WorldWideScience

Sample records for surface redox process

  1. Characterization of the surface redox process of adsorbed morin at glassy carbon electrodes

    International Nuclear Information System (INIS)

    Tesio, Alvaro Yamil; Granero, Adrian Marcelo; Fernandez, Hector; Zon, Maria Alicia

    2011-01-01

    The thermodynamic and kinetics of the adsorption of morin (MOR) on glassy carbon (GC) electrodes in 0.2 mol dm -3 phosphate buffer solutions (PBS, pH 7.00) was studied by both cyclic (CV) and square wave (SWV) voltammetries. The Frumkin adsorption isotherm was the best to describe the specific interaction of MOR with GC electrodes. The SWV allowed to characterize the thermodynamic and kinetics of surface quasi-reversible redox couple of MOR, using the combination of the 'quasi-reversible maximum' and the 'splitting of SW net peaks' methods. Average values obtained for the formal potential and the anodic transfer coefficient were (0.27 ± 0.02) V and (0.59 ± 0.09), respectively. Moreover, a value of formal rate constant (k s ) of 87 s -1 for the overall two-electron redox process was calculated. The SWV was also employed to generate calibration curves, which were linear in the range MOR bulk concentration (c MOR *) from 1.27 x 10 -7 to 2.50 x 10 -5 mol dm -3 . The lowest concentration experimentally measured for a signal to noise ratio of 3:1 was 1.25 x 10 -8 mol dm -3 (3 ppb).

  2. Modification of the glass surface induced by redox reactions and internal diffusion processes

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Deubener, Joachim; Yue, Yuanzheng

    In this paper we report a novel way to modify the glass surface in favor of some physical performances. The main step is to perform iso-thermal treatments on the selected silicate glasses containing transition metal at temperatures near the glass transition temperature for various durations under...

  3. Redox processes in radiation biology and cancer

    International Nuclear Information System (INIS)

    Greenstock, C.L.

    1981-01-01

    Free-radical intermediates, particularly the activated oxygen species OH, O - 2 , and 1 O 2 , are implicated in many types of radiation damage to biological systems. In addition, these same species may be formed, either directly or indirectly through biochemical redox reactions, in both essential and aberrant metabolic processes. Cell survival and adaptation to an environment containing ionizing radiation and other physical and chemical carcinogens ultimately depend upon the cell's ability to maintain optimal function in response to free-radical damage at the chemical level. Many of these feedback control mechanisms are redox controlled. Radiation chemical techniques using selective radical scavengers, such as product analysis and pulse radiolysis, enable us to generate, observe, and characterize individually the nature and reactivity of potentially damaging free radicals. From an analysis of the chemical kinetics of free-radical involvement in biological damage, redox mechanisms are proposed to describe the early processes of radiation damage, redox mechanisms are proposed to describe the early processes of radiation damage, its protection and sensitization, and the role of free radicals in radiation and chemical carcinogenesis

  4. Electrochemical redox processes involving soluble cerium species

    International Nuclear Information System (INIS)

    Arenas, L.F.; Ponce de León, C.; Walsh, F.C.

    2016-01-01

    Highlights: • The relevance of cerium in laboratory and industrial electrochemistry is considered. • The history of fundamental electrochemical studies and applications is considered. • The chemistry, redox thermodynamics and electrode kinetics of cerium are summarised. • The uses of cerium ions in synthesis, energy storage, analysis and environmental treatment are illustrated. • Research needs and development perspectives are discussed. - Abstract: Anodic oxidation of cerous ions and cathodic reduction of ceric ions, in aqueous acidic solutions, play an important role in electrochemical processes at laboratory and industrial scale. Ceric ions, which have been used for oxidation of organic wastes and off-gases in environmental treatment, are a well-established oxidant for indirect organic synthesis and specialised cleaning processes, including oxide film removal from tanks and process pipework in nuclear decontamination. They also provide a classical reagent for chemical analysis in the laboratory. The reversible oxidation of cerous ions is an important reaction in the positive compartment of various redox flow batteries during charge and discharge cycling. A knowledge of the thermodynamics and kinetics of the redox reaction is critical to an understanding of the role of cerium redox species in these applications. Suitable choices of electrode material (metal or ceramic; coated or uncoated), geometry/structure (2-or 3-dimensional) and electrolyte flow conditions (hence an acceptable mass transport rate) are critical to achieving effective electrocatalysis, a high performance and a long lifetime. This review considers the electrochemistry of soluble cerium species and their diverse uses in electrochemical technology, especially for redox flow batteries and mediated electrochemical oxidation.

  5. Information processing through a bio-based redox capacitor: signatures for redox-cycling.

    Science.gov (United States)

    Liu, Yi; Kim, Eunkyoung; White, Ian M; Bentley, William E; Payne, Gregory F

    2014-08-01

    Redox-cycling compounds can significantly impact biological systems and can be responsible for activities that range from pathogen virulence and contaminant toxicities, to therapeutic drug mechanisms. Current methods to identify redox-cycling activities rely on the generation of reactive oxygen species (ROS), and employ enzymatic or chemical methods to detect ROS. Here, we couple the speed and sensitivity of electrochemistry with the molecular-electronic properties of a bio-based redox-capacitor to generate signatures of redox-cycling. The redox capacitor film is electrochemically-fabricated at the electrode surface and is composed of a polysaccharide hydrogel with grafted catechol moieties. This capacitor film is redox-active but non-conducting and can engage diffusible compounds in either oxidative or reductive redox-cycling. Using standard electrochemical mediators ferrocene dimethanol (Fc) and Ru(NH3)6Cl3 (Ru(3+)) as model redox-cyclers, we observed signal amplifications and rectifications that serve as signatures of redox-cycling. Three bio-relevant compounds were then probed for these signatures: (i) ascorbate, a redox-active compound that does not redox-cycle; (ii) pyocyanin, a virulence factor well-known for its reductive redox-cycling; and (iii) acetaminophen, an analgesic that oxidatively redox-cycles but also undergoes conjugation reactions. These studies demonstrate that the redox-capacitor can enlist the capabilities of electrochemistry to generate rapid and sensitive signatures of biologically-relevant chemical activities (i.e., redox-cycling). Published by Elsevier B.V.

  6. Are bioassays useful tools to assess redox processes and biodegradation?

    DEFF Research Database (Denmark)

    Albrechtsen, Hans-Jørgen; Pedersen, Philip Grinder; Ludvigsen, L.

    2002-01-01

    sensitive hydrochemical or geochemical parameters, levels of hydrogen, and redox potential. However, all these approaches have to be evaluated against TEAP-bioassays as the most direct measure. We assessed successfully ongoing microbial-mediated redox processes by TEAP-bioassays in degradation studies...... of aromatic and chlorinated aliphatic compounds in landfill leachate plumes, and of pesticides in aquifers with various redox conditions....

  7. Fenton Redox Chemistry : Arsenite Oxidation by Metallic Surfaces

    NARCIS (Netherlands)

    Borges Freitas, S.C.; Van Halem, D.; Badruzzaman, A.B.M.; Van der Meer, W.G.J.

    2014-01-01

    Pre-oxidation of As(III) is necessary in arsenic removal processes in order to increase its efficiency. Therefore, the Fenton Redox Chemistry is defined by catalytic activation of H2O2 and currently common used for its redox oxidative properties. In this study the effect of H2O2 production catalysed

  8. Imaging dynamic redox processes with genetically encoded probes.

    Science.gov (United States)

    Ezeriņa, Daria; Morgan, Bruce; Dick, Tobias P

    2014-08-01

    Redox signalling plays an important role in many aspects of physiology, including that of the cardiovascular system. Perturbed redox regulation has been associated with numerous pathological conditions; nevertheless, the causal relationships between redox changes and pathology often remain unclear. Redox signalling involves the production of specific redox species at specific times in specific locations. However, until recently, the study of these processes has been impeded by a lack of appropriate tools and methodologies that afford the necessary redox species specificity and spatiotemporal resolution. Recently developed genetically encoded fluorescent redox probes now allow dynamic real-time measurements, of defined redox species, with subcellular compartment resolution, in intact living cells. Here we discuss the available genetically encoded redox probes in terms of their sensitivity and specificity and highlight where uncertainties or controversies currently exist. Furthermore, we outline major goals for future probe development and describe how progress in imaging methodologies will improve our ability to employ genetically encoded redox probes in a wide range of situations. This article is part of a special issue entitled "Redox Signalling in the Cardiovascular System." Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

    Directory of Open Access Journals (Sweden)

    Krishnamoorthy Arumugam

    2014-04-01

    Full Text Available Applications of redox processes range over a number of scientific fields. This review article summarizes the theory behind the calculation of redox potentials in solution for species such as organic compounds, inorganic complexes, actinides, battery materials, and mineral surface-bound-species. Different computational approaches to predict and determine redox potentials of electron transitions are discussed along with their respective pros and cons for the prediction of redox potentials. Subsequently, recommendations are made for certain necessary computational settings required for accurate calculation of redox potentials. This article reviews the importance of computational parameters, such as basis sets, density functional theory (DFT functionals, and relativistic approaches and the role that physicochemical processes play on the shift of redox potentials, such as hydration or spin orbit coupling, and will aid in finding suitable combinations of approaches for different chemical and geochemical applications. Identifying cost-effective and credible computational approaches is essential to benchmark redox potential calculations against experiments. Once a good theoretical approach is found to model the chemistry and thermodynamics of the redox and electron transfer process, this knowledge can be incorporated into models of more complex reaction mechanisms that include diffusion in the solute, surface diffusion, and dehydration, to name a few. This knowledge is important to fully understand the nature of redox processes be it a geochemical process that dictates natural redox reactions or one that is being used for the optimization of a chemical process in industry. In addition, it will help identify materials that will be useful to design catalytic redox agents, to come up with materials to be used for batteries and photovoltaic processes, and to identify new and improved remediation strategies in environmental engineering, for example the

  10. An Excel Workbook for Identifying Redox Processes in Ground Water

    Science.gov (United States)

    Jurgens, Bryant C.; McMahon, Peter B.; Chapelle, Francis H.; Eberts, Sandra M.

    2009-01-01

    The reduction/oxidation (redox) condition of ground water affects the concentration, transport, and fate of many anthropogenic and natural contaminants. The redox state of a ground-water sample is defined by the dominant type of reduction/oxidation reaction, or redox process, occurring in the sample, as inferred from water-quality data. However, because of the difficulty in defining and applying a systematic redox framework to samples from diverse hydrogeologic settings, many regional water-quality investigations do not attempt to determine the predominant redox process in ground water. Recently, McMahon and Chapelle (2008) devised a redox framework that was applied to a large number of samples from 15 principal aquifer systems in the United States to examine the effect of redox processes on water quality. This framework was expanded by Chapelle and others (in press) to use measured sulfide data to differentiate between iron(III)- and sulfate-reducing conditions. These investigations showed that a systematic approach to characterize redox conditions in ground water could be applied to datasets from diverse hydrogeologic settings using water-quality data routinely collected in regional water-quality investigations. This report describes the Microsoft Excel workbook, RedoxAssignment_McMahon&Chapelle.xls, that assigns the predominant redox process to samples using the framework created by McMahon and Chapelle (2008) and expanded by Chapelle and others (in press). Assignment of redox conditions is based on concentrations of dissolved oxygen (O2), nitrate (NO3-), manganese (Mn2+), iron (Fe2+), sulfate (SO42-), and sulfide (sum of dihydrogen sulfide [aqueous H2S], hydrogen sulfide [HS-], and sulfide [S2-]). The logical arguments for assigning the predominant redox process to each sample are performed by a program written in Microsoft Visual Basic for Applications (VBA). The program is called from buttons on the main worksheet. The number of samples that can be analyzed

  11. Surface Redox Chemistry of Immobilized Nanodiamond: Effects of Particle Size and Electrochemical Environment

    Science.gov (United States)

    Gupta, S.; McDonald, B.; Carrizosa, S. B.

    2017-07-01

    The size of the diamond particle is tailored to nanoscale (nanodiamond, ND), and the ND surface is engineered targeting specific (electrochemical and biological) applications. In this work, we investigated the complex surface redox chemistry of immobilized ND layer on conductive boron-doped diamond electrode with a broad experimental parameter space such as particle size (nano versus micron), scan rate, pH (cationic/acidic versus anionic/basic), electrolyte KCl concentration (four orders of magnitude), and redox agents (neutral and ionic). We reported on the significant enhancement of ionic currents while recording reversible oxidation of neutral ferrocene methanol (FcMeOH) by almost one order of magnitude than traditional potassium ferricyanide (K3Fe(CN)6) redox agent. The current enhancement is inversely related to ND particle diameter in the following order: 1 μm << 1000 nm < 100 nm < 10 nm ≤ 5 nm < 2 nm. We attribute the current enhancement to concurrent electrocatalytic processes, i.e. the electron transfer between redox probes and electroactive surface functional (e.g. hydroxyl, carboxyl, epoxy) moieties and the electron transfer mediated by adsorbed FcMeOH+ (or Fe(CN) 6 3+ ) ions onto ND surface. The first process is pH dependent since it depends upon ND surface functionalities for which the electron transfer is coupled to proton transfer. The adsorption mediated process is observed most apparently at slower scan rates owing to self-exchange between adsorbed FcMeOH+ ions and FcMeOH redox agent molecules in diffusion-limited bulk electrolyte solution. Alternatively, it is hypothesized that the surface functionality and defect sites ( sp 2-bonded C shell and unsaturated bonds) give rise to surface electronic states with energies within the band gap (midgap states) in undoped ND. These surface states serve as electron donors (and acceptors) depending upon their bonding (and antibonding) character and, therefore, they can support electrocatalytic redox

  12. Redox processes at a nanostructured interface under strong electric fields.

    Science.gov (United States)

    Steurer, Wolfram; Surnev, Svetlozar; Netzer, Falko P; Sementa, Luca; Negreiros, Fabio R; Barcaro, Giovanni; Durante, Nicola; Fortunelli, Alessandro

    2014-09-21

    Manipulation of chemistry and film growth via external electric fields is a longstanding goal in surface science. Numerous systems have been predicted to show such effects but experimental evidence is sparse. Here we demonstrate in a custom-designed UHV apparatus that the application of spatially extended, homogeneous, very high (>1 V nm(-1)) DC-fields not only changes the system energetics but triggers dynamic processes which become important much before static contributions appreciably modify the potential energy landscape. We take a well characterized ultrathin NiO film on a Ag(100) support as a proof-of-principle test case, and show how it gets reduced to supported Ni clusters under fields exceeding the threshold of +0.9 V nm(-1). Using an effective model, we trace the observed interfacial redox process down to a dissociative electron attachment resonant mechanism. The proposed approach can be easily implemented and generally applied to a wide range of interfacial systems, thus opening new opportunities for the manipulation of film growth and reaction processes at solid surfaces under strong external fields.

  13. Interactions between magnetite and humic substances: redox reactions and dissolution processes.

    Science.gov (United States)

    Sundman, Anneli; Byrne, James M; Bauer, Iris; Menguy, Nicolas; Kappler, Andreas

    2017-10-19

    Humic substances (HS) are redox-active compounds that are ubiquitous in the environment and can serve as electron shuttles during microbial Fe(III) reduction thus reducing a variety of Fe(III) minerals. However, not much is known about redox reactions between HS and the mixed-valent mineral magnetite (Fe 3 O 4 ) that can potentially lead to changes in Fe(II)/Fe(III) stoichiometry and even dissolve the magnetite. To address this knowledge gap, we incubated non-reduced (native) and reduced HS with four types of magnetite that varied in particle size and solid-phase Fe(II)/Fe(III) stoichiometry. We followed dissolved and solid-phase Fe(II) and Fe(III) concentrations over time to quantify redox reactions between HS and magnetite. Magnetite redox reactions and dissolution processes with HS varied depending on the initial magnetite and HS properties. The interaction between biogenic magnetite and reduced HS resulted in dissolution of the solid magnetite mineral, as well as an overall reduction of the magnetite. In contrast, a slight oxidation and no dissolution was observed when native and reduced HS interacted with 500 nm magnetite. This variability in the solubility and electron accepting and donating capacity of the different types of magnetite is likely an effect of differences in their reduction potential that is correlated to the magnetite Fe(II)/Fe(III) stoichiometry, particle size, and crystallinity. Our study suggests that redox-active HS play an important role for Fe redox speciation within minerals such as magnetite and thereby influence the reactivity of these Fe minerals and their role in biogeochemical Fe cycling. Furthermore, such processes are also likely to have an effect on the fate of other elements bound to the surface of Fe minerals.

  14. Decontamination of alpha contaminated metallic waste by cerium IV redox process

    International Nuclear Information System (INIS)

    Shah, J.G.; Dhami, P.S.; Gandhi, P.M.; Wattal, P.K.

    2012-01-01

    Decontamination of alpha contaminated metallic waste is an important aspect in the management of waste generated during dismantling and decommissioning of nuclear facilities. Present work on cerium redox process targets decontamination of alpha contaminated metallic waste till it qualifies for the non alpha waste category for disposal in near surface disposal facility. Recovery of the alpha radio nuclides and cerium from aqueous secondary waste streams was also studied deploying solvent extraction process and established. The alpha-lean secondary waste stream has been immobilised in cement based matrix for final disposal. (author)

  15. Single-molecule conductivity of non-redox and redox molecules at pure and gold-mined Au(111)-electrode surfaces

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Chi, Qijin; Ulstrup, Jens

    The structure, two-dimensional organization, and function of molecules immobilized on solid surfaces can be addressed in a degree of detail that has reached the level of the single-molecule. In this context redox molecules are “smart” molecules adding sophisticated electronic function. Redox meta...

  16. Morphology evolution and nanostructure of chemical looping transition metal oxide materials upon redox processes

    International Nuclear Information System (INIS)

    Qin, Lang; Cheng, Zhuo; Guo, Mengqing; Fan, Jonathan A.; Fan, Liang-Shih

    2017-01-01

    Transition metal are heavily used in chemical looping technologies because of their high oxygen carrying capacity and high thermal reactivity. These oxygen activities result in the oxide formation and oxygen vacancy formation that affect the nanoscale crystal phase and morphology within these materials and their subsequent bulk chemical behavior. In this study, two selected earlier transition metals manganese and cobalt as well as two selected later transition metals copper and nickel that are important to chemical looping reactions are investigated when they undergo cyclic redox reactions. We found Co microparticles exhibited increased CoO impurity presence when oxidized to Co_3O_4 upon cyclic oxidation; CuO redox cycles prefer to be limited to a reduced form of Cu_2O and an oxidized form of CuO; Mn microparticles were oxidized to a mixed phases of MnO and Mn_3O_4, which causes delamination during oxidation. For Ni microparticles, a dense surface were observed during the redox reaction. The atomistic thermodynamics methods and density functional theory (DFT) calculations are carried out to elucidate the effect of oxygen dissociation and migration on the morphological evolution of nanostructures during the redox processes. Our results indicate that the earlier transition metals (Mn and Co) tend to have stronger interaction with O_2 than the later transition metals (Ni and Cu). Also, our modified Brønsted−Evans−Polanyi (BEP) relationship for reaction energies and total reaction barriers reveals that reactions of earlier transition metals are more exergonic and have lower oxygen dissociation barriers than those of later transition metals. In addition, it was found that for these transition metal oxides the oxygen vacancy formation energies increase with the depth. The oxide in the higher oxidation state of transition metal has lower vacancy formation energy, which can facilitate forming the defective nanostructures. The fundamental understanding of these metal

  17. Redox regulation of fertilisation and the spermatogenic process

    Institute of Scientific and Technical Information of China (English)

    Junichi Fujii; Satoshi Tsunoda

    2011-01-01

    Oxidative stress is one of the major causes of male infertility; it damages spermatogenic cells, the spermatogenic process and sperm function. Recent advances in redox biology have revealed the signalling role of reactive oxygen species (ROS) that are generated by cells. While highly reactive oxidants, such as the hydroxyl radical, exert largely deleterious effects, hydrogen peroxide can feasibly serve as a signal mediator because it is moderately reactive and membrane permeable and because it can oxidize only limited numbers of functional groups of biological molecules. The amino acid side chain most sensitive to oxidation is cysteine sulphydryl, which is commonly involved in the catalysis of some enzymes. Although the reactivity of cysteine sulphhydryl is not very high in ordinary proteins, some phosphatases possess a highly reactive sulphydryl group at their catalytic centre and are thereby oxidatively inactivated by transiently elevated hydrogen peroxide levels after extracellular stimuli and under certain environmental conditions. Peroxiredoxins, in turn, show moderate hydrogen peroxide-reducing activity, and their role in the modulation of ROS-mediated signal transduction in ordinary cells, mediated by protecting phosphatases from oxidative inactivation, has attracted much attention. Although knowledge of the signalling role of ROS in the male reproductive system is limited at present, its significance is becoming a focal issue. Here, we present a review of the emerging signalling role of hydrogen peroxide in testes.

  18. Tip-surface interactions at redox responsive poly(ferrocenylsilane) (PFS) interface by AFM-based force spectroscopy

    International Nuclear Information System (INIS)

    Chung Hongjing; Song Jing; Vancso, G. Julius

    2009-01-01

    Poly(ferrocenylsilanes) (PFS) belong to the class of redox responsive organometallic polymers. Atomic force microscopy (AFM)-based single molecule force spectroscopy (SMFS) was used earlier to study single chain PFS response and redox energy driven single chain PFS molecular motors. Here we present further AFM investigations of force interactions between tip and a grafted PFS surface under potential control in electrochemical redox cycles. Typical tip-Au interaction is considered as reference in the force measurements. First the electrostatic component in the diffused double layer (DL) in NaClO 4 electrolyte environment was considered for a 'grafted to' PFS, which dominated the interplay between the tip and sample surface. The DL forces can also hinder the physisorption of PFS chain onto the tip when the voltage was applied at -0.1 V. On the other hand, if the tip contacted the PFS surface prior to the electrochemical process, physisorption of PFS chains governed the overall interaction regardless of subsequently applied surface potential. In addition, prolonged contact time, t c , may also contribute to the stability of tip-PFS bridging and detection of electrostatic forces between the tip-PFS interface. The results showed that tip-substrate interaction forces without PFS grafts have negligibly small force contributions under similar, electrochemically controlled, conditions used in single PFS chain based molecular motors.

  19. Anticancer Activity of Metal Complexes: Involvement of Redox Processes

    Science.gov (United States)

    Jungwirth, Ute; Kowol, Christian R.; Keppler, Bernhard K.; Hartinger, Christian G.; Berger, Walter; Heffeter, Petra

    2012-01-01

    Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of “activation by reduction” as well as the “hard and soft acids and bases” theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology. PMID:21275772

  20. In situ characterization of nanoscale catalysts during anodic redox processes

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Renu [National Institute of Standards and Technology; Crozier, Peter [Arizona State University; Adams, James [Arizona State University

    2013-09-19

    Controlling the structure and composition of the anode is critical to achieving high efficiency and good long-term performance. In addition to being a mixed electronic and ionic conductor, the ideal anode material should act as an efficient catalyst for oxidizing hydrogen, carbon monoxide and dry hydrocarbons without de-activating through either sintering or coking. It is also important to develop novel anode materials that can operate at lower temperatures to reduce costs and minimized materials failure associated with high temperature cycling. We proposed to synthesize and characterize novel anode cermets materials based on ceria doped with Pr and/or Gd together with either a Ni or Cu metallic components. Ceria is a good oxidation catalyst and is an ionic conductor at room temperature. Doping it with trivalent rare earths such as Pr or Gd retards sintering and makes it a mixed ion conductor (ionic and electronic). We have developed a fundamental scientific understanding of the behavior of the cermet material under reaction conditions by following the catalytic oxidation process at the atomic scale using a powerful Environmental Scanning Transmission Electron Microscope (ESTEM). The ESTEM allowed in situ monitoring of structural, chemical and morphological changes occurring at the cermet under conditions approximating that of typical fuel-cell operation. Density functional calculations were employed to determine the underlying mechanisms and reaction pathways during anode oxidation reactions. The dynamic behavior of nanoscale catalytic oxidation of hydrogen and methane were used to determine: ? Fundamental processes during anodic reactions in hydrogen and carbonaceous atmospheres ? Interfacial effects between metal particles and doped ceria ? Kinetics of redox reaction in the anode material

  1. Formation of poorly crystalline iron monosulfides: Surface redox reactions on high purity iron, spectroelectrochemical studies

    Energy Technology Data Exchange (ETDEWEB)

    Hansson, E.B. [Geological Institute, University of Copenhagen, Oster Voldgade 10, Copenhagen K, DK-1350 (Denmark); Odziemkowski, M.S. [Department of Earth Sciences, University of Waterloo, Waterloo, Ont., N2L 3G1 (Canada)]. E-mail: marek@sciborg.uwaterloo.ca; Gillham, R.W. [Department of Earth Sciences, University of Waterloo, Waterloo, Ont., N2L 3G1 (Canada)

    2006-11-15

    In the use of iron for reductive dehalogenation of chlorinated solvents in ground water, due to presence of sulfate-reducing bacteria the formation of hydrogen sulfide is expected. To simulate those processes the interface between 99.99% pure iron and 0.1 M NaHCO{sub 3} deoxygenated solution with 3.1 x 10{sup -5}-7.8 x 10{sup -3} M Na{sub 2}S . 9H{sub 2}O added was studied. The surface processes were characterised by the in situ normal Raman spectroscopy (NRS) and ex situ techniques; X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray (EDX). The open circuit potential (OCP) was monitored during in situ NRS measurements, and potentiodynamic anodic polarization measurements were carried out to reveal electrochemical behaviour of iron electrode. Open circuit potential-time transients indicated that the native oxide is unstable in deaerated bicarbonate solution and undergoes reductive dissolution (i.e. autoreduction) leaving the metallic Fe covered by Fe(OH){sub 2}, adsorbed OH{sup -}, and patches of 'magnetite-like' oxide. Immediately upon injection of the Na{sub 2}S-solution the iron interface undergoes complex redox surface processes and a poorly crystalline FeS film forms. Potentiodynamic anodic polarization measurements indicated a mechanical breakdown of the FeS film. The origin and initiation of this breakdown process is not clear but is probably a result of internal stress developed during film growth. Based on surface studies supported by electrochemical measurements, a conceptual model for the complex redox processes occurring at the iron interface is proposed. This model describes the structural development of a poorly crystalline FeS, which breaks down, allowing further dissolution of the Fe and formation of FeOOH at the interface. Simultaneously and despite the existence of thick layer of FeS the entrance of hydrogen was evident as the typical hydrogen cracks in bulk of the

  2. Chemical surface tuning electrocatalysis of redox-active nanoparticles

    DEFF Research Database (Denmark)

    Zhu, Nan; Ulstrup, Jens; Chi, Qijin

    This work focuses on electron transfer (ET) and electrocatalysis of inorganic hybrid Prussian blue nanoparticles (PBNPs, 6 nm) immobilized on different chemical surfaces. Through surface self-assembly chemistry, we have enabled to tune chemical properties of the electrode surface. Stable immobili...

  3. Visualization of red-ox proteins on the gold surface using enzymatic polypyrrole formation

    International Nuclear Information System (INIS)

    Ramanaviciene, A.; Kausaite-Minkstimiene, A.; Voronovic, J.; Ramanavicius, A.; Oztekin, Y.; Carac, G.; German, N.

    2011-01-01

    We describe a new method for the visualization of the activity of red-ox proteins on a gold interface. Glucose oxidase was selected as a model system. Surfaces were modified by adhesion of glucose oxidase on (a) electrochemically cleaned gold; (b) gold films modified with gold nanoparticles, (c) a gold surface modified with self-assembled monolayer, and (d) covalent immobilization of protein on the gold surface modified with a self-assembled monolayer. The simple optical method for the visualization of enzyme on the surfaces is based on the enzymatic formation of polypyrrole. The activity of the enzyme was quantified via enzymatic formation of polypyrrole, which was detected and investigated by quartz microbalance and amperometric techniques. The experimental data suggest that the enzymatic formation of the polymer may serve as a method to indicate the adhesion of active redox enzyme on such surfaces. (author)

  4. Reaction kinetics of metal deposition via surface limited red-ox replacement of underpotentially deposited metal monolayers

    International Nuclear Information System (INIS)

    Gokcen, Dincer; Bae, Sang-Eun; Brankovic, Stanko R.

    2011-01-01

    The study of the kinetics of metal deposition via surface limited red-ox replacement of underpotentially deposited metal monolayers is presented. The model system was Pt submonolayer deposition on Au(1 1 1) via red-ox replacement of Pb and Cu UPD monolayers on Au(1 1 1). The kinetics of a single replacement reaction was studied using the formalism of the comprehensive analytical model developed to fit the open circuit potential transients from deposition experiments. The practical reaction kinetics parameters like reaction half life, reaction order and reaction rate constant are determined and discussed with their relevance to design and control of deposition experiments. The effects of transport limitation and the role of the anions/electrolyte on deposition kinetics are investigated and their significance to design of effective deposition process is discussed.

  5. Recyclable surfaces for amine conjugation chemistry via redox reaction

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Inseong; Yeo, Woon Seok [Dept. of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul (Korea, Republic of); Bae, Se Won [Green Materials and Process Group, Research Institute of Sustainable Manufacturing System, Korea Institute of Industrial Technology, Cheonan (Korea, Republic of)

    2017-02-15

    In this study, we extended this strategy to present a switchable surface that allows surface functionalization and removal of functional groups repeatedly. The substrate presenting a benzoquinone acid group is first used to immobilize with an amine-containing (bio)molecule using well-known conjugation chemistry. The benzoquinone group is then converted to the corresponding hydroquinone by treating with a reducing agent. We have described a strategy for the dynamic control of surface properties with recyclability via a simple reduction/ oxidation reaction. A stimuli-responsive quinone derivative was harnessed for the repeated immobilization and release of (bio)molecules, and thus, for the repeated dynamic change of the surface properties according to the characteristics of the immobilized (bio)molecules.

  6. Subseafloor nitrogen redox processes at Loihi Seamount, Hawai

    Science.gov (United States)

    Wankel, S. D.; Sylvan, J. B.; LaRowe, D.; Huber, J. A.; Moyer, C. L.; Edwards, K. J.

    2014-12-01

    archaeal methanogens in the genera Methanococcus and Methanothermococcus. Members of the NO2- oxidizing phylum Nitrispirae are present in all four samples, and are very abundant in two of them. All this data together reveals that N redox processes are significant sources of energy in subsurface Loihi fluids, and possibly at diffuse flow hydrothermal sites elsewhere

  7. pH and redox responsive polymer for antifouling surface coating

    International Nuclear Information System (INIS)

    Lee, Kang Seok; In, Insik; Park, Sung Young

    2014-01-01

    Graphical abstract: Dual responsive surface with highly fouling resistance with the formation of a pH-dependent benzoic imine and redox-sensitive disulfide bond has been developed using a catechol/benzoic acid conjugated polymer and disulfide containing amine end-capped Pluronic. - Highlights: • Stimuli-responsive antifouling surface was prepared by layer-by-layer method. • The surface contact angle showed responsive behavior via pH and redox environments. • Simply coated polymer completely prevented cell adhesion onto surfaces. - Abstract: A dual environmentally responsive polymer with a highly fouling-resistant surface has been developed using poly[(hydroxyethyl methacrylate-g-benzoic acid)-co-(dimethylaminoethyl methacrylate-g-2-chloro-3′, 4′-dihydroxyacetophenone)] [poly[(HEMA-BA)-co-(DMAEMA-CCDP)], P1] as a coating material. The redox-sensitive disulfide containing amine end-capped Pluronic [(Plu-S-S-NH 2 ), P2] was then introduced over the P1 surface via the formation of a pH-dependent benzoic imine bond, where the polyethylene glycol (PEG) acts as an antifouling agent. The successful adhesion of P1 and the deposition of P2 onto the P1-coated substrate were ascertained with X-ray photoelectron spectroscopy (XPS). In vitro cell adhesion followed by scanning electron microscopy (SEM) indicated an excellent antifouling nature of the P2 layer. Consequently, the reattachment of Hela cells was strongly observed when P2 layered on P1-coated substrates (P1–P2) was pretreated at lower pH and high redox conditions. The P1–P2 bilayer-coated substrate has exhibited a great advantage in its effective antifouling behaviors with well-tuned cell attachment and detachment

  8. pH and redox responsive polymer for antifouling surface coating

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kang Seok [Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju, 380-702 (Korea, Republic of); In, Insik, E-mail: in1@ut.ac.kr [Department of Polymer Science and Engineering, Korea National University of Transportation, Chungju, 380-702 (Korea, Republic of); Department of IT Convergence, Korea National University of Transportation, Chungju, 380-702 (Korea, Republic of); Park, Sung Young, E-mail: parkchem@ut.ac.kr [Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju, 380-702 (Korea, Republic of); Department of IT Convergence, Korea National University of Transportation, Chungju, 380-702 (Korea, Republic of)

    2014-09-15

    Graphical abstract: Dual responsive surface with highly fouling resistance with the formation of a pH-dependent benzoic imine and redox-sensitive disulfide bond has been developed using a catechol/benzoic acid conjugated polymer and disulfide containing amine end-capped Pluronic. - Highlights: • Stimuli-responsive antifouling surface was prepared by layer-by-layer method. • The surface contact angle showed responsive behavior via pH and redox environments. • Simply coated polymer completely prevented cell adhesion onto surfaces. - Abstract: A dual environmentally responsive polymer with a highly fouling-resistant surface has been developed using poly[(hydroxyethyl methacrylate-g-benzoic acid)-co-(dimethylaminoethyl methacrylate-g-2-chloro-3′, 4′-dihydroxyacetophenone)] [poly[(HEMA-BA)-co-(DMAEMA-CCDP)], P1] as a coating material. The redox-sensitive disulfide containing amine end-capped Pluronic [(Plu-S-S-NH{sub 2}), P2] was then introduced over the P1 surface via the formation of a pH-dependent benzoic imine bond, where the polyethylene glycol (PEG) acts as an antifouling agent. The successful adhesion of P1 and the deposition of P2 onto the P1-coated substrate were ascertained with X-ray photoelectron spectroscopy (XPS). In vitro cell adhesion followed by scanning electron microscopy (SEM) indicated an excellent antifouling nature of the P2 layer. Consequently, the reattachment of Hela cells was strongly observed when P2 layered on P1-coated substrates (P1–P2) was pretreated at lower pH and high redox conditions. The P1–P2 bilayer-coated substrate has exhibited a great advantage in its effective antifouling behaviors with well-tuned cell attachment and detachment.

  9. Redox Cycling Realized in Paper-Based Biochemical Sensor for Selective Detection of Reversible Redox Molecules Without Micro/Nano Fabrication Process.

    Science.gov (United States)

    Yamamoto, So; Uno, Shigeyasu

    2018-02-28

    This paper describes a paper-based biochemical sensor that realizes redox cycling with close interelectrode distance. Two electrodes, the generator and collector electrodes, can detect steady-state oxidation and reduction currents when suitable potential is held at each electrode. The sensor has two gold plates on both sides of a piece of chromatography paper and defines the interelectrode distance by the thickness of the paper (180 μm) without any micro-fabrication processes. Our proposed sensor geometry has successfully exhibited signatures of redox cycling. As a result, the concentration of ferrocyanide as reversible redox molecules was successfully quantified under the interference by ascorbic acid as a strong irreversible reducing agent. This was possible because the ascorbic acids are completely consumed by the irreversible reaction, while maintaining redox cycling of reversible ferrocyanide. This suggests that a sensor based on the redox cycling method will be suitable for detecting target molecules at low concentration.

  10. The impact of surface coverage on the kinetics of electron transfer through redox monolayers on a silicon electrode surface

    International Nuclear Information System (INIS)

    Ciampi, Simone; Choudhury, Moinul H.; Ahmad, Shahrul Ainliah Binti Alang; Darwish, Nadim; Brun, Anton Le; Gooding, J.Justin

    2015-01-01

    Graphical abstract: The impact of surface coverage on the kinetics of electron transfer through redox monolayers on a silicon electrode surface. ABSTRACT: The impact of the coverage of ferrocene moieties, attached to a silicon electrode modified via hydrosilylation of a dialkyne, on the kinetics of electron transfer between the redox species and the electrode is explored. The coverage of ferrocene is controlled by varying the coupling time between azidomethylferrocene and the distal alkyne of the monolayer via the copper assisted azide-alkyne cycloaddition reaction. All other variables in the surface preparation are maintained identical. What is observed is that the higher the surface coverage of the ferrocene moieties the faster the apparent rates of electron transfer. This surface coverage-dependent kinetic effect is attributed to electrons hopping between ferrocene moieties across the redox film toward hotspots for the electron transfer event. The origin of these hotspots is tentatively suggested to result from minor amounts of oxide on the underlying silicon surface that reduce the barrier for the electron transfer.

  11. Concise Redox Deracemization of Secondary and Tertiary Amines with a Tetrahydroisoquinoline Core via a Nonenzymatic Process.

    Science.gov (United States)

    Ji, Yue; Shi, Lei; Chen, Mu-Wang; Feng, Guang-Shou; Zhou, Yong-Gui

    2015-08-26

    A concise deracemization of racemic secondary and tertiary amines with a tetrahydroisoquinoline core has been successfully realized by orchestrating a redox process consisted of N-bromosuccinimide oxidation and iridum-catalyzed asymmetric hydrogenation. This compatible redox combination enables one-pot, single-operation deracemization to generate chiral 1-substituted 1,2,3,4-tetrahydroisoquinolines with up to 98% ee in 93% yield, offering a simple and scalable synthetic technique for chiral amines directly from racemic starting materials.

  12. The effects of surface modification on carbon felt electrodes for use in vanadium redox flow batteries

    International Nuclear Information System (INIS)

    Kim, Ki Jae; Kim, Young-Jun; Kim, Jae-Hun; Park, Min-Sik

    2011-01-01

    Highlights: ► We observed the physical and chemical changes on the surface of carbon felts after various surface modifications. ► The surface area and chemistry of functional groups formed on the surface of carbon felt are critical to determine the kinetics of the redox reactions of vanadium ions. ► By incorporation of the surface modifications into the electrode preparation, the electrochemical activity of carbon felts could be notably enhanced. - Abstract: The surface of carbon felt electrodes has been modified for improving energy efficiency of vanadium redox flow batteries. For comparative purposes, the effects of various surface modifications such as mild oxidation, plasma treatment, and gamma-ray irradiation on the electrochemical properties of carbon felt electrodes were investigated at optimized conditions. The cell energy efficiency was improved from 68 to 75% after the mild oxidation of the carbon felt at 500 °C for 5 h. This efficiency improvement could be attributed to the increased surface area of the carbon felt electrode and the formation of functional groups on its surface as a result of the modification. On the basis of various structural and electrochemical characterizations, a relationship between the surface nature and electrochemical activity of the carbon felt electrodes is discussed.

  13. Redox front formation in an uplifting sedimentary rock sequence: An analogue for redox-controlling processes in the geosphere around deep geological repositories for radioactive waste

    International Nuclear Information System (INIS)

    Yoshida, H.; Metcalfe, R.; Yamamoto, K.; Murakami, Y.; Hoshii, D.; Kanekiyo, A.; Naganuma, T.; Hayashi, T.

    2008-01-01

    Subsurface redox fronts control the mobilization and fixation of many trace elements, including potential pollutants such as certain radionuclides. Any safety assessment for a deep geological repository for radioactive wastes needs to take into account adequately the long-term redox processes in the geosphere surrounding the repository. To build confidence in understanding these processes, a redox front in a reduced siliceous sedimentary rock distributed in an uplifting area in Japan has been studied in detail. Geochemical analyses show increased concentrations of Fe and trace elements, including rare earth elements (REEs), at the redox front, even though concentrations of reduced rock matrix constituents show little change. Detailed SEM observations revealed that fossilized microorganisms composed of amorphous granules made exclusively of Fe and Si occur in the rock's pore space. Microbial 16S rDNA analysis suggests that there is presently a zonation of different bacterial groups within the redox band, and bacterial zonation played an important role in the concentration of Fe-oxyhydroxides at the redox front. These water-rock-microbe interactions can be considered analogous to the processes occurring in the redox fronts that would develop around geological repositories for radioactive waste. Once formed, the Fe-oxyhydroxides within such a front would be preserved even after reducing conditions resume following repository closure

  14. Redox front formation in an uplifting sedimentary rock sequence: An analogue for redox-controlling processes in the geosphere around deep geological repositories for radioactive waste

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, H. [Nagoya University Museum, Material Research Section, Furocho, Nagoya 464-8602 (Japan)], E-mail: dora@num.nagoya-u.ac.jp; Metcalfe, R. [Quintessa Japan, Queen' s Tower A7-707, Minatomirai, Yokohama 220-6007 (Japan); Yamamoto, K. [Nagoya University Museum, Material Research Section, Furocho, Nagoya 464-8602 (Japan); Murakami, Y. [Japan Atomic Energy Agency (JAEA), Tono Geoscience Centre (Japan); Hoshii, D.; Kanekiyo, A.; Naganuma, T. [Hiroshima University, Higashi Hiroshima, Kagamiyama 1-4-4 (Japan); Hayashi, T. [Asahi University, Department of Dental Pharmacology, Hozumi, Gifu (Japan)

    2008-08-15

    Subsurface redox fronts control the mobilization and fixation of many trace elements, including potential pollutants such as certain radionuclides. Any safety assessment for a deep geological repository for radioactive wastes needs to take into account adequately the long-term redox processes in the geosphere surrounding the repository. To build confidence in understanding these processes, a redox front in a reduced siliceous sedimentary rock distributed in an uplifting area in Japan has been studied in detail. Geochemical analyses show increased concentrations of Fe and trace elements, including rare earth elements (REEs), at the redox front, even though concentrations of reduced rock matrix constituents show little change. Detailed SEM observations revealed that fossilized microorganisms composed of amorphous granules made exclusively of Fe and Si occur in the rock's pore space. Microbial 16S rDNA analysis suggests that there is presently a zonation of different bacterial groups within the redox band, and bacterial zonation played an important role in the concentration of Fe-oxyhydroxides at the redox front. These water-rock-microbe interactions can be considered analogous to the processes occurring in the redox fronts that would develop around geological repositories for radioactive waste. Once formed, the Fe-oxyhydroxides within such a front would be preserved even after reducing conditions resume following repository closure.

  15. Anaerobic microbial redox processes in a landfill leachate contaminated aquifer (Grindsted, Denmark)

    Science.gov (United States)

    Ludvigsen, L.; Albrechtsen, H.-J.; Heron, G.; Bjerg, P. L.; Christensen, T. H.

    1998-10-01

    The distribution of anaerobic microbial redox processes was investigated along a 305 m long transect of a shallow landfill-leachate polluted aquifer. By unamended bioassays containing sediment and groundwater, 37 samples were investigated with respect to methane production, sulfate, iron, and manganese reduction, and denitrification. Methane production was restricted to the most reduced part of the plume with rates of 0.003-0.055 nmol CH 4/g dry weight/day. Sulfate reduction was observed at rates of maximum 1.8 nmol SO 42-/g dry weight/day along with methane production in the plume, but sulfate reduction was also observed further downgradient of the landfill. Iron reduction at rates of 5-19 nmol Fe(II)/g dry weight/day was observed in only a few samples, but this may be related to a high detection limit for the iron reducing bioassay. Manganese reduction at rates of maximum 2.4 nmol Mn(II)/g dry weight/day and denitrification at rates of 0.2-37 nmol N 2O-N/g dry weight/day were observed in the less reduced part of the plume. All the redox processes were microbial processes. In many cases, several redox processes took place simultaneously, but in all samples one process dominated accounting for more than 70% of the equivalent carbon conversion. The bioassays showed that the redox zones in the plume identified from the groundwater composition (e.g. as methanogenic and sulfate reducing) locally hosted also other redox processes (e.g. iron reduction). This may have implications for the potential of the redox zone to degrade trace amounts of organic chemicals and suggests that unamended bioassays may be an important supplement to other approaches in characterizing the redox processes in an anaerobic plume.

  16. The importance of kinetics and redox in the biogeochemical cycling of iron in the surface ocean.

    Directory of Open Access Journals (Sweden)

    Peter L. Croot

    2012-06-01

    Full Text Available It is now well established that Iron (Fe is a limiting element in many regions of the open ocean. Our current understanding of the key processes which control iron distribution in the open ocean have been largely based on thermodynamic measurements performed under the assumption of equilibrium conditions. Using this equilibrium approach, researchers have been able to detect and quantify organic complexing ligands in seawater and examine their role in increasing the overall solubility of iron. Our current knowledge about iron bioavailability to phytoplankton and bacteria is also based heavily on carefully controlled laboratory studies where it is assumed the chemical species are in equilibrium in line with the free ion association model (FIAM and/or its successor the biotic ligand model (BLM. Similarly most field work on Fe biogeochemistry generally consists of a single profile which is in essence a ‘snap-shot’ in time of the system under investigation. However it is well known that the surface ocean is an extremely dynamic environment and it is unlikely if thermodynamic equilibrium between all the iron species present is ever truly achieved. In sunlit waters this is mostly due to the daily passage of the sun across the sky leading to photoredox processes which alter Fe speciation by cycling between redox states and between inorganic and organic species. Episodic deposition events, are also important perturbations to iron cycling as they bring new iron to the system altering the equilibrium between species and phases. Over the last 20 years the mesoscale iron enrichment experiments (e.g. IronEx I /II, SOIREE, EisenEx, SOFeX, EIFeX, SAGE, SEEDS and SERIES I /II and the FeCycle (I/II experiments have provided the first insights into processes altering iron speciation and distribution which occur over temporal scales of days to weeks. Here we utilize new field data collected in the open ocean on the redox and complexation kinetics of iron in the

  17. A highly permeable and enhanced surface area carbon-cloth electrode for vanadium redox flow batteries

    Science.gov (United States)

    Zhou, X. L.; Zhao, T. S.; Zeng, Y. K.; An, L.; Wei, L.

    2016-10-01

    In this work, a high-performance porous electrode, made of KOH-activated carbon-cloth, is developed for vanadium redox flow batteries (VRFBs). The macro-scale porous structure in the carbon cloth formed by weaving the carbon fibers in an ordered manner offers a low tortuosity (∼1.1) and a broad pore distribution from 5 μm to 100 μm, rendering the electrode a high hydraulic permeability and high effective ionic conductivity, which are beneficial for the electrolyte flow and ion transport through the porous electrode. The use of KOH activation method to create nano-scale pores on the carbon-fiber surfaces leads to a significant increase in the surface area for redox reactions from 2.39 m2 g-1 to 15.4 m2 g-1. The battery assembled with the present electrode delivers an energy efficiency of 80.1% and an electrolyte utilization of 74.6% at a current density of 400 mA cm-2, as opposed to an electrolyte utilization of 61.1% achieved by using a conventional carbon-paper electrode. Such a high performance is mainly attributed to the combination of the excellent mass/ion transport properties and the high surface area rendered by the present electrode. It is suggested that the KOH-activated carbon-cloth electrode is a promising candidate in redox flow batteries.

  18. Preparation and Biocompatible Surface Modification of Redox Altered Cerium Oxide Nanoparticle Promising for Nanobiology and Medicine

    KAUST Repository

    Nanda, Himansu Sekhar

    2016-11-03

    The biocompatible surface modification of metal oxide nanoparticles via surface functionalization technique has been used as an important tool in nanotechnology and medicine. In this report, we have prepared aqueous dispersible, trivalent metal ion (samarium)-doped cerium oxide nanoparticles (SmCNPs) as model redox altered CNPs of biological relevance. SmCNP surface modified with hydrophilic biocompatible (6-{2-[2-(2-methoxy-ethoxy)-ethoxy]-ethoxy}-hexyl) triethoxysilane (MEEETES) were prepared using ammonia-induced ethylene glycol-assisted precipitation method and were characterized using a variety of complementary characterization techniques. The chemical interaction of functional moieties with the surface of doped nanoparticle was studied using powerful 13C cross polarization magic angle sample spinning nuclear magnetic resonance spectroscopy. The results demonstrated the production of the extremely small size MEEETES surface modified doped nanoparticles with significant reduction in aggregation compared to their unmodified state. Moreover, the functional moieties had strong chemical interaction with the surface of the doped nanoparticles. The biocompatible surface modification using MEEETES should also be extended to several other transition metal ion doped and co-doped CNPs for the production of aqueous dispersible redox altered CNPs that are promising for nanobiology and medicine.

  19. Preparation and Biocompatible Surface Modification of Redox Altered Cerium Oxide Nanoparticle Promising for Nanobiology and Medicine

    KAUST Repository

    Nanda, Himansu Sekhar

    2016-01-01

    The biocompatible surface modification of metal oxide nanoparticles via surface functionalization technique has been used as an important tool in nanotechnology and medicine. In this report, we have prepared aqueous dispersible, trivalent metal ion (samarium)-doped cerium oxide nanoparticles (SmCNPs) as model redox altered CNPs of biological relevance. SmCNP surface modified with hydrophilic biocompatible (6-{2-[2-(2-methoxy-ethoxy)-ethoxy]-ethoxy}-hexyl) triethoxysilane (MEEETES) were prepared using ammonia-induced ethylene glycol-assisted precipitation method and were characterized using a variety of complementary characterization techniques. The chemical interaction of functional moieties with the surface of doped nanoparticle was studied using powerful 13C cross polarization magic angle sample spinning nuclear magnetic resonance spectroscopy. The results demonstrated the production of the extremely small size MEEETES surface modified doped nanoparticles with significant reduction in aggregation compared to their unmodified state. Moreover, the functional moieties had strong chemical interaction with the surface of the doped nanoparticles. The biocompatible surface modification using MEEETES should also be extended to several other transition metal ion doped and co-doped CNPs for the production of aqueous dispersible redox altered CNPs that are promising for nanobiology and medicine.

  20. Preparation and Biocompatible Surface Modification of Redox Altered Cerium Oxide Nanoparticle Promising for Nanobiology and Medicine

    Directory of Open Access Journals (Sweden)

    Himansu Sekhar Nanda

    2016-11-01

    Full Text Available The biocompatible surface modification of metal oxide nanoparticles via surface functionalization technique has been used as an important tool in nanotechnology and medicine. In this report, we have prepared aqueous dispersible, trivalent metal ion (samarium-doped cerium oxide nanoparticles (SmCNPs as model redox altered CNPs of biological relevance. SmCNP surface modified with hydrophilic biocompatible (6-{2-[2-(2-methoxy-ethoxy-ethoxy]-ethoxy}-hexyl triethoxysilane (MEEETES were prepared using ammonia-induced ethylene glycol-assisted precipitation method and were characterized using a variety of complementary characterization techniques. The chemical interaction of functional moieties with the surface of doped nanoparticle was studied using powerful 13C cross polarization magic angle sample spinning nuclear magnetic resonance spectroscopy. The results demonstrated the production of the extremely small size MEEETES surface modified doped nanoparticles with significant reduction in aggregation compared to their unmodified state. Moreover, the functional moieties had strong chemical interaction with the surface of the doped nanoparticles. The biocompatible surface modification using MEEETES should also be extended to several other transition metal ion doped and co-doped CNPs for the production of aqueous dispersible redox altered CNPs that are promising for nanobiology and medicine.

  1. The Electrochemical Properties of Biochars and How They Affect Soil Redox Properties and Processes

    Directory of Open Access Journals (Sweden)

    Stephen Joseph

    2015-07-01

    Full Text Available Biochars are complex heterogeneous materials that consist of mineral phases, amorphous C, graphitic C, and labile organic molecules, many of which can be either electron donors or acceptors when placed in soil. Biochar is a reductant, but its electrical and electrochemical properties are a function of both the temperature of production and the concentration and composition of the various redox active mineral and organic phases present. When biochars are added to soils, they interact with plant roots and root hairs, micro-organisms, soil organic matter, proteins and the nutrient-rich water to form complex organo-mineral-biochar complexes Redox reactions can play an important role in the development of these complexes, and can also result in significant changes in the original C matrix. This paper reviews the redox processes that take place in soil and how they may be affected by the addition of biochar. It reviews the available literature on the redox properties of different biochars. It also reviews how biochar redox properties have been measured and presents new methods and data for determining redox properties of fresh biochars and for biochar/soil systems.

  2. The synthesis of PdPt/carbon paper via surface limited redox replacement reactions for oxygen reduction reaction

    CSIR Research Space (South Africa)

    Motsoeneng, RG

    2015-09-01

    Full Text Available Surface-limited redox replacement reactions using the electrochemical atomic layer deposition (EC-ALD) technique were used to synthesize PdPt bimetallic electrocatalysts on carbon paper substrate. Electrocatalysts having different Pd:Pt ratio were...

  3. Heavy metal distributions in Peru Basin surface sediments in relation to historic, present and disturbed redox environments

    Science.gov (United States)

    Koschinsky, Andrea

    Heavy metal distributions in deep-sea surface sediments and pore water profiles from five areas in the Peru Basin were investigated with respect to the redox environment and diagenetic processes in these areas. The 10-20-cm-thick Mn oxide-rich and minor metal-rich top layer is underlain by an increase in dissolved Mn and Ni concentrations resulting from the reduction of the MnO 2 phase below the oxic zone. The mobilised associated metals like Co, Zn and Cu are partly immobilised by sorption on clay, organic or Fe compounds in the post-oxic environment. Enrichment of dissolved Cu, Zn, Ni, Co, Pb, Cd, Fe and V within the upper 1-5 cm of the oxic zone can be attributed to the degradation of organic matter. In a core from one area at around 22-25 cm depth, striking enrichments of these metals in dissolved and solid forms were observed. Offset distributions between oxygen penetration and Mn reduction and the thickness of the Mn oxide-rich layer indicate fluctuations of the Mn redox boundary on a short-term time scale. Within the objectives of the German ATESEPP research programme, the effect of an industrial impact such as manganese nodule mining on the heavy metal cycle in the surface sediment was considered. If the oxic surface were to be removed or disturbed, oxygen would penetrate deep into the formerly suboxic sediment and precipitate Mn 2+ and metals like Ni and Co which are preferably scavenged by MnO 2. The solid enrichments of Cd, V, and other metals formed in post-oxic environments would move downward with the new redox boundary until a new equilibrium between oxygen diffusion and consumption is reached.

  4. Theoretical and experimental study of redox processes combined with adsorption phenomena under conditions of square-wave voltammetry

    OpenAIRE

    Gulaboski, Rubin

    2001-01-01

    Theoretical models of four electrode reactions coupled with adsorption phenomena under conditions of square-wave voltammetry are developed: simple surface redox reaction, surface catalytic reaction, cathodic stripping reaction of I order, and cathodic stripping reaction of II order.

  5. Polypropylene non-woven fabric membrane via surface modification with biomimetic phosphorylcholine in Ce(IV)/HNO{sub 3} redox system

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Jie; Shi Qiang; Luan Shifang; Song Lingjie; Yang Huawei [State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Stagnaro, Paola [Istituto per Io Studio delle Macromolecole, Consiglio Nazionale delle Ricerche, Via de Marini 6, 16149 Genova (Italy); Yin Jinghua, E-mail: yinjh@ciac.jl.cn [State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

    2012-10-01

    Surface modification of polypropylene non-woven fabric membrane (NWF) for improving its hemocompatibility was developed by grafting a biomimic monomer, 2-methacryloyloxyethyl phosphorycholine (MPC). The NWF membrane surface was first activated by potassium peroxydisulfate to form hydroxyl groups, and then grafted with MPC using ceric (IV) ammonium nitrate as the redox initiator. The surface chemical changes before and after modification were confirmed by Fourier transform infrared spectroscopy with an ATR unit (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS); the water contact angle results showed the gradual changes in wettability from hydrophobic to hydrophilic surface. Meanwhile, the hemocompatibility of these samples was also evaluated by protein adsorption and platelet adhesion. These experimental results exhibited that the introduction of poly(MPC) onto the NWF membrane surfaces substantially improved their hemocompatibility. The feasibility and simplicity of this procedure may lead to potential applications of NWF membranes in biomedical separation and blood purification. - Graphical abstract: 2-methacryloyloxyethyl phosphorycholine (MPC), was grafted onto non-woven fabric (NWF) membrane surface by Ce(IV)/HNO{sub 3} redox system. The protein adsorption and platelet adhesion were substantially suppressed by the introduction of poly(MPC). Highlights: Black-Right-Pointing-Pointer MPC was successfully grafted onto NWF PP membrane surface. Black-Right-Pointing-Pointer Obviously enhanced hemocompatibility was acquired by the modified samples. Black-Right-Pointing-Pointer A facile redox grafting was adopted in the whole process.

  6. Bioelectrochemical probing of intracellular redox processes in living yeast cells—application of redox polymer wiring in a microfluidic environment

    DEFF Research Database (Denmark)

    Heiskanen, Arto; Coman, Vasile; Kostesha, Natalie

    2013-01-01

    utilizing a new double mediator system to map redox metabolism and screen for genetic modifications in Saccharomyces cerevisiae cells. The function of this new double mediator system based on menadione and osmium redox polymer (PVI-Os) is demonstrated. “Wiring” of S. cerevisiae cells using PVI-Os shows...... that microfluidic bioelectrochemical assays employing the menadione–PVI-Os double mediator system provides an effective means to conduct automated microbial assays. FigureMicrofluidic platform for bioelectrochemical assays using osmium redox polymer “wired” living yeast cells...

  7. Geomicrobial and Geochemical Redox Processes in a Landfill-Polluted Aquifer

    DEFF Research Database (Denmark)

    Ludvigsen, Liselotte; Heron, Gorm; Albrechtsen, Hans-Jørgen

    1995-01-01

    The distribution of different dominant microbial-mediated redox processes in a landfill leachate-polluted aquifer (Grindsted, Denmark) was investigated. The most probable number method was utilized for detecting bacteria able to use each of the electron acceptors, and unamended incubations were u...

  8. Certain aspects of the reactivity of carotenoids. Redox processes and complexation

    International Nuclear Information System (INIS)

    Polyakov, Nikolay E; Leshina, Tatyana V

    2006-01-01

    The published data on the redox reactions of carotenoids, their supramolecular inclusion complexes and the composition, properties and practical application of these complexes are generalised. Special attention is given to the effect of complexation on radical processes involving carotenoids and on the antioxidant activity of carotenoids.

  9. Effects of non-dissolved redox mediators on a hexavalent chromium bioreduction process

    Directory of Open Access Journals (Sweden)

    Jing Lian

    2016-03-01

    Full Text Available The effects of six non-dissolved redox mediators (RM immobilized in cellulose acetate beads on enhancing Cr(VI reduction by Mangrovibacter plantisponsor CR1 were investigated. In addition, the voltammetric behaviours and electron transfer capacities of the redox mediators were examined using electrochemical methods. Compared to the control beads, the Cr(VI bioreduction rate with 1-chloroanthraquinone cellulose acetate beads (1-CAQ/CA beads was increased up to 4.5-fold, which was mainly attributed to enhanced electron transfer by 1-CAQ. The redox mediators also improved the oxidation–reduction potential values of the Cr(VI bioreduction processes, which might assist in Cr(VI bioreduction. The role of the redox mediators was discussed based on the cyclic voltammetric characteristics (E0' of the redox mediators and the electrochemical impedance spectroscopy characteristics (Rct of the RM/CA beads. A linear correlation was found for the reaction constant k and the 1-CAQ concentration (C1-CAQ, which was k = 1.5674 C1-CAQ + 4.8506 (R2 = 0.9683. The Cr(VI bioreduction was affected by temperature, and the optimum pH for the Cr(VI bioreduction was 6.5. The results of repeated-batch operations showed that 1-CAQ/CA beads exhibited good stability and persistence. This study contributes to a better understanding of the effects of the redox mediator on Cr(VI bioreduction process and demonstrates its promising potential for environmental bioremediation applications.

  10. A multimodal optical and electrochemical device for monitoring surface reactions: redox active surfaces in porous silicon Rugate filters.

    Science.gov (United States)

    Ciampi, Simone; Guan, Bin; Darwish, Nadim A; Zhu, Ying; Reece, Peter J; Gooding, J Justin

    2012-12-21

    Herein, mesoporous silicon (PSi) is configured as a single sensing device that has dual readouts; as a photonic crystal sensor in a Rugate filter configuration, and as a high surface area porous electrode. The as-prepared PSi is chemically modified to provide it with stability in aqueous media and to allow for the subsequent coupling of chemical species, such as via Cu(I)-catalyzed cycloaddition reactions between 1-alkynes and azides ("click" reactions). The utility of the bimodal capabilities of the PSi sensor for monitoring surface coupling procedures is demonstrated by the covalent coupling of a ferrocene derivative, as well as by demonstrating ligand-exchange reactions (LER) at the PSi surface. Both types of reactions were monitored through optical reflectivity measurements, as well as electrochemically via the oxidation/reduction of the surface tethered redox species.

  11. Characterization of the Redox reaction of V(V) in Ammonia Buffers with Square-Wave Voltammetry

    OpenAIRE

    Mirceski, Valentin; Gulaboski, Rubin; Petrovska-Jovanovic, Simka; Stojanova, Kornelija

    2001-01-01

    The redox reaction of V(V) in ammonia buffers solution with pH = 8.60 was studied by means of square-wave and cyclic voltammetry. The redox reaction studied exhibits properties of a surface redox process in which both the reactant and the product of the redox reaction are immobilized on the electrode surface.

  12. Geochemistry of Natural Redox Fronts

    International Nuclear Information System (INIS)

    Hofmann, B.A.

    1999-05-01

    Redox fronts are important geochemical boundaries which need to be considered in safety assessment of deep repositories for radioactive waste. In most cases, selected host-rock formations will be reducing due to the presence of ferrous minerals, sulphides, etc. During construction and operation of the repository, air will be introduced into the formation. After repository closure, oxidising conditions may persist locally until all oxygen is consumed. In the case of high-level waste, radiolysis of water may provide an additional source of oxidants. Oxidising conditions within a repository are thus possible and potentially have a strong influence on the mobility of many elements. The rate of movement of redox fronts, the boundary between oxidising and reducing environments, and their influence on migrating radionuclides are thus important factors influencing repository performance. The present report is a review of elemental behaviour at natural redox fronts, based on published information and work of the author. Redox fronts are geochemically and geometrically variable manifestations of a global interface between generally oxidising geochemical milieux in contact with the atmosphere and generally reducing milieux in contact with rocks containing ferrous iron, sulphide and/or organic carbon. A classification of redox fronts based on a subdivision into continental near-surface, marine near-surface, and deep environments is proposed. The global redox interface is often located close to the surface of rocks and sediments and, sometimes, within bodies of water. Temperature conditions are close to ambient. A deeper penetration of the global redox front to depths of several kilometres is found in basins containing oxidised sediments (red beds) and in some hydrothermal circulation systems. Temperatures at such deep redox fronts may reach 200 o C. Both near-surface and deep redox fronts are sites of formation of economic deposits of redox-sensitive elements, particularly of

  13. Understanding controls on redox processes in floodplain sediments of the Upper Colorado River Basin

    Energy Technology Data Exchange (ETDEWEB)

    Noël, Vincent; Boye, Kristin; Kukkadapu, Ravi K.; Bone, Sharon; Lezama Pacheco, Juan S.; Cardarelli, Emily; Janot, Noémie; Fendorf, Scott; Williams, Kenneth H.; Bargar, John R.

    2017-12-15

    River floodplains, heavily used for water supplies, housing, agriculture, mining, and industry, may have water quality jeopardized by native or exogenous metals. Redox processes mediate the accumulation and release of these species in groundwater. Understanding the physicochemical, hydrological, and biogeochemical controls on the distribution and variability and variability of redox conditions is therefore critical to developing conceptual and numerical models of contaminants transport within floodplains. The distribution and intensity of redox activity at the Rifle, CO, site within the Upper Colorado River Basin (UCRB), are believed to be controlled by textural and compositional heterogeneities. Regionally, the UCRB is impacted by former uranium and vanadium ore processing, resulting in contaminations by U, Mo, V, As, Se, and Mn. Floodplains throughout the UCRB share sediment and groundwater characteristics, making redox activity regionally important to metal and radionuclide mobility. In this study, Fe and S speciation were used to track the distribution and stability of redox processes in sediment cores from three floodplain sites covering a 250 km range in the central portion of the UCRB. The results of the present study support the hypothesis that Fe(III) and sulfate reducing sediments are regionally important in the UCRB. The presence of organic carbon together with pore saturation were the key requirements for reducing conditions, dominated by sulfate-reduction. Sediment texture moderated the response of the system to external forcing, such as oxidant infusion, making fine-grain sediments resistant to change in comparison to coarser-grained sediments. Exposure to O2 and NO3- mediates the reactivity and longevity of freshly precipitated sulfides creating the potential for release of sequestered radionuclides and metals. The physical and chemical parameters of reducing zones evidenced in this study are thus thought to be key parameters on the dynamic exchange

  14. Factors Controlling Redox Speciation of Plutonium and Neptunium in Extraction Separation Processes

    Energy Technology Data Exchange (ETDEWEB)

    Paulenova, Alena [Principal Investigator; Vandegrift, III, George F. [Collaborator

    2013-09-24

    The objective of the project was to examine the factors controlling redox speciation of plutonium and neptunium in UREX+ extraction in terms of redox potentials, redox mechanism, kinetics and thermodynamics. Researchers employed redox-speciation extractions schemes in parallel to the spectroscopic experiments. The resulting distribution of redox species w studied uring spectroscopic, electrochemical, and spectro-electrochemical methods. This work reulted in collection of data on redox stability and distribution of redox couples in the nitric acid/nitrate electrolyte and the development of redox buffers to stabilize the desired oxidation state of separated radionuclides. The effects of temperature and concentrations on the redox behavior of neptunium were evaluated.

  15. The Role of Ru Redox in pH-Dependent Oxygen Evolution on Rutile Ruthenium Dioxide Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Stoerzinger, Kelsey A.; Rao, Reshma R.; Wang, Xiao Renshaw; Hong, Wesley T.; Rouleau, Christopher M.; Shao-Horn, Yang

    2017-05-01

    Rutile RuO2 is known to exhibit high catalytic activity for the oxygen evolution reaction (OER) and large pseudocapacitance associated with redox of surface Ru, however the mechanistic link between these properties and the role of pH is yet to be understood. Here we report that the OER activities of the (101), (001) and (111) RuO2 surfaces were found to increase while the potential of a pseudocapacitive feature just prior to OER shifted to lower potentials (“super-Nernstian” shift) with increasing pH on the reversible hydrogen electrode (RHE) scale. This behavior is in contrast to the (100) and (110) surfaces that have pH-independent Ru redox and OER activity. The link in catalytic and pseudocapacitive behavior illustrates the importance of this redox feature in generating active sites, building new mechanistic understanding of the OER.

  16. Insights into the redox components of dissolved organic matters during stabilization process.

    Science.gov (United States)

    Yuan, Ying; Xi, Bei-Dou; He, Xiao-Song; Ma, Yan; Zhang, Hui; Li, Dan; Zhao, Xin-Yu

    2018-05-01

    The changes of dissolved organic matter (DOM) components during stabilization process play significant effects on its redox properties but are little reported. Composting is a stabilization process of DOM, during which both the components and electron transfer capacities (ETCs) of DOM change. The redox components within compost-derived DOM during the stabilization process are investigated in this study. The results show that compost-derived DOM contained protein-like, fulvic-like, and humic-like components. The protein-like component decreases during composting, whereas the fulvic- and humic-like components increase during the process. The electron-donating capacity (EDC), electron-accepting capacity (EAC), and ETC of compost-derived DOM all increase during composting but their correlations with the components presented significant difference. The humic-like components were the main functional component responsible for both EDC and ETC, whereas the protein- and fluvic-like components show negative effects with the EAC, EDC, and ETC, suggesting that the components within DOM have specific redox properties during the stabilization process. These findings are very meaningful for better understanding the geochemical behaviors of DOM in the environment.

  17. Theoretical treatment of high-frequency, large-amplitude ac voltammetry applied to ideal surface-confined redox systems

    International Nuclear Information System (INIS)

    Bell, Christopher G.; Anastassiou, Costas A.; O’Hare, Danny; Parker, Kim H.; Siggers, Jennifer H.

    2012-01-01

    Highlights: ► Theory of ac voltammetry on ideal surface-confined redox systems. ► Analytical description of the harmonics and transient of the current response. ► Solution valid for high frequency, large-amplitude sinusoidal input voltage. ► Protocol for determining system parameters from experimental current responses. - Abstract: Large-amplitude ac voltammetry, where the applied voltage is a large-amplitude sinusoidal waveform superimposed onto a dc ramp, is a powerful method for investigating the reaction kinetics of surface-confined redox species. Here we consider the large-amplitude ac voltammetric current response of a quasi-reversible, ideal, surface-confined redox system, for which the redox reaction is described by Butler–Volmer theory. We derive an approximate analytical solution, which is valid whenever the angular frequency of the sine-wave is much larger than the rate of the dc ramp and the standard kinetic rate constant of the redox reaction. We demonstrate how the third harmonic and the initial transient of the current response can be used to estimate parameters of the electrochemical system, namely the kinetic rate constant, the electron transfer coefficient, the adsorption formal potential, the initial proportion of oxidised molecules and the linear double-layer capacitance.

  18. Enhanced Colloidal Stability of CeO2 Nanoparticles by Ferrous Ions: Adsorption, Redox Reaction, and Surface Precipitation.

    Science.gov (United States)

    Liu, Xuyang; Ray, Jessica R; Neil, Chelsea W; Li, Qingyun; Jun, Young-Shin

    2015-05-05

    Due to the toxicity of cerium oxide (CeO2) nanoparticles (NPs), a better understanding of the redox reaction-induced surface property changes of CeO2 NPs and their transport in natural and engineered aqueous systems is needed. This study investigates the impact of redox reactions with ferrous ions (Fe2+) on the colloidal stability of CeO2 NPs. We demonstrated that under anaerobic conditions, suspended CeO2 NPs in a 3 mM FeCl2 solution at pH 4.8 were much more stable against sedimentation than those in the absence of Fe2+. Redox reactions between CeO2 NPs and Fe2+ lead to the formation of 6-line ferrihydrite on the CeO2 surfaces, which enhanced the colloidal stability by increasing the zeta potential and hydrophilicity of CeO2 NPs. These redox reactions can affect the toxicity of CeO2 NPs by increasing cerium dissolution, and by creating new Fe(III) (hydr)oxide reactive surface layers. Thus, these findings have significant implications for elucidating the phase transformation and transport of redox reactive NPs in the environment.

  19. Examination and Mitigation of Electron Interception Processes in Dye-sensitized Solar Cells through Redox Shuttle and Photoelectrode Modification

    Science.gov (United States)

    Hoffeditz, William Lawrence

    With the dual challenges of meeting global energy demand and mitigating anthropogenic climate change, significant effort is being applied to generating power from renewable sources. The dye-sensitized solar cell (DSC) is a photovoltaic technology capable of generating electricity from sunlight, but suffers losses in efficiency due to deleterious electron transfer processes. Controlling these processes is essential if DSCs are to continue to advance, and this dissertation focuses on isolation, interrogation, and mitigation of these processes via controllable inorganic redox/coordination chemistry and atomic layer deposition (ALD). The redox shuttle is often the subject of innovation in DSCs, the goal being to increase obtainable photovoltage without sacrificing photocurrent. A copper redox shuttle with a favorable (II/I) redox potential for DSC use and intriguing inner-sphere reorganization energy was investigated. The shuttle completely replaces its tetradentate coordinating ligand upon oxidation with multiple pyridine molecules. This new species displays markedly slower electron interception, necessitating fabrication of a new counter electrode in order for the shuttle to function. Upon reduction, the tetradentate ligand re-coordinates, creating a dual-species shuttle that outperforms either species as a Cu(II/I) shuttle in isolation. Photoelectrode modification is also the subject of innovation in DSCs. ALD is ideally suited for this type of innovation as it can coat high aspect surfaces with metal-oxide films of uniform thickness. The ALD post-treatment technique is described and used to deposit Al2O3 around a TiO2 adsorbed zinc-porphyrin dye. This technique is shown to prevent dye degradation from ambient air and/or light. Additionally, the architecture allows the study of dye-influenced electron interception processes. It was found that the presence of dye increased interception, which was attributed to dye-mediated electron hopping and/or superexchange

  20. Organic molecules as tools to control the growth, surface structure, and redox activity of colloidal quantum dots.

    Science.gov (United States)

    Weiss, Emily A

    2013-11-19

    In order to achieve efficient and reliable technology that can harness solar energy, the behavior of electrons and energy at interfaces between different types or phases of materials must be understood. Conversion of light to chemical or electrical potential in condensed phase systems requires gradients in free energy that allow the movement of energy or charge carriers and facilitate redox reactions and dissociation of photoexcited states (excitons) into free charge carriers. Such free energy gradients are present at interfaces between solid and liquid phases or between inorganic and organic materials. Nanostructured materials have a higher density of these interfaces than bulk materials. Nanostructured materials, however, have a structural and chemical complexity that does not exist in bulk materials, which presents a difficult challenge: to lower or eliminate energy barriers to electron and energy flux that inevitably result from forcing different materials to meet in a spatial region of atomic dimensions. Chemical functionalization of nanostructured materials is perhaps the most versatile and powerful strategy for controlling the potential energy landscape of their interfaces and for minimizing losses in energy conversion efficiency due to interfacial structural and electronic defects. Colloidal quantum dots are semiconductor nanocrystals synthesized with wet-chemical methods and coated in organic molecules. Chemists can use these model systems to study the effects of chemical functionalization of nanoscale organic/inorganic interfaces on the optical and electronic properties of a nanostructured material, and the behavior of electrons and energy at interfaces. The optical and electronic properties of colloidal quantum dots have an intense sensitivity to their surface chemistry, and their organic adlayers make them dispersible in solvent. This allows researchers to use high signal-to-noise solution-phase spectroscopy to study processes at interfaces. In this

  1. Influence of redox condition in iron, silicon and hydrogen contents of leached glass surface

    International Nuclear Information System (INIS)

    Manara, A.; Lanza, F.; Della Mea, G.; Rossi, C.; Salvagno, G.

    1984-01-01

    Surface analysis has been conducted on samples leached in a Sochlet apparatus at 100 0 C in the presence and in the absence of air. The XPS technique was applied to analyze the content of iron and silicon while the nuclear reaction method was utilized to analyze the content of hydrogen. Samples leached in argon atmosphere have shown a smaller content of iron and silicon with respect to the samples leached in air atmosphere. The H concentration has shown the same behavior. The results are discussed in terms of possible formation of iron compounds in the different redox condition and of their different stabilities and in terms of their efficiency in reducing exchange between Na + and H + ions. 11 references, 3 figures, 1 table

  2. Composition and redox control of waste glasses: Recommendation for process control limit

    International Nuclear Information System (INIS)

    Jantzen, C.M.; Plodinec, M.J.

    1986-01-01

    An electrochemical series of redox couples, originally developed for Savannah River Laboratory glass frit 131 (SRL-131) as a reference composition, has been extended to two other alkali borosilicate compositions that are candidate glasses for nuclear waste immobilization. Since no dramatic differences were ascertained in the redox chemistry of selected multivalent elements in SRL-131 versus that in Savannah River Laboratory glass frit 165 (SRL-165) and in West Valley glass number-sign 205 (WV-205), the comprehensive electrochemical series can readily be applied to a range of nuclear waste glass compositions. In order to alleviate potential problems with foaming and precipitation of insolubles during the processing of the nuclear waste in these glass melts, the [Fe 2+ ]/[Fe 3+ ] ratio of the melt should be between 0.1 and 0.5. 27 refs., 4 figs., 2 tabs

  3. Solar fuel processing efficiency for ceria redox cycling using alternative oxygen partial pressure reduction methods

    International Nuclear Information System (INIS)

    Lin, Meng; Haussener, Sophia

    2015-01-01

    Solar-driven non-stoichiometric thermochemical redox cycling of ceria for the conversion of solar energy into fuels shows promise in achieving high solar-to-fuel efficiency. This efficiency is significantly affected by the operating conditions, e.g. redox temperatures, reduction and oxidation pressures, solar irradiation concentration, or heat recovery effectiveness. We present a thermodynamic analysis of five redox cycle designs to investigate the effects of working conditions on the fuel production. We focused on the influence of approaches to reduce the partial pressure of oxygen in the reduction step, namely by mechanical approaches (sweep gassing or vacuum pumping), chemical approaches (chemical scavenger), and combinations thereof. The results indicated that the sweep gas schemes work more efficient at non-isothermal than isothermal conditions, and efficient gas phase heat recovery and sweep gas recycling was important to ensure efficient fuel processing. The vacuum pump scheme achieved best efficiencies at isothermal conditions, and at non-isothermal conditions heat recovery was less essential. The use of oxygen scavengers combined with sweep gas and vacuum pump schemes further increased the system efficiency. The present work can be used to predict the performance of solar-driven non-stoichiometric redox cycles and further offers quantifiable guidelines for system design and operation. - Highlights: • A thermodynamic analysis was conducted for ceria-based thermochemical cycles. • Five novel cycle designs and various operating conditions were proposed and investigated. • Pressure reduction method affects optimal operating conditions for maximized efficiency. • Chemical oxygen scavenger proves to be promising in further increasing efficiency. • Formulation of quantifiable design guidelines for economical competitive solar fuel processing

  4. A Mechanistic Study of the Influence of Proton Transfer Processes on the Behavior of Thiol/Disulfide Redox Couples

    National Research Council Canada - National Science Library

    Shouji, Eiichi

    1998-01-01

    .... In order to elucidate the influence of proton transfers on these redox processes, special attention has been paid to the influence of various bases, including triethylamine, pyridine, 3-chloro...

  5. Redox properties of phenosafranine at zeolite-modified electrodes-Effect of surface modification and solution pH

    International Nuclear Information System (INIS)

    Easwaramoorthi, S.; Natarajan, P.

    2008-01-01

    Redox properties of cationic dye phenosafranine (3,7-diamino-5-phenylphenazenium chloride) (PS + ) were studied at zeolite-modified electrodes using Zeolite-Y and NaZSM-5. The peak current and peak potential of phenosafranine-adsorbed zeolite were found to be influenced by the pH of the electrolyte solution. Observation of a second redox couple is suggested to be due to formation of new species at low concentration from the reduced phenosafranine at the zeolite-modified electrodes. Titanium dioxide nanoparticles encapsulated in the cavities of the zeolite or anchored on the external surface of the zeolite do not seem to affect the redox properties of adsorbed PS + . When the cyclic voltammograms are recorded immediately after the electrode is immersed into the solution, the redox potential of PS + is found to be sensitive to the nature of the zeolite surface. The peak potential shifts towards positive region under continuous cycles as the surface hydroxyl groups get protonated in acidic electrolyte solution thereby forcing the movement of dye molecules from the zeolite surface to the zeolite electrode solution interface. The electron transfer rate constants for the adsorbed dye at the electrode are calculated to be 2.5 ± 0.2 s -1 and 3.5 ± 0.2 s -1 for the zeolite-Y electrode and the ZSM-5 electrode, respectively by the Laviron equation

  6. Investigation of Iron Oxide Morphology in a Cyclic Redox Water Splitting Process for Hydrogen Generation

    Directory of Open Access Journals (Sweden)

    Michael M. Bobek

    2012-10-01

    Full Text Available A solar fuels generation research program is focused on hydrogen production by means of reactive metal water splitting in a cyclic iron-based redox process. Iron-based oxides are explored as an intermediary reactive material to dissociate water molecules at significantly reduced thermal energies. With a goal of studying the resulting oxide chemistry and morphology, chemical assistance via CO is used to complete the redox cycle. In order to exploit the unique characteristics of highly reactive materials at the solar reactor scale, a monolithic laboratory scale reactor has been designed to explore the redox cycle at temperatures ranging from 675 to 875 K. Using high resolution scanning electron microscope (SEM and electron dispersive X-ray spectroscopy (EDS, the oxide morphology and the oxide state are quantified, including spatial distributions. These images show the change of the oxide layers directly after oxidation and after reduction. The findings show a significant non-stoichiometric O/Fe gradient in the atomic ratio following oxidation, which is consistent with a previous kinetics model, and a relatively constant, non-stoichiometric O/Fe atomic ratio following reduction.

  7. Accessible reactive surface area and abiotic redox reactivity of iron oxyhydroxides in acidic brines

    Science.gov (United States)

    Strehlau, Jennifer H.; Toner, Brandy M.; Arnold, William A.; Penn, R. Lee

    2017-01-01

    The reactivity of iron oxyhydroxide nanoparticles in low pH and high ionic strength solutions was quantified to assess abiotic contributions to oxidation-reduction chemistry in acidic brine environments, such as mine groundwater seepage, lakes in Western Australia, and acid mine drainage settings, which are of global interest for their environmental impacts and unique geomicrobiology. Factors expected to influence accessible and reactive surface area, including Fe(II) adsorption and aggregate size, were measured as a function of pH and CaCl2 concentration and related to the kinetics of redox reactions in aqueous suspensions of synthetic goethite (α-FeOOH), akaganeite (β-FeOOH), and ferrihydrite (Fe10O14(OH)2) nanoparticles. Aqueous conditions and iron oxyhydroxides were chosen based on characterization of natural iron-rich mine microbial mats located in Soudan Underground Mine State Park, Minnesota, USA. Quinone species were used as redox sensors because they are well-defined probes and are present in natural organic matter. Fe(II) adsorption to the iron oxyhydroxide mineral surfaces from aqueous solution was measurable only at pH values above 4 and either decreased or was not affected by CaCl2 concentration. Concentrations at or above 0.020 M CaCl2 in acetate buffer (pH 4.5) induced particle aggregation. Assessment of Fe(II) adsorption and particle aggregation in acidic brine suggested that accessible reactive surface area may be limited in acidic brines. This was supported by observations of decreasing benzoquinone reduction rate by adsorbed Fe(II) at high CaCl2 concentration. In contrast, the hydroquinone oxidation rate increased at high CaCl2 concentrations, which may be due to suppressed adsorption of Fe(II) generated by the reaction. Results suggest that iron geochemical cycling in acidic brine environments will be substantially different than for iron oxyhydroxides in low-saline waters with circumneutral pH. These findings have implications for acidic

  8. Redox processes in the safety case of deep geological repositories of radioactive wastes. Contribution of the European RECOSY Collaborative Project

    International Nuclear Information System (INIS)

    Duro, L.; Bruno, J.; Grivé, M.; Montoya, V.; Kienzler, B.; Altmaier, M.; Buckau, G.

    2014-01-01

    Highlights: • The RECOSY project produced results relevant for the Safety Case of nuclear disposal. • We classify the safety related features where RECOSY has contributed. • Redox processes effect the retention of radionuclides in all repository subsystems. - Abstract: Redox processes influence key geochemical characteristics controlling radionuclide behaviour in the near and far field of a nuclear waste repository. A sound understanding of redox related processes is therefore of high importance for developing a Safety Case, the collection of scientific, technical, administrative and managerial arguments and evidence in support of the safety of a disposal facility. This manuscript presents the contribution of the specific research on redox processes achieved within the EURATOM Collaborative Project RECOSY (REdox phenomena COntrolling SYstems) to the Safety Case of nuclear waste disposal facilities. Main objectives of RECOSY were related to the improved understanding of redox phenomena controlling the long-term release or retention of radionuclides in nuclear waste disposal and providing tools to apply the results to Performance Assessment and the Safety Case. The research developed during the project covered aspects of the near-field and the far-field aspects of the repository, including studies relevant for the rock formations considered in Europe as suitable for hosting an underground repository for radioactive wastes. It is the intention of this paper to highlight in which way the results obtained from RECOSY can feed the scientific process understanding needed for the stepwise development of the Safety Case associated with deep geological disposal of radioactive wastes

  9. Co-regulation of redox processes in freshwater wetlands as a function of organic matter availability?

    International Nuclear Information System (INIS)

    Alewell, C.; Paul, S.; Lischeid, G.; Storck, F.R.

    2008-01-01

    Wetlands have important filter functions in landscapes but are considered to be the biggest unknowns regarding their element dynamics under global climate change. Information on sink and source function of sulphur, nitrogen, organic matter and acidity in wetlands is crucial for freshwater regeneration. Recent results indicate that redox processes are not completely controlled by the sequential reduction chain (that is electron acceptor availability) but that electron donor availability may be an important regulator. Our hypothesis was that only sites which are limited in their electron donor availability (low concentrations of dissolved organic carbon (DOC)) follow the concept of the sequential reduction chain. We compared the results of two freshwater wetland systems: 1) three forested fens within a boreal spruce catchment in a low mountain range in southern Germany (high DOC regime) and 2) three floodplain soils within a groundwater enrichment area in the Rhein valley in northwest Switzerland (low DOC regime). Micro scale investigations (a few cm 3 ) with dialyse chambers as well as soil solution and groundwater concentrations at the forested fens (high DOC regime) indicated simultaneous consumption of nitrate and sulphate with release of iron, manganese and methane (CH 4 ) as well as an enrichment in stable sulphur isotopes indicating a co-existence of processes attributed to different redox gradients. Soil and aquifer gas measurements down to 4.6 m at the groundwater enrichment site (low DOC regime and carbon limitation) showed extreme high rates of metabolism with carbon dioxide (CO 2 ) , dinitrous oxide (N 2 O) and CH 4 concentrations reaching fifty, thirty and three times atmospheric concentrations, respectively. Simultaneously, groundwater oxygen (O 2 ) saturation was between 50 and 95%. We concluded that independent of DOC regime the sequential reduction chain was not a suitable concept in our systems. Instead of electron acceptor or donor availability

  10. Cu and Cu(Mn) films deposited layer-by-layer via surface-limited redox replacement and underpotential deposition

    Energy Technology Data Exchange (ETDEWEB)

    Fang, J.S., E-mail: jsfang@nfu.edu.tw [Department of Materials Science and Engineering, National Formosa University, Huwei 63201, Taiwan (China); Sun, S.L. [Department of Materials Science and Engineering, National Formosa University, Huwei 63201, Taiwan (China); Cheng, Y.L. [Department of Electrical Engineering, National Chi-Nan University, Nan-Tou 54561, Taiwan (China); Chen, G.S.; Chin, T.S. [Department of Materials Science and Engineering, Feng Chia University, Taichung 40724, Taiwan (China)

    2016-02-28

    Graphical abstract: - Abstract: The present paper reports Cu and Cu(Mn) films prepared layer-by-layer using an electrochemical atomic layer deposition (ECALD) method. The structure and properties of the films were investigated to elucidate their suitability as Cu interconnects for microelectronics. Previous studies have used primarily a vacuum-based atomic layer deposition to form a Cu metallized film. Herein, an entirely wet chemical process was used to fabricate a Cu film using the ECALD process by combining underpotential deposition (UPD) and surface-limited redox replacement (SLRR). The experimental results indicated that an inadequate UPD of Pb affected the subsequent SLRR of Cu and lead to the formation of PbSO{sub 4}. A mechanism is proposed to explain the results. Layer-by-layer deposition of Cu(Mn) films was successfully performed by alternating the deposition cycle-ratios of SLRR-Cu and UPD-Mn. The proposed self-limiting growth method offers a layer-by-layer wet chemistry-based deposition capability for fabricating Cu interconnects.

  11. Performance enhancement in vanadium redox flow battery using platinum-based electrocatalyst synthesized by polyol process

    International Nuclear Information System (INIS)

    Jeong, Sanghyun; Kim, Sunhoe; Kwon, Yongchai

    2013-01-01

    Sluggish reaction rate of [VO] 2+ /[VO 2 ] + redox couple is an obstacle to be addressed in vanadium redox flow battery (VRFB). To improve the slow reaction rate, Pt/C catalyst synthesized by polyol method is suggested. Its catalytic activity, reaction reversibility and charge–discharge performance are evaluated by half cell and single cell tests, while its crystal structure, particle size and particle distribution are measured by XRD and TEM. The XRD and TEM measurements show the polyol Pt/C catalyst has larger electrochemically active surface (EAS) area and smaller particle size than commercial Pt/C catalyst. When catalytic activities of all the catalysts are estimated, the Pt-included catalysts demonstrate high peak current ratio, small peak potential difference and high electron transfer rate constant, confirming that their catalytic activity and reaction reversibility are excellent. In charge–discharge performance tests, the catalysts indicate high efficiencies as well as low overpotential and internal resistance. Excellent performances of the Pt-included catalysts are attributed to positively charged Pts that serve as active sites for activating [VO] 2+ /[VO 2 ] + reaction. Indeed, adoption of the Pt-included catalysts, especially, use of the polyol Pt/C consisting of uniform and small particles helps improve performance of VRFB

  12. Impact of pH on hydrogen oxidizing redox processes in aquifers due to gas intrusions

    Science.gov (United States)

    Metzgen, Adrian; Berta, Marton; Dethlefsen, Frank; Ebert, Markus; Dahmke, Andreas

    2017-04-01

    Hydrogen production from excess energy and its storage can help increasing the efficiency of solar and wind in the energy mix. Therefore, hydrogen needs large-scale intermediate storage independent of the intended later use as hydrogen gas or as reactant to produce methane in the Sabatier process. A possible storage solution is using the geological subsurface such as caverns built in salt deposits or aquifers that are not used for drinking water production. However, underground storage of hydrogen gas potentially leads to accidental gas leakages into near-surface potable aquifers triggering subsequent geochemical processes. These leakages pose potential risks that are currently not sufficiently understood. To close this gap in knowledge, a high-pressure laboratory column system was used to simulate a hydrogen gas intrusion into a shallow aquifer. Water and sediment were gained from a sandy Pleistocene aquifer near Neumünster, Germany. In the first stage of the experiment, 100% hydrogen gas was used to simulate dissolved hydrogen concentrations between 800 and 4000 µM by varying pH2 between 2 and 15 bars. pH values rose to between 7.9 and 10.4, partly due to stripping CO2 from the groundwater used during H2 gas addition. In a second stage, the pH was regulated in a range of 6.7 to 7.9 by using a gas mixture of 99% H2 and 1% CO2 at 5 bars of total gas pressure. Observed processes included hydrogen oxidation, sulfate reduction, acetogenesis, formate production, and methanogenesis, which were independent of the hydrogen concentration. Hydrogen oxidation and sulfate reduction showed zeroth order reaction rates and rate constants (106 to 412 µM/h and 12 to 33 µM/h, respectively) in the pH range between 8 and 10. At pH levels between 7 and 8, both reactions started out faster near the column's inflow but then seemed limited towards the columns outflow, suggesting the dependence of sulfate reduction on the pH-value. Acetogenesis dominated the pH range between 8 and 10

  13. Modelling long-term redox processes and oxygen scavenging in fractured crystalline rocks

    International Nuclear Information System (INIS)

    Sidborn, Magnus

    2007-10-01

    Advanced plans for the construction of a deep geological repository for highly radioactive wastes from nuclear power plants have evolved during the past decades in many countries including Sweden. As part of the Swedish concept, the waste is to be encapsulated in canisters surrounded by low permeability backfill material. The copper canisters will be deposited at around 500 metres depth in granitic rock, which acts as a natural barrier for the transport of radionuclides to the ground surface. These natural and engineered barriers are chosen and designed to ensure the safety of the repository over hundred of thousands of years. One issue of interest for the safety assessment of such a repository is the redox evolution over long times. An oxidising environment would enhance the corrosion of the copper canisters, and increases the mobility of any released radionuclides. In the first part of the present thesis, the ability of the host rock to ensure a reducing environment at repository depth over long times was studied. A model framework was developed with the aim to capture all processes that are deemed to be important for the scavenging of intruding oxygen from the ground surface over long times. Simplifications allowing for analytical solutions were introduced for transparency reasons so that evaluation of results is straight-forward, and so that uncertain parameter values easily can be adjusted. More complex systems were solved numerically for cases when the analytical simplifications are not applicable, and to validate the simplifications underlying the analytical solutions. Results were presented for prevailing present day conditions as well as for conditions deemed to be likely during the melting phase of a period of glaciation. It was shown that the hydraulic properties have a great influence on the oxygen intrusion length downstream along flow-paths in the rock. An important parameter that determines the extent of interaction between the dissolved oxygen and

  14. Superhydrophobic surfaces by electrochemical processes.

    Science.gov (United States)

    Darmanin, Thierry; Taffin de Givenchy, Elisabeth; Amigoni, Sonia; Guittard, Frederic

    2013-03-13

    This review is an exhaustive representation of the electrochemical processes reported in the literature to produce superhydrophobic surfaces. Due to the intensive demand in the elaboration of superhydrophobic materials using low-cost, reproducible and fast methods, the use of strategies based on electrochemical processes have exponentially grown these last five years. These strategies are separated in two parts: the oxidation processes, such as oxidation of metals in solution, the anodization of metals or the electrodeposition of conducting polymers, and the reduction processed such as the electrodeposition of metals or the galvanic deposition. One of the main advantages of the electrochemical processes is the relative easiness to produce various surface morphologies and a precise control of the structures at a micro- or a nanoscale. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Redox behavior of a low-doped Pr-CeO_2(111) surface. A DFT+U study

    International Nuclear Information System (INIS)

    Milberg, Brian; Juan, Alfredo; Irigoyen, Beatriz

    2017-01-01

    Highlights: • Pr doping facilitates oxygen donation due to the easy formation of Pr"3"+/Pr"4"+ and Ce"3"+/Ce"4"+ redox couples. • Pr doping also favors the formation of superoxide (O_2"−) radicals on surface O-holes. • CO can be oxidized by superoxide radical forming a CO_2 molecule floating on the surface. • CO can also interact on the (O_2"−)/Pr"3"+ interphase and forms weakly adsorbed carbonate-type intermediates. - Abstract: In this work, we investigated the redox behavior (donation and replenishing of oxygen) of a low praseodymium (Pr)-doped CeO_2(111) surface. We considered a 3.7 at.% Pr doping and performed density functional calculations using the GGA formalism with the ‘U’ correction on Ce(4f) and Pr(4f) orbitals. Our results indicate that Pr doping promotes oxygen donation by lowering the energy necessary to form surface anionic vacancies. When the Ce_0_._9_6_3Pr_0_._0_3_7O_2(111) surface donates one oxygen, the two excess electrons locate on Pr and Ce cations and reduce them to Pr"3"+ and Ce"3"+ ones. Praseodymium doping also favors the activation of O_2 molecule on surface O-holes, leading to formation of a superoxide (O_2"−) radical as well as to reoxidation of the Ce"3"+ cation to Ce"4"+ one. Additionally, we used the CO molecular adsorption for testing the reactivity of those superoxide species. The calculations expose the ability of these radicals to oxidize CO forming a CO_2 molecule floating on the surface. However, when the superoxide is in the immediate vicinity of Pr dopant a carbonate-type species is formed. Our theoretical results may help to gain insight into redox properties and improved catalytic performance of low-doped Pr-CeO_2 solids.

  16. Interim glycol flowsheet reduction/oxidation (redox) model for the Defense Waste Processing Facility (DWPF)

    Energy Technology Data Exchange (ETDEWEB)

    Jantzen, C. M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Williams, M. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Zamecnik, J. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Missimer, D. M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-03-08

    Control of the REDuction/OXidation (REDOX) state of glasses containing high concentrations of transition metals, such as High Level Waste (HLW) glasses, is critical in order to eliminate processing difficulties caused by overly reduced or overly oxidized melts. Operation of a HLW melter at Fe+2/ΣFe ratios of between 0.09 and 0.33, a range which is not overly oxidizing or overly reducing, helps retain radionuclides in the melt, i.e. long-lived radioactive 99Tc species in the less volatile reduced Tc4+ state, 104Ru in the melt as reduced Ru+4 state as insoluble RuO2, and hazardous volatile Cr6+ in the less soluble and less volatile Cr+3 state in the glass. The melter REDOX control balances the oxidants and reductants from the feed and from processing additives such as antifoam. Currently, the Defense Waste Processing Facility (DWPF) is running a formic acid-nitric acid (FN) flowsheet where formic acid is the main reductant and nitric acid is the main oxidant. During decomposition formate and formic acid releases H2 gas which requires close control of the melter vapor space flammability. A switch to a nitric acid-glycolic acid (GN) flowsheet is desired as the glycolic acid flowsheet releases considerably less H2 gas upon decomposition. This would greatly simplify DWPF processing. Development of an EE term for glycolic acid in the GN flowsheet is documented in this study.

  17. Mass effect of redox reactions: A novel mode for surface plasmon resonance-based bioanalysis.

    Science.gov (United States)

    Yuan, Pei-Xin; Deng, Sheng-Yuan; Xin, Peng; Ji, Xu-Bo; Shan, Dan; Cosnier, Serge

    2015-12-15

    The pursuit of more specific and sensitive response is a perpetual goal for modern bioassays. This work proposed a novel label-free strategy about redox-related mass effect based on the surface plasmon resonance (SPR) technique for ultrasensitive determination of DNA. The protocol starts with the modification of SPR gilded disk with the capture DNA (cDNA). After the conjugation of immobilized cDNA with the target DNA (tDNA), the hybridization chain reaction was triggered by the introduction of mutual partial complementary primers to elongate the terminal into a nanoscale duplex. As it is reported that porphyrin could intercalate into the grooves of the double-stranded DNA (dsDNA) scaffold, multiple positive-charged Fe(III)meso-tetra(N-methyl-4-pyridyl) porphine (FeTMPyP) with symmetric structure were uptaken for in situ formation of porphyrin-dsDNA complex. Given FeTMPyP a highly efficient catalysis for the peroxide reduction, its presence as a biomimetic cofactor was validated via circular dichroism and UV-vis spectroscopy, demonstrating a tight binding as well as high catalytic activity and stability. Using 4-chloro-1-naphthol as a proton donor, the catalytic reduction of H2O2 would oxidize it into insoluble benzo-4-chloro-hexadienone, which simultaneously deposited on the heterogeneous interface, leading to a significant amplification in both SPR response and topological height profile. The signal increment was proportional to the concentration of tDNA, thus an ultrasensitive SPR-based DNA assay was developed with a linear range over four orders of magnitudes and a sub-femtomolar detection limit of 0.73 fM. The developed methodology exemplifies a different way of thinking about mass-sensing modes, extending conventional SPR-based DNA analysis to relevant biomedical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Nanoscale processes on insulating surfaces

    National Research Council Canada - National Science Library

    Gnecco, Enrico; Szymoński, Marek

    2009-01-01

    ... the group of Prof. Ernst Meyer in Basel, where he investigated friction processes on alkali halide surfaces in ultra high vacuum (UHV). The main result was the observation of a logarithmic velocity dependence of atomic friction, which was interpreted within a combination of the classical Tomlinson and Eyring models. After his Ph.D. he joined the ...

  19. Electro-deposition of Pd on carbon paper and Ni foam via surface limited redox-replacement reaction for oxygen reduction reaction

    CSIR Research Space (South Africa)

    Modibedi, RM

    2014-05-01

    Full Text Available Pd nanostructured catalysts were electrodeposited by surface-limited redox replacement reactions usingthe electrochemical atomic layer deposition technique. Carbon paper and Ni foam were used as substratesfor the electrodeposition of the metal...

  20. Time resolved XANES illustrates a substrate-mediated redox process in Prussian blue cultural heritage materials

    International Nuclear Information System (INIS)

    Gervais, Claire; Moretti, Giulia; Lanquille, Marie-Angélique; Réguer, Solenn

    2016-01-01

    The pigment Prussian blue is studied in heritage science because of its capricious fading behavior under light exposure. We show here that XANES can be used to study the photosensitivity of Prussian blue heritage materials despite X-ray radiation damage. We used an original approach based on X-ray photochemistry to investigate in depth the redox process of Prussian blue when it is associated with a cellulosic substrate, as in cyanotypes and watercolors. By modifying cation and proton contents of the paper substrate, we could tune both rate and extent of Prussian blue reduction. These results demonstrate that the photoreduction and fading of Prussian blue is principally mediated by the substrate and its interaction with the oxygen of the environment. (paper)

  1. Nitric-glycolic flowsheet reduction/oxidation (redox) model for the defense waste processing facility (DWPF)

    Energy Technology Data Exchange (ETDEWEB)

    Jantzen, C. M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Williams, M. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Edwards, T. B. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Trivelpiece, C. L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Ramsey, W. G. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-06-14

    Control of the REDuction/OXidation (REDOX) state of glasses containing high concentrations of transition metals, such as High Level Waste (HLW) glasses, is critical in order to eliminate processing difficulties caused by overly reduced or overly oxidized melts. Operation of a HLW melter at Fe+2/ΣFe ratios of between 0.09 and 0.33, retains radionuclides in the melt and thus the final glass. Specifically, long-lived radioactive 99Tc species are less volatile in the reduced Tc4+ state as TcO2 than as NaTcO4 or Tc2O7, and ruthenium radionuclides in the reduced Ru4+ state are insoluble RuO2 in the melt which are not as volatile as NaRuO4 where the Ru is in the +7 oxidation state. Similarly, hazardous volatile Cr6+ occurs in oxidized melt pools as Na2CrO4 or Na2Cr2O7, while the Cr+3 state is less volatile and remains in the melt as NaCrO2 or precipitates as chrome rich spinels. The melter REDOX control balances the oxidants and reductants from the feed and from processing additives such as antifoam.

  2. Reduction of Tc(VII) and Np(V) in solution by ferrous iron. A laboratory study of homogeneous and heterogeneous redox processes

    International Nuclear Information System (INIS)

    Cui, D.; Eriksen, T.E.

    1996-03-01

    The redox chemistry of Technetium and Neptunium in deep groundwater systems has been studied under well controlled conditions in laboratory experiments. The measured redox potentials in anoxic deep groundwater systems are consistent with redox reactions between Fe(II) in solution and hydrous Fe(III)-oxide phases. The fracture filling material and groundwater in transmissive fractures in bedrock constitute two different compartments in the groundwater system and experiments were therefore carried out in homogeneous Fe(II) containing solutions and in heterogeneous mixtures of solution with Fe(II) containing solid mineral phases. Reduction of the strongly sorbing neptunyl cation (NpO 2 + ) and the slightly sorbing pertechnetate anion (TcO 4 - ) by Fe(II) in solution was found to proceed very slowly, if at all, in reaction vessels with hydrophobic inner surfaces. However, in the heterogeneous systems we observed surface mediated reduction to the slightly soluble ( -8 mol*dm -3 ) tetravalent (hydr)oxides TcO 2 *nH 2 O (=Tc(OH) 4 ) and NpO 2 *nH 2 O (=Np(OH) 4 ) by Fe(II) sorbed on quartz,precipitated Fe(OH) 2 (s), Fe(II)CO 3 (s) and Fe(II) bearing minerals such as magnetite, hornblende and Fe(II)-chlorite. It is concluded that surface mediated redox-reactions will be the most effective pathway for the reduction of Tc(VII) and Np(V) in deep groundwater systems. On exposure of the surface-precipitated tetravalent (hydr)oxides to air saturated groundwater solutions the oxidative dissolution was found to be a very slow process and high concentration of hydrogen peroxide was required for oxidative dissolution. The slow rate of oxidative dissolution is most probably due to kinetic suppression of the reactions between dissolved oxygen and the precipitated (hydr)oxides. The kinetic suppression is caused by competing redox reactions at the surface of the Fe(II)-bearing minerals which consumes the dissolved oxygen. 30 refs, 22 figs

  3. Reduction of Tc(VII) and Np(V) in solution by ferrous iron. A laboratory study of homogeneous and heterogeneous redox processes

    Energy Technology Data Exchange (ETDEWEB)

    Cui, D.; Eriksen, T.E. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Chemistry

    1996-03-01

    The redox chemistry of Technetium and Neptunium in deep groundwater systems has been studied under well controlled conditions in laboratory experiments. The measured redox potentials in anoxic deep groundwater systems are consistent with redox reactions between Fe(II) in solution and hydrous Fe(III)-oxide phases. The fracture filling material and groundwater in transmissive fractures in bedrock constitute two different compartments in the groundwater system and experiments were therefore carried out in homogeneous Fe(II) containing solutions and in heterogeneous mixtures of solution with Fe(II) containing solid mineral phases. Reduction of the strongly sorbing neptunyl cation (NpO{sub 2}{sup +}) and the slightly sorbing pertechnetate anion (TcO{sub 4}{sup -}) by Fe(II) in solution was found to proceed very slowly, if at all, in reaction vessels with hydrophobic inner surfaces. However, in the heterogeneous systems we observed surface mediated reduction to the slightly soluble (<10{sub -8} mol*dm{sup -3}) tetravalent (hydr)oxides TcO{sub 2}*nH{sub 2}O (=Tc(OH){sub 4}) and NpO{sub 2}*nH{sub 2}O (=Np(OH){sub 4}) by Fe(II) sorbed on quartz,precipitated Fe(OH){sub 2}(s), Fe(II)CO{sub 3}(s) and Fe(II) bearing minerals such as magnetite, hornblende and Fe(II)-chlorite. It is concluded that surface mediated redox-reactions will be the most effective pathway for the reduction of Tc(VII) and Np(V) in deep groundwater systems. On exposure of the surface-precipitated tetravalent (hydr)oxides to air saturated groundwater solutions the oxidative dissolution was found to be a very slow process and high concentration of hydrogen peroxide was required for oxidative dissolution. The slow rate of oxidative dissolution is most probably due to kinetic suppression of the reactions between dissolved oxygen and the precipitated (hydr)oxides. The kinetic suppression is caused by competing redox reactions at the surface of the Fe(II)-bearing minerals which consumes the dissolved oxygen.

  4. Pt deposition on carbon paper and Ti mesh substrates by surface limited redox replacement

    CSIR Research Space (South Africa)

    Modibedi, M

    2011-12-01

    Full Text Available , the material used as gas diffusion layer for proton exchange membrane fuel cells (PEMFCs) and Ti-mesh. The deposition uses multiple redox replacement of underpotentially deposited Cu used as a sacrificial metal. The morphology and particle size of the deposited...

  5. Investigation of potential analytical methods for redox control of the vitrification process

    International Nuclear Information System (INIS)

    Goldman, D.S.

    1985-11-01

    An investigation was conducted to evaluate several analytical techniques to measure ferrous/ferric ratios in simulated and radioactive nuclear waste glasses for eventual redox control of the vitrification process. Redox control will minimize the melt foaming that occurs under highly oxidizing conditions and the metal precipitation that occurs under highly reducing conditions. The analytical method selected must have a rapid response for production problems with minimal complexity and analyst involvement. The wet-chemistry, Moessbauer spectroscopy, glass color analysis, and ion chromatography techniques were explored, with particular emphasis being placed on the Moessbauer technique. In general, all of these methods can be used for nonradioactive samples. The Moessbauer method can readily analyze glasses containing uranium and thorium. A shielded container was designed and built to analyze fully radioactive glasses with the Moessbauer spectrometer in a hot cell environment. However, analyses conducted with radioactive waste glasses containing 90 Sr and 137 Cs were unsuccessful, presumably due to background radiation problems caused by the samples. The color of glass powder can be used to analyze the ferrous/ferric ratio for low chromium glasses, but this method may not be as precise as the others. Ion chromatography was only tested on nonradioactive glasses, but this technique appears to have the required precision due to its analysis of both Fe +2 and Fe +3 and its anticipated adaptability for radioactivity samples. This development would be similar to procedures already in use for shielded inductively coupled plasma emission (ICP) spectrometry. Development of the ion chromatography method is therefore recommended; conventional wet-chemistry is recommended as a backup procedure

  6. The complex reaction kinetics of neptunium including redox and extraction process in 30% TBP-nitric acid system

    International Nuclear Information System (INIS)

    Hu Zhang; Zhan-yuan Liu; Xian-ming Zhou; Li Li

    2017-01-01

    In order to understand the complex and dynamic neptunium process chemistry in the TBP-HNO_3 system, the kinetics involved reversible redox reaction and extraction mass transfer was investigated. The results indicates that the mass transfer rate of Np(VI) is much faster than the redox reaction in aqueous solution. The concentrations of nitric acid and nitrous acid not only can change the Np(V) oxidation reaction and Np(VI) reduction reaction rate, but also can ultimately determine the distribution of neptunium extraction equilibrium. The variety of temperature can only influence the extraction equilibrium time, but cannot alter the equilibrium state of neptunium. (author)

  7. Applying the Nernst equation to simulate redox potential variations for biological nitrification and denitrification processes.

    Science.gov (United States)

    Chang, Cheng-Nan; Cheng, Hong-Bang; Chao, Allen C

    2004-03-15

    In this paper, various forms of Nernst equations have been developed based on the real stoichiometric relationship of biological nitrification and denitrification reactions. Instead of using the Nernst equation based on a one-to-one stoichiometric relation for the oxidizing and the reducing species, the basic Nernst equation is modified into slightly different forms. Each is suitable for simulating the redox potential (ORP) variation of a specific biological nitrification or denitrification process. Using the data published in the literature, the validity of these developed Nernst equations has been verified by close fits of the measured ORP data with the calculated ORP curve. The simulation results also indicate that if the biological process is simulated using an incorrect form of Nernst equation, the calculated ORP curve will not fit the measured data. Using these Nernst equations, the ORP value that corresponds to a predetermined degree of completion for the biochemical reaction can be calculated. Thus, these Nernst equations will enable a more efficient on-line control of the biological process.

  8. Investigation of iodine liberation process in redox titration of potassium iodate with sodium thiosulfate

    Energy Technology Data Exchange (ETDEWEB)

    Asakai, Toshiaki, E-mail: t-asakai@aist.go.jp [National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 3-9, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563 (Japan); Hioki, Akiharu [National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 3-9, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563 (Japan)

    2011-03-09

    Potassium iodate is often used as a reference material to standardize a sodium thiosulfate solution which is a familiar titrant for redox titrations. In the standardization, iodine (triiodide) liberated by potassium iodate in an acidic potassium iodide solution is titrated with a sodium thiosulfate solution. The iodine liberation process is significantly affected by the amount of acid, that of potassium iodide added, the waiting time for the liberation, and light; therefore, the process plays a key role for the accuracy of the titration results. Constant-voltage biamperometry with a modified dual platinum-chip electrode was utilized to monitor the amount of liberated iodine under several liberation conditions. Coulometric titration was utilized to determine the concentration of a sodium thiosulfate solution on an absolute basis. Potassium iodate was assayed by gravimetric titration with the sodium thiosulfate solution under several iodine liberation conditions. The liberation process was discussed from the changes in the apparent assay of potassium iodate. The information of the appropriate titration procedure obtained in the present study is useful for any analysts utilizing potassium iodate to standardize a thiosulfate solution.

  9. Investigation of iodine liberation process in redox titration of potassium iodate with sodium thiosulfate

    International Nuclear Information System (INIS)

    Asakai, Toshiaki; Hioki, Akiharu

    2011-01-01

    Potassium iodate is often used as a reference material to standardize a sodium thiosulfate solution which is a familiar titrant for redox titrations. In the standardization, iodine (triiodide) liberated by potassium iodate in an acidic potassium iodide solution is titrated with a sodium thiosulfate solution. The iodine liberation process is significantly affected by the amount of acid, that of potassium iodide added, the waiting time for the liberation, and light; therefore, the process plays a key role for the accuracy of the titration results. Constant-voltage biamperometry with a modified dual platinum-chip electrode was utilized to monitor the amount of liberated iodine under several liberation conditions. Coulometric titration was utilized to determine the concentration of a sodium thiosulfate solution on an absolute basis. Potassium iodate was assayed by gravimetric titration with the sodium thiosulfate solution under several iodine liberation conditions. The liberation process was discussed from the changes in the apparent assay of potassium iodate. The information of the appropriate titration procedure obtained in the present study is useful for any analysts utilizing potassium iodate to standardize a thiosulfate solution.

  10. Redox Interactions between Iron and Carbon in Planetary Mantles: Implications for Degassing and Melting Processes

    Science.gov (United States)

    Martin, A.; Righter, K.

    2009-01-01

    Carbon stability in planetary mantles has been studied by numerous authors because it is thought to be the source of C-bearing atmospheres and of C-rich lavas observed at the planetary surface. In the Earth, carbonaceous peridotites and eclogites compositions have been experimentally studied at mantle conditions [1] [2] [3]. [4] showed that the fO2 variations observed in martian meteorites can be explained by polybaric graphite-CO-CO2 equilibria in the Martian mantle. Based on thermodynamic calculations [4] and [5] inferred that the stable form of carbon in the source regions of the Martian basalts should be graphite (and/or diamond), and equilibrium with melts would be a source of CO2 for the martian atmosphere. Considering the high content of iron in the Martian mantle (approx.18.0 wt% FeO; [6]), compared to Earth s mantle (8.0 wt% FeO; [7]) Fe/C redox interactions should be studied in more detail.

  11. Plant redox proteomics

    DEFF Research Database (Denmark)

    Navrot, Nicolas; Finnie, Christine; Svensson, Birte

    2011-01-01

    PTMs in regulating enzymatic activities and controlling biological processes in plants. Notably, proteins controlling the cellular redox state, e.g. thioredoxin and glutaredoxin, appear to play dual roles to maintain oxidative stress resistance and regulate signal transduction pathways via redox PTMs......In common with other aerobic organisms, plants are exposed to reactive oxygen species resulting in formation of post-translational modifications related to protein oxidoreduction (redox PTMs) that may inflict oxidative protein damage. Accumulating evidence also underscores the importance of redox....... To get a comprehensive overview of these types of redox-regulated pathways there is therefore an emerging interest to monitor changes in redox PTMs on a proteome scale. Compared to some other PTMs, e.g. protein phosphorylation, redox PTMs have received less attention in plant proteome analysis, possibly...

  12. Maleimide-activated aryl diazonium salts for electrode surface functionalization with biological and redox-active molecules.

    Science.gov (United States)

    Harper, Jason C; Polsky, Ronen; Wheeler, David R; Brozik, Susan M

    2008-03-04

    A versatile and simple method is introduced for formation of maleimide-functionalized surfaces using maleimide-activated aryl diazonium salts. We show for the first time electrodeposition of N-(4-diazophenyl)maleimide tetrafluoroborate on gold and carbon electrodes which was characterized via voltammetry, grazing angle FTIR, and ellipsometry. Electrodeposition conditions were used to control film thickness and yielded submonolayer-to-multilayer grafting. The resulting phenylmaleimide surfaces served as effective coupling agents for electrode functionalization with ferrocene and the redox-active protein cytochrome c. The utility of phenylmaleimide diazonium toward formation of a diazonium-activated conjugate, followed by direct electrodeposition of the diazonium-modified DNA onto the electrode surface, was also demonstrated. Effective electron transfer was obtained between immobilized molecules and the electrodes. This novel application of N-phenylmaleimide diazonium may facilitate the development of bioelectronic devices including biofuel cells, biosensors, and DNA and protein microarrays.

  13. Impacts of shallow geothermal energy production on redox processes and microbial communities.

    Science.gov (United States)

    Bonte, Matthijs; Röling, Wilfred F M; Zaura, Egija; van der Wielen, Paul W J J; Stuyfzand, Pieter J; van Breukelen, Boris M

    2013-12-17

    Shallow geothermal systems are increasingly being used to store or harvest thermal energy for heating or cooling purposes. This technology causes temperature perturbations exceeding the natural variations in aquifers, which may impact groundwater quality. Here, we report the results of laboratory experiments on the effect of temperature variations (5-80 °C) on redox processes and associated microbial communities in anoxic unconsolidated subsurface sediments. Both hydrochemical and microbiological data showed that a temperature increase from 11 °C (in situ) to 25 °C caused a shift from iron-reducing to sulfate-reducing and methanogenic conditions. Bioenergetic calculations could explain this shift. A further temperature increase (>45 °C) resulted in the emergence of a thermophilic microbial community specialized in fermentation and sulfate reduction. Two distinct maxima in sulfate reduction rates, of similar orders of magnitude (5 × 10(-10) M s(-1)), were observed at 40 and 70 °C. Thermophilic sulfate reduction, however, had a higher activation energy (100-160 kJ mol(-1)) than mesophilic sulfate reduction (30-60 kJ mol(-1)), which might be due to a trade-off between enzyme stability and activity with thermostable enzymes being less efficient catalysts that require higher activation energies. These results reveal that while sulfate-reducing functionality can withstand a substantial temperature rise, other key biochemical processes appear more temperature sensitive.

  14. High surface area bio-waste based carbon as a superior electrode for vanadium redox flow battery

    Science.gov (United States)

    Maharjan, Makhan; Bhattarai, Arjun; Ulaganathan, Mani; Wai, Nyunt; Oo, Moe Ohnmar; Wang, Jing-Yuan; Lim, Tuti Mariana

    2017-09-01

    Activated carbon (AC) with high surface area (1901 m2 g-1) is synthesized from low cost bio-waste orange (Citrus sinensis) peel for vanadium redox flow battery (VRB). The composition, structure and electrochemical properties of orange peel derived AC (OP-AC) are characterized by elemental analyzer, field emission-scanning electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy. CV results show that OP-AC coated bipolar plate demonstrates improved electro-catalytic activity in both positive and negative side redox couples than the pristine bipolar plate electrode and this is ascribed to the high surface area of OP-AC which provides effective electrode area and better contact between the porous electrode and bipolar plate. Consequently, the performance of VRB in a static cell shows higher energy efficiency for OP-AC electrode than the pristine electrode at all current densities tested. The results suggest the OP-AC to be a promising electrode for VRB applications and can be incorporated into making conducting plastics electrode to lower the VRB cell stack weight and cost.

  15. Microbial redox processes in deep subsurface environments and the potential application of (perchlorate in oil reservoirs

    Directory of Open Access Journals (Sweden)

    Martin G Liebensteiner

    2014-09-01

    Full Text Available The ability of microorganisms to thrive under oxygen-free conditions in subsurface environments relies on the enzymatic reduction of oxidized elements, such as sulfate, ferric iron or CO2, coupled to the oxidation of inorganic or organic compounds. A broad phylogenetic and functional diversity of microorganisms from subsurface environments has been described using isolation-based and advanced molecular ecological techniques. The physiological groups reviewed here comprise iron-, manganese- and nitrate-reducing microorganisms. In the context of recent findings also the potential of chlorate and perchlorate [jointly termed (perchlorate] reduction in oil reservoirs will be discussed. Special attention is given to elevated temperatures that are predominant in the deep subsurface. Microbial reduction of (perchlorate is a thermodynamically favorable redox process, also at high temperature. However, knowledge about (perchlorate reduction at elevated temperatures is still scarce and restricted to members of the Firmicutes and the archaeon Archaeoglobus fulgidus. By analyzing the diversity and phylogenetic distribution of functional genes in (metagenome databases and combining this knowledge with extrapolations to earlier-made physiological observations we speculate on the potential of (perchlorate reduction in the subsurface and more precisely oil fields. In addition, the application of (perchlorate for bioremediation, souring control and microbial enhanced oil recovery are addressed.

  16. The behaviour of long-lived redox sensitive radionuclides in soil-plant system during the process of climate change

    Energy Technology Data Exchange (ETDEWEB)

    Semioshkina, N.; Staudt, C.; Kaiser, C. [Helmhotz Zetrum Muenchen (Germany); Proehl, G. [International Atomic Energy Agency - IAEA (International Atomic Energy Agency (IAEA)); Noseck, U.; Fahrenholz, C. [Gesellschaft fuer Anlagen- und Reaktorsicherheit - GRS (Germany)

    2014-07-01

    One important aspect of climate changes for the long-term safety assessment of radioactive waste repositories is its impact on exposure pathways for humans in the future, which are dependent on the environmental characteristics mentioned. It is conceivable that effects or processes occurring during climate changes lead to an increased accumulation and/or release of radionuclides in the biosphere resulting in higher doses compared to that calculated for discrete climate states. In order to shed light on this question key processes are identified which might lead to such an increased accumulation and/or release of radionuclides. The transition from one climate to another can cause changes in the physicochemical composition of radionuclides: some of them may become more available for plant uptake and due to this, their activity concentration in the plants increases. Other radionuclides maybe stronger bound to soil and their activity concentration in plants decreases. Such changes might also cause remobilization of radionuclides from localised areas with contaminated sediments, their re-suspension and transfer to the surrounding areas. A suitable illustration of the processes related to the changes of the redox potential is the examination of a dry lake or fen bed for agricultural purposes as pasture or ameliorated pasture. In these cases the accumulation of radionuclides in the lake or fen sediment is followed by their release and increasing mobility after agricultural processing of the dry bed of lake or fen. Ploughing of the soil leads to increased supply of oxygen to previous anoxic soil layers causing an increase in redox potential. The presented model describes a scenario, where the land is initially very humid and very low Eh-values cause high sorption and accumulation of radionuclides in soil particles. Then this land is dried out, the redox potential increases and redox sensitive radionuclides change their speciation and their behaviour. Such processes might

  17. Redox-active on-surface polymerization of single-site divalent cations from pure metals by a ketone-functionalized phenanthroline

    Energy Technology Data Exchange (ETDEWEB)

    Skomski, Daniel; Tempas, Christopher D.; Bukowski, Gregory S.; Smith, Kevin A.; Tait, Steven L., E-mail: tait@indiana.edu [Department of Chemistry, Indiana University, 800 E. Kirkwood Ave., Bloomington, Indiana 47405 (United States)

    2015-03-14

    Metallic iron, chromium, or platinum mixing with a ketone-functionalized phenanthroline ligand on a single crystal gold surface demonstrates redox activity to a well-defined oxidation state and assembly into thermally stable, one dimensional, polymeric chains. The diverging ligand geometry incorporates redox-active sub-units and bi-dentate binding sites. The gold surface provides a stable adsorption environment and directs growth of the polymeric chains, but is inert with regard to the redox chemistry. These systems are characterized by scanning tunnelling microscopy, non-contact atomic force microscopy, and X-ray photoelectron spectroscopy under ultra-high vacuum conditions. The relative propensity of the metals to interact with the ketone group is examined, and it is found that Fe and Cr more readily complex the ligand than Pt. The formation and stabilization of well-defined transition metal single-sites at surfaces may open new routes to achieve higher selectivity in heterogeneous catalysts.

  18. Zirconolite glass-ceramics for plutonium immobilization: The effects of processing redox conditions on charge compensation and durability

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yingjie, E-mail: yzx@ansto.gov.au; Gregg, Daniel J.; Kong, Linggen; Jovanovich, Miodrag; Triani, Gerry

    2017-07-15

    Zirconolite glass-ceramic samples doped with plutonium have been prepared via hot isostatic pressing. The effects of processing redox and plutonium loadings on plutonium valences, the presence of cation vacancies, zirconolite phase compositions, microstructures and durability have been investigated. Either tetravalent or trivalent plutonium ions may be incorporated on the Ca-site of CaZrTi{sub 2}O{sub 7} zirconolite with the Ca-site cation vacancies and the incorporation of Al{sup 3+} ions on the Ti-site for charge compensation. Plutonium and gadolinium (as a neutron absorber) are predominantly partitioned in zirconolite phases leading to the formation of chemically durable glass-ceramics suitable for the immobilization of impure plutonium wastes arising from the nuclear fuel cycle. - Highlights: •Plutonium validations of zirconolite glass-ceramics. •Effects of processing redox and plutonium loading. •Zirconolite phase compositions and plutonium valences. •Cation vacancies and chemical durability.

  19. Engineered Proteins: Redox Properties and Their Applications

    Science.gov (United States)

    Prabhulkar, Shradha; Tian, Hui; Wang, Xiaotang; Zhu, Jun-Jie

    2012-01-01

    Abstract Oxidoreductases and metalloproteins, representing more than one third of all known proteins, serve as significant catalysts for numerous biological processes that involve electron transfers such as photosynthesis, respiration, metabolism, and molecular signaling. The functional properties of the oxidoreductases/metalloproteins are determined by the nature of their redox centers. Protein engineering is a powerful approach that is used to incorporate biological and abiological redox cofactors as well as novel enzymes and redox proteins with predictable structures and desirable functions for important biological and chemical applications. The methods of protein engineering, mainly rational design, directed evolution, protein surface modifications, and domain shuffling, have allowed the creation and study of a number of redox proteins. This review presents a selection of engineered redox proteins achieved through these methods, resulting in a manipulation in redox potentials, an increase in electron-transfer efficiency, and an expansion of native proteins by de novo design. Such engineered/modified redox proteins with desired properties have led to a broad spectrum of practical applications, ranging from biosensors, biofuel cells, to pharmaceuticals and hybrid catalysis. Glucose biosensors are one of the most successful products in enzyme electrochemistry, with reconstituted glucose oxidase achieving effective electrical communication with the sensor electrode; direct electron-transfer-type biofuel cells are developed to avoid thermodynamic loss and mediator leakage; and fusion proteins of P450s and redox partners make the biocatalytic generation of drug metabolites possible. In summary, this review includes the properties and applications of the engineered redox proteins as well as their significance and great potential in the exploration of bioelectrochemical sensing devices. Antioxid. Redox Signal. 17, 1796–1822. PMID:22435347

  20. Rapid and Efficient Redox Processes within 2D Covalent Organic Framework Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    DeBlase, Catherine R. [Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853-1301, United States; Hernández-Burgos, Kenneth [Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853-1301, United States; Silberstein, Katharine E. [Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853-1301, United States; Rodríguez-Calero, Gabriel G. [Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853-1301, United States; Bisbey, Ryan P. [Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853-1301, United States; Abruña, Héctor D. [Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853-1301, United States; Dichtel, William R. [Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853-1301, United States

    2015-02-17

    Two-dimensional covalent organic frameworks (2D COFs) are ideally suited for organizing redox-active subunits into periodic, permanently porous polymer networks of interest for pseudocapacitive energy storage. Here we describe a method for synthesizing crystalline, oriented thin films of a redox-active 2D COF on Au working electrodes. The thickness of the COF film was controlled by varying the initial monomer concentration. A large percentage (80–99%) of the anthraquinone groups are electrochemically accessible in films thinner than 200 nm, an order of magnitude improvement over the same COF prepared as a randomly oriented microcrystalline powder. As a result, electrodes functionalized with oriented COF films exhibit a 400% increase in capacitance scaled to electrode area as compared to those functionalized with the randomly oriented COF powder. These results demonstrate the promise of redox-active COFs for electrical energy storage and highlight the importance of controlling morphology for optimal performance.

  1. Rapid and Efficient Redox Processes within 2D Covalent Organic Framework Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    DeBlase, Catherine R.; Hernández-Burgos, Kenneth; Silberstein, Katharine E.; Rodríguez-Calero, Gabriel G.; Bisbey, Ryan P.; Abruña, Héctor D.; Dichtel, William R.

    2015-03-24

    Two-dimensional covalent organic frameworks (2D COFs) are ideally suited for organizing redox-active subunits into periodic, permanently porous polymer networks of interest for pseudocapacitive energy storage. Here we describe a method for synthesizing crystalline, oriented thin films of a redox-active 2D COF on Au working electrodes. The thickness of the COF film was controlled by varying the initial monomer concentration. A large percentage (80–99%) of the anthraquinone groups are electrochemically accessible in films thinner than 200 nm, an order of magnitude improvement over the same COF prepared as a randomly oriented microcrystalline powder. As a result, electrodes functionalized with oriented COF films exhibit a 400% increase in capacitance scaled to electrode area as compared to those functionalized with the randomly oriented COF powder. These results demonstrate the promise of redox-active COFs for electrical energy storage and highlight the importance of controlling morphology for optimal performance.

  2. Simultaneous anionic and cationic redox

    Science.gov (United States)

    Jung, Sung-Kyun; Kang, Kisuk

    2017-12-01

    It is challenging to unlock anionic redox activity, accompanied by full utilization of available cationic redox process, to boost capacity of battery cathodes. Now, material design by tuning the metal-oxygen interaction is shown to be a promising solution.

  3. Surface migration in sorption processes

    International Nuclear Information System (INIS)

    Rasmuson, A.; Neretnieks, J.

    1983-03-01

    Diffusion rates of sorbing chemical species in granites and clays are in several experiments within the KBS study, higher than can be explained by pore diffusion only. One possible additional transport mechanism is transport of of sorbed molecules/ions along the intrapore surfaces. As a first step a literature investigation on on solid surfaces has been conducted. A lot of experimental evidence of the mobility of the sorbed molecules has been gathered through the years, particulary for metal surfaces and chemical engineering systems. For clays however, there are only a few articles, and for granites none. Two types of surface migration models have been proposed in the litterature: i) Surface flow as a result of a gradient in spreading pressure. ii) Surface diffusion as a result of a gradient in concentration. The surface flow model has only been applied to gaseous systems. However, it should be equally applicable to liquid systems. The models i) and ii) are conceptually very different. However, the resulting expressions for surface flux are complicated and it will not be an easy task to distinguish between them. There seem to be three ways of discriminating between the transport mechanisms: a) Temperature dependence. b) Concentration dependence. c) Order of magnitude. (Forf)

  4. Fluorescence correlation spectroscopy on electron transfer reactions : probing inter- and intramolecular redox processes

    NARCIS (Netherlands)

    Sen, S.

    2016-01-01

    We developed a new FRET-based technique, “Fluredox”, which allows fluorescence readout of the redox state of oxido-reductases at single molecule level. Commercially available red-absorbing fluorophore ATTO655 was selected for labeling Azurin, a small blue mononuclear copper protein. Single molecule

  5. Relating hyporheic fluxes, residence times, and redox-sensitive biogeochemical processes upstream of beaver dams

    Science.gov (United States)

    Briggs, Martin A.; Lautz, Laura; Hare, Danielle K.

    2013-01-01

    Abstract. Small dams enhance the development of patchy microenvironments along stream corridors by trapping sediment and creating complex streambed morphologies. This patchiness drives intricate hyporheic flux patterns that govern the exchange of O2 and redox-sensitive solutes between the water column and the stream bed. We used multiple tracer techniques, naturally occurring and injected, to evaluate hyporheic flow dynamics and associated biogeochemical cycling and microbial reactivity around 2 beaver dams in Wyoming (USA). High-resolution fiber-optic distributed temperature sensing was used to collect temperature data over 9 vertical streambed profiles and to generate comprehensive vertical flux maps using 1-dimensional (1-D) heat-transport modeling. Coincident with these locations, vertical profiles of hyporheic water were collected every week and analyzed for dissolved O2, pH, dissolved organic C, and several conservative and redox-sensitive solutes. In addition, hyporheic and net stream aerobic microbial reactivity were analyzed with a constant-rate injection of the biologically sensitive resazurin (Raz) smart tracer. The combined results revealed a heterogeneous system with rates of downwelling hyporheic flow organized by morphologic unit and tightly coupled to the redox conditions of the subsurface. Principal component analysis was used to summarize the variability of all redox-sensitive species, and results indicated that hyporheic water varied from oxic-stream-like to anoxic-reduced in direct response to the hydrodynamic conditions and associated residence times. The anaerobic transition threshold predicted by the mean O2 Damko

  6. Nicotinamide-NAD sequence: redox process and related behavior, behavior and properties of intermediate and final products

    International Nuclear Information System (INIS)

    Elving, P.J.; Schmakel, C.O.; Santhanam, K.S.V.

    1976-01-01

    Illustrations of the application of analytical chemical techniques to the study of chemical phenomena are given. In particular, electrochemical techniques and methodology and, to a lesser extent, spectrophotometry were used to investigate the solution behavior, adsorption, redox processes including coupled chemical reactions, and allied aspects of biologically significant compounds and of their intermediate and final redox products, e.g., the behavior of the free radicals produced by initial one-electron processes. This approach is illustrated by the consideration of the behavior in aqueous and nonaqueous media of a sequence of compounds ranging from nicotinamide (3-carbamoylpyridine) to NAD + and NADP + ; the latter compounds function as coenzymes for the pyridinoproteins which are principal components in the Krebs citric acid cycle and in the electron transport chain in biological redox reactions. The discussion is presented under the following section headings: interpretation of electrochemical behavior; mechanistic patterns; kinetic aspects of charge-transfer and chemical reactions; correlation with theoretically calculated parameters; and, mechanisms of biological oxidation-reduction reactions. The use of pulse radiolysis, chronopotentiometric, and cyclic voltammetric methods in studies on free radical dimerization rates is reviewed in the discussion of the kinetic aspects of charge-transfer and chemical reactions. (188 references)

  7. Exploring the entrance of proton pathways in cytochrome c oxidase from Paracoccus denitrificans: surface charge, buffer capacity and redox-dependent polarity changes at the internal surface.

    Science.gov (United States)

    Kirchberg, Kristina; Michel, Hartmut; Alexiev, Ulrike

    2013-03-01

    Cytochrome c oxidase (CcO), the terminal oxidase of cellular respiration, reduces molecular oxygen to water. The mechanism of proton pumping as well as the coupling of proton and electron transfer is still not understood in this redox-linked proton pump. Eleven residues at the aqueous-exposed surfaces of CcO from Paracoccus denitrificans have been exchanged to cysteines in a two-subunit base variant to yield single reactive cysteine variants. These variants are designed to provide unique labeling sites for probes to be used in spectroscopic experiments investigating the mechanism of proton pumping in CcO. To this end we have shown that all cysteine variants are enzymatically active. Cysteine positions at the negative (N-) side of the membrane are located close to the entrance of the D- and K-proton transfer pathways that connect the N-side with the catalytic oxygen reduction site. Labeling of the pH-indicator dye fluorescein to these sites allowed us to determine the surface potential at the cytoplasmic CcO surface, which corresponds to a surface charge density of -0.5 elementary charge/1000Å(2). In addition, acid-base titrations revealed values of CcO buffer capacity. Polarity measurements of the label environment at the N-side provided (i) site-specific values indicative of a hydrophilic and a more hydrophobic environment dependent on the label position, and (ii) information on a global change to a more apolar environment upon reduction of the enzyme. Thus, the redox state of the copper and heme centers inside the hydrophobic interior of CcO affect the properties at the cytoplasmic surface. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Redox Regulation of Mitochondrial Function

    Science.gov (United States)

    Handy, Diane E.

    2012-01-01

    Abstract Redox-dependent processes influence most cellular functions, such as differentiation, proliferation, and apoptosis. Mitochondria are at the center of these processes, as mitochondria both generate reactive oxygen species (ROS) that drive redox-sensitive events and respond to ROS-mediated changes in the cellular redox state. In this review, we examine the regulation of cellular ROS, their modes of production and removal, and the redox-sensitive targets that are modified by their flux. In particular, we focus on the actions of redox-sensitive targets that alter mitochondrial function and the role of these redox modifications on metabolism, mitochondrial biogenesis, receptor-mediated signaling, and apoptotic pathways. We also consider the role of mitochondria in modulating these pathways, and discuss how redox-dependent events may contribute to pathobiology by altering mitochondrial function. Antioxid. Redox Signal. 16, 1323–1367. PMID:22146081

  9. Redox fronts

    International Nuclear Information System (INIS)

    Chapman, N.; McKinley, I.; Shea, M.; Smellie, J.

    1993-01-01

    This article describes the investigations of redox fronts performed at the Osamu Utsumi mine. Results obtained by modelling groups on the rate of movement of the redox fronts and on the chemical reactions involved are discussed. Some of the most important rockwater interactions which occur at redox fronts can be modelled reasonably well but the complex redox chemistry of elements like sulphur is poorly simulated. The observed enrichment of many trace elements close to the redox fronts could be of significance for high-level waste repositories, but cannot be quantified by existing models. (author) 6 figs., 1 tab

  10. Redox Flow Batteries, a Review

    Energy Technology Data Exchange (ETDEWEB)

    Knoxville, U. Tennessee; U. Texas Austin; U, McGill; Weber, Adam Z.; Mench, Matthew M.; Meyers, Jeremy P.; Ross, Philip N.; Gostick, Jeffrey T.; Liu, Qinghua

    2011-07-15

    Redox flow batteries are enjoying a renaissance due to their ability to store large amounts of electrical energy relatively cheaply and efficiently. In this review, we examine the components of redox flow batteries with a focus on understanding the underlying physical processes. The various transport and kinetic phenomena are discussed along with the most common redox couples.

  11. Surface studies of plasma processed Nb samples

    International Nuclear Information System (INIS)

    Tyagi, Puneet V.; Doleans, Marc; Hannah, Brian S.; Afanador, Ralph; Stewart, Stephen; Mammosser, John; Howell, Matthew P; Saunders, Jeffrey W; Degraff, Brian D; Kim, Sang-Ho

    2015-01-01

    Contaminants present at top surface of superconducting radio frequency (SRF) cavities can act as field emitters and restrict the cavity accelerating gradient. A room temperature in-situ plasma processing technology for SRF cavities aiming to clean hydrocarbons from inner surface of cavities has been recently developed at the Spallation Neutron Source (SNS). Surface studies of the plasma-processed Nb samples by Secondary ion mass spectrometry (SIMS) and Scanning Kelvin Probe (SKP) showed that the NeO_2 plasma processing is very effective to remove carbonaceous contaminants from top surface and improves the surface work function by 0.5 to 1.0 eV.

  12. Surface reaction of SnII on goethite (α-FeOOH): surface complexation, redox reaction, reductive dissolution, and phase transformation.

    Science.gov (United States)

    Dulnee, Siriwan; Scheinost, Andreas C

    2014-08-19

    To elucidate the potential risk of (126)Sn migration from nuclear waste repositories, we investigated the surface reactions of Sn(II) on goethite as a function of pH and Sn(II) loading under anoxic condition with O2 level redox state and surface structure were investigated by Sn K edge X-ray absorption spectroscopy (XAS), goethite phase transformations were investigated by high-resolution transmission electron microscopy and selected area electron diffraction. The results demonstrate the rapid and complete oxidation of Sn(II) by goethite and formation of Sn(IV) (1)E and (2)C surface complexes. The contribution of (2)C complexes increases with Sn loading. The Sn(II) oxidation leads to a quantitative release of Fe(II) from goethite at low pH, and to the precipitation of magnetite at higher pH. To predict Sn sorption, we applied surface complexation modeling using the charge distribution multisite complexation approach and the XAS-derived surface complexes. Log K values of 15.5 ± 1.4 for the (1)E complex and 19.2 ± 0.6 for the (2)C complex consistently predict Sn sorption across pH 2-12 and for two different Sn loadings and confirm the strong retention of Sn(II) even under anoxic conditions.

  13. Surface Modification and Surface - Subsurface Exchange Processes on Europa

    Science.gov (United States)

    Phillips, C. B.; Molaro, J.; Hand, K. P.

    2017-12-01

    The surface of Jupiter's moon Europa is modified by exogenic processes such as sputtering, gardening, radiolysis, sulfur ion implantation, and thermal processing, as well as endogenic processes including tidal shaking, mass wasting, and the effects of subsurface tectonic and perhaps cryovolcanic activity. New materials are created or deposited on the surface (radiolysis, micrometeorite impacts, sulfur ion implantation, cryovolcanic plume deposits), modified in place (thermal segregation, sintering), transported either vertically or horizontally (sputtering, gardening, mass wasting, tectonic and cryovolcanic activity), or lost from Europa completely (sputtering, plumes, larger impacts). Some of these processes vary spatially, as visible in Europa's leading-trailing hemisphere brightness asymmetry. Endogenic geologic processes also vary spatially, depending on terrain type. The surface can be classified into general landform categories that include tectonic features (ridges, bands, cracks); disrupted "chaos-type" terrain (chaos blocks, matrix, domes, pits, spots); and impact craters (simple, complex, multi-ring). The spatial distribution of these terrain types is relatively random, with some differences in apex-antiapex cratering rates and latitudinal variation in chaos vs. tectonic features. In this work, we extrapolate surface processes and rates from the top meter of the surface in conjunction with global estimates of transport and resurfacing rates. We combine near-surface modification with an estimate of surface-subsurface (and vice versa) transport rates for various geologic terrains based on an average of proposed formation mechanisms, and a spatial distribution of each landform type over Europa's surface area. Understanding the rates and mass balance for each of these processes, as well as their spatial and temporal variability, allows us to estimate surface - subsurface exchange rates over the average surface age ( 50myr) of Europa. Quantifying the timescale

  14. Description of two-process surface topography

    International Nuclear Information System (INIS)

    Grabon, W; Pawlus, P

    2014-01-01

    After two machining processes, a large number of surface topography measurements were made using Talyscan 150 stylus measuring equipment. The measured samples were divided into two groups. The first group contained two-process surfaces of random nature, while the second group used random-deterministic textures of random plateau parts and portions of deterministic valleys. For comparison, one-process surfaces were also analysed. Correlation and regression analysis was used to study the dependencies among surface texture parameters in 2D and 3D systems. As the result of this study, sets of parameters describing multi-process surface topography were obtained for two-process surfaces of random and of random-deterministic types. (papers)

  15. The roles of anion and solvent transport during the redox switching process at a poly(butyl viologen) film studied by an EQCM

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Chih-Yu.; Liao, Chun-Hao [Department of Chemical Engineering, National Taiwan University, Taipei 10617 (China); Ho, Kuo-Chuan [Department of Chemical Engineering, National Taiwan University, Taipei 10617 (China); Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10617 (China)

    2008-02-15

    In this study, three electrolytes (KCl, LiCl, and KNO{sub 3}, each at 0.5 M in aqueous solution) were chosen to study the ion and solvent effect on the redox performance of poly(butyl viologen) (PBV) thin-films between its di-cation and radical-cation state, which is referred as its first redox couple. Before considering the role of ionic transport on the redox process, the exchange between ferrocyanide and anion should be completed. Since the deposition solution of PBV contains potassium ferrocyanide, the residual ferrocyanides inside the films would be exchanged by smaller anions from the bulk solution during the redox reaction of PBV. From cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) results, the exchange was almost complete around 50 cycles when scanning the potential within its first redox range. After completion of the exchange process, the transfer would reach a steady state. At 50 cycles, the EQCM results suggested that the transport involves anions and water only for both being extracted upon reduction and being inserted upon oxidation. Therefore, we could obtain the molar fluxes of Cl{sup -}, NO{sub 3}{sup -}, and water. Besides, the average numbers of accompanying water were calculated to be about 24.8 per Cl{sup -} and 14.2 per NO{sub 3}{sup -} upon redox switching process. The instantaneous water to anion molar ratios at any potential were also obtained for Cl{sup -} and NO{sub 3}{sup -}. (author)

  16. Redox zone II. Coupled modeling of groundwater flow, solute transport, chemical reactions and microbial processes in the Aespoe island

    Energy Technology Data Exchange (ETDEWEB)

    Samper, Javier; Molinero, Jorge; Changbing Yang; Guoxiang Zhang [Univ. Da Coruna (Spain)

    2003-12-01

    The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behaviour and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by Banwart et al. Later, Banwart presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by Molinero who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulphate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of Molinero and extends the preliminary microbial model of Zhang by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfaphe concentration, thus adding additional evidence for the possibility

  17. Redox zone II. Coupled modeling of groundwater flow, solute transport, chemical reactions and microbial processes in the Aespoe island

    International Nuclear Information System (INIS)

    Samper, Javier; Molinero, Jorge; Changbing Yang; Guoxiang Zhang

    2003-12-01

    The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behaviour and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by Banwart et al. Later, Banwart presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by Molinero who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulphate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of Molinero and extends the preliminary microbial model of Zhang by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfaphe concentration, thus adding additional evidence for the possibility

  18. Photolytic and radiolytic studies of redox processes in aqueous solutions of acridine yellow

    International Nuclear Information System (INIS)

    Micic, O.I.; Nenadovic, M.T.

    1981-01-01

    Irradiation by visible light of an aqueous solution containing acridine yellow as a sensitizer and EDTA or cysteine as an electron donor leads to the formation of reduced species which can later reduce several different electron acceptors. Methyl viologen, europium(III) salicylate, europium(III) EDTA complex or vanadium(III) salicylate were used as electron acceptors. In the presence of a catalyst reduction of water is accompanied by the evolution of hydrogen. The kinetics and mechanism of redox reactions occurring in such a system have been explored by pulse radiolysis. Optimum conditions for water reduction under continuous illumination are analysed and implications for an energy conversion system discussed. (author)

  19. Control of magnetism by electrical charge doping or redox reactions in a surface-oxidized Co thin film with a solid-state capacitor structure

    Science.gov (United States)

    Hirai, T.; Koyama, T.; Chiba, D.

    2018-03-01

    We have investigated the electric field (EF) effect on magnetism in a Co thin film with a naturally oxidized surface. The EF was applied to the oxidized Co surface through a gate insulator layer made of HfO2, which was formed using atomic layer deposition (ALD). The efficiency of the EF effect on the magnetic anisotropy in the sample with the HfO2 layer deposited at the appropriate temperature for the ALD process was relatively large compared to the previously reported values with an unoxidized Co film. The coercivity promptly and reversibly followed the variation in gate voltage. The modulation of the channel resistance was at most ˜0.02%. In contrast, a dramatic change in the magnetic properties including the large change in the saturation magnetic moment and a much larger EF-induced modulation of the channel resistance (˜10%) were observed in the sample with a HfO2 layer deposited at a temperature far below the appropriate temperature range. The response of these properties to the gate voltage was very slow, suggesting that a redox reaction dominated the EF effect on the magnetism in this sample. The frequency response for the capacitive properties was examined to discuss the difference in the mechanism of the EF effect observed here.

  20. Earth Surface Processes, Landforms and Sediment Deposits

    Science.gov (United States)

    Bridge, John; Demicco, Robert

    Earth surface processes, landforms and sediment deposits are intimately related - involving erosion of rocks, generation of sediment, and transport and deposition of sediment through various Earth surface environments. These processes, and the landforms and deposits that they generate, have a fundamental bearing on engineering, environmental and public safety issues; on recovery of economic resources; and on our understanding of Earth history. This unique textbook brings together the traditional disciplines of sedimentology and geomorphology to explain Earth surface processes, landforms and sediment deposits in a comprehensive and integrated way. It is the ideal resource for a two-semester course in sedimentology, stratigraphy, geomorphology, and Earth surface processes from the intermediate undergraduate to beginning graduate level. The book is also accompanied by a website hosting illustrations and material on field and laboratory methods for measuring, describing and analyzing Earth surface processes, landforms and sediments.

  1. Dynamics of biochemical processes and redox conditions in geochemically linked landscapes of oligotrophic bogs

    Science.gov (United States)

    Inisheva, L. I.; Szajdak, L.; Sergeeva, M. A.

    2016-04-01

    The biological activity in oligotrophic peatlands at the margins of the Vasyugan Mire has been studied. It is shown found that differently directed biochemical processes manifest themselves in the entire peat profile down to the underlying mineral substrate. Their activity is highly variable. It is argued that the notion about active and inert layers in peat soils is only applicable for the description of their water regime. The degree of the biochemical activity is specified by the physical soil properties. As a result of the biochemical processes, a micromosaic aerobic-anaerobic medium is developed under the surface waterlogged layer of peat deposits. This layer contains the gas phase, including oxygen. It is concluded that the organic and mineral parts of peat bogs represent a single functional system of a genetic peat profile with a clear record of the history of its development.

  2. Benthic flux of dissolved organic matter from lake sediment at different redox conditions and the possible effects of biogeochemical processes.

    Science.gov (United States)

    Yang, Liyang; Choi, Jung Hyun; Hur, Jin

    2014-09-15

    The benthic fluxes of dissolved organic carbon (DOC), chromophoric and fluorescent dissolved organic matter (CDOM and FDOM) were studied for the sediment from an artificial lake, based on laboratory benthic chamber experiments. Conservative estimates for the benthic flux of DOC were 71 ± 142 and 51 ± 101 mg m(-2) day(-1) at hypoxic and oxic conditions, respectively. Two humic-like (C1 and C2), one tryptophan-like (C3), and one microbial humic-like (C4) components were identified from the samples using fluorescence excitation emission matrices and parallel factor analysis (EEM-PARAFAC). During the incubation period, C3 was removed while C4 was accumulated in the overlying water with no significant difference in the trends between the redox conditions. The humification index (HIX) increased with time. The combined results for C3, C4 and HIX suggested that microbial transformation may be an important process affecting the flux behaviors of DOM. In contrast, the overall accumulations of CDOM, C1, and C2 in the overlying water occurred only for the hypoxic condition, which was possibly explained by their enhanced photo-degradation and sorption to redox-sensitive minerals under the oxic condition. Our study demonstrated significant benthic flux of DOM in lake sediment and also the possible involvement of biogeochemical transformation in the processes, providing insight into carbon cycling in inland waters. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Plasma surface interaction processes and possible synergisms

    International Nuclear Information System (INIS)

    Behrisch, R.; Roberto, J.B.

    1984-08-01

    The process determining the plasma surface interaction in today's high temperature plasma experiments are investigated following several lines. First, in plasma devices, the particle and energy fluxes to the different first wall areas the fluxes from the walls back into the plasma are measured and the boundary plasma parameters are determined. The surface composition and structure of the walls, limiters and divertor plates are analyzed following exposure to many discharges. Secondly, the different surface processes which are expected to contribute to the plasma surface interaction (particularly to hydrogen particle balance and impurity introduction) are studied in simulation experiments using well defined particle beams

  4. Surface Energy and Setting Process of Contacting Surfaces

    Directory of Open Access Journals (Sweden)

    M. V. Musokhranov

    2014-01-01

    Full Text Available The paper deals with a challenge in terms of ensuring an accuracy of the relative position of the conjugated surfaces that is to determine a coefficient of friction. To solve it, there is a proposal to use the surface energy, as a tool that influences the contacting parts nature. Presently, energy of the surface layers at best is only stated, but not used in practice.Analysis of the conditions of interaction between two contacting surfaces, such as seizing and setting cannot be explained only from the position of the roughness parameters. It is found that these phenomena are explained by the appearing gripe (setting bridges, which result from the energy of interaction between two or more adjacent surfaces. The emerging phenomenon such as micro welding, i.e. occurring bonds, is caused by the overflow of energy, according to the theory of physics, from the surface with a high level of energy to the surface with the smaller one to balance the system as a whole.The paper shows that through the use of process, controlling the depth of the surface layer and creating a certain structure, the energy level of the material as a whole can be specified. And this will allow us to provide the necessary performance and mechanical properties. It means to create as many gripe bridges as possible to ensure continuous positioning i.e. a fixed connection of the contacting surfaces.It was determined that to increase a value of the friction coefficient, the physical and mechanical properties of the surface layer of the parts material must be taken into account, namely, in the part body accumulate the energy to be consumed for forming the surface.The paper gives recommendations for including the parts of the surface energy in the qualitative indicators of characteristics. This will make a technologist, when routing a process, to choose such operations and modes to provide the designer-specified parameters not only of the accuracy and surface finish, but also of the

  5. Insights into the Surface Transformation and Electrochemical Dissolution Process of Bornite in Bioleaching

    Directory of Open Access Journals (Sweden)

    Hongbo Zhao

    2018-04-01

    Full Text Available In this work, density functional theory (DFT calculations, X-ray photoelectron spectroscopy (XPS and electrochemistry analysis were combined to analyze the electrochemical dissolution process of bornite during bioleaching. DFT calculations showed that bornite was a conductor with metallic conductivity. The formula of bornite may be (Cu+5Fe3+(S2−4 and the surface reconstruction of (111-S surface was discussed. Electrochemistry and XPS analysis showed that bornite tended to be directly oxidized with high conductivity when the potential was higher than 0.3 V vs. Ag/AgCl. Elemental sulfur (S0, FeOOH and CuS were the main intermediate species on the bornite surface during the oxidation process. The production of S0 and FeOOH on bornite surface can be significantly accelerated with increased redox potential, but no insoluble sulfate (SO42− formed on bornite surface in 0.3–0.65 V vs. Ag/AgCl. The oxidative dissolution of bornite was significantly accelerated with increasing redox potential, which was one important reason why mixed culture was more effective than single strains of A. caldus and L. ferriphilum in bornite bioleaching. The insoluble SO42− was formed mainly through the chemical reactions in solution and then covered the bornite surface in bioleaching. Based on the obtained results, a model for interpreting the dissolution process of bornite in bioleaching was proposed.

  6. Processing and finishing of granite surfaces

    OpenAIRE

    Klich, J. (Jiří); Hlaváček, P. (Petr); Ščučka, J. (Jiří); Sitek, L. (Libor); Foldyna, J. (Josef); Georgiovská, L. (Lucie); Souček, K. (Kamil); Staš, L. (Lubomír); Bortolussi, A.

    2013-01-01

    The article deals with granite surface processing and finishing by various methods including bush hammering, flaming, polishing, continuous and pulsating water jetting. Both optical and CT X-ray methods are used for analysis of surface and subsurface areas of tested samples. Advantages of pulsating water jetting compared to other techniques are discussed.

  7. Radon transport processes below the earth's surface

    International Nuclear Information System (INIS)

    Wilkening, M.

    1980-01-01

    Processes by which 222 Rn is transported from the soil to the earth's surface are reviewed. The mechanisms effective in transporting 222 Rn to the surface are related to the size and configuration of the spaces occupied by the soil gas which may vary from molecular interstices to large underground caverns. The near-surface transport processes are divided into two categories: (1) a microscopic process that includes molecular diffusion and viscous flow in fine capillaries and (2) macroscopic flow in fissures and channels. Underground air rich in 222 Rn can also reach the surface through cracks, fissures, and underground channels. This type of transport is shown for (1) a horizontal tunnel penetrating a fractured hillside, (2) a large underground cave, and (3) volcanic activity. Pressure differentials having various natural origins and thermal gradients are responsible for the transport in these examples. 222 Rn transport by ordinary molecular diffusion appears to be the dominant process

  8. Mechanisms and energetics of surface atomic processes

    International Nuclear Information System (INIS)

    Tsong, T.T.

    1991-01-01

    The energies involved in various surface atomic processes such as surface diffusion, the binding of small atomic clusters on the surface, the interaction between two adsorbed atoms, the dissociation of an atom from a small cluster or from a surface layer, the binding of kink size atoms or atoms at different adsorption sites to the surface etc., can be derived from an analysis of atomically resolved field ion microscope images and a kinetic energy measurement of low temperature field desorbed ions using the time-of-flight atom-probe field ion microscope. These energies can be used to compare with theories and to understand the transport of atoms on the surface in atomic reconstructions, epitaxial growth of surface layers and crystal growth, adsorption layer superstructure formation, and also why an atomic ordering or atomic reconstruction at the surface is energetically favored. Mechanisms of some of the surface atomic processes are also clarified from these quantitative, atomic resolution studies. In this paper work in this area is bris briefly reviewed

  9. Redox-capacitor to connect electrochemistry to redox-biology.

    Science.gov (United States)

    Kim, Eunkyoung; Leverage, W Taylor; Liu, Yi; White, Ian M; Bentley, William E; Payne, Gregory F

    2014-01-07

    It is well-established that redox-reactions are integral to biology for energy harvesting (oxidative phosphorylation), immune defense (oxidative burst) and drug metabolism (phase I reactions), yet there is emerging evidence that redox may play broader roles in biology (e.g., redox signaling). A critical challenge is the need for tools that can probe biologically-relevant redox interactions simply, rapidly and without the need for a comprehensive suite of analytical methods. We propose that electrochemistry may provide such a tool. In this tutorial review, we describe recent studies with a redox-capacitor film that can serve as a bio-electrode interface that can accept, store and donate electrons from mediators commonly used in electrochemistry and also in biology. Specifically, we (i) describe the fabrication of this redox-capacitor from catechols and the polysaccharide chitosan, (ii) discuss the mechanistic basis for electron exchange, (iii) illustrate the properties of this redox-capacitor and its capabilities for promoting redox-communication between biology and electrodes, and (iv) suggest the potential for enlisting signal processing strategies to "extract" redox information. We believe these initial studies indicate broad possibilities for enlisting electrochemistry and signal processing to acquire "systems level" redox information from biology.

  10. The impact of urea-induced unfolding on the redox process of immobilised cytochrome c.

    Science.gov (United States)

    Monari, Stefano; Millo, Diego; Ranieri, Antonio; Di Rocco, Giulia; van der Zwan, Gert; Gooijer, Cees; Peressini, Silvia; Tavagnacco, Claudio; Hildebrandt, Peter; Borsari, Marco

    2010-11-01

    We have studied the effect of urea-induced unfolding on the electron transfer process of yeast iso-1-cytochrome c and its mutant K72AK73AK79A adsorbed on electrodes coated by mixed 11-mercapto-1-undecanoic acid/11-mercapto-1-undecanol self-assembled monolayers. Electrochemical measurements, complemented by surface enhanced resonance Raman studies, indicate two distinct states of the adsorbed proteins that mainly differ with respect to the ligation pattern of the haem. The native state, in which the haem is axially coordinated by Met80 and His18, displays a reduction potential that slightly shifts to negative values with increasing urea concentration. At urea concentrations higher than 6 M, a second state prevails in which the Met80 ligand is replaced by an additional histidine residue. This structural change in the haem pocket is associated with an approximately 0.4 V shift of the reduction potential to negative values. These two states were found for both the wild-type protein and the mutant in which lysine residues 72, 73 and 79 had been substituted by alanines. The analysis of the reduction potentials, the reaction enthalpies and entropies as well as the rate constants indicates that these three lysine residues have an important effect on stabilising the protein structure in the adsorbed state and facilitating the electron transfer dynamics.

  11. Quantitative Modeling of Earth Surface Processes

    Science.gov (United States)

    Pelletier, Jon D.

    This textbook describes some of the most effective and straightforward quantitative techniques for modeling Earth surface processes. By emphasizing a core set of equations and solution techniques, the book presents state-of-the-art models currently employed in Earth surface process research, as well as a set of simple but practical research tools. Detailed case studies demonstrate application of the methods to a wide variety of processes including hillslope, fluvial, aeolian, glacial, tectonic, and climatic systems. Exercises at the end of each chapter begin with simple calculations and then progress to more sophisticated problems that require computer programming. All the necessary computer codes are available online at www.cambridge.org/9780521855976. Assuming some knowledge of calculus and basic programming experience, this quantitative textbook is designed for advanced geomorphology courses and as a reference book for professional researchers in Earth and planetary science looking for a quantitative approach to Earth surface processes. More details...

  12. The effect of picosecond laser pulses on redox-dependent processes in mice red blood cells studied in vivo

    Science.gov (United States)

    Voronova, Olga; Gening, Tatyana; Abakumova, Tatyana; Sysolyatin, Aleksey; Zolotovskiy, Igor; Antoneeva, Inna; Ostatochnikov, Vladimir; Gening, Snezhanna

    2014-02-01

    The study highlights the effect of different modes of in vivo laser irradiation of mice using a PFL8LA laser with λ = 1560 nm, pulse duration of 1,4•10-12 s, peak power of 3,72•103 W and average output power of 20•10-3 W on the lipid peroxidation parameters: conjugated dienes, ketodienes and conjugated trienes, malondialdehyde, Schiff bases and the activity of antioxidant enzymes - catalase, glutathione -S-transferase and superoxide dismutase in erythrocytes and plasma of mice. Two groups of mice received a total dose of 3.8 J/cm2 per group, but the 1st group was irradiated only once, while the 2nd - four times. Significant differences in the parameters of the 1st and 2nd groups indicate different effects of the irradiation modes on redox-dependent processes in red blood cells of mice.

  13. Surface quality in rapid prototype MMD process

    Directory of Open Access Journals (Sweden)

    Lisandro Vargas Henríquez

    2004-09-01

    Full Text Available This article summarises a Manufacturing Materials and Processes MSc thesis written for the Mechanical and Electrical Engineering Department. The paper shows the interaction of process, gap (deposition distance and extursion terminal velocity modelled process parameters for CEIF's (Centro de Equipos Interfacultades rapid prototype molten material deposit (MMD Titan SH-1 machine by analysing prototupes improved surface quality and resistence to tension and characterising material. The project applies experimental design criteria for orientating the selection of experimental process parameters. Acrylonitrile-buttadin-styrene (ABS had alredy been mechanically and physicochemically characterised (i.e the material used in the MMD process.

  14. THE PRODUCT DESIGN PROCESS USING STYLISTIC SURFACES

    Directory of Open Access Journals (Sweden)

    Arkadiusz Gita

    2017-06-01

    Full Text Available The increasing consumer requirements for the way what everyday use products look like, forces manufacturers to put more emphasis on product design. Constructors, apart from the functional aspects of the parts created, are forced to pay attention to the aesthetic aspects. Software for designing A-class surfaces is very helpful in this case. Extensive quality analysis modules facilitate the work and allow getting models with specific visual features. The authors present a design process of the product using stylistic surfaces based on the front panel of the moped casing. In addition, methods of analysis of the design surface and product technology are presented.

  15. Redox process at solid-liquid interfaces: studies with thin layers of green rusts electrodeposited on inert substrates

    International Nuclear Information System (INIS)

    Peulon, S.; Taghdai, Y.; Mercier, F.; Barre, N.; Legrand, L.; Chauss, A.

    2005-01-01

    Full text of publication follows: The redox reactions which can occur between radioelements and natural phases in the environment are taken still little into account although their importance is established on natural sites; the consequences are significant since they can modify radically the behaviour of the species by increasing or decreasing their migration. The iron compounds are very implicated in these redox processes because iron is one of the most abundant element on earth; moreover, it is also present in the containers used for the storage of the nuclear waste. We exhibited in previous works that electrochemistry is a convenient way to generate the main iron oxidation compounds as thin layers on different inert substrates. The electrochemical behaviour of these deposits that are adherent, homogeneous and well crystallized [1-3], was investigated with the principle advantage that iron metal and its reactivity is eliminate. Moreover, they could be analysed directly by techniques like IRRAS, XRD, SEM, EDS and XPS without any preparation. In the present study, we develop an original way to investigate redox processes at solid-liquid interfaces based on the utilisation of these thin layers; the samples are more commonly powders and/or pieces of corroded steel in the literature. Results obtained with two different systems, chromate and uranyl ions, in interaction with thin layers of sulfated green rusts are presented. Green rusts is chosen because it is a mixed Fe(II-III) compound which could be formed in anoxic conditions like in the case of the storage of the nuclear waste. After various contact times with the solutions containing the reactive species, the thin layers are characterised by different ex-situ methods. The results show clearly the oxidation of the green rust into a Fe(III) compound and the formation of a new solid phase on the electrode due to the reduction and the precipitation of the reactive species present initially in solution. Because thin

  16. Deep groundwater redox reactions in the Palmottu uranium deposit: The role of uranium and iron in these processes

    International Nuclear Information System (INIS)

    Bruno, J.; Cera, E.; Duro, L.; Ahonen, L.

    1996-12-01

    The reduction oxidation properties of the deep bedrock and groundwater are important geochemical factors with respect to the chemical stability of the multibarrier system, which isolates the disposed nuclear fuel from biosphere. In the report are described the results of the redox experiments carried out in the field using the natural groundwaters of Palmottu, in Nummi-Pusula, Finland. The experiments include (1) measurements of natural water redox potential values during four to eight hours continuous pumping; (2) monitoring of the redox-potential response to an artificial change of pH of the groundwater. Separate tests were made in iron and uranium-rich groundwaters, respectively. The data of the field experiments were used in the redox-modelling of the iron and uranium systems. In accordance with earlier knowledge, it was showed that dissolved iron is an important redox electrolyte in natural waters, at least at concentration levels of milligrams per liter. However, a striking observation was that in the absence of dissolved iron dissolved uranium (in concentrations of about 200 nM or more) seems to be able to give nernstian response on platinum electrode in acid/base titrations. The effective redox properties of the bedrock-groundwater system depend on the availability and reactivity of solid phases able to exchange electrons with dissolved redox electrolytes. The present results indicate that, in the bedrock/groundwater system of the Palmottu uranium mineralization, uranium minerals are important redox buffers. (orig.) (refs.)

  17. Monitoring the chemical nature of the carbon pool of Louisiana wetland soils undergoing erosion: carbon speciation and redox processes

    Science.gov (United States)

    Haywood, B.; Cook, R. L.; Hayes, M. P.; White, J. R.

    2017-12-01

    Wetlands account for approximately one third of all the soil carbon on the planet; however, due to erosion caused by a range of factors, including sea level rising, they are also some of the most vulnerable carbon pools. Small changes within this sequestered carbon pool can have a large impact on atmospheric CO2 levels. Thus, it is essential to understand how this sequestered carbon reacts to wetland loss in order to gain deeper insight into the global carbon cycle. In the study to be presented, Barataria Bay, Louisiana, USA is used as a model system for wetland loss. A sampling site and sampling grid has been established, and consists of three transects on and from an individual island. Each transect has five different distances ranging from 2 m inland to 8 m outland (into the water). At each of these different distances, depth profiles from 0 to 100 cm for inland samples, and 0-70 cm for submerged samples, were collected in order to identify spatial trends not only from inland to submerged, but also through the depth of the soil profile. Three types of samples were collected, namely water, pore water, and soil samples, with the latter being obtained from the combined collection of water and core samples. Samples have undergone spectroscopic characterizing including UV/Vis, fluorescence (excitation emission matrices, EEMs, and parallel factor, PARAFAC, analysis of the EEMs), nuclear magnetic resonance (NMR, solid state 13C), and electron pair resonance (EPR) spectroscopy in concert with inductively coupled plasma atomic emission spectroscopy to monitor the initial state of carbon speciation as well as redox processes. The data are used to establish a starting point on which to monitor changes within the carbon pool as the sampling site experience erosion over the next few years. The discussion will focus on the lability of different carbon pools and the potential lability-inducing mechanisms as well as the initial carbon speciation and redox state of the sampling

  18. Surface analytical techniques applied to minerals processing

    International Nuclear Information System (INIS)

    Smart, R.St.C.

    1991-01-01

    An understanding of the chemical and physical forms of the chemically altered layers on the surfaces of base metal sulphides, particularly in the form of hydroxides, oxyhydroxides and oxides, and the changes that occur in them during minerals processing lies at the core of a complete description of flotation chemistry. This paper reviews the application of a variety of surface-sensitive techniques and methodologies applied to the study of surface layers on single minerals, mixed minerals, synthetic ores and real ores. Evidence from combined XPS/SAM/SEM studies have provided images and analyses of three forms of oxide, oxyhydroxide and hydroxide products on the surfaces of single sulphide minerals, mineral mixtures and complex sulphide ores. 4 refs., 2 tabs., 4 figs

  19. Process for cleaning radioactively contaminated metal surfaces

    International Nuclear Information System (INIS)

    Mihram, R.G.; Snyder, G.A.

    1975-01-01

    A process is described for removing radioactive scale from a ferrous metal surface, including the steps of initially preconditioning the surface by contacting it with an oxidizing solution (such as an aqueous solution of an alkali metal permanganate or hydrogen peroxide), then, after removal or decomposition of the oxidizing solution, the metallic surface is contacted with a cleaning solution which is a mixture of a mineral acid and a complexing agent (such as sulfuric acid and oxalic acid), and which preferably contains a corrosion inhibitor. A final step in the process is the treatment of the spent cleaning solution containing radioactive waste materials in solution by adding a reagent selected from the group consisting of calcium hydroxide or potassium permanganate and an alkali metal hydroxide to thereby form easily recovered metallic compounds containing substantially all of the dissolved metals and radioactivity. (auth)

  20. Surface-Assisted Dynamic Search Processes.

    Science.gov (United States)

    Shin, Jaeoh; Kolomeisky, Anatoly B

    2018-03-01

    Many chemical and biological systems exhibit intermittent search phenomena when participating particles alternate between dynamic regimes with different dimensionalities. Here we investigate theoretically a dynamic search process of finding a small target on a two-dimensional surface starting from a bulk solution, which is an example of such an intermittent search process. Both continuum and discrete-state stochastic descriptions are developed. It is found that depending on the scanning length λ, which describes the area visited by the reacting molecule during one search cycle, the system can exhibit three different search regimes: (i) For small λ values, the reactant finds the target mostly via three-dimensional bulk diffusion; (ii) for large λ values, the reactant molecule associates to the target mostly via surface diffusion; and (iii) for intermediate λ values, the reactant reaches the target via a combination of three-dimensional and two-dimensional search cycles. Our analysis also shows that the mean search times have different scalings as a function of the size of the surface segment depending on the nature of the dynamic search regime. Search dynamics are also sensitive to the position of the target for large scanning lengths. In addition, it is argued that the continuum description underestimates mean search times and does not always correctly describe the most optimal conditions for the surface-assisted dynamic processes. The importance of our findings for real natural systems is discussed.

  1. Array processing for seismic surface waves

    Energy Technology Data Exchange (ETDEWEB)

    Marano, S.

    2013-07-01

    This dissertation submitted to the Swiss Federal Institute of Technology ETH in Zurich takes a look at the analysis of surface wave properties which allows geophysicists to gain insight into the structure of the subsoil, thus avoiding more expensive invasive techniques such as borehole drilling. This thesis aims at improving signal processing techniques for the analysis of surface waves in various directions. One main contribution of this work is the development of a method for the analysis of seismic surface waves. The method also deals with the simultaneous presence of multiple waves. Several computational approaches to minimize costs are presented and compared. Finally, numerical experiments that verify the effectiveness of the proposed cost function and resulting array geometry designs are presented. These lead to greatly improved estimation performance in comparison to arbitrary array geometries.

  2. Array processing for seismic surface waves

    International Nuclear Information System (INIS)

    Marano, S.

    2013-01-01

    This dissertation submitted to the Swiss Federal Institute of Technology ETH in Zurich takes a look at the analysis of surface wave properties which allows geophysicists to gain insight into the structure of the subsoil, thus avoiding more expensive invasive techniques such as borehole drilling. This thesis aims at improving signal processing techniques for the analysis of surface waves in various directions. One main contribution of this work is the development of a method for the analysis of seismic surface waves. The method also deals with the simultaneous presence of multiple waves. Several computational approaches to minimize costs are presented and compared. Finally, numerical experiments that verify the effectiveness of the proposed cost function and resulting array geometry designs are presented. These lead to greatly improved estimation performance in comparison to arbitrary array geometries

  3. Electrolytic plasma processing of steel surfaces

    International Nuclear Information System (INIS)

    Bejar, M.A; Araya, R.N; Baeza, B

    2006-01-01

    The thermo-chemical treatments of steels with plasma is normally carried out in low-pressure ionized gaseous atmospheres. Among the treatments used most often are: nitruration, carburization and boronized. A plasma can also generate at atmospheric pressure. One way to produce it is with an electrochemical cell that works at a relatively high inter-electrode voltage and under conditions of heavy gas generation. This type of plasma is known as electrolytic plasma. This work studies the feasibility of using electrolytic plasma for the surface processing of steels. Two processes were selected: boronized and nitruration., for the hardening of two types of steel: one with low carbon (1020) and one with low alloy (4140). In the case of the nitruration, the 1020 steel was first aluminized. The electrolytes were aqueous solutions of borax for the boronizing and urea for the nitruration. The electrolytic plasmas were classified qualitatively, in relation with their luminosity by low, medium and high intensity. The boronizing was carried out with low intensity plasmas for a period of one hour. The nitruration was performed with plasmas of different intensities and for period of a few minutes to half an hour. The test pieces processed by electrolytic plasma were characterized by micro-hardness tests and X-ray diffraction. The maximum surface hardnesses obtained for the 1020 and 4140 steels were the following: 300 and 700 HV for the boronizing, and 1650 and 1200 HV for the nitruration, respectively. The utilization of an electrolytic plasma permits the surface processing of steels, noticeably increasing their hardness. With this type of plasma some thermo-chemical surface treatments can be done very rapidly as well (CW)

  4. Redox behavior of a low-doped Pr-CeO{sub 2}(111) surface. A DFT+U study

    Energy Technology Data Exchange (ETDEWEB)

    Milberg, Brian [ITHES, UBA-CONICET, Departamento de Ingeniería Química, Pabellón de Industrias, Ciudad Universitaria, 1428 Buenos Aires (Argentina); Juan, Alfredo [Departamento de Física & IFISUR, UNS-CONICET, Avda. Alem 1253, 8000 Bahía Blanca (Argentina); Irigoyen, Beatriz, E-mail: beatriz@di.fcen.uba.ar [ITHES, UBA-CONICET, Departamento de Ingeniería Química, Pabellón de Industrias, Ciudad Universitaria, 1428 Buenos Aires (Argentina)

    2017-04-15

    Highlights: • Pr doping facilitates oxygen donation due to the easy formation of Pr{sup 3+}/Pr{sup 4+} and Ce{sup 3+}/Ce{sup 4+} redox couples. • Pr doping also favors the formation of superoxide (O{sub 2}{sup −}) radicals on surface O-holes. • CO can be oxidized by superoxide radical forming a CO{sub 2} molecule floating on the surface. • CO can also interact on the (O{sub 2}{sup −})/Pr{sup 3+} interphase and forms weakly adsorbed carbonate-type intermediates. - Abstract: In this work, we investigated the redox behavior (donation and replenishing of oxygen) of a low praseodymium (Pr)-doped CeO{sub 2}(111) surface. We considered a 3.7 at.% Pr doping and performed density functional calculations using the GGA formalism with the ‘U’ correction on Ce(4f) and Pr(4f) orbitals. Our results indicate that Pr doping promotes oxygen donation by lowering the energy necessary to form surface anionic vacancies. When the Ce{sub 0.963}Pr{sub 0.037}O{sub 2}(111) surface donates one oxygen, the two excess electrons locate on Pr and Ce cations and reduce them to Pr{sup 3+} and Ce{sup 3+} ones. Praseodymium doping also favors the activation of O{sub 2} molecule on surface O-holes, leading to formation of a superoxide (O{sub 2}{sup −}) radical as well as to reoxidation of the Ce{sup 3+} cation to Ce{sup 4+} one. Additionally, we used the CO molecular adsorption for testing the reactivity of those superoxide species. The calculations expose the ability of these radicals to oxidize CO forming a CO{sub 2} molecule floating on the surface. However, when the superoxide is in the immediate vicinity of Pr dopant a carbonate-type species is formed. Our theoretical results may help to gain insight into redox properties and improved catalytic performance of low-doped Pr-CeO{sub 2} solids.

  5. Redox Kinetics and Nonstoichiometry of Ce0.5Zr0.5O2−δ for Water Splitting and Hydrogen Production

    KAUST Repository

    Zhao, Zhenlong; Uddi, Mruthunjaya; Tsvetkov, Nikolai; Yildiz, Bilge; Ghoniem, Ahmed F.

    2017-01-01

    Water splitting and chemical fuel production as a promising carbon-neutral energy solution relies critically on an efficient electrochemical process over catalyst surfaces. The fundamentals within the surface redox pathways, including the complex

  6. The impact of urea-induced unfolding on the redox process of immobilised cytochrome c

    NARCIS (Netherlands)

    Monari, S.; Millo, D.; Ranieri, A.; di Rocco, G.; van der Zwan, G.; Gooijer, C.; Peressini, S.; Tavagnacco, C.; Hildebrandt, P.; Borsari, M.

    2010-01-01

    We have studied the effect of urea-induced unfolding on the electron transfer process of yeast iso-1-cytochrome c and its mutant K72AK73AK79A adsorbed on electrodes coated by mixed 11-mercapto-1-undecanoic acid/11-mercapto-1-undecanol self-assembled monolayers. Electrochemical measurements,

  7. ENVISAT Land Surface Processes. Phase 2

    Science.gov (United States)

    vandenHurk, B. J. J. M.; Su, Z.; Verhoef, W.; Menenti, M.; Li, Z.-L.; Wan, Z.; Moene, A. F.; Roerink, G.; Jia, I.

    2002-01-01

    This is a progress report of the 2nd phase of the project ENVISAT- Land Surface Processes, which has a 3-year scope. In this project, preparative research is carried out aiming at the retrieval of land surface characteristics from the ENVISAT sensors MERIS and AATSR, for assimilation into a system for Numerical Weather Prediction (NWP). Where in the 1st phase a number of first shot experiments were carried out (aiming at gaining experience with the retrievals and data assimilation procedures), the current 2nd phase has put more emphasis on the assessment and improvement of the quality of the retrieved products. The forthcoming phase will be devoted mainly to the data assimilation experiments and the assessment of the added value of the future ENVISAT products for NWP forecast skill. Referring to the retrieval of albedo, leaf area index and atmospheric corrections, preliminary radiative transfer calculations have been carried out that should enable the retrieval of these parameters once AATSR and MERIS data become available. However, much of this work is still to be carried out. An essential part of work in this area is the design and implementation of software that enables an efficient use of MODTRAN(sub 4) radiative transfer code, and during the current project phase familiarization with these new components has been achieved. Significant progress has been made with the retrieval of component temperatures from directional ATSR-images, and the calculation of surface turbulent heat fluxes from these data. The impact of vegetation cover on the retrieved component temperatures appears manageable, and preliminary comparison of foliage temperature to air temperatures were encouraging. The calculation of surface fluxes using the SEBI concept,which includes a detailed model of the surface roughness ratio, appeared to give results that were in reasonable agreement with local measurements with scintillometer devices. The specification of the atmospheric boundary conditions

  8. Hydroxylamine derivative in Purex process. Part 8. The kinetics and mechanism of the redox reaction of N-methylhydroxylamine and vanadium(V)

    International Nuclear Information System (INIS)

    Anyun Zhang; Shaanxi Normal Univ., Xi'an; Kai Li; Jingxin Hu

    2004-01-01

    The kinetic properties of the oxidation-reduction reaction between N-methylhydroxylamine (NMHAN) and vanadium(V) in nitric acid medium has been studied by spectrophotometry at 23.1 deg C. The rate equation of the redox reaction was determined as -d[V(V)]/dt = k[V(V)] [NMHAN] by investigating the influence of concentration of NMHAN, acidity, ionic strength and the ratio of initial concentration of V(V) to NMHAN on the reaction. The rate constant of the reaction k = 0.818 ± 0.051 (mol/l) -1 x s -1 at the ionic strength of 1.00 mol/l. The activation energy of the redox reaction was calculated to be 39.6 kJ/mol. A possibly radical mechanism of the redox reaction between NMHAN and V(V) has been suggested on the basis of electron spin resonance (ESR) spectra of nitroxyl radical, i.e., CH 3 NHO. It is helpful to understand and make the redox mechanism of NMHAN and Np(VI) clear in the reprocessing process of nuclear spent fuel. (author)

  9. Redox process catalysed by growing crystal-strengite, FePO4,2H2O, crystallizing from solution with iron(II) and hydroxylamine

    Science.gov (United States)

    Lundager Madsen, Hans Erik

    2014-09-01

    In an attempt to grow pure crystals of the iron(II) phosphate vivianite, Fe3(PO4)2,8H2O, from a solution of Mohr's salt, Fe(NH4)2(SO4)2,6H2O, added to a solution of ammonium phosphate, hydroxylammonium chloride, NH3OHCl, was added to the iron(II) stock solution to eliminate oxidation of iron(II) by oxygen from the air. However, the effect turned out to be the opposite of the expected: whereas hydroxylamine reduces iron(III) in bulk solution, it acted as a strong oxidant in the presence of growing iron phosphate crystals, causing the crystallization of the iron(III) phosphate strengite, FePO4,2H2O, as the only solid phase. Evidently the crystal surface catalyses oxidation of iron(II) by hydroxylamine. The usual composite kinetics of spiral growth and surface nucleation was found. The surface-nucleation part yielded edge free energy λ in the range 12-45 pJ/m, virtually independent of temperature and in the range typical for phosphates of divalent metals. The scatter of values for λ presumably arises from contributions from different crystal forms to the overall growth rate. The low mean value points to strong adsorption of iron(II), which is subsequently oxidized at the crystal surface, forming strengite. The state of the system did not tend to thermodynamic equilibrium, but to a metastable state, presumably controlled by the iron(II) rich surface layer of the crystal. In addition to crystal growth, it was possible to measure nucleation kinetics by light scattering (turbidimetry). A point of transition from heterogeneous to homogeneous nucleation was found, and from the results for the homogeneous domain a rather precise value of crystal surface free energy γ=55 mJ/m2 was found. This is a relatively low value as well, indicating that the redox process plays a role already at the nucleation stage.

  10. Two photon processes in surface photovoltage spectroscopy

    International Nuclear Information System (INIS)

    Craig, R.P.; Thurgate, S.M.

    1996-01-01

    Full text: A significant mid-gap effect has been found in Surface Photovoltage Spectroscopy measurements of cleaved GaAs, InP and Si wafer which is normally interpreted as arising from transitions between surface states and band edges. This large mid-gap effect common to various materials is puzzling as such a high proportion of mid-gap states seems unlikely. Most theories of surface states predict states that tail from the band edges into the gap or states that have a well defined energy in the gap. None propose a large state exactly at E G /2. We recently investigated the variation in SPS spectra with flux density. We find a non-linear correlation in the magnitude of Band-Bending arising from mid-gap and band-gap photon energies. We suggest that the mid-gap feature is due to a two photon absorption process leading to carrier pair generation mediated by mid-gap states in the continuum of band-gap surface states

  11. Destruction of commercial pesticides by cerium redox couple mediated electrochemical oxidation process in continuous feed mode

    International Nuclear Information System (INIS)

    Balaji, Subramanian; Chung, Sang Joon; Ryu, Jae-Yong; Moon, Il Shik

    2009-01-01

    Mediated electrochemical oxidation was carried out for the destruction of commercial pesticide formulations using cerium(IV) in nitric acid as the mediator electrolyte solution in a bench scale set up. The mediator oxidant was regenerated in situ using an electrochemical cell. The real application of this sustainable process for toxic organic pollutant destruction lies in its ability for long term continuous operation with continuous organic feeding and oxidant regeneration with feed water removal. In this report we present the results of fully integrated MEO system. The task of operating the continuous feed MEO system for a long time was made possible by continuously removing the feed water using an evaporator set up. The rate of Ce(IV) regeneration in the electrochemical cell and the consumption for the pesticide destruction was matched based on carbon content of the pesticides. It was found that under the optimized experimental conditions for Ce(III) oxidation, organic addition and water removal destruction efficiency of ca. 99% was obtained for all pesticides studied. It was observed that the Ce(IV) concentration was maintained nearly the same throughout the experiment. The stable operation for 6 h proved that the process can be used for real applications and for possible scale up for the destruction of larger volumes of toxic organic wastes.

  12. Atmospheric Processing of Volcanic Glass: Effects on Iron Solubility and Redox Speciation.

    Science.gov (United States)

    Maters, Elena C; Delmelle, Pierre; Bonneville, Steeve

    2016-05-17

    Volcanic ash from explosive eruptions can provide iron (Fe) to oceanic regions where this micronutrient limits primary production. Controls on the soluble Fe fraction in ash remain poorly understood but Fe solubility is likely influenced during atmospheric transport by condensation-evaporation cycles which induce large pH fluctuations. Using glass powder as surrogate for ash, we experimentally simulate its atmospheric processing via cycles of pH 2 and 5 exposure. Glass fractional Fe solubility (maximum 0.4%) is governed by the pH 2 exposure duration rather than by the pH fluctuations, however; pH 5 exposure induces precipitation of Fe-bearing nanoparticles which (re)dissolve at pH 2. Glass leaching/dissolution release Fe(II) and Fe(III) which are differentially affected by changes in pH; the average dissolved Fe(II)/Fetot ratio is ∼0.09 at pH 2 versus ∼0.18 at pH 5. Iron release at pH 2 from glass with a relatively high bulk Fe(II)/Fetot ratio (0.5), limited aqueous Fe(II) oxidation at pH 5, and possibly glass-mediated aqueous Fe(III) reduction may render atmospherically processed ash a significant source of Fe(II) for phytoplankton. By providing new insight into the form(s) of Fe associated with ash as wet aerosol versus cloud droplet, we improve knowledge of atmospheric controls on volcanogenic Fe delivery to the ocean.

  13. A high-resolution record of Holocene millennial-scale oscillations of surface water, foraminiferal paleoecology and sediment redox chemistry in the SE Brazilian margin

    Science.gov (United States)

    Dias, B. B.; Barbosa, C. F.; Albuquerque, A. L.; Piotrowski, A. M.

    2014-12-01

    Holocene millennial-scale oscillations and Bond Events (Bond et al. 1997) are well reported in the North Atlantic as consequence of fresh water input and weaking of the Atlantic Meridional Overturning Circulation (AMOC). It has been hypothesized that the effect of weaking of AMOC would lead to warming in the South Atlantic due to "heat piracy", causing surface waters to warm and a reorganization of surface circulation. There are few reconstructions of AMOC strength in the South Atlantic, and none with a high resolution Holocene record of changes of productivity and the biological pump. We reconstruct past changes in the surface water mass hydrography, productivity, and sediment redox changes in high-resolution in the core KCF10-01B, located 128 mbsl water depth off Cabo Frio, Brazil, a location where upwelling is strongly linked to surface ocean hydrography. We use Benthic Foraminiferal Accumulation Rate (BFAR) to reconstruct productivity, which reveals a 1.3kyr cyclicity during the mid- and late-Holocene. The geochemistry of trace and rare earth elements on foraminiferal Fe-Mn oxide coatings show changes in redox-sensitive elements indicating that during periods of high productivity there were more reducing conditions in sediment porewaters, producing a Ce anomaly and reduction and re-precipitation of Mn oxides. Bond events 1-7 were identified by a productivity increase along with reducing sediment conditions which was likely caused by Brazil Current displacement offshore allowing upwelling of the nutritive bottom water South Atlantic Central Waters (SACW) to the euphotic zone and a stronger local biological pump. In a global context, correlation with other records show that this occurred during weakened AMOC and southward displacement of the ITCZ. We conclude that Bond climatic events and millennial-scale variability of AMOC caused sea surface hydrographic changes off the Brazilian Margin leading to biological and geochemical changes recorded in coastal records

  14. Surface processing by high power excimer laser

    Energy Technology Data Exchange (ETDEWEB)

    Stehle, M [SOPRA, 92 - Bois-Colombes (France)

    1995-03-01

    Surface processing with lasers is a promising field of research and applications because lasers bring substantial advantages : laser beams work at distance, laser treatments are clean in respect of environment consideration and they offer innovative capabilities for surface treatment which cannot be reached by other way. Excimer lasers are pulsed, gaseous lasers which emit in UV spectral range - the most common are XeCl (308 nm), KrF (248 nm), ArF (193 nm). From 1980 up to 1994, many of them have been used for research, medical and industrial applications such as spectroscopy, PRK (photo-refractive keratotomy) and micro-machining. In the last six years, from 1987 up to 1993, efforts have been done in order to jump from 100 W average power up to 1 kW for XeCl laser at {lambda} = 308 nm. It was the aim of AMMTRA project in Japan as EU205 and EU213 Eureka projects in Europe. In this framework, SOPRA developed VEL (Very large Excimer Laser). In 1992, 1 kW (10 J x 100 Hz) millstone has been reached for the first time, this technology is based on X-Ray preionization and large laser medium (5 liters). Surface treatments based on this laser source are the main purpose of VEL Lasers. Some of them are given for instance : (a) Turbine blades made with metallic substrate and ceramic coatings on the top, are glazed in order to increase corrosion resistance of ceramic and metal sandwich. (b) Selective ablation of organic coatings deposited on fragile composite material is investigated in Aerospace industry. (c) Chock hardening of bulk metallic materials or alloys are investigated for automotive industry in order to increase wear resistance. (d) Ablation of thin surface oxides of polluted steels are under investigation in nuclear industry for decontamination. (J.P.N.).

  15. Surface processing by high power excimer laser

    International Nuclear Information System (INIS)

    Stehle, M.

    1995-01-01

    Surface processing with lasers is a promising field of research and applications because lasers bring substantial advantages : laser beams work at distance, laser treatments are clean in respect of environment consideration and they offer innovative capabilities for surface treatment which cannot be reached by other way. Excimer lasers are pulsed, gaseous lasers which emit in UV spectral range - the most common are XeCl (308 nm), KrF (248 nm), ArF (193 nm). From 1980 up to 1994, many of them have been used for research, medical and industrial applications such as spectroscopy, PRK (photo-refractive keratotomy) and micro-machining. In the last six years, from 1987 up to 1993, efforts have been done in order to jump from 100 W average power up to 1 kW for XeCl laser at λ = 308 nm. It was the aim of AMMTRA project in Japan as EU205 and EU213 Eureka projects in Europe. In this framework, SOPRA developed VEL (Very large Excimer Laser). In 1992, 1 kW (10 J x 100 Hz) millstone has been reached for the first time, this technology is based on X-Ray preionization and large laser medium (5 liters). Surface treatments based on this laser source are the main purpose of VEL Lasers. Some of them are given for instance : a) Turbine blades made with metallic substrate and ceramic coatings on the top, are glazed in order to increase corrosion resistance of ceramic and metal sandwich. b) Selective ablation of organic coatings deposited on fragile composite material is investigated in Aerospace industry. c) Chock hardening of bulk metallic materials or alloys are investigated for automotive industry in order to increase wear resistance. d) Ablation of thin surface oxides of polluted steels are under investigation in nuclear industry for decontamination. (J.P.N.)

  16. Aqueous liquid redox desulfurisation

    Energy Technology Data Exchange (ETDEWEB)

    Reicher, M.; Niemiec, B.; Katona, T.

    1999-12-01

    The LO-CAT II process is an aqueous liquid redox process which uses ferric and ferrous iron catalysts to oxidise hydrogen sulfide (from sour gas) to elemental sulfur: the relevant chemical equations are given. Chelating agents keep the iron in solution. The system is described under the headings of (i) LO-CAT chemistry, (ii) design parameters, (iii) startup challenges, (iv) present situation and (v) anticipated future conditions. Further improvements to the system are anticipated.

  17. Electro-deposition of Pd on Carbon paper and Ni foam via surface limited redox-replacement reaction for oxygen reduction reaction

    International Nuclear Information System (INIS)

    Modibedi, Remegia M.; Mathe, Mkhulu K.; Motsoeneng, Rapelang G.; Khotseng, Lindiwe E.; Ozoemena, Kenneth I.; Louw, Eldah K.

    2014-01-01

    Pd nanostructured catalysts were electrodeposited by surface-limited redox replacement reactions using the electrochemical atomic layer deposition technique. Carbon paper and Ni foam were used as substrates for the electrodeposition of the metal. Supported nanostructured Pd electrodes were characterized using electrochemical methods and scanning electron microscopy. Carbon paper and Ni foam produced good quality deposits with some agglomeration on Ni foam. The EDX profiles confirmed the presence of Pd particles. Cyclic voltammograms of the electrodeposited Pd on substrates showed features characteristic of polycrystalline Pd electrodes. In the acidic electrolyte a very weak oxygen reduction reaction (ORR) activity was observed on Pd/Carbon paper electrode when compared to Pd/Ni foam electrode. The Pd/Ni foam electrode showed improved ORR activity in alkaline medium

  18. Redox zonation for different groundwater flow paths during bank filtration: a case study at Liao River, Shenyang, northeastern China

    Science.gov (United States)

    Su, Xiaosi; Lu, Shuai; Yuan, Wenzhen; Woo, Nam Chil; Dai, Zhenxue; Dong, Weihong; Du, Shanghai; Zhang, Xinyue

    2018-03-01

    The spatial and temporal distribution of redox zones in an aquifer is important when designing groundwater supply systems. Redox zonation can have direct or indirect control of the biological and chemical reactions and mobility of pollutants. In this study, redox conditions are characterized by interpreting the hydrogeological conditions and water chemistry in groundwater during bank infiltration at a site in Shenyang, northeast China. The relevant redox processes and zonal differences in a shallow flow path and deeper flow path at the field scale were revealed by monitoring the redox parameters and chemistry of groundwater near the Liao River. The results show obvious horizontal and vertical components of redox zones during bank filtration. Variations in the horizontal extent of the redox zone were controlled by the different permeabilities of the riverbed sediments and aquifer with depth. Horizontally, the redox zone was situated within 17 m of the riverbank for the shallow flow path and within 200 m for the deep flow path. The vertical extent of the redox zone was affected by precipitation and seasonal river floods and extended to 10 m below the surface. During bank filtration, iron and manganese oxides or hydroxides were reductively dissolved, and arsenic that was adsorbed onto the medium surface or coprecipitated is released into the groundwater. This leads to increased arsenic content in groundwater, which poses a serious threat to water supply security.

  19. Studies on the process aspects related to chemical decontamination of chromium-containing alloys with redox processes

    International Nuclear Information System (INIS)

    Kumar, P.S.; Suresh, S.; Chandran, S.; Velmurugan, S.; Narasimhan, S.V.; Rajesh, P.

    2004-01-01

    Presence of chromium in the oxide layer makes oxidative pre-treatment with oxidizing agents such as potassium permanganate (KMnO 4 ) a must for the decontamination of stainless steels and other chromium containing alloys. The effectiveness of pre-treatment with oxidizing reagent varies with the conditions of treatment such as temperature, concentration and whether the medium is acidic or alkaline. A comparative study of the two acidic oxidizing agents, i.e., nitric acid-permanganate and permanganic acid was made. The dissolution behavior of copper and its oxide in permanganic acid was found to be comparable to that of chromium oxide. Citric acid and ascorbic acid were investigated as alternatives to oxalic acid for the reduction/decomposition of permanganate left over after the oxidizing pre-treatment step. It has been established that the reduction of chromate by citric acid is instantaneous only in presence of Mn 2+ ions. It has also been established that reduction of residual permanganate can be achieved with ascorbic acid and with minimum chemical requirement. The capabilities of nitrilotriacetic acid (NTA)-ascorbic acid mixture for the dissolution of hematite have been explored. This study would help to choose the suitable oxidizing agent, the reducing agent used for decomposition of permanganate and to optimize the concentration of reducing formulation so that the process of decontamination is achieved with a minimum requirement of chemicals. The generation of radioactive ion exchange resin as waste is therefore held at a minimum. Ion exchange studies with metal ion complexes of relevance to decontamination were carried out with a view to choose a suitable type of ion exchanger. It has been established that treatment of the ion exchange resin with brine solution can solve the problem of leaching out of non-ionic organics from the resin. (orig.)

  20. Photochemical Transformation Processes in Sunlit Surface Waters

    Science.gov (United States)

    Vione, D.

    2012-12-01

    Photochemical reactions are major processes in the transformation of hardly biodegradable xenobiotics in surface waters. They are usually classified into direct photolysis and indirect or sensitised degradation. Direct photolysis requires xenobiotic compounds to absorb sunlight, and to get transformed as a consequence. Sensitised transformation involves reaction with transient species (e.g. °OH, CO3-°, 1O2 and triplet states of chromophoric dissolved organic matter, 3CDOM*), photogenerated by so-called photosensitisers (nitrate, nitrite and CDOM). CDOM is a major photosensitiser: is it on average the main source of °OH (and of CO3-° as a consequence, which is mainly produced upon oxidation by °OH of carbonate and bicarbonate) and the only important source of 1O2 and 3CDOM* [1, 2]. CDOM origin plays a key role in sensitised processes: allochthonous CDOM derived from soil runoff and rich in fulvic and humic substances is usually more photoactive than autochthonous CDOM (produced by in-water biological processes and mainly consisting of protein-like material) or of CDOM derived from atmospheric deposition. An interesting gradual evolution of CDOM origin and photochemistry can be found in mountain lakes across the treeline, which afford a gradual transition of allochthonous- autochtonous - atmopheric CDOM when passing from trees to alpine meadows to exposed rocks [3]. Another important issue is the sites of reactive species photoproduction in CDOM. While there is evidence that smaller molecular weight fractions are more photoactive, some studies have reported considerable 1O2 reactivity in CDOM hydrophobic sites and inside particles [4]. We have recently addressed the problem and found that dissolved species in standard humic acids (hydrodynamic diameter pollutants to be assessed and modelled. For instance, it is possible to predict pollutant half-life times by knowing absorption spectrum, direct photolysis quantum yield and reaction rate constants with °OH, CO3

  1. Excimer laser surface modification: Process and properties

    Energy Technology Data Exchange (ETDEWEB)

    Jervis, T.R.; Nastasi, M. [Los Alamos National Lab., NM (United States); Hirvonen, J.P. [Technical Research Institute, Espoo (Finland). Metallurgy Lab.

    1992-12-01

    Surface modification can improve materials for structural, tribological, and corrosion applications. Excimer laser light has been shown to provide a rapid means of modifying surfaces through heat treating, surface zone refining, and mixing. Laser pulses at modest power levels can easily melt the surfaces of many materials. Mixing within the molten layer or with the gas ambient may occur, if thermodynamically allowed, followed by rapid solidification. The high temperatures allow the system to overcome kinetic barriers found in some ion mixing experiments. Alternatively, surface zone refinement may result from repeated melting-solidification cycles. Ultraviolet laser light couples energy efficiently to the surface of metallic and ceramic materials. The nature of the modification that follows depends on the properties of the surface and substrate materials. Alloying from both gas and predeposited layer sources has been observed in metals, semiconductors, and ceramics as has surface enrichment of Cr by zone refinement of stainless steel. Rapid solidification after melting often results in the formation of nonequilibrium phases, including amorphous materials. Improved surface properties, including tribology and corrosion resistance, are observed in these materials.

  2. Ediacaran Redox Fluctuations

    Science.gov (United States)

    Sahoo, S. K.; Jiang, G.; Planavsky, N. J.; Kendall, B.; Owens, J. D.; Anbar, A. D.; Lyons, T. W.

    2013-12-01

    Evidence for pervasive oxic conditions, and likely even deep ocean oxygenation has been documented at three intervals in the lower (ca. 632 Ma), middle (ca. 580 Ma) and upper (ca. 551 Ma) Ediacaran. The Doushantuo Formation in South China hosts large enrichments of redox-sensitive trace element (e.g., molybdenum, vanadium and uranium) in anoxic shales, which are indicative of a globally oxic ocean-atmosphere system. However, ocean redox conditions between these periods continue to be a topic of debate and remain elusive. We have found evidence for widespread anoxic conditions through much of the Ediacaran in the deep-water Wuhe section in South China. During most of the Ediacaran-early Cambrian in basinal sections is characterized by Fe speciation data and pyrite morphologies that indicate deposition under euxinic conditions with near-crustal enrichments of redox-sensitive element and positive pyrite-sulfur isotope values, which suggest low levels of marine sulfate and widespread euxinia. Our work reinforces an emerging view that the early Earth, including the Ediacaran, underwent numerous rises and falls in surface oxidation state, rather than a unidirectional rise as originally imagined. The Ediacaran ocean thus experienced repetitive expansion and contraction of marine chalcophilic trace-metal levels that may have had fundamental impact on the slow evolution of early animals and ecosystems. Further, this framework forces us to re-examine the relationship between Neoproterozoic oxygenation and metazoan diversification. Varying redox conditions through the Cryogenian and Ediacaran may help explain molecular clock and biomarker evidence for an early appearance and initial diversification of metazoans but with a delay in the appearance of most major metazoan crown groups until close to Ediacaran-Cambrian boundary.

  3. Investigation on the electrode process of the Mn(II)/Mn(III) couple in redox flow battery

    International Nuclear Information System (INIS)

    Xue Fangqin; Wang Yongliang; Wang Wenhong; Wang Xindong

    2008-01-01

    The Mn(II)/Mn(III) couple has been recognized as a potential anode for redox flow batteries to take the place of the V(IV)/V(V) in all-vanadium redox battery (VRB) and the Br 2 /Br - in sodium polysulfide/bromine (PSB) because it has higher standard electrode potential. In this study, the electrochemical behavior of the Mn(II)/Mn(III) couple on carbon felt and spectral pure graphite were investigated by cyclic voltammetry, steady polarization curve, electrochemical impedance spectroscopy, transient potential-step experiment, X-ray diffraction and charge-discharge experiments. Results show that the Mn(III) disproportionation reaction phenomena is obvious on the carbon felt electrode while it is weak on the graphite electrode owing to its fewer active sites. The reaction mechanism on carbon felt was discussed in detail. The reversibility of Mn(II)/Mn(III) is best when the sulfuric acid concentration is 5 M on the graphite electrode. Performance of a RFB employing Mn(II)/Mn(III) couple as anolyte active species and V(III)/V(II) as catholyte ones was evaluated with constant-current charge-discharge tests. The average columbic efficiency is 69.4% and the voltage efficiency is 90.4% at a current density of 20 mA cm -2 . The whole energy efficiency is 62.7% close to that of the all-vanadium battery and the average discharge voltage is about 14% higher than that of an all-vanadium battery. The preliminary exploration shows that the Mn(II)/Mn(III) couple is electrochemically promising for redox flow battery

  4. Process of treating surfaces of metals

    International Nuclear Information System (INIS)

    Kimura, T.; Murao, A.; Kuwahara, T.

    1975-01-01

    Both higher corrosion resistance and paint adherence are given to films formed on the surfaces of metals by treating the surfaces with aqueous solutions of one or more materials selected from the group consisting of water soluble vinyl monomer or water soluble high polymer and then irradiating with ionizing radioactive rays on the nearly dried surface film. When a water soluble inorganic compound is mixed with the above mentioned aqueous solution, the film properties are greatly improved. The inorganic ionic material should contain a cation from the group consisting of Ca, Mg, Zn, Cr, Al, Fe, and Ni. Electron beams may be used. (U.S.)

  5. Modification of surfaces and surface layers by non equilibrium processes

    International Nuclear Information System (INIS)

    Beamson, G.; Brennan, W.J.; Clark, D.T.; Howard, J.

    1988-01-01

    Plasmas are examples of non-equilibrium phenomena which are being used increasingly for the synthesis and modification of materials impossible by conventional routes. This paper introduces methods available by describing the construction and characteristics of some equipment used for the production of different types of plasmas and other non-equilibrium phenomena. This includes high energy ion beams. The special features, advantages and disadvantages of the techniques will be described. There are a multitude of potential application relevant to electronic, metallic, ceramic, and polymeric materials. However, scale-up from the laboratory to production equipment depends on establishing a better understanding of both the physics and chemistry of plasma as well as plasma-solid interactions. Examples are given of how such an understanding can be gained. The chemical analysis of polymer surfaces undergoing modification by inert gas, hydrogen or oxygen plasmas is shown to give physical information regarding the relative roles of diffusion of active species, and direct and radiative energy transfer from the plasma. Surface modification by plasma depositing a new material onto an existing substrate is discussed with particular reference to the deposition of amorphous carbon films. Applications of the unique properties of these films are outlined together with our current understanding of these properties based on chemical and physical methods of analysis of both the films and the plasmas producing them. Finally, surface modification by ion beams is briefly illustrated using examples from the electronics and metals industries where the modification has had a largely physical rather than chemical effect on the starting material. (orig.)

  6. Diffusion processes in bombardment-induced surface topography

    International Nuclear Information System (INIS)

    Robinson, R.S.

    1984-01-01

    A treatment is given of the problem of surface diffusion processes occurring during surface topography development, whenever a surface is simultaneously seeded with impurities and ion bombarded. The development of controllable topography and the importance of surface diffusion parameters, which can be obtained during these studies, are also analyzed. 101 refs.; 7 figs.; 2 tabs

  7. Redox Fluctuations Increase the Contribution of Lignin to Soil Respiration

    Science.gov (United States)

    Hall, S. J.; Silver, W. L.; Timokhin, V.; Hammel, K.

    2014-12-01

    Lignin mineralization represents a critical flux in the terrestrial carbon (C) cycle, yet little is known about mechanisms and environmental factors controlling lignin breakdown in mineral soils. Hypoxia has long been thought to suppress lignin decomposition, yet variation in oxygen (O2) availability in surface soils accompanying moisture fluctuations could potentially stimulate this process by generating reactive oxygen species via coupled biotic and abiotic iron (Fe) redox cycling. Here, we tested the impact of redox fluctuations on lignin breakdown in humid tropical forest soils during ten-week laboratory incubations. We used synthetic lignins labeled with 13C in either of two positions (aromatic methoxyl and propyl Cβ) to provide highly sensitive and specific measures of lignin mineralization not previously employed in soils. Four-day redox fluctuations increased the percent contribution of methoxyl C to soil respiration, and cumulative methoxyl C mineralization was equivalent under static aerobic and fluctuating redox conditions despite lower total C mineralization in the latter treatment. Contributions of the highly stable Cβ to mineralization were also equivalent in static aerobic and fluctuating redox treatments during periods of O2 exposure, and nearly doubled in the fluctuating treatment after normalizing to cumulative O2 exposure. Oxygen fluctuations drove substantial net Fe reduction and oxidation, implying that reactive oxygen species generated during abiotic Fe oxidation likely contributed to the elevated contribution of lignin to C mineralization. Iron redox cycling provides a mechanism for lignin breakdown in soils that experience conditions unfavorable for canonical lignin-degrading organisms, and provides a potential mechanism for lignin depletion in soil organic matter during late-stage decomposition. Thus, close couplings between soil moisture, redox fluctuations, and lignin breakdown provide potential a link between climate variability and

  8. Plasmonic tunnel junctions for single-molecule redox chemistry.

    Science.gov (United States)

    de Nijs, Bart; Benz, Felix; Barrow, Steven J; Sigle, Daniel O; Chikkaraddy, Rohit; Palma, Aniello; Carnegie, Cloudy; Kamp, Marlous; Sundararaman, Ravishankar; Narang, Prineha; Scherman, Oren A; Baumberg, Jeremy J

    2017-10-20

    Nanoparticles attached just above a flat metallic surface can trap optical fields in the nanoscale gap. This enables local spectroscopy of a few molecules within each coupled plasmonic hotspot, with near thousand-fold enhancement of the incident fields. As a result of non-radiative relaxation pathways, the plasmons in such sub-nanometre cavities generate hot charge carriers, which can catalyse chemical reactions or induce redox processes in molecules located within the plasmonic hotspots. Here, surface-enhanced Raman spectroscopy allows us to track these hot-electron-induced chemical reduction processes in a series of different aromatic molecules. We demonstrate that by increasing the tunnelling barrier height and the dephasing strength, a transition from coherent to hopping electron transport occurs, enabling observation of redox processes in real time at the single-molecule level.

  9. Redox reaction studies by nanosecond pulse radiolysis

    International Nuclear Information System (INIS)

    Moorthy, P.N.

    1979-01-01

    Free radicals are formed as intermediates in many chemical and biochemical reactions. An important type of reaction which they can undergo is a one electron or redox process. The direction and rate of such electron transfer reactions is governed by the relative redox potentials of the participating species. Because of the generally short lived nature of free radicals, evaluation of their redox potentials poses a number of problems. Two techniques are described for the experimental determination of the redox potentials of short lived species generated by either a nanosecond electron pulse or laser flash. In the first method, redox titration of the short lived species with stable molecules of known redox potential is carried out, employing the technique of fast kinetic spectrophotometry. Conversely, by the same method it is also possible to evaluate the one electron redox potentials of stable molecules by redox titration with free radicals of known redox potential produced as above. In the second method, electrochemical reduction or oxidation of the short lived species at an appropriate electrode (generally a mercury drop) is carried out at different fixed potentials, and the redox potential evaluated from the current-potential curves (polarograms). Full description of the experimental set up and theoretical considerations for interpretation of the raw data are given. The relative merits of the two methods and their practical applicability are discussed. (auth.)

  10. Dissecting Redox Biology Using Fluorescent Protein Sensors.

    Science.gov (United States)

    Schwarzländer, Markus; Dick, Tobias P; Meyer, Andreas J; Morgan, Bruce

    2016-05-01

    Fluorescent protein sensors have revitalized the field of redox biology by revolutionizing the study of redox processes in living cells and organisms. Within one decade, a set of fundamental new insights has been gained, driven by the rapid technical development of in vivo redox sensing. Redox-sensitive yellow and green fluorescent protein variants (rxYFP and roGFPs) have been the central players. Although widely used as an established standard tool, important questions remain surrounding their meaningful use in vivo. We review the growing range of thiol redox sensor variants and their application in different cells, tissues, and organisms. We highlight five key findings where in vivo sensing has been instrumental in changing our understanding of redox biology, critically assess the interpretation of in vivo redox data, and discuss technical and biological limitations of current redox sensors and sensing approaches. We explore how novel sensor variants may further add to the current momentum toward a novel mechanistic and integrated understanding of redox biology in vivo. Antioxid. Redox Signal. 24, 680-712.

  11. Isoprenoid quinones resolve the stratification of microbial redox processes in a biogeochemical continuum from the photic zone to deep anoxic sediments of the Black Sea.

    Science.gov (United States)

    Becker, Kevin W; Elling, Felix J; Schröder, Jan M; Lipp, Julius S; Goldhammer, Tobias; Zabel, Matthias; Elvert, Marcus; Overmann, Jörg; Hinrichs, Kai-Uwe

    2018-03-09

    The stratified water column of the Black Sea serves as a model ecosystem for studying the interactions of microorganisms with major biogeochemical cycles. Here we provide detailed analysis of isoprenoid quinones to study microbial redox processes in the ocean. In a continuum from the photic zone through the chemocline into deep anoxic sediments of the southern Black Sea, diagnostic quinones and inorganic geochemical parameters indicate niche segregation between redox processes and corresponding shifts in microbial community composition. Quinones specific for oxygenic photosynthesis and aerobic respiration dominate oxic waters, while quinones associated with thaumarchaeal ammonia-oxidation and bacterial methanotrophy, respectively, dominate a narrow interval in suboxic waters. Quinone distributions indicate highest metabolic diversity within the anoxic zone, with anoxygenic photosynthesis being a major process in its photic layer. In the dark anoxic layer, quinone profiles indicate occurrence of bacterial sulfur and nitrogen cycling, archaeal methanogenesis, and archaeal methanotrophy. Multiple novel ubiquinone isomers, possibly originating from unidentified intra-aerobic anaerobes, occur in this zone. The respiration modes found in the anoxic zone continue into shallow subsurface sediments, but quinone abundances rapidly decrease within the upper 50 cm below sea floor, reflecting the transition to lower energy availability. In the deep subseafloor sediments, quinone distributions and geochemical profiles indicate archaeal methanogenesis/methanotrophy and potentially bacterial fermentative metabolisms. We observed that sedimentary quinone distributions track lithology, which supports prior hypotheses that deep biosphere community composition and metabolisms are determined by environmental conditions during sediment deposition. Importance Microorganisms play crucial roles in global biogeochemical cycles. Yet, we have only a fragmentary understanding of the diversity

  12. Microbe-surface interactions in biofouling and biocorrosion processes.

    Science.gov (United States)

    Beech, Iwona B; Sunner, Jan A; Hiraoka, Kenzo

    2005-09-01

    The presence of microorganisms on material surfaces can have a profound effect on materials performance. Surface-associated microbial growth, i.e. a biofilm, is known to instigate biofouling. The presence of biofilms may promote interfacial physico-chemical reactions that are not favored under abiotic conditions. In the case of metallic materials, undesirable changes in material properties due to a biofilm (or a biofouling layer) are referred to as biocorrosion or microbially influenced corrosion (MIC). Biofouling and biocorrosion occur in aquatic and terrestrial habitats varying in nutrient content, temperature, pressure and pH. Interfacial chemistry in such systems reflects a wide variety of physiological activities carried out by diverse microbial populations thriving within biofilms. Biocorrosion can be viewed as a consequence of coupled biological and abiotic electron-transfer reactions, i.e. redox reactions of metals, enabled by microbial ecology. Microbially produced extracellular polymeric substances (EPS), which comprise different macromolecules, mediate initial cell adhesion to the material surface and constitute a biofilm matrix. Despite their unquestionable importance in biofilm development, the extent to which EPS contribute to biocorrosion is not well-understood. This review offers a current perspective on material/microbe interactions pertinent to biocorrosion and biofouling, with EPS as a focal point, while emphasizing the role atomic force spectroscopy and mass spectrometry techniques can play in elucidating such interactions.

  13. Paper spray mass spectrometry applied in the monitoring of a chemical system in dynamic chemical equilibrium: the redox process of methylene blue.

    Science.gov (United States)

    de Paula, Camila Cristina Almeida; Valadares, Alberto; Jurisch, Marina; Piccin, Evandro; Augusti, Rodinei

    2016-05-15

    The monitoring of chemical systems in dynamic equilibrium is not an easy task. This is due to the high rate at which the system returns to equilibrium after being perturbed, which hampers the possibility of following the aftereffects of the disturbance. In this context, it is necessary to use a fast analytical technique that requires no (or minimal) sample preparation, and which is capable of monitoring the species constituting the system in equilibrium. Paper spray ionization mass spectrometry (PS-MS), a recently introduced ambient ionization technique, has such characteristics and hence was chosen for monitoring a model system: the redox process of methylene blue. The model system evaluated herein was composed of three cationic species of methylene blue (MB), which coexist in a dynamic redox system: (1) [MB](+) of m/z 284 (cationic MB); (2) [MB + H + e](+•) of m/z 285 (the protonated form of a transient species resulting from the reduction of [MB](+) ); (3) [MB + 2H + 2e](+) or [leuco-MB + H](+) of m/z 286 (the protonated leuco form of MB). Aliquots of a MB solution were collected before and after the addition of a reducing agent (metallic zinc) and directly analyzed by PS-MS for identification of the predominant cationic species at different conditions. The mass spectra revealed that before the addition of the reducing agent the ion of m/z 284 (cationic MB) is the unique species. Upon the addition of the reducing agent and acid, however, the solution continuously undergo discoloration while reduced species derived directly from cationic MB (m/z 285 and 286) are detected in the mass spectra with increasing intensities. Fragmentation patterns obtained for each ionic species, i.e. [MB](+) , [MB + H + e](+•) and [leuco-MB + H](+) , shown to be consistent with the proposed structures. The PS-MS technique proved to be suitable for an in situ and 'near' real-time analysis of the dynamic equilibrium involving the redox of MB in aqueous medium. The data clearly

  14. Mineralogy of the Martian Surface: Crustal Composition to Surface Processes

    Science.gov (United States)

    Mustard, John F.

    1999-01-01

    Over the course of this award we have: 1) Completed and published the results of a study of the effects of hyperfine particles on reflectance spectra of olivine and quartz, which included the development of scattering codes. Research has also progressed in the analysis of the effects of fine particle sizes on clay spectra. 2) Completed the analysis of the mineralogy of dark regions, showed the insitu compositions are highly correlated to the SNC meteorites, and determined that the martian mantle was depleted in aluminum prior to 2-3 GA ago; Studies of the mineralogic heterogeneity of surficial materials on Mars have also been conducted. and 3) Performed initial work on the study of the physical and chemical processes likely to form and modify duricrust. This includes assessments of erosion rates, solubility and transport of iron in soil environments, and models of pedogenic crust formation.

  15. Surface processing: existing and potential applications of ultraviolet light.

    Science.gov (United States)

    Manzocco, Lara; Nicoli, Maria Cristina

    2015-01-01

    Solid foods represent optimal matrices for ultraviolet processing with effects well beyond nonthermal surface disinfection. UV radiation favors hormetic response in plant tissues and degradation of toxic compound on the product surface. Photoinduced reactions can also provide unexplored possibilities to steer structure and functionality of food biopolymers. The possibility to extensively exploit this technology will depend on availability of robust information about efficacious processing conditions and adequate strategies to completely and homogeneously process food surface.

  16. Thermal modification of activated carbon surface chemistry improves its capacity as redox mediator for azo dye reduction.

    Science.gov (United States)

    Pereira, L; Pereira, R; Pereira, M F R; van der Zee, F P; Cervantes, F J; Alves, M M

    2010-11-15

    The surface chemistry of a commercial AC (AC(0)) was selectively modified, without changing significantly its textural properties, by chemical oxidation with HNO(3) (AC(HNO3)) and O(2) (AC(O2)), and thermal treatments under H(2) (AC(H2)) or N(2) (AC(N2)) flow. The effect of modified AC on anaerobic chemical dye reduction was assayed with sulphide at different pH values 5, 7 and 9. Four dyes were tested: Acid Orange 7, Reactive Red 2, Mordant Yellow 10 and Direct Blue 71. Batch experiments with low amounts of AC (0.1 g L(-1)) demonstrated an increase of the first-order reduction rate constants, up to 9-fold, as compared with assays without AC. Optimum rates were obtained at pH 5 except for MY10, higher at pH 7. In general, rates increased with increasing the pH of point zero charge (pH(pzc)), following the trend AC(HNO3) granular biomass, AC(H2) also duplicated and increase 4.5-fold the decolourisation rates of MY10 and RR2, respectively. In this last experiment, reaction rate was independent of AC concentration in the tested range 0.1-0.6 g L(-1). Copyright © 2010 Elsevier B.V. All rights reserved.

  17. Zerodur polishing process for high surface quality and high efficiency

    International Nuclear Information System (INIS)

    Tesar, A.; Fuchs, B.

    1992-08-01

    Zerodur is a glass-ceramic composite importance in applications where temperature instabilities influence optical and mechanical performance, such as in earthbound and spaceborne telescope mirror substrates. Polished Zerodur surfaces of high quality have been required for laser gyro mirrors. Polished surface quality of substrates affects performance of high reflection coatings. Thus, the interest in improving Zerodur polished surface quality has become more general. Beyond eliminating subsurface damage, high quality surfaces are produced by reducing the amount of hydrated material redeposited on the surface during polishing. With the proper control of polishing parameters, such surfaces exhibit roughnesses of < l Angstrom rms. Zerodur polishing was studied to recommend a high surface quality polishing process which could be easily adapted to standard planetary continuous polishing machines and spindles. This summary contains information on a polishing process developed at LLNL which reproducibly provides high quality polished Zerodur surfaces at very high polishing efficiencies

  18. Redox front penetration in the fractured Toki Granite, central Japan: An analogue for redox reactions and redox buffering in fractured crystalline host rocks for repositories of long-lived radioactive waste

    International Nuclear Information System (INIS)

    Yamamoto, Koshi; Yoshida, Hidekazu; Akagawa, Fuminori; Nishimoto, Shoji; Metcalfe, Richard

    2013-01-01

    Highlights: • Deep redox front developed in orogenic granitic rock have been studied. • The process was controlled by the buffering capacity of minerals. • This is an analogue of redox front penetration into HLW repositories in Japan. - Abstract: Redox buffering is one important factor to be considered when assessing the barrier function of potential host rocks for a deep geological repository for long-lived radioactive waste. If such a repository is to be sited in fractured crystalline host rock it must be demonstrated that waste will be emplaced deeper than the maximum depth to which oxidizing waters can penetrate from the earth’s surface via fractures, during the assessment timeframe (typically 1 Ma). An analogue for penetration of such oxidizing water occurs in the Cretaceous Toki Granite of central Japan. Here, a deep redox front is developed along water-conducting fractures at a depth of 210 m below the ground surface. Detailed petrographical studies and geochemical analyses were carried out on drill core specimens of this redox front. The aim was to determine the buffering processes and behavior of major and minor elements, including rare earth elements (REEs), during redox front development. The results are compared with analytical data from an oxidized zone found along shallow fractures (up to 20 m from the surface) in the same granitic rock, in order to understand differences in elemental migration according to the depth below the ground surface of redox-front formation. Geochemical analyses by XRF and ICP-MS of the oxidized zone at 210 m depth reveal clear changes in Fe(III)/Fe(II) ratios and Ca depletion across the front, while Fe concentrations vary little. In contrast, the redox front identified along shallow fractures shows strong enrichments of Fe, Mn and trace elements in the oxidized zone compared with the fresh rock matrix. The difference can be ascribed to the changing Eh and pH of groundwater as it flows downwards in the granite, due to

  19. Auger processes in ion-surface collisions

    International Nuclear Information System (INIS)

    Zampieri, Guillermo.

    1985-01-01

    Bombardment of solid targets with low-energy noble gas ions can produce Auger electron emission from the target atoms and/or from the projectiles. In the case of Auger emission from the projectile, Auger emission was observed during the bombardment of Na, Mg, Al and Si with Ne + ions. This emission was studied as a function of the energy, incidence angle and charge state of the projectile. From the analysis, it is concluded that the emission originates in the decay in vacuum of excited and reflected Ne atoms, moving outside the surface. Auger emission was not observed during the bombardment of K, V and Ni with Ar + ions; Zr and Cs with Kr + , and Xe + ions, respectively; and Li and Be with He + ions. In the case of Auger emission from the target, studies of certain aspects of the Na, Mg and Al Auger electron emission spectra were made. The results allow to identify two components in the Auger feature, coresponding to two kinds of Auger transition. The total spectra results from the superposition of both kinds of emission. Auger spectra from K obtained during Ar + and K + bombardment of K-implanted Be, Mg, Al and Cu were also analyzed. Similar to the Na, Mg and Al Auger spectra, the K Auger feature is composed of an atomic like peak superimposed on a bandlike structure. Both components correspond to Auger transitions in K atoms with a 3p vacancy, occuring in vacuum and inside the solid, respectively. (M.E.L.) [es

  20. The Redox Code.

    Science.gov (United States)

    Jones, Dean P; Sies, Helmut

    2015-09-20

    The redox code is a set of principles that defines the positioning of the nicotinamide adenine dinucleotide (NAD, NADP) and thiol/disulfide and other redox systems as well as the thiol redox proteome in space and time in biological systems. The code is richly elaborated in an oxygen-dependent life, where activation/deactivation cycles involving O₂ and H₂O₂ contribute to spatiotemporal organization for differentiation, development, and adaptation to the environment. Disruption of this organizational structure during oxidative stress represents a fundamental mechanism in system failure and disease. Methodology in assessing components of the redox code under physiological conditions has progressed, permitting insight into spatiotemporal organization and allowing for identification of redox partners in redox proteomics and redox metabolomics. Complexity of redox networks and redox regulation is being revealed step by step, yet much still needs to be learned. Detailed knowledge of the molecular patterns generated from the principles of the redox code under defined physiological or pathological conditions in cells and organs will contribute to understanding the redox component in health and disease. Ultimately, there will be a scientific basis to a modern redox medicine.

  1. Hourly and daily variation of sediment redox potential in tidal wetland sediments

    Science.gov (United States)

    Catallo, W. James

    1999-01-01

    Variation of electrochemical oxidation-reduction (redox) potential was examined in surface salt march sediments under conditions of flooding and tidal simulation in mesocosms and field sites. Time series were generated of redox potential measured in sediment profiles at 2-10 cm depth using combination Pt-Ag/AgCl (ORP) electrodes. Redox potential data were acquired at rapid rates (1-55 samples/h) over extended periods (3-104 days) along with similar times series of temperature (water, air, soil) and pH. It was found that redox potential vaired as a result of water level changes and was unrelated to diurnal changes in temperature or pH, the latter of which changed by 370 mV redox potential decrease in under 48 hours). Attenuatoin of microbial activity by [gamma] y-radiation and toxic chemicals elimintated this response. In tidal salt marsh mesocosms where the sediment-plant assemblages were exposed to a simulated diurnal tide, redox potenial oscillations of 40-300 mV amplitude were recoded that has the same periodicity as the flood-drain cycle. Periodic redoc potential time series were observed repeatedly in sediments receiving tidal pulsing but not in those sediments exposed to static hydrological conditions. Data collected over 12 days from a coastal marsh site experiencing diurnal tides showed similar fluctuations in redox potential. Data from the experimentents indicated that (a) redox potential can be a dynamic, nonlinear variable in coastal and estuarine wetland sediments over hourly and daily scales, and the designs of biogeochemical experiments should reflect this, (b) redox potential can change rapidly and signigicantly in coastal wetland sediments in response of flooding and draining, (c) microbial community processes are primarily determinants of the time course of redox potential in wetland sediments, and elimination of inhibition of microbial activity (e.g. by pollutants) can significantly alter that behavior, and (d) fast redox potential dynamics appear

  2. Redox regulation of plant development.

    Science.gov (United States)

    Considine, Michael J; Foyer, Christine H

    2014-09-20

    We provide a conceptual framework for the interactions between the cellular redox signaling hub and the phytohormone signaling network that controls plant growth and development to maximize plant productivity under stress-free situations, while limiting growth and altering development on exposure to stress. Enhanced cellular oxidation plays a key role in the regulation of plant growth and stress responses. Oxidative signals or cycles of oxidation and reduction are crucial for the alleviation of dormancy and quiescence, activating the cell cycle and triggering genetic and epigenetic control that underpin growth and differentiation responses to changing environmental conditions. The redox signaling hub interfaces directly with the phytohormone network in the synergistic control of growth and its modulation in response to environmental stress, but a few components have been identified. Accumulating evidence points to a complex interplay of phytohormone and redox controls that operate at multiple levels. For simplicity, we focus here on redox-dependent processes that control root growth and development and bud burst. The multiple roles of reactive oxygen species in the control of plant growth and development have been identified, but increasing emphasis should now be placed on the functions of redox-regulated proteins, along with the central roles of reductants such as NAD(P)H, thioredoxins, glutathione, glutaredoxins, peroxiredoxins, ascorbate, and reduced ferredoxin in the regulation of the genetic and epigenetic factors that modulate the growth and vigor of crop plants, particularly within an agricultural context.

  3. Assessment of redox conditions based on fracture mineralogy

    International Nuclear Information System (INIS)

    Tullborg, E.L.

    1999-01-01

    The frequency and distribution of fracture minerals like calcite, Fe-oxides/hydroxides, and sulphides can be used in performance assessment since their presence reflects the redox processes that are active or have been active in the fractures. The advantage in using fracture minerals is that they undoubtedly represent conditions prior to disturbances caused by drilling or tunnel excavations. In addition, they give a continuous record from the surface to great depth. On the other hand the disadvantage is that the fracture mineral distribution is a result of both past and present processes such that the mineral distribution alone can not discriminate between old and recent processes. Nevertheless it is suggested that the fracture mineral distribution provides important information about the redox capacity in the fracture system. (author)

  4. Superhydrophobic coatings for aluminium surfaces synthesized by chemical etching process

    Directory of Open Access Journals (Sweden)

    Priya Varshney

    2016-10-01

    Full Text Available In this paper, the superhydrophobic coatings on aluminium surfaces were prepared by two-step (chemical etching followed by coating and one-step (chemical etching and coating in a single step processes using potassium hydroxide and lauric acid. Besides, surface immersion time in solutions was varied in both processes. Wettability and surface morphologies of treated aluminium surfaces were characterized using contact angle measurement technique and scanning electron microscopy, respectively. Microstructures are formed on the treated aluminium surfaces which lead to increase in contact angle of the surface (>150°. Also on increasing immersion time, contact angle further increases due to increase in size and depth of microstructures. Additionally, these superhydrophobic coatings show excellent self-cleaning and corrosion-resistant behavior. Water jet impact, floatation on water surface, and low temperature condensation tests assert the excellent water-repellent nature of coatings. Further, coatings are to be found mechanically, thermally, and ultraviolet stable. Along with, these coatings are found to be excellent regeneration ability as verified experimentally. Although aforesaid both processes generate durable and regenerable superhydrophobic aluminium surfaces with excellent self-cleaning, corrosion-resistant, and water-repellent characteristics, but one-step process is proved more efficient and less time consuming than two-step process and promises to produce superhydrophobic coatings for industrial applications.

  5. SURFACE CAST IRON STRENGTHENING USING COMBINED LASER AND ULTRASONIC PROCESSING

    Directory of Open Access Journals (Sweden)

    O. G. Devojno

    2013-01-01

    Full Text Available The paper provides an analysis of ultrasonic surface plastic deformation and subsequent laser thermal strengthening of gray cast iron parts in the regime of hardening from a solid state with the purpose to obtain strengthened surface layers of bigger depth and less roughness of the processed surface. Program complex ANSYS 11.0 has been used for calculation of temperature fields induced by laser exposure.  The appropriate regime of laser processing without surface fusion has been selected on the basis of the applied complex. The possibility of displacement in the bottom boundary of α–γ-transformation temperature  for СЧ20 with 900 °С up to 800 °С is confirmed due to preliminary ultrasonic surface plastic deformation of the surface that allows to expand technological opportunities of laser quenching  of gray  cast iron from a solid state. 

  6. Heterogeneous electron transfer of a two-centered heme protein: redox and electrocatalytic properties of surface-immobilized cytochrome C(4).

    Science.gov (United States)

    Monari, Stefano; Battistuzzi, Gianantonio; Borsari, Marco; Di Rocco, Giulia; Martini, Laura; Ranieri, Antonio; Sola, Marco

    2009-10-15

    The recombinant diheme cytochrome c(4) from the psycrophilic bacterium Pseudoalteromonas haloplanktis TAC 125 and its Met64Ala and Met164Ala variants, which feature a hydroxide ion axially bound to the heme iron at the N- and C-terminal domains, respectively, were found to exchange electrons efficiently with a gold electrode coated with a SAM of 11-mercapto-1-undecanoic acid. The mutation-induced removal of the redox equivalence of the two heme groups and changes in the net charge of the protein lobes yield two-centered protein systems with unprecedented properties in the electrode-immobilized state. The heterogeneous and intraheme electron transfer processes were characterized for these species in which the high- and low-potential heme groups are swapped over in the bilobal protein framework and experience a constrained (M64A) and unconstrained (M164A) orientation toward the electrode. The reduction thermodynamics for the native and mutated hemes were measured for the first time for a diheme cytochrome c. In the diffusing regime, they reproduce closely those for the corresponding centers in single-heme class-I cytochromes c, despite the low sequence identity. Larger differences are observed in the thermodynamics of the immobilized species and in the heterogeneous electron transfer rate constants. T-dependent kinetic measurements show that the proteins are positioned approximately 7 A from the HOOC-terminated SAM-coated electrode. Protein-electrode orientation and efficient intraheme ET enable the His,OH(-)-ligated heme A of the immobilized Met64Ala variant to carry out the reductive electrocatalysis of molecular oxygen. This system therefore constitutes a novel two-centered heme-based biocatalytic interface to be exploited for "third-generation" amperometric biosensing.

  7. Diffusion processes in bombardment-induced surface topography

    International Nuclear Information System (INIS)

    Robinson, R.S.

    1984-01-01

    The bombardment of surfaces with moderate energy ions can lead to the development of various micron-sized surface structures. These structures include ridges, ledges, flat planes, pits and cones. The causal phenomena in the production of these features are sputtering, ion reflection, redeposition of sputtered material, and surface diffusion of both impurity and target-atom species. The authors concentrate on the formation of ion bombardment-induced surface topography wherein surface diffusion is a dominant process. The most thoroughly understood aspect of this topography development is the generation of cone-like structures during sputtering. The formation of cones during sputtering has been attributed to three effects. These are: (1) the presence of asperities, defects, or micro-inclusions in the surface layers, (2) the presence of impurities on the surfaces, and (3) particular crystal orientations. (Auth.)

  8. Metabolic Control of Redox and Redox Control of Metabolism in Plants

    Science.gov (United States)

    Fernie, Alisdair R.

    2014-01-01

    Abstract Significance: Reduction-oxidation (Redox) status operates as a major integrator of subcellular and extracellular metabolism and is simultaneously itself regulated by metabolic processes. Redox status not only dominates cellular metabolism due to the prominence of NAD(H) and NADP(H) couples in myriad metabolic reactions but also acts as an effective signal that informs the cell of the prevailing environmental conditions. After relay of this information, the cell is able to appropriately respond via a range of mechanisms, including directly affecting cellular functioning and reprogramming nuclear gene expression. Recent Advances: The facile accession of Arabidopsis knockout mutants alongside the adoption of broad-scale post-genomic approaches, which are able to provide transcriptomic-, proteomic-, and metabolomic-level information alongside traditional biochemical and emerging cell biological techniques, has dramatically advanced our understanding of redox status control. This review summarizes redox status control of metabolism and the metabolic control of redox status at both cellular and subcellular levels. Critical Issues: It is becoming apparent that plastid, mitochondria, and peroxisome functions influence a wide range of processes outside of the organelles themselves. While knowledge of the network of metabolic pathways and their intraorganellar redox status regulation has increased in the last years, little is known about the interorganellar redox signals coordinating these networks. A current challenge is, therefore, synthesizing our knowledge and planning experiments that tackle redox status regulation at both inter- and intracellular levels. Future Directions: Emerging tools are enabling ever-increasing spatiotemporal resolution of metabolism and imaging of redox status components. Broader application of these tools will likely greatly enhance our understanding of the interplay of redox status and metabolism as well as elucidating and

  9. Apparatus and process for the surface treatment of carbon fibers

    Science.gov (United States)

    Paulauskas, Felix Leonard; Ozcan, Soydan; Naskar, Amit K.

    2016-05-17

    A method for surface treating a carbon-containing material in which carbon-containing material is reacted with decomposing ozone in a reactor (e.g., a hollow tube reactor), wherein a concentration of ozone is maintained throughout the reactor by appropriate selection of at least processing temperature, gas stream flow rate, reactor dimensions, ozone concentration entering the reactor, and position of one or more ozone inlets (ports) in the reactor, wherein the method produces a surface-oxidized carbon or carbon-containing material, preferably having a surface atomic oxygen content of at least 15%. The resulting surface-oxidized carbon material and solid composites made therefrom are also described.

  10. An investigation of laser processing of silica surfaces

    International Nuclear Information System (INIS)

    Weber, A.J.; Stewart, A.F.; Exarhos, G.J.; Stowell, W.K.

    1988-01-01

    An initial set of experiments has been conducted to determine the practicality of laser processing of optical substrates. In contrast to earlier work, a high average power CO 2 laser was used to flood load the entire surface of each test sample. Fused silica substrates were laser polished on both surfaces at power densities ranging from 150 to 350 W/cm 2 . During each test sequence sample surface temperatures were recorded using a thermal imaging system. Extensive pre- and post-test characterization revealed that surface roughness and scattering of bare silica surfaces were reduced while internal stress increased. Laser damage thresholds were found to increase only for certain conditions. Changes in the microstructure were observed. These preliminary experiments demonstrate that laser processing can dramatically improve the optical properties of fused silica substrates

  11. Plasma nitriding - an eco friendly surface hardening process

    International Nuclear Information System (INIS)

    Mukherjee, S.

    2015-01-01

    Surface hardening is a process of heating the metal such that the surface gets only hardened. This process is adopted for many components like gears, cams, and crankshafts, which desire high hardness on the outer surface with a softer core to withstand the shocks. So, to attain such properties processes like carburising, nitriding, flame hardening and induction hardening are employed. Amongst these processes nitriding is the most commonly used process by many industries. In nitriding process the steel material is heated to a temperature of around 550 C and then exposed to atomic nitrogen. This atomic nitrogen reacts with iron and other alloying elements and forms nitrides, which are very hard in nature. By this process both wear resistance and hardness of the product can be increased. The atomic nitrogen required for this process can be obtained using ammonia gas (gas nitriding), cyanide based salt bath (liquid nitriding) and plasma medium (plasma nitriding). However, plasma nitriding has recently received considerable industrial interest owing to its characteristic of faster nitrogen penetration, short treatment time, low process temperature, minimal distortion, low energy use and easier control of layer formation compared with conventional techniques such as gas and liquid nitriding. This process can be used for all ferrous materials including stainless steels. Plasma nitriding is carried out using a gas mixture of nitrogen and hydrogen gas at sub atmospheric pressures hence, making it eco-friendly in nature. Plasma nitriding allows modification of the surface layers and hardness profiles by changing the gas mixture and temperature. The wide applicable temperature range enables a multitude of applications, beyond the possibilities of gas or salt bath processes. This has led to numerous applications of this process in industries such as the manufacture of machine parts for plastics and food processing, packaging and tooling as well as pumps and hydraulic, machine

  12. Effects of low-pressure igneous processes and subduction on Fe3+/ΣFe and redox state of mantle eclogites from Lace (Kaapvaal craton)

    Science.gov (United States)

    Aulbach, S.; Woodland, A. B.; Vasilyev, P.; Galvez, M. E.; Viljoen, K. S.

    2017-09-01

    Reconstructing the redox state of the mantle is critical in discussing the evolution of atmospheric composition through time. Kimberlite-borne mantle eclogite xenoliths, commonly interpreted as representing former oceanic crust, may record the chemical and physical state of Archaean and Proterozoic convecting mantle sources that generated their magmatic protoliths. However, their message is generally obscured by a range of primary (igneous differentiation) and secondary processes (seawater alteration, metamorphism, metasomatism). Here, we report the Fe3+/ΣFe ratio and δ18 O in garnet from in a suite of well-characterised mantle eclogite and pyroxenite xenoliths hosted in the Lace kimberlite (Kaapvaal craton), which originated as ca. 3 Ga-old ocean floor. Fe3+/ΣFe in garnet (0.01 to 0.063, median 0.02; n = 16) shows a negative correlation with jadeite content in clinopyroxene, suggesting increased partitioning of Fe3+ into clinopyroxene in the presence of monovalent cations with which it can form coupled substitutions. Jadeite-corrected Fe3+/ΣFe in garnet shows a broad negative trend with Eu*, consistent with incompatible behaviour of Fe3+ during olivine-plagioclase accumulation in the protoliths. This trend is partially obscured by increasing Fe3+ partitioning into garnet along a conductive cratonic geotherm. In contrast, NMORB-normalised Nd/Yb - a proxy of partial melt loss from subducting oceanic crust (1) - shows no obvious correlation with Fe3+/ΣFe, nor does garnet δ18OVSMOW (5.14 to 6.21‰) point to significant seawater alteration. Median bulk-rock Fe3+/ΣFe is roughly estimated at 0.025. This observation agrees with V/Sc systematics, which collectively point to a reduced Archaean convecting mantle source to the igneous protoliths of these eclogites compared to the modern MORB source. Oxygen fugacites (fO2) relative to the fayalite-magnetite-quartz buffer (FMQ) range from Δlog ⁡ fO2 = FMQ-1.3 to FMQ-4.6. At those reducing conditions, the solubility

  13. The Redox Proteome*

    Science.gov (United States)

    Go, Young-Mi; Jones, Dean P.

    2013-01-01

    The redox proteome consists of reversible and irreversible covalent modifications that link redox metabolism to biologic structure and function. These modifications, especially of Cys, function at the molecular level in protein folding and maturation, catalytic activity, signaling, and macromolecular interactions and at the macroscopic level in control of secretion and cell shape. Interaction of the redox proteome with redox-active chemicals is central to macromolecular structure, regulation, and signaling during the life cycle and has a central role in the tolerance and adaptability to diet and environmental challenges. PMID:23861437

  14. Surface processing for bulk niobium superconducting radio frequency cavities

    Science.gov (United States)

    Kelly, M. P.; Reid, T.

    2017-04-01

    The majority of niobium cavities for superconducting particle accelerators continue to be fabricated from thin-walled (2-4 mm) polycrystalline niobium sheet and, as a final step, require material removal from the radio frequency (RF) surface in order to achieve performance needed for use as practical accelerator devices. More recently bulk niobium in the form of, single- or large-grain slices cut from an ingot has become a viable alternative for some cavity types. In both cases the so-called damaged layer must be chemically etched or electrochemically polished away. The methods for doing this date back at least four decades, however, vigorous empirical studies on real cavities and more fundamental studies on niobium samples at laboratories worldwide have led to seemingly modest improvements that, when taken together, constitute a substantial advance in the reproducibility for surface processing techniques and overall cavity performance. This article reviews the development of niobium cavity surface processing, and summarizes results of recent studies. We place some emphasis on practical details for real cavity processing systems which are difficult to find in the literature but are, nonetheless, crucial for achieving the good and reproducible cavity performance. New approaches for bulk niobium surface treatment which aim to reduce cost or increase performance, including alternate chemical recipes, barrel polishing and ‘nitrogen doping’ of the RF surface, continue to be pursued and are closely linked to the requirements for surface processing.

  15. Surface engineering of glazing materials and structures using plasma processes

    International Nuclear Information System (INIS)

    Anders, Andre; Monteiro, Othon R.

    2003-01-01

    A variety of coatings is commercially produced on a very large scale, including transparent conducting oxides and multi-layer silver-based low-emissivity and solar control coatings. A very brief review of materials and manufacturing process is presented and illustrated by ultrathin silver films and chevron copper films. Understanding the close relation between manufacturing processes and bulk and surface properties of materials is crucial for film growth and self-assembly processes

  16. Generalized kinetic model of reduction of molecular oxidant by metal containing redox

    International Nuclear Information System (INIS)

    Kravchenko, T.A.

    1986-01-01

    Present work is devoted to kinetics of reduction of molecular oxidant by metal containing redox. Constructed generalized kinetic model of redox process in the system solid redox - reagent solution allows to perform the general theoretical approach to research and to obtain new results on kinetics and mechanism of interaction of redox with oxidants.

  17. Surface topography of parallel grinding process for nonaxisymmetric aspheric lens

    International Nuclear Information System (INIS)

    Zhang Ningning; Wang Zhenzhong; Pan Ri; Wang Chunjin; Guo Yinbiao

    2012-01-01

    Workpiece surface profile, texture and roughness can be predicted by modeling the topography of wheel surface and modeling kinematics of grinding process, which compose an important part of precision grinding process theory. Parallel grinding technology is an important method for nonaxisymmetric aspheric lens machining, but there is few report on relevant simulation. In this paper, a simulation method based on parallel grinding for precision machining of aspheric lens is proposed. The method combines modeling the random surface of wheel and modeling the single grain track based on arc wheel contact points. Then, a mathematical algorithm for surface topography is proposed and applied in conditions of different machining parameters. The consistence between the results of simulation and test proves that the algorithm is correct and efficient. (authors)

  18. Plasma assisted surface coating/modification processes: An emerging technology

    Science.gov (United States)

    Spalvins, T.

    1986-01-01

    A broad understanding of the numerous ion or plasma assisted surface coating/modification processes is sought. An awareness of the principles of these processes is needed before discussing in detail the ion nitriding technology. On the basis of surface modifications arising from ion or plasma energizing and interactions, it can be broadly classified as deposition of distinct overlay coatings (sputtering-dc, radio frequency, magnetron, reactive; ion plating-diode, triode) and surface property modification without forming a discrete coating (ion implantation, ion beam mixing, laser beam irradiation, ion nitriding, ion carburizing, plasma oxidation). These techniques offer a great flexibility and are capable in tailoring desirable chemical and structural surface properties independent of the bulk properties.

  19. Plasma assisted surface coating/modification processes - An emerging technology

    Science.gov (United States)

    Spalvins, T.

    1987-01-01

    A broad understanding of the numerous ion or plasma assisted surface coating/modification processes is sought. An awareness of the principles of these processes is needed before discussing in detail the ion nitriding technology. On the basis of surface modifications arising from ion or plasma energizing and interactions, it can be broadly classified as deposition of distinct overlay coatings (sputtering-dc, radio frequency, magnetron, reactive; ion plating-diode, triode) and surface property modification without forming a discrete coating (ion implantation, ion beam mixing, laser beam irradiation, ion nitriding, ion carburizing, plasma oxidation. These techniques offer a great flexibility and are capable in tailoring desirable chemical and structural surface properties independent of the bulk properties.

  20. ANFIS Modeling of the Surface Roughness in Grinding Process

    OpenAIRE

    H. Baseri; G. Alinejad

    2011-01-01

    The objective of this study is to design an adaptive neuro-fuzzy inference system (ANFIS) for estimation of surface roughness in grinding process. The Used data have been generated from experimental observations when the wheel has been dressed using a rotary diamond disc dresser. The input parameters of model are dressing speed ratio, dressing depth and dresser cross-feed rate and output parameter is surface roughness. In the experimental procedure the grinding conditions...

  1. Structure and redox properties of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20 adsorbed on a silica surface. M05 computational study

    Directory of Open Access Journals (Sweden)

    Liudmyla K. Sviatenko

    2016-03-01

    Full Text Available The cluster approximation was applied at M05/tzvp level to model adsorption of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20 on (001 surface of α-quartz. Structures of the obtained CL-20–silica complexes confirm close to parallel orientation of the nitrocompound toward surface. The binding between CL-20 and silica surface was analyzed and bond energies were calculated applying the atoms in molecules (AIM method. Hydrogen bonds were found to significantly contribute in adsorption energy. An attaching of electron leads to significant deviation from coplanarity in complexes and to strengthening of hydrogen bonding. Redox properties of adsorbed CL-20 were compared with those of gas-phase and hydrated species by calculation of electron affinity, ionization potential, reduction Gibbs free energy, oxidation Gibbs free energy, reduction and oxidation potentials. It was shown that adsorbed CL-20 has lower ability to redox transformation as compared with hydrated one.

  2. The Combination of Vitamin K3 and Vitamin C Has Synergic Activity against Forms of Trypanosoma cruzi through a Redox Imbalance Process.

    Science.gov (United States)

    Cristina Desoti, Vânia; Lazarin-Bidóia, Danielle; Martins Ribeiro, Fabianne; Cardoso Martins, Solange; da Silva Rodrigues, Jean Henrique; Ueda-Nakamura, Tania; Vataru Nakamura, Celso; Farias Ximenes, Valdecir; de Oliveira Silva, Sueli

    2015-01-01

    Chagas' disease is an infection that is caused by the protozoan Trypanosoma cruzi, affecting millions of people worldwide. Because of severe side effects and variable efficacy, the current treatments for Chagas' disease are unsatisfactory, making the search for new chemotherapeutic agents essential. Previous studies have reported various biological activities of naphthoquinones, such as the trypanocidal and antitumor activity of vitamin K3. The combination of this vitamin with vitamin C exerted better effects against various cancer cells than when used alone. These effects have been attributed to an increase in reactive oxygen species generation. In the present study, we evaluated the activity of vitamin K3 and vitamin C, alone and in combination, against T. cruzi. The vitamin K3 + vitamin C combination exerted synergistic effects against three forms of T. cruzi, leading to morphological, ultrastructural, and functional changes by producing reactive species, decreasing reduced thiol groups, altering the cell cycle, causing lipid peroxidation, and forming autophagic vacuoles. Our hypothesis is that the vitamin K3 + vitamin C combination induces oxidative imbalance in T. cruzi, probably started by a redox cycling process that leads to parasite cell death.

  3. The Combination of Vitamin K3 and Vitamin C Has Synergic Activity against Forms of Trypanosoma cruzi through a Redox Imbalance Process.

    Directory of Open Access Journals (Sweden)

    Vânia Cristina Desoti

    Full Text Available Chagas' disease is an infection that is caused by the protozoan Trypanosoma cruzi, affecting millions of people worldwide. Because of severe side effects and variable efficacy, the current treatments for Chagas' disease are unsatisfactory, making the search for new chemotherapeutic agents essential. Previous studies have reported various biological activities of naphthoquinones, such as the trypanocidal and antitumor activity of vitamin K3. The combination of this vitamin with vitamin C exerted better effects against various cancer cells than when used alone. These effects have been attributed to an increase in reactive oxygen species generation. In the present study, we evaluated the activity of vitamin K3 and vitamin C, alone and in combination, against T. cruzi. The vitamin K3 + vitamin C combination exerted synergistic effects against three forms of T. cruzi, leading to morphological, ultrastructural, and functional changes by producing reactive species, decreasing reduced thiol groups, altering the cell cycle, causing lipid peroxidation, and forming autophagic vacuoles. Our hypothesis is that the vitamin K3 + vitamin C combination induces oxidative imbalance in T. cruzi, probably started by a redox cycling process that leads to parasite cell death.

  4. Monitoring local redox processes in LiNi0.5Mn1.5O4 battery cathode material by in operando EPR spectroscopy

    Science.gov (United States)

    Niemöller, Arvid; Jakes, Peter; Eurich, Svitlana; Paulus, Anja; Kungl, Hans; Eichel, Rüdiger-A.; Granwehr, Josef

    2018-01-01

    Despite the multitude of analytical methods available to characterize battery cathode materials, identifying the factors responsible for material aging is still challenging. We present the first investigation of transient redox processes in a spinel cathode during electrochemical cycling of a lithium ion battery by in operando electron paramagnetic resonance (EPR). The battery contains a LiNi0.5Mn1.5O4 (LNMO) spinel cathode, which is a material whose magnetic interactions are well understood. The evolution of the EPR signal in combination with electrochemical measurements shows the impact of Mn3+ on the Li+ motion inside the spinel. Moreover, state of charge dependent linewidth variations confirm the formation of a solid solution for slow cycling, which is taken over by mixed models of solid solution and two-phase formation for fast cycling due to kinetic restrictions and overpotentials. Long-term measurements for 480 h showed the stability of the investigated LNMO, but also small amounts of cathode degradation products became visible. The results point out how local, exchange mediated magnetic interactions in cathode materials are linked with battery performance and can be used for material characterization.

  5. Scaling behaviour of randomly alternating surface growth processes

    CERN Document Server

    Raychaudhuri, S

    2002-01-01

    The scaling properties of the roughness of surfaces grown by two different processes randomly alternating in time are addressed. The duration of each application of the two primary processes is assumed to be independently drawn from given distribution functions. We analytically address processes in which the two primary processes are linear and extend the conclusions to nonlinear processes as well. The growth scaling exponent of the average roughness with the number of applications is found to be determined by the long time tail of the distribution functions. For processes in which both mean application times are finite, the scaling behaviour follows that of the corresponding cyclical process in which the uniform application time of each primary process is given by its mean. If the distribution functions decay with a small enough power law for the mean application times to diverge, the growth exponent is found to depend continuously on this power-law exponent. In contrast, the roughness exponent does not depe...

  6. The influence of carrier density and doping type on lithium insertion and extraction processes at silicon surfaces

    International Nuclear Information System (INIS)

    McSweeney, W.; Lotty, O.; Glynn, C.; Geaney, H.; Holmes, J.D.; O’Dwyer, C.

    2014-01-01

    The Li + insertion and extraction characteristics at n-type and p-type Si(100) electrodes with different carrier density and doping type are investigated by cyclic voltammetry and constant current measurements. The insertion and extraction potentials are demonstrated to vary with cycling and the occurrence of an activation effect is shown in n-type electrodes where the charge capacity and voltammetric currents are found to be much higher than p-type electrodes. A rate-dependent redox process influenced by the surface region electronic density, which influences the magnitude of cyclic voltammetry current is found at Si(100) surface regions during Li insertion and extraction. At p-type Si(100) surface regions, a thin, uniform film forms at lower currents, while also showing a consistently high (>70%) Coulombic efficiency for Li extraction. The p-type Si(100) surface region does not undergo crack formation after deintercalation and the amorphization was demonstrated using transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) and Raman scattering demonstrate that highly doped n-type Si(100) retains Li as a silicide and converts to an amorphous phase as a two-step phase conversion process. The findings show the succinct dependence of Li insertion and extraction processes for uniformly doped Si(100) single crystals and how the doping type and its effect on the semiconductor-solution interface dominate Li insertion and extraction, composition, crystallinity changes and charge capacity

  7. High surface area carbon and process for its production

    Energy Technology Data Exchange (ETDEWEB)

    Romanos, Jimmy; Burress, Jacob; Pfeifer, Peter; Rash, Tyler; Shah, Parag; Suppes, Galen

    2016-12-13

    Activated carbon materials and methods of producing and using activated carbon materials are provided. In particular, biomass-derived activated carbon materials and processes of producing the activated carbon materials with prespecified surface areas and pore size distributions are provided. Activated carbon materials with preselected high specific surface areas, porosities, sub-nm (<1 nm) pore volumes, and supra-nm (1-5 nm) pore volumes may be achieved by controlling the degree of carbon consumption and metallic potassium intercalation into the carbon lattice during the activation process.

  8. Redox signaling in plants.

    Science.gov (United States)

    Foyer, Christine H; Noctor, Graham

    2013-06-01

    Our aim is to deliver an authoritative and challenging perspective of current concepts in plant redox signaling, focusing particularly on the complex interface between the redox and hormone-signaling pathways that allow precise control of plant growth and defense in response to metabolic triggers and environmental constraints and cues. Plants produce significant amounts of singlet oxygen and other reactive oxygen species (ROS) as a result of photosynthetic electron transport and metabolism. Such pathways contribute to the compartment-specific redox-regulated signaling systems in plant cells that convey information to the nucleus to regulate gene expression. Like the chloroplasts and mitochondria, the apoplast-cell wall compartment makes a significant contribution to the redox signaling network, but unlike these organelles, the apoplast has a low antioxidant-buffering capacity. The respective roles of ROS, low-molecular antioxidants, redox-active proteins, and antioxidant enzymes are considered in relation to the functions of plant hormones such as salicylic acid, jasmonic acid, and auxin, in the composite control of plant growth and defense. Regulation of redox gradients between key compartments in plant cells such as those across the plasma membrane facilitates flexible and multiple faceted opportunities for redox signaling that spans the intracellular and extracellular environments. In conclusion, plants are recognized as masters of the art of redox regulation that use oxidants and antioxidants as flexible integrators of signals from metabolism and the environment.

  9. Scaling behaviour of randomly alternating surface growth processes

    International Nuclear Information System (INIS)

    Raychaudhuri, Subhadip; Shapir, Yonathan

    2002-01-01

    The scaling properties of the roughness of surfaces grown by two different processes randomly alternating in time are addressed. The duration of each application of the two primary processes is assumed to be independently drawn from given distribution functions. We analytically address processes in which the two primary processes are linear and extend the conclusions to nonlinear processes as well. The growth scaling exponent of the average roughness with the number of applications is found to be determined by the long time tail of the distribution functions. For processes in which both mean application times are finite, the scaling behaviour follows that of the corresponding cyclical process in which the uniform application time of each primary process is given by its mean. If the distribution functions decay with a small enough power law for the mean application times to diverge, the growth exponent is found to depend continuously on this power-law exponent. In contrast, the roughness exponent does not depend on the timing of the applications. The analytical results are supported by numerical simulations of various pairs of primary processes and with different distribution functions. Self-affine surfaces grown by two randomly alternating processes are common in nature (e.g., due to randomly changing weather conditions) and in man-made devices such as rechargeable batteries

  10. Chloroplast Redox Poise

    DEFF Research Database (Denmark)

    Steccanella, Verdiana

    the redox status of the plastoquinone pool and chlorophyll biosynthesis. Furthermore, in the plant cell, the equilibrium between redox reactions and ROS signals is also maintained by various balancing mechanisms among which the thioredoxin reductase-thioredoxin system (TR-Trx) stands out as a mediator......The redox state of the chloroplast is maintained by a delicate balance between energy production and consumption and is affected by the need to avoid increased production of reactive oxygen species (ROS). Redox power and ROS generated in the chloroplast are essential for maintaining physiological...... metabolic pathways and for optimizing chloroplast functions. The redox poise of photosynthetic electron transport components like plastoquinone is crucial to initiate signaling cascades and might also be involved in key biosynthetic pathways such as chlorophyll biosynthesis. We, therefore, explored...

  11. Rechargable Lithium-Air Batteries: Investigation of Redox Mediators Using DEMS

    DEFF Research Database (Denmark)

    Christensen, Mathias Kjærgård; Storm, Mie Møller; Norby, Poul

    2016-01-01

    material or electrolyte is being decomposed. This is also seen with Thermally reduced Graphene Oxide (TrGO). The graphene based cathode is interesting as it exhibits a high surface area which in turn increases capacity. Using the additive LiI, functioning as a redox mediator, the discharge curve remains...... is observed without the redox mediator [2]. This results in higher energy densities and ideally higher cyclability due to the lower over-potentials. Using DEMS we have investigated the gas evolved in the process to determine the electron to oxygen ratio using both cathode materials mentioned. As has been...

  12. Characterization of redox conditions in groundwater contaminant plumes

    Science.gov (United States)

    Christensen, Thomas H.; Bjerg, Poul L.; Banwart, Steven A.; Jakobsen, Rasmus; Heron, Gorm; Albrechtsen, Hans-Jørgen

    2000-10-01

    Evaluation of redox conditions in groundwater pollution plumes is often a prerequisite for understanding the behaviour of the pollutants in the plume and for selecting remediation approaches. Measuring of redox conditions in pollution plumes is, however, a fairly recent issue and yet relative few cases have been reported. No standardised or generally accepted approach exists. Slow electrode kinetics and the common lack of internal equilibrium of redox processes in pollution plumes make, with a few exceptions, direct electrochemical measurement and rigorous interpretation of redox potentials dubious, if not erroneous. Several other approaches have been used in addressing redox conditions in pollution plumes: redox-sensitive compounds in groundwater samples, hydrogen concentrations in groundwater, concentrations of volatile fatty acids in groundwater, sediment characteristics and microbial tools, such as MPN counts, PLFA biomarkers and redox bioassays. This paper reviews the principles behind the different approaches, summarizes methods used and evaluates the approaches based on the experience from the reported applications.

  13. EXPERIMENTAL VALIDATION OF CUMULATIVE SURFACE LOCATION ERROR FOR TURNING PROCESSES

    Directory of Open Access Journals (Sweden)

    Adam K. Kiss

    2016-02-01

    Full Text Available The aim of this study is to create a mechanical model which is suitable to investigate the surface quality in turning processes, based on the Cumulative Surface Location Error (CSLE, which describes the series of the consecutive Surface Location Errors (SLE in roughing operations. In the established model, the investigated CSLE depends on the currently and the previously resulted SLE by means of the variation of the width of cut. The phenomenon of the system can be described as an implicit discrete map. The stationary Surface Location Error and its bifurcations were analysed and flip-type bifurcation was observed for CSLE. Experimental verification of the theoretical results was carried out.

  14. Particle dry deposition to water surfaces: Processes and consequences

    DEFF Research Database (Denmark)

    Pryor, S.C.; Barthelmie, R.J.

    2000-01-01

    flux to coastal waters, atmosphere-surface exchange represents a significant component of the total flux and may be particularly critical during the summertime when both the riverine input and ambient nutrient concentrations are often at a minimum. In this chapter, we present an overview...... of the physical and chemical processes which dictate the quantity (and direction) of atmosphere-surface fluxes of trace chemicals to (and above) water surfaces with particular emphasis on the role of particles. Dry deposition (transfer to the surface in the absence of precipitation) of particles is determined...... efforts to simulate and measure fluxes close to the coastline. These arise in part from the complexity of atmospheric flow in this region where energy and chemical fluxes are highly inhomogeneous in space and time and thermally generated atmospheric circulations are commonplace. (C) 2000 Elsevier Science...

  15. Monitoring tablet surface roughness during the film coating process

    DEFF Research Database (Denmark)

    Seitavuopio, Paulus; Heinämäki, Jyrki; Rantanen, Jukka

    2006-01-01

    The purpose of this study was to evaluate the change of surface roughness and the development of the film during the film coating process using laser profilometer roughness measurements, SEM imaging, and energy dispersive X-ray (EDX) analysis. Surface roughness and texture changes developing during...... the process of film coating tablets were studied by noncontact laser profilometry and scanning electron microscopy (SEM). An EDX analysis was used to monitor the magnesium stearate and titanium dioxide of the tablets. The tablet cores were film coated with aqueous hydroxypropyl methylcellulose, and the film...... coating was performed using an instrumented pilot-scale side-vented drum coater. The SEM images of the film-coated tablets showed that within the first 30 minutes, the surface of the tablet cores was completely covered with a thin film. The magnesium signal that was monitored by SEM-EDX disappeared after...

  16. Surface Dynamic Process Simulation with the Use of Cellular Automata

    International Nuclear Information System (INIS)

    Adamska-Szatko, M.; Bala, J.

    2010-01-01

    Cellular automata are known for many applications, especially for physical and biological simulations. Universal cellular automata can be used for modelling complex natural phenomena. The paper presents simulation of surface dynamic process. Simulation uses 2-dimensional cellular automata algorithm. Modelling and visualisation were created by in-house developed software with standard OpenGL graphic library. (authors)

  17. Redox phenomena controlling systems - a 7. framework programme collaborative project (2008-2012)

    International Nuclear Information System (INIS)

    2013-01-01

    The objective of this EURATOM collaborative project is to understand Redox phenomena controlling the long-term release/retention of radionuclides (ReCosy programme) in nuclear waste disposal and to provide tools to apply the results to safety assessment. The project has been organized into 6 task forces: 1) implications of Redox for safety, 2) development of Redox determination methods, 3) Redox response of defined and near-natural systems, 4) Redox reactions of radionuclides, 5) Redox processes in radionuclide transport, and 6) Redox reactions affecting the spent fuel source-term

  18. Processing of high level waste: Spectroscopic characterization of redox reactions in supercritical water. 1998 annual progress report

    International Nuclear Information System (INIS)

    Arrington, C.A. Jr.

    1998-01-01

    'The author is engaged in a collaborative research effort with Los Alamos staff scientists Steven Buelow, Jeanne Robinson, and Bernie Foy all staff members in group CST-6. The work proposed by these LANL staff scientists is directed towards the destruction of complexants and oxidation of chromium and technetium by hydrothermal processing in near critical or supercritical aqueous solutions. The work addresses two areas of investigation related to ongoing efforts at LANL: (1) kinetic studies of oxidation-reduction reactions in supercritical water; (2) measurement of physical properties of ionic solutes in supercritical water. All of the work during this first year was carried out at Los Alamos National Lab. During the Summer program at LANL all equipment and supplies were provided through Dr. Buelow''s program at LANL. The author has now set up a Raman spectroscopy lab at Furman. Using departmental funds he purchased an optical bench, a laser, and a CCD detector, and a grant from the Dreyfus Foundation assisted in the purchase of a Raman spectrometer. He is now able to carry out experiments using the Raman system at Furman. The plan is to continue the Summer collaboration at LANL and carry out experiments at Furman during the academic year.'

  19. Redox Biology in Neurological Function, Dysfunction, and Aging.

    Science.gov (United States)

    Franco, Rodrigo; Vargas, Marcelo R

    2018-04-23

    Reduction oxidation (redox) reactions are central to life and when altered, they can promote disease progression. In the brain, redox homeostasis is recognized to be involved in all aspects of central nervous system (CNS) development, function, aging, and disease. Recent studies have uncovered the diverse nature by which redox reactions and homeostasis contribute to brain physiology, and when dysregulated to pathological consequences. Redox reactions go beyond what is commonly described as oxidative stress and involve redox mechanisms linked to signaling and metabolism. In contrast to the nonspecific nature of oxidative damage, redox signaling involves specific oxidation/reduction reactions that regulate a myriad of neurological processes such as neurotransmission, homeostasis, and degeneration. This Forum is focused on the role of redox metabolism and signaling in the brain. Six review articles from leading scientists in the field that appraise the role of redox metabolism and signaling in different aspects of brain biology including neurodevelopment, neurotransmission, aging, neuroinflammation, neurodegeneration, and neurotoxicity are included. An original research article exemplifying these concepts uncovers a novel link between oxidative modifications, redox signaling, and neurodegeneration. This Forum highlights the recent advances in the field and we hope it encourages future research aimed to understand the mechanisms by which redox metabolism and signaling regulate CNS physiology and pathophysiology. Antioxid. Redox Signal. 00, 000-000.

  20. Hydroxylamine derivatives in the Purex Process Part VII. The redox reactive kinetics and mechanism of dimethylhydroxylamine and vanadium(V) in nitric medium

    International Nuclear Information System (INIS)

    Anyun Zhang; Institute of Research and Innovation, Chiba; Guoping Xiao; Chinese Inst. of Atomic Energy, Beijing; Jingxin Hu; Hui He

    2003-01-01

    The kinetics of the redox reaction between dimethylhydroxylamine (DMH) and vanadium(V) in nitric acid has been studied by spectrophotometry at 23.1 deg C. The rate equation of the reaction is determined as -d[V(V)]/dt=k[V(V)][DMH] by investigating the influence of the concentrations of V(V) and DMH, acidity, ionic strength and the ratio of the initial concentrations of reactants on the redox reaction. The rate constant of the reaction k = 9.95 ± 0.52 (mol/l) -1 x s -1 when the ionic strength is 1.00 mol/l. The activation energy of the reaction is 22.1 kJ/mol. A possible mechanism of the redox reaction has been suggested on the basis of an electron spin resonance(ESR) spectrum of dimethyl nitroxyl radical, (CH 3 ) 2 NO. (author)

  1. MICROSCALE METABOLIC, REDOX AND ABIOTIC REACTIONS IN HANFORD 300 AREA SUBSURFACE SEDIMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Beyenal, Haluk [WSU; McLEan, Jeff [JCVI; Majors, Paul [PNNL; Fredrickson, Jim [PNNL

    2013-11-14

    The Hanford 300 Area is a unique site due to periodic hydrologic influence of river water resulting in changes in groundwater elevation and flow direction. This area is also highly subject to uranium remobilization, the source of which is currently believed to be the region at the base of the vadose zone that is subject to period saturation due to the changes in the water levels in the Columbia River. We found that microbial processes and redox and abiotic reactions which operate at the microscale were critical to understanding factors controlling the macroscopic fate and transport of contaminants in the subsurface. The combined laboratory and field research showed how microscale conditions control uranium mobility and how biotic, abiotic and redox reactions relate to each other. Our findings extended the current knowledge to examine U(VI) reduction and immobilization using natural 300 Area communities as well as selected model organisms on redox-sensitive and redox-insensitive minerals. Using innovative techniques developed specifically to probe biogeochemical processes at the microscale, our research expanded our current understanding of the roles played by mineral surfaces, bacterial competition, and local biotic, abiotic and redox reaction rates on the reduction and immobilization of uranium.

  2. The esa earth explorer land surface processes and interactions mission

    Science.gov (United States)

    Labandibar, Jean-Yves; Jubineau, Franck; Silvestrin, Pierluigi; Del Bello, Umberto

    2017-11-01

    The European Space Agency (ESA) is defining candidate missions for Earth Observation. In the class of the Earth Explorer missions, dedicated to research and pre-operational demonstration, the Land Surface Processes and Interactions Mission (LSPIM) will acquire the accurate quantitative measurements needed to improve our understanding of the nature and evolution of biosphere-atmosphere interactions and to contribute significantly to a solution of the scaling problems for energy, water and carbon fluxes at the Earth's surface. The mission is intended to provide detailed observations of the surface of the Earth and to collect data related to ecosystem processes and radiation balance. It is also intended to address a range of issues important for environmental monitoring, renewable resources assessment and climate models. The mission involves a dedicated maneuvering satellite which provides multi-directional observations for systematic measurement of Land Surface BRDF (BiDirectional Reflectance Distribution Function) of selected sites on Earth. The satellite carries an optical payload : PRISM (Processes Research by an Imaging Space Mission), a multispectral imager providing reasonably high spatial resolution images (50 m over 50 km swath) in the whole optical spectral domain (from 450 nm to 2.35 μm with a resolution close to 10 nm, and two thermal bands from 8.1 to 9.1 μm). This paper presents the results of the Phase A study awarded by ESA, led by ALCATEL Space Industries and concerning the design of LSPIM.

  3. Integrated system of production information processing for surface mines

    Energy Technology Data Exchange (ETDEWEB)

    Li, K.; Wang, S.; Zeng, Z.; Wei, J.; Ren, Z. [China University of Mining and Technology, Xuzhou (China). Dept of Mining Engineering

    2000-09-01

    Based on the concept of geological statistic, mathematical program, condition simulation, system engineering, and the features and duties of each main department in surface mine production, an integrated system for surface mine production information was studied systematically and developed by using the technology of data warehousing, CAD, object-oriented and system integration, which leads to the systematizing and automating of the information management, data processing, optimization computing and plotting. In this paper, its overall object, system design, structure and functions and some key techniques were described. 2 refs., 3 figs.

  4. Electronic dissipation processes during chemical reactions on surfaces

    CERN Document Server

    Stella, Kevin

    2012-01-01

    Hauptbeschreibung Every day in our life is larded with a huge number of chemical reactions on surfaces. Some reactions occur immediately, for others an activation energy has to be supplied. Thus it happens that though a reaction should thermodynamically run off, it is kinetically hindered. Meaning the partners react only to the thermodynamically more stable product state within a mentionable time if the activation energy of the reaction is supplied. With the help of catalysts the activation energy of a reaction can be lowered. Such catalytic processes on surfaces are widely used in industry. A

  5. Electrically Reversible Redox-Switchable Polydopamine Films for Regulating Cell Behavior

    International Nuclear Information System (INIS)

    Tan, Guoxin; Liu, Yan; Wu, Yuxuan; Ouyang, Kongyou; Zhou, Lei; Yu, Peng; Liao, Jinwen; Ning, Chengyun

    2017-01-01

    Highlights: • The phenolic/quinone groups on polydopamine can redox-switchable reversible under electrical stimulation. • The quinone groups on PDA (oxidized PDA) enhanced cell spreading and proliferation. • The phenolic groups on PDA (reduced PDA) induced cell differentiation. - Abstract: Switchable surfaces that respond to external stimuli are important for regulating cell behavior. The results herein suggest that the redox process of polydopamine (PDA) is a switching reaction between oxidized polydopamine and reduced polydopamine, involving an interconversion of coupled two-proton (2H + ) and two-electron (2e − ) processes. The redox-switchable reversible surface potential arising from the potential-tunable redox reaction of the phenolic and quinone groups on PDA on titanium induced both cell adhesion and spreading. In vitro experiments demonstrated that the quinone groups on PDA greatly enhanced pre-osteoblasts MC3T3-E1 cell spreading and proliferation. Phenolic groups enhanced the induction of differentiation. The proposed methodology may allow further investigation of switchable surfaces for biological and medical applications.

  6. Nanostructured Electrocatalysts for All-Vanadium Redox Flow Batteries.

    Science.gov (United States)

    Park, Minjoon; Ryu, Jaechan; Cho, Jaephil

    2015-10-01

    Vanadium redox reactions have been considered as a key factor affecting the energy efficiency of the all-vanadium redox flow batteries (VRFBs). This redox reaction determines the reaction kinetics of whole cells. However, poor kinetic reversibility and catalytic activity towards the V(2+)/V(3+) and VO(2+)/VO2(+) redox couples on the commonly used carbon substrate limit broader applications of VRFBs. Consequently, modified carbon substrates have been extensively investigated to improve vanadium redox reactions. In this Focus Review, recent progress on metal- and carbon-based nanomaterials as an electrocatalyst for VRFBs is discussed in detail, without the intention to provide a comprehensive review on the whole components of the system. Instead, the focus is mainly placed on the redox chemistry of vanadium ions at a surface of various metals, different dimensional carbons, nitrogen-doped carbon nanostructures, and metal-carbon composites. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Mechanical and tribological properties of ion beam-processed surfaces

    International Nuclear Information System (INIS)

    Kodali, P.

    1998-01-01

    The intent of this work was to broaden the applications of well-established surface modification techniques and to elucidate the various wear mechanisms that occur in sliding contact of ion-beam processed surfaces. The investigation included characterization and evaluation of coatings and modified surfaces synthesized by three surface engineering methods; namely, beam-line ion implantation, plasma-source ion implantation, and DC magnetron sputtering. Correlation among measured properties such as surface hardness, fracture toughness, and wear behavior was also examined. This dissertation focused on the following areas of research: (1) investigating the mechanical and tribological properties of mixed implantation of carbon and nitrogen into single crystal silicon by beam-line implantation; (2) characterizing the mechanical and tribological properties of diamond-like carbon (DLC) coatings processed by plasma source ion implantation; and (3) developing and evaluating metastable boron-carbon-nitrogen (BCN) compound coatings for mechanical and tribological properties. The surface hardness of a mixed carbon-nitrogen implant sample improved significantly compared to the unimplanted sample. However, the enhancement in the wear factor of this sample was found to be less significant than carbon-implanted samples. The presence of nitrogen might be responsible for the degraded wear behavior since nitrogen-implantation alone resulted in no improvement in the wear factor. DLC coatings have low friction, low wear factor, and high hardness. The fracture toughness of DLC coatings has been estimated for the first time. The wear mechanism in DLC coatings investigated with a ruby slider under a contact stress of 1 GPa was determined to be plastic deformation. The preliminary data on metastable BCN compound coatings indicated high friction, low wear factor, and high hardness

  8. Carbon Redox-Polymer-Gel Hybrid Supercapacitors

    Science.gov (United States)

    Vlad, A.; Singh, N.; Melinte, S.; Gohy, J.-F.; Ajayan, P.M.

    2016-01-01

    Energy storage devices that provide high specific power without compromising on specific energy are highly desirable for many electric-powered applications. Here, we demonstrate that polymer organic radical gel materials support fast bulk-redox charge storage, commensurate to surface double layer ion exchange at carbon electrodes. When integrated with a carbon-based electrical double layer capacitor, nearly ideal electrode properties such as high electrical and ionic conductivity, fast bulk redox and surface charge storage as well as excellent cycling stability are attained. Such hybrid carbon redox-polymer-gel electrodes support unprecedented discharge rate of 1,000C with 50% of the nominal capacity delivered in less than 2 seconds. Devices made with such electrodes hold the potential for battery-scale energy storage while attaining supercapacitor-like power performances. PMID:26917470

  9. Redox processes in the rhizosphere of restored peatlands - The impact of vascular plant species on electrochemical properties of dissolved organic matter

    Science.gov (United States)

    Agethen, Svenja; Wolff, Franziska; Knorr, Klaus-Holger

    2016-04-01

    Restoration of cut over peatlands in Central Europe is challenging in a landscape overused for agriculture. Excess nutrient availability by excess fertilization triggers uncharacteristic vegetation that is one key driver for carbon cycling. Those nutrient rich systems are often dominated by graminoids, and were often found to emit substantial amounts of methane. Plants grown under nutrient rich conditions provide more labile carbon in rhizodeposition and litter that fuels methanogenesis. Such species often have aerenchyma that facilitates direct CH4 emissions to the atmosphere and therefore impair the climate cooling function of bogs. On the other hand, aerenchymatic tissue supplies oxygen to the rhizosphere, which may reduce methanogenesis or stimulate methane oxidation, as methanogenesis is a strictly anaerobic process. Which of the effects prevail is often unclear. Therefore, the aim of this study was to test the impact of different vegetation on rhizospheric redox conditions and methanogenesis, including aerenchymatic vascular plants that are dominant in restored cut over peatlands. As ombrotrophic peat is poor in inorganic electron acceptors (EAs) to suppress methanogenesis, we analyzed the electron acceptor (EACs) and electron donor capacities (EDCs) of dissolved organic matter (DOM) in the rhizosphere to understand the impact of vegetation on anaerobic organic matter degradation. We planted Juncus effusus, Eriophorum vaginatum, Eriophorum angustifolium, Sphagnum (mixture of S. magellanicum, S. papillosum, S. sec. acutifolia, 1/3 each) plus non-vegetated controls; six replicates per batch; in containers with untreated homogenized peat. The plants grow under constant conditions (20° C, 12h diurnal light cycles and 80% RH). Anoxic conditions were achieved by keeping the water table at +10 cm. For monitoring, the rhizosphere is equipped with suction and gas samplers. We measure dissolved CO2 and CH4 concentrations, inorganic EAs (NO3-, Fe(III), and SO42-) and

  10. Surface processes during purification of InP quantum dots

    Directory of Open Access Journals (Sweden)

    Natalia Mordvinova

    2014-08-01

    Full Text Available Recently, a new simple and fast method for the synthesis of InP quantum dots by using phosphine as phosphorous precursor and myristic acid as surface stabilizer was reported. Purification after synthesis is necessary to obtain samples with good optical properties. Two methods of purification were compared and the surface processes which occur during purification were studied. Traditional precipitation with acetone is accompanied by a small increase in photoluminescence. It occurs that during the purification the hydrolysis of the indium precursor takes place, which leads to a better surface passivation. The electrophoretic purification technique does not increase luminescence efficiency but yields very pure quantum dots in only a few minutes. Additionally, the formation of In(OH3 during the low temperature synthesis was explained. Purification of quantum dots is a very significant part of postsynthetical treatment that determines the properties of the material. But this subject is not sufficiently discussed in the literature. The paper is devoted to the processes that occur at the surface of quantum dots during purification. A new method of purification, electrophoresis, is investigated and described in particular.

  11. Application of Anodization Process for Cast Aluminium Surface Properties Enhancement

    Directory of Open Access Journals (Sweden)

    Włodarczyk-Fligier A.

    2016-09-01

    Full Text Available An huge interest is observed in last years in metal matrix composite, mostly light metal based, which have found their applications in many industry branches, among others in the aircraft industry, automotive-, and armaments ones, as well as in electrical engineering and electronics, where one of the most important issue is related to the corrosion resistance, especially on the surface layer of the used aluminium alloys. This elaboration presents the influence of ceramic phase on the corrosion resistance, quality of the surface layer its thickness and structure of an anodic layer formed on aluminium alloys. As test materials it was applied the aluminium alloys Al-Si-Cu and Al-Cu-Mg, for which heat treatment processes and corrosion tests were carried out. It was presented herein grindability test results and metallographic examination, as well. Hardness of the treated alloys with those ones subjected to corrosion process were compared.

  12. Estimation of surface absorptivity in laser surface heating process with experimental data

    International Nuclear Information System (INIS)

    Chen, H-T; Wu, X-Y

    2006-01-01

    This study applies a hybrid technique of the Laplace transform and finite-difference methods in conjunction with the least-squares method and experimental temperature data inside the test material to predict the unknown surface temperature, heat flux and absorptivity for various surface conditions in the laser surface heating process. In this study, the functional form of the surface temperature is unknown a priori and is assumed to be a function of time before performing the inverse calculation. In addition, the whole time domain is divided into several analysis sub-time intervals and then these unknown estimates on each analysis interval can be predicted. In order to show the accuracy of the present inverse method, comparisons are made among the present estimates, direct results and previous results, showing that the present estimates agree with the direct results for the simulated problem. However, the present estimates of the surface absorptivity deviate slightly from previous estimated results under the assumption of constant thermal properties. The effect of the surface conditions on the surface absorptivity and temperature is not negligible

  13. Probing Interfacial Processes on Graphene Surface by Mass Detection

    Science.gov (United States)

    Kakenov, Nurbek; Kocabas, Coskun

    2013-03-01

    In this work we studied the mass density of graphene, probed interfacial processes on graphene surface and examined the formation of graphene oxide by mass detection. The graphene layers were synthesized by chemical vapor deposition method on copper foils and transfer-printed on a quartz crystal microbalance (QCM). The mass density of single layer graphene was measured by investigating the mechanical resonance of the QCM. Moreover, we extended the developed technique to probe the binding dynamics of proteins on the surface of graphene, were able to obtain nonspecific binding constant of BSA protein of graphene surface in aqueous solution. The time trace of resonance signal showed that the BSA molecules rapidly saturated by filling the available binding sites on graphene surface. Furthermore, we monitored oxidation of graphene surface under oxygen plasma by tracing the changes of interfacial mass of the graphene controlled by the shifts in Raman spectra. Three regimes were observed the formation of graphene oxide which increases the interfacial mass, the release of carbon dioxide and the removal of small graphene/graphene oxide flakes. Scientific and Technological Research Council of Turkey (TUBITAK) grant no. 110T304, 109T209, Marie Curie International Reintegration Grant (IRG) grant no 256458, Turkish Academy of Science (TUBA-Gebip).

  14. New tools for redox biology: From imaging to manipulation.

    Science.gov (United States)

    Bilan, Dmitry S; Belousov, Vsevolod V

    2017-08-01

    Redox reactions play a key role in maintaining essential biological processes. Deviations in redox pathways result in the development of various pathologies at cellular and organismal levels. Until recently, studies on transformations in the intracellular redox state have been significantly hampered in living systems. The genetically encoded indicators, based on fluorescent proteins, have provided new opportunities in biomedical research. The existing indicators already enable monitoring of cellular redox parameters in different processes including embryogenesis, aging, inflammation, tissue regeneration, and pathogenesis of various diseases. In this review, we summarize information about all genetically encoded redox indicators developed to date. We provide the description of each indicator and discuss its advantages and limitations, as well as points that need to be considered when choosing an indicator for a particular experiment. One chapter is devoted to the important discoveries that have been made by using genetically encoded redox indicators. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Redox signaling in acute pancreatitis

    Science.gov (United States)

    Pérez, Salvador; Pereda, Javier; Sabater, Luis; Sastre, Juan

    2015-01-01

    Acute pancreatitis is an inflammatory process of the pancreatic gland that eventually may lead to a severe systemic inflammatory response. A key event in pancreatic damage is the intracellular activation of NF-κB and zymogens, involving also calcium, cathepsins, pH disorders, autophagy, and cell death, particularly necrosis. This review focuses on the new role of redox signaling in acute pancreatitis. Oxidative stress and redox status are involved in the onset of acute pancreatitis and also in the development of the systemic inflammatory response, being glutathione depletion, xanthine oxidase activation, and thiol oxidation in proteins critical features of the disease in the pancreas. On the other hand, the release of extracellular hemoglobin into the circulation from the ascitic fluid in severe necrotizing pancreatitis enhances lipid peroxidation in plasma and the inflammatory infiltrate into the lung and up-regulates the HIF–VEGF pathway, contributing to the systemic inflammatory response. Therefore, redox signaling and oxidative stress contribute to the local and systemic inflammatory response during acute pancreatitis. PMID:25778551

  16. Redox signaling in acute pancreatitis

    Directory of Open Access Journals (Sweden)

    Salvador Pérez

    2015-08-01

    Full Text Available Acute pancreatitis is an inflammatory process of the pancreatic gland that eventually may lead to a severe systemic inflammatory response. A key event in pancreatic damage is the intracellular activation of NF-κB and zymogens, involving also calcium, cathepsins, pH disorders, autophagy, and cell death, particularly necrosis. This review focuses on the new role of redox signaling in acute pancreatitis. Oxidative stress and redox status are involved in the onset of acute pancreatitis and also in the development of the systemic inflammatory response, being glutathione depletion, xanthine oxidase activation, and thiol oxidation in proteins critical features of the disease in the pancreas. On the other hand, the release of extracellular hemoglobin into the circulation from the ascitic fluid in severe necrotizing pancreatitis enhances lipid peroxidation in plasma and the inflammatory infiltrate into the lung and up-regulates the HIF–VEGF pathway, contributing to the systemic inflammatory response. Therefore, redox signaling and oxidative stress contribute to the local and systemic inflammatory response during acute pancreatitis.

  17. Redox Species of Redox Flow Batteries: A Review.

    Science.gov (United States)

    Pan, Feng; Wang, Qing

    2015-11-18

    Due to the capricious nature of renewable energy resources, such as wind and solar, large-scale energy storage devices are increasingly required to make the best use of the renewable power. The redox flow battery is considered suitable for large-scale applications due to its modular design, good scalability and flexible operation. The biggest challenge of the redox flow battery is the low energy density. The redox active species is the most important component in redox flow batteries, and the redox potential and solubility of redox species dictate the system energy density. This review is focused on the recent development of redox species. Different categories of redox species, including simple inorganic ions, metal complexes, metal-free organic compounds, polysulfide/sulfur and lithium storage active materials, are reviewed. The future development of redox species towards higher energy density is also suggested.

  18. Redox Species of Redox Flow Batteries: A Review

    Directory of Open Access Journals (Sweden)

    Feng Pan

    2015-11-01

    Full Text Available Due to the capricious nature of renewable energy resources, such as wind and solar, large-scale energy storage devices are increasingly required to make the best use of the renewable power. The redox flow battery is considered suitable for large-scale applications due to its modular design, good scalability and flexible operation. The biggest challenge of the redox flow battery is the low energy density. The redox active species is the most important component in redox flow batteries, and the redox potential and solubility of redox species dictate the system energy density. This review is focused on the recent development of redox species. Different categories of redox species, including simple inorganic ions, metal complexes, metal-free organic compounds, polysulfide/sulfur and lithium storage active materials, are reviewed. The future development of redox species towards higher energy density is also suggested.

  19. Detection of cracks on concrete surfaces by hyperspectral image processing

    Science.gov (United States)

    Santos, Bruno O.; Valença, Jonatas; Júlio, Eduardo

    2017-06-01

    All large infrastructures worldwide must have a suitable monitoring and maintenance plan, aiming to evaluate their behaviour and predict timely interventions. In the particular case of concrete infrastructures, the detection and characterization of crack patterns is a major indicator of their structural response. In this scope, methods based on image processing have been applied and presented. Usually, methods focus on image binarization followed by applications of mathematical morphology to identify cracks on concrete surface. In most cases, publications are focused on restricted areas of concrete surfaces and in a single crack. On-site, the methods and algorithms have to deal with several factors that interfere with the results, namely dirt and biological colonization. Thus, the automation of a procedure for on-site characterization of crack patterns is of great interest. This advance may result in an effective tool to support maintenance strategies and interventions planning. This paper presents a research based on the analysis and processing of hyper-spectral images for detection and classification of cracks on concrete structures. The objective of the study is to evaluate the applicability of several wavelengths of the electromagnetic spectrum for classification of cracks in concrete surfaces. An image survey considering highly discretized wavelengths between 425 nm and 950 nm was performed on concrete specimens, with bandwidths of 25 nm. The concrete specimens were produced with a crack pattern induced by applying a load with displacement control. The tests were conducted to simulate usual on-site drawbacks. In this context, the surface of the specimen was subjected to biological colonization (leaves and moss). To evaluate the results and enhance crack patterns a clustering method, namely k-means algorithm, is being applied. The research conducted allows to define the suitability of using clustering k-means algorithm combined with hyper-spectral images highly

  20. Novel CNC Grinding Process Control for Nanometric Surface Roughness for Aspheric Space Optical Surfaces

    Directory of Open Access Journals (Sweden)

    Jeong-Yeol Han

    2004-06-01

    Full Text Available Optics fabrication process for precision space optical parts includes bound abrasive grinding, loose abrasive lapping and polishing. The traditional bound abrasive grinding with bronze bond cupped diamond wheel leaves the machine marks of about 20 μm rms in height and the subsurface damage of about 1 μm rms in height to be removed by subsequent loose abrasive lapping. We explored an efficient quantitative control of precision CNC grinding. The machining parameters such as grain size, work-piece rotation speed and feed rate were altered while grinding the work-piece surfaces of 20-100 mm in diameter. The input grinding variables and the resulting surface quality data were used to build grinding prediction models using empirical and multi-variable regression analysis. The effectiveness of such grinding prediction models was then examined by running a series of precision CNC grinding operation with a set of controlled input variables and predicted output surface quality indicators. The experiment achieved the predictability down to ±20 nm in height and the surface roughness down to 36 nm in height. This study contributed to improvement of the process efficiency reaching directly the polishing and figuring process without the need for the loose abrasive lapping stage.

  1. Dynamics of gas-surface interactions atomic-level understanding of scattering processes at surfaces

    CERN Document Server

    Díez Muniño, Ricardo

    2013-01-01

    This book gives a representative survey of the state of the art of research on gas-surface interactions. It provides an overview of the current understanding of gas surface dynamics and, in particular, of the reactive and non-reactive processes of atoms and small molecules at surfaces. Leading scientists in the field, both from the theoretical and the experimental sides, write in this book about their most recent advances. Surface science grew as an interdisciplinary research area over the last decades, mostly because of new experimental technologies (ultra-high vacuum, for instance), as well as because of a novel paradigm, the ‘surface science’ approach. The book describes the second transformation which is now taking place pushed by the availability of powerful quantum-mechanical theoretical methods implemented numerically. In the book, experiment and theory progress hand in hand with an unprecedented degree of accuracy and control. The book presents how modern surface science targets the atomic-level u...

  2. UMTRA Surface Project management action process document: Final. Revision 2

    International Nuclear Information System (INIS)

    1996-06-01

    Title 1 of the UMTRCA authorized the DOE to undertake remedial actions at these designed sites and associated vicinity properties (VP), which contain uranium mill tailings and other residual radioactive materials (RRM) derived from the processing sites. Title 2 of the UMTRCA addresses uranium mill sites that were licensed at the time the UMTRCA was enacted. Cleanup of these Title 2 sites is the responsibility of the licensees. The cleanup of the Title 1 sites has been split into two separate projects: the Surface Project, which deals with the mill buildings, tailings, and contaminated soils at the sites and VPs; and the Ground Water Project, which is limited to the contaminated ground water at the sites. This management action process (MAP) document discusses the Uranium Mill Tailings Remedial Action (UMTRA) Surface Project. Since its inception through March 1996, the Surface Project (hereinafter called the Project) has cleaned up 16 of the 24 designated processing sites and approximately 5,000 VPs, reducing the risk to human health and the environment posed by the uranium mill tailings. Two of the 24 sites, Belfield and Bowman, North Dakota, will not be remediated at the request of the state, reducing the total number of sites to 22. By the start of FY1998, the remaining 6 processing sites and associated VPs will be cleaned up. The remedial action activities to be funded in FY1998 by the FY1998 budget request are remediation of the remaining Grand Junction, Colorado, VPs; closure of the Cheney disposal cell in Grand Junction, Colorado; and preparation of the completion reports for 4 completed sites

  3. UMTRA Surface Project management action process document: Final. Revision 2

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-06-01

    Title 1 of the UMTRCA authorized the DOE to undertake remedial actions at these designed sites and associated vicinity properties (VP), which contain uranium mill tailings and other residual radioactive materials (RRM) derived from the processing sites. Title 2 of the UMTRCA addresses uranium mill sites that were licensed at the time the UMTRCA was enacted. Cleanup of these Title 2 sites is the responsibility of the licensees. The cleanup of the Title 1 sites has been split into two separate projects: the Surface Project, which deals with the mill buildings, tailings, and contaminated soils at the sites and VPs; and the Ground Water Project, which is limited to the contaminated ground water at the sites. This management action process (MAP) document discusses the Uranium Mill Tailings Remedial Action (UMTRA) Surface Project. Since its inception through March 1996, the Surface Project (hereinafter called the Project) has cleaned up 16 of the 24 designated processing sites and approximately 5,000 VPs, reducing the risk to human health and the environment posed by the uranium mill tailings. Two of the 24 sites, Belfield and Bowman, North Dakota, will not be remediated at the request of the state, reducing the total number of sites to 22. By the start of FY1998, the remaining 6 processing sites and associated VPs will be cleaned up. The remedial action activities to be funded in FY1998 by the FY1998 budget request are remediation of the remaining Grand Junction, Colorado, VPs; closure of the Cheney disposal cell in Grand Junction, Colorado; and preparation of the completion reports for 4 completed sites.

  4. Using infrared thermography for understanding and quantifying soil surface processes

    Science.gov (United States)

    de Lima, João L. M. P.

    2017-04-01

    At present, our understanding of the soil hydrologic response is restricted by measurement limitations. In the literature, there have been repeatedly calls for interdisciplinary approaches to expand our knowledge in this field and eventually overcome the limitations that are inherent to conventional measuring techniques used, for example, for tracing water at the basin, hillslope and even field or plot scales. Infrared thermography is a versatile, accurate and fast technique of monitoring surface temperature and has been used in a variety of fields, such as military surveillance, medical diagnosis, industrial processes optimisation, building inspections and agriculture. However, many applications are still to be fully explored. In surface hydrology, it has been successfully employed as a high spatial and temporal resolution non-invasive and non-destructive imaging tool to e.g. access groundwater discharges into waterbodies or quantify thermal heterogeneities of streams. It is believed that thermal infrared imagery can grasp the spatial and temporal variability of many processes at the soil surface. Thermography interprets the heat signals and can provide an attractive view for identifying both areas where water is flowing or has infiltrated more, or accumulated temporarily in depressions or macropores. Therefore, we hope to demonstrate the potential for thermal infrared imagery to indirectly make a quantitative estimation of several hydrologic processes. Applications include: e.g. mapping infiltration, microrelief and macropores; estimating flow velocities; defining sampling strategies; identifying water sources, accumulation of waters or even connectivity. Protocols for the assessment of several hydrologic processes with the help of IR thermography will be briefly explained, presenting some examples from laboratory soil flumes and field.

  5. Influence of surface coverage on the chemical desorption process

    Energy Technology Data Exchange (ETDEWEB)

    Minissale, M.; Dulieu, F., E-mail: francois.dulieu@obspm.fr [LERMA, Université de Cergy Pontoise et Observatoire de Paris, UMR 8112 du CNRS. 5, mail Gay Lussac, 95031 Cergy Pontoise (France)

    2014-07-07

    In cold astrophysical environments, some molecules are observed in the gas phase whereas they should have been depleted, frozen on dust grains. In order to solve this problem, astrochemists have proposed that a fraction of molecules synthesized on the surface of dust grains could desorb just after their formation. Recently the chemical desorption process has been demonstrated experimentally, but the key parameters at play have not yet been fully understood. In this article, we propose a new procedure to analyze the ratio of di-oxygen and ozone synthesized after O atoms adsorption on oxidized graphite. We demonstrate that the chemical desorption efficiency of the two reaction paths (O+O and O+O{sub 2}) is different by one order of magnitude. We show the importance of the surface coverage: for the O+O reaction, the chemical desorption efficiency is close to 80% at zero coverage and tends to zero at one monolayer coverage. The coverage dependence of O+O chemical desorption is proved by varying the amount of pre-adsorbed N{sub 2} on the substrate from 0 to 1.5 ML. Finally, we discuss the relevance of the different physical parameters that could play a role in the chemical desorption process: binding energy, enthalpy of formation, and energy transfer from the new molecule to the surface or to other adsorbates.

  6. Decontamination Efficiency of Fish Bacterial Flora from Processing Surfaces

    Directory of Open Access Journals (Sweden)

    Birna Guðbjörnsdóttir

    2009-01-01

    Full Text Available There are numerous parameters that can influence bacterial decontamination during washing of machinery and equipment in a food processing establishment. Incomplete decontamination of bacteria will increase the risk of biofilm formation and consequently increase the risk of pathogen contamination or prevalence of other undesirable microorganisms such as spoilage bacteria in the processing line. The efficiency of a typical washing protocol has been determined by testing three critical parameters and their effects on bacterial decontamination. Two surface materials (plastic and stainless steel, water temperatures (7 and 25 °C and detergent concentrations (2 and 4 % were used for this purpose in combination with two types of detergents. Biofilm was prepared on the surfaces with undefined bacterial flora obtained from minced cod fillets. The bacterial flora of the biofilm was characterised by cultivation and molecular analysis of 16S rRNA genes. All different combinations of washing protocols tested were able to remove more than 99.9 % of the bacteria in the biofilm and reduce the cell number from 7 to 0 or 2 log units of bacteria/cm2. The results show that it is possible to use less diluted detergents than recommended with comparable success, and it is easier to clean surface material made of stainless steel compared to polyethylene plastic.

  7. Redox interplay between mitochondria and peroxisomes

    Directory of Open Access Journals (Sweden)

    Celien eLismont

    2015-05-01

    Full Text Available Reduction-oxidation or ‘redox’ reactions are an integral part of a broad range of cellular processes such as gene expression, energy metabolism, protein import and folding, and autophagy. As many of these processes are intimately linked with cell fate decisions, transient or chronic changes in cellular redox equilibrium are likely to contribute to the initiation and progression of a plethora of human diseases. Since a long time, it is known that mitochondria are major players in redox regulation and signaling. More recently, it has become clear that also peroxisomes have the capacity to impact redox-linked physiological processes. To serve this function, peroxisomes cooperate with other organelles, including mitochondria. This review provides a comprehensive picture of what is currently known about the redox interplay between mitochondria and peroxisomes in mammals. We first outline the pro- and antioxidant systems of both organelles and how they may function as redox signaling nodes. Next, we critically review and discuss emerging evidence that peroxisomes and mitochondria share an intricate redox-sensitive relationship and cooperate in cell fate decisions. Key issues include possible physiological roles, messengers, and mechanisms. We also provide examples of how data mining of publicly-available datasets from ‘omics’ technologies can be a powerful means to gain additional insights into potential redox signaling pathways between peroxisomes and mitochondria. Finally, we highlight the need for more studies that seek to clarify the mechanisms of how mitochondria may act as dynamic receivers, integrators, and transmitters of peroxisome-derived mediators of oxidative stress. The outcome of such studies may open up exciting new avenues for the community of researchers working on cellular responses to organelle-derived oxidative stress, a research field in which the role of peroxisomes is currently highly underestimated and an issue of

  8. Preparation of iron-deposited graphite surface for application as cathode material during electrochemical vat-dyeing process

    International Nuclear Information System (INIS)

    Anbu Kulandainathan, M.; Kiruthika, K.; Christopher, G.; Babu, K. Firoz; Muthukumaran, A.; Noel, M.

    2008-01-01

    Iron-deposited graphite surfaces were prepared, characterized and employed as cathode materials for electrochemical vat-dyeing process containing very low concentration of sodium dithionite. The electrodeposition, in presence of ammonium thiocyanate and gelatin or animal glue as binding additives, were found to give finer iron deposits for improved electrochemical dyeing application. The electrodeposits were characterized using scanning electron microscopy, electron-dispersive X-ray spectroscopy and X-ray diffraction methods, before and after electrochemical dyeing process. The electrochemical activity of the iron-deposited graphite electrodes always stored in water seems to depend on the surface-bound Fe 3+ /Fe 2+ redox species. Vat dyes like C.I. Vat Violet 1, C.I. Vat Green 1 and C.I. Vat Blue 4 could be efficiently dyed employing these above electrode materials. The colour intensity and washing fastness of the dyed fabrics were found to be equal with conventionally dyed fabrics. The electrodes could also be reused for the dyeing process

  9. Fasting, but Not Aging, Dramatically Alters the Redox Status of Cysteine Residues on Proteins in Drosophila melanogaster

    Directory of Open Access Journals (Sweden)

    Katja E. Menger

    2015-06-01

    Full Text Available Altering the redox state of cysteine residues on protein surfaces is an important response to environmental challenges. Although aging and fasting alter many redox processes, the role of cysteine residues is uncertain. To address this, we used a redox proteomic technique, oxidative isotope-coded affinity tags (OxICAT, to assess cysteine-residue redox changes in Drosophila melanogaster during aging and fasting. This approach enabled us to simultaneously identify and quantify the redox state of several hundred cysteine residues in vivo. Cysteine residues within young flies had a bimodal distribution with peaks at ∼10% and ∼85% reversibly oxidized. Surprisingly, these cysteine residues did not become more oxidized with age. In contrast, 24 hr of fasting dramatically oxidized cysteine residues that were reduced under fed conditions while also reducing cysteine residues that were initially oxidized. We conclude that fasting, but not aging, dramatically alters cysteine-residue redox status in D. melanogaster.

  10. Urbanization Process and Variation of Energy Budget of Land Surfaces

    Directory of Open Access Journals (Sweden)

    Ciro Gardi

    2007-06-01

    Full Text Available Urban areas are increasing at a rate much higher than human population growth in many part of the world; actually more than 73 towns in the world are larger than 1000 km2. The European Environmental Agency indicates an urban area average growth rate, over the last 20 years, of 20%. The urbanization process, and the consequent soil sealing, determines not only the losses of the ecological functions of the soil, but also a variation of the energy budget of land surfaces, that affect the microclimatic conditions (heat islands. The alteration of the energy budget are determined by the variations of albedo and roughness of surfaces, but especially by the net losses of evapotranspirating areas. In the present research we have assessed the variation of Parma territory energy budget, induced by the change in land use over the last 122 years. The urban area increase between 1881 and 2003 was 535%.

  11. Quantification of deexcitation processes for analyzing liquid surfaces

    International Nuclear Information System (INIS)

    Morgner, H.

    2014-01-01

    In the last two decades the mathematical tools for quantitative data evaluation have been developed for several surface spectroscopic techniques like Angular Resolved X-ray Photoelectron Spectroscopy (ARXPS), Neutral Impact Collision Ion Scattering Spectroscopy (NICISS) and Metastable Induced Electron Spectroscopy (MIES). Provided that the experimental data are of good quality, quantitative data processing can add a lot to the information that can be gained from surface spectroscopy. We give a selection of references that contain information on these methods. The emphasis of this contribution aims at providing motivation to apply quantitative data evaluation by presenting a few examples. We try to demonstrate, that careful data evaluation may lead to interesting insight into basic concepts as well as to results that are useful for practical applications

  12. Quantification of deexcitation processes for analyzing liquid surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Morgner, H., E-mail: hmorgner@rz.uni-leipzig.de

    2014-12-01

    In the last two decades the mathematical tools for quantitative data evaluation have been developed for several surface spectroscopic techniques like Angular Resolved X-ray Photoelectron Spectroscopy (ARXPS), Neutral Impact Collision Ion Scattering Spectroscopy (NICISS) and Metastable Induced Electron Spectroscopy (MIES). Provided that the experimental data are of good quality, quantitative data processing can add a lot to the information that can be gained from surface spectroscopy. We give a selection of references that contain information on these methods. The emphasis of this contribution aims at providing motivation to apply quantitative data evaluation by presenting a few examples. We try to demonstrate, that careful data evaluation may lead to interesting insight into basic concepts as well as to results that are useful for practical applications.

  13. Surface hardening of two cast irons by friction stir processing

    International Nuclear Information System (INIS)

    Fujii, Hidetoshi; Kikuchi, Toshifumi; Nogi, Kiyoshi; Yamaguchi, Yasufumi; Kiguchi, Shoji

    2009-01-01

    The Friction Stir Processing (FSP) was applied to the surface hardening of cast irons. Flake graphite cast iron (FC300) and nodular graphite cast iron (FCD700) were used to investigate the validity of this method. The matrices of the FC300 and FC700 cast irons are pearlite. The rotary tool is a 25mm diameter cylindrical tool, and the travelling speed was varied between 50 and 150mm/min in order to control the heat input at the constant rotation speed of 900rpm. As a result, it has been clarified that a Vickers hardness of about 700HV is obtained for both cast irons. It is considered that a very fine martensite structure is formed because the FSP generates the heat very locally, and a very high cooling rate is constantly obtained. When a tool without an umbo (probe) is used, the domain in which graphite is crushed and striated is minimized. This leads to obtaining a much harder sample. The hardness change depends on the size of the martensite, which can be controlled by the process conditions, such as the tool traveling speed and the load. Based on these results, it was clarified that the FSP has many advantages for cast irons, such as a higher hardness and lower distortion. As a result, no post surface heat treatment and no post machining are required to obtain the required hardness, while these processes are generally required when using the traditional methods.

  14. The microfluidic probe: operation and use for localized surface processing.

    Science.gov (United States)

    Perrault, Cecile M; Qasaimeh, Mohammad A; Juncker, David

    2009-06-04

    Microfluidic devices allow assays to be performed using minute amounts of sample and have recently been used to control the microenvironment of cells. Microfluidics is commonly associated with closed microchannels which limit their use to samples that can be introduced, and cultured in the case of cells, within a confined volume. On the other hand, micropipetting system have been used to locally perfuse cells and surfaces, notably using push-pull setups where one pipette acts as source and the other one as sink, but the confinement of the flow is difficult in three dimensions. Furthermore, pipettes are fragile and difficult to position and hence are used in static configuration only. The microfluidic probe (MFP) circumvents the constraints imposed by the construction of closed microfluidic channels and instead of enclosing the sample into the microfluidic system, the microfluidic flow can be directly delivered onto the sample, and scanned across the sample, using the MFP. . The injection and aspiration openings are located within a few tens of micrometers of one another so that a microjet injected into the gap is confined by the hydrodynamic forces of the surrounding liquid and entirely aspirated back into the other opening. The microjet can be flushed across the substrate surface and provides a precise tool for localized deposition/delivery of reagents which can be used over large areas by scanning the probe across the surface. In this video we present the microfluidic probe (MFP). We explain in detail how to assemble the MFP, mount it atop an inverted microscope, and align it relative to the substrate surface, and finally show how to use it to process a substrate surface immersed in a buffer.

  15. Interdependencies of Arctic land surface processes: A uniquely sensitive environment

    Science.gov (United States)

    Bowling, L. C.

    2007-12-01

    The circumpolar arctic drainage basin is composed of several distinct ecoregions including steppe grassland and cropland, boreal forest and tundra. Land surface hydrology throughout this diverse region shares several unique features such as dramatic seasonal runoff differences controlled by snowmelt and ice break-up; the storage of significant portions of annual precipitation as snow and in lakes and wetlands; and the effects of ephemeral and permanently frozen soils. These arctic land processes are delicately balanced with the climate and are therefore important indicators of change. The litany of recently-detected changes in the Arctic includes changes in snow precipitation, trends and seasonal shifts in river discharge, increases and decreases in the extent of surface water, and warming soil temperatures. Although not unique to the arctic, increasing anthropogenic pressures represent an additional element of change in the form of resource extraction, fire threat and reservoir construction. The interdependence of the physical, biological and social systems mean that changes in primary indicators have large implications for land cover, animal populations and the regional carbon balance, all of which have the potential to feed back and induce further change. In fact, the complex relationships between the hydrological processes that make the Artic unique also render observed historical change difficult to interpret and predict, leading to conflicting explanations. For example, a decrease in snow accumulation may provide less insulation to the underlying soil resulting in greater frost development and increased spring runoff. Similarly, melting permafrost and ground ice may lead to ground subsidence and increased surface saturation and methane production, while more complete thaw may enhance drainage and result in drier soil conditions. The threshold nature of phase change around the freezing point makes the system especially sensitive to change. In addition, spatial

  16. Redox dependent behaviour of molybdenum during magmatic processes in the terrestrial and lunar mantle: Implications for the Mo/W of the bulk silicate Moon

    Science.gov (United States)

    Leitzke, F. P.; Fonseca, R. O. C.; Sprung, P.; Mallmann, G.; Lagos, M.; Michely, L. T.; Münker, C.

    2017-09-01

    We present results of high-temperature olivine-melt, pyroxene-melt and plagioclase-melt partitioning experiments aimed at investigating the redox transition of Mo in silicate systems. Data for a series of other minor and trace elements (Sc, Ba, Sr, Cr, REE, Y, HFSE, U, Th and W) were also acquired to constrain the incorporation of Mo in silicate minerals. All experiments were carried out in vertical tube furnaces at 1 bar and temperatures ranging from ca. 1220 to 1300 °C. Oxygen fugacity was controlled via CO-CO2 gas mixtures and varied systematically from 5.5 log units below to 1.9 log units above the fayalite-magnetite-quartz (FMQ) redox buffer thereby covering the range in oxygen fugacities of terrestrial and lunar basalt genesis. Molybdenum is shown to be volatile at oxygen fugacities above FMQ and that its compatibility in pyroxene and olivine increases three orders of magnitude towards the more reducing conditions covered in this study. The partitioning results show that Mo is dominantly tetravalent at redox conditions below FMQ-4 and dominantly hexavalent at redox conditions above FMQ. Given the differences in oxidation states of the terrestrial (oxidized) and lunar (reduced) mantles, molybdenum will behave significantly differently during basalt genesis in the Earth (i.e. highly incompatible; average DMoperidotite/melt ∼ 0.008) and Moon (i.e. moderately incompatible/compatible; average DMoperidotite/melt ∼ 0.6). Thus, it is expected that Mo will strongly fractionate from W during partial melting in the lunar mantle, given that W is broadly incompatible at FMQ-5. Moreover, the depletion of Mo and the Mo/W range in lunar samples can be reproduced by simply assuming a primitive Earth-like Mo/W for the bulk silicate Moon. Such a lunar composition is in striking agreement with the Moon being derived from the primitive terrestrial mantle after core formation on Earth.

  17. Surfaces: processing, coating, decontamination, pollution, etc. Surface mastering to prevent component corrosion; Surfaces: traitement, revetements, decontamination, pollution, etc. Maitrise de la surface pour prevenir la corrosion des composants

    Energy Technology Data Exchange (ETDEWEB)

    Foucault, M. [Departement Corrosion Chimie, AREVA Centre Technique, BP 181, 71205 Le Creusot (France)

    2012-07-01

    In the primary and secondary circuits of nuclear Pressurized Water Reactors, AREVA uses several nickel-based alloys or austenitic stainless steels for the manufacture of safety components. The experience feedback of the last twenty years allows us to point out the major role hold by the component surface state in their life duration. In this paper, we present four examples of problem encountered and solved by a surface study and the definition and implementation of processes for the surface control of the repaired components. Then, we propose some ideas about the present needs in term of analysis means to improve the surface knowledge and control of the manufactured components. (author)

  18. Surface photo reaction processes using synchrotron radiation; Hoshako reiki ni yoru hyomenko hanno process

    Energy Technology Data Exchange (ETDEWEB)

    Imaizumi, Y. [Tohoku University, Sendai (Japan). Institute for Materials Research; Yoshigoe, A. [Toyohashi University of Technology, Aichi (Japan); Urisu, T. [Toyohashi University of Technology, Aichi (Japan). Institute for Molecular Science

    1997-08-20

    This paper introduces the surface photo reaction processes using synchrotron radiation, and its application. A synchrotron radiation process using soft X-rays contained in electron synchrotron radiated light as an excited light source has a possibility of high-resolution processing because of its short wave length. The radiated light can excite efficiently the electronic state of a substance, and can induce a variety of photochemical reactions. In addition, it can excite inner shell electrons efficiently. In the aspect of its application, it has been found that, if radiated light is irradiated on surfaces of solids under fluorine-based reaction gas or Cl2, the surfaces can be etched. This technology is utilized practically. With regard to radiated light excited CVD process, it may be said that anything that can be deposited by the ordinary plasma CVD process can be deposited. Its application to epitaxial crystal growth may be said a nano processing application in thickness direction, such as forming an ultra-lattice structure, the application being subjected to expectation. In micromachine fabricating technologies, a possibility is searched on application of a photo reaction process of the radiated light. 5 refs., 6 figs.

  19. Organic chemical degradation by remote study of the redox conditions

    Science.gov (United States)

    Fernandez, P. M.; Revil, A.; Binley, A. M.; Bloem, E.; French, H. K.

    2014-12-01

    Monitoring the natural (and enhanced) degradation of organic contaminants is essential for managing groundwater quality in many parts of the world. Contaminated sites often have limited access, hence non-intrusive methods for studying redox processes, which drive the degradation of organic compounds, are required. One example is the degradation of de-icing chemicals (glycols and organic salts) released to the soil near airport runways during winter. This issue has been broadly studied at Oslo airport, Gardermoen, Norway using intrusive and non-intrusive methods. Here, we report on laboratory experiments that aim to study the potential of using a self-potential, DCresistivity, and time-domain induced polarization for geochemical characterization of the degradation of Propylene Glycol (PG). PG is completely miscible in water, does not adsorb to soil particles and does not contribute to the electrical conductivity of the soil water. When the contaminant is in the unsaturated zone near the water table, the oxygen is quickly consumed and the gas exchange with the surface is insufficient to ensure aerobic degradation, which is faster than anaerobic degradation. Since biodegradation of PG is highly oxygen demanding, anaerobic pockets can exist causing iron and manganese reduction. It is hypothesised that nitrate would boost the degradation rate under such conditions. In our experiment, we study PG degradation in a sand tank. We provide the system with an electron highway to bridge zones with different redox potential. This geo-battery system is characterized by self-potential, resistivity and induced polarization anomalies. An example of preliminary results with self-potential at two different times of the experiment can be seen in the illustration. These will be supplemented with more direct information on the redox chemistry: in-situ water sampling, pH, redox potential and electrical conductivity measurements. In parallel, a series of batch experiments have been

  20. Characterization of Redox properties of humic materials

    International Nuclear Information System (INIS)

    Choppin, G.R.

    1995-01-01

    An important aspect of humic materials is the presence of stable free radicals as shown by the width of 1 H-NMR lines of humic acid in solution as well as ESR spectra of solid samples. Presumably, these are due to quinohdrone functional groups in the humic structure. These free radicals are assumed to be a source of the redox effects of humics in metal cations. Phenolic groups have also been proposed as a source of reduction potential in these substances. The reduction potential of humic material is 0.5-0.7 V (vs. the normal hydrogen electrode). In addition to this inherent redox property, humics undergo photolysis by sunlight in surface waters which results in the production of hydrogen peroxide. The latter can also result in redox reactions with metal cations. Such direct and indirect redox capability can have significant effects on the migration of reducible cations. Studies of the reduction of hexavalent actinide cations by humic acid showed the reactions Np O 2 2+ -> Np O 2 + (E 1/2 0 = 1.47 V) and Pu O 2 2+ -> Pu +4 (E 1/2 0 = 1.04 V) while U O 2 2+ was not reduced. The reduction of plutonium in sea water by humics is discussed. Evidence of the effects of redox by humic material on metal cations in natural waters and sediments are also reviewed. (authors). 16 refs., 2 figs., 1 tab

  1. Textural Analysis of Fatique Crack Surfaces: Image Pre-processing

    Directory of Open Access Journals (Sweden)

    H. Lauschmann

    2000-01-01

    Full Text Available For the fatique crack history reconstitution, new methods of quantitative microfractography are beeing developed based on the image processing and textural analysis. SEM magnifications between micro- and macrofractography are used. Two image pre-processing operatins were suggested and proved to prepare the crack surface images for analytical treatment: 1. Normalization is used to transform the image to a stationary form. Compared to the generally used equalization, it conserves the shape of brightness distribution and saves the character of the texture. 2. Binarization is used to transform the grayscale image to a system of thick fibres. An objective criterion for the threshold brightness value was found as that resulting into the maximum number of objects. Both methods were succesfully applied together with the following textural analysis.

  2. Redox Buffer Strength

    Science.gov (United States)

    de Levie, Robert

    1999-04-01

    The proper functioning of enzymes in bodily fluids requires that the pH be maintained within rather narrow limits. The first line of defense against large pH fluctuations in such fluids is the passive control provided by the presence of pH buffers. The ability of pH buffers to stabilize the pH is indicated by the buffer value b introduced in 1922 by van Slyke. It is equally important for many enzymes that the redox potential is kept within a narrow range. In that case, stability of the potential is most readily achieved with a redox buffer. In this communication we define the redox buffer strength by analogy with acid-base buffer strength.

  3. Dual Electrolytic Plasma Processing for Steel Surface Cleaning and Passivation

    Science.gov (United States)

    Yang, L.; Zhang, P.; Shi, J.; Liang, J.; Tian, W. B.; Zhang, Y. M.; Sun, Z. M.

    2017-10-01

    To remove the rust on rebars and passivate the fresh surfaces, electrodes reversing electrolytic plasma processing (EPP) was proposed and conducted in a 10 wt.% Na2CO3 aqueous solution. The morphology and the composition of the surface were investigated by SEM and XPS. Experimental results show that the rust on the surface was removed effectively by cathode EPP, and a passive film containing Cr2O3 was achieved by the succeeding anode EPP treatment, by a simple operation of reversing the bias. The corrosion resistance was evaluated in a 3.5 wt.% NaCl aqueous solution using an electrochemical workstation. In comparison, the corrosion resistance was improved by the succeeding anode EPP treatment, which is evidenced by a positive shift of the open-circuit potential, an increase in the electrochemical impedance representing the inner layer by 76.8% and the decrease in the corrosion current density by 49.6%. This is an effective and environment-friendly technique to clean and passivate rebars and similar steel materials.

  4. Land use and surface process domains on alpine hillslopes

    Science.gov (United States)

    Kuhn, Nikolaus J.; Caviezel, Chatrina; Hunziker, Matthias

    2015-04-01

    Shrubs and trees are generally considered to protect hillslopes from erosion. As a consequence, shrub encroachment on mountain pastures after abandoning grazing is not considered a threat to soils. However, the abandonment of mown or grazed grasslands causes a shift in vegetation composition and thus a change in landscape ecology and geomorphology. On many alpine slopes, current changes in land use and vegetation cover are accompanied by climate change, potentially generating a new geomorphic regime. Most of the debate focuses on the effect of land abandonment on water erosion rates. Generally, an established perennial vegetation cover improves the mechanical anchoring of the soil and the regulation of the soil water budget, including runoff generation and erosion. However, changing vegetation composition affects many other above- and below-ground properties like root density, -diversity and -geometry, soil structure, pore volume and acidity. Each combination of these properties can lead to a distinct scenario of dominating surface processes, often not reflected by common erosion risk assessment procedures. The study of soil properties along a chronosequence of green alder (alnusviridis) encroachment on the Unteralptal in central Switzerland reveals that shrub encroachment changes soil and vegetation properties towards an increase of resistance to run-off related erosion processes, but a decrease of slope stability against shallow landslides. The latter are a particular threat because of the currently increasing frequency of slide-triggering high magnitude rainfalls. The potential change of process domain on alpine pastures highlights the need for a careful use of erosion models when assessing future land use and climate scenarios. In mountains, but also other intensively managed agricultural landscapes, risk assessment without the appropriate reflection on the shifting relevance of surface processes carries the risk of missing future threats to environmental

  5. Investigation of ammonia air-surface exchange processes in a ...

    Science.gov (United States)

    Recent assessments of atmospheric deposition in North America note the increasing importance of reduced (NHx = NH3 + NH4+) forms of nitrogen (N) relative to oxidized forms. This shift in in the composition of inorganic nitrogen deposition has both ecological and policy implications. Deposition budgets developed from inferential models applied at the landscape scale, as well as regional and global chemical transport models, indicate that NH3 dry deposition contributes a significant portion of inorganic N deposition in many areas. However, the bidirectional NH3 flux algorithms employed in these models have not been extensively evaluated for North American conditions (e.g, atmospheric chemistry, meteorology, biogeochemistry). Further understanding of the processes controlling NH3 air-surface exchange in natural systems is critically needed. Based on preliminary results from the Southern Appalachian Nitrogen Deposition Study (SANDS), this presentation examines processes of NH3 air-surface exchange in a deciduous montane forest at the Coweeta Hydrologic Laboratory in western North Carolina. A combination of measurements and modeling are used to investigate net fluxes of NH3 above the forest and sources and sinks of NH3 within the canopy and forest floor. Measurements of biogeochemical NH4+ pools are used to characterize emission potential and NH3 compensation points of canopy foliage (i.e., green vegetation), leaf litter, and soil and their relation to NH3 fluxes

  6. The thioredoxin reductase--Thioredoxin redox system cleaves the interchain disulphide bond of botulinum neurotoxins on the cytosolic surface of synaptic vesicles.

    Science.gov (United States)

    Pirazzini, Marco; Azarnia Tehran, Domenico; Zanetti, Giulia; Lista, Florigio; Binz, Thomas; Shone, Clifford C; Rossetto, Ornella; Montecucco, Cesare

    2015-12-01

    Botulinum neurotoxins (BoNTs) are Janus toxins, as they are at the same time the most deadly substances known and one of the safest drugs used in human therapy. They specifically block neurotransmission at peripheral nerves through the proteolysis of SNARE proteins, i.e. the essential proteins which are the core of the neuroexocytosis machinery. Even if BoNTs are traditionally known as seven main serotypes, their actual number is much higher as each serotype exists in many different subtypes, with individual biological properties and little antigenic relations. Since BoNTs can be used as biological weapons, and the only currently available therapy is based on immunological approaches, the existence of so many different subtypes is a major safety problem. Nevertheless, all BoNT isoforms are structurally similar and intoxicate peripheral nerve endings via a conserved mechanism. They consist of two chains linked by a unique disulphide bond which must be reduced to enable their toxicity. We found that thioredoxin 1 and its reductase compose the cell redox system responsible for this reduction, and its inhibition via specific chemicals significantly reduces BoNTs activity, in vitro as well as in vivo. Such molecules can be considered as lead compounds for the development of pan-inhibitors. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Biotransformation of gabapentin in surface water matrices under different redox conditions and the occurrence of one major TP in the aquatic environment.

    Science.gov (United States)

    Henning, Nina; Kunkel, Uwe; Wick, Arne; Ternes, Thomas A

    2018-06-15

    Laboratory-scale incubation experiments in water/sediment systems were conducted to test the transformation behavior of the anticonvulsant gabapentin (GBP) under different environmental conditions (aerobic, anaerobic, with abiotic controls). GBP was transformed by biological processes as it was eliminated quickly under aerobic conditions (dissipation time 50% of initial concentration (DT 50 ): 2-7 days) whereas no decrease was observed under anaerobic conditions. Measurements via high resolution mass spectrometry (LC-Orbitrap-MS) revealed eight biological transformation products (TPs). Three of them were identified with reference standards (GBP-Lactam, TP186, TP213), while for the other five TPs tentative structures were proposed from information by MS 2 /MS 3 experiments. Furthermore, the quantitatively most relevant TP GBP-Lactam was formed via intramolecular amidation (up to 18% of initial GBP concentration). Incubation experiments with GBP-Lactam revealed a higher stability against biotic degradation (DT 50 : 12 days) in contrast to GBP, while it was stable under anaerobic and abiotic conditions. Besides GBP, GBP-Lactam was detected in surface water in the μg L -1 range. Finally, GBP and GBP-Lactam were found in potable water with concentrations up to 0.64 and 0.07 μg L -1 , respectively. According to the elevated environmental persistence of GBP-Lactam compared to GBP and its presumed enhanced toxicity, we recommend to involve GBP-Lactam into monitoring programs. Copyright © 2018 Elsevier Ltd. All rights reserved.

  8. Process for growing a film epitaxially upon an oxide surface and structures formed with the process

    Science.gov (United States)

    McKee, Rodney A.; Walker, Frederick J.

    1995-01-01

    A process and structure wherein a film comprised of a perovskite or a spinel is built epitaxially upon a surface, such as an alkaline earth oxide surface, involves the epitaxial build up of alternating constituent metal oxide planes of the perovskite or spinel. The first layer of metal oxide built upon the surface includes a metal element which provides a small cation in the crystalline structure of the perovskite or spinel, and the second layer of metal oxide built upon the surface includes a metal element which provides a large cation in the crystalline structure of the perovskite or spinel. The layering sequence involved in the film build up reduces problems which would otherwise result from the interfacial electrostatics at the first atomic layers, and these oxides can be stabilized as commensurate thin films at a unit cell thickness or grown with high crystal quality to thicknesses of 0.5-0.7 .mu.m for optical device applications.

  9. Redox-assisted Li+-storage in lithium-ion batteries

    International Nuclear Information System (INIS)

    Huang Qizhao; Wang Qing

    2016-01-01

    Interfacial charge transfer is the key kinetic process dictating the operation of lithium-ion battery. Redox-mediated charge propagations of the electronic (e − and h + ) and ionic species (Li + ) at the electrode–electrolyte interface have recently gained increasing attention for better exploitation of battery materials. This article briefly summarises the energetic and kinetic aspects of lithium-ion batteries, and reviews the recent progress on various redox-assisted Li + storage approaches. From molecular wiring to polymer wiring and from redox targeting to redox flow lithium battery, the role of redox mediators and the way of the redox species functioning in lithium-ion batteries are discussed. (topical review)

  10. MarsSI: Martian surface data processing information system

    Science.gov (United States)

    Quantin-Nataf, C.; Lozac'h, L.; Thollot, P.; Loizeau, D.; Bultel, B.; Fernando, J.; Allemand, P.; Dubuffet, F.; Poulet, F.; Ody, A.; Clenet, H.; Leyrat, C.; Harrisson, S.

    2018-01-01

    MarsSI (Acronym for Mars System of Information, https://emars.univ-lyon1.fr/MarsSI/, is a web Geographic Information System application which helps managing and processing martian orbital data. The MarsSI facility is part of the web portal called PSUP (Planetary SUrface Portal) developed by the Observatories of Paris Sud (OSUPS) and Lyon (OSUL) to provide users with efficient and easy access to data products dedicated to the martian surface. The portal proposes 1) the management and processing of data thanks to MarsSI and 2) the visualization and merging of high level (imagery, spectral, and topographic) products and catalogs via a web-based user interface (MarsVisu). The portal PSUP as well as the facility MarsVisu is detailed in a companion paper (Poulet et al., 2018). The purpose of this paper is to describe the facility MarsSI. From this application, users are able to easily and rapidly select observations, process raw data via automatic pipelines, and get back final products which can be visualized under Geographic Information Systems. Moreover, MarsSI also contains an automatic stereo-restitution pipeline in order to produce Digital Terrain Models (DTM) on demand from HiRISE (High Resolution Imaging Science Experiment) or CTX (Context Camera) pair-images. This application is funded by the European Union's Seventh Framework Programme (FP7/2007-2013) (ERC project eMars, No. 280168) and has been developed in the scope of Mars, but the design is applicable to any other planetary body of the solar system.

  11. Redox homeostasis: The Golden Mean of healthy living.

    Science.gov (United States)

    Ursini, Fulvio; Maiorino, Matilde; Forman, Henry Jay

    2016-08-01

    The notion that electrophiles serve as messengers in cell signaling is now widely accepted. Nonetheless, major issues restrain acceptance of redox homeostasis and redox signaling as components of maintenance of a normal physiological steady state. The first is that redox signaling requires sudden switching on of oxidant production and bypassing of antioxidant mechanisms rather than a continuous process that, like other signaling mechanisms, can be smoothly turned up or down. The second is the misperception that reactions in redox signaling involve "reactive oxygen species" rather than reaction of specific electrophiles with specific protein thiolates. The third is that hormesis provides protection against oxidants by increasing cellular defense or repair mechanisms rather than by specifically addressing the offset of redox homeostasis. Instead, we propose that both oxidant and antioxidant signaling are main features of redox homeostasis. As the redox shift is rapidly reversed by feedback reactions, homeostasis is maintained by continuous signaling for production and elimination of electrophiles and nucleophiles. Redox homeostasis, which is the maintenance of nucleophilic tone, accounts for a healthy physiological steady state. Electrophiles and nucleophiles are not intrinsically harmful or protective, and redox homeostasis is an essential feature of both the response to challenges and subsequent feedback. While the balance between oxidants and nucleophiles is preserved in redox homeostasis, oxidative stress provokes the establishment of a new radically altered redox steady state. The popular belief that scavenging free radicals by antioxidants has a beneficial effect is wishful thinking. We propose, instead, that continuous feedback preserves nucleophilic tone and that this is supported by redox active nutritional phytochemicals. These nonessential compounds, by activating Nrf2, mimic the effect of endogenously produced electrophiles (parahormesis). In summary

  12. Redox homeostasis: The Golden Mean of healthy living

    Directory of Open Access Journals (Sweden)

    Fulvio Ursini

    2016-08-01

    Full Text Available The notion that electrophiles serve as messengers in cell signaling is now widely accepted. Nonetheless, major issues restrain acceptance of redox homeostasis and redox signaling as components of maintenance of a normal physiological steady state. The first is that redox signaling requires sudden switching on of oxidant production and bypassing of antioxidant mechanisms rather than a continuous process that, like other signaling mechanisms, can be smoothly turned up or down. The second is the misperception that reactions in redox signaling involve “reactive oxygen species” rather than reaction of specific electrophiles with specific protein thiolates. The third is that hormesis provides protection against oxidants by increasing cellular defense or repair mechanisms rather than by specifically addressing the offset of redox homeostasis. Instead, we propose that both oxidant and antioxidant signaling are main features of redox homeostasis. As the redox shift is rapidly reversed by feedback reactions, homeostasis is maintained by continuous signaling for production and elimination of electrophiles and nucleophiles. Redox homeostasis, which is the maintenance of nucleophilic tone, accounts for a healthy physiological steady state. Electrophiles and nucleophiles are not intrinsically harmful or protective, and redox homeostasis is an essential feature of both the response to challenges and subsequent feedback. While the balance between oxidants and nucleophiles is preserved in redox homeostasis, oxidative stress provokes the establishment of a new radically altered redox steady state. The popular belief that scavenging free radicals by antioxidants has a beneficial effect is wishful thinking. We propose, instead, that continuous feedback preserves nucleophilic tone and that this is supported by redox active nutritional phytochemicals. These nonessential compounds, by activating Nrf2, mimic the effect of endogenously produced electrophiles

  13. Redox proteomics of tomato in response to Pseudomonas syringae infection

    Science.gov (United States)

    Balmant, Kelly Mayrink; Parker, Jennifer; Yoo, Mi-Jeong; Zhu, Ning; Dufresne, Craig; Chen, Sixue

    2015-01-01

    Unlike mammals with adaptive immunity, plants rely on their innate immunity based on pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) for pathogen defense. Reactive oxygen species, known to play crucial roles in PTI and ETI, can perturb cellular redox homeostasis and lead to changes of redox-sensitive proteins through modification of cysteine sulfhydryl groups. Although redox regulation of protein functions has emerged as an important mechanism in several biological processes, little is known about redox proteins and how they function in PTI and ETI. In this study, cysTMT proteomics technology was used to identify similarities and differences of protein redox modifications in tomato resistant (PtoR) and susceptible (prf3) genotypes in response to Pseudomonas syringae pv tomato (Pst) infection. In addition, the results of the redox changes were compared and corrected with the protein level changes. A total of 90 potential redox-regulated proteins were identified with functions in carbohydrate and energy metabolism, biosynthesis of cysteine, sucrose and brassinosteroid, cell wall biogenesis, polysaccharide/starch biosynthesis, cuticle development, lipid metabolism, proteolysis, tricarboxylic acid cycle, protein targeting to vacuole, and oxidation–reduction. This inventory of previously unknown protein redox switches in tomato pathogen defense lays a foundation for future research toward understanding the biological significance of protein redox modifications in plant defense responses. PMID:26504582

  14. Optimization of vibratory welding process parameters using response surface methodology

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Pravin Kumar; Kumar, S. Deepak; Patel, D.; Prasad, S. B. [National Institute of Technology Jamshedpur, Jharkhand (India)

    2017-05-15

    The current investigation was carried out to study the effect of vibratory welding technique on mechanical properties of 6 mm thick butt welded mild steel plates. A new concept of vibratory welding technique has been designed and developed which is capable to transfer vibrations, having resonance frequency of 300 Hz, into the molten weld pool before it solidifies during the Shielded metal arc welding (SMAW) process. The important process parameters of vibratory welding technique namely welding current, welding speed and frequency of the vibrations induced in molten weld pool were optimized using Taguchi’s analysis and Response surface methodology (RSM). The effect of process parameters on tensile strength and hardness were evaluated using optimization techniques. Applying RSM, the effect of vibratory welding parameters on tensile strength and hardness were obtained through two separate regression equations. Results showed that, the most influencing factor for the desired tensile strength and hardness is frequency at its resonance value, i.e. 300 Hz. The micro-hardness and microstructures of the vibratory welded joints were studied in detail and compared with those of conventional SMAW joints. Comparatively, uniform and fine grain structure has been found in vibratory welded joints.

  15. Ascorbate oxidase-dependent changes in the redox state of the apoplast modulate gene transcript accumulation leading to modified hormone signaling and orchestration of defense processes in tobacco.

    Science.gov (United States)

    Pignocchi, Cristina; Kiddle, Guy; Hernández, Iker; Foster, Simon J; Asensi, Amparo; Taybi, Tahar; Barnes, Jeremy; Foyer, Christine H

    2006-06-01

    The role of the redox state of the apoplast in hormone responses, signaling cascades, and gene expression was studied in transgenic tobacco (Nicotiana tabacum) plants with modified cell wall-localized ascorbate oxidase (AO). High AO activity specifically decreased the ascorbic acid (AA) content of the apoplast and altered plant growth responses triggered by hormones. Auxin stimulated shoot growth only when the apoplastic AA pool was reduced in wild-type or AO antisense lines. Oxidation of apoplastic AA in AO sense lines was associated with loss of the auxin response, higher mitogen-activated protein kinase activities, and susceptibility to a virulent strain of the pathogen Pseudomonas syringae. The total leaf glutathione pool, the ratio of reduced glutathione to glutathione disulfide, and glutathione reductase activities were similar in the leaves of all lines. However, AO sense leaves exhibited significantly lower dehydroascorbate reductase and ascorbate peroxidase activities than wild-type and antisense leaves. The abundance of mRNAs encoding antioxidant enzymes was similar in all lines. However, the day/night rhythms in the abundance of transcripts encoding the three catalase isoforms were changed in response to the AA content of the apoplast. Other transcripts influenced by AO included photorespiratory genes and a plasma membrane Ca(2+) channel-associated gene. We conclude that the redox state of the apoplast modulates plant growth and defense responses by regulating signal transduction cascades and gene expression patterns. Hence, AO activity, which modulates the redox state of the apoplastic AA pool, strongly influences the responses of plant cells to external and internal stimuli.

  16. Broad beam ion sources and some surface processes

    International Nuclear Information System (INIS)

    Neumann, H.; Scholze, F.; Tarz, M.; Schindler, A.; Wiese, R.; Nestler, M.; Blum, T.

    2005-01-01

    Modern broad-beam multi-aperture ion sources are widely used in material and surface technology applications. Customizing the generated ion beam properties (i. e. the ion current density profile) for specific demands of the application is a main challenge in the improvement of the ion beam technologies. First we introduce ion sources based on different plasma excitation principles shortly. An overview of source plasma and ion beam measurement methods deliver input data for modelling methods. This beam profile modelling using numerical trajectory codes and the validation of the results by Faraday cup measurements as a basis for ion beam profile design are described. Furthermore possibilities for ex situ and in situ beam profile control are demonstrated, like a special method for in situ control of a linear ion source beam profile, a grid modification for circular beam profile design and a cluster principle for broad beam sources. By means of these methods, the beam shape may be adapted to specific technological demands. Examples of broad beam source application in ion beam figuring of optical surfaces, modification of stainless steel, photo voltaic processes and deposition of EUVL-multilayer stacks are finally presented. (Author)

  17. Use of Radiotracers to Study Surface Water Processes

    International Nuclear Information System (INIS)

    2015-03-01

    This publication represents a sound knowledge base for the conduct of radiotracer studies in the environment, with papers on radiotracer methodology, radiation protection and regulation, data analysis and modelling. Environmental case histories from five Member States - Australia, Brazil, France, the Republic of Korea and Sweden - provide information on conducting studies involving he use of radioactive tracers. These case histories are not meant as guidelines for preparing a field study but can rather serve as examples of the type, caution and extent of work involved in environmental studies using radiotracers. This publication can provide guidance for conducting potential future training events in the use of radioactive traces in the environment and can serve as a key reference to all concerned directly with surface water processes

  18. Compartmentation of redox metabolism in malaria parasites.

    Directory of Open Access Journals (Sweden)

    Sebastian Kehr

    Full Text Available Malaria, caused by the apicomplexan parasite Plasmodium, still represents a major threat to human health and welfare and leads to about one million human deaths annually. Plasmodium is a rapidly multiplying unicellular organism undergoing a complex developmental cycle in man and mosquito - a life style that requires rapid adaptation to various environments. In order to deal with high fluxes of reactive oxygen species and maintain redox regulatory processes and pathogenicity, Plasmodium depends upon an adequate redox balance. By systematically studying the subcellular localization of the major antioxidant and redox regulatory proteins, we obtained the first complete map of redox compartmentation in Plasmodium falciparum. We demonstrate the targeting of two plasmodial peroxiredoxins and a putative glyoxalase system to the apicoplast, a non-photosynthetic plastid. We furthermore obtained a complete picture of the compartmentation of thioredoxin- and glutaredoxin-like proteins. Notably, for the two major antioxidant redox-enzymes--glutathione reductase and thioredoxin reductase--Plasmodium makes use of alternative-translation-initiation (ATI to achieve differential targeting. Dual localization of proteins effected by ATI is likely to occur also in other Apicomplexa and might open new avenues for therapeutic intervention.

  19. Multi-surface topography targeted plateau honing for the processing of cylinder liner surfaces of automotive engines

    Science.gov (United States)

    Lawrence, K. Deepak; Ramamoorthy, B.

    2016-03-01

    Cylinder bores of automotive engines are 'engineered' surfaces that are processed using multi-stage honing process to generate multiple layers of micro geometry for meeting the different functional requirements of the piston assembly system. The final processed surfaces should comply with several surface topographic specifications that are relevant for the good tribological performance of the engine. Selection of the process parameters in three stages of honing to obtain multiple surface topographic characteristics simultaneously within the specification tolerance is an important module of the process planning and is often posed as a challenging task for the process engineers. This paper presents a strategy by combining the robust process design and gray-relational analysis to evolve the operating levels of honing process parameters in rough, finish and plateau honing stages targeting to meet multiple surface topographic specifications on the final running surface of the cylinder bores. Honing experiments were conducted in three stages namely rough, finish and plateau honing on cast iron cylinder liners by varying four honing process parameters such as rotational speed, oscillatory speed, pressure and honing time. Abbott-Firestone curve based functional parameters (Rk, Rpk, Rvk, Mr1 and Mr2) coupled with mean roughness depth (Rz, DIN/ISO) and honing angle were measured and identified as the surface quality performance targets to be achieved. The experimental results have shown that the proposed approach is effective to generate cylinder liner surface that would simultaneously meet the explicit surface topographic specifications currently practiced by the industry.

  20. Formation and properties of electroactive fullerene based films with a covalently attached ferrocenyl redox probe

    International Nuclear Information System (INIS)

    Wysocka-Zolopa, Monika; Winkler, Krzysztof; Caballero, Ruben; Langa, Fernando

    2011-01-01

    Highlights: → Formation of redox active films of ferrocene derivatives of C 60 and palladium. → Fullerene moieties are covalently bonded to palladium atoms to form a polymeric network. → Electrochemical activity at both positive and negative potentials. → Charge transfer processes accompanied by transport of supporting electrolyte to and from the polymer layers. - Abstract: Redox active films have been produced via electrochemical reduction in a solution containing palladium(II) acetate and ferrocene derivatives of C 60 (Fc-C 60 and bis-Fc-C 60 ). In these films, fullerene moieties are covalently bonded to palladium atoms to form a polymeric network. Fc-C 60 /Pd and bis-Fc-C 60 /Pd films form uniform and relatively smooth layers on the electrode surface. These films are electrochemically active in both the positive and negative potential regions. At negative potentials, reduction of fullerene moiety takes place resulting in voltammetric behavior resembles typical of conducting polymers. In the positive potential range, oxidation of ferrocene is responsible for the formation of a sharp and symmetrical peak on the voltammograms. In this potential range, studied films behave as typical redox polymers. The charge associated with the oxidation process depends on the number of ferrocene units attached to the C 60 moiety. Oxidation and reduction of these redox active films are accompanied by transport of supporting electrolyte to and from the polymer layer. Films also show a higher permeability to anions than to cations.

  1. Gestalten of today: early processing of visual contours and surfaces.

    Science.gov (United States)

    Kovács, I

    1996-12-01

    While much is known about the specialized, parallel processing streams of low-level vision that extract primary visual cues, there is only limited knowledge about the dynamic interactions between them. How are the fragments, caught by local analyzers, assembled together to provide us with a unified percept? How are local discontinuities in texture, motion or depth evaluated with respect to object boundaries and surface properties? These questions are presented within the framework of orientation-specific spatial interactions of early vision. Key observations of psychophysics, anatomy and neurophysiology on interactions of various spatial and temporal ranges are reviewed. Aspects of the functional architecture and possible neural substrates of local orientation-specific interactions are discussed, underlining their role in the integration of information across the visual field, and particularly in contour integration. Examples are provided demonstrating that global context, such as contour closure and figure-ground assignment, affects these local interactions. It is illustrated that figure-ground assignment is realized early in visual processing, and that the pattern of early interactions also brings about an effective and sparse coding of visual shape. Finally, it is concluded that the underlying functional architecture is not only dynamic and context dependent, but the pattern of connectivity depends as much on past experience as on actual stimulation.

  2. Process for integrating surface drainage constraints on mine planning

    Energy Technology Data Exchange (ETDEWEB)

    Sawatsky, L.F; Ade, F.L.; McDonald, D.M.; Pullman, B.J. [Golder Associates Ltd., Calgary, AB (Canada)

    2009-07-01

    Surface drainage for mine closures must be considered during all phases of mine planning and design in order to minimize environmental impacts and reduce costs. This paper discussed methods of integrating mine drainage criteria and associated mine planning constraints into the mine planning process. Drainage constraints included stream diversions; fish compensation channels; collection receptacles for the re-use of process water; separation of closed circuit water from fresh water; and the provision of storage ponds. The geomorphic approach replicated the ability of natural channels to respond to local and regional changes in hydrology as well as channel disturbances from extreme flood events, sedimentation, debris, ice jams, and beaver activity. The approach was designed to enable a sustainable system and provide conveyance capacity for extreme floods without spillage to adjacent watersheds. Channel dimensions, bank and bed materials, sediment loads, bed material supplies and the hydrologic conditions of the analogue stream were considered. Hydrologic analyses were conducted to determine design flood flow. Channel routes, valley slopes, sinuosity, width, and depth were established. It was concluded that by incorporating the geomorphic technique, mine operators and designers can construct self-sustaining drainage systems that require little or no maintenance in the long-term. 7 refs.

  3. Redox regulation in cancer stem cells

    Science.gov (United States)

    Reactive oxygen species (ROS) and ROS-dependent (redox regulation) signaling pathways and transcriptional activities are thought to be critical in stem cell self-renewal and differentiation during growth and organogenesis. Aberrant ROS burst and dysregulation of those ROS-dependent cellular processe...

  4. Adsorption behavior of redox-active suppressor additives: Combined electrochemical and STM studies

    International Nuclear Information System (INIS)

    Hai, N.T.M.; Huynh, T.M.T.; Fluegel, A.; Mayer, D.; Broekmann, P.

    2011-01-01

    Highlights: → Janus Green B and safranine are prototypical redox-active leveler additives for copper electroplating. → Their redox-transitions lie within the copper potential window. → Reduced additives are identified as active species for the leveling effect. → Electro-reduction affects in particular the central aromatic cores of the additives. - Abstract: The redox chemistry and the related surface phase behavior of Safranine (SAF) and Janus Green B (JGB) have been studied by means of cyclic voltammetry in combination with in situ Scanning Tunneling Microscopy using HOPG (Highly Oriented Pyrolytic Graphite) and single crystalline Cu(1 0 0) as model substrates, both revealing different widths of the accessible potential windows. JGB and SAF serve as prototypical heterocyclic suppressor/leveler additives that are used for the metallization of 3D-TSVs (3D Through Silicon Vias) following a classical 'leveling' concept. SAF can be considered as the reductive decomposition product of JGB that is formed at the copper/electrolyte interface upon electroplating. Both additives reveal a pronounced pH-dependent redox-chemistry with redox-transitions lying close to or even beyond the anodic limit of the copper potential window. Affected by these redox-processes are in particular the aromatic cores of those heterocycles that can be (quasi)reversibly reduced by a two electron transfer process within the potential window of copper. Therefore we identify the reduced form of those dyes as the active components for the suppressing/leveling effect in copper plating. STM data clearly shows a dye surface phase behavior that is crucially determined by its potential-dependent redox-chemistry. This will be exemplarily discussed for the SAF dye. On chloride-modified Cu(1 0 0) mono-reduced SAF forms a structurally well-defined monolayer of cationic stacking polymers. However, this coupled anion/cation layer reveals only minor suppressing capabilities with respect to the copper

  5. 4"t"h Annual workshop proceedings of the collaborative project ''Redox phenomena controlling systems'' (7"t"h EC FP CP RECOSY)

    International Nuclear Information System (INIS)

    Altmaier, Marcus; Kienzler, Bernhard; Duro, Lara; Grive, Mireia; Montoya, Vanessa

    2012-01-01

    The EURATOM 7"t"h EC Framework Program Collaborative Project REdox phenomena Controlling SYstems (RECOSY) started in April 2008 and extends over 4 years. Although redox is not a new geochemical issue, different questions are still not resolved. For this reason, main objectives of RECOSY project are a) the sound understanding of redox phenomena controlling the long-term release/retention of radionuclides in nuclear waste disposal, b) providing tools to apply the result to Performance Assessment/Safety Case, c) training of next generation and d) documentation and communication of the results. To this aim, the project set up a consortium of 32 Beneficiaries/Contractors and 6 Associated Groups. The consortium includes key European Research Institutes, Universities, National Waste Management Agencies and SMEs, from 13 EURATOM signatory states, Russia, Japan, Korea, USA and one European Joint Research Centre. The ReCosy concept is innovative in the scientific approach to the redox phenomena. It includes i) advanced analytical tools, ii) investigations of processes responsible for redox control (thermodynamically and kinetically controlled processes, surface reactions and microbial processes,..), iii) provision of required data on redox controlling processes, and iv) response to disturbances in disposal systems. The work program is structured along six RTD workpackages (WP1-6). They cover near-field and far field aspects as well as all relevant host-rocks considered in Europe. In WP1, the scientific state-of-the-art and its application to Performance Assessment/Safety Case is documented and regularly updated. WP2 focuses on development of redox determination methods. WP3 focuses on redox response of defined and near-natural systems. WP4 studies the redox reactions of radionuclides. WP5 focuses on Redox processes in radionuclide transport and WP6 deals with redox reactions affecting the spent fuel source-term. Specific workpackages on knowledge management, education and

  6. 4{sup th} Annual workshop proceedings of the collaborative project ''Redox phenomena controlling systems'' (7{sup th} EC FP CP RECOSY)

    Energy Technology Data Exchange (ETDEWEB)

    Altmaier, Marcus; Kienzler, Bernhard; Duro, Lara; Grive, Mireia; Montoya, Vanessa (eds.)

    2012-07-01

    The EURATOM 7{sup th} EC Framework Program Collaborative Project REdox phenomena Controlling SYstems (RECOSY) started in April 2008 and extends over 4 years. Although redox is not a new geochemical issue, different questions are still not resolved. For this reason, main objectives of RECOSY project are a) the sound understanding of redox phenomena controlling the long-term release/retention of radionuclides in nuclear waste disposal, b) providing tools to apply the result to Performance Assessment/Safety Case, c) training of next generation and d) documentation and communication of the results. To this aim, the project set up a consortium of 32 Beneficiaries/Contractors and 6 Associated Groups. The consortium includes key European Research Institutes, Universities, National Waste Management Agencies and SMEs, from 13 EURATOM signatory states, Russia, Japan, Korea, USA and one European Joint Research Centre. The ReCosy concept is innovative in the scientific approach to the redox phenomena. It includes i) advanced analytical tools, ii) investigations of processes responsible for redox control (thermodynamically and kinetically controlled processes, surface reactions and microbial processes,..), iii) provision of required data on redox controlling processes, and iv) response to disturbances in disposal systems. The work program is structured along six RTD workpackages (WP1-6). They cover near-field and far field aspects as well as all relevant host-rocks considered in Europe. In WP1, the scientific state-of-the-art and its application to Performance Assessment/Safety Case is documented and regularly updated. WP2 focuses on development of redox determination methods. WP3 focuses on redox response of defined and near-natural systems. WP4 studies the redox reactions of radionuclides. WP5 focuses on Redox processes in radionuclide transport and WP6 deals with redox reactions affecting the spent fuel source-term. Specific workpackages on knowledge management, education

  7. A genome-wide screen in yeast identifies specific oxidative stress genes required for the maintenance of sub-cellular redox homeostasis

    NARCIS (Netherlands)

    Ayer, A.; Fellermeier, S.; Fife, C.; Li, S.S.; Smits, G.; Meyer, A.J.; Dawes, I.W.; Perrone, G.G.

    2012-01-01

    Maintenance of an optimal redox environment is critical for appropriate functioning of cellular processes and cell survival. Despite the importance of maintaining redox homeostasis, it is not clear how the optimal redox potential is sensed and set, and the processes that impact redox on a

  8. Surface passivation process of compound semiconductor material using UV photosulfidation

    Science.gov (United States)

    Ashby, Carol I. H.

    1995-01-01

    A method for passivating compound semiconductor surfaces by photolytically disrupting molecular sulfur vapor with ultraviolet radiation to form reactive sulfur which then reacts with and passivates the surface of compound semiconductors.

  9. New lab scale approaches for quantification of redox conditions

    Science.gov (United States)

    Fernandez, P. M.; Dathe, A.; Nadeem, S.; Bakken, L. R.; Bloem, E.; French, H. K.; Binley, A. M.

    2013-12-01

    Degradation of organic chemicals in the unsaturated zone is a process highly relevant for developing remediation techniques for protecting groundwater. Degradation causes changes in chemical composition of the water phase and gas releases. These changes can potentially be mapped with electrical resistivity measurements in the bulk soil and gas measurements at the soil surface. The redox potential combined with the local geological conditions determines the composition of available electron acceptors as well as microbial degradation pathways and how the soil system is affected in the long term. After oxygen and nitrate are depleted, manganese and iron should be reduced. However, in experiments conducted in the unsaturated zone at Gardermoen airport, Norway, it was found that for the degradation of the de-icing agent propylene glycol (PG), manganese and iron were preferred over nitrate as electron acceptor. A key hypothesis for the work presented is that for a designated soil, the redox potential affects gas releases and soil solution composition profoundly. As the redox potential decreases, the reactants of the degradation change and therefore the composition of the soil-water system changes. These changes can be quantified dynamically by gas measurements and changes in electrical conductivity of the pore water and electrical resistivity of the bulk soil. Batch experiments were conducted to examine whether nitrate is a preferred electron acceptor over iron and manganese oxides as described in classical redox reaction theory. Gas releases during PG and glutamate degradation were measured in a sandy pristine soil with and without nitrate under anaerobic condition during two weeks of incubation. Chemical reactions were quantified with the modelling tool ORCHESTRA. We are currently investigating whether dynamical measurements of electrical conductivity and bulk resistivity are suited to trace which electron acceptors (nitrate, manganese or iron) are being reduced. First

  10. Mitochondrial Energy and Redox Signaling in Plants

    Science.gov (United States)

    Schwarzländer, Markus

    2013-01-01

    Abstract Significance: For a plant to grow and develop, energy and appropriate building blocks are a fundamental requirement. Mitochondrial respiration is a vital source for both. The delicate redox processes that make up respiration are affected by the plant's changing environment. Therefore, mitochondrial regulation is critically important to maintain cellular homeostasis. This involves sensing signals from changes in mitochondrial physiology, transducing this information, and mounting tailored responses, by either adjusting mitochondrial and cellular functions directly or reprogramming gene expression. Recent Advances: Retrograde (RTG) signaling, by which mitochondrial signals control nuclear gene expression, has been a field of very active research in recent years. Nevertheless, no mitochondrial RTG-signaling pathway is yet understood in plants. This review summarizes recent advances toward elucidating redox processes and other bioenergetic factors as a part of RTG signaling of plant mitochondria. Critical Issues: Novel insights into mitochondrial physiology and redox-regulation provide a framework of upstream signaling. On the other end, downstream responses to modified mitochondrial function have become available, including transcriptomic data and mitochondrial phenotypes, revealing processes in the plant that are under mitochondrial control. Future Directions: Drawing parallels to chloroplast signaling and mitochondrial signaling in animal systems allows to bridge gaps in the current understanding and to deduce promising directions for future research. It is proposed that targeted usage of new technical approaches, such as quantitative in vivo imaging, will provide novel leverage to the dissection of plant mitochondrial signaling. Antioxid. Redox Signal. 18, 2122–2144. PMID:23234467

  11. Microfluidic redox battery.

    Science.gov (United States)

    Lee, Jin Wook; Goulet, Marc-Antoni; Kjeang, Erik

    2013-07-07

    A miniaturized microfluidic battery is proposed, which is the first membraneless redox battery demonstrated to date. This unique concept capitalizes on dual-pass flow-through porous electrodes combined with stratified, co-laminar flow to generate electrical power on-chip. The fluidic design is symmetric to allow for both charging and discharging operations in forward, reverse, and recirculation modes. The proof-of-concept device fabricated using low-cost materials integrated in a microfluidic chip is shown to produce competitive power levels when operated on a vanadium redox electrolyte. A complete charge/discharge cycle is performed to demonstrate its operation as a rechargeable battery, which is an important step towards providing sustainable power to lab-on-a-chip and microelectronic applications.

  12. Shewanella putrefaciens adhesion and biofilm formation on food processing surfaces

    DEFF Research Database (Denmark)

    Bagge, Dorthe; Hjelm, M.; Johansen, C.

    2001-01-01

    Laboratory model systems were developed for studying Shewanella putrefaciens adhesion and biofilm formation under batch and flow conditions. S. putrefaciens plays a major role in food spoilage and may cause microbially induced corrosion on steel surfaces. S. putrefaciens bacteria suspended in buf...... from surfaces, and indirect conductometry and found this combination sufficient to quantify bacteria on surfaces...

  13. Flat Graphene-Enhanced Electron Transfer Involved in Redox Reactions.

    Science.gov (United States)

    Pan, Meilan; Zhang, Yanyang; Shan, Chao; Zhang, Xiaolin; Gao, Guandao; Pan, Bingcai

    2017-08-01

    Graphene is easily warped in the out-of-plane direction because of its high in-plane Young's modulus, and exploring the influence of wrinkled graphene on its properties is essential for the design of graphene-based materials for environmental applications. Herein, we prepared wrinkled graphene (WGN-1 and WGN-2) by thermal treatment and compared their electrochemical properties with those of flat graphene nanosheets (FGN). FGN exhibit activities that are much better than those of wrinkled graphene nanosheets (WGN), not only in the electrochemical oxidation of methylene blue (MB) but also in the electrochemical reduction of nitrobenzene (NB). Transformation ratios of MB and NB in FGN, WGN-1, and WGN-2 were 97.5, 80.1, and 57.9% and 94.6, 92.1, and 81.2%, respectively. Electrochemical impedance spectroscopy and the surface resistance of the graphene samples increased in the following order: FGN reaction charges transfer faster across the reaction interfaces and along the surface of FGN than that of WGN, and wrinkles restrict reaction charge transfer and reduce the reaction rates. This study reveals that the morphology of the graphene (flat or wrinkle) greatly affects redox reaction activities and may have important implications for the design of novel graphene-based nanostructures and for our understanding of graphene wrinkle-dependent redox reactions in environmental processes.

  14. The electrochemical catalytic activity of single-walled carbon nanotubes towards VO2+/VO2+ and V3+/V2+ redox pairs for an all vanadium redox flow battery

    International Nuclear Information System (INIS)

    Li Wenyue; Liu Jianguo; Yan Chuanwei

    2012-01-01

    Highlights: ► SWCNT shows excellent electrochemical catalytic activity towards VO 2 + /VO 2+ and V 3+ /V 2+ redox couples. ► The anodic reactions are more sensitive to the surface oxygen atom content change compared with the cathodic reactions. ► The enhanced battery performance clearly demonstrated that the SWCNT is suitable to be used as an electrode catalyst for VRFB. - Abstract: Single-walled carbon nanotube (SWCNT) was used as an electrode catalyst for an all vanadium redox flow battery (VRFB). The electrochemical property of SWCNT towards VO 2 + /VO 2+ and V 3+ /V 2+ was carefully characterized by cyclic voltammetric (CV) and electrochemical impedance spectroscopy (EIS) measurements. The peak current values for these redox pairs were significantly higher on the modified glassy carbon electrode compared with those obtained on the bare electrode, suggesting the excellent electrochemical activity of the SWCNT. Moreover, it was proved that the anodic process was more dependent on the surface oxygen of the SWCNT than the cathodic process through changing its surface oxygen content. Detailed EIS analysis of different modified electrodes revealed that the charge and mass transfer processes were accelerated at the modified electrode–electrolyte interface, which could be ascribed to the large specific surface area, the surface defects and the oxygen functional groups of the SWCNT. The enhanced battery performance effectively demonstrated that the SWCNT was suitable to serve as an electrode catalyst for the VRFB.

  15. Acoustic emission-based in-process monitoring of surface generation in robot-assisted polishing

    DEFF Research Database (Denmark)

    Pilny, Lukas; Bissacco, Giuliano; De Chiffre, Leonardo

    2016-01-01

    The applicability of acoustic emission (AE) measurements for in-process monitoring of surface generation in the robot-assisted polishing (RAP) was investigated. Surface roughness measurements require interruption of the process, proper surface cleaning and measurements that sometimes necessitate...... automatic detection of optimal process endpoint allow intelligent process control, creating fundamental elements in development of robust fully automated RAP process for its widespread industrial application....... removal of the part from the machine tool. In this study, stabilisation of surface roughness during polishing rotational symmetric surfaces by the RAP process was monitored by AE measurements. An AE sensor was placed on a polishing arm in direct contact with a bonded abrasive polishing tool...

  16. Modelling sulfamethoxazole degradation under different redox conditions

    Science.gov (United States)

    Sanchez-Vila, X.; Rodriguez-Escales, P.

    2015-12-01

    Sulfamethoxazole (SMX) is a low adsorptive, polar, sulfonamide antibiotic, widely present in aquatic environments. Degradation of SMX in subsurface porous media is spatially and temporally variable, depending on various environmental factors such as in situ redox potential, availability of nutrients, local soil characteristics, and temperature. It has been reported that SMX is better degraded under anoxic conditions and by co-metabolism processes. In this work, we first develop a conceptual model of degradation of SMX under different redox conditions (denitrification and iron reducing conditions), and second, we construct a mathematical model that allows reproducing different experiments of SMX degradation reported in the literature. The conceptual model focuses on the molecular behavior and contemplates the formation of different metabolites. The model was validated using the experimental data from Barbieri et al. (2012) and Mohatt et al. (2011). It adequately reproduces the reversible degradation of SMX under the presence of nitrite as an intermediate product of denitrification. In those experiments degradation was mediated by the transient formation of a diazonium cation, which was considered responsible of the substitution of the amine radical by a nitro radical, forming the 4-nitro-SMX. The formation of this metabolite is a reversible process, so that once the concentration of nitrite was back to zero due to further advancement of denitrification, the concentration of SMX was fully recovered. The forward reaction, formation of 4-nitro SMX, was modeled considering a kinetic of second order, whereas the backward reaction, dissociation of 4-nitro-SMX back to the original compound, could be modeled with a first order degradation reaction. Regarding the iron conditions, SMX was degraded due to the oxidation of iron (Fe2+), which was previously oxidized from goethite due to the degradation of a pool of labile organic carbon. As the oxidation of iron occurred on the

  17. Using OSL dating to quantify rates of Earth surface processes

    Science.gov (United States)

    Rhodes, E. J.; Rittenour, T. M.

    2010-12-01

    In Optically Stimulated Luminescence (OSL), the dating signal is reset when mineral grains are exposed to light or heat, and gradually rebuilds during subsequent burial by interaction with ionising radiation. Quartz and feldspar provide useful OSL signals demonstrating rapid signal reduction in only seconds of light exposure. Age estimates ranging from under 1 year to around 200,000 years can be determined for a wide range of sedimentary contexts, including dunes, marine deposits, fluvial and glacial environments, and recent developments provide the framework for low temperature thermochronometric applications on timescales comparable with rapid climate fluctuations. In this presentation, we explore the range of applications for determining rates of Earth surface processes using OSL. We examine technical limitations, and provide a framework for overcoming current difficulties experienced in several specific regions and contexts. We will focus on OSL dating applications to glacigenic and fluvial records, along with use of the technique in tectonic and paleoseismic contexts. In many ways, these represent the most challenging environments for OSL; rapid high energy deposition is associated with incomplete signal zeroing, and the characteristics of quartz in many of these environments make it difficult to derive precise age estimates using this mineral. We will introduce innovative methods to overcome these limitations, both existing and those under development.

  18. Air plasma processing of poly(methyl methacrylate) micro-beads: Surface characterisations

    International Nuclear Information System (INIS)

    Liu Chaozong; Cui Naiyi; Osbeck, Susan; Liang He

    2012-01-01

    Highlights: ► PMMA micro-beads were processed using a rotary air plasma reactor. ► Surface chemistry and surface texture of PMMA micro-beads were characterised. ► Surface wettability was evaluated using “floating” water contact angle method. ► Surface oxidation and texture changes induced by air plasma attributed to the improvement of surface wettability. - Abstract: This paper reports the surface processing of poly(methyl methacrylate) (PMMA) micro-beads by using a rotary air plasma reactor, and its effects on surface properties. The surface properties, including surface wettability, surface chemistry and textures of the PMMA beads, were characterised. It was observed that the air plasma processing can improve the surface wettability of the PMMA microbeads significantly. A 15 min plasma processing can reduce the surface water contact angle of PMMA beads to about 50° from its original value of 80.3°. This was accompanied by about 8% increase in surface oxygen concentration as confirmed by XPS analysis. The optical profilometry examination revealed the air plasma processing resulted in a rougher surface that has a “delicate” surface texture. It is concluded that the surface chemistry and texture, induced by air plasma processing, co-contributed to the surface wettability improvement of PMMA micro-beads.

  19. Mesoporous tungsten oxynitride as electrocatalyst for promoting redox reactions of vanadium redox couple and performance of vanadium redox flow battery

    Science.gov (United States)

    Lee, Wonmi; Jo, Changshin; Youk, Sol; Shin, Hun Yong; Lee, Jinwoo; Chung, Yongjin; Kwon, Yongchai

    2018-01-01

    For enhancing the performance of vanadium redox flow battery (VRFB), a sluggish reaction rate issue of V2+/V3+ redox couple evaluated as the rate determining reaction should be addressed. For doing that, mesoporous tungsten oxide (m-WO3) and oxyniride (m-WON) structures are proposed as the novel catalysts, while m-WON is gained by NH3 heat treatment of m-WO3. Their specific surface area, crystal structure, surface morphology and component analysis are measured using BET, XRD, TEM and XPS, while their catalytic activity for V2+/V3+ redox reaction is electrochemically examined. As a result, the m-WON shows higher peak current, smaller peak potential difference, higher electron transfer rate constant and lower charge transfer resistance than other catalysts, like the m-WO3, WO3 nanoparticle and mesoporous carbon, proving that it is superior catalyst. Regarding the charge-discharge curve tests, the VRFB single cell employing the m-WON demonstrates high voltage and energy efficiencies, high specific capacity and low capacity loss rate. The excellent results of m-WON are due to the reasons like (i) reduced energy band gap, (ii) reaction familiar surface functional groups and (ii) greater electronegativity.

  20. Photochemical Transformation Processes in Sunlit Surface Waters (Invited)

    Science.gov (United States)

    Vione, D.

    2013-12-01

    Photochemical reactions are major processes in the transformation of hardly biodegradable xenobiotics in surface waters. They are usually classified into direct photolysis and indirect or sensitised degradation. Direct photolysis requires xenobiotic compounds to absorb sunlight, and to get transformed as a consequence. Sensitised transformation involves reaction with transient species (e.g. °OH, CO3-°, 1O2 and triplet states of chromophoric dissolved organic matter, 3CDOM*), photogenerated by so-called photosensitisers (nitrate, nitrite and CDOM). CDOM is a major photosensitiser: is it on average the main source of °OH (and of CO3-° as a consequence, which is mainly produced upon oxidation by °OH of carbonate and bicarbonate) and the only important source of 1O2 and 3CDOM* [1, 2]. CDOM origin plays a key role in sensitised processes: allochthonous CDOM derived from soil runoff and rich in fulvic and humic substances is usually more photoactive than autochthonous CDOM (produced by in-water biological processes and mainly consisting of protein-like material) or of CDOM derived from atmospheric deposition. An interesting gradual evolution of CDOM origin and photochemistry can be found in mountain lakes across the treeline, which afford a gradual transition of allochthonous- autochtonous - atmopheric CDOM when passing from trees to alpine meadows to exposed rocks [3]. Another important issue is the sites of reactive species photoproduction in CDOM. While there is evidence that smaller molecular weight fractions are more photoactive, some studies have reported considerable 1O2 reactivity in CDOM hydrophobic sites and inside particles [4]. We have recently addressed the problem and found that dissolved species in standard humic acids (hydrodynamic diameter pollutants to be assessed and modelled. For instance, it is possible to predict pollutant half-life times by knowing absorption spectrum, direct photolysis quantum yield and reaction rate constants with °OH, CO3

  1. Study to establish cost projections for production of Redox chemicals

    Science.gov (United States)

    Walther, J. F.; Greco, C. C.; Rusinko, R. N.; Wadsworth, A. L., III

    1982-01-01

    A cost study of four proposed manufacturing processes for redox chemicals for the NASA REDOX Energy Storage System yielded favorable selling prices in the range $0.99 to $1.91/kg of chromic chloride, anhydrous basis, including ferrous chloride. The prices corresponded to specific energy storage costs from under $9 to $17/kWh. A refined and expanded cost analysis of the most favored process yielded a price estimate corresponding to a storage cost of $11/kWh. The findings supported the potential economic viability of the NASA REDOX system.

  2. Redox Reactivity of Cerium Oxide Nanoparticles Induces the Formation of Disulfide Bridges in Thiol-Containing Biomolecules.

    Science.gov (United States)

    Rollin-Genetet, Françoise; Seidel, Caroline; Artells, Ester; Auffan, Mélanie; Thiéry, Alain; Vidaud, Claude

    2015-12-21

    The redox state of disulfide bonds is implicated in many redox control systems, such as the cysteine-cystine couple. Among proteins, ubiquitous cysteine-rich metallothioneins possess thiolate metal binding groups susceptible to metal exchange in detoxification processes. CeO2 NPs are commonly used in various industrial applications due to their redox properties. These redox properties that enable dual oxidation states (Ce(IV)/Ce(III)) to exist at their surface may act as oxidants for biomolecules. The interaction among metallothioneins, cysteine, and CeO2 NPs was investigated through various biophysical approaches to shed light on the potential effects of the Ce(4+)/Ce(3+) redox system on the thiol groups of these biomolecules. The possible reaction mechanisms include the formation of a disulfide bridge/Ce(III) complex resulting from the interaction between Ce(IV) and the thiol groups, leading to metal unloading from the MTs, depending on their metal content and cluster type. The formation of stable Ce(3+) disulfide complexes has been demonstrated via their fluorescence properties. This work provides the first evidence of thiol concentration-dependent catalytic oxidation mechanisms between pristine CeO2 NPs and thiol-containing biomolecules.

  3. Redox Control of Skeletal Muscle Regeneration.

    Science.gov (United States)

    Le Moal, Emmeran; Pialoux, Vincent; Juban, Gaëtan; Groussard, Carole; Zouhal, Hassane; Chazaud, Bénédicte; Mounier, Rémi

    2017-08-10

    Skeletal muscle shows high plasticity in response to external demand. Moreover, adult skeletal muscle is capable of complete regeneration after injury, due to the properties of muscle stem cells (MuSCs), the satellite cells, which follow a tightly regulated myogenic program to generate both new myofibers and new MuSCs for further needs. Although reactive oxygen species (ROS) and reactive nitrogen species (RNS) have long been associated with skeletal muscle physiology, their implication in the cell and molecular processes at work during muscle regeneration is more recent. This review focuses on redox regulation during skeletal muscle regeneration. An overview of the basics of ROS/RNS and antioxidant chemistry and biology occurring in skeletal muscle is first provided. Then, the comprehensive knowledge on redox regulation of MuSCs and their surrounding cell partners (macrophages, endothelial cells) during skeletal muscle regeneration is presented in normal muscle and in specific physiological (exercise-induced muscle damage, aging) and pathological (muscular dystrophies) contexts. Recent advances in the comprehension of these processes has led to the development of therapeutic assays using antioxidant supplementation, which result in inconsistent efficiency, underlying the need for new tools that are aimed at precisely deciphering and targeting ROS networks. This review should provide an overall insight of the redox regulation of skeletal muscle regeneration while highlighting the limits of the use of nonspecific antioxidants to improve muscle function. Antioxid. Redox Signal. 27, 276-310.

  4. A density functional theory study on redox reaction of uranium

    International Nuclear Information System (INIS)

    Toraishi, T.; Kawaguchi, M.; Tsuneda, T.; Tanaka, S.; Nagasaki, S.

    2005-01-01

    Full text of publication follows: Redox reactions are key issues for predicting the migration behavior of actinides in the geosphere, and therefore the chemical processes have to be profoundly understood. However, redox reactions basically involve several elemental processes, and in many cases only limited chemical information can be obtained experimentally. A theoretical approach gives further information which never can be obtained by experiments, such as precise thermodynamic data or reaction pathways of very rapid charge transfer reactions. For this reason, ab initio MO calculations have been applied in the last 5-6 years to the elucidation of redox processes in the U(VI)-Fe(II) or U(VI)-U(IV) system [1- 3]. Those studies provided extremely important chemical information. Nevertheless, the 'huge' calculation costs of ab initio MO techniques now interfere with the extension of the calculation to the 'real' size system: In order to deal with the practically important chemical reactions such as the reduction of actinides at solid surfaces, a large chemical system involving many atoms (electrons) has to be treated. Present ab initio MO techniques at CASSCF, CASPT2 or MRCI level, however, do not allow to handle such a large systems because of the high calculation costs. Density functional theory (DFT) calculations should be also feasible for such systems. Nevertheless, there are very few reports on redox processes of actinides calculated by DFT. This fact was based on the argument that DFT could not treat charge transfer phenomena accurately since the two-electron exchange integral term is not explicitly involved [1-3]. However this is no longer correct: the long-range corrected (LC) energy function was recently developed, and now the charge transfer reaction can safely be calculated by DFT [4]. In the present work, we employ the DFT technique to treat the reduction of U(VI) to U(V) by Fe(II) via the bi-nuclear complex system, and confirm the applicability of the

  5. Ceria-based electrospun fibers for renewable fuel production via two-step thermal redox cycles for carbon dioxide splitting.

    Science.gov (United States)

    Gibbons, William T; Venstrom, Luke J; De Smith, Robert M; Davidson, Jane H; Jackson, Gregory S

    2014-07-21

    Zirconium-doped ceria (Ce(1-x)Zr(x)O2) was synthesized through a controlled electrospinning process as a promising approach to cost-effective, sinter-resistant material structures for high-temperature, solar-driven thermochemical redox cycles. To approximate a two-step redox cycle for solar fuel production, fibrous Ce(1-x)Zr(x)O2 with relatively low levels of Zr-doping (0 rates of O2 release during reduction and CO production during reoxidation and by assessing post-cycling fiber crystallite sizes and surface areas. Sintering increases with reduction temperature but occurs primarily along the fiber axes. Even after 108 redox cycles with reduction at 1400 °C and oxidation with CO2 at 800 °C, the fibers maintain their structure with surface areas of ∼0.3 m(2) g(-1), higher than those observed in the literature for other ceria-based structures operating at similarly high temperature conditions. Total CO production and peak production rate stabilize above 3.0 mL g(-1) and 13.0 mL min(-1) g(-1), respectively. The results show the potential for electrospun oxides as sinter-resistant material structures with adequate surface area to support rapid CO2 splitting in solar thermochemical redox cycles.

  6. Identification of redox-sensitive cysteines in the arabidopsis proteome using OxiTRAQ, a quantitative redox proteomics method

    KAUST Repository

    Liu, Pei

    2014-01-28

    Cellular redox status plays a key role in mediating various physiological and developmental processes often through modulating activities of redox-sensitive proteins. Various stresses trigger over-production of reactive oxygen/nitrogen species which lead to oxidative modifications of redox-sensitive proteins. Identification and characterization of redox-sensitive proteins are important steps toward understanding molecular mechanisms of stress responses. Here, we report a high-throughput quantitative proteomic approach termed OxiTRAQ for identifying proteins whose thiols undergo reversible oxidative modifications in Arabidopsis cells subjected to oxidative stress. In this approach, a biotinylated thiol-reactive reagent is used for differential labeling of reduced and oxidized thiols. The biotin-tagged peptides are affinity purified, labeled with iTRAQ reagents, and analyzed using a paralleled HCD-CID fragmentation mode in an LTQ-Orbitrap. With this approach, we identified 195 cysteine-containing peptides from 179 proteins whose thiols underwent oxidative modifications in Arabidopsis cells following the treatment with hydrogen peroxide. A majority of those redox-sensitive proteins, including several transcription factors, were not identified by previous redox proteomics studies. This approach allows identification of the specific redox-regulated cysteine residues, and offers an effective tool for elucidation of redox proteomes. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Modern processes of sediment formation in Lake Towuti, Indonesia, as derived from the composition of lake surface sediments

    Science.gov (United States)

    Hasberg, Ascelina; Melles, Martin; Morlock, Marina; Vogel, Hendrik; Russel, James M.; Bijaksana, Satria

    2016-04-01

    In summer 2015, a drilling operation funded by the International Continental Scientific Drilling Program (ICDP) was conducted at Lake Towuti (2.75°S, 121.5°E), the largest tectonically formed lake (surface area: 561 km²) of the Republic Indonesia. The Towuti Drilling Project (TDP) recovered more than 1000 meters of sediment core from three sites. At all three sites replicate cores down to 133, 154, and 174 m below lake floor have penetrated the entire lake sediment record, which is expected to comprise the past ca. 650.000 years continuously. Lake Towutís sediment record thus can provide unique information for instance concerning the climatic and environmental history in the Indo-Pacific-Warm-Pool (IPWP) and concerning the evolutionary biology in SE Asia. For a better understanding of the palaeoenvironmental proxies to be analyzed on the drill cores, the modern processes of sediment formation in the lake and in its catchment - under known environmental conditions - were investigated on a set of 84 lake sediment surface samples. Sampling was conducted by grab sampler (UWITEC Corp., Austria) in a grid of 1 to 4 km resolution that covers the entire lake. The samples were analyzed for inorganic geochemical composition (XRF powder scans and ICP-MS), magnetic susceptibility (Kappabridge), grain-size distribution (laser scanner), biogenic components (smear-slide analyses), biogenic silica contents (leaching), and carbonate, total organic carbon (TOC), nitrogen (TN), and sulfur (TS) concentrations (elemental analyzer). The sediments close to the lake shores and in front of the major river inlets are characterized by mean grain sizes coarser than average and high magnetic susceptibilities presented by high ratios of Cr, Ni, Co, and Zr. This reflects higher energies due to wave action and fluvial sediment supply, as well as the occurrence of magnetic minerals particularly in the sand and gravel fractions of the sediments. In regions of deeper waters and more distal to

  8. Kynurenine pathway metabolites and enzymes involved in redox reactions.

    Science.gov (United States)

    González Esquivel, D; Ramírez-Ortega, D; Pineda, B; Castro, N; Ríos, C; Pérez de la Cruz, V

    2017-01-01

    Oxido-reduction reactions are a fundamental part of the life due to support many vital biological processes as cellular respiration and glucose oxidation. In the redox reactions, one substance transfers one or more electrons to another substance. An important electron carrier is the coenzyme NAD + , which is involved in many metabolic pathways. De novo biosynthesis of NAD + is through the kynurenine pathway, the major route of tryptophan catabolism, which is sensitive to redox environment and produces metabolites with redox capacity, able to alter biological functions that are controlled by redox-responsive signaling pathways. Kynurenine pathway metabolites have been implicated in the physiology process and in the physiopathology of many diseases; processes that also share others factors as dysregulation of calcium homeostasis, mitochondrial dysfunction, oxidative stress, inflammation and cell death, which impact the redox environment. This review examines in detail the available evidence in which kynurenine pathway metabolites participate in redox reactions and their effect on cellular redox homeostasis, since the knowledge of the main factors and mechanisms that lead to cell death in many neurodegenative disorders and other pathologies, such as mitochondrial dysfunction, oxidative stress and kynurenines imbalance, will allow to develop therapies using them as targets. This article is part of the Special Issue entitled 'The Kynurenine Pathway in Health and Disease'. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Electron beam processed plasticized epoxy coatings for surface protection

    International Nuclear Information System (INIS)

    Ibrahim, Mervat S.; Mohamed, Heba A.; Kandile, Nadia G.; Said, Hossam M.; Mohamed, Issa M.

    2011-01-01

    Highlights: · Coating formulations with EA 70%, HD 20%, and castor oil 10% under 1 Mrad pass -1 irradiation dose showed the best adhesion and passed bending tests. · The prepared EP-SF-An adduct improve anti-corrosion properties of coatings without any significant effect on physical, mechanical and chemical properties of the cured film. The optimum amount of aniline adduct as corrosion inhibitor was found to be 0.4 g for 100 g of coating formulation. · The corrosion inhibition efficiency of the prepared adduct competed the commercial efficiency. - Abstract: Epoxy acrylate oligomer (EA) was plasticized by adding different plasticizers such as epoxidized soybean oil, glycerol and castor oil and cured by electron beam (EB). Different irradiation doses (1, 2.5 and 5 Mrad pass -1 ) were used in the curing process. The effect of both different irradiation doses and plasticizers on the end use performance properties of epoxy acrylate coating namely, pencil hardness, bending test, adhesion test, acid and alkali resistance test were studied. It was observed that incorporation of castor oil in epoxy acrylate diluted by 1,6-hexanediol diacrylate (HD) monomer with a ratio (EA 70%, HD 20%, castor oil 10%) under 1 Mrad pass -1 irradiation dose improved the physical, chemical and mechanical properties of cured films than the other plasticizer. Sunflower free fatty acid was epoxidized in situ under well established conditions. The epoxidized sunflower free fatty acids (ESFA) were subjected to react with aniline in sealed ampoules under inert atmosphere at 140 deg. C. The produced adducts were added at different concentrations to epoxy acrylate coatings under certain EB irradiation dose and then evaluated as corrosion inhibitors for carbon steel surfaces in terms of weight loss measurements and corrosion resistance tests. It was found that, addition of 0.4 g of aniline adduct to 100 g epoxy acrylate formula may give the best corrosion protection for carbon steel and compete the

  10. Electrochemical and morphological analyses on the titanium surface modified by shot blasting and anodic oxidation processes

    Energy Technology Data Exchange (ETDEWEB)

    Szesz, Eduardo M., E-mail: eszesz@neoortho.com.br [Neoortho Research Institute, Rua Ângelo Domingos Durigan, 607-Cascatinha, CEP 82025-100 Curitiba, PR (Brazil); Pereira, Bruno L., E-mail: brnl7@hotmail.com [Physics Department, Universidade Federal do Paraná, 81531-980 Curitiba, PR (Brazil); Kuromoto, Neide K., E-mail: kuromoto@fisica.ufpr.br [Physics Department, Universidade Federal do Paraná, 81531-980 Curitiba, PR (Brazil); Marino, Claudia E.B., E-mail: claudiamarino@yahoo.com [Mechanical Engineering Department, Universidade Federal do Paraná, 81531-980 Curitiba, PR (Brazil); Souza, Gelson B. de, E-mail: gelsonbs@uepg.br [Physics Department, Universidade Estadual de Ponta Grossa, 84051-510 Ponta Grossa, PR (Brazil); Soares, Paulo, E-mail: pa.soares@pucpr.br [Mechanical Engineering Department, Pontifícia Universidade Católica do Paraná, 80215-901 Curitiba, PR (Brazil)

    2013-01-01

    In recent years, many surface modification processes have been developed in order to induce the osseointegration on titanium surface and thus to improve the implants' biocompatibility. In this work, Ti surface has been modified by shot blasting followed by anodic oxidation process in order to associate the good surface characteristics of both processes to obtain a rough and porous surface able to promote the titanium surface bioactivity. Commercially pure titanium (grade 2) plates were used on the surface treatments that were as follows: Shot blasting (SB) performed using alumina (Al{sub 2}O{sub 3}) particles, and anodic oxidation (AO) using NaOH electrolyte. The morphology, structural changes and the open-circuit potentials (OCP) of the surfaces were analyzed. It can be observed that an increase on the roughness of the blasted surface and a rough and porous surface happens after the AO process. The anodic film produced is thin and followed the blasted surface topography. It can be observed that there are small pores with regular shape covering the entire surface. X-ray diffraction results showed the presence of the anatase and rutile phases on the blasted and anodized surface after heat treatment at 600 °C/1 h. Concerning electrochemical measurements, when the different samples were submitted to open-circuit conditions in a physiological electrolyte, the protective effect increases with the oxidation process due to the oxide layer. When the surface was blasted, the OCP was more negative when compared with the Ti surface without surface treatments. - Highlights: ► A combination of shot blasting and anodic oxidation surface treatments is proposed. ► Both processes produced an increase in roughness compared to the polished surface. ► The combination of processes produced a rough and porous surface. ► Open circuit results show that the protective effect increases with oxidation process. ► The combination of processes presents the better results in this

  11. Electrochemistry and in situ scanning tunnelling microscopy of pure and redox-marked DNA- and UNA-based oligonucleotides on Au(111)-electrode surfaces

    DEFF Research Database (Denmark)

    Hansen, Allan Glargaard; Salvatore, Princia; Karlsen, K.

    2013-01-01

    the strongest and in accord with multiple site Ru-attachment. In situ STM disclosed molecular scale features in varying coverage on addition of the metal ions. The Ru-derivatives showed a bias voltage dependent broad maximum in the tunnelling current–overpotential correlation which could be correlated......We have studied adsorption and electrochemical electron transfer of several 13- and 15-base DNA and UNA (unlocked nucleic acids) oligonucleotides (ONs) linked to Au(111)-electrode surfaces via a 50-C6-SH group using cyclic voltammetry (CV) and scanning tunnelling microscopy in aqueous buffer under...

  12. Redox electrode materials for supercapatteries

    OpenAIRE

    Yu, Linpo; Chen, George Z.

    2016-01-01

    Redox electrode materials, including transition metal oxides and electronically conducting polymers, are capable of faradaic charge transfer reactions, and play important roles in most electrochemical energy storage devices, such as supercapacitor, battery and supercapattery. Batteries are often based on redox materials with low power capability and safety concerns in some cases. Supercapacitors, particularly those based on redox inactive materials, e.g. activated carbon, can offer high power...

  13. Thin film surface processing by ultrashort laser pulses (USLP)

    NARCIS (Netherlands)

    Scorticati, D.; Skolski, J.Z.P.; Romer, G.R.B.E.; Huis in 't Veld, A.J.; Workum, M.J.; Theelen, M.J.; Zeman, M.

    2012-01-01

    In this work, we studied the feasibility of surface texturing of thin molybdenum layers on a borosilicate glass substrate with Ultra-Short Laser Pulses (USLP). Large areas of regular diffraction gratings were produced consisting of Laserinduced periodic surface structures (LIPSS). A short pulsed

  14. Impact of Redox Reactions on Colloid Transport in Saturated Porous Media: An Example of Ferrihydrite Colloids Transport in the Presence of Sulfide.

    Science.gov (United States)

    Liao, Peng; Yuan, Songhu; Wang, Dengjun

    2016-10-18

    Transport of colloids in the subsurface is an important environmental process with most research interests centered on the transport in chemically stable conditions. While colloids can be formed under dynamic redox conditions, the impact of redox reactions on their transport is largely overlooked. Taking the redox reactions between ferrihydrite colloids and sulfide as an example, we investigated how and to what extent the redox reactions modulated the transport of ferrihydrite colloids in anoxic sand columns over a range of environmentally relevant conditions. Our results reveal that the presence of sulfide (7.8-46.9 μM) significantly decreased the breakthrough of ferrihydrite colloids in the sand column. The estimated travel distance of ferrihydrite colloids in the absence of sulfide was nearly 7-fold larger than that in the presence of 46.9 μM sulfide. The reduced breakthrough was primarily attributed to the reductive dissolution of ferrihydrite colloids by sulfide in parallel with formation of elemental sulfur (S(0)) particles from sulfide oxidation. Reductive dissolution decreased the total mass of ferrihydrite colloids, while the negatively charged S(0) decreased the overall zeta potential of ferrihydrite colloids by attaching onto their surfaces and thus enhanced their retention in the sand. Our findings provide novel insights into the critical role of redox reactions on the transport of redox-sensitive colloids in saturated porous media.

  15. Monolayer to MTS: using SEM, HIM, TEM and SERS to compare morphology, nanosensor uptake and redox potential in MCF7 cells

    Science.gov (United States)

    Jamieson, L. E.; Bell, A. P.; Harrison, D. J.; Campbell, C. J.

    2015-06-01

    Cellular redox potential is important for the control and regulation of a vast number of processes occurring in cells. When the fine redox potential balance within cells is disturbed it can have serious consequences such as the initiation or progression of disease. It is thought that a redox gradient develops in cancer tumours where the peripheral regions are well oxygenated and internal regions, further from vascular blood supply, become starved of oxygen and hypoxic. This makes treatment of these areas more challenging as, for example, radiotherapy relies on the presence of oxygen. Currently techniques for quantitative analysis of redox gradients are limited. Surface enhanced Raman scattering (SERS) nanosensors (NS) have been used to detect redox potential in a quantitative manner in monolayer cultured cells with many advantages over other techniques. This technique has considerable potential for use in multicellular tumour spheroids (MTS) - a three dimensional (3D) cell model which better mimics the tumour environment and gradients that develop. MTS are a more realistic model of the in vivo cellular morphology and environment and are becoming an increasingly popular in vitro model, replacing traditional monolayer culture. Imaging techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM) and helium ion microscopy (HIM) were used to investigate differences in morphology and NS uptake in monolayer culture compared to MTS. After confirming NS uptake, the first SERS measurements revealing quantitative information on redox potential in MTS were performed.

  16. Effect of gold nanoparticles on the structure and electron-transfer characteristics of glucose oxidase redox polyelectrolyte-surfactant complexes.

    Science.gov (United States)

    Cortez, M Lorena; Marmisollé, Waldemar; Pallarola, Diego; Pietrasanta, Lía I; Murgida, Daniel H; Ceolín, Marcelo; Azzaroni, Omar; Battaglini, Fernando

    2014-10-06

    Efficient electrical communication between redox proteins and electrodes is a critical issue in the operation and development of amperometric biosensors. The present study explores the advantages of a nanostructured redox-active polyelectrolyte-surfactant complex containing [Os(bpy)2Clpy](2+) (bpy=2,2'-bipyridine, py= pyridine) as the redox centers and gold nanoparticles (AuNPs) as nanodomains for boosting the electron-transfer propagation throughout the assembled film in the presence of glucose oxidase (GOx). Film structure was characterized by grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM), GOx incorporation was followed by surface plasmon resonance (SPR) and quartz-crystal microbalance with dissipation (QCM-D), whereas Raman spectroelectrochemistry and electrochemical studies confirmed the ability of the entrapped gold nanoparticles to enhance the electron-transfer processes between the enzyme and the electrode surface. Our results show that nanocomposite films exhibit five-fold increase in current response to glucose compared with analogous supramolecular AuNP-free films. The introduction of colloidal gold promotes drastic mesostructural changes in the film, which in turn leads to a rigid, amorphous interfacial architecture where nanoparticles, redox centers, and GOx remain in close proximity, thus improving the electron-transfer process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Compromised redox homeostasis, altered nitroso-redox balance, and therapeutic possibilities in atrial fibrillation.

    Science.gov (United States)

    Simon, Jillian N; Ziberna, Klemen; Casadei, Barbara

    2016-04-01

    Although the initiation, development, and maintenance of atrial fibrillation (AF) have been linked to alterations in myocyte redox state, the field lacks a complete understanding of the impact these changes may have on cellular signalling, atrial electrophysiology, and disease progression. Recent studies demonstrate spatiotemporal changes in reactive oxygen species production shortly after the induction of AF in animal models with an uncoupling of nitric oxide synthase activity ensuing in the presence of long-standing persistent AF, ultimately leading to a major shift in nitroso-redox balance. However, it remains unclear which radical or non-radical species are primarily involved in the underlying mechanisms of AF or which proteins are targeted for redox modification. In most instances, only free radical oxygen species have been assessed; yet evidence from the redox signalling field suggests that non-radical species are more likely to regulate cellular processes. A wider appreciation for the distinction of these species and how both species may be involved in the development and maintenance of AF could impact treatment strategies. In this review, we summarize how redox second-messenger systems are regulated and discuss the recent evidence for alterations in redox regulation in the atrial myocardium in the presence of AF, while identifying some critical missing links. We also examine studies looking at antioxidants for the prevention and treatment of AF and propose alternative redox targets that may serve as superior therapeutic options for the treatment of AF. © The Author 2016. Published by Oxford University Press on behalf of the European Society of Cardiology.

  18. The Redox Behaviour of Randomly Dispersed Single Walled Carbon Nanotubes both in the Absence and in the Presence of Adsorbed Glucose Oxidase

    Directory of Open Access Journals (Sweden)

    Gareth P. Keeley

    2006-12-01

    Full Text Available The electrochemical behaviour of SWCNTs randomly dispersed on gold and glassy carbon electrode surfaces was characterised via cyclic voltammetry and complex impedance spectroscopy, using the ferri/ferrocyanide couple as a redox active test probe . In subsequent investigations glucose oxidase (GOx was adsorbed onto the SWCNT ensemble without apparent denaturation of the enzyme. Cyclic voltammetry and potential step chronoamperometry were used to quantify and understand the process of electron transfer between the immobilised protein redox site and the working electrode. The effect of pH on the system was also investigated. In particular, we have shown that, for the calculation of electron transfer rate constants for surface-immobilised redox systems, chronoamperometry is preferable to voltammetry, which has been the technique of choice until now.

  19. Ruthenium nanocatalysis on redox reactions.

    Science.gov (United States)

    Veerakumar, Pitchaimani; Ramdass, Arumugam; Rajagopal, Seenivasan

    2013-07-01

    Nanoparticles have generated intense interest over the past 20 years due to their high potential applications in different areas such as catalysis, sensors, nanoscale electronics, fuel and solar cells and optoelectronics. As the large fractions of metal atoms are exposed to the surface, the use of metal nanoparticles as nanocatalysts allows mild reaction conditions and high catalytic efficiency in a large number of chemical transformations. They have emerged as sustainable heterogeneous catalysts and catalyst supports alternative to conventional materials. This review focuses on the synthesis, characterization and catalytic role of ruthenium nanoparticles (RuNPs) on the redox reactions of heteroatom containing organic compounds with the green reagent H2O2, a field that has attracted immense interest among the chemical, materials and industrial communities. We intend to present a broad overview of Ru nanocatalysts for redox reactions with an emphasis on their performance, stability and reusability. The growth in the chemistry of organic sulfoxides and N-oxides during last decade was due to their importance as synthetic intermediates for the production of a wide range of chemically and biologically active molecules. Thus design of efficient methods for the synthesis of sulfoxides and N-oxides becomes important. This review concentrates on the catalysis of RuNPs on the H2O2 oxidation of organic sulfides to sulfoxides and amines to N-oxides. The deoxygenation reactions of sulfoxides to sulfides and reduction of nitro compounds to amines are fundamental reactions in both chemistry and biology. Here, we also highlight the catalysis of metal nanoparticles on the deoxygenation of sulfoxides and sulfones and reduction of nitro compounds with particular emphasis on the mechanistic aspects.

  20. Redox markers for drought-induced nodule senescence, a process occurring after drought-induced senescence of the lowest leaves in soybean (Glycine max).

    Science.gov (United States)

    Marquez-Garcia, Belén; Shaw, Daniel; Cooper, James William; Karpinska, Barbara; Quain, Marian Dorcas; Makgopa, Eugene Matome; Kunert, Karl; Foyer, Christine Helen

    2015-09-01

    Water is an increasingly scarce resource that limits crop productivity in many parts of the world, and the frequency and severity of drought are predicted to increase as a result of climate change. Improving tolerance to drought stress is therefore important for maximizing future crop yields. The aim of this study was to compare the effects of drought on soybean (Glycine max) leaves and nodules in order to define phenotypic markers and changes in cellular redox state that characterize the stress response in different organs, and to characterize the relationships between leaf and nodule senescence during drought. Leaf and crown nodule metabolite pools were measured together with leaf and soil water contents, and leaf chlorophyll, total protein contents and chlorophyll a fluorescence quenching parameters in nodulated soybeans that were grown under either well-watered conditions or deprived of water for up to 21 d. Ureides, ascorbate, protein, chlorophyll and the ratios of variable chlorophyll a fluorescence (Fv') to maximal chlorophyll a fluorescence (Fm') fell to levels below detection in the oldest leaves after 21 d of drought. While these drought-induced responses were not observed in the youngest leaf ranks, the Fv'/Fm' ratios, pyridine nucleotide levels and the reduction state of the ascorbate pool were lower in all leaf ranks after 21 d of drought. In contrast to leaves, total nodule protein, pyridine nucleotides, ureides, ascorbate and glutathione contents increased as a result of the drought treatment. However, the nodule ascorbate pool was significantly less reduced as a result of drought. Higher levels of transcripts encoding two peroxiredoxins were detected in nodules exposed to drought stress but senescence-associated transcripts and other mRNAs encoding redox-related proteins were similar under both conditions. While the physiological impact of the drought was perceived throughout the shoot, stress-induced senescence occurred only in the oldest

  1. Improving the work function of the niobium surface of SRF cavities by plasma processing

    Science.gov (United States)

    Tyagi, P. V.; Doleans, M.; Hannah, B.; Afanador, R.; McMahan, C.; Stewart, S.; Mammosser, J.; Howell, M.; Saunders, J.; Degraff, B.; Kim, S.-H.

    2016-04-01

    An in situ plasma processing technique using chemically reactive oxygen plasma to remove hydrocarbons from superconducting radio frequency cavity surfaces at room temperature has been developed at the spallation neutron source, at Oak Ridge National Laboratory. To understand better the interaction between the plasma and niobium surface, surface studies on small samples were performed. In this article, we report the results from those surface studies. The results show that plasma processing removes hydrocarbons from top surface and improves the surface work function by 0.5-1.0 eV. Improving the work function of RF surface of cavities can help to improve their operational performance.

  2. Managing the cellular redox hub in photosynthetic organisms.

    Science.gov (United States)

    Foyer, Christine H; Noctor, Graham

    2012-02-01

    Light-driven redox chemistry is a powerful source of redox signals that has a decisive input into transcriptional control within the cell nucleus. Like photosynthetic electron transport pathways, the respiratory electron transport chain exerts a profound control over gene function, in order to balance energy (reductant and ATP) supply with demand, while preventing excessive over-reduction or over-oxidation that would be adversely affect metabolism. Photosynthetic and respiratory redox chemistries are not merely housekeeping processes but they exert a controlling influence over every aspect of plant biology, participating in the control of gene transcription and translation, post-translational modifications and the regulation of assimilatory reactions, assimilate partitioning and export. The number of processes influenced by redox controls and signals continues to increase as do the components that are recognized participants in the associated signalling pathways. A step change in our understanding of the overall importance of the cellular redox hub to plant cells has occurred in recent years as the complexity of the management of the cellular redox hub in relation to metabolic triggers and environmental cues has been elucidated. This special issue describes aspects of redox regulation and signalling at the cutting edge of current research in this dynamic and rapidly expanding field. © 2011 Blackwell Publishing Ltd.

  3. Pyridine nucleotides in regulation of cell death and survival by redox and non-redox reactions.

    Science.gov (United States)

    Novak Kujundžić, Renata; Žarković, Neven; Gall Trošelj, Koraljka

    2014-01-01

    Changes of the level and ratios of pyridine nucleotides determine metabolism- dependent cellular redox status and the activity of poly(ADP-ribose) polymerases (PARPs) and sirtuins, thereby influencing several processes closely related to cell survival and death. Pyridine nucleotides participate in numerous metabolic reactions whereby their net cellular level remains constant, but the ratios of NAD+/NADP+ and NADH/NADPH oscillate according to metabolic changes in response to diverse stress signals. In non-redox reactions, NAD+ is degraded and quickly, afterward, resynthesized in the NAD+ salvage pathway, unless overwhelming activation of PARP-1 consumes NAD+ to the point of no return, when the cell can no longer generate enough ATP to accommodate NAD+ resynthesis. The activity of PARP-1 is mandatory for the onset of cytoprotective autophagy on sublethal stress signals. It has become increasingly clear that redox status, largely influenced by the metabolism-dependent composition of the pyridine nucleotides pool, plays an important role in the synthesis of pro-apoptotic and anti-apoptotic sphingolipids. Awareness of the involvement of the prosurvival sphingolipid, sphingosine-1-phosphate, in transition from inflammation to malignant transformation has recently emerged. Here, the participation of pyridine nucleotides in redox and non-redox reactions, sphingolipid metabolism, and their role in cell fate decisions is reviewed.

  4. Manufacture of functional surfaces through combined application of tool manufacturing processes and Robot Assisted Polishing

    DEFF Research Database (Denmark)

    Eriksen, Rasmus Solmer; Arentoft, Mogens; Grønbæk, J.

    2012-01-01

    The tool surface topography is often a key parameter in the tribological performance of modern metal forming tools. A new generation of multifunctional surfaces is achieved by combination of conventional tool manufacturing processes with a novel Robot Assisted Polishing process. This novel surface...

  5. Redox chemistry of americium in nitric acid media

    Energy Technology Data Exchange (ETDEWEB)

    Picart, S.; Jobelin, I.; Armengol, G.; Adnet, JM

    2004-07-01

    The redox properties of the actinides are very important parameters for speciation studies and spent nuclear fuel reprocessing based on liquid-liquid extraction of actinides at different oxidation states (as in the Purex or Sesame process). They are also very useful for developing analytical tools including coulometry and redox titration. This study addressed the americium(IV)/americium(III) and americium(VI)/americium(V) redox couples, focusing on exhaustive acquisition of the thermodynamic and kinetic parameters of americium oxidation at an electrode in a complexing nitric acid medium. (authors)

  6. Redox chemistry of americium in nitric acid media

    International Nuclear Information System (INIS)

    Picart, S.; Jobelin, I.; Armengol, G.; Adnet, JM.

    2004-01-01

    The redox properties of the actinides are very important parameters for speciation studies and spent nuclear fuel reprocessing based on liquid-liquid extraction of actinides at different oxidation states (as in the Purex or Sesame process). They are also very useful for developing analytical tools including coulometry and redox titration. This study addressed the americium(IV)/americium(III) and americium(VI)/americium(V) redox couples, focusing on exhaustive acquisition of the thermodynamic and kinetic parameters of americium oxidation at an electrode in a complexing nitric acid medium. (authors)

  7. Coronal Structures as Tracers of Sub-Surface Processes

    Indian Academy of Sciences (India)

    tribpo

    dramatic differences in appearance and physical processes, all these structures share a common ... mena that indicate a close relationship between coronal and sub-photo- spheric processes. .... 8) maintaining the same chirality. Large scale ...

  8. Glutathione redox potential in the mitochondrial intermembrane space is linked to the cytosol and impacts the Mia40 redox state

    Science.gov (United States)

    Kojer, Kerstin; Bien, Melanie; Gangel, Heike; Morgan, Bruce; Dick, Tobias P; Riemer, Jan

    2012-01-01

    Glutathione is an important mediator and regulator of cellular redox processes. Detailed knowledge of local glutathione redox potential (EGSH) dynamics is critical to understand the network of redox processes and their influence on cellular function. Using dynamic oxidant recovery assays together with EGSH-specific fluorescent reporters, we investigate the glutathione pools of the cytosol, mitochondrial matrix and intermembrane space (IMS). We demonstrate that the glutathione pools of IMS and cytosol are dynamically interconnected via porins. In contrast, no appreciable communication was observed between the glutathione pools of the IMS and matrix. By modulating redox pathways in the cytosol and IMS, we find that the cytosolic glutathione reductase system is the major determinant of EGSH in the IMS, thus explaining a steady-state EGSH in the IMS which is similar to the cytosol. Moreover, we show that the local EGSH contributes to the partially reduced redox state of the IMS oxidoreductase Mia40 in vivo. Taken together, we provide a comprehensive mechanistic picture of the IMS redox milieu and define the redox influences on Mia40 in living cells. PMID:22705944

  9. Focusing on the Interfaces, Estuaries and Redox Transition Zones, for Understanding the Microbial Processes and Biogeochemical Cycling of Carbon under the Looming Influence of Global Warming and Anthropogenic Perturbations

    Science.gov (United States)

    Dang, H.; Jiao, N.

    2013-12-01

    Estuaries are the natural interface between terrestrial and marine ecosystems. These are also the zones where human activities exert the strongest impact on the earth and ocean environments. Due to high pressure from the effects of global warming and anthropogenic activities, many estuaries are deteriorating and experiencing significant change of the ecological processes and environmental functions. Certain fundamental microbial processes, including carbon fixation and respiration, have been changing as responses to and consequences of the altered estuarine environment and geochemistry. Increased inputs of terrigenous and anthropogenic organic materials and nutrients and elevated temperature make estuaries easy to be subjected to harmful algal blooms and hypoxic and even anoxic events. The change of the redox status of the estuarine and coastal waters and the increased nutrient loads such as that from terrestrial nitrate stimulate anaerobic respiration processes, such as nitrate reduction and denitrification. This may have strong negative impact on the marine environment, ecosystem and even climate, such as those caused by greenhouse gas production (N2O, CH4) by anaerobic microbial processes. In addition, some nutrients may be consumed by anaerobically respiring heterotrophic microorganisms, instead of being utilized by phytoplankton for carbon fixation. In this regard, the ecological function of the estuarine ecosystem may be altered and the ecological efficiency may be lowered, as less energy is produced by the microbial respiration process and less carbon is fixed by phytoplankton. However, on the other side, in hypoxic and anoxic waters, inorganic carbon fixation by anaerobic microorganisms may happen, such as those via the chemolithoautotrophic denitrifying sulfur oxidizing process and the anaerobic ammonium oxidation (anammox) process. Global warming and anthropogenic perturbations may have lowered the diversity, complexity, stability and sustainability of

  10. Lunar rock surfaces as detectors of solar processes

    International Nuclear Information System (INIS)

    Hartung, J.B.; Hunter College, New York, NY)

    1980-01-01

    Lunar rock surfaces exposed at or just below the lunar surface are considered as detectors of the solar wind, solar flares and solar-derived magnetic fields through their interactions with galactic cosmic rays. The degradation of the solar detector capabilities of lunar surface rocks by meteoroid impact erosion, accreta deposition, loose dust, and sputtering, amorphous layer formation and accelerated diffusion due to solar particles and illumination is discussed, and it is noted that the complex interactions of factors affecting the outer micron of exposed surface material has so far prevented the development of a satisfactory model for a particle detector on the submicron scale. Methods for the determination of surface exposure ages based on the accumulation of light solar wind noble gases, Fe and Mg, impact craters, solar flare tracks, and cosmogenic Kr isotopes are examined, and the systematic variations in the ages determined by the various clocks are discussed. It is concluded that a means of obtaining satisfactory quantitative rate or flux data has not yet been established

  11. Surface processing with ionized cluster beams: computer simulation

    International Nuclear Information System (INIS)

    Insepov, Z.; Yamada, I.

    1999-01-01

    Molecular Dynamics (MD) and Monte Carlo (MC) models of energetic gas cluster irradiation of a solid surface have been developed to investigate the phenomena of crater formation, sputtering, surface treatment, and the material hardness evaluation by irradiation with cluster ions. Theoretical estimation of crater dimensions formed with Ar gas cluster ion irradiation of different substrates, based on hydrodynamics and MD simulation, are presented. The atomic scale shock waves arising from cluster impact were obtained by calculating the pressure, temperature and mass-velocity of the target atoms. The crater depth is given as a unique 1/3 dependence on the cluster energy and on the cold material Brinell hardness number (BHN). A new 'true material hardness' scale which can be very useful for example for thin film coatings deposited on a soft substrate, is defined. This finding could be used as a new technique for measuring of a material hardness. Evolution of surface morphology under cluster ion irradiation was described by the surface relaxation equation which contains a term of crater formation at cluster impact. The formation of ripples on a surface irradiated with oblique cluster ion beams was predicted. MD and MC models of Decaborane ion (B 10 H 14 ) implantation into Si and the following rapid thermal annealing (RTA) have been developed

  12. Advantages of surface treatment processes by ionic sputtering

    International Nuclear Information System (INIS)

    Gantois, M.

    1976-01-01

    The use of high intensity glow-discharge permits to realize a superficial thermochemical treatment. Ions formed by discharge are accelerated against the surfaces to be treated; by effect of ion bombardment, surfaces get heated and a chemical reaction is developed depending on the composition of the ionized gas. The technique presents advantages, as the potential of the active gas might be freely chosen, and as many gases might be used, the decomposition of gases by pyrolysis and a homogeneous treatment (concerning nature of phases and thickness) all over the surface being not necessary. It is possible to develop layers of various nature, looking for those which offer the best properties to solve a technological problem (wear, friction, fatigue toughness, etc.). Some examples of nitruration, carbonitruration are considered [fr

  13. Seventh BES [Basic Energy Sciences] catalysis and surface chemistry research conference

    International Nuclear Information System (INIS)

    1990-03-01

    Research programs on catalysis and surface chemistry are presented. A total of fifty-seven topics are included. Areas of research include heterogeneous catalysis; catalysis in hydrogenation, desulfurization, gasification, and redox reactions; studies of surface properties and surface active sites; catalyst supports; chemical activation, deactivation; selectivity, chemical preparation; molecular structure studies; sorption and dissociation. Individual projects are processed separately for the data bases

  14. Seventh BES (Basic Energy Sciences) catalysis and surface chemistry research conference

    Energy Technology Data Exchange (ETDEWEB)

    1990-03-01

    Research programs on catalysis and surface chemistry are presented. A total of fifty-seven topics are included. Areas of research include heterogeneous catalysis; catalysis in hydrogenation, desulfurization, gasification, and redox reactions; studies of surface properties and surface active sites; catalyst supports; chemical activation, deactivation; selectivity, chemical preparation; molecular structure studies; sorption and dissociation. Individual projects are processed separately for the data bases. (CBS)

  15. Upper Meter Processes: Short Wind Waves, Surface Flow, and Micro-Turbulence

    National Research Council Canada - National Science Library

    Jaehne, Bernd

    2000-01-01

    The primary goal of this project was to advance the knowledge of small-scale air-sea interaction processes at the ocean surface, focussing on the dynamics of short waves, the surface flow field and the micro-turbulence...

  16. Shewanella putrefaciens Adhesion and Biofilm Formation on Food Processing Surfaces

    Science.gov (United States)

    Bagge, Dorthe; Hjelm, Mette; Johansen, Charlotte; Huber, Ingrid; Gram, Lone

    2001-01-01

    Laboratory model systems were developed for studying Shewanella putrefaciens adhesion and biofilm formation under batch and flow conditions. S. putrefaciens plays a major role in food spoilage and may cause microbially induced corrosion on steel surfaces. S. putrefaciens bacteria suspended in buffer adhered readily to stainless steel surfaces. Maximum numbers of adherent bacteria per square centimeter were reached in 8 h at 25°C and reflected the cell density in suspension. Numbers of adhering bacteria from a suspension containing 108 CFU/ml were much lower in a laminar flow system (modified Robbins device) (reaching 102 CFU/cm2) than in a batch system (reaching 107 CFU/cm2), and maximum numbers were reached after 24 h. When nutrients were supplied, S. putrefaciens grew in biofilms with layers of bacteria. The rate of biofilm formation and the thickness of the film were not dependent on the availability of carbohydrate (lactate or glucose) or on iron starvation. The number of S. putrefaciens bacteria on the surface was partly influenced by the presence of other bacteria (Pseudomonas fluorescens) which reduced the numbers of S. putrefaciens bacteria in the biofilm. Numbers of bacteria on the surface must be quantified to evaluate the influence of environmental factors on adhesion and biofilm formation. We used a combination of fluorescence microscopy (4′,6′-diamidino-2-phenylindole staining and in situ hybridization, for mixed-culture studies), ultrasonic removal of bacteria from surfaces, and indirect conductometry and found this combination sufficient to quantify bacteria on surfaces. PMID:11319118

  17. Effect of finishing process on the surface quality of Co-Cr-Mo dental alloys

    Directory of Open Access Journals (Sweden)

    Dorota Klimecka -Tatar

    2016-09-01

    Full Text Available Preparatory procedures for the material have a significant influence on the surface stereometry of the material. This study investigated the effect of the electropolishing process on the surface quality of metallic prosthetic constructions based on Co-Cr-Mo alloys. It has been found that the process of electropolishing prevents to excessive development of the surface of a material and consequently improves surface quality.

  18. Bacterial desorption from food container and food processing surfaces.

    Science.gov (United States)

    McEldowney, S; Fletcher, M

    1988-03-01

    The desorption ofStaphylococcus aureus, Acinetobacter calcoaceticus, and a coryneform from the surfaces of materials used for manufacturing food containers (glass, tin plate, and polypropylene) or postprocess canning factory conveyor belts (stainless steel and nylon) was investigated. The effect of time, pH, temperature, and adsorbed organic layers on desorption was studied.S. aureus did not detach from the substrata at any pH investigated (between pH 5 and 9).A. calcoaceticus and the coryneform in some cases detached, depending upon pH and substratum composition. The degree of bacterial detachment from the substrata was not related to bacterial respiration at experimental pH values. Bacterial desorption was not affected by temperature (4-30°C) nor by an adsorbed layer of peptone and yeast extract on the substrata. The results indicate that bacterial desorption, hence bacterial removal during cleaning or their transfer via liquids flowing over colonized surfaces, is likely to vary with the surface composition and the bacterial species colonizing the surfaces.

  19. Nano surface generation of grinding process using carbon nano tubes

    Indian Academy of Sciences (India)

    Nano surface finish has become an important parameter in the semiconductor, optical, electrical and mechanical industries. The materials used in these industries are classified as difficult to machine materials such as ceramics, glasses and silicon wafers. Machining of these materials up to nano accuracy is a great ...

  20. Influence of surface effects on subsecond processes in liquid metals

    International Nuclear Information System (INIS)

    Tkachenko, S.I.; Vorob'ev, V.S.; Khishchenko, K.V.

    2001-01-01

    Full Text: We discuss a problem of experimental-data interpretation during subsecond measurements of thermophysical properties of matter at high temperatures and pressures. Peculiarity of these measurements is optical opaqueness of matter under interesting conditions (T∼1 eV, ρ∼10 4 kg m -3 ), so only at assuming of bulk specimen uniformity one can obtain a temperature dependencies of the specific properties of matter. Changing circuit current and changing sample geometry we can avoid a development of hydromagnetic instability and decrease a nonuniform heating due to skin effect. As temperature of wire surface reaches the boiling temperature under normal pressure so part of internal energy is lost because of evaporation and surface radiation at high temperature. So one can register a surface temperature and ascribe it to the whole sample bulk. Computer simulation of wire explosion taking into account surface radiation losses was carried out. Typical phase tracks for matter were obtained in both case as in consideration of radiation losses as without it. Comparison of the results with data concerning to isobaric-expansion experiments and semi-empirical multi-phase equation of state were carried out. It was proposed uniformity criterion for investigation of thermophysical properties of liquid metal by subsecond wire explosion. (author)

  1. Earthquake rupture process recreated from a natural fault surface

    Science.gov (United States)

    Parsons, Thomas E.; Minasian, Diane L.

    2015-01-01

    What exactly happens on the rupture surface as an earthquake nucleates, spreads, and stops? We cannot observe this directly, and models depend on assumptions about physical conditions and geometry at depth. We thus measure a natural fault surface and use its 3D coordinates to construct a replica at 0.1 m resolution to obviate geometry uncertainty. We can recreate stick-slip behavior on the resulting finite element model that depends solely on observed fault geometry. We clamp the fault together and apply steady state tectonic stress until seismic slip initiates and terminates. Our recreated M~1 earthquake initiates at contact points where there are steep surface gradients because infinitesimal lateral displacements reduce clamping stress most efficiently there. Unclamping enables accelerating slip to spread across the surface, but the fault soon jams up because its uneven, anisotropic shape begins to juxtapose new high-relief sticking points. These contacts would ultimately need to be sheared off or strongly deformed before another similar earthquake could occur. Our model shows that an important role is played by fault-wall geometry, though we do not include effects of varying fluid pressure or exotic rheologies on the fault surfaces. We extrapolate our results to large fault systems using observed self-similarity properties, and suggest that larger ruptures might begin and end in a similar way, though the scale of geometrical variation in fault shape that can arrest a rupture necessarily scales with magnitude. In other words, fault segmentation may be a magnitude dependent phenomenon and could vary with each subsequent rupture.

  2. Improving the work function of the niobium surface of SRF cavities by plasma processing

    International Nuclear Information System (INIS)

    Tyagi, P.V.; Doleans, M.; Hannah, B.; Afanador, R.; McMahan, C.; Stewart, S.; Mammosser, J.; Howell, M.; Saunders, J.; Degraff, B.; Kim, S.-H.

    2016-01-01

    Highlights: • An in situ plasma processing for SNS SRF cavities has been developed to remove hydrocarbons from cavity surface. • Reactive oxygen plasma is very effective to remove hydrocarbons from niobium top surface. • Reactive oxygen plasma processing increases the work function of niobium surface in the range of 0.5–1.0 eV. • It was observed that hydrocarbons can migrate at plasma cleaned top surface from near surface regions when waiting in vacuum at room temperature. • Multiple cycles of plasma processing with waiting periods in between was found beneficial to mitigate such hydrocarbons migration at plasma cleaned surface. - Abstract: An in situ plasma processing technique using chemically reactive oxygen plasma to remove hydrocarbons from superconducting radio frequency cavity surfaces at room temperature has been developed at the spallation neutron source, at Oak Ridge National Laboratory. To understand better the interaction between the plasma and niobium surface, surface studies on small samples were performed. In this article, we report the results from those surface studies. The results show that plasma processing removes hydrocarbons from top surface and improves the surface work function by 0.5–1.0 eV. Improving the work function of RF surface of cavities can help to improve their operational performance.

  3. Surface enhancement of cold work tool steels by friction stir processing with a pinless tool

    Science.gov (United States)

    Costa, M. I.; Verdera, D.; Vieira, M. T.; Rodrigues, D. M.

    2014-03-01

    The microstructure and mechanical properties of enhanced tool steel (AISI D2) surfaces produced using a friction stir welding (FSW) related procedure, called friction stir processing (FSP), are analysed in this work. The surface of the tool steel samples was processed using a WC-Co pinless tool and varying processing conditions. Microstructural analysis revealed that meanwhile the original substrate structure consisted of a heterogeneous distribution of coarse carbides in a ferritic matrix, the transformed surfaces consisted of very small carbides, homogenously distributed in a ferrite- bainite- martensite matrix. The morphology of the surfaces, as well as its mechanical properties, evaluated by hardness and tensile testing, were found to vary with increasing tool rotation speed. Surface hardness was drastically increased, relative to the initial hardness of bulk steel. This was attributed to ferrite and carbide refinement, as well as to martensite formation during solid state processing. At the highest rotation rates, tool sliding during processing deeply compromised the characteristics of the processed surfaces.

  4. Organic cofactors participated more frequently than transition metals in redox reactions of primitive proteins.

    Science.gov (United States)

    Ji, Hong-Fang; Chen, Lei; Zhang, Hong-Yu

    2008-08-01

    Protein redox reactions are one of the most basic and important biochemical actions. As amino acids are weak redox mediators, most protein redox functions are undertaken by protein cofactors, which include organic ligands and transition metal ions. Since both kinds of redox cofactors were available in the pre-protein RNA world, it is challenging to explore which one was more involved in redox processes of primitive proteins? In this paper, using an examination of the redox cofactor usage of putative ancient proteins, we infer that organic ligands participated more frequently than transition metals in redox reactions of primitive proteins, at least as protein cofactors. This is further supported by the relative abundance of amino acids in the primordial world. Supplementary material for this article can be found on the BioEssays website. (c) 2008 Wiley Periodicals, Inc.

  5. Laser surface processing with controlled nitrogen-argon concentration levels for regulated surface life time

    Science.gov (United States)

    Obeidi, M. Ahmed; McCarthy, E.; Brabazon, D.

    2018-03-01

    Laser surface modification can be used to enhance the mechanical properties of a material, such as hardness, toughness, fatigue strength, and corrosion resistance. Surface nitriding is a widely used thermochemical method of surface modification, in which nitrogen is introduced into a metal or other material at an elevated temperature within a furnace. It is used on parts where there is a need for increased wear resistance, corrosion resistance, fatigue life, and hardness. Laser nitriding is a novel method of nitriding where the surface is heated locally by a laser, either in an atmosphere of nitrogen or with a jet of nitrogen delivered to the laser heated site. It combines the benefits of laser modification with those of nitriding. Recent work on high toughness tool steel samples has shown promising results due to the increased nitrogen gas impingement onto the laser heated region. Increased surface activity and nitrogen adsorption was achieved which resulted in a deeper and harder surface compared to conventional hardening methods. In this work, the effects of the laser power, pulse repetition frequency, and overlap percentage on laser surface treatment of 316 L SST steel samples with an argon-nitrogen jet will be presented. Resulting microstructure, phase type, microhardness, and wear resistance are presented.

  6. Surface modification of the metal plates using continuous electron beam process (CEBP)

    International Nuclear Information System (INIS)

    Kim, Jisoo; Kim, Jin-Seok; Kang, Eun-Goo; Park, Hyung Wook

    2014-01-01

    Highlights: • We performed surface modification of SM20C, SUS303, and Al6061 using CEBP. • We analyzed surface properties and microstructure after electron-beam irradiation. • The surface quality was improved after electron-beam irradiation. • The surface hardness for SM20C was increased by ∼50% after CEBP irradiation. - Abstract: The finishing process is an important component of the quality-control procedure for final products in manufacturing applications. In this study, we evaluated the performance of continuous electron-beam process as the final process for finishing SM20C (steel alloy), SUS303 (stainless steel alloy), and Al6061 (aluminum alloy) surfaces both on the initially smooth and rough surfaces. Surface modification of the metals was carried out by varying the feed and frequency of the continuous electron-beam irradiation procedure. The resulting surface roughness was examined with respect to the initial surface roughness of the metals. SM20C and SUS303 experienced an improvement in surface roughness, particularly for initially rough surfaces. Continuous electron-beam process produced craters during the process and the effect of this phenomenon on the resulting surface roughness was relatively large with the initially smooth SM20C and SUS303 alloy surfaces. For Al6061, the continuous electron-beam process was effective at improving its surface roughness even with the initially smooth surface under the optimized conditions of process; this was attributed to its low melting point. Scanning electron microscopy was used to identify metallurgical variation within the thin melted and re-solidification layers of the tested alloys. Changes in the surface contact angle and hardness before and after electron-beam irradiation were also examined

  7. Surface modification of the metal plates using continuous electron beam process (CEBP)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jisoo, E-mail: kimjisu16@unist.ac.kr [School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology, UNIST-gil 50, Eonyang-eup, Ulju-gun, Ulsan Metropolitan City 689-798 (Korea, Republic of); Kim, Jin-Seok, E-mail: totoro22@kitech.re.kr [Korea Institute of Industrial Technology (KITECH), KITECH Cheonan Headquarters 35-3 Hongcheon-ri, Ipjang-myeon, Cheonan-si, Chungcheongnam-do 330-825 (Korea, Republic of); Kang, Eun-Goo, E-mail: egkang@kitech.re.kr [Korea Institute of Industrial Technology (KITECH), KITECH Cheonan Headquarters 35-3 Hongcheon-ri, Ipjang-myeon, Cheonan-si, Chungcheongnam-do 330-825 (Korea, Republic of); Park, Hyung Wook, E-mail: hwpark@unist.ac.kr [School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology, UNIST-gil 50, Eonyang-eup, Ulju-gun, Ulsan Metropolitan City 689-798 (Korea, Republic of)

    2014-08-30

    Highlights: • We performed surface modification of SM20C, SUS303, and Al6061 using CEBP. • We analyzed surface properties and microstructure after electron-beam irradiation. • The surface quality was improved after electron-beam irradiation. • The surface hardness for SM20C was increased by ∼50% after CEBP irradiation. - Abstract: The finishing process is an important component of the quality-control procedure for final products in manufacturing applications. In this study, we evaluated the performance of continuous electron-beam process as the final process for finishing SM20C (steel alloy), SUS303 (stainless steel alloy), and Al6061 (aluminum alloy) surfaces both on the initially smooth and rough surfaces. Surface modification of the metals was carried out by varying the feed and frequency of the continuous electron-beam irradiation procedure. The resulting surface roughness was examined with respect to the initial surface roughness of the metals. SM20C and SUS303 experienced an improvement in surface roughness, particularly for initially rough surfaces. Continuous electron-beam process produced craters during the process and the effect of this phenomenon on the resulting surface roughness was relatively large with the initially smooth SM20C and SUS303 alloy surfaces. For Al6061, the continuous electron-beam process was effective at improving its surface roughness even with the initially smooth surface under the optimized conditions of process; this was attributed to its low melting point. Scanning electron microscopy was used to identify metallurgical variation within the thin melted and re-solidification layers of the tested alloys. Changes in the surface contact angle and hardness before and after electron-beam irradiation were also examined.

  8. Understanding the nanoscale redox-behavior of iron-anodes for rechargeable iron-air batteries

    Energy Technology Data Exchange (ETDEWEB)

    Weinrich, Henning [Forschungszentrum Julich (Germany). Inst. for Energy and Climate Research-Fundamental Electrochemistry (IEK-9); RWTH Aachen Univ., Aachen (Germany). Inst. of Physical Chemistry; Come, Jérémy [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Tempel, Hermann [Forschungszentrum Julich (Germany). Inst. for Energy and Climate Research-Fundamental Electrochemistry (IEK-9); Kungl, Hans [Forschungszentrum Julich (Germany). Inst. for Energy and Climate Research-Fundamental Electrochemistry (IEK-9); Eichel, Rüdiger-A. [Forschungszentrum Julich (Germany). Inst. for Energy and Climate Research-Fundamental Electrochemistry (IEK-9); Balke, Nina [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS)

    2017-10-10

    Iron-air cells provide a promising and resource-efficient alternative battery concept with superior area specific power density characteristics compared to state-of-the-art Li-air batteries and potentially superior energy density characteristics compared to present Li-ion batteries. Understanding charge-transfer reactions at the anode-electrolyte interface is the key to develop high-performance cells. By employing in-situ electrochemical atomic force microscopy (in-situ EC-AFM), in-depth insight into the electrochemically induced surface reaction processes on iron in concentrated alkaline electrolyte is obtained. The results highlight the formation and growth of the redox-layer on iron over the course of several oxidation/reduction cycles. By this means, a direct correlation between topography changes and the corresponding electrochemical reactions at the nanoscale could unambiguously be established. Here in this paper, the twofold character of the nanoparticulate redox-layer in terms of its passivating character and its contribution to the electrochemical reactions is elucidated. Furthermore, the evolution of single nanoparticles on the iron electrode surface is evaluated in unprecedented and artifact-free detail. Based on the dedicated topography analysis, a detailed structural model for the evolution of the redox-layer which is likewise elementary for corrosion science and battery research is derived.

  9. Effect of Surface Diffusion on Transfer Processes in Heterogeneous Systems

    Czech Academy of Sciences Publication Activity Database

    Levdansky, V.V.; Smolík, Jiří; Moravec, Pavel

    2008-01-01

    Roč. 51, 9-10 (2008), s. 2471-2481 ISSN 0017-9310 R&D Projects: GA ČR GA101/05/2214; GA ČR(CZ) GA101/05/2524; GA ČR GA104/07/1093 Institutional research plan: CEZ:AV0Z40720504 Keywords : adsorption * gas flow * surface diffusion Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.894, year: 2008

  10. Prospects of DLC coating as environment friendly surface treatment process.

    Science.gov (United States)

    Kim, S W; Kim, S G

    2011-06-01

    After first commercialization in 90's, the applications of diamond-like carbon (DLC) have been significantly expanded to tool, automobile parts, machineries and moulds to enhance wear and friction properties. Although DLC has many advantages like high hardness, low friction electrical insulating and chemical stability and has the possible market, its application in the field is still very limited due to the gaps of understanding between end-user and developer of its advantage of costing. Recently, one of the most popular issues in the surface modification is providing the long lasting super-hydrophilic or -hydrophobic properties on the material surface for the outdoor usage. A lot of material loss is caused due to water corrosion which has to do with the flow and contacts of water like fuel cell separator and air conditioner parts. The consequence of development of functional surface based on the hydrophilic or hydrophobic design for the important parts would be really helpful for materials to be cleaner and more energy effective. Here, we first reviewed the DLC technology and then examined the kind of surface modification as well as its merits and disadvantage. We also looked at how we can improve super-hydrophilic and super hydrophobic for the DLC coating layer as well as current status of technology and arts of DLC. In the end, we would like to suggest it as one of the environmental friendly industrial technology. Copyright © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

  11. Nanostructured surface processing by an intense pulsed ion beam irradiation

    International Nuclear Information System (INIS)

    Yatsuzuka, M.; Masuda, T.; Yamasaki, T.; Uchida, H.; Nobuhara, S.; Hashimoto, Y.; Yoshihara, Y.

    1997-01-01

    Metal surface modification by irradiating an intense pulsed ion beam (IPIB) with short pulse width has been studied experimentally. An IPIB irradiation to a target leads to rapid heating above its melting point. After the beam is turned off, the heated region is immediately cooled by thermal conduction at a cooling rate of typically 10 10 K/s. This rapid cooling and resolidification results in generation of nanostructured phase in the top of surface. The typical hydrogen IPIB parameters are 200 kV of energy, 500 A/cm 2 of current density and 70 ns of pulsewidth. The IPIB was irradiated on a pure titanium to generate nanocrystalline phase. The IPIB-irradiated surface was examined with X-ray diffraction, SEM, and HR-TEM. The randomly oriented lattice fringes as well as a halo diffraction pattern are observed in the HR-TEM micrograph of IPIB-irradiated titanium. The average grain size is found to be 32 nanometers

  12. Redox Regulation in Amyotrophic Lateral Sclerosis

    Science.gov (United States)

    Parakh, Sonam; Spencer, Damian M.; Halloran, Mark A.; Soo, Kai Y.; Atkin, Julie D.

    2013-01-01

    Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that results from the death of upper and lower motor neurons. Due to a lack of effective treatment, it is imperative to understand the underlying mechanisms and processes involved in disease progression. Regulations in cellular reduction/oxidation (redox) processes are being increasingly implicated in disease. Here we discuss the possible involvement of redox dysregulation in the pathophysiology of ALS, either as a cause of cellular abnormalities or a consequence. We focus on its possible role in oxidative stress, protein misfolding, glutamate excitotoxicity, lipid peroxidation and cholesterol esterification, mitochondrial dysfunction, impaired axonal transport and neurofilament aggregation, autophagic stress, and endoplasmic reticulum (ER) stress. We also speculate that an ER chaperone protein disulphide isomerase (PDI) could play a key role in this dysregulation. PDI is essential for normal protein folding by oxidation and reduction of disulphide bonds, and hence any disruption to this process may have consequences for motor neurons. Addressing the mechanism underlying redox regulation and dysregulation may therefore help to unravel the molecular mechanism involved in ALS. PMID:23533690

  13. Free energy surfaces from nonequilibrium processes without work measurement

    Science.gov (United States)

    Adib, Artur B.

    2006-04-01

    Recent developments in statistical mechanics have allowed the estimation of equilibrium free energies from the statistics of work measurements during processes that drive the system out of equilibrium. Here a different class of processes is considered, wherein the system is prepared and released from a nonequilibrium state, and no external work is involved during its observation. For such "clamp-and-release" processes, a simple strategy for the estimation of equilibrium free energies is offered. The method is illustrated with numerical simulations and analyzed in the context of tethered single-molecule experiments.

  14. Facile preparation of self-healing superhydrophobic CeO2 surface by electrochemical processes

    Science.gov (United States)

    Nakayama, Katsutoshi; Hiraga, Takuya; Zhu, Chunyu; Tsuji, Etsushi; Aoki, Yoshitaka; Habazaki, Hiroki

    2017-11-01

    Herein we report simple electrochemical processes to fabricate a self-healing superhydrophobic CeO2 coating on Type 304 stainless steel. The CeO2 surface anodically deposited on flat stainless steel surface is hydrophilic, although high temperature-sintered and sputter-deposited CeO2 surface was reported to be hydrophobic. The anodically deposited hydrophilic CeO2 surface is transformed to hydrophobic during air exposure. Specific accumulation of contaminant hydrocarbon on the CeO2 surface is responsible for the transformation to hydrophobic state. The deposition of CeO2 on hierarchically rough stainless steel surface produces superhydrophobic CeO2 surface, which also shows self-healing ability; the surface changes to superhydrophilic after oxygen plasma treatment but superhydrophobic state is recovered repeatedly by air exposure. This work provides a facile method for preparing a self-healing superhydrophobic surface using practical electrochemical processes.

  15. Surface Distresses Detection of Pavement Based on Digital Image Processing

    OpenAIRE

    Ouyang , Aiguo; Luo , Chagen; Zhou , Chao

    2010-01-01

    International audience; Pavement crack is the main form of early diseases of pavement. The use of digital photography to record pavement images and subsequent crack detection and classification has undergone continuous improvements over the past decade. Digital image processing has been applied to detect the pavement crack for its advantages of large amount of information and automatic detection. The applications of digital image processing in pavement crack detection, distresses classificati...

  16. Improvement in Surface Characterisitcs of Polymers for Subsequent Electroless Plating Using Liquid Assisted Laser Processing

    DEFF Research Database (Denmark)

    Marla, Deepak; Zhang, Yang; Jabbaribehnam, Mirmasoud

    2016-01-01

    Metallization of polymers is a widely used process in the electronic industry that involves their surface modification as a pre-treatment step. Laser-based surface modification is one of the commonly used techniques for polymers due to its speed and precision. The process involves laser heating...... of the polymer surface to generate a rough or porous surface. Laser processing in liquid generates superior surface characteristics that result in better metal deposition. In this study, a comparison of the surface characteristics obtained by laser processing in water vis-à-vis air along with the deposition...... characteristics are presented. In addition, a numerical model based on the finite volume method is developed to predict the temperature profile during the process. Based on the model results, it is hypothesized that physical phenomena such as vapor bubble generation and plasma formation may occur in the presence...

  17. Groundwater Discharge of Legacy Nitrogen to River Networks: Linking Regional Groundwater Models to Streambed Groundwater-Surface Water Exchange and Nitrogen Processing

    Science.gov (United States)

    Barclay, J. R.; Helton, A. M.; Briggs, M. A.; Starn, J. J.; Hunt, A.

    2017-12-01

    Despite years of management, excess nitrogen (N) is a pervasive problem in many aquatic ecosystems. More than half of surface water in the United States is derived from groundwater, and widespread N contamination in aquifers from decades of watershed N inputs suggest legacy N discharging from groundwater may contribute to contemporary N pollution problems in surface waters. Legacy N loads to streams and rivers are controlled by both regional scale flow paths and fine-scale processes that drive N transformations, such as groundwater-surface water exchange across steep redox gradients that occur at stream bed interfaces. Adequately incorporating these disparate scales is a challenge, but it is essential to understanding legacy N transport and making informed management decisions. We developed a regional groundwater flow model for the Farmington River, a HUC-8 basin that drains to the Long Island Sound, a coastal estuary that suffers from elevated N loads despite decades of management, to understand broad patterns of regional transport. To evaluate and refine the regional model, we used thermal infrared imagery paired with vertical temperature profiling to estimate groundwater discharge at the streambed interface. We also analyzed discharging groundwater for multiple N species to quantify fine scale patterns of N loading and transformation via denitrification at the streambed interface. Integrating regional and local estimates of groundwater discharge of legacy N to river networks should improve our ability to predict spatiotemporal patterns of legacy N loading to and transformation within surface waters.

  18. Stochastic Modeling and Deterministic Limit of Catalytic Surface Processes

    DEFF Research Database (Denmark)

    Starke, Jens; Reichert, Christian; Eiswirth, Markus

    2007-01-01

    Three levels of modeling, microscopic, mesoscopic and macroscopic are discussed for the CO oxidation on low-index platinum single crystal surfaces. The introduced models on the microscopic and mesoscopic level are stochastic while the model on the macroscopic level is deterministic. It can......, such that in contrast to the microscopic model the spatial resolution is reduced. The derivation of deterministic limit equations is in correspondence with the successful description of experiments under low-pressure conditions by deterministic reaction-diffusion equations while for intermediate pressures phenomena...

  19. Statistical and signal-processing concepts in surface metrology

    International Nuclear Information System (INIS)

    Church, E.L.; Takacs, P.Z.

    1986-03-01

    This paper proposes the use of a simple two-scale model of surface roughness for testing and specifying the topographic figure and finish of synchrotron-radiation mirrors. In this approach the effects of figure and finish are described in terms of their slope distribution and power spectrum, respectively, which are then combined with the system point spread function to produce a composite image. The result can be used to predict mirror performance or to translate design requirements into manufacturing specifications. Pacing problems in this approach are the development of a practical long-trace slope-profiling instrument and realistic statistical models for figure and finish errors

  20. Statistical and signal-processing concepts in surface metrology

    Energy Technology Data Exchange (ETDEWEB)

    Church, E.L.; Takacs, P.Z.

    1986-03-01

    This paper proposes the use of a simple two-scale model of surface roughness for testing and specifying the topographic figure and finish of synchrotron-radiation mirrors. In this approach the effects of figure and finish are described in terms of their slope distribution and power spectrum, respectively, which are then combined with the system point spread function to produce a composite image. The result can be used to predict mirror performance or to translate design requirements into manufacturing specifications. Pacing problems in this approach are the development of a practical long-trace slope-profiling instrument and realistic statistical models for figure and finish errors.

  1. Synthesis and characterization of redox-active ferric nontronite

    Energy Technology Data Exchange (ETDEWEB)

    Ilgen, A. G.; Kukkadapu, R. K.; Dunphy, D. R.; Artyushkova, K.; Cerrato, J. M.; Kruichak, J. N.; Janish, M. T.; Sun, C. J.; Argo, J. M.; Washington, R. E.

    2017-10-01

    Heterogeneous redox reactions on clay mineral surfaces control mobility and bioavailability of redox-sensitive nutrients and contaminants. Iron (Fe) residing in clay mineral structures can either catalyze or directly participate in redox reactions; however, chemical controls over its reactivity are not fully understood. In our previous work we demonstrated that converting a minor portion of Fe(III) to Fe(II) (partial reduction) in the octahedral sheet of natural Fe-rich clay mineral nontronite (NAu-1) activates its surface, making it redox-active. In this study we produced and characterized synthetic ferric nontronite (SIP), highlighting structural and chemical similarities and differences between this synthetic nontronite and its natural counterpart NAu-1, and probed whether mineral surface is redox-active by reacting it with arsenic As(III) under oxic and anoxic conditions. We demonstrate that synthetic nontronite SIP undergoes the same activation as natural nontronite NAu-1 following the partial reduction treatment. Similar to NAu-1, SIP oxidized As(III) to As(V) under both oxic (catalytic pathway) and anoxic (direct oxidation) conditions. The similar reactivity trends observed for synthetic nontronite and its natural counterpart make SIP an appropriate analog for laboratory studies. The development of chemically pure analogs for ubiquitous soil minerals will allow for systematic research of the fundamental properties of these minerals.

  2. Unleashing the Power and Energy of LiFePO4-Based Redox Flow Lithium Battery with a Bifunctional Redox Mediator.

    Science.gov (United States)

    Zhu, Yun Guang; Du, Yonghua; Jia, Chuankun; Zhou, Mingyue; Fan, Li; Wang, Xingzhu; Wang, Qing

    2017-05-10

    Redox flow batteries, despite great operation flexibility and scalability for large-scale energy storage, suffer from low energy density and relatively high cost as compared to the state-of-the-art Li-ion batteries. Here we report a redox flow lithium battery, which operates via the redox targeting reactions of LiFePO 4 with a bifunctional redox mediator, 2,3,5,6-tetramethyl-p-phenylenediamine, and presents superb energy density as the Li-ion battery and system flexibility as the redox flow battery. The battery has achieved a tank energy density as high as 1023 Wh/L, power density of 61 mW/cm 2 , and voltage efficiency of 91%. Operando X-ray absorption near-edge structure measurements were conducted to monitor the evolution of LiFePO 4 , which provides insightful information on the redox targeting process, critical to the device operation and optimization.

  3. Gradient nanostructured surface of a Cu plate processed by incremental frictional sliding

    DEFF Research Database (Denmark)

    Hong, Chuanshi; Huang, Xiaoxu; Hansen, Niels

    2015-01-01

    The flat surface of a Cu plate was processed by incremental frictional sliding at liquid nitrogen temperature. The surface treatment results in a hardened gradient surface layer as thick as 1 mm in the Cu plate, which contains a nanostructured layer on the top with a boundary spacing of the order...

  4. Surface conductivity dependent dynamic behaviour of an ultrafine atmospheric pressure plasma jet for microscale surface processing

    Energy Technology Data Exchange (ETDEWEB)

    Abuzairi, Tomy [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Electrical Engineering, Faculty of Engineering, Universitas Indonesia, Depok 16424 (Indonesia); Okada, Mitsuru [Department of Engineering, Shizuoka University, Hamamatsu 432-8561 (Japan); Bhattacharjee, Sudeep [Department of Physics, Indian Institute of Technology, Kanpur 208016 (India); Nagatsu, Masaaki, E-mail: nagatsu.masaaki@shizuoka.ac.jp [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Engineering, Shizuoka University, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8561 (Japan)

    2016-12-30

    Highlights: • Spatio-temporal behaviors of capillary APPJs are studied for various substrates. • Plasma irradiation area depended on the substrate conductivity and permittivity. • Surface irradiation area was significantly broadened in polymer-like substrate. • Effect of applying a substrate bias on the APPJ irradiation area was investigated. - Abstract: An experimental study on the dynamic behaviour of microcapillary atmospheric pressure plasma jets (APPJs) with 5 μm tip size for surfaces of different conductivity is reported. Electrical and spatio-temporal characteristics of the APPJs are monitored using high voltage probe, current monitor and high speed intensified charge couple device camera. From these experimental results, we presented a simple model to understand the electrical discharge characteristics of the capillary APPJs with double electrodes, and estimated the velocity of the ionization fronts in the jet and the electron density to be 3.5–4.2 km/s and 2–7 × 10{sup 17} m{sup −3}. By analyzing the dynamics of the microcapillary APPJs for different substrate materials, it was found that the surface irradiation area strongly depended on the substrate conductivity and permittivity, especially in the case of polymer-like substrate, surface irradiation area was significantly broadened probably due to the repelling behaviour of the plasma jets from the accumulated electrical charges on the polymer surface. The effect of applying a substrate bias in the range from −900 V to +900 V on the plasma irradiation onto the substrates was also investigated. From the knowledge of the present results, it is helpful for choosing the substrate materials for microscale surface modification.

  5. Surface conductivity dependent dynamic behaviour of an ultrafine atmospheric pressure plasma jet for microscale surface processing

    International Nuclear Information System (INIS)

    Abuzairi, Tomy; Okada, Mitsuru; Bhattacharjee, Sudeep; Nagatsu, Masaaki

    2016-01-01

    Highlights: • Spatio-temporal behaviors of capillary APPJs are studied for various substrates. • Plasma irradiation area depended on the substrate conductivity and permittivity. • Surface irradiation area was significantly broadened in polymer-like substrate. • Effect of applying a substrate bias on the APPJ irradiation area was investigated. - Abstract: An experimental study on the dynamic behaviour of microcapillary atmospheric pressure plasma jets (APPJs) with 5 μm tip size for surfaces of different conductivity is reported. Electrical and spatio-temporal characteristics of the APPJs are monitored using high voltage probe, current monitor and high speed intensified charge couple device camera. From these experimental results, we presented a simple model to understand the electrical discharge characteristics of the capillary APPJs with double electrodes, and estimated the velocity of the ionization fronts in the jet and the electron density to be 3.5–4.2 km/s and 2–7 × 10"1"7 m"−"3. By analyzing the dynamics of the microcapillary APPJs for different substrate materials, it was found that the surface irradiation area strongly depended on the substrate conductivity and permittivity, especially in the case of polymer-like substrate, surface irradiation area was significantly broadened probably due to the repelling behaviour of the plasma jets from the accumulated electrical charges on the polymer surface. The effect of applying a substrate bias in the range from −900 V to +900 V on the plasma irradiation onto the substrates was also investigated. From the knowledge of the present results, it is helpful for choosing the substrate materials for microscale surface modification.

  6. Hydrologic influence on redox dynamics in estuarine environments

    Science.gov (United States)

    Michael, H. A.; Kim, K. H.; Guimond, J. A.; Heiss, J.; Ullman, W. J.; Seyfferth, A.

    2017-12-01

    Redox conditions in coastal aquifers control reactions that impact nutrient cycling, contaminant release, and carbon budgets, with implications for water resources and ecosystem health. Hydrologic changes can shift redox boundaries and inputs of reactants, especially in dynamic coastal systems subject to fluctuations on tidal, lunar, and longer timescales. We present two examples of redox shifts in estuarine systems in Delaware, USA: a beach aquifer and a saltmarsh. Beach aquifers are biogeochemical hot spots due to mixing between fresh groundwater and infiltrating seawater. At Cape Henlopen, DE, geochemical measurements identified reactions in the intertidal aquifer that include cycling of carbon, nitrogen, iron, and sulfur. Measurements and modeling illustrate that redox potential as well as the locations of redox reactions shift on tidal to seasonal timescales and in response to changing beach and aquifer properties, impacting overall rates of reactions such as denitrification that reduces N loads to coastal waters. In the St. Jones National Estuarine Research Reserve, tidal fluctuations in channels cause periodic groundwater-surface water exchange, water table movement, and intermittent flooding that varies spatially across the saltmarsh. These changes create shifts in redox potential that are greatest near channels and in the top 20 cm of sediments. The magnitude of redox change depends on hydrologic setting (near channels or in marsh interior), hydrologic conditions (tidal stage, seasonal shifts), as well as prevalence of macropores created by crab burrows that change seasonally with crab activity. These shifts correspond to changes in porewater chemistry that have implications for nutrient cycling and carbon export to the ocean. Understanding hydrologic influence on redox geochemistry is critical for predicting how these systems and their ecosystem services may change in the future in response to anthropogenic and climate change.

  7. Surface light scattering: integrated technology and signal processing

    DEFF Research Database (Denmark)

    Lading, L.; Dam-Hansen, C.; Rasmussen, E.

    1997-01-01

    systems representing increasing levels of integration are considered. It is demonstrated that efficient signal and data processing can be achieved by evaluation of the statistics of the derivative of the instantaneous phase of the detector signal. (C) 1997 Optical Society of America....

  8. Surface modification of hydroturbine steel using friction stir processing

    Science.gov (United States)

    Grewal, H. S.; Arora, H. S.; Singh, H.; Agrawal, A.

    2013-03-01

    Friction stir processing (FSP) has proved to be a viable tool for enhancing the mechanical properties of materials, however, the major focus has been upon improving the bulk properties of light metals and their alloys. Hydroturbines are susceptible to damage owing to slurry and cavitation erosion. In this study, FSP of a commonly employed hydroturbine steel, 13Cr4Ni was undertaken. Microstructural characterization of the processed steel was conducted using optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and electron back scatter diffraction (EBSD) techniques. Mechanical characterization of the steel was undertaken in terms of microhardness and resistance to cavitation erosion (CE). FSP resulted in the refinement of the microstructure with reduction in grain size by a factor of 10. EBSD results confirmed the existence of submicron and ultrafine grained microstructure. The microhardness of the steel was found to enhance by 2.6 times after processing. The processed steel also showed 2.4 times higher resistance against cavitation erosion in comparison to unprocessed steel. The primary erosion mechanism for both the steels was identical in nature, with plastic deformation responsible for the loss of material.

  9. Surface morphology evolution in silicon during ion beam processing; TOPICAL

    International Nuclear Information System (INIS)

    Bedrossian P; Caturla, M; Diaz de la Rubia, T; Johnson, M

    1999-01-01

    The Semiconductor Industry Association (SIA) projects that the semiconductor chips used in personal computers and scientific workstations will reach five times the speed and ten times the memory capacity of the current pentium-class processor by the year 2007. However, 1 GHz on-chip clock speeds and 64 Gbits/Chip DRAM technology will not come easy and without a price. Such technologies will require scaling the minimum feature size of CMOS devices (the transistors in the silicon chip) down to below 100nm from the current 180 to 250 nm. This requirement has profound implications for device manufacturing. Existing processing techniques must increasingly be understood quantitatively and modeled with unprecedented precision. Indeed, revolutionary advances in the development of physics-based process simulation tools will be required to achieve the goals for cost efficient manufacturing, and to satisfy the needs of the defense industrial base. These advances will necessitate a fundamental improvement in our basic understanding of microstructure evolution during processing. In order to cut development time and costs, the semiconductor industry makes extensive use of simple models of dopant implantation, and of phenomenological models of defect annealing and diffusion. However, the production of a single device often requires more than 200 processing steps, and the cumulative effects of the various steps are far too complex to be treated with these models. The lack of accurate process modeling simulators is proving to be a serious impediment to the development of next generation devices. New atomic-level models are required to describe the point defect distributions produced by the implantation process, and the defect and dopant diffusion resulting from rapid thermal annealing steps. In this LDRD project, we investigated the migration kinetics of defects and dopants in silicon both experimentally and theoretically to provide a fundamental database for use in the development

  10. Thermal Diffusion Processes in Metal-Tip-Surface Interactions: Contact Formation and Adatom Mobility

    DEFF Research Database (Denmark)

    Sørensen, Mads Reinholdt; Jacobsen, Karsten Wedel; Jonsson, Hannes

    1996-01-01

    and the surface can occur by a sequence of atomic hop and exchange processes which become active on a millisecond time scale when the tip is about 3-5 Angstrom from the surface. Adatoms on the surface are stabilized by the presence of the tip and energy barriers for diffusion processes in the region under the tip......We have carried out computer simulations to identify and characterize various thermally activated atomic scale processes that can play an important role in room temperature experiments where a metal tip is brought close to a metal surface. We find that contact formation between the tip...

  11. A high volume cost efficient production macrostructuring process. [for silicon solar cell surface treatment

    Science.gov (United States)

    Chitre, S. R.

    1978-01-01

    The paper presents an experimentally developed surface macro-structuring process suitable for high volume production of silicon solar cells. The process lends itself easily to automation for high throughput to meet low-cost solar array goals. The tetrahedron structure observed is 0.5 - 12 micron high. The surface has minimal pitting with virtually no or very few undeveloped areas across the surface. This process has been developed for (100) oriented as cut silicon. Chemi-etched, hydrophobic and lapped surfaces were successfully texturized. A cost analysis as per Samics is presented.

  12. Tribological investigations of the applicability of surface functionalization for dry extrusion processes

    Science.gov (United States)

    Teller, Marco; Prünte, Stephan; Ross, Ingo; Temmler, André; Schneider, Jochen M.; Hirt, Gerhard

    2017-10-01

    Cold extrusion processes are characterized by large relative contact stresses combined with a severe surface enlargement of the workpiece. Under these process conditions a high risk for galling of workpiece material to the tool steel occurs especially in processing of aluminum and aluminum alloys. In order to reduce adhesive wear lubricants for separation of workpiece and tool surfaces are used. As a consequence additional process steps (e.g. preparation and cleaning of workpieces) are necessary. Thus, the realization of a dry forming process is aspired from an environmental and economic perspective. In this paper a surface functionalization with self-assembled-monolayers (SAM) of the tool steels AISI D2 (DIN 1.2379) and AISI H11 (DIN 1.2343) is evaluated by a process-oriented tribological test. The tribological experiment is able to resemble and scale the process conditions of cold extrusion related to relative contact stress and surface enlargement for the forming of pure aluminum (Al99.5). The effect of reduced relative contact stress, surface enlargement and relative velocity on adhesive wear and tool lifetime is evaluated. Similar process conditions are achievable by different die designs with decreased extrusion ratios and adjusted die angles. The effect of surface functionalization critically depends on the substrate material. The different microstructure and the resulting differences in surface chemistry of the two tested tool steels appear to affect the performance of the tool surface functionalization with SAM.

  13. Surface Nano Structures Manufacture Using Batch Chemical Processing Methods for Tooling Applications

    DEFF Research Database (Denmark)

    Tosello, Guido; Calaon, Matteo; Gavillet, J.

    2011-01-01

    The patterning of large surface areas with nano structures by using chemical batch processes to avoid using highenergy intensive nano machining processes was investigated. The capability of different surface treatment methods of creating micro and nano structured adaptable mould inserts for subse...

  14. Processing and properties of electrodeposited layered surface coatings

    DEFF Research Database (Denmark)

    Horsewell, Andy

    1998-01-01

    Hard chromium, produced by conventional dir ect curl ent (DC) electrodeposition, cannot be deposited to thicknesses gl enter than about 5 mu m because of the buildup of processing stresses which cause channel cracks in the coating. Much thicker chromium coatings map be produced by depositing a la...... geometry is almost always analogous to bending, and fracture resistance is provided through deviation of the channel crack by weak interfaces, resulting in 'terrace cracking'....

  15. Recycling and surface erosion processes in contemporary tokamaks

    International Nuclear Information System (INIS)

    McCracken, G.M.

    1979-03-01

    A number of global models have recently had considerable success in describing recycling. These are briefly reviewed. It is shown that large gas concentrations can build up in the walls and that these concentrations are seriously affected by erosion and deposition processes and by deliberate gettering with titanium. Finally, the measurement of the concentration of hydrogen in probes is discussed as a means of measuring plasma edge characteristics

  16. Influence of the surface layer characteristics on the regularities of the cutting process

    Directory of Open Access Journals (Sweden)

    Krainev Dmitriy V.

    2017-01-01

    Full Text Available The article considers the influence of the surface layer characteristics on the regularities of the cutting process and the formation of the quality of the surface machined. This effect has been confirmed by the study results of the combined cutting method with advanced plastic deformation (APD. The work estimates the impact of the change in the surface layer properties on the forces and temperature of cutting, stability of the chip formation and quality parameters of the surface machined.

  17. Redox speciation of final repository relevant elements using separation methods in combination with ICP mass spectrometry

    International Nuclear Information System (INIS)

    Graser, Carl-Heinrich

    2015-01-01

    The long-term safety assessment for nuclear waste repositories requires a detailed understanding of the chemistry of actinide elements in the geosphere. The development of advanced analytical tools is required to gain detailed insights into actinide redox speciation in a given system. The mobility of radionuclides is mostly determined by the geochemical conditions which control the redox state of radionuclides. Besides the longlived radionuclides plutonium (Pu) and neptunium (Np), which are key elements in high level nuclear waste, iron (Fe) represents a main component in natural systems controlling redox related geochemical processes. Analytical techniques for determining oxidation state distribution for redox sensitive radionuclides and other metal ions often have a lack of sensitivity. The detection limits of these methods (i.e. UV/vis, TRLFS, XANES) are in general in the range of ≥ 10 -6 mol.L -1 . As a consequence ultrasensitive new analytical techniques are required. Capillary electrophoresis (CE) and ion chromatography (IC) are powerful separation methods for metal ions. In the course of this thesis different speciation method for iron, neptunium and plutonium were optimized. With the optimized setup redox speciation analysis of these elements in different samples were done. Furthermore CE hyphenated to inductively coupled plasma sector field mass spectrometry (CE - ICP - SF - MS) was used to measure the redox speciation of Pu (III, IV, V, VI), Np (IV, V, VI) and Fe (II, III) at concentrations lower than 10 -7 mol.L -1 . CE coupling and separation parameters such as sample gas pressure, make up flow rate, capillary position, auxiliary gas flow, as well as the electrolyte system were optimized to obtain the maximum sensitivity. The methodes detection limits are 10 -12 mol.L -1 for Np and Pu. The various oxidation state species of Pu and Np in different samples were separated by application of an acetate based electrolyte system. The separation of Fe (II

  18. Effect of different machining processes on the tool surface integrity and fatigue life

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Chuan Liang [College of Mechanical and Electrical Engineering, Nanchang University, Nanchang (China); Zhang, Xianglin [School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan (China)

    2016-08-15

    Ultra-precision grinding, wire-cut electro discharge machining and lapping are often used to machine the tools in fine blanking industry. And the surface integrity from these machining processes causes great concerns in the research field. To study the effect of processing surface integrity on the fine blanking tool life, the surface integrity of different tool materials under different processing conditions and its influence on fatigue life were thoroughly analyzed in the present study. The result shows that the surface integrity of different materials was quite different on the same processing condition. For the same tool material, the surface integrity on varying processing conditions was quite different too and deeply influenced the fatigue life.

  19. Microscopic investigation of RF surfaces of 3 GHz niobium accelerator cavities following RF processing

    International Nuclear Information System (INIS)

    Graber, J.; Barnes, P.; Flynn, T.; Kirchgessner, J.; Knobloch, J.; Moffat, D.; Muller, H.; Padamsee, H.; Sears, J.

    1993-01-01

    RF processing of Superconducting accelerating cavities is achieved through a change in the electron field emission (FE) characteristics of the RF surface. The authors have examined the RF surfaces of several single-cell 3 GHz cavities, following RF processing, in a Scanning Electron Microscope (SEM). The RF processing sessions included both High Peak Power (P ≤ 50 kW) pulsed processing, and low power (≤ 20 W) continuous wave processing. The experimental apparatus also included a thermometer array on the cavity outer wall, allowing temperature maps to characterize the emission before and after RF processing gains. Multiple sites have been located in cavities which showed improvements in cavity behavior due to RF processing. Several SEM-located sites can be correlated with changes in thermometer signals, indicating a direct relationship between the surface site and emission reduction due to RF processing. Information gained from the SEM investigations and thermometry are used to enhance the theoretical model of RF processing

  20. Development of sustainable paper coatings using nanoscale industrial surface processing

    DEFF Research Database (Denmark)

    Markert, Frank; Breedveld, Leo; Lahti, Johanna

    in the PlasmaNice project, as environmental and social aspects are addressed using methods like life cycle check (LCC), life cycle assessment (LCA), and industrial risk assessment (RA) within the boundary of an economical production for different market segments. The results are intended to be used partly...... products, and the process and material developers providing new coatings with specific properties. The combination of RA and LCA/LCC within the early stages of product development provide a more holistic approach, It is commonly believed to be also economical beneficial as changes are easier to implement...

  1. Bifunctional redox flow battery

    International Nuclear Information System (INIS)

    Wen, Y.H.; Cheng, J.; Xun, Y.; Ma, P.H.; Yang, Y.S.

    2008-01-01

    A new bifunctional redox flow battery (BRFB) system, V(III)/V(II)-L-cystine(O 2 ), was systematically investigated by using different separators. It is shown that during charge, water transfer is significantly restricted with increasing the concentration of HBr when the Nafion 115 cation exchange membrane is employed. The same result can be obtained when the gas diffusion layer (GDL) hot-pressed separator is used. The organic electro-synthesis is directly correlated with the crossover of vanadium. When employing the anion exchange membrane, the electro-synthesis efficiency is over 96% due to a minimal crossover of vanadium. When the GDL hot-pressed separator is applied, the crossover of vanadium and water transfer are noticeably prevented and the electro-synthesis efficiency of over 99% is obtained. Those impurities such as vanadium ions and bromine can be eliminated through the purification of organic electro-synthesized products. The purified product is identified to be L-cysteic acid by IR spectrum. The BRFB shows a favorable discharge performance at a current density of 20 mA cm -2 . Best discharge performance is achieved by using the GDL hot-pressed separator. The coulombic efficiency of 87% and energy efficiency of about 58% can be obtained. The cause of major energy losses is mainly associated with the cross-contamination of anodic and cathodic active electrolytes

  2. Air/surface exchange processes of mercury and their linkage to atmospheric pools

    International Nuclear Information System (INIS)

    Bahlmann, Enno; Ebinghaus, Ralf

    2001-01-01

    The atmospheric mercury cycle is strongly linked to the terrestrial, aquatic and biologic cycle of mercury via air/surface exchange processes. In order to quantify mercury fluxes from and to the atmosphere to predict local and regional source contributions the methods for flux measurements as well as the physicochemical factors controlling air/surface exchange processes must be assessed. We will describe methods for the determination of mercury and mercury species in ambient air which are basic for investigation of air/surface exchange processes. Further on we will describe approaches for studying the physicochemical factors controlling this processes by using a new laboratory flux measurement system. (author)

  3. Improvement of Surface Properties of CP-Titanium by Thermo-Chemical Treatment (TCT) Process

    International Nuclear Information System (INIS)

    Jeong, Hyeon-Gyeong; Hur, Bo-Young; Lee, Dong-Geun; Lee, Yong-Tai; Yaskiv, O.

    2011-01-01

    The thermo-chemical treatment (TCT) process was applied to achieve surface hardening of CP titanium. The following three different surface modification conditions were tested so that the best surface hardening process could be selected:(a) PVD, (b) TCT+PVD, and (c) TCT+Aging+PVD. These specimens were tested and analyzed in terms of surface roughness, wear, friction coefficient, and the gradient of hardening from the surface of the matrix. The three test conditions were all beneficial to improve the surface hardness of CP titanium. Moreover, the TCT treated specimens, that is, (b) and (c), showed significantly improved surface hardness and low friction coefficients through the thickness up to 100um. This is due to the functionally gradient hardened surface improvement by the diffused interstitial elements. The hardened surface also showed improvement in bonding between the PVD and TCT surface, and this leads to improvement in wear resistance. However, TCT after aging treatment did not show much improvement in surface properties compared to TCT only. For the best surface hardening on CP titanium, TCT+PVD has advantages in surface durability and economics.

  4. Carbon activation process for increased surface accessibility in electrochemical capacitors

    Science.gov (United States)

    Doughty, Daniel H.; Eisenmann, Erhard T.

    2001-01-01

    A process for making carbon film or powder suitable for double capacitor electrodes having a capacitance of up to about 300 F/cm.sup.3 is disclosed. This is accomplished by treating in aqueous nitric acid for a period of about 5 to 15 minutes thin carbon films obtained by carbonizing carbon-containing polymeric material having a high degree of molecular directionality, such as polyimide film, then heating the treated carbon film in a non-oxidizing atmosphere at a non-graphitizing temperature of at least 350.degree. C. for about 20 minutes, and repeating alternately the nitric acid step and the heating step from 7 to 10 times. Capacitors made with this carbon may find uses ranging from electronic devices to electric vehicle applications.

  5. Study of the processes of adsorption of amine-containing surface-active substance on the surface of Aluminum powder

    Directory of Open Access Journals (Sweden)

    Antonina Dyuryagina

    2012-03-01

    Full Text Available Equilibrium characteristics of adsorption on a surface of a pigment depending on concentration factors and temperature of the dispersive environment are defined. Kinetic laws of superficial activity of binary, threefold homogeneous and heterogeneous modeling systems are studied. The estimation of mechanisms of process of adsorption is carried out.

  6. The process development of laser surface modification of commercially pure titanium (Grade 2) with rhenium

    Science.gov (United States)

    Kobiela, K.; Smolina, I.; Dziedzic, R.; Szymczyk, P.; Kurzynowski, T.; Chlebus, E.

    2016-12-01

    The paper presents the results of the process development of laser surface modification of commercially pure titanium with rhenium. The criterion of the successful/optimal process is the repetitive geometry of the surface, characterized by predictable and repetitive chemical composition over its entire surface as well as special mechanical properties (hardness and wear resistance). The analysis of surface geometry concluded measurements of laser penetration depth and heat affected zone (HAZ), the width of a single track as well as width of a clad. The diode laser installed on the industrial robot carried out the laser treatment. This solution made possible the continuous supply of powder to the substrate during the process. The aim of an investigation is find out the possibility of improving the tribological characteristics of the surface due to the rhenium alloying. The verification of the surface properties (tribological) concluded geometry measurements, microstructure observation, hardness tests and evaluation of wear resistance.

  7. A post-processing study on aluminum surface by fiber laser: Removing face milling patterns

    Science.gov (United States)

    Kayahan, Ersin

    2018-05-01

    The face milling process of the metal surface is a well-known machining process of using rotary cutters to remove material from a workpiece. Flat metal surfaces can be produced by a face milling process. However, in practice, visible, traced marks following the motion of points on the cutter's face are usually apparent. In this study, it was shown that milled patterns can be removed by means of 20 W fiber laser on the aluminum surface (AA7075). Experimental results also showed that roughened and hydrophobic surface can be produced with optimized laser parameters. It is a new approach to remove the patterns from the metal surface and can be explained through roughening by re-melting instead of ablation. The new method is a strong candidate to replace sandblasting the metal surface. It is also cheap and environmentally friendly.

  8. The theory of development of surface morphology by sputter erosion processes

    International Nuclear Information System (INIS)

    Carter, G.; Nobes, M.J.

    1984-01-01

    When a surface is bombarded by an energetic ion flux a rich variety of surface structures are observed to develop at the atomic, microscopic and macroscopic scales. Such structures include elevated, with respect to the surrounding surface, features such as mesas or plateaux, ridges, cones and pyramids and depressed features such as etch pits and cavities. These elementary features may be isolated or in profusion and frequently repetitive patterns of coordinated pyramidal structures, etch pits, surface ledges or facets and ripple or wave-like structures occur. The majority of the features arise rather directly from the erosion action of the sputtering process, particularly from differential erosion processes at different surface localities. The authors outline a general approach to sputter erosion induced surface morphology development based on the concept of the surface as an advancing wave. (Auth.)

  9. Metabolic and redox barriers in the skin exposed to drugs and xenobiotics.

    Science.gov (United States)

    Korkina, Liudmila

    2016-01-01

    Growing exposure of human skin to environmental and occupational hazards, to numerous skin care/beauty products, and to topical drugs led to a biomedical concern regarding sustainability of cutaneous chemical defence that is essential for protection against intoxication. Since skin is the largest extra-hepatic drug/xenobiotic metabolising organ where redox-dependent metabolic pathways prevail, in this review, publications on metabolic processes leading to redox imbalance (oxidative stress) and its autocrine/endocrine impact to cutaneous drug/xenobiotic metabolism were scrutinised. Chemical and photo-chemical skin barriers contain metabolic and redox compartments: their protective and homeostatic functions. The review will examine the striking similarity of adaptive responses to exogenous chemical/photo-chemical stressors and endogenous toxins in cutaneous metabolic and redox system; the role(s) of xenobiotics/drugs and phase II enzymes in the endogenous antioxidant defence and maintenance of redox balance; redox regulation of interactions between metabolic and inflammatory responses in skin cells; skin diseases sharing metabolic and redox problems (contact dermatitis, lupus erythematosus, and vitiligo) Due to exceptional the redox dependence of cutaneous metabolic pathways and interaction of redox active metabolites/exogenous antioxidants with drug/xenobiotic metabolism, metabolic tests of topical xenobiotics/drugs should be combined with appropriate redox analyses and performed on 3D human skin models.

  10. Identification of microbes from the surfaces of food-processing lines based on the flow cytometric evaluation of cellular metabolic activity combined with cell sorting.

    Science.gov (United States)

    Juzwa, W; Duber, A; Myszka, K; Białas, W; Czaczyk, K

    2016-09-01

    In this study the design of a flow cytometry-based procedure to facilitate the detection of adherent bacteria from food-processing surfaces was evaluated. The measurement of the cellular redox potential (CRP) of microbial cells was combined with cell sorting for the identification of microorganisms. The procedure enhanced live/dead cell discrimination owing to the measurement of the cell physiology. The microbial contamination of the surface of a stainless steel conveyor used to process button mushrooms was evaluated in three independent experiments. The flow cytometry procedure provided a step towards monitoring of contamination and enabled the assessment of microbial food safety hazards by the discrimination of active, mid-active and non-active bacterial sub-populations based on determination of their cellular vitality and subsequently single cell sorting to isolate microbial strains from discriminated sub-populations. There was a significant correlation (r = 0.97; p vitality and the identification of species from defined sub-populations, although the identified microbes were limited to culturable cells.

  11. Surface modification by electrolytic plasma processing for high Nb-TiAl alloys

    Science.gov (United States)

    Gui, Wanyuan; Hao, Guojian; Liang, Yongfeng; Li, Feng; Liu, Xiao; Lin, Junpin

    2016-12-01

    Metal surface modification by electrolytic plasma processing (EPP) is an innovative treatment widely commonly applied to material processing and pretreatment process of coating and galvanization. EPP involves complex processes and a great deal of parameters, such as preset voltage, current, solution temperature and processing time. Several characterization methods are presented in this paper for evaluating the micro-structure surfaces of Ti45Al8Nb alloys: SEM, EDS, XRD and 3D topography. The results showed that the oxide scale and other contaminants on the surface of Ti45Al8Nb alloys can be effectively removed via EPP. The typical micro-crater structure of the surface of Ti45Al8Nb alloys were observed by 3D topography after EPP to find that the mean diameter of the surface structure and roughness value can be effectively controlled by altering the processing parameters. The mechanical properties of the surface according to nanomechanical probe testing exhibited slight decrease in microhardness and elastic modulus after EPP, but a dramatic increase in surface roughness, which is beneficial for further processing or coating.

  12. In-situ investigation of hydrogen evolution behavior in vanadium redox flow batteries

    International Nuclear Information System (INIS)

    Wei, L.; Zhao, T.S.; Xu, Q.; Zhou, X.L.; Zhang, Z.H.

    2017-01-01

    Highlights: • An in-situ method to investigate hydrogen evolution in VRFBs is developed. • The rate of hydrogen evolution during battery operation is quantified. • The gas evolution behaviors in the charge process of VRFBs are observed. - Abstract: In this work, we conceived and fabricated a three-electrode electrochemical cell and transparent vanadium redox flow battery to in-situ investigate the hydrogen evolution reaction during battery operation. Experimental results show that operating temperature has a strong influence on the HER rate. In particular, compared with V"3"+ reduction reaction, HER is more sensitive to temperature variation. It is also found that, contrary to the conventional wisdom that side reactions occur at the late stage of the charge process, H_2 evolves at a relatively low SOC. About 0.26 and 1.94 mL H_2 were collected at an early (SOC lower than 20%) and end of the charge process, respectively, suggesting that attention to the hydrogen formation at the negative electrode in the early charge process should also be paid to during long-term battery operations. Moreover, the produced hydrogen gas at the negative side prefers to form macroscopically observable bubbles onto the electrode surface, covering the active sites for vanadium redox reactions, while oxygen evolution (including CO_2 production) at the positive side corrodes electrode surface and introduces certain oxygen-containing functional groups.

  13. Fabricating Super-hydrophobic Polydimethylsiloxane Surfaces by a Simple Filler-Dissolved Process

    Science.gov (United States)

    Lin, Yung-Tsan; Chou, Jung-Hua

    2010-12-01

    The self-cleaning effect of super-hydrophobic surfaces has attracted the attention of researchers. Typical ways of manufacturing super-hydrophobic surfaces include the use of either dedicated equipment or a complex chemical process. In this study, a simple innovative filler-dissolved method is developed using mainly powder salt and rinsing to form hydrophobic surfaces. This method can produce large super-hydrophobic surfaces with porous and micro rib surface structures. It can also be applied to curved surfaces, including flexible membranes. The contact angle of the manufactured artificial hydrophobic surface is about 160°. Furthermore, water droplets roll off the surface readily at a sliding angle of less than 5°, resembling the nonwetting lotus like effect.

  14. Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility

    OpenAIRE

    Kristina Wedege; Emil Dražević; Denes Konya; Anders Bentien

    2016-01-01

    Organic molecules are currently investigated as redox species for aqueous low-cost redox flow batteries (RFBs). The envisioned features of using organic redox species are low cost and increased flexibility with respect to tailoring redox potential and solubility from molecular engineering of side groups on the organic redox-active species. In this paper 33, mainly quinone-based, compounds are studied experimentially in terms of pH dependent redox potential, solubility and stability, combined ...

  15. Formation process of silver-polypyrrole coaxial nanocables synthesized by redox reaction between AgNO3 and pyrrole in the presence of poly(vinylpyrrolidone).

    Science.gov (United States)

    Chen, Aihua; Kamata, Kaori; Nakagawa, Masaru; Iyoda, Tomokazu; Haiqiao Wang, Haiqiao; Li, Xiaoyu

    2005-10-06

    We have recently demonstrated a one-step process to fabricate silver-polypyrrole (PPy) coaxial nanocables (Chen, A.; Wang, H.; Li, X. Chem. Commun. 2005, 14, 1863). The formation process of silver-PPy coaxial nanocables is discussed in this article. It was found from the results of TEM and SEM images that large numbers of silver atoms were formed when AgNO3 was added to a pyrrole solution. Then silver atoms transform to silver-PPy nanosheets with regular morphology, which will connect together to be more stable. Silver-PPy nanocables will be able to grow at the expense of the silver-PPy nanosheets. Poly(vinylpyrrolidone) (PVP) plays crucial roles in this process: as a capping agent to form silver nanowires, and as a dispersant of pyrrole monomers, which can influence the site at which pyrrole monomer exists. On the basis of experimental analysis, the possible mechanism was proposed. Because of the effect of PVP, silver ions and pyrrole monomers are apt to be adsorbed at the [111] and [100] facets of silver nanosheets, respectively. Obvious polymerization will take place on the boundary of the [111] and [100] facets. The PPy layer stays stable on the [100] facets. Meanwhile, newly formed silver atoms and silver nanosheets will further ripen and grow on the [111] facets. In a word, the morphology of final products and the formation process are determined by the reaction site between AgNO3 and the pyrrole monomer, which is influenced by PVP.

  16. Quantum dots use both LUMO and surface trap electrons in photoreduction process

    Energy Technology Data Exchange (ETDEWEB)

    Darżynkiewicz, Zbigniew M. [Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097 Warsaw (Poland); Division of Biophysics, Faculty of Physics, University of Warsaw, Żwirki i Wigury 93, 02-089 Warsaw (Poland); Pędziwiatr, Marta [Institute of Physics PAS, al. Lotników 32/46, 02-668 Warsaw (Poland); Grzyb, Joanna, E-mail: jgrzyb@ifpan.edu.pl [Institute of Physics PAS, al. Lotników 32/46, 02-668 Warsaw (Poland)

    2017-03-15

    Here, we explore a mechanism of quantum dots related photoreduction of two redox-active proteins, cytochrome c and ferredoxin, by detailed analysis of fluorescence decay and reconstruction of time-resolved emission spectra (TRES). We used two types of cadmium telluride quantum dots, with diameters of 2.6 nm and 3.9 nm and maximum emissions at 550 nm and at 650 nm, respectively, which are known to be able to reduce proteins with different efficiencies. First, we observed that for a pure quantum dots solution, the fluorescence decay can be well fitted by three components. The average fluorescence lifetimes, as well as separate time constants, depend on the nanocrystal diameter. In the presence of proteins, fluorescence decay is faster and cytochrome c has a greater impact than ferredoxin. The TRES experiment showed that a fraction of the medium τ decay component is dominant in a pure quantum dot solution, with the maximum corresponding to the steady-state spectrum. The addition of ferredoxin does not change this pattern, while the presence of cytochrome c strongly promotes the shortest τ. Additionally, potassium iodide titration experiments were used to verify the origin of individual decay components. We propose that reduction occurs by electron transfer from both conductive band and surface trap states.

  17. Redox Potentials of Ligands and Complexes – a DFT Approach

    African Journals Online (AJOL)

    NICO

    A review of the limited literature concerned with theoretical ways to predict experimentally measured redox potentials of ligands and ... electrode surface, over-potentials and high solvent resistance, ... A correlation coefficient of 0.969 in the linear relation with ... of E0' were performed in two steps, i.e. calculation of the free.

  18. Food-safe modification of stainless steel food processing surfaces to reduce bacterial biofilms.

    Science.gov (United States)

    Awad, Tarek Samir; Asker, Dalal; Hatton, Benjamin D

    2018-06-11

    Biofilm formation on stainless steel (SS) surfaces of food processing plants, leading to foodborne illness outbreaks, is enabled by the attachment and confinement within microscale cavities of surface roughness (grooves, scratches). We report Foodsafe Oil-based Slippery Coatings (FOSCs) for food processing surfaces that suppress bacterial adherence and biofilm formation by trapping residual oil lubricant within these surface cavities to block microbial growth. SS surfaces were chemically functionalized with alkylphosphonic acid to preferentially wet a layer of food grade oil. FOSCs reduced the effective surface roughness, the adhesion of organic food residue, and bacteria. FOSCs significantly reduced Pseudomonas aeruginosa biofilm formation on standard roughness SS-316 by 5 log CFU cm-2, and by 3 log CFU cm-2 for mirror-finished SS. FOSCs also enhanced surface cleanability, which we measured by bacterial counts after conventional detergent cleaning. Importantly, both SS grades maintained their anti-biofilm activity after erosion of the oil layer by surface wear with glass beads, which suggests there is a residual volume of oil that remains to block surface cavity defects. These results indicate the potential of such low-cost, scalable approaches to enhance the cleanability of SS food processing surfaces and improve food safety by reducing biofilm growth.

  19. Breast Cancer Redox Heterogeneity Detectable with Chemical Exchange Satruation Transfer (CEST) MRI

    Science.gov (United States)

    Cai, Kejia; Xu, He N.; Singh, Anup; Moon, Lily; Haris, Mohammad; Reddy, Ravinder; Li, Lin

    2014-01-01

    Purpose Tissue redox state is an important mediator of various biological processes in health and diseases such as cancer. Previously, we discovered that the mitochondrial redox state of ex vivo tissues detected by redox scanning (an optical imaging method) revealed interesting tumor redox state heterogeneity that could differentiate tumor aggressiveness. Because the noninvasive chemical exchange saturation transfer (CEST) MRI can probe the proton transfer and generate contrasts from endogenous metabolites, we aim to investigate if the in vivo CEST contrast is sensitive to proton transfer of the redox reactions so as to reveal the tissue redox states in breast cancer animal models. Procedures CEST MRI has been employed to characterize tumor metabolic heterogeneity and correlated with the redox states measured by the redox scanning in two human breast cancer mouse xenograft models, MDA-MB-231 and MCF-7. The possible biological mechanism on the correlation between the two imaging modalities was further investigated by phantom studies where the reductants and the oxidants of the representative redox reactions were measured. Results The CEST contrast is found linearly correlated with NADH concentration and the NADH redox ratio with high statistical significance, where NADH is the reduced form of nicotinamide adenine dinucleotide. The phantom studies showed that the reductants of the redox reactions have more CEST contrast than the corresponding oxidants, indicating that higher CEST effect corresponds to the more reduced redox state. Conclusions This preliminary study suggests that CEST MRI, once calibrated, might provide a novel noninvasive imaging surrogate for the tissue redox state and a possible diagnostic biomarker for breast cancer in the clinic. PMID:24811957

  20. A stability comparison of redox-active layers produced by chemical coupling of an osmium redox complex to pre-functionalized gold and carbon electrodes

    International Nuclear Information System (INIS)

    Boland, Susan; Foster, Kevin; Leech, Donal

    2009-01-01

    The production of stable redox active layers on electrode surfaces is a key factor for the development of practical electronic and electrochemical devices. Here, we report on a comparison of the stability of redox layers formed by covalently coupling an osmium redox complex to pre-functionalized gold and graphite electrode surfaces. Pre-treatment of gold and graphite electrodes to provide surface carboxylic acid groups is achieved via classical thiolate self-assembled monolayer formation on gold surfaces and the electro-reduction of an in situ generated aryldiazonium salt from 4-aminobenzoic acid on gold, glassy carbon and graphite surfaces. These surfaces have been characterized by AFM and electrochemical blocking studies. The surface carboxylate is then used to tether an osmium complex, [Os(2,2'-bipyridyl) 2 (4-aminomethylpyridine)Cl]PF 6 , to provide a covalently bound redox active layer, E 0 '' of 0.29 V (vs. Ag/AgCl in phosphate buffer, pH 7.4), on the pre-treated electrodes. The aryldiazonium salt-treated carbon-based surfaces showed the greatest stability, represented by a decrease of <5% in the peak current for the Os(II/III) redox transition of the immobilized complex over a 3-day period, compared to a decrease of 19% and 14% for the aryldiazonium salt treated and thiolate treated gold surfaces, respectively, over the same period

  1. Competing for phosphors under changing redox conditions: biological versus geochemical sinks

    Science.gov (United States)

    Gross, A.; Pett-Ridge, J.; Silver, W. L.

    2016-12-01

    Competing for phosphorus under changing redox conditions: biological versus geochemical sinksAvner Gross1, Jennifer Pett-Ridge2 and Whendee L Silver1 University of California Berkeley, Department of Environmental Science, Policy, & Management, Berkeley, CA, USA. Lawrence Livermore National Laboratory, Physical and Life Science Directorate, Livermore, CA, USA. The cycling of phosphorous (P) in highly weathered, humid tropical forest soils is tightly regulated by P sorption dynamics to the surfaces of Fe(III) (hydr)oxides and root and microbial demands for P. Periods of anoxic soil conditions, which are common in humid environments, induce the reduction of Fe (III) to Fe (II) and may release sorbed P into the soil solution. The microbial demand for P is influenced by the C and nutrient composition of their available substrates. Therefore, we hypothesize that soil redox conditions and substrate quality and availability will control the partitioning of P between microbial biomass and the soil mineral phase. The aim of this study was to examine how fluctuations in soil redox conditions and changes in microbial P demand affect the fate of new P that enters the soil solution. To achieve this aim we conducted a series of soil incubation experiments using a wet tropical soil from Puerto Rico (where redox conditions and P availability naturally oscillate) with a single pulse of phosphate (PO4), altering both the microbial activity and redox conditions. To follow the fate the added P, the added phosphate was labeled with 18O. As the exchange of oxygen between phosphate and water only occurs during biological processes, P-18O labeling can be used as an indicator of microbial use. To quantify sizes of the microbial and mineral P pools we used traditional chemical extractions in the bulk scale. We used NanoSIMS isotopic imaging to map the distribution of P-16O and P-18O and co-localization with Fe minerals at the nano scale. Our results show that the amount of the added P fixed

  2. Redox Conditions in Selected Principal Aquifers of the United States

    Science.gov (United States)

    McMahon, P.B.; Cowdery, T.K.; Chapelle, F.H.; Jurgens, B.C.

    2009-01-01

    Reduction/oxidation (redox) processes affect the quality of groundwater in all aquifer systems. Redox processes can alternately mobilize or immobilize potentially toxic metals associated with naturally occurring aquifer materials, contribute to the degradation or preservation of anthropogenic contami-nants, and generate undesirable byproducts, such as dissolved manganese (Mn2+), ferrous iron (Fe2+), hydrogen sulfide (H2S), and methane (CH4). Determining the kinds of redox processes that occur in an aquifer system, documenting their spatial distribution, and understanding how they affect concentrations of natural or anthropogenic contaminants are central to assessing and predicting the chemical quality of groundwater. This Fact Sheet extends the analysis of U.S. Geological Survey authors to additional principal aquifer systems by applying a framework developed by the USGS to a larger set of water-quality data from the USGS national water databases. For a detailed explanation, see the 'Introduction' in the Fact Sheet.

  3. Eco-friendly copper recovery process from waste printed circuit boards using Fe{sup 3+}/Fe{sup 2+} redox system

    Energy Technology Data Exchange (ETDEWEB)

    Fogarasi, Szabolcs [Babeş-Bolyai University, Faculty of Chemistry and Chemical Engineering, 11 Arany Janos Street, Cluj-Napoca RO-400028 (Romania); Imre-Lucaci, Florica [Babeş-Bolyai University, Interdisciplinary Research Institute on Bio-Nano-Sciences, 42 Treboniu Laurian Street, Cluj-Napoca RO-400271 (Romania); Egedy, Attila [University of Pannonia, Department of Process Engineering, Egyetem Str. 10, H-8200 Veszprém (Hungary); Imre-Lucaci, Árpád, E-mail: aimre@chem.ubbcluj.ro [Babeş-Bolyai University, Faculty of Chemistry and Chemical Engineering, 11 Arany Janos Street, Cluj-Napoca RO-400028 (Romania); Ilea, Petru [Babeş-Bolyai University, Faculty of Chemistry and Chemical Engineering, 11 Arany Janos Street, Cluj-Napoca RO-400028 (Romania)

    2015-06-15

    Highlights: • We developed an ecofriendly mediated electrochemical process for copper recovery. • The recovery of copper was achieved without mechanical pretreatment of the samples. • We identified the optimal flow rate for the leaching and electrowinning of copper. • The copper content of the obtained cathodic deposits was over 99.9%. - Abstract: The present study aimed at developing an original and environmentally friendly process for the recovery of copper from waste printed circuit boards (WPCBs) by chemical dissolution with Fe{sup 3+} combined with the simultaneous electrowinning of copper and oxidant regeneration. The recovery of copper was achieved in an original set-up consisting of a three chamber electrochemical reactor (ER) connected in series with a chemical reactor (CR) equipped with a perforated rotating drum. Several experiments were performed in order to identify the optimal flow rate for the dissolution of copper in the CR and to ensure the lowest energy consumption for copper electrodeposition in the ER. The optimal hydrodynamic conditions were provided at 400 mL/min, leading to the 75% dissolution of metals and to a low specific energy consumption of 1.59 kW h/kg Cu for the electrodeposition process. In most experiments, the copper content of the obtained cathodic deposits was over 99.9%.

  4. Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration

    Science.gov (United States)

    Hofer, Thomas S.; Hünenberger, Philippe H.

    2018-06-01

    The absolute intrinsic hydration free energy GH+,w a t ◦ of the proton, the surface electric potential jump χwa t ◦ upon entering bulk water, and the absolute redox potential VH+,w a t ◦ of the reference hydrogen electrode are cornerstone quantities for formulating single-ion thermodynamics on absolute scales. They can be easily calculated from each other but remain fundamentally elusive, i.e., they cannot be determined experimentally without invoking some extra-thermodynamic assumption (ETA). The Born model provides a natural framework to formulate such an assumption (Born ETA), as it automatically factors out the contribution of crossing the water surface from the hydration free energy. However, this model describes the short-range solvation inaccurately and relies on the choice of arbitrary ion-size parameters. In the present study, both shortcomings are alleviated by performing first-principle calculations of the hydration free energies of the sodium (Na+) and potassium (K+) ions. The calculations rely on thermodynamic integration based on quantum-mechanical molecular-mechanical (QM/MM) molecular dynamics (MD) simulations involving the ion and 2000 water molecules. The ion and its first hydration shell are described using a correlated ab initio method, namely resolution-of-identity second-order Møller-Plesset perturbation (RIMP2). The next hydration shells are described using the extended simple point charge water model (SPC/E). The hydration free energy is first calculated at the MM level and subsequently increased by a quantization term accounting for the transformation to a QM/MM description. It is also corrected for finite-size, approximate-electrostatics, and potential-summation errors, as well as standard-state definition. These computationally intensive simulations provide accurate first-principle estimates for GH+,w a t ◦, χwa t ◦, and VH+,w a t ◦, reported with statistical errors based on a confidence interval of 99%. The values obtained

  5. Characterization of surface processes on mineral surfaces in aqueous solutions. Annual report for fiscal year 1993

    International Nuclear Information System (INIS)

    Leckie, J.O.

    1993-11-01

    Performance assessments by Los Alamos National Laboratory for the DOE's Yucca Mountain Site Characterization Project (YMP) are being done investigating the environmental risk related to long-term disposal of hazardous wastes resulting from the use of radioactive materials that must subsequently be isolated from the environment. The YMP site, located in southwestern Nevada, is intended for the storage of high-level wastes generated by nuclear energy-related activities, including spent fuel and waste from reprocessed fuel rods. The work covered by this contract is necessary for producing a defensible model and dataset, and may be critical for evaluation of repository compliance. This work, performed by the Environmental Engineering and Science research group at Stanford University, will quantify the adsorption of uranyl on various minerals. The project's principle objective is to provide sorption coefficients for uranyl and other ions of interest to predict radionuclide movements form the repository to accessible environments. This adsorption data is essential for the unambiguous interpretation of field experiments and observations. In this report, details of the activity and progress made with respect to the study of uranyl adsorption on mineral surfaces is presented and discussed

  6. Continuous plutonium(IV) oxalate precipitation, filtration, and calcination process. [From product streams from Redox, Purex, or Recuplex solvent extraction plants

    Energy Technology Data Exchange (ETDEWEB)

    Beede, R L

    1956-09-27

    A continuous plutonium (IV) oxalate precipitation, filtration, and calcination process has been developed. Continuous and batch decomposition of the oxalate in the filtrates has been demonstrated. The processes have been demonstrated in prototype equipment. Plutonium (IV) oxalate was precipitated continuously at room temperature by the concurrent addition of plutonium (IV) nitrate feed and oxalic acid into the pan of a modified rotary drum filter. The plutonium (IV) oxalate was calcined to plutonium dioxide, which could be readily hydrofluorinated. Continuous decomposition of the oxalate in synthetic plutonium (IV) oxalate filtrates containing plutonium (IV) oxalate solids was demonstrated using co-current flow in a U-shaped reactor. Feeds containing from 10 to 100 g/1 Pu, as plutonium (IV) nitrate, and 1.0 to 6.5 M HNO/sub 3/, respectively, can be processed. One molar oxalic acid is used as the precipitant. Temperatures of 20 to 35/sup 0/C for the precipitation and filtration are satisfactory. Plutonium (IV) oxalate can be calcined at 300 to 400/sup 0/C in a screw-type drier-calciner to plutonium dioxide and hydrofluorinated at 450 to 550/sup 0/C. Plutonium dioxide exceeding purity requirements has been produced in the prototype equipment. Advantages of continuous precipitation and filtration are: uniform plutonium (IV) oxalate, improved filtration characteristics, elimination of heating and cooling facilities, and higher capacities through a single unit. Advantages of the screw-type drier-calciner are the continuous production of an oxide satisfactory for feed for the proposed plant vibrating tube hydrofluorinator, and ease of coupling continuous precipitation and filtration to this proposed hydrofluorinator. Continuous decomposition of oxalate in filtrates offers advantages in decreasing filtrate storage requirements when coupled to a filtrate concentrator. (JGB)

  7. Non destructive evaluation of residual stresses in welding and hard-surfacing processes

    International Nuclear Information System (INIS)

    Suarez, J.C.; Fernandez, L.M.; Cruz, C.; Aragon, B.; Merino, F.

    1995-01-01

    In this paper transversal and longitudinal stress profiles in welding and hard-surfacing by welding processes are presented. The stresses were measured by RMS of Barkhausen signal. In this work it is shown that in each case the level of stresses is strongly dependent on the number of weld beads of surfacing layers deposited. The subsequent deposition of new weld beads or surfacing layers produces a stress-relieving effect

  8. Reduction of Surface Roughness by Means of Laser Processing over Additive Manufacturing Metal Parts.

    Science.gov (United States)

    Alfieri, Vittorio; Argenio, Paolo; Caiazzo, Fabrizia; Sergi, Vincenzo

    2016-12-31

    Optimization of processing parameters and exposure strategies is usually performed in additive manufacturing to set up the process; nevertheless, standards for roughness may not be evenly matched on a single complex part, since surface features depend on the building direction of the part. This paper aims to evaluate post processing treating via laser surface modification by means of scanning optics and beam wobbling to process metal parts resulting from selective laser melting of stainless steel in order to improve surface topography. The results are discussed in terms of roughness, geometry of the fusion zone in the cross-section, microstructural modification, and microhardness so as to assess the effects of laser post processing. The benefits of beam wobbling over linear scanning processing are shown, as heat effects in the base metal are proven to be lower.

  9. Eco-friendly copper recovery process from waste printed circuit boards using Fe³⁺/Fe²⁺ redox system.

    Science.gov (United States)

    Fogarasi, Szabolcs; Imre-Lucaci, Florica; Egedy, Attila; Imre-Lucaci, Árpád; Ilea, Petru

    2015-06-01

    The present study aimed at developing an original and environmentally friendly process for the recovery of copper from waste printed circuit boards (WPCBs) by chemical dissolution with Fe(3+) combined with the simultaneous electrowinning of copper and oxidant regeneration. The recovery of copper was achieved in an original set-up consisting of a three chamber electrochemical reactor (ER) connected in series with a chemical reactor (CR) equipped with a perforated rotating drum. Several experiments were performed in order to identify the optimal flow rate for the dissolution of copper in the CR and to ensure the lowest energy consumption for copper electrodeposition in the ER. The optimal hydrodynamic conditions were provided at 400 mL/min, leading to the 75% dissolution of metals and to a low specific energy consumption of 1.59 kW h/kg Cu for the electrodeposition process. In most experiments, the copper content of the obtained cathodic deposits was over 99.9%. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. An Experimental Study of the Dropwise Condensation on Physically Processed Surface

    International Nuclear Information System (INIS)

    Choi, Jaeyoung; Chang, Soonheung; Watanabe, N.; Sambuichi, T.; Shiota, D.; Aritomi, M.

    2013-01-01

    Recent research by Kawakubo et al. derived empirical condensation heat transfer correlation suitable for wider range of operating condition in presence of non-condensable gas. However, their proposals of PCCS are focused on plane tube surface. To design better PCCS heat exchanger with high heat transfer coefficient new treatment on condensation surface can be considered in order to maintain dropwise condensation, the heat transfer coefficient of which has an order of magnitude larger than those of film condensation. Advanced research measure dropwise condensation heat transfer coefficient of Au and Cr coated surface based on number of droplet and droplet growth rate. However, coated surface is not desirable in power plant due to its duration of few years. On the other hand, physical processing (micro holes and patterns) on stainless steel and titanium surface is expected to perform better heat transfer, also is durable for the whole reactor lifetime. Since there is no published research about dropwise condensation for physically processed surface on SUS and Ti, the purposes of this research are to measure the condensation heat transfer coefficient and analyze its mechanism of enhanced heat transfer of treated SUS and Ti commonly used to nuclear plant. In the comparison of theoretical equation and experiment, it shows same result that heat transfer coefficient is proportional to maximum droplet diameter power to -0.321. Moreover, in the comparison of bare and processed surface, heat transfer coefficient decreases in processed surface

  11. Numerical study on formation process of helical nonneutral plasmas using electron injection from outside magnetic surfaces

    International Nuclear Information System (INIS)

    Nakamura, Kazutaka; Himura, Haruhiko; Masamune, Sadao; Sanpei, Akio; Isobe, Mitsutaka

    2009-01-01

    In order to investigate the formation process of helical nonneutral plasmas, we calculate the orbits of electron injected in the stochastic magnetic field when the closed helical magnetic surfaces is correspond with the equipotential surfaces. Contrary to the experimental observation, there are no electrons inward penetrating. (author)

  12. Upper Meter Processes: Short Wind Waves, Surface Flow, and Micro-Turbulence

    National Research Council Canada - National Science Library

    Jaehne, Bernd

    2000-01-01

    .... Since ground truth of the sea surface is still widely missing, a better understanding of the physics of these upper meter processes is of very important for the study of air-sea gas and momentum...

  13. Evaluation of optical functional surfaces on the injection moulding insert by micro milling process

    DEFF Research Database (Denmark)

    Li, Dongya; Davoudinejad, Ali; Zhang, Yang

    2017-01-01

    This study presents the optimization of micro milling process for manufacturing injection moulding inserts with an optical functionalsurface. The objective is the optimal surface functionality. Micro ridges were used as the microstructures to realize the function to generate contrast between...

  14. Cold pressure welding of aluminium-steel blanks: Manufacturing process and electrochemical surface preparation

    Science.gov (United States)

    Schmidt, Hans Christian; Homberg, Werner; Orive, Alejandro Gonzalez; Grundmeier, Guido; Hordych, Illia; Maier, Hans Jürgen

    2018-05-01

    In this study the manufacture of aluminium-steel blanks by cold pressure welding and their preparation for a welding process through electrochemical surface treatment are investigated and discussed. The cold pressure welding process was done with an incremental rolling tool that allows for the partial pressure welding of two blanks along a prepared path. The influence of the surface preparation by electrochemical deposition of bond promoting organosilane-based agents and roughening on a nano-scale is investigated and compared to conventional surface treatments. Coating the surfaces with a thin organosilane-based film incorporating specific functional groups should promote additional bonding between the mating oxide layers; its influence on the total weld strength is studied. Pressure welding requires suitable process strategies, and the current advances in the proposed incremental rolling process for the combination of mild steel and aluminium are presented.

  15. Simulation of dynamic processes when machining transition surfaces of stepped shafts

    Science.gov (United States)

    Maksarov, V. V.; Krasnyy, V. A.; Viushin, R. V.

    2018-03-01

    The paper addresses the characteristics of stepped surfaces of parts categorized as "solids of revolution". It is noted that in the conditions of transition modes during the switch to end surface machining, there is cutting with varied load intensity in the section of the cut layer, which leads to change in cutting force, onset of vibrations, an increase in surface layer roughness, a decrease of size precision, and increased wear of a tool's cutting edge. This work proposes a method that consists in developing a CNC program output code that allows one to process complex forms of stepped shafts with only one machine setup. The authors developed and justified a mathematical model of a technological system for mechanical processing with consideration for the resolution of tool movement at the stages of transition processes to assess the dynamical stability of a system in the process of manufacturing stepped surfaces of parts of “solid of revolution” type.

  16. Fabrication of superhydrophobic wood surfaces via a solution-immersion process

    Science.gov (United States)

    Liu, Changyu; Wang, Shuliang; Shi, Junyou; Wang, Chengyu

    2011-11-01

    Superhydrophobic wood surfaces were fabricated from potassium methyl siliconate (PMS) through a convenient solution-immersion method. The reaction involves a hydrogen bond assembly and a polycondensation process. The silanol was formed by reacting PMS aqueous solution with CO2, which was assembled on the wood surface via hydrogen bonds with the wood surface -OH groups. The polymethylsilsesquioxane coating was obtained through the polycondensation reaction of the hydroxyl between wood and silanol. The morphology of products were characterized using a scanning electron microscope (SEM), the surface chemical composition was determined using energy dispersive X-ray analysis (EDXA), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TGA) and contact angle measurement. Analytical results revealed that rough protuberances uniformly covered the wood surface, thus transforming the wood surface from hydrophilic to superhydrophobic. The water contact angle of the superhydrophobic wood surface was about 153° and a sliding angle was 4.6°.

  17. Quantitative proteomic characterization of redox-dependent post-translational modifications on protein cysteines

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Jicheng; Gaffrey, Matthew J.; Qian, Wei-Jun

    2017-01-01

    Protein cysteine thiols play a crucial role in redox signaling, regulation of enzymatic activity and protein function, and maintaining redox homeostasis in living systems. The unique chemical reactivity of thiol groups makes cysteine susceptible to oxidative modifications by reactive oxygen and nitrogen species to form a broad array of reversible and irreversible protein post-translational modifications (PTMs). The reversible modifications in particular are one of the major components of redox signaling and are involved in regulation of various cellular processes under physiological and pathological conditions. The biological significance of these redox PTMs in health and diseases has been increasingly recognized. Herein, we review the recent advances of quantitative proteomic approaches for investigating redox PTMs in complex biological systems, including the general considerations of sample processing, various chemical or affinity enrichment strategies, and quantitative approaches. We also highlight a number of redox proteomic approaches that enable effective profiling of redox PTMs for addressing specific biological questions. Although some technological limitations remain, redox proteomics is paving the way towards a better understanding of redox signaling and regulation in human health and diseases.

  18. Sedimentary cobalt concentrations track marine redox evolution

    Science.gov (United States)

    Swanner, Elizabeth; Planavsky, Noah; Lalonde, Stefan; Robbins, Jamie; Bekker, Andrey; Rouxel, Olivier; Konhauser, Kurt O.; Mojzsis, Stephen J.

    2013-04-01

    Oxygen production by photosynthesis drove the redox evolution of the atmosphere and ocean. Primary productivity by oxygenic photosynthesizers in the modern surface ocean is limited by trace nutrients such as iron, but previous studies have also observed high Co uptake associated with natural cyanobacterial populations. Constraining the size and variation of the oceanic reservoir of Co through time will help to understand the regulation of primary productivity and hence oxygenation through time. In this study, Co concentrations from iron formations (IF), shales and marine pyrites deposited over nearly 4 billion years of Earth's history are utilized to reconstruct secular changes in the mechanisms of Co removal from the oceanic reservoir. The Co reservoir prior to ~2 Ga was dominated by hydrothermal inputs and Fe(III)oxyhydroxides were likely involved in the removal of Co from the water column. Fe(II) oxidation in the water column resulted in the deposition of IF in the Archean and Paleoproterozoic, and the Co inventory of IF records a large oceanic reservoir of Co during this time. Lower Co concentrations in sediments during the Middle Proterozoic signify a decrease in the oceanic reservoir due to the expansion euxinic environments, corresponding to the results of previous studies. A transition to an oxidized deep ocean in the Phanerozoic is evidenced by correlation between Co and manganese (Mn) concentrations in hydrothermal and exhalative deposits, and in marine pyrites. This relationship between Co and Mn, signifying deposition of Co in association with Mn(IV)oxides, does not occur in the Precambrian. Mn(II) oxidation occurs at higher redox potentials than that required for Fe(II) oxidation, and the extent of Mn redox cycling prior to full ventilation of the oceans at the end of the Neoproterozoic was likely limited to spatially restricted oxic surface waters. In this regard, Co is another valuable redox proxy for tracking the growth and decline in oxygenated

  19. The role of original surface roughness in laser-induced periodic surface structure formation process on poly-carbonate films

    International Nuclear Information System (INIS)

    Csete, M.; Hild, S.; Plettl, A.; Ziemann, P.; Bor, Zs.; Marti, O.

    2004-01-01

    Poly-carbonate films containing different types of original surface roughness were illuminated by a polarized ArF excimer laser beam having a fluence of 4 mJ/cm 2 . Atomic force microscopy was applied to study the laser-induced periodic surface structure formation process at 0 deg. , 30 deg. and 45 deg. angles of incidence. The effect of initial surface structures on the intensity distribution was investigated in cases of: (a) grains on oriented and amorphous thick films; (b) holes on thin spin-coated films; and (c) nanoparticles arranged along micrometer long sides of hexagons below the spin-coated films. The presence of the scattering objects caused symmetry breaking, if the samples were illuminated by oblique incident 's' polarized beam. The Fourier analysis of the AFM pictures has shown the competition of structures having different periods. The characteristic of the permanent surface patterns proved that the interference of the incoming beam and the beams scattered on previously existing structures is the LIPSS generating feedback process. Ring-shaped structures having 228 nm diameter were produced

  20. Effect of Surface Densification on the Microstructure and Mechanical Properties of Powder Metallurgical Gears by Using a Surface Rolling Process

    Directory of Open Access Journals (Sweden)

    Jingguang Peng

    2016-10-01

    Full Text Available Powder metallurgy (PM components are widely used in the auto industry due to the advantage of net-shape forming, low cost, and high efficiency. Still, usage of PM components is limited in the auto industry when encountering rigorous situations, like heavy load, due to lower strength, hardness, wear resistance, and other properties compared to wrought components due to the existence of massive pores in the PM components. In this study, through combining the powder metallurgy process and rolling process, the pores in the PM components were decreased and a homogenous densified layer was formed on the surface, which resulted in the enhancement of the strength, hardness, wear resistance, and other properties, which can expand its range of application. In this paper, we study the impact of different rolling feeds on the performance of the components’ surfaces. We found that with the increase of the rolling feed, the depth of the densified layer increased.

  1. Redox electrodes comprised of polymer-modified carbon nanomaterials

    Science.gov (United States)

    Roberts, Mark; Emmett, Robert; Karakaya, Mehmet; Podila, Ramakrishna; Rao, Apparao; Clemson Physics Team; Clemson Chemical Engineering Team

    2013-03-01

    A shift in how we generate and use electricity requires new energy storage materials and systems compatible with hybrid electric transportation and the integration of renewable energy sources. Supercapacitors provide a solution to these needs by combining the high power, rapid switching, and exceptional cycle life of a capacitor with the high energy density of a battery. Our research brings together nanotechnology and materials chemistry to address the limitations of electrode materials. Paper electrodes fabricated with various forms of carbon nanomaterials, such as nanotubes, are modified with redox-polymers to increase the electrode's energy density while maintaining rapid discharge rates. In these systems, the carbon nanomaterials provide the high surface area, electrical conductivity, nanoscale and porosity, while the redox polymers provide a mechanism for charge storage through Faradaic charge transfer. The design of redox polymers and their incorporation into nanomaterial electrodes will be discussed with a focus on enabling high power and high energy density electrodes.

  2. Development of Statistical Process Control Methodology for an Environmentally Compliant Surface Cleaning Process in a Bonding Laboratory

    Science.gov (United States)

    Hutchens, Dale E.; Doan, Patrick A.; Boothe, Richard E.

    1997-01-01

    Bonding labs at both MSFC and the northern Utah production plant prepare bond test specimens which simulate or witness the production of NASA's Reusable Solid Rocket Motor (RSRM). The current process for preparing the bonding surfaces employs 1,1,1-trichloroethane vapor degreasing, which simulates the current RSRM process. Government regulations (e.g., the 1990 Amendments to the Clean Air Act) have mandated a production phase-out of a number of ozone depleting compounds (ODC) including 1,1,1-trichloroethane. In order to comply with these regulations, the RSRM Program is qualifying a spray-in-air (SIA) precision cleaning process using Brulin 1990, an aqueous blend of surfactants. Accordingly, surface preparation prior to bonding process simulation test specimens must reflect the new production cleaning process. The Bonding Lab Statistical Process Control (SPC) program monitors the progress of the lab and its capabilities, as well as certifies the bonding technicians, by periodically preparing D6AC steel tensile adhesion panels with EA-91 3NA epoxy adhesive using a standardized process. SPC methods are then used to ensure the process is statistically in control, thus producing reliable data for bonding studies, and identify any problems which might develop. Since the specimen cleaning process is being changed, new SPC limits must be established. This report summarizes side-by-side testing of D6AC steel tensile adhesion witness panels and tapered double cantilevered beams (TDCBs) using both the current baseline vapor degreasing process and a lab-scale spray-in-air process. A Proceco 26 inches Typhoon dishwasher cleaned both tensile adhesion witness panels and TDCBs in a process which simulates the new production process. The tests were performed six times during 1995, subsequent statistical analysis of the data established new upper control limits (UCL) and lower control limits (LCL). The data also demonstrated that the new process was equivalent to the vapor

  3. Effect of electropulsing on surface mechanical properties and microstructure of AISI 304 stainless steel during ultrasonic surface rolling process

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haibo [Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Key Laboratory of Advanced Materials, Tsinghua University, Beijing 100084 (China); Song, Guolin [Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Tang, Guoyi, E-mail: tanggy@mail.tsinghua.edu.cn [Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Key Laboratory of Advanced Materials, Tsinghua University, Beijing 100084 (China)

    2016-04-26

    The present work integrates 3D digital optical microscopy (OM), nano-indentation, X-ray diffraction (XRD), scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) to systematically investigate the effect of electropulsing on the surface mechanical properties and microstructure of AISI 304 stainless steel during the ultrasonic surface rolling process (USRP). Compared with the original USRP, the introduction of electropulsing with optimal parameters can effectively facilitate surface crack healing and improve surface hardness and wear resistance dramatically, and the residual compressive stress is further enhanced. Meanwhile, more martensite phase and fewer deformation twins can be found in the strengthened layer. Rapid improvement of the surface mechanical properties should be attributed to the ultra-refined grains, accelerated martensitic phase transformation and suppressed deformation twining induced by the coupling effect of USRP and electropulsing. The high strain rate given by USRP, increased stacking fault energy and accelerated dislocation mobility caused by electropulsing are likely the primary intrinsic reasons for the observed phenomena.

  4. Visualizing redox orbitals and their potentials in advanced lithium-ion battery materials using high-resolution x-ray Compton scattering

    OpenAIRE

    Hafiz, Hasnain; Suzuki, Kosuke; Barbiellini, Bernardo; Orikasa, Yuki; Callewaert, Vincent; Kaprzyk, Staszek; Itou, Masayoshi; Yamamoto, Kentaro; Yamada, Ryota; Uchimoto, Yoshiharu; Sakurai, Yoshiharu; Sakurai, Hiroshi; Bansil, Arun

    2017-01-01

    Abstract: Reduction-oxidation (redox) reactions are the key processes that underlie the batteries powering smartphones, laptops, and electric cars. A redox process involves transfer of electrons between two species. For example, in a lithium-ion battery, current is generated when conduction electrons from the lithium anode are transferred to the redox orbitals of the cathode material. The ability to visualize or image the redox orbitals and how these orbitals evolve under lithiation and delit...

  5. Preparation of SrCoOx thin films on LaAlO3 substrate and their reversible redox process at moderate temperatures

    Science.gov (United States)

    Hao, L.; Zhang, Z. F.; Xie, X. N.; Wang, H. R.; Yu, Q. X.; Zhu, H.

    2015-10-01

    Using magnetron sputtering and annealing techniques, we have prepared SrCoOx films on LaAlO3 and SrTiO3 substrates. Distinctly different structures of the films have been found on the two substrates. It is suggested that positive lattice mismatch between film and substrate promotes SrCoO2.5 films with an orthorhombic structure grown on SrTiO3 substrate, whereas negative lattice mismatch from LaAlO3 substrate is in favor of increasing the valence state of Co and thus the growth of oxygen-rich SrCoOx with a tetragonal structure. In addition to the structural characterization, magnetic and electrical measurements confirm that the oxygen content x is between 2.75 and 2.88 for the latter. Reversibility of the topotactic phase transformation between SrCoO2.5 and the oxygen-rich SrCoOx films has also been studied by changing the oxygen pressure during annealing process. Even in the presence of a negative lattice mismatch, the results reveal that the tetragonal SrCoOx films on LaAlO3 substrate retain high oxygen mobility identified before in cubic SrCoOx films.

  6. Impact of biostimulated redox processes on metal dynamics in an iron-rich creek soil of a former uranium mining area.

    Science.gov (United States)

    Burkhardt, Eva-Maria; Akob, Denise M; Bischoff, Sebastian; Sitte, Jana; Kostka, Joel E; Banerjee, Dipanjan; Scheinost, Andreas C; Küsel, Kirsten

    2010-01-01

    Understanding the dynamics of metals and radionuclides in soil environments is necessary for evaluating risks to pristine sites. An iron-rich creek soil of a former uranium-mining district (Ronneburg, Germany) showed high porewater concentrations of heavy metals and radionuclides. Thus, this study aims to (i) evaluate metal dynamics during terminal electron accepting processes (TEAPs) and (ii) characterize active microbial populations in biostimulated soil microcosms using a stable isotope probing (SIP) approach. In biostimulated soil slurries, concentrations of soluble Co, Ni, Zn, As, and unexpectedly U increased during Fe(III)-reduction. This suggests that there was a release of sorbed metals and As during reductive dissolution of Fe(III)-oxides. Subsequent sulfate-reduction was concurrent with a decrease of U, Co, Ni, and Zn concentrations. The relative contribution of U(IV) in the solid phase changed from 18.5 to 88.7% after incubation. The active Fe(III)-reducing population was dominated by delta-Proteobacteria (Geobacter) in (13)C-ethanol amended microcosms. A more diverse community was present in (13)C-lactate amended microcosms including taxa related to Acidobacteria, Firmicutes, delta-Proteobacteria, and beta-Proteobacteria. Our results suggested that biostimulated Fe(III)-reducing communities facilitated the release of metals including U to groundwater which is in contrast to other studies.

  7. Genetic Algorithm-Based Optimization for Surface Roughness in Cylindrically Grinding Process Using Helically Grooved Wheels

    Science.gov (United States)

    Çaydaş, Ulaş; Çelik, Mahmut

    The present work is focused on the optimization of process parameters in cylindrical surface grinding of AISI 1050 steel with grooved wheels. Response surface methodology (RSM) and genetic algorithm (GA) techniques were merged to optimize the input variable parameters of grinding. The revolution speed of workpiece, depth of cut and number of grooves on the wheel were changed to explore their experimental effects on the surface roughness of machined bars. The mathematical models were established between the input parameters and response by using RSM. Then, the developed RSM model was used as objective functions on GA to optimize the process parameters.

  8. Redox Couples with Unequal Diffusion Coefficients: Effect on Redox Cycling

    NARCIS (Netherlands)

    Mampallil Augustine, Dileep; Mathwig, Klaus; Kang, Shuo; Lemay, Serge Joseph Guy

    2013-01-01

    Redox cycling between two electrodes separated by a narrow gap allows dramatic amplification of the faradaic current. Unlike conventional electrochemistry at a single electrode, however, the mass-transport-limited current is controlled by the diffusion coefficient of both the reduced and oxidized

  9. Electrochemical behavior of two and one electron redox systems adsorbed on to micro- and mesoporous silicate materials: Influence of the channels and the cationic environment of the host materials

    International Nuclear Information System (INIS)

    Senthil Kumar, K.; Natarajan, P.

    2009-01-01

    Electrochemical behavior of two electron redox system, phenosafranine (PS + ) adsorbed on to micro- and mesoporous materials is investigated by cyclic voltammetry and differential pulse voltammetry using modified micro- and mesoporous host electrodes. Two redox peaks were observed when phenosafranine is adsorbed on the surface of microporous materials zeolite-Y and ZSM-5. However, only a single redox peak was observed in the modified electrode with phenosafranine encapsulated into the mesoporous material MCM-41 and when adsorbed on the external surface of silica. The observed redox peaks for the modified electrodes with zeolite-Y and ZSM-5 host are suggested to be primarily due to consecutive two electron processes. The peak separation ΔE and peak potential of phenosafranine adsorbed on zeolite-Y and ZSM-5 were found to be influenced by the pH of the electrolyte solution. The variation of the peak current in the cyclic voltammogram and differential pulse voltammetry with scan rate shows that electrodic processes are controlled by the nature of the surface of the host material. The heterogeneous electron transfer rate constants for phenosafranine adsorbed on to micro- and mesoporous materials were calculated using the Laviron model. Higher rate constant observed for the dye encapsulated into the MCM-41 indicates that the one-dimensional channel of the mesoporous material provides a more facile micro-environment for phenosafranine for the electron transfer reaction as compared to the microporous silicate materials. The stability of the modified electrode surface was investigated by multisweep cyclic voltammetry.

  10. Poorly processed reusable surface disinfection tissue dispensers may be a source of infection.

    Science.gov (United States)

    Kampf, Günter; Degenhardt, Stina; Lackner, Sibylle; Jesse, Katrin; von Baum, Heike; Ostermeyer, Christiane

    2014-01-21

    Reusable surface disinfectant tissue dispensers are used in hospitals in many countries because they allow immediate access to pre-soaked tissues for targeted surface decontamination. On the other hand disinfectant solutions with some active ingredients may get contaminated and cause outbreaks. We determined the frequency of contaminated surface disinfectant solutions in reusable dispensers and the ability of isolates to multiply in different formulations. Reusable tissue dispensers with different surface disinfectants were randomly collected from healthcare facilities. Solutions were investigated for bacterial contamination. The efficacy of two surface disinfectants was determined in suspension tests against two isolated species directly from a contaminated solution or after 5 passages without selection pressure in triplicate. Freshly prepared use solutions were contaminated to determine survival of isolates. 66 dispensers containing disinfectant solutions with surface-active ingredients were collected in 15 healthcare facilities. 28 dispensers from nine healthcare facilities were contaminated with approximately 107 cells per mL of Achromobacter species 3 (9 hospitals), Achromobacter xylosoxidans or Serratia marcescens (1 hospital each). In none of the hospitals dispenser processing had been adequately performed. Isolates regained susceptibility to the disinfectants after five passages without selection pressure but were still able to multiply in different formulations from different manufacturers at room temperature within 7 days. Neglecting adequate processing of surface disinfectant dispensers has contributed to frequent and heavy contamination of use-solutions based on surface active ingredients. Tissue dispenser processing should be taken seriously in clinical practice.

  11. Assessment of surface contamination level in an operating uranium ore processing facility of Jaduguda, India

    International Nuclear Information System (INIS)

    Meena, J.S.; Patnaik, R.L.; Jha, V.N.; Sahoo, S.K.; Ravi, P.M.; Tripathi, R.M.

    2014-01-01

    Radiological concern of the occupational workers and the area is given priority over other safety issue in confirmation with the stipulated guideline of national regulatory agency (AERB/FEFCF/SG-2, 2007). The key concern from the radiological hazard evaluation point of view is air activity, external gamma level and surface contamination. Present investigations was carried out to ascertain the surface contamination level of uranium ore processing facility at Jaduguda, Jharkhand. For a low grade uranium ore processing industry surface contamination is a major concern in product precipitation and recovery section. In view of this, the ore processing plant can broadly be classified into three areas i.e. ion exchange area, precipitation and product recovery section and other areas. The monitoring results incorporate the level of surface contamination of the plant during the last five years. The geometric mean activity of surface contamination level was 31.1, 34.5 and 9.8 Bq dm -2 in ion exchange, product precipitation and recovery and other areas with GSD of 2, 2.5 and 1.9. In most of the cases the surface contamination level was well within the recommended limit of 100 Bq dm -2 for M class uranium compound. Occasional cases of surface contamination levels exceeding the recommended limit were addressed and areas were decontaminated. Based on the study, modification in the design feature of the surface of the finished product section was also suggested so that the decontamination procedure can be more effectively implemented

  12. Processing method and processing device for liquid waste containing surface active agent and radioactive material

    International Nuclear Information System (INIS)

    Nishi, Takashi; Matsuda, Masami; Baba, Tsutomu; Yoshikawa, Ryozo; Yukita, Atsushi.

    1998-01-01

    Washing liquid wastes containing surface active agents and radioactive materials are sent to a deaerating vessel. Ozone is blown into the deaerating vessel. The washing liquid wastes dissolved with ozone are introduced to a UV ray irradiation vessel. UV rays are irradiated to the washing liquid wastes, and hydroxy radicals generated by photodecomposition of dissolved ozone oxidatively decompose surface active agents contained in the washing liquid wastes. The washing liquid wastes discharged from the UV ray irradiation vessel are sent to an activated carbon mixing vessel and mixed with powdery activated carbon. The surface active agents not decomposed in the UV ray irradiation vessel are adsorbed to the activated carbon. Then, the activated carbon and washing liquid wastes are separated by an activated carbon separating/drying device. Radioactive materials (iron oxide and the like) contained in the washing liquid wastes are mostly granular, and they are separated and removed from the washing liquid wastes in the activated carbon separating/drying device. (I.N.)

  13. Continuous processing of polymers in repetitively pulsed atmospheric pressure discharges with moving surfaces and gas flow

    Energy Technology Data Exchange (ETDEWEB)

    Bhoj, Ananth N [Department of Chemical and Biomolecular Engineering, University of Illinois, Urbana, IL 61801 (United States); Kushner, Mark J [Department of Electrical and Computer Engineering, Iowa State University, Ames, IA 50011 (United States)

    2007-11-21

    Atmospheric pressure corona discharges are industrially employed to treat large areas of commodity polymer sheets by creating new surface functional groups. The most common processes use oxygen containing discharges to affix oxygen to hydrocarbon polymers, thereby increasing their surface energy and wettability. The process is typically continuous and is carried out in a web configuration with film speeds of tens to hundreds of cm s{sup -1}. The densities and relative abundances of functional groups depend on the gas composition, gas flow rate and residence time of the polymer in the discharge zone which ultimately determine the magnitude and mole fractions of reactive fluxes to the surface. In this paper, results are discussed from a two-dimensional computational investigation of the atmospheric pressure plasma functionalization of a moving polypropylene sheet in repetitively pulsed He/O{sub 2}/H{sub 2}O discharges. O and OH typically initiate surface processing by hydrogen abstraction. These species are regenerated during every plasma pulse but are also largely consumed during the inter-pulse period. Longer-lived species such as O{sub 3} accumulate over many pulses and convect downstream with the gas flow. Optimizing the interplay between local rapid reactions, such as H abstraction which occurs dominantly in the discharge zone, and non-local slower processes, such as surface-surface reactions, may enable the customization of the relative abundance of surface functional groups.

  14. Continuous processing of polymers in repetitively pulsed atmospheric pressure discharges with moving surfaces and gas flow

    International Nuclear Information System (INIS)

    Bhoj, Ananth N; Kushner, Mark J

    2007-01-01

    Atmospheric pressure corona discharges are industrially employed to treat large areas of commodity polymer sheets by creating new surface functional groups. The most common processes use oxygen containing discharges to affix oxygen to hydrocarbon polymers, thereby increasing their surface energy and wettability. The process is typically continuous and is carried out in a web configuration with film speeds of tens to hundreds of cm s -1 . The densities and relative abundances of functional groups depend on the gas composition, gas flow rate and residence time of the polymer in the discharge zone which ultimately determine the magnitude and mole fractions of reactive fluxes to the surface. In this paper, results are discussed from a two-dimensional computational investigation of the atmospheric pressure plasma functionalization of a moving polypropylene sheet in repetitively pulsed He/O 2 /H 2 O discharges. O and OH typically initiate surface processing by hydrogen abstraction. These species are regenerated during every plasma pulse but are also largely consumed during the inter-pulse period. Longer-lived species such as O 3 accumulate over many pulses and convect downstream with the gas flow. Optimizing the interplay between local rapid reactions, such as H abstraction which occurs dominantly in the discharge zone, and non-local slower processes, such as surface-surface reactions, may enable the customization of the relative abundance of surface functional groups

  15. Auto-recognition of surfaces and auto-generation of material removal volume for finishing process

    Science.gov (United States)

    Kataraki, Pramod S.; Salman Abu Mansor, Mohd

    2018-03-01

    Auto-recognition of a surface and auto-generation of material removal volumes for the so recognised surfaces has become a need to achieve successful downstream manufacturing activities like automated process planning and scheduling. Few researchers have contributed to generation of material removal volume for a product but resulted in material removal volume discontinuity between two adjacent material removal volumes generated from two adjacent faces that form convex geometry. The need for limitation free material removal volume generation was attempted and an algorithm that automatically recognises computer aided design (CAD) model’s surface and also auto-generate material removal volume for finishing process of the recognised surfaces was developed. The surfaces of CAD model are successfully recognised by the developed algorithm and required material removal volume is obtained. The material removal volume discontinuity limitation that occurred in fewer studies is eliminated.

  16. Dominant rate process of silicon surface etching by hydrogen chloride gas

    International Nuclear Information System (INIS)

    Habuka, Hitoshi; Suzuki, Takahiro; Yamamoto, Sunao; Nakamura, Akio; Takeuchi, Takashi; Aihara, Masahiko

    2005-01-01

    Silicon surface etching and its dominant rate process are studied using hydrogen chloride gas in a wide concentration range of 1-100% in ambient hydrogen at atmospheric pressure in a temperature range of 1023-1423 K, linked with the numerical calculation accounting for the transport phenomena and the surface chemical reaction in the entire reactor. The etch rate, the gaseous products and the surface morphology are experimentally evaluated. The dominant rate equation accounting for the first-order successive reactions at silicon surface by hydrogen chloride gas is shown to be valid. The activation energy of the dominant surface process is evaluated to be 1.5 x 10 5 J mol - 1 . The silicon deposition by the gaseous by-product, trichlorosilane, is shown to have a negligible influence on the silicon etch rate

  17. Analysis of WEDM Process Parameters on Surface Roughness and Kerf using Taguchi Method

    Directory of Open Access Journals (Sweden)

    Asfana Banu

    2017-12-01

    Full Text Available In obtaining the best quality of engineering parts, the quality of machined surface plays an essential role. The fatigue strength, wear resistance, and corrosion of workpiece are some of the aspects of the qualities that can be improved. This paper investigates the effect of wire electrical discharge machining (WEDM process parameters on surface roughness and kerf on stainless steel using distilled water as dielectric fluid and brass wire as tool electrode. The selected process parameters are voltage open, wire speed, wire tension, voltage gap, and off time. Empirical models using Taguchi method were developed for the estimation of surface roughness and kerf. The analysis revealed that off time has major influence on surface roughness and kerf. The optimum machining parameters for minimum surface roughness and kerf were found to be 10 V open voltage, 2.84 µs off time, 12 m/min wire speed, 6.3 N wire tension, and 54.91 V voltage gap.

  18. Specifics of adsorption and chemical processes on the surface of gamma-irradiated vanadium dioxide

    International Nuclear Information System (INIS)

    Kaurkovskaya, V.N.; Dzyubenko, L.S.; Doroshenko, V.N.; Chujko, A.A.; Shakhov, A.P.

    2006-01-01

    Effect of γ-irradiation on electrophysical properties and processes of thermal desorption of water from the surface of vanadium oxides V 2 O 3 -VO 2-δ -VO 2+δ -V 2 O 5 was investigated by derivatography and electric conductivity. Content of adsorbed water at the surface and phase composition of the surface was demonstrated to change under the action of low radiation doses. Surface electric conductivity of the irradiated samples VO 2-δ in the process of chemical reactions of adsorbed following irradiation benzoic acid and ethanol was established to be much above than in irradiated-free ones. It is presumed that metal-semiconductor phase transition at the surface of VO 2-δ during chemical reaction is intensified by irradiation [ru

  19. The mechanism of mediated oxidation of carboxylates with ferrocene as redox catalyst in absence of grafting effects. An experimental and theoretical approach

    International Nuclear Information System (INIS)

    Hernández-Muñoz, Lindsay S.; Galano, Annia; Astudillo-Sánchez, Pablo D.; Abu-Omar, Mahdi M.; González, Felipe J.

    2014-01-01

    Graphical abstract: - Highlights: • The mechanism of mediated oxidation of carboxylates. • Thermodynamics of the mediated Kolbe and Non-Kolbe mechanisms. • The oxidation of acetate and diphenylacetate ions by using ferrocene as redox catalyst. • Simulation and DFT calculations of the mediated oxidation of carboxylates. • Radical and carbocationic pathways in the carboxylate oxidation in acetonitrile. - Abstract: The oxidation of tetrabutylammonium carboxylates by using ferrocene derivatives as redox mediators has been recently used to perform the covalent grafting of carbon surfaces with organic and organometallic groups. Due to the intervention of this surface process, a partial description of the reaction mechanism has only been stated. Therefore, this article concerns about two features of the oxidation of carboxylates mediated by ferrocene. In the first part, it is discussed that in the oxidation of acetate ions by using ferrocene as redox catalyst, the gap between both oxidation potentials is very high, which means that the homogeneous electron transfer between the acetate ion and the electrochemically generated ferrocenium ion is energetically unfavorable. However, by using density functional theory calculations, it has been shown that the whole set of coupled chemical reactions involved either in a Kolbe or Non-Kolbe pathway drive the overall mechanisms towards a thermodynamically favorable situation. In order to avoid the strong covalent grafting process that occurs during the mediated oxidation of acetate ions, the second part of this work deals with the oxidation of tetrabutylammonium diphenylacetate by using ferrocene as a redox mediator in acetonitrile on glassy carbon electrodes. With this carboxylate, no electrode inhibition process occurs and, therefore cyclic voltammetry simulation was done to propose the electrochemical and chemical steps that are present when a carboxylate oxidation is performed in the presence of ferrocene derivatives

  20. Effect of conditioner load on the polishing pad surface during chemical mechanical planarization process

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Cheol Min; Qin, Hong Yi; Hong, Seok Jun; Jeon, Sang Hyuk; Kulkarni, Atul; Kim, Tae Sun [Sungkyunkwan University, Suwon (Korea, Republic of)

    2016-12-15

    During the Chemical mechanical planarization (CMP), the pad conditioning process can affect the pad surface characteristics. Among many CMP process parameters, the improper applied load on the conditioner arm may have adverse effects on the polyurethane pad. In this work, we evaluated the pad surface properties under the various conditioner arm applied during pad conditioning process. The conditioning pads were evaluated for surface topography, surface roughness parameters such as Rt and Rvk and Material removal rate (MRR) and within-wafer non-uniformity after wafer polishing. We observed that, the pad asperities were collapsed in the direction of conditioner rotation and blocks the pad pores applied conditioner load. The Rvk value and MRR were founded to be in relation with 4 > 1 > 7 kgF conditioner load. Hence, this study shows that, 4 kgF applied load by conditioner is most suitable for the pad conditioning during CMP.

  1. Redox regulation of photosynthetic gene expression.

    Science.gov (United States)

    Queval, Guillaume; Foyer, Christine H

    2012-12-19

    Redox chemistry and redox regulation are central to the operation of photosynthesis and respiration. However, the roles of different oxidants and antioxidants in the regulation of photosynthetic or respiratory gene expression remain poorly understood. Leaf transcriptome profiles of a range of Arabidopsis thaliana genotypes that are deficient in either hydrogen peroxide processing enzymes or in low molecular weight antioxidant were therefore compared to determine how different antioxidant systems that process hydrogen peroxide influence transcripts encoding proteins targeted to the chloroplasts or mitochondria. Less than 10 per cent overlap was observed in the transcriptome patterns of leaves that are deficient in either photorespiratory (catalase (cat)2) or chloroplastic (thylakoid ascorbate peroxidase (tapx)) hydrogen peroxide processing. Transcripts encoding photosystem II (PSII) repair cycle components were lower in glutathione-deficient leaves, as were the thylakoid NAD(P)H (nicotinamide adenine dinucleotide (phosphate)) dehydrogenases (NDH) mRNAs. Some thylakoid NDH mRNAs were also less abundant in tAPX-deficient and ascorbate-deficient leaves. Transcripts encoding the external and internal respiratory NDHs were increased by low glutathione and low ascorbate. Regulation of transcripts encoding specific components of the photosynthetic and respiratory electron transport chains by hydrogen peroxide, ascorbate and glutathione may serve to balance non-cyclic and cyclic electron flow pathways in relation to oxidant production and reductant availability.

  2. Ab Initio Metadynamics Study of the VO2+/VO2+ Redox Reaction Mechanism at the Graphite Edge/Water Interface.

    Science.gov (United States)

    Jiang, Zhen; Klyukin, Konstantin; Alexandrov, Vitaly

    2018-06-08

    Redox flow batteries (RFBs) are promising electrochemical energy storage systems, for which development is impeded by a poor understanding of redox reactions occurring at electrode/electrolyte interfaces. Even for the conventional all-vanadium RFB chemistry employing V 2+ /V 3+ and VO 2 + /VO 2+ couples, there is still no consensus about the reaction mechanism, electrode active sites, and rate-determining step. Herein, we perform Car-Parrinello molecular dynamics-based metadynamics simulations to unravel the mechanism of the VO 2 + /VO 2+ redox reaction in water at the oxygen-functionalized graphite (112̅0) edge surface serving as a representative carbon-based electrode. Our results suggest that during the battery discharge aqueous VO 2 + /VO 2+ species adsorb at the surface C-O groups as inner-sphere complexes, exhibiting faster adsorption/desorption kinetics than V 2+ /V 3+ , at least at low vanadium concentrations considered in our study. We find that this is because (i) VO 2 + /VO 2+ conversion does not involve the slow transfer of an oxygen atom, (ii) protonation of VO 2 + is spontaneous and coupled to interfacial electron transfer in acidic conditions to enable VO 2+ formation, and (iii) V 3+ found to be strongly bound to oxygen groups of the graphite surface features unfavorable desorption kinetics. In contrast, the reverse process taking place upon charging is expected to be more sluggish for the VO 2 + /VO 2+ redox couple because of both unfavorable deprotonation of the VO 2+ water ligands and adsorption/desorption kinetics.

  3. Effects of physical and biogeochemical processes on aquatic ecosystems at the groundwater-surface water interface: An evaluation of a sulfate-impacted wild rice stream in Minnesota (USA)

    Science.gov (United States)

    Ng, G. H. C.; Yourd, A. R.; Myrbo, A.; Johnson, N.

    2015-12-01

    Significant uncertainty and variability in physical and biogeochemical processes at the groundwater-surface water interface complicate how surface water chemistry affects aquatic ecosystems. Questions surrounding a unique 10 mg/L sulfate standard for wild rice (Zizania sp.) waters in Minnesota are driving research to clarify conditions controlling the geochemistry of shallow sediment porewater in stream- and lake-beds. This issue raises the need and opportunity to carry out in-depth, process-based analysis into how water fluxes and coupled C, S, and Fe redox cycles interact to impact aquatic plants. Our study builds on a recent state-wide field campaign that showed that accumulation of porewater sulfide from sulfate reduction impairs wild rice, an annual grass that grows in shallow lakes and streams in the Great Lakes region of North America. Negative porewater sulfide correlations with organic C and Fe quantities also indicated that lower redox rates and greater mineral precipitation attenuate sulfide. Here, we focus on a stream in northern Minnesota that receives high sulfate loading from iron mining activity yet maintains wild rice stands. In addition to organic C and Fe effects, we evaluate the degree to which streambed hydrology, and in particular groundwater contributions, accounts for the active biogeochemistry. We collect field measurements, spanning the surrounding groundwater system to the stream, to constrain a reactive-transport model. Observations from seepage meters, temperature probes, and monitoring wells delineate upward flow that may lessen surface water impacts below the stream. Geochemical analyses of groundwater, porewater, and surface water samples and of sediment extractions reveal distinctions among the different domains and stream banks, which appear to jointly control conditions in the streambed. A model based on field conditions can be used to evaluate the relative the importance and the spatiotemporal scales of diverse flux and

  4. Surface preparation process of a uranium titanium alloy, in particular for chemical nickel plating

    International Nuclear Information System (INIS)

    Henri, A.; Lefevre, D.; Massicot, P.

    1987-01-01

    In this process the uranium alloy surface is attacked with a solution of lithium chloride and hydrochloric acid. Dissolved uranium can be recovered from the solution by an ion exchange resin. Treated alloy can be nickel plated by a chemical process [fr

  5. Surface modification on a glass surface with a combination technique of sol–gel and air brushing processes

    KAUST Repository

    Tsai, Meng-Yu; Hsu, Chin-Chi; Chen, Ping-Hei; Lin, Chao-Sung; Chen, Alexander

    2011-01-01

    This study fabricated the large area and optically transparent superhydrophobic silica based films on glass surface with optimized hardness. A silane coupling agent, tetraethoxysilane (TEOS), effectively bonds silica particles onto the glass substrate. Desired surface roughness was obtained by adjusting nano silica particles concentration of the precursors prepared by the sol-gel process. Silica suspension was coated onto the glass substrate by the air brushing methods. This method can deposit a uniform, transparent coating on the glass substrate efficiently. Diluting the precursor by adding ethanol or a mixture of D.I. water and ethanol further improved the transmittance and superhydrophobicity efficiency. The results showed that as the silica particle concentration and the thickness of the coating were increased, the surface roughness was enhanced. Rougher surface displayed a higher superhydrophobicity and lower transmittance. Therefore, the concentration of silica particle, volume of coatings, and the ratio of ethanol and D.I. water are of great importance to deposit a transparent, superhydrophobic coating on glass. © 2011 Elsevier B.V. All rights reserved.

  6. Surface modification on a glass surface with a combination technique of sol–gel and air brushing processes

    KAUST Repository

    Tsai, Meng-Yu

    2011-08-01

    This study fabricated the large area and optically transparent superhydrophobic silica based films on glass surface with optimized hardness. A silane coupling agent, tetraethoxysilane (TEOS), effectively bonds silica particles onto the glass substrate. Desired surface roughness was obtained by adjusting nano silica particles concentration of the precursors prepared by the sol-gel process. Silica suspension was coated onto the glass substrate by the air brushing methods. This method can deposit a uniform, transparent coating on the glass substrate efficiently. Diluting the precursor by adding ethanol or a mixture of D.I. water and ethanol further improved the transmittance and superhydrophobicity efficiency. The results showed that as the silica particle concentration and the thickness of the coating were increased, the surface roughness was enhanced. Rougher surface displayed a higher superhydrophobicity and lower transmittance. Therefore, the concentration of silica particle, volume of coatings, and the ratio of ethanol and D.I. water are of great importance to deposit a transparent, superhydrophobic coating on glass. © 2011 Elsevier B.V. All rights reserved.

  7. Topological characterization of antireflective and hydrophobic rough surfaces: are random process theory and fractal modeling applicable?

    Science.gov (United States)

    Borri, Claudia; Paggi, Marco

    2015-02-01

    The random process theory (RPT) has been widely applied to predict the joint probability distribution functions (PDFs) of asperity heights and curvatures of rough surfaces. A check of the predictions of RPT against the actual statistics of numerically generated random fractal surfaces and of real rough surfaces has been only partially undertaken. The present experimental and numerical study provides a deep critical comparison on this matter, providing some insight into the capabilities and limitations in applying RPT and fractal modeling to antireflective and hydrophobic rough surfaces, two important types of textured surfaces. A multi-resolution experimental campaign using a confocal profilometer with different lenses is carried out and a comprehensive software for the statistical description of rough surfaces is developed. It is found that the topology of the analyzed textured surfaces cannot be fully described according to RPT and fractal modeling. The following complexities emerge: (i) the presence of cut-offs or bi-fractality in the power-law power-spectral density (PSD) functions; (ii) a more pronounced shift of the PSD by changing resolution as compared to what was expected from fractal modeling; (iii) inaccuracy of the RPT in describing the joint PDFs of asperity heights and curvatures of textured surfaces; (iv) lack of resolution-invariance of joint PDFs of textured surfaces in case of special surface treatments, not accounted for by fractal modeling.

  8. Laser processing of metallic biomaterials: An approach for surface patterning and wettability control

    Science.gov (United States)

    Razi, Sepehr; Mollabashi, Mahmoud; Madanipour, Khosro

    2015-12-01

    Q -switched Nd:YAG laser is used to manipulate the surface morphology and wettability characteristic of 316L stainless steel (SS) and titanium biomaterials. Water and glycerol are selected as wettability testing liquids and the sessile drop method is used for the contact angle measurements. Results indicate that on both of the metals, wettability toward water improves significantly after the laser treatment. Different analyses including the study of the surface morphology, free energy and oxidation are assessed in correlation with wettability. Beside the important role of the laser-induced surface patterns, the increase in the surface roughness, oxygen content and the polar component of the surface energy, are detected as the most important physical and chemical phenomena controlling the improvement in the wettability. However, all the processed hydrophilic surfaces that are exposed to air become hydrophobic over time. The time dependency of the surface wettability is related to the chemical activities on the treated surfaces and the reduction of oxygen/carbon (O/C) ratio on them. The behavior is further studied with investigating the effect of the keeping environment and changes of the components of the surface tension. Results show that the pulsed laser treatment is a versatile approach to create either hydrophobic or super hydrophilic surfaces for industrial and medical applications.

  9. The redox-Mannich reaction.

    Science.gov (United States)

    Chen, Weijie; Seidel, Daniel

    2014-06-06

    A complement to the classic three-component Mannich reaction, the redox-Mannich reaction, utilizes the same starting materials but incorporates an isomerization step that enables the facile preparation of ring-substituted β-amino ketones. Reactions occur under relatively mild conditions and are facilitated by benzoic acid.

  10. Effects of Micromachining Processes on Electro-Osmotic Flow Mobility of Glass Surfaces

    Directory of Open Access Journals (Sweden)

    Norihisa Miki

    2013-03-01

    Full Text Available Silica glass is frequently used as a device material for micro/nano fluidic devices due to its excellent properties, such as transparency and chemical resistance. Wet etching by hydrofluoric acid and dry etching by neutral loop discharge (NLD plasma etching are currently used to micromachine glass to form micro/nano fluidic channels. Electro-osmotic flow (EOF is one of the most effective methods to drive liquids into the channels. EOF mobility is affected by a property of the micromachined glass surfaces, which includes surface roughness that is determined by the manufacturing processes. In this paper, we investigate the effect of micromaching processes on the glass surface topography and the EOF mobility. We prepared glass surfaces by either wet etching or by NLD plasma etching, investigated the surface topography using atomic force microscopy, and attempted to correlate it with EOF generated in the micro-channels of the machined glass. Experiments revealed that the EOF mobility strongly depends on the surface roughness, and therefore upon the fabrication process used. A particularly strong dependency was observed when the surface roughness was on the order of the electric double layer thickness or below. We believe that the correlation described in this paper can be of great help in the design of micro/nano fluidic devices.

  11. Determining Li+-Coupled Redox Targeting Reaction Kinetics of Battery Materials with Scanning Electrochemical Microscopy.

    Science.gov (United States)

    Yan, Ruiting; Ghilane, Jalal; Phuah, Kia Chai; Pham Truong, Thuan Nguyen; Adams, Stefan; Randriamahazaka, Hyacinthe; Wang, Qing

    2018-02-01

    The redox targeting reaction of Li + -storage materials with redox mediators is the key process in redox flow lithium batteries, a promising technology for next-generation large-scale energy storage. The kinetics of the Li + -coupled heterogeneous charge transfer between the energy storage material and redox mediator dictates the performance of the device, while as a new type of charge transfer process it has been rarely studied. Here, scanning electrochemical microscopy (SECM) was employed for the first time to determine the interfacial charge transfer kinetics of LiFePO 4 /FePO 4 upon delithiation and lithiation by a pair of redox shuttle molecules FcBr 2 + and Fc. The effective rate constant k eff was determined to be around 3.70-6.57 × 10 -3 cm/s for the two-way pseudo-first-order reactions, which feature a linear dependence on the composition of LiFePO 4 , validating the kinetic process of interfacial charge transfer rather than bulk solid diffusion. In addition, in conjunction with chronoamperometry measurement, the SECM study disproves the conventional "shrinking-core" model for the delithiation of LiFePO 4 and presents an intriguing way of probing the phase boundary propagations induced by interfacial redox reactions. This study demonstrates a reliable method for the kinetics of redox targeting reactions, and the results provide useful guidance for the optimization of redox targeting systems for large-scale energy storage.

  12. Effect of processing parameters of rotary ultrasonic machining on surface integrity of potassium dihydrogen phosphate crystals

    Directory of Open Access Journals (Sweden)

    Jianfu Zhang

    2015-09-01

    Full Text Available Potassium dihydrogen phosphate is an important optical crystal. However, high-precision processing of large potassium dihydrogen phosphate crystal workpieces is difficult. In this article, surface roughness and subsurface damage characteristics of a (001 potassium dihydrogen phosphate crystal surface produced by traditional and rotary ultrasonic machining are studied. The influence of process parameters, including spindle speed, feed speed, type and size of sintered diamond wheel, ultrasonic power, and selection of cutting fluid on potassium dihydrogen phosphate crystal surface integrity, was analyzed. The surface integrity, especially the subsurface damage depth, was affected significantly by the ultrasonic power. Metal-sintered diamond tools with high granularity were most suitable for machining potassium dihydrogen phosphate crystal. Cutting fluid played a key role in potassium dihydrogen phosphate crystal machining. A more precise surface can be obtained in machining with a higher spindle speed, lower feed speed, and using kerosene as cutting fluid. Based on the provided optimized process parameters for machining potassium dihydrogen phosphate crystal, a processed surface quality with Ra value of 33 nm and subsurface damage depth value of 6.38 μm was achieved.

  13. Optimization of CO2 Laser Cutting Process using Taguchi and Dual Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    M. Madić

    2014-09-01

    Full Text Available Selection of optimal cutting parameter settings for obtaining high cut quality in CO2 laser cutting process is of great importance. Among various analytical and experimental optimization methods, the application of Taguchi and response surface methodology is one of most commonly used for laser cutting process optimization. Although the concept of dual response surface methodology for process optimization has been used with success, till date, no experimental study has been reported in the field of laser cutting. In this paper an approach for optimization of CO2 laser cutting process using Taguchi and dual response surface methodology is presented. The goal was to determine the near optimal laser cutting parameter values in order to ensure robust condition for minimization of average surface roughness. To obtain experimental database for development of response surface models, Taguchi’s L25 orthogonal array was implemented for experimental plan. Three cutting parameters, the cutting speed (3, 4, 5, 6, 7 m/min, the laser power (0.7, 0.9, 1.1, 1.3, 1.5 kW, and the assist gas pressure (3, 4, 5, 6, 7 bar, were used in the experiment. To obtain near optimal cutting parameters settings, multi-stage Monte Carlo simulation procedure was performed on the developed response surface models.

  14. TEMPOL increases NAD+ and improves redox imbalance in obese mice

    Directory of Open Access Journals (Sweden)

    Mayumi Yamato

    2016-08-01

    Full Text Available Continuous energy conversion is controlled by reduction–oxidation (redox processes. NAD+ and NADH represent an important redox couple in energy metabolism. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL is a redox-cycling nitroxide that promotes the scavenging of several reactive oxygen species (ROS and is reduced to hydroxylamine by NADH. TEMPOL is also involved in NAD+ production in the ascorbic acid–glutathione redox cycle. We utilized the chemical properties of TEMPOL to investigate the effects of antioxidants and NAD+/NADH modulators on the metabolic imbalance in obese mice. Increases in the NAD+/NADH ratio by TEMPOL ameliorated the metabolic imbalance when combined with a dietary intervention, changing from a high-fat diet to a normal diet. Plasma levels of the superoxide marker dihydroethidium were higher in mice receiving the dietary intervention compared with a control diet, but were normalized with TEMPOL consumption. These findings provide novel insights into redox regulation in obesity.

  15. Anionic Redox Chemistry in Polysulfide Electrode Materials for Rechargeable Batteries.

    Science.gov (United States)

    Grayfer, Ekaterina D; Pazhetnov, Egor M; Kozlova, Mariia N; Artemkina, Sofya B; Fedorov, Vladimir E

    2017-12-22

    Classical Li-ion battery technology is based on the insertion of lithium ions into cathode materials involving metal (cationic) redox reactions. However, this vision is now being reconsidered, as many new-generation electrode materials with enhanced reversible capacities operate through combined cationic and anionic (non-metal) reversible redox processes or even exclusively through anionic redox transformations. Anionic participation in the redox reactions is observed in materials with more pronounced covalency, which is less typical for oxides, but quite common for phosphides or chalcogenides. In this Concept, we would like to draw the reader's attention to this new idea, especially, as it applies to transition-metal polychalcogenides, such as FeS 2 , VS 4 , TiS 3 , NbS 3 , TiS 4 , MoS 3 , etc., in which the key role is played by the (S-S) 2- /2 S 2- redox reaction. The exploration and better understanding of the anion-driven chemistry is important for designing advanced materials for battery and other energy-related applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Molecular Orbital Principles of Oxygen-Redox Battery Electrodes.

    Science.gov (United States)

    Okubo, Masashi; Yamada, Atsuo

    2017-10-25

    Lithium-ion batteries are key energy-storage devices for a sustainable society. The most widely used positive electrode materials are LiMO 2 (M: transition metal), in which a redox reaction of M occurs in association with Li + (de)intercalation. Recent developments of Li-excess transition-metal oxides, which deliver a large capacity of more than 200 mAh/g using an extra redox reaction of oxygen, introduce new possibilities for designing higher energy density lithium-ion batteries. For better engineering using this fascinating new chemistry, it is necessary to achieve a full understanding of the reaction mechanism by gaining knowledge on the chemical state of oxygen. In this review, a summary of the recent advances in oxygen-redox battery electrodes is provided, followed by a systematic demonstration of the overall electronic structures based on molecular orbitals with a focus on the local coordination environment around oxygen. We show that a π-type molecular orbital plays an important role in stabilizing the oxidized oxygen that emerges upon the charging process. Molecular orbital principles are convenient for an atomic-level understanding of how reversible oxygen-redox reactions occur in bulk, providing a solid foundation toward improved oxygen-redox positive electrode materials for high energy-density batteries.

  17. Molecular Controls of the Oxygenation and Redox Reactions of Hemoglobin

    Science.gov (United States)

    Henkens, Robert; Alayash, Abdu I.; Banerjee, Sambuddha; Crumbliss, Alvin L.

    2013-01-01

    Abstract Significance: The broad classes of O2-binding proteins known as hemoglobins (Hbs) carry out oxygenation and redox functions that allow organisms with significantly different physiological demands to exist in a wide range of environments. This is aided by allosteric controls that modulate the protein's redox reactions as well as its O2-binding functions. Recent Advances: The controls of Hb's redox reactions can differ appreciably from the molecular controls for Hb oxygenation and come into play in elegant mechanisms for dealing with nitrosative stress, in the malarial resistance conferred by sickle cell Hb, and in the as-yet unsuccessful designs for safe and effective blood substitutes. Critical Issues: An important basic principle in consideration of Hb's redox reactions is the distinction between kinetic and thermodynamic reaction control. Clarification of these modes of control is critical to gaining an increased understanding of Hb-mediated oxidative processes and oxidative toxicity in vivo. Future Directions: This review addresses emerging concepts and some unresolved questions regarding the interplay between the oxygenation and oxidation reactions of structurally diverse Hbs, both within red blood cells and under acellular conditions. Developing methods that control Hb-mediated oxidative toxicity will be critical to the future development of Hb-based blood substitutes. Antioxid. Redox Signal. 18, 2298–2313. PMID:23198874

  18. ETL 1 kW redox flow cell

    International Nuclear Information System (INIS)

    Nozaki, K.; Ozawa, T.

    1984-01-01

    A 1 kW scale redox flow cell system was set up in the laboratory (ETL), while three different types of batteries were also assembled by private companies in early 1983. In this article, this cell system is described. The concept of a modern type redox flow cell is based on a couple of fully soluble redox ions and a highly selective ion-exchange membrane. In the cell, the redox ion stored in a tank is flowed to and reduced on the electrode, while the other ion is also flowed to and oxidized on the other electrode. This electrochemical reaction produces electronic current in the external circuit and ionic current through the membrane sandwiched as a separator between the two electrodes. The reverse reaction proceeds in the charging process. In ETL, the concept was preliminarily tested, and conceptual design and cost estimation of the redox flow cells were carried out to confirm the feasibility; the R and D started on these bases in 1975

  19. Process comparison for fracture-induced formation of surface structures on polymer films

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Yueh-Ying [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Yang, Fuqian [Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506 (United States); Chen, Chia-Chieh [Institute of Nuclear Energy Research, Longtan, Taoyuan 32546, Taiwan (China); Lee, Sanboh, E-mail: sblee@mx.nthu.edu.tw [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2014-01-01

    Using three different splitting approaches such as point-load splitting, tension-splitting and peeling–splitting, different surface ripples were produced on poly(methyl methacrylate) (PMMA)-based polymer films. Independent of the splitting approaches, the spatial wavelength of the surface structures is a linear function of the film thickness with the approximately same differential ratio of the spatial wavelength to the film thickness. The apparent surface residual stress was calculated from the thickness dependence of the spatial frequency, and the magnitude of the apparent surface stress increased with the increase of the film thickness. After exposing the aged PMMA-based photoresist at liquid state to gamma-irradiation, the effects of aging and the gamma-irradiation were investigated on the splitting-induced formation of surface structures. For the peeling–splitting process, the differential ratio of the spatial wavelength to the film thickness for the aged samples is larger than that for non-aged samples. The point-load splitting could not produce any surface pattern on the gamma-irradiated films. None of the splitting approaches could form surface structures for polymer films exposed to irradiation of high dose. Both the spatial wavelength and the apparent surface stress increased with the film thickness for the irradiated polymer films. - Highlights: • Using splitting processes, surface ripples were formed on polymer films. • The surface ripples were induced by compressively apparent surface stress. • The spatial wavelength of the ripples is a linear function of the film thickness. • The spatial wavelength of the ripples is affected by gamma-ray irradiation. • The spatial wavelength of the ripples is affected by aging.

  20. Distribution and Characteristics of Boulder Halos at High Latitudes on Mars: Ground Ice and Surface Processes Drive Surface Reworking

    Science.gov (United States)

    Levy, J. S.; Fassett, C. I.; Rader, L. X.; King, I. R.; Chaffey, P. M.; Wagoner, C. M.; Hanlon, A. E.; Watters, J. L.; Kreslavsky, M. A.; Holt, J. W.; Russell, A. T.; Dyar, M. D.

    2018-02-01

    Boulder halos are circular arrangements of clasts present at Martian middle to high latitudes. Boulder halos are thought to result from impacts into a boulder-poor surficial unit that is rich in ground ice and/or sediments and that is underlain by a competent substrate. In this model, boulders are excavated by impacts and remain at the surface as the crater degrades. To determine the distribution of boulder halos and to evaluate mechanisms for their formation, we searched for boulder halos over 4,188 High Resolution Imaging Science Experiment images located between 50-80° north and 50-80° south latitude. We evaluate geological and climatological parameters at halo sites. Boulder halos are about three times more common in the northern hemisphere than in the southern hemisphere (19% versus 6% of images) and have size-frequency distributions suggesting recent Amazonian formation (tens to hundreds of millions of years). In the north, boulder halo sites are characterized by abundant shallow subsurface ice and high thermal inertia. Spatial patterns of halo distribution indicate that excavation of boulders from beneath nonboulder-bearing substrates is necessary for the formation of boulder halos, but that alone is not sufficient. Rather, surface processes either promote boulder halo preservation in the north or destroy boulder halos in the south. Notably, boulder halos predate the most recent period of near-surface ice emplacement on Mars and persist at the surface atop mobile regolith. The lifetime of observed boulders at the Martian surface is greater than the lifetime of the craters that excavated them. Finally, larger minimum boulder halo sizes in the north indicate thicker icy soil layers on average throughout climate variations driven by spin/orbit changes during the last tens to hundreds of millions of years.

  1. Redox properties of iron in porous ferrisilicates

    International Nuclear Information System (INIS)

    Lazar, K.; Pal-Borbely, G.; Szegedi, A.; Fejes, P.; Martinez, F.

    2006-01-01

    Insertion of iron into porous ferrisilicates may result in changes of the original structures. For example, this insertion enables the structure to take part in reversible Fe 2+ ↔ Fe 3+ redox process. This process may play an important role e.g. in catalytic procedures. The structure of the host may provide different locations for the iron. In microporous systems (analogous with zeolites, with characteristic pore sizes of 0.5 nm) the framework vs. extra-framework distinction is obvious, since these structures are strictly crystalline (in three dimensions). In contrast, mesoporous structures of 3 - 5 nm characteristic pore dimension, exhibit crystallinity uppermost in two dimensions, since their pore walls are partly amorphous. The appearance of the Fe 2+ ↔ Fe 3+ redox behaviour of iron in micro- and mesoporous systems, its correlation with coordination changes strongly depend on the structure. In general, crystallinity stabilizes the Fe 3+ state, and the Fe 3+ ↔ Fe 2+ change may be correlated with change of the position occupied in the structure. For demonstration, some examples are to be presented by comparing the behaviour of iron located in in microporous (MFI, FER, MCM-22) and mesoporous (MCM-41 and SBA-15) structures. (authors)

  2. Effect of Space Radiation Processing on Lunar Soil Surface Chemistry: X-Ray Photoelectron Spectroscopy Studies

    Science.gov (United States)

    Dukes, C.; Loeffler, M.J.; Baragiola, R.; Christoffersen, R.; Keller, J.

    2009-01-01

    Current understanding of the chemistry and microstructure of the surfaces of lunar soil grains is dominated by a reference frame derived mainly from electron microscopy observations [e.g. 1,2]. These studies have shown that the outermost 10-100 nm of grain surfaces in mature lunar soil finest fractions have been modified by the combined effects of solar wind exposure, surface deposition of vapors and accretion of impact melt products [1,2]. These processes produce surface-correlated nanophase Feo, host grain amorphization, formation of surface patinas and other complex changes [1,2]. What is less well understood is how these changes are reflected directly at the surface, defined as the outermost 1-5 atomic monolayers, a region not easily chemically characterized by TEM. We are currently employing X-ray Photoelectron Spectroscopy (XPS) to study the surface chemistry of lunar soil samples that have been previously studied by TEM. This work includes modification of the grain surfaces by in situ irradiation with ions at solar wind energies to better understand how irradiated surfaces in lunar grains change their chemistry once exposed to ambient conditions on earth.

  3. Analysis the complex interaction among flexible nanoparticles and materials surface in the mechanical polishing process

    Energy Technology Data Exchange (ETDEWEB)

    Han Xuesong, E-mail: hanxuesongphd@yahoo.com.cn [School of Mechanical Engineering, Tianjin University, 300072 (China); Gan, Yong X. [Department of Mechanical, Industrial and Manufacturing Engineering, University of Toledo, OH 43606 (United States)

    2011-02-01

    Mechanical polishing (MP), being the important technique of realizing the surface planarization, has already been widely applied in the area of microelectronic manufacturing and computer manufacturing technology. The surface planarization in the MP is mainly realized by mechanical process which depended on the microdynamic behavior of nanoparticle. The complex multibody interaction among nanoparticles and materials surface is different from interaction in the macroscopic multibody system which makes the traditional classical materials machining theory cannot accurately uncover the mystery of the surface generation in the MP. Large-scale classical molecular dynamic (MD) simulation of interaction among nanoparticles and solid surface has been carried out to investigate the physical essence of surface planarization. The particles with small impact angle can generate more uniform global planarization surface but the materials removal rate is lower. The shear interaction between particle and substrate may induce large friction torque and lead to the rotation of particle. The translation plus rotation makes the nanoparticle behaved like micro-milling tool. The results show that the nanoparticles may aggregrate together and form larger cluster thus deteriorate surface the quality. This MD simulation results illuminate that the f inal planarized surface can only be acquired by synergic behavior of all particles using various means such as cutting, impacting, scratching, indentation and so on.

  4. AFM surface imaging of AISI D2 tool steel machined by the EDM process

    International Nuclear Information System (INIS)

    Guu, Y.H.

    2005-01-01

    The surface morphology, surface roughness and micro-crack of AISI D2 tool steel machined by the electrical discharge machining (EDM) process were analyzed by means of the atomic force microscopy (AFM) technique. Experimental results indicate that the surface texture after EDM is determined by the discharge energy during processing. An excellent machined finish can be obtained by setting the machine parameters at a low pulse energy. The surface roughness and the depth of the micro-cracks were proportional to the power input. Furthermore, the AFM application yielded information about the depth of the micro-cracks is particularly important in the post treatment of AISI D2 tool steel machined by EDM

  5. AFM surface imaging of AISI D2 tool steel machined by the EDM process

    Science.gov (United States)

    Guu, Y. H.

    2005-04-01

    The surface morphology, surface roughness and micro-crack of AISI D2 tool steel machined by the electrical discharge machining (EDM) process were analyzed by means of the atomic force microscopy (AFM) technique. Experimental results indicate that the surface texture after EDM is determined by the discharge energy during processing. An excellent machined finish can be obtained by setting the machine parameters at a low pulse energy. The surface roughness and the depth of the micro-cracks were proportional to the power input. Furthermore, the AFM application yielded information about the depth of the micro-cracks is particularly important in the post treatment of AISI D2 tool steel machined by EDM.

  6. Method for atmospheric pressure reactive atom plasma processing for surface modification

    Science.gov (United States)

    Carr, Jeffrey W [Livermore, CA

    2009-09-22

    Reactive atom plasma processing can be used to shape, polish, planarize and clean the surfaces of difficult materials with minimal subsurface damage. The apparatus and methods use a plasma torch, such as a conventional ICP torch. The workpiece and plasma torch are moved with respect to each other, whether by translating and/or rotating the workpiece, the plasma, or both. The plasma discharge from the torch can be used to shape, planarize, polish, and/or clean the surface of the workpiece, as well as to thin the workpiece. The processing may cause minimal or no damage to the workpiece underneath the surface, and may involve removing material from the surface of the workpiece.

  7. Manipulating surface wettability and oil absorbency of diatomite depending on processing and ambient conditions

    Science.gov (United States)

    Özen, İlhan; Şimşek, Süleyman; Okyay, Gamze

    2015-03-01

    In this study, a diatomite sample, which is a natural inorganic mineral with inherently high water and oil absorption capacity, was subjected to grinding before surface modification. Afterwards, the diatomite surface was modified via facile methods using a fluorocarbon (FC) chemical and stearic acid (SA) in addition to the sol-gel fluorosilanization (FS) process. The water and oil wettability, and oil absorbency properties of the unmodified and modified diatomites were investigated in addition to diatomite characterizations such as chemical content, surface area, particle size distribution, morphology, and modification efficiency. It was revealed that the wettability was changed completely depending on the surface modification agent and the media used, while the oil absorbency property surprisingly did not change. On the other hand, the oil absorbency was worsened by the grinding process, whereas the wettability was not affected.

  8. Redox behavior of Tc(VII)/Tc(IV) under various reducing conditions in 0.1 M NaCl solutions

    International Nuclear Information System (INIS)

    Kobayashi, T.; Gaona, X.; Altmaier, M.; Scheinost, A.C.; Fellhauer, D.; European Commission Joint Research Centre, Karlsruhe

    2013-01-01

    Redox behaviour of Tc(VII)/Tc(IV) was investigated in 0.1 M NaCl solutions containing different reducing agents in the pH range 2 to 13 at 22 C under inert Ar atmosphere. In several samples, the 1 x 10 -5 mol/dm 3 (M) initially added TcO 4 - was reduced to form a Tc(IV) oxide solid phase with low solubility. The observed Tc redox transformation processes are systematized according to E h -pH conditions in solution, indicating that a borderline for the reduction of Tc(VII) to Tc(IV), TcO 4 - + 3e - + 4H + TcO 2 . xH 2 O(coll, hyd) + (2-x)H 2 O exists, independent of the reducing chemical system. This experimentally derived borderline is about 100 mV lower than the equilibrium line calculated from the reported standard redox potential of TcO 2 . 1.6H 2 O(s). This behaviour can be related to the existence of more soluble solid phase modifications, i.e. nanoparticulate Tc(IV) oxide species TcO 2 . xH 2 O(coll, hyd). The reaction kinetics likewise correlate to the redox potential measured in solution. Slow reduction of Tc(VII) to Tc(IV) was observed when the redox potential in the system was slightly below the above mentioned reduction borderline. Fast reduction was observed in the systems far below the borderline, but also in those systems containing Fe(II) solids, suggesting a specific surface mediated effect in the reduction process. EXAFS analysis on two magnetite samples indicate reduced Tc(IV) species which do not remain adsorbed at the reactive mineral surface and are incorporated in the magnetite structure. (orig.)

  9. The study of sub-surface damage distributions during grinding process on different abrasion materials

    Science.gov (United States)

    Kuo, Ching-Hsiang; Huang, Chien-Yao; Yu, Zong-Ru; Shu, Shyu-Cheng; Chang, Keng-Shou; Hsu, Wei-Yao

    2017-10-01

    The grinding process is the primary technology for curvature generation (CG) on glass optics. The higher material removal rate (MRR) leads to deeper sub-surface damage (SSD) on lens surface. The SSD must be removed by following lapping and polishing processes to ensure the lens quality. However, these are not an easy and an efficient process to remove the SSD from ground surface directly for aspheric surfaces with tens or hundreds microns departure from bestfit- sphere (BFS). An efficient fabrication procedure for large aspheric departure on glass materials must be considered. We propose 3-step fabrication procedures for aspheric surface with larger departure. 1st step is to generate a specific aspheric surface with depth less than 10 μm of SSD residual. 2nd step is to remove SSD and keep the aspheric form by using Zeeko polisher with higher MRR pad. Final step is to figure and finish the aspheric surface by using QED MRF machine. In this study, we focus on the 1st step to investigate the residual depth of SSD after grinding process on different abrasion materials. The materials of tested part are fused silica, S-NPH2, and S-PHM52. The cross grinding would be configured and depth of SSD/surface roughness would be evaluated in this study. The characteristic of SSD could be observed after etching by confocal microscope. The experimental results show the depth of SSD below 31.1 μm with #400 grinding wheel. And the near 10 μm depth of SSD would be achieved with #1,000 grinding wheel. It means the aspherization polishing on large parts with large departure from best fit sphere would be replaced. The fabrication of large aspheric part would be efficient.

  10. Influence of Wire Electrical Discharge Machining (WEDM) process parameters on surface roughness

    Science.gov (United States)

    Yeakub Ali, Mohammad; Banu, Asfana; Abu Bakar, Mazilah

    2018-01-01

    In obtaining the best quality of engineering components, the quality of machined parts surface plays an important role. It improves the fatigue strength, wear resistance, and corrosion of workpiece. This paper investigates the effects of wire electrical discharge machining (WEDM) process parameters on surface roughness of stainless steel using distilled water as dielectric fluid and brass wire as tool electrode. The parameters selected are voltage open, wire speed, wire tension, voltage gap, and off time. Empirical model was developed for the estimation of surface roughness. The analysis revealed that off time has a major influence on surface roughness. The optimum machining parameters for minimum surface roughness were found to be at a 10 V open voltage, 2.84 μs off time, 12 m/min wire speed, 6.3 N wire tension, and 54.91 V voltage gap.

  11. Effect of Build Angle on Surface Properties of Nickel Superalloys Processed by Selective Laser Melting

    Science.gov (United States)

    Covarrubias, Ernesto E.; Eshraghi, Mohsen

    2018-03-01

    Aerospace, automotive, and medical industries use selective laser melting (SLM) to produce complex parts through solidifying successive layers of powder. This additive manufacturing technique has many advantages, but one of the biggest challenges facing this process is the resulting surface quality of the as-built parts. The purpose of this research was to study the surface properties of Inconel 718 alloys fabricated by SLM. The effect of build angle on the surface properties of as-built parts was investigated. Two sets of sample geometries including cube and rectangular artifacts were considered in the study. It was found that, for angles between 15° and 75°, theoretical calculations based on the "stair-step" effect were consistent with the experimental results. Downskin surfaces showed higher average roughness values compared to the upskin surfaces. No significant difference was found between the average roughness values measured from cube and rectangular test artifacts.

  12. Electron Transfer in Flavodoxin-based Redox Maquettes

    NARCIS (Netherlands)

    Alagaratnam, S.

    2005-01-01

    Small redox proteins play the role of electron taxis in the cell, picking electrons up at one location and delivering them at another. While it is known that these reactions are the basis for the processes of energy generation by respiration and photosynthesis, the means by which these 'taxis'

  13. Land Surface Process and Air Quality Research and Applications at MSFC

    Science.gov (United States)

    Quattrochi, Dale; Khan, Maudood

    2007-01-01

    This viewgraph presentation provides an overview of land surface process and air quality research at MSFC including atmospheric modeling and ongoing research whose objective is to undertake a comprehensive spatiotemporal analysis of the effects of accurate land surface characterization on atmospheric modeling results, and public health applications. Land use maps as well as 10 meter air temperature, surface wind, PBL mean difference heights, NOx, ozone, and O3+NO2 plots as well as spatial growth model outputs are included. Emissions and general air quality modeling are also discussed.

  14. Bioinspired superhydrophobic surfaces, fabricated through simple and scalable roll-to-roll processing.

    Science.gov (United States)

    Park, Sung-Hoon; Lee, Sangeui; Moreira, David; Bandaru, Prabhakar R; Han, InTaek; Yun, Dong-Jin

    2015-10-22

    A simple, scalable, non-lithographic, technique for fabricating durable superhydrophobic (SH) surfaces, based on the fingering instabilities associated with non-Newtonian flow and shear tearing, has been developed. The high viscosity of the nanotube/elastomer paste has been exploited for the fabrication. The fabricated SH surfaces had the appearance of bristled shark skin and were robust with respect to mechanical forces. While flow instability is regarded as adverse to roll-coating processes for fabricating uniform films, we especially use the effect to create the SH surface. Along with their durability and self-cleaning capabilities, we have demonstrated drag reduction effects of the fabricated films through dynamic flow measurements.

  15. Evaporation phase change processes of water/methanol mixtures on superhydrophobic nanostructured surfaces

    Science.gov (United States)

    Chiang, Cheng-Kun; Lu, Yen-Wen

    2011-07-01

    Evaporation phenomena are a critical and frequently seen phase change process in many heat transfer applications. In this paper, we study the evaporation process of a sessile droplet on two topologically different surfaces, including smooth and nanostructured surfaces. The nanostructured surface has an array of high-aspect-ratio nanowires (height/diameter ~ 125) and is implemented by using a simple template-based nanofabrication method. It possesses superhydrophobicity (>140°) and low contact angle hysteresis (1.2-2.1°), allowing the liquid droplets to remain in the 'fakir' state throughout the evaporation processes. Sessile droplets of deionized (DI) water and water/methanol binary mixture test liquids with their contact angles and base diameters are monitored. The results show that the nanostructures play a critical role in the droplet dynamics during evaporation.

  16. Evaporation phase change processes of water/methanol mixtures on superhydrophobic nanostructured surfaces

    International Nuclear Information System (INIS)

    Chiang, Cheng-Kun; Lu, Yen-Wen

    2011-01-01

    Evaporation phenomena are a critical and frequently seen phase change process in many heat transfer applications. In this paper, we study the evaporation process of a sessile droplet on two topologically different surfaces, including smooth and nanostructured surfaces. The nanostructured surface has an array of high-aspect-ratio nanowires (height/diameter ∼ 125) and is implemented by using a simple template-based nanofabrication method. It possesses superhydrophobicity (>140°) and low contact angle hysteresis (1.2–2.1°), allowing the liquid droplets to remain in the 'fakir' state throughout the evaporation processes. Sessile droplets of deionized (DI) water and water/methanol binary mixture test liquids with their contact angles and base diameters are monitored. The results show that the nanostructures play a critical role in the droplet dynamics during evaporation

  17. Selection Criteria and Methods for Testing Different Surface Materials for Contact Frying Processes

    DEFF Research Database (Denmark)

    Ashokkumar, Saranya

    Inner surfaces of industrial process equipment for food are often coated to give the surfaces particular properties with respect to adhesion and cleanability. Existing coating materials (PTFE (Teflon®) or silicone based polymers) suffer from drawbacks when used in contact frying, because these co...... surface materials for contact frying processes. The surfaces selected for this purpose cover a wide spectrum of materials that range from hydrophobic to hydrophilic materials. The different surface materials investigated include stainless steel (reference),