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1

Reduction of aromatic nitrocompounds with hydrazine hydrate in the presence of an iron oxide hydroxide catalyst  

Microsoft Academic Search

The catalytic activities of several iron oxides and oxide hydroxides have been tested in the reduction of substituted nitroarenes using hydrazine hydrate as reducing agent. An iron oxide catalyst, prepared by rapid precipitation of iron hydroxides from solutions of iron(III)chloride, showed the highest activity mainly due to its large BET surface area compared to other iron oxides. Mössbauer spectroscopy and

M Benz; A. M van der Kraan; R Prins

1998-01-01

2

Hydrated Iron Sulfate Minerals by FT-IR, ESEM and XRD: Effects of Hydration, Metal Ions, and Oxidative State  

Microsoft Academic Search

Data from the Mars Exploration Rovers (MER) and orbital remote sensing have determined that iron-bearing sulfates and iron-sulfates account for much of the mineralogical variation on Martian chemical sediments. We have begun a comprehensive study to evaluate a suite of hydrated iron sulfate minerals at different levels of oxidation or mineral phases using micro-FT-IR, ESEM and XRD. Selected minerals include

R. Mielke; D. Blaney; K. Nordstrom; C. Aplers; M. Coleman

2007-01-01

3

Thermodynamics of dimethylarsinic acid and arsenate interactions with hydrated iron-(oxyhydr)oxide clusters: DFT calculations.  

PubMed

Dimethylarsinic Acid (DMA) belongs to an important class of organoarsenical compounds commonly detected in arsenic speciation studies of environmental samples and pyrolysis products of fossil fuels. Transformation of DMA under certain conditions leads to the formation of other forms of arsenic, which could be more toxic than DMA to biota, and more efficient in deactivating catalysts used in petrochemical refining. Published surface sensitive X-ray and infrared spectroscopic work suggested that DMA simultaneously forms inner- and outer-sphere complexes with iron-(oxyhydr)oxides. Computational work on the complexation of arsenicals with various surfaces of environmental and industrial interest provides useful information that aids in the interpretation of experimental spectroscopic data as well as predictions of thermodynamic favorability of surface interactions. We report herein Gibbs free energies of adsorption, ?G(ads), for various ligand exchange reactions between hydrated complexes of DMA and Fe-(oxyhydr)oxide clusters calculated using density functional theory (DFT) at the B3LYP/6-311+G(d,p) level. Calculations using arsenate were also performed for comparison. Calculated As-(O,Fe) distances and stretching frequencies of As-O bonds are also reported for comparison with experimental spectroscopic data. Gibbs free energies of desorption, ?G(des), due to reactions with phosphorus species at pH 7 are reported as well. Our results indicate that the formation of both inner- and outer-sphere DMA complexes is thermodynamically favorable, with the former having a more negative ?G(ads). Values of ?G(des) indicate that desorption favorability of DMA complexes increases in this order: bidentate < mondentate < outersphere. The significance of our results for the overall surface complexation mechanism of DMA is discussed. PMID:22029696

Adamescu, Adrian; Hamilton, I P; Al-Abadleh, Hind A

2011-11-14

4

Plasma-chemical synthesis of ultradispersed iron oxides with pigment qualification  

Microsoft Academic Search

The conditions are investigated for preparing ultradispersed iron oxides with pigment qualification (iron oxide pigments) via oxidation in electric arc low temperature plasma (LTP) of: iron dichloride (crystal hydrate), iron sulfate (monohydrate), roughly dispersed iron and burnt pyrites. Using a simplified one-dimensional model, calculations are made describing the motion, heating, melting and evaporation of iron particles of <50 µm size;

G. P. Vissokov; P. S. Pirgov

1996-01-01

5

Iron oxide modified minerals  

Microsoft Academic Search

Composites of iron oxide nanoparticles immobilized on the surface of various clay mineral matrices (muscovite, montmorillonite\\u000a and vermiculite) have been prepared by the alkaline oxidative hydrolysis of iron sulphate in the presence of mineral matrices.\\u000a The composites have been studied by Mössbauer spectroscopy, XRD, TEM and SQUID. Correspondence between the hyperfine parameters\\u000a and the iron oxide particle size and magnetic

M. Mashlan; H. Bartonkova; D. Jancik; J. Tucek; P. Martinec

6

Iron oxide modified minerals  

Microsoft Academic Search

Composites of iron oxide nanoparticles immobilized on the surface of various clay mineral matrices (muscovite, montmorillonite\\u000a and vermiculite) have been prepared by the alkaline oxidative hydrolysis of iron sulphate in the presence of mineral matrices.\\u000a The composites have been studied by Mössbauer spectroscopy, XRD, TEM and SQUID. Correspondence between the hyperfine parameters\\u000a and the iron oxide particle size and magnetic

M. Mashlan; H. Bartonkova; D. Jancik; J. Tucek; P. Martinec

2009-01-01

7

Enzymes of respiratory iron oxidation  

Microsoft Academic Search

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

Blake; R. II

1991-01-01

8

Enzymes of respiratory iron oxidation  

SciTech Connect

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

Blake, R. II.

1991-01-01

9

Hydration of Passive Oxide Films on Aluminum  

SciTech Connect

Models for the corrosion and pitting of passive metals such as aluminum usually involve the migration of point defects through the native oxide film as the rate limiting step. Hydration of the surface oxide could also influence the protective nature of the film. Secondary ion mass spectrometry (SIMS) has been used in conjunction with isotopic labeling to determine the extent and rate of passive film hydration on aluminum. The rates at which oxygen- and hydrogen-contianing species migrate through the film has been determined as a function of temperature and applied potential (cathodic and anodic polarization). The results suggest that defects such as hyroxide ions are prevalent and mobile in the oxide film, influencing the kinetics and mechanisms of corrosion processes.

Bunker, Bruce C.; Nelson, Gerald C.; Zavadil, K.; Barbour, J. C.; Wall, F. D.; Sullivan, J. P.; Windisch, Charles F.; Engelhard, Mark H.; Baer, Donald R.

2002-05-09

10

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

11

Enzymes of respiratory iron oxidation  

SciTech Connect

This report describes experimental progress in characterizing and identifying redox proteins in a number of iron-oxidizing bacteria. Sections of the paper are entitled (1) In Situ electrolysis was explored to achieve enhanced yields of iron-oxidizing bacteria, (2)Structure/function studies were performed on redox-active biomolecules from Thiobacillus ferrooxidans, (3) Novel redox-active biomolecules were demonstrated in other iron autotrophs, and (4) New probes of metalloprotein electron-transfer reactions were synthesized and characterized.

Blake, R. II.

1992-01-01

12

Enzymes of respiratory iron oxidation  

Microsoft Academic Search

This report describes experimental progress in characterizing and identifying redox proteins in a number of iron-oxidizing bacteria. Sections of the paper are entitled (1) In Situ electrolysis was explored to achieve enhanced yields of iron-oxidizing bacteria, (2)Structure\\/function studies were performed on redox-active biomolecules from Thiobacillus ferrooxidans, (3) Novel redox-active biomolecules were demonstrated in other iron autotrophs, and (4) New probes

Blake; R. II

1992-01-01

13

Iron Oxide Based High Temperature Desulfurization Sorbent  

Microsoft Academic Search

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

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

2009-01-01

14

Electrochemical behavior of hydrated molybdenum oxides in rechargeable lithium batteries  

Microsoft Academic Search

Oxide-hydrates of molybdenum (OHM) are investigated as 3-volt cathode materials for rechargeable lithium batteries. These\\u000a materials with different water content showed a much better performance than that of MoO3 as cathode of the rechargeable lithium battery. We report the electrochemical characteristics of Li\\/\\/OHM batteries using\\u000a the oxides and oxide-hydrates of molybdenum which were synthesized from molybdic acid. The oxide has

B. Yebka; C. Julien; G. A. Nazri

1999-01-01

15

Anaerobic oxidation of methane above gas hydrates at Hydrate Ridge, NE Pacific Ocean  

Microsoft Academic Search

At Hydrate Ridge (HR), Cascadia convergent margin, surface sediments contain mas- sive gas hydrates formed from methane that ascends together with fluids along faults from deeper reservoirs. Anaerobic oxidation of methane (AOM), mediated by a microbial consortium of archaea and sulfate-reducing bacteria, generates high concentrations of hydrogen sulfide in the surface sediments. The production of sulfide supports chemosynthetic communities that

Tina Treude; Antje Boetius; Katrin Knittel; Klaus Wallmann; Bo Barker Jørgensen

2003-01-01

16

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

17

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

18

Toluene and naphthalene sorption by iron oxide\\/clay composites  

Microsoft Academic Search

This study investigates the sorption of toluene and naphthalene by a sodium bentonite (BFN), an organoclay (WS35) and by their\\u000a respective iron oxide hydrate composites Mag_BFN and Mag_S35. The organic matter content of WS35 and Mag_S35, determined by\\u000a thermogravimetry, was used to obtain their organic matter sorption coefficients, which show that they are effective sorbents\\u000a to remove organic contaminants from

Marilda M. G. R. Vianna; Jo Dweck; Frank H. Quina; Flavio M. S. Carvalho; Claudio A. O. Nascimento

2010-01-01

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

Thermodynamic constraints on microbial iron oxide reduction  

Microsoft Academic Search

Iron oxides are ubiquitous reactive constituents of soils, sediments and aquifers. They exhibit large surface areas which bind trace metals, nutrients and organic molecules. Under suboxic conditions, iron oxides can reductively dissolve via several abiotic and microbial pathways. In particular, they serve as terminal electron acceptors for the oxidation of organic matter by iron reducing bacteria. The aim of our

S. Bonneville; T. Behrends; R. Haese; P. van Cappellen

2003-01-01

21

Iron or iron oxide grains in the interstellar medium?  

NASA Astrophysics Data System (ADS)

Iron grains have often been proposed as a component of circumstellar and interstellar grains. It is apparent that 'cosmic abundance' circumstellar shells should condense iron-rich particles such as metallic iron, iron/nickel alloys and iron carbides. It is not, however, clear that these grains can survive in this state in the interstellar medium. In this paper the chemistry of iron particles in the diffuse interstellar medium is examined and it is concluded that these grains cannot survive as pristine metallic iron-rich entities. The reactivity of iron, and in particular its reaction with interstellar gas-phase oxygen and sulphur species, will result in the rapid degradation of the metal to an oxide, sulphide or even sulphate. The lack of metallic phases in the mineralogy of primitive interplanetary dust particles is consistent with the absence of metallic particles in the interstellar medium.

Jones, A. P.

1990-07-01

22

Kinetics and mechanism of the catalytic hydration of propylene oxide  

Microsoft Academic Search

The kinetics of propylene oxide hydration in the presence of bis(ethane-1,2-diol)molybdate is reported. A mathematical description\\u000a of PO disappearance and propylene glycol formation is suggested. The most probable scheme for the process is presented. The\\u000a basic kinetic constants are calculated.

R. Z. Shaikhutdinov; L. A. Petukhov; N. V. Sapunov; Kh. E. Kharlampidi; A. A. Petukhov

2010-01-01

23

Exploring Microbial Iron Oxidation in Wetland Soils  

Microsoft Academic Search

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

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

2009-01-01

24

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

25

Iron-mediated oxidative stress in erythrocytes.  

PubMed Central

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

Rice-Evans, C; Baysal, E

1987-01-01

26

Nanosized Iron Oxide Colloids Strongly Enhance Microbial Iron Reduction? †  

PubMed Central

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

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

2010-01-01

27

Platinum Attachments on Iron Oxide Nanoparticle Surfaces  

SciTech Connect

Platinum nanoparticles supported on metal oxide surfaces have shown great potential as heterogeneous catalysts to accelerate electrochemical processes, such as the oxygen reduction reaction in fuel cells. Recently, the use of magnetic supports has become a promising research topic for easy separation and recovery of catalysts using magnets, such as Pt nanoparticles supported on iron oxide nanoparticles. The attachment of Pt on iron oxide nanoparticles is limited by the wetting ability of the Pt (metal) on ceramic surfaces. A study of Pt nanoparticle attachment on iron oxide nanoparticle surfaces in an organic solvent is reported, which addresses the factors that promote or inhibit such attachment. It was discovered that the Pt attachment strongly depends on the capping molecules of the iron oxide seeds and the reaction temperature. For example, the attachment of Pt nanoparticles on oleic acid coated iron oxide nanoparticles was very challenging, because of the strong binding between the carboxylic groups and iron oxide surfaces. In contrast, when nanoparticles are coated with oleic acid/tri-n-octylphosphine oxide or oleic acid/oleylamine, a significant increase in Pt attachment was observed. Electronic structure calculations were then applied to estimate the binding energies between the capping molecules and iron ions, and the modeling results strongly support the experimental observations.

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

2010-04-30

28

Vapor-phase hydration of propylene oxide over tricalcium phosphate  

Microsoft Academic Search

1.The catalytic activity of tricalcium phosphate in the vapor-phase hydration of propylene oxide to propylene glycol was studied.2.Calcium phosphate is a stable and selective catalyst for this reaction.3.The effect of temperature, contact time, and water excess on the glycol yield was studied. Considerable amounts of glycol were formed under the optimal conditions and the glycol yield reached 50–57% at 232°,

L. Kh. Freidlin; V. Z. Sharf

1960-01-01

29

Extracellular Iron Biomineralization by Photoautotrophic Iron-Oxidizing Bacteria ? †  

PubMed Central

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

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

2009-01-01

30

Microorganisms pumping iron: anaerobic microbial iron oxidation and reduction  

Microsoft Academic Search

Iron (Fe) has long been a recognized physiological requirement for life, yet for many microorganisms that persist in water, soils and sediments, its role extends well beyond that of a nutritional necessity. Fe(II) can function as an electron source for iron-oxidizing microorganisms under both oxic and anoxic conditions and Fe(III) can function as a terminal electron acceptor under anoxic conditions

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

2006-01-01

31

Synthesis and magnetic properties of iron-iron oxide nanoparticles  

Microsoft Academic Search

Monodisperse magnetic nanoparticles are of much interest for data storage and biomedical applications as well as for studies of the fundamental characteristics of magnetism on small length scales. In light of this attention, we have been investigating the properties of iron-iron oxide nanoparticles, prepared by modifying a recently developed solvent-based synthesis method that produces particles of well-defined size [1]. By

Anna Clausen; Yumi Ijiri

2004-01-01

32

Influence of Iron Reducing Bacteria on Phosphate and Arsenate Release and Sequestration Onto Iron Oxides  

Microsoft Academic Search

This study investigates the potential for iron oxides to capture phosphate and arsenate. While iron oxides clearly bind phosphate and arsenate, one should not assume that iron oxides would straightforwardly trap these contaminants. Instead, iron oxides in shallow groundwater sediments undergo chemical transformations that could lead to the release of sorbed contaminants. Most notably, scientists commonly observe that the biologically

L. H. MacDonald; L. R. Durrant; P. R. Jaffe

2008-01-01

33

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

34

Wet Chemistry of Spinel Iron oxide Particles  

Microsoft Academic Search

Various properties of spinel iron oxide nanograins are reviewed, illustrating the broad possibilities of wet chemistry for tailoring materials for a wide range of utilizations, fmm catalysis and sensors to cast magnetic materials.

J. P. Jolivet; C. Chan; P. Pren; E. Tronc

35

Magnetic properties of monodisperse iron oxide nanoparticles  

Microsoft Academic Search

We have synthesized a set of monodisperse iron oxide nanoparticles ranging from 7.8 to 17.9 nm by thermal decomposition methods. Based on the evidence of high-resolution transmission electron microscopy, the iron oxide nanoparticles appear as spherical dots with size standard deviations of less than 5%. Blocking temperatures of the set of nanoparticles were measured by the zero-field-cooled magnetization measurements. The

Chun-Rong Lin; Ray-Kuang Chiang; Jiun-Shen Wang; Ti-Wen Sung

2006-01-01

36

Selective catalytic hydration of ethylene oxide over niobium oxide supported on ?-alumina  

Microsoft Academic Search

Niobium oxide (Nb2O5) supported on ?-alumina (?-Al2O3) prepared by impregnation was studied for hydration of ethylene oxide. The effects of niobium oxide loadings, calcination temperature and molar ratio of water to ethylene oxide (EO) on the reaction performance were investigated. The structure and acidity of the catalysts were characterized by using X-ray diffraction (XRD), differential thermal analysis (DTA)-thermogravimetric (TG) and

Yingcheng Li; Shirun Yan; Bin Yue; Weimin Yang; Zaiku Xie; Qingling Chen; Heyong He

2004-01-01

37

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

Microsoft Academic Search

To shed light on the mechanism of superconductivity in sodium cobalt oxide bilayer-hydrate (BLH), we perform a density functional calculation with full structure optimization for BLH and its related nonsuperconducting phase, monolayer hydrate (MLH). We find that these hydrates have similar band structures, but a notable difference can be seen in the a1g band around the Fermi level. While its

Ryotaro Arita

2005-01-01

38

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

39

Electrodeposited amorphous iron(III) oxides as anodes for photoelectrolysis of water  

Microsoft Academic Search

Deposition of amorphous iron(III)-oxide films on a conducting glass substrate was achieved via a cathodic bias in a 0.1M hydrated ammonium iron(II) sulfate ((NH4)2Fe(SO4)2·6H2O) solution at ?1.6V versus Ag\\/AgCl. Analysis by X-ray absorption near edge structure confirmed the iron(III) feature of the amorphous films. The deposited films exhibited n-type semiconducting characteristics by showing photoresponses under an anodic bias. The Mott–Schottky

Pei-Shan Li; Hsisheng Teng

2007-01-01

40

Microorganisms pumping iron: anaerobic microbial iron oxidation and reduction.  

PubMed

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

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

2006-10-01

41

Platinum attachments on iron oxide nanoparticle surfaces  

Microsoft Academic Search

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

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

2010-01-01

42

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

43

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

44

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

SciTech Connect

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

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

1998-11-11

45

Thermodynamic constraints on microbial iron oxide reduction  

NASA Astrophysics Data System (ADS)

Iron oxides are ubiquitous reactive constituents of soils, sediments and aquifers. They exhibit large surface areas which bind trace metals, nutrients and organic molecules. Under suboxic conditions, iron oxides can reductively dissolve via several abiotic and microbial pathways. In particular, they serve as terminal electron acceptors for the oxidation of organic matter by iron reducing bacteria. The aim of our study was to determine the thermodynamic energy yields of dissimilatory iron reduction for different Fe(III) substrates. We used the facultative anaerobic gram-positive bacterium Shewanella putrefaciens as model iron reducing bacterium, with ferrihydrite, hematite, goethite or Fe(III)-salicylate as electron acceptor, and lactate as electron donor. Experiments were conducted in an anaerobic pH-stat batch reactor, equipped with a polarographic electrode to monitor in situ the dissolved ferrous iron activity. The stoichiometry of total Fe(II) production and acid consumption during the experiments indicated that lactate was oxidized to acetate. From the Fe(II) activity and redox potential measurements, free energy yields were calculated for Fe(III) reduction coupled to lactate oxidation. The results showed that the redox potential of the overall reaction was poised by equilibrium between the Fe(III)-substrate and aqueous Fe(II). Hence, the energy yields decreased in the order ferrihydrite > Fe(III)-salicylate > hematite > goethite. Accumulation of Fe(II) in solution only caused small decreases in the energy yields over the course of the experiments. Cessation of iron reduction, which was observed in all experiments, was therefore not due to thermodynamic limitation, but more likely reflected the decline in cell level of activity.

Bonneville, S.; Behrends, T.; Haese, R.; van Cappellen, P.

2003-04-01

46

[Iron homeostasis, a defense mechanism in oxidative stress].  

PubMed

Iron homeostasis consists in providing iron for a variety of biochemical processes and in limiting iron availability for Fenton reaction. Intracellular and systemic iron homeostasis is an important element in the defense against oxidative stress and is controlled by post-transcriptional regulatory mechanism IRP/IRE and hepcidin, a peptide that regulates iron absorption from diet and heme iron release by macrophages. Mutations in hepcidin gene as well as in genes involved in hepcidin regulation lead to the toxic accumulation of iron in the body and exacerbate oxidative stress. Reactive oxygen species influence labile iron pool through the transcriptional and posttranscriptional regulation of ferritin gene and through the release of iron from iron-sulfur proteins and from ferritin degraded in lysosomes. Alcohol-induced oxidative stress down-regulates hepcidin expression, increases iron absorption and leads to the excessive accumulation of iron and oxidative damage in the liver. PMID:21117319

Lipi?ski, Pawe?; Starzy?ski, Rafa? R; Sty?, Agnieszka; Straci?o, Monika

2010-01-01

47

Plasmodynamic synthesis of ultradispersed iron oxides  

NASA Astrophysics Data System (ADS)

Results of a pilot study of direct plasmochemical synthesis of ultradispersed crystalline iron oxide phases in a high-speed pulse jet of iron-containing electrodischarge plasma that effluxes into a closed volume with the air atmosphere are presented. The synthesized powder contains all main oxide phases, including magnetite Fe3O4, maghemite ?-Fe2O3, and hematite ?-Fe2O3. An important feature of the method is the formation of the metastable ?-Fe2O3 phase under normal conditions. The minimum average size of coherently diffracting domains (CDD) (particles) of the magnetic phases is observed when they are synthesized at air pressure of 1.0 atm. The powders have high magnetic properties comparable with those of compact iron oxides.

Sivkov, A. A.; Naiden, E. P.; Saigash, A. S.; Gerasimov, D. Yu.

2013-07-01

48

Hamaker constants of iron oxide nanoparticles.  

PubMed

The Hamaker constants for iron oxide nanoparticles in various media have been calculated using Lifshitz theory. Expressions for the dielectric responses of three iron oxide phases (magnetite, maghemite, and hematite) were derived from recently published optical data. The nonretarded Hamaker constants for the iron oxide nanoparticles interacting across water, A(1w1) = 33 - 39 zJ, correlate relatively well with previous reports, whereas the calculated values in nonpolar solvents (hexane and toluene), A(131) = 9 - 29 zJ, are much lower than the previous estimates, particularly for magnetite. The magnitude of van der Waals interactions varies significantly between the studied phases (magnetite < maghemite < hematite), which highlights the importance of a thorough characterization of the particles. The contribution of magnetic dispersion interactions for particle sizes in the superparamagnetic regime was found to be negligible. Previous conjectures related to colloidal stability and self-assembly have been revisited on the basis of the new Lifshitz values of the Hamaker constants. PMID:21644514

Faure, Bertrand; Salazar-Alvarez, German; Bergström, Lennart

2011-06-16

49

Iron oxide magnetic nanoparticles: A short review  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles have been enjoying great importance and wide scale applications during the last two decades due to their specific characteristics and applications. Iron oxide magnetic nanoparticles with appropriate surface chemistry have been implied in numerous applications such as biomedicine and cancer therapy, catalysis and in magnetic separation techniques. This review summarizes recent commercial, industrial and bio-engineering applications and brief study of the methods for the preparation of iron oxide magnetic nanoparticles with a control over the size, morphology and the magnetic properties. Some future applications of microwave irradiation for magnetic particle synthesis are also addressed.

Hasany, S. F.; Rehman, A.; Jose, R.; Ahmed, I.

2012-11-01

50

The Iron-Catalyzed Oxidation of Hydrazine by Nitric Acid  

SciTech Connect

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

Karraker, D.G.

2001-07-17

51

Oxide Dispersion Strengthened Iron Aluminide by CVD Coated Powders.  

National Technical Information Service (NTIS)

This 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 us...

A. Biswas A. J. Sherman

2006-01-01

52

Rechargeable 3 V Li cells using hydrated lamellar manganese oxide  

SciTech Connect

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

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

1996-11-01

53

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

PubMed

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

Liu, Chiung-Fang; Shih, Shin-Min

2004-08-15

54

Strontium desorption from bacteriogenic iron oxides (BIOS) subjected to microbial Fe(III) reduction  

Microsoft Academic Search

The effect of microbial reduction of bacteriogenic iron oxides (BIOS) on the release of sorbed Sr was examined using a naturally low-Sr BIOS (n-BIOS) collected from Chalk River, Canada, and a naturally high-Sr BIOS (Äspö-BIOS) collected from Äspö, Sweden. EXAFS analysis suggested that Sr was bound to the Äspö-BIOS as an outer-sphere complex of hydrated Sr2+. During reduction, Sr desorption

Sean Langley; Andrew G. Gault; Alex Ibrahim; Yoshio Takahashi; Rob Renaud; Danielle Fortin; Ian D. Clark; F. Grant Ferris

2009-01-01

55

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

56

21 CFR 73.200 - Synthetic iron oxide.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 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...

2013-04-01

57

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

58

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

59

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

SciTech Connect

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

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

2006-07-01

60

Adsorption Properties of As(III) on Iron Oxide Modified Filter Media  

Microsoft Academic Search

Iron oxide modified filter media was prepared and the content of the iron oxide on the surface, alkaline and antacid of iron oxide, the adsorption kinetics and isotherms were studied. Results showed the surface content of iron oxide calculated as Fe is 5.604 mg\\/g and the surface of iron oxide is stable. The adsorption of As (III) using iron oxide

Jincheng Li; Jie Li; Wenxiang Xia; Peng Li; Xuesong Ye

2011-01-01

61

Ferrous iron oxidation by anoxygenic phototrophic bacteria  

NASA Astrophysics Data System (ADS)

NATURAL oxidation of ferrous to ferric iron by bacteria such as Thiobacillus ferrooxidans or Gallionella ferruginea1, or by chemical oxidation2,3 has previously been thought always to involve molecular oxygen as the electron acceptor. Anoxic photochemical reactions4-6 or a photobiological process involving two photosystems7-9 have also been discussed as mechanisms of ferrous iron oxidation. The knowledge of such processes has implications that bear on our understanding of the origin of Precambrian banded iron formations10-14. The reducing power of ferrous iron increases dramatically at pH values higher than 2-3 owing to the formation of ferric hydroxy and oxyhydroxy compounds1,2,15 (Fig. 1). The standard redox potential of Fe3+/Fe2+ (E0 = +0.77 V) is relevant only under acidic conditions. At pH 7.0, the couples Fe(OH)3/Fe2+ (E'0 = -0.236V) or Fe(OH)3 + HCO-3FeCO3 (E'0 = +0.200 V) prevail, matching redox potentials measured in natural sediments9,16,17. It should thus be possible for Fe(n) around pH 7.0 to function as an electron donor for anoxygenic photosynthesis. The midpoint potential of the reaction centre in purple bacteria is around +0.45 V (ref. 18). Here we describe purple, non-sulphur bacteria that can indeed oxidize colourless Fe(u) to brown Fe(in) and reduce CO2 to cell material, implying that oxygen-independent biological iron oxidation was possible before the evolution of oxygenic photosynthesis.

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

1993-04-01

62

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; Joye, S. [Univ. of Georgia, Athens, GA (United States). Dept. of Marine Sciences

1998-09-01

63

Sulfur resistance and high activity of hydrated manganese sulfate in the catalytic oxidation of methanethiol  

Microsoft Academic Search

Hydration of manganese sulfate at a low reaction temperature (150°C) induces high heterogeneous catalytic activity and stability in the oxidation of methanethiol. The temperature of the reaction controls the reversible change of structure, i.e., hydration\\/dehydration processes as well as the associated changes of activity and selectivity.

Caroline Cellier; Eric M. Gaigneaux; Paul Grange

2004-01-01

64

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

65

Synthesis of Iron-Iron Oxide Core Shell Nanoclusters for Environmental Applications  

Microsoft Academic Search

Nanoscale iron particles have gained much attention recently for their potential application in the remediation of a wide variety of common environmental contaminants. Fe0 iron nanoparticles are difficult to synthesize by conventional methods. Here we report room-temperature synthesis of iron-iron oxide core-shell nanoclusters using a new type of source. Oxide shells act as passivation layers preventing further oxidation of the

Antony Jiji; You Qiang; Baer R; David E. McCready; Engelhard H

2004-01-01

66

Reduction of Soluble Iron and Reductive Dissolution of Ferric Iron-Containing Minerals by Moderately Thermophilic Iron-Oxidizing Bacteria  

Microsoft Academic Search

Five moderately thermophilic iron-oxidizing bacteria, including representative strains of the three classified species (Sulfobacillus thermosulfidooxidans, Sulfobacillus acidophilus, and Acidimicrobium ferrooxidans), were shown to be capable of reducing ferric iron to ferrous iron when they were grown under oxygen limitation conditions. Iron reduction was most readily observed when the isolates were grown as mixotrophs or hetero- trophs with glycerol as an

TONI A. M. BRIDGE; D. BARRIE JOHNSON

1998-01-01

67

Noncollinear coupling of iron layers through native iron oxide spacers  

SciTech Connect

We have found a magnetic superstructure in multilayers that consist of iron and its native oxide. Employing nuclear resonant scattering of synchrotron radiation from {sup 57}Fe probe layers, this manifests as 1/2-order Bragg peaks in the reflectivity curve. From the field dependence of their intensity, we deduce the existence of two magnetic sublattices that are canted by an angle of almost 90 deg. and rotate as one unit in low fields. For higher fields, the two sets of moments gradually align collinear to the external field. This behavior can be explained by a coupling of two adjacent Fe layers that is mediated by an antiferromagnetic order in the oxide spacer between them.

Diederich, Thomas; Couet, Sebastien; Roehlsberger, Ralf [Hamburger Synchrotronstrahlungslabor (HASYLAB), Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22603 Hamburg (Germany)

2007-08-01

68

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.

2013-08-01

69

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

PubMed Central

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

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

1988-01-01

70

Investigation of iron oxide reduction by TEM  

Microsoft Academic Search

An “environmental cell” located in a high voltage transmission electron microscope has been used to study the reduction of\\u000a single crystal iron oxides by hydrogen and hydrogen-argon mixtures. The cell enables a direct observation of the solid during\\u000a reaction, thus permitting the nucleation and growth of solid reaction products to be observed. Hematite was reduced at temperatures\\u000a in the range

Mann-Fu Rau; David Rieck; James W. Evans

1987-01-01

71

Optical properties of iron oxides  

NASA Astrophysics Data System (ADS)

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

Musfeldt, Janice

2012-02-01

72

Rapid discharge performance of composite electrode of hydrated sodium manganese oxide and acetylene black  

Microsoft Academic Search

Hydrated sodium manganese oxide was synthesized by reducing permanganate ion using ethanol by a sol–gel method. By including acetylene black in the synthetic reaction, we obtained composite materials in which sodium manganese oxide hydrate particles were small and mixed well with the acetylene black. We evaluated those composites as a lithium battery cathode and found that they showed 170mAhg?1 under

Mitsuhiro Hibino; Hirokazu Kawaoka; Haoshen Zhou; Itaru Honma

2004-01-01

73

Synthesis and Characterization of Magnetic Iron Oxide Nanoparticles  

SciTech Connect

This paper reports the synthesis and characterization of iron oxide nanoparticles and their assembly towards thin film materials. The results have provided important insights into the design of interfacial reactivities via iron nanoparticles for magnetic, catalytic and biological applications.

Wang, Lingyan; Luo, Jin; Maye, Mathew M.; Fan, Quan; Rendeng, Qiang; Wang, JQ; Engelhard, Mark H.; Wang, Chong M.; Lin, Yuehe; Altman, EI; Zhong, Chuan-Jian

2005-05-05

74

Iron oxide surface catalyzed oxidation of quinoline by hydrogen peroxide  

SciTech Connect

The objective of this research was to examine and compare the surface catalyzed loss of quinoline, a model pollutant, in the presence of three iron oxides: ferrihydrite, goethite, and a semicrystalline iron oxide. These are ubiquitous in the subsurface environment and have been implicated in the possible abiotic loss of contaminants when hydrogen peroxide is injected for augmenting bioremediation. This suggests the possible use of hydrogen peroxide specifically as an oxidant of some compounds in the subsurface. A comparison also reveals the best candidate for use in a supported oxide fixed bed treatment system utilizing hydrogen peroxide as an oxidant. The catalytic activity toward quinoline oxidation was highest for goethite, much less for the semicrystalline material, and negligible in the presence of ferrihydrite. Several water constituents affected reaction rates and stoichiometry by adsorption or through effects on solution chemistry. The stoichiometric efficiency relating quinoline loss to hydrogen peroxide decomposition was not a function of oxide concentration, nor was it affected by the presence of carbonate or phosphate that reduced the rate of hydrogen peroxide decomposition. The effect of humic acid on quinoline loss and hydrogen peroxide decomposition rate depended on its concentration, suggesting that it may act as a radical scavenger, radical chain promoter, and catalytic site inhibitor.

Valentine, R.L.; Wang, H.C.A. [Univ. of Iowa, Iowa City, IA (United States). Dept. of Civil and Environmental Engineering

1998-01-01

75

Chemical and Biological Oxidation of Iron in Acid Mine Water  

Microsoft Academic Search

Prior to limestone neutralization of acid water, ferrous iron needs to be oxidized to prevent downstream oxidation and the formation of acid. This study assessed the effect of various parameters on the biological and chemical rate of iron oxidation, both chemically and biologically. In batch experiments, it was found that although the use of support media had no effect on

N. R. Nengovhela; C. A. Strydom; J. P. Maree; H. A. Greben

2004-01-01

76

Synthesis and magnetic properties of iron oxide silica aerogel nanocomposites  

Microsoft Academic Search

Iron oxide silica nanocomposite aerogels were produced by sol gel procedure followed by the hypercritical evaporation of the solvent. Aerogels hosting maghemite were synthesized from the precursors TEOS and TMOS. Mean oxide particle size seems to be strongly influenced by the solvent. The magnetic properties of the iron oxide particles hosted in silica aerogeles pores were studied by means of

M. B. Fernández van Raap; F. H. Sanchez; A. G. Leyva; M. L. Japas; E. Cabanillas; H. Troiani

2007-01-01

77

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

78

Magnetic properties of polypyrrole-coated iron oxide nanoparticles  

Microsoft Academic Search

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 gamma-Fe2O3 phase for the concentrations

Raksha Sharma; Subhalakshmi Lamba; S. Annapoorni

2005-01-01

79

Reactive Condensation and Magnetic Properties of Iron Oxide Films  

Microsoft Academic Search

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

Yoshichika Bando; Shigeo Horii; Toshio Takada

1978-01-01

80

Magnetic nanobelts of iron-doped zinc oxide  

SciTech Connect

Magnetic nanobelts of iron-doped zinc oxide were fabricated by vapor-phase transport using zinc oxide, iron oxide, and graphite as source materials. The nanobelts grew mainly along [1010] orientation and enclosed by {+-}(0001) and {+-}(1210) surfaces. The measurements of x-ray diffraction, energy-dispersive x-ray spectroscopy, and high-resolution transmission electron microscopy demonstrated that iron was doped into the nanobelts. As a result, the nanobelts were magnetic.

Xu, C.X.; Sun, X.W.; Dong, Z.L.; Yu, M.B.; Xiong Yongzhong; Chen, J.S. [School of Electric and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Institute of Microelectronics, 11 Science Park Road, Science Park II, Singapore 117684 (Singapore); Data Storage Institute, 5 Engineering Drive 1, Singapore 117684 (Singapore)

2005-04-25

81

Fabrication and characterization of iron oxide nanoparticles filled polypyrrole nanocomposites  

Microsoft Academic Search

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

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

2009-01-01

82

Applications and potential toxicity of magnetic iron oxide nanoparticles.  

PubMed

Owing to their unique physical and chemical properties, magnetic iron oxide nanoparticles have become a powerful platform in many diverse aspects of biomedicine, including magnetic resonance imaging, drug and gene delivery, biological sensing, and hyperthermia. However, the biomedical applications of magnetic iron oxide nanoparticles arouse serious concerns about their pharmacokinetics, metabolism, and toxicity. In this review, the updated research on the biomedical applications and potential toxicity of magnetic iron oxide nanoparticles is summarized. Much more effort is required to develop magnetic iron oxide nanoparticles with improved biocompatible surface engineering to achieve minimal toxicity, for various applications in biomedicine. PMID:23019129

Liu, Gang; Gao, Jinhao; Ai, Hua; Chen, Xiaoyuan

2012-09-28

83

Iron oxide particles for molecular magnetic resonance imaging cause transient oxidative stress in rat macrophages  

Microsoft Academic Search

Iron oxide particles are a promising marker in molecular magnetic resonance imaging. They are used to label distinct cell populations either in vitro or in vivo. We investigated for the first time whether small citrate-coated very small superparamagnetic iron oxide particles (VSOPs) can lead to an increase in cellular oxidative stress. We incubated rat macrophages (RAW) in vitro with iron

Albrecht Stroh; Claus Zimmer; Cindy Gutzeit; Manuela Jakstadt; Franziska Marschinke; Tobias Jung; Herbert Pilgrimm; Tilman Grune

2004-01-01

84

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

85

Synthesis and magnetic properties of iron oxide nanoparticles\\/C and ?-Fe\\/iron oxide nanoparticles\\/C composites  

Microsoft Academic Search

Magnetic iron oxide nanoparticles\\/C and ?-Fe\\/iron oxide nanoparticles\\/C composites were synthesized through the formation of polymer gel with highly dispersed magnetic iron oxide nanoparticles in hydrothermal system, followed by carbonizing the gel at 400 and 1000°C under N2 atmosphere, respectively. The phase component, structure and magnetic properties of these magnetic composites were characterized by X-ray diffraction analysis, transmission electron microscopy

Ying Xiong; Jing Ye; Xiaoyu Gu; Qianwang Chen

2008-01-01

86

Synthesis and magnetic properties of iron oxide nanoparticles\\/C and alpha-Fe\\/iron oxide nanoparticles\\/C composites  

Microsoft Academic Search

Magnetic iron oxide nanoparticles\\/C and alpha-Fe\\/iron oxide nanoparticles\\/C composites were synthesized through the formation of polymer gel with highly dispersed magnetic iron oxide nanoparticles in hydrothermal system, followed by carbonizing the gel at 400 and 1000 °C under N2 atmosphere, respectively. The phase component, structure and magnetic properties of these magnetic composites were characterized by X-ray diffraction analysis, transmission electron

Ying Xiong; Jing Ye; Xiaoyu Gu; Qianwang Chen

2008-01-01

87

Ecology of neutrophilic iron-oxidizing bacteria in wetland soils  

Microsoft Academic Search

Wetland ecosystems are important as sites of rapid biogeochemical cycling of bioactive elements, among which iron features prominently. The redox cycling of iron exerts a strong influence on soil chemistry and the metabolism of plants and microorganisms. Studies have shown that bacteria play an important role in the process of iron oxidation in wetlands. This study explores the diversity and

J. Wang

2011-01-01

88

Superparamagnetic iron oxide nanoparticles with variable size and an iron oxidation state as prospective imaging agents.  

PubMed

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 r(1) and r(2) relaxivity measurements in water and diethylene glycol (for OH and CH(2) protons) have shown a decrease in the r(2)/r(1) 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 Fe(3)O(4) with the same particle size, but their r(1) 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

2013-01-04

89

Decoration of carbon nanotubes with iron oxide  

SciTech Connect

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

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

2006-04-15

90

Decoration of carbon nanotubes with iron oxide  

NASA Astrophysics Data System (ADS)

A magnetic composite of multiwalls carbon nanotubes (MWNTs) decorated with iron oxide nanoparticles was synthesized successfully by a simple and effective chemistry precipitation method. The composite was characterized by X-ray diffraction analysis (XRD), Mössbauer spectrum (MS), transmission electron microscopy (TEM), and Fourier transform spectroscopy (FTIR) techniques. The patterns of XRD and MS indicated that MWNTs, ?-Fe2O3, and Fe3O4 coexisted in the composite. The TEM observation indicated that the nanoparticles of iron oxide were attached on the surface of the MWNTs, and the sizes of the particles ranged from 25 to 80 nm. FTIR spectra showed that SO4- functional groups existed on the surface of MWNTs after modification by sodium dodecylbenzene sulfonic acid (SDBS), which could immobilize Fe3+ ions onto the MWNTs. The hysteresis loops of the MWNTs and decorated MWNTs were measured by vibrating sample magnetometer (VSM), and the results showed that the composite was ferromagnetism with the saturated magnetization of 20.07 emu/g, and the coercive of 163.44 Oe.

Huiqun, Cao; Meifang, Zhu; Yaogang, Li

2006-04-01

91

Sophorolipids-functionalized iron oxide nanoparticles.  

PubMed

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

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

2013-02-01

92

Dendronized iron oxide nanoparticles for multimodal imaging.  

PubMed

The synthesis of small-size dendrons and their grafting at the surface of iron oxide nanoparticles were achieved with the double objective to obtain a good colloidal stability with a mean hydrodynamic diameter smaller than 100 nm and to ensure the possibility of tuning the organic coating characteristics including morphology, functionalities, physico-chemical properties, grafting of fluorescent or targeting molecules. Magnetic resonance and fluorescence imaging are then demonstrated to be simultaneously possible using such versatile superparamagnetic iron oxide nanocrystals covered by a dendritic shell displaying either carboxylate or ammonium groups at their periphery which could be further labelled with a fluorescent dye. The grafting conditions of these functionalized dendrons at the surface of SPIO NPs synthesized by co-precipitation have been optimized as a function of the nature of the peripheral functional group. The colloidal stability has been investigated in water and osmolar media, and in vitro and in vivo MRI and optical imaging measurements have been performed showing encouraging biodistribution. PMID:21864894

Lamanna, Giuseppe; Kueny-Stotz, Marie; Mamlouk-Chaouachi, Hind; Ghobril, Cynthia; Basly, Brice; Bertin, Annabelle; Miladi, Imen; Billotey, Claire; Pourroy, Geneviève; Begin-Colin, Sylvie; Felder-Flesch, Delphine

2011-08-23

93

Battles with Iron: Manganese in Oxidative Stress Protection*  

PubMed Central

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

Aguirre, J. Dafhne; Culotta, Valeria C.

2012-01-01

94

Thermochemistry of iron manganese oxide spinels  

SciTech Connect

Oxide melt solution calorimetry has been performed on iron manganese oxide spinels prepared at high temperature. The enthalpy of formation of (Mn{sub x}Fe{sub 1-x}){sub 3}O{sub 4} at 298K from the oxides, tetragonal Mn{sub 3}O{sub 4} (hausmannite) and cubic Fe{sub 3}O{sub 4} (magnetite), is negative from x=0 to x=0.67 and becomes slightly positive for 0.670.6) spinels of intermediate compositions. The enthalpies of formation are discussed in terms of three factors: oxidation-reduction relative to the end-members, cation distribution, and tetragonality. A combination of measured enthalpies and Gibbs free energies of formation in the literature provides entropies of mixing. {delta}S{sub mix}, consistent with a cation distribution in which all trivalent manganese is octahedral and all other ions are randomly distributed for x>0.5, but the entropy of mixing appears to be smaller than these predicted values for x<0.4.

Guillemet-Fritsch, Sophie [Centre InterUniversitaire de Recherche et d'Ingenierie des Materiaux (CIRIMAT/LCMIE), Universite Paul Sabatier, Ba-hat timent 2R1, 118, route de Narbonne, 31062 Toulouse, Cedex 04 (France); Navrotsky, Alexandra [Thermochemistry Facility and NEAT ORU, University of California at Davis, One Shields Avenue, Davis, CA 95616-877 (United States)]. E-mail: anavrotsky@ucdavis.edu; Tailhades, Philippe [Centre InterUniversitaire de Recherche et d'Ingenierie des Materiaux (CIRIMAT/LCMIE), Universite Paul Sabatier, Ba-hat timent 2R1, 118, route de Narbonne, 31062 Toulouse, Cedex 04 (France); Coradin, Herve [Centre InterUniversitaire de Recherche et d'Ingenierie des Materiaux (CIRIMAT/LCMIE), Universite Paul Sabatier, Ba-hat timent 2R1, 118, route de Narbonne, 31062 Toulouse, Cedex 04 (France); Wang Miaojun [Thermochemistry Facility and NEAT ORU, University of California at Davis, One Shields Avenue, Davis, CA 95616-877 (United States)

2005-01-15

95

Anaerobic oxidation of methane above gas hydrates at Hydrate Ridge, Cascadia Margin (SO165, July/August 2002)  

NASA Astrophysics Data System (ADS)

The major aim of this study was the investigation of microbial anaerobic oxidation of methane (AOM) and sulfate reduction (SR) in methane enriched surface sediments at Hydrate Ridge, Cascadia Margin. At this site methane is oxidized with sulfate by a consortium of methane-oxidizing archaea and sulfate reducing bacteria (Boetius et al., 2000). Samples were obtained from sediment cores, which were retrieved from target locations by a TV-guided multicorer. To measure AOM and SR, radioactive tracers of methane (14CH_4) and sulfate (35SO_4) were added and incubated for 24 h at in situ temperature. O_2 and H_2S microgradients as well as pH profiles were measured by microelectrodes in intact cores immediately after retrieval in the cold room at 3^oC. Fields with distinct bacterial mats (Beggiatoa) and clams (Calyptogena or Acharax) were sampled to investigate the coupling of methane and sulfate cycles. The presence of Beggiatoa, Calyptogena and Acharax indicates a high production of hydrogen sulfide in the surface sediment Fluxes of sulfate, sulfide and methane are highest in Beggiatoa-fields and Calytogena-fields (20--100 mmol m-2 d-1). Acharax-fields show significantly lower methane turnover. The production of sulfide at Hydrate Ridge is directly coupled with SR and therefore as well with AOM. A high patchiness of methane-coupled sulfide production was observed.

Treude, T.; Ziebis, W.; Boetius, A.; Elvert, M.; Joergensen, B. B.

2003-04-01

96

Structural and magnetic properties of core-shell iron-iron oxide nanoparticles  

Microsoft Academic Search

We present studies of the structural and magnetic properties of core-shell iron-iron oxide nanoparticles. alpha-Fe nanoparticles were fabricated by sputtering and subsequently covered with a protective nanocrystalline oxide shell consisting of either maghaemite (gamma-Fe2O3) or partially oxidized magnetite (Fe3O4). We observed that the nanoparticles were stable against further oxidation, and Mössbauer spectroscopy at high applied magnetic fields and low temperatures

L. Theil Kuhn; A. Bojesen; L. Timmermann; M. Meedom Nielsen; S. Mørup

2002-01-01

97

Structural and magnetic properties of core–shell iron–iron oxide nanoparticles  

Microsoft Academic Search

We present studies of the structural and magnetic properties of core–shell iron–iron oxide nanoparticles. ?-Fe nanoparticles were fabricated by sputtering and subsequently covered with a protective nanocrystalline oxide shell consisting of either maghaemite (?-Fe2O3) or partially oxidized magnetite (Fe3O4). We observed that the nanoparticles were stable against further oxidation, and Mössbauer spectroscopy at high applied magnetic fields and low temperatures

L Theil Kuhn; A Bojesen; L Timmermann; M Meedom Nielsen; S Mørup

2002-01-01

98

Method for direct reduction of iron oxide utilizing induction heating  

Microsoft Academic Search

A method of reducing iron oxide by induction heating. The method involves the following steps: charging iron oxide and a carbonaceous material into the inlet end of a plurality of compartments whose walls comprise a material which is adaptable to being heated by induction wherein the plurality of compartments commonly share an induction coil means which surrounds the plurality of

Calderon

1985-01-01

99

Ultrasmall iron oxide nanoparticles: Synthesis, physicochemical, and magnetic properties  

Microsoft Academic Search

A new synthetic method leading to the formation of polycaprolactone (PCL)\\/iron oxide nanoparticles using polyvinylpyrrolidone (PVP) is described. The unique feature of this method is that the conventional polymerization step can be avoided. A stable colloidal dispersion of the PCL-coated iron oxide nanoparticles (PCLNP) is thus formed in the presence of PVP as a stabilizer. The PCLNP has a mean

Sung-Jin Bae; Ji-Ae Park; Jae-Jun Lee; Gang-Ho Lee; Tae-Jeong Kim; Done-Sik Yoo; Yongmin Chang

2009-01-01

100

Effects of iron oxide magnetic nanoparticles on osteoblast proliferation  

Microsoft Academic Search

Iron oxide nanoparticles are promising candidates for drug delivery systems to treat osteoporosis due to their biocompatibility and magnetic properties. Magnetite and maghemite nanoparticles were synthesized here using a co-precipitation method. The particles were characterized by transmission electron microscopy (TEM). Effects of CaP coating iron oxide magnetic nanoparticles on the proliferation of osteoblasts (OB) were determined after 1, 3 and

N. Tran; Rajesh Pareta; Thomas Webster

2009-01-01

101

TRACE ELEMENT BINDING DURING STRUCTURAL TRANSFORMATION IN IRON OXIDES  

EPA Science Inventory

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

102

Diffusional Growth of Oxide Scales on Cobalt-Iron Alloys  

Microsoft Academic Search

In this thesis the results of an experimental investigation and theoretical analysis of high temperature oxidation properties of cobalt-iron alloys are presented. Cobalt-iron alloys containing up to 70% iron were subjected to pure oxygen atmospheres with pressures ranging from 10?? to 1 atm at 1200°C. The reaction kinetics, oxide scale morphologies and spatial distributions of the reacting species in the

Peter Mayer

1973-01-01

103

Structural and magnetic properties of phase controlled iron oxide rods  

Microsoft Academic Search

Iron oxide rods are synthesized by thermal decomposition of iron (II) acetate at 700°C. The X-ray powder diffraction measurement confirms the hematite (?-Fe2O3) phase of iron oxide. We observed that the Morin transition depends on applied magnetic field and shift towards lower temperature with increase in applied magnetic field. The Morin temperature at applied field of 500 and 2000Oe is

R. K. Gupta; K. Ghosh; L. Dong; P. K. Kahol

2011-01-01

104

Biogeochemistry of iron oxidation in a circumneutral freshwater habitat  

Microsoft Academic Search

Iron(II) oxidation in natural waters at circumneutral pH, often regarded as an abiotic process, is frequently biologically mediated at iron-rich redox gradients. West Berry Creek, a small circumneutral tributary that flows through a mixed coniferous forest in Big Basin State Park, California, contains localized iron (hydr)oxide precipitates at points along its course where anoxic groundwater meets oxygenated creek water. These

Owen W. Duckworth; Sara J. M. Holmström; Jasquelin Peña; Garrison Sposito

2009-01-01

105

Biogeochemistry of Iron Oxidation in a Circumneutral Freshwater Habitat  

Microsoft Academic Search

Iron(II) oxidation in natural waters at circumneutral pH, often regarded as an abiotic process, may be biologically- mediated when it occurs in iron-rich redox gradients. West Berry Creek, a small circumneutral tributary flowing through a mixed coniferous forest in Big Basin State Park, California, contains localized iron (hydr)oxide precipitates at points along its course where anoxic groundwater meets oxygenated creek

O. Duckworth; S. Homstrom; J. Pena; E. Zacharias; G. Sposito

2007-01-01

106

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

Microsoft Academic Search

The feasibilities of (1) liberating free energy from dissimilative iron reduction and (2) coupling oxidative phosphorylation to electron transport to Fe(III) are sensitive to the aqueous chemistry of Fe(III). A systematic investigation of iron-reduction kinetics as a function of Fe(III) speciation indicated that in Pseudomonas sp. 200 (1) iron-reduction rate is functionally related to the concentrations of individual iron species

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

1986-01-01

107

Magnetite Dissolution and Authigenic Magnetic Iron Sulphide Formation in Gas Hydrate bearing Marine Sediments: Implications for Paleo- and Environmental Magnetic Studies  

Microsoft Academic Search

We present a mineral magnetic study of gas hydrate-bearing marine sediments drilled at southern Hydrate Ridge during ODP Leg 204 (Cascadia Margin, offshore Oregon). A combination of magnetic techniques and SEM observations has enabled identification and screening for the occurrence of magnetite and magnetic iron sulphides (greigite and pyrrhotite) in the studied sediments. Magnetite is detrital in origin whereas greigite

J. C. Larrasoana; A. P. Roberts; E. Gracia; R. J. Musgrave; E. Pinero; M. Vega; F. Martinez-Ruiz

2009-01-01

108

PRODUCTION OF POROUS PELLETS OF HYDRATED ORANGE OXIDE  

Microsoft Academic Search

An efficient and economical process has been developed for the ; continuous production of porous pellets of hydrated UOâ The pellet ; production operation consisted of feeding and mixing of UOâ powder with ; dilute aqueous ammonia followed by extruding and curing of the resulting paste. ; The feasibility of continuous mixing of an ammonia--water--UOâ mixture in a ; matter

P. W. Henline; E. W. Mautz; E. J. Walter

1957-01-01

109

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...

110

Magnetic and Mössbauer spectroscopy studies of nanocrystalline iron oxide aerogels  

NASA Astrophysics Data System (ADS)

A sol-gel synthesis was used to produce iron oxide aerogels. These nanocrystalline aerogels have a pore-solid structure similar to silica aerogels but are composed entirely of iron oxides. Mössbauer experiments and x-ray diffraction showed that the as-prepared aerogel is an amorphous or poorly crystalline iron oxide, which crystallized as a partially oxidized magnetite during heating in argon. After further heat treatment in air, the nanocrystallites are fully converted to maghemite. The particles are superparamagnetic at high temperatures, but the magnetic properties are strongly influenced by magnetic interactions between the particles at lower temperatures.

Carpenter, E. E.; Long, J. W.; Rolison, D. R.; Logan, M. S.; Pettigrew, K.; Stroud, R. M.; Kuhn, L. Theil; Hansen, B. Rosendahl; Mørup, S.

2006-04-01

111

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.

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

2013-01-01

112

Oxidation inhibits iron-induced blood coagulation.  

PubMed

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

113

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

114

Multiple hearth furnace for reducing iron oxide  

SciTech Connect

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

115

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.

Zhang, Guandong; Liao, Yifeng; Baker, Ian

2011-01-01

116

Synthesis and magnetic properties of iron oxide silica aerogel nanocomposites  

NASA Astrophysics Data System (ADS)

Iron oxide silica nanocomposite aerogels were produced by sol gel procedure followed by the hypercritical evaporation of the solvent. Aerogels hosting maghemite were synthesized from the precursors TEOS and TMOS. Mean oxide particle size seems to be strongly influenced by the solvent. The magnetic properties of the iron oxide particles hosted in silica aerogeles pores were studied by means of magnetometry and AC susceptometry. Interrelation between synthesis parameters, structure and magnetic behavior is discussed.

Fernández van Raap, M. B.; Sanchez, F. H.; Leyva, A. G.; Japas, M. L.; Cabanillas, E.; Troiani, H.

2007-09-01

117

The topography of iron oxide thin films (abstract)  

Microsoft Academic Search

The surface mophology of thin-film recording media is important for recording characteristics. STM analysis was done for iron oxide thin films prepared by a water vapor added rf-sputtering process.1 They were oxidized in an open air in the temperature range 300–350 °C in order to transfer magnetite thin films to gamma iron oxide thin films. The STM image of gamma

Zeng-Jun Zhou; Jun Jue Yan

1991-01-01

118

Iron Oxide-Coated on Glass Fibers for Arsenic Removal  

Microsoft Academic Search

A highly efficient adsorbent for arsenic removal from water has been prepared by impregnating high surface area iron oxides on glass fibers. Arsenic in water can easily and efficiently be removed by this adsorbent, without the need to pre-oxidize As(III) to As(V). The iron oxides coated on glass fibers (IOCGFs) can remove both arsenic species well below EPA MCL (10 ppb).

Jinwen Wang; Xuan Li; Jeffrey Scott Ince; Zhongren Yue; James Economy

2010-01-01

119

Magnetic behavior of iron and iron-oxide nanoparticle\\/polymer composites  

Microsoft Academic Search

An inert gas condensation technique was used to prepare nanometer-sized particles of metallic iron and iron oxide. The particles were passivated by the controlled oxidation of the particle surface leading to an Fe-oxide shell-Fe core structure. Nanoparticle–polymer composites were obtained by spin casting mixtures of nanoparticles and polymethylmethacrylate films. The magnetic properties of the nanoparticles compressed into pellets and dispersed

C Baker; S Ismat Shah; S. K Hasanain

2004-01-01

120

PhotoChemical Synthesis of Iron Oxide Nanowires Induced by Pulsed Laser Ablation of Iron Powder in Liquid Media  

Microsoft Academic Search

Iron oxide nanowires are synthesized by photochemical method through nanosecond pulsed laser ablation of iron powder in liquid media. The synthesis is tried using various wavelengths (248 and 532 nm) of pulsed laser at different liquids (water, ethanol, methanol, isopropanol and glycol). The solution of iron oxide nanowires is obtained only in methanol when the iron powder (size 60 mu

S. Mollah; S. J. Henley; C. E. Giusca; S. R. P. Silva

2010-01-01

121

Reversibility of exchange of alkaline-earth elements on hydrated tin and titanium oxides  

Microsoft Academic Search

The sorption of alkaline-earth elements by hydrated tin and titanium oxides was investigated. It was found that the reversibility of exchange, due to the stability of the sorption complex and to the conditions of competition in the system, is determined by a combination of the characteristics of the sorbate and the sorbent. The most important of these characteristics are their

T. N. Perekhozeva; L. M. Sharygin; S. M. Vovk

1988-01-01

122

Preparation of nanosized iron oxide and its application in low temperature CO oxidation  

Microsoft Academic Search

A method to prepare iron oxide material which has a higher surface area and nanosized particle was developed. It was used as a catalyst for CO oxidation at low temperature. Iron oxide materials were prepared by precipitation under constant pH value. The effects of preparation parameters, such as iron salt (FeCl3, Fe(NO3)3 and FeCl2), pH value (between 8 and 12),

Hsin-Yu Lin; Yu-Wen Chen; Wei-Jye Wang

2005-01-01

123

A laboratory study of anaerobic oxidation of methane in the presence of methane hydrate  

NASA Astrophysics Data System (ADS)

In order to mimic and study the process of anaerobic methane oxidation in methane hydrate regions we developed four high-pressure anaerobic bioreactors, designed to incubate environmental sediment samples, and enrich for populations of microbes associated with anaerobic methane oxidation (AMO). We obtained sediment inocula from a bacterial mat at the southern Hydrate Ridge, Cascadia, having cell counts approaching 1010 cells/cc. Ultimately, our goal is to produce an enriched culture of these microbes for characterization of the biochemical processes and chemical fluxes involved, as well as the unique adaptations required for, AMO. Molecular phylogenetic information along with results from fluorescent in situ hybridization indicate that consortia of Archaea and Bacteria are present which are related to those previously described for marine sediment AMO environments. Using a medium of enriched seawater and sediment in a 3:1 ratio, the system was incubated at 4° C under 43 atm of methane pressure; the temperature and pressure were kept constant. We have followed the reactions for seven months, particularly the vigorous consumption rates of dissolved sulfate and alkalinity production, as well as increases in HS-, and decreases in Ca concentrations. We also monitored the dissolved inorganic C (DIC) ? 13C values. The data were reproduced, and indicated that the process is extremely sensitive to changes in methane pressure. The rates of decrease in sulfate and increase in alkalinity concentrations were complimentary and showed considerable linearity with time. When the pressure in the reactor was decreased below the methane hydrate stability field, following the methane hydrate dissociation, sulfate reduction abruptly decreased. When the pressure was restored all the reactions returned to their previous rates. Much of the methane oxidation activity in the reactor is believed to occur in association with the methane hydrate. Upon the completion of one of the experiments, the chamber methane hydrate, liquid phase, and sediment were separated. FISH analyses of the dissociated hydrate fluid indicate a significant presence of Archaea in or on the hydrate. The cell densities in the bioreactor medium liquid phase were 7.2 x 107 cells/cc, and with the methane hydrate, 2.8 x 108 cells/cc.

Solem, R.; Bartlett, D.; Kastner, M.; Valentine, D.

2003-12-01

124

TPAP-catalyzed direct oxidation of primary alcohols to carboxylic acids through stabilized aldehyde hydrates.  

PubMed

We present a simple, mild, and highly effective method for the direct conversion of primary alcohols to carboxylic acids. TPAP serves as the catalyst, and NMO·H(2)O plays a dual role, acting as the co-oxidant and as a reagent for aldehyde hydrate stabilization. This previously unknown stabilizing effect of geminal diols by N-oxides is the key for the efficiency of the overall transformation. PMID:21793539

Schmidt, Andrea-Katharina C; Stark, Christian B W

2011-07-27

125

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

Microsoft Academic Search

Iron oxidizing bacteria are ubiquitous in marine and terrestrial environments on Earth, where they often display distinctive cell morphologies and are commonly encrusted by minerals, especially bacteriogenic iron oxides and silica. Putative microfossils of iron oxidizing bacteria have been found in jaspers as old as 490Ma and microbial iron oxidation may be an ancient metabolic pathway. In order to investigate

R. J. Leveille; S. Lui

2009-01-01

126

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

Microsoft Academic Search

Fe\\/Fe oxide nanoparticles, in which the core consists of metallic Fe and the shell is composed of Fe oxides, were obtained by reduction of an aqueous solution of FeCl3 within a NaBH4 solution, or, using a water-in-oil micro-emulsion with CTAB as the surfactant. The reduction was performed either in an inert atmosphere or in air, and passivation with air was

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

2007-01-01

127

Bonding of chlorophenols on iron and aluminum oxides  

SciTech Connect

The adsorption of 10 chlorophenols on synthetic, naturally occurring iron and aluminum oxides was studied to elucidate the mechanism of binding and relative bond strength of the chlorine-substituted phenols was identified by spectroscopic methods. Chlorophenolates were found to be chemisorbed on oxide surfaces via an inner-sphere coordination. Chlorophenols also bonded on oxides by weak physical forces (H bonding and condensation), but these types of weak bonding were identified only when adsorption occurred from the vapor phase onto dry surfaces. Physisorbed chlorophenols, unlike chemisorbed molecules, were readily removed from oxide surfaces by washing with water. Poorly crystallized iron and aluminum oxides showed similar mechanisms of chlorophenol binding, although the bond for chlorophenolate chemisorbed on iron oxide was stronger than that on aluminum oxide. Only physically adsorbed chlorophenols were detected on crystalline gibbsite, suggesting that the dominant (001) crystal face, with surface hydroxyl groups doubly coordinated to Al, was not specifically reactive with the chlorophenols. Chemisorption, however, was identified on the crystalline iron, geothite. From the extent of perturbation of aromatic ring electrons, the surface bond strength for chlorophenolates on aluminum oxide was found to correlate with the Lewis basicity of the phenolate anions (the higher the pK{sub {alpha}} of the chlorophenols, the stronger the surface bond). Nevertheless, the amount of chlorophenol adsorbed on noncrystalline iron oxide at controlled pH of 5.4 was limited by the extent of deprotonation (the lower the pK{sub a}, the more adsorption).

Kung, K.S.; McBride, M.B. (Cornell Univ., Ithaca, NY (United States))

1991-04-01

128

Chlorobenzene oxidation using ozone over iron oxide and manganese oxide catalysts  

Microsoft Academic Search

A low-temperature catalytic oxidation of chlorobenzene (CB) has been performed at temperatures of 60–210°C using ozone (O3) over iron oxide and manganese oxide, respectively. In the absence of ozone, CB conversion achieved with these two catalysts at 200°C was below 10%. However, addition of 1200ppm ozone results in a remarkable increase in CB conversion and the conversion reaches 91.7% at

Hou Chuan Wang; Hsu Shang Liang; Moo Been Chang

2011-01-01

129

Effects of Nitrous Oxide on Chloral Hydrate Sedation of Young Children  

PubMed Central

This study was performed to test the hypothesis that nitrous oxide augments the effects of chloral hydrate sedation of young children. Twenty children with a mean age of 32 months were sedated on two occasions with two different treatment regimens. All subjects received a standard dose of 50 mg/kg of chloral hydrate with or without nitrous oxide during each of two treatment visits. During one visit, the subjects received 50% nitrous oxide and 50% oxygen for a period of 20 minutes followed by 100% oxygen and, during the other visit, the reverse concentrations were used. All subjects were restrained in a Papoose Board* with an auxiliary head restraint. Successful sedation, as evident by lack of crying or movement which interrupted treatment, occurred in 84% of administrations. During the first twenty minutes, subjects receiving nitrous oxide moved and cried significantly less than when they were treated without nitrous oxide. During the remainder of the appointment, there was no difference in behavior between the two treatment regimens. Vital signs remained essentially unchanged throughout all treatment with the exception of transitory elevation of the pulse and respiratory rates, which usually occurred when the mouth prop was inserted and local anesthesia was administered. It is concluded that nitrous oxide augments the effect of chloral hydrate sedation of young children, but does not do so uniformly for all children receiving sedation. ImagesFig. 1Fig. 5

Houpt, Milton I.; Rosivack, R. Glenn; Rozenfarb, Nathan; Odont; Koenigsberg, Samuel R.

1986-01-01

130

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...

131

Reductive Dissolution of Iron Oxides and Iron-Rich Clays Enhanced by Sulfate-Reducing Bacteria  

Microsoft Academic Search

Iron oxides and iron-rich clays are abundant in low-temperature sedimentary environments where sulfate-reducing bacteria are also present. This study summarizes our research on reductive dissolution of ferrihydrite, goethite, hematite, magnetite, and a nontronite clay by Desulfovibrio spp. strain G-20 and strain G-11. The goal was twofold: (1) to understand the enzymatic processes of iron reduction by sulfate-reducing bacteria (SRB) using

C. L. Zhang

2003-01-01

132

The Color of Mars: Oxidation of Exogenic Metallic Iron  

Microsoft Academic Search

The origin of the maghemite inferred to be present in the martian soil by the Pathfinder and Viking magnetic properties experiments remains uncertain. Recent experimental results show that metallic iron can be oxidized into maghemite and hematite under conditions similar to the current martian environment. These data suggest that non-aqueous weathering of meteoritic iron could be the source of the

A. S. Yen; B. C. Murray

1998-01-01

133

Development of a Boron and Iron Oxide Delay System.  

National Technical Information Service (NTIS)

A new pyrotechnic composition consisting of boron and iron oxide has been developed for use in delays. The consolidated composition exhibits even burning characteristics, it is readily ignited from a percussion primer and has a good flame/particle output ...

G. Cleal M. Wilson P. P. Elischer

1986-01-01

134

Geochemical and Biological Implications of Anaerobic Methane Oxidation Associated with Gas Hydrates in the Gulf of Mexico  

NASA Astrophysics Data System (ADS)

An integrated lipid biomarker-carbon isotope approach reveals new insight to microbial methane oxidation in the Gulf of Mexico gas hydrate system. Hydrate-bearing and hydrate-free sediments were collected from the Gulf slope using a research submersible. Phospholipid fatty acids suggest that bacterial biomass is enhanced by up to 30-fold in gas hydrate-bearing sediment compared to hydrate-free sediment. Archaeal lipids are also abundant in hydrate-bearing sediment but only present in trace abundance in hydrate-free sediment. These results suggest that populations of Bacteria and Archaea are enriched at gas hydrate deposits in comparison to the normal marine sediment. In hydrate-bearing sediment, lipid biomarkers indicative of sulfate-reducing bacteria have \\delta13C values ranging from -48\\permil to -70\\permil and archaeal lipids indicative of methanogens have \\delta13C values ranging from -74.9\\permil to -99.3\\permil. These results suggest that sulfate-reducing bacteria and methanogens are involved in the oxidation of methane and contribute to increases in microbial biomass in gas hydrate samples. In the hydrate-free sample, fatty acid biomarkers have \\delta13C values ranging from -27.6\\permil to -39.6\\permil, indicating that crude oil (average about -27\\permil) and/or terrestrial organic carbon (average about -20\\permil) are the likely carbon sources. Our results provide convincing evidence that sulfate-reducing bacteria and methanogens play an important role in anaerobic methane oxidation in the Gulf of Mexico gas hydrates. The coupled activities of methane-oxidizing and sulfate-reducing bacteria in the presence of hydrocarbons result in sequestration of carbon as massive accumulations of authigenic carbonate rock, thus impacting models of climate change based on carbon budgets. geosccz/research.html

Zhang, C. L.; Pancost, R. D.; Qian, Y.; Sassen, R.; Wall, J. D.; Peacock, A.; White, D. C.; Huang, Y.

2001-12-01

135

Long term in vivo biotransformation of iron oxide nanoparticles.  

PubMed

The long term outcome of nanoparticles in the organism is one of the most important concerns raised by the development of nanotechnology and nanomedicine. Little is known on the way taken by cells to process and degrade nanoparticles over time. In this context, iron oxide superparamagnetic nanoparticles benefit from a privileged status, because they show a very good tolerance profile, allowing their clinical use for MRI diagnosis. It is generally assumed that the specialized metabolism which regulates iron in the organism can also handle iron oxide nanoparticles. However the biotransformation of iron oxide nanoparticles is still not elucidated. Here we propose a multiscale approach to study the fate of nanomagnets in the organism. Ferromagnetic resonance and SQUID magnetization measurements are used to quantify iron oxide nanoparticles and follow the evolution of their magnetic properties. A nanoscale structural analysis by electron microscopy complements the magnetic follow-up of nanoparticles injected to mice. We evidence the biotransformation of superparamagnetic maghemite nanoparticles into poorly-magnetic iron species probably stored into ferritin proteins over a period of three months. A putative mechanism is proposed for the biotransformation of iron-oxide nanoparticles. PMID:21392823

Levy, Michael; Luciani, Nathalie; Alloyeau, Damien; Elgrabli, Dan; Deveaux, Vanessa; Pechoux, Christine; Chat, Sophie; Wang, Guillaume; Vats, Nidhi; Gendron, François; Factor, Cécile; Lotersztajn, Sophie; Luciani, Alain; Wilhelm, Claire; Gazeau, Florence

2011-06-01

136

Tuning of Redox Properties of Iron and Iron Oxides via Encapsulation within Carbon Nanotubes  

Microsoft Academic Search

We report the tuning of the redox properties of iron and iron oxide nanoparticles by encapsulation within carbon nanotubes (CNTs) with varying inner diameters. Raman spectroscopy was employed to investigate the interaction of the encapsulated nanoparticles with the CNTs. A red shift of the Fe-O mode is observed in the nanoparticles deposited on the outer CNT surfaces with respect to

Wei Chen; Xiulian Pan; Xinhe Bao

2007-01-01

137

Iron and iron oxide-filled multi-walled carbon nanotubes: Electrical properties and memory devices  

Microsoft Academic Search

Electrical and morphological properties of neat iron- and iron oxide-filled multi-walled carbon nanotubes and its dispersion with a semiconducting polymer were investigated. The electrical properties of these carbon nanotubes changed significantly when exposed to different atmospheres. The current voltage characteristics of the films formed from the dispersions were obtained from planar devices with metallic electrodes. These devices were used as

Carlos E. Cava; Ricardo Possagno; Mariane C. Schnitzler; Paulo C. Roman; Marcela M. Oliveira; Carlos M. Lepiensky; Aldo J. G. Zarbin; Lucimara S. Roman

2007-01-01

138

Determination of the oxidation state for iron oxide minerals by energy-filtering TEM.  

PubMed

The oxidation state of iron oxide nanoparticles was determined using the two principally different technical realisations of energy filtering TEM, in one case using the JEOL 3010 equipped with a LaB6 cathode and a post-column GIF and in the second, the newly designed LIBRA 200FE equipped with an corrected in-column 90 degrees energy filter and a field emission gun (Schottky emitter). The samples studied were oxide-coated iron nanoparticles, and iron oxide inclusions in feldspars in granites. Five possible candidates exist for the iron-oxide phases: FeO, alpha-Fe2O3 (hematite), gamma-Fe2O3 (maghemite), Fe3O4 (magnetite) or alpha-FeO(OH) (goethite). Fingerprinting the O K-edge ELNES allows to distinguish between oxide phases with the same stochiometry and enables to make a first selection of possible candidates. The additional determination of the chemical composition allows unique identification of the phase present. For the oxide coated iron nanoparticles the most probable iron oxide phase of the shell is maghemite, which was additionally confirmed by HRTEM studies. The second studied system were iron oxide needles in alkali feldspar, where we obtained hematite as the most probable phase. There we additionally demonstrated the drastic changes of the ELNES of the O K-edge for the alkali feldspar and iron oxide needle by spatially resolved EELS. PMID:16466925

Golla-Schindler, U; Hinrichs, R; Bomati-Miguel, O; Putnis, A

2005-11-28

139

Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies  

Microsoft Academic Search

Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely\\u000a used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation,\\u000a structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application\\u000a briefly. In order to implement the practical application,

Wei Wu; Quanguo He; Changzhong Jiang

2008-01-01

140

Photoreductive Dissolution of Colloidal Iron Oxide: Effect of Citrate  

Microsoft Academic Search

The light-induced dissolution of the iron oxide, lepidocrocite (3,-FeOOH), has been investigated and found to be greatly enhanced in the presence of citrate. A conceptual model of the dissolution process is presented and validated through studies of citrate adsorption to lepidocrocite, net iron oxide dissolution under a variety of conditions, and solution phase redox reactions. The initial dissolution rate is

T. DAVID W AITE; FRANCOIS M. M. MOREL

1984-01-01

141

Iron deficiency suppresses ileal nitric oxide synthase activity  

Microsoft Academic Search

Intestinal motility disorders are more common in women of childbearing age who are prone to iron deficiency anemia. The neurotransmitters\\u000a nitric oxide (NO) and acetylcholine (ACh) play a key role in ileal smooth muscle relaxation and contraction, respectively.\\u000a Iron-containing heme is known to be a cofactor for nitric oxide synthase (NOS), the enzyme responsible for NO production.\\u000a Therefore we tested

Matthew I. Goldblatt; Seong-Ho Choi; Deborah A. Swartz-Basile; Atilla Nakeeb; Sushil K. Sarna; Henry A. Pitt

2001-01-01

142

Electrochemical behavior of reactively sputtered iron-doped nickel oxide  

Microsoft Academic Search

Iron-doped nickel oxide films were deposited by reactive sputtering from elemental and alloy targets in a 20% oxygen\\/argon atmosphere and were characterized for use as oxygen evolution catalysts. The incorporation of iron reduced the overpotential required for oxygen evolution by as much as 300 mV at a current density of 100 mA\\/cm² compared to undoped nickel oxide deposited under similar

Eric L. Miller; R. E. Rocheleau

1997-01-01

143

Crystallization process and magnetic properties of amorphous iron oxide nanoparticles  

Microsoft Academic Search

This paper studied the crystallization process, phase transition and magnetic properties of amorphous iron oxide nanoparticles prepared by the microwave heating technique. Thermal analysis and magnetodynamics studies revealed many interesting aspects of the amorphous iron oxide nanoparticles. The as-prepared sample was amorphous. Crystallization of the maghemite gamma-Fe2O3 (with an activation energy of 0.71 eV) and the hematite alpha-Fe2O3 (with an

N. D. Phu; D. T. Ngo; L. H. Hoang; N. H. Luong; N. Chau; N. H. Hai

2011-01-01

144

Structural and magnetic properties of nanostructured iron oxide  

Microsoft Academic Search

Nanostructured iron oxides are synthesized using ethylene glycol and polyvinyl pyrrolidone followed by calcinations. The X-ray powder diffraction measurement confirms the hematite phase of iron oxide. The synthesized hematite shows the Morin transition in the magnetization versus temperature (MvT) measurements. The nature of MvT depends on applied magnetic field. Magnetization versus magnetic field measurements confirm the antiferromagnetic behavior of hematite

R. K. Gupta; K. Ghosh; L. Dong; P. K. Kahol

2011-01-01

145

Photoreductive dissolution of colloidal iron oxides in natural waters  

Microsoft Academic Search

Size-separation (0.1-pm filtration and ultrafiltration) techniques and coulometric procedures have been used to investigate the photoreductive dissolution of iron oxides under conditions typical of natural waters. In the absence of organic agents, iron oxides are solubilized to varying degrees through photodissociation of ferric hydroxy groups at the colloid surface. The degree of dissolution is de- pendent principally on the chromophore

T. David Waite; Francois M. M. Morel

1984-01-01

146

Iron Oxide/Aluminum Fast Thermite Reaction  

NASA Astrophysics Data System (ADS)

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

Morgado, J.; Dura~Es, L.; Campos, J.; Portugal, A.

2004-07-01

147

Hydration, hydration, hydration.  

PubMed

Throughout the world, large numbers of manual workers perform physically demanding labour in conditions of high environmental heat stress. Although the importance of adequate hydration in combating heat stress is universally recognized, studies in a range of worker groups have demonstrated a disturbingly poor hydration level in a high proportion of at-risk workers. Management of work in hot environments traditionally focuses on environmental monitoring, while strategies to promote and ensure good hydration behaviour are often haphazard at best. An example is given of simple guidelines for adequate and appropriate fluid intake and practical recommendations to foster compliance. PMID:20008893

Miller, Veronica S; Bates, Graham P

2009-12-15

148

Iron oxide nanoparticles in geomicrobiology: from biogeochemistry to bioremediation.  

PubMed

Iron oxides are important constituents of soils and sediments and microbial iron reduction is considered to be a significant anaerobic respiration process in the subsurface, however low microbial reduction rates of macroparticulate Fe oxides in laboratory studies led to an underestimation of the role of Fe oxides in the global Fe redox cycle. Recent studies show the high potential of nano-sized Fe oxides in the environment as, for example, electron acceptor for microbial respiration, electron shuttle between different microorganisms, and scavenger for heavy metals. Biotic and abiotic reactivity of iron macroparticles differ significantly from nano-sized Fe oxides, which are usually much more reactive. Factors such as particle size, solubility, ferrous iron, crystal structure, and organic molecules were identified to influence the reactivity. This review discusses factors influencing the microbial reactivity of Fe oxides. It highlights the differences between natural and synthetic Fe oxides especially regarding the presence of organic molecules such as humic acids and natural organic matter. Attention is given to the transport behavior of Fe oxides in laboratory systems and in the environment, because of the high affinity of different contaminants to Fe oxide surfaces and associated co-transport of pollutants. The high reactivity of Fe oxides and their potential as adsorbents for different pollutants are discussed with respect to application and development of remediation technologies. PMID:23557995

Braunschweig, Juliane; Bosch, Julian; Meckenstock, Rainer U

2013-04-01

149

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

150

Epoxidation of propylene with nitrous oxide on Rb 2SO 4-modified iron oxide on silica catalysts  

Microsoft Academic Search

The catalytic activity of alkaline and earth alkaline-modified silica-supported metal oxide was investigated for epoxidizing propylene with nitrous oxide. Iron oxide gave the best results, and surprisingly chromium oxide also produced propylene oxide (PO). Unmodified iron oxide catalyst showed low oxidation activity and produced propanal (57% selectivity) in concert with small amounts of acrolein, allyl alcohol, and acetone. After modification,

Bart Moens; Hendrik De Winne; Steven Corthals; Hilde Poelman; Roger De Gryse; Vera Meynen; Pegie Cool; Bert F. Sels; Pierre A. Jacobs

2007-01-01

151

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

NASA Astrophysics Data System (ADS)

Reactions of laser-ablated iron oxides with CO in excess argon are investigated by infrared adsorption spectroscopy and density functional theoretical calculations. The carbonyl iron oxides OFe(CO)n (n = 1-3) and O2Fe(CO)m (m = 1, 2) are generated during sample deposition or annealing, whereas CO2 is greatly produced at the expense of these carbonyl iron oxides upon UV irradiation, showing the formation of intermediate carbonyl iron oxides in the oxidation of carbon monoxide to carbon dioxide. These intermediate carbonyl iron oxides are characterized on the basis of isotopic substitution, stepwise annealing, change of CO concentration and laser energy, and comparison with theoretical calculations. The overall agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts supports the identification of these complexes from the matrix infrared spectra. The reaction pathways for the formation of the products are proposed based on the experimental and theoretical results presented.

Lu, Zhang-Hui; Xu, Qiang

2011-01-01

152

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

PubMed

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

Bonnefoy, Violaine; Holmes, David S

2011-11-03

153

Iron-sulfur cluster synthesis, iron homeostasis and oxidative stress in Friedreich ataxia.  

PubMed

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

Vaubel, Rachael A; Isaya, Grazia

2012-08-11

154

Characteristics of hollow microtubes consisting of amorphous iron oxide nanoparticles produced by iron oxidizing bacteria, Leptothrix ochracea  

Microsoft Academic Search

Some features of characteristic iron oxide sheaths which the iron oxidizing bacteria Leptothrix ochracea (L. oceracea) formed were studied in order to make clear their morphology microstructure, chemical composition, and crystal structure through scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), and X-ray diffraction (XRD). Each sheath was a hollow tube with average outer and inner diameters of 1.1

H. Hashimoto; S. Yokoyama; H. Asaoka; Y. Kusano; Y. Ikeda; M. Seno; J. Takada; T. Fujii; M. Nakanishi; R. Murakami

2007-01-01

155

The Color of Mars: Oxidation of Exogenic Metallic Iron  

NASA Astrophysics Data System (ADS)

The origin of the maghemite inferred to be present in the martian soil by the Pathfinder and Viking magnetic properties experiments remains uncertain. Recent experimental results show that metallic iron can be oxidized into maghemite and hematite under conditions similar to the current martian environment. These data suggest that non-aqueous weathering of meteoritic iron could be the source of the pigmenting oxides in the soils on Mars. The discovery of 1% to 7% of a magnetic mineral, believed to be maghemite, by the Viking Landers [1] was confirmed by Pathfinder [2]. The conventional explanation for the origin of the ferric oxides on Mars is based on the dissolution and subsequent oxidation of ferrous iron from silicate minerals in aqueous environments [e.g., 3]. We present the idea that oxides of exogenic, rather than locally derived, iron could be responsible for the Mars surface spectra. This concept is not new [4], but here we introduce a pathway for oxidation without liquid water. New experiments which monitor the conductivity of electron-beam evaporated Fe show that metallic iron can be efficiently converted to oxide in the presence of ultraviolet radiation and oxygen. Analyses of the resulting oxide phases by FTIR techniques show both maghemite and hematite. A test of the meteoritic origin of at least some of the iron at the martian surface can be conducted with a measurement of the Ni content of the soil. Assuming an average of 7% Ni in iron meteorites and assuming roughly a quarter of the Fe at the martian surface is exogenic, 0.1% to 0.5% Ni should be present in the surface soil. [1] Hargraves et al., JGR, 82, 4547-4558, 1977. [2] Hviid et al., Science, 278, 1768-1770, 1997. [3] Burns, Geochimica et Cosmochem. Acta, 57, 4555-4574, 1993. [4] Gibson, Icarus, 13, 96-99, 1970.

Yen, A. S.; Murray, B. C.

1998-09-01

156

Acidic amorphous silica prepared from iron oxide of bacterial origin.  

PubMed

Microporous and mesoporous silica derived from biogenous iron oxide is an attractive catalyst for various organic reactions. Biogenous iron oxide contains structural silicon, and amorphous silica remains after iron oxide is dissolved in concentrated hydrochloric acid. The amorphous silica containing slight amounts of iron (Si/Fe = ?150) is composed of ?6-nm-diameter granular particles. The amorphous silica has a large surface area of 540 m(2)/g with micropores (1.4 nm) and mesopores (<3 nm). By using pyridine vapor as a probe molecule to evaluate the active sites in the amorphous silica, it was found that this material has strong Brønsted and Lewis acid sites. When the catalytic performance of this material was evaluated for reactions including the ring opening of epoxides and Friedel-Crafts-type alkylations, which are known to be catalyzed by acid catalysts, this material showed yields higher than those obtained with common silica materials. PMID:23331569

Hashimoto, Hideki; Itadani, Atsushi; Kudoh, Takayuki; Kuroda, Yasushige; Seno, Masaharu; Kusano, Yoshihiro; Ikeda, Yasunori; Nakanishi, Makoto; Fujii, Tatsuo; Takada, Jun

2013-02-04

157

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

SciTech Connect

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

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

2011-06-15

158

Preparation of iron oxides using ammonium iron citrate precursor: Thin films and nanoparticles  

NASA Astrophysics Data System (ADS)

Ammonium iron citrate (C6H8O7·nFe·nH3N) was used as a precursor for preparing both iron-oxide thin films and nanoparticles. Thin films of iron oxides were fabricated on silicon (111) substrate using a successive-ionic-layer-adsorption-and-reaction (SILAR) method and subsequent hydrothermal or furnace annealing. Atomic force microscopy (AFM) images of the iron-oxide films obtained under various annealing conditions show the changes of the micro-scale surface structures and the magnetic properties. Homogenous Fe3O4 nanoparticles around 4 nm in diameter were synthesized by hydrothermal reduction method at low temperature and investigated using transmission electron microscopy (TEM).

Park, Sangmoon

2009-09-01

159

Photocatalysis over titania on iron oxide  

NASA Astrophysics Data System (ADS)

Photocatalytic activity of TiO{2} deposited on spherical sub micron-sized Fe{2}O{3} particle was investigated under ultraviolet or visible light. The Fe{2}O{3} particles were prepared using a spray pyrolysis of aqueous Fe(NO{3})3 solution in air flow. TiO{2} was deposited on Fe{2}O{3} particle by irradiation of ultraviolet or visible light to the suspension of Fe{2}O{3} particle and a TiO{2} precursor. When TiO{2} was formed under visible light (TiO{2}/Fe{2}O{3}-VIS), there were reasonable trends in the phase shift of PAS signal and EDX signal of Ti. However, there was no trend for the case of ultra violet irradiation (TiO{2}/Fe{2}O{3}-UV). TiO{2}/Fe{2}O{3}-VIS showed higher rates of decomposition of organic compound, of decrease in contact angle of water drop, and of decrease in the number of E. coli under visible light than TiO{2}/Fe{2}O{3}-UV or TiO{2} film. From the results, it was suggested that TiO{2}/Fe{2}O{3}-VIS had a regular thin layer of TiO{2} compared to TiO{2}/Fe{2}O{3}-UV and the photo-generated carrier(s) in iron oxide migrated to the surface of TiO{2} in the case of TiO{2}/Fe{2}O{3}-VIS.

Kim, Kwi Cheol; Han, Chong Soo

2006-03-01

160

Capacity of human monocytes to phagocytose approved iron oxide MR contrast agents in vitro  

Microsoft Academic Search

To evaluate the capacity of human monocytes to phagocytose various approved iron oxide based magnetic resonance (MR) contrast agents and to optimize in vitro labeling of these cells. Human monocytes were incubated with two superparamagnetic iron oxide particles (SPIO) as well as two ultrasmall SPIO (USPIO) at varying iron oxide concentrations and incubation times. Iron uptake in monocytes was proven

Stephan Metz; Gabriel Bonaterra; Martina Rudelius; Marcus Settles; Ernst J. Rummeny; Heike E. Daldrup-Link

2004-01-01

161

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

Microsoft Academic Search

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

Blake; R. II

1991-01-01

162

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.

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

1963-01-01

163

Magnetic properties of polymer nanocomposites containing iron oxide nanoparticles  

Microsoft Academic Search

The magnetic behavior of polymer nanocomposites containing nanoparticles (?10nm) of oxidized magnetite in a polyvinyl alcohol matrix were investigated by means of Mossbauer transmission and conversion electron spectroscopy and magnetic measurements. The obtained results show that the base concentration of iron oxide nanoparticles within the polymer matrix volume greatly influences the magnetic properties of nanocomposites. The estimated lamellar distribution of

A. A. Novakova; V. Yu. Lanchinskaya; A. V. Volkov; T. S. Gendler; T. Yu. Kiseleva; M. A. Moskvina; S. B. Zezin

2003-01-01

164

Magnetic properties of polymer nanocomposites containing iron oxide nanoparticles  

Microsoft Academic Search

The magnetic behavior of polymer nanocomposites containing nanoparticles (~10nm) of oxidized magnetite in a polyvinyl alcohol matrix were investigated by means of Mossbauer transmission and conversion electron spectroscopy and magnetic measurements. The obtained results show that the base concentration of iron oxide nanoparticles within the polymer matrix volume greatly influences the magnetic properties of nanocomposites. The estimated lamellar distribution of

A. A. Novakova; V. Yu. Lanchinskaya; A. V. Volkov; T. S. Gendler; T. Yu. Kiseleva; M. A. Moskvina; S. B. Zezin

2003-01-01

165

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

166

The Oxidation of Iron in a Gel Using Consumer Chemicals  

Microsoft Academic Search

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.

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

2005-01-01

167

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

168

Removal of metal ions from water solutions by iron/cobalt oxide coated keramzite.  

PubMed

A method for coating hydrated iron, cobalt and iron/cobalt oxide on the surface of keramzite sand was developed. The coating parameters (pH, amount of coated metal, molar ratio Co/Fe, temperature of modification and time of treatment) controlling sorption ability of the coated layer were determined. The iron/cobalt coated keramzite thermally activated at 450 degrees C obtained at a molar ratio Co/Fe-0.516 is characterized and use for the removal of metal ions. The effect of contact time, solution pH, sorbate concentration, ionic strength and competing metal concentration on the sorption of copper, lead, zinc and cadmium was studied in batch experiments. The results reveal that the sorption rate of metal ions increases more rapidly in the initial period and reach metastable equilibrium within three hours. The sorption on coated keramzite follows both Langmuir and Freundlich's models. The data on the effect of pH showed that the sorption of all metal ions studied was markedly influenced by the solution pH. According to the concept of surface complexation model the experimental results support the assumption that metal adsorption at oxide coated keramzite sand could be better modeled as an innersphere surface reaction. The modified sorbent has a high selectivity towards copper and lead ions. The coated keramzite sand can be recommended as an efficient adsorbent for advanced water treatment of metal-bearing solutions and industrial wastewaters. PMID:11545353

Stefanova, R Y

2001-01-01

169

Estimating amounts of iron oxide from gradient echo images.  

PubMed

Rat legs directly injected with superparamagnetic iron oxide (SPIO) were studied by dual-echo, gradient-echo imaging. The amount of iron injected was estimated using a point dipole model for the SPIO injection site. Saturation magnetization of 6:1 PEG/amino modified silane-coated iron oxide particles with 5- to 6-nm core and 20-25 hydrodynamic diameter was approximately 110 emu/g of iron. Estimates of the amount of iron injected made from signal void volumes surrounding SPIO centers yielded erroneous results varying with sample orientation in the scanner and echo time (TE). For example, a 10 microL, 3-microg iron injection produced signal void volumes of 80 and 210 microL at TE of 9.8 and 25 ms, respectively, giving apparent iron contents of 6 +/- 1 and 10 +/- 2 microg respectively. A more effective approach uses the phase difference between two gradient recalled echo images. To estimate iron content, this approach fits the expected (3 cos(2)theta - 1)/(/r/3) spatial phase distribution to the observed phase differences. Extraneous phase effects made fitting phase at a single TE ineffective. With the dual echo method, 18 independent estimates were 2.48 +/- 0.26 microg std, independently of sample orientation. Estimates in empty control regions were -90 and -140 ng. A 1-microg injection indicated 0.5, 1.2, and 1.2 microg. PMID:19215047

Dixon, W Thomas; Blezek, Daniel J; Lowery, Lisa A; Meyer, Dan E; Kulkarni, Amit M; Bales, Brian C; Petko, Danielle L; Foo, Thomas K

2009-05-01

170

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

PubMed

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

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

2008-07-01

171

Preparation of iron oxides using ammonium iron citrate precursor: Thin films and nanoparticles  

SciTech Connect

Ammonium iron citrate (C{sub 6}H{sub 8}O{sub 7}.nFe.nH{sub 3}N) was used as a precursor for preparing both iron-oxide thin films and nanoparticles. Thin films of iron oxides were fabricated on silicon (111) substrate using a successive-ionic-layer-adsorption-and-reaction (SILAR) method and subsequent hydrothermal or furnace annealing. Atomic force microscopy (AFM) images of the iron-oxide films obtained under various annealing conditions show the changes of the micro-scale surface structures and the magnetic properties. Homogenous Fe{sub 3}O{sub 4} nanoparticles around 4 nm in diameter were synthesized by hydrothermal reduction method at low temperature and investigated using transmission electron microscopy (TEM). - Graphical abstract: Both iron-oxide thin films and nanoparticles (about 4 nm in diameter) are successfully achieved via successive-ionic-layer-adsorption-and-reaction and hydrothermal techniques in the use of ammonium iron citrate as a precursor.

Park, Sangmoon, E-mail: spark@silla.ac.k [Department of Engineering in Energy and Applied Chemistry, Silla University, Busan 617-736 (Korea, Republic of); USC NanoCenter, Department of Chemistry and Biochemistry, University of South Carolina, 1212 Greene Street, Columbia, SC 29208-0001 (United States); Condense Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States)

2009-09-15

172

Iron oxide-loaded liposomes for MR imaging.  

PubMed

In this study a liposome cell labeling system was developed for non-target-specific labeling of glioma cells with superparamagnetic iron oxide nanoparticles for magnetic resonance imaging (MRI). A high non-target-specific uptake is ideal for in vitro labeling of cells and subsequently for cell tracking and visualization of phagocytic cells in vivo. The preparation of iron oxide-loaded liposomes was optimized and the biological properties of the liposomes were investigated. Cytotoxicity and cell viability were examined and showed limited cytotoxic effects. Non-target-specific labeling of glioma cells in vitro for subsequent specific labeling of molecules for MR imaging was tested by T2*-weighted MRI at 3T. The glioma cells showed a strong initial uptake of the iron oxide liposomes and the uptake was not saturable within 24 h exposure. The uptake of liposomes was superior to non-coated magnetite nanoparticles. Using PEG-ylated liposomes, the non-specific uptake could be decreased fundamentally (86% lower) in comparison to conventional liposomes. Furthermore, the ability of liposomes as contrast agents for MR imaging was investigated. Cells labeled with iron oxide nanoparticles by treatment with liposomes showed a negative contrast in MRI and consequently successful cellular labeling. Thus, iron oxide-loaded liposomes are well suited for non-target-specific cell labeling for MR imaging. PMID:18508493

Meincke, Manuela; Schlorf, Thomas; Kossel, Elke; Jansen, Olav; Glueer, Claus-Christian; Mentlein, Rolf

2008-05-01

173

Iron(VI): Hypothetical Candidate for the Martian Oxidant  

Microsoft Academic Search

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

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

2000-01-01

174

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

175

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

176

Silica aerogel–iron oxide nanocomposites: structural and magnetic properties  

Microsoft Academic Search

Magnetic nanocomposites formed by iron oxide particles hosted in silica aerogels pores have been synthesized by sol–gel processes and supercritical evacuation of the solvent. Two iron-containing salts have been essayed: (A) Fe(NO3)·9H2O and (B) FeNa(EDTA)·2H2O. The synthetic routes made use of the gel pores as nanoreactors. Structural and magnetic properties have been studied by combining X-ray diffraction (XRD), N2 adsorption

L. Casas; A Roig; E Rodr??guez; E Molins; J Tejada; J Sort

2001-01-01

177

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.

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

2010-01-01

178

Modeling of iron oxide deposition by reactive ion beam sputtering  

SciTech Connect

An analytic model of deposition is applied on reactive ion beam sputtering to optimize the properties of iron oxide thin films. This model will be able to predict deposition rate and phase contents. Among its hypotheses, we assume oxygen adsorption at the surface of the target to explain variations of deposition rate for oxygen flow. This hypothesis is validated by chemical analyses on iron targets. An ellipsoidal distribution of probability is introduced to model sputtered matter distribution from iron target and to calculate sputtering yield. Comparison between experimental and calculated deposition rates validates previously assumed hypotheses.

Puech, Laurent [CEA, LETI, MINATEC, 38054 Grenoble (France); Institut Carnot, CIRIMAT, UMR CNRS 5085, 31062 Toulouse (France); CEA, LITEN, 38054 Grenoble (France); Dubarry, Christophe; Ravel, Guillaume; Vito, Eric de [CEA, LITEN, 38054 Grenoble (France)

2010-03-15

179

Core-shell iron–iron oxide nanoparticles: magnetic properties and interactions  

Microsoft Academic Search

We present studies of the magnetic properties of core-shell iron–iron oxide nanoparticles. By combining Mössbauer and X-ray absorption spectroscopy we have been able to measure the change from a Fe3O4-like to a ?-Fe2O3-like composition from the interface to the surface. Furthermore, we have observed exchange interactions across the core-shell interface.

L. Theil Kuhn; A. Bojesen; L. Timmermann; K. Fauth; E. Goering; E. Johnson; M. Meedom Nielsen; S. Mørup

2004-01-01

180

Characterization of iron oxide layers using Auger electron spectroscopy  

NASA Astrophysics Data System (ADS)

Metals can form several kinds of oxides. Iron forms wustite (FeO), magnetite (FeO + Fe2O3 or Fe3O4) and haematite (Fe2O3). Iron oxides, especially magnetite, are used for insulation between the lamellas of an electromotor made of electromagnetic sheet. In this work, iron oxide layers were characterized on industrial samples of electromagnetic sheet by AES depth profile analysis, and iron oxides with known chemical composition were used as reference samples, i.e. a magnetite mineral and a standard haematite reference sample. The magnetite mineral was chosen because it can be found in nature in a very pure form. The selection of reference samples was also verified on samples with an oxide layer of known composition, which were prepared by sputter deposition. The composition of the sputtered oxide layers was analysed by the weight-gain method and Rutherford backscattering without the use of standard reference materials (SRM), and the results were then compared with those obtained by AES depth profile analysis.

Bizjak, Milan; Zalar, Anton; Panjan, Peter; Zorko, Benjamin; Pra?ek, Borut

2007-02-01

181

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

182

Iron overload inhibits osteoblast biological activity through oxidative stress.  

PubMed

Iron overload has recently been connected with bone mineral density in osteoporosis. However, to date, the effect of iron overload on osteoblasts remains poorly understood. The purpose of this study is to examine osteoblast biological activity under iron overload. The osteoblast cells (hFOB1.19) were cultured in a medium supplemented with different concentrations (50, 100, and 200 ?M) of ferric ammonium citrate as a donor of ferric ion. Intracellular iron was measured with a confocal laser scanning microscope. Reactive oxygen species (ROS) were detected by 2,7-dichlorofluorescin diacetate fluorophotometry. Osteoblast biological activities were evaluated by measuring the activity of alkaline phosphatase (ALP) and mineralization function. Results indicated that iron overload could consequently increase intracellular iron concentration and intracellular ROS levels in a concentration-dependent manner. Additionally, ALP activity was suppressed, and a decline in the number of mineralized nodules was observed in in vitro cultured osteoblast cells. According to these results, it seems that iron overload probably inhibits osteoblast function through higher oxidative stress following increased intracellular iron concentrations. PMID:23334864

He, Yin-Feng; Ma, Yong; Gao, Chao; Zhao, Guo-Yang; Zhang, Lin-Lin; Li, Guang-Fei; Pan, Yun-Zhi; Li, Kai; Xu, You-Jia

2013-01-19

183

Luminescence studies of lanthanide oxides. I. Thermal and hydration effects on the metal ion site symmetry in europium oxide catalysts  

SciTech Connect

High-resolution luminescence spectroscopy has been used to study the site symmetry of Eu(III) ions in Eu/sub 2/O/sub 3/ prepared under conditions suitable for catalytic use. It was found that the Eu(III) site symmetry was a sensitive function of the pretreatment procedure, and it proved possible to determine the number of spectroscopically nonequivalent Eu(III) ions in the oxide material from an analysis of the fine structure within the emission bands. The site symmetry is altered primarily by thermal effects, and hydration of the oxide is not found to induce large changes in site symmetry.

Brittain, H.G. (Seton Hall Univ., South Orange, NJ); Perry, D.L.

1982-09-01

184

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

185

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

186

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

187

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

PubMed

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

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

2012-12-17

188

After more than a century, iron sponge still soaks up hydrogen sulfide problems  

SciTech Connect

The oldest and simplest method for removing H[sub 2]S and other sulfur compounds, such as mercaptans, from gaseous streams is the iron sponge process. The basic technique consists of passing a sour gas stream (one containing H[sub 2]S or mercaptans, or both) across a bed of hydrated iron oxide. The chemical reaction produces iron sulfide and a small amount of by-product water. Although not a common practice, the spent material may be regenerated by exposing it to oxygen, which converts the mixed iron sulfides to their original iron oxide form. The iron sponge technique originated in Europe more than 100 years ago, and the earliest operators used a naturally occurring form of hydrated iron oxide known as bog iron or bog ore. As refinements were made in the process, it was found that more efficient sulfur removal could be attained by uniformly distributing the iron oxide hydrate across a substrate, and that active iron oxide could be prepared synthetically. Continual improvements in the synthetic iron sponge's composition focused on such issues as the crystalline forms of the hydrated iron oxide, size distribution of the active iron oxide particulates, overall chemical composition, size and nature of the typical wood substrate, moisture content, and degree of buffering. Modern iron sponge products are prepared with careful attention to each of these issues. The synthetic materials are characterized by high quality and uniform composition, and their overall characteristics optimize performance in typical gas-sweetening applications.

Anerousis, J.P. (AccuChem Consultants, Austin, TX (United States))

1994-09-01

189

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

Microsoft Academic Search

Thermophilic (45–75°C) iron-reducing bacteria obtained from two sedimentary basins in Virginia and Colorado, USA, reduced amorphous Fe(III) oxyhydroxide to form magnetite-rich (>60% in most samples) iron oxides in acetate- or H2CO2-enriched cultures. The mineralogical compositions of the iron oxides were determined by X-ray diffraction and oxidation state analyses. Significantly lower Eh values ( ?100 mV). The pH values in acetate-enriched

Zhang Chuanlun; Liu Shi; Tommy J. Phelps; Dave R. Cole; Juske Horita; Steve M. Fortier; Mark Elless; John W. Valley

1997-01-01

190

Evolutionary relationships among sulfur- and iron-oxidizing eubacteria.  

PubMed Central

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

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

1992-01-01

191

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

EPA Science Inventory

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

192

Characterization of iron oxides and atmospheric corrosion of steel  

NASA Astrophysics Data System (ADS)

Research has been performed on steel coupons exposed to the atmosphere in order to improve the understanding of the formation and development of iron oxides which control atmospheric corrosion, and to establish data for predicting corrosion behavior taking place under specific atmospheric conditions. Improving the analytical techniques required for studying corrosion behavior was another goal of this research. Then, different analytical techniques can provide additional information, such as identification, fractions and layering of iron oxides formed on steels. The study of corrosion behavior was performed using three different analytical techniques, which provided information on the formation, development and layering of iron oxides on the corrosion products as a function of atmospheric conditions, exposure time and type of steel. In particular, the protective layer formed on weathering steel was investigated as a function of different amounts of alloying elements in the steel, atmospheric conditions and exposure times. Combined together, the results provided a better understanding of the atmospheric corrosion behavior of steel, and formed a part of database of the atmospheric corrosion characteristics. Accurate characterization of the iron oxides often formed on steel surfaces was one of the aims for this research. Seven iron oxides, goethite (?-FeOOH), akaganeite (?-FeOOH), lepidocrocite (?-FeOOH), ?-FeOOH, hematite (/alpha- F2O3), maghemite (?- F2O3) and magnetite (F3O4), which are often found in corrosion products present on steel, were characterized by Mossbauer spectroscopy, Raman spectrometry and x-ray diffraction analysis. Complete identification of the corrosion products formed on steel required more than one and most often three of the analytical techniques. In particular, the Mossbauer characterization of the iron oxides included measuring the relative recoilless fraction (F-value), which was defined as the ratio of recoil-free fractions of two different materials. The relative recoilless fractions of the iron oxides allowed the conversion of Mossbauer subspectral areas to the relative atomic, molecular, or weight fraction of each present in a mixed iron oxide sample. The characterization of the iron oxides was used to study the atmospheric corrosion behavior of weathering, copper bearing and carbon steels as a function of environmental condition, exposure time and type of steel. Goethite, akaganeite, lepidocrocite, maghemite and magnetite were identified in the corrosion products formed on the steel coupons. The formation of superparamagnetic goethite showed a correlation with the corrosion rate for seven types of steels. After long term exposure, superparamagnetic goethite on weathering steel, was the final iron oxide formed in the corrosion products. The conosion products typically formed in two layers. The protective layer, the inner layer, was formed by goethite and superparamagnetic maghemite. Increased amounts silicon and smaller amounts of phosphorus in the steel substrate increased the relative fraction of superparamagnetic goethite, in marine and rural environments. However, different amounts of nickel did not affect the formation of the iron oxides even after long term exposure. Increasing the silicon content in steel would be helpful in enhancing corrosion resistance for the long term lifetime of steel structures under atmospheric conditions.

Oh, Sei Jin

193

Iron oxides, dissolved silica, and regulation of marine phosphate concentration  

NASA Astrophysics Data System (ADS)

Phosphorous concentrations in iron oxide-rich sediments reflect orthophosphate levels in the water column from which iron oxides precipitated. Sediment P/Fe ratios are also strongly influenced by the concentrations of dissolved species that inhibit orthophosphate-to-ferrihydrite sorption, most notably silica. It may, therefore, be possible to use P/Fe ratios in iron oxide-rich sediments to estimate past dissolved P concentrations, if one considers the evolution of the silica cycle. A compilation of Fe and P data in iron oxide-rich sediments through time reveals an increase in P/Fe ratios after the Jurassic. We propose that this trend indicates evolution of the iron-oxide phosphate removal mechanism caused by decreasing levels of sorption inhibition by dissolved silica. The large difference in P/Fe ratios in Cenozoic versus older iron-oxide rich sediments can be linked with Si drawdown caused by the proliferation of siliceous plankton in the Cretaceous. There is also a late Mesozoic or Cenozoic increase in V/Fe ratios, which provides additional evidence for lower ferrihydrite anion sorption efficiency prior to diatom radiation. P/Fe ratios in iron oxide-rich sediments from the early and middle Phanerozoic are comparable to the ratios in iron formations previously presented as evidence for an early Precambrian phosphate crisis (Bjerrum and Canfield, 2002, Nature, 417:159-162). Given the compelling evidence for higher Si concentrations in the Precambrian compared to the Phanerozoic and dissolved P concentrations comparable to modern levels throughout the Phanerozoic, the presented trend of P/Fe ratios suggests dissolved P concentrations were higher in Precambrian than Phanerozoic oceans. High dissolved P levels in the Precambrian may have been linked to inhibited carbonate fluorapatite (CFA) formation as a result of persistently high levels of carbonate supersaturation. Carbonate ion substitution into CFA scales with the ambient carbonate ion activity and increases the solubility of the CFA. Substitution of the carbonate ion into the fluorapatite structure, therefore, results in an exponential increase in the levels of dissolved P needed for CFA precipitation. Elevated dissolved P concentrations in Precambrian oceans likely resulted in nitrogen-limited primary production on geological time scales.

Planavsky, N.; Reinhard, C.; Lyons, T.

2008-12-01

194

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

PubMed

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

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

2012-02-22

195

A study of the dispersity of iron oxide and iron oxide-noble metal (Me = Pd, Pt) supported systems  

Microsoft Academic Search

Samples of one-(Fe) and two-component (Fe-Pd and Fe-Pt) catalysts were prepared by incipient wetness impregnation of four\\u000a different supports: TiO2 (anatase), ?-Al2O3, activated carbon, and diatomite. The chosen synthesis conditions resulted in the formation of nanosized supported phases—iron\\u000a oxide (in the one-component samples), or iron oxide-noble metal (in the two-component ones). Different agglomeration degrees\\u000a of these phases were obtained as

Z. P. Cherkezova-Zheleva; M. G. Shopska; J. B. Krsti?; D. M. Jovanovi?; I. G. Mitov; G. B. Kadinov

2007-01-01

196

Preparation and characterization of iron/titanium-oxide composite particles  

NASA Astrophysics Data System (ADS)

The iron/titanium-oxide composite particles have been prepared using “in-situ” hydrogen-thermal reduction method. The composites were characterized by X-ray diffraction, physical property measurement system and Mössbauer spectroscopy. The powder X-ray diffraction patterns reveal the presence of crystalline ?-iron and titanium-oxide (FeTiO3/TiO2). The Mössbauer spectra of powders have been measured at room temperature, which indicated that the ?-iron and the high-spin iron(II/III) components were observed. The complex permittivity and permeability of the composites have been measured using vector network analyzers. Reflection loss of the iron/titanium-oxide composite powders dispersing in epoxy resin has been calculated using measured values of complex permittivity and permeability in the frequency range of 2-12 GHz. The maximum reflection loss of -36 dB was observed at 5.0 GHz. This study shows the possibility to obtain the novel dielectric and magnetic based microwave absorbers.

Tang, Xin; Huang, Jin; Kang, Linjie; Nie, Chang; Lin, Xing

2012-03-01

197

Fabrication of planar iron oxide nanocomposite films and investigation of their optical and magnetic properties  

Microsoft Academic Search

Iron oxide nanoparticles and polymer planar films with different number of layers of iron oxide nanoparticles have been fabricated by the layer-by-layer alternating adsorption technique. It was established that the thickness of the PAH\\/iron oxide film and its refractive index increases with the increase of the layer number. The microwave irradiation affects the thickness of the PAH\\/iron oxide film and

D. A. Gorin; D. O. Grigorev; A. M. Yashchenok; Yu. A. Koksharov; A. A. Neveshkin; A. V. Pavlov; G. B. Khomutov; H. Möhwald; G. B. Sukhorukov

2007-01-01

198

Deposition rates of oxidized iron on Mars  

NASA Astrophysics Data System (ADS)

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.

199

Metallic Iron and Iron Oxide as an Explanation for the Dark Material Observed on Saturn's Icy Satellites and Rings with Cassini VIMS  

NASA Astrophysics Data System (ADS)

The Visual and Infrared Mapping Spectrometer (VIMS) on Cassini has obtained spatially resolved spectra on satellites of Saturn. The Cassini Rev 49 Iapetus fly-by on September 10, 2007, provided data on both the dark material and the transition zone between the dark material and the visually bright ice. The dark material has low albedo with a linear increase in reflectance with wavelength, 3-micron water, and CO2 absorptions. The transition between bright and dark regions shows mixing with unusual optical properties including increased blue scattering and increasing strength of a UV absorber in areas with stronger ice absorptions. Similar spectral effects are observed on other Saturnian satellites and in the rings. We have been unable to match these spectral properties and trends using tholins and carbon compounds. However, the dark material is spectrally matched by fine-grained metallic iron plus nano-phase hematite and adsorbed water which contribute UV and 3-micron absorption, respectively. The blue scattering peak and UV absorption can be explained by Rayleigh scattering from sub-micron particles with a UV absorption, or a combination of Rayleigh scattering and Rayleigh absorption as has been attributed to spectral properties of the Moon. A new radiative transfer model that includes Rayleigh scattering and Rayleigh absorption has been constructed. Models of ice, sub-micron metallic iron, hydrated iron oxide, and trace CO2 explain the observed spectra. Rayleigh absorption requires high absorption coefficient nano-sized particles, which is also consistent with metallic iron. The UV absorber appears to have increased strength on satellite surfaces close to Saturn, with a corresponding decrease in metallic iron signature. A possible explanation is that the iron is oxidized closer to Saturn by oxygen in the extended atmosphere of Saturn's rings, or the dark material is simply covered by clean fine-grained ice particles, for example, from the E-ring.

Clark, Roger Nelson; Cruikshank, D. P.; Jaumann, R.; Brown, R. H.; Dalle Ore, C.; Stephan, K.; Hoefen, T. M.; Curchin, J. M.; Buratti, B. J.; Filacchione, G.; Baines, K. H.; Nicholson, P. D.

2010-10-01

200

Magneto-optical properties of iron oxide films  

Microsoft Academic Search

Iron oxide films have been grown onto MgO and oxidized silicon substrates using pulsed laser deposition with a 248 nm excimer laser. The films were deposited in a vacuum from an ?-Fe2O3 target. Films grown epitaxially on MgO consisted of the ferrimagnetic ?-Fe2O3 phase, with an average saturation magnetization of 353±26 kA\\/m. The Faraday rotation of the ?-Fe2O3 films was

T. Tepper; F. Ilievski; C. A. Ross; T. R. Zaman; R. J. Ram; S. Y. Sung; B. J. H. Stadler

2003-01-01

201

Kinetic Parameters of Binary Iron\\/Oxidant Pyrolants  

Microsoft Academic Search

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

Mojtaba Shamsipur; Seied Mahdi Pourmortazavi; Manochehr Fathollahi

2012-01-01

202

Iron oxide nanoparticles–chitosan composite based glucose biosensor  

Microsoft Academic Search

Iron oxide (Fe3O4) nanoparticles prepared using co-precipitation method have been dispersed in chitosan (CH) solution to fabricate nanocomposite film on indium–tin oxide (ITO) glass plate. Glucose oxidase (GOx) has been immobilized onto this CH–Fe3O4 nanocomposite film via physical adsorption. The size of the Fe3O4 nanoparticles estimated using X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) has been found to

Ajeet Kaushik; Raju Khan; Pratima R. Solanki; Pratibha Pandey; Javed Alam; Sharif Ahmad; B. D. Malhotra

2008-01-01

203

Iron oxide-chitosan nanobiocomposite for urea sensor  

Microsoft Academic Search

Urease (Ur) and glutamate dehydrogenase (GLDH) have been co-immobilized onto superparamegnatic iron oxide (Fe3O4) nanoparticles-chitosan (CH) based nanobiocomposite film deposited onto indium-tin-oxide (ITO) coated glass plate via physical adsorption for urea detection. The magnitude of magnetization (60.9emu\\/g) of Fe3O4 nanoparticles (?22nm) estimated using vibrating sample magnetometer (VSM) indicates superparamagnetic behaviour. It is shown that presence of Fe3O4 nanoparticles results in

Ajeet Kaushik; Pratima R. Solanki; Anees A. Ansari; G. Sumana; Sharif Ahmad; Bansi D. Malhotra

2009-01-01

204

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

Code of Federal Regulations, 2013 CFR

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

2013-07-01

205

Fabrication and magnetic properties of boron nitride nanocapsules encaging iron oxide nanoparticles  

Microsoft Academic Search

Boron nitride (BN) nanocapsules with iron oxide nanoparticles were fabricated by an arc discharge method, and the magnetic properties of these nanocapsules were investigated. High resolution electron microscopy showed that iron oxide nanoparticles of size 20nm were encapsulated by boron nitride sheets of width 4nm. Magnetization of the BN nanocapsules showed paramagnetism and the initial iron oxides showed ferromagnetism, which

Takanori Hirano; Takeo Oku; Katsuaki Suganuma

2000-01-01

206

Gas and humidity sensors based on iron oxide–polypyrrole nanocomposites  

Microsoft Academic Search

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

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

2002-01-01

207

Size dependent magnetic properties of iron oxide nanoparticles  

Microsoft Academic Search

?Fe2O3 nanoparticles has been synthesized by a combination of chemical and ultrasonication procedure and further stabilized with surfactant. Their magnetic properties are compared with the different fractions (10–12, 20–30, 100–150nm) of commercially available iron oxide. The sizes obtained from the scanning transmission electron micrographs are correlated with the magnetic properties of the particles.

Jhunu Chatterjee; Yousef Haik; Ching-Jen Chen

2003-01-01

208

Synthesis, properties, and applications of magnetic iron oxide nanoparticles  

Microsoft Academic Search

Magnetic nanoparticles exhibit many interesting properties that can be exploited in a variety of applications such as catalysis and in biomedicine. This review discusses the properties, applications, and syntheses of three magnetic iron oxides – hematite, magnetite, and maghemite – and outlines methods of preparation that allow control over the size, morphology, surface treatment and magnetic properties of their nanoparticles.

Amyn S. Teja; Pei-Yoong Koh

2009-01-01

209

Direct Observation of Iron Oxide Reduction Using High Voltage Microscopy.  

National Technical Information Service (NTIS)

The microstructure of reaction products resulting from gaseous reduction of iron oxide has been examined in situ and ex situ by high voltage electron microscopy (HVEM). In order to perform in situ experiments it was necessary to construct a special enviro...

N. J. Tighe P. R. Swann

1972-01-01

210

Factors influencing oxidation of iron pyrite in soil  

Microsoft Academic Search

Iron pyrites are waste products from mining operations and are also mined products. They have been used with varying success to supply Fe to plants, to supply S to plants, and to ameliorate sodic soils when oxidized to acid which forms gypsum in calcareous soil. Several forms of pyrite exist depending upon origin and crystallinity. Most of the literature indicates

A. Wallace; G. A. Wallace

1992-01-01

211

Stabilization and functionalization of iron oxide nanoparticles for biomedical applications  

Microsoft Academic Search

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

Esther Amstad; Marcus Textor; Erik Reimhult

2011-01-01

212

Magnetic properties of glasses with high iron oxide content  

Microsoft Academic Search

A study of the magnetic properties of glasses with high iron oxide content has been carried out. This glass series was obtained by recycling goethite (FeOOH) industrial waste, with dolomite and glass cullet as complementary raw materials. The magnetisation as a function of applied magnetic field for these glasses was measured. According to the magnetic behaviour, which closely correlates with

Maximina Romero-Perez; Jesús Ma. Rincón; Carlos J. R. González Oliver; Claudio D’Ovidio; Daniel Esparza

2001-01-01

213

Iron-Titanium Oxides and Oxygen Fugacities in Volcanic Rocks  

Microsoft Academic Search

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

I. S. E. Carmichael; J. Nicholls

1967-01-01

214

Thermosensitive liposomes entrapping iron oxide nanoparticles for controllable drug release  

NASA Astrophysics Data System (ADS)

Iron oxide nanoparticles can serve as a heating source upon alternative magnetic field (AMF) exposure. Iron oxide nanoparticles can be mixed with thermosensitive nanovehicles for hyperthermia-induced drug release, yet such a design and mechanism may not be suitable for controllable drug release applications in which the tissues are susceptible to environmental temperature change such as brain tissue. In the present study, iron oxide nanoparticles were entrapped inside of thermosensitive liposomes for AMF-induced drug release while the environmental temperature was maintained at a constant level. Carboxyfluorescein was co-entrapped with the iron oxide nanoparticles in the liposomes as a model compound for monitoring drug release and environmental temperature was maintained with a water circulator jacket. These experiments have been successfully performed in solution, in phantom and in anesthetized animals. Furthermore, the thermosensitive liposomes were administered into rat forearm skeletal muscle, and the release of carboxylfluorescein triggered by the external alternative magnetic field was monitored by an implanted microdialysis perfusion probe with an on-line laser-induced fluorescence detector. In the future such a device could be applied to simultaneous magnetic resonance imaging and non-invasive drug release in temperature-sensitive applications.

Tai, Lin-Ai; Tsai, Pi-Ju; Wang, Yu-Chao; Wang, Yu-Jing; Lo, Leu-Wei; Yang, Chung-Shi

2009-04-01

215

Iron-Oxide–Titanium Anode for Electrolysis of Chloride Solutions  

Microsoft Academic Search

Electrophysical, electrochemical, and corrosion properties of iron-oxide-titanium anode (IOTA) in the electrolysis of chloride solutions are studied. An optimum thickness of the active mass of the IOTA coating (300 µm) is substantiated. The anode lifetime during the production of sodium hypochlorite and electrotreatment of brackish water is defined by the corrosion wear of the coating active mass and is nine

F. V. Kupovich; A. M. Virnik

2001-01-01

216

A first-principles study of helium storage in oxides and at oxide-iron interfaces  

NASA Astrophysics Data System (ADS)

Density-functional theory calculations based on conventional as well as hybrid exchange-correlation functionals have been carried out to study the properties of helium in various oxides (Al2O3, TiO2, Y2O3, YAP, YAG, YAM, MgO, CaO, BaO, SrO) as well as at oxide-iron interfaces. Helium interstitials in bulk oxides are shown to be energetically more favorable than substitutional helium, yet helium binds to existing vacancies. The solubility of He in oxides is systematically higher than in iron and scales with the free volume at the interstitial site nearly independently of the chemical composition of the oxide. In most oxides, He migration is significantly slower and He-He binding is much weaker than in iron. To quantify the solubility of helium at oxide-iron interfaces two prototypical systems are considered (Fe--MgO, Fe--FeO--MgO). In both cases, the He solubility is markedly enhanced in the interface compared to either of the bulk phases. The results of the calculations allow to construct a schematic energy landscape for He interstitials in iron. The implications of these results are discussed in the context of helium sequestration in oxide dispersion strengthened steels, including the effects of interfaces and lattice strain.

Erhart, Paul

2012-06-01

217

Formation of water-soluble iron oxide nanoparticles derived from iron storage protein.  

PubMed

This paper reports novel findings of an investigation of the formation of water-soluble iron oxide nanoparticles from iron-storage protein ferritin. The strategy couples thermal removal of the protein shell on a planar substrate and subsequent sonication in aqueous solution under controlled temperature. Advantages of using ferritin as a precursor include well-defined core size, core composition, water-solubility and processibility. The formation of the nanoparticles was characterized using TEM, UV-Vis and FTIR techniques. Iron oxide nanoparticles in the size range of 5-20 nm diameters were produced. In addition to thermal treatment conditions, the sonication temperature of the nanoparticles in water was found to play an important role in determining the resulting particle size. This simple and effective route has important implications to the design of composite nanoparticles for potential magnetic, catalytic, biomedical sensing and other nanotechnological applications. PMID:15570948

Tominaga, Masato; Han, Li; Wang, Lingyan; Maye, Mathew M; Luo, Jin; Kariuki, Nancy; Zhong, Chuan-Jian

2004-09-01

218

Suppression of pyrite oxidation by iron 8-hydroxyquinoline.  

PubMed

One of the important approaches to prevent pyrite (FeS(2)) oxidation and subsequent formation of acid mine drainage (AMD) is to create a surface coating on pyrite. In this study, a coating of iron 8-hydroxyquinoline was formed by leaching pyrite with a 0.10 M H(2)O(2)/0.0034 M 8-hydroxyquinoline solution; stability of the coated pyrite was tested under various pH and temperature conditions. The results showed that iron 8-hydroxyquinoline coating could significantly suppress further pyrite oxidation by both chemical (H(2)O(2)) and biological ( e.g., Thiobacillus ferrooxidans) processes. At pH from 3.0 to 5.0 and temperature from 10-40 degrees C, the amount of SO(4)(2-) leached out by 0.10 M H(2)O(2) from the coated pyrite samples was 54.8-70.1% less than that from the uncoated controls. The oxidation of pyrite followed a pseudo-zero-order kinetics under the constant concentration of H(2)O(2). In the presence of microorganisms, sulfate leached out of the uncoated pyrite in 1 year accounted for 5.32% of the total pyrite in the system, with a concurrent pH drop to 2.35 under the ambient room temperatures. In contrast, the amount leached out from the coated samples was only 0.15% of the total pyrite and the final pH was 5.48. Thus, the coating decreased the leachability of pyrite by 97% in the inoculated systems. In comparison to the more widely studied iron phosphate coating, the advantage of iron 8-hydroxyquinoline coating was that it inhibited both chemical and biological pyrite oxidation, whereas iron phosphate coating could only inhibit chemical pyrite oxidation. PMID:12115042

Lan, Y; Huang, X; Deng, B

2002-08-01

219

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

Microsoft Academic Search

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

Yoshio Satot

1989-01-01

220

Chromium Substitution Effect on the Magnetic Structure of Iron Oxides  

NASA Astrophysics Data System (ADS)

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

Osman Murat, Ozkendir

2012-05-01

221

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

NASA Astrophysics Data System (ADS)

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

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

2008-10-01

222

Deep reduction behavior of iron oxide and its effect on direct CO oxidation  

NASA Astrophysics Data System (ADS)

Reduction of metal oxide oxygen carrier has been attractive for direct CO oxidation and CO2 separation. To investigate the reduction behaviors of iron oxide prepared by supporting Fe2O3 on ?-Al2O3 and its effect on CO oxidation, fluidized-bed combustion experiments, thermogravimetric analyzer (TGA) experiments, and density functional theory (DFT) calculations were carried out. Gas yield (?) increases significantly with the increase of temperature from 693 K to 1203 K, while carbon deposition decreases with the increase of temperature from 743 K to 1203 K, where temperature is a very important factor for CO oxidation by iron oxide. Further, it were quantitatively detected that the interaction between CO and Fe2O3, breakage of O-Fe bonds and formation of new C-O bonds, and effect of reduction degree were quantitatively detected. Based on adsorptions under different temperatures and reducing processes from Fe3+ into Fe2+, Fe+ and then into Fe, it was found that Fe2+ ? Fe+ was the reaction-controlling step and the high oxidation state of iron is active for CO oxidation, where efficient partial reduction of Fe2O3 into FeO rather than complete reduction into iron may be more energy-saving for CO oxidation.

Dong, Changqing; Liu, Xinglei; Qin, Wu; Lu, Qiang; Wang, Xiaoqiang; Shi, Simo; Yang, Yongping

2012-01-01

223

Nitrative and oxidative modifications of enolase are associated with iron in iron-overload rats and in vitro.  

PubMed

Iron overload is one of the most common iron-related toxicities, and liver is the major organ that is injured. Although oxidative stress is well accepted in the pathological mechanism of iron overload, nitrative modification in liver and the role of iron are relatively unknown. In this work, the nitrative and oxidative stress in liver was investigated in an iron-overload rat model. It was found that after 15 weeks of iron dextran administration, consistent with the increase of iron content in rat liver, both protein tyrosine nitration and protein oxidation were clearly elevated. By means of immunoprecipitation analysis, it was found that enolase nitration and oxidation status were significantly increased in iron-overload liver, whereas both ?-enolase expression and activity were clearly decreased. The effects of different forms of iron on NaNO(2)-H(2)O(2)- and peroxynitrite (ONOO(-))-dependent enolase nitration and oxidation were further investigated in vitro to elucidate the possible role of iron in enolase dysfunction in vivo. Compared with EDTA-Fe(III), ferric citrate, and ferritin, heme (hemin and hemoglobin) showed higher efficiency in catalyzing protein nitration in both models. Besides the major contribution of free iron (Fe(2+) and Fe(3+)) to catalyze protein oxidation, Fe(2+) also directly acted as a competitive inhibitor and produced a significant decrease in enzyme activity. These results suggest that the existence of various forms of iron is an important contributing factor to the elevated nitrative/oxidative modifications and diminished activity of ?-enolase in the development and progress of iron-overload-associated syndromes. PMID:21181420

Lu, Naihao; Li, Xueli; Li, Jinyang; Xu, Wenjing; Li, Hailing; Gao, Zhonghong

2010-12-23

224

Mechanistic investigation into the electrolytic formation of iron from iron(III) oxide in molten sodium hydroxide  

Microsoft Academic Search

Iron(III) oxide tablets were electrolytically reduced to iron in molten sodium hydroxide at 530 °C and recovered to produce\\u000a iron with 2 wt.% oxygen suitable for re-melting. The cell was operated at 1.7 V and an inert nickel anode was used. The thermodynamics\\u000a and mechanism of the process was also investigated. By controlling the activity of sodium oxide in the melt, the

A. Cox; Derek J. Fray

2008-01-01

225

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

226

Distribution and diversity of gallionella-like neutrophilic iron oxidizers in a tidal freshwater marsh  

Microsoft Academic Search

Microbial iron oxidation is an integral part of the iron redox cycle in wetlands. Nonetheless, relatively little\\u000ais known about the composition and ecology of iron-oxidizing communities in the soils and sediments of\\u000awetlands. In this study, sediment cores were collected across a freshwater tidal marsh in order to characterize\\u000athe iron-oxidizing bacteria (FeOB) and to link their distributions to

J. Wang; S. Vollrath; T. Behrends; P. L. E. Bodelier; G. Muyzer; F. Den Oudsten; M. Meima-Franke; P. Cappellen; H. J. Laanbroek

2011-01-01

227

Distribution and diversity of Gallionella-like neutrophilic iron oxidizers in a tidal freshwater marsh  

Microsoft Academic Search

Microbial iron oxidation is an integral part of the iron redox cycle in wetlands. Nonetheless, relatively little is known about the composition and ecology of iron-oxidizing communities in the soils and sediments of wetlands. In this study, sediment cores were collected across a freshwater tidal marsh in order to characterize the iron-oxidizing bacteria (FeOB) and to link their distributions to

J. Wang; S. Vollrath; T. Behrends; P. L. E. Bodelier; G. Muyzer; M. Meima-Franke; F. den Oudsten; P. Van Cappellen; H. J. Laanbroek

2011-01-01

228

Iron oxidation kinetics and autotrophic bacteria in acidified environments  

SciTech Connect

Iron oxidation in the presence of lake sediment collected from an acidic alpine lake was three orders of magnitude faster than in filtered lakewater without sediment. When kinetic rates in the presence of sediment were normalized on a surface area basis, they fell within a narrow range, and the assumption of a first order dependence of rate on surface area was supported. The relative influence on heterogeneous rate of ferrous iron oxidation of the five metal oxides studied can be ranked SiO[sub 2] [approx] Al[sub 2]O[sub 3] [much lt] Fe[sub 2] O[sub 3] [approx] MnO[sub 2] [approx] TiO[sub 2], with a difference of three orders of magnitude separating the aluminum and iron oxides. The rate constants on a surface area basis were, respectively, 1.8 [times] 10[sup 10], 4.6 [times] 10[sup 10], 1.4 [times] 10[sup 13], 2.3 [times] 10[sup 13] and 5.3 [times] 10[sup 13]M[sup [minus]2] atm[sup [minus]1] sec[sup [minus]1]m[sup [minus]2]. Studies at low oxygen concentrations suggested that at low pO[sub 2] oxygenation may not be first order with respect to oxygen concentration. Biological processes were found to enhance oxidation kinetics by two orders of magnitude on a surface area basis in comparison with a gamma irradiated control. Oxidation rate in the presence of irradiated sediment was in turn approximately 130 times greater than for oxidation in deionized water. The importance of biological activity in environments exhibiting photoreduction of iron was further studied by development of a polyclonal antibody test for the detection of the iron oxidizing autotroph Thiobacillus ferrooxidans. T. ferrooxidans was found in the Snake River and its tributaries in the Colorado Rocky mountains. Tests for T. ferrooxidans in samples collected at Lake Cristallina, Canton Ticino, Switzerland and McDonalds Branch, Lebanon State Forest, New Jersey were negative.

Barry, R.C.

1993-01-01

229

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

SciTech Connect

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

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

2011-01-21

230

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

231

Iron oxide formation in artificial ground waters  

Microsoft Academic Search

Artificial ground water containing 40 mg\\/l Ca and varying concentrations of Fe(II), Fe(III) and Si were rapidly oxidized with\\u000a air. The ferrihydrite forming is similar to those found in natural Finish ground waters.

U. Schwertmann; L. Carlson; H. Fechter

1984-01-01

232

Complexes of the proton and its hydrates with carbamoylphosphine oxide in wet dichloroethane solutions.  

PubMed

To better understand the complex equilibria involved in the UNEX process for acidic solvent extraction of radionuclides, the interaction of a carbamoylphosphine oxide ligand (L) with the proton of hydrated chlorinated cobalt(III)dicarbollide acid, H[Co(C2B9H8Cl3)2], has been studied in wet 1,2-dichlorethane (DCE) solution using IR and NMR (13C and 31P) spectroscopy. The formation of two groups of complexes has been determined. The first group contains three complexes with 1:1 composition of acid to ligand (Scheme 1). The second group of complexes has 1:2 composition in the equilibrium, shown in Scheme 2. Within each group, the complexes differ in composition only by the number of incorporated water molecules. The equilibria (Schemes 1 and 2) are both very sensitive to the content of self-associated water in solution and are driven by its concentration, which is unsteady and depends on the solution preparation history. The simultaneous presence of both anhydrous (I, II) and hydrated (III, IIIa, IV) proton solvates indicates that the enthalpies of carbamoylphosphine oxide complex formation with H+, H3O+, and H5O2(+) are very close to each other. PMID:16869702

Stoyanov, Evgenii S; Smirnov, Igor V; Fedotov, Martin A

2006-08-01

233

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.

2007-03-01

234

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

235

Oxidative effect of several intravenous iron complexes in the rat.  

PubMed

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

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

2013-05-17

236

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

PubMed

Au nanoparticles half-encapsulated in nano iron oxide are prepared and loaded on alumina as a support. The donation of electrons from nano iron oxide to Au nanoparticles is detected and both the properties of gold and iron oxide are adjusted by the donation. The properties are different from the bulk iron oxide supported gold catalysts, in which the iron oxide is little influenced by the electronic interaction between the two components. The catalyst shows noticeably promoted activity for the aerobic oxidation of 1-phenylethanol over Au-Al2O3 and Au-bulk FeOx. The enhanced catalytic behavior may result from the cooperative effect between the Au nanoparticles and nano iron oxide. PMID:23978992

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

2013-09-26

237

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

238

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

239

Cold catalytic recovery of loaded activated carbon using iron oxide-based nanoparticles  

Microsoft Academic Search

A novel approach for the recovery of spent activated carbon by an advanced oxidation process using iron oxide-based nanocatalysts was proposed and investigated. Model organic contaminants, such as ethylene glycol and phenol, were chosen for this study as water pollutants. It was shown that there are several advantages in using catalytic oxidation recovery of activated carbon with iron oxide-based nanocatalysts:

Altai Bach; Grigory Zelmanov; Raphael Semiat

2008-01-01

240

Crystallization of oxide high iron melts  

NASA Astrophysics Data System (ADS)

The data of thermal properties in terms of amorphous oxide melt of FeOx-SiO2-MeS (Me-Cu, Zn) system are presented in the article, temperature devitrifications of solid phase crystallization and melting are determined. Initial stages of crystal structure generation in terms of isothermal heating of amorphous alloy at the temperature 1023 ? depending on annealing duration are studied, phase composition and metal stay forms are determined.

Gulyaeva, R. I.; Selivanov, E. N.; Selmenskikh, N. I.

2011-05-01

241

Iron-dependent changes in cellular energy metabolism: influence on citric acid cycle and oxidative phosphorylation  

Microsoft Academic Search

Iron modulates the expression of the critical citric acid cycle enzyme aconitase via a translational mechanism involving iron regulatory proteins. Thus, the present study was undertaken to investigate the consequences of iron perturbation on citric acid cycle activity, oxidative phosphorylation and mitochondrial respiration in the human cell line K-562. In agreement with previous data iron increases the activity of mitochondrial

Horst Oexle; Erich Gnaiger; Günter Weiss

1999-01-01

242

Iron inhibits the nitric oxide synthesis elicited by asbestos in murine macrophages  

Microsoft Academic Search

Crocidolite fibers stimulated nitric oxide synthase (NOS) activity and expression in glial and alveolar murine macrophages: this effect was inhibited by iron supplementation and enhanced by iron chelation. We suggest that in these cells crocidolite stimulates NOS expression by decreasing the iron bioavailability and activating an iron-sensitive transcription factor.

Elisabetta Aldieri; Dario Ghigo; Maura Tomatis; Laura Prandi; Ivana Fenoglio; Costanzo Costamagna; Gianpiero Pescarmona; Amalia Bosia; Bice Fubini

2001-01-01

243

Nanovectors for anticancer agents based on superparamagnetic iron oxide nanoparticles  

PubMed Central

During the last decade, the application of nanotechnologies for anticancer drug delivery has been extensively explored, hoping to improve the efficacy and to reduce side effects of chemotherapy. The present review is dedicated to a certain kind of anticancer drug nanovectors developed to target tumors with the help of an external magnetic field. More particularly, this work treats anticancer drug nanoformulations based on superparamagnetic iron oxide nanoparticles coated with biocompatible polymers. The major purpose is to focus on the specific requirements and technological difficulties related to controlled delivery of antitumoral agents. We attempt to state the problem and its possible perspectives by considering the three major constituents of the magnetic therapeutic vectors: iron oxide nanoparticles, polymeric coating and anticancer drug.

Douziech-Eyrolles, Laurence; Marchais, Herve; Herve, Katel; Munnier, Emilie; Souce, Martin; Linassier, Claude; Dubois, Pierre; Chourpa, Igor

2007-01-01

244

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

245

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.

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

2010-01-01

246

Cation-exchange fiber reduces iron oxide leakage  

SciTech Connect

This article describes how addition of new fiber in powdered-resin precoat improves demineralizer crud-retention capability and reduces disposal cost for radioactive spent resin. Various attempts have been made to reduce the concentrations of iron oxide at the outlet of filter/demineralizer (FTD) vessels. Each vessel is fitted with an array of tubular septa that are precoated with powdered ion-exchange resin. The coatings perform filtering and ion-exchange actions on incoming feedwater, removing both suspended and dissolved solids. Experience at Duane Arnold Energy Center (CAED) indicates that use of a powdered-resin precoat containing cation-exchange fibers rather than cellulose fibers can reduce iron oxide levels in FTD effluent significantly.

MacClure, S.L.

1993-10-01

247

Promising iron oxide-based magnetic nanoparticles in biomedical engineering.  

PubMed

For the past few decades biomedical engineering has imprinted its significant impact on the map of science through its wide applications on many other fields. An important example obviously proving this fact is the versatile application of magnetic nanoparticles in theranostics. Due to preferable properties such as biocompatibility, non-toxicity compared to other metal derivations, iron oxide-based magnetic nanoparticles was chosen to be addressed in this review. Aim of this review is to give the readers a whole working window of these magnetic nanoparticles in the current context of science. Thus, preparation of magnetic iron oxide nanoparticles with the so-far techniques, methods of characterizing the nanoparticles as well as their most recent biomedical applications will be stated. PMID:23263800

Tran, Phuong Ha-Lien; Tran, Thao Truong-Dinh; Vo, Toi Van; Lee, Beom-Jin

2012-12-21

248

The Role of Reactive Transport Modeling in Understanding Biogeochemical Processes Associated With Iron Oxide Reduction  

Microsoft Academic Search

In a series of column and batch experiments, we are investigating mineral phase transformations during microbially mediated reduction of the iron oxide ferrihydrite. Quantification of the solid phase over time, using XAS and HRTEM, indicates that the primary sinks during iron oxide reduction, for both Fe (II) and Fe (III), are the secondary iron phases goethite and magnetite. While goethite

S. G. Benner; C. M. Hansel; S. Fendorf; K. U. Mayer

2002-01-01

249

Abiotic formation of elemental selenium and role of iron oxide surfaces  

Microsoft Academic Search

The possible abiotic reduction of selenite to form elemental Se was studied under controlled conditions in the presence of ferrous iron. The reduction of selenite and formation of Se (0) was found to be a surface- mediated reaction by iron oxides. Without the presence of the reactive surface of freshly precipitated iron oxides, the reduction reaction could not be detected,

Yu-Wei Chen; Hoang-Yen Thi Truong; Nelson Belzile

2008-01-01

250

Mössbauer and magnetization studies of iron oxide nanocrystals  

Microsoft Academic Search

Monodisperse iron oxide nanocrystals have been produced following non-hydrolytic, thermal decomposition routes. Spherically\\u000a shaped particles with diameter of 4 and 12 nm and cubic shaped particles with an edge length of 9 nm have been studied. The\\u000a particles have been shown to consist of mainly maghemite. A reduction of the saturation magnetic hyperfine field is observed\\u000a for the 4 nm particles as compared

Lennart Häggström; Saeed Kamali; Tore Ericsson; Per Nordblad; Anwar Ahniyaz; Lennart Bergström

251

Magneto-optical Properties of Iron Oxide Nanoclusters  

Microsoft Academic Search

We have developed a modified synthetic protocol for the growth of monodispersed, superparamagnetic, flower-like colloidal nanoclusters (CNCs) with 40-120 nm average diameters. Importantly, these are consisted of smaller iron oxide nanocrystals, also with adjustable size (12.2-7.7 nm). We show that their optical properties can be tuned by applying an external magnetic field. Spectrophotometric measurements under these conditions reveal a diffuse

Athanasia Kostopoulou; Ioannis Tsiaoussis; Alexandros Lappas

2010-01-01

252

Magnetic properties and magnetoresistance in small iron oxide cluster assemblies  

Microsoft Academic Search

We report the magnetic properties and magnetoresistance (MR) in small iron oxide (Fe3-xO4 and Fe3O4) cluster assemblies. Half-metallic Fe3O4 cluster assembly with grain size of 10-15 nm is shown to exhibit a MR value of about 8% at T=30 K and a peak around the Verwey transition temperature Tv=115 K which is a little lower than the Tv value (~120

D. L. Peng; T. Asai; N. Nozawa; T. Hihara; K. Sumiyama

2002-01-01

253

Synthesis and magnetic property of silica\\/iron oxides nanorods  

Microsoft Academic Search

To better understand the shape dependent property of binary nanostructure, magnetic silica\\/iron oxides (?-Fe2O3 and Fe3O4) nanocomposites in rodlike shape have been synthesized using ?-FeOOH nanorods as the starting material. The silica layer was coated on the surface of ?-FeOOH nanorods, which were prepared by hydrolyzing of FeCl3 under hydrothermal conditions. Silica\\/?-Fe2O3 nanorods were prepared by calcining silica\\/?-FeOOH nanorods, and

Wei-Wei Wang; Jia-Liang Yao

2010-01-01

254

Magnetic properties of aerosol synthesized iron oxide particles  

Microsoft Academic Search

Fine iron oxide particles have been prepared by an aerosol technique. The particles are spherical with a mean size of 0.1 mum. Heat treatment in air or nitrogen at various temperatures for various times leads to a variety of phase mixtures of alpha-Fe2O3, gamma-Fe2O3 and Fe3O4. The magnetic properties of these various samples are presented.

Z. X. Tang; S. Nafis; C. M. Sorensen; G. C. Hadjipanayis; K. J. Klabunde

1989-01-01

255

Cation-exchange fiber reduces iron oxide leakage  

Microsoft Academic Search

This article describes how addition of new fiber in powdered-resin precoat improves demineralizer crud-retention capability and reduces disposal cost for radioactive spent resin. Various attempts have been made to reduce the concentrations of iron oxide at the outlet of filter\\/demineralizer (FTD) vessels. Each vessel is fitted with an array of tubular septa that are precoated with powdered ion-exchange resin. The

MacClure

1993-01-01

256

Neutrophilic Iron-Oxidizing Microbes In The Marine Environment  

Microsoft Academic Search

Neutrophilic iron-oxidizing bacteria (FeOB) have been recognized, described, enriched for and isolated from terrestrial aquatic and soil habitats for over one hundred years. Microbiologists and geoscientists alike have appreciated the important role FeOB play in processes such as corrosion and mineral deposition. However, recognition of their role and activities has lagged considerably behind in marine realms. Over approximately the past

K. J. Edwards; C. Chan; B. Orcutt

2007-01-01

257

Niobian iron oxides as heterogeneous Fenton catalysts for environmental remediation  

Microsoft Academic Search

Heterogeneous Fenton or Fenton-like reagents consist of a mixture of an iron-containing solid matrix and a liquid medium with\\u000a 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.

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

2010-01-01

258

Niobian iron oxides as heterogeneous Fenton catalysts for environmental remediation  

Microsoft Academic Search

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

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

2010-01-01

259

Surface Reactivity of Core Shell Iron-Iron Oxide Nanoclusters towards Breakdown of Carbon Tetrachloride  

NASA Astrophysics Data System (ADS)

Zero-valent iron (ZVI) is one of the technologies for groundwater remediation to reduce contaminants by removal of mobile chlorinated hydrocarbons. Iron-Iron oxide (Fe/Fe3O4) nanoclusters (NCs) made in our laboratory using cluster deposition technique have enhanced reactivity towards targeted contaminants due to the presence of ZVI protected by a passivated oxide shell. Here, we investigate the effectiveness of the Fe/Fe3O4 NCs in reducing carbon tetrachloride (CT) under laboratory conditions. The reactivity of the NCs was investigated by conducting unbuffered aqueous batch experiments to reduce CT at room temperature. Initial results show that 80% of the degradation of CT resulted in the formation of dichloromethane (DCM) and chloroform (CF); the remainder likely followed a competing pathway to yield nonhazardous products such as CO. The production of undesirable hydrogenated products such as DCM and CF suggests that the dominant reaction pathway occurs through hydrogen (H) atom transfer via H atoms generated by corrosion of the iron. Comparative experiments with ZVI NCs prepared by other methods are underway and the results will be reported. Future work is to analyze and understand factors that control the reaction pathways between desirable and undesirable products.

Tarsem S., Maninder K.; Qiang, You; Kim, Hongseok; Amonette, James E.; Baer, Donald R.

2012-02-01

260

Magneto-optical properties of iron oxide films  

Microsoft Academic Search

Iron oxide films have been grown onto MgO and oxidized silicon substrates using pulsed laser deposition with a 248 nm excimer laser. The films were deposited in a vacuum from an alpha-Fe2O3 target. Films grown epitaxially on MgO consisted of the ferrimagnetic gamma-Fe2O3 phase, with an average saturation magnetization of 353+\\/-26 kA\\/m. The Faraday rotation of the gamma-Fe2O3 films was

T. Tepper; F. Ilievski; C. A. Ross; T. R. Zaman; R. J. Ram; S. Y. Sung; B. J. H. Stadler

2003-01-01

261

Superparamagnetic nanosystems based on iron oxide nanoparticles for biomedical imaging.  

PubMed

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

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

2011-04-01

262

Altering iron oxide nanoparticle surface properties induce cortical neuron cytotoxicity.  

PubMed

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

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

2011-12-06

263

Iron Minerals Formed by a Nuclear Explosion in a Salt Bed.  

PubMed

The nuclear event, Gnome, was carried out in halite in the Salado formation and yielded a varied mineral assemblage. The iron suppor members reacted in the salt melt and formed several iron oxide phases. The magnetite which formed during the fireball stage reached in various ways with the environment to form higher oxides and hydrated oxides. PMID:17810111

Nathans, M W; Smith, D K; Kahn, J S

1965-11-19

264

Ferrous iron oxidation by Thiobacillus ferrooxidans: inhibition with benzoic acid, sorbic acid, and sodium lauryl sulfate  

SciTech Connect

Thiobacillus ferrooxidans promote indirect oxidation of pyrite through the catalysis of the oxidation of ferrous iron to ferric iron, which is an effective oxidant of pyrite. These bacteria also may catalyze direct oxidation of pyrite by oxygen. A number of organic compounds, under laboratory conditions, can apparently inhibit both the oxidation of ferrous iron to ferric iron by T. ferrooxidans and the weathering of pyritic material by mixed cultures of acid mine drainage microorganisms. In this study, benzoic acid, sorbic acid, and sodium lauryl sulfate at low concentrations (5 to 10 mg/liter) each effectively inhibited bacterial oxidation of ferrous iron in batch cultures of Thiobacillus ferrooxidans. The rate of chemical oxidation of ferrous iron in low-pH, sterile batch reactors was not substantially affected at the tested concentrations (5 to 50 mg/liter) of any of the compounds.

Onysko, S.J.; Kleinmann, R.L.P.; Erickson, P.M.

1984-07-01

265

Surface engineering of iron oxide nanoparticles for targeted cancer therapy  

PubMed Central

Conspectus Nanotechnology provides a flexible platform for the development of effective therapeutic nanomaterials that can interact specifically with a target in a biological system and provoke a desired biological response. Of the nanomaterials studied, iron oxide nanoparticles have emerged as one of top candidates for cancer therapy due to their intrinsic superparamagnetism that enables no-invasive magnetic resonance imaging (MRI) and biodegradability favorable for in vivo application. A therapeutic superparamagnetic iron oxide nanoparticle (SPION) typically consists of three primary components: an iron oxide nanoparticle core that serves as both a carrier for therapeutics and contrast agent for MRI, a coating on the iron oxide nanoparticle that promotes favorable interactions between the SPION and biological system, and a therapeutic payload that performs designated function in vivo. Often, a targeting ligand is also included in the design that recognizes the receptors over-expressed on cancer cells. The body is a highly complex system that imposes multiple physiological and cellular barriers to foreign objects. Thus, the success of a therapeutic SPION largely relies on the proper design of the iron oxide core to ensure MRI detectability and more critically, the coating to render the ability to bypass these barriers. Strategies to bypass the physiological barriers such as liver, kidneys, and spleen, involve tuning the overall size and surface chemistry of the SPION to maximize blood half-life and facilitate the navigation in the body. Strategies to bypass cellular barriers include the use of targeting agents to maximize uptake of the SPION by cancer cells, and employing materials that promote desired intracellular trafficking and enable controlled drug release. The payload can be genes, proteins, chemotherapy drugs, or a combination of them. Each therapeutic requires a specific coating design to maximize the loading and achieve effective delivery and release. In this Account, we discuss the primary design parameters in developing therapeutic SPIONs with a focus on surface coating design to overcome the barriers imposed by the body’s defense system and provide examples of how these design parameters have been implemented to produce therapeutic SPIONs for specific therapeutic applications. Although there are still challenges to be addressed, SPIONs show great promise in successful diagnosis and treatment of the most devastating cancers. Once critical design parameters have been optimized, these nanoparticles, combined with imaging modalities, can serve as a truly multi-functional theranostic agent that not only performs a therapeutic function, but provides instant treatment feedback for the physician to adjust the treatment plan.

Kievit, Forrest M.; Zhang, Miqin

2011-01-01

266

The Effect of Surfactants On the Chromatographic Separation of Phenols On Papers Impregnated With Hydrated Cerium Oxide  

Microsoft Academic Search

The effect of surfactants on the chromatographic behaviour of 16 phenols of different nature have been observed on Whatman No 2 paper strips impregnated with hydrated cerium oxide. the movement of phenolic spots was observed in various mobile phase solvents with or without 4m ML 8m ML and 12m ML sodium dodecyl sulphate (SDS). It is observed that the use

S. K. Dabral

1989-01-01

267

Results demonstrating techniques for enhancing electrochemical reactions involving iron oxide in slags and C in liquid iron  

NASA Astrophysics Data System (ADS)

Two techniques are described for the enhancement of the kinetics of reduction of iron oxide from slags by carbon in molten iron. Laboratory experiments have shown that the rate of iron oxide reduction by carbon-saturated iron can be increased by 5 to 10 times when the reaction is carried out under a reduced-pressure atmosphere. This effect is thought to be the result of the increased volumetric gas evolution through the slag layer and the associated increase in slag stirring. A model is presented, which relates the mass-transfer coefficient for ferrous ions in the slag to its stirring that is controlled by varying the ambient pressure. Additional laboratory experiments examined the electrochemical nature of iron oxide reduction from slag by carbon in liquid iron. Results indicate that the reduction of iron oxide from slag is increased in the presence of an applied electric field. The external circuit allows for the separation of the half-cell reactions associated with iron oxide reduction and decarburization and increases the reaction area available for the individual reactions. These results have significant implications for several important slag metal reactions, which occur during ironmaking and steelmaking operations.

Pal, Uday B.; MacDonald, Scott A.; Woolley, David W.; Powell, Adam C.

2005-04-01

268

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

PubMed Central

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

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

1997-01-01

269

Mössbauer and calorimetric studies of portland cement hydration in the presence of black gram pulse  

NASA Astrophysics Data System (ADS)

Effect of different concentrations of naturally occurring admixture in the form of fine powder of black gram pulse (BGP) on the hydration of Portland cement was studied by isothermal calorimetry and 57Fe Mössbauer spectroscopy. The spectra were recorded for anhydrous cement and the hydration products at room temperature and 77 K. In the presence of BGP, the spectra showed superparamagnetic doublets at room temperature and the sextet at 77 K, due to the presence of fine particles of iron containing component. Mössbauer studies of hydration products confirmed the formation of nanosize hydration products containing Fe3 + . The isomer shift ( ?) and the quadrupole splitting (? E Q) values of C4AF in the cement confirmed iron in an octahedral and tetrahedral environment with +3 oxidation state. The high value of quadrupole splitting showed the high asymmetry of the electron environment around the iron atom. The overall mechanism of the hydration of cement in presence of BGP is discussed.

Rai, Sarita; Kurian, Sajith; Dwivedi, V. N.; Das, S. S.; Singh, N. B.; Gajbhiye, N. S.

2009-01-01

270

Toxicity assessments of nanoscale zerovalent iron and its oxidation products in medaka ( Oryzias latipes) fish  

Microsoft Academic Search

Iron-based nanotechnologies are increasingly used for environmental remediation; however, toxicologic impacts of iron nanoparticles on the aquatic ecosystem remain poorly understood. We treated larvae of medaka fish (Oryzias latipes) with thoroughly characterized solutions containing carboxymethyl cellulose (CMC)-stabilized nanoscale zerovalent iron (nZVI), aged nanoscale iron oxides (nFe-oxides) or ferrous ion (Fe[II]) for 12–14days’ aqueous exposure to assess the causal toxic effect(s)

Pei-Jen Chen; Chih-Hsiang Su; Chi-Yen Tseng; Shih-Wei Tan; Chiung-Hsiang Cheng

2011-01-01

271

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

Microsoft Academic Search

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

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

2007-01-01

272

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

273

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

Microsoft Academic Search

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

Tae-Jin Park

2007-01-01

274

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

275

Oxidation of phenolic acids by soil iron and manganese oxides  

Microsoft Academic Search

Phenolic acids are intermediary metabolites of many aromatic chemicals and may be involved in humus formation, allelopathy, and nutrient availability. Depending on their structures, six phenolic acids were shown to react at different rates with oxidized forms of Fe and Mn in a Palouse soil (fine-silty, mixed, mesic Pachic Ultic Haploxeroll). Increasing methoxy substitution on the aromatic ring of phenolic

R. G. Lehmann; H. H. Cheng; J. B. Harsh

2008-01-01

276

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

PubMed

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

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

2013-02-25

277

Iron-oxidizing bacteria: an environmental and genomic perspective.  

PubMed

In the 1830s, iron bacteria were among the first groups of microbes to be recognized for carrying out a fundamental geological process, namely the oxidation of iron. Due to lingering questions about their metabolism, coupled with difficulties in culturing important community members, studies of Fe-oxidizing bacteria (FeOB) have lagged behind those of other important microbial lithotrophic metabolisms. Recently, research on lithotrophic, oxygen-dependent FeOB that grow at circumneutral pH has accelerated. This work is driven by several factors including the recognition by both microbiologists and geoscientists of the role FeOB play in the biogeochemistry of iron and other elements. The isolation of new strains of obligate FeOB allowed a better understanding of their physiology and phylogeny and the realization that FeOB are abundant at certain deep-sea hydrothermal vents. These ancient microorganisms offer new opportunities to learn about fundamental biological processes that can be of practical importance. PMID:20565252

Emerson, David; Fleming, Emily J; McBeth, Joyce M

2010-01-01

278

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

279

Synthesis and magnetic properties of iron oxide–silica aerogel nanocomposites  

Microsoft Academic Search

Iron oxide–silica nanocomposite aerogels were produced by sol–gel procedure followed by the hypercritical evaporation of the solvent. Aerogels hosting maghemite were synthesized from the precursors TEOS and TMOS. Mean oxide particle size seems to be strongly influenced by the solvent. The magnetic properties of the iron oxide particles hosted in silica aerogeles pores were studied by means of magnetometry and

M. B. Fernández van Raap; F. H. Sanchez; A. G. Leyva; M. L. Japas; E. Cabanillas; H. Troiani

2007-01-01

280

HRTEM characterization of phase changes and the occurrence of maghemite during catalysis by an iron oxide  

Microsoft Academic Search

Nanoparticle iron oxide catalyst was studied to determine the phase changes that occur during catalysis experiments and to determine if these changes could explain the oxidative catalysis and deactivation mechanisms. The starting material was characterized as a mixture of glassy material, poorly crystalline iron hydroxides, and a small amount of highly crystalline ?-Fe2O3. Under oxidative (with respect to phase changes

Donald E. Miser; Eun-Jae Shin; Mohammad R. Hajaligol; Firooz Rasouli

2004-01-01

281

Dissolution Morphology of Iron (Oxy)(Hydr)Oxides Exposed to the Dissimilatory Iron-Reducing Bacterium Shewanella oneidensis MR1  

Microsoft Academic Search

Atomic force microscopy was used to compare the dissolution morphology of iron (oxy)(hydr)oxide coated slides exposed to the dissimilatory iron reducing bacterium Shewanella oneidensis MR-1 and a Type II protein secretion mutant unable to reduce iron minerals without an exogenous electron shuttle. Dissolution morphologies of slides exposed to the wild-type organism were heterogeneous and consistent with the morphology of bacterial

Mengni Zhang; Jason R. Dale; Thomas J. DiChristina; Andrew G. Stack

2009-01-01

282

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

Microsoft Academic Search

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

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

2012-01-01

283

Magnetic, electronic, and structural characterization of nonstoichiometric iron oxides at the nanoscale.  

PubMed

We have investigated the structural, magnetic, and electronic properties of nonstoichiometric iron oxide nanocrystals prepared by decomposition of iron(II) and iron(0) precursors in the presence of organic solvents and capping groups. The highly uniform, crystalline, and monodisperse nanocrystals that were produced enabled a full structural and compositional survey by electron microscopy and X-ray diffraction. The complex and metastable behavior of nonstoichiometric iron oxide (wüstite) at the nanoscale was studied by a combination of Mossbauer spectroscopy and magnetic characterization. Deposition from hydrocarbon solvents with subsequent self-assembly of iron oxide nanocrystals into superlattices allowed the preparation of continuous thin films suitable for electronic transport measurements. PMID:15521779

Redl, Franz X; Black, Charles T; Papaefthymiou, Georgia C; Sandstrom, Robert L; Yin, Ming; Zeng, Hao; Murray, Christopher B; O'Brien, Stephen P

2004-11-10

284

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

PubMed Central

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

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

2000-01-01

285

Microanalysis of iron oxidation states in earth and planetary materials  

NASA Astrophysics Data System (ADS)

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

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

1995-02-01

286

Microwave-assisted hydrothermal synthesis of coralloid nanostructured nickel hydroxide hydrate and thermal conversion to nickel oxide  

SciTech Connect

Coralloid nanostructured nickel hydroxide hydrate has been successfully synthesized by a simple microwave-assisted hydrothermal process using nickel sulfate hexahydrate as precursor and urea as hydrolysis-controlling agent. A pure coralloid nanostructured nickel oxide can be obtained from the nickel hydroxide hydrate after calcination at 400 deg. C. The thermal property, structure and morphology of samples were characterized by thermogravimetry (TG), temperature-programmed reduction (TPR), X-ray (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Lai, Teh-Long [Environmental Analysis Laboratory, Department of Chemistry, National Kaohsiung Normal University, Kaohsiung 802, Taiwan (China); Lai, Yuan-Lung [Department of Mechanical and Automation Engineering, Da-Yeh University, Changhua 515, Taiwan (China); Yu, Jen-Wei [Environmental Analysis Laboratory, Department of Chemistry, National Kaohsiung Normal University, Kaohsiung 802, Taiwan (China); Shu, Youn-Yuen, E-mail: shuyy@nknucc.nknu.edu.tw [Environmental Analysis Laboratory, Department of Chemistry, National Kaohsiung Normal University, Kaohsiung 802, Taiwan (China); Wang, Chen-Bin, E-mail: chenbin@ccit.edu.tw [Department of Applied Chemistry and Materials Science, Chung Cheng Institute of Technology, National Defense University, Tahsi, Taoyuan 335, Taiwan (China)

2009-10-15

287

Experimental determination and thermodynamic modeling of methane and nitrogen hydrates in the presence of THF, propylene oxide, 1,4-dioxane and acetone  

Microsoft Academic Search

Three-phase hydrate equilibria of the methane+water+cyclicether and nitrogen+water+cyclicether systems were measured by employing the temperature search method. Three cyclic ethers of THF, propylene oxide and 1,4-dioxane were chosen and their concentration was fixed at 3mol% relative to water. The addition of cyclic ethers caused the hydrate equilibrium pressure to be drastically lowered at a specified temperature and equivalently the hydrate

Y.-T. Seo; S.-P. Kang; H. Lee

2001-01-01

288

Lipid and carbon isotopic evidence of methane-oxidizing and sulfate-reducing bacteria in association with gas hydrates from the Gulf of Mexico  

Microsoft Academic Search

An integrated lipid biomarker carbon isotope approach reveals new insight to microbial methane oxidation in the Gulf of Mexico gas-hydrate system. Hydrate-bearing and hydrate-free sediments were collected from the Gulf of Mexico slope using a research submersible. Phospholipid fatty acids consist mainly of C16 C18 compounds, which are largely derived from bacteria. The phospholipid fatty acids suggest that total biomass

Chuanlun L. Zhang; Yiliang Li; Judy D. Wall; Lise Larsen; Roger Sassen; Yongsong Huang; Yi Wang; Aaron Peacock; David C. White; Juske Horita; David R. Cole

2002-01-01

289

The reduction of iron oxides by volatiles in a rotary hearth furnace process: Part II. The reduction of iron oxide\\/carbon composites  

Microsoft Academic Search

The reduction of iron oxide\\/carbon composite pellets with hydrogen at 900 ?C to 1000 ?C was studied. Compared to hydrogen,\\u000a the reduction by carbon was negligible at 900 ?C and below. However, significant carbon oxidation of the iron oxide\\/graphite\\u000a pellets by H2O generated from the reduction of Fe2O3 by H2 was observed. At higher temperatures, reduction by carbon complicates the

I. Sohn; R. J. Fruehan

2006-01-01

290

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

PubMed Central

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

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

2010-01-01

291

Iron oxide nanoparticle powders with high surface area  

NASA Astrophysics Data System (ADS)

Iron oxide nanomaterials with desired properties synthesized in the form of nanoparticle powders can find attractive applicability, e.g. in catalysis. Hence it is necessary to thoroughly characterize the materials by several measuring techniques. Two selected samples of amorphous Fe2O3 nanoparticles with high specific surface area values were prepared by the thermal treatment of different iron-bearing precursors. In addition to Mössbauer and microscopy methods, the nitrogen sorption based surface analysis is discussed from the viewpoint of textural morphology characterization of mentioned nanomaterials. The nitrogen adsorption-desorption isotherms have been measured and indicate the presence of micro and mesoporosity. One can conclude that the porosity arises from intra-aggregate voids and spaces formed by inter-particle contacts. The state of agglomeration can be estimated and appropriate application chosen.

K?ížek, M.; Pechoušek, J.; Tu?ek, J.; Šafá?ová, K.; Med?ík, I.; Machala, L.

2012-10-01

292

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.

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

2012-01-01

293

Aqueous dispersion of monodisperse magnetic iron oxide nanocrystals through phase transfer  

Microsoft Academic Search

A facile method was developed for completely transferring high quality monodisperse iron oxide nanocrystals from organic solvents to water. The as-prepared aqueous dispersions of iron oxide nanocrystals were extremely stable and could be functionalized for bioconjugation with biomolecules. These iron oxide nanocrystals showed negligible cytotoxicity to human breast cancer cells (SK-BR-3) and human dermal fibroblast cells. This method is general

William W. Yu; Emmanuel Chang; Christie M. Sayes; Rebekah Drezek; Vicki L. Colvin

2006-01-01

294

The detection of HBV DNA with gold-coated iron oxide nanoparticle gene probes  

Microsoft Academic Search

Gold-coated iron oxide nanoparticle Hepatitis B virus (HBV) DNA probes were prepared, and their application for HBV DNA measurement\\u000a was studied. Gold-coated iron oxide nanoparticles were prepared by the citrate reduction of tetra-chloroauric acid in the\\u000a presence of iron oxide nanoparticles which were added as seeds. With a fluorescence-based method, the maximal surface coverage\\u000a of hexaethiol 30-mer oligonucleotides and the

Dong Xi; XiaoPing Luo; QiangHua Lu; KaiLun Yao; ZuLi Liu; Qin Ning

2008-01-01

295

Magnetic Anisotropy and Magneto-Optical Properties of Iron Oxide Films  

Microsoft Academic Search

Iron oxide films were prepared by rf diode sputtering. Magnetic and magneto-optical properties of the iron oxide films are discussed. Perpendicular anisotropy was induced in sputtered iron oxide films (typically Ku{=}2× 105 erg\\/cm3). This perpendicular anisotropy was lost by annealing in air. The value of the Faraday constant thetaf was typically 2× 104 deg\\/cm at 633 nm. The absorption coefficient

Shuji Urabe; Takuhisa Numata; Seiji Inokuchi; Yoshifumi Sakurai

1986-01-01

296

Magnetic properties of ultrasmall iron oxide nanoclusters in a polymer matrix  

Microsoft Academic Search

The synthesis of iron oxide nanoclusters in the matrix of an interpolyelectrolyte complex based on poly(acrylic acid) and\\u000a polyethylenimine is described. The effect of the method of cluster formation (by the oxidation or reduction of iron ions)\\u000a on the magnetic properties of polymer nanocomposites was studied. The influence of the surface modification of iron oxide\\u000a nanoclusters in a polymer matrix

I. P. Suzdalev; Yu. V. Maksimov; V. E. Prusakov; V. V. Matveev; V. K. Imshennik; S. V. Novichikhin; A. B. Zezin; V. B. Rogozeva; S. P. Valueva

2008-01-01

297

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

298

Aqueous dispersion of monodisperse magnetic iron oxide nanocrystals through phase transfer  

NASA Astrophysics Data System (ADS)

A facile method was developed for completely transferring high quality monodisperse iron oxide nanocrystals from organic solvents to water. The as-prepared aqueous dispersions of iron oxide nanocrystals were extremely stable and could be functionalized for bioconjugation with biomolecules. These iron oxide nanocrystals showed negligible cytotoxicity to human breast cancer cells (SK-BR-3) and human dermal fibroblast cells. This method is general and versatile for many organic solvent-synthesized nanoparticles, including fluorescent semiconductor nanocrystals.

Yu, William W.; Chang, Emmanuel; Sayes, Christie M.; Drezek, Rebekah; Colvin, Vicki L.

2006-09-01

299

Various factors affecting photodecomposition of methylene blue by iron-oxides in an oxalate solution  

Microsoft Academic Search

The effect of various factors on the photodecomposition of methylene blue (MB) by iron oxides calcined at various temperatures in various concentrations of oxalate solutions was investigated by illuminating with UV, visible and solar radiation. Iron oxides were prepared by a gel evaporation method and calcined at 200–700°C. XRD showed that the as-synthesized iron oxides were amorphous, but formed maghemite

Fahmida Gulshan; Sayaka Yanagida; Yoshikazu Kameshima; Toshihiro Isobe; Akira Nakajima; Kiyoshi Okada

2010-01-01

300

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...

301

An Effective-Substrate Method to Investigate AN Iron Native Oxide Layer on AN Iron Substrate by Spectroscopic Ellipsometry  

NASA Astrophysics Data System (ADS)

An effective-substrate method was presented to obtain the optical constants of an iron native oxide layer with unknown optical constants and film thickness on an iron substrate with unknown optical constants by using spectroscopic ellipsometry (SE). "Thick" iron films were deposited on silicon wafer by magnetron sputtering and were exposed to air at room temperature. They were measured by spectroscopic ellipsometry during this procedure at different time points from ten minutes to seven months. Pseudo optical constants were calculated from the initially measured data and were introduced into the modeling work of subsequent measurements as an effective substrate in order to obtain the optical constants and film thickness of the native oxide layer. After obtaining the optical constants of the subsequent native oxide layer, they were employed in the modeling work of the initially measured data and the optical constants of the iron substrate and the film thickness of the initial native oxide layer was obtained.

Gao, Shang; Lian, Jie; Sun, Zhaozong; Wang, Xiao; Li, Ping; Li, Qinghao

2013-03-01

302

Iron oxide films in tribological surfaces of alloy steel  

NASA Astrophysics Data System (ADS)

The formation of iron oxide films and their roles in determining the dry wear properties of low alloy steel couples are described. Essentially, alpha-Fe2O3, haematites (Fe3O4), wustite (FeO) and oxide mixtures were the predominant compositions found in four regions of mild oxidational wear. The oxides were initially formed during subsequent rubbing and removal of material from the surfaces where oxidation, nucleation and agglomeration processes took place, followed by plastic deformation and work-hardening of underlying layers which supported the films. These films were found to be protective against wear; stable film of Fe3O4 reduced wear rate down to as low as 10-13 m3m-1, while loose particles of FeO maintained wear rate greater than 10-12 m3m-1. The wear protective nature of (alpha) -Fe2O3 and mixed films were found to lie between these extreme limits. Hence, the role of oxide films, in particular Fe3O4, is very significant in minimizing the wear and friction of alloy steel.

Sakrani, S. B.; Sullivan, J. L.

1998-02-01

303

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

Microsoft Academic Search

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

Michael J. Pullin; Stephen E. Cabaniss

2003-01-01

304

Iron sponge: still a top option for sour gas sweetening  

SciTech Connect

Engineering, research, and field data have been updated to present a detailed evaluation of gas sweetening via the iron sponge process. The iron sponge process is one of the oldest known methods for the removal of hydrogen sulfide and sulfur compounds from gas streams. The technique originated in Europe over 100 years ago and is still widely used today for gas sweetening. The process entails passing sour gas (i.e., a gas stream containing hydrogen sulfide and/or mercaptans) across a bed of hydrated iron oxide. The subsequent reaction with hydrogen sulfide produces iron sulfides and a small amount of byproduct water. The earliest operators actually employed a naturally occurring form of the hydrated iron oxide, referred to as bog iron or bog ore, but which is more correctly known as limonite (i.e., hydrous iron oxides that mineralogically are composed of various mixtures of goethite and/or legidocrocite).

Anerousis, J.P.; Whitman, S.K.

1985-02-18

305

Magnetic properties of iron oxides produced by bacterial oxidation of Fe 2+ under acid conditions  

Microsoft Academic Search

Iron oxides synthesized under acid conditions in a bioreactor using the bacteriumThiobacillus ferrooxidans or formed in nature under similar conditions resemble relatively “well”-crystallized ferrihydrites. Mssbauer spectra, however,\\u000a show up significant differences between these and ferrihydrites, indicating sulfate to play a major role in determining the\\u000a properties of the bacterial samples.

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

1990-01-01

306

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.

Wahajuddin; Arora, Sumit

2012-01-01

307

Iron oxide nanoparticles stabilized inside highly ordered mesoporous silica  

Microsoft Academic Search

Nanosized iron oxide, a moderately large band-gap semiconductor and an essential component of optoelectrical and magnetic\\u000a devices, has been prepared successfully inside the restricted internal pores of mesoporous silica material throughin-situ reduction during impregnation. The samples were characterized by powder XRD, TEM, SEM\\/EDS, N2 adsorption, FT-IR and UV-visible spectroscopies. Characterization data indicated well-dispersed isolated nanoclusters of\\u000a (Fe2O3)\\u000a n\\u000a , within

A. Bhaumik; S. Samanta; N. K. Mal

2005-01-01

308

Niobian iron oxides as heterogeneous Fenton catalysts for environmental remediation  

Microsoft Academic Search

\\u000a Heterogeneous Fenton or Fenton-like reagents consist of a mixture of an iron-containing solid matrix and a liquid medium with\\u000a 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.

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

309

Effect of solution chemistry on clay colloid release from an iron oxide-coated aquifer sand  

SciTech Connect

This research compared the influence of (1) dissolution of iron oxides and (2) alteration of electrostatic interactions on the mobilization of colloids in a clay- and iron oxide-coated sand obtained from an Atlantic Coastal Plain aquifer in which colloids have been found suspended only in anoxic groundwater. The sediment was flushed with solutions of varying ionic strength, pH, and reductant and surfactant concentrations, and the steady-state rates of clay colloid release and iron oxyhydroxide dissolution were measured. The clay release rates were directly related to the calculated detachment energies and unrelated to rates of iron(III) oxide dissolution, indicating that electrostatic interactions dominated the binding of colloids to grain coatings. Mobilization of colloids by iron(III) oxide dissolution through reductive dissolution was limited by high ionic strength. Flushing of the sediment by a natural groundwater with high dissolved organic carbon concentration released clay without rapidly dissolving iron oxides. 59 refs., 8 figs., 3 tabs.

Ryan, J.N. (Univ. of Colorado, Boulder, CO (United States)); Gschwend, P.M. (Massachusetts Inst. of Technology, Cambridge, MA (United States))

1994-09-01

310

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.

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

2010-01-01

311

NO oxidation kinetics on iron zeolites: influence of framework type and iron speciation  

Microsoft Academic Search

Zeolites having MFI, FER and *BEA topology were loaded with iron using solid state cation exchange method. The Fe:Al atomic\\u000a ratio was 1:4. The zeolites were characterized using nitrogen adsorption, FTIR and DR UV–Vis–NIR spectroscopy. The catalytic\\u000a activity in NO oxidation and the occurrence of NO\\u000a x\\u000a adsorption was determined in a fixed-bed mini reactor using gas mixtures containing oxygen

R. Brosius; D. Habermacher; J. A. Martens; L. Vradman; M. Herskowitz; L. ?apek; Z. Sobalík; J. D?de?ek; B. Wichterlová; V. Tokarová; O. Gonsiorová

2004-01-01

312

Reactions of metal ions at surfaces of hydrous iron oxide  

USGS Publications Warehouse

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

Hem, J. D.

1977-01-01

313

The isolation and use of iron-oxidizing, moderately thermophilic acidophiles from the Collie coal mine for the generation of ferric iron leaching solution.  

PubMed

Moderately thermophilic, iron-oxidizing acidophiles were enriched from coal collected from an open-cut mine in Collie, Western Australia. Iron-oxidizers were enriched in fluidized-bed reactors (FBR) at 60 degrees C and 70 degrees C; and iron-oxidation rates were determined. Ferrous iron oxidation by the microbiota in the original coal material was inhibited above 63;C. In addition to four iron-oxidizers, closely related to Sulfobacillus spp that had been earlier isolated from the 60 degrees C FBR, one heterotroph closely related to Alicyclobacillus spp was isolated. The Alicyclobacillus sp. isolated from the Collie coal mine tolerated a lower pH than known Alicyclobacillus spp and therefore may represent a new species. The optimum temperature for growth of the iron-oxidizing strains was approximately 50 degrees C and their maximum temperatures were approximately 60 degrees C. The FBR was adjusted to operate at 50 degrees C and was inoculated with all of the isolated iron-oxidizing strains. At 60 degrees C, an iron-oxidation rate of 0.5 g Fe(2+) l(-1) x h(-1) was obtained. At 50 degrees C, the iron-oxidation rate was only 0.3 g Fe(2+) l(-1) x h(-1). These rates compare favourably with the iron-oxidation rate of Acidianus brierleyi in shake-flasks, but are considerably lower than mesophilic iron-oxidation rates. PMID:12664157

Kinnunen, P H-M; Robertson, W J; Plumb, J J; Gibson, J A E; Nichols, P D; Franzmann, P D; Puhakka, J A

2002-12-19

314

Neutrophilic Iron-Oxidizing Microbes In The Marine Environment  

NASA Astrophysics Data System (ADS)

Neutrophilic iron-oxidizing bacteria (FeOB) have been recognized, described, enriched for and isolated from terrestrial aquatic and soil habitats for over one hundred years. Microbiologists and geoscientists alike have appreciated the important role FeOB play in processes such as corrosion and mineral deposition. However, recognition of their role and activities has lagged considerably behind in marine realms. Over approximately the past twenty years, however, there has been mounting interest and recognition of the presence and ubiquity of marine FeOB, particularly in the deep sea . Their role in rock and mineral weathering and alteration, mineral deposition, and biomass production in the deep sea has come into focus and is the subject of intense study. This paper will present an overview of marine FeOB including discussion of their habitats, diversity, and role in geochemical processes. In an effort to specifically target this elusive class of microbes, an observatory project for the study of FeOB and the marine microbial iron cycle has recently been launched--the Iron Microbial Observatory "FeMO", at the Loi'hi seamount, Hawaii. FeMO and FeOB isolated from Loi'hi are being used as model systems and testing grounds for studying mineral deposition and rock colonization in laboratory/field settings.

Edwards, K. J.; Chan, C.; Orcutt, B.

2007-12-01

315

Influence of synthetic superparamagnetic iron oxide on dendritic cells  

PubMed Central

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

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

2011-01-01

316

Slow Intravenous Iron Administration Does Not Aggravate Oxidative Stress and Inflammatory Biomarkers during Hemodialysis: A Comparative Study between Iron Sucrose and Iron Dextran  

Microsoft Academic Search

Background\\/Aims: Fast intravenous (i.v.) iron administration during hemodialysis (HD) is associated with the augmentation of oxidative stress and the increase in inflammatory biomarkers, which are also induced by the hemodialysis procedure itself. The aim of this study was to investigate if slow i.v. iron administration would aggravate the status of oxidative stress and inflammatory biomarkers during a hemodialysis session. Methods:

Pavlos Malindretos; Pantelis A. Sarafidis; Igor Rudenco; Vasilios Raptis; Kali Makedou; Areti Makedou; Dimirios M. Grekas

2007-01-01

317

Effects of dietary baicalin supplementation on iron overload-induced mouse liver oxidative injury  

Microsoft Academic Search

Iron overload is one of the most common metal related toxicity. Under this circumstance, excessive iron deposition in liver will lead to further injury such as hepatocellular necrosis, inflammation, fibrosis, and in some cases even to carcinoma. In this paper, the effect of a nature flavonoid, baicalin, on iron overload-induced mouse liver oxidative injury has been studied. It was found

Yuling Zhao; Hailing Li; Zhonghong Gao; Huibi Xu

2005-01-01

318

Mechanistic insight into halide oxidation by non-heme iron complexes. Haloperoxidase versus halogenase activity.  

PubMed

This work presents the first detailed study on mechanistic aspects of halide oxidation by non-heme iron complexes. We show that while iron(iii)-hydroperoxo complexes oxidise halides via oxygen atom transfer, the corresponding iron(iv)-oxo complex reacts via electron transfer. PMID:24136302

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

2013-10-29

319

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

Microsoft Academic Search

Mariprofundus ferrooxydans strain PV-1 is a lithoautotrophic iron-oxidizing proteobacterium isolated from the Loihi Seamount in Hawaii. As cells grow, they form filaments upon which iron minerals are deposited. Based on similarities in morphology, these structures appear to accumulate and form the bulk of iron mats at Loihi. Furthermore, Mariprofundus has been observed in a number of other seafloor mat samples

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

2006-01-01

320

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

Microsoft Academic Search

Terrestrial lavas commonly contain up to 10 wt% of iron. Furthermore, rocks returned from the Moon indicate lunar lava containing up to 25 wt% of iron and planetary scientists estimated that the martian mantle has about 18 wt% of iron. An experimental challenge in dealing with Fe-bearing silicate melts is that the oxidation state, controlling the proportions of ferric and

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

2005-01-01

321

Catalytic conversions of chloroolefins over iron oxide nanoparticles 2. Isomerization of dichlorobutenes over iron oxide nanoparticles stabilized on the surface of ultradispersed poly(tetrafluoroethylene)  

Microsoft Academic Search

Nanosized iron oxides stabilized on the surface of ultradispersed poly(tetrafluoroethylene) (UPTFE) granules were synthesized\\u000a by the thermal destruction of iron formate in boiling bed of UPTFE on the surface of heated mineral oil. The particle size\\u000a of nanoparticles (?6 nm) containing 5, 10, and 16 wt.% Fe depends weakly on the temperature of synthesis and iron to polymer\\u000a ratio. The

T. N. Rostovshchikova; M. S. Korobov; D. A. Pankratov; G. Yu. Yurkov; S. P. Gubin

2005-01-01

322

Modulation of intracellular iron levels by oxidative stress implicates a novel role for iron in signal transduction  

PubMed Central

Reactive oxygen species (ROS) display cytotoxicity that can be exacerbated by iron. Paradoxically, HeLa cells treated with the ROS-generators menadione and 2,3-dimethoxy-1,4-naphthoquinone display increased free labile iron. HeLa cells exposed to ROS undergo apoptosis but iron chelation limits the extent of cell death suggesting the rise in intracellular iron plays a signaling role in this pathway. This idea is supported by the fact that iron chelation also alters the pattern of ROS-induced phosphorylation of stress-activated protein kinases SAPK/JNK and p38 MAPK. Thus, ROS-induced increases in cellular free iron contribute to signaling events triggered during oxidative stress response.

Deb, Suman; Johnson, Erin E.; Robalinho-Teixeira, Raquel L.

2010-01-01

323

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

324

Preparation of Monodisperse Iron Oxide Nanoparticles via the Synthesis and Decomposition of Iron Fatty Acid Complexes  

NASA Astrophysics Data System (ADS)

Iron fatty acid complexes (IFACs) are prepared via the dissolution of porous hematite powder in hot unsaturated fatty acid. The IFACs are then decomposed in five different organic solvents under reflux conditions in the presence of the respective fatty acid. The XRD analysis results indicate that the resulting NPs comprise a mixture of wustite, magnetite, and maghemite phases. The solvents with a higher boiling point prompt the formation of larger NPs containing wustite as the major component, while those with a lower boiling point produce smaller NPs with maghemite as the major component. In addition, it is shown that unstable NPs with a mixed wustite-magnetite composition can be oxidized to pure maghemite by extending the reaction time or using an oxidizing agent.

Chen, Chih-Jung; Lai, Hsin-Yi; Lin, Chee-Cheng; Wang, Jiun-Shen; Chiang, Ray-Kuang

2009-11-01

325

Preparation of Monodisperse Iron Oxide Nanoparticles via the Synthesis and Decomposition of Iron Fatty Acid Complexes.  

PubMed

Iron fatty acid complexes (IFACs) are prepared via the dissolution of porous hematite powder in hot unsaturated fatty acid. The IFACs are then decomposed in five different organic solvents under reflux conditions in the presence of the respective fatty acid. The XRD analysis results indicate that the resulting NPs comprise a mixture of wustite, magnetite, and maghemite phases. The solvents with a higher boiling point prompt the formation of larger NPs containing wustite as the major component, while those with a lower boiling point produce smaller NPs with maghemite as the major component. In addition, it is shown that unstable NPs with a mixed wustite-magnetite composition can be oxidized to pure maghemite by extending the reaction time or using an oxidizing agent. PMID:20628451

Chen, Chih-Jung; Lai, Hsin-Yi; Lin, Chee-Cheng; Wang, Jiun-Shen; Chiang, Ray-Kuang

2009-07-30

326

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

327

Mercury mobilization by chemical and microbial iron oxide reduction in soils of French Guyana  

Microsoft Academic Search

Iron oxy(hydr)oxides (oxides) are important mercury sinks in tropical oxisols and the geochemistry of these two elements are\\u000a thus closely entwined. We hypothesized that bacterial Fe-oxide reduction in anoxic conditions could be a significant mechanism\\u000a for mobilizing associated Hg. Iron oxide and mercury solubilisation in presence of two chemical reducers (ascorbate and dithionite,\\u000a dissolving amorphous and amorphous plus well crystallized

Jennifer Harris-Hellal; Michel Grimaldi; Evelyne Garnier-Zarli; Noureddine Bousserrhine

2011-01-01

328

Mesophilic, Circumneutral Anaerobic Iron Oxidation as a Remediation Mechanism for Radionuclides, Nitrate and Perchlorate  

Microsoft Academic Search

Iron oxidation is a novel anaerobic metabolism where microorganisms obtain reducing equivalents from the oxidization of Fe(II) and assimilate carbon from organic carbon compounds or CO2. Recent evidence indicates that in combination with the activity of dissimilatory Fe(III)-reducing bacteria, anaerobic microbial Fe(II) oxidation can also contribute to the global iron redox cycle. Studies have also proved that Fe(II)- oxidation is

S. Bose; J. C. Thrash; J. D. Coates

2008-01-01

329

Catalytic cracking of catechols and hydroquinones in the presence of nano-particle iron oxide  

Microsoft Academic Search

Nano-particle “iron oxide” was found to be an effective catalyst for the pyrolytic conversion of phenolic and other environmentally harmful aromatic compounds evolved during the combustion and pyrolysis of biomass. Catalytic cracking and oxidation of catechol, 3-methylcatechol, hydroquinone, 2-methylhydroquinone, and 2,3-dimethylhydroquinone over the temperature range of 180–430°C and under partially oxidative conditions were studied using nano-particle “iron oxide”. We employed

Eun-Jae Shin; Donald E. Miser; W. Geoffrey Chan; Mohammad R. Hajaligol

2005-01-01

330

Iron-catalyzed tandem oxidative coupling and annulation: an efficient approach to construct polysubstituted benzofurans.  

PubMed

The combination of FeCl(3) x 6 H(2)O and di-tert-butyl peroxide offers a novel and efficient method for the construction of polysubstituted benzofurans 3 from the reaction of simple phenols 1 and beta-keto esters 2, which are expected to give coumarins in the well-known Pechmann condensation. A variety of phenols reacted with beta-keto esters to provide a range of benzofuran products in moderate to excellent yields. The regio-specific annulation was proven by the X-ray molecular structure of the product 3k. Hydrate of FeCl(3) is essential for an achievement of the present transformation. The kinetic isotopic effect (KIE) experiments were carried out by competition experiments and displayed a k(H)/k(D) = 1.0 +/- 0.1. The kinetic isotopic effect indicated that aromatic C-H bond cleavage is not involved in the rate-determining steps of the present transformation. Moreover, the results clearly demonstrate that the dichotomous catalytic behavior of the iron catalyst, which is transition-metal catalyst in the oxidative coupling step and Lewis acid in the condensation step. The possible intermediate 5 was synthesized and converted into the desired benzofuran 3a under the reaction conditions. A tentative mechanism of the formation of benzofurans 3 was proposed. PMID:19899754

Guo, Xingwei; Yu, Rong; Li, Haijun; Li, Zhiping

2009-12-01

331

Atomistic Simulations of Uranium Incorporation into Iron (Hydr)Oxides  

SciTech Connect

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

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

2011-04-29

332

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

333

XPS, IR, and Mossbauer studies of lithium phosphate glasses containing iron oxides  

Microsoft Academic Search

Lithium phosphate glasses with different iron oxide contents were prepared using a rapid quenching technique and their glass transition temperatures (Tg), densities (d), and refractive indexes (n) were measured. X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), and Mossbauer spectroscopy have been used to study structure of the glasses and oxidation states of iron. These results indicate that both the Fe2+

Guomei Wang; Jiaheng Lei; Huaishun Yun; Liping Guo; Baohui Jin

1991-01-01

334

Magnetic Behavior of O-Carboxymethylchitosan Bounded With Iron Oxide Particles  

Microsoft Academic Search

Two magnetic chitosan derivatives of O-carboxymethylchitosan bounded with iron oxide particles have been prepared by in situ coprecipitation and incorporation methods. The investigations were focused on structural and magnetic aspects-morphology of iron oxide particles and overall magnetic behavior of these two magnetic chitosan microspheres. It has been shown that the magnetic properties of the sample prepared by the incorporation method

A. Dusza; M. Wojtyniak; N. Nedelko; A. Slawska-Waniewska; J. M. Greneche; C. A. Rodrigues; C. Burger; C. Stringari; A. Debrassi

2010-01-01

335

Investigation of antioxidant property of iron oxide particlesby 1'-1'diphenylpicryl-hydrazyle (DPPH) method  

Microsoft Academic Search

We investigated the antioxidant properties of iron oxide particles. Particles of different sizes were synthesized and their antioxidant potency was investigated by using an in vitro system. The antioxidant capacity assay was done via a modified DPPH method for insoluble solid materials. The percentages of DPPH scavenging were calculated for iron oxide particles. The particles were found to show antioxidant

S. Paul; J. P. Saikia; S. K. Samdarshi; B. K. Konwar

2009-01-01

336

Investigation of antioxidant property of iron oxide particlesby 1?-1?diphenylpicryl-hydrazyle (DPPH) method  

Microsoft Academic Search

We investigated the antioxidant properties of iron oxide particles. Particles of different sizes were synthesized and their antioxidant potency was investigated by using an in vitro system. The antioxidant capacity assay was done via a modified DPPH method for insoluble solid materials. The percentages of DPPH scavenging were calculated for iron oxide particles. The particles were found to show antioxidant

S. Paul; J. P. Saikia; S. K. Samdarshi; B. K. Konwar

2009-01-01

337

On the synthesis and magnetic properties of multiwall carbon nanotube-superparamagnetic iron oxide nanoparticle nanocomposites  

Microsoft Academic Search

Multiwall carbon nanotubes (MWCNTs) possessing an average inner diameter of 150 nm were synthesized by template assisted chemical vapor deposition over an alumina template. Aqueous ferrofluid based on superparamagnetic iron oxide nanoparticles (SPIONs) was prepared by a controlled co-precipitation technique, and this ferrofluid was used to fill the MWCNTs by nanocapillarity. The filling of nanotubes with iron oxide nanoparticles was

T. N. Narayanan; A. P. Reena Mary; M. M. Shaijumon; Lijie Ci; P. M. Ajayan; M. R. Anantharaman

2009-01-01

338

Activated carbon\\/iron oxide magnetic composites for the adsorption of contaminants in water  

Microsoft Academic Search

In this work the adsorption features of activated carbon and the magnetic properties of iron oxides were combined in a composite to produce magnetic adsorbents. These magnetic particles can be used as adsorbent for a wide range of contaminants in water and can subsequently be removed from the medium by a simple magnetic procedure. Activated carbon\\/iron oxide magnetic composites were

Luiz C. A. Oliveira; Rachel. V. R. A. Rios; José D. Fabris; V. Garg; Karim Sapag; Rochel M. Lago

2002-01-01

339

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

Microsoft Academic Search

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

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

2011-01-01

340

Clay–iron oxide magnetic composites for the adsorption of contaminants in water  

Microsoft Academic Search

In this work, the adsorption features of clays with the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. These magnetic composites can be used as adsorbent for contaminants in water and can be subsequently removed from the medium by a simple magnetic process. The bentonite–iron oxide magnetic composites have been prepared with

Luiz C. A Oliveira; Rachel V. R. A Rios; José D Fabris; Karim Sapag; Vijayendra K Garg; Rochel M Lago

2003-01-01

341

A synthetic macromolecule as MRI detectable drug carriers: Aminodextran-coated iron oxide nanoparticles  

Microsoft Academic Search

A new synthetic macromolecule, aminodextran-coated iron oxide nanoparticles, was synthesized as drug carrier detectable using magnetic resonance imaging (MRI) technique. The synthesis process starts with a 2-step reaction that attaches a high density of amino groups to a dextran backbone. These macromolecules were coated with magnetic iron oxide molecules by a chemical reaction that can carry several molecules such as

Mohammad Reza Saboktakin; Roya M. Tabatabaie; Abel Maharramov; Mohammad Ali Ramazanov

2010-01-01

342

Intravenous Iron Exacerbates Oxidative DNA Damage in Peripheral Blood Lymphocytes in Chronic Hemodialysis Patients  

Microsoft Academic Search

Patients undergoing maintenance hemodialysis have elevated markers of oxidative stress, but the reasons for this are not fully understood. Intravenous administration of iron, which many of these patients receive, may provoke the generation of bioactive iron, which enhances oxidative stress and lipid peroxidation. In this study, 110 hemodialysis patients were randomly assigned to five groups that were administered single intravenous

Ko-Lin Kuo; Szu-Chun Hung; Yau-Huei Wei; Der-Cherng Tarng

343

Prevention of oxidant-induced cell death by lysosomotropic iron chelators  

Microsoft Academic Search

Intralysosomal iron powerfully synergizes oxidant-induced cellular damage. The iron chelator, desferrioxamine (DFO), protects cultured cells against oxidant challenge but pharmacologically effective concentrations of this drug cannot readily be achieved in vivo. DFO localizes almost exclusively within the lysosomes following endocytic uptake, suggesting that truly lysosomotropic chelators might be even more effective. We hypothesized that an amine derivative of ?-lipoamide (LM),

Hans L Persson; Zhengquan Yu; Oren Tirosh; John W Eaton; Ulf T Brunk

2003-01-01

344

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

National Technical Information Service (NTIS)

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 c...

R. Blake

1991-01-01

345

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

Microsoft Academic Search

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

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

2009-01-01

346

Enzymes of respiratory iron oxidation. Progress report, March 1990--June 1992  

SciTech Connect

This report describes experimental progress in characterizing and identifying redox proteins in a number of iron-oxidizing bacteria. Sections of the paper are entitled (1) In Situ electrolysis was explored to achieve enhanced yields of iron-oxidizing bacteria, (2)Structure/function studies were performed on redox-active biomolecules from Thiobacillus ferrooxidans, (3) Novel redox-active biomolecules were demonstrated in other iron autotrophs, and (4) New probes of metalloprotein electron-transfer reactions were synthesized and characterized.

Blake, R. II

1992-12-31

347

Iron Oxide Thin Film Deposition on Si(100) Substrate using MOCVD Method  

Microsoft Academic Search

We have deposited iron oxide thin films on Si(100) substrates using single molecular precursor in the range of 300–500°C by metal?organic chemical vapor deposition (MOCVD) method. Iron pentacarbonyl [Fe(CO)5] and oxygen gas were used as the iron source and oxidizing agent, respectively. The Si(100) wafer was used a substrate and it was cleaned by sequential ultrasonic baths of acetone, ethanol,

2008-01-01

348

Rotating ring-disk electrode and spectroelectrochemical studies on the oxidation of iron in alkaline solutions  

Microsoft Academic Search

The investigation of the anodic oxidation of iron in alkaline solutions is important because it is used as a cathodic reaction in Fe\\/Ni and Fe\\/air batteries, and it is also related to the corrosion of iron. The electrochemical oxidation of iron has been studied in concentrated alkaline solutions employing rotating ring-disk electrode voltammetric and in situ spectroelectrochemical techniques. While four

Haiyan Zhang

1994-01-01

349

Enzymes of respiratory iron oxidation. Progress report, March 1990June 1992  

Microsoft Academic Search

This report describes experimental progress in characterizing and identifying redox proteins in a number of iron-oxidizing bacteria. Sections of the paper are entitled (1) In Situ electrolysis was explored to achieve enhanced yields of iron-oxidizing bacteria, (2)Structure\\/function studies were performed on redox-active biomolecules from Thiobacillus ferrooxidans, (3) Novel redox-active biomolecules were demonstrated in other iron autotrophs, and (4) New probes

Blake; R. II

1992-01-01

350

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.

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

2013-01-01

351

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

352

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

353

Preparation of iron oxide-entrapped chitosan nanoparticles for stem cell labeling.  

PubMed

This study intended to prepare iron oxide nanoparticle-entrapped chitosan (CS) nanoparticles for stem cell labeling. The nanoparticles were synthesized by polymerizing iron oxide nanoparticle-associated methacrylic acid monomer in the presence of CS. TEM revealed that the well-defined iron oxide nanoparticles were successfully encapsulated inside the CS nanoparticles. The effect of CS at different [NH(2)]/[COOH] molar ratios on particle size, surface charge, thermal stability and magnetic properties was determined systematically. Internalization and localization of the coated nanoparticles were evaluated by atomic absorption spectrometry and confocal laser scanning microscopy. The Kusa O cell line was chosen as a stem cell model. Interestingly, the uptake of iron oxide-entrapped CS nanoparticles was remarkably enhanced under magnetization and the nanoparticles were mostly located inside cellular compartments. It can be concluded that the iron oxide-entrapped CS nanoparticles have a strong potential for stem cell labeling. PMID:20537238

Chaleawlert-Umpon, Saowaluk; Mayen, Varissaporn; Manotham, Krissanapong; Pimpha, Nuttaporn

2010-06-09

354

Porous iron oxide ribbons grown on graphene for high-performance lithium storage.  

PubMed

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

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

2012-05-29

355

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

PubMed Central

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

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

2012-01-01

356

Recovery of zinc from leach residues with minimum iron dissolution using oxidative leaching.  

PubMed

Leaching was performed to recover zinc from a zinc leach residue which contained 9.87% Zn and 4.93% Fe. During sulfuric acid leaching, Fe was dissolved as well as Zn which can reduce the Zn extraction efficiency. Leaching the residue in the presence of an oxidizing reagent such as hydrogen peroxide or manganese dioxide significantly reduced the iron content of the leach liquor. Effect of pH, temperature, solid/liquid ratio, reaction time and hydrogen peroxide or manganese dioxide concentration on the recovery of zinc and iron in non-oxidative and oxidative leaching conditions were investigated. By using the optimum oxidative leaching conditions, iron recovery reduced from 70% in non-oxidative leaching to 0.4 and 5% in the presence of MnO(2) and H(2)O(2), respectively, with acceptable Zn recovery. This reduction in the iron content was due to the different iron compounds formed at different conditions. PMID:20516004

Alizadeh, Reza; Rashchi, Fereshteh; Vahidi, Ehsan

2010-06-01

357

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

NASA Astrophysics Data System (ADS)

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

Baker, Colin C.

358

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

PubMed

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

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

2013-04-12

359

The Intracellular Siderophore Ferricrocin Is Involved in Iron Storage, Oxidative-Stress Resistance, Germination, and Sexual Development in Aspergillus nidulans  

PubMed Central

Iron is required by most organisms, but an excess of this metal is potentially toxic. Consequently, uptake and intracellular storage of iron are tightly controlled. The filamentous fungus A. nidulans lacks the iron storage compound ferritin but possesses an intracellular siderophore, which is accumulated in a highly regulated manner as iron-free desferri-ferricrocin or iron-containing ferricrocin via transcriptional regulation of the nonribosomal peptide synthetase SidC. Biosynthesis of desferri-ferricrocin was low during iron-replete conditions but up-regulated by both iron starvation and intracellular iron excess, the latter caused by either a shift from iron-depleted to high-iron conditions or deregulation of iron uptake. Consequently, ferricrocin constituted only about 5% of the total iron content under iron-replete conditions but up to 64% during conditions of intracellular excess. In contrast, during iron starvation, desferri-ferricrocin was accumulated, which appears to represent a proactive strategy to prevent iron toxicity. Accumulation of the intracellular siderophore was also up-regulated by oxidative stress, which underscores the intertwining of iron metabolism and oxidative stress. Lack of the intracellular siderophore causes pleiotropic effects, as SidC deficiency results in (i) less-efficient utilization of iron, indicated by reduced growth under iron-depleted conditions and a higher iron demand under iron-replete conditions, (ii) delayed germination under iron-depleted conditions, (iii) increased sensitivity of conidia to oxidative stress, and (iv) elimination of cleistothecia formation in homothallic conditions.

Eisendle, Martin; Schrettl, Markus; Kragl, Claudia; Muller, Daniela; Illmer, Paul; Haas, Hubertus

2006-01-01

360

The intracellular siderophore ferricrocin is involved in iron storage, oxidative-stress resistance, germination, and sexual development in Aspergillus nidulans.  

PubMed

Iron is required by most organisms, but an excess of this metal is potentially toxic. Consequently, uptake and intracellular storage of iron are tightly controlled. The filamentous fungus A. nidulans lacks the iron storage compound ferritin but possesses an intracellular siderophore, which is accumulated in a highly regulated manner as iron-free desferri-ferricrocin or iron-containing ferricrocin via transcriptional regulation of the nonribosomal peptide synthetase SidC. Biosynthesis of desferri-ferricrocin was low during iron-replete conditions but up-regulated by both iron starvation and intracellular iron excess, the latter caused by either a shift from iron-depleted to high-iron conditions or deregulation of iron uptake. Consequently, ferricrocin constituted only about 5% of the total iron content under iron-replete conditions but up to 64% during conditions of intracellular excess. In contrast, during iron starvation, desferri-ferricrocin was accumulated, which appears to represent a proactive strategy to prevent iron toxicity. Accumulation of the intracellular siderophore was also up-regulated by oxidative stress, which underscores the intertwining of iron metabolism and oxidative stress. Lack of the intracellular siderophore causes pleiotropic effects, as SidC deficiency results in (i) less-efficient utilization of iron, indicated by reduced growth under iron-depleted conditions and a higher iron demand under iron-replete conditions, (ii) delayed germination under iron-depleted conditions, (iii) increased sensitivity of conidia to oxidative stress, and (iv) elimination of cleistothecia formation in homothallic conditions. PMID:17030991

Eisendle, Martin; Schrettl, Markus; Kragl, Claudia; Müller, Daniela; Illmer, Paul; Haas, Hubertus

2006-10-01

361

Gas-bubble effects on the formation of colloidal iron oxide nanocrystals.  

PubMed

This paper reports that gas bubbles can be used to tailor the kinetics of the nucleation and growth of inorganic-nanocrystals in a colloidal synthesis. We conducted a mechanistic study of the synthesis of colloidal iron oxide nanocrystals using gas bubbles generated by boiling solvents or artificial Ar bubbling. We identified that bubbling effects take place through absorbing local latent heat released from the exothermic reactions involved in the nucleation and growth of iron oxide nanocrystals. Our results show that gas bubbles display a stronger effect on the nucleation of iron oxide nanocrystals than on their growth. These results indicate that the nucleation and growth of iron oxide nanocrystals may rely on different types of chemical reactions between the iron-oleate decomposition products: the nucleation relies on the strongly exothermic, multiple-bond formation reactions, whereas the growth of iron oxide nanocrystals may primarily depend upon single-bond formation reactions. The identification of exothermic reactions is further consistent with our results in the synthesis of iron oxide nanocrystals with boiling solvents at reaction temperatures ranging from 290 to 365 °C, by which we determined the reaction enthalpy in the nucleation of iron oxide nanocrystals to be -142 ± 12 kJ/mol. Moreover, our results suggest that a prerequisite for effectively suppressing secondary nucleation in a colloidal synthesis is that the primary nucleation must produce a critical amount of nuclei, and this finding is important for a priori design of colloidal synthesis of monodispersed nanocrystals in general. PMID:21702497

Lynch, Jared; Zhuang, Jiaqi; Wang, Tie; LaMontagne, Derek; Wu, Huimeng; Cao, Y Charles

2011-07-22

362

Mechanisms in oxidation and sintering of magnetite iron ore green pellets  

Microsoft Academic Search

Thermal volume changes and oxidation mechanisms in magnetite iron ore green pellets balled with 0.5% bentonite binder, as a function of raw material fineness and pellet porosity, are shown. When a pellet starts to oxidize, a shell of hematite is formed around the pellet while the core still is magnetite. Dilatation curves were measured under non-oxidizing and oxidizing atmospheres to

S. P. E. Forsmo; P.-O. Samskog; B. M. T. Björkman

2008-01-01

363

Kinetics of nitrobenzene oxidation and iron crystallization in fluidized-bed Fenton process  

Microsoft Academic Search

This research investigated the nitrobenzene oxidation and iron removal by fluidized-bed Fenton process using metal oxide as the carriers. It was found that the removal efficiency of nitrobenzene was not affected in the presence of metal oxide. However, metal oxide could retard the degradation rate of nitrobenzene with Fenton process due to ferrous adsorption\\/complexation onto its surface leaving insufficient free

Jin Anotai; Pasootah Sakulkittimasak; Nonglak Boonrattanakij; Ming-Chun Lu

2009-01-01

364

Lipid and carbon isotopic evidence of methane-oxidizing and sulfate-reducing bacteria in association with gas hydrates from the Gulf of Mexico  

NASA Astrophysics Data System (ADS)

An integrated lipid biomarker carbon isotope approach reveals new insight to microbial methane oxidation in the Gulf of Mexico gas-hydrate system. Hydrate-bearing and hydrate-free sediments were collected from the Gulf of Mexico slope using a research submersible. Phospholipid fatty acids consist mainly of C16 C18 compounds, which are largely derived from bacteria. The phospholipid fatty acids suggest that total biomass is enhanced 11 30-fold in gas-hydrate bearing sediment compared to hydrate-free sediment. Lipid biomarkers indicative of sulfate-reducing bacteria are strongly depleted in 13C (?13C = -48‰ to -70‰) in the hydrate-bearing samples, suggesting that they are involved in the oxidation of methane (?13C = -47‰ for thermogenic methane and -70‰ for biogenic methane). Isotopic properties of other biomarkers suggest that sulfur-oxidizing bacteria (Beggiatoa) may also contribute to the lipid pool in hydrate-bearing samples, which are characterized by less negative ?13C values (to -11.2‰). In the hydrate-free sample, fatty acid biomarkers have ?13C values of -27.6‰ to -39.6‰, indicating that crude oil (average ˜-27‰) or terrestrial organic carbon (average ˜-20‰) are the likely carbon sources. Our results provide the first lipid biomarker stable isotope evidence that sulfate- reducing bacteria play an important role in anaerobic methane oxidation in the Gulf of Mexico gas hydrates. The coupled activities of methane-oxidizing and sulfate-reducing organisms contribute to the development of ecosystems in deep-sea environments and result in sequestration of carbon as buried organic carbon and authigenic carbonates. These have implications for studying climate change based on carbon budgets.

Zhang, Chuanlun L.; Li, Yiliang; Wall, Judy D.; Larsen, Lise; Sassen, Roger; Huang, Yongsong; Wang, Yi; Peacock, Aaron; White, David C.; Horita, Juske; Cole, David R.

2002-03-01

365

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

366

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

PubMed

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

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

2002-07-01

367

Numerical simulation for electrochemical cultivation of iron oxidizing bacteria.  

PubMed

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

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

2002-04-01

368

Electrochemical synthesis of magnetic iron oxide nanoparticles with controlled size.  

PubMed

We present a novel and facile method enabling synthesis of iron oxide nanoparticles, which are composed mainly of maghemite according to X-ray diffraction (XRD) and Mössbauer spectroscopy studies. The proposed process is realized by anodic iron polarization in deaerated LiCl solutions containing both water and ethanol. Water seems to play an important role in the synthesis. Morphology of the product was studied by means of transmission electron microscopy and XRD. In the solution containing almost 100% of water a black suspension of round shaped maghemite nanoparticles of 20-40 nm size is obtained. Regulating water concentration allows to control nanoparticle size, which is reduced to 4-6 nm for 5% of water with a possibility to reach intermediate sizes. For 3% or lower water concentration nanoparticles are of a needle-like shape and form a reddish suspension. In this case phase determination is problematic due to a small particle size with the thickness of roughly 3 nm. However, XRD studies indicate the presence of ferrihydrite. Coercivities of the materials are similar to those reported for nanoparticle magnetite powders, whereas the saturation magnetization values are considerably smaller. PMID:22207821

Starowicz, Maria; Starowicz, Pawe?; Zukrowski, Jan; Przewo?nik, Janusz; Lema?ski, Andrzej; Kapusta, Czes?aw; Bana?, Jacek

2011-11-27

369

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

Microsoft Academic Search

In this research the catalytic effect of copper compounds (ionic, oxide and oxide nanopowder) on the oxidation of ferrous iron by aeration was studied experimentally. When copper exists in solution, the oxidation rate of iron(ii) will increase. The experimental results showed that the oxidation rate increases with an increasing copper concentration. From the experimental data it can be determined that

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

2012-01-01

370

Superparamagnetic iron oxide nanoparticle targeting of MSCs in vascular injury.  

PubMed

Vascular occlusion can result in fatal myocardial infarction, stroke or loss of limb in peripheral arterial disease. Interventional balloon angioplasty is a common first line procedure for vascular disease treatment, but long term success is limited by restenosis and neointimal hyperplasia. Cellular therapies have been proposed to mitigate these issues; however efficacy is low, in part due to poor cell retention. We show that magnetic targeting of mesenchymal stem cells gives rise to a 6-fold increase in cell retention following balloon angioplasty in a rabbit model using a clinically applicable permanent magnet. Cells labelled with superparamagnetic iron oxide nanoparticles exhibit no negative effects on cell viability, differentiation or secretion patterns. The increase in stem cell retention leads to a reduction in restenosis three weeks after cell delivery. PMID:23237516

Riegler, Johannes; Liew, Aaron; Hynes, Sean O; Ortega, Daniel; O'Brien, Timothy; Day, Richard M; Richards, Toby; Sharif, Faisal; Pankhurst, Quentin A; Lythgoe, Mark F

2012-12-11

371

Fabrication of iron oxide nanoparticles using laser ablation in liquids  

NASA Astrophysics Data System (ADS)

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

Iwamoto, T.; Ishigaki, T.

2013-06-01

372

Iron oxide nanoparticles stabilized inside highly ordered mesoporous silica  

NASA Astrophysics Data System (ADS)

Nanosized iron oxide, a moderately large band-gap semiconductor and an essential component of optoelectrical and magnetic devices, has been prepared successfully inside the restricted internal pores of mesoporous silica material through in-situ reduction during impregnation. The samples were characterized by powder XRD, TEM, SEM/EDS, N_{2} adsorption, FT-IR and UV-visible spectroscopies. Characterization data indicated well-dispersed isolated nanoclusters of (Fe_{2}O_{3})_{n}, within the internal surface of 2D-hexagonal mesoporous silica structure. No occluded Fe/Fe_{2}O_{3} crystallites were observed at the external surface of the mesoporous silica nanocomposites. Inorganic mesoporous host, such as hydrophilic silica in the pore walls, directs a physical constraint necessary to prevent the creation of large Fe_{2}O_{3} agglomerates and enables the formation of nanosized Fe_{2}O_{3} particles inside the mesopore.

Bhaumik, A.; Samanta, S.; Mal, N. K.

2005-11-01

373

Ferromagnetic Resonance of Superparamagnetic Iron Oxide Nanoparticles for Biomedical Applications  

NASA Astrophysics Data System (ADS)

Ferromagnetic Resonance (FMR) techniques were used to investigate superparamagnetic iron oxide (SPIO) nanoparticles (NP) with different coatings and sizes ranging from 5 to 50 nm in diameter. The samples were synthesized by standard procedures with or without coating and fractionated by differential centrifugations to generate particles of different sizes. In order to improve detection sensitivity of pathological tissue changes such as atherosclerosis, smaller particles of less than 10 nm were selected for contrast-enhanced magnetic resonance imaging (MRI). We have investigated uncoated, lipid encapsulated and dextran coated SPIO samples in liquid suspension, dry, and in mixed-with-wax forms. The angular dependence of the FMR of NP with easy axes aligned and frozen in wax was measured. Shapes and shifts of FMR lines for each sample was analyzed for size and anisotropy. Examples of rabbit's aorta MRI T2-weigted images showing proton relaxation time T2 shortening due to the pretreatment with SPIO will be presented and discussed.

Wosik, Jaroslaw; Xue, Lian; Xie, Lei-Ming; Chan, Dan

2003-03-01

374

Ferrous iron oxidation by Thiobacillus ferrooxidans: inhibition with benzoic acid, sorbic acid and sodium lauryl sulfate  

SciTech Connect

Acid mine drainage is formed by the weathering or oxidation of pyritic material exposed during coal mining. The rate of pyritic material oxidation can be greatly accelerated by certain acidophilic bacteria such as Thiobacillus ferrooxidans which catalyse the oxidation of ferrous to ferric iron. A number of organic compounds, under laboratory conditions, can apparently inhibit both the oxidation of ferrous to ferric iron by T. ferrooxidans and the weathering of pyritic material by mixed cultures of acid mine drainage micro-organisms. Sodium lauryl sulphate (SLS), an anionic surfactant has proved effective in this respect. Benzoic acid, sorbic acid and SLS at low concentrations, each effectively inhibited bacterial oxidation of ferrous iron in batch cultures of T. ferrooxidans. The rate of chemical oxidation of ferrous iron in low pH, sterile, batch reactors was not substantially affected at the tested concentrations of any of the compounds.

Onysko, S.J.

1984-07-01

375

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

Microsoft Academic Search

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

R Balasubramaniam; A. V Ramesh Kumar

2000-01-01

376

Exchange bias in core-shell iron-iron oxide nanoclusters  

NASA Astrophysics Data System (ADS)

An exchange bias study has been performed on core-shell iron-iron oxide (Fe-Fe3O4) nanoclusters (NCs) of sizes 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 and magnetic frustration by the defects and voids present at the interface. 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 disappears with large cooling field (>0.1 kOe). It may be caused by the competition between the magnetization reversal and the magnetostatic interactions.

Kaur, M.; McCloy, J. S.; Qiang, Y.

2013-05-01

377

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

Microsoft Academic Search

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

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

2008-01-01

378

Elevated Ferritin Production, Iron Containment, and Oxidant Resistance in Hemin-Treated Leukemia Cells  

Microsoft Academic Search

Hemin (ferriprotoporphyrin IX), the oxidized prosthetic group of hemoglobin, is a source of potentially cytotoxic iron, but in chronic low doses can induce cytoprotection against iron-stimulated oxidative stress. The latter property of hemin has been examined, using murine L1210 cells and three different oxidant generating systems: (i) glucose\\/glucose oxidase, (ii) near-ultraviolet irradiation, and (iii) dye-mediated photodynamic action. Cells treated with

Fubao Lin; Albert W. Girotti

1997-01-01

379

Phase-controlled preparation of iron (oxyhydr)oxide nanocrystallines for heavy metal removal  

Microsoft Academic Search

Obtaining cost-effective iron (oxyhydr)oxide nanocrystallines is the essential prerequisite for their future extensive applications\\u000a in environmental remediation, such as the removal of heavy metals from contaminated waters. Here, various phases of iron (oxyhydr)oxide\\u000a nanocrystallines were simply synthesized from the phase-controlled transformation of amorphous hydrous ferric- or ferrous-oxide\\u000a in thermal solution with a certain ethanol\\/water ratio and with the presence of

Xiongye Zhao; Xuejun Guo; Zhifeng Yang; Hong Liu; Qingqing Qian

2011-01-01

380

Chemical weathering on Mars: Rate of oxidation of iron dissolved in brines  

NASA Astrophysics Data System (ADS)

Salts believed to occur in Martian regolith imply that brines occur on Mars, which may have facilitated the oxidation of dissolved Fe(2+) ions after they were released during chemical weathering of basaltic ferromagnesian silicate and iron sulfide minerals. Calculations show that the rate of oxidation of Fe(2+) ions at -35 C in a 6M chloride-sulfate brine that might exist on Mars is about 106 times slower that the oxidation rate of iron in ice-cold terrestrial seawater.

Burns, Roger G.

1993-03-01

381

Synthesis and characterization of polyethylenimine-based iron oxide composites as novel contrast agents for MRI  

Microsoft Academic Search

Object Use of polyethylenimines (PEIs) of different molecular weight and selected carboxylated-PEI derivatives (PEI-COOH) in the synthesis and stabilization of iron oxide nanoparticles, to obtain possible multifunctional contrast agents. Materials and methods Oxidation of Fe(II) at slightly elevated pH and temperature resulted in the formation of highly soluble and stable nanocomposites of iron oxides and polymer. Composites were characterized and

A. Masotti; A. Pitta; G. Ortaggi; M. Corti; C. Innocenti; A. Lascialfari; Massimo Marinone; P. Marzola; A. Daducci; A. Sbarbati; E. Micotti; F. Orsini; G. Poletti; C. Sangregorio

2009-01-01

382

Concurrent Dual Contrast for Cellular Magnetic Resonance Imaging Using Gadolinium Oxide and Iron Oxide Nanoparticles  

PubMed Central

Rationale and Objectives. Concurrent visualization of differential targets in cellular and molecular imaging is valuable for resolving processes spatially and temporally, as in monitoring different cell subtypes. The purpose of this study was to demonstrate concurrent, dual (positive and negative) contrast visualization on magnetic resonance imaging (MRI) of two colocalized cell populations labeled with Gadolinium “Gd” oxide and iron “Fe” oxide nanoparticles. Materials and Methods. Human aortic endothelial cells (EC) and smooth muscle cells (SMC) were labeled with various concentrations of Gd oxide and Fe oxide, respectively. MRI on single- or mixed-cell samples was performed at 7 tesla. Proper cell phenotype expressions, cell uptake of contrast agents, and the effect of labeling on cell viability and proliferation were also determined. Results. Both contrast agents were efficiently taken up by cells, with viability and proliferation largely unaffected. On MRI, the positive contrast associated with Gd oxide-labeled EC and negative contrast associated with Fe oxide-labeled SMC discriminated the presence of each cell type, whether it existed alone or colocalized in a mixed-cell sample. Conclusion. It is feasible to use Gd oxide and Fe oxide for dual contrast and concurrent discrimination of two colocalized cell populations on MRI at 7 tesla.

Loai, Yasir; Ganesh, Tameshwar; Margaret Cheng, Hai-Ling

2012-01-01

383

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

PubMed Central

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

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

2009-01-01

384

Inhibition of copper-catalyzed cysteine oxidation by nanomolar concentrations of iron salts.  

PubMed

Problems caused by the presence of adventitious metals in buffers and reagents are well recognized in studies of metal-catalyzed oxidation reactions. In most cases, metal contamination leads to an increase in rate, and chelating agents are inhibitory. In the present study, however, the rate of copper-catalyzed oxidation of cysteine was found to be increased by buffer purification with Chelex resin or by addition of micromolar concentrations of the specific iron chelator desferrioxamine (DFO). These effects are attributable to inhibition of copper-catalyzed oxidation by adventitious iron. In purified buffer at pH 7.25, containing 0.4 microM copper, cysteine was oxidized at a rate of 32 microM/min. Addition of iron salts to this buffer caused a dose-related decrease in this rate, up to a maximum of 85%. A 50% decrease in rate was recorded at an iron concentration of only 11 nM. Other transition metals were without effect. Similar effects of purification or addition of DFO on the rate of cysteine oxidation were seen in Tris, glycylglycine, Mops, and Pipes buffers. Catalase decreased the rate of cysteine oxidation, but the sensitivity to iron was similar in the presence and absence of catalase. Copper-catalyzed oxidation of cysteamine and reduced glutathione was much less sensitive to inhibition by iron. Our results offer an explanation for the conflicting literature reports of the effects of chelating agents and catalase on cysteine oxidation, and emphasize the need for buffer purification or addition of DFO in studies concerned with the oxidation or cytotoxicity of this thiol. The exceptional sensitivity of copper-catalyzed cysteine oxidation to iron makes this an attractive system for monitoring the iron content of buffers, and may also have application for determining the free iron content of physiological fluids. PMID:14990354

Munday, Rex; Munday, Christine M; Winterbourn, Christine C

2004-03-15

385

Role of the Ferroportin Iron-Responsive Element in Iron and Nitric Oxide Dependent Gene Regulation  

Microsoft Academic Search

ABSTRACTThe newly described iron transporter, ferroportin (MTP1, IREG1), is expressed in a variety of tissues including the duodenum and cells of the mononuclear phagocyte system (MPS). In the MPS, ferroportin is hypothesized to be a major exporter of iron scavenged from senescent erythrocytes. Changes in iron metabolism, including the sequestration of iron in the MPS, are characteristic of both acute

Xiao-bing Liu; Ping Hill; David J. Haile

2002-01-01

386

Iron oxide mineralogy and stable iron isotope composition in a Gleysol with petrogleyic properties  

NASA Astrophysics Data System (ADS)

Properties of Fe oxides are poorly understood in soils with fluctuating water tables and variable redox conditions. The objective of this research was to (i) characterize the mineralogical composition of Fe oxides and (ii) determine the relationship to the stable Fe isotope ratio in a soil with temporally and spatially sharp redox gradients. The lowland Gleysol (Petrogleyic) is in Northwest Germany, and consists of oximorphic soil horizons (Ah 0-15 cm, Bg 15-35 cm, CrBg 35-70 cm) developed from Holocene fluvial loam overlaying glaciofluvial sand with reductomorphic properties (2Cr horizon, +70 cm). Field measurements during the course of 28 months included the monitoring of groundwater table, soil redox potential, and analysis of the soil solutions. Solid Fe phases were studied by room temperature and cryogenic 57Fe Mössbauer spectroscopy, and stable Fe isotope compositions by multiple collector inductively coupled plasma mass spectrometry. Permanent reducing conditions occurred in the 2Cr horizon with dissolved Fe concentrations of 44.8 mg L-1 (median). Total Fe increased from 50 g kg-1 (Ah) over 316 g kg-1 (Bg) up to 412 g kg-1 (CrBg), and was lowest in the 2Cr horizon (7 g kg-1). Ferrihydrite (51% of total Fe) was dominant over goethite (24%) in the Ah horizon. Conversely, nanogoethite dominated both the Bg (94%) and CrBg (86%) horizons. Iron in siderite amounted to 7% in the CrBg horizon. Iron isotope compositions yielded a range of ?57Fe values from +0.29‰ (Ah horizon) to -0.30‰ (Bg horizon). In contrast to the overlying CrBg (?57Fe = -0.19‰) and Bg horizons, the 2Cr horizon is characterized by a relatively high ?57Fe value of +0.22‰.

Mansfeldt, T.; Schuth, S.

2012-04-01

387

Noncompetitive inhibition by L-cysteine and activation by L-glutamate of the iron-oxidizing activity of a mixotrophic iron-oxidizing bacterium strain OKM-9.  

PubMed

A mesophilic, mixotrophic iron-oxidizing bacterium strain OKM-9 uses ferrous iron as a sole source of energy and L-glutamate as a sole source of cellular carbon. Uptake of L-glutamate into OKM-9 cells is absolutely dependent on ferrous iron oxidation. Thus, the Fe(2+)-dependent L-glutamate uptake system of strain OKM-9 is crucial for the bacterium to grow mixotrophically in iron medium with L-glutamate. The relationship between iron oxidation and L-glutamate transport activities was studied. Iron oxidase containing cytochrome a was purified 9-fold from the plasma membrane of OKM-9. A purified iron oxidase showed one rust-colored band following disc gel electrophoresis after incubation with Fe(2+). The Fe(2+)-dependent L-glutamate transport system was also purified 14.5-fold from the plasma membrane using the same purification steps as for iron oxidase. Fe(2+)-dependent L-glutamate and L-cysteine uptake activities of OKM-9 were 0.36 and 0.24 nmol/mg/min, respectively, when a concentration of 18 mM of these amino acids was used as a substrate. Both uptake activities were completely inhibited by potassium cyanide (KCN), suggesting that cytochrome a in the iron oxidase is involved in the transport process. The iron-oxidizing activity of strain OKM-9 was activated 1.7-fold by 80 mM L-glutamate. In contrast, the activity was noncompetitively inhibited by L-cysteine. The Michaelis constant of iron oxidase for Fe(2+) was 12.6 mM and the inhibition constant for L-cysteine was 41.6 mM. A marked inhibition of iron oxidase by 50 mM L-cysteine was completely reversed by the addition of 60 mM L-glutamate. The results suggest the possibility that iron oxidase has a binding site for L-cysteine and the cysteine first bound to the iron oxidase was replaced by the added L-glutamate. PMID:16233671

Sugio, Tsuyoshi; Inoue, Takao; Kitano, Yoshiki; Takeuchi, Fumiaki; Kamimura, Kazuo

2004-01-01

388

Plasma-induced grafting of cyclodextrin onto multiwall carbon nanotube/iron oxides for adsorbent application.  

PubMed

The magnetic composite of beta-cyclodextrin grafted onto multiwalled carbon nanotubes/iron oxides (denoted as MWCNTs/iron oxides/CD) was synthesized using the plasma-induced grafting technique and was developed for the removal of inorganic and organic pollutants from aqueous solutions. The characteristic results of Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and thermogravimetric analysis (TGA) showed that beta-CD was grafted onto the MWCNTs/iron oxides. The grafted beta-CD on the MWCNTs/iron oxides contributed to an enhancement of the adsorption capacity because of the strong abilities of the multiple hydroxyl groups and the inner cores of the hydrophobic cavity in beta-CD to form complexes with metal ions and organic pollutants. MWCNTs/iron oxides/CD can be separated and recovered from solution by magnetic separation. The adsorption of Pb(II) on MWCNTs/iron oxides/CD was found to be dependent on pH, and the adsorption of 1-naphthol was found to be independent of pH. The results show that the magnetic composite of MWCNTs/iron oxides/CD is a promising composite material for the preconcentration and separation of inorganic and organic pollutants from aqueous solutions in environmental pollution cleanup. PMID:20438087

Hu, Jun; Shao, Dadong; Chen, Changlun; Sheng, Guodong; Li, Jiaxing; Wang, Xiangke; Nagatsu, Masaaki

2010-05-27

389

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

390

Iron oxide nanoparticles-chitosan composite based glucose biosensor.  

PubMed

Iron oxide (Fe(3)O(4)) nanoparticles prepared using co-precipitation method have been dispersed in chitosan (CH) solution to fabricate nanocomposite film on indium-tin oxide (ITO) glass plate. Glucose oxidase (GOx) has been immobilized onto this CH-Fe(3)O(4) nanocomposite film via physical adsorption. The size of the Fe(3)O(4) nanoparticles estimated using X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) has been found to be approximately 22 nm. The CH-Fe(3)O(4) nanocomposite film and GOx/CH-Fe(3)O(4)/ITO bioelectrode have been characterized using UV-visible and Fourier transform infrared (FTIR) spectroscopic and scanning electron microscopy (SEM) techniques, respectively. This GOx/CH-Fe(3)O(4)/ITO nanocomposite bioelectrode has response time of 5s, linearity as 10-400 mgdL(-1) of glucose, sensitivity as 9.3 microA/(mgdLcm(2)) and shelf life of about 8 weeks under refrigerated conditions. The value of Michaelis-Menten (K(m)) constant obtained as 0.141 mM indicates high affinity of immobilized GOx towards the substrate (glucose). PMID:18692384

Kaushik, Ajeet; Khan, Raju; Solanki, Pratima R; Pandey, Pratibha; Alam, Javed; Ahmad, Sharif; Malhotra, B D

2008-07-01

391

Single-cell nanotoxicity assays of superparamagnetic iron oxide nanoparticles.  

PubMed

Properly evaluating the nanotoxicity of nanoparticles involves much more than bulk-cell assays of cell death by necrosis. Cells exposed to nanoparticles may undergo repairable oxidative stress and DNA damage or be induced into apoptosis. Exposure to nanoparticles may cause the cells to alter their proliferation or differentiation or their cell-cell signaling with neighboring cells in a tissue. Nanoparticles are usually more toxic to some cell subpopulations than others, and toxicity often varies with cell cycle. All of these facts dictate that any nanotoxicity assay must be at the single-cell level and must try whenever feasible and reasonable to include many of these other factors. Focusing on one type of quantitative measure of nanotoxicity, we describe flow and scanning image cytometry approaches to measuring nanotoxicity at the single-cell level by using a commonly used assay for distinguishing between necrotic and apoptotic causes of cell death by one type of nanoparticle. Flow cytometry is fast and quantitative, provided that the cells can be prepared into a single-cell suspension for analysis. But when cells cannot be put into suspension without altering nanotoxicity results, or if morphology, attachment, and stain location are important, a scanning image cytometry approach must be used. Both methods are described with application to a particular type of nanoparticle, a superparamagnetic iron oxide nanoparticle (SPION), as an example of how these assays may be applied to the more general problem of determining the effects of nanomaterial exposure to living cells. PMID:22975957

Eustaquio, Trisha; Leary, James F

2012-01-01

392

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

PubMed

Luminescence, induced by dehydration and by wetting with hydrazine and unsymmetrically substituted hydrazine, and related ESR spectra have been observed from several kaolinites, synthetically hydrated kaolinites, and metahalloysites. The amine-wetting luminescence results suggest that intercalation, not a chemiluminescence reaction, is the luminescence trigger. Correlation between hydration-induced luminescence and g = 2 ESR signals associated with O(-)-centres in several natural halloysites, and concurrent diminution of the intensity of both these signal types as a function of aging in two 8.4 angstroms synthetically hydrated, kaolinites, confirm a previously-reported relationship between the luminescence induced by dehydration and in the presence of O(-)-centres (holes, i.e., electron vacancies) in the tetrahedral sheet. Furthermore, the ESR spectra of the 8.4 angstroms hydrate showed a concurrent change in the line shape of the g = 4 signal from a shape usually associated with structural Fe in an ordered kaolinite, to a simpler one typically observed in more disordered kaolinite, halloysite, and montmorillonite. Either structural Fe centres and the O(-)-centres interact, or both are subject to factors previously associated with degree of order. The results question the long-term stability of the 8.4 angstroms hydrate, although XRD does not indicate interlayer collapse over this period. Complex inter-relationships are shown between intercalation, stored energy, structural Fe, and the degree of hydration which may be reflected in catalytic as well as spectroscopic properties of the clays. PMID:11542170

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

1989-01-01

393

A cast-mold approach to iron oxide and Pt/iron oxide nanocontainers and nanoparticles with a reactive concave surface.  

PubMed

We report the synthesis of various iron oxide nanocontainers and Pt-iron oxide nanoparticles based on a cast-mold approach, starting from nanoparticles having a metal core (either Au or AuPt) and an iron oxide shell. Upon annealing, the particles evolve to asymmetric core-shells and then to heterodimers. If iodine is used to leach Au out of these structures, asymmetric core-shells evolve into "nanocontainers", that is, iron oxide nanoparticles enclosing a cavity accessible through nanometer-sized pores, while heterodimers evolve into particles with a concave region. When starting from a metal domain made of AuPt, selective leaching of the Au atoms yields the same iron oxide nanoparticle morphologies but now encasing Pt domains (in their concave region or in their cavity). We found that the concave nanoparticles are capable of destabilizing Au nanocrystals of sizes matching that of the concave region. In addition, for the nanocontainers, we propose two different applications: (i) we demonstrate loading of the cavity region of the nanocontainers with the antitumoral drug cis-platin; and (ii) we show that nanocontainers encasing Pt domains can act as recoverable photocatalysts for the reduction of a model dye. PMID:21268642

George, Chandramohan; Dorfs, Dirk; Bertoni, Giovanni; Falqui, Andrea; Genovese, Alessandro; Pellegrino, Teresa; Roig, Anna; Quarta, Alessandra; Comparelli, Roberto; Curri, M Lucia; Cingolani, Roberto; Manna, Liberato

2011-01-26

394

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

395

Sorption of two aromatic acids onto iron oxides: experimental study and modeling.  

PubMed

The transport of aromatic carboxylate compounds in the environment can be strongly influenced by adsorption onto certain minerals, such as iron oxides and hydroxides, found in ground water and soils. Batch experiments with five iron oxides were conducted to quantify the contributions to adsorption from different iron mineral surfaces and compare adsorption characteristics of selected organic acids (gentisic acid (GA) and 1-hydroxy-2-naphthoic acid (HNA)). Because of their widespread abundance in soils and sediments, goethite, lepidocrocite, ferrihydrite, hematite, and magnetite were investigated. Sorption of two organic acids onto iron oxides was examined over a wide range of conditions (pH, ionic strength, and sorbate concentration). Specific surface area and mineral surface charge proved be important for the adsorption of these compounds. The sorption isotherm was described well by the Tempkin equation for both organic acids, with the adsorption constant higher for HNA than GA. For modeling the sorption edges of ferrihydrite and hematite, surface reactions involving the formation of mononuclear (1:1) surface species were proposed. These results indicate that the generalized two-layer model, with the assumption of homogeneous surface sites, could predict sorption on iron oxides over a range of pH conditions. The results of this study suggest that the mineralogy of the iron oxides and the pH value should be considered when predicting sorption of aromatic acids onto iron oxides and their fate in the soil and the environment. PMID:17303153

Hanna, K

2007-02-15

396

Characterization of Iron Oxides Commonly Formed as Corrosion Products on Steel  

NASA Astrophysics Data System (ADS)

For fundamental studies of the atmospheric corrosion of steel, it is useful to identify the iron oxide phases present in rust layers. The nine iron oxide phases, iron hydroxide (Fe(OH)2), iron trihydroxide (Fe(OH)3), goethite (?-FeOOH), akaganeite (?-FeOOH), lepidocrocite (?-FeOOH), feroxyhite (?-FeOOH), hematite (?-Fe2O3), maghemite (?-Fe2O3) and magnetite (Fe3O4) are among those which have been reported to be present in the corrosion coatings on steel. Each iron oxide phase is uniquely characterized by different hyperfine parameters from Mössbauer analysis, at temperatures of 300K, 77K and 4K. Many of these oxide phases can also be identified by use of Raman spectroscopy. The relative fraction of each iron oxide can be accurately determined from the Mössbauer subspectral area and recoil-free fraction of each phase. The different Mössbauer geometries also provide some depth dependent phase identification for corrosion layers present on the steel substrate. Micro-Raman spectroscopy can be used to uniquely identify each iron oxide phase to a high spatial resolution of about 1 µm.

Oh, Sei J.; Cook, D. C.; Townsend, H. E.

1998-12-01

397

Respiratory interactions of soil bacteria with (semi)conductive iron-oxide minerals.  

PubMed

Pure-culture studies have shown that dissimilatory metal-reducing bacteria are able to utilize iron-oxide nanoparticles as electron conduits for reducing distant terminal acceptors; however, the ecological relevance of such energy metabolism is poorly understood. Here, soil microbial communities were grown in electrochemical cells with acetate as the electron donor and electrodes (poised at 0.2 V versus Ag/AgCl) as the electron acceptors in the presence and absence of iron-oxide nanoparticles, and respiratory current generation and community structures were analysed. Irrespective of the iron-oxide species (hematite, magnetite or ferrihydrite), the supplementation with iron-oxide minerals resulted in large increases (over 30-fold) in current, while only a moderate increase (?10-fold) was observed in the presence of soluble ferric/ferrous irons. During the current generation, insulative ferrihydrite was transformed into semiconductive goethite. Clone-library analyses of 16S rRNA gene fragments PCR-amplified from the soil microbial communities revealed that iron-oxide supplementation facilitated the occurrence of Geobacter species affiliated with subsurface clades 1 and 2. We suggest that subsurface-clade Geobacter species preferentially thrive in soil by utilizing (semi)conductive iron oxides for their respiration. PMID:20561016

Kato, Souichiro; Nakamura, Ryuhei; Kai, Fumiyoshi; Watanabe, Kazuya; Hashimoto, Kazuhito

2010-12-01

398

Catalytic conversions of chloroolefins over iron oxide nanoparticles 1. Isomerization of dichlorobutenes in the presence of iron oxide nanopaticles immobilized on silicas with different structures  

Microsoft Academic Search

The influence of the support nature and electronic state of iron oxide nanoclusters on the catalytic properties of supported\\u000a systems was studied for dichlorobutene isomerization. A sample with a Fe content of 2.5 wt.% on the activated silica matrix\\u000a containing FeIII and FeII ions in the paramagnetic state exhibits the highest activity. The activity of iron on silica gel enhances

T. N. Rostovshchikova; V. V. Smirnov; M. V. Tsodikov; O. V. Bukhtenko; Yu. V. Maksimov; O. I. Kiseleva; D. A. Pankratov

2005-01-01

399

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

400

THE OXIDATION PROPERTIES OF IRON - NICKEL ALLOYS IN CARBON DIOXIDE - CARBON MONOXIDE ATMOSPHERES AT 1000°C  

Microsoft Academic Search

In this thesis, the results of oxidation tests carried out on iron- nickel alloys in carbon dioxide - carbon monoxide atmospheres at 1000°C are presented. Linear oxidation kinetics were observed for the formation of wustite on alloys containing up to 50 weight % nickel. Spinel oxides appear on alloys containing greater than 50 % nickel. A subscale developed in all

Larry Arthur Morris

1965-01-01

401

Oxidation State of Iron in SNC Meteorites as Studied by Mössbauer Spectroscopy  

Microsoft Academic Search

Mössbauer investigations of three meteorites of the type SNC-achondrites are reported. The results are compared with Mössbauer spectra of other meteorites, and selected terrestrial and lunar rocks. Through the oxidation state of iron in the pyroxenes and magnetic oxides studied, the work confirms that the mantle of the Earth is highly oxidized compared with the mantle of asteroidal bodies and

V W A Vieira; T V V Costa; H G Jensen; J M Knudsen; M Olsen; L Vistisen

1986-01-01

402

Oxidation state of iron in SNC meteorites as studied by Moessbauer spectroscopy  

Microsoft Academic Search

Moessbauer investigations of three meteorites of the type SNC-achondrites are reported. The results are compared with Moessbauer spectra of other meteorites, and selected terrestrial and lunar rocks. Through the oxidation state of iron in the pyroxenes and magnetic oxides studied, the work confirms that the mantle of the earth is highly oxidized compared with the mantle of asteroidal bodies and

V. W. A. Vieira; T. V. V. Costa; H. G. Jensen; J. M. Knudsen; M. Olsen

1986-01-01

403

Comparative Effects of Copper, Iron, Vanadium and Titanium on Low Density Lipoprotein Oxidation in vitro  

Microsoft Academic Search

Introduction: Oxidation of low density lipoprotein (LDL) has been strongly implicated in the phathogenesis of atherosclerosis. The use of oxidants in dietary food stuff may lead to the production of oxidized LDL and may increase both the development and the progression of atherosclerosis. The present work investigated the effects of some elements including: copper (Cu), iron (Fe), vanadium (V) and

Mohsen Ani; Ali Asghar Moshtaghie; Hassan Ahmadvand

2007-01-01

404

Induction of protein oxidation by intravenous iron in hemodialysis patients: Role of inflammation  

Microsoft Academic Search

Background: Oxidative stress and inflammation contribute to the high prevalence and severity of atherosclerosis, infections, and ?2-microglobulin amyloidosis; and thus, to reduced survival rate and quality of life in hemodialysis (HD) patients. Inflammation induces oxidative stress by production of the oxidants: superoxide anion, hydrogen peroxide, and hypochlorite. Intravenous iron (IVIR), administered in HD patients to correct anemia, can release free

David Tovbin; Dalia Mazor; Marina Vorobiov; Cidio Chaimovitz; Naomi Meyerstein

2002-01-01

405

Retention of strontium, cesium, lead and uranium by bacterial iron oxides from a subterranean environment  

Microsoft Academic Search

Bacteriogenic Fe oxides (BIOS) and groundwater samples were collected 195 m underground at the Stråssa Mine in central Sweden. Ferrous iron oxidizing bacteria, including stalked Gallionellaferruginea and filamenous Leptothrix sp., were prominent in the BIOS samples. The BIOS samples were found to contain only poorly ordered (amorphous) hydrous ferric oxide, as determined by X-ray diffraction. Inductively coupled plasma mass spectroscopy

F. G Ferris; R. O Hallberg; B Lyvén; K Pedersen

2000-01-01

406

Calculation of Oxidation Rates for Iron in CO-CO2.  

National Technical Information Service (NTIS)

A new method is proposed for calculating the oxidation of iron in the presence of carbon monoxide and carbon dioxide. It is assumed that the oxidation is limited by an internal oxidation step. The calculational method, based on methods previously used to ...

J. B. Condon

1988-01-01

407

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

Microsoft Academic Search

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

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

1992-01-01

408

Stoichiometry of bacterial anaerobic oxidation of elemental sulfur by ferric iron.  

PubMed

The conventional stoichiometry of the oxidation of elemental sulfur by ferric iron in Acidithiobacillus ferrooxidans was not in agreement with our experimental data in terms of ferrous iron and proton formation. Reaction modelling under the actual conditions of bacterial activity resulted in a different stoichiometry, where additional iron species participate in the process to affect the number of released protons. The suggested reaction equation may more accurately predict the intensity of environmental acidification during the anaerobic bioprocess. PMID:22249244

Kucera, Jiri; Zeman, Josef; Mandl, Martin; Cerna, Hana

2012-01-17

409

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

410

Preparation and characterization of silica coated iron oxide magnetic nano-particles  

Microsoft Academic Search

Iron oxide magnetic nano-particles have been prepared by precipitation in an aqueous solution of iron(II) and iron(III) chlorides under basic condition. Surface modifications have been carried out by using tetraethoxysilane (TEOS) and mercaptopropyltrimethoxysilane (MPTMS). The uncoated and coated particles have been characterized with transmission electron microscopy (TEM), energy dispersive X-ray (EDX) spectroscopy, thermal gravimetric analysis (TGA), and infrared (IR) and

Ying-Sing Li; Jeffrey S. Church; Andrea L. Woodhead; Filsun Moussa

2010-01-01

411

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.

Bond, Philip L.; Gihring, Thomas M.; Banfield, Jilian F.; Edwards, Katrina J.

2009-09-11

412

Surface oxides produced during discharge in water ambient iron surface: A conversion electron Mössbauer spectroscopic study  

Microsoft Academic Search

Oxide layers are produced on iron surface, under discharge in water ambient, applying both anodic and cathodic potentials to iron foil. Non-stoichiometric Fe1-xO containing different ratios of Fe3+ and Fe2+ has been detected by using CEMS. Corrosion of these samples in 0.5 M H2SO4 shows that, cathodically discharge treated iron foil has higher corrosion resistance as compared to the anodically

N. R. Bulakh; S. V. Ghaisas; S. A. Kulkarni; S. M. Kanetkar; S. B. Ogale; S. K. Date

1988-01-01

413

Surface oxides produced during discharge in water ambient iron surface: A conversion electron Mössbauer spectroscopic study  

Microsoft Academic Search

Oxide layers are produced on iron surface, under discharge in water ambient, applying both anodic and cathodic potentials\\u000a to iron foil. Non-stoichiometric Fe1?xO containing different ratios of Fe3+ and Fe2+ has been detected by using CEMS. Corrosion of these samples in 0.5 M H2SO4 shows that, cathodically discharge treated iron foil has higher corrosion resistance as compared to the anodically

N. R. Bulakh; S. V. Ghaisas; S. A. Kulkarni; S. M. Kanetkar; S. B. Ogale; S. K. Date

1988-01-01

414

Hydration effects on the molecular structure of silica-supported vanadium oxide catalysts: A combined IR, Raman, UV–vis and EXAFS study  

Microsoft Academic Search

The effect of hydration on the molecular structure of silica-supported vanadium oxide catalysts with loadings of 1–16wt.% V has been systematically investigated by infrared, Raman, UV–vis and EXAFS spectroscopy. IR and Raman spectra recorded during hydration revealed the formation of V–OH groups, characterized by a band at 3660cm?1. Hydroxylation was found to start instantaneously upon exposure to traces of water,

Daphne E. Keller; Tom Visser; Fouad Soulimani; Diek C. Koningsberger; Bert M. Weckhuysen

2007-01-01

415

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.

2012-01-01

416

Dissimilatory ferrous iron oxidation at a low pH: a novel trait identified in the bacterial subclass Rubrobacteridae.  

PubMed

A novel iron-oxidizing acidophilic actinobacterium was isolated from spoil material at an abandoned copper mine. Phylogenetic analysis placed the isolate within the Rubrobacteridae subclass of the Actinobacteria. Its optimum temperature and pH for growth are 30-35 degrees C and pH 3.0, respectively. Although it could catalyze the dissimilatory oxidation of ferrous iron, growth yields declined progressively in media containing ferrous iron concentrations >100 microM. The isolate, Pa33, did not grow or oxidize iron in the absence of organic carbon, and appeared to be an obligate heterotroph. Specific rates of iron oxidation were much smaller than those determined for the autotrophic iron-oxidizing proteobacterium Acidithiobacillus ferrooxidans and the heterotrophic iron-oxidizing actinobacterium Ferrimicrobium acidiphilum. Iron oxidation by isolate Pa33 appears to be a defensive mechanism, in which iron oxidation converts a soluble species to which the bacterium is sensitive to an oxidized species (ferric iron) that is highly insoluble in the spoil from which it was isolated. This is the first report of acidophily or dissimilatory iron oxidation within the Rubrobacteridae subclass and one of very few within the Actinobacteria phylum as a whole. PMID:18803673

Bryan, Christopher G; Johnson, David B

2008-09-18

417

Investigating the oxidation of alkenes by non-heme iron enzyme mimics.  

PubMed

Iron is emerging as a key player in the search for efficient and environmentally benign methods for the functionalisation of C-H bonds. Non-heme iron enzymes catalyse a diverse array of oxidative chemistry in nature, and small-molecule complexes designed to mimic the non-heme iron active site have great potential as C-H activation catalysts. Herein we report the synthesis of a series of organic ligands that incorporate key features of the non-heme iron active site. Iron(II) complexes of these ligands have been generated in situ and their ability to promote hydrocarbon oxidation has been investigated. Several of these systems promote the biomimetic dihydroxylation of cyclohexene at low levels, when hydrogen peroxide is used as the oxidant; allylic oxidation products are also observed. An investigation of ligand stability reveals formation of several breakdown products under the conditions of the oxidative turnover reactions. These products arise via oxidative decarboxylation, dehydration and deamination reactions. Taken together these results indicate that competing mechanisms are at play with these systems: biomimetic hydroxylation involving high-valent iron species, and allylic oxidation via Fenton chemistry and Haber-Weiss radical pathways. PMID:22858835

Barry, Sarah M; Mueller-Bunz, Helge; Rutledge, Peter J

2012-09-28

418

Oxidative precipitation of groundwater-derived ferrous iron in the subterranean estuary of a coastal bay  

NASA Astrophysics Data System (ADS)

Sediment cores from the intertidal zone of Waquoit Bay (Cape Cod, Massachusetts) yielded iron oxide-coated sands in the subterranean estuary, which underlies the head of the bay. The oxides were dark red, yellow and orange colors and are formed by the oxidation of ferrous iron-rich groundwater near the groundwater-seawater interface. Within these iron oxide-rich sediments, the concentration of the combined amorphous and crystalline forms of iron oxides ranged between 2500 and 4100 ppm of Fe. These concentrations were 4-6 times greater than the surface sands, and 10-15 times more Fe rich than sands collected from an off-site location. The precipitation of iron oxides in subterranean estuaries could act as a geochemical barrier by retaining and accumulating certain dissolved chemical species carried to the coast by groundwater. Indeed, phosphorus concentrations in the iron oxide-rich sands of Waquoit Bay were 5-7 times greater than the overlying surface sands.

Charette, Matthew A.; Sholkovitz, Edward R.

2002-05-01

419

Iron-dependent changes in cellular energy metabolism: influence on citric acid cycle and oxidative phosphorylation.  

PubMed

Iron modulates the expression of the critical citric acid cycle enzyme aconitase via a translational mechanism involving iron regulatory proteins. Thus, the present study was undertaken to investigate the consequences of iron perturbation on citric acid cycle activity, oxidative phosphorylation and mitochondrial respiration in the human cell line K-562. In agreement with previous data iron increases the activity of mitochondrial aconitase while it is reduced upon addition of the iron chelator desferrioxamine (DFO). Interestingly, iron also positively affects three other citric acid cycle enzymes, namely citrate synthase, isocitric dehydrogenase, and succinate dehydrogenase, while DFO decreases the activity of these enzymes. Consequently, iron supplementation results in increased formation of reducing equivalents (NADH) by the citric acid cycle, and thus in increased mitochondrial oxygen consumption and ATP formation via oxidative phosphorylation as shown herein. This in turn leads to downregulation of glucose utilization. In contrast, all these metabolic pathways are reduced upon iron depletion, and thus glycolysis and lactate formation are significantly increased in order to compensate for the decrease in ATP production via oxidative phosphorylation in the presence of DFO. Our results point to a complex interaction between iron homeostasis, oxygen supply and cellular energy metabolism in human cells. PMID:10556622

Oexle, H; Gnaiger, E; Weiss, G

1999-11-10

420

Synthesis, Morphology, and Magnetic Characterization of Iron Oxide Nanowires and Nanotubes  

Microsoft Academic Search

We have explored the synthesis of iron oxide particles, tubes, and fibrils within the pores of nanoporous polycarbonate and alumina membranes. The membranes contain uniformly distributed cylindrical pores with monodispersed diameters (varying between 20 and 200 nm) and thicknesses of 6 and 60 Ìm, respectively. By hydrolysis and polymerization of iron salts, particles of different sizes and phases were formed

Lorenza Suber; Patrizia Imperatori; Giovanni Ausanio; Fabio Fabbri; Herbert Hofmeister

2005-01-01

421

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

Microsoft Academic Search

BACKGROUND: Lung injury caused by both inhaled dusts and infectious agents depends on increased availability of iron and metal-catalyzed oxidative stress. Because inhaled particles, such as silica, and certain infections can cause secondary pulmonary alveolar proteinosis (PAP), we tested the hypothesis that idiopathic PAP is associated with an altered iron homeostasis in the human lung. METHODS: Healthy volunteers (n =

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

2008-01-01

422

The Role of Enhanced Heterotrophic Bacterial Growth on Iron Oxidation by Acidithiobacillus ferrooxidans  

Microsoft Academic Search

Addition of organic carbon substrate (glucose) profoundly affected the growth of cultures of acidophilic bacteria typical of acid mine drainage (AMD) sites: the iron-oxidizing autotrophic bacteria, Acidithiobacillus ferrooxidans , and a common heterotrophic strain, Acidiphilium acidophilum . Growth of A. ferrooxidans on soluble ferrous iron media was significantly inhibited in the presence of 1,000 mg\\/L glucose, regardless of the initial

Eric A. Marchand; Joann Silverstein

2003-01-01

423

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 ...

424

*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...

425

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

Microsoft Academic Search

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

C. S. Chan; J. F. Banfield

2002-01-01

426

Fatty acid-mediated intracellular iron translocation: A synergistic mechanism of oxidative injury  

Microsoft Academic Search

Fatty acid has been reported to be associated with cardiovascular diseases and cancer, but the possible mechanism remains unclear. Here, we reported a novel mechanism for the permissive role of fatty acid on iron intracellular translocation and subsequent oxidative injury. In vitro study from endothelial cells showed that iron alone had little effect, whereas in combination with PA (palmitic acid),

Dachun Yao; Weibin Shi; Yulan Gou; Xinrong Zhou; Tak Yee Aw; Yikai Zhou; Zhengxiang Liu

2005-01-01

427

Combined electro-photochemical oxidation for iron removal from ground water  

Microsoft Academic Search

Iron in water presents health hazard, its presence in water may cause taste and staining problems. Currently applied water treatment techniques consist of a combination of different methods to achieve the elimination of harmful pollutants. The aim of this study is to investigate the efficiency of the photo-assisted electrochemical oxidation process for the removal of dissolved iron as a cheaper

Hala A. Talaat; Montaser Y. Ghaly; Eman M. Kamel; Ahmed M. Awad; Enas M. Ahmed

2011-01-01

428

The catalysis of the oxygen evolution reaction by iron impurities in thin film nickel oxide electrodes  

Microsoft Academic Search

The effects of iron coprecipitated into thin film nickel oxide electrodes or introduced in the 25 weight percent KOH electrolyte were studied by a combination of galvanostatic and open-circuit decay methods. Effects on voltammetric behaviour and on the oxygen overpotential were observed in thin film electrodes with as little as 0.01% iron present. The overpotential was further lowered by 1%

Dennis A. Corrigan

1987-01-01

429

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

EPA Science Inventory

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

430

Multi-sulfate and Iron Oxide Assemblages Within the Valles Marineris Interior Layered Deposits  

NASA Astrophysics Data System (ADS)

MarsExpress OMEGA showed that many of the Interior Layered Deposits (ILDs) in Valles Marineris contain sulfates and proposed the sulfates as indicators of past aqueous activity in the Theiikian period (Gendrin etal, 2005; Bibring etal, 2005; Bibring etal, 2006). Better discrimination of the sulfate assemblages present and the stratigraphic relationships within the ILD is critical to understanding the environment during and since their formation. We present a method for identifying classes of sulfates present in a multi-sulfate exposure with MRO CRISM data. Multiple mineral phases can be defined by diagnostic absorptions in spatially distinct wavelength regions. Combinations of minerals phases is more complicated but can be resolved by identifying superposed absorption feature and assuming linear mixing. We focus on four wavelength regions: (a) 2.4 and 2.1 ?m, (b) 2.2 ?m, (c) 1.9 and 1.4 ?m, and (d) 0.9 ?m, in a methodical classification of possible sulfate types present. While there is some overlap in the wavelength regions, absorptions are sufficiently separate to be recognizable. Additionally, care must be taken to select geologically feasible minerals assemblages. (a) Hydrated sulfates have an absorption near 2.4 um due to probable interactions between the H2O and SO3 molecules (Cloutis etal, 2006). Monohydrated sulfates have a distinct absorption near 2.1 ?m due to combinations of H2O stretch and rotation vibrations of the single water molecule in a sulfate structure (Cloutis etal, 2006) which shifts with cation. Thus minerals such as kieserite (MgSO4 H2O) and szomolnokite (Fe2+SO4 H2O) can be distinguished in CRISM data. (b) The 2.21-2.26 ?m region is generally convex in sulfates, but gypsum (CaSO4 2H2O ) and jarosite group members (MFe3(SO4)2(OH)6) have absorptions there. The minimum within this wavelength region depends on the mineral present. (c)The ~1.9 ?m is due to the OH stretch and H2O bend combination tone and the ~1.4 ?m absorption is due to the 1st overtone of the OH stretch. Sulfates or other minerals with 2+ structural H2O are necessary for the deep water and hydroxyl absorptions in many spectra we observe. (d) Ferric and ferrous minerals have wide absorptions near 0.9 ?m due to charge transfer and electronic transition processes. Presence of a ~0.9 ?m absorption could indicate either a iron-bearing sulfate, a co-existing iron oxide, or both. Ferrous minerals such as olivine and pyroxene can be excluded by the position and width of their 1.0 and 2.0 ?m absorptions. An eastern Candor Chasma ILD has a multiple sulfate assemblage including mono- and polyhydrated sulfates with a variety of cations that are uniform within a specific layer. The sulfates are intimately or spatially mixed on the meter scale. The relative strengths of mono and polyhydrated sulfate absorptions vary with layering, indicating a degree of independence. Mineralogy and geomorphology is consistent with an evaporite sequence or groundwater alteration of ash or aeolian deposits. In addition, iron oxide spectral features overprint the sulfate spectra in some places and cut across layering in others, suggesting the iron-bearing phase may be either separate from the sulfate occurrences or spatially redistributed. Future work will better characterize the assemblage there and in other chasmata ILDs.

Roach, L. H.; Mustard, J. F.; Murchie, S. L.; Bishop, J. L.; Arvidson, R. E.; Morris, R. V.; Milliken, R. E.; Lichtenberg, K. A.

2007-12-01

431

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

EPA Science Inventory

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

432

NHC/iron cooperative catalysis: aerobic oxidative esterification of aldehydes with phenols.  

PubMed

An NHC/iron cooperative catalytic system mediates the aerobic oxidative esterification of aldehydes with phenols. The use of equimolar amounts of reactants led to good to excellent isolated yields of esters. PMID:21423962

Reddy, R Sudarshan; Rosa, João N; Veiros, Luís F; Caddick, Stephen; Gois, Pedro M P

2011-03-21

433

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

434

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

EPA Science Inventory

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

435

[The role of iron metabolism and oxidative stress in the pathogenesis of endometriosis].  

PubMed

Despite many years of extensive investigations and increasing number of studies, the pathogenesis of endometriosis remains unclear Accumulated data suggests that disrupted iron metabolism may induce oxidative stress in the peritoneal cavity of endometriosis patients. PMID:23488312

Polak, Grzegorz; Wertel, Iwona; Kwa?niewski, Wojciech; Derewianka-Polak, Magdalena; Kotarski, Jan

2013-01-01

436

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

PubMed Central

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

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

1979-01-01

437

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

SciTech Connect

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

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

1999-02-01

438

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

PubMed

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

Bacelar-Nicolau, P; Johnson, D B

1999-02-01

439

Layered niobic acid with self-exfoliatable nanosheets and adjustable acidity for catalytic hydration of ethylene oxide  

Microsoft Academic Search

Layered niobic acids (HxK1?xNb3O8, x=0–1) are reported as new solid acid catalysts for the selective hydration of ethylene oxide (EO). They are prepared by simply calcinating Nb2O5–K2CO3 mixture followed by an ion-exchange process in HNO3 solution of different concentrations. The highest selectivity for monoethylene glycol (MEG) is achieved over 95% with EO conversion of >99% at x of 0.7 under

Zhi-Jian Yang; Ye-Fei Li; Qing-Bin Wu; Nan Ren; Ya-Hong Zhang; Zhi-Pan Liu; Yi Tang

2011-01-01

440

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

Microsoft Academic Search

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

Wensheng Lu; Helmut Schmidt

2007-01-01

441

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

442

Increased RNA oxidative damage and iron content in skeletal muscle with aging and disuse atrophy  

PubMed Central

Muscle atrophy with aging or disuse is associated with deregulated iron homeostasis and increased oxidative stress likely inflicting damage to nucleic acids. Therefore, we investigated RNA and DNA oxidation, and iron homeostasis in gastrocnemius muscles. Disuse atrophy was induced in 6- and 32-month old male Fischer 344/Brown Norway rats by 14 days of hind limb suspension (HS). We show that RNA, but not DNA, oxidative damage increased 85% with age and 36% with HS in aged muscle. Additionally, non-heme iron levels increased 233% with aging and 83% with HS at old age, while staining for free iron was strongest in the smallest fibers. Simultaneously, the mRNA abundance of transferrin receptor-1 decreased by 80% with age and 48% with HS for young animals, while that of the hepcidin regulator hemojuvelin decreased 37% with age, but increased about 44% with disuse, indicating a dysregulation of iron homeostasis favoring increased intracellular free iron in atrophied muscles. RNA and DNA concentrations increased with age and were negatively correlated with muscle mass, whereas protein concentrations decreased with aging, indicating a preferential loss of protein compared to nucleic acids. Furthermore, xanthine oxidase activity increased with age, but not with HS, while mRNA abundance of the Y box-binding protein-1, which has been suggested to bind oxidized RNA, did not change with age or HS. These results suggest that RNA oxidation, possibly mediated by increased non-heme iron, might contribute to muscle atrophy due to disuse particularly in aged muscle.

Hofer, Tim; Marzetti, Emanuele; Xu, Jinze; Seo, Arnold Y.; Gulec, Sukru; Knutson, Mitchell D.; Leeuwenburgh, Christiaan; Dupont-Versteegden, Esther E.

2008-01-01

443

Evaluation of toxicity and oxidative stress induced by intravenous iron isomaltoside 1000 in a nonclinical model.  

PubMed

The physicochemical characteristics of intravenous iron complexes affect the extent of weakly-bound iron and thus the degree of oxidative stress. The new preparation iron isomaltoside 1000 (IIM) was compared to iron sucrose (IS) and a control group in terms of biochemistry, oxidative stress, inflammatory markers and iron deposition in the liver, heart and kidneys of healthy rats. Renal function was significantly impaired in the IIM group versus both IS and controls. Liver enzymes were also significantly higher in IIM-treated animals versus the other groups, indicative of hepatic injury. Systolic blood pressure was significantly lower following IIM administration compared to IS or control animals. Oxidative stress in the liver, heart and kidneys was greater in the IIM group, as indicated by significantly increased levels of malondialdehyde and antioxidant enzyme activity, accompanied