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1

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

NASA Astrophysics Data System (ADS)

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.

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

1998-07-01

2

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

Microsoft Academic Search

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

Norman Lazaroff; John Jollie; Patrick R. Dugan

1998-01-01

3

Aqueous precursors for electrochromic tungsten oxide hydrates  

Microsoft Academic Search

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

J. Livage; G. Guzman

1996-01-01

4

Enzymes of respiratory iron oxidation  

SciTech Connect

This report focuses on the progress made in three areas of research concerned with enzymes involved in respiratory iron oxidation. The three areas are as follows: development of an improved procedure for the routine large scale culture of iron oxidizing chemolithotrophs based on the in-situ electrolysis of the soluble iron in the growth medium; to perform iron oxidation kinetic studies on whole cells using the oxygen electrode; and to identify, separate, purify, and characterize the individual cellular components.

Blake, R. II.

1991-01-01

5

Competitive Oxidation and Hydration During Aqueous Alteration of Asteroids  

NASA Technical Reports Server (NTRS)

Introduction: Studies of chondrites show that incorporation of H2O ice during formation of asteroids followed by radioactive heating caused partial oxidation and hydration of primary reduced and anhydrous rocks. Oxidation of kamacite, phosphides, troilite and organic polymers occurred through consumption of water s oxygen and release of H2. Hydration caused formation of serpentine, saponite, chlorite, talc and hydrated salts. Since H2O was the major reactant in oxidation and hydration, these processes could have been competitive. Redox reactions in asteroids should have been closely connected to hydration (dehydration) during aqueous alteration and thermal metamorphism. For example, dehydration and reduction release H2O that can be consumed in oxidation and hydration, respectively. We model asteroidal processes in order to quantify the fate of H2O and water s oxygen in major redox and hydration/dehydration reactions. Model: Equilibrium compositions in the gas-solid-liquid

Zolotov, M. Y.; Mironenko, M. V.; Shock, E. L.

2005-01-01

6

Iron Oxide Based High Temperature Desulfurization Sorbent  

Microsoft Academic Search

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

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

2009-01-01

7

Recovery of iron oxide from coal fly ash  

DOEpatents

A high quality iron oxide concentrate, suitable as a feed for blast and electric reduction furnaces is recovered from pulverized coal fly ash. The magnetic portion of the fly ash is separated and treated with a hot strong alkali solution which dissolves most of the silica and alumina in the fly ash, leaving a solid residue and forming a precipitate which is an acid soluble salt of aluminosilicate hydrate. The residue and precipitate are then treated with a strong mineral acid to dissolve the precipitate leaving a solid residue containing at least 90 weight percent iron oxide.

Dobbins, Michael S. (Ames, IA); Murtha, Marlyn J. (Ames, IA)

1983-05-31

8

Iron biomineralization by anaerobic neutrophilic iron-oxidizing bacteria  

Microsoft Academic Search

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).

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

9

Rust in the Apollo 16 rocks. [hydration and oxidation processes in lunar environment  

NASA Technical Reports Server (NTRS)

Apollo 16 samples of all four rock types and from all stations contain evidence for hydration and oxidation - i.e., the presence of hydrated iron oxide, probably goethite. Rock 66095 contains native FeNi grains with a characteristic intergrowth of schreibersite and, to lesser extents, of cohenite. Troilite also contains sphalerite. The goethite contains 1.5-4.6 wt.% chlorine and occurs mainly on the edges of FeNi metal, causing a rust color in the cracks and space around the native metal grains, which also contain abundant chlorine. This observation suggests the presence of lawrencite (FeCl2), a phase that deliquesces and oxidizes very rapidly upon exposure to water or to a moist atmosphere.

Taylor, L. A.; Mao, H. K.; Bell, P. M.

1973-01-01

10

Iron, oxidative stress and gestational diabetes.  

PubMed

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

Zhuang, Taifeng; Han, Huijun; Yang, Zhenyu

2014-09-01

11

Iron, Oxidative Stress and Gestational Diabetes  

PubMed Central

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

Zhuang, Taifeng; Han, Huijun; Yang, Zhenyu

2014-01-01

12

21 CFR 186.1374 - Iron oxides.  

Code of Federal Regulations, 2013 CFR

...mixtures of iron (II) oxide (CAS Reg. No. 1345-25-1, black cubic crystals) and iron (III) oxide (CAS Reg. No. 1309-37-1, red-brown to black trigonal crystals). (b) In accordance with § 186.1(b)(1), the...

2013-04-01

13

21 CFR 186.1374 - Iron oxides.  

...mixtures of iron (II) oxide (CAS Reg. No. 1345-25-1, black cubic crystals) and iron (III) oxide (CAS Reg. No. 1309-37-1, red-brown to black trigonal crystals). (b) In accordance with § 186.1(b)(1), the...

2014-04-01

14

21 CFR 186.1374 - Iron oxides.  

Code of Federal Regulations, 2011 CFR

...mixtures of iron (II) oxide (CAS Reg. No. 1345-25-1, black cubic crystals) and iron (III) oxide (CAS Reg. No. 1309-37-1, red-brown to black trigonal crystals). (b) In accordance with § 186.1(b)(1), the...

2011-04-01

15

21 CFR 186.1374 - Iron oxides.  

Code of Federal Regulations, 2012 CFR

...mixtures of iron (II) oxide (CAS Reg. No. 1345-25-1, black cubic crystals) and iron (III) oxide (CAS Reg. No. 1309-37-1, red-brown to black trigonal crystals). (b) In accordance with § 186.1(b)(1), the...

2012-04-01

16

21 CFR 186.1374 - Iron oxides.  

Code of Federal Regulations, 2010 CFR

...mixtures of iron (II) oxide (CAS Reg. No. 1345-25-1, black cubic crystals) and iron (III) oxide (CAS Reg. No. 1309-37-1, red-brown to black trigonal crystals). (b) In accordance with § 186.1(b)(1), the...

2010-04-01

17

Tannin biosynthesis of iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

In this work, iron oxide nanoparticles synthesized with gallic acid and tannic acid are characterized using High-Resolution Transmission Electron Microscopy (HRTEM). Its size, form, and structure are compared with nanoparticles obtained previously using alfalfa biomass in order to find a simpler, consistent, and environmentally friendly method in the production of iron oxide nanoparticles.

Herrera-Becerra, R.; Rius, J. L.; Zorrilla, C.

2010-08-01

18

Nanosized Iron Oxide Colloids Strongly Enhance Microbial Iron Reduction? †  

PubMed Central

Microbial iron reduction is considered to be a significant subsurface process. The rate-limiting bioavailability of the insoluble iron oxyhydroxides, however, is a topic for debate. Surface area and mineral structure are recognized as crucial parameters for microbial reduction rates of bulk, macroaggregate iron minerals. However, a significant fraction of iron oxide minerals in the subsurface is supposed to be present as nanosized colloids. We therefore studied the role of colloidal iron oxides in microbial iron reduction. In batch growth experiments with Geobacter sulfurreducens, colloids of ferrihydrite (hydrodynamic diameter, 336 nm), hematite (123 nm), goethite (157 nm), and akaganeite (64 nm) were added as electron acceptors. The colloidal iron oxides were reduced up to 2 orders of magnitude more rapidly (up to 1,255 pmol h?1 cell?1) than bulk macroaggregates of the same iron phases (6 to 70 pmol h?1 cell?1). The increased reactivity was not only due to the large surface areas of the colloidal aggregates but also was due to a higher reactivity per unit surface. We hypothesize that this can be attributed to the high bioavailability of the nanosized aggregates and their colloidal suspension. Furthermore, a strong enhancement of reduction rates of bulk ferrihydrite was observed when nanosized ferrihydrite aggregates were added. PMID:19915036

Bosch, Julian; Heister, Katja; Hofmann, Thilo; Meckenstock, Rainer U.

2010-01-01

19

Extracellular Iron Biomineralization by Photoautotrophic Iron-Oxidizing Bacteria ? †  

PubMed Central

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

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

2009-01-01

20

Pyrite and oxidized iron mineral phases formed from pyrite oxidation in salt marsh and estuarine sediments  

NASA Astrophysics Data System (ADS)

We used scanning electron microscopy and energy dispersive X-ray analysis to examine sediments from vegetated portions of three salt marshes, the Great Sippewissett Marsh (Cape Cod, MA), Sapelo Island (Georgia), and the Hackensack Meadowlands (N.J.), and from the sediments of an estuary, Newark Bay (N.J.). Pyrite particles were abundant in sediments from all sites. Both fine grained pyrite crystals and framboids were found. Single, fine grained crystals (diameter = 0.2 to 2.0 micrometers) predominated in all samples, strong evidence for rapid formation of pyrite. We also found both microcrystalline and framboidal iron-oxyhydroxide phases in many of the sediment samples. This is evidence of pyrite oxidation within the sediments and suggests that iron is conserved in salt marshes even as pyrite is oxidized. The thermodynamic stability of iron phases in marsh sediments, and recent pyrite oxidation studies in coal, suggest goethite as the crystalline iron-oxyhydroxide phase present. In addition, we sometimes found a red amorphous coating on grass roots from the Great Sippewissett and Sapelo Island marshes. This coating is likely a form of hydrated iron (III) oxide.

Luther, George W., III; Giblin, Anne; Howarth, Robert W.; Ryans, Robert A.

1982-12-01

21

Arsenic Adsorption Onto Iron Oxides Minerals  

NASA Astrophysics Data System (ADS)

The predominant form of arsenic in water is as an inorganic ion. Under different redox conditions arsenic in water is stable in the +5 and +3 oxidation states. Arsenic oxidation state governs its toxicity, chemical form and solubility in natural and disturbed environments. As (III) is found in anoxic environments such as ground water , it is toxic and the common species is the neutral form, H3AsO3. As (V) is found in aerobic conditions such as surface water, it is less toxic and the common species in water are: H2AsO4 - and HAsO4 {- 2}. The water pH determines the predominant arsenate or arsenite species, however, both forms of arsenic can be detected in natural water systems. Iron oxides minerals often form in natural waters and sediments at oxic-anoxic boundaries. Over time they undergo transformation to crystalline forms, such as goethite or hematite. Both As(V) and As(III) sorbs strongly to iron oxides, however the sorption behavior of arsenic is dependent on its oxidation state and the mineralogy of the iron oxides. Competition between arsenic and others ions, such fluoride, sulphate and phosphate also play a role. On the other hand, calcium may increase arsenic adsorption onto iron oxides. Electrokinetic studies and adsorption experiments were carried out in order to determine which conditions favour arsenic adsorption. Hematite, goethite and magnetite as iron based sorbents were used. Test were also conducted with a laterite soil rich in iron minerals. The focus of this study is to evaluate physical and chemical conditions which favour arsenic adsorption onto iron oxides minerals, the results contribute to an understanding of arsenic behaviour in natural and disturbed environments. Furthermore, results could contribute in developing an appropriate remediation technology for arsenic removal in water using iron oxides minerals.

Aredes, S.; Klein, B.; Pawlik, M.

2004-12-01

22

21 CFR 73.2250 - Iron oxides.  

Code of Federal Regulations, 2013 CFR

...GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION...Identity. The color additives iron oxides consist...amounts consistent with good manufacturing practice. (d) Labeling. The color additive and any mixture...

2013-04-01

23

21 CFR 73.2250 - Iron oxides.  

...GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION...Identity. The color additives iron oxides consist...amounts consistent with good manufacturing practice. (d) Labeling. The color additive and any mixture...

2014-04-01

24

21 CFR 73.2250 - Iron oxides.  

Code of Federal Regulations, 2012 CFR

...GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION...Identity. The color additives iron oxides consist...amounts consistent with good manufacturing practice. (d) Labeling. The color additive and any mixture...

2012-04-01

25

Microorganisms pumping iron: anaerobic microbial iron oxidation and reduction.  

PubMed

Iron (Fe) has long been a recognized physiological requirement for life, yet for many microorganisms that persist in water, soils and sediments, its role extends well beyond that of a nutritional necessity. Fe(II) can function as an electron source for iron-oxidizing microorganisms under both oxic and anoxic conditions and Fe(III) can function as a terminal electron acceptor under anoxic conditions for iron-reducing microorganisms. Given that iron is the fourth most abundant element in the Earth's crust, iron redox reactions have the potential to support substantial microbial populations in soil and sedimentary environments. As such, biological iron apportionment has been described as one of the most ancient forms of microbial metabolism on Earth, and as a conceivable extraterrestrial metabolism on other iron-mineral-rich planets such as Mars. Furthermore, the metabolic versatility of the microorganisms involved in these reactions has resulted in the development of biotechnological applications to remediate contaminated environments and harvest energy. PMID:16980937

Weber, Karrie A; Achenbach, Laurie A; Coates, John D

2006-10-01

26

Exploring Microbial Iron Oxidation in Wetland Soils  

NASA Astrophysics Data System (ADS)

Iron is one of the most abundant elements on earth and is essential for life. Because of its importance, iron cycling and its interaction with other chemical and microbial processes has been the focus of many studies. Iron-oxidizing bacteria (FeOB) have been detected in a wide variety of environments. Among those is the rhizosphere of wetland plants roots which release oxygen into the soil creating suboxic conditions required by these organisms. It has been reported that in these rhizosphere microbial iron oxidation proceeds up to four orders of magnitude faster than strictly abiotic oxidation. On the roots of these wetland plants iron plaques are formed by microbial iron oxidation which are involved in the sequestering of heavy metals as well organic pollutants, which of great environmental significance.Despite their important role being catalysts of iron-cycling in wetland environments, little is known about the diversity and distribution of iron-oxidizing bacteria in various environments. This study aimed at developing a PCR-DGGE assay enabling the detection of iron oxidizers in wetland habitats. Gradient tubes were used to enrich iron-oxidizing bacteria. From these enrichments, a clone library was established based on the almost complete 16s rRNA gene using the universal bacterial primers 27f and 1492r. This clone library consisted of mainly ?- and β-Proteobacteria, among which two major clusters were closely related to Gallionella spp. Specific probes and primers were developed on the basis of this 16S rRNA gene clone library. The newly designed Gallionella-specific 16S rRNA gene primer set 122f/998r was applied to community DNA obtained from three contrasting wetland environments, and the PCR products were used in denaturing gradient gel electrophoresis (DGGE) analysis. A second 16S rRNA gene clone library was constructed using the PCR products from one of our sampling sites amplified with the newly developed primer set 122f/998r. The cloned 16S rRNA gene sequences all represented novel culturable iron oxidizers most closely related to Gallionella spp. Based on their nucleotide sequences four groups could be identified, which were comparable to the DGGE banding pattern obtained before with the gradient tubes enrichments. The above mentioned nested PCR-DGGE method was used to study the distribution and community composition of Gallionella-like iron-oxidizing bacteria under the influence of plants species, soil depth, as well as season. Soil samples from Appels, Belgium, an intertidal, freshwater marsh known to hold intensive iron cycling, were taken from 5 different vegetation types in April, July and October 2007. Soil cores were sliced at 1-cm intervals and subjected to chemical and molecular analyses. The DGGE patterns showed that the community of iron-oxidizing bacteria differed with vegetation type, and sediment depth. Samples taken in autumn held lower diversity in Gallionella-related iron oxidizers than those sampled in spring and summer.

Wang, J.; Muyzer, G.; Bodelier, P. L. E.; den Oudsten, F.; Laanbroek, H. J.

2009-04-01

27

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

PubMed

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

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

2014-10-01

28

The Electrical Properties of Native and Deposited Thin Aluminum Oxide Layers on Aluminum: Hydration Effects  

SciTech Connect

The electronic defect density of native, anodic, and synthetic Al oxide layers on Al were studied by solid state electrical measurement as a function of hydration OF the oxide. The non-hydrated synthetic Al oxide layers, which included electron cyclotron resonance (ECR) plasma deposited oxides as well as ECR plasma grown oxides, were highly insulating with electrical transport dominated by thermal emission from deep traps within the oxide. Following hydration these oxides and the native oxides exhibited a large increase in electronic defect density as evidenced by increases in the DC leakage current, reduction in the breakdown field, and increase in AC conductance. Elastic recoil detection of hydrogen revealed that hydration leads to hydrogen incorporation in the oxide films and hydrogen injection through the films into the Al layer below. The increase in electronic defect concentration is related to this hydrogenation and may play a significant role in localized corrosion initiation.

Barbour, J.C.; Copeland, R.G.; Dunn, R.G.; Missert, N.; Montes, L.P.; Son, K.-A.; Sullivan, J.P.

1998-11-11

29

Thermodynamics of Iron Oxidation in Metallurgical Slags  

NASA Astrophysics Data System (ADS)

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.

Matousek, Jan

2012-11-01

30

Laboratory experiments on the weathering of iron meteorites and carbonaceous chondrites by iron-oxidizing bacteria  

NASA Astrophysics Data System (ADS)

Batch culture experiments were performed to investigate the weathering of meteoritic material by iron-oxidizing bacteria. The aerobic, acidophilic iron oxidizer (A. ferrooxidans) was capable of oxidizing iron from both carbonaceous chondrites (Murchison and Cold Bokkeveld) and iron meteorites (York and Casas Grandes). Preliminary iron isotope results clearly show contrasted iron pathways during oxidation with and without bacteria suggesting that a biological role in meteorite weathering could be distinguished isotopically. Anaerobic iron-oxidizers growing under pH-neutral conditions oxidized iron from iron meteorites. These results show that rapid biologicallymediated alteration of extraterrestrial materials can occur in both aerobic and anaerobic environments. These results also demonstrate that iron can act as a source of energy for microorganisms from both iron and carbonaceous chondrites in aerobic and anaerobic conditions with implications for life on the early Earth and the possible use of microorganisms to extract minerals from asteroidal material.

Gronstal, A.; Pearson, V.; Kappler, A.; Dooris, C.; Anand, M.; Poitrasson, F.; Kee, T. P.; Cockell, C. S.

2009-03-01

31

The Exclusion of D2O from the Hydration Sphere of FeSO4{middle dot} 7H2O Oxidized by Thiobacillus ferrooxidans.  

PubMed

Infrared spectra demonstrate that neither FeSO(4) . 7H(2)O nor its bacterial or abiotic hydrated oxidation products incorporate deuterium in acid D(2)O solutions. Deuterium exchange occurred as bridging OD when bacterially oxidized iron was precipitated from D(2)O solutions as ferric hydroxysulfates. The exclusion of deuterium depended upon the stabilization of aquated Fe(II) and Fe(III) complexes by sulfate ions in outer-sphere coordination and is consistent with the requirement and postulated role of sulfate in iron oxidation by Thiobacillus ferrooxidans. PMID:17773337

Lazaroff, N

1983-12-23

32

Iron–iron oxide composite thin films prepared by chemical vapor deposition from iron pentacarbonyl  

Microsoft Academic Search

Iron–iron oxide (Fe–Fe3O4) composite thin films were prepared by an atmospheric-pressure chemical vapor deposition method. Iron pentacarbonyl and carbon dioxide gas were used as source materials. The effect of carbon dioxide mole fraction on the structure of the film is discussed. For both Fe–Fe3O4 and Fe–?-Fe2O3 films, the magnetic properties were obtained from the hysteresis curve of in-plane magnetization. The

Toshiro Maruyama; Yoshitaka Shinyashiki

1998-01-01

33

Rechargeable 3 V Li cells using hydrated lamellar manganese oxide  

SciTech Connect

The synthesis and the electrochemical features of hydrated lamellar manganese oxides are reported. The authors use the reduction of aqueous permanganate solution by fumaric acid and the oxidation of manganese hydroxide by an aqueous permanganate solution to obtain sol-gel birnessite and classical X-exchanged birnessites (X = Li, Al, Na), respectively. The high oxidation state of Mn associated with the 2D character of the hot lattice allows high specific capacities (150 to 200 Ah/kg) available in the potential range of 4 to 2 V. Interlayer water provides the structural stability of the host lattice required for long cycling. Rechargeable two-electrode Li cells using starved or flooded electrolytes were built with the cathodic materials. The batteries exhibit a satisfactory behavior with a specific capacity of 160 Ah/kg recovered after 30 cycles at the C/20 discharge-charge rate for the sol-gel birnessite. This paper demonstrates an interest in cathodic materials based on oxides containing structural water for use in secondary Li batteries.

Bach, S.; Pereira-Ramos, J.P. [CNRS, Thiais (France). Electrochimie, Catalyse et Synthese Organique; Baffier, N. [CNRS, Paris (France). Chimie Appliquee de l`Etat Solide

1996-11-01

34

The Exclusion of D2O from the Hydration Sphere of FeSO4 \\\\cdot 7H2O Oxidized by Thiobacillus ferrooxidans  

Microsoft Academic Search

Infrared spectra demonstrate that neither FeSO4 \\\\cdot 7H2O nor its bacterial or abiotic hydrated oxidation products incorporate deuterium in acid D2O solutions. Deuterium exchange occurred as bridging OD when bacterially oxidized iron was precipitated from D2O solutions as ferric hydroxysulfates. The exclusion of deuterium depended upon the stabilization of aquated Fe(II) and Fe(III) complexes by sulfate ions in outer-sphere coordination

Norman Lazaroff

1983-01-01

35

The Iron-Catalyzed Oxidation of Hydrazine by Nitric Acid  

SciTech Connect

To assess the importance of iron to hydrazine stability, the study of hydrazine oxidation by nitric acid has been extended to investigate the iron-catalyzed oxidation. This report describes those results.

Karraker, D.G.

2001-07-17

36

Low temperature synthesis of bilayer hydrated cesium cobalt oxide  

SciTech Connect

Bilayer hydrated Na{sub 0.35}CoO{sub 2}.1.3H{sub 2}O structure has re-directed superconductivity research in recent years. Here, we develop a low temperature synthesis method to prepare a novel hydrous Cs{sub 0.2}CoO{sub 2}.0.63H{sub 2}O compound in one step. The bilayer-hydrate of Cs{sub 0.2}CoO{sub 2}.0.63H{sub 2}O with a greatest interlayer spacing d=10.0(2) A among alkali cobalt oxides has been grown in crystal form. Magnetic susceptibility measurement of Cs{sub 0.2}CoO{sub 2}.0.63H{sub 2}O displays a paramagnetic behavior down to 1.9 K. With the assistance of low temperature molten CsOH solvent, crystals of Rb{sub 0.30}CoO{sub 2}.0.36H{sub 2}O and K{sub 0.35}CoO{sub 2}.0.4H{sub 2}O can be grown. The results provide the capability for preparing a novel hydrous structure and the systematic investigation of interlayer coupling effect of alkali ion insertion compounds. - Graphical abstract: BLH Cs{sub 0.2}CoO{sub 2}.0.63H{sub 2}O crystals grown from low temperature molten salt.

Tang, Horng Y. [Department of Applied Chemistry, National Chi Nan University, Puli, Taiwan (China)]. E-mail: hytang@ncnu.edu.tw; Lin, Hsiao Y. [Department of Applied Chemistry, National Chi Nan University, Puli, Taiwan (China); Wang, Ming J. [Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan (China); Liao, Ming Y. [Department of Applied Chemistry, National Chi Nan University, Puli, Taiwan (China); Hsu, Fon C. [Department of Materials Science, National Tsing Hua University, Hsinchu, Taiwan (China); Mok, Boon H. [Department of Materials Science, National Tsing Hua University, Hsinchu, Taiwan (China); Liu, Jean L. [Department of Applied Chemistry, National Chi Nan University, Puli, Taiwan (China); Beasley, Michael T. [Department of Applied Chemistry, National Chi Nan University, Puli, Taiwan (China); Sheu, Hwo S. [National Synchrotron Radiation Research Center, Hsinchu, Taiwan (China); Wu, Maw K. [Institute of Physics, Academia Sinica, Taipei, Taiwan (China)

2006-08-15

37

Electrodissolution of electrodeposited iron oxides  

SciTech Connect

Galvanostatic reduction of ferric oxide was studied in phosphate solutions over a range of pH values. The oxides were prepared on gold by anodic electrodeposition from dilute ferrous borate solution. With increased pH, the potential of the reduction arrests decreased and the charge associated with the arrest increased. A dependence of -60 mV/pH was observed except between pH 7.5 and 8.5 where the slope approximated -180 mV/pH. Above pH 7.5 the slope was consistent with the thermodynamic predicted slope of -180 mV/pH expected from reductive dissolution of ferric oxide forming soluble ferrous ions. At higher pH values, a slope of -60 mV/pH has been accounted for by oxide reduction to form a solid lower valent oxide.

Isaacs, H.S.; Ryan, M.P. [Brookhaven National Lab., Upton, NY (United States); Kalonousky, D.N. [State Univ. of New York, Stony Brook, NY (United States). Dept. of Materials Science; Virtanen, S. [Swiss Federal Inst. of Tech., Zurich (Switzerland). Inst. of Materials Chemistry and Corrosion

1996-12-31

38

Acid monolayer functionalized iron oxide nanoparticle catalysts  

NASA Astrophysics Data System (ADS)

Superparamagnetic iron oxide nanoparticle functionalization is an area of intensely active research, with applications across disciplines such as biomedical science and heterogeneous catalysis. This work demonstrates the functionalization of iron oxide nanoparticles with a quasi-monolayer of 11-sulfoundecanoic acid, 10-phosphono-1-decanesulfonic acid, and 11-aminoundecanoic acid. The carboxylic and phosphonic moieties form bonds to the iron oxide particle core, while the sulfonic acid groups face outward where they are available for catalysis. The particles were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectrometry (XPS), and dynamic light scattering (DLS). The sulfonic acid functionalized particles were used to catalyze the hydrolysis of sucrose at 80° and starch at 130°, showing a higher activity per acid site than the traditional solid acid catalyst Amberlyst-15, and comparing well against results reported in the literature for sulfonic acid functionalized mesoporous silicas. In sucrose catalysis reactions, the phosphonic-sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic-sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. Between the two sulfonic ligands, the phosphonates produced a more tightly packed monolayer, which corresponded to a higher sulfonic acid loading, lower agglomeration, lower recoverability through application of an external magnetic field, and higher activity per acid site for the hydrolysis of starch. Functionalizations with 11-aminoundecanoic acid resulted in some amine groups binding to the surfaces of iron oxide nanoparticles. This amine binding is commonly ignored in iron oxide nanoparticle syntheses and functionalizations for biomedical and catalytic applications, affecting understandings of surface charge and other material properties.

Ikenberry, Myles

39

Ferrous iron oxidation by anoxygenic phototrophic bacteria  

NASA Astrophysics Data System (ADS)

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 that bear on our understanding of the origin of Precambrian banded iron formations10-14. The reducing power of ferrous iron increases dramatically at pH values higher than 2-3 owing to the formation of ferric hydroxy and oxyhydroxy compounds1,2,15 (Fig. 1). The standard redox potential of Fe3+/Fe2+ (E0 = +0.77 V) is relevant only under acidic conditions. At pH 7.0, the couples Fe(OH)3/Fe2+ (E'0 = -0.236V) or Fe(OH)3 + HCO-3FeCO3 (E'0 = +0.200 V) prevail, matching redox potentials measured in natural sediments9,16,17. It should thus be possible for Fe(n) around pH 7.0 to function as an electron donor for anoxygenic photosynthesis. The midpoint potential of the reaction centre in purple bacteria is around +0.45 V (ref. 18). Here we describe purple, non-sulphur bacteria that can indeed oxidize colourless Fe(u) to brown Fe(in) and reduce CO2 to cell material, implying that oxygen-independent biological iron oxidation was possible before the evolution of oxygenic photosynthesis.

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

1993-04-01

40

Synthesis of iron oxide nanoflakes at lower temperature by air oxidation of iron foils  

NASA Astrophysics Data System (ADS)

Iron oxide ?-Fe2O3 nanoflakes have been synthesized on iron foil by a simple air oxidation process. Dry air flows constantly over the iron foils during the oxidation process in the temperature range of 350–600 °C with annealing periods of 1–6 h. Large quantities of nanoflakes with average tip and bottom diameters of 40 and 140 nm, respectively, and average lengths of 200 nm were obtained at a temperature of 450 °C and 6 h of annealing. These nanoflakes had a preferential growth direction of (110) with a 0.25 nm fringe spacing. Their surface morphology, phase purity, and crystal structures were confirmed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) analysis. Good-quality iron oxide nanoflakes can be obtained by optimizing the growth temperature and annealing period. Surface diffusion of iron atoms and iron oxide molecules was believed to be the growth mechanism of the nanoflakes because of the low oxidation temperature used.

Rashid, Norhana Mohamed; Li, Xuyang; Kishi, Naoki; Soga, Tetsuo

2014-11-01

41

Thermochemistry of iron manganese oxide spinels  

Microsoft Academic Search

Oxide melt solution calorimetry has been performed on iron manganese oxide spinels prepared at high temperature. The enthalpy of formation of (MnxFe1?x)3O4 at 298K from the oxides, tetragonal Mn3O4 (hausmannite) and cubic Fe3O4 (magnetite), is negative from x=0 to x=0.67 and becomes slightly positive for 0.67

Sophie Guillemet-Fritsch; Alexandra. Navrotsky; Philippe Tailhades; Hervé Coradin; Miaojun Wang

2005-01-01

42

Water clustering on nanostructured iron oxide films  

NASA Astrophysics Data System (ADS)

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.

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

43

Oxidation Potentials in Iron and Steel Making  

NASA Astrophysics Data System (ADS)

The state of oxidation of a pyrometallurgical process given by the partial pressure of oxygen and the temperature (the oxidation potential) is one of the important properties monitored and controlled in the smelting and refining of iron and the nonferrous metals. Solid electrolyte sensors based on ZrO2 and a reference electrode such as Cr/Cr2O3 to measure the oxygen pressure found early application in the steel industry, followed soon after in copper, nickel, lead, and zinc smelting. Similar devices are installed in automobile postcombustion/exhaust trains as part of emission control systems. The current discussion reviews this technology as applied in the primary steps of iron and steel making and refining.

Matousek, J. W.

2013-11-01

44

Optical properties of iron oxides  

NASA Astrophysics Data System (ADS)

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).

Musfeldt, Janice

2012-02-01

45

Combination Effects of Chloral Hydrate and Nitrous Oxide/Oxygen in the Mouse Staircase Test  

PubMed Central

The effects of chloral hydrate and/or nitrous oxide were assessed in the mouse staircase test. In this paradigm, the number of steps ascended is thought to reflect locomotor activity, whereas the number of rears is an index of anxiety. Chloral hydrate alone produced a dose-dependent decrease in the number of rears but no change in the number of steps ascended except at the highest dose. Nitrous oxide alone produced a concentration-related increase in the number of steps ascended but no change in rearing. When the two drugs were combined, nitrous oxide appeared to potentiate the rearing suppressant activity of chloral hydrate. Analysis of our experimental findings suggests that chloral hydrate exerts a specific anxiolytic drug effect that can be potentiated by concurrent treatment with nitrous oxide. PMID:3166349

Pruhs, Ronald J.; Kalbfleisch, John H.; Quock, Raymond M.

1988-01-01

46

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

PubMed

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

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

2014-11-01

47

Iron oxidation state in hydrous rhyolites  

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

48

Iron-Dependent Oxidation, Ubiquitination, and Degradation of Iron Regulatory Protein 2: Implications for Degradation of Oxidized Proteins  

Microsoft Academic Search

The ability of iron to catalyze formation of reactive oxygen species significantly contributes to its toxicity in cells and animals. Iron uptake and distribution is regulated tightly in mammalian cells, in part by iron regulatory protein 2 (IRP2), a protein that is degraded efficiently by the proteasome in iron-replete cells. Here, we demonstrate that IRP2 is oxidized and ubiquitinated in

Kazuhiro Iwai; Steven K. Drake; Nancy B. Wehr; Allan M. Weissman; Timothy Lavaute; Nagahiro Minato; Richard D. Klausner; Rodney L. Levine; Tracey A. Rouault

1998-01-01

49

Candidate anode materials for iron production by molten oxide electrolysis  

E-print Network

Molten oxide electrolysis (MOE) has been identified by the American Iron and Steel Institute (AISI) as one of four possible breakthrough technologies to alleviate the environmental impact of iron and steel production. This ...

Paramore, James D

2010-01-01

50

A novel regeneration of iron citrate solution by biooxidation of iron-oxidizing bacteria.  

PubMed

Liquid phase oxidation process using chelated iron solution is among the most promising techniques for the hydrogen sulfide removal due to its double advantage of waste minimization and resource recovery. Regeneration of chelated iron is a core reaction in this process. Regeneration of chelated iron in acidic solution is very difficult. In this paper, a novel regeneration of iron citrate in acidic solution by biooxidation of iron-oxidizing bacteria was reported firstly. By using such a process, the influence of iron-oxidizing bacteria on the regeneration rate was investigated. The results demonstrated the regeneration rate with the new technology was increased significantly. The process may contribute to the biooxidation of iron-oxidizing bacteria. Application of this novel process increased the regeneration rate under the optimum conditions, suggesting the iron citrate regeneration process may be a feasible and economical method in application. PMID:25242290

Wang, Y J; Li, D P; Liu, C; Zhan, G Q; He, X H

2014-11-01

51

High Temperature Oxidation of Iron-Chromium Alloys  

E-print Network

High Temperature Oxidation of Iron- Chromium Alloys Lars Mikkelsen Risø-PhD-2(EN) Risø National Laboratory Roskilde, Denmark June 2003 #12;Author: Lars Mikkelsen Title: High Temperature Oxidation of Iron and Peter H. Larsen for many good discussions during the work. #12;3 Abstract The high temperature oxidation

52

Chemical storage of hydrogen by modified iron oxides  

Microsoft Academic Search

Pure hydrogen may be supplied directly to polymer electrolyte fuel cell (PEFC) through the decomposition of water by reduced iron oxide at low temperatures <573K. Effects of various metal additives in the reduced iron oxide on the production of hydrogen from water have been examined at a temperature range 373–873K. The decomposition of water is caused by the oxidation of

K Otsuka; T Kaburagi; C Yamada; S Takenaka

2003-01-01

53

Mechanism of the Fischer-Tropsch synthesis on iron oxides  

SciTech Connect

It has been shown previously that in the hydrogenation of carbon monoxide the activity and the stability with time on stream of iron catalysts is much better when these catalysts are preoxidized rather than prereduced. For the iron supported catalysts (on an inorganic carrier like silica or alumina) the oxidized state of iron is particularly well maintained, together with the high activity for the catalysts of the aerogel type where strong oxide-oxide interactions can be developed.

Reymond, J.P.; Pommier, B.; Telchner, S.J.

1986-03-01

54

Compact Zwitterion-Coated Iron Oxide Nanoparticles for Biological Applications  

E-print Network

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 ...

Wei, He

55

Mineral resource of the month: iron oxide pigments  

USGS Publications Warehouse

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.

2008-01-01

56

Sophorolipids-functionalized iron oxide nanoparticles.  

PubMed

Functional iron oxide nanoparticles (NP) have been synthesized in a one and a two-step method using a natural functional glycolipid belonging to the family of sophorolipids (SL). These compounds, whose open acidic form is highly suitable for nanoparticle stabilization, are readily obtained by a fermentation process of the yeast Candida bombicola (polymorph Starmerella bombicola) in large amounts. The final carbohydrate coated iron oxide nanoparticles represent interesting potentially biocompatible materials for biomedical applications. According to the synthesis strategy, magnetic properties can eventually be tuned, thus putting in evidence the direct effect of the glycolipid on the final material's structure (maghemite and ferrihydrite have been obtained here). A combination of FT-IR, Dynamic Light Scattering (DLS) and UV-Vis experiments shows that SL complex the nanoparticle surface via their accessible COOH group thus forming stable colloids, whose hydrodynamic diameter mostly varies between 10 nm and 30 nm, both in water and in KCl-containing (0.01 M and 2 M) solutions. The materials can stand multiple filtration steps (up to 10) at different extents, where the largest recorded average aggregate size is 100 nm. In general, materials synthesized at T = 80 °C display better stability and smaller size distribution than those obtained at room temperature. PMID:23247504

Baccile, Niki; Noiville, Romain; Stievano, Lorenzo; Van Bogaert, Inge

2013-02-01

57

Ferrous iron sorption by hydrous metal oxides.  

PubMed

Ferrous iron is critical to a number of biogeochemical processes that occur in heterogeneous aquatic environments, including the abiotic reductive transformation of subsurface contaminants. The sorption of Fe(II) to ubiquitous soil minerals, particularly iron-free mineral phases, is not well understood. Colloidal TiO2, gamma-AlOOH, and gamma-Al2O2 were used as model hydrous oxides to investigate Fe(II) sorption to iron-free mineral surfaces. Rapid Fe(II) sorption during the first few hours is followed by a much slower uptake process that continues for extended periods (at least 30 days). For equivalent solution conditions, the extent of Fe(II) sorption decreases in the order TiO2 >gamma-Al2O3 >gamma-AlOOH. Short-term equilibrium sorption data measured over a wide range of conditions (pH, ionic strength, Fe(II)-to-sorbent ratio) are well described by the diffuse double layer model. Fe(II) sorption to TiO2 is best described by a single-site model that considers formation of two surface complexes, SOFe+ and SOFeOH0. For gamma-AlOOH and gamma-Al2O3, sorption data are best described by a two-site model that considers formation of SOFe+ complexes at weak- and strong-binding surface sites. Accurate description of sorption data for higher Fe(II) concentrations at alkaline pH conditions requires the inclusion of a Fe(II) surface precipitation reaction in the model formulation. The presence of common groundwater constituents (calcium, sulfate, bicarbonate, or fulvic acid) had no significant effect on Fe(II) sorption. These results demonstrate that iron-free soil minerals can exert a significant influence on Fe(II) sorption and speciation in heterogeneous aquatic systems. PMID:16337955

Nano, Genevieve Villaseñor; Strathmann, Timothy J

2006-05-15

58

Superparamagnetic Iron Oxide Nanoparticles with Variable Size and an Iron Oxidation State as Prospective Imaging Agents  

PubMed Central

Magnetite nanoparticles in the size range of 3.2-7.5 nm were synthesized in high yields under variable reaction conditions using high-temperature hydrolysis of the precursor iron(II) and iron(III) alkoxides in diethylene glycol solution. The average sizes of the particles were adjusted by changing the reaction temperature and time and by using a sequential growth technique. To obtain ?-iron(III) oxide particles in the same range of sizes, magnetite particles were oxidized with dry oxygen in diethylene glycol at room temperature. The products were characterized by DLS, TEM, X-ray powder diffractometry, TGA, chemical analysis, and magnetic measurements. NMR r1 and r2 relaxivity measurements in water and diethylene glycol (for OH and CH2 protons) have shown a decrease in the r2/r1 ratio with the particle size reduction, which correlates with the results of magnetic measurements on magnetite nanoparticles. Saturation magnetization of the oxidized particles was found to be 20% lower than that for Fe3O4 with the same particle size, but their r1 relaxivities are similar. Because the oxidation of magnetite is spontaneous under ambient conditions, it was important to learn that the oxidation product has no disadvantages as compared to its precursor and therefore may be a better prospective imaging agent because of its chemical stability. PMID:23249219

Kucheryavy, Pavel; He, Jibao; John, Vijay T.; Maharjan, Pawan; Spinu, Leonard; Goloverda, Galina Z.; Kolesnichenko, Vladimir L.

2013-01-01

59

Chlorobenzene oxidation using ozone over iron oxide and manganese oxide catalysts.  

PubMed

A low-temperature catalytic oxidation of chlorobenzene (CB) has been performed at temperatures of 60-210°C using ozone (O(3)) over iron oxide and manganese oxide, respectively. In the absence of ozone, CB conversion achieved with these two catalysts at 200°C was below 10%. However, addition of 1200 ppm ozone results in a remarkable increase in CB conversion and the conversion reaches 91.7% at 150°C for iron oxide, while 81.5% conversion is achieved with manganese oxide at 90°C. The activation energy of manganese oxide (48 kJ mol(-1)) is higher than that of iron oxide (43 kJ mol(-1)) without ozone. However, as ozone is added, the activation energy is significantly reduced to 20.0 kJ mol(-1) for iron oxide. CO and CO(2) are the only carbon-containing products detected in the effluent gas stream. For the long-term test, no obvious deactivation was found in iron oxide and ozone. However, in the case of manganese oxide and ozone, 3% reduction of CB conversion was observed. Slight deactivation might be attributed to a small amount of reaction byproducts (carboxylic acid species) and residual chloride (MnCl(2)) being deposited on the active sites of the catalysts. PMID:21227575

Wang, Hou Chuan; Liang, Hsu Shang; Chang, Moo Been

2011-02-28

60

Supported and mixed oxide catalysts based on iron and titanium for the oxidative decomposition of chlorobenzene  

Microsoft Academic Search

Iron oxide supported on titanium dioxide (Fe2O3\\/TiO2) and iron–titanium mixed oxide (Fe–Ti-oxide) catalysts were prepared via wetness impregnation and sol–gel methods, respectively. The catalytic activity of the two materials for the oxidation of chlorobenzene was studied and compared with the activity of pure titanium and iron oxides as well as MgO-supported iron oxide. Fe2O3\\/TiO2 and Fe–Ti-oxide have shown higher catalytic

Abbas Khaleel; Aysha Al-Nayli

2008-01-01

61

Enhancement of the performance of gas hydrate kinetic inhibitors with polyethylene oxide  

Microsoft Academic Search

Inclusion of polyethylene oxide into a kinetic inhibitor solution was found to enhance the performance of the inhibitor. Polyethylene oxide is a commercially available high molecular weight polymer that is not a kinetic inhibitor by itself. The hydrate formation experiments in the presence of the various inhibitor solutions were conducted in a vessel in a semi-batch manner at constant pressure

Ju Dong Lee; Peter Englezos

2005-01-01

62

Battles with Iron: Manganese in Oxidative Stress Protection*  

PubMed Central

The redox-active metal manganese plays a key role in cellular adaptation to oxidative stress. As a cofactor for manganese superoxide dismutase or through formation of non-proteinaceous manganese antioxidants, this metal can combat oxidative damage without deleterious side effects of Fenton chemistry. In either case, the antioxidant properties of manganese are vulnerable to iron. Cellular pools of iron can outcompete manganese for binding to manganese superoxide dismutase, and through Fenton chemistry, iron may counteract the benefits of non-proteinaceous manganese antioxidants. In this minireview, we highlight ways in which cells maximize the efficacy of manganese as an antioxidant in the midst of pro-oxidant iron. PMID:22247543

Aguirre, J. Dafhne; Culotta, Valeria C.

2012-01-01

63

40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Cobalt iron manganese oxide, carboxylic acid-modified...Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid-modified...identified generically as cobalt iron manganese oxide, carboxylic...

2013-07-01

64

40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).  

... 2014-07-01 false Cobalt iron manganese oxide, carboxylic acid-modified...Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid-modified...identified generically as cobalt iron manganese oxide, carboxylic...

2014-07-01

65

Magnetic coupling among spinel iron oxide microparticles by Mssbauer spectroscopy  

E-print Network

L-437 Magnetic coupling among spinel iron oxide microparticles by Mössbauer spectroscopy E. Tronc cristalline au sein d'agrégats est suggérée. Abstract 2014 Mössbauer spectra of hydrous spinel iron oxide particles with thermal fluctuations oftheir magnetization vector (M) among the easy directions

Boyer, Edmond

66

Recent advances in iron oxide nanocrystal technology for medical imaging  

Microsoft Academic Search

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

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

2006-01-01

67

Unusual oxidation states and electronic configurations of iron  

Microsoft Academic Search

A good correlation between electronic configuration and structural and chemical bonding factors makes possible the stabilization of unusual oxidation states of transition elements. Such a predictive approach is illustrated by the synthesis and characterization of the first six-coordinated high-spin iron(IV) and iron(V) oxides.

G. Demazeau; B. Buffat; M. Pouchard; P. Hagenmuller

1982-01-01

68

Progress in electrochemical synthesis of magnetic iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

Recently, magnetic iron oxide particles have been emerged as significant nanomaterials due to its extensive range of application in various fields. In this regard, synthesis of iron oxide nanoparticles with desirable properties and high potential applications are greatly demanded. Therefore, investigation on different iron oxide phases and their magnetic properties along with various commonly used synthetic techniques are remarked and thoroughly described in this review. Electrochemical synthesis as a newfound method with unique advantages is elaborated, followed by design approaches and key parameters to control the properties of the iron oxide nanoparticles. Additionally, since the dispersion of iron oxide nanoparticles is as important as its preparation, surface modification issue has been a serious challenge which is comprehensively discussed using different surfactants. Despite the advantages of the electrochemical synthesis method, this technique has been poorly studied and requires deep investigations on effectual parameters such as current density, pH, electrolyte concentration etc.

Ramimoghadam, Donya; Bagheri, Samira; Hamid, Sharifah Bee Abd

2014-11-01

69

PRECIPITATION CHEMISTRY OF MAGNESIUM SULFITE HYDRATES IN MAGNESIUM OXIDE SCRUBBING  

EPA Science Inventory

The report gives results of laboratory studies defining the precipitation chemistry of MgSO3 hydrates. The results apply to the design of Mg-based scrubbing processes for SO2 removal from combustion flue gas. In Mg-based scrubbing processes, MgSO3 precipitates as either trihydrat...

70

High Pressure Effects on the Iron-Iron Oxide and Nickel-Nickel Oxide Oxygen Fugacity Buffers  

E-print Network

High Pressure Effects on the Iron-Iron Oxide and Nickel- Nickel Oxide Oxygen Fugacity Buffers fugacity (fO2) buffer. These buffers are precisely known at 1 bar, but under high pressures corresponding to the conditions of the deep Earth, oxygen fugacity buffers are poorly calibrated. Reference (1 bar) fO2 buffers

Campbell, Andrew

71

Moessbauer spectroscopic study of phase conversions of an iron-containing oxide catalyst for oxidative dehydrogenation of butenes  

SciTech Connect

Moessbauer spectroscopy was used to study the structure of ..gamma..-Al/sub 2/O/sub 3/-supported iron oxide, which is catalytically active in the oxidative dehydrogenation of butenes to divinyl. The phase conversions of the catalyst were investigated after treating it in reducing (butenes) and reaction (butenes + oxygen + water vapor) media and after regeneration in a stream of oxygen. It is shown that the supported phase changes from a structure similar to hematite (..cap alpha..-Fe/sub 2/O/sub 3/) to spinel structure both under the effect of butenes and the reaction mixture. When this happens ion exchange occurs between the spinel and the support, with the formation of partly hydrated complexes of Fe/sup 2 +/ ions in an asymmetric environment of O/sup 2 -/ ions and OH/sup -/ groups of the lattice of the support. These complexes vanish upon reoxidation of the catalyst, and part of the spinel is oxidized to hematite.

Golub'ev, A.V.; Matveev, A.I.; Amirbekov, E.N.; Maksimov, Yu.V.; Suzdalev, I.P.

1988-06-01

72

Controlling barrier penetration via exothermic iron oxidation.  

PubMed

Exothermic iron oxidation is an elegant means to generate heat, with the potential to modulate barrier penetration if reaction kinetics can be controlled. This aim of this study was to gain a fundamental understanding of how these temperature change kinetics influenced barrier diffusion rate. Lidocaine transport through a hydrophilic carboxymethyl cellulose (CMC) gel was compared using two rapid iron oxidation reactions initiated by water (ExoRap(50), T(max)-47.7 ± 0.6 °C, t(max)-3.3 ± 0.6 min, ExoRap(60), T(max)-60.4 ± 0.3 °C, t(max)-9.3 ± 0.6 min) and a slower reaction initiated by oxygen (ExoSl(45)T(max)-ca. 44 °C, t(max) ca. 240 min). Temperature change induced by the oxygen initiated reaction (ExoSl(45)) was almost double those initiated by water (over 4h), but lidocaine diffusion was approximately 4 times higher for the latter (ExoRap(50), 555.61 ± 22.04 ?g/cm(2)/h; ExoRap(60), 663.1 ± 50.95 ?g/cm(2)/h; compared to ExoSl(45), 159.36 ± 29.44 ?g/cm(2)/h). The large influence of temperature change kinetics on lidocaine diffusion suggested that transport was heavily dependent on temperature induced structural changes of the barrier. CMC, like many polymers adsorbs more water when exposed to moderate increases in temperature and this appeared to be a critical determinant of lidocaine barrier diffusion rate. PMID:21055455

Wood, Daniel G; Brown, Marc B; Jones, Stuart A

2011-02-14

73

Reactive oxygen species-related activities of nano-iron metal and nano-iron oxides.  

PubMed

Nano-iron metal and nano-iron oxides are among the most widely used engineered and naturally occurring nanostructures, and the increasing incidence of biological exposure to these nanostructures has raised concerns about their biotoxicity. Reactive oxygen species (ROS)-induced oxidative stress is one of the most accepted toxic mechanisms and, in the past decades, considerable efforts have been made to investigate the ROS-related activities of iron nanostructures. In this review, we summarize activities of nano-iron metal and nano-iron oxides in ROS-related redox processes, addressing in detail the known homogeneous and heterogeneous redox mechanisms involved in these processes, intrinsic ROS-related properties of iron nanostructures (chemical composition, particle size, and crystalline phase), and ROS-related bio-microenvironmental factors, including physiological pH and buffers, biogenic reducing agents, and other organic substances. PMID:24673906

Wu, Haohao; Yin, Jun-Jie; Wamer, Wayne G; Zeng, Mingyong; Lo, Y Martin

2014-03-01

74

Surface Engineering of Core/Shell Iron/Iron Oxide Nanoparticles from Microemulsions for Hyperthermia  

PubMed Central

This paper describes the synthesis and surface engineering of core/shell-type iron/iron oxide nanoparticles for magnetic hyperthermia cancer therapy. Iron/iron oxide nanoparticles were synthesized from microemulsions of NaBH4 and FeCl3, followed by surface modification in which a thin hydrophobic hexamethyldisilazane layer - used to protect the iron core - replaced the CTAB coating on the particles. Phosphatidylcholine was then assembled on the nanoparticle surface. The resulting nanocomposite particles have a biocompatible surface and show good stability in both air and aqueous solution. Compared to iron oxide nanoparticles, the nanocomposites show much better heating in an alternating magnetic field. They are good candidates for both hyperthermia and magnetic resonance imaging applications. PMID:21833157

Zhang, Guandong; Liao, Yifeng; Baker, Ian

2011-01-01

75

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

NASA Technical Reports Server (NTRS)

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.

Napier, Mary E.; Stair, Peter C.

1992-01-01

76

Stabilization and functionalization of iron oxide nanoparticles for biomedical applications.  

PubMed

Superparamagnetic iron oxide nanoparticles (NPs) are used in a rapidly expanding number of research and practical applications in the biomedical field, including magnetic cell labeling separation and tracking, for therapeutic purposes in hyperthermia and drug delivery, and for diagnostic purposes, e.g., as contrast agents for magnetic resonance imaging. These applications require good NP stability at physiological conditions, close control over NP size and controlled surface presentation of functionalities. This review is focused on different aspects of the stability of superparamagnetic iron oxide NPs, from its practical definition to its implementation by molecular design of the dispersant shell around the iron oxide core and further on to its influence on the magnetic properties of the superparamagnetic iron oxide NPs. Special attention is given to the selection of molecular anchors for the dispersant shell, because of their importance to ensure colloidal and functional stability of sterically stabilized superparamagnetic iron oxide NPs. We further detail how dispersants have been optimized to gain close control over iron oxide NP stability, size and functionalities by independently considering the influences of anchors and the attached sterically repulsive polymer brushes. A critical evaluation of different strategies to stabilize and functionalize core-shell superparamagnetic iron oxide NPs as well as a brief introduction to characterization methods to compare those strategies is given. PMID:21629911

Amstad, Esther; Textor, Marcus; Reimhult, Erik

2011-07-01

77

Hydration thermodynamics of pyrochlore structured oxides from TG and first principles calculations.  

PubMed

In this contribution we investigate trends in the defect chemistry and hydration thermodynamics of rare-earth pyrochlore structured oxides, RE(2)X(2)O(7) (RE = La-Lu and X = Ti, Sn, Zr and Ce). First principles density functional theory (DFT) calculations have been performed to elucidate trends in the general defect chemistry and hydration enthalpy for the above-mentioned series. Further, to justify the use of such theoretical methods, the hydration properties of selected compositions were studied by means of thermogravimetric measurements. Both DFT calculations and TG measurements indicate that the hydration enthalpy becomes less exothermic with decreasing radii of RE ions within the RE(2)X(2)O(7) series (X = Ti, Sn, Zr and Ce), while it is less dependent on the X site ion. The observed hydration trends are discussed in connection with trends in the stability of both protons and oxygen vacancies and changes in the electronic density of states and bonding environment through the series. Finally, the findings are discussed with respect to existing correlations for other binary and ternary oxides. PMID:23001186

Bjørheim, Tor S; Besikiotis, Vasileios; Haugsrud, Reidar

2012-11-21

78

Intensification of the performance of kinetic inhibitors in the presence of polyethylene oxide and polypropylene oxide for simple gas hydrate formation in a flow mini-loop apparatus  

Microsoft Academic Search

The main objective of the present work is enhancement of the performance of gas hydrate kinetic inhibitors in the presence of polyethylene oxide (PEO) and polypropylene oxide (PPO) for simple gas hydrate formation in a flow mini-loop apparatus. PEO and PPO are high molecular weight polymers that are not kinetic inhibitors by their self. For this investigation, a laboratory flow

Mohammad Reza Talaghat

2010-01-01

79

Manganese and iron oxidation by fungi isolated from building stone.  

PubMed

Acid and nonacid generating fungal strains isolated from weathered sandstone, limestone, and granite of Spanish cathedrals were assayed for their ability to oxidize iron and manganese. In general, the concentration of the different cations present in the mineral salt media directly affected Mn(IV) oxide formation, although in some cases, the addition of glucose and nitrate to the culture media was necessary. Mn(II) oxidation in acidogenic strains was greater in a medium containing the highest concentrations of glucose, nitrate, and manganese. High concentrations of Fe(II), glucose, and mineral salts were optimal for iron oxidation. Mn(IV) precipitated as oxides or hydroxides adhered to the mycelium. Most of the Fe(III) remained in solution by chelation with organic acids excreted by acidogenic strains. Other metabolites acted as Fe(III) chelators in nonacidogenic strains, although Fe(III) deposits around the mycelium were also detected. Both iron and manganese oxidation were shown to involve extracellular, hydrosoluble enzymes, with maximum specific activities during exponential growth. Strains able to oxidize manganese were also able to oxidize iron. It is concluded that iron and manganese oxidation reported in this work were biologically induced by filamentous fungi mainly by direct (enzymatic) mechanisms. PMID:24190274

de la Torre, M A; Gomez-Alarcon, G

1994-01-01

80

Immobilisation of arsenic by iron(II)-oxidizing bacteria  

NASA Astrophysics Data System (ADS)

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.

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

2008-12-01

81

The interaction of DNA with phytoferritin during iron oxidation.  

PubMed

Phytoferritin from legume seeds is considered an iron supplement with great potential. Phytoferritin co-exists with plastid DNA in amyloplasts of legume seed cells where Fe(2+) is oxidized into Fe(3+), followed by storage within the inner cavity of the protein. In this study, the interaction of plasmid DNA with black bean (Phaseolus vulgaris L.) seed ferritin (BSF) during iron oxidation was studied. Results indicated that iron ions facilitated formation of apoBSF aggregates at a high iron loading (>48 Fe(2+)/shell). Interestingly, the co-existence of DNA and ferritin has a pronounced effect on iron uptake by ferritin. This view is confirmed by a pronounced increase in the rate of iron oxidation catalysed by apoBSF in the presence of DNA. On the other hand, the apoBSF exhibited a marked DNA-protective function against oxidative damage at a low loading of Fe(2+) (? 48 Fe(2+)/shell). However, outside this ratio, such an effect gradually decreased, because the added iron exceeded the iron binding capacity of ferritin. The current study advances the understanding of the interaction among multi-components in foodstuffs. PMID:24491733

Yang, Rui; Yang, Senpei; Liao, Xiayun; Deng, Jianjun; Zhao, Guanghua

2014-06-15

82

Iron oxide nanoparticles as a contrast agent for thermoacoustic tomography  

E-print Network

. Characterization of the SPION samples is executed through TAT, TEM, XPS, EDS, and a vector network analyzer with a dielectric probe kit. Onedimensional and phantom model imaging with an iron oxide nanoparticle contrast agent provide a two-fold improvement...

Keho, Aaron Lopez

2009-06-02

83

21 CFR 73.200 - Synthetic iron oxide.  

Code of Federal Regulations, 2013 CFR

...color additive mixtures for coloring foods. (b) Specifications...percent by weight of the finished food. (2) Synthetic iron oxide may be safely used for the coloring of dog and cat foods in an amount not exceeding...

2013-04-01

84

21 CFR 73.200 - Synthetic iron oxide.  

Code of Federal Regulations, 2012 CFR

...color additive mixtures for coloring foods. (b) Specifications...percent by weight of the finished food. (2) Synthetic iron oxide may be safely used for the coloring of dog and cat foods in an amount not exceeding...

2012-04-01

85

Surface modifications of iron oxide nanoparticles for biological applications  

E-print Network

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 ...

Insin, Numpon

2011-01-01

86

Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies  

PubMed Central

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

2008-01-01

87

Iron-oxide catalyzed silicon photoanode for water splitting  

E-print Network

This thesis presents an integrated study of high efficiency photoanodes for water splitting using silicon and iron-oxide. The fundamental limitations of silicon to water splitting applications were overcome by an ultrathin ...

Jun, Kimin

2011-01-01

88

SULFATE REQUIREMENT FOR IRON OXIDATION BY THIOBACILLUS FERROOXIDANS.  

PubMed

Lazaroff, Norman (British Columbia Research Council, Vancouver, B.C., Canada). Sulfate requirement for iron oxidation by Thiobacillus ferrooxidans. J. Bacteriol. 85:78-83. 1963.-The growth of Thiobacillus ferrooxidans is initially inhibited in media containing ferrous chloride in place of ferrous sulfate. This inhibition of growth is due to the requirement of a high relative proportion of sulfate ions to chloride (or other anions) for iron oxidation. Adaptation takes place, producing strains which are able to oxidize iron in media containing an initially unfavorable anionic composition. Adaptation is possibly due to the selection of spontaneous mutants capable of oxidizing iron in high chloride, low sulfate media. Such cells are found at a frequency of 10(-5) of the population of unadapted cultures. PMID:16561990

Lazaroff, N

1963-01-01

89

SULFATE REQUIREMENT FOR IRON OXIDATION BY THIOBACILLUS FERROOXIDANS  

PubMed Central

Lazaroff, Norman (British Columbia Research Council, Vancouver, B.C., Canada). Sulfate requirement for iron oxidation by Thiobacillus ferrooxidans. J. Bacteriol. 85:78–83. 1963.—The growth of Thiobacillus ferrooxidans is initially inhibited in media containing ferrous chloride in place of ferrous sulfate. This inhibition of growth is due to the requirement of a high relative proportion of sulfate ions to chloride (or other anions) for iron oxidation. Adaptation takes place, producing strains which are able to oxidize iron in media containing an initially unfavorable anionic composition. Adaptation is possibly due to the selection of spontaneous mutants capable of oxidizing iron in high chloride, low sulfate media. Such cells are found at a frequency of 10?5 of the population of unadapted cultures. PMID:16561990

Lazaroff, Norman

1963-01-01

90

Polymer-coated iron oxide nanoparticles for medical imaging  

E-print Network

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 ...

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

2010-01-01

91

Stem cell tracking using iron oxide nanoparticles  

PubMed Central

Superparamagnetic iron oxide nanoparticles (SPIONs) are an exciting advancement in the field of nanotechnology. They expand the possibilities of noninvasive analysis and have many useful properties, making them potential candidates for numerous novel applications. Notably, they have been shown that they can be tracked by magnetic resonance imaging (MRI) and are capable of conjugation with various cell types, including stem cells. In-depth research has been undertaken to establish these benefits, so that a deeper level of understanding of stem cell migratory pathways and differentiation, tumor migration, and improved drug delivery can be achieved. Stem cells have the ability to treat and cure many debilitating diseases with limited side effects, but a main problem that arises is in the noninvasive tracking and analysis of these stem cells. Recently, researchers have acknowledged the use of SPIONs for this purpose and have set out to establish suitable protocols for coating and attachment, so as to bring MRI tracking of SPION-labeled stem cells into common practice. This review paper explains the manner in which SPIONs are produced, conjugated, and tracked using MRI, as well as a discussion on their limitations. A concise summary of recently researched magnetic particle coatings is provided, and the effects of SPIONs on stem cells are evaluated, while animal and human studies investigating the role of SPIONs in stem cell tracking will be explored. PMID:24729700

Bull, Elizabeth; Madani, Seyed Yazdan; Sheth, Roosey; Seifalian, Amelia; Green, Mark; Seifalian, Alexander M

2014-01-01

92

Iron Oxide/Aluminum Fast Thermite Reaction  

NASA Astrophysics Data System (ADS)

The self-sustained thermite reaction between iron oxide (Fe2O3) and aluminum (Al) is commonly slow. This paper presents an experimental study to evaluate the reaction regression rates of these thermite mixtures with or without continuous electrical discharge. Two thermite compositions are tested: stoichiometric (Al2O3 and Fe as the only products) and over aluminized. To generate a fast and stable front propagation in thermite material, a long channel configuration is used and the reaction is assisted with a continuous electrical discharge between two copper plates (external confinement). The reaction velocity is evaluated by the regression rate, which is measured by optical methods. The assisted reaction is compared to the original self-sustained reaction, as a function of the composition. The electrical discharge level is also measured with a current monitor and oscilloscope. The thermodynamic properties of reaction products are predicted by a thermochemical code, named THOR, assuming an isobar adiabatic combustion and using HL equation of state.

Morgado, J.; Durães, L.; Campos, J.; Portugal, A.

2004-07-01

93

Geophys. J. Int. (2002) 150, 230240 Iron oxide formation in the active oxidation front  

E-print Network

Geophys. J. Int. (2002) 150, 230­240 Iron oxide formation in the active oxidation front above sapropel (S1). The upper half of sapropel S1 has been oxidized, and Fe oxides have precipitated in the oxidized sapropel. Zero-field- cooling (ZFC) and field-cooling (FC) saturation remanent magnetization (Mr

Utrecht, Universiteit

94

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

PubMed Central

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.

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

2014-01-01

95

Iron oxide-based nanomagnets in nanomedicine: fabrication and applications  

PubMed Central

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

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

2010-01-01

96

Electronic structure of sodium cobalt oxide: Comparing mono- and bilayer hydrate  

NASA Astrophysics Data System (ADS)

To shed light on the mechanism of superconductivity in sodium cobalt oxide bilayer-hydrate (BLH), we perform a density functional calculation with full structure optimization for BLH and its related nonsuperconducting phase, monolayer hydrate (MLH). We find that these hydrates have similar band structures, but a notable difference can be seen in the a1g band around the Fermi level. While its dispersion in the z direction is negligibly small for BLH, it is of the order of 0.1eV for MLH. This result implies that the three-dimensional feature of the a1g band may be the origin for the absence of superconductivity in MLH.

Arita, Ryotaro

2005-04-01

97

Ferrates (iron(VI) and iron(V)): Environmentally friendly oxidants and disinfectants  

Microsoft Academic Search

Iron(VI) and iron(V), known as ferrates, are powerful oxidants and their reactions with pollutants are typically fast with the formation of non-toxic by-products. Oxidations performed by Fe(VI) and Fe(V) show pH dependence; faster rates are observed at lower pH. Fe(VI) shows excellent disinfectant properties and can inactivate a wide variety of microorganisms at low Fe(VI) doses. Fe(VI) also possesses efficient

Virender K. Sharma; Futaba Kazama; Hu Jiangyong; Ajay K. Ray

2005-01-01

98

Iron-Sulfur Cluster Synthesis, Iron Homeostasis and Oxidative Stress in Friedreich Ataxia  

PubMed Central

Friedreich ataxia (FRDA) is an autosomal recessive, multi-systemic degenerative disease that results from reduced synthesis of the mitochondrial protein frataxin. Frataxin has been intensely studied since its deficiency was linked to FRDA in 1996. The defining properties of frataxin—(i) the ability to bind iron, (ii) the ability to interact with, and donate iron to, other iron-binding proteins, and (iii) the ability to oligomerize, store iron and control iron redox chemistry—have been extensively characterized with different frataxin orthologues and their interacting protein partners. This very large body of biochemical and structural data [reviewed in (Bencze et al., 2006)] supports equally extensive biological evidence that frataxin is critical for mitochondrial iron metabolism and overall cellular iron homeostasis and antioxidant protection [reviewed in (Wilson, 2006)]. However, the precise biological role of frataxin remains a matter of debate. Here, we review seminal and recent data that strongly link frataxin to the synthesis of iron-sulfur cluster cofactors (ISC), as well as controversial data that nevertheless link frataxin to additional iron-related processes. Finally, we discuss how defects in ISC synthesis could be a major (although likely not unique) contributor to the pathophysiology of FRDA via (i) loss of ISC-dependent enzymes, (ii) mitochondrial and cellular iron dysregulation, and (iii) enhanced iron-mediated oxidative stress. PMID:22917739

Vaubel, Rachael A.; Isaya, Grazia

2012-01-01

99

Analysis of iron oxide precipitates in constructed mine wastewater treatments  

SciTech Connect

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.

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

1996-10-01

100

Iron Oxide Hyperthermia And Radiation Cancer Treatment  

PubMed Central

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.

Cassim, SM; Giustini, AJ; Petryk, AA; Strawbridge, RA; Hoopes, PJ

2014-01-01

101

Synthesis of carbon-encapsulated iron nanoparticles via solid state reduction of iron oxide nanoparticles  

SciTech Connect

The encapsulation of iron nanoparticles in protective carbon cages leads to unique hybrid core-shell nanomaterials. Recent literature reports suggest that such nanocomposites can be obtained in a relatively simple process involving the solid state carbothermal reduction of iron oxide nanoparticles. This approach is very attractive because it does not require advanced equipment and consumes less energy in comparison to widely used plasma methods. The presented more-in-depth study shows that the carbothermal approach is sensitive to temperature and the process yield strongly depends on the morphology and crystallinity of the carbon material used as a reductant. - Graphical abstract: Reduction of iron oxide nanoparticles by carbon black at 1200 deg. C yields well crystallized carbon-encapsulated iron nanoparticles. Highlights: > Carbon-encapsulated iron nanoparticles were synthesized by carbothermal reduction of iron oxide nanoparticles. > The process has the highest selectivity at 1200 C. > Lower temperatures result in iron oxide nanoparticles wrapped in carbon matrix. > The encapsulation rate of Fe at 1200 deg. C was found to be 15%.

Bystrzejewski, M., E-mail: mibys@chem.uw.edu.pl [Dept of Chemistry, Warsaw University, Pasteura 1, 02-093 Warsaw (Poland)

2011-06-15

102

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

SciTech Connect

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].

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

103

The Oxidation Of Iron In A Gel Using Consumer Chemicals  

ERIC Educational Resources Information Center

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.

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

2005-01-01

104

Low-Temperature Formation of Magnetic Iron Oxides.  

National Technical Information Service (NTIS)

Elemental analysis and magnetic measurements of the surface of Mars have indicated the presence of an iron oxide with a considerable magnetic moment. Identification of the oxide phase(s) is an important subject as this may be used to identify the process ...

C. B. Koch, M. B. Madsen

1992-01-01

105

Mössbauer effect phase determination in iron oxide polyaniline nanocomposites  

NASA Astrophysics Data System (ADS)

Mössbauer effect spectroscopy and thermal analysis techniques were applied to characterize polyaniline composites successfully synthesized by embedding Fe oxide nanoparticles (about 10 13 nm) in a polymeric matrix in the presence of dodecyl benzene sulfonic acid and HCl (dopant). Thermal techniques provided quantitative information on iron oxide content and on polyaniline stability and transformations. Mössbauer results indicated that for the whole studied composition range, 3.4 to 100 iron oxide wt.%, composites hold maghemite particles. A preliminary study of the conductivity of the nanocomposites was performed. The largest conductivity was observed for a 8 wt.% maghemite composite where all particles are magnetically unblocked at room temperature within the Mössbauer time window.

Aphesteguy, J. C.; Jacobo, S. E.; Rodríguez Torres, C. E.; Fernández van Raap, M. B.; Sánchez, F. H.

2007-09-01

106

Ion-exchange chromatographic separation of anions on hydrated bismuth oxide impregnated papers  

SciTech Connect

A comparative study of the chromatographic behavior of anions, iodide, sulfide, phosphate, arsenate, arsenite, vanadate, chromate, dichromate, thiosulfate, thiocyanate, ferricyanide and ferrocyanide on papers impregnated with hydrated bismuth oxide and untreated Whatman no.1 paper has been made by employing identical aqueous, non-aqueous and mixed solvent system. Sharp and compact spots were obtained with impregnated papers whereas the opposite applied to plain papers. Various analytically important binary and ternary separations are reported.

Dabral, S.K.; Muktawat, K.P.S.; Rawat, J.P.

1988-04-01

107

Clathrate hydrates of oxidants in the ice shell of Europa.  

PubMed

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 approximately 1.7-7.6% by number contamination of oxidants resulting from radiolysis at the surface. Oxidant-hosting clathrates would consequently make up approximately 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 A (O2)2 absorption. PMID:16805702

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

2006-06-01

108

Iron-oxidation processes in an electroflocculation (electrocoagulation) cell.  

PubMed

The processes of iron oxidation in an electroflocculation cell were investigated for a pH range of 5-9 and electric currents of 0.05-0.4A (equivalent current densities of 8.6-69 A/m(2)). At all pH values and electric currents investigated, it was demonstrated and proven that for all practical purposes, the form of iron that dissolves from the anode is Fe(2+) (ferrous). The difference between the amount of theoretical dissolution as calculated by Faraday's law and the amount of observed dissolved iron ions may indicate two phenomena in electrochemical cells. The first is possible dissolution of the anode even without the operation of an electric current; this led to higher theoretical dissolution rates at lower pH. The second is the participation of some of the electrons of the electric current in reactions other than anode dissolution which led to lower theoretical dissolution rates at higher pH. Those other reactions did not lead to an increase in the local oxidation saturation level near the anode and did not affect iron-oxidation rates in the electroflocculation processes. The oxidation rates of the dissolved Fe(2+) (ferrous) to Fe(3+) (ferric) ions in electroflocculation processes were strongly dependent on the pH and were similar to the known oxidation rates of iron in non-electrochemical cells. PMID:19577360

Ben Sasson, Moshe; Calmano, Wolfgang; Adin, Avner

2009-11-15

109

Microstructural effects on the oxidation of iron aluminide  

NASA Astrophysics Data System (ADS)

This work addresses the impact of processing and microstructure on the oxide chemistry and short-term isothermal oxidation rate, over the first 24h of oxidation, for the B2 iron aluminide, Fe-40Al. Research interests in iron-aluminum alloys, used for high temperature structural applications, are primarily concerned with the improvement of high temperature oxidation performance and mechanical properties. The oxidation performance of alloys with aluminum contents below 20at% is dependent upon processing and microstructure. Before this work, it was not established if there was any impact of material processing and microstructure on the oxidation performance of the high aluminum content Fe-40Al alloy. This study utilized eight industrial processes to produce six different material conditions. Among the characteristics of the microstructures produced were grain sizes from 2 to ?500mum, oxygen contents from 0--2.6at%, and powder particle surface area-to-volume ratios from 0--0.6 m2/cm3. For the six materials tested, short-term (24h) isothermal oxidation rates were determined at 700, 750, and 800°C. The resultant rates were then used to determine the relationship between the oxidation rate constant and temperature. The chemistry, physical characteristics, and structure of the oxides formed were then characterized. It was concluded that microstructure has a limited impact on oxidation properties: no practical impact was observed on oxidation rate; an initial transient oxide layer formed independent of microstrucure; microstructure can be used to control the formation of oxide-metal interfacial voids, formed during the oxidation process; and oxide inclusion "pegs" serve to improve oxide adhesion. Additionally it was observed that contamination from hot pressing contributed to the formation of oxide nodules during oxidation. Overall the isothermal oxidation properties during the first 24h of exposure proved to be robust over many combinations of microstructures.

Hale, Peter M.

110

Community Genomic and Proteomic Analyses of Chemoautotrophic Iron-Oxidizing \\  

Microsoft Academic Search

We analyzed near-complete population (composite) genomic sequences for coexisting acidophilic iron- oxidizing Leptospirillum group II and III bacteria (phylum Nitrospirae) and an extrachromosomal plasmid from a Richmond Mine, Iron Mountain, CA, acid mine drainage biofilm. Community proteomic analysis of the genomically characterized sample and two other biofilms identified 64.6% and 44.9% of the predicted proteins of Leptospirillum groups II and

Daniela S. Aliaga Goltsman; Vincent J. Denef; Steven W. Singer; Nathan C. VerBerkmoes; Mark Lefsrud; Ryan S. Mueller; Gregory J. Dick; Christine L. Sun; Korin E. Wheeler; Adam Zemla; Brett J. Baker; Loren Hauser; Miriam Land; Manesh B. Shah; Michael P. Thelen; Robert L. Hettich; Jillian F. Banfield

2009-01-01

111

Extending the models for iron and sulfur oxidation in the extreme Acidophile Acidithiobacillus ferrooxidans  

Microsoft Academic Search

BACKGROUND: Acidithiobacillus ferrooxidans gains energy from the oxidation of ferrous iron and various reduced inorganic sulfur compounds at very acidic pH. Although an initial model for the electron pathways involved in iron oxidation has been developed, much less is known about the sulfur oxidation in this microorganism. In addition, what has been reported for both iron and sulfur oxidation has

Raquel Quatrini; Corinne Appia-Ayme; Yann Denis; Eugenia Jedlicki; David S. Holmes; Violaine Bonnefoy

2009-01-01

112

Ferrous iron oxidation and rusticyanin in halotolerant, acidophilic 'Thiobacillus prosperus'.  

PubMed

The halotolerant acidophile 'Thiobacillus prosperus' was shown to require chloride for growth. With ferrous iron as substrate, growth occurred at a rate similar to that of the well-studied acidophile Acidithiobacillus ferrooxidans. Previously, the salt (NaCl) requirement of 'T. prosperus' was not clear and its growth on ferrous iron was described as poor. A subtractive hybridization of cDNAs from ferrous-iron-grown and sulfur-grown 'T. prosperus' strain V6 led to identification of a cluster of genes similar to the rus operon reported to encode ferrous iron oxidation in A. ferrooxidans. However, the 'T. prosperus' gene cluster did not contain a homologue of cyc1, which is thought to encode a key cytochrome c in the pathway of electron transport from ferrous iron in A. ferrooxidans. Rusticyanin, another key protein in ferrous iron oxidation by A. ferrooxidans, was present in 'T. prosperus' at similar concentrations in cells grown on either ferrous iron or sulfur. PMID:19332831

Nicolle, James Le C; Simmons, Susan; Bathe, Stephan; Norris, Paul R

2009-04-01

113

Recent advances in iron oxide nanocrystal technology for medical imaging.  

PubMed

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 diseases. USPIO are investigated as blood pool agents with T1 weighted sequence for angiography, tumour permeability and tumour blood volume or steady-state cerebral blood volume and vessel size index measurements using T2 weighted sequences. Stem cell migration and immune cell trafficking, as well as targeted iron oxide nanoparticles for molecular imaging studies, are at the stage of proof of concept, mainly in animal models. PMID:17116343

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

2006-12-01

114

Development of Novel Biopolymer/Synthetic-Polymer/Iron Oxide Nanocomposites  

NASA Astrophysics Data System (ADS)

In this work we report the successful development of a family of magnetic nanocomposites based on chitosan or/and polyamide 6 matrix with dispersed iron oxide nanoparticles synthesized by chemical co-precipitation. The iron oxide contents varied from 5 up to 23 wt%, the nanocomposites were studied by FTIR, UV-vis, TGA, XRD, TEM and magnetometry. The FTIR analysis demonstrates an interaction between the amide group of the polyamide 6 and the ceramic material. In formic acid, the nanocomposites absorb in the UV-Vis range, and the magnitude of the band gap (optical), calculated using the band of higher wavelength, is between 2.16 and 2.19 eV. In nanocomposites with chitosan/polyamide 6 matrix the developed morphologies are spherulites of polyamide 6 surrounded by chitosan, with the iron oxide particles presumably in the form of ferrihidryte. The measured magnetic properties revealed a superparamagnetic character on the studied specimens.

Mena Montoya, Marleth; Carranza, Sugeheidy; Hinojosa, Moisés; González, Virgilio

2009-03-01

115

Multimodal Iron Oxide Nanoparticles for Hybrid Biomedical Imaging  

PubMed Central

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

Heidt, Timo; Nahrendorf, Matthias

2012-01-01

116

Arsenate adsorption onto iron oxide amended rice husk char.  

PubMed

In this study, rice husks were charred at 550 °C in a partially sealed ceramic vessel for 30minutes to create a high specific surface area (SSA) rice husk char (RHC). The RHC was then amended with iron oxides using dissolved ferric nitrate, Fe(NO3)3?9H2O, to provide a surface chemistry conducive to arsenic adsorption. The 550 °C iron oxide amended rice husk char's (550 IOA-RHC's) SSA was nearly 2.5 orders of magnitude higher and the arsenate adsorptive level was nearly 2 orders of magnitude higher than those reported for iron oxide amended sand, thus indicating a positive relationship between post-amendment SSA and arsenate adsorptive levels. Rice husks were then charred at temperatures ranging from 450 °C to 1050 °C to create an even higher SSA material, which might further increase arsenate adsorptive levels. The 950 °C RHC was chosen for amendment due to its high SSA and feasibility of being produced in the field. Once amended, the 950 °C iron oxide amended rice husk char (950 IOA-RHC) improved the arsenate adsorption capacity by thus confirming a positive relationship, though not a linear relationship, between post-amendment SSA and arsenic adsorptive capacity. Further study demonstrated that post-amendment mesoporous volume and mesoporous surface area appear to be better indicators of arsenic adsorptive capacity than SSA or iron content. PMID:24529452

Cope, Christopher O; Webster, Damon S; Sabatini, David A

2014-08-01

117

Electrolytic photodissociation of chemical compounds by iron oxide photochemical diodes  

DOEpatents

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.

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

1985-01-01

118

Electrolytic photodissociation of chemical compounds by iron oxide electrodes  

DOEpatents

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.

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

1984-01-01

119

New Insight into the Electrochromic Properties of Iron Oxides  

NASA Astrophysics Data System (ADS)

We report on the structural, optical and magnetic properties of iron oxide films that were electrochemically cycled in a LiOH aqueous solution. We found that the electrochromic phenomenon is linked to the transformation of the film morphology; it goes from round-shaped particles to platy morphology. Additionally, the following phenomena were observed: a gradual blue shift of the optical-absorption edge, an increase of the saturation magnetization and the appearance of new Raman bands. The change of these properties helped us to understand the coloration mechanism for electrochromism in iron oxides.

Garcia-Lobato, Marco A.; Martinez, Arturo I.; Zarate, Ramón A.; Castro-Roman, Manuel

2010-11-01

120

Nanoscale oxidation and complex oxide growth on single crystal iron surfaces and external electric field effects.  

PubMed

Oxidation of iron surfaces and oxide growth mechanisms have been studied using reactive molecular dynamics. Oxide growth kinetics on Fe(100), (110), and (111) surface orientations has been investigated at various temperatures and/or an external electric field. The oxide growth kinetics decreases in the order of (110), (111), and (100) surfaces at 300 K over 1 ns timescale while higher temperature increases the oxidation rate. The oxidation rate shows a transition after an initial high rate, implying that the oxide formation mechanism evolves, with iron cation re-ordering. In early stages of surface oxide growth, oxygen transport through iron interstitial sites is dominant, yielding non-stoichiometric wüstite characteristics. The dominant oxygen inward transport decreases as the oxide thickens, evolving into more stoichiometric oxide phases such as wüstite or hematite. This also suggests that cation outward transport increases correspondingly. In addition to oxidation kinetics simulations, formed oxide layers have been relaxed in the range of 600-1500 K to investigate diffusion characteristics, fitting these results into an Arrhenius relation. The activation energy of oxygen diffusion in oxide layers formed on Fe(100), (110), and (111) surfaces was estimated to be 0.32, 0.26, and 0.28 eV, respectively. Comparison between our modeling results and literature data is then discussed. An external electric field (10 MV cm(-1)) facilitates initial oxidation kinetics by promoting oxygen transport through iron lattice interstitial sites, but reaches self-limiting thickness, showing that similar oxide formation stages are maintained when cation transport increases. The effect of the external electric field on iron oxide structure, composition, and oxide activation energy is found to be minimal, whereas cation outward migration is slightly promoted. PMID:23247653

Jeon, Byoungseon; Van Overmeere, Quentin; van Duin, Adri C T; Ramanathan, Shriram

2013-02-14

121

Photocatalytic Oxidation of Isoprene on Hydrated Atmospheric Mineral Dusts  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

122

Core-shell iron-iron oxide nanoparticles synthesized by laser-induced pyrolysis.  

PubMed

Passivated iron nanoparticles (10-30 nm) have been synthesized by laser pyrolysis of a mixture of iron pentacarbonyl and ethylene vapors followed by controlled oxidation. The nanoparticles show a well-constructed iron-iron oxide core-shell structure, in which the thickness and nature (structure similar to maghemite, gamma-Fe2O3) of the shell is found to be independent of the initial conditions. On the other hand, the composition of the core is found to change with the particle size from the alpha-Fe structure to a highly disordered Fe phase (probably containing C atoms in its structure). The dependence of the magnetic properties on the particle size, iron oxide fraction, and temperature was also investigated. In the case of smaller particles, the magnetic data indicate the existence at low temperature of a large exchange anisotropy field, the magnitude of which increases with decreasing temperature in correspondence with the freezing of magnetic moments in the oxide shell. PMID:17193009

Bomatí-Miguel, Oscar; Tartaj, Pedro; Morales, Maria P; Bonville, Pierre; Golla-Schindler, Ute; Zhao, Xinqing Q; Veintemillas-Verdaguer, Sabino

2006-12-01

123

Evolutionary relationships among sulfur- and iron-oxidizing eubacteria.  

PubMed Central

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

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

1992-01-01

124

Unprecedented Selective Oxidation of Styrene Derivatives using a Supported Iron Oxide Nanocatalyst in Aqueous Medium  

EPA Science Inventory

Iron oxide nanoparticles supported on mesoporous silica-type materials have been successfully utilized in the aqueous selective oxidation of alkenes under mild conditions using hydrogen peroxide as a green oxidant. Catalysts could be easily recovered after completion of the reac...

125

Deposition rates of oxidized iron on Mars  

NASA Technical Reports Server (NTRS)

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.

Burns, R. G.

1993-01-01

126

Nanoscale powders of different iron oxide phases prepared by continuous laser irradiation of iron pentacarbonyl-containing gas precursors  

Microsoft Academic Search

Different iron oxide-based nanosized powders were obtained by the IR laser synthesis from gas phase reactants by using iron pentacarbonyl vapor as iron donor. In the flowing gas mixture, oxidizers (like nitrous oxide and air) and sensitizers (like sulfur hexafluoride and ethylene) have been used. A major amount of ?-Fe2O3 was obtained after a series of experiments in which ?-Fe2O3

I Morjan; R Alexandrescu; I Soare; F Dumitrache; I Sandu; I Voicu; A Crunteanu; E Vasile; V Ciupina; S Martelli

2003-01-01

127

Gas-phase uranyl, neptunyl, and plutonyl: hydration and oxidation studied by experiment and theory.  

PubMed

The following monopositive actinyl ions were produced by electrospray ionization of aqueous solutions of An(VI)O(2)(ClO(4))(2) (An = U, Np, Pu): U(V)O(2)(+), Np(V)O(2)(+), Pu(V)O(2)(+), U(VI)O(2)(OH)(+), and Pu(VI)O(2)(OH)(+); abundances of the actinyl ions reflect the relative stabilities of the An(VI) and An(V) oxidation states. Gas-phase reactions with water in an ion trap revealed that water addition terminates at AnO(2)(+)·(H(2)O)(4) (An = U, Np, Pu) and AnO(2)(OH)(+)·(H(2)O)(3) (An = U, Pu), each with four equatorial ligands. These terminal hydrates evidently correspond to the maximum inner-sphere water coordination in the gas phase, as substantiated by density functional theory (DFT) computations of the hydrate structures and energetics. Measured hydration rates for the AnO(2)(OH)(+) were substantially faster than for the AnO(2)(+), reflecting additional vibrational degrees of freedom in the hydroxide ions for stabilization of hot adducts. Dioxygen addition resulted in UO(2)(+)(O(2))(H(2)O)(n) (n = 2, 3), whereas O(2) addition was not observed for NpO(2)(+) or PuO(2)(+) hydrates. DFT suggests that two-electron three-centered bonds form between UO(2)(+) and O(2), but not between NpO(2)(+) and O(2). As formation of the UO(2)(+)-O(2) bonds formally corresponds to the oxidation of U(V) to U(VI), the absence of this bonding with NpO(2)(+) can be considered a manifestation of the lower relative stability of Np(VI). PMID:22656318

Rios, Daniel; Michelini, Maria C; Lucena, Ana F; Marçalo, Joaquim; Bray, Travis H; Gibson, John K

2012-06-18

128

DETERMINATION OF THE RATES AND PRODUCTS OF FERROUS IRON OXIDATION IN ARSENIC-CONTAMINATED POND WATER.  

EPA Science Inventory

Dissolved ferrous iron and arsenic in the presence of insufficient oxygenated ground water is released into a pond. When the mixing of ferrous iron and oxygenated water within the pond occurs, the ferrous iron is oxidized and precipitated as an iron oxide. Groups of experiments...

129

Hydration of calcium oxide surface predicted by reactive force field molecular dynamics.  

PubMed

In this work, we present the parametrization of Ca-O/H interactions within the reactive force field ReaxFF, and its application to study the hydration of calcium oxide surface. The force field has been fitted using density functional theory calculations on gas phase calcium-water clusters, calcium oxide bulk and surface properties, calcium hydroxide, bcc and fcc Ca, and proton transfer reactions in the presence of calcium. Then, the reactive force field has been used to study the hydration of the calcium oxide {001} surface with different water contents. Calcium oxide is used as a catalyzer in many applications such as CO(2) sequestration and biodiesel production, and the degree of surface hydroxylation is a key factor in its catalytic performance. The results show that the water dissociates very fast on CaO {001} bare surfaces without any defect or vacancy. The surface structure is maintained up to a certain amount of water, after which the surface undergoes a structural rearrangement, becoming a disordered calcium hydroxyl layer. This transformation is the most probable reason for the CaO catalytic activity decrease. PMID:22316164

Manzano, Hegoi; Pellenq, Roland J M; Ulm, Franz-Josef; Buehler, Markus J; van Duin, Adri C T

2012-03-01

130

PET\\/NIRF\\/MRI triple functional iron oxide nanoparticles  

Microsoft Academic Search

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.

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

2010-01-01

131

Melatonin prevents oxidative stress resulting from iron and erythropoietin administration  

Microsoft Academic Search

Intravenous iron (Fe) and recombinant human erythropoietin (rHuEPO) are routine treatments in the management of anemia in patients with chronic renal failure. We investigated the oxidative stress acutely induced by these therapies and whether pretreatment with oral melatonin (MEL) would have a beneficial effect. Nine patients (four women) were studied within 1 month of entering a chronic hemodialysis program in

José Herrera; Mayerly Nava; Freddy Romero; Bernardo Rodríguez-Iturbe

2001-01-01

132

Stabilization and functionalization of iron oxide nanoparticles for biomedical applications  

Microsoft Academic Search

Superparamagnetic iron oxide nanoparticles (NPs) are used in a rapidly expanding number of research and practical applications in the biomedical field, including magnetic cell labeling separation and tracking, for therapeutic purposes in hyperthermia and drug delivery, and for diagnostic purposes, e.g., as contrast agents for magnetic resonance imaging. These applications require good NP stability at physiological conditions, close control over

Esther Amstad; Marcus Textor; Erik Reimhult

2011-01-01

133

The adsorption of aquatic humic substances by iron oxides  

Microsoft Academic Search

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

E. Tipping

1981-01-01

134

Hydration kinetics of modified calcium sulphoaluminate oxides studied by aluminum — 27 NMR spectroscopy and proton magnetic relaxation: Experimental data  

Microsoft Academic Search

Hydration kinetics of Na2O-, MgO-, BaO- and TiO2- doped calcium sulphoaluminate oxides, has been followed using 27Al NMR and proton magnetic relaxation measurements. Aluminum — 27 NMR spectra of hydrated pastes show a narrow peak at 80 ppm corresponding to the hydroxy-aluminate ions in a liquid phase. According to the changes of intensity of this lines during the induction period

A. B. Kudryavtsev; T. V. Kouznetsova

1997-01-01

135

Vitamin combinations reduce oxidative stress and improve antioxidant status in patients with iron deficiency anemia  

Microsoft Academic Search

The purpose of the present study was to investigate whether oxidative stress occurs at the clinical onset of iron deficiency anemia and to find the influence of iron therapy and antioxidant vitamins on the oxidative stress parameters. A comparison was made with two other categories of anaemia, pernicious anaemia and haemolytic anaemia that are not characterized with iron deficiency. Oxidative

Veselina Gadjeva; Desislava Kuchukova; Radostina Georgieva

2005-01-01

136

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

E-print Network

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

Vallino, Joseph J.

137

Mineral leaching, iron precipitation, and the sulfate requirement for chemolithotrophic iron oxidation  

Microsoft Academic Search

The leaching of pyrite by Thiobacillus ferrooxidans results in formation of an aqueous Fe(III) sulfato complex that leaches pyrite and precipitates excess iron sulfate. However, until recently most general texts stated that the deposits formated by bacterial leaching of pyrite consited of ferric hydroxide, implying that the massive presence of sulfate played no role in the oxidation or precipitation of

Norman Lazaroff

1997-01-01

138

Evolution of Iron speciation during hydration of C4AF. , A. Bnard2,3  

E-print Network

phases are good candidates for metal retention in real cement, the role of the calcium-ferric aluminate showed a strong affinity for the hydration products of C4AF. The C4AF content in Portland cement is 2- 7 proportion of the trace metals in an actual cement will be associated with Fe phases. However, the metal

Paris-Sud XI, Université de

139

The rate of oxidation of ferrous iron in seawater and the partition of elements between iron oxides and seawater  

Microsoft Academic Search

At the Minamichita Beach Land (Mihama-cho, Aichi, Japan), seawater is pumped up from underground and is supplied to aquaria. The underground seawater containsca. 2 ppm of Fe (II), 0.1 ppm of Mn (II) and a little dissolved oxygen. Iron oxide is formed in the seawater when aerated. The oxidation rate of Fe (II) was measured to be 1.4×1014 mol?3l3 min?1,

Yoshio Satot

1989-01-01

140

Experimental study on the reducibility of graphene oxide by hydrazine hydrate  

NASA Astrophysics Data System (ADS)

In this paper, we focus on the reducibility of graphene oxide by hydrazine hydrate. The main emphasis is placed on the problem of the dosage of hydrazine hydrate and the reaction time on the reduction of chemical groups. This paper describes a system for the analysis of FT-IR. A model is developed for the FT-IR analysis using exponential decay function ( Y= Y0e - RX). The height of the peaks in FT-IR spectra of the chemical groups was fitted with exponential decay function. Decay constant R is given the name of Reducibility Factor R. Emphasis is placed on the decay constant R in the fitting functions by which the reducibility of the chemical groups on graphene oxide is evaluated. It is found that R is different for different chemical groups. The sequence is ROH> RC=O> RC-O-C. This means that C-O-C is the most difficult one to be reduced, OH is the most easy, and C=O is between C-O-C and OH. The experimental results reveal a basis for the research of the application of graphene oxide.

Zhu, Peiying; Shen, Ming; Xiao, Shuhua; Zhang, Dong

2011-02-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

142

Zinc sorption by iron oxides and soil samples  

E-print Network

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...

Yli-Halla, Markku Juhani

2012-06-07

143

Composition, nucleation, and growth of iron oxide concretions  

NASA Astrophysics Data System (ADS)

Iron oxide concretions are formed from post depositional, paleogroundwater chemical interaction with iron minerals in porous sedimentary rocks. The concretions record a history of iron mobilization and precipitation caused by changes in pH, oxidation conditions, and activity of bacteria. Transport limited growth rates may be used to estimate the duration of fluid flow events. The Jurassic Navajo Sandstone, an important hydrocarbon reservoir and aquifer on the Colorado Plateau, USA, is an ideal stratum to study concretions because it is widely distributed, well exposed and is the host for a variety of iron oxide concretions. Many of the concretions are nearly spherical and some consist of a rind of goethite that nearly completely fills the sandstone porosity and surrounds a central sandstone core. The interior and exterior host-rock sandstones are similar in detrital minerals, but kaolinite and interstratified illite-smectite are less abundant in the interior. Lepidocrocite is present as sand-grain rims in the exterior sandstone, but not present in the interior of the concretions. Widespread sandstone bleaching resulted from dissolution of early diagenetic hematite grain coatings by chemically reducing water that gained access to the sandstone through fault conduits. The iron was transported in solution and precipitated as iron oxide concretions by oxidation and increasing pH. Iron diffusion and advection growth time models place limits on minimum duration of the diagenetic, fluid flow events that formed the concretions. Concretion rinds 2 mm thick and 25 mm in radius would take place in 2000 years from transport by diffusion and advection and in 3600 years if transport was by diffusion only. Solid concretions 10 mm in radius would grow in 3800 years by diffusion or 2800 years with diffusion and advection. Goethite (?-FeO (OH)) and lepidocrocite (?-FeO (OH)) nucleated on K-feldspar grains, on illite coatings on sand grains, and on pore-filling illite, but not on clean quartz grains. Model results show that regions of detrital K-feldspar in the sandstone that consume H + more rapidly than diffusion to the reaction site determine concretion size, and spacing is related to diffusion and advection rates of supply of reactants Fe 2+, O 2, and H +.

Parry, W. T.

144

The identification by Raman microscopy and X-ray diffraction of iron-oxide pigments and of the red pigments found on Italian pottery fragments  

NASA Astrophysics Data System (ADS)

The technique of Raman microscopy has been used to identify and characterise the pigments used in red shards of medieval and earlier items of pottery which have been found in various archaeological sites in the South of Italy. The research has led to the identification, on the basis of their characteristic Raman/resonance Raman spectra, of the red pigments as iron(III) oxide (e.g. Indian Red, Red Ochre or Venetian Red) and the yellow pigments as hydrated iron(III) oxyhydroxide (e.g. Yellow Ochre and Mars Yellow). X-ray powder diffraction experiments confirm the conclusions drawn above.

Clark, Robin J. H.; Curri, M. Lucia

1998-01-01

145

Intratumoral Iron Oxide Nanoparticle Hyperthermia and Radiation Cancer Treatment  

PubMed Central

The potential synergism and benefit of combined hyperthermia and radiation for cancer treatment is well established, but has yet to be optimized clinically. Specifically, the delivery of heat via external arrays /applicators or interstitial antennas has not demonstrated the spatial precision or specificity necessary to achieve appropriate a highly positive therapeutic ratio. Recently, antibody directed and possibly even non-antibody directed iron oxide nanoparticle hyperthermia has shown significant promise as a tumor treatment modality. Our studies are designed to determine the effects (safety and efficacy) of iron oxide nanoparticle hyperthermia and external beam radiation in a murine breast cancer model. Methods MTG-B murine breast cancer cells (1 × 106) were implanted subcutaneous in 7 week-old female C3H/HeJ mice and grown to a treatment size of 150 mm3 +/? 50 mm3. Tumors were then injected locally with iron oxide nanoparticles and heated via an alternating magnetic field (AMF) generator operated at approximately 160 kHz and 400 - 550 Oe. Tumor growth was monitored daily using standard 3-D caliper measurement technique and formula. specific Mouse tumors were heated using a cooled, 36 mm diameter square copper tube induction coil which provided optimal heating in a 1 cm wide region in the center of the coil. Double dextran coated 80 nm iron oxide nanoparticles (Triton Biosystems) were used in all studies. Intra-tumor, peri-tumor and rectal (core body) temperatures were continually measured throughout the treatment period. Results Preliminary in vivo nanoparticle-AMF hyperthermia (167 KHz and 400 or 550 Oe) studies demonstrated dose responsive cytotoxicity which enhanced the effects of external beam radiation. AMF associated eddy currents resulted in nonspecific temperature increases in exposed tissues which did not contain nanoparticles, however these effects were minor and not injurious to the mice. These studies also suggest that iron oxide nanoparticle hyperthermia is more effective than nonnanoparticle tumor heating techniques when similar thermal doses are applied. Initial electron and light microscopy studies of iron oxide nanoparticle and AMF exposed tumor cells show a rapid uptake of particles and acute cytotoxicity following AMF exposure.

Hoopes, PJ; Strawbridge, RR; Gibson, UJ; Zeng, Q; Pierce, ZE; Savellano, M; Tate, JA; Ogden, JA; Baker, I; Ivkov, R; Foreman, AR

2014-01-01

146

Oxidative effect of several intravenous iron complexes in the rat.  

PubMed

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

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

2013-06-01

147

SULFATEREQUIREMENT FOR IRON OXIDATION BY THIOBACILLUSFERROOXIDANS  

Microsoft Academic Search

LAZAROFF, NORMAN(British Columbia Re- search Council, Vancouver, B.C.,Canada). Sulfate requirement forironoxidation byThio- bacillus ferrooxidans. J.Bacteriol. 85:78-83. 1963.-The growth ofThiobacillus ferrooxidans isinitially inhibited inmediacontaining ferrous chloride inplace offerrous sulfate. Thisinhibition ofgrowth isduetotherequirement ofahigh relative proportion ofsulfate ionstochloride (orother anions) forironoxidation. Adaptation takes place, producing strains which areableto oxidize ironinmediacontaining an initially unfavorable anionic composition. Adaptation is possibly duetotheselection ofspontaneous mutants capable

NORMAN LAZAROFF

148

Enzymes of respiratory iron oxidation. Progress report, March 1990--November 1991  

SciTech Connect

This report focuses on the progress made in three areas of research concerned with enzymes involved in respiratory iron oxidation. The three areas are as follows: development of an improved procedure for the routine large scale culture of iron oxidizing chemolithotrophs based on the in-situ electrolysis of the soluble iron in the growth medium; to perform iron oxidation kinetic studies on whole cells using the oxygen electrode; and to identify, separate, purify, and characterize the individual cellular components.

Blake, R. II

1991-12-31

149

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

PubMed

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. PMID:23978992

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

2013-10-21

150

Potential toxicity of superparamagnetic iron oxide nanoparticles (SPION)  

PubMed Central

Superparamagnetic iron oxide nanoparticles (SPION) are being widely used for various biomedical applications, for example, magnetic resonance imaging, targeted delivery of drugs or genes, and in hyperthermia. Although, the potential benefits of SPION are considerable, there is a distinct need to identify any potential cellular damage associated with these nanoparticles. Besides focussing on cytotoxicity, the most commonly used determinant of toxicity as a result of exposure to SPION, this review also mentions the importance of studying the subtle cellular alterations in the form of DNA damage and oxidative stress. We review current studies and discuss how SPION, with or without different surface coating, may cause cellular perturbations including modulation of actin cytoskeleton, alteration in gene expression profiles, disturbance in iron homeostasis and altered cellular responses such as activation of signalling pathways and impairment of cell cycle regulation. The importance of protein-SPION interaction and various safety considerations relating to SPION exposure are also addressed. PMID:22110864

Singh, Neenu; Jenkins, Gareth J.S.; Asadi, Romisa; Doak, Shareen H.

2010-01-01

151

Surface nature of nanoparticle gold\\/iron oxide aerogel catalysts  

Microsoft Academic Search

The aerogel catalysts investigated are constituted by two chemically different nanoparticle systems consisting of the gold phase and the iron oxide support. High-resolution transmission electronic microscopy (HRTEM) showed an increased surface roughness for aerogel particles with higher gold loading. X-ray photoelectron spectroscopy (XPS) revealed increases in the surface coverage of hydroxyl groups and the Fe2+\\/Fe3+ ratio due to the addition

Chien-Tsung Wang; Shih-Hung Ro

2006-01-01

152

Iron oxide-copper-gold deposits: an Andean view  

Microsoft Academic Search

Iron oxide-copper-gold (IOCG) deposits, defined primarily by their elevated magnetite and\\/or hematite contents, constitute a broad, ill-defined clan related to a variety of tectono-magmatic settings. The youngest and, therefore, most readily understandable IOCG belt is located in the Coastal Cordillera of northern Chile and southern Peru, where it is part of a volcano-plutonic arc of Jurassic through Early Cretaceous age.

Richard H. Sillitoe

2003-01-01

153

Nitrosative and oxidative modulation of iron regulatory proteins  

Microsoft Academic Search

.   Cytokine-driven nitric oxide (NO) synthase II provides cells with effectors for reactions at redox-sensitive site(s) of proteins.\\u000a Iron regulatory proteins (IRP1 and IRP2), two post-transcriptional regulators of gene expression, are particularly sensitive\\u000a to NO synthesis and to oxidative stress. IRP1 possesses a redox-active Fe-S cluster and can also exhibit aconitase activity.\\u000a IRP2 has no Fe-S cluster but exhibits several

C. Bouton

1999-01-01

154

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

E-print Network

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

Bekker, Andrey

155

Superparamagnetic nanosystems based on iron oxide nanoparticles for biomedical imaging.  

PubMed

Magnetic iron oxide nanoparticles and their dispersion in various mediums are of wide interest for their biomedical applications and physicochemical properties. MFe(2)O(4) or MOFe(2)O(3) (where M = Co, Li, Ni or Mn, for example) can be molecularly engineered to provide a wide range of magnetic properties. In this article, we survey the literature, integrating the results of our work to give a rational view on the synthesis, physicochemical properties and applications of MFe(2)O(4), especially for MRI. However, retrieving detailed biological information on a subcellular level is difficult, owing to the limited resolution and low sensitivity of the MRI technique. Thus, this article also concentrates on the development of a magnetic iron oxide nanoparticles/quantum dot hybrids, as a dual-mode magnetic-fluorescent probe. The synthesis and physicochemical properties of the magnetic iron oxide nanoparticles/quantum dot hybrids and, especially, its application as an MRI-fluorescent probe, will also be described. PMID:21542689

Liu, Fujun; Laurent, Sophie; Fattahi, Hassan; Vander Elst, Luce; Muller, Robert N

2011-04-01

156

Altering Iron Oxide Nanoparticle Surface Properties Induce Cortical Neuron Cytotoxicity  

PubMed Central

Superparamagnetic iron oxide nanoparticles, with diameters in the range of a few tens of nanometers, display the ability to cross the blood-brain barrier and are envisioned as diagnostic and therapeutic tools in neuro-medicine. However, despite the numerous applications being explored, insufficient information is available on their potential toxic effect on neurons. While iron oxide has been shown to pose a decreased risk of toxicity, surface functionalization, often employed for targeted delivery, can significantly alter the biological response. This aspect is addressed in the present study, which investigates the response of primary cortical neurons to iron oxide nanoparticles with coatings frequently used in biomedical applications: aminosilane, dextran, and polydimethylamine. Prior to administering the particles to neuronal cultures, each particle type was thoroughly characterized to assess the (1) size of individual nanoparticles, (2) concentration of the particles in solution and (3) agglomeration size and morphology. Culture results show that polydimethylamine functionalized nanoparticles induce cell death at all concentrations tested by swift and complete removal of the plasma membrane. Aminosilane coated particles affected metabolic activity only at higher concentrations while leaving the membrane intact and dextran-coated nanoparticles partially altered viability at higher concentrations. These findings suggest that nanoparticle characterization and primary cell-based cytotoxicity evaluation should be completed prior to applying nanomaterials to the nervous system. PMID:22111864

Rivet, Christopher J.; Yuan, Yuan; Borca-Tasciuc, Diana-Andra; Gilbert, Ryan J.

2014-01-01

157

Iron(VI): Hypothetical Candidate for the Martian Oxidant  

NASA Astrophysics Data System (ADS)

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 FeO 42- anion, were studied for their spectral and oxidative properties. Ferrate(VI) has distinctive spectroscopic features that make it available for detection by remote sensing reflectance spectra and contact measurements via Mössbauer spectroscopy, and the relevant miniaturized instrumentation has been developed or is under way, while for the returned samples XANES spectroscopy is shown to be a method of choice. Ferrate(VI) is capable of splitting water to yield molecular oxygen, and oxidizing organic carbon into CO 2. These activities were strongly abated after treatment at elevated temperatures, similar to observations with martian soil samples in the Viking mission.

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

2000-09-01

158

Electron uptake by iron-oxidizing phototrophic bacteria.  

PubMed

Oxidation-reduction reactions underlie energy generation in nearly all life forms. Although most organisms use soluble oxidants and reductants, some microbes can access solid-phase materials as electron-acceptors or -donors via extracellular electron transfer. Many studies have focused on the reduction of solid-phase oxidants. Far less is known about electron uptake via microbial extracellular electron transfer, and almost nothing is known about the associated mechanisms. Here we show that the iron-oxidizing photoautotroph Rhodopseudomonas palustris TIE-1 accepts electrons from a poised electrode, with carbon dioxide as the sole carbon source/electron acceptor. Both electron uptake and ruBisCo form I expression are stimulated by light. Electron uptake also occurs in the dark, uncoupled from photosynthesis. Notably, the pioABC operon, which encodes a protein system essential for photoautotrophic growth by ferrous iron oxidation, influences electron uptake. These data reveal a previously unknown metabolic versatility of photoferrotrophs to use extracellular electron transfer for electron uptake. PMID:24569675

Bose, A; Gardel, E J; Vidoudez, C; Parra, E A; Girguis, P R

2014-01-01

159

Aging of Iron (Hydr)oxides by Heat Treatment and Effects on Heavy  

E-print Network

Aging of Iron (Hydr)oxides by Heat Treatment and Effects on Heavy Metal Binding M E T T E A . S Ã? R and Environmental Engineering, University of Washington, Seattle, Washington 98195 Amorphous iron (hydr generated in waste incineration. In this study, iron oxides containing heavy metals (e.g., Pb, Hg, Cr

Frenkel, Anatoly

160

Reduction of Sintering during Annealing of FePt Nanoparticles Coated with Iron Oxide  

E-print Network

thermal decomposition of iron pentacarbonyl and polyol reduction of platinum salt.4 How- everReduction of Sintering during Annealing of FePt Nanoparticles Coated with Iron Oxide Chao LiuVised Manuscript ReceiVed October 12, 2004 FePt/iron oxide core/shell nanoparticles are synthesized by a two step

Laughlin, David E.

161

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...

162

Interactions of Fe(II) with the iron oxidizing bacterium Rhodopseudomonas palustris TIE-1  

E-print Network

Microbial anaerobic iron oxidation has long been of interest to biologists and geologists, both as a possible mechanism for the creation of banded iron formations before the rise of oxygen, and as a model system for organisms ...

Bird, Lina J. (Lina Joana)

2013-01-01

163

Competitive gettering of iron in silicon photovoltaics: Oxide precipitates versus phosphorus diffusion  

NASA Astrophysics Data System (ADS)

Experiments have been conducted to understand the behaviour of iron in silicon containing oxide precipitates and associated defects (dislocations and stacking faults), which is subjected to phosphorus diffusion gettering. Injection-dependent minority carrier lifetime measurements are analysed to provide quantitative information on the degree to which the precipitates and associated defects are decorated with iron impurities. These data are correlated with bulk iron measurements based on the photodissociation of FeB pairs. Iron in the vicinity of oxide precipitates in samples with relatively low levels of bulk iron contamination (< 5 × 1012 cm-3) can be gettered to some extent. Higher levels of bulk iron contamination (> 1.2 × 1013 cm-3) result in irreversible behaviour, suggesting iron precipitation in the vicinity of oxide precipitates. Bulk iron is preferentially gettered to the phosphorus diffused layer opposed to the oxide precipitates and associated defects.

Murphy, J. D.; McGuire, R. E.; Bothe, K.; Voronkov, V. V.; Falster, R. J.

2014-08-01

164

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

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

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

1997-01-01

165

Phase discrimination through oxidant selection in low-temperature atomic layer deposition of crystalline iron oxides.  

PubMed

Control over the oxidation state and crystalline phase of thin-film iron oxides was achieved by low-temperature atomic layer deposition (ALD), utilizing a novel iron precursor, bis(2,4-methylpentadienyl)iron. This low-temperature (T = 120 °C) route to conformal deposition of crystalline Fe3O4 or ?-Fe2O3 thin films is determined by the choice of oxygen source selected for the second surface half-reaction. The approach employs ozone to produce fully oxidized ?-Fe2O3 or a milder oxidant, H2O2, to generate the Fe(2+)/Fe(3+) spinel, Fe3O4. Both processes show self-limiting surface reactions and deposition rates of at least 0.6 Å/cycle, a significantly high growth rate at such mild conditions. We utilized this process to prepare conformal iron oxide thin films on a porous framework, for which ?-Fe2O3 is active for photocatalytic water splitting. PMID:23432093

Riha, Shannon C; Racowski, Joy M; Lanci, Michael P; Klug, Jeffrey A; Hock, Adam S; Martinson, Alex B F

2013-03-12

166

Low-temperature formation of magnetic iron oxides  

NASA Astrophysics Data System (ADS)

Elemental analysis and magnetic measurements of the surface of Mars have indicated the presence of an iron oxide with a considerable magnetic moment. Identification of the oxide phase(s) is an important subject as this may be used to identify the process of weathering on the martian surface as well as the composition of the Mars regolith itself. Consequently, interest was in evidence of new formation of strongly magnetic phases (e.g., magnetite, maghemite, feroxyhyte) in terrestrially derived Mars sample analogs. Within the group of Mars sample analogs derived from low-temperature weathering of basalts in Arctic regions, evidence of magnetic oxides formed at the outermost weathering rind was never observed. However, in one instance where the weathering products accumulating in a crack of a basaltic stone were investigated, evidence of magnetite was found. The experimental details are presented.

Koch, Chr. Bender; Madsen, M. B.

1993-09-01

167

Low-temperature formation of magnetic iron oxides  

NASA Technical Reports Server (NTRS)

Elemental analysis and magnetic measurements of the surface of Mars have indicated the presence of an iron oxide with a considerable magnetic moment. Identification of the oxide phase(s) is an important subject as this may be used to identify the process of weathering on the martian surface as well as the composition of the Mars regolith itself. Consequently, interest was in evidence of new formation of strongly magnetic phases (e.g., magnetite, maghemite, feroxyhyte) in terrestrially derived Mars sample analogs. Within the group of Mars sample analogs derived from low-temperature weathering of basalts in Arctic regions, evidence of magnetic oxides formed at the outermost weathering rind was never observed. However, in one instance where the weathering products accumulating in a crack of a basaltic stone were investigated, evidence of magnetite was found. The experimental details are presented.

Koch, Chr. Bender; Madsen, M. B.

1992-01-01

168

Preparation and characterization of iron oxide and hydroxide based nanomaterials  

NASA Astrophysics Data System (ADS)

Iron (Fe) oxides and hydroxides are common and abundant materials. They exhibit diverse crystal structures, properties and phenomena by virtue of which they find a wide range of scientific and technological applications. Controlled growth and manipulation of the specific structure and electronic behavior to meet the requirements of a given application is a challenging problem in view of many possible phases and composition of the resulting materials. The preparation method and experimental conditions will, therefore, significantly affect the properties and performance of Fe oxides and hydroxides. The goal of the project is to obtain Fe-based oxide/hydroxide catalytic materials and to derive a comprehensive understanding of the microstructure and electronic properties. The obvious relevance of the work it to optimize conditions to produce high quality Fe- based nanomaterials capable of dissociating the water molecules and produce hydrogen. The present approach to synthesize Fe oxides and hydroxides is based on a chemical route involving Fe-containing compounds. First step involved is the precipitation of Fe hydroxide/oxide particles from iron salts in an aqueous and non-aqueous media. The resultant precipitates consist of agglomerated nanoparticles. The size of the resulting Fe oxide and hydroxide nanoparticle depends on the concentration of the original solutions. After precipitation, a weak organic acid is added to obtain different concentrations. The samples were obtained at different intervals of time. Structure modification and dispersion of nanoparticles have been achieved and correlated with the concentration of the organic acid. It is demonstrated that the microstructure can be controlled in order to tune the materials' electronic behavior. In addition, the incorporation of various metal ions into the host matrix is explored in order to control the structure and electronic properties. The results are presented and discussed in detail in this dissertation.

Carbajal Franco, Guillermo

169

The growth of iron oxide, nickel oxide and cobalt oxide thin films by laser ablation from metal targets  

Microsoft Academic Search

Thin films of iron oxide, nickel oxide and cobalt oxide have been grown by the technique of laser ablation. The films have been deposited on [100] LaAlO3, SrTiO3, MgO and cubic zirconia (YSZ); on sapphire, mica, glass slides and Kapton. High quality c axis [100] oriented growth occurs for Fe3O4 and NiO on the first three substrates; on YSZ the

R. J. Kennedy

1995-01-01

170

Oxidative stress and renal injury with intravenous iron in patients with chronic kidney disease  

Microsoft Academic Search

Oxidative stress and renal injury with intravenous iron in patients with chronic kidney disease.BackgroundIntravenous iron is widely prescribed in patients with chronic kidney disease (CKD) and can cause oxidative stress. The relationship of oxidative stress and renal injury in patients with CKD is unknown. Whether renal injury can occur at a time point when transferrin is incompletely saturated is also

RAJIV AGARWAL; NINA VASAVADA; Nadine G. Sachs; SHAWN CHASE

2004-01-01

171

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

PubMed

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

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

2013-06-18

172

GAS-PHASE FLAME SYNTHESIS AND PROPERTIES OF MAGNETIC IRON OXIDE NANOPARTICLES WITH REDUCED OXIDATION STATE  

PubMed Central

Iron oxide nanoparticles of reduced oxidation state, mainly in the form of magnetite, have been synthesized utilizing a new continuous, gas-phase, nonpremixed flame method using hydrocarbon fuels. This method takes advantage of the characteristics of the inverse flame, which is produced by injection of oxidizer into a surrounding flow of fuel. Unlike traditional flame methods, this configuration allows for the iron particle formation to be maintained in a more reducing environment. The effects of flame temperature, oxygen-enrichment and fuel dilution (i.e. the stoichiometric mixture fraction), and fuel composition on particle size, Fe oxidation state, and magnetic properties are evaluated and discussed. The crystallite size, Fe(II) fraction, and saturation magnetization were all found to increase with flame temperature. Flames of methane and ethylene were used, and the use of ethylene resulted in particles containing metallic Fe(0), in addition to magnetite, while no Fe(0) was present in samples synthesized using methane. PMID:20228941

Kumfer, Benjamin M; Shinoda, Kozo; Jeyadevan, Balachandran; Kennedy, Ian M

2010-01-01

173

Pulsed-laser deposition of nanostructured iron oxide catalysts for efficient water oxidation.  

PubMed

Amorphous iron oxide nanoparticles were synthesized by pulsed-laser deposition (PLD) for functionalization of indium-tin oxide surfaces, resulting in electrodes capable of efficient catalysis in water oxidation. These electrodes, based on earth-abundant and nonhazardous iron metal, are able to sustain high current densities (up to 20 mA/cm2) at reasonably low applied potential (1.64 V at pH 11.8 vs reversible hydrogen electrode) for more than 1 h when employed as anodes for electrochemical water oxidation. The good catalytic performance proves the validity of PLD as a method to prepare nanostructured solid-state materials for catalysis, enabling control over critical properties such as surface coverage and morphology. PMID:24742340

Orlandi, Michele; Caramori, Stefano; Ronconi, Federico; Bignozzi, Carlo A; El Koura, Zakaria; Bazzanella, Nicola; Meda, Laura; Miotello, Antonio

2014-05-14

174

Selective Inhibition of the Oxidation of Ferrous Iron or Sulfur in Thiobacillus ferrooxidans  

PubMed Central

The oxidation of either ferrous iron or sulfur by Thiobacillus ferrooxidans was selectively inhibited or controlled by various anions, inhibitors, and osmotic pressure. Iron oxidation was more sensitive than sulfur oxidation to inhibition by chloride, phosphate, and nitrate at low concentrations (below 0.1 M) and also to inhibition by azide and cyanide. Sulfur oxidation was more sensitive than iron oxidation to the inhibitory effect of high osmotic pressure. These differences were evident not only between iron oxidation by iron-grown cells and sulfur oxidation by sulfur-grown cells but also between the iron and sulfur oxidation activities of the same iron-grown cells. Growth experiments with ferrous iron or sulfur as an oxidizable substrate confirmed the higher sensitivity of iron oxidation to inhibition by phosphate, chloride, azide, and cyanide. Sulfur oxidation was actually stimulated by 50 mM phosphate or chloride. Leaching of Fe and Zn from pyrite (FeS2) and sphalerite (ZnS) by T. ferrooxidans was differentially affected by phosphate and chloride, which inhibited the solubilization of Fe without significantly affecting the solubilization of Zn. PMID:10698768

Harahuc, Lesia; Lizama, Hector M.; Suzuki, Isamu

2000-01-01

175

Oxidation Potential, Not Crystal Structure, Controls the Oxidation State of Iron in Perovskite  

NASA Astrophysics Data System (ADS)

The mantle's oxidation state has broad implications on the state and evolution of the earth's interior. The relatively high oxidation potential of the upper mantle is such that iron is predominantly Fe2+ with small amounts of Fe3+ . Fe3+ is more stable than Fe2+ in the dominant lower mantle mineral, perovskite, despite the fact that the effect of pressure is to reduce the oxidizing potential of a system. It is therefore suggested that iron undergoes a disproportionation reaction of 3Fe2+ =2Fe3+ +Fe0 , controlled by the crystallography instead of oxidation potential. We crystallized synthetic enstatite glass with 5% Al2O3, 14% FeO, and 3% Fe2O3 in the laser-heated diamond anvil cell at 25-63 GPa and 1700-2800 K. We find that for temperatures <2200 K, the sample crystallizes to only perovskite, while at higher temperatures, the sample crystallizes to perovskite and stishovite as evident in x-ray diffraction, with 5-50 nm iron precipitates on grain boundaries. The precipitates have small amounts of dissolved oxygen, but are Mg- and Al- free. We interpret that the stishovite is forming due to the oxidation of the ferric iron to ferrous iron according to (Mg2+,Al3+)(Fe3+,Si4+)O3 +SiO2 + Fe0 while the lower-temperature samples crystallizing as approximately (Mg2+ Fe2+ Al3+ )(Fe3+ Al3+ Si4+ )O3. We observe 2.8(2) Å3 volume expansion of the perovskite and a 28(2) GPa decrease in compressibility of the perovskite relative to the perovskite forming at lower temperature, consistent with the proposed compositions of the perovskites. As the increased temperature increases the oxidation potential of the system, we suggest that the oxidation state of iron in perovskite is dependent on oxidation potential as opposed to perovskite's crystal structure. Transmission Electron Microscopy (TEM) coupled with Electron Energy Loss Spectroscopy (EELS) show iron precipitation on grain boundaries supporting the conclusion. We present a discussion of the results and implications for core formation and lower mantle dynamics.

Panero, W. R.; Pigott, J. S.; Watson, H. C.; Scharenberg, M.; Green, H. W.; McComb, D. W.; Williams, R. E.

2013-12-01

176

Progressive Sorption and Oxidation\\/Hydrolysis of Fe(II) Affects Cadmium Immobilization by Bacteria-Iron Oxide Composites  

Microsoft Academic Search

Iron-bacteria composite suspensions were prepared by exposure of Anoxybacillus flavithermus cells to increasing concentrations of Fe cations under different degrees of oxidation. Cd immobilization was investigated during and after the synthesis of the iron-bacteria composites via scanning electron microscopy and isotherm sorption experiments conducted at varied ratios of total iron to bacteria (expressed by the variable ?, mg Fe per

Christopher J. Daughney; Mohamad Fakih; Xavier Châtellier

2011-01-01

177

A new method for preparation of magnetite from iron oxyhydroxide or iron oxide and ferrous salt in aqueous solution  

NASA Astrophysics Data System (ADS)

In this study, a new method is proposed for the preparation of Fe 3O 4 from iron oxyhydroxides (goethite, akaganeite, lepidocrocite, feroxyhyte and ferrihydrite) or iron oxide (hematite) and ferrous salt in aqueous solution. The product is magnetite with various particle sizes. Products are characterized by X-ray powder diffraction, IR spectra and vibrating sample magnetometery.

Kahani, S. A.; Jafari, M.

2009-07-01

178

Influence of chemical weathering and aging of iron oxides on the potential iron solubility of Saharan dust during  

E-print Network

Influence of chemical weathering and aging of iron oxides on the potential iron solubility. In this study, we investigated how the nature of Fe minerals in the dust affects its potential Fe solubility minerals present in the samples and Fe solubilities of corresponding standard minerals. The calculated

Benning, Liane G.

179

Thermodynamics of hydration and oxidation in the proton conductor Gd-doped barium cerate from density functional theory calculations  

NASA Astrophysics Data System (ADS)

Hydration and oxidation of gadolinium-doped barium cerate, a system with highly promising properties when used as electrolyte for protonic ceramic fuel cells, are investigated by means of density functional calculations. The energy landscape of oxygen vacancies and interstitial protons in this strongly distorted orthorhombic perovskite is computed. Although the most stable sites for protons are found in the close vicinity of the dopant, the picture of a very complex energy landscape emerges, in which some sites far away from Gd are found more stable than other ones in its close vicinity, due to the highly distorted geometry of the host materials. The fully hydrated phase can be approximated by a structure with 16 local minima. Both hydration (water incorporation) and oxidation (oxygen incorporation) are found to be exothermic processes with reaction enthalpies of -1.34 eV/H2O molecule and -0.70 eV/O atom, respectively. The hole polaron resulting from the exothermic incorporation of oxygen is found localized on oxygens around the dopant (small polaron) and carries a spin magnetic moment. Finally, the competition between hydration and oxidation is studied and discussed as a function of oxygen and water partial pressures.

Hermet, Jessica; Bottin, François; Dezanneau, Guilhem; Geneste, Gregory

2012-05-01

180

Magnetic properties of iron oxides produced by bacterial oxidation of Fe2+ under acid conditions  

NASA Astrophysics Data System (ADS)

Iron oxides synthesized under acid conditions in a bioreactor using the bacterium Thiobacillus ferrooxidans or formed in nature under similar conditions resemble relatively “well”-crystallized ferrihydrites. Mössbauer spectra, however, show up significant differences between these and ferrihydrites, indicating sulfate to play a major role in determining the properties of the bacterial samples.

Murad, E.; Bigham, J. M.; Bowen, L. H.; Schwertmann, U.

1990-07-01

181

Arsenic Bioremediation by Biogenic Iron Oxides and Sulfides  

PubMed Central

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

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

182

Superparamagnetic iron oxide nanoparticles: magnetic nanoplatforms as drug carriers  

PubMed Central

A targeted drug delivery system is the need of the hour. Guiding magnetic iron oxide nanoparticles with the help of an external magnetic field to its target is the principle behind the development of superparamagnetic iron oxide nanoparticles (SPIONs) as novel drug delivery vehicles. SPIONs are small synthetic ?-Fe2O3 (maghemite) or Fe3O4 (magnetite) particles with a core ranging between 10 nm and 100 nm in diameter. These magnetic particles are coated with certain biocompatible polymers, such as dextran or polyethylene glycol, which provide chemical handles for the conjugation of therapeutic agents and also improve their blood distribution profile. The current research on SPIONs is opening up wide horizons for their use as diagnostic agents in magnetic resonance imaging as well as for drug delivery vehicles. Delivery of anticancer drugs by coupling with functionalized SPIONs to their targeted site is one of the most pursued areas of research in the development of cancer treatment strategies. SPIONs have also demonstrated their efficiency as nonviral gene vectors that facilitate the introduction of plasmids into the nucleus at rates multifold those of routinely available standard technologies. SPION-induced hyperthermia has also been utilized for localized killing of cancerous cells. Despite their potential biomedical application, alteration in gene expression profiles, disturbance in iron homeostasis, oxidative stress, and altered cellular responses are some SPION-related toxicological aspects which require due consideration. This review provides a comprehensive understanding of SPIONs with regard to their method of preparation, their utility as drug delivery vehicles, and some concerns which need to be resolved before they can be moved from bench top to bedside. PMID:22848170

Wahajuddin; Arora, Sumit

2012-01-01

183

Conquering the Dark Side: Colloidal Iron Oxide Nanoparticles  

PubMed Central

Nanomedicine approaches to atherosclerotic disease will have significant impact on the practice and outcomes of cardiovascular medicine. Iron oxide nanoparticles have been extensively used for nontargeted and targeted imaging applications based upon highly sensitive T2* imaging properties, which typically result in negative contrast effects that can only be imaged 24 or more hours after systemic administration due to persistent blood pool interference. Although recent advances involving MR pulse sequences have converted these dark contrast voxels into bright ones, the marked delays in imaging from persistent magnetic background interference and prominent dipole blooming effects of the magnetic susceptibility remain barriers to overcome. We report a T1-weighted (T1w) theranostic colloidal iron oxide nanoparticle platform, CION, which is achieved by entrapping oleate-coated magnetite particles within a cross-linked phospholipid nanoemulsion. Contrary to expectations, this formulation decreased T2 effects thus allowing positive T1w contrast detection down to low nanomolar concentrations. CION, a vascular constrained nanoplatform administered in vivo permitted T1w molecular imaging 1 hour after treatment without blood pool interference, although some T2 shortening effects on blood, induced by the superparamagnetic particles persisted. Moreover, CION was shown to encapsulate antiangiogenic drugs, like fumagillin, and retained them under prolonged dissolution, suggesting significant theranostic functionality. Overall, CION is a platform technology, developed with generally recognized as safe components, that overcomes the temporal and spatial imaging challenges associated with current iron oxide nanoparticle T2 imaging agents, and which has theranostic potential in vascular diseases for detecting unstable ruptured plaque or treating atherosclerotic angiogenesis. PMID:19908850

Senpan, Angana; Caruthers, Shelton D.; Rhee, Ilsu; Mauro, Nicholas A.; Pan, Dipanjan; Hu, Grace; Scott, Michael J.; Fuhrhop, Ralph W.; Gaffney, Patrick J.; Wickline, Samuel A.; Lanza, Gregory M.

2009-01-01

184

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....

185

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

E-print Network

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 ...

Wei, He

186

Resistive switching in iron-oxide-filled carbon nanotubes.  

PubMed

Iron-oxide-filled carbon nanotubes exhibit an intriguing charge bipolarization behavior which allows the material to be applied in resistive memory devices. Raman analysis conducted with an electric field applied in situ shows the Kohn anomalies and a strong modification of the electronic properties related to the applied voltage intensity. In addition, the I(D)/I(G) ratio indicated the reversibility of this process. The electrical characterization indicated an electronic transport governed by two main kinds of charge hopping, one between the filling and the nanotube and the other between the nanotube shells. PMID:24201829

Cava, Carlos E; Persson, Clas; Zarbin, Aldo J G; Roman, Lucimara S

2014-01-01

187

Comparison of Iron Oxide Nanoparticle and Waterbath Hyperthermia Cytotoxicity  

PubMed Central

The development of medical grade iron oxide nanoparticles (IONP) has renewed interest in hyperthermia cancer therapy. Because of their modifiable size and heating capabilities under an AC magnetic field (alternating magnetic field, AMF), IONPs have the potential to damage or kill cells in a manner more therapeutically efficient than previous hyperthermia techniques. The use of IONPs in hyperthermia cancer therapy has prompted numerous questions regarding the cytotoxic mechanism associated with IONP heat therapy and if such mechanism is different (more or less effective) with respect to conventional hyperthermia techniques.

Ogden, JA; Tate, JA; Strawbridge, RR; Ivkov, R; Hoopes, PJ

2014-01-01

188

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

PubMed Central

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

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

2010-01-01

189

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

E-print Network

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

Sparks, Donald L.

190

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

SciTech Connect

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.

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

1996-10-01

191

MCM-41-supported iron phosphate catalyst for partial oxidation of methane to oxygenates with oxygen and nitrous oxide  

Microsoft Academic Search

Iron phosphate supported on MCM-41 has been studied for partial oxidation of methane with both oxygen and nitrous oxide. Characterizations with XRD, Raman spectroscopy, XPS, and H2-TPR suggest that the supported iron phosphate species with loading amounts lower than 40 wt% are located and dispersed in the mesopores of MCM-41. Such iron phosphate species can be reduced more readily than the

Xiaoxing Wang; Ye Wang; Qinghu Tang; Qian Guo; Qinghong Zhang; Huilin Wan

2003-01-01

192

Superparamagnetic Iron Oxide Nanoparticles with Variable Size and an Iron Oxidation State as Prospective Imaging Agents  

E-print Network

temperature. The products were characterized by DLS, TEM, X-ray powder diffractometry, TGA, chemical analysis, it was important to learn that the oxidation product has no disadvantages as compared to its precursor

Spinu, Leonard

193

Red Dawn: Characterizing Iron Oxide Minerals in Atmospheric Dust  

NASA Astrophysics Data System (ADS)

Atmospheric dust is comprised of many components including small amounts of iron oxide minerals. Although the iron oxides make up a small weight percent of the bulk dust, they are important because of their roles in ocean fertilization, controls on climate, and as a potential health hazard to humans. Here we report on the iron oxide mineralogy in dust from a large dust storm, dubbed Red Dawn, which engulfed eastern Australia along a 3000 km front on 23 September 2009. Red Dawn originated from the lower Lake Eyre Basin of South Australia, western New South Wales (NSW) and southwestern Queensland and was the worst dust storm to have hit the city of Sydney in more than 60 years. Dust samples were collected from various locations across eastern Australia (Lake Cowal, Orange, Hornsby, Sydney) following the Red Dawn event. Our dust collection provides a good opportunity to study the physical and mineralogical properties of iron oxides from Red Dawn using a combination of reflectance spectroscopy, Mössbauer spectroscopy (MB), and magnetic measurements. Magnetization measurements from 20-400 K reveal that magnetite/maghemite, hematite and goethite are present in all samples with magnetite occurring in trace amounts (< 0.5wt%). However, the amount of magnetite/maghemite even in trace concentrations generally increases from Lake Cowal from west to east (0.01 to 0.29 wt%), with highest magnetite contents in the urban-Sydney sites. These observations indicate the additions of magnetite from local urban sources. Variable temperature Mössbauer spectroscopy (300 K and 4.2 K) indicate that goethite and hematite compose approximately 25-45 % of the Fe-bearing phases in the Orange and Lake Cowal samples. Goethite is more abundant than hematite in the Lake Cowal samples whereas the opposite is observed for Orange. Hematite is observed at both temperatures but goethite only at 4.2 K. The identification of goethite in Mössbauer analyses at low-temperature but not at room temperature indicates the presence of nanogoethite and small particle sizes (< 30 nm). Magnetization experiments indicates that some of the nanogoethite has remanence blocking temperatures above 300 K (and hence larger particle sizes) but it must be a small fraction of the total grain distribution considering that goethite was not indicated at 300 K with Mössbauer. Likewise, Mössbauer spectra indicate that the hematite component is still above the Morin transition (TM=265 K) and in its canted antiferromagnetic state even at 4.2 K. Suppression of the Morin transition in hematite can occur due to reduced crystallinity, cation substitution (e.g., Ti4+, Al 3+), or small particle effects (d< 100 nm). Finally, we compared reflectance with a magnetic parameter (hard isothermal remanent magnetization, HIRM) for ferric oxide abundance to assess the degree to which ferric oxide in these samples might absorb solar radiation. In samples for which both parameters were obtained, HIRM and average reflectance over the visible wavelengths are correlated as a group (r2=0.24). These results indicate that the ferric oxide minerals in Red Dawn dust absorb solar radiation. Much of this ferric oxide occurs likely as grain coatings of nanohematite and nanogoethite, thereby providing high surface area to enhance absorption of solar radiation.

Yauk, K.; Ottenfeld, C. F.; Reynolds, R. L.; Goldstein, H.; Cattle, S.; Berquo, T. S.; Moskowitz, B. M.

2012-12-01

194

Synthesis and lithium intercalation properties of nanocrystalline lithium iron oxides  

SciTech Connect

Lithium iron oxides Li{sub x}Fe{sub y}O{sub z} were synthesized by oxidizing Fe{sup 2+} with lithium peroxide in the presence of lithium hydroxide in aqueous solutions followed by firing the precursors at 200 {le} T {le} 800 C. The samples were characterized by X-ray powder diffraction, transmission electron microscopy, wet-chemical analyses, and surface-area measurements. The Li/Fe ratio in the samples depends on the concentrations and volumes of the reactants used in the synthesis. Samples fired at a lower temperature of 200 C with a nanocrystalline microstructure and optimum Li/Fe ratio exhibit a capacity of about 140 mAh/g in the range 1.5--4.3 V with excellent cyclability. On the other hand, samples fired at higher temperatures T {ge} 400 C with well-defined crystalline phases exhibit much lower capacity (< 50 mAh/g).

Kim, J.; Manthiram, A.

1999-12-01

195

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

PubMed

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

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

2013-09-01

196

Iron and manganese oxide mineralization in the Pacific  

USGS Publications Warehouse

Iron, manganese, and iron-manganese deposits occur in nearly all geomorphologic and tectonic environments in the ocean basins and form by one or more of four processes: (1) hydrogenetic precipitation from cold ambient seawater, (2) precipitation from hydrothermal fluids, (3) precipitation from sediment pore waters that have been modified from bottom water compositions by diagenetic reactions in the sediment column and (4) replacement of rocks and sediment. Iron and manganese deposits occur in five forms: nodules, crusts, cements, mounds and sediment-hosted stratabound layers. Seafloor oxides show a wide range of compositions from nearly pure iron to nearly pure manganese end members. Fe/Mn ratios vary from about 24 000 (up to 58% elemental Fe) for hydrothermal seamount ironstones to about 0.001 (up to 52% Mn) for hydrothermal stratabound manganese oxides from active volcanic arcs. Hydrogenetic Fe-Mn crusts that occur on most seamounts in the ocean basins have a mean Fe/Mn ratio of 0.7 for open-ocean seamount crusts and 1.2 for continental margin seamount crusts. Fe-Mn nodules of potential economic interest from the Clarion-Clipperton Zone have a mean Fe/Mn ratio of 0.3, whereas the mean ratio for nodules from elsewhere in the Pacific is about 0.7. Crusts are enriched in Co, Ni and Pt and nodules in Cu and Ni, and both have significant concentrations of Pb, Zn, Ba, Mo, V and other elements. In contrast, hydrothermal deposits commonly contain only minor trace metal contents, although there are many exceptions, for example, with Ni contents up to 0.66%, Cr to 1.2%, and Zn to 1.4%. Chondrite-normalized REE patterns generally show a positive Ce anomaly and abundant ??REEs for hydrogenetic and mixed hydrogenetic-diagenetic deposits, whereas the Ce anomaly is negative for hydrothermal deposits and ??REE contents are low. However, the Ce anomaly in crusts may vary from strongly positive in East Pacific crusts to slightly negative in West Pacific crusts, which may reflect the redox conditions of seawater. The concentration of elements in hydrogenetic Fe-Mn crusts depends on a wide variety of water column and crust surface characteristics, whereas concentration of elements in hydrothermal oxide deposits depends of the intensity of leaching, rock types leached, and precipitation of sulphides at depth in the hydrothermal system.

Hein, J.R.; Koschinsky, A.; Halbach, P.; Manheim, F. T.; Bau, M.; Kang, J.-K.; Lubick, N.

1997-01-01

197

Mesoporous iron oxide nanofibers and their loading capacity of curcumin.  

PubMed

Mesoporous iron oxide nanofibers were obtained by calcination of electrospun precursors at various temperatures. Their microstructure is influenced by the calcination temperature. As the calcination temperature is at 350 degrees C, the resultant iron oxide nanofibers largely consist of magnetic Fe3O4 and gamma-Fe2O3, with a specific surface area of about 120 m2/g and magnetization of about 66.5 Am2/kg. When the precursor calcined at 450 degrees C, the pure mesoporous alpha-Fe2O3 nanofibers with a specific surface area of about 92 m2/g are obtained and they show a high loading for curcumin. All the adjusted R-squares for the pseudo-second-order model overtop 0.99 in the initial curcumin ethanol solution concentrations of 30, 40 and 60 microg/mL, which suggests the pseudo-second-order kinetics model fit the adsorption kinetics of curcumin onto the mesoporous alpha-Fe2O3 nanofibers, and the adsorption can reach equilibrium in 60 min. While, Langmuir model (R2 = 0.9980) fits well the curcumin adsorption isotherm onto alpha-Fe2O3 mesoporous nanofibers, and the adsorption capacity is up to 12.48 mg/g at the curcumin concentration of 60 microg/mL. PMID:24734703

Wang, Qiuju; Liu, Ruijiang; Shen, Xiangqian; Zou, Lianli; Wu, Dingmei

2014-04-01

198

Magnetic tumor targeting of ?-glucosidase immobilized iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

199

Magnetic tumor targeting of ?-Glucosidase immobilized iron oxide nanoparticles  

PubMed Central

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, difficult to be monitored. In current 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 (MNP), 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 MNP remained 85.54%±6.9% relative activity and showed much better temperature stability. relative activity and showed much better temperature stability. The animal study results showed that ?-Glu-MNP display preferable pharmacokinetics characteristic in relation to MNP. With adscititious magnetic field on the surface of tumor, a significant quantity of ?-Glu-MNP was selectively delivered into a subcutaneous tumor of glioma-bearing mice. Remarkably, the enzyme activity of the delivered ?-Glu in tumor lesions showed as high as 20.123 ± 5.022 mU/g tissue with 2.14 of tumor/non-turmor of ?-Glu activity. PMID:23974977

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

2014-01-01

200

Ferrous iron oxidation under acidic conditions - The effect of ferric oxide surfaces  

NASA Astrophysics Data System (ADS)

In this study, the kinetics of Fe(II) oxidation in the presence of the iron oxyhydroxides ferrihydrite, Si-ferrihydrite, schwertmannite, lepidocrocite and goethite are investigated over the pH range 4-5.5. Despite limited sorption of Fe(II), the rate of Fe(II) oxidation is up to 70-fold faster than in the absence of any Fe oxyhydroxide phase over pH 4.5-5.5. Enhanced Fe(II) oxidation was minor or negligible at pH 4 with undetectable amounts of Fe(II) adsorbed to the iron oxyhydroxides at this pH. Heterogeneous rate constants derived from kinetic modeling were normalized to the concentration of adsorbed Fe(II) and deviated by no more than 13.8% at pH 4.5, 5 and 5.5, indicating that oxidation is proportional to the concentration of adsorbed Fe(II). Average rate constants were found to be: 2.12 ± 0.20, 1.30 ± 0.09, 1.69 ± 0.22, 1.20 ± 0.08 and 0.68 ± 0.09 M-1 s-1 for ferrihydrite, goethite, lepidocrocite, schwertmannite and Si-ferrihydrite, respectively. The role of reactive oxygen species, such as hydrogen peroxide, the hydroxyl radical and superoxide, towards the overall oxidation of Fe(II) was examined but found to have only a minor impact on Fe(II) oxidation when compared to the effect of heterogeneous oxidation.

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

2014-11-01

201

Characterization and Localization of Iron-Oxidizing Proteins in Acid Mine Drainage Biofilms  

Microsoft Academic Search

As molecular geomicrobiologists, we are interested in the microbially-produced molecules that effect geochemical transformations, particularly proteins involved in lithotrophic energy generation. We have identified two such proteins produced by Leptospirillum group II microbes, which dominate biofilms floating on acidic waters in the Richmond Mine at Iron Mountain, CA. Leptospirillum generates energy by iron oxidation, producing the ferric iron catalyst responsible

C. S. Chan; M. P. Thelen; M. Hwang; J. F. Banfield

2005-01-01

202

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

DOEpatents

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.

Liu, Chain T. (Oak Ridge, TN)

1988-03-15

203

Atomistic Simulations of Uranium Incorporation into Iron (Hydr)Oxides  

SciTech Connect

Atomistic simulations were carried out to characterize the coordination environments of U incorporated in three Fe-(hydr)oxide minerals: goethite, magnetite, and hematite. The simulations provided information on U-O and U-Fe distances, coordination numbers, and lattice distortion for U incorporated in different sites (e.g., unoccupied versus occupied sites, octahedral versus tetrahedral) as a function of the oxidation state of U and charge compensation mechanisms (i.e., deprotonation, vacancy formation, or reduction of Fe(III) to Fe(II)). For goethite, deprotonation of first shell hydroxyls enables substitution of U for Fe(III) with a minimal amount of lattice distortion, whereas substitution in unoccupied octahedral sites induced appreciable distortion to 7-fold coordination regardless of U oxidation states and charge compensation mechanisms. Importantly, U-Fe distances of ~3.6 Å were associated with structural incorporation of U and cannot be considered diagnostic of simple adsorption to goethite surfaces. For magnetite, the octahedral site accommodates U(V) or U(VI) with little lattice distortion. U substituted for Fe(III) in hematite maintained octahedral coordination in most cases. In general, comparison of the simulations with available experimental data provides further evidence for the structural incorporation of U in iron (hydr)oxide minerals.

Kerisit, Sebastien N.; Felmy, Andrew R.; Ilton, Eugene S.

2011-04-29

204

Characterization of Iron Dinitrosyl Species Formed in the Reaction of Nitric Oxide with a Biological Rieske Center  

E-print Network

Reactions of nitric oxide with cysteine-ligated iron?sulfur cluster proteins typically result in disassembly of the iron?sulfur core and formation of dinitrosyl iron complexes (DNICs). Here we report the first evidence ...

Wang, Hongxin

205

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

PubMed

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

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

2011-05-01

206

Formation of nitrous oxide (N2O) hydrate in soil mineral suspensions with electrolytes  

NASA Astrophysics Data System (ADS)

We have identified the effects of solid surface (illite, nontronite, sphalerite, kaolinite) and electrolyte (NaCl, KCl, CaCl2, MgCl2) types on the formation of N2O hydrate in this study. The hydrate formation experiments were conducted at hydrate forming condition (273.3K and 30 bar) by injecting N2O gas into the soil mineral suspensions with and without electrolytes in a 50mL pressurized vessel. The formation of N2O hydrate in aqueous electrolyte solutions was slower than that in deionized water. Ion charge and size were significant factors affecting N2O hydrate formation kinetic in electrolytes solutions. The addition of soil mineral suspensions accelerated the formation of N2O hydrate in the electrolyte solutions. Surface area and ionic strength of soil minerals highly influenced on formation kinetic of N2O hydrate. The hydrate formation times in the solid suspensions without electrolytes were very similar to that in the deionized water. The results obtained from this research could be indirectly applied to the fate of N2O sequestered into geological formations as well as its storage as a form of N2O hydrate.

Kyung, D.; Enkh-Amgalan, T.; Lee, W.

2013-05-01

207

Towards a Mechanistic Understanding of Anaerobic Iron Oxidation: Balancing Electron Uptake and Detoxification  

NASA Astrophysics Data System (ADS)

In recent years, significant progress has been made towards understanding the biochemical mechanisms used by bacteria for the anaerobic oxidation of Fe(II) in the environment. Most work to elucidate microbial anaerobic iron oxidation mechanisms has focused on photosynthetic iron oxidizers. However, a wide range of bacteria can couple iron oxidation to nitrate respiration in the absence of sunlight and oxygen. The growth benefit from anaerobic iron oxidation varies widely. In both photosynthetic and nitrate reducing bacteria, oxidation of Fe(II) likely represents an important detoxification strategy, and, in some cases, may have also evolved into a metabolic strategy. The extent to which electron donation from Fe(II) can be controlled and toxic reactions prevented or managed is central to the success of an iron oxidizing microorganism. We suggest that iron oxidizing microorganisms likely exist along a continuum including: 1) bacteria which inadvertantly oxidize Fe(II) by abiotic or biotic reactions with enzymes or chemical intermediates in their metabolic pathways (e.g. denitrification) and suffer from toxicity or energetic penalty, 2) Fe(II) tolerant bacteria that gain little or no growth benefit from iron oxidation but can manage the toxic reactions, and 3) bacteria which can efficiently accept electrons from Fe(II) to gain a growth advantage while preventing or mitigating the toxic reactions. Evidence from physiological, proteomic and biochemical experiments is used to place various bacterial species in each of these three classes.

Coates, J. D.; Carlson, H. K.; Clark, I.; Melnyk, R. A.

2011-12-01

208

Kinetics of starch oxidation using hydrogen peroxide as an environmentally friendly oxidant and an iron complex as a catalyst  

Microsoft Academic Search

Oxidized starch is heavily deployed as a surface sizing agent in the paper industry. The most common oxidation methods use transition metals as catalysts and perchlorines or iodates as oxidants, and thus a large amount of inorganic waste is produced. In the present work, iron tetrasulfophthalocyanine (FePcS), a cheap iron complex is used as a catalyst, and hydrogen peroxide (H2O2)

P. Tolvanen; P. Mäki-Arvela; A. B. Sorokin; T. Salmi; D. Yu. Murzin

2009-01-01

209

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

Microsoft Academic Search

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

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

1994-01-01

210

First Evidence for the Presence of Iron Oxidizing Zetaproteobacteria at the Levantine Continental Margins  

E-print Network

First Evidence for the Presence of Iron Oxidizing Zetaproteobacteria at the Levantine Continental that zetaproteobacterial populations were a dominant fraction of microbial community in the biofilm. We show for the first Evidence for the Presence of Iron Oxidizing Zetaproteobacteria at the Levantine Continental Margins. PLo

Cambridge, University of

211

Kinetic Studies of Iron Oxidation by Whole Cells of Ferrobacillus ferrooxidans  

PubMed Central

A colorimetric assay was developed for studying the kinetics of iron oxidation with whole cells of the chemoautotroph, Ferrobacillus ferrooxidans. The assay was more advantageous than the conventional method of Warburg manometry because of its simplicity, rapidity, and the small amount of cells required. The assay measured Fe3+ as a chloride complex which absorbs at 410 nm. Kinetic analysis showed the apparent Km for iron oxidation to be 5.4 × 10?3m in an unbuffered system and 2.2 × 10?3m in the presence of ?-alanine-SO42? buffer. Glycine and ?-alanine buffers were used in the measurement of the pH optimum for iron oxidation; the optimum ranged from 2.5 to 3.8. The effect of pH was primarily on the Vmax while the Km remained constant. Added SO42? was found to stimulate iron oxidation by increasing the Vmax of iron oxidation by whole cells, but it did not affect the Km. Results of assays of iron oxidation in systems containing various mole percentages of SO42? and Cl? indicated that Cl? did not inhibit iron oxidation but that SO42? was required. Sulfate could be partially replaced by HPO42? and HAsO42? but not by BO3?, MoO42?, NO3?, or Cl?; formate and MoO42? inhibited iron oxidation. PMID:5808080

Schnaitman, C. A.; Korczynski, M. S.; Lundgren, D. G.

1969-01-01

212

Non-heme iron hydroperoxo species in superoxide reductase as a catalyst for oxidation reactions.  

PubMed

The non-heme high-spin ferric iron hydroperoxo species formed in superoxide reductase catalyzes oxidative aldehyde deformylation through its nucleophilic character. This species also acts as an electrophile to catalyze oxygen atom transfer in sulfoxidation reactions, highlighting the oxidation potential of non-heme iron hydroperoxo species. PMID:25283601

Rat, S; Ménage, S; Thomas, F; Nivière, V

2014-10-21

213

Oxidative damage of bovine serum albumin and other enzyme proteins by iron-chelate complexes  

Microsoft Academic Search

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

Tetsuya Ogino; Shigeru Okada

1995-01-01

214

Iron Binding at Specific Sites within the Octameric HbpS Protects Streptomycetes from Iron-Mediated Oxidative Stress  

PubMed Central

The soil bacterium Streptomyces reticuli secretes the octameric protein HbpS that acts as a sensory component of the redox-signalling pathway HbpS-SenS-SenR. This system modulates a genetic response on iron- and haem-mediated oxidative stress. Moreover, HbpS alone provides this bacterium with a defence mechanism to the presence of high concentrations of iron ions and haem. While the protection against haem has been related to its haem-binding and haem-degrading activity, the interaction with iron has not been studied in detail. In this work, we biochemically analyzed the iron-binding activity of a set of generated HbpS mutant proteins and present evidence showing the involvement of one internal and two exposed D/EXXE motifs in binding of high quantities of ferrous iron, with the internal E78XXE81 displaying the tightest binding. We additionally show that HbpS is able to oxidize ferrous to ferric iron ions. Based on the crystal structure of both the wild-type and the mutant HbpS-D78XXD81, we conclude that the local arrangement of the side chains from the glutamates in E78XXE81 within the octameric assembly is a pre-requisite for interaction with iron. The data obtained led us to propose that the exposed and the internal motif build a highly specific route that is involved in the transport of high quantities of iron ions into the core of the HbpS octamer. Furthermore, physiological studies using Streptomyces transformants secreting either wild-type or HbpS mutant proteins and different redox-cycling compounds led us to conclude that the iron-sequestering activity of HbpS protects these soil bacteria from the hazardous side effects of peroxide- and iron-based oxidative stress. PMID:24013686

Wedderhoff, Ina; Kursula, Inari; Groves, Matthew R.; Ortiz de Orue Lucana, Dario

2013-01-01

215

The concept of delayed nucleation in nanocrystal growth demonstrated for the case of iron oxide nanodisks.  

PubMed

A comprehensive study of iron oxide nanocrystal growth through non-hydrolitic, surfactant-mediated thermal reaction of iron pentacarbonyl and an oxidizer has been conducted, which includes size control, anisotropic shape evolution, and crystallographic phase transition of monodisperse iron oxide colloidal nanocrystals. The reaction was monitored via in situ UV-vis spectroscopy, taking advantage of the color change accompanying the iron oxide colloid formation, allowing measurement of the induction time for nucleation. Features of the synthesis such as the size control and reproducibility are related to the occurrence of the observed delayed nucleation process. As a separate source of iron and oxygen is adopted, phase control could also be achieved by sequential injections of oxidizer. PMID:16448141

Casula, Maria F; Jun, Young-Wook; Zaziski, David J; Chan, Emory M; Corrias, Anna; Alivisatos, A Paul

2006-02-01

216

The concept of delayed nucleation in nanocrystal growthdemonstrated for the case of iron oxide nanodisks  

SciTech Connect

A comprehensive study of iron oxide nanocrystal growth through non-hydrolitic, surfactant-mediated thermal reaction of iron pentacarbonyl and an oxidizer has been conducted, which includes size control, anisotropic shape evolution, and crystallographic phase transition of monodisperse iron oxide colloidal nanocrystals. The reaction was monitored by in situ UV-Vis spectroscopy taking advantage of the color change accompanying the iron oxide colloid formation allowing measurement of the induction time for nucleation. Features of the synthesis such as the size control and reproducibility are related to the occurrence of the observed delayed nucleation process. As a separate source of iron and oxygen is adopted, phase control could also be achieved by sequential injections of oxidizer.

Casula, Maria F.; Jun, Young-wook; Zaziski, David J.; Chan, EmoryM.; Corrias, Anna; Alivisatos, Paul A.

2005-09-09

217

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

PubMed Central

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

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

2012-01-01

218

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

E-print Network

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

Volinsky, Alex A.

219

Dietary iron concentration may influence aging process by altering oxidative stress in tissues of adult rats.  

PubMed

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

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

2013-01-01

220

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

PubMed Central

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

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

2013-01-01

221

Identification of a membrane cytochrome c from neutrophilic, iron-oxidizing Mariprofundus ferrooxydans, strain PV-1  

NASA Astrophysics Data System (ADS)

Neutrophilic-iron oxidizing bacteria (FeOB) are a group of bacteria that can oxidize iron at -or near neutral pH, making them relevant in habitats with naturally high levels of reduced iron (i.e. Fe2+) such as hydrothermal vents. In the ocean, microorganisms in the Mariprofundus genus (zeta- Proteobacteria) are the only known organisms to chemolithoautotrophically oxidize iron. In order to identify the active bacterial oxidation of iron in the environment (i.e. in the deep biosphere), biomarkers for this functionality are needed. The aim of this study is to confirm the expression of potential functional biomarkers that are diagnostic of neutrophilic bacterial iron-oxidation. To this end, Mariprofundus ferrooxydans, strain PV-1 was cultivated in large batches and its proteins extracted via a methodology to circumvent protein binding to filamentous material. Proteins were assayed for redox-activity and for iron-oxidation activity. The bands of the gel that showed activity were analyzed via LC-MS/MS for identification of peptides and subsequently protein-matched to the M. ferrooxydans proteome database. The results indicate that a membrane cytochrome c with homology to the iron-oxidizing Cyt572 from Leptospirillum Group II is expressed in M. ferrooxydans when it is active. Other proteins associated with the electron transport chain of M. ferroxydans such as cbb3-type cytochrome oxidase subunits were identified and validated separately through reverse transcription followed by PCR amplification.

Barco, R. A.; Zhong, J.; Ramirez, G. A.; Reese, B. K.; Edwards, K. J.

2012-12-01

222

A New Method of Preparation of Magnetite Nanoparticles from Iron Oxide Hydroxide  

NASA Astrophysics Data System (ADS)

There are only two basic ways to produce magnetite at low temperature: by partial oxidation of a FeII salt solution with oxidant under alkaline condition and by precipitation of a mixed FeII/FeIII solution. At high temperature, the method involves reduction of iron oxide by a suitable reductant. Here we propose a new method of preparation of nanoparticle Fe3O4 from iron oxyhydroxides (goethite, akaganeite, lepidocrocite, feroxyhyte and ferrihydrite) or iron oxide (hematite) and ferrous salt in aqueous solution. Products characterized by X-ray powder diffraction, IR spectra and vibrating sample magentometery.

Kahani, S. A.; Jafari, M.

2007-08-01

223

Arsenic removal from water using flame-synthesized iron oxide nanoparticles with variable oxidation states.  

PubMed

We utilized gas-phase diffusion flame synthesis, which has potential for large-scale production of metal oxide nanoparticles, to produce iron oxide nanoparticles (IONPs) with variable oxidation states. The efficacy of these materials in removal of arsenate (As(V) ) from water was assessed. Two different flame configurations, a diffusion flame (DF) and an inverse diffusion flame (IDF), were employed to synthesize six different IONPs by controlling flame conditions. The IONPs produced in the IDF configuration (IDF-IONPs) had smaller particle diameters (4.8 - 8.2 nm) and larger surface areas (141-213 m(2)/g) than the IONPs produced in the DF configuration (29 nm, 36 m(2)/g), which resulted in their higher adsorption capacities. As(V) adsorption capacities of the IDF-IONPs increased when the IONPs were synthesized in more oxidizing conditions. The fully oxidized IDF-IONPs, maghemite (?-Fe2O3), showed the highest As(V) adsorption capacity, comparable to that of magnetite nanocrystals synthesized by thermal decomposition of iron pentacarbonyl and equivalent to three to four times higher capacity than that of a commonly used goethite-based adsorbent. All IONPs were magnetically responsive, which is of great importance for solid-liquid separation. This study demonstrates that the IONPs synthesized in gas-phase flame, particularly IDF-IONPs, are excellent adsorbents because of their high As(V) sorption capacity, potential for large-scale production, and useful magnetic property. PMID:23645964

Abid, Aamir D; Kanematsu, Masakazu; Young, Thomas M; Kennedy, Ian M

2013-02-01

224

Photoelectrochemical properties of plasma deposited iron oxide thin films  

SciTech Connect

Thin films of iron oxide were produced by the rf glow discharge decomposition of iron pentacarbonyl in the presence of oxygen. Emission spectra showed the presence of oxygen atoms, FeO, Fe(I), CO, Ar and N/sub 2/. Stoichiometric Fe/sub 2/O/sub 3/ was noted with deposition temperature greater than 300/sup 0/C and O/sub 2//Fe(CO)/sub 5/ feed ratios greater than 1. Carbon was detected in films deposited at temperatures of 250/sup 0/C or less. Amorphous films were produced below 200/sup 0/C. At higher temperatures, ..cap alpha..-Fe, wustite (FeO), magnitite (Fe/sub 3/O/sub 4/) and hematite (both ..cap alpha.. and ..gamma..) were detected. Crystallite size and degree of preferred orientation varied with deposition temperature and rf power level. Optical transmittance and reflectance were measured for the plasma deposited films. The absorption depth was less than 100 nm for light from 200 to 500 nm. Capacitance-voltage measurements were performed to determine electron concentration in the films. Resistivities and dielectric constants were determined. Electron mobility and depletion layer thickness were calculated from these data. Carrier concentrations were about 10/sup 16//cm/sup 3/ for all deposition conditions. The photoelectrochemical properties of the films were measured in 1 M NaOH.

Blair, C.S.

1984-03-01

225

Numerical simulation for electrochemical cultivation of iron oxidizing bacteria.  

PubMed

A numerical simulation model was constructed for electrochemical cultivation of iron oxidizing bacterium, Thiobacillus ferrooxidans, based on Monod's dual limitation equation. In this model, two limiting factors were examined, low supply of Fe(II) ion and dissolved oxygen, from empirical viewpoints. The simulation model was constructed taking into consideration the energy balance based on the amount of the electronic flow from the electrode to bacteria via an iron ion, and then to oxygen. The model consisted of a logarithmic bacterial growth phase during the first three days, followed by a plateau and growth limitation thereafter. The predicted results were in agreement with the actual growth under electrochemical cultivation. It was predicted the growth limiting factor would be changed from insufficient supply of Fe(II) ions to that of oxygen by decreasing the value of oxygen transfer constant K, which correlated with the aeration rate. The optimum aeration rate was determined for the ideal electrochemical cultivation. The algorithm described here can be used in any electrochemical cultivation by modifying the parameters for each system. PMID:11857276

Matsumoto, Norio; Yoshinaga, Hisao; Ohmura, Naoya; Ando, Akikazu; Saiki, Hiroshi

2002-04-01

226

The water dissociation reaction on clean and oxidized iron (110)  

NASA Astrophysics Data System (ADS)

The interaction of H2O with the clean Fe(110) surface, Fe(110) surfaces with absorbed oxygen, and Fe(110) surfaces after bulk oxygen penetration were investigated using UPS. At 225 K, surface absorbed hydroxyl groups are present on all surfaces studied. On initially clean Fe(110) and surfaces with up to half monolayer of absorbed oxygen, heating the hydroxyl layer produced at 225 to 360 K causes hydrogen and water desorption and additional oxygen deposition relative to the starting surface. Beyond one-half monolayer of initial oxygen coverage, dehydroxylation proceeded exclusively via water desorption with the quantitative restoration of the initial surface composition. These results demonstrate that the (110) surface of iron is passive toward oxidation by water alone below 360 K, after the first monolayer.

Dwyer, D. J.; Kelemen, S. R.; Kaldor, A.

1982-02-01

227

System for recycling char in iron oxide reducing kilns  

SciTech Connect

A method and means for improving the efficiency of the process for directly reducing ore containing iron oxide in a rotary kiln using a solid carbonaceous reducing agent, such as coal, introduced from the ore feed and discharge ends of the kiln, as both fuel and reductant, is disclosed wherein the charred coal or char found in the discharge product is recycled into the process at the discharge end of the kiln rather than the feed end as in the prior art. In particular, the recovered char, both coarse and finer particles, are transported to a recycle bin from which they are returned at a preselected rate to the kiln process by being injected along with the coal blown into the discharge end of the kiln. Alternatively, the recycle char alone may be fed without any coal at the discharge end of the kiln.

Baker, A.C.; Keran, V.P.

1983-03-08

228

Targeted magnetic iron oxide nanoparticles for tumor imaging and therapy  

PubMed Central

Magnetic iron oxide (IO) nanoparticles with a long blood retention time, biodegradability and low toxicity have emerged as one of the primary nanomaterials for biomedical applications in vitro and in vivo. IO nanoparticles have a large surface area and can be engineered to provide a large number of functional groups for cross-linking to tumor-targeting ligands such as monoclonal antibodies, peptides, or small molecules for diagnostic imaging or delivery of therapeutic agents. IO nanoparticles possess unique paramagnetic properties, which and generate significant susceptibility effects resulting in strong T2 and T2* contrast, as well as T1 effects at very low concentrations for magnetic resonance imaging (MRI), which is widely used for clinical oncology imaging. We review recent advances in the development of targeted IO nanoparticles for tumor imaging and therapy. PMID:18990940

Peng, Xiang-Hong; Qian, Ximei; Mao, Hui; Wang, Andrew Y; Chen, Zhuo (Georgia); Nie, Shuming; Shin, Dong M

2008-01-01

229

Compact Zwitterion-Coated Iron Oxide Nanoparticles for Biological Applications  

PubMed Central

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 to be hydrophilic and biocompatible. We report here the design and synthesis of a compact and water-soluble zwitterionic dopamine sulfonate (ZDS) ligand with strong binding affinity to SPIONs. After ligand exchange, the ZDS coated SPIONs exhibit small hydrodynamic diameters (HD), and stability with respect to time, pH, and salinity. Furthermore, small ZDS coated SPIONs were found to have a reduced non-specific affinity (compared to negatively charged SPIONs) towards serum proteins; streptavidin/dye functionalized SPIONs were bioactive and thus specifically targeted biotin receptors. PMID:22185195

Wei, He; Insin, Numpon; Lee, Jungmin; Han, Hee-Sun; Cordero, Jose M.; Liu, Wenhao; Bawendi, Moungi G.

2012-01-01

230

Heterobifunctional PEG Ligands for Bioconjugation Reactions on Iron Oxide Nanoparticles  

PubMed Central

Ever since iron oxide nanoparticles have been recognized as promising scaffolds for biomedical applications, their surface functionalization has become even more important. We report the synthesis of a novel polyethylene glycol-based ligand that combines multiple advantageous properties for these applications. The ligand is covalently bound to the surface via a siloxane group, while its polyethylene glycol backbone significantly improves the colloidal stability of the particle in complex environments. End-capping the molecule with a carboxylic acid introduces a variety of coupling chemistry possibilities. In this study an antibody targeting plasminogen activator inhibitor-1 was coupled to the surface and its presence and binding activity was assessed by enzyme-linked immunosorbent assay and surface plasmon resonance experiments. The results indicate that the ligand has high potential towards biomedical applications where colloidal stability and advanced functionality is crucial. PMID:25275378

Bloemen, Maarten; Van Stappen, Thomas; Willot, Pieter; Lammertyn, Jeroen; Koeckelberghs, Guy; Geukens, Nick; Gils, Ann; Verbiest, Thierry

2014-01-01

231

Iron oxide-based nanostructures for MRI and magnetic hyperthermia.  

PubMed

Many different nanostructures have been developed for biomedical applications to date. Among them, iron oxide nanoparticles have been very prominent in MRI in diagnostic radiology. Nowadays, nanoparticle-based therapeutic applications have gained increased interest, leading to the development of a great variety of different and, in parts, sophisticated nanoparticle formulations. Whereas nanotherapy has been confined to the preclinical phase, magnetic hyperthermia has entered into the clinical phase via controlled studies in patients. Owing to the versatility of nanoparticles, researchers envision the combination of multiple modalities (e.g., targeting, diagnostics and therapy) to one carrier. Nevertheless, such approaches have been challenging due to the necessity of the adaptation of at least partially counteracting parameters between the different modalities, which will be analyzed in this review. PMID:22994960

Hilger, Ingrid; Kaiser, Werner A

2012-09-01

232

Iron oxide nanoparticles in different modifications for antimicrobial phototherapy  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

233

Application of the static dephasing regime theory to superparamagnetic iron-oxide loaded cells.  

PubMed

The relaxation rates of iron-oxide nanoparticles compartmentalized within cells were studied and found to satisfy predictions of the static dephasing (SD) regime theory. THP-1 cells in cell culture were loaded using two different iron-oxide nanoparticles (superparamagnetic iron-oxide (SPIO) and ultrasmall SPIO (USPIO)) with four different iron concentrations (0.05, 0.1, 0.2, and 0.3 mg/ml) and for five different incubation times (6, 12, 24, 36, and 48 hr). Cellular iron-oxide uptake was assessed using a newly developed imaging version of MR susceptometry, and was found to be linear with both dose and incubation time. R(2)* sensitivity to iron-oxide loaded cells was found to be 70 times greater than for R(2), and 3100 times greater than for R(1). This differs greatly from uniformly distributed nanoparticles and is consistent with a cellular bulk magnetic susceptibility (BMS) relaxation mechanism. The cellular magnetic moment was large enough that R(2)' relaxivity agreed closely with SD regime theory predictions for all cell samples tested [R(2)'=2 pi/(9 x the square root of 3) x gamma LMD] where the local magnetic dose (LMD) is the sample magnetization due to the presence of iron-oxide particles). Uniform suspensions of SPIO and USPIO produced R(2)' relaxivities that were a factor of 3 and 8 less, respectively, than SD regime theory predictions. These results are consistent with theoretical estimates of the required mass of iron per compartment needed to guarantee SD-regime-dominant relaxivity. For cellular samples, R(2) was shown to be dependent on both the concentration and distribution of iron-oxide particles, while R(2)' was sensitive to iron-oxide concentration alone. This work is an important first step in quantifying cellular iron content and ultimately mapping the density of a targeted cell population. PMID:12111931

Bowen, Chris V; Zhang, Xiaowei; Saab, George; Gareau, Paula J; Rutt, Brian K

2002-07-01

234

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

235

Iron (Oxyhydr)Oxide Biosignatures in the Brushy Basin Member of the Jurassic Morrison Formation, Colorado Plateau, USA: Analog for Martian Diagenetic Iron  

NASA Astrophysics Data System (ADS)

Iron precipitates in modern microbial mats compared with iron cements in Jurassic alkaline saline lake sediments show that morphological and chemical biosignatures are present and preserved in oxidized, evaporative environments analogous to Mars.

Potter-McIntyre, S. L.; Chan, M. A.; McPherson, B. J.

2012-03-01

236

Interaction of functionalized superparamagnetic iron oxide nanoparticles with brain structures.  

PubMed

Super Paramagnetic Iron Oxide Nanoparticles (SPIONs) combined with magnetic resonance imaging (MRI) are under clinical evaluation to enhance detection of neurodegenerative diseases. A major improvement would be to link therapeutic drugs to the SPIONs to achieve targeted drug delivery, either at the cell surface or intracellularly, together with active disease detection, without inducing cell reaction. Our objectives were to define the characteristics of SPIONS able to achieve cell-specific interaction with brain-derived structures. Our system consisted in an iron oxide core (9-10 nm diameter) coated either with dextran (Sinerem and Endorem) or various functionalized polyvinyl alcohols (PVAs) (PVA-SPIONs). We investigated the cellular uptake, cytotoxicity, and interaction of these various nanoparticles with brain-derived endothelial cells, microglial cells, and differentiating three-dimensional aggregates. None of the nanoparticles coated with dextran or the various PVAs was cytotoxic or induced the production of the inflammatory mediator NO used as a reporter for cell activation. AminoPVA-SPIONs were taken up by isolated brain-derived endothelial and microglial cells at a much higher level than the other SPIONs, and no inflammatory activation of these cells was observed. AminoPVA-SPIONs did not invade brain cells aggregates lower than the first cell layer and did not induce inflammatory reaction in the aggregates. Fluorescent aminoPVA-SPIONs derivatized with a fluorescent reporter molecule and confocal microscopy demonstrated intracellular uptake by microglial cells. Fluorescent aminoPVA-SPIONs were well tolerated by mice. Therefore, functionalized aminoPVA-SPIONs represent biocompatible potential vector systems for drug delivery to the brain that may be combined with MRI detection of active lesions in neurodegenerative diseases. PMID:16608917

Cengelli, Feride; Maysinger, Dusica; Tschudi-Monnet, Florianne; Montet, Xavier; Corot, Claire; Petri-Fink, Alke; Hofmann, Heinrich; Juillerat-Jeanneret, Lucienne

2006-07-01

237

Mechanisms and factors affecting chromium oxide particle reduction in iron-chromium honeycombs  

NASA Astrophysics Data System (ADS)

In the production of iron chromium honeycombs, iron oxide and chromium oxide mixtures are reduced by hydrogen at elevated temperatures to produce a metallic alloy. The complete reduction of the iron oxide occurs prior to the reduction of the chromium oxide. The reduction of the chromium oxide particles within the iron matrix is affected by factors that include the diffusion of the reduced chromium away from the chromium oxide particle into the iron matrix, the diffusion of the gaseous reactants and products to and from the chromium oxide particles, and the porosity of the iron matrix, which changes as a result of sintering. The type of heat-treatment used, (isothermal or non-isothermal, i.e., holding at a specific temperature versus using a steadily increasing temperature) plays a vital role in how these factors will affect chromium oxide reduction. Experimental data were used in conjunction with sintering and dissolution models to obtain an understanding of the environment in which the chromium oxide particles reduce as a function of heat-treatment. This understanding will assist in the development of more effective processing steps for the reduction of metallic honeycombs from oxide mixtures.

McIntosh, Monique Sandra

238

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

E-print Network

Vacancy Coalescence during Oxidation of Iron Nanoparticles Andreu Cabot, Victor F. Puntes, Elena at Berkeley, Berkeley, California 94720 Received April 12, 2007; E-mail: alivis@berkeley.edu Iron oxide iron nanoparticles and subsequently oxidize them. A wide range of morphologies and compositions have

239

Gold and iron oxide associations under supergene conditions: An experimental approach  

NASA Astrophysics Data System (ADS)

Abstract-The interaction of gold hydroxo-chloro complexes with iron oxides (ferrihydrites, goethites) during coprecipitation experiments is investigated. Chemical analyses of solids and solutions are coupled with a detailed characterization of the iron oxides with various methods, including X-ray diffraction, High Resolution Transmission Electron Microscopy (HRTEM), and Mössbauer spectroscopy. HCl solutions containing varying amounts of AuCl 4- and ferric nitrate were titrated to neutral or alkaline pH, resulting in the coprecipitation of gold and iron oxide phases (ferrihydrite or goethite). Reference titrations were performed in the absence of iron. Most of the gold was removed from solution in the presence of iron oxides whereas gold remained dissolved in the reference samples. In association with iron oxides two forms of gold have been identified by HRTEM and 197Au Mössbauer spectroscopy: metallic gold as well as chloro and/or hydroxo combined gold. This combined gold is in a trivalent state as the primary product which means that a reduction process is not a necessary step for the adsorption of gold species on iron oxides. Metallic gold characterized in these products by means of HRTEM consists mainly of colloids ranging from 3-60 nm in diameter embedded in the ferrihydrite matrix, as isolated particles or as particles associated with goethite laths. The smallest metallic gold particles detected would be almost invisible to classical observation techniques used for solid phases. In our experiments, oxidation-reduction reactions between Fe 2+ and Au 3+ are responsible for the presence of metallic gold observed on the iron phases. Photochemical reactions may also take part in the reduction process. Colloidal gold and gold complexes could be associated to the iron oxides by strong electrostatic interactions. Our results suggest that poorly ordered iron oxides are highly efficient in trapping gold from solutions thanks to their high surface area, and favor gold precipitation during the first stage of the low temperature genesis of ironrich Au-containing systems.

Greffié, Catherine; Benedetti, Marc F.; Parron, Claude; Amouric, Marc

1996-05-01

240

Hollow iron oxide nanoshells are active and selective catalysts for the partial oxidation of styrene with molecular oxygen.  

PubMed

Well defined hollow iron oxide nanoshells are active, selective and recyclable catalysts for the oxidation of styrene into benzaldehyde using difficult-to-activate molecular oxygen as the sole oxidant. Using no noble metals, unprecedented conversion of 90% was maintained while high selectivity of 73% was able to be achieved. PMID:25188039

Rak, Monika Joanna; Lerro, Michael; Moores, Audrey

2014-10-25

241

Adsorption of fatty acids on iron (hydr)oxides from aqueous solutions.  

PubMed

The interaction of iron (hydr)oxides with fatty acids is related to many industrial and natural processes. To resolve current controversies about the adsorption configurations of fatty acids and the conditions of the maximum hydrophobicity of the minerals, we perform a detailed study of the adsorption of sodium laurate (dodecanoate) on 150 nm hematite (?-Fe(2)O(3)) particles as a model system. The methods used include in situ FTIR spectroscopy, ex situ X-ray photoelectron spectroscopy (XPS), measurements of the adsorption isotherm and contact angle, as well as the density functional theory (DFT) calculations. We found that the laurate adlayer is present as a mixture of inner-sphere monodentate mononuclear (ISMM) and outer-sphere (OS) hydration shared complexes independent of the solution pH. Protonation of the OS complexes does not influence the conformational order of the surfactant tails. One monolayer, which is filled through the growth of domains and is reached at the micellization/precipitation edge of laurate, makes the particles superhydrophobic. These results contradict previous models of the fatty acid adsorption and suggest new interpretation of literature data. Finally, we discovered that the fractions of both the OS laurate and its molecular form increase in D(2)O, which can be used for interpreting complex spectra. We discuss shortcomings of vibrational spectroscopy in determining the interfacial coordination of carboxylate groups. This work advances the current understanding of the oxide-carboxylate interactions and the research toward improving performance of fatty acids as surfactants, dispersants, lubricants, and anticorrosion reagents. PMID:21711036

Chernyshova, Irina V; Ponnurangam, Sathish; Somasundaran, Ponisseril

2011-08-16

242

Sulfur versus iron oxidation in an iron-thiolate model complex.  

PubMed

In the absence of base, the reaction of [Fe(II)(TMCS)]PF6 (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(IV)(O)(TMCS)]PF6), as previously observed in the presence of strong base (KO(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 Mössbauer spectroscopies. ESI-MS showed 3 to be formulated as [Fe(II)(TMCS) + 2O](+), while EXAFS analysis suggested that 3 was an O-bound iron(II)-sulfinate complex (Fe-O = 1.95 Å, Fe-S = 3.26 Å). 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. Mössbauer spectroscopy confirmed 4 to be a novel iron(IV) compound, different from 2, and EXAFS (Fe?O = 1.64 Å) and resonance Raman (?(Fe?O) = 831 cm(-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 (?(s)(SO2) ? 1000 cm (-1), ?(as)(SO2) ? 1150 cm (-1)). Investigations into the reactivity of 1 and 2 toward H(+) 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. PMID:21070030

McDonald, Aidan R; Bukowski, Michael R; Farquhar, Erik R; Jackson, Timothy A; Koehntop, Kevin D; Seo, Mi Sook; De Hont, Raymond F; Stubna, Audria; Halfen, Jason A; Münck, Eckard; Nam, Wonwoo; Que, Lawrence

2010-12-01

243

Synthesis, magnetic characterization and sensing applications of novel dextran-coated iron oxide nanorods  

PubMed Central

Monodisperse, water-soluble dextran-coated iron oxide (Fe3O4) nanorods were synthesized using a facile and scalable approach. Our room temperature method involves the mixing of an acidic solution of iron salts with a basic solution of ammonium hydroxide to facilitate initial formation of iron oxide crystals. The stability, crystalinity and shape of these nanorods depends on the time of addition of the dextran, as well as the degree of purity of the polymer. The as-synthesized nanorods exhibit unique magnetic properties, including superparamagnetic behavior and high spin-spin water relaxivity (R2). Additionally, they possess enhanced peroxidase activity when compared to those reported in the literature for spherical iron oxide nanoparticles. Thus, this high yield synthetic method for polymer-coated iron oxide nanorods will expedite their use in applications from magnetic sensors, devices and nanocomposites with magnetic and catalytic properties. PMID:20204168

Nath, Sudip; Kaittanis, Charalambos; Ramachandran, Vasanth; Dalal, Naresh; Perez, J. Manuel

2009-01-01

244

Induction of iron regulatory protein 1 RNA-binding activity by nitric oxide is associated with a concomitant increase in the labile iron pool: implications for DNA damage  

Microsoft Academic Search

Iron regulatory protein 1 (IRP1) is a bifunctional [4Fe–4S] protein that controls iron homeostasis. Switching off its function from an aconitase to an apo-IRP1 interacting with iron-responsive element-containing mRNAs depends on the reduced availability of iron in labile iron pool (LIP). Although the modulation of IRP1 by nitric oxide has been characterized, its impact on LIP remains unknown. Here, we

Pawel Lipinski; Rafal R. Starzynski; Jean-Claude Drapier; Cecile Bouton; Teresa Bartlomiejczyk; Barbara Sochanowicz; Ewa Smuda; Agnieszka Gajkowska; Marcin Kruszewski

2005-01-01

245

Morphology of graphite-supported iron-manganese catalyst particles: Formation of hollow spheres during oxidation  

SciTech Connect

Transmission electron microscopy (TEM) and Moessbauer spectroscopy (MES) were used to study the morphology of graphite-supported iron-manganese particles. Following oxidation at 500 K MES showed the iron in the particles to be fully oxidized. TEM showed all the particles to be torroidal in appearance. However, tilting resulting in no change in the apparent dimensions of the particles, yet the apparent distances between particles were sharply reduced. These results suggest the particles are actually spherical. On the basis of these experiments, and similar experiments with reduced particles, a model was developed: Following reduction the particles are spherical and consist of a metallic iron core surrounded by a shell of manganese oxide. During oxidation, iron ions diffuse through the manganese oxide shell to the particle surface. Eventually, this results in the formation of nearly spherical particles with hollow centers, inner shells of iron-manganese spinel, and outer shells of iron oxide. Upon an additional reduction the hollow center remains, but the shells phase segregate into regions of iron metal and manganese oxide.

Chen, A.A.; Vannice, M.A.; Phillips, J. (Pennsylvania State Univ., University Park (USA))

1989-04-01

246

Iron oxide/hydroxide nanoparticles with negatively charged shells show increased uptake in Caco-2 cells.  

PubMed

The absorption of commonly used ferrous iron salts from intestinal segments at neutral to slightly alkaline pH is low, mainly because soluble ferrous iron is easily oxidized to poorly soluble ferric iron and because ferrous iron, but not ferric iron, is carried by the divalent metal transporter DMT-1. Moreover, ferrous iron frequently causes gastrointestinal side effects. Iron hydroxide nanoparticles with neutral and hydrophilic carbohydrate shells are alternatively used to ferrous salts. In these formulations gastrointestinal side effects are rare because hundreds of ferric iron atoms are safely packed in nanoscaled cores surrounded by the solubilizing shell; nevertheless, iron bioavailability is even worse compared to ferrous salts. In this study the cell uptake of iron hydroxide and iron oxide nanoparticles (FeONP) with negatively charged shells of different chemical types and sizes was compared to the uptake of those with neutral hydrophilic shells, ferrous sulfate and ferric chloride. The nanoparticle uptake was measured in Caco-2 cells with the iron detecting ferrozine method and visualized by transmission electron microscopy. The toxicity was evaluated using the MTT assay. For nanoparticles with a negatively charged shell the iron uptake was about 40 times higher compared to those with neutral hydrophilic carbohydrate shell or ferric chloride and in the same range as ferrous sulfate. However, in contrast to ferrous sulfate, nanoparticles with negatively charged shells showed no toxicity. Two different uptake mechanisms were proposed: diffusion for hydroxide nanoparticles with neutral hydrophilic shell and adsorptive endocytosis for nanoparticles with negatively charged shells. It needs to be determined whether iron hydroxide nanoparticles with negatively charged shells also show improved bioavailability in iron-deficient patients compared to iron hydroxide nanoparticles with a neutral hydrophilic shell, which exist in the market today. PMID:22587679

Jahn, Markus R; Nawroth, Thomas; Fütterer, Sören; Wolfrum, Uwe; Kolb, Ute; Langguth, Peter

2012-06-01

247

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

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

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

2013-12-01

248

Environmental Catalysis on Iron Oxide–Silica Aerogels: Selective Oxidation of NH 3 and Reduction of NO by NH 3  

Microsoft Academic Search

The catalytic properties of mesoporous iron oxide–silica aerogels prepared by a sol–gel process combined with ensuing supercritical extraction with CO2 was investigated in the selective oxidation (SCO) of ammonia and the selective reduction (SCR) of NO by ammonia. The main parameters changed in the aerogel preparation were the type of base used as gelation agent, the iron content, and the

P. Fabrizioli; T. Bürgi; A. Baiker

2002-01-01

249

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

PubMed

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

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

250

Characterization of Delhi iron pillar rust by X-ray diffraction, Fourier transform infrared spectroscopy and Mössbauer spectroscopy  

Microsoft Academic Search

Rust samples obtained from the region just below the decorative bell capital of the Delhi iron pillar (DIP) have been analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Mössbauer spectroscopy. The identification of iron hydrogen phosphate hydrate in the crystalline form by XRD was unambiguous. Very weak diffraction from the oxyhydroxides\\/oxides of iron was observed indicating that

R Balasubramaniam; A. V Ramesh Kumar

2000-01-01

251

Mechanism of Ferrous Iron Binding and Oxidation by Ferritin from a Pennate Diatom*  

PubMed Central

A novel ferritin was recently found in Pseudo-nitzschia multiseries (PmFTN), a marine pennate diatom that plays a major role in global primary production and carbon sequestration into the deep ocean. Crystals of recombinant PmFTN were soaked in iron and zinc solutions, and the structures were solved to 1.65–2.2-? resolution. Three distinct iron binding sites were identified as determined from anomalous dispersion data from aerobically grown ferrous soaked crystals. Sites A and B comprise the conserved ferroxidase active site, and site C forms a pathway leading toward the central cavity where iron storage occurs. In contrast, crystal structures derived from anaerobically grown and ferrous soaked crystals revealed only one ferrous iron in the active site occupying site A. In the presence of dioxygen, zinc is observed bound to all three sites. Iron oxidation experiments using stopped-flow absorbance spectroscopy revealed an extremely rapid phase corresponding to Fe(II) oxidation at the ferroxidase site, which is saturated after adding 48 ferrous iron to apo-PmFTN (two ferrous iron per subunit), and a much slower phase due to iron core formation. These results suggest an ordered stepwise binding of ferrous iron and dioxygen to the ferroxidase site in preparation for catalysis and a partial mobilization of iron from the site following oxidation. PMID:23548912

Pfaffen, Stephanie; Abdulqadir, Raz; Le Brun, Nick E.; Murphy, Michael E. P.

2013-01-01

252

Physiochemical, mineralogical, and isotopic characterization of magnetite-rich iron oxides formed by thermophilic iron-reducing bacteria  

SciTech Connect

Thermophilic (45-75{degrees}C) iron-reducing bacteria obtained from two sedimentary basins in Virginia and Colorado, USA, reduced amorphous Fe(III) oxyhydroxide to form magnetite-rich (>60% in most samples) iron oxides in acetate- or H{sub 2}/CO{sub 2}-enriched cultures. The mineralogical compositions of the iron oxides were determined by X-ray diffraction and oxidation state analyses. Significantly lower Eh values (< -300 mV) occurred in the enrichment cultures than in the abiotic controls (Eh > -100 mV). The pH values in acetate-enriched cultures did not change significantly from the starting value siderite was formed in addition to magnetite. The microbial production of magnetic and siderite was consistent, on a thermodynamic basis, with Eh-pH conditions determined for these experiments. Examination of the magnetite-rich iron oxides by scanning electron microscopy showed extracellular aggregates of <200 nm and no distinguishable increase in particle size over a period of 20 days. Average values of oxygen isotope fractionation between the magnetite-rich iron oxides (io) and water (wt), expressed as 10{sup 3} ln {alpha}{sub io-wt}, ranged from -0.09% at 50{degrees}C to -1.08{per_thousand} at 70{degrees}C. These values did not differ significantly among various cultures of different growth rates, suggesting that a kinetic isotopic effect is either unimportant or reproducible during microbial magnetic formation. Results of this research indicate that studies combining microbial activity, solution chemistry, mineralogy, and oxygen isotopes can provide insight into the environmental conditions and mechanisms for biogenic iron mineral formation in natural systems. 62 refs., 6 figs., 3 tabs.

Zhang, Chuanlun; Liu, Shi; Phelps, T.J.; Elless, M. [Oak Ridge National Lab., TN (United States)] [and others] [Oak Ridge National Lab., TN (United States); and others

1997-11-01

253

Decaking of coal or oil shale during pyrolysis in the presence of iron oxides  

DOEpatents

A method for producing a fuel from the pyrolysis of coal or oil shale in the presence of iron oxide in an inert gas atmosphere. The method includes the steps of pulverizing feed coal or oil shale, pulverizing iron oxide, mixing the pulverized feed and iron oxide, and heating the mixture in a gas atmosphere which is substantially inert to the mixture so as to form a product fuel, which may be gaseous, liquid and/or solid. The method of the invention reduces the swelling of coals, such as bituminous coal and the like, which are otherwise known to swell during pyrolysis.

Khan, M. Rashid (Morgantown, WV)

1989-01-01

254

Decaking of coal or oil shale during pyrolysis in the presence of iron oxides  

DOEpatents

A method for producing a fuel from the pyrolysis of coal or oil shale in the presence of iron oxide in an inert gas atmosphere is described. The method includes the steps of pulverizing feed coal or oil shale, pulverizing iron oxide, mixing the pulverized feed and iron oxide, and heating the mixture in a gas atmosphere which is substantially inert to the mixture so as to form a product fuel, which may be gaseous, liquid and/or solid. The method of the invention reduces the swelling of coals, such as bituminous coal and the like, which are otherwise known to swell during pyrolysis. 4 figs., 8 tabs.

Rashid Khan, M.

1988-05-05

255

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

256

Oxidation and competitive retention of arsenic between iron- and manganese oxides  

NASA Astrophysics Data System (ADS)

Manganese (Mn) and iron (Fe) oxides are ubiquitous solids in terrestrial systems that have high sorptive capacities for many trace metals, including arsenic (As). Although numerous studies have characterized the effects of As adsorption onto Fe and Mn oxides individually, the fate of arsenic within mixed systems representative of natural environments has not been completely resolved. Here, we examine oxidation and competitive retention of As on goethite and birnessite using a Donnan reactor, where each oxide is isolated by a semi-permeable membrane through which arsenic can migrate. To initiate the Donnan reactor experiments, As(III) was simultaneously added to both chambers. Arsenic(III) injected into the birnessite chamber is rapidly oxidized to As(V) and then slowly redistributes across both chambers, while that added to the goethite chamber undergoes rapid adsorption; the adsorbed As(III) on goethite subsequently undergoes desorption and diffusion into the birnessite chamber followed by oxidation to As(V). With increased reaction time, As(V) is generated and preferentially partitioned onto goethite due to higher adsorption affinity compared to birnessite. Furthermore, the dissolved concentration of As(V) is controlled by the adsorption capacity of the goethite surface, which when saturated, leads to increased aqueous As concentrations; despite an increase in As(V) loading on birnessite with increasing initial As(III) concentration, the resulting aqueous As(V) concentration increase appreciably once the goethite surface is saturated. Our findings show that Mn oxides in soils act as a temporary sorbent of As, but operate primarily as strong oxidants responsible for transformation of As(III) to As(V), which can then strongly adsorb on the surrounding Fe oxide matrix.

Ying, Samantha C.; Kocar, Benjamin D.; Fendorf, Scott

2012-11-01

257

SUPPORTING INFORMATION Vacancy Coalescence During Oxidation of Iron Nanoparticles  

E-print Network

by decomposition of iron pentacarbonyl (99.999 %) in octadecene (90 %) in the presence of oleylamine (70 %) and/or trioctylamine (98 %). All chemicals were purchased from Sigma-Aldrich. Iron pentacarbonyl was stored below its.999 %), the temperature was raised to the target set point. A precursor solution of 0.4 ml of iron pentacarbonyl in 2 ml

258

Hawaiian submarine manganese-iron oxide crusts - A dating tool?  

USGS Publications Warehouse

Black manganese-iron oxide crusts form on most exposed rock on the ocean floor. Such crusts are well developed on the steep lava slopes of the Hawaiian Ridge and have been sampled during dredging and submersible dives. The crusts also occur on fragments detached from bedrock by mass wasting, on submerged coral reefs, and on poorly lithified sedimentary rocks. The thickness of the crusts was measured on samples collected since 1965 on the Hawaiian Ridge from 140 dive or dredge localities. Fifty-nine (42%) of the sites were collected in 2001 by remotely operated vehicles (ROVs). The thinner crusts on many samples apparently result from post-depositional breakage, landsliding, and intermittent burial of outcrops by sediment. The maximum crust thickness was selected from each dredge or dive site to best represent crusts on the original rock surface at that site. The measurements show an irregular progressive thickening of the crusts toward the northwest-i.e., progressive thickening toward the older volcanic features with increasing distance from the Hawaiian hotspot. Comparison of the maximum crust thickness with radiometric ages of related subaerial features supports previous studies that indicate a crust-growth rate of about 2.5 mm/m.y. The thickness information not only allows a comparison of the relative exposure ages of two or more features offshore from different volcanoes, but also provides specific age estimates of volcanic and landslide deposits. The data indicate that some of the landslide blocks within the south Kona landslide are the oldest exposed rock on Mauna Loa, Kilauea, or Loihi volcanoes. Crusts on the floors of submarine canyons off Kohala and East Molokai volcanoes indicate that these canyons are no longer serving as channelways for downslope, sediment-laden currents. Mahukona volcano was approximately synchronous with Hilo Ridge, both being younger than Hana Ridge. The Nuuanu landslide is considerably older than the Wailau landslide. The Waianae landslide southwest of Oahu has yielded samples with the greatest manganese-iron oxide crusts (9.5 mm thick) and therefore apparently represents the oldest submarine material yet found in the study area. The submarine volcanic field 100 km southwest of Oahu is apparently younger than the Waianae landslide. ?? 2004 Geological Society of America.

Moore, J.G.; Clague, D.A.

2004-01-01

259

Performance Optimization of Metallic Iron and Iron Oxide Nanomaterials for Treatment of Impaired Water Supplies  

NASA Astrophysics Data System (ADS)

Iron nanomaterials including nanoscale zero valent iron (NZVI), NZVI-based bimetallic reductants (e.g., Pd/NZVI) and naturally occurring nanoscale iron mineral phases represent promising treatment tools for impaired water supplies. However, questions pertaining to fundamental and practical aspects of their reactivity may limit their performance during applications. For NZVI treatment of pollutant source zones, a major hurdle is its limited reactive lifetime. In Chapter 2, we report the longevity of NZVI towards 1,1,1,2-tetrachloroethane (1,1,1,2-TeCA) and hexavalent chromium [Cr(VI)] in oxygen-free systems with various anionic co-solutes (e.g., Cl-, SO4 2-, ClO4-, HCO3 -, NO3-). Trends in longevity provide evidence that surface-associated Fe(II) species are responsible for Cr(VI) reduction, whereas 1,1,1,2-TeCA reduction depends on the accessibility of Fe(0) at the NZVI particle surface. In Chapter 3, we show that dithionite, previously utilized for in situ redox manipulation, can restore the reducing capacity of passivated NZVI treatment systems. Air oxidation of NZVI at pH ? 8 quickly exhausted reactivity despite a significant fraction of Fe(0) persisting in the particle core. Reduction of this passive layer by low dithionite concentrations restored suspension reactivity to levels of unaged NZVI, with multiple dithionite additions further improving pollutant removal. In Chapter 4, measurements of solvent kinetic isotope effects reveals that optimal Pd/NZVI reactivity results from accumulation of atomic hydrogen, which only occurs in NZVI-based systems due to their higher rates of corrosion. However, atomic hydrogen formation only occurs in aged Pd/NZVI suspensions for ˜2 weeks, after which any reactivity enhancement likely results from galvanic corrosion of Fe(0). Finally, the activity of hybrid nanostructures consisting of multi-walled carbon nanotubes decorated with of hematite nanoparticles (alphaFe 2O3/MWCNT) is explored in Chapter 5. Sorption of Cu(II) and Cr(VI) is enhanced in hybrid nanostructure systems beyond what would be expected from simple additive sorption capacities of their building blocks. The enhanced sorption capacity is in part derived from the greater surface area of hematite nanoparticles immobilized on MWCNTs relative to aggregated hematite suspensions. The hybrid alphaFe2O3/MWCNT may also exhibit unique surface chemistry, as supported by the tunable values of zeta potential measured as a function of the mass of alphaFe2O 3 deposited on the MWCNTs.

Xie, Yang

260

Performance Optimization of Metallic Iron and Iron Oxide Nanomaterials for Treatment of Impaired Water Supplies  

E-print Network

in the presence of iron and sulfur-containing compounds.iron systems [33]. We also cannot rule out the possibility of elemental sulfuriron sulfides such as tochilinite [25]. XPS confirmed the presence of reduced sulfur

Xie, Yang

2011-01-01

261

Removal of iron and arsenic (III) from drinking water using iron oxide-coated sand and limestone  

NASA Astrophysics Data System (ADS)

A method for removal of iron and arsenic (III) from contaminated water using iron oxide-coated sand and limestone has been developed for drinking water. For the intended use, sand was coated with ferric chloride and used as filtering media. Limestone was added onto the coated sand and the effect of limestone addition on removal efficiency of iron and arsenic was monitored. Both batch and column experiments were conducted to investigate the efficiency of coated sand and limestone as filtering media. Maximum removal of iron (99.8 %) was obtained with coated sand at a dose of 5 g/100 ml and by adding 0.2 g/100 ml of limestone at pH 7.3. Arsenic (III) removal efficiency increased with the increased dose of coated sand and was best removed at pH 7.12. The maximum adsorption capacity for arsenic (III) obtained from Langmuir model was found to be 0.075 mg/g and the kinetics data followed pseudo-first order better than pseudo-second order. Energy dispersive X-ray analysis and FT-IR study proved the removal of iron and arsenic. Column experiment showed removal of iron and arsenic (III) to <0.3 mg/l and 10 ?g/l, respectively, from an initial concentration of 20 mg/l (iron) and 200 ?g/l (arsenic).

Devi, Rashmi R.; Umlong, Iohborlang M.; Das, Bodhaditya; Borah, Kusum; Thakur, Ashim J.; Raul, Prasanta K.; Banerjee, Saumen; Singh, Lokendra

2014-06-01

262

A change in the oxidation state of iron: scandium is not innocent.  

PubMed

Through extensive molecular modelling of Fe(III/IV)-oxo and Fe(III)-hydroxo complexes it is shown here unambiguously that the assignment of the iron oxidation state of a Sc(3+)-capped iron-oxygen species should be revised. Iron in this Lewis-acid capped metal-bound oxygen system is Fe(III), coinciding with water as a secondary axial ligand to scandium. PMID:23772443

Swart, Marcel

2013-07-28

263

Biomedical properties and preparation of iron oxide-dextran nanostructures by MAPLE technique  

PubMed Central

Background In this work the chemical structure of dextran-iron oxide thin films was reported. The films were obtained by MAPLE technique from composite targets containing 10 wt. % dextran with 1 and 5 wt.% iron oxide nanoparticles (IONPs). The IONPs were synthesized by co-precipitation method. A KrF* excimer laser source (? = 248 nm, ?FWHM?25 ns, ? = 10 Hz) was used for the growth of the hybrid, iron oxide NPs-dextran thin films. Results Dextran coated iron oxide nanoparticles thin films were indexed into the spinel cubic lattice with a lattice parameter of 8.36 Å. The particle sized calculated was estimated at around 7.7 nm. The XPS shows that the binding energy of the Fe 2p3/2 of two thin films of dextran coated iron oxide is consistent with Fe3+ oxides. The atomic percentage of the C, O and Fe are 66.71, 32.76 and 0.53 for the films deposited from composite targets containing 1 wt.% maghemite and 64.36, 33.92 and 1.72 respectively for the films deposited from composite targets containing 5 wt.% maghemite. In the case of cells cultivated on dextran coated 5% maghemite ?-Fe2O3, the number of cells and the level of F-actin were lower compared to the other two types of thin films and control. Conclusions The dextran-iron oxide continuous thin films obtained by MAPLE technique from composite targets containing 10 wt.% dextran as well as 1 and 5 wt.% iron oxide nanoparticles synthesized by co-precipitation method presented granular surface morphology. Our data proved a good viability of Hep G2 cells grown on dextran coated maghemite thin films. Also, no changes in cells morphology were noticed under phase contrast microscopy. The data strongly suggest the potential use of iron oxide-dextran nanocomposites as a potential marker for biomedical applications. PMID:22410001

2012-01-01

264

Selective dissolution of magnetic iron oxides in the acidammonium oxalate/ferrous iron extraction method--I. Synthetic samples  

E-print Network

method--I. Synthetic samples Ingeborg H. M. van Oorschot and Mark J. Dekkers Utrecht University. The AAO-Fe(II) method preferentially dissolved the smaller iron oxides from the samples. For samples of magnetite and maghemite in the acid­ammonium oxalate method to see whether the method is suitable

Utrecht, Universiteit

265

Sulfur Versus Iron Oxidation in an Iron-Thiolate Model Complex  

SciTech Connect

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.

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

2011-12-31

266

Metal Ions-Stimulated Iron Oxidation in Hydroxylases Facilitates Stabilization of HIF-1? Protein  

PubMed Central

The exposure of cells to several metal ions stabilizes HIF-1? protein. However, the molecular mechanisms are not completely understood. They may involve inhibition of hydroxylation by either substitution of iron by metal ions or by iron oxidation in the hydroxylases. Here we provide evidence supporting the latter mechanism. We show that HIF-1? stabilization in human lung epithelial cells occurred following exposure to various metal and metalloid ions, including those that cannot substitute for iron in the hydroxylases. In each case addition of the reducing agent ascorbic acid (AA)* abolished HIF-1? protein stabilization. To better understand the role of iron oxidation in hydroxylase inhibition and to define the role of AA in the enzyme recovery we applied molecular modeling techniques. Our results indicate that the energy required for iron substitution by Ni(II) in the enzyme is high and unlikely to be achieved in a biological system. Additionally, computer modeling allowed us to identify a tridentate coordination of AA with the enzyme-bound iron, which explains the specific demand for AA as the iron reductant. Thus, the stabilization of HIF-1? by numerous metal ions that cannot substitute for iron in the enzyme, the alleviation of this effect by AA, and our computer modeling data support the hypothesis of iron oxidation in the hydroxylases following exposure to metal ions. PMID:19074761

Kaczmarek, Monika; Cachau, Raul E.; Topol, Igor A.; Kasprzak, Kazimierz S.; Ghio, Andy; Salnikow, Konstantin

2009-01-01

267

Synthesis and characterization of diblock copolymer templated iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

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.

Akcora, Pinar

268

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 ...

269

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 ...

270

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

EPA Science Inventory

Lung injury after 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 throu...

271

Catalytic Decomposition of Hydrogen Peroxide and 2-chlorophenol with iron oxides  

Microsoft Academic Search

The aim of this study was to examine the catalyzed decomposition of hydrogen peroxide and 2-chlorophenol (2-CP) in the presence of iron oxides. Granular ferrihydrite, goethite, and hematite were selected as catalysts in this study. 2-CP was used as the model compound because it is a typical toxic compound and has not been investigated in the catalytic decomposition by iron

Hsu-Hui Huang; Ming-Chun Lu; Jong-Nan Chen

2001-01-01

272

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

Microsoft Academic Search

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

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

273

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

PubMed

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

Bacelar-Nicolau, P; Johnson, D B

1999-02-01

274

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 ...

275

Abiotic formation of elemental selenium and role of iron oxide surfaces Yu-Wei Chen a  

E-print Network

Abiotic formation of elemental selenium and role of iron oxide surfaces Yu-Wei Chen a , Hoang: Elemental selenium Abiotic reduction Surface catalysis Laboratory simulation Lake sediments a b s t r a c

Belzile, Nelson

276

OXIDATION OF CYCLOHEXANE WITH AIR CATALYZED BY A STERICALLY HINDERED IRON (II) COMPLEX  

EPA Science Inventory

Oxidation of Cyclohexane with Air Catalyzed by a Sterically Hindered Iron(II) Complex. Thomas M. Becker, Michael A. Gonzalez* United States Environmental Protection Agency; National Risk Management Research Laboratory; Sustainable Technology Division; Clean Pr...

277

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

NASA Astrophysics Data System (ADS)

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.

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

2008-07-01

278

Lipidoid-Coated Iron Oxide Nanoparticles for Efficient DNA and siRNA delivery  

E-print Network

The safe, targeted and effective delivery of gene therapeutics remains a significant barrier to their broad clinical application. Here we develop a magnetic nucleic acid delivery system composed of iron oxide nanoparticles ...

Jiang, Shan

279

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

E-print Network

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

Dunin-Borkowski, Rafal E.

280

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...

281

Iron homeostatis and oxidative stress in idiopathic pulmonary alveolar proteinosis: a case-control study  

EPA Science Inventory

ABSTRACT: BACKGROUND: Lung injury caused by both inhaled dusts and infectious agents depends on increased availability of iron and metal-catalyzed oxidative stress. Because inhaled particles, such as silica, and certain infections can cause secondary pulmonary alveolar proteinosi...

282

Nitrogen Requirement of Iron-Oxidizing Thiobacilli for Acidic Ferric Sulfate Regeneration  

PubMed Central

Ammonium was shown to be a limiting nutrient for iron oxidation in cultures of Thiobacillus ferrooxidans. In addition, one strain was also able to assimilate nitrate, but not nitrite, for growth and coupled iron oxidation. Some amino acids (0.5 mM) were tested as a source of nitrogen; none clearly stimulated bacterial activity and inhibition was commonly encountered. Complex nitrogenous compounds were inhibitory at high concentrations (0.1 to 0.5%, wt/vol) and, at low concentrations, some clearly stimulated the bacterial iron oxidation in ammonium-limited cultures. Enhancement of iron oxidation by these compounds was also observed in ammonium-unlimited cultures, suggesting their possible role in providing trace nutrients and possibly carbon for the bacteria. PMID:16345391

Tuovinen, Olli H.; Panda, Fern A.; Tsuchiya, Henry M.

1979-01-01

283

Interaction of aromatic amines with iron oxides: implications for prebiotic chemistry.  

PubMed

The interaction of aromatic amines (aniline, p-chloroaniline, p-toludine and p-anisidine) with iron oxides (goethite, akaganeite and hematite) has been studied. Maximum uptake of amines was observed around pH 7. The adsorption data obtained at neutral pH were found to follow Langmuir adsorption. Anisidine was found to be a better adsorbate probably due to its higher basicity. In alkaline medium (pH?>?8), amines reacted on goethite and akaganeite to give colored products. Analysis of the products by GC-MS showed benzoquinone and azobenzene as the reaction products of aniline while p-anisidine afforded a dimer. IR analysis of the amine-iron oxide hydroxide adduct suggests that the surface acidity of iron oxide hydroxides is responsible for the interaction. The present study suggests that iron oxide hydroxides might have played a role in the stabilization of organic molecules through their surface activity and in prebiotic condensation reactions. PMID:23813329

Shanker, Uma; Singh, Gurinder; Kamaluddin

2013-06-01

284

Vapour phase approach for iron oxide nanoparticle synthesis from solid precursors  

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

285

Identification of iron oxide impurities in earliest industrial-scale processed platinum  

SciTech Connect

A detailed investigation of iron oxide inclusions in a 19th century Russian platinum coin is presented. Such coins represent the products of the first industrial-scale purification of platinum metal. The processed metal is far from pure, however, and two types of iron oxide inclusions are identified by electron microprobe and Raman microscopy. The results show that the inclusions mainly consist of magnetite and haematite. The Raman band of magnetite at 668 cm{sup -1} was found to shift to about 680 cm{sup -1} with an increase in the average oxidation state of the iron. It is concluded that the iron oxides are formed during the heating of the platinum metal powder in the manufacturing process.

Weerd, Jaap van der [Christopher Ingold Laboratories, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom); Rehren, Thilo [Institute of Archaeology, University College London, 31-34 Gordon Square, London WC1H 0PY (United Kingdom)]. E-mail: th.rehren@ucl.ac.uk; Firth, Steven [Christopher Ingold Laboratories, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom); Clark, Robin J.H. [Christopher Ingold Laboratories, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom)]. E-mail: r.j.h.clark@ucl.ac.uk

2004-09-15

286

Synthesis and characterization of CREKA-conjugated iron oxide nanoparticles for hyperthermia applications.  

PubMed

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 (IONPs) 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 IONP 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 IONPs. 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 52nm, were stable in phosphate buffered saline solution and media with 10% v/v fetal bovine serum over at least 12h, and generated enough heat to raise solution temperatures well into the hyperthermia range (41-45°C) when exposed to an AMF, owing to an average specific absorption rate of 83.5Wg(-1). 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 IONPs 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 with cisplatin or MMH treatments alone. PMID:24486913

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

2014-06-01

287

Hyperfine interactions associated with iron substituted superconducting oxides  

SciTech Connect

Theoretical and experimental Moessbauer spectroscopy studies have been made concerning charge and spin densities and magnetic hyperfine fields (H{sub hf}) in iron-substituted superconducting oxides. Calculations were carried out in the self-consistent-field embedded cluster model using local density theory (SCF-X{alpha}) with a variational atomic orbital basis. Spectral densities and changes in charge and spin density were monitored around neighboring Cu sites, as well as Fe impurity site, and La{sub 2}Cu{sub 1-x}Fe{sub x}O{sub 4} and YBa{sub 2}Cu{sub 3-x}Fe{sub x}O{sub 7-y} compounds. Moessbauer isomer shifts (IS), quadrupole splittings (QS) and H{sub hf} are obtained by fitting multiline models to the observed spectra and are compared with SCF-X{alpha} results for specific lattice sites. The influence of oxygen vacancies and partial oxygen disorder is modelled and compared with the experimental data on variable oxygen content and disorder. 10 refs., 3 tabs.

Ellis, D.E.; Dunlap, B.D. (Argonne National Lab., IL (USA)); Saitovitch, E.B.; Azevedo, I.S.; Scorzelli, R.B. (Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, RJ (Brazil)); Kimball, C.W. (Northern Illinois Univ., Dekalb, IL (USA))

1989-06-01

288

The Synthesis of Iron Oxide Nanoparticles via Seed-Mediated Process and its Cytotoxicity Studies  

Microsoft Academic Search

The development of a seed-mediated growth method for synthesis of iron oxide nanoparticles with tunable size distribution\\u000a and magnetic properties is reported. The detailed investigation of the size distribution of seed as well as iron oxide nanoparticles\\u000a during the growth process has been carried out using transmission electron microscopy (TEM). It was observed that the distribution\\u000a of size gradually becomes

J.-H. Huang; H. J. Parab; R. S. Liu; T.-C. Lai; M. Hsiao; C. H. Chen; D.-P. Tsai; Y.-K. Hwu

289

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

Microsoft Academic Search

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

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

2005-01-01

290

Correlation between structural and magnetic properties of sprayed iron oxide thin films  

NASA Astrophysics Data System (ADS)

The structural, optical and magnetic properties of iron oxide films were investigated. Raman spectroscopy results demonstrate that different iron oxide polymorphs can coexist in the sprayed films. It also showed that thickness plays an important role in the development of mixed or pure hematite films. Among the phases detected in the films are feroxyhyte and maghemite. Additionally, the control of the magnetic properties by varying the deposition temperature and thickness is established in this work.

Garcia-Lobato, M. A.; Martinez, Arturo I.; Castro-Roman, M.; Falcony, C.; Escobar-Alarcon, L.

2011-04-01

291

Thermodynamic analysis of the reactions of iron oxides: Dissolution in oxalic acid  

Microsoft Academic Search

The mechanism of dissolution of pure iron oxides by means of organic acids comprises two different chemical pathways: (a) non-reductive dissolution and (b) reductive dissolution. In this paper, the thermodynamic analysis of these pathways for the iron oxides-oxalic acid system is presented. In low acid solutions (pH higher than 3) the only triermodynamically stable complex ions of bivalent and trivalent

D. Panias; M. Taxiarchou; I. Douni; I. Paspaliaris; A. Kontopoulos

1996-01-01

292

Rinded iron-oxide concretions: hallmarks of altered siderite masses of both early and late diagenetic origin  

E-print Network

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 later diagenetic events. Distinctive concretions composed of heavy rinds of iron oxide that surround

Nebraska-Lincoln, University of

293

Methanogenesis facilitated by electric syntrophy via (semi)conductive iron-oxide minerals.  

PubMed

Methanogenesis is an essential part of the global carbon cycle and a key bioprocess for sustainable energy. Methanogenesis from organic matter is accomplished by syntrophic interactions among different species of microbes, in which interspecies electron transfer (IET) via diffusive carriers (e.g. hydrogen and formate) is known to be the bottleneck step. We report herein that the supplementation of soil microbes with (semi)conductive iron-oxide minerals creates unique interspecies interactions and facilitates methanogenesis. Methanogenic microbes were enriched from rice paddy field soil with either acetate or ethanol as a substrate in the absence or presence of (semi)conductive iron oxides (haematite or magnetite). We found that the supplementation with either of these iron oxides resulted in the acceleration of methanogenesis in terms of lag time and production rate, while the supplementation with an insulative iron oxide (ferrihydrite) did not. Clone-library analyses of 16S rRNA gene fragments PCR-amplified from the enrichment cultures revealed that the iron-oxide supplementation stimulated the growth of Geobacter spp. Furthermore, the addition of a specific inhibitor for methanogenesis suppressed the growth of Geobacter spp. These results suggest that Geobacter grew under syntrophic association with methanogens, and IET could occur via electric currents through (semi)conductive iron-oxide minerals (termed 'electric syntrophy'). Given the ubiquity of conductive minerals in nature, such energetic interactions may occur widely in soil and sediments and can be used to develop efficient bioenergy processes. PMID:22004041

Kato, Souichiro; Hashimoto, Kazuhito; Watanabe, Kazuya

2012-07-01

294

Magnetic iron oxide nanoparticles: Synthesis and surface coating techniques for biomedical applications  

NASA Astrophysics Data System (ADS)

Iron oxide nanoparticles are the most popular magnetic nanoparticles used in biomedical applications due to their low cost, low toxicity, and unique magnetic property. Magnetic iron oxide nanoparticles, including magnetite (Fe3O4) and maghemite (?-Fe2O3), usually exhibit a superparamagnetic property as their size goes smaller than 20 nm, which are often denoted as superparamagnetic iron oxide nanoparticles (SPIONs) and utilized for drug delivery, diagnosis, therapy, and etc. This review article gives a brief introduction on magnetic iron oxide nanoparticles in terms of their fundamentals of magnetism, magnetic resonance imaging (MRI), and drug delivery, as well as the synthesis approaches, surface coating, and application examples from recent key literatures. Because the quality and surface chemistry play important roles in biomedical applications, our review focuses on the synthesis approaches and surface modifications of iron oxide nanoparticles. We aim to provide a detailed introduction to readers who are new to this field, helping them to choose suitable synthesis methods and to optimize the surface chemistry of iron oxide nanoparticles for their interests.

Sun, Sheng-Nan; Wei, Chao; Zhu, Zan-Zan; Hou, Yang-Long; Subbu, S. Venkatraman; Xu, Zhi-Chuan

2014-03-01

295

Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp Rimicaris exoculata  

NASA Astrophysics Data System (ADS)

The Rimicaris exoculata shrimp is considered as a primary consumer that dominates the fauna of most Mid-Atlantic Ridge (MAR) hydrothermal ecosystems. These shrimps harbour in their gill chambers an important ectosymbiotic community of chemoautotrophic bacteria associated with iron oxide deposits. The structure and elemental composition of the mineral concretions associated with these bacteria have been investigated by using LM, ESEM, TEM STEM and EDX microanalyses. The nature of the iron oxides in shrimps obtained from the Rainbow vent field has also been determined by Mössbauer spectroscopy. This multidisciplinary approach has revealed that the three layers of mineral crust in the Rimicaris exoculata shrimps consist of large concretions formed by aggregated nanoparticles of two-line ferrihydrite and include other minor elements as Si, Ca, Mg, S and P, probably present as silicates cations, sulphates or phosphates respectively that may contribute to stabilise the ferrihydrite form of iron oxides. TEM-observations on the bacteria have revealed their close interactions with these minerals. Abiotic and biotic precipitation could occur within the gill chamber of Rimicaris exoculata, suggesting the biologically-mediated formation of the iron oxide deposits. The difference of the bacterial density in the three-mineral crust layers could be correlated to the importance of the iron oxide concretions and suggest that the first mineral particles precipitates on the lower layer which could be considered as the most likely location of iron-oxidizing bacteria.

Corbari, L.; Cambon-Bonavita, M.-A.; Long, G. J.; Grandjean, F.; Zbinden, M.; Gaill, F.; Compère, P.

2008-09-01

296

Long-term aerobic exercise increases redox-active iron through nitric oxide in rat hippocampus.  

PubMed

Adult hippocampus is highly vulnerable to iron-induced oxidative stress. Aerobic exercise has been proposed to reduce oxidative stress but the findings in the hippocampus are conflicting. This study aimed to observe the changes of redox-active iron and concomitant regulation of cellular iron homeostasis in the hippocampus by aerobic exercise, and possible regulatory effect of nitric oxide (NO). A randomized controlled study was designed in the rats with swimming exercise treatment (for 3 months) and/or an unselective inhibitor of NO synthase (NOS) (L-NAME) treatment. The results from the bleomycin-detectable iron assay showed additional redox-active iron in the hippocampus by exercise treatment. The results from nonheme iron content assay, combined with the redox-active iron content, showed increased storage iron content by exercise treatment. NOx (nitrate plus nitrite) assay showed increased NOx content by exercise treatment. The results from the Western blot assay showed decreased ferroportin expression, no changes of TfR1 and DMT1 expressions, increased IRP1 and IRP2 expression, increased expressions of eNOS and nNOS rather than iNOS. In these effects of exercise treatment, the increased redox-active iron content, storage iron content, IRP1 and IRP2 expressions were completely reversed by L-NAME treatment, and decreased ferroportin expression was in part reversed by L-NAME. L-NAME treatment completely inhibited increased NOx and both eNOS and nNOS expression in the hippocampus. Our findings suggest that aerobic exercise could increase the redox-active iron in the hippocampus, indicating an increase in the capacity to generate hydroxyl radicals through the Fenton reactions, and aerobic exercise-induced iron accumulation in the hippocampus might mainly result from the role of the endogenous NO. PMID:24184442

Chen, Qian; Xiao, De-Sheng

2014-01-30

297

Iron oxide nanoparticle hyperthermia and chemotherapy cancer treatment  

PubMed Central

The benefit of combining hyperthermia and chemotherapy to treat cancer is well established. However, combined therapy has not yet achieved standard of care status. The reasons are numerous and varied, however the lack of significantly greater tumor cell sensitivity to heat (as compared to normal cells) and the inability to deliver heat to the tumor in a precise manner have been major factors. Iron oxide nanoparticle (IONP) hyperthermia, alone and combined with other modalities, offers a new direction in hyperthermia cancer therapy via improved tumor targeting and an improved therapeutic ratio. Our preliminary studies have demonstrated tumor cell cytotoxicity (in vitro and in vivo) with IONP heat and cisplatinum (CDDP) doses lower than those necessary when using conventional heating techniques or cisplatinum alone. Ongoing studies suggest such treatment could be further improved through the use of targeted nanoparticles. Methods In vivo: IONPs (5mg of iron per gram of tumor) were administered into MTG-B flank tumors in female C3H-HEJ mice directly after cisplatinum chemotherapy (0.1ml/kg of body mass) was intraperitoneally injected. An 160 KHz, 350–450 Oe AMF (alternating magnetic field) was used to induce particle heating. In vitro: Mouse mammary adenocarcinoma cells (MTG-B) cells were grown and exposed to IONP hyperthermia and cisplatinum. IONPs not associated with cells were removed by washing prior to heat induction by an AMF field. Acute cell survival, via trypan blue assay, was used to quantify the level of cytotoxicity. Results In vitro studies, using IONP + cisplatinum, have demonstrated promising cytotoxicity enhancement. Ongoing studies are being pursued to further define the mechanism of action, temporal associations and pathophysiology of combined IONP hyperthermia and chemotherapy treatment. Preliminary in vivo IONP /cisplatinum studies have shown a tumor growth delay/volume reduction greater than either modality alone at comparable doses. Further enhancement of this treatment success appears to depend on a better understanding of IONP dose and tumor cell association, chemotherapy dose and administration technique, the spatial and temporal treatment relationship of the two modalities and optimal AMF - IONP coupling.

Petryk, AA; Giustini, AJ; Ryan, P; Strawbridge, RR; Hoopes, PJ

2014-01-01

298

Oxidative stress status in elite female volleyball athletes with depleted iron stores  

Microsoft Academic Search

BackgroundOxidative stress has been defined as a disturbance in the equilibrium status of pro-oxidant and antioxidant systems in favour of pro-oxidation. The elevated metabolic rate associated with exercise leads to increased mitochondrial oxygen consumption in tissues, free radical generation, metabolite oxidation and antioxidant depletion.ObjectiveThe aim of the present work was to examine the association of iron depletion and acute phase

J Martinovic; V Dopsaj; J Kotur-Stevuljevi?; M Dopsaj; G Nesic

2011-01-01

299

Metal regeneration of iron chelates in nitric oxide scrubbing  

DOEpatents

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 and 90 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. 34 figs.

Chang, S.G.; Littlejohn, D.; Shi, Y.

1997-08-19

300

Observation of tritium distribution in iron oxide with tritium micro autoradiography  

SciTech Connect

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)

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

301

An inorganic geochemical argument for coupled anaerobic oxidation of methane and iron reduction in marine sediments.  

PubMed

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

Riedinger, N; Formolo, M J; Lyons, T W; Henkel, S; Beck, A; Kasten, S

2014-03-01

302

Taurine supplementation reduces oxidative stress and protects the liver in an iron-overload murine model  

PubMed Central

We previously demonstrated that iron overload induces liver damage by causing the formation of reactive oxygen species (ROS). Taurine is a potent free radical scavenger that attenuates the damage caused by excessive oxygen free radicals. Therefore, the aim of the present study was to investigate whether taurine could reduce the hepatotoxicity of iron overload with regard to ROS production. Mice were intraperitoneally injected with iron 5 days/week for 13 weeks to achieve iron overload. It was found that iron overload resulted in liver dysfunction, increased apoptosis and elevated oxidative stress. Taurine supplementation increased liver taurine levels by 40% and led to improved liver function, as well as a reduction in apoptosis, ROS formation and mitochondrial swelling and an attenuation in the loss of the mitochondrial membrane potential. Treatment with taurine mediated a reduction in oxidative stress in iron-overloaded mice, attenuated liver lipid peroxidation, elevated antioxidant enzyme activities and maintained reduced glutathione levels. These results indicate that taurine reduces iron-induced hepatic oxidative stress, preserves liver function and inhibits hepatocyte apoptosis. Therefore, taurine may be a potential therapeutic drug to reduce liver damage caused by iron overload. PMID:25201602

ZHANG, ZEYU; LIU, DAN; YI, BO; LIAO, ZHANGPING; TANG, LEI; YIN, DONG; HE, MING

2014-01-01

303

Taurine supplementation reduces oxidative stress and protects the liver in an iron-overload murine model.  

PubMed

We previously demonstrated that iron overload induces liver damage by causing the formation of reactive oxygen species (ROS). Taurine is a potent free radical scavenger that attenuates the damage caused by excessive oxygen free radicals. Therefore, the aim of the present study was to investigate whether taurine could reduce the hepatotoxicity of iron overload with regard to ROS production. Mice were intraperitoneally injected with iron 5 days/week for 13 weeks to achieve iron overload. It was found that iron overload resulted in liver dysfunction, increased apoptosis and elevated oxidative stress. Taurine supplementation increased liver taurine levels by 40% and led to improved liver function, as well as a reduction in apoptosis, ROS formation and mitochondrial swelling and an attenuation in the loss of the mitochondrial membrane potential. Treatment with taurine mediated a reduction in oxidative stress in iron?overloaded mice, attenuated liver lipid peroxidation, elevated antioxidant enzyme activities and maintained reduced glutathione levels. These results indicate that taurine reduces iron?induced hepatic oxidative stress, preserves liver function and inhibits hepatocyte apoptosis. Therefore, taurine may be a potential therapeutic drug to reduce liver damage caused by iron overload. PMID:25201602

Zhang, Zeyu; Liu, Dan; Yi, Bo; Liao, Zhangping; Tang, Lei; Yin, Dong; He, Ming

2014-11-01

304

The Mechanism of Vapor Phase Hydration of Calcium Oxide: Implications for CO2 capture.  

PubMed

Lime-based sorbents are used for fuel- and flue-gas capture, thereby representing an economic and effective way to reduce CO2 emissions. Their use involves cyclic carbonation/calcination which results in a significant conversion reduction with increasing number of cycles. To reactivate spent CaO, vapor phase hydration is typically performed. However, little is known about the ultimate mechanism of such a hydration process. Here, we show that the vapor phase hydration of CaO formed after calcination of calcite (CaCO3) single crystals is a pseudomorphic, topotactic process, which progresses via an intermediate disordered phase prior to the final formation of oriented Ca(OH)2 nanocrystals. The strong structural control during this solid-state phase transition implies that the microstructural features of the CaO parent phase predetermine the final structural and physicochemical (reactivity and attrition) features of the product hydroxide. The higher molar volume of the product can create an impervious shell around unreacted CaO, thereby limiting the efficiency of the reactivation process. However, in the case of compact, sintered CaO structures, volume expansion cannot be accommodated in the reduced pore volume, and stress generation leads to pervasive cracking. This favors complete hydration but also detrimental attrition. Implications of these results in carbon capture and storage (CCS) are discussed. PMID:25233236

Kud?acz, Krzysztof; Rodriguez-Navarro, Carlos

2014-10-21

305

Interactions of proteins with biogenic iron oxyhydroxides and a new culturing technique to increase biomass yields of neutrophilic, iron-oxidizing bacteria  

PubMed Central

Neutrophilic, bacterial iron-oxidation remains one of the least understood energy-generating biological reactions to date. One of the reasons it remains under-studied is because there are inherent problems with working with iron-oxidizing bacteria (FeOB), including low biomass yields and interference from the iron oxides in the samples. In an effort to circumvent the problem of low biomass, a new large batch culturing technique was developed. Protein interactions with biogenic iron oxides were investigated confirming that such interactions are strong. Therefore, a protein extraction method is described to minimize binding of proteins to biogenic iron oxides. The combination of these two methods results in protein yields that are appropriate for activity assays in gels and for proteomic profiling. PMID:24910632

Barco, Roman A.; Edwards, Katrina J.

2014-01-01

306

On the corrosion resistance of the Delhi iron pillar  

Microsoft Academic Search

The nature of the protective passive layer on the corrosion resistant Delhi iron pillar (DIP) has been addressed based on a detailed characterization of its rust. Rust characterization clearly established that the major constituents of the scale were crystalline iron hydrogen phosphate hydrate (FePO4·H3PO4·4H2O), ?-, ?-, ?-FeOOH and magnetite. The iron oxide\\/oxyhydroxides were present in the amorphous form. The role

R. Balasubramaniam

2000-01-01

307

Iron  

MedlinePLUS

... shows that giving iron intravenously can improve some symptoms of heart failure. It is not yet known if taking an iron supplement by mouth would help.Attention deficit-hyperactivity disorder (ADHD). Developing research shows that taking iron sulfate ( ...

308

Iron oxidation and biomineralization by Mariprofundus ferrooxydans, a deep-sea microaerophilic lithoautotroph  

NASA Astrophysics Data System (ADS)

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.

Chan, C. S.; Emerson, D.; Fakra, S.; Edwards, K. J.

2007-12-01

309

Investigation of the hydration and dehydration of aluminium oxide-hydroxide using high frequency dielectric measurements between 300 kHz3 GHz  

Microsoft Academic Search

Aluminium oxide exists in several forms which on addition of water give a complex range of oxide-hydroxide; boehmite, bayerite and gibbsite. High frequency dielectric measurements {300 kHz-3 GHz} are reported on the hydrated and dehydration of certain of these oxide-hydroxides. The amplitude of the observed dielectric relaxation correlates approximately with the water content, however anomalies can be observed during dehydration

R. A. Pethrick; D. Hayward; K. Jeffrey; S. Affrossman; P. Wilford

1996-01-01

310

Cell adhesion of Shewanella oneidensis to iron oxide minerals: Effect of different single crystal faces  

PubMed Central

The results of experiments designed to test the hypothesis that near-surface molecular structure of iron oxide minerals influences adhesion of dissimilatory iron reducing bacteria are presented. These experiments involved the measurement, using atomic force microscopy, of interaction forces generated between Shewanella oneidensis MR-1 cells and single crystal growth faces of iron oxide minerals. Significantly different adhesive force was measured between cells and the (001) face of hematite, and the (100) and (111) faces of magnetite. A role for electrostatic interactions is apparent. The trend in relative forces of adhesion generated at the mineral surfaces is in agreement with predicted ferric site densities published previously. These results suggest that near-surface structure does indeed influence initial cell attachment to iron oxide surfaces; whether this is mediated via specific cell surface-mineral surface interactions or by more general interfacial phenomena remains untested.

Neal, Andrew L; Bank, Tracy L; Hochella, Michael F; Rosso, Kevin M

2005-01-01

311

Superparamagnetic iron oxide nanoparticles prepared by using an improved polyol method  

NASA Astrophysics Data System (ADS)

Superparamagnetic iron oxide nanoparticles were synthesized by thermal decomposition of iron (III) acetylacetonate (Fe(acac)3) in PEG containing poly(vinyl pyrrolidone) (PVP) or poly(ethylene imine) (PEI). The morphologies and phase compositions of the nanoparticles were determined by transmission electron microscopy and X-ray diffraction, respectively. The surface coating of the nanoparticles was recognized using Fourier transform infrared spectroscopy and the presence of the surface coating was confirmed by Thermogravimetric analyses. Magnetic properties were measured using superconducting quantum interference device. The zeta potentials and hydrodynamic sizes of the nanoparticles were determined using nano-particle and zeta potential analyzer. The superparamagnetic iron oxide nanoparticles with sizes from 4.1 nm to 14.9 nm were prepared in the present work, which could be tuned by varying factors such as the reaction temperature, the reaction time, and the PVP or PEI contents. The superparamagnetic nanoparticles were jointly coated with PEG/PVP or PEG/PEI. With hydrodynamic sizes smaller than 40 nm and neutral or positive zeta potentials these superparamagnetic iron oxide nanoparticles exhibited higher dispersion stability in deionized water and in phosphate buffered saline as compared with the superparamagnetic iron oxide nanoparticles coated with PEG alone. This work demonstrates that superparamagnetic iron oxide nanoparticles with modulated properties can be prepared simply by using the improved polyol method.

Zhang, Baolin; Tu, Zhijiang; Zhao, Fangyuan; Wang, Jun

2013-02-01

312

Preparation and magnetic resonance imaging effect of polyvinylpyrrolidone-coated iron oxide nanoparticles.  

PubMed

Polyvinylpyrrolidone (PVP)-coated iron oxide nanoparticles were prepared by the thermal decomposition of Fe(CO)(5) (iron pentacarbonyl) in one step. X-ray diffraction (XRD), transmission electron microscopy (TEM), electrophoretic light scattering (ELS), infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) together with the variation of the molar ratio of PVP/Fe(CO)(5), solvent, and molecular weight of PVP, were used to characterize the PVP-coated iron oxide nanoparticles. Fifty to hundred nanometer-sized iron oxide nanoclusters with a spherical shape were formed in dimethylformamide (DMF), used as a solvent, and exhibited an enhanced stability in the aqueous media. Their magnetic properties were investigated by superconducting quantum interface device (SQUID). The in vitro cytotoxicity test revealed that the PVP-coated iron oxide nanoparticles exhibited excellent biocompatibility by MTT assay. Magnetic resonance imaging (MRI) effect was observed with the administration of PVP-coated iron oxide nanoparticles through the marginal vein of rabbit, resulting in improved detection of the liver lesions. PMID:16767710

Lee, Ha Young; Lim, Nak Hyun; Seo, Jin A; Yuk, Soon Hong; Kwak, Byung Kook; Khang, Gilson; Lee, Hai Bang; Cho, Sun Hang

2006-10-01

313

Adsorption of iron cyanide complexes onto clay minerals, manganese oxide, and soil.  

PubMed

The adsorption characteristics of an iron cyanide complex, soluble Prussian blue KFe(III)[Fe(II)(CN)(6)], were evaluated for representative soil minerals and soil at pH 3.7, 6.4 and 9.7. Three specimen clay minerals (kaolinite, montmorillonite, and illite), two synthesized manganese oxides (birnessite and cryptomelane), and a Drummer soil from Indiana were used as the adsorbents. Surface protonation of variable charge sites increased with decreasing pH yielding positively charged sites on crystal edges and enhancing the attractive force between minerals and iron cyanide complexes. Anion adsorption on clays often is correlated to the metal content of the adsorbent, and a positive relationship was observed between iron or aluminum content and Prussian blue adsorption. Illite had high extractable iron and adsorbed more ferro-ferricyande anion, while kaolinite and montmorillonite had lower extractable iron and adsorbed less. However, less pH effect was observed on the adsorption of iron cyanide to manganese oxides. This may due to the manganese oxide mediated oxidation of ferrocyanide [Fe(II)(CN)(6)(4-)], to ferricyanide [Fe(III)(CN)(6)(3-)], which has a low affinity for manganese oxides. PMID:20665323

Kang, Dong-Hee; Schwab, A Paul; Johnston, C T; Banks, M Katherine

2010-09-01

314

Did iron-oxidizing chemolithotrophic bacteria play a role in the formation of early phosphorites?  

NASA Astrophysics Data System (ADS)

The oxygenation of Earth's atmosphere allowed for the diversification of metabolisms to include the use of oxygen and its derivatives as terminal electron acceptors, as in the chemolithotrophic oxidation of sulfide or ferrous iron. A growing number of oxygen-utilizing chemolithotrophs are being found to accumulate intracellular polyphosphate as an energy reserve that allows them to adapt to fluctuating redox conditions in their distinctive gradient habitats. Polyphosphate metabolism by chemolithotrophic bacteria is also thought to play an important role in the formation of phosphatic mineral deposits. Polyphosphate accumulation was recently discovered in marine twisted-stalk-forming iron bacteria. Here we present fossil evidence of iron-oxidizing bacteria preserved as filamentous iron oxides within phosphatic Paleoproterozoic stromatolites. The filaments include twisted stalks similar to those produced by modern iron-oxidizing bacteria, including those that accumulate polyphosphate. The association of fossil iron-oxidizing bacteria with some of the oldest known phosphorites might be explained by the ancient utilization of polyphosphate by chemolithotrophs in a world with burgeoning oxygen-Fe(II) gradients, providing evidence for a potential connection between Earth's oxygenation, polyphosphate metabolism, and the onset of phosphogenesis.

Crosby, Chris H.; Bailey, Jake V.; Sharma, Mukund

2014-05-01

315

Acute iron overload and oxidative stress in brain.  

PubMed

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

Piloni, Natacha E; Fermandez, Virginia; Videla, Luis A; Puntarulo, Susana

2013-12-01

316

Light Induced Dissolution of Iron Oxides in the Presence of Siderophores  

NASA Astrophysics Data System (ADS)

Iron is a micronutrient that is essential for a range of important enzymatic processes in most organisms. Iron deficiency is thought to be limiting the primary productivity in marine `High Nutrient Low Chlorophyll' (HNLC) regions which has a significant effect on global carbon cycling. Important iron sources in HNLC regions are upwelling and atmospheric dust inputs. However, the iron bioavailability from atmospheric dust is limited by the low solubility and slow dissolution kinetics of iron bearing minerals. Marine bacteria are known to facilitate weathering reactions by exudation of substances such as low molecular weight organic ligands including siderophores. We investigated if siderophore promoted photoreductive dissolution constitutes an important pathway for increasing the bioavailability of iron oxides. We used the microbial siderophores aerobactin and desferrioxamine-B (DFO-B). Aerobactin and desferrixoamines are excreted by marine and terrestrial bacteria. Aerobactin is a dihydroxamate siderophore containing the potentially photoreactive group alpha-hydroxy carboxylate. DFO-B is a trihydroxamate siderophore which forms soluble iron complexes that are not photoreactive (BARBEAU et al., 2003). Despite the structural differences, both siderophores accelerate iron oxide dissolution in irradiated suspensions compared to dissolution rates in the dark. This suggests that both siderophores are not involved in a light induced ligand to metal charge transfer reaction, but rather accelerate other photreductive dissolution mechanisms. Similarly it was observed that both ligands accelerate light induced dissolution of iron oxides in the presence of oxalate as a chromophore. The observations suggest that light induced dissolution of iron oxides in the presence of siderophores is an important pathway for bacterial iron acquisition. However, the formation of Fe(II) by this mechanism may also lead to an increase of the availability of iron to phytoplankton that generally does not produce siderophores or take up iron(III)siderophore complexes (BARBEAU et al., 2001). References Barbeau K., Rue E. L., Bruland K. W., and Butler A. (2001) Photochemical cycling of iron in the surface ocean mediated by microbial iron(III)-binding ligands. Nature 413(6854), 409-413. Barbeau K., Rue E. L., Trick C. G., Bruland K. T., and Butler A. (2003) Photochemical reactivity of siderophores produced by marine heterotrophic bacteria and cyanobacteria based on characteristic Fe(III) binding groups. Limnology and Oceanography 48(3), 1069-1078.

Kraemer, S. M.; Borer, P.; Sulzberger, B. A.

2003-12-01

317

Effect of iron oxide loading on the phase transformation and physicochemical properties of nanosized mesoporous ZrO{sub 2}  

SciTech Connect

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.

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

318

Quantum chemistry-based study of iron oxidation at the iron-water interface: An X-ray analysis aided study  

NASA Astrophysics Data System (ADS)

Using a quantum chemistry-based reactive force field and X-ray analyses, we explored and report the atomic-scale findings from a simulated iron oxidation process under a typical ambient condition. The initiation and growth of oxides were found to be highly dependent on the thermodynamics and availability of reactants. Three oxidation stages were identified until a high-density triplex structure was formed on iron surface, after which the oxidation of iron progressed at a significantly reduced speed. Results from this study will improve the knowledge base of understanding the passivation and depassivation of steel surface for more effective control of steel corrosion.

Pan, Tongyan

2011-08-01

319

Selective catalytic oxidation of H?S over iron oxide supported on alumina-intercalated Laponite clay catalysts.  

PubMed

A series of iron oxide supported on alumina-intercalated clay catalysts (named Fe/Al-Lap catalysts) with mesoporous structure and high specific surface area were prepared. The structural and chemical properties were studied by nitrogen sorption isotherms, X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (UV-vis DRS), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FTIR), H? temperature-programmed reduction (H?-TPR) and NH? temperature-programmed desorption (NH3-TPD) techniques. It was realized that iron oxide mainly existed in the form of isolated Fe(3+) in an oxidic environment. Fe/Al-Lap catalysts showed high catalytic activities in the temperature range of 120-200 °C without the presence of excessive O?. This can be attributed to the interaction between iron oxide and alumina, which improve the redox property of Fe(3+) efficiently. In addition, the strong acidity of catalysts and good dispersion of iron oxide were also beneficial to oxidation reaction. Among them, 7% Fe/Al-Lap catalyst presented the best catalytic performance at 180 °C. Finally, the catalytic and deactivation mechanisms were explored. PMID:23747468

Zhang, Xin; Dou, Guangyu; Wang, Zhuo; Li, Li; Wang, Yufei; Wang, Hailin; Hao, Zhengping

2013-09-15

320

Relationship between Increased Body Iron Stores, Oxidative Stress and Insulin Resistance in Healthy Men  

Microsoft Academic Search

Aim: The aim of our cross-sectional study was to assess the relationships between body iron stores, oxidative stress, impaired insulin sensitivity and carotid atherosclerosis in a cohort of healthy men in primary prevention of cardiovascular disease. Methods: We examined 151 volunteers, aged 35– 60 years. Anthropometric parameters, markers of metabolic syndrome, insulin resistance, inflammatory markers, parameters of oxidative stress and

Petr Syrovatka; Pavel Kraml; Jana Potockova; Lenka Fialova; Martin Vejrazka; Jirina Crkovska; Michal Andel

2009-01-01

321

Iron-oxide-supported nanocarbon in lithium-ion batteries, medical, catalytic, and environmental applications.  

PubMed

Owing to the three different orbital hybridizations carbon can adopt, the existence of various carbon nanoallotropes differing also in dimensionality has been already affirmed with other structures predicted and expected to emerge in the future. Despite numerous unique features and applications of 2D graphene, 1D carbon nanotubes, or 0D fullerenes, nanodiamonds, and carbon quantum dots, which have been already heavily explored, any of the existing carbon allotropes do not offer competitive magnetic properties. For challenging applications, carbon nanoallotropes are functionalized with magnetic species, especially of iron oxide nature, due to their interesting magnetic properties (superparamagnetism and strong magnetic response under external magnetic fields), easy availability, biocompatibility, and low cost. In addition, combination of iron oxides (magnetite, maghemite, hematite) and carbon nanostructures brings enhanced electrochemical performance and (photo)catalytic capability due to synergetic and cooperative effects. This work aims at reviewing these advanced applications of iron-oxide-supported nanocarbon composites where iron oxides play a diverse role. Various architectures of carbon/iron oxide nanocomposites, their synthetic procedures, physicochemical properties, and applications are discussed in details. A special attention is devoted to hybrids of carbon nanotubes and rare forms (mesoporous carbon, nanofoam) with magnetic iron oxide carriers for advanced environmental technologies. The review also covers the huge application potential of graphene/iron oxide nanocomposites in the field of energy storage, biomedicine, and remediation of environment. Among various discussed medical applications, magnetic composites of zero-dimensional fullerenes and carbon dots are emphasized as promising candidates for complex theranostics and dual magneto-fluorescence imaging. PMID:25000534

Tu?ek, Ji?í; Kemp, Kingsley Christian; Kim, Kwang Soo; Zbo?il, Radek

2014-08-26

322

Assessment of the extent of oxidative stress induced by intravenous ferumoxytol, ferric carboxymaltose, iron sucrose and iron dextran in a nonclinical model.  

PubMed

Intravenous (i.v.) iron is associated with a risk of oxidative stress. The effects of ferumoxytol, a recently approved i.v. iron preparation, were compared with those of ferric carboxymaltose, low molecular weight iron dextran and iron sucrose in the liver, kidneys and heart of normal rats. In contrast to iron sucrose and ferric carboxymaltose, low molecular weight iron dextran and ferumoxytol caused renal and hepatic damage as demonstrated by proteinuria and increased liver enzyme levels. Higher levels of oxidative stress in these tissues were also indicated, by significantly higher levels of malondialdehyde, significantly increased antioxidant enzyme activities, and a significant reduction in the reduced to oxidized glutathione ratio. Inflammatory markers were also significantly higher with ferumoxytol and low molecular weight iron dextran rats than iron sucrose and ferric carboxymaltose. Polarographic analysis suggested that ferumoxytol contains a component with a more positive reduction potential, which may facilitate iron-catalyzed formation of reactive oxygen species and thus be responsible for the observed effects. Only low molecular weight iron dextran induced oxidative stress and inflammation in the heart. PMID:21899208

Toblli, Jorge E; Cao, Gabriel; Oliveri, Leda; Angerosa, Margarita

2011-01-01

323

Beta-Thalassemia Major and Female Fertility: The Role of Iron and Iron-Induced Oxidative Stress  

PubMed Central

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

Roussou, Paraskevi; Tsagarakis, Nikolaos J.; Diamanti-Kandarakis, Evanthia

2013-01-01

324

Timing and setting of skarn and iron oxide formation at the Smältarmossen calcic iron skarn deposit, Bergslagen, Sweden  

NASA Astrophysics Data System (ADS)

Abundant iron oxide deposits including banded iron formations, apatite iron oxide ores, and enigmatic marble/skarn-hosted magnetite deposits occur in the Palaeoproterozoic Bergslagen region, southern Sweden. During the last 100 years, the latter deposit class has been interpreted as contact metasomatic skarn deposits, metamorphosed iron formations, or metamorphosed carbonate replacement deposits. Their origin is still incompletely understood. At the Smältarmossen mine, magnetite was mined from a ca. 50-m-thick calcic skarn zone at the contact between rhyolite and stratigraphically overlying limestone. A syn-volcanic dacite porphyry which intruded the footwall has numerous apophyses that extend into the mineralized zone. Whole-rock lithogeochemical and mineral chemical analyses combined with textural analysis suggests that the skarns formed by veining and replacement of the dacite porphyry and rhyolite. These rocks were added substantial Ca and Fe, minor Mg, Mn, and LREE, as well as trace Co, Sn, U, As, and Sr. In contrast, massive magnetite formed by pervasive replacement of limestone. Tectonic fabrics in magnetite and skarn are consistent with ore formation before or early during Svecokarelian ductile deformation. Whereas a syngenetic-exhalative model has previously been suggested, our results are more compatible with magnetite formation at ca. 1.89 Ga in a contact metasomatic skarn setting associated with the dacite porphyry.

Jansson, Nils F.; Allen, Rodney L.

2013-03-01

325

In-situ determination of the oxidation state of iron in Fe-bearing silicate melts  

NASA Astrophysics Data System (ADS)

Terrestrial lavas commonly contain up to 10 wt% of iron. Furthermore, rocks returned from the Moon indicate lunar lava containing up to 25 wt% of iron and planetary scientists estimated that the martian mantle has about 18 wt% of iron. An experimental challenge in dealing with Fe-bearing silicate melts is that the oxidation state, controlling the proportions of ferric and ferrous iron, is a function of composition, oxygen fugacity and temperature and may vary significantly. Further complications concerning iron originate from its potential to be either four-, six- or even five-fold coordinated in both valence states. Therefore, the oxidation state of iron was determined in air for various Fe-bearing silicate melts. Investigated samples were Na-disilicate (NS), one atmosphere anorthite-diopside eutectic (AD) and haplogranitic (HPG8) melts containing up to 20, 20 and 10 wt% of iron, respectively. XANES spectra at the Fe K-edge were collected for all the melts at beamline A1, HASYLAB, Hamburg, using a Si(111) 4-crystal monochromator. Spectra were collected for temperatures up to 1573 K using a Pt-Rh loop as heating device. The Fe oxidation state was determined from the centroid position of the pre-edge feature using the calibration of Wilke et al. (2004). XANES results suggest that oxidation state of iron does not change within error for NS melts with addition of Fe, while AD and HPG8 melts become more oxidised with increasing iron content. Furthermore, NS melts are well more oxidised than AD and HPG8 melts that exhibit relatively similar oxidation states for identical iron contents. The oxidation state of iron for NS melts appears to be slightly temperature-dependent within the temperature range investigated (1073-1573 K). However, this trend is stronger for AD and HPG8 melts. Assuming that glass reflects a picture of the homogeneous equilibria of the melt, the present in-situ Fe-oxidation states determined for these melts were compared to those obtained on quenched glasses from different temperatures, when possible, using wet-chemical analysis (i.e., K-dichromate potentiometry). Both datasets agree reasonably well (within 10 %). References: Wilke et al. (2004) Chemical Geology, 213, 71-87.

Courtial, P.; Wilke, M.; Potuzak, M.; Dingwell, D. B.

2005-12-01

326

Development of tungsten oxide hydrate phases during precipitation, room temperature ripening and hydrothermal treatment  

Microsoft Academic Search

Morphology and structure transformation of tungstic acid hydrate, H2WO4·nH2O precipitates, have been studied in aqueous phase with various levels of residual [Na+]s at room temperature and at 120 °C in autoclave. Spindle-shaped morphology is characteristic for the washing product of the freshly prepared precipitates. Residual sodium is a persistent contaminant in H2WO4·H2O. Sodium ion content in the solid phase has

Csaba Balázsi; Judit Pfeifer

2002-01-01

327

Iron-catalyzed propylene epoxidation by nitrous oxide: Toward understanding the nature of active iron sites with modified Fe-MFI and Fe-MCM-41 catalysts  

Microsoft Academic Search

Alkali metal salt (KCl)-modified Fe-MFI and Fe-MCM-41 containing iron species in different locations have been studied for the epoxidation of propylene with nitrous oxide. In the allylic oxidation of propylene without modification, the samples with iron species in the framework positions showed slightly higher activity for the formation of acrolein and allyl alcohol. After modification with KCl, propylene oxide (PO)

Qinghong Zhang; Qian Guo; Xiaoxing Wang; Tetsuya Shishido; Ye Wang

2006-01-01

328

Association of uranium with iron oxides typically formed on corroding steel surfaces.  

PubMed

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

Dodge, C J; Francis, A J; Gillow, J B; Halada, G P; Eng, C; Clayton, C R

2002-08-15

329

Superparamagnetic iron oxide nanoparticles as radiosensitizer via enhanced reactive oxygen species formation  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Ultrasmall citrate-coated SPIONs with {gamma}Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4} structure were prepared. Black-Right-Pointing-Pointer SPIONs uptaken by MCF-7 cells increase the ROS production for about 240%. Black-Right-Pointing-Pointer The SPION induced ROS production is due to released iron ions and catalytically active surfaces. Black-Right-Pointing-Pointer Released iron ions and SPION surfaces initiate the Fenton and Haber-Weiss reaction. Black-Right-Pointing-Pointer X-ray irradiation of internalized SPIONs leads to an increase of catalytically active surfaces. -- Abstract: Internalization of citrate-coated and uncoated superparamagnetic iron oxide nanoparticles by human breast cancer (MCF-7) cells was verified by transmission electron microscopy imaging. Cytotoxicity studies employing metabolic and trypan blue assays manifested their excellent biocompatibility. The production of reactive oxygen species in iron oxide nanoparticle loaded MCF-7 cells was explained to originate from both, the release of iron ions and their catalytically active surfaces. Both initiate the Fenton and Haber-Weiss reaction. Additional oxidative stress caused by X-ray irradiation of MCF-7 cells was attributed to the increase of catalytically active iron oxide nanoparticle surfaces.

Klein, Stefanie; Sommer, Anja [Department of Chemistry and Pharmacy, Physical Chemistry I and ICMM, Friedrich-Alexander University of Erlangen-Nuremberg, Egerlandstr. 3, D-91058 Erlangen (Germany)] [Department of Chemistry and Pharmacy, Physical Chemistry I and ICMM, Friedrich-Alexander University of Erlangen-Nuremberg, Egerlandstr. 3, D-91058 Erlangen (Germany); Distel, Luitpold V.R. [Department of Radiation Oncology, Friedrich Alexander University Erlangen-Nuremberg, Universitaetsstrasse 27, D-91054 Erlangen (Germany)] [Department of Radiation Oncology, Friedrich Alexander University Erlangen-Nuremberg, Universitaetsstrasse 27, D-91054 Erlangen (Germany); Neuhuber, Winfried [Department of Anatomy, Chair of Anatomy I, Friedrich Alexander University Erlangen-Nuremberg, Krankenhausstr. 9, D-91054 Erlangen (Germany)] [Department of Anatomy, Chair of Anatomy I, Friedrich Alexander University Erlangen-Nuremberg, Krankenhausstr. 9, D-91054 Erlangen (Germany); Kryschi, Carola, E-mail: kryschi@chemie.uni-erlangen.de [Department of Chemistry and Pharmacy, Physical Chemistry I and ICMM, Friedrich-Alexander University of Erlangen-Nuremberg, Egerlandstr. 3, D-91058 Erlangen (Germany)] [Department of Chemistry and Pharmacy, Physical Chemistry I and ICMM, Friedrich-Alexander University of Erlangen-Nuremberg, Egerlandstr. 3, D-91058 Erlangen (Germany)

2012-08-24

330

Comparison of various iron chelators and prochelators as protective agents against cardiomyocyte oxidative injury  

PubMed Central

Oxidative stress is a common denominator of numerous cardiovascular disorders. Free cellular iron catalyzes 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, aroylhydrazone prochelators BHAPI and BSIH-PD provided significant cytoprotection and displayed lower toxicity following 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 aroylhydrazone prochelator BSIH. BSIH efficiently protected both H9c2 rat cardiomyoblast-derived cells as well as isolated primary rat cardiomyocytes against hydrogen peroxide-induced mitochondrial and lysosomal dysregulation and cell death. At the same time, BSIH was non-toxic at concentrations up to its solubility limit (600 µM) and 72-hour 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

Jansová, Hana; Machá?ek, Miloslav; Wang, Qin; Hašková, Pavlína; Jirkovská, Anna; Pot??ková, Eliška; Kielar, Filip; Franz, Katherine J.; Šim?nek, Tomáš

2014-01-01

331

21 CFR 73.1200 - Synthetic iron oxide.  

...basis: Arsenic (as As), not more than 3 parts per million. Lead (as Pb), not more than 10 parts per million. Mercury (as Hg), not more than 3 parts per million. (c) Uses and restrictions. The color additive synthetic iron...

2014-04-01

332

Spectral reflectance properties (0.4-2.5 um) of secondary Fe-oxide, Fe-hydroxide, and Fe-sulfate-hydrate minerals associated with sulfide-bearing mine waste  

USGS Publications Warehouse

Fifteen Fe-oxide, Fe-hydroxide, and Fe-sulphate-hydrate mineral species commonly associated with sulphide bearing mine wastes were characterized by using X-ray powder diffraction and scanning electron microscope methods. Diffuse reflectance spectra of the samples show diagnostic absorption features related to electronic processes involving ferric and/or ferrous iron, and to vibrational processes involving water and hydroxyl ions. Such spectral features enable field and remote sensing based studies of the mineral distributions. Because secondary minerals are sensitive indicators of pH, Eh, relative humidity, and other environmental conditions, spectral mapping of these minerals promises to have important applications to mine waste remediation studies. This report releases digital (ascii) spectra (spectral_data_files.zip) of the fifteen mineral samples to facilitate usage of the data with spectral libraries and spectral analysis software. The spectral data are provided in a two-column format listing wavelength (in micrometers) and reflectance, respectively.

Crowley, J. K.; Williams, D. E.; Hammarstrom1, J. M.; Piatak, N.; Mars, J. C.; Chou, I-Ming

2006-01-01

333

Iron oxide nanoparticles stabilized with dendritic polyglycerols as selective MRI contrast agents  

NASA Astrophysics Data System (ADS)

Monodisperse small iron oxide nanoparticles functionalized with dendritic polyglycerol (dPG) or dendritic polyglycerol sulfate (dPGS) are prepared. They are highly stable in aqueous solutions as well as physiological media. In particular, oleic acid capped iron oxide particles (core diameter = 11 +/- 1 nm) were modified by a ligand exchange process in a one pot synthesis with dPG and dPGS bearing phosphonate as anchor groups. Dynamic light scattering measurements performed in water and different biological media demonstrate that the hydrodynamic diameter of the particles is only slightly increased by the ligand exchange process resulting in a final diameter of less than 30 nm and that the particles are stable in these media. It is also revealed by magnetic resonance studies that their magnetic relaxivity is reduced by the surface modification but it is still sufficient for high contrast magnetic resonance imaging (MRI). Additionally, incubation of dPGS functionalized iron oxide nanoparticles with human umbilical vein endothelial cells showed a 50% survival at 85 nM (concentration of nanoparticles). Surface plasmon resonance (SPR) studies demonstrate that the dPGS functionalized iron oxide nanoparticles inhibit L-selectin ligand binding whereas the particles containing only dPG do not show this effect. Experiments in a flow chamber with human myelogenous leukemia cells confirmed L-selectin inhibition of the dPGS functionalized iron oxide nanoparticles and with that the L-selectin mediated leukocyte adhesion. These results indicate that dPGS functionalized iron oxide nanoparticles are a promising contrast agent for inflamed tissue probed by MRI.Monodisperse small iron oxide nanoparticles functionalized with dendritic polyglycerol (dPG) or dendritic polyglycerol sulfate (dPGS) are prepared. They are highly stable in aqueous solutions as well as physiological media. In particular, oleic acid capped iron oxide particles (core diameter = 11 +/- 1 nm) were modified by a ligand exchange process in a one pot synthesis with dPG and dPGS bearing phosphonate as anchor groups. Dynamic light scattering measurements performed in water and different biological media demonstrate that the hydrodynamic diameter of the particles is only slightly increased by the ligand exchange process resulting in a final diameter of less than 30 nm and that the particles are stable in these media. It is also revealed by magnetic resonance studies that their magnetic relaxivity is reduced by the surface modification but it is still sufficient for high contrast magnetic resonance imaging (MRI). Additionally, incubation of dPGS functionalized iron oxide nanoparticles with human umbilical vein endothelial cells showed a 50% survival at 85 nM (concentration of nanoparticles). Surface plasmon resonance (SPR) studies demonstrate that the dPGS functionalized iron oxide nanoparticles inhibit L-selectin ligand binding whereas the particles containing only dPG do not show this effect. Experiments in a flow chamber with human myelogenous leukemia cells confirmed L-selectin inhibition of the dPGS functionalized iron oxide nanoparticles and with that the L-selectin mediated leukocyte adhesion. These results indicate that dPGS functionalized iron oxide nanoparticles are a promising contrast agent for inflamed tissue probed by MRI. Electronic supplementary information (ESI) available: A detailed description of the synthesis of the ligands as well as the preparation and functionalization of the iron oxide nanoparticles including their physico-chemical characterization are presented. Further, details of the cell experiments and the SPR experiments are given. Two representative movies are provided showing leukocyte rolling on the ligand coated surface of the flow chamber. See DOI: 10.1039/c3nr04793h

Nordmeyer, Daniel; Stumpf, Patrick; Gröger, Dominic; Hofmann, Andreas; Enders, Sven; Riese, Sebastian B.; Dernedde, Jens; Taupitz, Matthias; Rauch, Ursula; Haag, Rainer; Rühl, Eckart; Graf, Christina

2014-07-01

334

Magnetic resonance imaging of multifunctional pluronic stabilized iron-oxide nanoparticles in tumor-bearing mice  

Microsoft Academic Search

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

Tapan K. Jain; Susan P. Foy; Bernadette Erokwu; Sanja Dimitrijevic; Christopher A. Flask; Vinod Labhasetwar

2009-01-01

335

Site determination and magnetism of Mn doping in protein encapsulated iron oxide nanoparticles  

Microsoft Academic Search

Soft x-ray absorption spectroscopy, soft x-ray magnetic circular dichroism, and alternating current magnetic susceptibility were performed on 6.7 nm iron oxide nanoparticles doped with (5%-33%) Mn grown inside the horse-spleen ferritin protein cages and compared to similarly protein encapsulated pure Fe-oxide and Mn-oxide nanoparticles to determine the site of the Mn dopant and to quantify the magnetic behavior with varying

V. Pool; M. Klem; C. Jolley; E. A. Arenholz; T. Douglas; M. Young; Y. U. Idzerda

2010-01-01

336

Preparation and characterization of thermosensitive PNIPAA-coated iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

A new and facile approach was established to fabricate thermoresponsive poly(N-isopropylacrylamide) (PNIPAA) coated iron oxide nanoparticles in a non-aqueous medium. The morphology and structure of the nanoparticle-doped composite were analyzed by means of transmission electron microscopy (TEM), x-ray powder diffraction (XRD), and Fourier transformation infrared spectrometry (FTIR). The thermosensitivity of the composite was also investigated. Results indicated that the oil-soluble iron oxide nanoparticles encapsulated with PNIPAA, composed of an inorganic iron oxide core and biocompatible PNIPAA shell, were dispersed well in water and had a sphere-like shape. The PNIPAA-coated iron oxide nanoparticles with such a kind of core-shell structure showed excellent thermosensitivity. Namely, the aqueous suspension of PNIPAA-coated iron oxide nanoparticles dramatically changed from transparent to opaque as the temperature increased from room temperature to 38 °C, showing potential as optical transmittance switch materials and their significance in the fields of protein adsorption and purification controlled release, and drug delivery.

Zhang, Shengmao; Zhang, Linna; He, Benfang; Wu, Zhishen

2008-08-01

337

Recycling of a spent iron based catalyst for the complete oxidation of toluene: effect of palladium.  

PubMed

Complete oxidation of volatile organic compound (toluene) was carried out to assess the property and activity of the palladium-spent iron based catalyst. The properties of the prepared catalysts were characterized by using the Brunauer-Emmett-Teller method and by conducting temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy and field emission transmission electron microscopy. The addition of palladium to the spent iron based catalyst pretreated with oxalic acid shifted the conversion curve for the total oxidation of toluene to lower temperature. An increase in the toluene conversion due to palladium was highly related to the easier lattice oxygen mobility of the catalysts. Instrumental analysis suggested the presence of a strong interaction between palladium and iron oxide species. Moreover, in the case of reducing the Pd/Fe catalyst with hydrogen, palladium accelerated the reducing iron oxides, subsequently decreasing the toluene conversion. As a result, the oxidation states of palladium and iron had an important effect on the catalytic activity. PMID:25413115

Kim, Sang Chai; Nah, Jae Woon

2015-01-01

338

Spatially resolved energy electron loss spectroscopy studies of iron oxide nanoparticles.  

PubMed

The oxidation state of iron oxide nanoparticles co-generated with soot during a combustion process was studied using electron energy-loss spectroscopy (EELS). Spatially resolved EELS spectra in the scanning transmission electron microscopy mode were collected to detect changes in the oxidation state between the cores and surfaces of the particles. Quantification of the intensity ratio of the white lines of the iron L-ionization edge was used to measure the iron oxidation state. Quantitative results obtained from Pearson's method, which can be directly compared with the literature data, indicated that the L3 /L2-intensity ratio for these particles changes from 5.5 +/- 0.3 in the particles' cores to 4.4 +/- 0.3 at their surfaces. This change can be directly related to the reduction of the iron oxidation state at the surface of the particles. Experimental results indicate that the cores of the particles are composed of gamma-Fe2O3, which seems to be reduced to FeO at their surfaces. These results were also supported by the fine structure of the oxygen K-edge and by the significant chemical shift of the iron L-edge. PMID:16984669

Jasinski, Jacek; Pinkerton, Kent E; Kennedy, I M; Leppert, Valerie J

2006-10-01

339

Deposition of biogenic iron minerals in a methane oxidizing microbial mat.  

PubMed

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

Wrede, Christoph; Kokoschka, Sebastian; Dreier, Anne; Heller, Christina; Reitner, Joachim; Hoppert, Michael

2013-01-01

340

Study of Organic and Inorganic Binders on Strength of Iron Oxide Pellets  

NASA Astrophysics Data System (ADS)

Bentonite is a predominant binder used in iron ore pelletization. However, the presence of a high content of silica and alumina in bentonite is considered undesirable for ironmaking operations. The objective of this study was to identify the alternatives of bentonite for iron ore pelletization. To achieve this goal, different types of organic and inorganic binders were utilized to produce iron oxide pellets. The quality of these iron oxide pellets was compared with pellets made using bentonite. All pellets were tested for physical strength at different stages of pelletization to determine their ability to survive during shipping and handling. The results show that organic binders such as lactose monohydrate, hemicellulose, and sodium lignosulfonate can provide sufficient strength to indurated pellets.

Srivastava, Urvashi; Kawatra, S. Komar; Eisele, Timothy C.

2013-08-01

341

Deposition of Biogenic Iron Minerals in a Methane Oxidizing Microbial Mat  

PubMed Central

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

Wrede, Christoph; Dreier, Anne; Heller, Christina; Reitner, Joachim; Hoppert, Michael

2013-01-01

342

Nitric Oxide-Mediated Modulation of Iron Regulatory Proteins: Implication for Cellular Iron Homeostasis  

Microsoft Academic Search

ABSTRACTIron regulatory proteins (IRP1 and IRP2) control the synthesis of transferrin receptors (TfR) and ferritin by binding to iron-responsive elements (IREs) that are located in the 3? untranslated region (UTR) and the 5? UTR of their respective mRNAs. Cellular iron levels affect binding of IRPs to IREs and consequently expression of TfR and ferritin. Moreover, NO•, a redox species of

Sangwon Kim; Prem Ponka

2002-01-01

343

Does nitric oxide contribute to iron-dependent brain injury after experimental cerebral ischaemia?  

Microsoft Academic Search

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

A. Gámez; T. Carbonell; R. Rama

2003-01-01

344

Iron homeostasis and oxidative stress in idiopathic pulmonary alveolar proteinosis: a case-control study  

PubMed Central

Background Lung injury caused by both inhaled dusts and infectious agents depends on increased availability of iron and metal-catalyzed oxidative stress. Because inhaled particles, such as silica, and certain infections can cause secondary pulmonary alveolar proteinosis (PAP), we tested the hypothesis that idiopathic PAP is associated with an altered iron homeostasis in the human lung. Methods Healthy volunteers (n = 20) and patients with idiopathic PAP (n = 20) underwent bronchoalveolar lavage and measurements were made of total protein, iron, tranferrin, transferrin receptor, lactoferrin, and ferritin. Histochemical staining for iron and ferritin was done in the cell pellets from control subjects and PAP patients, and in lung specimens of patients without cardiopulmonary disease and with PAP. Lavage concentrations of urate, glutathione, and ascorbate were also measured as indices of oxidative stress. Results Lavage concentrations of iron, transferrin, transferrin receptor, lactoferrin, and ferritin were significantly elevated in PAP patients relative to healthy volunteers. The cells of PAP patients had accumulated significant iron and ferritin, as well as considerable amounts of extracellular ferritin. Immunohistochemistry for ferritin in lung tissue revealed comparable amounts of this metal-storage protein in the lower respiratory tract of PAP patients both intracellularly and extracellularly. Lavage concentrations of ascorbate, glutathione, and urate were significantly lower in the lavage fluid of the PAP patients. Conclusion Iron homeostasis is altered in the lungs of patients with idiopathic PAP, as large amounts of catalytically-active iron and low molecular weight anti-oxidant depletion are present. These findings suggest a metal-catalyzed oxidative stress in the maintenance of this disease. PMID:18215276

Ghio, Andrew J; Stonehuerner, Jacqueline G; Richards, Judy H; Crissman, Kay M; Roggli, Victor L; Piantadosi, Claude A; Carraway, Martha Sue

2008-01-01

345

Synthesis and characterization of ultra-small superparamagnetic iron oxide nanoparticles thinly coated with silica  

PubMed Central

Ultra-small superparamagnetic iron oxide nanoparticles (SPIOs) were synthesized by co-precipitation of iron chloride salts with ammonia and then encapsulated with thin (~2nm) layers of silica. The particles have been characterized for size, diffraction pattern, surface charge, and magnetic properties. This rapid and economical synthesis has a number of industrial applications; however, the silica-coated particles have been optimized for use in medical applications as MR contrast agents, biosensors, DNA capturing, bioseparation and enzyme immobilization PMID:19701448

Bumb, A; Brechbiel, M W; Choyke, P L; Fugger, L; Eggeman, A; Prabhakaran, D; Hutchinson, J; Dobson, P J

2008-01-01

346

Comparison of catalytic decomposition of hydrogen peroxide and catalytic degradation of phenol by immobilized iron oxides  

Microsoft Academic Search

Immobilized iron oxides on silica matrixes in fluidized bed reactors, including SiG1, SiG2, C1, and the commercial catalyst FeOOH, were used in the catalytic decomposition of H2O2 and the catalytic degradation of phenol. They were characterized using XRD, SEM, N2-sorption, and elucidation of the kinetics of dissolved iron by oxalic acid in dark surroundings. XRD patterns reveal that SiG1, SiG2,

Chun-Ping Huang; Yao-Hui Huang

2008-01-01

347

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

PubMed

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 (6000ft above the sea level). Iron supplementation (2mg elemental iron/kg, once daily for 15days) 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 (25mg/kg, once daily for the last 7days 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. PMID:24215938

Salama, Samir A; Omar, Hany A; Maghrabi, Ibrahim A; AlSaeed, Mohammed S; EL-Tarras, Adel E

2014-01-01

348

Iron-oxide aerogel and xerogel catalyst formulations: Characterization by 57Fe Mössbauer and XAFS spectroscopies  

NASA Astrophysics Data System (ADS)

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.

Huggins, Frank E.; Bali, Sumit; Huffman, Gerald P.; Eyring, Edward M.

2010-06-01

349

MR Imaging of Tumor Associated Macrophages with Clinically-Applicable Iron Oxide Nanoparticles  

PubMed Central

Purpose The presence of tumor-associated macrophages (TAMs) in breast cancer correlates strongly with poor outcome. The purpose of this study was to develop a clinically applicable, non-invasive diagnostic assay for selective targeting and visualization of TAMs in breast cancer, based on magnetic resonance (MR) imaging and clinically applicable iron oxide nanoparticles. Experimental Design F4/80-negative mammary carcinoma cells and F4/80-positive TAMs were incubated with iron oxide nanoparticles and were compared regarding MR signal changes and iron uptake. MMTV-PyMT transgenic mice harboring mammary carcinomas underwent nanoparticle-enhanced MR up to 1 hour (h) and at 24 h post injection (p.i.). The tumor enhancement on MR images was correlated with the presence and location of TAMs and nanoparticles on confocal microscopy. Results In vitro studies revealed that iron oxide nanoparticles are preferentially phagocytosed by TAMs, but not by malignant tumor cells. In vivo, all tumors demonstrated an initial contrast agent perfusion on immediate postcontrast MR images with gradual transendothelial leakage into the tumor interstitium. At 24 h p.i., all tumors demonstrated a persistent signal decline on MR scans. TAM-depletion via ?CSF1 mAb lead to significant inhibition of tumor nanoparticle enhancement. Detection of iron using DAB-enhanced Prussian Blue staining, and immunodetection of CD68 localized iron oxide nanoparticles to TAMs, indicating that the MR signal effects on delayed MR images were largely due to TAM-mediated uptake of contrast agent. Conclusion These data indicate that tumor-enhancement with clinically applicable iron oxide nanoparticles may serve as a new biomarker for long-term prognosis, related treatment decisions and the evaluation of new immune-targeted therapies. PMID:21791632

Daldrup-Link, Heike E.; Golovko, Daniel; Ruffell, Brian; DeNardo, David G.; Castaneda, Rosalinda; Ansari, Celina; Rao, Jianghong; Tikhomirov, Grigory A.; Wendland, Mike; Corot, Claire; Coussens, Lisa M.

2011-01-01

350

Advanced oxidation-resistant iron-based alloys for LWR fuel cladding  

NASA Astrophysics Data System (ADS)

Application of advanced oxidation-resistant iron alloys as light water reactor fuel cladding is proposed. The motivations are based on specific limitations associated with zirconium alloys, currently used as fuel cladding, under design-basis and beyond-design-basis accident scenarios. Using a simplified methodology, gains in safety margins under severe accidents upon transition to advanced oxidation-resistant iron alloys as fuel cladding are showcased. Oxidation behavior, mechanical properties, and irradiation effects of advanced iron alloys are briefly reviewed and compared to zirconium alloys as well as historic austenitic stainless steel cladding materials. Neutronic characteristics of iron-alloy-clad fuel bundles are determined and fed into a simple economic model to estimate the impact on nuclear electricity production cost. Prior experience with steel cladding is combined with the current understanding of the mechanical properties and irradiation behavior of advanced iron alloys to identify a combination of cladding thickness reduction and fuel enrichment increase (?0.5%) as an efficient route to offset any penalties in cycle length, due to higher neutron absorption in the iron alloy cladding, with modest impact on the economics.

Terrani, K. A.; Zinkle, S. J.; Snead, L. L.

2014-05-01

351

Iron Oxidation and Precipitation of Ferric Hydroxysulfates by Resting Thiobacillus ferrooxidans Cells.  

PubMed

The oxidation of ferrous ions, in acid solution, by resting suspensions of Thiobacillus ferrooxidans produced sediments consisting of crystalline jarosites, amorphous ferric hydroxysulfates, or both. These products differed conspicuously in chemical composition and infrared spectra from precipitates formed by abiotic oxidation under similar conditions. The amorphous sediments, produced by bacterial oxidation, exhibited a distinctive fibroporous microstructure when examined by scanning electron microscopy. Infrared spectra indicated outer-sphere coordination of Fe(III) by sulfate ions, as well as inner-sphere coordination by water molecules and bridging hydroxo groups. In the presence of excess sulfate and appropriate monovalent cations, jarosites, instead of amorphous ferric hydroxysulfates, precipitated from bacterially oxidized iron solutions. It is proposed that the jarositic precipitates result from the conversion of outer-sphere (T(d)) sulfate, present in a soluble polymeric Fe(III) complex, to inner-sphere (C(3v)) bridging sulfate. The amorphous precipitates result from the further polymerization of hydroxo-linked iron octahedra and charge stabilized aggregation of the resulting iron complexes in solution. This view was supported by observations that bacterially oxidized iron solutions gave rise to either amorphous or jarositic sediments in response to ionic environments imposed after oxidation had been completed and the bacteria had been removed by filtration. PMID:16345996

Lazaroff, N; Sigal, W; Wasserman, A

1982-04-01

352

Iron Oxidation and Precipitation of Ferric Hydroxysulfates by Resting Thiobacillus ferrooxidans Cells  

PubMed Central

The oxidation of ferrous ions, in acid solution, by resting suspensions of Thiobacillus ferrooxidans produced sediments consisting of crystalline jarosites, amorphous ferric hydroxysulfates, or both. These products differed conspicuously in chemical composition and infrared spectra from precipitates formed by abiotic oxidation under similar conditions. The amorphous sediments, produced by bacterial oxidation, exhibited a distinctive fibroporous microstructure when examined by scanning electron microscopy. Infrared spectra indicated outer-sphere coordination of Fe(III) by sulfate ions, as well as inner-sphere coordination by water molecules and bridging hydroxo groups. In the presence of excess sulfate and appropriate monovalent cations, jarosites, instead of amorphous ferric hydroxysulfates, precipitated from bacterially oxidized iron solutions. It is proposed that the jarositic precipitates result from the conversion of outer-sphere (Td) sulfate, present in a soluble polymeric Fe(III) complex, to inner-sphere (C3v) bridging sulfate. The amorphous precipitates result from the further polymerization of hydroxo-linked iron octahedra and charge stabilized aggregation of the resulting iron complexes in solution. This view was supported by observations that bacterially oxidized iron solutions gave rise to either amorphous or jarositic sediments in response to ionic environments imposed after oxidation had been completed and the bacteria had been removed by filtration. Images PMID:16345996

Lazaroff, Norman; Sigal, Warren; Wasserman, Andrew

1982-01-01

353

Iron oxide shell as the oxidation-resistant layer in SmCo5 @ Fe2O3 core-shell magnetic nanoparticles.  

PubMed

This paper presents a synthesis of magnetic nanoparticles of samarium cobalt alloys and the use of iron oxide as a coating layer to prevent the rapid oxidation of as-made Sm-Co nanoparticles. The colloidal nanoparticles of Sm-Co alloys were made in octyl ether using samarium acetylacetonate and dicobalt octacarbonyl as precursors in a mixture of 1,2-hexadecanediol, oleic acid, and trioctylphosphine oxide (TOPO). Such Sm-Co nanoparticle could be readily oxidized by air and formed a CoO antiferromagnetic layer. Exchange biasing was observed for the surface oxidized nanoparticles. In situ thermal decomposition of iron pentacarbonyl was used to create iron oxide shells on the Sm-Co nanoparticles. The iron oxide shell could prevent Sm-Co nanoparticles from rapid oxidation upon the exposure to air at ambient conditions. PMID:17455504

Teng, Xiaowei; Yang, Hong

2007-01-01

354

Iron oxide nanoparticles as drug delivery agents in MIA PaCa-2 pancreatic cells  

NASA Astrophysics Data System (ADS)

Oleic acid (OA)-Pluronic-coated iron oxide nanoparticles were synthesized and characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and Atomic Force Microscopy (AFM). FT-IR confirmed the bonding of oleic acid and Pluronic (surfactant) to the nanoparticles. AFM measurements on these nanoparticles indicated a root mean square (RMS) roughness, a measure of nanoparticle size of (50 +/- 20) nm. The efficiency of these functionalized nanoparticles was investigated by loading with 5-Fluorouracil (5-FU) in aqueous solution. AFM measurements were used to characterize modified iron oxide nanoparticles and pancreatic MIA PaCa-2 cells, including size distribution, stability and cellular uptake. Nanoparticles were added to MIA PaCa-2 cells and assayed for their cytotoxic effects after 24 and 48 hours. The outcome of this study demonstrated the effectiveness of oleic acid (OA)-Pluronic-coated iron oxide nanoparticles as a non-toxic drug delivery agent for pancreatic cancer.

Perry, Christopher; Randriamahefa, Alexandrine; Lokko, Carl; Evans, Whitney; Watkins, Julian; Carrell, Holly; King, Natalie; Patel, Darayas

2007-02-01

355

In situ functionalization and PEO coating of iron oxide nanocrystals using seeded emulsion polymerization.  

PubMed

Herein we demonstrate that seeded emulsion polymerization is a powerful tool to produce multiply functionalized PEO coated iron oxide nanocrystals. Advantageously, by simple addition of functional surfactants, functional monomers, or functional polymerizable linkers-solely or in combinations thereof-during the seeded emulsion polymerization process, a broad range of in situ functionalized polymer-coated iron oxide nanocrystals were obtained. This was demonstrated by purposeful modulation of the zeta potential of encapsulated iron oxide nanocrystals and conjugation of a dyestuff. Successful functionalization was unequivocally proven by TXRF. Furthermore, the spatial position of the functional groups can be controlled by choosing the appropriate spacers. In conclusion, this methodology is highly amenable for combinatorial strategies and will spur rapid expedited synthesis and purposeful optimization of a broad scope of nanocrystals. PMID:23530830

Kloust, Hauke; Schmidtke, Christian; Feld, Artur; Schotten, Theo; Eggers, Robin; Fittschen, Ursula E A; Schulz, Florian; Pöselt, Elmar; Ostermann, Johannes; Bastús, Neus G; Weller, Horst

2013-04-16

356

The Possible Side-Effects Of Iron Oxide Nanoparticles On Cell Functionality  

NASA Astrophysics Data System (ADS)

Iron oxide nanoparticles (NPs) are routinely used in biomedical applications, most commonly as magnetic resonance imaging (MRI) contrast agents. A wide variety of different NPs are currently being used for in vitro cell labeling in order to render these cells detectable for MRI upon transplantation. The effect of these particles on cell physiology is being made difficult by the wide varieties in cell labeling protocols, cell lines and NP types. Herein, the effects of a single type of iron oxide NPs, being magnetoliposomes (MLs), i.e. iron oxide nanocores each individually surrounded by a lipid bilayer, are described. It is shown that the incorporation of cationic lipids increases cellular uptake, with the risk of augmented toxicity. Furthermore, it is observed that high intracellular levels of fully biocompatible MLs affect cellular cytoskeleton and cell signaling. These data indicate the great need for thorough analysis of cell-NP interactions as several effects are transient and not easily studied using standard protocols.

Soenen, Stefaan J. H.; Nuytten, Nele; Himmelreich, Uwe; De Cuyper, Marcel

2010-10-01

357

2476 Biochemistry 1994, 33, 2476-2483 Molecular Structure of the Oxidized High-Potential Iron-Sulfur Protein Isolated  

E-print Network

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

Rayment, Ivan

358

Exposure to nitric oxide protects against oxidative damage but increases the labile iron pool in sorghum embryonic axes  

Microsoft Academic Search

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

Sebastian Jasid; Marcela Simontacchi; Susana Puntarulo

2008-01-01

359

Iron oxide nanoparticles stabilized with dendritic polyglycerols as selective MRI contrast agents.  

PubMed

Monodisperse small iron oxide nanoparticles functionalized with dendritic polyglycerol (dPG) or dendritic polyglycerol sulfate (dPGS) are prepared. They are highly stable in aqueous solutions as well as physiological media. In particular, oleic acid capped iron oxide particles (core diameter = 11 ± 1 nm) were modified by a ligand exchange process in a one pot synthesis with dPG and dPGS bearing phosphonate as anchor groups. Dynamic light scattering measurements performed in water and different biological media demonstrate that the hydrodynamic diameter of the particles is only slightly increased by the ligand exchange process resulting in a final diameter of less than 30 nm and that the particles are stable in these media. It is also revealed by magnetic resonance studies that their magnetic relaxivity is reduced by the surface modification but it is still sufficient for high contrast magnetic resonance imaging (MRI). Additionally, incubation of dPGS functionalized iron oxide nanoparticles with human umbilical vein endothelial cells showed a 50% survival at 85 nM (concentration of nanoparticles). Surface plasmon resonance (SPR) studies demonstrate that the dPGS functionalized iron oxide nanoparticles inhibit L-selectin ligand binding whereas the particles containing only dPG do not show this effect. Experiments in a flow chamber with human myelogenous leukemia cells confirmed L-selectin inhibition of the dPGS functionalized iron oxide nanoparticles and with that the L-selectin mediated leukocyte adhesion. These results indicate that dPGS functionalized iron oxide nanoparticles are a promising contrast agent for inflamed tissue probed by MRI. PMID:24991655

Nordmeyer, Daniel; Stumpf, Patrick; Gröger, Dominic; Hofmann, Andreas; Enders, Sven; Riese, Sebastian B; Dernedde, Jens; Taupitz, Matthias; Rauch, Ursula; Haag, Rainer; Rühl, Eckart; Graf, Christina

2014-08-21

360

Iron  

MedlinePLUS

... several factors [ 1 , 3 , 8 , 11-15 ]. Storage levels of iron have the greatest influence on iron ... RDA), Adequate Intakes (AI), and Tolerable Upper Intake Levels (UL). The RDA recommends the average daily intake ...

361

Colloidal Stability and Monodispersible Magnetic Iron Oxide Nanoparticles in Biotechnology Application  

NASA Astrophysics Data System (ADS)

Magnetic iron oxide nanoparticles are promising material for various biological applications. In the recent decades, magnetic iron oxide nanoparticles (MNPs) have great attention in biomedical applications such as drug delivery, magnetic resonance imaging (MRI) and magnetic fluid hyperthermia (MFH). This review focuses on the colloidal stability and monodispersity properties of MNPs, which pay more attention toward biomedical applications. The simplest and the most promising method for the synthesis of MNPs is co-precipitation. The biocompatible MNPs are more interested in MRI application. This review also apportions synthesis, characterization and applications of MNP in biological and biomedical as theranostics and imaging.

Shamili, K.; Rajesh, E. M.; Rajendran, R.; Madhan Shankar, S. R.; Elango, M.; Abitha Devi, N.

2013-02-01

362

Synthesis of Polystyrene Nanowires Doped with Iron Oxide Nanoparticles Using a Pulsed Laser  

NASA Astrophysics Data System (ADS)

We have developed a technique to synthesize polystyrene (PS) nanowires doped with iron oxide nanoparticles (nanoFeO) by sub-nanosecond pulsed laser irradiation. Scanning electron microscopy (SEM) images of the polymer nanowires with uniform diameters were obtained. The structure of the nanoFeO-PS nanowires was analyzed by scanning transmission electron microscopy (STEM) and energy-dispersive X-ray analysis (EDX). The polymer nanowires grew perpendicular to the surface of the source film, which contained iron oxide nanoparticles and dye molecules as a photoabsorber.

Sasaki, Michiko; Goto, Masahiro; Kasahara, Akira; Tosa, Masahiro; Chikyow, Toyohiro

2013-04-01

363

Development of an intelligent control system for ferrous iron oxidation by Thiobacillus ferrooxidans  

SciTech Connect

An intelligent control system (ICS) is being developed for ferrous iron oxidation by Thiobacillus ferroxidans. The ICS provides compterized data acquisition and control of process variables (temperature, Eh, pH, dissolved oxygen and carbon dioxide concentrations, and dilution rate) to maintain the ferrous iron oxidation at the highest possible rate. The ICS uses fuzzy logic for analysis of data inputs and implementation of control strategies. This paper provides preliminary information on the development of the ICS and its operation. 17 refs., 3 figs.

Light, M.D.; Torma, A.E.; Cordes, G.A.

1991-01-01

364

High-valent iron in chemical and biological oxidations.  

PubMed

Various aspects of the reactivity of iron(IV) in chemical and biological systems are reviewed. Accumulated evidence shows that the ferryl species [Fe(IV)O](2+) can be formed under a variety of conditions including those related to the ferrous ion-hydrogen peroxide system known as Fenton's reagent. Early evidence that such a species could hydroxylate typical aliphatic C-H bonds included regioselectivities and stereospecificities for cyclohexanol hydroxylation that could not be accounted for by a freely diffusing hydroxyl radical. Iron(IV) porphyrin complexes are also found in the catalytic cycles of cytochrome P450 and chloroperoxidase. Model oxo-iron(IV) porphyrin complexes have shown reactivity similar to the proposed enzymatic intermediates. Mechanistic studies using mechanistically diagnostic substrates have implicated a radical rebound scenario for aliphatic hydroxylation by cytochrome P450. Likewise, several non-heme diiron hydroxylases, AlkB (Omega-hydroxylase), sMMO (soluble methane monooxygenase), XylM (xylene monooxygenase) and T4moH (toluene monooxygenase) all show clear indications of radical rearranged products indicating that the oxygen rebound pathway is a ubiquitous mechanism for hydrocarbon oxygenation by both heme and non-heme iron enzymes. PMID:16516297

Groves, John T

2006-04-01

365

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...

366

Microwave-assisted combustion synthesis of nano iron oxide/iron-coated activated carbon, anthracite, cellulose fiber, and silica, with arsenic adsorption studies  

EPA Science Inventory

Combustion synthesis of iron oxide/iron coated carbons such as activated carbon, anthracite, cellulose fiber and silica is described. The reactions were carried out in alumina crucibles using a Panasonic kitchen microwave with inverter technology, and the reaction process was com...

367

Catechol-functionalized chitosan/iron oxide nanoparticle composite inspired by mussel thread coating and squid beak interfacial chemistry.  

PubMed

Biological materials offer a wide range of multifunctional and structural properties that are currently not achieved in synthetic materials. Herein we report on the synthesis and preparation of bioinspired organic/inorganic composites that mimic the key physicochemical features associated with the mechanical strengthening of both squid beaks and mussel thread coatings using chitosan as an initial template. While chitosan is a well-known biocompatible material, it suffers from key drawbacks that have limited its usage in a wider range of structural biomedical applications. First, its load-bearing capability in hydrated conditions remains poor, and second it completely dissolves at pH < 6, preventing its use in mild acidic microenvironments. In order to overcome these intrinsic limitations, a chitosan-based organic/inorganic biocomposite is prepared that mimics the interfacial chemistry of squid beaks and mussel thread coating. Chitosan was functionalized with catechol moieties in a highly controlled fashion and combined with superparamagnetic iron oxide (?-Fe2O3) nanoparticles to give composites that represent a significant improvement in functionality of chitosan-based biomaterials. The inorganic/organic (?-Fe2O3/catechol) interfaces are stabilized and strengthened by coordination bonding, resulting in hybrid composites with improved stability at high temperatures, physiological pH conditions, and acid/base conditions. The inclusion of superparamagnetic particles also makes the composites stimuli-responsive. PMID:23865752

Zvarec, Ondrej; Purushotham, Sreekanth; Masic, Admir; Ramanujan, Raju V; Miserez, Ali

2013-08-27

368

Sorption of ferric iron from ferrioxamine B to synthetic and biogenic layer type manganese oxides  

NASA Astrophysics Data System (ADS)

Siderophores are biogenic chelating agents produced in terrestrial and marine environments that increase the bioavailability of ferric iron. Recent work has suggested that both aqueous and solid-phase Mn(III) may affect siderophore-mediated iron transport, but scant information appears to be available about the potential roles of layer type manganese oxides, which are relatively abundant in soils and the oligotrophic marine water column. To probe the effects of layer type manganese oxides on the stability of aqueous Fe-siderophore complexes, we studied the sorption of ferrioxamine B [Fe(III)HDFOB +, an Fe(III) chelate of the trihydroxamate siderophore desferrioxamine B (DFOB)] to two synthetic birnessites [layer type Mn(III,IV) oxides] and a biogenic birnessite produced by Pseudomonas putida GB-1. We found that all of these predominantly Mn(IV) oxides greatly reduced the aqueous concentration of Fe(III)HDFOB + at pH 8. Analysis of Fe K-edge EXAFS spectra indicated that a dominant fraction of Fe(III) associated with the Mn(IV) oxides is not complexed by DFOB as in solution, but instead Fe(III) is specifically adsorbed to the mineral structure at multiple sites, thus indicating that the Mn(IV) oxides displaced Fe(III) from the siderophore complex. These results indicate that layer type manganese oxides, including biogenic minerals, may sequester iron from soluble ferric complexes. We conclude that the sorption of iron-siderophore complexes may play a significant role in the bioavailability and biogeochemical cycling of iron in marine and terrestrial environments.

Duckworth, Owen W.; Bargar, John R.; Sposito, Garrison

2008-07-01

369

Trace element cycling through iron oxide minerals during redox-driven dynamic recrystallization  

SciTech Connect

Microbially driven iron redox cycling in soil and sedimentary systems, including during diagenesis and fluid migration, may activate secondary abiotic reactions between aqueous Fe(II) and solid Fe(III) oxides. These reactions catalyze dynamic recrystallization of iron oxide minerals through localized and simultaneous oxidative adsorption of Fe(II) and reductive dissolution of Fe(III). Redox-active trace elements undergo speciation changes during this process, but the impact redox-driven recrystallization has on redox-inactive trace elements associated with iron oxides is uncertain. Here we demonstrate that Ni is cycled through the minerals goethite and hematite during redox-driven recrystallization. X-ray absorption spectroscopy demonstrates that during this process adsorbed Ni becomes progressively incorporated into the minerals. Kinetic studies using batch reactors containing aqueous Fe(II) and Ni preincorporated into iron oxides display substantial release of Ni to solution. We conclude that iron oxide recrystallization activated by aqueous Fe(II) induces cycling of Ni through the mineral structure, with adsorbed Ni overgrown in regions of Fe(II) oxidative adsorption and incorporated Ni released in regions of reductive dissolution of structural Fe(III). The redistribution of Ni among the mineral bulk, mineral surface, and aqueous solution appears to be thermodynamically controlled and catalyzed by Fe(II). Our work suggests that important proxies for ocean composition on the early Earth may be invalid, identifies new processes controlling micronutrient availability in soil, sedimentary, and aquatic ecosystems, and points toward a mechanism for trace element mobilization during diagenesis and enrichment in geologic fluids.

Frierdich, Andrew J.; Luo, Yun; Catalano, Jeffrey G. (WU)

2011-11-17

370

Fossilization of Iron-Oxidizing Bacteria at Hydrothermal Vents: a Useful Biosignature on Mars?  

NASA Astrophysics Data System (ADS)

Iron oxidizing bacteria are ubiquitous in marine and terrestrial environments on Earth, where they often display distinctive cell morphologies and are commonly encrusted by minerals, especially bacteriogenic iron oxides and silica. Putative microfossils of iron oxidizing bacteria have been found in jaspers as old as 490Ma and microbial iron oxidation may be an ancient metabolic pathway. In order to investigate the usefulness of mineralized iron oxidizing bacteria as a biosignature, we have examined mineral samples collected from relict hydrothermal systems along Explorer Ridge, NE Pacific Ocean. In addition, microaerophilic, neutrophilic iron oxidizing bacteria, isolated from Pacific hydrothermal vents, were grown in a Fe-enriched seawater medium at constant pH (6.5) and oxygen concentration (5 percent) in a controlled bioreactor system. Both natural samples and experimental products were examined with a combination of variable pressure scanning electron microscopy (SEM), field emission gun SEM, and in some cases by preparing samples with a focused ion beam (FIB) milling system. Natural seafloor samples display abundant filamentous forms often resembling, in both size and shape, the twisted stalks of Gallionella and the elongated filaments of Leptothrix. Generally, these filamentous features are 1-5 microns in diameter and up to several microns in length. Some samples consist entirely of low- density, porous masses of silica encrusted filamentous forms. Presumably, these masses were formed by a rapid precipitation by the influx of silica-rich fluids into a microbial mat dominated by bacteria with filamentous morphologies. The presence of rare, amorphous (unmineralized) filamentous matter rich in C and Fe suggests that these bacteria were iron oxidizers. There is no evidence that sulfur oxidizers were present. Filamentous features sectioned by FIB milling show internal material within semi-hollow tubular-like features. Silica encrustations also show pseudo-concentric growth bands. In the bioreactor cultures, constant conditions led to abundant microbial growth and formation of an iron oxyhydroxide precipitate, either in direct association with the cells or within the growth medium. This suggests that not all of the iron precipitation is biogenic in origin. Cells typically show a filamentous morphology reminiscent of the mineral-encrusted forms observed in the natural samples. Continuing work includes high-resolution TEM observations of cultured organisms, examination of 2-year long in situ seafloor incubation experiments, and bioreactor silicification experiments in order to better understand the roles of iron and silica in the 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 abiotically, as proposed for the subsurface of the Fe-dominated Rio Tinto (Spain) basin system. By analogy, similar subsurface or near-surface microaerophilic environments could have existed on Mars in the past. The distinctive morphologies and mineralization patterns of iron oxidizing bacteria could be a useful biosignature to search for on Mars. Deposits and biogenic features similar to those described here could theoretically be identified on Mars with existing imaging and analytical technologies. Therefore, future missions to Mars should target ancient hydrothermal systems, some of which have been putatively identified already.

Leveille, R. J.; Lui, S.

2009-05-01

371

Neutral metal cluster formation and oxidation reactions in the photolysis of iron carbonyl van der Waals complexes  

SciTech Connect

Iron pentacarbonyl van der Waals complexes and mixed complexes containing iron pentacarbonyl and oxygen, carbon dioxide, or water are produced in pulsed supersonic expansions and probed with ultraviolet multiphoton ionization time-of-flight mass spectroscopy. Photochemical rearrangement and oxidation reactions occur within these complexes prior to photoionization, resulting in the formation of neutral iron clusters, iron cluster carbonyls, and iron cluster monoxides. Two laser time-delayed experiments, as well as excimer laser wavelength and power dependences, are used to probe the mechanism of this fascinating photoinduced chemistry, which occurs in cluster species containing 1-25 iron atoms.

Wheeler, R.G.; Duncan, M.A.

1986-08-14

372

Association of trace elements with iron oxides during rock weathering  

SciTech Connect

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.

Koons, R.D.; Helmke, P.A.; Jackson, M.L.

1980-01-01

373

Iron oxide coatings on sand grains from the Atlantic coastal plain: High-resolution transmission electron microscopy characterization  

Microsoft Academic Search

Nanoscale characterization of so-called iron oxide coatings on aquifer sands is vital for understanding the fate and transport of naturally occurring and anthropogenic chemical species. These coatings, which typically have a strong reddish color, are commonly assumed to consist primarily of iron oxides and oxyhydroxides. This work shows that the yellowish red to strong brown coatings on sediments from an

R. L. Penn; C. Zhu; H. Xu; D. R. Veblen

2001-01-01

374

Efficient recovery of nano-sized iron oxide particles from synthetic acid-mine drainage (AMD) water using fuel cell  

E-print Network

Efficient recovery of nano-sized iron oxide particles from synthetic acid-mine drainage (AMD) water 2010 Keywords: AMD Energy Iron oxide Microbial fuel cell Particles a b s t r a c t Acid mine drainage rights reserved. 1. Introduction Acid-mine drainage (AMD) and acid rock drainage (ARD) are caused

375

Aqueous pyrite oxidation by dissolved oxygen and by ferric iron  

Microsoft Academic Search

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

C. O. Moses; D. K. Nordstrom; J. S. Herman; A. L. Mills

1987-01-01

376

Low-temperature iron-modified cobalt oxide system  

Microsoft Academic Search

Liquid-phase oxidation using a solid catalyst provides a potential method for removal of dissolved toxic organic pollutants from waste waters. Low-temperature heterogeneous oxidation of phenol on a cobalt oxide system modified with Fe has been studied. The conversion of phenol into nontoxic compounds occurs in air-equilibrated aqueous media. The major hydroxylated aromatic intermediates have been identified by UV–VIS spectroscopy and

M. Stoyanova; M. Georgieva

2001-01-01

377

Characterization of biogenic iron oxides collected by the newly designed liquid culture method using diffusion chambers.  

PubMed

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

Kikuchi, S; Makita, H; Takai, K; Yamaguchi, N; Takahashi, Y

2014-03-01

378

Uranium–lead ages of apatite from iron oxide ores of the Bafq District, East-Central Iran  

Microsoft Academic Search

Iron oxide–apatite (IOA) deposits, often referred to as Kiruna-type iron ore deposits, are known to have formed from the Proterozoic\\u000a to the Tertiary. They are commonly associated with calc–alkaline volcanic rocks and regional- to deposit-scale metasomatic\\u000a alteration. In the Bafq District in east Central Iran, economic iron oxide–apatite deposits occur within felsic volcanic tuffs\\u000a and volcanosedimentary sequences of Early Cambrian

Heinz-Günter Stosch; Rolf L. Romer; Farahnaz Daliran; Dieter Rhede

2011-01-01

379

L-edge XANES measurements of the oxidation state of tungsten in iron bearing and iron free silicate glasses  

SciTech Connect

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.

Danielson, L.R.; Righter, K.; Sutton, S.; Newville, M.; Le, L. (Jacobs Sverdrup Corp); (UofC); (NASA)

2008-04-28

380

Ab initio molecular dynamics study of manganese porphine hydration and interaction with nitric oxide  

E-print Network

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.

Kevin Leung; Craig J. Medforth

2007-01-23

381

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)

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.

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

2014-07-01

382

Oxidative stress and dermal toxicity of iron oxide nanoparticles in vitro.  

PubMed

A number of commercially available metal/metal oxide nanoparticles (NPs) such as superparamagnetic iron oxide (SPION) are utilized by the medical field for a wide variety of applications. These NPs may able to induce dermal toxicity via their physical nature and reactive surface properties. We hypothesize that SPION may be toxic to skin via the ability of particles to be internalized and thereby initiate oxidative stress, inducing redox-sensitive transcription factors affecting/leading to inflammation. Due to the skin's susceptibility to UV radiation, it is also of importance to address the combined effect of UVB and NPs co-exposure. To test this hypothesis, the effects of dextran-coated SPION of different sizes (15-50 nm) and manufacturers (MicroMod, Rostock-Warnemunde, Germany and KTH-Royal Institute of Technology, Stockholm, Sweden) were evaluated in two cell lines: normal human epidermal keratinocytes (HEK) and murine epidermal cells (JB6 P(+)). HEK cells exposed to 20 nm (KTH and MicroMod) had a decrease in viability, while the 15 and 50 nm particles were not cytotoxic. HEK cells were also capable of internalizing the KTH particles (15 and 20 nm) but not the MicroMod SPION (20 and 50 nm). IL-8 and IL-6 were also elevated in HEK cells following exposure to SPION. Exposure of JB6 P(+) cells to all SPIONs evaluated resulted in activation of AP-1. Exposure to SPION alone was not sufficient to induce NF-?B activation; however, co-exposure with UVB resulted in significant NF-?B induction in cells exposed to 15 and 20 nm KTH SPION and 50 nm MicroMod particles. Pre-exposure of JB6 P(+) cells to UVB followed by NPs induced a significant depletion of glutathione, release of cytokines, and cell damage as assessed by release of lactate dehydrogenase. Altogether, these data indicate that co-exposure to UVB and SPIONs was associated with induction of oxidative stress and release of inflammatory mediators. These results verify the need to thoroughly evaluate the adverse effects of UVB when evaluating dermal toxicity of engineered NPs on skin. PMID:22669739

Murray, Ashley R; Kisin, Elena; Inman, Alfred; Young, Shih-Houng; Muhammed, Mamoun; Burks, Terrance; Uheida, Abdusalam; Tkach, Alexey; Waltz, Micah; Castranova, Vincent; Fadeel, Bengt; Kagan, Valerian E; Riviere, Jim E; Monteiro-Riviere, Nancy; Shvedova, Anna A

2013-11-01

383

Iron Oxide and Sulfide Nanocrystals as Biomarkers P.R. Buseck,* M. Psfai,** R.E. Dunin-Borkowski, *** and M. Weyland ***  

E-print Network

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

Dunin-Borkowski, Rafal E.

384

Gas Hydrates  

Microsoft Academic Search

This review states contemporary views about gas hydrates, and also about non-stoichiometric clathrates with the general formula M·nH2O. The known types of the hydrates and their crystal structure are described. The thermodynamics of hydrate formation is considered. Methods of determining the composition of the hydrates are described. Factual information concerning the hydrates of individual gases and organic liquids and mixed

S. Sh Byk; V. I. Fomina

1968-01-01

385

Kinetics of the reduction of the zinc oxide in zinc ferrite with iron  

SciTech Connect

Electric arc furnace (EAF) dust, which can be considered as a by-product of the steel recycling process, contains significant quantities of recoverable zinc and iron, as well as hazardous elements such as cadmium, lead and chromium, which can be leached by ground water. The zinc in the EAF dust is found almost entirely in the form of either zinc oxide or zinc ferrite, the latter accounting for 20 to 50 percent of the total zinc. It is important that an efficient process be developed which renders the dust inert, while reclaiming the valuable metals to off-set processing costs. During the conventional carbothermic reduction processes, iron is formed, and this iron can participate in the reduction of the zinc oxide in zinc ferrite. In the present work, the reduction of the zinc oxide in zinc ferrite by iron according to the following reaction: ZnO{sup {sm_bullet}}Fe{sub 2}O{sub (s.s.)} + 2 Fe{sub (s)} = Zn{sub (g)} + 4 FeO{sub (s)} was studied in an argon atmosphere using a thermogravimetric technique. First, a thermodynamic analysis was performed using the F*A*C*T computational system. Then, the effects of briquette aspect ratio (l/d), temperature, zinc ferrite particle size, amount of iron added, as well as additions such as lime, sodium chloride, and calcium fluoride were investigated.

Donald, J.R.; Pickles, C.A. [Queen`s Univ., Kingston, Ontario (Canada). Dept. of Materials and Metallurgical Engineering

1995-12-31

386

Iron oxidation in different types of groundwater of Western Siberia  

Microsoft Academic Search

Background, aim, and scope  The groundwaters of Western Siberia contain high concentrations of iron, manganese, silicon, ammonium, and, in several cases,\\u000a hydrogen sulfide, carbonic acids, and dissolved organic substances. Generally, the groundwaters of Western Siberia can be\\u000a divided into two major types: one type with a relatively low concentration of humic substances and high hardness (water of\\u000a A type) and a

Leonid V. Serikov; Elena A. Tropina; Liudmila N. Shiyan; Fritz H. Frimmel; George Metreveli; Markus Delay

2009-01-01

387

Sorption of Ferric Iron from Ferrioxamine B to Synthetic and Biogenic Layer Type Manganese Oxides  

NASA Astrophysics Data System (ADS)

Siderophores are biogenic chelating agents produced in terrestrial and marine environments to increase the bioavailablity of ferric iron. Recent work has suggested that both aqueous and solid-phase Mn(III) may affect siderophore-mediated iron transport, but no information appears to be available about the effect of solid-phase Mn(IV). To probe the effects of predominantly Mn(IV) oxides, we studied the sorption reaction of ferrioxamine B [Fe(III)HDFOB+, an Fe(III) chelate of the trihydroxamate siderophore desferrioxamine B (DFOB)] with two synthetic birnessites [layer type Mn(III, IV) oxides] and a biogenic birnessite produced by Pseudomonas putida MnB1. We found that all of these predominantly Mn(IV) oxides greatly reduced the aqueous concentration of Fe(III)HDFOB+ over at pH 8. After 72 hours equilibration time, the sorption behavior for the synthetic birnessites could be accurately described by a Langmuir isotherm; for the biogenic oxide, a Freundlich isotherm was best utilized to model the sorption data. To study the molecular nature of the interaction between the Fe(III)HDFOB+ complex and the oxide surface, Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy was employed. Analysis of the EXAFS spectra indicated that Fe(III) associated with the Mn(IV) oxides is not complexed by DFOB as in solution, but instead Fe(III) is specifically adsorbed to into the mineral structure at multiple sites with no evidence of DFOB complexation, thus indicating that the Mn(IV) oxides displaced Fe(III) from the siderophore complex. These results indicate that manganese oxides, including biominerals, may strongly sequester iron from soluble ferric complexes and thus may play a significant role in the biogeochemical cycling of iron in marine and terrestrial environments.

Duckworth, O.; John, B.; Sposito, G.

2006-12-01

388

Iron-containing heterogeneous catalysts for partial oxidation of methane and epoxidation of propylene  

Microsoft Academic Search

Mesoporous molecular sieves containing iron sites with different dispersions and environments were studied for the partial oxidation of methane and the epoxidation of propylene. The tetrahedral Fe(III) sites incorporated inside the framework of SBA-15 showed higher HCHO selectivity under a similar CH4 conversion than the oligomeric FeOx clusters located in the mesopores in the partial oxidation of CH4 by O2.

Ye Wang; Wei Yang; Lüjuan Yang; Xiaoxing Wang; Qinghong Zhang

2006-01-01

389

Biomineralogy and Morphology of the Marine Iron-oxidizing Bacterium Mariprofundus ferrooxydans  

NASA Astrophysics Data System (ADS)

Mariprofundus ferrooxydans strain PV-1 is a lithoautotrophic iron-oxidizing proteobacterium isolated from the Loihi Seamount in Hawaii. As cells grow, they form filaments upon which iron minerals are deposited. Based on similarities in morphology, these structures appear to accumulate and form the bulk of iron mats at Loihi. Furthermore, Mariprofundus has been observed in a number of other seafloor mat samples (e.g. by microscopy and 16S rRNA gene sequencing of East Pacific Rise samples, C. M. Santelli unpublished data), suggesting that the occurrence of Mariprofundus is widespread. To learn about the effect of Mariprofundus on iron cycling, we are studying the processes by which it oxidizes iron and influences iron mineral formation. We are conducting studies on the spatial relationships between the cells, stalks, and minerals using scanning and transmission electron microscopy (SEM and TEM). Identification and imaging of stalk-bound, nanometer-sized iron oxyhydroxide minerals is being performed by high-resolution transmission electron microscopy (HRTEM). We have developed sample preparation methods to preserve in vivo spatial relationships, involving direct colonization of sample holders in cultures and in the environment. Method development has been performed on stalk-forming, iron-oxidizing Gallionella ferruginea cultures and terrestrial iron mats. Gallionella is morphologically and physiologically very similar to Mariprofundus, although 16S rRNA gene phylogeny shows that they are not closely related. Comparison of the terrestrial and marine iron-oxidizing bacteria (FeOB) gives us insight into adaptations that are particular to marine iron-oxidizers and those that are common to all FeOB. Light and fluorescence microscopy of Mariprofundus cultures has shown that a single bean-shaped cell lies at the end of each filament. SEM and TEM results have revealed that the filament is ribbon-like, sometimes twisted as with the classic Gallionella stalk, but sometimes not. Filaments formed in culture have been measured at 0.5 and 1.7 microns in width and as long as 70 microns. They are composed of a varying number of parallel subfilaments, each approximately 70 nm in width. HRTEM observations show that lightly-mineralized filaments are covered in nanometer-size, poorly crystalline, and possibly amorphous iron oxyhydroxides, which likely represent an early stage in filament mineralization. Highly-mineralized filaments are coated in lepidocrocite and akaganeite (both iron oxyhydroxides), in random crystallographic orientations. The more crystalline minerals probably result from recrystallization of the initially-deposited FeOOH and continued precipitation on the filament. We will revisit Loihi in October to collect fresh, undisturbed samples for electron microscopy, in order to compare cultured and natural samples. This work is being performed in conjunction with genomic and protein analyses aimed at identifying the genes involved in iron oxidation.

Chan, C. S.; Emerson, D.; Edwards, K. J.

2006-12-01

390

Infrared nanosecond pulsed laser irradiation of stainless steel: Micro iron-oxide zones generation  

NASA Astrophysics Data System (ADS)

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.

Ortiz-Morales, M.; Frausto-Reyes, C.; Soto-Bernal, J. J.; Acosta-Ortiz, S. E.; Gonzalez-Mota, R.; Rosales-Candelas, I.

2014-07-01

391

Superparamagnetic iron oxide nanoparticles impair endothelial integrity and inhibit nitric oxide production.  

PubMed

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

Astanina, Ksenia; Simon, Yvette; Cavelius, Christian; Petry, Sandra; Kraegeloh, Annette; Kiemer, Alexandra K

2014-11-01

392

Effect of iron doped lead oxide on the performance of lead acid batteries  

NASA Astrophysics Data System (ADS)

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.

Liu, Jianwen; Yang, Danni; Gao, Linxia; Zhu, Xinfeng; Li, Lei; Yang, Jiakuan

2011-10-01

393

Unraveling the origins of catalyst degradation in non-heme iron-based alkane oxidation.  

PubMed

A series of potentially tetradentate and pentadentate ligands modelled on BPMEN has been prepared and their iron(ii) bis(triflate) complexes have been isolated and characterised by spectroscopic and crystallographic techniques (BPMEN = N,N'-bis(pyridylmethyl)ethylenediamine). Changes to the BPMEN ligand have invariably led to complexes with different coordination modes or geometries and with inferior catalytic efficiencies for the oxidation of cyclohexane with H2O2. The reaction of an iron(ii) complex containing a pentadentate BPMEN-type ligand with O2 has resulted in ligand degradation via oxidative N-dealkylation and the isolation of a bis(hydroxo)-bridged dinuclear iron(iii) complex with a picolinate-type ligand. PMID:25310594

Grau, Michaela; Kyriacou, Andrew; Cabedo Martinez, Fernando; de Wispelaere, Irene M; White, Andrew J P; Britovsek, George J P

2014-10-28

394

Preparation of iron oxide nanoparticles from FeCl3 solid powder using microemulsions  

NASA Astrophysics Data System (ADS)

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.

Nassar, Nashaat; Husein, Maen

2006-05-01

395

Nitrite induces the extravasation of iron oxide nanoparticles in hypoxic tumor tissue.  

PubMed

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

Mistry, Nilesh; Stokes, Ashley M; Gambrell, James Van; Quarles, Christopher Chad

2014-04-01

396

Oxidative stress induced by iron in Hydrilla verticillata (l.f.) Royle: response of antioxidants.  

PubMed

The effect of iron (FeCl3) on chlorophyll content, lipid peroxidation product, potassium ion leakage (a measure of damage to the permeability barrier), and antioxidants was studied in Hydrilla verticillata. The effect of iron-induced damage to the plant was compared with those of N-ethyl maleimide (NEM), a sulfhydryl reagent, and cumene hydroperoxide (CHP), an organic peroxide known to induce lipid peroxidation by free radical formation. The level of lipid peroxidation product was increased in the plants treated with Fe, CHP, and CHP + NEM but not with NEM alone. A significant increase in potassium ion leakage to the external solution was observed by the addition of Fe, CHP, and CHP + NEM, while this did not increase significantly in NEM-treated plants. When NEM and CHP were added simultaneously, the results were the same as those obtained with high iron concentrations, suggesting a combined effect of thiol depletion and lipid peroxidation by Fe ions. In addition, the results indicated loss of glutathione (GSH) and increased oxidized glutathione (GSSG) under Fe stress, indicative of oxidative stress. The oxidative stress may increase the production of free radicals and subsequently resulted in peroxidation of lipids. Further, addition of iron increased the activity of superoxide dismutase (SOD) which may be due to enhanced production of oxygen free radical and related tissue damage. The results suggest that iron-induced damage in plants can be ascribed to a direct metal action on thiols and by toxic oxygen species. An increase in lipid peroxidation product and K+ leakage are the primary responses of iron toxicity on membrane damage. However, the decrease in chlorophyll content is part of the overall expression of iron toxicity. PMID:9469882

Sinha, S; Gupta, M; Chandra, P

1997-12-01

397

Understanding oxygen vacancy migration and clustering in barium strontiumcobalt iron oxide  

Microsoft Academic Search

In order to understand vacancy clustering and phase stability in oxygen-deficient barium strontium cobalt iron oxide (BSCF), we predict stability and activation energies for oxygen vacancy migration with plane wave Density Functional Theory. Using symmetry constrained search and Nudged Elastic Band method, we characterize the transition states for an oxygen anion moving into a nearby oxygen vacancy site that is

Shruba Ganopadhyay; Artëm E. Masunov; Talgat Inerbaev; Jaruwan Mesit; Ratan K. Guha; Ahmad K. Sleiti; Jay S. Kapat

2010-01-01

398

Kinetics of manganese oxide reduction from basic slags by carbon dissolved in liquid iron  

Microsoft Academic Search

The reduction of manganese oxide from a basic slag by carbon dissolved in liquid iron is a slow reaction, failing to approach equilibrium closely in 20 hr. Furthermore, the rate of stirring has no apparent effect on the reaction rate. This identifies the rate-controlling step as a chemical reaction at the interface. Only the model for the reaction O 2-

Weldon L. Daines; Robert D. Pehlke

1971-01-01

399

SURFACE COMPLEXATION MODEL TO DESCRIBE COMPETITIVE ARSENIC ADSORPTION ONTO IRON OXIDES  

EPA Science Inventory

The output of this work would be a set of self-consistent model parameters that would describe the adsorption of arsenic onto iron oxides in the presence of other solutes. The model could be used to predict the potential for removal of arsenic from drinking water by adsorpt...

400

Antibacterial Efficacy of Iron-Oxide Nanoparticles against Biofilms on Different Biomaterial Surfaces.  

PubMed

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

Thukkaram, Monica; Sitaram, Soundarya; Kannaiyan, Sathish Kumar; Subbiahdoss, Guruprakash

2014-01-01

401

Antibacterial Efficacy of Iron-Oxide Nanoparticles against Biofilms on Different Biomaterial Surfaces  

PubMed Central

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

Thukkaram, Monica; Sitaram, Soundarya; Kannaiyan, Sathish kumar; Subbiahdoss, Guruprakash

2014-01-01

402

Soluble microbial products decrease pyrite oxidation by ferric iron at pH < 2.  

PubMed

Research on microbial activity in acid mine drainage (AMD) has focused on transformations of iron and sulfur. However, carbon cycling, including formation of soluble microbial products (SMP) from cell growth and decay, is an important biogeochemical component of the AMD environment. Experiments were conducted to study the interaction of SMP with soluble ferric iron in acidic conditions, particularly the formation of complexes that inhibit its effectiveness as the primary oxidant of pyrite during AMD generation. The rate of pyrite oxidation by ferric iron in sterile suspensions at pH 1.8 was reduced by 87% in the presence of SMP produced from autoclaved cells at a ratio of 0.3 mg DOC per mg total soluble ferric iron. Inhibition of pyrite oxidation by SMP was shown to be comparable to, but weaker than, the effect of a chelating synthetic siderophore, DFAM. Two computational models incorporating SMP complexation were fitted to experimental results. Results suggest that bacterially produced organic matter can play a role in slowing pyrite oxidation. PMID:23777272

Yacob, Tesfayohanes; Pandey, Sachin; Silverstein, Joann; Rajaram, Harihar

2013-08-01

403

Electrolysis of Molten Iron Oxide with an Iridium Anode: The Role of Electrolyte Basicity  

E-print Network

Electrolysis of Molten Iron Oxide with an Iridium Anode: The Role of Electrolyte Basicity Hojong evolution is a critical enabling component for the technol- ogy. To this end, iridium has been evaluated to have a dramatic effect on the stability of the iridium anode. The rate of iridium loss in an acidic

Sadoway, Donald Robert

404

Draft Genome Sequence of the Iron-Oxidizing Acidophile Leptospirillum ferriphilum Type Strain DSM 14647  

PubMed Central

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

Cardenas, Juan Pablo; Lazcano, Marcelo; Ossandon, Francisco J.; Corbett, Melissa; Holmes, David S.

2014-01-01

405

Draft Genome Sequence of the Iron-Oxidizing Acidophile Leptospirillum ferriphilum Type Strain DSM 14647.  

PubMed

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

Cárdenas, Juan Pablo; Lazcano, Marcelo; Ossandon, Francisco J; Corbett, Melissa; Holmes, David S; Watkin, Elizabeth

2014-01-01

406

Experimental study of the thermal performance of thermosyphon heat pipe using iron oxide nanoparticles  

Microsoft Academic Search

This paper presents an experimental investigation regarding the use of solid nanoparticles added to water as a working fluid. Tests were made on a thermosyphon heat pipe. The experiment was performed in order to measure the temperature distribution and compare the heat transfer rate of the thermosyphon heat pipe with nanofluid and with DI-water. The iron oxide nanoparticles were obtained

Gabriela Huminic; Angel Huminic; Ion Morjan; Florian Dumitrache

2011-01-01

407

ATR-FTIR Spectroscopy Reveals Bond Formation During Bacterial Adhesion to Iron Oxide  

E-print Network

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

Chorover, Jon

408

Sorptive stabilization of organic matter in soils by hydrous iron oxides  

Microsoft Academic Search

Strong correlations between iron oxides (FeOx) and organic matter (OM) in soils have implied the importance of the former in stabilizing the latter. One mechanism thought to be important in this stabilization is sorption. We tested this possibility by reductively dissolving FeOx in a wide variety of soils and measuring the organic carbon (OC) that was solubilized. The OC dissolved

Rota Wagai; Lawrence M. Mayer

2007-01-01