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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

On the Iron Oxidation State in the Iron-Substituted ? Nickel Oxyhydroxides  

NASA Astrophysics Data System (ADS)

In order to improve the knowledge of the electrochemical cycling process that involves the hydrated iron-substituted nickel hydroxides, the cationic oxidation state distribution in ?-oxidized materials has been studied. Magnetic measurements and Mössbauer data show that, for small iron compositions, most of the iron ions are in the low-spin tetravalent state, while for higher iron concentrations, the Fe 3+ (HS) ions are stabilized. Comparison with the homologous cobalt system suggests that the oxidation state of the substituting cation varies in order to accommodate the crystal field imposed by the prevailing cations.

Demourgues-Guerlou, L.; Fournès, L.; Delmas, C.

1995-01-01

4

The role of terahertz polariton absorption in the characterization of crystalline iron sulfate hydrates.  

PubMed

Iron sulfate compounds have been used extensively to produce iron gall ink, a widely used writing ink in the western world from the 12th-20th centuries. Iron gall ink is well known to corrode writing supports, so detection of iron species is important for the preservation of historical artwork and documents. Iron(ii) sulfate readily changes hydration states and oxidizes in ambient conditions, forming compounds that contribute to this deterioration. In this study, five forms of iron sulfate are characterized by terahertz spectroscopy and solid-state density functional theory (DFT). The results have revealed that the room temperature spectra of FeSO4·7H2O and FeSO4·4H2O are remarkably similar, differing by only a single absorption feature. The identifying terahertz spectra provide an unambiguous metric to determine the relative concentrations of the most common hydrates FeSO4·7H2O and FeSO4·4H2O in a mixed sample. Complete spectral assignments of these species were accomplished by quantum mechanical simulations, with the exception being a single anomalous feature at approximately 40 cm(-1) in the heptahydrate. This peak is believed to be due to polariton absorption, brought about by the particular coordination structure of FeSO4·7H2O that results in a greater charge separation relative to the other iron sulfate crystals. PMID:25760695

Ruggiero, Michael T; Bardon, Tiphaine; Strli?, Matija; Taday, Philip F; Korter, Timothy M

2015-04-14

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

21 CFR 73.3125 - Iron oxides.  

Code of Federal Regulations, 2014 CFR

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

2014-04-01

7

21 CFR 73.3125 - Iron oxides.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

8

21 CFR 73.3125 - Iron oxides.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Iron oxides. 73.3125 Section 73.3125...CERTIFICATION Medical Devices § 73.3125 Iron oxides. (a) Identity and specifications. The color additive iron oxides (CAS Reg. No....

2011-04-01

9

21 CFR 73.3125 - Iron oxides.  

Code of Federal Regulations, 2012 CFR

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

2012-04-01

10

21 CFR 73.3125 - Iron oxides.  

Code of Federal Regulations, 2010 CFR

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

2010-04-01

11

Serpentine days, Porquerolles, 2012. XANES study of iron oxidation state in serpentines from ridge to subduction  

E-print Network

Serpentine days, Porquerolles, 2012. µXANES study of iron oxidation state in serpentines from to ultraslow spreading centers. Serpentine could thus be one of the most abundant hydrated minerals recycled serpentine (usually lizardite). The oxidation state of iron in lizardite is controlled

Nicollet, Christian

12

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

13

High-Temperature Oxidation of Iron Whiskers  

Microsoft Academic Search

Single crystal ?-iron whiskers have been used to study early stages in the oxidation of iron at high temperatures. Well defined oxide patterns are observed on clean iron surfaces and there are characteristic differences between the patterns on {100} and {110} faces. These differences tend to be eliminated if a natural oxide film is present before the high temperature oxidation

J. V. Laukonis; R. V. Coleman

1959-01-01

14

Gaseous reduction of iron oxides: Part III. Reduction-oxidation of porous and dense iron oxides and iron  

Microsoft Academic Search

The internal reduction of high-grade granular hematite ore in hydrogen and carbon monoxide, and also the internal oxidation\\u000a of porous iron granules in CO2-CO mixtures have been investigated. To assist the interpretation of the rate data for porous iron and iron oxides, rate measurements\\u000a have been made also with dense wustite, previously grown on iron by oxidation. The iron formed

E. T. Turkdogan; J. V. Vinters

1972-01-01

15

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

16

21 CFR 73.2250 - Iron oxides.  

Code of Federal Regulations, 2011 CFR

...OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2250 Iron oxides. (a) Identity... Iron oxides are safe for use in coloring cosmetics generally, including cosmetics applied to the area of the eye, in...

2011-04-01

17

21 CFR 73.2250 - Iron oxides.  

Code of Federal Regulations, 2010 CFR

...OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2250 Iron oxides. (a) Identity... Iron oxides are safe for use in coloring cosmetics generally, including cosmetics applied to the area of the eye, in...

2010-04-01

18

21 CFR 73.2250 - Iron oxides.  

Code of Federal Regulations, 2012 CFR

...OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2250 Iron oxides. (a) Identity... Iron oxides are safe for use in coloring cosmetics generally, including cosmetics applied to the area of the eye, in...

2012-04-01

19

Vacancy coalescence during oxidation of iron nanoparticles  

SciTech Connect

In the present work, we analyze the geometry and composition of the nanostructures obtained from the oxidation of iron nanoparticles. The initial oxidation of iron takes place by outward diffusion of cations through the growing oxide shell. This net material flow is balanced by an opposite flow of vacancies, which coalesce at the metal/oxide interface. Thus, the partial oxidation of colloidal iron nanoparticles leads to the formation of core-void-shell nanostructures. Furthermore, the complete oxidation of iron nanoparticles in the 3-8 nm size range leads to the formation of hollow iron oxide nanoparticles. We analyze the size and temperature range in which vacancy coalescence during oxidation of amine-stabilized iron nanoparticles takes place. Maghemite is the crystallographic structure obtained from the complete oxidation of iron nanoparticles under our synthetic conditions.

Cabot, Andreu; Puntes, Victor F.; Shevchenko, Elena; Yin, Yadong; Balcells, Lluis; Markus, Matthew A.; Hughes, Steven M.; Alivisatos, A. Paul

2007-06-14

20

Vacancy coalescence during oxidation of iron nanoparticles  

Microsoft Academic Search

In the present work, we analyze the geometry and composition of the nanostructures obtained from the oxidation of iron nanoparticles. The initial oxidation of iron takes place by outward diffusion of cations through the growing oxide shell. This net material flow is balanced by an opposite flow of vacancies, which coalesce at the metal\\/oxide interface. Thus, the partial oxidation of

Andreu Cabot; Victor F. Puntes; Elena Shevchenko; Yadong Yin; Lluis Balcells; Matthew A. Markus; Steven M. Hughes; A. Paul Alivisatos

2007-01-01

21

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

22

Metal ion binding to iron oxides  

Microsoft Academic Search

The biogeochemistry of trace elements (TE) is largely dependent upon their interaction with heterogeneous ligands including metal oxides and hydrous oxides of iron. The modeling of TE interactions with iron oxides has been pursued using a variety of chemical models. The objective of this work is to show that it is possible to model the adsorption of protons and TE

M. Ponthieu; F. Juillot; T. Hiemstra; W. H. van Riemsdijk; M. F. Benedetti

2006-01-01

23

Kinetics of iron oxidation upon polyphenol binding.  

PubMed

Polyphenol prevention of iron-mediated DNA damage occurs primarily through iron binding. Once bound, iron in the Fe(2+)-polyphenol complex autooxidizes to Fe(3+) in the presence of O(2). To determine the correlation between the rate of Fe(2+)-polyphenol autooxidation and polyphenol antioxidant ability, kinetic studies at pH = 6.0 in the presence of oxygen were performed using UV-vis spectrophotometry. Initial rates of iron-polyphenol complex oxidation for epigallocatechin gallate (EGCG), methyl-3,4,5-trihydroxybenzoate (MEGA), gallic acid (GA), epicatechin (EC), and methyl-3,4-dihydroxybenzoate (MEPCA) were in the range of 0.14-6.7 min(-1). Polyphenols with gallol groups have faster rates of iron oxidation than their catechol analogs, suggesting that stronger iron binding results in faster iron oxidation. Concentrations of polyphenol, Fe(2+), and O(2) were varied to investigate the dependence of the Fe(2+)-polyphenol autooxidation on these reactants for MEGA and MEPCA. For these analogous gallate and catecholate complexes of Fe(2+), iron oxidation reactions were first order in Fe(2+), polyphenol, and O(2), but gallate complexes show saturation behavior at much lower Fe(2+) concentrations. Thus, gallol-containing polyphenols promote iron oxidation at a significantly faster rate than analogous catechol-containing compounds, and iron oxidation rate also correlates strongly with polyphenol inhibition of DNA damage for polyphenol compounds with a single iron-binding moiety. PMID:20871896

Perron, Nathan R; Wang, Hsiao C; Deguire, Sean N; Jenkins, Michael; Lawson, Mereze; Brumaghim, Julia L

2010-11-01

24

Surface enhanced Raman spectroscopy of iron oxide thin films: Comparison with the passive film on iron  

SciTech Connect

Thin films (33 nm to 1.4 {micro}m) of iron oxides were deposited onto roughened silver substrates by laser ablation of Fe{sub 3}O{sub 4} and {gamma}-Fe{sub 2}O{sub 3} targets. Surface enhanced Raman (SER) spectra from the 33 to 37 nm thick films, both in air and in aqueous borate buffer (pH 8.4), were identical to SER spectra of the passive film formed on iron in the same solution; that is, all were characterized by a strong broad peak centered at approximately 530 to 580 cm{sup {minus}1}. The 33 to 37 nm thick films were potentiodynamically reduced in borate buffer. Electrochemical reduction of the ablated iron oxide films initiated at a more cathodic potential than that found for the passive film on iron. Thicker 178 nm films formed by laser ablation of Fe{sub 3}O{sub 4} exhibited spectra partially resembling the iron passive film and partially resembling the normal Raman spectrum of bulk Fe{sub 3}O{sub 4}. The 153 nm and 1.4 {micro}m thick films formed from Fe{sub 2}O{sub 3} and 1.3 {micro}m thick films formed from Fe{sub 3}O{sub 4} gave very weak Raman spectra that were characteristic of the bulk oxides, and did not resemble the iron passive film. The observation that the SER spectra from passive films on iron, as measured in this and previous studies, are identical to the SER spectra from thin films laser ablated from targets of Fe{sub 3}O{sub 4} and Fe{sub 2}O{sub 3} (in both cases, resulting in iron oxides most probably hydrated and of small particle size) permits the more accurate assignment of spectral features in future, as well as past SERS studies.

Oblonsky, L.J.; Schroeder, V.; Devine, T.M. [Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering; Virtanen, S. [Swiss Federal Inst. of Tech., Zurich (Switzerland). Inst. of Materials Chemistry and Corrosion

1997-05-01

25

46 CFR 148.275 - Iron oxide, spent; iron sponge, spent.  

Code of Federal Regulations, 2011 CFR

...Shipping 5 2011-10-01 2011-10-01 false Iron oxide, spent; iron sponge, spent. 148.275 Section 148.275 ...Special Requirements for Certain Materials § 148.275 Iron oxide, spent; iron sponge, spent. (a)...

2011-10-01

26

46 CFR 148.275 - Iron oxide, spent; iron sponge, spent.  

Code of Federal Regulations, 2012 CFR

...Shipping 5 2012-10-01 2012-10-01 false Iron oxide, spent; iron sponge, spent. 148.275 Section 148.275 ...Special Requirements for Certain Materials § 148.275 Iron oxide, spent; iron sponge, spent. (a)...

2012-10-01

27

46 CFR 148.275 - Iron oxide, spent; iron sponge, spent.  

Code of Federal Regulations, 2013 CFR

...Shipping 5 2013-10-01 2013-10-01 false Iron oxide, spent; iron sponge, spent. 148.275 Section 148.275 ...Special Requirements for Certain Materials § 148.275 Iron oxide, spent; iron sponge, spent. (a)...

2013-10-01

28

46 CFR 148.275 - Iron oxide, spent; iron sponge, spent.  

Code of Federal Regulations, 2014 CFR

...Shipping 5 2014-10-01 2014-10-01 false Iron oxide, spent; iron sponge, spent. 148.275 Section 148.275 ...Special Requirements for Certain Materials § 148.275 Iron oxide, spent; iron sponge, spent. (a)...

2014-10-01

29

Iron Homeostasis, Oxidative Stress, and DNA Damage  

Microsoft Academic Search

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

Rogerio Meneghini

1997-01-01

30

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

31

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

32

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

33

Enzymatic iron oxidation by Leptothrix discophora: identification of an iron-oxidizing protein.  

PubMed

An iron-oxidizing factor was identified in the spent culture medium of the iron- and manganese-oxidizing bacterial strain Leptothrix discophora SS-1. It appeared to be a protein, with an apparent molecular weight of approximately 150,000. Its activity could be demonstrated after fractionation of the spent medium by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A spontaneous mutant of L. discophora SS-1 was isolated which excreted neither manganese- nor iron-oxidizing activity, whereas excretion of other proteins seemed to be unaffected. Although the excretion of both metal-oxidizing factors was probably linked, the difference in other properties suggests that manganese and iron oxidation represent two different pathways. With a dot-blot assay, it was established that different bacterial species have different metal-oxidizing capacities. Whereas L. discophora oxidized both iron and manganese, Sphaerotilus natans oxidized only iron and two Pseudomonas spp. oxidized only manganese. PMID:1610168

Corstjens, P L; de Vrind, J P; Westbroek, P; de Vrind-de Jong, E W

1992-02-01

34

Enzymatic iron oxidation by Leptothrix discophora: identification of an iron-oxidizing protein.  

PubMed Central

An iron-oxidizing factor was identified in the spent culture medium of the iron- and manganese-oxidizing bacterial strain Leptothrix discophora SS-1. It appeared to be a protein, with an apparent molecular weight of approximately 150,000. Its activity could be demonstrated after fractionation of the spent medium by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A spontaneous mutant of L. discophora SS-1 was isolated which excreted neither manganese- nor iron-oxidizing activity, whereas excretion of other proteins seemed to be unaffected. Although the excretion of both metal-oxidizing factors was probably linked, the difference in other properties suggests that manganese and iron oxidation represent two different pathways. With a dot-blot assay, it was established that different bacterial species have different metal-oxidizing capacities. Whereas L. discophora oxidized both iron and manganese, Sphaerotilus natans oxidized only iron and two Pseudomonas spp. oxidized only manganese. Images PMID:1610168

Corstjens, P L; de Vrind, J P; Westbroek, P; de Vrind-de Jong, E W

1992-01-01

35

Ferrous iron oxidation by anoxygenic phototrophic bacteria  

Microsoft Academic Search

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

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

1993-01-01

36

Temperature dependence of graphene oxide reduced by hydrazine hydrate.  

PubMed

Graphene oxide (GO) was successfully prepared by a modified Hummer's method. The reduction effect and mechanism of the as-prepared GO reduced with hydrazine hydrate at different temperatures and time were characterized by x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), x-ray diffractions (XRD), Raman spectroscopy and thermo-gravimetric analysis (TGA). The results showed that the reduction effect of GO mainly depended on treatment temperature instead of treatment time. Desirable reduction of GO can only be obtained at high treatment temperature. Reduced at 95?°C for 3 h, the C/O atomic ratio of GO increased from 3.1 to 15.1, which was impossible to obtain at low temperatures, such as 80, 60 or 15?°C, even for longer reduction time. XPS, 13C NMR and FTIR results show that most of the epoxide groups bonded to graphite during the oxidation were removed from GO and form the sp(2) structure after being reduced by hydrazine hydrate at high temperature (>60?°C), leading to the electric conductivity of GO increasing from 1.5 × 10(-6) to 5 S cm(-1), while the hydroxyls on the surface of GO were not removed by hydrazine hydrate even at high temperature. Additionally, the FTIR, XRD and Raman spectrum indicate that the GO reduced by hydrazine hydrate can not be entirely restored to the pristine graphite structures. XPS and FTIR data also suggest that carbonyl and carboxyl groups can be reduced by hydrazine hydrate and possibly form hydrazone, but not a C = C structure. PMID:21178230

Ren, Peng-Gang; Yan, Ding-Xiang; Ji, Xu; Chen, Tao; Li, Zhong-Ming

2011-02-01

37

On the formation of iron(III) oxides via oxidation of iron(II)  

SciTech Connect

Formation of iron oxides in aqueous salt solutions is reviewed. The discussion is focused on the oxidation of iron(II) and the following hydrolysis process that leads to the formation of a solid phase from homogeneous solutions. Results from our own studies on the kinetics of the oxidation reactions and the ensuing growth processes are presented.

Bongiovanni, R.; Pelizzetti, E. [Torino Univ. (Italy). Dipt. di Chimica Analitica; Borgarello, E. [Eniricerche SpA, Milan (Italy); Meisel, D. [Argonne National Lab., IL (United States)

1994-09-01

38

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

39

21 CFR 73.2250 - Iron oxides.  

Code of Federal Regulations, 2014 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...

2014-04-01

40

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

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

41

IRON OXIDE NANOPARTICLE-INDUCED OXIDATIVE STRESS AND INFLAMMATION  

EPA Science Inventory

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

42

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

43

Removal of metallic iron on oxide slags  

SciTech Connect

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

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

2009-10-15

44

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

45

Metal ion binding to iron oxides  

NASA Astrophysics Data System (ADS)

The biogeochemistry of trace elements (TE) is largely dependent upon their interaction with heterogeneous ligands including metal oxides and hydrous oxides of iron. The modeling of TE interactions with iron oxides has been pursued using a variety of chemical models. The objective of this work is to show that it is possible to model the adsorption of protons and TE on a crystallized oxide (i.e., goethite) and on an amorphous oxide (HFO) in an identical way. Here, we use the CD-MUSIC approach in combination with valuable and reliable surface spectroscopy information about the nature of surface complexes of the TE. The other objective of this work is to obtain generic parameters to describe the binding of the following elements (Cd, Co, Cu, Ni, Pb, and Zn) onto both iron oxides for the CD-MUSIC approach. The results show that a consistent description of proton and metal ion binding is possible for goethite and HFO with the same set of model parameters. In general a good prediction of almost all the collected experimental data sets corresponding to metal ion binding to HFO is obtained. Moreover, dominant surface species are in agreement with the recently published surface complexes derived from X-ray absorption spectroscopy (XAS) data. Until more detailed information on the structure of the two iron oxides is available, the present option seems a reasonable approximation and can be used to describe complex geochemical systems. To improve our understanding and modeling of multi-component systems we need more data obtained at much lower metal ion to iron oxide ratios in order to be able to account eventually for sites that are not always characterized in spectroscopic studies.

Ponthieu, M.; Juillot, F.; Hiemstra, T.; van Riemsdijk, W. H.; Benedetti, M. F.

2006-06-01

46

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

47

Catalytic iron oxide for lime regeneration in carbonaceous fuel combustion  

DOEpatents

Lime utilization for sulfurous oxides absorption in fluidized combustion of carbonaceous fuels is improved by impregnation of porous lime particulates with iron oxide. The impregnation is achieved by spraying an aqueous solution of mixed iron sulfate and sulfite on the limestone before transfer to the fluidized bed combustor, whereby the iron compounds react with the limestone substrate to form iron oxide at the limestone surface. It is found that iron oxide present in the spent limestone acts as a catalyst to regenerate the spent limestone in a reducing environment. With only small quantities of iron oxide the calcium can be recycled at a significantly increased rate.

Shen, Ming-Shing (Rocky Point, NY); Yang, Ralph T. (Middle Island, NY)

1980-01-01

48

Defluoridation by Bacteriogenic Iron Oxides: Sorption Studies  

NASA Astrophysics Data System (ADS)

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

Evans, K.; Ferris, F.

2009-05-01

49

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

50

21 CFR 73.1200 - Synthetic iron oxide.  

Code of Federal Regulations, 2012 CFR

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

2012-04-01

51

21 CFR 73.1200 - Synthetic iron oxide.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

52

21 CFR 73.1200 - Synthetic iron oxide.  

Code of Federal Regulations, 2011 CFR

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

2011-04-01

53

21 CFR 73.1200 - Synthetic iron oxide.  

Code of Federal Regulations, 2010 CFR

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

2010-04-01

54

21 CFR 73.200 - Synthetic iron oxide.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Synthetic iron oxide. 73.200 Section 73.200...CERTIFICATION Foods § 73.200 Synthetic iron oxide. (a) Identity. (1) The color additive synthetic iron oxide consists of any one or any...

2010-04-01

55

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

56

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

57

Bacterial methane oxidation in sea-floor gas hydrate: Significance to life in extreme environments  

SciTech Connect

Samples of thermogenic hydrocarbon gases, from vents and gas hydrate mounds within a sea-floor chemosynthetic community on the Gulf of Mexico continental slope at about 540 m depth, were collected by research submersible. The study area is characterized by low water temperature (mean = 7 C), high pressure (about 5,400 kPa), and abundant structure II gas hydrate. Bacterial oxidation of hydrate-bound methane (CH{sub 4}) is indicated by three isotopic properties of gas hydrate samples. Relative to the vent gas from which the gas hydrate formed, (1) methane-bound methane is enriched in {sup 13}C by as much as 3.8% PDB (Peedee belemnite), (2) hydrate-bound methane is enriched in deuterium (D) by as much as 37% SMOW (standard mean ocean water), and (3) hydrate-bound carbon dioxide (CO{sub 2}) is depleted in {sup 13}C by as much as 22.4% PDB. Hydrate-associated authigenic carbonate rock is also depleted in {sup 13}C. Bacterial oxidation of methane is a driving force in chemosynthetic communities, and in the concomitant precipitation of authigenic carbonate rock that modifies sea-floor geology. Bacterial oxidation of hydrate-bound methane expands the potential boundaries of life in extreme environments.

Sassen, R.; MacDonald, I.R.; Guinasso, N.L. Jr.; Requejo, A.G.; Sweet, S.T.; Alcala-Herrera, J.; DeFreitas, D.A.; Schink, D.R. [Texas A and M Univ., College Station, TX (United States). Geochemical and Environmental Research Group] [Texas A and M Univ., College Station, TX (United States). Geochemical and Environmental Research Group; Joye, S. [Univ. of Georgia, Athens, GA (United States). Dept. of Marine Sciences] [Univ. of Georgia, Athens, GA (United States). Dept. of Marine Sciences

1998-09-01

58

Iron oxide from a seasonally anoxic lake  

NASA Astrophysics Data System (ADS)

The ferric oxide formed by oxidation of Fe(II) in Esthwaite Water, U.K., during the lake's seasonal thermal stratification and deep-water anoxia consists of amorphous particles which are approximately spherical or ellipsoidal, with diameters in the range 0.05-0.5 ?m. Concentrations in the lake are 1011-1012 particles per litre, corresponding to 3 mg l-1 Fe. Unlike iron oxides of similar chemical composition formed by oxidative mechanisms in soil-borne waters, the particles do not appear to be composed of small primary particles. This is possibly because in the lake they form slowly, at low supersaturation. The particles contain 30-40% by weight Fe. The carbon content is uncertain because of contamination but is in the range 4-18%. Humic carbon contributes at least 4-7% of the total weight. Other major elements present are P, N, Mn, Si, S. Ca and Mg, comprising between them up to 8% of the total weight. The particles are negatively charged probably because of adsorbed humic substances, and also phosphate and silicate. Their electrophoretic mobility-pH dependence is similar to those of synthetic iron oxides added to samples of surface Esthwaite Water. The calculated zeta potential is - 27 mV, which is sufficiently high to make flocculation slow under lake conditions. The low flocculation rate partially accounts for the formation of a well-defined peak of particulate iron in the water column of the lake.

Tipping, E.; Woof, C.; Cooke, D.

1981-09-01

59

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

60

Formulations for iron oxides dissolution  

DOEpatents

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

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

1992-01-01

61

Microbial oxidation of ferrous iron in acid mine water at sulfur and iron-sulfide mine  

Microsoft Academic Search

The microbial oxidation of ferrous iron in the acid mine water from the abandoned Matsuo sulfur and iron-sulfide mine area was investigated. The acid mine water had an extremely low pH value and contained a high concentration of ferrous iron (about 1,000 ppm). The ferrous iron was oxidized rapidly to the ferric form in the acid mine water. The oxidation

Norio Wakao; Yonekichi Sakurai; Hideo Shiota

1977-01-01

62

Method for preparing hydrous iron oxide gels and spherules  

DOEpatents

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

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

2003-07-29

63

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

64

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

65

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

66

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

67

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

68

Alcohol, iron-associated oxidative stress, and cancer  

Microsoft Academic Search

Oxidative stress is recognized to play an important role in the initiation and promotion events of carcinogenesis. Alcoholic liver disease is associated with significant oxidative stress as well as the hepatic accumulation of iron, a transition element also documented to initiate oxidative stress. The combined prooxidant potential of ethanol and iron is at least additive and possibly synergistic with respect

Dennis R. Petersen

2005-01-01

69

Nitric oxide and plant iron homeostasis.  

PubMed

Like all living organisms, plants demand iron (Fe) for important biochemical and metabolic processes. Internal imbalances, as a consequence of insufficient or excess Fe in the environment, lead to growth restriction and affect crop yield. Knowledge of signals and factors affecting each step in Fe uptake from the soil and distribution (long-distance transport, remobilization from old to young leaves, and storage in seeds) is necessary to improve our understanding of plant mineral nutrition. In this context, the role of nitric oxide (NO) is discussed as a key player in maintaining Fe homeostasis through its cross talk with hormones, ferritin, and frataxin and the ability to form nitrosyl-iron complexes. PMID:25612116

Buet, Agustina; Simontacchi, Marcela

2015-03-01

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 interpretation of high pressure experiments, specifically Fe-Ni exchange between metallic and oxide phases fugacity (fO2) buffer. These buffers are precisely known at 1 bar, but under high pressures corresponding

Campbell, Andrew

71

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.

U.S. Geological Survey

2008-01-01

72

Synthesis and characterization of iron oxide/cellulose nanocomposite film.  

PubMed

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

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

2015-03-01

73

Diffusion of Cu into rf-sputtered iron oxide films  

NASA Astrophysics Data System (ADS)

Diffusion of Cu into iron oxide films sputter deposited on Cu substrates is studied. After heating in H2 at 200 °C and in air at 300 °C, iron-free Cu oxide layers are formed on the film surfaces. X-ray diffraction method and magnetic measurement show that the Cu atoms diffuse in the iron oxide films without forming CuFe2O4. The crystal-grain size of the reduced and reoxidized films are 20 and 25 nm, respectively. Such fine crystal grains, which are favorable for low noise magnetic disk media application, are attributed to the peculiar Cu interdiffusion in the iron oxide films.

Ishii, Osamu

1988-05-01

74

Suspension Hydrogen Reduction of Iron Oxide Concentrates  

SciTech Connect

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

H.Y. Sohn

2008-03-31

75

Cardioprotective activity of iron oxide nanoparticles  

PubMed Central

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

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

2015-01-01

76

RESEARCH IRON OXIDE NANOPARTICLES Synthesis of Iron Oxide Nanoparticles with Biological Coatings  

E-print Network

For biological and biomedical applications, it is required to produce nanoparticles that are water soluble and biocompatible. Here, we report the synthesis of iron oxide nanoparticles coated with biological molecules (e.g., gluconic acid, lactobionic acid, or polyacrylic acid) via a co

David Dozier; Soubantika Palchoudhury; Yuping Bao, Ph.D.

77

Magnetic properties of iron-boron-oxide and iron-phosphor-oxide glasses prepared by sol-gel method  

Microsoft Academic Search

The authors present an investigation of magnetic properties of iron-boron-oxide (Fe-B-O) and iron-phosphor-oxide (Fe-P-) glasses prepared by sol-gel method. Magnetic properties of powders made from dried gel were measured as a function of calcination temperature up to 600°C. Magnetic moment of iron-oxide was enhanced by adding a small amount of boron.

K. Yamaguchi; T. Fujii; S. Kuranouchi; Y. Yamanobe; A. Ueno

1989-01-01

78

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

79

Iron-dependent oxidative stress in Chlorella vulgaris  

Microsoft Academic Search

The role of iron as catalyst for oxidative stress was studied during the development of Chlorella vulgaris cells. Increases on iron availability beyond 200 ?M led to a decrease in the growth rate of the cultures of C. vulgaris. Quantification of the EPR signals of POBN\\/lipid radicals adducts indicated that iron addition increased lipid radical content in the membranes (more

Maria Susana Estevez; Gabriela Malanga; Susana Puntarulo

2001-01-01

80

Magnetic Properties of Iron-added Titanium Oxide Nanotubes  

Microsoft Academic Search

Titanium oxide represents a promising candidate as the support material for dilute magnetic semiconductors (DMSs), especially in a nanostructured form. Titania nanotubes ordered arrays produced by anodization have been used in this study as the base material for the addition of a ferromagnetic component, iron in particular. Several routes such as titanium-iron films co-deposition before anodization, anodization in iron cations

Eugen Panaitescu; Pegah Hosseinpour; Laura H. Lewis; Latika Menon

2011-01-01

81

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

Code of Federal Regulations, 2014 CFR

... 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

82

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

83

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

84

Micronization of Iron Oxide Particles Using Gas Antisolvent Process  

Microsoft Academic Search

Iron oxide particles were micronized by supercritical carbon dioxide (CO2) as an antisolvent in a batch gas antisolvent (GAS) process. In the present study, the feasibility of GAS process to micronize the iron oxide particles using dimethyl sulfoxide (DMSO) as a solvent was investigated. In this direction, particle size and morphology changes were investigated with changing solution pressure (80–150 bar), temperature

Najmeh Vefgh; Feridun Esmaeilzadeh; Dariush Mowla; Ali Akbar Golchehreh

2012-01-01

85

Uptake And Intracellular Distribution Of Functionalized Iron Oxide Nanoparticles  

NASA Astrophysics Data System (ADS)

Iron oxide Nanoparticles represents promising nanocarrier for magnetic resonance imaging (MRI), targeted drug and gene delivery. In our study we investigated the interaction between lung alveolar epithelial cells and iron oxide NPs coated with L-Dihydroxyphenylalanina (L-Dopa)-TRITC. Our data suggest that particles crossed the plasma membrane with an energy-dependent process.

Panariti, A.; Lettiero, B.; Morjan, I.; Alexandreascu, R.; Wang, D.; Bucci, C.; Miserocchi, G.; Rivolta, I.

2010-10-01

86

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

E-print Network

a high magnetic signal com- pared to other magnetic iron oxides (for example, magnetite has a saturationSelective dissolution of magnetic iron oxides in the acid­ammonium oxalate/ferrous iron extraction. Synthetic samples containing a quartz matrix with 0.1 wt per cent of iron oxides were extracted with the AAO

Utrecht, Universiteit

87

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

88

Silica encapsulation of sonochemically synthesized iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

A facile sono-chemical approach was applied for the large scale synthesis of silica coated iron oxide magnetic nanoparticles (NPs) using inexpensive and non-toxic chemicals. The as-prepared silica coated magnetic iron oxide (Fe3O4@SiO2 core-shell) NPs have been characterized by XRD, TEM, EDS, and VSM. X-ray diffraction (XRD) and EDS analysis revealed that Fe3O4 NPs have been successfully coated by this simple method. Transmission electron microscopy (TEM) data demonstrated that the thickness of silica coating on iron oxide magnetic NPs is 10 - 15 nm on average. The magnetization curve from the vibrating sample magnetometer (VSM) measurement shows that the magnetization also decreased the as-synthesized silica coated iron oxide NPs compared to the freshly prepared bare iron oxide magnetic NPs, which is also evidence of the synthesis of Fe3O4@SiO2 core-shell NPs.

Islam, Md. Nazrul; Abbas, Mohamed; Sinha, Brajalal; Joeng, Jong-Ryul; Kim, CheolGi

2013-11-01

89

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...

90

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

Microsoft Academic Search

A common problem faced by drinking water studies is that of properly characterizing the corrosion products (CP) in iron pipescor synthetic Fe (hydr)oxides used to simulate the iron pipe used in municipal drinking-water systems. The present work compares the relative applicability of a suite of imaging and analytical techniques for the characterization of CPs and synthetic Fe oxide thin films

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

2008-01-01

91

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

Microsoft Academic Search

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

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

2010-01-01

92

Ecological succession among iron-oxidizing bacteria  

PubMed Central

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

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

2014-01-01

93

Microbially Induced Iron Oxidation: What, Where, How  

SciTech Connect

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

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

2000-08-15

94

Cell toxicity of superparamagnetic iron oxide nanoparticles.  

PubMed

The performance of nanoparticles for biomedical applications is often assessed by their narrow size distribution, suitable magnetic saturation and low toxicity effects. In this work, superparamagnetic iron oxide nanoparticles (SPIONs) with different size, shape and saturation magnetization levels were synthesized via a co-precipitation technique using ferrous salts with a Fe(3+)/Fe(2+) mole ratio equal to 2. A parametric study is conducted, based on a uniform design-of-experiments methodology and a critical polymer/iron mass ratio (r-ratio) for obtaining SPION with narrow size distribution, suitable magnetic saturation, and optimum biocompatibility is identified. Polyvinyl alcohol (PVA) has been used as the nanoparticle coating material, owing to its low toxicity. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay is used to investigate the cell biocompatibility/toxicity effects of the samples. From the MTT assay results, it is observed that the biocompatibility of the nanoparticles, based on cell viabilities, can be enhanced by increasing the r-ratio, regardless of the stirring rate. This effect is mainly due to the growth of the particle hydrodynamic size, causing lower cell toxicity effects. PMID:19476952

Mahmoudi, M; Simchi, A; Milani, A S; Stroeve, P

2009-08-15

95

Oxidation Inhibits Iron-Induced Blood Coagulation  

PubMed Central

Blood coagulation under physiological conditions is activated by thrombin, which converts soluble plasma fibrinogen (FBG) into an insoluble clot. The structure of the enzymatically-generated clot is very characteristic being composed of thick fibrin fibers susceptible to the fibrinolytic degradation. However, in chronic degenerative diseases, such as atherosclerosis, diabetes mellitus, cancer, and neurological disorders, fibrin clots are very different forming dense matted deposits (DMD) that are not effectively removed and thus create a condition known as thrombosis. We have recently shown that trivalent iron (ferric ions) generates hydroxyl radicals, which subsequently convert FBG into abnormal fibrin clots in the form of DMDs. A characteristic feature of DMDs is their remarkable and permanent resistance to the enzymatic degradation. Therefore, in order to prevent thrombotic incidences in the degenerative diseases it is essential to inhibit the iron-induced generation of hydroxyl radicals. This can be achieved by the pretreatment with a direct free radical scavenger (e.g. salicylate), and as shown in this paper by the treatment with oxidizing agents such as hydrogen peroxide, methylene blue, and sodium selenite. Although the actual mechanism of this phenomenon is not yet known, it is possible that hydroxyl radicals are neutralized by their conversion to the molecular oxygen and water, thus inhibiting the formation of dense matted fibrin deposits in human blood. PMID:23170793

Pretorius, Etheresia; Bester, Janette; Vermeulen, Natasha; Lipinski, Boguslaw

2013-01-01

96

Multiple hearth furnace for reducing iron oxide  

DOEpatents

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

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

2012-03-13

97

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

98

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

99

Magnetization measurements and XMCD studies on ion irradiated iron oxide and core-shell iron/iron-oxide nanomaterials  

SciTech Connect

Magnetite (Fe3O4) and core-shell iron/iron-oxide (Fe/Fe3O4) nanomaterials prepared by a cluster deposition system were irradiated with 5.5 MeV Si2+ ions and the structures determined by x-ray diffraction as consisting of 100% magnetite and 36/64 wt% Fe/FeO, respectively. However, x-ray magnetic circular dichroism (XMCD) indicates similar surfaces in the two samples, slightly oxidized and so having more Fe3+ than the expected magnetite structure, with XMCD intensity much lower for the irradiated core-shell samples indicating weaker magnetism. X-ray absorption spectroscopy (XAS) data lack the signature for FeO, but the irradiated core-shell system consists of Fe-cores with ~13 nm of separating oxide crystallite, so it is likely that FeO exists deeper than the probe depth of the XAS (~5 nm). Exchange bias (Hex) for both samples becomes increasingly negative as temperature is lowered, but the irradiated Fe3O4 sample shows greater sensitivity of cooling field on Hex. Loop asymmetries and Hex sensitivities of the irradiated Fe3O4 sample are due to interfaces and interactions between grains which were not present in samples before irradiation as well as surface oxidation. Asymmetries in the hysteresis curves of the irradiated core/shell sample are related to the reversal mechanism of the antiferromagnetic FeO and possibly some near surface oxidation.

Kaur, Maninder; Qiang, You; Jiang, Weilin; Pearce, Carolyn; McCloy, John S.

2014-12-02

100

Deferasirox removes cardiac iron and attenuates oxidative stress in the iron-overloaded gerbil.  

PubMed

Iron-induced cardiovascular disease is the leading cause of death in iron-overloaded patients. Deferasirox is a novel, once daily oral iron chelator that was recently approved for the treatment of transfusional iron overload. Here, we investigate whether deferasirox is capable of removing cardiac iron and improving iron-induced pathogenesis of the heart using the iron overload gerbil model. Animals were randomly divided into three groups: control, iron overload, and iron overload + deferasirox treatment. Iron-dextran was given 100 mg/kg per 5 days i.p for 10 weeks. Deferasirox treatment was taken post iron loading and was given at 100 mg/kg/day p.o for 1 or 3 months. Cardiac iron concentration was determined by inductively coupled plasma atomic emission spectroscopy. Compared with the untreated group, deferasirox treatment for 1 and 3 months decreased cardiac iron concentration 17.1% (P = 0.159) and 23.5% (P < 0.05), respectively. These treatment-associated reductions in cardiac iron were paralleled by decreases in tissue ferritin expression of 20% and 38% at 1 and 3 months, respectively (P < 0.05). Using oxyblot analysis and hydroethidine fluorescence, we showed that deferasirox significantly reduces cardiac protein oxidation and superoxide abundance by 36 and 47.1%, respectively (P < 0.05). Iron-induced increase in oxidative stress was also associated with increased phosphorylation of ERK-, p38-, and JNK-mitogen-activated protein kinase (MAPK). Interestingly, deferasirox treatment significantly diminished the phosphorylation of all three MAPK subfamilies. These results suggest that deferasirox may confer a cardioprotective effect against iron induced injury. PMID:19650117

Al-Rousan, Rabaa M; Paturi, Satyanarayana; Laurino, Joseph P; Kakarla, Sunil K; Gutta, Anil K; Walker, Ernest M; Blough, Eric R

2009-09-01

101

The impact of zirconium oxide radiopacifier on the early hydration behaviour of white Portland cement.  

PubMed

Zirconium oxide has been identified as a candidate radiopacifying agent for use in Portland cement-based biomaterials. During this study, the impact of 20 wt.% zirconium oxide on the hydration and setting reactions of white Portland cement (WPC) was monitored by powder X-ray diffraction (XRD), (29)Si and (27)Al magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), transmission electron microscopy (TEM) and Vicat apparatus. The presence of 20 wt.% zirconium oxide particles in the size-range of 0.2 to 5 ?m was found to reduce the initial and final setting times of WPC from 172 to 147 min and 213 to 191 min, respectively. Zirconium oxide did not formally participate in the chemical reactions of the hydrating cement; however, the surface of the zirconium oxide particles presented heterogeneous nucleation sites for the precipitation and growth of the early C-S-H gel products which accelerated the initial setting reactions. The presence of zirconium oxide was found to have little impact on the development of the calcium (sulpho)aluminate hydrate phases. PMID:25428091

Coleman, Nichola J; Li, Qiu

2013-01-01

102

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

103

Iron oxides from Modern to nm-scale balls...  

E-print Network

. as cells of dwarf bacteria (nannobacteria). In Fe oxide samples, are these small balls also nannobacterial from modern, living iron bacteria to rocks from Greenland over 3 billion years old, interesting of diverse objects...different "taxa" of bacteria? Fig. 2 is an iron crust on a pebble from a spring

Yang, Zong-Liang

104

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

105

Mechanisms of Selenate Adsorption on Iron Oxides and Hydroxides  

E-print Network

structure and attenuated total reflectance-Fourier transform infrared spectroscopies to determine SeO4 2 occurring iron oxide minerals and amorphous iron hydroxide coatings may be substantial in soils of selenate. Yamaguchi and colleagues (8) compared volume changes due to sulfate and selenate adsorption

Sparks, Donald L.

106

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

107

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

108

Dissolution of iron oxide nanoparticles inside polymer nanocapsules.  

PubMed

The structure of poly(organosiloxane) nanocapsules partially filled with iron oxide cores of different sizes was revealed by small angle X-ray scattering and X-ray diffraction. The nanocapsules are synthesized by the formation of a poly(organosiloxane) shell around iron oxide nanoparticles and the simultaneous partial dissolution of these cores. Due to the high scattering contrast of the iron oxide cores compared to the polymer shell, the particle size distribution of the cores inside the capsules can be measured by small angle X-ray scattering. Additional information can be revealed by X-ray diffraction, which gives insights into the formation of the polymer network and the structure of the iron oxide cores. The study shows how the crystallinity and size of the nanoparticles as well as the shape and width of the size distribution can be altered by the synthesis parameters. PMID:21993837

Möller, Johannes; Cebi, Melek; Schroer, Martin A; Paulus, Michael; Degen, Patrick; Sahle, Christoph J; Wieland, D C Florian; Leick, Sabine; Nyrow, Alexander; Rehage, Heinz; Tolan, Metin

2011-12-01

109

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

110

21 CFR 73.200 - Synthetic iron oxide.  

Code of Federal Regulations, 2011 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...

2011-04-01

111

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

112

Sulfates and Iron Oxides in Ophir Chasma, Mars  

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

113

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

114

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

115

Facile synthesis of magnetic iron oxide nanoparticles and their characterization  

NASA Astrophysics Data System (ADS)

Magnetic iron oxide nanoparticles are synthesized by suitable modification of the standard synthetic procedure without use of inert atmosphere and at room temperature. The facile synthesis procedure can be easily scaled up and is of important from industrial point of view for the commercial large scale production of magnetic iron oxide nanoparticles. The synthesized nanoparticles were characterized by thermal, dynamic light scattering, scanning electron microscopy and transmission electron microscopy analyses.

Jadhav, Sushilkumar A.; Patil, Suresh V.

2014-06-01

116

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

117

In Situ Iron Oxide Emplacement for Groundwater Arsenic Remediation  

E-print Network

Microscopy Si Elemental silica SiO32- Silicate SO42- Sulfate STIOCS Iron Oxide-Coated Sand specific throughput t Adsorption time tage Ageing time tbreakthrough Breakthrough time tcoat Coating time WHO World Health Organization XRD X-ray Diffraction...+ (2) Equation 1 represents the formation of ferric oxide, e.g. hematite (?-Fe2O3), as the end product. In Equation 2, the oxidation of Fe2+ produces iron oxyhydroxide (e.g. lepidocrocite ?-FeOOH), which results from oxygen-induced oxidation followed...

Abia, Thomas Sunday

2012-02-14

118

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

119

IRON  

EPA Science Inventory

The document surveys the effects of organic and inorganic iron that are relevant to humans and their environment. The biology and chemistry of iron are complex and only partially understood. Iron participates in oxidation reduction processes that not only affect its geochemical m...

120

In situ precipitation: a novel approach for preparation of iron-oxide magnetoliposomes  

PubMed Central

Background Conventional methods of preparing magnetoliposomes are complicated and inefficient. A novel approach for magnetoliposomes preparation was investigated in the study reported here. Methods FeCl3/FeCl2 solutions were hydrated with lipid films to obtain liposome-encapsulated iron ions by ultrasonic dispersion. Non-encapsulated iron ions were removed by dialysis. NH3 · H2O was added to the system to adjust the pH to a critical value. Four different systems were prepared. Each was incubated at a different temperature for a different length of time to facilitate the permeation of NH3 · H2O into the inner phase of the liposomes and the in situ formation of magnetic iron-oxide cores in the liposomes. Single-factor analysis and orthogonal-design experiments were applied to determinate the effects of alkalization pH, temperature, duration, and initial Fe concentration on encapsulation efficiency and drug loading. Results The magnetoliposomes prepared by in situ precipitation had an average particle size of 168±14 nm, zeta potential of ?26.2±1.9 mV and polydispersity index of 0.23±0.06. The iron-oxide cores were confirmed as Fe3O4 by X-ray diffraction and demonstrated a superparamagnetic response. Encapsulation efficiency ranged from 3% to 22%, while drug loading ranged from 0.2 to 1.58 mol Fe/mol lipid. The optimal conditions for in situ precipitation were found to be an alkalization pH of 12, temperature of 60°C, time of 60 minutes, and initial Fe concentration of 100 mM Fe3+ + 50 mM Fe2+. Conclusion In situ precipitation could be a simple and efficient approach for the preparation of iron-oxide magnetoliposomes. PMID:24920898

Xia, Shudong; Li, Peng; Chen, Qiang; Armah, Malik; Ying, Xiaoying; Wu, Jian; Lai, Jiangtao

2014-01-01

121

Iron, oxidative stress, and redox signaling in the cardiovascular system.  

PubMed

The redox state of the cell is predominantly dependent on an iron redox couple and is maintained within strict physiological limits. Iron is an essential metal for hemoglobin synthesis in erythrocytes, for oxidation-reduction reactions, and for cellular proliferation. The maintenance of stable iron concentrations requires the coordinated regulation of iron transport into plasma from dietary sources in the duodenum, from recycled senescent red cells in macrophages, and from storage in hepatocytes. The absorption of dietary iron, which is present in heme or nonheme form, is carried out by mature villus enterocytes of the duodenum and proximal jejunum. Multiple physiological processes are involved in maintaining iron homeostasis. These include its storage at the intracellular and extracellular level. Control of iron balance in the whole organism requires communication between sites of uptake, utilization, and storage. Key protein transporters and the molecules that regulate their activities have been identified. In this field, ferritins and hepcidin are the major regulator proteins. A variety of transcription factors may be activated depending on the level of oxidative stress, leading to the expression of different genes. Major preclinical and clinical trials have shown advances in iron-chelation therapy for the treatment of iron-overload disease as well as cardiovascular and chronic inflammatory diseases. PMID:24888568

Gudjoncik, Aurélie; Guenancia, Charles; Zeller, Marianne; Cottin, Yves; Vergely, Catherine; Rochette, Luc

2014-08-01

122

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

123

Feature Article Voltammetric Identification of Pedogenic Iron Oxides in Paleosol  

E-print Network

goethite and hematite to the overall magnetic properties is usually insignificant compared to the signalFeature Article Voltammetric Identification of Pedogenic Iron Oxides in Paleosol and Loess Toma oxides in the natural samples was below 2 wt% and below the detection limit of X-ray powder diffraction

Utrecht, Universiteit

124

21 CFR 73.200 - Synthetic iron oxide.  

Code of Federal Regulations, 2014 CFR

...mixtures for coloring foods. (b) Specifications...iron oxide for human food use shall conform to...following specifications: Arsenic (as As), not more...oxide for dog and cat food use shall conform to...following specifications: Arsenic (as As), not...

2014-04-01

125

21 CFR 73.200 - Synthetic iron oxide.  

Code of Federal Regulations, 2013 CFR

...mixtures for coloring foods. (b) Specifications...iron oxide for human food use shall conform to...following specifications: Arsenic (as As), not more...oxide for dog and cat food use shall conform to...following specifications: Arsenic (as As), not...

2013-04-01

126

21 CFR 73.200 - Synthetic iron oxide.  

Code of Federal Regulations, 2012 CFR

...mixtures for coloring foods. (b) Specifications...iron oxide for human food use shall conform to...following specifications: Arsenic (as As), not more...oxide for dog and cat food use shall conform to...following specifications: Arsenic (as As), not...

2012-04-01

127

The Oxidation of Iron in a Gel Using Consumer Chemicals  

NASA Astrophysics Data System (ADS)

The classic demonstration of the corrosion or oxidation of a steel nail in an agar gel may be conducted using inexpensive chemicals that are commonly available to the consumer on the retail market. The ferric ion produced is detected with salicylate to give a garnet-red color at the anodic areas where oxidation of iron occurs.

Wright, Stephen W.; Folger, Marsha R.; Quinn, Ryan P.

2005-11-01

128

ISOLATION AND PROPERTIES OF AN IRON-OXIDIZING THIOBACILLUS  

PubMed Central

Razzell, W. E. (British Columbia Research Council, Vancouver, Canada) and P. C. Trussell. Isolation and properties of an iron-oxidizing Thiobacillus. J. Bacteriol. 85:595–603. 1963. — An organism isolated from acidic copper-leaching waters has been shown to oxidize ferrous ions, sulfur, and metallic sulfides but exhibit peculiar responses to thiosulfate. The name Thiobacillus ferrooxidans has been used to describe it. A pH of 2.5 is optimal for growth on iron, sulfur, and metallic sulfides, but cells free from iron can be obtained from growth at pH 1.6, and sulfur cultures adjusted to pH 5.5 readily attain a pH of 1.8. A stationary cultivation procedure appears superior to percolation techniques for studying the oxidation of finely divided metallic sulfides. Concentrations of soluble copper in excess of 1 g per liter were obtained from chalcopyrite in less than 4 weeks. Chalcocite oxidation proceeded in the absence of iron. Sodium chloride inhibits iron oxidation without preventing oxidation of metallic sulfides by the organism. PMID:14042937

Razzell, W. E.; Trussell, P. C.

1963-01-01

129

ISOLATION AND PROPERTIES OF AN IRON-OXIDIZING THIOBACILLUS.  

PubMed

Razzell, W. E. (British Columbia Research Council, Vancouver, Canada) and P. C. Trussell. Isolation and properties of an iron-oxidizing Thiobacillus. J. Bacteriol. 85:595-603. 1963. - An organism isolated from acidic copper-leaching waters has been shown to oxidize ferrous ions, sulfur, and metallic sulfides but exhibit peculiar responses to thiosulfate. The name Thiobacillus ferrooxidans has been used to describe it. A pH of 2.5 is optimal for growth on iron, sulfur, and metallic sulfides, but cells free from iron can be obtained from growth at pH 1.6, and sulfur cultures adjusted to pH 5.5 readily attain a pH of 1.8. A stationary cultivation procedure appears superior to percolation techniques for studying the oxidation of finely divided metallic sulfides. Concentrations of soluble copper in excess of 1 g per liter were obtained from chalcopyrite in less than 4 weeks. Chalcocite oxidation proceeded in the absence of iron. Sodium chloride inhibits iron oxidation without preventing oxidation of metallic sulfides by the organism. PMID:14042937

RAZZELL, W E; TRUSELL, P C

1963-03-01

130

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

131

Possible involvement of iron-induced oxidative insults in neurodegeneration.  

PubMed

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

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

2015-02-19

132

Oxidation and Hydration of U3O8 Materials Following Controlled Exposure to Temperature and Humidity.  

PubMed

Chemical signatures correlated with uranium oxide processing are of interest to forensic science for inferring sample provenance. Identification of temporal changes in chemical structures of process uranium materials as a function of controlled temperatures and relative humidities may provide additional information regarding sample history. In this study, a high-purity ?-U3O8 sample and three other uranium oxide samples synthesized from reaction routes used in nuclear conversion processes were stored under controlled conditions over 2-3.5 years, and powder X-ray diffraction analysis and X-ray absorption spectroscopy were employed to characterize chemical speciation. Signatures measured from the ?-U3O8 sample indicated that the material oxidized and hydrated after storage under high humidity conditions over time. Impurities, such as uranyl fluoride or schoepites, were initially detectable in the other uranium oxide samples. After storage under controlled conditions, the analyses of the samples revealed oxidation over time, although the signature of the uranyl fluoride impurity diminished. The presence of schoepite phases in older uranium oxide material is likely indicative of storage under high humidity and should be taken into account for assessing sample history. The absence of a signature from a chemical impurity, such as uranyl fluoride hydrate, in an older material may not preclude its presence at the initial time of production. LA-UR-15-21495. PMID:25786096

Tamasi, Alison L; Boland, Kevin S; Czerwinski, Kenneth; Ellis, Jason K; Kozimor, Stosh A; Martin, Richard L; Pugmire, Alison L; Reilly, Dallas; Scott, Brian L; Sutton, Andrew D; Wagner, Gregory L; Walensky, Justin R; Wilkerson, Marianne P

2015-04-21

133

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.

134

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

135

Formation of hydrates from asymmetric and cyclic ketones in their oxidation by alkaline hexacyanoferrate(III)  

Microsoft Academic Search

\\u000a Abstract  Alkaline hexacyanoferrate(III) oxidizes 2-methyl-3-pentanone and 2-methylcyclohexanone quite rapidly. Kinetic data show second-order\\u000a kinetics with respect to hydroxide ion concentrations indicating the formation of hydrates by ketones in aqueous alkaline\\u000a medium before their reaction with the oxidant. The rate follows direct proportionality with respect to the concentrations\\u000a of hexacyanoferrate(III) and ketones. Externally added hexacyanoferrate(II) does not affect the reaction velocity indicating

Praveen Kumar Tandon; Santosh Kumar; Manish Srivastava; Santosh B. Singh

2008-01-01

136

Iron(VI) and iron(V) oxidation of thiocyanate.  

PubMed

Thiocyanate (SCN-) is used in many industrial processes and is commonly found in industrial and mining waste-waters. The removal of SCN- is required because of its toxic effects. The oxidation of thiocyanate (SCN-) by environmentally friendly oxidants, Fe(VI) and Fe(V), has been studied anaerobically using stopped-flow and premix pulse radiolysis techniques. The stoichiometry with Fe(VI) was determined to be 4HFeO(4-) + SCN(-) + 5H2O-->4Fe(OH)3 + SO4(2-) + CNO(-) + O2 + 2OH-. The rate law for the oxidation of SCN- by Fe(VI) was found to be -d[Fe(VI)]/dt = k11([H+]/([H+] + Ka,HFeO4)) [Fe(VI)][SCN-] where k11 = 2.04 +/- 0.04 x 10(3) M-1 s-1 and pKa,HFeO4 = 7.33. A mechanism is proposed that agrees with the observed reaction stoichiometry and rate law. The rate of oxidation of SCN- by Fe(V) was approximately 3 orders of magnitude faster than Fe(VI). The higher reactivity of Fe(V) with SCN- indicates that oxidations by Fe(VI) may be enhanced in the presence of appropriate one-electron-reducing agents. The results suggest that the effective removal of SCN- can be achieved by Fe(VI) and Fe(V). PMID:12380093

Sharma, Virender K; Burnett, Christopher R; O'Connor, Donald B; Cabelli, Diane

2002-10-01

137

Oxidative iron species and ocean challenges: a perspective.  

PubMed

The idea of using oxidative iron (Fe(6+)) to manage fouling and potentially invasive and pathogenic species in ballast water has merit and is attractive when viewed in the broadest context. Ferrate (Fe(6+)) has potential in ballast water management because it reduces a complex global problem to a single issue, viz.how to dispose of the waste which is predominantly Fe(3+). Waste iron disposal must be considered carefully because iron limits photosynthesis in oligotrophic oceans, alters physiological processes in bacteria and animals, produces reactive oxygen species, causes nitrosative stress and increased availability enhances the virulence of pathogenic bacteria. The case is made that the oxidative iron waste should be recycled rather than discharged into the ocean. PMID:18348007

Rittschof, Dan; Bonaventura, Celia; Wilker, Jonathan J; Van Dover, C L

2008-01-01

138

Bacterial oxidation of ferrous iron at low temperatures.  

PubMed

This study comprises the first report of ferrous iron oxidation by psychrotolerant, acidophilic iron-oxidizing bacteria capable of growing at 5 degrees C. Samples of mine drainage-impacted surface soils and sediments from the Norilsk mining region (Taimyr, Siberia) and Kristineberg (Skellefte district, Sweden) were inoculated into acidic ferrous sulfate media and incubated at 5 degrees C. Iron oxidation was preceded by an approximately 3-month lag period that was reduced in subsequent cultures. Three enrichment cultures were chosen for further work and one culture designated as isolate SS3 was purified by colony isolation from a Norilsk enrichment culture for determining the kinetics of iron oxidation. The 16S rRNA based phylogeny of SS3 and two other psychrotolerant cultures, SS5 from Norilsk and SK5 from Northern Sweden, was determined. Comparative analysis of amplified 16S rRNA gene sequences showed that the psychrotolerant cultures aligned within Acidithiobacillus ferrooxidans. The rate constant of iron oxidation by growing cultures of SS3 was in the range of 0.0162-0.0104 h(-1) depending on the initial pH. The oxidation kinetics followed an exponential pattern, consistent with a first order rate expression. Parallel iron oxidation by a mesophilic reference culture of Acidithiobacillus ferrooxidans was extremely slow and linear. Precipitates harvested from the 5 degrees C culture were identified by X-ray diffraction as mixtures of schwertmannite (ideal formula Fe(8)O(8)(OH)(6)SO(4)) and jarosite (KFe(3)(SO(4))(2)(OH)(6)). Jarosite was much more dominant in precipitates produced at 30 degrees C. PMID:17304566

Kupka, Daniel; Rzhepishevska, Olena I; Dopson, Mark; Lindström, E Börje; Karnachuk, Olia V; Tuovinen, Olli H

2007-08-15

139

Microbial reduction of crystalline iron(III) oxides: Influence of oxide surface area and potential for cell growth  

Microsoft Academic Search

Quantitative aspects of microbial crystalline iron(III) oxide reduction were examined using a dissimilatory iron(III) oxide-reducing bacterium (Shewanella alga strain BrY). The initial rate and long-term extent of reduction of a range of synthetic iron(III) oxides were linearly correlated with oxide surface area. Oxide reduction rates reached an asymptote at cell concentrations in excess of =1 x 10⁹\\/m² of oxide surface.

Eric E. Roden; John M. Zachara

1996-01-01

140

Development and use of iron oxide nanoparticles (Part 1): Synthesis of iron oxide nanoparticles for MRI  

PubMed Central

Contrast agents, such as iron oxide, enhance MR images by altering the relaxation times of tissues in which the agent is present. They can also be used to label targeted molecular imaging probes. Unfortunately, no molecular imaging probe is currently available on the clinical MRI market. A promising platform for MRI contrast agent development is nanotechnology, where superparamagnetic iron oxide nanoparticles (SPIONS) are tailored for MR contrast enhancement, and/or for molecular imaging. SPIONs can be produced using a range of methods and the choice of method will be influenced by the characteristics most important for a particular application. In addition, the ability to attach molecular markers to SPIONS heralds their application in molecular imaging. There are many reviews on SPION synthesis for MRI; however, these tend to be targeted to a chemistry audience. The development of MRI contrast agents attracts experienced researchers from many fields including some researchers with little knowledge of medical imaging or MRI. This situation presents medical radiation practitioners with opportunities for involvement, collaboration or leadership in research depending on their level of commitment and their ability to learn. Medical radiation practitioners already possess a large portion of the understanding, knowledge and skills necessary for involvement in MRI development and molecular imaging. Their expertise in imaging technology, patient care and radiation safety provides them with skills that are directly applicable to research on the development and application of SPIONs and MRI. In this paper we argue that MRI SPIONs, currently limited to major research centres, will have widespread clinical use in the future. We believe that knowledge about this growing area of research provides an opportunity for medical radiation practitioners to enhance their specialised expertise to ensure best practice in a truly multi-disciplinary environment. This review outlines how and why SPIONs can be synthesised and examines their characteristics and limitations in the context of MR imaging. PMID:21611034

Lodhia, J; Mandarano, G; Ferris, NJ; Eu, P; Cowell, SF

2010-01-01

141

Development and use of iron oxide nanoparticles (Part 1): Synthesis of iron oxide nanoparticles for MRI.  

PubMed

Contrast agents, such as iron oxide, enhance MR images by altering the relaxation times of tissues in which the agent is present. They can also be used to label targeted molecular imaging probes. Unfortunately, no molecular imaging probe is currently available on the clinical MRI market. A promising platform for MRI contrast agent development is nanotechnology, where superparamagnetic iron oxide nanoparticles (SPIONS) are tailored for MR contrast enhancement, and/or for molecular imaging. SPIONs can be produced using a range of methods and the choice of method will be influenced by the characteristics most important for a particular application. In addition, the ability to attach molecular markers to SPIONS heralds their application in molecular imaging.There are many reviews on SPION synthesis for MRI; however, these tend to be targeted to a chemistry audience. The development of MRI contrast agents attracts experienced researchers from many fields including some researchers with little knowledge of medical imaging or MRI. This situation presents medical radiation practitioners with opportunities for involvement, collaboration or leadership in research depending on their level of commitment and their ability to learn. Medical radiation practitioners already possess a large portion of the understanding, knowledge and skills necessary for involvement in MRI development and molecular imaging. Their expertise in imaging technology, patient care and radiation safety provides them with skills that are directly applicable to research on the development and application of SPIONs and MRI.In this paper we argue that MRI SPIONs, currently limited to major research centres, will have widespread clinical use in the future. We believe that knowledge about this growing area of research provides an opportunity for medical radiation practitioners to enhance their specialised expertise to ensure best practice in a truly multi-disciplinary environment. This review outlines how and why SPIONs can be synthesised and examines their characteristics and limitations in the context of MR imaging. PMID:21611034

Lodhia, J; Mandarano, G; Ferris, Nj; Eu, P; Cowell, Sf

2010-01-01

142

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

143

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

E-print Network

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

Chorover, Jon

144

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

145

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

146

Manganese- and iron-dependent marine methane oxidation.  

PubMed

Anaerobic methanotrophs help regulate Earth's climate and may have been an important part of the microbial ecosystem on the early Earth. The anaerobic oxidation of methane (AOM) is often thought of as a sulfate-dependent process, despite the fact that other electron acceptors are more energetically favorable. Here, we show that microorganisms from marine methane-seep sediment in the Eel River Basin in California are capable of using manganese (birnessite) and iron (ferrihydrite) to oxidize methane, revealing that marine AOM is coupled, either directly or indirectly, to a larger variety of oxidants than previously thought. Large amounts of manganese and iron are provided to oceans from rivers, indicating that manganese- and iron-dependent AOM have the potential to be globally important. PMID:19589998

Beal, Emily J; House, Christopher H; Orphan, Victoria J

2009-07-10

147

Manganese- and Iron-Dependent Marine Methane Oxidation  

NASA Astrophysics Data System (ADS)

Anaerobic methanotrophs help regulate Earth’s climate and may have been an important part of the microbial ecosystem on the early Earth. The anaerobic oxidation of methane (AOM) is often thought of as a sulfate-dependent process, despite the fact that other electron acceptors are more energetically favorable. Here, we show that microorganisms from marine methane-seep sediment in the Eel River Basin in California are capable of using manganese (birnessite) and iron (ferrihydrite) to oxidize methane, revealing that marine AOM is coupled, either directly or indirectly, to a larger variety of oxidants than previously thought. Large amounts of manganese and iron are provided to oceans from rivers, indicating that manganese- and iron-dependent AOM have the potential to be globally important.

Beal, Emily J.; House, Christopher H.; Orphan, Victoria J.

2009-07-01

148

The oxidation of iron-aluminum alloys  

SciTech Connect

This paper briefly summarizes studies related to the oxidation of Fe-Al alloys. Emphasis is placed on oxide phase composition, morphology, and the development of protective [alpha]-Al[sub 2]O[sub 3] scales on oxidation-resistant Fe-Al alloys both with and without ternary additions. 63 references.

Prescott, R.; Graham, M.J. (National Research Council, Ottawa, Ontario (Canada))

1992-08-01

149

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

150

Multifunctional Iron Oxide Nanoparticles for Diagnostics, Therapy and Macromolecule Delivery  

PubMed Central

In recent years, multifunctional nanoparticles (NPs) consisting of either metal (e.g. Au), or magnetic NP (e.g. iron oxide) with other fluorescent components such as quantum dots (QDs) or organic dyes have been emerging as versatile candidate systems for cancer diagnosis, therapy, and macromolecule delivery such as micro ribonucleic acid (microRNA). This review intends to highlight the recent advances in the synthesis and application of multifunctional NPs (mainly iron oxide) in theranostics, an area used to combine therapeutics and diagnostics. The recent applications of NPs in miRNA delivery are also reviewed. PMID:24396508

Yen, Swee Kuan; Padmanabhan, Parasuraman; Selvan, Subramanian Tamil

2013-01-01

151

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

152

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

153

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

154

A new uranyl oxide hydrate phase derived from spent fuel alteration  

NASA Astrophysics Data System (ADS)

An alteration phase that formed during the corrosion of commercial oxide spent nuclear fuel has been characterized with analytical transmission electron microscopy (AEM). The phase is a Cs?Ba uranyl molybdate oxide hydrate that has an orthorhombic structure related to the alkaline earth uranyl oxide hydrates of the protasite-group minerals. On the basis of the compositional analysis and a proposed model of the structure, the ideal structural formula is (Cs 0.8Ba 0.6)(UO 2) 5(MoO 2)O 4(OH) 6· nH 2O (where n is around 6). Low levels of strontium are also present in the phase. The estimated unit cell parameters are a = 0.754 nm, b = 0.654 nm, and c = 3.008 nm. Although many of the phases formed during corrosion of spent oxide fuel are similar to those observed in natural uraninite deposits, such as Peña Blanca in Mexico, there are important differences owing to the presence of fission products in the spent fuel. Thus, accurate determination of corrosion processes in actual radioactive waste forms is important. This study suggests that the natural U?Mo deposits at Shelby, WY, and Bates Mountain Tuff, NV, may be good analogues for the long-term behavior of U?Mo phases formed due to spent fuel corrosion.

Buck, E. C.; Wronkiewicz, D. J.; Finn, P. A.; Bates, J. K.

1997-09-01

155

Reactivity of an iron-oxygen oxidant generated upon oxidative decarboxylation of biomimetic iron(II) ?-hydroxy acid complexes.  

PubMed

Three biomimetic iron(II) ?-hydroxy acid complexes, [(Tp(Ph2))Fe(II)(mandelate)(H2O)] (1), [(Tp(Ph2))Fe(II)(benzilate)] (2), and [(Tp(Ph2))Fe(II)(HMP)] (3), together with two iron(II) ?-methoxy acid complexes, [(Tp(Ph2))Fe(II)(MPA)] (4) and [(Tp(Ph2))Fe(II)(MMP)] (5) (where HMP = 2-hydroxy-2-methylpropanoate, MPA = 2-methoxy-2-phenylacetate, and MMP = 2-methoxy-2-methylpropanoate), of a facial tridentate ligand Tp(Ph2) [where Tp(Ph2) = hydrotris(3,5-diphenylpyrazole-1-yl)borate] were isolated and characterized to study the mechanism of dioxygen activation at the iron(II) centers. Single-crystal X-ray structural analyses of 1, 2, and 5 were performed to assess the binding mode of an ?-hydroxy/methoxy acid anion to the iron(II) center. While the iron(II) ?-methoxy acid complexes are unreactive toward dioxygen, the iron(II) ?-hydroxy acid complexes undergo oxidative decarboxylation, implying the importance of the hydroxyl group in the activation of dioxygen. In the reaction with dioxygen, the iron(II) ?-hydroxy acid complexes form iron(III) phenolate complexes of a modified ligand (Tp(Ph2)*), where the ortho position of one of the phenyl rings of Tp(Ph2) gets hydroxylated. The iron(II) mandelate complex (1), upon decarboxylation of mandelate, affords a mixture of benzaldehyde (67%), benzoic acid (20%), and benzyl alcohol (10%). On the other hand, complexes 2 and 3 react with dioxygen to form benzophenone and acetone, respectively. The intramolecular ligand hydroxylation gets inhibited in the presence of external intercepting agents. Reactions of 1 and 2 with dioxygen in the presence of an excess amount of alkenes result in the formation of the corresponding cis-diols in good yield. The incorporation of both oxygen atoms of dioxygen into the diol products is confirmed by (18)O-labeling studies. On the basis of reactivity and mechanistic studies, the generation of a nucleophilic iron-oxygen intermediate upon decarboxylation of the coordinated ?-hydroxy acids is proposed as the active oxidant. The novel iron-oxygen intermediate oxidizes various substrates like sulfide, fluorene, toluene, ethylbenzene, and benzaldehyde. The oxidant oxidizes benzaldehyde to benzoic acid and also participates in the Cannizzaro reaction. PMID:24627956

Paria, Sayantan; Chatterjee, Sayanti; Paine, Tapan Kanti

2014-03-17

156

Growth Kinetics of Attached Iron-Oxidizing Bacteria  

PubMed Central

A model of growth and substrate utilization for ferrous-iron-oxidizing bacteria attached to the disks of a rotating biological contactor was developed and tested. The model describes attached bacterial growth as a saturation function in which the rate of substrate utilization is determined by a maximum substrate oxidation rate constant (P), a half-saturation constant (Ks), and the concentration of substrate within the rotating biological contactor (S1). The maximum oxidation rate constant was proportional to flow rate, and the substrate concentration in the reactor varied with influent substrate concentration (S0). The model allowed the prediction of metabolic constants and included terms for both constant and growth-rate-dependent maintenance energies. Estimates for metabolic constants of the attached population of acidophilic, chemolithotrophic, iron-oxidizing bacteria limited by ferrous iron were: maximum specific growth rate (?max), 1.14 h?1; half-saturation constant (Ks) for ferrous iron, 54.9 mg/liter; constant maintenance energy coefficient (m1), 0.154 h?1; growth-rate-dependent maintenance energy coefficient (m?), 0.07 h?1; maximum yield (Yg), 0.063 mg of organic nitrogen per mg of Fe(II) oxidized. PMID:16346863

Wichlacz, Paul L.; Unz, Richard F.

1985-01-01

157

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...

158

Synthesis and Processing of Iron (III) Oxide/Silica Nanopowder and Nanocomposite Structures  

E-print Network

iron oxide–silica coreshell powders compacted by using pulsed electric current sintering: Optical and magnetic properties,”iron oxide–silica coreshell powders compacted by using pulsed electric current sintering: Optical and magnetic properties,”

Chan, Kyle

2014-01-01

159

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

160

Magnetic resonance imaging contrast of iron oxide nanoparticles developed for hyperthermia is dominated by iron content  

PubMed Central

Purpose Magnetic iron oxide nanoparticles (MNPs) are used as contrast agents for magnetic resonance imaging (MRI) and hyperthermia for cancer treatment. The relationship between MRI signal intensity and cellular iron concentration for many new formulations, particularly MNPs having magnetic properties designed for heating in hyperthermia, is lacking. In this study, we examine the correlation between MRI T2 relaxation time and iron content in cancer cells loaded with various MNP formulations. Materials and methods Human prostate carcinoma DU-145 cells were loaded with starch-coated bionised nanoferrite (BNF), iron oxide (Nanomag® D-SPIO), Feridex™, and dextran-coated Johns Hopkins University (JHU) particles at a target concentration of 50 pg Fe/cell using poly-D-lysine transfection reagent. T2-weighted MRI of serial dilutions of these labelled cells was performed at 9.4 T and iron content quantification was performed using inductively coupled plasma mass spectrometry (ICP-MS). Clonogenic assay was used to characterise cytotoxicity. Results No cytotoxicity was observed at twice the target intracellular iron concentration (~100 pg Fe/cell). ICP-MS revealed highest iron uptake efficiency with BNF and JHU particles, followed by Feridex and Nanomag-D-SPIO, respectively. Imaging data showed a linear correlation between increased intracellular iron concentration and decreased T2 times, with no apparent correlation among MNP magnetic properties. Conclusions This study demonstrates that for the range of nanoparticle concentrations internalised by cancer cells the signal intensity of T2-weighted MRI correlates closely with absolute iron concentration associated with the cells. This correlation may benefit applications for cell-based cancer imaging and therapy including nanoparticle-mediated drug delivery and hyperthermia. PMID:24773041

Wabler, Michele; Zhu, Wenlian; Hedayati, Mohammad; Attaluri, Anilchandra; Zhou, Haoming; Mihalic, Jana; Geyh, Alison; DeWeese, Theodore L.; Ivkov, Robert; Artemov, Dmitri

2015-01-01

161

The Potential Waveform In The Optical Switching Of Hydrated Nickel Oxide  

NASA Astrophysics Data System (ADS)

In this work it has been analyzed the transient of the current flowing in an electrochemical cell in which the working electrode is constituted by a hydrated nickel oxide layer. The analysis of the current, utilizing a model for the diffusion mechanism of protons into the electrochromic material, allows to determine the diffusion coefficient for the oxidation and reduction processes. It ha5been observed that the diffusion coefficient for the bleaching process is larger than that one of the oxidation process. This fact could explain why the transition to the coloured phase occurs more rapidly than the inverse transition and with an apparently more simple function. Attempts have been made to put in correlation the eventual formation of metastable cristallographyc phases, observed by the X-rays diffraction technique, submitting the sample to a periodic potential, with a square waveform, for several cycles.

Pennisi, Agostino; Simone, Francesca

1989-03-01

162

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

163

OXYANION SORPTION TO HIGH SURFACE AREA IRON AND ALUMINUM OXIDES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sorption of selected oxyanions (Mo, As, and P) to high surface area iron and aluminum oxides was investigated using in situ Raman and ATR-FTIR spectroscopy, batch sorption methods, electrophoretic mobility measurements, and surface complexation modeling. In situ ATR-FTIR and Raman spectra were coup...

164

Efficient Formation of Iron Nanoparticle Catalysts on Silicon Oxide by  

E-print Network

Efficient Formation of Iron Nanoparticle Catalysts on Silicon Oxide by Hydroxylamine for CarbonO2. The solution phase catalyst deposition approach allows for submicron scale catalyst patterning. Patterned growth of nanotubes with this catalyst retains high degrees of surface cleanliness and leads

Javey, Ali

165

Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles  

E-print Network

Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles W. Brullot a in revised form 20 December 2011 Available online 3 February 2012 Keywords: Ferrofluid Polyethylene glycol Magneto-optics Magnetite Rheology a b s t r a c t Versatile ferrofluids based on polyethylene glycol

166

Interpretation of the postpeak in iron fluorides and oxides.  

PubMed

A broad post-edge peak (postpeak) in the core-loss spectrum of a relatively thick TEM specimen is readily accounted for by plural scattering of the transmitted electrons, involving a core-loss and a bulk plasmon. However, we observe a prominent postpeak, about 40 eV above iron L3 edge, even in very thin films of iron fluoride. The peak gradually disappears as fluorine is removed by electron irradiation, as indicated by decay of the fluorine K-edge and change in white-line ratio, but appears when an iron film is oxidized, therefore it appears to be characteristic of iron in an oxidized state. To study its origin, we performed real-space multiple-scattering (RSMS) calculations of the near-edge fine structure of the Fe L-edge, allowing us to discuss the origin of the postpeak within the framework of electron-scattering theory. In the belief that oxygen and fluorine anions in transition-metal compounds are strong backscatters, we propose that the postpeak is a common feature of transition metals in an oxidized state and can be used as an additional verification of such oxidization in an unknown sample. PMID:16764991

Wang, Feng; Egerton, Ray F; Malac, Marek

2006-01-01

167

RESEARCH PAPER Effects of iron oxide nanoparticles on polyvinyl alcohol  

E-print Network

RESEARCH PAPER Effects of iron oxide nanoparticles on polyvinyl alcohol: interfacial layer and bulk:1 and 14 nm for 50:1). The presence of polyvinyl alcohol (PVA) limits the particle growth (15 nm for 20 to the nanoparticle surface, the nanoparticles are found not only to increase the PVA cross-linking with an increase

Guo, John Zhanhu

168

Selective removal of phosphate from wastewater using hydrated metal oxides dispersed within anionic exchange media.  

PubMed

Hydrated ferric oxide (HFeO), hydrated zirconium oxide (HZrO) and hydrated copper oxide (HCuO) were immobilized within a microporous anion exchange resin (IRA-400), forming hybrid media for enhanced phosphate removal from aqueous systems. Empirical data from batch kinetic trials fitted the pseudo second order mechanism for chemical adsorption and each media was rate limited by intraparticle diffusion overall. These models were also used to predict the adsorption rate constants and the equilibrium adsorption capacities, which ranged from 26.51 to 30.44 mgP g(-1), and from 24.15 to 27.90 mgP g(-1) of media for the calculated and experimental capacities, respectively. The phosphate adsorption behavior by the hybrid materials fit both the Langmuir and Freundlich adsorption isotherms (R(2)>0.94), and the maximum adsorption capacities were 111.1 mgP g(-1) for HFeO, 91.74 mgP g(-1) for HZrO and 74.07 mgP g(-1) for HCuO. The effect of competing ions such as sulfate reduced these capacities to 18.52 mgP g(-1) for HFeO and 18.97 mgP g(-1) for HZrO. Despite this decrease, HFeO was capable of reducing the phosphate in a real wastewater matrix by 83%, and the HZrO media was able to reduce it by 86%, suggesting that such hybrid media have the potential for application at full scale. PMID:24630462

Acelas, Nancy Y; Martin, Benjamin D; López, Diana; Jefferson, Bruce

2015-01-01

169

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

170

Alkane oxidation by an iron complex-hydrogen peroxide system in acetonitrile. The model of methanemonooxygenase  

Microsoft Academic Search

The oxidation of methane and other light alkanes in the system iron complex — hydrogen peroxide has been studied. The efficiency of this system of alkane oxidation depends on water concentration. The catalytic methanol formation from methane with respect to the binuclear iron complex has been observed. The role of iron-oxocomplexes in oxidation of alkanes by methanemonooxygenase and model systems

A. M. Khenkin; V. S. Belova; A. E. Shilov

1990-01-01

171

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

172

A chameleon catalyst for nonheme iron-promoted olefin oxidation.  

PubMed

We report the chameleonic reactivity of two nonheme iron catalysts for olefin oxidation with H2O2 that switch from nearly exclusive cis-dihydroxylation of electron-poor olefins to the exclusive epoxidation of electron-rich olefins upon addition of acetic acid. This switching suggests a common precursor to the nucleophilic oxidant proposed to Fe(III)-?(2)-OOH and electrophilic oxidant proposed to Fe(V)(O)(OAc), and reversible coordination of acetic acid as a switching pathway. PMID:25251577

Iyer, Shyam R; Javadi, Maedeh Moshref; Feng, Yan; Hyun, Min Young; Oloo, Williamson N; Kim, Cheal; Que, Lawrence

2014-11-18

173

Oxidative stress and aging: the potential role of iron.  

PubMed

According to the free radical theory of aging proposed by Denham Harman more than 50 years ago, oxidatively modified cellular components accumulate continuously in the cells during the organism's lifespan leading to progressive decline of cellular functions. Since then, it has been shown that proteins, lipids, nucleic acids and other cell components undergo reversible and/or irreversible oxidative modifications during aging. Moreover, oxidized cell components can undergo further oxidative modifications leading to formation of products that cell degradation systems are incapable of removing. Accumulation of such non-degradable aggregates further inhibits the functionality of degradation systems, thus aggravating the effects and leading to a vicious cycle. In this presentation, we propose that the availability of intracellular iron in its redox active form (labile iron) represents the main catalyst that mediates extensive oxidative modifications of cellular components and ultimately leads to their accumulation and consequent cellular dysfunction. It is tempting to speculate that regulated restriction of labile iron may have positive effects on health in general and aging in particular. PMID:18477548

Galaris, Dimitrios; Mantzaris, Michalis; Amorgianiotis, Christos

2008-01-01

174

Oxidation, carburization and/or sulfidation resistant iron aluminide alloy  

DOEpatents

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

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

2003-08-19

175

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

PubMed

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

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

2011-10-25

176

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

PubMed Central

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

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

2011-01-01

177

Oxide Dispersion Strengthened Iron Aluminide by CVD Coated Powders  

SciTech Connect

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

Asit Biswas Andrew J. Sherman

2006-09-25

178

Study of nanocomposites based on iron oxides and pectin  

SciTech Connect

Mössbauer and X-ray diffraction study of nanocomposites based on iron oxides and pectin (PC) was carried out involving magnetization measurements. The concentrations of PC in nanocomposites varied from 0 to 10%. Mössbauer investigations of nanocomposites were carried out in the temperature range from 5 to 300 K. Many-state superparamagnetic relaxation model was used for spectra fitting. The magnetization, M(T,H), was measured in the temperature interval of 80-300 K and magnetic field up to 10 kOe. Formation of the 'iron-polymer' interface was not observed. Particle sizes were estimated using the Mössbauer and X-ray powder diffraction data.

Chistyakova, Nataliya I., E-mail: nchistyakova@yandex.ru; Shapkin, Alexey A., E-mail: nchistyakova@yandex.ru; Sirazhdinov, Ruslan R., E-mail: nchistyakova@yandex.ru; Gubaidulina, Tatiana V., E-mail: nchistyakova@yandex.ru; Kiseleva, Tatiana Yu., E-mail: nchistyakova@yandex.ru; Kazakov, Alexander P., E-mail: nchistyakova@yandex.ru; Rusakov, Vyacheslav S., E-mail: nchistyakova@yandex.ru [M. V. Lomonosov Moscow State University, Faculty of Physics, Leninskie gory, 119991 Moscow (Russian Federation)

2014-10-27

179

Iron Photolysis for Advanced Oxidation Processes  

E-print Network

of having harmful effects on the public if not properly eliminated. Advanced Oxidation Processes (AOPs Engineering Department, University of Arizona University of Arizona, Technology and Research Initiative Fund into effectively treating and recycling water to make use of what is accessible within such a low-water environment

Fay, Noah

180

The oxidation behavior of ODS iron aluminides  

SciTech Connect

Oxide-dispersed Fe-28at.%Al-2%Cr alloys were produced by a powder metallurgy technique followed by hot extrusion. A variety of stable oxides were added to the base alloy to assess the effect of these dopants on the oxidation behavior at 1200{degrees}C in air and O{sub 2}. An Al{sub 2}O{sub 3} dispersion flattened the {alpha}-Al{sub 2}O{sub 3} scale, but produced none of the other reactive element effects and had an adverse influence on the long-term oxidation behavior. A Y{sub 2}O{sub 3} dispersion improved the alumina scale adhesion relative to a Zr alloy addition at 1200{degrees} and 1300{degrees}C. However, the Y{sub 2}O{sub 3} dispersion was not as effective in improving scale adhesion in Fe{sub 3}Al as it is in FeCrAl. This inferior performance is attributed to a larger amount of interfacial void formation on ODS Fe{sub 3}Al.

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

1996-05-01

181

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

182

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

SciTech Connect

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

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

2005-05-11

183

Niobian iron oxides as heterogeneous Fenton catalysts for environmental remediation  

NASA Astrophysics Data System (ADS)

Heterogeneous Fenton or Fenton-like reagents consist of a mixture of an iron-containing solid matrix and a liquid medium with H2O2. The Fenton system is based on the reaction between Fe2 + and H2O2 to produce highly reactive intermediate hydroxyl radicals ( • OH), which are able to oxidize organic contaminants, whereas the Fenton-like reaction is based on the reaction between Fe3 + and H2O2. These heterogeneous systems offer several advantages over their homogeneous counterparts, such as no sludge formation, operation at near-neutral pH and the possibility of recycling the iron promoter. Some doping transition cations in the iron oxide structure are believed to enhance the catalytic efficiency for the oxidation of organic substrates in water. In this work, goethites synthesized in presence of niobium served as precursors for the preparation of magnetites (niobian magnetites) via chemical reduction with hydrogen at 400°C. These materials were used as Fenton-like catalysts. Both groups of (Nb, Fe)-oxide samples were characterized by 57Fe Mössbauer spectroscopy at 298 K. The results show that increasing niobium contents raise the catalytic potential for decomposition of methylene blue, which was, in this work, used as a model molecule for organic substrates in water.

Oliveira, Diana Q. L.; Oliveira, Luiz C. A.; Murad, Enver; Fabris, José D.; Silva, Adilson C.; de Menezes, Lucas Morais

2010-01-01

184

Intratumoral iron oxide nanoparticle hyperthermia and radiation cancer treatment  

NASA Astrophysics Data System (ADS)

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 x 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 non-nanoparticle 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, P. J.; Strawbridge, R. R.; Gibson, U. J.; Zeng, Q.; Pierce, Z. E.; Savellano, M.; Tate, J. A.; Ogden, J. A.; Baker, I.; Ivkov, R.; Foreman, A. R.

2007-02-01

185

Wear resistance of iron oxide thin films  

Microsoft Academic Search

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

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

1988-01-01

186

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

187

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

PubMed

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

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

2015-01-01

188

Synthesis and properties of magnetic iron oxide/platinum nanocomposites  

NASA Astrophysics Data System (ADS)

Iron oxide/platinum nanocomposites have been synthesized by the extractive-pyrolytic method (EPM) involving gradual decomposition of iron capronate and n-trioctylammonium hexachloroplatinate initially produced by solvent extraction. The content of platinum in the composites was 1.2 wt%, 2.4 wt% and 4.8 wt%. Phase composition, morphology and magnetic properties of the produced materials were investigated. XRD analysis and magnetic measurements show that the magnetic phase (magnetite Fe3O4) dominates in a carrier sample produced by the pyrolysis of iron carboxylate, but hematite ?-Fe2O3 exists there as an admixture. Referring to the TEM results, the produced composites contain ultra-disperse platinum particles on the carrier, and the mean size of these varies from 3 nm to 9 nm.

Serga, V.; Maiorov, M.; Kulikova, L.; Krumina, A.; Karashanova, D.

2015-03-01

189

Hydration of aldehydes and ketones in the presence of iron catalysts  

Microsoft Academic Search

1.A comparison has been made between the activities of iron catalysts prepared in different ways in a model reaction of the hydrogenation of C4, and C5 aldehydes and ketones in order to find the hydrogenating capability of these catalysts.2.In the presence of iron catalysts promoted with Cu, Pd, and Ni the carbonyl group is hydrogenated only at elevated pressure and

A. A. Balandin; A. I. Kukina; É. V. Toptygina

1962-01-01

190

Iron aluminide alloy container for solid oxide fuel cells  

DOEpatents

A container for fuel cells is made from an iron aluminide alloy. The container alloy preferably includes from about 13 to about 22 weight percent Al, from about 2 to about 8 weight percent Cr, from about 0.1 to about 4 weight percent M selected from Zr and Hf, from about 0.005 to about 0.5 weight percent B or from about 0.001 to about 1 weight percent C, and the balance Fe and incidental impurities. The iron aluminide container alloy is extremely resistant to corrosion and metal loss when exposed to dual reducing and oxidizing atmospheres at elevated temperatures. The alloy is particularly useful for containment vessels for solid oxide fuel cells, as a replacement for stainless steel alloys which are currently used.

Judkins, Roddie Reagan (Knoxville, TN); Singh, Prabhakar (Export, PA); Sikka, Vinod Kumar (Oak Ridge, TN)

2000-01-01

191

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

192

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

PubMed

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

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

2011-01-01

193

Versatile ferrofluids based on polyethylene glycol coated iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

194

Reflection spectra and magnetochemistry of iron oxides and natural surfaces  

NASA Technical Reports Server (NTRS)

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

Wasilewski, P.

1978-01-01

195

Iron Photolysis for Advanced Oxidation Processes  

E-print Network

.7 (H2SO4) 1mM H2O2 0.8mM H2O2 0.7mM H2O2 #12; Thanks to Water Sustainability Program and Saez research.05 mM FeII + 0.03 mM FeIII #12;Para-cresol degradation in photo- Fenton system 0 0.1 0.2 0.3 0.4 0.5 0 and ultraviolet light Advanced Oxidation #12;photo-Fenton system #12;Procedure 300 mL reactor, constantly stirred

Fay, Noah

196

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

197

Iron Supplementation and Oxidative Damage to DNA in Healthy Individuals with High Plasma Ascorbate  

Microsoft Academic Search

Previously, we have investigated the potential for a pro-oxidant interaction of iron and ascorbate in vivo in iron and ascorbate cosupplementation or ascorbate supplementation studies. In this study, for the first time, the effects of iron supplementation on oxidative damage to DNA in healthy individuals with plasma ascorbate levels at the upper end of the normal range were examined. Forty

Anna R. Proteggente; Timothy G. England; Catherine A. Rice-Evans; Barry Halliwell

2001-01-01

198

Magnetic properties of polypyrrole-coated iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2005-09-01

199

Iron Requirement for Mn(II) Oxidation by Leptothrix discophora SS-1?  

PubMed Central

A common form of biocatalysis of Mn(II) oxidation results in the formation of biogenic Mn(III, IV) oxides and is a key reaction in the geochemical cycling of Mn. In this study, we grew the model Mn(II)-oxidizing bacterium Leptothrix discophora SS-1 in media with limited iron (0.1 ?M iron/5.8 mM pyruvate) and sufficient iron (0.2 ?M iron/5.8 mM pyruvate). The influence of iron on the rate of extracellular Mn(II) oxidation was evaluated. Cultures in which cell growth was limited by iron exhibited reduced abilities to oxidize Mn(II) compared to cultures in medium with sufficient iron. While the extracellular Mn(II)-oxidizing factor (MOF) is thought to be a putative multicopper oxidase, Mn(II) oxidation in the presence of zero added Cu(II) was detected and the decrease in the observed Mn(II) oxidation rate in iron-limited cultures was not relieved when the medium was supplemented with Cu(II). The decline of Mn(II) oxidation under iron-limited conditions was not accompanied by siderophore production and is unlikely to be an artifact of siderophore complex formation with Mn(III). The temporal variations in mofA gene transcript levels under conditions of limited and abundant iron were similar, indicating that iron limitation did not interfere with the transcription of the mofA gene. Our quantitative PCR results provide a step forward in understanding the regulation of Mn(II) oxidation. The mechanistic role of iron in Mn(II) oxidation is uncertain; the data are consistent with a direct requirement for iron as a component of the MOF or an indirect effect of iron resulting from the limitation of one of many cellular functions requiring iron. PMID:19114505

El Gheriany, Iman A.; Bocioaga, Daniela; Hay, Anthony G.; Ghiorse, William C.; Shuler, Michael L.; Lion, Leonard W.

2009-01-01

200

Inkjet printing of sol-gel synthesized hydrated tungsten oxide nanoparticles for flexible electrochromic devices.  

PubMed

Tungsten oxide nanoparticles were synthesized via a sol-gel route using metallic tungsten as precursor, and were printed on a flexible electrode using inkjet printing in order to build solid-state electrochromic cells. Several spectroscopic techniques were used to characterize and compare tungsten oxide particles obtained from different origins. FTIR, Raman and X-ray diffraction spectroscopic measurements showed that the sol-gel synthesis described here produces nanoparticles mainly in an amorphous state with hexagonal crystalline domains and allowed the analysis of the hydration extent of those nanoparticles. The size was measured combining dynamic light scattering, sedimentation, and microscopic techniques (AFM), showing a consistent size of about 200 nm. The tungsten oxide nanoparticles were used to produce an ink formulation for application in inkjet printing. Solid-state electrochromic devices were assembled at room temperature, without sintering the tungsten oxide printed films, showing excellent contrast between on/off states. Electrochemical characterization of those films is described using cyclic voltammetry. The devices were then tested through spectroelectrochemistry by Visible/NIR absorption spectroscopy (400-2200 nm range), showing a dual spectroscopic response depending on the applied voltage. This phenomenon is attributed to the presence of two different crystalline states in accordance with results obtained from the spectroscopic characterization of the nanoparticles. The electrochromic cells had a good cycling stability showing high reversibility and a cyclability up to more than 50,000 cycles with a degradation of 25%. PMID:22321260

Costa, Cláudia; Pinheiro, Carlos; Henriques, Inês; Laia, César A T

2012-03-01

201

Deep oxidation of 1,2-dichlorobenzene over Ti-doped iron oxide.  

PubMed

Ti-doped iron oxides with worm-like mesopores were successfully prepared using CTAB as the structure-directing agent. The as-prepared catalysts were characterized by XRD, Raman, H2-TPR, XPS, TEM, and N2 adsorption/desorption. The catalytic properties for oxidation of 1,2-dichlorobenzene (o-DCB) were investigated. The results showed that Fe18Ti2Ox with 10 mol% Ti-doping shows the best catalytic activity, and the total conversion of o-DCB can be obtained at 350 °C. Moreover, Fe18Ti2Ox exhibits higher stability, CO2 selectivity and lower apparent activation energy. The high activity of Fe18Ti2Ox could be ascribed to the combined factors including a smaller crystallite size, excellent low-temperature reducibility, high surface active oxygen concentration and a synergic effect between TiO2 and mixed iron oxide (?-Fe2O3 and ?-Fe2O3). Acetate and formate species as intermediates were detected by in situ FTIR spectroscopy. A two-step redox mechanism of o-DCB decomposition on the surface of Ti-doped iron oxides was proposed. These results demonstrated that Ti-doped iron oxides could be developed as environmentally friendly catalysts for the deep oxidation of chlorinated volatile organic pollutants. PMID:24832548

Ma, Xiaodong; Suo, Xueyue; Cao, Huiqin; Guo, Jie; Lv, Lu; Sun, Hongwen; Zheng, Meihua

2014-07-01

202

Unification of catalytic water oxidation and oxygen reduction reactions: amorphous beat crystalline cobalt iron oxides.  

PubMed

Catalytic water splitting to hydrogen and oxygen is considered as one of the convenient routes for the sustainable energy conversion. Bifunctional catalysts for the electrocatalytic oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are pivotal for the energy conversion and storage, and alternatively, the photochemical water oxidation in biomimetic fashion is also considered as the most useful way to convert solar energy into chemical energy. Here we present a facile solvothermal route to control the synthesis of amorphous and crystalline cobalt iron oxides by controlling the crystallinity of the materials with changing solvent and reaction time and further utilize these materials as multifunctional catalysts for the unification of photochemical and electrochemical water oxidation as well as for the oxygen reduction reaction. Notably, the amorphous cobalt iron oxide produces superior catalytic activity over the crystalline one under photochemical and electrochemical water oxidation and oxygen reduction conditions. PMID:25469760

Indra, Arindam; Menezes, Prashanth W; Sahraie, Nastaran Ranjbar; Bergmann, Arno; Das, Chittaranjan; Tallarida, Massimo; Schmeißer, Dieter; Strasser, Peter; Driess, Matthias

2014-12-17

203

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

PubMed

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

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

2013-01-01

204

Abstract No. pan0505 Sorption of Heavy Metal Contaminants onto Hydrated Ferric Oxides: Mechanistic Modeling using X-ray  

E-print Network

Abstract No. pan0505 Sorption of Heavy Metal Contaminants onto Hydrated Ferric Oxides: Mechanistic the fate of heavy metal contaminants, such as lead, zinc, and nickel in soils and aquatic environments. Hence, to understand the mobility and bioavailability of these metal contaminants, these sorption

Sparks, Donald L.

205

Effects of green tea on iron accumulation and oxidative stress in livers of iron-challenged thalassemic mice.  

PubMed

Liver is affected by secondary iron overload in transfusions dependent b-thalassemia patients. The redox iron can generate reactive oxidants that damage biomolecules, leading to liver fibrosis and cirrhosis. Iron chelators are used to treat thalassemias to achieve negative iron balance and relieve oxidant-induced organ dysfunctions. Green tea (GT) (Camellia sinensis) catechins exhibit anti-oxidation, the inhibition of carcinogenesis, the detoxification of CYP2E1-catalyzed HepG2 cells and iron chelation. The purpose of this study was to investigate the effectiveness of GT in iron-challenged thalassemic mice. Heterozygous BKO type-thalassemia (BKO) mice (C57BL/6) experienced induced iron overload by being fed a ferrocene-supplemented diet (Fe diet) for 8 weeks, and by orally being given GT extract (300 mg/kg) and deferiprone (DFP) (50 mg/kg) for a further 8 weeks. Liver iron content (LIC) was analyzed by TPTZ colorimetric and Perl's staining techniques. Concentrations of liver reduced glutathione (GSH), collagen and malondialdehyde (MDA) were also measured. Dosages of the GT extract and DFP lowered LIC in the Fe diet-fed BKO mice effectively. The extract did not change any concentrations of liver glutathione, collagen and MDA in the BKO mice. Histochemical examination showed leukocyte infiltration in the near by hepatic portal vein and high iron accumulation in the livers of the iron-loaded BKO mice, however GT treatment lowered the elevated iron deposition. In conclusion, green tea inhibits or delays the deposition of hepatic iron in regularly iron-loaded thalassemic mice effectively. This will prevent the iron-induced generation of free radicals via Haber-Weiss and Fenton reactions, and consequently liver damage and fibrosis. Combined chelation with green tea would be investigated in beta-thalassemia patients with iron overload. PMID:20218965

Saewong, T; Ounjaijean, S; Mundee, Y; Pattanapanyasat, K; Fucharoen, S; Porter, J B; Srichairatanakool, S

2010-03-01

206

Evaluation of iron oxide nanoparticle biocompatibility  

PubMed Central

Nanotechnology is an exciting field of investigation for the development of new treatments for many human diseases. However, it is necessary to assess the biocompatibility of nanoparticles in vitro and in vivo before considering clinical applications. Our characterization of polyol-produced maghemite ?-Fe2O3 nanoparticles showed high structural quality. The particles showed a homogeneous spherical size around 10 nm and could form aggregates depending on the dispersion conditions. Such nanoparticles were efficiently taken up in vitro by human endothelial cells, which represent the first biological barrier to nanoparticles in vivo. However, ?-Fe2O3 can cause cell death within 24 hours of exposure, most likely through oxidative stress. Further in vivo exploration suggests that although ?-Fe2O3 nanoparticles are rapidly cleared through the urine, they can lead to toxicity in the liver, kidneys and lungs, while the brain and heart remain unaffected. In conclusion, ?-Fe2O3 could exhibit harmful properties and therefore surface coating, cellular targeting, and local exposure should be considered before developing clinical applications. PMID:21589646

Hanini, Amel; Schmitt, Alain; Kacem, Kamel; Chau, François; Ammar, Souad; Gavard, Julie

2011-01-01

207

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...

208

Accumulation of iron oxide nanoparticles by cultured primary neurons.  

PubMed

Magnetic iron oxide nanoparticles (IONPs) are frequently used for biomedical applications. Although nanoparticles can enter the brain, little is known so far on the uptake of IONPs in neurons and on their neurotoxic potential. Hence, we applied dimercaptosuccinate (DMSA)-coated IONPs to cultured primary rat cerebellar granule neurons. These IONPs had average hydrodynamic diameters of around 80?nm and 120?nm when dispersed in incubation medium in the absence and the presence of 10% fetal calf serum, respectively. Acute exposure of neurons with IONPs for up to 6?h did neither alter the cell morphology nor compromise cell viability, although neurons accumulated large amounts of IONPs in a time- and concentration-dependent manner which caused delayed toxicity. For the first 30?min of incubation of neurons at 37?°C with IONPs the cellular iron content increased proportionally to the concentration of IONPs applied irrespective of the absence and the presence of serum. IONP-exposure in the absence of serum generated maximal cellular iron contents of around 3000?nmol iron/mg protein after 4?h of incubation, while the accumulation in the presence of 10% serum was slower and reached already within 1?h maximal values of around 450?nmol iron/mg protein. For both incubation conditions was the increase in cellular iron contents significantly lowered by reducing the incubation temperature to 4?°C. Application of inhibitors of endocytotic pathways did not affect neuronal IONP accumulation in the absence of serum, while inhibitors of clathrin-mediated endocytosis lowered significantly the IONP accumulation in the presence of serum. These data demonstrate that DMSA-coated IONPs are not acutely toxic to cultured neurons and that a protein corona around the particles strongly affects their interaction with neurons. PMID:25510641

Petters, Charlotte; Dringen, Ralf

2015-02-01

209

Minimizing biofilm in the presence of iron oxides and humic substances  

Microsoft Academic Search

Based upon circumstantial evidence linking elevated coliform bacteria counts in drinking water distribution systems with unlined cast iron pipe, it was hypothesized that adsorption of humic substances by iron oxide containing corrosion products (CPs) can stimulate and\\/or support biofilm development. Using porous media consisting of iron-oxide-coated glass beads (IOCBs) or actual iron CPs, experiments were performed to evaluate the effectiveness

Phillip W Butterfield; Anne K Camper; Joel A Biederman; Alex M Bargmeyer

2002-01-01

210

Iron deficiency suppresses ileal nitric oxide synthase activity.  

PubMed

Intestinal motility disorders are more common in women of childbearing age who are prone to iron deficiency anemia. The neurotransmitters nitric oxide (NO) and acetylcholine (ACh) play a key role in ileal smooth muscle relaxation and contraction, respectively. Iron-containing heme is known to be a cofactor for nitric oxide synthase (NOS), the enzyme responsible for NO production. Therefore we tested the hypothesis that iron deficiency would downregulate ileal NOS activity without affecting the ileum's response to ACh. Twelve adult female prairie dogs were fed either an iron-supplemented (Fe+) (200 ppm) (n = 6) or an iron-deficient (Fe-) (8 ppm) (n = 6) diet for 8 weeks. Ileal circular muscle strips were harvested to measure responses to ACh and electrical field stimulation. Under nonadrenergic noncholinergic (NANC) conditions, Nomega-nitro-L-arginine (L-NNA), an NOS inhibitor, and VIP(10-28), a vasoactive intestinal peptide (VIP) inhibitor, were added prior to electrical field stimulation. NANC inhibitory responses are expressed as a percentage of optimal relaxation from EDTA. The excitatory response to ACh was similar in both groups (1.1 +/- 0.3 N/cm(2) vs. 1.5 +/- 0.3 N/cm(2), P = 0.45). The inhibitory response to electrical field stimulation under NANC conditions was greater in the Fe+ group (34.7 +/- 2.9%) compared to the Fe- group (23.9 +/- 3.2%; P<0.01). L-NNA eliminated the inhibitory response in the Fe+ group (0.02 +/- 0.02%) but not in the Fe- group (8.38 +/- 2.15%; P <0.01). VIP(10-28) led to greater relaxation in the Fe+ animals (45.8 +/- 6.6%) than in the Fe- animals (23.4 +/- 5.8%; P <0.05). Both L-NNA and VIP(10-28) had no inhibitory response (0.02 +/- 0.02%) in the Fe+ animals, whereas the Fe- animals had some residual inhibition (2.54 +/- 1.04%; P <0.05). These data suggest that ileal NANC relaxation is due to NOS and that iron deficiency results in (1) decreased NANC relaxation, (2) a compensatory relaxation due to a non-NOS, non-VIP mechanism, and (3) a normal excitatory response. We conclude that iron deficiency suppresses ileal NOS activity. PMID:11985981

Goldblatt, M I; Choi, S H; Swartz-Basile, D A; Nakeeb, A; Sarna, S K; Pitt, H A

2001-01-01

211

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

212

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

213

Green rust and iron oxide formation influences metolachlor dechlorination during zerovalent iron treatment.  

PubMed

Electron transfer from zerovalent iron (Fe0) to targeted contaminants is affected by initial Fe0 composition, the oxides formed during corrosion, and surrounding electrolytes. We previously observed enhanced metolachlor destruction by Fe0 when iron or aluminum salts were present in the aqueous matrix and Eh/pH conditions favored formation of green rusts. To understand these enhanced destruction rates, we characterized changes in Fe0 composition during treatment of metolachlor with and without iron and aluminum salts. Raman microspectroscopy and X-ray diffraction (XRD) indicated that the iron source was initially coated with a thin layer of magnetite (Fe3O4), maghemite (gamma-Fe2O3), and wüstite (FeO). Time-resolved analysis indicated that akaganeite (beta-FeOOH) was the dominant oxide formed during Fe0 treatment of metolachlor. Goethite (alpha-FeOOH) and some lepidocrocite (gamma-FeOOH) formed when Al2(SO4)3 was present, while goethite and magnetite (Fe3O4) were identified in Fe0 treatments containing FeSO4. Although conditions favoring formation of sulfate green rust (GR(II); Fe6(OH)12SO4) facilitated Fe0-mediated dechlorination of metolachlor, only adsorption was observed when GR(II) was synthesized (without Fe0) in the presence of metolachlor and Eh/pH changed to favor Fe(III)oxyhydroxide or magnetite formation. In contrast, dechlorination occurred when magnetite or natural goethite was amended with Fe(II) (as FeSO4) at pH 8 and continued as long as additional Fe(II) was provided. While metolachlor was not dechlorinated by GR(II) itself during a 48-h incubation, the GR(II) provided a source of Fe(II) and produced magnetite (and other oxide surfaces) that coordinated Fe(II), which then facilitated dechlorination. PMID:14655711

Satapanajaru, Tunlawit; Shea, Patrick J; Comfort, Steve D; Roh, Yul

2003-11-15

214

Engineered Iron Oxide-Adhesion Mutants of the Escherichia coli Phage lambda Receptor  

Microsoft Academic Search

Escherichia coli able to specifically adhere to iron oxide and not adhere to other metal oxides were constructed by genetic engineering. Concatamers of random oligonucleotides were introduced into a portion of a plasmid-borne lamB gene encoding an external domain of the phage lambda receptor. Bacteria able to adhere to iron oxide were selected by serial enrichment from the population of

Stanley Brown

1992-01-01

215

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

NASA Astrophysics Data System (ADS)

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

Rutter, Matthew

216

Anoxic photochemical oxidation of siderite generates molecular hydrogen and iron oxides  

PubMed Central

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.

2013-01-01

217

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

218

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

219

In Vivo Clearance and Toxicity of Monodisperse Iron Oxide Nanocrystals  

PubMed Central

Thermal decomposition of organometallic precursors have been found to generate highly crystalline iron oxide (IO) nanocrystals that display superior MR contrast and lower polydispersity than IO nanocrystals synthesized by aqueous precipitation. In the present study, the in vivo characteristics of IO nanocrystals prepared by the thermal decomposition route and then coated with a phospholipid containing a pendant poly(ethylene glycol) chain are examined. The size and surface chemistry of the IO nanocrystal influences the biodistibution, the rate of biodegradation and bioclearance, and the biodegradation products. We conclude that the in vivo fate of PEGylated monodisperse IO nanocrystals and the iron, phospholipid, and oleic acid biodegradation products may influence the cellular environments in the organs and blood that can determine their safety in the body. PMID:22646927

Gu, Luo; Fang, Ronnie H.; Sailor, Michael J.; Park, Ji-Ho

2012-01-01

220

Magnetic characteristics of iron-modified oxide layers on titanium  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

221

Synthesis, phase transition, and magnetic property of iron oxide materials: effect of sodium hydroxide concentrations  

Microsoft Academic Search

In this paper, a class of novel iron oxide particles has been fabricated through surfactant-directed structure approach in\\u000a hydrothermal reaction. The obtained iron oxide nanostructures with distinct morphologies, such as rhombohedra, octahedral,\\u000a plate-like, as well as dendritic, can be obtained by gradually increasing the concentrations of NaOH. The as-prepared iron\\u000a oxide particles were characterized utilizing scanning electronic microscopy (SEM), X-ray

Xiaohui Guo; Shengliang Zhong; Ji Zhang; Wanv Wang; Jianjiang Mao; Gang Xie

2010-01-01

222

Some aspects on porous properties of iron oxides containing foreign oxides reduced by hydrogen  

NASA Astrophysics Data System (ADS)

The objective of this study is to prepare suitable iron ores for industrial reduction processes. Therefore, the properties of porous, green and indurated hematite compacts as well as iron ore were investigated by quantitatively measuring pore volume, BET surface area and pore size distribution. Furthermore, the influence of foreign oxides on porous properties was investigated. Based on these data, the mechanism of sintering process of the compacts was discussed. The results obtained here suggest that the porosity of the compacts after almost 100 pct reduction does not depend upon whether the compacts were indurated or not. Therefore, it would be concluded that indurating the compact is not necessary for pulverized iron ores containing foreign oxides when reduced in the process such as a fluidized bed system.

Suzuki, Y.; Yamamoto, M.; Kotanigawa, T.; Nishida, K.

1981-12-01

223

Greenlighting photoelectrochemical oxidation of water by iron oxide.  

PubMed

Hematite (?-Fe2O3) is one of just a few candidate electrode materials that possess all of the following photocatalyst-essential properties for scalable application to water oxidation: excellent stability, earth-abundance, suitability positive valence-band-edge energy, and significant visible light absorptivity. Despite these merits, hematite's modest oxygen evolution reaction kinetics and its poor efficiency in delivering photogenerated holes, especially holes generated by green photons, to the electrode/solution interface, render it ineffective as a practical water-splitting catalyst. Here we show that hole delivery and catalytic utilization can be substantially improved through Ti alloying, provided that the alloyed material is present in ultrathin-thin-film form. Notably, the effects are most pronounced for charges photogenerated by photons with energy comparable to the band gap for excitation of Fe(3d)?Fe(3d) transitions (i.e., green photons). Additionally, at the optimum Ti substitution level the lifetimes of surface-localized holes, competent for water oxidation, are extended. Together these changes explain an overall improvement in photoelectrochemical performance, especially enhanced internal quantum efficiencies, observed upon Ti(IV) incorporation. PMID:25414974

Kim, Dong Wook; Riha, Shannon C; DeMarco, Erica J; Martinson, Alex B F; Farha, Omar K; Hupp, Joseph T

2014-12-23

224

Conductive iron oxides accelerate thermophilic methanogenesis from acetate and propionate.  

PubMed

Anaerobic digester is one of the attractive technologies for treatment of organic wastes and wastewater, while continuous development and improvements on their stable operation with efficient organic removal are required. Particles of conductive iron oxides (e.g., magnetite) are known to facilitate microbial interspecies electron transfer (termed as electric syntrophy). Electric syntrophy has been reported to enhance methanogenic degradation of organic acids by mesophilic communities in soil and anaerobic digester. Here we investigated the effects of supplementation of conductive iron oxides (magnetite) on thermophilic methanogenic microbial communities derived from a thermophilic anaerobic digester. Supplementation of magnetite accelerated methanogenesis from acetate and propionate under thermophilic conditions, while supplementation of ferrihydrite also accelerated methanogenesis from propionate. Microbial community analysis revealed that supplementation of magnetite drastically changed bacterial populations in the methanogenic acetate-degrading cultures, in which Tepidoanaerobacter sp. and Coprothermobacter sp. dominated. These results suggest that supplementation of magnetite induce electric syntrophy between organic acid-oxidizing bacteria and methanogenic archaea and accelerate methanogenesis even under thermophilic conditions. Findings from this study would provide a possibility for the achievement of stably operating thermophilic anaerobic digestion systems with high efficiency for removal of organics and generation of CH4. PMID:25488041

Yamada, Chihaya; Kato, Souichiro; Ueno, Yoshiyuki; Ishii, Masaharu; Igarashi, Yasuo

2014-12-01

225

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

EPA Science Inventory

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

226

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....

227

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

228

Synthesis and characterization of barium iron oxide and bismuth iron oxide epitaxial films  

Microsoft Academic Search

Much interest exists in perovskite oxide materials and the potential they have in possessing two or more functional properties. In recent years, research on developing new materials with simultaneous ferromagnetic and ferroelectric behavior is the key to addressing possible challenges of new storage information applications. This work examines the fundamental properties of a perovskite oxide, namely BaFeO3, and the investigation

Charlee J. Callender Bennett

2009-01-01

229

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

230

Effects of Iron Deficiency and Overload on Angiogenesis and Oxidative Stress – A Potential Dual Role for Iron in Breast Cancer  

PubMed Central

Estrogen alone cannot explain the differences in breast cancer (BC) recurrence and incidence rates in pre- and postmenopausal women. In the present study, we have tested a hypothesis that, in addition to estrogen, both iron deficiency due to menstruation and iron accumulation as a result of menstrual stop play important roles in menopause-related BC outcomes. We first tested this hypothesis in cell culture models mimicking the high estrogen and low iron premenopausal condition and the low estrogen and high iron postmenopausal condition, respectively. Subsequently, we examined this hypothesis in mice that were fed iron deficient and iron overload diets. We have shown that estrogen only slightly up-regulates vascular endothelial growth factor (VEGF), an angiogenic factor known to be important in BC recurrence. It is, rather, iron deficiency that significantly promotes VEGF by stabilizing hypoxia inducible factor-1? (HIF-1?). Conversely, high iron levels increase oxidative stress and sustain mitogen-activated protein kinase (MAPK) activation, which are mechanisms of known significance in BC development. Taken together, our results suggest, for the first time, that an iron deficiency-mediated pro-angiogenic environment could contribute to the high recurrence of BC in young patients, and iron accumulation-associated pro-oxidant conditions could lead to the high incidence of BC in older women. PMID:21193031

Jian, Jinlong; Yang, Qing; Dai, Jisen; Eckard, Jonathan; Axelrod, Debrah; Smith, Julia; Huang, Xi

2011-01-01

231

Enriched Iron(III)-Reducing Bacterial Communities are Shaped by Carbon Substrate and Iron Oxide Mineralogy.  

PubMed

Iron (Fe) oxides exist in a spectrum of structures in the environment, with ferrihydrite widely considered the most bioavailable phase. Yet, ferrihydrite is unstable and rapidly transforms to more crystalline Fe(III) oxides (e.g., goethite, hematite), which are poorly reduced by model dissimilatory Fe(III)-reducing microorganisms. This begs the question, what processes and microbial groups are responsible for reduction of crystalline Fe(III) oxides within sedimentary environments? Further, how do changes in Fe mineralogy shape oxide-hosted microbial populations? To address these questions, we conducted a large-scale cultivation effort using various Fe(III) oxides (ferrihydrite, goethite, hematite) and carbon substrates (glucose, lactate, acetate) along a dilution gradient to enrich for microbial populations capable of reducing Fe oxides spanning a wide range of crystallinities and reduction potentials. While carbon source was the most important variable shaping community composition within Fe(III)-reducing enrichments, both Fe oxide type and sediment dilution also had a substantial influence. For instance, with acetate as the carbon source, only ferrihydrite enrichments displayed a significant amount of Fe(III) reduction and the well-known dissimilatory metal reducer Geobacter sp. was the dominant organism enriched. In contrast, when glucose and lactate were provided, all three Fe oxides were reduced and reduction coincided with the presence of fermentative (e.g., Enterobacter spp.) and sulfate-reducing bacteria (e.g., Desulfovibrio spp.). Thus, changes in Fe oxide structure and resource availability may shift Fe(III)-reducing communities between dominantly metal-respiring to fermenting and/or sulfate-reducing organisms which are capable of reducing more recalcitrant Fe phases. These findings highlight the need for further targeted investigations into the composition and activity of speciation-directed metal-reducing populations within natural environments. PMID:23316187

Lentini, Christopher J; Wankel, Scott D; Hansel, Colleen M

2012-01-01

232

Enriched Iron(III)-Reducing Bacterial Communities are Shaped by Carbon Substrate and Iron Oxide Mineralogy  

PubMed Central

Iron (Fe) oxides exist in a spectrum of structures in the environment, with ferrihydrite widely considered the most bioavailable phase. Yet, ferrihydrite is unstable and rapidly transforms to more crystalline Fe(III) oxides (e.g., goethite, hematite), which are poorly reduced by model dissimilatory Fe(III)-reducing microorganisms. This begs the question, what processes and microbial groups are responsible for reduction of crystalline Fe(III) oxides within sedimentary environments? Further, how do changes in Fe mineralogy shape oxide-hosted microbial populations? To address these questions, we conducted a large-scale cultivation effort using various Fe(III) oxides (ferrihydrite, goethite, hematite) and carbon substrates (glucose, lactate, acetate) along a dilution gradient to enrich for microbial populations capable of reducing Fe oxides spanning a wide range of crystallinities and reduction potentials. While carbon source was the most important variable shaping community composition within Fe(III)-reducing enrichments, both Fe oxide type and sediment dilution also had a substantial influence. For instance, with acetate as the carbon source, only ferrihydrite enrichments displayed a significant amount of Fe(III) reduction and the well-known dissimilatory metal reducer Geobacter sp. was the dominant organism enriched. In contrast, when glucose and lactate were provided, all three Fe oxides were reduced and reduction coincided with the presence of fermentative (e.g., Enterobacter spp.) and sulfate-reducing bacteria (e.g., Desulfovibrio spp.). Thus, changes in Fe oxide structure and resource availability may shift Fe(III)-reducing communities between dominantly metal-respiring to fermenting and/or sulfate-reducing organisms which are capable of reducing more recalcitrant Fe phases. These findings highlight the need for further targeted investigations into the composition and activity of speciation-directed metal-reducing populations within natural environments. PMID:23316187

Lentini, Christopher J.; Wankel, Scott D.; Hansel, Colleen M.

2012-01-01

233

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.

234

Ultrasound-enhanced copper removal by hydrous iron oxide adsorption  

SciTech Connect

A model system to investigate ultrasound-enhanced removal of metallic ions from aqueous solution by hydrous ferric oxide (HFO) adsorption has been conducted. The experimental data indicate that ultrasonic treatment of pre-formed HFO flocs can lead to enhanced removal of metallic ions from aqueous solution and that the level of enhancement is strongly correlated with the solution pH. Ultrasonic treatment has been shown to be effective at lowering the final solution concentration of copper species in the pH range 7.5--9.5 at copper to iron molar concentration ratios of 10 and 30%.

Campos, H.R. [Univ. de Tarapaca, Arica (Chile); Wheat, P.E. [Univ. of Northern Iowa, Cedar Falls, IA (United States). Dept. of Industrial Technology

1996-12-31

235

Basic methods for measuring the reflectance color of iron oxides  

NASA Astrophysics Data System (ADS)

The main contribution of the present article consists in coherent description and interpretation of the principles of basic measuring methods and colorimeters for color classification and evaluation of light reflecting samples containing iron oxides. The chosen relevant theoretical background is based on the CIE tristimulus colorimetric system (X,Y,Z), the CIE colorimetric system (L*,a*,b*) and the Munsell colorimetric system (H,V,C). As an example of color identification and evaluation, some specific mathematical and graphical relationships between the soil redness rate and the corresponding hematite content are shown.

Pospisil, Jaroslav; Hrdy, Jan; Hrdy Jan, Jr.

2007-06-01

236

Effects of coating on magnetic properties in iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

237

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

238

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

239

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

240

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

241

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

PubMed Central

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

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

2012-01-01

242

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

243

Evaluation of Nanodispersion of Iron Oxides Using Various Polymers  

PubMed Central

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

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

2014-01-01

244

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

245

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

246

Cerebral Blood Volume MRI with Intravascular Superparamagentic Iron Oxide Nanoparticles  

PubMed Central

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

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

2013-01-01

247

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

248

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

249

Sulfonated polyether ether ketone and hydrated tin oxide proton conducting composites for direct methanol fuel cell applications  

Microsoft Academic Search

Composite membranes based on sulfonated polyether ether ketone (SPEEK) and hydrated tin oxide (SnO2·nH2O) were prepared and characterized. The formation of the composite substantially modified the properties of SPEEK in terms of durability and electrochemical performance. The structural and electrochemical performance of the samples were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, electrochemical impedance spectroscopy (EIS), water

Barbara Mecheri; Alessandra D’Epifanio; Enrico Traversa; Silvia Licoccia

2008-01-01

250

The production of magnetic nanoparticles of Iron Oxide by arc discharge in water  

NASA Astrophysics Data System (ADS)

Nanoparticles can be utilized for any practical application. In recent years; considerable attention has been paid to iron oxide magnetic. Iron oxide nanoparticles are the class of nanoparticle which can have useful magnetic properties. In this research, magnetic iron oxide nanoparticles were produced by Arc discharge method in water. Structural analysis carried out by X-ray diffraction analysis (XRD), Scanning Electron Microscopy (SEM), and Spectrophotometer. Various magnetic nanoparticles like iron carbide (Fe3c), magnetic iron oxide (magnetite /maghemite) are obtained by arc discharge method in water. In this work have been showed, the influence of the time duration on the number of magnetic nanoparticles and the influence of the gap between the two electrodes on particle structure and size distribution. Furthermore, when iron nanoparticles are used under applied magnetic field, the particles would move in the direction of magnetic field. When the magnetic field is removed, the particles stop moving and still remain stably suspend in the dielectric liquid.

Yousefi, Hamid Reza; Fathollah, Sara; Nikeyn, Maryam; Khatami, Shohreh

2012-10-01

251

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

SciTech Connect

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

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

1996-12-31

252

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

SciTech Connect

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

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

1996-04-01

253

A magnetic poly(dimethylesiloxane) composite membrane incorporated with uniformly dispersed, coated iron oxide nanoparticles  

Microsoft Academic Search

We report a new magnetic polymer membrane for MEMS application. The polymeric magnetic composite has coated iron oxide nanoparticles incorporated in a polydimethylsiloxane (PDMS) matrix. Existing magnetic polymeric materials have particle agglomeration problems, which result in rough surfaces and uneven mechanical and optical properties. We show that the use of iron oxide nanoparticles (10 nm in diameter) with fatty acid

Luna Cheng; Mu Chiao

2010-01-01

254

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

255

Ferrous iron oxidation and leaching of copper ore with halotolerant bacteria in ore columns  

Microsoft Academic Search

Growth on ferrous iron of a new isolate of the acidophile Thiobacillus prosperus occurred with a substrate oxidation rate similar to that of Acidithiobacillus ferrooxidans. As well as similar capacities for iron oxidation, these species were shown to possess similar, but not identical, clusters of genes (the rus operon) that encode proteins likely to be involved in transfer of electrons

Carol S. Davis-Belmar; James Le C. Nicolle; Paul R. Norris

2008-01-01

256

Iron oxide mineralogy in late Miocene red beds from La Gloria, Spain: rock-magnetic,  

E-print Network

Iron oxide mineralogy in late Miocene red beds from La Gloria, Spain: rock-magnetic, voltammetric techniques that are designed for the analysis of magnetic iron oxides are very sensitive. The same applies by rock-magnetic techniques (IRM component analysis) and by two less traditional methods: visible

Utrecht, Universiteit

257

Discovery of the recoverable high-pressure iron oxide Fe4O5  

E-print Network

Discovery of the recoverable high-pressure iron oxide Fe4O5 Barbara Lavinaa,b,1 , Przemyslaw Derac report the discovery of an iron oxide with for- mula Fe4O5, synthesized at high pressure and temperature,b a High Pressure Science and Engineering Center, University of Nevada, Las Vegas, NV 89154; b Department

Downs, Robert T.

258

Hydrogen storage and production by redox of iron oxide for polymer electrolyte fuel cell vehicles  

Microsoft Academic Search

Pseudo-storage of hydrogen and its recovery by redox of iron oxide have been proposed as a new method of the storage and supply of hydrogen for PEFC vehicles. Among the additives to iron oxide tested, Al, Cr, Zr, Ga and V were the effective elements enhancing both the reduction with H2 (storage of H2) and reoxidation with water (recovery of

K Otsuka; C Yamada; T Kaburagi; S Takenaka

2003-01-01

259

Fabrication, characterization and microwave properties of polyurethane nanocomposites reinforced with iron oxide and barium titanate  

E-print Network

with iron oxide and barium titanate nanoparticles Z. Guo a,*, S.-E. Lee a , H. Kim a , S. Park a , H.T. Hahn the introduction of the dielectric barium titanate nanoparticle into Fe2O3/PU nanocomposites. The permeability (PU) nanocomposites reinforced with magnetic iron oxide nanoparticles and/or dielectric barium

Guo, John Zhanhu

260

Growth and characterization of iron oxide nanocrystalline thin films via low-cost ultrasonic spray pyrolysis  

Microsoft Academic Search

The preparation and characterization of iron oxide nanocrystalline thin films by ultrasonic spray pyrolysis technique is reported. Iron oxide films were grown on quartz substrate at different deposition temperatures varying from 400°C to 700°C. Both orientation and the size of the crystallites were found to depend on the substrate temperature. The XRD results of nanocrystalline thin films revealed the magnetite

Rajendra N. Goyal; Davinder Kaur; Ashish K. Pandey

2009-01-01

261

Thiol-modified poly(ethylene glycol)-conjugated gold/ superparamagnetic iron oxide nanoparticles  

E-print Network

heterogeneities of tissues in the magnetic field (1). Cross-linked iron oxide (CLIO) and other iron oxideM), and poly(vinyl alcohol) (10 mg/mL) was irradiated with an electron beam at a dose of 6 kGy (3). Au Links: · Chapters in MICAD (SPIO) · Clinical trials (Feridex) · Drug information in FDA (Feridex

Levin, Judith G.

262

[Neutrophilic lithotrophic iron-oxidizing prokaryotes and their role in the biogeochemical processes of the iron cycle].  

PubMed

Biology of lithotrophic neutrophilic iron-oxidizing prokaryotes and their role in the processes of the biogeochemical cycle of iron are discussed. This group of microorganisms is phylogenetically, taxonomically, and physiologically heterogeneous, comprising three metabolically different groups: aerobes, nitrate-dependent anaerobes, and phototrophs; the latter two groups have been revealed relatively recently. Their taxonomy and metabolism are described. Materials on the structure and functioning of the electron transport chain in the course of Fe(II) oxidation by members of various physiological groups are discussed. Occurrence of iron oxidizers in freshwater and marine ecosystems, thermal springs, areas of hydrothermal activity, and underwater volcanic areas are considered. Molecular genetic techniques were used to determine the structure of iron-oxidizing microbial communities in various natural ecosystems. Analysis of stable isotope fractioning of 56/54Fe in pure cultures and model experiments revealed predominance of biological oxidation over abiotic ones in shallow aquatic habitats and mineral springs, which was especially pronounced under microaerobic conditions at the redox zone boundary. Discovery of anaerobic bacterial Fe(II) oxidation resulted in development of new hypotheses concerning the possible role of microorganisms and the mechanisms of formation of the major iron ore deposits in Precambrian and early Proterozoic epoch. Paleobiological data are presented on the microfossils and specific biomarkers retrieved from ancient ore samples and confirming involvement of anaerobic biogenic processes in their formation. PMID:25423717

Dubinina, G A; Sorokina, A Iu

2014-01-01

263

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

264

The effect of protein oxidation on hydration and water-binding in pork packaged in an oxygen-enriched atmosphere.  

PubMed

This study investigated the in situ oxidative process of myofibrillar proteins in boneless pork loin chops (Longissimus lumborum) packaged in an oxygen-enriched atmosphere (HiOx: 80% O2/20% CO2), an air-permeable polyvinylchloride (PVC) overwrap, or a partial vacuum (VP) throughout display at 2°C for up to 14, 7, and 21days, respectively. Samples stored in HiOx were susceptible to lipid (TBARS) and protein (carbonyls, sulfhydryls, and aggregation) oxidation, while samples in PVC and VP showed lesser oxidative changes. Water-holding capacity of raw muscle decreased (P<0.05) when stored in HiOx but not in PVC and VP. Upon salt and phosphate brine marination, HiOx and PVC muscle samples had improved hydration capacity during display compared with non-stored control, but display generally decreased hydration of VP samples. The result was in agreement with myofibril structural changes. Despite the enhanced hydration, HiOx muscle was least capable of withholding moisture upon cooking. PMID:24583326

Delles, Rebecca M; Xiong, Youling L

2014-06-01

265

Stability of water-stable C60 clusters to OH radical oxidation and hydrated electron reduction.  

PubMed

Reactions of water-stable C(60) clusters (nC(60)) in water with OH radicals (*OH) and hydrated electrons (e(aq)(-)), generated by steady-state gamma-radiation, were observed and characterized. Ordered C(60) clusters were relatively recalcitrant to highly reactive *OH and e(aq)(-) species, with only a fraction of carbons oxidized and reduced, respectively. Pulse radiolysis suggested that the reactions of nC(60) with OH* and e(aq)(-) were diffusion limited, with rate constants of (7.34 +/- 0.31) x 10(9) M(-1) s(-1) and (2.34 +/- 0.02) x 10(10) M(-1) s(-1), respectively. Quantum mechanical calculations of binding energy of the C(60)-OH adduct as a function of C(60) clustering degree indicate, despite an initial fast reaction, a slower overall conversion due to thermodynamic instability of C(60)-OH intermediates. The results imply that ordered clustering of C(60) in the aqueous phase significantly hinders C(60)'s fundamental reactivity with radical species. PMID:20397700

Lee, Jaesang; Song, Weihua; Jang, Seung S; Fortner, John D; Alvarez, Pedro J J; Cooper, William J; Kim, Jae-Hong

2010-05-15

266

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

267

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 Orué Lucana, Darío

2013-01-01

268

Hydration of Ordinary Portland Cements Made from Raw Mix Containing Transition Element Oxides 1 1 Communicated by F. Massazza  

Microsoft Academic Search

The subject of this paper is the study of the hydration process in cements made from raw mixes containing transition element oxides. The oxides used are ZrO2, V2O5, Ni2O3, CuO, Co2O3, MnO, Cr2O3, TiO2, MoO3, and ZnO, and their percentage in the raw mixes is 2% w\\/w. The cement pastes are cured in water for 24 h, 48 h, 7

G. Kakali; S. Tsivilis; A. Tsialtas

1998-01-01

269

Instability of waste plumes adsorbed on iron oxide in soils  

SciTech Connect

Iron (hydrous) oxide coatings on the solid matrix dominate adsorption in many soils. Their adsorption characteristics vary considerably with the composition of the soil pore water. If the latter is not sufficiently buffered, the contaminant distribution between solid and soluble soil phase, Kd (''distribution coefficient''), will change as intruding water differing in chemical composition from the original one in the system progresses through the plume environment. Thus the Kd's at different locations within the plume become time dependent, spatially variable and causally correlated. The conventional constant or stochastic Kd model is not capable of describing contaminant migration in such a situation. A geochemical equilibrium model, the so-called triple layer model, has been incorporated into a transport code and is used to calculate the adsorption processes and thus the Kd as a function of environmental parameters. The major processes occurring are: (1) accumulation of a proton reservoir on the surface itself; (2) development of a charge cloud at a distance of several angstroms from the surface, capable of accommodating contaminant ions; and (3) development of a net charge at the oxide/water interface and, consequently, the creation of a cation or anion exchange capacity of the oxide.

Gruber, J.

1987-03-01

270

Solution voltammetry of 4 nm magnetite iron oxide nanoparticles.  

PubMed

The voltammetry of solution-dispersed magnetite iron oxide Fe3O4 nanoparticles is described. Their currents are controlled by nanoparticle transport rates, as shown with potential step chronoamperometry and rotated disk voltammetry. In pH 2 citrate buffer with added NaClO4 electrolyte, solution cyclic voltammetry of these nanoparticles (average diameter 4.4 ± 0.9 nm, each containing ca. 30 Fe sites) displays an electrochemically irreversible oxidation with E(PEAK) at ca. +0.52 V and an irreversible reduction with E(PEAK) at ca. +0.2 V vs Ag/AgCl reference electrode. These processes are presumed to correspond to the formal potentials for one-electron oxidation of Fe(II) and reduction of Fe(III) at their different sites in the magnetite nanoparticle structure. The heterogeneous electrode reaction rates of the nanoparticles are very slow, in the 10(-5) cm/s range. The nanoparticles are additionally characterized by a variety of tools, e.g., TEM, UV/vis, and XPS spectroscopies. PMID:25046101

Roberts, Joseph J P; Westgard, John A; Cooper, Laura M; Murray, Royce W

2014-07-30

271

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, Natália Aboudib; de Valencia, Fernando Fortes; Siqueira, Egle Machado de Almeida

2013-01-01

272

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

273

Kinetic effects of sulfur oxidation on catalytic nitrile hydration: nitrile hydratase insights from bioinspired ruthenium(II) complexes.  

PubMed

Kinetic investigations inspired by the metalloenzyme nitrile hydratase were performed on a series of ruthenium(II) complexes to determine the effect of sulfur oxidation on catalytic nitrile hydration. The rate of benzonitrile hydration was quantified as a function of catalyst, nitrile, and water concentrations. Precatalysts L(n)RuPPh3 (n = 1-3; L(1) = 4,7-bis(2'-methyl-2'-mercapto-propyl)-1-thia-4,7-diazacyclononane; L(2) = 4-(2'-methyl-2'-sulfinatopropyl)-7-(2'-methyl-2'-mercapto-propyl)-1-thia-4,7-diazacyclononane; L(3) = 4-(2'-methyl-2'-sulfinatopropyl)-7-(2'-methyl-2'-sulfenato-propyl)-1-thia-4,7-diazacyclononane) were activated by substitution of triphenylphosphine with substrate in hot dimethylformamide solution. Rate measurements are consistent with a dynamic equilibrium between inactive aqua (L(n)Ru-OH2) and active nitrile (L(n)Ru-NCR) derivatives with K = 21 ± 1, 9 ± 0.9, and 23 ± 3 for L(1) to L(3), respectively. Subsequent hydration of the L(n)Ru-NCR intermediate yields the amide product with measured hydration rate constants (k's) of 0.37 ± 0.01, 0.82 ± 0.07, and 1.59 ± 0.12 M(-1) h(-1) for L(1) to L(3), respectively. Temperature dependent studies reveal that sulfur oxidation lowers the enthalpic barrier by 27 kJ/mol, but increases the entropic barrier by 65 J/(mol K). Density functional theory (DFT) calculations (B3LYP/LanL2DZ (Ru); 6-31G(d) (all other atoms)) support a nitrile bound catalytic cycle with lowering of the reaction barrier as a consequence of sulfur oxidation through enhanced nitrile binding and attack of the water nucleophile through a highly organized transition state. PMID:25397591

Kumar, Davinder; Nguyen, Tho N; Grapperhaus, Craig A

2014-12-01

274

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

PubMed

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

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

2015-03-16

275

An iron K-edge XANES study of iron and iron oxides for the cathodic disbonding of fusion bonded epoxy in alkaline aqueous solution  

SciTech Connect

Iron K-edge X-ray absorption near-edge structure (XANES) of laboratory-scale model oxide systems was studied to provide insights about the mechanism of cathodic disbonding of fusion bonded epoxy (FBE) from underground steel pipelines. Two model systems were studied: (1) thin film iron (500 {angstrom} thick) thermally oxidized at 240 C; and (2) thin film iron coated with FBE and cathodically disbonded. The thin film iron exhibited a trend of decreasing metallic character with increasing thermal oxidation times. After 122 h of oxidation, the oxidic character became predominant. The oxide appeared to abe a mixture of Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4}. The XANES data for the region under the cathodically disbonded FBE coating exhibited more metallic character than the region that maintained the bond integrity. Under the cathodic disbonding conditions of the present study ({minus}1.5 V-SCE in 1M KOH aqueous solution), the XANES results, although preliminary, support the oxide reduction and/or oxide dissolution mechanisms of disbonding.

Song, I.; Payer, J.H. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Materials Science and Engineering; Antonio, M.R. [Argonne National Lab., IL (United States). Chemistry Division

1995-07-01

276

Production of nanostructured iron oxide particles via aerosol decomposition  

SciTech Connect

Nanostructured iron oxide particles with average size below 100 nm were produced by aerosol decomposition method starting from an aqueous iron nitrate solution. Air, nitrogen, or mixture of hydrogen (7%) and nitrogen were used as the carrier gas. Gas-phase particle number size distributions were determined with a differential mobility analyzer. Particle morphology and crystallinity were studied with scanning (SEM) and transmission (TEM) electron microscopes. Crystalline phase composition of the particles was studied with X-ray diffraction (XRD). The average gas-phase diameter of particles produced in air or N{sub 2} reduced from 80 to 47 nm when temperature was increased from 500 to 1,100 C. In H{sub 2} rich environment, the reduction of average size was larger, from 80 nm at 500 C to 45 nm already at 900 C. SEM results showed that very small crystallites (5--10 nm) were formed on the surface of the particles produced in N{sub 2} at 500 C. When the processing temperature was increased to 700, 900 and 1,100 C, the crystallites on the particle surfaces were grown to 15--30, 30--60 and 60--180 nm, respectively. TEM results show that very small particles (< 50 nm) were single crystals and larger particles were polycrystalline with crystallite size of about 50 nm at 700 C in H{sub 2}/N{sub 2}. Magnetite particles were produced from aqueous iron nitrate solution at 500 C in H{sub 2}/N{sub 2} and at 900 C in N{sub 2} according to XRD results.

Joutsensaari, J.; Kauppinen, E.I. [VTT Chemical Technology (Finland). Aerosol Technology Group

1997-09-01

277

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

278

Synthesis and properties of catalysts produced by sorption of Fe/sup 3 +/ ions by hydrated antimony pentoxide  

SciTech Connect

Catalysts representing the Sb/sub 6/O/sub 13/ phase, containing isolated iron ions and associates, were synthesized by the method of sorption of Fe/sup 3 +/ ions from solutions of iron nitrate by hydrated antimony pentoxide, followed by heat treatment at 773/sup 0/K. The catalysts obtained are effective in the oxidative ammonolysis of propylene.

Zenkovets, G.A.; Tarasova, D.V.; Anufrienko, V.F.; Paukshtis, E.A.; Khomicheva, S.Y.; Olen'kova, I.P.; Nikoro, T.A.

1983-02-01

279

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

280

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

281

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

282

Iron oxide nanoparticle hyperthermia and chemotherapy cancer treatment  

NASA Astrophysics Data System (ADS)

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.

Petryk, A. A.; Giustini, A. J.; Ryan, P.; Strawbridge, R. R.; Hoopes, P. J.

2009-02-01

283

Colloidal stability of iron oxide nanoparticles with multivalent polymer surfactants.  

PubMed

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

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

2015-04-01

284

Growth of iron cobalt oxides by atomic layer deposition.  

PubMed

Thin films of iron cobalt oxides with spinel-type structure are made by the atomic layer deposition (ALD) technique using Fe(thd)3 (Hthd = 2,2,6,6-tetramethylheptane-3,5-dione), Co(thd)2, and ozone as precursors. Pulse parameters for ALD-type growth are established and such growth can be achieved at deposition temperatures between 185 and 310 degrees C. Films have been deposited on amorphous soda-lime glass and single-crystalline substrates of Si(100), MgO(100), and alpha-Al2O3(001) which all provide crystalline films, but with various orientations and crystallite sizes. Application of an external magnetic field during the film growth does not influence film growth characteristics (growth rate, crystallinity, topography etc.). Magnetization data are reported for phase-pure films of spinel-type structure with composition Fe2CoO4. PMID:18097492

Lie, Martin; Barnholt Klepper, Karina; Nilsen, Ola; Fjellvåg, Helmer; Kjekshus, Arne

2008-01-14

285

Bioconjugated iron oxide nanocubes: synthesis, functionalization, and vectorization.  

PubMed

A facile bottom-up approach for the synthesis of inorganic/organic bioconjugated nanoprobes based on iron oxide nanocubes as the core with a nanometric silica shell is demonstrated. Surface coating and functionalization protocols developed in this work offered good control over the shell thickness (8-40 nm) and enabled biovectorization of SiO2@Fe3O4 core-shell structures by covalent attachment of folic acid (FA) as a targeting unit for cellular uptake. The successful immobilization of folic acid was investigated both quantitatively (TGA, EA, XPS) and qualitatively (AT-IR, UV-vis, ?-potential). Additionally, the magnetic behavior of the nanocomposites was monitored after each functionalization step. Cell viability studies confirmed low cytotoxicity of FA@SiO2@Fe3O4 conjugates, which makes them promising nanoprobes for targeted internalization by cells and their imaging. PMID:25184762

Wortmann, Laura; Ilyas, Shaista; Niznansky, Daniel; Valldor, Martin; Arroub, Karim; Berger, Nadja; Rahme, Kamil; Holmes, Justin; Mathur, Sanjay

2014-10-01

286

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

287

Exchange bias in Core-Shell Iron-Iron Oxide Nanoclusters  

SciTech Connect

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

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

2013-04-03

288

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

289

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

NASA Astrophysics Data System (ADS)

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

Lin, Hao

290

Biocompatible capped iron oxide nanoparticles for Vibrio cholerae detection.  

PubMed

We report the studies relating to fabrication of an efficient immunosensor for Vibrio cholerae detection. Magnetite (iron oxide (Fe3O4)) nanoparticles (NPs) have been synthesized by the co-precipitation method and capped by citric acid (CA). These NPs were electrophoretically deposited onto indium-tin-oxide (ITO)-coated glass substrate and used for immobilization of monoclonal antibodies against Vibrio cholerae (Ab) and bovine serum albumin (BSA) for Vibrio cholerae detection using an electrochemical technique. The structural and morphological studies of Fe3O4 and CA-Fe3O4/ITO were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and dynamic light scattering (DLS) techniques. The average crystalline size of Fe3O4, CA-Fe3O4 nanoparticles obtained were about 29 ± 1 nm and 37 ± 1 nm, respectively. The hydrodynamic radius of the nanoparticles was found to be 77.35 nm (Fe3O4) and 189.51 nm (CA-Fe3O4) by DLS measurement. The results of electrochemical response studies of the fabricated BSA/Ab/CA-Fe2O3/ITO immunosensor exhibits a good detection range of 12.5-500 ng mL(-1) with a low detection limit of 0.32 ng mL(-1), sensitivity 0.03 ?/ng ml(-1) cm(-2), and reproducibility more than 11 times. PMID:25850702

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

2015-05-01

291

In vitro toxicity of iron oxide nanoparticle: oxidative damages on Hep G2 cells.  

PubMed

During the past years many studies have been done highlighting the great need for a more thorough understanding of cell-iron oxide nanoparticle interactions. To improve our knowledge in this field, there is a great need for standardized protocols that would allow to comparing the cytotoxic potential of any Fe2O3-NP type with previously studied particles. Several approaches are reported that several parameters which are of great importance for Fe2O3 nanoparticle induced toxicity. Nanoparticles because of their very small size can pass through the cell membrane and can make oxidative damage in all parts of the cells such as mitochondria, membrane, DNA due to high surface area. This study focuses on acute cytotoxicity of reactive oxygen species and DNA damaging effects of mentioned nanoparticles. Results showed increase of the oxidative damage leads cells to the apoptosis, therefore reduced cell viability. It is interesting that all of the results are concentration and time dependent. PMID:25497787

Sadeghi, Leila; Tanwir, Farzeen; Yousefi Babadi, Vahid

2015-02-01

292

Recent progress in magnetic iron oxide-semiconductor composite nanomaterials as promising photocatalysts  

NASA Astrophysics Data System (ADS)

Photocatalytic degradation of toxic organic pollutants is a challenging tasks in ecological and environmental protection. Recent research shows that the magnetic iron oxide-semiconductor composite photocatalytic system can effectively break through the bottleneck of single-component semiconductor oxides with low activity under visible light and the challenging recycling of the photocatalyst from the final products. With high reactivity in visible light, magnetic iron oxide-semiconductors can be exploited as an important magnetic recovery photocatalyst (MRP) with a bright future. On this regard, various composite structures, the charge-transfer mechanism and outstanding properties of magnetic iron oxide-semiconductor composite nanomaterials are sketched. The latest synthesis methods and recent progress in the photocatalytic applications of magnetic iron oxide-semiconductor composite nanomaterials are reviewed. The problems and challenges still need to be resolved and development strategies are discussed.

Wu, Wei; Changzhong Jiang, Affc; Roy, Vellaisamy A. L.

2014-11-01

293

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

294

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

SciTech Connect

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

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

2014-01-01

295

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

PubMed Central

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

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

2015-01-01

296

Oxidative damages by iron-chelate complexes depend on the interaction with the target molecules.  

PubMed

To elucidate that in iron-catalyzed oxidative damage the interaction of iron complex with the target molecules is important, the oxidative damage to plasmid DNA, protein and fatty acid has been compared using iron-chelate complexes with nitrilotriacetic acid (nta), citric acid, ethylenediamine-N,N'-diacetic acid (edda) and diethylenetriamine-N,N,N',N",N"-pentaacetic acid (dtpa). In the presence of hydrogen peroxide, plasmid pBR322 strand breaks occurred in the order of Fe-edda > Fe-citrate > Fe-nta > > Fe-dtpa. However, fragmentation of bovine serum albumin and diene conjugation of linoleic acid micelle occurred in the order of Fe-nta > Fe-edda > > Fe-citrate > Fe-dtpa = O, which were similar to hydroxyl radical production by these iron complexes and H2O2. Bleomycin-detectable free radical-promoting irons in these iron complexes were about 85% of iron in Fe-nta, Fe-citrate and Fe-edda, and only about 33% in Fe-dtpa. Not only hydroxyl radical productivity and free radical-promoting iron content in iron complex, but also the interaction of the complex with the target molecules determines the iron-catalyzed oxidative damage. PMID:8799330

Asaumi, A; Ogino, T; Akiyama, T; Kawabata, T; Okada, S

1996-05-01

297

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

298

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

299

Effects of Small Additions of Copper and Copper + Nickel on the Oxidation Behavior of Iron  

Microsoft Academic Search

This study was undertaken to investigate the effect of small amounts of copper and copper + nickel additions on the oxidation\\u000a rate and oxide\\/metal interface microstructure of iron. Three iron-based alloys were compared: 0.3 wt pct copper, 0.3 wt pct\\u000a copper-0.1 wt pct nickel, and 0.3 wt pct copper-0.05 wt pct nickel. Alloy samples were oxidized in air at 1150 °C for 60,\\u000a 300, and 600 seconds. Pure iron

Bryan Webler; Lan Yin; Seetharaman Sridhar

2008-01-01

300

An evaluation of iron oxide nanofluids in enhanced oil recovery application  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

301

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

USGS Publications Warehouse

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

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

2004-01-01

302

Synthesis and characterization of barium iron oxide and bismuth iron oxide epitaxial films  

NASA Astrophysics Data System (ADS)

Much interest exists in perovskite oxide materials and the potential they have in possessing two or more functional properties. In recent years, research on developing new materials with simultaneous ferromagnetic and ferroelectric behavior is the key to addressing possible challenges of new storage information applications. This work examines the fundamental properties of a perovskite oxide, namely BaFeO3, and the investigation of properties of a solid solution between BaFeO3 and BiFeO3. The growth and properties of epitaxial BaFeO3 thin films in the metastable cubic perovskite phase are examined. BaFeO3 films were grown on (012) LaAlO3 and (001) SrTiO3 single crystal substrates by pulsed-laser deposition. X-ray diffraction shows that in situ growth at temperatures between 650-850°C yields an oxygen-deficient BaFeO 2.5+x pseudo-cubic perovskite phase that is insulating and paramagnetic. Magnetization measurements on the asdeposited BaFeO3 films indicate non-ferromagnetic behavior. Annealing these films in 1 atm oxygen ambient converts the films into a pseudo-cubic BaFeO3-x phase that is ferromagnetic with a Curie temperature of 235 K. The observation of ferromagnetism with increasing oxygen content is consistent with superexchange coupling of Fe +4-O-Fe+4. The effects of anneal conditions on BaFeO3 are studied. X-ray characterization, such as reciprocal space maps, show more complex structure for as-grown BaFeO3-x epitaxial films. Epitaxial films grown at low laser energies are highly crystalline. However, they decompose after annealing. When grown at high laser energies, films exhibit complex structure which "cleans up" to a single pseudocubic or tetragonal structure upon ex situ anneal in oxygen ambient environment. Superlattices of BaFeO 3/SrTiO3 were synthesized to explore the nature of "cracking" in annealed BaFeO3, which occurs due to large change in lattice parameter. Magnetization of ex situ annealed BaFeO3-x epitaxial films were examined as a function of applied field direction and was not found to have a change in magnetization with direction of field, despite other research claims. Evidence supports that the unusually weak magnetization of BaFeO3-x is attributed to it being structurally and magnetically disordered. Alloys of a solid-solution between BiFeO3 and BaFeO3-x have been successfully created. X-ray characterizations demonstrate alloy epitaxial films via two-target continuous rotation method have been carried all the way to 80% solubility. In addition, alloy films via solid-solution targets method have been successfully fabricated at near both end-member-points and at the half-point showing that the solubility is possible over the entire range of the solid-solution. Bi0.9Ba0.1FeO3 epitaxial films are of high crystalline quality with rocking curves widths of less than 0.22°, are fully strained, and have highly unusual in-plane and out-of-plane lattice parameters. TEM imaging illustrates that, despite extreme c/a ratios up to 1.26, the films are single phase with sharp interfaces with substrates. SQUID magnetometry was utilized, revealing that the samples are weakly ferromagnetic with a magnetization of 0.2microB per Fe, more than an order of magnitude larger than that of pure BiFeO3. Magnetic hysteresis loops show unfamiliar "pinching," signaling a possible breakdown of the helical magnetic ordering in the fully strained samples. BaFeO3-x, though it can be made ferromagnetic, it is a highly complex material. In studying BaFeO3-x's properties, conclusions can be made that its weak magnetization and unusual structure is highly disordered, magnetically and structurally. The creation of a new solid solution (Bi, Ba)FeO3 by two methods shows that a solid solution between BiFeO3 and BaFeO3-x can be synthesized. Specifically the creation of the alloy Bi0.9Ba0.1FeO3-delta , shows that one can improve on BiFeO3's magnetic properties, and more importantly supports the case that BaFeO3-x exhibits magnetic and structural disorder.

Callender Bennett, Charlee J.

303

Iron oxide cluster induced barrier-free conversion of nitric oxide to ammonia.  

PubMed

Nitrogen oxide (NO) conversion to ammonia (NH3) over iron oxide clusters is investigated using density functional theory calculations. The introduction of NO and H2 over gas-phase Fe4O2 results in the formation of NH3 and H2O without activation barriers. The key reaction is barrier free conversion of NO to N and H2O where the physical origin rests on negative-negative repulsion of NO over iron oxide clusters. The by-product H2O can be a hydrogen source due to electrolysis or re-visiting Fe4O2 and hence, the reaction is self-sustainable. Furthermore, the above reactions are performed by depositing Fe4O2 clusters on graphene/Cu(111) where the barrier free conversion of NO to NH3 is also observed, predicting that such reaction can be applicable. Thus, low temperature conversion of NO to NH3 over Fe4O2 can be predicted. The detailed reaction pathway and mechanism are presented. PMID:25664360

Takahashi, Keisuke

2015-02-19

304

Physiological effects of magnetic iron oxide nanoparticles towards watermelon.  

PubMed

Nanoparticles (NPs) have been exploited in a diverse range of products in the past decade or so. However, the biosafety/environmental impact or legislation pertaining to this newly created, highly functional composites containing NPs (otherwise called nanomaterials) is generally lagging behind their technological innovation. To advance the agenda in this area, our current primary interest is focused on using crops as model systems as they have very close relationship with us. Thus, the objective of the present study was to evaluate the biological effects of magnetic iron oxide nanoparticles towards watermelon seedlings. We have systematically studied the physiological effects of Fe2O3 nanoparticles (nano-Fe2O3) on watermelon, and present the first evidence that a significant amount of Fe2O3 nanoparticles suspended in a liquid medium can be taken up by watermelon plants and translocated throughout the plant tissues. Changes in important physiological indicators, such as root activity, activity of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD), chlorophyll and malondialdehyde (MDA) contents, ferric reductase activity, root apoplastic iron content were clearly presented. Different concentrations of nano-Fe2O3 all increased seed germination, seedling growth, and enhanced physiological function to some degree; and the positive effects increased quickly and then slowed with an increase in the treatment concentrations. Changes in CAT, SOD and POD activities due to nano-Fe2O3 were significantly larger than that of the control. The 20 mg/L treatment had the most obvious effect on the increase of root activity. Ferric reductase activity, root apoplastic iron content, and watermelon biomass were significantly affected by exposure to nano-Fe2O3. Results of statistical analysis showed that there were significant differences in all the above indexes between the treatment at optimal concentration and the control. This proved that the proper concentration of nano-Fe2O3 could not only increase seed germination and seedling growth, but also ultimately improve physiological function and resistance to environmental stresses of watermelon. PMID:23882795

Li, Junli; Chang, Peter R; Huang, Jin; Wang, Yunqiang; Yuan, Hong; Ren, Hongxuan

2013-08-01

305

A cheaper, faster, better way to detect water of hydration on Solar System bodies  

Microsoft Academic Search

The 3.0-micrometers water of hydration absorption feature observed in the IR photometry of many low-albedo and some medium-albedo asteroids strongly correlates with the 0.7-micrometers Fe(+2) to Fe(+3) oxidized iron absorption feature observed in narrowband spectrophotometry of these asteroids. Using this relationship, an empirical algorithm for predicting the presence of water of hydration in the surface material of a Solar System

Faith Vilas

1994-01-01

306

Carboxymethyl cellulose coating decreases toxicity and oxidizing capacity of nanoscale zerovalent iron.  

PubMed

Nanoscale zerovalent iron (NZVI) with modified surface via coating with organic stabilizers has been documented with enhanced colloidal stability and dispersity. Therefore, the expanded application potential and accompanying intrinsic exposure of such nanoparticle can be anticipated. In our study, carboxymethyl cellulose (CMC)-stabilized NZVI (CNZVI) exerted minimized oxidative stress response and slower disruption of cell membrane integrity, resulting in mitigated cytotoxicity towards bacteria Agrobacterium sp. PH-08 as compared with the uncoated counterpart. The corrosive oxidation of both nanoparticles in oxygenic water provided a better understanding of coating effect. The decreased oxidative degradation of probe 4-chlorophenol with CNZVI than NZVI implicated a weaker oxidizing capacity, which might overweight massive adhesion-mediated redox damage and explain the different exposure outcome. However, enhanced evolution of iron oxide as well as the promoted production of hydrogen peroxide adversely demonstrated CMC-coating facilitated iron corrosion by oxygen, suggesting CMC was most likely to act as a radical scavenger and compete with organics or bacteria for oxidants. Moreover, XRD, XPS and TEM results showed that the spherical NZVI was oxidized to form needle-shaped iron oxide-hydroxide (?FeOOH) with no detectable oxidative stress for PH-08, alleviating worries regarding exotoxicological impact of iron nanotechnology. PMID:24287261

Zhou, Lei; Thanh, Thao Le; Gong, Jianyu; Kim, Jae-Hwan; Kim, Eun-Ju; Chang, Yoon-Seok

2014-06-01

307

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

308

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

309

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

NSDL National Science Digital Library

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

Banfield, Jilian F.

310

Effects of iron oxide nanoparticles on polyvinyl alcohol: interfacial layer and bulk nanocomposites thin film  

Microsoft Academic Search

Iron oxide (?-phase) nanoparticles with coercivity larger than 300 Oe have been fabricated at a mild temperature by an environmentally\\u000a benign method. The economic sodium chloride has been found to effectively serve as a solid spacer to disperse the iron precursor\\u000a and to prevent the nanoparticles from agglomeration. Higher ratios of sodium chloride to iron nitrate result in smaller nanoparticles

Zhanhu GuoDi; Di Zhang; Suying Wei; Zhe Wang; Amar B. Karki; Yuehao Li; Paul Bernazzani; David. P. Young; J. A. Gomes; David L. Cocke; Thomas C. Ho

2010-01-01

311

Preparation of nano-iron oxide red pigment powders by use of cyanided tailings.  

PubMed

On one hand, cyanided tailings are one kind of pollutants. On the other hand, they contain a lot of valuable elements. So utilization of them can bring social and environmental benefits. In this paper, cyanided tailings were used to prepare nano-iron oxide red pigment powders by an ammonia process with urea as precipitant. At first, cyanided tailings were oxidized by nitric acid. Then, the oxidizing mixture was separated into solid and liquid parts. The liquid mixture was reduced by scrap iron and the impurity of it was removed by use of NH3.H2O. Then, the seed crystal of gamma-FeOOH was obtained, when the pure liquid reacted with ammonia liquid at the selected experimental conditions. At last, nano-iron oxide red pigment powders were prepared. The structure, morphology and size distribution of seed crystal and iron oxide red were characterized systematically by means of X-ray diffraction (XRD), transmission electron microscope (TEM) and laser particle size analyzer (LPSA). The results revealed that typical iron oxide nanoparticles were alpha-Fe2O3 with particle size of 50-70 nm. Furthermore, the factors that affected the hue and quality of the seed crystal and iron oxide red pigment were also discussed. PMID:18164812

Dengxin, Li; Guolong, Gao; Fanling, Meng; Chong, Ji

2008-06-30

312

The crystal chemistry and structural analysis of uranium oxide hydrates. Final report, May 15, 1995--December 31, 1997  

SciTech Connect

The purpose of this research program was to develop a thorough understanding of the crystal-chemical and crystal-structural systematics of uranyl oxide hydrates which are the initial corrosion products of the UO{sub 2} in spent nuclear fuel and the principal phases in which actinides occur in the near surface environment. The scope of this program has been expanded to include all inorganic phases in which U{sup 6+} plays a significant structural role; currently 183 phases with known crystal structures.

Miller, M.L.; Ewing, R.C.

1998-11-01

313

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

314

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

315

Oxidant Generation Promotes Iron Sequestration in BEAS-2B Cells Exposed to Asbestos  

Microsoft Academic Search

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 through (1) generation of superoxide for ferrireduction, (2) up-regulation of divalent metal transporter-1 (DMT1) for intra-

Xinchao Wang; Yiming Wu; Jacqueline G. Stonehuerner; Lisa A. Dailey; Judy D. Richards; Ilona Jaspers; Claude A. Piantadosi; Andrew J. Ghio

2005-01-01

316

*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...

317

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 ...

318

Surface characterisation of dextran-coated iron oxide nanoparticles prepared by laser pyrolysis and coprecipitation  

NASA Astrophysics Data System (ADS)

The favoured mechanism of adsorption of dextran on the surface of maghemite nanoparticles (5 nm) prepared by laser pyrolysis seems to be the collective hydrogen bonding between dextran hydroxyl groups and iron oxide particle surface. After heating, the formation of a surface complex between the polysaccharide oxygen atoms and the surface iron atoms gave rise to a stronger bonding.

Carmen Bautista, M.; Bomati-Miguel, Oscar; del Puerto Morales, María; Serna, Carlos J.; Veintemillas-Verdaguer, Sabino

2005-05-01

319

Solid State Oxidative Deprotection of Trimethylsilyl Ethers with Iron (III) Nitrate and Montmorillonite Under Microwave Irradiation  

Microsoft Academic Search

Mixture of iron (III) nitrate and montmorillonite K10 oxidatively deprotect trimethylsilyl ethers to their corresponding carbonyl compounds under microwave irradiation in solventless system, in a short time and good yields.

Mohammad M. Mojtahedi; Mohammad R. Saidi; Mohammad Bolourtchian; Majid M. Heravi

1999-01-01

320

IRON OXIDES AND SULFIDES IN MAGNETOTACTIC BACTERIA: ELECTRON HOLOGRAPHY OF MAGNETIC MICROSTRUCTURE  

E-print Network

IRON OXIDES AND SULFIDES IN MAGNETOTACTIC BACTERIA: ELECTRON HOLOGRAPHY OF MAGNETIC MICROSTRUCTURE) Dept of Earth Sciences, University of Cambridge, UK Magnetotactic bacteria contain magnetosomes, which properties of crystals in magnetotactic bacteria collected from lakes and streams, in order to understand

Dunin-Borkowski, Rafal E.

321

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

322

Effects of Iron Oxides on the Rheological Properties of Cementitious Slurry  

SciTech Connect

Iron oxide has been considered a promising host for immobilizing and encapsulating radioactive 99Tc (t1/2=2.1x105 year), which significantly enhances the stability of 99Tc within a cementitious waste form. However, the flow behavior of cementitious slurry containing iron oxide has never been investigated to ensure its workability, which directly influences the preparation and performance of the cementitious waste form monolith. Variation in the rheological properties of the cementitious slurry were studied using rheometry and ultrasonic wave reflection to understand the effects of various iron oxides (magnetite, hematite, ferrihydrite, and goethite) during the cement setting and stiffening processes. The rheological behavior significantly varied with the addition of different chemical compounds of iron oxides. Complementary microscopic characteristics such as colloidal vibration currents, morphology, and particle size distributions further suggest that the most adverse alteration of cement setting and stiffening behavior caused by the presence of goethite may be attributed to its acicular shape.

Chung, Chul-Woo; Chun, Jaehun; Wang, Guohui; Um, Wooyong

2014-04-02

323

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...

324

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...

325

Synthesis and development of hydrophilic iron oxide nanoparticles for biomedical applications  

E-print Network

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

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

2014-01-01

326

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

327

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

E-print Network

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

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

2008-01-01

328

Interaction of Aromatic Amines with Iron Oxides: Implications for Prebiotic Chemistry  

NASA Astrophysics Data System (ADS)

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.

Shanker, Uma; Singh, Gurinder; Kamaluddin

2013-06-01

329

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

330

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.

331

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

332

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

2005-07-01

333

Crystallographic Orientation and Oxidation of Submicron Whiskers of Iron, Iron—Cobalt, and Cobalt  

Microsoft Academic Search

Individual single-crystal iron, iron—cobalt, and cobalt whiskers with diameters from 250 to 7000 Å have been studied by selected area electron diffraction. All of the iron and iron—cobalt diffraction patterns showed a normal bcc structure with the ?100? direction along the long axis of the whisker. All but one of the cobalt whiskers were hexagonal with the ?11.0? along the

F. E. Luborsky; E. F. Koch; C. R. Morelock

1963-01-01

334

Surface acid-base properties and hydration/dehydration mechanisms of aluminum (hydr)oxides.  

PubMed

In this paper, surface physiochemical properties of three typical aluminas, gamma-Al(OH)3, gamma-Al2O3, and alpha-Al2O3, were investigated by means of XRD, SEM, TEM, BET surface area, TG/DTA, and potentiometric titration techniques. Based on the titration data, surface protonation and deprotonation constants were determined using the constant capacitance model (CCM). The emphasis of this research was laid on the comparison of the crystal structure, surface hydration/dehydration and acid-base properties of these three typical alumina minerals. The calculation results revealed that the surface acidity of the aluminas is in the order of alpha-Al2O3>gamma-Al(OH)3>gamma-Al2O3 after being hydrated for 1 h. The correlation between the hydration/dehydration mechanisms of alumina and its acid/base properties is discussed. PMID:17275018

Yang, Xiaofang; Sun, Zhongxi; Wang, Dongsheng; Forsling, Willis

2007-04-15

335

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

336

Does hepatomegaly alter iron-dependent oxidative effects in human plasma?  

PubMed

A four-fold increase in the iron content of normal subjects was detected in plasma after 5 hours of iron administration. Iron supplementation had a surprisingly erratic effect on four patients with hepatomegaly secondary to heart insufficiency, since the increase in the iron content in the plasma after iron-dextran administration was either within the control range or significantly lower, independently of the initial values. Thiobarbituric acid reactive substances (TBARS) content was 2.5 +/- 0.2 and 4.3 +/- 0.4 microM for control and hepatomegalic subjects, respectively. The TBARS basal level was increased by iron supplementation. The difference between TBARS content in hepatomegalic and control subjects, after 5 hours of iron administration, was increased by 50% as compared to the difference in the basal content of TBARS. alpha-Tocopherol (alpha-T) content in plasma from subjects with hepatomegaly showed a significant decrease (-41%) as compared to control subjects. No significant difference over the basal level of alpha-T was measured after 5 hours of iron administration in any subject. The data presented here suggest that abnormal liver condition affects iron-dependent oxidative stress in plasma. Moreover, alpha-T does not seem to be the main antioxidant to control iron-dependent oxidative stress in plasma. PMID:12929730

Galleano, Monica; Lemberg, Abraham; Puntarulo, Susana

2003-07-01

337

The role of volatiles in the reduction of iron oxides  

NASA Astrophysics Data System (ADS)

With iron ore reduction processes using coal-ore pellets or mixtures, it is possible that volatiles from the coals can contribute to the overall reduction. By identifying the possible reducing species in the volatiles as H2/CO and simulating these constituents, the rates for H2 and CO were investigated in the temperature and reduction range of interest where hydrogen was the major reductant and studied in detail. In the initial stages of the present study, the fundamentals of hydrogen reduction of fine powder were found to be a complex mechanism of chemical kinetics and mass transfer. Complete uniform reduction for porous and dense iron ores were not observed contrary to existing work regarding this subject. Morphological observations of iron ores reduced at low and high temperatures showed a topochemical receding interface to be dominating with an intermediate region developing for higher temperature samples indicating the importance of pore mass transfer at the later stages of reduction. Although the activation energy of 50˜56 kJ/mole for these powder samples were comparable to the literature values for solely chemical kinetics controlled reactions, the reaction rates were not proportional to sample weight and also did not exhibit complete uniform internal reduction. The calculated mass transfer rates were comparable to the observed rate which suggested that bulk mass transfer is important to the mixed-control. The reaction rate at the mixed control regime was found to be first order with respect to hydrogen partial pressure. Results of reducing iron oxide powders in a mixture of He-40%H2 -5%CO and H2-1%H2S showed that H2S and CO which is involved with the volatiles does not affect the rate at the reduction range of interest indicating the role of volatiles is dominated by the hydrogen reduction. The single composite pellet experiments at 900 and 1000°C showed significant fixed carbon reduction to occur above 1000°C. Depending upon the type of carbon reductant in the composite pellet, secondary reactions with carbon and H2O was possible. Sintering of the pellets did not occur until a significant amount of reduction was obtained and thus for volatile reduction it is likely that the effects of sintering was negligible. To determine the possibility of volatile reduction, a layer of Fe 2O3 powders were spread over HV coals resulting in the reduction of the top layer by about 20% at 1000°C after 1000 seconds. The morphology of the reduced Fe2O3 layer indicated that the reduction is higher near the interface of Coal/Fe2O3. The volatile reduction of a single layer of composite pellet was found to be negligible. However, the reduction of Fe2O3 pellets at the top layer by the volatiles from the bottom layers of a three-layer pellet geometry was observed to be about 15%. From the morphological observations and the computed rates of bulk mass transfer, volatile reduction seems to be controlled by a mixed-controlled mechanism of bulk mass transfer and the limited-mixed control. Using the reduction information obtained from the single pellet experiments reduced in hydrogen, an empirical relationship was obtained to approximately predict the amount of volatile reduction up to 20%.

Sohn, Il

338

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

NASA Astrophysics Data System (ADS)

Lithotrophic growth on iron is a metabolism that has been found in a variety of neutral pH environments and is likely important in sustaining life in microaerophilic solutions, especially those low in organics. The composition of the microbial communities, especially the organisms that are responsible for iron oxidation, and carbon and nitrogen fixation, are not known, yet the ability to recognize these contributions is vital to our understanding of iron cycling in natural environments. Our approach has been to study the microbial community structure, mineralogy, and geochemistry of ~20 cm thick, 100's meters long, fluffy iron oxide-encrusted biological mats growing in the Piquette Mine tunnel, and to compare the results to those from geochemically similar environments. In situ measurements (Hydrolab) and geochemical characterization of bulk water samples and peepers (dialysis sampling vials) indicate that the environment is microaerobic, with micromolar levels of iron, high carbonate and sulfate, and typical groundwater nitrate and nitrite concentrations. 16S rDNA clone libraries show that the microbial mat and water contain communities with considerable diversity within the Bacterial domain, a large proportion of Nitrospira and Betaproteobacteria, and no Archaea. Because clone library data are not necessarily indicative of actual abundance, fluorescence in-situ hybridization (FISH) was performed on water, mat, and sediment samples from the Piquette mine and two circumneutral iron- and carbonate-rich springs in the Oregon Cascade Range. Domain- and phylum-level probes were chosen based on the clone library results (Nitrospira, Beta- and Gammaproteobacteria, Acidobacteria, Actinobacteria, Chloroflexi, and Planctomyces). FISH data reveal spatial associations between specific microbial groups and mineralized structures. The organisms responsible for making the mineralized sheaths that compose the bulk of the iron oxide mat are Betaproteobacteria (probably Leptothrix spp.). However, only a small proportion of the cells in the mat reside within the sheaths. Most are located on or around the sheaths, which provide a physical framework for the community. Preliminary results from FISH experiments on the iron-rich spring samples show some similarities, including an abundance of Betaproteobacteria. Enrichment and isolation experiments are being performed to identify the iron-oxidizing organisms. Iron-oxidizers have been enriched from all sites. In some cultures it has been difficult to isolate the iron-oxidizing organisms from a non-iron-oxidizing heterotroph, possibly indicating co-dependence. Knowledge of the microbial community structure and the metabolic activities of key members will enable us to better understand the processes and chemical conditions which generate iron oxide deposits found in the geologic record on Earth and possibly extraterrestrial habitats.

Chan, C. S.; Banfield, J. F.

2002-12-01

339

Enumeration and Detection of Anaerobic Ferrous Iron Oxidizing, Nitrate-Reducing Bacteria from Diverse European Sediments  

Microsoft Academic Search

Anaerobic, nitrate-dependent microbial oxidation of ferrous iron was recently recognized as a new type of metabolism. In order to study the occurrence of three novel groups of ferrous iron-oxidizing, nitrate-reducing bacteria (represented by strains BrG1, BrG2, and BrG3), 16S rRNA-targeted oligonucleotide probes were developed. In pure-culture experiments, these probes were shown to be suitable for fluorescent in situ hybrid- ization,

KRISTINA L. STRAUB; BERIT E. E. BUCHHOLZ-CLEVEN

1998-01-01

340

Ultrastable iron oxide nanoparticle colloidal suspensions using dispersants with catechol-derived anchor groups.  

PubMed

We have found catechol-derivative anchor groups which possess irreversible binding affinity to iron oxide and thus can optimally disperse superparamagnetic nanoparticles under physiologic conditions. This not only leads to ultrastable iron oxide nanoparticles but also allows close control over the hydrodynamic diameter and interfacial chemistry. The latter is a crucial breakthrough to assemble functionalized magnetic nanoparticles, e.g., as targeted magnetic resonance contrast agents. PMID:19835370

Amstad, Esther; Gillich, Torben; Bilecka, Idalia; Textor, Marcus; Reimhult, Erik

2009-12-01

341

High gradient magnetic separation of iron oxide minerals from soil clays  

E-print Network

HIGH GRADIENT MAGNETIC SEPARATION OF IRON OXIDE MINERALS FROM SOIL CLAYS A Thesis by DARRELL GENE SCHULZE Submitted to the Graduate College of Texas AIM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... December 1977 Major Subject: Soil Science HIGH GRADIENT MAGNETIC SEPARATION OF IRON OXIDE MINERALS FROM SOIL CLAYS A Thesis DARRELL GENE SCHULZE Approved as to style and content by: (Chairman of C ittee) epartm t) j (Member) (Membe December 1977...

Schulze, Darrell Gene

1977-01-01

342

Optical properties of crystalline and non-crystalline iron oxide thin films deposited by spray pyrolysis  

Microsoft Academic Search

Crystalline and non-crystalline iron oxide (?-Fe2O3) thin films were obtained by spray pyrolysis onto glass substrate at different temperatures. The results of X-ray diffraction showed that with increasing the deposition time, the film structure changed from non-crystalline to crystalline at the same substrate temperature. At different substrate temperatures and low deposition times (5min), iron oxide appears almost in non-crystalline form.

Alaa A. Akl

2004-01-01

343

Superparamagnetic Iron Oxide Nanoparticle-Based Delivery Systems for Biotherapeutics  

PubMed Central

Introduction Superparamagnetic iron oxide nanoparticle (SPION)-based carrier systems have many advantages over other nanoparticle-based systems. They are biocompatible, biodegradable, facilely tunable, and superparamagnetic and thus controllable by an external magnetic field. These attributes enable their broad biomedical applications. In particular, magnetically-driven carriers are drawing considerable interest as an emerging therapeutic delivery system because of their superior delivery efficiency. Area covered This article reviews the recent advances in use of SPION-based carrier systems to improve the delivery efficiency and target specificity of biotherapeutics. We examine various formulations of SPION-based delivery systems, including SPION micelles, clusters, hydrogels, liposomes, and micro/nanospheres, as well as their specific applications in delivery of biotherapeutics. Expert opinion Recently, biotherapeutics including therapeutic cells, proteins and genes have been studied as alternative treatments to various diseases. Despite the advantages of high target specificity and low adverse effects, clinical translation of biotherapeutics has been hindered by the poor stability and low delivery efficiency compared to chemical drugs. Accordingly, biotherapeutic delivery systems that can overcome these limitations are actively pursued. SPION-based materials can be ideal candidates for developing such delivery systems because of their excellent biocompatibility and superparamagnetism that enables long-term accumulation/retention at target sites by utilization of a suitable magnet. In addition, synthesis technologies for production of finely-tuned, homogeneous SPIONs have been well developed, which may promise their rapid clinical translation. PMID:23199200

Mok, Hyejung; Zhang, Miqin

2014-01-01

344

Magnetic resonance imaging of microvessels using iron-oxide nanoparticles  

NASA Astrophysics Data System (ADS)

The visualization of microstructures including blood vessels with an inner overall cross-sectional area below approximately 200 ?m remains beyond the capabilities of current clinical imaging modalities. But with magnetic resonance (MR) imaging, magnetic entities cause susceptibility artifacts in the images by disrupting the homogeneous magnetic field in a much larger scale than their actual size. As validated in this paper through simulation and in-vitro experiments, these artifacts can serve as a source of contrast, enabling microvessels with an inner diameter below the spatial resolution of any medical imaging modalities to be visualized using a clinical MR scanner. For such experiments, micron-sized agglomerations of iron-oxide (Fe3O4) nanoparticles were injected in microchannels with internal diameters of 200 and 50 ?m equivalent to a narrower artery or a larger arteriole, and down to a smaller arteriole, respectively. The results show the feasibility of the proposed method for micro-particle detection and the visualization of microvessels using a 1.5 T clinical MR scanner. It was confirmed that the method is reproducible and accurate at the sub-pixel level.

Olamaei, N.; Cheriet, F.; Martel, S.

2013-03-01

345

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

346

Synthesis and magnetic properties of gold coated iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

We report on synthesis, structural, and magnetic properties of chemically synthesized iron oxide (Fe3O4) and Fe3O4@Au core-shell nanoparticles. Structural characterization was done using x-ray diffraction and transmission electron microscopy, and the magnetite phase of the core (˜6nm) and fcc Au shell (thickness of ˜1nm) were confirmed. Magnetization (M) versus temperature (T) data at H =200Oe for zero-field-cooled and field-cooled modes exhibited a superparamagnetic blocking temperature TB˜35K (40K) for parent (core-shell) system. Enhanced coercivity (Hc˜200Oe) at 5K along with nonsaturating M-H loops observed for Fe3O4@Au nanoparticles indicate the possible role of spin disorder at the Au -Fe3O4 interface and weak exchange coupling between surface and core spins. Analysis of ac susceptibility (?' and ??) data shows that the interparticle interaction is reduced upon Au coating and the relaxation mechanism follows the Vogel-Fulcher law.

Pal, Susmita; Morales, Marienette; Mukherjee, Pritish; Srikanth, Hariharan

2009-04-01

347

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

PubMed Central

Purpose Combined therapeutic and diagnostic agents, “theranostics” are emerging valuable tools for noninvasive imaging and drug delivery. Here, we report on a solid biodegradable multifunctional nanoparticle that combines both features. Methods Poly(lactide-co-glycolide) nanoparticles were engineered to confine superparamagnetic iron oxide contrast for magnetic resonance imaging while enabling controlled drug delivery and targeting to specific cells. To achieve this dual modality, fatty acids were used as anchors for surface ligands and for encapsulated iron oxide in the polymer matrix. Results We demonstrate that fatty acid modified iron oxide prolonged retention of the contrast agent in the polymer matrix during degradative release of drug. Antibody-fatty acid surface modification facilitated cellular targeting and subsequent internalization in cells while inducing clustering of encapsulated fatty-acid modified superparamagnetic iron oxide during particle formulation. This induced clustered confinement led to an aggregation within the nanoparticle and, hence, higher transverse relaxivity, r2, (294 mM?1 s?1) compared with nanoparticles without fatty-acid ligands (160 mM?1 s?1) and higher than commercially available superparamagnetic iron oxide nanoparticles (89 mM?1 s?1). Conclusion Clustering of superparamagnetic iron oxide in poly(lactide-co-glycolide) did not affect the controlled release of encapsulated drugs such as methotrexate or clodronate and their subsequent pharmacological activity, thus highlighting the full theranostic capability of our system. PMID:23401099

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

2013-01-01

348

Vapour phase approach for iron oxide nanoparticle synthesis from solid precursors  

SciTech Connect

A new non-solution mediated approach to the synthesis of iron oxide nanoparticles directly from solid FeCl{sub 2} 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 (?-Fe{sub 2}O{sub 3}). 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{sup ?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{sup ?1}, which makes the material suitable for the formulation of ferrofluids or ferrogels with RF heating properties. - Graphical Abstract: Superparamagnetic iron oxide nanoparticles obtained by a novel vapour phase approach. Highlights: ? Novel vapour phase (non-solvent) approach for iron oxide nanoparticle synthesis. ? Attractive alternative approach to the present co-precipitation method. ? Better magnetic properties with high coercivity of nanoparticles. ? A high specific absorption rate (SAR) for hyperthermia applications.

Singh, Mandeep; Ulbrich, Pavel; Prokopec, Vadym [Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6 (Czech Republic); Svoboda, Pavel [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 120 00 Prague 2 (Czech Republic); Šantavá, Eva [Institute of Physics ASCR, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Št?pánek, František, E-mail: Frantisek.Stepanek@vscht.cz [Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6 (Czech Republic)

2013-04-15

349

Biosignatures in Spheroidal Iron Oxide-Rich Concretions from the Navajo Sandstone  

NASA Astrophysics Data System (ADS)

Spheroidal concretions composed of an iron oxide-rich cemented outer rind and a weakly-cemented core of bleached (iron depleted) sandstone are abundant in the Jurassic Navajo Sandstone of the Colorado Plateau. The formation of the spheroidal concretions has been previously described as a result of advective mixing between Fe(II)-rich reducing fluids with oxidizing fluids resulting in the subsequent abiotic precipitation of Fe(III) oxides forming the spheroidal concretions. The role of microbial biomineralization has been suggested as a potential mechanism of various other iron oxide formations, such as banded iron formations and iron-manganese nodules. Here we describe a series of qualitative and quantitative observations within the spheroidal concretions from the Jurassic Navajo Sandstone consistent with prior microbial activity. Spheroidal concretions were collected from Spencer Flat, east of Escalante, in south-central Utah, sectioned, and treated with dilute hydrochloric acid and acetone to remove traces of inorganic and organic carbon (C) from the surface of the samples. Elemental analysis of the treated specimens revealed elevated C as well as nitrogen (N) content with respect to the interior of the concretion (Rind, C, 0.06%, N, 0.006%; Interior, C, 0.009%, N, 0.003%). Elevated C and N values in the rind suggest carbon-nitrogen rich compounds consistent with biomolecules. Field Emission Scanning Electron Microscopy (FE-SEM) confirmed the presence of C as well as N and S via electron backscattering analysis. Additionally, structures morphologically consistent with bacterial cells have been observed via FE-SEM in association with a matrix that coated sand grains within the iron oxide-rich rind. Together these data suggest that microorganisms were associated with the iron oxide-rich spheroidal concretions. Microbial iron oxidation has been demonstrated to be ubiquitous microbial metabolism and is facilitated by a diversity of microorganisms in terrestrial surface and subsurface environments. Thus, Fe(II) and oxidizing fluids could have supported an iron oxidizing microbial community. Microbial catalysis and iron biomineralization may thus offer an alternative hypothesis regarding the formation and geochemical characteristics of the spheroidal iron oxide-rich concretions in the Jurassic Navajo Sandstone of the Colorado Plateau.

Spanbauer, T. L.; Kettler, R. M.; Loope, D. B.; Weber, K. A.

2009-12-01

350

The kinetics of formation of h 2 o and co 2 during iron oxide reduction  

Microsoft Academic Search

The kinetics of the chemical reaction-controlled reduction of iron oxides by H2\\/H2O and CO\\/CO2 gas mixtures are discussed. From an analysis of the systems it is concluded that the decomposition of the oxides takes place\\u000a by the two dimensional nucleation and lateral growth of oxygen vacancy clusters at the gas\\/oxide interface. The rates of decomposition\\u000a of the oxides under conditions

P. C. Hayes

1979-01-01

351

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

352

Nanoparticles of iron and vanadium oxides supported on iron substituted LDHs: Synthesis, textural characterization and their catalytic behavior in ethylbenzene dehydrogenation  

Microsoft Academic Search

Nanostructured catalysts derived from nanoparticles of iron or vanadium oxides supported on the matrices of iron substituted hydrotalcite-like anionic clays (layered double hydroxides, LDHs) have been obtained and tested in the process of ethylbenzene dehydrogenation to styrene. A simple synthesis method based on the LDHs “memory effect” has been used to prepare the new oxides-anionic clay structures. TEM analysis shows

Gabriela Carja; Yoshikazu Kameshima; Kiyoshi Okada

2008-01-01

353

Study of carbon encapsulated iron oxide/iron carbide nanocomposite for hyperthermia  

NASA Astrophysics Data System (ADS)

Magnetic nanocomposite has been synthesized successfully using biopolymer route which acts as a source of carbon for carbide formation. The present approach based on thermal decomposition represents a considerable advance over previous reports that often use high-energy procedures or costly and hazardous precursors. X-ray diffraction, high-resolution transmission electron microscopy and vibrating sample magnetometer have been used to characterize the composites. Multi phase formation is evident from X-ray diffraction in the as-prepared samples. Phase confirmation was further done from M (magnetization) versus T (temperature) curve indicating presence of different phases of carbide along with iron oxide. TEM study suggests formation of cuboidal shape nanocomposite using two different quenching conditions. Transmission electron microscopy also confirmed the formation of carbon layer in the vicinity of the Fe3O4/Fe3C nanoparticles. The magnetic measurement shows that the composite nanoparticles exhibit a maximum magnetization of 60 emu g-1 at room temperature. Biocompatibility study with three different cell lines (HeLa, MCF-7 and L929) confirms that these nanocomposites are biocompatible. Temperature versus time measurement in an AC field suggests good heating ability of the samples. These investigations indicate that these nanocomposites may be useful for bioapplications, in particular for hyperthermia.

Sharma, Madhulika; Mantri, Sanket; Bahadur, D.

2012-11-01

354

Synthesis and characterization of platinum decorated iron oxide nanoparticles for biomedical applications  

NASA Astrophysics Data System (ADS)

This dissertation focuses on the development of a bifunctional nanoparticle system that can potentially offer simultaneous imaging and therapy in the future. Recently, small platinum (Pt) nanoparticles (< 5 nm) have shown great potential in therapeutic applications, such as DNA dissociation, radiation therapy, and oxidative stress treatment. Therefore, the small Pt nanoparticles of size comparable to DNA grooves are chosen as potential therapeutic components in this research. However, such small sized Pt nanoparticles tends to aggregate, and are difficult to target. Therefore, this research reports the synthesis, characterization, and DNA interaction of small Pt decorated iron oxide nanoparticles. The iron oxide carriers provide stability to the small Pt nanoparticles, and can potentially serve as MRI contrast agents. The hypothesis of this research is that the Pt nanoparticles supported on iron oxide nanoparticle surfaces can effectively interact with DNA molecules similar to the free Pt nanoparticles. A reproducible synthetic technique was first developed to prepare iron oxide nanoparticles with excellent size control and narrow size distribution. Subsequently, two different approaches were utilized to produce multiple small Pt nanoparticle attached iron oxide nanoparticles. The first route involved attachment of Pt nanoparticles onto iron oxide seeds of various shapes in an organic solvent, followed by an aqueous phase transfer. Here, the shape of the nanoparticles was controlled to facilitate heterogeneous nucleation of Pt nanoparticles. The protective biocompatible polymer coating (polyacrylic acid) in this method could prevent interaction of the Pt nanoparticles with undesirable biomolecules. Several non-spherical iron oxide nanoparticles were explored, including whiskers, worms, plates, and flowers. In the second method, an aqueous phase ligand exchange process was performed first, prior to the deposition of multiple Pt nanoparticles. This facile method provided more accessibility of the Pt nanoparticles for DNA interactions. The DNA interaction of these nanoparticles was investigated using gel electrophoresis, electron microscopy, dynamic light scattering, and atomic absorption spectroscopy. By comparing with control DNA, we suggested that two possible interactions between DNA and Pt-iron oxide nanoparticles were present: (1) DNA molecules directly linked to the Pt-iron oxide nanoparticles, and (2) DNA molecules de-attached the Pt nanoparticles from the iron oxide support. This reported nanodrug system could potentially open up new possibilities in the design of therapeutic agents using multifunctional nanoparticles. Future efforts are to investigate the in vivo characteristics of this integrated nanostructure.

Palchoudhury, Soubantika

355

Size- and composition-dependent radio frequency magnetic permeability of iron oxide nanocrystals.  

PubMed

We investigate the size- and composition-dependent ac magnetic permeability of superparamagnetic iron oxide nanocrystals for radio frequency (RF) applications. The nanocrystals are obtained through high-temperature decomposition synthesis, and their stoichiometry is determined by Mössbauer spectroscopy. Two sets of oxides are studied: (a) as-synthesized magnetite-rich and (b) aged maghemite nanocrystals. All nanocrystalline samples are confirmed to be in the superparamagnetic state at room temperature by SQUID magnetometry. Through the one-turn inductor method, the ac magnetic properties of the nanocrystalline oxides are characterized. In magnetite-rich iron oxide nanocrystals, size-dependent magnetic permeability is not observed, while maghemite iron oxide nanocrystals show clear size dependence. The inductance, resistance, and quality factor of hand-wound inductors with a superparamagnetic composite core are measured. The superparamagnetic nanocrystals are successfully embedded into hand-wound inductors to function as inductor cores. PMID:25390073

Yun, Hongseok; Liu, Xiyu; Paik, Taejong; Palanisamy, Duraivelan; Kim, Jungkwun; Vogel, William D; Viescas, Arthur J; Chen, Jun; Papaefthymiou, Georgia C; Kikkawa, James M; Allen, Mark G; Murray, Christopher B

2014-12-23

356

Study of phase transformation in iron oxides using Laser Induced Breakdown Spectroscopy  

NASA Astrophysics Data System (ADS)

Synthetic magnetite (Fe 3O 4) was heated in air at 200-500 °C for different time periods to study its phase transformation to maghemite (?-Fe 2O 3) and hematite (?-Fe 2O 3). Laser Induced Breakdown Spectroscopy (LIBS) was used to take the spectra of these samples which were then compared to the spectra of standard iron oxide powders using linear correlation. The linear correlation procedure used showed probabilities of identification close to unity. Complementary techniques to LIBS, Fourier Transform Infrared (FTIR) spectroscopy and X-ray Diffraction (XRD) analysis were also used to characterize iron oxides. By taking advantage of the time gated detector capability of LIBS, the identification of iron oxide phases was found to be in good agreement with FTIR and XRD analysis. This study demonstrates that LIBS can be successfully applied to the characterization of the oxidation states of multivalent oxides of elements like Fe, Cr, Pb, and others.

Nasrazadani, S.; Namduri, H.

2006-05-01

357

Mineral and iron oxidation at low temperatures by pure and mixed cultures of acidophilic microorganisms.  

PubMed

An enrichment culture from a boreal sulfide mine environment containing a low-grade polymetallic ore was tested in column bioreactors for simulation of low temperature heap leaching. PCR-denaturing gradient gel electrophoresis and 16S rRNA gene sequencing revealed the enrichment culture contained an Acidithiobacillus ferrooxidans strain with high 16S rRNA gene similarity to the psychrotolerant strain SS3 and a mesophilic Leptospirillum ferrooxidans strain. As the mixed culture contained a strain that was within a clade with SS3, we used the SS3 pure culture to compare leaching rates with the At. ferrooxidans type strain in stirred tank reactors for mineral sulfide dissolution at various temperatures. The psychrotolerant strain SS3 catalyzed pyrite, pyrite/arsenopyrite, and chalcopyrite concentrate leaching. The rates were lower at 5 degrees C than at 30 degrees C, despite that all the available iron was in the oxidized form in the presence of At. ferrooxidans SS3. This suggests that although efficient At. ferrooxidans SS3 mediated biological oxidation of ferrous iron occurred, chemical oxidation of the sulfide minerals by ferric iron was rate limiting. In the column reactors, the leaching rates were much less affected by low temperatures than in the stirred tank reactors. A factor for the relatively high rates of mineral oxidation at 7 degrees C is that ferric iron remained in the soluble phase whereas, at 21 degrees C the ferric iron precipitated. Temperature gradient analysis of ferrous iron oxidation by this enrichment culture demonstrated two temperature optima for ferrous iron oxidation and that the mixed culture was capable of ferrous iron oxidation at 5 degrees C. PMID:17187443

Dopson, Mark; Halinen, Anna-Kaisa; Rahunen, Nelli; Ozkaya, Bestamin; Sahinkaya, Erkan; Kaksonen, Anna H; Lindström, E Börje; Puhakka, Jaakko A

2007-08-01

358

Parkinson's Disease Iron Deposition Caused by Nitric Oxide-Induced Loss of ?-Amyloid Precursor Protein.  

PubMed

Elevation of both neuronal iron and nitric oxide (NO) in the substantia nigra are associated with Parkinson's disease (PD) pathogenesis. We reported previously that the Alzheimer-associated ?-amyloid precursor protein (APP) facilitates neuronal iron export. Here we report markedly decreased APP expression in dopaminergic neurons of human PD nigra and that APP(-/-) mice develop iron-dependent nigral cell loss. Conversely, APP-overexpressing mice are protected in the MPTP PD model. NO suppresses APP translation in mouse MPTP models, explaining how elevated NO causes iron-dependent neurodegeneration in PD. PMID:25716857

Ayton, Scott; Lei, Peng; Hare, Dominic J; Duce, James A; George, Jessica L; Adlard, Paul A; McLean, Catriona; Rogers, Jack T; Cherny, Robert A; Finkelstein, David I; Bush, Ashley I

2015-02-25

359

Kinetics of reduction of iron oxides using microwaves as power source  

SciTech Connect

This work deals with kinetic description of carbothermic reduction of iron oxides using microwaves as power source. Previous researches show that it is possible to conduct this kind of process successfully, but real kinetic comparisons between conventional and microwaves procedure have been presented partially. The aim of this work is to describe reduction kinetics, taking into account how the iron oxide is reduced by microwaves compared with conventional energy supply. In this study the authors used iron ore in pellet shape and dust. They found that both, pellet and dust reduction stops when it reaches approximately 40%, even at whole power.

Gomez, I.; Aguilar, J.; Gonzalez, M.; Morales, J. [Univ. Autonoma de Nuevo Leon, San Nicolas de los Garza (Mexico). Facultad de Ingenieria Mecanica y Electrica

1996-12-31

360

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

361

Stable carbon isotopic evidence for methane oxidation in plumes above Hydrate Ridge, Cascadia Oregon Margin  

Microsoft Academic Search

The transport and consumption of methane in the water column in the vicinity of the cold seeps of Hydrate Ridge on the Cascadia Oregon Margin were characterized using measurements of the stable carbon isotope composition of methane. The 13C-CH4 values measured in the water column ranged from approximately 65 to 16, PDB. The combination of measured methane concentration data and

Nicholas J. Grant; Michael J. Whiticar

2002-01-01

362

Photocatalytic oxidation and removal of arsenite from water using slag-iron oxide-TiO 2 adsorbent  

Microsoft Academic Search

Photocatalytic oxidation of arsenite and simultaneous removal of the generated arsenate from aqueous solution were investigated. The whole process was performed using an adsorbent developed by loading iron oxide and TiO2 on municipal solid waste melted slag. The loading was carried out through chemical reactions and high-temperature process. In the removal process, arsenite was first oxidized to arsenate, and then

Fu-Shen Zhang; Hideaki Itoh

2006-01-01

363

Size dependence of inter- and intra-cluster interactions in core-shell iron-iron oxide nanoclusters  

SciTech Connect

The room temperature magnetic properties of core-shell iron-iron oxide nanoclusters (NCs) synthesized by a cluster deposition system have been investigated, and their dependence on mean cluster size has been discussed. In this study, the surface/boundary spins of clusters were not frozen and were thermally activated during the measurements. The inter-cluster interactions between clusters and intra-cluster interactions between the iron core (ferromagnetic) and iron oxide shell (ferrimagnetic) have been investigated by field dependent isothermal remanent magnetization and dc demagnetization measurements at room temperature. The Henkel plot and delta M plot support the existence of dipolar inter-cluster interactions which become stronger with the growth of cluster size. The derivative of the initial magnetization curve implies that smaller clusters require less field and time than the bigger ones to overcome various energy barriers before aligning along the field direction. Coercive field and magnetization are also correlated with the interaction parameters. To compare the room temperature magnetic results, one system was studied at low temperature, where exchange coupling at the interface between the oxide and metallic phases was observed through bias effect and anisotropy enhancement.

Kaur, Maninder; McCloy, John S.; Jiang, Weilin; Yao, Qi; Qiang, You

2012-06-15

364

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

365

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.degree. and 90.degree. C. to reduce NO present, produce ammonia or an ammonium ion, and produce free iron (II) (CHELATE) at a pH of between about 3 and 8. The process is useful to remove NO from flue gas and reduce pollution.

Chang, Shih-Ger (El Cerrito, CA); Littlejohn, David (Oakland, CA); Shi, Yao (Berkeley, CA)

1997-08-19

366

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

367

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

368

Role of surface complexed iron in oxidant generation and lung inflammation induced by silicates  

SciTech Connect

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. Silica and silicates were found to complex more than ten times the Fe(3+) onto their surfaces than did a biologically inactive dust, titanium dioxide. In vivo generation of oxidants by alveolar macrophages measured after exposure to dusts was increased by surface complexed iron. Also, acute inflammatory lung injury after intratracheal injection of silica dusts was made more severe by surface iron. The authors conclude that silica and silicate surfaces complex Fe(3+) to increase oxidant generation and mediator release by alveolar macrophages, and to increase acute lung injury in the rat.

Ghio, A.J.; Kennedy, T.P.; Whorton, A.R.; Crumbliss, A.L.; Hatch, G.E.

1993-01-01

369

Iron Oxides from Volcanic Soils as Potential Catalysts in the Water Gas Shift Reaction  

SciTech Connect

This study was focused on changes of the iron oxide mineralogy with temperature of two Chilean soils (Andisol and Ultisol) derived from volcanic materials and their use as iron-based catalysts in the water gas shift reaction (WGSR). Ultisol materials produced about twice as much hydrogen than did those from Andisol upon WGSR, but in both cases hydrogen yielding increased as the heating temperature of the soil materials increased from 124 deg. C to 500 deg. C. The room temperature Moessbauer spectra showed an increase of the relative proportion of the magnetically ordered components as temperature increased. Higher heating temperature produced a negative effect on the catalytic activity, whereas the organic matter destruction led to a positive effect, due to an increasing exposition of the iron oxide surfaces; heating the soil sample at 600 deg. C induced changes on the iron oxide mineralogy with a significant decrease of the catalytic activity.

Pizarro, C.; Escudey, M.; Moya, S.A. [Facultad de Quimica y Biologia, USACH, Av. L. B. O'Higgins 3363, Santiago 7254758 (Chile); Fabris, J.D. [Departamento de Quimica, ICEx-UFMG, Pampulha, 31270-901 Belo Horizonte, MG (Brazil)

2005-04-26

370

Ordered Mesoporous Carbon/Iron Oxide Nanoparticle Composites for Supercapacitor Applications  

NASA Astrophysics Data System (ADS)

Novel mesoporous carbon/iron oxide composites were prepared through a simple carbonization procedure of blends of block copolymer precursors containing the source of carbon, i.e., polyacrylonitrile-block-poly(t-butyl acrylate) (PtBA-b-PAN) with iron oxide nanoparticles. The addition of functionalized nanoparticles that selectively hydrogen bond with PAN segments was shown to induce order in otherwise disordered system. The ordered mesostructure of the composites was confirmed by both small x-ray scattering and transmission electron microscopy. The preparation of nanocomposites with pore structure was enabled by the high ?delity preservation of the phase-separated nanostructure between two polymer blocks driven by nanoparticle additive upon carbonization at 700oC. The electrochemical performance of the composite films was compared to that of the neat carbon and the mesoporous carbon without iron oxide nanoparticles. The mesoporous structure together with the high iron contents in such materials make them particularly promising for use in supercapacitor applications.

Lin, Ying; Wang, Xinyu; Watkins, James

2013-03-01

371

Electrochemical behaviour of Teflon-bonded iron oxide electrodes in alkaline solutions  

NASA Astrophysics Data System (ADS)

The electrochemical behaviour af Teflon-bonded iron oxide electrodes in 5.35 M KOH +0.65 M LiOH solution that contains various additives (such as thiourea, ethylenediaminetetraacetic acid (EDTA), hexamine and sodium sulfide) is examined by cyclic voltammetry. chronopotentiometry, open-circuit potential (OCP) decay and charge/discharge studies. The incorporation of Na2S in the alkaline electrolyte improves the performance of iron oxide electrodes by increasing the value of the OCP and decreasing the transient time. Moreover, the addition of Na 2S gives maximum capacity for the iron oxide electrode and a value of zero for {dE }/{dt }. The addition of thiourea lowers the performance of pressed iron electrodes. Thus, the incorporation of Na 2S in the alkaline electrolyte is essential for improving the performance of these electrodes.

Periasamy, P.; Ramesh Babu, B.; Venkatakrishna Iyer, S.

372

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

373

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

374

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

375

Life at the Energetic Edge: Kinetics of Circumneutral Iron Oxidation by Lithotrophic Iron-Oxidizing Bacteria Isolated from the Wetland-Plant Rhizosphere  

PubMed Central

Batch cultures of a lithotrophic Fe(II)-oxidizing bacterium, strain BrT, isolated from the rhizosphere of a wetland plant, were grown in bioreactors and used to determine the significance of microbial Fe(II) oxidation at circumneutral pH and to identify abiotic variables that affect the partitioning between microbial oxidation and chemical oxidation. Strain BrT grew only in the presence of an Fe(II) source, with an average doubling time of 25 h. In one set of experiments, Fe(II) oxidation rates were measured before and after the cells were poisoned with sodium azide. These experiments indicated that strain BrT accounted for 18 to 53% of the total iron oxidation, and the average cellular growth yield was 0.70 g of CH2O per mol of Fe(II) oxidized. In a second set of experiments, Fe(II) was constantly added to bioreactors inoculated with live cells, killed cells, or no cells. A statistical model fitted to the experimental data demonstrated that metabolic Fe(II) oxidation accounted for up to 62% of the total oxidation. The total Fe(II) oxidation rates in these experiments were strongly limited by the rate of Fe(II) delivery to the system and were also influenced by O2 and total iron concentrations. Additionally, the model suggested that the microbes inhibited rates of abiotic Fe(II) oxidation, perhaps by binding Fe(II) to bacterial exopolymers. The net effect of strain BrT was to accelerate total oxidation rates by up to 18% compared to rates obtained with cell-free treatments. The results suggest that neutrophilic Fe(II)-oxidizing bacteria may compete for limited O2 in the rhizosphere and therefore influence other wetland biogeochemical cycles. PMID:12147500

Neubauer, Scott C.; Emerson, David; Megonigal, J. Patrick

2002-01-01

376

Iron oxide nanoparticle hyperthermia and radiation cancer treatment  

NASA Astrophysics Data System (ADS)

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, S. M.; Giustini, A. J.; Petryk, A. A.; Strawbridge, R. A.; Hoopes, P. J.

2009-02-01

377

Physicochemical Characterization of Nebulized Superparamagnetic Iron Oxide Nanoparticles (SPIONs)  

PubMed Central

Abstract Background: Aerosol-mediated delivery of nano-based therapeutics to the lung has emerged as a promising alternative for treatment and prevention of lung diseases. Superparamagnetic iron oxide nanoparticles (SPIONs) have attracted significant attention for such applications due to their biocompatibility and magnetic properties. However, information is lacking about the characteristics of nebulized SPIONs for use as a therapeutic aerosol. To address this need, we conducted a physicochemical characterization of nebulized Rienso, a SPION-based formulation for intravenous treatment of anemia. Methods: Four different concentrations of SPION suspensions were nebulized with a one-jet nebulizer. Particle size was measured in suspension by transmission electron microscopy (TEM), photon correlation spectroscopy (PCS), and nanoparticle tracking analysis (NTA), and in the aerosol by a scanning mobility particle sizer (SMPS). Results: The average particle size in suspension as measured by TEM, PCS, and NTA was 9±2?nm, 27±7?nm, and 56±10?nm, respectively. The particle size in suspension remained the same before and after the nebulization process. However, after aerosol collection in an impinger, the suspended particle size increased to 159±46?nm as measured by NTA. The aerosol particle concentration increased linearly with increasing suspension concentration, and the aerodynamic diameter remained relatively stable at around 75?nm as measured by SMPS. Conclusions: We demonstrated that the total number and particle size in the aerosol were modulated as a function of the initial concentration in the nebulizer. The data obtained mark the first known independent characterization of nebulized Rienso and, as such, provide critical information on the behavior of Rienso nanoparticles in an aerosol. The data obtained in this study add new knowledge to the existing body of literature on potential applications of SPION suspensions as inhaled aerosol therapeutics. PMID:24801912

Graczyk, Halshka; Bryan, Louise C.; Lewinski, Nastassja; Suarez, Guillaume; Coullerez, Geraldine; Bowen, Paul

2015-01-01

378

Millimeter wave ferromagnetic resonance in gallium-substituted ?-iron oxide  

SciTech Connect

In millimeter wave frequency range, hexagonal ferrites with high uniaxial anisotropic magnetic fields are used as absorbers. These ferrites include M-type barium ferrite (BaFe{sub 12}O{sub 19}) and strontium ferrite (SrFe{sub 12}O{sub 19}), which have natural ferromagnetic resonant frequency range from 40 GHz to 60?GHz. However, the higher frequency range lacks suitable materials that support the higher frequency ferromagnetic resonance. A new series of gallium-substituted ?-iron oxides (?-Ga{sub x}Fe{sub 2?x}O{sub 3}) are synthesized which have ferromagnetic resonant frequencies appearing over the frequency range 30 GHz–150 GHz. The ?-Ga{sub x}Fe{sub 2?x}O{sub 3} is synthesized by the combination of reverse micelle and sol-gel techniques or the sol-gel method only. The particle sizes are observed to be smaller than 100 nm. In this paper, the free space magneto-optical approach has been employed to study these newly developed ?-Ga{sub x}Fe{sub 2?x}O{sub 3} particles in millimeter waves. This technique enables to obtain precise transmission spectra to determine the dielectric and magnetic properties of both isotropic and anisotropic ferrites in the millimeter wave frequency range from a single set of direct measurements. The transmittance and absorbance spectra of ?-Ga{sub x}Fe{sub 2?x}O{sub 3} are shown in this paper. Strong ferromagnetic resonances at different frequencies determined by the x parameter are found.

Chao, Liu, E-mail: liu.chao@tufts.edu; Afsar, Mohammed N. [Department of Electrical and Computer Engineering, Tufts University, Medford, Massachusetts 02155 (United States); Ohkoshi, Shin-ichi [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2014-05-07

379

Magnetic field calculations for iron oxide nanoparticles for MRI  

NASA Astrophysics Data System (ADS)

The susceptibility effects of superparamagnetic iron oxide nanoparticles (SPIONs) functionalized with triethylenglycol (TREG) and Polyethylen Glycol (PEG) has been studied, those nanoparticles have the necessary properties to be used in the clinic as contrast media in imaging by MRI[1-3]. We are considering the behavior of the magnetic field as plane wave to explain the electrical and magnetic field produced by SPIONs. Images were acquired on a 1.5T imager Philips, using mFFE Sequence. Three glass capillary tubes with a) TREG (10nm) concentration of 300 ?g/ml, and PEGCOOH 6000(10nm) with 300 ?g/ml, and 2% agarosa. Magnetic field simulations were calculated in Matlab. The plane wave that comes in contact with a sphere of radius a, an propagation constant k1, and it is in an homogeneous space k2. We consider that the electric field is linearly polarized on x-direction, with a propagation on z-positive-axis. The secondary induced field can be explained from the interior of the sphere and valid exterior points. The referred waves are transmitted and reflected, this is valid only when the wavelength is smaller than the radius of the sphere. The obtained vibrational mode is an answer of the electrical oscillation and this is projection of the disturbed magnetic field. TREG-SPIONs produce more serious susceptibility artefacts compared to PEG-SPIONs. This study is promissory due to the concordance of the results of the simulations and the inhomogeneities showed in the MR images.

Hernandez, Ricardo; Mendez Rojas, Miguel; Dies Suarez, Pilar; Hidalgo Tobón, Silvia

2014-11-01

380

Water oxidation catalysis with nonheme iron complexes under acidic and basic conditions: homogeneous or heterogeneous?  

PubMed

Thermal water oxidation by cerium(IV) ammonium nitrate (CAN) was catalyzed by nonheme iron complexes, such as Fe(BQEN)(OTf)2 (1) and Fe(BQCN)(OTf)2 (2) (BQEN = N,N'-dimethyl-N,N'-bis(8-quinolyl)ethane-1,2-diamine, BQCN = N,N'-dimethyl-N,N'-bis(8-quinolyl)cyclohexanediamine, OTf = CF3SO3(-)) in a nonbuffered aqueous solution; turnover numbers of 80 ± 10 and 20 ± 5 were obtained in the O2 evolution reaction by 1 and 2, respectively. The ligand dissociation of the iron complexes was observed under acidic conditions, and the dissociated ligands were oxidized by CAN to yield CO2. We also observed that 1 was converted to an iron(IV)-oxo complex during the water oxidation in competition with the ligand oxidation. In addition, oxygen exchange between the iron(IV)-oxo complex and H2(18)O was found to occur at a much faster rate than the oxygen evolution. These results indicate that the iron complexes act as the true homogeneous catalyst for water oxidation by CAN at low pHs. In contrast, light-driven water oxidation using [Ru(bpy)3](2+) (bpy = 2,2'-bipyridine) as a photosensitizer and S2O8(2-) as a sacrificial electron acceptor was catalyzed by iron hydroxide nanoparticles derived from the iron complexes under basic conditions as the result of the ligand dissociation. In a buffer solution (initial pH 9.0) formation of the iron hydroxide nanoparticles with a size of around 100 nm at the end of the reaction was monitored by dynamic light scattering (DLS) in situ and characterized by X-ray photoelectron spectra (XPS) and transmission electron microscope (TEM) measurements. We thus conclude that the water oxidation by CAN was catalyzed by short-lived homogeneous iron complexes under acidic conditions, whereas iron hydroxide nanoparticles derived from iron complexes act as a heterogeneous catalyst in the light-driven water oxidation reaction under basic conditions. PMID:23895380

Hong, Dachao; Mandal, Sukanta; Yamada, Yusuke; Lee, Yong-Min; Nam, Wonwoo; Llobet, Antoni; Fukuzumi, Shunichi

2013-08-19

381

Effect of iron supplementation on oxidative stress and antioxidant status in iron-deficiency anemia  

Microsoft Academic Search

This study was designed to measure the effect of iron supplementation on antioxidant status in iron-deficient anemia, including\\u000a the time for hemoglobin normalization and at the time of filling of iron body stores. The extent of plasma lipid peroxidation\\u000a was evaluated by measuring the levels of malondialdehyde and glutathione peroxidase (GSH-Px), and the activities of superoxide\\u000a dismutase (SOD) and catalase

Erdal Kurtoglu; Aysegul Ugur; Abdulkerim Kasim Baltaci; Levent Undar

2003-01-01

382

A spectroscopic investigation of phosphate adsorption onto iron oxides M. G. Nooney  

E-print Network

compounds applied. In fact, the capacity of most soils to retain phosphate is orders of magnitude greater abundant metal oxides in soils.6,7 However, the mechanisms of phosphate reactions with iron oxides of Chemistry, Texas A&M University, College Station, Texas 77843-3255 T. S. Murrell Department of Soil Science

Goodman, Wayne

383

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 electrolysis (MOE) is a carbon-free, electrochemical technique to decompose a metal oxide directly into liquid. Electrolysis is being investigated by the steel industry as a carbon-lean route that copes with the potential

Sadoway, Donald Robert

384

Studies of Optically Induced Magnetization Dynamics in Colloidal Iron Oxide Nanocrystals  

E-print Network

of oxidation on static FR in iron oxide nanocrystals (between Fe3O4 and y-Fe2O3) was studied. The results indicated FR signal is linearly correlated to the strength of optical transition between Fe2 and Fe3 in Fe3O4 for a given size of nanocrystals....

Hsia, Chih-Hao

2011-10-21

385

Iron carbide on titania surface modified with group VA oxides as Fischer-Tropsch catalysts  

Microsoft Academic Search

A catalyst is described comprising iron carbide supported on a surface modified titania wherein the support comprises an oxide of a metal selected form the group consisting of niobium, vanadium, tantalum or mixture thereof supported on the titania wherein at least a portion of the supported oxide of niobium, vanandium, tantalum or mixture is in a non-crystalline form. The amount

I. E. Wachs; R. A. Fiato; C. C. Chersich

1986-01-01

386

Iron carbide on titania surface modified with group VA oxides as Fisher-Tropsch catalysts  

Microsoft Academic Search

Catalysts comprising iron carbide on a surface modified titania support wherein said support comprises a surface modifying oxide of tantalum, niobium, vanadium and mixtures thereof supported on said titania wherein at least a portion of said surface modifying oxide is in a non-crystalline form. These catalysts are useful for Fischer-Tropsch hydrocarbon synthesis reactions. Preferably, at least about 25 wt. %

I. E. Wachs; C. C. Cherisch; R. A. Fiato

1985-01-01

387

An Interpretation of the Magnetic Properties of some Iron-Oxide Powders  

Microsoft Academic Search

The observed magnetic properties of fine dispersed powders of the ferromagnetic iron oxides are discussed in the light of modern theories of the magnetization of ferrites and of ferromagnetics containing non-magnetic inclusions. The individual powder particles are shown to be probably of single-domain size, and the relative coercivities of ?-ferric oxide powders of nearly spherical and of markedly acicular grains

W P Osmond

1952-01-01

388

Structure and magnetic properties of iron oxide dispersed silver based nanocluster composite  

Microsoft Academic Search

Magnetic nanocomposites composed of iron oxide and silver were fabricated by an inert gas condensation (IGC) method combined with co-evaporation, in situ oxidation, and in situ compaction techniques. The particle sizes of composite powder were controlled by varying helium gas pressure between 1 and 10 Torr, with the smallest one being about 10 nm at 1.0 Torr. The nanostructure of

T. Nakayama; T. A. Yamamoto; Y.-H. Choa; K. Niihara

2000-01-01

389

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

E-print Network

a greater thermo- dynamic stability but less surface area than the initial products. Heat treatment alsoAging of Iron (Hydr)oxides by Heat Treatment and Effects on Heavy Metal Binding M E T T E A . S Ø R)oxides are used to remove heavy metals from wastewater and in the treatment of air pollution control residues

Frenkel, Anatoly

390

Iron–Phthalocyanine Immobilized on Activated Carbon Black: A Selective Catalyst for Alkane Oxidation  

Microsoft Academic Search

Carbon black is tested as a support for iron–phthalocyanine within the frame of the oxidation of hydrocarbons witht-butylhydroperoxide as oxygen donor. The increased hydrophobicity of the carrier surface, with respect to zeolite Y, changes the adsorption behavior of the components in the reaction mixture towards the alkane. A major improvement in the oxidation conversion and efficiency of cyclohexane has been

Rudy F. Parton; Patricia E. Neys; Peter A. Jacobs; Rosario C. Sosa; Paul G. Rouxhet

1996-01-01

391

Electrochemical Deposition of Iron Nanoneedles on Titanium Oxide Nanotubes  

SciTech Connect

Iron as a catalyst has wide applications for hydrogen generation from ammonia, photodecomposition of organics, and carbon nanotube growth. Tuning the size and shape of iron is meaningful for improving the catalysis efficiency. It is the objective of this work to prepare nanostructured iron with high surface area via electrochemical deposition. Iron nanoneedles were successfully electrodeposited on Ti supported TiO2 nanotube arrays in a chlorine-based electrolyte containing 0.15 M FeCl2 {center_dot} 4H2O and 2.0 M HCl. Transmission electron microscopic analysis reveals that the average length of the nanoneedles is about 200 nm and the thickness is about 10 nm. It has been found that a high overpotential at the cathode made of Ti/TiO2 nanotube arrays is necessary for the formation of the nanoneedles. Cyclic voltammetry test indicates that the electrodeposition of iron nanoneedles is a concentration-limited process.

Gan Y. X.; Zhang L.; Gan B.J.

2011-10-01

392

Enzymatic- and temperature-sensitive controlled release of ultrasmall superparamagnetic iron oxides (USPIOs)  

PubMed Central

Background Drug and contrast agent delivery systems that achieve controlled release in the presence of enzymatic activity are becoming increasingly important, as enzymatic activity is a hallmark of a wide array of diseases, including cancer and atherosclerosis. Here, we have synthesized clusters of ultrasmall superparamagnetic iron oxides (USPIOs) that sense enzymatic activity for applications in magnetic resonance imaging (MRI). To achieve this goal, we utilize amphiphilic poly(propylene sulfide)-bl-poly(ethylene glycol) (PPS-b-PEG) copolymers, which are known to have excellent properties for smart delivery of drug and siRNA. Results Monodisperse PPS polymers were synthesized by anionic ring opening polymerization of propylene sulfide, and were sequentially reacted with commercially available heterobifunctional PEG reagents and then ssDNA sequences to fashion biofunctional PPS-bl-PEG copolymers. They were then combined with hydrophobic 12 nm USPIO cores in the thin-film hydration method to produce ssDNA-displaying USPIO micelles. Micelle populations displaying complementary ssDNA sequences were mixed to induce crosslinking of the USPIO micelles. By design, these crosslinking sequences contained an EcoRV cleavage site. Treatment of the clusters with EcoRV results in a loss of R2 negative contrast in the system. Further, the USPIO clusters demonstrate temperature sensitivity as evidenced by their reversible dispersion at ~75°C and re-clustering following return to room temperature. Conclusions This work demonstrates proof of concept of an enzymatically-actuatable and thermoresponsive system for dynamic biosensing applications. The platform exhibits controlled release of nanoparticles leading to changes in magnetic relaxation, enabling detection of enzymatic activity. Further, the presented functionalization scheme extends the scope of potential applications for PPS-b-PEG. Combined with previous findings using this polymer platform that demonstrate controlled drug release in oxidative environments, smart theranostic applications combining drug delivery with imaging of platform localization are within reach. The modular design of these USPIO nanoclusters enables future development of platforms for imaging and drug delivery targeted towards proteolytic activity in tumors and in advanced atherosclerotic plaques. PMID:21352596

2011-01-01

393

Water oxidation catalysis: electrocatalytic response to metal stoichiometry in amorphous metal oxide films containing iron, cobalt, and nickel.  

PubMed

Photochemical metal-organic deposition (PMOD) was used to prepare amorphous metal oxide films containing specific concentrations of iron, cobalt, and nickel to study how metal composition affects heterogeneous electrocatalytic water oxidation. Characterization of the films by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirmed excellent stoichiometric control of each of the 21 complex metal oxide films investigated. In studying the electrochemical oxidation of water catalyzed by the respective films, it was found that small concentrations of iron produced a significant improvement in Tafel slopes and that cobalt or nickel were critical in lowering the voltage at which catalysis commences. The best catalytic parameters of the series were obtained for the film of composition a-Fe20Ni80. An extrapolation of the electrochemical and XPS data indicates the optimal behavior of this binary film to be a manifestation of iron stabilizing nickel in a higher oxidation level. This work represents the first mechanistic study of amorphous phases of binary and ternary metal oxides for use as water oxidation catalysts, and provides the foundation for the broad exploration of other mixed-metal oxide combinations. PMID:23883103

Smith, Rodney D L; Prévot, Mathieu S; Fagan, Randal D; Trudel, Simon; Berlinguette, Curtis P

2013-08-01

394

What's the real role of iron-oxides in the optical properties of dust aerosols?  

NASA Astrophysics Data System (ADS)

Iron oxides compounds constitute an important component of mineral dust aerosol. Several previous studies have shown that these minerals are strong absorbers at visible wavelengths and thus that they play a critical role in the overall climate forcing caused by dust aerosol. When compiling a database of complex refractive indices of possible mineral species of iron-oxides to study their optical properties, we found that uniformly continuous optical constants for a single type of iron-oxides in the wavelength range between 0.2 and 50 ?m is very scarce and that the use of hematite to represent all molecular or mineral iron-oxides types is a popular hypothesis. However, the crucial problem is that three continuous datasets for complex refractive indices of hematite are employed in climate models, but there are significant differences between them. Thus, the real role of iron-oxides in the optical properties of dust aerosols becomes a key scientific question, and we address this problem by considering different refractive indices, size distributions, and more logical weight fractions and mixing states of hematite. Based on the microscopic observations, a semi-external mixture that employs an external mixture between Fe-aggregates and other minerals and partly internal mixing between iron-oxides and aluminosilicate particles is advised as the optimal approximation. The simulations demonstrate that hematite with a spectral refractive indices from Longtin et al. (1988) shows approximately equal absorbing capacity to the mineral illite over the whole wavelength region from 0.55 to 2.5 ?m, and only enhances the optical absorption of aerosol mixture at ? < 0.55 ?m. Using the dataset from Querry (1985) may overestimate the optical absorption of hematite at both visible and near-infrared wavelengths. More laboratory measurements of the refractive index of iron-oxides, especially for hematite and goethite in the visible spectrum, should therefore be taken into account when assessing the effect of mineral dust on climate forcing.

Zhang, X. L.; Wu, G. J.; Zhang, C. L.; Xu, T. L.; Zhou, Q. Q.

2015-02-01

395

Nonequilibrium iron oxide formation in some low-mass post-asymptotic giant branch stars  

NASA Technical Reports Server (NTRS)

Using experimental evidence that under highly oxidizing conditions gamma-Fe2O3 (maghemite) and Fe3O4 display refractory behavior, it is proposed that very low C/O ratios, that could be unique to evolving AGB stars, induce nonequilibrium formation of ferromagnetic iron oxide grains along with chondritic dust. The oxides are preferentially fractionated from chondritic dust in the stellar magnetic field which could account for the observed extreme iron underabundance in their photosphere. A search for the 1-2.5-micron IR absorption feature, or for diagnostic magnetite and maghemite IR absorption features, could show the validity of the model proposed.

Rietmeijer, Frans J. M.

1992-01-01

396

Hydrothermal doping of cobalt and magnetic properties in gamma iron oxide thin films  

Microsoft Academic Search

High coercivity (3.1 kOe) cobalt-doped gamma iron oxide (?-Fe2O3) thin films have been prepared by hydrothermal deposition of Fe3O4 followed by oxidation in air. Films deposited by hydrothermal treatment of a mixed solution of Fe(NO3)3 · 9H2O and CoCl2 · 6H2O in the presence of reduced iron powder at 140 °C for 6 h have the Fe3O4 phase. Controlled oxidation

Qianwang Chen; X. G. Li; Y. T. Qian; Y. H. Zhang

1997-01-01

397

New method of mechanical alloying of ODS steels using iron oxides  

Microsoft Academic Search

Processes of mechanical alloying of oxide-dispersion-strengthened reactor pressure-vessel steels by cold high-pressure torsion\\u000a of a powder mixture of low-stable Fe2O3 (Fe3O4) iron oxides and the bcc matrix alloyed with Y and Ti have been investigated using Mössbauer spectroscopy, X-ray diffraction\\u000a analysis, and electron microscopy. Some features of decomposition of iron oxides and phase transformations in the matrices\\u000a synthesized by mechanical

V. V. Sagaradze; A. V. Litvinov; V. A. Shabashov; N. F. Vil’danova; A. G. Mukoseev; K. A. Kozlov

2006-01-01

398

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

399

In Search of Biomarkers for Iron-Oxidizing Bacteria (FeOB)  

NASA Astrophysics Data System (ADS)

The molecular biology and biochemistry of iron oxidation, particularly among neutrophilic, chemolithoautotrophic iron oxidizing bacteria (FeOB), is poorly understood despite the important ecological and geochemical roles these microorganisms play globally. Mariprofundus ferrooxydans, strain PV-1, is the first FeOB isolate from the marine environment that has been shown to produce the twisted stalks containing Fe oxides that are typically seen in Fe deposits in the ocean floor. As a first step to determine what enzymes are associated with the process of iron oxidation in M. ferrooxydans, extracted proteins were assayed in-gel for redox activity and identified. Preliminary results will be highlighted. These results have implications for future development of diagnostic tools for FeOB presence or activity in habitats such as hydrothermal vents, exposed basaltic rock, and the deep subseafloor biosphere.

Barco, R. A.; Edwards, K. J.

2011-12-01

400

Production of ketones from sewage sludge over zirconia-supporting iron oxide catalysts in a steam atmosphere  

Microsoft Academic Search

Recovering useful hydrocarbons from sewage sludge using zirconia-supporting iron oxide catalysts was investigated. Zirconia has activity for decomposing water molecules to generate active oxygen and hydrogen species. These oxygen species spill over to the surface of iron oxide and react with hydrocarbons to produce oxygen-containing organic chemicals such as acetone. Thus, zirconia-supporting iron oxide catalyst has two kinds of active

Eri Fumoto; Yosuke Mizutani; Teruoki Tago; Takao Masuda

2006-01-01

401

Magnetic properties and structural characterization of iron oxide nanoparticles formed by Streptococcus suis Dpr and four mutants  

Microsoft Academic Search

Streptococcus suis Dpr belongs to the Dps family of bacterial and archaeal proteins that oxidize Fe2+ to Fe3+ to protect microorganisms from oxidative damage. The oxidized iron is subsequently deposited as ferrihydrite inside a protein\\u000a cavity, resulting in the formation of an iron core. The size and the magnetic properties of the iron core have attracted considerable\\u000a attention for nanotechnological

Teemu Haikarainen; Petriina Paturi; Johan Lindén; Sauli Haataja; Wolfram Meyer-Klaucke; Jukka Finne; Anastassios C. Papageorgiou

2011-01-01

402

Iron  

MedlinePLUS

Iron is a mineral that our bodies need for many functions. For example, iron is part of hemoglobin, a protein which carries ... It helps our muscles store and use oxygen. Iron is also part of many other proteins and ...

403

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

404

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

405

Diet, iron biomarkers and oxidative stress in a representative sample of Mediterranean population  

PubMed Central

Background The consumption pattern characterized by high consumption of vegetables, fruit, fish, olive oil and red wine has been associated with improvements in the total antioxidant capacity of individuals and reduced incidence of diseases related to oxidation. Also, high body iron levels may contribute to increase the oxidative stress by the generation of reactive oxygen species. The objective of this study is to analyze the relationship between antioxidant and pro-oxidant factors obtained from the diet and iron biomarkers on lipoprotein oxidation and total antioxidant capacity in a representative sample of the Mediterranean population. Methods Cross-sectional prospective study, carried out with 815 randomly selected subjects (425 women and 390 men). Dietary assessment (3-day food records), iron biomarkers (serum ferritin, serum iron and transferrin saturation), biochemical markers of lipoperoxidation (TBARS), antioxidant capacity (ORAC) and CRP (C-Reactive Protein) were determined. Multiple Linear Regression (MLR) models were applied to analyze the association between diet factors and iron biomarkers on TBARS and ORAC levels. Results We observed that lipoperoxidation measured by TBARS increased by age but no differences were observed by sex. Antioxidant capacity measured by ORAC is independent of age and sex. In general, increasing age, tobacco, heme iron intake from meat and fish and transferrin saturation were independently and positively associated with TBARS, while non-heme iron was negatively associated. Vegetables, vitamin C intake and serum ferritin were positively associated with ORAC, whereas saturated fatty acids and meat intake were negatively associated. Conclusions In our general population, we observed that oxidative stress is related to aging, but antioxidant capacity is not. The highest intake of dietary non-heme iron, vegetables and vitamin C intake exerts a protective effect against oxidation while the highest intake of dietary heme iron from meat and fish and saturated fatty acids are associated with increased oxidative stress. High levels of circulating iron measured by transferrin saturation are associated with increased oxidative stress in women however its association with the higher levels of serum ferritin is controversial. PMID:23866833

2013-01-01

406

Fur controls iron homeostasis and oxidative stress defense in the oligotrophic alpha-proteobacterium Caulobacter crescentus  

PubMed Central

In most bacteria, the ferric uptake regulator (Fur) is a global regulator that controls iron homeostasis and other cellular processes, such as oxidative stress defense. In this work, we apply a combination of bioinformatics, in vitro and in vivo assays to identify the Caulobacter crescentus Fur regulon. A C. crescentus fur deletion mutant showed a slow growth phenotype, and was hypersensitive to H2O2 and organic peroxide. Using a position weight matrix approach, several predicted Fur-binding sites were detected in the genome of C. crescentus, located in regulatory regions of genes not only involved in iron uptake and usage but also in other functions. Selected Fur-binding sites were validated using electrophoretic mobility shift assay and DNAse I footprinting analysis. Gene expression assays revealed that genes involved in iron uptake were repressed by iron-Fur and induced under conditions of iron limitation, whereas genes encoding iron-using proteins were activated by Fur under conditions of iron sufficiency. Furthermore, several genes that are regulated via small RNAs in other bacteria were found to be directly regulated by Fur in C. crescentus. In conclusion, Fur functions as an activator and as a repressor, integrating iron metabolism and oxidative stress response in C. crescentus. PMID:19520766

da Silva Neto, José F.; Braz, Vânia S.; Italiani, Valéria C. S.; Marques, Marilis V.

2009-01-01

407

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

408

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

409

Diversity of Ferrous Iron-Oxidizing, Nitrate-Reducing Bacteria and their Involvement in Oxygen-Independent Iron Cycling  

Microsoft Academic Search

In previous studies, three different strains (BrG1, BrG2, and BrG3) of ferrous iron-oxidizing, nitrate-reducing bacteria were obtained from freshwater sediments. All three strains were facultative anaerobes and utilized a variety of organic substrates and molecular hydrogen with nitrate as electron acceptor. In this study, analyses of 16S rDNA sequences showed that strain BrG1 was affiliated with the genus Acidovorax, strain

Kristina L. Straub; Wilhelm A. Schönhuber; Berit E. E. Buchholz-Cleven; Bernhard Schink

2004-01-01

410

Ceruloplasmin oxidation, a feature of Parkinson's disease CSF, inhibits ferroxidase activity and promotes cellular iron retention.  

PubMed

Parkinson's disease is a neurodegenerative disorder characterized by oxidative stress and CNS iron deposition. Ceruloplasmin is an extracellular ferroxidase that regulates cellular iron loading and export, and hence protects tissues from oxidative damage. Using two-dimensional electrophoresis, we investigated ceruloplasmin patterns in the CSF of human Parkinson's disease patients. Parkinson's disease ceruloplasmin profiles proved more acidic than those found in healthy controls and in other human neurological diseases (peripheral neuropathies, amyotrophic lateral sclerosis, and Alzheimer's disease); degrees of acidity correlated with patients' pathological grading. Applying an unsupervised pattern recognition procedure to the two-dimensional electrophoresis images, we identified representative pathological clusters. In vitro oxidation of CSF in two-dimensional electrophoresis generated a ceruloplasmin shift resembling that observed in Parkinson's disease and co-occurred with an increase in protein carbonylation. Likewise, increased protein carbonylation was observed in Parkinson's disease CSF, and the same modification was directly identified in these samples on ceruloplasmin. These results indicate that ceruloplasmin oxidation contributes to pattern modification in Parkinson's disease. From the functional point of view, ceruloplasmin oxidation caused a decrease in ferroxidase activity, which in turn promotes intracellular iron retention in neuronal cell lines as well as in primary neurons, which are more sensitive to iron accumulation. Accordingly, the presence of oxidized ceruloplasmin in Parkinson's disease CSF might be used as a marker for oxidative damage and might provide new insights into the underlying pathological mechanisms. PMID:22171055

Olivieri, Stefano; Conti, Antonio; Iannaccone, Sandro; Cannistraci, Carlo V; Campanella, Alessandro; Barbariga, Marco; Codazzi, Franca; Pelizzoni, Ilaria; Magnani, Giuseppe; Pesca, Mariasabina; Franciotta, Diego; Cappa, Stefano F; Alessio, Massimo

2011-12-14

411

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

412

Occurrence and activity of iron- and sulfur-oxidizing microorganisms in alkaline coal strip mine spoils  

Microsoft Academic Search

Spoils samples collected from a coal strip mine in southeastern Montana were examined for populations and activities of iron- and sulfur-oxidizing bacteria. Spoils examined were of three types: (a) acidic pyrite-rich waste coal, (b) oxidation halo material, and (c) alkaline material, which was the most widespread type. Bacterial numbers, sulfur oxidation, and14CO2 uptake activity declined to low levels in the

G. J. Olson; G. A. McFeters; K. L. Temple

1981-01-01

413

Efficient water oxidation catalysts based on readily available iron coordination complexes  

Microsoft Academic Search

Water oxidation catalysis constitutes the bottleneck for the development of energy-conversion schemes based on sunlight. To date, state-of-the-art homogeneous water oxidation catalysis is performed efficiently with expensive, toxic and earth-scarce transition metals, but 3d metal-based catalysts are much less established. Here we show that readily available, environmentally benign iron coordination complexes catalyse homogeneous water oxidation to give O2, with high

Julio Lloret Fillol; Zoel Codolà; Isaac Garcia-Bosch; Laura Gómez; Juan José Pla; Miquel Costas

2011-01-01

414

Risk of Oxidative Damage to Bone from Increased Iron Stores During Space Flight  

NASA Technical Reports Server (NTRS)

Iron stores are increased secondary to neocytolysis of red blood cells and a high dietary intake of iron during space flight. This raises concerns about the risk of excess iron causing oxidative damage in many tissues, including bone. Biomarkers of iron status, oxidative damage, and bone resorption during space flight were analyzed for 23 (16 M/7 F) International Space Station crewmembers as part of the Nutrition SMO project. Up to 5 in-flight blood samples and 24-h urine pools were collected over the course of the 4-6 month missions. Serum iron increased slightly during space flight and was decreased at landing (P < 0.0004). An increase in serum ferritin early in flight (217% in women and 68% in men, P < 0.0004), returning to preflight concentrations at landing, and a decrease in transferrin and transferrin receptors during flight indicated that a transient increase in iron stores occurred. No inflammatory response was observed during flight. The oxidative damage markers 8-hydroxy-2'-deoxyguanosine and prostaglandin F(sub 2(alpha)) were positively correlated (both P < 0.001) with serum ferritin. A greater area under the curve for ferritin during flight was correlated with greater changes in bone mineral density of several bone regions after flight (1). In a separate study (2), a ground-based investigation was conducted that examined the combined effects of radiation exposure and iron overload on sensitivity to radiation injury in several physiological systems in 12-wk male Sprague-Dawley rats. The rats were acclimated to an adequate iron diet (45 mg iron (ferric citrate)/kg diet) for 3 wk and then assigned to one of four groups: adequate iron (Fe) diet/no radiation, adequate Fe diet/ radiation, moderately high Fe diet (650 mg Fe (ferric citrate)/kg diet)/no radiation, and moderately high Fe diet/radiation. Animals remained on the assigned diet for 4 wk. Starting on day 14 of experimental diet treatment, animals were exposed to a fractionated dose (0.375 Gy) of Cs-137 every other day (3 Gy total dose). On day 29 (24 h after last radiation exposure), animals were euthanized. Oxidative stress markers in the liver, bone, eyes, and serum were assessed. There was evidence that the iron diet contributed to DNA damage as well as radiation exposure in the liver, eyes, and bone. Together, the results suggest that increased iron stores do constitute a risk factor for oxidative damage and bone resorption, during space flight and on Earth. Funded by the Human Health and Countermeasures Element of the NASA Human Research Program.

Zwart, S. R.; Smith, S. M.

2014-01-01

415

Synthesis and characterization of magnetic iron oxide for nanomaterial and nanosystem fabrication  

NASA Astrophysics Data System (ADS)

Nanostructured magnetic iron oxide exhibits interesting physical properties and has many applications. Properties of the iron oxide nanomaterial such as size, shape, morphology, and crystal phase need to be controlled by appropriate choice of a synthesis method. This research deals with the understanding of the aerosol route synthesis, structural and magnetic characterization, and surface functionalization of iron oxide for different applications. The iron oxide systems presented in this work include gamma-Fe2O 3, Fe3O4 , CuFe2O4, and silica coated gamma-Fe2O3 and Fe nanoparticles. Detailed mechanistic steps for synthesis of different crystal phases of iron oxide nanoparticles along with particle-particle interactions are considered to establish the final aerosol size distribution, shape, and properties of the end product. The transport characteristics and magnetic coagulation of ferrofluids in presence of external magnetic fields are studied using a light scattering technique. The results are used to explain the hindered transport of a ferrofluid in an in vitro human brain model for targeted drug delivery.

Basak, Soubir

416

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

417

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

418

Immobilisation of arsenic by iron(II)-oxidizing bacteria  

Microsoft Academic Search

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

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

2008-01-01

419

Solubilization of plutonium hydrous oxide by iron-reducing bacteria  

Microsoft Academic Search

The removal of plutonium from soils id challenging because of its strong sorption to soils and limited solubility, Microbial reduction of metals is known to affect the speciation and solubility of sparingly soluble metals in the environment, notably iron and manganese. The similarity in reduction potential for [alpha]-FeOOH(s) and hydrous PuO[sub 2](s) suggests that iron-reducing bacteria may also reduce and

Patricia A. Rusin; Leticia Quintana; James R. Brainard; B. A. Strietelmeler; C. Drew Tait; Scott A. Ekberg; Phillip D. Palmer; Thomas W. Newton; David L. Clark

1994-01-01

420

Hydrate detection  

SciTech Connect

Project objectives were: (1) to create methods of analyzing gas hydrates in natural sea-floor sediments, using available data, (2) to make estimates of the amount of gas hydrates in marine sediments, (3) to map the distribution of hydrates, (4) to relate concentrations of gas hydrates to natural processes and infer the factors that control hydrate concentration or that result in loss of hydrate from the sea floor. (VC)

Dillon, W.P.; Ahlbrandt, T.S.

1992-06-01

421

Hydrate detection  

SciTech Connect

Project objectives were: (1) to create methods of analyzing gas hydrates in natural sea-floor sediments, using available data, (2) to make estimates of the amount of gas hydrates in marine sediments, (3) to map the distribution of hydrates, (4) to relate concentrations of gas hydrates to natural processes and infer the factors that control hydrate concentration or that result in loss of hydrate from the sea floor. (VC)

Dillon, W.P.; Ahlbrandt, T.S.

1992-01-01

422

Anaerobic oxidation of ferrous iron by purple bacteria, a new type of phototrophic metabolism.  

PubMed Central

Anoxic iron-rich sediment samples that had been stored in the light showed development of brown, rusty patches. Subcultures in defined mineral media with ferrous iron (10 mmol/liter, mostly precipitated as FeCO3) yielded enrichments of anoxygenic phototrophic bacteria which used ferrous iron as the sole electron donor for photosynthesis. Two different types of purple bacteria, represented by strains L7 and SW2, were isolated which oxidized colorless ferrous iron under anoxic conditions in the light to brown ferric iron. Strain L7 had rod-shaped, nonmotile cells (1.3 by 2 to 3 microns) which frequently formed gas vesicles. In addition to ferrous iron, strain L7 used H2 + CO2, acetate, pyruvate, and glucose as substrate for phototrophic growth. Strain SW2 had small rod-shaped, nonmotile cells (0.5 by 1 to 1.5 microns). Besides ferrous iron, strain SW2 utilized H2 + CO2, monocarboxylic acids, glucose, and fructose. Neither strain utilized free sulfide; however, both strains grew on black ferrous sulfide (FeS) which was converted to ferric iron and sulfate. Strains L7 and SW2 grown photoheterotrophically without ferrous iron were purple to brownish red and yellowish brown, respectively; absorption spectra revealed peaks characteristic of bacteriochlorophyll a. The closest phototrophic relatives of strains L7 and SW2 so far examined on the basis of 16S rRNA sequences were species of the genera Chromatium (gamma subclass of proteobacteria) and Rhodobacter (alpha subclass), respectively. In mineral medium, the new isolates formed 7.6 g of cell dry mass per mol of Fe(II) oxidized, which is in good agreement with a photoautotrophic utilization of ferrous iron as electron donor for CO2 fixation. Dependence of ferrous iron oxidation on light and CO2 was also demonstrated in dense cell suspensions. In media containing both ferrous iron and an organic substrate (e.g., acetate, glucose), strain L7 utilized ferrous iron and the organic compound simultaneously; in contrast, strain SW2 started to oxidize ferrous iron only after consumption of the organic electron donor. Ferrous iron oxidation by anoxygenic phototrophs is understandable in terms of energetics. In contrast to the Fe3+/Fe2+ pair (E0 = +0.77 V) existing in acidic solutions, the relevant redox pair at pH 7 in bicarbonate-containing environments, Fe(OH)3 + HCO3-/FeCO3, has an E0' of +0.2 V. Ferrous iron at pH 7 can therefore donate electrons to the photosystem of anoxygenic phototrophs, which in purple bacteria has a midpoint potential around +0.45 V. The existence of ferrous iron-oxidizing anoxygenic phototrophs may offer an explanation for the deposition of early banded-iron formations in an assumed anoxic biosphere in Archean times. Images PMID:7811087

Ehrenreich, A; Widdel, F

1994-01-01

423

Tuning reactivity and mechanism in oxidation reactions by mononuclear nonheme iron(IV)-oxo complexes.  

PubMed

Mononuclear nonheme iron enzymes generate high-valent iron(IV)-oxo intermediates that effect metabolically important oxidative transformations in the catalytic cycle of dioxygen activation. In 2003, researchers first spectroscopically characterized a mononuclear nonheme iron(IV)-oxo intermediate in the reaction of taurine: ?-ketogultarate dioxygenase (TauD). This nonheme iron enzyme with an iron active center was coordinated to a 2-His-1- carboxylate facial triad motif. In the same year, researchers obtained the first crystal structure of a mononuclear nonheme iron(IV)-oxo complex bearing a macrocyclic supporting ligand, [(TMC)Fe(IV)(O)](2+) (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecene), in studies that mimicked the biological enzymes. With these breakthrough results, many other studies have examined mononuclear nonheme iron(IV)-oxo intermediates trapped in enzymatic reactions or synthesized in biomimetic reactions. Over the past decade, researchers in the fields of biological, bioinorganic, and oxidation chemistry have extensively investigated the structure, spectroscopy, and reactivity of nonheme iron(IV)-oxo species, leading to a wealth of information from these enzymatic and biomimetic studies. This Account summarizes the reactivity and mechanisms of synthetic mononuclear nonheme iron(IV)-oxo complexes in oxidation reactions and examines factors that modulate their reactivities and change their reaction mechanisms. We focus on several reactions including the oxidation of organic and inorganic compounds, electron transfer, and oxygen atom exchange with water by synthetic mononuclear nonheme iron(IV)-oxo complexes. In addition, we recently observed that the C-H bond activation by nonheme iron(IV)-oxo and other nonheme metal(IV)-oxo complexes does not follow the H-atom abstraction/oxygen-rebound mechanism, which has been well-established in heme systems. The structural and electronic effects of supporting ligands on the oxidizing power of iron(IV)-oxo complexes are significant in these reactions. However, the difference in spin states between nonheme iron(IV)-oxo complexes with an octahedral geometry (with an S = 1 intermediate-spin state) or a trigonal bipyramidal (TBP) geometry (with an S = 2 high-spin state) does not lead to a significant change in reactivity in biomimetic systems. Thus, the importance of the high-spin state of iron(IV)-oxo species in nonheme iron enzymes remains unexplained. We also discuss how the axial and equatorial ligands and binding of redox-inactive metal ions and protons to the iron-oxo moiety influence the reactivities of the nonheme iron(IV)-oxo complexes. We emphasize how these changes can enhance the oxidizing power of nonheme metal(IV)-oxo complexes in oxygen atom transfer and electron-transfer reactions remarkably. This Account demonstrates great advancements in the understanding of the chemistry of mononuclear nonheme iron(IV)-oxo intermediates within the last 10 years. PMID:24524675

Nam, Wonwoo; Lee, Yong-Min; Fukuzumi, Shunichi

2014-04-15

424

Photo-Fenton oxidation of azo dye Reactive Black B using an immobilized iron oxide as heterogeneous catalyst.  

PubMed

The heterogeneous oxidation of azo dye Reactive Black B (RBB) by the photo-Fenton system catalyzed with an immobilized iron oxide, B1 (supported with SiO2 grain), was investigated. Reactive Black B oxidation was carried out in an expended-bed reactor in which the effect of B1 dosage on the decolorization and degradation of RBB was examined. Through pseudo-first-order kinetic studies, decolorization was found to be faster than degradation with a fixed rate constant ratio. By determining the iron dissolution from B1, RBB oxidation was supposed to mainly occur on the B1 surface, which catalyzed the generation of hydroxyl radicals in the photo-Fenton reaction. Accordingly, the efficiency of photo-Fenton could reach 100% and 91.2% of decolorization and degradation, respectively, in 300 minutes. PMID:23697238

Shih, Yu-Jen; Ho, Chien-Hung; Huang, Yao-Hui

2013-04-01