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Sample records for structure redox properties

  1. Redox properties of structural Fe in clay minerals: 3. Relationships between smectite redox and structural properties.

    Science.gov (United States)

    Gorski, Christopher A; Klüpfel, Laura E; Voegelin, Andreas; Sander, Michael; Hofstetter, Thomas B

    2013-01-01

    Structural Fe in clay minerals is an important redox-active species in many pristine and contaminated environments as well as in engineered systems. Understanding the extent and kinetics of redox reactions involving Fe-bearing clay minerals has been challenging due to the inability to relate structural Fe(2+)/Fe(total) fractions to fundamental redox properties, such as reduction potentials (EH). Here, we overcame this challenge by using mediated electrochemical reduction (MER) and oxidation (MEO) to characterize the fraction of redox-active structural Fe (Fe(2+)/Fe(total)) in smectites over a wide range of applied EH-values (-0.6 V to +0.6 V). We examined Fe(2+)/Fe(total )- EH relationships of four natural Fe-bearing smectites (SWy-2, SWa-1, NAu-1, NAu-2) in their native, reduced, and reoxidized states and compared our measurements with spectroscopic observations and a suite of mineralogical properties. All smectites exhibited unique Fe(2+)/Fe(total) - EH relationships, were redox active over wide EH ranges, and underwent irreversible electron transfer induced structural changes that were observable with X-ray absorption spectroscopy. Variations among the smectite Fe(2+)/Fe(total) - EH relationships correlated well with both bulk and molecular-scale properties, including Fe(total) content, layer charge, and quadrupole splitting values, suggesting that multiple structural parameters determined the redox properties of smectites. The Fe(2+)/Fe(total) - EH relationships developed for these four commonly studied clay minerals may be applied to future studies interested in relating the extent of structural Fe reduction or oxidation to EH-values.

  2. Unique Intramolecular Electronic Communications in Mono-ferrocenylpyrimidine Derivatives: Correlation between Redox Properties and Structural Nature

    International Nuclear Information System (INIS)

    Xiang, Debo; Noel, Jerome; Shao, Huibo; Dupas, Georges; Merbouh, Nabyl; Yu, Hua-Zhong

    2015-01-01

    Highlights: • Unique intramolecular electronic communications (electron withdrawing and π-bond delocalization effects) exist in the mono-ferrocenylpyrimidine derivatives. • The redox potential shift correlates the pyrimidine ring torsion angle with the extent of electron delocalization. • The correlation between redox properties and structural nature in mono-ferrocenylpyrimidine derivatives is evident. - Abstract: The correlation between redox properties and structural nature in a complete set of mono-ferrocenylpyrimidine derivatives (2-ferrocenylpyrimidine, 2-FcPy; 4-ferrocenylpyrimidine, 4-FcPy; 5-ferrocenylpyrimidine, 5-FcPy) was evaluated by investigating the intramolecular electronic communications. Both conventional electrochemical measurements in organic solvents and thin-film voltammetric studies of these compounds were carried out. It was discovered that their formal potentials are significantly different from each other, and shift negatively in the order of 4-FcPy > 5-FcPy > 2-FcPy. This result suggests that the intramolecular electronic communication is dictated by the delocalization effect of the π-bonding systems in 2-FcPy, and that the electron-withdrawing effect of the nitrogen atoms in the pyrimidine ring plays the key role in 4-FcPy and 5-FcPy. The single crystal X-ray structure analyis and Density Functional Theory (DFT) calculation provided additional evidence (e.g., different torsion angles between the cyclopentadienyl and pyrimidine rings) to support the observed correlation between the redox properties and structural nature

  3. A theoretical probe of high-valence uranium and transuranium silylamides: Structural and redox properties

    Science.gov (United States)

    Zhong, Yu-Xi; Guo, Yuan-Ru; Pan, Qing-Jiang

    2016-02-01

    Relativistic density functional theory was used to explore the structural and redox properties of 18 prototypical actinyl silylamides including a variation of metals (U, Np and Pu), metal oxidation states (VI and V) and equatorial ligands. A theoretical approach associated with implicit solvation and spin-orbit/multiplet corrections was proved to be reliable. A marked shift of reduction potentials of actinyl silylamides caused by changes of equatorial coordination ligands and implicit solvation was elucidated by analyses of electronic structures and single-electron reduction mechanism.

  4. Spectroelectrochemical insights into structural and redox properties of immobilized endonuclease III and its catalytically inactive mutant

    Science.gov (United States)

    Moe, Elin; Rollo, Filipe; Silveira, Célia M.; Sezer, Murat; Hildebrandt, Peter; Todorovic, Smilja

    2018-01-01

    Endonuclease III is a Fe-S containing bifunctional DNA glycosylase which is involved in the repair of oxidation damaged DNA. Here we employ surface enhanced IR spectroelectrochemistry and electrochemistry to study the enzyme from the highly radiation- and desiccation-resistant bacterium Deinococcus radiodurans (DrEndoIII2). The experiments are designed to shed more light onto specific parameters that are currently proposed to govern damage search and recognition by endonucleases III. We demonstrate that electrostatic interactions required for the redox activation of DrEndoIII2 may result in high electric fields that alter its structural and thermodynamic properties. Analysis of inactive DrEndoIII2 (K132A/D150A double mutant) interacting with undamaged DNA, and the active enzyme interacting with damaged DNA also indicate that the electron transfer is modulated by subtle differences in the protein-DNA complex.

  5. 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

  6. Redox properties of structural Fe in clay minerals. 2. Electrochemical and spectroscopic characterization of electron transfer irreversibility in ferruginous smectite, SWa-1.

    Science.gov (United States)

    Gorski, Christopher A; Klüpfel, Laura; Voegelin, Andreas; Sander, Michael; Hofstetter, Thomas B

    2012-09-04

    Structural Fe in clay minerals is an important, albeit poorly characterized, redox-active phase found in many natural and engineered environments. This work develops an experimental approach to directly assess the redox properties of a natural Fe-bearing smectite (ferruginous smectite, SWa-1, 12.6 wt % Fe) with mediated electrochemical reduction (MER) and oxidation (MEO). By utilizing a suite of one-electron-transfer mediating compounds to facilitate electron transfer between structural Fe in SWa-1 and a working electrode, we show that the Fe2+/Fe3+ couple in SWa-1 is redox-active over a large range of potentials (from E(H) = -0.63 V to +0.61 V vs SHE). Electrochemical and spectroscopic analyses of SWa-1 samples that were subject to reduction and re-oxidation cycling revealed both reversible and irreversible structural Fe rearrangements that altered the observed apparent standard reduction potential (E(H)(ø)) of structural Fe. E(H)(ø)-values vary by as much as 0.56 V between SWa-1 samples with different redox histories. The wide range of E(H)-values over which SWa-1 is redox-active and redox history-dependent E(H)(ø)-values underscore the importance of Fe-bearing clay minerals as redox-active phases in a wide range of redox regimes.

  7. 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

  8. Reaction Mechanisms and Structural and Physicochemical Properties of Caffeic Acid Grafted Chitosan Synthesized in Ascorbic Acid and Hydroxyl Peroxide Redox System.

    Science.gov (United States)

    Liu, Jun; Pu, Huimin; Chen, Chong; Liu, Yunpeng; Bai, Ruyu; Kan, Juan; Jin, Changhai

    2018-01-10

    The ascorbic acid (AA) and hydroxyl peroxide (H 2 O 2 ) redox pair induced free radical grafting reaction is a promising approach to conjugate phenolic groups with chitosan (CS). In order to reveal the exact mechanisms of the AA/H 2 O 2 redox pair induced grafting reaction, free radicals generated in the AA/H 2 O 2 redox system were compared with hydroxyl radical ( • OH) produced in the Fe 2+ /H 2 O 2 redox system. Moreover, the structural and physicochemical properties of caffeic acid grafted CS (CA-g-CS) synthesized in these two redox systems were compared. Results showed that only ascorbate radical (Asc •- ) was produced in the AA/H 2 O 2 system. The reaction between Asc •- and CS produced novel carbon-centered radicals, whereas no new free radicals were detected when • OH reacted with CS. Thin layer chromatography, UV-vis, Fourier transform infrared, and nuclear magnetic resonance spectroscopic analyses all confirmed that CA was successfully grafted onto CS through Asc •- . However, CA could be hardly grafted onto CS via • OH. CA-g-CS synthesized through Asc •- exhibited lower thermal stability and crystallinity than the reaction product obtained through • OH. For the first time, our results demonstrated that the synthesis of CA-g-CS in the AA/H 2 O 2 redox system was mediated by Asc •- rather than • OH.

  9. Redox-active porous coordination polymers prepared by trinuclear heterometallic pivalate linking with the redox-active nickel(II) complex: synthesis, structure, magnetic and redox properties, and electrocatalytic activity in organic compound dehalogenation in heterogeneous medium.

    Science.gov (United States)

    Lytvynenko, A S; Kolotilov, S V; Kiskin, M A; Cador, O; Golhen, S; Aleksandrov, G G; Mishura, A M; Titov, V E; Ouahab, L; Eremenko, I L; Novotortsev, V M

    2014-05-19

    Linking of the trinuclear pivalate fragment Fe2CoO(Piv)6 by the redox-active bridge Ni(L)2 (compound 1; LH is Schiff base from hydrazide of 4-pyridinecarboxylic acid and 2-pyridinecarbaldehyde, Piv(-) = pivalate) led to formation of a new porous coordination polymer (PCP) {Fe2CoO(Piv)6}{Ni(L)2}1.5 (2). X-ray structures of 1 and 2 were determined. A crystal lattice of compound 2 is built from stacked 2D layers; the Ni(L)2 units can be considered as bridges, which bind two Fe2CoO(Piv)6 units. In desolvated form, 2 possesses a porous crystal lattice (SBET = 50 m(2) g(-1), VDR = 0.017 cm(3) g(-1) estimated from N2 sorption at 78 K). At 298 K, 2 absorbed a significant quantity of methanol (up to 0.3 cm(3) g(-1)) and chloroform. Temperature dependence of molar magnetic susceptibility of 2 could be fitted as superposition of χMT of Fe2CoO(Piv)6 and Ni(L)2 units, possible interactions between them were taken into account using molecular field model. In turn, magnetic properties of the Fe2CoO(Piv)6 unit were fitted using two models, one of which directly took into account a spin-orbit coupling of Co(II), and in the second model the spin-orbit coupling of Co(II) was approximated as zero-field splitting. Electrochemical and electrocatalytic properties of 2 were studied by cyclic voltammetry in suspension and compared with electrochemical and electrocatalytic properties of a soluble analogue 1. A catalytic effect was determined by analysis of the catalytic current dependency on concentrations of the substrate. Compound 1 possessed electrocatalytic activity in organic halide dehalogenation, and such activity was preserved for the Ni(L)2 units, incorporated into the framework of 2. In addition, a new property occurred in the case of 2: the catalytic activity of PCP depended on its sorption capacity with respect to the substrate. In contrast to homogeneous catalysts, usage of solid PCPs may allow selectivity due to porous structure and simplify separation of product.

  10. Effect of succinonitrile on electrical, structural, optical, and thermal properties of [poly(ethylene oxide)-succinonitrile]/LiI–I2 redox-couple solid polymer electrolyte

    International Nuclear Information System (INIS)

    Gupta, Ravindra Kumar; Rhee, Hee-Woo

    2012-01-01

    Effect of succinonitrile on electrical, structural, optical, and thermal properties of [poly(ethylene oxide)-succinonitrile]/LiI–I 2 redox-couple solid polymer electrolyte is reported for the first time. For the poly(ethylene oxide)-succinonitrile blend-based electrolyte electrical conductivity was noted as high as ∼3 × 10 −4 S cm −1 at 25 °C, which is an order of magnitude higher than that of pure poly(ethylene oxide)-based electrolyte. It also exhibited relatively better pseudo-activation energy (∼0.08 eV). X-ray diffractometry, polarized optical microscopy, and differential scanning calorimetry studies revealed that succinonitrile is helpful in reducing the poly(ethylene oxide) crystallinity due to its plasticizing property. FT-IR study showed significant modification of the poly(ethylene oxide) chain conformation due to the succinonitrile.

  11. Effects of countercations on the structures and redox and spectroscopic properties of diruthenium catecholate complexes with ligand-unsupported Ru-Ru bonds.

    Science.gov (United States)

    Chang, Ho-Chol; Mochizuki, Katsunori; Kitagawa, Susumu

    2005-05-30

    The molecular structures and physicochemical properties of diruthenium complexes with ligand-unsupported Ru-Ru bonds, generally formulated as [A2{Ru2(DTBCat)4}] (DTB = 3,5- or 3,6-di-tert-butyl; Cat(2-) = catecholate), were studied in detail by changing the countercations. First, the binding structures of the cations in a family of [{A(DME)n}2{Ru2(3,5-DTBCat)4}] (n = 2 for A+ = Li+ and Na+ and n = 1 for A+ = K+ and Rb+) were systematically examined to reveal the effects of the cations on the molecular structures and electrochemical properties. Second, the complex (n-Bu4N)2[Ru2(3,6-DTBCat)4] with a cation-free structure was synthesized using tetra-n-butylammonium cations. The complex clearly demonstrates first that the ligand-unsupported Ru-Ru bonds are essentially stabilized by the dianionic nature of the catecholate derivatives without any other bridging or supporting species. In contrast, the redox potentials and absorption spectra of the complexes can sensitively respond to the countercations depending upon the polarity of the solvents.

  12. 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)

  13. Structural and Redox Properties of Vanadium Complexes in Molten Salts of Interest for the Catalytic Oxidation of Sulfur Dioxide

    DEFF Research Database (Denmark)

    Boghosian, S.; Chrissanthopoulos, A.; Fehrmann, Rasmus

    2000-01-01

    Electronic absorption (UV/VIS) spectra have been obtained at 450 degrees C from V2O5-K2S2O7 molten mixtures in SO2 ( P-SO2 = 0 - 1.2 atm) gas atmospheres. The data are in agreement with the V-V reversible arrow V-IV equilibrium: (VO)(2)O(SO4)(4)(4-)(l) + SO2(g) - 2VO(SO4)(2)(2-)(l) + SO3(g). Sulfur...... and vibrational properties of the vanadium complexes formed in the molten salt-gas system V2O5-M2S2O7-M2SO4/SO2-O-2 (M = K or Cs). The spectral features and the exploitation of the relative Raman intensities indicate that the (VO)(2)O(SO4)(4)(+) dimeric complex unit which possesses a V-O-V bridge is formed...

  14. Redox properties of small semiconductor particles

    International Nuclear Information System (INIS)

    Liver, N.; Nitzan, A.

    1992-01-01

    The size dependence of electrical and thermodynamic quantities of intermediate-sized semiconductor particles in an electrolyte solution with a given redox pair are studied. The equilibrium constant for this system is then derived based on the relationship of the electrolytic redox components to the size, charges, and concentration of the semiconductor particles. 25 refs., 9 figs., 1 tab

  15. Redox properties of iron-bearing clays and MX-80 bentonite – Electrochemical and spectroscopic characterization

    Energy Technology Data Exchange (ETDEWEB)

    Hofstetter, Th. B.; Sosedova, Y.; Gorski, C.; Voegelin, A.; Sander, M.

    2014-03-15

    The characterization of the redox properties of Fe-bearing minerals in the presence and absence of dissolved Fe{sup 2+} is of major relevance for the assessment of redox reactions in natural and engineered environments such as radioactive waste repositories. In this study, we developed an electrochemical approach based on the use of soluble organic electron transfer mediators, which enabled us to quantify the redox properties of Fe-bearing clay minerals, MX- 80 bentonite and combinations of clay minerals, Fe oxides and dissolved Fe{sup 2+}. Using mediated electrochemical oxidation and reduction, we quantified the electron accepting and donating capacities of ferrous smectite SWa-1, Wyoming montmorillonite SWy-2 and MX-80 bentonite at pH 7.5. All structural Fe in clay minerals was redox-active in contrast to that present in other, not further defined phases of MX-80. The materials investigated were redoxactive over a very wide range of Eh-values, that is the Fe{sup 2+}/Fe{sub total} ratio of the minerals changed from 0 to 100 % between +600 and -600 mV (vs. SHE). Redox properties were highly path-dependent due to structural changes of the minerals as revealed from the study of native and redox-cycled clay minerals after repeated reduction and re-oxidation cycles. Irreversible alteration of the mineral structure, however, was less obvious for materials with lower total Fe content such as MX-80 bentonite and SWy-2. Systems containing native montmorillonites (SWy-2 or MX-80), goethite and dissolved Fe{sup 2+} were also able to buffer the reduction potential E{sub H} between 0 and -300 mV. Regardless of their Fe oxidation state, Fe-bearing minerals are redox-active over a wide potential range and therefore very relevant as redox buffers determining the fate of redox-active radionuclides and metals in waste repositories. (authors)

  16. Redox properties of iron-bearing clays and MX-80 bentonite – Electrochemical and spectroscopic characterization

    International Nuclear Information System (INIS)

    Hofstetter, Th. B.; Sosedova, Y.; Gorski, C.; Voegelin, A.; Sander, M.

    2014-03-01

    The characterization of the redox properties of Fe-bearing minerals in the presence and absence of dissolved Fe"2"+ is of major relevance for the assessment of redox reactions in natural and engineered environments such as radioactive waste repositories. In this study, we developed an electrochemical approach based on the use of soluble organic electron transfer mediators, which enabled us to quantify the redox properties of Fe-bearing clay minerals, MX- 80 bentonite and combinations of clay minerals, Fe oxides and dissolved Fe"2"+. Using mediated electrochemical oxidation and reduction, we quantified the electron accepting and donating capacities of ferrous smectite SWa-1, Wyoming montmorillonite SWy-2 and MX-80 bentonite at pH 7.5. All structural Fe in clay minerals was redox-active in contrast to that present in other, not further defined phases of MX-80. The materials investigated were redoxactive over a very wide range of Eh-values, that is the Fe"2"+/Fe_t_o_t_a_l ratio of the minerals changed from 0 to 100 % between +600 and -600 mV (vs. SHE). Redox properties were highly path-dependent due to structural changes of the minerals as revealed from the study of native and redox-cycled clay minerals after repeated reduction and re-oxidation cycles. Irreversible alteration of the mineral structure, however, was less obvious for materials with lower total Fe content such as MX-80 bentonite and SWy-2. Systems containing native montmorillonites (SWy-2 or MX-80), goethite and dissolved Fe"2"+ were also able to buffer the reduction potential E_H between 0 and -300 mV. Regardless of their Fe oxidation state, Fe-bearing minerals are redox-active over a wide potential range and therefore very relevant as redox buffers determining the fate of redox-active radionuclides and metals in waste repositories. (authors)

  17. Redox properties of clay-rich sediments as assessed by mediated electrochemical analysis : Separating pyrite, siderite and structural Fe in clay minerals

    NARCIS (Netherlands)

    Hoving, Alwina L.; Sander, Michael; Bruggeman, Christophe; Behrends, Thilo

    2017-01-01

    Redox reactions with Fe-containing minerals in clay-rich sediments largely affect the speciation, mobility, and (bio-) availability of redox-sensitive contaminants. Here, we use mediated electrochemical oxidation (MEO) and reduction (MER), to quantify the electron accepting and donating capacities

  18. Synthesis, Structure Elucidation, and Redox Properties of (superscript 99)Tc Complexes of Lacunary Wells-Dawson Polyoxometalates: Insights into Molecular (superscript 99)Tc-Metal Oxide Interactions

    International Nuclear Information System (INIS)

    McGregor, Donna; Burton-Pye, Benjamin P.; Howell, Robertha C.; Mbomekalle, Israel M.; Lukens, Wayne W. Jr.; Bian, Fang; Mausolf, Edward; Poineau, Frederic; Czerwinski, Kenneth R.; Francesconi, Lynn C.

    2011-01-01

    The isotope 99 Tc (β max , 293.7; half-life, 2.1 x 10 5 years) is an abundant product of uranium-235 fission in nuclear reactors and is present throughout the radioactive waste stored in underground tanks at the Hanford and Savannah River sites. Understanding and controlling the extensive redox chemistry of 99 Tc is important in identifying tunable strategies to separate 99 Tc from spent fuel and from waste tanks and, once separated, to identify and develop an appropriately stable waste form for 99 Tc. Polyoxometalates (POMs), nanometer-sized models for metal oxide solid-state materials, are used in this study to provide a molecular level understanding of the speciation and redox chemistry of incorporated 99 Tc. In this study, 99 Tc complexes of the (α 2 -P 2 W 17 O 61 ) 10- and (α 1 -P 2 W 17 O 61 ) 10- isomers were prepared. Ethylene glycol was used as a 'transfer ligand' to minimize the formation of TcO 2 · xH 2 O. The solution structures, formulations, and purity of TcVO(α 1 /α 2 -P 2 W 17 O 61 ) 7- were determined by multinuclear NMR. X-ray absorption spectroscopy of the complexes is in agreement with the formulation and structures determined from 31 P and 183 W NMR. Preliminary electrochemistry results are consistent with the EXAFS results, showing a facile reduction of the TcVO(α 1 -P 2 W 17 O 61 ) 7- species compared to the TcVO(α 2 -P 2 W 17 O 61 ) 7- analog. The α 1 defect is unique in that a basic oxygen atom is positioned toward the α 1 site, and the Tc V O center appears to form a dative metal-metal bond with a framework W site. These attributes may lead to the assistance of protonation events that facilitate reduction. Electrochemistry comparison shows that the ReV analogs are about 200 mV more difficult to reduce in accordance with periodic trends.

  19. Synthesis, structure elucidation and redox properties of 99Tc complexes of lacunary Wells Dawson polyoxometalates: insights into molecular 99Tc - metal oxide interactions

    International Nuclear Information System (INIS)

    McGregor, Donna; Burton-Pye, Benjamin P.; Howell, Robertha C.; Mbomekalle, Israel M.; Lukens, Wayne W. Jr; Bian, Fang; Mausolf, Edward; Poineau, Frederic; Czerwinski, Kenneth R; Francesconi, Lynn C.

    2011-01-01

    The isotope 99 Tc (β max : 250 keV, half-life: 2 x 10 5 year) is an abundant product of uranium-235 fission in nuclear reactors and is present throughout the radioactive waste stored in underground tanks at Hanford and Savannah River. Understanding and controlling the extensive redox chemistry of 99 Tc is important to identify tunable strategies to separate 99 Tc from spent fuel and from waste tanks and once separated, to identify and develop an appropriately stable waste-form for 99 Tc. Polyoxometalates (POMs), nanometer sized models for metal oxide solid-state materials, are used in this study to provide a molecular level understanding of the speciation and redox chemistry of incorporated 99 Tc. In this study, 99 Tc complexes of the (α 2 -P 2 W 17 O 61 ) 10- and (α 1 -P 2 W 17 O 61 ) 10- isomers were prepared. Ethylene glycol was used as a 'transfer ligand' to minimize the formation of TcO 2 · xH 2 O. The solution structures, formulations, and purity of Tc V O(α 1 /α 2 -P 2 W 17 O 61 ) 7- were determined by multinuclear NMR. X-ray Absorption Spectroscopy of the complexes are in agreement with the formulation and structures determined from 31 P and 183 W NMR. Preliminary electrochemistry results are consistent with the EXAFS results, showing a facile reduction of the Tc V O(α 1 -P 2 W 17 O 61 ) 7- species compared to the Tc V O(α 2 -P 2 W 17 O 61 ) 7- analog. The α 1 -defect is unique in that a basic oxygen atom is positioned toward the α 1 -site and the Tc V O center appears to form a dative metal-metal bond with a framework W site. These attributes may lead to the assistance of protonation events that facilitate reduction. Electrochemistry comparison shows that the Re V analogs are about 200 mV more difficult to reduce in accordance with periodic trends.

  20. 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.

  1. Investigation of the redox-dependent modulation of structure and dynamics in human cytochrome c.

    Science.gov (United States)

    Imai, Mizue; Saio, Tomohide; Kumeta, Hiroyuki; Uchida, Takeshi; Inagaki, Fuyuhiko; Ishimori, Koichiro

    2016-01-22

    Redox-dependent changes in the structure and dynamics of human cytochrome c (Cyt c) were investigated by solution NMR. We found significant structural changes in several regions, including residues 23-28 (loop 3), which were further corroborated by chemical shift differences between the reduced and oxidized states of Cyt c. These differences are essential for discriminating redox states in Cyt c by cytochrome c oxidase (CcO) during electron transfer reactions. Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion experiments identified that the region around His33 undergoes conformational exchanges on the μs-ms timescale, indicating significant redox-dependent structural changes. Because His33 is not part of the interaction site for CcO, our data suggest that the dynamic properties of the region, which is far from the interaction site for CcO, contribute to conformational changes during electron transfer to CcO. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. 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.

  3. Syntheses, structures and redox properties of some complexes containing the Os(dppe)Cp* fragment, including [{Os(dppe)Cp*}2(mu-C triple bondCC triple bond C)].

    Science.gov (United States)

    Bruce, Michael I; Costuas, Karine; Davin, Thomas; Halet, Jean-François; Kramarczuk, Kathy A; Low, Paul J; Nicholson, Brian K; Perkins, Gary J; Roberts, Rachel L; Skelton, Brian W; Smith, Mark E; White, Allan H

    2007-12-14

    The sequential conversion of [OsBr(cod)Cp*] (9) to [OsBr(dppe)Cp*] (10), [Os([=C=CH2)(dppe)Cp*]PF6 ([11]PF6), [Os(C triple bond CH)(dppe)Cp*] (12), [{Os(dppe)Cp*}2{mu-(=C=CH-CH=C=)}][PF6]2 ([13](PF6)2) and finally [{Os(dppe)Cp*}(2)(mu-C triple bond CC triple bond C)] (14) has been used to make the third member of the triad [{M(dppe)Cp*}2(mu-C triple bond CC triple bond C)] (M = Fe, Ru, Os). The molecular structures of []PF6, 12 and 14, together with those of the related osmium complexes [Os(NCMe)(dppe)Cp*]PF6 ([15]PF6) and [Os(C triple bond CPh)(dppe)Cp*] (16), have been determined by single-crystal X-ray diffraction studies. Comparison of the redox properties of 14 with those of its iron and ruthenium congeners shows that the first oxidation potential E1 varies as: Fe approximately Os < Ru. Whereas the Fe complex has been shown to undergo three sequential 1-electron oxidation processes within conventional electrochemical solvent windows, the Ru and Os compounds undergo no fewer than four sequential oxidation events giving rise to a five-membered series of redox related complexes [{M(dppe)Cp*}2(mu-C4)]n+ (n = 0, 1, 2, 3 and 4), the osmium derivatives being obtained at considerably lower potentials than the ruthenium analogues. These results are complimented by DFT and DT DFT calculations.

  4. Preparation, structure, and unique redox properties of mono-, bis-, and Tris(diarylmethylene)-1,3,5-trithianes and related compounds

    Science.gov (United States)

    Suzuki; Yoshino; Nishida; Ohkita; Tsuji

    2000-09-08

    A series of 1,3,5-trithianes 1-3 having diarylmethylene units were designed as novel electron donors giving highly colored cationic species upon oxidation. They were prepared along with the dithiane and dithiazine derivatives 4-6 by the reactions of lithiated heterocycles with diaryl ketones followed by dehydration. Voltammetric analyses indicate that a large structural change and/or transannular bonding are induced during their electrochemical oxidation. Mono(diarylmethylene) derivative 1a exhibits electrochromism with vivid change in color from faintly yellow to deep blue with concomitant rotation around the exocyclic bond. Both of the strongly colored salts obtained upon oxidation of 2,4-bis- and 2,4,6-tris(diarylmethylene)-1,3,5-trithianes (2aa and 3) consist of the dications with a 1,2,4-trithiane ring, suggesting the easy skeletal rearrangement of the transannular dications with a trithiabicylo[3.1.0]hexane ring. Upon reduction of these salts were obtained bright yellow 12 and 13, respectively, with high electron-donating properties due to the tetraarylbutadiene-type conjugation, thus giving another class of electrochromic compounds.

  5. Investigation of the redox-dependent modulation of structure and dynamics in human cytochrome c

    Energy Technology Data Exchange (ETDEWEB)

    Imai, Mizue [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810 (Japan); Saio, Tomohide [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810 (Japan); Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan); Kumeta, Hiroyuki [Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021 (Japan); Uchida, Takeshi [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810 (Japan); Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan); Inagaki, Fuyuhiko [Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021 (Japan); Ishimori, Koichiro, E-mail: koichiro@sci.hokudai.ac.jp [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810 (Japan); Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan)

    2016-01-22

    Redox-dependent changes in the structure and dynamics of human cytochrome c (Cyt c) were investigated by solution NMR. We found significant structural changes in several regions, including residues 23–28 (loop 3), which were further corroborated by chemical shift differences between the reduced and oxidized states of Cyt c. These differences are essential for discriminating redox states in Cyt c by cytochrome c oxidase (CcO) during electron transfer reactions. Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion experiments identified that the region around His33 undergoes conformational exchanges on the μs-ms timescale, indicating significant redox-dependent structural changes. Because His33 is not part of the interaction site for CcO, our data suggest that the dynamic properties of the region, which is far from the interaction site for CcO, contribute to conformational changes during electron transfer to CcO. - Highlights: • Solution structure and dynamics analysis for human Cyt c by NMR. • Structural changes responsible for the discrimination of the redox state in Cyt c. • Conformational exchange in the region outside of the interaction site for CcO. • Less flexibility and rigid structure of the interaction site on Cyt c for CcO.

  6. Plant cytoplasmic GAPDH: redox post-translational modifications and moonlighting properties

    Directory of Open Access Journals (Sweden)

    Mirko eZaffagnini

    2013-11-01

    Full Text Available Glyceraldehyde-3-phosphate dehydrogenase (GAPDH is a ubiquitous enzyme involved in glycolysis and shown, particularly in animal cells, to play additional roles in several unrelated non-metabolic processes such as control of gene expression and apoptosis. This functional versatility is regulated, in part at least, by redox post-translational modifications that alter GAPDH catalytic activity and influence the subcellular localization of the enzyme. In spite of the well established moonlighting (multifunctional properties of animal GAPDH, little is known about non-metabolic roles of GAPDH in plants. Plant cells contain several GAPDH isoforms with different catalytic and regulatory properties, located both in the cytoplasm and in plastids, and participating in glycolysis and the Calvin-Benson cycle. A general feature of all GAPDH proteins is the presence of an acidic catalytic cysteine in the active site that is overly sensitive to oxidative modifications, including glutathionylation and S-nitrosylation. In Arabidopsis, oxidatively-modified cytoplasmic GAPDH has been successfully used as a tool to investigate the role of reduced glutathione, thioredoxins and glutaredoxins in the control of different types of redox post-translational modifications. Oxidative modifications inhibit GAPDH activity, but might enable additional functions in plant cells. Mounting evidence support the concept that plant cytoplasmic GAPDH may fulfill alternative, non-metabolic functions that are triggered by redox post-translational modifications of the protein under stress conditions. The aim of this review is to detail the molecular mechanisms underlying the redox regulation of plant cytoplasmic GAPDH in the light of its crystal structure, and to provide a brief inventory of the well known redox-dependent multi-facetted properties of animal GAPDH, together with the emerging roles of oxidatively-modified GAPDH in stress signaling pathways in plants.

  7. Spectroscopic investigation of the redox properties of CoAPO molecular sieves

    NARCIS (Netherlands)

    Peeters, M.P.J.; Hooff, van J.H.C.; Sheldon, R.A.; Zholobenko, V.L.; Kustov, L.M.; Kazansky, V.B.; Balmoos, von R.; Higgins, J.B.; Treacy, M.M.J

    1993-01-01

    Acid sites in CoAPO-5 and CoAPO-11 and redox properties of these Co-substituted aluminophosphates have been investigated using UV- and IR-spectroscopy. The data obtained show that CoAPO exhibits quite unusual acidic and redox properties. The absence of the bridged OH-group seems to be a common

  8. Structural, optical, and redox properties of lamellar solids derived from copper(I) complexes and n-butylammonium uranyl phosphate and arsenate

    International Nuclear Information System (INIS)

    Jacob, A.T.; Ellis, A.B.

    1989-01-01

    A family of hydrated, layered solids has been prepared from intercalative ion-exchange reactions of n-butylammonium uranyl phosphate (BAUP) or arsenate (BAUAs), (n-C 4 H 9 NH 3 )UO 2 EO 4 ·3H 2 O (E = P, As), with Cu(LL) 2 + complexes (LL is dmp = 2,9-dimethyl-1,10-phenanthroline or bcp = 2,9-dimethyl-4,7-dipheyl-1,10-phenanthroline). The products obtained were analyzed as having compositions [Cu(LL) 2 ] x [BA] 1-x UO 2 EO 4 ·2H 2 O with x ∼ 0.2. X-ray powder diffraction data reveal that the compounds are single phases that can be indexed on the basis of a tetragonal unit cell. The solids exhibit absorption and photoluminescence (PL) properties characteristic of the Cu(LL) 2 + species; the Cu(I) complexes completely quench the uranyl PL. Once intercalated, the Cu(I) complexes can be oxidized by using Br 2 vapor and rereduced either by photochemical means or by N 2 H 4 vapor, as shown by changes in electronic and EPR spectra. 37 refs., 7 figs., 2 tabs

  9. Synthesis, spectroscopic and redox properties of the mononuclear ...

    Indian Academy of Sciences (India)

    Administrator

    magnetic susceptibility measurements, molar conductivity, cyclic voltammetry, mass ... gens donor atoms show DNA binding and antitumor ... trum can be correlated with the strength of the ... ties, the investigation of redox behaviour has a vital.

  10. Antioxidant activity and electrochemical elucidation of the enigmatic redox behavior of curcumin and its structurally modified analogues

    International Nuclear Information System (INIS)

    Jha, Niki S.; Mishra, Satyendra; Jha, Shailendra K.; Surolia, Avadhesha

    2015-01-01

    Highlights: • Structural analogues of curcumin have been synthesized. • Confirmation of redox behaviour emanates from H- shift from central methylene group in curcumin. • Mechanism of curcumin oxidation has been proposed. • Correlation between redox behavior and antioxidant activity has been established. - Abstract: Here, we report studies on the antioxidant activity and redox behavior of curcumin and its structurally modified synthetic analogues. We have synthesized a number of analogues of curcumin which abrogate its keto-enol tautomerism or substitute the methylene group at the centre of its heptadione moiety implicated in the hydride transfer and studied their redox property. From cyclic voltammetric studies, it is demonstrated that H- atom transfer from CH 2 group at the center of the heptadione link also plays an important role in the antioxidant properties of curcumin along with that of its phenolic –OH group. In addition, we also show that the conversion of 1, 3- dicarbonyl moiety of curcumin to an isosteric heterocycle as in pyrazole curcumin, which decreases its rotational freedom, leads to an improvement of its redox properties as well as its antioxidant activity

  11. Synthesis, spectral characterization and redox properties of iron (II ...

    Indian Academy of Sciences (India)

    Unknown

    Arylazoheterocycles and their chemistry of transition and non-transition metals have been explored for more than two decades.1 Owing to their pH-response, photoactivity, light electron communication, stabilization of low valent metal oxidation state, exhibition of serial redox states of complexes, isolation of anion radicals, ...

  12. Effect of redox conditions on bacterial community structure in Baltic Sea sediments with contrasting redox conditions

    NARCIS (Netherlands)

    Steenbergh, A.K.; Bodelier, P.L.E.; Slomp, C.P; Laanbroek, H.J.

    2014-01-01

    Phosphorus release from sediments can exacerbate the effect of eutrophication in coastal marine ecosystems. The flux of phosphorus from marine sediments to the overlying water is highly dependent on the redox conditions at the sediment-water interface. Bacteria are key players in the biological

  13. Effect of protonation, composition and isomerism on the redox properties and electron (de)localization of classical polyoxometalates

    Science.gov (United States)

    López, Xavier

    2017-10-01

    This publication reviews some relevant features related with the redox activity of two inorganic compounds: [XM12O40]q- (Keggin structure) and [X2M18O62]q- (Wells-Dawson structure). These are two well-known specimens of the vast Polyoxometalate (POM) family, which has been the subject of extensive experimental and theoretical research owing to their unmatched properties. In particular, their redox activity focus a great deal of attention from scientists due to their prospective related applications. POMs are habitually seen as `electron sponges' since many of them accept several electrons without losing their chemical identity. This makes them excellent models to study mechanisms of electrochemical nature. Their redox properties depend on: (i) the type and number of transition metal atoms in the structure, (ii) the basicity of the first reduced species and, occasionally, of the fully oxidized species; (iii) the size of the molecule, (iv) the overall negative charge of the POM, and (v) the size of the central heteroatom. In the last years, important collaboration between the experimental and theoretical areas has been usual on the development of POM science. In the present chapter three of these synergies are highlighted: the influence of the internal heteroatom upon the redox potentials of Keggin anions; the dependence of the redox waves of Fe-substituted Wells-Dawson compounds with pH; and the role of electron delocalization and pairing in mixed-metal Mo/W Wells-Dawson compounds in their ability to accept electrons. In these three cases, a complete understanding of the problem would not have been possible without the mutual benefit of experimental and computational data.

  14. Anthraquinone with Tailored Structure for Nonaqueous Metal-Organic Redox Flow Battery

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei; Xu, Wu; Cosimbescu, Lelia; Choi, Daiwon; Li, Liyu; Yang, Zhenguo

    2012-06-08

    A nonaqueous, hybrid metal-organic redox flow battery based on tailored anthraquinone structure is demonstrated to have an energy efficiency of {approx}82% and a specific discharge energy density similar to aqueous redox flow batteries, which is due to the significantly improved solubility of anthraquinone in supporting electrolytes.

  15. Anthraquinone with tailored structure for a nonaqueous metal-organic redox flow battery.

    Science.gov (United States)

    Wang, Wei; Xu, Wu; Cosimbescu, Lelia; Choi, Daiwon; Li, Liyu; Yang, Zhenguo

    2012-07-07

    A nonaqueous, hybrid metal-organic redox flow battery based on tailored anthraquinone structure is demonstrated to have an energy efficiency of ~82% and a specific discharge energy density similar to those of aqueous redox flow batteries, which is due to the significantly improved solubility of anthraquinone in supporting electrolytes.

  16. Activator Protein-1: redox switch controlling structure and DNA-binding.

    Science.gov (United States)

    Yin, Zhou; Machius, Mischa; Nestler, Eric J; Rudenko, Gabby

    2017-11-02

    The transcription factor, activator protein-1 (AP-1), binds to cognate DNA under redox control; yet, the underlying mechanism has remained enigmatic. A series of crystal structures of the AP-1 FosB/JunD bZIP domains reveal ordered DNA-binding regions in both FosB and JunD even in absence DNA. However, while JunD is competent to bind DNA, the FosB bZIP domain must undergo a large conformational rearrangement that is controlled by a 'redox switch' centered on an inter-molecular disulfide bond. Solution studies confirm that FosB/JunD cannot undergo structural transition and bind DNA when the redox-switch is in the 'OFF' state, and show that the mid-point redox potential of the redox switch affords it sensitivity to cellular redox homeostasis. The molecular and structural studies presented here thus reveal the mechanism underlying redox-regulation of AP-1 Fos/Jun transcription factors and provide structural insight for therapeutic interventions targeting AP-1 proteins. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  17. Activator Protein-1: redox switch controlling structure and DNA-binding

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Zhou; Machius, Mischa; Nestler, Eric J.; Rudenko, Gabby (Texas-MED); (Icahn)

    2017-09-07

    The transcription factor, activator protein-1 (AP-1), binds to cognate DNA under redox control; yet, the underlying mechanism has remained enigmatic. A series of crystal structures of the AP-1 FosB/JunD bZIP domains reveal ordered DNA-binding regions in both FosB and JunD even in absence DNA. However, while JunD is competent to bind DNA, the FosB bZIP domain must undergo a large conformational rearrangement that is controlled by a ‘redox switch’ centered on an inter-molecular disulfide bond. Solution studies confirm that FosB/JunD cannot undergo structural transition and bind DNA when the redox-switch is in the ‘OFF’ state, and show that the mid-point redox potential of the redox switch affords it sensitivity to cellular redox homeostasis. The molecular and structural studies presented here thus reveal the mechanism underlying redox-regulation of AP-1 Fos/Jun transcription factors and provide structural insight for therapeutic interventions targeting AP-1 proteins.

  18. Mechanisms for redox control and their effects upon modelled properties of Aespoe groundwaters

    International Nuclear Information System (INIS)

    Emren, A.T.

    1996-01-01

    In the literature, one finds several models for control of redox properties in groundwater. The proposals for redox controlling substances include iron oxides, chlorites, methane, pyrite and polysulphides. The CRACKER program, which has been successful in modelling of observed Aespoe groundwaters has been used to investigate the influence of several redox control models on the modelled properties of present and possible future Aespoe groundwaters. In the simulations, one or more of the possible redox reactions have been prevented from occurring. The groundwater has then been assumed to react with minerals distributed in the fracture walls. Due to the discreteness of mineral grains, a certain amount of fluctuations in groundwater properties is occurring. The process of sampling water for measurement has been simulated by letting about 900 waters from different locations mix. It has been found that some of the models have difficulties in explaining important groundwater properties, while other models perform quite well. With identical mineral sets, the properties of future groundwaters have been simulated. It is found that some changes in groundwater properties at elevated temperatures may be of importance for assessment of the safety of a future repository for spent nuclear fuel. The difference in behaviour is caused mostly by the fact that the solubility increases with temperature for some minerals, while it decreases for other minerals. (author)

  19. Changes in redox properties of humic acids upon sorption to alumina

    Science.gov (United States)

    Subdiaga, Edisson; Orsetti, Silvia; Jindal, Sharmishta; Haderlein, Stefan B.

    2016-04-01

    1. Introduction A prominent role of Natural Organic Matter (NOM) in biogeochemical processes is its ability to act as an electron shuttle, accelerating rates between a bulk electron donor and an acceptor. The underlying processes are reversible redox reactions of quinone moieties.1 This shuttling effect has been studied in two major areas: transformation of redox active pollutants and microbial respiration.2-3 Previous studies primarily compared effects in the presence or absence of NOM without addressing the redox properties of NOM nor its speciation. The interaction between humic acids (HA) and minerals might change properties and reactivity of organic matter. Specifically, we investigate whether changes in the redox properties of a HA occur upon sorption to redox inactive minerals. Since fractionation and conformational rearrangements of NOM moieties upon sorption are likely to happen, the redox properties of the NOM fractions upon sorption might differ as well. 2. Materials and methods Elliot Soil Humic Acid (ESHA), Pahokee Peat Humic Acid (PPHA) and Suwannee River Humic Acid (SRHA) were used as received from IHSS. Aluminum oxide (Al2O3) was suspended in 0.1M KCl. Sorption was studied at pH 7.0 in duplicate batch experiments for several HA/Al2O3 ratios. For the suspension (mineral + sorbed HA, plus dissolved HA), the filtrate (0.45μm) and the HA stock solution, the electron donating and accepting capacities (EDC and EAC) were determined following established procedures.4 3. Results All studied HA-Al2O3 systems showed similar behavior with regard to changes in redox properties. There was a significant increase in the EDC of the whole suspension compared to the stock solutions and the non-sorbed HA in the filtrate (up to 300% for PPHA). This effect was more pronounced with increasing amounts of sorbed HA in the suspension. Although ESHA had the highest sorption capacity on Al2O3 (~ 6 times higher than PPHA & SRHA), it showed the smallest changes in redox

  20. Nitrogen-Doped Graphene:Effects of nitrogen species on the properties of the vanadium redox flow battery

    International Nuclear Information System (INIS)

    Shi, Lang; Liu, Suqin; He, Zhen; Shen, Junxi

    2014-01-01

    Nitrogen-doped graphene nanosheets (NGS), prepared by a simple hydrothermal reaction of graphene oxide (GO) with urea as nitrogen source were studied as positive electrodes in vanadium redox flow battery (VRFB). The synthesized NGS with the nitrogen level as high as 10.12 atom% is proven to be a promising material for VRFB. The structures and electrochemical properties of the materials are investigated by scanning electron microscopy, X-ray photoelectron spectroscopy, cyclic voltammetry and electrochemical impendence spectroscopy. The results demonstrate that not only the nitrogen doping level but the nitrogen type in the NGS are significant for its catalytic activity towards the [VO] 2+ /[VO 2 ] + redox couple reaction. In more detail, among four types of nitrogen species (pyridinic-N, pyrrolic-N, quaternary-N, oxidic-N) doped into the graphene lattice, quaternary-N play mainly roles for improving the catalytic activity toward the [VO] 2+ /[VO 2 ] + couple reaction

  1. Response of humic-reducing microorganisms to the redox properties of humic substance during composting.

    Science.gov (United States)

    Zhao, Xinyu; He, Xiaosong; Xi, Beidou; Gao, Rutai; Tan, Wenbing; Zhang, Hui; Huang, Caihong; Li, Dan; Li, Meng

    2017-12-01

    Humic substance (HS) could be utilized by humus-reducing microorganisms (HRMs) as the terminal acceptors. Meanwhile, the reduction of HS can support the microbial growth. This process would greatly affect the redox conversion of inorganic and organic pollutants. However, whether the redox properties of HS lined with HRMs community during composting still remain unclear. This study aimed to assess the relationships between the redox capability of HS [i.e. humic acids (HA) and fulvic acids (FA)] and HRMs during composting. The results showed that the changing patterns of electron accepting capacity and electron donating capacity of HS were diverse during seven composting. Electron transfer capacities (ETC) of HA was significantly correlated with the functional groups (i.e. alkyl C, O-alkyl C, aryl C, carboxylic C, aromatic C), aromaticity and molecular weight of HA. Aromatic C, phenols, aryl C, carboxylic C, aromaticity and molecular weight of HS were the main structuralfeatures associated with the ETC of FA. Ten key genera of HRMs were found significantly determine these redox-active functional groups of HS during composting, thus influencing the ETC of HS in composts. In addition, a regulating method was suggested to enhance the ETC of HS during composting based on the relationships between the key HRMs and redox-active functional groups as well as environmental variables. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Effect of the L499M mutation of the ascomycetous Botrytis aclada laccase on redox potential and catalytic properties

    International Nuclear Information System (INIS)

    Osipov, Evgeny; Polyakov, Konstantin; Kittl, Roman; Shleev, Sergey; Dorovatovsky, Pavel; Tikhonova, Tamara; Hann, Stephan; Ludwig, Roland; Popov, Vladimir

    2014-01-01

    The structures of the ascomycetous B. aclada laccase and its L499M T1-site mutant have been solved at 1.7 Å resolution. The mutant enzyme shows a 140 mV lower redox potential of the type 1 copper and altered kinetic behaviour. The wild type and the mutant have very similar structures, which makes it possible to relate the changes in the redox potential to the L499M mutation Laccases are members of a large family of multicopper oxidases that catalyze the oxidation of a wide range of organic and inorganic substrates accompanied by the reduction of dioxygen to water. These enzymes contain four Cu atoms per molecule organized into three sites: T1, T2 and T3. In all laccases, the T1 copper ion is coordinated by two histidines and one cysteine in the equatorial plane and is covered by the side chains of hydrophobic residues in the axial positions. The redox potential of the T1 copper ion influences the enzymatic reaction and is determined by the nature of the axial ligands and the structure of the second coordination sphere. In this work, the laccase from the ascomycete Botrytis aclada was studied, which contains conserved Ile491 and nonconserved Leu499 residues in the axial positions. The three-dimensional structures of the wild-type enzyme and the L499M mutant were determined by X-ray crystallography at 1.7 Å resolution. Crystals suitable for X-ray analysis could only be grown after deglycosylation. Both structures did not contain the T2 copper ion. The catalytic properties of the enzyme were characterized and the redox potentials of both enzyme forms were determined: E 0 = 720 and 580 mV for the wild-type enzyme and the mutant, respectively. Since the structures of the wild-type and mutant forms are very similar, the change in the redox potential can be related to the L499M mutation in the T1 site of the enzyme

  3. Solvent Effect on Redox Properties of Hexanethiolate Monolayer-Protected Gold Nanoclusters

    OpenAIRE

    Su, B; Zhang, M; Shao, Y; Girault, HH

    2006-01-01

    The capacitance of monolayer-protected gold nanoclusters (MPCs), CMPC, in solution has been theoretically reconsidered from an electrostatic viewpoint, in which an MPC is considered as an isolated charged sphere within two dielectric layers, the intrinsic coating monolayer, and the bulk solvent. The model predicts that the bulk solvent provides an important contribution to CMPC and influences the redox properties of MPCs. This theoretical prediction is then examined experimentally by comparin...

  4. Measurement of the Structure and Molecular Dynamics of Ionic Solutions for Redox Flow Battery

    Science.gov (United States)

    Li, Zhixia; Robertson, Lily; Moore, Jeffery; Zhang, Yang

    Redox flow battery (RFB) is a promising electrical energy storage technology with great potential to finally realize alternative energy sources for the next-generation vehicles and at grid scales. The design of RFB is unique as the power scales separately from the energy capacity. The latter depends on the size of storage tanks and the concentration of the active materials. Redox-active organic molecules are excellent candidates with high synthetic tunability for both redox properties as well as, importantly, solubility. However, upon increasing concentrations, the flow cell has less cycling stability and more capacity fade. Further, after charging the battery, the viscosity increases while the ionic conductivity decreases, and thus the cell becomes overall ineffective. To understand the mechanism of the increased viscosity, we performed differential scanning calorimetry, wide and small angle X-rays scattering, and quasi-elastic neutron scattering measurements. Herein, we will present the measurement results and relative analysis.

  5. The structure of Plasmodium falciparum serine hydroxymethyltransferase reveals a novel redox switch that regulates its activities

    Energy Technology Data Exchange (ETDEWEB)

    Chitnumsub, Penchit; Ittarat, Wanwipa; Jaruwat, Aritsara; Noytanom, Krittikar [National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120 (Thailand); Amornwatcharapong, Watcharee [Mahidol University, Bangkok (Thailand); Pornthanakasem, Wichai [National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120 (Thailand); Chaiyen, Pimchai [Mahidol University, Bangkok (Thailand); Yuthavong, Yongyuth; Leartsakulpanich, Ubolsree [National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120 (Thailand)

    2014-06-01

    The crystal structure of P. falciparum SHMT revealed snapshots of an intriguing disulfide/sulfhydryl switch controlling the functional activity. Plasmodium falciparum serine hydroxymethyltransferase (PfSHMT), an enzyme in the dTMP synthesis cycle, is an antimalarial target because inhibition of its expression or function has been shown to be lethal to the parasite. As the wild-type enzyme could not be crystallized, protein engineering of residues on the surface was carried out. The surface-engineered mutant PfSHMT-F292E was successfully crystallized and its structure was determined at 3 Å resolution. The PfSHMT-F292E structure is a good representation of PfSHMT as this variant revealed biochemical properties similar to those of the wild type. Although the overall structure of PfSHMT is similar to those of other SHMTs, unique features including the presence of two loops and a distinctive cysteine pair formed by Cys125 and Cys364 in the tetrahydrofolate (THF) substrate binding pocket were identified. These structural characteristics have never been reported in other SHMTs. Biochemical characterization and mutation analysis of these two residues confirm that they act as a disulfide/sulfhydryl switch to regulate the THF-dependent catalytic function of the enzyme. This redox switch is not present in the human enzyme, in which the cysteine pair is absent. The data reported here can be further exploited as a new strategy to specifically disrupt the activity of the parasite enzyme without interfering with the function of the human enzyme.

  6. The structure of Plasmodium falciparum serine hydroxymethyltransferase reveals a novel redox switch that regulates its activities

    International Nuclear Information System (INIS)

    Chitnumsub, Penchit; Ittarat, Wanwipa; Jaruwat, Aritsara; Noytanom, Krittikar; Amornwatcharapong, Watcharee; Pornthanakasem, Wichai; Chaiyen, Pimchai; Yuthavong, Yongyuth; Leartsakulpanich, Ubolsree

    2014-01-01

    The crystal structure of P. falciparum SHMT revealed snapshots of an intriguing disulfide/sulfhydryl switch controlling the functional activity. Plasmodium falciparum serine hydroxymethyltransferase (PfSHMT), an enzyme in the dTMP synthesis cycle, is an antimalarial target because inhibition of its expression or function has been shown to be lethal to the parasite. As the wild-type enzyme could not be crystallized, protein engineering of residues on the surface was carried out. The surface-engineered mutant PfSHMT-F292E was successfully crystallized and its structure was determined at 3 Å resolution. The PfSHMT-F292E structure is a good representation of PfSHMT as this variant revealed biochemical properties similar to those of the wild type. Although the overall structure of PfSHMT is similar to those of other SHMTs, unique features including the presence of two loops and a distinctive cysteine pair formed by Cys125 and Cys364 in the tetrahydrofolate (THF) substrate binding pocket were identified. These structural characteristics have never been reported in other SHMTs. Biochemical characterization and mutation analysis of these two residues confirm that they act as a disulfide/sulfhydryl switch to regulate the THF-dependent catalytic function of the enzyme. This redox switch is not present in the human enzyme, in which the cysteine pair is absent. The data reported here can be further exploited as a new strategy to specifically disrupt the activity of the parasite enzyme without interfering with the function of the human enzyme

  7. Catalytic Efficiency of Basidiomycete Laccases: Redox Potential versus Substrate-Binding Pocket Structure

    Directory of Open Access Journals (Sweden)

    Olga A. Glazunova

    2018-04-01

    Full Text Available Laccases are copper-containing oxidases that catalyze a one-electron abstraction from various phenolic and non-phenolic compounds with concomitant reduction of molecular oxygen to water. It is well-known that laccases from various sources have different substrate specificities, but it is not completely clear what exactly provides these differences. The purpose of this work was to study the features of the substrate specificity of four laccases from basidiomycete fungi Trametes hirsuta, Coriolopsis caperata, Antrodiella faginea, and Steccherinum murashkinskyi, which have different redox potentials of the T1 copper center and a different structure of substrate-binding pockets. Enzyme activity toward 20 monophenolic substances and 4 phenolic dyes was measured spectrophotometrically. The kinetic parameters of oxidation of four lignans and lignan-like substrates were determined by monitoring of the oxygen consumption. For the oxidation of the high redox potential (>700 mV monophenolic substrates and almost all large substrates, such as phenolic dyes and lignans, the redox potential difference between the enzyme and the substrate (ΔE played the defining role. For the low redox potential monophenolic substrates, ΔE did not directly influence the laccase activity. Also, in the special cases, the structure of the large substrates, such as dyes and lignans, as well as some structural features of the laccases (flexibility of the substrate-binding pocket loops and some amino acid residues in the key positions affected the resulting catalytic efficiency.

  8. The redox properties of the natural iron-bearing clay mineral ferruginous smectite SWA-1: a combined electrochemical and spectroscopic study

    International Nuclear Information System (INIS)

    Gorski, Christopher A.; Voegelin, Andreas; Sander, Michael; Hofstetter, Thomas B.

    2012-01-01

    Document available in extended abstract form only. Iron-bearing clay minerals are ubiquitous in the environment and clay-mineral-based materials have been proposed to be part of backfill material in nuclear waste repositories. Laboratory and field studies have confirmed that structural iron (Fe) in clay minerals participates in redox reactions with organic pollutants, metals, and radionuclides, thus influencing their transport and reactivity. Knowledge of the redox properties of Fe-bearing clay minerals is therefore essential for understanding and predicting the fate, mobility, and bioavailability subsurface contaminants. A quantitative understanding of clay mineral redox behavior remains lacking, however, due to constraints in previous experimental approaches and the complex structural changes that accompany changes in the Fe oxidation state. This work provides a quantitative means for measuring the redox properties of Fe-bearing clay minerals, which can be applied to both field and laboratory studies tracking radionuclide-clay mineral redox reactions. Here we use mediated electrochemical reduction and oxidation to determine the electron accepting and donating capacities of several natural Fe-bearing clay minerals with different structural Fe content (2.3 to 21 wt-%) and varied redox histories. Results indicate that the fraction of redox-active Fe in clay minerals is mineral-dependent, and is linked to the thermodynamics of reduction and oxidation as well as to the ability of clay minerals to conduct electrons and facilitate structural re-arrangements required to maintain charge balance. The reduction potential (E H ) characteristics of a natural ferruginous smectite (SWa-1) were further characterized as a function of solution conditions and repeated Fe reduction and oxidation cycles. SWa-1 samples were analyzed with Moessbauer spectroscopy (MS) and X-ray absorption spectroscopy (XAS) to link observed redox potential behavior to structural properties and changes

  9. Diblock Polyelectrolytic Copolymers Containing Cationic Iron and Cobalt Sandwich Complexes: Living ROMP Synthesis and Redox Properties.

    Science.gov (United States)

    Gu, Haibin; Ciganda, Roberto; Hernandez, Ricardo; Castel, Patricia; Zhao, Pengxiang; Ruiz, Jaime; Astruc, Didier

    2016-04-01

    Diblock metallopolymer polyelectrolytes containing the two redox-robust cationic sandwich units [CoCp'Cp](+) and [FeCp'(η(6)-C6 Me6)](+) (Cp = η(5)-C5 H5; Cp' = η(5)-C5H4-) as hexafluorophosphate ([PF6](-)) salts are synthesized by ring-opening metathesis polymerization using Grubbs' third generation catalyst. Their electrochemical properties show full chemical and electrochemical reversibilities allowing fine determination of the copolymer molecular weight using Bard-Anson's electrochemical method by cyclic voltammetry. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Solvent effect on redox properties of hexanethiolate monolayer-protected gold nanoclusters.

    Science.gov (United States)

    Su, Bin; Zhang, Meiqin; Shao, Yuanhua; Girault, Hubert H

    2006-11-02

    The capacitance of monolayer-protected gold nanoclusters (MPCs), C(MPC), in solution has been theoretically reconsidered from an electrostatic viewpoint, in which an MPC is considered as an isolated charged sphere within two dielectric layers, the intrinsic coating monolayer, and the bulk solvent. The model predicts that the bulk solvent provides an important contribution to C(MPC) and influences the redox properties of MPCs. This theoretical prediction is then examined experimentally by comparing the redox properties of MPCs in four organic solvents: 1,2-dichloroethane (DCE), dichloromethane (DCM), chlorobenzene (CB), and toluene (TOL), in all of which MPCs have excellent solubility. Furthermore, this set of organic solvents features a dielectric constant in a range from 10.37 (DCE) to 2.38 (TOL), which is wide enough to probe the solvent effect. In these organic solvents, tetrahexylammonium bis(trifluoromethylsulfonyl)imide (THATf2N) is used as the supporting electrolyte. Cyclic and differential pulse voltammetric results provide concrete evidence that, despite the monolayer protection, the solvent plays a significant effect on the properties of MPCs in solution.

  11. Vegetation-induced spatial variability of soil redox properties in wetlands

    Science.gov (United States)

    Szalai, Zoltán; Jakab, Gergely; Kiss, Klaudia; Ringer, Marianna; Balázs, Réka; Zacháry, Dóra; Horváth Szabó, Kata; Perényi, Katalin

    2016-04-01

    Vegetation induced land patches may result spatial pattern of on soil Eh and pH. These spatial pattern are mainly emerged by differences of aeration and exudation of assimilates. Present paper focuses on vertical extent and temporal dynamics of these patterns in wetlands. Two study sites were selected: 1. a plain wetland on calcareous sandy parent material (Ceglédbercel, Danube-Tisza Interfluve, Hungary); 2. headwater wetland with calcareous loamy parent material (Bátaapáti, Hungary). Two vegetation patches were studied in site 1: sedgy (dominated by Carex riparia) and reedy (dominated by Phragmites australis). Three patches were studied in site2: sedgy1 (dominated by C vulpina), sedgy 2 (C. riparia); nettle-horsetail (Urtica dioica and Equisetum arvense). Boundaries between patches were studied separately. Soil redox, pH and temperature studied by automated remote controlled instruments. Three digital sensors (Ponsell) were installed in each locations: 20cm and 40cm sensors represent the solum and 100 cm sensor monitors the subsoil). Groundwater wells were installed near to triplets for soil water sampling. Soil Eh, pH and temperature values were recorded in each 10 minutes. Soil water sampling for iron and DOC were carried out during saturated periods. Spatial pattern of soil Eh is clearly caused by vegetation. We measured significant differences between Eh values of the studied patches in the solum. We did not find this kinds horizontal differences in the subsoil. Boundaries of the patches usually had more reductive soil environment than the core areas. We have found temporal dynamics of the spatial redox pattern. Differences were not so well expressed during wintertime. These spatial patterns had influence on the DOC and iron content of porewater, as well. Highest temporal dynamics of soil redox properties and porewater iron could be found in the boundaries. These observations refer to importance patchiness of vegetation on soil chemical properties in

  12. Recapitulating the Structural Evolution of Redox Regulation in Adenosine 5'-Phosphosulfate Kinase from Cyanobacteria to Plants.

    Science.gov (United States)

    Herrmann, Jonathan; Nathin, David; Lee, Soon Goo; Sun, Tony; Jez, Joseph M

    2015-10-09

    In plants, adenosine 5'-phosphosulfate (APS) kinase (APSK) is required for reproductive viability and the production of 3'-phosphoadenosine 5'-phosphosulfate (PAPS) as a sulfur donor in specialized metabolism. Previous studies of the APSK from Arabidopsis thaliana (AtAPSK) identified a regulatory disulfide bond formed between the N-terminal domain (NTD) and a cysteine on the core scaffold. This thiol switch is unique to mosses, gymnosperms, and angiosperms. To understand the structural evolution of redox control of APSK, we investigated the redox-insensitive APSK from the cyanobacterium Synechocystis sp. PCC 6803 (SynAPSK). Crystallographic analysis of SynAPSK in complex with either APS and a non-hydrolyzable ATP analog or APS and sulfate revealed the overall structure of the enzyme, which lacks the NTD found in homologs from mosses and plants. A series of engineered SynAPSK variants reconstructed the structural evolution of the plant APSK. Biochemical analyses of SynAPSK, SynAPSK H23C mutant, SynAPSK fused to the AtAPSK NTD, and the fusion protein with the H23C mutation showed that the addition of the NTD and cysteines recapitulated thiol-based regulation. These results reveal the molecular basis for structural changes leading to the evolution of redox control of APSK in the green lineage from cyanobacteria to plants. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  13. Thermochemical storage for CSP via redox structured reactors/heat exchangers: The RESTRUCTURE project

    Science.gov (United States)

    Karagiannakis, George; Pagkoura, Chrysoula; Konstandopoulos, Athanasios G.; Tescari, Stefania; Singh, Abhishek; Roeb, Martin; Lange, Matthias; Marcher, Johnny; Jové, Aleix; Prieto, Cristina; Rattenbury, Michael; Chasiotis, Andreas

    2017-06-01

    The present work provides an overview of activities performed in the framework of the EU-funded collaborative project RESTRUCTURE, the main goal of which was to develop and validate a compact structured reactor/heat exchanger for thermochemical storage driven by 2-step high temperature redox metal oxide cycles. The starting point of development path included redox materials qualification via both theoretical and lab-scale experimental studies. Most favorable compositions were cobalt oxide/alumina composites. Preparation of small-scale structured bodies included various approaches, ranging from perforated pellets to more sophisticated honeycomb geometries, fabricated by extrusion and coating. Proof-of-concept of the proposed novel reactor/heat exchanger was successfully validated in small-scale structures and the next step included scaling up of redox honeycombs production. Significant challenges were identified for the case of extruded full-size bodies and the final qualified approach related to preparation of cordierite substrates coated with cobalt oxide. The successful experimental evaluation of the pilot reactor/heat exchanger system constructed motivated the preliminary techno-economic evaluation of the proposed novel thermochemical energy storage concept. Taking into account experimental results, available technologies and standard design aspects a model for a 70.5 MWe CSP plant was defined. Estimated LCOE costs were calculated to be in the range of reference values for Combined Cycle Power Plants operated by natural gas. One of main cost contributors was the storage system itself, partially due to relatively high cost of cobalt oxide. This highlighted the need to identify less costly and equally efficient to cobalt oxide redox materials.

  14. Ambient redox synthesis of vanadium-doped manganese dioxide nanoparticles and their enhanced zinc storage properties

    Energy Technology Data Exchange (ETDEWEB)

    Alfaruqi, Muhammad Hilmy; Islam, Saiful; Mathew, Vinod; Song, Jinju; Kim, Sungjin; Tung, Duong Pham; Jo, Jeonggeun; Kim, Seokhun; Baboo, Joseph Paul; Xiu, Zhiliang; Kim, Jaekook, E-mail: jaekook@chonnam.ac.kr

    2017-05-15

    Highlights: • The V-doped MnO{sub 2} was prepared by a simple ambient redox reaction. • The V-doped MnO{sub 2} was tested as a cathode in aqueous zinc-ion batteries (ZIBs). • The doped cathode showed better zinc-storage properties than the bare cathode. • The present study facilitates the development of safe and reliable aqueous ZIBs. - Abstract: In this work, we demonstrate the first use of a V-doped MnO{sub 2} nanoparticle electrode for zinc-ion battery (ZIB) applications. The V-doped MnO{sub 2} was prepared via a simple redox reaction and the X-ray diffraction studies confirmed the formation of pure MnO{sub 2}, accompanied by an anisotropic expansion of MnO{sub 2} lattice, suggesting the incorporation of V-ions into the MnO{sub 2} framework. V doping of MnO{sub 2} not only increased the specific surface area but also improved the electronic conductivity. When Zn-storage properties were tested, the V-doped MnO{sub 2} electrode registered a higher discharge capacity of 266 mAh g{sup −1} compared to 213 mAh g{sup −1} for the pure MnO{sub 2} electrode. On prolonged cycling, the doped electrode retained 31% higher capacity than that of the bare MnO{sub 2} electrode and thereby demonstrated superior cycling performance. This study may pave the way towards understanding the enhancement of the energy storage properties via doping in electrodes of aqueous ZIB applications and also furthers the efforts for the practical realization of a potential eco-friendly battery system.

  15. 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

  16. Effect of dye structure and redox mediators on anaerobic azo and anthraquinone dye reduction

    Directory of Open Access Journals (Sweden)

    Mayara Carantino Costa

    2012-01-01

    Full Text Available We investigated the biological decolourisation of dyes with different molecular structures. The kinetic constant values (k1 achieved with azo dye Reactive Red 120 were 7.6 and 10.1 times higher in the presence of RM (redox mediators AQDS and riboflavin, respectively, than the assays lacking RM. The kinetic constant achieved with the azo dye Congo Red was 42 times higher than that obtained with the anthraquinone dye Reactive Blue 4. The effect of RM on dye reduction was more evident for azo dyes resistant to reductive processes, and ineffective for anthraquinone dyes because of the structural stability of the latter.

  17. A hypothesis for the minimal overall structure of the mammalian plasma membrane redox system.

    Science.gov (United States)

    de Grey, Aubrey D N J

    2003-05-01

    After a long period of frustration, many components of the mammalian plasma membrane redox system are now being identified at the molecular level. Some are apparently ubiquitous but are necessary only for a subset of electron donors or acceptors; some are present only in certain cell types; some appear to be associated with proton extrusion; some appear to be capable of superoxide production. The volume and variety of data now available have begun to allow the formulation of tentative models for the overall network of interactions of enzymes and substrates that together make up the plasma membrane redox system. Such a model is presented here. The structure discussed here is of the mammalian system, though parts of it may apply more or less accurately to fungal and plant cells too. Judging from the history of mitochondrial oxidative phosphorylation, it may be hoped that the development of models of the whole system - even if they undergo substantial revision thereafter - will markedly accelerate the pace of research in plasma membrane redox, by providing a coherent basis for the design of future experiments.

  18. Probing the electronic structure of redox species and direct determination of intrinsic reorganization energies of electron transfer reactions

    International Nuclear Information System (INIS)

    Wang, Xue-Bin; Wang, Lai-Sheng

    2000-01-01

    An experimental technique capable of directly determining the intrinsic reorganization energies of bimolecular electron transfer reactions is described. Appropriate solution phase redox species are prepared in the gas phase using electrospray ionization and probed using photodetachment spectroscopy. Five metal complex anions involved in the Fe 2+ -Fe 3+ redox couple are investigated and the intramolecular reorganization energies are measured directly from spectral features due to removing the most loosely bound 3d electron from the Fe(II)-complexes. The photodetachment spectra also yield electronic structure information about the Fe 2+ -Fe 3+ redox couple and provide a common electronic structure origin for the reducing capability of the Fe(II)-complexes, the most common redox reagents. (c) 2000 American Institute of Physics

  19. Redox properties of the nitronyl nitroxide antioxidants studied via their reactions with nitroxyl and ferrocyanide.

    Science.gov (United States)

    Bobko, A A; Khramtsov, V V

    2015-01-01

    Nitronyl nitroxides (NNs) are the paramagnetic probes that are capable of scavenging physiologically relevant reactive oxygen (ROS) and nitrogen (RNS) species, namely superoxide, nitric oxide (NO), and nitroxyl (HNO). NNs are increasingly considered as potent antioxidants and potential therapeutic agents. Understanding redox chemistry of the NNs is important for their use as antioxidants and as paramagnetic probes for discriminative detection of NO and HNO by electron paramagnetic resonance (EPR) spectroscopy. Here we investigated the redox properties of the two most commonly used NNs, including determination of the equilibrium and rate constants of their reduction by HNO and ferrocyanide, and reduction potential of the couple NN/hydroxylamine of nitronyl nitroxide (hNN). The rate constants of the reaction of the NNs with HNO were found to be equal to (1-2) × 10(4) M(-1)s(- 1) being close to the rate constants of scavenging superoxide and NO by NNs. The reduction potential of the NNs and iminonitroxides (INs, product of NNs reaction with NO) were calculated based on their reaction constants with ferrocyanide. The obtained values of the reduction potential for NN/hNN (E'0 ≈ 285 mV) and IN/hIN (E' ≈ 495 mV) are close to the corresponding values for vitamin C and vitamin E, correspondingly. The "balanced" scavenging rates of the NNs towards superoxide, NO, and HNO, and their low reduction potential being thermodynamically close to the bottom of the pecking order of oxidizing radicals, might be important factors contributing into their antioxidant activity.

  20. Structural Basis for Redox Regulation of Cytoplasmic and Chloroplastic Triosephosphate Isomerases from Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Laura Margarita López-Castillo

    2016-12-01

    Full Text Available In plants triosephosphate isomerase (TPI interconverts glyceraldehyde 3-phosphate (G3P and dihydroxyacetone phosphate (DHAP during glycolysis, gluconeogenesis, and the Calvin-Benson cycle. The nuclear genome of land plants encodes two tpi genes, one gene product is located in the cytoplasm and the other is imported into the chloroplast. Herein we report the crystal structures of the TPIs from the vascular plant Arabidopsis thaliana (AtTPIs and address their enzymatic modulation by redox agents. Cytoplasmic TPI (cTPI and chloroplast TPI (pdTPI share more than 60% amino acid identity and assemble as (β-α8 dimers with high structural homology. cTPI and pdTPI harbor two and one accessible thiol groups per monomer respectively. cTPI and pdTPI present a cysteine at an equivalent structural position (C13 and C15 respectively and cTPI also contains a specific solvent accessible cysteine at residue 218 (cTPI-C218. Site directed mutagenesis of residues pdTPI-C15, cTPI-C13 and cTPI-C218 to serine substantially decreases enzymatic activity, indicating that the structural integrity of these cysteines is necessary for catalysis. AtTPIs exhibit differential responses to oxidative agents, cTPI is susceptible to oxidative agents such as diamide and H2O2, whereas pdTPI is resistant to inhibition. Incubation of AtTPIs with the sulfhydryl conjugating reagents methylmethane thiosulfonate (MMTS and glutathione inhibits enzymatic activity. However, the concentration necessary to inhibit pdTPI is at least two orders of magnitude higher than the concentration needed to inhibit cTPI. Western-blot analysis indicates that residues cTPI-C13, cTPI-C218, and pdTPI-C15 conjugate with glutathione. In summary, our data indicate that AtTPIs could be redox regulated by the derivatization of specific AtTPI cysteines (cTPI-C13 and pdTPI-C15 and cTPI-C218. Since AtTPIs have evolved by gene duplication, the higher resistance of pdTPI to redox agents may be an adaptive consequence to

  1. Investigation of multi-state charge-storage properties of redox-active organic molecules in silicon-molecular hybrid devices for DRAM and Flash applications

    Science.gov (United States)

    Gowda, Srivardhan Shivappa

    Molecular electronics has recently spawned a considerable amount of interest with several molecules possessing charge-conduction and charge-storage properties proposed for use in electronic devices. Hybrid silicon-molecular technology has the promise of augmenting the current silicon technology and provide for a transitional path to future molecule-only technology. The focus of this dissertation work has been on developing a class of hybrid silicon-molecular electronic devices for DRAM and Flash memory applications utilizing redox-active molecules. This work exploits the ability of molecules to store charges with single-electron precision at room temperature. The hybrid devices are fabricated by forming self-assembled monolayers of redox-active molecules on Si and oxide (SiO2 and HfO2) surfaces via formation of covalent linkages. The molecules possess discrete quantum states from which electrons can tunnel to the Si substrate at discrete applied voltages (oxidation process, cell write), leaving behind a positively charged layer of molecules. The reduction (erase) process, which is the process of electrons tunneling back from Si to the molecules, neutralizes the positively charged molecular monolayer. Hybrid silicon-molecular capacitor test structures were electrically characterized with an electrolyte gate using cyclic voltammetry (CyV) and impedance spectroscopy (CV) techniques. The redox voltages, kinetics (write/erase speeds) and charge-retention characteristics were found to be strongly dependent on the Si doping type and densities, and ambient light. It was also determined that the redox energy states in the molecules communicate with the valence band of the Si substrate. This allows tuning of write and read states by modulating minority carriers in n- and p-Si substrates. Ultra-thin dielectric tunnel barriers (SiO2, HfO2) were placed between the molecules and the Si substrate to augment charge-retention for Flash memory applications. The redox response was

  2. Ambient redox synthesis of vanadium-doped manganese dioxide nanoparticles and their enhanced zinc storage properties

    Science.gov (United States)

    Alfaruqi, Muhammad Hilmy; Islam, Saiful; Mathew, Vinod; Song, Jinju; Kim, Sungjin; Tung, Duong Pham; Jo, Jeonggeun; Kim, Seokhun; Baboo, Joseph Paul; Xiu, Zhiliang; Kim, Jaekook

    2017-05-01

    In this work, we demonstrate the first use of a V-doped MnO2 nanoparticle electrode for zinc-ion battery (ZIB) applications. The V-doped MnO2 was prepared via a simple redox reaction and the X-ray diffraction studies confirmed the formation of pure MnO2, accompanied by an anisotropic expansion of MnO2 lattice, suggesting the incorporation of V-ions into the MnO2 framework. V doping of MnO2 not only increased the specific surface area but also improved the electronic conductivity. When Zn-storage properties were tested, the V-doped MnO2 electrode registered a higher discharge capacity of 266 mAh g-1 compared to 213 mAh g-1 for the pure MnO2 electrode. On prolonged cycling, the doped electrode retained 31% higher capacity than that of the bare MnO2 electrode and thereby demonstrated superior cycling performance. This study may pave the way towards understanding the enhancement of the energy storage properties via doping in electrodes of aqueous ZIB applications and also furthers the efforts for the practical realization of a potential eco-friendly battery system.

  3. Antinociceptive action and redox properties of citronellal, an essential oil present in lemongrass.

    Science.gov (United States)

    Quintans-Júnior, Lucindo; da Rocha, Ricardo Fagundes; Caregnato, Fernanda Freitas; Moreira, José Claudio Fonseca; da Silva, Francilene Amaral; Araújo, Adriano Antunes de Souza; dos Santos, João Paulo Almeida; Melo, Mônica Santos; de Sousa, Damião Pergentino; Bonjardim, Leonardo Rigoldi; Gelain, Daniel Pens

    2011-06-01

    Citronellal (CT) is a monoterpenoid and the major constituent of the mixture of terpenoids that give the citronella oil its lemon scent. Citronella oil is widely used around the world for various purposes and is mainly obtained from plants of the Cymbopogon genus, which are known as "lemongrass." Considering these plants have been used worldwide for various medicinal purposes, the interest of researchers to understand the biological activities of monoterpenoids related to the Cymbopogon genus has been increasing. In the present work, we investigated the antinociceptive action and the redox properties of CT. Our results indicate that intraperitoneal injection of CT was effective in reducing nociceptive face-rubbing behavior in both phases of the formalin test, which was also naloxone-sensitive. CT also evoked antinociceptive response in the capsaicin and glutamate tests. The total radical-trapping antioxidant parameter and total antioxidant reactivity assays indicate that CT at doses of 0.1 and 1 mg/mL exerts a significant antioxidant activity, which is probably related to its ability to scavenge superoxide and nitric oxide, but not H(2)O(2) or hydroxyl radicals, as evaluated separately by specific in vitro tests. These results show for the first time the antinociceptive potential of CT and indicate that the antioxidant properties of this compound may rely on its mechanism of biological actions because CT-containing natural products are used to treat various diseases related to oxidative stress and reactive species.

  4. 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

  5. Comparative sequence, structure and redox analyses of Klebsiella pneumoniae DsbA show that anti-virulence target DsbA enzymes fall into distinct classes.

    Directory of Open Access Journals (Sweden)

    Fabian Kurth

    Full Text Available Bacterial DsbA enzymes catalyze oxidative folding of virulence factors, and have been identified as targets for antivirulence drugs. However, DsbA enzymes characterized to date exhibit a wide spectrum of redox properties and divergent structural features compared to the prototypical DsbA enzyme of Escherichia coli DsbA (EcDsbA. Nonetheless, sequence analysis shows that DsbAs are more highly conserved than their known substrate virulence factors, highlighting the potential to inhibit virulence across a range of organisms by targeting DsbA. For example, Salmonella enterica typhimurium (SeDsbA, 86 % sequence identity to EcDsbA shares almost identical structural, surface and redox properties. Using comparative sequence and structure analysis we predicted that five other bacterial DsbAs would share these properties. To confirm this, we characterized Klebsiella pneumoniae DsbA (KpDsbA, 81 % identity to EcDsbA. As expected, the redox properties, structure and surface features (from crystal and NMR data of KpDsbA were almost identical to those of EcDsbA and SeDsbA. Moreover, KpDsbA and EcDsbA bind peptides derived from their respective DsbBs with almost equal affinity, supporting the notion that compounds designed to inhibit EcDsbA will also inhibit KpDsbA. Taken together, our data show that DsbAs fall into different classes; that DsbAs within a class may be predicted by sequence analysis of binding loops; that DsbAs within a class are able to complement one another in vivo and that compounds designed to inhibit EcDsbA are likely to inhibit DsbAs within the same class.

  6. The geometric structures, vibrational frequencies and redox properties of the actinyl coordination complexes ([AnO2(L)n](m); An = U, Pu, Np; L = H2O, Cl-, CO3(2-), CH3CO2(-), OH-) in aqueous solution, studied by density functional theory methods.

    Science.gov (United States)

    Austin, Jonathan P; Sundararajan, Mahesh; Vincent, Mark A; Hillier, Ian H

    2009-08-14

    The geometric and electronic structures of the aqua, chloro, acetato, hydroxo and carbonato complexes of U, Np and Pu in both their (VI) and (V) oxidation states, and in an aqueous environment, have been studied using density functional theory methods. We have obtained micro-solvated structures derived from molecular dynamics simulations and included the bulk solvent using a continuum model. We find that two different hydrogen bonding patterns involving the axial actinyl oxygen atoms are sometimes possible, and may give rise to different An-O bond lengths and vibrational frequencies. These alternative structures are reflected in the experimental An-O bond lengths of the aqua and carbonato complexes. The variation of the redox potential of the uranyl complexes with the different ligands has been studied using both BP86 and B3LYP functionals. The relative values for the four uranium complexes having anionic ligands are in surprisingly good agreement with experiment, although the absolute values are in error by approximately 1 eV. The absolute error for the aqua species is much less, leading to an incorrect order of the redox potentials of the aqua and chloro species.

  7. Porous Materials - Structure and Properties

    DEFF Research Database (Denmark)

    Nielsen, Anders

    1997-01-01

    The paper presents some viewpoints on the description of the pore structure and the modelling of the properties of the porous building materials. Two examples are given , where it has been possible to connect the pore structure to the properties: Shrinkage of autoclaved aerated concrete...

  8. Electrochemical Properties of Current Collector in the All-vanadium Redox Flow Battery

    International Nuclear Information System (INIS)

    Hwang, Gan-Jin; Oh, Yong-Hwan; Ryu, Cheol-Hwi; Choi, Ho-Sang

    2014-01-01

    Two commercial carbon plates were evaluated as a current collector (bipolar plate) in the all vanadium redox-flow battery (V-RFB). The performance properties of V-RFB were test in the current density of 60 mA/cm 2 . The electromotive forces (OCV at SOC 100%) of V-RFB using A and B current collector were 1.47 V and 1.54 V. The cell resistance of V-RFB using A current collector was 4.44-5.00 Ω·cm 2 and 3.28-3.75 Ω·cm 2 for charge and discharge, respectively. The cell resistance of V-RFB using B current collector was 4.19-4.42Ω·cm 2 and 4.71-5.49Ω·cm 2 for charge and discharge, respectively. The performance of V-RFB using each current collector was evaluated. The performance of V-RFB using A current collector was 93.1%, 76.8% and 71.4% for average current efficiency, average voltage efficiency and average energy efficiency, respectively. The performance of V-RFB using B current collector was 96.4%, 73.6% and 71.0% for average current efficiency, average voltage efficiency and average energy efficiency, respectively

  9. Thermodynamic and redox properties of graphene oxides for lithium-ion battery applications: a first principles density functional theory modeling approach.

    Science.gov (United States)

    Kim, Sunghee; Kim, Ki Chul; Lee, Seung Woo; Jang, Seung Soon

    2016-07-27

    Understanding the thermodynamic stability and redox properties of oxygen functional groups on graphene is critical to systematically design stable graphene-based positive electrode materials with high potential for lithium-ion battery applications. In this work, we study the thermodynamic and redox properties of graphene functionalized with carbonyl and hydroxyl groups, and the evolution of these properties with the number, types and distribution of functional groups by employing the density functional theory method. It is found that the redox potential of the functionalized graphene is sensitive to the types, number, and distribution of oxygen functional groups. First, the carbonyl group induces higher redox potential than the hydroxyl group. Second, more carbonyl groups would result in higher redox potential. Lastly, the locally concentrated distribution of the carbonyl group is more beneficial to have higher redox potential compared to the uniformly dispersed distribution. In contrast, the distribution of the hydroxyl group does not affect the redox potential significantly. Thermodynamic investigation demonstrates that the incorporation of carbonyl groups at the edge of graphene is a promising strategy for designing thermodynamically stable positive electrode materials with high redox potentials.

  10. Influence of aminosilane precursor concentration on physicochemical properties of composite Nafion membranes for vanadium redox flow battery applications

    Science.gov (United States)

    Kondratenko, Mikhail S.; Karpushkin, Evgeny A.; Gvozdik, Nataliya A.; Gallyamov, Marat O.; Stevenson, Keith J.; Sergeyev, Vladimir G.

    2017-02-01

    A series of composite proton-exchange membranes have been prepared via sol-gel modification of commercial Nafion membranes with [N-(2-aminoethyl)-3-aminopropyl]trimethoxysilane. The structure and physico-chemical properties (water uptake, ion-exchange capacity, vanadyl ion permeability, and proton conductivity) of the prepared composite membranes have been studied as a function of the precursor loading (degree of the membrane modification). If the amount of the precursor is below 0.4/1 M ratio of the amino groups of the precursor to the sulfonic groups of Nafion, the composite membranes exhibit decreased vanadium ion permeability while having relatively high proton conductivity. With respect to the use of a non-modified Nafion membrane, the performance of the composite membrane with an optimum precursor loading in a single-cell vanadium redox flow battery demonstrates enhanced energy efficiency in 20-80 mA cm-2 current density range. The maximum efficiency increase of 8% is observed at low current densities.

  11. 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.

  12. Crystal Structure of Green Fluorescent Protein Clover and Design of Clover-Based Redox Sensors.

    Science.gov (United States)

    Campbell, Benjamin C; Petsko, Gregory A; Liu, Ce Feng

    2018-02-06

    We have determined the crystal structure of Clover, one of the brightest fluorescent proteins, and found that its T203H/S65G mutations relative to wild-type GFP lock the critical E222 side chain in a fixed configuration that mimics the major conformer of that in EGFP. The resulting equilibrium shift to the predominantly deprotonated chromophore increases the extinction coefficient (EC), opposes photoactivation, and is responsible for the bathochromic shift. Clover's brightness can further be attributed to a π-π stacking interaction between H203 and the chromophore. Consistent with these observations, the Clover G65S mutant reversed the equilibrium shift, dramatically decreased the EC, and made Clover photoactivatable under conditions that activated photoactivatable GFP. Using the Clover structure, we rationally engineered a non-photoactivatable redox sensor, roClover1, and determined its structure as well as that of its parental template, roClover0.1. These high-resolution structures provide deeper insights into structure-function relationships in GFPs and may aid the development of excitation-improved ratiometric biosensors. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Structural Properties of Ferroelectric Perovskites

    National Research Council Canada - National Science Library

    Vanderbilt, David

    1998-01-01

    Under this research grant, we carried out realistic first-principles computer calculations of the ground-state and finite-temperature structural and dielectric properties of cubic perovskite materials...

  14. 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

  15. 3D Microstructure Effects in Ni-YSZ Anodes: Prediction of Effective Transport Properties and Optimization of Redox Stability

    Science.gov (United States)

    Pecho, Omar M.; Stenzel, Ole; Iwanschitz, Boris; Gasser, Philippe; Neumann, Matthias; Schmidt, Volker; Prestat, Michel; Hocker, Thomas; Flatt, Robert J.; Holzer, Lorenz

    2015-01-01

    This study investigates the influence of microstructure on the effective ionic and electrical conductivities of Ni-YSZ (yttria-stabilized zirconia) anodes. Fine, medium, and coarse microstructures are exposed to redox cycling at 950 °C. FIB (focused ion beam)-tomography and image analysis are used to quantify the effective (connected) volume fraction (Φeff), constriction factor (β), and tortuosity (τ). The effective conductivity (σeff) is described as the product of intrinsic conductivity (σ0) and the so-called microstructure-factor (M): σeff = σ0 × M. Two different methods are used to evaluate the M-factor: (1) by prediction using a recently established relationship, Mpred = εβ0.36/τ5.17, and (2) by numerical simulation that provides conductivity, from which the simulated M-factor can be deduced (Msim). Both methods give complementary and consistent information about the effective transport properties and the redox degradation mechanism. The initial microstructure has a strong influence on effective conductivities and their degradation. Finer anodes have higher initial conductivities but undergo more intensive Ni coarsening. Coarser anodes have a more stable Ni phase but exhibit lower YSZ stability due to lower sintering activity. Consequently, in order to improve redox stability, it is proposed to use mixtures of fine and coarse powders in different proportions for functional anode and current collector layers. PMID:28793523

  16. 3D Microstructure Effects in Ni-YSZ Anodes: Prediction of Effective Transport Properties and Optimization of Redox Stability

    Directory of Open Access Journals (Sweden)

    Omar M. Pecho

    2015-08-01

    Full Text Available This study investigates the influence of microstructure on the effective ionic and electrical conductivities of Ni-YSZ (yttria-stabilized zirconia anodes. Fine, medium, and coarse microstructures are exposed to redox cycling at 950 °C. FIB (focused ion beam-tomography and image analysis are used to quantify the effective (connected volume fraction (Φeff, constriction factor (β, and tortuosity (τ. The effective conductivity (σeff is described as the product of intrinsic conductivity (σ0 and the so-called microstructure-factor (M: σeff = σ0*M. Two different methods are used to evaluate the M-factor: (1 by prediction using a recently established relationship, Mpred = εβ0.36/τ5.17, and (2 by numerical simulation that provides conductivity, from which the simulated M-factor can be deduced (Msim. Both methods give complementary and consistent information about the effective transport properties and the redox degradation mechanism. The initial microstructure has a strong influence on effective conductivities and their degradation. Finer anodes have higher initial conductivities but undergo more intensive Ni coarsening. Coarser anodes have a more stable Ni phase but exhibit lower YSZ stability due to lower sintering activity. Consequently, in order to improve redox stability, it is proposed to use mixtures of fine and coarse powders in different proportions for functional anode and current collector layers.

  17. 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.

  18. H-shaped oligothiophenes with low band gaps and amphoteric redox properties

    KAUST Repository

    Luo, Jing

    2010-12-17

    H-shaped bridged oligothiophenes HT-1 and HT-2 were synthesized by two different approaches. Different from normal oligothiophenes, HT-1 and HT-2 showed low band gaps and amphoteric redox behaviors due to intramolecular charge transfer, which is further supported by time-dependent DFT calculations. © 2010 American Chemical Society.

  19. Nickel electrodes as a cheap and versatile platform for studying structure and function of immobilized redox proteins

    Energy Technology Data Exchange (ETDEWEB)

    Han, Xiao Xia [State Key Laboratory of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Strasse des 17. Juni 135, D-10623 Berlin (Germany); Li, Junbo [State Key Laboratory of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Öner, Ibrahim Halil [Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Strasse des 17. Juni 135, D-10623 Berlin (Germany); Zhao, Bing [State Key Laboratory of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Leimkühler, Silke [Institut für Biochemie und Biologie, Universität Potsdam, Karl-Liebknecht Straße 24-25, H. 25, Golm D-14476 (Germany); Hildebrandt, Peter [Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Strasse des 17. Juni 135, D-10623 Berlin (Germany); Weidinger, Inez M., E-mail: i.weidinger@mailbox.tu-berlin.de [Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Strasse des 17. Juni 135, D-10623 Berlin (Germany)

    2016-10-19

    Practical use of many bioelectronic and bioanalytical devices is limited by the need of expensive materials and time consuming fabrication. Here we demonstrate the use of nickel electrodes as a simple and cheap solid support material for bioelectronic applications. The naturally nanostructured electrodes showed a surprisingly high electromagnetic surface enhancement upon light illumination such that immobilization and electron transfer reactions of the model redox proteins cytochrome b{sub 5} (Cyt b{sub 5}) and cytochrome c (Cyt c) could be followed via surface enhanced resonance Raman spectroscopy. It could be shown that the nickel surface, when used as received, promotes a very efficient binding of the proteins upon preservation of their native structure. The immobilized redox proteins could efficiently exchange electrons with the electrode and could even act as an electron relay between the electrode and solubilized myoglobin. Our results open up new possibility for nickel electrodes as an exceptional good support for bioelectronic devices and biosensors on the one hand and for surface enhanced spectroscopic investigations on the other hand. - Highlights: • Nickel electrodes were used without further functionalization as supports for various redox proteins. • It was possible to monitor the immobilized proteins via surface enhanced Raman spectroscopy. • The native structure of the immobilized proteins was preserved and they could exchange electrons with the Ni electrode. • The immobilized redox proteins worked as an electron relay between electrode and solubilized myoglobin.

  20. Influence of Fenton's reagent treatment on electrochemical properties of graphite felt for all vanadium redox flow battery

    International Nuclear Information System (INIS)

    Gao, Chao; Wang, NanFang; Peng, Sui; Liu, SuQin; Lei, Ying; Liang, XinXing; Zeng, ShanShan; Zi, HuiFang

    2013-01-01

    Highlights: ► Highly hydroxyl-functionalized graphite felt has been obtained through Fenton's reagent treatment. ► Fenton's reagent treatment involves only one step, works under ambient conditions and will never produce any toxic gas. ► The treated graphite felt exhibits superior electrochemical performance in comparison to the untreated one. -- Abstract: An environmental, economic and highly effective method for carbon fiber hydroxylated-functionalization based on Fenton's reagent treatment is used to improve the electrochemical activity of graphite felt (GF) as the positive electrode in all vanadium redox flow battery (VRFB). The effect of H 2 O 2 content in Fenton's reagent on the structure and electrochemical properties of GF is investigated. The scanning electron microscope (SEM) indicates that the surface of the treated GF is etched increasingly with the content of H 2 O 2 . The Fourier transformation infrared (FTIR) spectroscopy shows that the peak intensity of hydroxyl groups on the treated felt is increased with the H 2 O 2 concentration, which is further verified by X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) show that the treated sample exhibits a higher electrochemical activity. A VRFB with the treated GF as electrodes exhibits higher coulombic, voltage and energy efficiency (98.8%, 75.1% and 74.2%) than that with the untreated GF (93.9%, 72.1% and 67.7%) at 60 mA cm −2 , and this method is even superior when compared with the reported methods

  1. Computational design of molecules for an all-quinone redox flow battery† †Electronic supplementary information (ESI) available: The list of computationally predicted candidate quinone molecules with interesting redox properties. See DOI: 10.1039/c4sc03030c Click here for additional data file.

    Science.gov (United States)

    Er, Süleyman; Suh, Changwon; Marshak, Michael P.

    2015-01-01

    Inspired by the electron transfer properties of quinones in biological systems, we recently showed that quinones are also very promising electroactive materials for stationary energy storage applications. Due to the practically infinite chemical space of organic molecules, the discovery of additional quinones or other redox-active organic molecules for energy storage applications is an open field of inquiry. Here, we introduce a high-throughput computational screening approach that we applied to an accelerated study of a total of 1710 quinone (Q) and hydroquinone (QH2) (i.e., two-electron two-proton) redox couples. We identified the promising candidates for both the negative and positive sides of organic-based aqueous flow batteries, thus enabling an all-quinone battery. To further aid the development of additional interesting electroactive small molecules we also provide emerging quantitative structure-property relationships. PMID:29560173

  2. 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.

  3. n-Dopants Based on Dimers of Benzimidazoline Radicals: Structures and Mechanism of Redox Reactions.

    Science.gov (United States)

    Zhang, Siyuan; Naab, Benjamin D; Jucov, Evgheni V; Parkin, Sean; Evans, Eric G B; Millhauser, Glenn L; Timofeeva, Tatiana V; Risko, Chad; Brédas, Jean-Luc; Bao, Zhenan; Barlow, Stephen; Marder, Seth R

    2015-07-20

    Dimers of 2-substituted N,N'-dimethylbenzimidazoline radicals, (2-Y-DMBI)2 (Y=cyclohexyl (Cyc), ferrocenyl (Fc), ruthenocenyl (Rc)), have recently been reported as n-dopants for organic semiconductors. Here their structural and energetic characteristics are reported, along with the mechanisms by which they react with acceptors, A (PCBM, TIPS-pentacene), in solution. X-ray data and DFT calculations both indicate a longer C-C bond for (2-Cyc-DMBI)2 than (2-Fc-DMBI)2 , yet DFT and ESR data show that the latter dissociates more readily due to stabilization of the radical by Fc. Depending on the energetics of dimer (D2 ) dissociation and of D2 -to-A electron transfer, D2 reacts with A to form D(+) and A(-) by either of two mechanisms, differing in whether the first step is endergonic dissociation or endergonic electron transfer. However, the D(+) /0.5 D2 redox potentials-the effective reducing strengths of the dimers-vary little within the series (ca. -1.9 V vs. FeCp2 (+/0) ) (Cp=cyclopentadienyl) due to cancelation of trends in the D(+/0) potential and D2 dissociation energy. The implications of these findings for use of these dimers as n-dopants, and for future dopant design, are discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. n-Dopants Based on Dimers of Benzimidazoline Radicals: Structures and Mechanism of Redox Reactions

    KAUST Repository

    Zhang, Siyuan

    2015-06-18

    Dimers of 2-substituted N,N\\'-dimethylbenzimidazoline radicals, (2-Y-DMBI)2 (Y=cyclohexyl (Cyc), ferrocenyl (Fc), ruthenocenyl (Rc)), have recently been reported as n-dopants for organic semiconductors. Here their structural and energetic characteristics are reported, along with the mechanisms by which they react with acceptors, A (PCBM, TIPS-pentacene), in solution. X-ray data and DFT calculations both indicate a longer C-C bond for (2-Cyc-DMBI)2 than (2-Fc-DMBI)2, yet DFT and ESR data show that the latter dissociates more readily due to stabilization of the radical by Fc. Depending on the energetics of dimer (D2) dissociation and of D2-to-A electron transfer, D2 reacts with A to form D+ and A- by either of two mechanisms, differing in whether the first step is endergonic dissociation or endergonic electron transfer. However, the D+/0.5D2 redox potentials-the effective reducing strengths of the dimers-vary little within the series (ca. -1.9V vs. FeCp2+/0) (Cp=cyclopentadienyl) due to cancelation of trends in the D+/0 potential and D2 dissociation energy. The implications of these findings for use of these dimers as n-dopants, and for future dopant design, are discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Transient behavior of redox flow battery connected to circuit based on global phase structure

    Science.gov (United States)

    Mannari, Toko; Hikihara, Takashi

    A Redox Flow Battery (RFB) is one of the promising energy storage systems in power grid. An RFB has many advantages such as a quick response, a large capacity, and a scalability. Due to these advantages, an RFB can operate in mixed time scale. Actually, it has been demonstrated that an RFB can be used for load leveling, compensating sag, and smoothing the output of the renewable sources. An analysis on transient behaviors of an RFB is a key issue for these applications. An RFB is governed by electrical, chemical, and fluid dynamics. The hybrid structure makes the analysis difficult. To analyze transient behaviors of an RFB, the exact model is necessary. In this paper, we focus on a change in a concentration of ions in the electrolyte, and simulate the change with a model which is mainly based on chemical kinetics. The simulation results introduces transient behaviors of an RFB in a response to a load variation. There are found three kinds of typical transient behaviors including oscillations. As results, it is clarified that the complex transient behaviors, due to slow and fast dynamics in the system, arise by the quick response to load.

  6. n-Dopants Based on Dimers of Benzimidazoline Radicals: Structures and Mechanism of Redox Reactions

    KAUST Repository

    Zhang, Siyuan; Naab, Benjamin D.; Jucov, Evgheni V.; Parkin, Sean; Evans, Eric G B; Millhauser, Glenn L.; Timofeeva, Tatiana V.; Risko, Chad; Bredas, Jean-Luc; Bao, Zhenan; Barlow, Stephen; Marder, Seth R.

    2015-01-01

    Dimers of 2-substituted N,N'-dimethylbenzimidazoline radicals, (2-Y-DMBI)2 (Y=cyclohexyl (Cyc), ferrocenyl (Fc), ruthenocenyl (Rc)), have recently been reported as n-dopants for organic semiconductors. Here their structural and energetic characteristics are reported, along with the mechanisms by which they react with acceptors, A (PCBM, TIPS-pentacene), in solution. X-ray data and DFT calculations both indicate a longer C-C bond for (2-Cyc-DMBI)2 than (2-Fc-DMBI)2, yet DFT and ESR data show that the latter dissociates more readily due to stabilization of the radical by Fc. Depending on the energetics of dimer (D2) dissociation and of D2-to-A electron transfer, D2 reacts with A to form D+ and A- by either of two mechanisms, differing in whether the first step is endergonic dissociation or endergonic electron transfer. However, the D+/0.5D2 redox potentials-the effective reducing strengths of the dimers-vary little within the series (ca. -1.9V vs. FeCp2+/0) (Cp=cyclopentadienyl) due to cancelation of trends in the D+/0 potential and D2 dissociation energy. The implications of these findings for use of these dimers as n-dopants, and for future dopant design, are discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Synthesis and properties of novel sulfonated poly(arylene ether sulfone) ionomers for vanadium redox flow battery

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Dongyang; Wang, Shuanjin; Xiao, Min; Meng, Yuezhong [The Key Laboratory of Low-carbon Chemistry and Energy Conservation of Guangdong Province, Institute of Optoelectronic and Functional Composite Materials, Sun Yat-Sen University, Guangzhou 510275 (China)

    2010-12-15

    Novel sulfonated poly(arylene ether sulfone)s with electron-withdrawing sulfone groups in each repeat unit were synthesized via step polymerization followed by post-sulfonation using chlorosulfonic acid. The sulfonation degree can be readily controlled by adjusting the feed ratio of the repeat unit of polymers to chlorosulfonic acid. The synthesized polymers are soluble in common aprotic solvents such as dimethyl sulfoxide, N,N'-dimethylacetamide and dimethylformamide, and can be cast into transparent membranes from their solutions. The ion exchange capacity, water uptake, swelling ratio, sulfonation degree, mechanical property, oxidative property, thermal property and proton conductivity were investigated in detail using different methodologies. As an objective to apply these polymers as separators for vanadium redox flow battery, the VO{sup 2+} permeability and cell performance for the single cell were examined and assessed. (author)

  8. Synthesis and properties of novel sulfonated poly(arylene ether sulfone) ionomers for vanadium redox flow battery

    Energy Technology Data Exchange (ETDEWEB)

    Chen Dongyang [Key Laboratory of Low-carbon Chemistry and Energy Conservation of Guangdong Province, Institute of Optoelectronic and Functional Composite Materials, Sun Yat-Sen University, Guangzhou 510275 (China); Wang Shuanjin, E-mail: wangshj@mail.sysu.edu.c [Key Laboratory of Low-carbon Chemistry and Energy Conservation of Guangdong Province, Institute of Optoelectronic and Functional Composite Materials, Sun Yat-Sen University, Guangzhou 510275 (China); Xiao Min [Key Laboratory of Low-carbon Chemistry and Energy Conservation of Guangdong Province, Institute of Optoelectronic and Functional Composite Materials, Sun Yat-Sen University, Guangzhou 510275 (China); Meng Yuezhong, E-mail: mengyzh@mail.sysu.edu.c [Key Laboratory of Low-carbon Chemistry and Energy Conservation of Guangdong Province, Institute of Optoelectronic and Functional Composite Materials, Sun Yat-Sen University, Guangzhou 510275 (China)

    2010-12-15

    Novel sulfonated poly(arylene ether sulfone)s with electron-withdrawing sulfone groups in each repeat unit were synthesized via step polymerization followed by post-sulfonation using chlorosulfonic acid. The sulfonation degree can be readily controlled by adjusting the feed ratio of the repeat unit of polymers to chlorosulfonic acid. The synthesized polymers are soluble in common aprotic solvents such as dimethyl sulfoxide, N,N'-dimethylacetamide and dimethylformamide, and can be cast into transparent membranes from their solutions. The ion exchange capacity, water uptake, swelling ratio, sulfonation degree, mechanical property, oxidative property, thermal property and proton conductivity were investigated in detail using different methodologies. As an objective to apply these polymers as separators for vanadium redox flow battery, the VO{sup 2+} permeability and cell performance for the single cell were examined and assessed.

  9. Recapitulating the Structural Evolution of Redox Regulation in Adenosine 5′-Phosphosulfate Kinase from Cyanobacteria to Plants*

    Science.gov (United States)

    Herrmann, Jonathan; Nathin, David; Lee, Soon Goo; Sun, Tony; Jez, Joseph M.

    2015-01-01

    In plants, adenosine 5′-phosphosulfate (APS) kinase (APSK) is required for reproductive viability and the production of 3′-phosphoadenosine 5′-phosphosulfate (PAPS) as a sulfur donor in specialized metabolism. Previous studies of the APSK from Arabidopsis thaliana (AtAPSK) identified a regulatory disulfide bond formed between the N-terminal domain (NTD) and a cysteine on the core scaffold. This thiol switch is unique to mosses, gymnosperms, and angiosperms. To understand the structural evolution of redox control of APSK, we investigated the redox-insensitive APSK from the cyanobacterium Synechocystis sp. PCC 6803 (SynAPSK). Crystallographic analysis of SynAPSK in complex with either APS and a non-hydrolyzable ATP analog or APS and sulfate revealed the overall structure of the enzyme, which lacks the NTD found in homologs from mosses and plants. A series of engineered SynAPSK variants reconstructed the structural evolution of the plant APSK. Biochemical analyses of SynAPSK, SynAPSK H23C mutant, SynAPSK fused to the AtAPSK NTD, and the fusion protein with the H23C mutation showed that the addition of the NTD and cysteines recapitulated thiol-based regulation. These results reveal the molecular basis for structural changes leading to the evolution of redox control of APSK in the green lineage from cyanobacteria to plants. PMID:26294763

  10. Redox kinetics and mechanism in silicate melts

    International Nuclear Information System (INIS)

    Cochain, B.

    2009-12-01

    This work contributes to better understand iron redox reactions and mechanisms in silicate melts. It was conducted on compositions in both Na 2 O-B 2 O 3 -SiO 2 -FeO and Na 2 O-Al 2 O 3 -SiO 2 -FeO systems. The influence of boron-sodium and aluminum-sodium substitutions and iron content on properties and structure of glasses and on the iron redox kinetics has been studied by Raman, Moessbauer and XANES spectroscopies at the B and Fe K-edges. In borosilicate glasses, an increase in iron content or in the Fe 3+ /ΣFe redox state implies a structural rearrangement of the BO 4 species in the glass network whereas the BO 3 and BO 4 relative proportions remain nearly constant. In all studied glasses and melts, Fe 3+ is a network former in tetrahedral coordination, unless for aluminosilicates of ratio Al/Na≥1 where Fe 3+ is a network modifier in five-fold coordination. Near Tg, diffusion of network modifying cations controls the iron redox kinetics along with a flux of electron holes. At liquidus temperatures, oxygen diffusion is considered to be the mechanism that governs redox reactions. This study shows the role played by the silicate network polymerization on the redox kinetics. In borosilicate melts, iron redox kinetics depends on the boron speciation between BO 3 and BO 4 that depends itself on the sodium content. Furthermore, an increase in the network-former/network-modifier ratio implies a decrease in oxygen diffusion that results in a slowing down of the redox kinetics. The obtained results allow a description of the iron redox kinetics for more complex compositions as natural lavas or nuclear waste model glasses. (author)

  11. First-principles molecular dynamics simulation study on electrolytes for use in redox flow battery

    Science.gov (United States)

    Choe, Yoong-Kee; Tsuchida, Eiji; Tokuda, Kazuya; Ootsuka, Jun; Saito, Yoshihiro; Masuno, Atsunobu; Inoue, Hiroyuki

    2017-11-01

    Results of first-principles molecular dynamics simulations carried out to investigate structural aspects of electrolytes for use in a redox flow battery are reported. The electrolytes studied here are aqueous sulfuric acid solutions where its property is of importance for dissolving redox couples in redox flow battery. The simulation results indicate that structural features of the acid solutions depend on the concentration of sulfuric acid. Such dependency arises from increase of proton dissociation from sulfuric acid.

  12. Structural properties of matrix metalloproteinases.

    Science.gov (United States)

    Bode, W; Fernandez-Catalan, C; Tschesche, H; Grams, F; Nagase, H; Maskos, K

    1999-04-01

    Matrix metalloproteinases (MMPs) are involved in extracellular matrix degradation. Their proteolytic activity must be precisely regulated by their endogenous protein inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). Disruption of this balance results in serious diseases such as arthritis, tumour growth and metastasis. Knowledge of the tertiary structures of the proteins involved is crucial for understanding their functional properties and interference with associated dysfunctions. Within the last few years, several three-dimensional MMP and MMP-TIMP structures became available, showing the domain organization, polypeptide fold and main specificity determinants. Complexes of the catalytic MMP domains with various synthetic inhibitors enabled the structure-based design and improvement of high-affinity ligands, which might be elaborated into drugs. A multitude of reviews surveying work done on all aspects of MMPs have appeared in recent years, but none of them has focused on the three-dimensional structures. This review was written to close the gap.

  13. Redox properties of biscyclopentadienyl uranium(V) imido-halide complexes: a relativistic DFT study.

    Science.gov (United States)

    Elkechai, Aziz; Kias, Farida; Talbi, Fazia; Boucekkine, Abdou

    2014-06-01

    Calculations of ionization energies (IE) and electron affinities (EA) of a series of biscyclopentadienyl imido-halide uranium(V) complexes Cp*2U(=N-2,6-(i)Pr2-C6H3)(X) with X =  F, Cl, Br, and I, related to the U(IV)/U(V) and U(V)/U(VI) redox systems, were carried out, for the first time, using density functional theory (DFT) in the framework of the relativistic zeroth order regular approximation (ZORA) coupled with the conductor-like screening model (COSMO) solvation approach. A very good linear correlation (R(2) =  0.993) was obtained, between calculated ionization energies at the ZORA/BP86/TZP level, and the experimental half-wave oxidation potentials E1/2. A similar linear correlation between the computed electron affinities and the electrochemical reduction U(IV)/U(III) potentials (R(2) =  0.996) is obtained. The importance of solvent effects and of spin-orbit coupling is definitively confirmed. The molecular orbital analysis underlines the crucial role played by the 5f orbitals of the central metal whereas the Nalewajski-Mrozek (N-M) bond indices explain well the bond distances variations following the redox processes. The IE variation of the complexes, i.e., IE(F) uranium charges and E1/2 in the reduction process of the U(V) species.

  14. Electrochemical properties and diffusion of a redox active surfactant incorporated in bicontinuous cubic and lamellar phase

    International Nuclear Information System (INIS)

    Kostela, J.; Elmgren, M.; Almgren, M.

    2005-01-01

    The objective of this study was to investigate the electrochemical behaviour of the divalent redox active surfactant, N-cetyl-N'-methylviologen (CMV), in bicontinuous cubic and lamellar phases. The liquid crystalline phases were prepared from the system glycerolmonooleate (GMO)-water (and brine)-cationic surfactant. A comparison of the phase behaviour of GMO with the monovalent cetyltrimethylammonium bromide (CTAB) and the divalent CMV surfactant showed that the surfactants gave about the same effect at the same surface charge density. The electrochemical measurements were made with a mixture of CTAB and CMV as the surfactant. Cyclic voltammetry was used to study the electrochemistry of CMV incorporated in the cubic and lamellar phases that were spread on a gold electrode. The E 0 -values in the cubic samples were more negative (-0.55 V versus SCE) than in the lamellar samples (-0.53 V versus SCE). This can be explained by the higher charge density in the lamellar phase. The diffusion coefficients were also measured in the cubic phase. The mass transport is slowed down about fifty times in the cubic phase compared to in the pure electrolyte. The concentration dependence on the diffusion coefficient was also investigated. No electron hopping could be observed, which suggest that diffusional movement of the redox probe is the main source of charge transport. By placing the samples on a conducting glass slide, spectroelectrochemical investigations were performed. In the lamellar phase strong dimerization was detected at high concentration of viologen, but much less in the cubic phase

  15. Grain boundary structure and properties

    International Nuclear Information System (INIS)

    Balluffi, R.W.

    1979-01-01

    An attempt is made to distinguish those fundamental aspects of grain boundaries which should be relevant to the problem of the time dependent fracture of high temperature structural materials. These include the basic phenomena which are thought to be associated with cavitation and cracking at grain boundaries during service and with the more general microstructural changes which occur during both processing and service. A very brief discussion of the current state of our knowledge of these fundamentals is given. Included are the following: (1) structure of ideal perfect boundaries; (2) defect structure of grain boundaries; (3) diffusion at grain boundaries; (4) grain boundaries as sources/sinks for point defects; (5) grain boundary migration; (6) dislocation phenomena at grain boundaries; (7) atomic bonding and cohesion at grain boundaries; (8) non-equilibrium properties of grain boundaries; and (9) techniques for studying grain boundaries

  16. Spatial variability in oceanic redox structure 1.8 billion years ago

    DEFF Research Database (Denmark)

    Poulton, Simon W.; Fralick, Philip W.; Canfield, Donald Eugene

    2010-01-01

    to reconstruct oceanic redox conditions from the 1.88- to 1.83-billion-year-old Animikie group from the Superior region, North America. We find that surface waters were oxygenated, whereas at mid-depths, anoxic and sulphidic (euxinic) conditions extended over 100 km from the palaeoshoreline. The spatial extent...

  17. 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

  18. The structural role and homogeneous redox equilibria of iron in peraluminous, metaluminous and peralkaline silicate melts

    Science.gov (United States)

    Dickenson, M. P.; Hess, P. C.

    1986-02-01

    The compositional dependence of the redox ratio (FeO/FeO1.5) has been experimentally determined in K2O-Al2O3-SiO2-Fe2O3-FeO (KASFF) and K2O-CaO-Al2O3-SiO2-Fe2O3-FeO (KCASFF) silicate melts. Compositions were equilibrated at 1,450° C in air, with 78 mol % SiO2. KASFF melts have from 1 to 5 mol % Fe2O3 and include both peraluminous (K2OAl2O3) compositions. KCASFF melts have 1 mol % Fe2O3 encompassing peraluminous, metaluminous (CaO+K2O>Al2O3) and peralkaline compositions. Peralkaline KASFF melts with 1 mol % Fe2O3 have low and constant values for the redox ratio, whereas in peraluminous melts the redox ratio increases with increasing (K2O/Al2O3). Increasing total iron concentration increases the redox ratio in peraluminous melts and slightly decreases the redox ratio in peralkaline melts. Substituting CaO for K2O at fixed total iron (1 mol %) increases the redox ratio in both peraluminous and metaluminous KCASFF melts; however, the redox ratio in peralkaline KCASFF melts is not affected by this exchange. These data indicate that Fe3+ is in four-fold coordination, with K+ or Ca2+ providing local charge balance. The tetrahedral ferric species is most stable in peralkaline melts and least stable in peraluminous melts, due to the competition between Al3+ and Fe3+ for charge balancing cations in the latter melt. Tetrahedral Fe3+ is also less stable when Ca2+ provides local charge balance. The data are consistent with a network modifying role for Fe2+ in the melt. The data are interpreted to reflect the effects of melt composition on the partitioning of K+ and Ca2+ and Fe3+ and Al3+ between various species in the melt. These relationships are discussed in terms of homogeneous equilibria between various iron-bearing and iron-free melt species. The results also reflect the effect of liquid composition on the exchange potentials μFe3+ Al-1 and μCa0.5K-1. The exchange potentials are relatively constant in peralkaline melts, but decrease in metaluminous and peraluminous

  19. Electrochemical properties and diffusion of a redox active surfactant incorporated in bicontinuous cubic and lamellar phase

    Energy Technology Data Exchange (ETDEWEB)

    Kostela, J. [Uppsala University, Department of Physical Chemistry, Box 579, S-75123 Uppsala (Sweden)]. E-mail: johan.kostela@fki.uu.se; Elmgren, M. [Uppsala University, Department of Physical Chemistry, Box 579, S-75123 Uppsala (Sweden); Almgren, M. [Uppsala University, Department of Physical Chemistry, Box 579, S-75123 Uppsala (Sweden)

    2005-05-30

    The objective of this study was to investigate the electrochemical behaviour of the divalent redox active surfactant, N-cetyl-N'-methylviologen (CMV), in bicontinuous cubic and lamellar phases. The liquid crystalline phases were prepared from the system glycerolmonooleate (GMO)-water (and brine)-cationic surfactant. A comparison of the phase behaviour of GMO with the monovalent cetyltrimethylammonium bromide (CTAB) and the divalent CMV surfactant showed that the surfactants gave about the same effect at the same surface charge density. The electrochemical measurements were made with a mixture of CTAB and CMV as the surfactant. Cyclic voltammetry was used to study the electrochemistry of CMV incorporated in the cubic and lamellar phases that were spread on a gold electrode. The E {sup 0}-values in the cubic samples were more negative (-0.55 V versus SCE) than in the lamellar samples (-0.53 V versus SCE). This can be explained by the higher charge density in the lamellar phase. The diffusion coefficients were also measured in the cubic phase. The mass transport is slowed down about fifty times in the cubic phase compared to in the pure electrolyte. The concentration dependence on the diffusion coefficient was also investigated. No electron hopping could be observed, which suggest that diffusional movement of the redox probe is the main source of charge transport. By placing the samples on a conducting glass slide, spectroelectrochemical investigations were performed. In the lamellar phase strong dimerization was detected at high concentration of viologen, but much less in the cubic phase.

  20. Cobalt(II) complexes with azole-pyridine type ligands for non-aqueous redox-flow batteries: Tunable electrochemistry via structural modification

    Science.gov (United States)

    Armstrong, Craig G.; Toghill, Kathryn E.

    2017-05-01

    A single species redox flow battery employing a new class of cobalt(II) complexes with 'tunable' tridentate azole-pyridine type ligands is reported. Four structures were synthesised and their electrochemical, physical and battery characteristics were investigated as a function of successive substitution of the ligand terminal pyridyl donors. The Co(II/I) and Co(III/II) couples are stable and quasi-reversible on gold and glassy carbon electrodes, however redox potentials are tunable allowing the cobalt potential difference to be preferentially increased from 1.07 to 1.91 V via pyridine substitution with weaker σ-donating/π-accepting 3,5-dimethylpyrazole groups. The charge-discharge properties of the system were evaluated using an H-type glass cell and graphite rod electrodes. The complexes delivered high Coulombic efficiencies of 89.7-99.8% and very good voltaic efficiencies of 70.3-81.0%. Consequently, energy efficiencies are high at 63.1-80.8%, marking an improvement on other similar non-aqueous systems. Modification of the ligands also improved solubility from 0.18 M to 0.50 M via pyridyl substitution with 3,5-dimethylpyrazole, though the low solubility of the complexes limits the overall energy capacity to between 2.58 and 12.80 W h L-1. Preliminary flow cell studies in a prototype flow cell are also demonstrated.

  1. Quasicrystals Structure and Physical Properties

    CERN Document Server

    Trebin, Hans-Rainer

    2003-01-01

    A comprehensive and up-to-date review, covering the broad range of this outstanding class of materials among intermetallic alloys. Starting with metallurgy and characterization, the authors continue on to structure and mathematical modeling. They use this basis to move on to dealing with electronic, magnetic, thermal, dynamic and mechanical properties, before finally providing an insight into surfaces and thin films. The authors belong to a research program on quasicrystals, sponsored by the German Research Society and managed by Hans-Rainer Trebin, such that most of the latest results are pre

  2. Lipid peroxidation regulates podocyte migration and cytoskeletal structure through redox sensitive RhoA signaling

    Directory of Open Access Journals (Sweden)

    Claudia Kruger

    2018-06-01

    Full Text Available Early podocyte loss is characteristic of chronic kidney diseases (CKD in obesity and diabetes. Since treatments for hyperglycemia and hypertension do not prevent podocyte loss, there must be additional factors causing podocyte depletion. The role of oxidative stress has been implicated in CKD but it is not known how exactly free radicals affect podocyte physiology. To assess this relationship, we investigated the effects of lipid radicals on podocytes, as lipid peroxidation is a major form of oxidative stress in diabetes. We found that lipid radicals govern changes in podocyte homeostasis through redox sensitive RhoA signaling: lipid radicals inhibit migration and cause loss of F-actin fibers. These effects were prevented by mutating the redox sensitive cysteines of RhoA. We therefore suggest that in diseases associated with increased lipid peroxidation, lipid radicals can determine podocyte function with potentially pathogenic consequences for kidney physiology. Keywords: Lipid peroxidation, Reactive lipids, Podocyte, RhoA, Cysteine, Chronic kidney disease

  3. Redox equilibria and the structural role of iron in alumino-silicate melts

    Science.gov (United States)

    Dickenson, M. P.; Hess, P. C.

    1982-01-01

    The relationship between the redox ratio Fe+2/(Fe+2+Fe+3) and the K2O/(K2O + Al2O3) ratio (K2O*) were experimentally investigated in silicate melts with 78 mol% SiO2 in the system SiO2-Al2O3-K2O-FeO-Fe2O3, in air at 1,400° C. Quenched glass compositions were analyzed by electron microprobe and wet chemical microtitration techniques. Minimum values of the redox ratio were obtained at K2O*≈0.5. The redox ratio in peralkaline melts (K2O*>0.5) increases slightly with K2O* whereas this ratio increases dramatically in peraluminous melts (K2O*<0.5) as K2O is replaced by Al2O3. These data indicate that all Fe+3 (and Al+3) occur as tetrahedral species charge balanced with K+ in peralkaline melts. In peraluminous melts, Fe+3 (and Al+3) probably occur as both tetrahedral species using Fe+2 as a charge-balancing cation and as network-modifying cations associated with non-bridging oxygen.

  4. A cell for extended x-ray absorption fine structure studies of oxygen sensitive products of redox reactions

    International Nuclear Information System (INIS)

    Furenlid, L.R.; Renner, M.W.; Fajer, J.

    1990-01-01

    We describe a cell suitable for extended x-ray absorption fine structure (EXAFS) studies of oxygen and/or water sensitive products of redox reactions. The cell utilizes aluminized Mylar windows that are transparent to x rays, provide low gas permeability, and allow vacuum to be maintained in the cell. The windows are attached to the glassware with an epoxy that resists attack by common organic solvents. Additional side arms allow multiple spectroscopic probes of the same sample under anaerobic and anhydrous conditions

  5. The Analgesic Acetaminophen and the Antipsychotic Clozapine Can Each Redox-Cycle with Melanin.

    Science.gov (United States)

    Temoçin, Zülfikar; Kim, Eunkyoung; Li, Jinyang; Panzella, Lucia; Alfieri, Maria Laura; Napolitano, Alessandra; Kelly, Deanna L; Bentley, William E; Payne, Gregory F

    2017-12-20

    Melanins are ubiquitous but their complexity and insolubility has hindered characterization of their structures and functions. We are developing electrochemical reverse engineering methodologies that focus on properties and especially on redox properties. Previous studies have shown that melanins (i) are redox-active and can rapidly and repeatedly exchange electrons with diffusible oxidants and reductants, and (ii) have redox potentials in midregion of the physiological range. These properties suggest the functional activities of melanins will depend on their redox context. The brain has a complex redox context with steep local gradients in O 2 that can promote redox-cycling between melanin and diffusible redox-active chemical species. Here, we performed in vitro reverse engineering studies and report that melanins can redox-cycle with two common redox-active drugs. Experimentally, we used two melanin models: a convenient natural melanin derived from cuttlefish (Sepia melanin) and a synthetic cysteinyldopamine-dopamine core-shell model of neuromelanin. One drug, acetaminophen (APAP), has been used clinically for over a century, and recent studies suggest that low doses of APAP can protect the brain from oxidative-stress-induced toxicity and neurodegeneration, while higher doses can have toxic effects in the brain. The second drug, clozapine (CLZ), is a second generation antipsychotic with polypharmacological activities that remain incompletely understood. These in vitro observations suggest that the redox activities of drugs may be relevant to their modes-of-action, and that melanins may interact with drugs in ways that affect their activities, metabolism, and toxicities.

  6. Electronic, Magnetic, and Redox Properties of [MFe(3)S(4)] Clusters (M = Cd, Cu, Cr) in Pyrococcus furiosus Ferredoxin.

    Science.gov (United States)

    Staples, Christopher R.; Dhawan, Ish K.; Finnegan, Michael G.; Dwinell, Derek A.; Zhou, Zhi Hao; Huang, Heshu; Verhagen, Marc F. J. M.; Adams, Michael W. W.; Johnson, Michael K.

    1997-12-03

    The ground- and excited-state properties of heterometallic [CuFe(3)S(4)](2+,+), [CdFe(3)S(4)](2+,+), and [CrFe(3)S(4)](2+,+) cubane clusters assembled in Pyrococcus furiosus ferredoxin have been investigated by the combination of EPR and variable-temperature/variable-field magnetic circular dichroism (MCD) studies. The results indicate Cd(2+) incorporation into [Fe(3)S(4)](0,-) cluster fragments to yield S = 2 [CdFe(3)S(4)](2+) and S = (5)/(2) [CdFe(3)S(4)](+) clusters and Cu(+) incorporation into [Fe(3)S(4)](+,0) cluster fragments to yield S = (1)/(2) [CuFe(3)S(4)](2+) and S = 2 [CuFe(3)S(4)](+) clusters. This is the first report of the preparation of cubane type [CrFe(3)S(4)](2+,+) clusters, and the combination of EPR and MCD results indicates S = 0 and S = (3)/(2) ground states for the oxidized and reduced forms, respectively. Midpoint potentials for the [CdFe(3)S(4)](2+,+), [CrFe(3)S(4)](2+,+), and [CuFe(3)S(4)](2+,+) couples, E(m) = -470 +/- 15, -440 +/- 10, and +190 +/- 10 mV (vs NHE), respectively, were determined by EPR-monitored redox titrations or direct electrochemistry at a glassy carbon electrode. The trends in redox potential, ground-state spin, and electron delocalization of [MFe(3)S(4)](2+,+) clusters in P. furiosus ferredoxin are discussed as a function of heterometal (M = Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Tl).

  7. Effective electrochemical method for investigation of hemoglobin unfolding based on the redox property of heme groups at glassy carbon electrodes.

    Science.gov (United States)

    Li, Xianchan; Zheng, Wei; Zhang, Limin; Yu, Ping; Lin, Yuqing; Su, Lei; Mao, Lanqun

    2009-10-15

    This study demonstrates a facile and effective electrochemical method for investigation of hemoglobin (Hb) unfolding based on the electrochemical redox property of heme groups in Hb at bare glassy carbon (GC) electrodes. In the native state, the heme groups are deeply buried in the hydrophobic pockets of Hb with a five-coordinate high-spin complex and thus show a poor electrochemical property at bare GC electrodes. Upon the unfolding of Hb induced by the denaturant of guanidine hydrochloride (GdnHCl), the fifth coordinative bond between the heme groups and the residue of the polypeptides (His-F8) is broken, and as a result, the heme groups initially buried deeply in the hydrophobic pockets dissociate from the polypeptide chains and are reduced electrochemically at GC electrodes, which can be used to probe the unfolding of Hb. The results on the GdnHCl-induced Hb unfolding obtained with the electrochemical method described here well coincide with those studied with other methods, such as UV-vis spectroscopy, fluorescence, and circular dichroism. The application of the as-established electrochemical method is illustrated to study the kinetics of GdnHCl-induced Hb unfolding, the GdnHCl-induced unfolding of another kind of hemoprotein, catalase, and the pH-induced Hb unfolding/refolding.

  8. Pyrene Molecular Orbital Shuffle-Controlling Excited State and Redox Properties by Changing the Nature of the Frontier Orbitals.

    Science.gov (United States)

    Merz, Julia; Fink, Julian; Friedrich, Alexandra; Krummenacher, Ivo; Al Mamari, Hamad H; Lorenzen, Sabine; Haehnel, Martin; Eichhorn, Antonius; Moos, Michael; Holzapfel, Marco; Braunschweig, Holger; Lambert, Christoph; Steffen, Andreas; Ji, Lei; Marder, Todd B

    2017-09-21

    We show that by judicious choice of substituents at the 2- and 7-positions of pyrene, the frontier orbital order of pyrene can be modified, giving enhanced control over the nature and properties of the photoexcited states and the redox potentials. Specifically, we introduced a julolidine-like moiety and Bmes 2 (mes=2,4,6-Me 3 C 6 H 2 ) as very strong donor (D) and acceptor (A), respectively, giving 2,7-D-π-D- and unsymmetric 2,7-D-π-A-pyrene derivatives, in which the donor destabilizes the HOMO-1 and the acceptor stabilizes the LUMO+1 of the pyrene core. Consequently, for 2,7-substituted pyrene derivatives, unusual properties are obtained. For example, very large bathochromic shifts were observed for all of our compounds, and unprecedented green light emission occurs for the D/D system. In addition, very high radiative rate constants in solution and in the solid state were recorded for the D-π-D- and D-π-A-substituted compounds. All compounds show reversible one-electron oxidations, and Jul 2 Pyr exhibits a second oxidation, with the largest potential splitting (ΔE=440 mV) thus far reported for 2,7-substituted pyrenes. Spectroelectrochemical measurements confirm an unexpectedly strong coupling between the 2,7-substituents in our pyrene derivatives. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Cellulose nanomaterials review: structure, properties and nanocomposites

    Science.gov (United States)

    Robert J. Moon; Ashlie Martini; John Nairn; John Simonsen; Jeff Youngblood

    2011-01-01

    This critical review provides a processing-structure-property perspective on recent advances in cellulose nanoparticles and composites produced from them. It summarizes cellulose nanoparticles in terms of particle morphology, crystal structure, and properties. Also described are the self-assembly and rheological properties of cellulose nanoparticle suspensions. The...

  10. Flexible strategy for immobilizing redox-active compounds using in situ generation of diazonium salts. Investigations of the blocking and catalytic properties of the layers.

    Science.gov (United States)

    Noël, Jean-Marc; Sjöberg, Béatrice; Marsac, Rémi; Zigah, Dodzi; Bergamini, Jean-François; Wang, Aifang; Rigaut, Stéphane; Hapiot, Philippe; Lagrost, Corinne

    2009-11-03

    A versatile two-step method is developed to covalently immobilize redox-active molecules onto carbon surfaces. First, a robust anchoring platform is grafted onto surfaces by electrochemical reduction of aryl diazonium salts in situ generated. Depending on the nature of the layer termini, -COOH or -NH(2), a further chemical coupling involving ferrocenemethylamine or ferrocene carboxylic acid derivatives leads to the covalent binding of ferrocene centers. The chemical strategy using acyl chloride activation is efficient and flexible, since it can be applied either to surface-reactive end groups or to reactive species in solution. Cyclic voltammetry analyses point to the covalent binding of ferrocene units restricted to the upper layers of the underlying aryl films, while AFM measurements show a lost of compactness of the layers after the chemical attachment of ferrocene centers. The preparation conditions of the anchoring layers were found to determine the interfacial properties of the resulted ferrocenyl-modified electrodes. The ferrocene units promoted effective redox mediation providing that the free redox probes are adequately chosen (i.e., vs size/formal potential) and the underlying layers exhibit strong blocking properties. For anchoring films with weaker blocking effect, the coexistence of two distinct phenomena, redox mediation and ET at pinholes could be evidenced.

  11. Predicting the Kinetic Properties Associated with Redox Imbalance after Oxidative Crisis in G6PD-Deficient Erythrocytes: A Simulation Study

    Directory of Open Access Journals (Sweden)

    Hanae Shimo

    2011-01-01

    Full Text Available It is well known that G6PD-deficient individuals are highly susceptible to oxidative stress. However, the differences in the degree of metabolic alterations among patients during an oxidative crisis have not been extensively studied. In this study, we applied mathematical modeling to assess the metabolic changes in erythrocytes of various G6PD-deficient patients during hydrogen peroxide- (H2O2- induced perturbation and predict the kinetic properties that elicit redox imbalance after exposure to an oxidative agent. Simulation results showed a discrepancy in the ability to restore regular metabolite levels and redox homeostasis among patients. Two trends were observed in the response of redox status (GSH/GSSG to oxidative stress, a mild decrease associated with slow recovery and a drastic decline associated with rapid recovery. The former was concluded to apply to patients with severe clinical symptoms. Low max and high mG6P of G6PD were shown to be kinetic properties that enhance consequent redox imbalance.

  12. 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.

  13. The influence of the Cys46/Cys55 disulfide bond on the redox and spectroscopic properties of human neuroglobin.

    Science.gov (United States)

    Bellei, Marzia; Bortolotti, Carlo Augusto; Di Rocco, Giulia; Borsari, Marco; Lancellotti, Lidia; Ranieri, Antonio; Sola, Marco; Battistuzzi, Gianantonio

    2018-01-01

    Neuroglobin is a monomeric globin containing a six-coordinate heme b, expressed in the nervous system, which exerts an important neuroprotective role. In the human protein (hNgb), Cys46 and Cys55 form an intramolecular disulfide bond under oxidizing conditions, whose cleavage induces a helix-to-strand rearrangement of the CD loop that strengthens the bond between the heme iron and the distal histidine. Hence, it is conceivable that the intramolecular disulfide bridge modulates the functionality of human neuroglobin by controlling exogenous ligand binding. In this work, we investigated the influence of the Cys46/Cys55 disulfide bond on the redox properties and on the pH-dependent conformational equilibria of hNgb, using UV-vis spectroelectrochemistry, cyclic voltammetry, electronic absorption spectroscopy and magnetic circular dichroism (MCD). We found that the SS bridge significantly affects the heme Fe(III) to Fe(II) reduction enthalpy (ΔH°' rc ) and entropy (ΔS°' rc ), mostly as a consequence of changes in the reduction-induced solvent reorganization effects, without affecting the axial ligand-binding interactions and the polarity and electrostatics of the heme environment. Between pH3 and 12, the electronic properties of the heme of ferric hNgb are sensitive to five acid-base equilibria, which are scarcely affected by the Cys46/Cys55 disulfide bridge. The equilibria occurring at extreme pH values induce heme release, while those occurring between pH5 and 10 alter the electronic properties of the heme without modifying its axial coordination and low spin state. They involve the sidechains of non-coordinating aminoacids close to the heme and at least one heme propionate. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. The iron member of the CPO-27 coordination polymer series: Synthesis, characterization, and intriguing redox properties

    DEFF Research Database (Denmark)

    Märcz, Matthias; Johnsen, Rune; Dietzel, Pascal D.C.

    2012-01-01

    The microporous coordination polymer CPO-27-Fe was synthesized from iron salts and 2,5-dihydroxyterephthalic acid by microwave assisted solvothermal synthesis. The crystal structures of the as-synthesized compounds were determined by Rietveld refinement from powder X-ray diffraction data using...

  15. Electrochemical properties of Sn/C nanoparticles fabricated by redox treatment and pulsed wire evaporation method

    Science.gov (United States)

    Song, Ju-Seok; Cho, Gyu-Bong; Ahn, Jou-Hyeon; Cho, Kwon-Koo

    2017-09-01

    Tin (Sn) based anode materials are the most promising anode materials for lithium-ion batteries due to their high theoretical capacity corresponding to the formation of Li4.4Sn composition (Li4.4Sn, 994 mAh/g). However, the applications of tin based anodes to lithium-ion battery system are generally limited by a large volume change (>260%) during lithiation and delithiation cycle, which causes pulverize and poor cycling stability. In order to overcome this shortcoming, we fabricate a Sn/C nanoparticle with a yolk-shell structure (Sn/void/C) by using pulsed wire evaporation process and oxidation/reduction heat treatment. Sn nanoparticles are encapsulated by a conductive carbon layer with structural buffer that leaves enough room for expansion and contraction during lithium insertion/desertion. We expect that the yolk-shell structure has the ability to accommodate the volume changes of tin and leading to an improved cycle performance. The Sn/Void/C anode with yolk-shell structure shows a high specific capacity of 760 mAh/g after 50 cycles.

  16. Challenges in computational evaluation of redox and magnetic properties of Fe-based sulfate cathode materials of Li- and Na-ion batteries

    Science.gov (United States)

    Shishkin, Maxim; Sato, Hirofumi

    2017-06-01

    Several Fe-based sulfates have been proposed recently as cathode materials characterized by a high average operating voltage (i.e. Li2Fe(SO4)2 and Na2Fe2(SO4)3) or low fabrication temperature (e.g. Na2Fe(SO4)2·2H2O)). In this work, we apply three methods to evaluate the redox potentials and magnetic properties of these materials: (1) local density functional theory (DFT) in Perdew-Burke-Ernzerhof parametrization; (2) rotationally invariant DFT  +  U and (3) DFT  +  U with magnetic exchange, suggested herein. The U parameters used for DFT  +  U calculations have been evaluated by using a linear response method (this applies to DFT  +  U as well as DFT  +  U calculations with a magnetic exchange term). Moreover, we have performed adjustments of U and, for the case of magnetic exchange, J parameters, to find better agreement with experimental measurements of redox and magnetic properties. We find that a self-consistent DFT  +  U/linear response approach yields quite overestimated redox potentials as compared to experiment. On the other hand, we also show that DFT  +  U calculations are not capable of providing a reasonably accurate description of both redox and magnetic properties for the case of Li2Fe(SO4)2, even when adjusted U parameters are employed. As a solution, we demonstrate that a DFT  +  U methodology augmented by a magnetic exchange term potentially provides more precise values for both the redox potentials and the magnetic moments of the Fe ions in the studied materials. Thus our work shows that for a more accurate description of redox and magnetic properties, further extensions of the DFT  +  U method, such as inclusion of the contribution of magnetic exchange, should be considered.

  17. Challenges in computational evaluation of redox and magnetic properties of Fe-based sulfate cathode materials of Li- and Na-ion batteries

    International Nuclear Information System (INIS)

    Shishkin, Maxim; Sato, Hirofumi

    2017-01-01

    Several Fe-based sulfates have been proposed recently as cathode materials characterized by a high average operating voltage (i.e. Li 2 Fe(SO 4 ) 2 and Na 2 Fe 2 (SO 4 ) 3 ) or low fabrication temperature (e.g. Na 2 Fe(SO 4 ) 2 ·2H 2 O)). In this work, we apply three methods to evaluate the redox potentials and magnetic properties of these materials: (1) local density functional theory (DFT) in Perdew–Burke–Ernzerhof parametrization; (2) rotationally invariant DFT  +   U ; and (3) DFT  +   U with magnetic exchange, suggested herein. The U parameters used for DFT  +   U calculations have been evaluated by using a linear response method (this applies to DFT  +   U as well as DFT  +   U calculations with a magnetic exchange term). Moreover, we have performed adjustments of U and, for the case of magnetic exchange, J parameters, to find better agreement with experimental measurements of redox and magnetic properties. We find that a self-consistent DFT  +   U /linear response approach yields quite overestimated redox potentials as compared to experiment. On the other hand, we also show that DFT  +   U calculations are not capable of providing a reasonably accurate description of both redox and magnetic properties for the case of Li 2 Fe(SO 4 ) 2 , even when adjusted U parameters are employed. As a solution, we demonstrate that a DFT  +   U methodology augmented by a magnetic exchange term potentially provides more precise values for both the redox potentials and the magnetic moments of the Fe ions in the studied materials. Thus our work shows that for a more accurate description of redox and magnetic properties, further extensions of the DFT  +   U method, such as inclusion of the contribution of magnetic exchange, should be considered. (paper)

  18. Structural property of platinum mononitride

    International Nuclear Information System (INIS)

    Yu, L.H.; Yao, K.L.; Liu, Z.L.; Zhang, Y.S.

    2007-01-01

    The structural stability and pressure-induced structural phase transition of platinum mononitride (PtN), as well as its electronic structure, were studied using the full potential augmented plane wave plus local orbitals method with the generalized gradient approximation (GGA) exchange-correlation functional. The total energy calculations show that the optimized wurtzite structure is most stable energetically among four structures: zinc blende, rocksalt, CsCl and wurtzite, which reveals the platinum mononitride PtN perhaps crystallizes in the wurtzite structure; the pressure of phase transition from wurtzite to rocksalt is predicted to be 41.4 GPa.The calculated bulk modulus of the wurtzite structure is 99.41 GPa, which is smaller than that of the other three structures and face-centered cubic Pt. The band structure calculations show wurtzite PtN is metallic

  19. Probing the chemistry, electronic structure and redox energetics in pentavalent organometallic actinide complexes

    Energy Technology Data Exchange (ETDEWEB)

    Graves, Christopher R [Los Alamos National Laboratory; Vaughn, Anthony E [Los Alamos National Laboratory; Morris, David E [Los Alamos National Laboratory; Kiplinger, Jaqueline L [Los Alamos National Laboratory

    2008-01-01

    Complexes of the early actinides (Th-Pu) have gained considerable prominence in organometallic chemistry as they have been shown to undergo chemistries not observed with their transition- or lanthanide metal counterparts. Further, while bonding in f-element complexes has historically been considered to be ionic, the issue of covalence remains a subject of debate in the area of actinide science, and studies aimed at elucidating key bonding interactions with 5f-orbitals continue to garner attention. Towards this end, our interests have focused on the role that metal oxidation state plays in the structure, reactivity and spectral properties of organouranium complexes. We report our progress in the synthesis of substituted U{sup V}-imido complexes using various routes: (1) Direct oxidation of U{sup IV}-imido complexes with copper(I) salts; (2) Salt metathesis with U{sup V}-imido halides; (3) Protonolysis and insertion of an U{sup V}-imido alkyl or aryl complex with H-N{double_bond}CPh{sub 2} or N{triple_bond}C-Ph, respectively, to form a U{sup V}-imido ketimide complex. Further, we report and compare the crystallographic, electrochemical, spectroscopic and magnetic characterization of the pentavalent uranium (C{sub 5}Me{sub 5}){sub 2}U({double_bond}N-Ar)(Y) series (Y = OTf, SPh, C{triple_bond}C-Ph, NPh{sub 2}, OPh, N{double_bond}CPh{sub 2}) to further interrogate the molecular, electronic, and magnetic structures of this new class of uranium complexes.

  20. Studies of Catalytic Properties of Inorganic Rock Matrices in Redox Reactions

    Directory of Open Access Journals (Sweden)

    Nikolay M. Dobrynkin

    2017-09-01

    Full Text Available Intrinsic catalytic properties of mineral matrices of various kinds (basalts, clays, sandstones were studied, which are of interest for in-situ heavy oil upgrading (i.e., underground to create advanced technologies for enhanced oil recovery. The elemental, surface and phase composition and matrix particle morphology, surface and acidic properties were studied using elemental analysis, X-ray diffraction, adsorption and desorption of nitrogen and ammonia. The data on the catalytic activity of inorganic matrices in ammonium nitrate decomposition (reaction with a large gassing, oxidation of hydrocarbons and carbon monoxide, and hydrocracking of asphaltenes into maltenes (the conversion of heavy hydrocarbons into more valuable light hydrocarbons were discussed. In order to check their applicability for the asphaltenes hydrocracking catalytic systems development, basalt and clay matrices were used as supports for iron/basalt, nickel/basalt and iron/clay catalysts. The catalytic activity of the matrices in the reactions of the decomposition of ammonium nitrate, oxidation of hydrocarbons and carbon monoxide, and hydrocracking of asphaltens was observed for the first time.

  1. Structure and stability of hexa-aqua V(III) cations in vanadium redox flow battery electrolytes.

    Science.gov (United States)

    Vijayakumar, M; Li, Liyu; Nie, Zimin; Yang, Zhenguo; Hu, JianZhi

    2012-08-07

    The vanadium(III) cation structure in mixed acid based electrolyte solution from vanadium redox flow batteries is studied by (17)O and (35/37)Cl nuclear magnetic resonance (NMR) spectroscopy, electronic spectroscopy and density functional theory (DFT) based computational modelling. Both computational and experimental results reveal that the V(III) species can complex with counter anions (sulfate/chlorine) depending on the composition of its solvation sphere. By analyzing the powder precipitate it was found that the formation of sulfate complexed V(III) species is the crucial process in the precipitation reaction. The precipitation occurs through nucleation of neutral species formed through deprotonation and ion-pair formation process. However, the powder precipitate shows a multiphase nature which warrants multiple reaction pathways for precipitation reaction.

  2. Structures and properties of anionic clay minerals

    International Nuclear Information System (INIS)

    Koch, Chr. Bender

    1998-01-01

    The Moessbauer spectra of pyroaurite-sjoegrenite-type compounds (PTC) (layered anion exchangers) are discussed with reference to the crystal structure, cation order, and crystallite morphology. It is shown that cation-ordered layers are produced in the synthesis of carbonate and sulphate types of green rust. In contrast, synthetic and natural pyroaurite only occurs as disordered types. The redox chemistry of Fe(III) within the metal hydroxide layer is illustrated with examples of electrochemical oxidation and reversible reduction by boiling glycerol. The chemistry of iron in the interlayer is exemplified by the intercalation of Fe-cyanide complexes in hydrotalcite. This reaction may be used as a probe for the charge distribution in the interlayer

  3. Structural and dynamical properties of Yukawa balls

    International Nuclear Information System (INIS)

    Block, D; Kroll, M; Arp, O; Piel, A; Kaeding, S; Ivanov, Y; Melzer, A; Henning, C; Baumgartner, H; Ludwig, P; Bonitz, M

    2007-01-01

    To study the structural and dynamical properties of finite 3D dust clouds (Yukawa balls) new diagnostic tools have been developed. This contribution describes the progress towards 3D diagnostics for measuring the particle positions. It is shown that these diagnostics are capable of investigating the structural and dynamical properties of Yukawa balls and gaining insight into their basic construction principles

  4. Structural relaxation: low temperature properties

    International Nuclear Information System (INIS)

    Cruz, F. de la

    1984-01-01

    We discuss the changes in transport and superconducting properties of amorphous Zr 70 Cu 30 , induced by thermal relaxation. The experimental results are used to investigate the relation between the microscopic parameters and the observed physical properties. It is shown that the density of eletronic states determines the shift Tc as well as the variation of the electrical resistivity. It is necessary to assume strong hybridization between s and d bands to understand the eletrodynamic response of the superconductor. (Author) [pt

  5. Structure, processing, and properties of potatoes

    Science.gov (United States)

    Lloyd, Isabel K.; Kolos, Kimberly R.; Menegaux, Edmond C.; Luo, Huy; McCuen, Richard H.; Regan, Thomas M.

    1992-06-01

    The objective of this experiment and lesson intended for high school students in an engineering or materials science course or college freshmen is to demonstrate the relation between processing, structure, and thermodynamic and physical properties. The specific objectives are to show the effect of structure and structural changes on thermodynamic properties (specific heat) and physical properties (compressive strength); to illustrate the first law of thermodynamics; to compare boiling a potato in water with cooking it in a microwave in terms of the rate of structural change and the energy consumed to 'process' the potato; and to demonstrate compression testing.

  6. Structure, processing, and properties of potatoes

    Science.gov (United States)

    Lloyd, Isabel K.; Kolos, Kimberly R.; Menegaux, Edmond C.; Luo, Huy; Mccuen, Richard H.; Regan, Thomas M.

    1992-01-01

    The objective of this experiment and lesson intended for high school students in an engineering or materials science course or college freshmen is to demonstrate the relation between processing, structure, and thermodynamic and physical properties. The specific objectives are to show the effect of structure and structural changes on thermodynamic properties (specific heat) and physical properties (compressive strength); to illustrate the first law of thermodynamics; to compare boiling a potato in water with cooking it in a microwave in terms of the rate of structural change and the energy consumed to 'process' the potato; and to demonstrate compression testing.

  7. Electrochemical properties of porous carbon black layer as an electron injector into iodide redox couple

    International Nuclear Information System (INIS)

    Kim, Jung-Min; Rhee, Shi-Woo

    2012-01-01

    Highlights: ► Carbon black (CB) porous layer for triiodide (I 3 − ) ion reduction is coated with spray coating method at 120 °C on the fluorine-doped tin oxide glass. ► The electrochemical impedance spectroscopy is analyzed for a symmetric cell and a new circuit model is applied to identify electrochemical parameters. ► Decreased particle size and increased thickness improve the catalytic activity because of the increase in the surface area and the conductivity of the CB layer. - Abstract: Electrochemical properties of carbon black (CB) porous layer as a counter electrode in dye-sensitized solar cells (DSC) are studied. CB electrode for triiodide (I 3 − ) ion reduction is coated with spray coating method on the fluorine-doped tin oxide glass at 120 °C. The CB particle size is varied from 20 nm to 90 nm and the CB electrode thickness is controlled from 1 μm to 9 μm by controlling the spraying time. The electrochemical impedance spectroscopy is analyzed for a symmetric cell and a new circuit model is applied to identify electrochemical parameters. As the CB particle size is decreased, the catalytic activity is improved because of the increase in the surface area and the conductivity of the CB layer. Increased CB electrode thickness also improves the catalytic activity and leads to the low charge transfer resistance at the electrolyte/CB electrode interface. The CB counter electrode with the particle size of 20 nm and the thickness of 9 μm for DSC shows the energy conversion efficiency of 7.2% with the highest fill factor (FF) of 65.6%, which is similar to the Pt counter electrode with FF of 65.8% and the efficiency of 7.6%.

  8. Steric/π-electronic insulation of the carbo-benzene ring: dramatic effects of tert-butyl vs phenyl crowns on geometric, chromophoric, redox and magnetic properties.

    Science.gov (United States)

    Listunov, Dymytrii; Duhayon, Carine; Poater, Albert; Mazères, Serge; Saquet, Alix; Maraval, Valérie; Chauvin, Remi

    2018-04-13

    Hexa-tert-butyl-carbo-benzene C18tBu6 and three phenylated counterparts C18tBumPh6-m (m = 4, 2) have been synthesized. The peralkylated version (m = 6) provides experimental access to intrinsic features of the insulated C18 core independently from the influence of π-conjugated substituent. Over the series, structural, spectroscopical and electrochemical properties are compared with those of the hexaphenylated reference (m = 0). Anchoring tBu substituents at the C18 macrocycle is shown to enhance stability and solubility, and to dramatically modify UV-vis absorption and redox properties. Whereas all the carbo-benzenes reported hitherto were obtained as dark-reddish/greenish solids, crystals and solutions of C18tBu6 happen to be yellow (max = 379 nm vs 472 nm for C18Ph6). By comparison to C18Ph6, reduction of C18tBu6 remains reversible but occurs at a twice higher absolute potential (E1/2 = -1.36 V vs -0.72 V). Systematic X-ray diffraction analyses and DFT calculations show that the C18 ring symmetry is the nearest to D6h for m = 6, indicating a maximum geometrical aromaticity. According to calculated nucleus independent chemical shifts, the macrocyclic magnetic aromaticity is also found to be maximum for C18tBu6: NICS(0)=-17.2 ppm, vs -18.0±0.1 ppm for the theoretical references C18H6 and C18F6, and -13.5 ppm for C18Ph6. Accurate correlations of NICS(0) with experimental or calculated maximum UV-vis absorption wavelength max and chemical hardness =ELUMO-EHOMO are evidenced. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Intermetallics structures, properties, and statistics

    CERN Document Server

    Steurer, Walter

    2016-01-01

    The focus of this book is clearly on the statistics, topology, and geometry of crystal structures and crystal structure types. This allows one to uncover important structural relationships and to illustrate the relative simplicity of most of the general structural building principles. It also allows one to show that a large variety of actual structures can be related to a rather small number of aristotypes. It is important that this book is readable and beneficial in the one way or another for everyone interested in intermetallic phases, from graduate students to experts in solid-state chemistry/physics/materials science. For that purpose it avoids using an enigmatic abstract terminology for the classification of structures. The focus on the statistical analysis of structures and structure types should be seen as an attempt to draw the background of the big picture of intermetallics, and to point to the white spots in it, which could be worthwhile exploring. This book was not planned as a textbook; rather, it...

  10. First-principles investigation of optoelectronic and redox properties of (Ta1-xNbx)ON compounds for photocatalysis

    KAUST Repository

    Harb, Moussab

    2015-01-01

    We investigate essential fundamental properties of monoclinic (Ta1-xNbx)ON (x = 0.0625, 0.125, 0.25, and 0.5) solid solution semiconductor materials for water splitting using first-principles computations on the basis of density functional theory (DFT) and density functional perturbation theory (DFPT) using the PBE and HSE06 functionals. The formation energies, band gaps, UV-vis optical absorption coefficients, dielectric constants, charge carrier effective masses, and band edge energy positions of these compounds are evaluated. Similarly to TaON, our calculations reveal strongly 3D delocalized characters of the band edge electronic states through the crystal lattices, high dielectric constants, small hole effective masses along the [001] direction, and small electron effective masses along the [100] direction. This leads to good exciton dissociation ability into free charge carriers, good hole mobility along the [001] direction, and good electron mobility along the [100] direction. The main difference, however, is related to their band edge positions with respect to water redox potentials. TaON with a calculated band gap energy of 3.0 eV is predicted as a good candidate for water oxidation and O2 evolution while the (Ta1-xNbx)ON materials (for 0.25 ≤ x ≤ 0.5) with calculated band gap energies between 2.8 and 2.9 eV reveal suitable band edge positions for water oxidation and H+ reduction. These results offer a grand opportunity for these compounds to be properly synthesized and tested for solar-driven overall water-splitting reactions.

  11. First-principles investigation of optoelectronic and redox properties of (Ta1-xNbx)ON compounds for photocatalysis

    KAUST Repository

    Harb, Moussab

    2015-03-05

    We investigate essential fundamental properties of monoclinic (Ta1-xNbx)ON (x = 0.0625, 0.125, 0.25, and 0.5) solid solution semiconductor materials for water splitting using first-principles computations on the basis of density functional theory (DFT) and density functional perturbation theory (DFPT) using the PBE and HSE06 functionals. The formation energies, band gaps, UV-vis optical absorption coefficients, dielectric constants, charge carrier effective masses, and band edge energy positions of these compounds are evaluated. Similarly to TaON, our calculations reveal strongly 3D delocalized characters of the band edge electronic states through the crystal lattices, high dielectric constants, small hole effective masses along the [001] direction, and small electron effective masses along the [100] direction. This leads to good exciton dissociation ability into free charge carriers, good hole mobility along the [001] direction, and good electron mobility along the [100] direction. The main difference, however, is related to their band edge positions with respect to water redox potentials. TaON with a calculated band gap energy of 3.0 eV is predicted as a good candidate for water oxidation and O2 evolution while the (Ta1-xNbx)ON materials (for 0.25 ≤ x ≤ 0.5) with calculated band gap energies between 2.8 and 2.9 eV reveal suitable band edge positions for water oxidation and H+ reduction. These results offer a grand opportunity for these compounds to be properly synthesized and tested for solar-driven overall water-splitting reactions.

  12. Structures and properties of spatially distorted porphyrins

    International Nuclear Information System (INIS)

    Golubchikov, Oleg A; Kuvshinova, Elizaveta M; Pukhovskaya, Svetlana G

    2005-01-01

    The published data on the structures and properties of porphyrins with distorted aromatic macrocycles are generalised and analysed. Data on the crystal structures, spectra and kinetics of formation and dissociation of their coordination derivatives are summarised. It is demonstrated that the distortion of the planar structure of the tetrapyrrole core is one of the most efficient means of controlling spectral, physicochemical and coordination properties of these compounds.

  13. Insights in the electronic structure and redox reaction energy in LiFePO4 battery material from an accurate Tran-Blaha modified Becke Johnson potential

    International Nuclear Information System (INIS)

    Araujo, Rafael B.; Almeida, J. de S; Ferreira da Silva, A.; Ahuja, Rajeev

    2015-01-01

    The main goals of this paper are to investigate the accuracy of the Tran-Blaha modified Becke Johnson (TB-mBJ) potential to predict the electronic structure of lithium iron phosphate and the related redox reaction energy with the lithium deintercalation process. The computed electronic structures show that the TB-mBJ method is able to partially localize Fe-3d electrons in LiFePO 4 and FePO 4 which usually is a problem for the generalized gradient approximation (GGA) due to the self interaction error. The energy band gap is also improved by the TB-mBJ calculations in comparison with the GGA results. It turned out, however, that the redox reaction energy evaluated by the TB-mBJ technique is not in good agreement with the measured one. It is speculated that this disagreement in the computed redox energy and the experimental value is due to the lack of a formal expression to evaluate the exchange and correlation energy. Therefore, the TB-mBJ is an efficient method to improve the prediction of the electronic structures coming form the standard GGA functional in LiFePO 4 and FePO 4 . However, it does not appear to have the same efficiency for evaluating the redox reaction energies for the investigated system

  14. Silicon nanowires: structure and properties

    International Nuclear Information System (INIS)

    Nezhdanov, A.V.; Mashin, A.I.; Razuvaev, A.G.; Ershov, A.V.; Ignatov, S.K.

    2006-01-01

    An attempt to grow silicon nanowires has been made by electron beam evaporation on highly oriented pyrolytic substrate. Needle-like objects are located along the normal to a substrate (density 2 x 10 11 cm -2 ). For modeling quasi-one-dimensional objects calculations of nuclear structure and energy spectra have been accomplished. A fullerene-like structure Si 24 is proposed as a basic atomic configuration of silicon nanowires [ru

  15. Fast electron transfer through a single molecule natively structured redox protein

    DEFF Research Database (Denmark)

    Della Pia, Eduardo Antonio; Chi, Qijin; Macdonald, J. Emyr

    2012-01-01

    The electron transfer properties of proteins are normally measured as molecularly averaged ensembles. Through these and related measurements, proteins are widely regarded as macroscopically insulating materials. Using scanning tunnelling microscopy (STM), we present new measurements of the conduc...

  16. Structure and Properties of Compressed Borate Glasses

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Bauer, U.; Behrens, H.

    While the influence of thermal history on the structure and properties of glasses has been thoroughly studied in the past century, the influence of pressure history has received considerably less attention. In this study, we investigate the pressure-induced changes in structure and properties in ......, hardness and crack formation from nanoindentation experiments, and overshoot in isobaric heat capacity from DSC experiments at ambient pressure. The influence of the initial boron speciation on the degree of changes in structure and properties will also be discussed....

  17. Structural Properties of Barium Stannate.

    Energy Technology Data Exchange (ETDEWEB)

    Phelan, D.; Han, F.; Lopez-Bezanilla, A.; Krogstad, M. J.; Gim, Y.; Rong, Y.; Zhang, J.; Parshall, D.; Zheng, H.; Cooper, S. L.; Feygenson, M.; Yang, Wenge; Chen, Yu-Sheng

    2018-06-01

    BaSnO3 has attracted attention as a transparent conducting oxide with high room temperature carrier mobility. We report a series of measurements that were carried out to assess the structure of BaSnO3 over a variety of length scales. Measurements included single crystal neutron and x-ray diffraction, Rietveld and pair distribution analysis of neutron powder diffraction, Raman scattering, and high-pressure x-ray diffraction. Results from the various diffraction probes indicate that both the long-range and local structures are consistent with the cubic symmetry. The diffraction data under pressure was consistent with a robustly cubic phase up to 48.9 GPa, which is supported by density functional calculations. Additionally, transverse phonon velocities were determined from measured dispersion of the transverse acoustic phonon branches, the results of which are in good agreement with previous theoretical estimates and ultrasound measurements.

  18. Grain boundary structure and properties

    International Nuclear Information System (INIS)

    Balluffi, R.W.

    1979-05-01

    An attempt is made to distinguish those fundamental aspects of grain boundaries which should be relevant to the problem of the time dependent fracture of high temperature structural materials. These include the basic phenomena which are thought to be associated with cavitation and cracking at grain boundaries during service and with the more general microstructural changes which occur during both processing and service. A very brief discussion of the current state of knowledge of these fundamentals is given

  19. Geochemistry of Natural Redox Fronts

    International Nuclear Information System (INIS)

    Hofmann, B.A.

    1999-05-01

    U, V, Cu, Ni, Au and Ag. The mineralogy of redox fronts is extremely complex, with redox fronts formed at elevated temperature showing more complex assemblages than lower temperature redox fronts. The redox behaviour of individual elements is discussed based on results from natural redox fronts and, to a more limited extent, on experimental evidence. Other aspects of redox fronts such as organic geochemistry, mineral phases, microbial activity, radiolysis and geochemical self-organisation are briefly reviewed. A short overview of active and fossil redox fronts in Northern Switzerland and Southwest Germany is given. The review also includes information on commercially available analytical methods suitable for redox front geochemistry. The general conclusion of this report is that there is widespread evidence that the elements U, Se, Pd and many others are systematically and efficiently immobilised at variable types of redox fronts. Co-precipitation is widely observed for the rare earth elements and perhaps for Th. While these general observations conform to the known geochemical properties of these elements, unexplained differences exist between the behaviour of some elements in different types of redox fronts, e.g. the strongly contrasting behaviour of the otherwise geochemically similar elements Ni and Co in the fossil meteorite Brunflo. Th is another element for which evidence of unusual geochemical behaviour exists at certain localities. A strong influence of local parameters that may be hard to identify appears to be one of the main obstacles in the interpretation of data from natural systems. The systematic overview of natural and human-induced redox fronts in this report allows types of redox fronts suitable for natural analogue studies to be identified. Particularly promising in this respect are weathering phenomena in homogeneous dumps of ore processing products (type IVb) and redox fronts formed by injection of seawater into deep oil reservoirs. (author)

  20. Structure and properties of metals

    CERN Document Server

    Kurzydlowski, K J

    1999-01-01

    Metals are one of the most widely used types of engineering materials. Some of their properties, e.g. elastic constants, can be directly related to the nature of the metallic bonds between the atoms. On the other hand, macro- and $9 microstructural features of metals, such as point defects, dislocations, grain boundaries, and second phase particles, control their yield, flow, and fracture stress. Images of microstructural elements can be obtained by modern $9 imaging techniques. Modern computer aided methods can be further used to obtain a quantitative description of these microstructures. These methods take advantage of the progress made in recent years in the field of image processing, $9 mathematical morphology and quantitative stereology. Quantitative description of the microstructures are used for modeling processes taking place under the action of applied load at a given temperature and test (service) environment. $9 These model considerations can be illustrated on the example of an austenitic stainless...

  1. The V3+-V5+ redox equilibrium reaction and magnetic properties of vanadium ions in binary alkali silicate glasses

    International Nuclear Information System (INIS)

    Singh, R.S.; Singh, S.P.

    2000-01-01

    The oxidation-reduction equilibrium in binary alkali silicate glasses containing V 3+ , V 4+ and V 5+ ions was studied at 1400 degC in air atmosphere. The ionic equation representing the V 3+ -V 5+ redox equilibrium reaction was used to represent the V 3+ -V 4+ -V 5+ redox reactions in glasses as V 4+ ion was an intermediate species. The V 3+ -V 5+ redox equilibrium was found to shift more towards the oxidized state with the increasing ionic radii of alkali ions or with the increasing concentration of alkali oxide in the same series of glasses. The slopes of the straight lines obtained on plotting log ([V 5+ ]/[V 3+ ][pO 2 ] 1/2 ) against mol% R 2 O (R + = Li + , Na + and K + ions) in binary alkali silicate glasses were approximately inversely proportional to the coulombic force between the alkali ions and nonbridging oxygen ions. This indicates the redox equilibrium shifted more towards oxidized state with increasing oxygen ion activity in the glass. The loss of vanadium from the glass melts with the duration of heat treatment was observed due to volatilization at high temperature, which did not influence the V 3+ -V 5+ redox equilibrium. Magnetic susceptibility of the present glasses, measured at room temperature, did not show any sign of paramagnetism which might be due to the presence of smaller concentration of V 3+ and V 4+ ions in the glass. Further, it indicated a strong diamagnetism because of the presence of higher proportion of vanadium in pentavalent state in the glasses. However, the optical absorption spectra or a silicate glass containing ions of vanadium indicated the presence of V 3+ , V 4+ and V 5+ ions. (author)

  2. Determining redox properties of clay-rich sedimentary deposits in the context of performance assessment of radioactive waste repositories : Conceptual and practical aspects

    NARCIS (Netherlands)

    Behrends, T.; Bruggeman, Christophe

    Redox reactions play a key factor controlling the mobility of redox sensitive radionuclides in clay-rich sediments which might serve as host formations for radioactive waste repositories. Assessing the redox speciation of radionuclides requires information about the redox conditions in the formation

  3. STRUCTURAL AND THERMOPHYSICAL PROPERTIES OF HARDENING CONCRETE

    Directory of Open Access Journals (Sweden)

    L. Krasulina

    2012-01-01

    Full Text Available Structural and thermophysical properties of thermally treated concrete have been studied in the paper. The paper demonstrates regularities of changes in structural and thermophysical properties of concrete during heat treatment process. It is established that stabilization of coefficient values for heat- and temperature conductivity of concrete corresponds to completion of the process pertaining to intensive formation of the material pore structure and indicates the possibility of transition from the stage of isothermal extraction to the stage of temperature decrease. The obtained results are confirmed by studies of strength growth kinetics of concrete samples.

  4. Synthesis, structure, NO-donor and redox activity of bis-(2-methylfuranethiolate)tetranitrosyl diiron

    Science.gov (United States)

    Sanina, N. A.; Kozub, G. I.; Kondratéva, T. A.; Korchagin, D. V.; Shilov, G. V.; Emelýanova, N. S.; Manzhos, R. A.; Krivenko, A. G.; Aldoshin, S. M.

    2014-10-01

    The new tetranitrosyl binuclear iron complex [Fe2(SС5H5O)2(NO)4] (I) has been synthesized by the reaction of aqueous solutions of anionic salts [Fе(S2O3)2(NO)2]3- and [SС5H5O]-. The latter one has been obtained by the reduction of methyl furfuryl disulfide by hydrazine hydrate in ethanol at T = 25 °C. The molecular and crystalline structure of I has been determined by X-ray method. The complex has binuclear structure of “μ-S” type with the distance between the iron atoms ∼2.70 Å. In the crystalline structure shortened intermolecular contacts of the nitrosyl groups of the adjacent molecules are observed. The maximum amount of NO generated by I in 1% aqueous solution of dimethylsulfoxide (DMSO) is ∼5 nM, and it reduces to zero in 8 min after decomposition starts in anaerobic conditions at Т = 25 °С, pH 6.5. As follows from the method of natural bond orbital analysis (NBO analysis), complex I has rather strong Fesbnd NO bond, as compared to other NO donors. Using CVA method, the values of reduction potentials for I in an aprotic solvent have been determined, and the scheme for its reduction has been suggested.

  5. Data base on structural materials aging properties

    International Nuclear Information System (INIS)

    Oland, C.B.

    1992-01-01

    The US Nuclear Regulatory Commission has initiated a Structural Aging Program at the Oak Ridge National Laboratory to identify potential structural safety issues related to continued service of nuclear power plants and to establish criteria for evaluating and resolving these issues. One of the tasks in this program focuses on the establishment of a Structural Materials Information Center where long-term and environment-dependent properties of concretes and other structural materials are being collected and assembled into a data base. These properties will be used to evaluate the current condition of critical structural components in nuclear power plants and to estimate the future performance of these materials during the continued service period

  6. Amphoteric Ion-Exchange Membranes with Significantly Improved Vanadium Barrier Properties for All-Vanadium Redox Flow Batteries.

    Science.gov (United States)

    Nibel, Olga; Rojek, Tomasz; Schmidt, Thomas J; Gubler, Lorenz

    2017-07-10

    All-vanadium redox flow batteries (VRBs) have attracted considerable interest as promising energy-storage devices that can allow the efficient utilization of renewable energy sources. The membrane, which separates the porous electrodes in a redox flow cell, is one of the key components in VRBs. High rates of crossover of vanadium ions and water through the membrane impair the efficiency and capacity of a VRB. Thus, membranes with low permeation rate of vanadium species and water are required, also characterized by low resistance and stability in the VRB environment. Here, we present a new design concept for amphoteric ion-exchange membranes, based on radiation-induced grafting of vinylpyridine into an ethylene tetrafluoroethylene base film and a two-step functionalization to introduce cationic and anionic exchange sites, respectively. During long-term cycling, redox flow cells containing these membranes showed higher efficiency, less pronounced electrolyte imbalance, and significantly reduced capacity decay compared to the cells with the benchmark material Nafion 117. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. 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)

  8. Microbial Fingerprints of Community Structure Correlate with Changes in Ecosystem Function Induced by Perturbing the Redox Environment

    Science.gov (United States)

    Mills, A. L.; Ford, R. M.; Vallino, J. J.; Herman, J. S.; Hornberger, G. M.

    2001-12-01

    Restoration of high-quality groundwater has been an elusive engineering goal. Consequently, natural microbially-mediated reactions are increasingly relied upon to degrade organic contaminants, including hydrocarbons and many synthetic compounds. Of concern is how the introduction of an organic chemical contaminant affects the indigenous microbial communities, the geochemistry of the aquifer, and the function of the ecosystem. The presence of functional redundancy in microbial communities suggests that recovery of the community after a disturbance such as a contamination event could easily result in a community that is similar in function to that which existed prior to the contamination, but which is compositionally quite different. To investigate the relationship between community structure and function we observed the response of a diverse microbial community obtained from raw sewage to a dynamic redox environment using an aerobic/anaerobic/aerobic cycle. To evaluate changes in community function CO2, pH, ammonium and nitrate levels were monitored. A phylogenetically-based DNA technique (tRFLP) was used to assess changes in microbial community structure. Principal component analysis of the tRFLP data revealed significant changes in the composition of the microbial community that correlated well with changes in community function. Results from our experiments will be discussed in the context of a metabolic model based the biogeochemistry of the system. The governing philosophy of this thermodynamically constrained metabolic model is that living systems synthesize and allocate cellular machinery in such a way as to "optimally" utilize available resources in the environment. The robustness of this optimization-based approach provides a powerful tool for studying relationships between microbial diversity and ecosystem function.

  9. Structural properties of the Hugoniot curve

    International Nuclear Information System (INIS)

    Chaisse, F.

    2002-01-01

    This report is devoted to the structural properties analysis of the HUGONIOT curve, independently of the equation of state (E 0 S) display. The general properties so coming out are applied to the shock waves interacting studies. When phase transitions are present we investigate the splitting of shock waves and also the rarefaction waves. To end with, we present the shock instabilities and the non-uniqueness of solutions when specific E 0 S are present. (author)

  10. Optical properties of the semiconductor quantum structure

    International Nuclear Information System (INIS)

    Haratizadeh, H.; Holtz, P.O.; Monemar, B.; Karlsoon, K.F.; Moskalenko, E.S.; Amano, H.; Akasaki, I.; Schoenfeld, W.V.; Garcia, J.M.; Petroff, P.M.

    2004-01-01

    Optical properties of the quantum structures have been discussed with emphasize of the AlGaN/GaN multiple quantum wells and InAs/GaAs quantum dot structures. We report on a detailed study of low temperature photoluminescence in Al 0 .07Ga 0 .93 N/GaN multiple quantum wells. The structures were nominally undoped multiple quantum well grown on sapphire substrate. The structure from discrete well width variations is here resolved in photoluminescence spectra. The results demonstrate that the theoretically estimated fields in this work are consistent with the experimental spectra

  11. Molecular basis for the redox control of nuclear transport of the structural chromatin protein Hmgb1

    International Nuclear Information System (INIS)

    Hoppe, George; Talcott, Katherine E.; Bhattacharya, Sanjoy K.; Crabb, John W.; Sears, Jonathan E.

    2006-01-01

    Oxidative stress can induce a covalent disulfide bond between protein and peptide thiols that is reversible through enzymatic catalysis. This process provides a post-translational mechanism for control of protein function and may also protect thiol groups from irreversible oxidation. High mobility group protein B1 (Hmgb1), a DNA-binding structural chromosomal protein and transcriptional co-activator was identified as a substrate of glutaredoxin. Hmgb1 contains 3 cysteines, Cys23, 45, and 106. In mild oxidative conditions, Cys23 and Cys45 readily form an intramolecular disulfide bridge, whereas Cys106 remains in the reduced form. The disulfide bond between Cys23 and Cys45 is a target of glutathione-dependent reduction by glutaredoxin. Endogenous Hmgb1 as well as GFP-tagged wild-type Hmgb1 co-localize in the nucleus of CHO cells. While replacement of Hmgb1 Cys23 and/or 45 with serines did not affect the nuclear distribution of the mutant proteins, Cys106-to-Ser and triple cysteine mutations impaired nuclear localization of Hmgb1. Our cysteine targeted mutational analysis suggests that Cys23 and 45 induce conformational changes in response to oxidative stress, whereas Cys106 appears to be critical for the nucleocytoplasmic shuttling of Hmgb1

  12. Multiphase composite coatings: structure and properties

    International Nuclear Information System (INIS)

    Yurov, V M; Guchenko, S A; Platonova, E S; Syzdykova, A Sh; Lysenko, E N

    2015-01-01

    The paper discusses the results of the research into the formation of ion-plasma multiphase coatings. The types of the formed structures are found to be not so diverse, as those formed, for example, in alloy crystallization. The structures observed are basically of globular type and, more rarely, of unclosed dissipative and cellular structures. It is shown that the properties of the coating formed in deposition are largely determined by its surface energy or surface tension. Since the magnitude of the surface tension (surface energy) in most cases is an additive quantity, each of the elements of the coating composition contributes to the total surface energy. In case of simultaneous sputtering of multiphase cathodes, high entropy coatings with an ordered cellular structure and improved mechanical properties are formed. (paper)

  13. Effect of geometry structure on critical properties

    Science.gov (United States)

    Jiang, Qing; Jiang, Xue-fan

    1997-02-01

    The effective-field renormalization group (EFRG) scheme is utilized to compute critical properties of the transverse Ising model (TIM) in a quantum-spin system. We distinguish differences between lattices of the same coordination number but of different structures and take effects of the first fluctuation correction into account. The improved results for the critical transverse field are obtained for several lattice structures even by considering the smallest possible cluster, which is in good agreement with series results.

  14. Structure and properties of interfaces in ceramics

    International Nuclear Information System (INIS)

    Bonnell, D.; Ruehle, M.; Chowdhry, U.

    1995-01-01

    The motivation for the symposium was the observation that interfaces in crystallographically and compositionally complex systems often dictate the performance and reliability of devices that utilize functional ceramics. The current level of understanding of interface-property relations in silicon-based devices required over 30 years of intensive research. Similar issues influence the relationship between atomic bonding at interfaces and properties in functional ceramic systems. The current understanding of these complex interfaces does not allow correlation between atomic structure and interface properties, in spite of their importance to a number of emerging technologies (wireless communications, radar-based positioning systems, sensors, etc.). The objective of this symposium was to focus attention on these fundamental issues by featuring recent theoretical and experimental work from various disciplines that impact the understanding of interface chemistry, structure, and properties. The emphasis was on relating properties of surfaces and interfaces to structure through an understanding of atomic level phenomena. Interfaces of interest include metal/ceramic, ceramic/ceramic, ceramic/vapor, etc., in electronic, magnetic, optical, ferroelectric, piezoelectric, and dielectric applications. Sixty one papers have been processed separately for inclusion on the data base

  15. Structural properties of Cd–Co ferrites

    Indian Academy of Sciences (India)

    36, No. 5, October 2013, pp. 919–922. c Indian Academy of Sciences. Structural properties of Cd–Co ferrites. S P DALAWAIa,∗. , T J SHINDEb, A B GADKARIc and P N VASAMBEKARa. aDepartment of Electronics, Shivaji University, Kolhapur 416 004, India. bDepartment of Physics, KRP Kanya Mahavidyalaya, Islampur ...

  16. Structural stability properties of Friedman cosmology

    International Nuclear Information System (INIS)

    Szydlowski, M.; Heller, M.; Pontificial Academy of Cracow, Krakow; Golda, Z.

    1984-01-01

    A dynamical system with Robertson-Walker symmetries and the equation of the state p = γepsilon, O <= γ <= 1, considered both as a conservative and nonconservative system, is studied with respect to its structural properties. Different cases are shown and analyzed on the phase space (x = Rsup(D), γ = (dx/dt)). (author)

  17. Diamond nanowires: fabrication, structure, properties, and applications.

    Science.gov (United States)

    Yu, Yuan; Wu, Liangzhuan; Zhi, Jinfang

    2014-12-22

    C(sp(3) )C-bonded diamond nanowires are wide band gap semiconductors that exhibit a combination of superior properties such as negative electron affinity, chemical inertness, high Young's modulus, the highest hardness, and room-temperature thermal conductivity. The creation of 1D diamond nanowires with their giant surface-to-volume ratio enhancements makes it possible to control and enhance the fundamental properties of diamond. Although theoretical comparisons with carbon nanotubes have shown that diamond nanowires are energetically and mechanically viable structures, reproducibly synthesizing the crystalline diamond nanowires has remained challenging. We present a comprehensive, up-to-date review of diamond nanowires, including a discussion of their synthesis along with their structures, properties, and applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Final Report - Crystal Settling, Redox, and High Temperature Properties of ORP HLW and LAW Glasses, VSL-09R1510-1, Rev. 0, dated 6/18/09

    Energy Technology Data Exchange (ETDEWEB)

    Kruger, Albert A.; Wang, C.; Gan, H.; Pegg, I. L.; Chaudhuri, M.; Kot, W.; Feng, Z.; Viragh, C.; McKeown, D. A.; Joseph, I.; Muller, I. S.; Cecil, R.; Zhao, W.

    2013-11-13

    The radioactive tank waste treatment programs at the U. S. Department of Energy (DOE) have featured joule heated ceramic melter technology for the vitrification of high level waste (HLW). The Hanford Tank Waste Treatment and Immobilization Plant (WTP) employs this same basic technology not only for the vitrification of HLW streams but also for the vitrification of Low Activity Waste (LAW) streams. Because of the much greater throughput rates required of the WTP as compared to the vitrification facilities at the West Valley Demonstration Project (WVDP) or the Defense Waste Processing Facility (DWPF), the WTP employs advanced joule heated melters with forced mixing of the glass pool (bubblers) to improve heat and mass transport and increase melting rates. However, for both HLW and LAW treatment, the ability to increase waste loadings offers the potential to significantly reduce the amount of glass that must be produced and disposed and, therefore, the overall project costs. This report presents the results from a study to investigate several glass property issues related to WTP HLW and LAW vitrification: crystal formation and settling in selected HLW glasses; redox behavior of vanadium and chromium in selected LAW glasses; and key high temperature thermal properties of representative HLW and LAW glasses. The work was conducted according to Test Plans that were prepared for the HLW and LAW scope, respectively. One part of this work thus addresses some of the possible detrimental effects due to considerably higher crystal content in waste glass melts and, in particular, the impact of high crystal contents on the flow property of the glass melt and the settling rate of representative crystalline phases in an environment similar to that of an idling glass melter. Characterization of vanadium redox shifts in representative WTP LAW glasses is the second focal point of this work. The third part of this work focused on key high temperature thermal properties of

  19. Silver Matrix Composites - Structure and Properties

    Directory of Open Access Journals (Sweden)

    Wieczorek J.

    2016-03-01

    Full Text Available Phase compositions of composite materials determine their performance as well as physical and mechanical properties. Depending on the type of applied matrix and the kind, amount and morphology of the matrix reinforcement, it is possible to shape the material properties so that they meet specific operational requirements. In the paper, results of investigations on silver alloy matrix composites reinforced with ceramic particles are presented. The investigations enabled evaluation of hardness, tribological and mechanical properties as well as the structure of produced materials. The matrix of composite material was an alloy of silver and aluminium, magnesium and silicon. As the reinforcing phase, 20-60 μm ceramic particles (SiC, SiO2, Al2O3 and Cs were applied. The volume fraction of the reinforcing phase in the composites was 10%. The composites were produced using the liquid phase (casting technology, followed by plastic work (the KOBO method. The mechanical and tribological properties were analysed for plastic work-subjected composites. The mechanical properties were assessed based on a static tensile and hardness tests. The tribological properties were investigated under dry sliding conditions. The analysis of results led to determination of effects of the composite production technology on their performance. Moreover, a relationship between the type of reinforcing phase and the mechanical and tribological properties was established.

  20. Synthesis, structural characterisation and bonding in an anionic hexavanadate bearing redox-active ferrocenyl groups at the periphery

    Czech Academy of Sciences Publication Activity Database

    Schulz, J.; Gyepes, Robert; Císařová, I.; Štěpnička, P.

    2010-01-01

    Roč. 34, č. 12 (2010), s. 2749-2756 ISSN 1144-0546 R&D Projects: GA MŠk(CZ) LC06070 Institutional research plan: CEZ:AV0Z40400503 Keywords : synthesis * redox-active ferrocenyl groups * ferrocene Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.631, year: 2010

  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. Structural properties of small rhodium clusters

    Energy Technology Data Exchange (ETDEWEB)

    Soon, Yee Yeen; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

    2015-04-24

    We report a systematic study of the structural properties of rhodium clusters at the atomistic level. A novel global-minimum search algorithm, known as parallel tempering multicanonical basin hopping plus genetic algorithm (PTMBHGA), is used to obtain the geometrical structures with lowest minima at the semi-empirical level where Gupta potential is used to describe the atomic interaction among the rhodium atoms. These structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The structures are optimized for different spin multiplicities. The ones with lowest energies will be taken as ground-state structures. In most cases, we observe only minor changes in the geometry and bond length of the clusters as a result of DFT-level re-optimization. Only in some limited cases, the initial geometries obtained from the PTMBHGA are modified by the re-optimization. The variation of structural properties, such as ground-state geometry, symmetry and binding energy, with respect to the cluster size is studied and agreed well with other results available in the literature.

  3. Nucleon structure and properties of dense matter

    International Nuclear Information System (INIS)

    Kutschera, M.; Pethick, C.J.; Illinois Univ., Urbana, IL

    1988-01-01

    We consider the properties of dense matter in a framework of the Skyrme soliton model and the chiral bag model. The influence of the nucleon structure on the equation of state of dense matter is emphasized. We find that in both models the energy per unit volume is proportional to n 4/3 , n being the baryon number density. We discuss the properties of neutron stars with a derived equation of state. The role of many-body effects is investigated. The effect of including higher order terms in the chiral lagrangian is examined. The phase transition to quark matter is studied. 29 refs., 6 figs. (author)

  4. Definition and properties of ideal amorphous structures

    International Nuclear Information System (INIS)

    Stachurski, Z.H.

    2002-01-01

    Full text: Amorphous structure is usually defined by what it is not (ie, no crystalline peaks in XRS, no bond correlation in NMR), rather than by what it is. The interest in defining the structure of non-crystalline materials is long standing; packing geometry of spheres, molecular structure of glassy SiO 2 , or the structure of atactic polymers are prime examples. The earliest definitions of amorphous structure were in terms of a microcrystallite model of Valenkov, or continuous random network by Zachariasen. The random close packing of spheres of equal size, and an amorphous structure, composed of freely jointed linear chains of hard spheres, has been described mathematically in terms of a linear homogeneous Poisson process. This paper aims to describe some geometrical, kinematic, and topological properties of these two ideal amorphous structures, which belong to the same amorphous class. The geometry of packing is elucidated, and the use of Voronoi tessellation method for measuring the structures is described. The ideal amorphous solid has no symmetry elements; its volume can not be divided into identical unit cells. However, there is a volume element small enough to allow the distinction of its nanoscopic inhomogeneities, and sufficiently large enough to represent, accurately the overall behaviour. We define this volume element, the representative volume element. Suitable boundary conditions must be prescribed for a choice of RVE, and satisfy certain requirements. Topologically, a catchment region on the Born-Oppenheimer potential energy surface over nuclear configuration space, is defined by Mezey and Bader as an energetically stable geometry of the open region of R 3 traversed by all the trajectories which terminate at a local maximum. Two topological properties will be described: (i) the boundaries of the catchment region as a direct geometrical correspondence to the Voronoi polyhedron for a given atom in a given structure, and (ii) the constriction points

  5. Redox-sensitive structural change in the A-domain of HMGB1 and its implication for the binding to cisplatin modified DNA

    International Nuclear Information System (INIS)

    Wang, Jing; Tochio, Naoya; Takeuchi, Aya; Uewaki, Jun-ichi; Kobayashi, Naohiro; Tate, Shin-ichi

    2013-01-01

    Highlights: •The structure of the oxidized A-domain of human HMGB1 was solved. •Phe38 ring was flipped in the oxidized structure from that in the reduced form. •The flipped ring disables the intercalation into the cisplatinated lesions. •The functionally relevant redox-dependent structural change was described. -- Abstract: HMGB1 (high-mobility group B1) is a ubiquitously expressed bifunctional protein that acts as a nuclear protein in cells and also as an inflammatory mediator in the extracellular space. HMGB1 changes its functions according to the redox states in both intra- and extra-cellular environments. Two cysteines, Cys23 and Cys45, in the A-domain of HMGB1 form a disulfide bond under oxidative conditions. The A-domain with the disulfide bond shows reduced affinity to cisplatin modified DNA. We have solved the oxidized A-domain structure by NMR. In the structure, Phe38 has a flipped ring orientation from that found in the reduced form; the phenyl ring in the reduced form intercalates into the platinated lesion in DNA. The phenyl ring orientation in the oxidized form is stabilized through intramolecular hydrophobic contacts. The reorientation of the Phe38 ring by the disulfide bond in the A-domain may explain the reduced HMGB1 binding affinity towards cisplatinated DNA

  6. Structure Analysis and Properties of Unleaded Brasses

    Directory of Open Access Journals (Sweden)

    Rzadkosz S.

    2015-04-01

    Full Text Available The analysis of brasses regarding their microstructure, mechanical properties and ecological characteristics has been presented. The influence of characteristic alloying elements contained in the brasses and the possibilities of replacing them with other elements have been assessed. The paper contains the results of studies on the influence of chosen additional elements shaping the structure and properties of unleaded alloys based on Cu-Zn system as the matrix. The research aimed at determining the mechanism and the intensity of influence of such additives as tellurium and bismuth. The microstructures were investigated with the help of light microscopy and scanning electron microscopy with X-ray microanalysis (SEM-EDS for determining significant changes of the properties.

  7. Structural and tunneling properties of Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2013-12-06

    We investigate the electronic structure and electron transport properties of Si nanowires attached to Au electrodes from first principles using density functional theory and the nonequilibrium Green\\'s function method. We systematically study the dependence of the transport properties on the diameter of the nanowires, on the growth direction, and on the length. At the equilibrium Au-nanowire distance we find strong electronic coupling between the electrodes and nanowires, which results in a low contact resistance. With increasing nanowire length we study the transition from metallic to tunneling conductance for small applied bias. For the tunneling regime we investigate the decay of the conductance with the nanowire length and rationalize the results using the complex band structure of the pristine nanowires. The conductance is found to depend strongly on the growth direction, with nanowires grown along the ⟨110⟩ direction showing the smallest decay with length and the largest conductance and current.

  8. Structural and tunneling properties of Si nanowires

    KAUST Repository

    Montes Muñ oz, Enrique; Gkionis, Konstantinos; Rungger, Ivan; Sanvito, Stefano; Schwingenschlö gl, Udo

    2013-01-01

    We investigate the electronic structure and electron transport properties of Si nanowires attached to Au electrodes from first principles using density functional theory and the nonequilibrium Green's function method. We systematically study the dependence of the transport properties on the diameter of the nanowires, on the growth direction, and on the length. At the equilibrium Au-nanowire distance we find strong electronic coupling between the electrodes and nanowires, which results in a low contact resistance. With increasing nanowire length we study the transition from metallic to tunneling conductance for small applied bias. For the tunneling regime we investigate the decay of the conductance with the nanowire length and rationalize the results using the complex band structure of the pristine nanowires. The conductance is found to depend strongly on the growth direction, with nanowires grown along the ⟨110⟩ direction showing the smallest decay with length and the largest conductance and current.

  9. Microstructure mechanical properties relationship in bainitic structures

    International Nuclear Information System (INIS)

    Altuna, M. A.; Gutierrez, I.

    2005-01-01

    In the present work, the microstructures and their mechanical properties have been studies in different bainitic structures. therefore, different bainitic morphologies have been produced by isothermal treatments carried out at different temperatures. For these steels, 400-450 degree centigree is the optimum range of temperatures in order to obtain bainitic structures. If the Temperature is higher, perlite is also formed and if it is lower, martensite is obtained during quenching. SEM and EBSD/OIM techniques were applied in order to study the microstructure. Tensile tests were carried out for mechanical characterization. (Author) 20 refs

  10. Structural and electronic properties of thallium compounds

    International Nuclear Information System (INIS)

    Paliwal, Neetu; Srivastava, Vipul

    2016-01-01

    The tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA has been used to calculate structural and electronic properties of thallium pnictides TlX (X=Sb, Bi) at high pressure. As a function of volume, the total energy is evaluated. Apart from this, the lattice parameter (a_0), bulk modulus (B_0), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed metallic behaviour in TlSb and TlBi compounds. The values of equilibrium lattice constants and bulk modulus are agreed well with the available data.

  11. Structural and electronic properties of thallium compounds

    Energy Technology Data Exchange (ETDEWEB)

    Paliwal, Neetu, E-mail: neetumanish@gmail.com [Department of Physics, AISECT University Bhopal, 464993 (India); Srivastava, Vipul [Department of Engineering Physics, NRI Institute of Research & Technology, Raisen Road, Bhopal, 462021 (India)

    2016-05-06

    The tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA has been used to calculate structural and electronic properties of thallium pnictides TlX (X=Sb, Bi) at high pressure. As a function of volume, the total energy is evaluated. Apart from this, the lattice parameter (a{sub 0}), bulk modulus (B{sub 0}), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed metallic behaviour in TlSb and TlBi compounds. The values of equilibrium lattice constants and bulk modulus are agreed well with the available data.

  12. The structural properties of sustainable, continuous change

    DEFF Research Database (Denmark)

    Håkonsson, Dorthe Døjbak; Klaas, Johann Peter; Carroll, Timothy

    2013-01-01

    this relationship by exploring what structural properties enable continuous change in inertia-generating organizations and what their performance consequences are in dynamic environments. The article has three main findings: First, employing managers who anticipate change is not enough to generate continuous change......; it is also necessary to raise both the rate of responsiveness and desired performance. Second, continuous change increases average organizational performance and reduces its variation. Third, organizations’ capacity for continuous change is counterintuitively limited by the organizations’ capacity to build...

  13. The effect of cycling on the nanoscale morphology and redox properties of poly[2,2′-bithiophene

    International Nuclear Information System (INIS)

    O’Neil, K.D.; Smith, A.; Forristal, T.A.; Semenikhin, O.A.

    2013-01-01

    The changes in the redox behavior and nanoscale morphology of poly[2,2′-bithiophene] deposited onto highly oriented pyrolytic graphite substrates upon repeated doping–undoping were studied. It was shown that repeated cycling resulted in very particular changes in the voltammetric response of the polymer films as well as their nanoscale morphology. Specifically, when the cycling was performed to relatively low anodic potentials, the overall doping–undoping charge did not change; however, the shape of voltammograms was consistently changing showing broadening of the voltammograms and reducing of the doping peak height in the anodic scan, as well as broadening and deterioration of the undoping peak in the reverse scan. Furthermore, a remarkable feature was observed that all voltammogram traces intersected at several characteristic potentials producing quasi-isosbestic points. With an increase in the anodic scan potential limit, the overall doping–undoping charge starts to decrease showing irreversible degradation of the polymer; however, the general pattern of the peak broadening could be still observed. Atomic force microscopic (AFM) studies of the polymer films cycled to various anodic limits showed that repeated cycling resulted in a gradual decrease in the degree of crystallinity, as revealed by AFM phase imaging, and an increase in the degree of disorder. Coupled with the changes in the redox behavior, these findings suggested the formation of more flexible and open polymer nanostructure that enables easier penetration of the dopant ions and solvent. However, at the same time, an increase in the degree of disorder reduced the interchain interactions and inhibited the formation of extended electronic states delocalized across neighboring polymer chains. This occurred at first without irreversible degradation of the polymer and a decrease in the overall doping–undoping charge. Cycling to higher anodic potentials resulted in irreversible degradation

  14. Mineralogy, geochemistry, porosity and redox properties of rocks from Forsmark. Compilation of data from the regional model volume for SR-Site

    Energy Technology Data Exchange (ETDEWEB)

    Sandstroem, Bjoern (WSP Sverige AB, Stockholm (Sweden)); Stephens, Michael B. (Geological Survey of Sweden, Uppsala (Sweden))

    2009-11-15

    This report is a compilation of the data acquired during the Forsmark site investigation programme on the mineralogy, geochemistry, redox properties and porosity of different rock types at Forsmark. The aim is to provide a final summary of the available data for use during the SR-Site modelling work. Data presented in this report represent the regional model volume and have previously been published in various SKB reports. The data have been extracted from the SKB database Sicada and are presented as calculated median values, data range and lower/upper quartile. The representativity of all samples used for the calculations have been evaluated and data from samples where there is insufficient control on the rock type have been omitted. Rock samples affected by alteration have been omitted from the unaltered samples and are presented separately based on type of alteration (e.g. oxidised or albitized rock)

  15. Excited state redox properties of phthalocyanines: influence of the axial ligand on the rates of relaxation and electron-transfer quenching of the lowest /sup 3/. pi pi. /sup */ excited state

    Energy Technology Data Exchange (ETDEWEB)

    Ferraudi, G J; Prasad, D R

    1874-01-01

    Laser flash excitations at 640 nm have been used to generate the transient spectra of the lowest-lying /sup 3/..pi pi../sup */ state of phthalocyaninatoruthenium(II) complexes. The properties of this excited state such as the properties of the maxima, lambda/sub max/ = 500 +/- 30 nm, and lifetimes, t/sub 1/2/ = 70-4500 ns, exhibit a large dependence on the electron-accepting and electron-withdrawing tendencies of the axial ligands. A similar influence was observed upon the rate of electron-transfer quenching of the /sup 3/..pi pi../sup */ state. Values between 10/sup 6/ and 10/sup 7/ dm/sup 3/ mol/sup -1/ s/sup -1/ for the self-exchange rate constant have been obtained, according to Marcus-Hush theoretical treatments, for (Ru(pc.)LL')/sup +//(/sup 3/..pi pi../sup */)(Ru(pc)LL') (L and L' = neutral axial ligands; pc = phthalocyaninate (2-)) and isoelectronic cobalt(III) and rhodium(III) couples. The redox properties of the ground and excited states are correlated with axial ligand-induced perturbations of the electronic structure.

  16. 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.

  17. Structural material properties for fusion application

    Energy Technology Data Exchange (ETDEWEB)

    Tavassoli, A-A. F.

    2008-10-15

    Materials properties requirements for structural applications in the forthcoming and future fusion machines are analyzed with emphasis on safety requirements. It is shown that type 316L(N) used in the main structural components of ITER is code qualified and together with limits imposed on its service conditions and neutron radiation levels, can adequately satisfy ITER vacuum vessel licensing requirements. For the in-vessel components, where nonconventional fabrication methods, such as HIPing, are used, design through materials properties, data is combined with tests on representative mockups to meet the requirements. For divertor parts, where the operating conditions are too severe for components to last throughout the reactor life, replacement of most exposed parts is envisaged. DEMO operating conditions require extension of ITER design criteria to high temperature and high neutron dose rules, as well as to compatibility with cooling and tritium breeding media, depending on the blanket concept retained. The structural material favoured in EU is Eurofer steel, low activation martensitic steel with good ductility and excellent resistance to radiation swelling. However, this material, like other ferritic / martensitic steels, requires post-weld annealing and is sensitive to low temperature irradiation embrittlement. Furthermore, it shows cyclic softening during fatigue, complicating design against fatigue and creep-fatigue. (au)

  18. Influence of organic additives on electrochemical properties of the positive electrolyte for all-vanadium redox flow battery

    International Nuclear Information System (INIS)

    Wu Xiaojuan; Liu Suqin; Wang Nanfang; Peng Sui; He Zhangxin

    2012-01-01

    Inositol and phytic acid have been employed as organic additives of the positive electrolyte for all-vanadium redox flow battery (VRFB) to improve its stability and electrochemical reversibility. Thermal stability of the V(V) electrolyte could be improved by both inositol and phytic acid additives. The results of cyclic voltammetry (CV), steady polarization curve and electrochemical impedance spectroscopy (EIS) show that the electrochemical activity of the electrolyte with additives is improved compared to the blank one. The diffusion coefficient of V(IV) species with inositol has been increased from 0.71–1.16 × 10 −6 to 3.11–5.15 × 10 −6 cm 2 s −1 and the exchange current density was raised from 2.8 × 10 −3 to 11.7 × 10 −3 A cm −2 . Moreover, electrochemical results suggest that the positive electrolytes with organic additives have better cycling stability. The VRFB employing positive electrolyte with inositol as additive exhibits excellent charge–discharge behavior with an average energy efficiency of 81.5% at a current density of 30 mA cm −2 . The UV–visible spectroscopy confirms that new substances in V(V) electrolyte are not formed with both inositol and phytic acid additives.

  19. Structure and properties of microcrystalline chitosan

    International Nuclear Information System (INIS)

    Pighinelli, Luciano; Guimaraes, Fernando Machado; Paz, Luan Rios; Zanin, Gabrielle Brehm; Kmiec, Marzena; Tedesco, Felipe Melleu; Reis, Victoria Oliva dos; Silva, Matheus Machado; Becker, Cristiane Miotto; Zehetmeyer, Gislene; Rasia, Gisele

    2016-01-01

    Full text: The microcrystalline chitosan is a modified form of chitosan; it has been elaborated from obtaining method of chitosan salts. It is characterized by special properties of the initial chitosan such as biocompatibility, bioactivity, non-toxic, biodegradability [1]. The objective of this study is to develop a different method to obtain the microcrystalline chitosan and the following characterization of the initial chitosan and MCCh. The material was characterized by FTIR, scanning of electron microscopy, SEM, nuclear magnetic resonance, NMR, and x-ray diffraction. The results indicate that the process to obtain MCCh, did not change the structure of the initial chitosan. The MCCh shows the same functional groups of the initial chitosan. The NMR results shows the acetylated and deacetylated groups. The morphology shows a homogeneous structure of surface. The X-ray diffraction shows the reduction of the crystallinity in the MCCh, indicating a bigger amorphous structure of the MCCh. The chitosan and its derivatives are polymers with excellent properties to be used in regenerative medicine because of ensure efficiency in healing process. This polysaccharide has a great potential to develop a new generation of biomaterials that can be used in regenerative medicine and tissue engineering [2]. References: [1]. LI, Q. et al. Applications and properties of chitosan. In: GOOSEN, M. F. A. (Ed.). Applications of chitin and chitosan. Basel: Technomic, 1997. p. 3-29; [2]. Luciano Pighinelli, Magdalena Kucharska, Dariuz Wawro. Preparation of Microcrystalline chitosan: (MCCh0/tricalcium phosphate complex with Hydroxyapatite in sponge and fibre from for hard tissue regeneration. (author)

  20. Structure and properties of microcrystalline chitosan

    Energy Technology Data Exchange (ETDEWEB)

    Pighinelli, Luciano; Guimaraes, Fernando Machado; Paz, Luan Rios; Zanin, Gabrielle Brehm; Kmiec, Marzena; Tedesco, Felipe Melleu; Reis, Victoria Oliva dos; Silva, Matheus Machado, E-mail: lpighinelli@hotmail.com [Universidade Luterana, Sao Paulo, SP (Brazil); Becker, Cristiane Miotto; Zehetmeyer, Gislene; Rasia, Gisele [Centro Universitario SENAI CIMATEC, Salvador, BA (Brazil). Instituto de Engenharia de Materiais Polimericos

    2016-07-01

    Full text: The microcrystalline chitosan is a modified form of chitosan; it has been elaborated from obtaining method of chitosan salts. It is characterized by special properties of the initial chitosan such as biocompatibility, bioactivity, non-toxic, biodegradability [1]. The objective of this study is to develop a different method to obtain the microcrystalline chitosan and the following characterization of the initial chitosan and MCCh. The material was characterized by FTIR, scanning of electron microscopy, SEM, nuclear magnetic resonance, NMR, and x-ray diffraction. The results indicate that the process to obtain MCCh, did not change the structure of the initial chitosan. The MCCh shows the same functional groups of the initial chitosan. The NMR results shows the acetylated and deacetylated groups. The morphology shows a homogeneous structure of surface. The X-ray diffraction shows the reduction of the crystallinity in the MCCh, indicating a bigger amorphous structure of the MCCh. The chitosan and its derivatives are polymers with excellent properties to be used in regenerative medicine because of ensure efficiency in healing process. This polysaccharide has a great potential to develop a new generation of biomaterials that can be used in regenerative medicine and tissue engineering [2]. References: [1]. LI, Q. et al. Applications and properties of chitosan. In: GOOSEN, M. F. A. (Ed.). Applications of chitin and chitosan. Basel: Technomic, 1997. p. 3-29; [2]. Luciano Pighinelli, Magdalena Kucharska, Dariuz Wawro. Preparation of Microcrystalline chitosan: (MCCh0/tricalcium phosphate complex with Hydroxyapatite in sponge and fibre from for hard tissue regeneration. (author)

  1. Synthesis, structure, and properties of azatriangulenium salts

    DEFF Research Database (Denmark)

    Laursen, B.W.; Krebs, Frederik C

    2001-01-01

    amines and, by virtue of its stepwise and irreversible nature, provides a powerful tool for the preparation of a wide variety of new heterocyclic carbenium salts. Several derivatives of the three new oxygen- and/or nitrogen-bridged triangulenium salts, azadioxa- (6), diazaoxa- (7......), and triazatriangulenium (4), have been synthesized and their physicochemical properties have been investigated. Crystal structures for compounds 2 b-PF6: 2d-PF6, 4b-BF4, 4c-BF4, 6e-BF4, and 8 are reported. The different packing modes found for the triazatriagulenium salts are discussed in relation to the electrostatic...

  2. Technological properties and structure of titanate melts

    International Nuclear Information System (INIS)

    Morozov, A.A.

    2002-01-01

    Power substantiation of existence of tough stream of complex anion ([TiO 6 ] 8- ) as a prevalent unit in titanate melts is given on the base of up-to-date knowledge about structure of metallurgical slags and results of investigations of thermophysical properties of these melts. It is shown that high crystallization ability of titanate melts at technological temperatures is determined by heterogeneity of liquid state - by presence up to 30 % of dispersed particles of solid phase solutions in matrix liquid [ru

  3. Fabrication and Properties of Multilayer Structures

    Science.gov (United States)

    1983-09-01

    according to both the high x-ray count and a Read camera pattern which showed only the 111 8 SiC reflection in a tight ± 30 distribution about the substrate...structural rearrangement. X-ray analysis of the deposited films at the composition of Pd2 Si using a Read camera indicated strong texturing. The...Phys. 35, 547 (1964). 11. C.A. Neubauer and J.R. Randen, Proc. IEEE 52, 1234 (1964). 12. W.A. Tiller, "Fabrication and Properties of Multilayer

  4. Steam reforming of bio-ethanol over Ni on Ce-ZrO2 support: Influence of redox properties on the catalyst reactivity

    Directory of Open Access Journals (Sweden)

    Sumittra Charojrochkul

    2006-11-01

    Full Text Available The steam reforming of ethanol over Ni on Ce-ZrO2 support, (Ni/ Ce-ZrO2 were studied. The catalyst provides significantly higher reforming reactivity and excellent resistance toward carbon deposition compared to Ni/Al2O3 under the same conditions. At the temperature above 800ºC, the main products from the reforming processes over Ni/Ce-ZrO2 were H2, CO, and CO2 with small amount of CH4 depending on the inlet ethanol/steam and oxygen/ethanol ratios, whereas high hydrocarbon compounds i.e., C2H4 and C2H6 were also observed from the reforming of ethanol over Ni/Al2O3 in the range of conditions studied (700- 1000ºC.These excellent ethanol reforming performances of Ni/Ce-ZrO2 in terms of stability, reactivity and product selectivities are due to the high redox property of Ce-ZrO2. During the ethanol reforming process, in addition to the reactions on Ni surface, the gas-solid reactions between the gaseous components presented in the system (C2H5OH, C2H6, C2H4, CH4, CO2, CO, H2O, and H2 and the lattice oxygen (Ox on Ce-ZrO2 surface also take place. Among these redox reactions, the reactions of adsorbed surface hydrocarbons with the lattice oxygen (Ox (CnHm + Ox → nCO + m/2(H2 + Ox-n can eliminate the formation of high hydrocarbons (C2H6 and C2H4, which easily decompose and form carbon species on Ni surface (CnHm→ nC + m/2H2.

  5. Planetary ring systems properties, structures, and evolution

    CERN Document Server

    Murray, Carl D

    2018-01-01

    Planetary rings are among the most intriguing structures of our solar system and have fascinated generations of astronomers. Collating emerging knowledge in the field, this volume reviews our current understanding of ring systems with reference to the rings of Saturn, Uranus, Neptune, and more. Written by leading experts, the history of ring research and the basics of ring–particle orbits is followed by a review of the known planetary ring systems. All aspects of ring system science are described in detail, including specific dynamical processes, types of structures, thermal properties and their origins, and investigations using computer simulations and laboratory experiments. The concluding chapters discuss the prospects of future missions to planetary rings, the ways in which ring science informs and is informed by the study of other astrophysical disks, and a perspective on the field's future. Researchers of all levels will benefit from this thorough and engaging presentation.

  6. Properties of multilayer nonuniform holographic structures

    International Nuclear Information System (INIS)

    Pen, E F; Rodionov, Mikhail Yu

    2010-01-01

    Experimental results and analysis of properties of multilayer nonuniform holographic structures formed in photopolymer materials are presented. The theoretical hypotheses is proved that the characteristics of angular selectivity for the considered structures have a set of local maxima, whose number and width are determined by the thicknesses of intermediate layers and deep holograms and that the envelope of the maxima coincides with the selectivity contour of a single holographic array. It is also experimentally shown that hologram nonuniformities substantially distort shapes of selectivity characteristics: they become asymmetric, the local maxima differ in size and the depths of local minima reduce. The modelling results are made similar to experimental data by appropriately choosing the nonuniformity parameters. (imaging and image processing. holography)

  7. Redox Additive-Improved Electrochemically and Structurally Robust Binder-Free Nickel Pyrophosphate Nanorods as Superior Cathode for Hybrid Supercapacitors.

    Science.gov (United States)

    Sankar, Kalimuthu Vijaya; Seo, Youngho; Lee, Su Chan; Chan Jun, Seong

    2018-03-07

    For several decades, one of the great challenges for constructing a high-energy supercapacitor has been designing electrode materials with high performance. Herein, we report for the first time to our knowledge a novel hybrid supercapacitor composed of battery-type nickel pyrophosphate one-dimensional (1D) nanorods and capacitive-type N-doped reduced graphene oxide as the cathode and anode, respectively, in an aqueous redox-added electrolyte. More importantly, ex situ microscopic images of the nickel pyrophosphate 1D nanorods revealed that the presence of the battery-type redox additive enhanced the charge storage capacity and cycling life as a result of the microstructure stability. The nickel pyrophosphate 1D nanorods exhibited their maximum specific capacitance (8120 mF cm -2 at 5 mV s -1 ) and energy density (0.22 mWh cm -2 at a power density of 1.375 mW cm -2 ) in 1 M KOH + 75 mg K 3 [Fe(CN) 6 ] electrolyte. On the other side, the N-doped reduced graphene oxide delivered an excellent electrochemical performance, demonstrating that it was an appropriate anode. A hybrid supercapacitor showed a high specific capacitance (224 F g -1 at a current density of 1 A g -1 ) and high energy density (70 Wh kg -1 at a power density of 750 W kg -1 ), as well as a long cycle life (a Coulombic efficiency of 96% over 5000 cycles), which was a higher performance than most of those in recent reports. Our results suggested that the materials and redox additive in this novel design hold great promise for potential applications in a next-generation hybrid supercapacitor.

  8. Extraordinary electronic properties in uncommon structure types

    Science.gov (United States)

    Ali, Mazhar Nawaz

    In this thesis I present the results of explorations into several uncommon structure types. In Chapter 1 I go through the underlying idea of how we search for new compounds with exotic properties in solid state chemistry. The ideas of exploring uncommon structure types, building up from the simple to the complex, using chemical intuition and thinking by analogy are discussed. Also, the history and basic concepts of superconductivity, Dirac semimetals, and magnetoresistance are briefly reviewed. In chapter 2, the 1s-InTaS2 structural family is introduced along with the discovery of a new member of the family, Ag0:79VS2; the synthesis, structure, and physical properties of two different polymorphs of the material are detailed. Also in this chapter, we report the observation of superconductivity in another 1s structure, PbTaSe2. This material is especially interesting due to it being very heavy (resulting in very strong spin orbit coulping (SOC)), layered, and noncentrosymmetric. Electronic structure calculations reveal the presence of a bulk 3D Dirac cone (very similar to graphene) that is gapped by SOC originating from the hexagonal Pb layer. In Chapter 3 we show the re-investigation of the crystal structure of the 3D Dirac semimetal, Cd3As2. It is found to be centrosymmetric, rather than noncentrosymmetric, and as such all bands are spin degenerate and there is a 4-fold degenerate bulk Dirac point at the Fermi level, making Cd3As2 a 3D electronic analog to graphene. Also, for the first time, scanning tunneling microscopy experiments identify a 2x2 surface reconstruction in what we identify as the (112) cleavage plane of single crystals; needle crystals grow with a [110] long axis direction. Lastly, in chapter 4 we report the discovery of "titanic" (sadly dubbed ⪉rge, nonsaturating" by Nature editors and given the acronym XMR) magnetoresistance (MR) in the non-magnetic, noncentrosymmetric, layered transition metal dichalcogenide WTe2; over 13 million% at 0.53 K in

  9. Exploring Redox Properties of Aromatic Amino Acids in Water: Contrasting Single Photon vs Resonant Multiphoton Ionization in Aqueous Solutions.

    Science.gov (United States)

    Roy, Anirban; Seidel, Robert; Kumar, Gaurav; Bradforth, Stephen E

    2018-04-12

    Direct measurements of the valence ionization energies and the reorganization energies of the three aromatic amino acids, l-tyrosine, l-tryptophan, and l-phenylalanine, in aqueous solution using the liquid microjet technique and two different photoemission methods-X-ray photoelectron spectroscopy (XPS) at 175 eV photon energy and resonant two-photon ionization (R2PI) using 2 × 267 nm (2 × 4.64 eV) UV laser light-are reported. l-Tryptophan has the lowest vertical ionization energy, 7.3 eV, followed by tyrosine (7.8 eV) and phenylalanine (∼8.7 eV). Essentially, no variation in recovered orbital energies is observed comparing near threshold ionization to X-ray ionization. Superior sensitivity of the (background-free) R2PI scheme for solutions with very low solute concentration (<2 mM) is demonstrated in contrast to the single-photon XPS measurements, which often requires solute concentrations of 0.1-1 molar. This higher sensitivity along with chemical selectivity of the R2PI technique can be exploited for both spectroscopic assignment and as an analytical tool. The nature of the adiabatic ionization energy for the three aromatic amino acids has been explored by the R2PI approach and by empirically formulating the correlation between the estimated ionization onset with electronic and nuclear relaxation on the excited state surface. Our results have implications for understanding one-electron transfer within enzymes and in redox situations where (ir)reversible deprotonation occurs such as those manifest in the biochemistry of oxidation damage.

  10. Structure and Properties of LENRA/ Silica Composite

    International Nuclear Information System (INIS)

    Mahathir Mohamed; Dahlan Mohd

    2010-01-01

    The sol-gel reaction using tetra ethoxysilane (TEOS) was conducted for modified natural rubber (NR) matrix to obtain in situ generated NR/ silica composite. The present of acrylate group in the modified NR chain turns the composite into radiation-curable. The maximum amount of silica generated in the matrix was 50 p hr by weight. During the sol-gel process the inorganic mineral was deposited in the rubber matrix forming hydrogen bonding between organic and inorganic phases. The composites obtained were characterized by various techniques including thermogravimetric analysis and infrared spectrometry to study their molecular structure. The increase in mechanical properties was observed for low silica contents ( 30 p hr) where more silica were generated, agglomerations were observed at the expense of the mechanical properties. From the DMTA data, it shows an increase of the interaction between the rubber and silica phases up to 30 p hr TEOS. Structure and morphology of the heterogeneous system were analyzed by transmission electron microscopy. The average particle sizes of between 150 nm to 300 nm were achieved for the composites that contain less than 20 p hr of TEOS. (author)

  11. Zinc and the modulation of redox homeostasis

    Science.gov (United States)

    Oteiza, Patricia I.

    2012-01-01

    Zinc, a redox inactive metal, has been long viewed as a component of the antioxidant network, and growing evidence points to its involvement in redox-regulated signaling. These actions are exerted through several mechanisms based on the unique chemical and functional properties of zinc. Overall, zinc contributes to maintain the cell redox balance through different mechanisms including: i) the regulation of oxidant production and metal-induced oxidative damage; ii) the dynamic association of zinc with sulfur in protein cysteine clusters, from which the metal can be released by nitric oxide, peroxides, oxidized glutathione and other thiol oxidant species; iii) zinc-mediated induction of the zinc-binding protein metallothionein, which releases the metal under oxidative conditions and act per se scavenging oxidants; iv) the involvement of zinc in the regulation of glutathione metabolism and of the overall protein thiol redox status; and v) a direct or indirect regulation of redox signaling. Findings of oxidative stress, altered redox signaling, and associated cell/tissue disfunction in cell and animal models of zinc deficiency, stress the relevant role of zinc in the preservation of cell redox homeostasis. However, while the participation of zinc in antioxidant protection, redox sensing, and redox-regulated signaling is accepted, the involved molecules, targets and mechanisms are still partially known and the subject of active research. PMID:22960578

  12. Attenuation of LDHA expression in cancer cells leads to redox-dependent alterations in cytoskeletal structure and cell migration.

    Science.gov (United States)

    Arseneault, Robert; Chien, Andrew; Newington, Jordan T; Rappon, Tim; Harris, Richard; Cumming, Robert C

    2013-09-28

    Aerobic glycolysis, the preferential use of glycolysis even in the presence of oxygen to meet cellular metabolic demands, is a near universal feature of cancer. This unique type of metabolism is thought to protect cancer cells from damaging reactive oxygen species (ROS) produced in the mitochondria. Using the cancer cell line MDA-MB-435 it is shown that shRNA mediated knockdown of lactate dehydrogenase A (LDHA), a key mediator of aerobic glycolysis, results in elevated mitochondrial ROS production and a concomitant decrease in cell proliferation and motility. Redox-sensitive proteins affected by oxidative stress associated with LDHA knockdown were identified by Redox 2D-PAGE and mass spectrometry. In particular, tropomyosin (Tm) isoforms Tm4, Tm5NM1 and Tm5NM5, proteins involved in cell migration and cytoskeletal dynamics, exhibited changes in disulfide bonding and co-localized with peri-nuclear actin aggregates in LDHA knockdown cells. In contrast, treatment with the thiol-based antioxidant N-acetylcysteine promoted the relocalization of Tms to cortical actin microfilaments and partially rescued the migration defects associated with attenuated LDHA expression. These results suggest that aerobic glycolysis and reduced mitochondrial ROS production create an environment conducive to cytoskeletal remodeling; key events linked to the high cell motility associated with cancer. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  13. Structure Property Studies for Additively Manufactured Parts

    Energy Technology Data Exchange (ETDEWEB)

    Milenski, Helen M [Univ. of Mexico, Los Alamos, NM (United States); Schmalzer, Andrew Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kelly, Daniel [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-08-17

    Since the invention of modern Additive Manufacturing (AM) processes engineers and designers have worked hard to capitalize on the unique building capabilities that AM allows. By being able to customize the interior fill of parts it is now possible to design components with a controlled density and customized internal structure. The creation of new polymers and polymer composites allow for even greater control over the mechanical properties of AM parts. One of the key reasons to explore AM, is to bring about a new paradigm in part design, where materials can be strategically optimized in a way that conventional subtractive methods cannot achieve. The two processes investigated in my research were the Fused Deposition Modeling (FDM) process and the Direct Ink Write (DIW) process. The objectives of the research were to determine the impact of in-fill density and morphology on the mechanical properties of FDM parts, and to determine if DIW printed samples could be produced where the filament diameter was varied while the overall density remained constant.

  14. Effects of interfacial Fe electronic structures on magnetic and electronic transport properties in oxide/NiFe/oxide heterostructures

    International Nuclear Information System (INIS)

    Liu, Qianqian; Chen, Xi; Zhang, Jing-Yan; Yang, Meiyin; Li, Xu-Jing; Jiang, Shao-Long; Liu, Yi-Wei; Cao, Yi; Wu, Zheng-Long; Feng, Chun; Ding, Lei; Yu, Guang-Hua

    2015-01-01

    Highlights: • The magnetic and transport properties of oxide/NiFe/oxide films were studied. • The oxide (SiO 2 , MgO and HfO 2 ) has different elemental electronegativity. • Redox reaction at different NiFe/oxide interface is dependent on the oxide layer. • Different interfacial electronic structures shown by XPS influence the properties. - Abstract: We report that the magnetic and electronic transport properties in oxide/NiFe(2 nm)/oxide film (oxide = SiO 2 , MgO or HfO 2 ) are strongly influenced by the electronic structure of NiFe/oxide interface. Magnetic measurements show that there exist magnetic dead layers in the SiO 2 sandwiched film and MgO sandwiched film, whereas there is no magnetic dead layer in the HfO 2 sandwiched film. Furthermore, in the ultrathin SiO 2 sandwiched film no magnetoresistance (MR) is detected, while in the ultrathin MgO sandwiched film and HfO 2 sandwiched film the MR ratios reach 0.35% and 0.88%, respectively. The investigation by X-ray photoelectron spectroscopy reveals that the distinct interfacial redox reactions, which are dependent on the oxide layers, lead to the variation of magnetic and transport properties in different oxide/NiFe/oxide heterostructures

  15. Investigations on structural iron electrochemical properties in layered silicates using massive mica electrodes

    International Nuclear Information System (INIS)

    Hadi, J.; Ignatiadis, I.; Tournassat, C.; Charlet, L.; Silvester, E.

    2012-01-01

    Document available in extended abstract form only. Nuclear waste repositories are being installed in deep excavated rock formations in some places in Europe to isolate and store radioactive waste. In France, the Callovo-Oxfordian formation (COx) is a potential candidate for a nuclear waste repository. The redox reactivity of COx clay rock samples are already under study using microscopic, spectrometric and wet analysis techniques. In order to cross and overcome certain limits by improvement in the knowledge, specific electrodes should be constructed and devoted to the deepening of the electrochemical behaviour of the COx system in different situations. Iron is one of the most common redox species in soils and sedimentary rocks. Iron-bearing phyllosilicates play key roles in various biogeochemical processes. The complexity of the physical and chemical changes involving their structural iron makes the studies of its redox properties challenging. Most of the recent reported efforts were focused on probing Fe redox on finely powdered clay particles, and have been hampered by inadequate interactions between particles and electrodes. Moreover, such experiments usually involve redox probe ions, thus adding supplementary difficulties in the determination of structural iron redox parameters such as redox potential (Eh) and kinetics. The present study aims at qualitatively investigating the above mentioned phenomena on minerals like iron-bearing micas. In the current work, we present initial insights regarding efforts to build a direct electrical interface between solid electrodes and conveniently shaped macroscopic mica crystals in order to investigate the redox properties of structural iron in dry and aqueous environments, in the presence of representative perturbations. A classical three electrode system has been used for voltammetric measurements. Platinum plate was the counter electrode. Potentials have been measured against either silver-silver chloride electrode or

  16. A density functional theory study on the active center of Fe-only hydrogenase: characterization and electronic structure of the redox states.

    Science.gov (United States)

    Liu, Zhi-Pan; Hu, P

    2002-05-08

    We have carried out extensive density functional theory (DFT) calculations for possible redox states of the active center in Fe-only hydrogenases. The active center is modeled by [(H(CH(3))S)(CO)(CN(-))Fe(p)(mu-DTN)(mu-CO)Fe(d)(CO)(CN(-))(L)](z)() (z is the net charge in the complex; Fe(p)= the proximal Fe, Fe(d) = the distal Fe, DTN = (-SCH(2)NHCH(2)S-), L is the ligand that bonds with the Fe(d) at the trans position to the bridging CO). Structures of possible redox states are optimized, and CO stretching frequencies are calculated. By a detailed comparison of all the calculated structures and the vibrational frequencies with the available experimental data, we find that (i) the fully oxidized, inactive state is an Fe(II)-Fe(II) state with a hydroxyl (OH(-)) group bonded at the Fe(d), (ii) the oxidized, active state is an Fe(II)-Fe(I) complex which is consistent with the assignment of Cao and Hall (J. Am. Chem. Soc. 2001, 123, 3734), and (iii) the fully reduced state is a mixture with the major component being a protonated Fe(I)-Fe(I) complex and the other component being its self-arranged form, Fe(II)-Fe(II) hydride. Our calculations also show that the exogenous CO can strongly bond with the Fe(II)-Fe(I) species, but cannot bond with the Fe(I)-Fe(I) complex. This result is consistent with experiments that CO tends to inhibit the oxidized, active state, but not the fully reduced state. The electronic structures of all the redox states have been analyzed. It is found that a frontier orbital which is a mixing state between the e(g) of Fe and the 2 pi of the bridging CO plays a key role concerning the reactivity of Fe-only hydrogenases: (i) it is unoccupied in the fully oxidized, inactive state, half-occupied in the oxidized, active state, and fully occupied in the fully reduced state; (ii) the e(g)-2 pi orbital is a bonding state, and this is the key reason for stability of the low oxidation states, such as Fe(I)-Fe(I) complexes; and (iii) in the e(g)-2 pi orbital

  17. [Relationships between microscope structure and thermodynamic properties

    International Nuclear Information System (INIS)

    Wu, R.S.; Lee, L.L.; Cochran, D.

    1990-01-01

    This paper exhibits on the molecular level, the relationships between the microscopic structure and thermodynamic properties of dilute supercritical solutions by application of the integral equation theories for molecular distribution functions. To solve the integral equations, the authors use Baxter's Wiener-Hopf factorization of the Ornstein-Zernike equations and then apply this method to binary Lennard-Jones mixtures. A number of closure relations have been used: such as the Percus-Yevick (PY), the reference hypernetted chain (RHNC), the hybrid mean spherical approximation (HMSA), and the reference interaction-site (RISM) methods. The authors examine the microstructures of several important classes of supercritical mixtures, including the usual attractive-type and the less known repulsive-type solutions. The clustering of solvent molecules for solvent-solute structures in the attractive mixtures and, correspondingly, the solvent cavitation in the repulsive mixtures are clearly demonstrated. These are shown to be responsible for the large negative growth of the solute partial molar volumes in the attractive case and the positive growth in the repulsive case

  18. Ionic properties of non-aqueous liquid and PVDF-based gel electrolytes containing a cesium thiolate/disulfide redox couple

    International Nuclear Information System (INIS)

    Renard, Ingrid; Li Hongmei; Marsan, Benoit

    2003-01-01

    Liquid electrolytes containing a cesium thiolate/disulfide redox couple, prepared from 5-mercapto-1-methyltetrazole cesium salt (CsT) and di-5-(1-methyltetrazole)disulfide (T 2 ) dissolved in several aprotic solvents and solvent mixtures, have been studied using various techniques. FTIR spectroscopy reveals that relatively strong interactions occur between the reduced species T - and DMSO or DMF while Cs + ions are very weakly coordinated to the S=O or C=O bond. It is shown that the electrolyte consisting of 1.55 mol kg -1 CsT in the solvent mixture DMSO/DMF (40/60%) exhibits the highest conductivity (1.1x10 -2 and 2.3x10 -2 S cm -1 at 23 and 80 deg. C, respectively), and that the presence of the oxidized species T 2 does not affect significantly its electrical properties up to a CsT:T 2 molar ratio of 5:1. Conductivity values as a function of salt concentration are discussed in terms of the effective number of charge carriers, taking into account the level of ionic association, and of the ionic mobility. Optically transparent gel electrolytes have been prepared by incorporation of the optimal liquid electrolyte into various amounts of poly(vinylidene fluoride) (PVDF). It is shown that ionic mobility is not much affected by the polymer concentration, suggesting that migration of ions occurs mainly through the solvent mixture surrounded by the PVDF matrix

  19. A high-throughput study of the redox properties of Nb-Ni oxide catalysts by low temperature CO oxidation: Implications in ethane ODH

    KAUST Repository

    Laveille, Paco; Biausque, Gregory; Zhu, Haibo; Basset, Jean-Marie; Caps, Valerie

    2013-01-01

    CO oxidation is used as a probe reaction to evaluate the redox properties of catalysts for the low temperature oxidative dehydrogenation (ODH) of ethane. Three series of Nb1-x-NixO nanocomposites with various Nb contents (x = 1, 0.95, 0.90, 0.85, 0.80) are prepared by a sol-gel route based on citrate and tested in a 16 parallel fixed-bed unit. Reductive and oxidative pre-treatments are shown to influence both the activity and the stability of the catalysts in CO oxidation. The extent of this effect depends on the Nb content of the composites, the Nb-rich samples being generally the most affected. However, the order of reactivity in CO oxidation is the same for the three series and is maintained whatever the conditions of the pre-treatment. It is the same as that observed in Nb1-x-NixO-catalyzed ethane ODH. © 2012 Elsevier B.V. All rights reserved.

  20. A high-throughput study of the redox properties of Nb-Ni oxide catalysts by low temperature CO oxidation: Implications in ethane ODH

    KAUST Repository

    Laveille, Paco

    2013-03-01

    CO oxidation is used as a probe reaction to evaluate the redox properties of catalysts for the low temperature oxidative dehydrogenation (ODH) of ethane. Three series of Nb1-x-NixO nanocomposites with various Nb contents (x = 1, 0.95, 0.90, 0.85, 0.80) are prepared by a sol-gel route based on citrate and tested in a 16 parallel fixed-bed unit. Reductive and oxidative pre-treatments are shown to influence both the activity and the stability of the catalysts in CO oxidation. The extent of this effect depends on the Nb content of the composites, the Nb-rich samples being generally the most affected. However, the order of reactivity in CO oxidation is the same for the three series and is maintained whatever the conditions of the pre-treatment. It is the same as that observed in Nb1-x-NixO-catalyzed ethane ODH. © 2012 Elsevier B.V. All rights reserved.

  1. Structure and properties of carbon black particles

    Science.gov (United States)

    Xu, Wei

    Structure and properties of carbon black particles were investigated using atomic force microscopy, gas adsorption, Raman spectroscopy, and X-ray diffraction. Supplementary information was obtained using TEM and neutron scattering. The AFM imaging of carbon black aggregates provided qualitative visual information on their morphology, complementary to that obtained by 3-D modeling based on TEM images. Our studies showed that carbon black aggregates were relatively flat. The surface of all untreated carbon black particles was found to be rough and its fractal dimension was 2.2. Heating reduced the roughness and fractal dimension for all samples heat treated at above 1300 K to 2.0. Once the samples were heat treated rapid cooling did not affect the surface roughness. However, rapid cooling reduced crystallite sizes, and different Raman spectra were obtained for carbon blacks of various history of heat treatment. By analyzing the Raman spectra we determined the crystallite sizes and identified amorphous carbon. The concentration of amorphous carbon depends on hydrogen content. Once hydrogen was liberated at increased temperature, the concentration of amorphous carbon was reduced and crystallites started to grow. Properties of carbon blacks at high pressure were also studied. Hydrostatic pressure did not affect the size of the crystallites in carbon black particles. The pressure induced shift in Raman frequency of the graphitic component was a result of increased intermolecular forces and not smaller crystallites. Two methods of determining the fractal dimension, the FHH model and the yardstick technique based on the BET theory were used in the literature. Our study proved that the FHH model is sensitive to numerous assumptions and leads to wrong conclusions. On the other hand the yardstick method gave correct results, which agreed with the AFM results.

  2. Structure and hydrodynamic properties of plectin molecules.

    Science.gov (United States)

    Foisner, R; Wiche, G

    1987-12-05

    Plectin is a cytoskeletal, high molecular weight protein of widespread and abundant occurrence in cultured cells and tissues. To study its molecular structure, the protein was purified from rat glioma C6 cells and subjected to chemical and biophysical analyses. Plectin's polypeptide chains have an apparent molecular weight of 300,000, as shown by one-dimensional sodium dodecyl sulfate/polyacrylamide electrophoresis. Cross-linking of non-denatured plectin in solution with dimethyl suberimidate and electrophoretic analyses on sodium dodecyl sulfate/agarose gels revealed that the predominant soluble plectin species was a molecule of 1200 X 10(3) Mr consisting of four 300 X 10(3) Mr polypeptide chains. Hydrodynamic properties of plectin in solution were obtained by sedimentation velocity centrifugation and high-pressure liquid chromatography analysis yielding a sedimentation coefficient of 10 S and a Stokes radius of 27 nm. The high f/fmin ratio of 4.0 indicated a very elongated shape of plectin molecules and an axial ratio of about 50. Shadowing and negative staining electron microscopy of plectin molecules revealed multiple domains: a rigid rod of 184 nm in length and 2 nm in diameter, and two globular heads of 9 nm diameter at each end of the rod. Circular dichroism spectra suggested a composition of 30% alpha-helix, 9% beta-structure and 61% random coil or aperiodic structure. The rod-like shape, the alpha-helix content as well as the thermal transition within a midpoint of 45 degrees C and the transition enthalpy (168 kJ/mol) of secondary structure suggested a double-stranded, alpha-helical coiled coil rod domain. Based on the available data, we favor a model of native plectin as a dumb-bell-like association of four 300 X 10(3) Mr polypeptide chains. Electron microscopy and turbidity measurements showed that plectin molecules self-associate into various oligomeric states in solutions of nearly physiological ionic strength. These interactions apparently involved

  3. 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.

  4. The Effect of Acidic and Redox Properties of V2O5/CeO2-ZrO2 Catalysts in Selective Catalytic Reduction of NO by NH3

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Riisager, Anders; Fehrmann, Rasmus

    2009-01-01

    V2O5 supported ZrO2 and CeO2–ZrO2 catalysts were prepared and characterized by N2 physisorption, XRPD, TPR, and NH3-TPD methods. The influence of calcination temperature from 400 to 600 °C on crystallinity, acidic and redox properties were studied and compared with the catalytic activity...... in the selective catalytic reduction (SCR) of NO with ammonia. The surface area of the catalysts decreased gradually with increasing calcination temperature. The SCR activity of V2O5/ZrO2 catalysts was found to be related with the support crystallinity, whereas V2O5/CeO2–ZrO2 catalysts were also dependent...... on acidic and redox properties of the catalyst. The V2O5/CeO2–ZrO2 catalysts showed high activity and selectivity for reduction of NO with NH3....

  5. Cerium-based metal organic frameworks with UiO-66 architecture: synthesis, properties and redox catalytic activity.

    Science.gov (United States)

    Lammert, Martin; Wharmby, Michael T; Smolders, Simon; Bueken, Bart; Lieb, Alexandra; Lomachenko, Kirill A; Vos, Dirk De; Stock, Norbert

    2015-08-14

    A series of nine Ce(iv)-based metal organic frameworks with the UiO-66 structure containing linker molecules of different sizes and functionalities were obtained under mild synthesis conditions and short reaction times. Thermal and chemical stabilities were determined and a Ce-UiO-66-BDC/TEMPO system was successfully employed for the aerobic oxidation of benzyl alcohol.

  6. A phosphate-dependent shift in redox state of cerium oxide nanoparticles and its effects on catalytic properties

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Sanjay; Dosani, Talib; Karakoti, Ajay S.; Kumar, Amit; Seal, Sudipta; Self, William

    2011-10-01

    Cerium oxide nanoparticles (CeNPs) have shown promise as catalytic antioxidants in cell culture and animal models as both superoxide dismutase and catalase mimetics. The reactivity of the cerium (Ce) atoms at the surface of its oxide particle is critical to such therapeutic properties, yet little is known about the potential for a protein or small molecule corona to form on these materials in vivo. Moreover Ce atoms in these active sites have the potential to interact with small molecule anions, peptides, or sugars when administered in culture or animal models. Several nanomaterials have been shown to alter or aggregate under these conditions, rendering them less useful for biomedical applications. In this work we have studied the change in catalytic properties of CeNPs when exposed to various biologically relevant conditions in vitro. We have found that CeNPs are resistant to broad changes in pH and also not altered by incubation in cell culture medium. However to our surprise phosphate anions significantly altered the characteristics of these nanomaterials and shifted the catalytic behavior due to the binding of phosphate anions to cerium. Given the abundance of phosphate in biological systems in an inorganic form, it is likely that the action of CeNPs as a catalyst may be strongly influenced by the local concentration of phosphate in the cells and/or tissues in which it has been introduced.

  7. 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...

  8. Synthesis route and structural properties of nanoferrites

    Energy Technology Data Exchange (ETDEWEB)

    Zaharieva, Katerina; Cherkezova-Zheleva, Zara; Kunev, Boris; Shopska, Maya; Mitov, Ivan [Institute of Catalysis, Bulgarian Academy of Sciences, Sofia (Bulgaria)

    2013-07-01

    The nano dimensional magnesium ferrite materials Mg{sub 0.25}Fe{sub 2.75}O{sub 4} , Mg{sub 0.5}Fe{sub 2.5}O{sub 4} and MgFe{sub 2}O{sub 4} with different stoichiometry were prepared by co-precipitation procedure using MgCl{sub 2} •6H{sub 2}O, FeCl{sub 2} •4H{sub 2}O and FeCl{sub 3} •6H{sub 2}O and NaOH as precipitant. The physicochemical methods - X-ray diffraction analysis, Moessbauer spectroscopy and FTIR spectroscopy were performed to investigate the structural properties of obtained nano size magnesium ferrite type samples. The registered experimental data were determined the presence of spinel ferrites and additional precursor phases as iron oxihydroxides and double layered hydroxides in ferrite materials MgxFe{sub 3-x}O{sub 4} (x=0.5;1). In the case of magnesium ferrite sample Mg{sub x}Fe{sub 3-x}O{sub 4} (x=0.25) the existence of non-stoichiometric spinel ferrite and intermediate phase - iron oxihydroxides were observed only. Key words: magnesium ferrites, co-precipitation, physicochemical methods.

  9. Structure and properties of hybrid coatings

    International Nuclear Information System (INIS)

    Pogrebnjak, A.D.; Vasilyuk, V.V.; Kravchenko, Yu.A.; Tyurin, Yu.N.; Alontseva, D.L.; Ponaryadov, V.V.; Ruzimov, Sh.M.

    2004-01-01

    Full text: This review report presents both the results obtained by the authors and those of other authors concerning investigations of structure and properties of hybrid coatings. Examples of such coatings as Al 2 O 3 /Cr/TiN/steel, TiC; TiN/Ti-V-Al; NiCr/steel; CrNiBSi/steel and others before and after electron beam irradiation had been considered. In these coatings the thickest layer was deposited using the high-velocity pulsed plasma jet, all others being deposited in vacuum by the vacuum-arc source or implanter. Advantages of the high-velocity pulsed plasma jet in comparison with other technologies had been demonstrated. A wide spectrum of analyzing methods had been applied for analyses: TEM, SEM with EDS, RBS, NRA, SIMS, XRD, tests for corrosion, wear, adhesion and hardness. The works had been funded by the Project 2M/03 54-2003 of the Ministry of Science and Education of Ukraine and STCU Project N3078

  10. Synthesis route and structural properties of nanoferrites

    International Nuclear Information System (INIS)

    Zaharieva, Katerina; Cherkezova-Zheleva, Zara; Kunev, Boris; Shopska, Maya; Mitov, Ivan

    2013-01-01

    The nano dimensional magnesium ferrite materials Mg 0.25 Fe 2.75 O 4 , Mg 0.5 Fe 2.5 O 4 and MgFe 2 O 4 with different stoichiometry were prepared by co-precipitation procedure using MgCl 2 •6H 2 O, FeCl 2 •4H 2 O and FeCl 3 •6H 2 O and NaOH as precipitant. The physicochemical methods - X-ray diffraction analysis, Moessbauer spectroscopy and FTIR spectroscopy were performed to investigate the structural properties of obtained nano size magnesium ferrite type samples. The registered experimental data were determined the presence of spinel ferrites and additional precursor phases as iron oxihydroxides and double layered hydroxides in ferrite materials MgxFe 3-x O 4 (x=0.5;1). In the case of magnesium ferrite sample Mg x Fe 3-x O 4 (x=0.25) the existence of non-stoichiometric spinel ferrite and intermediate phase - iron oxihydroxides were observed only. Key words: magnesium ferrites, co-precipitation, physicochemical methods

  11. Phase relations, crystal structures and physical properties of nuclear fuels

    International Nuclear Information System (INIS)

    Tagawa, Hiroaki; Fujino, Takeo; Tateno, Jun

    1975-07-01

    Phase relations, crystal structures and physical properties of the compounds for nuclear fuels are presented, including melting point, thermal expansion, diffusion and magnetic and electric properties. Emphasis is on oxides, carbides and nitrides of thorium, uranium and plutonium. (auth.)

  12. Surface morphology, structural and electrical properties of RF ...

    Indian Academy of Sciences (India)

    2018-05-19

    May 19, 2018 ... ITO thin films; sputtering; structure; electrical properties; AFM; Hall effect. 1. Introduction ... ness range (61–768 nm) and to see if this system present properties that .... using the Bragg equation, and the relation linking the inter-.

  13. Structural and electrochemical properties of polythiophene

    Energy Technology Data Exchange (ETDEWEB)

    Senthilkumar, B.; Thenamirtham, P. [Solid State Ionics and Energy Devices Laboratory, Department of Physics, Bharathiar University, Coimbatore 641 046 (India); Kalai Selvan, R., E-mail: selvankram@buc.edu.in [Solid State Ionics and Energy Devices Laboratory, Department of Physics, Bharathiar University, Coimbatore 641 046 (India)

    2011-08-15

    Polythiophenes (PTs) were prepared by chemical oxidative polymerization method in presence and absence of three different (cationic - CTAB, anionic - SDS and non-ionic - Triton X-100) surfactants using FeCl{sub 3} as oxidant. The prepared PTs were characterized by FT-IR, UV-Vis, XRD, SEM and cyclic voltammetry studies. The FT-IR spectra inferred the polymerization of thiophene and elucidate the corresponding functional groups of PTs. Our results on the UV-Vis spectra demonstrate the n-{pi}* electronic transition of the conjugated molecules. Further the red shift in the absorption peak confirms the longer conjugation length of PTs. The amorphous nature of the PTs was inferred from the XRD pattern. The PTs prepared with surfactant exhibited different morphology compared to PT prepared without surfactant. The specific capacitances (SC) of the prepared PTs were calculated using cyclic voltammetry technique, the PT prepared with TRITRON X-100 exhibited higher SC of 117 F/g compared to SC of surfactant free PT (78 F/g). Hence, the PTs prepared with surfactants were found to be suitable electrode materials for redox supercapacitors.

  14. Enhancing the Electronic Conductivity of Vanadium-tellurite Glasses by Tuning the Redox State

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Yue, Yuanzheng

    Transition metal oxides are used in a variety of electronic purposes, e.g., vanadium tellurite as cathode material in high-power demanding batteries. By tuning the redox state of vanadium, it is possible to achieve a lower internal resistance within the entire battery unit, thus a higher capacity....... In this work we vary the redox state of a given vanadium tellurite system by performing post heat-treatment in controlled atmosphere. This process is in theory not limited only to varying electronic conductivity, but also varying the glass structure, and hence, changing properties of the glasses, e.g, thermal...... and mechanical properties. Finally we give insight into the relation between the redox state and electronic conductivity....

  15. Structure and magnetic properties of Alnico ribbons

    Science.gov (United States)

    Zhang, Ce; Li, Ying; Han, Xu-Hao; Du, Shuai-long; Sun, Ji-bing; Zhang, Ying

    2018-04-01

    Al-Ni-Co alloy has been widely applied in various industrial fields due to its excellent thermal and magnetic stability. In this paper, new Al-Ni-Co ribbons are prepared by simple processes combining melt-spinning with annealing, and their phase transition, microstructure and magnetic properties are studied. The results show that after as-spun ribbons are annealed, the grain size of ribbons increases from 1.1 ± 0.3 μm to 4.8 ± 0.8 μm, but still much smaller than that of the bulk Al-Ni-Co alloy manufactured by traditional technologies. In addition, some rod-like Al70Co20Ni10-type, Al9Co2-type and Fe2Nb-type phases are precipitated at grain boundaries; simultaneously, the distinct spinodal decomposition microstructure with periodic ingredient variation is thoroughly formed in all grains by the reaction of α → α1 + α2. Furthermore, the α1 and α2 distribute alternately like a maze, the Fe-Co-rich α1 phase holds 35.9-47.3 vol%, while the Al-Ni-rich α2 phase occupies the rest. Finally, the coercivity of annealed ribbons can reach to 485.3 ± 76.6 Oe. If the annealed ribbons are further aged at 560 °C, their Hc even increases to 738.1 ± 81.0 Oe. The coercivity mechanism is discussed by the combination of microstructure and domain structure.

  16. Marine redox structure at the culmination of the Great Oxidation Event: Insights from the Zaonega Formation, Karelia, Russia

    Science.gov (United States)

    Kipp, M.; Lepland, A.; Buick, R.

    2017-12-01

    The availability of dissolved oxygen is thought to have been the dominant throttle on the evolution and diversification of eukaryotic life during the Proterozoic Eon [1]. In the mid-Proterozoic, during the interval that presaged the rise of eukaryotes to ecological dominance, oxygen scarcity is thought to have relegated eukaryotic organisms to slivers of oxygenated shallow oceans [2]. However, recent work has suggested that oxygen levels rose dramatically during the early Paleoproterozoic Great Oxidation Event before crashing to the low levels of the mid-Proterozoic [3]. Evidence from selenium isotopes in shales [4] and iodate concentrations in carbonates [5] has even suggested that wide swathes of continental shelves were oxic enough to support eukaryotic organisms at this time. How oxic though, and for how long, remain poorly constrained. Here we present new selenium geochemical data from the Zaonega Formation of Karelia, Russia that can help resolve those questions. Previous work has proposed that the Zaonega Formation, and correlative Francevillian Series of Gabon, record the establishment of an oxygen-rich atmosphere at the culmination of the GOE [6]. Our selenium isotope dataset provides a test for this hypothesis, and can also be used to assess the preservation of the geochemical signatures in the Zaonega Formation. These data point to regional redox fluctuations, but due to the short marine residence time of selenium, extrapolating these results to global phenomena remains difficult. 1. Reinhard, et al (2016) PNAS 2. Planavsky, et al (2014) Science 3. Bekker and Holland (2012) EPSL 4. Kipp, et al (2017) PNAS 5. Hardisty, et al (2014) Geology 6. Kump, et al (2011) Science

  17. Mixed-Metal, Structural, and Substitution Effects of Polyoxometalates on Electrochemical Behavior in a Redox Flow Battery

    International Nuclear Information System (INIS)

    Pratt, Harry D.; Pratt, William R.; Fang, Xikui; Hudak, Nicholas S.; Anderson, Travis M.

    2014-01-01

    Graphical abstract: - Highlights: • Testing of a flow battery with polyoxometalates. • Coulombic efficiency of 83% for an iron-based compound. • Both size and charge density influence battery performance. - Abstract: A pair of redox flow batteries containing polyoxometalates was tested as part of an ongoing program in stationary energy storage. The iron-containing dimer, (SiFe 3 W 9 (OH) 3 O 34 ) 2 (OH) 3 11− , cycled between (SiFe 3 W 9 (OH) 3 O 34 ) 2 (OH) 3 11− /(SiFe 3 W 9 (OH) 3 O 34 ) 2 (OH) 3 14− and (SiFe 3 W 9 (OH) 3 O 34 ) 2 (OH) 3 17− /(SiFe 3 W 9 (OH) 3 O 34 ) 2 (OH) 3 14− for the positive and negative electrode, respectively. This compound demonstrated a coulombic efficiency of 83% after 20 cycles with an electrochemical yield (measured discharge capacity as a percentage of theoretical capacity) of 55%. Cyclic voltammetry on the Lindqvist ion, cis-V 2 W 4 O 19 4− , showed quasi-reversible vanadium electrochemistry, but tungsten reduction was mostly irreversible. In a flow cell configuration, cis-V 2 W 4 O 19 4− had a coulombic efficiency of 45% (for a two-electron process) and an electrochemical yield of 16% after 20 cycles. The poor performance of cis-V 2 W 4 O 19 4− was attributed primarily to its higher charge density. Collectively, the results showed that both polyoxometalate size and charge density are both important parameters to consider in battery material performance

  18. 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.

  19. Structural, dielectric and electrical properties of ...

    Indian Academy of Sciences (India)

    Administrator

    Detailed studies of dielectric properties of the compound as a function of temperature at ... Microscope (Jeol, JSM-840), operated at 20 kV. The sin- tered pellet was .... grain boundaries, and provides the true picture of the electrical properties of ...

  20. Tools to Understand Structural Property Relationships for Wood Cell Walls

    Science.gov (United States)

    Joseph E. Jakes; Daniel J. Yelle; Charles R. Frihart

    2011-01-01

    Understanding structure-property relationships for wood cell walls has been hindered by the complex polymeric structures comprising these cell walls and the difficulty in assessing meaningful mechanical property measurements of individual cell walls. To help overcome these hindrances, we have developed two experimental methods: 1) two-dimensional solution state nuclear...

  1. Flexible Nanocellulose - Nanoparticle Composites: Structures and Properties

    OpenAIRE

    UTHPALA MANAVI GARUSINGHE

    2018-01-01

    Nanocellulose is biodegradable and renewable and has many attractive properties of technological interest. Therefore, nanocellulose can be converted into thin films, which is used in wide range of applications. However, the property range achievable with nanocellulose by itself still has limitations. This thesis focuses on the production of nanocellulose-inorganic nanoparticle composites to combine the advantage associated with both individual components together to extend the range of proper...

  2. Functional and structural studies of the disulfide isomerase DsbC from the plant pathogen Xylella fastidiosa reveals a redox-dependent oligomeric modulation in vitro.

    Science.gov (United States)

    Santos, Clelton A; Toledo, Marcelo A S; Trivella, Daniela B B; Beloti, Lilian L; Schneider, Dilaine R S; Saraiva, Antonio M; Crucello, Aline; Azzoni, Adriano R; Souza, Alessandra A; Aparicio, Ricardo; Souza, Anete P

    2012-10-01

    Xylella fastidiosa is a Gram-negative bacterium that grows as a biofilm inside the xylem vessels of susceptible plants and causes several economically relevant crop diseases. In the present study, we report the functional and low-resolution structural characterization of the X. fastidiosa disulfide isomerase DsbC (XfDsbC). DsbC is part of the disulfide bond reduction/isomerization pathway in the bacterial periplasm and plays an important role in oxidative protein folding. In the present study, we demonstrate the presence of XfDsbC during different stages of X. fastidiosa biofilm development. XfDsbC was not detected during X. fastidiosa planktonic growth; however, after administering a sublethal copper shock, we observed an overexpression of XfDsbC that also occurred during planktonic growth. These results suggest that X. fastidiosa can use XfDsbC in vivo under oxidative stress conditions similar to those induced by copper. In addition, using dynamic light scattering and small-angle X-ray scattering, we observed that the oligomeric state of XfDsbC in vitro may be dependent on the redox environment. Under reducing conditions, XfDsbC is present as a dimer, whereas a putative tetrameric form was observed under nonreducing conditions. Taken together, our findings demonstrate the overexpression of XfDsbC during biofilm formation and provide the first structural model of a bacterial disulfide isomerase in solution. © 2012 The Authors Journal compilation © 2012 FEBS.

  3. Organic bulk heterojunction photovoltaic structures: design, morphology and properties

    International Nuclear Information System (INIS)

    Bulavko, G V; Ishchenko, A A

    2014-01-01

    Main approaches to the design of organic bulk heterojunction photovoltaic structures are generalized and systematized. Novel photovoltaic materials based on fullerenes, organic dyes and related compounds, graphene, conjugated polymers and dendrimers are considered. The emphasis is placed on correlations between the chemical structure and properties of materials. The effect of morphology of the photoactive layer on the photovoltaic properties of devices is analyzed. Main methods of optimization of the photovoltaic properties are outlined. The bibliography includes 338 references

  4. Electronic structure and properties of rare earth and actinide intermetallics

    International Nuclear Information System (INIS)

    Kirchmayr, H.R.

    1984-01-01

    There are 188 contributions, experimental and theoretical, a few on rare earth and actinide elements but mostly on rare earth and actinide intermetallic compounds and alloys. The properties dealt with include 1) crystal structure, 2) magnetic properties and magnetic structure, 3) magnetic phase transformations and valence fluctuations, 4) electrical properties and superconductivity and their temperature, pressure and magnetic field dependence. A few papers deal with crystal growth and novel measuring methods. (G.Q.)

  5. Stimuli-responsive Materials and Structures with Electrically Tunable Mechanical Properties

    Science.gov (United States)

    Auletta, Jeffrey Thomas

    Electricity, a convenient stimulus, was used to manipulate the mechanical properties of two classes of materials, each with a different mechanism. In the first system, macroscale electroplastic elastomer hydrogels (EPEs) were reversibly cycled through soft and hard states by sequential application of oxidative and reductive potentials. Electrochemically reversible crosslinks were switched between strongly binding Fe3+ and weak to non-binding Fe2+, as determined by potentiometric titration.With the incorporation of graphene oxide (GO) into the EPE, a significant enhancement in modulus and toughness was observed, allowing for the preparation of thinner EPE samples, which could be reversibly cycled between soft and hard states over 30 minutes. Further characterization of this EPE by magnetic susceptibility measurements suggested the formation of multinuclear iron clusters within the gel. Copper-derived EPEs which exploited the same redox-controlled mechanism for switching between hard and soft states were also prepared. Here, the density of temporary crosslinks and the mechanical properties were controlled by reversibly switching between the +1 and +2 oxidation states, using a combination of electrochemical/air oxidation and chemical reduction. In addition to undergoing redox-controlled changes in modulus, these EPEs exhibited shape memory. In the second system, electroadhesion between ionomer layers was exploited to create laminate structures whose rigidity depended on the reversible polarization of the dielectric polymers. The role of the counter-ion in determining the intrinsic and electroadhesive properties of poly(ethylene-co-acrylic acid) ionomers in bi- and tri-layered laminate structures was examined. PEAA ionomers were prepared with three tetraalkylammonium cations (NR4 +, R = methyl, TMA+; ethyl, TEA+; and propyl, TPA+). Reflecting the increasing hydrophobicity of the longer alkyl chains, water uptake changed as a function of counterion with TMA+ > TEA

  6. Monodentate Schiff base ligands: their structural characterization, photoluminescence, anticancer, electrochemical and sensor properties.

    Science.gov (United States)

    Köse, Muhammet; Ceyhan, Gökhan; Tümer, Mehmet; Demirtaş, Ibrahim; Gönül, İlyas; McKee, Vickie

    2015-02-25

    Two Schiff base compounds, N,N'-bis(2-methoxy phenylidene)-1,5-diamino naphthalene (L(1)) and N,N'-bis(3,4,5-trimethoxy phenylidene)-1,5-diamino naphthalene (L(2)) were synthesized and characterized by the analytical and spectroscopic methods. The electrochemical and photoluminescence properties of the Schiff bases were investigated in the different conditions. The compounds L(1) and L(2) show the reversible redox processes at some potentials. The sensor properties of the Schiff bases were examined and color changes were observed upon addition of the metal cations, such as Hg(II), Cu(II), Co(II) and Al(III). The Schiff base compounds show the bathochromic shift from 545 to 585 nm. The single crystals of the compounds (L(1)) and (L(2)) were obtained from the methanol solution and characterized structurally by the X-ray crystallography technique. The molecule L(2) is centrosymmetric whereas the L(1) has no crystallographically imposed molecular symmetry. However, the molecular structures for these compounds are quite similar, differing principally in the conformation about methoxy groups and the dihedral angle between the two aromatic rings and diamine naphthalene. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Redox properties of free radicals

    International Nuclear Information System (INIS)

    Neta, P.

    1981-01-01

    Results of electron transfer reactions observed and monitored by pulse radiolysis are reported. This technique allows determination of the first one-electron reduction or oxidation of a compound rather than the overall two-electron transfer usually reported. Pulse radiolysis allows the determination of absolute rate constants for reactions of free radicals and helps elucidate the mechanisms involved. Studies using this technique to study radicals derived from quinones, nitro compounds, pyridines, phenols, and anilines are reported. Radicals of biochemical interest arising from riboflavin, ascorbic acid, vitamin K 3 , vitamin E, MAD + , porphyrins, etc. have also been studied

  8. Foundations of compositional models: structural properties

    Czech Academy of Sciences Publication Activity Database

    Jiroušek, Radim; Kratochvíl, Václav

    2015-01-01

    Roč. 44, č. 1 (2015), s. 2-25 ISSN 0308-1079 R&D Projects: GA ČR GA13-20012S Grant - others:GA ČR(CZ) GAP403/12/2175 Program:GA Institutional support: RVO:67985556 Keywords : multidimensional distribution * conditional independence * composition * semigraphoid properties * running intersection property Subject RIV: BA - General Mathematics Impact factor: 1.677, year: 2015 http://library.utia.cas.cz/separaty/2015/MTR/jirousek-0442412.pdf

  9. Structure, reactivity, and biological properties of hidantoines

    International Nuclear Information System (INIS)

    Oliveira, Silvania Maria de; Silva, Joao Bosco Paraiso da; Hernandes, Marcelo Zaldini; Lima, Maria do Carmo Alves de; Galdino, Suely Lins; Pitta, Ivan da Rocha

    2008-01-01

    Hydantoin (imidazolidine-2,4-dione) is a 2,4-diketotetrahydroimidazole discovered by Baeyer in 1861. Thiohydantoins and derivatives were prepared, having chemical properties similar to the corresponding carbonyl compounds. Some biological activities (antimicrobial, anticonvulsant, schistosomicidal) are attributed to the chemical reactivity and consequent affinity of hydantoinic rings towards biomacromolecules. Therefore, knowledge about the chemistry of hydantoins has increased enormously. In this review, we present important aspects such as reactivity of hydantoins, acidity of hydantoins, spectroscopy and crystallographic properties, and biological activities of hydantoin and its derivatives. (author)

  10. Redox characteristics of the eukaryotic cytosol

    DEFF Research Database (Denmark)

    López-Mirabal, H Reynaldo; Winther, Jakob R

    2007-01-01

    The eukaryotic cytoplasm has long been regarded as a cellular compartment in which the reduced state of protein cysteines is largely favored. Under normal conditions, the cytosolic low-molecular weight redox buffer, comprising primarily of glutathione, is highly reducing and reactive oxygen species...... (ROS) and glutathionylated proteins are maintained at very low levels. In the present review, recent progress in the understanding of the cytosolic thiol-disulfide redox metabolism and novel analytical approaches to studying cytosolic redox properties are discussed. We will focus on the yeast model...... organism, Saccharomyces cerevisiae, where the combination of genetic and biochemical approaches has brought us furthest in understanding the mechanisms underlying cellular redox regulation. It has been shown in yeast that, in addition to the enzyme glutathione reductase, other mechanisms may exist...

  11. Redox biotransformation and delivery of anthracycline anticancer antibiotics: How interpretable structure-activity relationships of lethality using electrophilicity and the London formula for dispersion interaction work.

    Science.gov (United States)

    Pang, Siu-Kwong

    2017-03-30

    Quantum chemical methods and molecular mechanics approaches face a lot of challenges in drug metabolism study because of their either insufficient accuracy or huge computational cost, or lack of clear molecular level pictures for building computational models. Low-cost QSAR methods can often be carried out even though molecular level pictures are not well defined; however, they show difficulty in identifying the mechanisms of drug metabolism and delineating the effects of chemical structures on drug toxicity because a certain amount of molecular descriptors are difficult to be interpreted. In order to make a breakthrough, it was proposed that mechanistically interpretable molecular descriptors were used to correlate with biological activity to establish structure-activity plots. The mechanistically interpretable molecular descriptors used in this study include electrophilicity and the mathematical function in the London formula for dispersion interaction, and they were calculated using quantum chemical methods. The biological activity is the lethality of anthracycline anticancer antibiotics denoted as log LD50, which were obtained by intraperitoneal injection into mice. The results reveal that the plots for electrophilicity, which can be interpreted as redox reactivity of anthracyclines, can describe oxidative degradation for detoxification and reductive bioactivation for toxicity induction. The plots for the dispersion interaction function, which represent the attraction between anthracyclines and biomolecules, can describe efflux from and influx into target cells of toxicity. The plots can also identify three structural scaffolds of anthracyclines that have different metabolic pathways, resulting in their different toxicity behavior. This structure-dependent toxicity behavior revealed in the plots can provide perspectives on design of anthracycline anticancer antibiotics. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  12. Redox functionality mediated by adsorbed oxygen on a Pd oxide film over a Pd(100) thin structure: a first-principles study

    International Nuclear Information System (INIS)

    Kusakabe, K; Ikuno, Y k; Nagara, H; Harada, K

    2009-01-01

    Stable oxygen sites on a PdO film over a Pd(100) thin structure with a (√5x√5)R27 o surface unit cell are determined using the first-principles electronic structure calculations with the generalized gradient approximation. The adsorbed monatomic oxygen goes to a site bridging two twofold-coordinated Pd atoms or to a site bridging a twofold-coordinated Pd atom and a fourfold-coordinated Pd atom. Estimated reaction energies of CO oxidation by reduction of the oxidized PdO film and N 2 O reduction mediated by oxidation of the PdO film are both exothermic. Motion of the adsorbed oxygen atom between the two stable sites is evaluated using the nudged elastic band method, where an energy barrier for a translational motion of the adsorbed oxygen may become ∼0.45 eV, which is low enough to allow fluxionality of the surface oxygen at high temperatures. The oxygen fluxionality is allowed by the existence of twofold-coordinated Pd atoms on the PdO film, whose local structure has a similarity to that of Pd catalysts for the Suzuki-Miyaura cross-coupling. Although NO x (including NO 2 and NO) reduction is not always catalyzed by the PdO film only, we conclude that continual redox reactions may happen mediated by oxygen-adsorbed PdO films over a Pd surface structure, when the influx of NO x and CO continues, and when the reaction cycle is kept on a well-designed oxygen surface.

  13. Structural Characteristics and Physical Properties of Tectonically Deformed Coals

    OpenAIRE

    Yiwen Ju; Zhifeng Yan; Xiaoshi Li; Quanlin Hou; Wenjing Zhang; Lizhi Fang; Liye Yu; Mingming Wei

    2012-01-01

    Different mechanisms of deformation could make different influence on inner structure and physical properties of tectonically deformed coal (TDC) reservoirs. This paper discusses the relationship between macromolecular structure and physical properties of the Huaibei-Huainan coal mine areas in southern North China. The macromolecular structure and pore characteristics are systematically investigated by using techniques such as X-ray diffraction (XRD), high-resolution transmission electron mic...

  14. 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.

  15. Structural and elastic properties of porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Matthai, C C [Department of Physics and Astronomy, University of Wales College of Cardiff, Cardiff CF2 3YB (United Kingdom); Gavartin, J L [Department of Physics and Astronomy, University of Wales College of Cardiff, Cardiff CF2 3YB (United Kingdom); Cafolla, A A [Department of Physics, Dublin City University, Dublin (Ireland)

    1995-01-15

    We have implemented a modified diffusion-limited aggregation model to simulate the porous silicon structure obtained by electrochemical dissolution. The resulting fractal structures were fully equilibrated using the molecular dynamics method. An analysis of the relaxed structure shows it to be quite stable with the presence of one-, two- and three-coordinated atoms as well as the four-coordinated atoms found in bulk silicon. It is suggested that the different substructures or nanocrystals might be responsible for the observed photoluminescence. ((orig.))

  16. Hydrothermal synthesis, crystal structure and luminescence property ...

    Indian Academy of Sciences (India)

    The design and construction of ... dination polymers. It is difficult to design coordination .... The first endotherm at about 180 ... graphic data for coordination polymer 1. ... Sheldrick G M 1997 SHELXS-97: Program for solution of crystal structures ...

  17. Electronic structure and optical properties of AIN under high pressure

    International Nuclear Information System (INIS)

    Li Zetao; Dang Suihu; Li Chunxia

    2011-01-01

    We have calculated the electronic structure and optical properties of Wurtzite structure AIN under different high pressure with generalized gradient approximation (GGA) in this paper. The total energy, density of state, energy band structure and optical absorption and reflection properties under high pressure are calculated. By comparing the changes of the energy band structure, we obtained AIN phase transition pressure for 16.7 GPa, which is a direct band structure transforming to an indirect band structure. Meanwhile, according to the density of states distribution and energy band structure, we analyzed the optical properties of AIN under high-pressure, the results showed that the absorption spectra moved from low-energy to high-energy. (authors)

  18. 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...

  19. Comparative Study of f-Element Electronic Structure across a Series of Multimetallic Actinide, Lanthanide-Actinide and Lanthanum-Actinide Complexes Possessing Redox-Active Bridging Ligands

    Energy Technology Data Exchange (ETDEWEB)

    Schelter, Eric J.; Wu, Ruilian; Veauthier, Jacqueline M.; Bauer, Eric D.; Booth, Corwin H.; Thomson, Robert K.; Graves, Christopher R.; John, Kevin D.; Scott, Brian L.; Thompson, Joe D.; Morris, David E.; Kiplinger, Jaqueline L.

    2010-02-24

    A comparative examination of the electronic interactions across a series of trimetallic actinide and mixed lanthanide-actinide and lanthanum-actinide complexes is presented. Using reduced, radical terpyridyl ligands as conduits in a bridging framework to promote intramolecular metal-metal communication, studies containing structural, electrochemical, and X-ray absorption spectroscopy are presented for (C{sub 5}Me{sub 5}){sub 2}An[-N=C(Bn)(tpy-M{l_brace}C{sub 5}Me4R{r_brace}{sub 2})]{sub 2} (where An = Th{sup IV}, U{sup IV}; Bn = CH{sub 2}C{sub 6}H{sub 5}; M = La{sup III}, Sm{sup III}, Yb{sup III}, U{sup III}; R = H, Me, Et) to reveal effects dependent on the identities of the metal ions and R-groups. The electrochemical results show differences in redox energetics at the peripheral 'M' site between complexes and significant wave splitting of the metal- and ligand-based processes indicating substantial electronic interactions between multiple redox sites across the actinide-containing bridge. Most striking is the appearance of strong electronic coupling for the trimetallic Yb{sup III}-U{sup IV}-Yb{sup III}, Sm{sup III}-U{sup IV}-Sm{sup III}, and La{sup III}-U{sup IV}-La{sup III} complexes, [8]{sup -}, [9b]{sup -} and [10b]{sup -}, respectively, whose calculated comproportionation constant K{sub c} is slightly larger than that reported for the benchmark Creutz-Taube ion. X-ray absorption studies for monometallic metallocene complexes of U{sup III}, U{sup IV}, and U{sup V} reveal small but detectable energy differences in the 'white-line' feature of the uranium L{sub III}-edges consistent with these variations in nominal oxidation state. The sum of this data provides evidence of 5f/6d-orbital participation in bonding and electronic delocalization in these multimetallic f-element complexes. An improved, high-yielding synthesis of 4{prime}-cyano-2,2{prime}:6{prime},2{double_prime}-terpyridine is also reported.

  20. On some fundamental properties of structural topology optimization problems

    DEFF Research Database (Denmark)

    Stolpe, Mathias

    2010-01-01

    We study some fundamental mathematical properties of discretized structural topology optimization problems. Either compliance is minimized with an upper bound on the volume of the structure, or volume is minimized with an upper bound on the compliance. The design variables are either continuous o....... The presented examples can be used as teaching material in graduate and undergraduate courses on structural topology optimization....

  1. Structure-function-property-design interplay in biopolymers: spider silk.

    Science.gov (United States)

    Tokareva, Olena; Jacobsen, Matthew; Buehler, Markus; Wong, Joyce; Kaplan, David L

    2014-04-01

    Spider silks have been a focus of research for almost two decades due to their outstanding mechanical and biophysical properties. Recent advances in genetic engineering have led to the synthesis of recombinant spider silks, thus helping to unravel a fundamental understanding of structure-function-property relationships. The relationships between molecular composition, secondary structures and mechanical properties found in different types of spider silks are described, along with a discussion of artificial spinning of these proteins and their bioapplications, including the role of silks in biomineralization and fabrication of biomaterials with controlled properties. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  2. New membrane structures with proton conducting properties

    DEFF Research Database (Denmark)

    Nørgaard, Casper Frydendal

    if higher operating temperature is enabled. One approach to obtain improved membranes in the aspects of applicable operating temperature and methanol permeability, which has attracted considerable attention, is the formation of composites by distributing inorganic fillers into Nafion or alternative polymers...... temperature and high relative humidity can cause excessive swelling of the membranes, yielding insufficient mechanical properties and breakdown of membrane function. Moreover, in the case of the Direct Methanol Fuel Cell (DMFC), their significant methanol permeability causes loss of efficiency. Higher...

  3. Meteorite Unit Models for Structural Properties

    Science.gov (United States)

    Agrawal, Parul; Carlozzi, Alexander A.; Karajeh, Zaid S.; Bryson, Kathryn L.

    2017-10-01

    To assess the threat posed by an asteroid entering Earth’s atmosphere, one must predict if, when, and how it fragments during entry. A comprehensive understanding of the asteroid material properties is needed to achieve this objective. At present, the meteorite material found on earth are the only objects from an entering asteroid that can be used as representative material and be tested inside a laboratory. Due to complex composition, it is challenging and expensive to obtain reliable material properties by means of laboratory test for a family of meteorites. In order to circumvent this challenge, meteorite unit models are developed to determine the effective material properties including Young’s modulus, compressive and tensile strengths and Poisson’s ratio, that in turn would help deduce the properties of asteroids. The meteorite unit model is a representative volume that accounts for diverse minerals, porosity, cracks and matrix composition.The Young’s Modulus and Poisson’s Ratio in the meteorite units are calculated by performing several hundreds of Monte Carlo simulations by randomly distributing the various phases inside these units. Once these values are obtained, cracks are introduced in these units. The size, orientation and distribution of cracks are derived by CT-scans and visual scans of various meteorites. Subsequently, simulations are performed to attain stress-strain relations, strength and effective modulus values in the presence of these cracks. The meteorite unit models are presented for H, L and LL ordinary chondrites, as well as for terrestrial basalt. In the case of the latter, data from the simulations is compared with experimental data to validate the methodology. These meteorite unit models will be subsequently used in fragmentation modeling of full scale asteroids.

  4. Nanoemulsions: formation, structure, and physical properties

    International Nuclear Information System (INIS)

    Mason, T G; Wilking, J N; Meleson, K; Chang, C B; Graves, S M

    2006-01-01

    We summarize procedures for producing 'nanoemulsions' comprised of nanoscale droplets, or 'nanoemulsions', methods for controlling the droplet size distribution and composition, and interesting physical properties of nanoemulsions. In contrast to more common microscale emulsions, nanoemulsions exhibit optical transparency at high droplet volume fractions, φ, surprisingly strong elasticity at low φ, and enhanced diffusive transport and shelf stability. For these reasons, nanoemulsions have great potential in a wide range of industries including pharmaceuticals, foods, and personal care products. (topical review)

  5. Environmental effects on properties of structural alloys

    International Nuclear Information System (INIS)

    Chopra, O.K.; Smith, D.L.

    1984-01-01

    Corrosion data are presented for several austenitic and ferritic steels exposed at temperatures between 700 and 755 K in flowing lithium and Pb-17Li environments. The results indicate that dissolution rates for both steels are an order of magnitude greater in Pb-Li than in lithium. Tensile data for cold-worked type 316 stainless steel show that a flowing environment has no effect on the tensile properties of type 316 stainless steel at temperatures between 473 and 773 K

  6. Structure Property Relationships in Organic Conjugated Systems

    OpenAIRE

    O'Neill, Luke; Lynch, Patrick; McNamara, Mary

    2005-01-01

    A series of π conjugated oligomers were studied by absorption and photoluminescence spectroscopy. A linear relationship between the positioning of the absorption and photoluminescence maxima plotted against inverse conjugation length is observed. The relationships are in good agreement with the simple particle in a box method, one of the earliest descriptions of the properties of one-dimensional organic molecules. In addition to the electronic transition energies, it was observed that the Sto...

  7. Structure Property Relationships in Organic Conjugated Systems

    OpenAIRE

    O'Neill, Luke

    2008-01-01

    A series of pi(п) conjugated oligomers containing 1 to 6 monomer units were studied by absorption and photoluminescence spectroscopies. The results are discussed and examined with regard to the variation of the optical properties with the increase of effective conjugation length. It was found that there was a linear relationship between the positioning of the absorption and photoluminescence maxima plotted against inverse conjugation length. The relationships are in good agreement with the si...

  8. Electron beam crosslinked PVC : structure property relationships

    International Nuclear Information System (INIS)

    Gupta, Neeraj K.; Sabharwal, Sunil

    2001-01-01

    PVC is used extensively for its insulating properties for the manufacture of wires and cables and for other applications. Its gradual degradation, oxidation and even dehydro chlorination restricts use for long lasting period in installations such as high temperature zones, underground cables, communication systems, electro-nuclear facilities, etc. The technological properties and performance characteristics of PVC based insulation can be improved via crosslinking by high-energy electrons. PVC is however a polymer, which on irradiation predominantly undergoes degradation. To avoid degradation, it needs to be compounded with sensitizing agents or multifunctional monomers so that crosslinking is the predominant reaction. Radiation cross linkable formulations are complex mixtures of resin and various additives incorporated for achieving desired technological and performance characteristics, ease of processing and improving quality. The proper choice of additives and sensitizing agents enable low dose requirements for efficient crosslinking and improvements in various technological properties. The purposes of this work was to investigate the effect of using a binary sensitizer blend of a trifunctional monomer and a rubber in PVC, and develop suitable electron beam cross linkable formulations for wire insulation. This paper presents some aspects of the investigations and development of insulation demonstrated at industrial scale

  9. Structure and properties of diamond and diamond-like films

    Energy Technology Data Exchange (ETDEWEB)

    Clausing, R.E. [Oak Ridge National Lab., TN (United States)

    1993-01-01

    This section is broken into four parts: (1) introduction, (2) natural IIa diamond, (3) importance of structure and composition, and (4) control of structure and properties. Conclusions of this discussion are that properties of chemical vapor deposited diamond films can compare favorably with natural diamond, that properties are anisotropic and are a strong function of structure and crystal perfection, that crystal perfection and morphology are functions of growth conditions and can be controlled, and that the manipulation of texture and thereby surface morphology and internal crystal perfection is an important step in optimizing chemically deposited diamond films for applications.

  10. Composition-structure-property relation of oxide glasses

    DEFF Research Database (Denmark)

    Hermansen, Christian

    also increases such properties. Yet, these rules are not strictly followed even for the simplest binary oxide glasses, such as alkali silicates, borates and phosphates. In this thesis it is argued that the missing link between composition and properties is the glass structure. Structural models...... are proposed based on topological selection rules and experimentally verified. The relation between structure and properties is evaluated using topological constraint theory, which in its essence is a theory that quantifies the two intuitions of the glass scientist. The end result is a quantitative model...

  11. Synthesis, electrochemistry, STM investigation of oligothiophene self-assemblies with superior structural order and electronic properties

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, Cheng-Yu [C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Liu, Yinghao; Yarotski, Dmitry [Center of Integrated Nanotechnologies, Materials Physics and Application Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Li, Hao [Theory Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Xu, Ping; Yen, Hung-Ju [C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Tretiak, Sergei, E-mail: serg@lanl.gov [Theory Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Wang, Hsing-Lin, E-mail: hwang@lanl.gov [C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2016-12-20

    Graphical abstract: STM imaging reveals differently oriented domains of self-assembled tetrathiophene molecules. - Highlights: • Optical and redox properties of oligothiophene derivatives are studied. • Packing pattern of self-assembly monolayer depends on the conjugation length. • Strong electronic coupling and three redox couples in cyclic voltamogram are observed in the hierarchical self-assembly. - Abstract: Three oligothiophene (terthiophene, tetrathiophene and pentathiophene) derivatives are synthesized and their monolayer self-assemblies on gold (Au) are prepared via Au–S covalent bond. Our UV–Vis experimental characterization of solution reveals the dependence of the optical properties on the conjugation length of the oligothiophenes, which compares well with Time-Dependent Density Functional Theory (TDDFT) simulations of spectra of individual chromophores. Photoluminescent spectra of thin films show pronounced red shifts compared to that of solutions, suggesting strong inter-oligomer interactions. The comparative studies of cyclic voltammograms of tetrathiophene from solution, cast film and self-assembled monolayer (SAM) indicate presence of one, two, and three oxidized species in these samples, respectively, suggesting a very strong electronic coupling between tetrathiophene molecules in the SAM. Scanning tunneling microscopy (STM) imaging of SAMs of the tetrathiophene on an atomically flat Au surface exhibits formation of monolayer assemblies with molecular order, and the molecular packing appears to show an overlay of oligothiophene molecules on top of another one. In contrast, the trimer and pentamer images show only aggregated species lacking long-range order on the molecular level. Such trends in going from disordered–ordered–disordered monolayer assemblies are mainly due to a delicate balance between inter-chromophore π–π couplings, hydrophobic interaction and the propensity to form Au–S covalent bond. Such hypothesis has been

  12. Non-volatile memory devices with redox-active diruthenium molecular compound

    International Nuclear Information System (INIS)

    Pookpanratana, S; Zhu, H; Bittle, E G; Richter, C A; Li, Q; Hacker, C A; Natoli, S N; Ren, T

    2016-01-01

    Reduction-oxidation (redox) active molecules hold potential for memory devices due to their many unique properties. We report the use of a novel diruthenium-based redox molecule incorporated into a non-volatile Flash-based memory device architecture. The memory capacitor device structure consists of a Pd/Al 2 O 3 /molecule/SiO 2 /Si structure. The bulky ruthenium redox molecule is attached to the surface by using a ‘click’ reaction and the monolayer structure is characterized by x-ray photoelectron spectroscopy to verify the Ru attachment and molecular density. The ‘click’ reaction is particularly advantageous for memory applications because of (1) ease of chemical design and synthesis, and (2) provides an additional spatial barrier between the oxide/silicon to the diruthenium molecule. Ultraviolet photoelectron spectroscopy data identified the energy of the electronic levels of the surface before and after surface modification. The molecular memory devices display an unsaturated charge storage window attributed to the intrinsic properties of the redox-active molecule. Our findings demonstrate the strengths and challenges with integrating molecular layers within solid-state devices, which will influence the future design of molecular memory devices. (paper)

  13. 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.

  14. Structure and Magnetic Properties of Lanthanide Nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Dickerson, James Henry [Vanderbilt Univ., Nashville, TN (United States)

    2014-06-01

    We have had considerable success on this project, particularly in the understanding of the relationship between nanostructure and magnetic properties in lanthanide nanocrystals. We also have successfully facilitated the doctoral degrees of Dr. Suseela Somarajan, in the Department of Physics and Astronomy, and Dr. Melissa Harrison, in the Materials Science Program. The following passages summarize the various accomplishments that were featured in 9 publications that were generated based on support from this grant. We thank the Department of Energy for their generous support of our research efforts in this area of materials science, magnetism, and electron microscopy.

  15. Electronic structure and properties of superheavy elements

    International Nuclear Information System (INIS)

    Pershina, V.

    2015-01-01

    Spectacular developments in the relativistic quantum theory and computational algorithms in the last few decades allowed for accurate calculations of properties of the superheavy elements (SHE) and their compounds. Often conducted in a close link to the experimental research, these investigations helped predict and interpret an outcome of sophisticated and expensive experiments with single atoms. Most of the works, particularly those related to the experimental studies, are overviewed in this publication. The role of relativistic effects being of paramount importance for the heaviest elements is elucidated.

  16. The Structure and Flexural Properties of Typha Leaves

    Directory of Open Access Journals (Sweden)

    Jingjing Liu

    2017-01-01

    Full Text Available The Typha leaf has a structure of lightweight cantilever beam, exhibiting excellent mechanical properties with low density. Especially, the leaf blade evolved high strength and low density with high porosity. In this paper, the structure of Typha leaf was characterized by microcomputed tomography (Micro-CT and scanning electron microscopy (SEM, and the relationship with flexural properties was analyzed. The three-point bending test was performed on leaves to examine flexural properties, which indicated that the flexural properties vary from the base to the apex in gradient. The cross-sectional geometry shape of the leaf blade presented a strong influence on the optimized flexural stiffness. The load carrying capacity of the leaf depended on the development level of the epidermal tissue, the vascular bundle, the mechanical tissue, and the geometric properties. The investigation can be the basis for lightweight structure design and the application in the bionic engineering field.

  17. Fused aromatic thienopyrazines: structure, properties and function

    KAUST Repository

    Mondal, Rajib

    2010-01-01

    Recent development of a fused aromatic thieno[3.4-b]pyrazine system and their application in optoelectronic devices are reviewed. Introduction of a fused aromatic unit followed by side chain engineering, dramatically enhanced the charge carrier mobility in thin film transistor devices and mobilities up to 0.2 cm2/Vs were achieved. The optoelectronic properties of these fused aromatic thienopyrazine polymers (Eg = 1.3 to 1.6 eV, HOMO = -4.9 to -5.2 V) were tuned by introduction of various fused aromatic rings within thienopyrazine. By balancing the fundamental properties of these polymers, both high charge carrier mobilities and moderate PCEs in solar cells were achieved. Further, effects of copolymerizing units are discussed. Low band gap semiconducting polymer (Eg ∼ 1 eV) with high field effect mobility (0.044 cm2/Vs) was obtained using cyclopentadithiophene as copolymerizing unit. Finally, a molecular design approach to enhance the absorption coefficients is discussed, which resulted in improved power conversion efficiency in bulk heterojunction solar cells. © 2010 The Royal Society of Chemistry.

  18. Probing Fe (III)/Fe (II) redox potential in a clayey material

    International Nuclear Information System (INIS)

    Tournassat, Christophe; Chainet, Fabien; Betelu, Stephanie; Hadi, Jebril; Gaucher, Eric C.; Ignatiadis, Ioannis; Greneche, Jean-Marc; Charlet, Laurent

    2010-01-01

    Document available in extended abstract form only. Redox is one of the main factors affecting the migration of redox-sensitive radionuclides. As a consequence reducing conditions are considered of strategic importance for the confinement properties of a clayey formation towards nuclear waste. A representative redox potential of clay formation such as Callovian- Oxfordian (COx) can be derived from thermodynamic calculations considering equilibrium between observed redox phases such as pyrite and siderite. However, there is little information on the reactivity of the different reservoirs of redox constituents in this type of complex material. The present study aims at investigating the reactivity of the Fe(III)/Fe(II) redox couple in the structure of clay minerals using different investigation methods: electrochemistry and O 2 reduction kinetic experiments. Clay modified electrodes were specifically designed to probe Fe(III)/Fe(II) redox potential in the structure of clay minerals. The clay fraction of a Callovian-Oxfordian argillite sample originating from the same level than ANDRA underground research laboratory was used after pre-treatment to remove organic matter and accessory minerals such as pyrite that could influence redox potential measurements. These electrodes were used to verify the validity of the model of Favre et al. (2006) that links the redox potential (E clay ) to the the Fe(II)/Fe tot ratio in the structure (m rel ), the pH and the sodium concentration in solution: equation 1. The good agreement between direct potential measurements and model prediction provides a strong evidence of the relevance of this model in our experimental conditions although the clay composition and its too low Fe content do not a priori fulfil the conditions set by Drits and Manceau (2000) for the calculation of K 0 parameter. Following the verification of the model, we tried to apply it to the specific case of a Callovian-Oxfordian sample that had been very well preserved

  19. Propriedades redox de ácidos húmicos isolados de um solo cultivado com cana-de-açúcar por longo tempo Redox properties of humic acids isolated from a soil Under long-term sugarcane cultivation

    Directory of Open Access Journals (Sweden)

    Marihus Altoé Baldotto

    2008-06-01

    Full Text Available A matéria orgânica do solo é o maior reservatório de C nos sistemas naturais. Em tais sistemas a qualidade e a estabilidade do C podem ser estimadas pelo aumento da concentração das frações humificadas que, dentre outros fatores, está condicionada ao balanço entre as perdas e os ganhos que envolvem as reações de oxidação e de redução da matéria orgânica do solo. O objetivo deste estudo foi avaliar a eletroquímica, usando titulações redox iodimétricas, de ácidos húmicos isolados de solos cultivados continuamente com cana-de-açúcar submetida ou não à queima da palha para a colheita ou à adição anual de vinhaça. Os ácidos húmicos apresentaram valores do potencial formal padrão do eletrodo entre 0,760 e 0,779 V a 25 ºC. A capacidade de oxidação dos ácidos húmicos variou de 1,01 a 3,44 mol c kg-1 a pH 5,0 e de 1,64 a 6,44 molc kg-1 a pH 7,0. Observou-se correlação positiva e significativa entre a capacidade de oxidação dos ácidos húmicos e suas concentrações de grupos funcionais fenólicos, quinonas e semiquinonas.Soil organic matter is the largest carbon reservoir in natural systems. In such systems the carbon quality and stability can be estimated based on the increase of humified fractions which, among other factors, is related to the balance between losses and accumulations involving oxidation and reduction reactions of the soil organic matter. The objective of this study was to evaluate the electrochemistry of humic acids isolated from soils cultivated continually with sugar-cane, with or without pre-harvest burning and annual vinasse application using iodimetric redox titrations. The formal electrode potentials of the humic acids had a similar pattern, with values between 0.760 and 0.779 V, at 25 ºC. The oxidation capacity of humic acids varied from 1.01 to 3.44 mol c kg-1 at pH 5.0 and from 1.64 to 6.44 mol c kg-1 at pH 7.0. Positive and significant correlations were observed between the

  20. Structural, optical and electrical properties of chemically deposited ...

    Indian Academy of Sciences (India)

    Structural, optical and electrical properties of chemically deposited nonstoichiometric copper ... One of these compounds, CuInSe2, with its optical absorption .... is clear from SEM images that the number of grains goes on increasing with the ...

  1. Structural properties of carbon nanotubes derived from 13C NMR

    KAUST Repository

    Abou-Hamad, E.; Babaa, M.-R.; Bouhrara, M.; Kim, Y.; Saih, Y.; Dennler, S.; Mauri, F.; Basset, Jean-Marie; Goze-Bac, C.; Wå gberg, T.

    2011-01-01

    We present a detailed experimental and theoretical study on how structural properties of carbon nanotubes can be derived from 13C NMR investigations. Magic angle spinning solid state NMR experiments have been performed on single- and multiwalled

  2. Thermodynamical properties and thermoelastic coupling of complex macroscopic structure

    International Nuclear Information System (INIS)

    Fabbri, M.; Sacripanti, A.

    1996-11-01

    Gross qualitative/quantitative analysis about thermodynamical properties and thermoelastic coupling (or elastocaloric effect) of complex macroscopic structure (running shoes) is performed by infrared camera. The experimental results showed the achievability of a n industrial research project

  3. Detonation-synthesis nanodiamonds: synthesis, structure, properties and applications

    Energy Technology Data Exchange (ETDEWEB)

    Dolmatov, Valerii Yu [Federal State Unitary Enterprise Special Design-Technology Bureau (FSUE SDTB) ' ' Tekhnolog' ' at the St Petersburg State Institute of Technology (Technical University) (Russian Federation)

    2007-04-30

    The review outlines the theoretical foundations and industrial implementations of modern detonation synthesis of nanodiamonds and chemical purification of the nanodiamonds thus obtained. The structure, key properties and promising fields of application of detonation-synthesis nanodiamonds are considered.

  4. Detonation-synthesis nanodiamonds: synthesis, structure, properties and applications

    International Nuclear Information System (INIS)

    Dolmatov, Valerii Yu

    2007-01-01

    The review outlines the theoretical foundations and industrial implementations of modern detonation synthesis of nanodiamonds and chemical purification of the nanodiamonds thus obtained. The structure, key properties and promising fields of application of detonation-synthesis nanodiamonds are considered.

  5. Manganites in Perovskite Superlattices: Structural and Electronic Properties

    KAUST Repository

    Jiwuer, Jilili

    2016-01-01

    Perovskite manganites are widely investigated compounds due to the discovery of the colossal magnetoresistance effect in 1994. They have a broad range of structural, electronic, magnetic properties and potential device applications in sensors

  6. Unveiling DNA structural properties of promoter regions of ...

    Indian Academy of Sciences (India)

    Aditya Kumar

    Unveiling DNA structural properties of promoter regions of prokaryotic transcriptome and their role in gene expression. Aditya Kumar. Assistant Professor. Molecular Biology & Biotechnology. Tezpur University. Tezpur – 784028, Assam ...

  7. Structure, health benefits, antioxidant property and processing and ...

    African Journals Online (AJOL)

    Structure, health benefits, antioxidant property and processing and storage of carotenoids. ... It is sensitive to heat, light and oxygen. Enzymatic ... Thermal treatment and freezing increases the extractability of b-carotene from the food matrices.

  8. Effect of spin polarization on the structural properties and bond ...

    Indian Academy of Sciences (India)

    ties such as structural, hardness, Young modulus and frac- ture toughness ... measurements showed that hardness ranged between 14.5 and 19GPa ... the relative binding forces, is a useful fundamental property. ..... strength [36,39]. Zhang et ...

  9. Ground state structures and properties of small hydrogenated silicon

    Indian Academy of Sciences (India)

    Unknown

    To understand the structural evolutions and properties of silicon cluster due to hydrogenation ... partly due to the growing importance of these systems in applications like .... of the system. Using the Lagrangian (1), equations of motions for the.

  10. Organogels thermodynamics, structure, solvent role, and properties

    CERN Document Server

    Guenet, Jean-Michel

    2016-01-01

    This book provides a physics-oriented introduction to organogels with a comparison to polymer thermoreversible gels whenever relevant. The past decade has seen the development of a wide variety of newly-synthesized molecules that can spontaneously self-assemble or crystallize from their organic or aqueous solutions to produce fibrillar networks, namely organogels, with potential applications in organic electronics, light harvesting, bio-imaging, non-linear optics, and the like. This compact volume presents a detailed outlook of these novel molecular systems with special emphasis upon their thermodynamics, morphology, molecular structure, and rheology. The definition of these complex systems is also tackled, as well as the role of the solvent. The text features numerous temperature-phase diagrams for a variety of organogels as well as illustrations of their structures at the microscopic, mesoscopic and macroscopic level. A review of some potential applications is provided including hybrid functional materials ...

  11. Structure-Property Relationships in Polycyanurate / Graphene Networks

    Science.gov (United States)

    2015-12-12

    Briefing Charts 3. DATES COVERED (From - To) 17 Nov 2015 – 12 Dec 2015 4. TITLE AND SUBTITLE Structure-Property Relationships in Polycyanurate...ANSI Std. 239.18 1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Structure-Property Relationships in...the attractive processing characteristics of LECy are retained in graphene oxide / LECy mixtures. Impurities, such as aryl phenols and transition metals

  12. Mechanical properties along interfaces of bonded structures in fusion reactors

    International Nuclear Information System (INIS)

    Hassan, M.H.; Kulcinski, G.L.

    1993-01-01

    Proper assessment of the mechanical properties along interfaces of bonded structures currently used in many fusion reactor designs is essential to compare the different fabrication techniques. A Mechanical Properties Microprobe (MPM) was used to measure hardness and Young's modules along the interfaces of Be/Cu bonded structure. The MPM was able to distinguish different fabrication techniques by a direct measurement of the hardness, Young's modules, and H/E 2 which reflects the ability of deformation of the interfacial region

  13. High-performance ceramics. Fabrication, structure, properties

    International Nuclear Information System (INIS)

    Petzow, G.; Tobolski, J.; Telle, R.

    1996-01-01

    The program ''Ceramic High-performance Materials'' pursued the objective to understand the chaining of cause and effect in the development of high-performance ceramics. This chain of problems begins with the chemical reactions for the production of powders, comprises the characterization, processing, shaping and compacting of powders, structural optimization, heat treatment, production and finishing, and leads to issues of materials testing and of a design appropriate to the material. The program ''Ceramic High-performance Materials'' has resulted in contributions to the understanding of fundamental interrelationships in terms of materials science, which are summarized in the present volume - broken down into eight special aspects. (orig./RHM)

  14. Determining the Mechanical Properties of Lattice Block Structures

    Science.gov (United States)

    Wilmoth, Nathan

    2013-01-01

    Lattice block structures and shape memory alloys possess several traits ideal for solving intriguing new engineering problems in industries such as aerospace, military, and transportation. Recent testing at the NASA Glenn Research Center has investigated the material properties of lattice block structures cast from a conventional aerospace titanium alloy as well as lattice block structures cast from nickel-titanium shape memory alloy. The lattice block structures for both materials were sectioned into smaller subelements for tension and compression testing. The results from the cast conventional titanium material showed that the expected mechanical properties were maintained. The shape memory alloy material was found to be extremely brittle from the casting process and only compression testing was completed. Future shape memory alloy lattice block structures will utilize an adjusted material composition that will provide a better quality casting. The testing effort resulted in baseline mechanical property data from the conventional titanium material for comparison to shape memory alloy materials once suitable castings are available.

  15. Using nonlinearity and spatiotemporal property modulation to control effective structural properties: dynamic rods

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel; Blekhman, Iliya I.

    2007-01-01

    What are the effective properties of a generally nonlinear material or structure, whose local properties are modulated in both space and time? It has been suggested to use spatiotemporal modulation of structural properties to create materials and structures with adjustable effective properties......, and to call these dynamic materials or spatiotemporal composites. Also, according to theoretical predictions, structural nonlinearity enhances the possibilities of achieving specific effective properties. For example, with an elastic rod having cubical elastic nonlinearities, it seems possible to control......, and exemplified. Then simple approximate analytical expressions are derived for the effective wave speed and natural frequencies for one-dimensional wave propagation in a nonlinear elastic rod, where the spatiotemporal modulation is imposed as a high-frequency standing wave, supposed to be given. Finally the more...

  16. Structure and electronic properties of azadirachtin.

    Science.gov (United States)

    de Castro, Elton A S; de Oliveira, Daniel A B; Farias, Sergio A S; Gargano, Ricardo; Martins, João B L

    2014-02-01

    We performed a combined DFT and Monte Carlo (13)C NMR chemical-shift study of azadirachtin A, a triterpenoid that acts as a natural insect antifeedant. A conformational search using a Monte Carlo technique based on the RM1 semiempirical method was carried out in order to establish its preferred structure. The B3LYP/6-311++G(d,p), wB97XD/6-311++G(d,p), M06/6-311++G(d,p), M06-2X/6-311++G(d,p), and CAM-B3LYP/6-311++G(d,p) levels of theory were used to predict NMR chemical shifts. A Monte Carlo population-weighted average spectrum was produced based on the predicted Boltzmann contributions. In general, good agreement between experimental and theoretical data was obtained using both methods, and the (13)C NMR chemical shifts were predicted highly accurately. The geometry was optimized at the semiempirical level and used to calculate the NMR chemical shifts at the DFT level, and these shifts showed only minor deviations from those obtained following structural optimization at the DFT level, and incurred a much lower computational cost. The theoretical ultraviolet spectrum showed a maximum absorption peak that was mainly contributed by the tiglate group.

  17. Redox regulation of cell proliferation: Bioinformatics and redox proteomics approaches to identify redox-sensitive cell cycle regulators.

    Science.gov (United States)

    Foyer, Christine H; Wilson, Michael H; Wright, Megan H

    2018-03-29

    Plant stem cells are the foundation of plant growth and development. The balance of quiescence and division is highly regulated, while ensuring that proliferating cells are protected from the adverse effects of environment fluctuations that may damage the genome. Redox regulation is important in both the activation of proliferation and arrest of the cell cycle upon perception of environmental stress. Within this context, reactive oxygen species serve as 'pro-life' signals with positive roles in the regulation of the cell cycle and survival. However, very little is known about the metabolic mechanisms and redox-sensitive proteins that influence cell cycle progression. We have identified cysteine residues on known cell cycle regulators in Arabidopsis that are potentially accessible, and could play a role in redox regulation, based on secondary structure and solvent accessibility likelihoods for each protein. We propose that redox regulation may function alongside other known posttranslational modifications to control the functions of core cell cycle regulators such as the retinoblastoma protein. Since our current understanding of how redox regulation is involved in cell cycle control is hindered by a lack of knowledge regarding both which residues are important and how modification of those residues alters protein function, we discuss how critical redox modifications can be mapped at the molecular level. Crown Copyright © 2018. Published by Elsevier Inc. All rights reserved.

  18. 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

  19. Optical properties of arbuscular mycorrhizal fungal structures

    International Nuclear Information System (INIS)

    Perez, Adverdi; V-Hernandez, Alejandra; Rudamas, Carlos; Dreyer, Beatriz

    2008-01-01

    It was already reported by B. Dreyer at al. [1] that all fungal structures, both intra- and extra-radical fluoresced under blue light excitation regardless of their state (dead or alive). The source of the so called autofluorescence appears to be localized in the fungal cell wall. This supports the use of photoluminescence for the evaluation of AM colonization. However, the interpretation of these results is still in discussion [1-4]. In this work, arbuscular mycorrhizal spores were isolated from the rhizosphere of mango (Mangifera indica L.) plants by the method of wet sieving and decanting of Gerdemann and Nicolson [5] and studied by photoluminescence spectroscopy. Our experimental setup consists of an epifluorescence microscope (EM) coupled to a CCD-spectrometer through an arrangement of a home-made-telescope + fiber optic. This experimental setup allows the capture of images of the mycorrhizal structures (as usual in a standard epifluorescence microscope) combined with measurements of their corresponding emission bands. The preliminary results based on images obtained by standard EM do not clearly show that the emission is originated in the fungal cell walls as reported in Ref. 1. On the other hand, a very broad emission band in the visible part of the electromagnetic spectrum was observed in these spores by exciting at 450-490 nm and 300- 380 nm. We obtain a Full Width at Half Maximum (FWHM) of around 200 nm for this emission band whichis centered at 515 nm. This broad band seems to be composed of two narrower bands peaked around 494 and 547 nm and with FWHM of 50 nm and 150 nm, respectively. The profile of the observed emission band is in good agreement with the bands reported in Ref. 1 for vesicles, arbuscules and spores measured using the λ-Scan of a confocal laser scanning microscope. However, our results for spores show that the maxima of the narrower bands are shifted to higher energies in comparison to the corresponding bands observed in Ref. 1

  20. Optical properties of semiconductors quantum microcavity structures

    International Nuclear Information System (INIS)

    Afshar, A.M.

    1996-12-01

    The principal phenomenon investigated in this thesis is vacuum Rabi coupling in semiconductor microcavity structures. In these structures quantum well excitons are embedded in a Fabry - Perot like cavity, defined by two semiconductor dielectric mirrors. In such a system the coupled exciton and cavity photon mode form a mixed - mode polariton, where on - resonance there are two branches, each having 50% exciton and 50% photon character. The separation between the upper and lower branches is a measure of the coupling strength where the strength is dependent on the exciton oscillator strength. This interaction is known as vacuum Rabi coupling, and clear anticrossing is seen when the exciton is tuned through the cavity. In our reflectivity experiments we demonstrate control of the coupling between the cavity mode and the exciton by varying temperature, applied electric or magnetic field. Modelling of the reflectivity spectra and the tuning was done using a Transfer Matrix Reflectivity (TMR) model or a linear dispersion model, where in both cases the excitons are treated as Lorentz oscillators. Temperature tuning is achieved because exciton energy decreases with temperature at a much faster rate than the cavity mode. We have demonstrated vacuum Rabi coupling of the cavity mode with both the heavy - hole and light - hole excitons. Electric field tuning is achieved via the quantum confined Stark effect which decreases the exciton energy with increasing field, whilst at the same time the cavity mode energy remains constant. A study of how the electric field reduction of exciton oscillator strength reduces the vacuum Rabi coupling strength is performed. We report the first observation in a semiconductor structure of motional narrowing, seen in both electric field and in temperature tuning experiments at high magnetic field. In magnetic field studies we show how magnetic field induced increase in exciton oscillator strength affects the vacuum Rabi coupling. We also show by

  1. Structural phase transition and elastic properties of samarium monopnictides

    International Nuclear Information System (INIS)

    Pagare, Gitanjali; Chouhan, Sunil Singh; Soni, Pooja; Sanyal, Sankar P.

    2011-01-01

    In recent years the monopnictides and monochalcogenides of the rare-earth elements with rocksalt structure (B 1 ) have aroused intensive interest due to the presence of strongly correlated f electrons in them. Under pressure, the nature of f-electrons of these compounds can be changed from localized to itinerant leading to significant changes in physical and chemical properties. These unusual structural, electronic, and high-pressure properties make them candidates for advanced industrial applications. For these applications they provide unique physical properties which cannot be achieved with other materials

  2. Composition-Structure-Property Relationships in Boroaluminosilicate Glasses

    DEFF Research Database (Denmark)

    Zheng, Qiuju; Potuzak, M.; Mauro, J.C.

    2012-01-01

    boroaluminosilicate glasses from peralkaline to peraluminous compositions by substituting Al2O3 for SiO2. Our results reveal a pronounced change in all the measured physical properties (density, elastic moduli, hardness, glass transition temperature, and liquid fragility) around [Al2O3]–[Na2O]=0. The structural......The complicated structural speciation in boroaluminosilicate glasses leads to a mixed network former effect yielding nonlinear variation in many macroscopic properties as a function of chemical composition. Here we study the composition–structure–property relationships in a series of sodium...

  3. Structured epitaxial graphene: growth and properties

    International Nuclear Information System (INIS)

    Hu Yike; Ruan Ming; Guo Zelei; Dong Rui; Palmer, James; Hankinson, John; Berger, Claire; Heer, Walt A de

    2012-01-01

    Graphene is generally considered to be a strong candidate to succeed silicon as an electronic material. However, to date, it actually has not yet demonstrated capabilities that exceed standard semiconducting materials. Currently demonstrated viable graphene devices are essentially limited to micrometre-sized ultrahigh-frequency analogue field effect transistors and quantum Hall effect devices for metrology. Nanoscopically patterned graphene tends to have disordered edges that severely reduce mobilities thereby obviating its advantage over other materials. Here we show that graphene grown on structured silicon carbide surfaces overcomes the edge roughness and promises to provide an inroad into nanoscale patterning of graphene. We show that high-quality ribbons and rings can be made using this technique. We also report on the progress towards high-mobility graphene monolayers on silicon carbide for device applications. (paper)

  4. Effects of Structural Correlations on Electronic Properties

    International Nuclear Information System (INIS)

    Pastawski, H.M.; Weisz, J.F.

    1984-01-01

    A one dimensional alloy model is treated in the nearest neighbour tight binding approximation in which the correlation of the atoms can be adjusted. The correlation can be changed from a situation in which there is a tendency for atoms to alternate to a situation in which the atoms are randomly located, consistent with a fixed concentration c for A c B 1-c . The results show that when there is short range order, at certain energies there is a tendency for localized states and formation of structure induced minimum in the density of states. The results for the ordered case are similar to those of Charge Density Wave (CDW). A smooth transition is carried out between this case and the randomly disordered case which behaves like the Anderson model for uncorrelated disorder. (M.W.O.) [pt

  5. Effect of long-term fertilization on humic redox mediators in multiple microbial redox reactions.

    Science.gov (United States)

    Guo, Peng; Zhang, Chunfang; Wang, Yi; Yu, Xinwei; Zhang, Zhichao; Zhang, Dongdong

    2018-03-01

    This study investigated the effects of different long-term fertilizations on humic substances (HSs), humic acids (HAs) and humins, functioning as redox mediators for various microbial redox biotransformations, including 2,2',4,4',5,5'- hexachlorobiphenyl (PCB 153 ) dechlorination, dissimilatory iron reduction, and nitrate reduction, and their electron-mediating natures. The redox activity of HSs for various microbial redox metabolisms was substantially enhanced by long-term application of organic fertilizer (pig manure). As a redox mediator, only humin extracted from soils with organic fertilizer amendment (OF-HM) maintained microbial PCB 153 dechlorination activity (1.03 μM PCB 153 removal), and corresponding HA (OF-HA) most effectively enhanced iron reduction and nitrate reduction by Shewanella putrefaciens. Electrochemical analysis confirmed the enhancement of their electron transfer capacity and redox properties. Fourier transform infrared analysis showed that C=C and C=O bonds, and carboxylic or phenolic groups in HSs might be the redox functional groups affected by fertilization. This research enhances our understanding of the influence of anthropogenic fertility on the biogeochemical cycling of elements and in situ remediation ability in agroecosystems through microorganisms' metabolisms. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Redox reactions in food fermentations

    DEFF Research Database (Denmark)

    Hansen, Egon Bech

    2018-01-01

    involves oxidative steps in the early part of the pathways whereas a multitude of different reactions are used as compensating reductions. Much of the diversity seen between food fermentations arise from the different routes and the different electron acceptors used by microorganisms to counterbalance...... and this contributes to the diversity in flavor, color, texture, and shelf life. The review concludes that these reactions are still only incompletely understood and that they represent an interesting area for fundamental research and also represent a fertile field for product development through a more conscious use...... of the redox properties of strains used to compose food cultures....

  7. Mechanical Properties for Reliability Analysis of Structures in Glassy Carbon

    CERN Document Server

    Garion, Cédric

    2014-01-01

    Despite its good physical properties, the glassy carbon material is not widely used, especially for structural applications. Nevertheless, its transparency to particles and temperature resistance are interesting properties for the applications to vacuum chambers and components in high energy physics. For example, it has been proposed for fast shutter valve in particle accelerator [1] [2]. The mechanical properties have to be carefully determined to assess the reliability of structures in such a material. In this paper, mechanical tests have been carried out to determine the elastic parameters, the strength and toughness on commercial grades. A statistical approach, based on the Weibull’s distribution, is used to characterize the material both in tension and compression. The results are compared to the literature and the difference of properties for these two loading cases is shown. Based on a Finite Element analysis, a statistical approach is applied to define the reliability of a structural component in gl...

  8. Comparative study of the physiochemical and structural properties of ...

    African Journals Online (AJOL)

    A comparative analysis of some physiochemical and structural parameters of brown (mature) and green (immature) coconut fibre as adsorbents was studied. The physiochemical and structural properties evaluated were surface area, moisture content, pH, bulk density, pore volume, porosity, ash content, tortuocity and metal ...

  9. Effect of annealing time on structural and magnetic properties of ...

    Indian Academy of Sciences (India)

    We studied the effects on the structural and magnetic properties of Fe3O4 thin films. The films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). XRD studies showed pure single phase spinel cubic structure of Fe3O4 with a preferential [111] ...

  10. Structure, composition and mechanical properties of the silk fibres of ...

    Indian Academy of Sciences (India)

    The silk egg case and orb web of spiders are elaborate structures that are assembled from a number of components. We analysed the structure, the amino acid and fibre compositions, and the tensile properties of the silk fibres of the egg case of Nephila clavata. SEM shows that the outer and inner covers of the egg case ...

  11. Thermodynamic and structural properties in complexing media

    International Nuclear Information System (INIS)

    Di Giandomenico, M.V.

    2007-10-01

    Protactinium is experiencing a renewal of interest in the frame of long-term energy production. Modelling the behaviour of this element in the geosphere requires thermodynamic and structural data relevant to environmental conditions. Now deep clayey formation are considered for the disposal of radioactive waste and high values of natural sulphate contents have been determined in pore water in equilibrium with clay surface. Because of its tendency to polymerisation, hydrolysis and sorption on all solid supports, the equilibria constants relative to monomer species were determined at tracer scale (ca. 10 - 12 M) with 233 Pa. The complexation constants of Pa(V) and sulphate ions were calculated starting from a systematic study of the apparent distribution coefficient D in the system TTA/Toluene/H 2 O/Na 2 SO 4 /HClO 4 /NaClO 4 and as a function of ionic strength, temperature, free sulphate, protons and chelatant concentration. First of all, the interaction between free species H + , SO 4 - , Na + leads to the formation of HSO 4 - and NaSO 4 - , for which concentrations depend upon the related thermodynamic constants. For this purpose a computer code was developed in order to determine all free species concentration. This iterative code takes into account the influence of temperature and ionic strength (SIT modelling) on thermodynamic constants. The direct measure of Pa(V) in the organic and aqueous phase by g-spectrometry had conducted to estimate the apparent distribution coefficient D as function of free sulphate ions. Complexation constants have been determined after a mathematical treatment of D. The extrapolation of these constants at zero ionic strength have been realized by SIT modelling at different temperatures. Besides, enthalpy and entropy values were calculated. Parallelly, the structural study of Pa(V) was performed using 231 Pa. XANES and EXAFS spectra show unambiguously the absence of the trans di-oxo bond that characterizes the other early actinide

  12. Polynuclear compounds of uranium: structure, reactivity and properties

    International Nuclear Information System (INIS)

    Mougel, V.

    2012-01-01

    The study and comprehension of actinide's fundamental chemistry have important implications both for the development of new nuclear fuel and for the nuclear fuel reprocessing. One of the major issues in these processes is the ease of uranium to undergo redox reactions and to form polynuclear assemblies, which largely perturb these processes. However, despite their relevance, only few synthetic routes towards polynuclear uranium assemblies are described in the literature, and most of the polynuclear complexes reported are formed by serendipity rather than by rational design. Moreover, polynuclear uranium compounds are highly promising for the design of magnetic materials with improved properties and for reactivity studies. The aim of this work is the synthesis of polynuclear uranium complexes and the study of their reactivity and coordination properties. New synthetic routes to uranium polynuclear assemblies were developed and the study of their physico-chemical properties was carried out. The first approach investigated was based on pentavalent uranyl chemistry. Uranyl(V) is known to form aggregates via an interaction between uranyl moieties often named cation-cation interaction, but the isolation of uranyl(V) complexes had been largely limited by its ease of disproportionation. We isolated the first stable uranyl(V) polynuclear assembly using Salen-type Schiff base ligand. Based on this result, a fine tuning of the ligand and counter-ion properties resulted in the isolation of a large family of uranyl(V) polynuclear assemblies and in a better understanding of the parameters ruling their stability. Moreover, rare examples of clear antiferromagnetic couplings were observed with these complexes. In addition, this synthetic path was used to build the first 5f-3d cluster presenting single molecule magnet properties. The second approach used in this thesis consisted in the synthesis of oxo/hydroxo uranium clusters. The controlled hydrolysis of trivalent uranium in

  13. De Novo Construction of Redox Active Proteins.

    Science.gov (United States)

    Moser, C C; Sheehan, M M; Ennist, N M; Kodali, G; Bialas, C; Englander, M T; Discher, B M; Dutton, P L

    2016-01-01

    Relatively simple principles can be used to plan and construct de novo proteins that bind redox cofactors and participate in a range of electron-transfer reactions analogous to those seen in natural oxidoreductase proteins. These designed redox proteins are called maquettes. Hydrophobic/hydrophilic binary patterning of heptad repeats of amino acids linked together in a single-chain self-assemble into 4-alpha-helix bundles. These bundles form a robust and adaptable frame for uncovering the default properties of protein embedded cofactors independent of the complexities introduced by generations of natural selection and allow us to better understand what factors can be exploited by man or nature to manipulate the physical chemical properties of these cofactors. Anchoring of redox cofactors such as hemes, light active tetrapyrroles, FeS clusters, and flavins by His and Cys residues allow cofactors to be placed at positions in which electron-tunneling rates between cofactors within or between proteins can be predicted in advance. The modularity of heptad repeat designs facilitates the construction of electron-transfer chains and novel combinations of redox cofactors and new redox cofactor assisted functions. Developing de novo designs that can support cofactor incorporation upon expression in a cell is needed to support a synthetic biology advance that integrates with natural bioenergetic pathways. © 2016 Elsevier Inc. All rights reserved.

  14. The structural heterogeneity and optical properties in chalcogenide glass films

    International Nuclear Information System (INIS)

    Shurgalin, Max; Fuflyigin, Vladimir N; Anderson, Emilia G

    2005-01-01

    The microscopic structure and optical properties of glassy films prepared by vapour phase deposition process from the germanium-arsenic-selenium family of chalcogenide glasses have been studied. A number of different molecular clusters or domains that can exist in the glass structure are found to play a significant role in determining the absorption characteristics and refractive index of the glass films. Modifications of the glass structure can be described by a variation of relative concentrations of the clusters and can be effected by modifications of film chemical composition and deposition conditions. Changes in absorption spectra are directly correlated with variation in relative concentrations of the structural fragments with different electronic bandgap properties. Experimental results suggest structural heterogeneity and support validity of the cluster structural model for the chalcogenide glasses

  15. NMR of proteins (4Fe-4S): structural properties and intramolecular electron transfer

    International Nuclear Information System (INIS)

    Huber, J.G.

    1996-01-01

    NMR started to be applied to Fe-S proteins in the seventies. Its use has recently been enlarged as the problems arising from the paramagnetic polymetallic clusters ware overcome. Applications to [4Fe-4S] are presented herein. The information derived thereof deepens the understanding of the redox properties of these proteins which play a central role in the metabolism of bacterial cells. The secondary structure elements and the overall folding of Chromatium vinosum ferredoxin (Cv Fd) in solution have been established by NMR. The unique features of this sequence have been shown to fold as an α helix at the C-terminus and as a loop between two cysteines ligand of one cluster: these two parts localize in close proximity from one another. The interaction between nuclear and electronic spins is a source of additional structural information for (4Fe-AS] proteins. The conformation of the cysteine-ligands, as revealed by the Fe-(S γ -C β -H β )Cys dihedral angles, is related to the chemical shifts of the signals associated with the protons of these residues. The longitudinal relaxation times of the protons depend on their distance to the cluster. A quantitative relationship has been established and used to show that the solution structure of the high-potential ferredoxin from Cv differs significantly from the crystal structure around Phe-48. Both parameters (chemical shifts and longitudinal relaxation times) give also insight into the electronic and magnetic properties of the [4Fe-4S] clusters. The rate of intramolecular electron transfer between the two [4FE-4S] clusters of ferredoxins has been measured by NMR. It is far slower in the case of Cv Fd than for shorter ferredoxins. The difference may be associated with changes in the magnetic and/or electronic properties of one cluster. The strong paramagnetism of the [4Fe-4S] clusters, which originally limited the applicability of NMR to proteins containing these cofactors, has been proven instrumental in affording new

  16. The Effect of Bedding Structure on Mechanical Property of Coal

    Directory of Open Access Journals (Sweden)

    Zetian Zhang

    2014-01-01

    Full Text Available The mechanical property of coal, influencing mining activity considerably, is significantly determined by the natural fracture distributed within coal mass. In order to study the effecting mechanism of bedding structure on mechanical property of coal, a series of uniaxial compression tests and mesoscopic tests have been conducted. The experimental results show that the distribution characteristic of calcite particles, which significantly influences the growth of cracks and the macroscopic mechanical properties of coal, is obviously affected by the bedding structure. Specifically, the uniaxial compression strength of coal sample is mainly controlled by bedding structure, and the average peak stress of specimens with axes perpendicular to the bedding planes is 20.00 MPa, which is 2.88 times the average amount of parallel ones. The test results also show a close relationship between the bedding structure and the whole deformation process under uniaxial loading.

  17. Structure and transport properties of nanostructured materials.

    Science.gov (United States)

    Sonwane, C G; Li, Q

    2005-03-31

    In the present manuscript, we have presented the simulation of nanoporous aluminum oxide using a molecular-dynamics approach with recently developed dynamic charge transfer potential using serial/parallel programming techniques (Streitz and Mintmire Phys. Rev. B 1994, 50, 11996). The structures resembling recently invented ordered nanoporous crystalline material, MCM-41/SBA-15 (Kresge et al. Nature 1992, 359, 710), and inverted porous solids (hollow nanospheres) with up to 10 000 atoms were fabricated and studied in the present work. These materials have been used for separation of gases and catalysis. On several occasions including the design of the reactor, the knowledge of surface diffusion is necessary. In the present work, a new method for estimating surface transport of gases based on a hybrid Monte Carlo method with unbiased random walk of tracer atom on the pore surface has been introduced. The nonoverlapping packings used in the present work were fabricated using an algorithm of very slowly settling rigid spheres from a dilute suspension into a randomly packed bed. The algorithm was modified to obtain unimodal, homogeneous Gaussian and segregated bimodal porous solids. The porosity of these solids was varied by densification using an arbitrary function or by coarsening from a highly densified pellet. The surface tortuosity for the densified solids indicated an inverted bell shape curve consistent with the fact that at very high porosities there is a reduction in the connectivity while at low porosities the pores become inaccessible or dead-end. The first passage time distribution approach was found to be more efficient in terms of computation time (fewer tracer atoms needed for the linearity of Einstein's plot). Results by hybrid discrete-continuum simulations were close to the discrete simulations for a boundary layer thickness of 5lambda.

  18. Transport properties of electrons in fractal magnetic-barrier structures

    Science.gov (United States)

    Sun, Lifeng; Fang, Chao; Guo, Yong

    2010-09-01

    Quantum transport properties in fractal magnetically modulated structures are studied by the transfer-matrix method. It is found that the transmission spectra depend sensitively not only on the incident energy and the direction of the wave vector but also on the stage of the fractal structures. Resonance splitting, enhancement, and position shift of the resonance peaks under different magnetic modulation are observed at four different fractal stages, and the relationship between the conductance in the fractal structure and magnetic modulation is also revealed. The results indicate the spectra of the transmission can be considered as fingerprints for the fractal structures, which show the subtle correspondence between magnetic structures and transport behaviors.

  19. 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.

  20. 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.

  1. Numerical calculations of effective elastic properties of two cellular structures

    International Nuclear Information System (INIS)

    Tuncer, Enis

    2005-01-01

    Young's moduli of regular two-dimensional truss-like and eye-shaped structures are simulated using the finite element method. The structures are idealizations of soft polymeric materials used in ferro-electret applications. In the simulations, the length scales of the smallest representative units are varied, which changes the dimensions of the cell walls in the structures. A power-law expression with a quadratic as the exponent term is proposed for the effective Young's moduli of the systems as a function of the solid volume fraction. The data are divided into three regions with respect to the volume fraction: low, intermediate and high. The parameters of the proposed power-law expression in each region are later represented as a function of the structural parameters, the unit-cell dimensions. The expression presented can be used to predict a structure/property relationship in materials with similar cellular structures. The contribution of the cell-wall thickness to the elastic properties becomes significant at concentrations >0.15. The cell-wall thickness is the most significant factor in predicting the effective Young's modulus of regular cellular structures at high volume fractions of solid. At lower concentrations of solid, the eye-shaped structure yields a lower Young's modulus than a truss-like structure with similar anisotropy. Comparison of the numerical results with those of experimental data for poly(propylene) show good agreement regarding the influence of cell-wall thickness on elastic properties of thin cellular films

  2. Predicting structural properties of fluids by thermodynamic extrapolation

    Science.gov (United States)

    Mahynski, Nathan A.; Jiao, Sally; Hatch, Harold W.; Blanco, Marco A.; Shen, Vincent K.

    2018-05-01

    We describe a methodology for extrapolating the structural properties of multicomponent fluids from one thermodynamic state to another. These properties generally include features of a system that may be computed from an individual configuration such as radial distribution functions, cluster size distributions, or a polymer's radius of gyration. This approach is based on the principle of using fluctuations in a system's extensive thermodynamic variables, such as energy, to construct an appropriate Taylor series expansion for these structural properties in terms of intensive conjugate variables, such as temperature. Thus, one may extrapolate these properties from one state to another when the series is truncated to some finite order. We demonstrate this extrapolation for simple and coarse-grained fluids in both the canonical and grand canonical ensembles, in terms of both temperatures and the chemical potentials of different components. The results show that this method is able to reasonably approximate structural properties of such fluids over a broad range of conditions. Consequently, this methodology may be employed to increase the computational efficiency of molecular simulations used to measure the structural properties of certain fluid systems, especially those used in high-throughput or data-driven investigations.

  3. High temperature structural and magnetic properties of cobalt nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Ait Atmane, Kahina [Univ. Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR CNRS 7086, 15 rue J.-A. de Baief, 75205 Paris Cedex 13 (France); Zighem, Fatih [Laboratoire Leon Brillouin, CEA CNRS UMR 12, IRAMIS, CEA-Saclay, 91191 Gif sur Yvette (France); Soumare, Yaghoub [Univ. Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR CNRS 7086, 15 rue J.-A. de Baief, 75205 Paris Cedex 13 (France); Ibrahim, Mona; Boubekri, Rym [Universite de Toulouse, LPCNO, INSA CNRS UMR 5215, 135 av. de Rangueil, 31077 Toulouse Cedex 4 (France); Maurer, Thomas [Laboratoire Leon Brillouin, CEA CNRS UMR 12, IRAMIS, CEA-Saclay, 91191 Gif sur Yvette (France); Margueritat, Jeremie [Univ. Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR CNRS 7086, 15 rue J.-A. de Baief, 75205 Paris Cedex 13 (France); Piquemal, Jean-Yves, E-mail: jean-yves.piquemal@univ-paris-diderot.fr [Univ. Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR CNRS 7086, 15 rue J.-A. de Baief, 75205 Paris Cedex 13 (France); Ott, Frederic; Chaboussant, Gregory [Laboratoire Leon Brillouin, CEA CNRS UMR 12, IRAMIS, CEA-Saclay, 91191 Gif sur Yvette (France); Schoenstein, Frederic; Jouini, Noureddine [LSPM, CNRS UPR 9001, Universite Paris XIII, Institut Galilee, 99 av. J.-B. Clement, 93430 Villetaneuse (France); Viau, Guillaume, E-mail: gviau@insa-toulouse.fr [Universite de Toulouse, LPCNO, INSA CNRS UMR 5215, 135 av. de Rangueil, 31077 Toulouse Cedex 4 (France)

    2013-01-15

    We present in this paper the structural and magnetic properties of high aspect ratio Co nanoparticles ({approx}10) at high temperatures (up to 623 K) using in-situ X ray diffraction (XRD) and SQUID characterizations. We show that the anisotropic shapes, the structural and texture properties are preserved up to 500 K. The coercivity can be modelled by {mu}{sub 0}H{sub C}=2(K{sub MC}+K{sub shape})/M{sub S} with K{sub MC} the magnetocrystalline anisotropy constant, K{sub shape} the shape anisotropy constant and M{sub S} the saturation magnetization. H{sub C} decreases linearly when the temperature is increased due to the loss of the Co magnetocrystalline anisotropy contribution. At 500 K, 50% of the room temperature coercivity is preserved corresponding to the shape anisotropy contribution only. We show that the coercivity drop is reversible in the range 300-500 K in good agreement with the absence of particle alteration. Above 525 K, the magnetic properties are irreversibly altered either by sintering or by oxidation. - Graphical abstract: We present in this paper the structural and magnetic properties of high aspect ratio Co nanorods ({approx}10) at high temperatures (up to 623 K) using in-situ X-ray diffraction and SQUID characterizations. We show that the anisotropic shapes, the structural and texture properties are preserved up to 500 K. Above 525 K, the magnetic properties are irreversibly altered either by sintering or by oxidation. Highlights: Black-Right-Pointing-Pointer Ferromagnetic Co nanorods are prepared using the polyol process. Black-Right-Pointing-Pointer The structural and texture properties of the Co nanorods are preserved up to 500 K. Black-Right-Pointing-Pointer The magnetic properties of the Co nanorods are irreversibly altered above 525 K.

  4. Practical improvements in soil redox potential (Eh) measurement for characterisation of soil properties. Application for comparison of conventional and conservation agriculture cropping systems

    Energy Technology Data Exchange (ETDEWEB)

    Husson, Olivier, E-mail: Olivier.husson@cirad.fr [CIRAD/PERSYST/UPR 115 AIDA and AfricaRice Centre, 01 BP 2031 Cotonou (Benin); Husson, Benoit, E-mail: bhusson@ideeaquaculture.com [IDEEAQUACULTURE, Parc Euromédecine 2, 39 Rue Jean Giroux, 34080 Montpellier (France); Brunet, Alexandre, E-mail: brunet.alexandre@outlook.com [CIRAD/US 49 Analyse, Avenue Agropolis, TA B-49/01, 34398 Montpellier Cedex (France); Babre, Daniel, E-mail: Daniel.babre@cirad.fr [CIRAD/US 49 Analyse, Avenue Agropolis, TA B-49/01, 34398 Montpellier Cedex (France); Alary, Karine, E-mail: Karine.alary@cirad.fr [CIRAD/US 49 Analyse, Avenue Agropolis, TA B-49/01, 34398 Montpellier Cedex (France); Sarthou, Jean-Pierre, E-mail: sarthou@ensat.fr [ENSAT/INRA/INP UMR AGIR. BP 52627, Chemin de Borde Rouge, 31326 Castanet-Tolosan Cedex (France); Charpentier, Hubert, E-mail: Charpentier.hub@wanadoo.fr [La Boisfarderie, Brives 36100 (France); Durand, Michel, E-mail: earldeslacs@orange.fr [Le Cazals, Castanet 81 150 (France); Benada, Jaroslav, E-mail: benada@vukrom.cz [Agrotest fyto, Kromeriz Institute, Havlíckova 2787, 76701 Kromeriz (Czech Republic); Henry, Marc, E-mail: henry@unistra.fr [UMR CNRS/UdS 7140, Université de Strasbourg, Institut Le Bel, 4, rue Blaise Pascal, CS 90032, Strasbourg 67081 (France)

    2016-02-04

    The soil redox potential (Eh) can provide essential information to characterise soil conditions. In practice, however, numerous problems may arise regarding: (i) Eh determination in soils, especially aerobic soils, e.g. variations in the instrumentation and methodology for Eh measurement, high spatial and temporal Eh variability in soils, irreversibility of the redox reaction at the surface electrode, chemical disequilibrium; and (ii) measurement interpretation. This study aimed at developing a standardised method for redox potential measurement in soils, in order to use Eh as a soil quality indicator. This paper presents practical improvements in soil Eh measurement, especially regarding the control of electromagnetic perturbations, electrode choice and preparation, soil sample preparation (drying procedure) and soil:water extraction rate. The repeatability and reproducibility of the measurement method developed are highlighted. The use of Eh corrected at pH7, pe+pH or rH{sub 2}, which are equivalent notions, is proposed to facilitate interpretation of the results. The application of this Eh measurement method allows characterisation of soil conditions with sufficient repeatability, reproducibility and accuracy to demonstrate that conservation agriculture systems positively alter the protonic and electronic balance of soil as compared to conventional systems. - Highlights: • Electromagnetic fields can dramatically perturb soil Eh measurement. • Our method overcomes the main difficulties in soil Eh measurement. • Accurate and reproducible measurement of mean soil Eh are achieved. • Eh{sub pH7}, pe+pH and rH{sub 2} are equivalent notions characterising electron activity. • Agricultural practices alter soil protonic and electronic characteristics.

  5. Measuring intracellular redox conditions using GFP-based sensors

    DEFF Research Database (Denmark)

    Björnberg, Olof; Ostergaard, Henrik; Winther, Jakob R

    2006-01-01

    Recent years have seen the development of methods for analyzing the redox conditions in specific compartments in living cells. These methods are based on genetically encoded sensors comprising variants of Green Fluorescent Protein in which vicinal cysteine residues have been introduced at solvent......-exposed positions. Several mutant forms have been identified in which formation of a disulfide bond between these cysteine residues results in changes of their fluorescence properties. The redox sensors have been characterized biochemically and found to behave differently, both spectroscopically and in terms...... of redox properties. As genetically encoded sensors they can be expressed in living cells and used for analysis of intracellular redox conditions; however, which parameters are measured depends on how the sensors interact with various cellular redox components. Results of both biochemical and cell...

  6. Study of electronic and structural properties of CaS

    International Nuclear Information System (INIS)

    Mirfenderski, M.; Akbarzdeh, H.; Mokhtari, A.

    2003-01-01

    The electronic and structural properties of CaS are calculated using full potential linearized augmented plane wave method within the local density approximation and generalized gradient approximation for the exchange -correlation energy. For both structures, NaCl structure (B1) and CsCl structure (B2), the obtained values for lattice parameters, bulk modulus and its pressure derivative and transition pressure are in reasonable agreement with the experimental values. For electronic properties, the obtained value for band gap is smaller than the experimental value as well as other calculated results based on density functional theory. Engel and Vosko calculated an exchange potential for some atoms within the so-called optimize-potential model and then used the virial relation and constructed a new exchange-correlation functional. We used that functional and obtained reasonable results for band gap. Finally we investigated the possibility for a third phase ( Zinc Blend structure) for this crystal

  7. Tribological properties of nanostripe surface structures-a design concept for improving tribological properties

    International Nuclear Information System (INIS)

    Miyake, K; Nakano, M; Korenaga, A; Mano, H; Ando, Y

    2010-01-01

    The tribological properties of nanostripe surface structures were investigated using a pin-on-plate tribometer in order to propose a design concept for improving the tribological properties. The authors used four kinds of nanostripe structures consisting of different combinations of materials (Fe-Au, C-SiC, Al-Al 2 O 3 and Al-Pt) fabricated by a process they had previously proposed. The frictional properties of the nanostripe structures depended on the materials that constituted the nanostripes. When the sliding direction in friction tests was parallel to the microgrooves, nanostripe structures remained on all surfaces even after friction tests. Based on the friction test results, the authors considered a design concept for nanostripe structures in tribological applications.

  8. Redox-active porous coordination polymer based on trinuclear pivalate: Temperature-dependent crystal rearrangement and redox-behavior

    Energy Technology Data Exchange (ETDEWEB)

    Lytvynenko, Anton S. [L.V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, Prospekt Nauki 31, Kiev 03028 (Ukraine); Kiskin, Mikhail A., E-mail: mkiskin@igic.ras.ru [N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninsky Prospect 31, GSP-1, 119991 Moscow (Russian Federation); Dorofeeva, Victoria N.; Mishura, Andrey M.; Titov, Vladimir E.; Kolotilov, Sergey V. [L.V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, Prospekt Nauki 31, Kiev 03028 (Ukraine); Eremenko, Igor L.; Novotortsev, Vladimir M. [N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninsky Prospect 31, GSP-1, 119991 Moscow (Russian Federation)

    2015-03-15

    Linking of trinuclear pivalate Fe{sub 2}NiO(Piv){sub 6} (Piv=O{sub 2}CC(CH{sub 3}){sub 3}) by 2,6-bis(4-pyridyl)-4-(1-naphthyl)pyridine (L) resulted in formation of 1D-porous coordination polymer Fe{sub 2}NiO(Piv){sub 6}(L)·Solv, which was characterized in two forms: DMSO solvate Fe{sub 2}NiO(Piv){sub 6}(L)(DMSO)·2.5DMSO (1) or water solvate Fe{sub 2}NiO(Piv){sub 6}(L)(H{sub 2}O) (2). X-ray structure of 1 was determined. Crystal lattice of 1 at 160 K contained open channels, filled by captured solvent, while temperature growth to 296 K led to the crystal lattice rearrangement and formation of closed voids. Redox-behavior of 2 was studied by cyclic voltammetry for a solid compound, deposited on glassy-carbon electrode. Redox-activity of L preserved upon incorporation in the coordination polymer. The presence of pores in desolvated sample Fe{sub 2}NiO(Piv){sub 6}(L) was confirmed by the measurements of N{sub 2} and H{sub 2} adsorption at 77 K. Potential barriers of the different molecules diffusion through pores were estimated by the means of molecular mechanics. - Graphical abstract: Redox-behavior of 1D-porous coordination polymer Fe{sub 2}NiO(Piv){sub 6}(L)(H{sub 2}O) was studied by cyclic voltammetry in thin film, deposited on glassy-carbon electrode. Redox-activity of L preserved upon incorporation in the coordination polymer. Potential barriers of different molecules diffusion through pores were estimated by the means of molecular mechanics. - Highlights: • Porous 1D coordination polymer was synthesized. • Temperature growth led to pores closing due to crystal lattice rearrangement. • Redox-activity of ligand preserved upon incorporation into coordination polymer. • Redox-properties of solid coordination polymer were studied in thin film. • Diffusion barriers were evaluated by molecular mechanics.

  9. Redox-Active Star Molecules Incorporating the 4-Benzoylpyridinium Cation - Implications for the Charge Transfer Along Branches vs. Across the Perimeter in Dendrimer

    Science.gov (United States)

    Leventis, Nicholas; Yang, Jinua; Fabrizio,Even F.; Rawashdeh, Abdel-Monem M.; Oh, Woon Su; Sotiriou-Leventis, Chariklia

    2004-01-01

    Dendrimers are self-repeating globular branched star molecules, whose fractal structure continues to fascinate, challenge, and inspire. Functional dendrimers may incorporate redox centers, and potential applications include antennae molecules for light harvesting, sensors, mediators, and artificial biomolecules. We report the synthesis and redox properties of four star systems incorporating the 4-benzoyl-N-alkylpyridinium cation; the redox potential varies along the branches but remains constant at fixed radii. Bulk electrolysis shows that at a semi-infinite time scale all redox centers are electrochemically accessible. However, voltammetric analysis (cyclic voltammetry and differential pulse voltammetry) shows that on1y two of the three redox-active centers in the perimeter are electrochemically accessible during potential sweeps as slow as 20 mV/s and as fast as 10 V/s. On the contrary, both redox centers along branches are accessible electrochemically within the same time frame. These results are explained in terms of slow through-space charge transfer and the globular 3-D folding of the molecules and are discussed in terms of their implications on the design of efficient redox functional dendrimers.

  10. Structurally bound sulfide and sulfate in apatite from the Philips Mine iron oxide - apatite deposit, New York, USA: A tracer of redox changes

    Science.gov (United States)

    Sadove, G.; Konecke, B.; Fiege, A.; Simon, A. C.

    2017-12-01

    Multiple competing hypotheses attempt to explain the genesis of iron oxide-apatite (IOA) ore deposits. Many studies have investigated the chemistry of apatite because the abundances of F and Cl can distinguish magmatic vs. hydrothermal processes. Recent experiments demonstrate that apatite incorporates S6+, S4+, and S2-, and that total sulfur (∑S) as well as the S6+/∑S ratio in apatite vary systematically as a function of oxygen fugacity [1], providing information about sulfur budget and redox. Here, we present results from X-ray absorption near-edge structure (XANES) spectroscopy at the S K-edge, electron microprobe analyses, cathodoluminescence (CL) imaging, and element mapping of apatite from the Philip's Mine IOA deposit, southern Adirondack Mountains, USA. The Philip's Mine apatite contains inclusions of pyrite and pyrrhotite, where the latter includes iron oxide and Ni-rich domains. The apatite also contains inclusions of monazite, and exhibits complex CL zonation coincident with variations in the abundances of REE and S. The presence of monazite fingerprints fluid-mediated dissolution-reprecipitation of originally REE-enriched apatite [2]. The S XANES spectra reveal varying proportions of structurally bound S6+ and S2-, as the S6+/∑S ratio ranges from sulfide-only to sulfate-only. Notably, sulfide-dominated domains contain higher S contents than sulfate-dominated regions. These observations are consistent with co-crystallization of apatite and monosulfide solid solution (MSS) at reducing conditions, followed by decomposition of MSS to pyrrhotite, pyrite and intermediate solid solution (ISS, which is not preserved; [3]). Metasomatism of that assemblage by an oxidized fluid resulted in formation of monazite in apatite and iron oxide domains in pyrrhotite. We conclude that the deposit formed by a H2S-Fe-rich volatile phase, possibly evolved from a rather primitive magmatic source, which is consistent with the low Ti content of magnetite. The deposit was

  11. Structural stability, electronic structure and mechanical properties of actinide carbides AnC (An = U, Np)

    International Nuclear Information System (INIS)

    Manikandan, M.; Santhosh, M.; Rajeswarapalanichamy, R.

    2016-01-01

    Ab initio calculations are performed to investigate the structural stability, electronic structure and mechanical properties of actinide carbides AnC (An=U, Np) for three different crystal structures, namely NaCl, CsCl and ZnS. Among the considered structures, NaCl structure is found to be the most stable structure for these carbides at normal pressure. A pressure induced structural phase transition from NaCl to ZnS is observed. The electronic structure reveals that these carbides are metals. The calculated elastic constants indicate that these carbides are mechanically stable at normal pressure.

  12. Distributing Correlation Coefficients of Linear Structure-Activity/Property Models

    Directory of Open Access Journals (Sweden)

    Sorana D. BOLBOACA

    2011-12-01

    Full Text Available Quantitative structure-activity/property relationships are mathematical relationships linking chemical structure and activity/property in a quantitative manner. These in silico approaches are frequently used to reduce animal testing and risk-assessment, as well as to increase time- and cost-effectiveness in characterization and identification of active compounds. The aim of our study was to investigate the pattern of correlation coefficients distribution associated to simple linear relationships linking the compounds structure with their activities. A set of the most common ordnance compounds found at naval facilities with a limited data set with a range of toxicities on aquatic ecosystem and a set of seven properties was studied. Statistically significant models were selected and investigated. The probability density function of the correlation coefficients was investigated using a series of possible continuous distribution laws. Almost 48% of the correlation coefficients proved fit Beta distribution, 40% fit Generalized Pareto distribution, and 12% fit Pert distribution.

  13. Effect of monohydric alcohols on structural properties of macromolecular solutions

    International Nuclear Information System (INIS)

    Giordano, R.; Wanderlingh, F.; Cordone, L.; Cupane, A.

    1983-01-01

    A report on the effects of monohydric alcohols on the thixotropic properties of a 1% (by weight) BSA solution is given. The presence of alcohols in the solution medium, even in a very small amount, weakens the structure responsible for the thixotropic properties: this effect increases with increasing alcohol concentration and alkyl group size. Indirect evidence relating the observed effects to the alteration, in the presence of alcohol, of protein-solvent hydrophobic interactions is also presented

  14. Rare Earth Borohydrides—Crystal Structures and Thermal Properties

    Directory of Open Access Journals (Sweden)

    Christoph Frommen

    2017-12-01

    Full Text Available Rare earth (RE borohydrides have received considerable attention during the past ten years as possible hydrogen storage materials due to their relatively high gravimetric hydrogen density. This review illustrates the rich chemistry, structural diversity and thermal properties of borohydrides containing RE elements. In addition, it highlights the decomposition and rehydrogenation properties of composites containing RE-borohydrides, light-weight metal borohydrides such as LiBH4 and additives such as LiH.

  15. Electronic structure and physical properties of 13C carbon composite

    OpenAIRE

    Zhmurikov, Evgenij

    2015-01-01

    This review is devoted to the application of graphite and graphite composites in science and technology. Structure and electrical properties, as so technological aspects of producing of high-strength artificial graphite and dynamics of its destruction are considered. These type of graphite are traditionally used in the nuclear industry. Author was focused on the properties of graphite composites based on carbon isotope 13C. Generally, the review relies on the original results and concentrates...

  16. Investigation of optical properties of Ag: PMMA nanocomposite structures

    Science.gov (United States)

    Ponelyte, S.; Palevicius, A.; Guobiene, A.; Puiso, J.; Prosycevas, I.

    2010-05-01

    In the recent years fundamental research involving the nanodimensional materials has received enormous momentum for observing and understanding new types of plasmonic materials and their physical phenomena occurring in the nanoscale. Mechanical and optical properties of these polymer based nanocomposite structures depend not only on type, dimensions and concentration of filler material, but also on a kind of polymer matrix used. By proper selection of polymer matrix and nanofillers, it is possible to engineer nanocomposite materials with certain favorable properties. One of the most striking features of nanocomposite materials is that they can expose unique optical properties that are not intrinsic to natural materials. In these researches, nanocomposite structures were formed using polymer (PMMA) as a matrix, and silver nanoparticles as fillers. By hot embossing procedure a diffraction grating was imprinted on formed layers. The effect of UV exposure time on nanocomposite structures morphology, optical (diffraction effectiveness, absorbance) and mechanical properties was investigated. Results were confirmed by UV-VIS spectrometer, Laser Diffractometer, PMT- 3 and AFM. Investigations proposed new nanocomposite structures as plasmonic materials with improved optical and mechanical properties, which may be applied for a number of technological applications: micro-electro-mechanical devices, optical devices, various plasmonic sensors, or even in DNA nanotechnology.

  17. Composition-Structure-Property Relations of Compressed Borosilicate Glasses

    Science.gov (United States)

    Svenson, Mouritz N.; Bechgaard, Tobias K.; Fuglsang, Søren D.; Pedersen, Rune H.; Tjell, Anders Ø.; Østergaard, Martin B.; Youngman, Randall E.; Mauro, John C.; Rzoska, Sylwester J.; Bockowski, Michal; Smedskjaer, Morten M.

    2014-08-01

    Hot isostatic compression is an interesting method for modifying the structure and properties of bulk inorganic glasses. However, the structural and topological origins of the pressure-induced changes in macroscopic properties are not yet well understood. In this study, we report on the pressure and composition dependences of density and micromechanical properties (hardness, crack resistance, and brittleness) of five soda-lime borosilicate glasses with constant modifier content, covering the extremes from Na-Ca borate to Na-Ca silicate end members. Compression experiments are performed at pressures ≤1.0 GPa at the glass transition temperature in order to allow processing of large samples with relevance for industrial applications. In line with previous reports, we find an increasing fraction of tetrahedral boron, density, and hardness but a decreasing crack resistance and brittleness upon isostatic compression. Interestingly, a strong linear correlation between plastic (irreversible) compressibility and initial trigonal boron content is demonstrated, as the trigonal boron units are the ones most disposed for structural and topological rearrangements upon network compaction. A linear correlation is also found between plastic compressibility and the relative change in hardness with pressure, which could indicate that the overall network densification is responsible for the increase in hardness. Finally, we find that the micromechanical properties exhibit significantly different composition dependences before and after pressurization. The findings have important implications for tailoring microscopic and macroscopic structures of glassy materials and thus their properties through the hot isostatic compression method.

  18. Process, structure, property and applications of metallic glasses

    Directory of Open Access Journals (Sweden)

    B. Geetha Priyadarshini

    2016-07-01

    Full Text Available Metallic glasses (MGs are gaining immense technological significance due to their unique structure-property relationship with renewed interest in diverse field of applications including biomedical implants, commercial products, machinery parts, and micro-electro-mechanical systems (MEMS. Various processing routes have been adopted to fabricate MGs with short-range ordering which is believed to be the genesis of unique structure. Understanding the structure of these unique materials is a long-standing unsolved mystery. Unlike crystalline counterpart, the outstanding properties of metallic glasses owing to the absence of grain boundaries is reported to exhibit high hardness, excellent strength, high elastic strain, and anti-corrosion properties. The combination of these remarkable properties would significantly contribute to improvement of performance and reliability of these materials when incorporated as bio-implants. The nucleation and growth of metallic glasses is driven by thermodynamics and kinetics in non-equilibrium conditions. This comprehensive review article discusses the various attributes of metallic glasses with an aim to understand the fundamentals of relationship process-structure-property existing in such unique class of material.

  19. Structural Dependence of Physical Properties in Sodium Boroaluminosilicate Glasses

    DEFF Research Database (Denmark)

    Zheng, Qiuju; Potuzak, Marcel; Mauro, John C.

    Boroaluminosilicate glasses have found applications in many fields. The extent and nature of the mixing of network formers like SiO2, B2O3, and Al2O3 play an important role in controlling the macroscopic properties. To understand the structure-property correlations in these glasses, we study...... a series of sodium boroaluminosilicate glasses with various [Al2O3]/[SiO2] ratios to access different regimes of sodium behavior. We determine dynamic properties, elastic moduli, and hardness of these glasses. The results reveal an existence of local minimum for density, fragility index, Young’s and shear...

  20. Correlation between fuel structure and mechanical properties of UO2

    International Nuclear Information System (INIS)

    Blank, H.; Mandler, R.; Matzke, H.; Routbort, J.; Werner, P.

    1982-10-01

    The relation between the structure of a UO 2 fuel and its mechanical properties are discussed and illustrated for particular types of UO 2 by measurements of fracture surface energy, hardness, fracture stress and of compressive deformation at 1870 and 1970 0 K. This gives the background for treating the question whether it is possible to find a simple experimental method for correlating the mechanical properties of UO 2 before irradiation with those after various irradiation histories. Hardness measurements might be such a method if combined with a detailed structural analysis and sufficient knowledge about the irradiation history

  1. Structure/property relationships in non-linear optical materials

    Energy Technology Data Exchange (ETDEWEB)

    Cole, J M [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France); [Durham Univ. (United Kingdom); Howard, J A.K. [Durham Univ. (United Kingdom); McIntyre, G J [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    The application of neutrons to the study of structure/property relationships in organic non-linear optical materials (NLOs) is described. In particular, charge-transfer effects and intermolecular interactions are investigated. Charge-transfer effects are studied by charge-density analysis and an example of one such investigation is given. The study of intermolecular interactions concentrates on the effects of hydrogen-bonding and an example is given of two structurally similar molecules with very disparate NLO properties, as a result of different types of hydrogen-bonding. (author). 3 refs.

  2. Structure and properties of Titanium for dental implants

    Directory of Open Access Journals (Sweden)

    M. Greger

    2009-10-01

    Full Text Available This paper describes manufacture of nano-structural titanium, its structure and properties. Nano-titanium has higher specific strength properties than ordinary (coarse-grained titanium. Nano-titanium was produced by the equal-channel angular pressing (ETAP process. The research it self was focused on physical base of strengthening and softening processes and developments occurring at the grain boundaries during the ECAP process at half-hot temperature. Strength of nano-titanium varies around 960 MPa, grain size around 300 nm.

  3. 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

  4. Low Velocity Impact Properties of Aluminum Foam Sandwich Structural Composite

    Directory of Open Access Journals (Sweden)

    ZHAO Jin-hua

    2018-01-01

    Full Text Available Sandwich structural composites were prepared by aluminum foam as core materials with basalt fiber(BF and ultra-high molecular weight polyethylene(UHMWPE fiber composite as faceplate. The effect of factors of different fiber type faceplates, fabric layer design and the thickness of the corematerials on the impact properties and damage mode of aluminum foam sandwich structure was studied. The impact properties were also analyzed to compare with aluminum honeycomb sandwich structure. The results show that BF/aluminum foam sandwich structural composites has bigger impact damage load than UHMWPE/aluminum foam sandwich structure, but less impact displacement and energy absorption. The inter-layer hybrid fabric design of BF and UHMWPE has higher impact load and energy absorption than the overlay hybrid fabric design faceplate sandwich structure. With the increase of the thickness of aluminum foam,the impact load of the sandwich structure decreases, but the energy absorption increases. Aluminum foam sandwich structure has higher impact load than the aluminum honeycomb sandwich structure, but smaller damage energy absorption; the damage mode of aluminum foam core material is mainly the fracture at the impact area, while aluminum honeycomb core has obvious overall compression failure.

  5. Molecular structure based property modeling: Development/ improvement of property models through a systematic property-data-model analysis

    DEFF Research Database (Denmark)

    Hukkerikar, Amol Shivajirao; Sarup, Bent; Sin, Gürkan

    2013-01-01

    models. To make the property-data-model analysis fast and efficient, an approach based on the “molecular structure similarity criteria” to identify molecules (mono-functional, bi-functional, etc.) containing specified set of structural parameters (that is, groups) is employed. The method has been applied...

  6. Mechanical properties and impact behavior of a microcellular structural foam

    Directory of Open Access Journals (Sweden)

    M. Avalle

    Full Text Available Structural foams are a relatively new class of materials with peculiar characteristics that make them very attractive in some energy absorption applications. They are currently used for packaging to protect goods from damage during transportation in the case of accidental impacts. Structural foams, in fact, have sufficient mechanical strength even with reduced weight: the balance between the two antagonist requirements demonstrates that these materials are profitable. Structural foams are generally made of microcellular materials, obtained by polymers where voids at the microscopic level are created. Although the processing technologies and some of the material properties, including mechanical, are well known, very little is established for what concerns dynamic impact properties, for the design of energy absorbing components made of microcellular foams. The paper reports a number of experimental results, in different loading conditions and loading speed, which will be a basis for the structural modeling.

  7. 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.

  8. Fabrication and properties of submicrometer structures of magnetic materials

    International Nuclear Information System (INIS)

    Martin, J.I.; Velez, M.; Nogues, J.; Schuller, I.K.

    1998-01-01

    The method of electron beam lithography is described. This technique allows to fabricate well defined submicrometer structures of magnetic materials, that are suitable to show and study interesting physical properties by transport measurements either in Superconductivity or in Magnetism. In particular, using these structures, we have analyzed pinning effects of the vortex lattice in superconductors and magnetization reversal processes in magnetic materials. (Author) 15 refs

  9. Band Gap Properties of Magnetoelectroelastic Grid Structures with Initial Stress

    International Nuclear Information System (INIS)

    Wang Yi-Ze; Li Feng-Ming

    2012-01-01

    The propagation of elastic waves in magnetoelectroelastic grid structures is studied. Band gap properties are presented and the effects of the magnetoelectroelastic coupling and initial stress are considered. Numerical calculations are performed using the plane-wave expansion method. The results show that the band gap width can be tuned by the initial stress. It is hoped that our results will be helpful for designing acoustic filters with magnetoelectroelastic materials and grid structures

  10. Path Integration Applied to Structural Systems with Uncertain Properties

    DEFF Research Database (Denmark)

    Nielsen, Søren R.K.; Köylüoglu, H. Ugur

    Path integration (cell-to-cell mapping) method is applied to evaluate the joint probability density function (jpdf) of the response of the structural systems, with uncertain properties, subject to white noise excitation. A general methodology to deal with uncertainties is outlined and applied...... to the friction controlled slip of a structure on a foundation where the friction coefficient is modelled as a random variable. Exact results derived using the total probability theorem are compared to the ones obtained via path integration....

  11. Structure and physical properties of bio membranes and model membranes

    International Nuclear Information System (INIS)

    Tibor Hianik

    2006-01-01

    Bio membranes belong to the most important structures of the cell and the cell organelles. They play not only structural role of the barrier separating the external and internal part of the membrane but contain also various functional molecules, like receptors, ionic channels, carriers and enzymes. The cell membrane also preserves non-equilibrium state in a cell which is crucial for maintaining its excitability and other signaling functions. The growing interest to the bio membranes is also due to their unique physical properties. From physical point of view the bio membranes, that are composed of lipid bilayer into which are incorporated integral proteins and on their surface are anchored peripheral proteins and polysaccharides, represent liquid s crystal of smectic type. The bio membranes are characterized by anisotropy of structural and physical properties. The complex structure of bio membranes makes the study of their physical properties rather difficult. Therefore several model systems that mimic the structure of bio membranes were developed. Among them the lipid monolayers at an air-water interphase, bilayer lipid membranes, supported bilayer lipid membranes and liposomes are most known. This work is focused on the introduction into the physical word of the bio membranes and their models. After introduction to the membrane structure and the history of its establishment, the physical properties of the bio membranes and their models are stepwise presented. The most focus is on the properties of lipid monolayers, bilayer lipid membranes, supported bilayer lipid membranes and liposomes that were most detailed studied. This lecture has tutorial character that may be useful for undergraduate and graduate students in the area of biophysics, biochemistry, molecular biology and bioengineering, however it contains also original work of the author and his co-worker and PhD students, that may be useful also for specialists working in the field of bio membranes and model

  12. Structure and Magnetic Properties of Rare Earth Doped Transparent Alumina

    Science.gov (United States)

    Limmer, Krista; Neupane, Mahesh; Chantawansri, Tanya

    Recent experimental studies of rare earth (RE) doped alumina suggest that the RE induced novel phase-dependent structural and magnetic properties. Motivated by these efforts, the effects of RE doping of alpha and theta alumina on the local structure, magnetic properties, and phase stability have been examined in this first principles study. Although a direct correlation between the magnetic field dependent materials properties observed experimentally and calculated from first principles is not feasible because of the applied field and the scale, the internal magnetic properties and other properties of the doped materials are evaluated. The RE dopants are shown to increase the substitutional site volume as well as increasingly distort the site structure as a function of ionic radii. Doping both the alpha (stable) and theta (metastable) phases enhanced the relative stability of the theta phase. The energetic doping cost and internal magnetic moment were shown to be a function of the electronic configuration of the RE-dopant, with magnetic moment directly proportional to the number of unpaired electrons and doping cost being inversely related.

  13. Kaxiras’s Porphyrin: DFT Modeling of Redox-Tuned Optical and Electronic Properties in a Theoretically Designed Catechol-Based Bioinspired Platform

    Directory of Open Access Journals (Sweden)

    Orlando Crescenzi

    2017-11-01

    Full Text Available A detailed computational investigation of the 5,6-dihydroxyindole (DHI-based porphyrin-type tetramer first described by Kaxiras as a theoretical structural model for eumelanin biopolymers is reported herein, with a view to predicting the technological potential of this unique bioinspired tetracatechol system. All possible tautomers/conformers, as well as alternative protonation states, were explored for the species at various degrees of oxidation and all structures were geometry optimized at the density functional theory (DFT level. Comparison of energy levels for each oxidized species indicated a marked instability of most oxidation states except the six-electron level, and an unexpected resilience to disproportionation of the one-electron oxidation free radical species. Changes in the highest energy occupied molecular orbital (HOMO–lowest energy unoccupied molecular orbital (LUMO gaps with oxidation state and tautomerism were determined along with the main electronic transitions: more or less intense absorption in the visible region is predicted for most oxidized species. Data indicated that the peculiar symmetry of the oxygenation pattern pertaining to the four catechol/quinone/quinone methide moieties, in concert with the NH centers, fine-tunes the optical and electronic properties of the porphyrin system. For several oxidation levels, conjugated systems extending over two or more indole units play a major role in determining the preferred tautomeric state: thus, the highest stability of the six-electron oxidation state reflects porphyrin-type aromaticity. These results provide new clues for the design of innovative bioinspired optoelectronic materials.

  14. Crystal structure, characterization and magnetic properties of a 1D ...

    Indian Academy of Sciences (India)

    Crystal structure, characterization and magnetic properties of a 1D copper(II) polymer incorporating a Schiff base with carboxylate side arm. SHYAMAPADA SHIT MADHUSUDAN NANDY CORRADO RIZZOLI CÉDRIC DESPLANCHES SAMIRAN MITRA. Regular Article Volume 128 Issue 6 June 2016 pp 913-920 ...

  15. Structure And Properties Of PVD Coatings Deposited On Cermets

    Directory of Open Access Journals (Sweden)

    Żukowska L.

    2015-06-01

    Full Text Available The main aim of the research is the investigation of the structure and properties of single-layer and gradient coatings of the type (Ti,AlN and Ti(C,N deposited by physical vapour deposition technology (PVD on the cermets substrate.

  16. Ab-initio theoretical predictions of structural properties of semiconductors

    International Nuclear Information System (INIS)

    Rodriguez, C.O.; Peltzer y Blanca, E.L.; Cappannini, O.M.

    1983-01-01

    Calculations of the total energies of Si, GaP and C together with related structural properties are presented. The results show good agreement with experimental values (differences of less than 6%). They also agree with other recent theoretical results. Calculations for Si and GaP have already been reported and are given here as a reference. (L.C.) [pt

  17. Ab-initio theoretical predictions of structure properties of semiconductors

    International Nuclear Information System (INIS)

    Rodriguez, C.O.; Peltzer y Blanca, E.L.; Cappannini, O.M.

    1983-01-01

    In this paper, calculations of the total energies and related structural properties of Si, GaP and C are presented showing good agreement with experimental values. The total energy is calculated within the local-density functional formalism using first principles non-local pseudopotentials. (A.C.A.S.) [pt

  18. Structural, elastic, electronic and optical properties of bi-alkali ...

    Indian Academy of Sciences (India)

    The structural parameters, elastic constants, electronic and optical properties of the bi-alkali ... and efficient method for the calculation of the ground-state ... Figure 2. Optimization curve (E–V) of the bi-alkali antimonides: (a) Na2KSb, (b) Na2RbSb, (c) Na2CsSb, .... ical shape of the charge distributions in the contour plots.

  19. Piezoelectric and mechanical properties of structured PZT-epoxy composites

    NARCIS (Netherlands)

    James, N.K.; Ende, D.A. van den; Lafont, U.; Zwaag, S. van der; Groen, W.A.

    2013-01-01

    Structured lead zirconium titanate (PZT)-epoxy composites are prepared by dielectrophoresis. The piezoelectric and dielectric properties of the composites as a function of PZT volume fraction are investigated and compared with the corresponding unstructured composites. The effect of poling voltage

  20. Structural, morphological and magnetic properties of La1 ...

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... Home; Journals; Bulletin of Materials Science; Volume 38; Issue 7. Structural, morphological and magnetic properties of La1−NaMnO3 ( ≤ ) nanoparticles produced by the solution combustion method. C O Ehi-Eromosele B I Ita K O Ajanaku A Edobor-Osoh O Aladesuyi S A Adalikwu F E Ehi- ...

  1. Major dimensions in food-web structure properties

    NARCIS (Netherlands)

    Vermaat, J.E.; Dunne, J. A.; Gilbert, A.J.

    2009-01-01

    The covariance among a range of 20 network structural properties of food webs plus net primary productivity was assessed for 14 published food webs using principal components analysis. Three primary components explained 84% of the variability in the data sets, suggesting substantial covariance among

  2. Size Induced Structural and Magnetic Properties of Nanostructured ...

    African Journals Online (AJOL)

    Their structural and magnetic properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) measurements. The average crystallite size of CoFe2O4was observed to increase from 23 to 65 nm as the annealing temperature was increased from ...

  3. Structural, energetic and electronic properties of intercalated boron ...

    Indian Academy of Sciences (India)

    2National Institute for R&D of Isotopic and Molecular Technologies, Cluj-Napoca 400 293, Romania. MS received 8 November 2010; revised 28 March 2012. Abstract. The effects of chirality and the intercalation of transitional metal atoms inside single walled BN nano- tubes on structural, energetic and electronic properties ...

  4. Synthesis, structure, thermal, transport and magnetic properties of VN ceramics

    Czech Academy of Sciences Publication Activity Database

    Huber, Š.; Jankovský, O.; Sedmidubský, D.; Luxa, J.; Klimová, K.; Hejtmánek, Jiří; Sofer, Z.

    2016-01-01

    Roč. 42, č. 16 (2016), s. 18779-18784 ISSN 0272-8842 R&D Projects: GA ČR GA13-20507S Institutional support: RVO:68378271 Keywords : vanadium mononitride * phase transition * electronic structure * heat capacity * transport properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.986, year: 2016

  5. Piezoelectric and mechanical properties of structured PZT–epoxy composites

    NARCIS (Netherlands)

    Kunnamkuzhakkal James, N.; Van den Ende, D.; Lafont, U.; Van der Zwaag, S.; Groen, W.A.

    2013-01-01

    Structured lead zirconium titanate (PZT)–epoxy composites are prepared by dielectrophoresis. The piezoelectric and dielectric properties of the composites as a function of PZT volume fraction are investigated and compared with the corresponding unstructured composites. The effect of poling voltage

  6. Synthesis, structural and optical properties of nanoparticles (Al, V ...

    Indian Academy of Sciences (India)

    The synthesis by the sol–gel method, structural and optical properties of ZnO, Zn0.99Al0.01O (AlZ),. Zn0.9V0.1O (VZ) ... drops of the resulting suspension containing the synthesized .... ZnO films on silicon substrate, they thought that this emis-.

  7. Electronic structure and optical properties of thorium monopnictides

    Indian Academy of Sciences (India)

    Unknown

    Indian Academy of Sciences. 165. Electronic structure and optical properties of thorium monopnictides. S KUMAR* and S AULUCK†. Physics Department, Institute of Engineering and Technology, M.J.P. Rohilkhand University, Bareilly 243 006,. India. †Department of Physics, Indian Institute of Technology, Roorkee 247 667, ...

  8. Structure and properties of compositions based on petroleum sulfonic acids

    Energy Technology Data Exchange (ETDEWEB)

    Tutorskii, I.A.; Sultanova, A.S.; Belkina, E.V.; Fomin, A.G. [Lomonosov Academy of Fine Chemical Technology, Moscow (Russian Federation)

    1995-03-01

    Colloidal characteristics of compositions based on petroleum sulfonic acids were studied. Neutralized heavy oil residue exhibits surface-active properties and contains an ultradisperse filler. Analysis of the compositions by size-exclusion-chromatography shows deep structural changes in the heavy acid residue upon neutralization with calcium carbonate.

  9. Structural properties of reflected Lévy processes

    DEFF Research Database (Denmark)

    Andersen, Lars Nørvang; Mandjes, Michel

    This paper considers a number of structural properties of reflected Lévy processes, where both one-sided reflection (at 0) and two-sided reflection (at both 0 and K > 0) are examined. With Vt being the position of the reflected process at time t, we focus on the analysis of ζ(t) := EVt and ξ(t) :...

  10. Intrinsic structure and friction properties of graphene and graphene

    Indian Academy of Sciences (India)

    In this paper, atomic structure of single-layered graphene oxide (GO) and chemically reduced graphene oxide (CRGO) nanosheets was investigated using atomic force microscopy and scanning tunnelingmicroscopy (AFM and STM). Furthermore, friction properties of the graphene and GO nanosheets were studied by ...

  11. Anomalous structural changes and elastic properties of bismuth oxide superconductors

    International Nuclear Information System (INIS)

    He, Y.S.; Xiang, J.; Chang, F.G.; Zhang, J.C.; He, A.S.; Wang, H.; Gu, B.L.

    1989-01-01

    Ultrasonic measurement revealed that there are anomalous structural changes near 200 K in single 2212 or 2223 phase samples of Bi(Pb)-Sr-Ca-Cu-O. Detailed study showed such anomalous changes are isothermal-like processes and have a characteristics of second order phase transition, accompanying with increases in lattice constants. The elastic properties of these ceramics and related systems are discussed

  12. Effect of heat treatment on structure and magnetic properties

    Indian Academy of Sciences (India)

    Fe46Co35Ni19/CNTs nanocomposites have been prepared by an easy two-step route including adsorption and heat treatment processes. We investigated the effect of heat treatment conditions on structure, morphology, nanoparticle sizes and magnetic properties of the Fe46Co35Ni19 alloy nanoparticles attached on the ...

  13. Structural, morphological and magnetic properties of La1 ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 38; Issue 7. Structural, morphological and magnetic properties of La1−NaMnO3 ( ≤ ) nanoparticles produced by the solution combustion method. C O Ehi-Eromosele B I Ita K O Ajanaku A Edobor-Osoh O Aladesuyi S A Adalikwu F E Ehi-Eromosele. Volume 38 ...

  14. 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.

  15. 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

  16. Structural and morphological properties of electroceramics for chemical sensors

    International Nuclear Information System (INIS)

    Tor Vergata, Via della Ricerca Scientifica, Roma (Italy). Dipartimento di Scienze e Tecnologie Chimiche)" data-affiliation=" (Universita' di Roma Tor Vergata, Via della Ricerca Scientifica, Roma (Italy). Dipartimento di Scienze e Tecnologie Chimiche)" >Enrico Traversa

    1996-01-01

    Ceramic materials possess a unique structure consisting of grains, grain boundaries, surfaces and pores, which makes them suitable for chemical sensors. The control of the chemical composition and microstructure of electrochemicals is fundamental for controlling their properties. Ceramics with a given composition and microstructure can be produced by controlling the different steps of their processing. The chemical processing of ceramics offer many advantages in terms of control and reproducibility, with respect to the conventional ceramics processing. Results are reported about the chemical processing of perovskite-type oxides for gas sensors and about the novel humidity-sensitive electrical properties of sol-gel processed alkali-doped titania films. The structural and morphological characterization of these materials permits the understanding of the sensitive electrical properties of the ceramics (71 refs.)

  17. High-Performance Oligomeric Catholytes for Effective Macromolecular Separation in Nonaqueous Redox Flow Batteries.

    Science.gov (United States)

    Hendriks, Koen H; Robinson, Sophia G; Braten, Miles N; Sevov, Christo S; Helms, Brett A; Sigman, Matthew S; Minteer, Shelley D; Sanford, Melanie S

    2018-02-28

    Nonaqueous redox flow batteries (NRFBs) represent an attractive technology for energy storage from intermittent renewable sources. In these batteries, electrical energy is stored in and extracted from electrolyte solutions of redox-active molecules (termed catholytes and anolytes) that are passed through an electrochemical flow cell. To avoid battery self-discharge, the anolyte and catholyte solutions must be separated by a membrane in the flow cell. This membrane prevents crossover of the redox active molecules, while simultaneously allowing facile transport of charge-balancing ions. A key unmet challenge for the field is the design of redox-active molecule/membrane pairs that enable effective electrolyte separation while maintaining optimal battery properties. Herein, we demonstrate the development of oligomeric catholytes based on tris(dialkylamino)cyclopropenium (CP) salts that are specifically tailored for pairing with size-exclusion membranes composed of polymers of intrinsic microporosity (PIMs). Systematic studies were conducted to evaluate the impact of oligomer size/structure on properties that are crucial for flow battery performance, including cycling stability, charge capacity, solubility, electron transfer kinetics, and crossover rates. These studies have led to the identification of a CP-derived tetramer in which these properties are all comparable, or significantly improved, relative to the monomeric counterpart. Finally, a proof-of-concept flow battery is demonstrated by pairing this tetrameric catholyte with a PIM membrane. After 6 days of cycling, no crossover is detected, demonstrating the promise of this approach. These studies provide a template for the future design of other redox-active oligomers for this application.

  18. Floor response spectra of buildings with uncertain structural properties

    International Nuclear Information System (INIS)

    Chen, P.C.

    1975-01-01

    All Category I equipment, such as reactors, vessels, and major piping systems of nuclear power plants, is required to withstand earthquake loadings in order to minimize risk of seismic damage. The equipment is designed by using response spectra of the floor on which the equipment is mounted. The floor response spectra are constructed usually from the floor response time histories which are obtained through a deterministic dynamic analysis. This analysis assumes that all structural parameters, such as mass, stiffness, and damping have been calculated precisely, and that the earthquakes are known. However, structural parameters are usually difficult to determine precisely if the structures are massive and/or irregular, such as nuclear containments and its internal structures with foundation soil incorporated into the analysis. Faced with these uncertainties, it has been the practice to broaden the floor response spectra peaks by +-10 percent of the peak frequencies on the basis of conservatism. This approach is based on engineering judgement and does not have an analytical basis to provide a sufficient level of confidence in using these spectra for equipment design. To insure reliable design, it is necessary to know structural response variations due to variations in structural properties. This consideration leads to the treatment of structural properties as random variables and the use of probabilistic methods to predict structural response more accurately. New results on floor response spectra of buildings with uncertain structural properties obtained by determining the probabilistic dynamic response from the deterministic dynamic response and its standard deviation are presented. The resulting probabilistic floor response spectra are compared with those obtained deterministically, and are shown to provide a more reliable method for determining seismic forces

  19. Structures and Redox Properties of Metal Complexes of the Electron-Deficient Diphosphine Chelate Ligand R,R-QuinoxP

    Czech Academy of Sciences Publication Activity Database

    Das, A. K.; Bulak, E.; Sarkar, B.; Lissner, F.; Schleid, T.; Niemeyer, M.; Fiedler, Jan; Kaim, W.

    2008-01-01

    Roč. 27, č. 2 (2008), s. 218-223 ISSN 0276-7333 R&D Projects: GA MŠk OC 139; GA MŠk OC 140 Institutional research plan: CEZ:AV0Z40400503 Keywords : 2,3-bis(tert-butylmethylphosphino)quinoxaline * radical complexes * phosphine ligand Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.815, year: 2008

  20. Properties of structural materials in liquid metal environment. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Borgstedt, H U [ed.

    1991-12-15

    The International Working Group on Fast Reactors (IWGFR) Specialists Meeting on Properties of Structural Materials in Liquid Metal Environment was held during June 18 to June 20, 1991, at the Nuclear Research Centre (Kernforschungszentrum) in Karlsruhe, Germany. The Specialists Meeting was divided into five technical sessions which addressed topics as follows: Creep-Rupture Behaviour of Structural Materials in Liquid Metal Environment; Behaviour of Materials in Liquid Metal Environments under Off-Normal Conditions;Fatigue and Creep-Fatigue of Structural Materials in Liquid Metal Environment; Crack Propagation in Liquid Sodium; and Conclusions and recommendations. Individual papers have been cataloged separately.

  1. One-Electron Theory of Metals. Cohesive and Structural Properties

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt

    The work described in the report r.nd the 16 accompanying publications is based upon a one-electron theory obtained within the local approximation to density-functional theory, and deals with the ground state of metals as obtained from selfconsistent electronic-structure calculations performed...... by means of the Linear Muffin-Tin Orbital (LMTO) method. It has been the goal of the work to establish how well this one-electron approach describes physical properties such as the crystal structures of the transition metals, the structural phase transitions in the alkali, alkaline earth, and rare earth...

  2. Band structures and localization properties of aperiodic layered phononic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yan Zhizhong, E-mail: zzyan@bit.edu.cn [Department of Applied Mathematics, Beijing Institute of Technology, Beijing 100081 (China); Zhang Chuanzeng [Department of Civil Engineering, University of Siegen, D-57078 Siegen (Germany)

    2012-03-15

    The band structures and localization properties of in-plane elastic waves with coupling of longitudinal and transverse modes oblique propagating in aperiodic phononic crystals based on Thue-Morse and Rudin-Shapiro sequences are studied. Using transfer matrix method, the concept of the localization factor is introduced and the correctness is testified through the Rytov dispersion relation. For comparison, the perfect periodic structure and the quasi-periodic Fibonacci system are also considered. In addition, the influences of the random disorder, local resonance, translational and/or mirror symmetries on the band structures of the aperiodic phononic crystals are analyzed in this paper.

  3. Conference Proceedings: Structuring oil and gas property transactions

    International Nuclear Information System (INIS)

    1999-01-01

    The 12 presentations at this conference dealt with issues concerning the legal aspects of oil and gas property transaction agreements. Several issues regarding sales and purchase negotiations of oil and gas property are reviewed and some of the basic principles of contract law are explained. Advantages, disadvantages and opportunities of structuring oil and gas property acquisitions, as well as their tax consequences are also identified. The issue of risk assessment regarding environmental consequences and how public concerns regarding the state of the environment has had an impact on oil and gas transactions, is addressed. Interest in this topic stems from the fact that improved enforcement of existing laws regarding the environment can potentially make purchasers liable for significant costs associated with remediation or clean-up of contaminated properties. refs., tabs., figs

  4. Microstructure characterization and magnetic properties of nano structured materials

    International Nuclear Information System (INIS)

    Sun, X.C.

    2000-01-01

    The present thesis deals with the unique microstructural properties and their novel magnetic properties of core-shell Ni-Ce nano composite particles, carbon encapsulated Fe, Co, and Ni nanoparticles and the nano crystallization behavior of typical ferromagnetic Fe 78 Si 9 B 13 ribbons. These properties have intensively been investigated by high resolution transmission electron microscopy (HREM), X-ray diffraction (XRD), scanning electron microscopy (Sem), X-ray energy dispersive spectroscopy (Eds.); selected area electron diffraction pattern (SAED), Ft-IR, differential scanning calorimeter (DSC). In addition, magnetic moments measurements at different temperatures and applied fields have been performed by transmission Moessbauer spectroscopy, superconducting quantum interference device magnetometer (SQUID), and vibrating sample magnetometer (VSM). The present studies may provide the insights for the better understanding of the correlation between the unique microstructure and novel magnetic properties for several magnetic nano structured materials. (Author)

  5. Microstructure characterization and magnetic properties of nano structured materials

    Energy Technology Data Exchange (ETDEWEB)

    Sun, X.C

    2000-07-01

    The present thesis deals with the unique microstructural properties and their novel magnetic properties of core-shell Ni-Ce nano composite particles, carbon encapsulated Fe, Co, and Ni nanoparticles and the nano crystallization behavior of typical ferromagnetic Fe{sub 78}Si{sub 9}B{sub 13} ribbons. These properties have intensively been investigated by high resolution transmission electron microscopy (HREM), X-ray diffraction (XRD), scanning electron microscopy (Sem), X-ray energy dispersive spectroscopy [eds.]; selected area electron diffraction pattern (SAED), Ft-IR, differential scanning calorimeter (DSC). In addition, magnetic moments measurements at different temperatures and applied fields have been performed by transmission Moessbauer spectroscopy, superconducting quantum interference device magnetometer (SQUID), and vibrating sample magnetometer (VSM). The present studies may provide the insights for the better understanding of the correlation between the unique microstructure and novel magnetic properties for several magnetic nano structured materials. (Author)

  6. Neutral Red and Ferroin as Reversible and Rapid Redox Materials for Redox Flow Batteries.

    Science.gov (United States)

    Hong, Jeehoon; Kim, Ketack

    2018-04-17

    Neutral red and ferroin are used as redox indicators (RINs) in potentiometric titrations. The rapid response and reversibility that are prerequisites for RINs are also desirable properties for the active materials in redox flow batteries (RFBs). This study describes the electrochemical properties of ferroin and neutral red as a redox pair. The rapid reaction rates of the RINs allow a cell to run at a rate of 4 C with 89 % capacity retention after the 100 th  cycle. The diffusion coefficients, electrode reaction rates, and solubilities of the RINs were determined. The electron-transfer rate constants of ferroin and neutral red are 0.11 and 0.027 cm s -1 , respectively, which are greater than those of the components of all-vanadium and Zn/Br 2 cells. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Relation between rheological and structural properties of suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Barcal, M; Sebor, G; Volsicky, Z

    1982-01-01

    The paper discusses results of investigations into separation processes for coal and kaolin suspensions. Effects of potassium chlorides and methanol additives on electrostatic potential of solid particles and on sedimentation rate are analyzed. Investigation results are shown in 5 diagrams. The relation between rheological and structural properties of coal and clay suspensions is investigated. Investigations show that the non-Newtonian behavior of suspensions cannot be attributed exclusively to the electrostatic and mechanical action of the solid phase particles. It is also caused by structure of the liquid phase, particularly on the surface of the solid particles, which depends mostly on hydrogen bonds. The internal structure of the liquid phase influences differential viscosity much more than the electrical surface properties of the solid phase. Bonds between the molecules of water and methanol are much stronger than bonds between water molecules alone. (9 refs.)

  8. 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.

  9. Computational design of molecules for an all-quinone redox flow battery.

    Science.gov (United States)

    Er, Süleyman; Suh, Changwon; Marshak, Michael P; Aspuru-Guzik, Alán

    2015-02-01

    Inspired by the electron transfer properties of quinones in biological systems, we recently showed that quinones are also very promising electroactive materials for stationary energy storage applications. Due to the practically infinite chemical space of organic molecules, the discovery of additional quinones or other redox-active organic molecules for energy storage applications is an open field of inquiry. Here, we introduce a high-throughput computational screening approach that we applied to an accelerated study of a total of 1710 quinone (Q) and hydroquinone (QH 2 ) ( i.e. , two-electron two-proton) redox couples. We identified the promising candidates for both the negative and positive sides of organic-based aqueous flow batteries, thus enabling an all-quinone battery. To further aid the development of additional interesting electroactive small molecules we also provide emerging quantitative structure-property relationships.

  10. Mechanical properties and structural of metal-ceramic tungsten heterogeneity

    International Nuclear Information System (INIS)

    Gnuchev, V.S.; Zasimchuk, E.Eh.; Kas'yan, K.N.; Kravchenko, V.S.; Rabinovich, E.M.; Kharchenko, V.K.; Sheina, I.V.

    1978-01-01

    The influence of the grain size and the structure nonuniformity of cermet tungsten has been studied on its stre--ngth properties at temperatures of 500, 1000, and 1500 deg C. It has been shown that at a high temperature, the samples having a coarse-grained structure (about 50/m) preserve a high level of strength with an elevated plasticity. In the samples having the fine-grained (about 16/m) and the coarse-grained (about 114/m) structure, an abrupt decrease in the plasticity is observed along with a decrease in the strength. By investigating the influence of the annealing conditions on the structure of tungsten, the temperature range of the secondary recrystallization (about 2000 to 2200 deg C) has been established. The rolling temperature of sintered tungsten does not exceed 1700 deg C; thus a supposition is made that the structural nonuniformity of the material is attributable to the process of primary recrystallization and the amount of admixtures present

  11. Electrochemistry and electrochemiluminescence from a redox-active metal-organic framework.

    Science.gov (United States)

    Xu, Yang; Yin, Xue-Bo; He, Xi-Wen; Zhang, Yu-Kui

    2015-06-15

    The marriage of metal-organic frameworks (MOFs) and electrochemiluminescence (ECL) can combine their merits together. Designing ECL-active MOF with a high electron transfer capacity and high stability is critical for ECL emission. Here we reported the ECL from a redox-active MOF prepared from {Ru[4,4'-(HO2C)2-bpy]2bpy}(2+) and Zn(2+); a property of MOFs has not been reported previously. The MOF structure is independent of its charge and is therefore stable electrochemically. The redox-activity and well-ordered porous structure of the MOF were confirmed by its electrochemical properties and ECL emission. The high ECL emission indicated the ease of electron transfer between the MOF and co-reactants. Furthermore, the MOF exhibited permselectivity, charge selectivity, and catalytic selectivity along with a stable and concentration-dependent ECL emission toward co-reactants. ECL mechanism was proposed based on the results. The detection and recovery of cocaine in the serum sample was used to validate the feasibility of MOF- based ECL system. The information obtained in this study provides a better understanding of the redox properties of MOFs and their potential electrochemical applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Structural properties of the Chinese air transportation multilayer network

    International Nuclear Information System (INIS)

    Hong, Chen; Zhang, Jun; Cao, Xian-Bin; Du, Wen-Bo

    2016-01-01

    Highlights: • We investigate the structural properties of the Chinese air transportation multilayer network (ATMN). • We compare two main types of layers corresponding to major and low-cost airlines. • It is found that small-world property and rich-club effect of the Chinese ATMN are mainly caused by major airlines. - Abstract: Recently multilayer networks are attracting great attention because the properties of many real-world systems cannot be well understood without considering their different layers. In this paper, we investigate the structural properties of the Chinese air transportation multilayer network (ATMN) by progressively merging layers together, where each commercial airline (company) defines a layer. The results show that the high clustering coefficient, short characteristic path length and large collection of reachable destinations of the Chinese ATMN can only emerge when several layers are merged together. Moreover, we compare two main types of layers corresponding to major and low-cost airlines. It is found that the small-world property and the rich-club effect of the Chinese ATMN are mainly caused by those layers corresponding to major airlines. Our work will highlight a better understanding of the Chinese air transportation network.

  13. How Are Property Investment Returns Determined? : Estimating the Micro-Structure of Asset Prices, Property Income, and Discount Rates

    OpenAIRE

    Shimizu, Chihiro

    2014-01-01

    How exactly should one estimate property investment returns? Investors in property aim to maximize capital gains from price increases and income generated by the property. How are the returns on investment in property determined based on its characteristics, and what kind of market characteristics does it have? Focusing on the Tokyo commercial property market and residential property market, the purpose of this paper was to break down and measure the micro-structure of property investment ret...

  14. Relaxation Mechanisms, Structure and Properties of Semi-Coherent Interfaces

    Directory of Open Access Journals (Sweden)

    Shuai Shao

    2015-10-01

    Full Text Available In this work, using the Cu–Ni (111 semi-coherent interface as a model system, we combine atomistic simulations and defect theory to reveal the relaxation mechanisms, structure, and properties of semi-coherent interfaces. By calculating the generalized stacking fault energy (GSFE profile of the interface, two stable structures and a high-energy structure are located. During the relaxation, the regions that possess the stable structures expand and develop into coherent regions; the regions with high-energy structure shrink into the intersection of misfit dislocations (nodes. This process reduces the interface excess potential energy but increases the core energy of the misfit dislocations and nodes. The core width is dependent on the GSFE of the interface. The high-energy structure relaxes by relative rotation and dilatation between the crystals. The relative rotation is responsible for the spiral pattern at nodes. The relative dilatation is responsible for the creation of free volume at nodes, which facilitates the nodes’ structural transformation. Several node structures have been observed and analyzed. The various structures have significant impact on the plastic deformation in terms of lattice dislocation nucleation, as well as the point defect formation energies.

  15. Structural and optical properties of Si-doped Ag clusters

    KAUST Repository

    Mokkath, Junais Habeeb

    2014-03-06

    The structural and optical properties of AgN and Ag N-1Si1 (neutral, cationic, and anionic) clusters (N = 5 to 12) are systematically investigated using the density functional based tight binding method and time-dependent density functional theory, providing insight into recent experiments. The gap between the highest occupied and lowest unoccupied molecular orbitals and therefore the optical spectrum vary significantly under Si doping, which enables flexible tuning of the chemical and optical properties of Ag clusters. © 2014 American Chemical Society.

  16. The structure and properties of fluoroplastic modified with titanium nanoparticles

    Science.gov (United States)

    Baronin, G. S.; Buznik, V. M.; Dmitriev, O. S.; Zavrazhina, C. V.; Mishchenko, S. V.; Zavrazhin, D. O.; Khudyakov, V. V.

    2017-12-01

    The results of studying the structure and properties of a mixture of polytetrafluoroethylene (PTFE) and fillers, which are composites of ultrafine polytetrafluoroethylene and titanium (TiFP) nanoparticles, are presented. These composites are obtained with pyrolytic redistribution of a powdered PTFE - (NH4)2TiF6 mixture. It has been found that the composite properties depend on the type and concentration of the inorganic filler and the composite production technology. The created composites exceed the original PTFE in a number of characteristics (deflection temperature, thermal conductivity and durability).

  17. Structural and optical properties of Si-doped Ag clusters

    KAUST Repository

    Mokkath, Junais Habeeb; Schwingenschlö gl, Udo

    2014-01-01

    The structural and optical properties of AgN and Ag N-1Si1 (neutral, cationic, and anionic) clusters (N = 5 to 12) are systematically investigated using the density functional based tight binding method and time-dependent density functional theory, providing insight into recent experiments. The gap between the highest occupied and lowest unoccupied molecular orbitals and therefore the optical spectrum vary significantly under Si doping, which enables flexible tuning of the chemical and optical properties of Ag clusters. © 2014 American Chemical Society.

  18. A short review of nanographenes: structures, properties and applications

    Science.gov (United States)

    Dai, Yafei; Liu, Yi; Ding, Kai; Yang, Jinlong

    2018-04-01

    Graphene has attracted great interest in the science and technology since it was exfoliated mechanically from the graphite in 2004. Although graphene has various potential applications, its practical applications are constrained enormously by its serious drawbacks, such as zero band gap, tendency of aggregation between layers and hydrophobicity, which mainly caused by the infinite planar hexagonal structure of graphene. Considering that the structural defects in the honeycomb lattice and the edges of graphene break the infinite structure and thus change the properties, which may improve the application efficiency, nanographene (NG) is proposed and attracts extensive attention. In this work, we review the structures of multifarious well-defined NGs synthesised in recent experiments. The effects of the shape, size, edges and substituents of NGs to the properties are discussed in detail and the regulation for various properties of NG is analysed. For the well-defined NGs, including planar and non-planar ones, the challenges and perspectives of their potential applications in nonlinear optical material, gas molecular detector and gas separation material, hydrogen storage material, and hole-transporting material in perovskite solar cells are envisioned.

  19. Stochasticity in materials structure, properties, and processing—A review

    Science.gov (United States)

    Hull, Robert; Keblinski, Pawel; Lewis, Dan; Maniatty, Antoinette; Meunier, Vincent; Oberai, Assad A.; Picu, Catalin R.; Samuel, Johnson; Shephard, Mark S.; Tomozawa, Minoru; Vashishth, Deepak; Zhang, Shengbai

    2018-03-01

    We review the concept of stochasticity—i.e., unpredictable or uncontrolled fluctuations in structure, chemistry, or kinetic processes—in materials. We first define six broad classes of stochasticity: equilibrium (thermodynamic) fluctuations; structural/compositional fluctuations; kinetic fluctuations; frustration and degeneracy; imprecision in measurements; and stochasticity in modeling and simulation. In this review, we focus on the first four classes that are inherent to materials phenomena. We next develop a mathematical framework for describing materials stochasticity and then show how it can be broadly applied to these four materials-related stochastic classes. In subsequent sections, we describe structural and compositional fluctuations at small length scales that modify material properties and behavior at larger length scales; systems with engineered fluctuations, concentrating primarily on composite materials; systems in which stochasticity is developed through nucleation and kinetic phenomena; and configurations in which constraints in a given system prevent it from attaining its ground state and cause it to attain several, equally likely (degenerate) states. We next describe how stochasticity in these processes results in variations in physical properties and how these variations are then accentuated by—or amplify—stochasticity in processing and manufacturing procedures. In summary, the origins of materials stochasticity, the degree to which it can be predicted and/or controlled, and the possibility of using stochastic descriptions of materials structure, properties, and processing as a new degree of freedom in materials design are described.

  20. Redox reactions in rare earth chloride molten electrolytes

    International Nuclear Information System (INIS)

    Khokhlov, V.A.; Novoselova, A.V.; Nikolaeva, E.V.; Tkacheva, O.Yu.; Salyulev, A.B.

    2007-01-01

    Rare earth (REM, Ln) solutions in chloride melts including MCI+LnCl 3 mixtures, where M - alkali metals, were investigated by potentiometry, voltammetry, conductometry in wide concentration and temperature intervals. Findings present complete and trusty information on the valent state of rare earths, structure and composition of complex ions affecting essentially on properties of electrolytes. It is demonstrated that the coexistence of rare earth ions with different oxidation level formed as a result of possible redox reactions: 2Ln 3+ + Ln ↔3Ln 2+ , Ln 2+ + Ln↔2Ln + and nM + + Ln↔nM + Ln n+ appears sharply in thermodynamic and transport properties of molten Ln-LnCl 3 and Ln-LnCl 3 -MCl systems [ru

  1. Electrolyte-gated transistors based on phenyl-C61-butyric acid methyl ester (PCBM) films: bridging redox properties, charge carrier transport and device performance.

    Science.gov (United States)

    Lan, Tian; Soavi, Francesca; Marcaccio, Massimo; Brunner, Pierre-Louis; Sayago, Jonathan; Santato, Clara

    2018-05-24

    The n-type organic semiconductor phenyl-C61-butyric acid methyl ester (PCBM), a soluble fullerene derivative well investigated for organic solar cells and transistors, can undergo several successive reversible, diffusion-controlled, one-electron reduction processes. We exploited such processes to shed light on the correlation between electron transfer properties, ionic and electronic transport as well as device performance in ionic liquid (IL)-gated transistors. Two ILs were considered, based on bis(trifluoromethylsulfonyl)imide [TFSI] as the anion and 1-ethyl-3-methylimidazolium [EMIM] or 1-butyl-1-methylpyrrolidinium [PYR14] as the cation. The aromatic structure of [EMIM] and its lower steric hindrance with respect to [PYR14] favor a 3D (bulk) electrochemical doping. As opposed to this, for [PYR14] the doping seems to be 2D (surface-confined). If the n-doping of the PCBM is pursued beyond the first electrochemical process, the transistor current vs. gate-source voltage plots in [PYR14][TFSI] feature a maximum that points to the presence of finite windows of high conductivity in IL-gated PCBM transistors.

  2. Atomic structures and electronic properties of phosphorene grain boundaries

    International Nuclear Information System (INIS)

    Guo, Yu; Zhou, Si; Bai, Yizhen; Zhao, Jijun; Zhang, Junfeng

    2016-01-01

    Grain boundary (GB) is one main type of defects in two-dimensional (2D) crystals, and has significant impact on the physical properties of 2D materials. Phosphorene, a recently synthesized 2D semiconductor, possesses a puckered honeycomb lattice and outstanding electronic properties. It is very interesting to know the possible GBs present in this novel material, and how their properties differ from those in the other 2D materials. Based on first-principles calculations, we explore the atomic structure, thermodynamic stability, and electronic properties of phosphorene GBs. A total of 19 GBs are predicted and found to be energetically stable with formation energies much lower than those in graphene. These GBs do not severely affect the electronic properties of phosphorene: the band gap of perfect phosphorene is preserved, and the electron mobilities are only moderately reduced in these defective systems. Our theoretical results provide vital guidance for experimental tailoring the electronic properties of phosphorene as well as the device applications using phosphorene materials. (paper)

  3. Review of Differences of Steel related Properties between Proposals of European Structural Codes

    DEFF Research Database (Denmark)

    Hertz, Kristian Dahl

    Differences of Steel related Properties between fire chapters of the Proposals of European Structural Codes are indicated for the same physical properties, the right properties are found and it is proposed to use these properties in all codes.......Differences of Steel related Properties between fire chapters of the Proposals of European Structural Codes are indicated for the same physical properties, the right properties are found and it is proposed to use these properties in all codes....

  4. Structure and Electronic Properties of Cerium Orthophosphate: Theory and Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Adelstein, Nicole; Mun, B. Simon; Ray, Hannah; Ross Jr, Phillip; Neaton, Jeffrey; De Jonghe, Lutgard

    2010-07-27

    Structural and electronic properties of cerium orthophosphate (CePO{sub 4}) are calculated using density functional theory (DFT) with the local spin-density approximation (LSDA+U), with and without gradient corrections (GGA-(PBE)+U), and compared to X-ray diffraction and photoemission spectroscopy measurements. The density of states is found to change significantly as the Hubbard parameter U, which is applied to the Ce 4f states, is varied from 0 to 5 eV. The calculated structural properties are in good agreement with experiment and do not change significantly with U. Choosing U = 3 eV for LDSA provides the best agreement between the calculated density of states and the experimental photoemission spectra.

  5. Structure-Property Relationship in High Tg Thermosetting Polyimides

    Science.gov (United States)

    Chuang, Kathy C.; Meador, Mary Ann B.; HardyGreen, DeNise

    2000-01-01

    This viewgraph presentation gives an overview of the structure-property relationship in high glass transition temperatures (T(sub g)) thermosetting polyimides. The objectives of this work are to replace MDA in PMR-15 with 2,2-substituted benzidine and to evaluate the thermo-oxidative stability and mechanical properties of DMBZ-15 against PMR-15. Details are given on the T(sub g) of polyimide resins, the x-ray crystal structure of 2,2-Bis(trifluoro)benzidine (BFBZ), the isothermal aging of polyimide resins at 288 C under 1 atm of circulating air, the compressive strength of polyimide composites, and a gas evaluation profile of DMBZ-15 polyimide resins.

  6. Structural and physicochemical properties of polar lipids from thermophilic archaea.

    Science.gov (United States)

    Ulrih, Natasa Poklar; Gmajner, Dejan; Raspor, Peter

    2009-08-01

    The essential general features required for lipid membranes of extremophilic archaea to fulfill biological functions are that they are in the liquid crystalline phase and have extremely low permeability of solutes that is much less temperature sensitive due to a lack of lipid-phase transition and highly branched isoprenoid chains. Many accumulated data indicate that the organism's response to extremely low pH is the opposite of that to high temperature. The high temperature adaptation does not require the tetraether lipids, while the adaptation of thermophiles to acidic environment requires the tetraether polar lipids. The presence of cyclopentane rings and the role of polar heads are not so straightforward regarding the correlations between fluidity and permeability of the lipid membrane. Due to the unique lipid structures and properties of archaeal lipids, they are a valuable resource in the development of novel biotechnological processes. This microreview focuses primarily on structural and physicochemical properties of polar lipids of (hyper)thermophilic archaea.

  7. Optical properties of a multibarrier structure under intense laser fields

    Science.gov (United States)

    Ospina, D. A.; Akimov, V.; Mora-Ramos, M. E.; Morales, A. L.; Tulupenko, V.; Duque, C. A.

    2015-11-01

    Using the diagonalization method and within the effective mass and parabolic band approximations, the energy spectrum and the wave functions are investigated in biased multibarrier structure taking into account the effects of nonresonant intense laser fields. We calculated the optical properties from the susceptibility using a nonperturbative formalism recently reported. We study the changes in the intersubband optical absorption coefficients and refraction index for several values of the dressing laser parameter and for some specific values of the electric field applied along the growth direction of the heterostructure. It is concluded from our study that the peaks in the optical absorption spectrum have redshifts or blueshifts as a function of the laser parameter and the electric field. These parameters could be suitable tools for tuning the electronic and optical properties of the multibarrier structure.

  8. Correlated structure-optical properties studies of plasmonic nanoparticles

    International Nuclear Information System (INIS)

    Ringe, Emilie; Duyne, Richard P Van; Marks, Laurence D

    2014-01-01

    Interest in nanotechnology is driven by unprecedented means to tailor the physical behaviour via structure and composition. Unlike bulk materials, minute changes in size and shape can affect the optical properties of nanoparticles. Characterization, understanding, and prediction of such structure-function relationships is crucial to the development of novel applications such as plasmonic sensors, devices, and drug delivery systems. Such knowledge has been recently vastly expanded through systematic, high throughput correlated measurements, where the localized surface plasmon resonance (LSPR) is probed optically and the particle shape investigated with electron microscopy. This paper will address some of the recent experimental advances in single particle studies that provide new insight not only on the effects of size, composition, and shape on plasmonic properties but also their interrelation. Plasmon resonance frequency and decay, substrate effects, size, shape, and composition will be explored for a variety of plasmonic systems

  9. Identification of material properties of sandwich structure with piezoelectric patches

    Directory of Open Access Journals (Sweden)

    Zemčík R.

    2008-11-01

    Full Text Available The work focuses on light-weight sandwich structures made of carbon-epoxy skins and foam core which have unique bending stiffness compared to conventional materials. The skins are manufactured by vacuum autoclave technology from unidirectional prepregs and the sandwich is then glued together. The resulting material properties of the structure usually differ from those provided by manufacturer or even those obtained from experimental tests on separate materials, which makes computational models unreliable. Therefore, the properties are identified using the combination of experimental analysis of the sandwich with attached piezoelectric transducer and corresponding static and modal finite element analyses. Simple mathematical optimization with repetitive finite element solution is used. The model is then verified by transient analysis when the piezoelectric patch is excited by harmonic signals covering the first two eigen-frequencies and the induced oscillations are measured by laser sensor.

  10. Mechanical properties of Composite Engineering Structures by Multivolume Micromechanical Modelling

    Directory of Open Access Journals (Sweden)

    B. Novotný

    2000-01-01

    Full Text Available Engineering structures often consist of elements having the character of a periodically repeated composite structure. A multivolume micromechanical model based on a representative cell division into r1 × r2 × r3 subcells with different elastic material properties has been used in this paper to derive macromechanical characteristics of the composite construction response to applied load and temperature changes. The multivolume method is based on ensuring the equilibrium of the considered volume on an average basis. In the same (average way, the continuity conditions of displacements and tractions at the interfaces between subcells and between neighboring representative elements are imposed, resulting in a homogenization procedure that eliminates the discrete nature of the composite model. The details of the method are shown for the case of a concrete block pavement. A parametric study is presented illustrating the influence of joint thickness, joint filling material properties and the quality of bonding between block and filler elements.

  11. Structural, optical and thermal properties of nanoporous aluminum

    International Nuclear Information System (INIS)

    Ghrib, Taher

    2015-01-01

    Highlights: • A simple electrochemical technique is presented and used to manufacture a porous aluminum layer. • Manufactured pores of 40 nm diameter and 200 nm depth are filled by nanocrystal of silicon and graphite. • Dimensions of pores increase with the anodization current which ameliorate the optical and thermal properties. • A new thermal method is presented which permit to determine the pores density and the layer thickness. • All properties show that the manufactured material can be used with success in solar cells. - Abstract: In this work the structural, thermal and optical properties of porous aluminum thin film formed with various intensities of anodization current in sulfuric acid are highlighted. The obtained pores at the surface are filled by sprayed graphite and nanocrystalline silicon (nc-Si) thin films deposited by plasma enhancement chemical vapor deposition (PECVD) which the role is to improve its optical and thermal absorption giving a structure of an assembly of three different media such as deposited thin layer (graphite or silicon)/(porous aluminum layer filled with the deposited layer)/(Al sample). The effect of anodization current on the microstructure of porous aluminum and the effect of the deposited layer were systematically studied by atomic force microscopy (AFM), transmission electron microscopy (TEM) and Raman spectroscopy. The thermal properties such as the thermal conductivity (K) and thermal diffusivity (D) are determined by the photothermal deflection (PTD) technique which is a non destructive technique. Based on this full characterization, it is demonstrated that the thermal and optical characteristics of these films are directly correlated to their micro-structural properties

  12. Bioinspired Cellular Structures: Additive Manufacturing and Mechanical Properties

    Science.gov (United States)

    Stampfl, J.; Pettermann, H. E.; Liska, R.

    Biological materials (e.g., wood, trabecular bone, marine skeletons) rely heavily on the use of cellular architecture, which provides several advantages. (1) The resulting structures can bear the variety of "real life" load spectra using a minimum of a given bulk material, featuring engineering lightweight design principles. (2) The inside of the structures is accessible to body fluids which deliver the required nutrients. (3) Furthermore, cellular architectures can grow organically by adding or removing individual struts or by changing the shape of the constituting elements. All these facts make the use of cellular architectures a reasonable choice for nature. Using additive manufacturing technologies (AMT), it is now possible to fabricate such structures for applications in engineering and biomedicine. In this chapter, we present methods that allow the 3D computational analysis of the mechanical properties of cellular structures with open porosity. Various different cellular architectures including disorder are studied. In order to quantify the influence of architecture, the apparent density is always kept constant. Furthermore, it is shown that how new advanced photopolymers can be used to tailor the mechanical and functional properties of the fabricated structures.

  13. Electronic structure properties of UO2 as a Mott insulator

    Science.gov (United States)

    Sheykhi, Samira; Payami, Mahmoud

    2018-06-01

    In this work using the density functional theory (DFT), we have studied the structural, electronic and magnetic properties of uranium dioxide with antiferromagnetic 1k-, 2k-, and 3k-order structures. Ordinary approximations in DFT, such as the local density approximation (LDA) or generalized gradient approximation (GGA), usually predict incorrect metallic behaviors for this strongly correlated electron system. Using Hubbard term correction for f-electrons, LDA+U method, as well as using the screened Heyd-Scuseria-Ernzerhof (HSE) hybrid functional for the exchange-correlation (XC), we have obtained the correct ground-state behavior as an insulator, with band gaps in good agreement with experiment.

  14. Field emission properties of an array of pyramidal structures

    Energy Technology Data Exchange (ETDEWEB)

    De Assis, Thiago A [Departamento de QuImica, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Borondo, F [Departamento de QuImica, Instituto Mixto de Ciencias Matematicas CSIC-UAM-UC3M-UCM, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); De Castilho, C M C; Brito Mota, F [Grupo de Fisica de SuperfIcies e Materiais, Instituto de Fisica, Universidade Federal da Bahia, Campus Universitario da Federacao, 40210-340, Salvador, BA (Brazil); Benito, R M, E-mail: t.albuquerque@uam.e, E-mail: f.borondo@uam.e, E-mail: caio@ufba.b, E-mail: fbmota@ufba.b, E-mail: rosamaria.benito@upm.e [Grupo de Sistemas Complejos, Departamento de Fisica y Mecanica, Escuela Tecnica Superior de Ingenieros Agronomos, Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain)

    2009-10-07

    The properties and efficiency of the emission current density produced by a metallic array of pyramidal structures are investigated. The theoretical results obtained by numerical integration of the corresponding Laplace equation using a finite differences scheme offer useful information for the optimization of field emission devices based on cathodes with this geometry. Our study shows that the inter-pyramidal distance strongly affects the current density, and even more important for this issue is the protrusion characteristics of these structures. Another relevant, although less important, parameter determining this density is the anode-cathode distance. The effect of the array characteristics on the maximum local electric field intensity is also discussed.

  15. Electric Field Structures in Thin Films: Formation and Properties

    DEFF Research Database (Denmark)

    Cassidy, Andrew; Plekan, Oksana; Balog, Richard

    2014-01-01

    A newly discovered class of molecular materials, so-called “spontelectrics”, display spontaneous electric fields. Here we show that the novel properties of spontelectrics can be used to create composite spontelectrics, illustrating how electric fields in solid films may be structured on the nanoscale...... by combining layers of different spontelectric materials. This is demonstrated using the spontelectric materials nitrous oxide, toluene, isoprene, isopentane, and CF2Cl2. These yield a variety of tailored electric field structures, with individual layers harboring fields between 107 and 108 V/m. Fields may...

  16. Metal Oxide Nano structures: Synthesis, Properties, and Applications

    International Nuclear Information System (INIS)

    Xu, L. H.; Patil, D. S.; Yang, J.; Xiao, J.

    2015-01-01

    In recent years, nano structured materials have attracted wide attention due to their fascinating optical and electrical properties, which make these materials potentially suitable for applications in electronics, optics, photonics, and sensors. Some metal oxides show a wide variety of morphologies such as nano wires, nano rods, nano tubes, nano rings, and nano belts. Synthesis and investigation of these metal-oxide nano structures are beneficial not only for understanding the fundamental phenomena in low dimensional systems, but also for developing new-generation nano devices with high performance.

  17. Structure and mechanical properties of the irradiated silicon

    International Nuclear Information System (INIS)

    Kalanov, M.U.; Khamraeva, R.N.; Ummatov, Kh.D.; Khajdarov, T.Kh.; Rustamova, V.M.

    2001-01-01

    In this work the results of study for radiation influence on phase content and mechanical properties of mono- and polycrystalline silicon are presented. Samples were irradiated at room temperature for 10 hours by X-quanta with mean energy 35 keV. Structural measurements were carried out on the DRON-UM1 with CuK α =1.542 Angstrom. Crystal internal friction was measurement by the ultrasonic resonance method at frequency 39 k Hz. Structure examinations show the impurity phase presence in the crystalline quartz form in the initial silicon mono- and polycrystals

  18. Electronic structure and optical properties of solid C60

    International Nuclear Information System (INIS)

    Mattesini, M.; Ahuja, R.; Sa, L.; Hugosson, H.W.; Johansson, B.; Eriksson, O.

    2009-01-01

    The electronic structure and the optical properties of face-centered-cubic C 60 have been investigated by using an all-electron full-potential method. Our ab initio results show that the imaginary dielectric function for high-energy values looks very similar to that of graphite, revealing close electronic structure similarities between the two systems. We have also identified the origin of different peaks in the dielectric function of fullerene by means of the calculated electronic density of states. The computed optical spectrum compares fairly well with the available experimental data for the Vis-UV absorption spectrum of solid C 60 .

  19. RaptorX-Property: a web server for protein structure property prediction.

    Science.gov (United States)

    Wang, Sheng; Li, Wei; Liu, Shiwang; Xu, Jinbo

    2016-07-08

    RaptorX Property (http://raptorx2.uchicago.edu/StructurePropertyPred/predict/) is a web server predicting structure property of a protein sequence without using any templates. It outperforms other servers, especially for proteins without close homologs in PDB or with very sparse sequence profile (i.e. carries little evolutionary information). This server employs a powerful in-house deep learning model DeepCNF (Deep Convolutional Neural Fields) to predict secondary structure (SS), solvent accessibility (ACC) and disorder regions (DISO). DeepCNF not only models complex sequence-structure relationship by a deep hierarchical architecture, but also interdependency between adjacent property labels. Our experimental results show that, tested on CASP10, CASP11 and the other benchmarks, this server can obtain ∼84% Q3 accuracy for 3-state SS, ∼72% Q8 accuracy for 8-state SS, ∼66% Q3 accuracy for 3-state solvent accessibility, and ∼0.89 area under the ROC curve (AUC) for disorder prediction. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

  20. Structural properties of silicon clusters: An empirical potential study

    International Nuclear Information System (INIS)

    Gong, X.G.; Zheng, Q.Q.; He Yizhen

    1993-09-01

    By using our newly proposed empirical interatomic potential for silicon, the structure and some dynamical properties of silicon cluster Si n (10 ≤ n ≤ 24) have been studied. It is found that the obtained results are close to those from ab-initio methods. From present results, we can gain a new insight into the understanding of the experimental data on the Si n clusters. (author). 20 refs, 6 figs

  1. Structural and electronic properties of hydrosilylated silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Baumer, A.

    2005-11-15

    The structural and electronic properties of alkyl-terminated Si surfaces prepared by thermallyinduced hydrosilylation have been studied in detail in the preceding chapters. Various surfaces have been used for the functionalization ranging from crystalline Si over amorphous hydrogenated Si to nanoscaled materials such as Si nanowires and nanoparticles. In each case, the alkyl-terminated surfaces have been compared to the native oxidized and H-terminated surfaces. (orig.)

  2. Emergent intelligent properties of progressively structured pattern recognition nets

    Energy Technology Data Exchange (ETDEWEB)

    Aleksander, I

    1983-07-01

    The n-tuple recognition net is seen as a building brick of a progression of network structures. The emergent intelligent properties of such systems are discussed. They include the amplification of confidence for the recognition of images that differ in small detail, a short term memory of the last seen image, sequence sensitivity, sequence sensitivity, sequence acceptance and saccadic inspection as an aid in scene analysis. 12 references.

  3. Negative binomial properties and clan structure in multiplicity distributions

    International Nuclear Information System (INIS)

    Giovannini, A.; Van Hove, L.

    1988-01-01

    We review the negative binomial properties measured recently for many multiplicity distributions of high energy hadronic, semi-leptonic reactions in selected rapidity intervals. We analyse them in terms of the ''clan'' structure which can be defined for any negative binomial distribution. By comparing reactions we exhibit a number of regularities for the average number N-bar of clans and the average charged multiplicity (n-bar) c per clan. 22 refs., 6 figs. (author)

  4. Material Properties Analysis of Structural Members in Pumpkin Balloons

    Science.gov (United States)

    Sterling, W. J.

    2003-01-01

    The efficient design, service-life qualification, and reliability predictions for lightweight aerospace structures require careful mechanical properties analysis of candidate structural materials. The demand for high-quality laboratory data is particularly acute when the candidate material or the structural design has little history. The pumpkin-shaped super-pressure balloon presents both challenges. Its design utilizes load members (tendons) extending from apex to base around the gas envelope to achieve a lightweight structure. The candidate tendon material is highly weight-efficient braided HM cord. Previous mechanical properties studies of Zylon have focused on fiber and yarn, and industrial use of the material in tensile applications is limited. For high-performance polymers, a carefully plamed and executed properties analysis scheme is required to ensure the data are relevant to the desired application. Because no directly-applicable testing standard was available, a protocol was developed based on guidelines fiom professional and industry organizations. Due to the liquid-crystalline nature of the polymer, the cord is very stiff, creeps very little, and does not yield. Therefore, the key material property for this application is the breaking strength. The pretension load and gauge length were found to have negligible effect on the measured breaking strength over the ranges investigated. Strain rate was found to have no effect on breaking strength, within the range of rates suggested by the standards organizations. However, at the lower rate more similar to ULDB operations, the strength was reduced. The breaking strength increased when the experiment temperature was decreased from ambient to 183K which is the lowest temperature ULDB is expected to experience. The measured strength under all test conditions was well below that resulting from direct scale-up of fiber strength based on the manufacturers data. This expected result is due to the effects of the

  5. Liposomes: structure, properties and methods of curative administration in organism

    Directory of Open Access Journals (Sweden)

    M. A. Kisyakova

    2010-07-01

    Full Text Available A review of data from scientific sources, devoted to problems of liposomes’ structure, properties and processes of formation was made. Advantages of liposomes used for medical purposes are shown. Methods of liposomes administration in an organism are characterised. Data on mechanisms of interaction between liposomes and cells, peculiarities of liposomes’ lipids composition and dependence of its tropism to definite organs and tissues are generalised.

  6. Structure/property relationships in multipass GMA welding of beryllium.

    Energy Technology Data Exchange (ETDEWEB)

    Hochanadel, P. W. (Patrick W.); Hults, W. L. (William L.); Thoma, D. J. (Dan J.); Dave, V. R. (Vivek R.); Kelly, A. M. (Anna Marie); Pappin, P. A. (Pallas A.); Cola, M. J. (Mark J.); Burgardt, P. (Paul)

    2001-01-01

    Beryllium is an interesting metal that has a strength to weight ratio six times that of steel. Because of its unique mechanical properties, beryllium is used in aerospace applications such as satellites. In addition, beryllium is also used in x-ray windows because it is nearly transparent to x-rays. Joining of beryllium has been studied for decades (Ref.l). Typically joining processes include braze-welding (either with gas tungsten arc or gas metal arc), soldering, brazing, and electron beam welding. Cracking which resulted from electron beam welding was recently studied to provide structure/property relationships in autogenous welds (Ref. 2). Braze-welding utilizes a welding arc to melt filler, and only a small amount of base metal is melted and incorporated into the weld pool. Very little has been done to characterize the braze-weld in terms of the structure/property relationships, especially with reference to multipass welding. Thus, this investigation was undertaken to evaluate the effects of multiple passes on microstructure, weld metal composition, and resulting material properties for beryllium welded with aluminum-silicon filler metal.

  7. (Biodegradable Ionomeric Polyurethanes Based on Xanthan: Synthesis, Properties, and Structure

    Directory of Open Access Journals (Sweden)

    T. V. Travinskaya

    2017-01-01

    Full Text Available New (biodegradable environmentally friendly film-forming ionomeric polyurethanes (IPU based on renewable biotechnological polysaccharide xanthan (Xa have been obtained. The influence of the component composition on the colloidal-chemical and physic-mechanical properties of IPU/Xa and based films, as well as the change of their properties under the influence of environmental factors, have been studied. The results of IR-, PMS-, DMA-, and X-ray scattering study indicate that incorporation of Xa into the polyurethane chain initiates the formation of a new polymer structure different from the structure of the pure IPU (matrix: an amorphous polymer-polymer microdomain has occurred as a result of the chemical interaction of Xa and IPU. It predetermines the degradation of the IPU/Xa films as a whole, unlike the mixed polymer systems, and plays a key role in the improvement of material performance. The results of acid, alkaline hydrolysis, and incubation into the soil indicate the increase of the intensity of degradation processes occurring in the IPU/Xa in comparison with the pure IPU. It has been shown that the introduction of Xa not only imparts the biodegradability property to polyurethane, but also improves the mechanical properties.

  8. Properties investigation of sulfonated poly(ether ether ketone)/polyacrylonitrile acid-base blend membrane for vanadium redox flow battery application.

    Science.gov (United States)

    Li, Zhaohua; Dai, Wenjing; Yu, Lihong; Liu, Le; Xi, Jingyu; Qiu, Xinping; Chen, Liquan

    2014-11-12

    Acid-base blend membrane prepared from sulfonated poly(ether ether ketone) (SPEEK) and polyacrylonitrile (PAN) was detailedly evaluated for vanadium redox flow battery (VRFB) application. SPEEK/PAN blend membrane exhibited dense and homogeneous cross-section morphology as scanning electron microscopy and energy-dispersive X-ray spectroscopy images show. The acid-base interaction of ionic cross-linking and hydrogen bonding between SPEEK and PAN could effectively reduce water uptake, swelling ratio, and vanadium ion permeability, and improve the performance and stability of blend membrane. Because of the good balance of proton conductivity and vanadium ion permeability, blend membrane with 20 wt % PAN (S/PAN-20%) showed higher Coulombic efficiency (96.2% vs 91.1%) and energy efficiency (83.5% vs 78.4%) than Nafion 117 membrane at current density of 80 mA cm(-2) when they were used in VRFB single cell. Besides, S/PAN-20% membrane kept a stable performance during 150 cycles at current density of 80 mA cm(-2) in the cycle life test. Hence the SPEEK/PAN acid-base blend membrane could be used as promising candidate for VRFB application.

  9. Structure and properties of cell membranes. Volume 3: Methodology and properties of membranes

    International Nuclear Information System (INIS)

    Benga, G.

    1985-01-01

    This book covers the topics: Quantum chemical approach to study the mechanisms of proton translocation across membranes through protein molecules; monomolecular films as biomembrane models; planar lipid bilayers in relation to biomembranes; relation of liposomes to cell membranes; reconstitution of membrane transport systems; structure-function relationships in cell membranes as revealed by X-ray techniques; structure-function relationships in cell membranes as revealed by spin labeling ESR; structure and dynamics of cell membranes as revealed by NMR techniques; the effect of dietary lipids on the composition and properties of biological membranes and index

  10. Materials science in microelectronics II the effects of structure on properties in thin films

    CERN Document Server

    Machlin, Eugene

    2005-01-01

    The subject matter of thin-films - which play a key role in microelectronics - divides naturally into two headings: the processing / structure relationship, and the structure / properties relationship. Part II of 'Materials Science in Microelectronics' focuses on the latter of these relationships, examining the effect of structure on the following: Electrical properties Magnetic properties Optical properties Mechanical properties Mass transport properties Interface and junction properties Defects and properties Captures the importance of thin films to microelectronic development Examines the cause / effect relationship of structure on thin film properties.

  11. Redox-sensitive GFP fusions for monitoring the catalytic mechanism and inactivation of peroxiredoxins in living cells

    Directory of Open Access Journals (Sweden)

    Verena Staudacher

    2018-04-01

    Full Text Available Redox-sensitive green fluorescent protein 2 (roGFP2 is a valuable tool for redox measurements in living cells. Here, we demonstrate that roGFP2 can also be used to gain mechanistic insights into redox catalysis in vivo. In vitro enzyme properties such as the rate-limiting reduction of wild type and mutant forms of the model peroxiredoxin PfAOP are shown to correlate with the ratiometrically measured degree of oxidation of corresponding roGFP2 fusion proteins. Furthermore, stopped-flow kinetic measurements of the oxidative half-reaction of PfAOP support the interpretation that changes in the roGFP2 signal can be used to map hyperoxidation-based inactivation of the attached peroxidase. Potential future applications of our system include the improvement of redox sensors, the estimation of absolute intracellular peroxide concentrations and the in vivo assessment of protein structure-function relationships that cannot easily be addressed with recombinant enzymes, for example, the effect of post-translational protein modifications on enzyme catalysis. Keywords: Peroxiredoxin, Redox sensor, roGFP2, H2O2, Plasmodium falciparum

  12. Mechanical properties of LMR structural materials at high temperature

    International Nuclear Information System (INIS)

    Kim, D. W.; Kuk, I. H.; Ryu, W. S. and others

    1999-03-01

    Austenitic stainless is used for the structural material of liquid metal reactor (LMR) because of good mechanical properties at high temperature. Stainless steel having more resistant to temperature by adding minor element has been developing for operating the LMR at higher temperature. Of many elements, nitrogen is a prospective element to modify type 316L(N) stainless steel because nitrogen is the most effective element for solid solution and because nitrogen retards the precipitation of carbide at grain boundary. Ti, Nb, and V are added to improve creep properties by stabilizing the carbides through forming MC carbide. Testing techniques of tensile, fatigue, creep, and creep-fatigue at high temperature are difficult. Moreover, testing times for creep and creep-fatigue tests are very long up to several tens of thousands hours because creep and creep-fatigue phenomena are time-dependent damage mechanism. So, it is hard to acquire the material data for designing LMR systems during a limited time. In addition, the integrity of LMR structural materials at the end of LMR life has to be predicted from the laboratory data tested during the short term because there is no data tested during 40 years. Therefore, the effect of elements on mechanical properties at high temperature was reviewed in this study and many methods to predict the long-term behaviors of structural materials by simulated modelling equation is shown in this report. (author). 32 refs., 9 tabs., 38 figs

  13. 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.

  14. Food structure: Its formation and relationships with other properties.

    Science.gov (United States)

    Joardder, Mohammad U H; Kumar, Chandan; Karim, M A

    2017-04-13

    Food materials are complex in nature as it has heterogeneous, amorphous, hygroscopic and porous properties. During processing, microstructure of food materials changes which significantly affects other properties of food. An appropriate understanding of the microstructure of the raw food material and its evolution during processing is critical in order to understand and accurately describe dehydration processes and quality anticipation. This review critically assesses the factors that influence the modification of microstructure in the course of drying of fruits and vegetables. The effect of simultaneous heat and mass transfer on microstructure in various drying methods is investigated. Effects of changes in microstructure on other functional properties of dried foods are discussed. After an extensive review of the literature, it is found that development of food structure significantly depends on fresh food properties and process parameters. Also, modification of microstructure influences the other properties of final product. An enhanced understanding of the relationships between food microstructure, drying process parameters and final product quality will facilitate the energy efficient optimum design of the food processor in order to achieve high-quality food.

  15. Composite Polymer Electrolytes: Nanoparticles Affect Structure and Properties

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2016-11-01

    Full Text Available Composite polymer electrolytes (CPEs can significantly improve the performance in electrochemical devices such as lithium-ion batteries. This review summarizes property/performance relationships in the case where nanoparticles are introduced to polymer electrolytes. It is the aim of this review to provide a knowledge network that elucidates the role of nano-additives in the CPEs. Central to the discussion is the impact on the CPE performance of properties such as crystalline/amorphous structure, dielectric behavior, and interactions within the CPE. The amorphous domains of semi-crystalline polymer facilitate the ion transport, while an enhanced mobility of polymer chains contributes to high ionic conductivity. Dielectric properties reflect the relaxation behavior of polymer chains as an important factor in ion conduction. Further, the dielectric constant (ε determines the capability of the polymer to dissolve salt. The atom/ion/nanoparticle interactions within CPEs suggest ways to enhance the CPE conductivity by generating more free lithium ions. Certain properties can be improved simultaneously by nanoparticle addition in order to optimize the overall performance of the electrolyte. The effects of nano-additives on thermal and mechanical properties of CPEs are also presented in order to evaluate the electrolyte competence for lithium-ion battery applications.

  16. 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)

  17. 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)

  18. 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.

  19. 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.

  20. An application of actinide elements for a redox flow battery

    International Nuclear Information System (INIS)

    Shiokawa, Yoshinobu; Yamana, Hajimu; Moriyama, Hirotake

    2000-01-01

    The electrochemical properties of U, Np, Pu and Am were discussed from the viewpoint of cell active materials. From the thermodynamic properties and the kinetics of electrode reactions, it is found that neptunium in the aqueous system can be utilized as an active material of the redox flow battery for the electric power storage. A new neptunium redox battery is proposed in the present article: the galvanic cell is expressed by (-)|Np 3+ , Np 4+ |NpO 2 + , NpO 2 2+ |(+). The neptunium battery is expected to have more excellent charge and discharge performance than the current vanadium battery, whereas the thermodynamic one of the former is comparable to the latter. For the development of a uranium redox battery, the application of the redox reactions in the non-aqueous solvents is essential. (author)

  1. Structure and optical properties of water covered Cu(110) surfaces

    International Nuclear Information System (INIS)

    Baghbanpourasl, A.

    2014-01-01

    In this thesis structural and optical properties of the water covered Cu(110) surface is studied using density functional theory within independent particle approximation. Several stable adsorption structures are studied such as water clusters (monomer, dimer, trimer, tetramer and pentamer), different hexagonal monolayers, partially dissociated water monolayers and three different types of chains among them a chain that consists of pentagon rings. For a copper surface in contact with water vapor, the energetically stable H 2 O/OH adsorbed structures are compared thermodynamically using adsorption free energy (change of free energy due to adsorption). Several phase diagrams with respect to temperature and pressure are calculated. It is found that among the large number of energetically stable structures (i.e. structures with positive adsorption energy ) only limited number of them are thermodynamically stable. These thermodynamically stable structures are the class of almost energetically degenerate hexagonal overlayers, one type of partially dissociated water structure that contains Bjerrum defect in the hydrogen bond network and pentagon chain. Since hydrogen atoms are light weight their vibrational effects can be considerable. Zero point vibration decreases the adsorption energy up to 0.1 eV and free energy of adsorbed molecules arising from vibrational degree of freedom can go up to -0.2 eV per adsorbed molecule at 500 Kelvin. However zero point energy and vibrational free energy of adsorbed molecules do not alter relative stability of the adsorbed structures. To account for the long range van der Waals interactions, a semi-empirical scheme is applied. Reflectance Anisotropy Spectroscopy (RAS) is a fast and non destructive optical method that can be used to prob the surface in different conditions such as vacuum and electro-chemical environment. Elasto-optic coeficients of bulk are calculated from first principles and the change of the RA spectrum of the bare Cu

  2. Research on working property and early age mechanical property of self-compacting concrete used in steel-concrete structure

    International Nuclear Information System (INIS)

    Zhao Yongguang

    2013-01-01

    Background: Self-compacting concrete that has good working property is the prerequisite of steel-concrete structure. The early age mechanical property of self-compacting concrete is the important parameter when design steel-concrete structure. Purpose: This paper attempts to research the working property and early age mechanical property of self-compacting concrete. Methods: Test is used to research the working property and early age mechanical property of self-compacting concrete. Results: Self-compacting concrete that could meet the requirement of steel-concrete structure has been mixed and parameters of early age mechanical property of self-compacting concrete which is necessary for design of steel-concrete structure have been presented. Conclusions: Base on the results, this paper can guide the construction of self-compacting concrete in steel-concrete structure and the design and construction of steel-concrete structure. (author)

  3. Structure and properties of copper after large strain deformation

    Energy Technology Data Exchange (ETDEWEB)

    Rodak, Kinga; Molak, Rafal M.; Pakiela, Zbigniew

    2010-05-15

    Structure and properties of Cu in dependence on strain (from {epsilon}{proportional_to} 0.9 to {epsilon}{proportional_to} 15) during multi-axial compression processing at room temperature was investigated. The evolution of dislocation structure, misorientation distribution and crystallite size were observed by using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipment with electron back scattered diffraction (EBSD) facility. The mechanical properties of yield strength (YS), ultimate tensile strength (UTS) and uniform elongation was performed on MTS QTest/10 machine equipped with digital image correlation method (DIC). The structure-flow stress relationship of multi-axial compression processing material at strains {epsilon}{proportional_to} 3.5 and {epsilon}{proportional_to} 5.5 is discussed. It is found that processing does not produce any drastic changes in deformation structure and the microstructural refinement is slow. These results indicate that dynamic recrystallization plays an important role during multi-axial compression process in this range of deformation (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Circulating Microparticles Alter Formation, Structure, and Properties of Fibrin Clots.

    Science.gov (United States)

    Zubairova, Laily D; Nabiullina, Roza M; Nagaswami, Chandrasekaran; Zuev, Yuriy F; Mustafin, Ilshat G; Litvinov, Rustem I; Weisel, John W

    2015-12-04

    Despite the importance of circulating microparticles in haemostasis and thrombosis, there is limited evidence for potential causative effects of naturally produced cell-derived microparticles on fibrin clot formation and its properties. We studied the significance of blood microparticles for fibrin formation, structure, and susceptibility to fibrinolysis by removing them from platelet-free plasma using filtration. Clots made in platelet-free and microparticle-depleted plasma samples from the same healthy donors were analyzed in parallel. Microparticles accelerate fibrin polymerisation and support formation of more compact clots that resist internal and external fibrinolysis. These variations correlate with faster thrombin generation, suggesting thrombin-mediated kinetic effects of microparticles on fibrin formation, structure, and properties. In addition, clots formed in the presence of microparticles, unlike clots from the microparticle-depleted plasma, contain 0.1-0.5-μm size granular and CD61-positive material on fibres, suggesting that platelet-derived microparticles attach to fibrin. Therefore, the blood of healthy individuals contains functional microparticles at the levels that have a procoagulant potential. They affect the structure and stability of fibrin clots indirectly through acceleration of thrombin generation and through direct physical incorporation into the fibrin network. Both mechanisms underlie a potential role of microparticles in haemostasis and thrombosis as modulators of fibrin formation, structure, and resistance to fibrinolysis.

  5. 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.

  6. Carbon nanotube on Si(001): structural and electronic properties

    International Nuclear Information System (INIS)

    Orellana, W.; Fazzio, A.; Miwa, R.W.

    2003-01-01

    Full text: The promising nanoscale technology based on carbon nanotubes has attracted much attention due to the unique electronic, chemical and mechanical properties of the nanotubes. Single-wall carbon nanotubes (SWCNs) provide an ideal atomically uniform one dimensional (1D) conductors, having a strong electronic confinement around its circumference, which can be retained up to room temperature[1]. This interesting property may lead one to consider SWCNs as 1D conductors for the development of nanoscale electronic devices. In this work the structural and electronic properties of the contact between a metallic (6,6) SWCN adsorbed on a silicon (001) surface are studied from first-principles total-energy calculations. We consider two adsorption sites for the tube on the Si(001) surface: on the top of the Si-dimer rows and on the surface 'trench' between two consecutive dimer rows. Our results show a chemical bond between the nanotube and Si(001) when the tube is located along the 'trench', which corresponds to the only bound structure. We find a binding energy per tube length of 0.21 eV/angstrom. We also verified that the binding energy depends on the rotation of the tube. Typically, a rotation of 15 deg can reduce the binding energy up to 0.07 eV/angstrom. Our calculated electronic properties indicate that the most stable structure shows a subband associated to the tube/surface bond that cross the Fermi level. This result indicates an enhanced metallic behavior along the tube/surface contact characterizing a 1D quantum wire. The charge transfer between the Si surface and the tube is also discussed. [1] Z. Yao, C. Dekker, and P. Avouris in Carbon Nanotubes, M. S. Dresselhaus, G. Dresselhaus, and P. Avouris Eds., (Springer, Berlin 2001), p. 147. (author)

  7. Entropy, related thermodynamic properties, and structure of methylisocyanate

    International Nuclear Information System (INIS)

    Davis, Phil S.; Kilpatrick, John E.

    2013-01-01

    Highlights: ► The thermodynamic properties of methylisocyanate have been determined by isothermal calorimetry from 15 to 298.15 K. ► The third law entropy has been compared with the entropy calculated by statistical thermodynamics. ► The comparisons are consistent with selected proposed molecular structures and vibrational frequencies. -- Abstract: The entropy and related thermodynamic properties of methylisocyanate, CH 3 NCO, have been determined by isothermal calorimetry. The entropy in the ideal gas state at 298.15 K and 1 atmosphere is S m o = 284.3 ± 0.6 J/K · mol. Other thermodynamic properties determined include: the heat capacity from 15 to 300 K, the temperature of fusion (T fus = 178.461 ± 0.024 K), the enthalpy of fusion (ΔH fus = 7455.2 ± 14.0 J/mol), the enthalpy of vaporization at 298.15 K (ΔH vap = 28768 ± 54 J/mol), and the vapor pressure from fusion to 300 K. Using statistical thermodynamics, the entropy in this same state has been calculated for various assumed structures for methylisocyante which have been proposed based on several spectroscopic and ab initio results. Comparisons between the experimental and calculated entropy have led to the following conclusions concerning historical differences among problematic structural properties: (1) The CNC/CNO angles can have the paired values of 140/180° or 135/173° respectively. It is not possible to distinguish between the two by this thermodynamic analysis. (2) The methyl group functions as a free rotor or near free rotor against the NCO rigid frame. The barrier to internal rotation is less than 2100 J/mol. (3) The CNC vibrational bending frequency is consistent with the more recently observed assignments at 165 and 172 cm −1 with some degree of anharmonicity or with a pure harmonic at about 158 cm −1

  8. Topological properties of complex networks in protein structures

    Science.gov (United States)

    Kim, Kyungsik; Jung, Jae-Won; Min, Seungsik

    2014-03-01

    We study topological properties of networks in structural classification of proteins. We model the native-state protein structure as a network made of its constituent amino-acids and their interactions. We treat four structural classes of proteins composed predominantly of α helices and β sheets and consider several proteins from each of these classes whose sizes range from amino acids of the Protein Data Bank. Particularly, we simulate and analyze the network metrics such as the mean degree, the probability distribution of degree, the clustering coefficient, the characteristic path length, the local efficiency, and the cost. This work was supported by the KMAR and DP under Grant WISE project (153-3100-3133-302-350).

  9. Structural and electronic properties of L-amino acids

    Science.gov (United States)

    Tulip, P. R.; Clark, S. J.

    2005-05-01

    The structural and electronic properties of four L-amino acids alanine, leucine, isoleucine, and valine have been investigated using density functional theory (DFT) and the generalized gradient approximation. Within the crystals, it is found that the constituent molecules adopt zwitterionic configurations, in agreement with experimental work. Lattice constants are found to be in good agreement with experimentally determined values, although certain discrepancies do exist due to the description of van der Waals interactions. We find that these materials possess wide DFT band gaps in the region of 5 eV, with electrons highly localized to the constituent molecules. It is found that the main mechanisms behind crystal formation are dipolar interactions and hydrogen bonding of a primarily electrostatic character, in agreement with current biochemical understanding of these systems. The electronic structure suggests that the amine and carboxy functional groups are dominant in determining band structure.

  10. Electronic structure and optical properties of metal doped tetraphenylporphyrins

    Science.gov (United States)

    Shah, Esha V.; Roy, Debesh R.

    2018-05-01

    A density functional scrutiny on the structure, electronic and optical properties of metal doped tetraphenylporphyrins MTPP (M=Fe, Co, Ni) is performed. The structural stability of the molecules is evaluated based on the electronic parameters like HOMO-LUMO gap (HLG), chemical hardness (η) and binding energy of the central metal atom to the molecular frame etc. The computed UltraViolet-Visible (UV-Vis) optical absorption spectra for all the compounds are also compared. The molecular structures reported are the lowest energy configurations. The entire calculations are carried out with a widely reliable functional, viz. B3LYP with a popular basis set which includes a scaler relativistic effect, viz. LANL2DZ.

  11. Structural and electronic properties of carbon nanotubes under hydrostatic pressures

    International Nuclear Information System (INIS)

    Zhang Ying; Cao Juexian; Yang Wei

    2008-01-01

    We studied the structural and electronic properties of carbon nanotubes under hydrostatic pressures based on molecular dynamics simulations and first principles band structure calculations. It is found that carbon nanotubes experience a hard-to-soft transition as external pressure increases. The bulk modulus of soft phase is two orders of magnitude smaller than that of hard phase. The band structure calculations show that band gap of (10, 0) nanotube increases with the increase of pressure at low pressures. Above a critical pressure (5.70GPa), band gap of (10, 0) nanotube drops rapidly and becomes zero at 6.62GPa. Moreover, the calculated charge density shows that a large pressure can induce an sp 2 -to-sp 3 bonding transition, which is confirmed by recent experiments on deformed carbon nanotubes

  12. 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

  13. Factors Controlling the Redox Activity of Oxygen in Perovskites: From Theory to Application for Catalytic Reactions

    Directory of Open Access Journals (Sweden)

    Chunzhen Yang

    2017-05-01

    Full Text Available Triggering the redox reaction of oxygens has become essential for the development of (electro catalytic properties of transition metal oxides, especially for perovskite materials that have been envisaged for a variety of applications such as the oxygen evolution or reduction reactions (OER and ORR, respectively, CO or hydrocarbons oxidation, NO reduction and others. While the formation of ligand hole for perovskites is well-known for solid state physicists and/or chemists and has been widely studied for the understanding of important electronic properties such as superconductivity, insulator-metal transitions, magnetoresistance, ferroelectrics, redox properties etc., oxygen electrocatalysis in aqueous media at low temperature barely scratches the surface of the concept of oxygen ions oxidation. In this review, we briefly explain the electronic structure of perovskite materials and go through a few important parameters such as the ionization potential, Madelung potential, and charge transfer energy that govern the oxidation of oxygen ions. We then describe the surface reactivity that can be induced by the redox activity of the oxygen network and the formation of highly reactive surface oxygen species before describing their participation in catalytic reactions and providing mechanistic insights and strategies for designing new (electro catalysts. Finally, we give a brief overview of the different techniques that can be employed to detect the formation of such transient oxygen species.

  14. Tuning of redox regulatory mechanisms, reactive oxygen species and redox homeostasis under salinity stress

    Directory of Open Access Journals (Sweden)

    Hossain eSazzad

    2016-05-01

    Full Text Available Soil salinity is a crucial environmental constraint which limits biomass production at many sites on a global scale. Saline growth conditions cause osmotic and ionic imbalances, oxidative stress and perturb metabolism, e.g. the photosynthetic electron flow. The plant ability to tolerate salinity is determined by multiple biochemical and physiological mechanisms protecting cell functions, in particular by regulating proper water relations and maintaining ion homeostasis. Redox homeostasis is a fundamental cell property. Its regulation includes control of reactive oxygen species (ROS generation, sensing deviation from and readjustment of the cellular redox state. All these redox related functions have been recognized as decisive factors in salinity acclimation and adaptation. This review focuses on the core response of plants to overcome the challenges of salinity stress through regulation of ROS generation and detoxification systems and to maintain redox homeostasis. Emphasis is given to the role of NADH oxidase (RBOH, alternative oxidase (AOX, the plastid terminal oxidase (PTOX and the malate valve with the malate dehydrogenase isoforms under salt stress. Overwhelming evidence assigns an essential auxiliary function of ROS and redox homeostasis to salinity acclimation of plants.

  15. Crystal structures and second-order NLO properties of borogermanates

    International Nuclear Information System (INIS)

    Zhang, Jian-Han; Kong, Fang; Xu, Xiang; Mao, Jiang-Gao

    2012-01-01

    Borogermanates are a class of very important compounds in materials chemistry. In this paper, the syntheses, structures, and properties of metal borogermanates are reviewed. Organically templated borogermanates with zeolite-like open-frameworks show potential applications as microporous materials. Many compounds in alkali or alkaline-earth borogermanate systems are structurally acentric or polar, some of which exhibit excellent Second Harmonic Generation (SHG) coefficients, wide transparency regions, and high optical-damage thresholds as well as excellent thermal stability. Most of the lanthanide borogermanates are structurally centrosymmetric and not SHG active; however, they are able to emit strong luminescence in visible or near-IR region. In the B-rich compounds, BO 3 and BO 4 groups can be polymerized into a variety of discrete polynuclear anionic cluster units or extended architectures via B–O–B bridges; whereas in the Ge-rich compounds, GeO 4 and GeO 6 polyhedra can also be polymerized. The combinations of borate and germinate afforded rich structural and topological types. - Graphical abstract: Borogermanates are a class of very important compounds in materials chemistry. Both BO x (x=3, 4) and GeO y (y=4, 6) polyhedra can be polymerized into a variety of discrete polynuclear anionic cluster units or extended architectures. The combinations of borate and germanate groups in the same oxide framework not only give rise to a rich structural chemistry, but also afford many polar compounds with good SHG properties. Highlights: ► Borogermanates are a class of new materials. ► They feature to be the combination of B and Ge atoms into the same oxide framework. ► They can form a large number of novel 2D and 3D framework structures. ► Some of them are acentric or polar with moderate strong SHG responses.

  16. Atomic-level structure and structure-property relationship in metallic glass

    Science.gov (United States)

    Cheng, Yongqiang

    One of the key tasks in material science is to understand the structure and structure-property relationship. The recently emerging bulk metallic glasses (BMGs) have demonstrated unique properties, especially intriguing mechanical properties such as their high strength and high propensity to localize deformation in shear bands. However, a comprehensive understanding of the structure of BMGs has been hindered by the complexity of these amorphous materials. Even more challenging is the structure-property correlation, which has been well established in crystals but has been seriously lacking for BMGs. This thesis presents a systematic study of the atomic-level structures of two representative BMGs, Cu-Zr and Cu-Zr-Al. The interpenetrating Cu-centered icosahedral clusters have been identified to be the primary structural feature. The fraction of icosahedra increases with increasing Cu or Al contents, and with decreasing cooling rate. The effect of Al in improving the icosahedral order is two-fold: the geometric effect due to the atomic-size mismatch and the chemical effect originated from the Cu-Al bond shortening. The resolved structure is used to study the structure-property relationship. The full icosahedra are found to be responsible for the dynamical slowdown of the supercooled liquid, which underlies the non-Arrhenius behavior, and explains the composition dependence of glass transition temperature, glass forming ability, and the room temperature strength. By simulated deformation, the initiation of plasticity and tendency for strain localization are also investigated. The full icosahedra are found to be the most rigid and resistant cluster with solid-like character, while the unstable clusters with liquid-like character serve as the fertile sites for initiating shear transformations. In addition, the elastic moduli are calculated and analyzed, and the origins of the different configurational dependence of shear modulus (G) and bulk modulus ( B) are explained. The

  17. Structural phase transition and electronic properties in samarium chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, Y. S., E-mail: yspanwar2011@gmail.com [Department of Physics, Govt. New Science College Dewas-455001 (India); Aynyas, Mahendra [Department of Physics, C.S.A. Govt. P.G. College, Sehore, 466001 (India); Pataiya, J.; Sanyal, Sankar P. [Department of Physics, Barkatullah University, Bhopal, 462026 (India)

    2016-05-06

    The electronic structure and high pressure properties of samarium monochalcogenides SmS, SmSe and SmTe have been reported by using tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA). The total energy as a function of volume is evaluated. It is found that these monochalcogenides are stable in NaCl-type structure under ambient pressure. We predict a structural phase transition from NaCl-type (B{sub 1}-phase) structure to CsCl-type (B{sub 2}-type) structure for these compounds. Phase transition pressures were found to be 1.7, 4.4 and 6.6 GPa, for SmS, SmSe and SmTe respectively. Apart from this, the lattice parameter (a{sub 0}), bulk modulus (B{sub 0}), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed that these compounds exhibit metallic character. The calculated values of equilibrium lattice parameter and phase transition pressure are in general good agreement with available data.

  18. Structure-topology-property correlations of sodium phosphosilicate glasses.

    Science.gov (United States)

    Hermansen, Christian; Guo, Xiaoju; Youngman, Randall E; Mauro, John C; Smedskjaer, Morten M; Yue, Yuanzheng

    2015-08-14

    In this work, we investigate the correlations among structure, topology, and properties in a series of sodium phosphosilicate glasses with [SiO2]/[SiO2 + P2O5] ranging from 0 to 1. The network structure is characterized by (29)Si and (31)P magic-angle spinning nuclear magnetic resonance and Raman spectroscopy. The results show the formation of six-fold coordinated silicon species in phosphorous-rich glasses. Based on the structural data, we propose a formation mechanism of the six-fold coordinated silicon, which is used to develop a quantitative structural model for predicting the speciation of the network forming units as a function of chemical composition. The structural model is then used to establish a temperature-dependent constraint description of phosphosilicate glass topology that enables prediction of glass transition temperature, liquid fragility, and indentation hardness. The topological constraint model provides insight into structural origin of the mixed network former effect in phosphosilicate glasses.

  19. Improvement in photoconductor film properties by changing dielectric layer structures

    International Nuclear Information System (INIS)

    Kim, S; Oh, K; Lee, Y; Jung, J; Cho, G; Jang, G; Cha, B; Nam, S; Park, J

    2011-01-01

    In recent times, digital X-ray detectors have been actively applied to the medical field; for example, digital radiography offers the potential of improved image quality and provides opportunities for advances in medical image management, computer-aided diagnosis and teleradiology. In this study, two candidate materials (HgI 2 and PbI 2 ) have been employed to study the influence of the dielectric structure on the performance of fabricated X-ray photoconducting films. Parylene C with high permittivity was deposited as a dielectric layer using a parylene deposition system (PDS 2060). The structural and morphological properties of the samples were evaluated field emission scanning electron microscopy and X-ray diffraction. Further, to investigate improvements in the electrical characteristics, a dark current in the dark room and sensitivity to X-ray exposure in the energy range of general radiography diagnosis were measured across the range of the operating voltage. The electric signals varied with the dielectric layer structure of the X-ray films. The PbI 2 film with a bottom dielectric layer showed optimized electric properties. On the other hand, in the case of HgI 2 , the film with a top dielectric layer showed superior electric characteristics. Further, although the sensitivity of the film decreased, the total electrical efficiency of the film improved as a result of the decrease in dark current. When a dielectric layer is deposited on a photoconductor, the properties of the photoconductor, such as hole-electron mobility, should be considered to improve the image quality in digital medical imaging application. In this study, we have thus demonstrated that the use of dielectric layer structures improves the performance of photoconductors.

  20. Modelling structure and properties of amorphous silicon boron nitride ceramics

    Directory of Open Access Journals (Sweden)

    Johann Christian Schön

    2011-06-01

    Full Text Available Silicon boron nitride is the parent compound of a new class of high-temperature stable amorphous ceramics constituted of silicon, boron, nitrogen, and carbon, featuring a set of properties that is without precedent, and represents a prototypical random network based on chemical bonds of predominantly covalent character. In contrast to many other amorphous materials of technological interest, a-Si3B3N7 is not produced via glass formation, i.e. by quenching from a melt, the reason being that the binary components, BN and Si3N4, melt incongruently under standard conditions. Neither has it been possible to employ sintering of μm-size powders consisting of binary nitrides BN and Si3N4. Instead, one employs the so-called sol-gel route starting from single component precursors such as TADB ((SiCl3NH(BCl2. In order to determine the atomic structure of this material, it has proven necessary to simulate the actual synthesis route.Many of the exciting properties of these ceramics are closely connected to the details of their amorphous structure. To clarify this structure, it is necessary to employ not only experimental probes on many length scales (X-ray, neutron- and electron scattering; complex NMR experiments; IR- and Raman scattering, but also theoretical approaches. These address the actual synthesis route to a-Si3B3N7, the structural properties, the elastic and vibrational properties, aging and coarsening behaviour, thermal conductivity and the metastable phase diagram both for a-Si3B3N7 and possible silicon boron nitride phases with compositions different from Si3N4: BN = 1 : 3. Here, we present a short comprehensive overview over the insights gained using molecular dynamics and Monte Carlo simulations to explore the energy landscape of a-Si3B3N7, model the actual synthesis route and compute static and transport properties of a-Si3BN7.

  1. Bismuth Silver Oxysulfide for Photoconversion Applications: Structural and Optoelectronic Properties

    KAUST Repository

    Baqais, Amal Ali Abdulallh; Curutchet, Antton; Ziani, Ahmed; Ait Ahsaine, Hassan; Sautet, Philippe; Takanabe, Kazuhiro; Le Bahers, Tangui

    2017-01-01

    Single-phase bismuth silver oxysulfide, BiAgOS, was prepared by a hydrothermal method. Its structural, morphological and optoelectronic properties were investigated and compared with bismuth copper oxysulfide (BiCuOS). Rietveld refinement of the powder X-ray diffraction (XRD) measurements revealed that the BiAgOS and BiCuOS crystals have the same structure as ZrSiCuAs: the tetragonal space group P4/nmm. X-ray photoelectron spectroscopy (XPS) analyses confirmed that the BiAgOS has a high purity, in contrast with BiCuOS, which tends to have Cu vacancies. The Ag has a monovalent oxidation state, whereas Cu is present in the oxidation states of +1 and +2 in the BiCuOS system. Combined with experimental measurements, density functional theory calculations employing the range-separated hybrid HSE06 exchange-correlation functional with spin-orbit coupling quantitatively elucidated photophysical properties such as ab-sorption coefficients, effective masses and dielectric constants. BiCuOS and BiAgOS were found to have indirect bandgaps of 1.1 and 1.5 eV, respectively. Both possess high dielectric constants and low electron and hole effective masses. Therefore, these materials are expected to have high exciton dissociation capabilities and excellent carrier diffusion properties. This study reveals that BiAgOS is a promising candidate for photoconversion applications.

  2. Bismuth Silver Oxysulfide for Photoconversion Applications: Structural and Optoelectronic Properties

    KAUST Repository

    Baqais, Amal Ali Abdulallh

    2017-09-18

    Single-phase bismuth silver oxysulfide, BiAgOS, was prepared by a hydrothermal method. Its structural, morphological and optoelectronic properties were investigated and compared with bismuth copper oxysulfide (BiCuOS). Rietveld refinement of the powder X-ray diffraction (XRD) measurements revealed that the BiAgOS and BiCuOS crystals have the same structure as ZrSiCuAs: the tetragonal space group P4/nmm. X-ray photoelectron spectroscopy (XPS) analyses confirmed that the BiAgOS has a high purity, in contrast with BiCuOS, which tends to have Cu vacancies. The Ag has a monovalent oxidation state, whereas Cu is present in the oxidation states of +1 and +2 in the BiCuOS system. Combined with experimental measurements, density functional theory calculations employing the range-separated hybrid HSE06 exchange-correlation functional with spin-orbit coupling quantitatively elucidated photophysical properties such as ab-sorption coefficients, effective masses and dielectric constants. BiCuOS and BiAgOS were found to have indirect bandgaps of 1.1 and 1.5 eV, respectively. Both possess high dielectric constants and low electron and hole effective masses. Therefore, these materials are expected to have high exciton dissociation capabilities and excellent carrier diffusion properties. This study reveals that BiAgOS is a promising candidate for photoconversion applications.

  3. Structural and magnetic properties of hcp and fcc Ni nanoparticles

    International Nuclear Information System (INIS)

    Gong, J.; Wang, L.L.; Liu, Y.; Yang, J.H.; Zong, Z.G.

    2008-01-01

    The face-centered-cubic (fcc) and hexagonal-close-packed (hcp) Ni nanoparticles were synthesized with citrate by sol-gel method and heat-treating technique. The structure, morphology and magnetic properties of the samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). Our XRD and TEM results suggested that hcp Ni nanoparticles were successfully synthesized when the heating temperature reaches 300 deg. C. With a further increase in temperature to 400 deg. C, a temperature-induced phase transformation of hcp to fcc was observed. Moreover, the VSM results demonstrated the existence of ferromagnetic behavior in the synthesized fcc and hcp Ni nanoparticles. Nevertheless, the magnetic measurement suggested that the magnetic properties in hcp nanoparticles is probably the sum of two contributions: superparamagnetic and ferromagnetic one. The unsaturated magnetization is much smaller than 47.6 emu/g for the fcc nanoparticles obtained at 400 deg. C and 55 emu/g for the bulk material. It was also found that changes of the stress, grain size and crystal structure during heat-treating have significant influences on the magnetic properties of the Ni nanoparticles

  4. Polycaprolactone/starch composite: Fabrication, structure, properties, and applications.

    Science.gov (United States)

    Ali Akbari Ghavimi, Soheila; Ebrahimzadeh, Mohammad H; Solati-Hashjin, Mehran; Abu Osman, Noor Azuan

    2015-07-01

    Interests in the use of biodegradable polymers as biomaterials have grown. Among the different polymeric composites currently available, the blend of starch and polycaprolactone (PCL) has received the most attention since the 1980s. Novamont is the first company that manufactured a PCL/starch (SPCL) composite under the trademark Mater-Bi®. The properties of PCL (a synthetic, hydrophobic, flexible, expensive polymer with a low degradation rate) and starch (a natural, hydrophilic, stiff, abundant polymer with a high degradation rate) blends are interesting because of the composite components have completely different structures and characteristics. PCL can adjust humidity sensitivity of starch as a biomaterial; while starch can enhance the low biodegradation rate of PCL. Thus, by appropriate blending, SPCL can overcome important limitations of both PCL and starch components and promote controllable behavior in terms of mechanical properties and degradation which make it suitable for many biomedical applications. This article reviewed the different fabrication and modification methods of the SPCL composite; different properties such as structural, physical, and chemical as well as degradation behavior; and different applications as biomaterials. © 2014 Wiley Periodicals, Inc.

  5. Properties, structure and machnining capabilities sintered corundum abrasives

    Directory of Open Access Journals (Sweden)

    Cz.J. Niżankowski

    2010-07-01

    Full Text Available The diversity of sintered corundum abrasives used in both bonded and in the embankment of abrasive tools currently poses substantialproblems for their choice of technology to specific tasks. Therefore performed a comparative study of ownership structures and capacitiesof elected representatives machnining sintered corundum abrasives of different generations, and this is normal sintered alumina,submicrocrystalline alumina sintered and nanocrystalline alumina sintered. Were studied some properties of a set of abrasive particles,physicochemical properties and structural and mechanical and technological properties. The studies used the method of microscopicmeasurement to determine the shape of abrasive particles, the pycnometer to determine the density of abrasive, a spectrometer todetermine the chemical composition of the magnetic analyzer for determining the magnetic fraction, scanning electron microscope toanalysis of abrasive grains and a special position to designate the machining capacity abrasive grains. The results showed a significantincrease in machining capacity sintered corundum abrasives with increasing degree of fragmentation of the crystallites sintered corundum abrasives and distinctive bands in the emerging microchip. The originality of the development provides a comparative summary ofproperties of sintered corundum abrasives of different generations and functions obtained by the author making the change in value indexof machininhcapacity grit from cutting speeds for different generations of sintered corundum.

  6. Influence of isothermal thermomechanical treatment on structure and properties of structural steels

    International Nuclear Information System (INIS)

    Smirnov, M.A.; Kaletin, A.Yu.; Schastlivthev, V.M.; Kaletina, Yu.V.

    1997-01-01

    A study is made into the structure and mechanical properties of steel 35KhGSA and 37KhN3A after isothermal hardening resulting in bainitic structure formation as well as after low-temperature thermomechanical treatment (LTTMT) combining the plastic deformation at the temperature of bainitic transformation and subsequent isothermal hardening. It is shown that LTTMT permits and essential enhancement of strength properties in steel 35KhGSA, high plasticity and impact strength being reserved. This is associated with bainitic structure refinement. In steel 37KhN3A the process of carbide formation takes place along with bainitic transformation, and LTTMT results in lesser strengthening. LTTMT is fount to not practically affect the tendency of structural steels to bainitic brittleness. This treatment promotes some shift of brittleness manifestation to lower temperatures

  7. Structural characterization and mechanical properties of polypropylene reinforced natural fibers

    Science.gov (United States)

    Karim, M. A. A.; Zaman, I.; Rozlan, S. A. M.; Berhanuddin, N. I. C.; Manshoor, B.; Mustapha, M. S.; Khalid, A.; Chan, S. W.

    2017-10-01

    Recently the development of natural fiber composite instead of synthetics fiber has lead to eco-friendly product manufacturing to meet various applications in the field of automotive, construction and manufacturing. The use of natural fibers offer an alternative to the reinforcing fibers because of their good mechanical properties, low density, renewability, and biodegradability. In this present research, the effects of maleic anhydride polypropylene (MAPP) on the mechanical properties and material characterization behaviour of kenaf fiber and coir fiber reinforced polypropylene were investigated. Different fractions of composites with 10wt%, 20wt% and 30wt% fiber content were prepared by using brabender mixer at 190°C. The 3wt% MAPP was added during the mixing. The composites were subsequently molded with injection molding to prepare the test specimens. The mechanical properties of the samples were investigated according to ISO 527 to determine the tensile strength and modulus. These results were also confirmed by the SEM machine observations of fracture surface of composites and FTIR analysis of the chemical structure. As the results, the presence of MAPP helps increasing the mechanical properties of both fibers and 30wt% kenaf fiber with 3wt% MAPP gives the best result compare to others.

  8. Structure and properties of tempo-oxidized cotton fibers

    Directory of Open Access Journals (Sweden)

    Milanovic Jovana

    2012-01-01

    Full Text Available In this paper, the influence of the catalytic oxidation using water soluble and stable nitroxyl radical 2,2´,6,6´-tetramethylpiperidine-1-oxyl (TEMPO on structure and properties of cotton fibers was studied. In particular, the selective TEMPO-mediated oxidation has become very interesting way for introduction of functional groups into cellulose fibers with the aim to obtain oxycellulose fibers with specific properties. Unmodified and modified fibers were characterized in terms of weight loss values, introduced functional groups and crystallinity index. Also, oxidized fibers were characterized in terms of the sorption, morphological, and physico-mechanical properties. The TEMPO-oxidized cotton fibers show a minimum increase of fineness (from 1.32 to 1.28 dtex and increase of crystallinity index (up to 91.9%, while the tensile strength of fibers decreases (up to 10.82 cN/tex. By the TEMPO-mediated oxidation of cotton fibers significant amount of carboxyl groups (up to 0.795 mmol/g cell can be introduced into cellulose fibers. Introduced hydrophilic carboxyl groups increases the sorption properties of oxidized fibers, that can be used directly or for further chemical modification.

  9. Crystal structure and thermal property of polyethylene glycol octadecyl ether

    International Nuclear Information System (INIS)

    Meng, Jie-yun; Tang, Xiao-fen; Li, Wei; Shi, Hai-feng; Zhang, Xing-xiang

    2013-01-01

    Highlights: ► The crystal structure of C18En for n ≥ 20 is a monoclinic system. ► Polyethylene glycol octadecyl ether crystallizes perfectly. ► The number of repeat units has significant effect on the melting, crystallizing temperature and enthalpy. ► The thermal stable temperature increases rapidly with increasing the number of repeat unit. - Abstract: The crystal structure, phase change property and thermal stable temperature (T d ) of polyethylene glycol octadecyl ether [HO(CH 2 CH 2 O) n C 18 H 37 , C18En] with various numbers of repeat units (n = 2, 10, 20 and 100) as phase change materials (PCMs) were investigated using temperature variable Fourier transformed infrared spectroscopy (FTIR), wide-angle X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TG). C18En crystallizes perfectly at 0 °C; and the crystal structure for n ≥ 20 is a monoclinic system. The number of repeat units has great effect on the phase change properties of C18En. The thermal stable temperature increases rapidly with increasing the number of repeat units. They approach to that of PEG-2000 as the number of repeat units is more than 10. T d increases rapidly with increasing the number of repeat units. C18En are a series of promising polymeric PCMs

  10. Modeling process-structure-property relationships for additive manufacturing

    Science.gov (United States)

    Yan, Wentao; Lin, Stephen; Kafka, Orion L.; Yu, Cheng; Liu, Zeliang; Lian, Yanping; Wolff, Sarah; Cao, Jian; Wagner, Gregory J.; Liu, Wing Kam

    2018-02-01

    This paper presents our latest work on comprehensive modeling of process-structure-property relationships for additive manufacturing (AM) materials, including using data-mining techniques to close the cycle of design-predict-optimize. To illustrate the processstructure relationship, the multi-scale multi-physics process modeling starts from the micro-scale to establish a mechanistic heat source model, to the meso-scale models of individual powder particle evolution, and finally to the macro-scale model to simulate the fabrication process of a complex product. To link structure and properties, a highefficiency mechanistic model, self-consistent clustering analyses, is developed to capture a variety of material response. The model incorporates factors such as voids, phase composition, inclusions, and grain structures, which are the differentiating features of AM metals. Furthermore, we propose data-mining as an effective solution for novel rapid design and optimization, which is motivated by the numerous influencing factors in the AM process. We believe this paper will provide a roadmap to advance AM fundamental understanding and guide the monitoring and advanced diagnostics of AM processing.

  11. Structural characterization and magnetic properties of steels subjected to fatigue

    International Nuclear Information System (INIS)

    Lo, C.C.H.; Tang, F.; Biner, S.B.; Jiles, D.C.

    2000-01-01

    Studies have been made on the effects of residual stress and microstructure on the variations of magnetic properties of steels during fatigue. Strain-controlled fatigue tests have been conducted on 0.2wt% C steel samples which were (1) cold-worked (2) cold-worked and annealed at 500 deg. C to relieve residual stress, and (3) annealed at 905 deg. C to produce a ferrite/pearlite structure. The changes of surface microstructure were studied by SEM replica technique. The dislocation structures of samples fatigued for different numbers of cycle were studied by TEM. In the initial stage of fatigue coercivity was found to behave differently for samples which have different residual stress levels. In the intermediate stage the magnetic hysteresis parameters became stable as the dislocation cell structure developed in the samples. In the final stage the magnetic parameters decreased dramatically. The decrease rate is related to the propagation rate of fatigue cracks observed in the SEM study, which was found to be dependent on the sample microstructure. The present results indicate that the magnetic inspection technique is able to differentiate the residual stress effects from the fatigue damage induced by cyclic loading, and therefore it is possible to detect the onset of fatigue failure in steel components via measurements of the changes in magnetic properties.--This work was sponsored by the National Science Foundation, under grant number CMS-9532056

  12. Geometry, electronic structures and optical properties of phosphorus nanotubes

    International Nuclear Information System (INIS)

    Hu, Tao; Hashmi, Arqum; Hong, Jisang

    2015-01-01

    Using a first principles approach, we investigated the geometry, electronic structures, and optical properties of phosphorus nanotubes (PNTs). Two possible 1D configurations, the so-called α-PNTs and β-PNTs, are proposed, which are structurally related to blue and black phosphorus monolayers, respectively. Hereby, we predict that both armchair and zigzag geometries can be synthesized in α-PNTs, but the zigzag form of β-PNT is highly unfavorable because of large strain and conformation energies. The band gap of α-PNTs is expected to be ∼2.67 eV, and this is insensitive to the chirality when the tube’s inner diameter is larger than 1.3 nm, while the armchair β-PNTs have a much smaller band gap. Interestingly, we find nearly flat band structures in the zigzag α-PNT system. This may indicate that an excited particle–hole pair has a huge effective mass. We also find asymmetric optical properties with respect to the polarization direction. The armchair α-PNT for parallel polarization shows a large refractive index of 2.6 near the ultraviolet wavelength, and also we find that the refractive index can be even smaller than 1 in certain frequency ranges. The zigzag tubes show very weak reflectivity for parallel polarization, while the armchair tube displays high reflectivity. (paper)

  13. Structure-property relations in amorphous carbon for photovoltaics

    International Nuclear Information System (INIS)

    Risplendi, Francesca; Cicero, Giancarlo; Bernardi, Marco; Grossman, Jeffrey C.

    2014-01-01

    Carbon is emerging as a material with great potential for photovoltaics (PV). However, the amorphous form (a-C) has not been studied in detail as a PV material, even though it holds similarities with amorphous Silicon (a-Si) that is widely employed in efficient solar cells. In this work, we correlate the structure, bonding, stoichiometry, and hydrogen content of a-C with properties linked to PV performance such as the electronic structure and optical absorption. We employ first-principles molecular dynamics and density functional theory calculations to generate and analyze a set of a-C structures with a range of densities and hydrogen concentrations. We demonstrate that optical and electronic properties of interest in PV can be widely tuned by varying the density and hydrogen content. For example, sunlight absorption in a-C films can significantly exceed that of a same thickness of a-Si for a range of densities and H contents in a-C. Our results highlight promising features of a-C as the active layer material of thin-film solar cells.

  14. About the optical properties of oxidized black silicon structures

    Science.gov (United States)

    Pincik, E.; Brunner, R.; Kobayashi, H.; Mikula, M.; Kučera, M.; Švec, P.; Greguš, J.; Vojtek, P.; Zábudlá, Z.; Imamura, K.; Zahoran, M.

    2017-02-01

    The paper deals with the optical and morphological properties of thermally oxidized black silicon (OBSi) nano-crystalline specimens produced by the surface structure chemical transfer method (SSCT). This method can produce a nano-crystalline Si black color layer on c-Si with a range of thickness of ∼50 nm to ∼300 nm by the contact of c-Si immersed in chemical solutions HF + H2O2 with a catalytic mesh. We present and discuss mainly the photoluminescence properties of both polished c-Si and OBSi structures, respectively. The similar photoluminescence (PL) behaviors recorded at liquid helium (6 K) and room temperatures on both polished crystalline Si and OBSi samples, respectively, indicate the similar origin of recorded luminescence light. As the positions of PL maxima of OBSi structures are mainly related to the size of Si nanocrystallites and SiO(x), we therefore suppose that the size of the dominant parts of the luminated OBSi nanostructure is pre-determined by the used polishing Si procedure, and/or the distribution function of the number of formed crystallites on their size is very similar. The blue shift of both PL spectra reaching almost value of 0.40 eV observed after the decrease of the sample temperature to 6 K we relate also with the change of the semiconductor band gap width.

  15. Electronic structure and magnetic properties of zigzag blue phosphorene nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Tao; Hong, Jisang, E-mail: hongj@pknu.ac.kr [Department of Physics, Pukyong National University, Busan 608-737 (Korea, Republic of)

    2015-08-07

    We investigated the electronic structure and magnetism of zigzag blue phosphorene nanoribbons (ZBPNRs) using first principles density functional theory calculations by changing the widths of ZBPNRs from 1.5 to 5 nm. In addition, the effect of H and O passivation was explored as well. The ZBPNRs displayed intra-edge antiferromagnetic ground state with a semiconducting band gap of ∼0.35 eV; and this was insensitive to the edge structure relaxation effect. However, the edge magnetism of ZBPNRs disappeared with H-passivation. Moreover, the band gap of H-passivated ZBPNRs was greatly enhanced because the calculated band gap was ∼1.77 eV, and this was almost the same as that of two-dimensional blue phosphorene layer. For O-passivated ZBPNRs, we also found an intra-edge antiferromagnetic state. Besides, both unpassivated and O-passivated ZBPNRs preserved almost the same band gap. We predict that the electronic band structure and magnetic properties can be controlled by means of passivation. Moreover, the edge magnetism can be also modulated by the strain. Nonetheless, the intrinsic physical properties are size independent. This feature can be an advantage for device applications because it may not be necessary to precisely control the width of the nanoribbon.

  16. Structure-property relations in amorphous carbon for photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Risplendi, Francesca; Cicero, Giancarlo [Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino (Italy); Bernardi, Marco [Department of Physics, University of California, Berkeley, California 94720 (United States); Grossman, Jeffrey C., E-mail: jcg@mit.edu [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2014-07-28

    Carbon is emerging as a material with great potential for photovoltaics (PV). However, the amorphous form (a-C) has not been studied in detail as a PV material, even though it holds similarities with amorphous Silicon (a-Si) that is widely employed in efficient solar cells. In this work, we correlate the structure, bonding, stoichiometry, and hydrogen content of a-C with properties linked to PV performance such as the electronic structure and optical absorption. We employ first-principles molecular dynamics and density functional theory calculations to generate and analyze a set of a-C structures with a range of densities and hydrogen concentrations. We demonstrate that optical and electronic properties of interest in PV can be widely tuned by varying the density and hydrogen content. For example, sunlight absorption in a-C films can significantly exceed that of a same thickness of a-Si for a range of densities and H contents in a-C. Our results highlight promising features of a-C as the active layer material of thin-film solar cells.

  17. Microphase separated structure and surface properties of fluorinated polyurethane resin

    International Nuclear Information System (INIS)

    Sudaryanto; Nishino, T.; Hori, Y.; Nakamae, K.

    2000-01-01

    The effect of fluorination on microphase separation and surface properties of segmented polyurethane (PU) resin were investigated. A series of fluorinated polyurethane resin (FPU) was synthesized by reacting a fluorinated diol with aromatic diisocyanate. The microphase separated structure of FPU was studied by thermal analysis, and small angle X-ray scattering (SAXS) as well as wide angle X-ray diffraction (WAXD). The surface structure and properties were characterized by X-ray photoelectron spectroscopy (XPS) and dynamic contact angle measurement. The incorporation of fluorine into hard segment brings the FPU to have a higher hard domain cohesion and increase the phase separation, however localization of fluorine on the surface could not be observed. On the other hands, localization of fluorine on the surface could be achieved for soft segment fluorinated PU without any significant change in microphase separated structure. The result from this study give an important basic information for designing PU coating material with a low surface energy and strong adhesion as well as for development of release film on pressure sensitive adhesive tape. (author)

  18. FINEMET type alloy without Si: Structural and magnetic properties

    International Nuclear Information System (INIS)

    Muraca, D.; Cremaschi, V.; Moya, J.; Sirkin, H.

    2008-01-01

    Magnetic and structural properties of a Finemet type alloy (Fe 73.5 Ge 15.5 Nb 3 B 7 Cu 1 ) without Si and high Ge content were studied. Amorphous material was obtained by the melt spinning technique and was heat treated at different temperatures for 1 h under high vacuum to induce the nanocrystallization of the sample. The softest magnetic properties were obtained between 673 and 873 K. The role of Ge on the ferromagnetic paramagnetic transition of the as-quenched alloys and its influence on the crystallization process were studied using a calorimetric technique. Moessbauer spectroscopy was employed in the nanocrystallized alloy annealed at 823 K to obtain the composition of the nanocrystals and the amorphous phase fraction. Using this data and magnetic measurements of the as-quenched alloy, the magnetic contribution of nanocrystals to the alloy annealed at 823 K was estimated via a linear model

  19. Structural and elastic properties of InN nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Quddus, Ehtesham B.; Wilson, Alina; Liu, Jie; Cai, Zhihua; Veereddy, Deepak; Tao, Xinyong; Li, Xiaodong; Koley, Goutam [Department of Electrical Engineering, University of South Carolina, Columbia, SC 29208 (United States); Webb, Richard A. [Department of Physics and Astronomy and USC Nanocenter, University of South Carolina, Columbia, SC 29208 (United States)

    2012-04-15

    Structural and elastic properties of InN nanowires (NWs) have been investigated. It was observed that the NWs bend spontaneously or upon meeting an obstacle in their growth path at angles that are multiples of 30 . Lithographically patterned trenches and barriers were found to influence the growth direction of the NWs, which depending on the angle of incidence, grew along the barrier or got deflected from it. Young's modulus of InN NWs, measured by three point bending method using a NW suspended across a trench, was found to be 266 GPa, which is in between the moduli of bulk and thin film InN. Overall, the InN NW properties were found to be very suitable for applications in nanoelectromechanical systems (NEMS) and sensors. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Microscopical Studies of Structural and Electronic Properties of Semiconductors

    CERN Multimedia

    2002-01-01

    The electronic and structural properties of point defects in semiconductors, e.g. radiation defects, impurities or passivating defects can excellently be studied by the hyperfine technique of Perturbed Angular Correlation (PAC). The serious limitation of this method, the small number of chemically different radioactive PAC probe atoms can be widely overcome by means of ISOLDE. Providing shortliving isotopes, which represent common dopants as well as suitable PAC probe atoms, the ISOLDE facility enables a much broader application of PAC to problems in semiconductor physics.\\\\ Using the probe atom $^{111m}$ Cd , the whole class of III-V compounds becomes accessible for PAC investigations. First successful experiments in GaAs, InP and GaP have been performed, concerning impurity complex formation and plasma induced defects. In Si and Ge, the electronic properties~-~especially their influence on acceptor-donor interaction~-~could be exemplarily st...

  1. Structural and optical properties of furfurylidenemalononitrile thin films

    Science.gov (United States)

    Ali, H. A. M.

    2013-03-01

    Thin films of furfurylidenemalononitrile (FMN) were deposited on different substrates at room temperature by thermal evaporation technique under a high vacuum. The structure of the powder was confirmed by Fourier transformation infrared (FTIR) technique. The unit cell dimensions were determined from X-ray diffraction (XRD) studies. The optical properties were investigated using spectrophotometric measurements of the transmittance and reflectance at normal incidence of light in the wavelength range from 200 to 2500 nm. The refractive index (n), the absorption index (k) and the absorption coefficient (α) were calculated. The analysis of the spectral behavior of the absorption coefficient in the absorption region revealed an indirect allowed transition. The refractive index dispersion was analyzed using the single oscillator model. Some dispersion parameters were estimated. Complex dielectric function and optical conductivity were determined. The influence of the irradiation with high-energy X-rays (6 MeV) on the studied properties was also investigated.

  2. Nanocomposites: synthesis, structure, properties and new application opportunities

    Directory of Open Access Journals (Sweden)

    Pedro Henrique Cury Camargo

    2009-03-01

    Full Text Available Nanocomposites, a high performance material exhibit unusual property combinations and unique design possibilities. With an estimated annual growth rate of about 25% and fastest demand to be in engineering plastics and elastomers, their potential is so striking that they are useful in several areas ranging from packaging to biomedical applications. In this unified overview the three types of matrix nanocomposites are presented underlining the need for these materials, their processing methods and some recent results on structure, properties and potential applications, perspectives including need for such materials in future space mission and other interesting applications together with market and safety aspects. Possible uses of natural materials such as clay based minerals, chrysotile and lignocellulosic fibers are highlighted. Being environmentally friendly, applications of nanocomposites offer new technology and business opportunities for several sectors of the aerospace, automotive, electronics and biotechnology industries.

  3. Diffusive, Structural, Optical, and Electrical Properties of Defects in Semiconductors

    CERN Multimedia

    Wagner, F E

    2002-01-01

    Electronic properties of semiconductors are extremely sensitive to defects and impurities that have localized electronic states with energy levels in the band gap of the semiconductor. Spectroscopic techniques like photoluminescence (PL), deep level transient spectroscopy (DLTS), or Hall effect, that are able to detect and characterize band gap states do not reveal direct information about their microscopic origin. To overcome this chemical "blindness", the present approach is to use radioactive isotopes as a tracer. Moreover, the recoil energies involved in $\\beta$ and $\\gamma$-decays can be used to create intrinsic isolated point defects (interstitials, vacancies) in a controlled way. A microscopic insight into the structure and the thermodynamic properties of complexes formed by interacting defects can be gained by detecting the hyperfine interaction between the nuclear moments of radioactive dopants and the electromagnetic fields present at the site of the radioactive nucleus. The understanding and the co...

  4. Properties of 40N3M powder structural steel

    International Nuclear Information System (INIS)

    Moskvina, T.P.; Gulyaev, A.P.; Gulyaev, I.A.; Byakov, S.V.; Melent'ev, I.V.; Morgun, G.N.

    1984-01-01

    Effect of the fabrication technique of compact slabs made of the 40N3M powder structural steel on mechanical properties with determination of a cold brittleness threshold was studied. It is established that after a thermal treatment at a density close to 100% a powder steel is sufficiently close to steel, rolled of an ingot, but is second in reference to steel in its ductility and impact strength. Properties of powder steel obtained by the method of dynamic hot forming (DHF) and hot extrusion are practically equal, but the first method has definite advantages as it allows to obtain details with a definitive form. The above investigation permits to recommend an application of the 40N3M powder steel fabricated by the DHF methods. The optimum thermal treatment course is: quenching+high annealing

  5. Structural and electronic properties of GaAsBi

    International Nuclear Information System (INIS)

    Achour, H.; Louhibi, S.; Amrani, B.; Tebboune, A.; Sekkal, N.

    2008-05-01

    The structural and electronic properties of the GaAs 1-x Bi x ternary alloy are investigated by means of two first principles and full potential methods, the linear augmented plane waves (FPLAPW) method and a recent version of the full potential linear muffin-tin orbitals method (FPLMTO) which enables an accurate treatment of the interstitial regions. In particular, we have found that the maximal GaBi mole fraction x for which GaBixAs 1-x remains a semiconductor is probably around x = 0.5. The electronic properties of (GaAs) m /(GaBi) n quantum well superlattices (SLs) have also been calculated and it is found that such SLs are semiconductors when m is larger or equal to n. (author)

  6. Morphology, structural and optical properties of iron oxide thin film photoanodes in photoelectrochemical cell: Effect of electrochemical oxidation

    Science.gov (United States)

    Maabong, Kelebogile; Machatine, Augusto G.; Hu, Yelin; Braun, Artur; Nambala, Fred J.; Diale, Mmantsae

    2016-01-01

    Hematite (α-Fe2O3) is a promising semiconductor as photoanode in solar hydrogen production from photoelectrolysis of water due to its appropriate band gap, low cost and high electrochemical stability in aqueous caustic electrolytes. Operation of such photoanode in a biased photoelectrochemical cell constitutes an anodization with consequent redox reactions at the electrode surface. α-Fe2O3 thin film photoanodes were prepared by simple and inexpensive dip coating method on fluorine doped tin oxide (FTO) glass substrate, annealed in air at 500 °C for 2 h, then electrochemically oxidized (anodized) in 1 M KOH at 500 mV for 1 min in dark and light conditions. Changes in structural properties and morphology of α-Fe2O3 nanoparticles films were investigated by XRD, Raman spectroscopy and a high resolution FE-SEM. The average grain size was observed to increase from 57 nm for pristine samples to 73 and 77 nm for anodized samples in dark and light respectively. Broadening and red shift in Raman spectra in anodized samples may be attributed to lattice expansion upon oxidation. The UV-visible measurements revealed enhanced absorption in the photoanodes after the treatment. The findings suggest that the anodization of the photoelectrode in a biased cell causes not only changes of the molecular structure at the surface, but also changes in the crystallographic structure which can be detected with x-ray diffractometry.

  7. Morphology, structural and optical properties of iron oxide thin film photoanodes in photoelectrochemical cell: Effect of electrochemical oxidation

    International Nuclear Information System (INIS)

    Maabong, Kelebogile; Machatine, Augusto G.; Hu, Yelin; Braun, Artur; Nambala, Fred J.; Diale, Mmantsae

    2016-01-01

    Hematite (α-Fe_2O_3) is a promising semiconductor as photoanode in solar hydrogen production from photoelectrolysis of water due to its appropriate band gap, low cost and high electrochemical stability in aqueous caustic electrolytes. Operation of such photoanode in a biased photoelectrochemical cell constitutes an anodization with consequent redox reactions at the electrode surface. α-Fe_2O_3 thin film photoanodes were prepared by simple and inexpensive dip coating method on fluorine doped tin oxide (FTO) glass substrate, annealed in air at 500 °C for 2 h, then electrochemically oxidized (anodized) in 1 M KOH at 500 mV for 1 min in dark and light conditions. Changes in structural properties and morphology of α-Fe_2O_3 nanoparticles films were investigated by XRD, Raman spectroscopy and a high resolution FE-SEM. The average grain size was observed to increase from ~57 nm for pristine samples to 73 and 77 nm for anodized samples in dark and light respectively. Broadening and red shift in Raman spectra in anodized samples may be attributed to lattice expansion upon oxidation. The UV–visible measurements revealed enhanced absorption in the photoanodes after the treatment. The findings suggest that the anodization of the photoelectrode in a biased cell causes not only changes of the molecular structure at the surface, but also changes in the crystallographic structure which can be detected with x-ray diffractometry.

  8. Morphology, structural and optical properties of iron oxide thin film photoanodes in photoelectrochemical cell: Effect of electrochemical oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Maabong, Kelebogile [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); Laboratory of High Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf (Switzerland); Department of Physics, University of Botswana, Private Bag 002, Gaborone (Botswana); Machatine, Augusto G. [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); Hu, Yelin [Laboratory of High Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf (Switzerland); Laboratory for Photonics and Interfaces, EPFL, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Braun, Artur [Laboratory of High Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf (Switzerland); Nambala, Fred J. [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); University of Zambia, Box 32379, Great East Road Campus, Lusaka (Zambia); Diale, Mmantsae, E-mail: mmantsae.diale@up.ac.za [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); Laboratory of High Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf (Switzerland)

    2016-01-01

    Hematite (α-Fe{sub 2}O{sub 3}) is a promising semiconductor as photoanode in solar hydrogen production from photoelectrolysis of water due to its appropriate band gap, low cost and high electrochemical stability in aqueous caustic electrolytes. Operation of such photoanode in a biased photoelectrochemical cell constitutes an anodization with consequent redox reactions at the electrode surface. α-Fe{sub 2}O{sub 3} thin film photoanodes were prepared by simple and inexpensive dip coating method on fluorine doped tin oxide (FTO) glass substrate, annealed in air at 500 °C for 2 h, then electrochemically oxidized (anodized) in 1 M KOH at 500 mV for 1 min in dark and light conditions. Changes in structural properties and morphology of α-Fe{sub 2}O{sub 3} nanoparticles films were investigated by XRD, Raman spectroscopy and a high resolution FE-SEM. The average grain size was observed to increase from ~57 nm for pristine samples to 73 and 77 nm for anodized samples in dark and light respectively. Broadening and red shift in Raman spectra in anodized samples may be attributed to lattice expansion upon oxidation. The UV–visible measurements revealed enhanced absorption in the photoanodes after the treatment. The findings suggest that the anodization of the photoelectrode in a biased cell causes not only changes of the molecular structure at the surface, but also changes in the crystallographic structure which can be detected with x-ray diffractometry.

  9. 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...

  10. Redox chemistry and natural organic matter (NOM): Geochemists' dream, analytical chemists' nightmare

    Science.gov (United States)

    Macalady, Donald L.; Walton-Day, Katherine

    2011-01-01

    Natural organic matter (NOM) is an inherently complex mixture of polyfunctional organic molecules. Because of their universality and chemical reversibility, oxidation/reductions (redox) reactions of NOM have an especially interesting and important role in geochemistry. Variabilities in NOM composition and chemistry make studies of its redox chemistry particularly challenging, and details of NOM-mediated redox reactions are only partially understood. This is in large part due to the analytical difficulties associated with NOM characterization and the wide range of reagents and experimental systems used to study NOM redox reactions. This chapter provides a summary of the ongoing efforts to provide a coherent comprehension of aqueous redox chemistry involving NOM and of techniques for chemical characterization of NOM. It also describes some attempts to confirm the roles of different structural moieties in redox reactions. In addition, we discuss some of the operational parameters used to describe NOM redox capacities and redox states, and describe nomenclature of NOM redox chemistry. Several relatively facile experimental methods applicable to predictions of the NOM redox activity and redox states of NOM samples are discussed, with special attention to the proposed use of fluorescence spectroscopy to predict relevant redox characteristics of NOM samples.

  11. Mechanical properties and structure of magnesium alloy AS31

    Directory of Open Access Journals (Sweden)

    A. Hanus

    2008-07-01

    Full Text Available Contemporary materials should possess high mechanical properties, physical and chemical, as well as technological ones, to ensure long and reliable use. The non-ferrous metals alloys used nowadays, including the magnesium alloys, meet the above-mentioned requirements and expectations regarding the contemporary materials.Magnesium alloys are primarily used in aeronautical and automobile industry in wide variety of structural characteristics because of their favorable combination of tensile strength (160 to 365 MPa, elastic modulus (45 GPa, and low density (1 740 kg/m3, which is two-thirds that of aluminum. Magnesium alloys have high strength-to-weight ratio (tensile strength/density, comparable to those of other structural metals. [1-6]Knowledge of the relaxation properties of metal materials at high temperatures is necessary for the verification of susceptibility of castings to the creation of defects during the production process. Temperature limits of materials where highest tension values are generated may be detected with tensile tests under high temperatures. The generated tensions in the casting are a cause of the creation and development of defects. At acoustic emission (hereinafter called the "AE" use, tensile tests at high temperatures may, among other things, be used for analysis of the AE signal sources and set, in more detail, the temperature limit of elastic-plastic deformations existence in the material under examination. The results of the temperature drop where tension at casting cooling is generated or its release at heating are basic data for controlled cooling mode (and temperature of casting knocking out of the form as well as necessary for the thermal mode for the casting tension reduction. [7-9]Knowledge of elastic-plastic properties at elevated temperatures is often important for complex evaluation of magnesium alloys. Objective of the work was focused on determination of changes of elastic-plastic properties of magnesium

  12. Structural phase transition and elastic properties of mercury chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Varshney, Dinesh, E-mail: vdinesh33@rediffmail.com [School of Physics, Vigyan Bhavan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India); Shriya, S. [School of Physics, Vigyan Bhavan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India); Khenata, R. [Laboratoire de Physique Quantique et de Modelisation Mathematique (LPQ3M), Departement de Technologie, Universite de Mascara, 29000 Mascara (Algeria)

    2012-08-15

    Pressure induced structural transition and elastic properties of ZnS-type (B3) to NaCl-type (B1) structure in mercury chalcogenides (HgX; X = S, Se and Te) are presented. An effective interionic interaction potential (EIOP) with long-range Coulomb, as well charge transfer interactions, Hafemeister and Flygare type short-range overlap repulsion extended up to the second neighbor ions and van der Waals interactions are considered. Emphasis is on the evaluation of the pressure dependent Poisson's ratio {nu}, the ratio R{sub BT/G} of B (bulk modulus) over G (shear modulus), anisotropy parameter, Shear and Young's modulus, Lame constant, Kleinman parameter, elastic wave velocity and thermodynamical property as Debye temperature. The Poisson's ratio behavior infers that Mercury chalcogenides are brittle in nature. To our knowledge this is the first quantitative theoretical prediction of the pressure dependence of elastic and thermodynamical properties explicitly the ductile (brittle) nature of HgX and still awaits experimental confirmations. Highlights: Black-Right-Pointing-Pointer Vast volume discontinuity in phase diagram infers transition from ZnS to NaCl structure. Black-Right-Pointing-Pointer The shear elastic constant C{sub 44} is nonzero confirms the mechanical stability. Black-Right-Pointing-Pointer Pressure dependence of {theta}{sub D} infers the softening of lattice with increasing pressure. Black-Right-Pointing-Pointer Estimated bulk, shear and tetragonal moduli satisfied elastic stability criteria. Black-Right-Pointing-Pointer In both B3 and B1 phases, C{sub 11} and C{sub 12} increase linearly with pressure.

  13. Structural and magnetic properties of nanocrystalline stannic substituted cobalt ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Abbas, Y.M., E-mail: ymabbas@live.com [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Mansour, S.A. [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Physics Department, Faculty of Science, King AbdulAziz University, Rabegh (Saudi Arabia); Ibrahim, M.H. [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Physics Department, Faculty of Science, King AbdulAziz University (Saudi Arabia); Ali, Shehab. E., E-mail: shehab_ali@science.suez.edu.eg [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt)

    2012-09-15

    The structural and magnetic properties of the spinel ferrite system Co{sub 1+x}Fe{sub 2-2x}Sn{sub x}O{sub 4} (x=0.0-1.0) have been studied. Samples in the series were prepared by the ceramic technique. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. Far infrared absorption spectra show two significant absorption bands, around 600 cm{sup -1} and 425 cm{sup -1}, which are respectively attributed to tetrahedral (A) and octahedral [B] vibrations of the spinel. Scanning Electron Microscopy (SEM) was used to study surface morphology. SEM images reveal particles in the nanosize range. The transmission electronic microscope (TEM) reveals that the grains are spherical in shape. TEM analysis confirmed the X-ray results. The magnetic properties of the prepared samples were characterized by using a vibrating sample magnetometer. - Highlights: Black-Right-Pointing-Pointer The spinel ferrite system has been formed at 1000 Degree-Sign C by using ceramic techniques. Black-Right-Pointing-Pointer Structural and microstructural evolutions have been studied using XRD and the Rietveld method. Black-Right-Pointing-Pointer The refinement result showed cationic distribution in the lattice is partially an inverse spinel. Black-Right-Pointing-Pointer The transmission electronic microscope analysis confirmed the X-ray results. Black-Right-Pointing-Pointer Magnetic properties of the samples were characterized by using a vibrating sample magnetometer.

  14. Structural and magnetic properties of nanocrystalline stannic substituted cobalt ferrite

    International Nuclear Information System (INIS)

    Abbas, Y.M.; Mansour, S.A.; Ibrahim, M.H.; Ali, Shehab. E.

    2012-01-01

    The structural and magnetic properties of the spinel ferrite system Co 1+x Fe 2−2x Sn x O 4 (x=0.0–1.0) have been studied. Samples in the series were prepared by the ceramic technique. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. Far infrared absorption spectra show two significant absorption bands, around 600 cm −1 and 425 cm −1 , which are respectively attributed to tetrahedral (A) and octahedral [B] vibrations of the spinel. Scanning Electron Microscopy (SEM) was used to study surface morphology. SEM images reveal particles in the nanosize range. The transmission electronic microscope (TEM) reveals that the grains are spherical in shape. TEM analysis confirmed the X-ray results. The magnetic properties of the prepared samples were characterized by using a vibrating sample magnetometer. - Highlights: ► The spinel ferrite system has been formed at 1000 °C by using ceramic techniques. ► Structural and microstructural evolutions have been studied using XRD and the Rietveld method. ► The refinement result showed cationic distribution in the lattice is partially an inverse spinel. ► The transmission electronic microscope analysis confirmed the X-ray results. ► Magnetic properties of the samples were characterized by using a vibrating sample magnetometer.

  15. Structure and properties of intermetallic ternary rare earth compounds

    International Nuclear Information System (INIS)

    Casper, Frederick

    2008-01-01

    The so called material science is an always growing field in modern research. For the development of new materials not only the experimental characterization but also theoretical calculation of the electronic structure plays an important role. A class of compounds that has attracted a great deal of attention in recent years is known as REME compounds. These compounds are often referred to with RE designating rare earth, actinide or an element from group 1-4, M representing a late transition metal from groups 8-12, and E belonging to groups 13-15. There are more than 2000 compounds with 1:1:1 stoichiometry belonging to this class of compounds and they offer a broad variety of different structure types. Although many REME compounds are know to exist, mainly only structure and magnetism has been determined for these compounds. In particular, in the field of electronic and transport properties relatively few efforts have been made. The main focus in this study is on compounds crystallizing in MgAgAs and LiGaGe structure. Both structures can only be found among 18 valence electron compounds. The f electrons are localized and therefor not count as valence electrons. A special focus here was also on the magnetoresistance effects and spintronic properties found among the REME compounds. An examination of the following compounds was made: GdAuE (E=In,Cd,Mg), GdPdSb, GdNiSb, REAuSn (RE=Gd,Er,Tm) and RENiBi (RE=Pr,Sm,Gd-Tm,Lu). The experimental results were compared with theoretic band structure calculations. The first half metallic ferromagnet with LiGaGe structure (GdPdSb) was found. All semiconducting REME compounds with MgAgAs structure show giant magnetoresistance (GMR) at low temperatures. The GMR is related to a metal-insulator transition, and the value of the GMR depends on the value of the spin-orbit coupling. Inhomogeneous DyNiBi samples show a small positive MR at low temperature that depends on the amount of metallic impurities. At higher fields the samples show a

  16. Structure and properties of intermetallic ternary rare earth compounds

    Energy Technology Data Exchange (ETDEWEB)

    Casper, Frederick

    2008-12-17

    The so called material science is an always growing field in modern research. For the development of new materials not only the experimental characterization but also theoretical calculation of the electronic structure plays an important role. A class of compounds that has attracted a great deal of attention in recent years is known as REME compounds. These compounds are often referred to with RE designating rare earth, actinide or an element from group 1-4, M representing a late transition metal from groups 8-12, and E belonging to groups 13-15. There are more than 2000 compounds with 1:1:1 stoichiometry belonging to this class of compounds and they offer a broad variety of different structure types. Although many REME compounds are know to exist, mainly only structure and magnetism has been determined for these compounds. In particular, in the field of electronic and transport properties relatively few efforts have been made. The main focus in this study is on compounds crystallizing in MgAgAs and LiGaGe structure. Both structures can only be found among 18 valence electron compounds. The f electrons are localized and therefor not count as valence electrons. A special focus here was also on the magnetoresistance effects and spintronic properties found among the REME compounds. An examination of the following compounds was made: GdAuE (E=In,Cd,Mg), GdPdSb, GdNiSb, REAuSn (RE=Gd,Er,Tm) and RENiBi (RE=Pr,Sm,Gd-Tm,Lu). The experimental results were compared with theoretic band structure calculations. The first half metallic ferromagnet with LiGaGe structure (GdPdSb) was found. All semiconducting REME compounds with MgAgAs structure show giant magnetoresistance (GMR) at low temperatures. The GMR is related to a metal-insulator transition, and the value of the GMR depends on the value of the spin-orbit coupling. Inhomogeneous DyNiBi samples show a small positive MR at low temperature that depends on the amount of metallic impurities. At higher fields the samples show a

  17. Mechanical and structural properties of sputtered Ni/Ti multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Senthil Kumar, M.; Boeni, P.; Tixier, S.; Clemens, D.; Horisberger, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    Ni/Ti bilayers have been prepared by dc-magnetron sputtering in order to study their mechanical and structural properties. A remarkable reduction of stress is observed when the Ni layers are sputtered reactively in argon with a high partial pressure of air. The high angle x-ray diffraction studies show a tendency towards amorphisation of the Ni layers with increasing air flow. The low angle measurements indicate a substantial reduction of interdiffusion resulting in smoother interfaces with increasing air content. (author) 2 figs., 2 refs.

  18. Structural, electronic and optical properties of carbon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, M L [California Univ., Berkeley (United States). Dept. of Physics

    1996-05-01

    Carbon nitride was proposed as a superhard material and a structural prototype, {beta}-C{sub 3}N{sub 4}, was examined using several theoretical models. Some reports claiming experimental verifications have been made recently. The current status of the theory and experiment is reviewed, and a detailed discussion is presented of calculations of the electronic and optical properties of this material. These calculations predict that {beta}-C{sub 3}N{sub 4} will have a minimum gap which is indirect at 6.4{+-}0.5 eV. A discussion of the possibility of carbon nitride nanotubes is also presented. (orig.)

  19. Optical constants and structural properties of thin gold films

    DEFF Research Database (Denmark)

    Yakubovsky, Dmitry I.; Arsenin, Aleksey V.; Stebunov, Yury V.

    2017-01-01

    We report a comprehensive experimental study of optical and electrical properties of thin polycrystalline gold films in a wide range of film thicknesses (from 20 to 200 nm). Our experimental results are supported by theoretical calculations based on the measured morphology of the fabricated gold...... rules for thin-film plasmonic and nanophotonic devices....... films. We demonstrate that the dielectric function of the metal is determined by its structural morphology. Although the fabrication process can be absolutely the same for different films, the dielectric function can strongly depend on the film thickness. Our studies show that the imaginary part...

  20. Alkyltributylphosphonium chloride ionic liquids: synthesis, physicochemical properties and crystal structure.

    Science.gov (United States)

    Adamová, Gabriela; Gardas, Ramesh L; Nieuwenhuyzen, Mark; Puga, Alberto V; Rebelo, Luís Paulo N; Robertson, Allan J; Seddon, Kenneth R

    2012-07-21

    A series of alkyltributylphosphonium chloride ionic liquids, prepared from tributylphosphine and the respective 1-chloroalkane, C(n)H(2n+1)Cl (where n = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12 or 14), is reported. This work is a continuation of an extended series of tetraalkylphosphonium ionic liquids, where the focus is on the variability of n and its impact on the physical properties, such as melting points/glass transitions, thermal stability, density and viscosity. Experimental density and viscosity data were interpreted using QPSR and group contribution methods and the crystal structure of propyl(tributyl)phosphonium chloride is detailed.

  1. Characterization, Microstructure, and Dielectric properties of cubic pyrochlore structural ceramics

    KAUST Repository

    Li, Yangyang

    2013-05-01

    The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the X-ray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering temperatures. The XRD patterns demonstrated that the synthesized BMN solid solutions had cubic phase pyrochlore-type structure when sintered at 1050°C or higher, and the lattice parameter (a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed the cubic phase pyrochlore-type structure of the synthesized BMN. According to the Scanning Electron Microscope (SEM) images, the grain size increased with increasing sintering temperature. Additionally, it was shown that the densities of the BMN ceramic tablets vary with sintering temperature. The calculated theoretical density for the BMN ceramic tablets sintered at different temperatures is about 6.7521 . The density of the respective measured tablets is usually amounting more than 91% and 5 approaching a maximum value of 96.5% for sintering temperature of 1150°C. The microstructure was investigated by using Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD). Combined with the results obtained from the STEM and XRD, the impact of sintering temperature on the macroscopic and microscopic structure was discussed. The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid solutions were measured to be 161-200 and (at room temperature and 100Hz-1MHz), respectively. The BMN solid

  2. Effect of Structure on Physical Properties of Polymers.

    Science.gov (United States)

    1979-12-31

    PORT NUMBE . J ! 2. GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER OSRT R’.-8 00 7 5 0 4_7_5_ Effecc of Structure on Physical Properties of -Final...Compatibility of Fluorosubstituted Styrene Polymers with PPO and PS. R. Vukovic , F.E. Karasz, W.J. MacKnight, (in press). (6) Compatibility of Ortho- and Para...fluorostyrene Copolymers with PPO and PS. R. Vukovic , F.E. Karasz, W.J. MacKnight, (in press). (7) Partial Miscibility in the System Poly (para

  3. Structural properties of recursively partitionable graphs with connectivity 2

    DEFF Research Database (Denmark)

    Baudon, Olivier; Bensmail, Julien; Foucaud, Florent

    2017-01-01

    , namely the ones of being online arbitrarily partitionable and recursively arbitrarily partitionable (OL-AP and R-AP for short, respectively), in which the subgraphs induced by a partition of G must not only be con-nected but also ful_l additional conditions. In this paper, we point out some structural...... properties of OL-AP and R-AP graphs with connectivity 2. In particular, we show that deleting a cut pair of these graphs results in a graph with a bounded number of components, some of whom have a small number of vertices. We obtain these results by studying a simple class of 2-connected graphs called...

  4. Electrochemical catalytic activity of tungsten trioxide- modified graphite felt toward VO2+/VO2+ redox reaction

    International Nuclear Information System (INIS)

    Shen, Yang; Xu, Hongfeng; Xu, Pengcheng; Wu, Xiaoxin; Dong, Yiming; Lu, Lu

    2014-01-01

    A novel graphite felt electrode modified with tungsten trioxide (WO 3 ) was developed to improve the electrochemical performance of graphite felt toward the VO 2 + /VO 2+ redox pair. WO 3 was prepared using a hydrothermal method, and the morphology of WO 3 structures was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical property of WO 3 -modified graphite felt toward VO 2 + /VO 2+ was carefully characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The hydrogen-vanadium redox flow battery (H-VRFB) test indicates that single cells using 1.1 mg cm −2 WO 3 -modified graphite felt exhibited excellent performance at 70 mA cm −2 , and the corresponding coulombic, voltage, and energy efficiencies were 99.1%, 88.66% and 87.86%, respectively

  5. CRITICAL MECHANICAL PROPERTIES OF STRUCTURAL LIGHT-WEIGHT CONCRETE AND THE EFFECTS OF THESE PROPERTIES ON THE DESIGN OF THE PAVEMENT STRUCTURE.

    Science.gov (United States)

    1965-01-01

    In this study, critical mechanical properties of structural lightweight concrete were determined and utilized in the evaluation of a design of concrete pavements. Also presented are the critical mechanical properties resulting from unrestrained and r...

  6. Structural and magnetic properties of Mn-implanted Si

    International Nuclear Information System (INIS)

    Zhou Shengqiang; Potzger, K.; Zhang Gufei; Muecklich, A.; Eichhorn, F.; Schell, N.; Groetzschel, R.; Schmidt, B.; Skorupa, W.; Helm, M.; Fassbender, J.; Geiger, D.

    2007-01-01

    Structural and magnetic properties in Mn-implanted, p-type Si were investigated. High resolution structural analysis techniques such as synchrotron x-ray diffraction revealed the formation of MnSi 1.7 nanoparticles already in the as-implanted samples. Depending on the Mn fluence, the size increases from 5 nm to 20 nm upon rapid thermal annealing. No significant evidence is found for Mn substituting Si sites either in the as-implanted or annealed samples. The observed ferromagnetism yields a saturation moment of 0.21μ B per implanted Mn at 10 K, which could be assigned to MnSi 1.7 nanoparticles as revealed by a temperature-dependent magnetization measurement

  7. Structure-Property Study of Piezoelectricity in Polyimides

    Science.gov (United States)

    Ounaies, Zoubeida; Park, Cheol; Harrison, Joycelyn S.; Smith, Joseph G.; Hinkley, Jeffrey

    1999-01-01

    High performance piezoelectric polymers are of interest to NASA as they may be useful for a variety of sensor applications. Over the past few years research on piezoelectric polymers has led to the development of promising high temperature piezoelectric responses in some novel polyimides. In this study, a series of polyimides have been studied with systematic variations in the diamine monomers that comprise the polyimide while holding the dianhydride constant. The effect of structural changes, including variations in the nature and concentration of dipolar groups, on the remanent polarization and piezoelectric coefficient is examined. Fundamental structure-piezoelectric property insight will enable the molecular design of polymers possessing distinct improvements over state-of-the-art piezoelectric polymers including enhanced polarization, polarization stability at elevated temperatures, and improved processability.

  8. Numerical investigation of elastic mechanical properties of graphene structures

    International Nuclear Information System (INIS)

    Georgantzinos, S.K.; Giannopoulos, G.I.; Anifantis, N.K.

    2010-01-01

    The computation of the elastic mechanical properties of graphene sheets, nanoribbons and graphite flakes using spring based finite element models is the aim of this paper. Interatomic bonded interactions as well as van der Waals forces between carbon atoms are simulated via the use of appropriate spring elements expressing corresponding potential energies provided by molecular theory. Each layer is idealized as a spring-like structure with carbon atoms represented by nodes while interatomic forces are simulated by translational and torsional springs with linear behavior. The non-bonded van der Waals interactions among atoms which are responsible for keeping the graphene layers together are simulated with the Lennard-Jones potential using appropriate spring elements. Numerical results concerning the Young's modulus, shear modulus and Poisson's ratio for graphene structures are derived in terms of their chilarity, width, length and number of layers. The numerical results from finite element simulations show good agreement with existing numerical values in the open literature.

  9. Structural properties of maize hybrids established by infrared spectra

    Directory of Open Access Journals (Sweden)

    Radenović Čedomir N.

    2015-01-01

    Full Text Available This paper discusses the application of the infrared (IR spectroscopy method for determination of structural properties of maize hybrid grains. The IR spectrum of maize grain has been registered in the following hybrids: ZP 341, ZP 434 and ZP 505. The existence of spectral bands varying in both number and intensity, as well as their shape, frequency and kinetics have been determined. They have been determined by valence oscillations and deformation oscillations of the following organic compounds: alkanes, alkenes, alkynes, amides, alcohols, ethers, carboxylic acids, esters and aldehydes and ketones, characteristic for biogenic compounds such as carbohydrates, proteins and lipids. In this way, possible changes in the grain structure of observed maize hybrids could be detected.

  10. Chemical structure and properties of low-molecular furin inhibitors

    Directory of Open Access Journals (Sweden)

    T. V. Osadchuk

    2016-12-01

    Full Text Available The review is devoted to the analysis of the relationship between a chemical structure and properties of low-molecular weight inhibitors of furin, the most studied proprotein convertase, which is involved in the development of some pathologies, such as oncologic diseases, viral and bacterial infections, etc. The latest data concerning the influence of peptides, pseudo-peptides, aromatic and heterocyclic compounds, some natural ones such as flavonoids, coumarins, and others on enzyme inactivation are considered. The power of furin inhibition is shown to rise with the increasing number of positively charged groups in the structure of these compounds. Peptidomimetics (Ki = 5-8 pM are shown to be the most effective furin inhibitors. The synthesized substances, however, have not been used in practical application yet. Nowadays it is very important to find more selective inhibitors, improve their stability, bioavailability and safety for the human organism.

  11. Structures and properties of naturally occurring polyether antibiotics.

    Science.gov (United States)

    Rutkowski, Jacek; Brzezinski, Bogumil

    2013-01-01

    Polyether ionophores represent a large group of natural, biologically active substances produced by Streptomyces spp. They are lipid soluble and able to transport metal cations across cell membranes. Several of polyether ionophores are widely used as growth promoters in veterinary. Polyether antibiotics show a broad spectrum of bioactivity ranging from antibacterial, antifungal, antiparasitic, antiviral, and tumour cell cytotoxicity. Recently, it has been shown that some of these compounds are able to selectively kill cancer stem cells and multidrug-resistant cancer cells. Thus, they are recognized as new potential anticancer drugs. The biological activity of polyether ionophores is strictly connected with their molecular structure; therefore, the purpose of this paper is to present an overview of their formula, molecular structure, and properties.

  12. Structural and dynamic properties of solid state ionics

    International Nuclear Information System (INIS)

    Sakuma, T.

    1995-01-01

    The structural and dynamic properties of solid state ionics are reviewed. The low temperature phase transition of the copper halide-chalcogen compounds by specific heat measurements, electrical conductivity measurements and x-ray diffraction measurements are explained. The structures of solid state ionics investigated by the usual x-ray diffraction method and the anomalous x-ray scattering (AXS) measurement are discussed. The expression of the diffuse scattering intensity including the correlations among the thermal displacements of atoms has been given and applied to α-AgI type solid state ionics and lithium sulphate. The presence of low-energy excitations in crystalline copper ion conductors and the superionic conducting glass is investigated by neutron inelastic scattering measurements. The relation between the excitation energy and the mass of the cations is discussed. (author). 141 refs., 21 figs., 7 tabs

  13. γ-Glutamyltranspeptidases: sequence, structure, biochemical properties, and biotechnological applications.

    Science.gov (United States)

    Castellano, Immacolata; Merlino, Antonello

    2012-10-01

    γ-Glutamyltranspeptidases (γ-GTs) are ubiquitous enzymes that catalyze the hydrolysis of γ-glutamyl bonds in glutathione and glutamine and the transfer of the released γ-glutamyl group to amino acids or short peptides. These enzymes are involved in glutathione metabolism and play critical roles in antioxidant defense, detoxification, and inflammation processes. Moreover, γ-GTs have been recently found to be involved in many physiological disorders, such as Parkinson's disease and diabetes. In this review, the main biochemical and structural properties of γ-GTs isolated from different sources, as well as their conformational stability and mechanism of catalysis, are described and examined with the aim of contributing to the discussion on their structure-function relationships. Possible applications of γ-glutamyltranspeptidases in different fields of biotechnology and medicine are also discussed.

  14. Freeze-Casting of Porous Biomaterials: Structure, Properties and Opportunities

    Directory of Open Access Journals (Sweden)

    Sylvain Deville

    2010-03-01

    Full Text Available The freeze-casting of porous materials has received a great deal of attention during the past few years. This simple process, where a material suspension is simply frozen and then sublimated, provides materials with unique porous architectures, where the porosity is almost a direct replica of the frozen solvent crystals. This review focuses on the recent results on the process and the derived porous structures with regards to the biomaterials applications. Of particular interest is the architecture of the materials and the versatility of the process, which can be readily controlled and applied to biomaterials applications. A careful control of the starting formulation and processing conditions is required to control the integrity of the structure and resulting properties. Further in vitro and in vivo investigations are required to validate the potential of this new class of porous materials.

  15. Structure and properties of calcium iron phosphate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Bin [School of Science, Southwest University of Science and Technology, Mianyang 621010 (China); Liang, Xiaofeng, E-mail: xfliangswust@gmail.com [Analytical and Testing Center, Southwest University of Science and Technology, Mianyang 621010 (China); School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010 (China); Wang, Cuiling; Yang, Shiyuan [School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010 (China)

    2013-11-15

    The structural properties of xCaO–(100 − x) (0.4Fe{sub 2}O{sub 3}–0.6P{sub 2}O{sub 5}) (x = 0, 10, 20, 30, 40, 50 mol%) glasses have been investigated by XRD, DTA, IR and Raman spectroscopy. XRD analysis has confirmed that the majority of samples are X-ray amorphous, and EDS analysis indicates that the glass matrix can accommodate ≈30 mol% CaO. IR and Raman spectra show that the glass structure consists predominantly of pyrophosphate (Q{sup 1}) units. IR spectra indicate that the phosphate network is depolymerized with the addition of CaO content. The density and glass transition temperature (T{sub g}) increase with increasing CaO content for the glasses. This behavior indicates that the addition of CaO improves the strength of the cross-links between the phosphate chains of the glass.

  16. Synthesis, Structure, and Properties of Refractory Hard-Metal Borides

    Science.gov (United States)

    Lech, Andrew Thomas

    As the limits of what can be achieved with conventional hard compounds, such as tungsten carbide, are nearing reach, super-hard materials are an area of increasing industrial interest. The refractory hard metal borides, such as ReB2 and WB4, offer an increasingly attractive alternative to diamond and cubic boron nitride as a next-generation tool material. In this Thesis, a thorough discussion is made of the progress achieved by our laboratory towards understanding the synthesis, structure, and properties of these extremely hard compounds. Particular emphasis is placed on structural manipulation, solid solution formation, and the unique crystallographic manifestations of what might also be called "super-hard metals".

  17. Manganites in Perovskite Superlattices: Structural and Electronic Properties

    KAUST Repository

    Jilili, Jiwuer

    2016-07-13

    Perovskite oxides have the general chemical formula ABO3, where A is a rare-earth or alkali-metal cation and B is a transition metal cation. Perovskite oxides can be formed with a variety of constituent elements and exhibit a wide range of properties ranging from insulators, metals to even superconductors. With the development of growth and characterization techniques, more information on their physical and chemical properties has been revealed, which diversified their technological applications. Perovskite manganites are widely investigated compounds due to the discovery of the colossal magnetoresistance effect in 1994. They have a broad range of structural, electronic, magnetic properties and potential device applications in sensors and spintronics. There is not only the technological importance but also the need to understand the fundamental mechanisms of the unusual magnetic and transport properties that drive enormous attention. Manganites combined with other perovskite oxides are gaining interest due to novel properties especially at the interface, such as interfacial ferromagnetism, exchange bias, interfacial conductivity. Doped manganites exhibit diverse electrical properties as compared to the parent compounds. For instance, hole doped La0.7Sr0.3MnO3 is a ferromagnetic metal, whereas LaMnO3 is an antiferromagnetic insulator. Since manganites are strongly correlated systems, heterojunctions composed of manganites and other perovskite oxides are sunject to complex coupling of the spin, orbit, charge, and lattice degrees of freedom and exhibit unique electronic, magnetic, and transport properties. Electronic reconstructions, O defects, doping, intersite disorder, magnetic proximity, magnetic exchange, and polar catastrophe are some effects to explain these interfacial phenomena. In our work we use first-principles calculations to study the structural, electronic, and magnetic properties of manganite based superlattices. Firstly, we investigate the electronic

  18. Iron phosphate glasses: Bulk properties and atomic scale structure

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, Kitheri; Stennett, Martin C.; Hyatt, Neil C.; Asuvathraman, R.; Dube, Charu L.; Gandy, Amy S.; Govindan Kutty, K. V.; Jolley, Kenny; Vasudeva Rao, P. R.; Smith, Roger

    2017-10-01

    Bulk properties such as glass transition temperature, density and thermal expansion of iron phosphate glass compositions, with replacement of Cs by Ba, are investigated as a surrogate for the transmutation of 137Cs to 137Ba, relevant to the immobilisation of Cs in glass. These studies are required to establish the appropriate incorporation rate of 137Cs in iron phosphate glass. Density and glass transition temperature increases with the addition of BaO indicating the shrinkage and reticulation of the iron phosphate glass network. The average thermal expansion coefficient reduces from 19.8 × 10-6 K-1 to 13.4 × 10-6 K-1, when 25 wt. % of Cs2O was replaced by 25 wt. % of BaO in caesium loaded iron phosphate glass. In addition to the above bulk properties, the role of Ba as a network modifier in the structure of iron phosphate glass is examined using various spectroscopic techniques. The FeII content and average coordination number of iron in the glass network was estimated using Mössbauer spectroscopy. The FeII content in the un-doped iron phosphate glass and barium doped iron phosphate glasses was 20, 21 and 22 ± 1% respectively and the average Fe coordination varied from 5.3 ± 0.2 to 5.7 ± 0.2 with increasing Ba content. The atomic scale structure was further probed by Fe K-edge X-ray absorption spectroscopy. The average coordination number provided by extended X-ray absorption fine structure spectroscopy and X-ray absorption near edge structure was in good agreement with that given by the Mössbauer data.

  19. Structure and property correlations in FeS

    Energy Technology Data Exchange (ETDEWEB)

    Kuhn, S.J. [Materials Science & Technology Division, Oak Ridge National Laboratory , Oak Ridge , TN 37831 (United States); Department of Physics , University of Notre Dame , Notre Dame , IN 46556 (United States); Kidder, M.K. [Chemical Sciences Division, Oak Ridge National Laboratory , Oak Ridge , TN 37831 (United States); Parker, D.S. [Materials Science & Technology Division, Oak Ridge National Laboratory , Oak Ridge , TN 37831 (United States); Cruz, C. dela [Quantum Condensed Matter Division, Oak Ridge National Laboratory , Oak Ridge , TN 37831 (United States); McGuire, M.A.; Chance, W.M.; Li, Li [Materials Science & Technology Division, Oak Ridge National Laboratory , Oak Ridge , TN 37831 (United States); Debeer-Schmitt, L. [Chemical and Engineering Materials Division, Oak Ridge National Laboratory , Oak Ridge , TN 37831 (United States); Ermentrout, J. [Materials Science & Technology Division, Oak Ridge National Laboratory , Oak Ridge , TN 37831 (United States); Littrell, K.C. [Chemical and Engineering Materials Division, Oak Ridge National Laboratory , Oak Ridge , TN 37831 (United States); Eskildsen, M.R. [Department of Physics , University of Notre Dame , Notre Dame , IN 46556 (United States); Sefat, A.S. [Materials Science & Technology Division, Oak Ridge National Laboratory , Oak Ridge , TN 37831 (United States)

    2017-03-15

    Highlights: • Similar to other iron chalcogenides of FeSe and FeTe, the structure and composition of FeS is highly correlated to its superconductivity. For iron-sulfide (FeS), we report the correlation between the structural details with its magnetic and superconducting properties. • While our FeS with a = 3.6772(7) Å is a filamentary superconductor coexisting with an antiferromagnetic phase, previously reported samples with a > 3.68 Å are bulk superconductors with no magnetism, and those with a ≈ 3.674 Å show magnetic properties. The a lattice of ≥3.68 Å seem to be crucial for causing bulk superconductivity in the tetragonal phase, which is relevant to iron stoichiometry and sulfur height from the iron plane. • For Fe{sub 0.93}S, we report evidence for the coexistence of antiferromagnetism at T{sub N} = 116 and filamentary superconductivity below T{sub c} = 4 K. While temperature neutron diffraction data reveals antiferromagnetic commensurate ordering with wave vector k{sub m} = (0.25,0.25,0), our magnetization results shows shielding and diamagnetism. - Abstract: For iron-sulfide (FeS), we investigate the correlation between the structural details, including its dimensionality and composition, with its magnetic and superconducting properties. We compare, theoretically and experimentally, the two-dimensional (2D) layered tetragonal (“t-FeS”) phase with the 3D hexagonal ('h-FeS') phase. X-ray diffraction reveals iron-deficient chemical compositions of t-Fe{sub 0.93(1)}S and h-Fe{sub 0.84(1)}S that show no low-temperature structural transitions. First-principles calculations reveal a high sensitivity of the 2D structure to the electronic and magnetic properties, predicting marginal antiferromagnetic instability for our compound (sulfur height of z{sub S} = 0.252) with an ordering energy of about 11 meV/Fe, while the 3D phase is magnetically stable. Experimentally, h-Fe{sub 0.84}S orders magnetically well above room

  20. Structural and optical properties of solid-state synthesized Au dendritic structures

    International Nuclear Information System (INIS)

    Gentile, A.; Ruffino, F.; Romano, L.; Boninelli, S.; Reitano, R.; Piccitto, G.; Grimaldi, M.G.

    2014-01-01

    Graphical abstract: - Highlights: • Au dendritic structures were produced on surfaces. • The chemical and structural properties of the dendritic structures are presented. • The optical properties of the dendritic structures are presented. • The ability of the dendritic structures to serve as light scattering centers is presented. - Abstract: Au dendrites (Au Ds) are synthesized, on various substrates, by a simple physical methodology involving the deposition of a thin Au film on a Si surface followed by thermal processes at high temperatures (>1273 K) in an inert ambient (N 2 ), using fast heating and cooling rates (1273 K/min). Microscopic analyses reveal the evolution, thanks to the thermal processes, of the Au film from a continuous coating to dendritic structures covering the entire sample surface. In particular, transmission electron microscopy analyses indicate that, below the Au surface, the dendritic structures consist of Si atoms originating from the substrate. Furthermore, optical characterizations reveal the ability of the Au Ds to serve as scattering centers in the infrared region. Finally, on the basis of the experimental observations, a phenomenological model for the growth of the Au Ds is proposed