WorldWideScience

Sample records for single-metal substituted goethites

  1. Aluminum substitution in goethite in lake ore

    Directory of Open Access Journals (Sweden)

    Carlson, L.

    1995-06-01

    Full Text Available The extent of substitution of Fe by Al in goethite in 32 lake ore samples collected from 11 lakes in Finland varied between 0 and 23 mol-%. The data indicated a negative relationship between Al-substitution and the particle size of lake ore. Differences in the Al-substitution were apparent between sampling sites, suggesting that kinetic and environmental variation in lake ore formation influences the substitution. Non-substituted goethite is formed in coarse-grained sediments with locally high concentrations of Fe due to iron-rich springs. Unit cell edge lengths and volumes of goethite varied as function of Al-subsitution but deviated from the Vegard relationship towards higher values.

  2. Acid mine drainage simulated leaching behavior of goethite and cobalt substituted goethite

    Science.gov (United States)

    Penprase, S. B.; Kimball, B. E.

    2015-12-01

    Though most modern day mining aims to eliminate the seepage of acid mine drainage (AMD) to the local watershed, historical mines regularly receive little to no remediation, and often release acidic, metal-rich drainage and particles to the environment. Treatment of AMD often includes neutralizing pH to facilitate the precipitation of Fe-oxides and dissolved trace metals, thereby forming Trace Metal Substituted (TMS) forms of known minerals, such as goethite (α-FeOOH). The stability of TMS precipitates is not fully understood. As a result, we conducted a 20 day leach experiment using laboratory synthesized pure (Gt) and cobalt-substituted (CoGt) goethites with a dilute ultrapure HCl solution (pH = 3.61) at T = 23.3±2.5ºC. Leached solids were characterized using X-ray diffraction (XRD) and scanning electron microscopy paired with energy dispersive spectroscopy (SEM-EDS). Leach solutions were sampled for pH and conductivity, and dissolved chemistry was determined with Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). Preliminary results indicate Gt and CoGt filtered leach solutions experienced constant pH (Gt = 3.9 ± 0.1, CoGt = 6.8 ± 0.2) and conductivity (Gt = 69 ± 6.6 μS/cm, CoGt = 81 ± 16 μS/cm) for t = 0-20 days. Micro-focused XRD results indicate that leached solids did not change in mineralogy throughout the experiment, and SEM images show minor disintegration along mineral grain edges, but little overall change in shape. Preliminary ICP-MS results show lower dissolved Fe concentrations for CoGt (1.1 ± 1.1 ppb) compared to Gt (17 ± 8.9 ppb) over time. Dissolved Co concentrations ranged from 560 - 830 ppb and increased over time. Compared to leaching of pure Gt, leaching of CoGt generated significantly higher pH, slightly higher conductivity, and significantly less dissolved Fe. During the CoGt leach, Co was preferentially leached over Fe. The differences in leaching behavior between pure and TMS goethite in the laboratory have implications for

  3. Structural properties and hyperfine characterization of Sn-substituted goethites

    Energy Technology Data Exchange (ETDEWEB)

    Larralde, A.L. [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina); Ramos, C.P. [Departamento de Fisica de la Materia Condensada, GIyA - CAC - CNEA, Av. Gral. Paz 1499 (1650), San Martin, Bs. As. (Argentina); Arcondo, B. [Departamento de Fisica, Facultad de Ingenieria, Universidad de Buenos Aires, Av. Paseo Colon 850 (C1063ACV), Bs. As. (Argentina); Tufo, A.E. [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina); Saragovi, C. [Departamento de Fisica de la Materia Condensada, GIyA - CAC - CNEA, Av. Gral. Paz 1499 (1650), San Martin, Bs. As. (Argentina); Sileo, E.E., E-mail: sileo@qi.fcen.uba.ar [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer Pure and tin-doped goethites were synthesized from Sn(II) solutions at ambient pressure and 70 Degree-Sign C. Black-Right-Pointing-Pointer The Rietveld refinement of PXRD data indicated that Sn partially substituted the Fe(III) ions. Black-Right-Pointing-Pointer The substitution provoked unit cell expansion, and a distortion of the coordination polyhedron. Black-Right-Pointing-Pointer {sup 119}Sn Moessbauer spectroscopy revealed that Sn(II) is incorporated as Sn(IV). Black-Right-Pointing-Pointer {sup 57}Fe Moessbauer spectroscopy showed a lower magnetic coupling as tin concentration increased. - Abstract: Tin-doped goethites obtained by a simple method at ambient pressure and 70 Degree-Sign C were characterized by inductively coupled plasma atomic emission spectrometry, scanning electron microscopy, Rietveld refinement of powder X-ray diffraction data, and {sup 57}Fe and {sup 119}Sn Moessbauer spectroscopy. The particles size and the length to width ratios decreased with tin-doping. Sn partially substituted the Fe(III) ions provoking unit cell expansion and increasing the crystallinity of the particles with enlarged domains that grow in the perpendicular and parallel directions to the anisotropic broadening (1 1 1) axis. Intermetallic E, E Prime and DC distances also change although the variations are not monotonous, indicating different variations in the coordination polyhedron. In general, the Sn-substituted samples present larger intermetallic distances than pure goethite, and the greatest change is shown in the E Prime distance which coincides with the c-parameter. {sup 119}Sn Moessbauer spectroscopy revealed that Sn(II) is incorporated as Sn(IV) in the samples. On the other hand, Fe(II) presence was not detected by {sup 57}Fe Moessbauer spectroscopy, suggesting the existence of vacancies in the Sn-doped samples. A lower magnetic coupling is also evidenced from the average magnetic hyperfine field values obtained as tin

  4. Molecular Interactions of Plutonium(VI) with Synthetic Manganese-Substituted Goethite

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yung-Jin; Schwaiger, Luna Kestrel; Booth, Corwin H.; Kukkadapu, Ravi K.; Cristiano, Elena; Kaplan, Daniel; Nitsche, Heino

    2010-03-09

    Plutonium(VI) sorption on the surface of well-characterized synthetic manganese-substituted goethite minerals (Fe1-xMnxOOH) was studied using X-ray absorption spectroscopy. We chose to study the influence of manganese as a minor component in goethite, because goethite rarely exists as a pure phase in nature. Manganese X-ray absorption near-edge structure measurements indicated that essentially all the Mn in the goethite existed as Mn(III), even though Mn was added during mineral synthesis as Mn(II). Importantly, energy dispersive X-ray analysis demonstrated that Mn did not exist as discrete phases and that it was homogeneously mixed into the goethite to within the limit of detection of the method. Furthermore, Mössbauer spectra demonstrated that all Fe existed as Fe(III), with no Fe(II) present. Plutonium(VI) sorption experiments were conducted open to air and no attempt was made to exclude carbonate. The use of X-ray absorption spectroscopy allows us to directly and unambiguously measure the oxidation state of plutonium in situ at the mineral surface. Plutonium X-ray absorption near-edge structure measurements carried out on these samples showed that Pu(VI) was reduced to Pu(IV) upon contact with the mineral. This reduction appears to be strongly correlated with mineral solution pH, coinciding with pH transitions across the point of zero charge of the mineral. Furthermore, extended X-ray absorption fine structure measurements show evidence of direct plutonium binding to the metal surface as an inner-sphere complex. This combination of extensive mineral characterization and advanced spectroscopy suggests that sorption of the plutonium onto the surface of the mineral was followed by reduction of the plutonium at the surface of the mineral to form an inner-sphere complex. Because manganese is often found in the environment as a minor component associated with major mineral components, such as goethite, understanding the molecular-level interactions of plutonium with

  5. Aluminum coprecipitates with Fe (hydr)oxides: Does isomorphous substitution of Al 3+ for Fe 3+ in goethite occur?

    Science.gov (United States)

    Bazilevskaya, Ekaterina; Archibald, Douglas D.; Aryanpour, Masoud; Kubicki, James D.; Martínez, Carmen Enid

    2011-08-01

    Iron (hydr)oxides are common in natural environments and typically contain large amounts of impurities, presumably the result of coprecipitation processes. Coprecipitation of Al with Fe (hydr)oxides occurs, for example, during alternating reduction-oxidation cycles that promote dissolution of Fe from Fe-containing phases and its re-precipitation as Fe-Al (hydr)oxides. We used chemical and spectroscopic analyses to study the formation and transformation of Al coprecipitates with Fe (hydr)oxides. In addition, periodic density functional theory (DFT) computations were performed to assess the structural and energetic effects of isolated or clustered Al atoms at 8 and 25 mol% Al substitution in the goethite structure. Coprecipitates were synthesized by raising the pH of dilute homogeneous solutions containing a range of Fe and Al concentrations (100% Fe to 100% Al) to 5. The formation of ferrihydrite in initial suspensions with ⩽20 mol% Al, and of ferrihydrite and gibbsite in initial suspensions with ⩾25 mol% Al was confirmed by infrared spectroscopic and synchrotron-based X-ray diffraction analyses. While base titrations showed a buffer region that corresponded to the hydrolysis of Fe in initial solutions with ⩽25 mol% Al, all of the Al present in these solutions was retained by the solid phases at pH 5, thus indicating Al coprecipitation with the primary Fe hydroxide precipitate. In contrast, two buffer regions were observed in solutions with ⩾30 mol% Al (at pH ˜2.25 for Fe 3+ and at pH ˜4 for Al 3+), suggesting the formation of Fe and Al (hydr)oxides as two separate phases. The Al content of initial coprecipitates influenced the extent of ferrihydrite transformation and of its transformation products as indicated by the presence of goethite, hematite and/or ferrihydrite in aged suspensions. DFT experiments showed that: (i) optimized unit cell parameters for Al-substituted goethites (8 and 25 mol% Al) in clustered arrangement (i.e., the formation of diaspore

  6. Aluminum Coprecipitates with Fe (hydr)oxides: Does Isomorphous Substitution of Al3plus for Fe3plus in Goethite Occur

    Energy Technology Data Exchange (ETDEWEB)

    E Bazilevskaya; D Archibald; M Aryanpour; J Kubicki; C Martinez

    2011-12-31

    Iron (hydr)oxides are common in natural environments and typically contain large amounts of impurities, presumably the result of coprecipitation processes. Coprecipitation of Al with Fe (hydr)oxides occurs, for example, during alternating reduction-oxidation cycles that promote dissolution of Fe from Fe-containing phases and its re-precipitation as Fe-Al (hydr)oxides. We used chemical and spectroscopic analyses to study the formation and transformation of Al coprecipitates with Fe (hydr)oxides. In addition, periodic density functional theory (DFT) computations were performed to assess the structural and energetic effects of isolated or clustered Al atoms at 8 and 25 mol% Al substitution in the goethite structure. Coprecipitates were synthesized by raising the pH of dilute homogeneous solutions containing a range of Fe and Al concentrations (100% Fe to 100% Al) to 5. The formation of ferrihydrite in initial suspensions with {<=}20 mol% Al, and of ferrihydrite and gibbsite in initial suspensions with {>=}25 mol% Al was confirmed by infrared spectroscopic and synchrotron-based X-ray diffraction analyses. While base titrations showed a buffer region that corresponded to the hydrolysis of Fe in initial solutions with {<=}25 mol% Al, all of the Al present in these solutions was retained by the solid phases at pH 5, thus indicating Al coprecipitation with the primary Fe hydroxide precipitate. In contrast, two buffer regions were observed in solutions with 30 mol% Al (at pH {approx}2.25 for Fe{sup 3+} and at pH {approx}4 for Al{sup 3+}), suggesting the formation of Fe and Al (hydr)oxides as two separate phases. The Al content of initial coprecipitates influenced the extent of ferrihydrite transformation and of its transformation products as indicated by the presence of goethite, hematite and/or ferrihydrite in aged suspensions. DFT experiments showed that: (i) optimized unit cell parameters for Al-substituted goethites (8 and 25 Mol% Al) in clustered arrangement (i.e., the

  7. Inhibition of trace element release during Fe(II)-activated recrystallization of Al-, Cr-, and Sn-substituted goethite and hematite.

    Science.gov (United States)

    Frierdich, Andrew J; Scherer, Michelle M; Bachman, Jonathan E; Engelhard, Mark H; Rapponotti, Brett W; Catalano, Jeffrey G

    2012-09-18

    Aqueous Fe(II) reacts with Fe(III) oxides by coupled electron transfer and atom exchange (ETAE) resulting in mineral recrystallization, contaminant reduction, and trace element cycling. Previous studies of Fe(II)-Fe(III) ETAE have explored the reactivity of either pure iron oxide phases or those containing small quantities of soluble trace elements. Naturally occurring iron oxides, however, contain substantial quantities of insoluble impurities (e.g., Al) which are known to affect the chemical properties of such minerals. Here we explore the effect of Al(III), Cr(III), and Sn(IV) substitution (1-8 mol %) on trace element release from Ni(II)-substituted goethite and Zn(II)-substituted hematite during reaction with aqueous Fe(II). Fe(II)-activated trace element release is substantially inhibited from both minerals when an insoluble element is cosubstituted into the structure, and the total amount of release decreases exponentially with increasing cosubstituent. The limited changes in surface composition that occur following reaction with Fe(II) indicate that Al, Cr, and Sn do not exsolve from the structure and that Ni and Zn released to solution originate primarily from the bulk rather than the particle exterior (upper ~3 nm). Incorporation of Al into goethite substantially decreases the amount of iron atom exchange with aqueous Fe(II) and, consequently, the amount of Ni release from the structure. This implies that trace element release inhibition caused by substituting insoluble elements results from a decrease in the amount of mineral recrystallization. These results suggest that naturally occurring iron oxides containing insoluble elements are less susceptible to Fe(II)-activated recrystallization and exhibit a greater retention of trace elements and contaminants than pure mineral phases.

  8. Probing the local environment of substitutional Al^{3+} in goethite using X-ray absorption spectroscopy and first-principles calculations

    Science.gov (United States)

    Ducher, Manoj; Blanchard, Marc; Vantelon, Delphine; Nemausat, Ruidy; Cabaret, Delphine

    2016-03-01

    We present experimental and calculated Al K-edge X-ray absorption near-edge structure (XANES) spectra of aluminous goethite with 10-33 mol% of AlOOH and diaspore. Significant changes are observed experimentally in the near- and pre-edge regions with increasing Al concentration in goethite. First-principles calculations based on density functional theory (DFT) reproduce successfully the experimental trends. This permits to identify the electronic and structural parameters controlling the spectral features and to improve our knowledge of the local environment of {Al}^{3+} in the goethite-diaspore partial solid solution. In the near-edge region, the larger peak spacing in diaspore compared to Al-bearing goethite is related to the nature (Fe or Al) of the first cation neighbours around the absorbing Al atom (Al*). The intensity ratio of the two near-edge peaks, which decreases with Al concentration, is correlated with the average distance of the first cations around Al* and the distortion of the {AlO}_6 octahedron. Finally, the decrease in intensity of the pre-edge features with increasing Al concentration is due to the smaller number of Fe atoms in the local environment of Al since Al atoms tend to cluster. In addition, it is found that the pre-edge features of the Al K-edge XANES spectra enable to probe indirectly empty 3 d states of Fe. Energetic, structural and spectroscopic results suggest that for Al concentrations around 10 mol%, Al atoms can be considered as isolated, whereas above 25 mol%, Al clusters are more likely to occur.

  9. Immobilization of 99-Technetium (VII) by Fe(II)-Goethite and Limited Reoxidation

    International Nuclear Information System (INIS)

    Um, Wooyong; Chang, Hyun-Shik; Icenhower, Jonathan P.; Lukens, Wayne W.; Serne, R. Jeffrey; Qafoku, Nikolla; Westsik, Joseph H.; Buck, Edgar C.; Smith, Steven C.

    2011-01-01

    Synthesized goethite was successfully used with addition of Fe(II) to sequester Tc present in both deionized water and simulated off-gas scrubber waste solutions. Pertechnetate concentration in solution decreased immediately when the pH was raised above 7 by addition of sodium hydroxide. Removal of Tc(VII) from solution occurred most likely as a result of heterogeneous surface-catalyzed reduction to Tc(IV) and subsequent co-precipitation onto the goethite. The final Tc-bearing solid was identified as goethite-dominated Fe(III)-(oxy)hydroxide based on XRD analysis, confirming the widespread observation of its characteristic acicular habit by TEM/SEM images. Analysis of the solid precipitate by XAFS showed that the dominant oxidation state of Tc was Tc(IV) and was in octahedral coordination with Tc-O, Fe-O, and Tc-Fe bond distances that are consistent with direct substitution of Tc for Fe in the goethite structure. In some experiments the final Tc-goethite product was subsequently armored with additional layers of freshly precipitated goethite. Successful incorporation of Tc(IV) within the goethite mineral lattice and subsequent goethite armoring can limit re-oxidation of Tc(IV) and its subsequent release from Tc-goethite waste forms, even when the final product is placed in oxidizing environments that typify shallow waste burial facilities.

  10. LDA + U and GGA + U studies of Al-rich and bulk goethite ({alpha}-FeOOH)

    Energy Technology Data Exchange (ETDEWEB)

    Fuente, Silvia A. [INQUISUR, Departamento de Quimica, Universidad Nacional del Sur, Av. Alem 1253, Bahia Blanca B8000CP (Argentina); Belelli, Patricia G., E-mail: pbelelli@plapiqui.edu.ar [IFISUR, Grupo de Materiales y Sistemas Cataliticos, Departamento de Fisica, Universidad Nacional del Sur, Av. Alem 1253, Bahia Blanca B8000CP (Argentina); Castellani, Norberto J. [IFISUR, Grupo de Materiales y Sistemas Cataliticos, Departamento de Fisica, Universidad Nacional del Sur, Av. Alem 1253, Bahia Blanca B8000CP (Argentina); Avena, Marcelo [INQUISUR, Departamento de Quimica, Universidad Nacional del Sur, Av. Alem 1253, Bahia Blanca B8000CP (Argentina)

    2013-01-15

    The electronic and structural properties of bulk goethite and Al-rich goethite were studied on the basis of spin-polarized DFT at the LDA + U and GGA(PW91) + U levels. Firstly, the periodic model of bulk goethite was optimized varying the value of U{sub eff}. Considering all the results obtained we can conclude that the bulk goethite described at the GGA + U level with U{sub eff} = 6 eV gives us the better agreement with different physical properties. The results of magnetic moments of Fe ions, the DOS analysis and the Bader atomic charges identify goethite as an antiferromagnetic Fe(III) compound. For Al-rich goethite the GGA + U (U{sub eff} = 6 eV) approach was used. The isomorphous substitution of one Fe ion with Al ion produces the reduction of the cell parameters with respect to the bulk goethite. Regarding the magnetic ordering, it was observed that Fe atoms surrounding the Al atom must have the same spin projection, i.e., spin-up or -down. The charge density was changed with the addition of Al ion, producing a depletion where the ion is located and some electron redistribution in the zone of the oxygen atoms surrounding the Al ion. This behavior produces some small magnetization in these O ions. -- Highlights: Black-Right-Pointing-Pointer We studied electronic and structural properties of bulk goethite and Al-rich goethite. Black-Right-Pointing-Pointer The goethite is well described with the GGA + U level using the U{sub eff} = 6 eV value. Black-Right-Pointing-Pointer The Al-rich goethite model has different magnetic structures with similar energies. Black-Right-Pointing-Pointer The isomorphic substitution of Fe by Al atom in goethite results in a lattice contraction.

  11. Neptunium speciation in humic acid - goethite system

    International Nuclear Information System (INIS)

    Kalmykov, St.; Khasanova, A.; Shcherbina, N.; Perminova, I.; Schafer, T.; Claret, F.; Teterin, Y.

    2007-01-01

    Full text of publication follows. Humic acids (HA) are known to have significant effect on metal ion speciation in the environment and may either enhance or depress their migration ability depending on geochemical conditions. This study deals with Np(V) behaviour in HA-goethite suspension at different pH values. The HA used in this study were enriched in hydroquinone group content that define their redox properties. The sorption of Np(V) by goethite in the presence of HA was studied in batch mode at pHs from 2.5 to 9. It was established that at low pH values the sorption of Np agrees with the sorption of HA by goethite and was significantly higher than in binary Np-goethite system. The scanning transmission X-ray microscopic (STXM) study done at National Synchrotron Light Source (BNL, USA) was used to characterize humic surface coatings on goethite. According to STXM, organic matter 'hot spots' were observed in the central region of goethite particles. These 'hot spots' revealed high amounts of C=C arom and aliphatic structures, whereas edge regions of goethite particles or the cloudy regions around this particle contained lower amounts of these organic functionalities. The particle edge structures and the surrounding of the particle were enriched in oxygen-containing functional groups. The enhanced Np sorption at low pH values was explained by its reduction to tetravalent state with formation of stable Np(IV) humates that was established by Vis-NIR spectrophotometry for binary Np(V)-HA solutions and XPS for ternary Np-HA-goethite system. At pH > 6 neptunium retention by HA-goethite suspension was slightly lower that in the absence of HA that is due to week Np(V) humic complexation in solution. According to STXM no detection of organics on goethite minerals by carbon K-edge measurements was possible and the results might be interpreted as an absence of organic matter sorption on the mineral phases under the conditions of batch-type studies. The absence of Np

  12. Immobilization and Limited Reoxidation of Technetium-99 by Fe(II)-Goethite

    International Nuclear Information System (INIS)

    Um, Wooyong; Chang, Hyun-shik; Icenhower, Jonathan P.; Qafoku, Nikolla; Smith, Steven C.; Serne, R. Jeffrey; Buck, Edgar C.; Kukkadapu, Ravi K.; Bowden, Mark E.; Westsik, Joseph H.; Lukens, Wayne W.

    2010-01-01

    -ray diffraction analysis. The presence of goethite in final Tc-goethite Sample 2-5 was also confirmed with the widespread observation of its characteristic acicular (needle-shaped) habit in transmission electron microscopy/scanning electron microscopy images. No Fe-carbonate minerals were found in any Tc-goethite samples, even in the experiments conducted with Tc-laden off-gas scrubber waste simulant containing high concentrations of ammonium carbonate. Analysis of the solid precipitate using x-ray absorption fine structure spectroscopy showed that the dominant oxidation state of Tc in the final Tc-goethite solid product was Tc(IV). Further, the Tc(IV) was in octahedral coordination with Tc-O, Fe-O, and Tc-Fe inter-atomic distances that are consistent with direct substitution of Tc for Fe in the magnetite or goethite structure. Powdered solids and monolithic cylindrical pellets of Tc-goethite were exposed to dilute leaching solutions (buffered at pH values of 4, 7, and 10), synthetic Hanford vadose zone pore water (pH = 7.2 and I = 0.05 M), and Integrated Disposal Facility glass leachate solution (pH = 9.7 and I = 1.67 M), simulating geochemical conditions in the postulated waste disposal vault for up to 180 days in static batch reactors. Although Tc-sequestered goethite samples were exposed to various fluids and different leaching conditions (air and water), the reduced Tc(IV) was not reoxidized to Tc(VII), even after 180 days of reaction in both solution and air conditions. In the circumneutral Hanford pore water solution, the concentration of leached Tc from the goethite pellet was very low, and an effective diffusion coefficient of 6.15 x 10 -11 cm 2 /s was calculated. Successful incorporation of Tc(IV) within the goethite mineral lattice and subsequent goethite armoring, as prepared for Sample 2-5, limited reoxidation of Tc(IV) and its subsequent release from the Tc-goethite waste form, even when the final product was placed in oxidizing environments that typify shallow

  13. Stable magnetic remanence in antiferromagnetic goethite.

    Science.gov (United States)

    Strangway, D W; McMahon, B E; Honea, R M

    1967-11-10

    Goethite, known to be antiferromagnetic, acquires thermoremanent magnetization at its Neel temperature of 120 degrees C. This remanence, extremely stable, is due to the presence of unbalanced spins in the antiferromagnetic structure; the spins may result from grain size, imperfections, or impurities.

  14. Adsorption of fulvic acid on goethite

    Science.gov (United States)

    Filius, Jeroen D.; Lumsdon, David G.; Meeussen, Johannes C. L.; Hiemstra, Tjisse; Van Riemsdijk, Willem H.

    2000-01-01

    The adsorption of fulvic acid by goethite was determined experimentally as a function of concentration, pH, and ionic strength. The data were described with the CD-MUSIC model of Hiemstra and Van Riemsdijk (1996), which allows the distribution of charge of the bound fulvate molecule over a surface region. Simultaneously, the concentration, pH, and salt dependency of the binding of fulvic acid can be described. Using the same parameters, the basic charging behavior of the goethite in the absence of fulvic acid could be described well. The surface species used in the model indicate that inner sphere coordination of carboxylic groups of the fulvate molecule is important at low pH, whereas at high pH the outer sphere coordination with reactive groups of the fulvate molecule with high proton affinity is important.

  15. Fractionation of humic acid upon adsorption to goethite

    NARCIS (Netherlands)

    Qin, Xiaopeng; Liu, Fei; Wang, Guangcai; Hou, Hong; Li, Fasheng; Weng, Liping

    2015-01-01

    The fractionation and replacement of humic acid (HA) during its interactions with goethite (or goethite-coated sand) were conducted using batch and column experiments. The weight-average molecular weight (Mw) of HA in solutions was determined by a high performance size exclusion chromatography

  16. Anisotropic Morphological Changes in Goethite during Fe(2+)-Catalyzed Recrystallization.

    Science.gov (United States)

    Joshi, Prachi; Gorski, Christopher A

    2016-07-19

    When goethite is exposed to aqueous Fe(2+), rapid and extensive Fe atom exchange can occur between solid-phase Fe(3+) and aqueous Fe(2+) in a process referred to as Fe(2+)-catalyzed recrystallization. This process can lead to the structural incorporation or release of trace elements, which has important implications for contaminant remediation and nutrient biogeochemical cycling. Prior work found that the process did not cause major changes to the goethite structure or morphology. Here, we further investigated if and how goethite morphology and aggregation behavior changed temporally during Fe(2+)-catalyzed recrystallization. On the basis of existing literature, we hypothesized that Fe(2+)-catalyzed recrystallization of goethite would not result in changes to individual particle morphology or interparticle interactions. To test this, we reacted nanoparticulate goethite with aqueous Fe(2+) at pH 7.5 over 30 days and used transmission electron microscopy (TEM), cryogenic TEM, and (55)Fe as an isotope tracer to observe changes in particle dimensions, aggregation, and isotopic composition over time. Over the course of 30 days, the goethite particles substantially recrystallized, and the particle dimensions changed anisotropically, resulting in a preferential increase in the mean particle width. The temporal changes in goethite morphology could not be completely explained by a single mineral-transformation mechanism but rather indicated that multiple transformation mechanisms occurred concurrently. Collectively, these results demonstrate that the morphology of goethite nanoparticles does change during recrystallization, which is an important step toward identifying the driving force(s) of recrystallization.

  17. Off-axis spin orientation in goethite nanoparticles

    DEFF Research Database (Denmark)

    Brok, Erik; Lefmann, Kim; Nilsen, Gøran Jan

    2017-01-01

    Neutron diffraction is a powerful technique for determining the magnetic structure of antiferromagnetic materials. However, for some of these, determining the detailed magnetic structure remains a challenge. In goethite (α-FeOOH) the antiferromagnetic unit cell coincides with the chemical unit cell...... structure of goethite has been challenging, and few detailed studies have been published. Even today, not all aspects of the magnetic structure are well established. Here, we investigate the magnetic structure of three samples of goethite nanoparticles with polarized neutron powder diffraction (xyz...... and, consequently, nuclear and magnetic diffraction peaks occur at the same positions. Analysis of diffraction data from goethite is further complicated by finite-size peak broadening, resulting from goethite commonly occurring in nanocrystalline form. For these reasons, determining the magnetic...

  18. Photodegradation of aniline by goethite doped with boron under ultraviolet and visible light irradiation

    International Nuclear Information System (INIS)

    Liu, Guanglong; Liao, Shuijiao; Zhu, Duanwei; Liu, Linghua; Cheng, Dongsheng; Zhou, Huaidong

    2011-01-01

    Highlights: → Goethite modified by boron was prepared by sol-gel method in presence of boron acid at the low temperature. → B-goethite has slight red shift in the band gap transition beside their stronger light absorption compared with pristine goethite. → The results showed that semiconductor photocatalytic reaction mechanism should exist in the process of aniline degradation with goethite and B-goethite as photocatalyst. -- Abstract: In the present study, goethite and goethite doped with boron (B-goethite) were employed to detect the presence or absence of semiconductor photocatalytic reaction mechanism in the reaction systems. B-goethite was prepared by sol-gel method in presence of boron acid in order to improve its photocatalystic efficiency under the ultraviolet and visible light irradiation. The optical properties of goethite and B-goethite were characterized by ultraviolet and visible absorption spectra and the result indicated that B-goethite has slight red shift in the band gap transition beside their stronger light absorption compared with pristine goethite. Degradation of aniline was investigated in presence of goethite and B-goethite in aqueous solution. It was found that the B-goethite photocatalyst exhibited enhanced ultraviolet and visible light photocatalytic activity in degradation of aniline compared with the pristine goethite. The photocatalytic degradation mechanism of B-goethite was discussed.

  19. Effect of equilibration time on Pu desorption from goethite

    International Nuclear Information System (INIS)

    Wong, Jennifer C.; Powell, Brian A.; Zavarin, Mavrik; Begg, James D.; Kersting, Annie B.

    2015-01-01

    It has been suggested that strongly sorbing ions such as plutonium may become irreversibly bound to mineral surfaces over time which has implications for near- and far-field transport of Pu. Batch adsorption-desorption data were collected as a function of time and pH to study the surface stability of Pu on goethite. Pu(IV) was adsorbed to goethite over the pH range 4.2 to 6.6 for different periods of time (1, 6, 15, 34 and 116 d). Following adsorption, Pu was leached from the mineral surface with desferrioxamine B (DFOB), a complexant capable of effectively competing with the goethite surface for Pu. The amount of Pu desorbed from the goethite was found to vary as a function of the adsorption equilibration time, with less Pu removed from the goethite following longer adsorption periods. This effect was most pronounced at low pH. Logarithmic desorption distribution ratios for each adsorption equilibration time were fit to a pH-dependent model. Model slopes decreased between 1 and 116 d adsorption time, indicating that overall Pu(IV) surface stability on goethite surfaces becomes less dependent on pH with greater adsorption equilibration time. The combination of adsorption and desorption kinetic data suggest that non-redox aging processes affect Pu sorption behavior on goethite.

  20. Magnetic properties of ultra-small goethite nanoparticles

    DEFF Research Database (Denmark)

    Brok, Erik; Frandsen, Cathrine; Madsen, Daniel Esmarch

    2014-01-01

    Goethite (α-FeOOH) is a common nanocrystalline antiferromagnetic mineral. However, it is typically difficult to study the properties of isolated single-crystalline goethite nanoparticles, because goethite has a strong tendency to form particles of aggregated nanograins often with low-angle grain...... boundaries. This nanocrystallinity leads to complex magnetic properties that are dominated by magnetic fluctuations in interacting grains. Here we present a study of the magnetic properties of 5.7 nm particles of goethite by use of magnetization measurements, inelastic neutron scattering and Mo...... temperatures most likely due to freezing of spins in canted spin structures. From hysteresis curves we estimate the saturation magnetization from uncompensated magnetic moments to be σs = 0.044 A m2 kg-1 at room temperature. Inelastic neutron scattering measurements show a strong signal from excitations...

  1. Structure of titanium-doped goethite rust

    International Nuclear Information System (INIS)

    Nakayama, Takenori; Ishikawa, Tatsuo; Konno, Toyohiko J.

    2005-01-01

    To investigate the influence of titanium addition on the formation and structure of goethite (α-FeOOH) rust which is one of main corrosion products of weathering steel, the artificially synthesized α-FeOOH rusts were prepared by hydrolysis of aqueous solutions of Fe(III) containing Ti(IV) at different atomic ratios (Ti/Fe) in the range 0-0.1. The obtained rusts particles were observed by TEM. Characterization by XRD, N 2 absorption, Moessbauer spectroscopy was also done. TEM observation revealed that the α-FeOOH rust particle size increased with the increase of Ti/Fe, and that Ti-enriched poorly crystalline particles were formed around the rust particles. XRD confirmed that the crystallite size increased with the increase of Ti/Fe, while the XRD peaks decreased in intensity. Specific surface area obtained by N 2 absorption increased with the increase of Ti/Fe. It is deduced from the obtained results that the addition of Ti(IV) increases the crystallite size of α-FeOOH, and produces double domain particles consisting of the particle core and a porous poorly crystalline shell. It is thought that such unique rust structure produced by titanium addition contributes to the protective properties of rust layer of the weathering steel

  2. Susceptibility of Goethite to Fe2+-Catalyzed Recrystallization over Time.

    Science.gov (United States)

    Joshi, Prachi; Fantle, Matthew S; Larese-Casanova, Philip; Gorski, Christopher A

    2017-10-17

    Recent work has shown that iron oxides, such as goethite and hematite, may recrystallize in the presence of aqueous Fe 2+ under anoxic conditions. This process, referred to as Fe 2+ -catalyzed recrystallization, can influence water quality by causing the incorporation/release of environmental contaminants and biological nutrients. Accounting for the effects of Fe 2+ -catalyzed recrystallization on water quality requires knowing the time scale over which recrystallization occurs. Here, we tested the hypothesis that nanoparticulate goethite becomes less susceptible to Fe 2+ -catalyzed recrystallization over time. We set up two batches of reactors in which 55 Fe 2+ tracer was added at two different time points and tracked the 55 Fe partitioning in the aqueous and goethite phases over 60 days. Less 55 Fe uptake occurred between 30 and 60 days than between 0 and 30 days, suggesting goethite recrystallization slowed with time. Fitting the data with a box model indicated that 17% of the goethite recrystallized after 30 days of reaction, and an additional 2% recrystallized between 30 and 60 days. The decreasing susceptibility of goethite to recrystallize as it reacted with aqueous Fe 2+ suggested that recrystallization is likely only an important process over short time scales.

  3. Surface properties and phosphate adsorption of binary systems containing goethite and kaolinite

    NARCIS (Netherlands)

    Wei, S.Y.; Tan, W.F.; Liu, F.; Zhao, W.; Weng, L.

    2014-01-01

    In soils goethite and kaolinite are often cemented together as a binary association, which has a significant influence on the physical and chemical properties of soils. In this study, the surface properties and phosphate adsorption of goethite, kaolinite, goethite-kaolinite association (GKA) and

  4. Liquid crystal phase behavior of sterically-stabilized goethite

    NARCIS (Netherlands)

    van den Pol, Esther; Petukhov, Andrei V.; Thies-Weesie, Dominique M.E.; Byelov, Dmytro V.; Vroege, Gert J.

    2010-01-01

    The liquid crystalline phase behavior of sterically-stabilized goethite particles in toluene was studied using small-angle X-ray scattering. The results were compared with those from charged particles in water, with and without magnetic field: similarly rich phase behavior was found. Furthermore,

  5. Competitive adsorption and photodegradation of salicylate and oxalate on goethite

    Czech Academy of Sciences Publication Activity Database

    Krýsa, J.; Jirkovský, Jaromír; Bajt, O.; Mailhot, G.

    2011-01-01

    Roč. 161, č. 1 (2011), s. 221-227 ISSN 0920-5861 R&D Projects: GA MŠk 1M0577 Institutional research plan: CEZ:AV0Z40400503 Keywords : goethite * oxalate * salicylate Subject RIV: CG - Electrochemistry Impact factor: 3.407, year: 2011

  6. Thermal treatment of natural goethite: Thermal transformation and physical properties

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Haibo [Laboratory for Nanomineralogy and Environmental Material, School of Resources and Environmental Engineering, Hefei University of Technology (China); School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology (Australia); Chen, Tianhu, E-mail: chentianhu@hfut.edu.cn [Laboratory for Nanomineralogy and Environmental Material, School of Resources and Environmental Engineering, Hefei University of Technology (China); Zou, Xuehua; Qing, Chengsong [Laboratory for Nanomineralogy and Environmental Material, School of Resources and Environmental Engineering, Hefei University of Technology (China); Frost, Ray L., E-mail: r.frost@qut.edu.au [School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology (Australia)

    2013-09-20

    Highlights: • We have characterized the thermal transformation of natural goethite. • The heated products showed a topotactical relationship to the original mineral. • The N2 adsorption isotherm provided the variation of surface area and pore size distribution with temperature. • The significant increase in surface area was attributed to the formation of regularly arranged slit-shaped micropores. • The hematite derived from heating goethite has application as an adsorbent and catalyst. - Abstract: XRD (X-ray diffraction), XRF (X-ray fluorescence), TG (thermogravimetry), FT-IES (Fourier transform infrared emission spectroscopy), FESEM (field emission scanning electron microscope), TEM (transmission electron microscope) and nitrogen–adsorption–desorption analysis were used to characterize the composition and thermal evolution of the structure of natural goethite. The in situ FT-IES demonstrated the start temperature (250 °C) of the transformation of natural goethite to hematite and the thermodynamic stability of protohematite between 250 and 600 °C. The heated products showed a topotactic relationship to the original mineral based on SEM analysis. Finally, the nitrogen–adsorption–desorption isotherm provided the variation of surface area and pore size distribution as a function of temperature. The surface area displayed a remarkable increase up to 350 °C, and then decreased above this temperature. The significant increase in surface area was attributed to the formation of regularly arranged slit-shaped micropores running parallel to elongated direction of hematite microcrystal. The main pore size varied from 0.99 nm to 3.5 nm when heating temperature increases from 300 to 400 °C. The hematite derived from heating goethite possesses high surface area and favors the possible application of hematite as an adsorbent as well as catalyst carrier.

  7. Thermal treatment of natural goethite: Thermal transformation and physical properties

    International Nuclear Information System (INIS)

    Liu, Haibo; Chen, Tianhu; Zou, Xuehua; Qing, Chengsong; Frost, Ray L.

    2013-01-01

    Highlights: • We have characterized the thermal transformation of natural goethite. • The heated products showed a topotactical relationship to the original mineral. • The N2 adsorption isotherm provided the variation of surface area and pore size distribution with temperature. • The significant increase in surface area was attributed to the formation of regularly arranged slit-shaped micropores. • The hematite derived from heating goethite has application as an adsorbent and catalyst. - Abstract: XRD (X-ray diffraction), XRF (X-ray fluorescence), TG (thermogravimetry), FT-IES (Fourier transform infrared emission spectroscopy), FESEM (field emission scanning electron microscope), TEM (transmission electron microscope) and nitrogen–adsorption–desorption analysis were used to characterize the composition and thermal evolution of the structure of natural goethite. The in situ FT-IES demonstrated the start temperature (250 °C) of the transformation of natural goethite to hematite and the thermodynamic stability of protohematite between 250 and 600 °C. The heated products showed a topotactic relationship to the original mineral based on SEM analysis. Finally, the nitrogen–adsorption–desorption isotherm provided the variation of surface area and pore size distribution as a function of temperature. The surface area displayed a remarkable increase up to 350 °C, and then decreased above this temperature. The significant increase in surface area was attributed to the formation of regularly arranged slit-shaped micropores running parallel to elongated direction of hematite microcrystal. The main pore size varied from 0.99 nm to 3.5 nm when heating temperature increases from 300 to 400 °C. The hematite derived from heating goethite possesses high surface area and favors the possible application of hematite as an adsorbent as well as catalyst carrier

  8. Oxygen reduction and evolution at single-metal active sites

    DEFF Research Database (Denmark)

    Calle-Vallejo, F.; Martínez, J.I.; García Lastra, Juan Maria

    2013-01-01

    overpotentials and is made of precious materials. A possible solution is the use of non-noble electrocatalysts with single-metal active sites. Here, on the basis of DFT calculations of adsorbed intermediates and a thermodynamic analysis, we compare the oxygen reduction (ORR) and evolution (OER) activities...... of functionalized graphitic materials and gas-phase porphyrins with late transition metals. We find that both kinds of materials follow approximately the same activity trends, and active sites with transition metals from groups 7 to 9 may be good ORR and OER electrocatalysts. However, spin analyses show more...... flexibility in the possible oxidation states of the metal atoms in solid electrocatalysts, while in porphyrins they must be +2. These observations reveal that the catalytic activity of these materials is mainly due to nearest-neighbor interactions. Based on this, we propose that this class of electrocatalysts...

  9. Mechanism of Non-Steady State Dissolution of Goethite in the Presence of Siderophores

    Science.gov (United States)

    Reichard, P. U.; Kretzschmar, R.; Kraemer, S. M.

    2003-12-01

    reproducible and the magnitude of dissolved iron corresponds to the reaction time of goethite with oxalate. Analogous non-steady state experiments were conducted, but with two other siderophores or citrate to induce non-steady state conditions: 40 microM of the bacterial siderophore desferrioxamine B (DFO-B), 40 microM of the fungal siderophore Ferrichrome, and 3 mM of citrate. Fast dissolution of iron was observed as a response to non-steady state. We also substituted the non-siderophore ligand oxalate by 500 microM citrate or 750 microM malonate and again observed fast dissolution after the non-steady state siderophore additions. Independent of the type of the ligands, a reproducible fast dissolution of iron followed by steady state dissolution was observed after the addition of the non-steady state ligand concentrations. Thus it can be said that the reproducible fast dissolution of iron under non-steady state conditions represents a general geochemical mechanism and an important process in the context of biological iron acquisition in natural systems. References Marschner, H., Roemheld, V. et al. (1986). "Different Strategies in Higher-Plants in Mobilization and Uptake of Iron". Journal of Plant Nutrition 9(3-7): 695-713. Roemheld, V. and Marschner, H. (1986)." Evidence for a Specific Uptake System for Iron Phytosiderophore in Roots of Grasses". Plant Physiology 80(1): 175-180.

  10. Magnetic properties of ultra-small goethite nanoparticles

    Science.gov (United States)

    Brok, E.; Frandsen, C.; Madsen, D. E.; Jacobsen, H.; Birk, J. O.; Lefmann, K.; Bendix, J.; Pedersen, K. S.; Boothroyd, C. B.; Berhe, A. A.; Simeoni, G. G.; Mørup, S.

    2014-09-01

    Goethite (α-FeOOH) is a common nanocrystalline antiferromagnetic mineral. However, it is typically difficult to study the properties of isolated single-crystalline goethite nanoparticles, because goethite has a strong tendency to form particles of aggregated nanograins often with low-angle grain boundaries. This nanocrystallinity leads to complex magnetic properties that are dominated by magnetic fluctuations in interacting grains. Here we present a study of the magnetic properties of 5.7 nm particles of goethite by use of magnetization measurements, inelastic neutron scattering and Mössbauer spectroscopy. The ‘ultra-small’ size of these particles (i.e. that the particles consist of one or only a few grains) allows for more direct elucidation of the particles' intrinsic magnetic properties. We find from ac and dc magnetization measurements a significant upturn of the magnetization at very low temperatures most likely due to freezing of spins in canted spin structures. From hysteresis curves we estimate the saturation magnetization from uncompensated magnetic moments to be σs = 0.044 A m2 kg-1 at room temperature. Inelastic neutron scattering measurements show a strong signal from excitations of the uniform mode (q = 0 spin waves) at temperatures of 100-250 K and Mössbauer spectroscopy studies show that the magnetic fluctuations are dominated by ‘classical’ superparamagnetic relaxation at temperatures above ˜170 K. From the temperature dependence of the hyperfine fields and the excitation energy of the uniform mode we estimate a magnetic anisotropy constant of around 1.0 × 105 J m-3.

  11. Adsorption behavior and mechanism of glufosinate onto goethite.

    Science.gov (United States)

    Xu, Jian; Gu, Xueyuan; Guo, Yong; Tong, Fei; Chen, Liangyan

    2016-08-01

    The adsorption of glufosinate (GLU), a widely used herbicide similar to glyphosate (GLY), onto goethite was investigated as a function of the pH, ionic strength, background cations and anions, heavy metal ions and fulvic acids (FAs) by using batch adsorption experiments. In situ ATR-FTIR spectroscopy and density functional theory (DFT) calculations were carried out to characterize the molecular interactions between GLU and goethite surfaces. The macroscopic results indicated that an increasing pH exerted an adverse effect on GLU adsorption because of the electrostatic repulsion, and the adsorption was not sensitive to ionic strengths or background cation types, indicating that an inner-sphere surface complex was involved. GLU adsorption can be considerably depressed by PO4(3-), SO4(2-), and a high level of FA because of the competitive effect, while being enhanced by Cu(2+) with a maximum adsorption at approximately pH5 because of the metal ion bridging effect. Other examined divalent metal cations (Cd(2+), Zn(2+), and Pb(2+)) showed almost no effect on GLU adsorption, indicating weak interaction between them. ATR-FTIR spectra and the DFT calculations further proved that GLU was bonded to goethite surfaces through the formation of a monodentate mononuclear inner-sphere complex between the phosphinic moiety and surface Fe(III) centers under an acidic condition. The results showed that GLU had a similar adsorption mechanism to that of GLY onto goethite, but with a lower adsorption affinity, possibly exerting higher mobility and risk in soils. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Water adsorption on goethite: Application of multilayer adsorption models

    Science.gov (United States)

    Hatch, C. D.; Tumminello, R.; Meredith, R.

    2016-12-01

    Adsorbed water on the surface of atmospheric mineral dust has recently been shown to significantly affect the ability of mineral dust aerosol to act as cloud condensation nuclei. We have studied water adsorption as a function of relative humidity (RH) on goethite (α-FeO(OH)), a common component of atmospheric mineral dust. The goethite surface area and particle size was determined using BET analysis and with N2 as an adsorbate and scanning electron microscopy, respectively. Water adsorption on the sample was monitored using horizontal attenuated total reflectance Fourier transform infrared (HATR-FTIR) spectroscopy equipped with a flow cell. Water content was determined using Beer's law and the optical constants for bulk water. The results were analyzed using Type II adsorption isotherms to model multilayer adsorption, including BET (Brunauer, Emmet and Teller), FHH (Frenkel, Halsey and Hill) and Freundlich. BET fits to experimental data provide parameters of monolayer coverage, while the FHH and Freundlich isotherms provide insights into multilayer adsorption mechanisms. Results indicate that goethite contains 5% H2O by mass at 50% RH, which increases to 12% by mass at 90% RH. Adsorption parameters and experimental results will be presented.

  13. Mineral transformations associated with goethite reduction by Methanosarcina barkeri

    Science.gov (United States)

    Liu, D.; Wang, Hongfang; Dong, H.; Qiu, X.; Dong, X.; Cravotta, C.A.

    2011-01-01

    To investigate the interaction between methanogens and iron-containing minerals in anoxic environments, we conducted batch culture experiments with Methanosarcina barkeri in a phosphate-buffered basal medium (PBBM) to bioreduce structural Fe(III) in goethite with hydrogen as the sole substrate. Fe(II) and methane concentrations were monitored over the course of the bioreduction experiments with wet chemistry and gas chromatography, respectively. Subsequent mineralogical changes were characterized with X-ray diffraction (XRD) and scanning electron microscopy (SEM). In the presence of an electron shuttle anthraquinone-2,6-disulfonate (AQDS), 30% Fe(III) in goethite (weight basis) was reduced to Fe(II). In contrast, only 2% Fe(III) (weight basis) was bioreduced in the absence of AQDS. Most of the bioproduced Fe(II) was incorporated into secondary minerals including dufr??nite and vivianite. Our data implied a dufr??nite-vivianite transformation mechanism where a metastable dufr??nite transformed to a more stable vivianite over extended time in anaerobic conditions. Methanogenesis was greatly inhibited by bioreduction of goethite Fe(III). These results have important implications for the methane flux associated with Fe(III) bioreduction and ferrous iron mineral precipitation in anaerobic soils and sediments. ?? 2011 Elsevier B.V.

  14. Mutual effects of cadmium and phosphate on their adsorption and desorption by goethite

    International Nuclear Information System (INIS)

    Wang, Kaijun; Xing, Baoshan

    2004-01-01

    Cd and phosphate have mutual influences on their sorption kinetics. - Adsorption of cadmium (Cd) and phosphate by oxides or soils has been extensively studied, but the adsorption/desorption kinetics and mutual effects of these two species in co-existing systems has received little attention. In this study, a batch equilibration method was used to investigate the effect of phosphate and its application time on Cd adsorption and desorption on goethite. The influence of Cd and its application time on phosphate sorption and desorption kinetics was also determined. For Cd adsorption, phosphate was introduced into the system by two sequences: pre-treating goethite at 40 deg. C for 1 week, and applying with Cd simultaneously. Similarly, for phosphate sorption, Cd was applied by pre-treating goethite at 40 deg. C for 1 week or simultaneous addition with phosphate. Results demonstrated that phosphate added to goethite enhanced Cd adsorption, and facilitated Cd release as compared to untreated goethite. Cadmium had slightly higher adsorption, but a significantly faster desorption rate from the goethite simultaneously treated with phosphate and Cd, as compared to phosphate-pretreated goethite. Cadmium and its application time had little impact on phosphate sorption by goethite. However, phosphate desorption kinetics was affected by Cd application time. When the sorption time was short (15 min), phosphate desorption was faster from the goethite that was simultaneously treated with phosphate and Cd, as compared to Cd pretreated or untreated goethite. In contrast, a longer sorption time (4 weeks) resulted in a higher desorption rate of phosphate from Cd pretreated goethite than simultaneously phosphate-Cd treated goethite. This study provided useful information on adsorption/desorption kinetics in complicated Cd-phosphate-goethite systems

  15. Gallium isotope fractionation during Ga adsorption on calcite and goethite

    Science.gov (United States)

    Yuan, Wei; Saldi, Giuseppe D.; Chen, JiuBin; Vetuschi Zuccolini, Marino; Birck, Jean-Louis; Liu, Yujie; Schott, Jacques

    2018-02-01

    Gallium (Ga) isotopic fractionation during its adsorption on calcite and goethite was investigated at 20 °C as a function of the solution pH, Ga aqueous concentration and speciation, and the solid to solution ratio. In all experiments Ga was found to be enriched in light isotopes at the solid surface with isotope fractionation △71Gasolid-solution up to -1.27‰ and -0.89‰ for calcite and goethite, respectively. Comparison of Ga isotopic data of this study with predictions for 'closed system' equilibrium and 'Rayleigh fractionation' models indicates that the experimental data are consistent with a 'closed system' equilibrium exchange between the fluid and the solid. The results of this study can be interpreted based on Ga aqueous speciation and the structure of Ga complexes formed at the solid surfaces. For calcite, Ga isotope fractionation is mainly triggered by increased Ga coordination and Ga-O bond length, which vary respectively from 4 and 1.84 Å in Ga(OH)4- to 6 and 1.94 Å in the >Ca-O-GaOH(OH2)4+ surface complex. For goethite, despite the formation of Ga hexa-coordinated >FeOGa(OH)20 surface complexes (Ga-O distances of 1.96-1.98 Å) both at acid and alkaline pH, a similar extent of isotope fractionation was found at acid and alkaline pH, suggesting that Ga(OH)4- is preferentially adsorbed on goethite for all investigated pH conditions. In addition, the observed decrease of Ga isotope fractionation magnitude observed with increasing Ga surface coverage for both calcite and goethite is likely related to the formation of Ga surface polymers and/or hydroxides with reduced Ga-O distances. This first study of Ga isotope fractionation during solid-fluid interactions suggests that the adsorption of Ga by oxides, carbonates or clay minerals could yield significant Ga isotope fractionation between secondary minerals and surficial fluids including seawater. Ga isotopes thus should help to better characterize the surficial biogeochemical cycles of gallium and its

  16. Goethite Bench-scale and Large-scale Preparation Tests

    Energy Technology Data Exchange (ETDEWEB)

    Josephson, Gary B.; Westsik, Joseph H.

    2011-10-23

    The Hanford Waste Treatment and Immobilization Plant (WTP) is the keystone for cleanup of high-level radioactive waste from our nation's nuclear defense program. The WTP will process high-level waste from the Hanford tanks and produce immobilized high-level waste glass for disposal at a national repository, low activity waste (LAW) glass, and liquid effluent from the vitrification off-gas scrubbers. The liquid effluent will be stabilized into a secondary waste form (e.g. grout-like material) and disposed on the Hanford site in the Integrated Disposal Facility (IDF) along with the low-activity waste glass. The major long-term environmental impact at Hanford results from technetium that volatilizes from the WTP melters and finally resides in the secondary waste. Laboratory studies have indicated that pertechnetate ({sup 99}TcO{sub 4}{sup -}) can be reduced and captured into a solid solution of {alpha}-FeOOH, goethite (Um 2010). Goethite is a stable mineral and can significantly retard the release of technetium to the environment from the IDF. The laboratory studies were conducted using reaction times of many days, which is typical of environmental subsurface reactions that were the genesis of this new process. This study was the first step in considering adaptation of the slow laboratory steps to a larger-scale and faster process that could be conducted either within the WTP or within the effluent treatment facility (ETF). Two levels of scale-up tests were conducted (25x and 400x). The largest scale-up produced slurries of Fe-rich precipitates that contained rhenium as a nonradioactive surrogate for {sup 99}Tc. The slurries were used in melter tests at Vitreous State Laboratory (VSL) to determine whether captured rhenium was less volatile in the vitrification process than rhenium in an unmodified feed. A critical step in the technetium immobilization process is to chemically reduce Tc(VII) in the pertechnetate (TcO{sub 4}{sup -}) to Tc(Iv)by reaction with the

  17. A study of sorption of cadmium by goethite in aqueous solution

    Directory of Open Access Journals (Sweden)

    N. Salami

    2002-06-01

    Full Text Available Investigation has been carried out on the potential of a locally sourced goethite for the removal of cadmium ion from aqueous solutions using batch equilibration technique. The maximum uptake of cadmium is 6.4  10-2 mg/g-goethite. The sorption kinetics appears to be rapid as equilibrium was attained within a period of 1 hour. The highest sorption capacity was obtained for particle size with diameter (Φ 0.09 mm. Both infrared spectrophotometric and X-ray diffraction (XRD techniques have also provided evidence for cadmium fixation on to the surface of the goethite. The sorption mechanism appears to follow Langmuir adsorption isotherm model. The Langmuir constants K and Xm (mass of Cd2+ required to form monolayer on the entire surface of the goethite were 0.096 mg/g-goethite and 0.075 mg/g-goethite, respectively.

  18. Reductive Dissolution of Goethite and Hematite by Reduced Flavins

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Zhi; Zachara, John M.; Wang, Zheming; Shi, Liang; Fredrickson, Jim K.

    2013-10-02

    The abiotic reductive dissolution of goethite and hematite by the reduced forms of flavin mononucleotide (FMNH2) and riboflavin (RBFH2), electron transfer mediators (ETM) secreted by the dissimilatory iron-reducing bacterium Shewanella, was investigated under stringent anaerobic conditions. In contrast to the rapid redox reaction rate observed for ferrihydrite and lepidocrocite (Shi et al., 2012), the reductive dissolution of crystalline goethite and hematite was slower, with the extent of reaction limited by the thermodynamic driving force at circumneutral pH. Both the initial reaction rate and reaction extent increased with decreasing pH. On a unit surface area basis, goethite was less reactive than hematite between pH 4.0 and 7.0. AH2DS, the reduced form of the well-studied synthetic ETM anthraquinone-2,6-disulfonate (AQDS), yielded higher rates than FMNH2 under most reaction conditions, despite the fact that FMNH2 was a more effective reductant than AH2DS for ferryhydrite and lepidocrocite. Two additional model compounds, methyl viologen and benzyl viologen, were investigated under similar reaction conditions to explore the relationship between reaction rate and thermodynamic properties. Relevant kinetic data from the literature were also included in the analysis to span a broad range of half-cell potentials. Other conditions being equal, the surface area normalized initial reaction rate (ra) increased as the redox potential of the reductant became more negative. A non-linear, parabolic relationship was observed between log ra and the redox potential for eight reducants at pH 7.0, as predicted by Marcus theory for electron transfer. When pH and reductant concentration were fixed, log ra was positively correlated to the redox potential of four Fe(III) oxides over a wide pH range, following a non-linear parabolic relationship as well.

  19. Adsorption of lanthanum to goethite in the presence of gluconate

    Energy Technology Data Exchange (ETDEWEB)

    Hull, Laurence C.; Sarah Pepper; Sue Clark

    2005-05-01

    Adsorption of Lanthanum to Goethite in the Presence of Gluconic Acid L. C. HULL,1 S. E. PEPPER2 AND S. B. CLARK2 1Idaho National Engineering and Environmental Laboratory, Idaho Falls, ID (hulllc@inel.gov) 2Washington State University, Pullman, WA (spepper@wsu.edu), (s_clark@wsu.edu) Lanthanide and trivalent-actinide elements in radioactive waste can pose risks to humans and ecological systems for many years. Organic complexing agents, from natural organic matter or the degradation of waste package components, can alter the mobility of these elements. We studied the effect of gluconic acid, as an analogue for cellulose degradation products, on the adsorption of lanthanum, representing lanthanide and trivalent-actinide elments, to goethite, representing natural iron minearals and degradation products of waste packages. Batch pH adsorption edge experiments were conducted with lanthanum alone, and with lanthanum and gluconate at a 1:1 mole ratio. Lanthanum concentrations studied were 0.1, 1, and 10 mM, covering a range from 10% to 1000% of the calculated available adsorption sites on goethite. In the absence of gluconate, lanthanum was primarily present in solution as free lanthanum ion. With gluconate present, free lanthanum concentration in solution decreased with increasing pH as step-wise deprotonation of the gluconate molecule increased the fraction lanthanum complexed with gluconate. Adsorption to the goethite surface was represented with the diffuse double-layer model. The number of adsorption sites and the intrinsic binding constants for the surface complexes were estimated from the pH adsorption edge data using the computer code FITEQL 4.0. Two surface reactions were used to fit the adsorption data in the absence of gluconate. A strong binding site with no proton release and a much higher concentration of weak binding sites with release of two protons per lanthanum adsorbed. The adsorption of lanthanum was not measurably affected by the presence of gluconate

  20. The transformation of ferrihydrite into goethite or hematite, revisited

    International Nuclear Information System (INIS)

    Cudennec, Yannick; Lecerf, Andre

    2006-01-01

    During the oxidation of iron, poorly crystallized phases are firstly formed: 2- and 6-line ferrihydrite, which presents for the last phase, a similarity with wustite FeO but also with hematite α-Fe 2 O 3 . Crystallization increases with time and the solid phase obtained is dependent on temperature and pH. Obviously, high temperature favours the formation of the oxide hematite α-Fe 2 O 3 . As for the pH factor, it is more complicated. Low and high values of pH (2-5 and 10-14) favour the formation of goethite α-FeOOH, while obtaining hematite is favoured at neutral pH (values around 7). Goethite or hematite are obtained either through a dissolution-crystallization process or in the solid state, through a topotactic transformation. Given the structural relationships observed between ferrihydrite and wustite and hematite, it is allowed to think that a structural continuity could exist between wustite Fe (1- x ) O and hematite via ferrihydrite

  1. Adsorption of levofloxacin onto goethite: Effects of pH, calcium and phosphate

    NARCIS (Netherlands)

    Qin, X.P.; Liu, F.; Wang, G.C.; Weng, L.; Li, L.

    2014-01-01

    Adsorption of levofloxacin (LEV), one of the extensively used antibiotics, onto goethite was investigated using batch experiments. The adsorption of LEV on goethite was pH-dependent. A maximum adsorption was reached at pH 6. Above or below pH 6, the adsorption decreased. In the presence of calcium

  2. a study of sorption of cadmium by goethite in aqueous solution

    African Journals Online (AJOL)

    Investigation has been carried out on the potential of a locally sourced goethite for the removal of cadmium ion from aqueous solutions using batch equilibration technique. The maximum uptake of cadmium is 6.4 ´ 10-2 mg/g-goethite. The sorption kinetics appears to be rapid as equilibrium was attained within a period of 1 ...

  3. Atomic scale study of thermal reduction of nano goethite coexisting with magnetite

    Science.gov (United States)

    singh, L. Herojit; Govindaraj, R.; Mythili, R.; Amarendra, G.; Sundar, C. S.

    2013-02-01

    Evolution of the local structure and magnetic properties of nano particles of goethite having magnetite as a composite due to controlled annealing treatments in vacuum has been studied using Mossbauer spectroscopy. Importance of size, defect associated with structural OH- for the observed structural and magnetic properties of goethite has been emphasized in this study. Present Mossbauer results show that thermal annealing at low temperatures (420-550 K) lead to a partial conversion / reduction of orthorhombic goethite to cubic spinel oxides such as maghemite and off-stochiometric magnetite. This study further establishes that annealing treatments beyond 650 K predominantly results in topotactic conversion of goethite to haematite. Underlying physics of the transitions of goethite to iron oxides and the important role of desorbed hydrogen for the orthorhombic to cubic structural transitions has been elucidated in this study.

  4. Atomic scale study of thermal reduction of nano goethite coexisting with magnetite

    Directory of Open Access Journals (Sweden)

    L. Herojit singh

    2013-02-01

    Full Text Available Evolution of the local structure and magnetic properties of nano particles of goethite having magnetite as a composite due to controlled annealing treatments in vacuum has been studied using Mossbauer spectroscopy. Importance of size, defect associated with structural OH- for the observed structural and magnetic properties of goethite has been emphasized in this study. Present Mossbauer results show that thermal annealing at low temperatures (420-550 K lead to a partial conversion / reduction of orthorhombic goethite to cubic spinel oxides such as maghemite and off-stochiometric magnetite. This study further establishes that annealing treatments beyond 650 K predominantly results in topotactic conversion of goethite to haematite. Underlying physics of the transitions of goethite to iron oxides and the important role of desorbed hydrogen for the orthorhombic to cubic structural transitions has been elucidated in this study.

  5. Ab Initio Molecular Dynamics of Uranium Incorporated in Goethite (α-FeOOH): Interpretation of X-ray Absorption Spectroscopy of Trace Polyvalent Metals.

    Science.gov (United States)

    Kerisit, Sebastien; Bylaska, Eric J; Massey, Michael S; McBriarty, Martin E; Ilton, Eugene S

    2016-11-21

    Incorporation of economically or environmentally consequential polyvalent metals into iron (oxyhydr)oxides has applications in environmental chemistry, remediation, and materials science. A primary tool for characterizing the local coordination environment of such metals, and therefore building models to predict their behavior, is extended X-ray absorption fine structure spectroscopy (EXAFS). Accurate structural information can be lacking yet is required to constrain and inform data interpretation. In this regard, ab initio molecular dynamics (AIMD) was used to calculate the local coordination environment of minor amounts of U incorporated in the structure of goethite (α-FeOOH). U oxidation states (VI, V, and IV) and charge compensation schemes were varied. Simulated trajectories were used to calculate the U L III -edge EXAFS function and fit experimental EXAFS data for U incorporated into goethite under reducing conditions. Calculations that closely matched the U EXAFS of the well-characterized mineral uraninite (UO 2 ), and constrained the S 0 2 parameter to be 0.909, validated the approach. The results for the U-goethite system indicated that U(V) substituted for structural Fe(III) in octahedral uranate coordination. Charge balance was achieved by the loss of one structural proton coupled to addition of one electron into the solid (-1 H + , +1 e - ). The ability of AIMD to model higher energy states thermally accessible at room temperature is particularly relevant for protonated systems such as goethite, where proton transfers between adjacent octahedra had a dramatic effect on the calculated EXAFS. Vibrational effects as a function of temperature were also estimated using AIMD, allowing separate quantification of thermal and configurational disorder. In summary, coupling AIMD structural modeling and EXAFS experiments enables modeling of the redox behavior of polyvalent metals that are incorporated in conductive materials such as iron (oxyhydr)oxides, with

  6. Spectral masking of goethite in abandoned mine drainage systems: implications for Mars

    Science.gov (United States)

    Cull, Selby; Cravotta,, Charles A.; Klinges, Julia Grace; Weeks, Chloe

    2014-01-01

    Remote sensing studies of the surface of Mars use visible- to near-infrared (VNIR) spectroscopy to identify hydrated and hydroxylated minerals, which can be used to constrain past environmental conditions on the surface of Mars. However, due to differences in optical properties, some hydrated phases can mask others in VNIR spectra, complicating environmental interpretations. Here, we examine the role of masking in VNIR spectra of natural precipitates of ferrihydrite, schwertmannite, and goethite from abandoned mine drainage (AMD) systems in southeastern Pennsylvania. Mixtures of ferrihydrite, schwertmannite, and goethite were identified in four AMD sites by using X-ray diffractometry (XRD), and their XRD patterns compared to their VNIR spectra. We find that both ferrihydrite and schwertmannite can mask goethite in VNIR spectra of natural AMD precipitates. These findings suggest that care should be taken in interpreting environments on Mars where ferrihydrite, schwertmannite, or goethite are found, as the former two may be masking the latter. Additionally, our findings suggest that outcrops on Mars with both goethite and ferrihydrite/schwertmannite VNIR signatures may have high relative abundances of goethite, or the goethite may exist in a coarsely crystalline phase.

  7. Interactions of calcium and fulvic acid at the goethite-water interface

    Science.gov (United States)

    Weng, Li Ping; Koopal, Luuk K.; Hiemstra, Tjisse; Meeussen, Johannes C. L.; Van Riemsdijk, Willem H.

    2005-01-01

    Interactions of calcium and fulvic acid (Strichen ) with the surface of goethite were studied with batch and titration experiments. The mutual influence of the interactions on the adsorption of fulvic acid, calcium ions and protons were examined. Adsorption of the fulvic acid to goethite decreased with increase in pH (pH range 3-11). Addition of Ca (1.0 mM) at intermediate and high pH significantly enhanced the adsorption of fulvic acid. Compared to the adsorption to pure goethite, the presence of fulvic acid enhanced the adsorption of Ca significantly. In comparison to the simple linear sum of Ca bound to fulvic acid and goethite, the interactions between goethite and fulvic acid led to a reduced adsorption of Ca at low pH and an enhanced adsorption at high pH. With the adsorption of fulvic acid, protons were released at low pH and coadsorbed at high pH. When Ca was added, fewer protons were released at low pH and fewer coadsorbed at high pH. The experimental results can be adequately described using a surface complexation model, the Ligand and Charge Distribution (LCD) model, in which the CD-MUSIC model for ion adsorption to mineral oxides and the NICA model for ion binding to humics are integrated. In the model calculations, adequate descriptions of the ternary system data (Ca-fulvic acid-goethite) were obtained with parameters derived from three binary systems (fulvic acid-goethite, Ca-goethite and Ca-fulvic acid) without further adjustment. The model calculations suggest that the interactions between Ca and fulvic acid at the surface of goethite are mainly due to the electrostatic effects.

  8. In situ preparation of magnetic nanocomposites of goethite in a styrene-maleimide copolymer template

    International Nuclear Information System (INIS)

    Sepulveda-Guzman, S.; Perez-Camacho, O.; Rodriguez-Fernandez, O.; Garcia-Zamora, M.

    2005-01-01

    Magnetic composites were prepared by in situ precipitation of α-FeOOH (goethite) using a new styrene-co-N-4 carboxybutylmaleimide cross-linked copolymer as template. Thermogravimetric analysis showed iron oxide content in the composites up to 45%. The iron oxide phase was identified as goethite by X-ray diffraction analysis. Transmission electron microscopy revealed that the crosslinking extent of polymeric templates affected both the shape and dimension of the goethite particles, and consequently, the magnetic behavior of the polymer/iron oxide composites

  9. A study of sorption of cadmium by goethite in aqueous solution

    African Journals Online (AJOL)

    goethite) sample was obtained from Geological Survey. Department of the Federal Ministry of Solid Mineral, Osogbo, Nigeria. The solid was reduced to fine particulate by grinding with the aid of mortal and pestle followed by sieving into various.

  10. Structure analysis of cation selective Cr-goethite as protective rust of weathering steel

    International Nuclear Information System (INIS)

    Konishi, Hiroyuki; Mizuki, Jun'ichiro; Yamashita, Masato; Uchida, Hitoshi

    2005-01-01

    We have performed extended X-ray absorption fine structure (EXAFS) analysis for artificial Cr-goethite to elucidate the local structure around Cr in Cr-goethite. The spectra were obtained using synchrotron radiation X-rays at the Photon Factory in Tsukuba. The first shell contributions were isolated by Fourier filtering EXAFS data, and the inverse Fourier transformed single-shell data were analyzed using a curve fitting method. The results show that Cr is coordinated with (7±1)O 2- ions. The protective characteristics of the Cr-goethite protective rust layer on weathering steel can be interpreted in terms of the O 2- coordination around Cr 3+ resulting in the creation of negative fixed charge in the Cr-goethite particles. (author)

  11. Dehydrogenation of goethite in Earth's deep lower mantle

    Science.gov (United States)

    Hu, Qingyang; Kim, Duck Young; Liu, Jin; Meng, Yue; Yang, Liuxiang; Zhang, Dongzhou; Mao, Wendy L.; Mao, Ho-kwang

    2017-02-01

    The cycling of hydrogen influences the structure, composition, and stratification of Earth’s interior. Our recent discovery of pyrite-structured iron peroxide (designated as the P phase) and the formation of the P phase from dehydrogenation of goethite FeO2H implies the separation of the oxygen and hydrogen cycles in the deep lower mantle beneath 1,800 km. Here we further characterize the residual hydrogen, x, in the P-phase FeO2Hx. Using a combination of theoretical simulations and high-pressure-temperature experiments, we calibrated the x dependence of molar volume of the P phase. Within the current range of experimental conditions, we observed a compositional range of P phase of 0.39 hydrogen and lower x, suggesting that dehydrogenation could be approaching completion at the high-temperature conditions of the lower mantle over extended geological time. Our observations indicate a fundamental change in the mode of hydrogen release from dehydration in the upper mantle to dehydrogenation in the deep lower mantle, thus differentiating the deep hydrogen and hydrous cycles.

  12. Comparison of the mineralogical effects of an experimental forest fire on a goethite/ferrihydrite soil with a topsoil that contains hematite, maghemite and goethite

    DEFF Research Database (Denmark)

    Nørnberg, Per; Vendelboe, Anders Lindblad; Gunnlaugsson, Haraldur Pall

    2009-01-01

    to 10 cm depth. This was not observed at the natural sites, which contained a mixture of goethite/ferrihydrite, hematite and maghemite down to 20 cm depth. The experimental forest fire left charcoal and ashes at the topsoil, produced high pH and decreased organic matter content, all of which...

  13. Adsorption of Phosphonates onto the Goethite-Water Interface.

    Science.gov (United States)

    Nowack; Stone

    1999-06-01

    The adsorption of one phosphonate, two hydroxyphosphonates, and five aminophosphonates onto the iron (hydr)oxide goethite (alpha-FeOOH) has been studied as a function of pH. At phosphonate concentrations significantly lower than the total number of available surface sites, nearly 100% adsorption is observed below pH 8.0. Adsorption decreases to negligible levels as the pH is increased to 12.0. Under the conditions just described, adsorption of nitrilotris(methylenephosphonic acid) as a function of pH is nearly independent of the ionic strength (from 1 mM to 1 M). At phosphonate concentrations close to the total number of available surface sites, adsorption decreases over a broader range in pH and reflects the number of phosphonate groups. At pH 7.2, the maximum extent of adsorption decreases as the number of phosphonate groups increases from one to five. Adsorption is modeled using a 2-pK constant capacitance model that postulates formation of a 1:1 surface complex involving one surface site and one phosphonate functional group. Denoting the fully deprotonated phosphonate ligand as La-, different protonation levels for adsorbed phosphonate species are represented by a series of equilibrium constants of the form For a phosphonate of charge a-, there are (a - 1) possible surface protonation levels. For a surface protonation level n, log betan,surf values derived from this modeling approach are related to the surface complex charge Z through the following linear relationship: Using this approach, adsorption as a function of phosphonate concentration and pH can be fully accounted for. Copyright 1999 Academic Press.

  14. Adsorption of phosphonates onto the goethite-water interface

    Energy Technology Data Exchange (ETDEWEB)

    Nowack, B.; Stone, A.T. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Geography and Environmental Engineering

    1999-06-01

    The adsorption of one phosphonate, two hydroxyphosphonates, and five aminophosphonates onto the iron (hydr)oxide goethite ({alpha}-FeOOH) has been studied as a function of pH. At phosphonate concentrations significantly lower than the total number of available surface sites, nearly 100% adsorption is observed below pH 8.0. Adsorption decreases to negligible levels as the pH is increased to 12.0. Under the conditions just described, adsorption of nitrilotris(methylenephosphonic acid) as a function of pH is nearly independent of the ionic strength (from 1 nM to 1 M). At phosphonate concentrations close to the total number of available surface sites, adsorption decreases over a broader range in pH and reflects the number of phosphonate groups. At pH 7.2, the maximum extent of adsorption decreases as the number of phosphonate groups increases from one to five. Adsorption is modeled using a 2-pK constant capacitance model that postulates formation of a 1:1 surface complex involving one surface site and one phosphonate functional group. Denoting the fully deprotonated phosphonate ligand as L{sup a{minus}}, different protonation levels for adsorbed phosphonate species are represented by a series of equilibrium constants. For a phosphonate of charge a{minus}, there are (a {minus} 1) possible surface protonation levels. For a surface protonation level n, log {beta}{sub n,surf} values derived from this modeling approach are related to the surface complex charge Z. Using this approach, adsorption as a function of phosphonate concentration and pH can be fully accounted for.

  15. Authigenic magnetite formation from goethite and hematite and chemical remanent magnetization acquisition

    Science.gov (United States)

    Till, J. L.; Nowaczyk, N.

    2018-03-01

    The iron oxyhydroxide goethite is unstable at elevated temperatures and can transform to magnetite under reducing conditions. In this study, various heating experiments were conducted to simulate Fe-mineral transformations during pyrogenic or burial diagenesis alteration in the presence of organic matter. Thermomagnetic measurements, capsule heating experiments and thermo-chemical remanence acquisition measurements were performed to determine the effect of organic carbon additions on samples containing synthetic microcrystalline goethite, microcrystalline hematite or nanocrystalline goethite. Changes in magnetic properties with heating were monitored to characterize the magnetic behavior of secondary magnetite and hematite formed during the experiments. Authigenic magnetite formed in all samples containing organic C, while goethite heated without organic C altered to poorly crystalline pseudomorphic hematite. The concentration of organic matter was found to have little influence on the rate or extent of reaction or on the characteristics of the secondary phases. Authigenic magnetite formed from microcrystalline goethite and hematite dominantly behaves as interacting single-domain particles, while nanophase goethite alters to a mixture of small single-domain and superparamagnetic magnetite. Authigenic magnetite and hematite both acquire a stable thermo-chemical remanence on heating to temperatures between 350 and 600°C, although the remanence intensity acquired below 500°C is much weaker than that at higher temperatures. Reductive transformation of fine-grained goethite or hematite is therefore a potential pathway for the production of authigenic magnetite and the generation of stable chemical remanence that may be responsible for remagnetization in organic matter-bearing sedimentary rocks.

  16. Solid-phase photocatalytic degradation of polystyrene plastic with goethite modified by boron under UV-vis light irradiation

    Science.gov (United States)

    Liu, Guanglong; Zhu, Duanwei; Zhou, Wenbing; Liao, Shuijiao; Cui, Jingzhen; Wu, Kang; Hamilton, David

    2010-02-01

    A novel photodegradable polyethylene-boron-goethite (PE-B-goethite) composite film was prepared by embedding the boron-doped goethite into the commercial polyethylene. The goethite catalyst was modified by boron in order to improve its photocatalytic efficiency under the ultraviolet and visible light irradiation. Solid-phase photocatalytic degradation of the PE-B-goethite composite film was carried out in an ambient air at room temperature under ultraviolet and visible light irradiation. The properties of composite films were compared with those of the pure PE films and the PE-goethite composite films through performing weight loss monitoring, scanning electron microscope (SEM) analysis, FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS). The photo-induced degradation of PE-B-goethite composite films was higher than that of the pure PE films and the PE-goethite composite films under the UV-irradiation, while there has been little change under the visible light irradiation. The weight loss of the PE-B-goethite (0.4 wt.%) composite film reached 12.6% under the UV-irradiation for 300 h. The photocatalytic degradation mechanism of the composite films was briefly discussed.

  17. Immobilization of 99-Technetium (VII) by Fe(II)-Goethite and Limited Reoxidation

    Energy Technology Data Exchange (ETDEWEB)

    W Um; H Chang; J Icenhower; W Lukens; R Serne; N Qafoku; J Westsik Jr.; E Buck; S Smith

    2011-12-31

    During the nuclear waste vitrification process volatilized {sup 99}Tc will be trapped by melter off-gas scrubbers and then washed out into caustic solutions, and plans are currently being contemplated for the disposal of such secondary waste. Solutions containing pertechnetate [{sup 99}Tc(VII)O{sub 4}{sup -}] were mixed with precipitating goethite and dissolved Fe(II) to determine if an iron (oxy)hydroxide-based waste form can reduce Tc(VII) and isolate Tc(IV) from oxygen. The results of these experiments demonstrate that Fe(II) with goethite efficiently catalyzes the reduction of technetium in deionized water and complex solutions that mimic the chemical composition of caustic waste scrubber media. Identification of the phases, goethite + magnetite, was performed using XRD, SEM and TEM methods. Analyses of the Tc-bearing solid products by XAFS indicate that all of the Tc(VII) was reduced to Tc(IV) and that the latter is incorporated into goethite or magnetite as octahedral Tc(IV). Batch dissolution experiments, conducted under ambient oxidizing conditions for more than 180 days, demonstrated a very limited release of Tc to solution (2-7 {micro}g Tc/g solid). Incorporation of Tc(IV) into the goethite lattice thus provides significant advantages for limiting reoxidation and curtailing release of Tc disposed in nuclear waste repositories.

  18. DECOLORIZATION OF BROMOCRESOL PURPLE (BCP PHOTOINDUCED BY A Fe (III OXYHYDROXYDE (GOETHITE

    Directory of Open Access Journals (Sweden)

    S BELATTAR

    2014-06-01

    Full Text Available This study focused on the decolorization of bromocresol purple (BCP using Fe (III oxyhydroxide (Goethite as an inducer. The mixture dye- Goethite in dark condition and ambient temperature, shows a reaction between the dye and the Fe (III oxyhydroxide. Indeed, the tracking of the reaction using UV-visible spectrophotometry showed a low decrease in the principal band of the dye. This reveal the existence of an interaction between the substrate and the Goethite whitch is important in acidic medium. The irradiation at 365 nm of mixture Goethite-BCP (1g.L-1- 10-4 M leads to a transformation of substrate. The decrease of the band at 432nm and the presence of an isosbestic point at 508 nm support the transformation of BCP.  The substrate kinetics disappearances are improved in acidic medium. The addition of hydrogen peroxide (5.10-3 mol.L-1 in a suspension of Goethite, accelerate significantly the rate of disappearance of the dye. Natural radiation tests showed that the degradation was faster than artificial one at 365 nm. Studies on mineralization using COD method certify that this method, compatible with the environment, may be considered in the treatment of wastewater.

  19. Evidence for Single Metal Two Electron Oxidative Addition and Reductive Elimination at Uranium

    OpenAIRE

    Gardner, Benedict M; Kefalidis, Christos E; Lu, Erli; Patel, Dipti; Mcinnes, Eric; Tuna, Floriana; Wooles, Ashley; Maron, Laurent; Liddle, Stephen

    2017-01-01

    Reversible single-metal two-electron oxidative addition and reductive elimination are common fundamental reactions for transition metals that underpin major catalytic transformations. However, these reactions have never been observed together in the f-block because these metals exhibit irreversible one- or multi-electron oxidation or reduction reactions. Here, we report that azobenzene oxidises sterically and electronically unsaturated uranium(III) complexes to afford a uranium(V)-imido compl...

  20. The influences of pH and ionic strength on the sorption of tylosin on goethite.

    Science.gov (United States)

    Guo, Xuetao; Yang, Chen; Wu, Yinai; Dang, Zhi

    2014-02-01

    As one of the widely used antibiotics in the world, the environmental risks of tylosin (TYL) received more and more attention. In order to assess its environmental fate and ecological effects accurately, it is necessary to understand the sorption properties of TYL on the soils/sediments. The sorption of TYL on goethite at different pH and ionic strength conditions were measured through a series of batch experiments and the sorption data of TYL were fitted by Freundlich and dual-mode sorption models. It was obvious that sorption was strongly dependent on pH and ionic strength. Sorption capacity of TYL increased as the pH increased and ionic strength decreased. The pH and ionic strength-dependent trends might be related with complexation between cationic/neutral TYL species and goethite. The sorption affinity of TYL on goethite decreased as ionic strength increased, which only occurred at higher TYL concentrations, suggested that inner complex might have dominated process at low concentrations and outer complex might occur at higher concentrations of TYL. Spectroscopic evidence indicated that tricarbonylamide and hydroxyl functional groups of TYL might be accounted for the sorption on mineral surfaces. The experimental data of TYL sorption could be fitted by surface complexation model (FITEQL), indicating that ≡FeOH with TYL interaction could be reasonably represented as a complex formation of a monoacid with discrete sites on goethite. The sorption mechanism of TYL might be related with surface complexation, electrostatic repulsion, and H-bounding on goethite. It should be noticed that the heterogeneous of sorption affinity of TYL on goethite at various environment to assess its environment risk.

  1. Arsenate and cadmium co-adsorption and co-precipitation on goethite

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Wei [Environment Research Institute, Shandong University, Jinan 250100 (China); Lv, Jitao; Luo, Lei [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); Yang, Kun [Department of Environmental Science, Zhejiang University, Hangzhou 310058 (China); Lin, Yongfeng; Hu, Fanbao [Environment Research Institute, Shandong University, Jinan 250100 (China); Zhang, Jing [State Key Laboratory of Synchrotron Radiation, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039 (China); Zhang, Shuzhen, E-mail: szzhang@rcees.ac.cn [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China)

    2013-11-15

    Highlights: • As enhances Cd adsorption amount on goethite. • Cd fixed through precipitation is more difficult to get released. • As in co-precipitates is easier to release than in its adsorption complexes. -- Abstract: Arsenate (As(V), AsO{sub 4}{sup 3−}) and cadmium (Cd) are among the toxic elements of most concern. Their sorption behaviors on goethite were studied by batch experiments (pH edges, isotherms and kinetics) and X-ray diffraction (XRD). Arsenic coordination environment was explored by X-ray absorbance fine structure (EXAFS) analysis. Sorption isotherms of both As(V) and Cd on goethite could be divided into the adsorption-dominated and precipitation-dominated parts, while their sorption showed different pH-dependency and sorption reversibility. Cadmium adsorption was enhanced in the presence of AsO{sub 4}{sup 3−}, which could be explained by the decrease in the electrostatic potential due to the sorption of AsO{sub 4}{sup 3−} and the formation of a ternary Cd–As(V)–goethite complex. Based on the EXAFS study, AsO{sub 4}{sup 3−} adsorbed on goethite mainly formed bidentate–binuclear complex. The high loadings of Cd changed the As(V)–Fe distance and its coordination number. However, Cd did not affect the As(V) adsorption amount in the adsorption-dominated region. When As(V) and Cd formed co-precipitates, their sorption amounts were both increased. The formation of co-precipitates decreased the mobility of Cd but increased the mobility of As(V) because less As(V) was sorbed on goethite through surface complexation. This study will provide better understandings on As(V) and Cd transport and useful information on their remediation strategies.

  2. Periodic density functional theory calculations of bulk and the (010 surface of goethite

    Directory of Open Access Journals (Sweden)

    Sparks Donald L

    2008-05-01

    Full Text Available Abstract Background Goethite is a common and reactive mineral in the environment. The transport of contaminants and anaerobic respiration of microbes are significantly affected by adsorption and reduction reactions involving goethite. An understanding of the mineral-water interface of goethite is critical for determining the molecular-scale mechanisms of adsorption and reduction reactions. In this study, periodic density functional theory (DFT calculations were performed on the mineral goethite and its (010 surface, using the Vienna Ab Initio Simulation Package (VASP. Results Calculations of the bulk mineral structure accurately reproduced the observed crystal structure and vibrational frequencies, suggesting that this computational methodology was suitable for modeling the goethite-water interface. Energy-minimized structures of bare, hydrated (one H2O layer and solvated (three H2O layers (010 surfaces were calculated for 1 × 1 and 3 × 3 unit cell slabs. A good correlation between the calculated and observed vibrational frequencies was found for the 1 × 1 solvated surface. However, differences between the 1 × 1 and 3 × 3 slab calculations indicated that larger models may be necessary to simulate the relaxation of water at the interface. Comparison of two hydrated surfaces with molecularly and dissociatively adsorbed H2O showed a significantly lower potential energy for the former. Conclusion Surface Fe-O and (FeO-H bond lengths are reported that may be useful in surface complexation models (SCM of the goethite (010 surface. These bond lengths were found to change significantly as a function of solvation (i.e., addition of two extra H2O layers above the surface, indicating that this parameter should be carefully considered in future SCM studies of metal oxide-water interfaces.

  3. Enhancement of arsenic adsorption during mineral transformation from siderite to goethite: mechanism and application.

    Science.gov (United States)

    Guo, Huaming; Ren, Yan; Liu, Qiong; Zhao, Kai; Li, Yuan

    2013-01-15

    Synthesized siderite was used to remove As(III) and As(V) from water solutions under anoxic conditions and oxic conditions. Results showed that As adsorption on synthetic siderite under anoxic conditions was around 10 mg/g calculated with Langmuir isotherm. However, the calculated As adsorption on synthetic siderite under oxic conditions ranged between 115 and 121 mg/g, which was around 11 times higher than that under anoxic conditions. It was found that 75% siderite was transformed into goethite during oxic adsorption. However, synthetic goethite had lower As adsorption capacity than siderite under oxic conditions, although its adsorption capacity was a little higher than siderite under anoxic conditions. It suggested that the coexistence of goethite and siderite bimineral during mineral transformation probably contributed to the robust adsorption capacity of siderite under oxic conditions. Results of extended X-ray absorption fine structure (EXAF) spectroscopy indicated both As(III) and As(V) formed inner-sphere complexes on the surface of As-treated solid regardless of substrates, including the bidentate binuclear corner-sharing ((2)C) complexes and the monodentate mononuclear corner-sharing ((1)V) complexes. Monodenate ((1)V) and bidentate ((2)C) complexes would be related to high As adsorption capacity of siderite under oxic conditions. It showed that more Fe atoms were coordinated with As atom in the monodentate complexes and the bidentate complexes of As(V)/As(III)-treated siderite under oxic conditions, in comparison with As(V)/As(III)-treated siderite under anoxic conditions and As(V)/As(III)-treated goethite. Calcinations of natural siderite resulting in the coexistence of goethite and siderite greatly increased As adsorption on the solid, which confirmed that the coexistence of bimineral during mineral transformation from siderite to goethite greatly enhanced As adsorption capacity of siderite adsorbent. The observation can be applied for modification of

  4. [Surface properties and adsorption characteristics for fluoride of goethite, kaolinite and their association].

    Science.gov (United States)

    Wei, Shi-Yong; Yang, Xiao-Hong

    2010-09-01

    The basic properties of goethite, kaolinite and their association were characterized using X-ray diffraction (XRD) , scanning electron microscopes (SEM), Fourier transform infrared spectroscopy (FT-IR), potentiometric titrations, specific surface area (SSA) and micropore analysis. Moreover, the adsorption capacity and adsorption models of fluoride by the investigated samples were studied. Results show that when kaolinite and goethite presented simultaneously in the same suspension system, goethite was apt to coat the surface of kaolinite and the interactions between them could occur rapidly. As a result, the binary association containing kaolinite and goethite was formed. The binary association possessed the pore diameter of 0.42 nm and 0.61 nm, specific surface area of 34.08 m2/g, surface fractal dimension of D = 2.726 and the pH(PZNPC) (pH of point of zero net proton charge) in the range of 5.50-6.50. At the initial pH 6. 00, the maximum adsorption capacity (q(max) of goethite, kaolinite and association was 4.506, 0.608 and 3.520 mg/g respectively. The adsorption of fluoride by the single kaolinite or goethite could be attributed to monolayer adsorption and the data of isotherm adsorption could be well fitted by Langmuir model (R2 = 0.991 and R2 = 0.964 respectively). The Freundlich model was suitable for describing the adsorption of fluoride by the binary association (R2 = 0.995), which indicated that the surface of the binary association is heterogeneous and is probably provided with multilayer adsorption sites. The adsorption mechanisms for fluoride by the investigated samples include anion ligand exchange, surface coordination and electrostatic attraction. In addition, F acting as a bond bridge between the surfaces of kaolinite and goethite contributed to the adsorption of fluoride too. Compared to the single goethite or kaolinite, the binary association exhibited the higher specific surface area, surface fractal dimension and adsorption capacity for fluoride

  5. Red mud carbonation using carbon dioxide: Effects of carbonate and calcium ions on goethite surface properties and settling.

    Science.gov (United States)

    Liang, Gaojie; Chen, Wenmi; Nguyen, Anh V; Nguyen, Tuan A H

    2018-05-01

    Carbonation using CO 2 appears as an attractive solution for disposing of red mud suspensions, an aluminum industry hazardous waste since it also offers an option for CO 2 sequestration. Here we report the novel findings that CO 3 2- together with Ca 2+ can significantly affect the surface properties and settling of goethite, a major component of red mud. Specifically, their effects on the goethite surface chemistry, colloidal interaction forces and settling in alkaline solutions are investigated. The surface potential becomes more negative by the formation of carbonate inner-sphere complexes on goethite surface. It is consistent with the strong repulsion, decreased particle size and settling velocity with increased carbonate concentrations as measured by atomic force microscopy, particle size analysis, and particle settling. Adding Ca 2+ that forms outer-sphere complexes with pre-adsorbed carbonate changes goethite surface charge negligibly. Changing repulsion to the attraction between goethite surfaces by increasing calcium dosage indicates the surface bridging, in accordance with the increased settling velocity. The adverse effect of carbonate on goethite flocculation is probably due to its specific chemisorption and competition with flocculants. By forming outer-sphere complexes together with the flocculant-calcium bridging effect, calcium ions can eliminate the negative influence of carbonate and improve the flocculation of goethite particles. These findings contribute to a better understanding of goethite particle interaction with salt ions and flocculants in controlling the particle behavior in the handling processes, including the red mud carbonation. Copyright © 2018 Elsevier Inc. All rights reserved.

  6. Utah and Czech Mars analog concretions; Aquatic hematite and goethite characterization

    Czech Academy of Sciences Publication Activity Database

    Kletetschka, Günther; Adachi, T.; Adamovič, Jiří; Mikula, V.; Chan, M.

    2007-01-01

    Roč. 71, 15 S1 (2007), A493-A493 ISSN 0046-564X. [Annual V. M. Goldschmidt Conference /17./. 19.08.2007-24.08.2007, Cologne] Institutional research plan: CEZ:AV0Z30130516 Keywords : Mars * concretions * hematite * goethite Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  7. Simulated solar light phototransformation of organophosphorus azinphos methyl at the surface of clays and goethite.

    Science.gov (United States)

    Menager, Matthieu; Sarakha, Mohamed

    2013-01-15

    The photochemical behavior of the pesticide azinphos methyl at the surface of clays (kaolinite, bentonite) and goethite was studied using Suntest setup (λ > 300 nm). The quantum yield on the clays was found to be roughly three times lower than that in aqueous solution. However, the photochemical efficiency was much higher at the surface of goethite owing to its photocatalytic activity through the hydroxyl radical production. The added humic substances on kaolonite show an inhibition of azinphos methyl degradation while the incorporation of iron(III) aquacomplexes leads to an important increase of the disappearance together with the formation of iron(II). Hydroxyl radical species were found to be formed either by excitation of goethite or clays. The goethite support acts as a more efficient catalyst for the formation of these reactive oxygen species. The photodecomposition reactions observed were (i) hydrolysis process leading to the formation of benzotriazone and the oxidation of the P = S bond giving rise to the formation of the oxon derivative, and (ii) homolytic cleavage of the N-C and C-S bonds of the organophosphorus bridge leading to the formation of dimers that appear to be specific to the irradiation at the surface of solid supports since they were not observed when the irradiation was performed in aqueous media: a statement that is related to the presence of aggregates at the surface of solid supports.

  8. Surface complexation of carbonate on goethite: IR spectroscopy, structure & charge distribution

    NARCIS (Netherlands)

    Hiemstra, T.; Rahnemaie, R.; Riemsdijk, van W.H.

    2004-01-01

    The adsorption of carbonate on goethite has been evaluated, focussing on the relation between the structure of the surface complex and corresponding adsorption characteristics, like pH dependency and proton co-adsorption. The surface structure of adsorbed CO3-2 has been assessed with (1) a

  9. Inner- and outer-sphere complexation of ions at the goethite-solution interface

    NARCIS (Netherlands)

    Rahnemaie, R.; Hiemstra, T.; Riemsdijk, van W.H.

    2006-01-01

    Formation of inner- and outer-sphere complexes of environmentally important divalent ions on the goethite surface was examined by applying the charge distribution CD model for inner- and outer-sphere complexation. The model assumes spatial charge distribution between the surface (0-plane) and the

  10. A study of selenium and tin sorption on granite and goethite

    International Nuclear Information System (INIS)

    Ticknor, K.V.; McMurry, J.

    1996-01-01

    Sensitivity analyses based on an illustrative performance assessment case study of a disposal concept for nuclear fuel waste have shown that radioisotopes of Se and Sn could have a significant effect on cumulative radioactive dose if they were to be transported through the geosphere without retardation. Static batch sorption methods, coupled with 2 n factorial experimental designs, were used to determine the extent to which Se and Sn can be sorbed by granite and goethite as a function of total dissolved solids concentration, (TDS), natural fulvic acid concentration as dissolved organic carbon, [DOC], pH and, for the studies with Se, the Se concentration, [Se]. Aqueous speciation and the saturation indices of solubility-controlling solid phases were estimated using the speciation code HARPHRQ with the HATCHES thermodynamic database. The experimental results indicated that Se sorption on granite was low and not affected by changes in [DOC] or [TDS]. Increased [Se] and increased pH decreased sorption. For Se sorption on goethite, the pH range was narrow but indicated that sorption decreased as pH increased. Increased [TDS] and [Se] lowered sorption on goethite, but changes in (DOC] had no effect on sorption. For Sn, increased pH, [TDS] and [DOC] decreased sorption on granite. For Sn sorption on goethite, increased [DOC] resulted in decreased sorption, but differences in [TDS] and pH had little consistent effect on sorption. (author)

  11. Modeling the binding of benzenecarboxylates by goethite: The ligand and charge distribution model

    NARCIS (Netherlands)

    Filius, J.D.; Meeussen, J.C.L.; Hiemstra, T.; Riemsdijk, van W.H.

    2001-01-01

    A heterogeneous complexation model approach has been developed to describe the adsorption of large organic molecules by goethite taking the full speciation of the adsorbed molecules into account. The essence of the model is the calculation of the mean mode of an adsorbed organic molecule, defined by

  12. Microstructure, Interaction Mechanisms, and Stability of Binary Systems Containing Goethite and Kaolinite

    NARCIS (Netherlands)

    Wei, S.Y.; Tan, W.F.; Zhao, W.; Yu, Y.T.; Liu, F.; Koopal, L.K.

    2012-01-01

    Goethite and kaolinite are ubiquitous in natural environments. In soils they are often cemented together as a binary association, which has a significant influence on the structure and properties of soils. In this study, the mineralogy (using X-ray diffraction [XRD], thermal analyses, and infrared

  13. Removal of caffeine from water by combining dielectric barrier discharge (DBD plasma with goethite

    Directory of Open Access Journals (Sweden)

    Jian Wang

    2017-07-01

    Full Text Available In this research, dielectric barrier discharge plasma was developed to cooperate with goethite for removing caffeine in aqueous solution. Goethite was characterized by X-ray diffraction and scanning electron microscopy. The effects of input power, initial concentration and catalysts concentration on the removal efficiency of caffeine were evaluated. Furthermore, the degradation pathways of caffeine were also discussed preliminarily. In the case of caffeine concentration at 50 mg L−1, the degradation efficiency of caffeine was improved from 41% to 94% after 24 min on the conditions of input power of 75 W by combining goethite catalysts (2.5 g L−1, while the energy efficiency could be enhanced 1.6–2.3 times compared to the single DBD reactor. The reaction mechanism experiments demonstrated that attack by hydroxyl radical and ozone was the main degradation process of caffeine in aqueous solution. These studies also provided a theoretical and practical basis for the application of DBD-goethite in treatment of caffeine from water.

  14. Adsorption and oxidation of fluoroquinolone antibacterial agents and structurally related amines with goethite.

    Science.gov (United States)

    Zhang, Huichun; Huang, Ching-Hua

    2007-01-01

    Seven members (ciprofloxacin, enrofloxacin, norfloxacin, ofloxacin, lomefloxacin, pipemidic acid, and flumequine) of the popular fluoroquinolone antibacterial agents (FQs) were found to adsorb strongly to goethite with 50-76% of the added FQ adsorbed under the experimental conditions. The adsorption isotherms fitted well to the Langmuir model. Adsorption was accompanied by slow oxidation of the FQs (except for flumequine) by goethite yielding a range of hydroxylated and dealkylated products. The oxidation kinetics showed different stages in reaction rate, mostly likely caused by accumulation of Fe(II) species on the oxide surface that slowed the reaction. Structurally related amines 1-phenylpiperazine, N-phenylmorpholine, aniline, and N,N-dimethylaniline were found to be oxidized by goethite without significant adsorption. The results strongly indicate that the carboxylic group of FQs is critical for adsorption while the piperazine ring is susceptible to oxidation. A radical mechanism is proposed for the oxidation of FQs by goethite which involves formation of a surface complex between the FQ and surface-bound Fe(III) through adsorption, and initial oxidation at the piperazinyl N1 atom to form radical intermediates that ultimately lead to the final products. This study indicates that Fe oxides in aquatic sediments may well play an important role in the natural attenuation of fluoroquinolone antibacterial agents.

  15. Effect of fulvic acid surface coatings on plutonium sorption and desorption kinetics on goethite.

    Science.gov (United States)

    Tinnacher, Ruth M; Begg, James D; Mason, Harris; Ranville, James; Powell, Brian A; Wong, Jennifer C; Kersting, Annie B; Zavarin, Mavrik

    2015-03-03

    The rates and extent of plutonium (Pu) sorption and desorption onto mineral surfaces are important parameters for predicting Pu mobility in subsurface environments. The presence of natural organic matter, such as fulvic acid (FA), may influence these parameters. We investigated the effects of FA on Pu(IV) sorption/desorption onto goethite in two scenarios: when FA was (1) initially present in solution or (2) found as organic coatings on the mineral surface. A low pH was used to maximize FA coatings on goethite. Experiments were combined with kinetic modeling and speciation calculations to interpret variations in Pu sorption rates in the presence of FA. Our results indicate that FA can change the rates and extent of Pu sorption onto goethite at pH 4. Differences in the kinetics of Pu sorption were observed as a function of the concentration and initial form of FA. The fraction of desorbed Pu decreased in the presence of FA, indicating that organic matter can stabilize sorbed Pu on goethite. These results suggest that ternary Pu-FA-mineral complexes could enhance colloid-facilitated Pu transport. However, more representative natural conditions need to be investigated to quantify the relevance of these findings.

  16. The effect of water content on the magnetic and structural properties of goethite

    International Nuclear Information System (INIS)

    Betancur, J.D.; Barrero, C.A.; Greneche, J.M.; Goya, G.F.

    2004-01-01

    We have studied the effect of water content on the magnetic and structural properties of goethite. For that purpose, four samples were prepared using two different hydrothermal methods, one of them is derived on the Fe(II) precursors and the other one from Fe(III) precursors. The samples were characterized by X-ray diffraction (XRD), TGA, BET, FTIR, Moessbauer spectrometry at RT, 77 and 4.2 K and ZFC and FC curves. The results suggest that the goethites from the Fe(II) precursors are less crystalline, have higher water contents and do not show magnetic ordered structure at RT in comparison to the goethites from the Fe(III) precursors. The goethites from the last systems exhibit good crystallinity, low water content and magnetic ordering at room temperature. Our results suggest that both structural and adsorbed water contents reduce the magnetic hyperfine field at 4.2 K. A linear correlation with regression coefficient of 0.91 between the saturation hyperfine field and both the structural hydroxyl content and the surface area could be derived

  17. Goethite (α-FeOOH) magnetic transition by ESR, Magnetometry and Mössbauer

    Energy Technology Data Exchange (ETDEWEB)

    Valezi, D.F., E-mail: dfvalezi@uel.br [Laboratory of Fluorescence and Electron Paramagnetic Resonance (LAFLURPE), Physics Department, CCE, State University of Londrina (UEL), 86057-970, Londrina, PR (Brazil); Piccinato, M.T. [Laboratory of Fluorescence and Electron Paramagnetic Resonance (LAFLURPE), Physics Department, CCE, State University of Londrina (UEL), 86057-970, Londrina, PR (Brazil); Sarvezuk, P.W.C.; Ivashita, F.F.; Paesano, A. [Physics Department, CCE, State University of Maringá (UEM), 87020-900, Maringá, PR (Brazil); Varalda, J.; Mosca, D.H. [Physics Department, Federal University of Paraná (UFPR), 81531-990, Curitiba, PR (Brazil); Urbano, A. [Laboratory of Thin Films and Materials, Physics Department, CCE, State University of Londrina (UEL), 86057-970, Londrina, PR (Brazil); Guedes, C.L.B. [Laboratory of Fluorescence and Electron Paramagnetic Resonance (LAFLURPE), Chemistry Department, CCE, State University of Londrina (UEL), 86057-970, Londrina, PR (Brazil); Di Mauro, E. [Laboratory of Fluorescence and Electron Paramagnetic Resonance (LAFLURPE), Physics Department, CCE, State University of Londrina (UEL), 86057-970, Londrina, PR (Brazil)

    2016-04-15

    A natural sample of the mineral goethite was characterized by X-band Electron Spin Resonance (ESR), vibrating sample Magnetometry and Mössbauer spectroscopy techniques, with the main objective of studying the magnetic transition from the antiferromagnetic to the paramagnetic state that this mineral undergoes upon reaching a certain critical temperature (Néel temperature). Although an ESR signal was not expected in goethite samples at room temperature, due to its antiferromagnetic arrangement, a resonance line was observed. This behavior was attributed to the existence of vacancies in the mineral structure. Increasing the temperature from RT to 352 K no significant change occurred in the ESR spectra. From 352 K, the goethite spectrum showed an additional ESR line, the intensity of this line grew until it stabilized at around 444 K. The appearance of this new resonance line, and its evolution with temperature, was attributed to two subsequent effects: firstly the spin flop effect from 352 to 372 K; and secondly, the transition to the paramagnetic state at T{sub N} = 372 K. Magnetometry and Mössbauer measurements corroborated this assumption and the transition temperature was identified by magnetometry as T{sub N} = 370 K. Simulations of the goethite ESR spectra in both antiferromagnetic and paramagnetic states were performed by deconvolution of the resonance lines into two contributions, one from species with vacancies in their vicinity, and another with complete vicinity. - Highlights: • We studied a magnetic transition of a natural goethite sample. • It was observed by ESR the spin flop effect and the transition to the PM state. • Spectra simulations showed ESR lines of different spins interactions with vicinity. • T{sub N} was determined as 372 and 370 K by ESR and Magnetometry respectively.

  18. Evidence for single metal two electron oxidative addition and reductive elimination at uranium.

    Science.gov (United States)

    Gardner, Benedict M; Kefalidis, Christos E; Lu, Erli; Patel, Dipti; McInnes, Eric J L; Tuna, Floriana; Wooles, Ashley J; Maron, Laurent; Liddle, Stephen T

    2017-12-01

    Reversible single-metal two-electron oxidative addition and reductive elimination are common fundamental reactions for transition metals that underpin major catalytic transformations. However, these reactions have never been observed together in the f-block because these metals exhibit irreversible one- or multi-electron oxidation or reduction reactions. Here we report that azobenzene oxidises sterically and electronically unsaturated uranium(III) complexes to afford a uranium(V)-imido complex in a reaction that satisfies all criteria of a single-metal two-electron oxidative addition. Thermolysis of this complex promotes extrusion of azobenzene, where H-/D-isotopic labelling finds no isotopomer cross-over and the non-reactivity of a nitrene-trap suggests that nitrenes are not generated and thus a reductive elimination has occurred. Though not optimally balanced in this case, this work presents evidence that classical d-block redox chemistry can be performed reversibly by f-block metals, and that uranium can thus mimic elementary transition metal reactivity, which may lead to the discovery of new f-block catalysis.

  19. Variabilidade de goethita e hematita via dissolução redutiva em solos de região tropical e subtropical Goethite and hematite variability via reductive dissolution in soils from tropical and subtropical regions

    Directory of Open Access Journals (Sweden)

    Alberto Vasconcellos Inda Junior

    2005-12-01

    combinou baixa substituição por Al3+ e alta ASE. A caracterização de populações heterogêneas de goethita pode ampliar a utilização deste óxido como indicador de processos pedogênicos em solos poligenéticos, bem como contribuir para um melhor entendimento do comportamento químico e físico desses solos.Iron oxides from 22 soil samples (19 from argillic B horizons; one from a plinthic B horizon; one from a cambic horizon and one from a C horizon were subjected to selective dissolution with sodium dithionite-citrate-bicarbonate at 20 ºC in time intervals of 5 to 3,840 minutes. Mean coherence lengths (MCL, specific surface area (SSA and iron by aluminum substitution (Al3+-substitution of goethite and hematite in untreated sub-samples and in selected sub-samples treated during selective dissolution were estimated by X ray diffraction analysis (XRD. The control of remaining goethite and hematite phases after each time interval of selective dissolution was carried out by differential X ray diffraction (DXRD. The crystal dissolution kinetics was described by segmentation of the iron dissolution curve as a time function at the intervals where dissolution occurred linearly. Dissolution rates of each linear segment were obtained by the angular coefficient of the straight line of each linear segment. In the latossolic goethitic samples, this methodology discriminated different phases of goethite (heterogeons populations regarding Al3+-substitution, MCL and SSA, making possible to classify goethite stability degrees (low, medium, high, and very high stability. Goethite samples from young pedogenic environments and latossolic hematitic samples were characterized by higher crystal homogeneity, which were classified as being of low and medium stability. In goethitic samples, crystal proportion with high stability (high Al3+-substitution and crystallinity in each population showed positive association with gibbisite proportion compared to caulinite in the samples. Hematite

  20. Iron Isotopes in Spherical Hematite and Goethite Concretions from the Navajo Sandstone (Utah, USA): A Prospective Study for "Martian Blueberries"

    Science.gov (United States)

    Busigny, V.; Dauphas, N.

    2006-03-01

    Iron isotopes of terrestrial hematite and goethite concretions provide clues on fluid transport, reservoir sizes, redox variations and biotic versus abiotic processes. This opens several avenues of research for future work on Martian blueberries.

  1. Substitutional analysis

    CERN Document Server

    Rutherford, Daniel Edwin

    2013-01-01

    Classic monograph, suitable for advanced undergraduates and graduate students. Topics include calculus of permutations and tableaux, semi-normal representation, orthogonal and natural representations, group characters, and substitutional equations. 1968 edition.

  2. Synthesis and characterization of boehmite γ-AIOOH and goethite α-FeOOH

    International Nuclear Information System (INIS)

    Corral C, N. G.; Granados C, F.

    2009-01-01

    The aluminum oxy-hydroxides (boehmite) and of iron (goethite) were synthesized by means of the Sol-Gel and oxidative hydrolysis methods, to be employees as adsorbent materials of the present Cd 2+ in aqueous solution. The synthesized materials were characterized by means of X-ray diffraction, infrared analysis and scanning electron microscopy, to identify their purity, elementary chemical composition and morphology. (Author)

  3. The adsorption and dissociation of water molecule on goethite (010) surface: A DFT approach

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Long, E-mail: shuweixia@ouc.edu.cn [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, College of Chemistry and Chemical Engineering (China); Xiu, Fangyuan [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, College of Chemistry and Chemical Engineering (China); Qiu, Meng [Qingdao Institute of Bioenergy and Bioprocess Technology (China); Xia, Shuwei; Yu, Liangmin [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, College of Chemistry and Chemical Engineering (China)

    2017-01-15

    Graphical abstract: The optimized structure of hydrated goethite (010) surface with medium water coverage (water density about 6.7 H{sub 2}O/nm{sup 2}). - Highlights: • Stable adsorption and dissociation structure of H{sub 2}O on goethite (010) surface was investigated by DFT. • Reasonable path for water dissociation was proposed by transitional state analysis. • The mechanism of water adsorption on goethite and binding nature were revealed by PDOS. - Abstract: Using density functional theory (DFT) calculation, we investigate the configuration, stability and electronic properties of fresh cleaved (010) goethite surface (Pnma) and this surface exposed to water monolayer at low, medium and high coverage. Water is predicted to be chemisorbed to the surface, together with the surface reconstruction. The interaction energy of the most stable configuration of both low and medium coverage per water molecule is almost the same (−1.17 eV), while that of high coverage is much lower (less than 1.03 eV). It indicates that highly hydrated surface is less stable. PDOS analysis reveals the adsorption of H{sub 2}O is due to the formation of Fe−O bond, caused by overlapping of Fe's 3d and O's 2p orbitals. Dissociation processes at low and medium water coverage are non-spontaneous; while at high coverage, it can undertake spontaneously both thermodynamically and dynamically. The dissociation paths of all three water coverage are the similar. The proton from one adsorbed water is likely to dissociate to bind to the vicinal surface μ{sub 3}−O as an intermediate product; the proton belonged to μ{sub 3}−O transferred to the neighbor surface μ{sub 2}−O as the dissociative configuration.

  4. Anomalous Particle Size Dependence of Magnetic Relaxation Phenomena in Goethite Nanoparticles

    DEFF Research Database (Denmark)

    Frandsen, Cathrine; Madsen, Daniel Esmarch; Boothroyd, Chris B.

    2015-01-01

    By use of Mossbauer spectroscopy we have studied the magnetic properties of samples of goethite nanoparticles with different particle size. The spectra are influenced by fluctuations of the magnetization directions, but the size dependence is not in accordance with the Neel-Brown expression...... for superparamagnetic relaxation of the magnetization vectors of the particles as a whole. The data suggest that the magnetic fluctuations can be explained by fluctuations of the magnetization directions of small interacting grains within the particles....

  5. Surface hydroxyl configuration of various crystal faces of hematite and goethite

    Energy Technology Data Exchange (ETDEWEB)

    Barron, V.; Torrent, J. [Universidad de Cordoba (Spain). Dept. de Ciencias y Recursos Agricolas y Forestales

    1996-02-10

    The surface properties of oxides and hydroxides depend on their surface hydroxyl configuration (SHC). Unfortunately, the SHC of the various Fe (hydr) oxides has not been systematically studied to date. This paper reports the SHC of the hematite {l_brace}100{r_brace}, {l_brace}110{r_brace}, {l_brace}012{r_brace}, {l_brace}104{r_brace}, {l_brace}018{r_brace}, {l_brace}113{r_brace}, and {l_brace}001{r_brace}, and the goethite {l_brace}100{r_brace}, {l_brace}010{r_brace}, {l_brace}110{r_brace}, and {l_brace}021{r_brace} faces, which are the most common in natural and synthetic specimens. Both minerals exhibit marked differences between faces, particularly with regard to the presence and proportion of singly, doubly, and triply coordinated OH groups. Pairs of contiguous singly coordinated OH groups, which are involved in the specific adsorption of phosphate and other ions, occur on all the goethite faces studied, but not on those of hematite. According to the hypotheses inherent in some models, the variable SHC of hematite and goethite faces should result in marked differences in proton and adsorption and, hence, surface charging properties.

  6. Oxidation of Cr(III) on birnessite surfaces: The effect of goethite and kaolinite.

    Science.gov (United States)

    Zhong, Laiyuan; Yang, Jiewen; Liu, Liming; Xing, Baoshan

    2015-11-01

    Oxidation of Cr(III) by manganese oxides may pose a potential threat to environments due to the formation of toxic Cr(VI) species. At present, it was still unclear whether the extent of Cr(III) oxidation and fate of Cr(VI) would be changed when manganese oxides co-exist with other minerals, the case commonly occurring in soils. This study investigated the influence of goethite and kaolinite on Cr(III) oxidation by birnessite under acidic pH condition (pH3.5) and background electrolyte of 0.01mol/L NaCl. Goethite was found not to affect Cr(III) oxidation, which was interpreted as the result of overwhelming adsorption of cationic Cr(III) onto the negatively-charged birnessite (point of zero charge (PZC)kaolinite (PZC<3.0), indicating its low affinity for Cr species. Reactions occurring in the present mixed systems were suggested, which could be partly representative of those in the soils and further indicates that the mobility and risk of Cr(VI) would be decreased if goethite was present. Copyright © 2015. Published by Elsevier B.V.

  7. Ageing in a system of polydisperse goethite boardlike particles showing rich phase behaviour

    Science.gov (United States)

    Reinink, A. B. G. M. Leferink op; van den Pol, E.; Byelov, D. V.; Petukhov, A. V.; Vroege, G. J.

    2012-11-01

    Using microradian x-ray scattering and polarized light microscopy the rich liquid crystalline phase behaviour of a polydisperse system of chromium-modified goethite particles has been studied for five years. We observe that the particles stay highly mobile over years and the rich phase behaviour keeps developing in novel and even surprising ways. While in many other colloidal systems particle size polydispersity suppresses the formation of ordered phases, goethite particles form multiple coexisting ordered phases. The particle polydispersity problem is then solved by particle exchange between coexisting phases. One usually expects that a less ordered phase (e.g., nematic) is formed first while crystallization of the smectic and columnar crystals might take a longer time. For goethite particles we find the opposite, i.e. the nematic phase grows over years at the expense of a better ordered smectic phase. Moreover, SAXS patterns revealed peak splitting for both the smectic and the columnar phase, meaning that the system displays fractionated crystallization. We further discovered that the centred rectangular columnar phase spontaneously forms out of the simple rectangular columnar phase. The reverse transition is observed as well. We explain the ease of these martensitic transitions by showing how slight rotation and translation of the particles triggers the transition.

  8. Oxidation of a Dimethoxyhydroquinone by Ferrihydrite and Goethite Nanoparticles: Iron Reduction versus Surface Catalysis.

    Science.gov (United States)

    Krumina, Lelde; Lyngsie, Gry; Tunlid, Anders; Persson, Per

    2017-08-15

    Hydroquinones are important mediators of electron transfer reactions in soils with a capability to reduce Fe(III) minerals and molecular oxygen, and thereby generating Fenton chemistry reagents. This study focused on 2,6-dimethoxy hydroquinone (2,6-DMHQ), an analogue to a common fungal metabolite, and its reaction with ferrihydrite and goethite under variable pH and oxygen concentrations. Combined wet-chemical and spectroscopic analyses showed that both minerals effectively oxidized 2,6-DMHQ in the presence of oxygen. Under anaerobic conditions the first-order oxidation rate constants decreased by one to several orders of magnitude depending on pH and mineral. Comparison between aerobic and anaerobic results showed that ferrihydrite promoted 2,6-DMHQ oxidation both via reductive dissolution and heterogeneous catalysis while goethite mainly caused catalytic oxidation. These results were in agreement with changes in the reduction potential (E H ) of the Fe(III) oxide/Fe(II) aq redox couple as a function of dissolved Fe(II) where E H of goethite was lower than ferrihydrite at any given Fe(II) concentration, which makes ferrihydrite more prone to reductive dissolution by the 2,6-DMBQ/2,6-DMHQ redox couple. This study showed that reactions between hydroquinones and iron oxides could produce favorable conditions for formation of reactive oxygen species, which are required for nonenzymatic Fenton-based decomposition of soil organic matter.

  9. Carbonate adsorption onto goethite as a function of pH and ionic strength

    International Nuclear Information System (INIS)

    Rundberg, R.S.; Albinsson, Y.

    1991-01-01

    The adsorption of carbonate onto geothite was studied as a function of both pH and ionic strength (NaClO 4 electrolyte) using 14 C tracer. The pH ranged from 2.5 to 11.6. The ionic strength was controlled by varying the NaClO 4 concentration and ranged from 0.01 to 0.1 molar. The results indicate that carbonate is adsorbed on goethite as primarily an inner-sphere complex at pH values above the point of zero charge. This is inferred from the lack of dependence on ionic strength in the adsorption of carbonate. Below the point of zero charge carbonate is adsorbed by an additional outer-sphere mechanism. An adsorption isotherm was measured at pH 7.0 with an electrolyte concentration of 0.01M. Deconvolution of the isotherm proved that at least two sorption mechanisms exist. These mechanisms lead to large distribution coefficients at low pH. Thereby making the complete removal and exclusion of carbonate from an aqueous goethite system difficult, for the purpose of characterizing a ''clean'' goethite surface

  10. Lead and selenite adsorption at water-goethite interfaces from first principles

    Science.gov (United States)

    Leung, Kevin; Criscenti, Louise J.

    2017-09-01

    The complexation of toxic and/or radioactive ions on to mineral surfaces is an important topic in geochemistry. We apply periodic-boundary-conditions density functional theory (DFT) molecular dynamics simulations to examine the coordination of Pb(II), SeO_32- , and their contact ion pairs to goethite (1 0 1) and (2 1 0) surfaces. The multitude of Pb(II) adsorption sites and possibility of Pb(II)-induced FeOH deprotonation make this a complex problem. At surface sites where Pb(II) is coordinated to three FeO and/or FeOH groups, and with judicious choices of FeOH surface group protonation states, the predicted Fe-Pb distances are in good agreement with EXAFS measurements. Trajectories where Pb(II) is in part coordinated to only two surface Fe-O groups exhibit larger fluctuations in Pb-O distances. Pb(II)/SeO_32- contact ion pairs are at least metastable on goethite (2 1 0) surfaces if the SeO_32- has a monodentate Se-O-Fe bond. Our DFT-based molecular dynamics calculations are a prerequisite for calculations of finite temperature equilibrium binding constants of Pb(II) and Pb(II)/SeO_32- ion pairs to goethite adsorption sites.

  11. Specific-heat measurement of single metallic, carbon, and ceramic fibers at very high temperature

    International Nuclear Information System (INIS)

    Pradere, C.; Goyheneche, J.M.; Batsale, J.C.; Dilhaire, S.; Pailler, R.

    2005-01-01

    The main objective of this work is to present a method for measuring the specific heat of single metallic, carbon, and ceramic fibers at very high temperature. The difficulty of the measurement is due to the microscale of the fiber (≅10 μm) and the important range of temperature (700-2700 K). An experimental device, a modelization of the thermal behavior, and an analytic model have been developed. A discussion on the measurement accuracy yields a global uncertainty lower than 10%. The characterization of a tungsten filament with thermal properties identical to those of the bulk allows the validation of the device and the thermal estimation method. Finally, measurements on carbon and ceramic fibers have been done at very high temperature

  12. Influence of Fulvic Acid Coatings on Plutonium Sorption to Goethite Colloids

    Science.gov (United States)

    Tinnacher, R. M.; Begg, J.; Powell, B. A.; Zavarin, M.; Kersting, A. B.

    2011-12-01

    Mineral colloids may enhance plutonium (Pu) mobility in subsurface environments on the field scale. However, the relevance of colloid-facilitated metal transport is strongly dependent on the kinetics of metal sorption/desorption reactions on colloidal surfaces. Furthermore, in the natural environment, natural organic matter (NOM) is ubiquitous, and mineral surfaces are often not 'bare' but naturally coated with NOM. At this point, it is not clear if and how NOM affects Pu interactions with mineral colloids. For instance, organic matter coatings could bind Pu thereby increasing the fraction of sorbed Pu onto colloids, or slowing down Pu desorption kinetics. This would further stabilize Pu associated with mineral particles, and enhance metal mobility. In addition, dissolved fractions of natural organic ligands may influence Pu sorption behavior based on two primary effects: (1) Pu-NOM solution complexation, and (2) NOM-driven control of Pu oxidation states. Both may indirectly affect metal-mineral interactions, as 'free' metals, metal-ligand complexes, and various Pu redox species potentially show different metal sorption affinities and kinetics. The primary goal of this study was the experimental characterization of Pu sorption behavior onto goethite colloids in ternary Pu-NOM-mineral colloid systems. In these systems, fulvic acid (FA), is either present in form of organic matter surface coatings or as dissolved organic ligands. Lab-scale metal sorption/desorption experiments were set up under controlled, chemical conditions (2 g/L goethite, PuTot=1E-10 M, FA=0.5, 5, 50 mg/L TOC, pH=4, I=0.01 M NaCl) in order to evaluate Pu sorption/desorption kinetics in (1) the absence of fulvic acid; (2) the presence of pre-equilibrated Pu-FA solution complexes; and (3) the presence of FA coatings on goethite particles. Both, Pu and FA sorption reactions were monitored over time, which allows for a comparison of Pu and FA sorption kinetics, and provides insights into the

  13. Solvent substitution

    International Nuclear Information System (INIS)

    1990-01-01

    The DOE Environmental Restoration and Waste Management Office of Technology Development and the Air Force Engineering and Services Center convened the First Annual International Workshop on Solvent Substitution on December 4--7, 1990. The primary objectives of this joint effort were to share information and ideas among attendees in order to enhance the development and implementation of required new technologies for the elimination of pollutants associated with industrial use of hazardous and toxic solvents; and to aid in accelerating collaborative efforts and technology transfer between government and industry for solvent substitution. There were workshop sessions focusing on Alternative Technologies, Alternative Solvents, Recovery/Recycling, Low VOC Materials and Treatment for Environmentally Safe Disposal. The 35 invited papers presented covered a wide range of solvent substitution activities including: hardware and weapons production and maintenance, paint stripping, coating applications, printed circuit boards, metal cleaning, metal finishing, manufacturing, compliance monitoring and process control monitoring. This publication includes the majority of these presentations. In addition, in order to further facilitate information exchange and technology transfer, the US Air Force and DOE solicited additional papers under a general ''Call for Papers.'' These papers, which underwent review and final selection by a peer review committee, are also included in this combined Proceedings/Compendium. For those involved in handling, using or managing hazardous and toxic solvents, this document should prove to be a valuable resource, providing the most up-to-date information on current technologies and practices in solvent substitution. Individual papers are abstracted separated

  14. Solvent substitution

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    The DOE Environmental Restoration and Waste Management Office of Technology Development and the Air Force Engineering and Services Center convened the First Annual International Workshop on Solvent Substitution on December 4--7, 1990. The primary objectives of this joint effort were to share information and ideas among attendees in order to enhance the development and implementation of required new technologies for the elimination of pollutants associated with industrial use of hazardous and toxic solvents; and to aid in accelerating collaborative efforts and technology transfer between government and industry for solvent substitution. There were workshop sessions focusing on Alternative Technologies, Alternative Solvents, Recovery/Recycling, Low VOC Materials and Treatment for Environmentally Safe Disposal. The 35 invited papers presented covered a wide range of solvent substitution activities including: hardware and weapons production and maintenance, paint stripping, coating applications, printed circuit boards, metal cleaning, metal finishing, manufacturing, compliance monitoring and process control monitoring. This publication includes the majority of these presentations. In addition, in order to further facilitate information exchange and technology transfer, the US Air Force and DOE solicited additional papers under a general Call for Papers.'' These papers, which underwent review and final selection by a peer review committee, are also included in this combined Proceedings/Compendium. For those involved in handling, using or managing hazardous and toxic solvents, this document should prove to be a valuable resource, providing the most up-to-date information on current technologies and practices in solvent substitution. Individual papers are abstracted separated.

  15. Sugar Substitutes

    Science.gov (United States)

    ... and drinks. You may have heard them called “artificial sweeteners” or “non-caloric sweeteners.” They can be used ... a food or drink contains. What sugar substitutes/artificial sweeteners are approved by the FDA? The following sugar ...

  16. Investigating sorption on iron-oxyhydroxide soil minerals by solid-state NMR spectroscopy: a 6Li MAS NMR study of adsorption and absorption on goethite

    DEFF Research Database (Denmark)

    Nielsen, Ulla Gro; Paik, Younkee; Julmis, Keinia

    2005-01-01

    High-resolution 2H MAS NMR spectra can be obtained for nanocrystalline particles of goethite (alpha-FeOOH, particle size approximately 4-10 nm) at room temperature, facilitating NMR studies of sorption under environmentally relevant conditions. Li sorption was investigated as a function of pH, th...... on the goethite surface. Even larger Li hyperfine shifts (289 ppm) were observed for Li+-exchanged goethite, which contains lithium ions in the tunnels of the goethite structure, confirming the Li assignment of the 145 ppm Li resonance to the surface sites. Udgivelsesdato: 2005-Oct-6...

  17. Zn isotopic fractionation caused by sorption on goethite and 2-Lines ferrihydrite

    Science.gov (United States)

    Juillot, F.; Maréchal, C.; Ponthieu, M.; Cacaly, S.; Morin, G.; Benedetti, M.; Hazemann, J. L.; Proux, O.; Guyot, F.

    2008-10-01

    Zn isotopic fractionation caused by sorption on 2-Lines ferrihydrite (Fh2L) and goethite was investigated to assess the role of reactions at the Fe-oxyhydroxide/water interface in changes of the isotopic distribution of Zn. Since sorption reactions are ubiquitous in Earth's surface environments, it is important to evaluate their influence on the isotopic distribution of Zn before it can be used to track and quantify contributions of various sources and/or biogeochemical processes involving this element. Our results show that Zn isotopes are fractionated upon sorption on Fe-oxyhydroxides with an enrichment of the heavy isotopes present on the solid's surface. This fractionation appears to proceed through an equilibrium mechanism and yields different (Δ 66/64Zn) sorbed-aqueous values for Zn sorption on goethite [(Δ 66/64Zn) sorbed-aqueous around +0.29‰] and Fh2L [(Δ 66/64Zn) sorbed-aqueous around +0.53‰]. These different magnitudes of Zn fractionation are related to structural differences between Zn complexes existing on the surface of goethite (octahedrally coordinated Zn by oxygen atoms) and Fh2L (tetrahedrally coordinated Zn by oxygen atoms), as evidenced by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy and CD-MUSIC modeling. These results show the importance of accounting for reactions at the Fe-oxyhydroxide/water interface when dealing with the isotopic distribution of Zn at the Earth's surface. Considering the large range of other possible sorbents (Mn or Al oxides, phyllosilicates, carbonates, biologic surfaces, etc.) and the importance of reactions at sorbent/water interfaces for other non-traditional stable isotopes (i.e. Cr, Fe, Ni and Cu) that are increasingly used in environmental studies, these results emphasize the need for further experimental studies that are needed to quantify the isotopic fractionation of these elements possibly accompanying their sorption.

  18. Measurements and modelling of Pm sorption onto TiO2 and goethite

    International Nuclear Information System (INIS)

    Jakobsson, A.M.; Albinsson, Y.; Rundberg, R.S.

    2004-01-01

    The sorption of Pm (1 x 10 -9 M) onto TiO 2 and goethite has been studied as a function of pH and ionic strength (0.01, 0.1 M NaClO 4 ) at ambient temperature under N 2 atmosphere. For both minerals studied there is no effect of the different ionic strengths and the sorption (log K a vs. pH) increases with a slope of ∝2. At the same pH sorption is lower on the more positively (or less negatively) charged goethite (pH pzc = 8.4) than on the TiO 2 (pH pzc = 6.2). A comparison to other trivalent cations sorbed on different substrates (made by extracting values from %-sorbed curves and calculating these to K a ) indicate a similar pH-dependence. The results have been fitted using a 1-pK basic stern model with FITEQL [1]. An a priori restriction was that only one sorption reaction stoichiometry at a time was to be used to keep the number of parameters as small as possible. Outersphere and mono-, bi- and tri-dentate inner-sphere complexes were fitted. For each fit the value of the capacitance was varied to find the value that provided the best fit. Two different site densities were used: 1 site/nm 2 and 2.31 sites/nm 2 . For the low site density the reaction which provides the best fit was: ≡ SOH 0.5- + Pm +3 ≡ SOHPm 2.5+ for both minerals. At the high site density the same reaction fits for TiO 2 while there are several reactions that are equivalent in the fit for goethite. (orig.)

  19. Equilibrium isotherms, kinetics, and thermodynamics studies for congo red adsorption using calcium alginate beads impregnated with nano-goethite.

    Science.gov (United States)

    Munagapati, Venkata Subbaiah; Kim, Dong-Su

    2017-07-01

    The present study is concerned with the batch adsorption of congo red (CR) from an aqueous solution using calcium alginate beads impregnated with nano-goethite (CABI nano-goethite) as an adsorbent. The optimum conditions for CR removal were determined by studying operational variables viz. pH, adsorbent dose, contact time, initial dye ion concentration and temperature. The CABI nano-goethite was characterized by Fourier transform infrared spectroscopy (FTIR), X- ray diffraction (XRD) and Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. The CR sorption data onto CABI nano-goethite were described using Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The results show that the best fit was achieved with the Langmuir isotherm model. The maximum adsorption capacity (181.1mg/g) of CR was occurred at pH 3.0. Kinetic studies showed that the adsorption followed a pseudo-second-order model. Desorption experiments were carried out to explore the feasibility of regenerating the adsorbent and the adsorbed CR from CABI nano-goethite. The best desorbing agent was 0.1M NaOH with an efficiency of 94% recovery. The thermodynamic parameters ΔG°, ΔH°, and ΔS° for the CR adsorption were determined by using adsorption capacities at five different temperatures (293, 303, 313, 323 and 303K). Results show that the adsorption process was endothermic and favoured at high temperature. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. The assembly of rotaxane-like dye/cyclodextrin/surface complexes on aluminium trihydroxide or goethite.

    Science.gov (United States)

    Cooper, Rachel J; Camp, Philip J; Gordon, Ross J; Henderson, David K; Henry, Dorothy C R; McNab, Hamish; De Silva, Sonali S; Tackley, Daniel; Tasker, Peter A; Wight, Paul

    2006-06-21

    Simple azo-dyes carrying phosphonic acid and arsonic acid substituents such as 4-(4-hydroxyphenyl azo)phenylphosphonic acid (5) and 4-(4-hydroxyphenylazo)phenylarsonic acid (6) bind more strongly to high surface area oxides such as aluminium trihydroxide and goethite than their carboxylic and sulfonic acid analogues and the phosphonate-functionalized dyes have been shown to have greater humidity fastness when printed onto commercial alumina-coated papers. Adsorption isotherm measurements provide evidence for the formation of ternary dye/cyclodextrin/surface complexes. Dyes which form such ternary complexes show higher light fastness when printed onto alumina coated papers in an ink formulation containing alpha-cyclodextrin.

  1. Surface Complexation Model for Strontium Sorption to Amorphous Silica and Goethite

    Energy Technology Data Exchange (ETDEWEB)

    Carroll, S; Robers, S; Criscenti, L; O' Day, P

    2007-11-30

    Strontium sorption to amorphous silica and goethite was measured as a function of pH and dissolved strontium and carbonate concentrations at 25 C. Strontium sorption gradually increases from 0 to 100% from pH 6 to 10 for both phases and requires multiple outer-sphere surface complexes to fit the data. All data are modeled using the triple layer model and the site-occupancy standard state; unless stated otherwise all strontium complexes are mononuclear. Strontium sorption to amorphous silica in the presence and absence of dissolved carbonate can be fit with tetradentate Sr{sup 2+} and SrOH{sup +} complexes on the {beta}-plane and a monodentate Sr{sup 2+} complex on the diffuse plane to account for strontium sorption at low ionic strength. Strontium sorption to goethite in the absence of dissolved carbonate can be fit with monodentate and tetradentate SrOH{sup +} complexes and a tetradentate binuclear Sr{sup 2+} species on the {beta}-plane. The binuclear complex is needed to account for enhanced sorption at high strontium surface loadings. In the presence of dissolved carbonate additional monodentate Sr{sup 2+} and SrOH{sup +} carbonate surface complexes on the {beta}-plane are needed to fit strontium sorption to goethite. Modeling strontium sorption as outer-sphere complexes is consistent with quantitative analysis of extended X-ray absorption fine structure (EXAFS) on selected sorption samples that show a single first shell of oxygen atoms around strontium indicating hydrated surface complexes at the amorphous silica and goethite surfaces. Strontium surface complexation equilibrium constants determined in this study combined with other alkaline earth surface complexation constants are used to recalibrate a predictive model based on Born solvation and crystal-chemistry theory. The model is accurate to about 0.7 log K units. More studies are needed to determine the dependence of alkaline earth sorption on ionic strength and dissolved carbonate and sulfate

  2. Transformation of goethite/ferrihydrite to hematite and maghemite under temperate humid conditions in Denmark

    DEFF Research Database (Denmark)

    Nørnberg, P.; Finster, K.; Gunnlaugsson, Haraldur Pall

    2012-01-01

    , in the same geographical region, and in extended areas with high iron content (8-40 %) in the topsoil. Hematite and particularly maghemite would normally not be expected to form under the temperate humid Danish climate, but be interpreted as the result of high temperature as found in tropical regions...... to fire. 1) The pH in the topsoil is 3.6 - 4.8 and thus not raised by ashes. 2) No charcoal is present. 3) There is no indication of fire outside the high iron content areas. 4) Goethite is present along with hematite and maghemite in microparticles, and the mineralogical zonation produced in a forest...

  3. Monosilicate adsorption by ferrihydrite and goethite at pH 3-6

    DEFF Research Database (Denmark)

    Hansen, Hans Christian Bruun; Raben-Lange, B.; Raulund-Rasmussen, Karsten

    1994-01-01

    The constant capacitance model and the Elovich equation were combined in the following mathematical expression enabling calculation of the amount of silicic acid adsorbed by iron oxides as a function of the Si concentration, pH, soil:solution ratio, and reaction time: [GRAPHICS] K(a1...... ferrihydrite and goethite at different pH (3-6), Si concentration (1-600 muM), solid:solution ratio (1:300, 1:1200) and reaction time (1-480h)....

  4. Surface complexation model for strontium sorption to amorphous silica and goethite

    Directory of Open Access Journals (Sweden)

    Criscenti Louise J

    2008-01-01

    Full Text Available Abstract Strontium sorption to amorphous silica and goethite was measured as a function of pH and dissolved strontium and carbonate concentrations at 25°C. Strontium sorption gradually increases from 0 to 100% from pH 6 to 10 for both phases and requires multiple outer-sphere surface complexes to fit the data. All data are modeled using the triple layer model and the site-occupancy standard state; unless stated otherwise all strontium complexes are mononuclear. Strontium sorption to amorphous silica in the presence and absence of dissolved carbonate can be fit with tetradentate Sr2+ and SrOH+ complexes on the β-plane and a monodentate Sr2+complex on the diffuse plane to account for strontium sorption at low ionic strength. Strontium sorption to goethite in the absence of dissolved carbonate can be fit with monodentate and tetradentate SrOH+ complexes and a tetradentate binuclear Sr2+ species on the β-plane. The binuclear complex is needed to account for enhanced sorption at hgh strontium surface loadings. In the presence of dissolved carbonate additional monodentate Sr2+ and SrOH+ carbonate surface complexes on the β-plane are needed to fit strontium sorption to goethite. Modeling strontium sorption as outer-sphere complexes is consistent with quantitative analysis of extended X-ray absorption fine structure (EXAFS on selected sorption samples that show a single first shell of oxygen atoms around strontium indicating hydrated surface complexes at the amorphous silica and goethite surfaces. Strontium surface complexation equilibrium constants determined in this study combined with other alkaline earth surface complexation constants are used to recalibrate a predictive model based on Born solvation and crystal-chemistry theory. The model is accurate to about 0.7 log K units. More studies are needed to determine the dependence of alkaline earth sorption on ionic strength and dissolved carbonate and sulfate concentrations for the development of

  5. X-ray photoelectron spectroscopy study of interaction of Np5+ with goethite α-FeOOH

    Directory of Open Access Journals (Sweden)

    Teterin Yury A.

    2005-01-01

    Full Text Available Neptunyl NpO2n+ complexes on the surface of goethite α-(FeOOH resulted from the interaction of neptunyl nitrate (NpO2NO3, 10-6 M in the aqueous media with the background electrolyte (NaClO4 of ionic force 0.1 M (pH = 7.0 ± 0.2 were formed and studied with the X-ray photo electron spectroscopy. The X-ray photoelectron spectroscopy ionic and elemental quantitative analysis of the goethite and products of its interaction with neptunyl and plutonyl nitrates was carried out. It was established that during the studied neptunyl nitrate - goethite interaction Np4+ and Np6+ com pounds did not to form, while the complexes of neptunyl group NpO21+ containing Np5+ ions with oxygen, water and/or car bon ate ions in the equatorial planes did.

  6. In situ ATR FTIR studies of SO4 adsorption on goethite in the presence of copper ions.

    Science.gov (United States)

    Beattie, D A; Chapelet, J K; Gräfe, M; Skinner, W M; Smith, E

    2008-12-15

    Despite the existence of many single ion sorption studies on iron and aluminum oxides, fewer studies have been reported that describe cosorption reactions. In this work, we present an in situ ATR FTIR study of synergistic adsorption of sulfate (SO4) and copper (Cu) on goethite, which is representative of the minerals and ions present in mine wastes, acid sulfate soils, and other industrial and agricultural settings. Sulfate adsorption was studied as a function of varying pH, and as a function of increasing concentration in the absence and presence of Cu. The presence of Cu ions in solution had a complex effect on the ability of SO4 ions to be retained on the goethite surface with increasing pH, with complete desorption occurring near pH 7 and 9 in the absence and presence of Cu, respectively. In addition, Cu ions altered the balance of inner vs outer sphere adsorbed SO4. The solid phase partitioning of SO4 at pH 3 and pH 5 was elevated by the presence of Cu; in both cases Cu increased the affinity of SO4 for the goethite surface. Complementary ex situ sorption edge studies of Cu on goethite in the absence and presence of SO4 revealed that the Cu adsorption edge shifted to lower pH (6.3 --> 5.6) in the presence of SO4, consistent with a decrease of the electrostatic repulsion between the goethite surface and adsorbing Cu. Based on the ATR FTIR and bulk sorption data we surmise that the cosorption products of SO4 and Cu at the goethite-water interface were not in the nature of ternary complexes under the conditions studied here. This information is critical for the evaluation of the onset of surface precipitates of copper-hydroxy sulfates as a function of pH and solution concentration.

  7. Monosilicate adsorption by ferrihydrite and goethite at pH 3-6

    DEFF Research Database (Denmark)

    Hansen, Hans Christian Bruun; Raben-Lange, B.; Raulund-Rasmussen, Karsten

    1994-01-01

    The constant capacitance model and the Elovich equation were combined in the following mathematical expression enabling calculation of the amount of silicic acid adsorbed by iron oxides as a function of the Si concentration, pH, soil:solution ratio, and reaction time: [GRAPHICS] K(a1) is the prot......The constant capacitance model and the Elovich equation were combined in the following mathematical expression enabling calculation of the amount of silicic acid adsorbed by iron oxides as a function of the Si concentration, pH, soil:solution ratio, and reaction time: [GRAPHICS] K(a1......) is the protolytic surface constant and K(Si) is the stability constant for the Fe oxide-silicate surface complex; -logK(a1) = 6.40-0.54(8-pH) and logK(Si) = 3.85 for ferrihydrite and goethite. Good agreement was found between calculated Si adsorption and the amount actually found to be adsorbed by synthetic...... ferrihydrite and goethite at different pH (3-6), Si concentration (1-600 muM), solid:solution ratio (1:300, 1:1200) and reaction time (1-480h)....

  8. Liberation of Adsorbed and Co-Precipitated Arsenic from Jarosite, Schwertmannite, Ferrihydrite, and Goethite in Seawater

    Directory of Open Access Journals (Sweden)

    Rodrigo Alarcón

    2014-07-01

    Full Text Available Sea level rise is able to change the geochemical conditions in coastal systems. In these environments, transport of contaminants can be controlled by the stability and adsorption capacity of iron oxides. The behavior of adsorbed and co-precipitated arsenic in jarosite, schwertmannite, ferrihydrite, and goethite in sea water (common secondary minerals in coastal tailings was investigated. The aim of the investigation was to establish As retention and transport under a marine flood scenario, which may occur due to climate change. Natural and synthetic minerals with co-precipitated and adsorbed As were contacted with seawater for 25 days. During this period As, Fe, Cl, SO4, and pH levels were constantly measured. The larger retention capability of samples with co-precipitated As, in relation with adsorbed As samples, reflects the different kinetics between diffusion, dissolution, and surface exchange processes. Ferrihydrite and schwertmannite showed good results in retaining arsenic, although schwertmannite holding capacity was enhanced due its buffering capacity, which prevented reductive dissolution throughout the experiment. Arsenic desorption from goethite could be understood in terms of ion exchange between oxides and electrolytes, due to the charge difference generated by a low point-of-zero-charge and the change in stability of surface complexes between synthesis conditions and natural media.

  9. Degradation and mineralization of phenol compounds with goethite catalyst and mineralization prediction using artificial intelligence.

    Directory of Open Access Journals (Sweden)

    Farhana Tisa

    Full Text Available The efficiency of phenol degradation via Fenton reaction using mixture of heterogeneous goethite catalyst with homogeneous ferrous ion was analyzed as a function of three independent variables, initial concentration of phenol (60 to 100 mg /L, weight ratio of initial concentration of phenol to that of H2O2 (1: 6 to 1: 14 and, weight ratio of initial concentration of goethite catalyst to that of H2O2 (1: 0.3 to 1: 0.7. More than 90 % of phenol removal and more than 40% of TOC removal were achieved within 60 minutes of reaction. Two separate models were developed using artificial neural networks to predict degradation percentage by a combination of Fe3+ and Fe2+ catalyst. Five operational parameters were employed as inputs while phenol degradation and TOC removal were considered as outputs of the developed models. Satisfactory agreement was observed between testing data and the predicted values (R2Phenol = 0.9214 and R2TOC= 0.9082.

  10. Nano size crystals of goethite, α-FeOOH: Synthesis and thermal transformation

    International Nuclear Information System (INIS)

    Christensen, Axel Norlund; Jensen, Torben R.; Bahl, Christian R.H.; DiMasi, Elaine

    2007-01-01

    An aqueous suspension of amorphous iron(III) hydroxide was kept at room temperature (298 K) for 23 years. During this period of time the pH of the liquid phase changed from 4.3 to 2.85, and nano size crystals of goethite, α-FeOOH crystallised from the amorphous iron(III) hydroxide. Transmission electron microscopy (TEM) investigations, Moessbauer spectra, and powder X-ray diffraction using Co Kα radiation showed that the only iron containing crystalline phase present in the recovered product was α-FeOOH. The size of these nano particles range from 10 to 100 nm measured by TEM. The thermal decomposition of α-FeOOH was investigated by time-resolved in situ synchrotron radiation powder X-ray diffraction and the data showed that the sample of α-FeOOH transformed to α-Fe 2 O 3 in the temperature range 444-584 K. A quantitative phase analysis shows the increase in scattered X-ray intensity from α-Fe 2 O 3 to follow the decrease of intensity from α-FeOOH in agreement with the topotactic phase transition. - Graphical abstract: Nano size crystals of goethite, α-FeOOH formed from amorphous iron(III) hydroxide after 23 years, and transforms faster to α-Fe 2 O 3 upon heating

  11. An XPS study of the adsorption of lead on goethite (α-FeOOH)

    Science.gov (United States)

    Abdel-Samad, Hesham; Watson, Philip R.

    1998-10-01

    The adsorption behavior of divalent metal ions on amphoteric surface hydroxyl groups of metal oxides is an important factor in the transport of subsurface environmental pollutants. We have studied the adsorption of lead ions from aqueous solution on the surface of the mineral goethite (α-FeOOH) as a function of pH and adsorbate concentration in 0.1 M NaNO 3 solution. Results obtained from the dried surface by X-ray photoelectron spectroscopy (XPS) are in good agreement with data from spectrophotometric analysis of lead ions remaining in the supernatant liquid. Lead adsorption as a function of pH shows an adsorption edge near pH 6 and maximizes by pH 7.5. The surface atomic Pb/Fe ratio at saturation as measured by XPS is 0.93 leading to an apparent high adsorption site density of 14.2 sites/nm 2. A characteristic low binding energy (BE) XPS feature is present in the Pb 4f XPS signal in the pH range 6-8. Comparison with literature predictions of the speciation of lead at a goethite surface suggests that this XPS feature is perhaps associated with a FeOPb + complex. At high Pb(II) concentrations some polynuclear complexes probably form. They may be responsible for the high site density value which, while crystallographically possible, is much higher than values reported by others working at lower Pb concentrations.

  12. Modeling Adsorption Kinetics of Magnesium and Phosphate Ions on Goethite by Empirical Equations

    Directory of Open Access Journals (Sweden)

    Malihe Talebi Atouei

    2017-06-01

    Full Text Available Introduction: Natural environments, including soils and sediments, are open and complex systems in which physico-chemical reactions are in semi equilibrium state. In these systems, bioavailability of plant nutrients, like phosphate, is influenced by environmental conditions and concentrations of other ions such as calcium and magnesium. Magnesium is a dominant cation in irrigation water and in the soil solution of calcareous soils. Recent evidences show relative increase in the concentration of magnesium in irrigation water. Because of the importance of chemical kinetics in controlling concentrations of these ions in the soil solution and for understanding their effects of adsorption kinetics of magnesium and phosphate ions, in this research, adsorption kinetics of these two ions on goethite is investigated as function of time and pH in single ion and binary ion systems. The experimental data are described by using the adsorption kinetics equations. These data are of the great importance in better understanding adsorption interactions and ion adsorption mechanism.With respect to the importance of these interactions from both economical and environmental point of view, in this research, the kinetics and thermodynamics of phosphate and Mg2adsorption interactions were investigated as function of pH on soil model mineral goethite in both single and binary ion systems. Materials and Methods: Kinetics experiments were performed in the presence of 0.2 mM magnesium and 0.4 mM phosphate in 0.1 M NaCl background solution and 3 g L-1 goethite concentration as function of pH and time (1, 5, 14, 24, 48. 72 and 168 h in single ion and binary ion systems. After reaction time, the suspensions were centrifuged and a sample of supernatant was taken for measuring ions equilibrium concentrations.Phosphate concentration was measured calorimetrically with the ammonium molybdate blue method by spectrophotometer (Jenway-6505 UV/Vis. Magnesium concentration was

  13. Do goethite surfaces really control the transport and retention of multi-walled carbon nanotubes in chemically heterogeneous porous media?

    Science.gov (United States)

    Transport and retention behavior of multiwalled carbon nanotubes (MWCNTs) was studied in mixtures of negatively charged quartz sand (QS) and positively charged goethite-coated sand (GQS) to assess the role of chemical heterogeneity. The linear equilibrium sorption model provided a good description o...

  14. Influence of calcium and phosphate on pH dependency of arsenite and arsenate adsorption to goethite

    NARCIS (Netherlands)

    Deng, Yingxuan; Li, Yongtao; Li, Xiaojing; Sun, Yang; Ma, Jie; Lei, Mei; Weng, Liping

    2018-01-01

    In the environment, simultaneous presence of arsenic (As) of different oxidation states is common, which hampers our understanding of As behavior. In the current study, the pH dependency of arsenite (As(III)) and arsenate (As(V)) adsorption to goethite under the influence of calcium (Ca2+) (as a

  15. Transformation of Goethite to Hematite Nanocrystallines by High Energy Ball Milling

    Directory of Open Access Journals (Sweden)

    O. M. Lemine

    2014-01-01

    Full Text Available α-Fe2O3 nanocrystallines were prepared by direct transformation via high energy ball milling treatment for α-FeOOH powder. X-ray diffraction, Rietveld analysis, TEM, and vibrating sample magnetometer (VSM are used to characterize the samples obtained after several milling times. Phase identification using Rietveld analysis showed that the goethite is transformed to hematite nanocrystalline after 40 hours of milling. HRTEM confirm that the obtained phase is mostly a single-crystal structure. This result suggested that the mechanochemical reaction is an efficient way to prepare some iron oxides nanocrystallines from raw materials which are abundant in the nature. The mechanism of the formation of hematite is discussed in text.

  16. Nanocrack Formation in Hematite through the Dehydration of Goethite and the Carbon Infiltration from Biotar

    Directory of Open Access Journals (Sweden)

    Yoshiaki Kashiwaya

    2010-01-01

    Full Text Available The cracks in nano-order are generated and propagated when the combined water is released during the dehydration. If the nanopore can be utilized for a reaction site, the overall reaction can be extremely accelerated. On the other hand, it is well known that woody biomass is an attractive alternative fuel for the reduction of CO2 emission. However, the process of biomass pyrolysis is disturbed by the tar which causes a clogging in gas tubing system. Hata et al. found that the tar was consumed almost 100% in the iron ore layer having nanocrack or nanopore. The nanocracks formed in hematite crystals after dehydration of goethite were about 4 nm in width, which is in excellent agreement with the result of BET measurement. When the carbon deposited from tar into the nanocracks, reduction reactions were occurred simultaneously. The deposited carbons completely infilled into the nanocracks and the void in the sample.

  17. Stochastic Simulation of Isotopic Exchange Mechanisms for Fe(II)-Catalyzed Recrystallization of Goethite

    Energy Technology Data Exchange (ETDEWEB)

    Zarzycki, Piotr [Energy; Institute; Rosso, Kevin M. [Pacific Northwest

    2017-06-15

    Understanding Fe(II)-catalyzed transformations of Fe(III)- (oxyhydr)oxides is critical for correctly interpreting stable isotopic distributions and for predicting the fate of metal ions in the environment. Recent Fe isotopic tracer experiments have shown that goethite undergoes rapid recrystallization without phase change when exposed to aqueous Fe(II). The proposed explanation is oxidation of sorbed Fe(II) and reductive Fe(II) release coupled 1:1 by electron conduction through crystallites. Given the availability of two tracer exchange data sets that explore pH and particle size effects (e.g., Handler et al. Environ. Sci. Technol. 2014, 48, 11302-11311; Joshi and Gorski Environ. Sci. Technol. 2016, 50, 7315-7324), we developed a stochastic simulation that exactly mimics these experiments, while imposing the 1:1 constraint. We find that all data can be represented by this model, and unifying mechanistic information emerges. At pH 7.5 a rapid initial exchange is followed by slower exchange, consistent with mixed surface- and diffusion-limited kinetics arising from prominent particle aggregation. At pH 5.0 where aggregation and net Fe(II) sorption are minimal, that exchange is quantitatively proportional to available particle surface area and the density of sorbed Fe(II) is more readily evident. Our analysis reveals a fundamental atom exchange rate of ~10-5 Fe nm-2 s-1, commensurate with some of the reported reductive dissolution rates of goethite, suggesting Fe(II) release is the rate-limiting step in the conduction mechanism during recrystallization.

  18. Stochastic Simulation of Isotopic Exchange Mechanisms for Fe(II)-Catalyzed Recrystallization of Goethite.

    Science.gov (United States)

    Zarzycki, Piotr; Rosso, Kevin M

    2017-07-05

    Understanding Fe(II)-catalyzed transformations of Fe(III)-(oxyhydr)oxides is critical for correctly interpreting stable isotopic distributions and for predicting the fate of metal ions in the environment. Recent Fe isotopic tracer experiments have shown that goethite undergoes rapid recrystallization without phase change when exposed to aqueous Fe(II). The proposed explanation is oxidation of sorbed Fe(II) and reductive Fe(II) release coupled 1:1 by electron conduction through crystallites. Given the availability of two tracer exchange data sets that explore pH and particle size effects (e.g., Handler et al. Environ. Sci. Technol. 2014 , 48 , 11302 - 11311 ; Joshi and Gorski Environ. Sci. Technol. 2016 , 50 , 7315 - 7324 ), we developed a stochastic simulation that exactly mimics these experiments, while imposing the 1:1 constraint. We find that all data can be represented by this model, and unifying mechanistic information emerges. At pH 7.5 a rapid initial exchange is followed by slower exchange, consistent with mixed surface- and diffusion-limited kinetics arising from prominent particle aggregation. At pH 5.0 where aggregation and net Fe(II) sorption are minimal, that exchange is quantitatively proportional to available particle surface area and the density of sorbed Fe(II) is more readily evident. Our analysis reveals a fundamental atom exchange rate of ∼10 -5 Fe nm -2 s -1 , commensurate with some of the reported reductive dissolution rates of goethite, suggesting Fe(II) release is the rate-limiting step in the conduction mechanism during recrystallization.

  19. Aggregation Rates of Sediments (Montmorillonite, Kaolinite, Illite and Goethite) with the Enveloped Φ6 Bacteriophage

    Science.gov (United States)

    Katz, A.; Block, K. A.; Peña, S.; Alimova, A.; Gottlieb, P.

    2015-12-01

    The interaction between sediments and viruses has been studied extensively from the prospective of virus survivability and infectivity. However, the role of soil organisms, including viruses in C and N sequestration in soil has not been studied as extensively. Φ6, a member of the cystoviridae family, is a bacteriophage that infects Pseudomonas syringae, a common plant pathogen known to readily form biofilms.The small mineral fraction (< 0.2 μm) of soil and Φ6 are colloidal particles, therefore aggregation can be explained by DLVO (Derjaguin & Landau, Verwey & Overbeek) theory. Time-resolved visible-light turbidity measurements were used to calculate the heteroaggregation rates of Φ6 with the sediments. Samples were suspended in a low-concentration cation buffer so that the kinetics were in the reaction limited cluster aggregation (RLCA) regime in where the probability of two particles adhering after collision is determined by the interaction forces between the particles.At neutral pH to slightly acidic pH, Φ6 is slightly negatively charged; montmorillonite and illite are negatively charged; and kaolinite and goethite are positively charged. In isolation, neither Φ6 nor the sediments aggregated in the modified buffer. However, in mixtures, Φ6 and montmorillonite, and Φ6 and illite, exhibited increases in turbidity, indicating heteroaggregation. Neither Φ6 and kaolinite, nor Φ6 and goethite, exhibited increased turbidity upon mixing indicating little or no aggregation. These results suggest that the interaction of the virus with the sediments is governed by hydrophobic rather than electrostatic forces. Heteroaggregation rates were calculated from the time rate of change of the turbidity.

  20. Kinetics of neptunium(V) sorption and desorption on goethite: An experimental and modeling study

    Science.gov (United States)

    Tinnacher, Ruth M.; Zavarin, Mavrik; Powell, Brian A.; Kersting, Annie B.

    2011-11-01

    Various sorption phenomena, such as aging, hysteresis and irreversible sorption, can cause differences between contaminant (ad)sorption and desorption behavior and lead to apparent sorption 'asymmetry'. We evaluate the relevance of these characteristics for neptunium(V) (Np(V)) sorption/desorption on goethite using a 34-day flow-cell experiment and kinetic modeling. Based on experimental results, the Np(V) desorption rate is much slower than the (ad)sorption rate, and appears to decrease over the course of the experiment. The best model fit with a minimum number of fitting parameters was achieved with a multi-reaction model including (1) an equilibrium Freundlich site (site 1), (2) a kinetically-controlled, consecutive, first-order site (site 2), and (3) a parameter ψ, which characterizes the desorption rate on site 2 based on a concept related to transition state theory (TST). This approach allows us to link differences in adsorption and desorption kinetics to changes in overall reaction pathways, without assuming different adsorption and desorption affinities (hysteresis) or irreversible sorption behavior a priori. Using modeling as a heuristic tool, we determined that aging processes are relevant. However, hysteresis and irreversible sorption behavior can be neglected within the time-frame (desorption over 32 days) and chemical solution conditions evaluated in the flow-cell experiment. In this system, desorption reactions are very slow, but they are not irreversible. Hence, our data do not justify an assumption of irreversible Np(V) sorption to goethite in transport models, which effectively limits the relevance of colloid-facilitated Np(V) transport to near-field environments. However, slow Np(V) desorption behavior may also lead to a continuous contaminant source term when metals are sorbed to bulk mineral phases. Additional long-term experiments are recommended to definitely rule out irreversible Np(V) sorption behavior at very low surface loadings and

  1. Goethite colloid enhanced Pu transport through a single saturated fracture in granite.

    Science.gov (United States)

    Lin, Jianfeng; Dang, Haijun; Xie, Jinchuan; Li, Mei; Zhou, Guoqing; Zhang, Jihong; Zhang, Haitao; Yi, Xiaowei

    2014-08-01

    α-FeOOH, a stable iron oxide in nature, can strongly absorb the low-solubility plutonium (Pu) in aquifers. However, whether Pu transports though a single saturated fracture can be enhanced in the presence of α-FeOOH colloids remains unknown. Experimental studies were carried out to evaluate Pu mobilization at different water flow velocity, as affected by goethite colloids with various concentrations. Goethite nanorods were used to prepare (α-FeOOH)-associated Pu suspensions with α-FeOOH concentration of (0-150) mgL(-1). The work experimentally evidenced that α-FeOOH colloid does enhance transport of Pu through fractured granites. The fraction of mobile (239)Pu (RPu, m=41.5%) associated with the α-FeOOH of an extremely low colloid concentration (0.2mgL(-1)) is much larger than that in absence of α-FeOOH (RPu, m=6.98%). However, plutonium mobility began to decrease when α-FeOOH concentration was increased to 1.0mgL(-1). On the other hand, the fraction of mobile Pu increased gradually with the water flow velocity. Based on the experimental data, the mechanisms underlying the (α-FeOOH)-associated plutonium transport are comprehensively discussed in view of its dynamic deposition onto the granite surfaces, which is decided mainly by the relative interaction between the colloid particle and the immobile surface. This interaction is a balance of electrostatic force (may be repulsive or attractive), the van der Walls force, and the shear stress of flow. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Redox characterization of the Fe(II)-catalyzed transformation of ferrihydrite to goethite

    Science.gov (United States)

    Jones, Adele M.; Collins, Richard N.; Waite, T. David

    2017-12-01

    The reduction potential of Fe(II)-Fe(III) (oxyhydr)oxide systems provides an important control on the biogeochemical cycling of redox-sensitive elements such as carbon and nitrogen as well as trace metals and organic contaminants in natural systems. As such, an in-depth understanding of the factors controlling the reduction potential of such systems is critical to predicting the likely transformation, transport and fate of these species in natural and perturbed environments. In this study the mineralogy and reduction potential of ferrihydrite suspensions at pH 6.50 and pH 7.00 were determined over the course of their Fe(II)-catalyzed transformation to lepidocrocite and goethite using X-ray absorption spectroscopy and mediated electrochemical approaches. The measured reduction potentials were compared to those of analogous Fe(II)-Fe(III) (oxyhydr)oxide suspensions reacted for 5 min containing pure ferrihydrite (Fh), lepidocrocite (L) and goethite (Gt). The reduction potentials of the pure Fe(II)-Fe(III) (oxyhydr)oxide suspensions were, respectively, +47.5, -13.5 and -122.3 mV vs. SHE at pH 6.5, and -22.9, -84.1 and -189.7 mV vs. SHE at pH 7. These values are in good agreement with reduction potentials calculated using the Nernst equation and reported thermodynamic solubility products indicating that these suspensions had reached equilibrium within 5 min. The reduction potential of the pH 6.50 Fe(II)-ferrihydrite suspension decreased from +47.4 mV to -126.4 mV over a week, and from -20.1 mV to -188.4 mV (all vs. SHE) after 24 h at pH 7. The changes in reduction potential over time matched well to those calculated from the relative proportion of each pure Fe(III) (oxyhydr)oxide present suggesting that Fe3+ activity was influenced by the mix of iron oxides present rather than the most insoluble solid species. Finally, evidence is provided that adsorbed Fe(II) has the capacity to reduce a significantly larger fraction of a reducible species than the aqueous Fe

  3. Electron transport in pure and substituted iron oxyhydroxides by small-polaron migration

    Energy Technology Data Exchange (ETDEWEB)

    Alexandrov, Vitaly, E-mail: vitali.alexandrov@pnnl.gov; Rosso, Kevin M. [Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354 (United States)

    2014-06-21

    Iron oxyhydroxides (FeOOH) are common crystalline forms of iron that play a critical role in technology and the natural environment via a variety of important reduction-oxidation reactions, including electrical semiconduction as an aspect. However, a basic understanding of the electron transport properties of these systems is still lacking. We examine the electron mobility in goethite (α-FeOOH), akaganéite (β-FeOOH), and lepidocrocite (γ-FeOOH) polymorphs by means of density functional theory based (DFT+U) calculations. We show that room temperature charge transport should be dominated by the small-polaron hopping type, and that the attendant mobility should be highest for pure goethite and akaganéite. Hopping pathways through the various lattices are discussed in terms of individual electron exchange steps and rates for each. Given the usual occurrence of compositional impurities in natural iron oxyhydroxides, we also investigate the effect of common stoichiometric defects on the electron hopping activation energies such as Al and Cr substitutional cations in goethite, and Cl anions in the channels of akaganéite.

  4. Hierarchical paramecium-like hollow and solid Au/Pt bimetallic nanostructures constructed using goethite as template

    Energy Technology Data Exchange (ETDEWEB)

    Liu Wei; Repo, Eveliina; Sillanpaeae, Mika [Laboratory of Applied Environmental Chemistry, University of Eastern Finland, Patteristonkatu 1, FI-50100 Mikkeli (Finland); Heikkilae, Mikko; Leskelae, Markku, E-mail: weiliuzk@yahoo.cn, E-mail: mika.sillanpaa@uef.fi [Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki, PO Box 55 (A.I. Virtasen aukio 1), FI-00014, Helsinki (Finland)

    2010-10-01

    Novel hollow and solid paramecium-like hierarchical Au/Pt bimetallic nanostructures were constructed using goethite as template via a seed-mediated growth method. Transmission electron microscopy (TEM), {xi}-potential measurement, UV-vis spectroscopy, energy dispersive x-ray spectroscopy (EDS), ICP-AES measurement, x-ray powder diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were utilized to systematically characterize the bimetallic nanostructures. It is found that the core structure of the paramecium-like bimetallic nanomaterial is closely related to reducing agent. When ascorbic acid is used as reducing agent, goethite serves as in situ sacrificed template and hollow paramecium-like bimetallic structure is obtained. When NH{sub 2}OH{center_dot}HCl is used, solid nanostructure with preserved goethite core is produced. Heating the reaction solution is necessary to obtain the paramecium-like morphology with rough interconnected Pt cilia shell. The thickness of Pt cilia layer can be controlled by adjusting the molar ratio of H{sub 2}PtCl{sub 6} to Au nanoseeds. The overgrowth of the rough Pt cilia is proposed to be via an autocatalytic and three-dimensional heterogeneous nucleation process first through flower-like morphology. Both the hollow and solid hierarchical paramecium-like Au/Pt bimetallic nanostructures show good catalytic activities.

  5. Hierarchical paramecium-like hollow and solid Au/Pt bimetallic nanostructures constructed using goethite as template

    International Nuclear Information System (INIS)

    Liu Wei; Repo, Eveliina; Sillanpaeae, Mika; Heikkilae, Mikko; Leskelae, Markku

    2010-01-01

    Novel hollow and solid paramecium-like hierarchical Au/Pt bimetallic nanostructures were constructed using goethite as template via a seed-mediated growth method. Transmission electron microscopy (TEM), ξ-potential measurement, UV-vis spectroscopy, energy dispersive x-ray spectroscopy (EDS), ICP-AES measurement, x-ray powder diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were utilized to systematically characterize the bimetallic nanostructures. It is found that the core structure of the paramecium-like bimetallic nanomaterial is closely related to reducing agent. When ascorbic acid is used as reducing agent, goethite serves as in situ sacrificed template and hollow paramecium-like bimetallic structure is obtained. When NH 2 OH·HCl is used, solid nanostructure with preserved goethite core is produced. Heating the reaction solution is necessary to obtain the paramecium-like morphology with rough interconnected Pt cilia shell. The thickness of Pt cilia layer can be controlled by adjusting the molar ratio of H 2 PtCl 6 to Au nanoseeds. The overgrowth of the rough Pt cilia is proposed to be via an autocatalytic and three-dimensional heterogeneous nucleation process first through flower-like morphology. Both the hollow and solid hierarchical paramecium-like Au/Pt bimetallic nanostructures show good catalytic activities.

  6. Hierarchical paramecium-like hollow and solid Au/Pt bimetallic nanostructures constructed using goethite as template

    Science.gov (United States)

    Liu, Wei; Repo, Eveliina; Heikkilä, Mikko; Leskelä, Markku; Sillanpää, Mika

    2010-10-01

    Novel hollow and solid paramecium-like hierarchical Au/Pt bimetallic nanostructures were constructed using goethite as template via a seed-mediated growth method. Transmission electron microscopy (TEM), ξ-potential measurement, UV-vis spectroscopy, energy dispersive x-ray spectroscopy (EDS), ICP-AES measurement, x-ray powder diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were utilized to systematically characterize the bimetallic nanostructures. It is found that the core structure of the paramecium-like bimetallic nanomaterial is closely related to reducing agent. When ascorbic acid is used as reducing agent, goethite serves as in situ sacrificed template and hollow paramecium-like bimetallic structure is obtained. When NH2OH·HCl is used, solid nanostructure with preserved goethite core is produced. Heating the reaction solution is necessary to obtain the paramecium-like morphology with rough interconnected Pt cilia shell. The thickness of Pt cilia layer can be controlled by adjusting the molar ratio of H2PtCl6 to Au nanoseeds. The overgrowth of the rough Pt cilia is proposed to be via an autocatalytic and three-dimensional heterogeneous nucleation process first through flower-like morphology. Both the hollow and solid hierarchical paramecium-like Au/Pt bimetallic nanostructures show good catalytic activities.

  7. Reversibility of sorption of plutonium-239 onto hematite and goethite colloids

    International Nuclear Information System (INIS)

    Lu, N.; Cotter, C.R.; Kitten, H.D.; Bentley, J.; Triay, I.R.

    1998-01-01

    Laboratory batch sorption experiments were conducted to evaluate: (1) sorption of plutonium-239 ( 239 Pu) on different iron oxide colloids (hematite and geothite), (2) sorption kinetics of colloidal Pu(IV) and soluble Pu(V) onto these two colloids, and (3) desorption of colloidal Pu(IV) and soluble Pu(V) from 239 Pu-loaded colloids as a function of time. Natural groundwater and carbonate-rich synthetic groundwater were used in this study. To examine the possible influence of bicarbonate on 239 Pu sorption, an additional set of experiments was conducted in sodium nitrate (NaNO 3 ) solutions under carbon dioxide free environments. Our results show that colloidal Pu(IV) as well as soluble Pu(V) was rapidly adsorbed by hematite and goethite colloids in both natural and synthetic groundwater. The amount of 239 Pu adsorbed by both iron oxide colloids in synthetic groundwater was higher than in natural groundwater. The presence of carbonate did not influence the sorption of 239 Pu. While sorption of soluble Pu(V) is a slow process, sorption of colloidal Pu(IV) occurs rapidly. Desorption of Pu from iron oxide colloids is much slower than the sorption processes. Our findings suggest that different sorption and desorption behaviors of 239 Pu by iron oxide colloids in groundwater may facilitate the transport of 239 Pu along potential flowpaths from the areas contaminated by radionuclide and release to the accessible environment. (orig.)

  8. Nano size crystals of goethite, α-FeOOH: Synthesis and thermal transformation

    Science.gov (United States)

    Christensen, Axel Nørlund; Jensen, Torben R.; Bahl, Christian R. H.; DiMasi, Elaine

    2007-04-01

    An aqueous suspension of amorphous iron(III) hydroxide was kept at room temperature (298 K) for 23 years. During this period of time the pH of the liquid phase changed from 4.3 to 2.85, and nano size crystals of goethite, α-FeOOH crystallised from the amorphous iron(III) hydroxide. Transmission electron microscopy (TEM) investigations, Mössbauer spectra, and powder X-ray diffraction using Co K α radiation showed that the only iron containing crystalline phase present in the recovered product was α-FeOOH. The size of these nano particles range from 10 to 100 nm measured by TEM. The thermal decomposition of α-FeOOH was investigated by time-resolved in situ synchrotron radiation powder X-ray diffraction and the data showed that the sample of α-FeOOH transformed to α-Fe 2O 3 in the temperature range 444-584 K. A quantitative phase analysis shows the increase in scattered X-ray intensity from α-Fe 2O 3 to follow the decrease of intensity from α-FeOOH in agreement with the topotactic phase transition.

  9. Magnetism of Al-substituted magnetite reduced from Al-hematite

    Science.gov (United States)

    Jiang, Zhaoxia; Liu, Qingsong; Zhao, Xiang; Roberts, Andrew P.; Heslop, David; Barrón, Vidal; Torrent, José

    2016-06-01

    Aluminum-substituted magnetite (Al-magnetite) reduced from Al-substituted hematite or goethite (Al-hematite or Al-goethite) is an environmentally important constituent of magnetically enhanced soils. In order to characterize the magnetic properties of Al-magnetite, two series of Al-magnetite samples were synthesized through reduction of Al-hematite by a mixed gas (80% CO2 and 20% CO) at 395°C for 72 h in a quartz tube furnace. Al-magnetite samples inherited the morphology of their parent Al-hematite samples, but only those transformed from Al-hematite synthesized at low temperature possessed surficial micropores, which originated from the release of structural water during heating. Surface micropores could thus serve as a practical fingerprint of fire or other high-temperature mineralogical alteration processes in natural environments, e.g., shear friction in seismic zones. In addition, Al substitution greatly affects the magnetic properties of Al-magnetite. For example, coercivity (Bc) increases with increasing Al content and then decreases slightly, while the saturation magnetization (Ms), Curie temperature (Tc), and Verwey transition temperature (Tv) all decrease with increasing Al content due to crystal defect formation and dilution of magnetic ions caused by Al incorporation. Moreover, different trends in the correlation between Tc and Bc can be used to discriminate titanomagnetite from Al-magnetite, which is likely to be important in environmental and paleomagnetic studies, particularly in soil.

  10. ATR-FTIR and density functional theory study of the structures, energetics, and vibrational spectra of phosphate adsorbed onto goethite.

    Science.gov (United States)

    Kubicki, James D; Paul, Kristian W; Kabalan, Lara; Zhu, Qing; Mrozik, Michael K; Aryanpour, Masoud; Pierre-Louis, Andro-Marc; Strongin, Daniel R

    2012-10-16

    Periodic plane-wave density functional theory (DFT) and molecular cluster hybrid molecular orbital-DFT (MO-DFT) calculations were performed on models of phosphate surface complexes on the (100), (010), (001), (101), and (210) surfaces of α-FeOOH (goethite). Binding energies of monodentate and bidentate HPO(4)(2-) surface complexes were compared to H(2)PO(4)(-) outer-sphere complexes. Both the average potential energies from DFT molecular dynamics (DFT-MD) simulations and energy minimizations were used to estimate adsorption energies for each configuration. Molecular clusters were extracted from the energy-minimized structures of the periodic systems and subjected to energy reminimization and frequency analysis with MO-DFT. The modeled P-O and P---Fe distances were consistent with EXAFS data for the arsenate oxyanion that is an analog of phosphate, and the interatomic distances predicted by the clusters were similar to those of the periodic models. Calculated vibrational frequencies from these clusters were then correlated with observed infrared bands. Configurations that resulted in favorable adsorption energies were also found to produce theoretical vibrational frequencies that correlated well with experiment. The relative stability of monodentate versus bidentate configurations was a function of the goethite surface under consideration. Overall, our results show that phosphate adsorption onto goethite occurs as a variety of surface complexes depending on the habit of the mineral (i.e., surfaces present) and solution pH. Previous IR spectroscopic studies may have been difficult to interpret because the observed spectra averaged the structural properties of three or more configurations on any given sample with multiple surfaces.

  11. Effects of single metal atom (Pt, Pd, Rh and Ru) adsorption on the photocatalytic properties of anatase TiO2

    Science.gov (United States)

    Jin, Cui; Dai, Ying; Wei, Wei; Ma, Xiangchao; Li, Mengmeng; Huang, Baibiao

    2017-12-01

    The effects of single metal atom (Pt, Pd, Rh and Ru) adsorption on the photocatalytic properties of anatase TiO2 are investigated by means of the first-principles calculations based on density functional theory (DFT). Our results show that the most stable adsorption site for single metal atom on anatase TiO2 (101) surface is the bridge site formed by two twofold coordinated oxygen (O2c) atoms at the step edge. Due to the charge transfer from metal atoms to anatase TiO2 (101) surface, the work function of adsorbed surface is significantly smaller than the clean one, indicating enhanced surface activity. Fukui functions are highly localized around the isolated metal atoms, indicating that single metal atoms on anatase TiO2 (101) surface serve as the active reduction and oxidation sites in the photocatalytic process. Photo-induced electrons in the electronically excited TiO2 photocatalyst can be transferred to target species through the deposited single atoms. The band structures of host TiO2 are almost unchanged upon the adsorption, and the metal induced states are located in the band gap of the host. Remarkably, due to the metal atoms adsorption, the upward shift of conduction band edge will improve the reducing capacity of anatase TiO2. Moreover, when single metal atoms are adsorbed, potential energy of topmost surface Ti atoms turns to get close to the vacuum level, which significantly facilitates the electron transfer for hydrogen evolution. Results in this work provide new insights into improving the photocatalytic performance by single metal atoms adsorption.

  12. Medicineringsfejl ved generisk substitution

    DEFF Research Database (Denmark)

    Rölfing, Jan

    2012-01-01

    Generic substitution is a major cause of medical mistakes in the general population. Danish legislation obligates pharmacies to substitute prescribed medicine with the cheapest equivalent formulation, despite variations in product name, packaging, shape and colour. Consequently, medical mistakes ...... occur. Scientific evidence on the consequences of generic substitution is sparse. Call upon fellow health workers to report medical mistakes to the national entities and scientific peers, in order to increase awareness and scientific evidence about the problem....

  13. Adsorption Equilibrium and Kinetics at Goethite-Water and Related Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Katz, Lynn Ellen [Univ. of Texas, Austin, TX (United States)

    2017-04-15

    This research study is an important component of a broader comprehensive project, “Geochemistry of Interfaces: From Surfaces to Interlayers to Clusters,” which sought to identify and evaluate the critical molecular phenomena at metal-oxide interfaces that control many geochemical and environmental processes. The primary goal of this research study was to better understand and predict adsorption of metal ions at mineral/water surfaces. Macroscopic data in traditional batch experiments was used to develop predictive models that characterize sorption in complex systems containing a wide range of background solution compositions. Our studies focused on systems involving alkaline earth metal (Mg2+, Ca2+, Sr2+, Ba2+) and heavy metal (Hg2+, Co2+, Cd2+, Cu2+, Zn2+, Pb2+) cations. The anions we selected for study included Cl-, NO3-, ClO4-, SO42-, CO32- and SeO32- and the background electrolyte cations we examined included (Na+, K+, Rb+ and Cs+) because these represent a range of ion sizes and have varying potentials for forming ion-pairs or ternary complexes with the metal ions studied. The research led to the development of a modified titration congruency approach for estimating site densities for mineral oxides such as goethite. The CD-MUSIC version of the surface complexation modeling approach was applied to potentiometric titration data and macroscopic adsorption data for single-solute heavy metals, oxyanions, alkaline earth metals and background electrolytes over a range of pH and ionic strength. The model was capable of predicting sorption in bi-solute systems containing multiple cations, cations and oxyanions, and transition metal cations and alkaline earth metal ions. Incorporation of ternary

  14. Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+, Mg2+, PO4 3-, and CO3 2- ions on goethite

    NARCIS (Netherlands)

    Stachowicz, M.; Hiemstra, T.; Riemsdijk, van W.H.

    2008-01-01

    Complex systems, simulating natural conditions like in groundwater, have rarely been studied, since measuring and in particular, modeling of such systems is very challenging. In this paper, the adsorption of the oxyanions of As(III) and As(V) on goethite has been studied in presence of various

  15. The reactivity of Fe(II) associated with goethite formed during short redox cycles toward Cr(VI) reduction under oxic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Tomaszewski, Elizabeth J.; Lee, Seungyeol; Rudolph, Jared; Xu, Huifang; Ginder-Vogel, Matthew (UW)

    2017-08-01

    Chromium (Cr) is a toxic metal that causes a myriad of health problems and enters the environment as a result of anthropogenic activities and/or natural processes. The toxicity and solubility of chromium is linked to its oxidation state; Cr(III) is poorly soluble and relatively nontoxic, while Cr(VI) is soluble and a known carcinogen. Solid Fe(II) in iron-bearing minerals, such as pyrite, magnetite, and green rusts, reduce the oxidation state of chromium, reducing its toxicity and mobility. However, these minerals are not the only potential sources of solid-associated Fe(II) available for Cr(VI) reduction. For example, ferric (Fe(III)) (hydr)oxides, such as goethite or hematite, can have Fe(II) in the solid without phase transformation; however, the reactivity of Fe(II) within Fe(III) (hydr)oxides with contaminants, has not been previously investigated. Here, we cyclically react goethite with dissolved Fe(II) followed by dissolved O2, leading to the formation of reactive Fe(II) associated with goethite. In separate reactors, the reactivity of this Fe(II) is probed under oxic conditions, by exposure to chromate (CrO42 -) after either one, two, three or four redox cycles. Cr is not present during redox cycling; rather, it is introduced to a subset of the solid after each oxidation half-cycle. Analysis of X-ray absorption near edge structure (XANES) spectra reveals that the extent of Cr(VI) reduction to Cr(III) depends not only on solid Fe(II) content but also surface area and mean size of ordered crystalline domains, determined by BET surface area analysis and X-ray diffraction (XRD), respectively. Shell-by-shell fitting of the extended X-ray absorption fine structure (EXAFS) spectra demonstrates chromium forms both single and double corner sharing complexes on the surface of goethite, in addition to sorbed Cr(III) species. Finally, transmission electron microscope (TEM) imaging and X-ray energy-dispersive spectroscopy (EDS) illustrate that Cr preferentially

  16. Neptunium redox behavior and sorption onto goethite and hematite in the presence of humic acids with different hydroquinone content

    International Nuclear Information System (INIS)

    Khasanova, A.B.; Kalmykov, St.N.; Perminova, I.V.; Clark, S.B.

    2007-01-01

    The effect of humic acids (HA) on neptunium redox behavior and sorption onto hematite, α-Fe 2 O 3 , and goethite, α-FeOOH, colloids was established in batch sorption experiments that were carried out in broad pH interval. The sorption isotherms were provided for two samples of HA: commercial sample of leonardite humic acid and its hydroquinone-enriched derivative obtained using formaldehyde copolycondensation. The distribution of Np fitted the distribution of hydroquinone-enriched HA at low pH values in case of both solids while the influence of parent HA on Np sorption was negligible. This is due to Np(V) reduction upon interaction with hydroquinone-enriched derivative having higher reducing capacity compared to the parent HA. The order of components addition was found to be significant for Np retention

  17. Application of surface complexation modelling: Nickel sorption on quartz, manganese oxide, kaolinite and goethite, and thorium on silica

    International Nuclear Information System (INIS)

    Olin, M.; Lehikoinen, J.

    1997-12-01

    The study is a follow-up to a previous modelling task on mechanistic sorption. The experimental work has been carried out at the Laboratory of Radiochemistry, University of Helsinki (HYRL), and the sorption modelling was performed using the HYDRAQL code. Parameters taken from the open literature were employed in the modelling phase. The thermodynamic data for aqueous solutions were extracted from the EQ3/6 database and subsequently modified for HYDRAQL where necessary. The experimental data were obtained from five different experiments, four of which concerned the adsorption of nickel. The first experimental system was a mixture of Nilsiae quartz and manganese dioxide. In the second experiment, quartz was equilibrated with a fresh and saline groundwater simulant instead of an electrolyte solution. The third and fourth experiments dealt with nickel adsorption from an electrolyte solution onto goethite and kaolinite surfaces respectively. In the fifth experiment, adsorption of thorium onto a quartz surface was investigated

  18. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Science.gov (United States)

    2010-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject to...

  19. Influence of the goethite (α-FeOOH) surface on the stability of distorted PuO2 and PuO2-x phases

    International Nuclear Information System (INIS)

    Taylor, Sandra D.; Becker, Udo; Powell, Brian A.

    2016-01-01

    Experiments by [Powell, B. A., Dai, Z. R., Zavarin, M., Zhao, P. H., Kersting, A. B.: Stabilization of plutonium nano-colloids by epitaxial distortion on mineral surfaces. Environ. Sci. Technol. 45, 2698 (2011).] deduced the heteroepitaxial growth of a bcc Pu 4 O 7 phase when sorbed onto goethite from d-spacing measurements obtained from selected-area electron diffraction (SAED) patterns. The structural and/or chemical modification of Pu(IV) oxide (PO) nanocolloids upon sorption to goethite, in turn, affects colloidal-transport of Pu in the subsurface. In this study, molecular simulations were applied to investigate mechanisms affecting the formation of non-fcc PO phases and to understand the influence of goethite in stabilizing the non-fcc PO phase. Analyses of the structure, chemistry, and formation energetics for several bulk PuO 2 and PuO 2-x phases, using ab initio methods, show that the formation of a non-fcc PO can occur from the lattice distortion (LD) of fcc PuO 2 upon sorption and formation of a PO-goethite interface. To strain and non-uniformly distort the PuO 2 lattice to match that of the goethite substrate at ambient conditions would require 88 kJ/mol Pu 4 O 8 . The formation of a hypostoichiometric PuO 2-x phase, such as the experimentally-deduced bcc, Ia anti 3 Pu 4 O 7 phase, requires more O-poor conditions and/or high energetic inputs (> +365 kJ/mol Pu 4 O 7 at O-rich conditions). Empirical methods were also applied to study the effect of lattice distortion on sorption energetics and adsorbate particle growth using simple heterointerfaces between cubic salts, where KCl clusters (notated as KCl LD ) of varying size and lattice mismatch (LM) were sorbed to a NaCl cluster. When the lattice of a KCl LD cluster has <15% LM with that of a NaCl substrate, the sorption of KCl LD onto NaCl is exothermic (<-80 kJ/mol) and the KCl LD cluster can reach sizes of ∝2-5 nm on the NaCl substrate. These models suggest that the lattice of a fcc PuO 2 particle can

  20. Electricity/oil substitution

    International Nuclear Information System (INIS)

    Melvin, J.G.

    1980-09-01

    The extent to which electricity could substitute for imported oil in Canada is assessed and it is concluded that the bulk of projected oil imports could be displaced. This substitution of electricity for oil could be largely completed within two decades, with existing technology, using Canadian resources. The substitution of electricity for imported oil would result in relatively low energy costs and would stimulate economic growth. Energy self-sufficiency through the substitution of electricity for oil is uniquely a Canadian option; it is not open to other industrial countries. The option exists because of Canada's resources of oil sands for essential liquid fuels, hydraulic and nuclear electrical potential, and natural gas as an interim source of energy. While other countries face an energy crisis due to declining supplies of oil, Canada faces opportunities. The policies of Federal and Provincial governments, as perceived by individual decision makers, will have a major influence on Canada's ability to realize opportunities. (auth)

  1. The substitutability of reinforcers

    OpenAIRE

    Green, Leonard; Freed, Debra E.

    1993-01-01

    Substitutability is a construct borrowed from microeconomics that describes a continuum of possible interactions among the reinforcers in a given situation. Highly substitutable reinforcers, which occupy one end of the continuum, are readily traded for each other due to their functional similarity. Complementary reinforcers, at the other end of the continuum, tend to be consumed jointly in fairly rigid proportion, and therefore cannot be traded for one another except to achieve that proportio...

  2. Synthesis of substituted pyrazines

    Science.gov (United States)

    Pagoria, Philip F.; Zhang, Mao Xi

    2016-10-04

    A method for synthesizing a pyrazine-containing material according to one embodiment includes contacting an iminodiacetonitrile derivative with a base and a reagent selected from a group consisting of hydroxylamine, a hydroxylamine salt, an aliphatic primary amine, a secondary amine, an aryl-substituted alkylamine a heteroaryl-substituted alkyl amine, an alcohol, an alkanolamine and an aryl alcoholamine. Additional methods and several reaction products are presented. ##STR00001##

  3. Effect of ethylenediamine-N,N'-disuccinic acid on Fenton and photo-Fenton processes using goethite as an iron source: optimization of parameters for bisphenol A degradation.

    Science.gov (United States)

    Huang, Wenyu; Brigante, Marcello; Wu, Feng; Hanna, Khalil; Mailhot, Gilles

    2013-01-01

    The main disadvantage of using iron mineral in Fenton-like reactions is that the decomposition rate of organic contaminants is slower than in classic Fenton reaction using ferrous ions at acidic pH. In order to overcome these drawbacks of the Fenton process, chelating agents have been used in the investigation of Fenton heterogeneous reaction with some Fe-bearing minerals. In this work, the effect of new iron complexing agent, ethylenediamine-N,N'-disuccinic acid (EDDS), on heterogeneous Fenton and photo-Fenton system using goethite as an iron source was tested at circumneutral pH. Batch experiments including adsorption of EDDS and bisphenol A (BPA) on goethite, H(2)O(2) decomposition, dissolved iron measurement, and BPA degradation were conducted. The effects of pH, H(2)O(2) concentration, EDDS concentration, and goethite dose were studied, and the production of hydroxyl radical ((•)OH) was detected. The addition of EDDS inhibited the heterogeneous Fenton degradation of BPA but also the formation of (•)OH. The presence of EDDS decreases the reactivity of goethite toward H(2)O(2) because EDDS adsorbs strongly onto the goethite surface and alters catalytic sites. However, the addition of EDDS can improve the heterogeneous photo-Fenton degradation of BPA through the propagation into homogeneous reaction and formation of photochemically efficient Fe-EDDS complex. The overall effect of EDDS is dependent on the H(2)O(2) and EDDS concentrations and pH value. The high performance observed at pH 6.2 could be explained by the ability of O (2) (•-) to generate Fe(II) species from Fe(III) reduction. Low concentrations of H(2)O(2) (0.1 mM) and EDDS (0.1 mM) were required as optimal conditions for complete BPA removal. These findings regarding the capability of EDDS/goethite system to promote heterogeneous photo-Fenton oxidation have important practical implications for water treatment technologies.

  4. Bone substitute biomaterials

    CERN Document Server

    Mallick, K

    2014-01-01

    Bone substitute biomaterials are fundamental to the biomedical sector, and have recently benefitted from extensive research and technological advances aimed at minimizing failure rates and reducing the need for further surgery. This book reviews these developments, with a particular focus on the desirable properties for bone substitute materials and their potential to encourage bone repair and regeneration. Part I covers the principles of bone substitute biomaterials for medical applications. One chapter reviews the quantification of bone mechanics at the whole-bone, micro-scale, and non-scale levels, while others discuss biomineralization, osteoductivization, materials to fill bone defects, and bioresorbable materials. Part II focuses on biomaterials as scaffolds and implants, including multi-functional scaffolds, bioceramics, and titanium-based foams. Finally, Part III reviews further materials with the potential to encourage bone repair and regeneration, including cartilage grafts, chitosan, inorganic poly...

  5. Miocene weathering environments in Western Australia-Inferences from the abundance and 13C/12C of Fe(CO3)OH in CID goethite

    Science.gov (United States)

    Fritz, Tyler O.; Yapp, Crayton J.

    2018-04-01

    The channel iron deposits (CID) of the Hamersley Province in Western Australia are dominated by pedogenic goethite/hematite-rich ooids and pisoids that were transported to, and deposited in, the meandering channels of Miocene rivers. Information about the Miocene weathering environments that produced the Fe(III) oxides is archived in the mole fraction (X) and δ13C of the Fe(CO3)OH component in solid solution in oolitic CID goethite (α-FeOOH). Values of X and δ13C were measured for 12 oolitic goethite samples from different depths in two cores drilled in CID of the Robe Formation of Mesa J. The weighted-average plateau values of X ranged from 0.0098 to 0.0334, which suggest ambient CO2 concentrations that ranged from ∼50,000 ppm V to perhaps as much as ∼200,000 ppm V at the time of goethite crystallization. In a vadose zone characterized by in situ production of CO2 with steady-state Fickian diffusive transport of the gas, such concentrations would correspond to modeled soil respiration rates (Q) ranging from about 10 to 30 mmol/m2/h. Values for Q of about 10 mmol/m2/h are reported for soils in modern tropical forests with MAP ≥ ∼2000 mm. However, model-derived values of Q that exceed 15 mmol/m2/h are larger than observed in modern systems. This could indicate that some of the CID goethites crystallized in conditions that were phreatic or near phreatic rather than vadose. The δ13C values of the Fe(CO3)OH component in these 12 CID samples ranged from -24.0‰ to -22.3‰, which are among the most negative measured to date. If they reflect steady-state diffusive transport of CO2 in vadose environments, the soil CO2 would have been derived from a source with δ13C values that ranged from ∼-31‰ to -29‰. If, on the other hand, the goethites crystallized in a nearly phreatic environment that was moderately acidic, the inferred δ13C of the ancient CO2 source would have been about -27.6‰ to -25.8‰. In either case, the δ13C values point to in situ

  6. Muon substituted free radicals

    International Nuclear Information System (INIS)

    Burkhard, P.; Fischer, H.; Roduner, E.; Strub, W.; Gygax, F.N.; Brinkman, G.A.; Louwrier, P.W.F.; McKenna, D.; Ramos, M.; Webster, B.C.

    1984-01-01

    Spin polarized energetic positive muons are injected as magnetic probes into unsaturated organic liquids. They are implemented via fast chemical processes ( -10 s) in various molecules. Of particular interest among these are muonium substituted free radicals. The technique allows determination of accurate rate coefficients for fast chemical reactions of radicals. Furthermore, radiochemical processes occuring in picoseconds after injection of the muon are studied. Of fundamental interest are also the structural and dynamical implications of substituting a proton by a muon, or in other terms, a hydrogen atom by a muonium atom. Selected examples for each of these three types of experiments are given. (Auth.)

  7. Modeling the adsorption of hydrogen, sodium, chloride and phthalate on goethite using a strict charge-neutral ion-exchange theory

    Science.gov (United States)

    Ndu, Udonna

    2017-01-01

    Simultaneous adsorption modeling of four ions was predicted with a strict net charge-neutral ion-exchange theory and its corresponding equilibrium and mass balance equations. An important key to the success of this approach was the proper collection of all the data, particularly the proton adsorption data, and the inclusion of variable concentrations of conjugate ions from the experimental pH adjustments. Using IExFit software, the ion-exchange model used here predicted the competitive retention of several ions on goethite by assuming that the co-adsorption or desorption of all ions occurred in the correct stoichiometries needed to maintain electroneutrality. This approach also revealed that the retention strength of Cl− ions on goethite increases in the presence of phthalate ions. That is, an anion-anion enhancement effect was observed. The retention of Cl− ions was much weaker than phthalate ions, and this also resulted in a higher sensitivity of the Cl− ions toward minor variations in the surface reactivity. The proposed model uses four goethite surface sites. The drop in retention of phthalate ions at low pH was fully described here as resulting from competitive Cl− reactions, which were introduced in increasing concentrations into the matrix as the conjugate base to the acid added to lower the pH. PMID:28464020

  8. Reactive transport of uranyl: fixation mode on silica and goethite; experiments in columns and closed reactors; simulations

    International Nuclear Information System (INIS)

    Gabriel, U.

    1998-01-01

    Uranium contaminated areas are found in mine waste disposal sites, former military areas, etc. The present study focuses on the identification or mechanisms which may lead contaminated soils to become a sudden potential threat to surface and ground waters. Mechanisms were studied on model material at two levels. On the molecular scale, the complexation of uranyl at trace metal concentrations was investigated with amorphous silica. Complexation is shown to occur via the formation of surface complexes, characterised by different time-resolved laser-induced luminescence spectra and life times and stoichiometry. On the macro-scale the transport behaviour of uranyl in a cristobalite-goethite-carbonate-uranyl system was investigated with laboratory column and batch experiments. Uranium mobility was found to be controlled by the interaction between physical transport and a reversible, rate-controlled, fixation reaction. Sorption was shown to be an ensemble of competing solution and surface complexation reactions, leading to an apparent non-linear (Langmuir-like) adsorption isotherm. Finally the impact of a sudden change in background geochemistry was studied. Conditions leading to a dramatic mobilization of uranium from mildly contaminated systems were experimentally identified. Maximal uranyl concentration are controlled by the total extractable uranyl in the system and limited by uranyl solubility. Evolution of the background geochemical conditions is thus an important part of contaminated sites risk assessment. (author)

  9. Adsorption of hydroxamate siderophores and EDTA on goethite in the presence of the surfactant sodium dodecyl sulfate

    Directory of Open Access Journals (Sweden)

    Xu Jide

    2009-06-01

    Full Text Available Abstract Siderophore-promoted iron acquisition by microorganisms usually occurs in the presence of other organic molecules, including biosurfactants. We have investigated the influence of the anionic surfactant sodium dodecyl sulfate (SDS on the adsorption of the siderophores DFOB (cationic and DFOD (neutral and the ligand EDTA (anionic onto goethite (α-FeOOH at pH 6. We also studied the adsorption of the corresponding 1:1 Fe(III-ligand complexes, which are products of the dissolution process. Adsorption of the two free siderophores increased in a similar fashion with increasing SDS concentration, despite their difference in molecule charge. In contrast, SDS had little effect on the adsorption of EDTA. Adsorption of the Fe-DFOB and Fe-DFOD complexes also increased with increasing SDS concentrations, while adsorption of Fe-EDTA decreased. Our results suggest that hydrophobic interactions between adsorbed surfactants and siderophores are more important than electrostatic interactions. However, for strongly hydrophilic molecules, such as EDTA and its iron complex, the influence of SDS on their adsorption seems to depend on their tendency to form inner-sphere or outer-sphere surface complexes. Our results demonstrate that surfactants have a strong influence on the adsorption of siderophores to Fe oxides, which has important implications for siderophore-promoted dissolution of iron oxides and biological iron acquisition.

  10. [Artificial bone substitutes].

    Science.gov (United States)

    Koníček, Petr

    Bone tissue substitutes are divided into basic classification with its pros and cons described. Arteficial bone grafts are especially pointed out in article, publishing our own experience with two specific synthetic preps. Finally there is a blink in the near future of bone tissue augmentation.

  11. D/H of late Miocene meteoric waters in Western Australia: Paleoenvironmental conditions inferred from the δD of (U-Th)/He-dated CID goethite

    Science.gov (United States)

    Yapp, Crayton J.; Shuster, David L.

    2017-09-01

    Nineteen (U-Th)/He ages were determined for eight samples from a core drilled in an ore-grade channel iron deposit (CID) of the Robe Pisolite (Robe Formation) of Mesa J in Western Australia. With one exception, uncorrected ages of the analyzed aliquots range from 6.7(±0.4) Ma to 30.2(±3.1) Ma, while molar ratios of Th/U range from 0.42 to 5.06. The exception is an aliquot with an apparent age of 2.7 Ma and Th/U of 5.70. A three-component mixing model involving one generation of goethite and two generations of hematite suggests that the age of crystallization of the oolitic goethites is ∼7(±1) Ma. If so, the goethites have effectively been closed systems for ∼7 million years and should preserve a stable hydrogen isotope record of late Miocene rainfall in the vicinity of Mesa J. Cenozoic movement of the Australian continent had placed Mesa J and environs in the subtropics at a paleolatitude of about 29 °S during the late Miocene. Al-adjusted δD values of oolitic goethite in the eight CID samples range from -153‰ to -146‰ and imply that the δD of the late Miocene meteoric waters ranged from -61‰ to -53‰, with an average of -56‰. These relatively negative δD values might indicate that near-coastal, late Miocene rain was derived primarily from summer-season tropical cyclones with storm tracks that extended into the subtropics of western Australia. The postulated late Miocene tropical cyclones would have occurred more often and/or exhibited greater intensity at a paleolatitude of 29 °S than is the case for modern sites at approximately 30 °S on the west coast of Australia (e.g., Perth). Higher fluxes of meteoric water in the Miocene summers would have facilitated dissolution and removal of BIF-sourced silica with concomitant enrichment in oxidized Fe. Moreover, wetter late Miocene summers could have promoted multiple cycles of microbially mediated dissolution and recrystallization of Fe(III) oxides in the aerobic systems. The oolitic textures may

  12. Adsorption of Nucleic Acid/Protein Supramolecular Complexes on Goethite: The Influence of Solution Interactions on Behavior at the Solution-Mineral Interface

    Science.gov (United States)

    Schmidt, M.; Martinez, C. E.

    2017-12-01

    Adsorption of biomolecule rich supramolecular complexes onto mineral surfaces plays an important role in the development of organo-mineral associations in soils. In this study, a series of supramolecular complexes of a model nucleic acid (deoxyribonucleic acid (DNA)) and protein (bovine serum albumin (BSA)) are synthesized, characterized and exposed to goethite to probe their adsorption behavior. To synthesize DNA/BSA complexes, a fixed DNA concentration (0.1 mg/mL) was mixed with a range of BSA concentrations (0.025-0.5 mg/mL) in 5 mM KCl at pH=5.0. Circular dichroism spectroscopy demonstrates strong, cooperative, Hill-type binding between DNA and BSA (Ka= 4.74 x 105 M-1) with DNA saturation achieved when BSA concentration reaches 0.4 mg/mL. Dynamic light scattering measurements of DNA/BSA complexes suggest binding accompanies disruption of DNA-DNA intermolecular electrostatic repulsion, resulting in a decrease of the DNA slow relaxation mode with increasing amount of BSA. Zeta potential measurements show increasing amounts of BSA lead to a reduction of negative charge on DNA/BSA complexes, in line with light scattering results. In situ attenuated total reflectance Fourier transform infrared spectroscopic studies of adsorption of DNA/BSA complexes onto goethite show that complexation of BSA with DNA appears to hinder direct coordination of DNA backbone phosphodiester groups with goethite, relative to DNA by itself. Furthermore, increasing amount of BSA (up to 0.4 mg/mL) in DNA/BSA complexes enhances DNA adsorption, possibly as a result of reduced repulsion between adsorbed DNA helices. When BSA concentration exceeds 0.4 mg/mL, a decrease in adsorbed DNA is observed. We hypothesize that this discrepancy in behavior between systems with BSA concentrations below and above saturation of DNA is caused by initial fast adsorption of loosely associated BSA on goethite, restricting access to goethite surface sites. Overall, these results highlight the impact of solution

  13. [Currently available skin substitutes].

    Science.gov (United States)

    Oravcová, Darina; Koller, Ján

    2014-01-01

    The current trend of burn wound care has shifted to more holistic approach of improvement in the long-term form and function of the healed burn wounds and quality of life. Autologous split or full-thickness skin graft are the best definitive burn wound coverage, but it is constrained by the limited available sources, especially in major burns. Donor site morbidities in term of additional wounds and scarring are also of concern of the autograft application. This has demanded the emergence of various skin substitutes in the management of acute burn injury as well as post burn reconstructions. This paper reviews currently available skin substitutes, produced in not for-profit skin banks as well as commercially available. They are divided according to type of material included, as biological, biosynthetic and synthetic and named respectively.

  14. Effect of co-existing kaolinite and goethite on the aggregation of graphene oxide in the aquatic environment.

    Science.gov (United States)

    Huang, Guanxing; Guo, Huiyuan; Zhao, Jian; Liu, Yonghong; Xing, Baoshan

    2016-10-01

    Broad applications of graphene oxide (GO) will result in the release of GO into aquatic environments, where clay minerals and metal (hydr)oxides are commonly present. Thereby the interactions between GO and a binary system containing clay minerals and metal (hydr)oxides can occur. We investigated the aggregation of GO with kaolinite and kaolinite-goethite associations (KGAs) in aquatic systems under different pHs, ionic strengths, and GO concentrations. GO suspension was unstable at low pHs, and the aggregation of GO occurred in the presence of KGA-4% and KGA-10% until pH 5 and 6, respectively. Kaolinite decreased the critical coagulation concentration (CCC) of GO at pH 5.5 from around 50 to 20 mM NaCl due to the reduced energy barrier. Heteroaggregation of GO with KGAs was extremely sensitive to ionic strength at pH 5.5, and the CCC of GO in the presence of KGA-10% increased from less than 1 mM NaCl to 5 mM NaCl with the increase of pH from 5.5 to 9. The heteroaggregation extent of GO with KGAs was enhanced firstly, then reduced with the increase of GO concentrations at pH 5.0, which is likely because KGA plates were more efficiently wrapped by large-size GO sheets with increasing GO concentrations. These findings are useful for understanding and predicting the fate of GO in the relatively complicated aquatic and soil environments where binary minerals co-exist. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Late Mio-Pliocene chemical weathering of the Yulong porphyry Cu deposit in the eastern Tibetan Plateau constrained by goethite (U-Th)/He dating: Implication for Asian summer monsoon

    Science.gov (United States)

    Deng, Xiao-Dong; Li, Jian-Wei; Shuster, David L.

    2017-08-01

    Chemical weathering has provided a potentially important feedback between tectonic forcing and climate evolution of the Asian continent, although precise constraints on the timing and history of weathering are only variably documented. Here, we use goethite (U-Th)/He and 4He/3He geochronology to constrain the timing and rates of chemical weathering at the Yulong porphyry Cu deposit on the eastern Tibetan Plateau. Goethite grains have (U-Th)/He ages ranging from 6.73 ± 0.51 to 0.53 ± 0.04 Ma that correlate with independent paleoclimatic proxies inferred from supergene Mn-oxides and loess deposits under variable tectonic regimes and vegetation zones over the southeastern Asia. This correlation indicates that regional climatic conditions, especially monsoonal precipitation, controlled chemical weathering and goethite precipitation in a vast area of southeastern Asia. The goethite ages suggest that the Asian summer monsoon was relatively strong from 7 to 4.6 Ma, but weakened between 4.6 and 4 Ma, and then significantly intensified from 4 to 2 Ma. The precipitation ages of goethites collected along a 100-m-thick weathering profile decrease with depth, and indicate a downward propagation of the weathering front at rates of table, which was possibly related to local surface uplift or reorganization of the river systems in southeastern Tibet during this period.

  16. Method for Transformation of Weakly Magnetic Minerals (Hematite, Goethite into Strongly Magnetic Mineral (Magnetite to Improve the Efficiency of Technologies for Oxidized Iron Ores Benefication

    Directory of Open Access Journals (Sweden)

    Ponomarenko, O.

    2015-03-01

    Full Text Available A new method for relatively simple transformation of weakly magnetic minerals (goethite (α-FeOOH and hematite (α-Fe2O3 into strongly magnetic mineral (magnetite (Fe3O4 was developed. It was shown, that transformation of structure and magnetic characteristics of go ethite and hematite are realized in the presence of starch at relatively low temperatures (in the range of 300—600 °С. Obtained results open up new possibilities for development of effective technologies for oxidized iron ore beneficiation.

  17. Interactions of low molecular weight aromatic acids and amino acids with goethite, kaolinite and bentonite with or without organic matter coating

    Science.gov (United States)

    Gao, Jiajia; Jansen, Boris; Cerli, Chiara; Kalbitz, Karsten

    2015-04-01

    Interaction of organic matter molecules with the soil's solid phase is a key factor influencing the stabilization of carbon in soils and thus forms a crucial aspect of the global carbon cycle. While subject of much research attention so far, we still have much to learn about such interactions at the molecular level; in particular in the light of competition between different classes of organic molecules and in the presence of previously adsorbed soil organic matter. We studied the interaction of a group of low molecular weight (LMW) aromatic acids (salicylic, syringic, vanillic and ferulic acid) and amino acids (lysine, glutamic, leucine and phenylalanine) on goethite, kaolinite and bentonite with and without previously adsorbed dissolved organic matter (DOM). For this we used batch experiments at pH = 6.0 where some of the organic compounds were positively charged (i.e. lysine) or negatively charged (i.e. glutamic and salicylic acid) while the minerals also displayed positively (i.e. goethite) or negatively charged surfaces (i.e. bentonite). We found much higher sorption of salicylic acid and lysine than other compounds. On the bare minerals we found a great variety of sorption strength, with salicylic acid strongly adsorbed, while syringic, vanillic and ferulic acid showed little or no adsorption. For the amino acids, protonated lysine showed a stronger affinity to negatively charged kaolinite and bentonite than other amino acids. While deprotonated glutamic acid showed the strongest adsorption on goethite. Leucine and phenylalanine showed hardly any adsorption on any of the minerals. When present concurrently, amino acids decreased the sorption of salicylic acid on the three types of mineral, while the presence of LMW aromatic acids increased the sorption of lysine on kaolinite and bentonite and the sorption of glutamic acid on goethite. The presence of previously adsorbed DOM reduced the sorption of salicylic acid and lysine. The results confirm that

  18. Resources, recycle, and substitution

    International Nuclear Information System (INIS)

    Wymer, R.G.

    A two-fold strategy appears necessary to ensure that the resource needs of the developed and developing nations are met. First, recycle and substitution must be encouraged in those instances where they do find application. Although these measures have limited applicability, they may be of vital importance in those instances where they do apply; in any event, they buy time. Second, practical and economical technologies must be developed to exploit the lower-grade and marginal ores and the oftentimes abundant but highly refractory ores, as well as to greatly increase the recovery of secondary elements present in the ores - elements whose form and amounts in the ores make them economically unrecoverable by themselves, but which are economically recoverable as by-products. It is often the case that if these elements are not recovered during the initial mining and milling operations, they are rendered unrecoverable, in a practical sense, forever. Furthermore, they may even become environmental pollutants. Specific examples of recovery from refractory ores, by-product recovery, and recycle are given. Also, some suggestions of substitutes for important resources are tabulated

  19. Substitution in recreation choice behavior

    Science.gov (United States)

    George L. Peterson; Daniel J. Stynes; Donald H. Rosenthal; John F. Dwyer

    1985-01-01

    This review discusses concepts and theories of substitution in recreation choice. It brings together the literature of recreation research, psychology, geography, economics, and transportation. Parallel and complementary developments need integration into an improved theory of substitution. Recreation decision behavior is characterized as a nested or sequential choice...

  20. Biological background of dermal substitutes

    NARCIS (Netherlands)

    van der Veen, V. C.; van der Wal, M.B.; van Leeuwen, M.C.; Ulrich, M.; Middelkoop, E.

    2010-01-01

    Dermal substitutes are of major importance in treating full thickness skin defects, both in acute and chronic wounds. In this review we will outline specific requirements of three classes of dermal substitutes:-natural biological materials, with a more or less intact extracellular matrix

  1. Removal of Ni(II), Zn(II) and Pb(II) ions from single metal aqueous solution using rice husk-based activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Taha, Mohd F., E-mail: faisalt@petronas.com.my; Shaharun, Maizatul S. [Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750, Perak Darul Ridzuan (Malaysia); Shuib, Anis Suhaila, E-mail: anisuha@petronas.com.my; Borhan, Azry [Chemical Engineering Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750, Perak Darul Ridzuan (Malaysia)

    2014-10-24

    An attempt was made to investigate the potential of rice husk-based activated carbon as an alternative low-cost adsorbent for the removal of Ni(II), Zn(II) and Pb(II) ions from single aqueous solution. Rice husk-based activated carbon was prepared via treatment of rice husk with NaOH followed by the carbonization process at 400°C for 2 hours. Three samples, i.e. raw rice husk, rice husk treated with NaOH and rice husk-based activated carbon, were analyzed for their morphological characteristics using field-emission scanning electron microscope/energy dispersive X-ray (FESEM/EDX). These samples were also analyzed for their carbon, hydrogen, nitrogen, oxygen and silica contents using CHN elemental analyzer and FESEM/EDX. The porous properties of rice husk-based activated carbon were determined by Brunauer-Emmett-Teller (BET) surface area analyzer, and its surface area and pore volume were 255 m{sup 2}/g and 0.17 cm{sup 2}/g, respectively. The adsorption studies for the removal of Ni(II), Zn(II) and Pb(II) ions from single metal aqueous solution were carried out at a fixed initial concentration of metal ion (150 ppm) with variation amount of adsorbent (rice husk-based activated carbon) as a function of varied contact time at room temperature. The concentration of each metal ion was analyzed using atomic absorption spectrophotometer (AAS). The results obtained from adsorption studies indicate the potential of rice husk as an economically promising precursor for the preparation of activated carbon for removal of Ni(II), Zn(II) and Pb(II) ions from single aqueous solution. Isotherm and kinetic model analyses suggested that the experimental data of adsorption studies fitted well with Langmuir, Freundlich and second-order kinetic models.

  2. Fe(II)/Cu(II) interaction on goethite stimulated by an iron-reducing bacteria Aeromonas Hydrophila HS01 under anaerobic conditions.

    Science.gov (United States)

    Tao, Liang; Zhu, Zhen-Ke; Li, Fang-Bai; Wang, Shan-Li

    2017-11-01

    Copper is a trace element essential for living creatures, but copper content in soil should be controlled, as it is toxic. The physical-chemical-biological features of Cu in soil have a significant correlation with the Fe(II)/Cu(II) interaction in soil. Of significant interest to the current study is the effect of Fe(II)/Cu(II) interaction conducted on goethite under anaerobic conditions stimulated by HS01 (a dissimilatory iron reduction (DIR) microbial). The following four treatments were designed: HS01 with α-FeOOH and Cu(II) (T1), HS01 with α-FeOOH (T2), HS01 with Cu(II) (T3), and α-FeOOH with Cu(II) (T4). HS01 presents a negligible impact on copper species transformation (T3), whereas the presence of α-FeOOH significantly enhanced copper aging contributing to the DIR effect (T1). Moreover, the violent reaction between adsorbed Fe(II) and Cu(II) leads to the decreased concentration of the active Fe(II) species (T1), further inhibiting reactions between Fe(II) and iron (hydr)oxides and decelerating the phase transformation of iron (hydr)oxides (T1). From this study, the effects of the Fe(II)/Cu(II) interaction on goethite under anaerobic conditions by HS01 are presented in three aspects: (1) the accelerating effect of copper aging, (2) the reductive transformation of copper, and (3) the inhibition effect of the phase transformation of iron (hydr)oxides. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Simple, heart-smart substitutions

    Science.gov (United States)

    ... food choices does not mean you have to sacrifice flavor. The key is to substitute less healthy ... trout, and mackerel. Shrimp has less cholesterol than chicken, pork, or beef. Choose lean meats. They have ...

  4. bis(n'-substituted a

    African Journals Online (AJOL)

    Preferred Customer

    substituted acetohydrazide) ... biological activity associated with their corresponding hydrazones attributed to the presence of the active ... Hence, in this paper, we are reporting eco-friendly synthesis of some new Schiff bases by condensing 2 ...

  5. N-substituted iminodiacetic acids

    International Nuclear Information System (INIS)

    Nunn, A.; Loberg, M.

    1982-01-01

    The chemical preparation of several new N-substituted iminodiacetic acid derivatives are described. These compounds when complexed with sup(99m)Tc provide useful radiopharmaceuticals for the external imaging of the hepatobiliary system. (U.K.)

  6. Approaches in Substitution of Organic Solvents

    DEFF Research Database (Denmark)

    Jacobsen, Thomas

    2000-01-01

    In substitution of harmful chemicals or products with less harmful or harmless ones, there are different approaches according to the different situations, the technical requirements to the substitutes, and the goals for the substitution. Three different cases are presented. The substitution process...

  7. Commercial formalin substitutes for histopathology

    DEFF Research Database (Denmark)

    Prentø, P; Lyon, H

    1997-01-01

    We compared the performance of six commercial fixatives proposed to be formalin substitutes with the performance of buffered formalin, Clarke's ethanol-acetic acid, and ethanol, using rat liver, small intestine, and kidney. We investigated the rate of penetration, mode of fixation, extent...... performed equally well on all tissues tested. While several of the commercial fixatives appeared to preserve liver tissue at 200x, the preservation of kidney, intestinal villi, and smooth muscle was unacceptable. Histological distortion, cell shrinkage and vacuolization were prominent when the substitutes...... was obtained by combining formalin fixation with antigen retrieval. We conclude that none of the proposed commercial substitutes for buffered formalin are adequate for critical histology or histopathology....

  8. Efficient synthesis of substituted dihydrotetraazapentacenes.

    Science.gov (United States)

    Seillan, Claire; Brisset, Hugues; Siri, Olivier

    2008-09-18

    We describe a versatile and very efficient synthesis of previously unknown substituted 5,14-dihydro-5,7,12,14-tetraazapentacenes (DHTAPs). A structural study by NMR spectroscopy showed that the conjugated pi-system of the pentacyclic skeleton rearranges depending on the electronic effect of the substituent(s).

  9. Tax rates as strategic substitutes

    NARCIS (Netherlands)

    H. Vrijburg (Hendrik); R.A. de Mooij (Ruud)

    2016-01-01

    textabstractThis paper analytically derives conditions under which the slope of the tax-reaction function is negative in a classical tax competition model. If countries maximize welfare, a negative slope (reflecting strategic substitutability) occurs under relatively mild conditions. The strategic

  10. Story of skeletally substituted benzenes

    Indian Academy of Sciences (India)

    Unknown

    corresponds to the out-of-plane distortion of the hydrogen atom connected to the heteroatoms, which is then ..... etc. exhibits significant localization.24 The skeletally substituted benzenes considered in the study with a wide ... involving cationic and anionic systems are expected to show considerable localization. In. Table 3.

  11. RETURNED FOOT EXTERIOR CHORD BROOCHES MADE OF A SINGLE METAL PIECE (TYPE ALMGREN 158 RECENTLY DISCOVERED IN THE WESTERN PLAIN OF ROMANIA.

    Directory of Open Access Journals (Sweden)

    Vitalie Bârcă

    2014-07-01

    Full Text Available This study, without aiming at exhaustiveness, attempts, based on returned foot exterior chord brooches made of a single metal pieces (type Almgren 158 discovered in 2010 following the rescue archaeological excavations performed as a result of the construction of the Arad-Timişoara Highway, respectively section Arad-Seceani, in a series of Sarmatian graves of the cemetery investigated at Hunedoara Timișană, Șagu commune, Arad county, to analyse the brooches in this type discovered in the western territories of Romania.The author examines the four specimens at Hunedoara Timișană within a broader context and concludes that similar brooches in both the Barbarian and Roman environments, where they are imports, date mainly to the chronological interval comprised between the last two decades of the 2nd c. – early 4th c. AD (stages C1a-C2.The analysis of the graves in the cemetery showed that the graves where returned foot exterior chord brooches were found date sometime in the chronological interval comprised between the end of the 2nd c. AD and the third quarter of the 3rd c. AD. Moreover, the author notes that the distribution area of this brooch type is mainly the Barbarian world of German origin (the Przeworsk culture environment or that in constant contact with the latter. Based on the analysis of the distribution area of the Almgren 158 type brooches it was concluded they originate in the Przeworsk culture environment from where they disseminated in the neighbouring south and south-east cultural environments. Last but not least, the author reaches the conclusion that brooches of the type were assumed by the Sarmatians in the Pannonian Plain from the German populations (most likely the Vandals living in the northern vicinity of the area they inhabited. Another conclusion is that such returned foot exterior chord brooches are lacking from the north and north-west Pontic areas, including the Chernyakhov area. Finally, the author argues that

  12. Smart Phones and their Substitutes

    DEFF Research Database (Denmark)

    Bødker, Mads; Gimpel, Gregory; Hedman, Jonas

    2009-01-01

    Drawing on data from a longitudinal field study, this paper investigates the influence of existing, better and stand-alone technology substitutes on the use of smart phones. By applying prospect theory, media richness theory, and business model literature, the purpose of this paper is to improve...... our understanding of the role of substitutes, device content fit issues, and implications for business models by asking the question: What is an effective business model to address the relationship between user preference and the fit of the smart phone and everyday task? The field study data suggest...... the need for business models to recognize that adoption decisions are reference-dependent and strongly influenced by the fit between task and smart phone....

  13. Substituting oil by electric power

    International Nuclear Information System (INIS)

    Lichtenberg, H.

    1981-01-01

    Parting from the development of primary energy use the author refers to the latest investigations and results presented on the 1980 World Energy Conference and with special regard to oil points out the threatening exhaustion of fossil energy resources. Maintaining the economic structure of the Federal Republic of Germany implies an orientation away from oil. Due to its flexible application technology and quasi-inexhaustible energy resources electric power may substantially contribute to oil substitution which as a matter of fact is of particular interest in connection with the heat market. Coal alone cannot substitute both oil and nuclear energy. Thus, the above postulates the use of the latter. Leaving nuclear energy inactive today will effect an increase in the demand for oil the negative consequences of which would weight heavily upon the anyhow unbalanced import/export ratio of the Federal Republic of Germany. (orig.) [de

  14. 40 CFR 721.9100 - Substituted quinoline.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted quinoline. 721.9100... Substances § 721.9100 Substituted quinoline. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as substituted quinoline (PMN P-93-1183) is...

  15. Substituted Indoleacetic Acids Tested in Tissue Cultures

    DEFF Research Database (Denmark)

    Engvild, Kjeld Christensen

    1978-01-01

    Monochloro substituted IAA inhibited shoot induction in tobacco tissue cultures about as much as IAA. Dichloro substituted IAA inhibited shoot formation less. Other substituted IAA except 5-fluoro- and 5-bromoindole-3-acetic acid were less active than IAA. Callus growth was quite variable...

  16. Substituted Indoleacetic Acids Tested in Tissue Cultures

    DEFF Research Database (Denmark)

    Engvild, Kjeld Christensen

    1978-01-01

    Monochloro substituted IAA inhibited shoot induction in tobacco tissue cultures about as much as IAA. Dichloro substituted IAA inhibited shoot formation less. Other substituted IAA except 5-fluoro- and 5-bromoindole-3-acetic acid were less active than IAA. Callus growth was quite variable and not...... and not correlated with auxin strength measured in the Avena coleoptile test....

  17. 40 CFR 721.9488 - Substituted resorcinols.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted resorcinols. 721.9488... Substances § 721.9488 Substituted resorcinols. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as substituted resorcinols (PMNs P-95-1103, P...

  18. Natural arsenic attenuation via metal arsenate precipitation in soils contaminated with metallurgical wastes: III. Adsorption versus precipitation in clean As(V)/goethite/Pb(II)/carbonate systems

    International Nuclear Information System (INIS)

    Vaca-Escobar, Katherine; Villalobos, Mario; Ceniceros-Gómez, Agueda E.

    2012-01-01

    Soil contamination with As and potentially harmful metals is a widespread problem around the world especially from mining and metallurgical wastes, which release substantial amounts of these elements to the environment in potentially mobile species. Recently, it has been found that in various Mexican soils contaminated with these types of wastes, arsenate is not in the form of sorbed species on Fe oxides present in the soils, as generally reported in the literature, but in the form of very insoluble compounds such as Pb, Cu and Ca arsenates. Here a thermodynamic model is applied and validated with the results from wet chemical experiments to determine the fundamental geochemical conditions governing the mobility of As in the presence of Pb. For this purpose, a relatively simple but fundamental system of goethite (α-FeOOH)/As(V)/Pb(II)/carbonate was defined as a function of the As(V)/Fe(III) ratio, in a pH range of 5–10. The speciation model included the simultaneous inclusion of triple layer surface complexation and arsenate precipitation equilibria. The model predicts that from very low total As(V)/Fe(III) molar ratios (0.012 at pH 7) the precipitation mechanism significantly influences the attenuation of As(V), and rapidly becomes the dominant process over the adsorption mechanism. Model results identify the quantitative conditions of predominance for each mechanism and describe the transition conditions in which relatively large fractions of adsorbed, precipitated and dissolved As(V) species prevail. Experimental measurements at selected As(V)/Fe(III) ratios and pH confirmed the predictions and validated the coupled thermodynamic model utilized.

  19. What happened to blood substitutes?

    Science.gov (United States)

    Stowell, C P

    2005-11-01

    Concerns about the safety and adequacy of the blood supply have fostered twenty years of research into the so-called "blood substitutes" among them the oxygen carriers based on modified hemoglobin. Although none of these materials has yet been licensed for use in North America or Europe, the results of research and clinical trials have increased our understanding of oxygen delivery and its regulation. In particular, the examination of the basis for the vasoactivity observed with some of the hemoglobin based oxygen carriers has led to the insight that several colligative properties of hemoglobin solutions, such as their diffusion coefficient for oxygen, viscosity and colloid oncotic pressure, are important determinants of efficacy.

  20. Biologic and synthetic skin substitutes: An overview.

    Science.gov (United States)

    Halim, Ahmad Sukari; Khoo, Teng Lye; Mohd Yussof, Shah Jumaat

    2010-09-01

    The current trend of burn wound care has shifted to more holistic approach of improvement in the long-term form and function of the healed burn wounds and quality of life. This has demanded the emergence of various skin substitutes in the management of acute burn injury as well as post burn reconstructions. Skin substitutes have important roles in the treatment of deep dermal and full thickness wounds of various aetiologies. At present, there is no ideal substitute in the market. Skin substitutes can be divided into two main classes, namely, biological and synthetic substitutes. The biological skin substitutes have a more intact extracellular matrix structure, while the synthetic skin substitutes can be synthesised on demand and can be modulated for specific purposes. Each class has its advantages and disadvantages. The biological skin substitutes may allow the construction of a more natural new dermis and allow excellent re-epithelialisation characteristics due to the presence of a basement membrane. Synthetic skin substitutes demonstrate the advantages of increase control over scaffold composition. The ultimate goal is to achieve an ideal skin substitute that provides an effective and scar-free wound healing.

  1. Biologic and synthetic skin substitutes: An overview

    Directory of Open Access Journals (Sweden)

    Halim Ahmad

    2010-10-01

    Full Text Available The current trend of burn wound care has shifted to more holistic approach of improvement in the long-term form and function of the healed burn wounds and quality of life. This has demanded the emergence of various skin substitutes in the management of acute burn injury as well as post burn reconstructions. Skin substitutes have important roles in the treatment of deep dermal and full thickness wounds of various aetiologies. At present, there is no ideal substitute in the market. Skin substitutes can be divided into two main classes, namely, biological and synthetic substitutes. The biological skin substitutes have a more intact extracellular matrix structure, while the synthetic skin substitutes can be synthesised on demand and can be modulated for specific purposes. Each class has its advantages and disadvantages. The biological skin substitutes may allow the construction of a more natural new dermis and allow excellent re-epithelialisation characteristics due to the presence of a basement membrane. Synthetic skin substitutes demonstrate the advantages of increase control over scaffold composition. The ultimate goal is to achieve an ideal skin substitute that provides an effective and scar-free wound healing.

  2. Statistical Physics of Complex Substitutive Systems

    Science.gov (United States)

    Jin, Qing

    Diffusion processes are central to human interactions. Despite extensive studies that span multiple disciplines, our knowledge is limited to spreading processes in non-substitutive systems. Yet, a considerable number of ideas, products, and behaviors spread by substitution; to adopt a new one, agents must give up an existing one. This captures the spread of scientific constructs--forcing scientists to choose, for example, a deterministic or probabilistic worldview, as well as the adoption of durable items, such as mobile phones, cars, or homes. In this dissertation, I develop a statistical physics framework to describe, quantify, and understand substitutive systems. By empirically exploring three collected high-resolution datasets pertaining to such systems, I build a mechanistic model describing substitutions, which not only analytically predicts the universal macroscopic phenomenon discovered in the collected datasets, but also accurately captures the trajectories of individual items in a complex substitutive system, demonstrating a high degree of regularity and universality in substitutive systems. I also discuss the origins and insights of the parameters in the substitution model and possible generalization form of the mathematical framework. The systematical study of substitutive systems presented in this dissertation could potentially guide the understanding and prediction of all spreading phenomena driven by substitutions, from electric cars to scientific paradigms, and from renewable energy to new healthy habits.

  3. Substitution dynamical systems spectral analysis

    CERN Document Server

    Queffélec, Martine

    2010-01-01

    This volume mainly deals with the dynamics of finitely valued sequences, and more specifically, of sequences generated by substitutions and automata. Those sequences demonstrate fairly simple combinatorical and arithmetical properties and naturally appear in various domains. As the title suggests, the aim of the initial version of this book was the spectral study of the associated dynamical systems: the first chapters consisted in a detailed introduction to the mathematical notions involved, and the description of the spectral invariants followed in the closing chapters. This approach, combined with new material added to the new edition, results in a nearly self-contained book on the subject. New tools - which have also proven helpful in other contexts - had to be developed for this study. Moreover, its findings can be concretely applied, the method providing an algorithm to exhibit the spectral measures and the spectral multiplicity, as is demonstrated in several examples. Beyond this advanced analysis, many...

  4. Controversial issues of maternity substitution

    Directory of Open Access Journals (Sweden)

    Andy Pușcă

    2009-06-01

    Full Text Available Substitute maternity consists in a woman carrying a pregnancy (the implant of an embryo, at therequest of a sterile couple, most of the times in exchange of a sum of money, with her commitment tounconditionally give away the newborn after birth to the couple she concluded the agreement with. Manycontroversies emerged in what concerns the contract between the sterile couple and the carrying mother,especially when this contract is by onerous title, which happens in most of the cases. In that a civil contract? Is ita sales contract for the child? Is it a contract to provide services? Is it body marketing? Between total prohibitionand excessive liberalism, the middle way, which is the regulation according to ethical religious, cultural andsocial norms of each community, represents a realistic solution.

  5. An Integrated Experimental-Modelling Procedure Applied to the Design of a Field Scale Goethite Nanoparticle Injection for the Remediation of Contaminated Sites

    Science.gov (United States)

    Bianco, C.; Tosco, T.; Sethi, R.

    2017-12-01

    Nanoremediation is a promising in-situ technology for the reclamation of contaminated aquifers. It consists in the subsurface injection of a reactive colloidal suspension for the in-situ treatment of pollutants. The overall success of this technology at the field scale is strictly related to the achievement of an effective and efficient emplacement of the nanoparticles (NP) inside the contaminated area. Mathematical models can be used to support the design of nanotechnology-based remediation by effectively assessing the expected NP mobility at the field scale. Several analytical and numerical tools have been developed in recent years to model the transport of NPs in simplified geometry and boundary conditions. The numerical tool MNMs was developed by the authors of this work to simulate colloidal transport in 1D Cartesian and radial coordinates. A new modelling tool, MNM3D (Micro and Nanoparticle transport Model in 3D geometries), was also proposed for the simulation of injection and transport of NP suspensions in generic complex scenarios. MNM3D accounts for the simultaneous dependency of NP transport on water ionic strength and velocity. The software was developed to predict the NP mobility at different stages of a nanoremediation application, from the design stage to the prediction of the long-term fate after injection. In this work an integrated experimental-modelling procedure is applied to support the design of a field scale injection of goethite NPs carried out in the framework of the H2020 European project Reground. Column tests are performed at different injection flowrates using natural sand collected at the contaminated site as porous medium. The tests are interpreted using MNMs to characterize the NP mobility and derive the constitutive equations describing the suspension behavior in the natural porous medium. MNM3D is then used to predict NP behavior during the field scale injection and to assess the long-term mobility of the injected slurry. Finally

  6. Type Substitution for Object-Oriented Programming

    DEFF Research Database (Denmark)

    Schwartzbach, Michael Ignatieff; Palsberg, Jens

    1990-01-01

    Genericity allows the substitution of types in a class. This is usually obtained through parameterized classes, although they are inflexible since any class can be inherited but is not in itself parameterized. We suggest a new genericity mechanism, type substitution, which is a subclassing concep...

  7. Educators Take Another Look at Substitutes

    Science.gov (United States)

    Zubrzycki, Jaclyn

    2012-01-01

    The mythology surrounding the substitute teacher is not a pretty one: Paper airplanes, lost learning, bullying. But as schools collect more information about teacher absenteeism and its consequences, districts and schools are exploring ways to professionalize substitute teaching--or experiment with alternative ways of coping with teacher absences.…

  8. Strategic Resource Extraction And Substitute Development

    NARCIS (Netherlands)

    Michielsen, T.O.

    2013-01-01

    Abstract We analyze a dynamic game between a buyer and a seller of an exhaustible resource. The seller chooses resource supply; the buyer can pay a fixed cost to invent a perfect substitute for the resource at any time. In closed-loop equilibrium, the buyer adopts the substitute when the resource is

  9. Multisensory integration, sensory substitution and visual rehabilitation

    DEFF Research Database (Denmark)

    Proulx, Michael J; Ptito, Maurice; Amedi, Amir

    2014-01-01

    Sensory substitution has advanced remarkably over the past 35 years since first introduced to the scientific literature by Paul Bach-y-Rita. In this issue dedicated to his memory, we describe a collection of reviews that assess the current state of neuroscience research on sensory substitution, v......, visual rehabilitation, and multisensory processes....

  10. Current bone substitutes for implant dentistry.

    Science.gov (United States)

    Yamada, Masahiro; Egusa, Hiroshi

    2017-09-15

    Alveolar ridge augmentation is essential for success in implant therapy and depends on the biological performance of bone graft materials. This literature review aims to comprehensively explain the clinically relevant capabilities and limitations of currently available bone substitutes for bone augmentation in light of biomaterial science. The biological performance of calcium phosphate-based bone substitutes was categorized according to space-making capability, biocompatibility, bioabsorption, and volume maintenance over time. Each category was reviewed based on clinical studies, preclinical animal studies, and in vitro studies. Currently available bone substitutes provide only osteoconduction as a scaffold but not osteoinduction. Particle size, sensitivity to enzymatic or chemical dissolution, and mechanical properties affect the space-making capability of bone substitutes. The nature of collagen fibers, particulate size, and release of calcium ions influence the biocompatibility of bone substitutes. Bioabsorption of bone substitutes is determined by water solubility (chemical composition) and acid resistance (integrity of apatite structure). Bioabsorption of remnant bone substitute material and volume maintenance of the augmented bone are inversely related. It is necessary to improve the biocompatibility of currently available bone substitutes and to strike an appropriate balance between bioabsorption and volume maintenance to achieve ideal bone remodeling. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  11. Substitute Teachers: Making Lost Days Count

    Science.gov (United States)

    True, Charlene; Butler, Kyle; Sefton, Rachel

    2011-01-01

    As K-12 teachers and administrators grow increasingly concerned with issues of accountability, research-based methods, and intervention strategies, little discussion exists on the impact of substitute teachers in the classroom. In the rush to analyze test scores, are the days covered by substitute teachers even considered? Though districts are…

  12. Substitution between cars within the household

    DEFF Research Database (Denmark)

    De Borger, Bruno; Mulalic, Ismir; Rouwendal, Jan

    2016-01-01

    In this paper we study the demand for car kilometres in two-car households, focusing on the substitution between cars of different fuel efficiency in response to fuel price changes. We use a large sample of detailed Danish data on two-car households to estimate – for each car owned by the household...... – own and cross-price effects of increases in fuel costs per kilometre. The empirical results show that failure to capture substitution between cars within the household can result in substantial misspecification biases. Ignoring substitution, the basic model yielded fuel price elasticities of 0.......98 and 1.41 for the primary and secondary cars, respectively. Accounting for substitution effects, these figures reduce to, respectively, 0.32 and 0.45. Consistent with substitution behaviour, we find that the fuel price elasticity of fuel demand exceeds the elasticity of kilometre demands with respect...

  13. Uproar over Milk Substitutes Act.

    Science.gov (United States)

    1993-11-15

    Health policy activists lobbied 7 years for the Infant Milk Substitutes, Feeding Bottles and Infant Food Bill. Proponents of the bill say that it basically curtails unethical marketing practices, not the sales of baby foods, and argue that it was conceived to reduce the trend of mothers over-diluting commercial milk in order to reduce household expenses as well as stem the potential erosion of knowledge on locally available weaning foods. Even though the bill will become an Act only after its rules and regulations have been finalized, the government has already banned baby food advertisements on television and in other electronic media under its control. Women's groups now argue that the bill tends to focus almost exclusively upon the welfare of children and compromises the position of women who can not lactate adequately. Moreover, they hold that the bill may be used to compel wives to stay out of the formal workforce so that they may feed their babies. The intention of the bill may be meaningless without complementary legislation addressing the problems of working mothers. Specifically, amendments to the Maternity Benefits Act of 1961 would extend maternity leave to 4 months after delivery and lengthen the duration of nursing breaks. It is, however, feared that these changes may reduce employment prospects for women.

  14. Substituted Hydroxyapatites with Antibacterial Properties

    Directory of Open Access Journals (Sweden)

    Joanna Kolmas

    2014-01-01

    Full Text Available Reconstructive surgery is presently struggling with the problem of infections located within implantation biomaterials. Of course, the best antibacterial protection is antibiotic therapy. However, oral antibiotic therapy is sometimes ineffective, while administering an antibiotic at the location of infection is often associated with an unfavourable ratio of dosage efficiency and toxic effect. Thus, the present study aims to find a new factor which may improve antibacterial activity while also presenting low toxicity to the human cells. Such factors are usually implemented along with the implant itself and may be an integral part of it. Many recent studies have focused on inorganic factors, such as metal nanoparticles, salts, and metal oxides. The advantages of inorganic factors include the ease with which they can be combined with ceramic and polymeric biomaterials. The following review focuses on hydroxyapatites substituted with ions with antibacterial properties. It considers materials that have already been applied in regenerative medicine (e.g., hydroxyapatites with silver ions and those that are only at the preliminary stage of research and which could potentially be used in implantology or dentistry. We present methods for the synthesis of modified apatites and the antibacterial mechanisms of various ions as well as their antibacterial efficiency.

  15. Substituted Hydroxyapatites with Antibacterial Properties

    Science.gov (United States)

    Kolmas, Joanna; Groszyk, Ewa; Kwiatkowska-Różycka, Dagmara

    2014-01-01

    Reconstructive surgery is presently struggling with the problem of infections located within implantation biomaterials. Of course, the best antibacterial protection is antibiotic therapy. However, oral antibiotic therapy is sometimes ineffective, while administering an antibiotic at the location of infection is often associated with an unfavourable ratio of dosage efficiency and toxic effect. Thus, the present study aims to find a new factor which may improve antibacterial activity while also presenting low toxicity to the human cells. Such factors are usually implemented along with the implant itself and may be an integral part of it. Many recent studies have focused on inorganic factors, such as metal nanoparticles, salts, and metal oxides. The advantages of inorganic factors include the ease with which they can be combined with ceramic and polymeric biomaterials. The following review focuses on hydroxyapatites substituted with ions with antibacterial properties. It considers materials that have already been applied in regenerative medicine (e.g., hydroxyapatites with silver ions) and those that are only at the preliminary stage of research and which could potentially be used in implantology or dentistry. We present methods for the synthesis of modified apatites and the antibacterial mechanisms of various ions as well as their antibacterial efficiency. PMID:24949423

  16. Substituted androstanes as aromatase inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Levina, Inna S [N.D.Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow (Russian Federation)

    1998-11-30

    The synthesis and structure-activity relationships of inhibitors of steroid aromatase which catalyses the last stage of a multistep biotransformation of cholesterol into estrogens, viz., aromatisation of C{sub 19}-steroids into C{sub 18}-phenolic steroids, are discussed. Compounds of the androstane series which are structurally related to the natural substrate, viz., androst-4-ene-3,17-dione, are the subjects of consideration. The review encompasses problems of synthesis of various substituted androstanes and their aromatase-inhibiting activities and structural requirements for selective specific aromatase inhibitors based on in vitro and in vivo structure-activity studies of compounds synthesised, their biological properties and the results of clinical trials. Special attention is paid to practical applications of aromatase inhibitors in the treatment of hormone-dependent mammary and ovarian tumours as well as benign prostatic tumours. In writing this report, the author has used all the information currently available in the chemical, biochemical, endocrinological and medicinal literature as well as in patents. The bibliography includes 173 references.

  17. Substituted androstanes as aromatase inhibitors

    Science.gov (United States)

    Levina, Inna S.

    1998-11-01

    The synthesis and structure-activity relationships of inhibitors of steroid aromatase which catalyses the last stage of a multistep biotransformation of cholesterol into estrogens, viz., aromatisation of C19-steroids into C18-phenolic steroids, are discussed. Compounds of the androstane series which are structurally related to the natural substrate, viz., androst-4-ene-3,17-dione, are the subjects of consideration. The review encompasses problems of synthesis of various substituted androstanes and their aromatase-inhibiting activities and structural requirements for selective specific aromatase inhibitors based on in vitro and in vivo structure-activity studies of compounds synthesised, their biological properties and the results of clinical trials. Special attention is paid to practical applications of aromatase inhibitors in the treatment of hormone-dependent mammary and ovarian tumours as well as benign prostatic tumours. In writing this report, the author has used all the information currently available in the chemical, biochemical, endocrinological and medicinal literature as well as in patents. The bibliography includes 173 references.

  18. Modeling competitive substitution in a polyelectrolyte complex

    International Nuclear Information System (INIS)

    Peng, B.; Muthukumar, M.

    2015-01-01

    We have simulated the invasion of a polyelectrolyte complex made of a polycation chain and a polyanion chain, by another longer polyanion chain, using the coarse-grained united atom model for the chains and the Langevin dynamics methodology. Our simulations reveal many intricate details of the substitution reaction in terms of conformational changes of the chains and competition between the invading chain and the chain being displaced for the common complementary chain. We show that the invading chain is required to be sufficiently longer than the chain being displaced for effecting the substitution. Yet, having the invading chain to be longer than a certain threshold value does not reduce the substitution time much further. While most of the simulations were carried out in salt-free conditions, we show that presence of salt facilitates the substitution reaction and reduces the substitution time. Analysis of our data shows that the dominant driving force for the substitution process involving polyelectrolytes lies in the release of counterions during the substitution

  19. Elasticity of Substitution and Antidumping Measures

    DEFF Research Database (Denmark)

    Drud Hansen, Jørgen; Meinen, Philipp; Nielsen, Jørgen Ulff-Møller

    therefore also vary inversely with the elasticity of substitution at least for countries which have a strong focus on prices in the determination of their anti-dumping measures. We test this for ten countries from 1990 to 2009 using data on anti-dumping from Chad Bown (2010) and US-data at 8-digit level......Abstract This paper analyzes the role of the elasticity of substitution for anti-dumping decisions across countries. In monopolistic competition models with cost heterogeneous firms across countries, price differences vary inversely with the elasticity of substitution. Anti-dumping duties should...

  20. Biologic and synthetic skin substitutes: An overview

    OpenAIRE

    Halim, Ahmad Sukari; Khoo, Teng Lye; Mohd. Yussof, Shah Jumaat

    2010-01-01

    The current trend of burn wound care has shifted to more holistic approach of improvement in the long-term form and function of the healed burn wounds and quality of life. This has demanded the emergence of various skin substitutes in the management of acute burn injury as well as post burn reconstructions. Skin substitutes have important roles in the treatment of deep dermal and full thickness wounds of various aetiologies. At present, there is no ideal substitute in the market. Skin substit...

  1. Vitreous substitutes:challenges and directions

    Directory of Open Access Journals (Sweden)

    Qian-Ying Gao

    2015-06-01

    Full Text Available Thenatural vitreous body has a fine structure and complex functions. The imitation of the natural vitreous body by vitreous substitutes is a challenging work for both researchers and ophthalmologists. Gases, silicone oil, heavy silicone oil and hydrogels, particularly the former two vitreous substitutes are clinically widely used with certain complications. Those, however, are not real artificial vitreous due to lack of structure and function like the natural vitreous body. This article reviews the situations, challenges, and future directions in the development of vitreous substitutes, particularly the experimental and clinical use of a new artificial foldable capsular vitreous body .

  2. Questioning nuclear waste substitution: a case study.

    Science.gov (United States)

    Marshall, Alan

    2007-03-01

    This article looks at the ethical quandaries, and their social and political context, which emerge as a result of international nuclear waste substitution. In particular it addresses the dilemmas inherent within the proposed return of nuclear waste owned by Japanese nuclear companies and currently stored in the United Kingdom. The UK company responsible for this waste, British Nuclear Fuels Limited (BNFL), wish to substitute this high volume intermediate-level Japanese-owned radioactive waste for a much lower volume of much more highly radioactive waste. Special focus is given to ethical problems that they, and the UK government, have not wished to address as they move forward with waste substitution. The conclusion is that waste substitution can only be considered an ethical practice if a set of moderating conditions are observed by all parties. These conditions are listed and, as of yet, they are not being observed.

  3. Towards hemerythrin-based blood substitutes: Comparative ...

    Indian Academy of Sciences (India)

    related reactivity is lower than that of hemoglobin, which may warrant investigation of hemerythrin as raw material for artificial oxygen carriers ('blood substitutes'). We report here the first biological tests for hemerythrin and its chemical derivatives, ...

  4. Symbolic Substitution Methods For Optical Computing

    Science.gov (United States)

    Murdocca, M. J.; Huang, A.

    1989-02-01

    Symbolic substitution is a method of computing based on parallel binary pattern replacement, that can be implemented with simple optical components and regular free-space interconnection schemes. A two-dimensional pattern is searched for in parallel in an array and is replaced with another pattern. Pattern transformation rules can be applied sequentially or in parallel to realize complex functions. When the substitution space is modified to be loge SIT connected for N binary spots, and masks are allowed to customize the system, then optical digital circuits using symbolic substitution for network interconnects can be made nearly as efficient in terms of gate count and circuit depth as conventional arbitrary interconnection schemes allow. We describe an optical setup that requires no more than a fanin and fanout of two using optically nonlinear logic devices and a free space interconnection scheme based on symbolic substitution.

  5. Synthesis and biological activities of substituted N ...

    African Journals Online (AJOL)

    use

    2011-12-07

    Dec 7, 2011 ... The present study describes the synthesis, antioxidant and antibacterial activities of substituted N'- benzoylhydrazone derivatives, to ... addition, the dramatically rising prevalence of multidrug- resistant microbial infections has ...... extract of Chinese green tea (Camellia sinensis) on Listeria monocytogenes.

  6. SYNTHESIS OF SUBSTITUTED FLAVONE DERIVATIVES AS ...

    African Journals Online (AJOL)

    Preferred Customer

    results showed that this skeletal framework exhibited marked potency as antimicrobial agents. KEY WORDS. KEY WORDS: Chalcone ... It showed significant role in pharmaceutical effects [1] including leishmanicidal activity, oviposter ... new substituted flavone derivative as potent antimicrobial agent. EXPERIMENTAL.

  7. Transnationalism and integration : complements or Substitutes?

    NARCIS (Netherlands)

    Dekker, B.; Siegel, M.

    2013-01-01

    This paper investigates the relationship between transnational practices and integration by testing whether they are substitutes or complements. For this purpose, we use a multidimensional transnationalism index. The index includes three dimensions of transnational practices, including migrants'

  8. Development of a diesel substitute fuel

    Energy Technology Data Exchange (ETDEWEB)

    Reiter, Anton; Mair-Zelenka, Philipp [Graz Univ. of Technology (Austria). Inst. of Chemical Engineering and Environmental Technology; Zeymer, Marc [OMV Refining and Marketing GmbH, Vienna (Austria). MRDI-D Product Development and Innovation

    2013-06-01

    Substitute fuels composed of few real chemical compounds are an alternative characterisation approach for conventional fuels as opposed to the traditional pseudo-component method. With the algorithm proposed in this paper the generation of such substitutes will be facilitated and well-established thermodynamic methods can be applied for physical property-data prediction. Based on some quality criteria like true boiling-point curve, liquid density, C/H ratio, or cloud point of a target fuel a surrogate which meets these properties is determined by fitting its composition. The application and capabilities of the algorithm developed are demonstrated by means of an exemplary diesel substitute fuel. The substitute mixture obtained can be generated and used for evaluation of property-prediction methods. Furthermore this approach can help to understand the effects of mixing fossil fuels with biogenic compounds. (orig.)

  9. 47 CFR 76.110 - Substitutions.

    Science.gov (United States)

    2010-10-01

    ... blackout rules at § 76.111, substitute a program from any other television broadcast station. Programs... CABLE TELEVISION SERVICE Network Non-duplication Protection, Syndicated Exclusivity and Sports Blackout...

  10. Substituted hydroxyapatites for biomedical applications: A review

    Czech Academy of Sciences Publication Activity Database

    Šupová, Monika

    2015-01-01

    Roč. 41, č. 8 (2015), s. 9203-9231 ISSN 0272-8842 Institutional support: RVO:67985891 Keywords : bioapatite * calcium phosphate * hydroxyapatite * substitution Subject RIV: JJ - Other Materials Impact factor: 2.758, year: 2015

  11. Synthesis of substituted 2-cyanoarylboronic esters

    DEFF Research Database (Denmark)

    Lysén, Morten; Hansen, Henriette M; Begtrup, Mikael

    2006-01-01

    The synthesis of substituted 2-cyanoarylboronic esters is described via lithiation/in situ trapping of the corresponding methoxy-, trifluoromethyl-, fluoro-, chloro-, and bromobenzonitriles. The crude arylboronic esters were obtained in high yields and purities and with good regioselectivities....

  12. Substitution within the Danish printing industry

    DEFF Research Database (Denmark)

    Larsen, Henrik Fred; Bøg, Carsten

    2009-01-01

    The implementation of the EU REACH regulation will most probably promote substitution within sectors handling a lot of different chemicals like the printing industry. With the aim of being at the cutting edge of this development the Danish EPA together with the Danish printing industry and IPU...... are running a substitution project. A major part of the work has been mapping the presence of chemicals which are potential candidates for substitution (e.g. PBT, CMR, vPvB, EDS) within the Danish printing industry and this work was recently finished. The mapping comprises a combination of a literature study...... total 15 substances) were found in the Danish printing industry. This paper presents the results of the mapping of chemical candidates and the first results on preparing for actual substitutions....

  13. Towards hemerythrin-based blood substitutes

    Indian Academy of Sciences (India)

    related reactivity is lower than that of hemoglobin, which may warrant investigation of hemerythrin as raw material for artificial oxygen carriers ('blood substitutes'). We report here the first biological tests for hemerythrin and its chemical derivatives, ...

  14. Adsorption of Pb(II) ions present in aqueous solution on the oxy hydroxides: boehmite (γ-AIOOH), goethite (α-FeOOH) and manganite (γ-MnOOH)

    International Nuclear Information System (INIS)

    Arreola L, J. E.

    2013-01-01

    Boehmite, goethite and manganite were synthesized by different methods and characterized using X-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimetric study , N 2 physisorption measurements, scanning electron microscopy (Sem), semiquantitative elemental analysis (EDS), as well as additional studies were determined the surface active sites concentration and zero point of charge. Furthermore, we studied the Pb(II) ion adsorption capacity present in aqueous solution on these synthesized materials by batch-type experiments at room temperature, as a function of contact time between the phases liquid-solid system (adsorption kinetics), initial concentration of the adsorbate (adsorption isotherms), ph and temperature. The adsorption equilibrium time of adsorption processes in these studied systems was found at 60 minutes for boehmite and 30 minutes for goethite and manganite respectively after contacting the solid-liquid phase systems. The adsorption capacity of the lead ions on these adsorbent materials depended of lead concentration, ph and temperature of the systems. Were evaluated lead adsorption capacities in these materials to different contact times using an initial concentration of 20 mg/L of Pb(II) ions at ph = 4, the results of three systems were adjusted to second pseudo kinetic model order. With respect to the study of the adsorbate concentration effect, boehmite-Pb(II) and goethite-Pb(II) systems were adjusted to Langmuir isotherm model which proposes that the adsorption is carried out in a monolayer, moreover manganite-Pb(II) system was adjusted Temp kin isotherm model, which assumes that the adsorption heat of all the molecules in the layer decreases linearly with coverage due to adsorbent-adsorbate interactions and adsorption is characterized by a uniform distribution of the binding energies. Were studied the ph effect of Pb(II) ions solution on the adsorption capacity of such adsorbents, it was found that as the ph increases lead solution

  15. Product portfolio optimization based on substitution

    DEFF Research Database (Denmark)

    Myrodia, Anna; Moseley, A.; Hvam, Lars

    2017-01-01

    The development of production capabilities has led to proliferation of the product variety offered to the customer. Yet this fact does not directly imply increase of manufacturers' profitability, nor customers' satisfaction. Consequently, recent research focuses on portfolio optimization through...... substitution and standardization techniques. However when re-defining the strategic market decisions are characterized by uncertainty due to several parameters. In this study, by using a GAMS optimization model we present a method for supporting strategic decisions on substitution, by quantifying the impact...

  16. Substitutability between Equity REITs and Mortgage REITs

    OpenAIRE

    Ming-Long Lee; Kevin C.H. Chiang

    2004-01-01

    This study extends Seck’s (1996) approach to investigate the degree of substitutability between equity real estate investment trusts (EREITs) and mortgage real estate investment trusts (MREITs). The variance ratio test and the variance decomposition of forecast errors yield results indicating the existence of informational commonality between EREITs and MREITs. The findings indicate that the two types of REITs are substitutable. A direct implication is that investors who believe they have s...

  17. Competition Among Near-Substitutable Systems

    Science.gov (United States)

    2012-09-01

    the context of the dominant “Weapon System Franchise ” model of competition for major defense acquisition programs (MDAPs). Competition between near...leading to the award of a franchise . AoAs or other cost-effectiveness analyses can be pivotal in bringing attention to near-substitute systems. However...Symposium, 18-19 Sep 2012, Fort Belvoir, VA. U.S. Government or Federal Rights License 14. ABSTRACT We define near-substitutable systems as systems that

  18. Trace maps of general substitutional sequences

    International Nuclear Information System (INIS)

    Kolar, M.; Nori, F.

    1990-01-01

    It is shown that for arbitrary n, there exists a trace map for any n-letter substitutional sequence. Trace maps are explicitly obtained for the well-known circle and Rudin-Shapiro sequences which can be defined by means of substitution rules on three and four letters, respectively. The properties of the two trace maps and their consequences for various spectral properties are briefly discussed

  19. Diphosphorus-substituted derivatives of ketones

    International Nuclear Information System (INIS)

    Novikova, Z.S.; Kurkin, A.N.; Lutsenko, I.F.

    1986-01-01

    The structure of C,0-diphosphorus-substituted derivatives of ketones formed in the phosphorylation of sodium enolates of C-phosphorus-substituted ketones depends on the structure of the phosphorus-containing group in the molecule of the original ketone; increase in the electron-acceptor power of the substituents on the phosphorus atom and rise in its valence favor the formation of β-phosphorus-containing vinyl esters of phosphorus acids

  20. Substituting missing data in compositional analysis

    Energy Technology Data Exchange (ETDEWEB)

    Real, Carlos, E-mail: carlos.real@usc.es [Area de Ecologia, Departamento de Biologia Celular y Ecologia, Escuela Politecnica Superior, Universidad de Santiago de Compostela, 27002 Lugo (Spain); Angel Fernandez, J.; Aboal, Jesus R.; Carballeira, Alejo [Area de Ecologia, Departamento de Biologia Celular y Ecologia, Facultad de Biologia, Universidad de Santiago de Compostela, 15782 Santiago de Compostela (Spain)

    2011-10-15

    Multivariate analysis of environmental data sets requires the absence of missing values or their substitution by small values. However, if the data is transformed logarithmically prior to the analysis, this solution cannot be applied because the logarithm of a small value might become an outlier. Several methods for substituting the missing values can be found in the literature although none of them guarantees that no distortion of the structure of the data set is produced. We propose a method for the assessment of these distortions which can be used for deciding whether to retain or not the samples or variables containing missing values and for the investigation of the performance of different substitution techniques. The method analyzes the structure of the distances among samples using Mantel tests. We present an application of the method to PCDD/F data measured in samples of terrestrial moss as part of a biomonitoring study. - Highlights: > Missing values in multivariate data sets must be substituted prior to analysis. > The substituted values can modify the structure of the data set. > We developed a method to estimate the magnitude of the alterations. > The method is simple and based on the Mantel test. > The method allowed the identification of problematic variables in a sample data set. - A method is presented for the assessment of the possible distortions in multivariate analysis caused by the substitution of missing values.

  1. 40 CFR Appendix B to Subpart G of... - Substitutes Subject to Use Restrictions and Unacceptable Substitutes

    Science.gov (United States)

    2010-07-01

    ... Conditions Application Substitute Decision Conditions Comments CFC-12 Automobile Motor Vehicle Air... refrigerant. CFC-12 Automobile Motor Vehicle Air Conditioning (New equipment only) R-152a as a substitute for... excluding the space enclosed by the ducting in the HVAC module. Refrigerants—Acceptable Subject to Narrowed...

  2. Substitution between Cars within the Household

    DEFF Research Database (Denmark)

    de Borger, Bruno; Mulalic, Ismir; Rouwendal, Jan

    In this paper we study the demand for car kilometres in two-car households, focusing on the substitution between cars in response to fuel price changes. We use a large sample of detailed Danish data on two-car households to estimate—for each car owned by the household—own and cross-price effects...... of increases in fuel costs per kilometre. The empirical results show that failure to capture substitution between cars within the household can result in substantial misspecification biases. Ignoring substitution, we estimate fuel price elasticities of –0.81 and -0.65 for the primary and secondary cars...... efficient car, finding partial support for the underlying hypothesis. More importantly, the results of this extended model emphasize the importance of behavioural differences related to the position of the most fuel efficient car in the household, suggesting that households’ fuel efficiency choices...

  3. Substitute energy resource policy in Japan

    International Nuclear Information System (INIS)

    Umehara, Katsuhiko

    1980-01-01

    Japan depends 88% of energy resources and 99.8% of petroleum on imports. The solution of energy problems is now made internationally. As the means for Japan, there are the substitution of other resources for petroleum and its promotion. However, this involves the considerable funds for the development and utilization, which must be borne by the people in the form of tax. For governmental financing, a special account must be set up for the particular purpose. In the research and development of new energy resources, new institution is required. The following matters are described: petroleum shortage coming even in 1980s, the international need of substitute energy development, the need for establishing measures for substitute energy resources, acquisition of the funds, special-account governmental financing, and an institute of new energy development. (author)

  4. [Contingency management in opioid substitution treatment].

    Science.gov (United States)

    Specka, M; Böning, A; Scherbaum, N

    2011-07-01

    The majority of opiate-dependent patients in substitution treatment show additional substance-related disorders. Concomitant use of heroin, alcohol, benzodiazepines or cocaine compromises treatment success. Concomitant drug use may be treated by using contingency management (CM) which is based on learning theory. In CM, abstinence from drugs, as verified by drug screenings, is reinforced directly and contingently. Reinforcers used in CM studies with substituted patients were, amongst others, vouchers and take-home privileges. Studies in the USA show a medium average effect of CM on drug consumption rates and abstinence. The effects decrease markedly after the end of the intervention. We discuss whether CM is applicable within the German substitution treatment system and how it can be combined with other interventions such as selective detoxification treatments or cognitive-behavioural programmes. © Georg Thieme Verlag KG Stuttgart · New York.

  5. Biomaterials in search of a meniscus substitute.

    Science.gov (United States)

    Rongen, Jan J; van Tienen, Tony G; van Bochove, Bas; Grijpma, Dirk W; Buma, Pieter

    2014-04-01

    The menisci fulfill key biomechanical functions in the tibiofemoral (knee) joint. Unfortunately meniscal injuries are quite common and most often treated by (partial) meniscectomy. However, some patients experience enduring symptoms, and, more importantly, it leads to an increased risk for symptomatic osteoarthritis. Over the past decades, researchers have put effort in developing a meniscal substitute able to prevent osteoarthritis and treat enduring clinical symptoms. Grossly, two categories of substitutes are observed: First, a resorbable scaffold mimicking biomechanical function which slowly degrades while tissue regeneration and organization is promoted. Second, a non resorbable, permanent implant which mimics the biomechanical function of the native meniscus. Numerous biomaterials with different (material) properties have been used in order to provide such a substitute. Nevertheless, a clinically applicable cartilage protecting material is not yet emerged. In the current review we provide an overview, and discuss, these different materials and extract recommendations regarding material properties for future developmental research. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Substitution between cars within the household

    DEFF Research Database (Denmark)

    De Borger, Bruno; Mulalic, Ismir; Rouwendal, Jan

    The purpose of this paper is to study to what extent two-car households substitute the use of their less fuel efficient car by the use of their more fuel efficient car after an increase in fuel prices. Based on a simple theoretical framework we use a large sample of detailed Danish data on two-car...... households to estimate, for each car owned by the household, own and cross-price effects of increases in fuel costs per kilometer. The empirical results point at important substitution effects, so that models that estimate responses to fuel prices on the implicit or explicit assumption of one car per...

  7. Substituting freshwater: Can ocean desalination and water recycling capacities substitute for groundwater depletion in California?

    Science.gov (United States)

    Badiuzzaman, Pierre; McLaughlin, Eoin; McCauley, Darren

    2017-12-01

    While the sustainability of resource depletion is a longstanding environmental concern, wider attention has recently been given to growing water scarcity and groundwater depletion. This study seeks to test the substitutability assumption embedded in weak sustainability indicators using a case study of Californian water supply. The volume of groundwater depletion is used as a proxy for unsustainable water consumption, and defined by synthesising existing research estimates into low, medium and high depletion baselines. These are compared against projected water supply increases from ocean desalination and water recycling by 2035, to determine whether new, drought-proof water sources can substitute for currently unsustainable groundwater consumption. Results show that the maximum projected supply of new water, 2.47 million acre-feet per year (MAF/yr), is sufficient to meet low depletion estimates of 2.02 MAF/yr, but fails to come near the high depletion estimate of 3.44 MAF/yr. This does not necessarily indicate physical limitations of substitutability, but more so socio-economic limitations influenced by high comparative costs. By including capacities in demand-substitutability via urban water conservation, maximum predicted capacities reach 5.57 MAF/yr, indicating wide room for substitution. Based on these results, investment in social and institutional capital is an important factor to enhance demand-side substitutability of water and other natural resources, which has been somewhat neglected by the literature on the substitutability of natural resources. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. substitution line for resistance to stripe rust

    Indian Academy of Sciences (India)

    2011-08-19

    Aug 19, 2011 ... c Indian Academy of Sciences. RESEARCH ARTICLE. Molecular cytogenetic characterization of a new wheat Secale africanum. 2R a. (2D) substitution line for resistance to stripe rust. MENGPING LEI, GUANGRONG LI, SUFEN ZHANG, CHENG LIU and ZUJUN YANG. ∗. School of Life Science and ...

  9. Biological activities of substituted trichostatic acid derivatives

    Indian Academy of Sciences (India)

    New substituted trichostatic acid derivatives have been synthesized and evaluated for their biological activities towards the H661 non-small lung cancer cell line. These syntheses were achieved by alkylation of propiophenones to introduce the side chain with a terminal precursor of hydroxamic acid and aminobenzamide ...

  10. 3-Substituted 2-phenyl-indoles

    DEFF Research Database (Denmark)

    Johansson, Karl Henrik; Jørgensen, T.B.; Gloriam, D.E.

    2013-01-01

    -indoles with a variety of substituents at the indole 3-position. Herein we describe the development of optimised and efficient synthetic routes to a series of new 2-phenyl-indole building blocks 3 to 9 and show that these can be used to generate a broad variety of 3-substituted 2-phenyl-indoles of interest to medicinal...

  11. chromic transitions in phenyl-substituted polythiophenes

    African Journals Online (AJOL)

    The solvatochromic and thermochromic behaviours of phenyl-substituted polythiophenes were studied. The pristine polymers, upon dissolution in chloroform, exhibited blue-shifted absorption. The solid films of the polymers showed significant blue-shifted as well as red-shifted absorptions when heated. While the addition of ...

  12. CHROMIC TRANSITIONS IN PHENYL-SUBSTITUTED ...

    African Journals Online (AJOL)

    a

    in order to explain the relationship between optical properties and chemical structure [1-6]. These studies have also opened new possibilities for applications in chemical and biochemical sensors [7-10]. The chromic behaviours of substituted polythiophenes depend on conformational transitions of the polythiophene ...

  13. Fossil Fuels, Backstop Technologies, and Imperfect Substitution

    NARCIS (Netherlands)

    van der Meijden, G.C.; Pittel, Karen; van der Ploeg, Frederick; Withagen, Cees

    2014-01-01

    This chapter studies the transition from fossil fuels to backstop technologies in a general equilibrium model in which growth is driven by research and development. The analysis generalizes the existing literature by allowing for imperfect substitution between fossil fuels and the new energy

  14. Symptomatic hemorrhagic complications associated with dural substitutes

    Directory of Open Access Journals (Sweden)

    Po-Yuan Chen

    2018-01-01

    Conclusion: The increased risk of hemorrhagic complications associated with craniotomy is modified by choice of dural replacement. Our results could assist clinicians in their decision-making with respect to the optimal timing for synthetic dural substitutes in patients with tumor infiltration of the patient's dura, severe brain swelling in traumatic brain injury, or a result of shrinkage from exposure and electrocautery.

  15. Additive and Substitutive Borrowing against Semantic Broadening ...

    African Journals Online (AJOL)

    additive borrowing from substitutive ones. Architecture, Iron-Smelting and Pottery within the Realm of. African Past. The architectural power of African societies is .... paa roof. ---. Kihehe. G62 likang'a roof lwangiko 'roof'. Runyambo JE21 omusakaaro roof ibaati 'roof'. Luzinza. JE23 oluswi roof. ---. Kijita. JE25 oluswi roof. ---.

  16. Additive and Substitutive Borrowing against Semantic Broadening ...

    African Journals Online (AJOL)

    The thrust of this paper lies on semantic changes associated with additive and substitutive borrowing in Bantu-speaking communities in Tanzania. Due to contact of languages, semantic differences of the terms related to architectural structures emanate. Apart from data from a few elderly native speakers, research was ...

  17. A DENSITY FUNCTIONAL THEORY STUDY OF SUBSTITUTED ...

    African Journals Online (AJOL)

    In this work the electronic and thermodynamic properties of both neutral and radical cationic oligothiophene chains with up to eight thiophene units, substituted and bridged oligothiophenes are investigated by performing hybrid DFT (BH and HLYP) and Hartree-Fock calculations using 6-31G* and 6-311G** basis sets.

  18. Electrochemical oxidation of substituted benzylamines in aquo ...

    Indian Academy of Sciences (India)

    Electrochemical oxidation of nine para- and meta-substituted benzylamines in varying mole fractions of acetic acid in water has been investigated in the presence of 0.1 M sulphuric acid as supporting electrolyte. The oxidation potentials correlate well with Hammett's substituent constants affording negative reaction ...

  19. Asymmetric Hydrogenation of 3-Substituted Pyridinium Salts

    NARCIS (Netherlands)

    Renom-Carrasco, Marc; Gajewski, Piotr; Pignataro, Luca; de Vries, Johannes G.; Piarulli, Umberto; Gennari, Cesare; Lefort, Laurent

    2016-01-01

    The use of an equivalent amount of an organic base leads to high enantiomeric excess in the asymmetric hydrogenation of N-benzylated 3-substituted pyridinium salts into the corresponding piperidines. Indeed, in the presence of Et3N, a Rh-JosiPhos catalyst reduced a range of pyridinium salts with ee

  20. Endogenous cueing attenuates object substitution masking.

    Science.gov (United States)

    Germeys, Filip; Pomianowska, I; De Graef, P; Zaenen, P; Verfaillie, K

    2010-07-01

    Object substitution masking (OSM) is a form of visual masking in which a briefly presented target surrounded by four small dots is masked by the continuing presence of the four dots after target offset. A major parameter in the prediction of OSM is the time required for attention to be directed to the target following its onset. Object substitution theory (Di Lollo et al. in J Exp Psychol Gen 129:481-507, 2000) predicts that the sooner attention can be focused at the target's location, the less masking will ensue. However, recently Luiga and Bachmann (Psychol Res 71:634-640, 2007) presented evidence that precueing of attention to the target location prior to target-plus-mask onset by means of a central (endogenous) arrow cue does not reduce OSM. When attention was cued exogenously, OSM was attenuated. Based on these results, Luiga and Bachmann argued that object substitution theory should be adapted by differentiating the ways of directing attention to the target location. The goal of the present study was to further examine the dissociation between the effects of endogenous and exogenous precueing on OSM. Contrary to Luiga and Bachmann, our results show that prior shifts of attention to the target location initiated by both exogenous and endogenous cues reduce OSM as predicted by object substitution theory and its computational model CMOS.

  1. P. Electricity demand, substitution and resources

    International Nuclear Information System (INIS)

    1976-01-01

    This report discusses the demand for electricity in New Zealand, the accuracy of demand predictions, and whether some other form of energy could be substituted for electricity. It then discusses past and possible future electricity generation in New Zealand by geothermal steam and hydro power and the resources of gas and coal that could be made available for electricity generation

  2. Synthesis of enantiopure 3-substituted morpholines

    DEFF Research Database (Denmark)

    Bornholdt, Jan; Felding, Jakob; Kristensen, Jesper Langgaard

    2010-01-01

    Enantiopure 3-substituted morpholines were assembled through ring-opening of a N-2-benzothiazolesulfonyl (Bts) activated aziridine with organocuprates followed by a ring annulation reaction with a vinylsulfonium salt under microwave conditions. Deprotection of the N-Bts group proceeds under very ...

  3. Coal as a Substitute for Carbon Black

    Science.gov (United States)

    Kushida, R. O.

    1982-01-01

    New proposal shows sprayed coal powder formed by extrusion of coal heated to plastic state may be inexpensive substitute for carbon black. Carbon black is used extensively in rubber industry as reinforcing agent in such articles as tires and hoses. It is made from natural gas and petroleum, both of which are in short supply.

  4. Trace maps for arbitrary substitution sequences

    International Nuclear Information System (INIS)

    Avishai, Y.

    1993-01-01

    The discovery of quasi-crystals and their 1-dimensional modeling have led to a deep mathematical study of Schroedinger operators with an arbitrary deterministic potential sequence. In this work we address this problem and find trace maps for an arbitrary substitution sequence. our trace maps have lower dimensionality than those of Kolar and Nori, which make them quite attractive for actual applications. (authors)

  5. Synthesis and electrochemical studies of phenylazo substituted ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 112; Issue 6. Synthesis and electrochemical studies of phenylazo substituted tetraaza macrocyclic complexes of Ni(II). Randhir Singh Suresh Kumar Amarendra Bhattacharya. Inorganic and Analytical Volume 112 Issue 6 December 2000 pp 601-605 ...

  6. Substitution between cars within the household

    NARCIS (Netherlands)

    de Borger, B.; Mulalic, I.; Rouwendal, J.

    2016-01-01

    In this paper we study the demand for car kilometres in two-car households, focusing on the substitution between cars of different fuel efficiency in response to fuel price changes. We use a large sample of detailed Danish data on two-car households to estimate - for each car owned by the household

  7. Substitute fluid examinations for liquid manure

    Directory of Open Access Journals (Sweden)

    Schrader Kevin

    2017-01-01

    Full Text Available For the farming industry it is essential to use liquid manure as natural fertilizer. Through new agricultural regulation 2015 in Germany the industry must develop new liquid manure spreader systems because the ammonia and methane emission are limited. In a research project the University of Applied Sciences Zwickau and some other industry partners will develop such a new innovative liquid manure spreader. The new liquid manure spreader should use pulsating air to distribute the liquid manure exactly. The pulsating air, which flows through the pipelines, should be analysed at a test station. For examinations at this test station it is important to find another substitute fluid because liquid manure smells strong, is not transparent and is also not homogeneous enough for scientific investigations. Furthermore it is important to ensure that the substitute fluid is, like liquid manure, a non-Newtonian fluid. The substitute fluid must be a shear-thinning substance - this means the viscosity decrease at higher shear rate. Many different samples like soap-water-farragoes, jelly-water-farragoes, agar-water-farragoes, soap-ethanol-farragoes and more are, for the project, examined in regard of their physical properties to find the best substitute fluid. The samples are examined at the rotational viscometer for viscosity at various shear rates and then compared with the viscosity values of liquid manure.

  8. Law of substitution for mixed arrays

    International Nuclear Information System (INIS)

    Koudelka, A.J.

    1987-01-01

    The nuclear safety justification of a mixed array of dissimilar fissile units of metal units and dilute solution units, according to Clayton, has been a persistent and nagging problem. Dissimilar uranium metal or dissimilar uranium solution units in a mixed array can also create a modeling nightmare for the nuclear criticality safety engineer. Now, a calculational method known as the Law of Substitution has been developed to ensure that the k/sub eff/ of an array of uranium metal and uranium solution units will satisfy any k/sub eff/ limit set by the nuclear safety engineer. The nuclear criticality safety engineer can utilize the Law of Substitution to safely mix or substitute different uranium metal units, different uranium solution units, and more importantly, uranium metal and dilute UO 2 solution units in an array. The Law of Substitution is as follows: (1) calculate the k/sub eff/ of each unit type in its own infinite planar array. (2) Determine the edge-to-edge spacing of the infinite planar array of each type of unit to satisfy a desired k/sub eff/. (3) Select the largest edge-to-edge spacing from among the similar units in their infinite planar arrays and use that spacing for the finite or infinite planar array of mixed units

  9. doped cadmium potassium phosphate hexahydrate: A substitutional ...

    Indian Academy of Sciences (India)

    Single crystal EPR studies of VO(II)-doped cadmium potassium phosphate hexahydrate (CPPH) have been carried out at room temperature. The angular variation spectra in the three orthogonal planes indicate that the paramagnetic impurity has entered the lattice only substitutionally in place of Cd(II). Spin Hamiltonian ...

  10. Synthesis and electrochemical studies of phenylazo substituted ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Synthesis and characterization of some phenyl azo substituted tetraaza macrocyclic complexes of Ni(II) are reported. Electrochemical behaviour of these macrocyclic complexes has been examined using polarographic, voltammetric and spectroscopic techniques. These studies show that both the ligand and the ...

  11. Substitution treatment for opioid addicts in Germany

    Directory of Open Access Journals (Sweden)

    Gerlach Ralf

    2007-02-01

    Full Text Available Abstract Background After a long and controversial debate methadone maintenance treatment (MMT was first introduced in Germany in 1987. The number of patients in MMT – first low because of strict admission criteria – increased considerably since the 1990s up to some 65,000 at the end of 2006. In Germany each general practitioner (GP, who has completed an additional training in addiction medicine, is allowed to prescribe substitution drugs to opioid dependent patients. Currently 2,700 GPs prescribe substitution drugs. Psychosocial care should be made available to all MMT patients. Results The results of research studies and practical experiences clearly indicate that patients benefit substantially from MMT with improvements in physical and psychological health. MMT proves successful in attaining high retention rates (65 % to 85 % in the first years, up to 50 % after more than seven years and plays a major role in accessing and maintaining ongoing medical treatment for HIV and hepatitis. MMT is also seen as a vital factor in the process of social re-integration and it contributes to the reduction of drug related harms such as mortality and morbidity and to the prevention of infectious diseases. Some 10 % of MMT patients become drug-free in the long run. Methadone is the most commonly prescribed substitution medication in Germany, although buprenorphine is attaining rising importance. Access to MMT in rural areas is very patchy and still constitutes a problem. There are only few employment opportunities for patients participating in MMT, although regular employment is considered unanimously as a positive factor of treatment success. Substitution treatment in German prisons is heterogeneous in access and treatment modalities. Access is very patchy and the number of inmates in treatment is limited. Nevertheless, substitution treatment plays a substantial part in the health care system provided to drug users in Germany. Conclusion In Germany, a

  12. Signalization and stimulus-substitution in Pavlov's theory of conditioning.

    Science.gov (United States)

    García-Hoz, Víctor

    2003-11-01

    The concept of conditioning as signalization proposed by Ivan P. Pavlov (1927, 1928) is studied in relation to the theory of stimulus-substitution, which is also attributed to him. In the so-called theory of stimulus-substitution a distinction must be made between an empirical principle of substitution and an actual theory of substitution, which can adopt different forms. The Pavlovian theory of substitution--which conceives substitution as a substitution of the unconditioned stimulus (US) by the conditioned stimulus (CS) in the activation of the representation of the former--can be understood as an explanation or model of signalization. Signalization and substitution are answers to different questions, and the level of analysis to which signalization corresponds, is that which concerns the nature of conditioning as an operation of the animal in the environment.

  13. Convergent synthesis of 6-substituted phenanthridines via anionic ring closure

    DEFF Research Database (Denmark)

    Lysén, M.; Kristensen, Jesper Langgaard; Vedsø, P.

    2002-01-01

    Chemical equation presented The addition of organometallic derivatives to the cyano group of 2-(2-fluorophenyl)benzonitrile followed by intramolecular nucleophilic substitution produces 6-substituted phenanthridines. Alkyllithiums, aryllithiums, and sterically nondemanding lithium amides reacted ...

  14. Characterization of hydroxyapatite substituted with silicon

    International Nuclear Information System (INIS)

    Silva, H.M. da; Soares, G.A.; Mateescu, M.; Anselme, K.; Palard, M.; Champion, E.

    2009-01-01

    Incorporation of silicon (Si) ions into hydroxyapatite structure (HA) influences on physical, chemical and physiological properties. Some studies reported the improved bioactivity Si substitution, and it also accelerates the biomineralization process. The main objective of this work is to characterize stoichiometric hydroxyapatite and hydroxyapatite substituted with 1.13% in weight of Si (SiHA) using a wet precipitation method followed by a heat treatment. SEM/EDS, AFM, DRX and FTIR analyses were used to characterize the samples. EDS and FTIR results confirmed the presence of Si. Silicon induces small changes on crystal structure of HA, not detected on X-ray diffraction patterns of sintered tablets of SiHA and HA. No secondary phases were observed, that indicates the Si had entered the HA lattice. (author)

  15. Meat analogues: Health promising sustainable meat substitutes.

    Science.gov (United States)

    Kumar, Pavan; Chatli, M K; Mehta, Nitin; Singh, Parminder; Malav, O P; Verma, Akhilesh K

    2017-03-24

    There is a scarcity of protein of high biological value due to rapid increase in the world population and limited natural resources. Meat is a good source of protein of high biological value but converting the vegetable protein into animal protein is not economical. There is a trend of production of healthy and delicious meat free food for satisfaction of vegetarian and personal well beings. This resulted in increasing use of low cost vegetable protein such as textured soy protein, mushroom, wheat gluten, pulses etc as a substitute for animal-protein. These simulated meat-like products, with similar texture, flavor, color, and nutritive value can be substituted directly for meat to all sections of the society.

  16. What governs nitrogen configuration in substituted aminophosphines?

    OpenAIRE

    Wodrich, Matthew D.; Vargas, Alfredo; Morgantini, Pierre-Yves; Merino, Gabriel; Corminboeuf, Anne-Clémence

    2009-01-01

    The trigonal planar geometry of the nitrogen atom in commonly used phosphoramidite ligands is not in line with the traditional valence shell electron pair repulsion (VSEPR) model. In this work, the effects governing nitrogen configuration in several substituted aminophosphines, A2PNB2 (A or B¼H, F, Cl, Br, Me, OMe, BINOP), are examined using modern computational analytic tools. The electron delocalization descriptions provided by both electron localization function (ELF) and block localized w...

  17. Substitution biases in price indices during transition

    Czech Academy of Sciences Publication Activity Database

    Hanousek, Jan; Filer, Randall K.

    2004-01-01

    Roč. 21, č. 2 (2004), s. 167-177 ISSN 0167-8000 R&D Projects: GA MŠk ME 595 Institutional research plan: CEZ:AV0Z7085904 Keywords : price liberalization * substitution bias * transition economies Subject RIV: AH - Economics http://search. ebscohost .com/login.aspx?direct=true&db=a9h&AN=17109091&site=ehost-live

  18. Neutron scattering from a substitutional mass defect

    International Nuclear Information System (INIS)

    Williams, R.D.; Lovesey, S.W.

    1985-06-01

    The dynamic structure factor is calculated for a low concentration of light mass scatterers substituted in a cubic crystal matrix. A new numerical method for the exact calculation is demonstrated. A local density of states for the low momentum transfer limit, and the shifts and widths of the oscillator peaks in the high momentum transfer limit are derived. The limitations of an approximation which decouples the defect from the lattice is discussed. (author)

  19. Not-so-healthy sugar substitutes?

    OpenAIRE

    Swithers, Susan E.

    2016-01-01

    Replacing sugar-sweetened beverages with diet soft drinks containing sugar substitutes that provide few or no calories has been suggested as one strategy for promoting improved public health outcomes. However, current scientific evidence indicates that routine consumption of beverages with non-nutritive sweeteners not only fails to prevent disease, but is associated with increases in risks for the same health outcomes associated with sugar-sweetened beverages, including type 2 diabetes, cardi...

  20. Gd-substituted Bi-2223 superconductor

    Indian Academy of Sciences (India)

    resistivity with a view to study metal-to-insulator transition, (2) the XRD patterns of the specimens with a view to study the .... values [4] of the transition temperatures for Gd-substituted (BiPb)-2212 specimens. The specimens of Batches I and II with x > 0.4 .... (retd) P N Dheer and Dr R G Sharma. 540. Pramana – J. Phys., Vol.

  1. 40 CFR 721.640 - Amine substituted metal salts.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Amine substituted metal salts. 721.640... Substances § 721.640 Amine substituted metal salts. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as amine substituted metal salts...

  2. 40 CFR 721.2527 - Substituted diphenylazo dye (generic name).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted diphenylazo dye (generic... Specific Chemical Substances § 721.2527 Substituted diphenylazo dye (generic name). (a) Chemical substance... substituted diphenylazo dye (PMN P-95-514) is subject to reporting under this section for the significant new...

  3. 21 CFR 184.1259 - Cocoa butter substitute.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Cocoa butter substitute. 184.1259 Section 184.1259... Listing of Specific Substances Affirmed as GRAS § 184.1259 Cocoa butter substitute. (a) The common or usual name for the triglyceride 1-palmitoyl-2-oleoyl-3-stearin is “cocoa butter substitute primarily...

  4. Freeze substitution in 3 hours or less.

    Science.gov (United States)

    McDonald, K L; Webb, R I

    2011-09-01

    Freeze substitution is a process for low temperature dehydration and fixation of rapidly frozen cells that usually takes days to complete. New methods for freeze substitution have been developed that require only basic laboratory tools: a platform shaker, liquid nitrogen, a metal block with holes for cryotubes and an insulated container such as an ice bucket. With this equipment, excellent freeze substitution results can be obtained in as little as 90 min for cells of small volume such as bacteria and tissue culture cells. For cells of greater volume or that have significant diffusion barriers such as cuticles or thick cell walls, one can extend the time to 3 h or more with dry ice. The 3-h method works well for all manner of specimens, including plants and Caenorhabditis elegans as well as smaller samples. Here, we present the basics of the techniques and some results from Nicotiana leaves, C. elegans adult worms, Escherichia coli and baby hamster kidney tissue culture cells. © 2011 The Authors Journal of Microscopy © 2011 Royal Microscopical Society.

  5. Substitution and addition reactions of •OH with p-substituted-phenols

    Science.gov (United States)

    Albarrán, Guadalupe; Galicia-Jiménez, Eduardo; Mendoza, Edith; Schuler, Robert H.

    2017-04-01

    The directing effect of a hydroxyl group on the substitution and addition reactions of •OH to the substituted and free positions in aromatic rings of p-substituted-phenols were studied in aqueous solutions containing either K3Fe(CN)6 as an oxidant of the substituted hydroxycyclohexadienyl radical initially formed or using ascorbic acid. The results showed that the attack of the •OH to the substituted position (ipso position) was followed by elimination of the substituent producing hydroquinone. The addition reaction of the •OH to the free position on the ring produced 4-substituent-catechol and 4-substituent-resorcinol derivatives. Identification and quantification of the radiolytic products were carried out using high performance liquid chromatography. The results of the yields are given for the p-halogen-phenols (p-X-Ph) p-F-Ph, p-Cl-Ph, p-Br-Ph and p-I-Ph. Other compounds, p-nitro-Ph, p-OH-benzoic acid, p-OH-benzonitrile, p-OH-benzaldehyde, p-OH-anisole and p-OH-benzyl alcohol (represented as p-Z-Ph), were only studied using K3Fe(CN)6 as the oxidant. The results show that the p-X-Ph are attacked by the •OH at the ipso position to the halogen in the proportion 1:0.53:0.46:0.11 for F>Cl>Br>I. The •OH attacked at the ipso position to the p-Z-Phs through a substitution reaction, which depended on the substituent group. Thus, the strongly deactivating groups produced less hydroquinone, indicating less substitution reaction than the strongly activating groups.

  6. Constant-Length Random Substitutions and Gibbs Measures

    Science.gov (United States)

    Maldonado, C.; Trejo-Valencia, L.; Ugalde, E.

    2018-04-01

    This work is devoted to the study of processes generated by random substitutions over a finite alphabet. We prove, under mild conditions on the substitution's rule, the existence of a unique process which remains invariant under the substitution, and which exhibits a polynomial decay of correlations. For constant-length substitutions, we go further by proving that the invariant state is precisely a Gibbs measure which can be obtained as the projective limit of its natural Markovian approximations. We end up the paper by studying a class of substitutions whose invariant state is the unique Gibbs measure for a hierarchical two-body interaction.

  7. Alkylation of N-substituted 2-phenylacetamides

    Directory of Open Access Journals (Sweden)

    SLOBODAN D. PETROVIC

    2004-10-01

    Full Text Available Various N-substituted phenylacetamides were alkylated using different alkylating agents under neutral and basic conditions. Reactions were performed at different reaction temperatures and in various solvents. Also, a number of various catalysts were used including phase-transfer catalysts. Reactions were followed using GC or GC-MS technique and the presence as well as the yields of the alkylation products were established. Generally, the best yield and high selectivity in the studied reactions were achieved under basic conditions where in the certain cases some products, mostly N-product, were obtained solely in quantitative yields.

  8. Chemical substitution in the undergraduate chemistry curriculum

    Science.gov (United States)

    Brook, Bryan David

    A recommended method for source reduction of pollutants is chemical substitution, in which hazardous materials are substituted for less hazardous materials. Here lab experiments and demonstrations were designed using household chemicals. The advantages include easy accessibility to low cost materials and minimal waste in comparison to traditional experiments. Students also showed more interest in performing experiments using familiar products. A Handbook of Household Chemicals was created. Using chemicals in the Handbook, qualitative and quantitative experiments are described that only require simple equipment. In addition, chemicals are identified in a quantitative analysis experiment with applications for upper level classes. Experiments requiring the use of water condensers were modified using an ice cooled condenser. The condenser, developed in our laboratory, is useful for distillation and reflux experiments where running water is not practical. Finally, demonstrations were designed for an overhead projector to be used in large classrooms. The experiments and demos can be used in any secondary school, college or university. The laboratory exercises can also accompany long distance learning and Internet chemistry courses. Several experiments using consumer products have been incorporated into the Pennsylvania Department of Education Science In Motion project. The program provides a van equipped with instruments and chemicals to be taken to local schools. Overall, the experiments discussed here provide a safe and low-cost alternative to traditional experiments.

  9. Fluorescence of Hydroxyphenyl-Substituted "Click" Triazoles.

    Science.gov (United States)

    Meisner, Quinton J; Accardo, Joseph V; Hu, Guoxiang; Clark, Ronald J; Jiang, De-En; Zhu, Lei

    2018-03-22

    The structural and optical properties of hydroxyphenyl-substituted-1,2,3-triazole molecules ("click" triazoles) are described. "Click" triazoles are prepared from the copper(I)-catalyzed azide-alkyne cycloaddition reactions. The alkyne-derived C4 substituent of a "click" triazole engages in electronic conjugation more effectively with the triazolyl core than the azide-derived N1 substituent. Furthermore, triazolyl group exerts a stronger electron-withdrawing effect on the N1 than the C4 substituent. Therefore, the placement of an electron-donating group at either C4 or N1 position and the presence or the absence of an intramolecular hydrogen bond (HB) have profound influences on the optical properties of these compounds. The reported "click" triazoles have fluorescence quantum yields in the range of 0.1-0.3 and large apparent Stokes shifts (8000-13 000 cm -1 ) in all tested solvents. Deprotonation of "click" triazoles with a C4 hydroxyphenyl group increases their Stokes shifts; while the opposite (or quenching) occurs to the triazoles with an N1 hydroxyphenyl substituent. For the triazoles that contain intramolecular HBs, neither experimental nor computational results support a model of excited state intramolecular proton transfer (ESIPT). Rather, the excited state internal (or intramolecular) charge transfer (ICT) mechanism is more suitable to explain the fluorescence properties of the hydroxyphenyl-substituted "click" triazoles; specifically, the large Stokes shifts of these compounds.

  10. Advances in Osteobiologic Materials for Bone Substitutes.

    Science.gov (United States)

    Hasan, Anwarul; Byambaa, Batzaya; Morshed, Mahboob; Cheikh, Mohammad Ibrahim; Shakoor, Rana Abdul; Mustafy, Tanvir; Marei, Hany

    2018-04-27

    A significant challenge in the current orthopedics is the development of suitable osteobiologic materials that can replace the conventional allografts, autografts and xenografts, and thereby serve as implant materials as bone substitutes for bone repair or remodeling. The complex biology behind the nano-microstructure of bones and their repair mechanisms, which involve various types of chemical and biomechanical signaling amongst different cells, has set strong requirements for biomaterials to be used in bone tissue engineering. This review presents an overview of various types of osteobiologic materials to facilitate the formation of the functional bone tissue and healing of the bone, covering metallic, ceramic, polymeric and cell-based graft substitutes, as well as some biomolecular strategies including stem cells, extracellular matrices, growth factors and gene therapies. Advantages and disadvantages of each type, particularly from the perspective of osteoinductive and osteoconductive capabilities, are discussed. Although the numerous challenges of bone regeneration in tissue engineering and regenerative medicine are yet to be entirely addressed, further advancements in osteobiologic materials will pave the way towards engineering fully functional bone replacement grafts. This article is protected by copyright. All rights reserved.

  11. Muon-Substituted Malonaldehyde: Transforming a Transition State into a Stable Structure by Isotope Substitution.

    Science.gov (United States)

    Goli, Mohammad; Shahbazian, Shant

    2016-02-12

    Isotope substitutions are usually conceived to play a marginal role on the structure and bonding pattern of molecules. However, a recent study [Angew. Chem. Int. Ed. 2014, 53, 13706-13709; Angew. Chem. 2014, 126, 13925-13929] further demonstrates that upon replacing a proton with a positively charged muon, as the lightest radioisotope of hydrogen, radical changes in the nature of the structure and bonding of certain species may take place. The present report is a primary attempt to introduce another example of structural transformation on the basis of the malonaldehyde system. Accordingly, upon replacing the proton between the two oxygen atoms of malonaldehyde with the positively charged muon a serious structural transformation is observed. By using the ab initio nuclear-electronic orbital non-Born-Oppenheimer procedure, the nuclear configuration of the muon-substituted species is derived. The resulting nuclear configuration is much more similar to the transition state of the proton transfer in malonaldehyde rather than to the stable configuration of malonaldehyde. The comparison of the "atoms in molecules" (AIM) structure of the muon-substituted malonaldehyde and the AIM structure of the stable and the transition-state configurations of malonaldehyde also unequivocally demonstrates substantial similarities of the muon-substituted malonaldehyde to the transition state. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Competition Derived from Innovation as a Substitution Threat

    DEFF Research Database (Denmark)

    Howells, John

    2003-01-01

    This paper is a review of the role of innovation as substitution threat. The interesting strategy for those facing what in retrospect proves to be full substitution is the strategy of 'switch' to the substituting technology. the context-dependent uncedrtainty involved in the switch decision is ex...... transistor. The case material is used to introduce the problem competition policy has when faced with competition derived from innovation.......This paper is a review of the role of innovation as substitution threat. The interesting strategy for those facing what in retrospect proves to be full substitution is the strategy of 'switch' to the substituting technology. the context-dependent uncedrtainty involved in the switch decision...

  13. Tissue reaction and material characteristics of four bone substitutes

    DEFF Research Database (Denmark)

    Jensen, S S; Aaboe, M; Pinholt, E M

    1996-01-01

    The aim of the present study was to qualitatively and quantitatively compare the tissue reactions around four different bone substitutes used in orthopedic and craniofacial surgery. Cylinders of two bovine bone substitutes (Endobon and Bio-Oss) and two coral-derived bone substitutes (Pro Osteon 500......-Oss was osseointegrated to a higher degree than the other biomaterials. Material characteristics obtained by diffuse reflectance infrared Fourier transform spectrometry analysis and energy-dispersive spectrometry did not explain the differences in biologic behavior....

  14. Technological substitution options for controlling greenhouse gas emissions

    International Nuclear Information System (INIS)

    Barbier, E.B.; Burgess, J.C.; Pearce, D.W.

    1991-01-01

    This chapter is concerned with technological options for greenhouse gas substitution. The authors interpret the term substitution to exclude energy conservation/efficiency measures, investments in afforestation (sinks), and greenhouse gas removal or abatement technologies. Their working definition of greenhouse gas substitution includes (1) replacement technologies, for example, substituting a greenhouse gas technology with a nongreenhouse gas technology; and (2) reduction technologies, for example, substituting a greenhouse gas technology with an alternative technology that reduces greenhouse gas emissions. Essentially, replacement technologies involve 100 percent reduction in CO 2 ; reduction technologies involve a partial reduction in CO 2 . Of the man-made sources of greenhouse gases, energy is the most important and is expected to contribute to at least half of the global warming effect in the near future. The majority of this impact is from fossil fuel combustion as a source of carbon dioxide (CO 2 ), although fossil fuels also contribute significantly to methane (CH 4 ), to nitrous oxide (N 2 O), and to low-level ozone (O 3 ) through production of various nitrogen gases (NO x ) and carbon monoxide (CO). This study analyzes the available greenhouse gas substitutions and their costs. The authors concentrate particularly on substitutions for fossil-fuel combustion and CFC production and consumption. They conclude by summarizing the potential for greenhouse gas substitution, the cost-effectiveness of the various options and the design of incentives for substitution

  15. Import Substitution in Regional Industrial Production: Theoretical and Practical Aspects

    Directory of Open Access Journals (Sweden)

    Yevgeniy Georgievich Animitsa

    2015-09-01

    Full Text Available The article proves the important role of import substitution in the economic security protection of state and its regions, especially in times of crisis, geopolitical and economical instability. The authors argue that the problem of import substitution is not modern, trendy scientific stream. The issue of displacement of import goods by domestic ones was brought up in famous classic theories of mercantilists. The particular emphasis is placed on the analysis and systematization of different scientific approaches, which are utilized by native and foreign scientists to bring out the matter of “import substitution,” to determine its essential characteristics. The authors suggest their own interpretation of the import substitution notion. In the article, the most significant pro and contra arguments in import substitution policy are defined. The regional aspects in the import substitution are approved: case study — organization of industrial import substitution in the Sverdlovsk region. In the article, the authors analyze the subject matter of the Program “Development of Intraregional Industrial Cooperation and Implementation of an Import Substitution in Branches of Industry in the Sverdlovsk Region.” It is resumed, that active policy of import substitution in the industry may become the driver of regional economic development.

  16. Time and Money - Are they Substitutes?

    DEFF Research Database (Denmark)

    Bonke, Jens; Deding, Mette; Lausten, Mette

    In this paper, we analyse the distribution of time and money for Danish wage earner couples, where time is defined as leisure time and money as extended income, i.e. the sum of disposable income and the value of housework. The hypothesis is that individuals being rich in one dimension are more...... likely to be poor in the other dimension, such that individuals can be classified as either money-poor/time-rich or money-rich/time-poor. We analyse two different distributions of income, where the first assumes no sharing and the second complete sharing of income between spouses. The data are from...... the Danish Time-Use Survey 2001, merged with register data. Results show that the substitution of money for time is more prominent for women than for men, because they have a larger income share of time-intensive value of housework, while men have the larger share of disposable income. Furthermore, when...

  17. Hazardous Solvent Substitution Data System tutorial

    Energy Technology Data Exchange (ETDEWEB)

    Twitchell, K.E.; Skinner, N.L.

    1993-07-01

    This manual is the tutorial for the Hazardous Solvent Substitution Data System (HSSDS), an online, comprehensive system of information on alternatives to hazardous solvents and related subjects. The HSSDS data base contains product information, material safety data sheets, toxicity reports, usage reports, biodegradable data, product chemical element lists, and background information on solvents. HSSDS use TOPIC{reg_sign} to search for information based on a query defined by the user. TOPIC provides a full text retrieval of unstructured source documents. In this tutorial, a series of lessons is provided that guides the user through basic steps common to most queries performed with HSSDS. Instructions are provided for both window-based and character-based applications.

  18. Semiconducting behavior of substitutionally doped bilayer graphene

    Science.gov (United States)

    Mousavi, Hamze; Khodadadi, Jabbar; Grabowski, Marek

    2018-02-01

    In the framework of the Green's functions approach, random tight-binding model and using the coherent potential approximation, electronic characteristics of the bilayer graphene are investigated by exploring various forms of substitutional doping of a single or both layers of the system by either boron and (or) nitrogen atoms. The results for displacement of the Fermi level resemble the behavior of acceptor or donor doping in a conventional semiconductor, dependent on the impurity type and concentration. The particular pattern of doping of just one layer with one impurity type is most efficient for opening a gap within the energy bands which could be tuned directly by impurity concentration. Doping both layers at the same time, each with one impurity type, leads to an anomaly whereby the gap decreases with increasing impurity concentration.

  19. Development of a piezoelectric bone substitute material

    CERN Document Server

    Al-Bader, Y A

    2000-01-01

    The thesis deals with the preparation and testing of ceramic compositions to be used as bone substitute. The proposed composition consisted of calcium enriched calcium phosphate, kaolin and barium titanate in different ratios. The homogeneous powder mixture was dry pressed at different pressures and fired at temperatures up to 1350 degC for different soaking times. The physical properties of the fired compacts that were tested are bulk density and porosity. These were determined as function of pressing pressure, firing temperature and soaking time for different compositions. The mechanical properties investigated were the ultimate compressive strength and Young's modulus, which were determined for different compositions and forming pressures. The electrical properties investigated were D.C. characteristics (resistivity) and A.C. characteristics (A.C. resistivity, dielectric constant, dielectric loss and loss tangent). The piezoelectric behaviour of the fired compacts was investigated and the piezoelectric coe...

  20. Gas substitution method and device for glovebox

    Energy Technology Data Exchange (ETDEWEB)

    Eto, Jun-ya

    1996-09-10

    The device of the present invention comprises (1) a gas substituting channel which allows only discharge of gases in a main body box, (2) a balloon disposed in the main body box, (3) a gas supply channel for supplying atmospheric gases to the balloon, and (4) a direction control means for connecting/switching the space in the balloon to the supply channel and the space out of the balloon in the main body box. The balloon is inflated to discharge the gases out of the balloon in the main body box from the main body box. The atmospheric gases in the balloon at which the total amount of oxygen is reduced are sent to the space out of the balloon in the main body box. The inside of the main body box is formed by the atmospheric gases having lowered oxygen concentration. This operation is repeated twice or three times. (I.S.)

  1. Hazardous Solvent Substitution Data System tutorial

    International Nuclear Information System (INIS)

    Twitchell, K.E.; Skinner, N.L.

    1993-07-01

    This manual is the tutorial for the Hazardous Solvent Substitution Data System (HSSDS), an online, comprehensive system of information on alternatives to hazardous solvents and related subjects. The HSSDS data base contains product information, material safety data sheets, toxicity reports, usage reports, biodegradable data, product chemical element lists, and background information on solvents. HSSDS use TOPIC reg-sign to search for information based on a query defined by the user. TOPIC provides a full text retrieval of unstructured source documents. In this tutorial, a series of lessons is provided that guides the user through basic steps common to most queries performed with HSSDS. Instructions are provided for both window-based and character-based applications

  2. Packing and Disorder in Substituted Fullerenes

    KAUST Repository

    Tummala, Naga Rajesh

    2016-07-15

    Fullerenes are ubiquitous as electron-acceptor and electron-transport materials in organic solar cells. Recent synthetic strategies to improve the solubility and electronic characteristics of these molecules have translated into a tremendous increase in the variety of derivatives employed in these applications. Here, we use molecular dynamics (MD) simulations to examine the impact of going from mono-adducts to bis- and tris-adducts on the structural, cohesive, and packing characteristics of [6,6]-phenyl-C60-butyric acid methyl ester (PCBM) and indene-C60. The packing configurations obtained at the MD level then serve as input for density functional theory calculations that examine the solid-state energetic disorder (distribution of site energies) as a function of chemical substitution. The variations in structural and site-energy disorders reflect the fundamental materials differences among the derivatives and impact the performance of these materials in thin-film electronic devices.

  3. Polyphosphates substitution for zeolite to in detergents

    International Nuclear Information System (INIS)

    Restrepo V, Gloria M.; Ocampo G, Aquiles; Saldarriaga M, Carlos

    1996-01-01

    The detergents, as well as the cleaning products, contain active ingredients that are good to increase their efficiency and some of them, as the sodium Tripoli-phosphate (TPF), they have turned out to be noxious for the environment. The zeolites use in the formulation of detergents has grown substantially since they fulfill the same function of the TPF and they have been recommended ecologically as substitutes from these when not being polluting. The objective of this work is to obtain a zeolite with appropriate characteristics for its use in the formulation of detergents, reproducing those of the zeolites used industrially. The zeolite synthesis is studied 4A starting from hydro-gels of different composition, varying the operation conditions and using two raw materials: (sodium meta-silicate, commercial degree and metallic aluminum) and clay type kaolin like silica source and aluminum It is looked for to get a product of beveled cubic morphology, or spherical, with glass size between 1 and 3 microns and that it possesses good capacity of conical exchange. Since the capacity and speed of ionic exchange is influenced by the particle size, time of contact and temperature, experimentation conditions settle down to measure the exchange of ions calcium and magnesium in watery solutions that they simulate the real situation of a laundry process in the country. This way the ability of the zeolite 4A obtained to diminish the concentration of these ions in the laundry waters is evaluated and its possibilities like component in the formulation of detergents non-phosphatates. Of the synthesized zeolites, the best in agreement is chosen with chemical properties as ionic and physical exchange capacity as crystalline, particle size and color, to prepare a detergent in which the polyphosphates is substituted partial and totally for the synthesized zeolite

  4. Substituted Pyrazinecarboxamides: Synthesis and Biological Evaluation

    Directory of Open Access Journals (Sweden)

    Katarina Kralova

    2006-03-01

    Full Text Available Condensation of the corresponding chlorides of some substituted pyrazine-2-carboxylic acids (pyrazine-2-carboxylic acid, 6-chloropyrazine-2-carboxylic acid, 5-tert-butylpyrazine-2-carboxylic acid or 5-tert-butyl-6-chloropyrazine-2-carboxylic acid withvarious ring-substituted aminothiazoles or anilines yielded a series of amides. Thesyntheses, analytical and spectroscopic data of thirty newly prepared compounds arepresented. Structure-activity relationships between the chemical structures and the anti-mycobacterial, antifungal and photosynthesis-inhibiting activity of the evaluatedcompounds are discussed. 3,5-Bromo-4-hydroxyphenyl derivatives of substitutedpyrazinecarboxylic acid, 16-18, have shown the highest activity against Mycobacteriumtuberculosis H37Rv (54-72% inhibition. The highest antifungal effect againstTrichophyton mentagrophytes, the most susceptible fungal strain tested, was found for5-tert-butyl-6-chloro-N-(4-methyl-1,3-thiazol-2-ylpyrazine-2-carboxamide (8, MIC =31.25 μmol·mL-1. The most active inhibitors of oxygen evolution rate in spinachMolecules 2006, 11 243 chloroplasts were the compounds 5-tert-butyl-6-chloro-N-(5-bromo-2-hydroxyphenyl- pyrazine-2-carboxamide (27, IC50 = 41.9 μmol·L-1 and 5-tert-butyl-6-chloro-N-(1,3- thiazol-2-yl-pyrazine-2-carboxamide (4, IC50 = 49.5 μmol·L-1.

  5. Control of Chemical Risks by Substitution of Harmful Substances

    DEFF Research Database (Denmark)

    Jacobsen, Thomas

    1997-01-01

    Substitution of volatile, organic solvents with non-volatile, low-toxic esters of fatty acids for cleaning purposes in offset printing has successfully been implemented in several European countries. Similar substitutions in other industrial cleaning processes seem possible, especially regarding...

  6. 40 CFR 721.4596 - Diazo substituted carbomonocyclic metal complex.

    Science.gov (United States)

    2010-07-01

    ... metal complex. 721.4596 Section 721.4596 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.4596 Diazo substituted carbomonocyclic metal complex. (a) Chemical... as a diazo substituted carbomonocyclic metal complex (PMN P-94-1039) is subject to reporting under...

  7. Sublattice imbalance of substitutionally doped nitrogen in graphene

    DEFF Research Database (Denmark)

    Lawlor, James A.; Gorman, Paul D.; Power, Stephen

    2014-01-01

    Motivated by the recently observed sublattice asymmetry of substitutional nitrogen impurities in CVD grown graphene, we show, in a mathematically transparent manner, that oscillations in the local density of states driven by the presence of substitutional impurities are responsible for breaking t...

  8. Maximum potential cost-savings attributable to generic substitution ...

    African Journals Online (AJOL)

    Treatment, however, can become more affordable through generic substitution. Objective: To determine the maximum potential cost-saving through generic substitution for both originator and more expensive generic items while observing the prescribing patterns of antipsychotics. Method: Antipsychotic medicine usage was ...

  9. Effect of Honey as Partial Sugar Substitute on Pasting Properties ...

    African Journals Online (AJOL)

    The effect of partial substitution of sugar with liquid honey on the pasting properties of cooked dough made from cassava-wheat composite (10:90) flour as well as the sensory preference and shelf stability of its bread was investigated. Sucrose (S) in the bread recipe formulation was substituted with honey (H) at levels 0, 10, ...

  10. Applicable technical method for freeze-substitution of high pressure ...

    African Journals Online (AJOL)

    bmshsj

    2011-11-02

    Nov 2, 2011 ... Cryo-fixation and freeze substitution followed by microscopy are commonly used sample preparation methods for visualizing the morphology of intracellular organelles. Freeze substitution is an especially important preparative step because it enables the preservation of intracellular structures in cryo-fixed.

  11. Stabilisation of the [6]-prismane structure by silicon substitution

    Indian Academy of Sciences (India)

    Asif Equbal

    effect of substitution on its mechanical properties.15–21. While the synthesis of lower prismanes (n < 6) was. *For correspondence. †Dedicated to the memory of the late Professor Charusita. Chakravarty. readily achieved,22–25 ..... The light green color in the ring indicates silicon atoms. of all Ge-substituted-benzene dimers ...

  12. Substitution as a Device of Grammatical Cohesion in English Contexts

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Hasannejad

    2012-05-01

    Full Text Available The present study set out to investigate the effect of teaching substitution as a kind of grammatical cohesion on the true identification of confusing substitution elements with cohesive or non-cohesive roles in different contexts and also the production of modal, reporting and conditional contexts through clausal substitution acquaintance. To this end, the following procedures were taken. First 120 male and female EFL students were selected from Iranshahr Azad University. Having administered the language proficiency test, researchers selected 80 students as intermediate subjects according to their TOEFL band scores. First, pretests of cohesion identification (substitution and production of modal, reporting and conditional environments were administered to both control and experimental groups. Then, the experimental group was exposed to the teaching of the above-said above-mentioned cohesive device. Finally, post-tests of substitution elements’ identification and modal, reporting and conditional contexts’ production through clausal substitution familiarity were administered. The results showed that cohesive device treatment helped students on the true identification of substitution elements. Another finding proved that EFL students might have no difficulty in learning certain rules or classification of rules and application of their clausal substitution knowledge in creating modal, reporting and conditional contexts. Our findings can have implications for the field of language learning and teaching.

  13. Effects of Dietary Substitution of Rubber Seed Cake for Groundnut ...

    African Journals Online (AJOL)

    Three hundred (300) five weeks old, Anak broilers were used in a 4-week experiment to determine the effect of dietary substitution of rubber seed cake for groundnut cake on the performance of broilers at the finisher phase. Graded levels of rubber seed cake (0, 25, 50, 75 and 100%) substituted corresponding levels of ...

  14. Preparation and nucleophilic substitution of the 2,4,6 ...

    African Journals Online (AJOL)

    Three methods for preparation of D-amino acids by nucleophilic substitution on derivatives of their L-antipodes have been attempted. Nucleophilic substitution on optically active phenylalanine ethyl ester triphenylpyridinium salt yielded partial inverted azide products. The N,N-disulfonylimide intermediate of the same ester ...

  15. MOLECULAR THERMODYNAMICS IN THE DESIGN OF SUBSTITUTE SOLVENTS

    Science.gov (United States)

    The use of physical properties and fluid behavior from molecular thermodynamics can lead to better decision making in the design of substitute solvents and can greatly reduce the expense and time required to find substitutes compared to designing solvents by experiment. this pape...

  16. 76 FR 39062 - Substitution in Case of Death of Claimant

    Science.gov (United States)

    2011-07-05

    ... AFFAIRS 38 CFR Parts 3, 14, and 20 RIN 2900-AN91 Substitution in Case of Death of Claimant AGENCY: Department of Veterans Affairs. ACTION: Reopening of public comment period. SUMMARY: In response to a request... proposed rule, ``Substitution in Case of Death of Claimant'' (76 FR 8666), published in the Federal...

  17. Exploring meat substitutes: consumer experiences and contextual factors

    NARCIS (Netherlands)

    Elzerman, J.E.; Boekel, van M.A.J.S.; Luning, P.A.

    2013-01-01

    Purpose – Meat substitutes can be environmentally more sustainable alternatives to meat. However, the image of these products in The Netherlands is still low. The purpose of this paper is to explore consumers' experiences and sensory expectations of meat substitutes and the appropriateness of the

  18. 40 CFR 721.4594 - Substituted azo metal complex dye.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted azo metal complex dye. 721... Substances § 721.4594 Substituted azo metal complex dye. (a) Chemical substance and significant new uses... dye (PMN P-94-499) is subject to reporting under this section for the significant new uses described...

  19. Studies on meso-substituted free-base octamethoxyporphyrins

    Indian Academy of Sciences (India)

    Administrator

    These are characterized by 1H NMR and other spectroscopic methods. The optical absorption spectra of these meso-substituted free-base porphyrin derivatives exhibit a hypsochromic shift compared to the unsubstituted octamethoxy free-base derivative. The emission data of these meso-substituted free-base derivatives ...

  20. 40 CFR 721.10048 - Substituted anthraquinone (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted anthraquinone (generic... Specific Chemical Substances § 721.10048 Substituted anthraquinone (generic). (a) Chemical substance and... anthraquinone (PMN P-02-869) is subject to reporting under this section for the significant new uses described...

  1. 40 CFR 721.2025 - Substituted phenylimino carbamate derivative.

    Science.gov (United States)

    2010-07-01

    ... derivative. 721.2025 Section 721.2025 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.2025 Substituted phenylimino carbamate derivative. (a) Chemical... as a substituted phenylimino carbamate derivative (PMN P-91-487) is subject to reporting under this...

  2. Crystal structures of unsymmetrically mixed β-pyrrole substituted ...

    Indian Academy of Sciences (India)

    The normal-coordinate structural decomposition analysis of these structures revealed mainly saddle distortion of the macrocycle ... Unsymmetrical mixed substituted porphyrins; β-pyrrole substituted porphyrins; NSD analysis;. Hirshfeld surface ..... out-of-plane (Doop) displacement values of the macro- cycle based on the ...

  3. Maximum parsimony, substitution model, and probability phylogenetic trees.

    Science.gov (United States)

    Weng, J F; Thomas, D A; Mareels, I

    2011-01-01

    The problem of inferring phylogenies (phylogenetic trees) is one of the main problems in computational biology. There are three main methods for inferring phylogenies-Maximum Parsimony (MP), Distance Matrix (DM) and Maximum Likelihood (ML), of which the MP method is the most well-studied and popular method. In the MP method the optimization criterion is the number of substitutions of the nucleotides computed by the differences in the investigated nucleotide sequences. However, the MP method is often criticized as it only counts the substitutions observable at the current time and all the unobservable substitutions that really occur in the evolutionary history are omitted. In order to take into account the unobservable substitutions, some substitution models have been established and they are now widely used in the DM and ML methods but these substitution models cannot be used within the classical MP method. Recently the authors proposed a probability representation model for phylogenetic trees and the reconstructed trees in this model are called probability phylogenetic trees. One of the advantages of the probability representation model is that it can include a substitution model to infer phylogenetic trees based on the MP principle. In this paper we explain how to use a substitution model in the reconstruction of probability phylogenetic trees and show the advantage of this approach with examples.

  4. Exchange Rate Volatility, Currency Substitution and Monetary Policy ...

    African Journals Online (AJOL)

    This article analyses the implications of currency substitution and exchange rate volatility for monetary policy in Nigeria. It adopts the unrestricted portfolio balance model of currency substitution, incorporating exchange rate volatility within the framework of the Vector Error Correction (VEC) technique. Results from both ...

  5. Cation substitution induced blue-shift of optical band gap

    Indian Academy of Sciences (India)

    Cation substitution induced blue-shift of optical band gap in nanocrystalline Zn ( 1 − x ) Ca x O thin films deposited by sol–gel dip coating technique ... thin films giving 13.03% enhancement in theenergy gap value due to the electronic perturbation caused by cation substitution as well as deterioration in crystallinity.

  6. 40 CFR 721.5278 - Substituted naphthalenesulfonic acid, alkali salt.

    Science.gov (United States)

    2010-07-01

    ..., alkali salt. 721.5278 Section 721.5278 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5278 Substituted naphthalenesulfonic acid, alkali salt. (a) Chemical... as a substituted naphthalenesulfonic acid, alkali salt (PMN P-95-85) is subject to reporting under...

  7. 40 CFR 721.8900 - Substituted halogenated pyridinol, alkali salt.

    Science.gov (United States)

    2010-07-01

    ..., alkali salt. 721.8900 Section 721.8900 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.8900 Substituted halogenated pyridinol, alkali salt. (a) Chemical... as substituted halogenated pyridinols, alkali salts (PMNs P-88-1271 and P-88-1272) are subject to...

  8. 19 CFR 143.16 - Substitution of warehouse entry.

    Science.gov (United States)

    2010-04-01

    ... 19 Customs Duties 2 2010-04-01 2010-04-01 false Substitution of warehouse entry. 143.16 Section 143.16 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT... warehouse entry. The importer may substitute an entry for warehouse at any time within 1 year from the date...

  9. A Group Action Method for Construction of Strong Substitution Box

    Science.gov (United States)

    Jamal, Sajjad Shaukat; Shah, Tariq; Attaullah, Atta

    2017-06-01

    In this paper, the method to develop cryptographically strong substitution box is presented which can be used in multimedia security and data hiding techniques. The algorithm of construction depends on the action of a projective general linear group over the set of units of the finite commutative ring. The strength of substitution box and ability to create confusion is assessed with different available analyses. Moreover, the ability of resistance against malicious attacks is also evaluated. The substitution box is examined by bit independent criterion, strict avalanche criterion, nonlinearity test, linear approximation probability test and differential approximation probability test. This substitution box is equated with well-recognized substitution boxes such as AES, Gray, APA, S8, prime of residue, Xyi and Skipjack. The comparison shows encouraging results about the strength of the proposed box. The majority logic criterion is also calculated to analyze the strength and its practical implementation.

  10. Vitreous Substitutes: Old and New Materials in Vitreoretinal Surgery

    Directory of Open Access Journals (Sweden)

    Camilla Alovisi

    2017-01-01

    Full Text Available Recent developments in vitreoretinal surgery have increased the need for suitable vitreous substitutes. A successful substitute should maintain all the physical and biochemical properties of the original vitreous, be easy to manipulate, and be long lasting. Substitutes can be gaseous or liquid, both of which have associated advantages and disadvantages related to their physical properties and use. Furthermore, new surgical techniques with smaller vitreoretinal instruments have driven the use of more viscous substitutes. In this review, we analyze and discuss the most frequently used vitreous substitutes and look ahead to future alternatives. We classify these compounds based on their composition and structure, discuss their clinical use with respect to their associated advantages and disadvantages, and analyze how new vitreoretinal surgical techniques have modified their use.

  11. Vitreous Substitutes: Old and New Materials in Vitreoretinal Surgery

    Science.gov (United States)

    Panico, Claudio; Eandi, Chiara M.

    2017-01-01

    Recent developments in vitreoretinal surgery have increased the need for suitable vitreous substitutes. A successful substitute should maintain all the physical and biochemical properties of the original vitreous, be easy to manipulate, and be long lasting. Substitutes can be gaseous or liquid, both of which have associated advantages and disadvantages related to their physical properties and use. Furthermore, new surgical techniques with smaller vitreoretinal instruments have driven the use of more viscous substitutes. In this review, we analyze and discuss the most frequently used vitreous substitutes and look ahead to future alternatives. We classify these compounds based on their composition and structure, discuss their clinical use with respect to their associated advantages and disadvantages, and analyze how new vitreoretinal surgical techniques have modified their use. PMID:28785482

  12. Antimony substitution in SmFeAsO

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Daniel; Braun, Hans F. [Universitaet Bayreuth (Germany)

    2015-07-01

    In the iron based compounds structural and magnetic phase transitions can be suppressed by applying external hydrostatic pressure and superconductivity emerges. Beside hydrostatic pressure, it is possible to apply chemical pressure by the substitution of atoms in the compounds with smaller ones. Such a substitution was successful for example in LaFeAs{sub 1-x}P{sub x}O, where the parent compound shows a structural and a spin-density-wave transition and the P doped samples become superconducting. We are interested in the opposite way and substitute the As by the bigger Sb. In literature, the substitution in the La-1111 compounds was possible up to a substitution level of 40 %. With Sm, instead of La, we used a smaller rare-earth metal. We present the results obtained on polycrystalline samples characterized by Xray powder diffraction and resistivity measurements.

  13. Electrotactile and vibrotactile displays for sensory substitution systems

    Science.gov (United States)

    Kaczmarek, Kurt A.; Webster, John G.; Bach-Y-rita, Paul; Tompkins, Willis J.

    1991-01-01

    Sensory substitution systems provide their users with environmental information through a human sensory channel (eye, ear, or skin) different from that normally used or with the information processed in some useful way. The authors review the methods used to present visual, auditory, and modified tactile information to the skin and discuss present and potential future applications of sensory substitution, including tactile vision substitution (TVS), tactile auditory substitution, and remote tactile sensing or feedback (teletouch). The relevant sensory physiology of the skin, including the mechanisms of normal touch and the mechanisms and sensations associated with electrical stimulation of the skin using surface electrodes (electrotactile, or electrocutaneous, stimulation), is reviewed. The information-processing ability of the tactile sense and its relevance to sensory substitution is briefly summarized. The limitations of current tactile display technologies are discussed.

  14. Potential radiosensitizing agents. 5. 2-Substituted benzimidazole derivatives

    International Nuclear Information System (INIS)

    Gupta, R.P.; Larroquette, C.A.; Agrawal, K.C.

    1982-01-01

    A series of 2-substituted benzimidazoles and their derivatives have been synthesized and tested for their ability to selectively sensitize hypoxic Chinese hamster cells (V-79) toward the lethal effect of ionizing radiation. These compounds were prepared by reacting the 2-substituted benzimidazoles with 1,2-epoxy-3-methoxypropane in the presence of potassium carbonate. Reaction of the 2-nitro and 2-methylfonyl analogue with the epoxide also yielded a cyclized material, which was confirmed to be a benzimidazo[2,1-b]oxazole. In an attempt to increase the electron affinity, 5- or 6-nitro-2-substituted-benzimidazoles were also synthesized and then reacted with the epoxide to yield the corresponding 1-substituted derivatives. The results of the biological tests for the radiosensitizing activity of these agents against Chinese hamster cells (V-79) in culture indicated that the 2-nitro-substituted analogues were the most effective sensitizers in this series

  15. REACH-related substitution within the Danish printing industry

    DEFF Research Database (Denmark)

    Larsen, Henrik Fred; Bøg, Carsten; Markussen, Helene

    The accomplishment of the EU REACH regulation will most probably promote substitution within sectors handling a lot of different chemicals like the printing industry. With the aim of being at the cutting edge of this development the Danish EPA together with the Danish printing industry and IPU...... are running a substitution project. A major part of the work has been mapping the presence of chemicals which are potential candidates for substitution (e.g. PBT, CMR, vPvB, EDS) within the Danish printing industry. The mapping comprises a combination of a literature study and an investigation of the actual...... fulfil one or more of the criteria (e.g. CMR, EDS) for the REACH Annex XIV candidate list (authorisation). The paper presents the results of the mapping of chemical candidates and the first results of the actual substitutions. Keywords: REACH, chemicals, substitution, printing industry....

  16. Substitution site and effects on magnetism in Sr-for-Ca substituted CaBaCo4O7

    Science.gov (United States)

    Aurelio, G.; Curiale, J.; Bardelli, F.; Junqueira Prado, R.; Hennet, L.; Cuello, G.; Campo, J.; Thiaudière, D.

    2015-10-01

    Cationic substitutions in the novel magnetoelectric compound CaBaCo4O7 lead to profound changes in its magnetic and electric behaviors. In this work, we present a structural study of the isovalent substitution Sr-for-Ca in CaBaCo4O7. X-ray diffraction, as well as neutron powder diffraction experiments, are reported for a series of samples Ca1-xSrxBaCo4O7 with 0 ≤ x ≤ 0.10 . Special emphasis is given to the identification of the substitution site, as Sr has also been reported to substitute for Ba in this crystal structure. The solubility limit for Sr at the Ca site is shown to be at x ≃ 0.08 . The variation of lattice constants with Sr-doping firmly supports the Sr-for-Ca substitution. Rietveld refinements of the Sr-substituted samples are presented, and used as starting point to analyse the local structure around Sr by means of X-ray absorption spectroscopy at the Sr K-edge. Both the near-edge absorption and the extended absorption fine-structure confirm the substitution of Sr for Ca, giving definite support to the proposed nominal formula. In addition, macroscopic magnetization measurements are presented which reveal the striking effects of Sr-substitution over the magnetic landscape of this puzzling compound.

  17. Preparation and characterization of synthesized goethite and ...

    African Journals Online (AJOL)

    Instrumental characterization such as Fourier Transform Infrared (FTIR) for the surface functional groups, Scanning electron microscopy (SEM) for the shapes and morphology of both samples, X-Ray Fluorescence (XRF) to obtain the elemental composition, BET surface area determination and particle nano-sizer to ...

  18. Hazardous Solvent Substitution Data System reference manual

    International Nuclear Information System (INIS)

    Branham-Haar, K.A.; Twitchell, K.E.

    1993-07-01

    Concern for the environment, in addition to Federal regulation, mandate the replacement of hazardous solvents with safer cleaning agents. Manufacturers are working to produce these replacement solvents. As these products are developed, potential users need to be informed of their availability. To promote the use of these new products instead of traditional solvents, the Idaho National Engineering Laboratory (INEL) has developed the Hazardous Solvent Substitution Data System (HSSDS). The HSSDS provides a comprehensive system of information on alternatives to hazardous solvents and related subjects, and it makes that information available to solvent users, industrial hygienists, and process engineers. The HSSDS uses TOPIC reg-sign, a text retrieval system produced by Verity, Inc., to allow a user to search for information on a particular subject. TOPIC reg-sign produces a listing of the retrieved documents and allows the use to examine the documents individually and to use the information contained in them. This reference manual does not replace the comprehensive TOPIC reg-sign user documentation (available from Verity, Inc.), or the HSSDS Tutorial (available from the INEL). The purpose of this reference manual is to provide enough instruction on TOPIC reg-sign so the user may begin accessing the data contained in the HSSDS

  19. Substituted amylose matrices for oral drug delivery

    Science.gov (United States)

    Moghadam, S. H.; Wang, H. W.; Saddar El-Leithy, E.; Chebli, C.; Cartilier, L.

    2007-03-01

    High amylose corn starch was used to obtain substituted amylose (SA) polymers by chemically modifying hydroxyl groups by an etherification process using 1,2-epoxypropanol. Tablets for drug-controlled release were prepared by direct compression and their release properties assessed by an in vitro dissolution test (USP XXIII no 2). The polymer swelling was characterized by measuring gravimetrically the water uptake ability of polymer tablets. SA hydrophilic matrix tablets present sequentially a burst effect, typical of hydrophilic matrices, and a near constant release, typical of reservoir systems. After the burst effect, surface pores disappear progressively by molecular association of amylose chains; this allows the creation of a polymer layer acting as a diffusion barrier and explains the peculiar behaviour of SA polymers. Several formulation parameters such as compression force, drug loading, tablet weight and insoluble diluent concentration were investigated. On the other hand, tablet thickness, scanning electron microscope analysis and mercury intrusion porosimetry showed that the high crushing strength values observed for SA tablets were due to an unusual melting process occurring during tabletting although the tablet external layer went only through densification, deformation and partial melting. In contrast, HPMC tablets did not show any traces of a melting process.

  20. Some comments on the substituted judgement standard.

    Science.gov (United States)

    Egonsson, Dan

    2010-02-01

    On a traditional interpretation of the substituted judgement standard (SJS) a person who makes treatment decisions on behalf of a non-competent patient (e.g. concerning euthanasia) ought to decide as the patient would have decided had she been competent. I propose an alternative interpretation of SJS in which the surrogate is required to infer what the patient actually thought about these end-of-life decisions. In clarifying SJS it is also important to differentiate the patient's consent and preference. If SJS is part of an autonomy ideal of the sort found in Kantian ethics, consent seems more important than preference. From a utilitarian perspective a preference-based reading of SJS seems natural. I argue that the justification of SJS within a utilitarian framework will boil down to the question whether a non-competent patient can be said to have any surviving preferences. If we give a virtue-ethical justification of SJS the relative importance of consent and preferences depends on which virtue one stresses--respect or care. I argue that SJS might be an independent normative method for extending the patient's autonomy, both from a Kantian and a virtue ethical perspective.

  1. Substituted amylose matrices for oral drug delivery

    International Nuclear Information System (INIS)

    Moghadam, S H; Wang, H W; El-Leithy, E Saddar; Chebli, C; Cartilier, L

    2007-01-01

    High amylose corn starch was used to obtain substituted amylose (SA) polymers by chemically modifying hydroxyl groups by an etherification process using 1,2-epoxypropanol. Tablets for drug-controlled release were prepared by direct compression and their release properties assessed by an in vitro dissolution test (USP XXIII no 2). The polymer swelling was characterized by measuring gravimetrically the water uptake ability of polymer tablets. SA hydrophilic matrix tablets present sequentially a burst effect, typical of hydrophilic matrices, and a near constant release, typical of reservoir systems. After the burst effect, surface pores disappear progressively by molecular association of amylose chains; this allows the creation of a polymer layer acting as a diffusion barrier and explains the peculiar behaviour of SA polymers. Several formulation parameters such as compression force, drug loading, tablet weight and insoluble diluent concentration were investigated. On the other hand, tablet thickness, scanning electron microscope analysis and mercury intrusion porosimetry showed that the high crushing strength values observed for SA tablets were due to an unusual melting process occurring during tabletting although the tablet external layer went only through densification, deformation and partial melting. In contrast, HPMC tablets did not show any traces of a melting process

  2. The role of biomass in US industrial interfuel substitution

    International Nuclear Information System (INIS)

    Jones, Clifton T.

    2014-01-01

    The role of biomass in US industrial interfuel substitution in the industrial sector has typically been analyzed using data for the four traditional fuels of coal, oil, electricity and natural gas. However, the use of biomass as an industrial fuel in the US has grown, and now exceeds that of coal. Using data from 1960 to 2011, interfuel substitution in the US industrial sector is modeled with a dynamic linear logit model which includes biomass alongside the other four traditional fuels. Adding biomass to the model reduces somewhat the estimated own-price and cross-price elasticities for the other four fuels, while revealing that biomass and natural gas are substitute fuels. This implies that previous studies excluding biomass may have overestimated the potential for interfuel substitution, giving policy makers an inaccurate impression of the ability of carbon taxes or other environmental regulation to reduce greenhouse gas (GHG) emissions. - Highlights: • Biomass usage by the US industrial sector now exceeds coal usage. • Previous interfuel substitution studies have not included biomass as a fuel. • Linear logit model is used to examine role of biomass in interfuel substitution. • Including biomass in the model lowers estimated price elasticities for traditional fuels. • Biomass is found to be a substitute for natural gas for industrial users

  3. Substituent effects in surface-initiated ATRP of substituted styrenes

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Sampa, E-mail: ssaha@polymers.iitd.ac.in; Baker, Gregory L.

    2015-12-30

    Graphical abstract: - Highlights: • Suitably substituted styrenes can lead to rapid synthesis of uniform and thick polystyrene brushes (>100 nm in 1 h) from gold surface via surface initiated ATRP. • High growth rates were observed for styrenes substituted with electron withdrawing groups in meta/para positions. • Electron donors at meta sites show surprisingly fast growth rates, which may be due to steric inhibition of termination. • Surface polymerization rates for substituted styrenes followed the Hammett relation with ρ = 0.51, similar to conventional radical polymerization in solution. - Abstract: Surface initiated atom transfer radical polymerization (ATRP) of substituted styrenes leads to rapid synthesis of uniform and thick substituted polystyrene brushes (>100 nm in 1 h) from gold surface. High growth rates were observed for styrenes substituted with electron withdrawing groups in meta/para positions. The effects seen in surface and solution polymerizations are similar for styrenes with electron withdrawing groups, and for electron donors in ortho and para positions. However, electron donors at meta sites have surprisingly fast growth rates, which may be due to steric inhibition of termination. The overall surface polymerization rates for substituted styrenes was analyzed and found to follow the Hammett relation with ρ = 0.51. The ratio of k{sub p} to k{sub t}, is as an indicator of the likelihood that a reaction will reach high degrees of polymerization before termination.

  4. Enhanced osteoconductivity of sodium-substituted hydroxyapatite by system instability.

    Science.gov (United States)

    Sang Cho, Jung; Um, Seung-Hoon; Su Yoo, Dong; Chung, Yong-Chae; Hye Chung, Shin; Lee, Jeong-Cheol; Rhee, Sang-Hoon

    2014-07-01

    The effect of substituting sodium for calcium on enhanced osteoconductivity of hydroxyapatite was newly investigated. Sodium-substituted hydroxyapatite was synthesized by reacting calcium hydroxide and phosphoric acid with sodium nitrate followed by sintering. As a control, pure hydroxyapatite was prepared under identical conditions, but without the addition of sodium nitrate. Substitution of calcium with sodium in hydroxyapatite produced the structural vacancies for carbonate ion from phosphate site and hydrogen ion from hydroxide site of hydroxyapatite after sintering. The total system energy of sodium-substituted hydroxyapatite with structural defects calculated by ab initio methods based on quantum mechanics was much higher than that of hydroxyapatite, suggesting that the sodium-substituted hydroxyapatite was energetically less stable compared with hydroxyapatite. Indeed, sodium-substituted hydroxyapatite exhibited higher dissolution behavior of constituent elements of hydroxyapatite in simulated body fluid (SBF) and Tris-buffered deionized water compared with hydroxyapatite, which directly affected low-crystalline hydroxyl-carbonate apatite forming capacity by increasing the degree of apatite supersaturation in SBF. Actually, sodium-substituted hydroxyapatite exhibited markedly improved low-crystalline hydroxyl-carbonate apatite forming capacity in SBF and noticeably higher osteoconductivity 4 weeks after implantation in calvarial defects of New Zealand white rabbits compared with hydroxyapatite. In addition, there were no statistically significant differences between hydroxyapatite and sodium-substituted hydroxyapatite on cytotoxicity as determined by BCA assay. Taken together, these results indicate that sodium-substituted hydroxyapatite with structural defects has promising potential for use as a bone grafting material due to its enhanced osteoconductivity compared with hydroxyapatite. © 2013 Wiley Periodicals, Inc.

  5. Associations between generic substitution and patient-related factors

    DEFF Research Database (Denmark)

    Østergaard Rathe, Jette

    for Pharmacoepidemiology, Karolinska Institutet, Department of Medicine Solna, Stockholm, Sweden 3. Danish Quality Unit of General Practice, Odense, Denmark Background Generic substitution means that chemically equivalent but less expensive drugs are dispensed in place of a brand name product. Although generic medicines...... by definition are bioequivalent to their brand name counterparts there are concerns about whether generic substitution is always accompanied by clinical equivalence in terms of effectiveness and that it may cause concerns and thereby causing some skepticism towards generic substitution. There is, however...

  6. Prioritizing substitution of organic solvents in industrial cleaning processes

    DEFF Research Database (Denmark)

    Rasmussen, Pia Brunn; Jacobsen, Thomas

    1997-01-01

    A method for prioritizing the substitution of volatile organic compounds (VOC) used in industrial cleaning processes is developed. The result is a matrix, which, if all information can be obtained, gives a comprehensive description of the effects, exposure and emission of VOC, as well...... as the prospects for performing the substitution with a vegetable ester. It can be a tool for companies to decide which cleaning process has the highest demand for substitution, if there is a choice between several processes, but it may also be a tool to convince companies to use non-volatile, low-toxic cleaning...

  7. LONG TERM EVOLUTION OF BONE RECONSTRUCTION WITH BONE GRAFT SUBSTITUTES

    Directory of Open Access Journals (Sweden)

    O. V. Martynenko

    2017-06-01

    Full Text Available The review involves clinical and experimental data, constitutive modeling, and computational investigations towards an understanding on how mechanical cyclic loads for long periods of time affect damage evolution in a reconstructed bone, as well as, lifetime reduction of bone graft substitutes after advanced core decompression. The outcome of the integrated model discussed in this paper will be how damage growth in femur after advanced core decompression subjected to mechanical cyclic loading under creep and fatigue conditions may be controlled in order to optimize design and processing of bone graft substitutes, and extend lifetime of bone substitutes.

  8. Chitosan Dermal Substitute and Chitosan Skin Substitute Contribute to Accelerated Full-Thickness Wound Healing in Irradiated Rats

    Directory of Open Access Journals (Sweden)

    Abu Bakar Mohd Hilmi

    2013-01-01

    Full Text Available Wounds with full-thickness skin loss are commonly managed by skin grafting. In the absence of a graft, reepithelialization is imperfect and leads to increased scar formation. Biomaterials can alter wound healing so that it produces more regenerative tissue and fewer scars. This current study use the new chitosan based biomaterial in full-thickness wound with impaired healing on rat model. Wounds were evaluated after being treated with a chitosan dermal substitute, a chitosan skin substitute, or duoderm CGF. Wounds treated with the chitosan skin substitute showed the most re-epithelialization (33.2 ± 2.8%, longest epithelial tongue (1.62 ± 0.13 mm, and shortest migratory tongue distance (7.11 ± 0.25 mm. The scar size of wounds treated with the chitosan dermal substitute (0.13 ± 0.02 cm and chitosan skin substitute (0.16 ± 0.05 cm were significantly decreased (P<0.05 compared with duoderm (0.45 ± 0.11 cm. Human leukocyte antigen (HLA expression on days 7, 14, and 21 revealed the presence of human hair follicle stem cells and fibroblasts that were incorporated into and surviving in the irradiated wound. We have proven that a chitosan dermal substitute and chitosan skin substitute are suitable for wound healing in full-thickness wounds that are impaired due to radiation.

  9. Osseointegration of subperiosteal implants using bovine bone substitute and various membranes

    DEFF Research Database (Denmark)

    Aaboe, Merete; Schou, S.; Hjørting-Hansen, E.

    2000-01-01

    Osseointegration, subperiosteal implant, bone substitute, bovine bone, guided bone, regeneration, histology, rabbits......Osseointegration, subperiosteal implant, bone substitute, bovine bone, guided bone, regeneration, histology, rabbits...

  10. Suitability of various plant derived gelling agents as agar substitute ...

    African Journals Online (AJOL)

    Suitability of various plant derived gelling agents as agar substitute in microbiological growth media. Abdul Mateen, Shaukat Hussain, Shams Ur Rehman, Basharat Mahmood, Muhammad Aslam Khan, Abdul Rashid, Majid Sohail, Muhammad Farooq, S Jawad Ahmed Shah ...

  11. Property Model-Based Chemcal Substitution and Chemical Formulation Design

    DEFF Research Database (Denmark)

    Jhamb, Spardha Virendra; Liang, Xiaodong; Hukkerikar, Amol Shivajirao

    with environmentally benign chemicals. Additionally, the decisions taken during chemical product design also have an impact on the process and product performance and are influenced by company strategy, availability of market and government policies [2]. Hence, undoubtedly there is a need to develop a systematic...... it is desired to come up with alternative substitutes for the undesirable chemicals, the trial an error based approach will have a very large search space. This could be avoided by having predictive models coupled with the desired target properties, making the identification of these substitutes easier...... and safety) properties, and then to generate, evaluate and identify candidates that can replace them. The presentation will discuss the general methodology for chemical substitution, which caters to different problem definitions depending on the reason for substitution. The associated property modeling tools...

  12. Modified broken rice starch as fat substitute in sausages

    Directory of Open Access Journals (Sweden)

    Valéria Maria Limberger

    2011-09-01

    Full Text Available The demand for low-fat beef products has led the food industry to use fat substitutes such as modified starch. About 14% of broken rice is generated during processing. Nevertheless, this by-product contains high levels of starch; being therefore, great raw material for fat substitution. This study evaluated the applicability of chemically and physically modified broken rice starch as fat substitute in sausages. Extruded and phosphorylated broken rice was used in low-fat sausage formulation. All low-fat sausages presented about 55% reduction in the fat content and around 28% reduction in the total caloric value. Fat replacement with phosphorylated and extruded broken rice starch increased the texture acceptability of low-fat sausages, when compared to low-fat sausages with no modified broken rice. Results suggest that modified broken rice can be used as fat substitute in sausage formulations, yielding lower caloric value products with acceptable sensory characteristics.

  13. Long term substitution treatment (maintenance treatment of opioid dependent persons

    Directory of Open Access Journals (Sweden)

    Wirl, Charlotte

    2007-03-01

    Full Text Available Health political background: Methadone substitution treatment in Germany is introduced in 1988 in the framework of a scientific pilot study in North Rhein Westphalia. Recent statistics show that by now a broad offer of substitution treatment exists. From 1 June 2002 to 31 December 2003 113,000 substitution treatments have been recorded as being started of which around 56,000 have been recorded as ongoing treatments by 1 December 2003. Scientific background: Substitution treatment (treatment of opioid-dependent persons using substitution substances is one part of addiction treatment. Its goals are harm reduction and the stabilisation of opioid dependent persons. Integration of opioid-dependent persons in a treatment-setting, reduction of consumption of psychoactive substances, reduction of risk behaviour (primarily related to infectious diseases, decrease of mortality and improvements concerning the social, psychic and physic situation are seen as a success of substitution treatment as maintenance therapy. Research questions: The aim of this HTA report is to investigate which indicators can be used to evaluate the effectiveness of substitution treatment. Based on these indicators an evaluation of the medical, social and economical benefit of substitution treatment - also in relation to abstinence oriented treatment - is carried out. Methods: A systematic literature search was performed in 31 international databases which yielded 2451 articles with publication date between 1995 and February 2005. Results: After a twofold selection process 32 publications were included for assessment and 276 publications were used as background literature. Despite serious restrictions due to selection bias and dropout in most studies focusing on substitution treatment, reduction of consumption of illegal opioids, reduction of risk behaviour, criminal behaviour, mortality and incidence of HIV can be seen as an empirically proven success of substitution treatment

  14. Industrialization in Sub-Saharan Africa and import substitution policy

    Directory of Open Access Journals (Sweden)

    Ana Paula F. Mendes

    2014-03-01

    Full Text Available This article aims to contribute to the understanding of the process of import substitution in Sub-Saharan Africa. The process of industrialization in Sub-Saharan Africa occurred in two phases: a first step, even very early during the colonial regime began around the 1920s and ended in the late forties; a second phase of industrialization began in the late fifties and gained momentum in the sixties, when import substitution was implemented more widely. Although these countries were the last to embark on the strategy of import substitution, they followed the same steps of Latin American countries, and as the structural domestic and external constraints were too strong, the failure of the policy of import substitution arrived early and the negative impact on these economies had a greater magnitude.

  15. Factors Affecting the Form of Substitute Family Care

    Directory of Open Access Journals (Sweden)

    Monika Chrenková

    2015-11-01

    Full Text Available Recently, the system of care for endangered children has changed from the institutional as well as legislative point of view. In one of the partial areas of ongoing changes, research activities realised within the Students’ Grant Competition called The Factors Affecting the Form of Substitute Family Care are being focused. We deal with this topic because various forms of substitute family care are distinguished in the Czech Republic, where children are placed for various reasons, but we do not know the correct context of such placements. The main aim of the realised research was to find out the frequency of choosing a given form of placing children in substitute family care according to followed variables. The research sample of the quantitative research was consisted of children placed in one of the forms of substitute family care in the Moravian-Silesian region.

  16. Computational Modeling of Degradation of Substituted Benzyltrimethyl Ammonium: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Long, H.; Pivovar, B. S.

    2014-09-01

    The degradation of cations on the alkaline exchange membranes is the major challenge for alkaline membrane fuel cells. In this paper, we investigated the degradation barriers by density functional theory for substituted benzyltrimethyl ammonium (BTMA+) cations, which is one of the most commonly used cations for alkaline exchange membranes. We found that substituted cations with electron-releasing substituent groups at meta-position of the benzyl ring could result in improved degradation barriers. However, after investigating more than thirty substituted BTMA+ cations with ten different substituent groups, the largest improvement of degradation barriers is only 1.6 kcal/mol. This implies that the lifetime of alkaline membrane fuel cells could increase from a few months to a few years by using substituted BTMA+ cations, an encouraging but still limited improvement for real-world applications.

  17. Performance of chicken broilers fed with diets substituted with ...

    African Journals Online (AJOL)

    Performance of chicken broilers fed with diets substituted with mulberry leaf powder. Carlina Freddie Simol, Andrew Alek Tuen, Humrawali Hazid Ahmad Khan, John Keen Chubo, Patricia Jie Hung King, Kian Huat Ong ...

  18. The Substitutability Concept: A Need for Further Development

    Science.gov (United States)

    Christensen, James E.; Yoesting, Dean R.

    1977-01-01

    The possibility that participants in sport and games of a similar nature will find satisfaction in substituting one type of recreation for another is a possible factor to consider in planning and managing recreation facilities. (JD)

  19. Macroporous synthetic hydroxyapatite bioceramics for bone substitute applications

    CSIR Research Space (South Africa)

    Thomas, ME

    1999-08-01

    Full Text Available An improved strategy is described for the manufacture of macroporous hydroxyapatite bioceramics for bone substitute applications. This is based on a modified fugitive phase technique, which allows production of relatively open, high-strength devices...

  20. Weak preservation of local neutral substitution rates across mammalian genomes

    Directory of Open Access Journals (Sweden)

    Karro John E

    2009-05-01

    Full Text Available Abstract Background The rate at which neutral (non-functional bases undergo substitution is highly dependent on their location within a genome. However, it is not clear how fast these location-dependent rates change, or to what extent the substitution rate patterns are conserved between lineages. To address this question, which is critical not only for understanding the substitution process but also for evaluating phylogenetic footprinting algorithms, we examine ancestral repeats: a predominantly neutral dataset with a significantly higher genomic density than other datasets commonly used to study substitution rate variation. Using this repeat data, we measure the extent to which orthologous ancestral repeat sequences exhibit similar substitution patterns in separate mammalian lineages, allowing us to ascertain how well local substitution rates have been preserved across species. Results We calculated substitution rates for each ancestral repeat in each of three independent mammalian lineages (primate – from human/macaque alignments, rodent – from mouse/rat alignments, and laurasiatheria – from dog/cow alignments. We then measured the correlation of local substitution rates among these lineages. Overall we found the correlations between lineages to be statistically significant, but too weak to have much predictive power (r2 5%. These correlations were found to be primarily driven by regional effects at the scale of several hundred kb or larger. A few repeat classes (e.g. 7SK, Charlie8, and MER121 also exhibited stronger conservation of rate patterns, likely due to the effect of repeat-specific purifying selection. These classes should be excluded when estimating local neutral substitution rates. Conclusion Although local neutral substitution rates have some correlations among mammalian species, these correlations have little predictive power on the scale of individual repeats. This indicates that local substitution rates have changed

  1. Protein substitute for children and adults with phenylketonuria.

    Science.gov (United States)

    Yi, Sarah H L; Singh, Rani H

    2015-02-27

    Phenylketonuria is an inherited metabolic disorder characterised by an absence or deficiency of the enzyme phenylalanine hydroxylase. The aim of treatment is to lower blood phenylalanine concentrations to the recommended therapeutic range to prevent developmental delay and support normal growth. Current treatment consists of a low-phenylalanine diet in combination with a protein substitute which is free from or low in phenylalanine. Guidance regarding the use, dosage, and distribution of dosage of the protein substitute over a 24-hour period is unclear, and there is variation in recommendations among treatment centres. This is an update of a Cochrane review first published in 2005, and previously updated in 2008. To assess the benefits and adverse effects of protein substitute, its dosage, and distribution of dose in children and adults with phenylketonuria who are adhering to a low-phenylalanine diet. We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register which consists of references identified from comprehensive electronic database searches and hand searches of relevant journals and abstract books of conference proceedings. We also contacted manufacturers of the phenylalanine-free and low-phenylalanine protein substitutes for any data from published and unpublished randomised controlled trials.Date of the most recent search of the Group's Inborn Errors of Metabolism Trials Register: 03 April 2014. All randomised or quasi-randomised controlled trials comparing: any dose of protein substitute with no protein substitute; an alternative dosage; or the same dose, but given as frequent small doses throughout the day compared with the same total daily dose given as larger boluses less frequently. Both authors independently extracted data and assessed trial quality. Three trials (69 participants) are included in this review. One trial investigated the use of protein substitute in 16 participants, while a further two trials investigated the

  2. Diastereoselective Au-Catalyzed Allene Cycloisomerizations to Highly Substituted Cyclopentenes.

    Science.gov (United States)

    Reeves, Ryan D; Phelps, Alicia M; Raimbach, William A T; Schomaker, Jennifer M

    2017-07-07

    Site- and regiocontrolled Au-catalyzed allene carbocyclizations furnish highly substituted cyclopentenes in >1:1 dr. Significant substitution on the substrate is tolerated, with potential to install five contiguous stereocenters after alkene functionalization. Major challenges include identifying a Au/Cu catalyst that controls both the relative rates of allene epimerization/cyclization and the facial selectivity in addition of a metal enolate to the allene. Experiments to achieve stereodivergent cyclizations and transform key cyclopentenes into useful synthetic building blocks are described.

  3. Self-assembled nanoparticles of dextrin substituted with hexadecanethiol

    OpenAIRE

    Gonçalves, Catarina; Martins, J. A. R.; Gama, F. M.

    2007-01-01

    The amphiphilic molecule dextrin-VA-SC16 (dexC16) was synthesized and studied in this work. DexC16 has a hydrophilic dextrin backbone with grafted acrylate groups (VA) substituted with hydrophobic 1- exadecanethiol (C16). A versatile synthetic method was developed allowing control of the dextrin degree of substitution with the hydrophobic chains (DSC16, number of alkyl chains per 100 dextrin glucopyranoside residues). Materials with different DSC16 were prepared and characterized using 1H ...

  4. Economic substitution for US wheat food use by class

    OpenAIRE

    Marsh, Thomas L.

    2005-01-01

    Wheat for food use is conceptualised as an input into flour production and demand is derived from an industry profit function to quantify price responsiveness and economic substitutability across wheat classes. Price and substitution elasticities are estimated for hard red winter, hard red spring, soft red wheat, soft white winter and durum wheat. In general, hard red winter and spring wheat varieties are much more responsive to their own price than are soft wheat varieties and durum wheat. S...

  5. Laser ablation of Bi-substituted gadolinium iron garnet films

    International Nuclear Information System (INIS)

    Watanabe, N.; Hayashida, K.; Kawano, K.; Higuchi, K.; Ohkoshi, M.; Tsushima, K.

    1995-01-01

    Bi-substituted gadolinium iron garnet films were deposited by laser ablation. The composition, the structure and the magnetic properties of the films were found to be strongly dependent both on the compositions of the targets and on the pressure of oxygen. The highest values of Bi-substitution up to x=1.44 with uniform composition were obtained, after annealing in air. ((orig.))

  6. Perspective on the substitution of electricity for oil

    International Nuclear Information System (INIS)

    De Guise, Yvon.

    1981-06-01

    The prospects for substitution of electricity for oil are discussed. Current oil use in Canada and abroad is reviewed along with studies giving projections of future use. The author shows that electricity is in a position to adequately substitute for oil in most situations. While electricity comprised 34 percent of Canadian primary energy supply in 1979, it is expected to increase to 50 percent in 2000

  7. Anthropogenic areas as incidental substitutes for original habitat.

    Science.gov (United States)

    Martínez-Abraín, Alejandro; Jiménez, Juan

    2016-06-01

    One speaks of ecological substitutes when an introduced species performs, to some extent, the ecosystem function of an extirpated native species. We suggest that a similar case exists for habitats. Species evolve within ecosystems, but habitats can be destroyed or modified by natural and human-made causes. Sometimes habitat alteration forces animals to move to or remain in a suboptimal habitat type. In that case, the habitat is considered a refuge, and the species is called a refugee. Typically refugee species have lower population growth rates than in their original habitats. Human action may lead to the unintended generation of artificial or semiartificial habitat types that functionally resemble the essential features of the original habitat and thus allow a population growth rate of the same magnitude or higher than in the original habitat. We call such areas substitution habitats and define them as human-made habitats within the focal species range that by chance are partial substitutes for the species' original habitat. We call species occupying a substitution habitat adopted species. These are 2 new terms in conservation biology. Examples of substitution habitats are dams for European otters, wheat and rice fields for many steppeland and aquatic birds, and urban areas for storks, falcons, and swifts. Although substitution habitats can bring about increased resilience against the agents of global change, the conservation of original habitat types remains a conservation priority. © 2016 Society for Conservation Biology.

  8. Characterization of hair follicle development in engineered skin substitutes.

    Directory of Open Access Journals (Sweden)

    Penkanok Sriwiriyanont

    Full Text Available Generation of skin appendages in engineered skin substitutes has been limited by lack of trichogenic potency in cultured postnatal cells. To investigate the feasibility and the limitation of hair regeneration, engineered skin substitutes were prepared with chimeric populations of cultured human keratinocytes from neonatal foreskins and cultured murine dermal papilla cells from adult GFP transgenic mice and grafted orthotopically to full-thickness wounds on athymic mice. Non-cultured dissociated neonatal murine-only skin cells, or cultured human-only skin keratinocytes and fibroblasts without dermal papilla cells served as positive and negative controls respectively. In this study, neonatal murine-only skin substitutes formed external hairs and sebaceous glands, chimeric skin substitutes formed pigmented hairs without sebaceous glands, and human-only skin substitutes formed no follicles or glands. Although chimeric hair cannot erupt readily, removal of upper skin layer exposed keratinized hair shafts at the skin surface. Development of incomplete pilosebaceous units in chimeric hair corresponded with upregulation of hair-related genes, LEF1 and WNT10B, and downregulation of a marker of sebaceous glands, Steroyl-CoA desaturase. Transepidermal water loss was normal in all conditions. This study demonstrated that while sebaceous glands may be involved in hair eruption, they are not required for hair development in engineered skin substitutes.

  9. A study of photon interaction parameters in lung tissue substitutes

    Directory of Open Access Journals (Sweden)

    H C Manjunatha

    2014-01-01

    Full Text Available The study of photon interaction with different composite materials has become a topic of prime importance for radiation physicists. Some parameters of dosimetric interest are the mass attenuation coefficient, effective atomic number, and electron density; these help in the basic understanding of photon interactions with composite materials. The photon interaction parameters such as mass attenuation coefficient (μ/ρ, effective atomic number (Z eff , and effective electron density (N el must be identical for the phantom material and their tissue. In the present study, we have evaluated the photon interaction parameters such as (μ/ρ, Z eff and N el of 13 lung tissue substitutes. The variations of these parameters of lung tissue substitutes with photon energy are graphically represented. The photon interaction parameters of lung tissue substitutes are compared with that of lung tissue. The variation of photon interaction parameters of the studied lung tissue substitutes is similar that of the lung. Logically, it can be shown that Alderson lung is good substitute for lung than the other substitutes.

  10. A study of photon interaction parameters in lung tissue substitutes.

    Science.gov (United States)

    Manjunatha, H C

    2014-04-01

    The study of photon interaction with different composite materials has become a topic of prime importance for radiation physicists. Some parameters of dosimetric interest are the mass attenuation coefficient, effective atomic number, and electron density; these help in the basic understanding of photon interactions with composite materials. The photon interaction parameters such as mass attenuation coefficient (μ/ρ), effective atomic number (Zeff), and effective electron density (N el) must be identical for the phantom material and their tissue. In the present study, we have evaluated the photon interaction parameters such as (μ/ρ), Z eff and N el of 13 lung tissue substitutes. The variations of these parameters of lung tissue substitutes with photon energy are graphically represented. The photon interaction parameters of lung tissue substitutes are compared with that of lung tissue. The variation of photon interaction parameters of the studied lung tissue substitutes is similar that of the lung. Logically, it can be shown that Alderson lung is good substitute for lung than the other substitutes.

  11. Cannabis as a substitute for alcohol and other drugs

    Directory of Open Access Journals (Sweden)

    Reiman Amanda

    2009-12-01

    Full Text Available Abstract Background Substitution can be operationalized as the conscious choice to use one drug (legal or illicit instead of, or in conjunction with, another due to issues such as: perceived safety; level of addiction potential; effectiveness in relieving symptoms; access and level of acceptance. This practice of substitution has been observed among individuals using cannabis for medical purposes. This study examined drug and alcohol use, and the occurrence of substitution among medical cannabis patients. Methods Anonymous survey data were collected at the Berkeley Patient's Group (BPG, a medical cannabis dispensary in Berkeley, CA. (N = 350 The sample was 68% male, 54% single, 66% White, mean age was 39; 74% have health insurance (including MediCal, 41% work full time, 81% have completed at least some college, 55% make less than $40,000 a year. Seventy one percent report having a chronic medical condition, 52% use cannabis for a pain related condition, 75% use cannabis for a mental health issue. Results Fifty three percent of the sample currently drinks alcohol, 2.6 was the average number of drinking days per week, 2.9 was the average number of drinks on a drinking occasion. One quarter currently uses tobacco, 9.5 is the average number of cigarettes smoked daily. Eleven percent have used a non-prescribed, non OTC drug in the past 30 days with cocaine, MDMA and Vicodin reported most frequently. Twenty five percent reported growing up in an abusive or addictive household. Sixteen percent reported previous alcohol and/or drug treatment, and 2% are currently in a 12-step or other recovery program. Forty percent have used cannabis as a substitute for alcohol, 26% as a substitute for illicit drugs and 66% as a substitute for prescription drugs. The most common reasons given for substituting were: less adverse side effects (65%, better symptom management (57%, and less withdrawal potential (34% with cannabis. Conclusion The substitution of one

  12. Fine structure study on low concentration zinc substituted hydroxyapatite nanoparticles

    International Nuclear Information System (INIS)

    Hu, Wei; Ma, Jun; Wang, Jianglin; Zhang, Shengmin

    2012-01-01

    The fine structure of zinc substituted hydroxyapatite was studied using experimental analysis and first-principles calculations. The synthetic hydroxyapatite nanoparticles containing low Zn concentration show rod-like morphology. The crystallite sizes and unit-cell volumes tended to decrease with the increased Zn concentration according to X-ray diffraction patterns. The Zn K-edge X-ray absorption spectra and fitting results suggest that the hydroxyapatite doped with 0.1 mole% zinc is different in the zinc coordination environments compared with that containing more zinc. The density function theory calculations were performed on zinc substituted hydroxyapatite. Two mechanisms included replacing calcium by zinc and inserting zinc along the hydroxyl column and were investigated, and the related substitution energies were calculated separately. It is found that the substitution energies are negative and lowest for inserting zinc between the two oxygen atoms along the hydroxyl column (c-axis). Combined with the spectral analysis, it is suggested that the inserting mechanism is favored for low concentration zinc substituted hydroxyapatite. Highlights: ► We investigate the fine structure of hydroxyapatite with low content of Zn. ► XANES spectra are similar but a little different at low zinc content. ► Zinc ions influence hydroxyapatite crystal formation and lattice parameters. ► Formation energies are calculated according to plane-wave density function theory. ► Low content of zinc prefers to locate at hydroxyl column in hydroxyapatite lattice.

  13. Characteristics of Magnetic Properties of Substituted Hexagonal Ferrites

    Directory of Open Access Journals (Sweden)

    Vladimir Jancarik

    2006-01-01

    Full Text Available The samples of barium hexaferrite BaFe12-2x(Me1Me2xO19 with x from 0.0 to 0.6 were prepared by variousmethods. The cationic preference of mainly divalent Me1 = Zn, Co, Ni, Sn ions and tetravalent Me2 = Ti, Zr, Ir, Sn, Ru ionsand their combinations in substituted Ba ferrites was investigated. The substitutions were performed to reduce the grain sizeand high magnetic uniaxial anisotropy field of the M-type Ba ferrite without affecting the magnetic polarisation. The goal isto reach the properties of ferrite proper for high-density magnetic recording and microwave absorption devices. Magneticproperties were determined as a function of the substitution level x. The specific saturation magnetic polarisation Js–m andremanence Js–rincreased with small x due to the substitution of non-magnetic and less magnetic ions in 4f1 and 4f2 sites. Thesteep decrease of coercivity Hc with increasing x may be caused by the Co2+ preference of 4f2 site and Ti4+or Zr4+ions preference of 2b and slightly in 4f1 sites. The temperature coefficient of the coercivity TKHc was very low (0.01kA.m-1.°C-1for the Co-Zr substitutions and positive for the rest of samples.

  14. A test of the substitution-habitat hypothesis in amphibians.

    Science.gov (United States)

    Martínez-Abraín, Alejandro; Galán, Pedro

    2017-12-08

    Most examples that support the substitution-habitat hypothesis (human-made habitats act as substitutes of original habitat) deal with birds and mammals. We tested this hypothesis in 14 amphibians by using percentage occupancy as a proxy of habitat quality (i.e., higher occupancy percentages indicate higher quality). We classified water body types as original habitat (no or little human influence) depending on anatomical, behavioral, or physiological adaptations of each amphibian species. Ten species had relatively high probabilities (0.16-0.28) of occurrence in original habitat, moderate probability of occurrence in substitution habitats (0.11-0.14), and low probability of occurrence in refuge habitats (0.05-0.08). Thus, the substitution-habitat hypothesis only partially applies to amphibians because the low occupancy of refuges could be due to the negligible human persecution of this group (indicating good conservation status). However, low occupancy of refuges could also be due to low tolerance of refuge conditions, which could have led to selective extinction or colonization problems due to poor dispersal capabilities. That original habitats had the highest probabilities of occupancy suggests amphibians have a good conservation status in the region. They also appeared highly adaptable to anthropogenic substitution habitats. © 2017 Society for Conservation Biology.

  15. Import Substitution as a Factor of Regional Economic Growth

    Directory of Open Access Journals (Sweden)

    Sukhanova Irina Fedorovna

    2014-11-01

    Full Text Available The current state of import substitution in Russia is considered. The authors’ definition is given to the concept of import substitution. The features of short-term and longterm strategies of import substitution are opened. The authors prove the need of diversification of the directions of foreign economic activity by reorientation of the foreign trade communications of Russia to the markets of the countries of CIS, the customs union and CES as well as the countries of the Asia Pacific region. The reasons of growth of import deliveries of foodstuff are opened. The comparative analysis of food consumption level in Russia is conducted. The food coefficients dependence on the most important food are calculated. The comparative analysis of productive indicators of domestic agricultural production with similar indicators of the foreign states is made. The strategies of import substitution for domestic agriculture taking into account its specifics and production potential, is offered. The assessment of potential of import substitution of Saratov region is presented. The priority actions on ensuring food security and growth of economy of the region are offered.

  16. Boryl- and Silyl-Substituted Mixed Sandwich Compounds of Scandium.

    Science.gov (United States)

    Braunschweig, Holger; Damme, Alexander; Dück, Klaus; Krummenacher, Ivo; Paprocki, Valerie; Radacki, Krzysztof; Ramler, Jacqueline; Schiller, Carl; Schneider, Christoph

    2018-02-16

    An improved, one-pot synthesis of the linear sandwich compound [Sc(η 5 -C 5 H 5 )(η 8 -C 8 H 8 )] is presented. The synthetic procedure is amenable to boryl- and silyl-substituted cyclopentadienyl and cyclooctatetraenyl ligands, thereby yielding the first functionalized derivatives. We found that the synthesis of the silyl-substituted mixed sandwich complexes produces higher yields when the ligand exchange is carried out stepwise, by isolating the intermediate trimethylsilylated half-sandwich complex [Sc(η 8 -C 8 H 7 SiMe 3 )Cl(THF)] (THF=tetrahydrofuran). The molecular structures of the parent complex, as well as of its mono-boryl-substituted derivatives, have been determined by single-crystal X-ray diffraction. In addition, the optical and electrochemical properties of the mixed sandwich complexes are reported. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Pesticide Substitution: Combining Food Safety with Environmental Quality

    DEFF Research Database (Denmark)

    Fantke, Peter

    2015-01-01

    % by defining adequate substitution scenarios. Comprehensive scenarios need to also consider worker and environmental burden, and information on crop rotation, pest pressure, environmental conditions, application costs and efficacy. Such scenarios help to increase food safety and more sustainable use......Various pesticides are authorized for use on agricultural food crops. Despite regulatory risk assessments aiming at ensuring consumer and environmental safety, pesticides contribute to human and environmental impacts. Guidance is needed to optimize pesticide use practice and minimize human...... and environmental exposure. Comparative pesticide substitution scenarios are presented to address this need. In a case study on wheat, different pesticides have been compared with respect to their substitution potential with focus on human health. Results demonstrate that health impacts can be reduced up to 99...

  18. Caviar substitute produced from roes of rainbow trout (Oncorhynchus mykiss

    Directory of Open Access Journals (Sweden)

    Thaís Moron Machado

    2016-04-01

    Full Text Available The caviar substitute is obtained from processed fish roe, resulting in a product similar to the authentic caviar, prepared with sturgeon roe. The objective of this study was to develop a caviar substitute from roes of rainbow trout, Oncorhynchus mykiss. Four treatments were tested and we followed the steps of saline wash, drain, immersion in saline solution containing lactic acid for pH adjustment (4.3 to 4.5, salt addition (1.5 or 3%, traditional pasteurization or fast heat treatment, cooling and storage (0 to 4°C. The products were subjected to the physical, chemical, microbiological and sensory analyses and showed stability and safety for consumption up to 180 days in storage under refrigeration (0 to 4°C. Consumers showed preference for product containing 1.5% NaCl and subjected to fast heat treatment. The results suggest that caviar substitute developed with rainbow trout roes presents potential to production.

  19. Fibrous growth of strontium substituted hydroxyapatite and its drug release

    International Nuclear Information System (INIS)

    Suganthi, R.V.; Elayaraja, K.; Joshy, M.I. Ahymah; Chandra, V. Sarath; Girija, E.K.; Kalkura, S. Narayana

    2011-01-01

    The effect of strontium on the crystallization of helical ribbon of hydroxyapatite (HAp) was investigated by single diffusion technique in silica gel matrix at 27 deg. C and physiological pH. Fibers of HAp were obtained on addition of strontium. The length of the HAp fibers, were found to decrease as the strontium substitution increases. The presence of strontium ion increased the crystallinity as well as crystallite size of HAp. The strontium substituted HAp (Sr-HAp) has similar stoichiometry to that of biological apatite. Sr-HAp was found to have increased surface area (35%) compared to control. Further, strontium substitution leads to an enhancement of in vitro bioactivity. The cumulative in-vitro amoxicillin drug release in phosphate buffer solution (PBS, pH 7.2) showed a prolonged release profile for Sr-HAp.

  20. Fibrous growth of strontium substituted hydroxyapatite and its drug release

    Energy Technology Data Exchange (ETDEWEB)

    Suganthi, R.V.; Elayaraja, K.; Joshy, M.I. Ahymah; Chandra, V. Sarath [Crystal Growth Centre, Anna University, Chennai 600 025 (India); Girija, E.K. [Department of Physics, Periyar University, Salem 636 011 (India); Kalkura, S. Narayana, E-mail: kalkura@yahoo.com [Crystal Growth Centre, Anna University, Chennai 600 025 (India)

    2011-04-08

    The effect of strontium on the crystallization of helical ribbon of hydroxyapatite (HAp) was investigated by single diffusion technique in silica gel matrix at 27 deg. C and physiological pH. Fibers of HAp were obtained on addition of strontium. The length of the HAp fibers, were found to decrease as the strontium substitution increases. The presence of strontium ion increased the crystallinity as well as crystallite size of HAp. The strontium substituted HAp (Sr-HAp) has similar stoichiometry to that of biological apatite. Sr-HAp was found to have increased surface area (35%) compared to control. Further, strontium substitution leads to an enhancement of in vitro bioactivity. The cumulative in-vitro amoxicillin drug release in phosphate buffer solution (PBS, pH 7.2) showed a prolonged release profile for Sr-HAp.

  1. Synthesis of Randomly Substituted Anionic Cyclodextrins in Ball Milling.

    Science.gov (United States)

    Jicsinszky, László; Caporaso, Marina; Calcio Gaudino, Emanuela; Giovannoli, Cristina; Cravotto, Giancarlo

    2017-03-19

    A number of influencing factors mean that the random substitution of cyclodextrins (CD) in solution is difficult to reproduce. Reaction assembly in mechanochemistry reduces the number of these factors. However, lack of water can improve the reaction outcomes by minimizing the reagent's hydrolysis. High-energy ball milling is an efficient, green and simple method for one-step reactions and usually reduces degradation and byproduct formation. Anionic CD derivatives have successfully been synthesized in the solid state, using a planetary ball mill. Comparison with solution reactions, the solvent-free conditions strongly reduced the reagent hydrolysis and resulted in products of higher degree of substitution (DS) with more homogeneous DS distribution. The synthesis of anionic CD derivatives can be effectively performed under mechanochemical activation without significant changes to the substitution pattern but the DS distributions were considerably different from the products of solution syntheses.

  2. Synthesis of Randomly Substituted Anionic Cyclodextrins in Ball Milling

    Directory of Open Access Journals (Sweden)

    László Jicsinszky

    2017-03-01

    Full Text Available A number of influencing factors mean that the random substitution of cyclodextrins (CD in solution is difficult to reproduce. Reaction assembly in mechanochemistry reduces the number of these factors. However, lack of water can improve the reaction outcomes by minimizing the reagent’s hydrolysis. High-energy ball milling is an efficient, green and simple method for one-step reactions and usually reduces degradation and byproduct formation. Anionic CD derivatives have successfully been synthesized in the solid state, using a planetary ball mill. Comparison with solution reactions, the solvent-free conditions strongly reduced the reagent hydrolysis and resulted in products of higher degree of substitution (DS with more homogeneous DS distribution. The synthesis of anionic CD derivatives can be effectively performed under mechanochemical activation without significant changes to the substitution pattern but the DS distributions were considerably different from the products of solution syntheses.

  3. Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines

    Directory of Open Access Journals (Sweden)

    Satoru Mori

    2017-10-01

    Full Text Available Phthalocyanines and subphthalocyanines are attracting attention as functional dyes that are applicable to organic solar cells, photodynamic therapy, organic electronic devices, and other applications. However, phthalocyanines are generally difficult to handle due to their strong ability to aggregate, so this property must be controlled for further applications of phthalocyanines. On the other hand, trifluoroethoxy-substituted phthalocyanines are known to suppress aggregation due to repulsion of the trifluoroethoxy group. Furthermore, the electronic characteristics of phthalocyanines are significantly changed by the strong electronegativity of fluorine. Therefore, it is expected that trifluoroethoxy-substituted phthalocyanines can be applied to new industrial fields. This review summarizes the synthesis and application of trifluoroethoxy-substituted phthalocyanine and subphthalocyanine derivatives.

  4. Selected polyethylene glycols as DOP substitutes. Addendum 1

    International Nuclear Information System (INIS)

    Gerber, B.V.

    1981-01-01

    The recommendation is made that Polyethylene glycol (PEG) 400 be considered as a substitute for DOP in aerosol generators producing a polydisperse distribution for testing the integrity of filters and for testing respirator fit. Further, the recommendation is made that pentaethylene glycol (PTAEG) and possibly hexaethylene glycol be considered as a substitute for DOP in aerosol generators thermally producing monodisperse aerosol for quality acceptance tests according tu US federal specifications and standards. The toxicology data base available on the polyethylene glycol family of chemical compounds is discussed and the conclusion is drawn that the probability of approval and acceptance as a non-hazardous substance in the filter and filter media test role is high. Data and analysis supporting PTAEG performance equivalent to DOP in the filter and filter media test role are given or referenced. Cost and availability of the substitute materials is discussed. Conclusions based on the present data and information are given and recommendations for further work are made

  5. Cost comparison of femoral head banking versus bone substitutes.

    Science.gov (United States)

    Leung, Hon-Bong; Fok, Margaret Woon-Man; Chow, Lorraine Chi-Yan; Yen, Chi-Hung

    2010-04-01

    To compare the costs of femoral head banking versus bone substitutes. Records of femoral head banking from 1998 to 2008 were reviewed. The cost of allogenic cancellous bone graft was calculated by estimating the direct expenditure of femoral head procurement, screening tests, and storage, and then divided by the amount of bone harvested. 326 females and 141 males (mean age, 80.3 years) donated 470 femoral heads. Each transplantable femoral head costs US$978. Each gram of transplantable allogenic bone graft costs US$86, compared with US$9 to 26 per gram for commercially available bone substitutes. Compared with bone substitutes, femoral head banking in Hong Kong was less economical. Unless allografts yield superior outcomes, harvesting femoral heads for general usage (such as filling bone voids for fresh fractures) is not justified from a financial perspective, especially in banks dedicated to procuring bone from femoral heads only.

  6. Fish mislabelling in France: substitution rates and retail types

    Directory of Open Access Journals (Sweden)

    Julien Bénard-Capelle

    2015-01-01

    Full Text Available Market policies have profound implications for consumers as well as for the management of resources. One of the major concerns in fish trading is species mislabelling: the commercial name used does not correspond to the product, most often because the product is in fact a cheaper or a more easily available species. Substitution rates depend heavily on species, some often being sold mislabelled while others rarely or never mislabelled. Rates also vary largely depending on countries. In this study, we analyse the first market-wide dataset collected for France, the largest sea food market in Europe, for fish species substitution. We sequenced and analysed 371 samples bearing 55 commercial species names, collected in fishmonger shops, supermarkets and restaurants; the largest dataset assembled to date in an European country. Sampling included fish fillets, both fresh and frozen, and prepared meals. We found a total of 14 cases of mislabelling in five species: bluefin tuna, cod, yellowfin tuna, sole and seabream, setting the overall substitution rate at 3.7% CI [2.2–6.4], one of the lowest observed for comparable surveys with large sampling. We detected no case of species mislabelling among the frozen fillets or in industrially prepared meals, and all the substitutions were observed in products sold in fishmongers shops or restaurants. The rate of mislabelling does not differ between species, except for bluefin tuna. Despite a very small sample size (n = 6, the rate observed for this species (83.3% CI [36–99] stands in sharp contrast with the low substitution rate observed for the other substituted species. In agreement with studies from other countries, this work shows that fish mislabelling can vary greatly within a country depending on the species. It further suggests that more efforts should be directed to the control of high value species like bluefin tuna.

  7. Mapping the Trajectory of Nucleophilic Substitution at Silicon Using a peri-Substituted Acenaphthyl Scaffold.

    Science.gov (United States)

    Hupf, Emanuel; Olaru, Marian; Raţ, Ciprian I; Fugel, Malte; Hübschle, Christian B; Lork, Enno; Grabowsky, Simon; Mebs, Stefan; Beckmann, Jens

    2017-08-04

    The second-order nucleophilic substitution (S N 2) reaction at a silicon atom is scrutinized by means of snapshots along a pseudoreaction coordinate. Phosphine and fluoride represent both attacking and leaving groups in the modeled S N 2 reaction. In the experimentally obtained 5-diphenylphosphinoacenaphth-6-yl-dimethylfluorosilane, 1, the phosphine and fluorosilane moieties are forced into immediate proximity through an acenaphthyl scaffold, that is, they exhibit peri interactions that serve as the model of the reactant ion-molecule complex and starting point for a theoretical potential-energy surface (PES) scan. Upon dissociation of fluoride, the experimentally obtained silylphosphonium cation 2 serves as a model of the product and end point of the PES scan. The pseudoreaction pathway is studied using geometric, energetic, spectroscopic, molecular-orbital, and topological real-space bonding indicators. It becomes evident that it is crucial to combine such methods to understand the pseudoreaction because they reveal different aspects based on different sensitivity to dispersive, electrostatic, and polar-covalent contributions to bonding, as shown by the reduced density gradient analysis. For example, atoms-in-molecules theory describes a late topological catastrophe, whereas the electron localizability indicator describes an early concerted reaction and natural resonance theory describes a more gradual change of properties. This case study encourages the use of a well-balanced toolbox equipped with complementary methods to emphasize different aspects of bonding. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Exfoliation and thermal transformations of Nb-substituted layered titanates

    DEFF Research Database (Denmark)

    Song, H.; Sjåstad, Anja O.; Fjellvåg, Helmer

    2011-01-01

    Single-layer Nb-substituted titanate nanosheets of ca. 1 nm thickness were obtained by exfoliating tetrabutylammonium (TBA)-intercalated Nb-substituted titanates in water. AFM images and turbidity measurements reveal that the exfoliated nanosheets crack and corrugate when sonicated. Upon heating...... factors for increasing the transformation temperatures for conversion of the nanosheets to anatase and finally into rutile. It is further tempting to link the delay in crystallization to morphology limitations originating from the nanosheets. The present work shows that layered Nb-titanates...

  9. Bioactivity And Bone Formation In Silicon-Substituted Hydroxyapatite

    Directory of Open Access Journals (Sweden)

    Ulvan Ozad

    2012-06-01

    Full Text Available Bioactivity and successful bone formation in silicon-substituted hydroxyapatite bone grafts were investigated by using scanning electron microscopy and electron dispersive x-ray spectroscopy. Areas of bone formation have been detected in scanning electron microscopy; and, arranged lamellar collagen has been observed. 20.8% average carbon content rise has been detected between bone graft and the produced bone; and, this has been confirmed to be a gradual increase throughout the interphase. Obvious bone formation and maturation were observed in the samples. Carbon content gradually increased from bone graft to the bone formed, confirming formation of new bone and dissociation of silicon-substituted bone graft.

  10. Synthesis and biological evaluation of 2-substituted benzimidazole derivatives

    Directory of Open Access Journals (Sweden)

    Gurusamy Mariappan

    2015-09-01

    Full Text Available A novel series of 2-substituted benzimidazole derivatives (3a–3j were synthesized by the reaction of 2-chloro methyl benzimidazole with substituted primary aromatic amines. All the compounds were characterized by UV, IR, 1H NMR, mass spectral data and CHN elemental analysis. The synthesized derivatives were screened for analgesic and anti-inflammatory activities. All the compounds showed significant effect at 100 mg/kg p.o. and the experimental data are statistically significant at p < 0.01 level.

  11. Researcher’s Perspective of Substitution Method on Text Steganography

    Science.gov (United States)

    Zamir Mansor, Fawwaz; Mustapha, Aida; Azah Samsudin, Noor

    2017-08-01

    The linguistic steganography studies are still in the stage of development and empowerment practices. This paper will present several text steganography on substitution methods based on the researcher’s perspective, all scholar paper will analyse and compared. The objective of this paper is to give basic information in the substitution method of text domain steganography that has been applied by previous researchers. The typical ways of this method also will be identified in this paper to reveal the most effective method in text domain steganography. Finally, the advantage of the characteristic and drawback on these techniques in generally also presented in this paper.

  12. Remoção de metais pesados de efluentes aquosos pela zeólita natural escolecita - influência da temperatura e do pH na adsorção em sistemas monoelementares Heavy metals removal from wastewater by the natural zeolite scolecite - temperature and pH influence in single-metal solutions

    Directory of Open Access Journals (Sweden)

    Ricardo Sarti Jimenez

    2004-10-01

    Full Text Available Cation exchange capabilities of a Brazilian natural zeolite, identified as scolecite, were evaluated for application in wastewater control. We investigated the process of sorption of chromium(III, nickel(II, cadmium(II and manganese(II in synthetic aqueous effluents, including adsorption isotherms of single-metal solutions. The natural zeolite showed the ability to take up the tested heavy metals in the order Cr(III > Cd(II > Ni(II > Mn(II, and this could be related to the valence and the hydration radius of the metal cations. The influence of temperature (25, 40 and 60 ºC and initial pH value (from 4 to 6 was also evaluated. It was found that the adsorption increased substantially when the temperature was raised to 60 ºC and that maximum adsorption capacity was observed at pH 6. These results demonstrate that scolecite can be used for removal of heavy metals from aqueous effluents, under optimized conditions.

  13. Porcine wound models for skin substitution and burn treatment.

    NARCIS (Netherlands)

    Middelkoop, E.; Bogaerdt, A.J. van den; Lamme, E.N.; Hoekstra, M.J.; Brandsma, K.; Ulrich, M.M.

    2004-01-01

    Skin regeneration is an important field of tissue engineering. Especially in larger burns and chronic wounds, present treatments are insufficient in preventing scar formation and promoting healing. Initial screening of potentially interesting products for skin substitution is usually done by in

  14. An environmentally benign one pot synthesis of substituted ...

    Indian Academy of Sciences (India)

    Instance of Plagiarism in Journal of Chemical Sci- ences and withdrawal of published article. The Journal of Chemical Sciences office received a complaint from an alert reader to the effect that the paper 'An environmentally benign one pot syn- thesis of substituted quinolines catalysed by fluo- roboric acid based ionic ...

  15. Stereochemistry of substitution at trico-ordinate phosphorus

    DEFF Research Database (Denmark)

    Nielsen, John; Dahl, Otto

    1984-01-01

    and 31P) from reactant and product diastereoisomers have been assigned, and the stereo-chemistry of the substitution reactions have been determined by 31P n.m.r. monitoring. The outcome varies from complete inversion to complete lack of stereoselectivity. During the initial stages many of the non...

  16. Report on the first government-funded opioid substitution ...

    African Journals Online (AJOL)

    Background. Although pharmacological opioid substitution treatment (OST) is a well-established treatment modality for heroin addiction, it is a relatively recent introduction in low- and middle-income countries. Objective. To report on a pilot OST programme initiated in 2013 that was the only public-funded programme in ...

  17. Investigation on applicability of substitute beam-column frame for ...

    African Journals Online (AJOL)

    ... of the sway frame moment magnification provision for the design of slender reinforced concrete columns in sway frames according to EBCS 2: 1995. A special feature of the moment magnification method in EBCS 2: 1995 is the introduction of the concept of substitute frame for the determination of the storey buckling load.

  18. Iron-substituted AB5-type MH electrode

    Indian Academy of Sciences (India)

    substituted AB5-type MH electrode. SUMITA SRIVASTAVAa,∗ and R K UPADHYAYAb. aDepartment of Physics, Government P.G. College, Uttarkashi 249 193, India. bDepartment of Physics, Government P.G. College, Rishikesh 249 201, India.

  19. Interpretation of substitution experiments by homogenisation two-group method

    International Nuclear Information System (INIS)

    Sotic, O.

    1970-02-01

    This paper describes methods for interpretation of progressive substitution experiments for determining material buckling in homogeneous two-group approximation. These methods were applied for experiments on the zero power RB reactor in Vinca. Experiments were done on the reflected heavy water reactor core, the lattice pitch had unisotropy properties

  20. VEGETABLE OILS AS SUBSTITUTION FOR DIESEL OIL Test results ...

    African Journals Online (AJOL)

    REFERENCES. (1) 'lbe Ethiopian Herald, Ed. "Brazil heavy depending on plants for fuel". Sunday, 24 April 1983, p.6. [2] Pischinger, G. "Consumption Data and. Consideration on Three Approaches to. Diesel oil Substitution". Internal publi- cation of Volkswagen AG, Wolfsburg,. 1981. [ 3] Tewolde Berhan G /Egziabher and.

  1. substitute for Zn(II) in zinc fingers?

    Indian Academy of Sciences (India)

    Zinc finger domains consist of sequences of amino acids containing cysteine and histidine residues tetrahedrally coordinated to a zinc ion. The role of zinc in a DNA binding finger was considered purely structural due to the absence of redox chemistry in zinc. However, whether other metals e.g. Co(II) or Cd(II) can substitute ...

  2. Synthesis of 3-Substituted 1,4-Benzodiazepin-2-ones

    Directory of Open Access Journals (Sweden)

    Kyungjin Kim

    1998-01-01

    Full Text Available The preparation of 3-substituted 1,4-benzodiazepines by benzodiazepine enolate alkylation has been explored. Employing this approach, multigram quantities of benzodiazepine 1 have been prepared for animal studies to evaluate a new approach for the treatment of the autoimmune disease systemic lupus erythematosus (SLE.

  3. KINETICS OF SUBSTITUTION OF CIS-BIS(MALONATO ...

    African Journals Online (AJOL)

    Preferred Customer

    substrate exists predominantly as the diaquospecies and amino acids (glycine, DL-alanine and DL-phenylalanine) as the zwitterion at ... KEY WORDS: Substitution, cis-bis(malonato)diaquochromate(III), Amino acids ... chromium(III) ion results in an impairment of intravenous glucose tolerance and diabetics like symptoms in ...

  4. Effect of substitution of titanium by magnesium and niobium on ...

    Indian Academy of Sciences (India)

    Administrator

    Effect of substitution of titanium by magnesium and niobium on structure and piezoelectric properties in (Bi1/2. Na1/2. )TiO3 ceramics. ZHOU CHANG-RONG*, LIU XIN-YU, LI WEI-ZHOU. † and YUAN CHANG-LAI. Department of Information Material Science and Engineering, Guilin University of Electronic Technology,. Guilin ...

  5. SO2 policy and input substitution under spatial monopoly

    International Nuclear Information System (INIS)

    Gerking, Shelby; Hamilton, Stephen F.

    2010-01-01

    Following the U.S. Clean Air Act Amendments of 1990, electric utilities dramatically increased their utilization of low-sulfur coal from the Powder River Basin (PRB). Recent studies indicate that railroads hauling PRB coal exercise a substantial degree of market power and that relative price changes in the mining and transportation sectors were contributing factors to the observed pattern of input substitution. This paper asks the related question: To what extent does more stringent SO 2 policy stimulate input substitution from high-sulfur coal to low-sulfur coal when railroads hauling low-sulfur coal exercise spatial monopoly power? The question underpins the effectiveness of incentive-based environmental policies given the essential role of market performance in input, output, and abatement markets in determining the social cost of regulation. Our analysis indicates that environmental regulation leads to negligible input substitution effects when clean and dirty inputs are highly substitutable and the clean input market is mediated by a spatial monopolist. (author)

  6. Effects of substituting fishmeal with immobilized urea periodate ...

    African Journals Online (AJOL)

    Digitaria exilis (Staph) and Rice (Oryza sativa (L.) straws for substituting fishmeal from the reference diet (crude protein, 32.6%) at 15, 30, 45 and 60% test materials inclusion levels. Ten fish were stocked in triplicate replication in circular plastic tanks ...

  7. Sodium-carbonate co-substituted hydroxyapatite ceramics

    Directory of Open Access Journals (Sweden)

    Zoltan Z. Zyman

    2013-12-01

    Full Text Available Powders of sodium-carbonate co-substituted hydroxyapatite, having sodium content in the range of 0.25–1.5 wt.% with a 0.25 wt.% step, were prepared by a precipitation-solid state reaction route. Compacts of the powders were sintered in a CO2 flow (4 mL/min at 1100 °C for 2 h. The sintered ceramics contained sodium and carbonate ions in the ranges of 0–1.5 wt.% and 1.3–6 wt.%, respectively, which are typical impurity concentrations in biological apatite. A relationship between sodium and carbonate contents and the type of carbonate substitution was found. The total carbonate content progressively increased with the sodium content. The obtained ceramics showed an AB-type carbonate substitution. However, the substitution became more B-type as the sodium content increased. As a result, the carbonation was almost B-type (94 % for the highest sodium content (1.5 wt.%.

  8. Calculating stocking rates for game ranches: substitution ratios for ...

    African Journals Online (AJOL)

    Reports on a study conducted to quantify the overlap in ungulate resource-use on a game ranch, and to demonstrate how these indices of overlap can be incorporated into substitution ratios for calculating stocking rates. Illustrates with tables. Keywords:Aepyceros melampus; Animal units; Blue wildebeest; Burchell's zebra; ...

  9. The Effects of Substituting Soyabean Meal for Breadfruit Meal on ...

    African Journals Online (AJOL)

    The effects of substituting soyabean meal for breadfruit (Tricuria africana) meal in diets fed to Heterobranchus bidorsalis (♂) x Clarias gariepinus (♀) hybrid fingerlings on diet acceptability, growth responses and cost benefit of fed catfishes were studied. The acceptability of breadfruit based diets by Heterobranchus ...

  10. Effect of nickel oxide substitution on bioactivity and mechanical ...

    Indian Academy of Sciences (India)

    glass revealed that isomorphic substitution of nickel in the silicate network in tetrahedral coordination or as modifier in higher coordination do not adversely affect the existing glass structure. The present work aims to measure the bioactivity and mechanical properties of base glass and nickel oxide substi- tute bioactive glass ...

  11. The kinetics of substitution reaction of oxydiacetate and ...

    Indian Academy of Sciences (India)

    DOI 10.1007/s12039-015-0952-5. The kinetics of substitution reaction of oxydiacetate and thiodiacetate copper(II) complexes with 1,10-phenanthroline and 2,2'-bipyridine. JOANNA PRANCZK, DAGMARA JACEWICZ∗, DARIUSZ WYRZYKOWSKI,. ALEKSANDRA TESMAR and LECH CHMURZY ´NSKI. Faculty of Chemistry ...

  12. Kinetics and mechanism of the oxidation of substituted ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 115; Issue 2. Kinetics and mechanism of the oxidation of substituted benzylamines by cetyltrimethylammonium permanganate. Raghvendra Shukla Pradeep K Sharma László Kótai Kalyan K Banerji. Physical and Theoretical Volume 115 Issue 2 April 2003 pp 129-134 ...

  13. The Synthesis of Substituted Piperazine-cholesterol Conjugates for ...

    African Journals Online (AJOL)

    A small library of cholesterol-piperazine conjugates were synthesized by the reaction of cholesteryl chloroformate with a set of substituted piperazines in dichloromethane at room temperature. The conjugates, all obtained in good to excellent yields, were synthesized to be key components of nucleic acid transfection ...

  14. Heart failure after aortic valve substitution due to severe hypothyroidism

    DEFF Research Database (Denmark)

    Munk, Kim; Sørensen, Stine Heidenheim; Andersen, Niels Holmark

    2008-01-01

    We report a case of a 70-year-old female with considerable co-morbidities (Type 2 diabetes, Leiden factor V mutation, mild to moderate chronic obstructive pulmonary disease) and a recent biological aortic valve substitution, who was admitted due to circulatory collapse caused by severe heart...

  15. Substitution Value of toasted Pigeon pea ( Cajanus cajan ) seed ...

    African Journals Online (AJOL)

    One hundred and eighty 7-day old broilers were used in a 28-day feeding trial to determine the substitution value of toasted pigeon pea seeds meal (TPSM) for soybean meal and maize in boiler starter diet. The brown coat coloured pigeon pea seeds were toasted at 100oC for 15minutes and milled. The inclusion levels of ...

  16. Regioselective Upper Rim Substitution of Calix[4]arenes

    Czech Academy of Sciences Publication Activity Database

    Hudeček, O.; Cuřínová, Petra; Budka, J.; Lhoták, P.

    2011-01-01

    Roč. 67, č. 29 (2011), s. 5213-5218 ISSN 0040-4020 R&D Projects: GA ČR GA203/09/0691; GA AV ČR IAAX08240901 Institutional support: RVO:67985858 Keywords : calixarene * electrophilic substitution * anion recognition Subject RIV: CC - Organic Chemistry Impact factor: 3.025, year: 2011

  17. Phase developments and dielectric responses of barium substituted ...

    Indian Academy of Sciences (India)

    Phase developments and dielectric responses of barium substituted four-layer CaBi4Ti4O15 Aurivillius. HUILING DU. ∗. , XIANG SHI and HUILU LI. College of Materials Science and Engineering, Xi'an University of Science and Technology, Xi'an 710054, China. MS received 26 December 2010; revised 8 February 2011.

  18. Miracle fruit: An alternative sugar substitute in sour beverages.

    Science.gov (United States)

    Rodrigues, Jéssica Ferreira; Andrade, Rafaela da Silva; Bastos, Sabrina Carvalho; Coelho, Sandra Bragança; Pinheiro, Ana Carla Marques

    2016-12-01

    High sugar consumption has been related to several chronic diseases and thus, many alternative sweeteners have been extensively researched. However, there is still controversy regarding the harmful effects of their consumption, mainly regarding the use of artificial sweeteners, controversy which increases the demand for natural sweeteners, such as miracle fruit. This tropical plant grows in West Africa is named for its unique ability of changing a sour taste into sweet. Therefore, this study aimed to characterize the temporal profile of miracle fruit and assess its sugar substitute power in sour beverages through time-intensity and temporal dominance of sensations tests. For this, unsweetened lemonade and lemonades with sugar, sucralose and previous miracle fruit ingestions were evaluated. We noted that the dynamic profile of lemonade ingested after miracle fruit ingestion indicates that it seems to be a good sugar substitute, since it provides high sweetness intensity and persistence, reduced product sourness and an absence of aftertastes. The miracle fruit also provided a sensory profile similar to that of sucralose, an established and recognized sugar substitute. The results of this study provide important information for future applications of miracle fruit as a sugar substitute in sour beverages, providing an alternative use for a natural substance as a sweetening agent. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Substitution and defect chemistry of La-Cu-O systems

    International Nuclear Information System (INIS)

    Gai, P.L.; McCarron, E.M.; Kunchur, M.

    1991-01-01

    In this paper substitutional effects of strontium in La-Cu-O system and defects accommodating stoichiometric deviations is investigated. The extended shear defects are analyzed using electron microscopy and the role in superconducting transport properties has been examined by magnetic measurements. The initial results suggest that the defects enhance flux pinning

  20. The kinetics of substitution reaction of oxydiacetate and ...

    Indian Academy of Sciences (India)

    ... Journals; Journal of Chemical Sciences; Volume 127; Issue 10. The kinetics of substitution reaction of oxydiacetate and thiodiacetate copper(II) complexes with 1,10-phenanthroline and 2,2'-bipyridine. Joanna Pranczk Dagmara Jacewicz Dariusz Wyrzykowski Aleksandra Tesmar Lech Chmurzyński. Volume 127 Issue 10 ...

  1. Quantum Dots Embedded in Graphene Nanoribbons by Chemical Substitution

    DEFF Research Database (Denmark)

    Carbonell-Sanroma, Eduard; Brandimarte, Pedro; Balog, Richard

    2017-01-01

    Bottom-up chemical reactions of selected molecular precursors on a gold surface can produce high quality graphene nanoribbons (GNRs). Here, we report on the formation of quantum dots embedded in an armchair GNR by substitutional inclusion of pairs of boron atoms into the GNR backbone. The boron...

  2. Cu 2 + and Al 3 + co-substituted cobalt ferrite

    Indian Academy of Sciences (India)

    X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, field emissionscanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM) are used for studying the effect of variation in the Cu–Al substitution and its impact on particle size, magnetic properties such as Ms and Hc.

  3. Solventless Substitution Reaction of Solid Phosphine Ligands with ...

    African Journals Online (AJOL)

    The reaction rates are enhanced by para-substituted electron-donating phosphines. These results are similar to those obtained from studies utilizing benzene and xylene as solvents. The products have been characterized by FTIR and NMR spectroscopy and by MS. The complex Fe2(C5H5)2(CO)4 was found to act as a ...

  4. Effect of Grain Tef ( Eragrostis tef (Zucc.) Trotter) Flour Substitutions ...

    African Journals Online (AJOL)

    There is an increased global interest in the food industry to develop and market functional foods in which scientific investigations are limited in Ethiopia. Tef injera functional character can be further enhanced by substitution with flaxseed which is known to bear functional ingredients (α-linolenic acid an ω-3 fatty acid, ...

  5. Effects of substituting sunflower seed cake with Acacia tortilis pods ...

    African Journals Online (AJOL)

    A study was undertaken to avaluate the effects of substituting sunflower seed cake with Acacia tortilis pods as a protein source in supplementing Small East African goats fed a basal diet of Brachiaria brizantha hay. Twenty-four growing female goats with mean body weight of 9. 71 = 1.56 kg were used in a growth ...

  6. preparation and nucleophilic substitution of the 2,4,6

    African Journals Online (AJOL)

    Mgina

    pyridinium salt 3 during preparation or could be the consequence of the nucleophilic substitution reaction. In case of the first presumption, racemization of 3 might have happened via acid mediated tautomerization of the vinylogous compound 5 , an intermediate formed during preparation of the triphenylpyridinium salt ...

  7. 1,3- and 1,4-Substituted tetrazolium salts

    International Nuclear Information System (INIS)

    Voitekhovich, Sergei V; Gaponik, Pavel N; Ivashkevich, Oleg A

    2002-01-01

    The published data on the synthesis, physicochemical properties, structures and reactions of 1,3-(1,3,5)- and 1,4-(1,4,5)-substituted tetrazolium salts are systematised and generalised. Their applications as starting compounds in the preparative chemistry of heterocyclic derivatives and some other branches of science and technology are reviewed. The bibliography includes 122 references.

  8. Synthesis, characterization of N-, S-, O-substituted naphtho- and ...

    Indian Academy of Sciences (India)

    Sci. Vol. 124, No. 3, May 2012, pp. 657–667. c Indian Academy of Sciences. Synthesis, characterization of N-, S-, O-substituted naphtho- and benzoquinones and a structural study. CEMIL IBIS. ∗ and NAHIDE GULSAH DENIZ. Engineering Faculty, Department of Chemistry, Division of Organic Chemistry, Istanbul University,.

  9. Colorimetric Sugar Sensing Using Boronic Acid-Substituted Azobenzenes

    Directory of Open Access Journals (Sweden)

    Yuya Egawa

    2014-02-01

    Full Text Available In association with increasing diabetes prevalence, it is desirable to develop new glucose sensing systems with low cost, ease of use, high stability and good portability. Boronic acid is one of the potential candidates for a future alternative to enzyme-based glucose sensors. Boronic acid derivatives have been widely used for the sugar recognition motif, because boronic acids bind adjacent diols to form cyclic boronate esters. In order to develop colorimetric sugar sensors, boronic acid-conjugated azobenzenes have been synthesized. There are several types of boronic acid azobenzenes, and their characteristics tend to rely on the substitute position of the boronic acid moiety. For example, o-substitution of boronic acid to the azo group gives the advantage of a significant color change upon sugar addition. Nitrogen-15 Nuclear Magnetic Resonance (NMR studies clearly show a signaling mechanism based on the formation and cleavage of the B–N dative bond between boronic acid and azo moieties in the dye. Some boronic acid-substituted azobenzenes were attached to a polymer or utilized for supramolecular chemistry to produce glucose-selective binding, in which two boronic acid moieties cooperatively bind one glucose molecule. In addition, boronic acid-substituted azobenzenes have been applied not only for glucose monitoring, but also for the sensing of glycated hemoglobin and dopamine.

  10. DFT analysis of the nucleophilicity of substituted pyridines and ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 128; Issue 4. DFT analysis of the nucleophilicity of substituted pyridines and prediction of new molecules having nucleophilic character stronger than 4-pyrrolidino pyridine. Kaustavmoni Deka Prodeep Phukan. Regular Articles Volume 128 Issue 4 April 2016 pp 633- ...

  11. Basicities of some 9-substituted acridine-4-carboxamides: A density ...

    Indian Academy of Sciences (India)

    Acid-base properties of drugs are important in understanding the behaviour of these compounds under physiological condition. In order to understand such behaviour the proton affinities of acridine 4-carboxamides with substitution (R) at the 9-position are theoretically studied, and considered for the basic sites of both the ...

  12. Placebo substitution for tnethyldopa in geriatric hypertensive patients

    African Journals Online (AJOL)

    Abstract The aim of this study was to obtain an objective evaluation of the possibly inappropriate anti- hypertensive therapy of elderly patients; this was done by means ofplacebo substitution for methyl- dopa, one ofthe drugs taken by all the participat- ing patients. Forty patients were recruited from a hospital outpatient clinic ...

  13. A new class of efficient 4-[(nitro substituted-phenyl ...

    Indian Academy of Sciences (India)

    A new class of efficient colorimetric chemosensors derived from 4-[(nitro substituted-phenyl)-hydrazonomethyl]-1-phenyl-1H-pyrazole-3-carboxylate have been synthesized and characterized. The synthesized receptors exhibit instant color change from yellow to dark purple along with significant bathochromicshifts when ...

  14. Tonemic Substitution in Ekwulobia Igbo: A Descriptive Account ...

    African Journals Online (AJOL)

    This paper presents an analysis of the tonal behavior of level tones in the Ekwulobia variety of Igbo. It gives a descriptive account of the peculiar tonal patterning of words in this lect. This unique tonal pattern is linked to insignificant and regular tonemic substitution realized especially on nouns and verbs in grammatical ...

  15. Placebo substitution for methyldopa in geriatric hypertensive patients

    African Journals Online (AJOL)

    The aim of this study was to obtain an objective evaluation of the possibly inappropriate antihypertensive therapy of elderly patients; this was done by means of placebo substitution for methyldopa, one of the drugs taken by all the participating patients. Forty patients were recruited from a hospital outpatient clinic and ...

  16. Elasticity of substitution and anti-dumping decisions

    DEFF Research Database (Denmark)

    Hansen, Jørgen Drud; Meinen, Philipp; Nielsen, Jørgen Ulff-Møller

    2014-01-01

    Motivated by a monopolistic competition model with market segmentation and international price discrimination, this paper analyzes whether there is an inverse relation between the elasticity of substitution and final ad valorem anti-dumping duties across products. We test this for 19 countries...

  17. Preparation, characterization and biological activity of C8-substituted cytokinins

    Czech Academy of Sciences Publication Activity Database

    Zahajská, Lenka; Nisler, Jaroslav; Voller, Jiří; Gucký, Tomáš; Pospíšil, Tomáš; Spíchal, Lukáš; Strnad, Miroslav

    2017-01-01

    Roč. 135, MAR (2017), s. 115-127 ISSN 0031-9422 Institutional support: RVO:61389030 Keywords : potential purine antagonists * arabidopsis-thaliana * nucleosides * derivatives * thidiazuron * specificity * receptors * kinetin * Organic synthesis * Cytokinin bioassay * AHK3 and CRE1/AHK4 bacterial receptor assay * C8-substituted cytokinin Subject RIV: CE - Biochemistry OBOR OECD: Organic chemistry Impact factor: 3.205, year: 2016

  18. 31 CFR 240.3 - Electronic checks and substitute checks.

    Science.gov (United States)

    2010-07-01

    ... using an electronic check, but this part does not create any right for the presenting bank to return the.... Any financial institution that creates a substitute check or electronic check shall prevent... destroyed, in a manner consistent with federal banking agency guidelines for safeguarding customer...

  19. Competing for Consciousness: Prolonged Mask Exposure Reduces Object Substitution Masking

    Science.gov (United States)

    Goodhew, Stephanie C.; Visser, Troy A. W.; Lipp, Ottmar V.; Dux, Paul E.

    2011-01-01

    In object substitution masking (OSM) a sparse, temporally trailing 4-dot mask impairs target identification, even though it has different contours from, and does not spatially overlap with the target. Here, we demonstrate a previously unknown characteristic of OSM: Observers show reduced masking at prolonged (e.g., 640 ms) relative to intermediate…

  20. Synthesis of new biphenyl-substituted quinoline derivatives ...

    Indian Academy of Sciences (India)

    corrosion inhibitors, preservatives and as solvents for resins and terpenes. Furthermore, these compounds find applications in transition metal catalysis for uniform polymerization and luminescence chemistry.8,9 Owing to this, the synthesis of substituted quinolines has been a subject of great focus in organic chemistry. ∗.

  1. effect of cassava flour processing methods and substitution level

    African Journals Online (AJOL)

    MASAMBA

    produce bread. This study was carried out to assess the effect of using two differently processed cassava flour (fermented and unfermented) and substitution level on proximate ... to improve the bread characteristics from different cassava processing methods and assessing ..... Tobago. Journal of Curriculum and Teaching.

  2. Thermal characteristics of pure and substituted gel grown Gd ...

    Indian Academy of Sciences (India)

    Unknown

    heptamolybdate crystals. It was thought worthwhile to investigate the thermal behaviour of these materials in greater detail as IR spectroscopy results suggest water of hydration present in the pure Gd-heptamolybdate only but not the ones substituted by barium. This paper reports the results of thermal characteristics of the ...

  3. Effect of increasing lanthanum substitution and the sintering ...

    Indian Academy of Sciences (India)

    Administrator

    Young's modulus of the microwave sintered samples (8.8–12.5 and 160–180 GPa) are higher than that for conventional sintered (8–10 and 135–155 GPa) samples. Keywords. Microwave sintering; La-substituted SBTi ceramics; mechanical properties. 1. Introduction. In recent years, bismuth layer-structured ferroelectrics.

  4. Effect of increasing lanthanum substitution and the sintering ...

    Indian Academy of Sciences (India)

    Compared with SBTi ceramics and other lanthanide-substituted compositions, the incorporation of La3+ results in clear improvement in properties for SBLT ( ∼ 0.75) with respect to the values of hardness and Young's modulus of the microwave sintered samples (8.8–12.5 and 160–180 GPa) are higher than that for ...

  5. The Synthesis of Substituted Piperazine-cholesterol Conjugates for ...

    African Journals Online (AJOL)

    NICO

    piperazines by way of a carbamate linker. An advantage of the strategy utilized was that it afforded the desired compounds in high yields. Moreover, the approach allowed for incorporation of functional diversity on the piperazine head group because of the significant variety of commercially available substituted piperazines.

  6. influence of the substitution on the electronic properties of perylene ...

    African Journals Online (AJOL)

    Preferred Customer

    -31+G*//B3LYP/6-31G** level. Substitution of the PDI with COOCF3 reduces the energies of both the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) with the only exception of PDI4 derivative.

  7. An extended gravity model with substitution applied to international trade

    NARCIS (Netherlands)

    Bikker, J.A.

    The traditional gravity model has been applied many times to international trade flows, especially in order to analyze trade creation and trade diversion. However, there are two fundamental objections to the model: it cannot describe substitutions between flows and it lacks a cogent theoretical

  8. Clinical review: impact of statin substitution policies on patient outcomes

    DEFF Research Database (Denmark)

    Atar, Dan; Carmena, Rafael; Clemmensen, Peter

    2009-01-01

    BACKGROUND: The increasing awareness of cost issues in health care has led to the increasing use of policy-driven substitution of branded for generic medications, particularly relative to statin treatment for cardiovascular diseases. While there are potential short-term health care savings, the c...

  9. Clinical review: impact of statin substitution policies on patient outcomes

    NARCIS (Netherlands)

    Atar, Dan; Carmena, Rafael; Clemmensen, Peter; K-Laflamme, Annik; Wassmann, Sven; Lansberg, Peter; Hobbs, Richard

    2009-01-01

    The increasing awareness of cost issues in health care has led to the increasing use of policy-driven substitution of branded for generic medications, particularly relative to statin treatment for cardiovascular diseases. While there are potential short-term health care savings, the consequences for

  10. Structural and spectroscopic investigation of lanthanum-substituted ...

    Indian Academy of Sciences (India)

    Administrator

    Si MAS NMR spectroscopies. The refinements of powder XRD patterns of the substituted compounds by the Rietveld method showed that the lanthanum occupied the two metal sites, i.e. (4f) and. (6h) sites into the apatite structure, with a clear preference for the (6h) sites. A progressive shift of the free oxygen O(4) towards ...

  11. Influence of higher sodium substitutions on magnetic entropy ...

    Indian Academy of Sciences (India)

    N SETHULAKSHMI1, I A AL OMARI2 and M R ANANTHARAMAN1,∗. 1Department of ... stitution of 0.6 are having the largest entropy change, and the entropy change increases with applied magnetic field for all compositions. The change in entropy also decreases with increase in substitution of sodium. A notable change.

  12. Nitration of Substituted Phenols by Different Efficient Heterogeneous ...

    African Journals Online (AJOL)

    Nitration of substituted phenols were carried out by the mixture of sodium nitrite and wet SiO2 (50% w/w) in the presence of four different efficient heterogeneous systems: 1) oxalic acid dihydrate (I), 2) sodium hydrogen sulphate (II), 3) aluminum hydrogen sulphate (III) and 4) silica sulphuric acid (IV) in CH2Cl2 at room ...

  13. SUBSTITUTION REACTIONS FOR THE DETOXIFICATION OF HAZARDOUS CHEMICALS

    Science.gov (United States)

    Chemical Treatment is one of several treatment techniques used for the remediation of toxic and hazardous chemicals. Chemical treatment in this report is defined as substitution of halogens by hydrogens for the conversion of halogenated organic toxicant into its native hydrocarb...

  14. Theoretical studies on proton transfer reaction of 3 (5)-substituted ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 126; Issue 1. Theoretical studies on proton transfer reaction of 3(5)-substituted pyrazoles ... Abstract. The inter and intra molecular proton transfer reactions of a series of pyrazole derivatives have been studied by using density functional theory (DFT) andMP2 methods ...

  15. Substitution reactions of [Pd (bipy)(malonate)] explored with a ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 128; Issue 8. Substitution reactions of [Pd(bipy)(malonate)] explored with a different set of ligands: Kinetic and mechanistic interpretation in aqueous medium and at pH 7.4. SUMON RAY PARNAJYOTI KARMAKAR ANIMESH CHATTOPADHYAY DEBABRATA NANDI ...

  16. Infrared absorption spectroscopic study of Nd substituted Zn–Mg ...

    Indian Academy of Sciences (India)

    Unknown

    dependent behaviour of force constant are attributed to the cation oxygen bond distances. The structural distortion in case of chromium substituted nickel ferrites was studied by Ghatage et al (1996) and the existence of fine structure is attributed to the Jahn-Teller effect. The IR spectra of Cd, Co, Mg, Ni, Zn, Cu etc containing ...

  17. Synthesis and characterization of new meso-substituted ...

    Indian Academy of Sciences (India)

    The synthesis and characterization of new meso-substituted unsymmetrical metalloporphyrins has been described. A new modified Adler method ... P Bandgar1 Pradip B Gujarathi1. Organic Chemistry Research Laboratory, School of Chemical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431 606 ...

  18. Synthesis of some substituted pyrazole derivatives as antiprotozoal ...

    African Journals Online (AJOL)

    Compounds incorporating a pyrazole moiety have attracted a great deal of research owing to its therapeutic utility of the templates as useful drug molecule scaffolding. We report the synthesis of Pyrazoles moiety substituted with anilines at the fifth position of the ring as anti-protozoal lead moiety. All the compounds were ...

  19. Synthesis of meta-substituted monodentate phosphinite ligands and ...

    Indian Academy of Sciences (India)

    To demonstrate the synthetic usefulness of 4a and 4b, these ligands were tested in the rhodium catalyzed hydroformylation of 1-octene. The diethylamine substituted ligand 4a was found to be highly active, whereas4bwas less reactive but revealed slightly better regioselectivity of 62% under optimized conditions.

  20. Synthesis and Antibacterial Activity of Some 2-Substituted ...

    African Journals Online (AJOL)

    2-Substituted tinidazole analogues were designed, synthesized and characterized. The synthesized compounds were tested for their antibacterial activity against Gram-positive (B. subtilis and S. aureus) and Gram-negative (E. coli (entero pathogen) and S. typhimurium) bacteria using agar well diffusion method.

  1. 12 CFR 229.53 - Substitute check indemnity.

    Science.gov (United States)

    2010-01-01

    ... expenses of representation) related to the substitute check. (2) Comparative negligence. (i) If a loss... negligence or failure to act in good faith, then the indemnity amount described in paragraph (b)(1) of this section shall be reduced in proportion to the amount of negligence or bad faith attributable to the...

  2. The synthesis of some unsaturated 4-substituted-g-lactones

    OpenAIRE

    SUREN HUSINEC; VLADIMIR SAVIC

    2000-01-01

    The synthesis of conjugated and nonconjugated unsaturated 4-substituted lactones of type 1 and 2 are described. The type 1 lactone was prepared by a two step procedure employing Bredereck's reagent. The type 2 lactone was synthesised by combining the Claisen-Ireland rearrangement and selenolactonisation.

  3. The synthesis of some unsaturated 4-substituted-g-lactones

    Directory of Open Access Journals (Sweden)

    SUREN HUSINEC

    2000-02-01

    Full Text Available The synthesis of conjugated and nonconjugated unsaturated 4-substituted lactones of type 1 and 2 are described. The type 1 lactone was prepared by a two step procedure employing Bredereck's reagent. The type 2 lactone was synthesised by combining the Claisen-Ireland rearrangement and selenolactonisation.

  4. 76 FR 8666 - Substitution in Case of Death of Claimant

    Science.gov (United States)

    2011-02-15

    ..., if any, is limited to the amount of the expense of last sickness and burial. This provision would... substituted on the basis of having borne the expense of last sickness and burial. Proposed paragraph (g)(4..., environmental, public health and safety, and other advantages; distributive impacts; and equity). The Executive...

  5. Microbial preparation of metal-substituted magnetite nanoparticles.

    Science.gov (United States)

    Moon, Ji-Won; Roh, Yul; Lauf, Robert J; Vali, Hojatollah; Yeary, Lucas W; Phelps, Tommy J

    2007-07-01

    A microbial process that exploits the ability of iron-reducing microorganisms to produce copious amounts of extra-cellular metal (M)-substituted magnetite nanoparticles using akaganeite and dopants of dissolved form has previously been reported. The objectives of this study were to develop methods for producing M-substituted magnetite nanoparticles with a high rate of metal substitution by biological processes and to identify factors affecting the production of nano-crystals. The thermophilic and psychrotolerant iron-reducing bacteria had the ability to form M-substituted magnetite nano-crystals (M(y)Fe(3-y)O(4)) from a doped precursor, mixed-M iron oxyhydroxide, (M(x)Fe(1-x)OOH, xmagnetite compared to the previous method, in which the precursor was pure akaganeite and the dopants were present as soluble metal salts. The mixed precursor method was especially advantageous in the case of toxic metals such as Cr and Ni. Also this new method increased the production rate and magnetic properties of the product, while improving crystallinity, size control and scalability.

  6. New substituted indene derivatives from bicyclic Baylis-Hillman acetate

    Directory of Open Access Journals (Sweden)

    Hassen AMRI

    2015-04-01

    Full Text Available A convenient protocol for the synthesis of highly functionalized indenes 4 has been developed. The coupling reaction of bicyclic Baylis-Hillman acetate 2 with nitroalkane salts in basic conditions led to the corresponding substituted indenes in good yields and high purity.

  7. Studies on meso-substituted free-base octamethoxyporphyrins

    Indian Academy of Sciences (India)

    Administrator

    Studies on meso-substituted free-base octamethoxyporphyrins. PRADEEPTA K PANDA and V KRISHNAN. Department of Inorganic and Physical Chemistry, Indian Institute of Science,. Bangalore 560 012, India. Octamethoxyporphyrin, with eight electron-donating methoxy groups, is the most electron-rich porphyrin and ...

  8. Equilibrium and kinetic studies on ligand substitution reactions of ...

    Indian Academy of Sciences (India)

    Unknown

    The rate constants and equilibrium constants are correlated to the hardness and softness of the ligands and the Co(III) of cobaloxime. Keywords. Alkylcobaloximes; ligand substitution reactions; hard and soft ligands. 1. Introduction. B12-based enzymes are among the few cofactors known till now contain a metal–carbon.

  9. 12 CFR 27.6 - Substitute monitoring program.

    Science.gov (United States)

    2010-01-01

    ... 12 Banks and Banking 1 2010-01-01 2010-01-01 false Substitute monitoring program. 27.6 Section 27.6 Banks and Banking COMPTROLLER OF THE CURRENCY, DEPARTMENT OF THE TREASURY FAIR HOUSING HOME LOAN... (12 CFR 202.13(d)). A bank collecting the data in compliance with § 27.3 of this part will be in...

  10. Substitution of lucerne hay by ammoniated wheat straw in growth ...

    African Journals Online (AJOL)

    Lucerne hay (LH) was substituted by urea-ammoniated wheat straw (AWS) in four lamb-growth diets, all containing 60% roughage. ... Die ekonomiese voordeel van die verplasing van 'n hoë kwaliteit ruvoer, soos LH, met'n goedkoper bron (AKS), moet opgeweeg word teen die laer DMI en GDT, sowel as die nadelige effek ...

  11. Substituting maize grain with barley grain in concentrates fed to ...

    African Journals Online (AJOL)

    The aim of the study was to determine the effect of substituting maize grain with barley grain in the diet of lactating Jersey cows grazing kikuyu-ryegrass pasture. Sixty Jersey cows were blocked in terms of number of days in milk, lactation number, milk yield and live weight and randomly assigned to one of five treatments (n ...

  12. Structure and magnetic properties of Zr–Mn substituted strontium ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 5. Structure and magnetic properties of Zr–Mn substituted strontium hexaferrite Sr(Zr,Mn) x Fe 12 − 2 x O 19 nanoparticles synthesized by sol–gel auto-combustion method. S ALAMOLHODA S M MIRKAZEMI Z GHIAMI M NIYAIFAR. Volume 39 Issue 5 ...

  13. Synthesis and microwave dielectric properties of Ca substituted ...

    Indian Academy of Sciences (India)

    Keywords. Patch antenna; theoretical density; phase; ceramics. Abstract. Microwave dielectric ceramics in Sr1-CaLa4Ti4.93Zr0.07O17 (0 ≤ ≤ 0.5) composition series were processed via a solid-state sintering rout. X-ray diffraction revealed single phase ceramics. Ca substitutions for Sr tuned f towards zero with ...

  14. Pregnancy Outcomes in Women With Aortic Valve Substitutes

    NARCIS (Netherlands)

    Heuvelman, Helena J.; Arabkhani, Bardia; Cornette, Jerome M. J.; Pieper, Petronella G.; Bogers, Ad J. J. C.; Takkenberg, Johanna J. M.; Roos-Hesselink, Jolien W.

    2013-01-01

    Young women who require aortic valve replacement need information on the potential cardiac and obstetric complications of pregnancy for the different valve substitutes available. We, therefore, assessed the pregnancy outcomes in women who had received an autograft, homograft, or mechanical valve in

  15. Synthesis of 1-Substituted-4-(Pyridin-4-yl)

    African Journals Online (AJOL)

    Purpose: To synthesize a new series of 1-substituted-4-(pyridin-4-yl) [1,2,4] triazolo [4,3-a]quinazolin- 5(4H)-ones and evaluate them for H1-antihistaminic activity with negligible side effects in guinea pigs. Methods: The synthesized compounds were characterized by Infrared spectroscopy (IR), proton nuclear magnetic ...

  16. Substitution af organiske opløsningsmidler med estre af

    DEFF Research Database (Denmark)

    Jacobsen, Thomas

    1999-01-01

    Substitution of organic solvents, which are harmful to both man and environment, is often possible. Cleaning of machines in offset printing may to a large extent be performed with products, which are neither volatile nor toxic to man and environment. Apparently this experience may be transferred ...

  17. The Effect of Solvent on the Ligand Substitution Reactions of ...

    African Journals Online (AJOL)

    NJD

    A2 and kobs as variables. At least six half-lives were monitored and fitted for each ligand concentration and these recorded traces were averaged to obtain the final kobs value. Since hydroxo- cobalamin is inert to substitution,1,5 values of kobs were converted into a pH-independent value, k, using Equation 2, where KCo is.

  18. Protein substitution to produce a processed cheese with high ...

    African Journals Online (AJOL)

    Multiple studies report the beneficial effects of BCAAs supplementation to improve plasma amino acids imbalance, several neurologic diseases, protein energy malnutrition, and subsequently the survival rate of cirrhotic patients. Methods: In the present study we used a protein substitution technique to synthesize a new ...

  19. Synthesis of substituted guanidines using Zn–Al hydrotalcite catalyst

    Indian Academy of Sciences (India)

    Abstract. Substituted guanidines were synthesized by the guanylation of amines with carbodiimides using. Zn–Al hydrotalcite (Zn-Al HT) catalyst. Zn–Al HT was prepared by co-precipitation method and charac- terized by X-ray powder diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman and.

  20. Placebo substitution for tnethyldopa in geriatric hypertensive patients

    African Journals Online (AJOL)

    A list of random numbers was used to allocate the subjects eligible for the study into two groups of 20 patients each. One group remained on their treatment, which included methyldopa, while an identical placebo tablet was substituted for methyldopa in the other group. The rest of the prescription remained unaltered.

  1. Bioefficacy And Economics Of Ronozyme™ P As A Substitute For ...

    African Journals Online (AJOL)

    The biological and economic efficiencies of Ronozyme ™ p as a substitute for bone meal in female Turkey poults was investigated. A total of eighty local female poults were brooded and fed commercial broiler starter diet containing 23% CP and 2800kcal/kg ME from day-old to four weeks of age. Sixty (60) female poults ...

  2. Substitution reactions of [Pd(bipy)(malonate)] explored with a ...

    Indian Academy of Sciences (India)

    −3. NaClO4. Table 1. Metal-Ligand ratios and structures of the product complexes. Metal:Ligand. Ligand. Structure ratio. Product complex. L1 Thioglycolic acid. HS ..... O. Scheme 1. Plausible mechanistic pathway. molecules substitute the bidentate malonate in a consec- utive fashion. Among the three sulphur donor ligands.

  3. Aligning protein sequence and analysing substitution pattern using ...

    Indian Academy of Sciences (India)

    Prakash

    [Xu H S, Ren W K, Liu X H and Li X Q 2010 Aligning protein sequence and analysing substitution pattern using a class-specific matrix; J. Biosci. .... 1996). It contains classified information of protein domains in SCOP and PDB-style files with coordinates for each. SCOP domain. In order to deal with the alignment problem.

  4. Function Substitution in Partial Differential Equations: Nonhomogeneous Boundary Conditions

    Directory of Open Access Journals (Sweden)

    T. V. Oblakova

    2017-01-01

    Full Text Available The paper considers a mixed initial-boundary value problem for a parabolic equation with nonhomogeneous boundary conditions. The classical approach to search for analytical solution of such problems in the first phase involves variable substitution, leading to a problem with homogeneous boundary conditions. Reference materials [1] give, as a rule, the simplest types of variable substitutions where new and old unknown functions differ by a term, linear in the spatial variable. The form of this additive term depends on the type of the boundary conditions, but is in no way related to the equation under consideration. Moreover, in the case of the second boundary-value problem, it is necessary to use a quadratic additive, since a linear substitution for this type of conditions may be unavailable. The courseware [2] - [4], usually, ends only with the first boundary-value problem generally formulated.The paper considers a substitution that takes into account, in principle, the form of a linear differential operator. Namely, as an additive term, it is proposed to use the parametrically time-dependent solution of the boundary value problem for an ordinary differential equation obtained from the original partial differential equation by the method of separation of the Fourier variables.The existence of the proposed substitution for boundary conditions of any type is proved by the example of a non-stationary heat-transfer equation with the heat exchange available with the surrounding medium. In this case, the additive term is a linear combination of hyperbolic functions. It is shown that, in addition to the "insensitivity" to the type of boundary conditions, the advantages of a new substitution in comparison with the traditional linear (or quadratic one include a much simpler structure of the solution obtained. Just the described approach allows us to obtain a solution with a clearly distinguished stationary component, in case a stationarity occurs, for

  5. [Anti-arrhythmic action of some amidinohydrazone substituted benzophenones. 1. Synthesis of new amidinohydrazone and N-phenylamidinohydrazone substituted benzophenones].

    Science.gov (United States)

    Richter, P H; Kasbohm, K; Besch, A; Hagen, A

    1992-10-01

    The title compounds are synthesized as a rule by condensation of substituted benzophenones and derivatives of aminoguanidine in the presence of up to 2.5 moles of an anorganic acid. They can be obtained alternatively via corresponding hydrazones, thiosemicarbazones or methylthiothiocarbonylhydrazones.

  6. Substitution Effects and Linear Free Energy Relationships During Reduction of 4- Benzoyl-n-(4-substituted Benzyl)pyridinium Cations

    Science.gov (United States)

    Leventis, Nicholas; Zhang, Guo-Hui; Rawashdeh, Abdel-Monem M.; Sotiriou-Leventis, Chariklia; Gray, Hugh R. (Technical Monitor)

    2003-01-01

    In analogy to 4-(para-substituted benzoyl)-N-methylpyridinium cations (1-X's), the title species (2-X's, -X = -OCH3, -CH3, -H, -Br, -COCH3, -NO2) undergo two reversible, well-separated (E(sub 1/2) greater than or equal to 650 mV) one-electron reductions. The effect of substitution on the reduction potentials of 2-X's is much weaker than the effect of the same substituents on 1-X's: the Hammett rho-values are 0.80 and 0.93 for the 1st- and 2nd-e reduction of 2-X's vs. 2.3 and 3.3 for the same reductions of 1-X's, respectively. Importantly, the nitro group of 2-NO2 undergoes reduction before the 2nd-e reduction of the 4-benzoylpyridinium system. These results suggest that the redox potentials of the 4-benzoylpyridinium system can be course-tuned via p-benzoyl substitution and fine-tuned via para-benzyl substitution. Introducing the recently derived substituent constant of the -NO2(sup)- group (sigma para-NO2(sup)- = -0.97) yields an excellent correlation for the 3rd-e reduction of 2- NO2 (corresponding to the reduction of the carbonyl group) with the 2nd-e reduction of the other 2-X's, and confirms the electron donating properties of -NO2(sup)-.

  7. Estimating intertemporal and intratemporal substitutions when both income and substitution effects are present: the role of durable goods

    Czech Academy of Sciences Publication Activity Database

    Pakoš, Michal

    2011-01-01

    Roč. 29, č. 3 (2011), s. 439-454 ISSN 0735-0015 Institutional research plan: CEZ:AV0Z70850503 Keywords : durable goods * intertemporal substitution * nonhomotheticity Subject RIV: AH - Economics Impact factor: 1.779, year: 2011

  8. Educating T-Shaped professionals to meet substitution challenges and developing business models for substitution and recycling

    Science.gov (United States)

    Arroyo, Ana; Mendibil Eguiluz, Javier; Sánchez Cupido, Laura

    2018-03-01

    One strategy to overcome the challenges related to critical raw materials (CRMs) is their substitution and recycling. However, the bright scientific idea, proof of concept or laboratory demonstration need to cross the valley of death in order to become stated as ‘a substitute’ instead of ‘a potential substitute’. Most PhD students and Post Docs specialize within a given thematic area; for example on specific materials or on substitution in a certain application. This specialization could limit the ability to generate innovations and profitable business models if there are not enough tools and skills to transform new knowledge and research results into an appealing value proposition towards customers and to a business opportunity for the current markets. The project proposes a framework for developing substitution and recycling related cross-sectorial skills and tools. These are applied for training business-related competences e.g. teamwork, management, communication, value proposition and business models design, especially within RTOs and industries. The proposed learning itinerary can radically improve the path from scientific proof of concept into innovation and lean start up or industrial market launch. The developed framework is tested by a pilot group having several topics within the areas of substitution and recycling of critical raw materials.

  9. Spectral properties of substituted coumarins in solution and polymer matrices.

    Science.gov (United States)

    Donovalová, Jana; Cigáň, Marek; Stankovičová, Henrieta; Gašpar, Jan; Danko, Martin; Gáplovský, Anton; Hrdlovič, Pavol

    2012-03-14

    The absorption and fluorescence spectra of substituted coumarins (2-oxo-2H-chromenes) were investigated in solvents and in polymer matrices. The substitutions involved were: (1) by groups with varying electron donating ability such as CH₃, OCH₃ and N(CH₃)₂, mainly, but not exclusively, in positions 7 and (2), by either CHO or 4-PhNHCONHN=CH- in position 3. While the spectra of non-substituted coumarin-3-carbaldehyde has absorptions at approximately 305 and 350 nm, substitution at position 7 leads to remarkable changes in the shape of the absorption spectrum and shifts the absorption to a longer wavelength. Similarly, the replacement of the formyl group with a semicarbazide group substantially influences the shape of the absorption spectrum, and coumarins which have only N(CH₃)₂ in position 7 experience small changes. These changes are associated with the increasing intramolecular charge transfer (ICT) character and increasing conjugation length of the chromophoric system, respectively, in the studied molecules. The fluorescence is almost negligible for derivatives which have H in this position. With increasing electron donating ability, and the possibility of a positive mesomeric (+M) effect of the substituent in position 7 of the coumarin moiety, the fluorescence increases, and this increase is most intense when N(CH₃)₂ substitutes in this position, for both 3-substituted derivatives. Spectral measurements of the studied coumarins in polymer matrices revealed that the absorption and fluorescence maxima lay within the maxima for solvents, and that coumarins yield more intense fluorescence in polymer matrices than when they are in solution. The quantum yield of derivatives which have a dimethylamino group in position 7 in polymer matrices approaches 1, and the fluorescence lifetime is within the range of 0.5-4 ns. The high quantum yield of 7-dimethylamino derivatives qualifies them as laser dyes which have k(F) higher than k(nr) in the given medium

  10. Spectral Properties of Substituted Coumarins in Solution and Polymer Matrices

    Directory of Open Access Journals (Sweden)

    Jana Donovalová

    2012-03-01

    Full Text Available The absorption and fluorescence spectra of substituted coumarins (2-oxo-2H-chromenes were investigated in solvents and in polymer matrices. The substitutions involved were: (1 by groups with varying electron donating ability such as CH3, OCH3 and N(CH32, mainly, but not exclusively, in positions 7 and (2, by either CHO or 4-PhNHCONHN=CH- in position 3. While the spectra of non-substituted coumarin-3-carbaldehyde has absorptions at approximately 305 and 350 nm, substitution at position 7 leads to remarkable changes in the shape of the absorption spectrum and shifts the absorption to a longer wavelength. Similarly, the replacement of the formyl group with a semicarbazide group substantially influences the shape of the absorption spectrum, and coumarins which have only N(CH32 in position 7 experience small changes. These changes are associated with the increasing intramolecular charge transfer (ICT character and increasing conjugation length of the chromophoric system, respectively, in the studied molecules. The fluorescence is almost negligible for derivatives which have H in this position. With increasing electron donating ability, and the possibility of a positive mesomeric (+M effect of the substituent in position 7 of the coumarin moiety, the fluorescence increases, and this increase is most intense when N(CH32 substitutes in this position, for both 3-substituted derivatives. Spectral measurements of the studied coumarins in polymer matrices revealed that the absorption and fluorescence maxima lay within the maxima for solvents, and that coumarins yield more intense fluorescence in polymer matrices than when they are in solution. The quantum yield of derivatives which have a dimethylamino group in position 7 in polymer matrices approaches 1, and the fluorescence lifetime is within the range of 0.5–4 ns. The high quantum yield of 7-dimethylamino derivatives qualifies them as laser dyes which have kF higher than knr in the given medium. This

  11. Stereotype threat and social function in opioid substitution therapy patients.

    Science.gov (United States)

    von Hippel, Courtney; Henry, Julie D; Terrett, Gill; Mercuri, Kimberly; McAlear, Karen; Rendell, Peter G

    2017-06-01

    People with a history of substance abuse are subject to widespread stigmatization. It seems likely that this societal disapproval will result in feelings of stereotype threat, or the belief that one is the target of demeaning stereotypes. If so, stereotype threat has the potential to contribute to functional difficulties including poor social outcomes. Eighty drug users on opioid substitution therapy and 84 demographically matched controls completed measures of mental health and social function. The opioid substitution therapy group were additionally asked to complete a measure that focused on their feelings of stereotype threat in relation to their drug use history. Bivariate correlations and hierarchical regression analyses were conducted to establish the magnitude and specificity of the relationship between stereotype threat and social functioning. Relative to controls, the opioid substitution therapy group reported higher levels of negative affect and schizotypy, and poorer social functioning, with all three of these indices significantly correlated with their feelings of stereotype threat. The results also showed that stereotype threat contributed significant unique variance to social functioning in the opioid substitution therapy group, even after taking into account other background, clinical, and mental health variables. Social functioning is an important aspect of recovery, yet these data indicate that people with a history of drug abuse who believe they are the target of stereotypical attitudes have poorer social functioning. This relationship holds after controlling for the impact of other variables on social functioning, including mental health. The theoretical and practical implications of these findings are discussed. Concerns about being stereotyped can shape the social experiences of opioid substitution therapy patients. Opioid substitution therapy patients who feel negatively stereotyped experience greater social function deficits, and this

  12. Multifaceted Material Substitution: The Case of NdFeB Magnets, 2010-2015

    Science.gov (United States)

    Smith, Braeton J.; Eggert, Roderick G.

    2016-07-01

    Substitution is an important response for material users when faced with disruption to the availability or price of an essential material. In economic terms, substitution refers to the ability of firms to alter their patterns of material use in response to exogenous market shocks. Substitution comes in different forms which vary from situation to situation. This paper uses expert opinion to identify the specific forms of substitution that occurred in permanent magnets, specifically neodymium-iron-boron magnets, following the significant increase in rare earth prices in 2010-2011. The paper provides a framework for understanding the multifaceted nature of substitution and assesses the relative importance of five different types of substitution. Technology-for-element, grade-for-grade, and system-for-system substitution appear to have been more important than element-for-element and magnet-for-magnet substitution. Cost pass-through and absorption were also important responses.

  13. Ortho-substituted triptycene-based diamines, monomers, and polymers, methods of making and uses thereof

    KAUST Repository

    Ghanem, Bader Saleh

    2017-04-13

    Described herein are ortho-dimethyl-substituted and tetramethyi-substituted triptycene-containing diamine monomers and microporous triptycene-based poiyimides and poiyamides, and methods of making the monomers and polymers.

  14. Steric Effects of Solvent Molecules on SN2 Substitution Dynamics.

    Science.gov (United States)

    Liu, Xu; Xie, Jing; Zhang, Jiaxu; Yang, Li; Hase, William L

    2017-04-20

    Influences of solvent molecules on S N 2 reaction dynamics of microsolvated F - (H 2 O) n with CH 3 I, for n = 0-3, are uncovered by direct chemical dynamics simulations. The direct substitution mechanism, which is important without microsolvation, is quenched dramatically upon increasing hydration. The water molecules tend to force reactive encounters to proceed through the prereaction collision complex leading to indirect reaction. In contrast to F - (H 2 O), reaction with higher hydrated ions shows a strong propensity for ion desolvation in the entrance channel, diminishing steric hindrance for nucleophilic attack. Thus, nucleophilic substitution avoids the potential energy barrier with all of the solvent molecules intact and instead occurs through the less solvated barrier, which is energetically unexpected because the former barrier has a lower energy. The work presented here reveals a trade-off between reaction energetics and steric effects, with the latter found to be crucial in understanding how hydration influences microsolvated S N 2 dynamics.

  15. Erfaringer med substitution af PVC ved renere teknologi og brancheaftaler

    DEFF Research Database (Denmark)

    Jørgensen, Ulrik

    Rapporten gennemgår den danske debat om PVC og de miljøpolitiske tiltag, der har været gennemført. Et survey i danske plastvirksomheder gennemført i projektet viser, at industrien er forberedt på at gennemføre en omfattende substitution af PVC, hvis der stilles politisk krav om det eller markedet...... efterspørger det. Til gengæld viser brancheaftalerne sig at være et svagt instrument og der peges på et behov for en opfølgning af de gode resultater, der er opnået med substitution af PVC i en række renere teknologi projekter, som har fået statslig støtte....

  16. Generic substitution: micro evidence from register data in Norway.

    Science.gov (United States)

    Dalen, Dag Morten; Furu, Kari; Locatelli, Marilena; Strøm, Steinar

    2011-02-01

    The importance of prices, doctor and patient characteristics, and market institutions for the likelihood of choosing generic drugs instead of the more expensive original brand-name version are examined. Using an extensive dataset extracted from The Norwegian Prescription Database containing all prescriptions dispensed to individuals in February 2004 and 2006 on 23 different drugs (chemical substances) in Norway, we find strong evidence for the importance of both doctor and patient characteristics for the choice probabilities. The price difference between brand and generic versions and insurance coverage both affect generic substitution. Moreover, controlling for the retail chain affiliation of the dispensing pharmacy, we find that pharmacies play an important role in promoting generic substitution. In markets with more recent entry of generic drugs, brand-name loyalty proves to be much stronger, giving less explanatory power to our demand model.

  17. Sudden polarization effect in methyl-substituted twisted polyenes

    International Nuclear Information System (INIS)

    Baraldi, I.; Bruni, M.C.; Momicchioli, F.; Ponterini, G.

    1981-01-01

    Sudden polarization effect was investigated for a special type of nonsymmetric biradical systems, i.e. terminally twisted polyenes methyl substituted at the rotated CH 2 group. Systems with 2 to 4 conjugated double bonds were studied. Dipole moments of S 0 , S 1 and S 2 states were calculated within the framework of the INDO approximations, by using a dual basis of SCF MOs (open shell and closed shell) and performing differently sized CIs (selected with reference to the basic 3 x 3 CI biradical description). The resulting excited-state polarization characteristics (size and suddenness) are discussed with reference to the previously studied unsubstituted polyenes. In this respect the most important point is that CH 3 substitution at the terminal twisted methylene markedly enhances the polarization size (approximately 2D). This indicates that small perturbations occurring at one radical site may cause unexpectedly large changes in charge distributions of excited biradicals. (author)

  18. Gold-catalyzed oxidation of substituted phenols by hydrogen peroxide

    KAUST Repository

    Cheneviere, Yohan

    2010-10-20

    Gold nanoparticles deposited on inorganic supports are efficient catalysts for the oxidation of various substituted phenols (2,6-di-tert-butyl phenol and 2,3,6-trimethyl phenol) with aqueous hydrogen peroxide. By contrast to more conventional catalysts such as Ti-containing mesoporous silicas, which convert phenols to the corresponding benzoquinones, gold nanoparticles are very selective to biaryl compounds (3,3′,5,5′-tetra-tert-butyl diphenoquinone and 2,2′,3,3′,5,5′-hexamethyl-4,4′- biphenol, respectively). Products yields and selectivities depend on the solvent used, the best results being obtained in methanol with yields >98%. Au offers the possibility to completely change the selectivity in the oxidation of substituted phenols and opens interesting perspectives in the clean synthesis of biaryl compounds for pharmaceutical applications. © 2010 Elsevier B.V. All rights reserved.

  19. Kinetic Description of Heterogeneous Catalytic Processes Using Adsorption Substitution Reactions

    Science.gov (United States)

    Stytsenko, V. D.

    2018-02-01

    Complex heterogeneous catalytic processes involving strongly chemisorbed particles (SCPs) are considered: syntheses of methanol, pyrocatechol, and diphenylamine and hydrogenation of CO and benzene. Nonstationary transformations of SCPs (CO and benzene) during continuous analysis of the gas phase are studied with mass spectrometric, flame ionization and thermal conductivity detectors. It is shown that the adsorption substitution reaction (ASR) proceeds before catalysis under typical conditions of these processes; in other words, the substitution reaction, rather than Langmuir adsorption equilibrium, determines the composition of reactive species on the catalyst surface. Consequently, ASRs and chemical transformations of SCPs must be considered for kinetic description of heterogeneous catalytic processes. It is shown that the ASRs allow us to describe these catalytic processes simply and adequately, and the obtained models can be used for the regulation and optimization of processes.

  20. Substituted 4-hydroxy-1,2,3-triazoles

    DEFF Research Database (Denmark)

    Pippione, Agnese C.; Dosio, Franco; Ducime, Alex

    2015-01-01

    Bioisosterism and scaffold hopping are two widely used approaches in medicinal chemistry for the purpose of lead optimization. The study highlights the physicochemical properties of the 4-hydroxy-1,2,3-triazole scaffold, a less investigated heterocyclic system. Synthetic strategies to obtain...... different N-substituted 4-hydroxy-1,2,3-triazole isomers are presented, and their role as possible isosteres of the carboxylic acid is discussed. The aim is to use this system to modulate the acidic moieties present in lead compounds and, at the same time, to regiodirect substituents in set directions......, through targeted substitution on the three nitrogen atoms of the triazole ring. Through this approach, compounds having enhanced binding affinity, will be sought. Two examples of bioisosteric applications of this moiety are presented. In the first example, a classical bioisosteric approach mimicking...

  1. Effects of metastability on hydrogen sorption in fluorine substituted hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Pinatel, E.R.; Corno, M.; Ugliengo, P.; Baricco, M., E-mail: marcello.baricco@unito.it

    2014-12-05

    Highlights: • Fluorine substitution in simple metal hydrides has been modelled. • The stability of the MH{sub (1−x)}F{sub x} solid solutions has been discussed. • Conditions for reversibility of sorption reactions have been suggested. - Abstract: In this work ab initio calculations and Calphad modelling have been coupled to describe the effect of fluorine substitution on the thermodynamics of hydrogenation–dehydrogenation in simple hydrides (NaH, AlH{sub 3} and CaH{sub 2}). These example systems have been used to discuss the conditions required for the formation of a stable hydride–fluoride solid solution necessary to obtain a reversible hydrogenation reaction.

  2. UV action spectroscopy of protonated PAH derivatives. Methyl substituted quinolines

    DEFF Research Database (Denmark)

    Klærke, Benedikte; Holm, Anne; Andersen, Lars Henrik

    2011-01-01

    Aims. We investigate the production of molecular photofragments upon UV excitation of PAH derivatives, relevant for the interstellar medium. Methods. The action absorption spectra of protonated gas-phase methyl-substituted quinolines (CH3−C9H7NH+) have been recorded in the 215–338 nm spectral range...... using the electrostatic storage ring ELISA, an electrospray ion source and 3 ns UV laser pulses. Results. It is shown that the absorption profile is both redshifted and broadened when moving the methyl group from the heterocycle containing nitrogen to the homoatomic ring. The absorption profiles...... the estimated IR relaxation time. Photophysical properties of both nitrogen containing and methyl-substituted PAHs are interesting in an astrophysical context in connection with identifying the aromatic component of the interstellar medium....

  3. Cement substitution by a combination of metakaolin and limestone

    Energy Technology Data Exchange (ETDEWEB)

    Antoni, M., E-mail: mathieu.antoni@epfl.ch [EPFL-STI-IMX-Laboratoires des Materiaux de Construction, Station12, CH-1015 Lausanne (Switzerland); Rossen, J. [EPFL-STI-IMX-Laboratoires des Materiaux de Construction, Station12, CH-1015 Lausanne (Switzerland); Martirena, F. [CIDEM-UCLV, Universidad Las Villas, Santa Clara (Cuba); Scrivener, K. [EPFL-STI-IMX-Laboratoires des Materiaux de Construction, Station12, CH-1015 Lausanne (Switzerland)

    2012-12-15

    This study investigates the coupled substitution of metakaolin and limestone in Portland cement (PC). The mechanical properties were studied in mortars and the microstructural development in pastes by X-ray diffraction, thermogravimetry analysis, mercury intrusion porosimetry and isothermal calorimetry. We show that 45% of substitution by 30% of metakaolin and 15% of limestone gives better mechanical properties at 7 and 28 days than the 100% PC reference. Our results show that calcium carbonate reacts with alumina from the metakaolin, forming supplementary AFm phases and stabilizing ettringite. Using simple mass balance calculations derived from thermogravimetry results, we also present the thermodynamic simulation for the system, which agrees fairly well with the experimental observations. It is shown that gypsum addition should be carefully balanced when using calcined clays because it considerably influences the early age strength by controlling the very rapid reaction of aluminates.

  4. Local structures around the substituted elements in mixed layered oxides.

    Science.gov (United States)

    Akama, Shota; Kobayashi, Wataru; Amaha, Kaoru; Niwa, Hideharu; Nitani, Hiroaki; Moritomo, Yutaka

    2017-03-02

    The chemical substitution of a transition metal (M) is an effective method to improve the functionality of a material, such as its electrochemical, magnetic, and dielectric properties. The substitution, however, causes local lattice distortion because the difference in the ionic radius (r) modifies the local interatomic distances. Here, we systematically investigated the local structures in the pure (x = 0.0) and mixed (x = 0.05 or 0.1) layered oxides, Na(M 1-x M' x )O 2 (M and M' are the majority and minority transition metals, respectively), by means of extended X-ray absorption fine structure (EXAFS) analysis. We found that the local interatomic distance (d M-O ) around the minority element approaches that around the majority element to reduces the local lattice distortion. We further found that the valence of the minority Mn changes so that its ionic radius approaches that of the majority M.

  5. On structural inelasticity of modal substitution in freight transport

    DEFF Research Database (Denmark)

    Rich, Jeppe; Kveiborg, Ole; Overgård, Christian Hansen

    2011-01-01

    At the European level there is an increasing focus on how freight transport can be moved from trucks on roads to more environmentally friendly modes such as rail and ship. A large proportion of the transport services between OD pairs, however, cannot be substituted since there is only one...... alternative available. The paper investigates the magnitude of this ‘‘structural inelasticity” of modal substitution in freight transport due to a sparser layout of rail and ship-based freight networks compared to road. In the analysis we use a recent Scandinavian freight demand model covering more than 800...... zones. We find that the structural inelasticity is very significant – in particular for transportation over less than 500 km. Moreover, the inelasticity varies greatly with commodity groups and between OD pairs, and it depends strongly on the port and rail infrastructure. The results suggest that pure...

  6. Navigation with a sensory substitution device in congenitally blind individuals.

    Science.gov (United States)

    Chebat, Daniel-Robert; Schneider, Fabien C; Kupers, Ron; Ptito, Maurice

    2011-05-11

    Vision allows for obstacle detection and avoidance. The compensatory mechanisms involved in maintaining these functions in blind people using their remaining intact senses are poorly understood. We investigated the ability of congenitally blind participants to detect and avoid obstacles using the tongue display unit, a sensory substitution device that uses the tongue as a portal to the brain. We found that congenitally blind were better than sighted control participants in detecting and avoiding obstacles using the tongue display unit. Obstacles size and avoidance strategy had a significant effect on performance: large obstacles were better detected than small ones and step-around obstacles were better avoided than step-over ones. These data extend our earlier findings that when using a sensory substitution device, blind participants outperform sighted controls not only in a virtual navigation task but also during effective navigation within a human-sized obstacle course.

  7. Tax Substitution and Accounting Firms: perceptions of the implementation process

    Directory of Open Access Journals (Sweden)

    Sergio Roberto da Silva

    2016-06-01

    Full Text Available The Accounting advisory services has been of great importance to the performance of Brazilian companies. The purpose of this research is to identify the experience that the accounting officer of external accounting advice obtained in the adoption of the ICMS tax substitution regime. The study sought to identify what were the main questions, which updates the actions of matter, the impact of the issue in accounting firms, if they had a work overload or not. The survey was conducted through multi case studies in a total of four cases of accounting firms. They were interviewed four managers / owners of accounting offices in the city of Guarulhos, Brazil. A research protocol applied to the four cases has been prepared. The result of the research was that accountants had difficulty with the systematic, calculating and filing of invoices where there was incidence of tax substitution.

  8. Substitution of Organic Solvents in Selected Industrial Cleaning Processes

    DEFF Research Database (Denmark)

    Jacobsen, Thomas; Rasmussen, Pia Brunn

    1997-01-01

    Volatile organic solvents (VOC)are becoming increasingly unwanted in industrial processes. Substitution of VOC with non-volatile, low-toxic compounds is a possibility to reduce VOC-use. It has been successfully demonstrated, that organic solvents used in cleaning processes in sheet offset printing...... can be replaced with monoesters of fatty acids from vegetable oils (VOFA). The paper describes the selection of other industrial cleaning or degreasing processes where VOC could be replaced by VOFA. Manual degreasing and cleaning processes in metal industry, maintenance and repair of vehicles......, and industrial coating processes are likely candidates for substitution of VOC with VOFA. Requirements to the resulting surfaces may, however, hinder the replacement. This is especially important when the surface has to be coated in a subsequent step....

  9. Ab initio studies on proton affinities of substituted furans

    International Nuclear Information System (INIS)

    Lee, Gab Yong; Lee, Hyun Mee

    1998-01-01

    The geometry of furan, relevant to the binding of bis-furan lexitropsin that contains this ring to the base pair of minor groove of DNA, is optimized by semiempirical (MNDO) and ab initio (Hartree-Fock) methods. The proton affinity and electronic structure are evaluated at the 6-31G and 6-31G level of theory for the optimized geometry. The proton affinities are also studied for various substituted furans with the electron donating and -withdrawing groups to estimate the substituent effect on the proton affinity of furans. It has been found that the electron-donating substituents increase the proton affinity of of furan, whereas the electron-withdrawing substituents decrease it. This result can be explained with atomic charge and electron density at oxygen of substituted furans

  10. Electric Power Distribution System Model Simplification Using Segment Substitution

    Energy Technology Data Exchange (ETDEWEB)

    Reiman, Andrew P.; McDermott, Thomas E.; Akcakaya, Murat; Reed, Gregory F.

    2018-05-01

    Quasi-static time-series (QSTS) simulation is used to simulate the behavior of distribution systems over long periods of time (typically hours to years). The technique involves repeatedly solving the load-flow problem for a distribution system model and is useful for distributed energy resource (DER) planning. When a QSTS simulation has a small time step and a long duration, the computational burden of the simulation can be a barrier to integration into utility workflows. One way to relieve the computational burden is to simplify the system model. The segment substitution method of simplifying distribution system models introduced in this paper offers model bus reduction of up to 98% with a simplification error as low as 0.2% (0.002 pu voltage). In contrast to existing methods of distribution system model simplification, which rely on topological inspection and linearization, the segment substitution method uses black-box segment data and an assumed simplified topology.

  11. Navigation with a sensory substitution device in congenitally blind individuals

    DEFF Research Database (Denmark)

    Chebat, Daniel-Robert; Schneider, Fabien C; Kupers, Ron

    2011-01-01

    Vision allows for obstacle detection and avoidance. The compensatory mechanisms involved in maintaining these functions in blind people using their remaining intact senses are poorly understood. We investigated the ability of congenitally blind participants to detect and avoid obstacles using...... the tongue display unit, a sensory substitution device that uses the tongue as a portal to the brain. We found that congenitally blind were better than sighted control participants in detecting and avoiding obstacles using the tongue display unit. Obstacles size and avoidance strategy had a significant...... effect on performance: large obstacles were better detected than small ones and step-around obstacles were better avoided than step-over ones. These data extend our earlier findings that when using a sensory substitution device, blind participants outperform sighted controls not only in a virtual...

  12. Substitutionality of Ge atoms in ion implanted AlSb

    International Nuclear Information System (INIS)

    Yu, K.M.; Moll, A.J.; Chan, N.; Walukiewicz, W.; Becla, P.

    1995-01-01

    The substitution of Ge atoms into ion implanted AlSb is investigated by extended x-ray absorption fine structure spectroscopy. Our results reveal that in the as-implanted material, the implanted Ge atoms are equally distributed between two specific sites, one surrounded by Al atoms and the other surrounded by Sb atoms. After annealing at 750 degree C for 5 s, the coordination number of the Ge atoms increases from ∼3 to ∼4 indicating solid phase regrowth of the implantation induced amorphous surface layer. Moreover, in the annealed AlSb, the substitution of Ge atoms into the Al sublattice dominates with an estimated Ge Al :[Ge Sb ]∼0.8:0.2. These results suggest that Ge atoms act preferentially as donor species in AlSb

  13. Antibactericidal effect of some substituted-1, 2, 4-triazole derivatives

    International Nuclear Information System (INIS)

    Singh, R.J.

    2011-01-01

    The syntheses of a series of some substituted-1, 2, 4-triazole derivatives are described. The reaction of sodium salt of a-sulphonated of stearic acid hydrazide (1) with carbon disulphide in alcoholic KOH yielded the corresponding sodium 1-(4-amino-5-mercapto-4H-[1, 2, 4]-triazol-3yl)-heptadecane-1-sulfonate (2). The reaction of compound (2) with urea, chloroacetyl chloride, chloroacetaldehyde and phenacyl bromides yielded the substituted 1, 2, 4-triazole derivatives (3), (4), (5) and (6) respectively. All the synthesized compounds were characterized by IR, PMR, Mass spectral data and elemental analyses. All newly synthesized compounds have been assayed for their antibacterial activities against S. aureus, E. coli, B. subtilis and P. aeruginosa. (author)

  14. Current-voltage characteristics of carbon nanotubes with substitutional nitrogen

    DEFF Research Database (Denmark)

    Kaun, C.C.; Larade, B.; Mehrez, H.

    2002-01-01

    We report ab initio analysis of current-voltage (I-V) characteristics of carbon nanotubes with nitrogen substitution doping. For zigzag semiconducting tubes, doping with a single N impurity increases current flow and, for small radii tubes, narrows the current gap. Doping a N impurity per nanotube...... unit cell generates a metallic transport behavior. Nonlinear I-V characteristics set in at high bias and a negative differential resistance region is observed for the doped tubes. These behaviors can be well understood from the alignment/mis-alignment of the current carrying bands in the nanotube leads...... due to the applied bias voltage. For a armchair metallic nanotube, a reduction of current is observed with substitutional doping due to elastic backscattering by the impurity....

  15. Credit counseling: a substitute for consumer financial literacy?

    OpenAIRE

    Disney, Richard; Gathergood, John; Weber, Jörg

    2015-01-01

    Is financial literacy a substitute or complement for financial advice? In this paper we analyze the decision by consumers to seek financial advice in the form of credit counseling concerning their credit and debt. Credit counseling is an important component of the consumer credit sector for consumers facing debt problems. We combine instrumental variable approaches to account for the endogeneity of an individual’s financial situation to financial literacy, and the endogeneity of financial lit...

  16. Structural characterization of Mg substituted on A / B sites in ...

    Indian Academy of Sciences (India)

    Manojit De

    2017-06-19

    Jun 19, 2017 ... In the present paper, we are reporting the synthesis of pure nickel and magnesium ferrite [NiFe2O4,. MgFe2O4] and magnesium-substituted nickel ferrite (Ni1−xMg x/y. Fe2−yO4 .... Grants Commission, New Delhi, India, for financial assistance through MRP (F. No. 41 954/2012(SR)). MD is thankful to UGC ...

  17. Occurrence of aflatoxins in oilseeds providing cocoa-butter substitutes.

    Science.gov (United States)

    Kershaw, S J

    1982-01-01

    Four oilseeds providing cocoa-butter substitutes--shea, pentadecima, illipe, and salseed--when tested as substrates for aflatoxin production by two strains of Aspergillus parasiticus, gave varying levels of aflatoxin. Aflatoxins were found at low levels occurring naturally in moldy shea-nuts, but none of 21 commercial shea-nut samples contained greater than 20 micrograms of aflatoxin B1 per kg. PMID:6808919

  18. Tobacco Product Demand, Cigarette Taxes, and Market Substitution

    OpenAIRE

    Da Pra, Michelle; Arnade, Carlos Anthony

    2009-01-01

    This paper presents a model of estimated demand for four tobacco products: cigarettes, cigars, chewing tobacco, and smoking tobacco products. Own elasticities and cross-price elasticities are used to obtain insights into the effectiveness and implications of new policy measures. Of particular interest is whether substitution of various tobacco products varies by market outlet. Several variations of the tobacco product outlet-choice model were estimated using iterative SUR. Four separate produ...

  19. Differentiation theory : intersensory substitution and the use of the sonicguide

    OpenAIRE

    Aitken, Stuart

    1981-01-01

    This thesis investigates the possibilities and parameters of intersensory substitution - the provision through one sense of information normally provided through another sense. An artificial ultrasonic echo-location device, providing, through sound, information usually provided through sight, was used. A series of interlinked cross-sectional and longitudinal studies was run, using both blind and simulated blind subjects of a range of ages. Infants, pre-school children,...

  20. The effect of cobalt substitution on magnetic hardening of magnetite

    Energy Technology Data Exchange (ETDEWEB)

    Mozaffari, M., E-mail: mozafari@sci.ui.ac.ir [Department of Physics, Faculty of Science, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of); Hadadian, Y. [Physics Department, Razi University, Taghebostan, Kermanshah (Iran, Islamic Republic of); Aftabi, A. [Department of Physics, University of Kurdistan, Sanandaj 66177-15175 (Iran, Islamic Republic of); Oveisy Moakhar, M. [Physics Department, Razi University, Taghebostan, Kermanshah (Iran, Islamic Republic of)

    2014-03-15

    In this work cobalt-substituted magnetite (Co{sub x}Fe{sub 1−x}Fe{sub 2}O{sub 4}, x=0, 0.25, 0.50 and 0.75) nanoparticles were synthesized by coprecipitation method and their structural and magnetic properties were investigated. X-ray diffraction was carried out and the results show that all of the samples have single phase spinel structure. Microstructure of the samples was studied using a field emission scanning electron microscope and the results show that particle sizes of the prepared nanoparticles were uniform and in the 50–55 nm range. Room temperature magnetic properties of the nanoparticles were measured by an alternating gradient force magnetometer and the results revealed that substituting cobalt for iron in magnetite structure, changes the magnetite from a soft magnetic material to a hard one. So that coercivity changes from 0 (a superparamagnetic state) to 337 Oe (a hard magnetic material), which is a remarkable change. Curie temperatures of the samples were determined by recording their susceptibility-temperature (χ–T) curves and the results show that by increasing cobalt content, Curie temperature of the samples also increases. Also χ–T curves of the samples were recorded from above Curie temperature to room temperature (first cooling), while the curves in the second heating and second cooling have the same behaviour as the first cooling curve. The results depict that all samples have different behaviour in the first cooling and in the first heating processes. This shows remarkable changes of the cation distribution in the course of first heating. - Highlights: • It is possible to get Co substituted magnetite nanoparticles by coprecipitation method. • Prepared nanoparticles have different cation distribution in comparison with that of bulk counterparts. • Co substitution increases coercivity of the magnetite.