Sample records for hydrated iron oxide

  1. Cesium adsorption in hydrated iron oxide particles suspensions: an NMR study.

    PubMed

    Gossuin, Yves; Colet, Jean-Marie; Roch, Alain; Muller, Robert N; Gillis, Pierre

    2002-07-01

    137Cs is an important component of nuclear waste which may pollute water. Its migration in natural environments is slowed down by adsorption on minerals. Cesium adsorption on akaganeite (beta-FeOOH) particles, dextran-coated ferrihydrite (5 Fe(2)O(3)-9H(2)O) particles, and ferritin in aqueous solutions is studied with (133)Cs nuclear magnetic resonance measurements. The longitudinal relaxation time (T(1)) of (133)Cs in the presence of such magnetic particles depends on whether the ions bind to the particle or not. T(1) of (133)Cs ions in aqueous solutions containing the same amount of magnetized particles will not depend on cesium concentration if relaxation is governed by diffusion (when cesium is not able to bind), but it will depend on cesium concentration if exchange governs relaxation (when cesium is able to bind). The method is successfully tested using TEMPO, a nitroxide stable free radical whose relaxation is due to diffusion. (133)Cs relaxation in solutions of ferritin, akaganeite, and dextran-coated ferrihydrite particles is found to result from a cationic exchange of cesium ions between particles surface and bulk ions, owing to adsorption. The effect of pH on (133)Cs relaxation in solutions of the particles is consistent with the adsorption properties of cations on hydrated iron oxides. PMID:12202142

  2. Amphorous hydrated Fe(III) sulfate: metastable product and bio-geochemical marker of iron oxidizing thiobacilli

    NASA Astrophysics Data System (ADS)

    Lazaroff, Norman; Jollie, John; Dugan, Patrick R.

    1998-07-01

    Chemolithotrophic iron oxidation by Thiobacillus ferrooxidans and other iron oxidizing thiobacilli produce an Fe(III) sulfato complex that polymerizes as x-ray amorphous filaments approximately 40 nm in diameter. The precursor complex in solutionis seen by ATR-FTIR spectroscopy to have a sulfate spectrum resembling the v(subscript 3) and v(subscript 1) vibrational modes of the precipitated polymer. Chemically similar precipitates prepared by oxidation of acid ferrous sulfate with hydrogen peroxide have a different micromorphology, higher iron/sulfur ratio and acid solubility than the bacterial product. They possess coalescing globular microstructures composed of compacted micro-fibrils. Scanning electron microscopy and diffuse reflectance FTIR show the formation of iron polymer on the surface of immobilized cells of T. ferrooxidans, oxidizing iron during the corrosion of steel. Although spatially separated form the steel coupons by a membrane filter, the cell walls become covered with tufts of amorphous hydrated Fe(III) sulfate. The metastable polymer is converted to crystalline goethite, lepidocrocite, and magnetite in that order, as the pH rises due to proton reduction at cathodic sites on the steel. The instability of the iron polymer to changes in pH is also evidenced by the loss of sulfate when washed with lithium hydroxide solution at pH 8. Under those conditions there is little change in micromorphology, but restoration of sulfate with sulfuric acid at pH 2.5, fails to re-establish the original chemical structure. Adding sulfate salts of appropriate cations to solutions of the Fe(III) sulfato complex or suspensions of its precipitated polymer in dilute sulfuric acid, result in dissociation of the metastable complex followed by crystallization of ferric ions and sulfate in jarosites. Jarosites and other derivatives of iron precipitation by iron oxidizing thiobacilli, form conspicuous deposits in areas of natural pyrite leaching. The role of iron oxidizing thiobacilli in pyrite leaching, biohydrometallurgy, acid mine drainage, and the cycle of iron and sulfur in nature, has been studied for nearly 50 years. The manifestation of those activities, so widespread on Earth, can be a clue for seeking evidence of life elsewhere.

  3. Leaching of oxidic zinc materials with chlorine and chlorine hydrate

    NASA Astrophysics Data System (ADS)

    Thomas, B. K.; Fray, D. J.

    1981-06-01

    Low grade zinc ores and residues were leached in chlorine water and chlorine hydrate water mixtures. It was found that the rate of leaching Adrar ore and Electric Arc Furnace dust obeyed a shrinking core diffusion model, whereas, the rate of leaching of Turkish ore appeared to be controlled by a surface reaction. In all cases, lead leached with the zinc but the iron oxides remained virtually undissolved.

  4. Aqueous precursors for electrochromic tungsten oxide hydrates

    Microsoft Academic Search

    J. Livage; G. Guzman

    1996-01-01

    Tungsten oxide hydrates WO3 · nH2O are formed upon the acidification of tungstate aqueous solutions. Different amorphous or crystalline phases can be obtained depending on the experimental conditions (pH, concentration, temperature). The chemical mechanisms for the formation of these hydrates are discussed and the electrochromic properties of thin films deposited from these solutions are described. Hydrogen peroxide H2O2 reacts with

  5. 21 CFR 73.3125 - Iron oxides.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 2013-04-01 false Iron oxides. 73.3125 Section 73.3125...CERTIFICATION Medical Devices § 73.3125 Iron oxides. (a) Identity and specifications. The color additive iron oxides (CAS Reg. No....

  6. 21 CFR 73.3125 - Iron oxides.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 2014-04-01 false Iron oxides. 73.3125 Section 73.3125...CERTIFICATION Medical Devices § 73.3125 Iron oxides. (a) Identity and specifications. The color additive iron oxides (CAS Reg. No....

  7. 21 CFR 73.3125 - Iron oxides.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 2012-04-01 false Iron oxides. 73.3125 Section 73.3125...CERTIFICATION Medical Devices § 73.3125 Iron oxides. (a) Identity and specifications. The color additive iron oxides (CAS Reg. No....

  8. 21 CFR 73.3125 - Iron oxides.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2010-04-01 false Iron oxides. 73.3125 Section 73.3125...CERTIFICATION Medical Devices § 73.3125 Iron oxides. (a) Identity and specifications. The color additive iron oxides (CAS Reg. No....

  9. Iron Oxide Based High Temperature Desulfurization Sorbent

    Microsoft Academic Search

    Ju Shangguan; Pengfei Hou; Yongjun Zhu; Litong Liang; Fang Shen; Huiling Fan; Maoqian Miao

    2009-01-01

    Iron oxide sorbent is used as high temperature desulfurization sorbent due to high sulfur capacity, easy regeneration and recovery elemental sulfur. In this paper, the iron oxide based high-temperature sorbent was obtained by mixing iron oxide with calcium oxide, extrudating and calcinating. The sulfidation, reduction and regeneration performance for the prepared iron oxide based desulfurization sorbent were conducted. The phases

  10. Iron biomineralization by anaerobic neutrophilic iron-oxidizing bacteria

    Microsoft Academic Search

    Jennyfer Miot; Karim Benzerara; Guillaume Morin; Andreas Kappler; Sylvain Bernard; Martin Obst; Céline Férard; Fériel Skouri-Panet; Jean-Michel Guigner; Nicole Posth; Matthieu Galvez; Gordon E. Brown; François Guyot

    2009-01-01

    Minerals formed by bio-oxidation of ferrous iron (Fe(II)) at neutral pH, their association with bacterial ultrastructures as well as their impact on the metabolism of iron-oxidizing bacteria remain poorly understood. Here, we investigated iron biomineralization by the anaerobic nitrate-dependent iron-oxidizing bacterium Acidovorax sp. strain BoFeN1 in the presence of dissolved Fe(II) using electron microscopy and Scanning Transmission X-ray Microscopy (STXM).

  11. Picqu et al Mechanical behaviour of iron oxide scale Mechanical behaviour of iron oxide scale

    E-print Network

    Paris-Sud XI, Université de

    of thick, brittle layers on metal substrates. Application is to the iron oxide behaviour during hot rolling or less thick iron oxide layer, hot rolling indeed consists in co-deforming a ceramic coating on a metalPicqué et al Mechanical behaviour of iron oxide scale 1 Mechanical behaviour of iron oxide scale

  12. Iron, Oxidative Stress and Gestational Diabetes

    PubMed Central

    Zhuang, Taifeng; Han, Huijun; Yang, Zhenyu

    2014-01-01

    Both iron deficiency and hyperglycemia are highly prevalent globally for pregnant women. Iron supplementation is recommended during pregnancy to control iron deficiency. The purposes of the review are to assess the oxidative effects of iron supplementation and the potential relationship between iron nutrition and gestational diabetes. High doses of iron (~relative to 60 mg or more daily for adult humans) can induce lipid peroxidation in vitro and in animal studies. Pharmaceutical doses of iron supplements (e.g., 10× RDA or more for oral supplements or direct iron supplementation via injection or addition to the cell culture medium) for a short or long duration will induce DNA damage. Higher heme-iron intake or iron status measured by various biomarkers, especially serum ferritin, might contribute to greater risk of gestational diabetes, which may be mediated by iron oxidative stress though lipid oxidation and/or DNA damage. However, information is lacking about the effect of low dose iron supplementation (?60 mg daily) on lipid peroxidation, DNA damage and gestational diabetes. Randomized trials of low-dose iron supplementation (?60 mg daily) for pregnant women are warranted to test the relationship between iron oxidative stress and insulin resistance/gestational diabetes, especially for iron-replete women. PMID:25255832

  13. Extracellular Iron Biomineralization by Photoautotrophic Iron-Oxidizing Bacteria

    Microsoft Academic Search

    Jennyfer Miot; Karim Benzerara; Martin Obst; Andreas Kappler; Florian Hegler; Sebastian Schadler; Camille Bouchez; Francois Guyot; Guillaume Morin

    2009-01-01

    Iron oxidation at neutral pH by the phototrophic anaerobic iron-oxidizing bacterium Rhodobacter sp. strain SW2 leads to the formation of iron-rich minerals. These minerals consist mainly of nano-goethite (-FeOOH), which precipitates exclusively outside cells, mostly on polymer fibers emerging from the cells. Scanning transmission X-ray microscopy analyses performed at the C K-edge suggest that these fibers are composed of a

  14. Iron Homeostasis, Oxidative Stress, and DNA Damage

    Microsoft Academic Search

    Rogerio Meneghini

    1997-01-01

    Cellular DNA damage under prooxidant conditions has been shown to be mediated by iron. In fact, iron is an important element in the establishment of a prooxidant status in the cell. It is discussed that there exists a mutual dependence between iron metabolism and oxidative stress. Changes in the former by means of genetic manipulation bring about modification in the

  15. Indium Sorption to Iron Oxides

    NASA Astrophysics Data System (ADS)

    White, S. J.; Sacco, S. A.; Hemond, H.; Hussain, F. A.; Runkel, R. L.; Walton-Day, K. E.; Kimball, B. A.; Shine, J. P.

    2014-12-01

    Indium is an increasingly important metal in semiconductors and electronics, and its use is growing rapidly as a semiconductive coating (as indium tin oxide) for liquid crystal displays (LCDs) and flat panel displays. It also has uses in important energy technologies such as light emitting diodes (LEDs) and photovoltaic cells. Despite its rapid increase in use, very little is known about the environmental behavior of indium, and concerns are being raised over the potential health effects of this emerging metal contaminant. One source of indium to the environment is acid mine drainage from the mining of lead, zinc, and copper sulfides. In our previous studies of a stream in Colorado influenced by acid mine drainage from lead and zinc mining activities, indium concentrations were found to be 10,000 times those found in uncontaminated rivers. However, the speciation and mobility of indium could not be reliably modeled because sorption constants to environmental sorbents have not been determined. In this study, we generate sorption constants for indium to ferrihydrite in the laboratory over a range of pHs, sorbent to sorbate ratios, and ionic strengths. Ferrihydrite is one of the most important sorbents in natural systems, and sorption to amorphous iron oxides such as ferrihydrite is thought to be one of the main removal mechanisms of metals from the dissolved phase in aqueous environments. Because of its relatively low solubility, we also find that indium hydroxide precipitation can dominate indium's partitioning at micromolar concentrations of indium. This precipitation may be important in describing indium's behavior in our study stream in Colorado, where modeling sorption to iron-oxides does not explain the complete removal of indium from the dissolved phase when the pH of the system is artificially raised to above 8. This study contributes much-needed data about indium's aqueous behavior, in order to better understand its fate, transport, and impacts in the environment.

  16. Iron-mediated oxidative stress in erythrocytes.

    PubMed Central

    Rice-Evans, C; Baysal, E

    1987-01-01

    Erythrocytes subjected extracellularly to iron-mediated oxidant stress undergo haemoglobin oxidation and membrane damage, which can be modulated by maintaining the energy requirements of the cells. The results presented here suggest that a balance exists between the oxidation state of the haemoglobin and the oxidative deterioration of the membrane lipids, which is dependent on the metabolic state of the erythrocytes. These findings have important implications for thalassaemic erythrocytes that may be exposed to excess plasma iron levels, in which excessive membrane-bound iron in the form of haemichromes is a characteristic feature and in which cellular ATP levels are lowered. Images Fig. 1. Fig. 3. PMID:3663112

  17. Facile and Sustainable Synthesis of Shaped Iron Oxide Nanoparticles: Effect of Iron Precursor Salts on the Shapes of Iron Oxides

    NASA Astrophysics Data System (ADS)

    Sayed, Farheen N.; Polshettiwar, Vivek

    2015-05-01

    A facile and sustainable protocol for synthesis of six different shaped iron oxides is developed. Notably, all the six shapes of iron oxides can be synthesised using exactly same synthetic protocol, by simply changing the precursor iron salts. Several of the synthesised shapes are not reported before. This novel protocol is relatively easy to implement and could contribute to overcome the challenge of obtaining various shaped iron oxides in economical and sustainable manner.

  18. Ferrous iron oxidation by anoxygenic phototrophic bacteria

    Microsoft Academic Search

    Friedrich Widdel; Sylvia Schnell; Silke Heising; Armin Ehrenreich; Bernhard Assmus; Bernhard Schink

    1993-01-01

    NATURAL oxidation of ferrous to ferric iron by bacteria such as Thiobacillus ferrooxidans or Gallionella ferruginea1, or by chemical oxidation2,3 has previously been thought always to involve molecular oxygen as the electron acceptor. Anoxic photochemical reactions4-6 or a photobiological process involving two photosystems7-9 have also been discussed as mechanisms of ferrous iron oxidation. The knowledge of such processes has implications

  19. Extracellular Iron Biomineralization by Photoautotrophic Iron-Oxidizing Bacteria ? †

    PubMed Central

    Miot, Jennyfer; Benzerara, Karim; Obst, Martin; Kappler, Andreas; Hegler, Florian; Schädler, Sebastian; Bouchez, Camille; Guyot, François; Morin, Guillaume

    2009-01-01

    Iron oxidation at neutral pH by the phototrophic anaerobic iron-oxidizing bacterium Rhodobacter sp. strain SW2 leads to the formation of iron-rich minerals. These minerals consist mainly of nano-goethite (?-FeOOH), which precipitates exclusively outside cells, mostly on polymer fibers emerging from the cells. Scanning transmission X-ray microscopy analyses performed at the C K-edge suggest that these fibers are composed of a mixture of lipids and polysaccharides or of lipopolysaccharides. The iron and the organic carbon contents of these fibers are linearly correlated at the 25-nm scale, which in addition to their texture suggests that these fibers act as a template for mineral precipitation, followed by limited crystal growth. Moreover, we evidence a gradient of the iron oxidation state along the mineralized fibers at the submicrometer scale. Fe minerals on these fibers contain a higher proportion of Fe(III) at cell contact, and the proportion of Fe(II) increases at a distance from the cells. All together, these results demonstrate the primordial role of organic polymers in iron biomineralization and provide first evidence for the existence of a redox gradient around these nonencrusting, Fe-oxidizing bacteria. PMID:19592528

  20. Extracellular iron biomineralization by photoautotrophic iron-oxidizing bacteria.

    PubMed

    Miot, Jennyfer; Benzerara, Karim; Obst, Martin; Kappler, Andreas; Hegler, Florian; Schädler, Sebastian; Bouchez, Camille; Guyot, François; Morin, Guillaume

    2009-09-01

    Iron oxidation at neutral pH by the phototrophic anaerobic iron-oxidizing bacterium Rhodobacter sp. strain SW2 leads to the formation of iron-rich minerals. These minerals consist mainly of nano-goethite (alpha-FeOOH), which precipitates exclusively outside cells, mostly on polymer fibers emerging from the cells. Scanning transmission X-ray microscopy analyses performed at the C K-edge suggest that these fibers are composed of a mixture of lipids and polysaccharides or of lipopolysaccharides. The iron and the organic carbon contents of these fibers are linearly correlated at the 25-nm scale, which in addition to their texture suggests that these fibers act as a template for mineral precipitation, followed by limited crystal growth. Moreover, we evidence a gradient of the iron oxidation state along the mineralized fibers at the submicrometer scale. Fe minerals on these fibers contain a higher proportion of Fe(III) at cell contact, and the proportion of Fe(II) increases at a distance from the cells. All together, these results demonstrate the primordial role of organic polymers in iron biomineralization and provide first evidence for the existence of a redox gradient around these nonencrusting, Fe-oxidizing bacteria. PMID:19592528

  1. Seed-mediated synthesis of iron oxide and gold/iron oxide nanoparticles.

    PubMed

    Nguyen, Dung The; Park, Dong-Wha; Kim, Kyo-Seon

    2011-08-01

    In this study, we prepared magnetic iron oxide and gold/iron oxide nanoparticles (NPs) and characterized their morphologies and properties by XRD, TEM, EDX, VSM and UV-vis measurements. The magnetite iron oxide NPs of 10 nm were synthesized by coprecipitation of Fe2+ and Fe+3 in the solution of NH4OH and then they were used as seed particles for the subsequent growth to prepare the magnetite NPs of different particle sizes and also to prepare gold/iron oxide composite NPs. All those magnetite NPs are superparamagnetic and the gold/iron oxide composite NPs combine the optical and magnetic properties, which are contributed by gold and iron oxide components, respectively. PMID:22103160

  2. Coupled modeling of gas hydrate formation and anaerobic methane oxidation in near-surface sediments at Hydrate Ridge

    NASA Astrophysics Data System (ADS)

    Haeckel, M.; Rickert, D.; Suess, E.

    2001-12-01

    A comprehensive one-dimensional transport-reaction model (C. CANDI) was modified to investigate the formation of near-surface methane gas hydrates through ascending methane-bearing fluids at the sea floor of the southern summit of Hydrate Ridge, Cascadia Margin. A considerable salinity increase was observed 120 cm below the sediment-surface. A hydrate layer was almost unaffected from sampling and the adjacent sediment visually dry and fragmented. The piece of hydrate was removed immediately from the sediment before dissociation could commence. Samples separated in that way showed chloride concentrations up to 800 mM, a salt-enrichment of about 1.5 times the seawater salinity. Corresponding ? 18O and ? D profiles indicate that chloride anomalies certainly originated from hydrate formation. The enhanced diagenetic model C.CANDI was applied to pore water chloride and sulfate profiles using steady state as well as non-steady state approaches to simulate the response of gas hydrate formation to varying fluid-flow rates and time. Upward fluid flow rates of 20 cm/yr, as determined by the model, are sufficient to account for the pore water sulfate profiles that arise from methane oxidation. The potential maximum concentration of dissolved methane in interstitial water in the presence of gas hydrate is given by thermodynamic considerations. The general trend of the measured chloride concentrations can be described by a source function for hydrate that produces significant quantities of gas hydrate at 120 cm sediment depth, the lower model boundary. Integrated hydrate formation rates of 102-103 mol m-2 h-1 were determined by the non-steady state modeling approach. These rates are about 10 times smaller than values reported from hydrate formation from water solution in the laboratory and several orders of magnitude larger than values calculated for Blake Ridge sediments (ODP 997).

  3. Biogeochemistry of Arsenic in Iron Oxide Systems

    Microsoft Academic Search

    Paul R. Grossl; Matthew J. Eick; Markus Grafe

    The bioavailability of arsenic (As) in aerobic systems is governed by its adsorption onto metal oxide - most frequently iron (Fe) oxide - solid phases. The focus of this study is on how naturally occurring soil constituents (i.e. humic substances, silica, and phosphate) enhance the bioavailability of arsenate (As(V) oxyanion) and what effect enhanced As bioavailability has on food crops.

  4. Platinum attachments on iron oxide nanoparticle surfaces

    Microsoft Academic Search

    Soubantika Palchoudhury; Yaolin Xu; Wei An; C. Heath Turner; Yuping Bao

    2010-01-01

    Platinum nanoparticles supported on metal oxide surfaces have shown great potential as heterogeneous catalysts to accelerate electrochemical processes, such as the oxygen reduction reaction in fuel cells. Recently, the use of magnetic supports has become a promising research topic for easy separation and recovery of catalysts using magnets, such as Pt nanoparticles supported on iron oxide nanoparticles. The attachment of

  5. Iron oxides stimulate sulfate-driven anaerobic methane oxidation in seeps.

    PubMed

    Sivan, Orit; Antler, Gilad; Turchyn, Alexandra V; Marlow, Jeffrey J; Orphan, Victoria J

    2014-10-01

    Seep sediments are dominated by intensive microbial sulfate reduction coupled to the anaerobic oxidation of methane (AOM). Through geochemical measurements of incubation experiments with methane seep sediments collected from Hydrate Ridge, we provide insight into the role of iron oxides in sulfate-driven AOM. Seep sediments incubated with (13)C-labeled methane showed co-occurring sulfate reduction, AOM, and methanogenesis. The isotope fractionation factors for sulfur and oxygen isotopes in sulfate were about 40‰ and 22‰, respectively, reinforcing the difference between microbial sulfate reduction in methane seeps versus other sedimentary environments (for example, sulfur isotope fractionation above 60‰ in sulfate reduction coupled to organic carbon oxidation or in diffusive sedimentary sulfate-methane transition zone). The addition of hematite to these microcosm experiments resulted in significant microbial iron reduction as well as enhancing sulfate-driven AOM. The magnitude of the isotope fractionation of sulfur and oxygen isotopes in sulfate from these incubations was lowered by about 50%, indicating the involvement of iron oxides during sulfate reduction in methane seeps. The similar relative change between the oxygen versus sulfur isotopes of sulfate in all experiments (with and without hematite addition) suggests that oxidized forms of iron, naturally present in the sediment incubations, were involved in sulfate reduction, with hematite addition increasing the sulfate recycling or the activity of sulfur-cycling microorganisms by about 40%. These results highlight a role for natural iron oxides during bacterial sulfate reduction in methane seeps not only as nutrient but also as stimulator of sulfur recycling. PMID:25246590

  6. Iron oxides stimulate sulfate-driven anaerobic methane oxidation in seeps

    PubMed Central

    Sivan, Orit; Antler, Gilad; Turchyn, Alexandra V.; Marlow, Jeffrey J.; Orphan, Victoria J.

    2014-01-01

    Seep sediments are dominated by intensive microbial sulfate reduction coupled to the anaerobic oxidation of methane (AOM). Through geochemical measurements of incubation experiments with methane seep sediments collected from Hydrate Ridge, we provide insight into the role of iron oxides in sulfate-driven AOM. Seep sediments incubated with 13C-labeled methane showed co-occurring sulfate reduction, AOM, and methanogenesis. The isotope fractionation factors for sulfur and oxygen isotopes in sulfate were about 40‰ and 22‰, respectively, reinforcing the difference between microbial sulfate reduction in methane seeps versus other sedimentary environments (for example, sulfur isotope fractionation above 60‰ in sulfate reduction coupled to organic carbon oxidation or in diffusive sedimentary sulfate–methane transition zone). The addition of hematite to these microcosm experiments resulted in significant microbial iron reduction as well as enhancing sulfate-driven AOM. The magnitude of the isotope fractionation of sulfur and oxygen isotopes in sulfate from these incubations was lowered by about 50%, indicating the involvement of iron oxides during sulfate reduction in methane seeps. The similar relative change between the oxygen versus sulfur isotopes of sulfate in all experiments (with and without hematite addition) suggests that oxidized forms of iron, naturally present in the sediment incubations, were involved in sulfate reduction, with hematite addition increasing the sulfate recycling or the activity of sulfur-cycling microorganisms by about 40%. These results highlight a role for natural iron oxides during bacterial sulfate reduction in methane seeps not only as nutrient but also as stimulator of sulfur recycling. PMID:25246590

  7. IRON OXIDE NANOPARTICLE-INDUCED OXIDATIVE STRESS AND INFLAMMATION

    EPA Science Inventory

    Nanoparticle Physicochemical Characterizations We first focused on creating NP systems that could be used to test our hypotheses and assessing their stability in aqueous media. The iron oxide NP systems were not stable in cell culture medium o...

  8. The Low Temperature Oxidation of Iron

    Microsoft Academic Search

    H. R. Nelson

    1938-01-01

    An electron diffraction study of the oxide films formed on abraded iron specimens by heating in air at temperatures ranging from 80° to 260°C has failed to detect structural effects due to a ``critical temperature'' in the neighborhood of 200°C. ?-Fe2O3 was found on specimens which were oxidized at any temperature above about 130°C provided the period of oxidation exceeded

  9. Removal of metallic iron on oxide slags

    SciTech Connect

    Shannon, G.N.; Fruehan, R.J.; Sridhar, S. [Carnegie Mellon University, Pittsburgh, PA (United States). Dept. of Material Science & Engineering

    2009-10-15

    It is possible, in some cases, for ground coal particles to react with gasifier gas during combustion, allowing the ash material in the coal to form phases besides the expected slag phase. One of these phases is metallic iron, because some gasifiers are designed to operate under a reducing atmosphere (pO{sub 2}) of approximately 10{sup -4} atm). Metallic iron can become entrained in the gas stream and deposit on, and foul, downstream equipment. To improve the understanding of the reaction between different metallic iron particles and gas, which eventually oxidizes them, and the slag that the resulting oxide dissolves in, the kinetics of iron reaction on slag were predicted using gas-phase mass-transfer limitations for the reaction and were compared with diffusion in the slag; the reaction itself was observed under confocal scanning laser microscopy. The expected rates for iron droplet removal are provided based on the size and effective partial pressure of oxygen, and it is found that decarburization occurs before iron reaction, leading to an extra 30- to 100-second delay for carbon-saturated particles vs pure iron particles. A pure metallic iron particle of 0.5 mg should be removed in about 220 seconds at 1400{sup o}C and in 160 seconds at 1600{sup o}C.

  10. Water column methane oxidation adjacent to an area of active hydrate dissociation, Eel river Basin

    Microsoft Academic Search

    DAVID L. VALENTINE; Douglas C Blanton; WILLIAM S. REEBURGH; Miriam Kastner

    2001-01-01

    The role of methane clathrate hydrates in the global methane budget is poorly understood because little is known about how much methane from decomposing hydrates actually reaches the atmosphere. In an attempt to quantify the role of water column methanotrophy (microbial methane oxidation) as a control on methane release, we measured water column methane profiles (concentration and ?13C) and oxidation

  11. Wastewater Treatment Technology Based on Iron Oxides

    Microsoft Academic Search

    J. D. Navratil

    \\u000a Iron oxides have been used in a variety of forms for wastewater treatment. In most precipitation processes ferric ions are\\u000a used to treat basic aqueous solutions by forming a ferric hydroxide floc to scavenge radioactive and heavy metal contaminants.\\u000a In adsorption processes, a variety of iron containing minerals have been utilised. Since 1970, we have utilised ferrites and\\u000a the mineral

  12. Thermodynamics of Iron Oxidation in Metallurgical Slags

    NASA Astrophysics Data System (ADS)

    Matousek, Jan

    2012-11-01

    The state of oxidation of a pyrometallurgical process, given by the partial pressure of oxygen and the temperature, is one of the important properties monitored and controlled in the smelting and refining of iron and the nonferrous metals. This article reviews the thermodynamic background for this quantity and examines some empirical methods for its estimation and use. The emphasis is on copper smelting, but the same principles apply to iron, nickel, lead, and zinc processes.

  13. Defluoridation by Bacteriogenic Iron Oxides: Sorption Studies

    NASA Astrophysics Data System (ADS)

    Evans, K.; Ferris, F.

    2009-05-01

    At concentrations above 1 mg/L, fluoride in drinking water can lead to dental and skeletal fluorosis, a disease that causes mottling of the teeth, calcification of ligaments, crippling bone deformities and many other physiological disorders that can, ultimately, lead to death. Conservative estimates are that fluorosis afflicts tens of millions of people worldwide. As there is no treatment for fluorosis, prevention is the only means of controlling the disease. While numerous defluoridation techniques have been explored, no single method has been found to be both effective and inexpensive enough to implement widely. Our research began in India, with a large-scale geochemical study of the groundwater in a fluoride-contaminated region of Orissa. Having developed a better understanding of the geochemical relationships that exist between fluoride and other parameters present in an affected area, as well as the complex relationships that arise among those parameters that can impact the presence of fluoride, we began investigating certain remediation scenarios involving iron oxides. A common approach to remediation involves the partitioning of fluoride from groundwater by sorption onto a variety of materials, one of the most effective of which is iron oxide whose surface area acts as a scavenger for fluoride. In the presence of iron oxidizing bacteria, the oxidation rate of iron has been shown to be ˜6 times greater than in their absence; fluoride should, therefore, be removed from an aqueous environment by bacteriogenic iron oxides (BIOS) much more quickly than by abiotic iron oxides. Most recently, sorption studies have been conducted using both BIOS and synthetic hydrous ferric oxides in order to compare the behavior between biotic and abiotic sorbents. These studies have provided sorption isotherms that allow comparison of fluoride removed by sorption to BIOS versus synthetic iron oxides. Sorption affinity constants have also been determined, which allow for the prediction of fluoride removal in a wide variety of groundwater systems. Sorption isotherms and affinity constants show the use of BIOS to be a promising technique for the remediation of fluoride in groundwater.

  14. Characterization of iron oxide layers using Auger electron spectroscopy

    Microsoft Academic Search

    Milan Bizjak; Anton Zalar; Peter Panjan; Benjamin Zorko; Borut Pracek

    2007-01-01

    Metals can form several kinds of oxides. Iron forms wustite (FeO), magnetite (FeO+Fe2O3 or Fe3O4) and haematite (Fe2O3). Iron oxides, especially magnetite, are used for insulation between the lamellas of an electromotor made of electromagnetic sheet. In this work, iron oxide layers were characterized on industrial samples of electromagnetic sheet by AES depth profile analysis, and iron oxides with known

  15. Kinetic study of the hydration of magnesium oxide for a chemical heat pump

    Microsoft Academic Search

    Yukitaka Kato; Norimichi Yamashita; Kei Kobayashi; Yoshio Yoshizawa

    1996-01-01

    A kinetic study of the hydration of magnesium oxide was performed to test the possibility of developing a magnesium oxide\\/water chemical heat pump. The hydration rate of magnesium oxide was measured by a gravimetric analysis with a sample of average particle size 10 ?m for the reaction temperature 373–423 K and the reaction vapor pressure 12.3–47.4 kPa. It was a

  16. 21 CFR 73.1200 - Synthetic iron oxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 2014-04-01 false Synthetic iron oxide. 73.1200 Section 73.1200...CERTIFICATION Drugs § 73.1200 Synthetic iron oxide. (a) Identity. (1) The color additive synthetic iron oxide consists of any one or any...

  17. 21 CFR 73.1200 - Synthetic iron oxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 2012-04-01 false Synthetic iron oxide. 73.1200 Section 73.1200...CERTIFICATION Drugs § 73.1200 Synthetic iron oxide. (a) Identity. (1) The color additive synthetic iron oxide consists of any one or any...

  18. 21 CFR 73.1200 - Synthetic iron oxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 2013-04-01 false Synthetic iron oxide. 73.1200 Section 73.1200...CERTIFICATION Drugs § 73.1200 Synthetic iron oxide. (a) Identity. (1) The color additive synthetic iron oxide consists of any one or any...

  19. 21 CFR 73.1200 - Synthetic iron oxide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2010-04-01 false Synthetic iron oxide. 73.1200 Section 73.1200...CERTIFICATION Drugs § 73.1200 Synthetic iron oxide. (a) Identity. (1) The color additive synthetic iron oxide consists of any one or any...

  20. 21 CFR 73.1200 - Synthetic iron oxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Synthetic iron oxide. 73.1200 Section 73.1200...CERTIFICATION Drugs § 73.1200 Synthetic iron oxide. (a) Identity. (1) The color additive synthetic iron oxide consists of any one or any...

  1. The analysis of magnesium oxide hydration in three-phase reaction system

    SciTech Connect

    Tang, Xiaojia; Guo, Lin; Chen, Chen; Liu, Quan; Li, Tie; Zhu, Yimin, E-mail: ntp@dlmu.edu.cn

    2014-05-01

    In order to investigate the magnesium oxide hydration process in gas–liquid–solid (three-phase) reaction system, magnesium hydroxide was prepared by magnesium oxide hydration in liquid–solid (two-phase) and three-phase reaction systems. A semi-empirical model and the classical shrinking core model were used to fit the experimental data. The fitting result shows that both models describe well the hydration process of three-phase system, while only the semi-empirical model right for the hydration process of two-phase system. The characterization of the hydration product using X-Ray diffraction (XRD) and scanning electron microscope (SEM) was performed. The XRD and SEM show hydration process in the two-phase system follows common dissolution/precipitation mechanism. While in the three-phase system, the hydration process undergo MgO dissolution, Mg(OH){sub 2} precipitation, Mg(OH){sub 2} peeling off from MgO particle and leaving behind fresh MgO surface. - Graphical abstract: There was existence of a peeling-off process in the gas–liquid–solid (three-phase) MgO hydration system. - Highlights: • Magnesium oxide hydration in gas–liquid–solid system was investigated. • The experimental data in three-phase system could be fitted well by two models. • The morphology analysis suggested that there was existence of a peel-off process.

  2. Water clustering on nanostructured iron oxide films

    NASA Astrophysics Data System (ADS)

    Merte, Lindsay R.; Bechstein, Ralf; Peng, Guowen; Rieboldt, Felix; Farberow, Carrie A.; Zeuthen, Helene; Knudsen, Jan; Lægsgaard, Erik; Wendt, Stefan; Mavrikakis, Manos; Besenbacher, Flemming

    2014-06-01

    The adhesion of water to solid surfaces is characterized by the tendency to balance competing molecule-molecule and molecule-surface interactions. Hydroxyl groups form strong hydrogen bonds to water molecules and are known to substantially influence the wetting behaviour of oxide surfaces, but it is not well-understood how these hydroxyl groups and their distribution on a surface affect the molecular-scale structure at the interface. Here we report a study of water clustering on a moiré-structured iron oxide thin film with a controlled density of hydroxyl groups. While large amorphous monolayer islands form on the bare film, the hydroxylated iron oxide film acts as a hydrophilic nanotemplate, causing the formation of a regular array of ice-like hexameric nanoclusters. The formation of this ordered phase is localized at the nanometre scale; with increasing water coverage, ordered and amorphous water are found to coexist at adjacent hydroxylated and hydroxyl-free domains of the moiré structure.

  3. Iron blast furnace slag/hydrated lime sorbents for flue gas desulfurization.

    PubMed

    Liu, Chiung-Fang; Shih, Shin-Min

    2004-08-15

    Sorbents prepared from iron blast furnace slag (BFS) and hydrated lime (HL) through the hydration process have been studied with the aim to evaluate their reactivities toward SO2 under the conditions prevailing in dry or semidry flue gas desulfurization processes. The BFS/HL sorbents, having large surface areas and pore volumes due to the formation of products of hydration, were highly reactive toward SO2, as compared with hydrated lime alone (0.24 in Ca utilization). The sorbent reactivity increased as the slurrying temperature and time increased and as the particle size of BFS decreased; the effects of the liquid/solid ratio and the sorbent drying conditions were negligible. The structural properties and the reactivity of sorbent were markedly affected by the BFS/HL ratio; the sorbent with 30/70 ratio had the highest 1 h utilization of Ca, 0.70, and SO2 capture, 0.45 g SO2/g sorbent. The reactivity of a sorbent was related to its initial specific surface area (Sg0) and molar content of Ca (M(-1)); the 1 h utilization of Ca increased almost linearly with increasing Sg0/M. The results of this study are useful to the preparation of BFS/HL sorbents with high reactivity for use in the dry and semidry processes to remove SO2 from the flue gas. PMID:15382877

  4. Formulations for iron oxides dissolution

    DOEpatents

    Horwitz, Earl P. (Argonne, IL); Chiarizia, Renato (Argonne, IL)

    1992-01-01

    A mixture of a di- or polyphosphonic acid and a reductant wherein each is present in a sufficient amount to provide a synergistic effect with respect to the dissolution of metal oxides and optionally containing corrosion inhibitors and pH adjusting agents.

  5. Evolution of iron speciation during hydration of C{sub 4}AF

    SciTech Connect

    Rose, J. [CEREGE Equipe physico-chimie des interfaces, UMR 6635 CNRS/Universite Paul Cezanne Aix-MarseilleIII-IFRE PSME 112, Europole Mediterraneen de l'Arbois, BP 80, 13545 Aix en Provence Cedex 4 (France) and ARDEVIE, Europole Mediterraneen de l'Arbois, BP 80, 13545 Aix en Provence Cedex 4 (France)]. E-mail: rose@cerege.fr; Benard, A. [ARDEVIE, Europole Mediterraneen de l'Arbois, BP 80, 13545 Aix en Provence Cedex 4 (France); INERIS, Domaine du Petit Arbois, BP 33, 13545 Aix en Provence (France); El Mrabet, S. [CEREGE Equipe physico-chimie des interfaces, UMR 6635 CNRS/Universite Paul Cezanne Aix-MarseilleIII-IFRE PSME 112, Europole Mediterraneen de l'Arbois, BP 80, 13545 Aix en Provence Cedex 4 (France); ARDEVIE, Europole Mediterraneen de l'Arbois, BP 80, 13545 Aix en Provence Cedex 4 (France); Masion, A. [CEREGE Equipe physico-chimie des interfaces, UMR 6635 CNRS/Universite Paul Cezanne Aix-MarseilleIII-IFRE PSME 112, Europole Mediterraneen de l'Arbois, BP 80, 13545 Aix en Provence Cedex 4 (France); ARDEVIE, Europole Mediterraneen de l'Arbois, BP 80, 13545 Aix en Provence Cedex 4 (France); Moulin, I. [LERM, 10, rue Mercoeur, 75011 Paris (France); Briois, V. [LURE Laboratoire pour l'Utilisation du Rayonnement Electromagnetique, Universite Paris-Sud, Orsay, France European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex (France); Olivi, L. [ELETTRA Sincrotrone Trieste S.c.p.A. S. S. 14, Km. 163.5 in AREA Science Park, I-34012 Basovizza, TS (Italy); Bottero, J.-Y. [CEREGE Equipe physico-chimie des interfaces, UMR 6635 CNRS/Universite Paul Cezanne Aix-MarseilleIII-IFRE PSME 112, Europole Mediterraneen de l'Arbois, BP 80, 13545 Aix en Provence Cedex 4 (France); ARDEVIE, Europole Mediterraneen de l'Arbois, BP 80, 13545 Aix en Provence Cedex 4 (France)

    2006-07-01

    It is now well accepted and demonstrated that calcium silicate, calcium aluminate and calcium sulfo aluminate (ettringite, AFm) phases exhibit a good capability to fix metals and metalloids. Unfortunately the role of minor phases and especially calcium-ferric aluminate phase, shorthand C{sub 4}AF is not well defined. In other systems like in soils or sediments iron phases play a key role in the fixation of pollutant. In cement sorption isotherms, indicated that various metals can be retained by the C{sub 4}AF hydrated products. Therefore the capabilities of those phase to retain heavy metal should not be neglected. Previous investigations have shown that the minerals formed during the hydration of C{sub 4}AF are similar to those formed from C3A (pure tri-calcium aluminate) under comparable conditions. Nevertheless no investigation was conducted at the molecular level and there is still a controversy whether Fe substitutes for Al in the hydrated minerals in whole or in part, or if it forms FeOOH clusters scattered throughout the matrix. In this context we have conducted XAS experiments using synchrotron radiation. It was found that the hydration of C{sub 4}AF forms C{sub 3}AH{sub 6} (hydrogarnet) in which Fe randomly substitutes for Al as well as an amorphous FeOOH phase. Intermediate products like AFm (i.e., an ill organized lamellar phase) are also formed but rapidly evolve to C{sub 3}AH{sub 6}; iron does not seem to be incorporated in the AFm structure.

  6. Effect of hydration in metHb: reversible changes monitored by ESR of iron.

    PubMed

    Martin Neto, L; Tabak, M; Nascimento, O R

    1990-12-01

    The dehydration of human and bovine methemoglobins was monitored using ESR spectroscopy of the iron signal. The interconversion of the Fe(III) signal between the high spin form (at g approximately 6) in solution and low spin form (at g approximately 2) was quantitatively studied as a function of hydration. The dehydration process leads also to a loss of paramagnetism resulting in the appearance of about 40% Fe(II) below 0.40 grH2O/grHb. The remaining 60% of Fe(III) ESR signal is distributed as the residual high spin form (at g approximately 6, 5%) and low spin form (hemichromes H and P, 55%). The formation of hemichrome P was explained as resulting from the coordination of the cysteine residue at beta 93 with the iron atom which follows the rupture of the proximal histidine bond. Experiments with hemoglobins where the sulphur atom of cysteine beta 93 was blocked (N-ethylmaleimide) did not showed the hemichrome P, confirming the involvement of the sulphur atom. This implies that the dehydration process induces displacements and torsion of the F helix, drastically changing the iron coordination at proximal site. In agreement with this proposition the Fe(II) symmetry is pentacoordinated with the disrupted bond to the proximal histidine at fifth coordination. This is also supported by ESR experiments with nitrosyl complex at low hydrations. All conformational changes were reversibly modulated by hydration degree and partially by lyophilization rate. A one-cycle dehydration of bovine hemoglobin followed by solubilization shows 100% reversibility of hemichrome P. Increasing the number of cycles of dehydration-hydration reduces the reversibility degree. With three cycles a reversibility of 70%-75% is observed. The level of 0.40 grH2O/grHb was the critical hydration for the molecules to return to aquo met form and correspond also to a minimal water content necessary to cover all protein surface as obtained from other techniques. PMID:1964956

  7. Inhibited phase behavior of gas hydrates in graphene oxide: influences of surface and geometric constraints.

    PubMed

    Kim, Daeok; Kim, Dae Woo; Lim, Hyung-Kyu; Jeon, Jiwon; Kim, Hyungjun; Jung, Hee-Tae; Lee, Huen

    2014-11-01

    Porous materials have provided us unprecedented opportunities to develop emerging technologies such as molecular storage systems and separation mechanisms. Pores have also been used as supports to contain gas hydrates for the application in gas treatments. Necessarily, an exact understanding of the properties of gas hydrates in confining pores is important. Here, we investigated the formation of CO2, CH4 and N2 hydrates in non-interlamellar voids in graphene oxide (GO), and their thermodynamic behaviors. For that, low temperature XRD and P-T traces were conducted to analyze the water structure and confirm hydrate formation, respectively, in GO after its exposure to gaseous molecules. Confinement and strong interaction of water with the hydrophilic surface of graphene oxide reduce water activity, which leads to the inhibited phase behavior of gas hydrates. PMID:25232710

  8. Method for preparing hydrous iron oxide gels and spherules

    DOEpatents

    Collins, Jack L.; Lauf, Robert J.; Anderson, Kimberly K.

    2003-07-29

    The present invention is directed to methods for preparing hydrous iron oxide spherules, hydrous iron oxide gels such as gel slabs, films, capillary and electrophoresis gels, iron monohydrogen phosphate spherules, hydrous iron oxide spherules having suspendable particles homogeneously embedded within to form composite sorbents and catalysts, iron monohydrogen phosphate spherules having suspendable particles of at least one different sorbent homogeneously embedded within to form a composite sorbent, iron oxide spherules having suspendable particles homogeneously embedded within to form a composite of hydrous iron oxide fiber materials, iron oxide fiber materials, hydrous iron oxide fiber materials having suspendable particles homogeneously embedded within to form a composite, iron oxide fiber materials having suspendable particles homogeneously embedded within to form a composite, dielectric spherules of barium, strontium, and lead ferrites and mixtures thereof, and composite catalytic spherules of barium or strontium ferrite embedded with oxides of Mg, Zn, Pb, Ce and mixtures thereof. These variations of hydrous iron oxide spherules and gel forms prepared by the gel-sphere, internal gelation process offer more useful forms of inorganic ion exchangers, catalysts, getters, dielectrics, and ceramics.

  9. Iron oxide nanoparticle platform for biomedical applications.

    PubMed

    Xie, J; Huang, J; Li, X; Sun, S; Chen, X

    2009-01-01

    Progress in nanosynthesis has succeeded in making nanoscale particles from iron oxide under precise quality control. Given the recent great advances in polymer manufacturing, antibody purification, DNA/RNA synthesis and magnetic resonance imaging (MRI), such iron oxide nanoparticles (IONPs) have been enriched with many variables and attracted great interest in studying their potential biomedical applications. After nearly two decades' effort, IONPs have become a powerful platform in many diverse aspects of biomedicine, including MRI, gene and drug delivery, and hyperthermia. While some studies are still at the proof-of-concept stage, others have now been widely used in clinics. With the on-going efforts to enhance their targeting ability and endow more functions, IONPs' future applications are highly expected. PMID:19355885

  10. RESEARCH PAPER Effects of iron oxide nanoparticles on polyvinyl alcohol

    E-print Network

    Guo, John Zhanhu

    RESEARCH PAPER Effects of iron oxide nanoparticles on polyvinyl alcohol: interfacial layer and bulk Abstract Iron oxide (a-phase) nanoparticles with coercivity larger than 300 Oe have been fabricated to effectively serve as a solid spacer to disperse the iron precursor and to prevent the nanoparticles from

  11. Iron Deficiency Diminishes Gallbladder Neuronal Nitric Oxide Synthase

    Microsoft Academic Search

    Deborah A. Swartz-Basile; Matthew I. Goldblatt; Cindy Blaser; Philip A. Decker; Steven A. Ahrendt; Sushil K. Sarna; Henry A. Pitt

    2000-01-01

    Background. Iron deficiency has been demonstrated in the prairie dog to result in cholesterol crystal formation and altered biliary motility. Gallbladder filling and emptying are influenced by both inhibitory and excitatory stimuli, with nitric oxide (NO) playing a key role in normal relaxation. Iron is a cofactor for nitric oxide synthase. Therefore, we tested the hypothesis that iron deficiency would

  12. Optical properties of iron oxides

    NASA Astrophysics Data System (ADS)

    Musfeldt, Janice

    2012-02-01

    Magnetoelectric coupling in materials like multiferroics, dilute magnetic semiconductors, and topological insulators has attracted a great deal of attention, although most work has been done in the static limit. Optical spectroscopy offers a way to investigate the dynamics of charge-spin coupling, an area where there has been much less effort. Using these techniques, we discovered that charge fluctuation in LuFe2O4, the prototypical charge ordered multiferroic, has an onset well below the charge ordering transition, supporting the ``order by fluctuation'' mechanism for the development of charge order superstructure. Bragg splitting and large magneto-optical contrast suggest a low temperature monoclinic distortion that can be driven by both temperature and magnetic field. At the same time, dramatic splitting of the LuO2 layer phonon mode is attributed to charge-rich/poor proximity effects, and its temperature dependence reveals the antipolar nature of the W layer pattern. Using optical techniques, we also discovered that ?-Fe2O3, a chemically-similar parent compound and one of the world's oldest and most iconic antiferromagnetic materials, appears more red in applied magnetic field than in zero field conditions. This effect is driven by a field-induced reorientation of magnetic order. The oscillator strength lost in the color band is partially transferred to the magnon side band, a process that also reveals a new exciton pattern induced by the modified exchange coupling. Analysis of the exciton pattern exposes C2/c monoclinic symmetry in the high field phase of hematite. Taken together, these findings advance our understanding of iron-based materials under extreme conditions. [4pt] Collaborators include: X. S. Xu, P. Chen, Q. -C. Sun, T. V. Brinzari (Tennessee); S. McGill (NHMFL); J. De Groot, M. Angst, R. P. Hermann (Julich); A. D. Christianson, B. C. Sales, D. Mandrus (ORNL); A. P. Litvinchuk (Houston); J. -W. Kim (Ames); Z. Islam (Argonne); N. Lee, S. -W. Cheong (Rutgers).

  13. Iron oxidation state in hydrous rhyolites

    NASA Astrophysics Data System (ADS)

    Humphreys, M.; Brooker, R.; Fraser, D.; Smith, V. C.

    2012-12-01

    Recent studies have suggested that the Earth's mantle at subduction zones is oxidized relative to that at mid-ocean ridges. One possible origin of the oxidation is thought to be hydrous fluids, which are released into the mantle from the down-going slab during subduction. However, this is controversial; other studies have concluded that there is no intrinsic difference in oxidation state. One potential problem in determining primary oxidation states is that magmas produced by partial melting of the sub-arc mantle undergo significant degassing and crystallisation near the earth's surface, which may overprint the oxidation state of the primary melt. H2O contents of melt inclusions may be affected by partial re-equilibration. The effect of H2O on Fe oxidation state is unclear, although theoretical arguments typically predict increasing Fe3+/?Fe during shallow degassing as a result of preferential diffusion of H2 out of the melt: FeO (m) + H2O (m) = Fe2O3 (m) + H2 (g) [1] We used XANES to measure Fe3+/Fe2+ in cylinders of rhyolitic obsidian that had been hydrated in gold capsules in cold-seal apparatus. Runs were performed at 850-900 °C under H2O-saturated conditions for short run times (20-80 minutes). Surprisingly, we find a positive correlation between Fe3+/?Fe and H2O content of the glass. This is inconsistent with the effects of reaction [1], but can be explained by considering the acid-base properties of the hydrous melt. In particular, basic behaviour of FeO but amphoteric behaviour of Fe2O3, and changes in melt basicity relating to dissolution of H2O, can explain increasing Fe3+/Fe2+ with increasing H2O. We discuss the implications of these results for using melt compositions to infer the oxidation state of the earth's mantle.

  14. Reaction between Hydrosulfide and Iron\\/cerium (hydr)oxide: Hydrosulfide Oxidation and Iron Dissolution Kinetics

    Microsoft Academic Search

    Catalin F. Petre; Faïçal Larachi

    2006-01-01

    Hydrosulfide oxidation and iron dissolution kinetics were studied at normal pressure, under inert (N2) atmosphere, in a liquid–solid mechanically-stirred slurry reactor. The kinetic variables undergoing variations were: hydrosulfide\\u000a initial concentration (0.90–3.30 mmol\\/L), oxide initial surface area (16–143 m2\\/L) and pH (8.0–11.0). The hydrosulfide consumption and products (thiosulfate and polysulfide) formation were quantified by\\u000a means of capillary electrophoresis, while iron dissolution was monitored

  15. Synthesis and characterization of iron, iron oxide and iron carbide nanostructures

    NASA Astrophysics Data System (ADS)

    Snovski, Ron; Grinblat, Judith; Sougrati, Moulay-Tahar; Jumas, Jean-Claude; Margel, Shlomo

    2014-01-01

    Magnetic iron oxide (Fe3O4 and ?-Fe2O3) and iron carbide (Fe3C) nanoparticles of different geometrical shapes: cubes, spheres, rods and plates, have been prepared by thermal decomposition of a mixture containing the metal precursor Fe(CO)5 and the stabilizer polyvinylpyrrolidone (PVP) at 300 °C in a sealed cell under inert atmosphere. The thermal decomposition process was performed for 4 or 24 h at ([PVP]/[Fe(CO)5]) (w/v) ratio of 1:1 or 1:5. Elemental iron nanospheres embedded within a mixture of amorphous and graphitic carbon coating were obtained by hydrogen reduction of the prepared iron oxide and iron carbide nanoparticles at 450 °C. The formation of the graphitic carbon phase at such a low temperature is unique and probably obtained by catalysis of the elemental iron nanoparticles. Changing the annealing time period and the ([PVP]/[Fe(CO)5]) ratio allowed control of the composition, size, size distribution, crystallinity, geometrical shape and magnetic properties of the different magnetic nanoparticles.

  16. Fabrication and characterization of iron oxide nanoparticles filled polypyrrole nanocomposites

    Microsoft Academic Search

    Zhanhu Guo; Koo Shin; Amar B. Karki; David P. Young; Richard B. Kaner; H. Thomas Hahn

    2009-01-01

    The effect of iron oxide nanoparticle addition on the physicochemical properties of the polypyrrole (PPy) was investigated.\\u000a In the presence of iron oxide nanoparticles, PPy was observed in the form of discrete nanoparticles, not the usual network\\u000a structure. PPy showed crystalline structure in the nanocomposites and pure PPy formed without iron oxide nanoparticles. PPy\\u000a exhibited amorphous structure and nanoparticles were

  17. Reactive Condensation and Magnetic Properties of Iron Oxide Films

    Microsoft Academic Search

    Yoshichika Bando; Shigeo Horii; Toshio Takada

    1978-01-01

    Films of iron oxides such alpha-Fe3O3 and Fe3O4 were prepared by evaporating iron in a low pressure atmosphere of oxygen gas and investigated by X-ray and electron diffraction and Mössbauer effect measurements. The formation range of iron oxides was determined as functions of the substrate temperature and the deposition rate at an oxygen pressure of 4× 10-4 Torr. The oxide

  18. Kinetics of dissolution and bio-availability of iron in amorphous siliceous iron oxides

    E-print Network

    Seaman, John C.

    1990-01-01

    KINETICS OF DISSOLUTION AND BIO-AVAILABILITY OF IRON IN AMORPHOUS SILICEOUS IRON OXIDES A Thesis By John C. Seaman Submitted to the Graduate College of Texas AIIM University in partial fulfillment of the requirements for the degree of MASTER... OF SCIENCE December 1990 Major Subject: Soil Science KINETICS OF DISSOLUTION AND BIO-AVAILABILITY OF IRON IN AMORPHOUS SILICEOUS IRON OXIDES A Thesis By John C. Seaman Approved as to style and content by: Richard H. Loeppert (Chair of Committee...

  19. Compact Zwitterion-Coated Iron Oxide Nanoparticles for Biological Applications

    E-print Network

    Wei, He

    The potential of superparamagnetic iron oxide nanoparticles (SPIONs) in various biomedical applications, including magnetic resonance imaging (MRI), sensing, and drug delivery, requires that their surface be derivatized ...

  20. Synthesis and characterization of iron oxide-cellulose nanocomposite films

    NASA Astrophysics Data System (ADS)

    Mun, Seongcheol; Yadav, Mithilesh; Kim, Joo-Hyung; Kim, Jaehwan

    2015-04-01

    Iron oxide/cellulose nanocomposite film is fabricated by impregnation of iron oxide nanoparticles into a regenerated cellulose film. The crystal structure, chemical functional group, morphological analysis, thermal stability and mechanical properties of the nanocomposite films are investigated by the wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mechanical pull test. The investigated results show that the iron oxide is interacted with hydroxyl groups of the regenerated cellulose film. The tensile strength and elastic modulus of iron oxide/cellulose films are significantly enhanced up to 39% and 57% of pristine regenerated cellulose film, respectively.

  1. Mineral resource of the month: iron oxide pigments

    USGS Publications Warehouse

    U.S. Geological Survey

    2008-01-01

    The article discusses iron oxide pigments, which have been used as colorants since human began painting as they resist color change due to sunlight exposure, have good chemical resistance and are stable under normal ambient conditions. Cyprus, Italy and Spain are among the countries that are known for the production of iron oxide pigments. Granular forms of iron oxides and nano-sized materials are cited as developments in the synthetic iron oxide pigment industry which are being used in computer disk drives and nuclear magnetic resonance imaging.

  2. Synthesis and characterization of iron oxide/cellulose nanocomposite film.

    PubMed

    Yadav, Mithilesh; Mun, Seongcheol; Hyun, Jinho; Kim, Jaehwan

    2015-03-01

    Iron oxide/cellulose high-performance nanocomposite film is successfully prepared by impregnation of iron oxide nanoparticles into a regenerated cellulose film. The structure, thermal stability and mechanical properties of the nanocomposite films are investigated by the wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mechanical pull test. The investigation results reveal that the iron oxide is bound to hydroxyl groups of the regenerated cellulose film by hydrogen bonding. Compared with the regenerated cellulose, the tensile strength and elastic modulus of iron oxide/cellulose high-performance films are significantly improved by about 39% and 57%, respectively. PMID:25530000

  3. Kinetics of dissolution and bio-availability of iron in amorphous siliceous iron oxides 

    E-print Network

    Seaman, John C.

    1990-01-01

    microbial chelate deferroxamine methanesulfonate (DFOB), 3) the ability of a Pseudomonas species to acquire necessary levels of Fe for growth from these oxides. CHAPTERII MINERALOGY AND COMPOSITION OF AMORPHOUS SILICEOUS IRON OXIDES REVIEW...KINETICS OF DISSOLUTION AND BIO-AVAILABILITY OF IRON IN AMORPHOUS SILICEOUS IRON OXIDES A Thesis By John C. Seaman Submitted to the Graduate College of Texas AIIM University in partial fulfillment of the requirements for the degree of MASTER...

  4. Suspension Hydrogen Reduction of Iron Oxide Concentrates

    SciTech Connect

    H.Y. Sohn

    2008-03-31

    The objective of the project is to develop a new ironmaking technology based on hydrogen and fine iron oxide concentrates in a suspension reduction process. The ultimate objective of the new technology is to replace the blast furnace and to drastically reduce CO2 emissions in the steel industry. The goals of this phase of development are; the performance of detailed material and energy balances, thermochemical and equilibrium calculations for sulfur and phosphorus impurities, the determination of the complete kinetics of hydrogen reduction and bench-scale testing of the suspension reduction process using a large laboratory flash reactor.

  5. Cardioprotective activity of iron oxide nanoparticles.

    PubMed

    Xiong, Fei; Wang, Hao; Feng, Yidong; Li, Yunman; Hua, Xiaoqing; Pang, Xingyun; Zhang, Song; Song, Lina; Zhang, Yu; Gu, Ning

    2015-01-01

    Iron oxide nanoparticles (IONPs) are chemically inert materials and have been mainly used for imaging applications and drug deliveries. However, the possibility whether they can be used as therapeutic drugs themselves has not yet been explored. We reported here that Fe2O3 nanoparticles (NPs) can protect hearts from ischemic damage at the animal, tissue and cell level. The cardioprotective activity of Fe2O3 NPs requires the integrity of nanoparticles and is not dependent upon their surface charges and molecules that were integrated into nanoparticles. Also, Fe2O3 NPs showed no significant toxicity towards normal cardiomyocytes, indicative of their potential to treat cardiovascular diseases. PMID:25716309

  6. Cardioprotective activity of iron oxide nanoparticles

    PubMed Central

    Xiong, Fei; Wang, Hao; Feng, Yidong; Li, Yunman; Hua, Xiaoqing; Pang, Xingyun; Zhang, Song; Song, Lina; Zhang, Yu; Gu, Ning

    2015-01-01

    Iron oxide nanoparticles (IONPs) are chemically inert materials and have been mainly used for imaging applications and drug deliveries. However, the possibility whether they can be used as therapeutic drugs themselves has not yet been explored. We reported here that Fe2O3 nanoparticles (NPs) can protect hearts from ischemic damage at the animal, tissue and cell level. The cardioprotective activity of Fe2O3 NPs requires the integrity of nanoparticles and is not dependent upon their surface charges and molecules that were integrated into nanoparticles. Also, Fe2O3 NPs showed no significant toxicity towards normal cardiomyocytes, indicative of their potential to treat cardiovascular diseases. PMID:25716309

  7. Sputtered iron oxide/silicon heterostructures

    NASA Astrophysics Data System (ADS)

    Kardauskas, M. J.; Fonash, S. J.; Ashok, S.; Krishnaswamy, S. V.; Messier, R. F.

    1981-03-01

    Sputtered Fe3O4 films are shown to form rectifying junctions to p-type silicon but ohmic contacts to n-type Si. It is pointed out that ohmic contacts to the Fe3O4 can be provided by Au, Al, or spray-deposited ITO. The redox couple Fe(CN)6(3-)/Fe(CN)6(4-) also seems to make an effective ohmic contact to this iron oxide. It is found that the photovoltaic and electrical characteristics of the Fe3O4/p-Si heterojunction depend strongly on the Fe3O4 film thickness.

  8. Shifts in oxidation states of cerium oxide nanoparticles detected inside intact hydrated cells and organelles.

    PubMed

    Szymanski, Craig J; Munusamy, Prabhakaran; Mihai, Cosmin; Xie, Yumei; Hu, Dehong; Gilles, Mary K; Tyliszczak, Tolek; Thevuthasan, Suntharampillai; Baer, Donald R; Orr, Galya

    2015-09-01

    Cerium oxide nanoparticles (CNPs) have been shown to induce diverse biological effects, ranging from toxic to beneficial. The beneficial effects have been attributed to the potential antioxidant activity of CNPs via certain redox reactions, depending on their oxidation state or Ce(3+)/Ce(4+) ratio. However, this ratio is strongly dependent on the environment and age of the nanoparticles and it is unclear whether and how the complex intracellular environment impacts this ratio and the possible redox reactions of CNPs. To identify any changes in the oxidation state of CNPs in the intracellular environment and better understand their intracellular reactions, we directly quantified the oxidation states of CNPs outside and inside intact hydrated cells and organelles using correlated scanning transmission x-ray and super resolution fluorescence microscopies. By analyzing hundreds of small CNP aggregates, we detected a shift to a higher Ce(3+)/Ce(4+) ratio in CNPs inside versus outside the cells, indicating a net reduction of CNPs in the intracellular environment. We further found a similar ratio in the cytoplasm and in the lysosomes, indicating that the net reduction occurs earlier in the internalization pathway. Together with oxidative stress and toxicity measurements, our observations identify a net reduction of CNPs in the intracellular environment, which is consistent with their involvement in potentially beneficial oxidation reactions, but also point to interactions that can negatively impact the health of the cells. PMID:26056725

  9. In Situ Iron Oxide Emplacement for Groundwater Arsenic Remediation 

    E-print Network

    Abia, Thomas Sunday

    2012-02-14

    Iron oxide-bearing minerals have long been recognized as an effective reactive media for arsenic-contaminated groundwater remediation. This research aimed to develop a technique that could facilitate in situ oxidative precipitation of Fe3+ in a soil...

  10. Decoration of carbon nanotubes with iron oxide

    SciTech Connect

    Cao Huiqun [State Key Laboratory for Modification of Chemical Fibers and Polymer Material, College of Material Science and Engineer, Donghua University, Shanghai, 200051 (China); Zhu Meifang [State Key Laboratory for Modification of Chemical Fibers and Polymer Material, College of Material Science and Engineer, Donghua University, Shanghai, 200051 (China)]. E-mail: zmf@dhu.edu.cn; Li Yaogang [State Key Laboratory for Modification of Chemical Fibers and Polymer Material, College of Material Science and Engineer, Donghua University, Shanghai, 200051 (China)

    2006-04-15

    A magnetic composite of multiwalls carbon nanotubes (MWNTs) decorated with iron oxide nanoparticles was synthesized successfully by a simple and effective chemistry precipitation method. The composite was characterized by X-ray diffraction analysis (XRD), Moessbauer spectrum (MS), transmission electron microscopy (TEM), and Fourier transform spectroscopy (FTIR) techniques. The patterns of XRD and MS indicated that MWNTs, {gamma}-Fe{sub 2}O{sub 3}, and Fe{sub 3}O{sub 4} coexisted in the composite. The TEM observation indicated that the nanoparticles of iron oxide were attached on the surface of the MWNTs, and the sizes of the particles ranged from 25 to 80 nm. FTIR spectra showed that SO{sub 4} {sup -} functional groups existed on the surface of MWNTs after modification by sodium dodecylbenzene sulfonic acid (SDBS), which could immobilize Fe{sup 3+} ions onto the MWNTs. The hysteresis loops of the MWNTs and decorated MWNTs were measured by vibrating sample magnetometer (VSM), and the results showed that the composite was ferromagnetism with the saturated magnetization of 20.07 emu/g, and the coercive of 163.44 Oe.

  11. SUPPORTING INFORMATION Vacancy Coalescence During Oxidation of Iron Nanoparticles

    E-print Network

    surfactant solution under vigorous stirring. The decomposition time of the iron carbonyl dependsS1 SUPPORTING INFORMATION Vacancy Coalescence During Oxidation of Iron Nanoparticles Andreu Cabot,1, University of California at Berkeley, Berkeley, CA 94720 Synthesis. Iron nanoparticles were obtained

  12. Fabrication and Characterization of Iron Oxide Thin Films Prepared By the Thermal Oxidation of Iron

    NASA Astrophysics Data System (ADS)

    Saleem, Muhammad

    Iron oxide thin films were deposited by electron beam (e-beam) evaporation from pure iron. Two types of evaporation were done. Firstly, iron was deposited in vacuum, and secondly, the reactive evaporation of iron was carried out in an oxygen atmosphere. Films were post-annealed in air in the temperature range 200 °C to 500 °C. The structural properties were investigated by X-ray diffraction, revealed the growth of ?-Fe2O 3 (hematite). The films were polycrystalline with nanocrystallite size. The chemical properties of the films were determined from X-ray photoelectron spectroscopy, and highly reactive nature of iron oxide films was elucidated. The surface morphological properties of the films were determined using atomic force microscopy. The surface roughness and lateral mean grain size of the films were increased with annealing. The optical properties of the films, including the refractive index, extinction coefficient, absorption coefficient, and band gap were determined from spectrophotometric measurements. Films were highly transparent and exhibited high values of refractive indices. All the films had direct as well as indirect band gaps. The direct band gap values were 2.21 ± 0.03 eV and indirect band gap values were 1.98 ± 0.02 eV.

  13. Widespread oxidized and hydrated amorphous silicates in CR chondrites matrices: Implications for alteration conditions and H2 degassing of asteroids

    NASA Astrophysics Data System (ADS)

    Le Guillou, Corentin; Changela, Hitesh G.; Brearley, Adrian J.

    2015-06-01

    The CR chondrites carry one of the most pristine records of the solar nebula materials that accreted to form planetesimals. They have experienced very variable degrees of aqueous alteration, ranging from incipient alteration in their matrices to the complete hydration of all of their components. In order to constrain their chemical alteration pathways and the conditions of alteration, we have investigated the mineralogy and Fe oxidation state of silicates in the matrices of 8 CR chondrites, from type 3 to type 1. Fe-L edge X-ray Absorption Near Edge Structure (XANES) was performed on matrix FIB sections using synchrotron-based scanning transmission X-ray microscopy (STXM). The Fe3+ / ? Fe ratio of submicron silicate particles was obtained and coordinated with TEM observations. In all the least altered CR chondrites (QUE 99177, EET 87770, EET 92042, LAP 02342, GRA 95229 and Renazzo), we find that the matrices consist of abundant submicron Fe-rich hydrated amorphous silicate grains, mixed with nanometer-sized phyllosilicates. The Fe3+ / ? Fe ratios of both amorphous and nanocrystalline regions are very high with values ranging from 68 to 78%. In the most altered samples (Al Rais and GRO 95577), fine-grained phyllosilicates also have a high Fe3+ / ? Fe ratio (around 70%), whereas the coarse, micrometer-sized phyllosilicates are less oxidized (down to 55%) and have a lower iron content. These observations suggest the following sequence: submicron Fe2+-amorphous silicate particles were the building blocks of CR matrices; after accretion they were quickly hydrated and oxidized, leading to a metastable, amorphous gel-like phase. Nucleation and growth of crystalline phyllosilicates was kinetically-limited in most type 3 and 2 CRs, but increased as alteration became more extensive in Al Rais and GRO 95577. The decreasing Fe3+ / ? Fe ratio is interpreted as a result of the transfer of Fe3+ from silicates to oxides during growth, while aqueous alteration progressed (higher temperature, longer duration, change of fluid composition). In a fully closed system, equilibrium thermodynamics suggest that the water to rock ratios, typically assumed to be low (<1) for chondrites, should primarily control the iron valency of the silicates and predict a lower Fe3+ / ? Fe ratio. Such a high Fe3+ / ? Fe value could be accounted for, however, if the system was partially open, at least with respect to H2 (and other gases as well). Rapid degassing of the fluid would have favored more oxidizing fluid conditions. Recently proposed scenarios involving some degree of water D/H increase through Rayleigh isotopic fractionation are supported by these results.

  14. Application of Superparamagnetic Iron Oxide for Hepatic Tumor Diagnosis

    Microsoft Academic Search

    Akihiro Tanimoto; Sachio Kuribayashi

    Superparamagnetic iron oxide (SPIO) particles as magnetic resonance (MR) contrast media are composed of iron oxide crystals coated with dextran or carboxydextran. These particles are sequestered by phagocytic Kupffer cells in normal reticuloendothelial system (RES), but are not retained in tumor tissue. Consequently, a significant differences in T2\\/T2* relaxation between normal RES tissue and tumors occurs, resulting in increased lesion

  15. In Situ Iron Oxide Emplacement for Groundwater Arsenic Remediation

    E-print Network

    Abia, Thomas Sunday

    2012-02-14

    onto the surface as ferric oxide. The iron oxide (FeOx) emplacement process was significantly affected by (1) the initial surface area and surface-bound iron content of the sand, (2) the pH and solubility of the coating reagents, (3) the stability...

  16. Thermal transition behaviour of iron oxide–polypyrrole nanocomposites

    Microsoft Academic Search

    Komilla Suri; S. Annapoorni; R. P. Tandon; C. Rath; V. K. Aggrawal

    2003-01-01

    Distinct thermal transitions have been observed in nanocomposites based on iron oxide–polypyrrole prepared by simultaneous gelation and polymerization process. The transition behaviour for various iron oxide–polypyrrole compositions was investigated with the help of differential scanning calorimetery. It has been observed that the samples show a magnetic to nonmagnetic transition at 410 °C. The presence of exothermic peak at 410 °C

  17. Recent advances in iron oxide nanocrystal technology for medical imaging

    Microsoft Academic Search

    Claire Corot; Philippe Robert; Jean-Marc Idée; Marc Port

    2006-01-01

    Superparamagnetic iron oxide particles (SPIO and USPIO) have a variety of applications in molecular and cellular imaging. Most of the recent research has concerned cellular imaging with imaging of in vivo macrophage activity. According to the iron oxide nanoparticle composition and size which influence their biodistribution, several clinical applications are possible: detection liver metastases, metastatic lymph nodes, inflammatory and\\/or degenerative

  18. TRACE ELEMENT BINDING DURING STRUCTURAL TRANSFORMATION IN IRON OXIDES

    EPA Science Inventory

    Iron (hydr)oxides often control the mobility of inorganic contaminants in soils and sediments. A poorly ordered form of ferrihydrite is commonly produced during rapid oxidation of ferrous iron at sharp redox fronts encountered during discharge of anoxic/suboxic waters into terre...

  19. Complement receptor type 2conjugated superparamagnetic iron oxide nanoparticles

    E-print Network

    Levin, Judith G.

    Complement receptor type 2­conjugated superparamagnetic iron oxide nanoparticles [CR2-Fc-SPIO] Kam: Complement receptor type 2­conjugated gold/superparamagnetic iron oxide nanoparticles Abbreviated name: CR2, and oligodendroglial cells. SPIO nanoparticles are sometimes modified with dextran, poly(ethylene glycol) (PEG

  20. MAGNETIC PROPERTIES OF AMORPHOUS IRON (ill) OXIDE THIN FILMS T. Shigematsu, Y. Bando and T. Takada

    E-print Network

    Paris-Sud XI, Université de

    the preparation of iron oxide films by reactive evaporation method /1, 2/. We obtained the films of iron oxide) oxide films were prepared by deposition of iron metal in an oxygen atmosphere of SxlO"1 * torr, the same as those in the previous works /1,2/. An iron oxide film was obtained by evaporation of iron

  1. Recovery of iron oxide concentrate from high-sulfur and low-grade pyrite cinder using an innovative beneficiating process

    Microsoft Academic Search

    Binbin He; Xike Tian; Yan Sun; Chao Yang; Yanglin Zeng; Yanxin Wang; Suxin Zhang; Zhenbang Pi

    2010-01-01

    A high quality iron oxide concentrate, suitable as a feed for blast and electric reduction furnaces was recovered from high-sulfur and low-grade pyrite cinder. Pyrite cinder was treated with a hot strong alkali solution which dissolved most of the silica and alumina, leaving a solid residue and forming a precipitate which was an acid-soluble salt of aluminosilicate hydrate. The residue

  2. Leaching of oxidic zinc materials with chlorine and chlorine hydrate

    Microsoft Academic Search

    B. K. Thomas; D. J. Fray

    1981-01-01

    Low grade zinc ores and residues were leached in chlorine water and chlorine hydrate water mixtures. It was found that the rate of leaching Adrar ore and Electric Arc Furnace dust obeyed a shrinking core diffusion model, whereas, the rate of leaching of Turkish ore appeared to be controlled by a surface reaction. In all cases, lead leached with the

  3. Evaluation of tumoral enhancement by superparamagnetic iron oxide particles: comparative studies with ferumoxtran and anionic iron oxide nanoparticles

    Microsoft Academic Search

    P. Y. Brillet; F. Gazeau; A. Luciani; B. Bessoud; C.-A. Cuénod; N. Siauve; J.-N. Pons; J. Poupon; O. Clément

    2005-01-01

    This study was designed to compare tumor enhancement by superparamagnetic iron oxide particles, using anionic iron oxide nanoparticles (AP) and ferumoxtran. In vitro, relaxometry and media with increasing complexity were used to assess the changes in r2 relaxivity due to cellular internalization. In vivo, 26 mice with subcutaneously implanted tumors were imaged for 24 h after injection of particles to describe

  4. A Simple Way to Synthesize Superparamagnetic Iron Oxide Nanoparticles in Air Atmosphere: Iron Ion Concentration Effect

    Microsoft Academic Search

    Oznur Karaagac; Hakan Kockar; Seda Beyaz; Taner Tanrisever

    2010-01-01

    We have synthesized iron oxide nanoparticles in air atmosphere by coprecipitation. The ratio of was fixed at 2\\/3. The total amount of iron ions in the solution was varied from 250 mmol to 12.5 mmol. X-ray diffraction (XRD) patterns showed the characteristic peaks of iron oxide phases. We observed that the crystallinity reduced and particle sizes calculated from XRD patterns

  5. Ecological succession among iron-oxidizing bacteria

    PubMed Central

    Fleming, Emily J; Cetini?, Ivona; Chan, Clara S; Whitney King, D; Emerson, David

    2014-01-01

    Despite over 125 years of study, the factors that dictate species dominance in neutrophilic iron-oxidizing bacterial (FeOB) communities remain unknown. In a freshwater wetland, we documented a clear ecological succession coupled with niche separation between the helical stalk-forming Gallionellales (for example, Gallionella ferruginea) and tubular sheath-forming Leptothrix ochracea. Changes in the iron-seep community were documented using microscopy and cultivation-independent methods. Quantification of Fe-oxyhydroxide morphotypes by light microscopy was coupled with species-specific fluorescent in situ hybridization (FISH) probes using a protocol that minimized background fluorescence caused by the Fe-oxyhydroxides. Together with scanning electron microscopy, these techniques all indicated that Gallionellales dominated during early spring, with L. ochracea becoming more abundant for the remainder of the year. Analysis of tagged pyrosequencing reads of the small subunit ribosomal RNA gene (SSU rRNA) collected during seasonal progression supported a clear Gallionellales to L. ochracea transition, and community structure grouped according to observed dominant FeOB forms. Axis of redundancy analysis of physicochemical parameters collected from iron mats during the season, plotted with FeOB abundance, corroborated several field and microscopy-based observations and uncovered several unanticipated relationships. On the basis of these relationships, we conclude that the ecological niche of the stalk-forming Gallionellales is in waters with low organic carbon and steep redoxclines, and the sheath-forming L. ochracea is abundant in waters that contain high concentrations of complex organic carbon, high Fe and Mn content and gentle redoxclines. Finally, these findings identify a largely unexplored relationship between FeOB and organic carbon. PMID:24225888

  6. Multiple hearth furnace for reducing iron oxide

    DOEpatents

    Brandon, Mark M. (Charlotte, NC); True, Bradford G. (Charlotte, NC)

    2012-03-13

    A multiple moving hearth furnace (10) having a furnace housing (11) with at least two moving hearths (20) positioned laterally within the furnace housing, the hearths moving in opposite directions and each moving hearth (20) capable of being charged with at least one layer of iron oxide and carbon bearing material at one end, and being capable of discharging reduced material at the other end. A heat insulating partition (92) is positioned between adjacent moving hearths of at least portions of the conversion zones (13), and is capable of communicating gases between the atmospheres of the conversion zones of adjacent moving hearths. A drying/preheat zone (12), a conversion zone (13), and optionally a cooling zone (15) are sequentially positioned along each moving hearth (30) in the furnace housing (11).

  7. Iron oxide nanoparticle enhancement of radiation cytotoxicity

    NASA Astrophysics Data System (ADS)

    Mazur, Courtney M.; Tate, Jennifer A.; Strawbridge, Rendall R.; Gladstone, David J.; Hoopes, P. Jack

    2013-02-01

    Iron oxide nanoparticles (IONPs) have been investigated as a promising means for inducing tumor cell-specific hyperthermia. Although the ability to generate and use nanoparticles that are biocompatible, tumor specific, and have the ability to produce adequate cytotoxic heat is very promising, significant preclinical and clinical development will be required for clinical efficacy. At this time it appears using IONP-induced hyperthermia as an adjunct to conventional cancer therapeutics, rather than as an independent treatment, will provide the initial IONP clinical treatment. Due to their high-Z characteristics, another option is to use intracellular IONPs to enhance radiation therapy without excitation with AMF (production of heat). To test this concept IONPs were added to cell culture media at a concentration of 0.2 mg Fe/mL and incubated with murine breast adenocarcinoma (MTG-B) cells for either 48 or 72 hours. Extracellular iron was then removed and all cells were irradiated at 4 Gy. Although samples incubated with IONPs for 48 hrs did not demonstrate enhanced post-irradiation cytotoxicity as compared to the non-IONP-containing cells, cells incubated with IONPs for 72 hours, which contained 40% more Fe than 48 hr incubated cells, showed a 25% decrease in clonogenic survival compared to their non-IONP-containing counterparts. These results suggest that a critical concentration of intracellular IONPs is necessary for enhancing radiation cytotoxicity.

  8. Microbially Induced Iron Oxidation: What, Where, How

    SciTech Connect

    SCHIERMEYER,ELISA M.; PROVENCIO,PAULA P.; NORTHUP,DIANA E.

    2000-08-15

    From the results of the different bacterial cells seen, it is fairly certain that Gallionella is present because of the bean-shaped cells and twisted stalks found with the TEM. The authors cannot confirm, though, what other iron-oxidizing genera exist in the tubes, since the media was only preferential and not one that isolated a specific genus of bacteria. Based on the environment in which they live and the source of the water, they believe their cultures contain Gallionella, Leptothrix, and possibly Crenothrix and Sphaerotilus. They believe the genus Leptothrix rather than Sphaerotilus exist in the tubes because the water source was fresh, unlike the polluted water in which Sphaerotilus are usually found. The TEM preparations worked well. The cryogenic method rapidly froze the cells in place and allowed them to view their morphology. The FAA method, as stated previously, was the best of the three methods because it gave the best contrast. The gluteraldehyde samples did not come out as well. It is possible that the gluteraldehyde the authors prepared was still too concentrated and did not mix well. Although these bacteria were collected from springs and then cultured in an environment containing a presumably pure iron-bearing metal, it seems the tube already containing Manganese Gradient Medium could be used with a piece of metal containing these bacteria. A small piece of corroding metal could then be inserted into the test tube and cultured to study the bacteria.

  9. Iron oxide nanoparticle enhancement of radiation cytotoxicity

    PubMed Central

    Mazur, Courtney M.; A.Tate, Jennifer; Strawbridge, Rendall R.; Gladstone, David J.; Hoopes, P. Jack

    2014-01-01

    Iron oxide nanoparticles (IONPs) have been investigated as a promising means for inducing tumor cell-specific hyperthermia. Although the ability to generate and use nanoparticles that are biocompatible, tumor specific, and have the ability to produce adequate cytotoxic heat is very promising, significant preclinical and clinical development will be required for clinical efficacy. At this time it appears using IONP-induced hyperthermia as an adjunct to conventional cancer therapeutics, rather than as an independent treatment, will provide the initial IONP clinical treatment. Due to their high-Z characteristics, another option is to use intracellular IONPs to enhance radiation therapy without excitation with AMF (production of heat). To test this concept IONPs were added to cell culture media at a concentration of 0.2 mg Fe/mL and incubated with murine breast adenocarcinoma (MTG-B) cells for either 48 or 72 hours. Extracellular iron was then removed and all cells were irradiated at 4 Gy. Although samples incubated with IONPs for 48 hrs did not demonstrate enhanced post-irradiation cytotoxicity as compared to the non-IONP-containing cells, cells incubated with IONPs for 72 hours, which contained 40% more Fe than 48 hr incubated cells, showed a 25% decrease in clonogenic survival compared to their non-IONP-containing counterparts. These results suggest that a critical concentration of intracellular IONPs is necessary for enhancing radiation cytotoxicity. PMID:25301998

  10. Leaching of oxidic zinc materials with chlorine and chlorine hydrate

    Microsoft Academic Search

    B. K. Thomas; D. J. Fray

    1981-01-01

    Low grade zinc ores and residues were leached in chlorine water and chlorine hydrate water mixtures. It was found that the\\u000a rate of leaching Adrar ore and Electric Arc Furnace dust obeyed a shrinking core diffusion model, whereas, the rate of leaching\\u000a of Turkish ore appeared to be controlled by a surface reaction. In all cases, lead leached with the

  11. Kinetics of the reaction of iron blast furance slag\\/hydrated lime sorbents with SO 2 at low temperatures: effects of sorbent preparation conditions

    Microsoft Academic Search

    Chiung-Fang Liu; Shih-Min Shih

    2004-01-01

    Sorbents highly reactive towards SO2 have been prepared from iron blast furnace slag and hydrated lime under different hydration conditions. The reaction of the dry sorbents with SO2 has been studied under the conditions similar to those in the bag filters in the spray-drying flue gas desulfurization system. The reaction was well described by a modified surface coverage model which

  12. Interaction of fluorescent sensor with superparamagnetic iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Karunakaran, Chockalingam; Jayabharathi, Jayaraman; Sathishkumar, Ramalingam; Jayamoorthy, Karunamoorthy

    2013-06-01

    To sense superparamagnetic iron oxides (Fe2O3 and Fe3O4) nanocrystals a sensitive bioactive phenanthroimidazole based fluorescent molecule, 2-(4-fluorophenyl)-1-phenyl-1H-phenanthro [9,10-d] imidazole has been designed and synthesized. Electronic spectral studies show that phenanthroimidazole is bound to the surface of iron oxide semiconductors. Fluorescent enhancement has been explained on the basis of photo-induced electron transfer (PET) mechanism and apparent binding constants have been deduced. Binding of phenanthroimidazole with iron oxide nanoparticles lowers the HOMO and LUMO energy levels of phenanthroimidazole molecule. Chemical affinity between the nitrogen atom of the phenanthroimidazole and Fe2+ and Fe3+ ions on the surface of the nano-oxide may result in strong binding of the phenanthroimidazole derivative with the nanoparticles. The electron injection from the photoexcited phenanthroimidazole to the iron oxides conduction band explains the enhanced fluorescence.

  13. Studies of the kinetics and mechanisms of perfluoroether reactions on iron and oxidized iron surfaces

    NASA Technical Reports Server (NTRS)

    Napier, Mary E.; Stair, Peter C.

    1992-01-01

    Polymeric perfluoroalkylethers are being considered for use as lubricants in high temperature applications, but have been observed to catalytically decompose in the presence of metals. X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) were used to explore the decomposition of three model fluorinated ethers on clean polycrystalline iron surfaces and iron surfaces chemically modified with oxygen. Low temperature adsorption of the model fluorinated ethers on the clean, oxygen modified and oxidized iron surfaces was molecular. Thermally activated defluorination of the three model compounds was observed on the clean iron surface at remarkably low temperatures, 155 K and below, with formation of iron fluoride. Preferential C-F bond scission occurred at the terminal fluoromethoxy, CF3O, of perfluoro-1-methoxy-2-ethoxy ethane and perfluoro-1-methoxy-2-ethoxy propane and at CF3/CF2O of perfluoro-1,3-diethoxy propane. The reactivity of the clean iron toward perfluoroalkylether decomposition when compared to other metals is due to the strength of the iron fluoride bond and the strong electron donating ability of the metallic iron. Chemisorption of an oxygen overlayer lowered the reactivity of the iron surface to the adsorption and decomposition of the three model fluorinated ethers by blocking active sites on the metal surface. Incomplete coverage of the iron surface with chemisorbed oxygen results in a reaction which resembles the defluorination reaction observed on the clean iron surface. Perfluoro-1-methoxy-2-ethoxy ethane reacts on the oxidized iron surface at 138 K, through a Lewis acid assisted cleavage of the carbon oxygen bond, with preferential attack at the terminal fluoromethoxy, CF3O. The oxidized iron surface did not passivate, but became more reactive with time. Perfluoro-1-methoxy-2-ethoxy propane and perfluoro-1,3-diethoxy propane desorbed prior to the observation of decomposition on the oxidized iron surface.

  14. Prediction of iron oxide contents using diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Marques, José, Jr.; Arantes Camargo, Livia

    2015-04-01

    Determining soil iron oxides using conventional analysis is relatively unfeasible when large areas are mapped, with the aim of characterizing spatial variability. Diffuse reflectance spectroscopy (DRS) is rapid, less expensive, non-destructive and sometimes more accurate than conventional analysis. Furthermore, this technique allows the simultaneous characterization of many soil attributes with agronomic and environmental relevance. This study aims to assess the DRS capability to predict iron oxides content -hematite and goethite - , characterizing their spatial variability in soils of Brazil. Soil samples collected from an 800-hectare area were scanned in the visible and near-infrared spectral range. Moreover, chemometric calibration was obtained through partial least-squares regression (PLSR). Then, spatial distribution maps of the attributes were constructed using predicted values from calibrated models through geostatistical methods. The studied area presented soils with varied contents of iron oxides as examples for the Oxisols and Entisols. In the spectra of each soil is observed that the reflectance decreases with the content of iron oxides present in the soil. In soils with a high content of iron oxides can be observed more pronounced concavities between 380 and 1100 nm which are characteristic of the presence of these oxides. In soils with higher reflectance it were observed concavity characteristics due to the presence of kaolinite, in agreement with the low iron contents of those soils. The best accuracy of prediction models [residual prediction deviation (RPD) = 1.7] was obtained for goethite within the visible region (380-800 nm), and for hematite (RPD = 2.0) within the visible near infrared (380-2300 nm). The maps of goethite and hematite predicted showed the spatial distribution pattern similar to the maps of clay and iron extracted by dithionite-citrate-bicarbonate, being consistent with the iron oxide contents of soils present in the study area. These results confirm the value of DRS in the mapping of iron oxides in large areas at detailed scale.

  15. Oxidative stress and the homeodynamics of iron metabolism.

    PubMed

    Bresgen, Nikolaus; Eckl, Peter M

    2015-01-01

    Iron and oxygen share a delicate partnership since both are indispensable for survival, but if the partnership becomes inadequate, this may rapidly terminate life. Virtually all cell components are directly or indirectly affected by cellular iron metabolism, which represents a complex, redox-based machinery that is controlled by, and essential to, metabolic requirements. Under conditions of increased oxidative stress—i.e., enhanced formation of reactive oxygen species (ROS)—however, this machinery may turn into a potential threat, the continued requirement for iron promoting adverse reactions such as the iron/H2O2-based formation of hydroxyl radicals, which exacerbate the initial pro-oxidant condition. This review will discuss the multifaceted homeodynamics of cellular iron management under normal conditions as well as in the context of oxidative stress. PMID:25970586

  16. Oxidative Stress and the Homeodynamics of Iron Metabolism

    PubMed Central

    Bresgen, Nikolaus; Eckl, Peter M.

    2015-01-01

    Iron and oxygen share a delicate partnership since both are indispensable for survival, but if the partnership becomes inadequate, this may rapidly terminate life. Virtually all cell components are directly or indirectly affected by cellular iron metabolism, which represents a complex, redox-based machinery that is controlled by, and essential to, metabolic requirements. Under conditions of increased oxidative stress—i.e., enhanced formation of reactive oxygen species (ROS)—however, this machinery may turn into a potential threat, the continued requirement for iron promoting adverse reactions such as the iron/H2O2-based formation of hydroxyl radicals, which exacerbate the initial pro-oxidant condition. This review will discuss the multifaceted homeodynamics of cellular iron management under normal conditions as well as in the context of oxidative stress. PMID:25970586

  17. Immobilisation of arsenic by iron(II)-oxidizing bacteria

    NASA Astrophysics Data System (ADS)

    Kappler, A.; Hohmann, C.; Winkler, E.; Muehe, M.; Morin, G.

    2008-12-01

    Arsenic-contaminated groundwater is an environmental problem that affects about 1-2% of the world's population. As arsenic-contaminated water is also used for irrigating rice fields, the uptake of arsenic via rice is in some cases even higher than via drinking water. Arsenic is often of geogenic origin and in many cases bound to iron(III) minerals. Microbial iron(III) reduction leads to dissolution of Fe(III) minerals and thus the arsenic bound to these minerals is released to the environment. In turn, iron(II)-oxidizing bacteria have the potential to co-precipitate or sorb arsenic during iron(II) oxidation followed by iron(III) mineral formation. Here, we present work on arsenic co-precipitation and immobilization by anaerobic and aerobic iron(II)-oxidizing bacteria. Co-precipitation batch experiments with pure cultures of nitrate-dependent, phototrophic, and microaerophilic Fe(II)-oxidizing bacteria are used to quantify the amount of arsenic that can be immobilized during microbial iron mineral precipitation. Iron and arsenic speciation and redox state are determined by X- ray diffraction and synchrotron-based X-ray absorption methods (EXAFS, XANES). Microcosm experiments are set-up either with liquid media or with rice paddy soil amended with arsenic. Rice paddy soil from arsenic contaminated rice fields in China that include a natural population of Fe(II)-oxidizing microorganisms is used as inoculum. Dissolved and solid-phase arsenic and iron are quantified, Arsenic speciation is determined and the iron minerals are identified. Additionally, Arsenic uptake into the rice plant is quantified and a gene expression pattern in rice (Oryza sativa cv Gladia) is determined by microarrays as a response to the presence of Fe(II)-oxidizing bacteria.

  18. Surface modifications of iron oxide nanoparticles for biological applications

    E-print Network

    Insin, Numpon

    2011-01-01

    Iron oxides magnetic nanoparticles (MPs) of high crystallinity, high magnetization, and size-monodispersity were synthesized with oleic acid as their native ligands. These hydrophobic and non-functionalized MPs have magnetic ...

  19. Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

    PubMed Central

    2008-01-01

    Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed. PMID:21749733

  20. Polymer-coated iron oxide nanoparticles for medical imaging

    E-print Network

    Chen, Suelin, Ph.D. Massachusetts Institute of Technology

    2010-01-01

    One of the most versatile and safe materials used in medicine are polymer-coated iron oxide nanoparticles. This dissertation describes several formulations for in vivo imaging applications. The paramagnetic polymer-coated ...

  1. Sulfates and Iron Oxides in Ophir Chasma, Mars

    NASA Astrophysics Data System (ADS)

    Wendt, L.; Gross, C.; Kneissl, T.; Sowe, M.; Combe, J.-P.; Ledeit, L.; McGuire, P. C.; Neukum, G.

    2010-03-01

    We identified sulfates, including jarosite, and iron oxides in Ophir Chasma around and within Ophir Mensa, based on OMEGA and CRISM data. This suggests sulfate formation both before or during ILD deposition and after their erosion.

  2. Electronic properties of calcium borate glasses containing iron oxide

    Microsoft Academic Search

    M. Gawish; M. N. Saleh

    1976-01-01

    The electronic properties of calcium borate glasses containing iron oxide have been investigated. It was found that glasses with an Fe2O3 content less than 20 mole% were amorphous, while those above 20 mole% were devitrified. It was observed that increasing the iron molar content in the amorphous samples caused an increase in their dc conductivity, ac conductivity, dielectric constant, and

  3. In vitro demonstration of anaerobic oxidation of methane coupled to sulphate reduction in sediment from a marine gas hydrate area

    Microsoft Academic Search

    Katja Nauhaus; Antje Boetius; Martin Kruger; Friedrich Widdel

    2002-01-01

    Summary Anaerobic oxidation of methane (AOM) and sulphate reduction were examined in sediment samples from a marine gas hydrate area (Hydrate Ridge, NE Pacific). The sediment contained high numbers of microbial consortia consisting of organisms that affi- liate with methanogenic archaea and with sulphate- reducing bacteria. Sediment samples incubated under strictly anoxic conditions in defined mineral medium (salinity as in

  4. Iron oxide-based nanomagnets in nanomedicine: fabrication and applications

    PubMed Central

    Meng Lin, Meng; Kim, Hyung-Hwan; Kim, Hyuck; Muhammed, Mamoun; Kyung Kim, Do

    2010-01-01

    Iron oxide-based nanomagnets have attracted a great deal of attention in nanomedicine over the past decade. Down to the nanoscale, superparamagnetic iron oxide nanoparticles can only be magnetized in the presence of an external magnetic field, which makes them capable of forming stable colloids in a physio-biological medium. Their superparamagnetic property, together with other intrinsic properties, such as low cytotoxicity, colloidal stability, and bioactive molecule conjugation capability, makes such nanomagnets ideal in both in-vitro and in-vivo biomedical applications. In this review, a chemical, physical, and biological synthetic approach to prepare iron oxide-based nanomagnets with different physicochemical properties was illustrated and compared. The growing interest in iron oxide-based nanomagnets with multifunctionalities was explored in cancer diagnostics and treatment, focusing on their combined roles in a magnetic resonance contrast agent, hyperthermia, and magnetic force assisted drug delivery. Iron oxides as magnetic carriers in gene therapy were reviewed with a focus on the sophisticated design and construction of magnetic vectors. Finally, the iron oxide-based nanomagnet also represents a very promising tool in particle/cell interfacing in controlling cellular functionalities, such as adhesion, proliferation, differentiation, and cell patterning, in stem cell therapy and tissue engineering applications. PMID:22110854

  5. Synthesis and heating effect of iron/iron oxide composite and iron oxide nanoparticles.

    PubMed

    Zeng, Q; Baker, I; Loudis, J A; Liao, Y F; Hoopes, P J

    2007-02-01

    Fe/Fe oxide nanoparticles, in which the core consists of metallic Fe and the shell is composed of Fe oxides, were obtained by reduction of an aqueous solution of FeCl3 within a NaBH4 solution, or, using a water-in-oil micro-emulsion with CTAB as the surfactant. The reduction was performed either in an inert atmosphere or in air, and passivation with air was performed to produce the Fe/Fe3O4 core/shell composite. Phase identification and particle size were determined by X-ray diffraction and TEM. Thermal analysis was performed using a differential scanning calorimeter. The quasistatic magnetic properties were measured using a VSM, and the specific absorption rates (SARs) of both Fe oxide and Fe/Fe3O4 composite nanoparticles either dispersed in methanol or in an epoxy resin were measured by Luxtron fiber temperature sensors in an alternating magnetic field of 150 Oe at 250 kHz. It was found that the preparation conditions, including the concentrations of solutions, the mixing procedure and the heat treatment, influence the particle size, the crystal structure and consequently the magnetic properties of the particles. Compared with Fe oxides, the saturation magnetization (MS ) of Fe/Fe3O4 particles (100-190 emu/g) can be twice as high, and the coercivity (HC ) can be tunable from several Oe to several hundred Oe. Hence, the SAR of Fe/Fe3O4 composite nanoparticles can be much higher than that of Fe oxides, with a maximum SAR of 345 W/g. The heating behavior is related to the magnetic behavior of the nanoparticles. PMID:25301983

  6. Synthesis and heating effect of iron/iron oxide composite and iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Zeng, Q.; Baker, I.; Loudis, J. A.; Liao, Y. F.; Hoopes, P. J.

    2007-02-01

    Fe/Fe oxide nanoparticles, in which the core consists of metallic Fe and the shell is composed of Fe oxides, were obtained by reduction of an aqueous solution of FeCl 3 within a NaBH 4 solution, or, using a water-in-oil micro-emulsion with CTAB as the surfactant. The reduction was performed either in an inert atmosphere or in air, and passivation with air was performed to produce the Fe/Fe 3O 4 core/shell composite. Phase identification and particle size were determined by X-ray diffraction and TEM. Thermal analysis was performed using a differential scanning calorimeter. The quasistatic magnetic properties were measured using a VSM, and the specific absorption rates (SARs) of both Fe oxide and Fe/Fe 3O 4 composite nanoparticles either dispersed in methanol or in an epoxy resin were measured by Luxtron fiber temperature sensors in an alternating magnetic field of 150 Oe at 250 kHz. It was found that the preparation conditions, including the concentrations of solutions, the mixing procedure and the heat treatment, influence the particle size, the crystal structure and consequently the magnetic properties of the particles. Compared with Fe oxides, the saturation magnetization (MS) of Fe/Fe 3O 4 particles (100-190 emu/g) can be twice as high, and the coercivity (H C) can be tunable from several Oe to several hundred Oe. Hence, the SAR of Fe/Fe 3O 4 composite nanoparticles can be much higher than that of Fe oxides, with a maximum SAR of 345 W/g. The heating behavior is related to the magnetic behavior of the nanoparticles.

  7. Evaluation of the thermodynamic properties of hydrated metal oxide nanoparticles by INS techniques

    SciTech Connect

    Spencer, Elinor [Virginia Polytechnic Institute and State University] [Virginia Polytechnic Institute and State University; Ross, Dr. Nancy [Virginia Polytechnic Institute and State University] [Virginia Polytechnic Institute and State University; Parker, Stewart F. [ISIS Facility, Rutherford Appleton Laboratory (ISIS)] [ISIS Facility, Rutherford Appleton Laboratory (ISIS); Kolesnikov, Alexander I [ORNL] [ORNL

    2013-01-01

    In this contribution we will present a detailed methodology for the elucidation of the following aspects of the thermodynamic properties of hydrated metal oxide nanoparticles from high-resolution, low-temperature inelastic neutron scattering (INS) data: (i) the isochoric heat capacity and entropy of the hydration layers both chemi- and physisorbed to the particle surface; (ii) the magnetic contribution to the heat capacity of the nanoparticles. This will include the calculation of the vibrational density of states (VDOS) from the raw INS spectra, and the subsequent extraction of the thermodynamic data from the VDOS. This technique will be described in terms of a worked example namely, cobalt oxide (Co3O4 and CoO). To complement this evaluation of the physical properties of metal oxide nanoparticle systems, we will emphasise the importance of high-resolution, high-energy INS for the determination of the structure and dynamics of the water species, namely molecular (H2O) and dissociated water (OH, hydroxyl), confined to the oxide surfaces. For this component of the chapter we will focus on INS investigations of hydrated isostructural rutile (a-TiO2) and cassiterite (SnO2) nanoparticles. We will complete this discussion of nanoparticle analysis by including an appraisal of the INS instrumentation employed in such studies with particular focus on TOSCA [ISIS, Rutherford Appleton Laboratory (RAL), U.K.] and the newly developed spectrometer SEQUOIA [SNS, Oak Ridge National Laboratory (ORNL), U.S.A].

  8. Analysis of iron oxide precipitates in constructed mine wastewater treatments

    SciTech Connect

    Partezana, J.M. [Saint Vincent College, Latrobe, PA (United States)

    1996-10-01

    The purpose or this research project is to characterize iron oxide precipitates collected from abandoned mine drainage (AMD) treatment facilities in order to determine whether these precipitates have possible commercial value. The treatment facilities use constructed wetlands to raise pH levels to near neutral levels and to remove iron and other heavy metals from AMD polluted water. The main commercial value of interest is in the use of pigments in products such as paints, clay and brick. The precipitates arc characterized for composition and quality against natural and synthetic commercial pigment products. Various processing techniques were developed for sample preparation. Analysis tests include: general pigment tests, heavy metals, anions, particle size, and particle composition. Results show that the iron oxide precipitates are chemically similar to the commercial iron oxide but will require additional processing to meet pigment qualifications.

  9. Genomic insights into microbial iron oxidation and iron uptake strategies in extremely acidic environments.

    PubMed

    Bonnefoy, Violaine; Holmes, David S

    2012-07-01

    This minireview presents recent advances in our understanding of iron oxidation and homeostasis in acidophilic Bacteria and Archaea. These processes influence the flux of metals and nutrients in pristine and man-made acidic environments such as acid mine drainage and industrial bioleaching operations. Acidophiles are also being studied to understand life in extreme conditions and their role in the generation of biomarkers used in the search for evidence of existing or past extra-terrestrial life. Iron oxidation in acidophiles is best understood in the model organism Acidithiobacillus ferrooxidans. However, recent functional genomic analysis of acidophiles is leading to a deeper appreciation of the diversity of acidophilic iron-oxidizing pathways. Although it is too early to paint a detailed picture of the role played by lateral gene transfer in the evolution of iron oxidation, emerging evidence tends to support the view that iron oxidation arose independently more than once in evolution. Acidic environments are generally rich in soluble iron and extreme acidophiles (e.g. the Leptospirillum genus) have considerably fewer iron uptake systems compared with neutrophiles. However, some acidophiles have been shown to grow as high as pH 6 and, in the case of the Acidithiobacillus genus, to have multiple iron uptake systems. This could be an adaption allowing them to respond to different iron concentrations via the use of a multiplicity of different siderophores. Both Leptospirillum spp. and Acidithiobacillus spp. are predicted to synthesize the acid stable citrate siderophore for Fe(III) uptake. In addition, both groups have predicted receptors for siderophores produced by other microorganisms, suggesting that competition for iron occurs influencing the ecophysiology of acidic environments. Little is known about the genetic regulation of iron oxidation and iron uptake in acidophiles, especially how the use of iron as an energy source is balanced with its need to take up iron for metabolism. It is anticipated that integrated and complex regulatory networks sensing different environmental signals, such as the energy source and/or the redox state of the cell as well as the oxygen availability, are involved. PMID:22050575

  10. Synthesis and Characterization of CREKA-Conjugated Iron Oxide Nanoparticles for Hyperthermia Applications

    PubMed Central

    Kruse, Anastasia M.; Meenach, Samantha A.; Anderson, Kimberly W.; Hilt, J. Zach

    2014-01-01

    One of the current challenges in the systemic delivery of nanoparticles in cancer therapy applications is the lack of effective tumor localization. Iron oxide nanoparticles coated with crosslinked dextran were functionalized with the tumor homing peptide CREKA, which binds to fibrinogen complexes in the extracellular matrix of tumors. This allows for the homing of these nanoparticles to tumor tissue. The iron oxide nanoparticle core allows for particle heating upon exposure to an alternating magnetic field (AMF) while the dextran coating stabilizes the particles in suspension and decreases the cytotoxicity of the system. Magnetically mediated hyperthermia (MMH) allows for the heating of tumor tissue to increase the efficacy of traditional cancer treatments using the iron oxide nanoparticles. While MMH provides the opportunity for localized heating, this method is currently limited by the lack of particle penetration into tumor tissue, even after effective targeted delivery to the tumor site. The CREKA-conjugated nanoparticles presented were characterized for their size, stability, heating capabilities and biocompatibility. The particles had a hydrated diameter of 52 nm, were stable in PBS and media with 10% v/v FBS over at least twelve hours, and generated enough heat to raise solution temperatures well into the hyperthermia range (41 – 45 °C) when exposed to an AMF due to an average specific absorption rate (SAR) of 83.5 W/g. Cytotoxicity studies demonstrated that the particles have low cytotoxicity over long exposure times at low concentrations. A fibrinogen clotting assay was used to determine the binding affinity of CREKA-conjugated particles, which was significantly greater than the binding affinity of dextran, only coated iron oxide nanoparticles demonstrating the potential for this particle system to effectively home to a variety of tumor locations. Finally, it was shown that in vitro MMH increased the effects of cisplatin compared to cisplatin or MMH treatments alone. PMID:24486913

  11. Heterogeneous deformation and recrystallisation of iron base oxide dispersion strengthened

    E-print Network

    Cambridge, University of

    Heterogeneous deformation and recrystallisation of iron base oxide dispersion strengthened PM2000 The recrystallisation behaviour of PM2000 oxide dispersion strengthened ferritic alloy has been investigated for tube) alloys, such as PM2000 and MA956, makes them prime candidates for the proposed heat exchangers.8

  12. Preventing oxidation of iron sulfide minerals by polyethylene polyamines

    E-print Network

    Belzile, Nelson

    Preventing oxidation of iron sulfide minerals by polyethylene polyamines Yu-Wei Chen a,*, Yuerong provide an effective protective layer for sulfidic ores and significantly reduce the penetration an important catalyzing role in the oxidation of sulfides and acid mine generation. Polyethylene polyamines

  13. The Oxidation Of Iron In A Gel Using Consumer Chemicals

    ERIC Educational Resources Information Center

    Wright, Stephen W.; Folger, Marsha R.; Quinn, Ryan P.; Sauls, Frederick C.; Krone, Diane

    2005-01-01

    An experiment is conducted for the oxidation of iron in a gel using consumer chemicals, which is pertinent to the students' understanding of redox chemistry and of the relative oxidation potentials of various metals. The experiment can be carried out with consumer chemicals that might be purchased at a supermarket and commonly found in the home.

  14. Characteristic of hydrous iron (III) oxides prepared by homogeneous precipitation of iron (III) sulphate with urea

    NASA Astrophysics Data System (ADS)

    Bakardjieva, S.; Štengl, V.; Šubrt, J.; Ve?erníková, E.

    2005-04-01

    Hydrous iron (III) oxides agglomerated into uniform porous spherical clusters with submicrometre size and high specific surface area were obtained. Homogeneous precipitation of iron (III) sulphate was carried out in boiling aqueous solution that contained excess of urea. The prepared precursor precipitates were heated for 2 h at various temperature (from 200 to 800 °C) to yield fine iron oxides powders. The structure evolution during heating of powders was investigated by X-ray diffraction (XRD). The morphology and microstructure characteristics were also obtained by means of scanning electron microscopy (SEM), (BET) and (BJH). In order to see the phase transition temperature thermogravimetric analysis/differential thermal analysis studies were performed. It was found that formation of different hydrous iron (III) oxides was affected by experimental conditions: aging time, mixing procedure, pH and temperature.

  15. Clathrate Hydrates of Oxidants in the Ice Shell of Europa

    NASA Astrophysics Data System (ADS)

    Hand, Devin P.; Chyba, Christopher F.; Carlson, Robert W.; Cooper, John F.

    2006-06-01

    Europa's icy surface is radiolytically modified by high-energy electrons and ions, and photolytically modified by solar ultraviolet photons. Observations from the Galileo Near Infrared Mapping Spectrometer, ground-based telescopes, the International Ultraviolet Explorer, and the Hubble Space Telescope, along with laboratory experiment results, indicate that the production of oxidants, such as H2O2, O2, CO2, and SO2, is a consequence of the surface radiolytic chemistry. Once created, some of the products may be entrained deeper into the ice shell through impact gardening or other resurfacing processes. The temperature and pressure environments of regions within the europan hydrosphere are expected to permit the formation of mixed clathrate compounds. The formation of carbon dioxide and sulfur dioxide clathrates has been examined in some detail. Here we add to this analysis by considering oxidants produced radiolytically on the surface of Europa. Our results indicate that the bulk ice shell could have a ~1.7-7.6% by number contamination of oxidants resulting from radiolysis at the surface. Oxidant-hosting clathrates would consequently make up ~12-53% of the ice shell by number relative to ice, if oxidants were entrained throughout. We examine, in brief, the consequences of such contamination on bulk ice shell thickness and find that clathrate formation could lead to substantially thinner ice shells on Europa than otherwise expected. Finally, we propose that double occupancy of clathrate cages by O2 molecules could serve as an explanation for the observation of condensed-phase O2 on Europa. Clathrate-sealed, gas-filled bubbles in the near surface ice could also provide an effective trapping mechanism, though they cannot explain the 5771 Å (O2)2 absorption.

  16. Iron(VI): Hypothetical Candidate for the Martian Oxidant

    Microsoft Academic Search

    A. I. Tsapin; M. G. Goldfeld; G. D. McDonald; K. H. Nealson; B. Moskovitz; P. Solheid; K. M. Kemner; S. D. Kelly; K. A. Orlandini

    2000-01-01

    As a result of the Viking missions of the early 1970s, the presence of a strong oxidant in martian soil was suggested. Here we present a hypothesis, testable by near-term missions, that iron(VI) is a likely contributor to the martian oxidative pool. In this context, ferrate(VI) salts, with FeO42? anion, were studied for their spectral and oxidative properties. Ferrate(VI) has

  17. Possible involvement of iron-induced oxidative insults in neurodegeneration.

    PubMed

    Asano, Takeshi; Koike, Masato; Sakata, Shin-ichi; Takeda, Yukiko; Nakagawa, Tomoko; Hatano, Taku; Ohashi, Satoshi; Funayama, Manabu; Yoshimi, Kenji; Asanuma, Masato; Toyokuni, Shinya; Mochizuki, Hideki; Uchiyama, Yasuo; Hattori, Nobutaka; Iwai, Kazuhiro

    2015-02-19

    Involvement of iron in the development of neurodegenerative disorders has long been suggested, and iron that cannot be stored properly is suggested to induce iron toxicity. To enhance iron uptake and suppress iron storage in neurons, we generated transgenic (Tg) mice expressing iron regulatory protein 2 (IRP2), a major regulator of iron metabolism, in a neuron-specific manner. Although very subtle, IRP2 was expressed in all regions of brain examined. In the Tg mice, mitochondrial oxidative insults were observed including generation of 4-hydroxynonenal modified proteins, which appeared to be removed by a mitochondrial quality control protein Parkin. Inter-crossing of the Tg mice to Parkin knockout mice perturbed the integrity of neurons in the substantia nigra and provoked motor symptoms. These results suggest that a subtle, but chronic increase in IRP2 induces mitochondrial oxidative insults and accelerates neurodegeneration in a mouse model of Parkinson's disease. Thus, the IRP2 Tg may be a useful tool to probe the roles of iron-induced mitochondrial damages in neurodegeraration research. PMID:25549542

  18. Effects of Intravenous Polymaltose Iron on Oxidant Stress and Non-Transferrin-Bound Iron in Hemodialysis Patients

    Microsoft Academic Search

    Fathi Driss; François Vrtovsnik; Sandrine Katsahian; Catherine Michel; Gabriel Baron; Amir Kolta; Nadia Sedrati; Françoise Mignon; Ioav Cabantchik; Bernard Grandchamp

    2005-01-01

    Background: The use of intravenous iron to correct anemia in end-stage renal diseases (ESRD) has been suspected of catalyzing the production of activated oxygen species and promoting oxidative damage. We investigated the pro-oxidative potential of injected iron in hemodialysis patients. Methods: In study A, 65 patients with ESRD were studied. 20 patients received weekly infusions of iron polymaltose (maltofer), whereas

  19. Role of Surface Precipitation in Copper Sorption by the Hydrous Oxides of Iron and Aluminum

    E-print Network

    Chorover, Jon

    Role of Surface Precipitation in Copper Sorption by the Hydrous Oxides of Iron and Aluminum K. G precipitation; sorption; isotherms; X-ray diffraction; hydrous iron oxide; hydrous aluminum oxide; copper. INTRODUCTION Hydrous oxides of iron (HFO) and aluminum (HAO) are important mineral components of natural

  20. Effect of green tea on iron status and oxidative stress in iron-loaded rats.

    PubMed

    Ounjaijean, S; Thephinlap, C; Khansuwan, U; Phisalapong, C; Fucharoen, S; Porter, J B; Srichairatanakool, S

    2008-07-01

    Plasma non-transferrin bound iron (NTBI) is potentially toxic and contributes to the generation of reactive oxygen species (ROS), consequently leading to tissue damage and organ dysfunction. Iron chelators and antioxidants are used for treatment of thalassemia patients. Green tea (GT) contains catechins derivatives that have many biological activities. The purpose of this study was to investigate the iron-chelating and free-radical scavenging capacities of green tea extract in vivo. Rats were injected ip with ferric citrate together with orally administered GT extract (GTE) for 4 months. Blood was collected monthly for measurement of iron overload and oxidative stress indicators. Plasma iron (PI) and total iron-binding capacity (TIBC) were quantified using bathophenanthroline method. Plasma NTBI was assayed with NTA chelation/HPLC. Plasma malonyldialdehyde (MDA) was determined by using the TBARS method. Erythrocyte oxidative stress was assessed using flow cytometry. Levels of PI, TIBC, NTBI and MDA, and erythrocyte ROS increased in the iron-loaded rats. Intervention with GT extract markedly decreased the PI and TIBC concentrations. It also lowered the transferrin saturation and effectively inhibited formation of NTBI. It also decreased the levels of erythrocyte ROS in week 4, 12 and 16. Therefore, green tea extract can decrease iron in plasma as well as eliminate lipid peroxidation in plasma, and destroy formation of erythrocyte ROS in the rats challenged with iron. The bifunctional effects could be beneficial in alleviating the iron and oxidative stress toxicity. In prospective, these GTE activities should be further examined in thalassemic animals or humans. PMID:18673149

  1. Peroxide oxidation of iron in coal mine drainage

    Microsoft Academic Search

    C. A. Cole; A. E. Molinski; N. Rieg; F. Backus

    1977-01-01

    Ferrous iron in a coal mine drainage water at Wildwood, Pennsylvania, was found to be oxidizing and precipitating in a small receiving stream. A cascade aeration system and a 3800-m³ cement settling basin were installed in an effort to remove the iron from the nearly all 400 m³\\/d flow but were only partially successful. Of the 30 to 40 mg\\/1

  2. Multimodal Iron Oxide Nanoparticles for Hybrid Biomedical Imaging

    PubMed Central

    Heidt, Timo; Nahrendorf, Matthias

    2012-01-01

    Iron oxide core nanoparticles are attractive imaging agents because their material properties allow the tuning of pharmacokinetics as well as attachment of multiple moieties to their surface. In addition to affinity ligands, these include fluorochromes and radioisotopes for detection with optical and nuclear imaging. As the iron oxide core can be detected by MRI, options for combining imaging modalities are manifold. Already, preclinical imaging strategies combine non-invasive imaging with higher resolution techniques such as intravital microscopy to gain unprecedented insight into steady state biology and disease. Going forward, hybrid iron oxide nanoparticles will likely help to merge modalities, creating a synergy that enables imaging in basic research and, potentially, also in the clinic. PMID:23065771

  3. Annealing effects on 5 nm iron oxide nanoparticles.

    PubMed

    Vargas, J M; Lima, E; Socolovsky, L M; Knobel, M; Zanchet, D; Zysler, R D

    2007-09-01

    Morphological, structural and magnetic properties of 4.8 nm iron oxide nanoparticles have been investigated after annealing under inert atmosphere at different temperatures. The as-prepared iron oxide nanoparticles have been synthesized by chemical route from high temperature reaction of Fe(acac)3 solution in presence of oleic acid and oleylamine surfactant. Annealing the particles at low temperatures (Tann = 573 K) produces an increment of the mean size from 4.8 nm to 6.0 nm, preserving the same morphology. The coercive field of the annealed sample has a small increasing with respect to the as-prepared sample in agreement with the mean particle volume change. Annealing at higher temperature (Tann = 823 K) leads to a bimodal size distribution of the iron oxide nanoparticles with 6.0 nm and 17 nm mean sizes respectively, where the bigger particles dominate the observed magnetic properties. PMID:18019166

  4. Safety assessment of chronic oral exposure to iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Chamorro, Susana; Gutiérrez, Lucía; Vaquero, María Pilar; Verdoy, Dolores; Salas, Gorka; Luengo, Yurena; Brenes, Agustín; José Teran, Francisco

    2015-05-01

    Iron oxide nanoparticles with engineered physical and biochemical properties are finding a rapidly increasing number of biomedical applications. However, a wide variety of safety concerns, especially those related to oral exposure, still need to be addressed for iron oxide nanoparticles in order to reach clinical practice. Here, we report on the effects of chronic oral exposure to low doses of ?-Fe2O3 nanoparticles in growing chickens. Animal observation, weight, and diet intake reveal no adverse signs, symptoms, or mortality. No nanoparticle accumulation was observed in liver, spleen, and duodenum, with feces as the main excretion route. Liver iron level and duodenal villi morphology reflect the bioavailability of the iron released from the partial transformation of ?-Fe2O3 nanoparticles in the acid gastric environment. Duodenal gene expression studies related to the absorption of iron from ?-Fe2O3 nanoparticles indicate the enhancement of a ferric over ferrous pathway supporting the role of mucins. Our findings reveal that oral administration of iron oxide nanoparticles is a safe route for drug delivery at low nanoparticle doses.

  5. Photocatalytic Oxidation of Isoprene on Hydrated Atmospheric Mineral Dusts

    NASA Astrophysics Data System (ADS)

    Hoffmann, M. R.; Kameel, F. R.; Colussi, A. J.

    2011-12-01

    Mineral dust aerosols, an important fraction in the tropospheric aerosol budget, contain transition metal-based semiconductor particles that absorb light and may support diverse chemical transformations. Dust aerosol is primary, mostly originates from deserts, but includes fly ash emitted by power plants, and can be carried over long distances. We propose that such semiconductor particles may produce secondary organic aerosol (SOA) via surface-activated photochemical processes in aqueous media. Isoprene, the most abundant anthropogenic VOC is deemed to be incorporated into SOA by various mechanisms that remain to be fully characterized. We suggest that condensed-phase chemistry, in addition to gas-phase transformations, plays an important role in SOA formation. Isoprene is only slightly soluble in water, but it would react at diffusionally-controlled rates with photochemically generated OH-radicals in aqueous phase to produce more complex, polar compounds via oxidation and polymerization processes. We have found that the similar products are formed in the photolysis of aqueous hydrogen peroxide solutions or titanium dioxide suspensions in the presence of dissolved isoprene, as revealed by HPLC analysis with online high-resolution positive ion electrospray ionization mass spectrometric detection, and 1H and 13C nuclear magnetic resonance spectrometry. In contrast, hematite suspensions display negligible photocatalytic activity toward isoprene oxidation. These results suggest that atmospheric heterogeneous semiconductor photocatalysis of isoprene may play a significant role in global secondary organic aerosol formation under overly dusty conditions. Full product characterization is underway that aims at identifying species that may have adverse health/respiratory effects.

  6. Electrolytic photodissociation of chemical compounds by iron oxide electrodes

    DOEpatents

    Somorjai, Gabor A. (Berkeley, CA); Leygraf, Christofer H. (Berkeley, CA)

    1984-01-01

    Chemical compounds can be dissociated by contacting the same with a p/n type semi-conductor diode having visible light as its sole source of energy. The diode consists of low cost, readily available materials, specifically polycrystalline iron oxide doped with silicon in the case of the n-type semi-conductor electrode, and polycrystalline iron oxide doped with magnesium in the case of the p-type electrode. So long as the light source has an energy greater than 2.2 electron volts, no added energy source is needed to achieve dissociation.

  7. Electrolytic photodissociation of chemical compounds by iron oxide photochemical diodes

    DOEpatents

    Somorjai, Gabor A. (Berkeley, CA); Leygraf, Christofer H. (Berkeley, CA)

    1985-01-01

    Chemical compounds can be dissociated by contacting the same with a p/n type semi-conductor photochemical diode having visible light as its sole source of energy. The photochemical diode consists of low cost, readily available materials, specifically polycrystalline iron oxide doped with silicon in the case of the n-type semi-conductor electrode, and polycrystalline iron oxide doped with magnesium in the case of the p-type electrode. So long as the light source has an energy greater than 2.2 electron volts, no added energy source is needed to achieve dissociation.

  8. Bioextraction of iron from iron oxides. Final report, August 15, 1983-August 14, 1986

    SciTech Connect

    Arnold, R.G.; DiChristina, T.J.; Hoffmann, M.R.

    1986-01-01

    The feasibilities of (1) liberating free energy from dissimilative iron reduction and (2) coupling oxidative phosphorylation to electron transport to Fe(III) are sensitive to the aqueous chemistry of Fe(III). A systematic investigation of iron-reduction kinetics as a function of Fe(III) speciation indicated that in Pseudomonas sp. 200 (1) iron-reduction rate is functionally related to the concentrations of individual iron species and (2) direct contact between Fe(III) and the ferrireductase of Pseudomonas sp. 200 is required for electron transfer. When Fe(III) is provided as an iron oxide, overall reduction rate is much slower, though still dependent upon provision of an Fe(III)-complexing ligand. Again, direct contact between oxide surface and microorganism is requisite to iron reduction. In Pseudomonas sp. 200 there are both a constitutive and an inducible pathway for electron transport to Fe(III). The species is able to maximize development of useable chemical energy from respiration by regulating both the synthesis of ferrireductase and the direction of electron transfer when alternative (branched) pathways are present. 218 refs., 80 figs., 32 tabs.

  9. Implications of the band gap problem on oxidation and hydration in acceptor-doped barium zirconate

    NASA Astrophysics Data System (ADS)

    Lindman, Anders; Erhart, Paul; Wahnström, Göran

    2015-06-01

    Charge carrier concentrations in acceptor-doped proton-conducting perovskites are to a large extent determined by the hydration and oxidation of oxygen vacancies, which introduce protons and holes, respectively. First-principles modeling of these reactions involves calculation of formation energies of charged defects, which requires an accurate description of the band gap and the position of the band edges. Since density-functional theory (DFT) with local and semilocal exchange-correlation functionals (LDA and GGA) systematically fails to predict these quantities this can have serious implications on the modeling of defect reactions. In this study we investigate how the description of band gap and band-edge positions affects the hydration and oxidation in acceptor-doped BaZrO3. First-principles calculations are performed in combination with thermodynamic modeling in order to obtain equilibrium charge carrier concentrations at different temperatures and partial pressures. Three different methods have been considered: DFT with both semilocal (PBE) and hybrid (PBE0) exchange-correlation functionals, and many-body perturbation theory within the G0W0 approximation. All three methods yield similar results for the hydration reaction, which are consistent with experimental findings. For the oxidation reaction, on the other hand, there is a qualitative difference. PBE predicts the reaction to be exothermic, while the two others predict an endothermic behavior. Results from thermodynamic modeling are compared with available experimental data, such as enthalpies, concentrations, and conductivities, and only the results obtained with PBE0 and G0W0 , with an endothermic oxidation behavior, give a satisfactory agreement with experiments.

  10. Evolutionary relationships among sulfur- and iron-oxidizing eubacteria.

    PubMed Central

    Lane, D J; Harrison, A P; Stahl, D; Pace, B; Giovannoni, S J; Olsen, G J; Pace, N R

    1992-01-01

    Some 37 reverse transcriptase, partial 16S rRNA sequences from sulfur- and/or iron-oxidizing eubacteria, including sequences from species of the genera Thiobacillus, Thiothrix, Thiomicrospira, Acidophilium, "Leptospirillum," Thiovulum, and Chlorobium, have been determined. In addition, 16S sequences from a number of unnamed sulfur- and/or iron-oxidizing bacteria from hydrothermal vent sites, from invertebrate-bacterial endosymbioses, and from various mineral recovery operations also have been determined. The majority of sequences place their bacterial donors in one or another of the subdivisions of the Proteobacteria. However, three unnamed facultatively thermophilic iron-oxidizing isolates, Alv, BC, and TH3, are affiliated with the gram-positive division. One H2S-oxidizer, from the genus Thiovulum, is affiliated with Campylobacter, Wolinella, and other genera in what appears to be a new subdivision of the Proteobacteria. Three "Leptospirillum"-helical vibrioid isolates, BU-1, LfLa, and Z-2, exhibit no clear phylum level affiliation at all, other than their strong relationship to each other. A picture is emerging of an evolutionary widespread capacity for sulfur and/or iron oxidation among the eubacteria. PMID:1729214

  11. The oxidation behavior of ODS iron aluminides

    Microsoft Academic Search

    B. A. Pint; P. F. Tortorelli; I. G. Wright

    1996-01-01

    Oxide-dispersed Fe-28at.%Al-2%Cr alloys were produced by a powder metallurgy technique followed by hot extrusion. A variety of stable oxides were added to the base alloy to assess the effect of these dopants on the oxidation behavior at 1200°C in air and Oâ. An AlâOâ dispersion flattened the α-AlâOâ scale, but produced none of the other reactive element effects and had

  12. Deposition rates of oxidized iron on Mars

    NASA Technical Reports Server (NTRS)

    Burns, R. G.

    1993-01-01

    The reddened oxidized surface of Mars is indicative of temporal interactions between the Martian atmosphere and its surface. During the evolution of the Martian regolith, primary ferromagnesian silicate and sulfide minerals in basaltic rocks apparently have been oxidized to secondary ferric-bearing assemblages. To evaluate how and when such oxidized deposits were formed on Mars, information about the mechanisms and rates of chemical weathering of Fe(2+)-bearing minerals has been determined. In this paper, mechanisms and rates of deposition of ferric oxide phases on the Martian surface are discussed.

  13. Ordered mesoporous silica nanoparticles with and without embedded iron oxide nanoparticles: structure evolution during synthesis

    E-print Network

    Gruner, Sol M.

    Ordered mesoporous silica nanoparticles with and without embedded iron oxide nanoparticles of hexagonally ordered mesoporous silica nanoparticles with and without embedded iron oxide particles. Oleic acid surfactant, hexadecyltrimethylammonium bromide (CTAB). MCM-41 type silica and composite nanoparticles

  14. Kinetic Parameters of Binary Iron\\/Oxidant Pyrolants

    Microsoft Academic Search

    Mojtaba Shamsipur; Seied Mahdi Pourmortazavi; Manochehr Fathollahi

    2012-01-01

    The thermal properties of pyrotechnic mixtures containing iron powder as fuel and KNO3, KClO3, and KClO4 as oxidants are reported. The thermogravimetry–differential thermal analysis results for pure components and corresponding pyrotechnic mixtures revealed that the melting point, decomposition temperature, and rate of oxygen releasing of the oxidants have dominant effects on ignition reaction of the pyrotechnic mixtures. The apparent activation

  15. Synthesis and stabilisation of superparamagnetic iron oxide nanoparticle dispersions

    Microsoft Academic Search

    K. Mandel; F. Hutter; C. Gellermann; G. Sextl

    2011-01-01

    Superparamagnetic iron oxide nanoparticles (magnetite (Fe3O4) and\\/or maghemite (?-Fe2O3)) were precipitated with ammonium hydroxide from a solution of Fe(II)- and Fe(III)-chlorides in water under ambient conditions. The agglomerated nanoparticles were dispersed by addition of nitric acid to a sol and stabilised with a polycarboxylate backbone polyethylene oxide side chain combpolymer (MELPERS4343, BASF, Germany). In this work focus was put on

  16. The effect of Os addition on sputtered iron oxide films

    Microsoft Academic Search

    O. Ishii; F. Yoshimura; A. Terada; I. Sato

    1987-01-01

    The features of grain growth in Os-added iron oxide films are investigated for the purpose of developing high signal-to-noise ratio (SNR) magnetic recording media. The average grain size of sputter-deposited ?-Fe2O3 films is markedly decreased by Os addition. The grains grow during the reduction process, from ?-Fe2O3 to Fe3O4, and maintain the same size in subsequent oxidation, from Fe3O4 to

  17. Behavior of iron aluminides in oxidizing and sulfidizing environments

    SciTech Connect

    Tortorelli, P.F.; DeVan, J.H.; DiStefano, J.R.

    1989-01-01

    To date, use of iron aluminides based on Fe/sub 3/Al (less than or equal to30 at. % Al) or FeAl (30--50 at. % Al) for structural applications has been limited by their low ductility and poor fracture toughness at room temperature and inadequate strength above 600/degree/C. However, in recent years, a renewed effort has been devoted to the development of ductile iron aluminides with increased strength, particularly in view of their good potential for use in hostile environments. While it is expected that such aluminides will be able to form oxide scales for corrosion protection in oxidizing high temperature environments, resistance to degradation in oxidizing salt or oxidizing/sulfidizing gas environments has not been adequately addressed as a function of compositional and microstructural changes. This paper reviews and extends results for iron aluminides exposed to an oxidizing/sulfidizing gas and presents the first data for corrosion of this class of materials by an aggressive oxidizing molten nitrate salt of 48.5NaNO/sub 3/--50.5KNO/sub 3/--1Na/sub 2/O/sub 2/. 14 refs., 11 figs.

  18. Iron-Titanium Oxides and Oxygen Fugacities in Volcanic Rocks

    Microsoft Academic Search

    I. S. E. Carmichael; J. Nicholls

    1967-01-01

    It is shown that in silicate liquids the ferric-ferrous equilibrium is controlled by temperature, oxygen fugacity, and the composition of the liquid, particularly its alkali content. Thus, if the iron-titanium oxide minerals that precipitate from a silicate liquid reflect the ferricferrous equilibrium, the oxygen geobarometer of Buddington and Lindsley will have to be calibrated, especially for such volcanics as phonolites

  19. RESEARCH PAPER Fabrication and characterization of iron oxide nanoparticles

    E-print Network

    Guo, John Zhanhu

    al. 2004) testing. In addition, granular polypyrrole nanocomposites have been reported as a candidateRESEARCH PAPER Fabrication and characterization of iron oxide nanoparticles filled polypyrrole nanocomposites Zhanhu Guo Æ Koo Shin Æ Amar B. Karki Æ David P. Young Æ Richard B. Kaner Æ H. Thomas Hahn

  20. Iron Oxides in a Soil Developed from Basalt

    Microsoft Academic Search

    A. T. Goulart; J. D. FABRIS; M. E DE; JESUS FILHO; J. M. D. COEY; G. M. DA COSTA

    1998-01-01

    A dusky red Oxisol forming on a tholeiitic basalt is found to contain varying proportion of aluminous hematite (Hm) and titanoaluminous maghemite (Mh) in the different size fractions. Maghemite is the main iron oxide in the sand and silt fractions whereas Hm is dominant in the clay fraction, together with gibbsite (Gb), kaolinite (Ka), rutile (Rt) (and probably anatase, An)

  1. The adsorption of aquatic humic substances by iron oxides

    Microsoft Academic Search

    E. Tipping

    1981-01-01

    The interactions of humic substances from Esthwaite Water with hydrous iron oxides ( -FeOOH, -Fe 2 O 3 , amorphous Fe-gel) have been examined by measuring adsorption isotherms and by microelectrophoresis. In Na + -Cl - -HCO 3 - at I = 0.002 M (medium I) the extent of adsorption decreases with increasing pH. The results are consistent with a

  2. Energy absorption of superparamagnetic iron oxide nanoparticles by microwave irradiation

    Microsoft Academic Search

    Do Kyung Kim; M. Shahrooz Amin; Shihab Elborai; Se-Hee Lee; Yüksel Koseoglu; Markus Zahn; Mamoun Muhammed

    2005-01-01

    The main complexity in hyperthermia is generating and controlling the temperature distribution within tumor cells without damaging the normal tissue. Superparamagnetic iron oxide nanoparticles (SPIONs) with a diameter of 11 nm were prepared by controlled coprecipitation and coated with oleic acid to prevent agglomeration and flocculation in the solvent. In situ monitoring of the temperature increment was performed to interpret

  3. Oxidation resistant iron and nickel alloys for high temperature use

    NASA Technical Reports Server (NTRS)

    Hill, V. L.; Misra, S. K.; Wheaton, H. L.

    1970-01-01

    Iron-base and nickel-base alloys exhibit good oxidation resistance and improved ductility with addition of small amounts of yttrium, tantalum /or hafnium/, and thorium. They can be used in applications above the operating temperatures of the superalloys, if high strength materials are not required.

  4. Gas and humidity sensors based on iron oxide–polypyrrole nanocomposites

    Microsoft Academic Search

    Komilla Suri; S. Annapoorni; A. K. Sarkar; R. P. Tandon

    2002-01-01

    Nanocomposites of iron oxide and polypyrrole were prepared by simultaneous gelation and polymerization process. This resulted in the formation of mixed iron oxide phase for lower polypyrrole concentration, stabilizing to a single cubic iron oxide phase at higher polypyrrole concentration. The composites in the pellet form were used for humidity and gas sensing investigations. Their sensitivity to humidity was found

  5. The Effect of Iron Oxide on Dissimilatory Nitrate Reduction to Ammonium (DNRA) in Lignin Cellulose medium

    E-print Network

    Vallino, Joseph J.

    The Effect of Iron Oxide on Dissimilatory Nitrate Reduction to Ammonium (DNRA) in Lignin Cellulose that may be more harmful than nitrate. In order to reduce ammonium production I proposed to add iron oxide oxidizing bacteria capable of DNRA. It was concluded that the iron addition actually prevented the reduction

  6. Photoluminescence spectral change in layered titanate oxide intercalated with hydrated Eu3+.

    PubMed

    Ida, Shintaro; Unal, Ugur; Izawa, Kazuyoshi; Altuntasoglu, Ozge; Ogata, Chikako; Inoue, Taishi; Shimogawa, Kenji; Matsumoto, Yasumichi

    2006-11-30

    A number of interesting photoluminescence properties of titanate layered oxide intercalated with hydrated Eu3+ have been demonstrated. Photoluminescence intensity of Eu3+ decreased rapidly with time during irradiation by UV light having energy higher than the band gap energy of the host TiO (Ti(1.81)O4) layer. This is presumably due to the decrease in energy transfer from the host TiO layer to Eu3+ as a result of the change in the hydration state of water molecules surrounding Eu3+, which is caused by the hole produced in the TiO valence band. When irradiation was discontinued, the emission intensity gradually recovered. The recovery time increased when the water in the interlayer is removed by heat treatment. This indicates that the state of interlayer water changes during irradiation and returns to its initial state after discontinuation of irradiation. The excitation spectra changed drastically at any given wavelength upon irradiation with UV light. A comparison of the excitation spectra before and after irradiation reveals that only the excitation peak at around the irradiation wavelength decreased upon irradiation, as in the case of spectral hole burning. The hydration state of water molecules surrounding Eu3+ presumably changes depending on the irradiation wavelength, leading to the above spectral change because the Eu/TiO film has a superlattice structure producing holes with different energies. PMID:17125354

  7. Total Synthesis of Fostriecin: Via a Regio- and Stereoselective Polyene Hydration, Oxidation and Hydroboration Sequence

    PubMed Central

    Gao, Dong; O’Doherty, George A.

    2010-01-01

    A total synthesis of the fostriecin has been achieved in 24 steps from enyne 11. The lactone moiety was installed by a Leighton allylation and Grubbs ring-closing metathesis (RCM) reaction. The highly reactive Z,Z,E-triene moiety was installed via a late stage Suzuki-Miyaura cross coupling of a remarkably stable Z-vinyl boronate. The relative and absolute stereocenters of the C-8,9,11 triol were generated with a regio- and stereoselective asymmetric hydration/oxidation sequence. PMID:20687585

  8. Simultaneous reductive dissolution of iron oxide and oxidation of iodide in ice.

    NASA Astrophysics Data System (ADS)

    Kim, Kitae; Choi, Wonyong

    2015-04-01

    Iron is an important trace element controlling the metabolism and growth of all kinds of living species. Especially, the bio-availability of iron has been regarded as the limiting factor for primary productivity in HNLC (High Nutrients Low Chlorophyll) regions including Southern ocean. The dissolution of iron oxide provides enhanced the bio-availability of iron for phytoplankton growth. The halogen chemistry in polar regions is related to various important environmental processes such as Antarctic Ozone Depletion Event(ODE), mercury depletion, oxidative processes in atmosphere, and the formation of CCN (Cloud Condensation Nuclei). In this study, we investigated the reductive dissolution of iron oxide particles to produce Fe(II)aq and simultaneous oxidation of I- (iodide) to I3- (tri-iodide) in ice phase under UV irradiation or dark condition. The reductive generation of Fe(II)aq from iron oxides and oxidation of iodide to I3- were negligible in water but significantly accelerated in frozen solution both in the presence and absence of light. The enhanced reductive generation of Fe(II)aq and oxidative formation of I3- in ice were observed regardless of the various types of iron oxides [hematite (?-Fe2O3) maghemite (?- Fe2O3), goethite (?-FeOOH), lepidocrocite (?-FeOOH) and, magnetite (Fe3O4)]. We explained that the enhanced redox production of Fe(II)aq and I3- in ice is contributed to the freeze concentration of iodides, protons, and dissolved oxygen in the unfrozen solution. When the concentration of both iodides and protons were raised by 10-fold each, the formation of Fe(II)aq in water under UV irradiation was approached to those in ice. The outdoor experiments were carried out under ambient solar radiation in winter season of mid-latitude (Pohang, Korea: 36°N latitude) and also confirmed that the production of Fe(II)aq via reductive dissolution of iron oxide and I3- generation via I- oxidation were enhanced in frozen solution. These results suggest that iron oxide particles in mineral dust and iodide trapped in ice or snow media (acidic aerosol, ice/snow on sea ice, icebergs, ice sheets, etc) might follow ice (photo-)chemical processes and can provide bioavailable iron and active iodine species when they melt.

  9. Low-temperature hydration, oxidation and hydrogen production from Oman peridotite

    NASA Astrophysics Data System (ADS)

    Miller, H. M.; Mayhew, L.; Templeton, A. S.

    2013-12-01

    Peridotite in the shallow subsurface undergoes hydration and oxidation (serpentinization) during reactions with percolating fluids, generating hydrogen gas and releasing magnesium, iron, and calcium into solution. In the presence of fluids enriched in dissolved carbon dioxide, extensive precipitation of carbonate minerals occurs. This reaction has large-scale implications for mitigating climate change by providing a stable, geological carbon repository. The Samail Ophiolite in Oman contains large quantities of ultramafic rocks that are currently undergoing serpentinization at low temperatures (30°C) and forming carbonate minerals. The production of hydrogen gas provides an electron donor for subsurface chemolithoautotrophic life which can contribute to carbon cycling in the subsurface as microorganisms utilize carbon dioxide as an inorganic carbon source. Serpentinization reactions require the oxidation of Fe (II) to Fe (III) to reduce water to H2, but the mechanisms of hydrogen generation in low-temperature systems is poorly characterized. To address this question, we conducted low temperature (100°C) water-rock reactions with Oman peridotite, measured H2 and characterized the speciation of Fe-bearing minerals before and after water-rock interaction using micro-X-ray Absorption Near Edge Structure (?XANES) spectra obtained from Stanford Synchrotron Radiation Lightsource. The experimental water-rock reactions produce H2 at a pH of 9, which corresponds with observations of ultrabasic springs in the Samail ophiolite and the presence of H2 in these spring waters. Significant hydrogen production occurs for two and a half months of reaction, peaking at 400 nmol/gram of reacted peridotite and then steadily decreases with time. These maximum values of hydrogen production from Oman peridotite are greater than observed by our laboratory and others during aqueous alteration of San Carlos peridotite and isolated pyroxenes and olivines (e.g. Mayhew et al. 2013 [1]). The products of low-temperature serpentinization, as determined by least squares fits of model spectra to sample ?XANES spectra, include serpentine minerals, altered olivines and Fe(III) minerals. X-ray fluorescence (?XRF) maps of the distribution of Fe-bearing phases reveal extensive alteration of pyroxenes to a mixture of Fe(II) and Fe(III)-bearing phases during the 100°C water-rock interactions, while olivine grains are only incipiently altered along fracture networks, suggesting an important role for pyroxenes in low temperature H2-generating reactions. The serpentinization reactions in the Oman peridotite are producing significant levels of hydrogen at a low temperature within the habitability limit for life, suggesting Oman provides a subsurface niche for hydrogen-utilizing microorganisms. The microbiology of the Oman subsurface is important to consider when investigating carbonation reactions aimed for carbon capture and sequestration because microbial life can affect carbon availability, and the injection of CO2 into the aquifer may significantly alter the ecosystem. [1] Mayhew et al. 2013. Nature Geoscience

  10. Wear resistance of iron oxide thin films

    NASA Astrophysics Data System (ADS)

    Chen, Mao-Min; Lin, Judy; Wu, Tsai-Wei; Castillo, Gilbert

    1988-04-01

    Magnetite films (Fe3O4) were reactively sputtered onto (100) silicon substrates in an Ar+O2 gas environment from a target containing Fe and 0.75 at. % Os. The films were then oxidized in air to form ?-Fe2O3. The wear resistance of the films was evaluated using an oscillatory wear tester and a contact start/stop tester with IBM 3380 type of sliders. Magnetite films exhibited poor durability independent of the deposition substrate temperature and oxygen partial pressure. Upon oxidizing the magnetite films in air at elevated temperatures, the wear resistance increased. For fixed deposition conditions, the wear resistance of the film increased with oxidation temperature. However, too high an oxidation temperature will transform the film into ?-Fe2O3, which is antiferromagnetic material. For a fixed oxidation temperature of 300 °C, the wear resistance of the film increased with increasing deposition substrate temperature. Durable ?-Fe2O3 thin film can be produced by depositing 1000-Å-thick film at 325 °C and subsequently oxidizing the film at 300 °C. A visible wear track was detected only after 16 000 contact start/stop cycles for ?-Fe2O3 film media without additional layers of overcoat or lubricant in ambient environment. The friction coefficient was low and remained stable with sliding cycles. The dependence of friction coefficient of the film on deposition conditions will be discussed.

  11. Chromium Substitution Effect on the Magnetic Structure of Iron Oxides

    NASA Astrophysics Data System (ADS)

    Osman Murat, Ozkendir

    2012-05-01

    The local magnetic and electronic structures of chromium substituted iron oxide polycrystalline samples are investigated via Fe L-edge x-ray absorption near-edge structural and magnetic circular dichroism measurements. A strong dependence of atomic magnetic levels on the applied external magnetic field is observed. The magnetic behavior of Cr-doped iron oxides are determined to be dominantly governed by the d—d hybridization between Fe and Cr valence levels. In addition, the formation of CrO2 and Cr2O3 chromium oxide clusters in the sample are observed to determine the magnetic ordering, i.e. anti-ferromagnetic or ferromagnetic with the changing external magnetic fields. The results highly agree with the previous studies.

  12. Oxidation, carburization and/or sulfidation resistant iron aluminide alloy

    DOEpatents

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    2003-08-19

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or Zro.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B. .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  13. Effects of sulfur containing amino acids on iron and nitric oxide stimulated catecholamine oxidation.

    PubMed

    Biasetti, M; Dawson, R

    2002-06-01

    Taurine is a free amino acid found in high concentrations in tissues containing catecholamines. The ability of taurine and its metabolic precursors to inhibit or stimulate catecholamine oxidation and subsequent quinone formation was examined. Ferric chloride was used as the catalyzing agent to stimulate L-dopa or norepinephrine oxidation and NO donors were also examined for their actions to stimulate quinone formation. Taurine attenuated iron-stimulated quinone formation from catecholamines suggesting that it may function as an endogenous antioxidant. Several other sulfur-containing amino acids (homocysteic acid, cysteine sulfinic acid and SAM) were found to inhibit catecholamine oxidation. Among other amino acids tested, homocysteine had biphasic effects; attenuating L-dopa oxidation catalyzed by ferric chloride and potentiating norepinephrine's oxidation catalyzed by both ferric chloride and sodium nitroprusside (SNP). Homotaurine and homocysteine (1 or 10 mM) greatly stimulated SNP-induced norepinephrine oxidation. Homotaurine potentiated quinone formation in the presence of ferric iron and this effect was attenuated by desferroxamine. In order to exclude a possible NO/iron interaction in SNP's oxidizing action, SIN-1 chloride, a specific NO-donor, was tested as an oxidizing agent. The failure of desferroxamine or taurine to attenuate SIN-1 oxidation of norepinephrine suggests that peroxynitrite-mediated oxidation was likely the dominant mechanism. Our results show that endogenous sulfur containing amino acids, like taurine, could serve a protective role to reduce cellular damage associated with both NO and metal-stimulated catecholamine oxidation. PMID:12107762

  14. Hydration-Responsive Folding and Unfolding in Graphene Oxide Liquid Crystal Phases

    PubMed Central

    Guo, Fei; Kim, Franklin; Han, Tae Hee; Shenoy, Vivek B.; Huang, Jiaxing; Hurt, Robert H.

    2011-01-01

    Graphene oxide is promising as a plate-like giant molecular building block for the assembly of new carbon materials. Its water dispersibility, liquid crystallinity, and ease of reduction offer advantages over other carbon precursors if its fundamental assembly rules can be identified. This article shows that graphene oxide sheets of known lateral dimension form nematic liquid crystal phases with transition points in agreement with the Onsager hard-plate theory. The liquid crystal phases can be systematic ordered into defined supramolecular patterns using surface anchoring, complex fluid flow, and micro-confinement. Graphene oxide is seen to exhibit homeotropic surface anchoring at interfaces driven by excluded volume entropy and by adsorption enthalpy associated with its partially hydrophobic basal planes. Surprisingly, some of the surface-ordered graphene oxide phases dry into graphene oxide solids that undergo a dramatic anisotropic swelling upon rehydration to recover their initial size and shape. This behavior is shown to be a unique hydration-responsive folding and unfolding transition. During drying, surface tension forces acting parallel to the layer planes cause a buckling instability that stores elastic energy in accordion-folded structures in the dry solid. Subsequent water infiltration reduces interlayer frictional forces and triggers release of the stored elastic energy in the form of dramatic unidirectional expansion. We explain the folding/unfolding phenomena by quantitative nanomechanics, and introduce the potential of liquid crystal-derived graphene oxide phases as new stimuli-response materials. PMID:21877716

  15. Hydration-responsive folding and unfolding in graphene oxide liquid crystal phases.

    PubMed

    Guo, Fei; Kim, Franklin; Han, Tae Hee; Shenoy, Vivek B; Huang, Jiaxing; Hurt, Robert H

    2011-10-25

    Graphene oxide is promising as a plate-like giant molecular building block for the assembly of new carbon materials. Its water dispersibility, liquid crystallinity, and ease of reduction offer advantages over other carbon precursors if its fundamental assembly rules can be identified. This article shows that graphene oxide sheets of known lateral dimension form nematic liquid crystal phases with transition points in agreement with the Onsager hard-plate theory. The liquid crystal phases can be systematically ordered into defined supramolecular patterns using surface anchoring, complex fluid flow, and microconfinement. Graphene oxide is seen to exhibit homeotropic surface anchoring at interfaces driven by excluded volume entropy and by adsorption enthalpy associated with its partially hydrophobic basal planes. Surprisingly, some of the surface-ordered graphene oxide phases dry into graphene oxide solids that undergo a dramatic anisotropic swelling upon rehydration to recover their initial size and shape. This behavior is shown to be a unique hydration-responsive folding and unfolding transition. During drying, surface tension forces acting parallel to the layer planes cause a buckling instability that stores elastic energy in accordion-folded structures in the dry solid. Subsequent water infiltration reduces interlayer frictional forces and triggers release of the stored elastic energy in the form of dramatic unidirectional expansion. We explain the folding/unfolding phenomena by quantitative nanomechanics and introduce the potential of liquid crystal-derived graphene oxide phases as new stimuli-response materials. PMID:21877716

  16. Selective stabilization of aliphatic organic carbon by iron oxide

    PubMed Central

    Adhikari, Dinesh; Yang, Yu

    2015-01-01

    Stabilization of organic matter in soil is important for natural ecosystem to sequestrate carbon and mitigate greenhouse gas emission. It is largely unknown what factors govern the preservation of organic carbon in soil, casting shadow on predicting the response of soil to climate change. Iron oxide was suggested as an important mineral preserving soil organic carbon. However, ferric minerals are subject to reduction, potentially releasing iron and decreasing the stability of iron-bound organic carbon. Information about the stability of iron-bound organic carbon in the redox reaction is limited. Herein, we investigated the sorptive interactions of organic matter with hematite and reductive release of hematite-bound organic matter. Impacts of organic matter composition and conformation on its sorption by hematite and release during the reduction reaction were analyzed. We found that hematite-bound aliphatic carbon was more resistant to reduction release, although hematite preferred to sorb more aromatic carbon. Resistance to reductive release represents a new mechanism that aliphatic soil organic matter was stabilized by association with iron oxide. Selective stabilization of aliphatic over aromatic carbon can greatly contribute to the widely observed accumulation of aliphatic carbon in soil, which cannot be explained by sorptive interactions between minerals and organic matter. PMID:26061259

  17. Selective stabilization of aliphatic organic carbon by iron oxide.

    PubMed

    Adhikari, Dinesh; Yang, Yu

    2015-01-01

    Stabilization of organic matter in soil is important for natural ecosystem to sequestrate carbon and mitigate greenhouse gas emission. It is largely unknown what factors govern the preservation of organic carbon in soil, casting shadow on predicting the response of soil to climate change. Iron oxide was suggested as an important mineral preserving soil organic carbon. However, ferric minerals are subject to reduction, potentially releasing iron and decreasing the stability of iron-bound organic carbon. Information about the stability of iron-bound organic carbon in the redox reaction is limited. Herein, we investigated the sorptive interactions of organic matter with hematite and reductive release of hematite-bound organic matter. Impacts of organic matter composition and conformation on its sorption by hematite and release during the reduction reaction were analyzed. We found that hematite-bound aliphatic carbon was more resistant to reduction release, although hematite preferred to sorb more aromatic carbon. Resistance to reductive release represents a new mechanism that aliphatic soil organic matter was stabilized by association with iron oxide. Selective stabilization of aliphatic over aromatic carbon can greatly contribute to the widely observed accumulation of aliphatic carbon in soil, which cannot be explained by sorptive interactions between minerals and organic matter. PMID:26061259

  18. Oxide Dispersion Strengthened Iron Aluminide by CVD Coated Powders

    SciTech Connect

    Asit Biswas Andrew J. Sherman

    2006-09-25

    This I &I Category2 program developed chemical vapor deposition (CVD) of iron, aluminum and aluminum oxide coated iron powders and the availability of high temperature oxidation, corrosion and erosion resistant coating for future power generation equipment and can be used for retrofitting existing fossil-fired power plant equipment. This coating will provide enhanced life and performance of Coal-Fired Boilers components such as fire side corrosion on the outer diameter (OD) of the water wall and superheater tubing as well as on the inner diameter (ID) and OD of larger diameter headers. The program also developed a manufacturing route for readily available thermal spray powders for iron aluminide coating and fabrication of net shape component by powder metallurgy route using this CVD coated powders. This coating can also be applid on jet engine compressor blade and housing, industrial heat treating furnace fixtures, magnetic electronic parts, heating element, piping and tubing for fossil energy application and automotive application, chemical processing equipment , heat exchanger, and structural member of aircraft. The program also resulted in developing a new fabrication route of thermal spray coating and oxide dispersion strengthened (ODS) iron aluminide composites enabling more precise control over material microstructures.

  19. In vivo biodistribution of iron oxide nanoparticles: an overview

    NASA Astrophysics Data System (ADS)

    Tate, Jennifer A.; Petryk, Alicia A.; Giustini, Andrew J.; Hoopes, P. Jack

    2011-03-01

    Iron oxide nanoparticles present a promising alternative to conventional energy deposition-based tissue therapies. The success of such nanoparticles as a therapeutic for diseases like cancer, however, depends heavily on the particles' ability to localize to tumor tissue as well as provide minimal toxicity to surrounding tissues and key organs such as those involved in the reticuloendothelial system (RES). We present here the results of a long term clearance study where mice injected intravenously with 2 mg Fe of 100 nm dextran-coated iron oxide nanoparticles were sacrificed at 14 and 580 days post injection. Histological analysis showed accumulation of the nanoparticles in some RES organs by the 14 day time point and clearance of the nanoparticles by the 580 day time point with no obvious toxicity to organs. An additional study reported herein employs 20 nm and 110 nm starch-coated iron oxide nanoparticles at 80 mg Fe/kg mouse in a size/biodistribution study with endpoints at 4, 24 and 72 hours. Preliminary results show nanoparticle accumulation in the liver and spleen with some elevated iron accumulation in tumoral tissues with differences between the 20 nm and the 110 nm nanoparticle depositions.

  20. Rare earth element partitioning between hydrous ferric oxides and acid mine water during iron oxidation

    Microsoft Academic Search

    Philip L. Verplanck; D. Kirk Nordstrom; Howard E. Taylor; Briant A. Kimball

    2004-01-01

    Ferrous iron rapidly oxidizes to Fe (III) and precipitates as hydrous Fe (III) oxides in acid mine waters. This study examines the effect of Fe precipitation on the rare earth element (REE) geochemistry of acid mine waters to determine the pH range over which REEs behave conservatively and the range over which attenuation and fractionation occur. Two field studies were

  1. Synergistic fire retardancy of colemanite, a natural hydrated calcium borate, in high-impact polystyrene containing brominated epoxy and antimony oxide

    Microsoft Academic Search

    Cevdet Kaynak; Nihat Ali Isitman

    2011-01-01

    This study explores for the first time the synergistic fire retardant action of natural hydrated calcium borate, namely the mineral colemanite, which partially replaces antimony oxide in brominated flame retardant high-impact polystyrene compounds. Various antimony oxide to hydrated calcium borate ratios were employed keeping the brominated flame retardant additive at a constant loading level. With partial colemanite substitution for antimony

  2. Intermediates of CO oxidation on iron oxides: An experimental and theoretical study

    SciTech Connect

    Lu Zhanghui; Xu Qiang [National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, Osaka 563-8577 (Japan); Graduate School of Engineering, Kobe University, Nada Ku, Kobe, Hyogo 657-8501 (Japan)

    2011-01-21

    Reactions of laser-ablated iron oxides with CO in excess argon are investigated by infrared adsorption spectroscopy and density functional theoretical calculations. The carbonyl iron oxides OFe(CO){sub n} (n= 1-3) and O{sub 2}Fe(CO){sub m} (m= 1, 2) are generated during sample deposition or annealing, whereas CO{sub 2} is greatly produced at the expense of these carbonyl iron oxides upon UV irradiation, showing the formation of intermediate carbonyl iron oxides in the oxidation of carbon monoxide to carbon dioxide. These intermediate carbonyl iron oxides are characterized on the basis of isotopic substitution, stepwise annealing, change of CO concentration and laser energy, and comparison with theoretical calculations. The overall agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts supports the identification of these complexes from the matrix infrared spectra. The reaction pathways for the formation of the products are proposed based on the experimental and theoretical results presented.

  3. Zinc sorption by iron oxides and soil samples 

    E-print Network

    Yli-Halla, Markku Juhani

    1989-01-01

    ZINC SORPTION BY IRON OMIDES AND SOIL SAMPLES A Thesis MARKKU JUHANI YLI-HALLA Submitted to the Office of Graduate Studies Texas A&M University in a partial fulfillment of the requirements for the degree of MASTEF. OR SCIENCE May 1989 Majo...'r Subject: Soil Science ZINC SORPTION BY IRON OXIDES AND SOIL SAMPLES A Thesis by MARKKU JUHANI YLI-HALLA Approved as to style and content by: Richard H. Loeppert (Chair of Committee) A. Clearfield (Membe ) Joe B. Dixon (Member) E. C. A. Runge...

  4. Zinc sorption by iron oxides and soil samples

    E-print Network

    Yli-Halla, Markku Juhani

    1989-01-01

    ZINC SORPTION BY IRON OMIDES AND SOIL SAMPLES A Thesis MARKKU JUHANI YLI-HALLA Submitted to the Office of Graduate Studies Texas A&M University in a partial fulfillment of the requirements for the degree of MASTEF. OR SCIENCE May 1989 Majo...'r Subject: Soil Science ZINC SORPTION BY IRON OXIDES AND SOIL SAMPLES A Thesis by MARKKU JUHANI YLI-HALLA Approved as to style and content by: Richard H. Loeppert (Chair of Committee) A. Clearfield (Membe ) Joe B. Dixon (Member) E. C. A. Runge...

  5. Iron oxide nanoparticle impregnated mesoporous silicas as platforms for the growth of carbon nanotubes

    Microsoft Academic Search

    D. Barreca; W. J. Blau; G. M. Croke; F. A. Deeney; F. C. Dillon; J. D. Holmes; C. Kufazvinei; M. A. Morris; T. R. Spalding; E. Tondello

    2007-01-01

    Iron oxide nanoparticles have been deposited on the exterior of and inside the pores of hexagonal mesoporous silica by a direct synthesis technique with iron phthalocyanine as precursor. Iron loadings were between 0.4wt.% – 3.2wt.%. XPS and Mössbauer spectroscopic studies showed that the initial form of the iron oxide nanoparticles was [Fe2O3]. Samples of these iron-loaded materials were stirred in

  6. Mössbauer and Magnetic Studies of Nanocrystalline Iron, Iron Oxide and Iron Carbide Powders Prepared from Synthetic Ferrihydrite

    NASA Astrophysics Data System (ADS)

    Schneeweiss, O.; Grygar, T.; David, B.; Zboril, R.; Filip, J.; Mashlan, M.

    2008-10-01

    Mössbauer spectroscopy and magnetic measurements were used for an analysis of nanocrystalline iron oxides (hematite ?-Fe2O3, magnetite Fe3O4), Hägg carbide (Fe5C2), and ?-Fe prepared by thermal treatment of synthetic ferrihydrite in various atmospheres. The transformation of ferrihydrite precursor was monitored by the measurements of temperature dependence of magnetic moment (thermomagnetic curves). Under optimized temperature and time, hematite nanoparticles were prepared by heating in vacuum. Application of hydrogen atmosphere yielded magnetite or ?-Fe. Annealing in ethylene resulted in the formation of iron carbides.

  7. Half-encapsulated Au nanoparticles by nano iron oxide: promoted performance of the aerobic oxidation of 1-phenylethanol

    NASA Astrophysics Data System (ADS)

    Zhao, Jianbo; Liu, Hong; Ye, Shuang; Cui, Yuming; Xue, Nianhua; Peng, Luming; Guo, Xuefeng; Ding, Weiping

    2013-09-01

    Au nanoparticles half-encapsulated in nano iron oxide are prepared and loaded on alumina as a support. The donation of electrons from nano iron oxide to Au nanoparticles is detected and both the properties of gold and iron oxide are adjusted by the donation. The properties are different from the bulk iron oxide supported gold catalysts, in which the iron oxide is little influenced by the electronic interaction between the two components. The catalyst shows noticeably promoted activity for the aerobic oxidation of 1-phenylethanol over Au-Al2O3 and Au-bulk FeOx. The enhanced catalytic behavior may result from the cooperative effect between the Au nanoparticles and nano iron oxide.

  8. Thermodynamics of Uranyl Minerals: Enthalpies of Formation of Uranyl Oxide Hydrates

    SciTech Connect

    K. Kubatko; K. Helean; A. Navrotsky; P.C. Burns

    2005-05-11

    The enthalpies of formation of seven uranyl oxide hydrate phases and one uranate have been determined using high-temperature oxide melt solution calorimetry: [(UO{sub 2}){sub 4}O(OH){sub 6}](H{sub 2}O){sub 5}, metaschoepite; {beta}-UO{sub 2}(OH){sub 2}; CaUO{sub 4}; Ca(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 8}, becquerelite; Ca(UO{sub 2}){sub 4}O{sub 3}(OH){sub 4}(H{sub 2}O){sub 2}; Na(UO{sub 2})O(OH), clarkeite; Na{sub 2}(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 7}, the sodium analogue of compreignacite and Pb{sub 3}(UO{sub 2}){sub 8}O{sub 8}(OH){sub 6}(H{sub 2}O){sub 2}, curite. The enthalpy of formation from the binary oxides, {Delta}H{sub f-ox}, at 298 K was calculated for each compound from the respective drop solution enthalpy, {Delta}H{sub ds}. The standard enthalpies of formation from the elements, {Delta}H{sub f}{sup o}, at 298 K are -1791.0 {+-} 3.2, -1536.2 {+-} 2.8, -2002.0 {+-} 3.2, -11389.2 {+-} 13.5, -6653.1 {+-} 13.8, -1724.7 {+-} 5.1, -10936.4 {+-} 14.5 and -13163.2 {+-} 34.4 kJ mol{sup -1}, respectively. These values are useful in exploring the stability of uranyl oxide hydrates in auxiliary chemical systems, such as those expected in U-contaminated environments.

  9. Oxidative effect of several intravenous iron complexes in the rat.

    PubMed

    Bailie, George R; Schuler, Catherine; Leggett, Robert E; Li, Hsin; Li, Hsin-Dat; Patadia, Hiten; Levin, Robert

    2013-06-01

    The objective of this study was to compare the oxidative stress induced in rat internal organs by the administration of the following clinically used intravenous (IV) iron (Fe) containing compounds: iron sucrose (IS), iron dextran (ID), ferric carboxymaltose and ferumoxytol. Groups of six adult rats received 1 mg/kg of each compound weekly for 5 doses. Seven days following the last dose, animals were euthanized and tissue samples of heart, lung, liver, and kidney were obtained, washed in warmed saline and frozen under liquid nitrogen and stored at -80 °C for analysis for nitrotyrosine (NT) and dinitro phenyl (DNP) as markers of oxidative stress. All tissues showed a similar pattern of oxidative stress. All Fe products stimulated an increase in the tissue concentration of both NT and DNP. In general, DNP was stimulated significantly less than NT except for IS. DNP was stimulated to an equal degree except for ID where NT was significantly higher than the NT concentrations in all other Fe compounds. ID produced over 10-fold the concentration of NT than any other Fe. IV Fe compounds present a risk of oxidative stress to a variety of internal organs. However, we found that IS was the least damaging and ID was the worst. PMID:23681275

  10. Removal and recovery of phosphate from municipal wastewaters using a polymeric anion exchanger bound with hydrated ferric oxide nanoparticles.

    PubMed

    Martin, B D; Parsons, S A; Jefferson, B

    2009-01-01

    A new type of ion exchange media which is highly selective for phosphate, and can be easily regenerated has been investigated. The media consists of hydrated ferric oxide nanoparticles dispersed within the pore structures of polymeric anion exchanger beads. The media combines the durability and mechanical strength of ion exchange resins with the high sorption capacity of ferric oxide for phosphate. The media was trialled in fixed bed mini column experiments with real final effluent from two UK sewage treatment works, one with treatment based on chemical precipitation with iron chloride salts into an activated sludge process (population >250,000), and one based on trickling filter treatment with no specific phosphorus removal process (population <10,000). Results show that the media has high capacity for removing phosphate, reaching capacity at 4000 and 1300 bed volumes for the chemical precipitation and trickling filter works respectively, with performance greatly exceeding that of a standard anion exchanger, Amberlite IRA-410. Also trialled was the media's ability to elute the phosphorus after breakthrough, with the aim of recovering and processing it into a useful product. A one step regenerative process using a single solution containing 4% NaOH and 2% NaCl was passed through the resin bed and the phosphorus concentration of each bed volume leaving the column analysed. 80% of the phosphorus was eluted in the first bed volume. Subsequent tests investigated the performance of the media after successive partial regenerations of one bed volume of the NaOH/NaCl solution. There was no loss of performance observed after ten regeneration cycles, and levels of eluted phosphate were consistently high. These results suggest that the media has high potential for the removal and recovery of phosphate from wastewater streams. Additionally, the small volume of regenerant required translates to a very small operational footprint. PMID:19923770

  11. Wear resistance of iron oxide thin films

    Microsoft Academic Search

    Mao-Min Chen; Judy Lin; Tsai-Wei Wu; Gilbert Castillo

    1988-01-01

    Magnetite films (Fe3O4) were reactively sputtered onto (100) silicon substrates in an Ar+O2 gas environment from a target containing Fe and 0.75 at. % Os. The films were then oxidized in air to form ?-Fe2O3. The wear resistance of the films was evaluated using an oscillatory wear tester and a contact start\\/stop tester with IBM 3380 type of sliders. Magnetite

  12. Iron oxide particles as a catalyst in chemical oxidation of organic contaminants

    SciTech Connect

    Gurol, M.D.; Lin, S.S.; Bhat, N. [Drexel Univ., Philadelphia, PA (United States)

    1995-12-31

    This research addresses the use of ozone and hydrogen peroxide in the presence of iron oxide particles which provide a catalytic surface for conversion to hydroxyl free radical. N-butylchloride (BuCl) and monochlorobenzene (MCB) were oxidized using goethite as the catalyst. The effect of varying the dosage of hydrogen peroxide or ozone, the mass and the size of the geothite particles, the mixing speed, and the gas flow rate for ozonation was investigated. The effect of water quality in terms of pH, carbonate alkalinity and initial organic concentration on reaction rates was addressed as well. Experimental observations showed that varying the stirring speed in the reactor or the size of the iron oxide particles did not have any significant effect on the oxidation rates, indicating that the rate was controlled by the intrinsic reaction rates on iron oxide surfaces. The presence of hydrogen peroxide significantly increased the removal of BuCl, and higher dosages caused considerably higher removal. Results also demonstrated a strong dependence of BuCl removal on the iron oxide dosage. MCB adsorbed strongly on goethite, but was oxidized effectively by ozone. Hydrogen peroxide decomposed rapidly in the presence of goethite at a rate directly proportional to the rate of BuCl oxidation. These results indicate that the interaction of hydrogen peroxide with goethite particles leads to the formation of hydroxyl free radical, which is responsible for oxidation of BuCl. Similarly, ozone decomposed in the presence of goethite. The oxidation efficiency for hydrogen peroxide/goethite remained unaffected when the pH and the alkalinity were varied. Furthermore, the ozone/goethite system provided mineralization as measured by the removal of the total organic carbon. Hence, both of these oxidation processes promise to be effective in oxidation of organic compounds, and may not suffer from the limitations of other radical processes.

  13. Iron-mediated anaerobic oxidation of methane in brackish coastal sediments.

    PubMed

    Egger, Matthias; Rasigraf, Olivia; Sapart, Célia J; Jilbert, Tom; Jetten, Mike S M; Röckmann, Thomas; van der Veen, Carina; Bând?, Narcisa; Kartal, Boran; Ettwig, Katharina F; Slomp, Caroline P

    2015-01-01

    Methane is a powerful greenhouse gas and its biological conversion in marine sediments, largely controlled by anaerobic oxidation of methane (AOM), is a crucial part of the global carbon cycle. However, little is known about the role of iron oxides as an oxidant for AOM. Here we provide the first field evidence for iron-dependent AOM in brackish coastal surface sediments and show that methane produced in Bothnian Sea sediments is oxidized in distinct zones of iron- and sulfate-dependent AOM. At our study site, anthropogenic eutrophication over recent decades has led to an upward migration of the sulfate/methane transition zone in the sediment. Abundant iron oxides and high dissolved ferrous iron indicate iron reduction in the methanogenic sediments below the newly established sulfate/methane transition. Laboratory incubation studies of these sediments strongly suggest that the in situ microbial community is capable of linking methane oxidation to iron oxide reduction. Eutrophication of coastal environments may therefore create geochemical conditions favorable for iron-mediated AOM and thus increase the relevance of iron-dependent methane oxidation in the future. Besides its role in mitigating methane emissions, iron-dependent AOM strongly impacts sedimentary iron cycling and related biogeochemical processes through the reduction of large quantities of iron oxides. PMID:25412274

  14. Effects of High Dietary Iron and Gamma Radiation on Oxidative Stress and Bone 

    E-print Network

    Yuen, Evelyn P

    2013-04-19

    Astronauts in space flight missions are exposed to increased iron (Fe) stores and galactic cosmic radiation, both of which independently induce oxidative stress. Oxidative stress can result in protein, lipid, and DNA oxidation. Recent evidence has...

  15. Increased oxidative stress and iron overload in Jordanian ?-thalassemic children.

    PubMed

    Abdalla, Maher Y; Fawzi, Mohammad; Al-Maloul, Salem R; El-Banna, Nasser; Tayyem, Reema F; Ahmad, Iman M

    2011-01-01

    ?-Thalassemia (?-thal) is associated with abnormal synthesis of hemoglobin (Hb). Repeated blood transfusions in patients with ?-thal major (?-TM) leads to an enhanced generation of reactive oxygen species (ROS), and subjects patients to peroxidative injury. We studied the antioxidant status and oxidative damage to children with ?-thal in Jordan. Samples from 40 children with ?-thal and 40 healthy controls were used. All children were under 13 years of age. Our results showed that plasma thiobarbituric acid reactive substances (TBARS) were elevated in ?-thalassemic children compared to controls together with compensatory increase in superoxide dismutase (SOD) activity and decrease in catalase (CAT) activity. Elevated serum ferritin showed positive correlation with elevated liver enzyme levels except gamma glutamyl transferase (GGT), confirming liver involvement due to iron overload. Serum ferritin also showed a positive correlation with elevated TBARS and SOD, suggesting that iron overload is involved in the oxidative stress shown in cells. PMID:21250883

  16. Dendronized iron oxide colloids for imaging the sentinel lymph node

    NASA Astrophysics Data System (ADS)

    Jouhannaud, J.; Garofalo, A.; Felder-Flesch, D.; Pourroy, G.

    2015-03-01

    Various methods have been used in medicine for more than one century to explore the lymphatic system. Radioactive colloids (RuS labelled with 99mTc) or/and Vital Blue dye are injected around the primary tumour and detected by means of nuclear probe or visual colour inspection respectively. The simultaneous clinical use of both markers (dye and radionuclide) improves the sensitivity of detection close to 100%. Superparamagnetic iron oxides (SPIOs) are currently receiving much attention as strong T2 weighted magnetic resonance imaging contrast agents that can be potentially used for preoperative localization of sentinel nodes, but also for peroperative detection of sentinel node using hand-held probes. In that context, we present the elaboration of dendronized iron oxide nanoparticles elaborated at the Institute of Physics and Chemistry of Materials of Strasbourg.

  17. Reflection spectra and magnetochemistry of iron oxides and natural surfaces

    NASA Technical Reports Server (NTRS)

    Wasilewski, P.

    1978-01-01

    The magnetic properties and spectral characteristics of iron oxides are distinctive. Diagnostic features in reflectance spectra (0.5 to 2.4 micron) for alpha Fe2O3, gamma Fe2O3, and FeOOH include location of Fe3(+) absorption features, intensity ratios at various wavelengths, and the curve shape between 1.2 micron and 2.4 micron. The reflection spectrum of natural rock surfaces are seldom those of the bulk rock because of weathering effects. Coatings are found to be dominated by iron oxides and clay. A simple macroscopic model of rock spectra (based on concepts of stains and coatings) is considered adequate for interpretation of LANDSAT data. The magnetic properties of materials associated with specific spectral types and systematic changes in both spectra and magnetic properties are considered.

  18. Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Brullot, W.; Reddy, N. K.; Wouters, J.; Valev, V. K.; Goderis, B.; Vermant, J.; Verbiest, T.

    2012-06-01

    Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles were obtained by a facile protocol and thoroughly characterized. Superparamagnetic iron oxide nanoparticles synthesized using a modified forced hydrolysis method were functionalized with polyethylene glycol silane (PEG silane), precipitated and dried. These functionalized particles are dispersable in a range of solvents and concentrations depending on the desired properties. Examples of tunable properties are magnetic behavior, optical and magneto-optical response, thermal features and rheological behavior. As such, PEG silane functionalized particles represent a platform for the development of new materials that have broad applicability in e.g. biomedical, industrial or photonic environments. Magnetic, optical, magneto-optical, thermal and rheological properties of several ferrofluids based on PEG coated particles with different concentrations of particles dispersed in low molecular mass polyethylene glycol were investigated, establishing the applicability of such materials.

  19. Surface modification of hydrophobic iron oxide nanoparticles for clinical applications

    Microsoft Academic Search

    Kyoungja Woo; Jangwon Hong

    2005-01-01

    Monodisperse superparamagnetic iron oxide nanoparticles (SPIONs) were prepared by thermal decomposition of Fe(CO)5 and by consecutive aeration in organic medium. The resultant hydrophobic SPION surface was modified to be hydrophilic via Fe-S covalent bond with bi-functional 3-mercaptopropionic acid and then, the terminal carboxylic acid group was esterified with dextran for biocompatibility. Analysis by water dispersity, transmission electron microscopy, X-ray diffraction,

  20. Effects of coating on magnetic properties in iron oxide nanoparticles

    Microsoft Academic Search

    B. Bittova; J. Poltierova-Vejpravova; A. G. Roca; M. P. Morales; V. Tyrpekl

    2010-01-01

    We have studied influence of surface modification on physical properties of iron oxide nanoparticles. We compared samples prepared by thermal decomposition of organic precursor in the presence of oleic acid, and the particles prepared by coprecipitation and partially coated by SiO2 or modified by citric acid and subsequently covered by photoactive TiO2 layer, respectively. Samples were characterised using TEM and

  1. Mössbauer Studies of Small Particles of Iron Oxides in Soil

    Microsoft Academic Search

    N. H. Gangas; A. Simopoulos; A. Kostikas; N. J. Yassoglou; S. Filippakis

    1973-01-01

    Abstract--A soil of Attica (Greece) has been studied by M6ssbauer spectroscopy and magnetization measurements,in order to ascertain the nature and form of iron oxides present in it. The room tempera- ture spectra consist of a paramagnetic doublet and a small magnetic sextet. At liquid nitrogen tempera- ture the magnetic,component,increases considerably at the cost of the paramagnetic,component. This behavior is typical

  2. Magnetical studies on thin films of iron oxides

    Microsoft Academic Search

    Jaime Osorio; Juan Uribe; Cesar Barrero; Doris Girata; Alvaro Morales; Axel Hoffmann; Ramon Gancedo

    2008-01-01

    We have grown hematite (alpha-Fe2O3) thin films on stainless steel and silicon dioxide (SiO2) substrates and magnetite (Fe3O4) thin films on silicon substrates by RF magnetron sputtering process. Conversion Electron Mössbauer (CEM) spectra of these films exhibit hyperfine parameter values which are characteristic of these iron oxides. Magnetization measurements parallel to the plane of the film as a function of

  3. Oxidative transformation of contaminants using colloidal zero-valent iron

    Microsoft Academic Search

    Andrew J. Feitz; Sung Hee Joo; Jing Guan; Quan Sun; David L. Sedlak; T. David Waite

    2005-01-01

    It has recently been demonstrated that nano scale zero-valent iron (nZVI) oxidizes the herbicide molinate when it is used in the presence of oxygen. Further batch and column experiments were conducted to investigate the potential application of nZVI for the treatment of contaminants. Results of batch studies reveal a rapid initial degradation of molinate followed by slower degradation over more

  4. Preparation of iron oxide-based calcium sensors for MRI

    Microsoft Academic Search

    Tatjana Atanasijevic; Alan Jasanoff

    2007-01-01

    We describe a protocol for the preparation of a family of calcium indicators for MRI. The indicators consist of superparamagnetic iron oxide nanoparticles functionalized with the calcium-sensing protein, calmodulin, and its target peptides. Calcium-dependent protein–protein interactions drive particle clustering and produce large changes in T2 relaxivity. To prepare these indicators, interacting polypeptides are purified, biotinylated and then conjugated to streptavidin-coated

  5. Radiation-Induced Chemical Changes to Iron Oxides.

    PubMed

    Reiff, Sarah C; LaVerne, Jay A

    2015-06-18

    The radiolysis of a variety of iron oxide powders with different amounts of associated water has been performed using ? rays and 5 MeV (4)He ions. Adsorbed water was characterized by both temperature-programmed desorption and diffuse reflection infrared Fourier transform spectroscopy to reveal a variety of active sites on the surface. Molecular hydrogen production was found only from water adsorbed on Fe2O3, and the yield was several orders of magnitude greater than that of bulk water. Aqueous slurries of FeO, Fe3O4, and Fe2O3 examined as a function of water fraction gave different yields of H2 depending on the oxide type and the amount of water. Examination of the iron oxide powders following irradiation by X-ray diffraction showed no change in crystal structure. Raman spectroscopy of the oxides revealed the formation of islands of Fe2O3 on the surfaces of FeO and Fe3O4. X-ray photoelectron spectroscopy of the oxides revealed the general formation of oxygen species following radiolysis. PMID:25580798

  6. Original Contribution Iron chelators can protect against oxidative stress through ferryl heme reduction

    Microsoft Academic Search

    Brandon J. Reeder; Robert C. Hider; Michael T. Wilson

    Iron chelators such as desferrioxamine have been shown to ameliorate oxidative damage in vivo. The mechanism of this therapeutic action under non-iron-overload conditions is, however, complex, as desferrioxamine has properties that can impact on oxidative damage independent of its capacity to act as an iron chelator. Desferrioxamine can act as a reducing agent to remove cytotoxic ferryl myoglobin and hemoglobin

  7. Magnetic properties of polypyrrole-coated iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Sharma, Raksha; Lamba, Subhalakshmi; Annapoorni, S.

    2005-09-01

    Iron oxide nanoparticles were prepared using the sol-gel process. In situ polymerization of a pyrrole monomer in the presence of oxygen in an iron oxide-ethanol suspension resulted in an iron oxide polypyrrole nanocomposite. The structure and magnetic properties of the nanocomposites with varying pyrrole concentrations are investigated. X-ray diffraction studies indicate the presence of the ?-Fe2O3 phase for the concentrations investigated. FTIR studies confirm the presence of polypyrrole. TEM studies show agglomeration in uncoated samples and in samples with a lower concentration of polypyrrole. Agglomeration is greatly reduced for samples coated with a higher concentration of polypyrrole. The ac susceptibility measurements performed in the temperature range 77-300 K show the presence of blocking, indicating the superparamagnetic phase. The blocking temperature is found to depend on the pyrrole concentration. Monte Carlo studies for an array of polydispersed single domain magnetic particles, based on an interacting random anisotropy model, were also carried out, and the blocking temperatures obtained from the simulation of the field cooled-zero field cooled magnetization compare favourably with experimental results.

  8. Reducing arsenic accumulation in rice grain through iron oxide amendment.

    PubMed

    Farrow, Eric M; Wang, Jianmin; Burken, Joel G; Shi, Honglan; Yan, Wengui; Yang, John; Hua, Bin; Deng, Baolin

    2015-08-01

    Effects of soil-arsenic (As), phosphorus and iron oxide on As accumulation in rice grain were investigated. Cultivars that have significantly different sensitivity to As, straighthead-resistant Zhe 733 and straighthead-susceptible Cocodrie, were used to represent different cultivar varieties. The grain accumulation of other elements of concern, selenium (Se), molybdenum (Mo), and cadmium (Cd) was also monitored. Results demonstrated that high soil-As not only resulted in high grain-As, but could also result in high grain-Se, and Zhe 733 had significantly less grain-As than Cocodrie did. However, soil-As did not impact grain-Mo and Cd. Among all elements monitored, iron oxide amendment significantly reduced grain-As for both cultivars, while the phosphate application only reduced grain-Se for Zhe 733. Results also indicated that cultivar type significantly impacted grain accumulation of all monitored trace elements. Therefore, applying iron oxide to As-contaminated land, in addition to choosing appropriate rice cultivar, can effectively reduce the grain accumulation of As. PMID:25910688

  9. Iron-oxidizing microbial ecosystems thrived in late Paleoproterozoic redox-stratified oceans

    E-print Network

    Bekker, Andrey

    Iron-oxidizing microbial ecosystems thrived in late Paleoproterozoic redox-stratified oceans Noah Keywords: iron-bacteria iron-formations Fe-isotopes rare earth elements Paleoproterozoic stromatolites We conducted a geochemical and petrographic study of the 1.89billion year old Gunflint and Biwabik iron

  10. The impact of zirconium oxide nanoparticles on the hydration chemistry and biocompatibility of white Portland cement.

    PubMed

    Li, Qiu; Deacon, Andrew D; Coleman, Nichola J

    2013-01-01

    Zirconium oxide (ZrO2) has been nominated as a radiopacifying agent for use in MTA-like Portland cement-based root-filling materials. This research examines the impact of 20 wt% ZrO2 nanoparticles in the size range 50 to 75 nm on the early hydration chemistry of white Portland cement. Nano-ZrO2 was found to accelerate the degree of hydration by 26% within the first 24 h by presenting efficient nucleation sites for the precipitation and growth of the early C-S-H gel products. The presence of nano-ZrO2 was also found to divert the fate of the aluminium-bearing reaction products by lowering the ettringite to monosulphate ratio, reducing the size of the ettringite crystals and by increasing the Al:Si ratio of the C-S-H gel phase. The chemical and microstructural changes conferred upon the cement matrix by the nano-ZrO2 particles had a positive impact on in vitro biocompatibility with respect to MG63 osteosarcoma cells (via MTT assay). PMID:24088838

  11. Evaluation of Characterization Techniques for Iron Pipe Corrosion Products and Iron Oxide Thin Films

    SciTech Connect

    Borch, Thomas; Camper, Anne K.; Biederman, Joel A.; Butterfield, Phillip; Gerlach, Robin; Amonette, James E.

    2008-10-01

    A common problem faced by drinking water studies is that of properly characterizing the corrosion products (CP) in iron pipescor synthetic Fe (hydr)oxides used to simulate the iron pipe used in municipal drinking-water systems. The present work compares the relative applicability of a suite of imaging and analytical techniques for the characterization of CPs and synthetic Fe oxide thin films and provide an overview of the type of data that each instrument can provide as well as their limitations to help researchers and consultants choose the best technique for a given task. Crushed CP from a water distribution system and synthetic Fe oxide thin films formed on glass surfaces were chosen as test samples for this evaluation. The CP and synthetic Fe oxide thin films were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray powder diffractometry (XRD), grazing incident diffractometry (GID), transmission electron microscopy (TEM), selected area electron diffraction, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared, Mössbauer spectroscopy, Brunauer-Emmett-Teller N2 adsorption and Fe concentration was determined by the ferrozine method. XRD and GID were found to be the most suitable techniques for identification of the mineralogical composition of CP and synthetic Fe oxide thin films, respectively. AFM and a combined ToF-SIMS-AFM approach proved excellent for roughness and depth profiling analysis of synthetic Fe oxide thin films, respectively. Corrosion products were difficult to study by AFM due to their surface roughness, while synthetic Fe oxide thin films resisted most spectroscopic methods due to their limited thickness (118 nm). XPS analysis is not recommended for mixtures of Fe (hydr)oxides due to their spectral similarities. SEM and TEM provided great detail on mineralogical morphology.

  12. REMOVAL OF ARSENIC FROM GROUNDWATER USING NATURALLY OCCURRING IRON OXIDES IN RURAL REGIONS OF MONGOLIA

    EPA Science Inventory

    We have found that the iron oxide particles produced by grinding naturally occurring iron ores are very effective in removing arsenic from water. The arsenic adsorption isothermal of the particles h...

  13. Effects of High Dietary Iron and Gamma Radiation on Oxidative Stress and Bone

    E-print Network

    Yuen, Evelyn P

    2013-04-19

    linked oxidative stress to bone loss with aging and estrogen deficiency. Whether the increased iron stores and radiation that astronauts face are exacerbating their extreme bone loss while in space is unclear. We hypothesized that elevated iron levels...

  14. Interaction of nitric oxide with non-haem iron sites of Escherichia coli bacterioferritin: reduction of nitric oxide to nitrous oxide and oxidation of iron(II) to iron(III).

    PubMed Central

    Le Brun, N E; Andrews, S C; Moore, G R; Thomson, A J

    1997-01-01

    The bacterioferritin (BFR) of Escherichia coli consists of 24 identical subunits, each containing a dinuclear metal-binding site consisting of two histidines and four carboxylic acid residues. Earlier studies showed that the characterization of iron binding to BFR could be aided by EPR analysis of iron-nitrosyl species resulting from the addition of NO to the protein [Le Brun, Cheesman, Andrews, Harrison, Guest, Moore and Thomson (1993) FEBS Lett. 323, 261-266]. We now report data from gas chromatographic head space analysis combined with EPR spectroscopy to show that NO is not an inert probe: iron(II)-BFR catalyses the reduction of NO to N2O, resulting in oxidation of iron(II) at the dinuclear centre and the subsequent detection of mononuclear iron(III). In the presence of excess reductant (sodium ascorbate), iron(II)-BFR also catalyses the reduction of NO to N2O, giving rise to three mononuclear iron-nitrosyl species which are detectable by EPR. One of these, a dinitrosyl-iron complex of S = 1/2, present at a maximum of one per subunit, is shown by EPR studies of site-directed variants of BFR not to be located at the dinuclear centre. This is consistent with a proposal that the diferric form of the centre is unstable and breaks down to form mononuclear iron species. PMID:9337865

  15. Rescuing hepatocytes from iron-catalyzed oxidative stress using vitamins B1 and B6

    Microsoft Academic Search

    Rhea Mehta; Liana Dedina; Peter J. O’Brien

    2011-01-01

    In the following rescue experiments, iron-mediated hepatocyte oxidative stress cytotoxicity was found to be prevented if vitamin B1 or B6 was added 1h after treatment with iron. The role of iron in catalyzing Fenton-mediated oxidative damage has been implicated in iron overload genetic diseases, carcinogenesis (colon cancer), Alzheimer’s disease and complications associated with the metabolic syndrome through the generation of

  16. Multifunctional iron-based metal oxide nanostructured materials: Synthesis, characterization, and properties

    Microsoft Academic Search

    Tae-Jin Park

    2007-01-01

    Iron-based metal oxides, such as iron oxides, iron-containing perovskites, and iron-containing perovskite composites or solid solutions, are promising materials for the design and synthesis of technologically important multifunctional materials. They are noteworthy for their unique and diverse properties including electronic, magnetic, and elastic ones. Stimulated by interest in the bulk properties of these materials as well as scientific potential and

  17. Microanalysis of iron oxidation states in earth and planetary materials

    NASA Astrophysics Data System (ADS)

    Bajt, S.; Sutton, S. R.; Delaney, J. S.

    1995-02-01

    Initial studies have been made on quantifying Fe oxidation states in different iron-bearing minerals using K-edge XANES. The energy of a weak pre-edge peak in the XANES spectrum due to 1s-3d electron transition was used to quantify ferric/ferrous ratios with microprobe spatial resolution. The estimated accuracy of the technique was +/- 10% in terms of Fe3+/((Fe2+ + Fe3+)). The detection limit was ~ 100 ppm with a synchrotron beam of ~ 100 ?m in diameter. The pre-edge peak energy in well-characterized samples with known Fe oxidation states was found to be a linear function of the ferric/(ferrous) ratio. The technique was applied to altered magnetics (ideally Fe3O4), and various silicates and oxides from meteorites.

  18. Sorption and filtration of metals using iron-oxide-coated sand

    Microsoft Academic Search

    Mark M. Benjamin; Ronald S. Sletten; Robert P. Bailey; Thomas Bennett

    1996-01-01

    Iron oxides are good adsorbents for uncomplexed metals, some metal-ligand complexes, and many metal oxyanions. However, the adsorbent properties of these oxides are not fully exploited in wastewater treatment operations because of difficulties associated with their separation from the aqueous phase. This paper describes experiments in which iron oxides were coated onto the surface of ordinary filter sand, and this

  19. Anoxic photochemical oxidation of siderite generates molecular hydrogen and iron oxides

    PubMed Central

    Kim, J. Dongun; Yee, Nathan; Nanda, Vikas; Falkowski, Paul G.

    2013-01-01

    Photochemical reactions of minerals are underappreciated processes that can make or break chemical bonds. We report the photooxidation of siderite (FeCO3) by UV radiation to produce hydrogen gas and iron oxides via a two-photon reaction. The calculated quantum yield for the reaction suggests photooxidation of siderite would have been a significant source of molecular hydrogen for the first half of Earth’s history. Further, experimental results indicate this abiotic, photochemical process may have led to the formation of iron oxides under anoxic conditions. The reaction would have continued through the Archean to at least the early phases of the Great Oxidation Event, and provided a mechanism for oxidizing the atmosphere through the loss of hydrogen to space, while simultaneously providing a key reductant for microbial metabolism. We propose that the photochemistry of Earth-abundant minerals with wide band gaps would have potentially played a critical role in shaping the biogeochemical evolution of early Earth. PMID:23733945

  20. Cobalt-promoted Iron Oxide Nanoparticles for the Selective Oxidative Dehydrogenation of Cyclohexane

    NASA Astrophysics Data System (ADS)

    Rutter, Matthew

    Recent work has shown that both cobalt and iron oxide nanoparticles are active for the oxidative dehydrogenation (ODH) of cyclohexane to benzene, the former more active than the latter. Further study has shown that the addition of gold species as a minority component into iron oxide nanocrystals increases the selectivity of the reaction to benzene. Since a primary motivation for this work is the addition of catalysts in jet fuels to facilitate the dehydrogenation and cracking reactions preceding their combustion, a low-cost, sacrificial catalyst is sought after. In this application, catalyst nanoparticles suspended in the fuel stream will dehydrogenate cyclic alkanes (cyclohexane) to their aromatic counterparts (benzene). Alkenes and aromatics have a much higher rate of combustion, which decreases the amount of uncombusted fuel in the exhaust, thereby increasing performance. As these catalysts are not recyclable, there is significant impetus to substitute cheaper base metals for expensive noble metals. In this work, iron oxide nanoparticles are doped with varying levels of cobalt to examine the effect of cobalt content and oxidation state on the selectivity and activity of the iron oxide for the oxidative dehydrogenation of cyclohexane, used as a model cyclic alkane in jet fuel. We have shown previously that small (˜5nm) cobalt oxide nanoparticles favor the production of benzene over the partial dehydrogenation products cyclohexene and cyclohexadiene, or the complete oxidation product carbon dioxide. It is the aim of this work to examine the surface of these cobalt-iron oxide nanoparticles to determine the conditions most favorable for this selective oxidative dehydrogenation. Cobalt-doped iron nanoparticles were prepared by a surfactant-free hydrothermal co-precipitation technique that enabled a high degree of composition control and size control. These samples were characterized via Transmission Electron Microscopy (TEM), powder X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), BET N2 Physisorption, and CO Temperature Programmed Reduction (CO-TPR). These characterizations helped us to correlate the selectivity and activity data for each catalyst in an attempt to understand what roles the surface species played. It was found that iron oxide nanoparticles doped with 2-10 mol% cobalt formed a stable surface phase, enriched in Co (20 at%), independent of the bulk concentration. XPS measurements indicate this phase is rich in octahedral Co2+ cations. The selectivity to benzene was much higher in the Co-promoted iron oxide samples. This high concentration of octahedral cobalt(II) cations appear to have a strong promotional effect on the weakly held surface oxygen sites which have been shown previously to be the active sites for this reaction. Addition of cobalt also promoted the activity of the iron oxide nanoparticles; and stabilized them against particle growth under the reaction conditions, typically held at several different temperatures up to 370 °C, in a mixture of 0.4% cyclohexane and 4% oxygen, for several hours.

  1. Synthesis and Evaluation of Nanostructured Gold-Iron Oxide Catalysts for the Oxidative Dehydrogenation of Cyclohexane

    NASA Astrophysics Data System (ADS)

    Wu, Peng

    Shape-controlled iron oxide and gold-iron oxide catalysts with a cubic inverse spinel structure were studied in this thesis for the oxidative dehydrogenation of cyclohexane. The structure of iron oxide and gold-iron oxide catalysts has no major impact on their oxidative dehydrogenation activity. However, the product selectivity is influenced. Both cyclohexene and benzene are formed on bare iron oxide nanoshapes, while benzene is the only dehydrogenation product in the presence of gold. The selectivity of benzene over CO2 depends strongly on the stability of the iron oxide support and the gold-support interaction. The highest benzene yield has been observed on gold-iron oxide octahedra. {111}-bound nanooctahedra are highly stable in reaction conditions at 300 °C, while {100}-bound nanocubes start to sinter above 250 °C. The highest benzene yield has been observed on gold-iron oxide nanooctahedra, which are likely to have gold atoms, and few-atom gold clusters strongly-bound on their surface. Cationic gold appears to be the active site for benzene formation. An all-organic method to prepare Au-FeOx nano-catalysts is needed due to the inconvenience of the half-organic, half-inorganic synthesis process discussed above. Several methods from the literature to prepare gold-iron oxide nanocomposites completely in organic solvents were reviewed and followed. FeOx Au synthesis procedures in literatures are initially designed for a Au content of over 70%. This approach was tried here to prepare composites with a much lower Au content (2-5 atom. %). Heat treatment is required to bond Au and FeOx NPs in the organic-phase syntheses. Au-FeOx-4 was obtained as a selective catalyst for the ODH of cyclohexane. A Audelta+ peak is observed in the UV-Vis spectrum of sample Au-FeOx-4. This different Au delta+ form may be cationic Au nano-clusters interacting with the FeOx support. It has been demonstrated that cationic gold is responsible for dehydrogenation behavior. Furthermore, the yield of benzene in preliminary ODH tests of Au-FeOx-4 also proved the interaction between Au and FeOx. That explains the dehydrogenation activity of sample Au-FeO x-4. Therefore, the synthesis parameters of sample Au-FeOx-4 are recommended in further studies. Thermodynamic equilibria governing the cyclohexane dehydrogenation reaction and the phase transformation of the iron oxides used as catalysts have been considered as a reference, in a separate chapter. The all-organic method by thermolysis described in this thesis work can be used in preparations of Au/FeOx so that the density of Au cations is maximized. Gold deposition in an organic phase helps to manipulate the surface dispersion of Au, perhaps more precisely than doping Au in the inorganic phase. Such materials can be good not only for the ODH reaction, but also for the WGS reaction. This newly developed synthesis method is worth exploring in future.

  2. Biological iron oxidation by Gallionella spp. in drinking water production under fully aerated conditions.

    PubMed

    de Vet, W W J M; Dinkla, I J T; Rietveld, L C; van Loosdrecht, M C M

    2011-11-01

    Iron oxidation under neutral conditions (pH 6.5-8) may be a homo- or heterogeneous chemically- or a biologically-mediated process. The chemical oxidation is supposed to outpace the biological process under slightly alkaline conditions (pH 7-8). The iron oxidation kinetics and growth of Gallionella spp. - obligatory chemolithotrophic iron oxidizers - were assessed in natural, organic carbon-containing water, in continuous lab-scale reactors and full-scale groundwater trickling filters in the Netherlands. From Gallionella cell numbers determined by qPCR, balances were made for all systems. The homogeneous chemical iron oxidation occurred in accordance with the literature, but was retarded by a low water temperature (13 °C). The contribution of the heterogeneous chemical oxidation was, despite the presence of freshly formed iron oxyhydroxides, much lower than in previous studies in ultrapure water. This could be caused by the adsorption of natural organic matter (NOM) on the iron oxide surfaces. In the oxygen-saturated natural water with a pH ranging from 6.5 to 7.7, Gallionella spp. grew uninhibited and biological iron oxidation was an important, and probably the dominant, process. Gallionella growth was not even inhibited in a full-scale filter after plate aeration. From this we conclude that Gallionella spp. can grow under neutral pH and fully aerated conditions when the chemical iron oxidation is retarded by low water temperature and inhibition of the autocatalytic iron oxidation. PMID:21889183

  3. Magnetic characteristics of iron-modified oxide layers on titanium

    NASA Astrophysics Data System (ADS)

    Rudnev, V. S.; Adigamova, M. V.; Lukiyanchuk, I. V.; Tkachenko, I. A.; Morozova, V. P.; Ustinov, A. Yu.; Kharitonskii, P. V.; Frolov, A. M.

    2014-12-01

    Iron-modified TiO2 coatings on titanium exhibiting ferromagnetic properties are formed by combining plasma electrolytic oxidation (PEO) and impregnation with subsequent annealing. It is found that iron is contained in the composition of dispersed particles with sizes of 1-10 ?m distributed over the surface of the coatings. It is shown that the coercive force of the coating on titanium samples is 20-70 Oe. The composition, structure, and magnetic properties of the samples with coatings prepared via direct PEO and by combining PEO and impregnation are compared. It is concluded that impregnation and annealing procedures can be used to impart ferromagnetic properties to PEO coatings with different compositions, e.g., protective coatings and coatings applied in catalysis or medicine.

  4. Soluble Iron in Alveolar Macrophages Modulates Iron Oxide Particle-Induced Inflammatory Response via Prostaglandin E2 Synthesis

    EPA Science Inventory

    Ambient particulate matter (PM)-associated metals have been shown to play an important role in cardiopulmonary health outcomes. To study the modulation of inflammation by PM-associated soluble metal, we investigated intracellular solubility of radiolabelled iron oxide (59...

  5. Compact zwitterion-coated iron oxide nanoparticles for in vitro and in vivo imaging

    E-print Network

    Wei, He

    We have recently developed compact and water-soluble zwitterionic dopamine sulfonate (ZDS) ligand coated superparamagnetic iron oxide nanoparticles (SPIONs) for use in various biomedical applications. The defining ...

  6. AN EFFICIENT AND ECOFRIENDLY OXIDATION OF ALKENES USING IRON NITRATE AND MOLECULAR OXYGEN

    EPA Science Inventory

    An environmentally friendly solventless oxidation of alkenes is accomplished efficiently using relatively benign iron nitrate as catalyst in the pressence of molecular oxygen under pressurized conditions....

  7. Partial oxidation of {alpha}-olefins over iron antimony oxide - influence of carbon number

    SciTech Connect

    Steen, E. van; Schnobel, M.; O`Connor, C.T. [Univ. of Cape Town, Rondebosch (South Africa)

    1996-10-01

    Iron antimony oxide is a well known catalyst for the partial oxidation of propane and 1-butene. Kinetic studies of the partial oxidation of {alpha}-olefins (C{sub 2}-C{sub 9}) revealed that the activity showed a maximum at C{sub 4}. The main products of the partial oxidation of {alpha}-olefins (larger than C{sub 2}) are the conjugated alkenal (acrolein) and dienes. The selectivity to these desired products decreases with increasing chain length probably caused by both the decrease in number of allylic hydrogen atoms and the shielding of them. Ethene could only be oxidized at relatively high temperatures (over 450{degrees}C) and the only observed products were CO and CO{sub 2} indicating the need for the presence of allylic hydrogen for low temperature selective partial oxidation. Increasing the carbon number increases the yield of CO and CO{sub 2} due to shielding of the allylic hydrogen.

  8. THE EFFECTS OF IRON(II) ON ARSENIC(III) OXIDATION AND ARSENIC SORPTION/DESORPTION ON MANGANESE OXIDES

    E-print Network

    Sparks, Donald L.

    THE EFFECTS OF IRON(II) ON ARSENIC(III) OXIDATION AND ARSENIC SORPTION/DESORPTION ON MANGANESE © 2014 Yun Wu All Rights Reserved #12;THE EFFECTS OF IRON(II) ON ARSENIC(III) OXIDATION AND ARSENIC, Caroline Golt on arsenic speciation and UD Soil Test Lab. I thank all current and previous members

  9. Arsenic Bioremediation by Biogenic Iron Oxides and Sulfides

    PubMed Central

    Couture, Raoul-Marie; Van Cappellen, Philippe; Corkhill, Claire L.; Charnock, John M.; Polya, David A.; Vaughan, David; Vanbroekhoven, Karolien; Lloyd, Jonathan R.

    2013-01-01

    Microcosms containing sediment from an aquifer in Cambodia with naturally elevated levels of arsenic in the associated groundwater were used to evaluate the effectiveness of microbially mediated production of iron minerals for in situ As remediation. The microcosms were first incubated without amendments for 28 days, and the release of As and other geogenic chemicals from the sediments into the aqueous phase was monitored. Nitrate or a mixture of sulfate and lactate was then added to stimulate biological Fe(II) oxidation or sulfate reduction, respectively. Without treatment, soluble As concentrations reached 3.9 ± 0.9 ?M at the end of the 143-day experiment. However, in the nitrate- and sulfate-plus-lactate-amended microcosms, soluble As levels decreased to 0.01 and 0.41 ± 0.13 ?M, respectively, by the end of the experiment. Analyses using a range of biogeochemical and mineralogical tools indicated that sorption onto freshly formed hydrous ferric oxide (HFO) and iron sulfide mineral phases are the likely mechanisms for As removal in the respective treatments. Incorporation of the experimental results into a one-dimensional transport-reaction model suggests that, under conditions representative of the Cambodian aquifer, the in situ precipitation of HFO would be effective in bringing groundwater into compliance with the World Health Organization (WHO) provisional guideline value for As (10 ppb or 0.13 ?M), although soluble Mn release accompanying microbial Fe(II) oxidation presents a potential health concern. In contrast, production of biogenic iron sulfide minerals would not remediate the groundwater As concentration below the recommended WHO limit. PMID:23666325

  10. Effects of coating on magnetic properties in iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Bittova, B.; Poltierova-Vejpravova, J.; Roca, A. G.; Morales, M. P.; Tyrpekl, V.

    2010-01-01

    We have studied influence of surface modification on physical properties of iron oxide nanoparticles. We compared samples prepared by thermal decomposition of organic precursor in the presence of oleic acid, and the particles prepared by coprecipitation and partially coated by SiO2 or modified by citric acid and subsequently covered by photoactive TiO2 layer, respectively. Samples were characterised using TEM and XRD, further magnetic studies such as temperature dependence of magnetization and a.c. susceptibility show superparamagnetic behavior for all samples at room temperature. The effects of coating on dipolar inter particle interactions are discussed.

  11. Iron oxide hydroxide nanoflower assisted removal of arsenic from water

    SciTech Connect

    Raul, Prasanta Kumar, E-mail: prasanta.drdo@gmail.com [Defence Research Laboratory, Post Bag No. 2, Tezpur 784001, Assam (India); Devi, Rashmi Rekha; Umlong, Iohborlang M. [Defence Research Laboratory, Post Bag No. 2, Tezpur 784001, Assam (India); Thakur, Ashim Jyoti [Department of Chemical Sciences, Tezpur University, Napaam, Tezpur 784028, Assam (India); Banerjee, Saumen; Veer, Vijay [Defence Research Laboratory, Post Bag No. 2, Tezpur 784001, Assam (India)

    2014-01-01

    Graphical abstract: Non-magnetic polycrystalline iron oxide hydroxide nanoparticle with flower like morphology is found to play as an effective adsorbent media to remove As(III) from 300 ?g L{sup ?1} to less than 10 ?g L{sup ?1} from drinking water over wide range of pH. TEM image clearly reveals that the nanoparticle looks flower like morphology with average particle size less than 20 nm. The maximum sorption capacity of the sorbent is found to be 475 ?g g{sup ?1} for arsenic at room temperature and the data fitted to different isotherm models indicate the heterogeneity of the adsorbent surface. The material can be regenerated up to 70% using dilute hydrochloric acid and it would be utilized for de-arsenification purposes. - Highlights: • The work includes synthesis of iron oxide hydroxide nanoflower and its applicability for the removal of arsenic from water. • The nanoparticle was characterized using modern instrumental methods like FESEM, TEM, BET, XRD, etc. • The maximum sorption capacity of the sorbent is found to be 475 ?g g{sup ?1} for arsenic at room temperature. • The sorption is multilayered on the heterogeneous surface of the nano adsorbent. • The mechanism of arsenic removal of IOH nanoflower follows both adsorption and ion-exchange. - Abstract: Non-magnetic polycrystalline iron oxide hydroxide nanoparticle with flower like morphology is found to play as an effective adsorbent media to remove As(III) from 300 ?g L{sup ?1} to less than 10 ?g L{sup ?1} from drinking water over wide range of pH. The nanoparticle was characterized by X-ray powder diffraction analysis (XRD), BET surface area, FTIR, FESEM and TEM images. TEM image clearly reveals flower like morphology with average particle size less than 20 nm. The nanoflower morphology is also supported by FESEM images. The maximum sorption capacity of the sorbent is found to be 475 ?g g{sup ?1} for arsenic and the data fitted to different isotherm models indicate the heterogeneity of the adsorbent surface. Study on adsorption kinetics shows that adsorption of arsenic onto iron oxide hydroxide nanoflower follows pseudo-second order kinetic. The material can be regenerated up to 70% using dilute hydrochloric acid and it would be utilized for de-arsenification purposes.

  12. Reactions of metal ions at surfaces of hydrous iron oxide

    USGS Publications Warehouse

    Hem, J.D.

    1977-01-01

    Cu, Ag and Cr concentrations in natural water may be lowered by mild chemical reduction involving ferric hydroxide-ferrous ion redox processes. V and Mo solubilities may be controlled by precipitation of ferrous vanadate or molybdate. Concentrations as low as 10-8.00 or 10-9.00 M are readily attainable for all these metals in oxygen-depleted systems that are relatively rich in Fe. Deposition of manganese oxides such as Mn3O4 can be catalyzed in oxygenated water by coupling to ferrous-ferric redox reactions. Once formed, these oxides may disproportionate, giving Mn4+ oxides. This reaction produces strongly oxidizing conditions at manganese oxide surfaces. The solubility of As is significantly influenced by ferric iron only at low pH. Spinel structures such as chromite or ferrites of Cu, Ni, and Zn, are very stable and if locally developed on ferric hydroxide surfaces could bring about solubilities much below 10-9.00 M for divalent metals near neutral pH. Solubilities calculated from thermodynamic data are shown graphically and compared with observed concentrations in some natural systems. ?? 1977.

  13. The effects of pH, ionic strength, and iron–fulvic acid interactions on the kinetics of non-photochemical iron transformations. I. Iron(II) oxidation and iron(III) colloid formation

    Microsoft Academic Search

    Michael J. Pullin; Stephen E. Cabaniss

    2003-01-01

    Flow injection analysis was used to study the effect of a fulvic acid on the kinetics of iron(II) oxidation and iron colloid formation under conditions approximating fresh natural waters. While iron(II) oxidation in high-carbonate inorganic solutions is predicted well by a recently proposed homogeneous model, it overestimates the oxidation rate in low-carbonate solutions, possibly due to the formation of an

  14. Dysregulation of hepatic iron with aging: implications for heat stress-induced oxidative liver injury.

    PubMed

    Bloomer, Steven A; Brown, Kyle E; Buettner, Garry R; Kregel, Kevin C

    2008-04-01

    Environmental heat stress is associated with an age-related increase in hepatic oxidative damage and an exaggerated state of oxidative stress. The purpose of this investigation was to evaluate the regulation of hepatic iron after heat stress. A secondary aim was to determine a potential role for iron in heat stress-induced liver injury. Hyperthermia-induced alterations in hepatic iron were evaluated in young (6 mo) and old (24 mo) Fischer 344 rats by exposing them to a two-heat stress protocol. Livers were harvested at several time points after the second heating and assayed for labile and nonheme iron. In the control condition, there was no difference in labile iron between age groups. Both labile iron and storage iron were not altered by hyperthermia in young rats, but both were increased immediately after heating in old rats. To evaluate a role for iron in liver injury, hepatic iron content was manipulated in young and old rats, and then both groups were exposed to heat stress. Iron administration to young rats significantly increased hepatic iron content and ferritin but did not affect markers of lipid peroxidation under control conditions or after heat stress. In old rats, iron chelation with deferoxamine prevented the increase in nonheme iron, labile iron, ferritin, and lipid peroxidation after heat stress. These results suggest that iron may play a role in hepatic injury after hyperthermia. Thus, dysregulation of iron may contribute to the gradual decline in cellular and physiological function that occurs with aging. PMID:18272664

  15. Role of humic substances in promoting autotrophic growth in nitrate-dependent iron-oxidizing bacteria.

    PubMed

    Kanaparthi, Dheeraj; Conrad, Ralf

    2015-05-01

    Nitrate-dependent iron oxidation was discovered in 1996 and has been reported from various environments ever since. To date, despite the widespread nature of this process, all attempts to cultivate chemolithoautotrophic nitrate-dependent iron oxidizers have been unsuccessful. The present study was focused on understanding the influence of natural chelating agents of iron, like humic substances, on the culturability, activity, and enumeration, of these microorganisms. Pure culture studies conducted with Thiobacillus denitrificans showed a constant increase in cell mass with a corresponding nitrate-dependent iron oxidation activity only when Fe(II) was provided together with humic substances, compared to no growth in control incubations without humic substances. The presence of a relatively strong chelating agent, such as EDTA, inhibited the growth of Thiobacillus denitrificans. It was concluded that complex formation between humic substances and iron was required for chemolithoautotrophic nitrate-dependent iron oxidation. Most probable number enumerations showed that numbers of chemolithoautotrophic nitrate-dependent iron-oxidizing bacteria were one to three orders of magnitude higher in the presence of humic substances compared to media without. Similar results were obtained when potential nitrate-dependent iron oxidation activity was determined in soil samples. In summary, this study showed that humic substances significantly enhanced the growth and activity of autotrophic nitrate-dependent iron-oxidizing microorganisms, probably by chelation of iron. PMID:25864167

  16. Evidence for equilibrium iron isotope fractionation by nitrate-reducing iron(II)-oxidizing bacteria

    PubMed Central

    Kappler, A.; Johnson, C.M.; Crosby, H.A.; Beard, B.L.; Newman, D.K.

    2010-01-01

    Iron isotope fractionations produced during chemical and biological Fe(II) oxidation are sensitive to the proportions and nature of dissolved and solid-phase Fe species present, as well as the extent of isotopic exchange between precipitates and aqueous Fe. Iron isotopes therefore potentially constrain the mechanisms and pathways of Fe redox transformations in modern and ancient environments. In the present study, we followed in batch experiments Fe isotope fractionations between Fe(II)aq and Fe(III) oxide/hydroxide precipitates produced by the Fe(III) mineral encrusting, nitrate-reducing, Fe(II)-oxidizing Acidovorax sp. strain BoFeN1. Isotopic fractionation in 56Fe/54Fe approached that expected for equilibrium conditions, assuming an equilibrium ?56FeFe(OH)3 – Fe(II)aq fractionation factor of +3.0 ‰. Previous studies have shown that Fe(II) oxidation by this Acidovorax strain occurs in the periplasm, and we propose that Fe isotope equilibrium is maintained through redox cycling via coupled electron and atom exchange between Fe(II)aq and Fe(III) precipitates in the contained environment of the periplasm. In addition to the apparent equilibrium isotopic fractionation, these experiments also record the kinetic effects of initial rapid oxidation, and possible phase transformations of the Fe(III) precipitates. Attainment of Fe isotope equilibrium between Fe(III) oxide/hydroxide precipitates and Fe(II)aq by neutrophilic, Fe(II)-oxidizing bacteria or through abiologic Fe(II)aq oxidation is generally not expected or observed, because the poor solubility of their metabolic product, i.e. Fe(III), usually leads to rapid precipitation of Fe(III) minerals, and hence expression of a kinetic fractionation upon precipitation; in the absence of redox cycling between Fe(II)aq and precipitate, kinetic isotope fractionations are likely to be retained. These results highlight the distinct Fe isotope fractionations that are produced by different pathways of biological and abiological Fe(II) oxidation. PMID:21076519

  17. Evidence for equilibrium iron isotope fractionation by nitrate-reducing iron(II)-oxidizing bacteria.

    PubMed

    Kappler, A; Johnson, C M; Crosby, H A; Beard, B L; Newman, D K

    2010-05-10

    Iron isotope fractionations produced during chemical and biological Fe(II) oxidation are sensitive to the proportions and nature of dissolved and solid-phase Fe species present, as well as the extent of isotopic exchange between precipitates and aqueous Fe. Iron isotopes therefore potentially constrain the mechanisms and pathways of Fe redox transformations in modern and ancient environments. In the present study, we followed in batch experiments Fe isotope fractionations between Fe(II)(aq) and Fe(III) oxide/hydroxide precipitates produced by the Fe(III) mineral encrusting, nitrate-reducing, Fe(II)-oxidizing Acidovorax sp. strain BoFeN1. Isotopic fractionation in (56)Fe/(54)Fe approached that expected for equilibrium conditions, assuming an equilibrium ?(56)Fe(Fe(OH)3 - Fe(II)aq) fractionation factor of +3.0 ‰. Previous studies have shown that Fe(II) oxidation by this Acidovorax strain occurs in the periplasm, and we propose that Fe isotope equilibrium is maintained through redox cycling via coupled electron and atom exchange between Fe(II)(aq) and Fe(III) precipitates in the contained environment of the periplasm. In addition to the apparent equilibrium isotopic fractionation, these experiments also record the kinetic effects of initial rapid oxidation, and possible phase transformations of the Fe(III) precipitates. Attainment of Fe isotope equilibrium between Fe(III) oxide/hydroxide precipitates and Fe(II)(aq) by neutrophilic, Fe(II)-oxidizing bacteria or through abiologic Fe(II)(aq) oxidation is generally not expected or observed, because the poor solubility of their metabolic product, i.e. Fe(III), usually leads to rapid precipitation of Fe(III) minerals, and hence expression of a kinetic fractionation upon precipitation; in the absence of redox cycling between Fe(II)(aq) and precipitate, kinetic isotope fractionations are likely to be retained. These results highlight the distinct Fe isotope fractionations that are produced by different pathways of biological and abiological Fe(II) oxidation. PMID:21076519

  18. Testing for Discrete vs. Agglomerated Nanoparticles of 'Iron Oxides'

    NASA Astrophysics Data System (ADS)

    Penn, R. L.; Erbs, J. J.; Jentzsch, T. L.

    2007-05-01

    Nanoparticles of 'iron oxides' such as ferrihydrite, goethite, hematite and magnetite are found in nature as discrete or agglomerated ('clumped') particles, and with or without dopants such as Al, as and Si. The presence of clumping has important repercussions on both physical and chemical properties of these compounds. We present evidence from a number of nanoparticle systems in which dc and ac susceptibility measurements at low temperatures provide a non-destructive way to assess the presence of agglomeration and the roles of the dopants in modifying such behavior. In addition, we use quantitative kinetics for Fe (III) reduction or Fe(II) oxidation by quinones as our main chemical tool for sample aliquots.

  19. Nickel aluminides and nickel-iron aluminides for use in oxidizing environments

    DOEpatents

    Liu, Chain T. (Oak Ridge, TN)

    1988-03-15

    Nickel aluminides and nickel-iron aluminides treated with hafnium or zirconium, boron and cerium to which have been added chromium to significantly improve high temperature ductility, creep resistance and oxidation properties in oxidizing environments.

  20. Macroscopic and microscopic biodistribution of intravenously administered iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Misra, Adwiteeya; Petryk, Alicia A.; Strawbridge, Rendall R.; Hoopes, P. Jack

    2015-03-01

    Iron oxide nanoparticles (IONP) are being developed for use as a cancer treatment. They have demonstrated efficacy when used either as a monotherapy or in conjunction with conventional chemotherapy and radiation. The success of IONP as a therapeutic tool depends on the delivery of a safe and controlled cytotoxic thermal dose to tumor tissue following activation with an alternating magnetic field (AMF). Prior to clinical approval, knowledge of IONP toxicity, biodistribution and physiological clearance is essential. This preliminary time-course study determines the acute toxicity and biodistribution of 110 nm dextran-coated IONP (iron) in mice, 7 days post systemic, at doses of 0.4, 0.6, and 1.0 mg Fe/ g mouse bodyweight. Acute toxicity, manifested as changes in the behavior of mice, was only observed temporarily at 1.0 mg Fe/ g mouse bodyweight, the highest dose administered. Regardless of dose, mass spectrometry and histological analysis demonstrated over 3 mg Fe/g tissue in organs within the reticuloendotheilial system (i.e. liver, spleen, and lymph nodes). Other organs (brain, heart, lungs, and kidney) had less than 0.5 mg Fe/g tissue with iron predominantly confined to the organ vasculature.

  1. Influence of synthetic superparamagnetic iron oxide on dendritic cells

    PubMed Central

    Mou, Yongbin; Chen, Baoan; Zhang, Yu; Hou, Yayi; Xie, Hao; Xia, Guohua; Tang, Meng; Huang, Xiaofeng; Ni, Yanhong; Hu, Qingang

    2011-01-01

    Background: This study investigated the influence of synthetic superparamagnetic iron oxide (SPIO) on dendritic cells and provides a possible method for labeling these cells. Methods: SPIO nanoparticles were prepared, and their morphology and magnetic properties were characterized. The particles were endocytosed by dendritic cells generated from mouse bone marrow. Labeling efficiency and cellular uptake were analyzed by Prussian blue staining and quantitative spectrophotometric assay. Meanwhile, the surface molecules, cellular apoptosis, and functional properties of the SPIO-labeled dendritic cells were explored by flow cytometry and the mixed lymphocyte reaction assay. Results: The synthetic nanoparticles possessed a spherical shape and good superparamagnetic behavior. The mean concentration of iron in immature and mature dendritic cells was 31.8 ± 0.7 ?g and 35.6 ± 1.0 ?g per 1 × 106 cells, respectively. After 12 hours of incubation with SPIO at a concentration of 25 ?g/mL, nearly all cells were shown to contain iron. Interestingly, cellular apoptosis and surface expression of CD80, CD86, major histocompatibility II, and chemokine receptor 7 in mature dendritic cells were not affected to any significant extent by SPIO labeling. T cell activation was maintained at a low ratio of dendritic cells to T cells. Conclusion: SPIO nanoparticles have good superparamagnetic behavior, highly biocompatible characteristics, and are suitable for use in further study of the migratory behavior and biodistribution of dendritic cells in vivo. PMID:21980240

  2. Morphology of biogenic iron oxides records microbial physiology and environmental conditions: toward interpreting iron microfossils.

    PubMed

    Krepski, S T; Emerson, D; Hredzak-Showalter, P L; Luther, G W; Chan, C S

    2013-09-01

    Despite the abundance of Fe and its significance in Earth history, there are no established robust biosignatures for Fe(II)-oxidizing micro-organisms. This limits our ability to piece together the history of Fe biogeochemical cycling and, in particular, to determine whether Fe(II)-oxidizers played a role in depositing ancient iron formations. A promising candidate for Fe(II)-oxidizer biosignatures is the distinctive morphology and texture of extracellular Fe(III)-oxyhydroxide stalks produced by mat-forming microaerophilic Fe(II)-oxidizing micro-organisms. To establish the stalk morphology as a biosignature, morphologic parameters must be quantified and linked to the microaerophilic Fe(II)-oxidizing metabolism and environmental conditions. Toward this end, we studied an extant model organism, the marine stalk-forming Fe(II)-oxidizing bacterium, Mariprofundus ferrooxydans PV-1. We grew cultures in flat glass microslide chambers, with FeS substrate, creating opposing oxygen/Fe(II) concentration gradients. We used solid-state voltammetric microelectrodes to measure chemical gradients in situ while using light microscopy to image microbial growth, motility, and mineral formation. In low-oxygen (2.7-28 ?m) zones of redox gradients, the bacteria converge into a narrow (100 ?m-1 mm) growth band. As cells oxidize Fe(II), they deposit Fe(III)-oxyhydroxide stalks in this band; the stalks orient directionally, elongating toward higher oxygen concentrations. M. ferrooxydans stalks display a narrow range of widths and uniquely biogenic branching patterns, which result from cell division. Together with filament composition, these features (width, branching, and directional orientation) form a physical record unique to microaerophilic Fe(II)-oxidizer physiology; therefore, stalk morphology is a biosignature, as well as an indicator of local oxygen concentration at the time of formation. Observations of filamentous Fe(III)-oxyhydroxide microfossils from a ~170 Ma marine Fe-Si hydrothermal deposit show that these morphological characteristics can be preserved in the microfossil record. This study demonstrates the potential of morphological biosignatures to reveal microbiology and environmental chemistry associated with geologic iron formation depositional processes. PMID:23790206

  3. Application of a novel plasma-induced CD/MWCNT/iron oxide composite in zinc decontamination.

    PubMed

    Yang, Shitong; Guo, Zhiqiang; Sheng, Guodong; Wang, Xiangke

    2012-10-01

    Herein, ?-cyclodextrin (?-CD) was grafted onto magnetic MWCNT/iron oxide particles by using low temperature plasma-induced technique to synthesize a novel nanocomposite. The prepared composite (denoted as CD/MWCNT/iron oxide) exhibited high magnetic property (saturation magnetization M(s)=37.8 emu/g) and good dispersion property in aqueous solution. Batch experiments were conducted to evaluate the application potential of CD/MWCNT/iron oxide in the decontamination of Zn(II) from aqueous solutions. The sorption amount of Zn(II) on CD/MWCNT/iron oxide was higher than that of Zn(II) on MWCNT/iron oxides and oxidized MWCNTs, indicating that the grafted ?-CD could enhance the sorption capacity of CD/MWCNT/iron oxide composite toward Zn(II) by providing multiple hydroxyl functional groups. Due to its high magnetic, CD/MWCNT/iron oxide could be easily separated from aqueous solution with an external magnetic field. Regeneration studies suggested that CD/MWCNT/iron oxide can support long term use as a cost-effective material in sewage treatment with minimum replacement costs. PMID:22840045

  4. Rapid Spectrophotometric Technique for Quantifying Iron in Cells Labeled with Superparamagnetic Iron Oxide Nanoparticles: Potential Translation to the Clinic

    PubMed Central

    Dadashzadeh, Esmaeel R.; Hobson, Matthew; Bryant, L. Henry; Dean, Dana D.; Frank, Joseph A.

    2012-01-01

    Labeling cells with superparamagnetic iron oxide (SPIO) nanoparticles provides the ability to track cells by Magnetic Resonance Imaging. Quantifying intracellular iron concentration in SPIO labeled cells would allow for the comparison of agents and techniques used to magnetically label cells. Here we describe a rapid spectrophotometric technique (ST) to quantify iron content of SPIO labeled cells, circumventing the previous requirement of an overnight acid digestion. Following lysis with 10% SDS of magnetically labeled cells, quantification of SPIO doped or labeled cells was performed using commonly available spectrophotometric instrument(s) by comparing absorptions at 370 and 750 nm with correction for turbidity of cellular products to determine iron content of each sample. Standard curves demonstrated high linear correlation (R2 = 0.998) between absorbance spectra of iron oxide nanoparticles and concentration in known SPIO doped cells. Comparisons of the ST to ICP-MS or NMR relaxometric (R2) determinations of intracellular iron contents in SPIO containing samples resulted in significant linear correlation between the techniques (R2 vs. ST, R2>0.992, p<0.0001, ST vs. ICP-MS, R2>0.995, p<0.0001) with the limit of detection of ST for iron = 0.66?g/ml. We have developed a rapid straightforward protocol that does not require overnight acid digestion for quantifying iron oxide content in magnetically labeled cells using readily available analytic instrumentation that should greatly expedite advances in comparing SPIO agents and protocols for labeling cells. PMID:23109392

  5. Magnetic tumor targeting of ?-glucosidase immobilized iron oxide nanoparticles.

    PubMed

    Zhou, Jie; Zhang, Jian; David, Allan E; Yang, Victor C

    2013-09-20

    Directed enzyme/prodrug therapy (DEPT) has promising application for cancer therapy. However, most current DEPT strategies face shortcomings such as the loss of enzyme activity during preparation, low delivery and transduction efficiency in vivo and difficultly of monitoring. In this study, a novel magnetic directed enzyme/prodrug therapy (MDEPT) was set up by conjugating ?-glucosidase (?-Glu) to aminated, starch-coated, iron oxide magnetic iron oxide nanoparticles (MNPs), abbreviated as ?-Glu-MNP, using glutaraldehyde as the crosslinker. This ?-Glu-MNP was then characterized in detail by size distribution, zeta potential, FTIR spectra, TEM, SQUID and magnetophoretic mobility analysis. Compared to free enzyme, the conjugated ?-Glu on MNPs retained 85.54% ± 6.9% relative activity and showed much better temperature stability. The animal study results showed that ?-Glu-MNP displays preferable pharmacokinetics characteristics in relation to MNPs. With an adscititious magnetic field on the surface of a tumor, a significant quantity of ?-Glu-MNP was selectively delivered into a subcutaneous tumor of a glioma-bearing mouse. Remarkably, the enzyme activity of the delivered ?-Glu in tumor lesions showed as high as 20.123±5.022 mU g(-1) tissue with 2.14 of tumor/non-tumor ?-Glu activity. PMID:23974977

  6. Magnetic tumor targeting of ?-glucosidase immobilized iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhou, Jie; Zhang, Jian; David, Allan E.; Yang, Victor C.

    2013-09-01

    Directed enzyme/prodrug therapy (DEPT) has promising application for cancer therapy. However, most current DEPT strategies face shortcomings such as the loss of enzyme activity during preparation, low delivery and transduction efficiency in vivo and difficultly of monitoring. In this study, a novel magnetic directed enzyme/prodrug therapy (MDEPT) was set up by conjugating ?-glucosidase (?-Glu) to aminated, starch-coated, iron oxide magnetic iron oxide nanoparticles (MNPs), abbreviated as ?-Glu-MNP, using glutaraldehyde as the crosslinker. This ?-Glu-MNP was then characterized in detail by size distribution, zeta potential, FTIR spectra, TEM, SQUID and magnetophoretic mobility analysis. Compared to free enzyme, the conjugated ?-Glu on MNPs retained 85.54% ± 6.9% relative activity and showed much better temperature stability. The animal study results showed that ?-Glu-MNP displays preferable pharmacokinetics characteristics in relation to MNPs. With an adscititious magnetic field on the surface of a tumor, a significant quantity of ?-Glu-MNP was selectively delivered into a subcutaneous tumor of a glioma-bearing mouse. Remarkably, the enzyme activity of the delivered ?-Glu in tumor lesions showed as high as 20.123±5.022 mU g-1 tissue with 2.14 of tumor/non-tumor ?-Glu activity.

  7. Evaluation of Nanodispersion of Iron Oxides Using Various Polymers

    PubMed Central

    Tanaka, Y.; Ueyama, H.; Ogata, M.; Daikoku, T.; Morimoto, M.; Kitagawa, A.; Imajo, Y.; Tahara, T.; Inkyo, M.; Yamaguchi, N.; Nagata, S.

    2014-01-01

    In order to create Fe2O3 and Fe2O3·H2O nanoparticles, various polymers were used as dispersing agents, and the resulting effects on the dispersibility and nanoparticulation of the iron oxides were evaluated. It was revealed that not only the solution viscosity but also the molecular length of the polymers and the surface tension of the particles affected the dispersibility of Fe2O3 and Fe2O3·H2O particles. Using the dispersing agents 7.5% hydroxypropylcellulose-SSL, 6.0% Pharmacoat 603, 5.0% and 6.5% Pharmacoat 904 and 7.0% Metolose SM-4, Fe2O3 nanoparticles were successfully fabricated by wet milling using Ultra Apex Mill. Fe2O3·H2O nanoparticles could also be produced using 5.0% hydroxypropylcellulose-SSL and 4.0 and 7.0% Pharmacoat 904. The index for dispersibility developed in this study appears to be an effective indicator of success in fabricating nanoparticles of iron oxides by wet milling using Ultra Apex Mill. PMID:24799739

  8. Cerebral blood volume MRI with intravascular superparamagnetic iron oxide nanoparticles.

    PubMed

    Kim, Seong-Gi; Harel, Noam; Jin, Tao; Kim, Tae; Lee, Phil; Zhao, Fuqiang

    2013-08-01

    The cerebral blood volume (CBV) is a crucial physiological indicator of tissue viability and vascular reactivity. Thus, noninvasive CBV mapping has been of great interest. For this, ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, including monocrystalline iron oxide nanoparticles, can be used as long-half-life, intravascular susceptibility agents of CBV MRI measurements. Moreover, CBV-weighted functional MRI (fMRI) with USPIO nanoparticles provides enhanced sensitivity, reduced large vessel contribution and improved spatial specificity relative to conventional blood oxygenation level-dependent fMRI, and measures a single physiological parameter that is easily interpretable. We review the physiochemical and magnetic properties, and pharmacokinetics, of USPIO nanoparticles in brief. We then extensively discuss quantifications of baseline CBV, vessel size index and functional CBV change. We also provide reviews of dose-dependent sensitivity, vascular filter function, specificity, characteristics and impulse response function of CBV fMRI. Examples of CBV fMRI specificity at the laminar and columnar resolution are provided. Finally, we briefly review the application of CBV measurements to functional and pharmacological studies in animals. Overall, the use of USPIO nanoparticles can determine baseline CBV and its changes induced by functional activity and pharmacological interventions. PMID:23208650

  9. Strategies for the biofunctionalization of gold and iron oxide nanoparticles.

    PubMed

    Fratila, Raluca M; Mitchell, Scott G; del Pino, Pablo; Grazu, Valeria; de la Fuente, Jesús M

    2014-12-23

    The field of nanotechnology applied to medicine (nanomedicine) is developing at a fast pace and is expected to provide solutions for early diagnosis, targeted therapy, and personalized medicine. However, designing nanomaterials for biomedical applications is not a trivial task. Avoidance of the immune system, stability in physiological media, control over the interaction of a nanomaterial with biological entities such as proteins and cell membranes, low toxicity, and optimal bioperformance are critical for the success of the designed nanomaterial. In this Feature Article we provide a concise overview of some of the most recent advances concerning the derivatization of gold and iron oxide nanoparticles for bioapplications. The most important aspects relating to the functionalization of gold and iron oxide nanoparticles with carbohydrates, peptides, nucleic acids, and antibodies are covered, highlighting the recent contributions from our research group. We suggest tips for the appropriate (bio)functionalization of these inorganic nanoparticles in order to preserve the biological activity of the attached biomolecules and ensure their subsequent stability in physiological media. PMID:24911468

  10. Evaluation of nanodispersion of iron oxides using various polymers.

    PubMed

    Tanaka, Y; Ueyama, H; Ogata, M; Daikoku, T; Morimoto, M; Kitagawa, A; Imajo, Y; Tahara, T; Inkyo, M; Yamaguchi, N; Nagata, S

    2014-01-01

    In order to create Fe2O3 and Fe2O3·H2O nanoparticles, various polymers were used as dispersing agents, and the resulting effects on the dispersibility and nanoparticulation of the iron oxides were evaluated. It was revealed that not only the solution viscosity but also the molecular length of the polymers and the surface tension of the particles affected the dispersibility of Fe2O3 and Fe2O3·H2O particles. Using the dispersing agents 7.5% hydroxypropylcellulose-SSL, 6.0% Pharmacoat 603, 5.0% and 6.5% Pharmacoat 904 and 7.0% Metolose SM-4, Fe2O3 nanoparticles were successfully fabricated by wet milling using Ultra Apex Mill. Fe2O3·H2O nanoparticles could also be produced using 5.0% hydroxypropylcellulose-SSL and 4.0 and 7.0% Pharmacoat 904. The index for dispersibility developed in this study appears to be an effective indicator of success in fabricating nanoparticles of iron oxides by wet milling using Ultra Apex Mill. PMID:24799739

  11. Iron oxide reduction in deep Baltic Sea sediments: the potential role of anaerobic oxidation of methane

    NASA Astrophysics Data System (ADS)

    Egger, Matthias; Slomp, Caroline P.; Dijkstra, Nikki; Sapart, Célia J.; Risgaard-Petersen, Nils; Kasten, Sabine; Riedinger, Natascha; Barker Jørgensen, Bo

    2015-04-01

    Methane is a powerful greenhouse gas and its emission from marine sediments to the atmosphere is largely controlled by anaerobic oxidation of methane (AOM). Traditionally, sulfate is considered to be the most important electron acceptor for AOM in marine sediments. However, recent studies have shown that AOM may also be coupled to the reduction of iron (Fe) oxides (Beal et al., 2009; Riedinger et al., 2014; Egger et al., 2014). In the Baltic Sea, the transition from the Ancylus freshwater phase to the Littorina brackish/marine phase (A/L-transition) ca. 9-7 ka ago (Zillén et al., 2008) resulted in the accumulation of methanogenic brackish/marine sediments overlying Fe-oxide rich lacustrine deposits. The downward diffusion of methane from the brackish/marine sediments into the lake sediments leads to an ideal diagenetic system to study a potential coupling between Fe oxide reduction and methane oxidation. Here, we use porewater and sediment geochemical data obtained at sites M0063 and M0065 during the IODP Baltic Sea Paleoenvironment Expedition 347 in 2013 to identify the potential mechanisms responsible for the apparent Fe oxide reduction in the non-sulfidic limnic sediments below the A/L transition. In this presentation, we will review the various explanations for the elevated ferrous Fe in the porewater in the lake sediments and we will specifically address the potential role of the reaction of methane with Fe-oxides. References: Beal E. J., House C. H. and Orphan V. J. (2009) Manganese- and iron-dependent marine methane oxidation. Science 325, 184-187. Egger M., Rasigraf O., Sapart C. J., Jilbert T., Jetten M. S. M., Röckmann T., van der Veen C., Banda N., Kartal B., Ettwig K. F. and Slomp C. P. (2014) Iron-mediated anaerobic oxidation of methane in brackish coastal sediments. Environ. Sci. Technol. 49, 277-283. Riedinger N., Formolo M. J., Lyons T. W., Henkel S., Beck A. and Kasten S. (2014) An inorganic geochemical argument for coupled anaerobic oxidation of methane and iron reduction in marine sediments. Geobiology 12, 172-181. Zillén L., Conley D. J., Andrén T., Andrén E. and Björck S. (2008) Past occurrences of hypoxia in the Baltic Sea and the role of climate variability, environmental change and human impact. Earth-Science Rev. 91, 77-92.

  12. Chemical characterization of iron oxide precipitates from wetlands constructed to treat polluted mine drainage

    SciTech Connect

    Fish, C.L.; Partezana, J.M. [Saint Vincent College, Latrobe, PA (United States); Hedin, R.S. [Hedin Environmental, Pittsburgh, PA (United States)

    1996-12-31

    The passive treatment of abandoned mine drainage using wetlands will produce a significant amount of iron rich sludge which will require costly removal and disposal. An alternative to disposal may be the use of this iron oxide material as pigments which could defray some of these costs. In this research, iron deposits from five alkaline mine drainage wetlands were collected and a series of standard tests were run. The tests included loss on ignition, moisture, pH, acid soluble metals, oil absorption, and water soluble matter. The results of these tests were compared to those achieved using commercially available natural and synthetic iron oxides. The results indicate that iron oxides from constructed wetlands have chemical properties that are intermediate to those of natural and synthetic iron oxide products.

  13. Growth of epitaxial films of iron oxide, nickel oxide, cobalt oxide, strontium hexagonal ferrite, and yttrium iron garnet by laser ablation (abstract)

    SciTech Connect

    Kennedy, R.J. [Physics Department, Florida A& M University, Tallahassee, Florida 32307 (United States)] [Physics Department, Florida A& M University, Tallahassee, Florida 32307 (United States)

    1996-04-01

    Thin films of iron oxide, nickel oxide, cobalt oxide, strontium hexagonal ferrite, and yttrium iron garnet have been grown by laser ablation. With the exception of Co{sub 3}O{sub 4} deposited on LaAlO{sub 3}, the first three materials deposited on [100] LaAlO{sub 3}, SrTiO{sub 3}, and MgO result in high quality {ital c} axis [100] growth. Co{sub 3}O{sub 4} deposited on LaAlO{sub 3} produces highly oriented but random in-plane growth. Similar highly oriented but random in-plane growth occurs for all three materials deposited on glass. The same three materials deposited on cubic zirconia grow [111] oriented and twinned. Strontium hexagonal ferrite and yttrium iron garnet have been deposited on [111] large lattice constant garnet. Epitaxial [0001] films are obtained for the former while the latter gives [111]-oriented films. For yttrium iron garnet the closeness of lattice match to the substrate necessitates that the mosaicity (rocking curves) obtained from area maps be compared to the growth temperatures and pressures to determine the optimum growth conditions for epitaxiality. {copyright} {ital 1996 American Institute of Physics.}

  14. Effect of radiation energy and intracellular iron dose on iron oxide nanoparticle enhancement of radiation cytotoxicity

    NASA Astrophysics Data System (ADS)

    Mazur, Courtney M.; Strawbridge, Rendall R.; Thompson, Ella S.; Petryk, Alicia A.; Gladstone, David J.; Hoopes, P. Jack

    2015-03-01

    Iron oxide nanoparticles (IONPs) are one of several high-Z materials currently being investigated for their ability to enhance the cytotoxic effects of therapeutic ionizing radiation. Studies with iron oxide, silver, gold, and hafnium oxide suggest radiation dose, radiation energy, cell type, and the type and level of metallic nanoparticle are all critical factors in achieving radiation enhancement in tumor cells. Using a single 4 Gy radiation dose, we compared the level of tumor cell cytotoxicity at two different intracellular iron concentrations and two different radiation energies in vitro. IONPs were added to cell culture media at concentrations of 0.25 mg Fe/mL and 1.0 mg Fe/mL and incubated with murine breast adenocarcinoma (MTG-B) cells for 72 hours. Extracellular iron was then removed and cells were irradiated at either 662 keV or 10 MV. At the 0.25 mg Fe/mL dose (4 pg Fe/cell), radiation energy did not affect the level of cytotoxicity. However with 1.0 mg Fe/mL (9 pg Fe/cell), the higher 10 MV radiation energy resulted in 50% greater cytotoxicity as compared to cells without IONPs irradiated at this energy. These results suggest IONPs may be able to significantly enhance the cytotoxic effects of radiation and improve therapeutic ratio if they can be selectively associated with cancer cells and/or tumors. Ongoing in vivo studies of IONP radiation enhancement in a murine tumor model are too immature to draw conclusions from at this time, however preliminary data suggests similar effectiveness of IONP radiation enhancement at 6 MV and 18 MV energy levels. In addition to the IONP-based radiation enhancement demonstrated here, the use of tumor-localized IONP with an externally delivered, non-toxic alternating magnetic field affords the opportunity to selectively heat and kill tumor cells. Combining IONP-based radiation sensitization and heat-based cytotoxicity provides a unique and potentially highly effective opportunity for therapeutic ratio enhancement.

  15. Iron-Oxide Minerals Affect Extracellular Electron-Transfer Paths of Geobacter spp

    PubMed Central

    Kato, Souichiro; Hashimoto, Kazuhito; Watanabe, Kazuya

    2013-01-01

    Some bacteria utilize (semi)conductive iron-oxide minerals as conduits for extracellular electron transfer (EET) to distant, insoluble electron acceptors. A previous study demonstrated that microbe/mineral conductive networks are constructed in soil ecosystems, in which Geobacter spp. share dominant populations. In order to examine how (semi)conductive iron-oxide minerals affect EET paths of Geobacter spp., the present study grew five representative Geobacter strains on electrodes as the sole electron acceptors in the absence or presence of (semi)conductive iron oxides. It was found that iron-oxide minerals enhanced current generation by three Geobacter strains, while no effect was observed in another strain. Geobacter sulfurreducens was the only strain that generated substantial amounts of currents both in the presence and absence of the iron oxides. Microscopic, electrochemical and transcriptomic analyses of G. sulfurreducens disclosed that this strain constructed two distinct types of EET path; in the absence of iron-oxide minerals, bacterial biofilms rich in extracellular polymeric substances were constructed, while composite networks made of mineral particles and microbial cells (without polymeric substances) were developed in the presence of iron oxides. It was also found that uncharacterized c-type cytochromes were up-regulated in the presence of iron oxides that were different from those found in conductive biofilms. These results suggest the possibility that natural (semi)conductive minerals confer energetic and ecological advantages on Geobacter, facilitating their growth and survival in the natural environment. PMID:23363619

  16. Adsorption and desorption of natural organic matter on iron oxide. Mechanisms and models

    Microsoft Academic Search

    Baohua Gu; Z. Chen; L. Llang; J. F. McCarthy; J. Schmitt

    1994-01-01

    This study was undertaken to elucidate the interaction mechanism between NOM (natural organic matter) and iron oxide surfaces and to develop a predictive model for NOM adsorption and desorption. Results indicated that ligand exchange between carboxyl\\/hydroxyl functional groups of NOM and iron oxide surfaces was the dominant interaction mechanism, especially under acidic or slightly acidic pH conditions. This conclusion was

  17. Mid-infrared reflectance spectra and optical constants of six iron oxide/oxyhydroxide phases

    E-print Network

    Glotch, Timothy D.

    Mid-infrared reflectance spectra and optical constants of six iron oxide/oxyhydroxide phases iron oxide/oxyhydrox- ide phases--magnetite, maghemite, goethite, lepidocrocite, akaganéite of these optical constants could aid in radiative transfer models of terrestrial dust as well as Mars, the Moon

  18. Synthesis and characterization of iron oxide\\/polymer composite nanoparticles with pendent functional groups

    Microsoft Academic Search

    Shupeng Liu; Xiaohui Wei; Maoquan Chu; Jinliang Peng; Yuhong Xu

    2006-01-01

    We describe in this paper an approach to synthesize superparamagnetic iron oxide nanoparticles in the presence of polymerized lactic acid. The resulted particles consisted of clusters of iron oxide monocrystals, embedded inside the polymer chains. The composite particles synthesized in situ were highly dispersible in aqueous solution with good stability. X-ray diffraction and magnetometer data all confirmed the crystalline structure

  19. Iron uncouples oxidative phosphorylation in brain mitochondria isolated from vitamin E-deficient rats

    Microsoft Academic Search

    Govind T. Vatassery; Eugene G. DeMaster; James C. K. Lai; W. Ed Smith; Hung T. Quach

    2004-01-01

    Few, if any, studies have examined the effect of vitamin E deficiency on brain mitochondrial oxidative phosphorylation. The latter was studied using brain mitochondria isolated from control and vitamin E-deficient rats (13 months of deficiency) after exposure to iron, an inducer of oxidative stress. Mitochondria were treated with iron (2 to 50 ?M) added as ferrous ammonium sulfate. Rates of

  20. Synthesis and Characterization of Silica-Coated Iron Oxide Nanoparticles in Microemulsion: The Effect of Nonionic

    E-print Network

    Tan, Weihong

    Synthesis and Characterization of Silica-Coated Iron Oxide Nanoparticles in Microemulsion, Arthur Hebard,§ and Weihong Tan*,, Department of Chemistry, McKnight Brain Institute, and Department-coated iron oxide nanoparticles. Three different nonionic surfactants (Triton X-100, Igepal CO-520, and Brij

  1. Fe3O4 thin films sputter deposited from iron oxide targets Yingguo Penga)

    E-print Network

    Laughlin, David E.

    Fe3O4 thin films sputter deposited from iron oxide targets Yingguo Penga) Data Storage Systems on 14 November 2002 Fe3O4 thin films have been directly sputter deposited from a target consisting report our investiga- tions of the deposition of Fe3O4 thin films rf sputtered from an iron oxide target

  2. Genome Sequence of the Acidophilic Iron Oxidizer Ferrimicrobium acidiphilum Strain T23T

    PubMed Central

    Eisen, Sebastian; Poehlein, Anja; Johnson, D. Barrie; Daniel, Rolf; Schlömann, Michael

    2015-01-01

    Extremely acidophilic iron-oxidizing bacteria have largely been characterized for the phyla Proteobacteria and Nitrospira. Here, we report the draft genome of an iron-oxidizing and -reducing heterotrophic mesophile of the Actinobacteria, Ferrimicrobium acidiphilum, which was isolated from an abandoned pyrite mine. The genome sequence comprises 3.08 Mb. PMID:25931604

  3. A novel strategy for surface modification of superparamagnetic iron oxide nanoparticles for lung cancer imaging

    E-print Network

    Gao, Jinming

    and targeted therapy of lung cancer. Recently, superparamagnetic nanoparticles (e.g., Fe3O4,3­5 MnFe2O4 6A novel strategy for surface modification of superparamagnetic iron oxide nanoparticles for lung Superparamagnetic iron oxide (SPIO) nanoparticles are widely used in magnetic resonance imaging (MRI) as versatile

  4. Sorption of anions of iodine by iron oxides and kaolinite

    SciTech Connect

    Couture, R.A.; Seitz, M.G.

    1983-01-01

    The sorption of iodide, iodate, and periodate ions by kaolinite, hematite and pelagic red clay in buffer solutions and sea water was studied. Iodate ions (IO/sup -//sub 3/) are strongly absorbed by hematite (Fe/sub 2/O/sub 3/) at pH values up to 9. The reaction is rapid and reversible and apparently occurs by replacement of OH/sup -/ ionson the surface. Periodate ions (IO/sup -//sub 4/) are more strongly sorbed by Fe/sub 2/O/sub 3/ than IO/sup -//sub 3/ ions; iodide ions (I/sup -/) appear to be less strongly sorbed. At pH 4, hematite-free, goethitefree kaolinite sorbs IO/sup -//sub 3/ only slightly and I/sup -/ not at all. IO/sup -//sub 3/ is stable relative to I/sup -/ in the presence of oxygen, and occurs in surface waters and in seawater. Small amounts of finely divided iron oxides, which are present in many types of sediments, may play a major role in the geochemistry of iodine by absorbing IO/sup -//sub 3/. For example, in one experiment pelagic red clay was found to be about as active as reagent Fe/sub 2/O/sub 3/ in removing dissolved IO/sup -//sub 3/ from seawater. This result suggests that pelagic red clay may be an appropriate host for disposal of radioactive iodine-129. Experiments on sorption of radioactive I/sup -/ by sedimentary minerals are reported in the literature. In many of these experiments, some of the iodine is likely to have been in the IO/sup -//sub 3/ or IO/sup -//sub 4/ form, which would have been sorbed by iron oxide impurities. The results of sorption experiments with radioactive iodine are considered dubious unless the oxidation state and the mineralogical purity are established.

  5. Iron isotope fractionation during microbial dissimilatory iron oxide reduction in simulated Archaean seawater.

    PubMed

    Percak-Dennett, E M; Beard, B L; Xu, H; Konishi, H; Johnson, C M; Roden, E E

    2011-05-01

    The largest Fe isotope excursion yet measured in marine sedimentary rocks occurs in shales, carbonates, and banded iron formations of Neoarchaean and Paleoproterozoic age. The results of field and laboratory studies suggest a potential role for microbial dissimilatory iron reduction (DIR) in producing this excursion. However, most experimental studies of Fe isotope fractionation during DIR have been conducted in simple geochemical systems, using pure Fe(III) oxide substrates that are not direct analogues to phases likely to have been present in Precambrian marine environments. In this study, Fe isotope fractionation was investigated during microbial reduction of an amorphous Fe(III) oxide-silica coprecipitate in anoxic, high-silica, low-sulphate artificial Archaean seawater at 30 °C to determine if such conditions alter the extent of reduction or isotopic fractionations relative to those observed in simple systems. The Fe(III)-Si coprecipitate was highly reducible (c. 80% reduction) in the presence of excess acetate. The coprecipitate did not undergo phase conversion (e.g. to green rust, magnetite or siderite) during reduction. Iron isotope fractionations suggest that rapid and near-complete isotope exchange took place among all Fe(II) and Fe(III) components, in contrast to previous work on goethite and hematite, where exchange was limited to the outer few atom layers of the substrate. Large quantities of low-?(56)Fe Fe(II) (aqueous and solid phase) were produced during reduction of the Fe(III)-Si coprecipitate. These findings shed new light on DIR as a mechanism for producing Fe isotope variations observed in Neoarchaean and Paleoproterozoic marine sedimentary rocks. PMID:21504536

  6. The poisoning action of iron on electrolytic silver catalysts used for partial oxidation of methanol

    SciTech Connect

    Jingfa, Deng; Xinhe, Bao; Shuzhong, Dong (Fudan Univ., Shanghai (China))

    1991-06-01

    Poisoning of silver catalysts used for partial oxidation of methanol has been investigated by combined surface techniques including XPS, SIMS, SEM, TDS, TPRS, work function measurement, and microreactor studies. Results show that the oxidation path is governed mainly by surface iron loading. Once Fe{sub 2}O{sub 3} is present at the catalyst surface, the catalytic performance degrades rapidly. The surface characteristics of iron depend strongly on the iron loading on the surface.

  7. Competition for oxygen by iron and 2,4,6-trichlorophenol oxidizing bacteria in boreal groundwater

    Microsoft Academic Search

    Jörg H. Langwaldt; Jaakko A. Puhakka

    2003-01-01

    Kinetics of simultaneous iron and 2,4,6-trichlorophenol (TCP) oxidation by groundwater enriched cultures were studied in order to reveal the competition for oxygen in aerobic in situ bioremediation of boreal groundwater. Chemical iron oxidation at near neutral pH in synthetic groundwater depended by the first order on the concentrations of ferrous iron and dissolved oxygen and by the second order on

  8. Control of structure and particle size of iron oxide on carrier oxide by the sol-gel method using organic polydentate ligands

    Microsoft Academic Search

    Fujio Mizukami; Mamoru Fujii; Shu-Ichi Niwa; Makoto Toba

    1994-01-01

    It was tried to control the structure and particle size of iron oxide supported on a carrier by regulating the hydrolytic polymerization of aquo iron complexes with organic polydentate ligands. The iron oxide\\/carrier composites were prepared by calcining carrier oxides impregnated with organic ligands and Fe(NO3)3·9H2O. When ligands were diacetone alcohol and ethanol, the structure of the iron oxide was

  9. Porous Iron Oxide Ribbons Grown on Graphene for High-Performance Lithium Storage

    PubMed Central

    Yang, Shubin; Sun, Yi; Chen, Long; Hernandez, Yenny; Feng, Xinliang; Müllen, Klaus

    2012-01-01

    A well-designed nanostructure of transition metal oxides has been regarded as a key to solve their problems of large volume changes during lithium insertion-desertion processes which are associated with pulverization of the electrodes and rapid capacity decay. Here we report an effective approach for the fabrication of porous iron oxide ribbons by controlling the nucleation and growth of iron precursor onto the graphene surface and followed by an annealing treatment. The resultant iron oxide ribbons possess large aspect ratio, porous structure, thin feature and enhanced open-edges. These characteristics are favorable for the fast diffusion of lithium ions and electrons, and meanwhile can effectively accommodate the volume change of iron oxides during the cycling processes. As a consequence, the graphene-induced porous iron oxide ribbons exhibit a high reversible capacity and excellent cycle stability for lithium storage. PMID:22645643

  10. Iron oxide/cassava starch-supported Ziegler-Natta catalysts for in situ ethylene polymerization.

    PubMed

    Chancharoenrith, Sittikorn; Kamonsatikul, Choavarit; Namkajorn, Montree; Kiatisevi, Supavadee; Somsook, Ekasith

    2015-03-01

    Iron oxide nanoparticles were used as supporters for in situ polymerization to produce polymer nanocomposites with well-dispersed fillers in polymer matrix. Iron oxide could be sustained as colloidal solutions by cassava starch to produce a good dispersion of iron oxide in the matrix. New supports based on iron oxide/cassava starch or cassava starch for Ziegler-Natta catalysts were utilized as heterogeneous supporters for partially hydrolyzed triethylaluminum. Then, TiCl4 was immobilized on the supports as catalysts for polymerization of ethylene. High-density polyethylene (HDPE) composites were obtained by the synthesized catalysts. A good dispersion of iron oxide/cassava starch particles was observed in the synthesized polymer matrix promoting to good mechanical properties of HDPE. PMID:25498641

  11. Clinical efficacy of two forms of intravenous iron--saccharated ferric oxide and cideferron--for iron deficiency anemia.

    PubMed

    Araki, T; Takaai, M; Miyazaki, A; Ohshima, S; Shibamiya, T; Nakamura, T; Yamamoto, K

    2012-12-01

    Over 90% of iron deficiency anemia cases are due to iron deficiency associated with depletion of stored iron or inadequate intake. Parenteral iron supplementation is an important part of the management of anemia, and some kinds of intravenous iron are used. However, few studies have evaluated the clinical efficacy of these drugs. The purpose of this study was to compare and assess the clinical efficacy of two types of intravenous iron injection, saccharated ferric oxide (SFO) and cideferron (CF). Medical records were obtained for 91 unrelated Japanese anemia patients treated with SFO (n = 37) or CF (n = 54) from May 2005 to May 2010 at Gunma University Hospital. Patients treated with blood transfusion, erythropoietin or oral iron were excluded. Hemoglobin (Hb) values measured on day 0, 7 and 14 were used to assess the efficacy of intravenous irons. A significant increase was observed in the mean Hb value by day 14 of administration in both the CF group and SFO group, and the mean Hb increase due to administration of CF for 7 days was comparable to that of SFO for 14 days. Age and sex did not affect improvement of Hb value. CF is fast acting and highly effective compared with SFO for the treatment of iron deficiency anemia. The use of CF may shorten a therapeutic period for iron deficiency anemia, and CF may be feasible for reducing the hospitalization period. PMID:23346769

  12. Oxygen diffusion and oxide phase formation in iron under swift heavy ion irradiation

    SciTech Connect

    Roller, Tobias; Bolse, Wolfgang [Institut fuer Strahlenphysik, Universitaet Stuttgart, Allmandring 3, 70569 Stuttgart (Germany)

    2007-02-01

    While irradiating thin iron films deposited on silicon wafers with swift heavy ions in the energy range of a few MeV/amu, we have observed that the iron surface oxidizes due to the residual oxygen in the irradiation chamber, induced by the energy deposition by the ion. We have investigated these processes in detail using Rutherford backscattering spectrometry and conversion electron Moessbauer spectroscopy. We found that two different types of oxidation processes were active, depending on the electronic energy loss of the incident ions. Irradiations above the track formation threshold S{sub ec}{sup Fe} of iron resulted in diffusion-controlled dissolution of oxygen in the iron bulk. Below S{sub ec}{sup Fe}, but above the track formation threshold of iron oxide, chemical reaction and homogeneous oxide phase formation took place in a surface layer, while almost no oxygen diffusion into the iron bulk could be observed anymore. These phenomena are discussed in terms of the oxygen mobility in the excited ion tracks in iron and iron oxide. The effective diffusion constant estimated for swift heavy ion induced oxygen diffusion in iron is larger by a factor of 100-1000 than the one reported for thermally activated oxygen diffusion in molten iron.

  13. Magnetic properties of iron-oxide passivated iron nanoparticles synthesized by a gas condensation technique

    NASA Astrophysics Data System (ADS)

    Baker, Colin C.

    Gas phase synthesis processes involve the generation of metal atoms through various means, and the homogeneous nucleation and subsequent condensation and coagulation of nanoparticles. Inert gas condensation (IGC) is a desirable process for the synthesis of metal nanoparticles because it is a relatively simple process capable of producing large quantities of nanoparticles, and since it utilizes vacuum deposition, it offers high purity particles and does not require hazardous chemicals. In this research, the results of the IGC synthesis of iron nanoparticles are presented. The iron nanoparticles are passivated in-situ by slowly introducing oxygen into the chamber to form ferrimagnetic Fe3O4 gamma-Fe2O3 shell/alpha-Fe ferromagnetic core nanoparticles. The magnetic properties of these particles are investigated as a function of passivation layer thickness and particle concentration. The oxide-passivated particles exhibit an exchange bias when cooled below a blocking temperature, which depends on the thickness of the oxide layer present. It was found that the exchange bias increased with oxide thickness. Similarly the blocking temperature also increased with oxide layer thickness. The blocking temperature in all cases, however, was found to be much lower than the Neel temperature for Fe-oxides. The nanoparticles also exhibit a spin glass transition below a characteristic freezing temperature, as evident by a sharp increase in the magnetic moment of the samples. Fe nanoparticle-polymer composite films were also obtained by spin casting mixtures of nanoparticles and polymethylmethacrylate (PMMA). The magnetic properties of these composites were compared to those of particles compressed into pellets. It was observed that when the particles were dispersed into the nanocomposite, the coercivity was increased, suggesting a heightened anisotropy barrier. Similarly, the magnetic relaxation results indicated that the particles dispersed in the PMMA exhibited significantly reduced relaxations through the entire temperature range, as compared to the non-dispersed compressed pellets. It is hoped that this research will result in a greater understanding of the interaction effects between magnetic species. The Fe-oxide/Fe shell/core interactions, may give researchers a better understanding of short-range exchange interactions, while Fe/PMMA composites may elucidate the nature and scope of longer-range dipolar interactions.

  14. Water oxidation catalysis by birnessite@iron oxide core-shell nanocomposites.

    PubMed

    Elmaci, Gökhan; Frey, Carolin E; Kurz, Philipp; Zümreo?lu-Karan, Birgül

    2015-03-16

    In this work, magnetic nanocomposite particles were prepared for water oxidation reactions. The studied catalysts consist of maghemite (?-Fe2O3), magnetite (Fe3O4), and manganese ferrite (MnFe2O4) nanoparticles as cores coated in situ with birnessite-type manganese oxide shells and were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermal, chemical, and surface analyses, and magnetic measurements. The particles were found to be of nearly spherical core-shell architectures with average diameter of 150 nm. Water oxidation catalysis was examined using Ce(4+) as the sacrificial oxidant. All core-shell particles were found to be active water oxidation catalysts. However, the activity was found to depend on a variety of factors like the type of iron oxide core, the structure and composition of the shell, the coating characteristics, and the surface properties. Catalysts containing magnetite and manganese ferrite as core materials displayed higher catalytic activities per manganese ion (2650 or 3150 mmolO2 molMn(-1) h(-1)) or per mass than nanoiron oxides (no activity) or birnessite alone (1850 mmolO2 molMn(-1) h(-1)). This indicates synergistic effects between the MnOx shell and the FeOx core of the composites and proves the potential of the presented core-shell approach for further catalyst optimization. Additionally, the FeOx cores of the particles allow magnetic recovery of the catalyst and might also be beneficial for applications in water-oxidizing anodes because the incorporation of iron might enhance the overall conductivity of the material. PMID:25710557

  15. Dietary Iron Concentration May Influence Aging Process by Altering Oxidative Stress in Tissues of Adult Rats

    PubMed Central

    Arruda, Lorena Fernandes; Arruda, Sandra Fernandes; Campos, Natália Aboudib; de Valencia, Fernando Fortes; Siqueira, Egle Machado de Almeida

    2013-01-01

    Iron is an essential element. However, in its free form, iron participates in redox-reactions, leading to the production of free radicals that increase oxidative stress and the risk of damaging processes. Living organisms have an efficient mechanism that regulates iron absorption according to their iron content to protect against oxidative damage. The effects of restricted and enriched-iron diets on oxidative stress and aging biomarkers were investigated. Adult Wistar rats were fed diets containing 10, 35 or 350 mg/kg iron (adult restricted-iron, adult control-iron and adult enriched-iron groups, respectively) for 78 days. Rats aged two months were included as a young control group. Young control group showed higher hemoglobin and hematocrit values, lower levels of iron and lower levels of MDA or carbonyl in the major studied tissues than the adult control group. Restricted-iron diet reduced iron concentrations in skeletal muscle and oxidative damage in the majority of tissues and also increased weight loss. Enriched-iron diet increased hematocrit values, serum iron, gamma-glutamyl transferase, iron concentrations and oxidative stress in the majority of tissues. As expected, young rats showed higher mRNA levels of heart and hepatic L-Ferritin (Ftl) and kidneys SMP30 as well as lower mRNA levels of hepatic Hamp and interleukin-1 beta (Il1b) and also lower levels of liver protein ferritin. Restricted-iron adult rats showed an increase in heart Ftl mRNA and the enriched-iron adult rats showed an increase in liver nuclear factor erythroid derived 2 like 2 (Nfe2l2) and Il1b mRNAs and in gut divalent metal transporter-1 mRNA (Slc11a2) relative to the control adult group. These results suggest that iron supplementation in adult rats may accelerate aging process by increasing oxidative stress while iron restriction may retards it. However, iron restriction may also impair other physiological processes that are not associated with aging. PMID:23593390

  16. Isothermal and thermal cycling oxidation of hot-dip aluminide coating on flake/spheroidal graphite cast iron

    E-print Network

    Volinsky, Alex A.

    cast iron Meng-Bin Lin a, , Chaur-Jeng Wang a , Alex A. Volinsky b a Department of Mechanical online 17 June 2011 Keywords: Hot-dip Al Flake graphite cast iron Spheroidal graphite cast iron High-temperature oxidation Two types of cast iron, flake graphite and spheroidal graphite cast iron, with ferrite matrix

  17. The presence of an iron oxide layer at the enamel\\/steel interface in one-coat porcelain enamelling

    Microsoft Academic Search

    D. Ritchie; H. A. Schaeffer; D. White

    1983-01-01

    The chemical measurement of the iron oxide present in the enamel was not in agreement with the iron oxide content calculated from diffusion profiles. This discrepancy could only be explained by assuming that a layer of iron oxide about 1 µm thick was present at the interface. An examination of the phenomena associated with this type of enamelling, the constant

  18. Vacancy Coalescence during Oxidation of Iron Nanoparticles Andreu Cabot, Victor F. Puntes, Elena Shevchenko, Yadong Yin,,| Lluis Balcells,

    E-print Network

    nanoparticles under a range of temperatures and times. The formation of a first thin oxide layer on the iron that the growth of 4 nm thick oxide layers in iron films can take 600 years at room Materials Science DivisionVacancy Coalescence during Oxidation of Iron Nanoparticles Andreu Cabot, Victor F. Puntes, Elena

  19. Pilot scale application of nanosized iron oxides as electron acceptors for bioremediation

    NASA Astrophysics Data System (ADS)

    Bosch, Julian; Fritzsche, Andreas; Frank-Fahle, Beatrice; Lüders, Tilmann; Höss, Sebastian; Eisenmann, Heinrich; Held, Thomas; Totsche, Kai U.; Meckenstock, Rainer U.

    2014-05-01

    Microbial reduction of ferric iron is a major biogeochemical process in groundwater aquifer ecosystems and often associated with the degradation of organic contaminants, as bacteria couple iron reduction to the oxidation reduced carbon like e.g. BTEX. Yet in general the low bioavailability of natural iron oxides limits microbial reduction rates. However, nanosized iron oxides have an unequally enhanced bioavailability and reactivity compared to their respective bulk, macro-sized, and more crystalline materials. At the same time, nanosized iron oxides can be produced in stable colloidal suspensions, permitting efficient injections into contaminated aquifers. We examined the reactivity of nanosized synthetic colloidal iron oxides in microbial iron reduction. Application of colloidal nanoparticles led to a strong and sustainable enhancement of microbial reaction rates in batch experiments and sediment columns. Toluene oxidation was increased five-fold as compared to bulk, non-colloidal ferrihydrite as electron acceptor. Furthermore, we developed a unique approach for custom-tailoring the subsurface mobility of these particles after being injected into a contaminant plume. In a field pilot application, we injected 18 m3 of an iron oxide nanoparticle solution into a BTEX contaminated aquifer with a maximum excess pressure as low as 0.2 bar. The applied suspension showed a superior subsurface mobility, creating a reactive zone of 4 m height (corresponding to the height of the confined aquifer) and 6 m in diameter. Subsequent monitoring of BTEX, microbial BTEX degradation metabolites, ferrous iron generation, stable isotopes fractionation, microbial populations, and methanogenesis demonstrated the strong impact of our approach. Mathematic processed X-ray diffractograms and FTIR spectra provided a semi-quantitatively estimate of the long-term fate of the iron oxide colloids in the aquifer. Potential environmental risks of the injection itself were monitored with ecotoxicological investigations. Our data suggest that the injection of ferric iron nanoparticles as electron acceptors into contaminated aquifers for the enhancement of microbial contaminant degradation might develop into a novel bioremediation strategy.

  20. Fabrication of iron oxide nanoparticles using laser ablation in liquids

    NASA Astrophysics Data System (ADS)

    Iwamoto, T.; Ishigaki, T.

    2013-06-01

    Nanoparticles of iron oxides were synthesized through the ablation of the bulk-targets of Fe, Fe3O4, and Fe2O3 in water by the irradiation of a Nd:YAG laser. Our samples prepared via the laser ablation method displayed small (ca. 1 nm in diameter) and large (over 5 nm in diameter) particles. The small particles were well-dispersed, whereas large particles were agglomerated. The FeO and Fe3O4 phases were formed in the synthesized powders irrespective of the kind of targets. The formation of the other phases, Fe and Fe2O3, changed depending on the the kind of targets used in the laser ablation. Poly(N-vinyl-2-pyrrolidone) (PVP) as a protective reagent was employed to disperse large particles in our samples, and accordingly, their dispersibility was improved as mole concentration of PVP increased.

  1. Colloidal stability of iron oxide nanoparticles with multivalent polymer surfactants.

    PubMed

    Choi, Young-Wook; Lee, Hoik; Song, Youngjun; Sohn, Daewon

    2015-04-01

    This paper introduces a new approach for preparing magnetic colloidal suspensions with electrostatic repulsion between particles and polyelectrolyte surfactants. The surface charge of the iron oxide particles was positive in acidic aqueous conditions; however the surface charge of the colloid was negative in basic aqueous conditions due to the amphoteric property of Fe2O3. The long-term colloidal stability and particle distribution of the multivalent charged polymers, Poly(4-vinylbenzenesulfonate sodium salt) (PSS), Poly(acrylic acid) (PAA), and Poly(allylamine hydrochloride) (PAH) were compared with the monovalent surfactant sodium dodecyl sulfate (SDS). Both mono- and multivalent surfactant molecules showed good colloidal stability for extended periods of time. However, the particle distribution was dependent on the hydrophobicity of the surfactants' functional groups. Polyelectrolytes with a negatively charged functional group showed good long-term stability of particles and a narrow particle distribution regardless of the acid dissociation constant (pKa) of the polymer. PMID:25526296

  2. Iron oxide nanoparticles in different modifications for antimicrobial phototherapy

    NASA Astrophysics Data System (ADS)

    Tuchina, Elena S.; Kozina, Kristina V.; Shelest, Nikita A.; Kochubey, Vyacheslav I.; Tuchin, Valery V.

    2014-03-01

    The main goal of this study was to investigate the sensitivity of microorganisms to combined action of blue light and iron oxide nanoparticles. Two strains of Staphylococcus aureus - methicillin-sensitive and meticillin-resistant were used. As a blue light source LED with spectral maximum at 405 nm was taken. The light exposure was ranged from 5 to 30 min. The Fe2O3 (diameter ˜27 nm), Fe3O4 nanoparticles (diameter ˜19 nm), and composite Fe2O3/TiO2 nanoparticles (diameter ˜100 nm) were synthesized. It was shown that irradiation by blue light caused from 20% to 88% decrease in the number of microorganisms treated with nanoparticles. Morphological changes in bacterial cells after phototreatment were analyzed using scanning electron microscope.

  3. The role of antioxidants and iron chelators in the treatment of oxidative stress in thalassemia.

    PubMed

    Fibach, Eitan; Rachmilewitz, Eliezer A

    2010-08-01

    On the basis of all the presented data, one can conclude that oxidative stress plays a major role in the pathophysiology of thalassemia and other congenital and acquired hemolytic anemias. Free extracellular (labile plasma iron, LPI) and intracellular (labile iron pool, LIP) iron species that have been identified in thalassemic blood cells are responsible for generation of oxidative stress by catalyzing formation of oxygen radicals over the antioxidant capacity of the cell. Consequently, there is a rationale for iron chelation to eliminate the free-iron species, which in this respect, act like antioxidants. In addition, antioxidants such as vitamin E and polyphenols are also capable of ameliorating increased oxidative stress parameters and, given together with iron chelators, may provide a substantial improvement in the pathophysiology of hemolytic anemias and particularly in thalassemia. PMID:20712766

  4. Strain induced anomalous red shift in mesoscopic iron oxide prepared by a novel technique

    Microsoft Academic Search

    T. N. Narayanan; D. Sakthi Kumar; Yasuhiko Yoshida; M. R. Anantharaman

    2008-01-01

    Nano magnetic oxides are promising candidates for high density magnetic storage and other applications. Nonspherical mesoscopic\\u000a iron oxide particles are also candidate materials for studying the shape, size and strain induced modifications of various\\u000a physical properties viz. optical, magnetic and structural. Spherical and nonspherical iron oxides having an aspect ratio,\\u000a ?2, are synthesized by employing starch and ethylene glycol and

  5. Cobalt, nickel/iron, and titanium oxide electrodes for water oxidation

    NASA Astrophysics Data System (ADS)

    Selloni, Annabella

    2014-03-01

    Water splitting on metal oxide surfaces has attracted enormous interest for more than forty years. While a great deal of work has focused on titanium dioxide (TiO2) , recently cobalt and mixed Ni-Fe oxides have also emerged as promising electrocatalysts for water oxidation due to their low cost and high activity. In this talk I shall discuss various aspects of water oxidation on cobalt (hydro-)oxides, pure and mixed nickel and iron (hydro-)oxides, and TiO2\\ surfaces. Using DFT +U calculations, I shall examine the composition and structure of cobalt and Ni-Fe oxides under electrochemical conditions, and present studies of the oxygen evolution reaction (OER) on the relevant stable compounds. I shall also present hybrid functional calculations of the first proton-coupled-electron transfer at the water/TiO2 interface in the presence of a photoexcited hole. Our results provide evidence that the proton and electron transfers are not concerted but rather represent two sequential processes. They also suggest that the OER is faster at higher pH, as indeed observed experimentally. This work was supported by DoE-BES, Division of Chemical Sciences, Geosciences and Biosciences under Award DE-FG02-12ER16286.

  6. Exchange bias in Core-Shell Iron-Iron Oxide Nanoclusters

    SciTech Connect

    Kaur, Maninder; McCloy, John S.; Qiang, You

    2013-04-03

    An exchange bias study has been performed on core-shell iron-iron oxide (Fe-Fe3O4) nanoclusters (NCs) of size 11 nm and 14 nm carrying a different core to shell ratio. NCs show complicated behaviors due to competition between interfacial exchange and Zeeman energy in the presence of magnetic field during cooling. These behaviors are accompanied by the evolution of size- dependent cluster structures in the ferromagnetic-core/ferri- or antiferro-magnetic-shell. Smaller clusters have larger coercive field, exchange bias field, and vertical magnetization shift due to the greater contribution from frozen spins of shell/interfaces. These smaller clusters thus also show more dramatic changes with the training effect. Both sizes of clusters display an additional anomaly of the upper part of the hysteresis loop at 10 K under low cooling field (0.1 kOe). This anomaly decreases with number of loop cycles with same field, and disappear with large cooling field (> 0.1 kOe). It may be caused by the competition between the magnetization reversal and the magnetostatic interactions.

  7. Lipoic acid and acetyl-carnitine reverse iron-induced oxidative stress in human fibroblasts.

    PubMed

    Lal, Ashutosh; Atamna, Wafa; Killilea, David W; Suh, Jung H; Ames, Bruce N

    2008-01-01

    Iron overload occurs frequently in thalassemia and other disorders that require regular blood transfusions. Excess iron is toxic owing to the generation of free radicals that lead to oxidation of biomolecules and tissue damage. In order to identify compounds that reduce oxidative injury from iron, we evaluated alpha-lipoic acid (LA), a multifunctional antioxidant, in iron-overloaded primary human fibroblasts (IMR-90). Oxidant stress was measured using dichlorodihydrofluorescein diacetate that is converted to the fluorescent dichlorofluorescein (DCF) upon oxidation. Exposure to ferric ammonium citrate (FAC) increased the iron-content of IMR-90 cells and caused a rise in oxidant appearance. The addition of LA improved the cellular redox status and attenuated the iron-mediated rise in oxidants in a dose-dependent manner. The R- and RS-enantiomers of LA demonstrated similar antioxidant activity. N-tert-butyl hydroxylamine (NtBHA) treated cells also exhibited a decrease in DCF fluorescence, but at a much higher concentration compared with LA. The combination acetyl-L-carnitine (ALCAR) and LA exhibited superior antioxidant effect at all dose levels. We conclude that LA is highly effective in reversing oxidative stress arising from iron overload and that its antioxidant efficacy is further enhanced in combination with ALCAR. PMID:18284845

  8. Density Functional Theory Investigation of Proton Diffusion in Tungsten Oxide And Its Hydrates

    NASA Astrophysics Data System (ADS)

    Lin, Hao

    Fast proton conduction mechanism is of key importance for achieving high performance in fuel cell membranes, batteries, supercapacitors, and electrochromic materials. Enhanced proton diffusion is often observed in hydrated materials where it is thought to occur via the famous Grotthuss mechanism through pathways formed by structural water. Using first-principles calculations, we demonstrate that proton diffusion in tungsten oxide dihydrate (WO3·2H 2O), a known good proton conductor, takes place within the layers of corner-sharing WO6 octahedra without direct involvement of structural water. The calculated proton migration barrier in WO3·2H 2O is in good agreement with the experimental value inferred from the temperature dependence of conductivity. The preferred proton diffusion path in WO3·2H2O is essentially the same as in gamma-WO 3. In contrast to the small intercalation voltages calculated for WO 3 and WO3·2H2O, we find that proton absorption in the monohydrate WO3·H2O is energetically highly favorable. However, strong proton-proton repulsion limits the equilibrium H content at zero voltage. We find a fast one-dimensional diffusion channel in WO3·H2O at dilute proton concentrations, but much higher barriers are expected at near-equilibrium concentrations due to strong repulsive interactions with other protons. Our results illustrate that low proton diffusion barriers and low insertion voltages both contribute to fast proton transport in bulk WO3·2H2O and gamma-WO 3.

  9. Biocompatible capped iron oxide nanoparticles for Vibrio cholerae detection.

    PubMed

    Sharma, Anshu; Baral, Dinesh; Rawat, Kamla; Solanki, Pratima R; Bohidar, H B

    2015-05-01

    We report the studies relating to fabrication of an efficient immunosensor for Vibrio cholerae detection. Magnetite (iron oxide (Fe(3)O(4))) nanoparticles (NPs) have been synthesized by the co-precipitation method and capped by citric acid (CA). These NPs were electrophoretically deposited onto indium-tin-oxide (ITO)-coated glass substrate and used for immobilization of monoclonal antibodies against Vibrio cholerae (Ab) and bovine serum albumin (BSA) for Vibrio cholerae detection using an electrochemical technique. The structural and morphological studies of Fe(3)O(4) and CA-Fe(3)O(4)/ITO were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and dynamic light scattering (DLS) techniques. The average crystalline size of Fe(3)O(4), CA-Fe(3)O(4) nanoparticles obtained were about 29 ± 1 nm and 37 ± 1 nm, respectively. The hydrodynamic radius of the nanoparticles was found to be 77.35 nm (Fe(3)O(4)) and 189.51 nm (CA-Fe(3)O(4)) by DLS measurement. The results of electrochemical response studies of the fabricated BSA/Ab/CA-Fe(2)O(3)/ITO immunosensor exhibits a good detection range of 12.5-500 ng mL(-1) with a low detection limit of 0.32 ng mL(-1), sensitivity 0.03 ?/ng ml(-1) cm(-2), and reproducibility more than 11 times. PMID:25850702

  10. The effect of Os addition on sputtered iron oxide films

    NASA Astrophysics Data System (ADS)

    Ishii, O.; Yoshimura, F.; Terada, A.; Sato, I.

    1987-04-01

    The features of grain growth in Os-added iron oxide films are investigated for the purpose of developing high signal-to-noise ratio (SNR) magnetic recording media. The average grain size of sputter-deposited ?-Fe2O3 films is markedly decreased by Os addition. The grains grow during the reduction process, from ?-Fe2O3 to Fe3O4, and maintain the same size in subsequent oxidation, from Fe3O4 to ?-Fe2O3. Moreover, the reduction temperature decreases by 100 °C above 0.88 at. % Os addition. As a result, the grain size of ?-Fe2O3 films decreases from 84 to 35 nm as the Os content increases from 0 to over 0.88 at. %. In addition to the refining effect, an accelerating effect on the reducing reaction brings about an increase in the saturation magnetization and in the squareness ratio of ?-Fe2O3 films. Consequently, an Os-added ?-Fe2O3 thin-film disk has higher output voltage and SNR than other disks.

  11. Rare earth element partitioning between hydrous ferric oxides and acid mine water during iron oxidation

    USGS Publications Warehouse

    Verplanck, P.L.; Nordstrom, D.K.; Taylor, H.E.; Kimball, B.A.

    2004-01-01

    Ferrous iron rapidly oxidizes to Fe (III) and precipitates as hydrous Fe (III) oxides in acid mine waters. This study examines the effect of Fe precipitation on the rare earth element (REE) geochemistry of acid mine waters to determine the pH range over which REEs behave conservatively and the range over which attenuation and fractionation occur. Two field studies were designed to investigate REE attenuation during Fe oxidation in acidic, alpine surface waters. To complement these field studies, a suite of six acid mine waters with a pH range from 1.6 to 6.1 were collected and allowed to oxidize in the laboratory at ambient conditions to determine the partitioning of REEs during Fe oxidation and precipitation. Results from field experiments document that even with substantial Fe oxidation, the REEs remain dissolved in acid, sulfate waters with pH below 5.1. Between pH 5.1 and 6.6 the REEs partitioned to the solid phases in the water column, and heavy REEs were preferentially removed compared to light REEs. Laboratory experiments corroborated field data with the most solid-phase partitioning occurring in the waters with the highest pH. ?? 2004 Elsevier Ltd. All rights reserved.

  12. The complex interplay of iron metabolism, reactive oxygen species, and reactive nitrogen species: insights into the potential of various iron therapies to induce oxidative and nitrosative stress.

    PubMed

    Koskenkorva-Frank, Taija S; Weiss, Günter; Koppenol, Willem H; Burckhardt, Susanna

    2013-12-01

    Production of minute concentrations of superoxide (O2(*-)) and nitrogen monoxide (nitric oxide, NO*) plays important roles in several aspects of cellular signaling and metabolic regulation. However, in an inflammatory environment, the concentrations of these radicals can drastically increase and the antioxidant defenses may become overwhelmed. Thus, biological damage may occur owing to redox imbalance-a condition called oxidative and/or nitrosative stress. A complex interplay exists between iron metabolism, O2(*-), hydrogen peroxide (H2O2), and NO*. Iron is involved in both the formation and the scavenging of these species. Iron deficiency (anemia) (ID(A)) is associated with oxidative stress, but its role in the induction of nitrosative stress is largely unclear. Moreover, oral as well as intravenous (iv) iron preparations used for the treatment of ID(A) may also induce oxidative and/or nitrosative stress. Oral administration of ferrous salts may lead to high transferrin saturation levels and, thus, formation of non-transferrin-bound iron, a potentially toxic form of iron with a propensity to induce oxidative stress. One of the factors that determine the likelihood of oxidative and nitrosative stress induced upon administration of an iv iron complex is the amount of labile (or weakly-bound) iron present in the complex. Stable dextran-based iron complexes used for iv therapy, although they contain only negligible amounts of labile iron, can induce oxidative and/or nitrosative stress through so far unknown mechanisms. In this review, after summarizing the main features of iron metabolism and its complex interplay with O2(*-), H2O2, NO*, and other more reactive compounds derived from these species, the potential of various iron therapies to induce oxidative and nitrosative stress is discussed and possible underlying mechanisms are proposed. Understanding the mechanisms, by which various iron formulations may induce oxidative and nitrosative stress, will help us develop better tolerated and more efficient therapies for various dysfunctions of iron metabolism. PMID:24036104

  13. Iron supplementation at high altitudes induces inflammation and oxidative injury to lung tissues in rats

    SciTech Connect

    Salama, Samir A., E-mail: salama.3@buckeyemail.osu.edu [High Altitude Research Center, Taif University, Al-Haweiah, Taif 21974 (Saudi Arabia); Department of Biochemistry, Faculty of Pharmacy, Al-Azhar University, Cairo 11751 (Egypt); Department of Pharmacology and GTMR Unit, College of Clinical Pharmacy, Taif University, Al-Haweiah, Taif 21974 (Saudi Arabia); Omar, Hany A. [Department of Pharmacology, Faculty of Pharmacy, Beni-Suef University, Beni-Suef 62514 (Egypt); Maghrabi, Ibrahim A. [Department of Clinical Pharmacy, College of Clinical Pharmacy, Taif University, Al-Haweiah, Taif 21974 (Saudi Arabia); AlSaeed, Mohammed S. [Department of Surgery, College of Medicine, Taif University, Al-Haweiah, Taif 21974 (Saudi Arabia); EL-Tarras, Adel E. [High Altitude Research Center, Taif University, Al-Haweiah, Taif 21974 (Saudi Arabia)

    2014-01-01

    Exposure to high altitudes is associated with hypoxia and increased vulnerability to oxidative stress. Polycythemia (increased number of circulating erythrocytes) develops to compensate the high altitude associated hypoxia. Iron supplementation is, thus, recommended to meet the demand for the physiological polycythemia. Iron is a major player in redox reactions and may exacerbate the high altitudes-associated oxidative stress. The aim of this study was to explore the potential iron-induced oxidative lung tissue injury in rats at high altitudes (6000 ft above the sea level). Iron supplementation (2 mg elemental iron/kg, once daily for 15 days) induced histopathological changes to lung tissues that include severe congestion, dilatation of the blood vessels, emphysema in the air alveoli, and peribronchial inflammatory cell infiltration. The levels of pro-inflammatory cytokines (IL-1?, IL-6, and TNF-?), lipid peroxidation product and protein carbonyl content in lung tissues were significantly elevated. Moreover, the levels of reduced glutathione and total antioxidant capacity were significantly reduced. Co-administration of trolox, a water soluble vitamin E analog (25 mg/kg, once daily for the last 7 days of iron supplementation), alleviated the lung histological impairments, significantly decreased the pro-inflammatory cytokines, and restored the oxidative stress markers. Together, our findings indicate that iron supplementation at high altitudes induces lung tissue injury in rats. This injury could be mediated through excessive production of reactive oxygen species and induction of inflammatory responses. The study highlights the tissue injury induced by iron supplementation at high altitudes and suggests the co-administration of antioxidants such as trolox as protective measures. - Highlights: • Iron supplementation at high altitudes induced lung histological changes in rats. • Iron induced oxidative stress in lung tissues of rats at high altitudes. • Iron increased the levels of IL-1?, IL-6 and TNF-? in lung tissues at high altitudes. • Trolox alleviated the iron-induced histological and biochemical changes to the lungs.

  14. An evaluation of iron oxide nanofluids in enhanced oil recovery application

    NASA Astrophysics Data System (ADS)

    Guan, Beh Hoe; Khalid, M. Hanafi M.; Matraji, Herman Hari; Chuan, Lee Kean; Soleimani, Hassan

    2014-10-01

    This paper evaluates the oil recover efficiency of Iron Oxide (Fe2O3) nanofluids in EOR. Iron Oxide nanoparticles were synthesized at two different temperatures via sol-gel method. TEM results show that the Fe2O3 prepared at 300°C and 600°C were ranged from 10-25nm and 30-90nm, respectively. Results showed that the nanofluid composed of Iron Oxide nanoparticles prepared at 300°C gives 10% increase in the oil recovery in comparison with Fe2O3 nanoparticles calcined at 600°C.

  15. Biosynthesis of stable iron oxide nanoparticles in aqueous extracts of Hordeum vulgare and Rumex acetosa plants.

    PubMed

    Makarov, Valentin V; Makarova, Svetlana S; Love, Andrew J; Sinitsyna, Olga V; Dudnik, Anna O; Yaminsky, Igor V; Taliansky, Michael E; Kalinina, Natalia O

    2014-05-27

    We report the synthesis and characterization of amorphous iron oxide nanoparticles from iron salts in aqueous extracts of monocotyledonous (Hordeum vulgare) and dicotyledonous (Rumex acetosa) plants. The nanoparticles were characterized by TEM, absorbance spectroscopy, SAED, EELS, XPS, and DLS methods and were shown to contain mainly iron oxide and iron oxohydroxide. H. vulgare extracts produced amorphous iron oxide nanoparticles with diameters of up to 30 nm. These iron nanoparticles are intrinsically unstable and prone to aggregation; however, we rendered them stable in the long term by addition of 40 mM citrate buffer pH 3.0. In contrast, amorphous iron oxide nanoparticles (diameters of 10-40 nm) produced using R. acetosa extracts are highly stable. The total protein content and antioxidant capacity are similar for both extracts, but pH values differ (H. vulgare pH 5.8 vs R. acetosa pH 3.7). We suggest that the presence of organic acids (such oxalic or citric acids) plays an important role in the stabilization of iron nanoparticles, and that plants containing such constituents may be more efficacious for the green synthesis of iron nanoparticles. PMID:24784347

  16. Secoisolariciresinol diglucoside abrogates oxidative stress-induced damage in cardiac iron overload condition.

    PubMed

    Puukila, Stephanie; Bryan, Sean; Laakso, Anna; Abdel-Malak, Jessica; Gurney, Carli; Agostino, Adrian; Belló-Klein, Adriane; Prasad, Kailash; Khaper, Neelam

    2015-01-01

    Cardiac iron overload is directly associated with cardiac dysfunction and can ultimately lead to heart failure. This study examined the effect of secoisolariciresinol diglucoside (SDG), a component of flaxseed, on iron overload induced cardiac damage by evaluating oxidative stress, inflammation and apoptosis in H9c2 cardiomyocytes. Cells were incubated with 50 ?5M iron for 24 hours and/or a 24 hour pre-treatment of 500 ? M SDG. Cardiac iron overload resulted in increased oxidative stress and gene expression of the inflammatory mediators tumor necrosis factor-?, interleukin-10 and interferon ?, as well as matrix metalloproteinases-2 and -9. Increased apoptosis was evident by increased active caspase 3/7 activity and increased protein expression of Forkhead box O3a, caspase 3 and Bax. Cardiac iron overload also resulted in increased protein expression of p70S6 Kinase 1 and decreased expression of AMP-activated protein kinase. Pre-treatment with SDG abrogated the iron-induced increases in oxidative stress, inflammation and apoptosis, as well as the increased p70S6 Kinase 1 and decreased AMP-activated protein kinase expression. The decrease in superoxide dismutase activity by iron treatment was prevented by pre-treatment with SDG in the presence of iron. Based on these findings we conclude that SDG was cytoprotective in an in vitro model of iron overload induced redox-inflammatory damage, suggesting a novel potential role for SDG in cardiac iron overload. PMID:25822525

  17. Secoisolariciresinol Diglucoside Abrogates Oxidative Stress-Induced Damage in Cardiac Iron Overload Condition

    PubMed Central

    Puukila, Stephanie; Bryan, Sean; Laakso, Anna; Abdel-Malak, Jessica; Gurney, Carli; Agostino, Adrian; Belló-Klein, Adriane; Prasad, Kailash; Khaper, Neelam

    2015-01-01

    Cardiac iron overload is directly associated with cardiac dysfunction and can ultimately lead to heart failure. This study examined the effect of secoisolariciresinol diglucoside (SDG), a component of flaxseed, on iron overload induced cardiac damage by evaluating oxidative stress, inflammation and apoptosis in H9c2 cardiomyocytes. Cells were incubated with 50 ?5M iron for 24 hours and/or a 24 hour pre-treatment of 500 ? M SDG. Cardiac iron overload resulted in increased oxidative stress and gene expression of the inflammatory mediators tumor necrosis factor-?, interleukin-10 and interferon ?, as well as matrix metalloproteinases-2 and -9. Increased apoptosis was evident by increased active caspase 3/7 activity and increased protein expression of Forkhead box O3a, caspase 3 and Bax. Cardiac iron overload also resulted in increased protein expression of p70S6 Kinase 1 and decreased expression of AMP-activated protein kinase. Pre-treatment with SDG abrogated the iron-induced increases in oxidative stress, inflammation and apoptosis, as well as the increased p70S6 Kinase 1 and decreased AMP-activated protein kinase expression. The decrease in superoxide dismutase activity by iron treatment was prevented by pre-treatment with SDG in the presence of iron. Based on these findings we conclude that SDG was cytoprotective in an in vitro model of iron overload induced redox-inflammatory damage, suggesting a novel potential role for SDG in cardiac iron overload. PMID:25822525

  18. Iron oxide thin film growth on Al 2O 3/NiAl(1 1 0)

    NASA Astrophysics Data System (ADS)

    Handke, Bartosz; Simonsen, Jens Bæk; Bech, Martin; Li, Zheshen; Møller, Preben Juul

    2006-12-01

    The electronic structure and the growth morphology of iron oxide thin films were studied by means of Synchrotron Radiation Photoelectron Spectroscopy (SRPES) and Low Energy Electron Diffraction (LEED). A thin well-ordered alumina film on a NiAl(1 1 0) single crystal surface as a template for iron oxide growth was employed. Two different methods of iron oxide film preparation were applied. In the first attempt, iron deposited at room temperature was subsequently annealed in oxygen. Even though a whole layer of iron was oxidized, an expected long-range order was not achieved. The second attempt was to perform reactive deposition. For this reason iron was evaporated in oxygen ambient at elevated substrate temperature. This method turned out to be more efficient. Diffused but clear LEED patterns of six-fold symmetry indicating hexagonal surface atoms arrangement were observed. From the PES measurements, binding energies for Fe2p for grown iron oxide film were established as well as energy distribution curves for the valence band. Growth curves based on Fe3p core-level peak intensities for iron and iron oxide were plotted identifying type of film growth for both deposition methods. Based upon these results we have found evidence for interdiffusion in the interface between alumina and iron oxide at the early stages of growth. Further deposition led to formation of Fe 3O 4(1 1 1) (magnetite) overlayer. Moreover, the quality of the film could also be improved by long-time annealing at temperatures not exceeding 575 K. Higher annealing temperature caused disappearance of LEED pattern indicating loss of long-range ordering.

  19. Early diagenetic quartz formation at a deep iron oxidation front in the Eastern Equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Meister, Patrick; Chapligin, Bernhard; Picard, Aude; Meyer, Hanno; Fischer, Cornelius; Rettenwander, Daniel; Amthauer, Georg; Vogt, Christoph; Aiello, Ivano

    2015-04-01

    The mechanisms of early diagenetic quartz formation under low-temperature conditions are still poorly understood. We studied lithified cherts consisting of microcrystalline quartz recovered from ODP Site 1226 in the Eastern Equatorial Pacific. The cherts occur near the base of a 420-m-thick Miocene-Holocene sequence within unlithified nannofossil and diatom ooze. Palaeo-temperatures reconstructed from ?18O values in the cherts are near to present porewater temperatures and a sharp depletion in dissolved silica occurs around 385 mbsf indicating that silica precipitation is still ongoing. Also a deep iron oxidation front occurs at the same depth, which is caused by upward diffusing nitrate from an oxic seawater aquifer in the underlying basaltic crust. Sequential iron extraction and analysis of the X-ray absorption near-edge structure (XANES) revealed that iron in the cherts predominantly occurs as illite and amorphous iron oxide, whereas iron in the nannofossil and diatom ooze occurs mainly as smectites. Mössbauer spectroscopy confirmed that the illite iron in the cherts is largely oxidized. A possible mechanisms that may be operative is quartz precipitation initiated by adsorption of silica to freshly precipitated iron oxides. The decrease in porewater silica concentration below opal-A and opal-CT saturation then allows for the precipitation of the thermodynamically more stable phase: quartz. We suggest that the formation of early-diagenetic chert at iron oxidation fronts is an important process in suboxic zones of silica-rich sediments. The largest iron oxidation front ever occurred during the great oxidation event ca. 2.5 Ga ago, when large amounts of iron and chert beds were deposited.

  20. Ligand-Enhanced Abiotic Iron Oxidation and the Effects of Chemical versus Biological Iron Cycling in Anoxic Environments

    PubMed Central

    2013-01-01

    This study introduces a newly isolated, genetically tractable bacterium (Pseudogulbenkiania sp. strain MAI-1) and explores the extent to which its nitrate-dependent iron-oxidation activity is directly biologically catalyzed. Specifically, we focused on the role of iron chelating ligands in promoting chemical oxidation of Fe(II) by nitrite under anoxic conditions. Strong organic ligands such as nitrilotriacetate and citrate can substantially enhance chemical oxidation of Fe(II) by nitrite at circumneutral pH. We show that strain MAI-1 exhibits unambiguous biological Fe(II) oxidation despite a significant contribution (?30–35%) from ligand-enhanced chemical oxidation. Our work with the model denitrifying strain Paracoccus denitrificans further shows that ligand-enhanced chemical oxidation of Fe(II) by microbially produced nitrite can be an important general side effect of biological denitrification. Our assessment of reaction rates derived from literature reports of anaerobic Fe(II) oxidation, both chemical and biological, highlights the potential competition and likely co-occurrence of chemical Fe(II) oxidation (mediated by microbial production of nitrite) and truly biological Fe(II) oxidation. PMID:23402562

  1. Electrophoretic lithium iron phosphate/reduced graphene oxide composite for lithium ion battery cathode application

    NASA Astrophysics Data System (ADS)

    Huang, Yuan; Liu, Hao; Lu, Yi-Chun; Hou, Yanglong; Li, Quan

    2015-06-01

    A binder/additive free composite electrode of lithium iron phosphate/reduced graphene oxide with ultrahigh lithium iron phosphate mass ratio (91.5 wt% of lithium iron phosphate) is demonstrated using electrophoresis. The quasi-spherical lithium iron phosphate particles are uniformly connected to and/or wrapped by three-dimensional networks of reduced graphene oxide nanosheets, with intimate contact formed between the two. Enhanced capacity is achieved in the electrophoretic composite cathode, when compared to either the conventional one or composite cathode formed by mechanically mixing lithium iron phosphate and reduced graphene oxide. The present methodology is simple and does not disturb the active material growth process. It can be generally applied to a variety of active material systems for both cathode and anode applications in lithium ion batteries.

  2. Long-range electron transfer triggers mechanistic differences between iron(IV)-oxo and iron(IV)-imido oxidants.

    PubMed

    Kumar, Suresh; Faponle, Abayomi S; Barman, Prasenjit; Vardhaman, Anil Kumar; Sastri, Chivukula V; Kumar, Devesh; de Visser, Sam P

    2014-12-10

    Nature often utilizes molecular oxygen for oxidation reactions through monoxygenases and dioxygenases. In many of these systems, a high-valent iron(IV)-oxo active species is found. In recent years, evidence has accumulated of possible iron(IV)-imido and iron(V)-nitrido intermediates in enzymatic catalysis, although little is known about their activity. In this work, we report a detailed combined kinetics and computational study on the difference in reactivity and chemical properties of nonheme iron(IV)-oxo compared with iron(IV)-tosylimido. We show here that iron(IV)-tosylimido complex is much more reactive with sulfides than the corresponding iron(IV)-oxo complex; however, the reverse trend is obtained for hydrogen atom abstraction reactions. The latter proceed with a relatively small kinetic isotope effect of kH/kD = 7 for the iron(IV)-tosylimido complex. Moreover, a Hammett analysis of hydrogen atom abstraction from para-X-benzyl alcohol reveals a slope of close to zero for the iron(IV)-oxo, whereas a strong negative slope is found for the iron(IV)-tosylimido complex. These studies implicate dramatic changes in the reaction mechanisms and suggest a considerable charge transfer in the transition states. Density functional theory calculations were performed to support the experiments and confirm an initial long-range electron transfer for the iron(IV)-tosylimido complex with substrates, due to a substantially larger electron affinity compared with the iron(IV)-oxo species. As a consequence, it also reacts more efficiently in electrophilic addition reactions such as those with sulfides. By contrast, the long-range electron transfer for the iron(IV)-tosylimido complex results in a rate constant that is dependent on the ?*xz ? ?*z(2) excitation energy, which raises the hydrogen atom abstraction barrier above that found for the iron(IV)-oxo. On the other hand, sulfimidation has much earlier electron transfer steps with respect to sulfoxidation. All data has been analyzed and rationalized with valence bond models and thermochemical cycles. Our studies highlight the catalytic potential of iron(IV)-tosylimido complexes in chemistry and biology. PMID:25392052

  3. Leaching of pyrite by acidophilic heterotrophic iron-oxidizing bacteria in pure and mixed cultures

    SciTech Connect

    Bacelar-Nicolau, P.; Johnson, D.B. [Univ. of Wales, Bangor (United Kingdom). School of Biological Sciences

    1999-02-01

    Seven strains of heterotrophic iron-oxidizing acidophilic bacteria were examined to determine their abilities to promote oxidative dissolution of pyrite (FeS{sub 2}) when they were grown in pure cultures and in mixed cultures with sulfur-oxidizing Thiobacillus spp. Only one of the isolates (strain T-24) oxidized pyrite when it was grown in pyrite-basal salts medium. However, when pyrite-containing cultures were supplemented with 0.02% (wt/vol) yeast extract, most of the isolates oxidized pyrite, and one (strain T-24) promoted rates of mineral dissolution similar to the rates observed with the iron-oxidizing autotroph Thiobacillus ferroxidans. Pyrite oxidation by another isolate (strain T-21) occurred in cultures containing between 0.005 and 0.05% (wt/vol) yeast extract but was completely inhibited in cultures containing 0.5% yeast extract. Ferrous iron was also needed for mineral dissolution by the iron-oxidizing heterotrophs, indicating that these organisms oxidize pyrite via the indirect mechanism. Mixed cultures of three isolates (strains T-21, T-232, and T-24) and the sulfur-oxidizing autotroph Thiobacillus thiooxidans promoted pyrite dissolution; since neither strains T-21 and T-23 nor T. thiooxidans could oxidize this mineral in yeast extract-free media, this was a novel example of bacterial synergism. Mixed cultures of strains T-21 and T-23 and the sulfur-oxidizing mixotroph Thiobacillus acidophilus also oxidized pyrite but to a lesser extent than did mixed cultures containing T. thiooxidans. Pyrite leaching by strain T -23 grown in an organic compound-rich medium and incubated either shaken or unshaken was also assessed. The potential environmental significance of iron-oxidizing heterotrophs in accelerating pyrite oxidation is discussed.

  4. Leaching of Pyrite by Acidophilic Heterotrophic Iron-Oxidizing Bacteria in Pure and Mixed Cultures

    PubMed Central

    Bacelar-Nicolau, Paula; Johnson, D. Barrie

    1999-01-01

    Seven strains of heterotrophic iron-oxidizing acidophilic bacteria were examined to determine their abilities to promote oxidative dissolution of pyrite (FeS2) when they were grown in pure cultures and in mixed cultures with sulfur-oxidizing Thiobacillus spp. Only one of the isolates (strain T-24) oxidized pyrite when it was grown in pyrite-basal salts medium. However, when pyrite-containing cultures were supplemented with 0.02% (wt/vol) yeast extract, most of the isolates oxidized pyrite, and one (strain T-24) promoted rates of mineral dissolution similar to the rates observed with the iron-oxidizing autotroph Thiobacillus ferrooxidans. Pyrite oxidation by another isolate (strain T-21) occurred in cultures containing between 0.005 and 0.05% (wt/vol) yeast extract but was completely inhibited in cultures containing 0.5% yeast extract. Ferrous iron was also needed for mineral dissolution by the iron-oxidizing heterotrophs, indicating that these organisms oxidize pyrite via the “indirect” mechanism. Mixed cultures of three isolates (strains T-21, T-23, and T-24) and the sulfur-oxidizing autotroph Thiobacillus thiooxidans promoted pyrite dissolution; since neither strains T-21 and T-23 nor T. thiooxidans could oxidize this mineral in yeast extract-free media, this was a novel example of bacterial synergism. Mixed cultures of strains T-21 and T-23 and the sulfur-oxidizing mixotroph Thiobacillus acidophilus also oxidized pyrite but to a lesser extent than did mixed cultures containing T. thiooxidans. Pyrite leaching by strain T-23 grown in an organic compound-rich medium and incubated either shaken or unshaken was also assessed. The potential environmental significance of iron-oxidizing heterotrophs in accelerating pyrite oxidation is discussed. PMID:9925586

  5. Preparation and characterization of BaSnO 3 powders by hydrothermal synthesis from tin oxide hydrate gel

    Microsoft Academic Search

    Wensheng Lu; Helmut Schmidt

    2007-01-01

    BaSnO3 powders have been prepared from the tin oxide hydrate gel and the Ba(OH)2 solution via hydrothermal synthesis route. The influence of the process parameters on the characteristics of BaSnO3 has been studied. A powder with the single-phase of BaSnO3 can be obtained only when the concentration of Ba(OH)2 solution is no less than 0.2 M and the ratio of Ba:Sn

  6. Mutations of ferric uptake regulator ( fur ) impair iron homeostasis, growth, oxidative stress survival, and virulence of Xanthomonas campestris pv. campestris

    Microsoft Academic Search

    Thichakorn Jittawuttipoka; Ratiboot Sallabhan; Paiboon Vattanaviboon; Mayuree Fuangthong; Skorn Mongkolsuk

    2010-01-01

    Iron is essential in numerous cellular functions. Intracellular iron homeostasis must be maintained for cell survival and\\u000a protection against iron’s toxic effects. Here, we characterize the roles of Xanthomonas campestris pv. campestris (Xcc) fur, which encodes an iron sensor and a transcriptional regulator that acts in iron homeostasis, oxidative stress, and virulence.\\u000a Herein, we isolated spontaneous Xcc fur mutants that

  7. An experimental study for enhancing the catalytic effects of various copper forms on the oxidation of ferrous iron.

    PubMed

    Babak, Manizhe Moradi Shahre; Goharrizi, Ataallah Soltani; Mirzaei, Mohammad; Roayaei, Emad

    2013-01-01

    In this research the catalytic effect of copper compounds (ionic, oxide and oxide nanopowder) on the oxidation of ferrous iron by aeration was studied experimentally. When copper exists in solution, the oxidation rate of iron(II) will increase. The experimental results showed that the oxidation rate increases with an increasing copper concentration. From the experimental data it can be determined that the copper oxide nanopowder is the most effective for the oxidation reaction among the used copper forms. Aeration is the most economical oxidation method when water exhibits a high ferrous iron concentration. PMID:23530309

  8. Ozone decomposition and benzene oxidation catalysts based on iron and manganese oxides as industrial wastes from water decontamination by ozone treatment

    Microsoft Academic Search

    L. A. Zaloznaya; S. N. Tkachenko; G. V. Egorova; I. S. Tkachenko; A. V. Sobolev; E. Z. Golosman; V. A. Troshina; V. V. Lunin

    2009-01-01

    Effective ozone decomposition catalysts were created on the basis of iron oxides as side products from natural water treated\\u000a with ozone at water treatment plants. Iron oxide catalysts doped with manganese oxide are by 40% more active in benzene oxidation.\\u000a These iron-manganese catalysts can be recommended for industrial manufacture by the designed technologies and application\\u000a in ozone decomposition and benzene

  9. The influence of four iron oxide forms on the growth of grain sorghum seedlings

    E-print Network

    Rich, Pat Albert

    1959-01-01

    ?a ~ taken frow the sero to six-inch depth ia a field sear george West, Texas. The soil characteristics nest nearly watched those described for 6oliad sandy lean. Thc relatively high iiwe content pre- suued iron deficiency, and coarse texture were... deficiency of iron linitiag aornal chlorophyll production. The chewicals aced for the soil treataents were four differeat iron oxides, sanely, henatite, naguetite, synthetic nagnetlte, and synthetic naghewite. The sources of the hesatite aad wagaetite...

  10. An Archaeal Iron-Oxidizing Extreme Acidophile Important in Acid Mine Drainage

    NSDL National Science Digital Library

    Banfield, Jilian F.

    This scientific paper describes the isolation, identification and physiology a new species of iron-oxidizing Archaea capable of growth at pH 0. This species was isolated from an acid mine drainage site at Iron Mountain, California. Additionally, the authors also discuss the ecological niche occupied by this species and other closely related Thermoplasmales, their contribution to acid mine drainage and their impact on iron and sulfur cycles.

  11. Role of iron in oxidative stress in skeletal muscle atrophied by immobilization

    Microsoft Academic Search

    Hisao Kondo; Midori Miura; Junko Kodama; Syed M. Ahmed; Yoshinori Itokawa

    1992-01-01

    To clarify the role of iron in oxidative stress in skeletal muscle atrophied by immobilization, we investigated the effect of deferoxamine — an iron-chelating agent. Deferoxamine, iron-saturated deferoxamine and double-distilled water (control) were administered subcutaneously from the 4th day after immobilization via osmotic pumps to male Wistar rats (14 weeks old), one ankle joint of which was immobilized in the

  12. Evidence suggesting that iron and calcium are interrelated in oxidant-induced DNA damage

    Microsoft Academic Search

    Muralikrishna S Golconda; Norishi Ueda; Sudhir V Shah

    1993-01-01

    Evidence suggesting that iron and calcium are interrelated in oxidant-induced DNA damage. The effect of iron chelators and agents that buffer cytosolic-free calcium ([Ca2+]i) on hydrogen peroxide-induced DNA strand breaks in LLC-PK1 cells has not been previously examined. In addition, the interrelationship between iron and calcium in the pathogenesis of DNA damage has not been studied in any model of

  13. Luminescence and ESR studies of relationships between O(-)-centres and structural iron in natural and synthetically hydrated kaolinites

    NASA Technical Reports Server (NTRS)

    Coyne, L. M.; Costanzo, P. M.; Theng, B. K.

    1989-01-01

    Luminescence, induced by dehydration and by wetting with hydrazine and unsymmetrically substituted hydrazine, and related ESR spectra have been observed from several kaolinites, synthetically hydrated kaolinites, and metahalloysites. The amine-wetting luminescence results suggest that intercalation, not a chemiluminescence reaction, is the luminescence trigger. Correlation between hydration-induced luminescence and g = 2 ESR signals associated with O(-)-centres in several natural halloysites, and concurrent diminution of the intensity of both these signal types as a function of aging in two 8.4 angstroms synthetically hydrated, kaolinites, confirm a previously-reported relationship between the luminescence induced by dehydration and in the presence of O(-)-centres (holes, i.e., electron vacancies) in the tetrahedral sheet. Furthermore, the ESR spectra of the 8.4 angstroms hydrate showed a concurrent change in the line shape of the g = 4 signal from a shape usually associated with structural Fe in an ordered kaolinite, to a simpler one typically observed in more disordered kaolinite, halloysite, and montmorillonite. Either structural Fe centres and the O(-)-centres interact, or both are subject to factors previously associated with degree of order. The results question the long-term stability of the 8.4 angstroms hydrate, although XRD does not indicate interlayer collapse over this period. Complex inter-relationships are shown between intercalation, stored energy, structural Fe, and the degree of hydration which may be reflected in catalytic as well as spectroscopic properties of the clays.

  14. Methyl red removal from water by iron based metal-organic frameworks loaded onto iron oxide nanoparticle adsorbent

    NASA Astrophysics Data System (ADS)

    Dadfarnia, S.; Haji Shabani, A. M.; Moradi, S. E.; Emami, S.

    2015-03-01

    The objective followed by this research is the synthesis of iron based metal organic framework loaded on iron oxide nanoparticles (Fe3O4@MIL-100(Fe)) and the study of its capability for the removal of methyl red. Effective parameters in the selection of a new adsorbent, i.e. adsorption capacity, thermodynamics, and kinetics were investigated. All the studies were carried out in batch experiments. Removal of methyl red from aqueous solutions varied with the amount of adsorbent, methyl red contact time, initial concentration of dye, adsorbent dosage, and solution pH. The capability of the synthesized adsorbent in the removal of methyl red was compared with the metal organic framework (MIL-100(Fe)) and iron oxide nanoparticles. The results show that Fe3O4@MIL-100(Fe) nanocomposite exhibits an enhanced adsorption capacity.

  15. Vapour phase approach for iron oxide nanoparticle synthesis from solid precursors

    NASA Astrophysics Data System (ADS)

    Singh, Mandeep; Ulbrich, Pavel; Prokopec, Vadym; Svoboda, Pavel; Šantavá, Eva; Št?pánek, František

    2013-04-01

    A new non-solution mediated approach to the synthesis of iron oxide nanoparticles directly from solid FeCl2 salt precursors has been developed. The method is rapid, simple and scalable. The structural properties and the phase of the resulting iron oxide particles has been determined by a range of methods including XRD, FT-IR and Mössbauer spectroscopy, and the phase is shown to be maghemite (?-Fe2O3). The magnetic properties of the iron oxide particles have been measured using SQUID, confirming superparamagnetic behaviour of the powder and a saturation magnetization of 53.0 emu g-1 at 300 K. Aqueous dispersions at increasing concentrations were prepared and their heating rate under a 400 kHz alternating magnetic field measured. The specific absorption rate (SAR) of the iron oxide was found to be 84.8 W g-1, which makes the material suitable for the formulation of ferrofluids or ferrogels with RF heating properties.

  16. Synthesis and development of hydrophilic iron oxide nanoparticles for biomedical applications

    E-print Network

    Wei, He, Ph.D. Massachusetts Institute of Technology

    2014-01-01

    Uniformly sized superparamagnetic iron oxide nanoparticles (SPIONs) with inorganic diameters of 3-35 nm were synthesized. New surface ligand coatings were designed and synthesized, and the resulting hydrophilic SPIONs in ...

  17. Oxidation of phosphine by iron(III) chloride complexes supported on activated charcoal

    SciTech Connect

    Rakitskaya, T.L.; Kostyukova, I.S.; Red'ko, T.D.

    1988-06-01

    It has been discovered that iron(III) chloride complexes supported on activated charcoal oxidize phosphine under normal conditions. The process accelerates as the concentration of the chloride ions and the proton acid increases.

  18. Magnetic microstructures of chains and clusters of iron oxide and sulfide nanocrystals in bacteria

    E-print Network

    Dunin-Borkowski, Rafal E.

    Magnetic microstructures of chains and clusters of iron oxide and sulfide nanocrystals in bacteria of intracellular ferrimagnetic magnetite (Fe3O4) and greigite (Fe3S4) nanocrystals inside magnetotactic bacteria

  19. Surface binding vs. sequestration; the uptake of benzohydroxamic acid at iron(III) oxide surfaces 

    E-print Network

    Tasker, Peter; Harris, S.G.; Brechin, E.K.; White, Fraser J; Rio-Echevarria I.M.

    2008-01-01

    Benzohydroxamic acid is shown to be an unexpectedly good ligand for iron(III) oxides, favouring surface attachment to the formation of trisbenzohydroxamato complexes, which are known to have very high thermodynamic stability ...

  20. Eco-Friendly Magnetic Iron Oxide Pillared Montmorillonite for Advanced Catalytic Degradation of Dichlorophenol

    EPA Science Inventory

    Eco-friendly pillared montmorillonites, in which the pillars consist of iron oxide are expected to have interesting and unusual magnetic properties that are applicable for environmental decontamination. Completely ?green? and effective composite was synthesized using mild reactio...

  1. Mössbauer study of iron in high oxidation states in the K Fe O system

    NASA Astrophysics Data System (ADS)

    Dedushenko, Sergey K.; Perfiliev, Yurii D.; Saprykin, Aleksandr A.

    2008-07-01

    Oxidation of metallic iron by potassium superoxide leads to the formation of ferrate(V). Under room temperature this compound is unstable and instantly decomposes by disproportionation mechanism. Grinding the substance into powder accelerates the decomposition process.

  2. IRON-PEROXYMONOSULFATE: A NOVEL SULFATE RADICAL BASED ADVANCED OXIDATION TECHNOLOGY FOR DEGRADATION OF PCBS

    EPA Science Inventory

    This study investigates the degradation of recalcitrant polychlorinated biphenyl (PCBs) using sulfate radical-based advanced oxidation technologies. Sulfate radicals are generated through coupling of peroxymonosulfate (PMS) with iron (Fe(II), Fe(III)). Sulfate radicals have very ...

  3. DOI: 10.1002/cmdc.200800091 Superparamagnetic Iron Oxide NanoparticleAptamer Bioconjugates for

    E-print Network

    Zhang, Liangfang

    DOI: 10.1002/cmdc.200800091 Superparamagnetic Iron Oxide Nanoparticle­Aptamer Bioconjugates for the diagnosis and treatment of cancer. One of the most promising diagnostic agents is superpara- magnetic iron interactions. The hydroxy and carbonyl groups on the surface of the TCL-SPION make them apt for the formu

  4. Microbial Communities Associated with Biogenic Iron Oxide Mineralization in Circumneutral pH Environments

    Microsoft Academic Search

    C. S. Chan; J. F. Banfield

    2002-01-01

    Lithotrophic growth on iron is a metabolism that has been found in a variety of neutral pH environments and is likely important in sustaining life in microaerophilic solutions, especially those low in organics. The composition of the microbial communities, especially the organisms that are responsible for iron oxidation, and carbon and nitrogen fixation, are not known, yet the ability to

  5. SUSTAINABLE MINE DRAINAGE TREATMENT THROUGH THE PASSIVE PRODUCTION OF SALEABLE IRON OXIDE SOLIDS1

    Microsoft Academic Search

    Robert S. Hedin

    Iron is the most common metal contaminant of coal mine drainage. Its treatment creates a metal-rich sludge whose management accounts for a substantial portion of the total treatment costs. For decades, researchers have searched unsuccessfully for cost-mitigating uses for mine drainage sludge. This paper describes our progress in the development of a passive treatment process that yields iron oxide sludge

  6. ROLE OF SURFACE COMPLEXED IRON IN OXIDANT GENERATION AND LUNG INFLAMMATION INDUCED BY SILICATES

    EPA Science Inventory

    The hypothesis was tested that silica and silicate dusts complex iron on their surface and that this iron increases 1) in vitro oxidant generation, and mediator release by alveolar macrophages, and 2) acute inflammatory lung injury. ilica and silicates were found to complex more ...

  7. Quantitative determination of elemental sulfur at the arsenopyrite surface after oxidation by ferric iron: mechanistic implications

    Microsoft Academic Search

    Molly M. McGuire; Jillian F. Banfield; Robert J. Hamers

    2001-01-01

    : The elemental sulfur formed at the arsenopyrite surface after oxidation by ferric iron was quantitatively measured by extraction in perchloroethylene and subsequent quantitative analysis by HPLC. Reactions with ferric iron in perchloric acid solutions or in sulfuric acid solutions (both at pH = 1 and 42°C, which approximate extreme acid mine drainage conditions) produced elemental sulfur in quantities greater

  8. XAS Study of Iron and Arsenic Speciation during Fe(II) Oxidation in

    E-print Network

    van Geen, Alexander

    in controlling the mobility and fate of arsenic in groundwater (e.g., 4-7). The sorption of As onto ironXAS Study of Iron and Arsenic Speciation during Fe(II) Oxidation in the Presence of As(III) S . T H than As(V) by aerating reducing groundwater. Introduction The recent finding that groundwaters from

  9. OXIDANT GENERATION PROMOTES IRON SEQUESTRATION IN BEAS-2B CELLS EXPOSED TO ASBESTOS

    EPA Science Inventory

    Lung injury following asbestos exposure is associated with an oxidative stress that is catalyzed by iron in the fiber matrix, complexed to the surface, or both. We tested the hypothesis that the cellular response to asbestos includes the transport and sequestration of this iron ...

  10. A laboratory study to determine the effect of iron oxides on proton NMR measurements

    E-print Network

    Knight, Rosemary

    in the laboratory, or in the field using a well-logging device or a system deployed at the earth's surface. NMRA laboratory study to determine the effect of iron oxides on proton NMR measurements Kristina and mineralogic form of iron on measured proton nuclear magnetic resonance NMR relaxation rates. Five samples

  11. Photo-Fenton oxidation of phenol with magnetite as iron source Marco Minella,1

    E-print Network

    Photo-Fenton oxidation of phenol with magnetite as iron source Marco Minella,1 Giulia Marchetti,1 irradiation. Very interestingly, the photo-Fenton degradation of phenol was also observed under neutral to promote photo-Fenton reactions even under circumneutral pH conditions, the limited iron leaching and its

  12. Repeated fMRI Using Iron Oxide Contrast Agent in Awake, Behaving Macaques at 3 Tesla

    Microsoft Academic Search

    Francisca P. Leite; Doris Tsao; Wim Vanduffel; Denis Fize; Yuka Sasaki; Larry L. Wald; Anders M. Dale; Ken K. Kwong; Guy A. Orban; Bruce R. Rosen; Roger B. H. Tootell; Joseph B. Mandeville

    2002-01-01

    Iron oxide contrast agents have been employed extensively in anesthetized rodents to enhance fMRI sensitivity and to study the physiology of cerebral blood volume (CBV) in relation to blood oxygen level-dependent (BOLD) signal following neuronal activation. This study quantified the advantages of exogenous agent for repeated neuroimaging in awake, nonhuman primates using a clinical 3 Tesla scanner. A monocrystalline iron

  13. Pro-oxidant Iron Is Present in Human Pulmonary Epithelial Lining Fluid: Implications for Oxidative Stress in the Lung

    Microsoft Academic Search

    J. M. C. Gutteridge; S. Mumby; G. J. Quinlan; K. F. Chung; T. W. Evans

    1996-01-01

    Bronchoalveolar lavage (BAL) provides a sample of lung surface lining fluid. Several pulmonary diseases appear to involve tissue damage caused by reactive oxygen species generated by inhaled oxidants or by phagocytic cells activated within the lung. We show that BAL from normal healthy controls contain chelatable redox active iron that is pro-oxidant towards free radical reactions. Adult patients with the

  14. Synthesis and characterization of diblock copolymer templated iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Akcora, Pinar

    2005-07-01

    Templating ordered assemblies of magnetic oxide nanoparticles within self-assembled diblock copolymers of varying morphologies is an important problem with a wide applicability such as in electromagnetics, optical devices, metal catalysts, medicine and biology. In this thesis, the effects of different polymer structures on particle ordering and resultant magnetic properties have been investigated using various microstructure and magnetic characterization tools. Ring-opening metathesis polymerization (ROMP) of norbornene and functionalized norbornene monomers has been used to synthesize diblock copolymers of narrow polydispersities using Grubbs' catalyst. These block copolymers can be used as templates to form inorganic nanoparticles. In this research, the structural and physical understanding of the inorganic-copolymer system was studied by small-angle neutron and x-ray scattering techniques and transmission electron microscopy. Synthesis of gamma-Fe2O3 nanoparticles has been achieved within novel block copolymers of (norbornene)-b-(deuterated norbornene dicarboxylic) acid and (norbornene methanol-(norbornene dicarboxylic acid). The polymer morphologies were controlled by varying the volume fractions of the constituent blocks. The pure norbornene based diblock copolymer morphologies were demonstrated by electron microscopy for the first tune. Spherical, cylindrical and lamellar morphologies of these novel diblock copolymers were reported. The block ratios of the synthesized polymers were determined using gel permeation chromatography-light scattering, elemental analysis and UV-VIS spectroscopy. Solution phase doping and submersion of thin films in metal salt solutions were employed as metal doping methods and the observed nanoparticle structures were compared to those of the undoped copolymer morphologies. This project reports on the types of templating structures and dispersion of the nanoparticles. The effects of particle, interactions on the microphase separation and magnetic properties were also investigated. The knowledge gained from understanding the templating mechanism in block copolymer/iron oxide nanocomposites can be applied to other similar systems for a variety of biological and catalyst applications.

  15. Enhancing oxidation of TNT and RDX in wastewater: pre-treatment with elemental iron.

    PubMed

    Oh, S Y; Cha, D K; Chiu, P C; Kim, B J

    2003-01-01

    Munitions manufacturing wastewater is commonly treated by adsorption to activated carbon. We are proposing a new munitions manufacturing wastewater treatment system consisting of a reductive pre-treatment process and subsequent Fenton's oxidation to mineralize energetic compounds such as TNT and RDX. The pre-treatment involves reduction of electron-withdrawing nitro groups of TNT and RDX with elemental iron. The iron-treated explosives are then oxidized by Fenton's reagent through the addition of H2O2. The objective of this work is to investigate the feasibility of using elemental iron to convert TNT and RDX to reduction products which may be more oxidizable in subsequent Fenton's oxidation. Results of batch reduction experiments with elemental iron showed complete removal of TNT and RDX and formation of the reduction products within 60 minutes. Results of column experiments showed a rapid and complete removal of TNTand RDX within 9.7 minutes retention time. Fitting observed effluent concentrations to a one-dimensional advection-dispersion equation, we were able to predict the concentration profiles of TNT and RDX in the iron column and calculate the iron column length required for the desired removal. The results of Fenton's oxidation experiments showed that iron pre-treatment enhanced both the rate and extent of TNT and RDX mineralization by Fenton's oxidation. PMID:12862222

  16. Thalassaemic erythrocytes: cellular suicide arising from iron and glutathione-dependent oxidation reactions?

    PubMed

    Scott, M D; Eaton, J W

    1995-12-01

    Both beta-thalassaemic red blood cells and normal red blood cells (RBC) artificially loaded with unpaired alpha-haemoglobin chains exhibit increased amounts of membrane-bound haem and iron. In the model beta-thalassaemic RBC the amount of free haem and iron was as much as 20 times that which could have been contributed by the entrapped alpha-haemoglobin chains alone. This excess haem/iron arises from destabilization of haemoglobin via reactions between ferric iron (Fe3+), initially contributed by the unpaired alpha chains, and cytoplasmic constituents, primarily reduced glutathione (GSH). Indeed, in the presence of Fe3+ (100 microM) addition of even small amounts of GSH (0.5 mM) to dilute RBC haemolysates (0.15 mg haemoglobin/dl) greatly accelerated methaemoglobin formation. In contrast, lysates from GSH-depleted RBC demonstrated a significantly reduced rate of iron-mediated haemoglobin oxidation which was reversible by addition of GSH. The initiation, and subsequent propagation, of Fe(3+)-mediated haemoglobin oxidation was significantly inhibited by iron chelators. Finally, Fe(3+)-driven haemoglobin oxidation was synergized by low amounts of H2O2, an oxidant spontaneously generated in thalassaemic RBC. To summarize, the release of small amounts of free iron from unpaired alpha-haemoglobin chains in the beta-thalassaemic RBC can initiate self-amplifying redox reactions which simultaneously deplete cellular reducing potential (e.g. GSH), oxidize additional haemoglobin, and accelerate the red cell destruction. PMID:8547123

  17. Tunable room-temperature ferromagnet using an iron-oxide and graphene oxide nanocomposite.

    PubMed

    Lin, Aigu L; Rodrigues, J N B; Su, Chenliang; Milletari, M; Loh, Kian Ping; Wu, Tom; Chen, Wei; Neto, A H Castro; Adam, Shaffique; Wee, Andrew T S

    2015-01-01

    Magnetic materials have found wide application ranging from electronics and memories to medicine. Essential to these advances is the control of the magnetic order. To date, most room-temperature applications have a fixed magnetic moment whose orientation is manipulated for functionality. Here we demonstrate an iron-oxide and graphene oxide nanocomposite based device that acts as a tunable ferromagnet at room temperature. Not only can we tune its transition temperature in a wide range of temperatures around room temperature, but the magnetization can also be tuned from zero to 0.011?A?m(2)/kg through an initialization process with two readily accessible knobs (magnetic field and electric current), after which the system retains its magnetic properties semi-permanently until the next initialization process. We construct a theoretical model to illustrate that this tunability originates from an indirect exchange interaction mediated by spin-imbalanced electrons inside the nanocomposite. PMID:26100970

  18. Tunable room-temperature ferromagnet using an iron-oxide and graphene oxide nanocomposite

    PubMed Central

    Lin, Aigu L.; Rodrigues, J. N. B.; Su, Chenliang; Milletari, M.; Loh, Kian Ping; Wu, Tom; Chen, Wei; Neto, A. H. Castro; Adam, Shaffique; Wee, Andrew T. S.

    2015-01-01

    Magnetic materials have found wide application ranging from electronics and memories to medicine. Essential to these advances is the control of the magnetic order. To date, most room-temperature applications have a fixed magnetic moment whose orientation is manipulated for functionality. Here we demonstrate an iron-oxide and graphene oxide nanocomposite based device that acts as a tunable ferromagnet at room temperature. Not only can we tune its transition temperature in a wide range of temperatures around room temperature, but the magnetization can also be tuned from zero to 0.011?A?m2/kg through an initialization process with two readily accessible knobs (magnetic field and electric current), after which the system retains its magnetic properties semi-permanently until the next initialization process. We construct a theoretical model to illustrate that this tunability originates from an indirect exchange interaction mediated by spin-imbalanced electrons inside the nanocomposite. PMID:26100970

  19. Gaseous reduction of iron oxides: Part IV. mathematical analysis of partial internal reduction-diffusion control

    Microsoft Academic Search

    R. H. Tien; E. T. Turkdogan

    1972-01-01

    In this mathematical analysis of gaseous reduction of iron oxides, the partial internal reduction of the porous oxide and\\u000a gas diffusion in the porous iron layer are considered simultaneously in deriving the rate equation. The rate equation, derived\\u000a by partly analytical and partly numerical solutions, is well substantiated by the experimental results obtained previously.\\u000a The following parameters, determined previously, are

  20. Phase change induced by polypyrrole in iron-oxide polypyrrole nanocomposite

    Microsoft Academic Search

    Komilla Suri; S. Annapoorni; R. P. Tandon

    2001-01-01

    Nanocomposites of polypyrrole and iron oxide were prepared using simultaneous gelation and polymerization processes. Varied\\u000a amounts of pyrrole monomer were added to a solution containing iron nitrate as precursor and 2-methoxy ethanol as solvent.\\u000a The presence of oxide and polypyrrole was confirmed by using X-ray and FTIR techniques. Some of these nanocomposites exhibited\\u000a magnetic behaviour. SEM studies of powders indicated

  1. Surface Complexation of Actinides with Iron Oxides: Implications for Radionuclide Transport in Near-Surface Aquifers

    Microsoft Academic Search

    J. L. Jerden Jr; A. J. Kropf; Y. Tsai

    2005-01-01

    The surface complexation of actinides with iron oxides plays a key role in actinide transport and retardation in geosphere-biosphere systems. The development of accurate actinide transport models therefore requires a mechanistic understanding of surface complexation reactions (i.e. knowledge of chemical speciation at mineral\\/fluid interfaces). Iron oxides are particularly important actinide sorbents due to their pH dependent surface charges, relatively high

  2. Magnetic Steering of Iron Oxide Microparticles Using Propulsion Gradient Coils in MRI

    Microsoft Academic Search

    Jean-Baptiste Mathieu; Sylvain Martel

    2006-01-01

    Steering micro-carriers being tracked by an MRI system may be very attractive in oncology. Here, iron oxide microparticles have been steered in a Y-shaped microchannel placed between a Maxwell pair (dB\\/dz=443 mT\\/m) located in the center of an MRI bore. A suspension of 10.82 mum iron oxide particles was injected into the channel and a magnetic gradient generated by the

  3. Molecular Mechanisms by Which Iron Induces Nitric Oxide Synthesis in Cultured Proximal Tubule Cells

    Microsoft Academic Search

    Liguang Chen; Yiping Wang; Lukas K. Kairaitis; Yang Wang; Bao-Hong Zhang; David C. H. Harris

    2001-01-01

    Nitric oxide (NO) levels are increased after exposure of cultured proximal tubule cells (PTC) to non-haem iron, potentially contributing to PTC injury in disease states associated with increased iron exposure, including proteinuric renal disease. The mechanisms underlying this observed increase were investigated. After 3 h exposure to 400 ?M nitrilotriacetate (NTA)-Fe, inducible nitric oxide synthase (iNOS) mRNA expression was significantly

  4. Magnetic studies of iron oxide nanoparticles coated with oleic acid and Pluronic® block copolymer

    Microsoft Academic Search

    M. A. Morales; Tapan Kumar Jain; V. Labhasetwar; D. L. Leslie-Pelecky

    2005-01-01

    We have prepared and studied iron-oxide nanoparticles coated with oleic acid (OA) and Pluronic® polymer. The mean diameter of the iron-oxide nanoparticles was 9.3(+\\/-)0.8 nm. Saturation magnetization values measured at 10 K varied from 66.1(+\\/-0.7) emu\\/g to 98.7(+\\/-0.5) emu\\/g. At 300 K the loops showed negligible coercive field. The peaks in zero-field-cooled susceptibility decreased from 280 to 168 K with

  5. Magnetic studies of iron oxide nanoparticles coated with oleic acid and Pluronic® block copolymer

    Microsoft Academic Search

    M. A. Morales; Tapan Kumar Jain; V. Labhasetwar; D. L. Leslie-Pelecky

    2005-01-01

    We have prepared and studied iron-oxide nanoparticles coated with oleic acid (OA) and Pluronic® polymer. The mean diameter of the iron-oxide nanoparticles was 9.3(±)0.8 nm. Saturation magnetization values measured at 10 K varied from 66.1(±0.7) emu?g to 98.7(±0.5) emu?g. At 300 K the loops showed negligible coercive field. The peaks in zero-field-cooled susceptibility decreased from 280 to 168 K with

  6. Iron chelators increase the resistance of Ataxia telangeictasia cells to oxidative stress

    Microsoft Academic Search

    Rodney E. Shackelford; Ryan P. Manuszak; Cybele D. Johnson; Daniel J. Hellrung; Charles J. Link; Suming Wang

    2004-01-01

    Ataxia telangeictasia (A-T) is an autosomal recessive disorder characterized by immune dysfunction, genomic instability, chronic oxidative damage, and increased cancer incidence. Previously, desferal was found to increase the resistance of A-T, but not normal cells to exogenous oxidative stress in the colony forming-efficiency assay, suggesting that iron metabolism is dysregulated in A-T. Since desferal both chelates iron and modulates gene

  7. CEMS spectra of non-spherical nanoparticles in oxidized iron thin films

    Microsoft Academic Search

    J. Rubín; F. Jiménez-Villacorta; J. Bartolomé; C. Prieto

    2008-01-01

    Room temperature CEMS spectra and field-cooled and zero field-cooled hysteresis loops have been measured on oxidized iron\\u000a films of 100 nm thickness. The iron films were sputtered on a Si substrate, while the substrate temperature, T\\u000a s, was kept at 200 K and 300 K, and subsequently oxidized. The magnetization of the T\\u000a s = 200 K sample decreases ca. 40% with respect to

  8. CEMS spectra of non-spherical nanoparticles in oxidized iron thin films

    Microsoft Academic Search

    J. Rubín; F. Jiménez-Villacorta; J. Bartolomé; C. Prieto

    Room temperature CEMS spectra and field-cooled and zero field-cooled hysteresis loops have been measured on oxidized iron\\u000a films of 100 nm thickness. The iron films were sputtered on a Si substrate, while the substrate temperature, T\\u000a s, was kept at 200 K and 300 K, and subsequently oxidized. The magnetization of the T\\u000a s = 200 K sample decreases ca. 40% with respect to

  9. Enhancing Fenton oxidation of TNT and RDX through pretreatment with zero-valent iron

    Microsoft Academic Search

    Seok-Young Oh; Pei C. Chiu; Byung J. Kim; Daniel K. Cha

    2003-01-01

    The effect of reductive treatment with elemental iron on the rate and extent of TOC removal by Fenton oxidation was studied for the explosives 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) using a completely stirred tank reactor (CSTR). The results support the hypothesis that TNT and RDX are reduced with elemental iron to products that are oxidized more rapidly and completely by

  10. Protection of cultured rat gastric cells against oxidant stress by iron chelation

    Microsoft Academic Search

    Noriaki Yajima; Hideyuki Hiraishi; Takashi Harada

    1995-01-01

    Reactive oxygen metabolites may be involved in the pathogenesis of ethanol-, nonsteroidal antiinflammatory drug-,Helicobacter pylori-, or ischemia\\/reoxygenation-induced gastric mucosal injuryin vivo. Iron plays a critical role in mediating oxidant injuryin vitro. The present study examined a possible role of lipid peroxidation in inducing oxidant damage by determining the effect of iron chelation on cytotoxicity and on lipid peroxidation in cultured

  11. Characterization of nanocrystalline ?-Fe2O3 thin films grown by reactive evaporation and oxidation of iron

    Microsoft Academic Search

    M Saleem; M F Al-Kuhaili; S M A Durrani; I A Bakhtiari

    2012-01-01

    Iron oxide thin films, with an ?-Fe2O3 phase, were deposited by two techniques. The first was evaporation of iron in vacuum, followed by oxidation through annealing in air. The second was reactive evaporation of iron in an oxygen atmosphere. This was also followed by annealing in air. The structural, morphological and chemical properties of the films were investigated. All films

  12. Sulfur Versus Iron Oxidation in an Iron-Thiolate Model Complex

    SciTech Connect

    A McDonald; M Bukowski; E Farquhar; T Jackson; K Koehntop; M Seo; R De Hont; A Stubna; J Halfen; E Munck

    2011-12-31

    In the absence of base, the reaction of [Fe{sup II}(TMCS)]PF{sub 6} (1, TMCS = 1-(2-mercaptoethyl)-4,8,11-trimethyl-1,4,8,11-tetraazacyclotetradecane) with peracid in methanol at -20 C did not yield the oxoiron(IV) complex (2, [Fe{sup IV}(O)(TMCS)]PF{sub 6}), as previously observed in the presence of strong base (KO{sup t}Bu). Instead, the addition of 1 equiv of peracid resulted in 50% consumption of 1. The addition of a second equivalent of peracid resulted in the complete consumption of 1 and the formation of a new species 3, as monitored by UV-vis, ESI-MS, and Moessbauer spectroscopies. ESI-MS showed 3 to be formulated as [Fe{sup II}(TMCS) + 2O]{sup +}, while EXAFS analysis suggested that 3 was an O-bound iron(II)-sulfinate complex (Fe-O = 1.95 {angstrom}, Fe-S = 3.26 {angstrom}). The addition of a third equivalent of peracid resulted in the formation of yet another compound, 4, which showed electronic absorption properties typical of an oxoiron(IV) species. Moessbauer spectroscopy confirmed 4 to be a novel iron(IV) compound, different from 2, and EXAFS (Fe{double_bond}O = 1.64 {angstrom}) and resonance Raman ({nu}{sub Fe{double_bond}O} = 831 cm{sup -1}) showed that indeed an oxoiron(IV) unit had been generated in 4. Furthermore, both infrared and Raman spectroscopy gave indications that 4 contains a metal-bound sulfinate moiety ({nu}{sub s}(SO{sub 2}) {approx} 1000 cm{sup -1}, {nu}{sub as}(SO{sub 2}) {approx} 1150 cm{sup -1}). Investigations into the reactivity of 1 and 2 toward H{sup +} and oxygen atom transfer reagents have led to a mechanism for sulfur oxidation in which 2 could form even in the absence of base but is rapidly protonated to yield an oxoiron(IV) species with an uncoordinated thiol moiety that acts as both oxidant and substrate in the conversion of 2 to 3.

  13. Hydrogen Reduction of Zinc and Iron Oxides Containing Mixtures

    NASA Astrophysics Data System (ADS)

    de Siqueira, Rogério Navarro C.; de Albuquerque Brocchi, Eduardo; de Oliveira, Pamela Fernandes; Motta, Marcelo Senna

    2013-10-01

    Zinc is a metal of significant technological importance and its production from secondary sources has motivated the development of alternative processes, such as the chemical treatment of electrical arc furnace (EAF) dust. Currently, the extraction of zinc from the mentioned residue using a carbon-containing reducing agent is in the process of being established commercially and technically. In the current study, the possibility of reducing zinc from an EAF dust sample through a H2 constant flux in a horizontal oven is studied. The reduction of a synthetic oxide mixture of analogous composition is also investigated. The results indicated that the reduction process is thermodynamically viable for temperatures higher than 1123 K (850 °C), and all zinc metal produced is transferred to the gas stream, enabling its complete separation from iron. The same reaction in the presence of zinc crystals was considered for synthesizing FeZn alloys. However, for the experimental conditions employed, although ZnO reduction was indeed thermodynamically hindered because of the presence of zinc crystals (the metal's partial pressure was enhanced), the zinc metal's escape within the gaseous phase could not be effectively avoided.

  14. Sea-urchin-like iron oxide nanostructures for water treatment.

    PubMed

    Lee, Hyun Uk; Lee, Soon Chang; Lee, Young-Chul; Vrtnik, Stane; Kim, Changsoo; Lee, Sanggap; Lee, Young Boo; Nam, Bora; Lee, Jae Won; Park, So Young; Lee, Sang Moon; Lee, Jouhahn

    2013-11-15

    To obtain adsorbents with high capacities for removing heavy metals and organic pollutants capable of quick magnetic separation, we fabricated unique sea-urchin-like magnetic iron oxide (mixed ?-Fe2O3/Fe3O4 phase) nanostructures (called u-MFN) with large surface areas (94.1m(2) g(-1)) and strong magnetic properties (57.9 emu g(-1)) using a simple growth process and investigated their potential applications in water treatment. The u-MFN had excellent removal capabilities for the heavy metals As(V) (39.6 mg g(-1)) and Cr(VI) (35.0 mg g(-1)) and the organic pollutant Congo red (109.2 mg g(-1)). The u-MFN also displays excellent adsorption of Congo red after recycling. Because of its high adsorption capacity, fast adsorption rate, and quick magnetic separation from treated water, the u-MFN developed in the present study is expected to be an efficient magnetic adsorbent for heavy metals and organic pollutants in aqueous solutions. PMID:24021165

  15. PET/NIRF/MRI triple functional iron oxide nanoparticles.

    PubMed

    Xie, Jin; Chen, Kai; Huang, Jing; Lee, Seulki; Wang, Jinhua; Gao, Jinhao; Li, Xingguo; Chen, Xiaoyuan

    2010-04-01

    Engineered nanoparticles with theranostic functions have attracted a lot of attention for their potential role in the dawning era of personalized medicine. Iron oxide nanoparticles (IONPs), with their advantages of being non-toxic, biodegradable and inexpensive, are candidate platforms for the buildup of theranostic nanostructures; however, progress in using them has been limited largely due to inefficient drug loading and delivery. In the current study, we utilized dopamine to modify the surface of IONPs, yielding nanoconjugates that can be easily encapsulated into human serum albumin (HSA) matrices (clinically utilized drug carriers). This nanosystem is well-suited for dual encapsulation of IONPs and drug molecules, because the encapsulation is achieved in a way that is similar to common drug loading. To assess the biophysical characteristics of this novel nanosystem, the HSA coated IONPs (HSA-IONPs) were dually labeled with (64)Cu-DOTA and Cy5.5, and tested in a subcutaneous U87MG xenograft mouse model. In vivo positron emission tomography (PET)/near-infrared fluorescence (NIRF)/magnetic resonance imaging (MRI) tri-modality imaging, and ex vivo analyses and histological examinations were carefully conducted to investigate the in vivo behavior of the nanostructures. With the compact HSA coating, the HSA-IONPs manifested a prolonged circulation half-life; more impressively, they showed massive accumulation in lesions, high extravasation rate, and low uptake of the particles by macrophages at the tumor area. PMID:20092887

  16. Fabrication of Iron Oxide Nanoparticle Monolayers by Electrophoretic Deposition

    NASA Astrophysics Data System (ADS)

    Krejci, Alex; Gonzalo-Juan, Isabel; Dickerson, James

    2012-02-01

    Magnetic nanoparticle (NP) films are potentially useful in a variety of applications, such as magnetic storage media and ultra-strong permanent magnets. Monolayers of magnetic NPs are specifically interesting as the monolayer geometry maximizes film interactions with dissimilar materials below and above the monolayer. However, many potential commercial and industrial applications of NP films rely on fabrication techniques that are facile, rapid, and site-selective which create homogenous, densely packed, defect-free thin films. Electrophoretic deposition (EPD) is a technique for forming thin films that meets all of these criteria. This work shows, for the first time, EPD's utility in forming monolayers of magnetic NPs. Iron oxide NPs (˜14nm) have been synthesized using a solution phase synthesis technique. Repeated centrifugation of the particles prepares the NPs for EPD. The particles are then deposited onto silicon substrates with EPD using dc electric fields. Analysis of the films using scanning electron microscopy and atomic force microscopy shows the particles deposit as NP monolayers. The monolayer density and deposition rate are controlled by varying the suspension concentration and the deposition time. Future research will focus on creating long-range order within the monolayers.

  17. Magnetical studies on thin films of iron oxides

    NASA Astrophysics Data System (ADS)

    Osorio, Jaime; Uribe, Juan; Barrero, Cesar; Girata, Doris; Morales, Alvaro; Hoffmann, Axel; Gancedo, Ramon

    2008-03-01

    We have grown hematite (?-Fe2O3) thin films on stainless steel and silicon dioxide (SiO2) substrates and magnetite (Fe3O4) thin films on silicon substrates by RF magnetron sputtering process. Conversion Electron Mössbauer (CEM) spectra of these films exhibit hyperfine parameter values which are characteristic of these iron oxides. Magnetization measurements parallel to the plane of the film as a function of temperature, M(T), were done at a constant field of 1 kOe to ?-Fe2O3 films and at 200 Oe to Fe3O4 films. The M(T) curve of the ?-Fe2O3 film showed a linear increasing of magnetization from 5 K to 160 K, related with the Morin transition. While the temperature of the Fe3O4 film is decreased, a sharp decrease in magnetization is observed at 123 K, associated to the Verwey transition. We carried out measurements of magnetization as a function of applied magnetic field, the loops of ?-Fe2O3 film exhibits hysteresis which is related to their weakly ferromagnetic behavior and the loops of the Fe3O4 film at 300 and 110 K show a magnetic value around 5 memu at 3 KOe in the curves.

  18. Inverse-Photoemission Spectroscopy of Iron Oxides, Silver

    NASA Astrophysics Data System (ADS)

    Kim, Bongsoo

    1990-01-01

    I measured the inverse-photoemission spectra (IPES) of iron oxides grown on an Fe substrate, and calculated the band structure of paramagnetic FeO to analyze the IPES. The band calculation showed some overlap between Fe _3_{rm d} states and O_2_{rm p} states in the region of occupied states, and s,p-like states of Fe in the unoccupied region. Isochromatic IPES showed structures at ~2.5 eV and ~7.5 eV above the Fermi energy. I estimate the full band gap of FeO as 2.5 eV from the IPES data. Angle-resolved inverse-photoemission spectra (ARIPES) have been measured on single-crystal Ag. The results are compared with the predictions of bulk band-structure theory and a free-electron model. The latter gives good agreement for the structure with a final state near the Fermi energy. Band theory is needed for the structure 17 eV above the Fermi energy. This structure is very nondispersive, indicating the existence of a very flat band throughout the IXUL plane.

  19. Ameliorating role of rutin on oxidative stress induced by iron overload in hepatic tissue of rats.

    PubMed

    Aziza, Samy Ali Hussein; Azab, Mohammed El-Said; El-Shall, Soheir Kamal

    2014-08-01

    Iron is an essential element that participates in several metabolic activities of cells; however, excess iron is a major cause of iron-induced oxidative stress and several human diseases. Natural flavonoids, as rutin, are well-known antioxidants and could be efficient protective agents. Therefore, the present study was undertaken to evaluate the protective influence of rutin supplementation to improve rat antioxidant systems against IOL-induced hepatic oxidative stress. Sixty male albino rats were randomly divided to three equal groups. The first group, the control, the second group, iron overload group, the third group was used as iron overload+rutin group. Rats received six doses of ferric hydroxide polymaltose (100 mg kg(-1) b.wt.) as one dose every two days, by intraperitoneal injections (IP) and administrated rutin (50 mg kg(-1) b.wt.) as one daily oral dose until the sacrificed day. Blood samples for serum separation and liver tissue specimens were collected three times, after three, four and five weeks from the onset of the experiment. Serum iron profiles total iron, Total Iron Binding Capacity (TIBC), Unsaturated Iron Binding Capacity (UIBC), transferrin (Tf) and Transferrin Saturation% (TS%)}, ferritin, albumin, total Protein, total cholesterol, triacylglycerols levels and aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were determined. Moreover, total iron in the liver, L-malondialdehyde (L-MDA), glutathione (GSH), Nitric Oxide (NO) and Total Nucleic Acid (TNA) levels and glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD) activities were also determined. The obtained results revealed that, iron overload (IOL) resulted in significant increase in serum iron, TIBC, Tf, TS% and ferritin levels and AST and ALT activities and also increased liver iron, L-MDA and NO levels. Meanwhile, it decreased serum UIBC, total cholesterol, triacylglycerols, albumin, total protein and liver GSH, TNA levels and Gpx, CAT and SOD activities when compared with the control group. Rutin administration to iron-overloaded rats resulted in significant decrease in serum total iron, TIBC, Tf, TS%, ferritin levels and AST and ALT activities and liver total iron, L-MDA and NO levels with significant increases in serum UIBC, albumin, total protein and total cholesterol levels and in liver GSH, CAT and SOD activities compared with the IOL group. This study provides in vivo evidence that rutin administration can improve the antioxidant defense systems against IOL-induced hepatic oxidative stress in rats. This protective effect in liver of iron-loaded rats may be due to both antioxidant and metal chelation activities. PMID:26031015

  20. Induced Clustered Nanoconfinement of Superparamagnetic Iron Oxide in Biodegradable Nanoparticles Enhances Transverse Relaxivity for Targeted Theranostics

    PubMed Central

    Ragheb, Ragy R. T.; Kim, Dongin; Bandyopadhyay, Arunima; Chahboune, Halima; Bulutoglu, Beyza; Ezaldein, Harib; Criscione, Jason M.; Fahmy, Tarek M.

    2013-01-01

    Purpose Combined therapeutic and diagnostic agents, “theranostics” are emerging valuable tools for noninvasive imaging and drug delivery. Here, we report on a solid biodegradable multifunctional nanoparticle that combines both features. Methods Poly(lactide-co-glycolide) nanoparticles were engineered to confine superparamagnetic iron oxide contrast for magnetic resonance imaging while enabling controlled drug delivery and targeting to specific cells. To achieve this dual modality, fatty acids were used as anchors for surface ligands and for encapsulated iron oxide in the polymer matrix. Results We demonstrate that fatty acid modified iron oxide prolonged retention of the contrast agent in the polymer matrix during degradative release of drug. Antibody-fatty acid surface modification facilitated cellular targeting and subsequent internalization in cells while inducing clustering of encapsulated fatty-acid modified superparamagnetic iron oxide during particle formulation. This induced clustered confinement led to an aggregation within the nanoparticle and, hence, higher transverse relaxivity, r2, (294 mM?1 s?1) compared with nanoparticles without fatty-acid ligands (160 mM?1 s?1) and higher than commercially available superparamagnetic iron oxide nanoparticles (89 mM?1 s?1). Conclusion Clustering of superparamagnetic iron oxide in poly(lactide-co-glycolide) did not affect the controlled release of encapsulated drugs such as methotrexate or clodronate and their subsequent pharmacological activity, thus highlighting the full theranostic capability of our system. PMID:23401099

  1. Uptake and clearance analysis of Technetium(99m) labelled iron oxide nanoparticles in a rabbit brain.

    PubMed

    Nadeem, Muhammad; Ahmad, Munir; Saeed, M A; Shaari, Amiruddin; Riaz, Saira; Naseem, Shahzad; Rashid, Khalid

    2015-06-01

    Nanoparticles as solid colloidal particles are extensively studied and used as anticancer drug delivery agents because of their physical properties. This current research aims to prepare water base suspension of uncoated iron oxide nanoparticles and their biodistribution study to different organs, especially the brain, by using a single photon emission computed tomography gamma camera. The water-based suspension of iron oxide nanoparticles was synthesised by a reformed version of the co-precipitation method and labelled with Tc(99m) for intravenous injection. The nanoparticles were injected without surface modification. X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and transmission electron microscope (TEM) techniques were used for characterisation. Peaks of XRD and EDS indicate that the particles are magnetite and exist in aqueous suspension. The average diameter of iron oxide nanoparticles without any surface coating determined by TEM is 10 nm. These particles are capable of evading the reticuloendothelial system and can cross the blood-brain barrier in the rabbit. The labelling efficiency of iron oxide nanoparticles labelled with Tc(99m) is 85%, which is good for the biodistribution study. The sufficient amount of iron oxide nanoparticles concentration in the brain as compared with the surrounding soft tissues and their long blood retention time indicates that the water-based suspension of iron oxide nanoparticles may be an option for drug delivery into the brain. PMID:26023157

  2. Synthesis of phase-pure and monodisperse iron oxide nanoparticles by thermal decomposition

    NASA Astrophysics Data System (ADS)

    Hufschmid, Ryan; Arami, Hamed; Ferguson, R. Matthew; Gonzales, Marcela; Teeman, Eric; Brush, Lucien N.; Browning, Nigel D.; Krishnan, Kannan M.

    2015-06-01

    Superparamagnetic iron oxide nanoparticles (SPIONs) are used for a wide range of biomedical applications requiring precise control over their physical and magnetic properties, which are dependent on their size and crystallographic phase. Here we present a comprehensive template for the design and synthesis of iron oxide nanoparticles with control over size, size distribution, phase, and resulting magnetic properties. We investigate critical parameters for synthesis of monodisperse SPIONs by organic thermal decomposition. Three different, commonly used, iron containing precursors (iron oleate, iron pentacarbonyl, and iron oxyhydroxide) are evaluated under a variety of synthetic conditions. We compare the suitability of these three kinetically controlled synthesis protocols, which have in common the use of iron oleate as a starting precursor or reaction intermediate, for producing nanoparticles with specific size and magnetic properties. Monodisperse particles were produced over a tunable range of sizes from approximately 2-30 nm. Reaction parameters such as precursor concentration, addition of surfactant, temperature, ramp rate, and time were adjusted to kinetically control size and size-distribution, phase, and magnetic properties. In particular, large quantities of excess surfactant (up to 25 : 1 molar ratio) alter reaction kinetics and result in larger particles with uniform size; however, there is often a trade-off between large particles and a narrow size distribution. Iron oxide phase, in addition to nanoparticle size and shape, is critical for establishing magnetic properties such as differential susceptibility (dm/dH) and anisotropy. As an example, we show the importance of obtaining the required size and iron oxide phase for application to Magnetic Particle Imaging (MPI), and describe how phase purity can be controlled. These results provide much of the information necessary to determine which iron oxide synthesis protocol is best suited to a particular application.

  3. Synthesis of phase-pure and monodisperse iron oxide nanoparticles by thermal decomposition.

    PubMed

    Hufschmid, Ryan; Arami, Hamed; Ferguson, R Matthew; Gonzales, Marcela; Teeman, Eric; Brush, Lucien N; Browning, Nigel D; Krishnan, Kannan M

    2015-06-18

    Superparamagnetic iron oxide nanoparticles (SPIONs) are used for a wide range of biomedical applications requiring precise control over their physical and magnetic properties, which are dependent on their size and crystallographic phase. Here we present a comprehensive template for the design and synthesis of iron oxide nanoparticles with control over size, size distribution, phase, and resulting magnetic properties. We investigate critical parameters for synthesis of monodisperse SPIONs by organic thermal decomposition. Three different, commonly used, iron containing precursors (iron oleate, iron pentacarbonyl, and iron oxyhydroxide) are evaluated under a variety of synthetic conditions. We compare the suitability of these three kinetically controlled synthesis protocols, which have in common the use of iron oleate as a starting precursor or reaction intermediate, for producing nanoparticles with specific size and magnetic properties. Monodisperse particles were produced over a tunable range of sizes from approximately 2-30 nm. Reaction parameters such as precursor concentration, addition of surfactant, temperature, ramp rate, and time were adjusted to kinetically control size and size-distribution, phase, and magnetic properties. In particular, large quantities of excess surfactant (up to 25?:?1 molar ratio) alter reaction kinetics and result in larger particles with uniform size; however, there is often a trade-off between large particles and a narrow size distribution. Iron oxide phase, in addition to nanoparticle size and shape, is critical for establishing magnetic properties such as differential susceptibility (dm/dH) and anisotropy. As an example, we show the importance of obtaining the required size and iron oxide phase for application to Magnetic Particle Imaging (MPI), and describe how phase purity can be controlled. These results provide much of the information necessary to determine which iron oxide synthesis protocol is best suited to a particular application. PMID:26059262

  4. Iron-tellurium-selenium mixed oxide catalysts for the selective oxidation of propylene to acrolein

    SciTech Connect

    Patel, B.M.; Price, G.L. (Dept. of Chemical Engineering, Louisiana State Univ., Baton Rouge, LA (US))

    1990-05-01

    This paper reports on iron-tellurium-selenium mixed oxide catalysts prepared by coprecipitation from aqueous solution investigated for the propylene to acrolein reaction in the temperature range 543-773 K. Infrared spectroscopy, electron dispersive X-ray analysis, X-ray diffraction, and isotopic tracer techniques have also been employed to characterize this catalytic system. Properties of the Fe-Te-Se mixed oxide catalysts have been compared with Fe-Te mixed oxides in an effort to deduce the functionality of Se. The selenium in the Fe-Te-Se-O catalyst has been found to be the hydrocarbon activating site. The activation energies for the acrolein and carbon dioxide formation are 71 and 54 kJ/mol, respectively. Reactions carried out with {sup 18}O{sub 2} have shown lattice oxygen to be primarily responsible for the formation of both acrolein and carbon dioxide. The initial and rate-determining step for acrolein formation is hydrogen abstraction as determined by an isotope effect associated with the C{sub 3}D{sub 6} reaction. No isotope effect is observed for carbon dioxide formation from C{sub 3}D{sub 6} suggesting that CO{sub 2} is formed by parallel, not consecutive, oxidation of propylene.

  5. Observation of tritium distribution in iron oxide with tritium micro autoradiography

    SciTech Connect

    Isobe, K.; Hayashi, T.; Nakamura, H.; Kobayashi, K.; Yamanishi, T. [Tritium Technology Group, Japan Atomic Energy Agency, Tokai-mura Naka- gun, Ibaraki, 319-1195 (Japan); Okuno, K. [Faculty of Science, Shizuoka Univ., 836 Ohya, Suruga-ku, Shizuoka city, Shizuoka, 422-8529 (Japan)

    2008-07-15

    To clarify the tritium permeation behavior, tritium distribution in iron oxidized in high temperature water was observed with tritium micro autoradiography. It was found that tritium was distributed homogeneously in the iron metal. However the oxide surface (magnetite) was found to contain a very low concentration of tritium. The inner layer of oxide could strongly effect the tritium permeation. From a comparison with the permeation experiment that had been reported in Ref. 1, it was suggested that tritium would mainly diffuse other path except the oxide lattice. According to the chemical form of tritium, which was released from iron surface into water, two assumptions were suggested. One is based on the different combination of tritium on the water-surface interface. The other is based on the oxidation mechanism. (authors)

  6. Microbial Iron(II) Oxidation in Littoral Freshwater Lake Sediment: The Potential for Competition between Phototrophic vs. Nitrate-Reducing Iron(II)-Oxidizers

    PubMed Central

    Melton, E. D.; Schmidt, C.; Kappler, A.

    2012-01-01

    The distribution of neutrophilic microbial iron oxidation is mainly determined by local gradients of oxygen, light, nitrate and ferrous iron. In the anoxic top part of littoral freshwater lake sediment, nitrate-reducing and phototrophic Fe(II)-oxidizers compete for the same e? donor; reduced iron. It is not yet understood how these microbes co-exist in the sediment and what role they play in the Fe cycle. We show that both metabolic types of anaerobic Fe(II)-oxidizing microorganisms are present in the same sediment layer directly beneath the oxic-anoxic sediment interface. The photoferrotrophic most probable number counted 3.4·105?cells·g?1 and the autotrophic and mixotrophic nitrate-reducing Fe(II)-oxidizers totaled 1.8·104 and 4.5·104?cells·g?1 dry weight sediment, respectively. To distinguish between the two microbial Fe(II) oxidation processes and assess their individual contribution to the sedimentary Fe cycle, littoral lake sediment was incubated in microcosm experiments. Nitrate-reducing Fe(II)-oxidizing bacteria exhibited a higher maximum Fe(II) oxidation rate per cell, in both pure cultures and microcosms, than photoferrotrophs. In microcosms, photoferrotrophs instantly started oxidizing Fe(II), whilst nitrate-reducing Fe(II)-oxidizers showed a significant lag-phase during which they probably use organics as e? donor before initiating Fe(II) oxidation. This suggests that they will be outcompeted by phototrophic Fe(II)-oxidizers during optimal light conditions; as phototrophs deplete Fe(II) before nitrate-reducing Fe(II)-oxidizers start Fe(II) oxidation. Thus, the co-existence of the two anaerobic Fe(II)-oxidizers may be possible due to a niche space separation in time by the day-night cycle, where nitrate-reducing Fe(II)-oxidizers oxidize Fe(II) during darkness and phototrophs play a dominant role in Fe(II) oxidation during daylight. Furthermore, metabolic flexibility of Fe(II)-oxidizing microbes may play a paramount role in the conservation of the sedimentary Fe cycle. PMID:22666221

  7. Surface Functionalization of Oxide-Covered Zinc and Iron with Phosphonated Phenylethynyl Phenothiazine.

    PubMed

    Rechmann, Julian; Sarfraz, Adnan; Götzinger, Alissa C; Dirksen, Elena; Müller, Thomas J J; Erbe, Andreas

    2015-07-01

    Phenothiazines are redox-active, fluorescent molecules with potential applications in molecular electronics. Phosphonated phenylethynyl phenothiazine can be easily obtained in a four-step synthesis, yielding a molecule with a headgroup permitting surface linkage. Upon modifying hydroxylated polycrystalline zinc and iron, both covered with their respective native oxides, ultrathin organic layers were formed and investigated by use of infrared (IR) reflection spectroscopy, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), contact angle measurement, and ellipsometry. While stable monolayers with upright oriented organic molecules were formed on oxide-covered iron, multilayer formation is observed on oxide-covered zinc. ToF-SIMS measurements reveal a bridging bidentate bonding state of the organic compound on oxide-covered iron, whereas monodentate complexes were observed on oxide-covered zinc. Both organically modified and unmodified surfaces exhibit reactive wetting, but organic modification makes the surfaces initially more hydrophobic. Cyclic voltammetry (CV) indicates redox activity of the multilayers formed on oxide-covered zinc. On the other hand, the monolayers on oxide-covered iron desorb after electrochemical modifications in the state of the oxide, but are stable at open circuit conditions. Exploiting an electronic coupling of phenothiazines to oxides may thus assist in corrosion protection. PMID:26057456

  8. Effect of bicarbonate on iron-mediated oxidation of low-density lipoprotein

    NASA Astrophysics Data System (ADS)

    Arai, Hirofumi; Berlett, Barbara S.; Chock, P. Boon; Stadtman, Earl R.

    2005-07-01

    Oxidation of low-density lipoprotein (LDL) may play an important role in atherosclerosis. We studied the effects of bicarbonate/CO2 and phosphate buffer systems on metal ion-catalyzed oxidation of LDL to malondialdehyde (MDA) and to protein carbonyl and MetO derivatives. Our results revealed that LDL oxidation in mixtures containing free iron or heme derivatives was much greater in bicarbonate/CO2 compared with phosphate buffer. However, when copper was substituted for iron in these mixtures, the rate of LDL oxidation in both buffers was similar. Iron-catalyzed oxidation of LDL was highly sensitive to inhibition by phosphate. Presence of 0.3-0.5 mM phosphate, characteristic of human serum, led to 30-40% inhibition of LDL oxidation in bicarbonate/CO2 buffer. Iron-catalyzed oxidation of LDL to MDA in phosphate buffer was inhibited by increasing concentrations of albumin (10-200 ?M), whereas MDA formation in bicarbonate/CO2 buffer was stimulated by 10-50 ?M albumin but inhibited by higher concentrations. However, albumin stimulated the oxidation of LDL proteins to carbonyl derivatives at all concentrations examined in both buffers. Conversion of LDL to MDA in bicarbonate/CO2 buffer was greatly stimulated by ADP, ATP, and EDTA but only when EDTA was added at a concentration equal to that of iron. At higher than stoichiometric concentrations, EDTA prevented oxidation of LDL. Results of these studies suggest that interactions between bicarbonate and iron or heme derivatives leads to complexes with redox potentials that favor the generation of reactive oxygen species and/or to the generation of highly reactive CO2 anion or bicarbonate radical that facilitates LDL oxidation. Freely available online through the PNAS open access option.Abbreviations: LDL, low-density lipoprotein; MDA, malondialdehyde; MetO, methionine sulfoxide.

  9. Size dependence of inter- and intra-cluster interactions in core-shell iron-iron oxide nanoclusters

    SciTech Connect

    Kaur, Maninder; McCloy, John S.; Jiang, Weilin; Yao, Qi; Qiang, You

    2012-06-15

    The room temperature magnetic properties of core-shell iron-iron oxide nanoclusters (NCs) synthesized by a cluster deposition system have been investigated, and their dependence on mean cluster size has been discussed. In this study, the surface/boundary spins of clusters were not frozen and were thermally activated during the measurements. The inter-cluster interactions between clusters and intra-cluster interactions between the iron core (ferromagnetic) and iron oxide shell (ferrimagnetic) have been investigated by field dependent isothermal remanent magnetization and dc demagnetization measurements at room temperature. The Henkel plot and delta M plot support the existence of dipolar inter-cluster interactions which become stronger with the growth of cluster size. The derivative of the initial magnetization curve implies that smaller clusters require less field and time than the bigger ones to overcome various energy barriers before aligning along the field direction. Coercive field and magnetization are also correlated with the interaction parameters. To compare the room temperature magnetic results, one system was studied at low temperature, where exchange coupling at the interface between the oxide and metallic phases was observed through bias effect and anisotropy enhancement.

  10. Iron oxide nanoparticles embedded onto 3D mesochannels of KIT-6 with different pore diameters and their excellent magnetic properties.

    PubMed

    Alam, Sher; Anand, Chokkalingam; Zaidi, S M J; Naidu, Talapaneni Siddulu; Al-Deyab, Salem S; Vinu, Ajayan

    2011-03-01

    Here, we report the results of our detailed study on the fabrication of iron oxide magnetic nanoparticles confined in mesoporous silica KIT-6 with a 3D structure and large, tunable pore diameters. It was confirmed by XRD, nitrogen adsorption, high-resolution (HR) TEM, and magnetic measurements that highly dispersed iron oxide nanoparticles are occupied inside the mesochannels of KIT-6. We also demonstrated that the size of the iron oxide nanoparticle can be controlled by simply changing the pore diameter of the KIT-6 and the weight percentage of the iron oxide nanoparticles. The effect of the weight percentage and size of the iron oxide nanoparticles, and the textural parameters of the support on the magnetic properties of iron oxide/KIT-6 has been demonstrated. The magnetization increases with decreasing iron content in the pore channels of KIT-6, whereas coercivity decreases for the same samples. Among the KIT-6 materials studied, KIT-6 with 7.5?wt?% of iron showed the highest saturation magnetic moment and magnetic remanence. However, all the samples register a coercivity of around 2000?Oe, which is generally observed for the hard magnetic materials. In addition, we have found a paramagnetic-to-superparamagnetic transition at low temperature for samples with different iron content at low temperature. The cause for this exciting transition is also discussed in detail. Magnetic properties of the iron oxide loaded KIT-6 were also compared with pure iron oxide and iron oxide loaded over SBA-15. It was found that iron oxide loaded KIT-6 showed the highest magnetization due to its 3D structure and large pore volume. The pore diameter of the iron oxide loaded KIT-6 support also plays a critical role in controlling the magnetization and the blocking temperature, which has a direct relation to the particle diameter and increases from 48 to 63?K with an increase in the pore diameter of the support from 8 to 11.3?nm. PMID:21344658

  11. An inorganic geochemical argument for coupled anaerobic oxidation of methane and iron reduction in marine sediments.

    PubMed

    Riedinger, N; Formolo, M J; Lyons, T W; Henkel, S; Beck, A; Kasten, S

    2014-03-01

    Here, we present results from sediments collected in the Argentine Basin, a non-steady state depositional marine system characterized by abundant oxidized iron within methane-rich layers due to sediment reworking followed by rapid deposition. Our comprehensive inorganic data set shows that iron reduction in these sulfate and sulfide-depleted sediments is best explained by a microbially mediated process-implicating anaerobic oxidation of methane coupled to iron reduction (Fe-AOM) as the most likely major mechanism. Although important in many modern marine environments, iron-driven AOM may not consume similar amounts of methane compared with sulfate-dependent AOM. Nevertheless, it may have broad impact on the deep biosphere and dominate both iron and methane cycling in sulfate-lean marine settings. Fe-AOM might have been particularly relevant in the Archean ocean, >2.5 billion years ago, known for its production and accumulation of iron oxides (in iron formations) in a biosphere likely replete with methane but low in sulfate. Methane at that time was a critical greenhouse gas capable of sustaining a habitable climate under relatively low solar luminosity, and relationships to iron cycling may have impacted if not dominated methane loss from the biosphere. PMID:24460948

  12. Iron supplementation and oxidative damage to DNA in healthy individuals with high plasma ascorbate.

    PubMed

    Proteggente, A R; England, T G; Rice-Evans, C A; Halliwell, B

    2001-10-19

    Previously, we have investigated the potential for a pro-oxidant interaction of iron and ascorbate in vivo in iron and ascorbate cosupplementation or ascorbate supplementation studies. In this study, for the first time, the effects of iron supplementation on oxidative damage to DNA in healthy individuals with plasma ascorbate levels at the upper end of the normal range were examined. Forty female and male volunteers (mean plasma ascorbate approximately equal to 70 micromol/L) were supplemented with a daily dose of syrup (ferrous glycine sulphate equivalent to 12.5 mg iron) for 6 weeks. Serum ferritin, transferrin bound iron, % saturation of transferrin and plasma ascorbate were assessed and the mean dietary intakes of all subjects were estimated through food frequency questionnaires. Oxidative damage to DNA bases from white blood cells was measured by gas chromatography/mass spectrometry with selected-ion monitoring (GC/MS-SIM), using isotope-labelled standards for quantification. Iron supplementation did not affect any of the iron status parameters. There were also no detrimental effects, over the period under investigation, in terms of oxidative damage to DNA. However, the effects of larger doses or of longer supplementation periods should also be investigated. PMID:11594780

  13. Effect of iron oxide loading on the phase transformation and physicochemical properties of nanosized mesoporous ZrO{sub 2}

    SciTech Connect

    Basahel, S.N. [Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, 21589 Jeddah (Saudi Arabia)] [Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, 21589 Jeddah (Saudi Arabia); Ali, Tarek T. [Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, 21589 Jeddah (Saudi Arabia) [Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, 21589 Jeddah (Saudi Arabia); Chemistry Department, Faculty of Science, Sohag University, 82524 Sohag (Egypt); Narasimharao, K. [Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, 21589 Jeddah (Saudi Arabia)] [Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, 21589 Jeddah (Saudi Arabia); Bagabas, A.A. [Petrochemicals Research Institute (PRI), King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, 11442 Riyadh (Saudi Arabia)] [Petrochemicals Research Institute (PRI), King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, 11442 Riyadh (Saudi Arabia); Mokhtar, M., E-mail: mmokhtar2000@yahoo.com [Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, 21589 Jeddah (Saudi Arabia)

    2012-11-15

    Highlights: ? Modified preparation method for nanosized iron oxide supported ZrO{sub 2} catalysts. ? Systematic study of effect of high iron oxide loading over ZrO{sub 2}. ? Influence of iron oxide on the stabilization of tetragonal ZrO{sub 2} phase. ? A mesoporous nature of zirconia changed upon changing iron oxide loading. ? Surface to bulk migration of iron oxide evidenced by XPS technique. -- Abstract: Mesoporous ZrO{sub 2}-supported iron oxide materials were prepared with nominal loadings of iron oxide of 5, 10, 15 and 20 wt.% using a modified co-precipitation method. The physicochemical properties of the catalysts were characterized by thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, Raman spectroscopy, high resolution transmission electron microscopy, N{sub 2} adsorption, X-ray photoelectron spectroscopy and infrared spectroscopy methods. A delay in the ZrO{sub 2} phase transformation as a result of the incorporation of iron was determined using TG/DSC measurements. XRD, Raman spectroscopy and HRTEM results revealed that an increase of iron oxide loading from 5 to 15 wt.% enhanced the transformation of the monoclinic to tetragonal phase. Unexpectedly, 20 wt.% iron oxide loading was required for complete tetragonal structure stabilization due to the mesoporosity of the ZrO{sub 2} support. Iron oxide loadings from 5 to 15 wt.% showed an increase in the BET-surface area due to the presence of amorphous iron oxide on the surface. XPS and FTIR results indicated that increasing the iron oxide content to 20 wt.% resulted in stabilization of the tetragonal zirconia phase as a result of surface-to-bulk migration and incorporation of Fe{sup 3+} ions in the ZrO{sub 2} lattice.

  14. Iron Oxides from Volcanic Soils as Potential Catalysts in the Water Gas Shift Reaction

    SciTech Connect

    Pizarro, C.; Escudey, M.; Moya, S.A. [Facultad de Quimica y Biologia, USACH, Av. L. B. O'Higgins 3363, Santiago 7254758 (Chile); Fabris, J.D. [Departamento de Quimica, ICEx-UFMG, Pampulha, 31270-901 Belo Horizonte, MG (Brazil)

    2005-04-26

    This study was focused on changes of the iron oxide mineralogy with temperature of two Chilean soils (Andisol and Ultisol) derived from volcanic materials and their use as iron-based catalysts in the water gas shift reaction (WGSR). Ultisol materials produced about twice as much hydrogen than did those from Andisol upon WGSR, but in both cases hydrogen yielding increased as the heating temperature of the soil materials increased from 124 deg. C to 500 deg. C. The room temperature Moessbauer spectra showed an increase of the relative proportion of the magnetically ordered components as temperature increased. Higher heating temperature produced a negative effect on the catalytic activity, whereas the organic matter destruction led to a positive effect, due to an increasing exposition of the iron oxide surfaces; heating the soil sample at 600 deg. C induced changes on the iron oxide mineralogy with a significant decrease of the catalytic activity.

  15. Magnetic iron oxides in the cementation technology of the boron-containing radioactive waste

    NASA Astrophysics Data System (ADS)

    Fedotov, M. A.; Gorbunova, O. A.; Fedorova, O. V.; Folmanis, G. E.; Kovalenko, L. V.

    2015-04-01

    Two ways of synthesis of non-detachable dispersed particles of magnetic materials useful for the boron-containing waste cementation process regulation were developed. Powder XRD showed that the method of carbothermic recovery of nanoscale iron hydroxide allows obtaining a mixture of iron oxides with content of the magnetic phase up to 70%. Method of low-temperature hydrogen reduction of the raw materials allows obtaining various compositions of a-iron and iron oxides with the possibility to change the size of the final particles in a wide range. The possibility of using composites of magnetic iron oxides and metal oxide compositions instead of ferromagnetic rods with VEP of boron-containing liquid radioactive waste in the fluidized field was studied. It was shown that the use of fine and nano particles of the iron oxides in the pre-treatment of the boron-containing LRW increases the strength of the final compounds and accelerates the cement setting compounds from 13 to 5-9 days.

  16. Metal regeneration of iron chelates in nitric oxide scrubbing

    DOEpatents

    Chang, Shih-Ger (El Cerrito, CA); Littlejohn, David (Oakland, CA); Shi, Yao (Berkeley, CA)

    1997-08-19

    The present invention relates to a process of using metal particles to reduce NO to NH.sub.3. More specifically, the invention concerns an improved process to regenerate iron (II) (CHELATE) by reduction of iron (II) (CHELATE) (NO) complex, which process comprises: a) contacting an aqueous solution containing iron (II) (CHELATE) (NO) with metal particles at between about 20.degree. and 90.degree. C. to reduce NO present, produce ammonia or an ammonium ion, and produce free iron (II) (CHELATE) at a pH of between about 3 and 8. The process is useful to remove NO from flue gas and reduce pollution.

  17. Iron oxidation and biomineralization by Mariprofundus ferrooxydans, a deep-sea microaerophilic lithoautotroph

    NASA Astrophysics Data System (ADS)

    Chan, C. S.; Emerson, D.; Fakra, S.; Edwards, K. J.

    2007-12-01

    The ocean crust contains a large reservoir of reduced iron, available for microbial energy generation. Some of this ferrous iron is mobilized by fluids in hydrothermal fields at seamounts and mid-ocean ridges. A microaerophilic iron oxidizer, Mariprofundus ferrooxydans has been identified (by molecular methods and microscopy) at various sites, and appears to be a key iron-oxidizing bacterium (FeOB) in the deep sea. Originally isolated from microbial mats near vents at the Loihi Seamount in Hawaii, Mariprofundus is distinctive because it forms an extracellular iron-mineralized stalk-like structure. We aim to understand its metabolism and mineral formation using a multidisciplinary approach, including electron microscopy, x-ray spectroscopy, time-lapse light microscopic imaging of live cells, and genomic and biochemical analyses. Microscopy and spectroscopy work shows that as the cells grow, they excretes iron and organic-rich fibrils that make up the stalk, at a rate of ~2 microns/hr. Stalk growth appears to be parallel to the direction of Fe and oxygen gradients. The Mariprofundus genome contains several terminal oxidases/peroxidases, including two cbb3-type cytochrome oxidases with a high affinity for oxygen, consistent with the microaerophilic lifestyle of these organisms. However, we have not identified genes for metabolisms other than aerobic iron oxidation, nor have we found any genes similar to known or suspected iron oxidases, though the genome (2.87 Mb) is rich in cytochromes (32 of 2922 genes). Thus, we are performing experiments to extract and analyze proteins from both cultured and environmental samples in order to find ones that will oxidize iron. UV-Vis spectra of extracts suggest that c-type cytochromes are particularly abundant, so these are candidates for further investigation. In combination with the microscopy and spectroscopy studies, these are the first steps towards understanding the complete pathway of iron from uptake through mineral formation and growth.

  18. Acute iron overload and oxidative stress in brain.

    PubMed

    Piloni, Natacha E; Fermandez, Virginia; Videla, Luis A; Puntarulo, Susana

    2013-12-01

    An in vivo model in rat was developed by intraperitoneally administration of Fe-dextran to study oxidative stress triggered by Fe-overload in rat brain. Total Fe levels, as well as the labile iron pool (LIP) concentration, in brain from rats subjected to Fe-overload were markedly increased over control values, 6h after Fe administration. In this in vivo Fe overload model, the ascorbyl (A)/ascorbate (AH(-)) ratio, taken as oxidative stress index, was assessed. The A/AH(-) ratio in brain was significantly higher in Fe-dextran group, in relation to values in control rats. Brain lipid peroxidation indexes, thiobarbituric acid reactive substances (TBARS) generation rate and lipid radical (LR) content detected by Electron Paramagnetic Resonance (EPR), in Fe-dextran supplemented rats were similar to control values. However, values of nuclear factor-kappaB deoxyribonucleic acid (NF?B DNA) binding activity were significantly increased (30%) after 8h of Fe administration, and catalase (CAT) activity was significantly enhanced (62%) 21h after Fe administration. Significant enhancements in Fe content in cortex (2.4 fold), hippocampus (1.6 fold) and striatum (2.9 fold), were found at 6h after Fe administration. CAT activity was significantly increased after 8h of Fe administration in cortex, hippocampus and striatum (1.4 fold, 86, and 47%, respectively). Fe response in the whole brain seems to lead to enhanced NF-?B DNA binding activity, which may contribute to limit oxygen reactive species-dependent damage by effects on the antioxidant enzyme CAT activity. Moreover, data shown here clearly indicate that even though Fe increased in several isolated brain areas, this parameter was more drastically enhanced in striatum than in cortex and hippocampus. However, comparison among the net increase in LR generation rate, in different brain areas, showed enhancements in cortex lipid peroxidation, without changes in striatum and hippocampus LR generation rate after 6h of Fe overload. This information has potential clinical relevance, as it could be the key to understand specific brain damage occurring in conditions of Fe overload. PMID:24120471

  19. Millimeter wave ferromagnetic resonance in gallium-substituted ?-iron oxide

    SciTech Connect

    Chao, Liu, E-mail: liu.chao@tufts.edu; Afsar, Mohammed N. [Department of Electrical and Computer Engineering, Tufts University, Medford, Massachusetts 02155 (United States); Ohkoshi, Shin-ichi [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2014-05-07

    In millimeter wave frequency range, hexagonal ferrites with high uniaxial anisotropic magnetic fields are used as absorbers. These ferrites include M-type barium ferrite (BaFe{sub 12}O{sub 19}) and strontium ferrite (SrFe{sub 12}O{sub 19}), which have natural ferromagnetic resonant frequency range from 40 GHz to 60?GHz. However, the higher frequency range lacks suitable materials that support the higher frequency ferromagnetic resonance. A new series of gallium-substituted ?-iron oxides (?-Ga{sub x}Fe{sub 2?x}O{sub 3}) are synthesized which have ferromagnetic resonant frequencies appearing over the frequency range 30 GHz–150 GHz. The ?-Ga{sub x}Fe{sub 2?x}O{sub 3} is synthesized by the combination of reverse micelle and sol-gel techniques or the sol-gel method only. The particle sizes are observed to be smaller than 100 nm. In this paper, the free space magneto-optical approach has been employed to study these newly developed ?-Ga{sub x}Fe{sub 2?x}O{sub 3} particles in millimeter waves. This technique enables to obtain precise transmission spectra to determine the dielectric and magnetic properties of both isotropic and anisotropic ferrites in the millimeter wave frequency range from a single set of direct measurements. The transmittance and absorbance spectra of ?-Ga{sub x}Fe{sub 2?x}O{sub 3} are shown in this paper. Strong ferromagnetic resonances at different frequencies determined by the x parameter are found.

  20. Iron oxide nanoparticle hyperthermia and radiation cancer treatment

    NASA Astrophysics Data System (ADS)

    Cassim, S. M.; Giustini, A. J.; Petryk, A. A.; Strawbridge, R. A.; Hoopes, P. J.

    2009-02-01

    It is established that heat can enhance the effect of radiation cancer treatment. Due to the ability to localize thermal energy using nanoparticle hyperthermia, as opposed to other, less targeted, hyperthermia modalities, it appears such enhancement could be accomplished without complications normally associated with systemic or regional hyperthermia. This study employs non-curative (suboptimal), doses of heat and radiation, in an effort to determine the therapeutic enhancement potential for IONP hyperthermia and radiation. Methods: MTG-B murine breast adenocarcinoma cell are inoculated into the right flanks of female CH3/HEJ mice and grown to volumes of 150mm3+ /- 40 mm3. A single dose of 15 Gy (6 MeV) radiation was uniformly delivered to the tumor. A pre-defined thermal dose is delivered by direct injection of iron oxide nanoparticles into the tumor. By adjusting the field strength of the 160 KHz alternating magnetic field (AMF) an intra-tumoral temperature between 41.5 and 43 degrees Celsius was maintained for 10min. The alternating magnetic field was delivered by a water-cooled 36mm diameter square copper tube induction coil operating at 160 kHz with variable magnet field strengths up to 450 Oe . The primary endpoint of the study is the number of days required for the tumor to achieve a volume 3 fold greater than the volume at the time of treatment (tumor regrowth delay). Results: Preliminary results suggest the addition of a modest IONP hyperthermia to 15 Gy radiation achieved an approximate 50% increase in tumor regrowth delay as compared to a 15 Gy radiation treatment alone. The therapeutic effects of IONP heat and radiation combined were considered additive, however in mice that demonstrated complete response (no tumor present after 30 days), the effect was considered superadditive or synergistic. Although this data is very encouraging from a multimodality cancer therapy standpoint, additional temporal and dose related information is clearly necessary to optimize the therapy.

  1. Water oxidation catalysis with nonheme iron complexes under acidic and basic conditions: homogeneous or heterogeneous?

    PubMed

    Hong, Dachao; Mandal, Sukanta; Yamada, Yusuke; Lee, Yong-Min; Nam, Wonwoo; Llobet, Antoni; Fukuzumi, Shunichi

    2013-08-19

    Thermal water oxidation by cerium(IV) ammonium nitrate (CAN) was catalyzed by nonheme iron complexes, such as Fe(BQEN)(OTf)2 (1) and Fe(BQCN)(OTf)2 (2) (BQEN = N,N'-dimethyl-N,N'-bis(8-quinolyl)ethane-1,2-diamine, BQCN = N,N'-dimethyl-N,N'-bis(8-quinolyl)cyclohexanediamine, OTf = CF3SO3(-)) in a nonbuffered aqueous solution; turnover numbers of 80 ± 10 and 20 ± 5 were obtained in the O2 evolution reaction by 1 and 2, respectively. The ligand dissociation of the iron complexes was observed under acidic conditions, and the dissociated ligands were oxidized by CAN to yield CO2. We also observed that 1 was converted to an iron(IV)-oxo complex during the water oxidation in competition with the ligand oxidation. In addition, oxygen exchange between the iron(IV)-oxo complex and H2(18)O was found to occur at a much faster rate than the oxygen evolution. These results indicate that the iron complexes act as the true homogeneous catalyst for water oxidation by CAN at low pHs. In contrast, light-driven water oxidation using [Ru(bpy)3](2+) (bpy = 2,2'-bipyridine) as a photosensitizer and S2O8(2-) as a sacrificial electron acceptor was catalyzed by iron hydroxide nanoparticles derived from the iron complexes under basic conditions as the result of the ligand dissociation. In a buffer solution (initial pH 9.0) formation of the iron hydroxide nanoparticles with a size of around 100 nm at the end of the reaction was monitored by dynamic light scattering (DLS) in situ and characterized by X-ray photoelectron spectra (XPS) and transmission electron microscope (TEM) measurements. We thus conclude that the water oxidation by CAN was catalyzed by short-lived homogeneous iron complexes under acidic conditions, whereas iron hydroxide nanoparticles derived from iron complexes act as a heterogeneous catalyst in the light-driven water oxidation reaction under basic conditions. PMID:23895380

  2. Partial oxidation (?aging?) and surface modification decrease the toxicity of nano-sized zero valent iron.

    EPA Science Inventory

    Nanosize zero-valent iron (nZVI) is used as a redox-active catalyst for in situ remediation of contaminated ground waters. In aqueous environments, nZVI oxidizes over time (i.e., ?ages?) to magnetite and other oxides. For remediation, hi...

  3. Oxidative stress-mediated hepatotoxicity of iron and copper: Role of Kupffer cells

    Microsoft Academic Search

    Luis A. Videla; Virginia Fernández; Gladys Tapia; Patricia Varela

    2003-01-01

    Iron- or copper-mediated catalysis leads to the generation of reactive oxygen species (ROS) that can attack biomolecules directly, with the consequent enhancement in membrane lipid peroxidation, DNA damage, and protein oxidation. Reactive nitrogen species (RNS) can also be formed, leading to nitration of aromatic structures in addition to the oxidative deterioration of cellular components. Kupffer cells, the resident macrophages of

  4. Enzymatic- and temperature-sensitive controlled release of ultrasmall superparamagnetic iron oxides (USPIOs)

    PubMed Central

    2011-01-01

    Background Drug and contrast agent delivery systems that achieve controlled release in the presence of enzymatic activity are becoming increasingly important, as enzymatic activity is a hallmark of a wide array of diseases, including cancer and atherosclerosis. Here, we have synthesized clusters of ultrasmall superparamagnetic iron oxides (USPIOs) that sense enzymatic activity for applications in magnetic resonance imaging (MRI). To achieve this goal, we utilize amphiphilic poly(propylene sulfide)-bl-poly(ethylene glycol) (PPS-b-PEG) copolymers, which are known to have excellent properties for smart delivery of drug and siRNA. Results Monodisperse PPS polymers were synthesized by anionic ring opening polymerization of propylene sulfide, and were sequentially reacted with commercially available heterobifunctional PEG reagents and then ssDNA sequences to fashion biofunctional PPS-bl-PEG copolymers. They were then combined with hydrophobic 12 nm USPIO cores in the thin-film hydration method to produce ssDNA-displaying USPIO micelles. Micelle populations displaying complementary ssDNA sequences were mixed to induce crosslinking of the USPIO micelles. By design, these crosslinking sequences contained an EcoRV cleavage site. Treatment of the clusters with EcoRV results in a loss of R2 negative contrast in the system. Further, the USPIO clusters demonstrate temperature sensitivity as evidenced by their reversible dispersion at ~75°C and re-clustering following return to room temperature. Conclusions This work demonstrates proof of concept of an enzymatically-actuatable and thermoresponsive system for dynamic biosensing applications. The platform exhibits controlled release of nanoparticles leading to changes in magnetic relaxation, enabling detection of enzymatic activity. Further, the presented functionalization scheme extends the scope of potential applications for PPS-b-PEG. Combined with previous findings using this polymer platform that demonstrate controlled drug release in oxidative environments, smart theranostic applications combining drug delivery with imaging of platform localization are within reach. The modular design of these USPIO nanoclusters enables future development of platforms for imaging and drug delivery targeted towards proteolytic activity in tumors and in advanced atherosclerotic plaques. PMID:21352596

  5. Effects of hydrazine hydrate treatment on the performance of reduced graphene oxide film as counter electrode in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Qiu, Leifei; Zhang, Haiyan; Wang, Wenguang; Chen, Yiming; Wang, Rong

    2014-11-01

    The reduced graphene oxide (RGO) counter electrodes were prepared by drop casting method and followed by heat treatment. The as-prepared RGO counter electrodes were used as substitution for Pt counter electrode in dye-sensitized solar cells (DSSCs). The effects of hydrazine hydrate in graphene oxide (GO) suspension on the performance of RGO counter electrodes were investigated. The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements revealed that a moderate amount of hydrazine hydrate can enhance the catalytic activity of the RGO film toward the reduction of I3- and decrease the sheet resistance of the film. The efficiency (?) of DSSC based on the RGO counter electrodes with optimum addition of hydrazine hydrate increased from 1.826% to 2.622% under a simulated solar illumination of 100 mW cm-2 (AM 1.5).

  6. What's the real role of iron-oxides in the optical properties of dust aerosols?

    NASA Astrophysics Data System (ADS)

    Zhang, X. L.; Wu, G. J.; Zhang, C. L.; Xu, T. L.; Zhou, Q. Q.

    2015-02-01

    Iron oxides compounds constitute an important component of mineral dust aerosol. Several previous studies have shown that these minerals are strong absorbers at visible wavelengths and thus that they play a critical role in the overall climate forcing caused by dust aerosol. When compiling a database of complex refractive indices of possible mineral species of iron-oxides to study their optical properties, we found that uniformly continuous optical constants for a single type of iron-oxides in the wavelength range between 0.2 and 50 ?m is very scarce and that the use of hematite to represent all molecular or mineral iron-oxides types is a popular hypothesis. However, the crucial problem is that three continuous datasets for complex refractive indices of hematite are employed in climate models, but there are significant differences between them. Thus, the real role of iron-oxides in the optical properties of dust aerosols becomes a key scientific question, and we address this problem by considering different refractive indices, size distributions, and more logical weight fractions and mixing states of hematite. Based on the microscopic observations, a semi-external mixture that employs an external mixture between Fe-aggregates and other minerals and partly internal mixing between iron-oxides and aluminosilicate particles is advised as the optimal approximation. The simulations demonstrate that hematite with a spectral refractive indices from Longtin et al. (1988) shows approximately equal absorbing capacity to the mineral illite over the whole wavelength region from 0.55 to 2.5 ?m, and only enhances the optical absorption of aerosol mixture at ? < 0.55 ?m. Using the dataset from Querry (1985) may overestimate the optical absorption of hematite at both visible and near-infrared wavelengths. More laboratory measurements of the refractive index of iron-oxides, especially for hematite and goethite in the visible spectrum, should therefore be taken into account when assessing the effect of mineral dust on climate forcing.

  7. Laser sintering of magnesia with nanoparticles of iron oxide and aluminum oxide

    NASA Astrophysics Data System (ADS)

    García, L. V.; Mendivil, M. I.; Roy, T. K. Das; Castillo, G. A.; Shaji, S.

    2015-05-01

    Nanoparticles of iron oxide (Fe2O3, 20-40 nm) and aluminum oxide (Al2O3, 50 nm) were mixed in different concentrations (3, 5 and 7 wt%) in a magnesium oxide (MgO) matrix. The mixture pellet was irradiated with 532 nm output from a Q-switched Nd:YAG laser using different laser fluence and translation speed for sintering. The refractory samples obtained were analyzed using X-ray diffraction technique, scanning electron microscopy and X-ray photoelectron spectroscopy. The results showed that the samples irradiated at translation speed of 110 ?m/s and energy fluence of 1.7 J/cm2 with a concentration of 5 and 7 wt% of Fe2O3 presented the MgFe2O4 spinel-type phase. With the addition of Al2O3 nanoparticles, at a translation speed of 110 ?m/s and energy fluence of 1.7 J/cm2, there were the formations of MgAl2O4 spinel phase. The changes in morphologies and microstructure due to laser irradiation were analyzed.

  8. Nonequilibrium iron oxide formation in some low-mass post-asymptotic giant branch stars

    NASA Astrophysics Data System (ADS)

    Rietmeijer, Frans J. M.

    1992-11-01

    Using experimental evidence that under highly oxidizing conditions gamma-Fe2O3 (maghemite) and Fe3O4 display refractory behavior, it is proposed that very low C/O ratios, that could be unique to evolving AGB stars, induce nonequilibrium formation of ferromagnetic iron oxide grains along with chondritic dust. The oxides are preferentially fractionated from chondritic dust in the stellar magnetic field which could account for the observed extreme iron underabundance in their photosphere. A search for the 1-2.5-micron IR absorption feature, or for diagnostic magnetite and maghemite IR absorption features, could show the validity of the model proposed.

  9. Degradation of organophosphorus pesticide parathion methyl on nanostructured titania-iron mixed oxides

    NASA Astrophysics Data System (ADS)

    Henych, Ji?í; Štengl, Václav; Slušná, Michaela; Matys Grygar, Tomáš; Janoš, Pavel; Kurá?, Pavel; Štastný, Martin

    2015-07-01

    Titania-iron mixed oxides with various Ti:Fe ratio were prepared by homogeneous hydrolysis of aqueous solutions of titanium(IV) oxysulphate and iron(III) sulphate with urea as a precipitating agent. The synthesized samples were characterized by X-ray diffraction, Raman and infrared spectroscopy, scanning and transmission electron microscopy, XRF analysis, specific surface area (BET) and porosity determination (BJH). These oxides were used for degradation of organophosporus pesticide parathion methyl. The highest degradation efficiency approaching <70% was found for the samples with Ti:Fe ratio 0.25:1 and 1:0.25. Contrary, parathion methyl was not degraded on the surfaces of pure oxides. In general, the highest degradation rate exhibited samples consisted of the iron or titanium oxide containing a moderate amount of the admixture. However, distinct correlations between the degradation rate and the sorbent composition were not identified.

  10. Production of ketones from sewage sludge over zirconia-supporting iron oxide catalysts in a steam atmosphere

    Microsoft Academic Search

    Eri Fumoto; Yosuke Mizutani; Teruoki Tago; Takao Masuda

    2006-01-01

    Recovering useful hydrocarbons from sewage sludge using zirconia-supporting iron oxide catalysts was investigated. Zirconia has activity for decomposing water molecules to generate active oxygen and hydrogen species. These oxygen species spill over to the surface of iron oxide and react with hydrocarbons to produce oxygen-containing organic chemicals such as acetone. Thus, zirconia-supporting iron oxide catalyst has two kinds of active

  11. Iron regulatory protein 1 outcompetes iron regulatory protein 2 in regulating cellular iron homeostasis in response to nitric oxide.

    PubMed

    Sty?, Agnieszka; Galy, Bruno; Starzy?ski, Rafal R; Smuda, Ewa; Drapier, Jean-Claude; Lipi?ski, Pawel; Bouton, Cécile

    2011-07-01

    In mammals, iron regulatory proteins (IRPs) 1 and 2 posttranscriptionally regulate expression of genes involved in iron metabolism, including transferrin receptor 1, the ferritin (Ft) H and L subunits, and ferroportin by binding mRNA motifs called iron responsive elements (IREs). IRP1 is a bifunctional protein that mostly exists in a non-IRE-binding, [4Fe-4S] cluster aconitase form, whereas IRP2, which does not assemble an Fe-S cluster, spontaneously binds IREs. Although both IRPs fulfill a trans-regulatory function, only mice lacking IRP2 misregulate iron metabolism. NO stimulates the IRE-binding activity of IRP1 by targeting its Fe-S cluster. IRP2 has also been reported to sense NO, but the intrinsic function of IRP1 and IRP2 in NO-mediated regulation of cellular iron metabolism is controversial. In this study, we exposed bone marrow macrophages from Irp1(-/-) and Irp2(-/-) mice to NO and showed that the generated apo-IRP1 was entirely responsible for the posttranscriptional regulation of transferrin receptor 1, H-Ft, L-Ft, and ferroportin. The powerful action of NO on IRP1 also remedies the defects of iron storage found in IRP2-null bone marrow macrophages by efficiently reducing Ft overexpression. We also found that NO-dependent IRP1 activation, resulting in increased iron uptake and reduced iron sequestration and export, maintains enough intracellular iron to fuel the Fe-S cluster biosynthetic pathway for efficient restoration of the citric acid cycle aconitase in mitochondria. Thus, IRP1 is the dominant sensor and transducer of NO for posttranscriptional regulation of iron metabolism and participates in Fe-S cluster repair after exposure to NO. PMID:21566147

  12. Role of manganese in protection against oxidative stress under iron starvation in cyanobacterium Anabaena 7120.

    PubMed

    Kaushik, Manish Singh; Srivastava, Meenakshi; Verma, Ekta; Mishra, Arun Kumar

    2015-06-01

    The cyanobacterium Anabaena sp. PCC 7120 was grown in presence and absence of iron to decipher the role of manganese in protection against the oxidative stress under iron starvation and growth, manganese uptake kinetics, antioxidative enzymes, lipid peroxidation, electrolyte leakage, thiol content, total peroxide, proline and NADH content was investigated. Manganese supported the growth of cyanobacterium Anabaena 7120 under iron deprived conditions where maximum uptake rate of manganese was observed with lower Km and higher Vmax values. Antioxidative enzymes were also found to be elevated in iron-starved conditions. Estimation of lipid peroxidation and electrolyte leakage depicted the role of manganese in stabilizing the integrity of the membrane which was considered as the prime target of oxygen free radicals in oxidative stress. The levels of total peroxide, thiol, proline and NADH content, which are the representative of oxidative stress response in Anabaena 7120, were also showed increasing trends in iron starvation. Hence, the results discerned, clearly suggested the role of manganese in protection against the oxidative stress in cyanobacterium Anabaena 7120 under iron starvation either due to its antioxidative properties or involvement as cofactor in a number of antioxidative enzymes. PMID:25572501

  13. Association of uranium with iron oxides typically formed on corroding steel surfaces.

    PubMed

    Dodge, C J; Francis, A J; Gillow, J B; Halada, G P; Eng, C; Clayton, C R

    2002-08-15

    Decontamination of metal surfaces contaminated with low levels of radionuclides is a major concern at Department of Energy facilities. The development of an environmentally friendly and cost-effective decontamination process requires an understanding of their association with the corroding surfaces. We investigated the association of uranium with the amorphous and crystalline forms of iron oxides commonly formed on corroding steel surfaces. Uranium was incorporated with the oxide by addition during the formation of ferrihydrite, goethite, green rust II, lepidocrocite, maghemite, and magnetite. X-ray diffraction confirmed the mineralogical form of the oxide. EXAFS analysis at the U L(III) edge showed that uranium was present in hexavalent form as a uranyl oxyhydroxide species with goethite, maghemite, and magnetite and as a bidentate inner-sphere complex with ferrihydrite and lepidocrocite. Iron was present in the ferric form with ferrihydrite, goethite, lepidocrocite, and maghemite; whereas with magnetite and green rust II, both ferrous and ferric forms were present with characteristic ferrous:total iron ratios of 0.65 and 0.73, respectively. In the presence of the uranyl ion, green rust II was converted to magnetite with concomitantreduction of uranium to its tetravalent form. The rate and extent of uranium dissolution in dilute HCl depended on its association with the oxide: uranium present as oxyhydroxide species underwent rapid dissolution followed by a slow dissolution of iron; whereas uranium present as an inner-sphere complex with iron resulted in concomitant dissolution of the uranium and iron. PMID:12214641

  14. Comparison of various iron chelators and prochelators as protective agents against cardiomyocyte oxidative injury.

    PubMed

    Jansová, Hana; Machá?ek, Miloslav; Wang, Qin; Hašková, Pavlína; Jirkovská, Anna; Pot??ková, Eliška; Kielar, Filip; Franz, Katherine J; Sim?nek, Tomáš

    2014-09-01

    Oxidative stress is a common denominator of numerous cardiovascular disorders. Free cellular iron catalyzes the formation of highly toxic hydroxyl radicals, and iron chelation may thus be an effective therapeutic approach. However, using classical iron chelators in diseases without iron overload poses risks that necessitate more advanced approaches, such as prochelators that are activated to chelate iron only under disease-specific oxidative stress conditions. In this study, three cell-membrane-permeable iron chelators (clinically used deferasirox and experimental SIH and HAPI) and five boronate-masked prochelator analogs were evaluated for their ability to protect cardiac cells against oxidative injury induced by hydrogen peroxide. Whereas the deferasirox-derived agents TIP and TRA-IMM displayed negligible protection and even considerable toxicity, the aroylhydrazone prochelators BHAPI and BSIH-PD provided significant cytoprotection and displayed lower toxicity after prolonged cellular exposure compared to their parent chelators HAPI and SIH, respectively. Overall, the most favorable properties in terms of protective efficiency and low inherent cytotoxicity were observed with the aroylhydrazone prochelator BSIH. BSIH efficiently protected both H9c2 rat cardiomyoblast-derived cells and isolated primary rat cardiomyocytes against hydrogen peroxide-induced mitochondrial and lysosomal dysregulation and cell death. At the same time, BSIH was nontoxic at concentrations up to its solubility limit (600 ?M) and in 72-h incubation. Hence, BSIH merits further investigation for prevention and/or treatment of cardiovascular disorders associated with a known (or presumed) component of oxidative stress. PMID:24992833

  15. Effect of bicarbonate on iron-mediated oxidation of low-density lipoprotein

    Microsoft Academic Search

    Hirofumi Arai; Barbara S. Berlett; P. Boon Chock; Earl R. Stadtman

    2005-01-01

    Oxidation of low-density lipoprotein (LDL) may play an important role in atherosclerosis. We studied the effects of bicarbonate\\/CO2 and phosphate buffer systems on metal ion-catalyzed oxidation of LDL to malondialdehyde (MDA) and to protein carbonyl and MetO derivatives. Our results revealed that LDL oxidation in mixtures containing free iron or heme derivatives was much greater in bicarbonate\\/CO2 compared with phosphate

  16. Magnetic resonance imaging of multifunctional pluronic stabilized iron-oxide nanoparticles in tumor-bearing mice

    Microsoft Academic Search

    Tapan K. Jain; Susan P. Foy; Bernadette Erokwu; Sanja Dimitrijevic; Christopher A. Flask; Vinod Labhasetwar

    2009-01-01

    We are investigating the magnetic resonance imaging characteristics of magnetic nanoparticles (MNPs) that consist of an iron-oxide magnetic core coated with oleic acid (OA), then stabilized with a pluronic or tetronic block copolymer. Since pluronics and tetronics vary structurally, and also in the ratio of hydrophobic (poly[propylene oxide]) and hydrophilic (poly[ethylene oxide]) segments in the polymer chain and in molecular

  17. Beta-thalassemia major and female fertility: the role of iron and iron-induced oxidative stress.

    PubMed

    Roussou, Paraskevi; Tsagarakis, Nikolaos J; Kountouras, Dimitrios; Livadas, Sarantis; Diamanti-Kandarakis, Evanthia

    2013-01-01

    Endocrine complications due to haemosiderosis are present in a significant number of patients with beta-thalassemia major (BTM) worldwide and often become barriers in their desire for parenthood. Thus, although spontaneous fertility can occur, the majority of females with BTM is infertile due to hypogonadotropic hypogonadism (HH) and need assisted reproductive techniques. Infertility in these women seems to be attributed to iron deposition and iron-induced oxidative stress (OS) in various endocrine organs, such as hypothalamus, pituitary, and female reproductive system, but also through the iron effect on other organs, such as liver and pancreas, contributing to the impaired metabolism of hormones and serum antioxidants. Nevertheless, the gonadal function of these patients is usually intact and fertility is usually retrievable. Meanwhile, a significant prooxidants/antioxidants imbalance with subsequent increased (OS) exists in patients with BTM, which is mainly caused by tissue injury due to overproduction of free radicals by secondary iron overload, but also due to alteration in serum trace elements and antioxidant enzymes. Not only using the appropriate antioxidants, essential trace elements, and minerals, but also regulating the advanced glycation end products, could probably reduce the extent of oxidative damage and related complications and retrieve BTM women's infertility. PMID:24396593

  18. Iron deficiency symptoms in grapevine as affected by the iron oxide and carbonate contents of model substrates

    Microsoft Academic Search

    I. Díaz; M. C. del Campillo; M. Cantos; J. Torrent

    2009-01-01

    Accurate assessment of the specific influence of calcium carbonate and iron (Fe) oxides in soil on Fe deficiency symptoms\\u000a in plants has so far been made difficult by the covariance between their contents in many soils populations. In order to overcome\\u000a this problem, we designed a completely randomized block experiment in which grapevine (cv. 161–49C) was pot-grown in substrates\\u000a consisting

  19. Diversity of Ferrous Iron-Oxidizing, Nitrate-Reducing Bacteria and their Involvement in Oxygen-Independent Iron Cycling

    Microsoft Academic Search

    Kristina L. Straub; Wilhelm A. Schönhuber; Berit E. E. Buchholz-Cleven; Bernhard Schink

    2004-01-01

    In previous studies, three different strains (BrG1, BrG2, and BrG3) of ferrous iron-oxidizing, nitrate-reducing bacteria were obtained from freshwater sediments. All three strains were facultative anaerobes and utilized a variety of organic substrates and molecular hydrogen with nitrate as electron acceptor. In this study, analyses of 16S rDNA sequences showed that strain BrG1 was affiliated with the genus Acidovorax, strain

  20. Various factors affecting photodecomposition of methylene blue by iron-oxides in an oxalate solution.

    PubMed

    Gulshan, Fahmida; Yanagida, Sayaka; Kameshima, Yoshikazu; Isobe, Toshihiro; Nakajima, Akira; Okada, Kiyoshi

    2010-05-01

    The effect of various factors on the photodecomposition of methylene blue (MB) by iron oxides calcined at various temperatures in various concentrations of oxalate solutions was investigated by illuminating with UV, visible and solar radiation. Iron oxides were prepared by a gel evaporation method and calcined at 200-700 degrees C. XRD showed that the as-synthesized iron oxides were amorphous, but formed maghemite (gamma-Fe(2)O(3)) at 200-400 degrees C and hematite (alpha-Fe(2)O(3)) at > or =500 degrees C. The effect of the various iron oxides, their contents, the oxalate concentration and wavelength of the light source (UV, visible and solar) were all found to strongly influence MB photodecomposition. The optimal contents of the iron oxides increased greatly from 25 to 2000 mg/L at higher calcining temperatures. The MB photodecomposition rate at each optimal iron oxide content was related to the calcining temperature in the order 700 degrees C6, consistent with the presence of iron-oxalate complexes. A much higher concentration of hydroxyl radicals was generated in the present system compared with those from a commercial TiO(2) (ST-01), as determined by the coumarin method. Since this process does not require the addition of hydrogen peroxide and shows good efficiency even under solar light, it is an economically viable method for pre-treating and/or decolorizing wastewaters containing dyes. PMID:20188391

  1. Iron

    MedlinePLUS

    Iron is a mineral that our bodies need for many functions. For example, iron is part of hemoglobin, a protein which carries ... It helps our muscles store and use oxygen. Iron is also part of many other proteins and ...

  2. The effect of iron oxide as an inhibition layer on iron-zinc reactions during Hot-Dip galvanizing

    NASA Astrophysics Data System (ADS)

    Jordan, C. E.; Marder, A. R.

    1998-04-01

    A study was conducted on the effect of a uniform oxide layer on the galvanizing reaction in 0.20 wt pct Al-Zn and pure Zn baths at 450 °C. In the 0.20 wt pct Al-Zn bath, poor wettability of the oxide layer was observed. No significant liquid Zn penetration of the oxide occurred and, therefore, attack of the steel substrate to form localized Fe-Zn growth did not occur. It was found that the iron oxide acted as a physical barrier or inhibition layer in the pure Zn bath, similar to the Fe2Al5 inhibition layer that forms at the steel interface in Al-Zn baths. The inhibition effect of the oxide in the pure Zn bath was temporary, since cracks and other macrodefects in the oxide acted as fast diffusion paths for Zn. Localized Fe-Zn growth (outbursts) formed at the steel/coating interface, and the number of outbursts was generally inversely proportional to the oxide layer thickness at constant immersion times. Increased immersion time for a constant oxide layer thickness led to an increase in the number of outbursts. These results simulate the diffusion short circuit mechanisms for Fe2Al5 inhibition layer breakdown in Al-containing Zn baths.

  3. Optimizing the Imperfect Oxidation Performance of Iron Aluminides

    Microsoft Academic Search

    Bruce A. Pint; K. L. More; P. F. Tortorelli; W. D. Porter; Ian G. Wright

    2001-01-01

    Iron aluminides (Fe3Al-based) are attractive corrosion-resistant, high temperature materials due to their excellent sulfidation resistance and large Al reservoir. However, at high temperatures (>1000°C) iron aluminides show excessive scale spallation compared to doped FeCrAl. This behavior is attributed to the inherently high coefficient of thermal expansion of these materials which results in higher cooling strains in the alumina scale. Although

  4. Solubilization of plutonium hydrous oxide by iron-reducing bacteria

    Microsoft Academic Search

    Patricia A. Rusin; Leticia Quintana; James R. Brainard; B. A. Strietelmeler; C. Drew Tait; Scott A. Ekberg; Phillip D. Palmer; Thomas W. Newton; David L. Clark

    1994-01-01

    The removal of plutonium from soils id challenging because of its strong sorption to soils and limited solubility, Microbial reduction of metals is known to affect the speciation and solubility of sparingly soluble metals in the environment, notably iron and manganese. The similarity in reduction potential for [alpha]-FeOOH(s) and hydrous PuO[sub 2](s) suggests that iron-reducing bacteria may also reduce and

  5. Effect of iron oxide loading on magnetoferritin structure in solution as revealed by SAXS and SANS.

    PubMed

    Melníková, L; Petrenko, V I; Avdeev, M V; Garamus, V M; Almásy, L; Ivankov, O I; Bulavin, L A; Mitróová, Z; Kop?anský, P

    2014-11-01

    Synthetic biological macromolecule of magnetoferritin containing an iron oxide core inside a protein shell (apoferritin) is prepared with different content of iron. Its structure in aqueous solution is analysed by small-angle synchrotron X-ray (SAXS) and neutron (SANS) scattering. The loading factor (LF) defined as the average number of iron atoms per protein is varied up to LF=800. With an increase of the LF, the scattering curves exhibit a relative increase in the total scattered intensity, a partial smearing and a shift of the match point in the SANS contrast variation data. The analysis shows an increase in the polydispersity of the proteins and a corresponding effective increase in the relative content of magnetic material against the protein moiety of the shell with the LF growth. At LFs above ?150, the apoferritin shell undergoes structural changes, which is strongly indicative of the fact that the shell stability is affected by iron oxide presence. PMID:25249246

  6. Deposition of Biogenic Iron Minerals in a Methane Oxidizing Microbial Mat

    PubMed Central

    Wrede, Christoph; Dreier, Anne; Heller, Christina; Reitner, Joachim; Hoppert, Michael

    2013-01-01

    The syntrophic community between anaerobic methanotrophic archaea and sulfate reducing bacteria forms thick, black layers within multi-layered microbial mats in chimney-like carbonate concretions of methane seeps located in the Black Sea Crimean shelf. The microbial consortium conducts anaerobic oxidation of methane, which leads to the formation of mainly two biomineral by-products, calcium carbonates and iron sulfides, building up these chimneys. Iron sulfides are generated by the microbial reduction of oxidized sulfur compounds in the microbial mats. Here we show that sulfate reducing bacteria deposit biogenic iron sulfides extra- and intracellularly, the latter in magnetosome-like chains. These chains appear to be stable after cell lysis and tend to attach to cell debris within the microbial mat. The particles may be important nuclei for larger iron sulfide mineral aggregates. PMID:23843725

  7. Nitric oxide accumulation is required to protect against iron-mediated oxidative stress in frataxin-deficient Arabidopsis plants

    Microsoft Academic Search

    Mariana Martin; María José Rodríguez Colman; Diego F. Gómez-Casati; Lorenzo Lamattina; Eduardo Julián Zabaleta

    2009-01-01

    Frataxin is a mitochondrial protein that is conserved throughout evolution. In yeast and mammals, frataxin is essential for cellular iron (Fe) homeostasis and survival during oxidative stress. In plants, frataxin deficiency causes increased reactive oxygen species (ROS) production and high sensitivity to oxidative stress. In this work we show that a knock-down T-DNA frataxin-deficient mutant of Arabidopsis thaliana (atfh-1) contains

  8. Noncovalent magnetic control and reversible recovery of graphene oxide using iron oxide and magnetic surfactants.

    PubMed

    McCoy, Thomas M; Brown, Paul; Eastoe, Julian; Tabor, Rico F

    2015-01-28

    The unique charging properties of graphene oxide (GO) are exploited in the preparation of a range of noncovalent magnetic GO materials, using microparticles, nanoparticles, and magnetic surfactants. Adsorption and desorption are controlled by modification of pH within a narrow window of <2 pH units. The benefit conferred by using charge-based adsorption is that the process is reversible, and the GO can be captured and separated from the magnetic nanomaterial, such that both components can be recycled. Iron oxide (Fe2O3) microparticles form a loosely flocculated gel network with GO, which is demonstrated to undergo magnetic compressional dewatering in the presence of an external magnetic field. For composites formed from GO and Fe2O3 nanoparticles, it is found that low Fe2O3:GO mass ratios (<5:1) favor flocculation of GO, whereas higher ratios (>5:1) cause overcharging of the surfaces resulting in restabilization. The effectiveness of the GO adsorption and magnetic capture process is demonstrated by separating traditionally difficult-to-recover gold nanoparticles (d ? 10 nm) from water. The fully recyclable nature of the assembly and capture process, combined with the vast adsorption capacity of GO, presents obvious and appealing advantages for applications in decontamination and water treatment. PMID:25590575

  9. Differential Behaviour of Cell Membranes towards Iron-Induced Oxidative Damage and the Effects of Melatonin

    Microsoft Academic Search

    P. L. Tang; M. F. Xu; Z. M. Qian

    1997-01-01

    The ability of melatonin to protect iron-induced lipid peroxidation was studied in various rat cell membranes. The concentration of cellular membrane malondialdehyde (MDA) was used as an index of induced oxidative membrane damage. Cell membranes from the brain, heart, kidney and liver of the male Sprague-Dawley rat were incubated with ferric ammonium citrate (20 ?g\\/ml iron) alone for 3 h

  10. Does nitric oxide contribute to iron-dependent brain injury after experimental cerebral ischaemia?

    Microsoft Academic Search

    A. Gámez; T. Carbonell; R. Rama

    2003-01-01

    Experimental and clinical data suggest that iron has a key role in cerebral ischaemia. We measure infarct volume and analyse\\u000a the nitric oxide responses to brain injury in rat stroke model after increased oral iron intake. Permanent middle cerebral\\u000a artery occlusion (MCAO) was performed in a group of 20 male Wistar rats, 10 of which were fed with a control

  11. High-temperature oxidation\\/sulfidation resistance of iron-aluminide coatings

    Microsoft Academic Search

    P. F. Tortorelli; I. G. Wright; G. M. Goodwin; M. Howell

    1996-01-01

    Iron aluminides containing > 20-25 at. % Al have oxidation and sulfidation resistance at temperatures well above those at which these alloys have adequate mechanical strength. Accordingly, these alloys may find application as coatings or claddings on more conventional higher-strength materials which are generally less corrosion-resistant at high temperatures. To this end, iron-aluminide coatings were prepared by gas tungsten arc

  12. A reactive sputtering method for preparation of berthollide type of iron oxide films

    Microsoft Academic Search

    M. Naoe; Y. Hoshi; S. Yamanaka

    1982-01-01

    In order to prepare berthollide type of iron oxide (i.e., nonstoichiometric magnetite; FeOx:1.34<×<1.5) thin films, iron targets were sputtered in pure water vapor at the pressure of 2×10?3 Torr by using a high rate sputtering apparatus with faced targets. The composition and crystal structure of the obtained films strongly depend on input power Pt and substrate temperature T2. The increase

  13. Degradation of obsolete DDT by Fenton oxidation with zero-valent iron

    Microsoft Academic Search

    R. Boussahel; D. Harik; M. Mammar; S. Lamara-Mohamed

    2007-01-01

    We report in this paper the preliminary results obtained during degradation tests of obsolete DDT by Fenton oxidation with zero-valent iron. Iron powder, treated beforehand by a solution of H2SO4, was introduced into a glass engine containing a solution of distilled water doped by known quantities of obsolete pesticide and hydrogen peroxide. A continuous mechanical agitation was then applied and

  14. Advanced oxidation of natural organic matter using hydrogen peroxide and iron-coated pumice particles

    Microsoft Academic Search

    M. Kitis; S. S. Kaplan

    2007-01-01

    The oxidative removal of natural organic matter (NOM) from waters using hydrogen peroxide and iron-coated pumice particles as heterogeneous catalysts was investigated. Two NOM sources were tested: humic acid solution and a natural source water. Iron coated pumice removed about half of the dissolved organic carbon (DOC) concentration at a dose of 3000mgl?1 in 24h by adsorption only. Original pumice

  15. Treatment with the Iron Chelator, Deferoxamine Mesylate, Alters Serum Markers of Oxidative Stress in Stroke Patients

    Microsoft Academic Search

    Magdy Selim

    2010-01-01

    The iron chelator, deferoxamine mesylate (DFO), has shown neuroprotective effects, mediated via suppression of iron-induced\\u000a hydroxyl radical formation, in various animal models of ischemic and hemorrhagic stroke. Therefore, the objective of this\\u000a study was to investigate whether DFO can exert similar actions in stroke patients, by examining the effects of treatment with\\u000a DFO on biological markers of oxidative stress, namely

  16. Taurine Supplementation Reduces Oxidative Stress and Improves Cardiovascular Function in an Iron-Overload Murine Model

    Microsoft Academic Search

    Gavin Y. Oudit; Maria G. Trivieri; Neelam Khaper; Taneya Husain; Greg J. Wilson; Peter Liu; Michael J. Sole; Peter H. Backx

    2010-01-01

    Background—Iron overload has an increasing worldwide prevalence and is associated with significant cardiovascular morbidity and mortality. Elevated iron levels in the myocardium lead to impaired systolic and diastolic function and elevated oxidative stress. Taurine accounts for 25% to 50% of the amino acid pool in myocardium, possesses antioxidant properties, and can inhibit L-type Ca2 channels. Thus, we hypothesized that this

  17. Impact of iron, chelators, and free fatty acids on lipid oxidation in low-moisture crackers.

    PubMed

    Barden, Leann; Vollmer, Daniel; Johnson, David; Decker, Eric

    2015-02-18

    This research strove to understand the relationship between physical structure and oxidative stability in crackers since mechanisms of lipid oxidation are poorly understood in low-moisture foods. Confocal microscopy showed that lipids formed a continuous matrix surrounding starch granules, and starch-lipid, lipid-air, and protein-lipid interfaces were observed. Unlike bulk oils, meats, and emulsions, lipid hydroperoxides exhibited greater stability in low-moisture crackers as hexanal formation was delayed >20 d. Iron, added at 10 times the concentrations normally found in enriched flour, did not increase oxidation rates compared to the control. EDTA may reduce endogenous iron activity but not as greatly as in other matrices. Addition of fatty acids up to 1.0% of total lipid weight did not statistically affect lipid oxidation lag phases. The unique structure of low-moisture foods clearly affects their resistance to metal-promoted lipid oxidation. PMID:25641252

  18. Nitrogen loss from soil through anaerobic ammonium oxidation coupled to iron reduction

    NASA Astrophysics Data System (ADS)

    Yang, Wendy H.; Weber, Karrie A.; Silver, Whendee L.

    2012-08-01

    The oxidation of ammonium is a key step in the nitrogen cycle, regulating the production of nitrate, nitrous oxide and dinitrogen. In marine and freshwater ecosystems, anaerobic ammonium oxidation coupled to nitrite reduction, termed anammox, accounts for up to 67% of dinitrogen production. Dinitrogen production through anaerobic ammonium oxidation has not been observed in terrestrial ecosystems, but the anaerobic oxidation of ammonium to nitrite has been observed in wetland soils under iron-reducing conditions. Here, we incubate tropical upland soil slurries with isotopically labelled ammonium and iron(III) to assess the potential for anaerobic ammonium oxidation coupled to iron(III) reduction, otherwise known as Feammox, in these soils. We show that Feammox can produce dinitrogen, nitrite or nitrate in tropical upland soils. Direct dinitrogen production was the dominant Feammox pathway, short-circuiting the nitrogen cycle and resulting in ecosystem nitrogen losses. Rates were comparable to aerobic nitrification and to denitrification, the latter being the only other process known to produce dinitrogen in terrestrial ecosystems. We suggest that Feammox could fuel nitrogen losses in ecosystems rich in poorly crystalline iron minerals, with low or fluctuating redox conditions.

  19. Reduction of iron-oxide-carbon composites: part I. Estimation of the rate constants

    SciTech Connect

    Halder, S.; Fruehan, R.J. [Praxair Inc., Tonawanda, NY (United States). Technological Center

    2008-12-15

    A new ironmaking concept using iron-oxide-carbon composite pellets has been proposed, which involves the combination of a rotary hearth furnace (RHF) and an iron bath smelter. This part of the research focuses on studying the two primary chemical kinetic steps. Efforts have been made to experimentally measure the kinetics of the carbon gasification by CO{sub 2} and wustite reduction by CO by isolating them from the influence of heat- and mass-transport steps. A combined reaction model was used to interpret the experimental data and determine the rate constants. Results showed that the reduction is likely to be influenced by the chemical kinetics of both carbon oxidation and wustite reduction at the temperatures of interest. Devolatilized wood-charcoal was observed to be a far more reactive form of carbon in comparison to coal-char. Sintering of the iron-oxide at the high temperatures of interest was found to exert a considerable influence on the reactivity of wustite by virtue of altering the internal pore surface area available for the reaction. Sintering was found to be predominant for highly porous oxides and less of an influence on the denser ores. It was found using an indirect measurement technique that the rate constants for wustite reduction were higher for the porous iron-oxide than dense hematite ore at higher temperatures (> 1423 K). Such an indirect mode of measurement was used to minimize the influence of sintering of the porous oxide at these temperatures.

  20. Iron-oxide aerogel and xerogel catalyst formulations: Characterization by 57Fe Mössbauer and XAFS spectroscopies

    NASA Astrophysics Data System (ADS)

    Huggins, Frank E.; Bali, Sumit; Huffman, Gerald P.; Eyring, Edward M.

    2010-06-01

    Iron in various iron-oxide aerogel and xerogel catalyst formulations (?85% Fe 2O 3; ?10% K, Co, Cu, or Pd) developed for possible use in Fischer-Tropsch synthesis (FTS) or the water-gas-shift (WGS) reaction has been examined by 57Fe Mössbauer spectroscopy. The seventeen samples consisted of both as-prepared and calcined aerogels and xerogels and their products after use as catalysts for FTS or the WGS reaction. Complementary XAFS spectra were obtained on the occurrence of the secondary elements in some of the same materials. A broad, slightly asymmetric, two-peak Mössbauer spectrum was obtained from the different as-prepared and calcined catalyst formulations in the majority of cases. Such spectra could only be satisfactorily fit with three quadrupole doublet components, but no systematic trends in the isomer shift and quadrupole splitting parameters and area ratios of the individual components could be discerned that reflected variations in the composition or preparation of the aerogel or xerogel materials. However, significant reductions were noted in the Mössbauer effective thickness (recoilless absorption effect per unit mass of iron) parameter, ?eff/ g, determined at room temperature, for aerogels and xerogels compared to bulk iron oxides, reflecting the openness and lack of rigidity of the aerogel and xerogel structures. Mössbauer measurements for two aerogels over the range from 15 to 292 K confirmed the greatly diminished nature of this parameter at room temperature. Major increases in the effective thickness parameter were observed when the open structure of the aerogel or xerogel collapsed during calcination resulting in the formation of iron oxides (hematite, spinel ferrite). Similar structural changes were indicated by increases in this parameter after use of iron-oxide aerogels as catalysts for FTS or the WGS reaction, during which the iron-oxide aerogel was converted to a mixture of nonstoichiometric magnetite and the Hägg carbide, ?-Fe 5C 2, or nonstoichiometric magnetite, respectively.

  1. The Effect of Gold and Iron-Oxide Nanoparticles on Biofilm-Forming Pathogens

    PubMed Central

    Sathyanarayanan, Madhu Bala; Balachandranath, Reneta; Genji Srinivasulu, Yuvasri; Kannaiyan, Sathish Kumar; Subbiahdoss, Guruprakash

    2013-01-01

    Microbial biofilms on biomaterial implants or devices are hard to eliminate by antibiotics due to their protection by exopolymeric substances that embed the organisms in a matrix, impenetrable for most antibiotics and immune-cells. Application of metals in their nanoparticulated form is currently considered to resolve bacterial infections. Gold and iron-oxide nanoparticles are widely used in different medical applications, but their utilisation to eradicate biofilms on biomaterials implants is novel. Here, we studied the effect of gold and iron oxide nanoparticles on Staphylococcus aureus and Pseudomonas aeruginosa biofilms. We report that biofilm growth was reduced at higher concentrations of gold and iron-oxide nanoparticles compared to absence of nanoparticles. Thus nanoparticles with appropriate concentration could show significant reduction in biofilm formation. PMID:24187645

  2. Exposure to nitric oxide protects against oxidative damage but increases the labile iron pool in sorghum embryonic axes

    Microsoft Academic Search

    Sebastian Jasid; Marcela Simontacchi; Susana Puntarulo

    2008-01-01

    Sodium nitroprusside (SNP) and diethylenetriamine NONOate (DETA NONOate), were used as the source of exogenous NO to study the effect of NO upon germination of sorghum (Sorghum bicolor (L.) Moench) seeds through its possible interaction with iron. Modulation of cellular Fe status could be an important factor for the establishment of oxidative stress and the regulation of plant physiology. Fresh

  3. Wet oxidation of sandy iron sediment containing EDTA

    SciTech Connect

    Halverson, W.C.; Jordan, R.A. III [JGC Corporation, Surry, VA (United States)

    1995-12-31

    Sediment contaminated with a complex organic such as ethylenediamine tetraacetic acid, may be decomposed utilizing incineration or wet oxidation. Essential wet oxidation utilizes Fenton`s reagent which is hydrogen peroxide in the presence of a catalyst such as ferrous sulfate react together at low pH. The organic contaminant is oxidized to carbon oxide, ammonia gas and water. The water will contain the residue which consists of metal oxides and sulfate salt, mainly ammonium sulfate. The paper will review the relationships between the various independent variables such as pH, peroxide consumption, off gas content and the dependent variable-EDTA destruction levels.

  4. Stable Strontium Isotopic Fractionation During Sorption onto Magnetic Nano-Humid Acid Coated Iron Oxide Particles

    NASA Astrophysics Data System (ADS)

    Liu, H.-C.; You, C.-F.; Tu, Y.-J.

    2012-04-01

    The mobility of strontium (Sr) through hydrological systems is critically governed by sorption reactions of solid phases such as iron oxides and clay minerals. Inorganic precipitated and bacteriogenic iron oxides are widespread in marine and fresh systems fed by iron-rich supplies, which may impact the global Sr cycle. A series of laboratory batch experiments of Sr sorption onto humid acid coated magnetic nano iron oxides using high purity in-house standard were performed in this study and aimed for gaining a better understanding of mechanisms controlling Sr mobility. The results indicate that Sr sorption is a function of pH, 100 % Sr remains unbounded at pH <4 and more than 85 % absorbed at pH >8. Temperature controlled experiments in the range of 5 - 35 degrees C indicate a positive relationship between sorption capacity and temperature. Measurements of stable Sr isotopes (?88Sr and ?87Sr) in batch experiments show that lighter isotopes reacted preferentially with iron oxides, and a negligible pH effect on isotopic fractionation. To calculate the degree of the kinetic isotope effect, Rayleigh fractionation model is applied to evaluate the isotope fractionation factor, ? is 0.99985 at pH 8.17 (equals to ?88Sr ~ 0.15 ‰). Temperature exerts only minor isotopic fractionation effect and reveals more importance at lower temperatures. This new finding provides crucial information for a detail evaluation of sorption processes in natural environments.

  5. The diagnostic value of iron oxide nanoparticles for imaging of myocardial inflammation - quo vadis?

    PubMed

    Bietenbeck, Michael; Florian, Anca; Sechtem, Udo; Yilmaz, Ali

    2015-01-01

    Cardiovascular magnetic resonance (CMR) is an integral part in the diagnostic work-up of cardiac inflammatory diseases. In this context, superparamagnetic iron oxide-based contrast agents can provide additional diagnostic information regarding the assessment of myocardial infarction and myocarditis. After intravenous administration, these nanoparticles are taken up by activated monocytes and macrophages, which predominantly accumulate in regions associated with inflammation as was successfully shown in recent preclinical studies. Furthermore, first clinical studies with a new iron oxide-complex that was clinically approved for the treatment of iron deficiency anaemia recently demonstrated a superior diagnostic value of iron oxide nanoparticles compared to gadolinium-based compounds for imaging of myocardial inflammation in patients with acute myocardial infarction. In this article, we outline the basic features of superparamagnetic iron oxide-based contrast agents and review recent studies using such nanoparticles for cardiac imaging in case of acute myocardial infarction as well as acute myocarditis. Moreover, we highlight the translational potential of these agents and possible research applications with regard to imaging and therapy. PMID:26152269

  6. Improved dynamic response assessment for intra-articular injected iron oxide nanoparticles.

    PubMed

    Crowe, L A; Tobalem, F; Gramoun, A; Delattre, B M A; Grosdemange, K; Salaklang, J; Redjem, A; Petri-Fink, A; Hofmann, H; Vallée, J-P

    2012-11-01

    The emerging importance of nanoparticle technology, including iron oxide nanoparticles for monitoring development, progression, and treatment of inflammatory diseases such as arthritis, drives development of imaging techniques. Studies require an imaging protocol that is sensitive and quantifiable for the detection of iron oxide over a wide range of concentrations. Conventional signal loss measurements of iron oxide nanoparticle containing tissues saturate at medium concentrations and show a nonlinear/nonproportional intensity to concentration profile due to the competing effects of T? and T? relaxation. A concentration calibration phantom and an in vivo study of intra-articular injection in a rat knee of known concentrations of iron oxide were assessed using the difference-ultrashort echo time sequence giving a positive, quantifiable, unambiguous iron signal and monotonic, increasing concentration response over a wide concentration range in the phantom with limited susceptibility artifacts and high contrast in vivo to all other tissues. This improved dynamic response to concentration opens possibilities for quantification due to its linear nature at physiologically relevant concentrations. PMID:22294467

  7. Role of iron surface oxidation layers in decomposition of azo-dye water pollutants in weak acidic solutions

    Microsoft Academic Search

    Jerzy A. Mielczarski; Gonzalo Montes Atenas; Ela Mielczarski

    2005-01-01

    While decomposition of water pollutants in the presence of metallic iron can be strongly influenced by the nature and structure of the iron surface layer, the composition and structure of the layer produced and transformed in the decomposition process, have been meagerly investigated. The studies presented here establish strong relationships between the composition and structure of the iron oxidized surface

  8. Mechanism of Ubiquinol Oxidation by the bc1 Complex: Role of the Iron Sulfur Protein and Its Mobility

    E-print Network

    Crofts, Antony R.

    Mechanism of Ubiquinol Oxidation by the bc1 Complex: Role of the Iron Sulfur Protein and Its of the C-terminal extrinsic domain of the iron sulfur protein. None of the structures shows a static that the same conserved docking surface on the iron sulfur protein interacts with cytochrome c1

  9. 2476 Biochemistry 1994, 33, 2476-2483 Molecular Structure of the Oxidized High-Potential Iron-Sulfur Protein Isolated

    E-print Network

    Rayment, Ivan

    2476 Biochemistry 1994, 33, 2476-2483 Molecular Structure of the Oxidized High-Potential Iron-Sulfur" ABSTRACT: The high-potential iron-sulfur protein (iso-form 11)isolated from Ectothiorhodospira vacuolata. vacuolata molecule contains mostly reverse turns that wrap around the iron-sulfur cluster with cysteine

  10. Reactivity of iron carbonyl complexes in a hydrated sodium-Y zeolite matrix and catalysis of the resulting hydride anion HFeâ(CO)âââ» for water-gas-shift reaction

    Microsoft Academic Search

    Masakazu Iwamoto; Shinichiro Nakamura; Hideto Kusano; Shuichi Kagawa

    1986-01-01

    Iron carbonyls Fe(CO)â, Feâ(CO)â, and Feâ(CO)ââ have been introduced into a hydrated Na-Y zeolite. Fe(CO)â was only weakly adsorbed on the zeolite. Feâ(CO)â and Feâ(CO)ââ were reactive in the hydrated zeolite cages to yield a hydride anion species HFeâ(CO)âââ» which was characterized by IR absorption bands at 2044, 1987, 1950, and 1645 cm⁻¹, UV-vis spectrum at 540 nm, and gas-phase

  11. The iron(III)-catalyzed oxidation of DTPA in an aqueous solution / longy Steven Harry Christiansen 

    E-print Network

    Christiansen, Steven Harry

    1988-01-01

    THE IRON(III) -CATALYZED OXIDATION OF DTPA IN AN AQUEOUS SOLUTION A Thesis by STEVEN HARRY CHRISTIANSEN Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE... August 1988 Major Subject: Chemistry THE IRON(III) -CATALYZED OXIDATION OF DTPA IN AN AQUEOUS SOLUTION A Thesis by STEVEN HARRY CHRISTIANSEN Approved as to style and content by: A. E. Martell (Chair of Committee) M. B. Hall (Member) R. H...

  12. Template assisted self-assembly of iron oxide nanoparticles: An x-ray structural analysis

    SciTech Connect

    Mishra, D. [Department of Physics, Ruhr-University Bochum, 44780 Bochum (Germany); Institut fuer Optik und Atomare Physik, Technische Universitaet Berlin, Strasse des 17. Juni 135, 10623 Berlin (Germany); Zabel, H. [Department of Physics, Ruhr-University Bochum, 44780 Bochum (Germany); Ulyanov, S. V. [St.-Petersburg State University, Ul'yanovskaya ul.1, Petrodvorets, St.-Petersburg 198904 (Russian Federation); St.-Petersburg University of Commerce and Economics, St.-Petersburg 194018 (Russian Federation); Romanov, V. P. [St.-Petersburg State University, Ul'yanovskaya ul.1, Petrodvorets, St.-Petersburg 198904 (Russian Federation); Uzdin, V. M. [St.-Petersburg State University, Ul'yanovskaya ul.1, Petrodvorets, St.-Petersburg 198904 (Russian Federation); St.-Petersburg National Research University of Information Technologies, Mechanics and Optics, 49, Kronverkskij, St.-Petersburg 197101 (Russian Federation)

    2014-02-07

    We have fabricated by e-beam lithography periodic arrays of rectangular shaped trenches of different widths into Si substrates. The trenches were filled with iron oxide nanoparticles, 20?nm in diameter, by spin-coating them onto the Si substrate. The trenches have the purpose to assist the self-assembly of the iron oxide nanoparticles. Using x-ray scattering techniques, we have analyzed the structure factor of the trenches before and after filling in order to determine the filling factor. We present a theoretical analysis of the x-ray scattering function within the distorted-wave Born approximation and we present a quantitative comparison between theory and experiment.

  13. Textural and Mineralogical Characteristics of Microbial Fossils in Modern and Ancient Iron (oxyhydr)oxides

    NASA Astrophysics Data System (ADS)

    Potter, S. L.; Chan, M. A.; McPherson, B. J.

    2012-12-01

    The Jurassic Brushy Basin Member of the Morrison Formation contains extensive alkaline saline lacustrine deposits rich in diagenetic iron (oxyhydr)oxides that are well exposed on the Colorado Plateau of the southwestern USA. These early diagenetic iron (oxyhydr)oxide minerals are associated with preserved diatoms and other algal forms, identified via scanning electron microscope (SEM) in thin sections of representative samples. The minerals are also associated with macroscopic bioturbation features (e.g., charophytes, burrows and fossilized dinosaur bones). Algal forms with cellular elaboration are identified by HF dissolution of bioturbation structures and examination with SEM. Collectively, these features suggest biomediated textures are preserved in early diagenetic iron (oxyhydr)oxides, and can persist for tens of millions of years. Modern microbially precipitated iron (oxyhydr)oxides and ~100ka tufa terraces from a cold spring system along Ten Mile Graben in southern Utah, USA are compared with the Morrison examples to identify modern microbial fossils and document any differences and preservation changes during diagenesis over geologic time. Two distinct suites of elements (1. C, Fe, As and 2. C, S, Se) are associated with microbial fossils in both the modern and ancient tufas, as well as the ancient Morrison specimens. The occurrence of these distinctive trace element configurations in the iron (oxyhydr)oxide minerals suggest the suites could be potential markers for biosignatures. The presence of ferrihydrite in ~100ka fossil microbial mats suggests this thermodynamically unstable mineral may also be used as a biomarker. Diagnostic trace element suites and unusual mineral phases warrant further study for their potential as biomarkers. These terrestrial iron (oxyhydr)oxide examples will: 1) document specific biomediated textures and what their origins might be (related to different processes or species), 2) show how they might persist or respond to diagenesis over time, and 3) provide a "ground truth" library of textures to explore and compare in extraterrestrial iron (oxyhydr)oxides where we hope to detect preserved evidence of life. Well-documented biomarkers in terrestrial deposits are valuable references and benchmarks for the search for extinct and preserved microbial exolife in iron oxide minerals of Mars.

  14. Interaction of Fe(II) with phosphate and sulfate on iron oxide surfaces

    NASA Astrophysics Data System (ADS)

    Hinkle, Margaret A. G.; Wang, Zimeng; Giammar, Daniel E.; Catalano, Jeffrey G.

    2015-06-01

    Sulfate and phosphate, oxoanions common in natural systems, affect iron oxide growth and dissolution processes, the adsorption behavior of divalent cations, and iron oxide phase transformations. These oxoanions may thus influence Fe(II) adsorption behavior and subsequently alter the mechanisms and products of Fe(II)-catalyzed Fe(III) oxide recrystallization processes, such as trace metal repartitioning. In this study, the macroscopic and molecular-scale effects of the coadsorption of Fe(II) and sulfate or phosphate onto Fe(III) oxide surfaces were investigated. Macroscopic adsorption edges show that both sulfate and phosphate increase Fe(II) adsorption and that Fe(II) increases sulfate and phosphate adsorption. Attenuated total reflectance Fourier transform infrared spectroscopy shows that the cooperative adsorption behavior of oxoanions and aqueous Fe(II) likely results from a combination of ternary complexation and electrostatic interactions. Surface complexation modeling requires the inclusion of ternary complexes to simulate all conditions of the macroscopic data, further suggesting that these oxoanions and Fe(II) form ternary complexes on Fe(III) oxide surfaces. Despite clear evidence in previous research for Fe(II) oxidation upon adsorption on iron oxide surfaces, this work shows that Fe(II) also displays macroscopic and molecular-scale behaviors associated with divalent (i.e., non-oxidative) cation adsorption. Prior work has shown that metal release from iron oxides caused by ET-AE reactions is directly proportional to the macroscopically-determined Fe(II) surface coverage. Predicting the effects of sulfate and phosphate on processes controlled by ET-AE reactions at redox interfaces, such as mineral phase transformations and trace element repartitioning, may thus not require the explicit consideration of electron transfer processes.

  15. Transformation of vivianite by anaerobic nitrate-reducing iron-oxidizing bacteria.

    PubMed

    Miot, J; Benzerara, K; Morin, G; Bernard, S; Beyssac, O; Larquet, E; Kappler, A; Guyot, F

    2009-06-01

    In phosphate-rich environments, vivianite (Fe(II)(3)(PO(4))(2), 8H(2)O) is an important sink for dissolved Fe(II) and is considered as a very stable mineral due to its low solubility at neutral pH. In the present study, we report the mineralogical transformation of vivianite in cultures of the nitrate-reducing iron-oxidizing bacterial strain BoFeN1 in the presence of dissolved Fe(II). Vivianite was first transformed into a greenish phase consisting mostly of an amorphous mixed valence Fe-phosphate. This precipitate became progressively orange and the final product of iron oxidation consisted of an amorphous Fe(III)-phosphate. The sub-micrometer analysis by scanning transmission X-ray microscopy of the iron redox state in samples collected at different stages of the culture indicated that iron was progressively oxidized at the contact of the bacteria and at a distance from the cells in extracellular minerals. Iron oxidation in the extracellular minerals was delayed by a few days compared with cell-associated Fe-minerals. This led to strong differences of Fe redox in between these two types of minerals and finally to local heterogeneities of redox within the sample. In the absence of dissolved Fe(II), vivianite was not significantly transformed by BoFeN1. Whereas Fe(II) oxidation at the cell contact is most probably directly catalyzed by the bacteria, vivianite transformation at a distance from the cells might result from oxidation by nitrite. In addition, processes leading to the export of Fe(III) from bacterial oxidation sites to extracellular minerals are discussed including some involving colloids observed by cryo-transmission electron microscopy in the culture medium. PMID:19573166

  16. Iron-mediated oxidation induces conformational changes within the redox-sensing protein HbpS.

    PubMed

    Ortiz de Orué Lucana, Darío; Roscher, Mareike; Honigmann, Alf; Schwarz, Julia

    2010-09-01

    HbpS is an extracellular oligomeric protein, which has been shown to act in concert with the two-component system SenS-SenR during the sensing of redox stress. HbpS can bind and degrade heme under oxidative stress conditions, leading to a free iron ion. The liberated iron is subsequently coordinated on the protein surface. Furthermore, HbpS has been shown to modulate the phosphorylation state of the sensor kinase SenS as, in the absence of oxidative stress conditions, HbpS inhibits SenS autophosphorylation whereas the presence of heme or iron ions and redox-stressing agents enhances it. Using HbpS wild type and mutants as well as different biochemical and biophysical approaches, we show that iron-mediated oxidative stress induces both secondary structure and overall intrinsic conformational changes within HbpS. We demonstrate in addition that HbpS is oxidatively modified, leading to the generation of highly reactive carbonyl groups and tyrosine-tyrosine bonds. Further examination of the crystal structure and subsequent mutational analyses allowed the identification of the tyrosine residue participating in dityrosine formation, which occurs between two monomers within the octomeric assembly. Therefore, it is proposed that oxidative modifications causing structural and conformational changes are responsible for the control of SenS and hence of the HbpS-SenS-SenR signaling cascade. PMID:20571030

  17. Rotating biological contactor for biochemical ferrous iron oxidation in the treatment of coal mine drainage. Master's thesis

    Microsoft Academic Search

    Olem

    1975-01-01

    Pilot scale testing of the rotating biological contactor for the oxidation of ferrous iron in acid coal mine drainage has shown the process to be dependable, efficient, and economically comparable to purely chemical methods of iron oxidation. The 0.5 meter device consisted of four sets of plastic discs affixed to a centralized shaft. As the discs rotated half immersed in

  18. Rinded iron-oxide concretions: hallmarks of altered siderite masses of both early and late diagenetic origin

    E-print Network

    Nebraska-Lincoln, University of

    Rinded iron-oxide concretions: hallmarks of altered siderite masses of both early and late-0118, USA Associate Editor ­ Peter Talling ABSTRACT Iron-bearing concretions are valuable records of oxidation states of subsurface waters, but the first concretions to form can be altered drastically during

  19. Culture of Acidiphilium cryptum BV1 with halotolerant Alicyclobacillus -like spp.: effects on cell growth and iron oxidation

    Microsoft Academic Search

    L. E. Rodgers; P. J. Holden; L. J. R. Foster

    2002-01-01

    Acidiphilium cryptum was co-isolated with two Alicyclobacillus-like species from a terrestrial saline mine site. Co-cultivation of A. cryptum BV1 with the Alicyclobacillus-like species under saline conditions resulted in faster cell growth and increased iron oxidation compared with the pure mono-cultures. The rates of iron oxidation relative to cell numbers increased three fold.

  20. Aggregation and disaggregation of iron oxide nanoparticles: Influence of particle concentration, pH and natural organic matter

    Microsoft Academic Search

    Mohammed Baalousha

    2009-01-01

    The surface coating, aggregation behavior and aggregate structure of unpurified iron oxide nanoparticles (NPs) at variable pH and in the absence and presence of natural organic matter (NOM, Suwannee River humic acid, SRHA) have been previously studied in Baalousha et al. [Baalousha, M., Manciulea, A., Cumberland, S., Kendall, K., Lead, J.R., Aggregation and surface properties of iron oxide nanoparticles; influence

  1. Geochemical niches of iron-oxidizing acidophiles in acidic coal mine drainage.

    PubMed

    Jones, Daniel S; Kohl, Courtney; Grettenberger, Christen; Larson, Lance N; Burgos, William D; Macaladya, Jennifer L

    2015-02-01

    A legacy of coal mining in the Appalachians has provided a unique opportunity to study the ecological niches of iron-oxidizing microorganisms. Mine-impacted, anoxic groundwater with high dissolved-metal concentrations emerges at springs and seeps associated with iron oxide mounds and deposits. These deposits are colonized by iron-oxidizing microorganisms that in some cases efficiently remove most of the dissolved iron at low pH, making subsequent treatment of the polluted stream water less expensive. We used full-cycle rRNA methods to describe the composition of sediment communities at two geochemically similar acidic discharges, Upper and Lower Red Eyes in Somerset County, PA, USA. The dominant microorganisms at both discharges were acidophilic Gallionella-like organisms, “Ferrovum” spp., and Acidithiobacillus spp. Archaea and Leptospirillum spp. accounted for less than 2% of cells. The distribution of microorganisms at the two sites could be best explained by a combination of iron(II) concentration and pH. Populations of the Gallionella-like organisms were restricted to locations with pH>3 and iron(II) concentration of >4 mM, while Acidithiobacillus spp. were restricted to pH<3 and iron(II) concentration of <4 mM. Ferrovum spp. were present at low levels in most samples but dominated sediment communities at pH<3 and iron(II) concentration of >4 mM. Our findings offer a predictive framework that could prove useful for describing the distribution of microorganisms in acid mine drainage, based on readily accessible geochemical parameters. PMID:25501473

  2. Prebiotic Oxidative Polymerization of 2,3 Dimercaptopropanol on the Surface of Iron(III) Hydroxide Oxide

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    1994-01-01

    The oxidation of 2,3-Dimercapto-1-propanol by ferric ions on the surface of iron (III) hydroxide oxide yielded polydisulfide polymers. This polymerization occured readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron (III) hydroxide oxide (20 mg, 160 micro mole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the mineral phase. Reactions at higher dithiol concentrations with the same ratio of dithiol to mineral gave a higher yield of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis will be discussed.

  3. Prebiotic polymerization: Oxidative polymerization of 2, 3-dimercapto-1-propanol on the surface of iron(III) hydroxide oxide

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    1995-01-01

    The oxidation of 2, 3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the Fe(OH)O phase. Reactions carried out at the same ratio of dithiol to Fe(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

  4. Prebiotic Polymerization: Oxidative Polymerization of 2,3 Dimercapto-1- Propanol on the Surface of Iron(III) Hydroxide Oxide

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    1995-01-01

    The oxidation of 2,3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the FE(OH)O phase. Reactions carried out at the same ratio of dithiol to FE(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

  5. Association of trace elements with iron oxides during rock weathering

    SciTech Connect

    Koons, R.D.; Helmke, P.A.; Jackson, M.L.

    1980-01-01

    The association of trace elements with Fe oxides during the early stages of rock weathering was determined by analysis of fresh diabase and granite rocks, their associated whole and size-separated saprolites, and goethite by neutron activation and X-ray fluorescence. The same elements are found to be associated with Fe oxides when the results are interpreted by analysis of correlation, by the distribution of elements in the various size fractions by the effects of removing free Fe oxides, and by direct analysis of geothite from the saprolite. The elements Co, Cr, Mn, Sc, Th, U, Zn, and the heavy rare-earth elements during the weathering of diabase, and As, Co, Cr, Sc, Th, U, Zn, and the heavy rare-earth elements during the weathering of granite are associated with Fe oxides. The concentrations of Mn are too low in this system to separate the effects of Mn oxides from those of Fe oxides.

  6. Characterization of biogenic iron oxides collected by the newly designed liquid culture method using diffusion chambers.

    PubMed

    Kikuchi, S; Makita, H; Takai, K; Yamaguchi, N; Takahashi, Y

    2014-03-01

    We designed a new culture method for neutrophilic iron-oxidizing bacteria using liquid medium (i) to study the formation and mineralogical characteristics of biogenic iron oxides (BIOS) and (ii) to apply BIOS to various scientific and engineering applications. An iron-oxidizing bacterium, Mariprofundus ferrooxydans PV-1(T) (ATCC, BAA-1020), was cultured using a set of diffusion chambers to prepare a broad anoxic-oxic interface, upon which BIOS formation is typically observed in natural environments. Iron oxide precipitates were generated in parallel with bacterial growth. A scanning electron microscopy analysis indicated that the morphological features of the iron oxide precipitates in the medium (in vitro BIOS) were similar to those of BIOS collected from natural deep-sea hydrothermal environments in the Northwest Eifuku Seamount field in the northern Mariana Arc (in situ BIOS). Further chemical speciation of both the in vitro and in situ BIOS was examined with X-ray absorption fine structure (XAFS). A bulk XAFS analysis showed that the minerals in both BIOS were mainly ferrihydrite and oligomeric stages of amorphous iron oxyhydroxides with edge-sharing octahedral linkages. The amount of in vitro BIOS produced with the diffusion-chamber method was greater than those produced previously with other culture methods, such as gel-stabilized gradient and batch liquid culture methods. The larger yields of BIOS produced with the new culture method will allow us to clarify in the future the mineralization mechanisms during bacterial growth and to examine the physicochemical properties of BIOS, such as their adsorption to and coprecipitation with various elements and substances. PMID:24382149

  7. Microbial Iron Mats at the Mid-Atlantic Ridge and Evidence that Zetaproteobacteria May Be Restricted to Iron-Oxidizing Marine Systems

    PubMed Central

    Scott, Jarrod J.; Breier, John A.; Luther, George W.; Emerson, David

    2015-01-01

    Chemolithoautotrophic iron-oxidizing bacteria play an essential role in the global iron cycle. Thus far, the majority of marine iron-oxidizing bacteria have been identified as Zetaproteobacteria, a novel class within the phylum Proteobacteria. Marine iron-oxidizing microbial communities have been found associated with volcanically active seamounts, crustal spreading centers, and coastal waters. However, little is known about the presence and diversity of iron-oxidizing communities at hydrothermal systems along the slow crustal spreading center of the Mid-Atlantic Ridge. From October to November 2012, samples were collected from rust-colored mats at three well-known hydrothermal vent systems on the Mid-Atlantic Ridge (Rainbow, Trans-Atlantic Geotraverse, and Snake Pit) using the ROV Jason II. The goal of these efforts was to determine if iron-oxidizing Zetaproteobacteria were present at sites proximal to black smoker vent fields. Small, diffuse flow venting areas with high iron(II) concentrations and rust-colored microbial mats were observed at all three sites proximal to black smoker chimneys. A novel, syringe-based precision sampler was used to collect discrete microbial iron mat samples at the three sites. The presence of Zetaproteobacteria was confirmed using a combination of 16S rRNA pyrosequencing and single-cell sorting, while light micros-copy revealed a variety of iron-oxyhydroxide structures, indicating that active iron-oxidizing communities exist along the Mid-Atlantic Ridge. Sequencing analysis suggests that these iron mats contain cosmopolitan representatives of Zetaproteobacteria, but also exhibit diversity that may be uncommon at other iron-rich marine sites studied to date. A meta-analysis of publically available data encompassing a variety of aquatic habitats indicates that Zetaproteobacteria are rare if an iron source is not readily available. This work adds to the growing understanding of Zetaproteobacteria ecology and suggests that this organism is likely locally restricted to iron-rich marine environments but may exhibit wide-scale geographic distribution, further underscoring the importance of Zetaproteobacteria in global iron cycling. PMID:25760332

  8. Oxidation Reduction Potential of Complex Iron Compounds in Yeast

    Microsoft Academic Search

    Thomas B. Coolidge

    1931-01-01

    WHEN an alkaline extract of yeast is saturated with ammonium sulphate there is precipitated, with the protein, cytochrome `C' and a complex iron compound giving no visible spectrum. The latter can be separated from the proteins slowly by ultra-filtration. It remains in solution when the protein, with the cytochrome `C', is precipitated by trichloracetic acid.

  9. ARSENIC MOBILITY FROM IRON OXIDE SOLIDS PRODUCED DURING WATER TREATMENT

    EPA Science Inventory

    The Arsenic Rule under the Safe Drinking Water Act will require certain drinking water suppliers to add to or modify their existing treatment in order to comply with the new 10 ppb arsenic standard. One of the treatment options is co-precipitation of arsenic with iron. This tre...

  10. Measuring the Kinetics of the Reduction of Iron Oxide with Carbon Monoxide in a Fluidized Bed

    NASA Astrophysics Data System (ADS)

    Bohnt, C. D.; Cleeton, J. P.; Miiller, C. M.; Scotr, S. A.; Dennis, J. S.

    Combusting a solid fuel in the presence of a metal oxide rather than air, chemical looping combustion, generates CO2suitable for sequestration and the reduced metal. For the case of iron, the reduced oxide can be re-oxidized with steam to produce high-purity hydrogen. The reduction reactions of iron oxide in carbon monoxide and carbon dioxide mixtures were investigated in a fluidized bed. Activation energies and pre-exponential factors for the reactions (i) 3 Fe2O3+CO?2 Fe3O4+CO2 and?(ii)0.947 Fe3O4+0.788 CO?3 Fe0.947O+0.788 CO2?were determined. The reaction order was verified to be unity, and the change in rate with conversion was examined.

  11. Ab initio molecular dynamics study of manganese porphine hydration and interaction with nitric oxide

    E-print Network

    Kevin Leung; Craig J. Medforth

    2007-01-23

    The authors use ab initio molecular dynamics and the density functional theory+U (DFT+U) method to compute the hydration environment of the manganese ion in manganese (II) and manganese (III) porphines (MnP) dispersed in liquid water. These are intended as simple models for more complex water soluble porphyrins, which have important physiological and electrochemical applications. The manganese ion in Mn(II)P exhibits significant out-of-porphine plane displacement and binds strongly to a single H2O molecule in liquid water. The Mn in Mn(III)P is on average coplanar with the porphine plane and forms a stable complex with two H2O molecules. The residence times of these water molecules exceed 15 ps. The DFT+U method correctly predicts that water displaces NO from Mn(III)P-NO, but yields an ambiguous spin state for the MnP(II)-NO complex.

  12. Dose-Dependent Increase of Oxidative Damage in the Testes of Rats Subjected to Acute Iron Overload

    Microsoft Academic Search

    Florencia Lucesoli; Marina Caligiuri; Maria F. Roberti; Juan C. Perazzo; Cesar G. Fraga

    1999-01-01

    This study describes the in vivo response of rat testes to acute iron overload. Male Wistar rats (250–300 g) were injected ip with iron dextran at doses of 250 (Fe250), 500 (Fe500), or 1000 mg\\/kg body wt (Fe1000) or with saline (C). Parameters of oxidative stress and iron toxicity were measured 20 h after injection. Total iron content was 3.5-,

  13. Iron Oxide and Sulfide Nanocrystals as Biomarkers P.R. Buseck,* M. Psfai,** R.E. Dunin-Borkowski, *** and M. Weyland ***

    E-print Network

    Dunin-Borkowski, Rafal E.

    Iron Oxide and Sulfide Nanocrystals as Biomarkers P.R. Buseck,* M. Pósfai,** R.E. Dunin magnetic crystals of iron oxide or iron sulfide, which are used as internal compasses for orienting of iron sulfide crystals in a multicelled magnetotactic prokaryote, in which non-magnetic mackinawite (Fe

  14. Infrared nanosecond pulsed laser irradiation of stainless steel: Micro iron-oxide zones generation

    NASA Astrophysics Data System (ADS)

    Ortiz-Morales, M.; Frausto-Reyes, C.; Soto-Bernal, J. J.; Acosta-Ortiz, S. E.; Gonzalez-Mota, R.; Rosales-Candelas, I.

    2014-07-01

    Nanosecond-pulsed, infrared (1064 nm) laser irradiation was used to create periodic metal oxide coatings on the surface of two samples of commercial stainless steel at ambient conditions. A pattern of four different metal oxide zones was created using a galvanometer scanning head and a focused laser beam over each sample. This pattern is related to traverse direction of the laser beam scanning. Energy-dispersive X-ray spectroscopy (EDS) was used to find the elemental composition and Raman spectroscopy to characterize each oxide zone. Pulsed laser irradiation modified the composition of the stainless steel samples, affecting the concentration of the main components within each heat affected zone. The Raman spectra of the generated oxides have different intensity profiles, which suggest different oxide phases such as magnetite and maghemite. In addition, these oxides are not sensible to the laser power of the Raman system, as are the iron oxide powders reported in the literature. These experiments show that it is possible to generate periodic patterns of various iron oxide zones by laser irradiation, of stainless steel at ambient conditions, and that Raman spectroscopy is a useful punctual technique for the analysis and inspection of small oxide areas.

  15. Infrared nanosecond pulsed laser irradiation of stainless steel: micro iron-oxide zones generation.

    PubMed

    Ortiz-Morales, M; Frausto-Reyes, C; Soto-Bernal, J J; Acosta-Ortiz, S E; Gonzalez-Mota, R; Rosales-Candelas, I

    2014-07-15

    Nanosecond-pulsed, infrared (1064 nm) laser irradiation was used to create periodic metal oxide coatings on the surface of two samples of commercial stainless steel at ambient conditions. A pattern of four different metal oxide zones was created using a galvanometer scanning head and a focused laser beam over each sample. This pattern is related to traverse direction of the laser beam scanning. Energy-dispersive X-ray spectroscopy (EDS) was used to find the elemental composition and Raman spectroscopy to characterize each oxide zone. Pulsed laser irradiation modified the composition of the stainless steel samples, affecting the concentration of the main components within each heat affected zone. The Raman spectra of the generated oxides have different intensity profiles, which suggest different oxide phases such as magnetite and maghemite. In addition, these oxides are not sensible to the laser power of the Raman system, as are the iron oxide powders reported in the literature. These experiments show that it is possible to generate periodic patterns of various iron oxide zones by laser irradiation, of stainless steel at ambient conditions, and that Raman spectroscopy is a useful punctual technique for the analysis and inspection of small oxide areas. PMID:24699286

  16. Early diagenetic quartz formation at a deep iron oxidation front in the Eastern Equatorial Pacific - A modern analogue for banded iron/chert formations?

    NASA Astrophysics Data System (ADS)

    Meister, Patrick; Chapligin, Bernhard; Picard, Aude; Meyer, Hanno; Fischer, Cornelius; Rettenwander, Daniel; Amthauer, Georg; Vogt, Christoph; Aiello, Ivano W.

    2014-07-01

    The mechanisms of early diagenetic quartz formation under low-temperature conditions are still poorly understood. In this study we investigated lithified cherts consisting of microcrystalline quartz recovered near the base of a 420 m thick Miocene-Holocene sequence of nannofossil and diatom ooze at a drill site in the Eastern Equatorial Pacific (Ocean Drilling Program Site 1226). Precipitation seems still ongoing based on a sharp depletion in dissolved silica at the depth of the cherts. Also, palaeo-temperatures reconstructed from ?18O values in the cherts are in the range of adjacent porewater temperatures. Opal-A dissolution appears to control silica concentration throughout the sequence, while the solution remains oversaturated with respect to quartz. However, at the depth of the sharp depletion in dissolved silica, quartz is still saturated while the more soluble silica phases are strongly undersaturated. Hence, precipitation of quartz was initiated by an auxiliary process. A process, previously observed to assist in the nucleation of quartz is the adsorption of silica on freshly precipitated iron oxides. Indeed, a deep iron oxidation front is present at 400 m below seafloor, which is caused by upward diffusing nitrate from an oxic seawater aquifer in the underlying oceanic crust. Sequential iron extraction showed a higher content of the adsorbed iron hydroxide fraction in the chert than in the adjacent nannofossil and diatom ooze. X-ray absorption near-edge structure (XANES) spectroscopy revealed that iron in the cherts predominantly occurs in illite and amorphous iron oxide, whereas iron in the nannofossil and diatom ooze occurs mainly in smectite. Mössbauer spectroscopy also indicated the presence of illite that is to 97% oxidized. Two possible mechanisms may be operative during early diagenetic chert formation at iron oxidation fronts: (1) silica precipitation is catalysed by adsorption to freshly precipitated iron oxide surfaces, and (2) porewater silica concentration is locally decreased below opal-A and opal-CT saturation allowing for precipitation of the thermodynamically more stable phase: quartz. This mechanism of chert formation at the iron oxidation front in suboxic zones may explain why early-diagenetic microcrystalline chert only occurs sporadically in modern marine sediments. It may also serve as a modern analogue for the deposition of much more abundant banded iron/chert formations at the time of the great oxidation event around 2.4 Ga BP, which was probably the largest iron oxidation front in Earth's history.

  17. L-edge XANES measurements of the oxidation state of tungsten in iron bearing and iron free silicate glasses

    SciTech Connect

    Danielson, L.R.; Righter, K.; Sutton, S.; Newville, M.; Le, L. (Jacobs Sverdrup Corp); (UofC); (NASA)

    2008-04-28

    W{sup 4+} is relevant to core formation but W{sup 6+} may also occur. Silicate glasses show W{sup 6+} above IW and mixed valence below IW. The transition to W{sup 4+} only, appears to happen at or below IW-2 for iron free systems, but below IW-3 for iron bearing systems. Tungsten is important in constraining core formation of the Earth because this element is a moderately siderophile element (depleted {approx} 10 relative to chondrites) and, as a member of the Hf-W isotopic system, it is useful in constraining the timing of core formation. A number of previous experimental studies have been carried out to determine the silicate solubility and metal-silicate partitioning behavior of W, including its concomitant oxidation state. However, results of previous studies (Fig. 1) are inconsistent on whether W occurs as W{sup 4+} or W{sup 6+}. It is assumed that W{sup 4+} is the cation valence relevant to core formation. Given the sensitivity to silicate composition of high valence cations, knowledge of the oxidation state of W over a wide range of fO{sub 2} is critical to understanding the oxidation state of the mantle and core formation processes. This study seeks to measure the W valence and change in valence state over the range of fO{sub 2} most relevant to core formation, around IW-2.

  18. Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

    Microsoft Academic Search

    Werner Weiss; Wolfgang Ranke

    2002-01-01

    Metal-oxide-based catalysts are used for many important synthesis reactions in the chemical industry. A better understanding of the catalyst operation can be achieved by studying elementary reaction steps on well-defined model catalyst systems. For the dehydrogenation of ethylbenzene to styrene in the presence of steam both unpromoted and potassium promoted iron-oxide catalysts are active. Here we review the work done

  19. Aluminum but not iron treatment induces pro-oxidant events in the rat brain

    Microsoft Academic Search

    Stephen C. Bondy; Syed F. Ali; Shirley Guo-Ross

    1998-01-01

    In an attempt to delineate the capacity of aluminum (Al) to promote pro-oxidant events, several indices of oxidative stress\\u000a have been determined in brains and livers of rats exposed to an Al salt, either alone or in combination with an iron (Fe)\\u000a compound. Treatment with Al over a 3-wk period increased both cortical levels of glutathione (GSH) and the rates

  20. Effect of heat treatment on reactively sputtered iron oxide thin films

    Microsoft Academic Search

    J. K. Lin; J. M. Sivertsen; J. H. Judy

    1985-01-01

    A pure Fe target was used to deposit iron oxide thin films by reactive rf sputtering. Both ‘‘regular’’ and ‘‘wet’’ H2 were used as reducing atmospheres to produce Fe3O4. Other parameters such as the nature of the substrate material, substrate table rotation during sputtering, and grain size were studied. The ?-Fe2O3, formed by subsequent oxidation in air at elevated temperatures,

  1. The Association of Cobalt with Iron and Manganese (Oxyhydr)oxides in Marine Sediment

    Microsoft Academic Search

    Anthony Stockdale; William Davison; Hao Zhang; John Hamilton-Taylor

    2010-01-01

    Formation and dissolution of authigenic Fe and Mn (oxyhydr)oxides influence cycling of trace metals in oxic\\/suboxic surface\\u000a sediments. We used the diffusive gradients in thin films technique (DGT) to estimate the association of cobalt with iron and\\u000a manganese oxides. We compared Co, Fe and Mn maxima measured by DGT in the pore waters of fresh and aged marine sediment cores

  2. Synthesis, Characterization and Cytotoxicity Evaluation of Nitric Oxide-Iron Oxide magnetic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Haddad, P. S.; Britos, T. N.; Santos, M. C.; Seabra, A. B.; Palladino, M. V.; Justo, G. Z.

    2015-05-01

    The present work is focused on the synthesis, characterization and cytotoxic evaluation of superparamagnetic iron oxide nanoparticles (SPIONs). SPIONs have been proposed for an increasing number of biomedical applications, such as drug-delivery. To this end, toxicological studies of their potential effects in biological systems must be better evaluated. The aim of this study was to examine the in vitro cytotoxicity of thiolated (SH) and S-nitrosated (S-NO) SPIONs in cancer cell lines. SPIONs were prepared by the coprecipitation method using ferrous and ferric chlorides in aqueous solution. The nanoparticles (Fe3O4) were coated with thiol containing molecule cysteine (Cys) (molar ratio SPIONs:ligand = 1:20), leading to the formation of an aqueous dispersion of thiolated nanoparticles (SH- SPIONs). These particles were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The results obtained showed that Cys-SPIONs have a mean diameter of 14 nm at solid state and present super paramagnetic behavior at room temperature. Thiol groups on the surface of the nanoparticles were nitrosated through the addition of sodium nitrite leading to the formation of S-NOCys-SPIONs (S-nitrosated-Cys-SPIONs), which act as spontaneous nitric oxide (NO) donor). The cytotoxicity of thiolated and S-nitrosated nanoparticles was evaluated in acute T cell leukemia (Jurkat cell line) and Lewis lung carcinoma (3LL) cells. The results showed that at low concentrations thiolated (Cys) and S- nitrosated (S-NOCyst) SPIONs display low cytotoxicity in both cell types. However, at higher concentrations, Cys-SPIONs exhibited cytotoxic effects, whereas S-NOCys-SPIONs protected them, and also promoted cell proliferation.

  3. An electron-yield EXAFS study of anodic-oxide and hydrated-oxide films on pure aluminium

    Microsoft Academic Search

    S. M. El-mashri; R. G. Jones; A. J. Forty

    1983-01-01

    The molecular structures of the amorphous films formed on pure aluminium by anodic oxidation in sodium tartrate and phosphoric acid electrolytes, which are known to give quite different oxide morphologies, have been investigated using the technique of electron-yield EXAFS. The Al-0 ‘bond length’ derived from the EXAFS is found to be different for these two types of film, which suggests

  4. Conductive iron oxide minerals accelerate syntrophic cooperation in methanogenic benzoate degradation.

    PubMed

    Zhuang, Li; Tang, Jia; Wang, Yueqiang; Hu, Min; Zhou, Shungui

    2015-08-15

    Recent studies have suggested that conductive iron oxide minerals can facilitate syntrophic metabolism of the methanogenic degradation of organic matter, such as ethanol, propionate and butyrate, in natural and engineered microbial ecosystems. This enhanced syntrophy involves direct interspecies electron transfer (DIET) powered by microorganisms exchanging metabolic electrons through electrically conductive minerals. Here, we evaluated the possibility that conductive iron oxides (hematite and magnetite) can stimulate the methanogenic degradation of benzoate, which is a common intermediate in the anaerobic metabolism of aromatic compounds. The results showed that 89-94% of the electrons released from benzoate oxidation were recovered in CH4 production, and acetate was identified as the only carbon-bearing intermediate during benzoate degradation. Compared with the iron-free controls, the rates of methanogenic benzoate degradation were enhanced by 25% and 53% in the presence of hematite and magnetite, respectively. This stimulatory effect probably resulted from DIET-mediated methanogenesis in which electrons transfer between syntrophic partners via conductive iron minerals. Phylogenetic analyses revealed that Bacillaceae, Peptococcaceae, and Methanobacterium are potentially involved in the functioning of syntrophic DIET. Considering the ubiquitous presence of iron minerals within soils and sediments, the findings of this study will increase the current understanding of the natural biological attenuation of aromatic hydrocarbons in anaerobic environments. PMID:25827267

  5. Minimizing biofilm in the presence of iron oxides and humic substances.

    PubMed

    Butterfield, Phillip W; Camper, Anne K; Biederman, Joel A; Bargmeyer, Alex M

    2002-09-01

    Based upon circumstantial evidence linking elevated coliform bacteria counts in drinking water distribution systems with unlined cast iron pipe, it was hypothesized that adsorption of humic substances by iron oxide containing corrosion products (CPs) can stimulate and/or support biofilm development. Using porous media consisting of iron-oxide-coated glass beads (IOCBs) or actual iron CPs, experiments were performed to evaluate the effectiveness of different corrosion control and disinfection treatments in reducing biofilm when humic substances were the carbon source. Free chlorine was the most effective treatment in minimizing biofilm. Addition of phosphate alone did not significantly reduce biofilm using the CPs, but there was weak evidence it did using the IOCBs. The combination of free chlorine and phosphate was more effective at minimizing biofilm than free chlorine alone when CPs were the media. The presence of humic substances was a major factor when considering biofilm minimization based on results of experiments using both types of iron oxide media. The combination of humic substances and CPs led to an increase in biofilm biomass when free chlorine was not present, similar to conditions that could occur at distribution system dead-ends. Treatment to raise the pH to 9 did not reduce biofilm in experiments using both media, and actually increased biofilm in the experiment using CPs under the conditions tested. PMID:12369535

  6. Discovery of the recoverable high-pressure iron oxide Fe4O5

    PubMed Central

    Lavina, Barbara; Dera, Przemyslaw; Kim, Eunja; Meng, Yue; Downs, Robert T.; Weck, Philippe F.; Sutton, Stephen R.; Zhao, Yusheng

    2011-01-01

    Phases of the iron–oxygen binary system are significant to most scientific disciplines, directly affecting planetary evolution, life, and technology. Iron oxides have unique electronic properties and strongly interact with the environment, particularly through redox reactions. The iron–oxygen phase diagram therefore has been among the most thoroughly investigated, yet it still holds striking findings. Here, we report the discovery of an iron oxide with formula Fe4O5, synthesized at high pressure and temperature. The previously undescribed phase, stable from 5 to at least 30 GPa, is recoverable to ambient conditions. First-principles calculations confirm that the iron oxide here described is energetically more stable than FeO + Fe3O4 at pressure greater than 10 GPa. The calculated lattice constants, equation of states, and atomic coordinates are in excellent agreement with experimental data, confirming the synthesis of Fe4O5. Given the conditions of stability and its composition, Fe4O5 is a plausible accessory mineral of the Earth’s upper mantle. The phase has strong ferrimagnetic character comparable to magnetite. The ability to synthesize the material at accessible conditions and recover it at ambient conditions, along with its physical properties, suggests a potential interest in Fe4O5 for technological applications. PMID:21969537

  7. Iron is not involved in oxidative stress-mediated cytotoxicity of doxorubicin and bleomycin

    PubMed Central

    Kaiserová, H; den Hartog, G J M; Šim?nek, T; Schröterová, L; Kvasni?ková, E; Bast, A

    2006-01-01

    Background and purpose: The anticancer drugs doxorubicin and bleomycin are well-known for their oxidative stress-mediated side effects in heart and lung, respectively. It is frequently suggested that iron is involved in doxorubicin and bleomycin toxicity. We set out to elucidate whether iron chelation prevents the oxidative stress-mediated toxicity of doxorubicin and bleomycin and whether it affects their antiproliferative/proapoptotic effects. Experimental approach: Cell culture experiments were performed in A549 cells. Formation of hydroxyl radicals was measured in vitro by electron paramagnetic resonance (EPR). We investigated interactions between five iron chelators and the oxidative stress-inducing agents (doxorubicin, bleomycin and H2O2) by quantifying oxidative stress and cellular damage as TBARS formation, glutathione (GSH) consumption and lactic dehydrogenase (LDH) leakage. The antitumour/proapoptotic effects of doxorubicin and bleomycin were assessed by cell proliferation and caspase-3 activity assay. Key results: All the tested chelators, except for monohydroxyethylrutoside (monoHER), prevented hydroxyl radical formation induced by H2O2/Fe2+ in EPR studies. However, only salicylaldehyde isonicotinoyl hydrazone and deferoxamine protected intact A549 cells against H2O2/Fe2+. Conversely, the chelators that decreased doxorubicin and bleomycin-induced oxidative stress and cellular damage (dexrazoxane, monoHER) were not able to protect against H2O2/Fe2+. Conclusions and implications: We have shown that the ability to chelate iron as such is not the sole determinant of a compound protecting against doxorubicin or bleomycin-induced cytotoxicity. Our data challenge the putative role of iron and hydroxyl radicals in the oxidative stress-mediated cytotoxicity of doxorubicin and bleomycin and have implications for the development of new compounds to protects against this toxicity. PMID:17031387

  8. Nitrite induces the extravasation of iron oxide nanoparticles in hypoxic tumor tissue.

    PubMed

    Mistry, Nilesh; Stokes, Ashley M; Gambrell, James Van; Quarles, Christopher Chad

    2014-04-01

    Nitrite undergoes reconversion to nitric oxide under conditions characteristic of the tumor microenvironment, such as hypoxia and low pH. This selective conversion of nitrite into nitric oxide in tumor tissue has led to the possibility of using nitrite to enhance drug delivery and the radiation response. In this work, we propose to serially characterize the vascular response of brain tumor-bearing rats to nitrite using contrast-enhanced R2 * mapping. Imaging is performed using a multi-echo gradient echo sequence at baseline, post iron oxide nanoparticle injection and post-nitrite injection, whilst the animal is breathing air. The results indicate that nitrite sufficiently increases the vascular permeability in C6 gliomas, such that the iron oxide nanoparticles accumulate within the tumor tissue. When animals breathed 100% oxygen, the contrast agent remained within the vasculature, indicating that the conversion of nitrite to nitric oxide occurs in the presence of hypoxia within the tumor. The hypoxia-dependent, nitrite-induced extravasation of iron oxide nanoparticles observed herein has implications for the enhancement of conventional and nanotherapeutic drug delivery. PMID:24470164

  9. Superparamagnetic iron oxide nanoparticles impair endothelial integrity and inhibit nitric oxide production.

    PubMed

    Astanina, Ksenia; Simon, Yvette; Cavelius, Christian; Petry, Sandra; Kraegeloh, Annette; Kiemer, Alexandra K

    2014-11-01

    Superparamagnetic iron oxide nanoparticles (SPION) are widely used both clinically and experimentally for diverse in vivo applications, such as contrast enhancement in magnetic resonance imaging, hyperthermia and drug delivery. Biomedical applications require particles to have defined physical and chemical properties, and to be stable in biological media. Despite a suggested low cytotoxic action, adverse reactions of SPION in concentrations relevant for biomedical use have not yet been studied in sufficient detail. In the present work we employed Endorem®, dextran-stabilized SPION approved as an intravenous contrast agent, and compared its action to a set of other nanoparticles with potential for magnetic resonance imaging applications. SPION in concentrations relevant for in vivo applications were rapidly taken up by endothelial cells and exhibited no direct cytotoxicity. Electric cell impedance sensing measurements demonstrated that SPION, but not BaSO4/Gd nanoparticles, impaired endothelial integrity, as was confirmed by increased intercellular gap formation in endothelial monolayers. These structural changes induced the subcellular translocation and inhibition of the cytoprotective and anti-atherosclerotic enzyme endothelial NO-synthase and reduced NO production. Lipopolysaccharide-induced inflammatory NO production of macrophages was not affected by SPION. In conclusion, our data suggest that SPION might substantially alter endothelial integrity and function at therapeutically relevant doses, which are not cytotoxic. PMID:25123083

  10. Iron toxicity mediated by oxidative stress enhances tissue damage in an animal model of diabetes.

    PubMed

    Sampaio, Ana Flávia S; Silva, Maisa; Dornas, Waleska C; Costa, Daniela C; Silva, Marcelo E; Dos Santos, Rinaldo C; de Lima, Wanderson G; Pedrosa, Maria Lúcia

    2014-04-01

    Although iron is a first-line pro-oxidant that modulates clinical manifestations of various systemic diseases, including diabetes, the individual tissue damage generated by active oxidant insults has not been demonstrated in current animal models of diabetes. We tested the hypothesis that oxidative stress is involved in the severity of the tissues injury when iron supplementation is administered in a model of type 1 diabetes. Streptozotocin (Stz)-induced diabetic and non-diabetic Fischer rats were maintained with or without a treatment consisting of iron dextran ip at 0.1 mL day(-1) doses administered for 4 days at intervals of 5 days. After 3 weeks, an extensive increase (p < 0.001) in the production of reactive oxygen species (ROS) in neutrophils of the diabetic animals on iron overload was observed. Histological analysis revealed that this treatment also resulted in higher (p < 0.05) tissue iron deposits, a higher (p < 0.001) number of inflammatory cells in the pancreas, and apparent cardiac fibrosis, as shown by an increase (p < 0.05) in type III collagen levels, which result in dysfunctional myocardial. Carbonyl protein modification, a marker of oxidative stress, was consistently higher (p < 0.01) in the tissues of the iron-treated rats with diabetes. Moreover, a significant positive correlation was found between ROS production and iron pancreas stores (r = 0.42, p < 0.04), iron heart stores (r = 0.54, p < 0.04), and change of the carbonyl protein content in pancreas (r = 0.49, p < 0.009), and heart (r = 0.48, p < 0.02). A negative correlation was still found between ROS production and total glutathione content in pancreas (r = -0.50, p < 0.03) and heart (r = -0.45, p < 0.04). In conclusion, our results suggest that amplified toxicity in pancreatic and cardiac tissues in rats with diabetes on iron overload might be attributed to increased oxidative stress. PMID:24549594

  11. Organic phase synthesis of monodisperse iron oxide nanocrystals using iron chloride as precursor

    E-print Network

    Gao, Hongjun

    decomposition of iron organometallic compounds in high boiling point organic solu- tions in the presence and heated to 130 C for 1 h under N2 flow protection. The solution was then heated up to 317 C and kept at this temperature for 2 h. The reaction solution was solid-like as cooling down to room temperature

  12. Crystallization and magnetic properties of amorphous iron–chromium oxide nanoparticles synthesized by sonochemistry

    NASA Astrophysics Data System (ADS)

    Phu Nguyen, Dang; Tran, Quoc Tuan; Trinh, Xuan Sy; Cao Hoang, Thanh; Nguyen, Hoang Nam; Hai Nguyen, Hoang

    2012-03-01

    Amorphous iron–chromium oxide Fe2?xCrxO3 (x=0, 0.05, 0.10, 0.15, 0.20) nanoparticles were synthesized by sonochemical method at 80?°C. Crystallization process of the annealed samples showed a strong ferromagnetic behavior due to the existence of the maghemite phase. The effect of chromium replacing iron in the crystallization process of Fe2?xCrxO3 nanoparticles was systematically studied by adjusting initial concentration of Cr3+. The activation energy of the samples deduced from thermal analysis and increased with doping chromium showed that the existence of chromium can significantly slow down the ageing effect of the amorphous iron oxide.

  13. Antibacterial activity of magnetic iron oxide nanoparticles synthesized by laser ablation in liquid.

    PubMed

    Ismail, Raid A; Sulaiman, Ghassan M; Abdulrahman, Safa A; Marzoog, Thorria R

    2015-08-01

    In this study, (50-110nm) magnetic iron oxide (?-Fe2O3) nanoparticles were synthesized by pulsed laser ablation of iron target in dimethylformamide (DMF) and sodium dodecyl sulfate (SDS) solutions. The structural properties of the synthesized nanoparticles were investigated by using Fourier Transform Infrared (FT-IR) spectroscopy, UV-VIS absorption, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). The effect of laser fluence on the characteristics of these nanoparticles was studied. Antibacterial activities of iron oxide nanoparticles were tested against Gram-positive; Staphylococcus aureus and Gram-negative; Escherichia coli, Pseudomonas aeruginosa and Serratia marcescens. The results showed a noteworthy inhibition on both bacterial strains. The preparation conditions were found to affect significantly the antibacterial activity of these nanoparticles. The synthesized magnetic nanoparticles were used to capture rapidly S. aureus bacteria under the magnetic field effect. PMID:26042717

  14. Preparation of iron oxide nanoparticles from FeCl3 solid powder using microemulsions

    NASA Astrophysics Data System (ADS)

    Nassar, Nashaat; Husein, Maen

    2006-05-01

    Nanoparticles of iron oxide were prepared by subjecting iron chloride powder to (w/o) microemulsions consisting of sodium bis(2-ethylhexyl) sulfosuccinate (AOT), isooctane and water. FeCl3 was first dissolved in the water pools of the microemulsion, and then reacted with NaOH added as an aqueous solution to form iron oxide. The amount of NaOH solution was limited so that single microemulsion phase is obtained. This technique serves as an in-situ nanoparticle preparation technique aimed at minimizing particle aggregation associated with particle transportation to required sites. In this study, the effects of AOT concentration and water to AOT mole ratio on the nanoparticle size were investigated. UV/Vis spectrophotometry and transmission electron microscopy (TEM) were used to measure the particle size distribution.

  15. Iron oxide nanoparticles embedded in activated carbons prepared from hydrothermally treated waste biomass.

    PubMed

    Hao, Wenming; Björkman, Eva; Yun, Yifeng; Lilliestråle, Malte; Hedin, Niklas

    2014-03-01

    Particles of iron oxide (Fe3O4 ; 20–40 nm) were embedded within activated carbons during the activation of hydrothermally carbonized (HTC) biomasses in a flow of CO2. Four different HTC biomass samples (horse manure, grass cuttings, beer production waste, and biosludge) were used as precursors for the activated carbons. Nanoparticles of iron oxide formed from iron catalyst included in the HTC biomasses. After systematic optimization, the activated carbons had specific surface areas of about 800 m2g1. The pore size distributions of the activated carbons depended strongly on the degree of carbonization of the precursors. Activated carbons prepared from highly carbonized precursors had mainly micropores, whereas those prepared from less carbonized precursors contained mainly mesopores. Given the strong magnetism of the activated carbon–nano-Fe3O4 composites, they could be particularly useful for water purification. PMID:24678001

  16. Rapidly reversible redox transformation in nanophase manganese oxides at room temperature triggered by changes in hydration

    PubMed Central

    Birkner, Nancy; Navrotsky, Alexandra

    2014-01-01

    Chemisorption of water onto anhydrous nanophase manganese oxide surfaces promotes rapidly reversible redox phase changes as confirmed by calorimetry, X-ray diffraction, and titration for manganese average oxidation state. Surface reduction of bixbyite (Mn2O3) to hausmannite (Mn3O4) occurs in nanoparticles under conditions where no such reactions are seen or expected on grounds of bulk thermodynamics in coarse-grained materials. Additionally, transformation does not occur on nanosurfaces passivated by at least 2% coverage of what is likely an amorphous manganese oxide layer. The transformation is due to thermodynamic control arising from differences in surface energies of the two phases (Mn2O3 and Mn3O4) under wet and dry conditions. Such reversible and rapid transformation near room temperature may affect the behavior of manganese oxides in technological applications and in geologic and environmental settings. PMID:24733903

  17. Estimation of Free Iron Oxides in Soils and Clays by a Photolytic Method

    Microsoft Academic Search

    A. S. De Endredy

    1963-01-01

    The extraction of naturally occurring free iron oxides from soils and clays with oxalate solutions is distinctly photosensitive. Apparently wave- lengths around 366 m~, the near ultra-violet region, are the most efficient; this radiation is predominant in the emission of a medium-pressure mercury arc lamp. A qualitative consideration of the dissolution process indicates that in all probability electron transfer from

  18. In Situ Groundwater Arsenic Removal Using Iron Oxide-Coated Sand

    E-print Network

    Yu, Hongxu

    2010-10-12

    environment for in situ removal of arsenic. A sand filter with a fresh iron oxide coating can treat thousands of pore volumes of water contaminated with dozens of ppb arsenic before the coating needs to be regenerated. Arsenic breakthrough curves through...

  19. Antibacterial Efficacy of Iron-Oxide Nanoparticles against Biofilms on Different Biomaterial Surfaces

    PubMed Central

    Thukkaram, Monica; Sitaram, Soundarya; Kannaiyan, Sathish kumar; Subbiahdoss, Guruprakash

    2014-01-01

    Biofilm growth on the implant surface is the number one cause of the failure of the implants. Biofilms on implant surfaces are hard to eliminate by antibiotics due to the protection offered by the exopolymeric substances that embed the organisms in a matrix, impenetrable for most antibiotics and immune cells. Application of metals in nanoscale is considered to resolve biofilm formation. Here we studied the effect of iron-oxide nanoparticles over biofilm formation on different biomaterial surfaces and pluronic coated surfaces. Bacterial adhesion for 30?min showed significant reduction in bacterial adhesion on pluronic coated surfaces compared to other surfaces. Subsequently, bacteria were allowed to grow for 24?h in the presence of different concentrations of iron-oxide nanoparticles. A significant reduction in biofilm growth was observed in the presence of the highest concentration of iron-oxide nanoparticles on pluronic coated surfaces compared to other surfaces. Therefore, combination of polymer brush coating and iron-oxide nanoparticles could show a significant reduction in biofilm formation. PMID:25332720

  20. Draft Genome Sequence of the Iron-Oxidizing Acidophile Leptospirillum ferriphilum Type Strain DSM 14647

    PubMed Central

    Cárdenas, Juan Pablo; Lazcano, Marcelo; Ossandon, Francisco J.; Corbett, Melissa; Holmes, David S.

    2014-01-01

    The genomic features of the Leptospirillum ferriphilum type strain DSM 14647 are described here. An analysis of the predicted genes enriches our knowledge of the molecular basis of iron oxidation, improves our understanding of its role in industrial bioleaching, and suggests how it is adapted to live at extremely low pH. PMID:25377718

  1. Biocompatible surfactin-stabilized superparamagnetic iron oxide nanoparticles as contrast agents for magnetic resonance imaging

    Microsoft Academic Search

    Zhenyu Liao; Hanjie Wang; Xiaodong Wang; Chunling Wang; Xiufeng Hu; Xiaohong Cao; Jin Chang

    2010-01-01

    We have reported the ability of Bacillus natto TK-1 to produce surfactin which shows strong antitumor activity and appears less toxic to the normal cells. This report describes the use of the natural surfactin to stabilize superparamagnetic iron oxide nanoparticles (SPION) which can serve as a sensitive contrast agent for magnetic resonance imaging (MRI). The results showed that the organic

  2. Magnetic microstructure of chains and clusters of iron oxide and sulfide nanocrystals in bacteria

    E-print Network

    Dunin-Borkowski, Rafal E.

    Magnetic microstructure of chains and clusters of iron oxide and sulfide nanocrystals in bacteria M Magnetotactic bacteria contain intracellular, membrane-bound ferrimagnetic nanocrystals (magnetosomes) that have of magnetotactic bacteria provide a natural laboratory in which the magnetic properties of nanometer

  3. Induction of ROS, mitochondrial damage and autophagy in lung epithelial cancer cells by iron oxide nanoparticles

    Microsoft Academic Search

    Mohd Imran Khan; Akbar Mohammad; Govil Patil; S. A. H. Naqvi; L. K. S. Chauhan; Iqbal Ahmad

    Autophagy has attracted a great deal of research interest in tumor therapy in recent years. An attempt was made in this direction and now we report that iron oxide NPs synthesized by us selectively induce autophagy in cancer cells (A549) and not in normal cells (IMR-90). It was also noteworthy that autophagy correlated with ROS production as well as mitochondrial

  4. Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications

    Microsoft Academic Search

    Ajay Kumar Gupta; Mona Gupta

    2005-01-01

    Superparamagnetic iron oxide nanoparticles (SPION) with appropriate surface chemistry have been widely used experimentally for numerous in vivo applications such as magnetic resonance imaging contrast enhancement, tissue repair, immunoassay, detoxification of biological fluids, hyperthermia, drug delivery and in cell separation, etc. All these biomedical and bioengineering applications require that these nanoparticles have high magnetization values and size smaller than 100nm

  5. Ferrous iron oxidation by denitrifying bacteria in profundal sediments of a deep lake (Lake Constance)

    Microsoft Academic Search

    Simone Hauck; Marcus Benz; Andreas Brune; Bernhard Schink

    2001-01-01

    Profundal sediments of Lake Constance were sampled at 60 130 m water depth and studied with respect to the population sizes and depth distribution of mixotrophic and lithotrophic iron oxidizing, denitrifying bacteria. The sediment cores showed a distinct stratification with oxygen and nitrate being consumed within the first centimeter of the sediment. The sediment contained large amounts of acid extractable

  6. Surface modification of iron oxide nanoparticles and their conjuntion with water soluble polymers for biomedical application

    Microsoft Academic Search

    Nguyen Thanh Huong; Lam Thi Kieu Giang; Nguyen Thanh Binh; Le Quoc Minh

    2009-01-01

    Superparamagnetic iron oxide nanoparticles (SPION) coated with suitable bio-compatible substances have been used in biomedicine, particularly in magnetic resonance imaging (MRI), tissue engineering, and hyperthermia and drug delivery. In this study, we describe the synthesis of SPION and its surface modification for in-vitro experiments. The particle diameter and structure were estimated by FESEM, TEM, XRD analyses. The saturation magnetization was

  7. Isolation and characterization of an acidophilic, heterotrophic bacterium capable of oxidizing ferrous iron.

    PubMed Central

    Johnson, D B; Ghauri, M A; Said, M F

    1992-01-01

    A heterotrophic bacterium, isolated from an acidic stream in a disused pyrite mine which contained copious growths of "acid streamers," displayed characteristics which differentiated it from previously described mesophilic acidophiles. The isolate was obligately acidophilic, with a pH range of 2.0 to 4.4 and an optimum pH of 3.0. The bacterium was unable to fix carbon dioxide but oxidized ferrous iron, although at a slower rate than either Thiobacillus ferrooxidans or Leptospirillum ferrooxidans. Elemental sulfur and manganese(II) were not oxidized. In liquid media, the isolate produced macroscopic streamerlike growths. Microscopic examination revealed that the bacterium formed long (greater than 100 microns) filaments which tended to disintegrate during later growth stages, producing single, motile cells and small filaments. The isolate did not appear to utilize the energy from ferrous iron oxidation. Both iron (ferrous or ferric) and an organic substrate were necessary to promote growth. The isolate displayed a lower tolerance to heavy metals than other iron-oxidizing acidophiles, and growth was inhibited by exposure to light. There was evidence of extracellular sheath production by the isolate. In this and some other respects, the isolate resembles members of the Sphaerotilus-Leptothrix group of filamentous bacteria. The guanine-plus-cytosine content of the isolate was 62 mol%, which is less than that recorded for Sphaerotilus-Leptothrix spp. and greater than those of L. ferrooxidans and most T. ferrooxidans isolates. Images PMID:1622207

  8. Dielectric Properties and Conductivity of Iron Oxide-Barium Titanate Composites

    Microsoft Academic Search

    A. Kupreviciute; J. Banys; T. Ramoska; R. Sobiestianskas; F. M. M. Alawneh; N. Gharbi; D. C. Lupascu

    2011-01-01

    Sintered composites of iron oxide plus barium titanate in form of core-shell structures are investigated by impedance spectroscopy. The measurements were performed in the frequency and temperature ranges 20 Hz to 1 MHz and 150 K to 510 K, respectively. The composites exhibit strong low-frequency dispersion of electrical modulus and dielectric permittivity which is caused by different mechanisms of electron

  9. Fabrication, characterization and microwave properties of polyurethane nanocomposites reinforced with iron oxide and barium titanate

    E-print Network

    Guo, John Zhanhu

    with iron oxide and barium titanate nanoparticles Z. Guo a,*, S.-E. Lee a , H. Kim a , S. Park a , H.T. Hahn titanate nanoparticles fabricated by the surface-initiated-polymerization approach were investigated the introduction of the dielectric barium titanate nanoparticle into Fe2O3/PU nanocomposites. The permeability

  10. Fractal Iron Oxide Single-Crystal Dendritic Micro-Pines of Magnetic

    E-print Network

    Wang, Zhong L.

    Fractal Iron Oxide Single-Crystal Dendritic Micro-Pines of Magnetic a-Fe2O3: Large-Scale Synthesis,2] Fractal structures are common in nature across all length scales, from self-assembled molecules. On the nanoscale, dendritic fractals are one type of hyperbranched structure which are generally formed

  11. Iron oxide nanoparticle encapsulated diatoms for magnetic delivery of small molecules to tumors.

    PubMed

    Todd, Trever; Zhen, Zipeng; Tang, Wei; Chen, Hongmin; Wang, Geoffrey; Chuang, Yen-Jun; Deaton, Kayley; Pan, Zhengwei; Xie, Jin

    2014-02-21

    Small molecules can be co-loaded with iron oxide nanoparticles onto diatoms. With an external magnetic field, the diatoms, after systemic administration, can be attracted to tumors. This study suggests a great potential of diatoms as a novel and powerful therapeutic vehicle. PMID:24424277

  12. In Situ Groundwater Arsenic Removal Using Iron Oxide-Coated Sand 

    E-print Network

    Yu, Hongxu

    2010-10-12

    environment for in situ removal of arsenic. A sand filter with a fresh iron oxide coating can treat thousands of pore volumes of water contaminated with dozens of ppb arsenic before the coating needs to be regenerated. Arsenic breakthrough curves through...

  13. Expeditious organic?free assembly: morphologically controlled synthesis of iron oxides using microwaves

    EPA Science Inventory

    A microwave hydrothermal method is developed for the synthesis of iron oxides, a-Fe2O3, ß-FeOOH, and the junction of a-Fe2O3?ß-FeOOH. This method is absolutely organic-free, and various structures could be obtained simply by changing th...

  14. Biocompatibility of chitosan-coated iron oxide nanoparticles with osteoblast cells

    PubMed Central

    Shi, Si-Feng; Jia, Jing-Fu; Guo, Xiao-Kui; Zhao, Ya-Ping; Chen, De-Sheng; Guo, Yong-Yuan; Cheng, Tao; Zhang, Xian-Long

    2012-01-01

    Background: Bone disorders (including osteoporosis, loosening of a prosthesis, and bone infections) are of great concern to the medical community and are difficult to cure. Therapies are available to treat such diseases, but all have drawbacks and are not specifically targeted to the site of disease. Chitosan is widely used in the biomedical community, including for orthopedic applications. The aim of the present study was to coat chitosan onto iron oxide nanoparticles and to determine its effect on the proliferation and differentiation of osteoblasts. Methods: Nanoparticles were characterized using transmission electron microscopy, dynamic light scattering, x-ray diffraction, zeta potential, and vibrating sample magnetometry. Uptake of nanoparticles by osteoblasts was studied by transmission electron microscopy and Prussian blue staining. Viability and proliferation of osteoblasts were measured in the presence of uncoated iron oxide magnetic nanoparticles or those coated with chitosan. Lactate dehydrogenase, alkaline phosphatase, total protein synthesis, and extracellular calcium deposition was studied in the presence of the nanoparticles. Results: Chitosan-coated iron oxide nanoparticles enhanced osteoblast proliferation, decreased cell membrane damage, and promoted cell differentiation, as indicated by an increase in alkaline phosphatase and extracellular calcium deposition. Chitosan-coated iron oxide nanoparticles showed good compatibility with osteoblasts. Conclusion: Further research is necessary to optimize magnetic nanoparticles for the treatment of bone disease. PMID:23118539

  15. Experimental and Molecular Dynamics Simulations of Tribochemical Reactions with ZDDP: Zinc Phosphate–Iron Oxide Reaction

    Microsoft Academic Search

    Clotilde Minfray; Thierry Le Mogne; Jean-Michel Martin; Tasuku Onodera; Sayaka Nara; Shuko Takahashi; Hideyuki Tsuboi; Michihisa Koyama; Akira Endou; Hiromitsu Takaba; Momoji Kubo; Carlos A. Del Carpio; Akira Miyamoto

    2008-01-01

    Zinc phosphate glass is considered to be the main constituent of tribofilms generated under boundary lubrication with zinc dialkyldithiophosphate (ZDDP), a well-known antiwear additive. The reaction occurring during friction between zinc phosphate glasses and steel native iron oxide layer is investigated by both an experimental approach and by Molecular Dynamics simulations (MD). The importance of this “tribochemical” reaction in the

  16. Reuse of waste silica as adsorbent for metal removal by iron oxide modification

    Microsoft Academic Search

    Fuangfa Unob; Benjawan Wongsiri; Nuchnicha Phaeon; Mahitti Puanngam; Juwadee Shiowatana

    2007-01-01

    Silica gel is widely used in research laboratories, especially for the purification of organic compounds. Consequently, waste silica gel is generated in increasing amounts. In this work, waste silica was modified by coating its surface with iron oxide aiming to obtain an effective adsorbent for metal removal from wastewater. In the preparation of the adsorbent, the optimal pretreatment temperature and

  17. Kinetics and Mechanism of Iodide Oxidation by Iron(III): A Clock Reaction Approach

    ERIC Educational Resources Information Center

    Bauer, Jurica; Tomisic, Vladislav; Vrkljan, Petar B. A.

    2008-01-01

    A simple method for studying the kinetics of a chemical reaction is described and the significance of reaction orders in deducing reaction mechanisms is demonstrated. In this student laboratory experiment, oxidation of iodide by iron(III) ions in an acidic medium is transformed into a clock reaction. By means of the initial rates method, it is…

  18. The Oxidation of Iron: Experiment, Simulation, and Analysis in Introductory Chemistry

    ERIC Educational Resources Information Center

    Schubert, Frederic E.

    2015-01-01

    In this exercise, an actual chemical reaction, oxidation of iron in air, is studied along with a related analogue simulation of that reaction. The rusting of steel wool is carried out as a class effort. The parallel simulation is performed by students working in small groups. The analogue for the reacting gas is a countable set of discrete marble…

  19. Thiol-modified poly(ethylene glycol)-conjugated gold/ superparamagnetic iron oxide nanoparticles

    E-print Network

    Levin, Judith G.

    ) Synthesis [PubMed] A solution of SPIO nanoparticles (0.1 g/L), AuHCl4 (0.5 mM), 2-propanol (4.125 mThiol-modified poly(ethylene glycol)-conjugated gold/ superparamagnetic iron oxide nanoparticles nanoparticles Abbreviated name: PEG-S-Au/SPIO Synonym: PEG-S-Au/Feridex Agent category: Nanoparticle Target: Non

  20. ATR-FTIR Spectroscopy Reveals Bond Formation During Bacterial Adhesion to Iron Oxide

    E-print Network

    Chorover, Jon

    ATR-FTIR Spectroscopy Reveals Bond Formation During Bacterial Adhesion to Iron Oxide Sanjai J contribute to bacterial adhesion at positively charged surfaces, direct bonding of cell surface The contribution of various bacterial surface functional groups to adhesion at hematite and ZnSe surfaces

  1. Reductive Dissolution of Biogenic Manganese Oxides in the Presence of a Hydrated Biofilm

    Microsoft Academic Search

    Brandy Toner; Garrison Sposito

    2005-01-01

    The chemical reactivity of the biogenic Mn oxide produced by Pseudomonas putida strain MnB1 was assessed in the presence of bacterial cells and biofilm through reductive dissolution experiments at pH 4.4, 5.2, and 6.0. The reactivity of the biogenic Mn oxide was compared to that of a synthetic (chemically produced) birnessite at pH 6.0. In addition, the effect of bacterial

  2. Activation of Persulfate by Iron Filings and Oxidation of 1,4-Dioxane

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Zhong, H.; Yan, N.; Brusseau, M. L.

    2014-12-01

    The use of iron filings to promote in-situ activation of persulfate for permeable reactive barrier systems is investigated with batch and column experiments. The application of the approach was illustrated for oxidation of 1,4-dioxane. The results of the batch experiments showed that in the absence of the iron filings both persulfate decomposition and dioxane degradation were slow, with pseudo first-order half-lives of 160 d-1 and 6.3 d-1, respectively. In the presence of the iron filings, persulfate decomposition and dioxane degradation was much faster, with reductions in concentrations of 86% and 34% in the first 30 minutes, respectively. Approximately 10% of the dioxane injected into a column packed with iron filings was degraded. Analysis of persulfate and sulfate concentrations in the column effluent produced balanced total sulfur. The rate coefficient obtained from the column experiments was similar to the value obtained from the batch experiments.

  3. Hexadecylamine Adsorption at the Iron Oxide–Oil Interface

    PubMed Central

    2013-01-01

    The adsorption behavior of a model additive, hexadecylamine, onto an iron surface from hexadecane oil has been characterized using polarized neutron reflectometry, sum-frequency generation spectroscopy, solution depletion isotherm, and X-ray photoelectron spectroscopy (XPS). The amine showed a strong affinity for the metal surface, forming a dense monolayer at relatively low concentrations; a layer thickness of 16 (±3) Å at low concentrations, increasing to 20 (±3) Å at greater amine concentrations, was determined from the neutron data. These thicknesses suggest that the molecules in the layer are tilted. Adsorption was also indicated by sum-frequency generation spectroscopy and XPS, the latter indicating that the most dominant amine–surface interaction was via electron donation from the nitrogen lone pair to the positively charged iron ions. Sum-frequency generation spectroscopy was used to determine the alkyl chain conformation order and orientation on the surface. PMID:24106786

  4. Effects of Iron Chelators, Iron Salts, and Iron Oxide Nanoparticles on the Proliferation and the Iron Content of Oligodendroglial OLN-93 Cells

    Microsoft Academic Search

    Michaela Hohnholt; Mark Geppert; Ralf Dringen

    2010-01-01

    The oligodendroglial cell line OLN-93 was used as model system to investigate the consequences of iron deprivation or iron\\u000a excess on cell proliferation. Presence of ferric or ferrous iron chelators inhibited the proliferation of OLN-93 cells in\\u000a a time and concentration dependent manner, while the application of a molar excess of ferric ammonium citrate (FAC) prevented\\u000a the inhibition of proliferation

  5. Mineralized iron oxidizing bacteria from hydrothermal vents: targeting biosignatures on Mars

    NASA Astrophysics Data System (ADS)

    Leveille, R. J.

    2010-12-01

    Putative hydrothermal systems have been identified on Mars based on orbital imagery and rover-based analyses. Based on Earth analogs, hydrothermal systems on Mars would be highly attractive for their potential for preserving organic and inorganic biosignatures. For example, iron oxidizing bacteria are ubiquitous in marine and terrestrial hydrothermal systems, where they often display distinctive cell morphologies and are commonly encrusted by minerals, especially bacteriogenic iron oxides and silica. Microfossils of iron oxidizing bacteria have been found in ancient Si-Fe deposits and iron oxidation may be an ancient and widespread metabolic pathway. In order to investigate mineralized iron oxidizing bacteria as a biosignature, we have examined samples collected from extinct hydrothermal vents along Explorer Ridge, NE Pacific Ocean. In addition, microaerophilic iron oxidizing bacteria, isolated from active Pacific hydrothermal vents, were grown in a Fe-enriched seawater medium at constant pH (6.5) and O2 concentration (5%) in a controlled bioreactor system. Samples and experimental products were examined with a combination of variable-pressure and field-emission scanning electron microscopy (SEM), in some cases by preparing samples with a focused ion beam (FIB) milling system. Light-toned seafloor samples display abundant filamentous forms resembling, in both size and shape (1-5 microns in diameter and up to several microns in length), the twisted stalks of Gallionella and the elongated filaments of Leptothrix. Some samples consist entirely of low-density masses of silica (>90% Si) encrusted filamentous forms. The presence of unmineralized filamentous matter rich in C and Fe suggests that these are the remains of iron oxidizing bacteria. Mineralized filaments sectioned by FIB show variable internal material within semi-hollow, tubular-like features. Silica encrustations also show pseudo-concentric growth bands. In the bioreactor runs, abundant microbial growth and formation of an iron oxyhydroxide precipitate, either in direct association with the cells or within the growth medium, were observed. Preliminary analyses suggest that these precipitates are different from abiotic precipitates. Continuing work includes high-resolution TEM observations of cultured organisms and biogenic iron minerals, Raman and reflectance spectroscopy of precipitates, examination of seafloor incubation experiments, and bioreactor silicification experiments in order to better understand the Fe-Si fossilization process. Microaerophilic iron oxidation could have existed on the early Earth in environments containing small amounts of oxygen produced either by locally-concentrated photosynthetic microorganisms (e.g., cyanobacteria) or by chemical reactions. By analogy, similar subsurface or near-surface microaerophilic environments could have existed on Mars in the past, including in low-temperature hydrothermal systems. The distinctive morphologies and Fe-Si mineralization patterns of iron oxidizing bacteria could be a useful biosignature to search for on Mars. Deposits and features similar to those described here could be identified on Mars with existing technologies, and thus hydrothermal systems represent an attractive target for future surface and sample return missions.

  6. What Oxidation State of Iron Determines the Amethyst Colour?

    Microsoft Academic Search

    S. K. Dedushenko; I. B. Makhina; A. A. Mar'in; V. A. Mukhanov; Yu. D. Perfiliev

    2004-01-01

    A colourless quartz crystal doped with 57Fe3+ was obtained by hydrothermal synthesis in an NH4F solution. The crystal was transformed into violet amethyst by gamma-irradiation. The change in colour was accompanied by\\u000a changes in the Mssbauer spectrum that can be interpreted as the conversion of trivalent iron into the tetravalent state:\\u000a Fe3+?Fe4+.

  7. Behavior of iron aluminides in oxidizing and sulfidizing environments

    Microsoft Academic Search

    P. F. Tortorelli; J. H. DeVan; J. R. DiStefano

    1989-01-01

    To date, use of iron aluminides based on FeâAl (less than or equal to30 at. % Al) or FeAl (30--50 at. % Al) for structural applications has been limited by their low ductility and poor fracture toughness at room temperature and inadequate strength above 600\\/degree\\/C. However, in recent years, a renewed effort has been devoted to the development of ductile

  8. Conduction models of semiconducting calcium borate glasses containing iron oxide

    Microsoft Academic Search

    M. N. Saleh; M. M. Gawish

    1980-01-01

    The ac electrical resistivity, dielectric constant, and dielectric loss of the calcium borate glass system are investigated in order to determine the conduction models of the system. The glass series contains different iron concentrations in the system of molar composition (70-x)B2O3-30CaO-xFe2O3 with x up to 32%. The electronic properties are measured from 77 to 800 °K in the frequency range

  9. Oxidative damage of bovine serum albumin and other enzyme proteins by iron-chelate complexes.

    PubMed

    Ogino, T; Okada, S

    1995-12-14

    Direct oxidative protein damage by iron-nitrilotriacetate (NTA), as well as physiological iron complexes, iron-citrate and iron-ADP was studied in the presence or absence of H2O2, using bovine serum albumin (BSA), glucose-6-phosphate dehydrogenase (G-6-PD), glutathione reductase (GSSGRase) and catalase as the target proteins. Both Fe(III)NTA+H2O2 and Fe(II)NTA+H2O2 caused marked BSA fragmentation which accompanied the decrease in the intrinsic tryptophan fluorescence and appearance of bityrosine fluorescence. However, Fe(III)citrate+H2O2 showed only slight BSA fragmentation. In the absence of H2O2, Fe(II) NTA but not Fe(III)NTA caused similar but slight BSA fragmentation, which depended on the molecular oxygen. Fe(II)citrate also showed O2-dependent BSA fragmentation to a comparable degree, however, Fe(II)ADP showed no detectable BSA damage. BSA fragmentation by Fe(II)NTA+O2 and by Fe(III)NTA+H2O2 resulted in the appearance of the new alpha-amino groups. Electron spin resonance study using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trapping reagent showed DMPO-OH spin adduct, which suggests the presence of hydroxyl radical, in Fe(III)NTA+H2O2, but not in Fe(II)NTA+O2 system. Fe(II)NTA inactivated G-6-PD and GSSGRase in a O2-dependent manner, however, G-6-PD was more susceptible to the damage. This enzyme inactivation also accompanied the protein fragmentation and was not due to simple sulfhydryl oxidation. Catalase was not significantly inactivated nor fragmented by Fe(II)NTA+O2. These findings suggest that the interaction between proteins and iron-chelate complexes is important in iron catalyzed oxidative damage, and that the structure of the chelating agent may determine the target molecules. PMID:8541312

  10. Iron Partitioning And Oxidation State In Mg-Perovskite And Ferropericlase At Lower Mantle Conditions

    NASA Astrophysics Data System (ADS)

    Auzende, A.; Badro, J.; Gloter, A.

    2005-12-01

    Many processes that occur within the Earth are determined by the physical properties of the lower mantle. Albeit their thermodynamic stability in the lower mantle, the physical and chemical properties of its two main phases, namely (Mg,Fe)SiO3 magnesium silicate perovskite and (Mg,Fe)O ferropericlase, are affected by variations in the chemistry of iron. We report results concerning the behaviour of iron under lower mantle conditions. Iron partitioning experiments between Mg-perovskite and ferropericlase were conducted on samples synthesized from a San Carlos olivine compressed in a laser-heated diamond anvil cell. Recovered run products were thinned to electron transparency by focused ion beam and studied by analytical transmission electron microscopy (ATEM). Energy-dispersive x-ray measurements were used to calculate the partitioning coefficients of the iron between the phases at relevant lower mantle conditions. As the oxidation state of iron is known to influence the distribution of iron in the mantle phases, there is a strong motivation to achieve a quantitative determination of Fe3+ content in the lower mantle assemblage Mg-perovskite and ferropericlase. The Fe3+ /Fe concentrations were determined by electron energy loss spectroscopy. We also heated a (Mg0.83 Fe0.17)O at 92 GPa and investigated the recovered samples by ATEM. We see no evidence of decomposition into magnesium oxide and ferrous rich oxide components, which is at odds with a recent report. Our work provides important data on Fe/Mg partitioning and the oxidation state in the two main phases of lower mantle.

  11. Heterogeneous photodegradation of bisphenol A with iron oxides and oxalate in aqueous solution.

    PubMed

    Li, F B; Li, X Z; Li, X M; Liu, T X; Dong, J

    2007-07-15

    To understand the degradation of endocrine disrupting chemicals (EDCs) with existence of iron oxides and polycarboxylic acids in the natural environment, the photodegradation of bisphenol A (BPA) at the interface of iron oxides under UV illumination was conducted. Four iron oxides were prepared by a hydrothermal process and then sintered at different temperatures of 65, 280, 310, and 420 degrees C named "IO-65," "IO-280," "IO-310," and "IO-420," respectively. The prepared iron oxides were characterized by X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) methods. The XRD pattern of IO-65 showed a crystal structure of lepidocrocite (gamma-FeOOH) and that of IO-420 demonstrated a crystal structure of hematite (alpha-Fe(2)O(3)), while IO-280 and IO-310 have the mixed crystal structures of maghemite (gamma-Fe(2)O(3)) and hematite. The BET results revealed that the specific surface areas decreased with the increase of sintering temperature. The results demonstrated that the photodegradation of BPA depends strongly on the properties of iron oxides and oxalate, and pH. The properties of iron oxides influenced strongly the dependence of the BPA degradation on the oxalate concentration. The optimal initial concentrations of oxalate for BPA degradation under UV illumination were determined to be 2.0, 2.0, 2.4, and 2.0 mM for IO-65, IO-280, IO-310, and IO-420, respectively. The first-order kinetic constants k for BPA degradation under UV illumination in the presence of oxalate with the optimal initial concentration are ranked as IO-280>IO-310>IO-65>IO-420. The experiments demonstrated that the optimal pH value should be in the range of 3-4. Furthermore, the dependence of BPA degradation should be also attributable to the formation of the dissolved Fe-oxalate in the solution and the adsorbed Fe-oxalate on the surface of iron oxides, and also the formation of hydrogen peroxide. PMID:17451730

  12. Effect of iron doped lead oxide on the performance of lead acid batteries

    NASA Astrophysics Data System (ADS)

    Liu, Jianwen; Yang, Danni; Gao, Linxia; Zhu, Xinfeng; Li, Lei; Yang, Jiakuan

    2011-10-01

    In order to investigate effect of iron on the performance of lead acid batteries, we systematically study the chemical characteristics, electrochemical characteristics, battery capacity and cycle life using iron-doped lead oxide in this article. Cyclic voltammetry results show that positive discharge current decreases sharply with the increasing content of Fe2O3 from 0.05 wt.% to 2 wt.%. The release of H2 and O2 are promoted accompanying the increase of Fe2O3 contents. The chemical analysis confirms that the strength of Fe3+, Fe2+ concentration is simultaneously increased with the increase of iron contents after 50 voltammetry cycles. X-ray diffraction phase analysis shows that the amount of PbSO4 increases with the increasing iron content in the positive plates after 50 discharge cycles. Morphologies of positive plates show that many agglomerates from PbSO4 crystals appear. The SEM observations illustrate that there is a lower porosity and specific surface area in the positive active material with iron after 50 discharge cycles. The mechanism of iron decreasing capacity, cycle-life and promoting the release of H2 and O2 has been elucidated in details. We support it is the “redox-diffusion” process of multiple-valence iron and formation of PbSO4 on electrodes that result in above performances.

  13. Efficient oxidative dechlorination and aromatic ring cleavage of chlorinated phenols catalyzed by iron sulfophthalocyanine

    SciTech Connect

    Sorokin, A.; Meunier, B. [Laboratoire de Chimie de Coordination du CNRS, Toulouse (France); Seris, J.L. [Elf-Aquitaine, Artix (France)

    1995-05-26

    An efficient method has been developed for the catalytic oxidation of pollutants that are not easily degraded. The products of the hydrogen peroxide (H{sub 2}O{sub 2}) oxidation of 2,4,6-trichlorophenol (TCP) catalyzed by the iron complex 2,9,16,23-tetrasulfophthalocyanine (FePcS) were observed to be chloromaleic, chlorofumaric, maleic, and fumaric acids from dechlorination and aromatic cycle cleavage, as well as additional products that resulted from oxidative coupling. Quantitative analysis of the TCP oxidation reaction revealed that up to two chloride ions were released per TCP molecule. This chemical system, consisting of an environmentally safe oxidant (H{sub 2}O{sub 2}) and an easily accessible catalyst (FePcS), can perform several key steps in the oxidative mineralization of TCP, a paradigm of recalcitrant pollutants. 20 refs., 4 figs., 2 tabs.

  14. The rates of desulfurization of liquid iron by solid CaO and CaO-saturated liquid iron oxide at 1600‡c

    NASA Astrophysics Data System (ADS)

    Saelim, A.; Gaskell, D. R.

    1983-06-01

    The rates of desulfurization of Fe-O-S melts by CaO crucibles and by CaO-saturated liquid iron oxide have been measured at 1600 ‡C. It was found that irons containing 1.62 wt pct and 0.64 wt pct sulfur and 0.070 wt pct oxygen are desulfurized by a reaction with the containing CaO crucible which does not involve the formation of a CaS product layer. The rate of desulfurization reaction is controlled by diffusion of sulfur in the iron melt, and a value of 6.7 ±1.7 × 10-5 cm2 per second was obtained for the diffusion coefficient of sulfur in liquid iron. Iron containing 0.088 wt pct sulfur and 0.070 wt pct oxygen is not desulfurized by solid CaO. The rate of desulfurization of liquid iron containing 0.088 wt pct sulfur and 0.070 wt pct oxygen by CaO-saturated liquid iron oxide is significantly greater than that calculated on the assumption of diffusion control in the metal phase, and evidence is presented in support of speculation that the reaction rate is enhanced by Marangoni turbulence at the slag-metal interface. The addition of 4 wt pct CaF2 to the CaO-saturated liquid iron oxide has no influence on the rate of desulfurization of the melt.

  15. Ferrous iron oxidation by foam immobilized Acidithiobacillus ferrooxidans: Experiments and modeling.

    PubMed

    Jaisankar, S; Modak, J M

    2009-01-01

    Ferrous iron bio-oxidation by Acidithiobacillus ferrooxidans immobilized on polyurethane foam was investigated. Cells were immobilized on foams by placing them in a growth environment and fully bacterially activated polyurethane foams (BAPUFs) were prepared by serial subculturing in batches with partially bacterially activated foam (pBAPUFs). The dependence of foam density on cell immobilization process, the effect of pH and BAPUF loading on ferrous oxidation were studied to choose operating parameters for continuous operations. With an objective to have high cell densities both in foam and the liquid phase, pretreated foams of density 50 kg/m(3) as cell support and ferrous oxidation at pH 1.5 to moderate the ferric precipitation were preferred. A novel basket-type bioreactor for continuous ferrous iron oxidation, which features a multiple effect of stirred tank in combination with recirculation, was designed and operated. The results were compared with that of a free cell and a sheet-type foam immobilized reactors. A fivefold increase in ferric iron productivity at 33.02 g/h/L of free volume in foam was achieved using basket-type bioreactor when compared to a free cell continuous system. A mathematical model for ferrous iron oxidation by Acidithiobacillus ferrooxidans cells immobilized on polyurethane foam was developed with cell growth in foam accounted by an effectiveness factor. The basic parameters of simulation were estimated using the experimental data on free cell growth as well as from cell attachment to foam under nongrowing conditions. The model predicted the phase of both oxidation of ferrous in shake flasks by pBAPUFs as well as by fully activated BAPUFs for different cell loadings in foam. Model for stirred tank basket bioreactor predicted within 5% both transient and steady state of the experiments closely for the simulated dilution rates. Bio-oxidation at high Fe(2+) concentrations were simulated with experiments when substrate and product inhibition coefficients were factored into cell growth kinetics. PMID:19610075

  16. An updated examination of gas sweetening by the iron sponge process

    SciTech Connect

    Anerousis, J.P.; Whitman, S.K.

    1984-09-01

    A detailed evaluation of gas sweetening via iron sponge (hydrated iron oxide) has been undertaken due to the apparent lack of comprehensive engineering, research, and field data related to this process. Key areas reviewed include composition of the sweetening media, unit design considerations, and operational parameters. The investigations discussed in this paper provide quantifiable proof that the iron sponge process continues to be a viable alternative for hydrogen sulfide and mercaptan removal, provided the sweetening equipment is properly designed and operated.

  17. Iron(II) oxide determination in rocks and minerals

    Microsoft Academic Search

    Sandra Andrade; Raphael Hypolito; Horstpeter H. G. J. Ulbrich; Marinês L. Silva

    2002-01-01

    The determination of FeO of geologic materials by modern instrumental methods (such as atomic absorption spectroscopy (AAS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray fluorescence (XRF), etc.) cannot distinguish between different oxidation states of elements. In many cases, the oxidation state of Fe has to be known in order to perform several chemical calculations (norms, etc.) and discuss the

  18. Phagocytosis, Oxidative Burst, and Produced Reactive Species are Affected by Iron Deficiency Anemia and Anemia of Chronic Diseases in Elderly

    Microsoft Academic Search

    I. M. M. Paino; J. C. Miranda; C. M. Marzocchi-Machado; E. J. Cesarino; F. A. de Castro; A. M. de Souza

    2009-01-01

    Iron and oxidative stress have a regulatory interplay. During the oxidative burst, phagocytic cells produce free radicals\\u000a such as hypochlorous acid (HOCl). Nevertheless, scarce studies evaluated the effect of either iron deficiency anemia (IDA)\\u000a or anemia of chronic disease (ACD) on phagocyte function in the elderly. The aim of the present study was to determine the\\u000a oxidative burst, phagocytosis, and

  19. Facile synthesis of iron oxides/reduced graphene oxide composites: application for electromagnetic wave absorption at high temperature

    PubMed Central

    Zhang, Lili; Yu, Xinxin; Hu, Hongrui; Li, Yang; Wu, Mingzai; Wang, Zhongzhu; Li, Guang; Sun, Zhaoqi; Chen, Changle

    2015-01-01

    Iron oxides/reduced graphene oxide composites were synthesized by facile thermochemical reactions of graphite oxide and FeSO4·7H2O. By adjusting reaction temperature, ?-Fe2O3/reduced graphene oxide and Fe3O4/reduced graphene oxide composites can be obtained conveniently. Graphene oxide and reduced graphene oxide sheets were demonstrated to regulate the phase transition from ?-Fe2O3 to Fe3O4 via ?-Fe2O3, which was reported for the first time. The hydroxyl groups attached on the graphene oxide sheets and H2 gas generated during the annealing of graphene oxide are believed to play an important role during these phase transformations. These samples showed good electromagnetic wave absorption performance due to their electromagnetic complementary effect. These samples possess much better electromagnetic wave absorption properties than the mixture of separately prepared Fe3O4 with rGO, suggesting the crucial role of synthetic method in determining the product properties. Also, these samples perform much better than commercial absorbers. Most importantly, the great stability of these composites is highly advantageous for applications as electromagnetic wave absorption materials at high temperatures. PMID:25788158

  20. Aqueous pyrite oxidation by dissolved oxygen and by ferric iron

    NASA Astrophysics Data System (ADS)

    Moses, Carl O.; Kirk Nordstrom, D.; Herman, Janet S.; Mills, Aaron L.

    1987-06-01

    Rates of aqueous, abiotic pyrite oxidation were measured in oxygen-saturated and anaerobic Fe(III)-saturated solutions with initial pH from 2 to 9. These studies included analyses of sulfite, thiosulfate, polythionates and sulfate and procedures for cleaning oxidation products from pyrite surfaces were evaluated. Pyrite oxidation in oxygen-saturated solutions produced (1) rates that were only slightly dependent on initial pH, (2) linear increases in sulfoxy anions and (3) thiosulfate and polythionates at pH > 3.9. Intermediate sulfoxy anions were observed only at high stirring rates. In anaerobic Fe(III)-saturated solutions, no intermediates were observed except traces of sulfite at pH 9. The faster rate of oxidation in Fe(III)-saturated solutions supports a reaction mechanism in which Fe(III) is the direct oxidant of pyrite in both aerobic and anaerobic systems. The proposal of this mechanism is also supported by theoretical considerations regarding the low probability of a direct reaction between paramagnetic molecular oxygen and diamagnetic pyrite. Results from a study of sphalerite oxidation support the hypothesis that thiosulfate is a key intermediate in sulfate production, regardless of the bonding structure of the sulfide mineral.