investigated. This review presents the current trends in research on metal oxide/graphene composites for supercapacitors. Furthermore, methods are suggested to improve the properties of electrochemical capacitor electrodes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Methane Emissions from Landfill: Isotopic Evidence for Low Percentage of Oxidation from Gas Wells, Active and Closed Cells

NASA Astrophysics Data System (ADS)

Lowry, David; Fisher, Rebecca; Zazzeri, Giulia; al-Shalaan, Aalia; France, James; Lanoisellé, Mathias; Nisbet, Euan

2017-04-01

Large landfill sites remain a significant source of methane emissions in developed and developing countries, with a global estimated flux of 29 Tg / yr in the EDGAR 2008 database. This is significantly lower than 20 years ago due to the introduction of gas extraction systems, but active cells still emit significant amounts of methane before the gas is ready for extraction. Historically the methane was either passively oxidized through topsoil layers or flared. Oxidation is still the primary method of methane removal in many countries, and covered, remediated cells across the world continue to emit small quantities of methane. The isotopic signatures of methane from landfill gas wells, and that emitted from active and closed cells have been characterized for more than 20 UK landfills since 2011, with more recent work in Kuwait and Hong Kong. Since 2013 the emission plumes have been identified by a mobile measurement system (Zazzeri et al., 2015). Emissions in all 3 countries have a characteristic δ13C signature of -58 ± 3 ‰ dominated by emissions from the active cells, despite the hot, dry conditions of Kuwait and the hot, humid conditions of Hong Kong. Gas well samples define a similar range. Surface emissions from closed cells and closed landfills are mostly in the range -56 to -52 ‰Ṫhese are much more depleted values than those observed in the 1990s (up to -35 ) when soil oxidation was the dominant mechanism of methane removal. Calculations using isotopic signatures of the amount of methane oxidised in these closed areas before emission to atmosphere range from 5 to 15%, but average less than 10%, and are too small to calculate from the high-emitting active cells. Compared to other major methane sources, landfills have the most consistent isotopic signature globally, and are distinct from the more 13C-enriched natural gas, combustion and biomass burning sources. Zazzeri, G. et al. (2015) Plume mapping and isotopic characterization of anthropogenic methane sources, Atmospheric Environment, 110, 151-162, doi.org/10.1016/j.atmosenv.2015.03.029.

Dirac topological insulator in the dz2 manifold of a honeycomb oxide

NASA Astrophysics Data System (ADS)

Lado, J. L.; Pardo, V.

2016-09-01

We show by means of ab initio calculations and tight-binding modeling that an oxide system based on a honeycomb lattice can sustain topologically nontrivial states if a single orbital dominates the spectrum close to the Fermi level. In such a situation, the low-energy spectrum is described by two Dirac equations that become nontrivially gapped when spin-orbit coupling (SOC) is switched on. We provide one specific example but the recipe is general. We discuss a realization of this starting from a conventional spin-1/2 honeycomb antiferromagnet whose states close to the Fermi energy are dz2 orbitals. Switching off magnetism by atomic substitution and ensuring that the electronic structure becomes two-dimensional is sufficient for topologicality to arise in such a system. By deriving a tight-binding Wannier Hamiltonian, we find that the gap in such a model scales linearly with SOC, opposed to other oxide-based topological insulators, where smaller gaps tend to appear by construction of the lattice. We show that the quantum spin Hall state in this system survives in the presence of off-plane magnetism and the orbital magnetic field and we discuss its Landau level spectra, showing that our recipe provides a dz2 realization of the Kane-Mele model.

Complete Genome Sequence of Sulfuriferula sp. Strain AH1, a Sulfur-Oxidizing Autotroph Isolated from Weathered Mine Tailings from the Duluth Complex in Minnesota

PubMed Central

Roepke, Elizabeth W.; Hua, An An; Flood, Beverly E.; Bailey, Jake V.

2017-01-01

ABSTRACT We report the closed and annotated genome sequence of Sulfuriferula sp. strain AH1. Strain AH1 has a 2,877,007-bp chromosome that includes a partial Sox system for inorganic sulfur oxidation and a complete nitrogen fixation pathway. It also has a single 39,138-bp plasmid with genes for arsenic and mercury resistance. PMID:28798167

Nitrous oxide emissions from one-step partial nitritation/anammox processes.

PubMed

Yang, Jingjing; Trela, Jozef; Plaza, Elzbieta

2016-12-01

Measurements of nitrous oxide were made at pilot- and full-scale plants to evaluate greenhouse gas emissions from one-step partial nitritation/anammox processes applied in moving bed biofilm reactors treating reject water. It was found that 0.51-1.29% and 0.35-1.33% of the total nitrogen loads in the pilot- and full-scale reactor, respectively, were emitted as nitrous oxide. Between 80 and 90% of nitrous oxide emissions were in gaseous form and the rest amount was found in the reactor effluent; over 90% of nitrous oxide emissions occurred in the aerated period and less than 8% in the non-aerated period in the full-scale study. Nitrous oxide productions/consumptions were closely related to aeration and the nitrogen loads applied in the system.

Design of catalytic monoliths for closed-cycle carbon dioxide lasers

NASA Technical Reports Server (NTRS)

Herz, R. K.; Guinn, K.; Goldblum, S.; Noskowski, E.

1989-01-01

Pulsed carbon dioxide (CO2) lasers have many applications in aeronautics, space research, weather monitoring and other areas. Full exploitation of the potential of these lasers in hampered by the dissociation of CO2 that occurs during laser operation. The development of closed-cycle CO2 lasers requires active CO-O2 recombination (CO oxidation) catalyst and design methods for implementation of catalysts in CO2 laser systems. A monolith catalyst section model and associated design computer program, LASCAT, are presented to assist in the design of a monolith catalyst section of a closed cycle CO2 laser system. Using LASCAT,the designer is able to specify a number of system parameters and determine the monolith section performance. Trade-offs between the catalyst activity, catalyst dimensions, monolith dimensions, pressure drop, O2 conversion, and other variables can be explored and adjusted to meet system design specifications. An introduction describes a typical closed-cycle CO2 system, and indicates some advantages of a closed cycle laser system over an open cycle system and some advantages of monolith support over other types of supports. The development and use of a monolith catalyst model is presented. The results of a design study and a discussion of general design rules are given.

The Central Role of Biometals Maintains Oxidative Balance in the Context of Metabolic and Neurodegenerative Disorders

PubMed Central

Pokusa, Michal

2017-01-01

Traditionally, oxidative stress as a biological aspect is defined as an imbalance between the free radical generation and antioxidant capacity of living systems. The intracellular imbalance of ions, disturbance in membrane dynamics, hypoxic conditions, and dysregulation of gene expression are all molecular pathogenic mechanisms closely associated with oxidative stress and underpin systemic changes in the body. These also include aspects such as chronic immune system activation, the impairment of cellular structure renewal, and alterations in the character of the endocrine secretion of diverse tissues. All of these mentioned features are crucial for the correct function of the various tissue types in the body. In the present review, we summarize current knowledge about the common roots of metabolic and neurodegenerative disorders induced by oxidative stress. We discuss these common roots with regard to the way that (1) the respective metal ions are involved in the maintenance of oxidative balance and (2) the metabolic and signaling disturbances of the most important biometals, such as Mg2+, Zn2+, Se2+, Fe2+, or Cu2+, can be considered as the central connection point between the pathogenesis of both types of disorders and oxidative stress. PMID:28751933

High Temperature Chemistry at NASA: Hot Topics

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.

2014-01-01

High Temperature issues in aircraft engines Hot section: Ni and Co based Superalloys Oxidation and Corrosion (Durability) at high temperatures. Thermal protection system (TPS) and RCC (Reinforced Carbon-Carbon) on the Space Shuttle Orbiter. High temperatures in other worlds: Planets close to their stars.

A Resettable Keypad Lock with Visible Readout Based on Closed Bipolar Electrochemistry and Electrochromic Poly(3-methylthiophene) Films.

PubMed

Wang, Lei; Lian, Wenjing; Liu, Hongyun

2016-03-24

A closed bipolar electrode (BPE) system was developed with electrochromic poly(3-methylthiophene) (PMT) films electropolymerized on the ITO/rGO electrode as one pole of BPE in the reporting reservoir and the bare ITO electrode as another pole of BPE in the analyte reservoir, in which rGO represents reduced graphene oxide. Under a suitable driving voltage (Vtot), the electrochemical reduction/oxidation of electroactive probes, such as H2O2/glutathione (Glu), in the analyte reservoir could induce the reversible color change of PMT films in the reporting reservoir between blue and red. Based on this, a keypad lock with H2O2 , Glu, and Vtot =-3.0 V as the three inputs and the color change of PMT films as the visible output was established. This system was easily operated and did not need to synthesize the complex compounds or DNA molecules. The security system was easy to reset and could be used repeatedly. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fingerprinting Bacterial and Fungal Manganese Oxidation via Stable Oxygen Isotopes of Manganese Oxides

NASA Astrophysics Data System (ADS)

Sutherland, K. M.; Wankel, S. D.; Hansel, C. M.

2016-12-01

Manganese (Mn) oxides are a ubiquitous mineralogical component of surface Earth and Mars. Mn(III/IV) oxides are potent environmental sorbents and oxidants that play a crucial role in the fate of organic matter. The processes by which Mn(II) oxidation occurs in natural systems are poorly understood, but a number of studies have implicated microogranisms as the primary agents of Mn(II) oxidation in terrestrial and marine environments. The ability of microorganisms to oxidize Mn(II) to Mn(III/IV) oxides transcends the boundaries of biological domain, with an abundance of well-characterized prokaryotes as well as eukaryotic fungi with the ability to oxidize Mn(II) to Mn(III/IV) oxides. Biological Mn(II) oxidation proceeds directly through enzymatic activity or indirectly through the production of reactive oxygen species. Building upon earlier research suggesting that stable oxygen isotope fractionation could be used to fingerprint unique Mn(II)-oxidizing organisms or distinct oxidation pathways, here we use culture-based studies of Mn(II)-oxidizing bacteria and fungi to determine the kinetic oxygen isotope effects associated with Mn(II) oxidation. Since the oxygen molecules in Mn(III/IV) oxides are comprised of oxygen from both precursor water and molecular oxygen, we used a two-fold approach to constrain isotope fractionation with respect to each oxygen source. We used open system oxidation experiments using oxygen-18 labeled water in parallel with closed system Rayleigh distillation oxidation experiments to fully constrain isotope fractionation associated with oxygen atom incorporation during Mn(II) oxidation. Our results suggest commonalities among fractionation factors from groups of Mn(II)-oxidizing organisms that have similar oxidation mechanisms. These results suggest that stable oxygen isotopes of Mn(III/IV) oxides have the potential to distinguish between Mn(II) oxidation pathways in nature, providing a way to determine which groups of Mn(II) oxidizers may be active in present and past surface Earth environments.

Corona-discharge air-purification system

NASA Technical Reports Server (NTRS)

Wydeven, T. J.; Flamm, D. L.

1979-01-01

Plasma reaction chamber removes trace contaminants from spacecraft, submarines, and other closed environments by oxidizing contaminants to produce carbon dioxide and water. Contaminants are alcohols, esters, hydrogen sulfide, and ammonia. Others are lubricant solvents such as Freons, aromatics, and Ketones. Contaminants are removed from chamber by scrubber.

Clay enhancement of methane, low molecular weight hydrocarbon and halocarbon conversion by methanotrophic bacteria

DOEpatents

Apel, William A.; Dugan, Patrick R.

1995-01-01

An apparatus and method for increasing the rate of oxidation of toxic vapors by methanotrophic bacteria. The toxic vapors of interest are methane and trichloroethylene. The apparatus includes a gas phase bioreactor within a closed loop pumping system or a single pass system. The methanotrophic bacteria include Methylomonas methanica, Methylosinus trichosporium, and uncharacterized environmental enrichments.

Clay enhancement of methane, low molecular weight hydrocarbon and halocarbon conversion by methanotrophic bacteria

DOEpatents

Apel, William A.; Dugan, Patrick R.

1995-04-04

An apparatus and method for increasing the rate of oxidation of toxic vapors by methanotrophic bacteria. The toxic vapors of interest are methane and trichloroethylene. The apparatus includes a gas phase bioreactor within a closed loop pumping system or a single pass system. The methanotrophic bacteria include Methylomonas methanica, Methylosinus trichosporium, and uncharacterized environmental enrichments.

Kinetics of Cyclic Oxidation and Cracking and Finite Element Analysis of MA956 and Sapphire/MA956 Composite System

NASA Technical Reports Server (NTRS)

Lee, Kang N.; Arya, Vinod K.; Halford, Gary R.; Barrett, Charles A.

1996-01-01

Sapphire fiber-reinforced MA956 composites hold promise for significant weight savings and increased high-temperature structural capability, as compared to unreinforced MA956. As part of an overall assessment of the high-temperature characteristics of this material system, cyclic oxidation behavior was studied at 1093 C and 1204 C. Initially, both sets of coupons exhibited parabolic oxidation kinetics. Later, monolithic MA956 exhibited spallation and a linear weight loss, whereas the composite showed a linear weight gain without spallation. Weight loss of the monolithic MA956 resulted from the linking of a multiplicity of randomly oriented and closely spaced surface cracks that facilitated ready spallation. By contrast, cracking of the composite's oxide layer was nonintersecting and aligned nominally parallel with the orientation of the subsurface reinforcing fibers. Oxidative lifetime of monolithic MA956 was projected from the observed oxidation kinetics. Linear elastic, finite element continuum, and micromechanics analyses were performed on coupons of the monolithic and composite materials. Results of the analyses qualitatively agreed well with the observed oxide cracking and spallation behavior of both the MA956 and the Sapphire/MA956 composite coupons.

Use of human wastes oxidized to different degrees in cultivation of higher plants on the soil-like substrate intended for closed ecosystems

NASA Astrophysics Data System (ADS)

Tikhomirov, A. A.; Kudenko, Yu. A.; Ushakova, S. A.; Tirranen, L. S.; Gribovskaya, I. A.; Gros, J.-B.; Lasseur, Ch.

2010-09-01

To close mass exchange loops in bioregenerative life support systems more efficiently, researchers of the Institute of Biophysics SB RAS (Krasnoyarsk, Russia) have developed a procedure of wet combustion of human wastes and inedible parts of plants using H 2O 2 in alternating electromagnetic field. Human wastes pretreated in this way can be used as nutrient solutions to grow plants in the phototrophic unit of the LSS. The purpose of this study was to explore the possibilities of using human wastes oxidized to different degrees to grow plants cultivated on the soil-like substrate (SLS). The treated human wastes were analyzed to test their sterility. Then we investigated the effects produced by human wastes oxidized to different degrees on growth and development of wheat plants and on the composition of microflora in the SLS. The irrigation solution contained water, substances extracted from the substrate, and certain amounts of the mineralized human wastes. The experiments showed that the human wastes oxidized using reduced amounts of 30% H 2O 2: 1 ml/g of feces and 0.25 ml/ml of urine were still sterile. The experiments with wheat plants grown on the SLS and irrigated by the solution containing treated human wastes in the amount simulating 1/6 of the daily diet of a human showed that the degree of oxidation of human wastes did not significantly affect plant productivity. On the other hand, the composition of the microbiota of irrigation solutions was affected by the oxidation level of the added metabolites. In the solutions supplemented with partially oxidized metabolites yeast-like microscopic fungi were 20 times more abundant than in the solutions containing fully oxidized metabolites. Moreover, in the solutions containing incompletely oxidized human wastes the amounts of phytopathogenic bacteria and denitrifying microorganisms were larger. Thus, insufficiently oxidized sterile human wastes added to the irrigation solutions significantly affect the composition of the microbiological component of these solutions, which can ultimately unbalance the system as a whole.

Death from Nitrous Oxide.

PubMed

Bäckström, Björn; Johansson, Bengt; Eriksson, Anders

2015-11-01

Nitrous oxide is an inflammable gas that gives no smell or taste. It has a history of abuse as long as its clinical use, and deaths, although rare, have been reported. We describe two cases of accidental deaths related to voluntary inhalation of nitrous oxide, both found dead with a gas mask covering the face. In an attempt to find an explanation to why the victims did not react properly to oncoming hypoxia, we performed experiments where a test person was allowed to breath in a closed system, with or without nitrous oxide added. Vital signs and gas concentrations as well as subjective symptoms were recorded. The experiments indicated that the explanation to the fact that neither of the descendents had reacted to oncoming hypoxia and hypercapnia was due to the inhalation of nitrous oxide. This study raises the question whether nitrous oxide really should be easily, commercially available. © 2015 American Academy of Forensic Sciences.

Band offset engineering of 2DEG oxide systems on Si

NASA Astrophysics Data System (ADS)

Jin, Eric; Kornblum, Lior; Kumah, Divine; Zou, Ke; Broadbridge, Christine; Ngai, Joseph; Ahn, Charles; Walker, Fred

2015-03-01

The discovery of 2-dimensional electron gases (2DEGs) at perovskite oxide interfaces has sparked much interest in recent years due to their large carrier densities when compared with semiconductor heterostructures. For device applications, these oxide systems are plagued by low room temperature electrical mobilities. We present an approach to combine the high carrier density of 2DEG oxides with a higher mobility medium in order to realize the combined benefits of higher mobility and carrier density. We grow epitaxial films of the interfacial oxide system LaTiO3/SrTiO3 (LTO/STO) on silicon by molecular beam epitaxy. Magnetotransport measurements show that the sheet carrier densities of the heterostructures scale with the number of LTO/STO interfaces, consistent with the presence of a 2DEG at each interface. Sheet carrier densities of 8.9 x 1014 cm-2 per interface are measured. Band offsets between the STO and Si are obtained, showing that the conduction band edge of the STO is close in energy to that of silicon, but in a direction that hinders carrier transfer to the silicon substrate. Through modification of the STO/Si interface, we suggest an approach to raise the band offset in order to move the 2DEG from the oxide into the silicon.

Ordered Fe(II)Ti(IV)O3 Mixed Monolayer Oxide on Rutile TiO2(011).

PubMed

Halpegamage, Sandamali; Ding, Pan; Gong, Xue-Qing; Batzill, Matthias

2015-08-25

Oxide monolayers supported or intermixed with an oxide support are potential nanocatalysts whose properties are determined by the interplay with the support. For fundamental studies of monolayer oxides on metal oxide supports, well-defined systems are needed, but so far, the synthesis of monolayer oxides with long-range order on single-crystal oxide surfaces is rare. Here, we show by a combination of scanning tunneling microscopy, photoemission spectroscopy, and density functional theory (DFT)-based computational analysis that the rutile TiO2(011) surface supports the formation of an ordered mixed FeTiO3 monolayer. Deposition of iron in a slightly oxidizing atmosphere (10(-8) Torr O2) and annealing to 300 °C results in a well-ordered surface structure with Fe in a 2+ charge state and Ti in a 4+ charge states. Low-energy ion scattering suggests that the cation surface composition is close to half Fe and half Ti. This surface is stable in ultrahigh vacuum to annealing temperatures of 300 °C before the iron is reduced. DFT simulations confirm that a surface structure with coverage of 50% FeO units is stable and forms an ordered structure. Although distinct from known bulk phases of the iron-titanium oxide systems, the FeTiO3 monolayer exhibits some resemblance to the ilmenite structure, which may suggest that a variety of different mixed oxide phases (of systems that exist in a bulk ilmenite phase) may be synthesized in this way on the rutile TiO2(011) substrate.

Comammox in drinking water systems.

PubMed

Wang, Yulin; Ma, Liping; Mao, Yanping; Jiang, Xiaotao; Xia, Yu; Yu, Ke; Li, Bing; Zhang, Tong

2017-06-01

The discovery of complete ammonia oxidizer (comammox) has fundamentally upended our perception of the global nitrogen cycle. Here, we reported four metagenome assembled genomes (MAGs) of comammox Nitrospira that were retrieved from metagenome datasets of tap water in Singapore (SG-bin1 and SG-bin2), Hainan province, China (HN-bin3) and Stanford, CA, USA (ST-bin4). Genes of phylogenetically distinct ammonia monooxygenase subunit A (amoA) and hydroxylamine dehydrogenase (hao) were identified in these four MAGs. Phylogenetic analysis based on ribosomal proteins, AmoA, hao and nitrite oxidoreductase (subunits nxrA and nxrB) sequences indicated their close relationships with published comammox Nitrospira. Canonical ammonia-oxidizing microbes (AOM) were also identified in the three tap water samples, ammonia-oxidizing bacteria (AOB) in Singapore's and Stanford's samples and ammonia-oxidizing archaea (AOA) in Hainan's sample. The comammox amoA-like sequences were also detected from some other drinking water systems, and even outnumbered the AOA and AOB amoA-like sequences. The findings of MAGs and the occurrences of AOM in different drinking water systems provided a significant clue that comammox are widely distributed in drinking water systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Novel Low-Power, High-Performance, Zero-Maintenance Closed-Path Trace Gas Eddy Covariance System with No Water Vapor Dilution or Spectroscopic Corrections

NASA Astrophysics Data System (ADS)

Sargent, S.; Somers, J. M.

2015-12-01

Trace-gas eddy covariance flux measurement can be made with open-path or closed-path analyzers. Traditional closed-path trace-gas analyzers use multipass absorption cells that behave as mixing volumes, requiring high sample flow rates to achieve useful frequency response. The high sample flow rate and the need to keep the multipass cell extremely clean dictates the use of a fine-pore filter that may clog quickly. A large-capacity filter cannot be used because it would degrade the EC system frequency response. The high flow rate also requires a powerful vacuum pump, which will typically consume on the order of 1000 W. The analyzer must measure water vapor for spectroscopic and dilution corrections. Open-path analyzers are available for methane, but not for nitrous oxide. The currently available methane analyzers have low power consumption, but are very large. Their large size degrades frequency response and disturbs the air flow near the sonic anemometer. They require significant maintenance to keep the exposed multipass optical surfaces clean. Water vapor measurements for dilution and spectroscopic corrections require a separate water vapor analyzer. A new closed-path eddy covariance system for measuring nitrous oxide or methane fluxes provides an elegant solution. The analyzer (TGA200A, Campbell Scientific, Inc.) uses a thermoelectrically-cooled interband cascade laser. Its small sample-cell volume and unique sample-cell configuration (200 ml, 1.5 m single pass) provide excellent frequency response with a low-power scroll pump (240 W). A new single-tube Nafion® dryer removes most of the water vapor, and attenuates fluctuations in the residual water vapor. Finally, a vortex intake assembly eliminates the need for an intake filter without adding volume that would degrade system frequency response. Laboratory testing shows the system attenuates the water vapor dilution term by more than 99% and achieves a half-power band width of 3.5 Hz.

Trace Contaminant Control: An In-Depth Study of a Silica-Titania Composite for Photocatalytic Remediation of Closed-Environment Habitat Air

NASA Technical Reports Server (NTRS)

Coutts, Janelle L.

2013-01-01

This collection of studies focuses on a PCO system for the oxidation of a model compound, ethanol, using an adsorption-enhanced silica-TiO2 composite (STC) as the photocatalyst; studies are aimed at addressing the optimization of various parameters including light source, humidity, temperature, and possible poisoning events for use as part of a system for gaseous trace-contaminant control system in closed-environment habitats. The first goal focused on distinguishing the effect of photon flux (i.e., photons per unit time reaching a surface) from that of photon energy (i.e., wavelength) of a photon source on the PCO of ethanol. Experiments were conducted in a bench-scale annular reactor packed with STC pellets and irradiated with either a UV-A fluorescent black light blue lamp O max=365 nm) at its maximum light intensity or a UV-C germicidal lamp O. max=254 nm) at three levels of light intensity. The STC-catalyzed oxidation of ethanol was found to follow zero-order kinetics with respect to CO2 production, regardless of the photon source. Increased photon flux led to increased EtOH removal, mineralization, and oxidation rate accompanied by lower intermediate concentration in the effluent. The oxidation rate was higher in the reactor irradiated by UV-C than by UV-A (38.4 vs. 31.9 nM s-1 ) at the same photon flux, with similar trends for mineralization (53.9 vs. 43.4%) and reaction quantum efficiency (i.e., photonic efficiency, 63.3 vs. 50.1 nmol C02 mol photons-1 ). UV-C irradiation also led to decreased intermediate concentration in the effluent compared to UV -A irradiation. These results demonstrated that STC-catalyzed oxidation is enhanced by both increased photon flux and photon energy. The effect of temperature and relative humidity on the STC-catalyzed degradation of ethanol was also determined using the UV-A light source at its maximum intensity.

Oocyte exposure to ZnO nanoparticles inhibits early embryonic development through the γ-H2AX and NF-κB signaling pathways.

PubMed

Liu, Jing; Zhao, Yong; Ge, Wei; Zhang, Pengfei; Liu, Xinqi; Zhang, Weidong; Hao, Yanan; Yu, Shuai; Li, Lan; Chu, Meiqiang; Min, Lingjiang; Zhang, Hongfu; Shen, Wei

2017-06-27

The impacts of zinc oxide nanoparticles on embryonic development following oocyte stage exposure are unknown and the underlying mechanisms are sparsely understood. In the current investigation, intact nanoparticles were detected in ovarian tissue in vivo and cultured cells in vitro under zinc oxide nanoparticles treatment. Zinc oxide nanoparticles exposure during the oocyte stage inhibited embryonic development. Notably, in vitro culture data closely matched in vivo embryonic data, in that the impairments caused by Zinc oxide nanoparticles treatment passed through cell generations; and both gamma-H2AX and NF-kappaB pathways were involved in zinc oxide nanoparticles caused embryo-toxicity. Copper oxide and silicon dioxide nanoparticles have been used to confirm that particles are important for the toxicity of zinc oxide nanoparticles. The toxic effects of zinc oxide nanoparticles emanate from both intact nanoparticles and Zn2+. Our investigation along with others suggests that zinc oxide nanoparticles are toxic to the female reproductive system [ovaries (oocytes)] and subsequently embryo-toxic and that precaution should be taken regarding human exposure to their everyday use.

Oocyte exposure to ZnO nanoparticles inhibits early embryonic development through the γ-H2AX and NF-κB signaling pathways

PubMed Central

Liu, Jing; Zhao, Yong; Ge, Wei; Zhang, Pengfei; Liu, Xinqi; Zhang, Weidong; Hao, Yanan; Yu, Shuai; Li, Lan; Chu, Meiqiang; Min, Lingjiang; Zhang, Hongfu; Shen, Wei

2017-01-01

The impacts of zinc oxide nanoparticles on embryonic development following oocyte stage exposure are unknown and the underlying mechanisms are sparsely understood. In the current investigation, intact nanoparticles were detected in ovarian tissue in vivo and cultured cells in vitro under zinc oxide nanoparticles treatment. Zinc oxide nanoparticles exposure during the oocyte stage inhibited embryonic development. Notably, in vitro culture data closely matched in vivo embryonic data, in that the impairments caused by Zinc oxide nanoparticles treatment passed through cell generations; and both gamma-H2AX and NF-kappaB pathways were involved in zinc oxide nanoparticles caused embryo-toxicity. Copper oxide and silicon dioxide nanoparticles have been used to confirm that particles are important for the toxicity of zinc oxide nanoparticles. The toxic effects of zinc oxide nanoparticles emanate from both intact nanoparticles and Zn2+. Our investigation along with others suggests that zinc oxide nanoparticles are toxic to the female reproductive system [ovaries (oocytes)] and subsequently embryo-toxic and that precaution should be taken regarding human exposure to their everyday use. PMID:28487501

Magnetic order close to superconductivity in the iron-based layered LaO1-xFxFeAs systems

NASA Astrophysics Data System (ADS)

de La Cruz, Clarina; Huang, Q.; Lynn, J. W.; Li, Jiying; , W. Ratcliff, II; Zarestky, J. L.; Mook, H. A.; Chen, G. F.; Luo, J. L.; Wang, N. L.; Dai, Pengcheng

2008-06-01

Following the discovery of long-range antiferromagnetic order in the parent compounds of high-transition-temperature (high-Tc) copper oxides, there have been efforts to understand the role of magnetism in the superconductivity that occurs when mobile `electrons' or `holes' are doped into the antiferromagnetic parent compounds. Superconductivity in the newly discovered rare-earth iron-based oxide systems ROFeAs (R, rare-earth metal) also arises from either electron or hole doping of their non-superconducting parent compounds. The parent material LaOFeAs is metallic but shows anomalies near 150K in both resistivity and d.c. magnetic susceptibility. Although optical conductivity and theoretical calculations suggest that LaOFeAs exhibits a spin-density-wave (SDW) instability that is suppressed by doping with electrons to induce superconductivity, there has been no direct evidence of SDW order. Here we report neutron-scattering experiments that demonstrate that LaOFeAs undergoes an abrupt structural distortion below 155K, changing the symmetry from tetragonal (space group P4/nmm) to monoclinic (space group P112/n) at low temperatures, and then, at ~137K, develops long-range SDW-type antiferromagnetic order with a small moment but simple magnetic structure. Doping the system with fluorine suppresses both the magnetic order and the structural distortion in favour of superconductivity. Therefore, like high-Tc copper oxides, the superconducting regime in these iron-based materials occurs in close proximity to a long-range-ordered antiferromagnetic ground state.

Inclusion of products of physicochemical oxidation of organic wastes in matter recycling of biological-technical life support systems.

NASA Astrophysics Data System (ADS)

Tikhomirov, Alexander A.; Kudenko, Yurii; Trifonov, Sergei; Ushakova, Sofya

Inclusion of products of human and plant wastes' `wet' incineration in 22 medium using alter-nating current into matter recycling of biological-technical life support system (BTLSS) has been considered. Fluid and gaseous components have been shown to be the products of such processing. In particular, the final product contained all necessary for plant cultivation nitrogen forms: NO2, NO3, NH4+. As the base solution included urine than NH4+ form dominated. At human solid wastes' mineralization NO2 NH4+ were registered in approximately equal amount. Comparative analysis of mineral composition of oxidized human wastes' and standard Knop solutions has been carried out. On the grounds of that analysis the dilution methods of solutions prepared with addition of oxidized human wastes for their further use for plant irrigation have been suggested. Reasonable levels of wheat productivity cultivated at use of given solutions have been obtained. CO2, N2 and O2 have been determined to be the main gas components of the gas admixture emitted within the given process. These gases easily integrate in matter recycling process of closed ecosystem. The data of plants' cultivation feasibility in the atmosphere obtained after closing of gas loop including physicochemical facility and vegetation chamber with plants-representatives of LSS phototrophic unit has been received. Conclusion of advance research on creation of matter recycling process in the integrated physical-chemical-biological model system has been drawn.

Tetrametallic molecular catalysts for photochemical water oxidation.

PubMed

Sartorel, Andrea; Bonchio, Marcella; Campagna, Sebastiano; Scandola, Franco

2013-03-21

Among molecular water oxidation catalysts (WOCs), those featuring a reactive set of four multi-redox transition metals can leverage an extraordinary interplay of electronic and structural properties. These are of particular interest, owing to their close structural, and possibly functional, relationship to the oxygen evolving complex of natural photosynthesis. In this review, special attention is given to two classes of tetrametallic molecular WOCs: (i) M(4)O(4) cubane-type structures stabilized by simple organic ligands, and (ii) systems in which a tetranuclear metal core is stabilized by coordination of two polyoxometalate (POM) ligands. Recent work in this rapidly evolving field is reviewed, with particular emphasis on photocatalytic aspects. Special attention is given to studies addressing the mechanistic complexity of these systems, sometimes overlooked in the rush for oxygen evolving performance. The complementary role of molecular WOCs and their relationship with bulk oxides and heterogeneous catalysis are discussed.

Oxidation of diesel soot on binary oxide CuCr(Co)-based monoliths.

PubMed

Soloviev, Sergiy O; Kapran, Andriy Y; Kurylets, Yaroslava P

2015-02-01

Binary oxide systems (CuCr2O4, CuCo2O4), deposited onto cordierite monoliths of honeycomb structure with a second support (finely dispersed Al2O3), were prepared as filters for catalytic combustion of diesel soot using internal combustion engine's gas exhausts (O2, NOx, H2O, CO2) and O3 as oxidizing agents. It is shown that the second support increases soot capacity of aforementioned filters, and causes dispersion of the particles of spinel phases as active components enhancing thereby catalyst activity and selectivity of soot combustion to CO2. Oxidants used can be arranged with reference to decreasing their activity in a following series: O3≫NO2>H2O>NO>O2>CO2. Ozone proved to be the most efficient oxidizing agent: the diesel soot combustion by O3 occurs intensively (in the presence of copper chromite based catalyst) even at closing to ambient temperatures. Results obtained give a basis for the conclusion that using a catalytic coating on soot filters in the form of aforementioned binary oxide systems and ozone as the initiator of the oxidation processes is a promising approach in solving the problem of comprehensive purification of automotive exhaust gases at relatively low temperatures, known as the "cold start" problem. Copyright © 2014. Published by Elsevier B.V.

Structural and chemical characterization of terbia thin films grown on hexagonally close packed metal substrates

NASA Astrophysics Data System (ADS)

Cartas, William

Rare earth oxides (REOs) exhibit favorable catalytic performance for a diverse set of chemical transformations, including both partial and complete oxidation reactions. I will discuss our efforts to develop thin film systems of terbia for model surface science investigations of a REO that is effectively reducible, and which is thus expected to promote complete oxidation chemistry of adsorbed species. The growth of terbia on Cu(111) is shown to produce a complex surface that exhibits multiple phases of the oxide as well as exposed substrate. Growing the film on Pt(111) results in more uniform, single phase, and closed film. We used low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) to characterize the structural properties of terbia thin films grown on Pt(111) in ultrahigh vacuum (UHV) using physical vapor deposition. We find that the REO grows as a high quality Tb2O 3(111) film, and adopts oxygen-deficient fluorite structures wherein the metal cations form a hexagonal lattice in registry with the Pt(111) substrate, while oxygen vacancies are randomly distributed within the film. The Tb 2O3(111) films are thermally stable when heated to 1000 K in UHV. LEED and STM show that a fraction of the Tb2O3 forms hexagonal islands when first deposited, and further depositions typically result in three dimensional growth of the film. The Tb2O3 (111) / Pt(111) system produces a coincidence structure, seen very clearly in LEED images. We have also found that Tb2O3(111) films can be oxidized in UHV by exposure to plasma-generated atomic oxygen beams. The oxidized films have an estimated TbO2 stoichiometry and decompose to Tb2O3 during heating, with O2 desorption starting at about 500 K. Terbia films oxidized at 90 K show a weakly bound state of oxygen that is likely chemisorbed. Temperature programmed reaction spectroscopy (TPRS) studies using methanol show that increased oxygen in the film does not modify the chemical selectivity of the film; however, the increased oxygen content does increase the activity of the film toward methanol dehydrogenation. We have found that when methanol is adsorbed onto the terbia-Pt(111) system, it reacts to form formaldehyde and water and reduces the surface. The development of high-quality terbia thin films on Pt(111) provides new opportunities to investigate oxidation chemistry on an REO that has distinct reduction and oxidation properties.

Magnetohydrodynamics (MHD) Engineering Test Facility (ETF) 200 MWe power plant Conceptual Design Engineering Report (CDER)

NASA Technical Reports Server (NTRS)

1981-01-01

The reference conceptual design of the magnetohydrodynamic (MHD) Engineering Test Facility (ETF), a prototype 200 MWe coal-fired electric generating plant designed to demonstrate the commercial feasibility of open cycle MHD, is summarized. Main elements of the design, systems, and plant facilities are illustrated. System design descriptions are included for closed cycle cooling water, industrial gas systems, fuel oil, boiler flue gas, coal management, seed management, slag management, plant industrial waste, fire service water, oxidant supply, MHD power ventilating

Magnetohydrodynamics (MHD) Engineering Test Facility (ETF) 200 MWe power plant Conceptual Design Engineering Report (CDER)

NASA Astrophysics Data System (ADS)

1981-09-01

The reference conceptual design of the magnetohydrodynamic (MHD) Engineering Test Facility (ETF), a prototype 200 MWe coal-fired electric generating plant designed to demonstrate the commercial feasibility of open cycle MHD, is summarized. Main elements of the design, systems, and plant facilities are illustrated. System design descriptions are included for closed cycle cooling water, industrial gas systems, fuel oil, boiler flue gas, coal management, seed management, slag management, plant industrial waste, fire service water, oxidant supply, MHD power ventilating

Air pollutant production by algal cell cultures

NASA Technical Reports Server (NTRS)

Fong, F.; Funkhouser, E. A.

1982-01-01

The production of phytotoxic air pollutants by cultures of Chlorella vulgaris and Euglena gracilis is considered. Algal and plant culture systems, a fumigation system, and ethylene, ethane, cyanide, and nitrogen oxides assays are discussed. Bean, tobacco, mustard green, cantaloupe and wheat plants all showed injury when fumigated with algal gases for 4 hours. Only coleus plants showed any resistance to the gases. It is found that a closed or recycled air effluent system does not produce plant injury from algal air pollutants.

Revisiting the BaO2/BaO redox cycle for solar thermochemical energy storage.

PubMed

Carrillo, A J; Sastre, D; Serrano, D P; Pizarro, P; Coronado, J M

2016-03-21

The barium peroxide-based redox cycle was proposed in the late 1970s as a thermochemical energy storage system. Since then, very little attention has been paid to such redox couples. In this paper, we have revisited the use of reduction-oxidation reactions of the BaO2/BaO system for thermochemical heat storage at high temperatures. Using thermogravimetric analysis, reduction and oxidation reactions were studied in order to find the main limitations associated with each process. Furthermore, the system was evaluated through several charge-discharge stages in order to analyse its possible degradation after repeated cycling. Through differential scanning calorimetry the heat stored and released were also determined. Oxidation reaction, which was found to be slower than reduction, was studied in more detail using isothermal tests. It was observed that the rate-controlling step of BaO oxidation follows zero-order kinetics, although at high temperatures a deviation from Arrhenius behaviour was observed probably due to hindrances to anionic oxygen diffusion caused by the formation of an external layer of BaO2. This redox couple was able to withstand several redox cycles without deactivation, showing reaction conversions close to 100% provided that impurities are previously eliminated through thermal pre-treatment, demonstrating the feasibility of this system for solar thermochemical heat storage.

Petrographic and Isotopic Evidence for Siderite Precursors to Iron Oxide Cements

NASA Astrophysics Data System (ADS)

Loope, D.

2015-12-01

The origin of iron oxide mineralization in the Navajo Sandstone on the Colorado Plateau is important because of the different forms of distinct self-organization exhibited by these systems, the potential importance of the cements as geochronometers, and their use as analogs for similar mineralization on other planets. We consider this mineralization to be the product of microbially mediated oxidation of siderite in evolving groundwater systems. Iron oxide grain coatings were dissolved and the iron precipitated as siderite during a reducing phase of diagenesis. Upon invasion by oxidizing waters, iron-oxidizing bacteria colonized the redox interface between siderite-cemented and porous sandstone. Precipitation of iron oxide at this interface generated acid that facilitated further siderite dissolution. One difficulty in testing this hypothesis is that siderite is destroyed by the cm-scale transport of iron during oxidation. There are two lines of evidence that support the presence of a siderite precursor in these systems. 1)Rhombic grains that we interpret to be iron oxide pseudomorphs after siderite occur where in-situ oxidation rather than dissolution of the siderite precursor has occurred. 2) The δ56Fe values of these iron oxide cements are typically negative. We have measured the δ56Fe value of Navajo Sandstone to be 0.2‰; a value in good agreement with previous workers (Chan et al., 2006; Busigny and Dauphas, 2007). Bleaching of the sandstones apparently results in near complete removal of Fe with little change in the δ56Fe values of the bulk sandstone. The δ56Fe values of iron oxide cements have a median value of -0.8‰; similar to the value we obtained from ferroan carbonate (-0.86‰). Iron oxide from samples that comprise largely rhombic grains has similar δ56Fe values (-0.5‰) to those obtained from cements produced by siderite dissolution and subsequent oxidation (-0.4‰). Our interpretation is that siderite precipitated from an aqueous solution in which the δ56Fe value was <0.2‰ yielding siderite with δ56Fe values that ranged upward from -1.4‰. Invasion of the Navajo by oxidizing waters resulted in microbially mediated oxidation of the siderite concretions. The strongly negative values of the Fe oxides result from the near-quantitative oxidation of the siderite in a closed system.

40 CFR 63.9306 - What are my continuous parameter monitoring system (CPMS) installation, operation, and...

Code of Federal Regulations, 2012 CFR

2012-07-01

... device to the atmosphere. (ii) Car-seal or lock-and-key valve closures. Secure any bypass line valve in the closed position with a car-seal or a lock-and-key type configuration. You must visually inspect... components for integrity and electrical connections for continuity, oxidation, and galvanic corrosion. (d...

ENVIRONMENTAL TECHNOLOGY VERIFICATION--TEST REPORT OF MOBILE SOURCE EMISSION CONTROL DEVICES, CUMMINS EMISSION SOLUTIONS AND CUMMINS FILTRATION DIESEL OXIDATION CATALYST AND CLOSED CRANKCASE VENTILATION SYSTEM

EPA Science Inventory

The U.S. EPA has created the Environmental Technology Verification (ETV) Program. ETV seeks to provide high-quality, peer-reviewed data on technology performance. The Air Pollution Control Technology (APCT) Verification Center, a center under the ETV Program, is operated by Res...

Recycling of LiCl-KCl eutectic based salt wastes containing radioactive rare earth oxychlorides or oxides

NASA Astrophysics Data System (ADS)

Eun, H. C.; Cho, Y. Z.; Son, S. M.; Lee, T. K.; Yang, H. C.; Kim, I. T.; Lee, H. S.

2012-01-01

Recycling of LiCl-KCl eutectic salt wastes containing radioactive rare earth oxychlorides or oxides was studied to recover renewable salts from the salt wastes and to minimize the radioactive wastes by using a vacuum distillation method. Vaporization of the LiCl-KCl eutectic salt was effective above 900 °C and at 5 Torr. The condensations of the vaporized salt were largely dependent on temperature gradient. Based on these results, a recycling system of the salt wastes as a closed loop type was developed to obtain a high efficiency of the salt recovery condition. In this system, it was confirmed that renewable salt was recovered at more than 99 wt.% from the salt wastes, and the changes in temperature and pressure in the system could be utilized to understand the present condition of the system operation.

Containment system for supercritical water oxidation reactor

DOEpatents

Chastagner, Philippe

1994-01-01

A system for containment of a supercritical water oxidation reactor in the event of a rupture of the reactor. The system includes a containment for housing the reaction vessel and a communicating chamber for holding a volume of coolant, such as water. The coolant is recirculated and sprayed to entrain and cool any reactants that might have escaped from the reaction vessel. Baffles at the entrance to the chamber prevent the sprayed coolant from contacting the reaction vessel. An impact-absorbing layer is positioned between the vessel and the containment to at least partially absorb momentum of any fragments propelled by the rupturing vessel. Remote, quick-disconnecting fittings exterior to the containment, in cooperation with shut-off valves, enable the vessel to be isolated and the system safely taken off-line. Normally-closed orifices throughout the containment and chamber enable decontamination of interior surfaces when necessary.

Containment system for supercritical water oxidation reactor

DOEpatents

Chastagner, P.

1994-07-05

A system is described for containment of a supercritical water oxidation reactor in the event of a rupture of the reactor. The system includes a containment for housing the reaction vessel and a communicating chamber for holding a volume of coolant, such as water. The coolant is recirculated and sprayed to entrain and cool any reactants that might have escaped from the reaction vessel. Baffles at the entrance to the chamber prevent the sprayed coolant from contacting the reaction vessel. An impact-absorbing layer is positioned between the vessel and the containment to at least partially absorb momentum of any fragments propelled by the rupturing vessel. Remote, quick-disconnecting fittings exterior to the containment, in cooperation with shut-off valves, enable the vessel to be isolated and the system safely taken off-line. Normally-closed orifices throughout the containment and chamber enable decontamination of interior surfaces when necessary. 2 figures.

Dioxygenase-like reactivity of an isolable superoxo-nickel(II) complex.

PubMed

Company, Anna; Yao, Shenglai; Ray, Kallol; Driess, Matthias

2010-08-16

Although O(2) activation by metals such as iron and copper has been a matter of intensive research in the last decades, this type of chemistry for nickel systems is still in its infancy. Moreover, studies regarding the oxidizing ability of the resulting "Ni(n)-O(2)" species towards exogenous substrates are scarce. In this work, we report on the reactivity of an isolable and thermally stable mononuclear superoxo-nickel compound [Ni(II)(beta-diketiminato)(O(2))] (1) towards different types of organic substrates. In addition, we have been able to prove that the beta-diketiminato ligand can undergo partial intramolecular oxidation due to close proximity between the isopropyl groups of the beta-diketiminato-aryl and the superoxo subunits. Compound 1 performs hydrogen-atom abstraction from O-H and N-H groups and most importantly it shows an unprecedented dioxygenase-like reactivity in the oxidation of 2,4,6-tri-tert-butylphenol. The latter reaction most likely occurs through the mediation of a putative [Ni(III)-oxo] intermediate, affording an unprecedented oxidation product of the phenol that incorporates two oxygen atoms from a single O(2) subunit. Results presented herein provide evidence of the striking oxidizing ability of dioxygen-nickel species and further support the viability to use such systems as oxidation catalysts analogous to its heavy metal congener, palladium.

Ammonia oxidation kinetics determine niche separation of nitrifying Archaea and Bacteria.

PubMed

Martens-Habbena, Willm; Berube, Paul M; Urakawa, Hidetoshi; de la Torre, José R; Stahl, David A

2009-10-15

The discovery of ammonia oxidation by mesophilic and thermophilic Crenarchaeota and the widespread distribution of these organisms in marine and terrestrial environments indicated an important role for them in the global nitrogen cycle. However, very little is known about their physiology or their contribution to nitrification. Here we report oligotrophic ammonia oxidation kinetics and cellular characteristics of the mesophilic crenarchaeon 'Candidatus Nitrosopumilus maritimus' strain SCM1. Unlike characterized ammonia-oxidizing bacteria, SCM1 is adapted to life under extreme nutrient limitation, sustaining high specific oxidation rates at ammonium concentrations found in open oceans. Its half-saturation constant (K(m) = 133 nM total ammonium) and substrate threshold (

Comparative analysis of nitrifying bacteria associated with freshwater and marine aquaria.

PubMed Central

Hovanec, T A; DeLong, E F

1996-01-01

Three nucleic acid probes, two for autotrophic ammonia-oxidizing bacteria of the beta subdivision of the class Proteobacteria and one for alpha subdivision nitrite-oxidizing bacteria, were developed and used to study nitrifying bacterial phylotypes associated with various freshwater and seawater aquarium biofilters. Nitrosomonas europaea and related species were detected in all nitrifying seawater systems and accounted for as much as 20% of the total eubacterial rRNA. In contrast, nitrifying bacteria belonging to the beta-proteobacterial subdivision were detected in only two samples from freshwater aquaria showing vigorous nitrification rates. rRNA originating from nitrite-oxidizing alpha subdivision proteobacteria was not detected in samples from either aquarium environment. The data obtained indicate that chemolithotrophic ammonia oxidation in the freshwater aquaria was not due to beta-proteobacterial phylotypes related to members of the genus Nitrosomonas and their close relatives, the organisms usually implicated in freshwater nitrification. It is likely that nitrification in natural environments is even more complex than nitrification in these simple systems and is less well characterized with regard to the microorganisms responsible. PMID:8702281

Monolith catalysts for closed-cycle carbon dioxide lasers

NASA Technical Reports Server (NTRS)

Herz, Richard K.

1994-01-01

The general subject area of the project involved the development of solid catalysts that have high activity at low temperature for the oxidation of gases such as CO. The original application considered was CO oxidation in closed-cycle CO2 lasers. The scope of the project was subsequently extended to include oxidation of gases in addition to CO and applications such as air purification and exhaust gas emission control. The primary objective of the final phase grant was to develop design criteria for the formulation of new low-temperature oxidation catalysts utilizing Monte Carlo simulations of reaction over NASA-developed catalysts.

Ion-exchange chromatography separation applied to mineral recycle in closed systems

NASA Technical Reports Server (NTRS)

Ballou, E.; Spitze, L. A.; Wong, F. W.; Wydeven, T.; Johnson, C. C.

1981-01-01

As part of the controlled ecological life support system (CELSS) program, a study is being made of mineral separation on ion-exchange columns. The purpose of the mineral separation step is to allow minerals to be recycled from the oxidized waste products of plants, man, and animals for hydroponic food production. In the CELSS application, relatively large quantities of minerals in a broad concentration range must be recovered by the desired system, rather than the trace quantities and very low concentrations treated in analytical applications of ion-exchange chromatography. Experiments have been carried out to assess the parameters pertinent to the scale-up of ion-exchange chromatography and to determine feasibility. Preliminary conclusions are that the column scale-up is in a reasonable size range for the CELSS application. The recycling of a suitable eluent, however, remains a major challenge to the suitability of using ion exchange chromatography in closed systems.

Method of shielding a liquid-metal-cooled reactor

DOEpatents

Sayre, Robert K.

1978-01-01

The primary heat transport system of a nuclear reactor -- particularly for a liquid-metal-cooled fast-breeder reactor -- is shielded and protected from leakage by establishing and maintaining a bed of a powdered oxide closely and completely surrounding all components thereof by passing a gas upwardly therethrough at such a rate as to slightly expand the bed to the extent that the components of the system are able to expand without damage and yet the particles of the bed remain close enough so that the bed acts as a guard vessel for the system. Preferably the gas contains 1 to 10% oxygen and the gas is passed upwardly through the bed at such a rate that the lower portion of the bed is a fixed bed while the upper portion is a fluidized bed, the line of demarcation therebetween being high enough that the fixed bed portion of the bed serves as guard vessel for the system.

Studies of protein oxidation as a product quality attribute on a scale-down model for cell culture process development.

PubMed

Lee, Nacole D; Kondragunta, Bhargavi; Uplekar, Shaunak; Vallejos, Jose; Moreira, Antonio; Rao, Govind

2015-01-01

Of importance to the biological properties of proteins produced in cell culture systems are the complex post-translational modifications that are affected by variations in process conditions. Protein oxidation, oxidative modification to intracellular proteins that involves cleavage of the polypeptide chain, and modifications of the amino acid side chains can be affected by such process variations. Dissolved oxygen is a parameter of increasing interest since studies have shown that despite the necessity of oxygen for respiration, there may also be some detrimental effects of oxygen to the cell. Production and accumulation of reactive oxygen species can cause damage to proteins as a result of oxidation of the cell and cellular components. Variation, or changes to cell culture products, can affect function, clearance rate, immunogenicity, and specific activity, which translates into clinical implications. The effect of increasing dissolved oxygen on protein oxidation in immunoglobulin G3-producing mouse hybridoma cells was studied using 50 mL high-throughput mini-bioreactors that employ non-invasive optical sensor technology for monitoring and closed feedback control of pH and dissolved oxygen. Relative protein carbonyl concentration of proteins produced under varying levels of dissolved oxygen was measured by enzyme-linked immunosorbent assay and used as an indicator of oxidative damage. A trend of increasing protein carbonyl content in response to increasing dissolved oxygen levels under controlled conditions was observed. Protein oxidation, oxidative modification to intracellular proteins that involves cleavage of the polypeptide chain, and modifications of the amino acid side chains can be affected by variations in dissolved oxygen levels in cell culture systems. Studies have shown that despite the necessity of oxygen for respiration, there may be detrimental effects of oxygen to the cell. Production and accumulation of reactive oxygen species can cause damage to proteins as a result of oxidation of the cell and cellular components, affecting function, clearance rate, immunogenicity, and specific activity, which translates into clinical implications. The effect of increasing dissolved oxygen on protein oxidation in immunoglobulin G3-producing mouse hybridoma cells was studied using 50 mL high-throughput mini-bioreactors that employ non-invasive optical sensor technology for monitoring and closed feedback control of pH and dissolved oxygen. Protein carbonyl concentration of proteins produced under varying levels of dissolved oxygen was measured by enzyme-linked immunosorbent assay and used as an indicator of oxidative damage. A trend of increasing protein carbonyl content in response to increasing dissolved oxygen levels under controlled conditions was observed. © PDA, Inc. 2015.

Symposium on Advanced Methods of Catalyst Characterization, November 1-2, 1982.

DTIC Science & Technology

1983-05-18

RD- R136 209 SYMPOSIUM ON DVNCED METHODS OF CTLYST / OARRCTERIZATION OVEMBER 1-2 1982(U) LEHIGH UNIV BETHLEHEM PR K KLIER 18 MRY 83 NBGB04-82-G-B893...Experimental Station. Wilmington, DE 19898 10:45 K1.5 Preliminary Investigation of the Palladium-Tungsten-yAl 203 Catalyst System by Transmission Electron...location and amounts of oxides and sulfides, and sintering and redispersion. Systems and conditions are sufficiently close tothose of industrial

Aqueous Mesocosm Techniques Enabling the Real-Time Measurement of the Chemical and Isotopic Kinetics of Dissolved Methane and Carbon Dioxide.

PubMed

Chan, Eric W; Kessler, John D; Shiller, Alan M; Joung, DongJoo; Colombo, Frank

2016-03-15

Previous studies of microbially mediated methane oxidation in oceanic environments have examined the many different factors that control the rates of oxidation. However, there is debate on what factor(s) are limiting in these types of environments. These factors include the availability of methane, O2, trace metals, nutrients, the density of cell population, and the influence that CO2 production may have on pH. To look at this process in its entirety, we developed an automated mesocosm incubation system with a Dissolved Gas Analysis System (DGAS) coupled to a myriad of analytical tools to monitor chemical changes during methane oxidation. Here, we present new high temporal resolution techniques for investigating dissolved methane and carbon dioxide concentrations and stable isotopic dynamics during aqueous mesocosm and pure culture incubations. These techniques enable us to analyze the gases dissolved in solution and are nondestructive to both the liquid media and the analyzed gases enabling the investigation of a mesocosm or pure culture experiment in a completely closed system, if so desired.

Effects of Curculigoside on Memory Impairment and Bone Loss via Anti-Oxidative Character in APP/PS1 Mutated Transgenic Mice.

PubMed

Zhao, Lu; Liu, Sha; Wang, Yin; Zhang, Qiaoyan; Zhao, Wenjuan; Wang, Zejian; Yin, Ming

2015-01-01

Alzheimer's disease (AD) and osteoporosis are two closely related multifactorial progressively degenerative diseases that predominantly affect aged people. These two diseases share many common risk factors, including old age, being female, smoking, excessive drinking, low estrogen, and vitamin D3 levels. Additionally, oxidative damage and the dysfunction of the antioxidant system play important roles in the pathogenesis of osteoporosis and AD. Aβ not only leads to impaired memory but also plays a crucial role in the demineralization process of bone tissues of older people and women with menopause. Curculigoside can promote calcium deposition and increase the levels of ALP and Runx2 in osteoblasts under oxidative stress via anti-oxidative character. Therefore, we investigated the effects of CUR on the spatial learning and memory by the Morris water maze and brain immunohistochemistry, and bone microstructure and material properties of femurs by micro-computed tomography and mechanical testing in APP/PS1 mutated transgenic mice. Oral administration of CUR can significantly enhance learning performance and ameliorate bone loss in APP/PS1 mutated transgenic mice, and the mechanism may be related to its antioxidant effect. Based on these results, CUR has real potential as a new natural resource for developing medicines or dietary supplements for the prevention and treatment of the two closely linked multifactorial progressive degenerative disorders, AD and osteoporosis.

Does the sympathetic nervous system contribute to the pathophysiology of metabolic syndrome?

PubMed Central

Moreira, Marina C. dos Santos; Pinto, Izabella S. de Jesus; Mourão, Aline A.; Fajemiroye, James O.; Colombari, Eduardo; Reis, Ângela A. da Silva; Freiria-Oliveira, André H.; Ferreira-Neto, Marcos L.; Pedrino, Gustavo R.

2015-01-01

The metabolic syndrome (MS), formally known as syndrome X, is a clustering of several risk factors such as obesity, hypertension, insulin resistance, and dislypidemia which could lead to the development of diabetes and cardiovascular diseases (CVD). The frequent changes in the definition and diagnostic criteria of MS are indications of the controversy and the challenges surrounding the understanding of this syndrome among researchers. Obesity and insulin resistance are leading risk factors of MS. Moreover, obesity and hypertension are closely associated to the increase and aggravation of oxidative stress. The recommended treatment of MS frequently involves change of lifestyles to prevent weight gain. MS is not only an important screening tool for the identification of individuals at high risk of CVD and diabetes but also an indicator of suitable treatment. As sympathetic disturbances and oxidative stress are often associated with obesity and hypertension, the present review summarizes the role of sympathetic nervous system and oxidative stress in the MS. PMID:26379553

Portable optical spectroscopy for accurate analysis of ethane in exhaled breath

NASA Astrophysics Data System (ADS)

Patterson, Claire S.; McMillan, Lesley C.; Longbottom, Christopher; Gibson, Graham M.; Padgett, Miles J.; Skeldon, Kenneth D.

2007-05-01

We report on a maintenance-free, ward-portable, tunable diode laser spectroscopy system for the ultra-sensitive detection of ethane gas. Ethane is produced when cellular lipids are oxidized by free radicals. As a breath biomarker, ethane offers a unique measure of such oxidative stress. The ability to measure real-time breath ethane fluctuations will open up new areas in non-invasive healthcare. Instrumentation for such a purpose must be highly sensitive and specific to the target gas. Our technology has a sensitivity of 70 parts per trillion and a 1 s sampling rate. Based on a cryogenically cooled lead-salt laser, the instrument has a thermally managed closed-loop refrigeration system, eliminating the need for liquid coolants. Custom LabVIEW software allows automatic control by a laptop PC. We have field tested the instrument to ensure that target performance is sustained in a range of environments. We outline the novel applications underway with the instrument based on an in vivo clinical assessment of oxidative stress.

Clumped isotope effects during OH and Cl oxidation of methane

NASA Astrophysics Data System (ADS)

Whitehill, Andrew R.; Joelsson, Lars Magnus T.; Schmidt, Johan A.; Wang, David T.; Johnson, Matthew S.; Ono, Shuhei

2017-01-01

A series of experiments were carried out to determine the clumped (13CH3D) methane kinetic isotope effects during oxidation of methane by OH and Cl radicals, the major sink reactions for atmospheric methane. Experiments were performed in a 100 L quartz photochemical reactor, in which OH was produced from the reaction of O(1D) (from O3 photolysis) with H2O, and Cl was from photolysis of Cl2. Samples were taken from the reaction cell and analyzed for methane (12CH4, 12CH3D, 13CH4, 13CH3D) isotopologue ratios using tunable infrared laser direct absorption spectroscopy. Measured kinetic isotope effects for singly substituted species were consistent with previous experimental studies. For doubly substituted methane, 13CH3D, the observed kinetic isotope effects closely follow the product of the kinetic isotope effects for the 13C and deuterium substituted species (i.e., 13,2KIE = 13KIE × 2KIE). The deviation from this relationship is 0.3‰ ± 1.2‰ and 3.5‰ ± 0.7‰ for OH and Cl oxidation, respectively. This is consistent with model calculations performed using quantum chemistry and transition state theory. The OH and Cl reactions enrich the residual methane in the clumped isotopologue in open system reactions. In a closed system, however, this effect is overtaken by the large D/H isotope effect, which causes the residual methane to become anti-clumped relative to the initial methane. Based on these results, we demonstrate that oxidation of methane by OH, the predominant oxidant for tropospheric methane, will only have a minor (∼0.3‰) impact on the clumped isotope signature (Δ13CH3D, measured as a deviation from a stochastic distribution of isotopes) of tropospheric methane. This paper shows that Δ13CH3D will provide constraints on methane source strengths, and predicts that Δ12CH2D2 can provide information on methane sink strengths.

Solar-Driven Reduction of Aqueous Protons Coupled to Selective Alcohol Oxidation with a Carbon Nitride-Molecular Ni Catalyst System.

PubMed

Kasap, Hatice; Caputo, Christine A; Martindale, Benjamin C M; Godin, Robert; Lau, Vincent Wing-Hei; Lotsch, Bettina V; Durrant, James R; Reisner, Erwin

2016-07-27

Solar water-splitting represents an important strategy toward production of the storable and renewable fuel hydrogen. The water oxidation half-reaction typically proceeds with poor efficiency and produces the unprofitable and often damaging product, O2. Herein, we demonstrate an alternative approach and couple solar H2 generation with value-added organic substrate oxidation. Solar irradiation of a cyanamide surface-functionalized melon-type carbon nitride ((NCN)CNx) and a molecular nickel(II) bis(diphosphine) H2-evolution catalyst (NiP) enabled the production of H2 with concomitant selective oxidation of benzylic alcohols to aldehydes in high yield under purely aqueous conditions, at room temperature and ambient pressure. This one-pot system maintained its activity over 24 h, generating products in 1:1 stoichiometry, separated in the gas and solution phases. The (NCN)CNx-NiP system showed an activity of 763 μmol (g CNx)(-1) h(-1) toward H2 and aldehyde production, a Ni-based turnover frequency of 76 h(-1), and an external quantum efficiency of 15% (λ = 360 ± 10 nm). This precious metal-free and nontoxic photocatalytic system displays better performance than an analogous system containing platinum instead of NiP. Transient absorption spectroscopy revealed that the photoactivity of (NCN)CNx is due to efficient substrate oxidation of the material, which outweighs possible charge recombination compared to the nonfunctionalized melon-type carbon nitride. Photoexcited (NCN)CNx in the presence of an organic substrate can accumulate ultralong-lived "trapped electrons", which allow for fuel generation in the dark. The artificial photosynthetic system thereby catalyzes a closed redox cycle showing 100% atom economy and generates two value-added products, a solar chemical, and solar fuel.

Bioreactors for removing methyl bromide following contained fumigations

USGS Publications Warehouse

Miller, L.G.; Baesman, S.M.; Oremland, R.S.

2003-01-01

Use of methyl bromide (MeBr) as a quarantine, commodity, or structural fumigant is under scrutiny because its release to the atmosphere contributes to the depletion of stratospheric ozone. A closed-system bioreactor consisting of 0.5 L of a growing culture of a previously described bacterium, strain IMB-1, removed MeBr (> 110 ??mol L-1) from recirculating air. Strain IMB-1 grew slowly to high cell densities in the bioreactor using MeBr as its sole carbon and energy source. Bacterial oxidation of MeBr produced CO2 and hydrobromic acid (HBr), which required continuous neutralization with NaOH for the system to operate effectively. Strain IMB-1 was capable of sustained oxidation of large amounts of MeBr (170 mmol in 46 d). In an open-system bioreactor (10-L fermenter), strain IMB-1 oxidized a continuous supply of MeBr (220 ??mol L-1 in air). Growth was continuous, and 0.5 mol of MeBr was removed from the air supply in 14 d. The specific rate of MeBr oxidation was 7 ?? 10-16 mol cell-1 h-1. Bioreactors such as these can therefore be used to remove large quantities of contaminant MeBr, which opens the possibility of biodegradation as a practical means for its disposal.

Functional Studies on Oligotropha carboxidovorans Molybdenum-Copper CO Dehydrogenase Produced in Escherichia coli.

PubMed

Kaufmann, Paul; Duffus, Benjamin R; Teutloff, Christian; Leimkühler, Silke

2018-04-30

The Mo/Cu-dependent CO dehydrogenase (CODH) from Oligotropha carboxidovorans is an enzyme that is able to catalyze both the oxidation of CO to CO 2 and the oxidation of H 2 to protons and electrons. Despite the close to atomic resolution structure (1.1 Å), significant uncertainties have remained with regard to the reaction mechanism of substrate oxidation at the unique Mo/Cu center, as well as the nature of intermediates formed during the catalytic cycle. So far, the investigation of the role of amino acids at the active site was hampered by the lack of a suitable expression system that allowed for detailed site-directed mutagenesis studies at the active site. Here, we report on the establishment of a functional heterologous expression system of O. carboxidovorans CODH in Escherichia coli. We characterize the purified enzyme in detail by a combination of kinetic and spectroscopic studies and show that it was purified in a form with characteristics comparable to those of the native enzyme purified from O. carboxidovorans. With this expression system in hand, we were for the first time able to generate active-site variants of this enzyme. Our work presents the basis for more detailed studies of the reaction mechanism for CO and H 2 oxidation of Mo/Cu-dependent CODHs in the future.

Materials for advanced turbine engines. Volume 1: Advanced blade tip seal system

NASA Technical Reports Server (NTRS)

Zelahy, J. W.; Fairbanks, N. P.

1982-01-01

Project 3, the subject of this technical report, was structured toward the successful engine demonstration of an improved-efficiency, long-life, tip-seal system for turbine blades. The advanced tip-seal system was designed to maintain close operating clearances between turbine blade tips and turbine shrouds and, at the same time, be resistant to environmental effects including high-temperature oxidation, hot corrosion, and thermal cycling. The turbine blade tip comprised an environmentally resistant, activated-diffussion-bonded, monocrystal superalloy combined with a thin layer of aluminium oxide abrasive particles entrapped in an electroplated NiCr matrix. The project established the tip design and joint location, characterized the single-crystal tip alloy and abrasive tip treatment, and established the manufacturing and quality-control plans required to fully process the blades. A total of 171 blades were fully manufactured, and 100 were endurance and performance engine-tested.

Photocatalytic post-treatment in waste water reclamation systems

NASA Technical Reports Server (NTRS)

Cooper, Gerald; Ratcliff, Matthew A.; Verostko, Charles E.

1989-01-01

A photocatalytic water purification process is described which effectively oxidizes organic impurities common to reclaimed waste waters and humidity condensates to carbon dioxide at ambient temperatures. With this process, total organic carbon concentrations below 500 ppb are readily achieved. The temperature dependence of the process is well described by the Arrhenius equation and an activation energy barrier of 3.5 Kcal/mole. The posttreatment approach for waste water reclamation described here shows potential for integration with closed-loop life support systems.

Modeling of simultaneous anaerobic methane and ammonium oxidation in a membrane biofilm reactor.

PubMed

Chen, Xueming; Guo, Jianhua; Shi, Ying; Hu, Shihu; Yuan, Zhiguo; Ni, Bing-Jie

2014-08-19

Nitrogen removal by using the synergy of denitrifying anaerobic methane oxidation (DAMO) and anaerobic ammonium oxidation (Anammox) microorganisms in a membrane biofilm reactor (MBfR) has previously been demonstrated experimentally. In this work, a mathematical model is developed to describe the simultaneous anaerobic methane and ammonium oxidation by DAMO and Anammox microorganisms in an MBfR for the first time. In this model, DAMO archaea convert nitrate, both externally fed and/or produced by Anammox, to nitrite, with methane as the electron donor. Anammox and DAMO bacteria jointly remove the nitrite fed/produced, with ammonium and methane as the electron donor, respectively. The model is successfully calibrated and validated using the long-term (over 400 days) dynamic experimental data from the MBfR, as well as two independent batch tests at different operational stages of the MBfR. The model satisfactorily describes the methane oxidation and nitrogen conversion data from the system. Modeling results show the concentration gradients of methane and nitrogen would cause stratification of the biofilm, where Anammox bacteria mainly grow in the biofilm layer close to the bulk liquid and DAMO organisms attach close to the membrane surface. The low surface methane loadings result in a low fraction of DAMO microorganisms, but the high surface methane loadings would lead to overgrowth of DAMO bacteria, which would compete with Anammox for nitrite and decrease the fraction of Anammox bacteria. The results suggest an optimal methane supply under the given condition should be applied not only to benefit the nitrogen removal but also to avoid potential methane emissions.

Dermal application of nitric oxide releasing acidified nitrite-containing liniments significantly reduces blood pressure in humans.

PubMed

Opländer, Christian; Volkmar, Christine M; Paunel-Görgülü, Adnana; Fritsch, Thomas; van Faassen, Ernst E; Mürtz, Manfred; Grieb, Gerrit; Bozkurt, Ahmet; Hemmrich, Karsten; Windolf, Joachim; Suschek, Christoph V

2012-02-15

Vascular ischemic diseases, hypertension, and other systemic hemodynamic and vascular disorders may be the result of impaired bioavailability of nitric oxide (NO). NO but also its active derivates like nitrite or nitroso compounds are important effector and signal molecules with vasodilating properties. Our previous findings point to a therapeutical potential of cutaneous administration of NO in the treatment of systemic hemodynamic disorders. Unfortunately, no reliable data are available on the mechanisms, kinetics and biological responses of dermal application of nitric oxide in humans in vivo. The aim of the study was to close this gap and to explore the therapeutical potential of dermal nitric oxide application. We characterized with human skin in vitro and in vivo the capacity of NO, applied in a NO-releasing acidified form of nitrite-containing liniments, to penetrate the epidermis and to influence local as well as systemic hemodynamic parameters. We found that dermal application of NO led to a very rapid and significant transepidermal translocation of NO into the underlying tissue. Depending on the size of treated skin area, this translocation manifests itself through a significant systemic increase of the NO derivates nitrite and nitroso compounds, respectively. In parallel, this translocation was accompanied by an increased systemic vasodilatation and blood flow as well as reduced blood pressure. We here give evidence that in humans dermal application of NO has a therapeutic potential for systemic hemodynamic disorders that might arise from local or systemic insufficient availability of NO or its bio-active NO derivates, respectively. Copyright © 2012 Elsevier Inc. All rights reserved.

Redox control of gas compositions in Philippine volcanic-hydrothermal systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giggenbach, W.F.

1993-10-01

Gas samples from five volcanic-hydrothermal systems in the Philippines were analyzed for CO{sub 2}, H{sub 2}S, NH{sub 3}, H{sub 2}, He, Ne, Ar, N{sub 2}, CH{sub 4} and CO. Even in systems with sulfate minerals as common components of alteration assemblages, indicating highly immature, oxidizing conditions at depth, the redox potential governing the concentrations of the reactive gases CO{sub 2}, H{sub 2}S, H{sub 2}, CH{sub 4} and CO approaches closely that expected for attainment of equilibrium with rock in more mature, reduced systems. The finding suggests that overall fluid compositions reflect more closely redox conditions established at the advancing frontmore » of interaction with primary rock rather than those of equilibrium with the set of secondary minerals left behind. With the exception of CO and NH{sub 3}, the close agreement in the compositions of gas samples, taken from pools and deep wells indicates that the secondary processes have only a slight effect on the vapors during their rise from drilled depths (1.8 km) to the surface and that samples from natural features may be taken to be representative of redox conditions at drilled depths.« less

How the multiple antioxidant properties of ascorbic acid affect lipid oxidation in oil-in-water emulsions.

PubMed

Uluata, Sibel; McClements, D Julian; Decker, Eric A

2015-02-18

Lipid oxidation is a serious problem for oil-containing food products because it negatively affects shelf life and nutritional composition. An antioxidant strategy commonly employed to prevent or delay oxidation in foods is to remove oxygen from the closed food-packaging system. An alternative technique is use of an edible oxygen scavenger to remove oxygen within the food. Ascorbic acid (AA) is a particularly promising antioxidant because of its natural label and multiple antioxidative functions. In this study, AA was tested as an oxygen scavenger in buffer and an oil-in-water (O/W) emulsion. The effects of transition metals on the ability of AA to scavenge oxygen were determined. Headspace oxygen decrease less than 1% in the medium-chain triacylglycerol (MCT) O/W emulsion system (pH 3 and 7). AA was able to almost completely remove dissolved oxygen (DO) in a buffered solution. Transition metals (Fe(2+) and Cu(+)) significantly accelerated the degradation of AA; however, iron and copper only increased DO depletion rates, by 10.6-16.4% from day 1 to 7, compared to the control. AA (2.5-20 mM) decreased DO in a 1% O/W emulsion system 32.0-64.0% and delayed the formation of headspace hexanal in the emulsion from 7 to over 20 days. This research shows that, when AA is used in an O/W emulsion system, oxidation of the emulsion system can be delay by multiple mechanisms.

Operating room fires: a closed claims analysis.

PubMed

Mehta, Sonya P; Bhananker, Sanjay M; Posner, Karen L; Domino, Karen B

2013-05-01

To assess patterns of injury and liability associated with operating room (OR) fires, closed malpractice claims in the American Society of Anesthesiologists Closed Claims Database since 1985 were reviewed. All claims related to fires in the OR were compared with nonfire-related surgical anesthesia claims. An analysis of fire-related claims was performed to identify causative factors. There were 103 OR fire claims (1.9% of 5,297 surgical claims). Electrocautery was the ignition source in 90% of fire claims. OR fire claims more frequently involved older outpatients compared with other surgical anesthesia claims (P < 0.01). Payments to patients were more often made in fire claims (P < 0.01), but payment amounts were lower (median $120,166) compared to nonfire surgical claims (median $250,000, P < 0.01). Electrocautery-induced fires (n = 93) increased over time (P < 0.01) to 4.4% claims between 2000 and 2009. Most (85%) electrocautery fires occurred during head, neck, or upper chest procedures (high-fire-risk procedures). Oxygen served as the oxidizer in 95% of electrocautery-induced OR fires (84% with open delivery system). Most electrocautery-induced fires (n = 75, 81%) occurred during monitored anesthesia care. Oxygen was administered via an open delivery system in all high-risk procedures during monitored anesthesia care. In contrast, alcohol-containing prep solutions and volatile compounds were present in only 15% of OR fires during monitored anesthesia care. Electrocautery-induced fires during monitored anesthesia care were the most common cause of OR fires claims. Recognition of the fire triad (oxidizer, fuel, and ignition source), particularly the critical role of supplemental oxygen by an open delivery system during use of the electrocautery, is crucial to prevent OR fires. Continuing education and communication among OR personnel along with fire prevention protocols in high-fire-risk procedures may reduce the occurrence of OR fires.

Beneficial effects of the heme oxygenase-1/carbon monoxide system in patients with severe sepsis/septic shock.

PubMed

Takaki, Shoji; Takeyama, Naoshi; Kajita, Yuka; Yabuki, Teru; Noguchi, Hiroki; Miki, Yasuo; Inoue, Yasusuke; Nakagawa, Takashi; Noguchi, Hiroshi

2010-01-01

We evaluated the relations among the arterial carbon monoxide (CO) concentration, heme oxygenase (HO)-1 expression by monocytes, oxidative stress, plasma levels of cytokines and bilirubin, and the outcome of patients with severe sepsis or septic shock. Thirty-six patients who fulfilled the criteria for severe sepsis or septic shock and 21 other patients without sepsis during their stay in the intensive care unit were studied. HO-1 protein expression by monocytes, arterial CO, oxidative stress, bilirubin, and cytokines were measured. Arterial blood CO, cytokine, and bilirubin levels, and monocyte HO-1 protein expression were higher in patients with severe sepsis/septic shock than in non-septic patients. Increased HO-1 expression was related to the arterial CO concentration and oxidative stress. There was a positive correlation between survival and increased HO-1 protein expression or a higher CO level. Arterial CO and monocyte HO-1 protein expression were increased in critically ill patients, particularly those with severe sepsis or septic shock, suggesting that oxidative stress is closely related to HO-1 expression. The HO-1/CO system may play an important role in sepsis.

[On specific properties of the mitochondrial oxidative phosphorylation system operating as a supercomplex].

PubMed

Nesterov, S V; Skorobogatova, Iu A; Iaguzhinskiĭ, L S

2014-01-01

This paper represents the study of endogenous and exogenous fatty acids affecting the mitochondrial phosphorylation system effectiveness depending on temperature. The experiment was set up under conditions in which the oxidative phosphorylation system operates as a supercomplex. Rat liver mitochondria were isolated without purposive fatty acids removal from membranes, then studied in hypotonic medium (120 mOsm). We managed to detect a very narrow interval 19 ± 1°C where the fatty acid uncoupling effect is weak up to disappearing. At the same small temperature range, a structural rearrangement that takes place in the enzyme system is accompanied with denser packing of membrane protein complexes. Thus, at the temperatures close to 19°C the supercomplex works in the specific regime protected (or partially protected) from the uncoupling effect of fatty acids. Here we also discuss a physiological significance of the increased ATP-synthesis effectiveness at lower temperatures and the most probable character of structural rearrangement taking place at 19°C in the enzymes in the mitochondrial membrane.

Process for depositing epitaxial alkaline earth oxide onto a substrate and structures prepared with the process

DOEpatents

McKee, Rodney A.; Walker, Frederick J.

1996-01-01

A process and structure involving a silicon substrate utilize molecular beam epitaxy (MBE) and/or electron beam evaporation methods and an ultra-high vacuum facility to grow a layup of epitaxial alkaline earth oxide films upon the substrate surface. By selecting metal constituents for the oxides and in the appropriate proportions so that the lattice parameter of each oxide grown closely approximates that of the substrate or base layer upon which oxide is grown, lattice strain at the film/film or film/substrate interface of adjacent films is appreciably reduced or relieved. Moreover, by selecting constituents for the oxides so that the lattice parameters of the materials of adjacent oxide films either increase or decrease in size from one parameter to another parameter, a graded layup of films can be grown (with reduced strain levels therebetween) so that the outer film has a lattice parameter which closely approximates that of, and thus accomodates the epitaxial growth of, a pervoskite chosen to be grown upon the outer film.

Peat Land Oxidation Enhances Subsidence in the Venice Watershed

NASA Astrophysics Data System (ADS)

Gambolati, Giuseppe; Putti, Mario; Teatini, Pietro; Camporese, Matteo; Ferraris, Stefano; Stori, Giuseppe Gasparetto; Nicoletti, Vincenzo; Silvestri, Sonia; Rizzetto, Federica; Tosi, Luigi

2005-06-01

The southernmost part of the Venice Lagoon catchment was progressively reclaimed from marshland starting from the end of the 19th century and finishing in the late 1930s (Figure 1). As a major result, the area was turned into a fertile farmland. At present, the area is kept dry by a distributed drainage system that collects the water from a capillary network of ditches, and pumps it into the lagoon or the sea. By its very origin this area lies below sea level and progressively sinks mainly because of bio-oxidation of the histosols (soils with high organic content) that represent a large fraction of the outcropping soil in the area. The bio-oxidation process occurs in close connection with the agricultural practices and is currently responsible for a subsidence rate of between 1.5 and 2 cm/yr. The Venice Organic Soil Subsidence (VOSS) project was undertaken with the objective of understanding the process of land settlement in this area, quantifying past and present subsidence rates, and advancing possible remedial measures that would not penalize the current agricultural activities of the area. The study, conducted in close collaboration with the local Land Reclamation Authority (Consorzio di Bonifica) and the farmland owners, is focused on a hydrologically controlled catchment, the Zennare Basin (Venice, Italy).

Potential technology transfers of research on low-temperature carbon monoxide-oxygen recombination catalysts

NASA Technical Reports Server (NTRS)

Poziomek, Edward J.

1990-01-01

Results from research on catalytic recombination of CO-O2 for stable closed-cycle operation of CO2 lasers hold much promise for a variety of technology transfer. Expansion of CO2 laser remote sensing applications toward chemical detection and pollution monitoring would certainly be expected. However, the catalysts themselves may be especially effective in low-temperature oxidation of a number of chemicals in addition to CO. It is therefore of interest to compare the CO-O2 catalysts with chemical systems designed for chemical sensing, air purification and process catalysis. Success in understanding the catalytic mechanisms of the recombination of CO-O2 could help to shed light on how catalyst systems operate. New directions in low-temperature oxidation catalysts, coatings for chemical sensors and sorbents for air purification could well emerge.

Water and waste water reclamation in a 21st century space colony

NASA Technical Reports Server (NTRS)

Jebens, H. J.; Johnson, R. D.

1977-01-01

The paper presents the results of research on closed-life support systems initiated during a system design study on space colonization and concentrates on the water and waste water components. Metabolic requirements for the 10,000 inhabitants were supplied by an assumed earth-like diet from an intensive agriculture system. Condensed atmospheric moisture provided a source of potable water and a portion of the irrigation water. Waste water was reclaimed by wet oxidation. The dual-water supply required the condensation of 175 kg/person-day of atmospheric water and the processing of 250 kg/person-day of waste water.

Protein Oxidation: Key to Bacterial Desiccation Resistance?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fredrickson, Jim K.; Li, Shu-Mei W.; Gaidamakova, E.

For extremely ionizing radiation resistant bacteria, survival has been attributed to protection of proteins from oxidative damage during irradiation, with the result that repair systems survive and function with far greater efficiency during recovery than in sensitive bacteria. Here we examined the relationship between survival of dry-climate soil bacteria and the level of cellular protein oxidation induced by desiccation. Bacteria were isolated from surface soils of the shrub-steppe of the U.S. Department of Energy’s Hanford Site in Washington state. A total of 63 isolates were used for phylogenetic analysis. The majority of isolates were closely related to members of themore » genus Deinococcus, with Chelatococcus, Methylobacterium and Bosea also among the genera identified. Desiccation-resistant isolates accumulated high intracellular manganese and low iron concentrations compared to sensitive bacteria. In vivo, proteins of desiccation-resistant bacteria were protected from oxidative modifications that introduce carbonyl groups in sensitive bacteria during drying. We present the case that survival of bacteria that inhabit dry-climate soils are highly dependent on mechanisms which limit protein oxidation during dehydration.« less

Role of Yb3+ ions on enhanced ~2.9 μm emission from Ho3+ ions in low phonon oxide glass system

PubMed Central

Balaji, Sathravada; Gupta, Gaurav; Biswas, Kaushik; Ghosh, Debarati; Annapurna, Kalyandurg

2016-01-01

The foremost limitation of an oxide based crystal or glass host to demonstrate mid- infrared emissions is its high phonon energy. It is very difficult to obtain radiative mid-infrared emissions from these hosts which normally relax non-radiatively between closely spaced energy levels of dopant rare earth ions. In this study, an intense mid-infrared emission around 2.9 μm has been perceived from Ho3+ ions in Yb3+/Ho3+ co-doped oxide based tellurite glass system. This emission intensity has increased many folds upon Yb3+: 985 nm excitation compared to direct Ho3+ excitations due to efficient excited state resonant energy transfer through Yb3+: 2F5/2 → Ho3+: 5I5 levels. The effective bandwidth (FWHM) and cross-section (σem) of measured emission at 2.9 μm are assessed to be 180 nm and 9.1 × 10−21 cm2 respectively which are comparable to other crystal/glass hosts and even better than ZBLAN fluoride glass host. Hence, this Ho3+/Yb3+ co-doped oxide glass system has immense potential for the development of solid state mid-infrared laser sources operating at 2.9 μm region. PMID:27374129

Investigation of styrene in the liver perfusion/cell culture system. No indication of styrene-7,8-oxide as the principal mutagenic metabolite produced by the intact rat liver.

PubMed

Beije, B; Jenssen, D

1982-03-01

Mutagenic effect of styrene and styrene-7,8-oxide was studied with the isolated perfused rat liver as metabolizing system and Chinese hamster V79 cells as genetic target cells. Styrene-7,8-oxide which is mutagenic per se was rapidly metabolized by the perfused rat liver. Thus no mutagenic effect was detected neither in the perfusion medium nor in the bile. However when styrene was added to the perfusion system, an increase in V79 mutants was observed regardless of where in the circulating perfusion medium the V79 cells were placed: the same effect was obtained with V79 cells close to the liver as well as at a distance from the liver. No mutagenic effect was observed in the bile. Simultaneous analysis of the styrene-7,8-oxide concentration in the perfusion medium, suggest that this metabolite is not the cause of the mutagenic effect observed during perfusion with styrene. The effect of the two test compounds on some liver functions was also studied. Both styrene and styrene-7,8-oxide changed the bile flow without affecting bile acid secretion: styrene caused a reduction in bile flow as compared to control perfusions and styrene-7,8-oxide increased the bile flow. Styrene, but not styrene-7,8-oxide, reduced gluconeogenesis from lactate. Styrene had no effect on the liver's capacity to incorporate amino acids into plasma proteins, whereas styrene-7,8-oxide reduced the amino acid incorporation. The microsomal cytochrome P-450 content was not affected by the two test compounds. No alteration in microsomal N- and C-oxygenation of N,N-dimethylaniline (DMA) was observed with styrene-7,8-oxide or the lower styrene dose used (240 mumol), whereas the higher styrene concentration (480 mumol) reduced N-oxygenation and thus also the total DNA metabolism. It is suggested that the results on styrene and styrene-7,8-oxide found here using the liver perfusion/cell culture system mimic the metabolism expected to be found in the intact animal, thus indicating that styrene-7,8-oxide is not the principal mutagenic metabolite of styrene in vivo.

Evaluation of adsorption effects on measurements of ammonia, acetic acid, and methanol

NASA Astrophysics Data System (ADS)

Yokelson, R. J.; Christian, T. J.; Bertschi, I. T.; Hao, W. M.

2003-10-01

We examined how adsorption and desorption of gases from inlets and a cell could affect the accuracy of closed-cell FTIR measurements of carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), nitric oxide (NO), nitrogen dioxide (NO2), methanol (CH3OH), acetic acid (CH3COOH), and ammonia (NH3). When standards were delivered to the cell through a stainless steel inlet, temporarily reduced transmission was observed for CH3OH and NH3. However, a halocarbon wax coated inlet (normally used on the system) had excellent transmission (comparable to room temperature Teflon) for both CH3OH and NH3, even at temperatures as low as 5°C. Thus the wax is valuable for coating sampling system components that cannot be fashioned from Teflon. The instrument had a delayed response (˜10-40 s) for NH3 only, which was attributed to passivation of the Pyrex multipass cell. To determine sampling artifacts that could arise from the complex sample matrix presented by smoke, the closed-cell FTIR system was intercompared with an open-path FTIR system (which is immune to sampling artifacts) in well-mixed smoke. A similar cell passivation delay for NH3 was the only artifact found in this test. Overall, the results suggest that ˜10 s is sufficient to detect >80% of an NH3/CO ratio sampled by our fast-flow, closed-cell system. Longer sampling times or consecutive samples return better results. In field campaigns the closed-cell system sampling times were normally 10 to >100 s so NH3 was probably underestimated by 5-15%.

Solar Metal Sulfate-Ammonia Based Thermochemical Water Splitting Cycle for Hydrogen Production

NASA Technical Reports Server (NTRS)

T-Raissi, Ali (Inventor); Muradov, Nazim (Inventor); Huang, Cunping (Inventor)

2014-01-01

Two classes of hybrid/thermochemical water splitting processes for the production of hydrogen and oxygen have been proposed based on (1) metal sulfate-ammonia cycles (2) metal pyrosulfate-ammonia cycles. Methods and systems for a metal sulfate MSO.sub.4--NH3 cycle for producing H2 and O2 from a closed system including feeding an aqueous (NH3)(4)SO3 solution into a photoctalytic reactor to oxidize the aqueous (NH3)(4)SO3 into aqueous (NH3)(2)SO4 and reduce water to hydrogen, mixing the resulting aqueous (NH3)(2)SO4 with metal oxide (e.g. ZnO) to form a slurry, heating the slurry of aqueous (NH4)(2)SO4 and ZnO(s) in the low temperature reactor to produce a gaseous mixture of NH3 and H2O and solid ZnSO4(s), heating solid ZnSO4 at a high temperature reactor to produce a gaseous mixture of SO2 and O2 and solid product ZnO, mixing the gaseous mixture of SO2 and O2 with an NH3 and H2O stream in an absorber to form aqueous (NH4)(2)SO3 solution and separate O2 for aqueous solution, recycling the resultant solution back to the photoreactor and sending ZnO to mix with aqueous (NH4)(2)SO4 solution to close the water splitting cycle wherein gaseous H2 and O2 are the only products output from the closed ZnSO4--NH3 cycle.

Nonenzymic spectrophotometric determination of potential poison ivy cross-reactors.

PubMed

Quattrone, A J

1977-03-01

I describe an inexpensive, nonenzymic analytical system for prescreening substances that might cross-react as Rhus toxing (e.g., poison ivy, poison oak, and sumac allergens) on human skin. By spectrophotometric assay after incubation with an oxidizing mixture of Cu(II)ammine complex and ammonium persulfate, I could accurately and reproducibly determine o-quinoidal products of several potential synthetic cross-reactors and native poison ivy allergen, and could distinguish these from catecholamines, resorcinol, p-hydroquinone, and a closely related phenol. A good correlation was obtained between this nonenzymic technique and an enzymic assay. This Cu(II)ammine/persulfate oxidative assay, however, is inexpensive and obviates any spectral interference from enzymic proteins.

Mechanisms of Dyslipoproteinemias in Systemic Lupus Erythematosus

PubMed Central

Borba, Eduardo F.; Carvalho, Jozelio F.; Bonfá, Eloísa

2006-01-01

Autoimmunity and inflammation are associated with marked changes in lipid and lipoprotein metabolism in SLE. Autoantibodies and cytokines are able to modulate lipoprotein lipase (LPL) activity, a key enzyme in lipid metabolism, with a consequent “lupus pattern” of dyslipoproteinemia characterized by elevated levels of very low-density lipoprotein cholesterol (VLDL) and triglycerides (TG) and lower high-density lipoprotein cholesterol (HDL) levels. This pattern favors an enhanced LDL oxidation with a subsequent deleterious foam cell formation. Autoantibodies and immunocomplexes may aggravate this oxidative injury by inducing accumulation and deposition of oxLDL in endothelial cells. Drugs and associated diseases usually magnify the close interaction of these factors and further promote the proatherogenic environment of this disease. PMID:17162363

Methane oxidation at a surface-sealed boreal landfill.

PubMed

Einola, Juha; Sormunen, Kai; Lensu, Anssi; Leiskallio, Antti; Ettala, Matti; Rintala, Jukka

2009-07-01

Methane oxidation was studied at a closed boreal landfill (area 3.9 ha, amount of deposited waste 200,000 tonnes) equipped with a passive gas collection and distribution system and a methane oxidative top soil cover integrated in a European Union landfill directive-compliant, multilayer final cover. Gas wells and distribution pipes with valves were installed to direct landfill gas through the water impermeable layer into the top soil cover. Mean methane emissions at the 25 measuring points at four measurement times (October 2005-June 2006) were 0.86-6.2 m(3) ha(-1) h(-1). Conservative estimates indicated that at least 25% of the methane flux entering the soil cover at the measuring points was oxidized in October and February, and at least 46% in June. At each measurement time, 1-3 points showed significantly higher methane fluxes into the soil cover (20-135 m(3) ha(-1) h(-1)) and methane emissions (6-135 m(3) ha(-1) h(-1)) compared to the other points (< 20 m(3) ha(-1) h(-1) and < 10 m(3) ha(-1) h(-1), respectively). These points of methane overload had a high impact on the mean methane oxidation at the measuring points, resulting in zero mean oxidation at one measurement time (November). However, it was found that by adjusting the valves in the gas distribution pipes the occurrence of methane overload can be to some extent moderated which may increase methane oxidation. Overall, the investigated landfill gas treatment concept may be a feasible option for reducing methane emissions at landfills where a water impermeable cover system is used.

Arsenite oxidation by the phyllosphere bacterial community associated with Wolffia australiana.

PubMed

Xie, Wan-Ying; Su, Jian-Qiang; Zhu, Yong-Guan

2014-08-19

Speciation is a key determinant in the toxicity, behavior, and fate of arsenic (As) in the environment. However, little is known about the transformation of As species mediated by floating macrophytes and the phyllosphere bacteria in aquatic and wetland environment. In this study, Wolffia australiana, a rootless floating duckweed, was cultured with (W+B) or without (W-B) phyllosphere bacteria to investigate its ability in arsenite (As(III)) oxidation. Results showed that sterile W. australiana did not oxidize As(III) in the growth medium or in plant tissue, whereas W. australiana with phyllpsphere bacteria displayed substantial As(III) oxidation in the medium. Quantitative PCR of As redox-related functional genes revealed the dominance of the arsenite oxidase (aioA) gene in the phyllosphere bacterial community. These results demonstrate that the phyllosphere bacteria were responsible for the As(III) oxidation in the W+B system. The rapid oxidation of As(III) by the phyllosphere bacterial community may suppress As accumulation in plant tissues under phosphate rich conditions. The aioA gene library showed that the majority of the phyllosphere arsenite-oxidizing bacteria related either closely to unidentified bacteria found in paddy environments or distantly to known arsenite-oxidizing bacteria. Our research suggests a previously overlooked diversity of arsenite-oxidizing bacteria in the phyllosphere of aquatic macrophytes which may have a substantial impact on As biogeochemistry in water environments, warranting further exploration.

Oxygen isotope analysis of bacterial and fungal manganese oxidation.

PubMed

Sutherland, K M; Wankel, S D; Hansel, C M

2018-07-01

The ability of micro-organisms to oxidize manganese (Mn) from Mn(II) to Mn(III/IV) oxides transcends boundaries of biological clade or domain. Many bacteria and fungi oxidize Mn(II) to Mn(III/IV) oxides directly through enzymatic activity or indirectly through the production of reactive oxygen species. Here, we determine the oxygen isotope fractionation factors associated with Mn(II) oxidation via various biotic (bacteria and fungi) and abiotic Mn(II) reaction pathways. As oxygen in Mn(III/IV) oxides may be derived from precursor water and molecular oxygen, we use a twofold approach to determine the isotope fractionation with respect to each oxygen source. Using both 18 O-labeled water and closed-system Rayleigh distillation approaches, we constrain the kinetic isotope fractionation factors associated with O atom incorporation during Mn(II) oxidation to -17.3‰ to -25.9‰ for O 2 and -1.9‰ to +1.8‰ for water. Results demonstrate that stable oxygen isotopes of Mn(III/IV) oxides have potential to distinguish between two main classes of biotic Mn(II) oxidation: direct enzymatic oxidation in which O 2 is the oxidant and indirect enzymatic oxidation in which superoxide is the oxidant. The fraction of Mn(III/IV) oxide-associated oxygen derived from water varies significantly (38%-62%) among these bio-oxides with only weak relationship to Mn oxidation state, suggesting Mn(III) disproportionation may account for differences in the fraction of mineral-bound oxygen from water and O 2 . Additionally, direct incorporation of molecular O 2 suggests that Mn(III/IV) oxides contain a yet untapped proxy of δ18OO2 of environmental O 2 , a parameter reflecting the integrated influence of global respiration, photorespiration, and several other biogeochemical reactions of global significance. © 2018 John Wiley & Sons Ltd.

Origin of stratiform sediment-hosted manganese carbonate ore deposits: Examples from Molango, Mexico, and TaoJiang, China

USGS Publications Warehouse

Okita, P.M.; Shanks, Wayne C.

1992-01-01

Carbonate and sulfide minerals from the Molango, Mexico, and TaoJiang, China, Mn deposits display similar and distinctive ??34S and ??13C patterns in intervals of manganese carbonate mineralization. ??13C-values for Mn-bearing carbonate range from -17.8 to +0.5??? (PDB), with the most negative values occurring in high-grade ore zones that are composed predominantly of rhodochrosite. In contrast, calcite from below, within and above Mn-carbonate zones at Molango has ??13C???0??? (PDB). Markedly negative ??13C data indicate that a large proportion of the carbon in Mn-carbonates was derived from organic matter oxidation. Diagenetic reactions using MnO2 and SO2-4 to oxidize sedimentary organic matter were the principle causes of such 12C enrichment. Pyrite content and sulfide ?? 34S-values also show distinctive variations. In unmineralized rocks, very negative ??34S-values (avg. < -21??? CDT) and abundant pyrite content suggest that pyrite formed from diagenetic, bacteriogenic sulfate reduction. In contrast, Mn-bearing horizons typically contain only trace amounts of pyrite (e.g., <0.5 wt% S with ??34S-values 34S-enriched, in some cases to nearly the value for contemporaneous seawater. 34S-enriched pyrite from the Mn-carbonate intervals indicates sulfide precipitation in an environment that underwent extensive SO2-4 reduction, and was largely a closed system with regard to exchange of sulfate and dissolved sulfide with normal seawater. The occasional occurrence of 34S-depleted pyrite within Mn-carbonate zones dominated by 34S-enriched pyrite is evidence that closed-system conditions were intermittent and limited to local pore waters and did not involve entire sedimentary basins. Mn-carbonate precipitation may have occluded porosity in the surficial sediments, thus establishing an effective barrier to SO2-4 exchange with overlying seawater. Similar isotopic and mineralogic characteristics from both the Molango and TaoJiang deposits, widely separated in geologic time and space, suggest they were formed similarly by MnO2 precipitation at the margins of dysaerobic to anoxic marine basins. Mn-carbonate formed predominantly by early-diagenetic reduction of Mn-oxides via oxidation of organic matter in near-surface sediments. In addition to MnCO3 precipitation, organic matter oxidation reactions resulted in oxidation of FeS to Fe-oxides such as magnetite, maghemite and hematite. The latter process explains anomalously low pyrite content and abundant Fe-oxide minerals in ore zones dominated by rhodochrosite. ?? 1992.

Some TEM observations of Al2O3 scales formed on NiCrAl alloys

NASA Technical Reports Server (NTRS)

Smialek, J.; Gibala, R.

1979-01-01

The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids were observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. The voids resulted from an excess number of oxygen vacancies near the oxidemetal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidation of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al, Cr)2O3 and Ni(Al, Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationship between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

Density functional theory studies of oxygen and carbonate binding to a dicopper patellamide complex.

PubMed

Latifi, Reza; Bagherzadeh, Mojtaba; Milne, Bruce F; Jaspars, Marcel; de Visser, Sam P

2008-12-01

In this work we present results of density functional theory (DFT) calculations on dicopper patellamides and their affinity for molecular oxygen and carbonate. Patellamides are cyclic octapeptides that are produced by a cyanobacterium, and may show promise as therapeutics. Thus, carbonate binding to a dicopper patellamide center gives a stable cyclic octapeptide with a twist of almost 90 degrees . The system exists in close-lying open-shell singlet and triplet spin states with two unpaired electrons in orthogonal sigma* orbitals on each metal center. Subsequently, we replaced carbonate with dioxygen and found a stable Cu2(mu-O)2 diamond shaped patellamide core. In this structure the original dioxygen bond is significantly weakened to essentially a single bond, which should enable the system to transfer these oxygen atoms to substrates. We predicted the IR and Raman spectra of the Cu2(mu-O)2 diamond shaped patellamide structure using density functional theory and found a considerable isotope effect on the O-O stretch vibration for 16O2 versus 18O2 bound structures. Our studies reveal that carbonate forms an extremely stable complex with dicopper patellamide, but that additional molecular oxygen to this system does not give a potential oxidant. Therefore, it is more likely that carbonate prepares the system for dioxygen binding by folding it into the correct configuration followed in the proposed catalytic cycle by a protonation event preceding dioxygen binding to enable the system to reorganize to form a stable Cu2(mu-O)2-patellamide cluster. Alternatively, carbonate may act as an inhibitor that blocks the catalytic activity of the system. It is anticipated that the Cu2(mu-O)2-patellamide structure is a potential active oxidant of the dicopper patellamide complex.

Adaptability of the oxidative capacity of motoneurons

NASA Technical Reports Server (NTRS)

Chalmers, G. R.; Roy, R. R.; Edgerton, V. R.

1992-01-01

Previous studies have demonstrated that a chronic change in neuronal activation can produce a change in soma oxidative capacity, suggesting that: (i) these 2 variables are directly related in neurons and (ii) ion pumping is an important energy requiring activity of a neuron. Most of these studies, however, have focused on reduced activation levels of sensory systems. In the present study the effect of a chronic increase or decrease in motoneuronal activity on motoneuron oxidative capacity and soma size was studied. In addition, the effect of chronic axotomy was studied as an indicator of whether cytoplasmic volume may also be related to the oxidative capacity of motoneurons. A quantitative histochemical assay for succinate dehydrogenase activity was used as a measure of motoneuron oxidative capacity in experimental models in which chronic electromyography has been used to verify neuronal activity levels. Spinal transection reduced, and spinal isolation virtually eliminated lumbar motoneuron electrical activity. Functional overload of the plantaris by removal of its major synergists was used to chronically increase neural activity of the plantaris motor pool. No change in oxidative capacity or soma size resulted from either a chronic increase or decrease in neuronal activity level. These data indicate that the chronic modulation of ionic transport and neurotransmitter turnover associated with action potentials do not induce compensatory metabolic responses in the metabolic capacity of the soma of lumbar motoneurons. Soma oxidative capacity was reduced in the axotomized motoneurons, suggesting that a combination of axoplasmic transport, intracellular biosynthesis and perhaps neurotransmitter turnover represent the major energy demands on a motoneuron. While soma oxidative capacity may be closely related to neural activity in some neural systems, e.g. visual and auditory, lumbar motoneurons appear to be much less sensitive to modulations in chronic activity levels.

Piezoelectric axial flow microvalve

DOEpatents

Gemmen, Randall; Thornton, Jimmy; Vipperman, Jeffrey S.; Clark, William W.

2007-01-09

This invention is directed to a fuel cell operable with a quantity of fuel and a quantity of an oxidizer to produce electrical power, the fuel cell including a fuel cell body including a labyrinth system structured to permit the fuel and the oxidizer to flow therethrough; at least a first catalyst in fluid communication with the labyrinth; and at least a first microvalve operably disposed within at least a portion of the labyrinth. The microvalve utilizes a deflectable member operable upon the application of a voltage from a voltage source. The microvalve includes an elongated flow channel formed therein and extending substantially longitudinally between the first and second ends to permit substantially longitudinal flow of the fluid therethrough and between the first and second ends; and the deflectable member disposed on the valve body, the deflectable member including at least a first piezoelectric portion that is piezoelectrically operable to deflect the deflectable member between an open position and a closed position upon the application of a voltage, the deflectable member in the closed position being operable to resist the flow of the fluid through the flow channel.

Nitric oxide cycle in mammals and the cyclicity principle.

PubMed

Reutov, V P

2002-03-01

This paper continues a series of reports considering nitric oxide (NO) and its cyclic conversions in mammals. Numerous facts are summarized with the goal of developing a general concept that would allow the statement of the multiple effects of NO on various systems of living organisms in the form of a short and comprehensive law. The current state of biological aspects of NO research is analyzed in term of elucidation of possible role of these studies in the system of biological sciences. The general concept is based on a notion on cyclic conversions of NO and its metabolites. NO cycles in living organisms and nitrogen turnover in the biosphere and also the Bethe nitrogen-carbon cycle in star matter are considered. A hypothesis that the cyclic organization of processes in living organisms and the biosphere reflects the evolution of life is proposed: the development of physiological functions and metabolism are suggested to be closely related to space and evolution of the Earth as a planet of the Solar System.

Strategies to optimize the biocompatibility of iron oxide nanoparticles - ;SPIONs safe by design;

NASA Astrophysics Data System (ADS)

Janko, Christina; Zaloga, Jan; Pöttler, Marina; Dürr, Stephan; Eberbeck, Dietmar; Tietze, Rainer; Lyer, Stefan; Alexiou, Christoph

2017-06-01

Various nanoparticle systems have been developed for medical applications in recent years. For constant improvement of efficacy and safety of nanoparticles, a close interdisciplinary interplay between synthesis, physicochemical characterizations and toxicological investigations is urgently needed. Based on combined toxicological data, we follow a ;safe-by design; strategy for our superparamagnetic iron oxide nanoparticles (SPION). Using complementary interference-free toxicological assay systems, we initially identified agglomeration tendencies in physiological fluids, strong uptake by cells and improvable biocompatibility of lauric acid (LA)-coated SPIONs (SPIONLA). Thus, we decided to further stabilize those particles by an artificial protein corona consisting of serum albumin. This approach finally lead to increased colloidal stability, augmented drug loading capacity and improved biocompatibility in previous in vitro assays. Here, we show in whole blood ex vivo and on isolated red blood cells (RBC) that a protein corona protects RBCs from hemolysis by SPIONs.

A proposed mechanism for Pt/SnO(x)-catalyzed CO oxidation

NASA Technical Reports Server (NTRS)

Schryer, David R.; Upchurch, Billy T.; Sidney, Barry D.; Brown, Kenneth G.; Hoflund, Gar B.; Herz, Richard K.

1991-01-01

A mechanism for Pt/SnO(x)-catalyzed CO oxidation is proposed, which is consistent with a broad range of experimental observations. CO oxidation catalysts with high activity at or near room temperature are used in closed-cycle CO2 lasers and air purification.

Is the mu-oxo-mu-peroxodiiron intermediate of a ribonucleotide reductase biomimetic a possible oxidant of epoxidation reactions?

PubMed

de Visser, Sam P

2008-01-01

Density functional calculations on a mu-oxo-mu-peroxodiiron complex (1) with a tetrapodal ligand BPP (BPP=N,N-bis(2-pyridylmethyl)-3-aminopropionate) are presented that is a biomimetic of the active site region of ribonucleotide reductase (RNR). We have studied all low-lying electronic states and show that it has close-lying broken-shell singlet and undecaplet (S=0, 5) ground states with essentially two sextet spin iron atoms. In strongly distorted electronic systems in which the two iron atoms have different spin states, the peroxo group moves considerably out of the plane of the mu-oxodiiron group due to orbital rearrangements. The calculated absorption spectra of (1,11)1 are in good agreement with experimental studies on biomimetics and RNR enzyme systems. Moreover, vibrational shifts in the spectrum due to (18)O(2) substitution of the oxygen atoms in the peroxo group follow similar trends as experimental observations. To identify whether the mu-oxo-mu-1,2-peroxodiiron or the mu-oxo-mu-1,1-peroxodiiron complexes are able to epoxidize substrates, we studied the reactivity patterns versus propene. Generally, the reactions are stepwise via radical intermediates and proceed by two-state reactivity patterns on competing singlet and undecaplet spin state surfaces. However, both the mu-oxo-mu-1,2-peroxodiiron and mu-oxo-mu-1,1-peroxodiiron complex are sluggish oxidants with high epoxidation barriers. The epoxidation barriers for the mu-oxo-mu-1,1-peroxodiiron complex are significantly lower than the ones for the mu-oxo-mu-1,2-peroxodiiron complex but still are too high to be considered for catalytic properties. Thus, theory has ruled out two possible peroxodiiron catalysts as oxidants in RNR enzymes and biomimetics and the quest to find the actual oxidant in the enzyme mechanism continues.

In-situ diagnostics for metalorganic chemical vapor deposition of yttrium barium copper oxide

NASA Astrophysics Data System (ADS)

Tripathi, Ashok Burton

A new stagnation flow MOCVD research reactor is described that is designed to serve as a testbed to develop tools for "intelligent" thin film deposition, such as in-situ sensors and diagnostics, control algorithms, and thin film growth models. The reactor is designed in particular for the deposition of epitaxial YBa2Cu3O 7-delta on MgO, although with minor modifications it would be suitable for deposition of any metal-oxide thin films. The reactor is specifically designed to permit closed-loop thermal and stoichiometric control of the film growth process. Closed-loop control of precursor flow rates is accomplished by using ultraviolet absorption spectroscopy on each precursor line. Also integrated into the design is a Fourier Transform Infrared (FTIR) spectroscopy system which collects real-time, in-situ infrared polarized reflectance spectra of the film as it grows. Numerical simulation was used extensively to optimize the fluid dynamics and heat transfer to provide uniform fluxes to the substrate. As a result, thickness uniformity across the substrate is typically within 3% from the center to the edge of the substrate. Experimental studies of thin films grown in the Y/Ba/Cu/O system have been carried out. The films have been characterized by Rutherford Backscattering Spectrometry and X-ray Diffraction. Results indicate c-axis oriented grains with pure 1:2:3 phase YBCO, good spatial uniformity, and a low degree of c-axis wobble. Experimental growth data is used in a gas phase and surface chemistry model to calculate sticking coefficients for yttrium oxide, barium oxide, and copper oxide on YBCO. In-situ FTIR and Coherent Gradient Sensing (CGS) analysis of growing films has been performed, yielding accurate substrate temperature, film thickness monitoring, and full-field, real-time curvature maps of the films. In addition, we have implemented CGS to obtain full-field in-situ images of local curvature during oxygenation and deoxygenation of YBCO films. An analysis of the oxygen diffusion is performed, and diffusivity constants are presented for a variety of temperature and film conditions.

Evaluating remedial alternatives for an acid mine drainage stream: Application of a reactive transport model

USGS Publications Warehouse

Runkel, R.L.; Kimball, B.A.

2002-01-01

A reactive transport model based on one-dimensional transport and equilibrium chemistry is applied to synoptic data from an acid mine drainage stream. Model inputs include streamflow estimates based on tracer dilution, inflow chemistry based on synoptic sampling, and equilibrium constants describing acid/base, complexation, precipitation/dissolution, and sorption reactions. The dominant features of observed spatial profiles in pH and metal concentration are reproduced along the 3.5-km study reach by simulating the precipitation of Fe(III) and Al solid phases and the sorption of Cu, As, and Pb onto freshly precipitated iron-(III) oxides. Given this quantitative description of existing conditions, additional simulations are conducted to estimate the streamwater quality that could result from two hypothetical remediation plans. Both remediation plans involve the addition of CaCO3 to raise the pH of a small, acidic inflow from ???2.4 to ???7.0. This pH increase results in a reduced metal load that is routed downstream by the reactive transport model, thereby providing an estimate of post-remediation water quality. The first remediation plan assumes a closed system wherein inflow Fe(II) is not oxidized by the treatment system; under the second remediation plan, an open system is assumed, and Fe(II) is oxidized within the treatment system. Both plans increase instream pH and substantially reduce total and dissolved concentrations of Al, As, Cu, and Fe(II+III) at the terminus of the study reach. Dissolved Pb concentrations are reduced by ???18% under the first remediation plan due to sorption onto iron-(III) oxides within the treatment system and stream channel. In contrast, iron(III) oxides are limiting under the second remediation plan, and removal of dissolved Pb occurs primarily within the treatment system. This limitation results in an increase in dissolved Pb concentrations over existing conditions as additional downstream sources of Pb are not attenuated by sorption.

Closeup side view of Space Shuttle Main Engine (SSME) 2059 ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Close-up side view of Space Shuttle Main Engine (SSME) 2059 mounted in a SSME Engine Handler near the Drying Area in the High Bay section of the SSME Processing Facility. The prominent features of the SSME in this view are the hot-gas expansion nozzle extending from the approximate image center toward the image right. The main-engine components extend from the approximate image center toward image right until it meets up with the mount for the SSME Engine Handler. The engine is rotated to a position where the major components in the view are the Low-Pressure Fuel Turbopump Discharge Duct with reflective foil insulation on the upper side of the engine, the Low-Pressure Oxidizer Turbopump and its Discharge Duct on the right side of the engine assembly extending itself down and wrapping under the bottom side of the assembly to the High-Pressure Oxidizer Turbopump pump. The High-Pressure Oxidizer Turbopump Discharge Duct exists the turbopump and extends up to the top side of the assembly where it enters the main oxidizer valve. The sphere on the lower side of the engine assembly is an accumulator that is part of the SSMEs POGO suppression system. - Space Transportation System, Space Shuttle Main Engine, Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Implications of a More Comprehensive Nitrogen Cycle in a Global Biogeochemical Ocean Model

NASA Astrophysics Data System (ADS)

Six, K. D.; Ilyina, T.

2016-02-01

Nitrogen plays a crucial role for nearly all living organisms in the Earth system. Changes in the marine nitrogen cycle not only alter the marine biota, but will also have an impact on the marine carbon cycle and, in turn, on climate due to the close coupling of the carbon-nitrogen cycle. The understanding of processes and controls of the marine nitrogen cycle is therefore a prerequisite to reduce uncertainties in the prediction of future climate. Nevertheless, most ocean biogeochemical components of modern Earth system models have a rather simplistic representation of marine N-cycle mainly focusing on nitrate. Here we present results of the HAMburg Ocean Carbon Cycle model (HAMOCC) as part of the MPI-ESM which was extended by a prognostic representation of ammonium and nitrite to resolve important processes of the marine N-cycle such as nitrification and anaerobic ammonium oxidation (anammox). Additionally, we updated the production of nitrous oxide, an important greenhouse gas, allowing for two sources from oxidation of ammonium (nitrification) and from reduction of nitrite (nitrifier-denitrification) at low oxygen concentrations. Besides an extended model data comparison we discuss the following aspects of the N-cycle by model means: (1) contribution of anammox to the loss of fixed nitrogen, and (2) production and emission of marine nitrous oxide.

Phytoremediation of 1,4-dioxane-containing recovered groundwater.

PubMed

Ferro, Ari M; Kennedy, Jean; LaRue, James C

2013-01-01

The results of a pilot-scale phytoremediation study are reported in this paper. Small plots of trees established on a closed municipal waste landfill site were irrigated with recovered groundwater containing 1,4-dioxane (dioxane) and other volatile organic compounds (VOCs). The plots were managed to minimize the leaching of irrigation water, and leaching was quantified by the use of bromide tracer. Results indicated that the dioxane (2.5 microg/L) was effectively removed, probably via phytovolatilization, and that a full-scale phytoremediation system could be used. A system is now in place at the site in which the recovered groundwater can be treated using two different approaches. A physical treatment system (PTS) will be used during the winter months, and a 12 ha phytoremediation system (stands of coniferous trees) will be used during the growing season. The PTS removes VOCs using an air-stripper, and destroys dioxane using a photo-catalytic oxidation process. Treated water will be routed to the local sewer system. The phytoremediation system, located on the landfill, will be irrigated with effluent from the PTS air-stripper containing dioxane. Seasonal use of the phytoremediation system will reduce reliance on the photo-catalytic oxidation process that is extremely energy consumptive and expensive to operate.

Analytical Capability of Plasma Spectrometry Team

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallimore, David L.

2012-07-19

Samples analyzed were: (1) Pu and U metal; (2) Pu oxide for nuclear fuel; (3) {sup 238}Pu oxide for heat source; and (4) Nuclear forensic samples - filters, swipes. Sample preparations that we did were: metal dissolution, marple filter dissolution, Pu oxide closed vessel acid digestion, and column separation to remove Pu.

LLNL demonstration of liquid gun propellant destruction in a 0.1 gallon per minute scale reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cena, R.J.; Thorsness, C.B.; Coburn, T.T.

1994-06-01

The Lawrence Livermore National Laboratory (LLNL) has built and operated a pilot plant for processing oil shale using recirculating hot solids. This pilot plant, was adapted in 1993 to demonstrate the feasibility of decomposing a liquid gun propellant (LGP), LP XM46, a mixture of 76% HAN (NH{sub 3}OHNO{sub 3}) and 24% TEAN (HOCH{sub 2}CH{sub 2}){sub 3} NHNO{sub 3} diluted 1:3 in water. In the Livermore process, the LPG is thermally treated in a moving packed bed of ceramic spheres, where TEAN and HAN decompose, forming a suite of gases including: methane, carbon monoxide, oxygen, nitrogen oxides, ammonia and molecular nitrogen.more » The ceramic spheres are circulated and heated, providing the energy required for thermal decomposition. The authors performed an extended one day (8 hour) test of the solids recirculation system, with continuous injection of approximately 0.1 gal/min of LGP, diluted 1:3 in water, for a period of eight hours. The apparatus operated smoothly over the course of the eight hour run during which 144 kg of solution was processed, containing 36 kg of LGP. Continuous on-line gas analysis was invaluable in tracking the progress of the experiment and quantifying the decomposition products. The reactor was operated in two modes, a {open_quotes}Pyrolysis{close_quotes} mode, where decomposition products were removed from the moving bed reactor exit, passing through condensers to a flare, and in a {open_quotes}Combustion{close_quotes} mode, where the products were oxidized in air lift pipe prior to exiting the system. In the {open_quotes}Pyrolysis{close_quotes} mode, driver gases were recycled producing a small, concentrated stream of decomposition products. In the {open_quotes}Combustion mode{close_quotes}, the driver gases were not recycled, resulting in 40 times higher gas flow rates and correspondingly lower concentrations of nitrogen bearing gases.« less

Diversity of microbial communities correlated to physiochemical parameters in a digestion basin of a zero-discharge mariculture system.

PubMed

Cytryn, Eddie; Gelfand, Ilya; Barak, Yoram; van Rijn, Jaap; Minz, Dror

2003-01-01

Bacterial community structure and physiochemical parameters were examined in a sedimentation basin of a zero-discharge mariculture system. The system consisted of an intensively stocked fish basin from which water was recirculated through two separate treatment loops. Surface water from the basin was pumped over a trickling filter in one loop while bottom-water was recirculated through a sedimentation basin followed by a fluidized bed reactor in the other. Ammonia oxidation to nitrate in the trickling filter and organic matter digestion together with nitrate reduction in the sedimentation basin and fluidized bed reactor, allowed zero-discharge operation of the system. Relatively high concentrations of oxygen, nitrate, sulphate and organic matter detected simultaneously in the digestion basin suggested the potential for a wide range of microbially-mediated transformation processes. In this study, physiochemical parameters were correlated to bacterial diversity and distribution in horizontal and vertical profiles within this basin in an effort to obtain a basic understanding of the chemical and microbial processes in this system. Chemical activity and microbial diversity, the latter measured by denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR) amplified 16S rDNA fragments, were higher in the sludge layer than in the overlying aqueous layer of the basin. Chemical parameters in sludge samples close to the basin inlet suggested enhanced microbial activity relative to other sampling areas with evidence of both nitrate and sulphate reduction. Four of the nine DGGE bands identified in this zone were affiliated with the Bacteroidetes phylum. Detected sequences closely related to sequences of organisms involved in the sulphur cycle included Desulfovibrio, Dethiosulfovibrio and apparent sulphur oxidizers from the gamma-proteobacteria. In addition, a number of sequences from the beta and alpha-proteobacteria were identified.

Plasma reactor waste management systems

NASA Technical Reports Server (NTRS)

Ness, Robert O., Jr.; Rindt, John R.; Ness, Sumitra R.

1992-01-01

The University of North Dakota is developing a plasma reactor system for use in closed-loop processing that includes biological, materials, manufacturing, and waste processing. Direct-current, high-frequency, or microwave discharges will be used to produce plasmas for the treatment of materials. The plasma reactors offer several advantages over other systems, including low operating temperatures, low operating pressures, mechanical simplicity, and relatively safe operation. Human fecal material, sunflowers, oats, soybeans, and plastic were oxidized in a batch plasma reactor. Over 98 percent of the organic material was converted to gaseous products. The solids were then analyzed and a large amount of water and acid-soluble materials were detected. These materials could possibly be used as nutrients for biological systems.

A new approach for crystallization of copper(ii) oxide hollow nanostructures with superior catalytic and magnetic response

NASA Astrophysics Data System (ADS)

Singh, Inderjeet; Landfester, Katharina; Chandra, Amreesh; Muñoz-Espí, Rafael

2015-11-01

We report the synthesis of copper(ii) oxide hollow nanostructures at ambient pressure and close to room temperature by applying the soft templating effect provided by the confinement of droplets in miniemulsion systems. Particle growth can be explained by considering a mechanism that involves both diffusion and reaction control. The catalytic reduction of p-nitrophenol in aqueous media is used as a model reaction to prove the catalytic activity of the materials: the synthesized hollow structures show nearly 100 times higher rate constants than solid CuO microspheres. The kinetic behavior and the order of the reduction reaction change due to the increase of the surface area of the hollow structures. The synthesis also leads to modification of physical properties such as magnetism.We report the synthesis of copper(ii) oxide hollow nanostructures at ambient pressure and close to room temperature by applying the soft templating effect provided by the confinement of droplets in miniemulsion systems. Particle growth can be explained by considering a mechanism that involves both diffusion and reaction control. The catalytic reduction of p-nitrophenol in aqueous media is used as a model reaction to prove the catalytic activity of the materials: the synthesized hollow structures show nearly 100 times higher rate constants than solid CuO microspheres. The kinetic behavior and the order of the reduction reaction change due to the increase of the surface area of the hollow structures. The synthesis also leads to modification of physical properties such as magnetism. Electronic supplementary information (ESI) available: Associated structural and morphological analysis, XPS characterization, BET surface area, catalytic measurements, recycle tests of the catalyst, and magnetic characterizations. See DOI: 10.1039/c5nr05579b

Closeup view of the top of Space Shuttle Main Engine ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Close-up view of the top of Space Shuttle Main Engine (SSME) 2057 mounted in a SSME Engine Handler in the Vertical Processing area of the SSME Processing Facility at Kennedy Space Center. The most prominent components in this view is the large Low-Pressure Oxidizer Turbopump (LPOTP) Discharge Duct wrapping itself around the right side of the engine assembly. The smaller tube to the left of LPOTP Discharge Duct is the High-Pressure Oxidizer Duct used to supply the turbine of the LPOTP. The other major feature in this view is the Low-Pressure Fuel Turbopump at the top of the engine assembly. - Space Transportation System, Space Shuttle Main Engine, Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Recycling plant, human and animal wastes to plant nutrients in a closed ecological system

NASA Technical Reports Server (NTRS)

Meissner, H. P.; Modell, M.

1979-01-01

The essential minerals for plant growth are nitrogen, phosphorous, potassium (macronutrients), calcium, magnesium, sulfur (secondary nutrients), iron, manganese, boron, copper, zinc, chlorine, sodium, and molybdenum (micronutrients). The first step in recycling wastes will undoubtedly be oxidation of carbon and hydrogen to CO2 and H2O. Transformation of minerals to plant nutrients depends upon the mode of oxidation to define the state of the nutrients. For the purpose of illustrating the type of processing required, ash and off-gas compositions of an incineration process were assumed and subsequent processing requirements were identified. Several processing schemes are described for separating out sodium chloride from the ash, leading to reformulation of a nutrient solution which should be acceptable to plants.

Compositional control of continuously graded anode functional layer

NASA Astrophysics Data System (ADS)

McCoppin, J.; Barney, I.; Mukhopadhyay, S.; Miller, R.; Reitz, T.; Young, D.

2012-10-01

In this work, solid oxide fuel cells (SOFC's) are fabricated with linear-compositionally graded anode functional layers (CGAFL) using a computer-controlled compound aerosol deposition (CCAD) system. Cells with different CGAFL thicknesses (30 um and 50 um) are prepared with a continuous compositionally graded interface deposited between the electrolyte and anode support current collecting regions. The compositional profile was characterized using energy dispersive X-ray spectroscopic mapping. An analytical model of the compound aerosol deposition was developed. The model predicted compositional profiles for both samples that closely matched the measured profiles, suggesting that aerosol-based deposition methods are capable of creating functional gradation on length scales suitable for solid oxide fuel cell structures. The electrochemical performances of the two cells are analyzed using electrochemical impedance spectroscopy (EIS).

Dual Expander Cycle Rocket Engine with an Intermediate, Closed-cycle Heat Exchanger

NASA Technical Reports Server (NTRS)

Greene, William D. (Inventor)

2008-01-01

A dual expander cycle (DEC) rocket engine with an intermediate closed-cycle heat exchanger is provided. A conventional DEC rocket engine has a closed-cycle heat exchanger thermally coupled thereto. The heat exchanger utilizes heat extracted from the engine's fuel circuit to drive the engine's oxidizer turbomachinery.

Thermal and oxidative stability of the Ocimum basilicum L. essential oil/β-cyclodextrin supramolecular system.

PubMed

Hădărugă, Daniel I; Hădărugă, Nicoleta G; Costescu, Corina I; David, Ioan; Gruia, Alexandra T

2014-01-01

Ocimum basilicum L. essential oil and its β-cyclodextrin (β-CD) complex have been investigated with respect to their stability against the degradative action of air/oxygen and temperature. This supramolecular system was obtained by a crystallization method in order to achieve the equilibrium of complexed-uncomplexed volatile compounds in an ethanol/water solution at 50 °C. Both the raw essential oil and its β-CD complex have been subjected to thermal and oxidative degradation conditions in order to evaluate the protective capacity of β-CD. The relative concentration of the O. basilicum L. essential oil compounds, as determined by GC-MS, varies accordingly with their sensitivity to the thermal and/or oxidative degradation conditions imposed. Furthermore, the relative concentration of the volatile O. basilicum L. compounds found in the β-CD complex is quite different in comparison with the raw material. An increase of the relative concentration of linalool oxide from 0.3% to 1.1%, in addition to many sesquiterpene oxides, has been observed. β-CD complexation of the O. basilicum essential oil modifies the relative concentration of the encapsulated volatile compounds. Thus, linalool was better encapsulated in β-CD, while methylchavicol (estragole) was encapsulated in β-CD at a concentration close to that of the raw essential oil. Higher relative concentrations from the degradation of the oxygenated compounds such as linalool oxide and aromadendren oxide were determined in the raw O. basilicum L. essential oil in comparison with the corresponding β-CD complex. For the first time, the protective capability of natural β-CD for labile basil essential oil compounds has been demonstrated.

Thermal and oxidative stability of the Ocimum basilicum L. essential oil/β-cyclodextrin supramolecular system

PubMed Central

Hădărugă, Nicoleta G; Costescu, Corina I; David, Ioan; Gruia, Alexandra T

2014-01-01

Summary Ocimum basilicum L. essential oil and its β-cyclodextrin (β-CD) complex have been investigated with respect to their stability against the degradative action of air/oxygen and temperature. This supramolecular system was obtained by a crystallization method in order to achieve the equilibrium of complexed–uncomplexed volatile compounds in an ethanol/water solution at 50 °C. Both the raw essential oil and its β-CD complex have been subjected to thermal and oxidative degradation conditions in order to evaluate the protective capacity of β-CD. The relative concentration of the O. basilicum L. essential oil compounds, as determined by GC–MS, varies accordingly with their sensitivity to the thermal and/or oxidative degradation conditions imposed. Furthermore, the relative concentration of the volatile O. basilicum L. compounds found in the β-CD complex is quite different in comparison with the raw material. An increase of the relative concentration of linalool oxide from 0.3% to 1.1%, in addition to many sesquiterpene oxides, has been observed. β-CD complexation of the O. basilicum essential oil modifies the relative concentration of the encapsulated volatile compounds. Thus, linalool was better encapsulated in β-CD, while methylchavicol (estragole) was encapsulated in β-CD at a concentration close to that of the raw essential oil. Higher relative concentrations from the degradation of the oxygenated compounds such as linalool oxide and aromadendren oxide were determined in the raw O. basilicum L. essential oil in comparison with the corresponding β-CD complex. For the first time, the protective capability of natural β-CD for labile basil essential oil compounds has been demonstrated. PMID:25550747

Animal protein production modules in biological life support systems: Novel combined aquaculture techniques based on the closed equilibrated biological aquatic system (C.E.B.A.S.)

NASA Astrophysics Data System (ADS)

Blüm, V.; Andriske, M.; Kreuzberg, K.; Schreibman, M. P.

Based on the experiences made with the Closed Equilibrated Biological Aquatic System (C.E.B.A.S.) which was primarily deveoloped for long-term and multi-generation experiments with aquatic animals and plants in a space station highly effective fresh water recycling modules were elaborated utilizing a combination of ammonia oxidizing bacteria filters and higher plants. These exhibit a high effectivity to eliminate phosphate and anorganic nitrogen compounds and arc. in addidition. able to contribute to the oxygen supply of the aquatic animals. The C.E.B.A.S. filter system is able to keep a closed artificial aquatic ecosystem containing teleost fishes and water snails biologically stable for several month and to eliminate waste products deriving from degraded dead fishes without a decrease of the oxygen concentration down to less than 3.5 mg/l at 25 °C. More advanced C.E.B.A.S. filter systems, the BIOCURE filters, were also developed for utilization in semiintensive and intensive aquaculture systems for fishes. In fact such combined animal-plant aquaculture systems represent highly effective productions sites for human food if proper plant and fish species are selected The present papers elucidates ways to novel aquaculture systems in which herbivorous fishes are raised by feeding them with plant biomass produced in the BIOCURE filters and presents the scheme of a modification which utilizes a plant species suitable also for human nutrition. Special attention is paid to the benefits of closed aquaculture system modules which may be integrated into bioregenerative life support systems of a higher complexity for, e. g.. lunar or planetary bases including some psychologiccal aspects of the introduction of animal protein production into plant-based life support systems. Moreover, the basic reproductive biological problems of aquatic animal breeding under reduced gravity are explained leading to a disposition of essential research programs in this context.

Formation of Residual Gases from Source Materials in Closed Crystal Growth Systems

NASA Technical Reports Server (NTRS)

Palosz, W.; Rose, M. Franklin (Technical Monitor)

2001-01-01

Different, non-constituent cases are present in crystal growth systems and may affect processes like growth rate in PVT or voids formation and detached solidification in melt growth systems. The presence of the gas may be detrimental or advantageous depending on its amount and composition, and on the process in question. The presence of the cases, their amount and composition, can be caused and changed by diffusion through and desorption from the growth container material. We have investigated these phenomena for silica glass ampoules. We also found, that residual cases can be generated by the source materials: even very high purity commercial elements and compounds may contain trace amounts of impurities, particularly oxides. The oxides may have low volatilities themselves but their reaction with other species, particularly carbon and hydrogen, may produce volatile compounds like water or carbon oxides. The amount of the gas and its composition is dependent on the original purity of the material (oxide contaminants) and the heat treatment of the source prior to sealing. In many cases. particularly at temperatures below about 900 C and in well-outgassed ampoules, this mechanism dominates. The problem is of a particular importance in sealed systems where the amount and composition of the gas cannot be directly controlled. Therefore, a reasonable knowledge and understanding of the origin, composition, magnitude, and change with time of gases present in sealed ampoules may be important for a meaningful control and interpretation of crystal growth processes. We have investigated this phenomenon in more details for a number of elements and compounds, primarily for II-VI and IV-VI materials. Different source pre-treatment and annealing procedures were applied, and subsequent consecutive annealings and measurements were done to determine the origin and development of the gas in the systems.

Evaluation of a lower-powered analyzer and sampling system for eddy-covariance measurements of nitrous oxide fluxes

NASA Astrophysics Data System (ADS)

Brown, Shannon E.; Sargent, Steve; Wagner-Riddle, Claudia

2018-03-01

Nitrous oxide (N2O) fluxes measured using the eddy-covariance method capture the spatial and temporal heterogeneity of N2O emissions. Most closed-path trace-gas analyzers for eddy-covariance measurements have large-volume, multi-pass absorption cells that necessitate high flow rates for ample frequency response, thus requiring high-power sample pumps. Other sampling system components, including rain caps, filters, dryers, and tubing, can also degrade system frequency response. This field trial tested the performance of a closed-path eddy-covariance system for N2O flux measurements with improvements to use less power while maintaining the frequency response. The new system consists of a thermoelectrically cooled tunable diode laser absorption spectrometer configured to measure both N2O and carbon dioxide (CO2). The system features a relatively small, single-pass sample cell (200 mL) that provides good frequency response with a lower-powered pump ( ˜ 250 W). A new filterless intake removes particulates from the sample air stream with no additional mixing volume that could degrade frequency response. A single-tube dryer removes water vapour from the sample to avoid the need for density or spectroscopic corrections, while maintaining frequency response. This eddy-covariance system was collocated with a previous tunable diode laser absorption spectrometer model to compare N2O and CO2 flux measurements for two full growing seasons (May 2015 to October 2016) in a fertilized cornfield in Southern Ontario, Canada. Both spectrometers were placed outdoors at the base of the sampling tower, demonstrating ruggedness for a range of environmental conditions (minimum to maximum daily temperature range: -26.1 to 31.6 °C). The new system rarely required maintenance. An in situ frequency-response test demonstrated that the cutoff frequency of the new system was better than the old system (3.5 Hz compared to 2.30 Hz) and similar to that of a closed-path CO2 eddy-covariance system (4.05 Hz), using shorter tubing and no dryer, that was also collocated at the site. Values of the N2O fluxes were similar between the two spectrometer systems (slope = 1.01, r2 = 0.96); CO2 fluxes as measured by the short-tubed eddy-covariance system and the two spectrometer systems correlated well (slope = 1.03, r2 = 0.998). The new lower-powered tunable diode laser absorption spectrometer configuration with the filterless intake and single-tube dryer showed promise for deployment in remote areas.

Preliminary calculations related to the accident at Three Mile Island

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirchner, W.L.; Stevenson, M.G.

This report discusses preliminary studies of the Three Mile Island Unit 2 (TMI-2) accident based on available methods and data. The work reported includes: (1) a TRAC base case calculation out to 3 hours into the accident sequence; (2) TRAC parametric calculations, these are the same as the base case except for a single hypothetical change in the system conditions, such as assuming the high pressure injection (HPI) system operated as designed rather than as in the accident; (3) fuel rod cladding failure, cladding oxidation due to zirconium metal-steam reactions, hydrogen release due to cladding oxidation, cladding ballooning, cladding embrittlement,more » and subsequent cladding breakup estimates based on TRAC calculated cladding temperatures and system pressures. Some conclusions of this work are: the TRAC base case accident calculation agrees very well with known system conditions to nearly 3 hours into the accident; the parametric calculations indicate that, loss-of-core cooling was most influenced by the throttling of High-Pressure Injection (HPI) flows, given the accident initiating events and the pressurizer electromagnetic-operated valve (EMOV) failing to close as designed; failure of nearly all the rods and gaseous fission product gas release from the failed rods is predicted to have occurred at about 2 hours and 30 minutes; cladding oxidation (zirconium-steam reaction) up to 3 hours resulted in the production of approximately 40 kilograms of hydrogen.« less

Low survivorship of dauer larva in the nematode Caenorhabditis japonica, a potential comparative system for a model organism, C. elegans.

PubMed

Tanaka, Ryusei; Okumura, Etsuko; Kanzaki, Natsumi; Yoshiga, Toyoshi

2012-05-01

The nematode dauer larva (DL) is a non-aging diapause stage. The DL of the model nematode Caenorhabditis elegans has been studied as a model system for aging and longevity. However, information on DL in other nematode species is limited. In this study, the survivorship, storage, energy consumption, and oxidative stress tolerance of Caenorhabditis japonica DL were examined. C. japonica is a close relative of C. elegans, but has species-specific phoretic associations with the shield bug Parastrachia japonensis. Also, its DL has a much longer lifespan than C. elegans in a biological setting. However, when C. japonica DLs were detached from their phoretic host, they did not survive more than 10 days while more than 80% of C. elegans survived under the same conditions. Also, C. japonica DL showed more active movement (swimming) and lower tolerance to oxidative stress than C. elegans DL. Because the concentration of triacylglycerol (TAG), the energy source of nematodes, did not decrease significantly during the experiment, exhaustion of the energy reservoir did not cause the low survivorship of C. japonica. Instead, low tolerance to oxidizing stress and increased production of reactive oxygen species in C. japonica were the main causes of the reduced survivorship. The fact that C. japonica DL cannot survive away from its insect host indicates that its longevity is increased by unknown factors derived from the host. Despite these significant differences between C. japonica and C. elegans, these two species are phylogenetically closely related (they are derived from a common ancestor). Therefore, C. japonica could be a good comparative system for C. elegans, and further physiological and molecular analyses of C. japonica DL may provide important information about the internal and external factors affecting the longevity of nematodes in general. Copyright © 2012 Elsevier Inc. All rights reserved.

Stabilization and functionalization of iron oxide nanoparticles for biomedical applications

NASA Astrophysics Data System (ADS)

Amstad, Esther; Textor, Marcus; Reimhult, Erik

2011-07-01

Superparamagnetic iron oxide nanoparticles (NPs) are used in a rapidly expanding number of research and practical applications in the biomedical field, including magnetic cell labeling separation and tracking, for therapeutic purposes in hyperthermia and drug delivery, and for diagnostic purposes, e.g., as contrast agents for magnetic resonance imaging. These applications require good NP stability at physiological conditions, close control over NP size and controlled surface presentation of functionalities. This review is focused on different aspects of the stability of superparamagnetic iron oxide NPs, from its practical definition to its implementation by molecular design of the dispersant shell around the iron oxide core and further on to its influence on the magnetic properties of the superparamagnetic iron oxide NPs. Special attention is given to the selection of molecular anchors for the dispersant shell, because of their importance to ensure colloidal and functional stability of sterically stabilized superparamagnetic iron oxide NPs. We further detail how dispersants have been optimized to gain close control over iron oxide NP stability, size and functionalities by independently considering the influences of anchors and the attached sterically repulsive polymer brushes. A critical evaluation of different strategies to stabilize and functionalize core-shell superparamagnetic iron oxide NPs as well as a brief introduction to characterization methods to compare those strategies is given.Superparamagnetic iron oxide nanoparticles (NPs) are used in a rapidly expanding number of research and practical applications in the biomedical field, including magnetic cell labeling separation and tracking, for therapeutic purposes in hyperthermia and drug delivery, and for diagnostic purposes, e.g., as contrast agents for magnetic resonance imaging. These applications require good NP stability at physiological conditions, close control over NP size and controlled surface presentation of functionalities. This review is focused on different aspects of the stability of superparamagnetic iron oxide NPs, from its practical definition to its implementation by molecular design of the dispersant shell around the iron oxide core and further on to its influence on the magnetic properties of the superparamagnetic iron oxide NPs. Special attention is given to the selection of molecular anchors for the dispersant shell, because of their importance to ensure colloidal and functional stability of sterically stabilized superparamagnetic iron oxide NPs. We further detail how dispersants have been optimized to gain close control over iron oxide NP stability, size and functionalities by independently considering the influences of anchors and the attached sterically repulsive polymer brushes. A critical evaluation of different strategies to stabilize and functionalize core-shell superparamagnetic iron oxide NPs as well as a brief introduction to characterization methods to compare those strategies is given. This article was submitted as part of a collection of articles on surface nanotechnology for biological applications. Other papers on this topic can be found in issue 2 of vol. 3 (2011). This issue can be found from the Nanoscale homepage [http://www.rsc.org/nanoscale].

Surface- and tip-enhanced Raman spectroscopy reveals spin-waves in iron oxide nanoparticles

NASA Astrophysics Data System (ADS)

Rodriguez, Raul D.; Sheremet, Evgeniya; Deckert-Gaudig, Tanja; Chaneac, Corinne; Hietschold, Michael; Deckert, Volker; Zahn, Dietrich R. T.

2015-05-01

Nanomaterials have the remarkable characteristic of displaying physical properties different from their bulk counterparts. An additional degree of complexity and functionality arises when oxide nanoparticles interact with metallic nanostructures. In this context the Raman spectra due to plasmonic enhancement of iron oxide nanocrystals are here reported showing the activation of spin-waves. Iron oxide nanoparticles on gold and silver tips are found to display a band around 1584 cm-1 attributed to a spin-wave magnon mode. This magnon mode is not observed for nanoparticles deposited on silicon (111) or on glass substrates. Metal-nanoparticle interaction and the strongly localized electromagnetic field contribute to the appearance of this mode. The localized excitation that generates this mode is confirmed by tip-enhanced Raman spectroscopy (TERS). The appearance of the spin-waves only when the TERS tip is in close proximity to a nanocrystal edge suggests that the coupling of a localized plasmon with spin-waves arises due to broken symmetry at the nanoparticle border and the additional electric field confinement. Beyond phonon confinement effects previously reported in similar systems, this work offers significant insights on the plasmon-assisted generation and detection of spin-waves optically induced.Nanomaterials have the remarkable characteristic of displaying physical properties different from their bulk counterparts. An additional degree of complexity and functionality arises when oxide nanoparticles interact with metallic nanostructures. In this context the Raman spectra due to plasmonic enhancement of iron oxide nanocrystals are here reported showing the activation of spin-waves. Iron oxide nanoparticles on gold and silver tips are found to display a band around 1584 cm-1 attributed to a spin-wave magnon mode. This magnon mode is not observed for nanoparticles deposited on silicon (111) or on glass substrates. Metal-nanoparticle interaction and the strongly localized electromagnetic field contribute to the appearance of this mode. The localized excitation that generates this mode is confirmed by tip-enhanced Raman spectroscopy (TERS). The appearance of the spin-waves only when the TERS tip is in close proximity to a nanocrystal edge suggests that the coupling of a localized plasmon with spin-waves arises due to broken symmetry at the nanoparticle border and the additional electric field confinement. Beyond phonon confinement effects previously reported in similar systems, this work offers significant insights on the plasmon-assisted generation and detection of spin-waves optically induced. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01277e

Characterization of methane oxidation in a simulated landfill cover system by comparing molecular and stable isotope mass balances.

PubMed

Schulte, Marcel; Jochmann, Maik A; Gehrke, Tobias; Thom, Andrea; Ricken, Tim; Denecke, Martin; Schmidt, Torsten C

2017-11-01

Biological methane oxidation may be regarded as a method of aftercare treatment for landfills to reduce climate relevant methane emissions. It is of social and economic interest to estimate the behavior of bacterial methane oxidation in aged landfill covers due to an adequate long-term treatment of the gas emissions. Different approaches assessing methane oxidation in laboratory column studies have been investigated by other authors recently. However, this work represents the first study in which three independent approaches, ((i) mass balance, (ii) stable isotope analysis, and (iii) stoichiometric balance of product (CO 2 ) and reactant (CH 4 ) by CO 2 /CH 4 -ratio) have been compared for the estimation of the biodegradation by a robust statistical validation on a rectangular, wide soil column. Additionally, an evaluation by thermal imaging as a potential technique for the localization of the active zone of bacterial methane oxidation has been addressed in connection with stable isotope analysis and CO 2 /CH 4 -ratios. Although landfills can be considered as open systems the results for stable isotope analysis based on a closed system correlated better with the mass balance than calculations based on an open system. CO 2 /CH 4 -ratios were also in good agreement with mass balance. In general, highest values for biodegradation were determined from mass balance, followed by CO 2 /CH 4 -ratio, and stable isotope analysis. The investigated topsoil proved to be very suitable as a potential cover layer by removing up to 99% of methane for CH 4 loads of 35-65gm -2 d -1 that are typical in the aftercare phase of landfills. Finally, data from stable isotope analysis and the CO 2 /CH 4 -ratios were used to trace microbial activity within the reactor system. It was shown that methane consumption and temperature increase, as a cause of high microbial activity, correlated very well. Copyright © 2017 Elsevier Ltd. All rights reserved.

SONOS Nonvolatile Memory Cell Programming Characteristics

NASA Technical Reports Server (NTRS)

MacLeod, Todd C.; Phillips, Thomas A.; Ho, Fat D.

2010-01-01

Silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile memory is gaining favor over conventional EEPROM FLASH memory technology. This paper characterizes the SONOS write operation using a nonquasi-static MOSFET model. This includes floating gate charge and voltage characteristics as well as tunneling current, voltage threshold and drain current characterization. The characterization of the SONOS memory cell predicted by the model closely agrees with experimental data obtained from actual SONOS memory cells. The tunnel current, drain current, threshold voltage and read drain current all closely agreed with empirical data.

JTEC panel report on advanced composites in Japan

NASA Technical Reports Server (NTRS)

Diefendorf, R. J.; Grisaffe, S. J.; Hillig, W. B.; Perepezko, J. H.; Pipes, R. B.; Sheehan, J. E.

1991-01-01

The JTEC Panel on Advanced Composites visited Japan and surveyed the status and future directions of Japanese high performance ceramic and carbon fibers and their composites in metal, intermetallic, ceramic and carbon matrices. The panel's interests included not only what composite systems were chosen, but also how these systems were developed. A strong carbon and fiber industry makes Japan the leader in carbon fiber technology. Japan has initiated an oxidation resistant carbon/carbon composite program. The goals for this program are ambitious, and it is just starting, but its progress should be closely monitored in the United States.

Evidence against the nuclear in situ binding of arsenicals-oxidative stress theory of arsenic carcinogenesis

EPA Science Inventory

A large amount of evidence suggests that arsenicals act via oxidative stress in causing cancer in humans and experimental animals. It is possible that arsenicals could bind in situ close to nuclear DNA followed by Haber-Weiss type oxidative DNA damage. Therefore, we tested this...

Project NEO Specific Impulse Testing Solutions

NASA Technical Reports Server (NTRS)

Baffa, Bill

2018-01-01

The Neo test stand is currently configured to fire a horizontally mounted rocket motor with up to 6500 lbf thrust. Currently, the Neo test stand can measure flow of liquid propellant and oxidizer, pressures residing in the closed system up to the combustion chamber. The current configuration does not have the ability to provide all data needed to compute specific impulse. This presents three methods to outfit the NEO test fixture with instrumentation allowing for calculation of specific impulse.

Perinatal low-protein diet alters brainstem antioxidant metabolism in adult offspring.

PubMed

Ferreira, Diorginis Soares; Liu, Yuri; Fernandes, Mariana Pinheiro; Lagranha, Claudia Jacques

2016-10-01

Studies in humans and animal models have established a close relationship between early environment insult and subsequent risk of development of non-communicable diseases, including the cardiovascular. Whereas experimental evidences highlight the early undernutrition and the late cardiovascular disease relation, the central mechanisms linking the two remain unknown. Owing to the oxidative balance influence in several pathologies, the aim of the present study was to evaluate the effects of maternal undernutrition (i.e. a low-protein (LP) diet) on oxidative balance in the brainstem. Male rats from mothers fed with an LP diet (8% casein) throughout the perinatal period (i.e. gestation and lactation) showed 10× higher lipid peroxidation levels than animals treated with normoprotein (17% casein) at 100 days of age. In addition, we observed the following reductions in enzymatic activities: superoxide dismutase, 16%; catalase, 30%; glutathione peroxidase, 34%; glutathione-S-transferase, 51%; glutathione reductase, 23%; glucose-6-phosphate dehydrogenase, 31%; and in non-enzymatic glutathione system, 46%. This study is the first to focus on the role of maternal LP nutrition in oxidative balance in a central nervous system structure responsible for cardiovascular control in adult rats. Our data observed changes in oxidative balance in the offspring, therefore, bring a new concept related to early undernutrition and can help in the development of a new clinical strategy to combat the effects of nutritional insult. Wherein the central oxidative imbalance is a feasible mechanism underlying the hypertension risk in adulthood triggered by maternal LP diet.

High- T c superconductivity at the interface between the CaCuO 2 and SrTiO 3 insulating oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di Castro, D.; Cantoni, C.; Ridolfi, F.

2015-09-28

At interfaces between complex oxides it is possible to generate electronic systems with unusual electronic properties, which are not present in the isolated oxides. One important example is the appearance of superconductivity at the interface between insulating oxides, although, until now, with very low T c. We report the occurrence of high T c superconductivity in the bilayer CaCuO 2/SrTiO 3, where both the constituent oxides are insulating. In order to obtain a superconducting state, the CaCuO 2/SrTiO 3 interface must be realized between the Ca plane of CaCuO 2 and the TiO 2 plane of SrTiO 3. Only inmore » this case can oxygen ions be incorporated in the interface Ca plane, acting as apical oxygen for Cu and providing holes to the CuO 2 planes. In addition, a detailed hole doping spatial profile can be obtained by scanning transmission electron microscopy and electron-energy-loss spectroscopy at the O K edge, clearly showing that the (super)conductivity is confined to about 1–2 CaCuO 2 unit cells close to the interface with SrTiO 3. The results obtained for the CaCuO 2/SrTiO 3 interface can be extended to multilayered high T c cuprates, contributing to explaining the dependence of T c on the number of CuO 2 planes in these systems.« less

An evaluation of continuous emissions monitoring systems for improving industrial boiler efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eckerlin, H.M.; Hall, R.C.

1996-12-31

An experimental evaluation of currently available continuous emissions monitoring systems has been conducted at an industrial boiler facility. The analyzers used in the study represented a range of sensors and sampling systems. The performance of three systems was monitored and compared over a six-month period. Careful records were also kept on installation, calibration and maintenance requirements. Research results suggest that (at present) the close-coupled extractive systems using a zirconium oxide sensor (for O{sub 2}) and a catalytic combustibles sensor (for CO/combustibles) offer the most reliable, trouble-free performance. The project also provided valuable insights on a variety of issues relating tomore » the continuous monitoring of emissions from industrial boilers.« less

An evaluation of continuous emissions monitoring systems for improving industrial boiler efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eckerlin, H.M.; Hall, R.C.

1996-05-01

An experimental evaluation of currently available continuous emissions monitoring systems has been conducted at an industrial boiler facility. The analyzers used in the study represented a range of sensors and sampling systems. The performance of three systems was monitored and compared over a six-month period. Careful records were also kept on installation, calibration and maintenance requirements. Research results suggest that (at present) the close-coupled extractive systems using a zirconium oxide sensor (for O{sub 2}) and a catalytic combustibles sensor (for CO/combustibles) offer the most reliable, trouble-free performance. The project also provided valuable insights on a variety of issues relating tomore » the continuous monitoring of emissions from industrial boilers.« less

Detailed Multi-dimensional Modeling of Direct Internal Reforming Solid Oxide Fuel Cells.

PubMed

Tseronis, K; Fragkopoulos, I S; Bonis, I; Theodoropoulos, C

2016-06-01

Fuel flexibility is a significant advantage of solid oxide fuel cells (SOFCs) and can be attributed to their high operating temperature. Here we consider a direct internal reforming solid oxide fuel cell setup in which a separate fuel reformer is not required. We construct a multidimensional, detailed model of a planar solid oxide fuel cell, where mass transport in the fuel channel is modeled using the Stefan-Maxwell model, whereas the mass transport within the porous electrodes is simulated using the Dusty-Gas model. The resulting highly nonlinear model is built into COMSOL Multiphysics, a commercial computational fluid dynamics software, and is validated against experimental data from the literature. A number of parametric studies is performed to obtain insights on the direct internal reforming solid oxide fuel cell system behavior and efficiency, to aid the design procedure. It is shown that internal reforming results in temperature drop close to the inlet and that the direct internal reforming solid oxide fuel cell performance can be enhanced by increasing the operating temperature. It is also observed that decreases in the inlet temperature result in smoother temperature profiles and in the formation of reduced thermal gradients. Furthermore, the direct internal reforming solid oxide fuel cell performance was found to be affected by the thickness of the electrochemically-active anode catalyst layer, although not always substantially, due to the counter-balancing behavior of the activation and ohmic overpotentials.

Water-oxidation catalysis by synthetic manganese oxides--systematic variations of the calcium birnessite theme.

PubMed

Frey, Carolin E; Wiechen, Mathias; Kurz, Philipp

2014-03-21

Layered manganese oxides from the birnessite mineral family have been identified as promising heterogeneous compounds for water-oxidation catalysis (WOC), a key reaction for the conversion of renewable energy into storable fuels. High catalytic rates were especially observed for birnessites which contain calcium as part of their structures. With the aim to systematically improve the catalytic performance of such oxide materials, we used a flexible synthetic route to prepare three series of calcium birnessites, where we varied the calcium concentrations, the ripening times of the original precipitates and the temperature of the heat treatment following the initial synthetic steps (tempering) during the preparation process. The products were carefully analysed by a number of analytical techniques and then probed for WOC activity using the Ce(4+)-system. We find that our set of twenty closely related manganese oxides shows large, but somewhat systematic alterations in catalytic rates, indicating the importance of synthesis parameters for maximum catalytic performance. The catalyst of the series for which the highest water-oxidation rate was found is a birnessite of medium calcium content (Ca : Mn ratio 0.2 : 1) that had been subjected to a tempering temperature of 400 °C. On the basis of the detailed analysis of the results, a WOC reaction scheme for birnessites is proposed to explain the observed trends in reactivity.

Investigation into 9(S)-HPODE-derived allene oxide to cyclopentenone cyclization mechanism via diradical oxyallyl intermediates

PubMed Central

Hebert, Sebastien P.; Cha, Jin K.; Brash, Alan R.; Schlegel, H. Bernhard

2016-01-01

The cyclopentane core is ubiquitous among a large number of biologically relevant natural products. Cyclopentenones have been shown to be versatile intermediates for the stereoselective preparation of highly substituted cyclopentane derivatives. Allene oxides are oxygenated fatty acids which are involved in the pathways of cyclopentenone biosynthesis in plants and marine invertebrates; however, their cyclization behavior is not well understood. Recent work by Brash and co-workers (J. Biol. Chem. 2013, 288, 20797) revealed an unusual cyclization property of the 9(S)-HPODE-derived allene oxides: the previously unreported 10Z-isomer cyclizes to a cis-dialkylcyclopentenone in hexane/isopropyl alcohol (100:3,v/v), but the known 10E-isomer does not yield cis-cyclopentenone under the same conditions. The mechanism for cyclization has been investigated for unsubstituted and methyl substituted vinyl allene oxide using a variety of methods including CASSCF, ωB97xD, and CCSD(T) and basis sets up to cc-pVTZ. The lowest energy pathway proceeds via homolytic cleavage of the epoxide ring, formation of an oxyallyl diradical, which closes readily to a cyclopropanone intermediate. The cyclopropanone opens to the requisite oxyallyl which closes to the experimentally observed product, cis-cyclopentenone. The calculations show that the open shell, diradical pathway is lower in energy than the closed shell reactions of allene oxide to cyclopropanone, and cyclopropanone to cyclopentenone. PMID:26976802

Kinetic Effects Of Increased Proton Transfer Distance On Proton-Coupled Oxidations Of Phenol-Amines

PubMed Central

Rhile, Ian J.

2011-01-01

To test the effect of varying the proton donor-acceptor distance in proton-coupled electron transfer (PCET) reactions, the oxidation of a bicyclic amino-indanol (2) is compared with that of a closely related phenol with an ortho CPh2NH2 substituent (1). Spectroscopic, structural, thermochemical and computational studies show that the two amino-phenols are very similar, except that the O⋯N distance (dON) is >0.1 Å longer in 2 than in 1. The difference in dON is 0.13 ± 0.03 Å from X-ray crystallography and 0.165 Å from DFT calculations. Oxidations of these phenols by outer-sphere oxidants yield distonic radical cations •OAr–NH3+ by concerted proton-electron transfer (CPET). Simple tunneling and classical kinetic models both predict that the longer donor-acceptor distance in 2 should lead to slower reactions, by ca. two orders of magnitude, as well as larger H/D kinetic isotope effects (KIEs). However, kinetic studies show that the compound with the longer proton-transfer distance, 2, exhibits smaller KIEs and has rate constants that are quite close to those of 1. For example, the oxidation of 2 by the triarylamminium radical cation N(C6H4OMe)3•+ (3a+) occurs at (1.4 ± 0.1) × 104 M-1 s-1, only a factor of two slower than the closely related reaction of 1 with N(C6H4OMe)2(C6H4Br)•+ (3b+). This difference in rate constants is well accounted for by the slightly different free energies of reaction: ΔG°(2 + 3a+) = +0.078 V vs. ΔG°(1 + 3b+) = +0.04 V. The two phenol-amines do display some subtle kinetic differences: for instance, compound 2 has a shallower dependence of CPET rate constants on driving force (Brønsted α, Δln(k)/Δln(Keq)). These results show that the simple tunneling model is not a good predictor of the effect of proton donor-acceptor distance on concerted-electron transfer reactions involving strongly hydrogen-bonded systems. Computational analysis of the observed similarity of the two phenols emphasizes the importance of the highly anharmonic O⋯H⋯N potential energy surface and the influence of proton vibrational excited states. PMID:21919508

Severe oxidative stress in an acute inflammatory demyelinating model in the rhesus monkey.

PubMed

Dunham, Jordon; van de Vis, Reinofke; Bauer, Jan; Wubben, Jacqueline; van Driel, Nikki; Laman, Jon D; 't Hart, Bert A; Kap, Yolanda S

2017-01-01

Oxidative stress is increasingly implicated as a co-factor of tissue injury in inflammatory/demyelinating disorders of the central nervous system (CNS), such as multiple sclerosis (MS). While rodent experimental autoimmune encephalomyelitis (EAE) models diverge from human demyelinating disorders with respect to limited oxidative injury, we observed that in a non-human primate (NHP) model for MS, namely EAE in the common marmoset, key pathological features of the disease were recapitulated, including oxidative tissue injury. Here, we investigated the presence of oxidative injury in another NHP EAE model, i.e. in rhesus macaques, which yields an acute demyelinating disease, which may more closely resemble acute disseminated encephalomyelitis (ADEM) than MS. Rhesus monkey EAE diverges from marmoset EAE by abundant neutrophil recruitment into the CNS and destructive injury to white matter. This difference prompted us to investigate to which extent the oxidative pathway features elicited in MS and marmoset EAE are reflected in the acute rhesus monkey EAE model. The rhesus EAE brain was characterized by widespread demyelination and active lesions containing numerous phagocytic cells and to a lesser extent T cells. We observed induction of the oxidative stress pathway, including injury, with a predilection of p22phox expression in neutrophils and macrophages/microglia. In addition, changes in iron were observed. These results indicate that pathogenic mechanisms in the rhesus EAE model may differ from the marmoset EAE and MS brain due to the neutrophil involvement, but may in the end lead to similar induction of oxidative stress and injury.

Survey of flue gas desulfurization systems: Dickerson Station, Potomac Electric Power Co. Final report, Feb--Aug 1975

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isaacs, G.A.

1975-09-01

Results are given of a survey of a flue gas desulfurization system, utilizing the Chemico/Basic MgO-SO2 removal/recovery process, that has been retrofitted to handle approximately half of the exhaust gas from the 190 MW unit 3 at Potomac Electric Power Company's Dickerson Station. The system was installed at a cost of SO.5 million. The boiler burns 2% sulfur coal and is equipped with a 94% efficient electrostatic precipitator. A single two-stage scrubber/absorber is used. The liquor streams for the two stages are separate, both operating in a closed-loop mode. Magnesium oxide (MgO) is regenerated off-site. (GRA)

Advances in hydrogel delivery systems for tissue regeneration.

PubMed

Toh, Wei Seong; Loh, Xian Jun

2014-12-01

Hydrogels are natural or synthetic polymer networks that have high water-absorbing capacity and closely mimic native extracellular matrices. As hydrogel-based cell delivery systems are being increasingly employed in regenerative medicine, several advances have been made in the hydrogel chemistry and modification for enhanced control of cell fate and functions, and modulation of cell and tissue responses against oxidative stress and inflammation in the tissue environment. This review aims to provide the state-of-the-art overview of the recent advances in field, discusses new perspectives and challenges in the regeneration of specific tissues, and highlights some of the limitations of current systems for possible future advancements. Copyright © 2014 Elsevier B.V. All rights reserved.

Formation of Ordered and Disordered Dielectric/metal Nanowire Arrays and their Plasmonic Behavior

DTIC Science & Technology

2007-01-01

sheath geometry. 2. EXPERIMENTAL PROCEDURES Several different nanowire systems have been grown, including random Ga2O3 nanowires, InAs...nanowires, ZnO nanowires, as well as Au lines produced by e-beam lithography. The growth of the Ga2O3 nanowires was achieved by the controlled oxidation...CLOSELY-SPACED PARALLEL ZnO NANOWIRES AND CROSSED Ga2O3 NANOWIRES. As discussed above, due to the far separation of the gold colloid catalyst in the

Open-cage fullerene-like graphitic carbons as catalysts for oxidative dehydrogenation of isobutane.

PubMed

Liang, Chengdu; Xie, Hong; Schwartz, Viviane; Howe, Jane; Dai, Sheng; Overbury, Steven H

2009-06-10

We report herein a facile synthesis of fullerene-like cages, which can be opened and closed through simple thermal treatments. A glassy carbon with enclosed fullerene-like cages of 2-3 nm was synthesized through a soft-template approach that created open mesopores of 7 nm. The open mesopores provided access to the fullerene-like cages, which were opened and closed through heat treatments in air and inert gas at various temperatures. Catalytic measurements showed that the open cages displayed strikingly higher activity for the oxidative dehydrogenation of isobutane in comparison to the closed ones. We anticipate that this synthesis approach could unravel an avenue for pursuing fundamental understanding of the unique catalytic properties of graphitic carbon nanostructures.

Advanced turbine blade tip seal system

NASA Technical Reports Server (NTRS)

Zelahy, J. W.

1981-01-01

An advanced blade/shroud system designed to maintain close clearance between blade tips and turbine shrouds and at the same time, be resistant to environmental effects including high temperature oxidation, hot corrosion, and thermal cycling is described. Increased efficiency and increased blade life are attained by using the advanced blade tip seal system. Features of the system include improved clearance control when blade tips preferentially wear the shrouds and a superior single crystal superalloy tip. The tip design, joint location, characterization of the single crystal tip alloy, the abrasive tip treatment, and the component and engine test are among the factors addressed. Results of wear testing, quality control plans, and the total manufacturing cycle required to fully process the blades are also discussed.

Development of a prototype experiment for treating CELSS and PCELSS wastes to produce nutrients for plant growth

NASA Technical Reports Server (NTRS)

1983-01-01

Future long term spaceflights require extensive recycling of wastes to minimize the need for resupplying the vessel. The recycling occurs in a fully or partially closed environment life support system (CELSS or PCELSS). The National Aeronautics and Space Administration (NASA) is interested in converting wastewater into potable water or water for hydroponic farming as part of a CELSS. The development of technologies for wastewater treatment that produce a minimum of by-products is essential. One process that achieves good conversion of moderately concentrated organic wastes in water (1 to 20% by weight) completely to carbon dioxide and water is oxidation in supercritical water. Both air (or oxygen) and many organics are completely miscible with supercritical water, so there are no interphase mass transport resistances that limits the overall oxidation reaction. The temperature of supercritical water, which must be above 374 C, is also sufficient to have rapid reaction kinetics for the oxidations.

Effect of water on hydrogen permeability. [Stirling engines

NASA Technical Reports Server (NTRS)

Hulligan, D. D.; Tomazic, W. A.

1984-01-01

Doping of hydrogen with CO or CO2 was developed to reduce hydrogen permeation in Stirling engines by forming low permeability oxide coatings in the heater tubes. An end product of this process is water - which can condense in the cold parts of the engine system. If the water vapor is reduced to a low enough level, the hydrogen can reduce the oxide coating resulting in increased permeability. The equilibrium level of water (oxygen bearing gas) required to avoid reduction of the oxide coating was investigated. Results at 720 C and 13.8 MPa have shown that: (1) pure hydrogen will reduce the coating; (2) 500 ppm CO (500 ppm water equivalent) does not prevent the reduction; and (3) 500 ppm CO2 (1000 ppm water) appears to be close to the equilibrium level. Further tests are planned to define the equilibrium level more precisely and to extend the data to 820 C and 3.4, 6.9, and 13.8 MPa.

Excessive Hepatic Mitochondrial TCA Cycle and Gluconeogenesis in Humans with Nonalcoholic Fatty Liver Disease

PubMed Central

Sunny, Nishanth E.; Parks, Elizabeth J.; Browning, Jeffrey D.; Burgess, Shawn C.

2013-01-01

Summary Approximately one-third of the U.S. population has nonalcoholic fatty liver disease (NAFLD), a condition closely associated with insulin resistance and increased risk of liver injury. Dysregulated mitochondrial metabolism is central in these disorders, but the manner and degree of dysregulation are disputed. This study tested whether humans with NAFLD have abnormal in vivo hepatic mitochondrial metabolism. Subjects with low (3.0%) and high (17%) intrahepatic triglyceride (IHTG) were studied using 2H and 13C tracers to evaluate systemic lipolysis, hepatic glucose production, and mitochondrial pathways (TCA cycle, anaplerosis, and ketogenesis). Individuals with NAFLD had 50% higher rates of lipolysis and 30% higher rates of gluconeogenesis. There was a positive correlation between IHTG content and both mitochondrial oxidative and anaplerotic fluxes. These data indicate that mitochondrial oxidative metabolism is ∼2-fold greater in those with NAFLD, providing a potential link between IHTG content, oxidative stress, and liver damage. PMID:22152305

Genome-Guided Analysis and Whole Transcriptome Profiling of the Mesophilic Syntrophic Acetate Oxidising Bacterium Syntrophaceticus schinkii

PubMed Central

Manzoor, Shahid; Bongcam-Rudloff, Erik; Schnürer, Anna; Müller, Bettina

2016-01-01

Syntrophaceticus schinkii is a mesophilic, anaerobic bacterium capable of oxidising acetate to CO2 and H2 in intimate association with a methanogenic partner, a syntrophic relationship which operates close to the energetic limits of microbial life. Syntrophaceticus schinkii has been identified as a key organism in engineered methane-producing processes relying on syntrophic acetate oxidation as the main methane-producing pathway. However, due to strict cultivation requirements and difficulties in reconstituting the thermodynamically unfavourable acetate oxidation, the physiology of this functional group is poorly understood. Genome-guided and whole transcriptome analyses performed in the present study provide new insights into habitat adaptation, syntrophic acetate oxidation and energy conservation. The working draft genome of Syntrophaceticus schinkii indicates limited metabolic capacities, with lack of organic nutrient uptake systems, chemotactic machineries, carbon catabolite repression and incomplete biosynthesis pathways. Ech hydrogenase, [FeFe] hydrogenases, [NiFe] hydrogenases, F1F0-ATP synthase and membrane-bound and cytoplasmic formate dehydrogenases were found clearly expressed, whereas Rnf and a predicted oxidoreductase/heterodisulphide reductase complex, both found encoded in the genome, were not expressed under syntrophic growth condition. A transporter sharing similarities to the high-affinity acetate transporters of aceticlastic methanogens was also found expressed, suggesting that Syntrophaceticus schinkii can potentially compete with methanogens for acetate. Acetate oxidation seems to proceed via the Wood-Ljungdahl pathway as all genes involved in this pathway were highly expressed. This study shows that Syntrophaceticus schinkii is a highly specialised, habitat-adapted organism relying on syntrophic acetate oxidation rather than metabolic versatility. By expanding its complement of respiratory complexes, it might overcome limiting bioenergetic barriers, and drive efficient energy conservation from reactions operating close to the thermodynamic equilibrium, which might enable S. schinkii to occupy the same niche as the aceticlastic methanogens. The knowledge gained here will help specify process conditions supporting efficient and robust biogas production and will help identify mechanisms important for the syntrophic lifestyle. PMID:27851830

Oxidation and evaporation of sulfur species at atmospheric entry of iron sulfide fine particles

NASA Astrophysics Data System (ADS)

Isobe, H.; Murozono, K.

2017-12-01

Micrometeorites have the most abundant flux in current accumulation of planetary materials to the Earth. Micrometeorites are heated and reacted with upper atmosphere at atmospheric entry. Evaporation of meteoritic materials, especially sulfur species, may have environmental effect at upper atmosphere (e.g. Court and Sephton, 2011; Tomkins et al., 2016). Troilite is typical FeS phase in chondritic meteorites. In this study, quick heating and cooling experiments of FeS reagent particles were carried out with a fine particles free falling apparatus with controlled gas flow (Isobe and Gondo, 2013). Starting material reagent is inhomogeneous mixture of troilite, iron oxide and iron metal. Oxygen fugacity was controlled to FMQ +1.5 log unit. Maximum temperature of the particles was higher than 1400°C for approximately 0.5 seconds. Run products with rounded shape and smooth surface show the particles were completely melted. Chemical compositions of particles analyzed on cross sections are generally well homogenized from inhomogeneous starting materials by complete melting. Molar ratios of Fe in melted regions are close to 0.5, while compositions of S and O are various. Varieties of S and O compositions show various degree of oxidation and evaporation of sulfur. Distribution of compositions of melted regions in Fe-S-O system is plotted in liquidus compositions of FeO and FeS saturated melt. Troilite in micrometeorite is melted and oxidized by atmospheric entry. Compositions of FeS melt in fine spherules are following Fe-S-O phase relations even in a few seconds. Molar ratios of Fe in melt are close to 0.5, while compositions of S and O are various. Varieties of S and O compositions show various degree of oxidation and evaporation of sulfur. Evaporation of sulfur from meteoritic materials in atmospheric entry heating may depend on oxygen fugacity of the upper atmosphere. Sulfur supply from meteoritic materials to atmosphere may be limited on planets with oxygen-free atmosphere.

Trace metal-rich Quaternary hydrothermal manganese oxide and barite deposit, Milos Island, Greece

USGS Publications Warehouse

Hein, J.R.; Stamatakis, G.; Dowling, J.S.

2000-01-01

The Cape Vani Mn oxide and barite deposit on Milos Island offers an excellent opportunity to study the three-dimensional characteristics of a shallow-water hydrothermal system. Milos Island is part of the active Aegean volcanic arc. A 1 km long basin located between two dacitic domes in northwest Milos is filled with a 35-50 m thick section of Quaternary volcaniclastic and pyroclastic rocks capped by reef limestone that were hydrothermally mineralized by Mn oxides and barite. Manganese occurs as thin layers, as cement of sandstone and as metasomatic replacement of the limestone, including abundant fossil shells. Manganese minerals include chiefly δ-MnO2, pyrolusite and ramsdellite. The MnO contents for single beds range up to 60%. The Mn oxide deposits are rich in Pb (to 3.4%), BaO (to 3.1%), Zn (to 0.8%), As (to 0.3%), Sb (to 0.2%) and Ag (to 10 ppm). Strontium isotopic compositions of the Mn oxide deposits and sulphur isotopic compositions of the associated barite show that the mineralizing fluids were predominantly sea water. The Mn oxide deposit formed in close geographical proximity to sulphide-sulphate-Au-Ag deposits and the two deposit types probably formed from the same hydrothermal system. Precipitation of Mn oxide took place at shallow burial depths and was promoted by the mixing of modified sea water (hydrothermal fluid) from which the sulphides precipitated at depth and sea water that penetrated along faults and fractures in the Cape Vani volcaniclastic and tuff deposits. The hydrothermal fluid was formed from predominantly sea water that was enriched in metals leached from the basement and overlying volcanogenic rocks. The hydrothermal fluids were driven by convection sustained by heat from cooling magma chambers. Barite was deposited throughout the time of Mn oxide mineralization, which occurred in at least two episodes. Manganese mineralization occurred by both focused and diffuse flow, the fluids mineralizing the beds of greatest porosity and filling dilatational fractures along with barite.

Effect of Time and Deposition Method on Quality of Phosphonic Acid Modifier Self-Assembled Monolayers on Indium Zinc Oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sang, Lingzi; Knesting, Kristina M.; Bulusu, Anuradha

Phosphonic acid (PA) self-assembled monolayers (SAMs) are utilized at critical interfaces between transparent conductive oxides (TCO) and organic active layers in organic photovoltaic devices (OPVs). The effects of PA deposition method and time on the formation of close-packed, high-quality monolayers is investigated here for SAMs fabricated by solution deposition, micro-contact printing, and spray coating. The solution deposition isotherm for pentafluorinated benzylphosphonic acid (F5BnPA) on indium-doped zinc oxide (IZO) is studied using polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS) at room temperature as a model PA/IZO system. Fast surface adsorption occurs within the first min; however, well-oriented high-quality SAMs are reached only aftermore » -48 h, presumably through a continual process of molecular adsorption/desorption and monolayer filling accompanied by molecular reorientation. Two other rapid, soak-free deposition techniques, micro-contact printing and spray coating, are also explored. SAM quality is compared for deposition of phenyl phosphonic acid (PPA), F13-octylphosphonic acid (F13OPA), and pentafluorinated benzyl phosphonic acid (F5BnPA) by solution deposition, micro-contact printing and spray coating using PM-IRRAS. In contrast to micro-contact printing and spray coating techniques, 48-168 h solution deposition at both room temperature and 70 degrees C result in contamination- and surface etch-free close-packed monolayers with good reproducibility. SAMs fabricated by micro-contact printing and spray coating are much less well ordered.« less

Controlling enzymatic activity by immobilization on graphene oxide

NASA Astrophysics Data System (ADS)

Bolibok, Paulina; Wiśniewski, Marek; Roszek, Katarzyna; Terzyk, Artur P.

2017-04-01

In this study, graphene oxide (GO) has been applied as a matrix for enzyme immobilization. The protein adsorption capacity of GO is much higher than of other large surface area carbonaceous materials. Its structure and physicochemical properties are reported beneficial also for enzymatic activity modifications. The experimental proof was done here that GO-based biocatalytic systems with immobilized catalase are modifiable in terms of catalyzed reaction kinetic constants. It was found that activity and stability of catalase, considered here as model enzyme, closely depend on enzyme/GO ratio. The changes in kinetic parameters can be related to secondary structure alterations. The correlation between enzyme/GO ratio and kinetic and structure parameters is reported for the first time and enables the conscious control of biocatalytic processes and their extended applications. The biological activity of obtained biocatalytic systems was confirmed in vitro by the use of functional test. The addition of immobilized catalase improved the cells' viability after they were exposed to hydrogen peroxide and tert-butyl-hydroperoxide used as source of reactive oxygen species.

Mechanisms of lithium transport in amorphous polyethylene oxide.

PubMed

Duan, Yuhua; Halley, J W; Curtiss, Larry; Redfern, Paul

2005-02-01

We report calculations using a previously reported model of lithium perchlorate in polyethylene oxide in order to understand the mechanism of lithium transport in these systems. Using an algorithm suggested by Voter, we find results for the diffusion rate which are quite close to experimental values. By analysis of the individual events in which large lithium motions occur during short times, we find that no single type of rearrangement of the lithium environment characterizes these events. We estimate the free energies of the lithium ion as a function of position during these events by calculation of potentials of mean force and thus derive an approximate map of the free energy as a function of lithium position during these events. The results are consistent with a Marcus-like picture in which the system slowly climbs a free energy barrier dominated by rearrangement of the polymer around the lithium ions, after which the lithium moves very quickly to a new position. Reducing the torsion forces in the model causes the diffusion rates to increase.

Linking TFT-LCD wastewater treatment performance to microbial population abundance of Hyphomicrobium and Thiobacillus spp.

PubMed

Fukushima, Toshikazu; Whang, Liang-Ming; Chen, Po-Chun; Putri, Dyah Wulandari; Chang, Ming-Yu; Wu, Yi-Ju; Lee, Ya-Ching

2013-08-01

This study investigated the linkage between performance of two full-scale membrane bioreactor (MBR) systems treating thin-film transistor liquid crystal display (TFT-LCD) wastewater and the population dynamics of dimethylsulfoxide (DMSO)/dimethylsulfide (DMS) degrading bacteria. High DMSO degradation efficiencies were achieved in both MBRs, while the levels of nitrification inhibition due to DMS production from DMSO degradation were different in the two MBRs. The results of real-time PCR targeting on DMSO/DMS degrading populations, including Hyphomicrobium and Thiobacillus spp., indicated that a higher DMSO oxidation efficiency occurred at a higher Hyphomicrobium spp. abundance in the systems, suggesting that Hyphomicrobium spp. may be more important for complete DMSO oxidation to sulfate compared with Thiobacillus spp. Furthermore, Thiobacillus spp. was more abundant during poor nitrification, while Hyphomicrobium spp. was more abundant during good nitrification. It is suggested that microbial population of DMSO/DMS degrading bacteria is closely linking to both DMSO/DMS degradation efficiency and nitrification performance. Copyright © 2013 Elsevier Ltd. All rights reserved.

Estimating Agricultural Nitrous Oxide Emissions

USDA-ARS?s Scientific Manuscript database

Nitrous oxide emissions are highly variable in space and time and different methodologies have not agreed closely, especially at small scales. However, as scale increases, so does the agreement between estimates based on soil surface measurements (bottom up approach) and estimates derived from chang...

The phylogenetic distribution and ecological role of carbon monoxide oxidation in the genus Burkholderia.

PubMed

Weber, Carolyn F; King, Gary M

2012-01-01

Burkholderia is a physiologically and ecologically diverse genus that occurs commonly in assemblages of soil and rhizosphere bacteria. Although Burkholderia is known for its heterotrophic versatility, we demonstrate that 14 distinct environmental isolates oxidized carbon monoxide (CO) and possessed the gene encoding the catalytic subunit of form I CO dehydrogenase (coxL). DNA from a Burkholderia isolate obtained from a passalid beetle also contained coxL as do the genomic sequences of species H160 and Ch1-1. Isolates were able to consume CO at concentrations ranging from 100 ppm (vol/vol) to sub-ambient (< 60 ppb (vol/vol)). High concentrations of pyruvate inhibited CO uptake (> 2.5 mM), but mixotrophic consumption of CO and pyruvate occurred when initial pyruvate concentrations were lower (c. 400 lM). With the exception of an isolate most closely related to Burkholderia cepacia, all CO-oxidizing isolates examined were members of a nonpathogenic clade and were most closely related to Burkholderia species, B. caledonica, B. fungorum, B. oxiphila, B. mimosarum, B. nodosa, B. sacchari, B. bryophila, B. ferrariae, B. ginsengesoli, and B. unamae. However, none of these type strains oxidized CO or contained coxL based on results from PCR analyses. Collectively, these results demonstrate that the presence of CO oxidation within members of the Burkholderia genus is variable but it is most commonly found among rhizosphere inhabitants that are not closely related to B. cepacia.

Stable isotope analysis of molecular oxygen from silicates and oxides using CO2 laser extraction

NASA Technical Reports Server (NTRS)

Perry, Eugene

1996-01-01

A laser-excited system for determination of the oxygen isotope composition of small quantities of silicate and oxide minerals was constructed and tested at JSC. This device is the first reported to use a commercially available helium cryostat to transfer and purify oxygen gas quantitatively within the system. The system uses oxygen gas instead of the conventional CO2 for mass spectrometer analyses. This modification of technique permits determination of all three stable oxygen isotopes, an essential requirement for oxygen isotope analysis of meteoritic material. Tests of the system included analysis of standard silicate materials NBS 28 and UWMG2 garnet, six SNC meteorites, and inclusions and chondrules from the Allende meteorite. Calibration with terrestrial standards was excellent. Meteorite values are close to published values and show no evidence of terrestrial oxygen contamination. The one limitation observed is that, in some runs on fine-grained SNC matrix material, sample results were affected by other samples in the sample holder within the reaction chamber. This reemphasizes the need for special precautions in dealing with fine-grained, reactive samples. Performance of the JSC instrument compares favorably with that of any other instrument currently producing published oxygen isotope data.

Hypoglycemia: Role of Hypothalamic Glucose-Inhibited (GI) Neurons in Detection and Correction.

PubMed

Zhou, Chunxue; Teegala, Suraj B; Khan, Bilal A; Gonzalez, Christina; Routh, Vanessa H

2018-01-01

Hypoglycemia is a profound threat to the brain since glucose is its primary fuel. As a result, glucose sensors are widely located in the central nervous system and periphery. In this perspective we will focus on the role of hypothalamic glucose-inhibited (GI) neurons in sensing and correcting hypoglycemia. In particular, we will discuss GI neurons in the ventromedial hypothalamus (VMH) which express neuronal nitric oxide synthase (nNOS) and in the perifornical hypothalamus (PFH) which express orexin. The ability of VMH nNOS-GI neurons to depolarize in low glucose closely parallels the hormonal response to hypoglycemia which stimulates gluconeogenesis. We have found that nitric oxide (NO) production in low glucose is dependent on oxidative status. In this perspective we will discuss the potential relevance of our work showing that enhancing the glutathione antioxidant system prevents hypoglycemia associated autonomic failure (HAAF) in non-diabetic rats whereas VMH overexpression of the thioredoxin antioxidant system restores hypoglycemia counterregulation in rats with type 1 diabetes.We will also address the potential role of the orexin-GI neurons in the arousal response needed for hypoglycemia awareness which leads to behavioral correction (e.g., food intake, glucose administration). The potential relationship between the hypothalamic sensors and the neurocircuitry in the hindbrain and portal mesenteric vein which is critical for hypoglycemia correction will then be discussed.

Exploring Lithium-Cobalt-Nickel Oxide Spinel Electrodes for ≥3.5 V Li-Ion Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Eungje; Blauwkamp, Joel; Castro, Fernando C.

2016-10-19

Recent reports have indicated that a manganese oxide spinel component, when embedded in a relatively small concentration in layered xLi2MnO3(1-x)LiMO2 (M=Ni, Mn, Co) electrode systems, can act as a stabilizer that increases their capacity, rate capability, cycle life, and first-cycle efficiency. These findings prompted us to explore the possibility of exploiting lithiated cobalt oxide spinel stabilizers by taking advantage of (1) the low mobility of cobalt ions relative to manganese and nickel ions in close-packed oxides and (2) their higher potential (~3.6 V vs. Li0) relative to manganese oxide spinels (~2.9 V vs. Li0) for the spinel-to-lithiated spinel electrochemical reaction.more » In particular, we have revisited the structural and electrochemical properties of lithiated spinels in the LiCo1-xNixO2 (0x0.2) system, first reported almost 25 years ago, by means of high-resolution (synchrotron) X-ray diffraction, transmission electron microscopy, nuclear magnetic resonance spectroscopy, electrochemical cell tests, and theoretical calculations. The results provide a deeper understanding of the complexity of intergrown layered/lithiated spinel LiCo1-xNixO2 structures, when prepared in air between 400 and 800 C, and the impact of structural variations on their electrochemical behavior. These structures, when used in low concentration, offer the possibility of improving the cycling stability, energy, and power of high energy (≥3.5 V) lithium-ion cells.« less

Exploring Lithium-Cobalt-Nickel Oxide Spinel Electrodes for ≥3.5 V Li-Ion Cells

DOE PAGES

Lee, Eungje; Blauwkamp, Joel; Castro, Fernando C.; ...

2016-10-04

Some recent reports have indicated that a manganese oxide spinel component, when embedded in a relatively small concentration in layered xLi 2MnO 3center dot(1-x)LiMO 2 (M = Ni, Mn, or Co) electrode systems, can act as a stabilizer that increases their capacity, rate capability, cycle life, and first-cycle efficiency. Our findings prompted us to explore the possibility of exploiting lithiated cobalt oxide spinel stabilizers by taking advantage of (1) the low mobility of cobalt ions relative to that of manganese and nickel ions in close-packed oxides and (2) their higher potential (similar to 3.6 V vs Li0) relative to manganesemore » oxide spinels (similar to 2.9 V vs Li0) for the spinel-to-lithiated spinel electrochemical reaction. In particular, we revisited the structural and electrochemical properties of lithiated spinels in the LiCo 1-xNi xO 2 (0 <= x <= 0.2) system, first reported almost 25 years ago, by means of high-resolution (synchrotron) X-ray diffraction, transmission electron microscopy, nuclear magnetic resonance spectroscopy, electrochemical cell tests, and theoretical calculations. These results provide a deeper understanding of the complexity of intergrown layered/lithiated spinel LiCo 1-xNi xO 2 structures when prepared in air between 400 and 800 degrees C and the impact of structural variations on their electrochemical behavior. These structures, when used in low concentrations, offer the possibility of improving the cycling stability, energy, and power of high energy (>= 3.5 V) lithium-ion cells.« less

[Oxidative stress and vascular function].

PubMed

Urbański, Karol; Nowak, Michal; Guzik, Tomasz J

2013-01-01

The maintenance of blood vessel homeostasis is closely associated with Reactive Oxygen and Nitrogen Species (ROS and RNS) production in the blood vessel wall. The main molecules taking part in this process are nitric oxide (NO), superoxide anion (O2*-), hydrogen peroxide (H2O2) and their derivatives. The production of these factors occurs in health and disease, however the increased ROS release is often referred to as oxidative stress. While initially oxidative stress was considered systemically, recent data indicate that it occurs locally in subcellular spaces and may be a result of dysfunction of individual enzyme systems. Oxidative stress induces inflammation, proliferation and migration of vascular smooth muscle cells, may regulate apoptosis and the function of the cells of vascular wall, finally leading to dysfunction of endothelium, media and adventitia, leading to cardiovascular diseases such as atherosclerosis, hypertension or heart failure. It is believed that a family of NADPH oxidases is the main source of ROS in the vessel wall, but also in other organs and tissues. It consists of seven known and quite precisely characterized homologues (NOX1, NOX2, NOX3, NOX4, NOX5, DUOX1 and DUOX2) which often have very distinct activity and cellular localization and function. Besides harmful actions, we are beginning to understand the protective effects of ROS and RNS. They have many functions regulating redox-sensitive gene expression and influencing a proper function of cells and vessels. NOX4 has been particularly well characterized in this respect. Thus, the maintenance of the right homeostasis depends not only on ROS removing capabilities, but especially on preserving the adequate level of ROS production.

Analysis of solid propellant combustion in a closed vessel including secondary reaction

NASA Technical Reports Server (NTRS)

Benreuven, M.; Summerfield, M.

1980-01-01

A theory for combustion of solid propellants in a closed vessel is presented allowing for residual exothermic chemical reaction in the bulk of the gas in the vessel. Particular attention is given to propellants exhibiting thick gaseous flame zones such as nitrocellulose, double-base and nitramine propellants. For these, the reaction at high pressures is assumed to involve mainly the oxidation of residual hydrocarbons by NO. It is shown that the direct dynamic coupling between the exothermicity, the molecular weight reduction and the changing pressure can influence the dp/dt-p traces obtained, in a manner not directly related to mass burning rate of the solid. Energy and species conservation equations are derived for the bulk of the vessel in differential form; the system is solved numerically. The results show the effect of extended chemical reaction upon measurable combustion characteristics such as dp/dt-p and burn rate pressure exponent, demonstrating its potential importance in interpretation of closed vessel firing data, depending on the pace of the residual gas phase reactions.

ARIES Oxide Production Program Annual Report - FY14

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelley, Evelyn A.; Dinehart, Steven Mark

A summary of the major accomplishments (September), milestones, financial summary, project performance and issues facing the ARIES Oxide Production Program at the close of FY14 is presented in this Executive Summary. Annual accomplishments are summarized in the body of the report.

Detailed Multi‐dimensional Modeling of Direct Internal Reforming Solid Oxide Fuel Cells

PubMed Central

Tseronis, K.; Fragkopoulos, I.S.; Bonis, I.

2016-01-01

Abstract Fuel flexibility is a significant advantage of solid oxide fuel cells (SOFCs) and can be attributed to their high operating temperature. Here we consider a direct internal reforming solid oxide fuel cell setup in which a separate fuel reformer is not required. We construct a multidimensional, detailed model of a planar solid oxide fuel cell, where mass transport in the fuel channel is modeled using the Stefan‐Maxwell model, whereas the mass transport within the porous electrodes is simulated using the Dusty‐Gas model. The resulting highly nonlinear model is built into COMSOL Multiphysics, a commercial computational fluid dynamics software, and is validated against experimental data from the literature. A number of parametric studies is performed to obtain insights on the direct internal reforming solid oxide fuel cell system behavior and efficiency, to aid the design procedure. It is shown that internal reforming results in temperature drop close to the inlet and that the direct internal reforming solid oxide fuel cell performance can be enhanced by increasing the operating temperature. It is also observed that decreases in the inlet temperature result in smoother temperature profiles and in the formation of reduced thermal gradients. Furthermore, the direct internal reforming solid oxide fuel cell performance was found to be affected by the thickness of the electrochemically‐active anode catalyst layer, although not always substantially, due to the counter‐balancing behavior of the activation and ohmic overpotentials. PMID:27570502

Synthesis, characterization and evaluation of CO-oxidation catalysts for high repetition rate CO2 TEA lasers

NASA Technical Reports Server (NTRS)

Moser, Thomas P.

1990-01-01

An extremely active class of noble metal catalysts supported on titania was developed and fabricated at Hughes for the recombination of oxygen (O2) and carbon monoxide (CO) in closed-cycle CO2 TEA lasers. The incipient wetness technique was used to impregnate titania and alumina pellets with precious metals including platinum and palladium. In particular, the addition of cerium (used as an oxygen storage promoter) produced an extremely active Pt/Ce/TiO2 catalyst. By comparison, the complementary Pt/Ce/ gamma-Al2O3 catalyst was considerably less active. In general, chloride-free catalyst precursors proved critical in obtaining an active catalyst while also providing uniform metal distributions throughout the support structure. Detailed characterization of the Pt/Ce/TiO2 catalyst demonstrated uniform dendritic crystal growth of the metals throughout the support. Electron spectroscopy for Chemical Analysis (ESCA) analysis was used to characterize the oxidation states of Pt, Ce and Ti. The performance of the catalysts was evaluated with an integral flow reactor system incorporating real time analysis of O2 and CO. With this system, the transient and steady-state behavior of the catalysts were evaluated. The kinetic evaluation was complemented by tests in a compact, closed-cycle Hughes CO2 TEA laser operating at a pulse repetition rate of 100 Hz with a catalyst temperature of 75 to 95 C. The Pt/Ce/TiO2 catalyst was compatible with a C(13)O(16)2 gas fill.

Open-cage Fullerene-like Graphitic Carbons as Catalysts for Oxidative Dehydrogenation of Isobutane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang, Chengdu; Xie, Hong; Schwartz, Viviane

We report herein a facile synthesis of fullerene-like cages, which can be opened and closed through simple thermal treatments. A glassy carbon with enclosed fullerene-like cages of 2-3 nm was synthesized through a soft-template approach that created open mesopores of 7 nm. The open mesopores provided access to the fullerene-like cages, which were opened and closed through heat treatments in air and inert gas at various temperatures. Catalytic measurements showed that the open cages displayed strikingly higher activity for the oxidative dehydrogenation of isobutane in comparison to the close ones. We anticipate that this synthesis approach could unravel an avenuemore » for pursuing fundamental understanding of the unique catalytic properties of graphitic carbon nanostructures.« less

Electrodes from carbon nanotubes/NiO nanocomposites synthesized in modified Watts bath for supercapacitors

NASA Astrophysics Data System (ADS)

Hakamada, Masataka; Abe, Tatsuhiko; Mabuchi, Mamoru

2016-09-01

A modified Watts bath coupled with pulsed current electroplating is used to uniformly deposit ultrafine nickel oxide particles (diameter < 4 nm) on multiwalled carbon nanotubes. The capacitance of the multiwalled carbon nanotubes/nickel oxide electrodes was as high as 2480 F g-1 (per mass of nickel oxide), which is close to the theoretical capacitance of NiO.

High-temperature Raman spectroscopy of solid oxide fuel cell materials and processes.

PubMed

Pomfret, Michael B; Owrutsky, Jeffrey C; Walker, Robert A

2006-09-07

Chemical and material processes occurring in high temperature environments are difficult to quantify due to a lack of experimental methods that can probe directly the species present. In this letter, Raman spectroscopy is shown to be capable of identifying in-situ and noninvasively changes in material properties as well as the formation and disappearance of molecular species on surfaces at temperatures of 715 degrees C. The material, yttria-stabilized zirconia or YSZ, and the molecular species, Ni/NiO and nanocrystalline graphite, factor prominently in the chemistry of solid oxide fuel cells (SOFCs). Experiments demonstrate the ability of Raman spectroscopy to follow reversible oxidation/reduction kinetics of Ni/NiO as well as the rate of carbon disappearance when graphite, formed in-situ, is exposed to a weakly oxidizing atmosphere. In addition, the Raman active phonon mode of YSZ shows a temperature dependent shift that correlates closely with the expansion of the lattice parameter, thus providing a convenient internal diagnostic for identifying thermal gradients in high temperature systems. These findings provide direct insight into processes likely to occur in operational SOFCs and motivate the use of in-situ Raman spectroscopy to follow chemical processes in these high-temperature, electrochemically active environments.

Hexavalent Americium recovery using Copper(III) periodate

DOE PAGES

McCann, Kevin; Brigham, Derek M.; Morrison, Samuel; ...

2016-10-31

Separation of americium from the lanthanides is considered one of the most difficult separation steps in closing the nuclear fuel cycle. One approach to this separation could involve oxidizing americium to the hexavalent state to form a linear dioxo cation while the lanthanides remain as trivalent ions. This work considers aqueous soluble Cu 3+ periodate as an oxidant under molar nitric acid conditions to separate hexavalent Am with diamyl amylphosphonate (DAAP) in n-dodecane. Initial studies assessed the kinetics of Cu 3+ periodate autoreduction in acidic media to aid in development of the solvent extraction system. Following characterization of the Cumore » 3+ periodate oxidant, solvent extraction studies optimized the recovery of Am from varied nitric acid media and in the presence of other fission product, or fission product surrogate, species. Short aqueous/organic contact times encouraged successful recovery of Am (distribution values as high as 2) from nitric acid media in the absence of redox active fission products. In the presence of a post-plutonium uranium redox extraction (post-PUREX) simulant aqueous feed, precipitation of tetravalent species (Ce, Ru, Zr) occurred and the distribution values of 241Am were suppressed, suggesting some oxidizing capacity of the Cu 3+ periodate is significantly consumed by other redox active metals in the simulant. Furthermore, the manuscript demonstrates Cu 3+ periodate as a potentially viable oxidant for Am oxidation and recovery and notes the consumption of oxidizing capacity observed in the presence of the post-PUREX simulant feed will need to be addressed for any approach seeking to oxidize Am for separations relevant to the nuclear fuel cycle.« less

Hexavalent Americium Recovery Using Copper(III) Periodate

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCann, Kevin; Brigham, Derek M.; Morrison, Samuel

2016-11-21

Separation of americium from the lanthanides is considered one of the most difficult separation steps in closing the nuclear fuel cycle. One approach to this separation could involve oxidizing americium to the hexavalent state to form a linear dioxo cation while the lanthanides remain as trivalent ions. This work considers aqueous soluble Cu3+ periodate as an oxidant under molar nitric acid conditions to separate hexavalent Am with diamyl amylphosphonate (DAAP) in n-dodecane. Initial studies assessed the kinetics of Cu3+ periodate auto-reduction in acidic media to aid in development of the solvent extraction system. Following characterization of the Cu3+ periodate oxidant,more » solvent extraction studies optimized the recovery of Am from varied nitric acid media and in the presence of other fission product, or fission product surrogate, species. Short aqueous/organic contact times encouraged successful recovery of Am (distribution values as high as 2) from nitric acid media in the absence of redox active fission products. In the presence of a post-PUREX simulant aqueous feed, precipitation of tetravalent species (Ce, Ru, Zr) occurred and the distribution values of 241Am were suppressed, suggesting some oxidizing capacity of the Cu3+ periodate is significantly consumed by other redox active metals in the simulant. The manuscript demonstrates Cu3+ periodate as a potentially viable oxidant for Am oxidation and recovery and notes the consumption of oxidizing capacity observed in the presence of the post-PUREX simulant feed will need to be addressed for any approach seeking to oxidize Am for separations relevant to the nuclear fuel cycle.« less

Advanced development of non-discoloring EVA-based PV encapsulants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holley, W.H.; Galica, J.P.; Argo, S.C.

1996-01-01

The purpose of this investigation was to better define the problem of field yellowing of EVA-based PV encapsulant, through laboratory study of probable chemical mechanisms and the development of stabilization strategies for protecting EVA from discoloration. EVA from fielded modules was analyzed for vinyl acetate content, unsaturation, and additive levels. These test results were then compared to results from Xenon Arc Weather-Ometer aged glass/EVA/glass laminates made in the laboratory. Variables evaluated in Weather-Ometer aged laminates included ``standard-cure`` A9918P EVA, ``fast-cure`` 15295P EVA, low iron glass superstrate containing cerium oxide, and systematic elimination or addition of specific additives. Six significant findingsmore » were revealed: 1) Improved ``standard-cure`` and ``fast-cure`` type EVA encapsulants, formulations X9903P and X15303P, respectively, showed little or no yellowing after extended Weather-Ometer exposure; 2) The use of {open_quote}{open_quote}fast-cure{close_quote}{close_quote} EVA reduced discoloration when compared with {open_quote}{open_quote}standard-cure{close_quote}{close_quote} A9918P EVA; 3) Glass superstrate containing cerium oxide resulted in a reduced rate of EVA discoloration; 4) {open_quote}{open_quote}Fast-cure{close_quote}{close_quote} EVA used with glass superstrate containing cerium oxide showed no visible yellowing after 32 weeks in the Weather-Ometer{emdash}a period estimated to be roughly equivalent to 20{endash}30 years of exposure in the Southwest; 5) Severely discolored EVA samples from the field showed no measurable loss of acetate group and little detectable unsaturation; and 6) EVA encapsulant with a Tefzel cover exhibited no yellowing after extended Weather-Ometer exposure. {copyright} {ital 1996 American Institute of Physics.}« less

Regenerable Air Purification System for Gas-Phase Contaminant Control

NASA Technical Reports Server (NTRS)

Constantinescu, Ileana C.; Qi, Nan; LeVan, M. Douglas; Finn, Cory K.; Finn, John E.; Luna, Bernadette (Technical Monitor)

2000-01-01

A regenerable air purification system (RAPS) that uses water vapor to displace adsorbed contaminants from an. adsorbent column into a closed oxidation loop is under development through cooperative R&D between Vanderbilt University and NASA Ames Research Center. A unit based on this design can be used for removing trace gas-phase contaminants from spacecraft cabin air or from polluted process streams including incinerator exhaust. Recent work has focused on fabrication and operation of a RAPS breadboard at NASA Ames, and on measurement of adsorption isotherm data for several important organic compounds at Vanderbilt. These activities support the use and validation of RAPS modeling software also under development at Vanderbilt, which will in turn be used to construct a prototype system later in the project.

Recondensation of chondritic material in the early solar system: Results of thermodynamic simulation

NASA Technical Reports Server (NTRS)

Dorofeyeva, V. A.; Makalkin, A. B.; Mironenko, M. V.; Vityazev, A. V.

1993-01-01

We have performed a thermodynamic simulation of the recondensation of evaporated meteoritic material. We suggest that evaporation and recondensation occurred in impact events during the intercollision of planetesimals during the early evolution of the solar system. The source materials adopted for our model are the chondrites CI Orgueil and H5 Richardton. These chondrites are representative examples of the two extremes regarding volatile content and oxidation state. We calculated equilibrium mineral compositions of the closed systems of the Orgueil's and Richardton's elemental composition at the P-T conditions characteristic of the explosion cloud formed at a planetesimal collision. The P-T conditions are as follows: 10(exp -4) bar, and 1500 and 2000 K. The results are presented.

Magnetically tunable 1D Coulomb drag: Theory

NASA Astrophysics Data System (ADS)

Tylan-Tyler, Anthony; Tang, Yuhe; Levy, Jeremy

In this work, we examine the Coulomb drag effect in 1D nanowires in close proximity, focusing on experimental parameters relevant to complex-oxide nanostructures. Previous work on this problem examined Coulomb drag through quantum point contacts, where effective capacitive coupling between the 2D leads of the system generates the drag voltage. In our case, the entire system is composed of 1D components and thus a more careful treatment of the Coulomb interactions is required. This more complex environment then leads to the ability to switch the drag voltage by an applied magnetic field without altering the current supplied to the drive system. We gratefully acknowledge financial support from ONR N00014-15-1-2847 and DOE DE-SC0014417.

Developmental status of thermionic materials.

NASA Technical Reports Server (NTRS)

Yang, L.; Chin, J.

1972-01-01

Description of the reference materials selected for the major components of the unit cell of a thermionic pile element (TFE), the out-of-pile and in-pile test results, and current efforts for improving the life and performance of thermionic fuel elements. The component materials are required to withstand the fuel burnup and fast neutron fluence dictated by the thermionic reactor system. Tungsten was selected as the cladding material because of its compatibility with both the carbide and the oxide fuel materials. Niobium was selected as the collector material because its thermal expansion coefficient matches closely with that of the thin aluminum oxide layer used to electrically insulate the collector from the TFE sheath. An unfueled converter has performed stably over 41,000 hr. Accelerated irradiation tests have attained burnups equivalent to that for 40,000 hr of the thermionic reactor under consideration.

Relationship of microstructure properties to oxygen impurities in nanocrystalline silicon photovoltaic materials

NASA Astrophysics Data System (ADS)

Xu, H.; Wen, C.; Liu, H.; Li, Z. P.; Shen, W. Z.

2013-03-01

We have fully investigated the correlation of microstructure properties and oxygen impurities in hydrogenated nanocrystalline silicon photovoltaic films. The achievement has been realized through a series of different hydrogen dilution ratio treatment by plasma enhanced chemical vapor deposition system. Raman scattering, x-ray diffraction, and ultraviolet-visible transmission techniques have been employed to characterize the physical structural characterization and to elucidate the structure evolution. The bonding configuration of the oxygen impurities was investigated by x-ray photoelectron spectroscopy and the Si-O stretching mode of infrared-transmission, indicating that the films were well oxidized in SiO2 form. Based on the consistence between the proposed structure factor and the oxygen content, we have demonstrated that there are two dominant disordered structure regions closely related to the post-oxidation contamination: plate-like configuration and clustered microvoids.

PHARMACOLOGIC SUPPRESSION OF OXIDATIVE DAMAGE AND DENDRITIC DEGENERATION FOLLOWING KAINIC ACID-INDUCED EXCITOTOXICITY IN MOUSE CEREBRUM

PubMed Central

Zaja-Milatovic, Snjezana; Gupta, Ramesh C.; Aschner, Michael; Montine, Thomas J.; Milatovic, Dejan

2008-01-01

Intense seizure activity associated with status epilepticus and excitatory amino acid (EAA) imbalance initiates oxidative damage and neuronal injury in CA1 of the ventral hippocampus. We tested the hypothesis that dendritic degeneration of pyramidal neurons in the CA1 hippocampal area resulting from seizure-induced neurotoxicity is modulated by cerebral oxidative damage. Kainic acid (KA, 1 nmol/5 μl) was injected intracerebroventricularly to C57Bl/6 mice. F2-isoprostanes (F2-IsoPs) and F4-neuroprostanes (F4-NeuroPs) were used as surrogate measures of in vivo oxidative stress and biomarkers of lipid peroxidation. Nitric oxide synthase (NOS) activity was quantified by evaluating citrulline level and pyramidal neuron dendrites and spines were evaluated using rapid Golgi stains and a Neurolucida system. KA produced severe seizures in mice immediately after its administration and a significant (p<0.001) increase in F2-IsoPs, F4-NeuroPs and citrulline levels were seen 30 min following treatment. At the same time, hippocampal pyramidal neurons showed significant (p<0.001) reduction in dendritic length and spine density. In contrast, no significant change in neuronal dendrite and spine density or F2-IsoP, F4-NeuroPs and citrulline levels were found in mice pretreated with Vitamin E (α-tocopherol, 100 mg/kg, ip) for 3 days, or with N-tert-butyl-α-phenylnitrone (PBN, 200 mg/kg, ip) or ibuprofen (inhibitors of cyclooxygenase, COX, 14 μg/ml of drinking water) for 2 weeks prior to KA treatment. These findings indicate novel interactions among free radical-induced generation of F2-IsoPs and F4-NeuroPs, nitric oxide and dendritic degeneration, closely associate oxidative damage to neuronal membranes with degeneration of the dendritic system, and point to possible interventions to limit severe damage in acute neurological disorders. PMID:18556069

Reforming results of a novel radial reactor for a solid oxide fuel cell system with anode off-gas recirculation

NASA Astrophysics Data System (ADS)

Bosch, Timo; Carré, Maxime; Heinzel, Angelika; Steffen, Michael; Lapicque, François

2017-12-01

A novel reactor of a natural gas (NG) fueled, 1 kW net power solid oxide fuel cell (SOFC) system with anode off-gas recirculation (AOGR) is experimentally investigated. The reactor operates as pre-reformer, is of the type radial reactor with centrifugal z-flow, has the shape of a hollow cylinder with a volume of approximately 1 L and is equipped with two different precious metal wire-mesh catalyst packages as well as with an internal electric heater. Reforming investigations of the reactor are done stand-alone but as if the reactor would operate within the total SOFC system with AOGR. For the tests presented here it is assumed that the SOFC system runs on pure CH4 instead of NG. The manuscript focuses on the various phases of reactor operation during the startup process of the SOFC system. Startup process reforming experiments cover reactor operation points at which it runs on an oxygen to carbon ratio at the reactor inlet (ϕRI) of 1.2 with air supplied, up to a ϕRI of 2.4 without air supplied. As confirmed by a Monte Carlo simulation, most of the measured outlet gas concentrations are in or close to equilibrium.

Redox-Active Bis(phenolate) N-Heterocyclic Carbene [OCO] Pincer Ligands Support Cobalt Electron Transfer Series Spanning Four Oxidation States.

PubMed

Harris, Caleb F; Bayless, Michael B; van Leest, Nicolaas P; Bruch, Quinton J; Livesay, Brooke N; Bacsa, John; Hardcastle, Kenneth I; Shores, Matthew P; de Bruin, Bas; Soper, Jake D

2017-10-16

A new family of low-coordinate Co complexes supported by three redox-noninnocent tridentate [OCO] pincer-type bis(phenolate) N-heterocyclic carbene (NHC) ligands are described. Combined experimental and computational data suggest that the charge-neutral four-coordinate complexes are best formulated as Co(II) centers bound to closed-shell [OCO] 2- dianions, of the general formula [(OCO)Co II L] (where L is a solvent-derived MeCN or THF). Cyclic voltammograms of the [(OCO)Co II L] complexes reveal three oxidations accessible at potentials below 1.2 V vs Fc + /Fc, corresponding to generation of formally Co(V) species, but the true physical/spectroscopic oxidation states are much lower. Chemical oxidations afford the mono- and dications of the imidazoline NHC-derived complex, which were examined by computational and magnetic and spectroscopic methods, including single-crystal X-ray diffraction. The metal and ligand oxidation states of the monocationic complex are ambiguous; data are consistent with formulation as either [( S OCO)Co III (THF) 2 ] + containing a closed-shell [ S OCO] 2- diphenolate ligand bound to a S = 1 Co(III) center, or [( S OCO • )Co II (THF) 2 ] + with a low-spin Co(II) ion ferromagnetically coupled to monoanionic [ S OCO • ] - containing a single unpaired electron distributed across the [OCO] framework. The dication is best described as [( S OCO 0 )Co II (THF) 3 ] 2+ , with a single unpaired electron localized on the d 7 Co(II) center and a doubly oxidized, charge-neutral, closed-shell S OCO 0 ligand. The combined data provide for the first time unequivocal and structural evidence for [OCO] ligand redox activity. Notably, varying the degree of unsaturation in the NHC backbone shifts the ligand-based oxidation potentials by up to 400 mV. The possible chemical origins of this unexpected shift, along with the potential utility of the [OCO] pincer ligands for base-metal-mediated organometallic coupling catalysis, are discussed.

Use resources of human exometabolites of different oxidation levels for higher plants cultivation on the soil-like substrate as applied to closed ecosystems

NASA Astrophysics Data System (ADS)

Tikhomirov, Alexander A.; Kudenko, Yurii; Ushakova, Sofya; Tirranen, Lyalya; Gribovskaya, Illiada; Gros, Jean-Bernard; Lasseur, Christophe

The technology of ‘wet incineration' of human exometabolites and inedible plants biomass by means of H2 O2 in alternating electromagnetic field to increase a closure of mass exchange processes in bioregenerative life support systems (BLSS) was developed at the Institute of Biophysics of the Siberian Branch of Russian Academy of Sciences (Krasnoyarsk, Russia). Human exometabolites mineralized can be used in a nutrient solution for plants cultivation in the BLSS phototrophic link. The objective of the given work appears to be the study of use resources of human exometabolites of different oxidation levels processed by the abovementioned method for higher plants cultivation on the soil-like substrate (SLS). The mineralized human wastes were tested for the purpose of their sterility. Then the effect of human exometabolites of different oxidation levels both on wheat productivity and on the SLS microflora composition was examined. The SLS extract with a definite amount of human mineralized wastes was used as an irrigation solution. The conducted experiments demonstrated that the H2 O2 decreasing to 1 ml on 1 g of feces and to 0.25 ml on 1 ml of urine had not affected the sterility of mineralized human wastes. Wheat cultivation on the SLS with the addition in an irrigation solution of mineralized human wastes in the amount simulating 1/6 of a daily human diet showed the absence of basic dependence of plants productivity on oxidation level of human exometabolites. Yet the analysis of the microflora composition of the irrigation solutions demonstrated its dependence on the oxidation level of the exometabolites introduced. The amount of yeast-like fungi increased in 20 times in the solutions containing less oxidized exometabolites in comparison with the variant in which the human wastes were subjected to a full-scale oxidation. Besides, the solutions with less oxidized exometabolites displayed a bigger content of plant pathogenic bacteria and denitrifies. Consequently the introduction of sterile human exometabolites of a deficient oxidation level in irrigation solutions significantly affects the composition of a microbiological element of these solutions that may result in disruption of the BLSS system on the whole.

Oxidative stress in MeHg-induced neurotoxicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farina, Marcelo, E-mail: farina@ccb.ufsc.br; Aschner, Michael; Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN

2011-11-15

Methylmercury (MeHg) is an environmental toxicant that leads to long-lasting neurological and developmental deficits in animals and humans. Although the molecular mechanisms mediating MeHg-induced neurotoxicity are not completely understood, several lines of evidence indicate that oxidative stress represents a critical event related to the neurotoxic effects elicited by this toxicant. The objective of this review is to summarize and discuss data from experimental and epidemiological studies that have been important in clarifying the molecular events which mediate MeHg-induced oxidative damage and, consequently, toxicity. Although unanswered questions remain, the electrophilic properties of MeHg and its ability to oxidize thiols have beenmore » reported to play decisive roles to the oxidative consequences observed after MeHg exposure. However, a close examination of the relationship between low levels of MeHg necessary to induce oxidative stress and the high amounts of sulfhydryl-containing antioxidants in mammalian cells (e.g., glutathione) have led to the hypothesis that nucleophilic groups with extremely high affinities for MeHg (e.g., selenols) might represent primary targets in MeHg-induced oxidative stress. Indeed, the inhibition of antioxidant selenoproteins during MeHg poisoning in experimental animals has corroborated this hypothesis. The levels of different reactive species (superoxide anion, hydrogen peroxide and nitric oxide) have been reported to be increased in MeHg-exposed systems, and the mechanisms concerning these increments seem to involve a complex sequence of cascading molecular events, such as mitochondrial dysfunction, excitotoxicity, intracellular calcium dyshomeostasis and decreased antioxidant capacity. This review also discusses potential therapeutic strategies to counteract MeHg-induced toxicity and oxidative stress, emphasizing the use of organic selenocompounds, which generally present higher affinity for MeHg when compared to the classically studied agents.« less

Conservation of Oxidative Protein Stabilization in an Insect Homologue of Parkinsonism-Associated Protein DJ-1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Jiusheng; Prahlad, Janani; Wilson, Mark A.

2012-08-21

DJ-1 is a conserved, disease-associated protein that protects against oxidative stress and mitochondrial damage in multiple organisms. Human DJ-1 contains a functionally essential cysteine residue (Cys106) whose oxidation is important for regulating protein function by an unknown mechanism. This residue is well-conserved in other DJ-1 homologues, including two (DJ-1{alpha} and DJ-1{beta}) in Drosophila melanogaster. Because D. melanogaster is a powerful model system for studying DJ-1 function, we have determined the crystal structure and impact of cysteine oxidation on Drosophila DJ-1{beta}. The structure of D. melanogaster DJ-1{beta} is similar to that of human DJ-1, although two important residues in the humanmore » protein, Met26 and His126, are not conserved in DJ-1{beta}. His126 in human DJ-1 is substituted with a tyrosine in DJ-1{beta}, and this residue is not able to compose a putative catalytic dyad with Cys106 that was proposed to be important in the human protein. The reactive cysteine in DJ-1 is oxidized readily to the cysteine-sulfinic acid in both flies and humans, and this may regulate the cytoprotective function of the protein. We show that the oxidation of this conserved cysteine residue to its sulfinate form (Cys-SO{sub 2{sup -}}) results in considerable thermal stabilization of both Drosophila DJ-1{beta} and human DJ-1. Therefore, protein stabilization is one potential mechanism by which cysteine oxidation may regulate DJ-1 function in vivo. More generally, most close DJ-1 homologues are likely stabilized by cysteine-sulfinic acid formation but destabilized by further oxidation, suggesting that they are biphasically regulated by oxidative modification.« less

Structural changes in the nano-oxide layer with annealing in specular spin valves

NASA Astrophysics Data System (ADS)

Jang, S. H.; Kim, Y. W.; Kang, T.; Kim, H. J.; Kim, K. Y.

2003-05-01

We investigated microstructural changes in a nano-oxide layer (NOL) with annealing in specular spin valves (SVs) by cross-sectional transmission electron microscopy and x-ray photoelectron spectroscopy analysis. In the SV annealed at high temperature of 400 °C, an increase in thickness and a local breakdown of the NOL were observed. This local coarsening of the NOL is closely related to the formation of Mn oxides in the oxide-rich part of the NOL through Mn diffusion. Thus, the chemical structure of the NOL changes to the structure with Mn oxide-rich content after annealing.

Protein phylogenies provide evidence of a radical discontinuity between arthropod and vertebrate immune systems.

PubMed

Hughes, A L

1998-03-01

Protein phylogenies were used to test the hypothesis that aspects of the innate immune system of vertebrates have been conserved since the last common ancestor of vertebrates and arthropods. The phylogeny of lysozymes showed evidence of conservation of function, but phylogenies of seven other protein families did not. Natural resistance-associated macrophage protein, nitric oxide synthetase, and serine protease families all showed a pattern of gene duplication within vertebrates after their divergence from arthropods, giving rise to immune system-expressed genes in vertebrates. Insect hemolin, a member of the immunoglobulin superfamily, was found not to be closely related to members of that family having an immune system role in vertebrates; rather, it appeared most closely related to both arthropod and vertebrate molecules expressed in the nervous system. Thus, hemolin seems to have evolved its role independently in insects, probably through duplication of a neuroglian-like ancestor. Furthermore, vertebrate immune system-expressed serpins, chitinases, and pentraxins were found to lack orthologous relationships with arthropod members of the same families also functioning in immunity. Therefore members of these families have evolved immune system functions independently in the two phyla. It is now widely recognized that the specific immune system of vertebrates has no counterpart in invertebrates; these phylogenetic analyses suggest that there is a similar evolutionary discontinuity with respect to innate immunity as well.

COATED ALLOYS

DOEpatents

Harman, C.G.; O'Bannon, L.S.

1958-07-15

A coating is described for iron group metals and alloys, that is particularly suitable for use with nickel containing alloys. The coating is glassy in nature and consists of a mixture containing an alkali metal oxide, strontium oxide, and silicon oxide. When the glass coated nickel base metal is"fired'' at less than the melting point of the coating, it appears the nlckel diffuses into the vitreous coating, thus providing a closely adherent and protective cladding.

Probing individual tunneling fluctuators with coherently controlled tunneling systems

NASA Astrophysics Data System (ADS)

Meißner, Saskia M.; Seiler, Arnold; Lisenfeld, Jürgen; Ustinov, Alexey V.; Weiss, Georg

2018-05-01

Josephson junctions made from aluminum and its oxide are the most commonly used functional elements for superconducting circuits and qubits. It is generally known that the disordered thin film AlOx contains atomic tunneling systems. Coherent tunneling systems may couple strongly to a qubit via their electric dipole moment, giving rise to spectral level repulsion. In addition, slowly fluctuating tunneling systems are observable when they are located close to coherent ones and distort their potentials. This interaction causes telegraphic switching of the coherent tunneling systems' energy splitting. Here, we measure such switching induced by individual fluctuators on timescales from hours to minutes using a superconducting qubit as a detector. Moreover, we extend the range of measurable switching times to millisecond scales by employing a highly sensitive single-photon qubit swap spectroscopy and statistical analysis of the measured qubit states.

Xenobiotica-metabolizing enzymes in the skin of rat, mouse, pig, guinea pig, man, and in human skin models.

PubMed

Oesch, F; Fabian, E; Landsiedel, Robert

2018-06-18

Studies on the metabolic fate of medical drugs, skin care products, cosmetics and other chemicals intentionally or accidently applied to the human skin have become increasingly important in order to ascertain pharmacological effectiveness and to avoid toxicities. The use of freshly excised human skin for experimental investigations meets with ethical and practical limitations. Hence information on xenobiotic-metabolizing enzymes (XME) in the experimental systems available for pertinent studies compared with native human skin has become crucial. This review collects available information of which-taken with great caution because of the still very limited data-the most salient points are: in the skin of all animal species and skin-derived in vitro systems considered in this review cytochrome P450 (CYP)-dependent monooxygenase activities (largely responsible for initiating xenobiotica metabolism in the organ which provides most of the xenobiotica metabolism of the mammalian organism, the liver) are very low to undetectable. Quite likely other oxidative enzymes [e.g. flavin monooxygenase, COX (cooxidation by prostaglandin synthase)] will turn out to be much more important for the oxidative xenobiotic metabolism in the skin. Moreover, conjugating enzyme activities such as glutathione transferases and glucuronosyltransferases are much higher than the oxidative CYP activities. Since these conjugating enzymes are predominantly detoxifying, the skin appears to be predominantly protected against CYP-generated reactive metabolites. The following recommendations for the use of experimental animal species or human skin in vitro models may tentatively be derived from the information available to date: for dermal absorption and for skin irritation esterase activity is of special importance which in pig skin, some human cell lines and reconstructed skin models appears reasonably close to native human skin. With respect to genotoxicity and sensitization reactive-metabolite-reducing XME in primary human keratinocytes and several reconstructed human skin models appear reasonably close to human skin. For a more detailed delineation and discussion of the severe limitations see the Conclusions section in the end of this review.

Determination of diffusing species from marker experiments in the system Ni Ti O

NASA Astrophysics Data System (ADS)

Schirmer, S.; Lindner, J. K. N.; Mändl, S.

2007-04-01

Surface modification of NiTi for improved biocompatibility is a pressing issue. Using oxygen plasma immersion ion implantation (PIII), it is possible to form closed TiO2 layers on NiTi3 on NiTi. Using 60Ni marker ions implanted at 180 keV, it is shown conclusively that mobile Ni are the diffusing species, with the onset of diffusion occurring between 300 and 400 °C. Additionally, Ni is selectively removed from the oxide by preferential sputtering from the surface.

Carbon dioxide and water vapor high temperature electrolysis

NASA Technical Reports Server (NTRS)

Isenberg, Arnold O.; Verostko, Charles E.

1989-01-01

The design, fabrication, breadboard testing, and the data base obtained for solid oxide electrolysis systems that have applications for planetary manned missions and habitats are reviewed. The breadboard tested contains sixteen tubular cells in a closely packed bundle for the electrolysis of carbon dioxide and water vapor. The discussion covers energy requirements, volume, weight, and operational characteristics related to the measurement of the reactant and product gas compositions, temperature distribution along the electrolyzer tubular cells and through the bundle, and thermal energy losses. The reliability of individual cell performance in the bundle configuration is assessed.

Fast formation of supergene Mn oxides/hydroxides under acidic conditions in the oxic/anoxic transition zone of a shallow aquifer.

PubMed

Schäffner, F; Merten, D; Pollok, K; Wagner, S; Knoblauch, S; Langenhorst, F; Büchel, G

2015-12-01

Extensive uranium mining in the former German Democratic Republic (GDR) in eastern Thuringia and Saxony took place during the period of 1946-1990. During mining activities, pelitic sediments rich in organic carbon and uranium were processed and exposed to oxygen. Subsequent pyrite oxidation and acidic leaching lead to partial contamination of the area with heavy metals and acid mine drainage (AMD) even few years after completion of remediation. One of those areas is the former heap Gessen (Ronneburg, Germany) were the residual contamination can be found 10 m under the base of the former heap containing partly permeable drainage channels. Actually, in such a system, a rapid but locally restricted mineralization of Mn oxides takes place under acidic conditions. This formation can be classified as a natural attenuation process as certain heavy metals, e.g., Cd (up to 6 μg/g), Ni (up to 311 μg/g), Co (up to 133 μg/g), and Zn (up to 104 μg/g) are bound to this phases. The secondary minerals occur as colored layers close to the shallow aquifer in glacial sediments and could be identified as birnessite and todorokite as Mn phase. The thermodynamic model shows that even small changes in the system are sufficient to shift either the pH or the Eh in the direction of stable Mn oxide phases in this acidic system. As a consequence of 9-15-year-long formation process (or even less), the supergene mineralization provides a cost-efficient contribution for remediation (natural attenuation) strategies of residual with heavy metals (e.g., Cd, Co, Ni, Zn) contaminated substrates.

Quantitative detection of RO2 radicals and other products from cyclohexene ozonolysis with ammonium-CI3-TOF and acetate-CI-API-TOF

NASA Astrophysics Data System (ADS)

Hansel, A.; Scholz, W.; Mentler, B.; Fischer, L.; Berndt, T.

2017-12-01

The performance of the novel ammonium-CI3-TOF utilizing NH4+ adduct ion chemistry to measure quantitatively first generation oxidized product molecules (OMs) as well as highly oxidized organic molecules (HOMs) was investigated for the first time. The gas-phase ozonolysis of cyclohexene served as a test system in order to evaluate the capability of the detection systems. Experiments have been carried out in the TROPOS free-jet flow system at close to atmospheric conditions. Product ion signals were simultaneously observed by the ammonium-CI3-TOF and the acetate-CI-API-TOF. Both instruments are in remarkable good agreement within a factor of two for HOMs. For OMs not containing an OOH group the acetate technique can considerably underestimate OM concentrations by 2-3 orders of magnitude. First steps of cyclohexene ozonolysis generate ten different (m/z product peaks) main products comprising 92% of observed OMs. The remaining 8% are distributed over several (m/z peaks) minor products that can be attributed to HOMs, predominately to highly oxidized RO2 radicals. Summing up, observed ammonium-CI3-TOF products yield 4.9 x 109 molecules cm-³ in excellent agreement with the amount of reacted cyclohexene of 5.0 x 109 molecules cm-³ for reactant concentrations of [O3] = 2.25 x 1012 molecules cm-³ and [cyclohexene] = 2.0 x 1012 molecules cm-³ and a reaction time of 7.9 s. NH4+ adduct ion chemistry based CIMS techniques offer a unique opportunity for complete detection of the whole product distribution, and consequently, for a much better understanding of atmospheric oxidation processes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marinov, N.M.; Westbrook, C.K.; Cloutman, L.D.

Work being carried out at LLNL has concentrated on studies of the role of chemical kinetics in a variety of problems related to hydrogen combustion in practical combustion systems, with an emphasis on vehicle propulsion. Use of hydrogen offers significant advantages over fossil fuels, and computer modeling provides advantages when used in concert with experimental studies. Many numerical {open_quotes}experiments{close_quotes} can be carried out quickly and efficiently, reducing the cost and time of system development, and many new and speculative concepts can be screened to identify those with sufficient promise to pursue experimentally. This project uses chemical kinetic and fluid dynamicmore » computational modeling to examine the combustion characteristics of systems burning hydrogen, either as the only fuel or mixed with natural gas. Oxidation kinetics are combined with pollutant formation kinetics, including formation of oxides of nitrogen but also including air toxics in natural gas combustion. We have refined many of the elementary kinetic reaction steps in the detailed reaction mechanism for hydrogen oxidation. To extend the model to pressures characteristic of internal combustion engines, it was necessary to apply theoretical pressure falloff formalisms for several key steps in the reaction mechanism. We have continued development of simplified reaction mechanisms for hydrogen oxidation, we have implemented those mechanisms into multidimensional computational fluid dynamics models, and we have used models of chemistry and fluid dynamics to address selected application problems. At the present time, we are using computed high pressure flame, and auto-ignition data to further refine the simplified kinetics models that are then to be used in multidimensional fluid mechanics models. Detailed kinetics studies have investigated hydrogen flames and ignition of hydrogen behind shock waves, intended to refine the detailed reactions mechanisms.« less

Morphological Control of Co3O4 and Its Photocatalytic Properties

EPA Science Inventory

Cobaltosic oxide (Co3O4), a p-type semiconductor, belongs to the normal spinel crystal structure based on a cubic close packing array of oxide ions. The size, surface, geometry, and crystal phase of catalysts are important parameters for controlling their chemical, optical, and ...

Two-Dimensional Algal Collection and Assembly by Combining AC-Dielectrophoresis with Fluorescence Detection for Contaminant-Induced Oxidative Stress Sensing.

PubMed

Siebman, Coralie; Velev, Orlin D; Slaveykova, Vera I

2015-06-15

An alternative current (AC) dielectrophoretic lab-on-chip setup was evaluated as a rapid tool of capture and assembly of microalga Chlamydomonas reinhardtii in two-dimensional (2D) close-packed arrays. An electric field of 100 V·cm⁻¹, 100 Hz applied for 30 min was found optimal to collect and assemble the algae into single-layer structures of closely packed cells without inducing cellular oxidative stress. Combined with oxidative stress specific staining and fluorescence microscopy detection, the capability of using the 2D whole-cell assembly on-chip to follow the reactive oxygen species (ROS) production and oxidative stress during short-term exposure to several environmental contaminants, including mercury, methylmercury, copper, copper oxide nanoparticles (CuO-NPs), and diuron was explored. The results showed significant increase of the cellular ROS when C. reinhardtii was exposed to high concentrations of methylmercury, CuO-NPs, and 10⁻⁵ M Cu. Overall, this study demonstrates the potential of combining AC-dielectrophoretically assembled two-dimensional algal structures with cell metabolic analysis using fluorescence staining, as a rapid analytical tool for probing the effect of contaminants in highly impacted environment.

Characterization of the arsenite oxidizer Aliihoeflea sp. strain 2WW and its potential application in the removal of arsenic from groundwater in combination with Pf-ferritin.

PubMed

Corsini, Anna; Colombo, Milena; Muyzer, Gerard; Cavalca, Lucia

2015-09-01

A heterotrophic arsenite-oxidizing bacterium, strain 2WW, was isolated from a biofilter treating arsenic-rich groundwater. Comparative analysis of 16S rRNA gene sequences showed that it was closely related (98.7 %) to the alphaproteobacterium Aliihoeflea aesturari strain N8(T). However, it was physiologically different by its ability to grow at relatively low substrate concentrations, low temperatures and by its ability to oxidize arsenite. Here we describe the physiological features of strain 2WW and compare these to its most closely related relative, A. aestuari strain N8(T). In addition, we tested its efficiency to remove arsenic from groundwater in combination with Pf-ferritin. Strain 2WW oxidized arsenite to arsenate between pH 5.0 and 8.0, and from 4 to 30 °C. When the strain was used in combination with a Pf-ferritin-based material for arsenic removal from natural groundwater, the removal efficiency was significantly higher (73 %) than for Pf-ferritin alone (64 %). These results showed that arsenite oxidation by strain 2WW combined with Pf-ferritin-based material has a potential in arsenic removal from contaminated groundwater.

Oxidation Kinetics and Strength Degradation of Carbon Fibers in a Cracked Ceramic Matrix Composite

NASA Technical Reports Server (NTRS)

Halbig, Michael C.

2003-01-01

Experimental results and oxidation modeling will be presented to discuss carbon fiber susceptibility to oxidation, the oxidation kinetics regimes and composite strength degradation and failure due to oxidation. Thermogravimetric Analysis (TGA) was used to study the oxidation rates of carbon fiber and of a pyro-carbon interphase. The analysis was used to separately obtain activation energies for the carbon constituents within a C/SiC composite. TGA was also conducted on C/SiC composite material to study carbon oxidation and crack closure as a function of temperature. In order to more closely match applications conditions C/SiC tensile coupons were also tested under stressed oxidation conditions. The stressed oxidation tests show that C/SiC is much more susceptible to oxidation when the material is under an applied load where the cracks are open and allow for oxygen ingress. The results help correlate carbon oxidation with composite strength reduction and failure.

Effect of the introduction of oxide ion vacancies into cubic fluorite-type rare earth oxides on the NO decomposition catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masui, Toshiyuki; Nagai, Ryosuke; Imanaka, Nobuhito, E-mail: imanaka@chem.eng.osaka-u.ac.jp

2014-12-15

Cubic fluorite-type solid solutions based on Pr{sub 6}O{sub 11} and CeO{sub 2} were synthesized and oxide anion vacancies were intentionally introduced into the cubic fluorite-type lattice through the charge compensating mechanism by Mg{sup 2+} and/or Ca{sup 2+} doping into their lattices. The oxide anion vacancies bring about positive effect on NO decomposition catalysis. The reason for the increase in the catalytic activity was attributed to defect fluorite-type structures close to the C-type cubic one, because C-type cubic rare earth oxides, in which one-quarter of the oxygen atoms in the fluorite-type structure are removed, show high NO decomposition activity. In particular,more » the positive effect of the formation of oxide anion vacancies was significant for Pr{sub 6}O{sub 11} and its solid solutions, because the molar volume of Pr{sub 6}O{sub 11} is larger than that of CeO{sub 2}, and Pr{sub 6}O{sub 11} contains Pr{sup 3+} as well as Pr{sup 4+} and thereby a small amount of oxide anion vacancies exist inherently in the lattice. - Graphical abstract: Oxide anion vacancies intentionally introduced into the cubic fluorite-type lattice bring about positive effect on NO decomposition catalysis. - Highlights: • Cubic fluorite-type solid solutions were synthesized. • Oxide anion vacancies were intentionally introduced into the cubic fluorite-type lattice. • The oxide anion vacancies bring about positive effect on NO decomposition catalysis. • The activity was enhanced by making the structure close to the C-type cubic one.« less

Nitrotoga-like bacteria are previously unrecognized key nitrite oxidizers in full-scale wastewater treatment plants.

PubMed

Lücker, Sebastian; Schwarz, Jasmin; Gruber-Dorninger, Christiane; Spieck, Eva; Wagner, Michael; Daims, Holger

2015-03-01

Numerous past studies have shown members of the genus Nitrospira to be the predominant nitrite-oxidizing bacteria (NOB) in nitrifying wastewater treatment plants (WWTPs). Only recently, the novel NOB 'Candidatus Nitrotoga arctica' was identified in permafrost soil and a close relative was enriched from activated sludge. Still, little is known about diversity, distribution and functional importance of Nitrotoga in natural and engineered ecosystems. Here we developed Nitrotoga 16S rRNA-specific PCR primers and fluorescence in situ hybridization (FISH) probes, which were applied to screen activated sludge samples from 20 full-scale WWTPs. Nitrotoga-like bacteria were detected by PCR in 11 samples and reached abundances detectable by FISH in seven sludges. They coexisted with Nitrospira in most of these WWTPs, but constituted the only detectable NOB in two systems. Quantitative FISH revealed that Nitrotoga accounted for nearly 2% of the total bacterial community in one of these plants, a number comparable to Nitrospira abundances in other WWTPs. Spatial statistics revealed that Nitrotoga coaggregated with ammonia-oxidizing bacteria, strongly supporting a functional role in nitrite oxidation. This activity was confirmed by FISH in combination with microradiography, which revealed nitrite-dependent autotrophic carbon fixation by Nitrotoga in situ. Correlation of the presence or absence with WWTP operational parameters indicated low temperatures as a main factor supporting high Nitrotoga abundances, although in incubation experiments these NOB remained active over an unexpected range of temperatures, and also at different ambient nitrite concentrations. In conclusion, this study demonstrates that Nitrotoga can be functionally important nitrite oxidizers in WWTPs and can even represent the only known NOB in engineered systems.

2013 Early Career Achievement Award--Proteomics of muscle- and species-specificity in meat color stability.

PubMed

Suman, S P; Rentfrow, G; Nair, M N; Joseph, P

2014-03-01

Meat color is the most important quality trait influencing consumer purchase decisions. The interinfluential interactions between myoglobin and biomolecules govern color stability in meat. The advances in proteomics, such as high throughput analytical tools in mass spectrometry, 2-dimensional electrophoresis, and bioinformatics, offer themselves as robust techniques to characterize the proteome basis of muscle- and species-specific meat color phenomena. Differential abundance of chaperones and antioxidant proteins contributes to muscle-specific color stability in beef; the greater abundance of chaperones and antioxidant proteins in color-stable Longissimus lumborum than in color-labile Psoas major protects myoglobin and contributes to superior color stability of beef Longissimus steaks. Lipid oxidation-induced myoglobin oxidation is more critical to beef color than pork color due to the inherent differences in myoglobin chemistry; the number of nucleophilic histidine residues adducted by reactive aldehydes is greater in beef myoglobin than in pork myoglobin. Preferential adduction of secondary products of lipid oxidation to beef myoglobin accelerates metmyoglobin formation at a greater degree than in its pork counterpart. Mass spectrometric investigations revealed that although cherry-red carboxymyoglobin is more stable than oxymyoglobin, both redox forms undergo lipid oxidation-induced oxidation in model systems. The accuracy of mass spectrometry to detect the molecular mass of proteins has been applied to differentiate myoglobins from closely related meat animals, such as goats and sheep or emu and ostrich. In addition, this approach indicated that turkey myoglobin is 350 Da greater in molecular mass than beef myoglobin, and the unique biochemistry of turkey myoglobin could be responsible for its greater thermostability in model systems as well as the pink color defect observed in fully cooked uncured turkey products.

Regenerable Air Purification System for Gas-Phase Contaminant Control

NASA Technical Reports Server (NTRS)

Constantinescu, Ileana C.; Finn, John E.; LeVan, M. Douglas; Lung, Bernadette (Technical Monitor)

2000-01-01

Tests of a pre-prototype regenerable air purification system (RAPS) that uses water vapor to displace adsorbed contaminants from an adsorbent column have been performed at NASA Ames Research Center. A unit based on this design can be used for removing trace gas-phase contaminants from spacecraft cabin air or from polluted process streams including incinerator exhaust. During the normal operation mode, contaminants are removed from the air on the column. Regeneration of the column is performed on-line. During regeneration, contaminants are displaced and destroyed inside the closed oxidation loop. In this presentation we discuss initial experimental results for the performance of RAPS in the removal and treatment of several important spacecraft contaminant species from air.

Oxidation of TD nickel at 1050 C and 1200 C as compared with three grades of nickel of different purity

NASA Technical Reports Server (NTRS)

Lowell, C. E.; Grisaffe, S. J.; Deadmore, D. L.

1972-01-01

The isothermal oxidation of three nickels of different purity, Ni-200, Ni-270, and JM-Ni, was compared with that of TD-Ni in air at 1050 and 1200 C. The samples were oxidized as ground, as polished, or as annealed and polished. Weight change, metal loss, scale thickness, oxide morphology, and scale texture were determined. In degree of oxidation, TD-Ni was nearly the same as the higher purity materials, Ni-270 and JM-Ni; and less pure Ni-200 oxidized more than the others. However, in microstructure and scale texture the TD-Ni more closely resembled Ni-200. Grinding only charged the texture of the oxides of Ni_200 and TD-Ni.

Oxidative Weathering and Microbial Diversity of an Inactive Seafloor Hydrothermal Sulfide Chimney

PubMed Central

Li, Jiangtao; Cui, Jiamei; Yang, Qunhui; Cui, Guojie; Wei, Bingbing; Wu, Zijun; Wang, Yong; Zhou, Huaiyang

2017-01-01

When its hydrothermal supply ceases, hydrothermal sulfide chimneys become inactive and commonly experience oxidative weathering on the seafloor. However, little is known about the oxidative weathering of inactive sulfide chimneys, nor about associated microbial community structures and their succession during this weathering process. In this work, an inactive sulfide chimney and a young chimney in the early sulfate stage of formation were collected from the Main Endeavor Field of the Juan de Fuca Ridge. To assess oxidative weathering, the ultrastructures of secondary alteration products accumulating on the chimney surface were examined and the presence of possible Fe-oxidizing bacteria (FeOB) was investigated. The results of ultrastructure observation revealed that FeOB-associated ultrastructures with indicative morphologies were abundantly present. Iron oxidizers primarily consisted of members closely related to Gallionella spp. and Mariprofundus spp., indicating Fe-oxidizing species likely promote the oxidative weathering of inactive sulfide chimneys. Abiotic accumulation of Fe-rich substances further indicates that oxidative weathering is a complex, dynamic process, alternately controlled by FeOB and by abiotic oxidization. Although hydrothermal fluid flow had ceased, inactive chimneys still accommodate an abundant and diverse microbiome whose microbial composition and metabolic potential dramatically differ from their counterparts at active vents. Bacterial lineages within current inactive chimney are dominated by members of α-, δ-, and γ-Proteobacteria and they are deduced to be closely involved in a diverse set of geochemical processes including iron oxidation, nitrogen fixation, ammonia oxidation and denitrification. At last, by examining microbial communities within hydrothermal chimneys at different formation stages, a general microbial community succession can be deduced from early formation stages of a sulfate chimney to actively mature sulfide structures, and then to the final inactive altered sulfide chimney. Our findings provide valuable insights into the microbe-involved oxidative weathering process and into microbial succession occurring at inactive hydrothermal sulfide chimney after high-temperature hydrothermal fluids have ceased venting. PMID:28785251

Microlith-Based Catalytic Reactor for Air Quality and Trace Contaminant Control Applications

NASA Technical Reports Server (NTRS)

Vilekar, Saurabh; Hawley, Kyle; Junaedi, Christian; Crowder, Bruce; Prada, Julian; Mastanduno, Richard; Perry, Jay L.; Kayatin, Matthew J.

2015-01-01

Traditionally, gaseous compounds such as methane, carbon monoxide, and trace contaminants have posed challenges for maintaining clean air in enclosed spaces such as crewed spacecraft cabins as they are hazardous to humans and are often difficult to remove by conventional adsorption technology. Catalytic oxidizers have provided a reliable and robust means of disposing of even trace levels of these compounds by converting them into carbon dioxide and water. Precision Combustion, Inc. (PCI) and NASA - Marshall (MSFC) have been developing, characterizing, and optimizing high temperature catalytic oxidizers (HTCO) based on PCI's patented Microlith® technology to meet the requirements of future extended human spaceflight explorations. Current efforts have focused on integrating the HTCO unit with a compact, simple recuperative heat exchanger to reduce the overall system size and weight while also reducing its energy requirements. Previous efforts relied on external heat exchangers to recover the waste heat and recycle it to the oxidizer to minimize the system's power requirements; however, these units contribute weight and volume burdens to the overall system. They also result in excess heat loss due to the separation of the HTCO and the heat recuperator, resulting in lower overall efficiency. Improvements in the recuperative efficiency and close coupling of HTCO and heat recuperator lead to reductions in system energy requirements and startup time. Results from testing HTCO units integrated with heat recuperators at a variety of scales for cabin air quality control and heat melt compactor applications are reported and their benefits over previous iterations of the HTCO and heat recuperator assembly are quantified in this paper.

Climate mitigation is not the only benefit of a national energy system

NASA Astrophysics Data System (ADS)

Clack, C.

2016-12-01

Many speculate that the main driving force for a continental scale energy system is for climate mitigation. While this is a strong driver, there are multiple co-benefits that emerge from such a transition when purely driven by costs. These components could be managed within a planned system to provide a close-to-optimal solution that enhances the probability of realization. It is shown that these co-benefits of a continental scale electric system occur at costs lower than existing ones. That means there are multiple additional savings without extra costs or effort. The disadvantage is coordination between large geographic regions that could cause more complexity in planning. The main finding from different versions of the NEWS simulator is that carbon mitigation is enhanced by larger systems. In addition, there are increased jobs, reduced water consumption, Sulphur dioxide emissions, Nitrogen oxide emissions, a more distributed electric system and a lower cost of electricity.

Downhole steam generator having a downhole oxidant compressor

DOEpatents

Fox, R.L.

1981-01-07

Am improved apparatus is described for the downhole injection of steam into boreholes, for tertiary oil recovery. It includes an oxidant supply, a fuel supply, an igniter, a water supply, an oxidant compressor, and a combustor assembly. The apparatus is designed for efficiency, preheating of the water, and cooling of the combustion chamber walls. The steam outlet to the borehole is provided with pressure-responsive doors for closing the outlet in response to flameout. (DLC)

Electrical Characterization of Spherical Copper Oxide Memristive Array Sensors

DTIC Science & Technology

2014-03-27

Quartz Tube Furnace . . . . . . . 37 3.3.2.2 Thermal Oxidation in Air on a Hot Plate . . . . . . . . . 38 3.4 Experimental Setup for Electrical...closed hot plate . . . 80 B.1 Oxidation rates for copper at 100 °C by two different formulas . . . . . . . . . 81 xi List of Tables Table Page 2.1 The... Tectonics Inc. and manufactured by Canfield Technologies using a proprietary fabrication method. As received, the copper spheres may have contaminants

Literature Survey on Long-Term Storage of Petroleum Products, Artillery Storage Program

DTIC Science & Technology

1946-05-31

Oil .... . o . . . 70 ADDITION AGENTS . •• . ....... ....... 72 Oxidation Inhibitors 73 Oxidation Inhibitors in Turbine Oils • . . 73 Oxidation...also been considered. The oils found qost suitable for storage media should probably be closely related to transformer or turbine oils. In addition to...from those who have been using transformer anid turbine oils, and there are reports on these oils aind the changes which liave occurred over a period

Thermochemical cyclic system for decomposing H/sub 2/O and/or CO/sub 2/ by means of cerium-titanium-sodium-oxygen compounds

DOEpatents

Bamberger, C.E.

1980-04-24

A thermochemical closed cyclic process for the decomposition of water and/or carbon dioxide to hydrogen and/or carbon monoxide begins with the reaction of ceric oxide (CeO/sub 2/), titanium dioxide (TiO/sub 2/) and sodium titanate (Na/sub 2/TiO/sub 3/) to form sodium cerous titanate (NaCeTi/sub 2/O/sub 6/) and oxygen. Sodium cerous titanate (NaCeTi/sub 2/O/sub 6/) reacted with sodium carbonate (Na/sub 2/CO/sub 3/) in the presence of steam, produces hydrogen. The same reaction, in the absence of steam, produces carbon monoxide. The products, ceric oxide and sodium titanate, obtained in either case, are treated with carbon dioxide and water to produce ceric oxide, titanium dioxide, sodium titanate, and sodium bicarbonate. After dissolving sodium bicarbonate from the mixture in water, the remaining insoluble compounds are used as starting materials for a subsequent cycle. The sodium bicarbonate can be converted to sodium carbonate by heating and returned to the cycle.

Rare-earth doped gadolinia based phosphors for potential multicolor and white light emitting deep UV LEDs.

PubMed

Bedekar, Vinila; Dutta, Dimple P; Mohapatra, M; Godbole, S V; Ghildiyal, R; Tyagi, A K

2009-03-25

Gadolinium oxide host and europium/dysprosium/terbium doped gadolinium oxide nanoparticles were synthesized using the sonochemical technique. Gadolinium oxide nanocrystals were also co-doped with total 2 mol% of Eu(3+)/Dy(3+),Eu(3+)/Tb(3+),Dy(3+)/Tb(3+), and also Eu(3+)/Dy(3+)/Tb(3+) ions, by the same method. The nanoparticles obtained were characterized using powder x-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) techniques. The size of the particles ranged from 15 to 30 nm. The triple doped samples showed multicolor emission on single wavelength excitation. The photoluminescence results were correlated with the lifetime data to get an insight into the luminescence and energy transfer processes taking place in the system. On excitation at 247 nm, the novel nanocrystalline Gd(2)O(3):RE (RE = Dy, Tb) phosphor resulted in having very impressive CIE chromaticity coordinates of x = 0.315 and y = 0.316, and a correlated color temperature of 6508 K, which is very close to standard daylight.

Thermochemical cyclic system for decomposing H.sub.2 O and/or CO.sub.2 by means of cerium-titanium-sodium-oxygen compounds

DOEpatents

Bamberger, Carlos E.

1982-01-01

A thermochemical closed cyclic process for the decomposition of water and/or carbon dioxide to hydrogen and/or carbon monoxide begins with the reaction of ceric oxide (CeO.sub.2), titanium dioxide (TiO.sub.2) and sodium titanate (Na.sub.2 TiO.sub.3) to form sodium cerous titanate (NaCeTi.sub.2 O.sub.6) and oxygen. Sodium cerous titanate (NaCeTi.sub.2 O.sub.6) reacted with sodium carbonate (Na.sub.2 CO.sub.3) in the presence of steam, produces hydrogen. The same reaction, in the absence of steam, produces carbon monoxide. The products, ceric oxide and sodium titanate, obtained in either case, are treated with carbon dioxide and water to produce ceric oxide, titanium dioxide, sodium titanate, and sodium bicarbonate. After dissolving sodium bicarbonate from the mixture in water, the remaining insoluble compounds are used as starting materials for a subsequent cycle. The sodium bicarbonate can be converted to sodium carbonate by heating and returned to the cycle.

Structural evolution of epitaxial SrCoO x films near topotactic phase transition

DOE PAGES

Jeen, Hyoung Jeen; Lee, Ho Nyung

2015-12-18

Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoO x) epitaxially grown by pulsed laser epitaxy (PLE) as a model system to study the oxidation-driven evolution of the structure, electronic, and magnetic properties. We grew coherently strained SrCoO 2.5thin films and performed post-annealing at various temperaturesmore » for topotactic conversion into the perovskite phase (SrCoO 3-δ). We clearly observed significant changes in electronic transport, magnetism, and microstructure near the critical temperature for the topotactic transformation from the brownmillerite to the perovskite phase. Furthermore, the overall crystallinity was well maintained without much structural degradation, indicating that topotactic phase control can be a useful tool to control the physical properties repeatedly via redox reactions.« less

Prevalence of Nitrosomonas cluster 7 populations in the ammonia-oxidizing community of a submerged membrane bioreactor treating urban wastewater under different operation conditions.

PubMed

Cerrone, F; Poyatos, J M; Molina-Muñoz, M; Cortés-Lorenzo, C; González-López, J; Rodelas, B

2013-07-01

A pilot-scale ultrafiltration membrane bioreactor (MBR) was used for the aerobic treatment of urban wastewater in four experimental stages influenced by seasonal temperature and different sets of operation conditions. The structure of the ammonia-oxidizing bacteria (AOB) community was profiled by temperature gradient gel electrophoresis (TGGE), based on the amplification and separation of partial ammonia-monoxygenase subunit A (amoA) genes. Canonical correspondence analysis revealed that temperature, hydraulic retention time and percentage of ammonia removal had a significant effect on the fingerprints of AOB communities. Phylogenetic analysis conducted on amoA/AmoA sequences of reamplified TGGE bands showed, however, that closely related ammonia-oxidizing populations inhabited the sludge of the MBR in all experimental stages. Nitrosomonas cluster 7 populations (N. europaea-N. eutropha cluster) prevailed under all conditions tested, even when the MBR was operated under complete biomass retention or at low temperatures, suggesting that the high ammonia concentrations in the system were determinant to select r-strategist AOB.

Efficient epoxidation of a terminal alkene containing allylic hydrogen atoms: trans-methylstyrene on Cu{111}.

PubMed

Cropley, Rachael L; Williams, Federico J; Urquhart, Andrew J; Vaughan, Owain P H; Tikhov, Mintcho S; Lambert, Richard M

2005-04-27

The selective oxidation of trans-methylstyrene, a phenyl-substituted propene that contains labile allylic hydrogen atoms, has been studied on Cu{111}. Mass spectrometry and synchrotron fast XPS were used to detect, respectively, desorbing gaseous products and the evolution of surface species as a function of temperature and time. Efficient partial oxidation occurs yielding principally the epoxide, and the behavior of the system is sensitive to the order in which reactants are adsorbed. The latter is understandable in terms of differences in the spatial distribution of oxygen adatoms; isolated adatoms lead to epoxidation, while islands of "oxidic" oxygen do not. NEXAFS data taken over a range of coverages and in the presence and absence of coadsorbed oxygen indicate that the adsorbed alkene lies essentially flat with the allylic hydrogen atoms close to the surface. The photoemission results and comparison with the corresponding behavior of styrene on Cu{111} strongly suggest that allylic hydrogen abstraction is indeed a critical factor that limits epoxidation selectivity. An overall mechanism consistent with the structural and reactive properties is proposed.

NO-assisted molecular-beam epitaxial growth of nitrogen substituted EuO

NASA Astrophysics Data System (ADS)

Wicks, R.; Altendorf, S. G.; Caspers, C.; Kierspel, H.; Sutarto, R.; Tjeng, L. H.; Damascelli, A.

2012-04-01

We have investigated a method for substituting oxygen with nitrogen in EuO thin films, which is based on molecular beam epitaxy distillation with NO gas as the oxidizer. By varying the NO gas pressure, we produce crystalline, epitaxial EuO1 -xNx films with good control over the films' nitrogen concentration. In situ x-ray photoemission spectroscopy reveals that nitrogen substitution is connected to the formation Eu3+4f6 and a corresponding decrease in the number of Eu2+4f7, indicating that nitrogen is being incorporated in its 3- oxidation state. While small amounts of Eu3+ in over-oxidized Eu1-δO thin films lead to a drastic suppression of the ferromagnetism, the formation of Eu3+ in EuO1-xNx still allows the ferromagnetic phase to exist with an unaffected Tc, thus providing an ideal model system to study the interplay between the magnetic f7 (J = 7/2) and the non-magnetic f6 (J = 0) states close to the Fermi level.

Chemical reactivity parameters (HSAB) applied to magma evolution and ore formation

NASA Astrophysics Data System (ADS)

Vigneresse, Jean-Louis

2012-11-01

Magmas are commonly described through the usual content of 10 major oxides. This requires a complex dimensional plot. Concepts of hard-soft acid-base (HSAB) interactions allow estimating chemical reactivity of elements, such as electronegativity, i.e. the chemical potential changed of sign, hardness and electrophilicity. For complex system, those values result from equalization methods, i.e. the equalization of the respective chemical potentials, or from ab-initio computations through density functional theory (DFT). They help to characterize silicate magmas by a single value describing their reactivity. Principles of minimum electrophilicity (mEP), maximum hardness (MHP) and minimum polarizability (mPP) indicate trends towards regions of higher stability. Those parameters are plotted within a fitness landscape diagram, highlighting toward which principle reactions trend. Major oxides, main minerals and magmas determine the respective fields in which evolve natural rocks. Three poles are identified, represented by silica and alkalis, whereas oxidation forms the third trend. Mantle-derived rocks show a large variation in electrophilicity compared to hardness. They present all characters of a closed chemical system, being simply described by the free Gibbs energy. Conversely, rocks contaminated within the continental crust show a large variation in hardness between a silica pole and an alkaline, defining two separate trends. The trends show the character of an open chemical system, requiring a Grand Potential description (i.e. taking into account the difference in chemical potential). The terms open and closed systems refer to thermodynamical description, implying contamination for the crust and recycling for the mantle. The specific role of alkalis contrasts with other cations, pointing to their behavior in modifying silicate polymer structures. A second application deals with the reactivity of the melt and its fluid phase. It leads to a better understanding on the mechanisms that control sequestration and transport of metals within the different phases during igneous activity. Based on high gas/melt partitioning for metals and similar reactivity, the gaseous phase is more attractive for metals than silicate melts. The presence of halogens in the fluid phase tends to reinforce hardness, making the fluid phase attractive for hard metals such as Sn or W. Conversely, the presence of S decreases hardness of the fluid phase that becomes attractive for soft metals such as Au, Ag and Cu.

A grey box model of glucose fermentation and syntrophic oxidation in microbial fuel cells.

PubMed

de Los Ángeles Fernandez, Maria; de Los Ángeles Sanromán, Maria; Marks, Stanislaw; Makinia, Jacek; Gonzalez Del Campo, Araceli; Rodrigo, Manuel; Fernandez, Francisco Jesus

2016-01-01

In this work, the fermentative and oxidative processes taking place in a microbial fuel cell (MFC) fed with glucose were studied and modeled. The model accounting for the bioelectrochemical processes was based on ordinary, Monod-type differential equations. The model parameters were estimated using experimental results obtained from three H-type MFCs operated at open or closed circuits and fed with glucose or ethanol. The experimental results demonstrate that similar fermentation processes were carried out under open and closed circuit operation, with the most important fermentation products being ethanol (with a yield of 1.81molmol(-1) glucose) and lactic acid (with a yield of 1.36molmol(-1) glucose). A peak in the electricity generation was obtained when glucose and fermentation products coexisted in the liquid bulk. However, almost 90% of the electricity produced came from the oxidation of ethanol. Copyright © 2015 Elsevier Ltd. All rights reserved.

Quantitative structure-activity relationships (QSARs) for the transformation of organic micropollutants during oxidative water treatment.

PubMed

Lee, Yunho; von Gunten, Urs

2012-12-01

Various oxidants such as chlorine, chlorine dioxide, ferrate(VI), ozone, and hydroxyl radicals can be applied for eliminating organic micropollutant by oxidative transformation during water treatment in systems such as drinking water, wastewater, and water reuse. Over the last decades, many second-order rate constants (k) have been determined for the reaction of these oxidants with model compounds and micropollutants. Good correlations (quantitative structure-activity relationships or QSARs) are often found between the k-values for an oxidation reaction of closely related compounds (i.e. having a common organic functional group) and substituent descriptor variables such as Hammett or Taft sigma constants. In this study, we developed QSARs for the oxidation of organic and some inorganic compounds and organic micropollutants transformation during oxidative water treatment. A number of 18 QSARs were developed based on overall 412 k-values for the reaction of chlorine, chlorine dioxide, ferrate, and ozone with organic compounds containing electron-rich moieties such as phenols, anilines, olefins, and amines. On average, 303 out of 412 (74%) k-values were predicted by these QSARs within a factor of 1/3-3 compared to the measured values. For HO(·) reactions, some principles and estimation methods of k-values (e.g. the Group Contribution Method) are discussed. The developed QSARs and the Group Contribution Method could be used to predict the k-values for various emerging organic micropollutants. As a demonstration, 39 out of 45 (87%) predicted k-values were found within a factor 1/3-3 compared to the measured values for the selected emerging micropollutants. Finally, it is discussed how the uncertainty in the predicted k-values using the QSARs affects the accuracy of prediction for micropollutant elimination during oxidative water treatment. Copyright © 2012 Elsevier Ltd. All rights reserved.

Exchange biased and closed-flux pseudo spin-valve materials, device applications, and electrical reliability

NASA Astrophysics Data System (ADS)

Bae, Seongtae

Since giant magnetoresistance (GMR) and tunneling magnetoresistance (TMR) spinvalve effects were developed for the last two decades after discovered, world wide researches on applying these effects for various kinds of solid state active devices has provided a strong impact on challenging new functional micro-magnetoelectronic devices. In particular, recently developed nano-structured magnetic spin-valve thin film materials for spin-electronic devices are now considered as building blocks of state-of-the-art electronic engineering. This research has been concentrated on developing and designing magneto-electronic solid state devices with high thermal and electrical stability using an alpha-Fe 2O3 and NiO oxide anti-ferromagnetic exchange biased GMR bottom spin-valves (BSV), NiFe/Cu/Co and NiFe/Cu/CoFe based closed-flux metallic pseudo spin-valves, and PtMn exchange biased TMR spin-valves. The category covering this research is divided into four main research steps. First is to investigate exchange bias coupling characteristics of alpha-Fe2 O3 and NiO oxide Anti-ferromagnetic materials (AF)/Ferromagnetic (F) layer systems for optimizing exchange biased BSV and to study magnetic properties of various kinds of magnetic thin films including single through multi-layered structures for the fundamental research on NiFe/Cu/Co and NiFe/Cu/CoFe closed-flux metallic pseudo spin-valves. Second is to develop and improve new kinds of BSVs and closed-flux metallic spinvalves by controlling process parameters in terms of crystalline orientation texture of AF and F layers, interfacial surface roughness, grain size (its size distribution), chemical composition, and kinetics of sputtering film growth. Third is to design, to fabricate, and to investigate the magnetic and electrical properties of magneto-electronic devices as well as their applications such as GMR magnetoresistive random access memory (MRAM), GMR read head, TMR read head, and new kinds of GMR solid state devices, which can be promisingly substituted for current microelectronic devices. Finally, the last is to focus on studying electrical reliability of GMR read sensor and GMR MRAM cell in terms of electromigration-induced failures of various kinds of magnetic thin films, which are currently used in GMR spin-valve materials, and is to investigate the effects of current (or voltage) induced dielectric breakdown in aluminum oxide tunnel barrier under various testing conditions on the electrical stability of real TMR read sensors.

Rare isotope studies involving catalytic oxidation of CO over platinum-tin oxide

NASA Technical Reports Server (NTRS)

Upchurch, Billy T.; Wood, George M., Jr.; Hess, Robert V.; Hoyt, Ronald F.

1987-01-01

Results of studies utilizing normal and rare oxygen isotopes in the catalytic oxidation of carbon monoxide over a platinum-tin oxide catalyst substrate are presented. Chemisorption of labeled carbon monoxide on the catalyst followed by thermal desorption yielded a carbon dioxide product with an oxygen-18 composition consistent with the formation of a carbonate-like intermediate in the chemisorption process. The efficacy of a method developed for the oxygen-18 labeling of the platinum-tin oxide catalyst surface for use in closed cycle pulsed care isotope carbon dioxide lasers is demonstrated for the equivalent of 10 to the 6th power pulses at 10 pulses per second.

Phospholipase A₂: the key to reversing long-term memory impairment in a gastropod model of aging.

PubMed

Watson, Shawn N; Wright, Natasha; Hermann, Petra M; Wildering, Willem C

2013-02-01

Memory failure associated with changes in neuronal circuit functions rather than cell death is a common feature of normal aging in diverse animal species. The (neuro)biological foundations of this phenomenon are not well understood although oxidative stress, particularly in the guise of lipid peroxidation, is suspected to play a key role. Using an invertebrate model system of age-associated memory impairment that supports direct correlation between behavioral deficits and changes in the underlying neural substrate, we show that inhibition of phospholipase A(2) (PLA(2)) abolishes both long-term memory (LTM) and neural defects observed in senescent subjects and subjects exposed to experimental oxidative stress. Using a combination of behavioral assessments and electrophysiological techniques, we provide evidence for a close link between lipid peroxidation, provocation of phospholipase A(2)-dependent free fatty acid release, decline of neuronal excitability, and age-related long-term memory impairments. This supports the view that these processes suspend rather than irreversibly extinguish the aging nervous system's intrinsic capacity for plasticity. Copyright © 2013 Elsevier Inc. All rights reserved.

Simulated glass transition of poly(ethylene oxide) bulk and film: a comparative study.

PubMed

Wu, Chaofu

2011-09-29

Stepwise cooling molecular dynamics (MD) simulations have been carried out on the bulk and film models for poly(ethylene oxide) (PEO) to understand glass transition of amorphous polymer films. Three types of properties--density, energy, and dynamics--are computed and plotted against the temperature for the two systems. It has been confirmed that all these properties can reveal glass transition in both PEO bulk and film systems. All the determined glass transition temperatures (T(g)'s) drop in the same order of magnitude to the experimental data available. Among various methods, the T(g)'s obtained from the density and energy data are close to each other if the same space regions are defined, which can suggest the same free volume theory, and dynamic T(g)'s obtained from mean-squared displacements (MSDs) are highest, which can suggest the kinetic theory for structural relaxation. Consistently, all these T(g)'s obtained using different methods show that the T(g)'s of PEO film are lower than those of PEO bulk. The free surface layers of polymer films dictate this offset. © 2011 American Chemical Society

Deficiency of eNOS exacerbates early-stage NAFLD pathogenesis by changing the fat distribution.

PubMed

Nozaki, Yuichi; Fujita, Koji; Wada, Koichiro; Yoneda, Masato; Shinohara, Yoshiyasu; Imajo, Kento; Ogawa, Yuji; Kessoku, Takaomi; Nakamuta, Makoto; Saito, Satoru; Masaki, Naohiko; Nagashima, Yoji; Terauchi, Yasuo; Nakajima, Atsushi

2015-12-17

Although many factors and molecules that are closely associated with non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH) have been reported, the role of endothelial nitric oxide synthase (eNOS)-derived nitric oxide (NO) in the pathogenesis of NAFLD/NASH remains unclear. We therefore investigated the role of eNOS-derived NO in NAFLD pathogenesis using systemic eNOS-knockout mice fed a high-fat diet. eNOS-knockout and wild-type mice were fed a basal diet or a high-fat diet for 12 weeks. Lipid accumulation and inflammation were evaluated in the liver, and various factors that are closely associated with NAFLD/NASH and hepatic tissue blood flow were analyzed. Lipid accumulation and inflammation were more extensive in the liver and lipid accumulation was less extensive in the visceral fat tissue in eNOS-knockout mice, compared with wild-type mice, after 12 weeks of being fed a high-fat diet. While systemic insulin resistance was comparable between the eNOS-knockout and wild-type mice fed a high-fat diet, hepatic tissue blood flow was significantly suppressed in the eNOS-knockout mice, compared with the wild-type mice, in mice fed a high-fat diet. The microsomal triglyceride transfer protein activity was down-regulated in eNOS-knockout mice, compared with wild-type mice, in mice fed a high-fat diet. A deficiency of eNOS-derived NO may exacerbate the early-stage of NASH pathogenesis by changing the fat distribution in a mouse model via the regulation of hepatic tissue blood flow.

Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock.

PubMed

Bagnoud, Alexandre; Chourey, Karuna; Hettich, Robert L; de Bruijn, Ino; Andersson, Anders F; Leupin, Olivier X; Schwyn, Bernhard; Bernier-Latmani, Rizlan

2016-10-14

The Opalinus Clay formation will host geological nuclear waste repositories in Switzerland. It is expected that gas pressure will build-up due to hydrogen production from steel corrosion, jeopardizing the integrity of the engineered barriers. In an in situ experiment located in the Mont Terri Underground Rock Laboratory, we demonstrate that hydrogen is consumed by microorganisms, fuelling a microbial community. Metagenomic binning and metaproteomic analysis of this deep subsurface community reveals a carbon cycle driven by autotrophic hydrogen oxidizers belonging to novel genera. Necromass is then processed by fermenters, followed by complete oxidation to carbon dioxide by heterotrophic sulfate-reducing bacteria, which closes the cycle. This microbial metabolic web can be integrated in the design of geological repositories to reduce pressure build-up. This study shows that Opalinus Clay harbours the potential for chemolithoautotrophic-based system, and provides a model of microbial carbon cycle in deep subsurface environments where hydrogen and sulfate are present.

Physical/chemical closed-loop water-recycling

NASA Technical Reports Server (NTRS)

Herrmann, Cal C.; Wydeven, Theodore

1991-01-01

Water needs, water sources, and means for recycling water are examined in terms appropriate to the water quality requirements of a small crew and spacecraft intended for long duration exploration missions. Inorganic, organic, and biological hazards are estimated for waste water sources. Sensitivities to these hazards for human uses are estimated. The water recycling processes considered are humidity condensation, carbon dioxide reduction, waste oxidation, distillation, reverse osmosis, pervaporation, electrodialysis, ion exchange, carbon sorption, and electrochemical oxidation. Limitations and applications of these processes are evaluated in terms of water quality objectives. Computerized simulation of some of these chemical processes is examined. Recommendations are made for development of new water recycling technology and improvement of existing technology for near term application to life support systems for humans in space. The technological developments are equally applicable to water needs on Earth, in regions where extensive water recycling is needed or where advanced water treatment is essential to meet EPA health standards.

Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock

PubMed Central

Bagnoud, Alexandre; Chourey, Karuna; Hettich, Robert L.; de Bruijn, Ino; Andersson, Anders F.; Leupin, Olivier X.; Schwyn, Bernhard; Bernier-Latmani, Rizlan

2016-01-01

The Opalinus Clay formation will host geological nuclear waste repositories in Switzerland. It is expected that gas pressure will build-up due to hydrogen production from steel corrosion, jeopardizing the integrity of the engineered barriers. In an in situ experiment located in the Mont Terri Underground Rock Laboratory, we demonstrate that hydrogen is consumed by microorganisms, fuelling a microbial community. Metagenomic binning and metaproteomic analysis of this deep subsurface community reveals a carbon cycle driven by autotrophic hydrogen oxidizers belonging to novel genera. Necromass is then processed by fermenters, followed by complete oxidation to carbon dioxide by heterotrophic sulfate-reducing bacteria, which closes the cycle. This microbial metabolic web can be integrated in the design of geological repositories to reduce pressure build-up. This study shows that Opalinus Clay harbours the potential for chemolithoautotrophic-based system, and provides a model of microbial carbon cycle in deep subsurface environments where hydrogen and sulfate are present. PMID:27739431

Redox-dependent regulation of epidermal growth factor receptor signaling.

PubMed

Heppner, David E; van der Vliet, Albert

2016-08-01

Tyrosine phosphorylation-dependent cell signaling represents a unique feature of multicellular organisms, and is important in regulation of cell differentiation and specialized cell functions. Multicellular organisms also contain a diverse family of NADPH oxidases (NOXs) that have been closely linked with tyrosine kinase-based cell signaling and regulate tyrosine phosphorylation via reversible oxidation of cysteine residues that are highly conserved within many proteins involved in this signaling pathway. An example of redox-regulated tyrosine kinase signaling involves the epidermal growth factor receptor (EGFR), a widely studied receptor system with diverse functions in normal cell biology as well as pathologies associated with oxidative stress such as cancer. The purpose of this Graphical Redox Review is to highlight recently emerged concepts with respect to NOX-dependent regulation of this important signaling pathway. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Demonstration of Electrochemical Cell Properties by a Simple, Colorful Oxidation-reduction Experiment.

ERIC Educational Resources Information Center

Hendricks, Lloyd J.; And Others

1982-01-01

Describes apparatus/methodology and provides background information for an experiment demonstrating electrochemical concepts and properties of electrochemical cells. The color of a solution close to an electrode is changed from that of the bulk solution to either of two contrasting colors depending on whether the reaction is oxidation or…

Low-Temperature CO-Oxidation Catalysts for Long-Life CO2 Lasers

NASA Technical Reports Server (NTRS)

Schryer, David R. (Editor); Hoflund, Gar B. (Editor)

1990-01-01

Low-temperature CO-oxidation catalysts are necessary for closed-cycle pulsed CO2 lasers as well as for other applications, including air purification. The papers presented in this volume discuss several such catalysts, including information on catalyst preparation, techniques for enhancing catalyst performance, laboratory and laser test results, and mechanistic considerations.

RT-MATRIX: Measuring Total Organic Carbon by Photocatalytic Oxidation of Volatile Organic Compounds

NASA Technical Reports Server (NTRS)

2008-01-01

Volatile organic compounds (VOCs) inevitably accumulate in enclosed habitats such as the International Space Station and the Crew Exploration Vehicle (CEV) as a result of human metabolism, material off-gassing, and leaking equipment. Some VOCs can negatively affect the quality of the crew's life, health, and performance; and consequently, the success of the mission. Air quality must be closely monitored to ensure a safe living and working environment. Currently, there is no reliable air quality monitoring system that meets NASA's stringent requirements for power, mass, volume, or performance. The ultimate objective of the project -- the development of a Real-Time, Miniaturized, Autonomous Total Risk Indicator System (RT.MATRIX).is to provide a portable, dual-function sensing system that simultaneously determines total organic carbon (TOC) and individual contaminants in air streams.

Reproducing Phenomenology of Peroxidation Kinetics via Model Optimization

NASA Astrophysics Data System (ADS)

Ruslanov, Anatole D.; Bashylau, Anton V.

2010-06-01

We studied mathematical modeling of lipid peroxidation using a biochemical model system of iron (II)-ascorbate-dependent lipid peroxidation of rat hepatocyte mitochondrial fractions. We found that antioxidants extracted from plants demonstrate a high intensity of peroxidation inhibition. We simplified the system of differential equations that describes the kinetics of the mathematical model to a first order equation, which can be solved analytically. Moreover, we endeavor to algorithmically and heuristically recreate the processes and construct an environment that closely resembles the corresponding natural system. Our results demonstrate that it is possible to theoretically predict both the kinetics of oxidation and the intensity of inhibition without resorting to analytical and biochemical research, which is important for cost-effective discovery and development of medical agents with antioxidant action from the medicinal plants.

Development and research program for a soil-based bioregenerative agriculture system to feed a four person crew at a Mars base

NASA Astrophysics Data System (ADS)

Silverstone, S.; Nelson, M.; Alling, A.; Allen, J.

For humans to survive during long-term missions on the Martian surface, bioregenerative life support systems including food production will decrease requirements for launch of Earth supplies, and increase mission safety. It is proposed that the development of ``modular biospheres''- closed system units that can be air-locked together and which contain soil-based bioregenerative agriculture, horticulture, with a wetland wastewater treatment system is an approach for Mars habitation scenarios. Based on previous work done in long-term life support at Biosphere 2 and other closed ecological systems, this consortium proposes a research and development program called Mars On Earth™ which will simulate a life support system designed for a four person crew. The structure will consist of /6 × 110 square meter modular agricultural units designed to produce a nutritionally adequate diet for 4 people, recycling all air, water and waste, while utilizing a soil created by the organic enrichment and modification of Mars simulant soils. Further research needs are discussed, such as determining optimal light levels for growth of the necessary range of crops, energy trade-offs for agriculture (e.g. light intensity vs. required area), capabilities of Martian soils and their need for enrichment and elimination of oxides, strategies for use of human waste products, and maintaining atmospheric balance between people, plants and soils.

The oxidation state of Hadean magmas and implications for early Earth's atmosphere.

PubMed

Trail, Dustin; Watson, E Bruce; Tailby, Nicholas D

2011-11-30

Magmatic outgassing of volatiles from Earth's interior probably played a critical part in determining the composition of the earliest atmosphere, more than 4,000 million years (Myr) ago. Given an elemental inventory of hydrogen, carbon, nitrogen, oxygen and sulphur, the identity of molecular species in gaseous volcanic emanations depends critically on the pressure (fugacity) of oxygen. Reduced melts having oxygen fugacities close to that defined by the iron-wüstite buffer would yield volatile species such as CH(4), H(2), H(2)S, NH(3) and CO, whereas melts close to the fayalite-magnetite-quartz buffer would be similar to present-day conditions and would be dominated by H(2)O, CO(2), SO(2) and N(2) (refs 1-4). Direct constraints on the oxidation state of terrestrial magmas before 3,850 Myr before present (that is, the Hadean eon) are tenuous because the rock record is sparse or absent. Samples from this earliest period of Earth's history are limited to igneous detrital zircons that pre-date the known rock record, with ages approaching ∼4,400 Myr (refs 5-8). Here we report a redox-sensitive calibration to determine the oxidation state of Hadean magmatic melts that is based on the incorporation of cerium into zircon crystals. We find that the melts have average oxygen fugacities that are consistent with an oxidation state defined by the fayalite-magnetite-quartz buffer, similar to present-day conditions. Moreover, selected Hadean zircons (having chemical characteristics consistent with crystallization specifically from mantle-derived melts) suggest oxygen fugacities similar to those of Archaean and present-day mantle-derived lavas as early as ∼4,350 Myr before present. These results suggest that outgassing of Earth's interior later than ∼200 Myr into the history of Solar System formation would not have resulted in a reducing atmosphere.

The role of geochemistry and energetics in the evolution of modern respiratory complexes from a proton-reducing ancestor.

PubMed

Schut, Gerrit J; Zadvornyy, Oleg; Wu, Chang-Hao; Peters, John W; Boyd, Eric S; Adams, Michael W W

2016-07-01

Complex I or NADH quinone oxidoreductase (NUO) is an integral component of modern day respiratory chains and has a close evolutionary relationship with energy-conserving [NiFe]-hydrogenases of anaerobic microorganisms. Specifically, in all of biology, the quinone-binding subunit of Complex I, NuoD, is most closely related to the proton-reducing, H2-evolving [NiFe]-containing catalytic subunit, MbhL, of membrane-bound hydrogenase (MBH), to the methanophenzine-reducing subunit of a methanogenic respiratory complex (FPO) and to the catalytic subunit of an archaeal respiratory complex (MBX) involved in reducing elemental sulfur (S°). These complexes also pump ions and have at least 10 homologous subunits in common. As electron donors, MBH and MBX use ferredoxin (Fd), FPO uses either Fd or cofactor F420, and NUO uses either Fd or NADH. In this review, we examine the evolutionary trajectory of these oxidoreductases from a proton-reducing ancestral respiratory complex (ARC). We hypothesize that the diversification of ARC to MBH, MBX, FPO and eventually NUO was driven by the larger energy yields associated with coupling Fd oxidation to the reduction of oxidants with increasing electrochemical potential, including protons, S° and membrane soluble organic compounds such as phenazines and quinone derivatives. Importantly, throughout Earth's history, the availability of these oxidants increased as the redox state of the atmosphere and oceans became progressively more oxidized as a result of the origin and ecological expansion of oxygenic photosynthesis. ARC-derived complexes are therefore remarkably stable respiratory systems with little diversity in core structure but whose general function appears to have co-evolved with the redox state of the biosphere. This article is part of a Special Issue entitled Respiratory Complex I, edited by Volker Zickermann and Ulrich Brandt. Copyright © 2016 Elsevier B.V. All rights reserved.

Matrix-assisted laser-induced gas-phase aggregation of C 60 oxides

NASA Astrophysics Data System (ADS)

Barrow, Mark P.; Tower, Nicole J.; Taylor ^*, , Roger; Drewello, Thomas

1998-08-01

Matrix-assisted laser desorption/ionisation of C 60 oxides, in conjunction with reflectron time-of-flight mass spectrometry, leads to an unprecedented gas-phase aggregation resulting in the formation of C 120O n- ·. products. The analysis of the product distribution obtained for oxides of varying oxygen content strongly suggests that the structures of these species are closely related to oxo-bridged isolated fullerene cages rather than to species featuring a fused giant fullerene core.

Rotenone induces oxidative stress and dopaminergic neuron damage in organotypic substantia nigra cultures.

PubMed

Testa, Claudia M; Sherer, Todd B; Greenamyre, J Timothy

2005-03-24

Rotenone, a pesticide and complex I inhibitor, causes nigrostriatal degeneration similar to Parkinson disease pathology in a chronic, systemic, in vivo rodent model [M. Alam, W.J. Schmidt, Rotenone destroys dopaminergic neurons and induces parkinsonian symptoms in rats, Behav. Brain Res. 136 (2002) 317-324; R. Betarbet, T.B. Sherer, G. MacKenzie, M. Garcia-Osuna, A.V. Panov, J.T. Greenamyre, Chronic systemic pesticide exposure reproduces features of Parkinson's disease, Nat. Neurosci. 3 (2000) 1301-1306; S.M. Fleming, C. Zhu, P.O. Fernagut, A. Mehta, C.D. DiCarlo, R.L. Seaman, M.F. Chesselet, Behavioral and immunohistochemical effects of chronic intravenous and subcutaneous infusions of varying doses of rotenone, Exp. Neurol. 187 (2004) 418-429; T.B. Sherer, J.H. Kim, R. Betarbet, J.T. Greenamyre, Subcutaneous rotenone exposure causes highly selective dopaminergic degeneration and alpha-synuclein aggregation, Exp. Neurol. 179 (2003) 9-16.]. To better investigate the role of mitochondria and complex I inhibition in chronic, progressive neurodegenerative disease, we developed methods for long-term culture of rodent postnatal midbrain organotypic slices. Chronic complex I inhibition over weeks by low dose (10-50 nM) rotenone in this system lead to dose- and time-dependent destruction of substantia nigra pars compacta neuron processes, morphologic changes, some neuronal loss, and decreased tyrosine hydroxylase (TH) protein levels. Chronic complex I inhibition also caused oxidative damage to proteins, measured by protein carbonyl levels. This oxidative damage was blocked by the antioxidant alpha-tocopherol (vitamin E). At the same time, alpha-tocopherol also blocked rotenone-induced reductions in TH protein and TH immunohistochemical changes. Thus, oxidative damage is a primary mechanism of mitochondrial toxicity in intact dopaminergic neurons. The organotypic culture system allows close study of this and other interacting mechanisms over a prolonged time period in mature dopaminergic neurons with intact processes, surrounding glia, and synaptic connections.

Welding shield for coupling heaters

DOEpatents

Menotti, James Louis

2010-03-09

Systems for coupling end portions of two elongated heater portions and methods of using such systems to treat a subsurface formation are described herein. A system may include a holding system configured to hold end portions of the two elongated heater portions so that the end portions are abutted together or located near each other; a shield for enclosing the end portions, and one or more inert gas inlets configured to provide at least one inert gas to flush the system with inert gas during welding of the end portions. The shield may be configured to inhibit oxidation during welding that joins the end portions together. The shield may include a hinged door that, when closed, is configured to at least partially isolate the interior of the shield from the atmosphere. The hinged door, when open, is configured to allow access to the interior of the shield.

Preliminary input to the space shuttle reaction control subsystem failure detection and identification software requirements (uncontrolled)

NASA Technical Reports Server (NTRS)

Bergmann, E.

1976-01-01

The current baseline method and software implementation of the space shuttle reaction control subsystem failure detection and identification (RCS FDI) system is presented. This algorithm is recommended for conclusion in the redundancy management (RM) module of the space shuttle guidance, navigation, and control system. Supporting software is presented, and recommended for inclusion in the system management (SM) and display and control (D&C) systems. RCS FDI uses data from sensors in the jets, in the manifold isolation valves, and in the RCS fuel and oxidizer storage tanks. A list of jet failures and fuel imbalance warnings is generated for use by the jet selection algorithm of the on-orbit and entry flight control systems, and to inform the crew and ground controllers of RCS failure status. Manifold isolation valve close commands are generated in the event of failed on or leaking jets to prevent loss of large quantities of RCS fuel.

Accuracy and Precision in Measurements of Biomass Oxidative Ratio and Carbon Oxidation State

NASA Astrophysics Data System (ADS)

Gallagher, M. E.; Masiello, C. A.; Randerson, J. T.; Chadwick, O. A.; Robertson, G. P.

2007-12-01

Ecosystem oxidative ratio (OR) is a critical parameter in the apportionment of anthropogenic CO2 between the terrestrial biosphere and ocean carbon reservoirs. OR is the ratio of O2 to CO2 in gas exchange fluxes between the terrestrial biosphere and atmosphere. Ecosystem OR is linearly related to biomass carbon oxidation state (Cox), a fundamental property of the earth system describing the bonding environment of carbon in molecules. Cox can range from -4 to +4 (CH4 to CO2). Variations in both Cox and OR are driven by photosynthesis, respiration, and decomposition. We are developing several techniques to accurately measure variations in ecosystem Cox and OR; these include elemental analysis, bomb calorimetry, and 13C nuclear magnetic resonance spectroscopy. A previous study, comparing the accuracy and precision of elemental analysis versus bomb calorimetry for pure chemicals, showed that elemental analysis-based measurements are more accurate, while calorimetry- based measurements yield more precise data. However, the limited biochemical range of natural samples makes it possible that calorimetry may ultimately prove most accurate, as well as most cost-effective. Here we examine more closely the accuracy of Cox and OR values generated by calorimetry on a large set of natural biomass samples collected from the Kellogg Biological Station-Long Term Ecological Research (KBS-LTER) site in Michigan.

Reduction Dynamics of Doped Ceria, Nickel Oxide, and Cermet Composites Probed Using In Situ Raman Spectroscopy

PubMed Central

Shearing, Paul R.; Brightman, Edward; Brett, Dan J. L.; Brandon, Nigel P.; Cohen, Lesley F.

2016-01-01

The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single‐step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance. PMID:27595058

Reduction Dynamics of Doped Ceria, Nickel Oxide, and Cermet Composites Probed Using In Situ Raman Spectroscopy.

PubMed

Maher, Robert C; Shearing, Paul R; Brightman, Edward; Brett, Dan J L; Brandon, Nigel P; Cohen, Lesley F

2016-01-01

The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single-step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance.

Experimental bandstructure of the 5 d transition metal oxide IrO2

NASA Astrophysics Data System (ADS)

Kawasaki, Jason; Nie, Yuefeng; Uchida, Masaki; Schlom, Darrell; Shen, Kyle

2015-03-01

In the 5 d iridium oxides the close energy scales of spin-orbit coupling and electron-electron correlations lead to emergent quantum phenomena. Much research has focused on the ternary iridium oxides, e.g. the Ruddlesden-Poppers An + 1BnO3 n + 1 , which exhibit behavior from metal to antiferromagnetic insulator ground states, share common features with the cuprates, and may host a number of topological phases. The binary rutile IrO2 is another important 5 d oxide, which has technological importance for spintronics due to its large spin Hall effect and also applications in catalysis. IrO2 is expected to share similar physics as its perovskite-based cousins; however, due to bond-length distortions of the IrO6 octahedra in the rutile structure, the extent of similarities remains an open question. Here we use angle-resolved photoemission spectroscopy to perform momentum-resolved measurements of the electronic structure of IrO2 . IrO2 thin films were grown by molecular beam epitaxy on TiO2 (110) substrates using an Ir e-beam source and distilled ozone. Films were subsequently transferred through ultrahigh vacuum to a connected ARPES system. Combined with first-principles calculations we explore the interplay of spin-orbit coupling and correlations in IrO2 .

Denitrification: an important pathway for nitrous oxide production in tropical mangrove sediments (Goa, India).

PubMed

Fernandes, Sheryl Oliveira; Bharathi, P A Loka; Bonin, Patricia C; Michotey, Valérie D

2010-01-01

Net nitrous oxide production and denitrification activity were measured in two mangrove ecosystems of Goa, India. The relatively pristine site Tuvem was compared to Divar, which is prone to high nutrient input. Stratified sampling at 2-cm intervals within the 0- to 10-cm depth range showed that N2O production at both the locations decreased with depth. Elevated denitrification activity at Divar resulted in maximum production of up to 1.95 nmol N2O-N g(-1) h(-1) at 2 to 4 cm, which was three times higher than at Tuvem. Detailed investigations to understand the major pathway contributing to N2O production performed at Tuvem showed that incomplete denitrification was responsible for up to 43 to 93% of N2O production. Nitrous oxide production rates closely correlated to nitrite concentration (n = 15; r = -0.47; p < 0.05) and denitrifier abundance (r = 0.55; p < 0.05), suggesting that nitrite utilization by microbial activity leads to N2O production. Nitrous oxide production through nitrification was below detection, affirming that denitrification is the major pathway responsible for production of the greenhouse gas. Net N2O production in these mangrove systems are comparatively higher than those reported from other natural estuarine sediments and therefore warrant mitigation measures.

Water-Vapor-Mediated Close-Spaced Vapor Transport Growth of Epitaxial Gallium Indium Phosphide Films on Gallium Arsenide Substrates

DOE PAGES

Greenaway, Ann L.; Bachman, Benjamin F.; Boucher, Jason W.; ...

2018-01-12

Ga 1–xIn xP is a technologically important III–V ternary semiconductor widely utilized in commercial and record-efficiency solar cells. We report the growth of Ga 1–xIn xP by water-vapor-mediated close-spaced vapor transport. Because growth of III–V semiconductors in this system is controlled by diffusion of metal oxide species, we find that congruent transport from the mixed powder source requires complete annealing to form a single alloy phase. Growth from a fully alloyed source at water vapor concentrations of ~7000 ppm in H 2 at 850 °C affords smooth films with electron mobility of 1070 cm 2 V –1 s –1 andmore » peak internal quantum efficiency of ~90% for carrier collection in a nonaqueous photoelectrochemical test cell.« less

Water-Vapor-Mediated Close-Spaced Vapor Transport Growth of Epitaxial Gallium Indium Phosphide Films on Gallium Arsenide Substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenaway, Ann L.; Bachman, Benjamin F.; Boucher, Jason W.

Ga 1–xIn xP is a technologically important III–V ternary semiconductor widely utilized in commercial and record-efficiency solar cells. We report the growth of Ga 1–xIn xP by water-vapor-mediated close-spaced vapor transport. Because growth of III–V semiconductors in this system is controlled by diffusion of metal oxide species, we find that congruent transport from the mixed powder source requires complete annealing to form a single alloy phase. Growth from a fully alloyed source at water vapor concentrations of ~7000 ppm in H 2 at 850 °C affords smooth films with electron mobility of 1070 cm 2 V –1 s –1 andmore » peak internal quantum efficiency of ~90% for carrier collection in a nonaqueous photoelectrochemical test cell.« less

Responses of motor and sensory neurons of rodents to spaceflight

NASA Technical Reports Server (NTRS)

Ishihara, A.; Ohira, Y.; Roy, R. R.; Nagaoka, S.; Sekiguchi, C.; Edgerton, V. R.

2000-01-01

Spinal motoneurons innervating skeletal muscles comprised predominantly of high oxidative fibers, i.e. slow oxidative and fast oxidative glycolytic, have higher oxidative enzyme activities than motoneurons innervating skeletal muscles comprised primarily of low oxidative fibers, i.e. fast glycolytic. These findings suggest that there is a close relationship between the oxidative phosphorylation capacity of a motoneuron and of the muscle fibers that it innervates. Since some skeletal muscles become faster and less oxidative after 4-14 days of spaceflight, it might be expected that oxidative enzyme activities in some motoneurons also may decrease after spaceflight. In addition, there is significant muscular atrophy after even short spaceflights and, therefore, it may be expected that some motoneurons associated with these muscles also would atrophy. In the present paper, we examine the issue of whether spaceflight induces changes in the oxidative enzyme activity and/or size of spinal motoneurons.

Distribution, activity and function of short-chain alkane degrading phylotypes in hydrothermal vent sediments

NASA Astrophysics Data System (ADS)

Adams, M. M.; Joye, S. B.; Hoarfrost, A.; Girguis, P. R.

2012-12-01

Global geochemical analyses suggest that C2-C4 short chain alkanes are a common component of the utilizable carbon pool in deep-sea sediments worldwide and have been found in diverse ecosystems. From a thermodynamic standpoint, the anaerobic microbial oxidation of these aliphatic hydrocarbons is more energetically yielding than the anaerobic oxidation of methane (AOM). Therefore, the preferential degradation of these hydrocarbons may compete with AOM for the use of oxidants such as sulfate, or other potential oxidants. Such processes could influence the fate of methane in the deep-sea. Sulfate-reducing bacteria (SRB) from hydrocarbon seep sediments of the Gulf of Mexico and Guaymas Basin have previously been enriched that anaerobically oxidize short chain alkanes to generate CO2 with the preferential utilization of 12C-enriched alkanes (Kniemeyer et al. 2007). Different temperature regimens along with multiple substrates were tested and a pure culture (deemed BuS5) was isolated from mesophilic enrichments with propane or n-butane as the sole carbon source. Through comparative sequence analysis, strain BuS5 was determined to cluster with the metabolically diverse Desulfosarcina / Desulfococcus cluster, which also contains the SRB found in consortia with anaerobic, methane-oxidizing archaea in seep sediments. Enrichments from a terrestrial, low temperature sulfidic hydrocarbon seep also corroborated that propane degradation occurred with most bacterial phylotypes surveyed belonging to the Deltaproteobacteria, particularly Desulfobacteraceae (Savage et al. 2011). To date, no microbes capable of ethane oxidation or anaerobic C2-C4 alkane oxidation at thermophilic temperature have been isolated. The sediment-covered, hydrothermal vent systems found at Middle Valley (Juan de Fuca Ridge, eastern Pacific Ocean) are a prime environment for investigating mesophilic to thermophilic anaerobic oxidation of short-chain alkanes, given the elevated temperatures and dissolved hydrocarbon species characteristic of these metalliferous sediments. These systems are also characterized by sharp physicochemical gradients that have been shown to have a pronounced effect on microbial ecology and activity. Sediments were collected from a Middle Valley field with relatively high concentrations of short-chain alkanes and incubated in anaerobic batch reactors with each individual alkane (C1, C2, C3 and C4, respectively) at a range of temperatures (25, 55 and 75 °C) to mimic environmental physico-chemical conditions in a closed system. Stable carbon isotope ratios and radiotracer incubations provide clear evidence for C2-C4 alkane oxidation in the sediments over time. Upon identifying sediments with anaerobic alkane oxidation activity, microbial communities were screened via 16S rRNA pyrosequencing, and key phylotypes were then quantified using both molecular and microscopic methods. There were shifts in overall community composition and putative alkane-oxidizing phylotypes after the incubation period with the alkane substrates. These are the first evidence to date indicating that anaerobic C2-C4 alkane oxidation occurs across a broad range of temperatures in metalliferous sediments.

The legacy of biosphere 2 for the study of biospherics and closed ecological systems

NASA Astrophysics Data System (ADS)

Allen, J. P.; Nelson, M.; Alling, A.

The unprecedented challenges of creating Biosphere 2, the world's first laboratory for biospherics, the study of global ecology and long-term closed ecological system dynamics, led to breakthrough developments in many fields, and a deeper understanding of the opportunities and difficulties of material closure. This paper will review accomplishments and challenges, citing some of the key research findings and publications that have resulted from the experiments in Biosphere 2. Engineering accomplishments included development of a technique for variable volume to deal with pressure differences between the facility and outside environment, developing methods of atmospheric leak detection and sealing, while achieving new standards of closure, with an annual atmospheric leakrate of less than 10%, or less than 300 ppm per day. This degree of closure permitted detailed tracking of carbon dioxide, oxygen, and trice gases such as nitrous oxide and ethylene over the seasonal variability of two years. Full closure also necessitated developing new approaches and technologies for complete air, water, and wastewater recycle and reuse within the facility. The development of a soil-based highly productive agricultural system was a first in closed ecological systems, and much was learned about managing a wide variety of crops using non-chemical means of pest and disease control. Closed ecological systems have different temporal biogeochemical cycling and ranges of atmospheric components because of their smaller reservoirs of air, water and soil, and higher concentration of biomass, and Biosphere 2 provided detailed examination and modeling of these accelerated cycles over a period of closure which measured in years. Medical research inside Biosphere 2 included the effects on humans of lowered oxygen: the discovery that human productivity can be maintained with good health with lowered atmospheric oxygen levels could lead to major economies on the design of space stations and planetary/lunar settlements. The improved health resulting from the calorie-restricted but nutrient dense Biosphere 2 diet was the first such scientifically controlled experiment with humans. The success of Biosphere 2 in creating a diversity of terrestrial and marine environments, from rainforest to coral reef, allowed detailed studies with comprehensive measurements such that the dynamics of these complex biomic systems are now better understood. The coral reef ecosystem, the largest artificial reef ever built, catalyzed methods of study now being applied to planetary coral reef systems. Restoration ecology advanced through the creation and study of the dynamics of adaptation and self-organization of the biomes in Biosphere 2. The international interest that Biosphere 2 generated has given new impetus to the public recognition of the sciences of biospheres (biospherics), biomes and closed ecological life systems. The facility, although no longer a materially-closed ecological system, is being used as an educational facility by Columbia University as an introduction to the study of the biosphere and complex system ecology and for carbon dioxide impacts utilizing the complex ecosystems created in Biosphere '.The many lessons learned from Biosphere 2 are being used by its key team of creators in their design and operation of a laboratory-sized closed ecological system, the Laboratory Biosphere, in operation as of March 2002, and for the design of a Mars on Earth ™ prototype life support system for manned missions to Mars and Mars surface habitats. Biosphere 2 is an important foundation for future advances in biospherics and closed ecological system research.

Assessing the Cost of Helping: The Roles of Body Condition and Oxidative Balance in the Seychelles Warbler (Acrocephalus sechellensis)

PubMed Central

van de Crommenacker, Janske; Komdeur, Jan; Richardson, David S.

2011-01-01

In cooperatively breeding species, helping close relatives may provide important fitness benefits. However, helping can be energetically expensive and may result in increased generation of reactive oxygen species. Consequently, an oxidant/antioxidant imbalance can lead to higher oxidative stress susceptibility. Given the potential costs of helping, it may be that only individuals with a sufficiently good body condition and/or stable oxidative balance can afford to help. Knowledge about relationships between social status and oxidative balance in cooperatively breeding systems is still limited. Studying these relationships is important for understanding the costs of helping and physiological pressures of reproduction. Here we evaluate the relationship between helping behaviour, body condition and oxidative balance in a wild population of the cooperatively breeding Seychelles warbler (Acrocephalus sechellensis). In this species, some subordinate individuals help dominant birds with the rearing of young, while others refrain from any assistance. We assessed body condition and oxidative parameters of birds of different social status caught during different breeding stages. We found that, prior to breeding, female subordinates that did not subsequently help (non-helpers) had significantly lower body condition and higher ROMs (reactive oxygen metabolites) than helpers and dominants. During the later stages of breeding, body condition was low in dominants and helpers, but high in non-helpers. Differences in oxidative balance between individuals of different social status were found only during nest care: Dominant males occupied with guarding behaviours tended to have relatively high oxidative stress susceptibility. Furthermore, dominant and helper females showed elevated antioxidant capacity (measured as OXY) in the weeks just prior to egg-laying, possibly representing a change in their reproductive physiology. The results imply that an individuals' oxidative balance may be influenced by factors related to reproduction, which can differ with sex and—within cooperative breeding systems—social status. PMID:22046283

First-Principles Mechanistic Analysis of Dimethyl Ether Electro-Oxidation on Monometallic Single-Crystal Surfaces

DOE PAGES

Herron, Jeffrey A.; Ferrin, Peter; Mavrikakis, Manos

2014-08-27

Dimethyl ether is an attractive alternative to petroleum fuels due to its physical properties, comparable energy density to methanol and ethanol, and minimal deleterious environmental/toxicological effects. For direct fuel cells, it has a number of advantages over other prominent fuels, including easier storage with respect to hydrogen, lower toxicity and crossover when compared to methanol, and more facile complete oxidation as compared to ethanol (which includes a relatively difficult to break C–C bond). However, the dimethyl ether electro-oxidation reaction is poorly understood, hindering the development of improved electrocatalysts. Using periodic, self-consistent (PW91-GGA) density functional theory calculations, we evaluate the thermochemistrymore » of dimethyl ether (DME) electro-oxidation, at the elementary step level, on 12 model, closed-packed facets of pure transition metals: Au, Ag, Cu, Pt, Pd, Ni, Ir, Rh, Co, Os, Ru, and Re. From the calculated thermochemistry, we determine the most probable reaction paths on each of these surfaces, focusing on Pt as a model system. Our results predict two key electro-oxidation peaks. At lower potentials, there is a peak corresponding to partial oxidation of DME to CO (and other surface poisoning species) or complete oxidation to CO 2 via formic acid as a key intermediate. A second, higher-potential peak is due to complete oxidation of adsorbed CO (and other surface poisoning species) to CO 2. Assuming the catalysts remain in their metallic state during the DME electro-oxidation process, our results suggest that the onset potential of the surfaces increases in the order Cu < Ni < Os < Rh < Ir < Co < Ru < Pt < Ag < Pd < Re < Au. Using our results, we construct a theoretical phase diagram showing predicted catalyst activity based on two key reactivity descriptors, the free energies of adsorbed CO and OH. Here, we compare all results to methanol electro-oxidation to understand key mechanistic differences and their impacts on optimal catalyst design for direct DME fuel cells.« less

Control of arsenic mobilization in paddy soils by manganese and iron oxides.

PubMed

Xu, Xiaowei; Chen, Chuan; Wang, Peng; Kretzschmar, Ruben; Zhao, Fang-Jie

2017-12-01

Reductive mobilization of arsenic (As) in paddy soils under flooded conditions is an important reason for the relatively high accumulation of As in rice, posing a risk to food safety and human health. The extent of As mobilization varies widely among paddy soils, but the reasons are not well understood. In this study, we investigated As mobilization in six As-contaminated paddy soils (total As ranging from 73 to 122 mg kg -1 ) in flooded incubation and pot experiments. Arsenic speciation in the solution and solid phases were determined. The magnitude of As mobilization into the porewater varied by > 100 times among the six soils. Porewater As concentration correlated closely with the concentration of oxalate-extractable As, suggesting that As associated with amorphous iron (oxyhydr)oxides represents the potentially mobilizable pool of As under flooded conditions. Soil containing a high level of manganese oxides showed the lowest As mobilization, likely because Mn oxides retard As mobilization by slowing down the drop of redox potential upon soil flooding and maintaining a higher arsenate to arsenite ratio in the solid and solution phases. Additions of a synthetic Mn oxide (hausmannite) to two paddy soils increased arsenite oxidation, decreased As mobilization into the porewater and decreased As concentrations in rice grain and straw. Consistent with previous studies using simplified model systems or pure mineral phases, the present study shows that Mn oxides and amorphous Fe (oxyhydr)oxides are important factors controlling reductive As mobilization in As-contaminated paddy soils. In addition, this study also suggests a potential mitigation strategy using exogenous Mn oxides to decrease As uptake by rice in paddy soils containing low levels of indigenous Mn oxides, although further work is needed to verify its efficacy and possible secondary effects under field conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ultralow-power complementary metal-oxide-semiconductor inverters constructed on Schottky barrier modified nanowire metal-oxide-semiconductor field-effect-transistors.

PubMed

Ma, R M; Peng, R M; Wen, X N; Dai, L; Liu, C; Sun, T; Xu, W J; Qin, G G

2010-10-01

We show that the threshold voltages of both n- and p-channel metal-oxide-semiconductor field-effect-transistors (MOSFETs) can be lowered to close to zero by adding extra Schottky contacts on top of nanowires (NWs). Novel complementary metal-oxide-semiconductor (CMOS) inverters are constructed on these Schottky barrier modified n- and p-channel NW MOSFETs. Based on the high performances of the modified n- and p-channel MOSFETs, especially the low threshold voltages, the as-fabricated CMOS inverters have low operating voltage, high voltage gain, and ultra-low static power dissipation.

Biotic Interactions in Microbial Communities as Modulators of Biogeochemical Processes: Methanotrophy as a Model System

PubMed Central

Ho, Adrian; Angel, Roey; Veraart, Annelies J.; Daebeler, Anne; Jia, Zhongjun; Kim, Sang Yoon; Kerckhof, Frederiek-Maarten; Boon, Nico; Bodelier, Paul L. E.

2016-01-01

Microbial interaction is an integral component of microbial ecology studies, yet the role, extent, and relevance of microbial interaction in community functioning remains unclear, particularly in the context of global biogeochemical cycles. While many studies have shed light on the physico-chemical cues affecting specific processes, (micro)biotic controls and interactions potentially steering microbial communities leading to altered functioning are less known. Yet, recent accumulating evidence suggests that the concerted actions of a community can be significantly different from the combined effects of individual microorganisms, giving rise to emergent properties. Here, we exemplify the importance of microbial interaction for ecosystem processes by analysis of a reasonably well-understood microbial guild, namely, aerobic methane-oxidizing bacteria (MOB). We reviewed the literature which provided compelling evidence for the relevance of microbial interaction in modulating methane oxidation. Support for microbial associations within methane-fed communities is sought by a re-analysis of literature data derived from stable isotope probing studies of various complex environmental settings. Putative positive interactions between active MOB and other microbes were assessed by a correlation network-based analysis with datasets covering diverse environments where closely interacting members of a consortium can potentially alter the methane oxidation activity. Although, methanotrophy is used as a model system, the fundamentals of our postulations may be applicable to other microbial guilds mediating other biogeochemical processes. PMID:27602021

Vaporization chemistry of hypo-stoichiometric (U,Pu)O 2

NASA Astrophysics Data System (ADS)

Viswanathan, R.; Krishnaiah, M. V.

2001-04-01

Calculations were performed on hypo-stoichiometric uranium plutonium di-oxide to examine its vaporization behavior as a function of O/ M ( M= U+ Pu) ratio and plutonium content. The phase U (1- y) Pu yO z was treated as an ideal solid solution of (1- y)UO 2+ yPuO (2- x) such that x=(2- z)/ y. Oxygen potentials for different desired values of y, z, and temperature were used as the primary input to calculate the corresponding partial pressures of various O-, U-, and Pu-bearing gaseous species. Relevant thermodynamic data for the solid phases UO 2 and PuO (2- x) , and the gaseous species were taken from the literature. Total vapor pressure varies with O/M and goes through a minimum. This minimum does not indicate a congruently vaporizing composition. Vaporization behavior of this system can at best be quasi-congruent. Two quasi-congruently vaporizing compositions (QCVCs) exist, representing the equalities (O/M) vapor=(O/M) mixed-oxide and (U/Pu) vapor=(U/Pu) mixed-oxide, respectively. The (O/M) corresponding to QCVC1 is lower than that corresponding to QCVC2, but very close to the value where vapor pressure minimum occurs. The O/M values of both QCVCs increase with decrease in plutonium content. The vaporization chemistry of this system, on continuous vaporization under dynamic condition, is discussed.

Polymeric micellar pH-sensitive drug delivery system for doxorubicin.

PubMed

Hrubý, Martin; Konák, Cestmír; Ulbrich, Karel

2005-03-02

A novel polymeric micellar pH-sensitive system for delivery of doxorubicin (DOX) is described. Polymeric micelles were prepared by self-assembly of amphiphilic diblock copolymers in aqueous solutions. The copolymers consist of a biocompatible hydrophilic poly(ethylene oxide) (PEO) block and a hydrophobic block containing covalently bound anthracycline antibiotic DOX. The starting block copolymers poly(ethylene oxide)-block-poly(allyl glycidyl ether) (PEO-PAGE) with a very narrow molecular weight distribution (Mw/Mn ca. 1.05) were prepared by anionic ring opening polymerization using sodium salt of poly(ethylene oxide) monomethyl ether as macroinitiator and allyl glycidyl ether as functional monomer. The copolymers were covalently modified via reactive double bonds by the addition of methyl sulfanylacetate. The resulting ester subsequently reacted with hydrazine hydrate yielding polymer hydrazide. The hydrazide was coupled with DOX yielding pH-sensitive hydrazone bonds between the drug and carrier. The resulting conjugate containing ca. 3 wt.% DOX forms micelles with Rh(a)=104 nm in phosphate-buffered saline. After incubation in buffers at 37 degrees C DOX was released faster at pH 5.0 (close to pH in endosomes; 43% DOX released within 24 h) than at pH 7.4 (pH of blood plasma; 16% DOX released within 24 h). Cleavage of hydrazone bonds between DOX and carrier continues even after plateau in the DOX release from micelles incubated in aqueous solutions is reached.

Difference in oxidative stress tolerance between rice cultivars estimated with chlorophyll fluorescence analysis.

PubMed

Kasajima, Ichiro

2017-04-26

Oxidative stress is considered to be involved in growth retardation of plants when they are exposed to a variety of biotic and abiotic stresses. Despite its potential importance in improving crop production, comparative studies on oxidative stress tolerance between rice (Oryza sativa L.) cultivars are limited. This work describes the difference in term of oxidative stress tolerance between 72 rice cultivars. 72 rice cultivars grown under naturally lit greenhouse were used in this study. Excised leaf discs were subjected to a low concentration of methyl viologen (paraquat), a chemical reagent known to generate reactive oxygen species in chloroplast. Chlorophyll fluorescence analysis using a two-dimensional fluorescence meter, ion leakage analysis as well as the measurement of chlorophyll contents were used to evaluate the oxidative stress tolerance of leaf discs. Furthermore, fluorescence intensities were finely analyzed based on new fluorescence theories that we have optimized. Treatment of leaf discs with methyl viologen caused differential decrease of maximum quantum yield of photosystem II (Fv/Fm) between cultivars. Decrease of Fv/Fm was also closely correlated with increase of ion leakage and decrease of chlorophyll a/b ratio. Fv/Fm was factorized into photochemical and non-photochemical parameters to classify rice cultivars into sensitive and tolerant ones. Among the 72 compared rice cultivars, the traditional cultivar Co13 was identified as the most tolerant to oxidative stress. Koshihikari, a dominant modern Japonica cultivar in Japan as well as IR58, one of the modern Indica breeding lines exhibited a strong tolerance to oxidative stress. Close correlation between Fv/Fm and chlorophyll a/b ratio provides a simple method to estimate oxidative stress tolerance, without measurement of chlorophyll fluorescence with special equipment. The fact that modern cultivars, especially major cultivars possessed tolerance to oxidative stress suggests that oxidative stress tolerance is one of the agricultural traits prerequisite for improvement of modern rice cultivars. Data presented in this study would enable breeding of rice cultivars having strong tolerance to oxidative stress.

Fuel cell tubes and method of making same

DOEpatents

Borglum, Brian P.

1999-11-30

A method of manufacturing porous ceramic tubes for fuel cells with improved properties and higher manufacturing yield is disclosed. The method involves extruding a closed end fuel cell tube, such as an air electrode of a solid oxide fuel cell, in which the closed end also functions as the sintering support. The resultant fuel cell tube has a superior porosity distribution which allows improved diffusion of oxygen at the closed end of the tube during operation of the fuel cell. Because this region has the highest current density, performance enhancement and improved reliability of the fuel cell tube result. Furthermore, the higher manufacturing yield associated with the present method decreases the overall fuel cell cost. A method of manufacturing porous ceramic tubes for fuel cells with improved properties and higher manufacturing yield is disclosed. The method involves extruding a closed end fuel cell tube, such as an air electrode of a solid oxide fuel cell, in which the closed end also functions as the sintering support. The resultant fuel cell tube has a superior porosity distribution which allows improved diffusion of oxygen at the closed end of the tube during operation of the fuel cell. Because this region has the highest current density, performance enhancement and improved reliability of the fuel cell tube result. Furthermore, the higher manufacturing yield associated with the present method decreases the overall fuel cell cost.

Ambient-temperature co-oxidation catalysts

NASA Technical Reports Server (NTRS)

Upchurch, Billy T.; Schryer, David R.; Brown, Kenneth G.; Kielin, Erik J.

1991-01-01

Oxidation catalysts which operate at ambient temperature were developed for the recombination of carbon monoxide (CO) and oxygen (O2) dissociation products which are formed during carbon dioxide (CO2) laser operation. Recombination of these products to regenerate CO2 allows continuous operation of CO2 lasers in a closed cycle mode. Development of these catalyst materials provides enabling technology for the operation of such lasers from space platforms or in ground based facilities without constant gas consumption required for continuous open cycle operation. Such catalysts also have other applications in various areas outside the laser community for removal of CO from other closed environments such as indoor air and as an ambient temperature catalytic converter for control of auto emissions.

Reactive iron in marine sediments

NASA Technical Reports Server (NTRS)

Canfield, Donald E.

1989-01-01

The influence of reactive iron oxides on sediment pore-water chemistry is considered in detail. A carefully calibrated extraction scheme is used to determine the depth distributions of reactive iron phases at two very different localities: the relatively iron-rich Mississippi Delta and the relatively iron-poor FOAM site in Long Island Sound. Closed system incubations are used to characterize the rates of reaction between sulfide and both naturally occurring and pure iron mineral phases. Rates of iron liberation to pore solution are measured in the presence and absence of sulfate reduction, and the origin of dissolved iron in organic-rich sediments is speculated upon.

Selective cleavage of the C(α)-C(β) linkage in lignin model compounds via Baeyer-Villiger oxidation.

PubMed

Patil, Nikhil D; Yao, Soledad G; Meier, Mark S; Mobley, Justin K; Crocker, Mark

2015-03-21

Lignin is an amorphous aromatic polymer derived from plants and is a potential source of fuels and bulk chemicals. Herein, we present a survey of reagents for selective stepwise oxidation of lignin model compounds. Specifically, we have targeted the oxidative cleavage of Cα-Cβ bonds as a means to depolymerize lignin and obtain useful aromatic compounds. In this work, we prepared several lignin model compounds that possess structures, characteristic reactivity, and linkages closely related to the parent lignin polymer. We observed that selective oxidation of benzylic hydroxyl groups, followed by Baeyer-Villiger oxidation of the resulting ketones, successfully cleaves the Cα-Cβ linkage in these model compounds.

The Legacy of Biosphere 2 for Biospherics and Closed Ecological System Research

NASA Astrophysics Data System (ADS)

Allen, J.; Alling, A.; Nelson, M.

The unprecedented challenges of creating Biosphere 2, the world's first laboratory for biospherics, the study of global ecology and long-term closed ecological system dynamics led to breakthrough developments in many fields, and a deeper understanding of the opportunities and difficulties of material closure. This paper will review these accomplishments and challenges, citing some of the key research accomplishments and publications which have resulted from the experiments in Biosphere 2. Engineering accomplishments included development of a technique for variable volume to deal with pressure differences between the facility and outside environment, developing methods of leak detection and sealing, and achieving new standards of closure, with an annual atmospheric leakrate of less than 10%, or less than 300 ppm per day. This degree of closure permitted detailed tracking of carbon dioxide, oxygen, and trace gases such as nitrous oxide and ethylene over the seasonal variability of two years. Full closure also necessitated developing new approaches and technologies for complete air, water, and wastewater recycle and reuse within the facility. The development of a soil-based highly productive agricultural system was a first in closed ecological systems, and much was learned about managing a wide variety of crops using non-chemical means of pest and disease control. Closed ecological systems have different temporal b ogeochemical cycling and ranges ofi atmospheric components because of their smaller reservoirs of air, water and soil, and higher concentration of biomass, and Biosphere 2 provided detailed examination and modeling of these accelerated cycles over a period of closure which measured in years. Medical research inside Biosphere 2 included the effects on humans of lowered oxygen: the discovery that human productivity can be maintained down to 15% oxygen could lead to major economies on the design of space stations and planetary/lunar settlements. The improved health resulting from the calorie-restricted but nutrient dense Biosphere 2 diet was the first such scientifically-controlled experiment with humans. The success of Biosphere in creating a diversity of terrestrial and marine environments, from rainforest to coral reef, allowed detailed studies with comprehensive measurements such that the dynamics of these complex biomic systems can be better understood. The coral reef ecosystem, the largest artificial reef ever built, catalyzed methods of study now being applied to planetary coral reef systems. Restoration ecology can learn much from the creation and dynamics of adaptation of the biomes in Biosphere 2. The international interest that Biosphere 2 generated has given new impetus to the public recognition of the sciences of biospheres, biospherics, biomes and closed ecological life systems. The facility is still being used as an educational facility by Columbia University as an introduction to the study of the biosphere and complex system ecology. The many lessons learned from Biosphere 2, from its successes, surprises and challenges, is being used by its key team of creators as the foundations for their design of a laboratory-sized closed ecological system and Mars on Earth prototype life support system for Mars exploration and can be an important foundation for future advances in biospherics and closed ecological system research.

Experimental study on filtration and continuous regeneration of a particulate filter system for heavy-duty diesel engines.

PubMed

Tang, Tao; Zhang, Jun; Cao, Dongxiao; Shuai, Shijin; Zhao, Yanguang

2014-12-01

This study investigated the filtration and continuous regeneration of a particulate filter system on an engine test bench, consisting of a diesel oxidation catalyst (DOC) and a catalyzed diesel particulate filter (CDPF). Both the DOC and the CDPF led to a high conversion of NO to NO2 for continuous regeneration. The filtration efficiency on solid particle number (SPN) was close to 100%. The post-CDPF particles were mainly in accumulation mode. The downstream SPN was sensitively influenced by the variation of the soot loading. This phenomenon provides a method for determining the balance point temperature by measuring the trend of SPN concentration. Copyright © 2014. Published by Elsevier B.V.

LaRC-developed catalysts for CO2 lasers

NASA Technical Reports Server (NTRS)

Upchurch, Billy T.; Kielin, Erik J.; Miller, Irvin M.

1990-01-01

Pulsed CO2 lasers have many remote sensing applications from space, airborne, and ground platforms. The NASA Laser Atmospheric Wind Sounder (LAWS) system will be designed to measure wind velocities from polar earth orbit for a period of up to three years. Accordingly, this and other applications require a closed-cycle pulsed CO2 laser which necessitates the use of an efficient CO-O2 recombination catalyst for these dissociation products which otherwise would degrade the laser operation. The required catalyst must not only operate at low temperatures but also must operate efficiently for long time periods. The research effort at NASA LaRC has centered around development and testing of CO oxidation catalysts for closed-cycle, pulsed, common and rare-isotope CO2 lasers. Researchers examined available commercial catalysts both in a laser and under simulated closed-cycle laser conditions with efforts aimed toward a thorough understanding of the fundamental catalytic reaction. These data were used to design and synthesize new catalyst compositions to better meet the catalyst requirements for closed-cycle pulsed CO2 lasers. Syntheses and test results for catalysts developed at Langley Research Center which have significantly better long-term decay characteristics than previously available catalysts and at the same time operate quite well under lower temperature conditions are discussed.

Ultrafast electron and energy transfer in dye-sensitized iron oxide and oxyhydroxide nanoparticles.

PubMed

Gilbert, Benjamin; Katz, Jordan E; Huse, Nils; Zhang, Xiaoyi; Frandsen, Cathrine; Falcone, Roger W; Waychunas, Glenn A

2013-10-28

An emerging area in chemical science is the study of solid-phase redox reactions using ultrafast time-resolved spectroscopy. We have used molecules of the photoactive dye 2',7'-dichlorofluorescein (DCF) anchored to the surface of iron(III) oxide nanoparticles to create iron(II) surface atoms via photo-initiated interfacial electron transfer. This approach enables time-resolved study of the fate and mobility of electrons within the solid phase. However, complete analysis of the ultrafast processes following dye photoexcitation of the sensitized iron(III) oxide nanoparticles has not been reported. We addressed this topic by performing femtosecond transient absorption (TA) measurements of aqueous suspensions of uncoated and DCF-sensitized iron oxide and oxyhydroxide nanoparticles, and an aqueous iron(III)-dye complex. Following light absorption, excited state relaxation times of the dye of 115-310 fs were found for all samples. Comparison between TA dynamics on uncoated and dye-sensitized hematite nanoparticles revealed the dye de-excitation pathway to consist of a competition between electron and energy transfer to the nanoparticles. We analyzed the TA data for hematite nanoparticles using a four-state model of the dye-sensitized system, finding electron and energy transfer to occur on the same ultrafast timescale. The interfacial electron transfer rates for iron oxides are very close to those previously reported for DCF-sensitized titanium dioxide (for which dye-oxide energy transfer is energetically forbidden) even though the acceptor states are different. Comparison of the alignment of the excited states of the dye and the unoccupied states of these oxides showed that the dye injects into acceptor states of different symmetry (Ti t2gvs. Fe eg).

Investigation of base pairs containing oxidized guanine using ab initio method and ABEEMσπ polarizable force field.

PubMed

Liu, Cui; Wang, Yang; Zhao, Dongxia; Gong, Lidong; Yang, Zhongzhi

2014-02-01

The integrity of the genetic information is constantly threatened by oxidizing agents. Oxidized guanines have all been linked to different types of cancers. Theoretical approaches supplement the assorted experimental techniques, and bring new sight and opportunities to investigate the underlying microscopic mechanics. Unfortunately, there is no specific force field to DNA system including oxidized guanines. Taking high level ab initio calculations as benchmark, we developed the ABEEMσπ fluctuating charge force field, which uses multiple fluctuating charges per atom. And it was applied to study the energies, structures and mutations of base pairs containing oxidized guanines. The geometries were obtained in reference to other studies or using B3LYP/6-31+G* level optimization, which is more rational and timesaving among 24 quantum mechanical methods selected and tested by this work. The energies were determined at MP2/aug-cc-pVDZ level with BSSE corrections. Results show that the constructed potential function can accurately simulate the change of H-bond and the buckled angle formed by two base planes induced by oxidized guanine, and it provides reliable information of hydrogen bonding, stacking interaction and the mutation processes. The performance of ABEEMσπ polarizable force field in predicting the bond lengths, bond angles, dipole moments etc. is generally better than those of the common force fields. And the accuracy of ABEEMσπ PFF is close to that of the MP2 method. This shows that ABEEMσπ model is a reliable choice for further research of dynamics behavior of DNA fragment including oxidized guanine. Copyright © 2013 Elsevier Inc. All rights reserved.

Radical production efficiency and electrical characteristics of a coplanar barrier discharge built by multilayer ceramic technology

NASA Astrophysics Data System (ADS)

Jõgi, Indrek; Erme, Kalev; Levoll, Erik; Stamate, Eugen

2017-11-01

The present study investigated the electrical characteristics and radical production efficiency of a coplanar barrier discharge (CBD) device manufactured by Kyocera by multilayer ceramic technology. The device consisted of a number of linear electrodes with electrode and gap widths of 0.75 mm, immersed into a ceramic dielectric barrier. A closed flow-through system necessary for the measurements was prepared by placing a quartz plate at a height of 3 mm from the ceramic barrier. The production of nitrogen radicals was determined from the removal of a trace amount of NO in pure N2 gas, while the production of oxygen radicals was determined by ozone production in pure O2 or synthetic air. The production efficiency of N and O radicals and NO oxidation in synthetic air was comparable with the efficiency of a volume barrier discharge device. The power density per unit of surface area of the CBD device was more than two times larger than that of a similar volume barrier discharge setup, which makes the CBD device a compact alternative for gas treatment. The production of ozone and different nitrogen oxides was also evaluated for the open system of the CBD which is usable for surface treatment. The ozone concentration of this system was nearly independent from the input power, while the concentration of nitrogen oxides increased with input power. The open system of the CBD was additionally tested for the treatment of a silicon surface. An increase of applied power decreased the time required to reduce the water contact angle below 10 degrees but also started to have an impact on the surface roughness.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Westover, Tyler; Emerson, Rachel Marie

Torrefaction is the thermal treatment of materials in the absence of oxygen in the temperature range of 200 to 300 °C and has been shown to improve handling and grinding properties, hydrophobicity, volatiles content, energy density, and combustion performance of renewable energy biomass feedstock materials. The disadvantages of torrefaction are its relative high cost compared to the low value input feedstock material and the energy that can be lost to volatized gases. This work will demonstrate a new technology developed by Advanced Torrefaction Systems (ATS), known as TorreCat™ Technology, that uses an oxidation catalyst in a closed system to combustmore » and destroy volatile organic compounds (VOCs) and other byproducts produced in the torrefaction process. An oxidation catalyst is a substance, or a combination of substances, that accelerate the rate of a chemical reaction without being consumed by the reaction. Catalytic combustion is a reaction that occurs at temperatures 50% lower than traditional combustion, such that essentially no NOx is created. The output of the oxidation catalyst (flue gas) consists mainly of superheated steam and inert gases (carbon dioxide and nitrogen), which can be used for heat in the thermal treatment process. INL has previously developed a pilot-scale Continuous-Feed Thermal Treatment System (CFTTS) that has 10 kg/hr capacity but does not reform the flue gas to reduce environmental concerns or capture all available heat from the biomass material. Using the TorreCat™ technology in INL’s thermal treatment system will demonstrate increased thermal efficiencies during the treatment process as well as reduced environmental impact and clean-up costs. The objective of this project is to determine the effectiveness of the Torrecat™ technology to reform the flue gas and capture as much of its heat content as possible.« less

Community structure of planktonic methane-oxidizing bacteria in a subtropical reservoir characterized by dominance of phylotype closely related to nitrite reducer

NASA Astrophysics Data System (ADS)

Kojima, Hisaya; Tokizawa, Riho; Kogure, Kouhei; Kobayashi, Yuki; Itoh, Masayuki; Shiah, Fuh-Kwo; Okuda, Noboru; Fukui, Manabu

2014-07-01

Methane-oxidizing bacteria (MOB) gain energy from the oxidation of methane and may play important roles in freshwater ecosystems. In this study, the community structure of planktonic MOB was investigated in a subtropical reservoir. Bacterial community structure was investigated through the analysis of the 16S rRNA gene. Three groups of phylogenetically distinct MOB were detected in the clone libraries of polymerase chain reaction products obtained with universal primers. The groups belonged to the class Gammaproteobacteria, the class Alphaproteobacteria, and the candidate phylum NC10. The last group, which consists of close relatives of the nitrite reducer `Candidatus Methylomirabilis oxyfera', was frequently detected in the clone libraries of deep-water environments. The presence of 3 groups of MOB in deep water was also shown by a cloning analysis of the pmoA gene encoding particulate methane monooxygenase. The dominance of `M. oxyfera'-like organisms in deep water was confirmed by catalyzed reporter deposition-fluorescence in situ hybridization, in which cells stained with a specific probe accounted for 16% of total microbial cells. This is the first study to demonstrate that close relatives of the nitrite reducer can be major component of planktonic MOB community which may affect carbon flow in aquatic ecosystems.

How peroxisomes affect aflatoxin biosynthesis in Aspergillus flavus.

PubMed

Reverberi, Massimo; Punelli, Marta; Smith, Carrie A; Zjalic, Slaven; Scarpari, Marzia; Scala, Valeria; Cardinali, Giorgia; Aspite, Nicaela; Pinzari, Flavia; Payne, Gary A; Fabbri, Anna A; Fanelli, Corrado

2012-01-01

In filamentous fungi, peroxisomes are crucial for the primary metabolism and play a pivotal role in the formation of some secondary metabolites. Further, peroxisomes are important site for fatty acids β-oxidation, the formation of reactive oxygen species and for their scavenging through a complex of antioxidant activities. Oxidative stress is involved in different metabolic events in all organisms and it occurs during oxidative processes within the cell, including peroxisomal β-oxidation of fatty acids. In Aspergillus flavus, an unbalance towards an hyper-oxidant status into the cell is a prerequisite for the onset of aflatoxin biosynthesis. In our preliminary results, the use of bezafibrate, inducer of both peroxisomal β-oxidation and peroxisome proliferation in mammals, significantly enhanced the expression of pex11 and foxA and stimulated aflatoxin synthesis in A. flavus. This suggests the existence of a correlation among peroxisome proliferation, fatty acids β-oxidation and aflatoxin biosynthesis. To investigate this correlation, A. flavus was transformed with a vector containing P33, a gene from Cymbidium ringspot virus able to induce peroxisome proliferation, under the control of the promoter of the Cu,Zn-sod gene of A. flavus. This transcriptional control closely relates the onset of the antioxidant response to ROS increase, with the proliferation of peroxisomes in A. flavus. The AfP33 transformant strain show an up-regulation of lipid metabolism and an higher content of both intracellular ROS and some oxylipins. The combined presence of a higher amount of substrates (fatty acids-derived), an hyper-oxidant cell environment and of hormone-like signals (oxylipins) enhances the synthesis of aflatoxins in the AfP33 strain. The results obtained demonstrated a close link between peroxisome metabolism and aflatoxin synthesis.

Oxidation of Inconel 625 superalloy upon treatment with oxygen or hydrogen plasma at high temperature

NASA Astrophysics Data System (ADS)

Vesel, Alenka; Drenik, Aleksander; Elersic, Kristina; Mozetic, Miran; Kovac, Janez; Gyergyek, Tomaz; Stockel, Jan; Varju, Jozef; Panek, Radomir; Balat-Pichelin, Marianne

2014-06-01

Initial stages of Inconel 625 superalloy (Ni60Cr30Mo10Ni4Nb1) oxidation upon short treatment with gaseous plasma at different temperatures up to about 1600 K were studied. Samples were treated for different periods up to a minute by oxygen or hydrogen plasma created with a microwave discharge in the standing-wave mode at a pressure of 40 Pa and a power 500 W. Simultaneous heating of the samples was realized by focusing concentrated solar radiation from a 5 kW solar furnace directly onto the samples. The morphological changes upon treatment were monitored using scanning electron microscopy, compositional depth profiling was performed using Auger electron spectroscopy, while structural changes were determined by X-ray diffraction. The treatment in oxygen plasma caused formation of metal oxide clusters of three dimensional crystallites initially rich in nickel oxide with the increasing chromium oxide content as the temperature was increasing. At about 1100 K iron and niobium oxides prevailed on the surface causing a drop of the material emissivity at 5 μm. Simultaneously the NiCr2O4 compound started growing at the interface between the oxide film and bulk alloy and the compound persisted up to temperatures close to the Inconel melting point. Intensive migration of minority alloying elements such as Fe and Ti was observed at 1600 K forming mixed surface oxides of sub-micrometer dimensions. The treatment in hydrogen plasma with small admixture of water vapor did not cause much modification unless the temperature was close to the melting point. At such conditions aluminum segregated on the surface and formed well-defined Al2O3 crystals.

Closed DTU fuel cycle with Np recycle and waste transmutation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beller, D.E.; Sailor, W.C.; Venneri, F.

1999-09-01

A nuclear energy scenario for the 21st century that included a denatured thorium-uranium-oxide (DTU) fuel cycle and new light water reactors (LWRs) supported by accelerator-driven transmutation of waste (ATW) systems was previously described. This coupled system with the closed DTU fuel cycle provides several improvements beyond conventional LWR (CLWR) (once-through, UO{sub 2} fuel) nuclear technology: increased proliferation resistance, reduced waste, and efficient use of natural resources. However, like CLWR fuel cycles, the spent fuel in the first one-third core discharged after startup contains higher-quality Pu than the equilibrium fuel cycle. To eliminate this high-grade Pu, Np is separated and recycledmore » with Th and U--rather than with higher actinides [(HA) including Pu]. The presence of Np in the LWR feed greatly increases the production of {sup 238}Pu so that a few kilograms of Pu generated enough alpha-decay heat that the separated Pu is highly resistant to proliferation. This alternate process also simplifies the pyrochemical separation of fuel elements (Th and U) from HAs. To examine the advantages of this concept, the authors modeled a US deployment scenario for nuclear energy that includes DTU-LWRs plus ATW`s to burn the actinides produced by these LWRs and to close the back-end of the DTU fuel cycle.« less

Analysis and design of a 3rd order velocity-controlled closed-loop for MEMS vibratory gyroscopes.

PubMed

Wu, Huan-ming; Yang, Hai-gang; Yin, Tao; Jiao, Ji-wei

2013-09-18

The time-average method currently available is limited to analyzing the specific performance of the automatic gain control-proportional and integral (AGC-PI) based velocity-controlled closed-loop in a micro-electro-mechanical systems (MEMS) vibratory gyroscope, since it is hard to solve nonlinear functions in the time domain when the control loop reaches to 3rd order. In this paper, we propose a linearization design approach to overcome this limitation by establishing a 3rd order linear model of the control loop and transferring the analysis to the frequency domain. Order reduction is applied on the built linear model's transfer function by constructing a zero-pole doublet, and therefore mathematical expression of each control loop's performance specification is obtained. Then an optimization methodology is summarized, which reveals that a robust, stable and swift control loop can be achieved by carefully selecting the system parameters following a priority order. Closed-loop drive circuits are designed and implemented using 0.35 μm complementary metal oxide semiconductor (CMOS) process, and experiments carried out on a gyroscope prototype verify the optimization methodology that an optimized stability of the control loop can be achieved by constructing the zero-pole doublet, and disturbance rejection capability (D.R.C) of the control loop can be improved by increasing the integral term.

Design of a microfluidic sensor for high-sensitivity Copper (II) sensing applications

NASA Astrophysics Data System (ADS)

Gibson, Ceri; Byrne, Patrick; Gray, David; MacCraith, Brian D.; Paull, Brett; Tyrrell, Eadaoin

2003-03-01

An all-plastic micro-sensor system for remote measurement of copper (II) ions in the aqueous environment has been developed. The sensing structure was designed for ease of milling and fabricated in poly (methyl methacrylate) (PMMA) using a hot-embossing technique. Issues of sealing the structure were studied extensively and an efficient protocol has been established. The detection system comprises a compact photo-multiplier tube and integrated photon counting system. This method has advantages of low sample volume, (creating a minimal volume of waste), low exposure to contaminants due to the closed system, no moving parts and employs a robust polymer material which is resistant to the environment of intended use. The sensor operates on the principle of flow injection analysis and has been tested using a chemiluminescence (FIA-CL) reaction arising from the complexation of copper with 1,10-phenanthroline and subsequent oxidation by hydrogen peroxide.

Deficiency of iNOS-derived NO accelerates lipid accumulation-independent liver fibrosis in non-alcoholic steatohepatitis mouse model.

PubMed

Nozaki, Yuichi; Fujita, Koji; Wada, Koichiro; Yoneda, Masato; Kessoku, Takaomi; Shinohara, Yoshiyasu; Imajo, Kento; Ogawa, Yuji; Nakamuta, Makoto; Saito, Satoru; Masaki, Naohiko; Nagashima, Yoji; Terauchi, Yasuo; Nakajima, Atsushi

2015-04-01

Although many of the factors and molecules closely associated with non-alcoholic steatohepatitis (NASH) have been reported, the role of inducible nitric oxide synthase (iNOS)-derived nitric oxide (NO) on the progression of NASH remains unclear. We therefore investigated the role of iNOS-derived NO in NASH pathogenesis with a long-term follow-up study using systemic iNOS-knockout mice under high-fat diet (HFD) conditions. iNOS-knockout and wild-type mice were fed a basal or HFD for 10 or 48 weeks. Lipid accumulation, fibrosis, and inflammation were evaluated, and various factors and molecules closely associated with NASH were analyzed. Marked fibrosis and inflammation (indicators of NASH) were observed in the livers of iNOS-knockout mice compared to wild-type mice after 48 weeks of a HFD; however, lipid accumulation in iNOS-knockout mice livers was less than in the wild-type. Increased expressions of various cytokines that are transcriptionally controlled by NF-kB in iNOS-deficient mice livers were observed during HFD conditions. iNOS-derived NO may play a protective role against the progression to NASH during an HFD by preventing fibrosis and inflammation, which are mediated by NF-kB activation in Kupffer cells. A lack of iNOS-derived NO accelerates progression to NASH without excessive lipid accumulation.

Copper-Hydroperoxo Mediated N-Debenzylation Chemistry Mimicking Aspects of Copper Monoxygenases

PubMed Central

Maiti, Debabrata; Narducci Sarjeant, Amy A.; Karlin, Kenneth D.

2008-01-01

Substantial oxidative N-debenzylation reaction along with PhCH=O formation occurs from a hydroperoxo copper(II) complex which has a dibenzylamino substrate (-N(CH2Ph)2 appended as a substituent on one pyridyl group of its tripodal tetradentate TMPA {≡ TPA ≡ tris(2-pyridylmethyl)amine)} ligand framework. During the course of the (LN(CH2Ph)2)CuII(−OOH) reactivity, formation of a substrate and −OOH (an oxygen atom) derived alkoxo CuII(−OR) complex occurs. The observation that the same CuII(−OR) species occurs from CuI/PhIO chemistry suggests the possibility that a copper-oxo (cupryl) reactive intermediate forms during alkoxo species formation, and new ESI-MS data obtained provides some further support for this high-valent intermediate. Net H-atom abstraction chemistry is proposed, based on kinetic isotope effect studies provided here and that previously published for a closely related CuII(−OOH) species incorporating dimethylamine (-N(CH3)2) as the internal substrate (J. Am. Chem. Soc. 2007, 129, 6720-6721); the CuI/PhIO reactivity, with similar isotope effect results, provides further support. The reactivity of these chemical systems closely resembles proposed oxidative N-dealkylation mechanisms effected by the copper-monooxygenases dopamine β-monooxygenase (DβM) or peptidylglycine-α-hydroxylating monooxygenase (PHM). PMID:18783212

Dynamic Modeling, Model-Based Control, and Optimization of Solid Oxide Fuel Cells

NASA Astrophysics Data System (ADS)

Spivey, Benjamin James

2011-07-01

Solid oxide fuel cells are a promising option for distributed stationary power generation that offers efficiencies ranging from 50% in stand-alone applications to greater than 80% in cogeneration. To advance SOFC technology for widespread market penetration, the SOFC should demonstrate improved cell lifetime and load-following capability. This work seeks to improve lifetime through dynamic analysis of critical lifetime variables and advanced control algorithms that permit load-following while remaining in a safe operating zone based on stress analysis. Control algorithms typically have addressed SOFC lifetime operability objectives using unconstrained, single-input-single-output control algorithms that minimize thermal transients. Existing SOFC controls research has not considered maximum radial thermal gradients or limits on absolute temperatures in the SOFC. In particular, as stress analysis demonstrates, the minimum cell temperature is the primary thermal stress driver in tubular SOFCs. This dissertation presents a dynamic, quasi-two-dimensional model for a high-temperature tubular SOFC combined with ejector and prereformer models. The model captures dynamics of critical thermal stress drivers and is used as the physical plant for closed-loop control simulations. A constrained, MIMO model predictive control algorithm is developed and applied to control the SOFC. Closed-loop control simulation results demonstrate effective load-following, constraint satisfaction for critical lifetime variables, and disturbance rejection. Nonlinear programming is applied to find the optimal SOFC size and steady-state operating conditions to minimize total system costs.

Isotope Exchange in Oxide Catalyst

NASA Technical Reports Server (NTRS)

Hess, Robert V.; Miller, Irvin M.; Schryer, David R.; Sidney, Barry D.; Wood, George M., Jr.; Hoyt, Ronald F.; Upchurch, Billy T.; Brown, Kenneth G.

1987-01-01

Replacement technique maintains level of CO2/18 in closed-cycle CO2 lasers. High-energy, pulsed CO2 lasers using rare chemical isotopes must be operated in closed cycles to conserve gas. Rare isotopes operated in closed cycles to conserve gas. Rare isotopes as CO2/18 used for improved transmission of laser beam in atmosphere. To maintain laser power, CO2 must be regenerated, and O2 concentration kept below few tenths of percent. Conditions achieved by recombining CO and O2.

METHOD 415.3 - MEASUREMENT OF TOTAL ORGANIC ...

EPA Pesticide Factsheets

2.0 SUMMARY OF METHOD2.1 In both TOC and DOC determinations, organic carbon in the water sample is oxidized to form carbon dioxide (CO2), which is then measured by a detection system. There are two different approaches for the oxidation of organic carbon in water samples to carbon dioxide gas: (a) combustion in an oxidizing gas and (b) UV promoted or heat catalized chemical oxidation with a persulfate solution. Carbon dioxide, which is released from the oxidized sample, is detected by a conductivity detector or by a nondispersive infrared (NDIR) detector. Instruments using any combination of the above technologies may be used in this method.2.2. Setteable solids and floating matter may cause plugging of valves, tubing, and the injection needle port. The TOC procedure allows the removal of settleable solids and floating matter. The suspended matter is considered part of the sample. The resulting water sample is then considered a close approximation of the original whole water sample for the purpose of TOC measurement.2.3. The DOC procedure requires that the sample be passed through a 0.45 um filter prior to analysis.2.4. The TOC and DOC procedures require that all inorganic carbon be removed from the sample before the sample is analyzed for organic carbon content. If the inorganic carbon (IC) is not completely removed, significant error will occur. The inorganic carbon interference is removed by converting the mineralized IC to CO2 by acidification and

Health Risks of Food Oxidation.

PubMed

Estévez, Mario; Li, Zhuqing; Soladoye, Olugbenga P; Van-Hecke, Thomas

The impact of dietary habits on our health is indisputable. Consumer's concern on aging and age-related diseases challenges scientists to underline the potential role of food on the extension and guarantee of lifespan and healthspan. While some dietary components and habits are generally regarded as beneficial for our health, some others are being found to exert potential toxic effects and hence, contribute to the onset of particular health disorders. Among the latter, lipid and protein oxidation products formed during food production, storage, processing, and culinary preparation have been recently identified as potentially harmful to humans. Upon intake, food components are further degraded and oxidized during the subsequent digestion phases and the pool of compounds formed in the lumen is in close contact with the lamina propria of the intestines. Some of these oxidation products have been found to promote inflammatory conditions in the gut (i.e., bowel diseases) and are also reasonably linked to the onset of carcinogenic processes. Upon intestinal uptake, some species are distributed by the bloodstream causing an increase in oxidative stress markers and impairment of certain physiological processes through alteration of specific gene expression pathways. This chapter summarizes the most recent discoveries on this topic with particular stress on challenges that we face in the near future: understanding the molecular basis of disease, the suitability of using living animals vs in vitro model systems and the necessity of using massive genomic techniques and versatile mass spectrometric technology. © 2017 Elsevier Inc. All rights reserved.

CO oxidation on Ru-Pt bimetallic nanoclusters supported on TiO2(101): The effect of charge polarization

NASA Astrophysics Data System (ADS)

Jia, Chuanyi; Zhong, Wenhui; Deng, Mingsen; Jiang, Jun

2018-03-01

Pt-based catalyst is widely used in CO oxidation, while its catalytic activity is often undermined because of the CO poisoning effect. Here, using density functional theory, we propose the use of a Ru-Pt bimetallic cluster supported on TiO2 for CO oxidation, to achieve both high activity and low CO poisoning effect. Excellent catalytic activity is obtained in a Ru1Pt7/TiO2(101) system, which is ascribed to strong electric fields induced by charge polarization between one Ru atom and its neighboring Pt atoms. Because of its lower electronegativity, the Ru atom donates electrons to neighboring Pt. This induces strong electric fields around the top-layered Ru, substantially promoting the adsorption of O2/CO + O2 and eliminating the CO poisoning effect. In addition, the charge polarization also drives the d-band center of the Ru1Pt7 cluster to up-shift to the Fermi level. For surface O2 activation/CO oxidation, the strong electric field and d-band center close to the Fermi level can promote the adsorption of O2 and CO as well as reduce the reaction barrier of the rate-determining step. Meanwhile, since O2 easily dissociates on Ru1Pt7/TiO2(101) resulting in unwanted oxidation of Ru and Pt, a CO-rich condition is necessary to protect the catalyst at high temperature.

Measuring the Thermodynamics of the Alloy/Scale Interface

NASA Technical Reports Server (NTRS)

Copland, Evan

2004-01-01

A method is proposed for the direct measurement of the thermodynamic properties of the alloy and oxide compound at the alloy/scale interface observed during steady-state oxidation. The thermodynamic properties of the alloy/scale interface define the driving force for solid-state transport in the alloy and oxide compound. Accurate knowledge of thermodynamic properties of the interface will advance our understanding of oxidation behavior. The method is based on the concept of local equilibrium and assumes that an alloy+scale equilibrium very closely approximates the alloy/scale interface observed during steady-state oxidation. The thermodynamics activities of this alloy+scale equilibrium are measured directly by Knudsen effusion-cell mass spectrometer (KEMS) using the vapor pressure technique. The theory and some practical considerations of this method are discussed in terms of beta-NiAl oxidation.

Automatic electrochemical ambient air monitor for chloride and chlorine

DOEpatents

Mueller, Theodore R.

1976-07-13

An electrochemical monitoring system has been provided for determining chloride and chlorine in air at levels of from about 10-1000 parts per billion. The chloride is determined by oxidation to chlorine followed by reduction to chloride in a closed system. Chlorine is determined by direct reduction at a platinum electrode in 6 M H.sub.2 SO.sub.4 electrolyte. A fully automated system is utilized to (1) acquire and store a value corresponding to electrolyte-containing impurities, (2) subtract this value from that obtained in the presence of air, (3) generate coulometrically a standard sample of chlorine mixed with air sample, and determine it as chlorine and/or chloride, and (4) calculate, display, and store for permanent record the ratio of the signal obtained from the air sample and that obtained with the standard.

Life sciences and space research XXIII(3): Natural and artificial ecosystems; Proceedings of the Topical Meetings of the 27th COSPAR Plenary Meeting, Espoo, Finland, July 18-29, 1988

NASA Technical Reports Server (NTRS)

Macelroy, R. D. (Editor); Tibbitts, T. W. (Editor); Thompson, B. G. (Editor); Volk, T. (Editor)

1989-01-01

The present conference discusses topics in the fields of higher plant growth under controlled environmental conditions, waste oxidation, carbon cycling, and biofermentor design and operation. Attention is given to CO2 and O2 effects on the development and fructification of wheat in closed systems, transpiration during life cycle in controlled wheat growth, sources and processing of CELSS wastes, waste-recycling in bioregenerative life support, and the effect of iodine disinfection products on higher plants. Also discussed are carbon cycling by cellulose-fermenting nitrogen-fixing bacteria, a bioreactor design with sunlight supply and operations systems for use in the space environment, gas bubble coalescence in reduced gravity conditions, and model system studies of a phase-separated membrane bioreactor.

Integrated systems analysis of persistent polar pollutants in the water cycle.

PubMed

van der Voet, E; Nikolic, I; Huppes, G; Kleijn, R

2004-01-01

Persistent polar pollutants (P3) are difficult to degrade in standard waste water treatment plants. As a result, they end up in the effluent and are emitted to the surface water. In some areas, this problem is aggravated through "closed loop recycling", causing concentrations of P3 in surface water to build up over time. This could cause violation of (future) EU regulations. In the P-THREE project, various alternative waste water treatment techniques are investigated regarding their effectiveness in eliminating these substances, especially membrane bioreactor treatment and advanced oxidation processes, MBR and AOP. The integrated systems analysis which is the subject of this paper assesses these techniques in a broader systems context: (1) the life-cycle of the P3, (2) the life cycle of the WWTPs, and (3) the WWTP life cycle costs.

Substrate availability drives spatial patterns in richness of ammonia-oxidizing bacteria and archaea in temperate forest soils

Treesearch

J.S. Norman; J.E. Barrett

2016-01-01

We sought to investigate the drivers of richness of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in temperate forest soils. We sampled soils across four experimental watersheds in the Coweeta Hydrologic Laboratory, North Carolina USA. These watersheds are geographically close, but vary in soil chemistry due to differences in land use history. While we...

Extracellular pH monitoring for use in closed-loop vagus nerve stimulation

NASA Astrophysics Data System (ADS)

Cork, Simon C.; Eftekhar, Amir; Mirza, Khalid B.; Zuliani, Claudio; Nikolic, Konstantin; Gardiner, James V.; Bloom, Stephen R.; Toumazou, Christofer

2018-02-01

Objective. Vagal nerve stimulation (VNS) has shown potential benefits for obesity treatment; however, current devices lack physiological feedback, which limit their efficacy. Changes in extracellular pH (pHe) have shown to be correlated with neural activity, but have traditionally been measured with glass microelectrodes, which limit their in vivo applicability. Approach. Iridium oxide has previously been shown to be sensitive to fluctuations in pH and is biocompatible. Iridium oxide microelectrodes were inserted into the subdiaphragmatic vagus nerve of anaesthetised rats. Introduction of the gut hormone cholecystokinin (CCK) or distension of the stomach was used to elicit vagal nerve activity. Main results. Iridium oxide microelectrodes have sufficient pH sensitivity to readily detect changes in pHe associated with both CCK and gastric distension. Furthermore, a custom-made Matlab script was able to use these changes in pHe to automatically trigger an implanted VNS device. Significance. This is the first study to show pHe changes in peripheral nerves in vivo. In addition, the demonstration that iridium oxide microelectrodes are sufficiently pH sensitive as to measure changes in pHe associated with physiological stimuli means they have the potential to be integrated into closed-loop neurostimulating devices.

Creep and stress rupture of oxide dispersion strengthened mechanically alloyed Inconel alloy MA 754

NASA Technical Reports Server (NTRS)

Howson, T. E.; Tien, J. K.; Stulga, J. E.

1980-01-01

The creep and stress rupture behavior of the mechanically alloyed oxide dispersion strengthened nickel-base alloy MA 754 was studied at 760, 982 and 1093 C. Tensile specimens with a fine, highly elongated grain structure, oriented parallel and perpendicular to the longitudinal grain direction were tested at various stresses in air under constant load. It was found that the apparent stress dependence was large, with power law exponents ranging from 19 to 33 over the temperature range studied. The creep activation energy, after correction for the temperature dependence of the elastic modulus, was close to but slightly larger than the activation energy for self diffusion. Rupture was intergranular and the rupture ductility as measured by percentage elongation was generally low, with values ranging from 0.5 to 16 pct. The creep properties are rationalized by describing the creep rates in terms of an effective stress which is the applied stress minus a resisting stress consistent with the alloy microstructure. Values of the resisting stress obtained through a curve fitting procedure are found to be close to the values of the particle by-pass stress for this oxide dispersion strengthened alloy, as calculated from the measured oxide particle distribution.

Closed-cage tungsten oxide clusters in the gas phase.

PubMed

Singh, D M David Jeba; Pradeep, T; Thirumoorthy, Krishnan; Balasubramanian, Krishnan

2010-05-06

During the course of a study on the clustering of W-Se and W-S mixtures in the gas phase using laser desorption ionization (LDI) mass spectrometry, we observed several anionic W-O clusters. Three distinct species, W(6)O(19)(-), W(13)O(29)(-), and W(14)O(32)(-), stand out as intense peaks in the regular mass spectral pattern of tungsten oxide clusters suggesting unusual stabilities for them. Moreover, these clusters do not fragment in the postsource decay analysis. While trying to understand the precursor material, which produced these clusters, we found the presence of nanoscale forms of tungsten oxide. The structure and thermodynamic parameters of tungsten clusters have been explored using relativistic quantum chemical methods. Our computed results of atomization energy are consistent with the observed LDI mass spectra. The computational results suggest that the clusters observed have closed-cage structure. These distinct W(13) and W(14) clusters were observed for the first time in the gas phase.

Binding of group 15 and group 16 oxides by a concave host containing an isophthalamide unit.

PubMed

Eckelmann, Jens; Saggiomo, Vittorio; Fischmann, Svenja; Lüning, Ulrich

2012-01-01

A bi-macrocycle with an incorporated isophthalamide substructure was synthesized by double amide formation between an isophthaloyl dichloride and two equivalents of a bis(alkenyloxy)aniline, followed by ring-closing metathesis and hydrogenation. In contrast to many related isophthalamides, the concave host exhibits a better binding for oxides, such as DMSO or pyridine-N-oxide, than for halide anions. A general method for a quick estimation of the strength of binding derived from only a few data points is presented and gives an estimated K(ass) of pyridine-N-oxide of ca. 40 M(-1), NMR titration confirms 25 M(-1).

Correlation between surface morphology and electrical properties of VO2 films grown by direct thermal oxidation method

NASA Astrophysics Data System (ADS)

Yoon, Joonseok; Park, Changwoo; Park, Sungkyun; Mun, Bongjin Simon; Ju, Honglyoul

2015-10-01

We investigate surface morphology and electrical properties of VO2 films fabricated by direct thermal oxidation method. The VO2 film prepared with oxidation temperature at 580 °C exhibits excellent qualities of VO2 characteristics, e.g. a metal-insulator transition (MIT) near 67 °C, a resistivity ratio of ∼2.3 × 104, and a bandgap of 0.7 eV. The analysis of surface morphology with electrical resistivity of VO2 films reveals that the transport properties of VO2 films are closely related to the grain size and surface roughness that vary with oxidation annealing temperatures.

Hexavalent chromium induces reactive oxygen species and impairs the antioxidant power of human erythrocytes and lymphocytes: Decreased metal reducing and free radical quenching ability of the cells.

PubMed

Husain, Nazim; Mahmood, Riaz

2017-08-01

The toxicity of hexavalent chromium [Cr(VI)] in biological systems is thought to be closely associated with the generation of free radicals and reactive oxygen species. These species are produced when Cr(VI) is reduced to its trivalent form in the cell. This process results in oxidative stress due to an imbalance between the detoxifying ability of the cell and the production of free radicals. We have studied the effect of potassium dichromate (K 2 Cr 2 O 7 ), a [Cr(VI)] compound, on the antioxidant power of human erythrocytes and lymphocytes under in vitro conditions. Incubation of erythrocytes and lymphocytes with different concentrations of K 2 Cr 2 O 7 resulted in a marked dose-dependent decrease in reduced glutathione and an increase in oxidized glutathione and reactive oxygen species levels. The antioxidant power of the cells was decreased, as determined by metal reducing and free radical quenching assays. These results show that [Cr(VI)] upregulates the generation of reactive oxygen species and, as a consequence, the cellular antioxidant defences are compromised. The resulting oxidative stress may contribute to Cr(VI)-induced cellular damage.

Optimization of an oxide dispersion strengthened Ni-Cr-Al alloy for gas turbine engine vanes

NASA Technical Reports Server (NTRS)

Klarstrom, D. L.; Grierson, R.

1975-01-01

The investigation was carried out to determine the optimum alloy within the Ni-16Cr-Al-Y2O3 system for use as a vane material in advanced aircraft gas turbine engines. Six alloys containing nominally 4%, 5% and 6% Al with Y2O3 levels of 0.8% and 1.2% were prepared by mechanical attrition. Six small-scale, rectangular extrusions were produced from each powder lot for property evaluation. The approximate temperatures for incipient melting were found to be 1658 K (2525 F), 1644 K (2500 F) and 1630 K (2475 F) for the 4%, 5% and 6% aluminum levels, respectively. With the exception of longitudinal crystallographic texture, the eight extrusions selected for extensive evaluation either exceeded or were close to mechanical property goals. Major differences between the alloys became apparent during dynamic oxidation testing, and in particular during the 1366 K (2000 F)/500 hour Mach 1 tests carried out by NASA-Lewis. An aluminum level of 4.75% was subsequently judged to be optimum based on considerations of dynamic oxidation resistance, susceptibility to thermal fatigue cracking and melting point.

Computational and Experimental Study of Neuroglobin and Mutants

NASA Astrophysics Data System (ADS)

Nelson, Lauren; Cho, Samuel; Kim-Shaprio, Daniel

Neuroglobin (Ngb) is a hexacoordinated heme protein that is closely related to hemoglobin and myoglobin and normally found in the brain and nervous systems. It is involved in cellular oxygen homeostasis and reversibly binds to oxygen with a higher binding affinity than hemoglobin. To protect the brain tissue from hypoxic or ischemic conditions, Ngb increases oxygen availability. We have previously shown that a mutant form of Ngb reduces nitrite to nitric oxide 50x faster than myoglobin and 500x faster than hemoglobin. It also tightly binds to carbon monoxide (CO) with an association rate that is 500x faster than hemoglobin. To analyze the structure of neuroglobin and the characteristics causing these phenomena, we performed 3 sets of 1 microsecond molecular dynamic (MD) simulations of wild-type oxidized and reduced human Ngb and their C46A, C55A, H64L, and H64Q mutants. We also directly compare our MD simulations with time-resolved absorption spectroscopy. These studies will help identify treatments for diseases involving low nitric oxide availability and carbon monoxide poisoning. This research was supported by an NIH NSRA predoctoral fellowship in the Structural and Computational Biophysics Program training Grant (T32GM095440-05).

Plasma-assisted oxide removal from ruthenium-coated EUV optics

NASA Astrophysics Data System (ADS)

Dolgov, A.; Lee, C. J.; Bijkerk, F.; Abrikosov, A.; Krivtsun, V. M.; Lopaev, D.; Yakushev, O.; van Kampen, M.

2018-04-01

An experimental study of oxide reduction at the surface of ruthenium layers on top of multilayer mirrors and thin Ru/Si films is presented. Oxidation and reduction processes were observed under conditions close to those relevant for extreme ultraviolet lithography. The oxidized ruthenium surface was exposed to a low-temperature hydrogen plasma, similar to the plasma induced by extreme ultraviolet radiation. The experiments show that hydrogen ions are the main reducing agent. Furthermore, the addition of hydrogen radicals increases the reduction rate beyond that expected from simple flux calculations. We show that low-temperature hydrogen plasmas can be effective for reducing oxidized top surfaces. Our proof-of-concept experiments show that an in situ, EUV-generated plasma cleaning technology is feasible.

Curcumin, inflammation, and chronic diseases: how are they linked?

PubMed

He, Yan; Yue, Yuan; Zheng, Xi; Zhang, Kun; Chen, Shaohua; Du, Zhiyun

2015-05-20

It is extensively verified that continued oxidative stress and oxidative damage may lead to chronic inflammation, which in turn can mediate most chronic diseases including cancer, diabetes, cardiovascular, neurological, inflammatory bowel disease and pulmonary diseases. Curcumin, a yellow coloring agent extracted from turmeric, shows strong anti-oxidative and anti-inflammatory activities when used as a remedy for the prevention and treatment of chronic diseases. How oxidative stress activates inflammatory pathways leading to the progression of chronic diseases is the focus of this review. Thus, research to date suggests that chronic inflammation, oxidative stress, and most chronic diseases are closely linked, and the antioxidant properties of curcumin can play a key role in the prevention and treatment of chronic inflammation diseases.

Nuclear thermionic converter. [tungsten-thorium oxide rods

NASA Technical Reports Server (NTRS)

Phillips, W. M.; Mondt, J. F. (Inventor)

1977-01-01

Efficient nuclear reactor thermionic converter units are described which can be constructed at low cost and assembled in a reactor which requires a minimum of fuel. Each converter unit utilizes an emitter rod with a fluted exterior, several fuel passages located in the bulges that are formed in the rod between the flutes, and a collector receiving passage formed through the center of the rod. An array of rods is closely packed in an interfitting arrangement, with the bulges of the rods received in the recesses formed between the bulges of other rods, thereby closely packing the nuclear fuel. The rods are constructed of a mixture of tungsten and thorium oxide to provide high power output, high efficiency, high strength, and good machinability.

Development and research program for a soil-based bioregenerative agriculture system to feed a four person crew at a Mars base.

PubMed

Silverstone, S; Nelson, M; Alling, A; Allen, J

2003-01-01

For humans to survive during long-term missions on the Martian surface, bioregenerative life support systems including food production will decrease requirements for launch of Earth supplies, and increase mission safety. It is proposed that the development of "modular biospheres"--closed system units that can be air-locked together and which contain soil-based bioregenerative agriculture, horticulture, with a wetland wastewater treatment system is an approach for Mars habitation scenarios. Based on previous work done in long-term life support at Biosphere 2 and other closed ecological systems, this consortium proposes a research and development program called Mars On Earth(TM) which will simulate a life support system designed for a four person crew. The structure will consist of 6 x 110 square meter modular agricultural units designed to produce a nutritionally adequate diet for 4 people, recycling all air, water and waste, while utilizing a soil created by the organic enrichment and modification of Mars simulant soils. Further research needs are discussed, such as determining optimal light levels for growth of the necessary range of crops, energy trade-offs for agriculture (e.g. light intensity vs. required area), capabilities of Martian soils and their need for enrichment and elimination of oxides, strategies for use of human waste products, and maintaining atmospheric balance between people, plants and soils. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

High Temperature Solar Electrothermal Processing-III. Zinc from Zinc Oxide at 1200-1675K Using a Non-Consumable Anode.

DTIC Science & Technology

1987-09-09

and the flow of Ar, about 5 1/min, begun. The heliostat was set to track with the doors closed. The instrumentation was activated. Then both furnace...experiment, we closed both doors, stowed the heliostat and reopened the doors to provide good ventilation to the concentrator room. Then we disconnected the

49 CFR 177.838 - Class 4 (flammable solid) materials, Class 5 (oxidizing) materials, and Division 4.2 (pyroforic...

Code of Federal Regulations, 2010 CFR

2010-10-01

... not be piled closer than 15 cm (5.9 inches) from the top of any motor vehicle with a closed body. (d)-(e) [Reserved] (f) Nitrates, except ammonium nitrate having organic coating, must be loaded in closed... covered. Ammonium nitrate having organic coating must not be loaded in all-metal vehicles, other than...

Mitochondrial and Ubiquitin Proteasome System Dysfunction in Ageing and Disease: Two Sides of the Same Coin?

PubMed Central

Ross, Jaime M.; Olson, Lars; Coppotelli, Giuseppe

2015-01-01

Mitochondrial dysfunction and impairment of the ubiquitin proteasome system have been described as two hallmarks of the ageing process. Additionally, both systems have been implicated in the etiopathogenesis of many age-related diseases, particularly neurodegenerative disorders, such as Alzheimer’s and Parkinson’s disease. Interestingly, these two systems are closely interconnected, with the ubiquitin proteasome system maintaining mitochondrial homeostasis by regulating organelle dynamics, the proteome, and mitophagy, and mitochondrial dysfunction impairing cellular protein homeostasis by oxidative damage. Here, we review the current literature and argue that the interplay of the two systems should be considered in order to better understand the cellular dysfunction observed in ageing and age-related diseases. Such an approach may provide valuable insights into molecular mechanisms underlying the ageing process, and further discovery of treatments to counteract ageing and its associated diseases. Furthermore, we provide a hypothetical model for the heterogeneity described among individuals during ageing. PMID:26287188

Oxidation Of Manganese At Kimberley, Gale Crater: More Free Oxygen In Mars' Past?

NASA Technical Reports Server (NTRS)

Lanza, N. L.; Wiens, R. C.; Arvidson, R. E.; Clark, B. C.; Fischer, W. W.; Gellert, R.; Grotzinger, J. P.; Hurowitz, J. A.; McLennan, S. M.; Morris, R. V.;

Impact of methionine oxidation on calmodulin structural dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCarthy, Megan R.; Thompson, Andrew R.; Nitu, Florentin

2015-01-09

Highlights: • We measured the distance distribution between two spin labels on calmodulin by DEER. • Two structural states, open and closed, were resolved at both low and high Ca. • Ca shifted the equilibrium toward the open state by a factor of 13. • Methionine oxidation, simulated by glutamine substitution, decreased the Ca effect. • These results have important implications for aging in muscle and other tissues. - Abstract: We have used electron paramagnetic resonance (EPR) to examine the structural impact of oxidizing specific methionine (M) side chains in calmodulin (CaM). It has been shown that oxidation of eithermore » M109 or M124 in CaM diminishes CaM regulation of the muscle calcium release channel, the ryanodine receptor (RyR), and that mutation of M to Q (glutamine) in either case produces functional effects identical to those of oxidation. Here we have used site-directed spin labeling and double electron–electron resonance (DEER), a pulsed EPR technique that measures distances between spin labels, to characterize the structural changes resulting from these mutations. Spin labels were attached to a pair of introduced cysteine residues, one in the C-lobe (T117C) and one in the N-lobe (T34C) of CaM, and DEER was used to determine the distribution of interspin distances. Ca binding induced a large increase in the mean distance, in concert with previous X-ray crystallography and NMR data, showing a closed structure in the absence of Ca and an open structure in the presence of Ca. DEER revealed additional information about CaM’s structural heterogeneity in solution: in both the presence and absence of Ca, CaM populates both structural states, one with probes separated by ∼4 nm (closed) and another at ∼6 nm (open). Ca shifts the structural equilibrium constant toward the open state by a factor of 13. DEER reveals the distribution of interprobe distances, showing that each of these states is itself partially disordered, with the width of each population ranging from 1 to 3 nm. Both mutations (M109Q and M124Q) decrease the effect of Ca on the structure of CaM, primarily by decreasing the closed-to-open equilibrium constant in the presence of Ca. We propose that Met oxidation alters CaM’s functional interaction with its target proteins by perturbing this Ca-dependent structural shift.« less

High aeration rate enhances flow stratification in full-scale oxidation ditch.

PubMed

Diamantis, Vasileios; Papaspyrou, Ioannis; Melidis, Parasxos; Aivasidis, Alexander

2010-02-01

Aerated channel reactors with a uniform field of aeration may display flow stratification and short-circuit phenomena in wastewater treatment systems. In this study, we present data suggesting that flow stratification is closely related to the aeration rate and the arrangement of aerators. A full-scale oxidation ditch, with a total volume of 6,500 m(3) and a membrane-diffused aerated zone of 60 x 7 x 5 m (length-width-depth), was selected for water velocity measurements. Two profiles of the oxidation ditch were studied in detail: the first one was at the end of the aerated zone and the second one at the end of the anoxic zone. The results of this work demonstrate that the horizontal water velocity at the end of the aerated zone displayed significant stratification, with maximum velocity near the water surface (0.5-0.7 m/s) and almost zero velocity at a depth of 2.5 m. At the end of the anoxic zone, water velocity was uniform and equal to 0.27-0.31 m/s. Increasing the aeration rate from 1,800 to 4,300 m(3)/h, almost 90% of the water flow was found to discharge through the upper-half of the channel reactor profile. Different options to mitigate flow stratification of the oxidation ditch are discussed in this paper.

Refractory of Furnaces to Reduce Environmental Impact

NASA Astrophysics Data System (ADS)

Hanzawa, Shigeru

2011-10-01

The energy load of furnaces used in the manufacturing process of ceramics is quite large. Most of the environmental impact of ceramics manufacturing is due to the CO2 produced from this high energy load. To improve this situation, R&D has focused on furnace systems and techniques of control in order to reduce energy load. Since furnaces are comprised of refractory, consideration of their mechanical and thermal characteristics is important. Herein are described several refractory types which were chosen through comparison of the characteristics which contribute to heat capacity reduction, heat insulating reinforcement and high emissivity, thereby improving thermal radiation heat transfer efficiency to the ceramic articles. One selected refractory material which will reduce the environmental impact of a furnace, chosen considering low heat capacity and high emissivity characteristics, is SiC. In this study, thermal radiation heat transfer efficiency improvement and its effect on ceramic articles in the furnace and oxidation behaviour were investigated at 1700K. A high density SiC refractory, built into the furnace at construction, has relatively high oxidation durability and has the ability to reduce environmental impact-CO2 by 10 percent by decreasing the furnace's energy load. However, new oxidation prevention techniques for SiC will be necessary for long-term use in industrial furnaces, because passive to active oxidation transition behaviour of commercial SiC refractory is coming to close ideal.

Solution Structures of Mycobacterium tuberculosis Thioredoxin C and Models of the Intact Thioredoxin System Suggest New Approaches to Inhibitor and Drug Design

PubMed Central

Olson, Andrew L.; Neumann, Terrence S.; Cai, Sheng; Sem, Daniel S.

2012-01-01

Here we report the NMR solution structures of Mycobacterium tuberculosis (M. tuberculosis) thioredoxin C in both oxidized and reduced states, with discussion of structural changes that occur in going between redox states. The NMR solution structure of the oxidized TrxC corresponds closely to that of the crystal structure, except in the C-terminal region. It appears that crystal packing effects have caused an artifactual shift in the α4 helix in the previously reported crystal structure, compared to the solution structure. Based on these TrxC structures, chemical shift mapping, a previously reported crystal structure of the M. tuberculosis thioredoxin reductase (not bound to a Trx) and structures for intermediates in the E. coli thioredoxin catalytic cycle, we have modeled the complete M. tuberculosis thioredoxin system for the various steps in the catalytic cycle. These structures and models reveal pockets at the TrxR/TrxC interface in various steps in the catalytic cycle, which can be targeted in the design of uncompetitive inhibitors as potential anti-mycobacterial agents, or as chemical genetic probes of function. PMID:23229911

Exploiting the Pleiotropic Antioxidant Effects of Established Drugs in Cardiovascular Disease

PubMed Central

Steven, Sebastian; Münzel, Thomas; Daiber, Andreas

2015-01-01

Cardiovascular disease is a leading cause of death and reduced quality of life worldwide. Arterial vessels are a primary target for endothelial dysfunction and atherosclerosis, which is accompanied or even driven by increased oxidative stress. Recent research in this field identified different sources of reactive oxygen and nitrogen species contributing to the pathogenesis of endothelial dysfunction. According to lessons from the past, improvement of endothelial function and prevention of cardiovascular disease by systemic, unspecific, oral antioxidant therapy are obviously too simplistic an approach. Source- and cell organelle-specific antioxidants as well as activators of intrinsic antioxidant defense systems might be more promising. Since basic research demonstrated the contribution of different inflammatory cells to vascular oxidative stress and clinical trials identified chronic inflammatory disorders as risk factors for cardiovascular events, atherosclerosis and cardiovascular disease are closely associated with inflammation. Therefore, modulation of the inflammatory response is a new and promising approach in the therapy of cardiovascular disease. Classical anti-inflammatory therapeutic compounds, but also established drugs with pleiotropic immunomodulatory abilities, demonstrated protective effects in various models of cardiovascular disease. However, results from ongoing clinical trials are needed to further evaluate the value of immunomodulation for the treatment of cardiovascular disease. PMID:26251902

Storage stability of screwpress-extracted oils and residual meals from CELSS candidate oilseed crops

NASA Astrophysics Data System (ADS)

Stephens, S. D.; Watkins, B. A.; Nielsen, S. S.

1997-01-01

The efficacy of using screwpress extraction for oil was studied with three Controlled Ecological Life-Support System (CELSS) candidate oilseed crops (soybean, peanut, and canola), since use of volatile organic solvents for oil extraction likely would be impractical in a closed system. Low oil yields from initial work indicated that a modification of the process is necessary to increase extraction efficiency. The extracted oil from each crop was tested for stability and sensory characteristics. When stored at 23 degC, canola oil and meal were least stable to oxidative rancidity, whereas peanut oil and meal were least stable to hydrolytic rancidity. When stored at 65 degC, soybean oil and canola meal were least stable to oxidative rancidity, whereas peanut oil and meal were least stable to hydrolytic rancidity. Sensory evaluation of the extracted oils used in bread and salad dressing indicated that flavor, odor intensity, acceptability, and overall preference may be of concern for screwpress-extracted canola oil when it is used in an unrefined form. Overall results with screwpress-extracted crude oils indicated that soybean oil may be more stable and acceptable than canola or peanut under typical storage conditions.

A Long-Term Cultivation of an Anaerobic Methane-Oxidizing Microbial Community from Deep-Sea Methane-Seep Sediment Using a Continuous-Flow Bioreactor

PubMed Central

Aoki, Masataka; Ehara, Masayuki; Saito, Yumi; Yoshioka, Hideyoshi; Miyazaki, Masayuki; Saito, Yayoi; Miyashita, Ai; Kawakami, Shuji; Yamaguchi, Takashi; Ohashi, Akiyoshi; Nunoura, Takuro; Takai, Ken; Imachi, Hiroyuki

2014-01-01

Anaerobic oxidation of methane (AOM) in marine sediments is an important global methane sink, but the physiological characteristics of AOM-associated microorganisms remain poorly understood. Here we report the cultivation of an AOM microbial community from deep-sea methane-seep sediment using a continuous-flow bioreactor with polyurethane sponges, called the down-flow hanging sponge (DHS) bioreactor. We anaerobically incubated deep-sea methane-seep sediment collected from the Nankai Trough, Japan, for 2,013 days in the bioreactor at 10°C. Following incubation, an active AOM activity was confirmed by a tracer experiment using 13C-labeled methane. Phylogenetic analyses demonstrated that phylogenetically diverse Archaea and Bacteria grew in the bioreactor. After 2,013 days of incubation, the predominant archaeal components were anaerobic methanotroph (ANME)-2a, Deep-Sea Archaeal Group, and Marine Benthic Group-D, and Gammaproteobacteria was the dominant bacterial lineage. Fluorescence in situ hybridization analysis showed that ANME-1 and -2a, and most ANME-2c cells occurred without close physical interaction with potential bacterial partners. Our data demonstrate that the DHS bioreactor system is a useful system for cultivating fastidious methane-seep-associated sedimentary microorganisms. PMID:25141130

Computational studies of the geometry and electronic structure of an all-inorganic and homogeneous tetra-Ru-polyoxotungstate catalyst for water oxidation and its four subsequent one-electron oxidized forms.

PubMed

Quiñonero, David; Kaledin, Alexey L; Kuznetsov, Aleksey E; Geletii, Yurii V; Besson, Claire; Hill, Craig L; Musaev, Djamaladdin G

2010-01-14

Geometry and electronic structure of five species [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](10-) (1), [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](9-) (2), [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](8-) (3), [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](7-) (4), and [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](6-) (5) with different oxidation states of Ru centers were studied at the density functional and COSMO levels of theory. These species are expected to be among the possible intermediates of the recently reported 1-catalyzed water oxidation (Geletii, Y. V.; Botar, B.; Kogerler, P.; Hillesheim, D. A.; Musaev, D. G.; Hill, C. L. Angew. Chem. Int. Ed. 2008, 47, 3896-3899 and Sartorel, A.; Carraro, M.; Scorrano, G.; Zorzi, R. D.; Geremia, S.; McDaniel, N. D.; Bernhard, S.; Bonchio, M. J. Am. Chem. Soc. 2008, 130, 5006-5007). It was shown that RI-BP86 correctly describes the geometry and energy of the low-lying electronic states of compound 1, whereas the widely used B3LYP approach overestimates the energy of its high-spin states. Including the solvent and/or countercation effects into calculations improves the agreement between the calculated and experimental data. It was found that the several HOMOs and LUMOs of the studied complexes are bonding and antibonding orbitals of the [Ru(4)O(4)(OH)(2)(H(2)O)(4)](6+) core, and four subsequent one-electron oxidations of 1, leading to formation of 2, 3, 4, and 5, respectively, involve only {Ru(4)} core orbitals. In other words, catalyst instability due to ligand oxidation in the widely studied Ru-blue dimer, [(bpy)(2)(O)Ru(V)-(mu-O)-Ru(V)(O)(bpy)(2)](4+), is not operable for 1: the latter all-inorganic catalyst is predicted to be stable under water oxidation turnover conditions. The calculated HOMOs and LUMOs of all the studied species are very close in energy and exhibit a "quasi-continuum" or "nanoparticle-type" electronic structure similar to that of nanosized transition metal clusters. This conclusion closely correlates with the experimentally reported oxidation and reduction features of 1 and explains the unusual linear dependence of oxidation potential versus charges for these compounds. The decrease in total negative charge of the system via 1 > 2 > 3 > 4 > 5, on average, decreases the {Ru(4)}-{SiW(10)} distance. It is predicted that at higher pH compound 1 will, initially, release protons from the mu-O(Ru) oxygen centers.

Wet-spun, porous, orientational graphene hydrogel films for high-performance supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Kou, Liang; Liu, Zheng; Huang, Tieqi; Zheng, Bingna; Tian, Zhanyuan; Deng, Zengshe; Gao, Chao

2015-02-01

Supercapacitors with porous electrodes of graphene macroscopic assembly are supposed to have high energy storage capacity. However, a great number of ``close pores'' in porous graphene electrodes are invalid because electrolyte ions cannot infiltrate. A quick method to prepare porous graphene electrodes with reduced ``close pores'' is essential for higher energy storage. Here we propose a wet-spinning assembly approach based on the liquid crystal behavior of graphene oxide to continuously spin orientational graphene hydrogel films with ``open pores'', which are used directly as binder-free supercapacitor electrodes. The resulting supercapacitor electrodes show better electrochemical performance than those with disordered graphene sheets. Furthermore, three reduction methods including hydrothermal treatment, hydrazine and hydroiodic acid reduction are used to evaluate the specific capacitances of the graphene hydrogel film. Hydrazine-reduced graphene hydrogel film shows the highest capacitance of 203 F g-1 at 1 A g-1 and maintains 67.1% specific capacitance (140 F g-1) at 50 A g-1. The combination of scalable wet-spinning technology and orientational structure makes graphene hydrogel films an ideal electrode material for supercapacitors.Supercapacitors with porous electrodes of graphene macroscopic assembly are supposed to have high energy storage capacity. However, a great number of ``close pores'' in porous graphene electrodes are invalid because electrolyte ions cannot infiltrate. A quick method to prepare porous graphene electrodes with reduced ``close pores'' is essential for higher energy storage. Here we propose a wet-spinning assembly approach based on the liquid crystal behavior of graphene oxide to continuously spin orientational graphene hydrogel films with ``open pores'', which are used directly as binder-free supercapacitor electrodes. The resulting supercapacitor electrodes show better electrochemical performance than those with disordered graphene sheets. Furthermore, three reduction methods including hydrothermal treatment, hydrazine and hydroiodic acid reduction are used to evaluate the specific capacitances of the graphene hydrogel film. Hydrazine-reduced graphene hydrogel film shows the highest capacitance of 203 F g-1 at 1 A g-1 and maintains 67.1% specific capacitance (140 F g-1) at 50 A g-1. The combination of scalable wet-spinning technology and orientational structure makes graphene hydrogel films an ideal electrode material for supercapacitors. Electronic supplementary information (ESI) available: The schematic diagram for fabricating graphene oxide hydrogel films, stress-strain curves and TGA curves of three GHFs, a digital photo of the test device for the two-electrode system, and comparison of the electrochemical performance of our GHF-HZ supercapacitors. See DOI: 10.1039/c4nr07038k

The catalytic behavior of precisely synthesized Pt–Pd bimetallic catalysts for use as diesel oxidation catalysts

DOE PAGES

Wong, Andrew P.; Kyriakidou, Eleni A.; Toops, Todd J.; ...

2016-04-17

The demands of stricter diesel engine emission regulations have created challenges for current exhaust systems. With advances in low-temperature internal combustion engines and their operations, advances must also be made in vehicle exhaust catalysts. Most current diesel oxidation catalysts use heavy amounts of precious group metals (PGMs) for hydrocarbon (HC), CO, and NO oxidation. These catalysts are expensive and are most often synthesized with poor bimetallic interaction and dispersion. In this paper, the goal was to study the effect of aging on diesel emission abatement of Pt–Pd bimetallic nanoparticles precisely prepared with different morphologies: well dispersed core–shell vs. well dispersedmore » homogeneously alloyed vs. poorly dispersed, poorly alloyed particles. Alumina and silica supports were studied. Particle morphology and dispersion were analyzed before and after hydrothermal treatments by XRD, EDX, and STEM. Reactivity as a function of aging was measured in simulated diesel engine exhaust. While carefully controlled bimetallic catalyst nanoparticle structure has a profound influence on initial or low temperature catalytic activity, the differences in behavior disappear with higher temperature aging as thermodynamic equilibrium is achieved. The metallic character of Pt-rich alumina-supported catalysts is such that behavior rather closely follows the Pt–Pd metal phase diagram. Nanoparticles disparately composed as well-dispersed core–shell (via seq-SEA), well-dispersed homogeneously alloyed (via co-SEA), and poorly dispersed, poorly alloyed (via co-DI) end up as well alloyed, large particles of almost the same size and activity. With Pd-rich systems, the oxidation of Pd also figures into the equilibrium, such that Pd-rich oxide phases appear in the high temperature forms along with alloyed metal cores. Finally, the small differences in activity after high temperature aging can be attributed to the synthesis methods, sequential SEA and co-DI which give rise, after aging, to a bimetallic surface enriched in Pd.« less

Intermixing and thermal oxidation of ZrO2 thin films grown on a-Si, SiN, and SiO2 by metallic and oxidic mode magnetron sputtering

NASA Astrophysics Data System (ADS)

Coloma Ribera, R.; van de Kruijs, R. W. E.; Sturm, J. M.; Yakshin, A. E.; Bijkerk, F.

2017-03-01

The initial growth of DC sputtered ZrO2 on top of a-Si, SiN, and SiO2 layers has been studied by in vacuo high-sensitivity low energy ion scattering for two gas deposition conditions with different oxygen contents (high-O and low-O conditions). This unique surface sensitive technique allowed the determination of surface composition and thicknesses required to close the ZrO2 layer on all three substrates for both conditions. The ZrO2 layer closes similarly on all substrates due to more favorable enthalpies of formation for ZrO2 and ZrSiO4, resulting in passivation of the Si from the substrate. However, this layer closes at about half of the thickness (˜1.7 nm) for low-O conditions due to less oxidative conditions and less energetic particles arriving at the sample, which leads to less intermixing via silicate formation. In contrast, for high-O conditions, there is more ZrSiO4 and/or SiOx formation, giving more intermixing (˜3.4 nm). In vacuo X-ray photoelectron spectroscopy (XPS) measurements revealed similar stoichiometric ZrO2 layers deposited by both conditions and a higher interaction of the ZrO2 layer with the underlying a-Si for high-O conditions. In addition, oxygen diffusion through low-O ZrO2 films on a-Si has been investigated by ex situ angular-resolved XPS of samples annealed in atmospheric oxygen. For temperatures below 400 °C, no additional oxidation of the underlying a-Si was observed. This, together with the amorphous nature and smoothness of these samples, makes ZrO2 a good candidate as an oxidation protective layer on top of a-Si.

Redox equilibria in hydroxylamine oxidoreductase. Electrostatic control of electron redistribution in multielectron oxidative processes.

PubMed

Kurnikov, Igor V; Ratner, Mark A; Pacheco, A Andrew

2005-02-15

We report results of continuum electrostatics calculations of the cofactor redox potentials, and of the titratable group pK(a) values, in hydroxylamine oxidoreductase (HAO). A picture of a sophisticated multicomponent control of electron flow in the protein emerged from the studies. First, we found that neighboring heme cofactors strongly interact electrostatically, with energies of 50-100 mV. Thus, cofactor redox potentials depend on the oxidation state of other cofactors, and cofactor redox potentials in the active (partially oxidized) enzyme differ substantially from the values obtained in electrochemical redox titration experiments. We found that, together, solvent-exposed heme 1 (having a large negative redox potential) and heme 2 (having a large positive redox potential) form a lock for electrons generated during the oxidation reaction The attachment of HAO's physiological electron transfer partner cytochrome c(554) results in a positive shift in the redox potential of heme 1, and "opens the electron gate". Electrons generated as a result of hydroxylamine oxidation travel to heme 3 and heme 8, which have redox potentials close to 0 mV versus NHE (this result is in partial disagreement with an existing experimental redox potential assignment). The closeness of hemes 3 and 8 from different enzyme subunits allows redistribution of the four electrons generated as a result of hydroxylamine oxidation, among the three enzyme subunits. For the multielectron oxidation process to be maximally efficient, the redox potentials of the electron-accepting cofactors should be roughly equal, and electrostatic interactions between extra electrons on these cofactors should be minimal. The redox potential assignments presented in the paper satisfy this general rule.

Oxidative and Anti-Oxidative Stress Markers in Chronic Glaucoma: A Systematic Review and Meta-Analysis

PubMed Central

Benoist d’Azy, Cédric; Pereira, Bruno; Chiambaretta, Frédéric

2016-01-01

Chronic glaucoma is a multifactorial disease among which oxidative stress may play a major pathophysiological role. We conducted a systematic review and meta-analysis to evaluate the levels of oxidative and antioxidative stress markers in chronic glaucoma compared with a control group. The PubMed, Cochrane Library, Embase and Science Direct databases were searched for studies reporting oxidative and antioxidative stress markers in chronic glaucoma and in healthy controls using the following keywords: “oxidative stress” or “oxidant stress” or “nitrative stress” or “oxidative damage” or “nitrative damage” or “antioxidative stress” or “antioxidant stress” or “antinitrative stress” and “glaucoma”. We stratified our meta-analysis on the type of biomarkers, the type of glaucoma, and the origin of the sample (serum or aqueous humor). We included 22 case-control studies with a total of 2913 patients: 1614 with glaucoma and 1319 healthy controls. We included 12 studies in the meta-analysis on oxidative stress markers and 19 on antioxidative stress markers. We demonstrated an overall increase in oxidative stress markers in glaucoma (effect size = 1.64; 95%CI 1.20–2.09), ranging from an effect size of 1.29 in serum (95%CI 0.84–1.74) to 2.62 in aqueous humor (95%CI 1.60–3.65). Despite a decrease in antioxidative stress marker in serum (effect size = –0.41; 95%CI –0.72 to –0.11), some increased in aqueous humor (superoxide dismutase, effect size = 3.53; 95%CI 1.20–5.85 and glutathione peroxidase, effect size = 6.60; 95%CI 3.88–9.31). The differences in the serum levels of oxidative stress markers between glaucoma patients and controls were significantly higher in primary open angle glaucoma vs primary angle closed glaucoma (effect size = 12.7; 95%CI 8.78–16.6, P < 0.001), and higher in pseudo-exfoliative glaucoma vs primary angle closed glaucoma (effect size = 12.2; 95%CI 8.96–15.5, P < 0.001). In conclusion, oxidative stress increased in glaucoma, both in serum and aqueous humor. Malonyldialdehyde seemed the best biomarkers of oxidative stress in serum. The increase of some antioxidant markers could be a protective response of the eye against oxidative stress. PMID:27907028

Photoionization of oxidized coenzyme Q in microemulsion: laser flash photolysis study in biomembrane-like system.

PubMed

Li, Kun; Wang, Mei; Wang, Jin; Zhu, Rongrong; Sun, Dongmei; Sun, Xiaoyu; Wang, Shi-Long

2013-01-01

Photoexcitation to generate triplet state has been proved to be the main photoreaction in homogeneous system for many benzoquinone derivatives, including oxidized coenzyme Q (CoQ) and its analogs. In the present study, microemulsion of CoQ, a heterogeneous system, is employed to mimic the distribution of CoQ in biomembrane. The photochemistry of CoQ(10) in microemulsion and cyclohexane is investigated and compared using laser flash photolysis and results show that CoQ(10) undergoes photoionization via a monophotonic process to generate radical cation of CoQ(10) in microemulsion and photoexcitation to generate excited triplet state in cyclohexane. Meanwhile, photoreactions of duroquinone (DQ) and CoQ(0) in microemulsion are also investigated to analyze the influence of molecular structure on the photochemistry of benzoquinone derivatives in microemulsion. Results suggest that photoexcitation, which is followed by excited state-involved hydrogen-abstraction reaction, is the main photoreaction for DQ and CoQ(0) in microemulsion. However, photoexcited CoQ(0) also leads to the formation of hydrated electrons. The isoprenoid side chain-involved high resonance stabilization is proposed to explain the difference in photoreactions of CoQ(0) and CoQ(10) in microemulsion. Considering that microemulsion is close to biomembrane system, its photoionization in microemulsion may be helpful to understand the real photochemistry of biological quinones in biomembrane system. © 2012 Tongji University. Photochemistry and Photobiology © 2012 The American Society of Photobiology.

Superconductivity in highly disordered dense carbon disulfide.

PubMed

Dias, Ranga P; Yoo, Choong-Shik; Struzhkin, Viktor V; Kim, Minseob; Muramatsu, Takaki; Matsuoka, Takahiro; Ohishi, Yasuo; Sinogeikin, Stanislav

2013-07-16

High pressure plays an increasingly important role in both understanding superconductivity and the development of new superconducting materials. New superconductors were found in metallic and metal oxide systems at high pressure. However, because of the filled close-shell configuration, the superconductivity in molecular systems has been limited to charge-transferred salts and metal-doped carbon species with relatively low superconducting transition temperatures. Here, we report the low-temperature superconducting phase observed in diamagnetic carbon disulfide under high pressure. The superconductivity arises from a highly disordered extended state (CS4 phase or phase III[CS4]) at ~6.2 K over a broad pressure range from 50 to 172 GPa. Based on the X-ray scattering data, we suggest that the local structural change from a tetrahedral to an octahedral configuration is responsible for the observed superconductivity.

The role of oxidative stress and antioxidants in male fertility

PubMed Central

Walczak–Jedrzejowska, Renata; Wolski, Jan Karol

2013-01-01

Oxidative stress results from the imbalance between production of the reactive oxygen species (ROS) and the protective effect of the antioxidant system responsible for their neutralization and removal. An excess of ROS causes a pathological reaction resulting in damage to cells and tissues. Spermatozoa are particularly vulnerable to the harmful effects of ROS. Oxidative stress affects their activity, damages DNA structure, and accelerates apoptosis, all of which consequently decrease their numbers, hinders motility and development of normal morphology, and impairs function. This leads to disturbances in fertility or embryo development disorder. The main cellular source of ROS in the semen are immature sperm cells and white blood cells. The increase in the number of leukocytes may be due to infection and inflammation, but can also be secondary to harmful environmental factors, long sexual abstinence, or varicocele. The protective antioxidant system in the semen is composed of enzymes, as well as nonenzymatic substances, which closely interact with each other to ensure optimal protection against ROS. Non–enzymatic antioxidants include vitamins A, E, C, and B complex, glutathione, pantothenic acid, coenzyme Q10 and carnitine, and micronutrients such as zinc, selenium, and copper. It seems that a deficiency of any of them can cause a decrease in total antioxidant status. In vitro and in vivo that studies demonstrate many antioxidants possess a beneficial effect on fertility and, therefore, their use is recommended as supportive therapy for the treatment of infertility in men. PMID:24578993

The role of oxidative stress and antioxidants in male fertility.

PubMed

Walczak-Jedrzejowska, Renata; Wolski, Jan Karol; Slowikowska-Hilczer, Jolanta

2013-01-01

Oxidative stress results from the imbalance between production of the reactive oxygen species (ROS) and the protective effect of the antioxidant system responsible for their neutralization and removal. An excess of ROS causes a pathological reaction resulting in damage to cells and tissues. Spermatozoa are particularly vulnerable to the harmful effects of ROS. Oxidative stress affects their activity, damages DNA structure, and accelerates apoptosis, all of which consequently decrease their numbers, hinders motility and development of normal morphology, and impairs function. This leads to disturbances in fertility or embryo development disorder. The main cellular source of ROS in the semen are immature sperm cells and white blood cells. The increase in the number of leukocytes may be due to infection and inflammation, but can also be secondary to harmful environmental factors, long sexual abstinence, or varicocele. The protective antioxidant system in the semen is composed of enzymes, as well as nonenzymatic substances, which closely interact with each other to ensure optimal protection against ROS. Non-enzymatic antioxidants include vitamins A, E, C, and B complex, glutathione, pantothenic acid, coenzyme Q10 and carnitine, and micronutrients such as zinc, selenium, and copper. It seems that a deficiency of any of them can cause a decrease in total antioxidant status. In vitro and in vivo that studies demonstrate many antioxidants possess a beneficial effect on fertility and, therefore, their use is recommended as supportive therapy for the treatment of infertility in men.

Illumina sequencing of fungi associated with manganese oxide deposits in cave systems

NASA Astrophysics Data System (ADS)

Zorn, B. T.; Santelli, C. M.; Carmichael, S. K.; Pepe-Ranney, C. P.; Roble, L.; Carmichael, M.; Bräuer, S.

2013-12-01

The environmental cycling of manganese (Mn) remains relatively poorly characterized when compared with other metals such as iron. However, fungi have been observed to produce Mn(III/IV) oxides resembling buserite, birnessite, and todorokite on the periphery of vegetative hyphae, hyphal branching points and at the base of fruiting bodies. Recent studies indicate that some of these oxides may be generated by a two-stage reaction with soluble Mn(II) and biogenic reactive oxygen species for some groups of fungi, in particular the Ascomycota. These oxides can provide a versatile protective barrier or aid in the capture of trace metals in the environment, although the exact evolutionary function and trigger is unclear. In this study, two caves in the southern Appalachians, a pristine cave and an anthropogenically impacted cave, were compared by analyzing fungal community assemblages in manganese oxide rich deposits. Quantitative PCR data indicated that fungi are present in a low abundance (<1%) in all locations sampled within the caves. Among amplified DNA sequences retrieved in an 18S rDNA clone library, over 88% were representative of the phylum Basidiomycota (predominantly Agaricomycetes), 2.74% of Ascomycota, 2.28% of Blastocladiomycota and Chytridiomycota, 0.46% of Zygomycota, and 3.65% of Eukarya or Fungi incertae sedis. Using Illumina's MiSeq to sequence amplicons of the fungal ITS1 gene has yielded roughly 100,000-200,000 paired-end reads per sample. These data are currently being analyzed to compare fungal communities before and after induced Mn oxidation in the field. In addition, sites within the pristine cave are being compared with analogous sites in the impacted cave. Culturing efforts have thus far yielded Mn oxide producing members of the orders Glomerales and Pleosporales as well as two Genus incertae sedis (Fungal sp. YECT1, and Fungal sp. YECT3, growing on discarded electrical tape) that do not appear to be closely related to any other known Mn oxidizing fungi.

Impact of Oxidative Dissolution on Black Shale Fracturing: Implication for Shale Fracturing Treatment Design

NASA Astrophysics Data System (ADS)

You, L.; Chen, Q.; Kang, Y.; Cheng, Q.; Sheng, J.

2017-12-01

Black shales contain a large amount of environment-sensitive compositions, e.g., clay minerals, carbonate, siderite, pyrite, and organic matter. There have been numerous studies on the black shales compositional and pore structure changes caused by oxic environments. However, most of the studies did not focus on their ability to facilitate shale fracturing. To test the redox-sensitive aspects of shale fracturing and its potentially favorable effects on hydraulic fracturing in shale gas reservoirs, the induced microfractures of Longmaxi black shales exposed to deionized water, hydrochloric acid, and hydrogen peroxide at room-temperature for 240 hours were imaged by scanning electron microscopy (SEM) and CT-scanning in this paper. Mineral composition, acoustic emission, swelling, and zeta potential of the untreated and oxidative treatment shale samples were also recorded to decipher the coupled physical and chemical effects of oxidizing environments on shale fracturing processes. Results show that pervasive microfractures (Fig.1) with apertures ranging from tens of nanometers to tens of microns formed in response to oxidative dissolution by hydrogen peroxide, whereas no new microfracture was observed after the exposure to deionized water and hydrochloric acid. The trajectory of these oxidation-induced microfractures was controlled by the distribution of phyllosilicate framework and flaky or stringy organic matter in shale. The experiments reported in this paper indicate that black shales present the least resistance to crack initiation and subcritical slow propagation in hydrogen peroxide, a process we refer to as oxidation-sensitive fracturing, which are closely related to the expansive stress of clay minerals, dissolution of redox-sensitive compositions, destruction of phyllosilicate framework, and the much lower zeta potential of hydrogen peroxide solution-shale system. It could mean that the injection of fracturing water with strong oxidizing aqueous solution may play an important role in improving hydraulic fracturing of shale formation by reducing the energy requirements for crack growth. However, additional work is needed to the selection of highly-effective, economical, and environmentally friendly oxidants.

Effect of short-term, high-dose methylprednisolone on oxidative stress in children with acute immune thrombocytopenia.

PubMed

Cura, Musa; Koç, Ahmet; Aksoy, Nurten; Özdemir, Zeynep Canan

2016-12-01

Immune thrombocytopenia (ITP) is the most common cause of acquired childhood thrombocytopenia and is characterized by increased immune-mediated destruction of circulating thrombocytes. Oxidative damage may be involved in ITP pathogenesis; paraoxonase (PON) and arylesterase (ARE) enzymes are closely associated with the cellular antioxidant system. We investigated the effect of short-term high-dose methylprednisolone (HDMP) treatment on the total oxidant status (TOS), total antioxidant capacity (TAC), oxidative stress index (OSI), and PON and ARE enzymatic activity in children with acute ITP. Thirty children with acute ITP constituted the study group and 30 healthy children constituted the control group. Children with acute ITP were treated with HDMP: 30 mg/kg for 3 days, then 20 mg/kg for 4 days. The TOS, TAC, OSI, PON, and ARE levels were determined before and after 7 days of HDMP treatment. The TAC level ( P <0.001), and PON ( P <0.001) and ARE (P=0.001) activities were lower and the TOS ( P =0.003) and OSI ( P <0.001) levels were higher in children with acute ITP than those in healthy children in the control group. We also observed statistically significant increases in the TAC ( P <0.01), PON ( P <0.001) and ARE levels ( P =0.001) and decreases in the TOS ( P <0.05) and OSI levels ( P <0.05) with 7 days of HDMP treatment compared to their values before treatment. Our study demonstrated increased oxidative stress (OSI and TOC) and decreased antioxidant capacity (TAC), PON, and ARE in ITP patients and that steroid treatment could be effective in reducing the oxidative stress.

Removal of PCDD/Fs, PCP and mercury from sediments: Thermal oxidation versus pyrolysis.

PubMed

Chang, Moo-Been; Hsu, Yen-Chen; Chang, Shu-Hao

2018-05-07

A continuous pilot-scale system (CPS) equipped with effective air pollution control devices (APCDs) is used for remediating the sediments contaminated with PCDD/Fs, PCP and Hg simultaneously. The removal efficiencies of these three pollutants in sediments collected from seawater pond and river, respectively, are evaluated via thermal treatment processes. PAHs and CBz formed during thermal oxidation and pyrolysis are also analyzed for better understanding the behaviors of chlorinated organic compounds. Experimental results indicate that low-molecular-weight PAHs are closely related to the formation of CBz, PCDD/Fs, and CPs, while low chlorinated PCDD/Fs and CBz are predominant in flue gas with thermal oxidation. However, the PM concentration is higher in thermal oxidation than pyrolysis due to the higher air flow rate of thermal oxidation. It may bring more particles out of the furnace and have a greater potential to form PCDD/Fs within APCDs. Besides, the high air flow also dilutes the Hg vapor in flue gas and would require more energy to condense and collect Hg with the quench tower. Furthermore, for removal of total amount of PCDD/Fs, pyrolysis is better than thermal oxidation. Thus, pyrolysis is more suitable for remediating the contaminated sediment. The removal efficiencies of PCDD/Fs, PCP and Hg in sediments achieved with pyrolysis increase with increasing operating temperature and retention time in CPS. Overall, the residual concentrations of PCDD/Fs and PCP in river sediment are higher than that in seawater-pond sediment since significant formation of tar is observed due to higher organic matter content in river sediment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Exploring the no-man's land between molecular nanomagnets and magnetic nanoparticles.

PubMed

Gatteschi, Dante; Fittipaldi, Maria; Sangregorio, Claudio; Sorace, Lorenzo

2012-05-14

The comparison of the structural and magnetic properties of molecular nanomagnets (MNM) and magnetic nanoparticles (MNP) can be instructive to get a deeper understanding of the magnetic behavior on the intermediate scale between molecular and bulk objects. In this respect iron oxo based clusters are particularly interesting, since they provide an increasing number of molecular systems with sizes close to that of iron oxide MNP. In this Minireview we report a survey of literature data aimed at improving our understanding of the emergence of MNP properties from MNM ones. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Source Term Experiments Project (STEP): Aerosol characterization system

NASA Astrophysics Data System (ADS)

Schlenger, B. J.; Dunn, P. F.

A series of four experiments is being conducted at Argonne National Laboratory's TREAT Reactor. They were designed to provide some of the necessary data regarding magnitude and release rates of fission products from degraded fuel pins, physical and chemical characteristics of released fission products, and aerosol formation and transport phenomena. These are in pile experiments, whereby the test fuel is heated by neutron induced fission and subsequent clad oxidation in steam environments that simulate as closely as practical predicted reactor accident conditions. The test sequences cover a range of pressure and fuel heatup rate, and include the effect of Aq/In/Cd control rod material.

Closeup View of the Space Shuttle Main Engine (SSME) 2044 ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Close-up View of the Space Shuttle Main Engine (SSME) 2044 mounted in a SSME Engine Handler in the SSME processing Facility at Kennedy Space Center. This view shows SSME 2044 with its expansion nozzle removed and an Engine Leak-Test Plug is set in the throat of the Main Combustion Chamber in the approximate center of the image, the insulated, High-Pressure Fuel Turbopump sits below that and the Low Pressure Oxidizer Turbopump Discharge Duct sits towards the top of the engine assembly in this view. - Space Transportation System, Space Shuttle Main Engine, Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Influence of nano-oxide layer on the giant magnetoresistance and exchange bias of NiMn/Co/Cu/Co spin valve sensors

NASA Astrophysics Data System (ADS)

Gupta, Anoop; Mohanan, Senthilnathan; Kinyanjui, Michael; Chuvilin, Andrey; Kaiser, Ute; Herr, Ulrich

2010-05-01

NiMn is an interesting material for achieving a high exchange bias in spin valve systems. We investigated the influence of a nano-oxide layer (NOL) inserted in the pinned Co layer on the magnetotransport properties of NiMn/Co/Cu/Co spin valve sensors. The samples were annealed at 350 °C for 10 min to achieve the antiferromagnetic L10 ordered structure of NiMn. The NOL has been characterized by small angle x-ray reflectivity, transmission electron microscopy (TEM), and energy filtered TEM. The inclusion of the NOL leads to an increase in the giant magnetoresistance (GMR) by 20 % indicating a high degree of specular reflection at the NOL. For NOL positions close to the NiMn/Co interface, a decrease in the exchange bias field (Hex) is observed. The best combination of high GMR value and large Hex was found when the NOL was inserted in the center of the pinned Co layer.

Cathodoluminescence Study of Hafnium Oxide

NASA Astrophysics Data System (ADS)

Purcell, Emily; Hengehold, Robert; McClory, John

2011-10-01

Hafnium dioxide (HfO2) is increasingly being used in place of silicon oxide as a gate insulator in field effect transistors. This is primarily due to its high dielectric constant, κ, of 25. Samples of HfO2 were grown by either atomic layer deposition (ALD) or pulsed laser deposition (PLD), with the PLD samples having assorted substrate temperatures during deposition (300 C, 500 C, and 750 C). Cathodoluminescence (CL) was chosen as the technique used for studying these HfO2 samples. The CL system used was capable of beam energies ranging from 1 keV to 20 keV and beam currents ranging from 10 μA to 50 μA. A Monte Carlo calculation using CASINO software was performed in order to determine the beam energy for the desired depth of penetration. Measurements were taken at sample temperatures ranging from 7K (closed cycled cryostat) to 300K (room temperature), as well as at various beam energies and beam currents. Comparison will be made between the PLD and ALD spectra.

Disappearance of nodal gap across the insulator-superconductor transition in a copper-oxide superconductor.

PubMed

Peng, Yingying; Meng, Jianqiao; Mou, Daixiang; He, Junfeng; Zhao, Lin; Wu, Yue; Liu, Guodong; Dong, Xiaoli; He, Shaolong; Zhang, Jun; Wang, Xiaoyang; Peng, Qinjun; Wang, Zhimin; Zhang, Shenjin; Yang, Feng; Chen, Chuangtian; Xu, Zuyan; Lee, T K; Zhou, X J

2013-01-01

The parent compound of the copper-oxide high-temperature superconductors is a Mott insulator. Superconductivity is realized by doping an appropriate amount of charge carriers. How a Mott insulator transforms into a superconductor is crucial in understanding the unusual physical properties of high-temperature superconductors and the superconductivity mechanism. Here we report high-resolution angle-resolved photoemission measurement on heavily underdoped Bi₂Sr₂-xLaxCuO(₆+δ) system. The electronic structure of the lightly doped samples exhibit a number of characteristics: existence of an energy gap along the nodal direction, d-wave-like anisotropic energy gap along the underlying Fermi surface, and coexistence of a coherence peak and a broad hump in the photoemission spectra. Our results reveal a clear insulator-superconductor transition at a critical doping level of ~0.10 where the nodal energy gap approaches zero, the three-dimensional antiferromagnetic order disappears, and superconductivity starts to emerge. These observations clearly signal a close connection between the nodal gap, antiferromagnetism and superconductivity.

Species-Specific Standard Redox Potential of Thiol-Disulfide Systems: A Key Parameter to Develop Agents against Oxidative Stress

NASA Astrophysics Data System (ADS)

Mirzahosseini, Arash; Noszál, Béla

2016-11-01

Microscopic standard redox potential, a new physico-chemical parameter was introduced and determined to quantify thiol-disulfide equilibria of biological significance. The highly composite, codependent acid-base and redox equilibria of thiols could so far be converted into pH-dependent, apparent redox potentials (E’°) only. Since the formation of stable metal-thiolate complexes precludes the direct thiol-disulfide redox potential measurements by usual electrochemical techniques, an indirect method had to be elaborated. In this work, the species-specific, pH-independent standard redox potentials of glutathione were determined primarily by comparing it to 1-methylnicotinamide, the simplest NAD+ analogue. Secondarily, the species-specific standard redox potentials of the two-electron redox transitions of cysteamine, cysteine, homocysteine, penicillamine, and ovothiol were determined using their microscopic redox equilibrium constants with glutathione. The 30 different, microscopic standard redox potential values show close correlation with the respective thiolate basicities and provide sound means for the development of potent agents against oxidative stress.

Antioxidant Systems are Regulated by Nitric Oxide-Mediated Post-translational Modifications (NO-PTMs)

PubMed Central

Begara-Morales, Juan C.; Sánchez-Calvo, Beatriz; Chaki, Mounira; Valderrama, Raquel; Mata-Pérez, Capilla; Padilla, María N.; Corpas, Francisco J.; Barroso, Juan B.

2016-01-01

Nitric oxide (NO) is a biological messenger that orchestrates a plethora of plant functions, mainly through post-translational modifications (PTMs) such as S-nitrosylation or tyrosine nitration. In plants, hundreds of proteins have been identified as potential targets of these NO-PTMs under physiological and stress conditions indicating the relevance of NO in plant-signaling mechanisms. Among these NO protein targets, there are different antioxidant enzymes involved in the control of reactive oxygen species (ROS), such as H2O2, which is also a signal molecule. This highlights the close relationship between ROS/NO signaling pathways. The major plant antioxidant enzymes, including catalase, superoxide dismutases (SODs) peroxiredoxins (Prx) and all the enzymatic components of the ascorbate-glutathione (Asa-GSH) cycle, have been shown to be modulated to different degrees by NO-PTMs. This mini-review will update the recent knowledge concerning the interaction of NO with these antioxidant enzymes, with a special focus on the components of the Asa-GSH cycle and their physiological relevance. PMID:26909095

Physical/chemical closed-loop water-recycling for long-duration missions

NASA Technical Reports Server (NTRS)

Herrmann, Cal C.; Wydeven, Ted

1990-01-01

Water needs, water sources, and means for recycling water are examined in terms appropriate to the water quality requirements of a small crew and spacecraft intended for long duration exploration missions. Inorganic, organic, and biological hazards are estimated for waste water sources. Sensitivities to these hazards for human uses are estimated. The water recycling processes considered are humidity condensation, carbon dioxide reduction, waste oxidation, distillation, reverse osmosis, pervaporation, electrodialysis, ion exchange, carbon sorption, and electrochemical oxidation. Limitations and applications of these processes are evaluated in terms of water quality objectives. Computerized simulation of some of these chemical processes is examined. Recommendations are made for development of new water recycling technology and improvement of existing technology for near term application to life support systems for humans in space. The technological developments are equally applicable to water needs on earth, in regions where extensive water ecycling is needed or where advanced water treatment is essential to meet EPA health standards.

A new aerobic chemolithoautotrophic arsenic oxidizing microorganism isolated from a high Andean watershed.

PubMed

Anguita, Javiera M; Rojas, Claudia; Pastén, Pablo A; Vargas, Ignacio T

2018-02-01

Biological arsenic oxidation has been suggested as a key biogeochemical process that controls the mobilization and fate of this metalloid in aqueous environments. To the best of our knowledge, only four aerobic chemolithoautotrophic arsenite-oxidizing (CAO) bacteria have been shown to grow via direct arsenic oxidation and to have the essential genes for chemolithoautotrophic arsenite oxidation. In this study, a new CAO bacterium was isolated from a high Andean watershed evidencing natural dissolved arsenic attenuation. The bacterial isolate, designated TS-1, is closely related to the Ancylobacter genus, in the Alphaproteobacteria class. Results showed that TS-1 has genes for arsenite oxidation and carbon fixation. The dependence of bacterial growth from arsenite oxidation was demonstrated. In addition, a mathematical model was suggested and the kinetic parameters were obtained by simultaneously fitting the biomass growth, arsenite depletion curves, and arsenate production. This research increases the knowledge of chemolithoautotrophic arsenic oxidizing microorganisms and its potential role as a driver for natural arsenic attenuation.

Manganese(II)-oxidizing Bacillus spores in Guaymas Basin hydrothermal sediments and plumes.

PubMed

Dick, Gregory J; Lee, Yifan E; Tebo, Bradley M

2006-05-01

Microbial oxidation and precipitation of manganese at deep-sea hydrothermal vents are important oceanic biogeochemical processes, yet nothing is known about the types of microorganisms or mechanisms involved. Here we report isolation of a number of diverse spore-forming Mn(II)-oxidizing Bacillus species from Guaymas Basin, a deep-sea hydrothermal vent environment in the Gulf of California, where rapid microbially mediated Mn(II) oxidation was previously observed. mnxG multicopper oxidase genes involved in Mn(II) oxidation were amplified from all Mn(II)-oxidizing Bacillus spores isolated, suggesting that a copper-mediated mechanism of Mn(II) oxidation could be important at deep-sea hydrothermal vents. Phylogenetic analysis of 16S rRNA and mnxG genes revealed that while many of the deep-sea Mn(II)-oxidizing Bacillus species are very closely related to previously recognized isolates from coastal sediments, other organisms represent novel strains and clusters. The growth and Mn(II) oxidation properties of these Bacillus species suggest that in hydrothermal sediments they are likely present as spores that are active in oxidizing Mn(II) as it emerges from the seafloor.

Experimental and Modeling Studies on the Microstructures and Properties of Oxidized Aluminum Nitride Ceramic Substrates

NASA Astrophysics Data System (ADS)

Cao, Ye; Xu, Haixian; Zhan, Jun; Zhang, Hao; Wei, Xin; Wang, Jianmin; Cui, Song; Tang, Wenming

2018-05-01

Oxidation of aluminum nitride (AlN) ceramic substrates doped with 2 wt.% Y2O3 was performed in air at temperatures ranging from 1000 to 1300 °C for various lengths of time. Microstructure, bending strength, and thermal conductivity of the oxidized AlN substrates were studied experimentally and also via mathematical models. The results show that the oxide layer formed on the AlN substrates is composed of α-Al2O3 nanocrystallines and interconnected micropores. Longitudinal and transverse cracks are induced in the oxide layer under tensile and shear stresses, respectively. Intergranular oxidation of the AlN grains close to the oxide layer/AlN interface also occurs, leading to widening and cracking of the AlN grain boundaries. These processes result in the monotonous degradation of bending strength and thermal conductivity of the oxidized AlN substrates. Two mathematic models concerning these properties of the oxidized AlN substrates versus the oxide layer thickness were put forward. They fit well with the experimental results.

49 CFR 177.838 - Class 4 (flammable solid) materials, Class 5 (oxidizing) materials, and Division 4.2 (pyroforic...

Code of Federal Regulations, 2011 CFR

2011-10-01

... closed; pick-up and delivery. All of that portion of the lading of any motor vehicle transporting Class 4... vehicle and shall be covered by such body, by tarpaulins, or other suitable means, and if such motor vehicle has a tailboard or tailgate, it shall be closed and secured in place during such transportation...

High morning blood pressure surge is associated with oxidative stress and paraoxonase 1 activity in newly diagnosed hypertensive patients.

PubMed

Kaypaklı, Onur; Gür, Mustafa; Harbalıoğlu, Hazar; Şeker, Taner; Selek, Şahabettin

Both oxidative stress and morning surge (MS) of blood pressure (BP) were found to be closely related with cardiovascular and cerebrovascular diseases. We investigated the association between MS of BP and oxidative stress in newly diagnosed hypertensive patients. We prospectively included 237 newly diagnosed hypertensive patients in the present study (mean age: 51.6 ± 11.7 years). The patients were classified according to the extent of the sleep-through surge as follows: the top decile of sleep-through surge (>47.2 mmHg, n = 27; EMShigh group), versus all others (n = 210, EMSlow group). Total antioxidant capacity (TAC) and total oxidant status (TOS) levels were determined by using an automated measurement method. The oxidative stress index (OSI) was calculated as the ratio of TOS to TAC. Serum paraoxonase 1 (PON-1) activity was measured spectrophotometrically. Patients in EMShigh group were found to have higher hs-CRP, TOS, and OSI values and lower TAC and PON-1 values (p < 0.01, for all). MS of BP was associated with hs-CRP, PON-1, TOS, TAC, and OSI levels in bivariate analysis. Multivariate linear regression analysis showed that MS of BP was significantly associated with PON-1(β = -0.206, p < 0.001), OSI (β = 0.602, p < 0.001) and hs-CRP (β = 0.210, p < 0.001). Present study shows that OSI is increased and antioxidant PON-1 activity is decreased in patients with enhanced MS of BP. There is a close association between high MS of BP and oxidative stress markers in newly diagnosed hypertensive patients.

Selective oxidation of benzyl alcohols to benzoic acid catalyzed by eco-friendly cobalt thioporphyrazine catalyst supported on silica-coated magnetic nanospheres.

PubMed

Li, Huan; Cao, Lan; Yang, Changjun; Zhang, Zhehui; Zhang, Bingguang; Deng, Kejian

2017-10-01

A novel magnetically recoverable thioporphyrazine catalyst (CoPz(S-Bu) 8 /SiO 2 @Fe 3 O 4 ) was prepared by immobilization of the cobalt octkis(butylthio) porphyrazine complex (CoPz(S-Bu) 8 ) on silica-coated magnetic nanospheres (SiO 2 @Fe 3 O 4 ). The composite CoPz(S-Bu) 8 /SiO 2 @Fe 3 O 4 appeared to be an active catalyst in the oxidation of benzyl alcohol in aqueous solution using hydrogen peroxide (H 2 O 2 ) as oxidant under Xe-lamp irradiation, with 36.4% conversion of benzyl alcohol, about 99% selectivity for benzoic acid and turnover number (TON) of 61.7 at ambient temperature. The biomimetic catalyst CoPz(S-Bu) 8 was supported on the magnetic carrier SiO 2 @Fe 3 O 4 so as to suspend it in aqueous solution to react with substrates, utilizing its lipophilicity. Meanwhile the CoPz(S-Bu) 8 can use its unique advantages to control the selectivity of photocatalytic oxidation without the substrate being subjected to deep oxidation. The influence of various reaction parameters on the conversion rate of benzyl alcohol and selectivity of benzoic acid was investigated in detail. Moreover, photocatalytic oxidation of substituted benzyl alcohols was obtained with high conversion and excellent selectivity, specifically conversion close to 70%, selectivity close to 100% and TON of 113.6 for para-position electron-donating groups. The selectivity and eco-friendliness of the biomimetic photocatalyst give it great potential for practical applications. Copyright © 2017. Published by Elsevier B.V.

Interfacing epitaxial oxides to gallium nitride

NASA Astrophysics Data System (ADS)

Losego, Mark Daniel

Molecular beam epitaxy (MBE) is lauded for its ability to control thin film material structures at the atomic level. This precision of control can improve performance of microelectronic devices and cultivate the development of novel device structures. This thesis explores the utility of MBE for designing interfaces between oxide epilayers and the wide band gap semiconductor gallium nitride (GaN). The allure of wide gap semiconductor microelectronics (like GaN, 3.4 eV) is their ability to operate at higher frequencies, higher powers, and higher temperatures than current semiconductor platforms. Heterostructures between ferroelectric oxides and GaN are also of interest for studying the interaction between GaN's fixed polarization and the ferroelectric's switchable polarization. Two major obstacles to successful integration of oxides with GaN are: (1) interfacial trap states; and (2) small electronic band offsets across the oxide/nitride interface due to the semiconductor's large band gap. For this thesis, epitaxial rocksalt oxide interfacial layers (˜8 eV band gap) are investigated as possible solutions to overcoming the challenges facing oxide integration with GaN. The cubic close-packed structure of rocksalt oxides forms a suitable epitaxial interface with the hexagonal close-packed wurtzite lattice of GaN. Three rocksalt oxide compounds are investigated in this thesis: MgO, CaO, and YbO. All are found to have a (111) MO || (0001) GaN; <1 10> MO || <11 20> GaN epitaxial relationship. Development of the epilayer microstructure is dominated by the high-energy polar growth surface (drives 3D nucleation) and the interfacial symmetry, which permits the formation of twin boundaries. Using STEM, strain relief for these ionicly bonded epilayers is observed to occur through disorder within the initial monolayer of growth. All rocksalt oxides demonstrate chemical stability with GaN to >1000°C. Concurrent MBE deposition of MgO and CaO is known to form complete solid solutions. By controlling the composition of these alloys, the oxide's lattice parameter can be engineered to match GaN and reduce interfacial state density. Compositional control is a universal challenge to oxide MBE, and the MgO-CaO system (MCO) is further complicated by magnesium's high volatility and the lack of a thermodynamically stable phase. Through a detailed investigation of MgO's deposition rate and subsequent impact on MCO composition, the process space for achieving lattice-matched compositions to GaN are fully mapped. Lattice-matched compositions are demonstrated to have the narrowest off-axis rocking curve widths ever reported for an epitaxial oxide deposited directly on GaN (0.7° in φ-circle for 200 reflection). Epitaxial deposition of the ferroelectric (Ba,Sr)TiO3 by hot RF sputtering on GaN surfaces is also demonstrated. Simple MOS capacitors are fabricated from epitaxial rocksalt oxides and (Ba,Sr)TiO3 layers deposited on n-GaN substrates. Current-voltage measurements reveal that BST epilayers have 5 orders of magnitude higher current leakage than rocksalt epilayers. This higher leakage is attributed to the smaller band offset expected at this interface; modeling confirms that electronic transport occurs by Schottky emission. In contrast, current transport across the rocksalt oxide/GaN interface occurs by Frenkel-Poole emission and can be reduced with pre-deposition surface treatments. Finally, through this work, it is realized that the integration of oxides with III-nitrides requires an appreciation of many different fields of research including materials science, surface science, and electrical engineering. By recognizing the importance that each of these fields play in designing oxide/III-nitride interfaces, this thesis has the opportunity to explore other related phenomena including accessing metastable phases through MBE (ytterbium monoxide), spinodal decomposition in metastable alloys (MCO), how polar surfaces grown by MBE compensate their bound surface charge, room temperature epitaxy, and the use of surface modification to achieve selective epitaxial deposition (SeEDed growth).

Binding of group 15 and group 16 oxides by a concave host containing an isophthalamide unit

PubMed Central

Eckelmann, Jens; Saggiomo, Vittorio; Fischmann, Svenja

2012-01-01

Summary A bi-macrocycle with an incorporated isophthalamide substructure was synthesized by double amide formation between an isophthaloyl dichloride and two equivalents of a bis(alkenyloxy)aniline, followed by ring-closing metathesis and hydrogenation. In contrast to many related isophthalamides, the concave host exhibits a better binding for oxides, such as DMSO or pyridine-N-oxide, than for halide anions. A general method for a quick estimation of the strength of binding derived from only a few data points is presented and gives an estimated K ass of pyridine-N-oxide of ca. 40 M−1, NMR titration confirms 25 M−1. PMID:22423268

Determination of the composition of HgCdTe oxide films by neutron activation analysis

NASA Astrophysics Data System (ADS)

Gnade, B.; Simmons, A.; Little, D.; Strong, R.

1987-04-01

The composition of HgCdTe oxides grown by anodic oxidation in a standard KOH/ethylene glycol solution has been determined by neutron activation analysis (NAA). This technique is not hindered by the difficulties normally associated with methods using ion beams or electron beams. Neutron activation analysis has the advantage of being quantitative, and also NAA is not affected by the chemical composition of the matrix. The analysis of the KOH/ethylene glycol oxide film by neutron activation yields Hg:Cd:Te ratios of 0.534:0.19:1, in close agreement with Rutherford backscattering spectroscopy analysis (R.L. Strong et al., J. Vac. Sci. Technol. A4 (4) (1986) 1992).

Pathway to oxide photovoltaics via band-structure engineering of SnO

DOE PAGES

Peng, Haowei; Bikowski, Andre; Zakutayev, Andriy; ...

2016-10-04

All-oxide photovoltaics could open rapidly scalable manufacturing routes, if only oxide materials with suitable electronic and optical properties were developed. SnO has exceptional doping and transport properties among oxides, but suffers from a strongly indirect band gap. Here, we address this shortcoming by band-structure engineering through isovalent but heterostructural alloying with divalent cations (Mg, Ca, Sr, and Zn). Furthermore, using first-principles calculations, we show that suitable band gaps and optical properties close to that of direct semiconductors are achievable, while the comparatively small effective masses are preserved in the alloys. Initial thin film synthesis and characterization support the feasibility ofmore » the approach.« less

Element exchange in a water-and gas-closed biological life support system

NASA Astrophysics Data System (ADS)

1997-01-01

Liquid human wastes and household water used for nutrition of wheat made possible to realize 24% closure for the mineral exchange in an experiment with a 2-component version of ``Bios-3'' life support system (LSS) Input-output balances of revealed, that elements (primarily trace elements) within the system. The structural materials (steel, titanium), expanded clay aggregate, and catalytic furnace catalysts. By the end of experiment, the permanent nutrient solution, plants, and the human diet gradually built up Ni, Cr, Al, Fe, V, Zn, Cu, and Mo. Thorough selection and pretreatment of materials can substantially reduce this accumulation. To enhance closure of the mineral exchange involves processing of human- metabolic wastes and inedible biomes inside LSS. An efficient method to oxidize wastes by hydrogen peroxide in a quartz reactor at the temperature of 80°C controlled electromagnetic field is proposed.

Element exchange in a water-and gas-closed biological life support system

NASA Astrophysics Data System (ADS)

Gribovskaya, I. V.; Kudenko, Yu. A.; Gitelson, J. I.

1997-01-01

Liquid human wastes and household water used for nutrition of wheat made possible to realize 24% closure for the mineral exchange in an experiment with a 2-component version of ``Bios-3'' life support system (LSS) Input-output balances of revealed, that elements (primarily trace elements) within the system. The structural materials (steel, titanium), expanded clay aggregate, and catalytic furnace catalysts. By the end of experiment, the permanent nutrient solution, plants, and the human diet gradually built up Ni, Cr, Al, Fe, V, Zn, Cu, and Mo. Thorough selection and pretreatment of materials can substantially reduce this accumulation. To enhance closure of the mineral exchange involves processing of human- metabolic wastes and inedible biomes inside LSS. An efficient method to oxidize wastes by hydrogen peroxide in a quartz reactor at the temperature of 80 degC controlled electromagnetic field is proposed.

Space Electrochemical Research and Technology

NASA Technical Reports Server (NTRS)

Wilson, Richard M. (Compiler)

1996-01-01

Individual papers presented at the conference address the following topics: development of a micro-fiber nickel electrode for nickel-hydrogen cell, high performance nickel electrodes for space power application, bending properties of nickel electrodes for nickel-hydrogen batteries, effect of KOH concentration and anions on the performance of a Ni-H2 battery positive plate, advanced dependent pressure vessel nickel hydrogen spacecraft cell and battery design, electrolyte management considerations in modern nickel hydrogen and nickel cadmium cell and battery design, a novel unitized regenerative proton exchange membrane fuel cell, fuel cell systems for first lunar outpost - reactant storage options, the TMI regenerable solid oxide fuel cell, engineering development program of a closed aluminum-oxygen semi-cell system for an unmanned underwater vehicle, SPE OBOGS on-board oxygen generating system, hermetically sealed aluminum electrolytic capacitor, sol-gel technology and advanced electrochemical energy storage materials, development of electrochemical supercapacitors for EMA applications, and high energy density electrolytic capacitor.

Multistep Oxidation of Diethynyl Oligophenylamine-Bridged Diruthenium and Diiron Complexes.

PubMed

Zhang, Jing; Guo, Shen-Zhen; Dong, Yu-Bao; Rao, Li; Yin, Jun; Yu, Guang-Ao; Hartl, František; Liu, Sheng Hua

2017-01-17

Homo-dinuclear nonlinear complexes [{M(dppe)Cp*} 2 {μ-(-C≡C) 2 X}] (dppe = 1,2-bis(diphenylphosphino)ethane; Cp* = η 5 -C 5 Me 5 ; X = triphenylamine (TPA), M = Ru (1a) and Fe (1b); X = N,N,N',N'-tetraphenylphenylene-1,4-diamine (TPPD), M = Ru (2a)) were prepared and characterized by 1 H, 13 C, and 31 P NMR spectroscopy and single-crystal X-ray diffraction (1a, 2a). Attempts to prepare the diiron analogue of 2a were not successful. Experimental data obtained from cyclic voltammetry, square wave voltammetry, UV-vis-NIR (NIR = near-infrared) spectro-electrochemistry, and very informative IR spectro-electrochemistry in the C≡C stretching region, combined with density functional theory calculations, afford to make an emphasizing assessment of the close association between the metal-ethynyl termini and the oligophenylamine bridge core as well as their respective involvement in sequential one-electron oxidations of these complexes. The anodic behavior of the homo-bimetallic complexes depends strongly both on the metal center and the length of the oligophenylamine bridge core. The poorly separated first two oxidations of diiron complex 1b are localized on the electronically nearly independent Fe termini. In contrast, diruthenium complex 1a exhibits a significantly delocalized character and a marked electronic communication between the ruthenium centers through the diethynyl-TPA bridge. The ruthenium-ethynyl halves in 2a, separated by the doubly extended and more flexible TPPD bridge core, show a lower degree of electronic coupling, resulting in close-lying first two anodic waves and the NIR electronic absorption of [2a] + with an indistinctive intervalence charge transfer character. Finally, the third anodic waves in the voltammetric responses of the homo-bimetallic complexes are associated with the concurrent exclusive oxidation of the TPA or TPPD bridge cores.

Petrogenesis and metallogenesis of the Wajilitag and Puchang Fe-Ti oxide-rich intrusive complexes, northwestern Tarim Large Igneous Province

NASA Astrophysics Data System (ADS)

Zhang, Dongyang; Zhang, Zhaochong; Huang, He; Cheng, Zhiguo; Charlier, Bernard

2018-04-01

The Wajilitag and Puchang intrusive complexes of the Tarim large igneous province (TLIP) are associated with significant resources of Fe-Ti oxide ores. These two mafic-ultramafic intrusions show differences in lithology and mineral chemistry. Clinopyroxenite and melagabbro are the dominant rock types in the Wajilitag complex, whereas the Puchang complex is generally gabbroic and anorthositic in composition with minor plagioclase-bearing clinopyroxenites in the marginal zone. Disseminated Fe-Ti oxide ores are found in the Wajilitag complex and closely associated with clinopyroxenites, whereas the Puchang complex hosts massive to disseminated Fe-Ti oxide ores mainly within its gabbroic rocks. The Wajilitag intrusive rocks are characterized by a restricted range of initial 87Sr/86Sr ratios (0.7038-0.7048) and positive εNd(t) (+0.04 - +3.01), indicating insignificant involvement of continental crustal contamination. The slightly higher initial 87Sr/86Sr ratios (0.7039-0.7059) and lower εNd(t) values (-1.05 - +2.35) of the Puchang intrusive rocks also suggest that the isotopic characteristics was controlled primarily by their mantle source, rather than by crustal contamination. Both complexes have Sr-Nd isotopic compositions close the neighboring kimberlitic rocks and their hosted mantle xenoliths in the TLIP. This indicates that the ferrobasaltic parental magmas were most probably originated from partial melting of a metasomatized subcontinental lithospheric mantle, modified recently with subduction-related materials by the impingement of the ascending mantle plume. The recycled subduction-related materials preserved in the lithospheric mantle could play a key role in the formation of the parental Fe-rich magmas in the context of an overall LIP system. The distinct variations in mineral assemblage for each complex and modeled results indicated that the Wajilitag and Puchang complexes experienced different crystallization path. Fe-Ti oxides in Wajilitag joined the liquidus earlier in the crystallization sequence, especially relative to the crystallization of plagioclase. This is attributed to the relatively high TFeO, TiO2 and initial H2O contents of the parental magma. In combination with definitive field and petrological evidence, the enrichment of highly incompatible elements (e.g., Zr, Hf, Nb and Ta) and the depletion of rare earth elements in the Fe-Ti oxide ores is consistent with the plausible interpretation that the ores could be formed by fractional crystallization and crystal accumulation of the Fe-Ti oxide crystals from the ferrobasaltic parental magmas. A considerable amount of the Fe-Ti oxides in the Puchang has transported and sunk from higher up in the chamber to the underlying unconsolidated silicate crystal pile. The highly dense Fe-Ti oxide crystal slurries further tended to effective accumulate Fe-Ti oxides to form high-grade Fe-Ti oxide ore bodies, and subsequent rapid collapse and intrusive into lower lithologies within the complex under a H2O-rich environment during the late-stage of magmatic differentiation. The development of massive Fe-Ti oxide ores in the case of the Puchang, could plausibly result from a combination of the protracted differentiation history of a Fe highly enriched parental magma and the later addition of external H2O from the country rocks (e.g., carbonates) to the slowly cooling magma chamber.

Exobiochemistry

NASA Technical Reports Server (NTRS)

Jones, Harry

2001-01-01

Exobiochemistry is the putative biochemistry of extraterrestrial life. It suggests the possible energy and material bases of extraterrestrial life and could help detect it. The diverse biochemistry of Earth indicates that a wide range of exobiochemistry is possible on other planets. An exobiochemistry will probably use the same energy sources as Earths ecology, light, biological organic material, and more rarely abiotic chemicals. Extraterrestrial life will be based on familiar chemical principles and probably capture, store, and release energy using oxidation-reduction reactions. Extraterrestrial life will give chemical indications of its existence. Key elements will be concentrated, stored, and recycled, altering their availability and isotopic composition. Any significant departure from chemical equilibrium would be good evidence for exobiochemistry, but an integrated system of departures from the expected equilibrium would be better. Exobiochemistry can be expected to include closed biogeochemical cycles of the major life supporting elements and may well show the complex dynamic close-coupled interactions that characterize the terrestrial biosphere. Terrestrial biochemistry provides a basis for generalization and extrapolation but it does not set bounds on exobiochemistry. In exobiochemistry we can expect: 1. closed chemical cycles that recycle materials, nutrients, and catalysts, 2. organisms with complementary metabolisms that cooperate to close the chemical cycles, 3. a high probability of a carbon and water chemistry, but some possibility of a non-carbon or non-water chemistry in extreme environments, and, 4. life similar to bacteria more prevalent than higher plants and animals.

Scope for improved eco-efficiency varies among diverse cropping systems.

PubMed

Carberry, Peter S; Liang, Wei-li; Twomlow, Stephen; Holzworth, Dean P; Dimes, John P; McClelland, Tim; Huth, Neil I; Chen, Fu; Hochman, Zvi; Keating, Brian A

2013-05-21

Global food security requires eco-efficient agriculture to produce the required food and fiber products concomitant with ecologically efficient use of resources. This eco-efficiency concept is used to diagnose the state of agricultural production in China (irrigated wheat-maize double-cropping systems), Zimbabwe (rainfed maize systems), and Australia (rainfed wheat systems). More than 3,000 surveyed crop yields in these three countries were compared against simulated grain yields at farmer-specified levels of nitrogen (N) input. Many Australian commercial wheat farmers are both close to existing production frontiers and gain little prospective return from increasing their N input. Significant losses of N from their systems, either as nitrous oxide emissions or as nitrate leached from the soil profile, are infrequent and at low intensities relative to their level of grain production. These Australian farmers operate close to eco-efficient frontiers in regard to N, and so innovations in technologies and practices are essential to increasing their production without added economic or environmental risks. In contrast, many Chinese farmers can reduce N input without sacrificing production through more efficient use of their fertilizer input. In fact, there are real prospects for the double-cropping systems on the North China Plain to achieve both production increases and reduced environmental risks. Zimbabwean farmers have the opportunity for significant production increases by both improving their technical efficiency and increasing their level of input; however, doing so will require improved management expertise and greater access to institutional support for addressing the higher risks. This paper shows that pathways for achieving improved eco-efficiency will differ among diverse cropping systems.

Scope for improved eco-efficiency varies among diverse cropping systems

PubMed Central

Carberry, Peter S.; Liang, Wei-li; Twomlow, Stephen; Holzworth, Dean P.; Dimes, John P.; McClelland, Tim; Huth, Neil I.; Chen, Fu; Hochman, Zvi; Keating, Brian A.

2013-01-01

Global food security requires eco-efficient agriculture to produce the required food and fiber products concomitant with ecologically efficient use of resources. This eco-efficiency concept is used to diagnose the state of agricultural production in China (irrigated wheat–maize double-cropping systems), Zimbabwe (rainfed maize systems), and Australia (rainfed wheat systems). More than 3,000 surveyed crop yields in these three countries were compared against simulated grain yields at farmer-specified levels of nitrogen (N) input. Many Australian commercial wheat farmers are both close to existing production frontiers and gain little prospective return from increasing their N input. Significant losses of N from their systems, either as nitrous oxide emissions or as nitrate leached from the soil profile, are infrequent and at low intensities relative to their level of grain production. These Australian farmers operate close to eco-efficient frontiers in regard to N, and so innovations in technologies and practices are essential to increasing their production without added economic or environmental risks. In contrast, many Chinese farmers can reduce N input without sacrificing production through more efficient use of their fertilizer input. In fact, there are real prospects for the double-cropping systems on the North China Plain to achieve both production increases and reduced environmental risks. Zimbabwean farmers have the opportunity for significant production increases by both improving their technical efficiency and increasing their level of input; however, doing so will require improved management expertise and greater access to institutional support for addressing the higher risks. This paper shows that pathways for achieving improved eco-efficiency will differ among diverse cropping systems. PMID:23671071

Mass exchange in an experimental new-generation life support system model based on biological regeneration of environment.

PubMed

Tikhomirov, A A; Ushakova, S A; Manukovsky, N S; Lisovsky, G M; Kudenko, Yu A; Kovalev, V S; Gubanov, V G; Barkhatov, Yu V; Gribovskaya, I V; Zolotukhin, I G; Gros, J B; Lasseur, Ch

2003-01-01

An experimental model of a biological life support system was used to evaluate qualitative and quantitative parameters of the internal mass exchange. The photosynthesizing unit included the higher plant component (wheat and radish), and the heterotrophic unit consisted of a soil-like substrate, California worms, mushrooms and microbial microflora. The gas mass exchange involved evolution of oxygen by the photosynthesizing component and its uptake by the heterotroph component along with the formation and maintaining of the SLS structure, growth of mushrooms and California worms, human respiration, and some other processes. Human presence in the system in the form of "virtual human" that at regular intervals took part in the respirative gas exchange during the experiment. Experimental data demonstrated good oxygen/carbon dioxide balance, and the closure of the cycles of these gases was almost complete. The water cycle was nearly 100% closed. The main components in the water mass exchange were transpiration water and the watering solution with mineral elements. Human consumption of the edible plant biomass (grains and roots) was simulated by processing these products by a unique physicochemical method of oxidizing them to inorganic mineral compounds, which were then returned into the system and fully assimilated by the plants. The oxidation was achieved by "wet combustion" of organic biomass, using hydrogen peroxide following a special procedure, which does not require high temperature and pressure. Hydrogen peroxide is produced from the water inside the system. The closure of the cycle was estimated for individual elements and compounds. Stoichiometric proportions are given for the main components included in the experimental model of the system. Approaches to the mathematical modeling of the cycling processes are discussed, using the data of the experimental model. Nitrogen, as a representative of biogenic elements, shows an almost 100% closure of the cycle inside the system. The proposed experimental model of a biological system is discussed as a candidate for potential application in the investigations aimed at creating ecosystems with largely closed cycles of the internal mass exchange. The formation and maintenance of sustainable cycling of vitally important chemical elements and compounds in biological life support systems (BLSS) is an extremely pressing problem. To attain the stable functioning of biological life support systems (BLSS) and to maintain a high degree of closure of material cycles in than, it is essential to understand the character of mass exchange processes and stoichiometnc proportions of the initial and synthesized components of the system. c2003 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

The transient oxidation of single crystal NiAl+Zr. M.S. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Doychak, J. K.

1983-01-01

The 800 C oxidation of oriented single crystals of Zr doped beta-NiAl was studied using transmission electron microscopy. The oxide phases and metal-oxide orientation relationships were determined to characterize the transient stages of oxidation prior to the transformation to or formation of alpha-Al2O3. On (001) and (012) metal orientations, NiAl2O4 was the first oxide to form followed by delta-Al2O3 which becomes the predominant oxide phase. All oxides were highly epitaxially related to the metal; the orientation relationships being function of parallel cation close-packed directions in the meta and oxide. On (011) and (111) metal orientations, gamma-Al2O3 became the predominant oxide phase rather than delta-Al2O3, indicating a structural stability from the highly epitaxial oxides. The relative concentration of aluminum in the oxide scales increased with time indicating preferential gamma-or delta-Al2O3 growth. The striking feature common to the orientation relationships is the alignment of 100 m and 110 ox directions, believed to result from the minimal 3 percent mismatch between the corresponding (100)m and (110)ox planes.

Arsenite and Ferrous Iron Oxidation Linked to Chemolithotrophic Denitrification for the Immobilization of Arsenic in Anoxic Environments

PubMed Central

Sun, Wenjie; Sierra-Alvarez, Reyes; Milner, Lily; Oremland, Ron; Field, Jim A.

2014-01-01

The objective of this study was to explore a bioremediation strategy based on injecting NO3− to support the anoxic oxidation of ferrous iron (Fe(II)) and arsenite (As(III)) in the subsurface as a means to immobilize As in the form of arsenate (As(V)) adsorbed onto biogenic ferric (Fe(III)) (hydr)oxides. Continuous flow sand filled columns were used to simulate a natural anaerobic groundwater and sediment system with co-occurring As(III) and Fe(II) in the presence (SF1) or absence (SF2) of nitrate, respectively. During operation for 250 days, the average influent arsenic concentration of 567 µg l−1 was reduced to 10.6 (±9.6) µg l−1 in the effluent of column SF1. The cumulative removal of Fe(II) and As(III) in SF1 was 6.5–10-fold higher than that in SF2. Extraction and measurement of the mass of iron and arsenic immobilized on the sand packing of the columns was close to the iron and arsenic removed from the aqueous phase during column operation. The dominant speciation of the immobilized iron and arsenic was Fe(III) and As(V) in SF1, compared with Fe(II) and As(III) in SF2. The speciation was confirmed by XRD and XPS. The results indicate that microbial oxidation of As(III) and Fe(II) linked to denitrification resulted in the enhanced immobilization of aqueous arsenic in anaerobic environments by forming Fe(III) (hydr)oxides coated sands with adsorbed As(V). PMID:19764221

A Theoretical Investigation of Oxidation Efficiency of a Volatile Removal Assembly Reactor Under Microgravity Conditions

NASA Technical Reports Server (NTRS)

Guo, Boyun

2005-01-01

Volatile Removal Assembly (VRA) is a subsystem of the Closed Environment Life Support System (CELSS) installed in the International Space Station. It is used for removing contaminants (volatile organics) in the wastewater produced by the space station crews. The major contaminants are formic acid, ethanol, and propylene glycol. The VRA contains a slim packbed reactor (3.5 cm diameter and four 28 cm long tubes in series) to perform catalyst oxidation of wastewater at elevated pressure and temperature under microgravity conditions. In the reactor, the contaminants are burned with oxygen gas (O2) to form water and carbon dioxide (CO2) that dissolves in the water stream. Optimal design of the reactor requires a thorough understanding about how the reactor performs under microgravity conditions. The objective of this study was to develop a mathematical model to interpret experimental data obtained from normal and microgravity conditions, and to predict the performance of VRA reactor under microgravity conditions. Catalyst oxidation kinetics and the total oxygen-water contact area control the efficiency of catalyst oxidation for mass transfer, which depends on oxygen gas holdup and distribution in the reactor. The process involves bubbly flow in porous media with chemical reactions in microgravity environment. This presents a unique problem in fluid dynamics that has not been studied. Guo et al. (2004) developed a mathematical model that predicts oxygen holdup in the VRA reactor. No mathematical model has been found in the literature that can be used to predict the efficiency of catalyst oxidation under microgravity conditions.

Systematic Identification of Promoters for Methane Oxidation Catalysts Using Size- and Composition-Controlled Pd-Based Bimetallic Nanocrystals.

PubMed

Willis, Joshua J; Goodman, Emmett D; Wu, Liheng; Riscoe, Andrew R; Martins, Pedro; Tassone, Christopher J; Cargnello, Matteo

2017-08-30

Promoters enhance the performance of catalytic active phases by increasing rates, stability, and/or selectivity. The process of identifying promoters is in most cases empirical and relies on testing a broad range of catalysts prepared with the random deposition of active and promoter phases, typically with no fine control over their localization. This issue is particularly relevant in supported bimetallic systems, where two metals are codeposited onto high-surface area materials. We here report the use of colloidal bimetallic nanocrystals to produce catalysts where the active and promoter phases are colocalized to a fine extent. This strategy enables a systematic approach to study the promotional effects of several transition metals on palladium catalysts for methane oxidation. In order to achieve these goals, we demonstrate a single synthetic protocol to obtain uniform palladium-based bimetallic nanocrystals (PdM, M = V, Mn, Fe, Co, Ni, Zn, Sn, and potentially extendable to other metal combinations) with a wide variety of compositions and sizes based on high-temperature thermal decomposition of readily available precursors. Once the nanocrystals are supported onto oxide materials, thermal treatments in air cause segregation of the base metal oxide phase in close proximity to the Pd phase. We demonstrate that some metals (Fe, Co, and Sn) inhibit the sintering of the active Pd metal phase, while others (Ni and Zn) increase its intrinsic activity compared to a monometallic Pd catalyst. This procedure can be generalized to systematically investigate the promotional effects of metal and metal oxide phases for a variety of active metal-promoter combinations and catalytic reactions.

Photolysis and oxidation of azidophenyl-substituted radicals: delocalization in heteroatom-based radicals.

PubMed

Serwinski, Paul R; Esat, Burak; Lahti, Paul M; Liao, Yi; Walton, Richard; Lan, Jiang

2004-08-06

2-(4-Azidophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (14), 2-(4-azidophenyl)benzimidazole-1-oxide-3-oxyl (16), 2-(4-azidophenyl)-1,2,6-triphenylverdazyl (19), 2-(3-azidophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (21), and (3-azidophenyl)-N-tert-butyl-N-aminoxyl (25) were photolyzed in frozen solution to give S = 3/2 state ESR spectra of the corresponding nitrenophenyl radicals with the following zero-field splitting parameters: |D/hc| = 0.277 cm(-1), |E/hc| < or = 0.002 cm(-1) (7 from 14); |D/hc| = 0.256 cm(-1), |E/hc| < or = 0.002 cm(-1) (8 from 16); |D/hc| = 0.288 cm(-1), |E/hc| < or = 0.002 cm(-1) (9 from 19); |D/hc| = 0.352 cm(-1), |E/hc| = 0.006 cm(-1) (10 from 21); |D/hc| = 0.336 cm(-1), |E/hc| = 0.004 cm(-1) (11 from 25). UB3LYP/6-31G computations and ESR spectroscopic analyses suggest that these are nitreno radicals, even para-linked systems with possible quinonoidal resonance forms. Neat samples of azidophenyl radicals 14 and 21 showed bulk paramagnetic behavior, consistent with the lack of close contacts in their crystal structures. Efforts to make photolabile coordination complexes of 14 and 21 with paramagnetic transition metal ions were unsuccessful: Cu(ClO4)2 x 6H2O instead oxidized them to the corresponding diamagnetic nitrosonium perchlorate salts. Copyright 2004 American Chemical Society

Laboratory Simulated Acid-Sulfate Weathering of Basaltic Materials: Implications for Formation of Sulfates at Meridiani Planum and Gusev Crater, Mars

NASA Technical Reports Server (NTRS)

Golden, D. C.; Ming, Douglas W.; Morris, Richard V.; Mertzman, A.

2006-01-01

Acid-sulfate weathering of basaltic materials is a candidate formation process for the sulfate-rich outcrops and rocks at the MER rover Opportunity and Spirit landing sites. To determine the style of acid-sulfate weathering on Mars, we weathered basaltic materials (olivine-rich glassy basaltic sand and plagioclase feldspar-rich basaltic tephra) in the laboratory under different oxidative, acid-sulfate conditions and characterized the alteration products. We investigated alteration by (1) sulfuric-acid vapor (acid fog), (2) three-step hydrothermal leaching treatment approximating an open system and (3) single-step hydrothermal batch treatment approximating a "closed system." In acid fog experiments, Al, Fe, and Ca sulfates and amorphous silica formed from plagioclase-rich tephra, and Mg and Ca sulfates and amorphous silica formed from the olivine-rich sands. In three-step leaching experiments, only amorphous Si formed from the plagioclase-rich basaltic tephra, and jarosite, Mg and Ca sulfates and amorphous silica formed from olivine-rich basaltic sand. Amorphous silica formed under single-step experiments for both starting materials. Based upon our experiments, jarosite formation in Meridiani outcrop is potential evidence for an open system acid-sulfate weathering regime. Waters rich in sulfuric acid percolated through basaltic sediment, dissolving basaltic phases (e.g., olivine) and forming jarosite, other sulfates, and iron oxides. Aqueous alteration of outcrops and rocks on the West Spur of the Columbia Hills may have occurred when vapors rich in SO2 from volcanic sources reacted with basaltic materials. Soluble ions from the host rock (e.g., olivine) reacted with S to form Ca-, Mg-, and other sulfates along with iron oxides and oxyhydroxides.

SLIP CASTING METHOD

DOEpatents

Allison, A.G.

1959-09-01

S>A process is described for preparing a magnesium oxide slip casting slurry which when used in conjunction with standard casting techniques results in a very strong "green" slip casting and a fired piece of very close dimensional tolerance. The process involves aging an aqueous magnestum oxide slurry, having a basic pH value, until it attains a specified critical viscosity at which time a deflocculating agent is added without upsetting the basic pH value.

Steric effects in the design of Co-Schiff base complexes for the catalytic oxidation of lignin models to para-benzoquinones

Treesearch

Berenger Biannic; Joseph J. Bozell; Thomas Elder

2014-01-01

New Co-Schiff base complexes that incorporate a sterically hindered ligand and an intramolecular bulky piperazine base in close proximity to the Co center are synthesized. Their utility as catalysts for the oxidation of para-substituted lignin model phenols with molecular oxygen is examined. Syringyl and guaiacyl alcohol, as models of S and G units in lignin, are...

Catalyst for carbon monoxide oxidation

NASA Technical Reports Server (NTRS)

Upchurch, Billy T. (Inventor); Miller, Irvin M. (Inventor); Brown, David R. (Inventor); Davis, Patricia (Inventor); Schryer, David R. (Inventor); Brown, Kenneth G. (Inventor); Vannorman, John D. (Inventor)

1990-01-01

A catalyst is disclosed for the combination of CO and O2 to form CO2, which includes a platinum group metal (e.g., platinum); a reducable metal oxide having multiple valence states (e.g., SnO2); and a compound which can bind water to its structure (e.g., silica gel). This catalyst is ideally suited for application to high-powered pulsed, CO2 lasers operating in a sealed or closed-cycle condition.

Catalyst for carbon monoxide oxidation

NASA Technical Reports Server (NTRS)

Upchurch, Billy T. (Inventor); Miller, Irvin M. (Inventor); Brown, David R. (Inventor); Davis, Patricia P. (Inventor); Schryer, David R. (Inventor); Brown, Kenneth G. (Inventor); Vannorman, John D. (Inventor)

1991-01-01

A catalyst for the combination of CO and O2 to form CO2 which includes a platinum group metal, e.g., platinum; a reducible metal oxide having mulitple valence states, e.g., SnO2; and a compound which can bind water to its structure, e.g., silica gel. This catalyst is ideally suited for application to high powered, pulsed, CO2 lasers operating in a sealed or closed cycle condition.

Redox-dependent open and closed forms of the active site of the bacterial respiratory nitric-oxide reductase revealed by cyanide binding studies.

PubMed

Grönberg, Karin L C; Watmough, Nicholas J; Thomson, Andrew J; Richardson, David J; Field, Sarah J

2004-04-23

The bacterial respiratory nitric-oxide reductase (NOR) catalyzes the respiratory detoxification of nitric oxide in bacteria and Archaea. It is a member of the well known super-family of heme-copper oxidases but has a [heme Fe-non-heme Fe] active site rather than the [heme Fe-Cu(B)] active site normally associated with oxygen reduction. Paracoccus denitrificans NOR is spectrally characterized by a ligand-to-metal charge transfer absorption band at 595 nm, which arises from the high spin ferric heme iron of a micro-oxo-bridged [heme Fe(III)-O-Fe(III)] active site. On reduction of the nonheme iron, the micro-oxo bridge is broken, and the ferric heme iron is hydroxylated or hydrated, depending on the pH. At present, the catalytic cycle of NOR is a matter of much debate, and it is not known to which redox state(s) of the enzyme nitric oxide can bind. This study has used cyanide to probe the nature of the active site in a number of different redox states. Our observations suggest that the micro-oxo-bridged [heme Fe(III)-O-Fe(III)] active site represents a closed or resting state of NOR that can be opened by reduction of the non-heme iron.

Origin of the Chemical and Kinetic Stability of Graphene Oxide

PubMed Central

Zhou, Si; Bongiorno, Angelo

2013-01-01

At moderate temperatures (≤ 70°C), thermal reduction of graphene oxide is inefficient and after its synthesis the material enters in a metastable state. Here, first-principles and statistical calculations are used to investigate both the low-temperature processes leading to decomposition of graphene oxide and the role of ageing on the structure and stability of this material. Our study shows that the key factor underlying the stability of graphene oxide is the tendency of the oxygen functionalities to agglomerate and form highly oxidized domains surrounded by areas of pristine graphene. Within the agglomerates of functional groups, the primary decomposition reactions are hindered by both geometrical and energetic factors. The number of reacting sites is reduced by the occurrence of local order in the oxidized domains, and due to the close packing of the oxygen functionalities, the decomposition reactions become – on average – endothermic by more than 0.6 eV. PMID:23963517

The effect of real-time aging on the oxidation and wear of highly cross-linked UHMWPE acetabular liners.

PubMed

Wannomae, Keith K; Christensen, Steven D; Freiberg, Andrew A; Bhattacharyya, Shayan; Harris, William H; Muratoglu, Orhun Kamil

2006-03-01

Irradiation decreases the wear of ultra-high molecular weight polyethylene (UHMWPE) but generates residual free radicals, precursors to long-term oxidation. Melting or annealing is used in quenching free radicals. We hypothesized that irradiated and once-annealed UHMWPE would oxidize while irradiated and melted UHMWPE would not, and that the oxidation in the former would increase wear. Acetabular liners were real-time aged by immersion in an aqueous environment that closely mimicked the temperature and oxygen concentration of synovial fluid. After 95 weeks of real-time aging, once-annealed components were oxidized; the melted components were not. The wear rate of the real-time aged irradiated and once-annealed components was higher than the literature reported values of other contemporary highly cross-linked UHMWPEs. Single annealing after irradiation used with terminal gamma sterilization may adversely affect the long-term oxidative stability of UHMWPE components.

Research on Oxidation Wear Behavior of a New Hot Forging Die Steel

NASA Astrophysics Data System (ADS)

Shi, Yuanji; Wu, Xiaochun

2018-01-01

Dry sliding tests for the hot forging die steel DM were performed in air under the test temperature at 400-700 °C and the time of 0.5-4 h by a UMT-3 high-temperature wear tester. The wear behavior and characteristics were studied systematically to explore the general characters in severe oxidation conditions. The results showed that a mild-to-severe oxidation wear transition occurred with an increase in the test temperature and duration. The reason was clarified as the unstable M6C carbides coarsening should be responsible for the severe delamination of tribo-oxide layer. More importantly, an intense oxidation wear with lower wear rates was found when the experimental temperature reaches 700 °C or after 4 h of test time at 600 °C, which was closely related to the degradation behavior during wear test. Furthermore, a new schematic diagram of oxidation wear of DM steel was proposed.

Origin of the chemical and kinetic stability of graphene oxide.

PubMed

Zhou, Si; Bongiorno, Angelo

2013-01-01

At moderate temperatures (≤ 70°C), thermal reduction of graphene oxide is inefficient and after its synthesis the material enters in a metastable state. Here, first-principles and statistical calculations are used to investigate both the low-temperature processes leading to decomposition of graphene oxide and the role of ageing on the structure and stability of this material. Our study shows that the key factor underlying the stability of graphene oxide is the tendency of the oxygen functionalities to agglomerate and form highly oxidized domains surrounded by areas of pristine graphene. Within the agglomerates of functional groups, the primary decomposition reactions are hindered by both geometrical and energetic factors. The number of reacting sites is reduced by the occurrence of local order in the oxidized domains, and due to the close packing of the oxygen functionalities, the decomposition reactions become - on average - endothermic by more than 0.6 eV.

Operation of staged membrane oxidation reactor systems

DOEpatents

Repasky, John Michael

2012-10-16

A method of operating a multi-stage ion transport membrane oxidation system. The method comprises providing a multi-stage ion transport membrane oxidation system with at least a first membrane oxidation stage and a second membrane oxidation stage, operating the ion transport membrane oxidation system at operating conditions including a characteristic temperature of the first membrane oxidation stage and a characteristic temperature of the second membrane oxidation stage; and controlling the production capacity and/or the product quality by changing the characteristic temperature of the first membrane oxidation stage and/or changing the characteristic temperature of the second membrane oxidation stage.

Competition for ammonia influences the structure of chemotrophic communities in geothermal springs.

PubMed

Hamilton, Trinity L; Koonce, Evangeline; Howells, Alta; Havig, Jeff R; Jewell, Talia; de la Torre, José R; Peters, John W; Boyd, Eric S

2014-01-01

Source waters sampled from Perpetual Spouter hot spring (pH 7.03, 86.4°C), Yellowstone National Park, WY, have low concentrations of total ammonia, nitrite, and nitrate, suggesting nitrogen (N) limitation and/or tight coupling of N cycling processes. Dominant small-subunit rRNA sequences in Perpetual Spouter source sediments are closely affiliated with the ammonia-oxidizing archaeon "Candidatus Nitrosocaldus yellowstonii" and the putatively nitrogen-fixing (diazotrophic) bacterium Thermocrinis albus, respectively, suggesting that these populations may interact at the level of the bioavailable N pool, specifically, ammonia. This hypothesis was evaluated by using a combination of geochemical, physiological, and transcriptomic analyses of sediment microcosms. Amendment of microcosms with allylthiourea, an inhibitor of ammonia oxidation, decreased rates of acetylene reduction (a proxy for N2 fixation) and nitrite production (a proxy for ammonia oxidation) and decreased transcript levels of structural genes involved in both nitrogen fixation (nifH) and ammonia oxidation (amoA). In contrast, amendment of microcosms with ammonia stimulated nitrite production and increased amoA transcript levels while it suppressed rates of acetylene reduction and decreased nifH transcript levels. Sequencing of amplified nifH and amoA transcripts from native sediments, as well as microcosms, at 2 and 4 h postamendment, indicates that the dominant and responsive populations involved in ammonia oxidation and N2 fixation are closely affiliated with Ca. Nitrosocaldus yellowstonii and T. albus, respectively. Collectively, these results suggest that ammonia-oxidizing archaea, such as Ca. Nitrosocaldus yellowstonii, have an apparent affinity for ammonia that is higher than that of the diazotrophs present in this ecosystem. Depletion of the bioavailable N pool through the activity of ammonia-oxidizing archaea likely represents a strong selective pressure for the inclusion of organisms capable of nitrogen fixation in geothermal communities. These observations help to explain the strong pattern in the codistribution of ammonia-oxidizing archaea and diazotrophs in circumneutral-to-alkaline geothermal springs.

Competition for Ammonia Influences the Structure of Chemotrophic Communities in Geothermal Springs

PubMed Central

Hamilton, Trinity L.; Koonce, Evangeline; Howells, Alta; Havig, Jeff R.; Jewell, Talia; de la Torre, José R.; Peters, John W.

2014-01-01

Source waters sampled from Perpetual Spouter hot spring (pH 7.03, 86.4°C), Yellowstone National Park, WY, have low concentrations of total ammonia, nitrite, and nitrate, suggesting nitrogen (N) limitation and/or tight coupling of N cycling processes. Dominant small-subunit rRNA sequences in Perpetual Spouter source sediments are closely affiliated with the ammonia-oxidizing archaeon “Candidatus Nitrosocaldus yellowstonii” and the putatively nitrogen-fixing (diazotrophic) bacterium Thermocrinis albus, respectively, suggesting that these populations may interact at the level of the bioavailable N pool, specifically, ammonia. This hypothesis was evaluated by using a combination of geochemical, physiological, and transcriptomic analyses of sediment microcosms. Amendment of microcosms with allylthiourea, an inhibitor of ammonia oxidation, decreased rates of acetylene reduction (a proxy for N2 fixation) and nitrite production (a proxy for ammonia oxidation) and decreased transcript levels of structural genes involved in both nitrogen fixation (nifH) and ammonia oxidation (amoA). In contrast, amendment of microcosms with ammonia stimulated nitrite production and increased amoA transcript levels while it suppressed rates of acetylene reduction and decreased nifH transcript levels. Sequencing of amplified nifH and amoA transcripts from native sediments, as well as microcosms, at 2 and 4 h postamendment, indicates that the dominant and responsive populations involved in ammonia oxidation and N2 fixation are closely affiliated with Ca. Nitrosocaldus yellowstonii and T. albus, respectively. Collectively, these results suggest that ammonia-oxidizing archaea, such as Ca. Nitrosocaldus yellowstonii, have an apparent affinity for ammonia that is higher than that of the diazotrophs present in this ecosystem. Depletion of the bioavailable N pool through the activity of ammonia-oxidizing archaea likely represents a strong selective pressure for the inclusion of organisms capable of nitrogen fixation in geothermal communities. These observations help to explain the strong pattern in the codistribution of ammonia-oxidizing archaea and diazotrophs in circumneutral-to-alkaline geothermal springs. PMID:24242238

Manganese oxide shuttling in pre-GOE oceans - evidence from molybdenum and iron isotopes

NASA Astrophysics Data System (ADS)

Kurzweil, Florian; Wille, Martin; Gantert, Niklas; Beukes, Nicolas J.; Schoenberg, Ronny

2016-10-01

The local occurrence of oxygen-rich shallow marine water environments has been suggested to significantly predate atmospheric oxygenation, which occurred during the Great Oxidation Event (GOE) ca. 2.4 billion years ago. However, the potential influence of such 'oxygen oases' on the mobility, distribution and isotopic composition of redox sensitive elements remains poorly understood. Here, we provide new molybdenum and iron isotopic data from shallow marine carbonate and silicate iron formations of the Koegas Subgroup, South Africa, that confirm local ocean redox stratification prior to the GOE. Mn concentrations correlate negatively with both δ98 Mo and δ56 Fe values, which highlights the substantial role of particulate manganese for the cycling of Mo and Fe in the Paleoproterozoic oceans. Based on these trends we propose that pore water molybdate was recharged (1) by the diffusional transport of seawater molybdate with high δ98 Mo and (2) by the re-liberation of adsorbed molybdate with low δ98 Mo during Mn oxide dissolution within the sediment. The relative contribution of isotopically light Mo is highest close to a Mn chemocline, where the flux of Mn oxides is largest, causing the negative correlation of Mn concentrations and δ98 Mo values in the Koegas sediments. The negative correlation between δ56 Fe values and Mn concentrations is likely related to Fe isotope fractionation during Fe(II) oxidation by Mn oxides, resulting in lower δ56 Fe values in the uppermost water column close to a Mn chemocline. We argue that the preservation of these signals within Paleoproterozoic sediments implies the existence of vertically extended chemoclines with a smoother gradient, probably as a result of low atmospheric oxygen concentrations. Furthermore, we suggest that abiotic oxidation of Fe(II) by a Mn oxide particle shuttle might have promoted the deposition of the Koegas iron formations.

Facile Routes To Improve Performance of Solution-Processed Amorphous Metal Oxide Thin Film Transistors by Water Vapor Annealing.

PubMed

Park, Won-Tae; Son, Inyoung; Park, Hyun-Woo; Chung, Kwun-Bum; Xu, Yong; Lee, Taegweon; Noh, Yong-Young

2015-06-24

Here, we report on a simple and high-rate oxidization method for producing solution-based compound mixtures of indium zinc oxide (IZO) and indium gallium zinc oxide (IGZO) metal-oxide semiconductors (MOS) for thin-film transistor (TFT) applications. One of the issues for solution-based MOS fabrication is how to sufficiently oxidize the precursor in order to achieve high performance. As the oxidation rate of solution processing is lower than vacuum-based deposition such as sputtering, devices using solution-processed MOS exhibit relatively poorer performance. Therefore, we propose a method to prepare the metal-oxide precursor upon exposure to saturated water vapor in a closed volume for increasing the oxidization efficiency without requiring additional oxidizing agent. We found that the hydroxide rate of the MOS film exposed to water vapor is lower than when unexposed (≤18%). Hence, we successfully fabricated oxide TFTs with high electron mobility (27.9 cm(2)/V·s) and established a rapid process (annealing at 400 °C for 5 min) that is much shorter than the conventional as-deposited long-duration annealing (at 400 °C for 1 h) whose corresponding mobility is even lower (19.2 cm(2)/V·s).

Phylogenetic analysis of the hyperthermophilic pink filament community in Octopus Spring, Yellowstone National Park

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reysenbach, A.L.; Wickham, G.S.; Pace, N.R.

1994-06-01

This study uses a molecular phylogenetic approach to characterize the pink filament community at the outflow of Octopus Spring in Yellowstone National Park. The temperature range of the spring is from 84 to 88 C. The authors show that the pink filaments are most closely related to the hydrogen-oxidizing bacterium Aquifex pyrophilus and a close relative Hydrogenobacter thermophilus. 38 refs., 4 figs., 1 tab.

Acute lung injury following refrigeration coil deicing.

PubMed

McKeown, Nathanael J; Burton, Brent T

2012-03-01

We report a case of a worker who developed ALI requiring mechanical ventilatory support after attempting to melt ice condensate by applying the flame of an oxy-acetylene torch to refrigeration coils charged with a halocarbon refrigerant in a closed environment. A discussion of possible etiologies are discussed, including phosgene, carbonyl fluoride, and nitrogen oxides. Primary prevention with adequate respiratory protection is recommended whenever deicing is performed in a closed space environment.

A Simple Experiment To Measure the Content of Oxygen in the Air Using Heated Steel Wool

ERIC Educational Resources Information Center

Vera, Francisco; Rivera, Rodrigo; Nunez, Cesar

2011-01-01

The typical experiment to measure the oxygen content in the atmosphere uses the rusting of steel wool inside a closed volume of air. Two key aspects of this experiment that make possible a successful measurement of the content of oxygen in the air are the use of a closed atmosphere and the use of a chemical reaction that involves the oxidation of…

Characterization of the glaze and in-glaze pigments of the nineteenth-century relief tiles from the Pena National Palace, Sintra, Portugal

NASA Astrophysics Data System (ADS)

Coutinho, M. L.; Veiga, J. P.; Alves, L. C.; Mirão, J.; Dias, L.; Lima, A. M.; Muralha, V. S.; Macedo, M. F.

2016-07-01

The glaze and in-glaze pigments of the historical nineteenth-century glazed tiles from the Pena National Palace (Sintra, Portugal) were characterized using a multi-analytical approach. Chemical composition and microstructural characterization were ascertained by µ-PIXE, µ-Raman, optical microscopy and VP-SEM-EDS. The manufacturing technique and colour palette in these tiles were found to be close to the ceramic pigments used in traditional majolica. The blue and purple colours derive from cobalt oxide and manganese oxide, respectively. A mixture of Pb-Sn-Sb yellow with cobalt oxide and iron oxide was used for green and dark yellow, respectively, while grey tonalities consist of a complex mixture of cobalt oxide, manganese oxide and Pb-Sn-Sb yellow in different proportions. Results obtained allowed the determination of the oxides and elements used in pigments as well as production techniques, resorting to traditional majolica manufacture, although the tiles were produced by the end of the nineteenth century.

Electrosynthesis of Biomimetic Manganese-Calcium Oxides for Water Oxidation Catalysis--Atomic Structure and Functionality.

PubMed

González-Flores, Diego; Zaharieva, Ivelina; Heidkamp, Jonathan; Chernev, Petko; Martínez-Moreno, Elías; Pasquini, Chiara; Mohammadi, Mohammad Reza; Klingan, Katharina; Gernet, Ulrich; Fischer, Anna; Dau, Holger

2016-02-19

Water-oxidizing calcium-manganese oxides, which mimic the inorganic core of the biological catalyst, were synthesized and structurally characterized by X-ray absorption spectroscopy at the manganese and calcium K edges. The amorphous, birnesite-type oxides are obtained through a simple protocol that involves electrodeposition followed by active-site creation through annealing at moderate temperatures. Calcium ions are inessential, but tune the electrocatalytic properties. For increasing calcium/manganese molar ratios, both Tafel slopes and exchange current densities decrease gradually, resulting in optimal catalytic performance at calcium/manganese molar ratios of close to 10 %. Tracking UV/Vis absorption changes during electrochemical operation suggests that inactive oxides reach their highest, all-Mn(IV) oxidation state at comparably low electrode potentials. The ability to undergo redox transitions and the presence of a minor fraction of Mn(III) ions at catalytic potentials is identified as a prerequisite for catalytic activity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polychromatic spectral pattern analysis of ultra-weak photon emissions from a human body.

PubMed

Kobayashi, Masaki; Iwasa, Torai; Tada, Mika

2016-06-01

Ultra-weak photon emission (UPE), often designated as biophoton emission, is generally observed in a wide range of living organisms, including human beings. This phenomenon is closely associated with reactive oxygen species (ROS) generated during normal metabolic processes and pathological states induced by oxidative stress. Application of UPE extracting the pathophysiological information has long been anticipated because of its potential non-invasiveness, facilitating its diagnostic use. Nevertheless, its weak intensity and UPE mechanism complexity hinder its use for practical applications. Spectroscopy is crucially important for UPE analysis. However, filter-type spectroscopy technique, used as a conventional method for UPE analysis, intrinsically limits its performance because of its monochromatic scheme. To overcome the shortcomings of conventional methods, the authors developed a polychromatic spectroscopy system for UPE spectral pattern analysis. It is based on a highly efficient lens systems and a transmission-type diffraction grating with a highly sensitive, cooled, charge-coupled-device (CCD) camera. Spectral pattern analysis of the human body was done for a fingertip using the developed system. The UPE spectrum covers the spectral range of 450-750nm, with a dominant emission region of 570-670nm. The primary peak is located in the 600-650nm region. Furthermore, application of UPE source exploration was demonstrated with the chemiluminescence spectrum of melanin and coexistence with oxidized linoleic acid. Copyright © 2016 Elsevier B.V. All rights reserved.

Evaluation of modeled cloud chemistry mechanism against laboratory irradiation experiments: The HxOy/iron/carboxylic acid chemical system

NASA Astrophysics Data System (ADS)

Long, Yoann; Charbouillot, Tiffany; Brigante, Marcello; Mailhot, Gilles; Delort, Anne-Marie; Chaumerliac, Nadine; Deguillaume, Laurent

2013-10-01

Currently, cloud chemistry models are including more detailed and explicit multiphase mechanisms based on laboratory experiments that determine such values as kinetic constants, stability constants of complexes and hydration constants. However, these models are still subject to many uncertainties related to the aqueous chemical mechanism they used. Particularly, the role of oxidants such as iron and hydrogen peroxide in the oxidative capacity of the cloud aqueous phase has typically never been validated against laboratory experimental data. To fill this gap, we adapted the M2C2 model (Model of Multiphase Cloud Chemistry) to simulate irradiation experiments on synthetic aqueous solutions under controlled conditions (e.g., pH, temperature, light intensity) and for actual cloud water samples. Various chemical compounds that purportedly contribute to the oxidative budget in cloud water (i.e., iron, oxidants, such as hydrogen peroxide: H2O2) were considered. Organic compounds (oxalic, formic and acetic acids) were taken into account as target species because they have the potential to form iron complexes and are good indicators of the oxidative capacity of the cloud aqueous phase via their oxidation in this medium. The range of concentrations for all of the chemical compounds evaluated was representative of in situ measurements. Numerical outputs were compared with experimental data that consisted of a time evolution of the concentrations of the target species. The chemical mechanism in the model describing the “oxidative engine” of the HxOy/iron (HxOy = H2O2, HO2rad /O2rad - and HOrad ) chemical system was consistent with laboratory measurements. Thus, the degradation of the carboxylic acids evaluated was closely reproduced by the model. However, photolysis of the Fe(C2O4)+ complex needs to be considered in cloud chemistry models for polluted conditions (i.e., acidic pH) to correctly reproduce oxalic acid degradation. We also show that iron and formic acid lead to a stable complex whose photoreactivity has currently not been investigated. The updated aqueous chemical mechanism was compared with data from irradiation experiments using natural cloud water. The new reactions considered in the model (i.e., iron complex formation with oxalic and formic acids) correctly reproduced the experimental observations.

Oxidative acylation using thioacids

NASA Technical Reports Server (NTRS)

Liu, R.; Orgel, L. E.

1997-01-01

Several important prebiotic reactions, including the coupling of amino acids into polypeptides by the formation of amide linkages, involve acylation. Theae reactions present a challenge to the understanding of prebiotic synthesis. Condensation reactions relying on dehydrating agents are either inefficient in aqueous solution or require strongly acidic conditions and high temperatures. Activated amino acids such as thioester derivatives have therefore been suggested as likely substrates for prebiotic peptide synthesis. Here we propose a closely related route to amide bond formation involving oxidative acylation by thioacids. We find that phenylalanine, leucine and phenylphosphate are acylated efficiently in aqueous solution by thioacetic acid and an oxidizing agent. From a prebiotic point of view, oxidative acylation has the advantage of proceeding efficiently in solution and under mild conditions. We anticipate that oxidative acylation should prove to be a general method for activating carboxylic acids, including amino acids.

Gum and deposit formation from jet turbine and diesel fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayo, F.R.; Lan, B.Y.

1983-09-01

The present paper describes measurements of rates of oxidation and soluble gum formation in both pure hydrocarbons and in mixed hydrocarbon fuels. Some patterns which appear can be explained on the basis of what is known about co-oxidation of hydrocarbon mixtures. The oxidations were conducted in an oil bath at 130/sup 0/C. Gum formation is closely associated with oxidation. The compounds that copolymerize with oxygen to produce polyperoxides require the least amount of oxygen to yield a mg of gum; among other pure hydrocarbons and fuels, the rates of gum formation and oxygen absorption decrease together. The most useful approachmore » to understanding and reducing gum and deposit formation will come through understanding the effects of condensed aromatic and heterocyclic compounds on the oxidation rates of fuels. 4 figures. 4 tables.« less

Oxidative Stress is Increased in Serum from Mexican Patients with Relapsing-Remitting Multiple Sclerosis

PubMed Central

Ortiz, Genaro Gabriel; Macías-Islas, Miguel Ángel; Pacheco-Moisés, Fermín P.; Cruz-Ramos, José A.; Sustersik, Silvia; Barba, Elías Alejandro; Aguayo, Adriana

2009-01-01

Objective: To determine the oxidative stress markers in serum from patients with relapsing-remitting multiple sclerosis. Methods: Blood samples from healthy controls and 22 patients 15 women (7 aged from 20 to 30 and 8 were > 40 years old) and 7 men (5 aged from 20 to 30 and 2 were > 40 years old) fulfilling the McDonald Criteria and classified as having Relapsing-Remitting Multiple Sclerosis accordingly with Lublin were collected for oxidative stress markers quantification. Results: Nitric oxide metabolites (nitrates/nitrites), lipid peroxidation products (malondialdehyde plus 4-hidroxialkenals), and glutathione peroxidase activity were significantly increased in serum of subjects with relapsing-remitting multiple sclerosis in comparison with that of healthy controls. These data support the hypothesis that multiple sclerosis is a component closely linked to oxidative stress. PMID:19242067

Biogenic Mn-Oxides in Subseafloor Basalts

PubMed Central

Ivarsson, Magnus; Broman, Curt; Gustafsson, Håkan; Holm, Nils G.

2015-01-01

The deep biosphere of the subseafloor basalts is recognized as a major scientific frontier in disciplines like biology, geology, and oceanography. Recently, the presence of fungi in these environments has involved a change of view regarding diversity and ecology. Here, we describe fossilized fungal communities in vugs in subseafloor basalts from a depth of 936.65 metres below seafloor at the Detroit Seamount, Pacific Ocean. These fungal communities are closely associated with botryoidal Mn oxides composed of todorokite. Analyses of the Mn oxides by Electron Paramagnetic Resonance spectroscopy (EPR) indicate a biogenic signature. We suggest, based on mineralogical, morphological and EPR data, a biological origin of the botryoidal Mn oxides. Our results show that fungi are involved in Mn cycling at great depths in the seafloor and we introduce EPR as a means to easily identify biogenic Mn oxides in these environments. PMID:26107948

Failure Investigation of an Intra-Manifold Explosion in a Horizontally-Mounted 870 lbf Reaction Control Thruster

NASA Technical Reports Server (NTRS)

Durning, Joseph G., III; Westover, Shayne C.; Cone, Darren M.

2011-01-01

In June 2010, an 870 lbf Space Shuttle Orbiter Reaction Control System Primary Thruster experienced an unintended shutdown during a test being performed at the NASA White Sands Test Facility. Subsequent removal and inspection of the thruster revealed permanent deformation and misalignment of the thruster valve mounting plate. Destructive evaluation determined that after three nominal firing sequences, the thruster had experienced an energetic event within the fuel (monomethylhydrazine) manifold at the start of the fourth firing sequence. The current understanding of the phenomenon of intra-manifold explosions in hypergolic bipropellant thrusters is documented in literature where it is colloquially referred to as a ZOT. The typical ZOT scenario involves operation of a thruster in a gravitational field with environmental pressures above the triple point pressure of the propellants. Post-firing, when the thruster valves are commanded closed, there remains a residual quantity of propellant in both the fuel and oxidizer (nitrogen tetroxide) injector manifolds known as the "dribble volume". In an ambient ground test configuration, these propellant volumes will drain from the injector manifolds but are impeded by the local atmospheric pressure. The evacuation of propellants from the thruster injector manifolds relies on the fluids vapor pressure to expel the liquid. The higher vapor pressure oxidizer will evacuate from the manifold before the lower vapor pressure fuel. The localized cooling resulting from the oxidizer boiling during manifold draining can result in fuel vapor migration and condensation in the oxidizer passage. The liquid fuel will then react with the oxidizer that enters the manifold during the next firing and may produce a localized high pressure reaction or explosion within the confines of the oxidizer injector manifold. The typical ZOT scenario was considered during this failure investigation, but was ultimately ruled out as a cause of the explosion. Converse to the typical ZOT failure mechanism, the failure of this particular thruster was determined to be the result of liquid oxidizer being present within the fuel manifold.

Genome-Guided Analysis of Clostridium ultunense and Comparative Genomics Reveal Different Strategies for Acetate Oxidation and Energy Conservation in Syntrophic Acetate-Oxidising Bacteria

PubMed Central

Manzoor, Shahid; Schnürer, Anna; Müller, Bettina

2018-01-01

Syntrophic acetate oxidation operates close to the thermodynamic equilibrium and very little is known about the participating organisms and their metabolism. Clostridium ultunense is one of the most abundant syntrophic acetate-oxidising bacteria (SAOB) that are found in engineered biogas processes operating with high ammonia concentrations. It has been proven to oxidise acetate in cooperation with hydrogenotrophic methanogens. There is evidence that the Wood-Ljungdahl (WL) pathway plays an important role in acetate oxidation. In this study, we analysed the physiological and metabolic capacities of C. ultunense strain Esp and strain BST on genome scale and conducted a comparative study of all the known characterised SAOB, namely Syntrophaceticus schinkii, Thermacetogenium phaeum, Tepidanaerobacter acetatoxydans, and Pseudothermotoga lettingae. The results clearly indicated physiological robustness to be beneficial for anaerobic digestion environments and revealed unexpected metabolic diversity with respect to acetate oxidation and energy conservation systems. Unlike S. schinkii and Th. phaeum, C. ultunense clearly does not employ the oxidative WL pathway for acetate oxidation, as its genome (and that of P. lettingae) lack important key genes. In both of those species, a proton motive force is likely formed by chemical protons involving putative electron-bifurcating [Fe-Fe] hydrogenases rather than proton pumps. No genes encoding a respiratory Ech (energy-converting hydrogenase), as involved in energy conservation in Th. phaeum and S. schinkii, were identified in C. ultunense and P. lettingae. Moreover, two respiratory complexes sharing similarities to the proton-translocating ferredoxin:NAD+ oxidoreductase (Rnf) and the Na+ pumping NADH:quinone hydrogenase (NQR) were predicted. These might form a respiratory chain that is involved in the reduction of electron acceptors rather than protons. However, involvement of these complexes in acetate oxidation in C. ultunense and P. lettingae needs further study. This genome-based comparison provides a solid platform for future meta-proteomics and meta-transcriptomics studies and for metabolic engineering, control, and monitoring of SAOB. PMID:29690652

Genome-Guided Analysis of Clostridium ultunense and Comparative Genomics Reveal Different Strategies for Acetate Oxidation and Energy Conservation in Syntrophic Acetate-Oxidising Bacteria.

PubMed

Manzoor, Shahid; Schnürer, Anna; Bongcam-Rudloff, Erik; Müller, Bettina

2018-04-23

Syntrophic acetate oxidation operates close to the thermodynamic equilibrium and very little is known about the participating organisms and their metabolism. Clostridium ultunense is one of the most abundant syntrophic acetate-oxidising bacteria (SAOB) that are found in engineered biogas processes operating with high ammonia concentrations. It has been proven to oxidise acetate in cooperation with hydrogenotrophic methanogens. There is evidence that the Wood-Ljungdahl (WL) pathway plays an important role in acetate oxidation. In this study, we analysed the physiological and metabolic capacities of C. ultunense strain Esp and strain BS T on genome scale and conducted a comparative study of all the known characterised SAOB, namely Syntrophaceticus schinkii , Thermacetogenium phaeum , Tepidanaerobacter acetatoxydans , and Pseudothermotoga lettingae . The results clearly indicated physiological robustness to be beneficial for anaerobic digestion environments and revealed unexpected metabolic diversity with respect to acetate oxidation and energy conservation systems. Unlike S. schinkii and Th. phaeum , C. ultunense clearly does not employ the oxidative WL pathway for acetate oxidation, as its genome (and that of P. lettingae ) lack important key genes. In both of those species, a proton motive force is likely formed by chemical protons involving putative electron-bifurcating [Fe-Fe] hydrogenases rather than proton pumps. No genes encoding a respiratory Ech (energy-converting hydrogenase), as involved in energy conservation in Th. phaeum and S. schinkii, were identified in C. ultunense and P. lettingae . Moreover, two respiratory complexes sharing similarities to the proton-translocating ferredoxin:NAD⁺ oxidoreductase (Rnf) and the Na⁺ pumping NADH:quinone hydrogenase (NQR) were predicted. These might form a respiratory chain that is involved in the reduction of electron acceptors rather than protons. However, involvement of these complexes in acetate oxidation in C. ultunense and P. lettingae needs further study. This genome-based comparison provides a solid platform for future meta-proteomics and meta-transcriptomics studies and for metabolic engineering, control, and monitoring of SAOB.

A protective role for nitric oxide and salicylic acid for arsenite phytotoxicity in rice (Oryza sativa L.).

PubMed

Singh, Amit Pal; Dixit, Garima; Kumar, Amit; Mishra, Seema; Kumar, Navin; Dixit, Sameer; Singh, Pradyumna Kumar; Dwivedi, Sanjay; Trivedi, Prabodh Kumar; Pandey, Vivek; Dhankher, Om Prakash; Norton, Gareth J; Chakrabarty, Debasis; Tripathi, Rudra Deo

2017-06-01

Nitric oxide (NO) and salicylic acid (SA) are important signaling molecules in plant system. In the present study both NO and SA showed a protective role against arsenite (As III ) stress in rice plants when supplied exogenously. The application of NO and SA alleviated the negative impact of As III on plant growth. Nitric oxide supplementation to As III treated plants greatly decreased arsenic (As) accumulation in the roots as well as shoots/roots translocation factor. Arsenite exposure in plants decreased the endogenous levels of NO and SA. Exogenous supplementation of SA not only enhanced endogenous level of SA but also the level of NO through enhanced nitrate reductase (NR) activity, whether As III was present or not. Exogenously supplied NO decreased the NR activity and level of endogenous NO. Arsenic accumulation was positively correlated with the expression level of OsLsi1, a transporter responsible for As III uptake. The endogenous level of NO and SA were positively correlated to each other either when As III was present or not. This close relationship indicates that NO and SA work in harmony to modulate the signaling response in As III stressed plants. Copyright © 2017. Published by Elsevier Masson SAS.

Rapid Evaporation of Water on Graphene/Graphene-Oxide: A Molecular Dynamics Study.

PubMed

Li, Qibin; Xiao, Yitian; Shi, Xiaoyang; Song, Shufeng

2017-09-07

To reveal the mechanism of energy storage in the water/graphene system and water/grapheme-oxide system, the processes of rapid evaporation of water molecules on the sheets of graphene and graphene-oxide are investigated by molecular dynamics simulations. The results show that both the water/graphene and water/grapheme-oxide systems can store more energy than the pure water system during evaporation. The hydroxyl groups on the surface of graphene-oxide are able to reduce the attractive interactions between water molecules and the sheet of graphene-oxide. Also, the radial distribution function of the oxygen atom indicates that the hydroxyl groups affect the arrangement of water molecules at the water/graphene-oxide interface. Therefore, the capacity of thermal energy storage of the water/graphene-oxide system is lower than that of the water/graphene system, because of less desorption energy at the water/graphene-oxide interface. Also, the evaporation rate of water molecules on the graphene-oxide sheet is slower than that on the graphene sheet. The Leidenfrost phenomenon can be observed during the evaporation process in the water/grapheme-oxide system.

Rapid Evaporation of Water on Graphene/Graphene-Oxide: A Molecular Dynamics Study

PubMed Central

Li, Qibin; Xiao, Yitian; Shi, Xiaoyang; Song, Shufeng

2017-01-01

To reveal the mechanism of energy storage in the water/graphene system and water/grapheme-oxide system, the processes of rapid evaporation of water molecules on the sheets of graphene and graphene-oxide are investigated by molecular dynamics simulations. The results show that both the water/graphene and water/grapheme-oxide systems can store more energy than the pure water system during evaporation. The hydroxyl groups on the surface of graphene-oxide are able to reduce the attractive interactions between water molecules and the sheet of graphene-oxide. Also, the radial distribution function of the oxygen atom indicates that the hydroxyl groups affect the arrangement of water molecules at the water/graphene-oxide interface. Therefore, the capacity of thermal energy storage of the water/graphene-oxide system is lower than that of the water/graphene system, because of less desorption energy at the water/graphene-oxide interface. Also, the evaporation rate of water molecules on the graphene-oxide sheet is slower than that on the graphene sheet. The Leidenfrost phenomenon can be observed during the evaporation process in the water/grapheme-oxide system. PMID:28880207

Nickel/metal hydride secondary batteries using an alkaline solid polymer electrolyte

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vassal, N.; Salmon, E.; Fauvarque, J.F.

1999-01-01

Sealed alkaline solid polymer electrolyte nickel/metal hydride laboratory cells have been constructed and tested to evaluate their properties. Studies of the cycle life, self-discharge, and behavior of cells at different temperatures were carried out. The first results on the electrochemical behavior of an alkaline solid polymer electrolyte [based on poly(ethylene oxide), potassium hydroxide, and water] medium are presented here and show good reversibility of this all-solid-state system for more than 500 cycles, without significant loss of capacity and with a reasonable average discharge efficiency (close to 80%). The temperature-dependence study allowed the determination of optimum operating conditions between 0 andmore » 40 C. Characteristics of the solid polymer electrolyte based Ni/MH cells are compared to those of several other rechargeable battery systems.« less

Apparatus for producing nanoscale ceramic powders

DOEpatents

Helble, Joseph J.; Moniz, Gary A.; Morse, Theodore F.

1997-02-04

An apparatus provides high temperature and short residence time conditions for the production of nanoscale ceramic powders. The apparatus includes a confinement structure having a multiple inclined surfaces for confining flame located between the surfaces so as to define a flame zone. A burner system employs one or more burners to provide flame to the flame zone. Each burner is located in the flame zone in close proximity to at least one of the inclined surfaces. A delivery system disposed adjacent the flame zone delivers an aerosol, comprising an organic or carbonaceous carrier material and a ceramic precursor, to the flame zone to expose the aerosol to a temperature sufficient to induce combustion of the carrier material and vaporization and nucleation, or diffusion and oxidation, of the ceramic precursor to form pure, crystalline, narrow size distribution, nanophase ceramic particles.

Apparatus for producing nanoscale ceramic powders

DOEpatents

Helble, Joseph J.; Moniz, Gary A.; Morse, Theodore F.

1995-09-05

An apparatus provides high temperature and short residence time conditions for the production of nanoscale ceramic powders. The apparatus includes a confinement structure having a multiple inclined surfaces for confining flame located between the surfaces so as to define a flame zone. A burner system employs one or more burners to provide flame to the flame zone. Each burner is located in the flame zone in close proximity to at least one of the inclined surfaces. A delivery system disposed adjacent the flame zone delivers an aerosol, comprising an organic or carbonaceous carrier material and a ceramic precursor, to the flame zone to expose the aerosol to a temperature sufficient to induce combustion of the carrier material and vaporization and nucleation, or diffusion and oxidation, of the ceramic precursor to form pure, crystalline, narrow size distribution, nanophase ceramic particles.

Superconductivity in highly disordered dense carbon disulfide

PubMed Central

Dias, Ranga P.; Yoo, Choong-Shik; Struzhkin, Viktor V.; Kim, Minseob; Muramatsu, Takaki; Matsuoka, Takahiro; Ohishi, Yasuo; Sinogeikin, Stanislav

2013-01-01

High pressure plays an increasingly important role in both understanding superconductivity and the development of new superconducting materials. New superconductors were found in metallic and metal oxide systems at high pressure. However, because of the filled close-shell configuration, the superconductivity in molecular systems has been limited to charge-transferred salts and metal-doped carbon species with relatively low superconducting transition temperatures. Here, we report the low-temperature superconducting phase observed in diamagnetic carbon disulfide under high pressure. The superconductivity arises from a highly disordered extended state (CS4 phase or phase III[CS4]) at ∼6.2 K over a broad pressure range from 50 to 172 GPa. Based on the X-ray scattering data, we suggest that the local structural change from a tetrahedral to an octahedral configuration is responsible for the observed superconductivity. PMID:23818624

Novel aquatic modules for bioregenerative life-support systems based on the closed equilibrated biological aquatic system (c.e.b.a.s.)

NASA Astrophysics Data System (ADS)

Bluem, Volker; Paris, Frank

2002-06-01

The closed equilibrated biological aquatic system (C.E.B.A.S) is a man-made aquatic ecosystem which consists of four subcomponents: an aquatic animal habitat, an aquatic plant bioreactor, an ammonia oxidizing bacteria filter and a data acquisition/control unit. It is a precursor for different types of fish and aquatic plant production sites which are disposed for the integration into bioregenerative life-support systems. The results of two successful spaceflights of a miniaturized C.E.B.A.S version (the C.E.B.A.S. MINI MODULE) allow the optimization of aquatic food production systems which are already developed in the ground laboratory and open new aspects for their utilization as aquatic modules in space bioregenerative life support systems. The total disposition offers different stages of complexity of such aquatic modules starting with simple but efficient aquatic plant cultivators which can be implemented into water recycling systems and ending up in combined plant/fish aquaculture in connection with reproduction modules and hydroponics applications for higher land plants. In principle, aquaculture of fishes and/or other aquatic animals edible for humans offers optimal animal protein production under lowered gravity conditions without the tremendous waste management problems connected with tetrapod breeding and maintenance. The paper presents details of conducted experimental work and of future dispositions which demonstrate clearly that aquaculture is an additional possibility to combine efficient and simple food production in space with water recycling utilizing safe and performable biotechnologies. Moreover, it explains how these systems may contribute to more variable diets to fulfill the needs of multicultural crews.

Thaumarchaeotes abundant in refinery nitrifying sludges express amoA but are not obligate autotrophic ammonia oxidizers

PubMed Central

Mußmann, Marc; Brito, Ivana; Pitcher, Angela; Sinninghe Damsté, Jaap S.; Hatzenpichler, Roland; Richter, Andreas; Nielsen, Jeppe L.; Nielsen, Per Halkjær; Müller, Anneliese; Daims, Holger; Wagner, Michael; Head, Ian M.

2011-01-01

Nitrification is a core process in the global nitrogen cycle that is essential for the functioning of many ecosystems. The discovery of autotrophic ammonia-oxidizing archaea (AOA) within the phylum Thaumarchaeota has changed our perception of the microbiology of nitrification, in particular since their numerical dominance over ammonia-oxidizing bacteria (AOB) in many environments has been revealed. These and other data have led to a widely held assumption that all amoA-encoding members of the Thaumarchaeota (AEA) are autotrophic nitrifiers. In this study, 52 municipal and industrial wastewater treatment plants were screened for the presence of AEA and AOB. Thaumarchaeota carrying amoA were detected in high abundance only in four industrial plants. In one plant, thaumarchaeotes closely related to soil group I.1b outnumbered AOB up to 10,000-fold, and their numbers, which can only be explained by active growth in this continuous culture system, were two to three orders of magnitude higher than could be sustained by autotrophic ammonia oxidation. Consistently, 14CO2 fixation could only be detected in AOB but not in AEA in actively nitrifying sludge from this plant via FISH combined with microautoradiography. Furthermore, in situ transcription of archaeal amoA, and very weak in situ labeling of crenarchaeol after addition of 13CO2, was independent of the addition of ammonium. These data demonstrate that some amoA-carrying group I.1b Thaumarchaeota are not obligate chemolithoautotrophs. PMID:21930919

The emerging role of skeletal muscle oxidative metabolism as a biological target and cellular regulator of cancer-induced muscle wasting.

PubMed

Carson, James A; Hardee, Justin P; VanderVeen, Brandon N

2016-06-01

While skeletal muscle mass is an established primary outcome related to understanding cancer cachexia mechanisms, considerable gaps exist in our understanding of muscle biochemical and functional properties that have recognized roles in systemic health. Skeletal muscle quality is a classification beyond mass, and is aligned with muscle's metabolic capacity and substrate utilization flexibility. This supplies an additional role for the mitochondria in cancer-induced muscle wasting. While the historical assessment of mitochondria content and function during cancer-induced muscle loss was closely aligned with energy flux and wasting susceptibility, this understanding has expanded to link mitochondria dysfunction to cellular processes regulating myofiber wasting. The primary objective of this article is to highlight muscle mitochondria and oxidative metabolism as a biological target of cancer cachexia and also as a cellular regulator of cancer-induced muscle wasting. Initially, we examine the role of muscle metabolic phenotype and mitochondria content in cancer-induced wasting susceptibility. We then assess the evidence for cancer-induced regulation of skeletal muscle mitochondrial biogenesis, dynamics, mitophagy, and oxidative stress. In addition, we discuss environments associated with cancer cachexia that can impact the regulation of skeletal muscle oxidative metabolism. The article also examines the role of cytokine-mediated regulation of mitochondria function, followed by the potential role of cancer-induced hypogonadism. Lastly, a role for decreased muscle use in cancer-induced mitochondrial dysfunction is reviewed. Copyright © 2015 Elsevier Ltd. All rights reserved.

Determination of fast ozone oxidation rate for textile dyes by using a continuous quench-flow system.

PubMed

Gomes, Arlindo C; Nunes, José C; Simões, Rogério M S

2010-06-15

To study the fast kinetic decolourisation of textile dyes by ozone a continuous quench-flow system was used. This system has not been used before for these purposes. Reaction times in the range of 7-3000 ms were explored. The reaction was quenched with potassium iodide, which proved to be very effective, and the indigo method was used to follow the ozone concentration. Dyes from the most representative chemical classes currently used in the textile industry, i.e. azo and anthraquinone, were selected. Using the initial slope method, the effect of dye and ozone concentrations was researched and the kinetic equations thus established. Using tert-butyl alcohol, as radical scavenger, and pH close to 2.5, the second-order rate constant of the reactant dyes at 280 K varies in the range of 1.20x10(4)-7.09x10(5)M(-1)s(-1); the Acid Orange 7 exhibiting thus its lowest value, the Acid Blue 45 its highest value and the Acid Green 25 and 27 and Direct Yellow 4 intermediate values (approximately 1.6x10(5)M(-1)s(-1)). Without radical scavenger and the pH close to 4, the reaction rate increases one order of magnitude, but, on the reverse, the efficiency of ozone to decolourisation decreases. Copyright 2010 Elsevier B.V. All rights reserved.

Selective Oxidation and Ammoxidation of Olefins by Heterogeneous Catalysis.

ERIC Educational Resources Information Center

Grasselli, Robert K.

1986-01-01

Shows how the ammoxidation of olefins can be understood in terms of free radicals and surface bound organometallic intermediates. Also illustrates the close intellectual relationships between heterogeneous catalysis and organometallic chemistry. (JN)

76 FR 64090 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-17

... Special Emphasis Panel, Oxidative Stress, Aging, and Transmitters. Date: November 9-10, 2011. Time: 8 a.m...: Center for Scientific Review Special Emphasis Panel, Fellowships: Physiology and Pathobiology of...

Process for thermochemically producing hydrogen

DOEpatents

Bamberger, Carlos E.; Richardson, Donald M.

1976-01-01

Hydrogen is produced by the reaction of water with chromium sesquioxide and strontium oxide. The hydrogen producing reaction is combined with other reactions to produce a closed chemical cycle for the thermal decomposition of water.

Plutonium storage criteria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, D.; Ascanio, X.

1996-05-01

The Department of Energy has issued a technical standard for long-term (>50 years) storage and will soon issue a criteria document for interim (<20 years) storage of plutonium materials. The long-term technical standard, {open_quotes}Criteria for Safe Storage of Plutonium Metals and Oxides,{close_quotes} addresses the requirements for storing metals and oxides with greater than 50 wt % plutonium. It calls for a standardized package that meets both off-site transportation requirements, as well as remote handling requirements from future storage facilities. The interim criteria document, {open_quotes}Criteria for Interim Safe Storage of Plutonium-Bearing Solid Materials{close_quotes}, addresses requirements for storing materials with less thanmore » 50 wt% plutonium. The interim criteria document assumes the materials will be stored on existing sites, and existing facilities and equipment will be used for repackaging to improve the margin of safety.« less

The Energetics of Oxide Multilayer Systems: SOFC Cathode and Electrolyte Materials

NASA Astrophysics Data System (ADS)

Kemik, Nihan

Complex oxides are evoking a surge of scientific and technological interest due to the unexpected properties of their interfaces which have been shown to differ from the constituent materials. Layered oxide structures have found wide use in applications ranging from electronic and magnetic devices to solid oxide fuel cells (SOFCs). For devices such as SOFCs which utilize multilayers at elevated temperatures, it is critical to know the relative stabilities of these interfaces since they directly influence the device performance. In this work, we explored the energetics of two oxide multilayer systems which are relevant for SOFCs components using high temperature solution calorimetry and differential scanning calorimetry (DSC). The fundamental understanding of the interfacial and structural properties of multilayers combined with the information about phase stabilities is essential in materials selection for components for intermediate temperature SOFC's. For cathode materials, we investigated the family of perovskite oxides, La0.7Sr0.3MO3, where M=Mn and Fe, as well as their solid solution phase. Manganites have been the most investigated cathode material, while the ferrites are also being considered for future use due to their thermodynamic stability and close thermal expansion coefficient with the commonly used electrolyte materials. For the bulk La0.7Sr0.3FexMn1-xO 3 solid solution, high temperature oxide melt drop solution calorimetry was performed to determine the enthalpies of formation from binary oxides and the enthalpy of mixing. It was shown that the symmetry of the perovskite structure, the valence of transition metal, and the energetics are highly interdependent and the balance between the different valence states of the Mn and Fe ions is the main factor in determining the energetics. The energetics of interfaces in multilayered structures was investigated by high temperature oxide melt solution calorimetry for the first time. The drop solution calorimetry results of La0.7Sr0.3MnO3(LSMO)/La0.7 Sr0.3FeO3(LSFO) multilayers and LSMO film are highly exothermic and differ from the bulk material with the same composition. The magnetic and electronic properties of LSMO/LSFO superlattices are highly dependent on the thickness and the structure of the individual layers. Resonant X-Ray reflectivity (XRR) technique was utilized to characterize the structure of the LSMO/LSFO superlattices. It was shown that the XRR spectra taken at the Mn and Fe absorption edges can provide more structural information than the spectra at the X-ray energy of a conventional Cu source. With this non-destructive technique, we demonstrated the ability to compare the intermixing behavior and thickness regularity throughout the thickness of different superlattice structures. For electrolyte materials, we studied the yttria stabilized zirconia (YSZ) /Al2O3 multilayer system. Differential scanning calorimetry (DSC) was used to study the crystallization of the YSZ layers to explore the effect of the interfaces on phase stabilities. It was observed that the crystallization temperature increased and the enthalpy became more exothermic as the interfacial area increased. This work demonstrated that DSC is a promising technique to study the thin film reactions and explore the interfacial enthalpies in oxide multilayer systems.

Microstructural characterization of the cycling behavior of electrodeposited manganese oxide supercapacitors using 3D electron tomography

NASA Astrophysics Data System (ADS)

Dalili, N.; Clark, M. P.; Davari, E.; Ivey, D. G.

2016-10-01

Manganese oxide has been investigated extensively as an electrochemical capacitor or supercapacitor electrode material. Manganese oxide is inexpensive to fabricate and exhibits relatively high capacitance values, i.e., in excess of 200 F g-1 in many cases; the actual value depends very much on the fabrication method and test conditions. The cycling behavior of Mn oxide, fabricated using anodic electrodeposition, is investigated using slice and view techniques, via a dual scanning electron microscope (SEM) and focused ion beam (FIB) instrument to generate three-dimensional (3D) images, coupled with electrochemical characterization. The initial as-fabricated electrode has a rod-like appearance, with a fine-scale, sheet-like morphology within the rods. The rod-like structure remains after cycling, but there are significant morphological changes. These include partial dissolution of Mn oxide followed by redeposition of Mn oxide in regions close to the substrate. The redeposited material has a finer morphology than the original as-fabricated Mn oxide. The Mn oxide coverage is also better near the substrate. These effects result in an increase in the specific capacitance.

Culture-Independent Identification of Manganese-Oxidizing Genes from Deep-Sea Hydrothermal Vent Chemoautotrophic Ferromanganese Microbial Communities Using a Metagenomic Approach

NASA Astrophysics Data System (ADS)

Davis, R.; Tebo, B. M.

2013-12-01

Microbial activity has long been recognized as being important to the fate of manganese (Mn) in hydrothermal systems, yet we know very little about the organisms that catalyze Mn oxidation, the mechanisms by which Mn is oxidized or the physiological function that Mn oxidation serves in these hydrothermal systems. Hydrothermal vents with thick ferromanganese microbial mats and Mn oxide-coated rocks observed throughout the Pacific Ring of Fire are ideal models to study the mechanisms of microbial Mn oxidation, as well as primary productivity in these metal-cycling ecosystems. We sampled ferromanganese microbial mats from Vai Lili Vent Field (Tmax=43°C) located on the Eastern Lau Spreading Center and Mn oxide-encrusted rhyolytic pumice (4°C) from Niua South Seamount on the Tonga Volcanic Arc. Metagenomic libraries were constructed and assembled from these samples and key genes known to be involved in Mn oxidation and carbon fixation pathways were identified in the reconstructed genomes. The Vai Lili metagenome assembled to form 121,157 contiguous sequences (contigs) greater than 1000bp in length, with an N50 of 8,261bp and a total metagenome size of 593 Mbp. Contigs were binned using an emergent self-organizing map of tetranucleotide frequencies. Putative homologs of the multicopper Mn-oxidase MnxG were found in the metagenome that were related to both the Pseudomonas-like and Bacillus-like forms of the enzyme. The bins containing the Pseudomonas-like mnxG genes are most closely related to uncultured Deltaproteobacteria and Chloroflexi. The Deltaproteobacteria bin appears to be an obligate anaerobe with possible chemoautotrophic metabolisms, while the Chloroflexi appears to be a heterotrophic organism. The metagenome from the Mn-stained pumice was assembled into 122,092 contigs greater than 1000bp in length with an N50 of 7635 and a metagenome size of 385 Mbp. Both forms of mnxG genes are present in this metagenome as well as the genes encoding the putative Mn oxidases McoA and MopA. The greater diversity of Mn oxidase pathways in this metagenome suggests a more diverse Mn oxidizing microbial community in the cold pumice sample. Key enzymes for four of the six known carbon fixation pathways (the Calvin Cycle, the reductive TCA cycle, the Wood-Ljungdahl pathway, and the 3-hydroxypropionate/4-hydroxybutyrate Cycle) were also identified in both samples indicating primary production occurs via a diverse community of carbon fixing organisms. Together, these samples contain active, diverse populations of Mn oxidizing bacteria living in association with microbial communities supported by chemoautotrophic carbon fixation.

Microbial life associated with low-temperature alteration of ultramafic rocks in the Leka ophiolite complex.

PubMed

Daae, F L; Økland, I; Dahle, H; Jørgensen, S L; Thorseth, I H; Pedersen, R B

2013-07-01

Water-rock interactions in ultramafic lithosphere generate reduced chemical species such as hydrogen that can fuel subsurface microbial communities. Sampling of this environment is expensive and technically demanding. However, highly accessible, uplifted oceanic lithospheres emplaced onto continental margins (ophiolites) are potential model systems for studies of the subsurface biosphere in ultramafic rocks. Here, we describe a microbiological investigation of partially serpentinized dunite from the Leka ophiolite (Norway). We analysed samples of mineral coatings on subsurface fracture surfaces from different depths (10-160 cm) and groundwater from a 50-m-deep borehole that penetrates several major fracture zones in the rock. The samples are suggested to represent subsurface habitats ranging from highly anaerobic to aerobic conditions. Water from a surface pond was analysed for comparison. To explore the microbial diversity and to make assessments about potential metabolisms, the samples were analysed by microscopy, construction of small subunit ribosomal RNA gene clone libraries, culturing and quantitative-PCR. Different microbial communities were observed in the groundwater, the fracture-coating material and the surface water, indicating that distinct microbial ecosystems exist in the rock. Close relatives of hydrogen-oxidizing Hydrogenophaga dominated (30% of the bacterial clones) in the oxic groundwater, indicating that microbial communities in ultramafic rocks at Leka could partially be driven by H2 produced by low-temperature water-rock reactions. Heterotrophic organisms, including close relatives of hydrocarbon degraders possibly feeding on products from Fischer-Tropsch-type reactions, dominated in the fracture-coating material. Putative hydrogen-, ammonia-, manganese- and iron-oxidizers were also detected in fracture coatings and the groundwater. The microbial communities reflect the existence of different subsurface redox conditions generated by differences in fracture size and distribution, and mixing of fluids. The particularly dense microbial communities in the shallow fracture coatings seem to be fuelled by both photosynthesis and oxidation of reduced chemical species produced by water-rock reactions. © 2013 John Wiley & Sons Ltd.

A redox-stratified ocean 3.2 billion years ago

NASA Astrophysics Data System (ADS)

Satkoski, Aaron M.; Beukes, Nicolas J.; Li, Weiqiang; Beard, Brian L.; Johnson, Clark M.

2015-11-01

Before the Great Oxidation Event (GOE) 2.4-2.2 billion years ago it has been traditionally thought that oceanic water columns were uniformly anoxic due to a lack of oxygen-producing microorganisms. Recently, however, it has been proposed that transient oxygenation of shallow seawater occurred between 2.8 and 3.0 billion years ago. Here, we present a novel combination of stable Fe and radiogenic U-Th-Pb isotope data that demonstrate significant oxygen contents in the shallow oceans at 3.2 Ga, based on analysis of the Manzimnyama Banded Iron Formation (BIF), Fig Tree Group, South Africa. This unit is exceptional in that proximal, shallow-water and distal, deep-water facies are preserved. When compared to the distal, deep-water facies, the proximal samples show elevated U concentrations and moderately positive δ56Fe values, indicating vertical stratification in dissolved oxygen contents. Confirmation of oxidizing conditions using U abundances is robustly constrained using samples that have been closed to U and Pb mobility using U-Th-Pb geochronology. Although redox-sensitive elements have been commonly used in ancient rocks to infer redox conditions, post-depositional element mobility has been rarely tested, and U-Th-Pb geochronology can constrain open- or closed-system behavior. The U abundances and δ56Fe values of the Manzimnyama BIF suggest the proximal, shallow-water samples record precipitation under stronger oxidizing conditions compared to the distal deeper-water facies, which in turn indicates the existence of a discrete redox boundary between deep and shallow ocean waters at this time; this work, therefore, documents the oldest known preserved marine redox gradient in the rock record. The relative enrichment of O2 in the upper water column is likely due to the existence of oxygen-producing microorganisms such as cyanobacteria. These results provide a new approach for identifying free oxygen in Earth's ancient oceans, including confirming the age of redox proxies, and indicate that cyanobacteria evolved prior to 3.2 Ga.

Ferrosilicon smelting in a direct current furnace

DOEpatents

Dosaj, Vishu D.; May, James B.

1992-12-29

The present invention is a process for smelting ferrosilicon alloy. The process comprises adding a carbon source and tailings comprising oxides of silicon and iron to a substantially closed furnace. Heat is supplied to the furnace by striking a direct current arc between a cathode electrode and an anode functional hearth. In a preferred embodiment of the present invention, the cathode electrode is hollow and feed to the substantially closed furnace is through the hollow electrode.

pH-regulated chemical oscillators.

PubMed

Orbán, Miklós; Kurin-Csörgei, Krisztina; Epstein, Irving R

2015-03-17

The hydrogen ion is arguably the most ubiquitous and important species in chemistry. It also plays a key role in nearly every biological process. In this Account, we discuss systems whose behavior is governed by oscillations in the concentration of hydrogen ion. The first chemical oscillators driven by changes in pH were developed a quarter century ago. Since then, about two dozen new pH oscillators, systems in which the periodic variation in pH is not just an indicator but an essential prerequisite of the oscillatory behavior, have been discovered. Mechanistic understanding of their behavior has grown, and new ideas for their practical application have been proposed and, in some cases, tested. Here we present a catalog of the known pH oscillators, divide them into mechanistically based categories based on whether they involve a single oxidant and reductant or an oxidant and a pair of reductants, and describe general mechanisms for these two major classes of systems. We also describe in detail the chemistry of one example from each class, hydrogen peroxide-sulfide and ferricyanide-iodate-sulfite. Finally, we consider actual and potential applications. These include using pH oscillators to induce oscillation in species that would otherwise be nonoscillatory, creating novel spatial patterns, generating periodic transitions between vesicle and micelle states, stimulating switching between folded and random coil states of DNA, building molecular motors, and designing pulsating drug delivery systems. We point out the importance for future applications of finding a batch pH oscillator, one that oscillates in a closed system for an extended period of time, and comment on the progress that has been made toward that goal.

A Prototype Ice-Melting Probe for Collecting Biological Samples from Cryogenic Ice at Low Pressure

NASA Astrophysics Data System (ADS)

Davis, Ashley

2017-08-01

In the Solar System, the surface of an icy moon is composed of irregular ice formations at cryogenic temperatures (<200 K), with an oxidized surface layer and a tenuous atmosphere at very low pressure (<10-6 atm). A lander mission, whose aim is to collect and analyze biological samples from the surface ice, must contain a device that collects samples without refreezing liquid and without sublimation of ice. In addition, if the samples are biological in nature, then precautions must be taken to ensure the samples do not overheat or mix with the oxidized layer. To achieve these conditions, the collector must maintain temperatures close to maintenance or growth conditions of the organism (<293 K), and it must separate or neutralize the oxidized layer and be physically gentle. Here, we describe a device that addresses these requirements and is compatible with low atmospheric pressure while using no pumps. The device contains a heated conical probe with a central orifice, which is forced into surface ice and directs the meltwater upward into a reservoir. The force on the probe is proportional to the height of meltwater (pressure) obtained in the system and allows regulation of the melt rate and temperature of the sample. The device can collect 5-50 mL of meltwater from the surface of an ice block at 233-208 K with an environmental pressure of less than 10-2 atm while maintaining a sample temperature between 273 and 293 K. These conditions maintain most biological samples in a pristine state and maintain the integrity of most organisms' structure and function.

Metal-catalyzed protein tyrosine nitration in biological systems.

PubMed

Campolo, Nicolás; Bartesaghi, Silvina; Radi, Rafael

2014-11-01

Protein tyrosine nitration is an oxidative postranslational modification that can affect protein structure and function. It is mediated in vivo by the production of nitric oxide-derived reactive nitrogen species (RNS), including peroxynitrite (ONOO(-)) and nitrogen dioxide ((•)NO₂). Redox-active transition metals such as iron (Fe), copper (Cu), and manganese (Mn) can actively participate in the processes of tyrosine nitration in biological systems, as they catalyze the production of both reactive oxygen species and RNS, enhance nitration yields and provide site-specificity to this process. Early after the discovery that protein tyrosine nitration can occur under biologically relevant conditions, it was shown that some low molecular weight transition-metal centers and metalloproteins could promote peroxynitrite-dependent nitration. Later studies showed that nitration could be achieved by peroxynitrite-independent routes as well, depending on the transition metal-catalyzed oxidation of nitrite (NO₂(-)) to (•)NO₂ in the presence of hydrogen peroxide. Processes like these can be achieved either by hemeperoxidase-dependent reactions or by ferrous and cuprous ions through Fenton-type chemistry. Besides the in vitro evidence, there are now several in vivo studies that support the close relationship between transition metal levels and protein tyrosine nitration. So, the contribution of transition metals to the levels of tyrosine nitrated proteins observed under basal conditions and, specially, in disease states related with high levels of these metal ions, seems to be quite clear. Altogether, current evidence unambiguously supports a central role of transition metals in determining the extent and selectivity of protein tyrosine nitration mediated both by peroxynitrite-dependent and independent mechanisms.

Molecular beacon anchored onto a graphene oxide substrate

NASA Astrophysics Data System (ADS)

Darbandi, Arash; Datta, Debopam; Patel, Krunal; Lin, Gary; Stroscio, Michael A.; Dutta, Mitra

2017-09-01

In this article, we report a graphene oxide-based nanosensor incorporating semiconductor quantum dots linked to DNA-aptamers that functions as a ‘turn-off’ fluorescent nanosensor for detection of low concentrations of analytes. A specific demonstration of this turn-off aptasensor is presented for the case of the detection of mercury (II) ions. In this system, ensembles of aptamer-based quantum-dot sensors are anchored onto graphene oxide (GO) flakes which provide a platform for analyte detection in the vicinity of GO. Herein, the operation of this ensemble-based nanosensor is demonstrated for mercury ions, which upon addition of mercury, quenching of the emission intensity from the quantum dots is observed due to resonance energy transfer between quantum dots and the gold nanoparticle connected via a mercury target aptamer. A key result is that the usually dominant effect of quenching of the quantum dot due to close proximity to the GO can be reduced to negligible levels by using a linker molecule in conjunctions with the aptamer-based nanosensor. The effect of ionic concentration of the background matrix on the emission intensity was also investigated. The sensor system is found to be highly selective towards mercury and exhibits a linear behavior (r 2 > 0.99) in the nanomolar concentration range. The detection limit of the sensor towards mercury with no GO present was found to be 16.5 nM. With GO attached to molecular beacon via 14 base, 35 base, and 51 base long linker DNA, the detection limit was found to be 38.4 nM, 9.45 nM, and 11.38 nM; respectively.

Catalytic and electrochemical behaviour of solid oxide fuel cell operated with simulated-biogas mixtures

NASA Astrophysics Data System (ADS)

Dang-Long, T.; Quang-Tuyen, T.; Shiratori, Y.

2016-06-01

Being produced from organic matters of wastes (bio-wastes) through a fermentation process, biogas mainly composed of CH4 and CO2 and can be considered as a secondary energy carrier derived from solar energy. To generate electricity from biogas through the electrochemical process in fuel cells is a state-of-the-art technology possessing higher energy conversion efficiency without harmful emissions compared to combustion process in heat engines. Getting benefits from high operating temperature such as direct internal reforming ability and activation of electrochemical reactions to increase overall system efficiency, solid oxide fuel cell (SOFC) system operated with biogas becomes a promising candidate for distributed power generator for rural applications leading to reductions of environmental issues caused by greenhouse effects and bio-wastes. CO2 reforming of CH4 and electrochemical oxidation of the produced syngas (H2-CO mixture) are two main reaction processes within porous anode material of SOFC. Here catalytic and electrochemical behavior of Ni-ScSZ (scandia stabilized-zirconia) anode in the feed of CH4-CO2 mixtures as simulated-biogas at 800 °C were evaluated. The results showed that CO2 had strong influences on both reaction processes. The increase in CO2 partial pressure resulted in the decrease in anode overvoltage, although open-circuit voltage was dropped. Besides that, the simulation result based on a power-law model for equimolar CH4-CO2 mixture revealed that coking hazard could be suppressed along the fuel flow channel in both open-circuit and closed-circuit conditions.

Extremely acid Permian lakes and ground waters in North America

USGS Publications Warehouse

Benison, K.C.; Goldstein, R.H.; Wopenka, B.; Burruss, R.C.; Pasteris, J.D.

1998-01-01

Evaporites hosted by red beds (red shales and sandstones), some 275-265 million years old, extend over a large area of the North American mid- continent. They were deposited in non-marine saline lakes, pans and mud- flats, settings that are typically assumed to have been alkaline. Here we use laser Raman microprobe analyses of fluid inclusions trapped in halites from these Permian deposits to argue for the existence of highly acidic (pH < 1) lakes and ground waters. These extremely acidic systems may have extended over an area of 200,000 km2. Modern analogues of such systems may be natural acid lake and groundwater systems (pH ~2-4) in southern Australia. Both the ancient and modern acid systems are characterized by closed drainage, arid climate, low acid-neutralizing capacity, and the oxidation of minerals such as pyrite to generate acidity. The discovery of widespread ancient acid lake and groundwater systems demands a re-evaluation of reconstructions of surface conditions of the past, and further investigations of the geochemistry and ecology of acid systems in general.

Incineration for resource recovery in a closed ecological life support system

NASA Technical Reports Server (NTRS)

Upadhye, R. S.; Wignarajah, K.; Wydeven, T.

1993-01-01

A functional schematic, including mass and energy balance, of a solid waste processing system for a controlled ecological life support system (CELSS) was developed using Aspen Plus, a commercial computer simulation program. The primary processor in this system is an incinerator for oxidizing organic wastes. The major products derived from the incinerator are carbon dioxide and water, which can be recycled to a crop growth chamber (CGC) for food production. The majority of soluble inorganics are extracted or leached from the inedible biomass before they reach the incinerator, so that they can be returned directly to the CGC and reused as nutrients. The heat derived from combustion of organic compounds in the incinerator was used for phase-change water purification. The waste streams treated by the incinerator system conceptualized in this work are inedible biomass from a CGC, human urine (including urinal flush water) and feces, humidity condensate, shower water, and trash. It is estimated that the theoretical minimum surface area required for the radiator to reject the unusable heat output from this system would be 0.72 sq m/person at 298 K.

Thinning and mounting a Texas Instruments 3-phase CCD

NASA Technical Reports Server (NTRS)

Lesser, M. P.; Leach, R. W.; Angel, J. R. P.

1986-01-01

Thin CCDs with precise control of thickness and surface quality allow astronomers to optimize chips for specific applications. A means of mechanically thinning a TI 800 x 800 CCD with an abrasive slurry of aluminum oxide is presented. Using the same techniques, the abrasives can be replaced with a chemical solution to eliminate subsurface damage. A technique of mounting the CCD which retains the high quality surface generated during thinning is also demonstrated. This requires the backside of the chip to be bonded to a glass window which closely matches silicon's thermal expansion properties. Thinned CCDs require backside treatment to enhance blue and UV quantum efficiency. Two methods are discussed which may be effective with this mounting system.

Shock tube measurements of growth constants in the branched-chain ethane-carbon monoxide-oxygen system

NASA Technical Reports Server (NTRS)

Brokaw, R. S.; Brabbs, T. A.; Snyder, C. A.

1985-01-01

Exponential free radical growth constants have been measured for ethane carbon monoxide oxygen mixtures by monitoring the growth of oxygen atom concentration as manifested by CO flame band emission. Data were obtained over the temperature range of 1200 to 1700 K. The data were analyzed using an ethane oxidation mechanism involving seven elementary reaction steps. Calculated growth constants were close to experimental values at lower temperatures, up to about 1400 K, but at higher temperatures computed growth constants were considerably smaller than experiment. In attempts to explain these results additional branching reactions were added to the mechanism. However, these additional reactions did not appreciably change calculated growth constants.

Application of photosynthetic N2-fixing cyanobacteria to the CELSS program

NASA Technical Reports Server (NTRS)

Packer, L.; Fry, I.; Belkin, S.

1986-01-01

Commercially available air lift fermentors were used to simultaneously monitor biomass production, N2-fixation, photosynthesis, respiration, and sensitivity to oxidative damage during growth under various nutritional and light regimes, to establish a data base for the integration of these organisms into a Closed Ecological Life Support System (CELSS) program. Certain cyanobacterial species have the unique ability to reduce atmospheric N2 to organic nitrogen. These organisms combine the ease of cultivation characteristics of prokaryotes with the fully developed photosynthetic apparatus of higher plants. This, along with their ability to adapt to changes in their environment by modulation of certain biochemical pathways, make them attractive candidates for incorporation into the CELSS program.

A PAC containing the human mitochondrial DNA polymerase gamma gene (POLG) maps to chromosome 15q25

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, R.L.; Meltzer, P.S.; Anziano, P.

The human mitochondrial DNA (mtDNA) is a closed circular, 16,569-bp double-stranded DNA, encoding 13 genes whose protein products are subunits of the oxidative phosphorylation system required for synthesis of most of the ATP consumed by eukaryotic cells. Point mutations of the mtDNA that cause multi-tissue, loss-of-energy syndromes, called mitochondrial encephalomyopathies (e.g., MERRF and MELAS), have been identified. In addition, large-scale deletions of the human mtDNA have been identified and are the molecular bases for the neonatal and adolescent onset loss-of-energy syndromes Pearson and Kearns-Sayer, respectively. 5 refs., 1 fig.

The NASA pollution-reduction technology program for small jet aircraft engines

NASA Technical Reports Server (NTRS)

Fear, J. S.

1976-01-01

Three advanced combustor concepts, designed for the AiResearch TFE 731-2 turbofan engine, were evaluated in screening tests. Goals for carbon monoxide and unburned hydrocarbons were met or closely approached with two of the concepts with relatively modest departures from conventional combustor design practices. A more advanced premixing/prevaporizing combustor, while appearing to have the potential for meeting the oxides of nitrogen goal as well, will require extensive development to make it a practical combustion system. Smoke numbers for the two combustor concepts were well within the EPA smoke standard. Phase 2, Combustor-Engine Compatibility Testing, which is in its early stages, and planned Phase 3, Combustor-Engine Demonstration Testing, are also described.

Reaction pathways in atomistic models of thin film growth

NASA Astrophysics Data System (ADS)

Lloyd, Adam L.; Zhou, Ying; Yu, Miao; Scott, Chris; Smith, Roger; Kenny, Steven D.

2017-10-01

The atomistic processes that form the basis of thin film growth often involve complex multi-atom movements of atoms or groups of atoms on or close to the surface of a substrate. These transitions and their pathways are often difficult to predict in advance. By using an adaptive kinetic Monte Carlo (AKMC) approach, many complex mechanisms can be identified so that the growth processes can be understood and ultimately controlled. Here the AKMC technique is briefly described along with some special adaptions that can speed up the simulations when, for example, the transition barriers are small. Examples are given of such complex processes that occur in different material systems especially for the growth of metals and metallic oxides.

Near-perfect broadband absorption from hyperbolic metamaterial nanoparticles

NASA Astrophysics Data System (ADS)

Riley, Conor T.; Smalley, Joseph S. T.; Brodie, Jeffrey R. J.; Fainman, Yeshaiahu; Sirbuly, Donald J.; Liu, Zhaowei

2017-02-01

Broadband absorbers are essential components of many light detection, energy harvesting, and camouflage schemes. Current designs are either bulky or use planar films that cause problems in cracking and delamination during flexing or heating. In addition, transferring planar materials to flexible, thin, or low-cost substrates poses a significant challenge. On the other hand, particle-based materials are highly flexible and can be transferred and assembled onto a more desirable substrate but have not shown high performance as an absorber in a standalone system. Here, we introduce a class of particle absorbers called transferable hyperbolic metamaterial particles (THMMP) that display selective, omnidirectional, tunable, broadband absorption when closely packed. This is demonstrated with vertically aligned hyperbolic nanotube (HNT) arrays composed of alternating layers of aluminum-doped zinc oxide and zinc oxide. The broadband absorption measures >87% from 1,200 nm to over 2,200 nm with a maximum absorption of 98.1% at 1,550 nm and remains large for high angles. Furthermore, we show the advantages of particle-based absorbers by transferring the HNTs to a polymer substrate that shows excellent mechanical flexibility and visible transparency while maintaining near-perfect absorption in the telecommunications region. In addition, other material systems and geometries are proposed for a wider range of applications.

Investigating combustion as a method of processing inedible biomass produced in NASA's biomass production chamber

NASA Technical Reports Server (NTRS)

Dreschel, T. W.; Wheeler, R. M.; Hinkle, C. R.; Sager, J. C.; Knott, W. M.

1991-01-01

The Controlled Ecological Life Support System (CELSS) Breadboard Project at the John F. Kennedy Space Center is a research program to integrate and evaluate biological processes to provide air, water, and food for humans in closed environments for space habitation. This project focuses on the use of conventional crop plants as grown in the Biomass Production Chamber (BPC) for the production and recycling of oxygen, food, and water. The inedible portion of these crops has the potential to be converted to edible biomass or directly to the elemental constituents for direct recycling. Converting inedible biomass directly, by combustion, to carbon dioxide, water, and minerals could provide a baseline for estimating partitioning of the mass balance during recycling in a CELSS. Converting the inedible biomass to carbon dioxide and water requires the same amount of oxygen that was produced by photosynthesis. The oxygen produced during crop growth is just equal to the oxygen required to oxidize all the biomass produced during growth. Thus, the amount of oxygen produced that is available for human consumption is in proportion to the amount of biomass actually utilized by humans. The remaining oxygen must be available to oxidize the rest of the biomass back to carbon dioxide and water or the system will not be a regenerative one.

Sequential growth for lifetime extension in biomimetic polypyrrole actuator systems

NASA Astrophysics Data System (ADS)

Sarrazin, J. C.; Mascaro, Stephen A.

2015-04-01

Electroactive polymers (EAPs) present prospective use in actuation and manipulation devices due to their low electrical activation requirements, biocompatibility, and mechanical performance. One of the main drawbacks with EAP actuators is a decrease in performance over extended periods of operation caused by over-oxidation of the polymer and general polymer degradation. Synthesis of the EAP material, polypyrrole with an embedded metal helix allows for sequential growth of the polymer during operation. The helical metal electrode acts as a scaffolding to support the polymer, and direct the 3-dimensional change in volume of the polymer along the axis of the helix during oxidative and reductive cycling. The metal helix also provides a working metal electrode through the entire length of the polymer actuator to distribute charge for actuation, as well as for sequential growth steps during the lifetime of operation of the polymer. This work demonstrates the method of sequential growth can be utilized after extended periods of use to partially restore electrical and mechanical performance of polypyrrole actuators. Since the actuation must be temporarily stopped to allow for a sequential growth cycle to be performed and reverse some of the polymer degradation, these actuator systems more closely mimic natural muscle in their analogous maintenance and repair.

Zinc oxide nanoparticles inhibit murine photoreceptor-derived cell proliferation and migration via reducing TGF-β and MMP-9 expression in vitro.

PubMed

Guo, Da Dong; Li, Qing Ning; Li, Chun Min; Bi, Hong Sheng

2015-04-01

To investigate behaviour and expression of transforming growth factor-β (TGF-β) and matrix metalloproteinases (MMP-9) in murine photoreceptor-derived cells (661W) after incubation with zinc oxide (ZnO) nanoparticles. We explored effects of ZnO nanoparticles on 661W cells using a real-time cell electronic sensing system, flow cytometry, multiple function microplate reading, real-time quantitative PCR detection system and enzyme-linked immunosorbent assay respectively. Our results indicate that ZnO nanoparticles induced overload of calcium and reactive oxygen species within cells, causing formation of apoptotic bodies, disruption of cell cycle distribution, and reduction in expression of TGF-β and MMP-9, to suppress cell proliferation and migration. Our findings show that disruption of intracellular calcium homoeostasis and overproduction of reactive oxygen species were closely associated with reduction of TGF-β and MMP-9 in 661W cells under ZnO nanoparticle treatment. Results of our study indicate that ZnO nanoparticles suppressed cell proliferation and migration, and reduced production of TGF-β and MMP-9 at both gene and protein levels. Our findings contribute to the understanding of the molecular mechanisms that reduced TGF-β and MMP-9 levels inhibit cell proliferation and migration under ZnO nanoparticle influence. © 2015 John Wiley & Sons Ltd.

Identification of Mn(II)-oxidizing bacteria from a low-pH contaminated former uranium mine.

PubMed

Akob, Denise M; Bohu, Tsing; Beyer, Andrea; Schäffner, Franziska; Händel, Matthias; Johnson, Carol A; Merten, Dirk; Büchel, Georg; Totsche, Kai Uwe; Küsel, Kirsten

2014-08-01

Biological Mn oxidation is responsible for producing highly reactive and abundant Mn oxide phases in the environment that can mitigate metal contamination. However, little is known about Mn oxidation in low-pH environments, where metal contamination often is a problem as the result of mining activities. We isolated two Mn(II)-oxidizing bacteria (MOB) at pH 5.5 (Duganella isolate AB_14 and Albidiferax isolate TB-2) and nine strains at pH 7 from a former uranium mining site. Isolate TB-2 may contribute to Mn oxidation in the acidic Mn-rich subsoil, as a closely related clone represented 16% of the total community. All isolates oxidized Mn over a small pH range, and isolates from low-pH samples only oxidized Mn below pH 6. Two strains with different pH optima differed in their Fe requirements for Mn oxidation, suggesting that Mn oxidation by the strain found at neutral pH was linked to Fe oxidation. Isolates tolerated Ni, Cu, and Cd and produced Mn oxides with similarities to todorokite and birnessite, with the latter being present in subsurface layers where metal enrichment was associated with Mn oxides. This demonstrates that MOB can be involved in the formation of biogenic Mn oxides in both moderately acidic and neutral pH environments. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Identification of Mn(II)-Oxidizing Bacteria from a Low-pH Contaminated Former Uranium Mine

PubMed Central

Bohu, Tsing; Beyer, Andrea; Schäffner, Franziska; Händel, Matthias; Johnson, Carol A.; Merten, Dirk; Büchel, Georg; Totsche, Kai Uwe; Küsel, Kirsten

2014-01-01

Biological Mn oxidation is responsible for producing highly reactive and abundant Mn oxide phases in the environment that can mitigate metal contamination. However, little is known about Mn oxidation in low-pH environments, where metal contamination often is a problem as the result of mining activities. We isolated two Mn(II)-oxidizing bacteria (MOB) at pH 5.5 (Duganella isolate AB_14 and Albidiferax isolate TB-2) and nine strains at pH 7 from a former uranium mining site. Isolate TB-2 may contribute to Mn oxidation in the acidic Mn-rich subsoil, as a closely related clone represented 16% of the total community. All isolates oxidized Mn over a small pH range, and isolates from low-pH samples only oxidized Mn below pH 6. Two strains with different pH optima differed in their Fe requirements for Mn oxidation, suggesting that Mn oxidation by the strain found at neutral pH was linked to Fe oxidation. Isolates tolerated Ni, Cu, and Cd and produced Mn oxides with similarities to todorokite and birnessite, with the latter being present in subsurface layers where metal enrichment was associated with Mn oxides. This demonstrates that MOB can be involved in the formation of biogenic Mn oxides in both moderately acidic and neutral pH environments. PMID:24928873

Identification of Mn(II)-oxidizing bacteria from a low-pH contaminated former uranium mine

USGS Publications Warehouse

Akob, Denise M.; Bohu, Tsing; Beyer, Andrea; Schäffner, Franziska; Händel, Matthias; Johnson, Carol A.; Merten, Dirk; Büchel, Georg; Totsche, Kai Uwe; Küsel, Kirsten

2014-01-01

Biological Mn oxidation is responsible for producing highly reactive and abundant Mn oxide phases in the environment that can mitigate metal contamination. However, little is known about Mn oxidation in low-pH environments, where metal contamination often is a problem as the result of mining activities. We isolated two Mn(II)-oxidizing bacteria (MOB) at pH 5.5 (Duganella isolate AB_14 and Albidiferax isolate TB-2) and nine strains at pH 7 from a former uranium mining site. Isolate TB-2 may contribute to Mn oxidation in the acidic Mn-rich subsoil, as a closely related clone represented 16% of the total community. All isolates oxidized Mn over a small pH range, and isolates from low-pH samples only oxidized Mn below pH 6. Two strains with different pH optima differed in their Fe requirements for Mn oxidation, suggesting that Mn oxidation by the strain found at neutral pH was linked to Fe oxidation. Isolates tolerated Ni, Cu, and Cd and produced Mn oxides with similarities to todorokite and birnessite, with the latter being present in subsurface layers where metal enrichment was associated with Mn oxides. This demonstrates that MOB can be involved in the formation of biogenic Mn oxides in both moderately acidic and neutral pH environments.

Physical-chemical treatment of wastes: a way to close turnover of elements in LSS

NASA Astrophysics Data System (ADS)

Kudenko, Yu A.; Gribovskaya, I. V.; Zolotukhin, I. G.

2000-05-01

"Man-plants-physical-chemical unit" system designed for space stations or terrestrial ecohabitats to close steady-state mineral, water and gas exchange is proposed. The physical-chemical unit is to mineralize all inedible plant wastes and physiological human wastes (feces, urine, gray water) by electromagnetically activated hydrogen peroxide in an oxidation reactor. The final product is a mineralized solution containing all elements balanced for plants' requirements. The solution has been successfully used in experiments to grow wheat, beans and radish. The solution was reusable: the evaporated moisture was replenished by the phytotron condensate. Sodium salination of plants was precluded by evaporating reactor-mineralized urine to sodium saturation concentration to crystallize out NaCl which can be used as food for the crew. The remaining mineralized product was brought back for nutrition of plants. The gas composition of the reactor comprises O 2, N 2, CO 2, NH 3, H 2. At the reactor's output hydrogen and oxygen were catalyzed into water, NH 3 was converted in a water trap into NH 4 and used for nutrition of plants. A special accessory at the reactor's output may produce hydrogen peroxide from intrasystem water and gas which makes possible to close gas loops between LSS components.

D/H of late Miocene meteoric waters in Western Australia: Paleoenvironmental conditions inferred from the δD of (U-Th)/He-dated CID goethite

NASA Astrophysics Data System (ADS)

Yapp, Crayton J.; Shuster, David L.

2017-09-01

Nineteen (U-Th)/He ages were determined for eight samples from a core drilled in an ore-grade channel iron deposit (CID) of the Robe Pisolite (Robe Formation) of Mesa J in Western Australia. With one exception, uncorrected ages of the analyzed aliquots range from 6.7(±0.4) Ma to 30.2(±3.1) Ma, while molar ratios of Th/U range from 0.42 to 5.06. The exception is an aliquot with an apparent age of 2.7 Ma and Th/U of 5.70. A three-component mixing model involving one generation of goethite and two generations of hematite suggests that the age of crystallization of the oolitic goethites is ∼7(±1) Ma. If so, the goethites have effectively been closed systems for ∼7 million years and should preserve a stable hydrogen isotope record of late Miocene rainfall in the vicinity of Mesa J. Cenozoic movement of the Australian continent had placed Mesa J and environs in the subtropics at a paleolatitude of about 29 °S during the late Miocene. Al-adjusted δD values of oolitic goethite in the eight CID samples range from -153‰ to -146‰ and imply that the δD of the late Miocene meteoric waters ranged from -61‰ to -53‰, with an average of -56‰. These relatively negative δD values might indicate that near-coastal, late Miocene rain was derived primarily from summer-season tropical cyclones with storm tracks that extended into the subtropics of western Australia. The postulated late Miocene tropical cyclones would have occurred more often and/or exhibited greater intensity at a paleolatitude of 29 °S than is the case for modern sites at approximately 30 °S on the west coast of Australia (e.g., Perth). Higher fluxes of meteoric water in the Miocene summers would have facilitated dissolution and removal of BIF-sourced silica with concomitant enrichment in oxidized Fe. Moreover, wetter late Miocene summers could have promoted multiple cycles of microbially mediated dissolution and recrystallization of Fe(III) oxides in the aerobic systems. The oolitic textures may be indicative of such recycling. However, the oolitic goethites of Mesa J were closed systems after ∼7 Ma. Therefore, the climate in the vicinity of Mesa J seems to have changed in the late Miocene to conditions that did not favor widespread recycling of Fe (III) oxides-perhaps changing from seasonally wet to the modern dry climate.

Template-free magnesium oxide hollow sphere inclusion in organic-inorganic hybrid films via sol-gel reaction.

PubMed

Kang, Eun-Seok; Takahashi, Masahide; Tokuda, Yomei; Yoko, Toshinobu

2006-06-06

Magnesium oxide hollow spheres without a template core were conveniently prepared by stabilized bubble formation in a hybrid solution containing a magnesium acetate precursor, thus avoiding the complicated preparation process using a template. The hollow sphere could be aligned along the radial striation by spin coating, and its diameter from a micrometer to submicrometer dimension could be easily modified by the solution composition. It was also possible to control the open or closed hollow sphere by changing the solvent. Thus, the produced magnesium oxide hollow sphere is envisioned to have applications in many areas such as medicine, analysis, optics, and so on.

40 CFR 63.4293 - What work practice standards must I meet?

Code of Federal Regulations, 2010 CFR

2010-07-01

... option, the organic HAP overall control efficiency option, or the oxidizer outlet organic HAP... must be conveyed from one location to another in closed containers or pipes. (4) Mixing vessels which...

40 CFR 63.983 - Closed vent systems.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 10 2010-07-01 2010-07-01 false Closed vent systems. 63.983 Section 63... Emission Standards for Closed Vent Systems, Control Devices, Recovery Devices and Routing to a Fuel Gas System or a Process § 63.983 Closed vent systems. (a) Closed vent system equipment and operating...

Prediction of Combustion Instability with Detailed Chemical Kinetics

DTIC Science & Technology

2014-12-01

global reaction where the fuel and oxidizer react to form water and carbon dioxide . The production of carbon monoxide is a known intermediate step in... radially inward on a sleeve which turns the flow in the axial direction with minimal swirl. The oxidizer is decomposed hydrogen peroxide, which is...unburnt mixture in the vicinity of the recirculating hot products. This also causes the hot gas near the back step to move radially inwards, close to the

Inhabitancy of active Nitrosopumilus-like ammonia-oxidizing archaea and Nitrospira nitrite-oxidizing bacteria in the sponge Theonella swinhoei

PubMed Central

Feng, Guofang; Sun, Wei; Zhang, Fengli; Karthik, Loganathan; Li, Zhiyong

2016-01-01

Nitrification directly contributes to the ammonia removal in sponges, and it plays an indispensable role in sponge-mediated nitrogen cycle. Previous studies have demonstrated genomic evidences of nitrifying lineages in the sponge Theonella swinhoei. However, little is known about the transcriptional activity of nitrifying community in this sponge. In this study, combined DNA- and transcript-based analyses were performed to reveal the composition and transcriptional activity of the nitrifiers in T. swinhoei from the South China Sea. Transcriptional activity of ammonia-oxidizing archaea (AOA) and nitrite-oxidizing bacteria (NOB) in this sponge were confirmed by targeting their nitrifying genes,16S rRNA genes and their transcripts. Phylogenetic analysis coupled with RDP rRNA classification indicated that archaeal 16S rRNA genes, amoA (the subunit of ammonia monooxygenase) genes and their transcripts were closely related to Nitrosopumilus-like AOA; whereas nitrifying bacterial 16S rRNA genes, nxrB (the subunit of nitrite oxidoreductase) genes and their transcripts were closely related to Nitrospira NOB. Quantitative assessment demonstrated relative higher abundances of nitrifying genes and transcripts of Nitrosopumilus-like AOA than those of Nitrospira NOB in this sponge. This study illustrated the transcriptional potentials of Nitrosopumilus-like archaea and Nitrospira bacteria that would predominantly contribute to the nitrification functionality in the South China Sea T. swinhoei. PMID:27113140

Rapid synthesis of tin oxide nanostructures by microwave-assisted thermal oxidation for sensor applications

NASA Astrophysics Data System (ADS)

Phadungdhitidhada, S.; Ruankham, P.; Gardchareon, A.; Wongratanaphisan, D.; Choopun, S.

2017-09-01

In the present work nanostructures of tin oxides were synthesized by a microwave-assisted thermal oxidation. Tin precursor powder was loaded into a cylindrical quartz tube and further radiated in a microwave oven. The as-synthesized products were characterized by scanning electron microscope, transmission electron microscope, and x-ray diffractometer. The results showed that two different morphologies of SnO2 microwires (MWs) and nanoparticles (NPs) were obtained in one minute of microwave radiation under atmospheric ambient. A few tens of the SnO2 MWs with the length of 10-50 µm were found. Some parts of the MWs were decorated with the SnO2 NPs. However, most of the products were SnO2 NPs with the diameter ranging from 30-200 nm. Preparation under loosely closed system lead to mixed phase SnO-SnO2 NPs with diameter of 30-200 nm. The single-phase of SnO2 could be obtained by mixing the Sn precursor powders with CuO2. The products were mostly found to be SnO2 nanowires (NWs) and MWs. The diameter of SnO2 NWs was less than 50 nm. The SnO2 NPs, MWs, and NWs were in the cassiterite rutile structure phase. The SnO NPs was in the tetragonal structure phase. The growth direction of the SnO2 NWs was observed in (1 1 0) and (2 2 1) direction. The ethanol sensor performance of these tin oxide nanostructures showed that the SnO-SnO2 NPs exhibited extremely high sensitivity. Invited talk at 5th Thailand International Nanotechnology Conference (Nano Thailand-2016), 27-29 November 2016, Nakhon Ratchasima, Thailand.

Post-Stroke Depression Modulation and in Vivo Antioxidant Activity of Gallic Acid and Its Synthetic Derivatives in a Murine Model System.

PubMed

Nabavi, Seyed Fazel; Habtemariam, Solomon; Di Lorenzo, Arianna; Sureda, Antoni; Khanjani, Sedigheh; Nabavi, Seyed Mohammad; Daglia, Maria

2016-04-28

Gallic acid (3,4,5-trihydroxybenzoic acid, GA) is a plant secondary metabolite, which shows antioxidant activity and is commonly found in many plant-based foods and beverages. Recent evidence suggests that oxidative stress contributes to the development of many human chronic diseases, including cardiovascular and neurodegenerative pathologies, metabolic syndrome, type 2 diabetes and cancer. GA and its derivative, methyl-3-O-methyl gallate (M3OMG), possess physiological and pharmacological activities closely related to their antioxidant properties. This paper describes the antidepressive-like effects of intraperitoneal administration of GA and two synthetic analogues, M3OMG and P3OMG (propyl-3-O-methylgallate), in balb/c mice with post-stroke depression, a secondary form of depression that could be due to oxidative stress occurring during cerebral ischemia and the following reperfusion. Moreover, this study determined the in vivo antioxidant activity of these compounds through the evaluation of superoxide dismutase (SOD) and catalase (Cat) activity, thiobarbituric acid-reactive substances (TBARS) and reduced glutathione (GSH) levels in mouse brain. GA and its synthetic analogues were found to be active (at doses of 25 and 50 mg/kg) in the modulation of depressive symptoms and the reduction of oxidative stress, restoring normal behavior and, at least in part, antioxidant endogenous defenses, with M3OMG being the most active of these compounds. SOD, TBARS, and GSH all showed strong correlation with behavioral parameters, suggesting that oxidative stress is tightly linked to the pathological processes involved in stroke and PSD. As a whole, the obtained results show that the administration of GA, M3OMG and P3OMG induce a reduction in depressive symptoms and oxidative stress.

Post-Stroke Depression Modulation and in Vivo Antioxidant Activity of Gallic Acid and Its Synthetic Derivatives in a Murine Model System

PubMed Central

Nabavi, Seyed Fazel; Habtemariam, Solomon; Di Lorenzo, Arianna; Sureda, Antoni; Khanjani, Sedigheh; Nabavi, Seyed Mohammad; Daglia, Maria

2016-01-01

Gallic acid (3,4,5-trihydroxybenzoic acid, GA) is a plant secondary metabolite, which shows antioxidant activity and is commonly found in many plant-based foods and beverages. Recent evidence suggests that oxidative stress contributes to the development of many human chronic diseases, including cardiovascular and neurodegenerative pathologies, metabolic syndrome, type 2 diabetes and cancer. GA and its derivative, methyl-3-O-methyl gallate (M3OMG), possess physiological and pharmacological activities closely related to their antioxidant properties. This paper describes the antidepressive-like effects of intraperitoneal administration of GA and two synthetic analogues, M3OMG and P3OMG (propyl-3-O-methylgallate), in balb/c mice with post-stroke depression, a secondary form of depression that could be due to oxidative stress occurring during cerebral ischemia and the following reperfusion. Moreover, this study determined the in vivo antioxidant activity of these compounds through the evaluation of superoxide dismutase (SOD) and catalase (Cat) activity, thiobarbituric acid-reactive substances (TBARS) and reduced glutathione (GSH) levels in mouse brain. GA and its synthetic analogues were found to be active (at doses of 25 and 50 mg/kg) in the modulation of depressive symptoms and the reduction of oxidative stress, restoring normal behavior and, at least in part, antioxidant endogenous defenses, with M3OMG being the most active of these compounds. SOD, TBARS, and GSH all showed strong correlation with behavioral parameters, suggesting that oxidative stress is tightly linked to the pathological processes involved in stroke and PSD. As a whole, the obtained results show that the administration of GA, M3OMG and P3OMG induce a reduction in depressive symptoms and oxidative stress. PMID:27136579

Arsenite and ferrous iron oxidation linked to chemolithotrophic denitrification for the immobilization of arsenic in anoxic environments

USGS Publications Warehouse

Sun, W.; Sierra-Alvarez, R.; Milner, L.; Oremland, R.; Field, J.A.

2009-01-01

The objective of this study was to explore a bioremediation strategy based on injecting NO3- to support the anoxic oxidation of ferrous iron (Fe(II)) and arsenite (As(III)) in the subsurface as a means to immobilize As in the form of arsenate (As(V)) adsorbed onto biogenic ferric (Fe(III)) (hydr)oxides. Continuous flows and filled columns were used to simulate a natural anaerobic groundwater and sediment system with co-occurring As(III) and Fe(II) in the presence (column SF1) or absence (column SF2) of nitrate, respectively. During operation for 250 days, the average influent arsenic concentration of 567 ??g L-1 was reduced to 10.6 (??9.6) ??g L-1 in the effluent of column SF1. The cumulative removal of Fe(II) and As(III) in SF1 was 6.5 to 10-fold higher than that in SF2. Extraction and measurement of the mass of iron and arsenic immobilized on the sand packing of the columns were close to the iron and arsenic removed from the aqueous phase during column operation. The dominant speciation of the immobilized iron and arsenic was Fe(III) and As(V) in SF1, compared with Fe(II) and As(III) in SF2. The speciation was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results indicate that microbial oxidation of As(III) and Fe(II) linked to denitrification resulted in the enhanced immobilization of aqueous arsenic in anaerobic environments by forming Fe(III) (hydr)oxide coated sands with adsorbed As(V). ?? 2009 American Chemical Society.

Thermal diffusivity and conductivity of thorium- uranium mixed oxides

NASA Astrophysics Data System (ADS)

Saoudi, M.; Staicu, D.; Mouris, J.; Bergeron, A.; Hamilton, H.; Naji, M.; Freis, D.; Cologna, M.

2018-03-01

Thorium-uranium oxide pellets with high densities were prepared at the Canadian Nuclear Laboratories (CNL) by co-milling, pressing, and sintering at 2023 K, with UO2 mass contents of 0, 1.5, 3, 8, 13, 30, 60 and 100%. At the Joint Research Centre, Karlsruhe (JRC-Karlsruhe), thorium-uranium oxide pellets were prepared using the spark plasma sintering (SPS) technique with 79 and 93 wt. % UO2. The thermal diffusivity of (Th1-xUx)O2 (0 ≤ x ≤ 1) was measured at CNL and at JRC-Karlsruhe using the laser flash technique. ThO2 and (Th,U)O2 with 1.5, 3, 8 and 13 wt. % UO2 were found to be semi-transparent to the infrared wavelength of the laser and were coated with graphite for the thermal diffusivity measurements. This semi-transparency decreased with the addition of UO2 and was lost at about 30 wt. % of UO2 in ThO2. The thermal conductivity was deduced using the measured density and literature data for the specific heat capacity. The thermal conductivity for ThO2 is significantly higher than for UO2. The thermal conductivity of (Th,U)O2 decreases rapidly with increasing UO2 content, and for UO2 contents of 60% and higher, the conductivity of the thorium-uranium oxide fuel is close to UO2. As the mass difference between the Th and U atoms is small, the thermal conductivity decrease is attributed to the phonon scattering enhanced by lattice strain due to the introduction of uranium in ThO2 lattice. The new results were compared to the data available in the literature and were evaluated using the classical phonon transport model for oxide systems.

Cinetica de oxidacion de polimeros conductores: poli-3,4- etilendioxitiofeno

NASA Astrophysics Data System (ADS)

Caballero Romero, Maria

Films of poly-3,4-ethylenedioxythiophene (PEDOT) perchlorate used as electrodes in liquid electrolytes incorporate anions and solvent during oxidation for charge and osmotic balance: the film swells. During reduction the film shrinks, closes its structure trapping counterions getting then rising conformational packed states by expulsion of counterions and solvent. Here by potential step from the same reduced initial state to the same oxidized final state the rate coefficient, the activation energy and reaction orders related to the counterion concentration in solution and to the concentration of active centers in the polymer film, were attained following the usual methodology used for chemical and electrochemical kinetics. Now the full methodology was repeated using different reduced-shrunk or reduced-conformational compacted initial states every time. Those initial states were attained by reduction of the oxidized film at rising cathodic potentials for the same reduction time each. Rising reduced and conformational compacted states give slower subsequent oxidation rates by potential step to the same anodic potential every time. The activation energy, the reaction coefficient and reaction orders change for rising conformational compacted initial states. Decreasing rate constants and increasing activation energies are obtained for the PEDOT oxidation from increasing conformational compacted initial states. The experimental activation energy presents two linear ranges as a function of the initial reduced-compacted state. Using as initial states for the oxidation open structures attained by reduction at low cathodic potentials, activation energies attained were constant: namely the chemical activation energy. Using as initial states for the oxidation deeper reduced, closed and packed conformational structures, the activation energy includes two components: the constant chemical energy plus the conformational energy required to relax the conformational structure generating free volume which allows the entrance of the balancing counterions required for the reaction. The conformational energy increases linearly as a function of the reduction-compaction potential. The kinetic magnitudes include conformational and structural information. The Chemical Kinetics becomes Structural (or conformational) Chemical Kinetics.

Ambient temperature and cardiovascular biomarkers in a repeated-measure study in healthy adults: A novel biomarker index approach.

PubMed

Wu, Shaowei; Yang, Di; Pan, Lu; Shan, Jiao; Li, Hongyu; Wei, Hongying; Wang, Bin; Huang, Jing; Baccarelli, Andrea A; Shima, Masayuki; Deng, Furong; Guo, Xinbiao

2017-07-01

Associations of ambient temperature with cardiovascular morbidity and mortality have been well documented in numerous epidemiological studies, but the underlying pathways remain unclear. We investigated whether systemic inflammation, coagulation, systemic oxidative stress, antioxidant activity and endothelial function may be the mechanistic pathways associated with ambient temperature. Forty study participants underwent repeated blood collections for 12 times in Beijing, China in 2010-2011. Ambient temperature and air pollution data were measured in central monitors close to student residences. We created five indices as the sum of weighted biomarker percentiles to represent the overall levels of 15 cardiovascular biomarkers in five pathways (systemic inflammation: hs-CRP, TNF-α and fibrinogen; coagulation: fibrinogen, PAI-1, tPA, vWF and sP-selectin; systemic oxidative stress: Ox-LDL and sCD36: antioxidant activity: EC-SOD and GPX1; and endothelial function: ET-1, E-selectin, ICAM-1 and VCAM-1). We used generalized mixed-effects models to estimate temperature effects controlling for air pollution and other covariates. There were significant decreasing trends in the adjusted means of biomarker indices over the lowest to the highest quartiles of daily temperatures before blood collection. A 10°C decrease at 2-d average daily temperature were associated with increases of 2.5% [95% confidence interval (CI): 0.7, 4.2], 1.6% (95% CI: 0.1, 3.1), 2.7% (95% CI: 0.5, 4.8), 5.5% (95% CI: 3.8, 7.3) and 2.0% (95% CI: 0.3, 3.8) in the indices for systemic inflammation, coagulation, systemic oxidative stress, antioxidant activity and endothelial function, respectively. In contrast, the associations between ambient temperature and individual biomarkers had substantial variation in magnitude and strength. The altered cardiovascular biomarker profiles in healthy adults associated with ambient temperature changes may help explain the temperature-related cardiovascular morbidity and mortality. The biomarker index approach may serve as a novel tool to capture ambient temperature effects. Copyright © 2017. Published by Elsevier Inc.

Highly efficient aerobic oxidation of alcohols by using less-hindered nitroxyl-radical/copper catalysis: optimum catalyst combinations and their substrate scope.

PubMed

Sasano, Yusuke; Kogure, Naoki; Nishiyama, Tomohiro; Nagasawa, Shota; Iwabuchi, Yoshiharu

2015-04-01

The oxidation of alcohols into their corresponding carbonyl compounds is one of the most fundamental transformations in organic chemistry. In our recent report, 2-azaadamantane N-oxyl (AZADO)/copper catalysis promoted the highly chemoselective aerobic oxidation of unprotected amino alcohols into amino carbonyl compounds. Herein, we investigated the extension of the promising AZADO/copper-catalyzed aerobic oxidation of alcohols to other types of alcohol. During close optimization of the reaction conditions by using various alcohols, we found that the optimum combination of nitroxyl radical, copper salt, and solution concentration was dependent on the type of substrate. Various alcohols, including highly hindered and heteroatom-rich ones, were efficiently oxidized into their corresponding carbonyl compounds under mild conditions with lower amounts of the catalysts. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of anodic and chemical oxides grown on p-type InP with applications to surface passivation for n(+)-p solar cell fabrication

NASA Technical Reports Server (NTRS)

Faur, Maria; Faur, Mircea; Goradia, Manju; Goradia, Chandra; Jenkins, Phillip; Jayne, Douglas; Weinberg, Irving

1991-01-01

Most of the previously reported InP anodic oxides were grown on a n-type InP with applications to fabrication of MISFET structures and were described as a mixture of In2O3 and P2O5 stoichiometric compounds or nonstoichiometric phases which have properties similar to crystalline compounds In(OH)3, InPO4, and In(PO3)3. Details of the compositional change of the anodic oxides grown under different anodization conditions were previously reported. The use of P-rich oxides grown either by anodic or chemical oxidation are investigated for surface passivation of p-type InP and as a protective cap during junction formation by closed-ampoule sulfur diffusion. The investigation is based on but not limited to correlations between PL intensity and X-ray photoelectron spectroscopy (XPS) chemical composition data.

Water Vapor Effects on Silica-Forming Ceramics

NASA Technical Reports Server (NTRS)

Opila, E. J.; Greenbauer-Seng, L. (Technical Monitor)

2000-01-01

Silica-forming ceramics such as SiC and Si3N4 are proposed for applications in combustion environments. These environments contain water vapor as a product of combustion. Oxidation of silica-formers is more rapid in water vapor than in oxygen. Parabolic oxidation rates increase with the water vapor partial pressure with a power law exponent value close to one. Molecular water vapor is therefore the mobile species in silica. Rapid oxidation rates and large amounts of gases generated during the oxidation reaction in high water vapor pressures may result in bubble formation in the silica and nonprotective scale formation. It is also shown that silica reacts with water vapor to form Si(OH)4(g). Silica volatility has been modeled using a laminar flow boundary layer controlled reaction equation. Silica volatility depends on the partial pressure of water vapor, the total pressure, and the gas velocity. Simultaneous oxidation and volatilization reactions have been modeled with paralinear kinetics.

Partial oxidation power plant with reheating and method thereof

DOEpatents

Newby, Richard A.; Yang, Wen-Ching; Bannister, Ronald L.

1999-01-01

A system and method for generating power having an air compression/partial oxidation system, a turbine, and a primary combustion system. The air compression/partial oxidation system receives a first air stream and a fuel stream and produces a first partially oxidized fuel stream and a first compressed air stream therefrom. The turbine expands the first partially oxidized fuel stream while being cooled by the first compressed air stream to produce a heated air stream. The heated air stream is injected into the expanding first partially oxidized fuel stream, thereby reheating it in the turbine. A second partially oxidized fuel stream is emitted from the turbine. The primary combustion system receives said second partially oxidized fuel stream and a second air stream, combusts said second partially oxidized fuel stream, and produces rotating shaft power and an emission stream therefrom.

Oxidation kinetics of Haynes 230 alloy in air at temperatures between 650 and 850 °C

NASA Astrophysics Data System (ADS)

Jian, Li; Jian, Pu; Bing, Hua; Xie, Guangyuan

Haynes 230 alloy was oxidized in air at temperatures between 650 and 850 °C. Thermogravimetry was used to measure the kinetics of oxidation. The formed oxides were identified by the thin film (small angle) X-ray diffraction technique. Cr 2O 3 and MnCr 2O 4 were found in the oxide scale. Multi-stage oxidation kinetics was observed, and each stage follows Wagner's parabolic law. The first slow oxidation stage corresponded to the growth of an Cr 2O 3 layer, controlled by Cr ions diffusion through the dense Cr 2O 3 scale. The faster second stage was a result of rapid diffusion of Mn ions passing through the established Cr 2O 3 scale to form MnCr 2O 4 on top of the Cr 2O 3 layer. A duplex oxide scale is expected. The third stage, with a rate close to that of the first stage, only appeared for oxidation in the intermediate temperature range, i.e., 750-800 °C, which can be explained by the interruption of the Mn flux that forms MnCr 2O 4.

Iron oxides alter methanogenic pathways of acetate in production water of high-temperature petroleum reservoir.

PubMed

Pan, Pan; Hong, Bo; Mbadinga, Serge Maurice; Wang, Li-Ying; Liu, Jin-Feng; Yang, Shi-Zhong; Gu, Ji-Dong; Mu, Bo-Zhong

2017-09-01

Acetate is a key intermediate in anaerobic crude oil biodegradation and also a precursor for methanogenesis in petroleum reservoirs. The impact of iron oxides, viz. β-FeOOH (akaganéite) and magnetite (Fe 3 O 4 ), on the methanogenic acetate metabolism in production water of a high-temperature petroleum reservoir was investigated. Methane production was observed in all the treatments amended with acetate. In the microcosms amended with acetate solely about 30% of the acetate utilized was converted to methane, whereas methane production was stimulated in the presence of magnetite (Fe 3 O 4 ) resulting in a 48.34% conversion to methane. Methane production in acetate-amended, β-FeOOH (akaganéite)-supplemented microcosms was much faster and acetate consumption was greatly improved compared to the other conditions in which the stoichiometric expected amounts of methane were not produced. Microbial community analysis showed that Thermacetogenium spp. (known syntrophic acetate oxidizers) and hydrogenotrophic methanogens closely related to Methanothermobacter spp. were enriched in acetate and acetate/magnetite (Fe 3 O 4 ) microcosms suggesting that methanogenic acetate metabolism was through hydrogenotrophic methanogenesis fueled by syntrophic acetate oxidizers. The acetate/β-FeOOH (akaganéite) microcosms, however, differed by the dominance of archaea closely related to the acetoclastic Methanosaeta thermophila. These observations suggest that supplementation of β-FeOOH (akaganéite) accelerated the production of methane further, driven the alteration of the methanogenic community, and changed the pathway of acetate methanogenesis from hydrogenotrophic methanogenesis fueled by syntrophic acetate oxidizers to acetoclastic.

Efficient determination of average valence of manganese in manganese oxides by reaction headspace gas chromatography.

PubMed

Xie, Wei-Qi; Gong, Yi-Xian; Yu, Kong-Xian

2017-08-18

This work investigates a new reaction headspace gas chromatographic (HS-GC) technique for efficient quantifying average valence of manganese (Mn) in manganese oxides. This method is on the basis of the oxidation reaction between manganese oxides and sodium oxalate under the acidic condition. The carbon dioxide (CO 2 ) formed from the oxidation reaction can be quantitatively analyzed by headspace gas chromatography. The data showed that the reaction in the closed headspace vial can be completed in 20min at 80°C. The relative standard deviation of this reaction HS-GC method in the precision testing was within 1.08%, the relative differences between the new method and the reference method (titration method) were no more than 5.71%. The new HS-GC method is automated, efficient, and can be a reliable tool for the quantitative analysis of average valence of manganese in the manganese oxide related research and applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigation of Hydrogen-Like Muonium States in Nb-Doped SnO2 Films

NASA Astrophysics Data System (ADS)

Rabis, Annett; Prokscha, Thomas; Fabbri, Emiliana; Salman, Zaher; Schmidt, Thomas; Suter, Andreas

Little is known about the characteristics of hydrogen states in thin films of SnO2 and Nb doped SnO2 (NTO) and its influence on the electrical properties in these materials, which are promising candidates for metal-oxide supports in polymer electrolyte fuel cells. Here, we used low-energy muon spin rotation/relaxation (LE-μSR) to study hydrogen-like muonium (Mu) states between 5 and 300 K in undoped and Nb doped SnO2 films with Nb doping levels of 0.1 and 2%, respectively. The films were prepared by reactive DC magnetron sputtering on undoped Si substrates. Film thicknesses varied between 75 and 200 nm, and muons were implanted close to the surface at a mean depth of 10 nm, in the center of the films, and in some cases close to the NTO/Si interface. Our results of transverse-field and longitudinal-field μSR show striking similarities to recent bulk μSR measurements on various zirconia systems [Vieira et al., Phys. Rev. B 94, 115207 (2016)]. This suggests that in the NTO systems the same Mu configurations exist which are the interstitial site with a deep, isotropic atomic Mu state, and, as the dominant fraction, the oxygen bound configuration with polaronic character.

pH-oscillations in the bromate-sulfite reaction in semibatch and in gel-fed batch reactors

NASA Astrophysics Data System (ADS)

Poros, Eszter; Kurin-Csörgei, Krisztina; Szalai, István; Rábai, Gyula; Orbán, Miklós

2015-06-01

The simplest bromate oxidation based pH-oscillator, the two component BrO3--SO32- flow system was transformed to operate under semibatch and closed arrangements. The experimental preconditions of the pH-oscillations in semibatch configuration were predicted by model calculations. Using this information as guideline large amplitude (ΔpH˜3), long lasting (11-24 h) pH-oscillations accompanied with only a 20% increase of the volume in the reactor were measured when a mixture of Na2SO3 and H2SO4 was pumped into the solution of BrO3- with a very low rate. Batch-like pH-oscillations, similar in amplitude and period time appeared when the sulfite supply was substituted by its dissolution from a gel layer prepared previously in the reactor in presence of high concentration of Na2SO3. The dissolution vs time curve and the pH-oscillations in the semibatch and closed systems were successfully simulated. Due to the simplicity in composition and in experimental technique, the semibatch and batch-like BrO3--SO32- pH-oscillators may become superior to their CSTR (continuous flow stirred tank reactor) version in some present and future applications.

Pt/SnO2-based CO-oxidation catalysts for long-life closed-cycle CO2 lasers

NASA Technical Reports Server (NTRS)

Schryer, David R.; Upchurch, Billy T.; Hess, Robert V.; Wood, George M.; Sidney, Barry D.; Miller, Irvin M.; Brown, Kenneth G.; Vannorman, John D.; Schryer, Jacqueline; Brown, David R.

1990-01-01

Noble-metal/tin-oxide based catalysts such as Pt/SnO2 have been shown to be good catalysts for the efficient oxidation of CO at or near room temperature. These catalysts require a reductive pretreatment and traces of hydrogen or water to exhibit their full activity. Addition of Palladium enhances the activity of these catalysts with about 15 to 20 percent Pt, 4 percent Pd, and the balance SnO2 being an optimum composition. Unfortunately, these catalysts presently exhibit significant decay due in part to CO2 retention, probably as a bicarbonate. Research on minimizing the decay in activity of these catalysts is currently in progress. A proposed mechanism of CO oxidation on Pt/SnO2-based catalysts has been developed and is discussed.

Oxidation of C/SiC Composites at Reduced Oxygen Partial Pressures

NASA Technical Reports Server (NTRS)

Opila, E. J.; Serra, J. L.

2007-01-01

T-300 carbon fibers and T-300 carbon fiber reinforced silicon carbide composites (C/SiC) were oxidized in flowing reduced oxygen partial pressure environments at a total pressure of one atmosphere (0.5 atm O2, 0.05 atm O2 and 0.005 atm O2, balance argon). Experiments were conducted at four temperatures (816deg, 1149deg, 1343deg, and 1538 C). The oxidation kinetics were monitored using thermogravimetric analysis. T-300 fibers were oxidized to completion for times between 0.6 and 90 h. Results indicated that fiber oxidation kinetics were gas phase diffusion controlled. Oxidation rates had an oxygen partial pressure dependence with a power law exponent close to one. In addition, oxidation rates were only weakly dependent on temperature. The C/SiC coupon oxidation kinetics showed some variability, attributed to differences in the number and width of cracks in the SiC seal coat. In general, weight losses were observed indicating oxidation of the carbon fibers dominated the oxidation behavior. Low temperatures and high oxygen pressures resulted in the most rapid consumption of the carbon fibers. At higher temperatures, the lower oxidation rates were primarily attributed to crack closure due to SiC thermal expansion, rather than oxidation of SiC since these reduced rates were observed even at the lowest oxygen partial pressures where SiC oxidation is minimal.

Biogeochemistry of the sulfur oxidizer Thiomicrospira thermophila

NASA Astrophysics Data System (ADS)

Houghton, J.; Fike, D. A.; Wills, E.; Foustoukos, D.

2013-12-01

Near-seafloor hydrothermal environments such as diffuse flow venting or subsurface mixing are characterized by rapidly changing conditions and steep chemical and thermal gradients. Microorganisms living in these environments can take advantage of these changes by switching among metabolic pathways rather than specializing. We present reaction stoichiometry and rates for T. thermophila grown in a closed system both at ambient and elevated pressure (50 bars) that demonstrate substantial metabolic flexibility, shifting between up to 5 different sulfur cycling reactions over a 24 hour period. Based on the stoichiometry between S2O3 consumed and SO4 produced, three reactions are sulfur oxidation and two are disproportionation, which has not previously been demonstrated for Thiomicrospira strains. Reactants include S2O3, elemental S (both polymeric S chains and S8 rings), HS-, and O2, while products include polymeric elemental S, SO4, HS-, and polysulfides. The presence of μmolal concentrations of HS- has been confirmed during the time series only when stoichiometry predicts disproportionation. Production of HS- in the presence of elemental S results in abiotic conversion to polysulfides, keeping the sulfide concentrations low in solution. The transition from oxidation to disproportionation appears to be triggered by a depletion in dissolved oxygen and the rate of reaction is a second order function of S2O3 and O2 concentrations. Growth was tested at conditions spanning their pH tolerance (5.0 - 8.0) using a citrate buffer (pH 5.0), unbuffered media (initial pH 7.0), and Tris buffer (pH 8.0). The highest rates are observed at pH 8.0 with rates decreasing as a function of pH. The lowest rate occurs at pH 5.0 and exhibits pseudo-first order behavior over a 24 hour period, likely due to a long lag and very slow growth. Repeat injections after the culture is acclimated to the experimental conditions result in very high pseudo-first order rates due to rapid consumption of all available thiosulfate prior to oxygen depletion. Results from high-pressure closed system experiments (at 50 bars, buffered at pH 5.0) exhibit comparable rates to the corresponding ambient pressure condition. Future work will address the effect of dissolved O2 on sulfur disproportionation using continuous culturing of T. thermophila at deep-sea pressure conditions (>200 bar).

Multistage treatment system for raw leachate from sanitary landfill combining biological nitrification-denitrification/solar photo-Fenton/biological processes, at a scale close to industrial--biodegradability enhancement and evolution profile of trace pollutants.

PubMed

Silva, Tânia F C V; Silva, M Elisabete F; Cunha-Queda, A Cristina; Fonseca, Amélia; Saraiva, Isabel; Sousa, M A; Gonçalves, C; Alpendurada, M F; Boaventura, Rui A R; Vilar, Vítor J P

2013-10-15

A multistage treatment system, at a scale close to the industrial, was designed for the treatment of a mature raw landfill leachate, including: a) an activated sludge biological oxidation (ASBO), under aerobic and anoxic conditions; b) a solar photo-Fenton process, enhancing the bio-treated leachate biodegradability, with and without sludge removal after acidification; and c) a final polishing step, with further ASBO. The raw leachate was characterized by a high concentration of humic substances (HS) (1211 mg CHS/L), representing 39% of the dissolved organic carbon (DOC) content, and a high nitrogen content, mainly in the form of ammonium nitrogen (>3.8 g NH4(+)-N/L). In the first biological oxidation step, a 95% removal of total nitrogen and a 39% mineralization in terms of DOC were achieved, remaining only the recalcitrant fraction, mainly attributed to HS (57% of DOC). Under aerobic conditions, the highest nitrification rate obtained was 8.2 mg NH4(+)-N/h/g of volatile suspended solids (VSS), and under anoxic conditions, the maximum denitrification rate obtained was 5.8 mg (NO2(-)-N + NO3(-)-N)/h/g VSS, with a C/N consumption ratio of 2.4 mg CH3OH/mg (NO2(-)-N + NO3(-)-N). The precipitation of humic acids (37% of HS) after acidification of the bio-treated leachate corresponds to a 96% DOC abatement. The amount of UV energy and H2O2 consumption during the photo-Fenton reaction was 30% higher in the experiment without sludge removal and, consequently, the reaction velocity was 30% lower. The phototreatment process led to the depletion of HS >80%, of low-molecular-weight carboxylate anions >70% and other organic micropollutants, thus resulting in a total biodegradability increase of >70%. The second biological oxidation allowed to obtain a final treated leachate in compliance with legal discharge limits regarding water bodies (with the exception of sulfate ions), considering the experiment without sludge. Finally, the high efficiency of the overall treatment process was further reinforced by the total removal percentages attained for the identified organic trace contaminants (>90%). Copyright © 2013 Elsevier Ltd. All rights reserved.

Incineration of biomass and utilization of product gas as a CO2 source for crop production in closed systems: gas quality and phytotoxicity.

PubMed

Bubenheim, D L; Patterson, M; Wignarajah, K; Flynn, M

1997-01-01

This study addressed the recycle of carbon from inedible biomass to CO2 for utilization in crop production. Earlier work identified incineration as an attractive approach to resource recovery from solid wastes because the products are well segregated. Given the effective separation of carbon into the gaseous product stream from the incinerator in the form of CO2 we captured the gaseous stream produced during incineration of wheat inedible biomass and utilized it as the CO2 source for crop production. Injection rate was based on maintenance of CO2 concentration in the growing environment. The crop grown in the closed system was lettuce. Carbon was primarily in the form of CO2 in the incinerator product gas with less than 8% of carbon compounds appearing as CO. Nitrogen oxides and organic compounds such as toluene, xylene, and benzene were present in the product gas at lower concentrations (< 4 micromol mol-1); sulfur containing compounds were below the detection limits. Direct utilization of the gaseous product of the incinerator as the CO2 source was toxic to lettuce grown in a closed chamber. Net photosynthetic rates of the crop was suppressed more than 50% and visual injury symptoms were visible within 3 days of the introduction of the incinerator gas. Even the removal of the incinerator gas alter two days of crop exposure and replacement with pure CO2 did not eliminate the toxic effects. Both organic and inorganic components of the incinerator gas are candidates for the toxin.

Incineration of biomass and utilization of product gas as a CO2 source for crop production in closed systems: gas quality and phytotoxicity

NASA Astrophysics Data System (ADS)

1997-01-01

This study addressed the recycle of carbon from inedible biomass to CO2 for utilization in crop production. Earlier work identified incineration as an attractive approach to resource recovery from solid wastes because the products are well segregated. Given the effective separation of carbon into the gaseous product stream from the incinerator in the form of CO2 we captured the gaseous stream produced during incineration of wheat inedible biomass and utilized it as the CO2 source for crop production. Injection rate was based on maintenance of CO2 concentration in the growing environment. The crop grown in the closed system was lettuce. Carbon was primarily in the form of CO2 in the incinerator product gas with less than 8% of carbon compounds appearing as CO. Nitrogen oxides and organic compounds such as toluene, xylene, and benzene were present in the product gas at lower concentrations (<4 μmol mol-1) sulfur containing compounds were below the detection limits. Direct utilization of the gaseous product of the incinerator as the CO2 source was toxic to lettuce grown in a closed chamber. Net photosynthetic rates of the crop was suppressed more than 50% and visual injury symptoms were visible within 3 days of the introduction of the incinerator gas. Even the removal of the incinerator gas after two days of crop exposure and replacement with pure CO2 did not eliminate the toxic effects. Both organic and inorganic components of the incinerator gas are candidates for the toxin.

Incineration of biomass and utilization of product gas as a CO_2 source for crop production in closed systems: gas quality and phytotoxicity

NASA Astrophysics Data System (ADS)

Bubenheim, D. L.; Patterson, M.; Wignarajah, K.; Flynn, M.

1997-01-01

This study addressed the recycle of carbon from inedible biomass to CO_2 for utilization in crop production. Earlier work identified incineration as an attractive approach to resource recovery from solid wastes because the products are well segregated. Given the effective separation of carbon into the gaseous product stream from the incinerator in the form of CO_2 we captured the gaseous stream produced during incineration of wheat inedible biomass and utilized it as the CO_2 source for crop production. Injection rate was based on maintenance of CO_2 concentration in the growing environment. The crop grown in the closed system was lettuce. Carbon was primarily in the form of CO_2 in the incinerator product gas with less than 8% of carbon compounds appearing as CO. Nitrogen oxides and organic compounds such as toluene, xylene, and benzene were present in the product gas at lower concentrations (<4 mumol mol^-1) sulfur containing compounds were below the detection limits. Direct utilization of the gaseous product of the incinerator as the CO_2 source was toxic to lettuce grown in a closed chamber. Net photosynthetic rates of the crop was suppressed more than 50% and visual injury symptoms were visible within 3 days of the introduction of the incinerator gas. Even the removal of the incinerator gas after two days of crop exposure and replacement with pure CO_2 did not eliminate the toxic effects. Both organic and inorganic components of the incinerator gas are candidates for the toxin.

Ferrosilicon smelting in a direct current furnace

DOEpatents

Dosaj, V.D.; May, J.B.

1992-12-29

The present invention is a process for smelting ferrosilicon alloy. The process comprises adding a carbon source and tailings comprising oxides of silicon and iron to a substantially closed furnace. Heat is supplied to the furnace by striking a direct current arc between a cathode electrode and an anode functional hearth. In a preferred embodiment of the present invention, the cathode electrode is hollow and feed to the substantially closed furnace is through the hollow electrode. 1 figure.

Effect of metal oxides and black carbon (soot) on SO[sub 2]/O[sub 2]/H[sub 2]O reaction systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chughtai, A.R.; Brooks, M.E.; Smith, D.M.

1993-08-01

Particulates of atmospheric interest, including soot, oxidized soot, and oxides of transition metals, [open quotes]fellow travelers[close quotes] in the combustion of solid or liquid fossil fuels, have been examined for their influence on the heterogeneous oxidation of S(IV) to S(VI), both with and without the presence of simulated solar radiation. Under all conditions, MnO[sub 2] has been found to be the most active of the materials in this study. Effectiveness for the oxidation of SO[sub 2] in the presence of oxygen and water vapor decreases in the order: MnO[sub 2] [much gt] V[sub 2]O[sub 5] > CuO > Fe[sub 2]O[submore » 3] > Al[sub 2]O[sub 3] > Soot > TiO[sub 2] = SiO[sub 2] (cab-o-sil) [approximately] ZnO > ozonized soot = blank. The oxidation of SO[sub 2] also was carried out in the presence of soot-MnO[sub 2], soot-V[sub 2]O[sub 5], and soot-Fe[sub 2]O[sub 3] mixtures. The respective sulfate yields were found to be significantly higher than those obtained under similar conditions for the individual substrates. Other combinations, such as MnO[sub 2]/V[sub 2]O[sub 5] and MnO[sub 2]/Fe[sub 2]O[sub 3], yielded sulfate at levels higher than those obtained by any of the transition metal oxides or other oxide mixtures used. The mixing ratio of 1:0.75 (wt/wt) in the MnO[sub 2]/V[sub 2]O[sub 5] mixture was found to be optimum. With this mixture the sulfate yield was nearly twice the amount obtained if only MnO[sub 2] was used and nearly four times the amount if V[sub 2]O[sub 5] was used alone. Extensive analyses of the optimum mixture, to detect any unique identity, were inconclusive. 49 refs., 9 figs.« less

Using metatranscriptomics to understand the roles of Fe(II)-oxidizing microbes in marine hydrothermal vents

NASA Astrophysics Data System (ADS)

Glazer, B. T.; Mcallister, S.; Polson, S. W.; Chan, C. S. Y.

2015-12-01

Fe(II)-oxidizing microbes (FeOM) are thought to be key players in marine Fe cycling, particularly at hydrothermal vents. However, we do not have tools to track their activity, largely because we do not know the genes involved in neutrophilic chemolithotrophic Fe oxidation. Researchers have used gene homology between FeOM isolates to suggest several genes that may be involved in Fe(II) oxidation, including the Fe oxidase cyc2 found in the Zetaproteobacteria type strain Mariprofundus ferrooxydans, as well as all other known neutrophilic microaerophilic FeOM. Although many Zetaproteobacteria are found within natural Fe mats, close relatives of Fe(II)-oxidizing isolates are rarely present. Therefore, one goal of this study was to determine the activity of putative Fe(II) oxidation genes in dominant OTUs found in natural environments. We collected Fe mats from hydrothermal vents at Loihi Seamount, Hawaii, preserving RNA in situ. By analyzing metatranscriptomes of different Fe mat niches, we were able to determine the OTUs involved and the gene expression patterns associated with Fe(II) oxidation in the marine environment. Analysis of metatranscriptomic data confirms that the Zetaproteobacteria express the various genes necessary to support the Fe mat community through chemoautotrophic growth. Globally ubiquitous and even some rare species of the Zetaproteobacteria were active, with different relative abundances depending on Fe mat niches defined by fluid flow and geochemistry. Initial results show that genes thought to be involved in the electron transport pathway from Fe(II) to O2, including cyc2, are some of the most highly expressed genes in marine Fe microbial mats. Species-specific variants of these genes suggest that many of the Zetaproteobacteria species, spanning the breadth of the diversity of the class, are expressing genes necessary for Fe(II) oxidation within natural Fe mat niches. Understanding the differential expression of these genes in different niches will enable us to quantify the activity of marine FeOM and their effect on Fe and associated element cycling within deep and coastal marine systems.

Targeted Metagenomic Survey of the Fe-Cycling Microbial Community at Chocolate Pots Hot Springs, Yellowstone National Park

NASA Astrophysics Data System (ADS)

Fortney, N. W.; He, S.; Kulkarni, A.; Friedrich, M. W.; Boyd, E. S.; Roden, E. E.

2016-12-01

Chocolate Pots hot springs (CP) is a circumneutral pH, Fe-rich geothermal feature located in Yellowstone National Park. Fe-based metabolic processes are deeply rooted in the tree of life and studying environments like CP are important for us to study to gain insight into ancient Earth ecosystems. Recently identified features on Mars are indicative of near-surface hydrothermal environments and studies of modern Earth systems like CP allow us a glimpse into how life may have potentially arisen on other rocky worlds. Previous enrichment culture studies of the microbial community present at CP identified close relatives of dissimilatory Fe-reducing bacteria (DIRB), including Geobacter metallireducens and Melioribacter roseus. However, the question still remains as to the composition and activity of the microbial community in situ. Here we used 13C stable isotope probing to gain an understanding of the Fe cycling microbial community at CP. Fe-Si oxide sediments collected from near the hot spring vent were incubated under in situ conditions and amended with 13C-acetate or -bicarbonate to target DIRB and Fe-oxidizing bacteria, respectively. 16S rRNA gene amplicon libraries along with shotgun metagenomic libraries were obtained from both sets of incubations. Differential read coverage mapping of metagenomic reads identified a set of taxonomic bins that showed a response to the incubation treatments. We searched the Fe-reducing incubation bins for homologues of genes involved in known extracellular electron transfer (EET) systems such as Pcc and MtrAB, as well as putative porins proximal to multiheme cytochrome c genes. We also searched bins from the Fe-oxidizing incubations for these EET systems in addition to homologues of the outer membrane cytochrome c Cyc2. The Fe-oxidizing bins were also examined for genes encoding RuBisCo to identify potential chemolithoautotrophs. Our targeted metagenomic analysis will identify which organisms are likely to be part of an active Fe cycle and shed light on the potential for an internally coupled Fe and C cycle within the CP vent pool and sediments.

Interspecific differences in the antioxidant capacity of two Laridae species exposed to metals.

PubMed

Espín, Silvia; Martínez-López, Emma; Jiménez, Pedro; María-Mojica, Pedro; García-Fernández, Antonio J

2016-05-01

The main aim of the present study was to assess the concentration of metals (Pb, Cd, Hg, Cu and Zn) in blood, and elucidate their potential effects on oxidative stress biomarkers in red blood cells of Audouin's gull (Ichthyaetus audouinii) and Slender-billed gull (Chroicocephalus genei) chicks in Southeastern Spain. For this purpose, total glutathione (GSH) content, antioxidant enzymes activities (glutathione peroxidase, GPx; superoxide dismutase, SOD; catalase, CAT and glutathione-S-transferase, GST), and lipid peroxidation (TBARS) were analyzed. In general, metal exposure in both species can be considered low, except for Hg in Audouin's gull. Our findings show higher antioxidant levels in Audouin's gull than in Slender-billed gull; probably due to a combination of different basal antioxidant capacity between species, and to an up-regulation of the antioxidant system in Audouin's gull as a response to the higher Hg, Cu and Zn concentrations. This could reduce the production of TBARS keeping them at lower levels than those found in Slender-billed gull. In spite of this, the significantly higher Hg levels found in Audouin's gull (13.6µg/dl wet weight) in comparison to Slender-billed gull (2.7µg/dl), likely related to their different diet and the former consuming discarded fish, were able to produce lipid peroxidation in this species. The positive effect of Hg on SOD activity in Slender-billed gull, and of Pb on GSH levels in Audouin's gull, could reflect the necessity of the organism to upregulate these antioxidants to balance the increased oxidative stress caused by metals. The degree of metal exposure seems to be essential in the response of the antioxidant system, which may suffer up or down-regulations depending on metal concentrations. This study supports the interactive effects of metals on oxidative stress biomarkers, the complexity of the antioxidant system and the close cooperation between antioxidants, which requires the study of several metals and biomarkers to evaluate oxidative stress and damage in wild birds. Copyright © 2016 Elsevier Inc. All rights reserved.

Partial oxidation power plant with reheating and method thereof

DOEpatents

Newby, R.A.; Yang, W.C.; Bannister, R.L.

1999-08-10

A system and method are disclosed for generating power having an air compression/partial oxidation system, a turbine, and a primary combustion system. The air compression/partial oxidation system receives a first air stream and a fuel stream and produces a first partially oxidized fuel stream and a first compressed air stream therefrom. The turbine expands the first partially oxidized fuel stream while being cooled by the first compressed air stream to produce a heated air stream. The heated air stream is injected into the expanding first partially oxidized fuel stream, thereby reheating it in the turbine. A second partially oxidized fuel stream is emitted from the turbine. The primary combustion system receives said second partially oxidized fuel stream and a second air stream, combusts said second partially oxidized fuel stream, and produces rotating shaft power and an emission stream therefrom. 2 figs.

77 FR 28886 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-16

..., Functional and Cognitive Neuroscience Integrated Review Group; Sensorimotor Integration Study Section. Date... and Developmental Neuroscience Integrated Review Group; Neural Oxidative Metabolism and Death Study...: Molecular, Cellular and Developmental Neuroscience Integrated Review Group; Neurodifferentiation, Plasticity...

Parameters of oxidative stress in saliva from patients with aggressive and chronic periodontitis.

PubMed

Acquier, Andrea B; De Couto Pita, Alejandra K; Busch, Lucila; Sánchez, Gabriel A

2017-05-01

Free radicals play an important role in the onset and progression of many diseases. The aim of this study was to investigate the contribution of oxidative stress in the pathology of aggressive (AgP) and chronic (CP) periodontitis and its relation with the clinical periodontal status. Eighty subjects were divided into two groups: 20 patients with AgP and 20 patients with CP with their 20 corresponding matched controls, based on clinical attachment loss (CAL), probing pocket depth (PPD), and bleeding on probing (BOP). Saliva reactive oxygen species (ROS), lipid peroxidation, and non-enzymatic antioxidant defences were measured by luminol-dependent chemiluminescence assay, as thiobarbituric acid-reactive substances (TBARs) and total radical-trapping antioxidant potential (TRAP), respectively. Pearson's correlation and multivariate analysis were used to determine the relationship between ROS and TBARs and the clinical parameters. ROS and TBARs were increased in AgP while TRAP was decreased, comparing with CP. In AgP, a strong and positive correlation was observed between ROS and TBARs and they were closely associated with CAL and PPD. In AgP, but not in CP, oxidative stress is a high contributor to periodontal pathology and it is closely associated with the clinical periodontal status.

Intracellular energy depletion triggers programmed cell death during petal senescence in tulip.

PubMed

Azad, A K; Ishikawa, Takayuki; Ishikawa, Takahiro; Sawa, Y; Shibata, H

2008-01-01

Programmed cell death (PCD) in petals provides a model system to study the molecular aspects of organ senescence. In this study, the very early triggering signal for PCD during the senescence process from young green buds to 14-d-old petals of Tulipa gesneriana was determined. The opening and closing movement of petals of intact plants increased for the first 3 d and then gradually decreased. DNA degradation and cytochrome c (Cyt c) release were clearly observed in 6-d-old flowers. Oxidative stress or ethylene production can be excluded as the early signal for petal PCD. In contrast, ATP was dramatically depleted after the first day of flower opening. Sucrose supplementation to cut flowers maintained their ATP levels and the movement ability for a longer time than in those kept in water. The onset of DNA degradation, Cyt c release, and petal senescence was also delayed by sucrose supplementation to cut flowers. These results suggest that intracellular energy depletion, rather than oxidative stress or ethylene production, may be the very early signal to trigger PCD in tulip petals.

Intracellular energy depletion triggers programmed cell death during petal senescence in tulip

PubMed Central

Azad, A. K.; Ishikawa, Takayuki; Ishikawa, Takahiro; Shibata, H.

2008-01-01

Programmed cell death (PCD) in petals provides a model system to study the molecular aspects of organ senescence. In this study, the very early triggering signal for PCD during the senescence process from young green buds to 14-d-old petals of Tulipa gesneriana was determined. The opening and closing movement of petals of intact plants increased for the first 3 d and then gradually decreased. DNA degradation and cytochrome c (Cyt c) release were clearly observed in 6-d-old flowers. Oxidative stress or ethylene production can be excluded as the early signal for petal PCD. In contrast, ATP was dramatically depleted after the first day of flower opening. Sucrose supplementation to cut flowers maintained their ATP levels and the movement ability for a longer time than in those kept in water. The onset of DNA degradation, Cyt c release, and petal senescence was also delayed by sucrose supplementation to cut flowers. These results suggest that intracellular energy depletion, rather than oxidative stress or ethylene production, may be the very early signal to trigger PCD in tulip petals. PMID:18515833

Chirality induction and amplification in the 2,2,2-trifluoroethanol⋅⋅⋅propylene oxide adduct.

PubMed

Thomas, Javix; Jäger, Wolfgang; Xu, Yunjie

2014-07-07

Chirality induction and amplification in a model system, that is, the 2,2,2-trifluoroethanol (TFE)⋅⋅⋅propylene oxide (PO) adduct, were investigated using free-space and cavity-based Fourier transform microwave spectroscopy, complemented with high level ab initio calculations. Rotational spectra of four out of eight predicted TFE⋅⋅PO adducts were assigned, and the remaining four were shown to relax to the geometries of the four observed in a jet expansion. The g+ TFE⋅⋅⋅S-PO adduct was found to be favored over that of g- TFE⋅⋅⋅S-PO by a factor of 2.8 at 60 K. This difference contrasts the TFE dimer for which an extreme case of chirality synchronization was previously reported. All TFE⋅⋅⋅PO conformers observed take on the open arrangement, in contrast to 2-fluoroethanol⋅⋅⋅PO, which prefers the closed arrangement. Furthermore, perfluorination at CH3 increases the hydrogen-bonding energy by about 70 % over its ethanol counterpart. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Conductance Quantization in Resistive Random Access Memory

NASA Astrophysics Data System (ADS)

Li, Yang; Long, Shibing; Liu, Yang; Hu, Chen; Teng, Jiao; Liu, Qi; Lv, Hangbing; Suñé, Jordi; Liu, Ming

2015-10-01

The intrinsic scaling-down ability, simple metal-insulator-metal (MIM) sandwich structure, excellent performances, and complementary metal-oxide-semiconductor (CMOS) technology-compatible fabrication processes make resistive random access memory (RRAM) one of the most promising candidates for the next-generation memory. The RRAM device also exhibits rich electrical, thermal, magnetic, and optical effects, in close correlation with the abundant resistive switching (RS) materials, metal-oxide interface, and multiple RS mechanisms including the formation/rupture of nanoscale to atomic-sized conductive filament (CF) incorporated in RS layer. Conductance quantization effect has been observed in the atomic-sized CF in RRAM, which provides a good opportunity to deeply investigate the RS mechanism in mesoscopic dimension. In this review paper, the operating principles of RRAM are introduced first, followed by the summarization of the basic conductance quantization phenomenon in RRAM and the related RS mechanisms, device structures, and material system. Then, we discuss the theory and modeling of quantum transport in RRAM. Finally, we present the opportunities and challenges in quantized RRAM devices and our views on the future prospects.

Conductance Quantization in Resistive Random Access Memory.

PubMed

Li, Yang; Long, Shibing; Liu, Yang; Hu, Chen; Teng, Jiao; Liu, Qi; Lv, Hangbing; Suñé, Jordi; Liu, Ming

2015-12-01

The intrinsic scaling-down ability, simple metal-insulator-metal (MIM) sandwich structure, excellent performances, and complementary metal-oxide-semiconductor (CMOS) technology-compatible fabrication processes make resistive random access memory (RRAM) one of the most promising candidates for the next-generation memory. The RRAM device also exhibits rich electrical, thermal, magnetic, and optical effects, in close correlation with the abundant resistive switching (RS) materials, metal-oxide interface, and multiple RS mechanisms including the formation/rupture of nanoscale to atomic-sized conductive filament (CF) incorporated in RS layer. Conductance quantization effect has been observed in the atomic-sized CF in RRAM, which provides a good opportunity to deeply investigate the RS mechanism in mesoscopic dimension. In this review paper, the operating principles of RRAM are introduced first, followed by the summarization of the basic conductance quantization phenomenon in RRAM and the related RS mechanisms, device structures, and material system. Then, we discuss the theory and modeling of quantum transport in RRAM. Finally, we present the opportunities and challenges in quantized RRAM devices and our views on the future prospects.

Assessment of N2O emission from a photobioreactor treating ammonia-rich swine wastewater digestate.

PubMed

Mezzari, Melissa P; da Silva, Márcio L B; Nicoloso, Rodrigo S; Ibelli, Adriana M G; Bortoli, Marcelo; Viancelli, Aline; Soares, Hugo M

2013-12-01

This study investigated the interactions between naturally occurring bacteria and the microalgae Chlorella vulgaris within a lab scale photobioreactor treating ammonia-rich swine wastewater digestate effluent. Nitrification and denitrification were assessed by targeting ammonia monoxygenases (amoA), nitrate (narG), nitrite (nirS), nitric oxide (norB) and nitrous oxide (nosZ) reductases genes. Oxygen produced from microalgae photosynthesis stimulated nitrification. Under limiting carbon availability (i.e., <1.44 for mg TOC/mg NO2-N and 1.72 for mg TOC/mg NO3-N), incomplete denitrification led to accumulation of NO2 and NO3. Significant N2O emission (up to 118 μg N2O-N) was linked to NO2 metabolism in Chlorella. The addition of acetate as external carbon source recovered heterotrophic denitrification activity suppressing N2O emission. Effluent methane concentrations trapped within photobioreactor was removed concomitantly with ammonia. Overall, closed photobioreactors can be built to effectively remove nitrogen and mitigate simultaneously greenhouse gases emissions that would occur otherwise in open microalgae-based wastewater treatment systems. Copyright © 2013 Elsevier Ltd. All rights reserved.

Distribution and characterization of anammox in a swine wastewater activated sludge facility.

PubMed

Yamagishi, Takao; Takeuchi, Mio; Wakiya, Yuichiro; Waki, Miyoko

2013-01-01

Anaerobic ammonium oxidation (anammox) is a novel biological nitrogen removal process that oxidizes NH4(+) to N2 with NO2(-) as an electron acceptor. The purpose of this study was to examine the potential activity and characteristics of anammox in a conventional swine wastewater treatment facility, which uses an activated sludge system consisting of three cascade aeration tanks equipped with ceramic support material. Anammox activity was estimated by a (15)N tracer assay method and was detected in all the sludge and biofilm samples in each aeration tank. Biofilm taken from the third aeration tank, in which the dissolved oxygen concentration was 7.5 mg/L and the wastewater included a high concentration of NO3(-), showed by far the highest anammox activity. A clone library analysis showed the existence of anammox bacteria closely related to 'Candidatus Jettenia asiatica' and 'Ca. Brocadia caroliniensis'. The optimum conditions for anammox activity were a pH of 6.7-7.2, a temperature of 35 °C, a NO2(-) concentration of 10 mmol/L or less, and an NH4(+) concentration of 32 mmol/L or less.

Thermophysical and Thermomechanical Properties of Thermal Barrier Coating Systems

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

2000-01-01

Thermal barrier coatings have been developed for advanced gas turbine and diesel engine applications to improve engine reliability and fuel efficiency. However, the issue of coating durability under high temperature cyclic conditions is still of major concern. The coating failure is closely related to thermal stresses and oxidation in the coating systems. Coating shrinkage cracking resulting from ceramic sintering and creep at high temperatures can further accelerate the coating failure process. The purpose of this paper is to address critical issues such as ceramic sintering and creep, thermal fatigue and their relevance to coating life prediction. Novel test approaches have been established to obtain critical thermophysical and thermomechanical properties of the coating systems under near-realistic temperature and stress gradients encountered in advanced engine systems. Emphasis is placed on the dynamic changes of the coating thermal conductivity and elastic modulus, fatigue and creep interactions, and resulting failure mechanisms during the simulated engine tests. Detailed experimental and modeling results describing processes occurring in the thermal barrier coating systems provide a framework for developing strategies to manage ceramic coating architecture, microstructure and properties.

π vs σ-Radical States of One-Electron Oxidized DNA/RNA Bases: A Density Functional Theory Study

PubMed Central

Kumar, Anil; Sevilla, Michael D.

2013-01-01

As a result of their inherent planarity, DNA base radicals generated by one electron oxidation/reduction or bond cleavage form π- or σ-radicals. While most DNA base systems form π-radicals there are a number of nucleobase analogs such as one-electron oxidized 6-azauraci1, 6-azacytosine, and 2-thiothymine or one-electron reduced 5-bromouracil that form more reactive σ-radicals. Elucidating the availability of these states within DNA, base radical electronic structure is important to the understanding of the reactivity of DNA base radicals in different environments. In this work, we address this question by the calculation of the relative energies of π- and σ-radical states in DNA/RNA bases and their analogs. We used density functional theory B3LYP/6-31++G** method to optimize the geometries of π- and σ-radicals in Cs symmetry (i.e., planar) in the gas phase and in solution using the polarized continuum model (PCM). The calculations predict that σ- and π-radical states in one electron oxidized bases of thymine, T(N3-H)•, and uracil, U(N3-H)• are very close in energy, i.e., the π-radical is only ca. 4 kcal/mol more stable than the σ-radical. For the one electron oxidized radicals of cytosine, C•+, C(N4-H)•, adenine, A•+, A(N6-H)•, and guanine, G•+, G(N2-H)•, G(N1-H)• the π-radicals are ca. 16 to 41 kcal/mol more stable than their corresponding σ-radicals. Inclusion of solvent (PCM) is found to stabilize the π- over σ-radical of each of the systems. U(N3-H)• with three discrete water molecules in the gas phase, is found to form a three-electron σ bond between N3 atom of uracil and O atom of a water molecule but on inclusion of full solvation and discrete hydration the π-radical remains most stable.. PMID:24000793

π- vs σ-radical states of one-electron-oxidized DNA/RNA bases: a density functional theory study.

PubMed

Kumar, Anil; Sevilla, Michael D

2013-10-03

As a result of their inherent planarity, DNA base radicals generated by one-electron oxidation/reduction or bond cleavage form π- or σ-radicals. While most DNA base systems form π-radicals, there are a number of nucleobase analogues such as one-electron-oxidized 6-azauraci1, 6-azacytosine, and 2-thiothymine or one-electron reduced 5-bromouracil that form more reactive σ-radicals. Elucidating the availability of these states within DNA, base radical electronic structure is important to the understanding of the reactivity of DNA base radicals in different environments. In this work, we address this question by the calculation of the relative energies of π- and σ-radical states in DNA/RNA bases and their analogues. We used density functional theory B3LYP/6-31++G** method to optimize the geometries of π- and σ-radicals in Cs symmetry (i.e., planar) in the gas phase and in solution using the polarized continuum model (PCM). The calculations predict that σ- and π-radical states in one-electron-oxidized bases of thymine, T(N3-H)(•), and uracil, U(N3-H)(•), are very close in energy; i.e., the π-radical is only ca. 4 kcal/mol more stable than the σ-radical. For the one-electron-oxidized radicals of cytosine, C(•+), C(N4-H)(•), adenine, A(•+), A(N6-H)(•), and guanine, G(•+), G(N2-H)(•), G(N1-H)(•), the π-radicals are ca. 16-41 kcal/mol more stable than their corresponding σ-radicals. Inclusion of solvent (PCM) is found to stabilize the π- over σ-radical of each of the systems. U(N3-H)(•) with three discrete water molecules in the gas phase is found to form a three-electron σ bond between the N3 atom of uracil and the O atom of a water molecule, but on inclusion of full solvation and discrete hydration, the π-radical remains most stable.

Quantification of methane emissions from 15 Danish landfills using the mobile tracer dispersion method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mønster, Jacob; Samuelsson, Jerker, E-mail: jerker.samuelsson@fluxsense.se; Kjeldsen, Peter

2015-01-15

Highlights: • Quantification of whole landfill site methane emission at 15 landfills. • Multiple on-site source identification and quantification. • Quantified methane emission from shredder waste and composting. • Large difference between measured and reported methane emissions. - Abstract: Whole-site methane emissions from 15 Danish landfills were assessed using a mobile tracer dispersion method with either Fourier transform infrared spectroscopy (FTIR), using nitrous oxide as a tracer gas, or cavity ring-down spectrometry (CRDS), using acetylene as a tracer gas. The landfills were chosen to represent the different stages of the lifetime of a landfill, including open, active, and closed coveredmore » landfills, as well as those with and without gas extraction for utilisation or flaring. Measurements also included landfills with biocover for oxidizing any fugitive methane. Methane emission rates ranged from 2.6 to 60.8 kg h{sup −1}, corresponding to 0.7–13.2 g m{sup −2} d{sup −1}, with the largest emission rates per area coming from landfills with malfunctioning gas extraction systems installed, and the smallest emission rates from landfills closed decades ago and landfills with an engineered biocover installed. Landfills with gas collection and recovery systems had a recovery efficiency of 41–81%. Landfills where shredder waste was deposited showed significant methane emissions, with the largest emission from newly deposited shredder waste. The average methane emission from the landfills was 154 tons y{sup −1}. This average was obtained from a few measurement campaigns conducted at each of the 15 landfills and extrapolating to annual emissions requires more measurements. Assuming that these landfills are representative of the average Danish landfill, the total emission from Danish landfills were calculated at 20,600 tons y{sup −1}, which is significantly lower than the 33,300 tons y{sup −1} estimated for the national greenhouse gas inventory for 2011.« less

Combined experimental and theoretical study on the reactivity of compounds I and II in horseradish peroxidase biomimetics.

PubMed

Ji, Li; Franke, Alicja; Brindell, Małgorzata; Oszajca, Maria; Zahl, Achim; van Eldik, Rudi

2014-10-27

For the exploration of the intrinsic reactivity of two key active species in the catalytic cycle of horseradish peroxidase (HRP), Compound I (HRP-I) and Compound II (HRP-II), we generated in situ [Fe(IV) O(TMP(+.) )(2-MeIm)](+) and [Fe(IV) O(TMP)(2-MeIm)](0) (TMP=5,10,15,20-tetramesitylporphyrin; 2-MeIm=2-methylimidazole) as biomimetics for HRP-I and HRP-II, respectively. Their catalytic activities in epoxidation, hydrogen abstraction, and heteroatom oxidation reactions were studied in acetonitrile at -15 °C by utilizing rapid-scan UV/Vis spectroscopy. Comparison of the second-order rate constants measured for the direct reactions of the HRP-I and HRP-II mimics with the selected substrates clearly confirmed the outstanding oxidizing capability of the HRP-I mimic, which is significantly higher than that of HRP-II. The experimental study was supported by computational modeling (DFT calculations) of the oxidation mechanism of the selected substrates with the involvement of quartet and doublet HRP-I mimics ((2,4) Cpd I) and the closed-shell triplet spin HRP-II model ((3) Cpd II) as oxidizing species. The significantly lower activation barriers calculated for the oxidation systems involving (2,4) Cpd I than those found for (3) Cpd II are in line with the much higher oxidizing efficiency of the HRP-I mimic proven in the experimental part of the study. In addition, the DFT calculations show that all three reaction types catalyzed by HRP-I occur on the doublet spin surface in an effectively concerted manner, whereas these reactions may proceed in a stepwise mechanism with the HRP-II mimic as oxidant. However, the high desaturation or oxygen rebound barriers during CH bond activation processes by the HRP-II mimic predict a sufficient lifetime for the substrate radical formed through hydrogen abstraction. Thus, the theoretical calculations suggest that the dissociation of the substrate radical may be a more favorable pathway than desaturation or oxygen rebound processes. Importantly, depending on the electronic nature of the oxidizing species, that is, (2,4) Cpd I or (3) Cpd II, an interesting region-selective conversion phenomenon between sulfoxidation and H-atom abstraction was revealed in the course of the oxidation reaction of dimethylsulfide. The combined experimental and theoretical study on the elucidation of the intrinsic reactivity patterns of the HRP-I and HRP-II mimics provides a valuable tool for evaluating the particular role of the HRP active species in biological systems. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanoparticles in natural systems I: The effective reactive surface area of the natural oxide fraction in field samples

NASA Astrophysics Data System (ADS)

Hiemstra, Tjisse; Antelo, Juan; Rahnemaie, Rasoul; van Riemsdijk, Willem H.

2010-01-01

Information on the particle size and reactive surface area of natural samples is essential for the application of surface complexation models (SCM) to predict bioavailability, toxicity, and transport of elements in the natural environment. In addition, this information will be of great help to enlighten views on the formation, stability, and structure of nanoparticle associations of natural organic matter (NOM) and natural oxide particles. Phosphate is proposed as a natively present probe ion to derive the effective reactive surface area of natural samples. In the suggested method, natural samples are equilibrated (⩾10 days) with 0.5 M NaHCO 3 (pH = 8.5) at various solid-solution ratios. This matrix fixes the pH and ionic strength, suppresses the influence of Ca 2+ and Mg 2+ ions by precipitation these in solid carbonates, and removes NOM due to the addition of activated carbon in excess, collectively leading to the dominance of the PO 4-CO 3 interaction in the system. The data have been interpreted with the charge distribution (CD) model, calibrated for goethite, and the analysis results in an effective reactive surface area (SA) and a reversibly bound phosphate loading Γ for a series of top soils. The oxidic SA varies between about 3-30 m 2/g sample for a large series of representative agricultural top soils. Scaling of our data to the total iron and aluminum oxide content (dithionite-citrate-bicarbonate extractable), results in the specific surface area between about 200-1200 m 2/g oxide for most soils, i.e. the oxide particles are nano-sized with an equivalent diameter in the order of ˜1-10 nm if considered as non-porous spheres. For the top soils, the effective surface area and the soil organic carbon fraction are strongly correlated. The oxide particles are embedded in a matrix of organic carbon (OC), equivalent to ˜1.4 ± 0.2 mg OC/m 2 oxide for many soils of the collection, forming a NOM-mineral nanoparticle association with an average NOM volume fraction of ˜80%. The average mass density of such a NOM-mineral association is ˜1700 ± 100 kg/m 3 (i.e. high-density NOM). The amount of reversibly bound phosphate is rather close to the amount of phosphate that is extractable with oxalate. The phosphate loading varies remarkably ( Γ ≈ 1-3 μmol/m 2 oxide) in the samples. As discussed in part II of this paper series ( Hiemstra et al., 2010), the phosphate loading ( Γ) of field samples is suppressed by surface complexation of NOM, where hydrophilic, fulvic, and humic acids act as a competitor for (an)ions via site competition and electrostatic interaction.

Formulation and evaluation of chitosan/polyethylene oxide nanofibers loaded with metronidazole for local infections.

PubMed

Zupančič, Špela; Potrč, Tanja; Baumgartner, Saša; Kocbek, Petra; Kristl, Julijana

2016-12-01

Nanofibers combined with an antimicrobial represent a powerful strategy for treatment of various infections. Local infections usually have a low fluid volume available for drug release, whereas pharmacopoeian dissolution tests include a much larger receptor volume. Therefore, the development of novel drug-release methods that more closely resemble the in-vivo conditions is necessary. We first developed novel biocompatible and biodegradable chitosan/polyethylene oxide nanofibers using environmentally friendly electrospinning of aqueous polymer solutions, with the inclusion of the antimicrobial metronidazole. Here, the focus is on the characterization of these nanofibers, which have high potential for bioadhesion and retention at the site of application. These can be used where prolonged retention of the delivery system at an infected target site is needed. Drug release was studied using three in-vitro methods: a dissolution apparatus (Apparatus 1 of the European Pharmacopoeia), vials, and a Franz diffusion cell. In contrast to other studies, here the Franz diffusion cell method was modified to introduce a small volume of medium with the nanofibers in the donor compartment, where the nanofibers swelled, eroded, and released the metronidazole, which then diffused into the receptor compartment. This set-up with nanofibers in a limited amount of medium released the drug more slowly compared to the other two in-vitro methods that included larger volumes of medium. These findings show that drug release from nanofibers strongly depends on the release method used. Therefore, in-vitro test methods should closely resemble the in-vivo conditions for more accurate prediction of drug release at a therapeutic site. Copyright © 2016 Elsevier B.V. All rights reserved.

Functionally relevant diversity of closely related Nitrospira in activated sludge.

PubMed

Gruber-Dorninger, Christiane; Pester, Michael; Kitzinger, Katharina; Savio, Domenico F; Loy, Alexander; Rattei, Thomas; Wagner, Michael; Daims, Holger

2015-03-01

Nitrospira are chemolithoautotrophic nitrite-oxidizing bacteria that catalyze the second step of nitrification in most oxic habitats and are important for excess nitrogen removal from sewage in wastewater treatment plants (WWTPs). To date, little is known about their diversity and ecological niche partitioning within complex communities. In this study, the fine-scale community structure and function of Nitrospira was analyzed in two full-scale WWTPs as model ecosystems. In Nitrospira-specific 16S rRNA clone libraries retrieved from each plant, closely related phylogenetic clusters (16S rRNA identities between clusters ranged from 95.8% to 99.6%) within Nitrospira lineages I and II were found. Newly designed probes for fluorescence in situ hybridization (FISH) allowed the specific detection of several of these clusters, whose coexistence in the WWTPs was shown for prolonged periods of several years. In situ ecophysiological analyses based on FISH, relative abundance and spatial arrangement quantification, as well as microautoradiography revealed functional differences of these Nitrospira clusters regarding the preferred nitrite concentration, the utilization of formate as substrate and the spatial coaggregation with ammonia-oxidizing bacteria as symbiotic partners. Amplicon pyrosequencing of the nxrB gene, which encodes subunit beta of nitrite oxidoreductase of Nitrospira, revealed in one of the WWTPs as many as 121 species-level nxrB operational taxonomic units with highly uneven relative abundances in the amplicon library. These results show a previously unrecognized high diversity of Nitrospira in engineered systems, which is at least partially linked to niche differentiation and may have important implications for process stability.

Space Shuttle RCS Oxidizer Leak Repair for STS-26

NASA Technical Reports Server (NTRS)

Delventhal, R. A.; Faget, N. M.

1989-01-01

Following propellant loading of the Space Shuttle's reaction control system (RCS) for mission STS 26, an oxidizer leak was detected in the left orbital maneuvering system (OMS) pod, where the RCS is located. Subsequent investigation determined that the leak was isolated at a mechanical Dynatube fitting near the RCS nitrogen tetroxide tank. An intense effort was initiated to design, fabricate, and qualify a sealing device to stop the oxidizer leak externally so that the Space Shuttle launch could proceed. It was discovered that sealing devices called clamshells were widely used throughout the petrochemical and power generation industries to stop leaks developed in large diameter pipes which carry steam or other hazardous fluids. These clamshells are available in different diameters and strengths and are placed around the pipe at the location of the leak. A sealing compound is then injected under high pressure into the clamshell to stop the leak. This technology was scaled down and applied to the problem of stopping the leak on the Orbiter, which was on a half-inch diameter line in a nearly inaccessible location. Many obstacles had to be overcome such as determining that the sealing material would be compatible with the nitrogen tetroxide and ensuring that the clamshell would actually fit around the Dynatube fitting without interfering with other lines which were in close proximity. The effort at the NASA Johnson Space Center included materials compatibility testing of several sealants, design of a clamshell to fit in the confined compartment, and manufacture and qualification of the flight hardware. A clamshell was successfully placed around the Dynatube fitting on the Orbiter and the oxidizer leak was terminated. Then it was decided to apply this technology further and design clamshells for other mechanical fittings onboard the Orbiter and develop sealing compounds which will be compatible with fuels such as monomethyl hydrazine (MMH). The potential exists for using this type of sealing device in numerous other applications throughout the aerospace industry.

Electrochemical incineration of omeprazole in neutral aqueous medium using a platinum or boron-doped diamond anode: degradation kinetics and oxidation products.

PubMed

Cavalcanti, Eliane Bezerra; Garcia-Segura, Sergi; Centellas, Francesc; Brillas, Enric

2013-04-01

The electrochemical incineration of omeprazole, a widely prescribed gastrointestinal drug which is detected in natural waters, has been studied in a phosphate buffer of pH 7.0 by anodic oxidation with electrogenerated H(2)O(2) (AO-H(2)O(2)) operating at constant current density (j). The experiments were carried out in a cell equipped with either a Pt or a boron-doped diamond (BDD) anode and an air-diffusion cathode to continuously produce H(2)O(2). In these systems, organics are mainly oxidized by hydroxyl radicals formed at the Pt or BDD surface from water oxidation. A partial total organic carbon (TOC) abatement close to 78% for omeprazole was achieved by AO-H(2)O(2) with a BDD anode after consumption of 18 Ah L(-1) at 100 mA cm(-2), whereas the alternative use of Pt did not allow mineralizing the drug. However, the drug was totally removed using both anodes, although it decayed more rapidly using BDD. In this latter system, increasing j accelerated the degradation process, but lowering the mineralization current efficiency. Greater drug content also enhanced the degradation rate with higher mineralization degree and current efficiency. The kinetics for omeprazole decay always followed a pseudo-first-order reaction and its rate constant increased with increasing j and with decreasing its concentration. Seven heteroaromatic intermediates and four hydroxylated derivatives were detected by LC-MS, while nine short-linear carboxylic acids were identified and quantified by ion-exclusion HPLC. These acids were largely accumulated using Pt and rapidly removed using BDD, thus explaining the partial mineralization of omeprazole achieved by AO-H(2)O(2) with the latter anode. The release of inorganic ions such as NO(3)(-), NH(4)(+) and SO(4)(2-) was followed by ionic chromatography. A plausible reaction sequence for omeprazole mineralization involving all intermediates detected is proposed. Copyright © 2013 Elsevier Ltd. All rights reserved.

Modeling Geometric Arrangements of TiO2-Based Catalyst Substrates and Isotropic Light Sources to Enhance the Efficiency of a Photocatalystic Oxidation (PCO) Reactor

NASA Technical Reports Server (NTRS)

Richards, Jeffrey T.; Levine, Lanfang H.; Husk, Geoffrey K.

2011-01-01

The closed confined environments of the ISS, as well as in future spacecraft for exploration beyond LEO, provide many challenges to crew health. One such challenge is the availability of a robust, energy efficient, and re-generable air revitalization system that controls trace volatile organic contaminants (VOCs) to levels below a specified spacecraft maximum allowable concentration (SMAC). Photocatalytic oxidation (PCO), which is capable of mineralizing VOCs at room temperature and of accommodating a high volumetric flow, is being evaluated as an alternative trace contaminant control technology. In an architecture of a combined air and water management system, placing a PCO unit before a condensing heat exchanger for humidity control will greatly reduce the organic load into the humidity condensate loop ofthe water processing assembly (WPA) thereby enhancing the life cycle economics ofthe WPA. This targeted application dictates a single pass efficiency of greater than 90% for polar VOCs. Although this target was met in laboratory bench-scaled reactors, no commercial or SBIR-developed prototype PCO units examined to date have achieved this goal. Furthermore, the formation of partial oxidation products (e.g., acetaldehyde) was not eliminated. It is known that single pass efficiency and partial oxidation are strongly dependent upon the contact time and catalyst illumination, hence the requirement for an efficient reactor design. The objective of this study is to maximize the apparent contact time and illuminated catalyst surface area at a given reactor volume and volumetric flow. In this study, a Ti02-based photocatalyst is assumed to be immobilized on porous substrate panels and illumination derived from linear isotropic light sources. Mathematical modeling using computational fluid dynamics (CFD) analyses were performed to investigate the effect of: 1) the geometry and configuration of catalyst-coated substrate panels, 2) porosity of the supporting substrate, and 3) varying the light source and spacing on contact time and illuminated catalyst area.

The relationship between CK and CV chondrites

NASA Astrophysics Data System (ADS)

Greenwood, R. C.; Franchi, I. A.; Kearsley, A. T.; Alard, O.

2010-03-01

CK chondrites are highly oxidized meteorites containing abundant magnetite and trace amounts of Fe,Ni metal. Although the group is predominately composed of equilibrated meteorites (types 4-6), in recent years a significant number of new samples have been classified as being either CK3 or CK3-anomalous. These unequilibrated CKs often display a close affinity with members of the CV oxidized subgroup. CKs and CVs (oxidized subgroup) may therefore form a continuum and by implication could be derived from a single common parent body. To investigate the relationship between these two groups a detailed study of the oxygen isotope composition, opaque mineralogy and major and trace element geochemistry of a suite of CV and CK chondrites has been undertaken. The results of oxygen isotope analysis confirm the close affinity between CV and CK chondrites, while excluding the possibility of a linkage between the CO and CK groups. Magnetites in both CV and CK chondrites show significant compositional similarities, but high Ti contents are a diagnostic feature of the latter group. The results of major and trace element analysis demonstrate that both CV and CK chondrites show overlapping variation. Supporting evidence for a single common source for both groups comes from their similar cosmic-ray exposure age distributions. Recent reflectance spectral analysis is consistent with both the CVs and CKs being derived from Eos family asteroids, which are believed to have formed by the catastrophic disruption of a single large asteroid. Thus, a range of evidence appears to be consistent with CV and CK chondrites representing samples from a single thermally stratified parent body. In view of the close similarity between CV and CK chondrites some modification of the present classification scheme may be warranted, possibly involving integration of the two groups. One means of achieving this would be to reassigned CK chondrites to a subgroup of the oxidized CVs. It is recognized that a full evaluation of this proposal may require further study of the still poorly understood CK3 chondrites.