Effects of quercetin on hemoglobin-dependent redox reactions: relationship to iron-overload rat liver injury.

PubMed

Lu, Nai-Hao; Chen, Chao; He, Ying-Jie; Tian, Rong; Xiao, Qiang; Peng, Yi-Yuan

2013-01-01

Flavonoids have been widely reported to protect liver injury in iron-overload diseases, where the mechanism of this therapeutic action is dependent on their antioxidant effects, including free radical scavenging and metal-chelating. In this study, in contrast to the significant decrease in iron content, quercetin (Qu) from lower diet (0.3%, w/w) showed pro-oxidant ability on protein carbonyl formation and exhibited unobvious effect on iron-overload rat liver injury. Furthermore, the anti- and pro-oxidant activities of Qu on hemoglobin (Hb)-dependent redox reactions (i.e. the oxidative stability of Hb and its cytotoxic ferryl intermediate, Hb-induced protein oxidation) were investigated to illustrate the elevated protein oxidation in lower Qu-treated iron-overload rat. It was found that superoxide (O₂·⁻) and hydrogen peroxide (H₂O₂) were generated during the reaction between Qu and Hb. Qu, however, effectively reduced ferryl intermediate back to ferric Hb in a biphasic kinetic reaction. Moreover, Qu could significantly aggravate Hb-H₂O₂-induced protein oxidation at low concentrations and exhibit protective effects at high concentrations. Different from the classic antioxidant mechanisms of Qu, the dual effects on Hb redox reactions in vitro, therefore, may provide new insights into the physiological and pharmacological implications of Qu with iron-overload disease.

High Energy-Density and Reversibility of Iron Fluoride Cathode Enabled Via an Intercalation-Extrusion Reaction

DOE PAGES

Fan, Xiulin; Hu, Enyuan; Ji, Xiao; ...

2018-05-30

Iron fluoride, an intercalation-conversion cathode for lithium ion batteries, promises a high theoretical energy density of 1922 Wh Kg –1. However, poor electrochemical reversibility due to repeated breaking/reformation of metal-fluoride bonds poses a grand challenge for its practical application. Here we report that both a high reversibility over 1000 cycles and a high capacity of 420 mAh g –1 can be realized by concerted doping of cobalt and oxygen into iron fluoride. In the doped nanorods, an energy density of ~1000 Wh Kg –1 with a decay rate of 0.03% per cycle is achieved. The anion and cation’s co-substitutions thermodynamicallymore » reduce conversion-reaction potential and shift the reaction from less reversible intercalation-conversion reaction in iron fluoride to a highly reversible intercalation-extrusion reaction in doped material. Furthermore, the co-substitution strategy to tune the thermodynamic features of the reactions could be extended to other high energy conversion materials for improved performance.« less

High Energy-Density and Reversibility of Iron Fluoride Cathode Enabled Via an Intercalation-Extrusion Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Xiulin; Hu, Enyuan; Ji, Xiao

Iron fluoride, an intercalation-conversion cathode for lithium ion batteries, promises a high theoretical energy density of 1922 Wh Kg –1. However, poor electrochemical reversibility due to repeated breaking/reformation of metal-fluoride bonds poses a grand challenge for its practical application. Here we report that both a high reversibility over 1000 cycles and a high capacity of 420 mAh g –1 can be realized by concerted doping of cobalt and oxygen into iron fluoride. In the doped nanorods, an energy density of ~1000 Wh Kg –1 with a decay rate of 0.03% per cycle is achieved. The anion and cation’s co-substitutions thermodynamicallymore » reduce conversion-reaction potential and shift the reaction from less reversible intercalation-conversion reaction in iron fluoride to a highly reversible intercalation-extrusion reaction in doped material. Furthermore, the co-substitution strategy to tune the thermodynamic features of the reactions could be extended to other high energy conversion materials for improved performance.« less

The evaluation of experimental data in fast range for n + 56Fe(n,inl)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian, Jing; Herman, M.; Ge, Zhigang

Iron is one of the five materials selected for evaluation within the pilot international evaluation project CIELO. Analysis of experimental data for n+ 56Fe reaction is the basis for constraining theoretical calculations and eventual creation of the evaluated file. The detail analysis was performed for inelastic cross sections of neutron induced reactions with 56Fe in the fast range up to 20 MeV where there are significant differences among the main evaluated libraries, mainly caused by the different inelastic scattering cross section measurements. Gamma-ray production cross sections provide a way to gain experimental information about the inelastic cross section. Large discrepanciesmore » between experimental data for the 847-keV gamma ray produced in the 56Fe(n,n 1'γ) reaction were analyzed. In addition, experimental data for elastic scattering cross section between 9.41~11 MeV were used to deduce the inelastic cross section from the unitarity constrain.« less

The evaluation of experimental data in fast range for n + 56Fe(n,inl)

DOE PAGES

Qian, Jing; Herman, M.; Ge, Zhigang; ...

2017-09-13

Iron is one of the five materials selected for evaluation within the pilot international evaluation project CIELO. Analysis of experimental data for n+ 56Fe reaction is the basis for constraining theoretical calculations and eventual creation of the evaluated file. The detail analysis was performed for inelastic cross sections of neutron induced reactions with 56Fe in the fast range up to 20 MeV where there are significant differences among the main evaluated libraries, mainly caused by the different inelastic scattering cross section measurements. Gamma-ray production cross sections provide a way to gain experimental information about the inelastic cross section. Large discrepanciesmore » between experimental data for the 847-keV gamma ray produced in the 56Fe(n,n 1'γ) reaction were analyzed. In addition, experimental data for elastic scattering cross section between 9.41~11 MeV were used to deduce the inelastic cross section from the unitarity constrain.« less

Evidence for Ni-56 yields Co-56 yields Fe-56 decay in type Ia supernovae

NASA Technical Reports Server (NTRS)

Kuchner, Marc J.; Kirshner, Robert P.; Pinto, Philip A.; Leibundgut, Bruno

1994-01-01

In the prevailing picture of Type Ia supernovae (SN Ia), their explosive burning produces Ni-56, and the radioactive decay chain Ni-56 yields Co-56 yields Fe-56 powers the subsequent emission. We test a central feature of this theory by measuring the relative strengths of a (Co III) emission feature near 5900 A and a (Fe III) emission feature near 4700 A. We measure 38 spectra from 13 SN Ia ranging from 48 to 310 days after maximum light. When we compare the observations with a simple multilevel calculation, we find that the observed Fe/Co flux ratio evolves as expected when the Fe-56/Co-56 abundance ratio follows from Ni-56 yields Co-56 yields Fe-56 decay. From this agreement, we conclude that the cobalt and iron atoms we observe through SN Ia emission lines are produced by the radioactive decay of Ni-56, just as predicted by a wide range of models for SN Ia explosions.

Kinetics and Mechanism of Iodide Oxidation by Iron(III): A Clock Reaction Approach

ERIC Educational Resources Information Center

Bauer, Jurica; Tomisic, Vladislav; Vrkljan, Petar B. A.

2008-01-01

A simple method for studying the kinetics of a chemical reaction is described and the significance of reaction orders in deducing reaction mechanisms is demonstrated. In this student laboratory experiment, oxidation of iodide by iron(III) ions in an acidic medium is transformed into a clock reaction. By means of the initial rates method, it is…

Nitrous Oxide-dependent Iron-catalyzed Coupling Reactions of Grignard Reagents.

PubMed

Döhlert, Peter; Weidauer, Maik; Enthaler, Stephan

2015-01-01

The formation of carbon-carbon bonds is one of the fundamental transformations in chemistry. In this regard the application of palladium-based catalysts has been extensively investigated during recent years, but nowadays research focuses on iron catalysis, due to sustainability, costs and toxicity issues; hence numerous examples for iron-catalyzed cross-coupling reactions have been established, based on the coupling of electrophiles (R(1)-X, X = halide) with nucleophiles (R(2)-MgX). Only a small number of protocols deals with the iron-catalyzed oxidative coupling of nucleophiles (R(1)-MgX + R(2)-MgX) with the aid of oxidants (1,2-dihaloethanes). However, some issues arise with these oxidants; hence more recently the potential of the industrial waste product nitrous oxide (N(2)O) was investigated, because the unproblematic side product N(2) is formed. Based on that, we demonstrate the catalytic potential of easily accessible iron complexes in the oxidative coupling of Grignard reagents. Importantly, nitrous oxide was essential to obtain yields up to >99% at mild conditions (e.g. 1 atm, ambient temperature) and low catalyst loadings (0.1 mol%) Excellent catalyst performance is realized with turnover numbers of up to 1000 and turnover frequencies of up to 12000 h(-1). Moreover, a good functional group tolerance is observed (e.g. amide, ester, nitrile, alkene, alkyne). Afterwards the reaction of different Grignard reagents revealed interesting results with respect to the selectivity of cross-coupling product formation.

Iron-chelating agents never suppress Fenton reaction but participate in quenching spin-trapped radicals.

PubMed

Li, Linxiang; Abe, Yoshihiro; Kanagawa, Kiyotada; Shoji, Tomoko; Mashino, Tadahiko; Mochizuki, Masataka; Tanaka, Miho; Miyata, Naoki

2007-09-19

Hydroxyl radical formation by Fenton reaction in the presence of an iron-chelating agent such as EDTA was traced by two different assay methods; an electron spin resonance (ESR) spin-trapping method with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and high Performance liquid chromatography (HPLC)-fluorescence detection with terephthalic acid (TPA), a fluorescent probe for hydroxyl radicals. From the ESR spin-trapping measurement, it was observed that EDTA seemed to suppress hydroxyl radical formation with the increase of its concentration. On the other hand, hydroxyl radical formation by Fenton reaction was not affected by EDTA monitored by HPLC assay. Similar inconsistent effects of other iron-chelating agents such as nitrylotriacetic acid (NTA), diethylenetriamine penta acetic acid (DTPA), oxalate and citrate were also observed. On the addition of EDTA solution to the reaction mixture 10 min after the Fenton reaction started, when hydroxyl radical formation should have almost ceased but the ESR signal of DMPO-OH radicals could be detected, it was observed that the DMPO-OH* signal disappeared rapidly. With the simultaneous addition of Fe(II) solution and EDTA after the Fenton reaction ceased, the DMPO-OH* signal disappeared more rapidly. The results indicated that these chelating agents should enhance the quenching of [DMPO-OH]* radicals by Fe(II), but they did not suppress Fenton reaction by forming chelates with iron ions.

Regeneration and reuse of iron catalyst for Fenton-like reactions.

PubMed

Cao, Guo-min; Sheng, Mei; Niu, Wen-feng; Fei, Yu-lei; Li, Dong

2009-12-30

Fenton and Fenton-like reactions employed for oxidative treatment of a typical industrial wastewater generate a large amount of ferric hydroxide sludge which has to be properly disposed at a high cost. This paper presents a simple and cost-effective method for recovering the iron catalyst from the iron hydroxide sludge for oxidative treatment of industrial wastewaters. The sludge was dewatered, dried and baked at 350-400 degrees C for 20-30 min; the residual solids were dissolved in sulfuric acid to form the reusable catalyst for Fenton and Fenton-like reactions. The recovered catalyst was highly effective for the oxidative pretreatment of a fine chemical wastewater to improve its biodegradability; the resulting COD removal and BOD(5)/COD ratio of the treated stream remained nearly unchanged during the time period when the regenerated catalyst was reused six times. The simple and effective catalyst regeneration method will make Fenton and Fenton-like oxidation a more cost-effective wastewater treatment alternative.

The Reaction between Iron(II) Iodide and Potassium Dichromate(VI) in Acidified Aqueous Solution

ERIC Educational Resources Information Center

Talbot, Christopher

2013-01-01

This "Science note" teaching lesson explores the possible reaction between the ions in a reaction mixture consisting of iron(II) iodide and potassium dichromate(VI) in acidified aqueous solution. The electrode potentials will be used to deduce any spontaneous reactions under standard thermodynamic conditions (298 K, 1 bar (approximately…

The reactions of cobalt, iron and nickel in SO2 atmospheres Similarities and differences

NASA Technical Reports Server (NTRS)

Jacobson, N. S.; Worrell, W. L.

1985-01-01

The reactions of cobalt, iron and nickel in SO2 atmospheres are reviewed and compared. A mixed oxide-sulfide product layer is observed in all cases. Cobalt and nickel exhibit similar behavior. The observed rates are near the sulfidation rates, and the reaction rate is strongly influenced by the outward diffusion of metal through an interconnected sulfide network. A continuous interconnected sulfide is not observed in the oxide-sulfide scales formed on iron, and the reaction rates are more difficult to summarize. The differences and similarities among the three metals are explained in terms of the absence of scale-gas equilibrium and the ratio of the metal diffusivity in the corresponding oxide and sulfide.

The reactions of cobalt, iron and nickel in SO-2 atmospheres: Similarities and differences

NASA Technical Reports Server (NTRS)

Jacobson, N. S.; Worrell, W. L.

1984-01-01

The reactions of cobalt, iron and nickel in SO2 atmospheres are reviewed and compared. A mixed oxide-sulfide product layer is observed in all cases. Cobalt and nickel exhibits similar behavior. The observed rates are near the sulfidation rates, and the reaction rate is strongly influenced by the outward diffusion of metal through an interconnected sulfide network. A continuous interconnected sulfide is not observed in the oxide-sulfide scales formed on iron, and the reaction rates are more difficult to summarize. The differences and similarities among the three metals are explained in terms of the absence of scale-gas equilibrium and the ratio of the metal diffusivity in the corresponding oxide and sulfide.

Effects of Pressure and Temperature on the Kinetics of Iron-magnesite Redox Reaction: Implication for the Genesis of Ultradeep Diamonds

NASA Astrophysics Data System (ADS)

Zhu, F.; Li, J.; Liu, J.; Lai, X.; Chen, B.; Meng, Y.

2016-12-01

Diamonds may be the products of redox reaction between carbonates in the subducted slabs and iron metal in the mantle [1]. Given the relatively low temperatures of the subducted slabs, however, it remains to be shown that such reaction can occur at sufficiently fast rate. To examine the influence of pressure and temperature (P-T) on the kinetics of iron-carbonate redox reaction, we performed in-situ synchrotron X-ray diffraction (XRD) experiments at the Advanced Photon Source, Argonne National Laboratory, using laser-heated diamond anvil cells. The starting material consists of an iron foil sandwiched between two magnesite pellets. Data were collected between 1050 and 1800 K at 50-100 K intervals, at seven pressures between 12 and 40 GPa, corresponding the depths where most ultradeep diamonds originated [2]. We obtained constraints on the Fe-MgCO3reaction boundary, which was located between the estimated temperatures on the surface of cold slabs near 1400 K and inside their interiors near 1000 K, and it had a similar slope as the slab geotherm [3]. Furthermore, the experiments revealed a significant effect of pressure on the extent and rate of the reaction. The XRD patterns showed that below 15 GPa the initial reaction products were iron carbides, which reacted with magnesite to form diamonds when the reaction completed in 60 minutes at 1300 to 1500 K. Above 18 GPa only iron carbides were observed in the XRD patterns even when all the iron was consumed, and iron carbides still coexisted with magnesite after 100 to 160 minutes at 1600 to 1800 K. Our results suggest that diamonds can be produced from iron-carbonate redox reaction at slab-mantle boundary conditions at the deeper part of the upper mantle, but diamond growth through this reaction is slow or kinetically hindered in the lower mantle. References[1] Palyanov, Y. N. et al. (2013). Proc. Nat. Aca. Sci., 110(51), 20408-20413. [2] Stachel, T. et al. (2005). Elements, 1(2), 73-78. [3] Eberle et al. (2002). Phys

The nitroxide Tempo inhibits hydroxyl radical production from the Fenton-like reaction of iron(II)-citrate with hydrogen peroxide.

PubMed

Shi, Fengqiang; Zhang, Peifeng; Mao, Yujia; Wang, Can; Zheng, Meiqing; Zhao, Zhongwei

2017-01-29

In vivo physiological ligand citrate can bind iron(II) ions to form the iron(II)-citrate complex. Inhibition of hydroxyl radical (OH) production from the Fenton-like reaction of iron(II)-citrate with H 2 O 2 is biologically important, as this reaction may account for one of the mechanisms of the labile iron pool in vivo to induce oxidative stress and pathological conditions. Nitroxides have promising potentials as therapeutic antioxidants. However, there are controversial findings indicating that they not only act as antioxidants but also as pro-oxidants when engaged in Fenton reactions. Although the underlying mechanisms are proposed to be the inhibition or enhancement of the OH production by nitroxides, the proposed elucidations are only based on assessing biological damages and not demonstrated directly by measuring the OH production in the presence of nitroxides. In this study, therefore, we employed EPR and fluorescence spectroscopies to show direct evidence that nitroxide 2,2,6,6-tetramethyl-piperidine-1-oxyl (Tempo) inhibited OH production from the Fenton-like reaction of iron(II)-citrate with H 2 O 2 by up to 90%. We also demonstrated spectrophotometrically, for the first time, that this inhibition was due to oxidation of the iron(II)-citrate by Tempo with a stoichiometry of Tempo:Iron(III)-citrate = 1.1:1.0. A scheme was proposed to illustrate the roles of nitroxides engaged in Fenton/Fenton-like reactions. Copyright © 2016 Elsevier Inc. All rights reserved.

An isoelectronic NO dioxygenase reaction using a nonheme iron(III)-peroxo complex and nitrosonium ion.

PubMed

Yokoyama, Atsutoshi; Han, Jung Eun; Karlin, Kenneth D; Nam, Wonwoo

2014-02-18

Reaction of a nonheme iron(III)-peroxo complex, [Fe(III)(14-TMC)(O2)](+), with NO(+), a transformation which is essentially isoelectronic with that for nitric oxide dioxygenases [Fe(III)(O2˙(-)) + NO], affords an iron(IV)-oxo complex, [Fe(IV)(14-TMC)(O)](2+), and nitrogen dioxide (NO2), followed by conversion to an iron(III)-nitrato complex, [Fe(III)(14-TMC)(NO3)(F)](+).

Use of Moessbauer spectroscopy to study reaction products of polyphenols and iron compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gust, J.; Suwalski, J.

1994-05-01

Moessbauer spectroscopy was used to study parameters of the reaction products of iron compounds (Fe[sup III]) and polyphenols with hydroxyl (OH) groups in ortho positions. Polyphenols used in the reaction were catechol, pyrogallol, gallic acid, and oak tannin. The Fe-containing compounds were hydrated ferric sulfate (Fe[sub 2][SO[sub 4

An isoelectronic NO dioxygenase reaction using a nonheme iron(III)-peroxo complex and nitrosonium ion†

PubMed Central

Yokoyama, Atsutoshi; Han, Jung Eun; Karlin, Kenneth D.; Nam, Wonwoo

2014-01-01

Reaction of a nonheme iron(III)-peroxo complex, [FeIII(14-TMC)(O2)]+, with NO+, a transformation which is essentially isoelectronic with that for nitric oxide dioxygenases [Fe(III)(O2•−) + NO], affords an iron(IV)-oxo complex, [FeIV(14-TMC)(O)]2+, and nitrogen dioxide (NO2), followed by conversion to an iron(III)-nitrato complex, [FeIII(14-TMC)(NO3)(F)]+. PMID:24394960

Appearance of Membrane-bound Iron-Sulfur Centers and the Photosystem I Reaction Center during Greening of Barley Leaves 1

PubMed Central

Baltimore, Barbara G.; Malkin, Richard

1977-01-01

Dark-grown barley (Hordeum vulgare) etioplasts were examined for their content of membrane-bound iron-sulfur centers by electron paramagnetic resonance spectroscopy at 15K. They were found to contain the high potential iron-sulfur center characterized (in the reduced state) by an electron paramagnetic resonance g value of 1.89 (the “Rieske” center) but did not contain any low potential iron-sulfur centers. Per mole of cytochrome f, dark-grown etioplasts and fully developed chloroplasts had the same content of the Rieske center. During greening of etioplasts under continuous light, low potential bound iron-sulfur centers appear. In addition, the photosystem I reaction center, as measured by the photooxidation of P700 at 15K, also became functional; during greening the appearance of a photoreducible low potential iron-sulfur center paralleled the appearance of P700 photoactivity. These findings indicate the close association of the low potential iron-sulfur centers with the photosystem I reaction center; they also support the concept that the development of stable charge separation in the photosystem I reaction center requires, in addition to P700, a low potential iron-sulfur center. PMID:16660048

Rates for neutron-capture reactions on tungsten isotopes in iron meteorites. [Abstract only

NASA Technical Reports Server (NTRS)

Masarik, J.; Reedy, R. C.

1994-01-01

High-precision W isotopic analyses by Harper and Jacobsen indicate the W-182/W-183 ratio in the Toluca iron meteorite is shifted by -(3.0 +/- 0.9) x 10(exp -4) relative to a terrestrial standard. Possible causes of this shift are neutron-capture reactions on W during Toluca's approximately 600-Ma exposure to cosmic ray particles or radiogenic growth of W-182 from 9-Ma Hf-182 in the silicate portion of the Earth after removal of W to the Earth's core. Calculations for the rates of neutron-capture reactions on W isotopes were done to study the first possibility. The LAHET Code System (LCS) which consists of the Los Alamos High Energy Transport (LAHET) code and the Monte Carlo N-Particle(MCNP) transport code was used to numerically simulate the irradiation of the Toluca iron meteorite by galactic-cosmic-ray (GCR) particles and to calculate the rates of W(n, gamma) reactions. Toluca was modeled as a 3.9-m-radius sphere with the composition of a typical IA iron meteorite. The incident GCR protons and their interactions were modeled with LAHET, which also handled the interactions of neutrons with energies above 20 MeV. The rates for the capture of neutrons by W-182, W-183, and W-186 were calculated using the detailed library of (n, gamma) cross sections in MCNP. For this study of the possible effect of W(n, gamma) reactions on W isotope systematics, we consider the peak rates. The calculated maximum change in the normalized W-182/W-183 ratio due to neutron-capture reactions cannot account for more than 25% of the mass 182 deficit observed in Toluca W.

Multistep Reduction Kinetics of Fine Iron Ore with Carbon Monoxide in a Micro Fluidized Bed Reaction Analyzer

NASA Astrophysics Data System (ADS)

Chen, Hongsheng; Zheng, Zhong; Chen, Zhiwei; Yu, Wenzhou; Yue, Junrong

2017-04-01

The reduction kinetics of Brazilian hematite by CO is investigated in a Micro Fluidized Bed Reaction Analyzer (MFBRA) using an analyzing method based on Johnson-Mehl-Avrami (JMA) model at temperatures of 973 K (700 °C), 1023 K (750 °C), 1073 K (800 °C), and 1123 K (850 °C). The solid products at different reduction stages are evaluated by SEM/EDS and XRD technologies. Results indicate that the reduction process is better to be discussed in terms of a parallel reaction model that consists of the reactions of hematite to wüstite and wüstite to iron, rather than a stepwise route. Meanwhile, the controlling mechanism of the reduction process is found to vary with temperature and the degree of conversion. The overall process is controlled by the gas-solid reaction occurring at the iron/wüstite interface in the initial stages, and then is limited by the nucleation of wüstite, and finally shifts to diffusion control. Moreover, the reactions of hematite to wüstite and wüstite to iron take place simultaneously but with different time dependences, and the apparent activation energies of hematite to wüstite and wüstite to iron are determined as 83.61 and 80.40 KJ/mol, respectively.

Solution behavior of iron(III) and iron(II) porphyrins in DMSO and reaction with superoxide. Effect of neighboring positive charge on thermodynamics, kinetics and nature of iron-(su)peroxo product.

PubMed

Duerr, K; Troeppner, O; Olah, J; Li, J; Zahl, A; Drewello, T; Jux, N; Harvey, J N; Ivanović-Burmazović, I

2012-01-14

The solution behavior of iron(III) and iron(II) complexes of 5(4),10(4),15(4),20(4)-tetra-tert-butyl-5,10,15,20-tetraphenylporphyrin (H(2)tBuTPP) and the reaction with superoxide (KO(2)) in DMSO have been studied in detail. Applying temperature and pressure dependent NMR studies, the thermodynamics of the low-spin/high-spin equilibrium between bis- and mono-DMSO Fe(II) forms have been quantified (K(DMSO) = 0.082 ± 0.002 at 298.2 K, ΔH° = +36 ± 1 kJ mol(-1), ΔS° = +101 ± 4 J K(-1) mol(-1), ΔV° = +16 ± 2 cm(3) mol(-1)). This is a key activation step for substitution and inner-sphere electron transfer. The superoxide binding constant to the iron(II) form of the studied porphyrin complex was found to be (9 ± 0.5) × 10(3) M(-1), and does not change significantly in the presence of the externally added crown ether in DMSO (11 ± 4) × 10(3) M(-1). The rate constants for the superoxide binding (k(on) = (1.30 ± 0.01) × 10(5) M(-1) s(-1)) and release (k(off) = 11.6 ± 0.7 s(-1)) are not affected by the presence of the external crown ether in solution. The resulting iron(II)-superoxide adduct has been characterized (mass spectrometry, EPR, high-pressure UV/Vis spectroscopy) and upon controlled addition of a proton source it regenerates the starting iron(II) complex. Based on DFT calculations, the reaction product without neighboring positive charge has iron(II)-superoxo character in both high-spin side-on and low-spin end-on forms. The results are compared to those obtained for the analogous complex with covalently attached crown ether, and more general conclusions regarding the spin-state equilibrium of iron(II) porphyrins, their reaction with superoxide and the electronic structure of the product species are drawn.

Evaluation of Neutron Reactions on Iron Isotopes for CIELO and ENDF/B-VIII.0

DOE PAGES

Herman, M.; Trkov, A.; Capote, R.; ...

2018-02-01

A new suite of evaluations for 54,56,57,58Fe has been developed in the framework of the CIELO international collaboration. New resolved resonance ranges were evaluated for 54Fe and 57Fe, while modifications were applied to resonances in 56Fe. The low energy part of the 56Fe file is almost totally based on measurements. At higher energies in 56Fe and in the whole fast neutron range for minor isotopes the evaluation consists of model predictions carefully adjusted to available experimental data. We also make use of the high quality and well experimentally-constrained dosimetry evaluations from the IRDFF library. Special attention was dedicated to themore » elastic angular distributions, which were found to affect results of the integral benchmarking. The new set of iron evaluations was developed in concert with other CIELO evaluations and they were tested together in the integral experiments before being adopted for the ENDF/B-VIII.0 library.« less

Evaluation of Neutron Reactions on Iron Isotopes for CIELO and ENDF/B-VIII.0

NASA Astrophysics Data System (ADS)

Herman, M.; Trkov, A.; Capote, R.; Nobre, G. P. A.; Brown, D. A.; Arcilla, R.; Danon, Y.; Plompen, A.; Mughabghab, S. F.; Jing, Q.; Zhigang, G.; Tingjin, L.; Hanlin, L.; Xichao, R.; Leal, L.; Carlson, B. V.; Kawano, T.; Sin, M.; Simakov, S. P.; Guber, K.

2018-02-01

A new suite of evaluations for 54,56,57,58Fe has been developed in the framework of the CIELO international collaboration. New resolved resonance ranges were evaluated for 54Fe and 57Fe, while modifications were applied to resonances in 56Fe. The low energy part of the 56Fe file is almost totally based on measurements. At higher energies in 56Fe and in the whole fast neutron range for minor isotopes the evaluation consists of model predictions carefully adjusted to available experimental data. We also make use of the high quality and well experimentally-constrained dosimetry evaluations from the IRDFF library. Special attention was dedicated to the elastic angular distributions, which were found to affect results of the integral benchmarking. The new set of iron evaluations was developed in concert with other CIELO evaluations and they were tested together in the integral experiments before being adopted for the ENDF/B-VIII.0 library.

Evaluation of Neutron Reactions on Iron Isotopes for CIELO and ENDF/B-VIII.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herman, M.; Trkov, A.; Capote, R.

A new suite of evaluations for 54,56,57,58Fe has been developed in the framework of the CIELO international collaboration. New resolved resonance ranges were evaluated for 54Fe and 57Fe, while modifications were applied to resonances in 56Fe. The low energy part of the 56Fe file is almost totally based on measurements. At higher energies in 56Fe and in the whole fast neutron range for minor isotopes the evaluation consists of model predictions carefully adjusted to available experimental data. We also make use of the high quality and well experimentally-constrained dosimetry evaluations from the IRDFF library. Special attention was dedicated to themore » elastic angular distributions, which were found to affect results of the integral benchmarking. The new set of iron evaluations was developed in concert with other CIELO evaluations and they were tested together in the integral experiments before being adopted for the ENDF/B-VIII.0 library.« less

In situ Mössbauer investigation of iron oxide catalyst in water gas shift reaction - Impact of oxyreduction potential and temperature

NASA Astrophysics Data System (ADS)

Cherkezova-Zheleva, Z.; Mitov, I.

2010-03-01

The aim of the study is to obtain the exact state of iron oxide catalyst active phase in reaction conditions, as well as the correlation between the active phase and catalytic properties of iron-containing catalysts. In situ Mössbauer spectroscopy is the major investigation technique. It is established that the change of reaction conditions (temperature and gas reaction mixture) lead to redistribution of the relative weight of spectra components and influence mainly tetrahedrally and octahedrally coordinated cations in Fe3O4 phase. It was concluded, that the active sites of the catalyst in studied reaction are probably pairs of Fe3++Fe2+-(Fe2.5+) ions, i.e. the mixed valance iron ions. The obtained catalytic activity can be explained with combination of the natural thermo-activated and catalytically induced electron exchange and better synchronizing of oxidation and reduction steps of the catalytic reaction.

Functionalization of multi-walled carbon nanotubes with iron phthalocyanine via a liquid chemical reaction for oxygen reduction in alkaline media

NASA Astrophysics Data System (ADS)

Yan, Xiaomei; Xu, Xiao; Liu, Qin; Guo, Jia; Kang, Longtian; Yao, Jiannian

2018-06-01

Iron single-atom catalyst in form of iron-nitrogen-carbon structure possesses the excellent catalytic activity in various chemical reactions. However, exploring a sustainable and stable single-atom metal catalyst still faces a great challenge due to low yield and complicated synthesis. Here, we report a functional multi-wall carbon nanotubes modified with iron phthalocyanine molecules via a liquid chemical reaction and realize the performance of similar single-atom catalysis for oxygen reduction reaction. A serial of characterizations strongly imply the structure change of iron phthalocyanine molecule and its close recombination with multi-wall carbon nanotubes, which are in favor of ORR catalysis. Compared to commercial platinum-carbon catalyst, composites exhibit superior activity for oxygen reduction reaction with higher half-wave potential (0.86 V), lower Tafel slope (38 mV dec-1), higher limiting current density and excellent electrochemical stability. The corresponding Zinc-air battery also presents higher maximum power density and discharge stability. Therefore, these findings provide a facile route to synthesize a highly efficient non-precious metal carbon-based catalyst.

Iron deficiency, but not anemia, upregulates iron absorption in breast-fed peruvian infants.

PubMed

Hicks, Penni D; Zavaleta, Nelly; Chen, Zhensheng; Abrams, Steven A; Lönnerdal, Bo

2006-09-01

Iron absorption in adults is regulated by homeostatic mechanisms that decrease absorption when iron status is high. There are few data, however, regarding the existence of a similar homeostatic regulation in infants. We studied 2 groups of human milk-fed infants using (57)Fe (given as ferrous sulfate without any milk) and (58)Fe (given at the time of a breast-milk feeding) stable isotopes to determine whether healthy infants at risk for iron deficiency would regulate their iron absorption based on their iron status. We studied 20 Peruvian infants at 5-6 mo of age and 18 infants at 9-10 mo of age. We found no effect of infant hemoglobin concentration on iron absorption with 5-6 mo-old infants absorbing 19.2 +/- 2.1% and 9- to 10-mo-old infants absorbing 25.8 +/- 2.6% of the (57)Fe dose. For (58)Fe, 5- to 6-mo-old infants absorbed 42.6 +/- 5.0% and 9 to 10-mo-old infants absorbed 51.9 +/- 10.3%. Following log transformation, iron absorption from (57)Fe (r = -0.61, P = < 0.001) and (58)Fe (r = -0.61, P = < 0.001) were inversely correlated to serum ferritin (S-Ft). For both the (57)Fe and (58)Fe doses, infants with S-Ft <12 mg/L (n = 11) had significantly higher iron absorption than those with S-Ft >12 mg/L. We concluded that iron absorption in infants is related to iron status as assessed by serum ferritin but not hemoglobin concentration. Infants with low iron status upregulate iron absorption from breast milk at both 5-6 and 9-10 mo of age.

Reactivity of catecholamine-driven Fenton reaction and its relationships with iron(III) speciation.

PubMed

Melin, Victoria; Henríquez, Adolfo; Freer, Juanita; Contreras, David

2015-03-01

Fenton reaction is the main source of free radicals in biological systems. The reactivity of this reaction can be modified by several factors, among these iron ligands are important. Catecholamine (dopamine, epinephrine, and norepinephrine) are able to form Fe(III) complexes whose extension in the coordination number depends upon the pH. Fe(III)-catecholamine complexes have been related with the development of several pathologies. In this work, the ability of catecholamines to enhance the oxidative degradation of an organic substrate (veratryl alcohol, VA) through Fenton and Fenton-like reactions was studied. The initial VA degradation rate at different pH values and its relationship to the different iron species present in solution were determined. Furthermore, the oxidative degradation of VA after 24 hours of reaction and its main oxidation products were also determined. The catecholamine-driven Fenton and Fenton-like systems showed higher VA degradation compared to unmodified Fenton or Fenton-like systems, which also showed an increase in the oxidation state of the VA degradation product. All of this oxidative degradation takes place at pH values lower than 5.50, where the primarily responsible species would be the Fe(III) mono-complex. The presence of Fe(III) mono-complex is essential in the ability of catecholamines to increase the oxidative capacity of Fenton systems.

Iron isotope biogeochemistry of Neoproterozoic marine shales

NASA Astrophysics Data System (ADS)

Kunzmann, Marcus; Gibson, Timothy M.; Halverson, Galen P.; Hodgskiss, Malcolm S. W.; Bui, Thi Hao; Carozza, David A.; Sperling, Erik A.; Poirier, André; Cox, Grant M.; Wing, Boswell A.

2017-07-01

Iron isotopes have been widely applied to investigate the redox evolution of Earth's surface environments. However, it is still unclear whether iron cycling in the water column or during diagenesis represents the major control on the iron isotope composition of sediments and sedimentary rocks. Interpretation of isotopic data in terms of oceanic redox conditions is only possible if water column processes dominate the isotopic composition, whereas redox interpretations are less straightforward if diagenetic iron cycling controls the isotopic composition. In the latter scenario, iron isotope data is more directly related to microbial processes such as dissimilatory iron reduction. Here we present bulk rock iron isotope data from late Proterozoic marine shales from Svalbard, northwestern Canada, and Siberia, to better understand the controls on iron isotope fractionation in late Proterozoic marine environments. Bulk shales span a δ 56Fe range from -0.45 ‰ to +1.04 ‰ . Although δ 56Fe values show significant variation within individual stratigraphic units, their mean value is closer to that of bulk crust and hydrothermal iron in samples post-dating the ca. 717-660 Ma Sturtian glaciation compared to older samples. After correcting for the highly reactive iron content in our samples based on iron speciation data, more than 90% of the calculated δ 56Fe compositions of highly reactive iron falls in the range from ca. -0.8 ‰ to +3 ‰ . An isotope mass-balance model indicates that diagenetic iron cycling can only change the isotopic composition of highly reactive iron by < 1 ‰ , suggesting that water column processes, namely the degree of oxidation of the ferrous seawater iron reservoir, control the isotopic composition of highly reactive iron. Considering a long-term decrease in the isotopic composition of the iron source to the dissolved seawater Fe(II) reservoir to be unlikely, we offer two possible explanations for the Neoproterozoic δ 56Fe trend. First, a

Iron and oxygen isotope fractionation during iron UV photo-oxidation: Implications for early Earth and Mars

NASA Astrophysics Data System (ADS)

Nie, Nicole X.; Dauphas, Nicolas; Greenwood, Richard C.

2017-01-01

Banded iron formations (BIFs) contain appreciable amounts of ferric iron (Fe3+). The mechanism by which ferrous iron (Fe2+) was oxidized into Fe3+ in an atmosphere that was globally anoxic is highly debated. Of the three scenarios that have been proposed to explain BIF formation, photo-oxidation by UV photons is the only one that does not involve life (the other two are oxidation by O2 produced by photosynthesis, and anoxygenic photosynthesis whereby Fe2+ is directly used as electron donor in place of water). We experimentally investigated iron and oxygen isotope fractionation imparted by iron photo-oxidation at a pH of 7.3. The iron isotope fractionation between precipitated Fe3+-bearing lepidocrocite and dissolved Fe2+ follows a Rayleigh distillation with an instantaneous 56Fe/54Fe fractionation factor of + 1.2 ‰. Such enrichment in the heavy isotopes of iron is consistent with the values measured in BIFs. We also investigated the nature of the mass-fractionation law that governs iron isotope fractionation in the photo-oxidation experiments (i.e., the slope of the δ56Fe-δ57Fe relationship). The experimental run products follow a mass-dependent law corresponding to the high-T equilibrium limit. The fact that a ∼3.8 Gyr old BIF sample (IF-G) from Isua (Greenland) falls on the same fractionation line confirms that iron photo-oxidation in the surface layers of the oceans was a viable pathway to BIF formation in the Archean, when the atmosphere was largely transparent to UV photons. Our experiments allow us to estimate the quantum yield of the photo-oxidation process (∼0.07 iron atom oxidized per photon absorbed). This yield is used to model iron oxidation on early Mars. As the photo-oxidation proceeds, the aqueous medium becomes more acidic, which slows down the reaction by changing the speciation of iron to species that are less efficient at absorbing UV-photons. Iron photo-oxidation in centimeter to meter-deep water ponds would take months to years to

Intravenous Iron Therapy in Patients with Iron Deficiency Anemia: Dosing Considerations

PubMed Central

Myers, Jennifer; Goodnough, Lawrence Tim

2015-01-01

Objective. To provide clinicians with evidence-based guidance for iron therapy dosing in patients with iron deficiency anemia (IDA), we conducted a study examining the benefits of a higher cumulative dose of intravenous (IV) iron than what is typically administered. Methods. We first individually analyzed 5 clinical studies, averaging the total iron deficit across all patients utilizing a modified Ganzoni formula; we then similarly analyzed 2 larger clinical studies. For the second of the larger studies (Study 7), we also compared the efficacy and retreatment requirements of a cumulative dose of 1500 mg ferric carboxymaltose (FCM) to 1000 mg iron sucrose (IS). Results. The average iron deficit was calculated to be 1531 mg for patients in Studies 1–5 and 1392 mg for patients in Studies 6-7. The percentage of patients who were retreated with IV iron between Days 56 and 90 was significantly (p < 0.001) lower (5.6%) in the 1500 mg group, compared to the 1000 mg group (11.1%). Conclusions. Our data suggests that a total cumulative dose of 1000 mg of IV iron may be insufficient for iron repletion in a majority of patients with IDA and a dose of 1500 mg is closer to the actual iron deficit in these patients. PMID:26257955

The calculation and evaluation for n+54,56,57,58Fe reactions

NASA Astrophysics Data System (ADS)

Han, Yinlu; Xu, Yongli; Guo, Hairui; Zhang, Zhengjun; Liang, Haiying; Cai, Chonghai; Shen, Qingbiao

2017-09-01

All cross sections of neutron-induced reactions, angular distributions, double differential cross sections, angle-integrated spectra, γ-ray production cross sections and energy spectra for 54,56,57,58Fe are calculated by using theoretical models at incident neutron energies from 0.1 to 200 MeV. The present consistent theoretical calculated results are in good agreement with recent experimental data. The present evaluated data are compared with the existing experimental data and evaluated results from ENDF/B-VII, JENDL-4, JEFF-3, and the results are given in ENDF/B format.

A Comparison of Golf Shoe Designs Highlights Greater Ground Reaction Forces with Shorter Irons

PubMed Central

Worsfold, Paul; Smith, Neal A.; Dyson, Rosemary J.

2007-01-01

In an effort to reduce golf turf damage the traditional metal spike golf shoe has been redesigned, but shoe-ground biomechanical evaluations have utilised artificial grass surfaces. Twenty-four golfers wore three different golf shoe traction designs (traditional metal spikes, alternative spikes, and a flat-soled shoe with no additional traction) when performing shots with a driver, 3 iron and 7 iron. Ground action forces were measured beneath the feet by two natural grass covered force platforms. The maximum vertical force recorded at the back foot with the 3 iron and 7 iron was 0.82 BW (body weight) and at the front foot 1.1 BW approximately in both the metal spike and alternative spike golf shoe designs. When using the driver these maximal vertical values were 0.49 BW at the back foot and 0.84 BW at the front foot. Furthermore, as performance of the backswing and then downswing necessitates a change in movement direction the range of force generated during the complete swing was calculated. In the metal spike shoe the vertical force generated at the back foot with both irons was 0.67 BW and at the front foot 0.96 BW with the 3 iron and 0.92 BW with the 7 iron. The back foot vertical force generated with the driver was 0.33 BW and at the front foot 0.83 BW wearing the metal spike shoe. Results indicated the greater force generation with the irons. When using the driver the more horizontal swing plane associated with the longer club reduced vertical forces at the back and front foot. However, the mediolateral force generated across each foot in the metal and alternative spike shoes when using the driver was greater than when the irons were used. The coefficient of friction was 0. 62 at the back and front foot whichever shoe was worn or club used. Key pointsDuring the golf swing ground reaction forces at the golf shoe to natural grass turf interface were greater with irons than with the longer driver.In the golf swing maximal vertical forces were greater at the

A model for Cryogenian iron formation

NASA Astrophysics Data System (ADS)

Cox, Grant M.; Halverson, Galen P.; Poirier, André; Le Heron, Daniel; Strauss, Justin V.; Stevenson, Ross

2016-01-01

The Neoproterozoic Tatonduk (Alaska) and Holowilena (South Australia) iron formations share many characteristics including their broadly coeval (Sturtian) ages, intimate association with glaciogenic sediments, and mineralogy. We show that these shared characteristics extend to their neodymium (εNd) and iron isotope (δ56Fe) systematics. In both regions δ56Fe values display a distinct up-section trend to isotopically heavier values, while εNd values are primitive and similar to non-ferruginous mudstones within these successions. The δ56Fe profiles are consistent with oxidation of ferruginous waters during marine transgression, and the εNd values imply that much of this iron was sourced from the leaching of continental margin sediments largely derived from continental flood basalts. Rare earth element data indicate a secondary hydrothermal source for this iron.

Solution phase and membrane immobilized iron-based free radical reactions: Fundamentals and applications for water treatment

NASA Astrophysics Data System (ADS)

Lewis, Scott Romak

Membrane-based separation processes have been used extensively for drinking water purification, wastewater treatment, and numerous other applications. Reactive membranes synthesized through functionalization of the membrane pores offer enhanced reactivity due to increased surface area at the polymer-solution interface and low diffusion limitations. Oxidative techniques utilizing free radicals have proven effective for both the destruction of toxic organics and non-environmental applications. Most previous work focuses on reactions in the homogeneous phase; however, the immobilization of reactants in membrane pores offers several advantages. The use of polyanions immobilized in a membrane or chelates in solution prevents ferric hydroxide precipitation at near-neutral pH, a common limitation of iron(Fe(II/III))-catalyzed hydrogen peroxide (H 2O2) decomposition. The objectives of this research are to develop a membrane-based platform for the generation of free radicals, degrade toxic organic compounds using this and similar solution-based reactions, degrade toxic organic compounds in droplet form, quantify hydroxyl radical production in these reactions, and develop kinetic models for both processes. In this study, a functionalized membrane containing poly(acrylic acid) (PAA) was used to immobilize iron ions and conduct free radical reactions by permeating H2O2 through the membrane. The membrane's responsive behavior to pH and divalent cations was investigated and modeled. The conversion of Fe(II) to Fe(III) in the membrane and its effect on the decomposition of hydrogen peroxide were monitored and used to develop kinetic models for predicting H2O2 decomposition in these systems. The rate of hydroxyl radical production, and hence contaminant degradation can be varied by changing the residence time, H2O2 concentration, and/or iron loading. Using these membrane-immobilized systems, successful removal of toxic organic compounds, such as pentachlorophenol (PCP), from water

46 CFR 56.25-10 - Flange facings.

Code of Federal Regulations, 2011 CFR

2011-10-01

... (incorporated by reference; see 46 CFR 56.01-2). (b) When bolting class 150 standard steel flanges to flat face cast iron flanges, the steel flange must be furnished with a flat face, and bolting must be in accordance with § 56.25-20 of this part. Class 300 raised face steel flanges may be bolted to class 250...

46 CFR 56.25-10 - Flange facings.

Code of Federal Regulations, 2013 CFR

2013-10-01

... (incorporated by reference; see 46 CFR 56.01-2). (b) When bolting class 150 standard steel flanges to flat face cast iron flanges, the steel flange must be furnished with a flat face, and bolting must be in accordance with § 56.25-20 of this part. Class 300 raised face steel flanges may be bolted to class 250...

46 CFR 56.25-10 - Flange facings.

Code of Federal Regulations, 2012 CFR

2012-10-01

... (incorporated by reference; see 46 CFR 56.01-2). (b) When bolting class 150 standard steel flanges to flat face cast iron flanges, the steel flange must be furnished with a flat face, and bolting must be in accordance with § 56.25-20 of this part. Class 300 raised face steel flanges may be bolted to class 250...

46 CFR 56.25-10 - Flange facings.

Code of Federal Regulations, 2014 CFR

2014-10-01

... (incorporated by reference; see 46 CFR 56.01-2). (b) When bolting class 150 standard steel flanges to flat face cast iron flanges, the steel flange must be furnished with a flat face, and bolting must be in accordance with § 56.25-20 of this part. Class 300 raised face steel flanges may be bolted to class 250...

46 CFR 56.25-10 - Flange facings.

Code of Federal Regulations, 2010 CFR

2010-10-01

... (incorporated by reference; see 46 CFR 56.01-2). (b) When bolting class 150 standard steel flanges to flat face cast iron flanges, the steel flange must be furnished with a flat face, and bolting must be in accordance with § 56.25-20 of this part. Class 300 raised face steel flanges may be bolted to class 250...

Visualizing the Reaction Cycle in an Iron(II)- and 2-(Oxo)-glutarate-Dependent Hydroxylase.

PubMed

Mitchell, Andrew J; Dunham, Noah P; Martinie, Ryan J; Bergman, Jonathan A; Pollock, Christopher J; Hu, Kai; Allen, Benjamin D; Chang, Wei-Chen; Silakov, Alexey; Bollinger, J Martin; Krebs, Carsten; Boal, Amie K

2017-10-04

Iron(II)- and 2-(oxo)-glutarate-dependent oxygenases catalyze diverse oxidative transformations that are often initiated by abstraction of hydrogen from carbon by iron(IV)-oxo (ferryl) complexes. Control of the relative orientation of the substrate C-H and ferryl Fe-O bonds, primarily by direction of the oxo group into one of two cis-related coordination sites (termed inline and offline), may be generally important for control of the reaction outcome. Neither the ferryl complexes nor their fleeting precursors have been crystallographically characterized, hindering direct experimental validation of the offline hypothesis and elucidation of the means by which the protein might dictate an alternative oxo position. Comparison of high-resolution X-ray crystal structures of the substrate complex, an Fe(II)-peroxysuccinate ferryl precursor, and a vanadium(IV)-oxo mimic of the ferryl intermediate in the l-arginine 3-hydroxylase, VioC, reveals coordinated motions of active site residues that appear to control the intermediate geometries to determine reaction outcome.

Iron-Catalyzed Enantioselective Cross-Coupling Reactions of α-Chloroesters with Aryl Grignard Reagents.

PubMed

Jin, Masayoshi; Adak, Laksmikanta; Nakamura, Masaharu

2015-06-10

The first iron-catalyzed enantioselective cross-coupling reaction between an organometallic compound and an organic electrophile is reported. Synthetically versatile racemic α-chloro- and α-bromoalkanoates were coupled with aryl Grignard reagents in the presence of catalytic amounts of an iron salt and a chiral bisphosphine ligand, giving the products in high yields with acceptable and synthetically useful enantioselectivities (er up to 91:9). The produced α-arylalkanoates were readily converted to the corresponding α-arylalkanoic acids with high optical enrichment (er up to >99:1) via simple deprotections/recrystallizations. The results of radical probe experiments are consistent with a mechanism that involves the formation of an alkyl radical intermediate, which undergoes subsequent enantioconvergent arylation in an intermolecular manner. The developed asymmetric coupling offers not only facile and practical access to various chiral α-arylalkanoic acid derivatives, which are of significant pharmaceutical importance, but also a basis of controlling enantioselectivity in an iron-catalyzed organometallic transformation.

Steady-state studies of the reactions of H2O-CO and CO2-H2 mixtures with liquid iron

NASA Astrophysics Data System (ADS)

Sasaki, Y.; Belton, G. R.

1998-08-01

Studies have been made of the steady-stata composition of liquid iron exposed to high flow rates of H2O-CO mixtures at 1550 °C to 1700 °C and CO2-H2 mixtures at 1600 °C. Values of the steady-state activity of oxygen have been established by measurement of either the carbon concentration or the silicon concentration when the iron was held in a silica crucible. Additions of sulfur or selenium to the iron have been found to result in steady-state oxygen activities, which differ significantly from those expected from water-gas equilibrium. The results are interpreted to show that the ratio of the apparent first-order rate constants for the reactions of H2O and CO2 with liquid iron is about 3 at 1600 °C. It is shown that the dependencies of the rate constants on the activities of sulfur, oxygen, and selenium must, even if complex, be similar for the H2O and CO2 reactions with liquid iron, to a good approximation.

Iron isotope fractionation during hydrothermal ore deposition and alteration

NASA Astrophysics Data System (ADS)

Markl, Gregor; von Blanckenburg, Friedhelm; Wagner, Thomas

2006-06-01

Iron isotopes fractionate during hydrothermal processes. Therefore, the Fe isotope composition of ore-forming minerals characterizes either iron sources or fluid histories. The former potentially serves to distinguish between sedimentary, magmatic or metamorphic iron sources, and the latter allows the reconstruction of precipitation and redox processes. These processes take place during ore formation or alteration. The aim of this contribution is to investigate the suitability of this new isotope method as a probe of ore-related processes. For this purpose 51 samples of iron ores and iron mineral separates from the Schwarzwald region, southwest Germany, were analyzed for their iron isotope composition using multicollector ICP-MS. Further, the ore-forming and ore-altering processes were quantitatively modeled using reaction path calculations. The Schwarzwald mining district hosts mineralizations that formed discontinuously over almost 300 Ma of hydrothermal activity. Primary hematite, siderite and sulfides formed from mixing of meteoric fluids with deeper crustal brines. Later, these minerals were partly dissolved and oxidized, and secondary hematite, goethite and iron arsenates were precipitated. Two types of alteration products formed: (1) primary and high-temperature secondary Fe minerals formed between 120 and 300 °C, and (2) low-temperature secondary Fe minerals formed under supergene conditions (<100 °C). Measured iron isotope compositions are variable and cover a range in δ56Fe between -2.3‰ and +1.3‰. Primary hematite ( δ56Fe: -0.5‰ to +0.5‰) precipitated by mixing oxidizing surface waters with a hydrothermal fluid that contained moderately light Fe ( δ56Fe: -0.5‰) leached from the crystalline basement. Occasional input of CO 2-rich waters resulted in precipitation of isotopically light siderite ( δ56Fe: -1.4 to -0.7‰). The difference between hematite and siderite is compatible with published Fe isotope fractionation factors. The observed

Iron isotope fractionation during microbially stimulated Fe(II) oxidation and Fe(III) precipitation

USGS Publications Warehouse

Balci, N.; Bullen, T.D.; Witte-Lien, K.; Shanks, Wayne C.; Motelica, M.; Mandernack, K.W.

2006-01-01

Interpretation of the origins of iron-bearing minerals preserved in modern and ancient rocks based on measured iron isotope ratios depends on our ability to distinguish between biological and non-biological iron isotope fractionation processes. In this study, we compared 56Fe/54Fe ratios of coexisting aqueous iron (Fe(II)aq, Fe(III)aq) and iron oxyhydroxide precipitates (Fe(III)ppt) resulting from the oxidation of ferrous iron under experimental conditions at low pH (<3). Experiments were carried out using both pure cultures of Acidothiobacillus ferrooxidans and sterile controls to assess possible biological overprinting of non-biological fractionation, and both SO42- and Cl- salts as Fe(II) sources to determine possible ionic/speciation effects that may be associated with oxidation/precipitation reactions. In addition, a series of ferric iron precipitation experiments were performed at pH ranging from 1.9 to 3.5 to determine if different precipitation rates cause differences in the isotopic composition of the iron oxyhydroxides. During microbially stimulated Fe(II) oxidation in both the sulfate and chloride systems, 56Fe/54Fe ratios of residual Fe(II)aq sampled in a time series evolved along an apparent Rayleigh trend characterized by a fractionation factor ??Fe(III)aq-Fe(II)aq???1.0022. This fractionation factor was significantly less than that measured in our sterile control experiments (???1.0034) and that predicted for isotopic equilibrium between Fe(II)aq and Fe(III)aq (???1.0029), and thus might be interpreted to reflect a biological isotope effect. However, in our biological experiments the measured difference in 56Fe/54Fe ratios between Fe(III)aq, isolated as a solid by the addition of NaOH to the final solution at each time point under N2-atmosphere, and Fe(II)aq was in most cases and on average close to 2.9??? (??Fe(III)aq-Fe(II)aq ???1.0029), consistent with isotopic equilibrium between Fe(II)aq and Fe(III)aq. The ferric iron precipitation experiments

Morphological transformation during activation and reaction of an iron Fischer-Tropsch catalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, N.B.; Kohler, S.; Harrington, M.

1995-12-31

The purpose of this project is to support the development of slurry-phase bubble column processes being studied at the La Porte Alternative Fuel Development Unit. This paper describes the aspects of Sandia`s recent work regarding the advancement and understanding of the iron catalyst used in the slurry phase process. A number of techniques were used to understand the chemical and physical effects of pretreatment and reaction on the attrition and carbon deposition characteristics of iron catalysts. Unless otherwise stated, the data discussed was derived form experiments carried out on the catalyst chosen for the summer 1994 Fischer-Tropsch run at LaPorte,more » UCI 1185-78-370, (an L 3950 type) that is 88% Fe{sub 2}O{sub 3}, 11% CuO, and 0.052%K{sub 2}O.« less

Thermal neutron capture cross section for 56Fe(n ,γ )

NASA Astrophysics Data System (ADS)

Firestone, R. B.; Belgya, T.; Krtička, M.; Bečvář, F.; Szentmikloṡi, L.; Tomandl, I.

2017-01-01

The 56Fe(n ,γ ) thermal neutron capture cross section and the 57Fe level scheme populated by this reaction have been investigated in this work. Singles γ -ray spectra were measured with an isotopically enriched 56Fe target using the guided cold neutron beam at the Budapest Reactor, and γ γ -coincidence data were measured with a natural Fe target at the LWR-15 research reactor in Řež, Czech Republic. A detailed level scheme consisting of 448 γ rays populating/depopulating 97 levels and the capture state in 57Fe has been constructed, and ≈99 % of the total transition intensity has been placed. The transition probability of the 352-keV γ ray was determined to be Pγ(352 ) =11.90 ±0.07 per 100 neutron captures. The 57Fe level scheme is substantially revised from earlier work and ≈33 previously assigned levels could not be confirmed while a comparable number of new levels were added. The 57Feγ -ray cross sections were internally calibrated with respect to 1H and 32Sγ -ray cross section standards using iron(III) acetylacetonate (C15H21FeO6) and iron pyrite (FeS2) targets. The thermal neutron cross section for production of the 352-keV γ -ray cross section was determined to be σγ(352 ) =0.2849 ±0.015 b. The total 56Fe(n ,γ ) thermal radiative neutron cross section is derived from the 352-keV γ -ray cross section and transition probability as σ0=2.394 ±0.019 b. A least-squares fit of the γ rays to the level scheme gives the 57Fe neutron separation energy Sn=7646.183 ±0.018 keV.

40 CFR 420.56 - Pretreatment standards for new sources (PSNS).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 28 2010-07-01 2010-07-01 true Pretreatment standards for new sources (PSNS). 420.56 Section 420.56 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS IRON AND STEEL MANUFACTURING POINT SOURCE CATEGORY Vacuum Degassing...

An x-ray absorption study of the iron site in bacterial photosynthetic reaction centers.

PubMed Central

Bunker, G; Stern, E A; Blankenship, R E; Parson, W W

1982-01-01

Measurements were made of the extended x-ray absorption fine structure (EXAFS) of the iron site in photosynthetic reaction centers from the bacterium Rhodopseudomonas sphaeroides. Forms with two quinones, two quinones with added o-phenanthroline, and one quinone were studied. Only the two forms containing two quinones maintained their integrity and were analyzed. The spectra show directly that the added o-phenanthroline does not chelate the iron atom. Further analysis indicates that the iron is octahedrally coordinated by nitrogen and/or oxygen atoms located at various distances, with the average value of about 2.14 A. The analysis suggests that most of the ligands are nitrogens and that three of the nitrogen ligands belong to histidine rings. This interpretation accounts for several unusual features of the EXAFS spectrum. We speculate that the quinones are bound to the histidine rings in some manner. Qualitative features of the absorption edge spectra also are discussed and are related to the Fe-ligand distance. PMID:6977382

Iron-silicate reaction at CMB and formation of core signature in plume source region: An experimental approach

NASA Astrophysics Data System (ADS)

Ohtani, E.; Sakai, T.; Kondo, T.; Miyahara, M.; Terasaki, H.

2006-12-01

Recent progress of laser heating diamond anvil cell (LHDAC) techniques made it possible to achieve the conditions of pressures and temperatures exceeding the core-mantle boundary conditions, i.e., 130 GPa and 3000-3500 K, and we can now be possible to study the recovered samples from the condition of the core- mantle boundary. We used the focused ion beam (FIB) method for preparation of the recovered samples and the analytical transmission electron microscope (ATEM) for their characterization, which are the ideal tools for studying the recovered samples from mega-bar conditions. In order to clarify the structure of the bottom of the CMB region, we have conducted high pressure and temperature experiments on the reaction between metallic iron and post-perovskite which can simulate the chemical reactions at CMB. We have conducted reaction experiments between molten iron and post-perovskite at the conditions equivalent to the CMB, 139 GPa and 3000 K. Significant amounts of oxygen up to 6.3 wt. percent and silicon up to 4.0 wt. percent are dissolved in metallic iron, and the solubility of silicon and oxygen in metallic iron can readily account for 7-10 wt. percent of the core density deficit. The dissolution of silicon into molten iron in the primordial magma ocean with the depth of the deep lower mantle can account for the Mg/Si ratio of the mantle higher than that of C1-chondrite. The dihedral angle between post-perovskite and molten iron is around 67 degrees, which is larger than that of perovskite and molten iron, 51 degrees (Takafuji et al., 2004). A core signature has been reported as Re and Os isotope anomalies in the plume magmas originating from the core-mantle boundary region, and such isotopic anomalies can be easily generated by contamination of 0.5-1 wt. percent of the trapped core metal at CMB (e.g., Brandon et al., 2005). A significant disturbance is expected at CMB to form a mixing region of the mantle and core materials as was suggested by Kellogg et al

Level density and mechanism of deuteron-induced reactions on Fe 54 , 56 , 58

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramirez, A. P. D.; Voinov, A. V.; Grimes, S. M.

Here, deuteron elastic cross sections, as well as neutron, proton, and α-particle emission spectra, from d+ 54,56,58Fe reactions have been measured with deuteron beam energies of 5, 7, and 9 MeV. Optical model parameters have been tested against our experimental data. The fraction of total reaction cross section responsible for the formation of compound nuclei has been deduced from the angular distributions. The degree of discrepancy between calculated and experimental compound cross sections was found to increase with increasing neutron number. The nuclear level densities of the residual nuclei 55Co, 57Co, 55Fe, 57Fe, 52Mn, and 54Mn have been deduced frommore » the compound double differential cross sections. The Gilbert-Cameron model with Iljinov parameter systematics [A. S. Iljinov and M. V. Mebel, Nucl. Phys. A 543, 517 (1992)] was found to have a good agreement with our results.« less

Level density and mechanism of deuteron-induced reactions on Fe 54 , 56 , 58

DOE PAGES

Ramirez, A. P. D.; Voinov, A. V.; Grimes, S. M.; ...

2015-07-06

Here, deuteron elastic cross sections, as well as neutron, proton, and α-particle emission spectra, from d+ 54,56,58Fe reactions have been measured with deuteron beam energies of 5, 7, and 9 MeV. Optical model parameters have been tested against our experimental data. The fraction of total reaction cross section responsible for the formation of compound nuclei has been deduced from the angular distributions. The degree of discrepancy between calculated and experimental compound cross sections was found to increase with increasing neutron number. The nuclear level densities of the residual nuclei 55Co, 57Co, 55Fe, 57Fe, 52Mn, and 54Mn have been deduced frommore » the compound double differential cross sections. The Gilbert-Cameron model with Iljinov parameter systematics [A. S. Iljinov and M. V. Mebel, Nucl. Phys. A 543, 517 (1992)] was found to have a good agreement with our results.« less

New reaction tester accurate within 56 microseconds

NASA Technical Reports Server (NTRS)

Brown, H.

1972-01-01

Testing device measures simple and disjunctive reaction time of human subject to light stimuli. Tester consists of reaction key, logic card, panel mounted neon indicators, and interconnecting wiring. Device is used for determining reaction times of patients undergoing postoperative neurological therapy.

46 CFR 56.50-95 - Overboard discharges and shell connections.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., or ductile cast iron specification listed in Table 56.60-1(a). Lead or other heat sensitive materials... flooding. Brittle materials such as cast iron shall not be used in such service. Where nonmetallic... inch, except that the use of suitable corrosion-resistant material of lesser thickness will be given...

46 CFR 56.50-95 - Overboard discharges and shell connections.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., or ductile cast iron specification listed in Table 56.60-1(a). Lead or other heat sensitive materials... flooding. Brittle materials such as cast iron shall not be used in such service. Where nonmetallic... inch, except that the use of suitable corrosion-resistant material of lesser thickness will be given...

Effective Construction of High-quality Iron Oxy-hydroxides and Co-doped Iron Oxy-hydroxides Nanostructures: Towards the Promising Oxygen Evolution Reaction Application

NASA Astrophysics Data System (ADS)

Zhang, Xinyu; An, Li; Yin, Jie; Xi, Pinxian; Zheng, Zhiping; Du, Yaping

2017-03-01

Rational design of high efficient and low cost electrocatalysts for oxygen evolution reaction (OER) plays an important role in water splitting. Herein, a general gelatin-assisted wet chemistry method is employed to fabricate well-defined iron oxy-hydroxides and transitional metal doped iron oxy-hydroxides nanomaterials, which show good catalytic performances for OER. Specifically, the Co-doped iron oxy-hydroxides (Co0.54Fe0.46OOH) show the excellent electrocatalytic performance for OER with an onset potential of 1.52 V, tafel slope of 47 mV/dec and outstanding stability. The ultrahigh oxygen evolution activity and strong durability, with superior performance in comparison to the pure iron oxy-hydroxide (FeOOH) catalysts, originate from the branch structure of Co0.54Fe0.46OOH on its surface so as to provide many active edge sites, enhanced mass/charge transport capability, easy release oxygen gas bubbles, and strong structural stability, which are advantageous for OER. Meanwhile, Co-doping in FeOOH nanostructures constitutes a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal-air batteries, regenerative fuel cells, and other important clean energy devices. This work may provide a new insight into constructing the promising water oxidation catalysts for practical clean energy application.

Effective Construction of High-quality Iron Oxy-hydroxides and Co-doped Iron Oxy-hydroxides Nanostructures: Towards the Promising Oxygen Evolution Reaction Application.

PubMed

Zhang, Xinyu; An, Li; Yin, Jie; Xi, Pinxian; Zheng, Zhiping; Du, Yaping

2017-03-08

Rational design of high efficient and low cost electrocatalysts for oxygen evolution reaction (OER) plays an important role in water splitting. Herein, a general gelatin-assisted wet chemistry method is employed to fabricate well-defined iron oxy-hydroxides and transitional metal doped iron oxy-hydroxides nanomaterials, which show good catalytic performances for OER. Specifically, the Co-doped iron oxy-hydroxides (Co 0.54 Fe 0.46 OOH) show the excellent electrocatalytic performance for OER with an onset potential of 1.52 V, tafel slope of 47 mV/dec and outstanding stability. The ultrahigh oxygen evolution activity and strong durability, with superior performance in comparison to the pure iron oxy-hydroxide (FeOOH) catalysts, originate from the branch structure of Co 0.54 Fe 0.46 OOH on its surface so as to provide many active edge sites, enhanced mass/charge transport capability, easy release oxygen gas bubbles, and strong structural stability, which are advantageous for OER. Meanwhile, Co-doping in FeOOH nanostructures constitutes a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal-air batteries, regenerative fuel cells, and other important clean energy devices. This work may provide a new insight into constructing the promising water oxidation catalysts for practical clean energy application.

Evaluation of the mercaptobenzothiazole degradation by combined adsorption process and Fenton reaction using iron mining residue.

PubMed

Martins, Adriana Lau da Silva; Teixeira, Luís Alberto César; da Fonseca, Fabiana Valéria; Yokoyama, Lídia

2017-08-01

The present study investigated the degradation of mercaptobenzothiazole (MBT), evaluating homogeneous and heterogeneous systems. An iron mineral residue from the desliming step of iron mining was used as a source in the Fenton-like reaction (advanced oxidation process). A granulometric analysis of the residue was performed and yielded fractions with high hematite (Fe 2 O 3 ) and low quartz content in sieves from 74 to below 44 mm. In this particle size range, the hematite content from 58.9% to 67.4% and the Brunauer-Emmett-Teller area from 0.1345 to 1.3137 m 2  g -1 were obtained. The zeta potential curves as a function of pH were obtained for the residue, the MBT solution and mixtures thereof. The adsorption of MBT in the residue and its degradation through the Fenton-like reaction were investigated. Adsorption tests and the Fenton-like reaction were carried out, where the MBT species and the residue are oppositely charged, yielding, respectively, 10% MBT adsorption on the surface of the residue and 100% MBT degradation by the Fenton-like reaction at pH 3, hydrogen peroxide concentration of 25 mg L -1 , residue concentration of 3 g L -1 , 200 rpm and 25°C, from a 100 mg L -1 MBT solution. MBT degradation was found to occur mainly by the heterogeneous Fenton-like process.

Reactions of metal ions at surfaces of hydrous iron oxide

USGS Publications Warehouse

Hem, J.D.

1977-01-01

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

4′-CyanoPLP presents better prospect for the experimental detection of elusive cyclic intermediate radical in the reaction of lysine 5,6-aminomutase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maity, Amarendra Nath; Ke, Shyue-Chu, E-mail: ke@mail.ndhu.edu.tw

2015-02-06

Graphical abstract: The results of our calculations suggest that the reaction of 4′-cyanoPLP with lysine 5,6-aminomutase offers better prospect for the experimental detection of elusive cyclic azacyclopropylcarbinyl radical, which is proposed to be a key intermediate in the reaction of pyridoxal-5′-phosphate dependent radical aminomutases. - Highlights: • 4′-CyanoI{sup ·} is the lowest energy radical intermediate in the reaction of 5,6-LAM. • 4′-CyanoPLP offers good prospect for the experimental observation of elusive I{sup ·}. • The calculated HFCCs would help to characterize 4′-cyanoI{sup ·} by EPR. - Abstract: The results of our calculations suggest that the reaction of 4′-cyanoPLP with lysinemore » 5,6-aminomutase offers better prospect for the experimental detection of elusive cyclic azacyclopropylcarbinyl radical (I{sup ·}), which is proposed to be a key intermediate in the reaction of pyridoxal-5′-phosphate dependent radical aminomutases. We have calculated the corresponding hyperfine coupling constants (HFCCs) for {sup 14}N and {sup 13}C of cyano group using several basis sets to help the characterization of 4′-cyanoI{sup ·}.« less

An impact-induced terrestrial atmosphere and iron-water reactions during accretion of the Earth

NASA Technical Reports Server (NTRS)

Lange, M. A.; Ahrens, T. J.

1985-01-01

Shock wave data and theoretical calculations were used to derive models of an impact-generated terrestrial atmosphere during accretion of the Earth. The models showed that impacts of infalling planetesimals not only provided the entire budget of terrestrial water but also led to a continuous depletion of near-surface layers of water-bearing minerals of their structural water. This resulted in a final atmospheric water reservoir comparable to the present day total water budget of the Earth. The interaction of metallic iron with free water at the surface of the accreting Earth is considered. We carried out model calcualtions simulating these processes during accretion. It is assumed that these processes are the prime source of the terrestrial FeO component of silicates and oxides. It is demonstrated that the iron-water reaction would result in the absence of atmospheric/hydrospheric water, if homogeneous accretion is assumed. In order to obtain the necessary amount of terrestrial water, slightly heterogeneous accretion with initially 36 wt% iron planetesimals, as compared with a homogeneous value of 34 wt% is required.

Effect Of Reaction Environments On The Reactivity Of PCB (2-Chlorobiphenyl) Over Activated Carbon Impregnated With Palladized Iron

EPA Science Inventory

Reactive activated carbon (RAC) impregnated with palladized iron nanoparticles has been developed to treat polychlorinated biphenyls (PCBs). In this study, we evaluated the effects of various reaction environments on the adsorption-mediated dechlorination of 2-chlorobiphenyl (2-...

Drug‐specific hypophosphatemia and hypersensitivity reactions following different intravenous iron infusions

PubMed Central

Hvas, Christian L.; Dahlerup, Jens F.

2017-01-01

Aims Intravenous (IV) iron infusions have been associated with hypophosphataemia (HP) and hypersensitivity reactions (HSRs). No studies have compared the side effects of ferric carboxymaltose (FCM) with those of isomaltoside 1000 (ISM). This study aimed to describe the occurrence of HP and HSRs following the administration of either FCM or ISM. Methods Data on 231 outpatients treated with IV iron infusions, between November 2011 and April 2014, were collected. During that period, the department made a switch from FCM to ISM and then back to FCM. Of the 231 patients, 39 received both FCM and ISM during the period. The prevalences of HP and HSRs were compared between the two drugs. Results We found more HP events when FCM was given (64 vs. 9; P < 0.01). In contrast, more patients had mild HSRs when ISM was given (2.5% vs. 10.7%; P < 0.01). A comparison of the two drugs in the subpopulation who received both drug types (n = 39) revealed a difference in phosphate decrease (P < 0.01), with the most marked decrease occurring with FCM. Nine patients who had HSRs were exposed to both drugs. No potential HSR crossover between the two drugs was found. Conclusion We found a higher risk of HP with FCM administration when compared to ISM administration. Conversely, we found a higher risk of mild HSRs with ISM administration when compared to FCM administration. The impacts of the two types of side effects should be considered when choosing an IV iron drug. PMID:27859495

Drug-specific hypophosphatemia and hypersensitivity reactions following different intravenous iron infusions.

PubMed

Bager, Palle; Hvas, Christian L; Dahlerup, Jens F

2017-05-01

Intravenous (IV) iron infusions have been associated with hypophosphataemia (HP) and hypersensitivity reactions (HSRs). No studies have compared the side effects of ferric carboxymaltose (FCM) with those of isomaltoside 1000 (ISM). This study aimed to describe the occurrence of HP and HSRs following the administration of either FCM or ISM. Data on 231 outpatients treated with IV iron infusions, between November 2011 and April 2014, were collected. During that period, the department made a switch from FCM to ISM and then back to FCM. Of the 231 patients, 39 received both FCM and ISM during the period. The prevalences of HP and HSRs were compared between the two drugs. We found more HP events when FCM was given (64 vs. 9; P < 0.01). In contrast, more patients had mild HSRs when ISM was given (2.5% vs. 10.7%; P < 0.01). A comparison of the two drugs in the subpopulation who received both drug types (n = 39) revealed a difference in phosphate decrease (P < 0.01), with the most marked decrease occurring with FCM. Nine patients who had HSRs were exposed to both drugs. No potential HSR crossover between the two drugs was found. We found a higher risk of HP with FCM administration when compared to ISM administration. Conversely, we found a higher risk of mild HSRs with ISM administration when compared to FCM administration. The impacts of the two types of side effects should be considered when choosing an IV iron drug. © 2016 The British Pharmacological Society.

Benthic iron cycling in a high-oxygen environment: Implications for interpreting the Archean sedimentary iron isotope record.

PubMed

McCoy, V E; Asael, D; Planavsky, N

2017-09-01

The most notable trend in the sedimentary iron isotope record is a shift at the end of the Archean from highly variable δ 56 Fe values with large negative excursions to less variable δ 56 Fe values with more limited negative values. The mechanistic explanation behind this trend has been extensively debated, with two main competing hypotheses: (i) a shift in marine redox conditions and the transition to quantitative iron oxidation; and (ii) a decrease in the signature of microbial iron reduction in the sedimentary record because of increased bacterial sulfate reduction (BSR). Here, we provide new insights into this debate and attempt to assess these two hypotheses by analyzing the iron isotope composition of siderite concretions from the Carboniferous Mazon Creek fossil site. These concretions precipitated in an environment with water column oxygenation, extensive sediment pile dissimilatory iron reduction (DIR) but limited bacterial sulfate reduction (BSR). Most of the concretions have slightly positive iron isotope values, with a mean of 0.15‰ and limited iron isotope variability compared to the Archean sedimentary record. This limited variability in an environment with high DIR and low BSR suggests that these conditions alone are insufficient to explain Archean iron isotope compositions. Therefore, these results support the idea that the unusually variable and negative iron isotope values in the Archean are due to dissimilatory iron reduction (DIR) coupled with extensive water column iron cycling. © 2017 John Wiley & Sons Ltd.

Reduced Uranium Phases Produced from Anaerobic Reaction with Nanoscale Zerovalent Iron.

PubMed

Tsarev, Sergey; Collins, Richard N; Fahy, Adam; Waite, T David

2016-03-01

Nanoscale zerovalent iron (nZVI) has shown potential to be an effective remediation agent for uranium-contaminated subsurface environments, however, the nature of the reaction products and their formation kinetics have not been fully elucidated over a range of environmentally relevant conditions. In this study, the oxygen-free reaction of U(VI) with varying quantities of nZVI was examined at pH 7 in the presence of both calcium and carbonate using a combination of X-ray absorption spectroscopy, X-ray diffraction and transmission electron microscopy. It was observed that the structure of the reduced U solid phases was time dependent and largely influenced by the ratio of nZVI to U in the system. At the highest U:Fe molar ratio examined (1:4), nanoscale uraninite (UO2) was predominantly formed within 1 day of reaction. At lower U:Fe molar ratios (1:21), evidence was obtained for the formation of sorbed U(IV) and U(V) surface complexes which slowly transformed to UO2 nanoparticles that were stable for up to 1 year of anaerobic incubation. After 8 days of reaction at the lowest U:Fe molar ratio examined (1:110), sorbed U(IV) was still the major form of U associated with the solid phase. Regardless of the U:Fe molar ratio, the anaerobic corrosion of nZVI resulted in the slow formation of micron-sized fibrous chukanovite (Fe2(OH)2CO3) particles.

Oxygen reduction reaction properties of nitrogen-incorporated nanographenes synthesized using in-liquid plasma from mixture of ethanol and iron phthalocyanine

NASA Astrophysics Data System (ADS)

Amano, Tomoki; Kondo, Hiroki; Takeda, Keigo; Ishikawa, Kenji; Hiramatsu, Mineo; Sekine, Makoto; Hori, Masaru

2018-04-01

Nanographenes were synthesized using in-liquid plasma from a mixture of iron phthalocyanine and ethanol. In a previous study, micrometer-scale flakes with nitrogen incorporation were obtained. A nonprecious metal catalytic activity was observed with 3.13 electrons in an oxygen reduction reaction under an acidic solute condition. Large-surface-area, high-graphene-crystallinity, and iron-carbon-bonding sites were found owing to a high catalytic activity in Fe-N/nanographene.

Practical Iron- and Cobalt-Catalyzed Cross-Coupling Reactions between N-Heterocyclic Halides and Aryl or Heteroaryl Magnesium Reagents.

PubMed

Kuzmina, Olesya M; Steib, Andreas K; Fernandez, Sarah; Boudot, Willy; Markiewicz, John T; Knochel, Paul

2015-05-26

The reaction scope of iron- and cobalt-catalyzed cross-coupling reactions in the presence of isoquinoline (quinoline) in the solvent mixture tBuOMe/THF has been further investigated. Various 2-halogenated pyridine, pyrimidine, and triazine derivatives were arylated under these mild conditions in excellent yields. The presence of isoquinoline allows us to perform Fe-catalyzed cross-coupling reactions between 6-chloroquinoline and aryl magnesium reagents. Furthermore, it was found that the use of 10% N,N-dimethylquinoline-8-amine increases the yields of some Co-catalyzed cross-coupling reactions with chloropyridines bearing electron-withdrawing substituents. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparative safety of intravenous Ferumoxytol versus Ferric Carboxymaltose for the Treatment of Iron Deficiency Anemia: rationale and study design of a randomized double-blind study with a focus on acute hypersensitivity reactions.

PubMed

Adkinson, N Franklin; Strauss, William E; Bernard, Kristine; Kaper, Robert F; Macdougall, Iain C; Krop, Julie S

2017-01-01

Intravenous (IV) iron is often used to treat iron deficiency anemia in patients who are unable to tolerate or are inadequately managed with oral iron. However, IV iron treatment has been associated with acute hypersensitivity reactions. The comparative risk of adverse events (AEs) with IV iron preparations has been assessed by a few randomized controlled trials, which are most often limited by small patient numbers, which lack statistical power to identify differences in low-frequency AE such as hypersensitivity reactions. Ferumoxytol versus Ferric Carboxymaltose for the Treatment of Iron Deficiency Anemia (FIRM) is a randomized, double-blind, international, multicenter, Phase III study designed to compare the safety of ferumoxytol and ferric carboxymaltose (FCM). The study includes adults with hemoglobin <12.0 g/dL (females) or <14.0 g/dL (males), transferrin saturation ≤20% or ferritin ≤100 ng/mL within 60 days of dosing, and a history of unsatisfactory or nontolerated oral iron therapy or in whom oral iron therapy is inappropriate. Patients are randomized (1:1) to ferumoxytol 510 mg or FCM 750 mg, each given intravenously on days 1 and 8. Primary end points are the incidence of moderate-to-severe hypersensitivity reactions, including anaphylaxis, and moderate-to-severe hypotension. All potential hypersensitivity and hypotensive reactions will be adjudicated by a blinded, independent Clinical Events Committee. A secondary safety end point is the composite frequency of moderate-to-severe hypersensitivity reactions, including anaphylaxis, serious cardiovascular events, and death. Secondary efficacy end points include mean change in hemoglobin and mean change in hemoglobin per milligram of iron administered from baseline to week 5. Urinary excretion of phosphorus and the occurrence of hypophosphatemia after IV iron administration will be examined as well as the mechanisms of such hypophosphatemia in a substudy. FIRM will provide data on the comparative safety of

Petrographic and Isotopic Evidence for Siderite Precursors to Iron Oxide Cements

NASA Astrophysics Data System (ADS)

Loope, D.

2015-12-01

The origin of iron oxide mineralization in the Navajo Sandstone on the Colorado Plateau is important because of the different forms of distinct self-organization exhibited by these systems, the potential importance of the cements as geochronometers, and their use as analogs for similar mineralization on other planets. We consider this mineralization to be the product of microbially mediated oxidation of siderite in evolving groundwater systems. Iron oxide grain coatings were dissolved and the iron precipitated as siderite during a reducing phase of diagenesis. Upon invasion by oxidizing waters, iron-oxidizing bacteria colonized the redox interface between siderite-cemented and porous sandstone. Precipitation of iron oxide at this interface generated acid that facilitated further siderite dissolution. One difficulty in testing this hypothesis is that siderite is destroyed by the cm-scale transport of iron during oxidation. There are two lines of evidence that support the presence of a siderite precursor in these systems. 1)Rhombic grains that we interpret to be iron oxide pseudomorphs after siderite occur where in-situ oxidation rather than dissolution of the siderite precursor has occurred. 2) The δ56Fe values of these iron oxide cements are typically negative. We have measured the δ56Fe value of Navajo Sandstone to be 0.2‰; a value in good agreement with previous workers (Chan et al., 2006; Busigny and Dauphas, 2007). Bleaching of the sandstones apparently results in near complete removal of Fe with little change in the δ56Fe values of the bulk sandstone. The δ56Fe values of iron oxide cements have a median value of -0.8‰; similar to the value we obtained from ferroan carbonate (-0.86‰). Iron oxide from samples that comprise largely rhombic grains has similar δ56Fe values (-0.5‰) to those obtained from cements produced by siderite dissolution and subsequent oxidation (-0.4‰). Our interpretation is that siderite precipitated from an aqueous solution

The Effect of Temperature and Ionic Strength on the Oxidation of Iodide by Iron(III): A Clock Reaction Kinetic Study

ERIC Educational Resources Information Center

Bauer, Jurica; Tomisic, Vladislav; Vrkljan, Petar B. A.

2012-01-01

A laboratory exercise has recently been reported in which the students use the initial rates method based on the clock reaction approach to deduce the rate law and propose a reaction mechanism for the oxidation of iodide by iron(III) ions. The same approach is used in the exercise proposed herein; the students determine the dependence of the…

Copper(I)- and copper(0)-promoted homocoupling and homocoupling-hydrodehalogenation reactions of dihalogenoclathrochelate precursors for C-C conjugated iron(II) bis-cage complexes.

PubMed

Varzatskii, Oleg A; Shul'ga, Sergey V; Belov, Alexander S; Novikov, Valentin V; Dolganov, Alexander V; Vologzhanina, Anna V; Voloshin, Yan Z

2014-12-28

Iron(II) dibromo- and diiodoclathrochelates undergo copper(I)-promoted reductive homocoupling in HMPA at 70-80 °C leading to C-C conjugated dibromo- and diiodo-bis-clathrochelates in high yields. Under the same conditions, their dichloroclathrochelate analog does not undergo the same homocoupling reaction, so the target dichloro-bis-cage product was obtained in high yield via dimerization of its heterodihalogenide iodochloromonomacrobicyclic precursor. The use of NMP as a solvent at 120-140 °C gave the mixture of bis-clathrochelates resulting from a tandem homocoupling-hydrodehalogenation reaction: the initial acetonitrile copper(I) solvato-complex at a high temperature underwent re-solvatation and disproportionation leading to Cu(II) ions and nano-copper, which promoted the hydrodehalogenation process even at room temperature. The most probable pathway of this reaction in situ includes hydrodehalogenation of the already formed dihalogeno-bis-clathrochelate via the formation of reduced anion radical intermediates. As a result, chemical transformations of the iron(II) dihalogenoclathrochelates in the presence of an acetonitrile copper(I) solvato-complex were found to depend both on the nature of halogen atoms in their ribbed chelate fragments and on reaction conditions (i.e. solvent and temperature). The C-C conjugated iron(II) dihalogeno-bis-clathrochelates easily undergo nucleophilic substitution with various N,S-nucleophiles giving ribbed-functionalized bis-cage species. These iron(II) complexes were characterized by elemental analysis, MALDI-TOF mass spectrometry, IR, UV-Vis, (1)H and (13)C NMR spectroscopy, and by X-ray diffraction; their electrochemical properties were studied by cyclic voltammetry. The isomeric shift values in (57)Fe Mössbauer spectra of such cage compounds allowed identifying them as low-spin iron(II) complexes, while those of the quadrupole splitting are the evidence for a significant TP distortion of their FeN6-coordination polyhedra

Results of the First American Prospective Study of Intravenous Iron in Oral Iron-Intolerant Iron-Deficient Gravidas.

PubMed

Auerbach, Michael; James, Stephanie E; Nicoletti, Melissa; Lenowitz, Steven; London, Nicola; Bahrain, Huzefa F; Derman, Richard; Smith, Samuel

2017-12-01

Anemia affects up to 42% of gravidas. Neonatal iron deficiency is associated with low birth weight, delayed growth and development, and increased cognitive and behavioral abnormalities. While oral iron is convenient, up to 70% report significant gastrointestinal toxicity. Intravenous iron formulations allowing replacement in one visit with favorable side-effect profiles decrease rates of anemia with improved hemoglobin responses and maternal fetal outcomes. Seventy-four oral iron-intolerant, second- and third-trimester iron-deficient gravidas were questioned for oral iron intolerance and treated with intravenous iron. All received 1000 mg of low-molecular-weight iron dextran in 250 mL normal saline. Fifteen minutes after a test dose, the remainder was infused over the balance of 1 hour. Subjects were called at 1, 2, and 7 days to assess delayed reactions. Four weeks postinfusion or postpartum, hemoglobin levels and iron parameters were measured. Paired t test was used for hemoglobin and iron; 58/73 women were questioned about interval growth and development of their babies. Seventy-three of 74 enrolled subjects completed treatment. Sixty had paired pre- and posttreatment data. The mean pre- and posthemoglobin concentrations were 9.7 and 10.8 g/dL (P < .00001), transferrin saturations 11.7% and 22.6% (P = .0003), and ferritins 14.5 and 126.3 ng/mL, respectively (P < .000001). Six experienced minor infusion reactions. All resolved. Data for 58 infants were available; one was low on its growth charts for 11 months. The remaining 57 were normal. None were diagnosed with iron deficiency anemia. Intravenous iron has less toxicity and is more effective, supporting moving it closer to frontline therapy. Copyright © 2017 Elsevier Inc. All rights reserved.

Generation of Oxidants From the Reaction of Nanoparticulate Zero-Valent Iron and Oxygen for the use in Contaminant Remediation

NASA Astrophysics Data System (ADS)

Keenan, C. R.; Lee, C.; Sedlak, D. L.

2007-12-01

The reaction of zero-valent iron (ZVI) with oxygen can lead to the formation of oxidants, which may be used to transform recalcitrant contaminants including non-polar organics and certain metals. Nanoparticulate iron might provide a practical mechanism of remediating oxygen-containing groundwater and contaminated soil. To gain insight into the reaction mechanism and to quantify the yield of oxidants, experiments were performed with model organic compounds in the presence of nanoparticulate zero-valent iron and oxygen. At pH values below 5, ZVI nanoparticles were oxidized within 30 minutes with a stoichiometry of approximately two Fe0 oxidized per O2 consumed. Using the oxidation of methanol and ethanol to formaldehyde and acetaldehyde, respectively, we found that less than 2% of the consumed oxygen was converted to reactive oxidants under acidic conditions. The yield of aldehydes increased with pH up to pH 7, with maximum oxidant yields of around 5% relative to the mass of ZVI added. The increase of aldehyde yield with pH was attributable to changes in the processes responsible for oxidant production. At pH values below 5, the corrosion of ZVI by oxygen produces hydrogen peroxide, which subsequently reacts with ferrous iron [Fe(II)] via the Fenton reaction. At higher pH values, the aldehydes are produced when Fe(II), the initial product of ZVI oxidation, reacts with oxygen. The decrease in oxidant yield at pH values above 7 may be attributable to precipitation of Fe(II). The oxidation of benzoic acid and 2-propanol to para-hydroxybenzoic acid and acetone, respectively, followed a very different trend compared to the primary alcohols. In both cases, the highest product yields (approximately 2% with respect to ZVI added) were observed at pH 3. Yields decreased with increasing pH, with no oxidized product detected at neutral pH. These results suggest that two different oxidants may be produced by the system: hydroxyl radical (OH-·) at acidic pH and a more selective

Water-Rock Interaction Simulations of Iron Oxide Mobilization and Precipitation: Implications of Cross-diffusion Reactions for Terrestrial and Mars 'Blueberry' Hematite Concretions

NASA Astrophysics Data System (ADS)

Park, A. J.; Chan, M. A.; Parry, W. T.

2005-12-01

Modeling of how terrestrial concretions form can provide valuable insights into understanding water-rock interactions that led to the formation of hematite concretions at Meridiani Planum, Mars. Numerical simulations of iron oxide concretions in the Jurassic Navajo Sandstone of southern Utah provide physical and chemical input parameters for emulating conditions that may have prevailed on Mars. In the terrestrial example, iron oxide coatings on eolian sand grains are reduced and mobilized by methane or petroleum. Precipitation of goethite or hematite occurs as Fe interacts with oxygen. Conditions that produced Navajo Sandstone concretions can range from a regional scale that is strongly affected by advection of large pore volumes of water, to small sub-meter scale features that are dominantly controlled by diffusive processes. Hematite concretions are results of a small-scale cross-diffusional process, where Fe and oxygen are supplied from two opposite sides from the 'middle' zone of mixing where concretions precipitate. This is an ideal natural system where Liesegang banding and other self-organized patterns can evolve. A complicating variable here is the sedimentologic (both mineralogic and textural) heterogeneity that, in reality, may be the key factor controlling the nucleation and precipitation habits (including possible competitive growth) of hematite concretions. Sym.8 water-rock interaction simulator program was used for the Navajo Sandstone concretions. Sym.8 is a water-rock simulator that accounts for advective and diffusive mass-transfer, and equilibrium and kinetic reactions. The program uses a dynamic composite media texture model to address changing sediment composition and texture to be consistent with the reaction progress. Initial one-dimensional simulation results indicate precipitation heterogeneity in the range of sub-meters, e.g., possible banding and distribution of iron oxide nodules may be centimeters apart for published diffusivities and

Coal desulfurization. [using iron pentacarbonyl

NASA Technical Reports Server (NTRS)

Hsu, G. C. (Inventor)

1979-01-01

Organic sulfur is removed from coal by treatment with an organic solution of iron pentacarbonyl. Organic sulfur compounds can be removed by reaction of the iron pentacarbonyl with coal to generate CO and COS off-gases. The CO gas separated from COS can be passed over hot iron fillings to generate iron pentacarbonyl.

How low does iron go? Chasing the active species in fe-catalyzed cross-coupling reactions.

PubMed

Bedford, Robin B

2015-05-19

The catalytic cross-coupling reactions of organic halides or related substrates with organometallic nucleophiles form the cornerstone of many carbon-carbon bond-forming processes. While palladium-based catalysts typically mediate such reactions, there are increasing concerns about the long-term sustainability of palladium in synthesis. This is due to the high cost of palladium, coupled with its low natural abundance, environmentally deleterious extraction (∼6 g of metal are produced per ton of ore), toxicity, and competition for its use from the automotive and consumer electronics sectors. Therefore, there is a growing interest in replacing palladium-based catalysts with those incorporating more earth-abundant elements. With its low cost, high natural abundance, and low toxicity, iron makes a particularly appealing alternative, and accordingly, the development of iron-catalyzed cross-coupling is undergoing explosive growth. However, our understanding of the mechanisms that underpin the iron-based catalytic cycles is still very much in its infancy. Mechanistic insight into catalytic reactions is not only academically important but also allows us to maximize the efficiency of processes or even to develop entirely new transformations. Key to the development of robust mechanistic models for cross-coupling is knowing the lowest oxidation state in the cycle. Once this is established, we can explore subsequent redox processes and build the catalytic manifold. Until we know with confidence what the lowest oxidation state is, any cycles proposed are largely just guesswork. To date, Fe(-II), Fe(-I), Fe(0), Fe(I), and Fe(II) have been proposed as contenders for the lowest-oxidation-state species in the cycle in iron-catalyzed cross-coupling; the aim of this Account is to pull together the various pieces of evidence in support, or otherwise, of each of these suggestions in turn. There currently exists no direct evidence that oxidation states below Fe(0) are active in the

Relative Incidence of Acute Adverse Events with Ferumoxytol Compared to Other Intravenous Iron Compounds: A Matched Cohort Study.

PubMed

Wetmore, James B; Weinhandl, Eric D; Zhou, Jincheng; Gilbertson, David T

2017-01-01

Concerns persist about adverse reactions to intravenous (IV) iron. We aimed to determine the relative safety of ferumoxytol compared to other IV iron compounds. This retrospective cohort study with propensity-score matching for patients and drug doses used the Medicare 20% random sample to identify patients (1) without chronic kidney disease (non-CKD) and (2) with non-dialysis-dependent chronic kidney disease (NDD-CKD) who received a first dose of IV iron in 2010-2012. Exposures were ferumoxytol, iron sucrose, sodium ferric gluconate, or iron dextran. Outcomes were hypersensitivity symptoms, anaphylaxis, emergency department (ED) encounters, hospitalizations, and death after acute IV iron exposure. In the primary analysis for reactions on the day of or following exposure, there was no difference in hypersensitivity symptoms (hazard ratio 1.04, 95% confidence interval 0.94-1.16) or hypotension (0.83, 0.52-1.34) between 4289 non-CKD ferumoxytol users and an equal number of users of other compounds; results were similar for 7358 NDD-CKD patients and an equal number of controls. All-cause ED encounters or hospitalizations were less common in both the non-CKD (0.56, 0.45-0.70) and NDD-CKD ferumoxytol-treated patients (0.83, 0.71-0.95). Fewer than 10 deaths occurred in both the non-CKD and NDD-CKD ferumoxytol users and in matched controls; the hazard for death did not differ significantly between ferumoxytol users and controls in the non-CKD patients (2.00, 0.33-11.97) or in the NDD-CKD patients (0.25, 0.04-1.52). Multiple sensitivity analyses showed similar results. Ferumoxytol did not appear to be associated with more adverse reactions than other compounds for the treatment of iron-deficiency anemia in both non-CKD and NDD-CKD patients.

Reaction between hydrous wadsleyite and iron: Implication for water distribution in Earth's transition zone

NASA Astrophysics Data System (ADS)

Zhu, F.; Li, J.; Liu, J.; Dong, J.

2017-12-01

The mantle transition zone (TZ) is considered as a potential water reservoir due to large capacities of wadsleyite and ringwoodite to store water in the structures. Whether it is a hydrous layer or an empty reservoir, however, is still under debate. Because the TZ may contain metallic iron1, 2 and water is an oxidizing agent at > 5 GPa, the stability of coexisting iron and TZ hydrous phases needs to be examined. In this study, we conducted multi-anvil experiments on iron with synthetic hydrous wadsleyite or forsterite and water under TZ pressure-temperature conditions. Similar rapid reactions were observed for both types of starting materials, producing ferropericlase, iron-bearing wadsleyite or ringwoodite, and iron hydride. The results imply that a hydrous TZ is incompatible with a reduced state, and that water distribution of TZ is confined to subducting slabs and slab-mantle boundaries, where water or hydrous phases in slab must oxidize the adjacent mantle before they can hydrate the silicates. In contrast, the bulk transition zone may be mostly dry. The iron hydride produced from this slab-mantle interaction may sink to greater depths due to their low melting temperature3, thus providing a pathway for hydrogen to enter the lower mantle and core. References 1. O'Neill HSC, McCammon C, Canil D, Rubie D, Ross C, Seifert F. Mossbauer spectroscopy of mantle transition zone phases and determination of minimum Fe3+ content. American Mineralogist 1993, 78(3-4): 456-460. 2. Rohrbach A, Ballhaus C, Golla-Schindler U, Ulmer P, Kamenetsky VS, Kuzmin DV. Metal saturation in the upper mantle. Nature 2007, 449(7161): 456-458. 3. Sakamaki K, Takahashi E, Nakajima Y, Nishihara Y, Funakoshi K, Suzuki T, et al. Melting phase relation of FeH x up to 20GPa: Implication for the temperature of the Earth's core. Physics of the Earth and Planetary Interiors 2009, 174(1): 192-201.

Weekly iron folate supplementation in adolescent girls--an effective nutritional measure for the management of iron deficiency anaemia.

PubMed

Joshi, Mohan; Gumashta, Raghvendra

2013-03-20

Nutritional anaemia in India is common morbidity seen in late adolescent and young female population. There are many conflicting opinions regarding dosage of iron folic acid supplementation for managing this simple nutritional deficiency disorder. Hence, this 'Randomized Controlled Trial' was undertaken in adolescent girls suffering from Iron Deficiency Anaemia visiting 'Urban Health and Training Centre' situated in urban slum area. The aim of this study was to assess the (a) Impact of weekly iron folic acid supplementation in comparison with daily iron supplementation for the management of Iron Deficiency Anaemia in adolescent girls visiting 'Urban Health and Training Centre'; (b) Adverse drug reaction profile in 'Weekly Iron Folic Acid Supplementation' and 'Daily Iron Folic Acid Supplementation' regimes; (c) Compliance profile for 'Weekly Iron Folic Acid Supplementation' and 'Daily Iron Folic Acid Supplementation' regimes in adolescent girls. Randomized controlled trial was conducted in adolescent girls visiting 'Urban Health and Training Centre' during the study period June, 2011 to October, 2012. The 120 anaemic (Haemoglobin < 12 gm%) adolescent girls (10-19 years) were distributed randomly by block randomization in two groups; one receiving daily Iron and Folic Acid supplementation and in other group receiving weekly Iron and Folic Acid supplementation for 3 months. All the study subjects were given de-worming (Albendazole 400 mg) and required health education separately. Both the groups were monitored for Haemoglobin estimation, compliance and adverse drug reactions, if any. Open-Epi Statistical Software was used for data analysis. The mean age of study subjects in 'Daily Iron and Folic Acid Supplementation' and 'Weekly Iron and Folic Acid Supplementation' group was 13.48 and 13.55 years respectively. Their mean pre intervention Haemoglobin was 10.1±1.1 gm/dl and 10.4±1.1 gm/dl respectively. The mean rise in Haemoglobin after lean period of 1 month in

Stopped-in-loop flow analysis system for successive determination of trace vanadium and iron in drinking water using their catalytic reactions.

PubMed

Ayala Quezada, Alejandro; Ohara, Keisuke; Ratanawimarnwong, Nuanlaor; Nacapricha, Duangjai; Murakami, Hiroya; Teshima, Norio; Sakai, Tadao

2015-11-01

An automated stopped-in-loop flow analysis (SILFA) system is proposed for the successive catalytic determination of vanadium and iron. The determination of vanadium was based on the p-anisidine oxidation by potassium bromate in the presence of Tiron as an activator to form a reddish dye, which has an absorption maximum at 510 nm. The selectivity of the vanadium determination was greatly improved by adding diphosphate as a masking agent of iron. For the iron determination, an iron-catalyzed oxidative reaction of p-anisidine by hydrogen peroxide with 1,10-phenanthroline as an activator to produce a reddish dye (510 nm) was employed. The SILFA system consisted of two peristaltic pumps, two six-port injection valves, a four-port selection valve, a heater device, a spectrophotometric detector and a data acquisition device. One six-port injection valve was used for the isolation of a mixed solution of standard/sample and reagent to promote each catalytic reaction, and another six-port injection valve was used for switching the reagent for vanadium or iron to achieve selective determination of each analyte. The above mentioned four-port selection valve was used to select standard solutions or sample. These three valves and the two peristaltic pumps were controlled by a built-in programmable logic controller in a touchscreen controller. The obtained results showed that the proposed SILFA monitoring system constituted an effective approach for the selective determination of vanadium and iron. The limits of detection, 0.052 and 0.55 µg L(-1), were obtained for vanadium and iron, respectively. The proposed system was successfully applied to drinking water samples without any preconcentration procedures. Copyright © 2015 Elsevier B.V. All rights reserved.

Understanding the nanoscale redox-behavior of iron-anodes for rechargeable iron-air batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weinrich, Henning; Come, Jérémy; Tempel, Hermann

Iron-air cells provide a promising and resource-efficient alternative battery concept with superior area specific power density characteristics compared to state-of-the-art Li-air batteries and potentially superior energy density characteristics compared to present Li-ion batteries. Understanding charge-transfer reactions at the anode-electrolyte interface is the key to develop high-performance cells. By employing in-situ electrochemical atomic force microscopy (in-situ EC-AFM), in-depth insight into the electrochemically induced surface reaction processes on iron in concentrated alkaline electrolyte is obtained. The results highlight the formation and growth of the redox-layer on iron over the course of several oxidation/reduction cycles. By this means, a direct correlation between topographymore » changes and the corresponding electrochemical reactions at the nanoscale could unambiguously be established. Here in this paper, the twofold character of the nanoparticulate redox-layer in terms of its passivating character and its contribution to the electrochemical reactions is elucidated. Furthermore, the evolution of single nanoparticles on the iron electrode surface is evaluated in unprecedented and artifact-free detail. Based on the dedicated topography analysis, a detailed structural model for the evolution of the redox-layer which is likewise elementary for corrosion science and battery research is derived.« less

The effects of metamorphism on iron mineralogy and the iron speciation redox proxy

NASA Astrophysics Data System (ADS)

Slotznick, Sarah P.; Eiler, John M.; Fischer, Woodward W.

2018-03-01

As the most abundant transition metal in the Earth's crust, iron is a key player in the planetary redox budget. Observations of iron minerals in the sedimentary record have been used to describe atmospheric and aqueous redox environments over the evolution of our planet; the most common method applied is iron speciation, a geochemical sequential extraction method in which proportions of different iron minerals are compared to calibrations from modern sediments to determine water-column redox state. Less is known about how this proxy records information through post-depositional processes, including diagenesis and metamorphism. To get insight into this, we examined how the iron mineral groups/pools (silicates, oxides, sulfides, etc.) and paleoredox proxy interpretations can be affected by known metamorphic processes. Well-known metamorphic reactions occurring in sub-chlorite to kyanite rocks are able to move iron between different iron pools along a range of proxy vectors, potentially affecting paleoredox results. To quantify the effect strength of these reactions, we examined mineralogical and geochemical data from two classic localities where Silurian-Devonian shales, sandstones, and carbonates deposited in a marine sedimentary basin with oxygenated seawater (based on global and local biological constraints) have been regionally metamorphosed from lower-greenschist facies to granulite facies: Waits River and Gile Mountain Formations, Vermont, USA and the Waterville and Sangerville-Vassalboro Formations, Maine, USA. Plotting iron speciation ratios determined for samples from these localities revealed apparent paleoredox conditions of the depositional water column spanning the entire range from oxic to ferruginous (anoxic) to euxinic (anoxic and sulfidic). Pyrrhotite formation in samples highlighted problems within the proxy as iron pool assignment required assumptions about metamorphic reactions and pyrrhotite's identification depended on the extraction techniques

Penning trap mass measurement of 56Cu

NASA Astrophysics Data System (ADS)

Valverde, A. A.; Brodeur, M.; Bollen, G.; Eibach, M.; Gulyuz, K.; Hamacker, A.; Izzo, C.; Ong, W.-J.; Puentes, D.; Redshaw, M.; Ringle, R.; Sandler, R.; Schwarz, S.; Sumithrarachchi, C. S.; Surbrook, J.; Villari, A. C. C.; Yandow, I. T.

2017-09-01

The doubly-magic nucleus 56Ni is one of the most important waiting point nuclei in the rp-process. While we now know that it is not the endpoint of the rp-process, which continues to the Sn-Sb-Te cycle, the flow around this nucleus is still not well understood. A pathway bypassing 56Ni through the 55Ni(p, γ)56Cu reaction exists, but the rate depends on the Q value of this reaction, which has not been experimentally determined. Mass measurements were undertaken using the LEBIT 9.4T Penning trap mass spectrometer at the National Superconducting Cyclotron Laboratory to rectify this situation. This work was supported in part by the National Science Foundation.

Iron Stain on Wood

Treesearch

Mark Knaebe

2013-01-01

Iron stain, an unsightly blue–black or gray discoloration, can occur on nearly all woods. Oak, redwood, cypress, and cedar are particularly prone to iron stain because these woods contain large amounts of tannin-like extractives. The discoloration is caused by a chemical reaction between extractives in the wood and iron in steel products, such as nails, screws, and...

[Heme-iron in the human body].

PubMed

Balla, József; Balla, György; Lakatos, Béla; Jeney, Viktória; Szentmihályi, Klára

2007-09-09

Iron is essential for all living organism, although in excess amount it is dangerous via catalyzing the formation of reactive oxygen species. Absorption of iron is strictly controlled resulting in a fine balance of iron-loss and iron-uptake. In countries where the ingestion of heme-iron is significant by meal, great part of iron content in the body originates from heme. Heme derived from food is absorbed by a receptor-mediated manner by enterocytes of small intestine then it is degraded in a reaction catalyzed by heme oxygenase. Iron released from the porphyrin ring leaves enterocytes as transferrin associated iron. Prosthetic group of several proteins contains heme, therefore, it is synthesized by all cells. One of the most significant heme proteins is hemoglobin which transports oxygen in the erythrocytes. Hemoglobin released from erythrocyte during intravascular hemolysis binds to haptoglobin and is taken up by cells of the monocyte-macrophage lineage. Oxidation of hemoglobin (ferro) to methemoglobin (ferri) is inhibited by the structure of hemoglobin although it is not hindered. Superoxide anion is also formed in the reaction that initiates further free radical reactions. In contrast to ferrohemoglobin, methemoglobin readily releases heme, therefore, oxidation of hemoglobin drives the formation of free heme in plasma. Heme binds to a plasma protein, hemopexin, and is internalized by cells of monocyte-macrophage lineage in a receptor-mediated manner, then degraded in reaction catalysed by heme oxygenase. Heme is also taken up by plasma lipoproteins and endothelial cells leading to oxidation of LDL and subsequent endothelial cell damage. The purpose of this work was to summarize the processes related to heme.

Tracing iron-carbon redox from surface to core

NASA Astrophysics Data System (ADS)

McCammon, C. A.; Cerantola, V.; Bykova, E.; Kupenko, I.; Bykov, M.; Chumakov, A. I.; Rüffer, R.; Dubrovinsky, L. S.

2017-12-01

Numerous redox reactions separate the Earth's oxidised surface from its reduced core. Many involve iron, the Earth's most abundant element and the mantle's most abundant transition element. Most iron redox reactions (although not all) also involve other elements, including carbon, where iron-carbon interactions drive a number of important processes within the Earth, for example diamond formation. Many of the Earth's redox boundaries are sharp, much like the seismic properties that define them, for example between the lower mantle and the core. Other regions that appear seismically homogeneous, for example the lower mantle, harbour a wealth of reactions between oxidised and reduced phases of iron and carbon. We have undertaken many experiments at high pressure and high temperature on phases containing iron and carbon using synchrotron-based X-rays to probe structures and iron oxidation states. Results demonstrate the dominant role that crystal structures play in determining the stable oxidation states of iron and carbon, even when oxygen fugacity (and common sense) would suggest otherwise. Iron in bridgmanite, for example, occurs predominantly in its oxidised form (ferric iron) throughout the lower mantle, despite the inferred reducing conditions. Newly discovered structures of iron carbonate also stabilise ferric iron, while simultaneously reducing some carbon to diamond to balance charge. Other high-pressure iron carbonates appear to be associated with the emerging zoo of iron oxide phases, involving transitions between ferrous and ferric iron through the exchange of oxygen. The presentation will trace redox relations between iron and carbon from the Earth's surface to its core, with an emphasis on recent experimental results.

Determination of low concentrations of iron, arsenic, selenium, cadmium, and other trace elements in natural samples using an octopole collision/reaction cell equipped quadrupole-inductively coupled plasma mass spectrometer.

PubMed

Dial, Angela R; Misra, Sambuddha; Landing, William M

2015-04-30

Accurate determination of trace metals has many applications in environmental and life sciences, such as constraining the cycling of essential micronutrients in biological production and employing trace metals as tracers for anthropogenic pollution. Analysis of elements such as Fe, As, Se, and Cd is challenged by the formation of polyatomic mass spectrometric interferences, which are overcome in this study. We utilized an Octopole Collision/Reaction Cell (CRC)-equipped Quadrupole-Inductively Coupled Plasma Mass Spectrometer for the rapid analysis of small volume samples (~250 μL) in a variety of matrices containing HNO3 and/or HCl. Efficient elimination of polyatomic interferences was demonstrated by the use of the CRC in Reaction Mode (RM; H2 gas) and in Collision-Reaction Mode (CRM; H2 and He gas), in addition to hot plasma (RF power 1500 W) and cool plasma (600 W) conditions. It was found that cool plasma conditions with RM achieved the greatest signal sensitivity while maintaining low detection limits (i.e. (56) Fe in 0.44 M HNO3 has a sensitivity of 160,000 counts per second (cps)-per-1 µg L(-1) and a limit of detection (LoD) of 0.86 ng L(-1) ). The average external precision was ≤ ~10% for minor (≤10 µg L(-1) ) elements measured in a 1:100 dilution of NIST 1643e and for iron in rainwater samples under all instrumental operating conditions. An improved method has been demonstrated for the rapid multi-element analysis of trace metals that are challenged by polyatomic mass spectrometric interferences, with a focus on (56) Fe, (75) As, (78) Se and (111) Cd. This method can contribute to aqueous environmental geochemistry and chemical oceanography, as well as other fields such as forensic chemistry, agriculture, food chemistry, and pharmaceutical sciences. Copyright © 2015 John Wiley & Sons, Ltd.

Effect of thiamine hydrochloride on the redox reactions of iron at pyrite surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pesic, B.; Oliver, D.J.

1990-01-01

The present investigation is a part of our studies on the electro chemical aspects of pyrite bioleaching involving Thiobacillus ferrooxidans. Previously (1,2) we have examined the effect of T. ferrooxidans and their metabolic products on the redox reactions of Fe[sup 2+]/Fe[sup 3+] couple at the pyrite surface. Results obtained suggest that beyond 1. 5 days during their growth in a batch fermenter, the bacteria and their metabolic products completely cover the pyrite surface and shut down all electron transfer across the electrode-solution interface. In addition, it has been observed that the bacteria serve as the nucleation site for jarosite formation,more » which is found detrimental to bioleaching. In the present work we have focussed on the effect of the presence of vitamins on the redox chemistry of iron. Our examination of the effect of the presence of thiamine hydrochloride in the redox behavior of Fe[sup 2+]/Fe[sup 3+] at the pyrite surface has revealed that thiamine hydrochloride does not undergo chemical interaction with ferrous or ferric iron. However, it may adsorb onto the pyrite surface causing polarization of the pyrite electrode.« less

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

EPA Science Inventory

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

Ligand iron catalysts for selective hydrogenation

DOEpatents

Casey, Charles P.; Guan, Hairong

2010-11-16

Disclosed are iron ligand catalysts for selective hydrogenation of aldehydes, ketones and imines. A catalyst such as dicarbonyl iron hydride hydroxycyclopentadiene) complex uses the OH on the five member ring and hydrogen linked to the iron to facilitate hydrogenation reactions, particularly in the presence of hydrogen gas.

Effects of Na2SO4 on iron and nickel reduction in a high-iron and low-nickel laterite ore

NASA Astrophysics Data System (ADS)

Wang, Xiao-ping; Sun, Ti-chang; Chen, Chao; Kou, Jue

2018-04-01

This study investigates the reactions of Na2SO4 and its effects on iron and nickel reduction in the roasting of a high-iron and low-nickel laterite ore through gas composition, X-ray diffraction, and scanning electron microscope analyses. Results showed that a reduction reaction of Na2SO4 to SO2 was performed with roasting up to 600°C. However, no clear influence on iron and nickel reductions appeared, because only a small amount of Na2SO4 reacted to produce SO2. Na2SO4 reacted completely at 1000°C, mainly producing troilite and nepheline, which remarkably improves selective reduction of nickel. Furthermore, the production of low-melting-point minerals, including troilite and nepheline, accelerated nickel reduction and delayed iron reduction, which is attributed to the concurrent production of magnesium magnetite, whose structure is more stable than the structure of magnetite. Reduction reactions of Na2SO4 resulted in weakening of the reduction atmosphere, and the main product of Na2SO4 changed and delayed the reduction of iron. Eventually, iron metallization was effectively controlled during laterite ore reduction roasting, leading to iron mainly being found in wustite and high iron-containing olivine.

Reactive iron in marine sediments

NASA Technical Reports Server (NTRS)

Canfield, Donald E.

1989-01-01

The influence of reactive iron oxides on sediment pore-water chemistry is considered in detail. A carefully calibrated extraction scheme is used to determine the depth distributions of reactive iron phases at two very different localities: the relatively iron-rich Mississippi Delta and the relatively iron-poor FOAM site in Long Island Sound. Closed system incubations are used to characterize the rates of reaction between sulfide and both naturally occurring and pure iron mineral phases. Rates of iron liberation to pore solution are measured in the presence and absence of sulfate reduction, and the origin of dissolved iron in organic-rich sediments is speculated upon.

46 CFR 56.50-60 - Systems containing oil.

Code of Federal Regulations, 2014 CFR

2014-10-01

... °F must be of seamless steel. (See § 56.50-65 of this part.) (k) Oil piping drains, strainers and... is of steel construction, all welded, and not concealed. (d) Piping subject to internal head pressure... installed on the outside of the oil tanks must be made of steel, ductile cast iron ASTM A 395 (incorporated...

46 CFR 56.50-60 - Systems containing oil.

Code of Federal Regulations, 2012 CFR

2012-10-01

... °F must be of seamless steel. (See § 56.50-65 of this part.) (k) Oil piping drains, strainers and... is of steel construction, all welded, and not concealed. (d) Piping subject to internal head pressure... installed on the outside of the oil tanks must be made of steel, ductile cast iron ASTM A 395 (incorporated...

46 CFR 56.50-60 - Systems containing oil.

Code of Federal Regulations, 2011 CFR

2011-10-01

... °F must be of seamless steel. (See § 56.50-65 of this part.) (k) Oil piping drains, strainers and... is of steel construction, all welded, and not concealed. (d) Piping subject to internal head pressure... installed on the outside of the oil tanks must be made of steel, ductile cast iron ASTM A 395 (incorporated...

46 CFR 56.50-60 - Systems containing oil.

Code of Federal Regulations, 2010 CFR

2010-10-01

... °F must be of seamless steel. (See § 56.50-65 of this part.) (k) Oil piping drains, strainers and... is of steel construction, all welded, and not concealed. (d) Piping subject to internal head pressure... installed on the outside of the oil tanks must be made of steel, ductile cast iron ASTM A 395 (incorporated...

46 CFR 56.50-60 - Systems containing oil.

Code of Federal Regulations, 2013 CFR

2013-10-01

... °F must be of seamless steel. (See § 56.50-65 of this part.) (k) Oil piping drains, strainers and... is of steel construction, all welded, and not concealed. (d) Piping subject to internal head pressure... installed on the outside of the oil tanks must be made of steel, ductile cast iron ASTM A 395 (incorporated...

Sodium ascorbate kills Candida albicans in vitro via iron-catalyzed Fenton reaction: importance of oxygenation and metabolism

PubMed Central

Avci, Pinar; Freire, Fernanda; Banvolgyi, Andras; Mylonakis, Eleftherios; Wikonkal, Norbert M; Hamblin, Michael R

2016-01-01

Aim: Ascorbate can inhibit growth and even decrease viability of various microbial species including Candida albicans. However the optimum conditions and the mechanism of action are unclear. Materials/methodology: Candida albicans shaken for 90 min in a buffered solution of ascorbate (90 mM) gave a 5-log reduction of cell viability, while there was no killing without shaking, in growth media with different carbon sources or at 4°C. Killing was inhibited by the iron chelator 2,2′-bipyridyl. Hydroxyphenyl fluorescein probe showed the intracellular generation of hydroxyl radicals. Results/conclusion: Ascorbate-mediated killing of C. albicans depends on oxygenation and metabolism, involves iron-catalyzed generation of hydroxyl radicals via Fenton reaction and depletion of intracellular NADH. Ascorbate could serve as a component of a topical antifungal therapy. PMID:27855492

Formation of Gas-Phase Formate in Thermal Reactions of Carbon Dioxide with Diatomic Iron Hydride Anions.

PubMed

Jiang, Li-Xue; Zhao, Chongyang; Li, Xiao-Na; Chen, Hui; He, Sheng-Gui

2017-04-03

The hydrogenation of carbon dioxide involves the activation of the thermodynamically very stable molecule CO 2 and formation of a C-H bond. Herein, we report that HCO 2 - and CO can be formed in the thermal reaction of CO 2 with a diatomic metal hydride species, FeH - . The FeH - anions were produced by laser ablation, and the reaction with CO 2 was analyzed by mass spectrometry and quantum-chemical calculations. Gas-phase HCO 2 - was observed directly as a product, and its formation was predicted to proceed by facile hydride transfer. The mechanism of CO 2 hydrogenation in this gas-phase study parallels similar behavior of a condensed-phase iron catalyst. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Preliminary studies on physicochemical properties of Angelica sinensis polysaccharide-iron complex].

PubMed

Wang, Kai-ping; Zhang, Yu; Dai, Li-quan

2006-05-01

To study some physicochemical properties of Angelica sinensis polysaccharide-iron complex (APC). Based on the qualitatively identified reactions of iron (III), the qualitatively identified reactions of APC were found out by comparing hydroxide. The content of iron (III) in APC was determined with iodometry. The stability of APC under physiological pH conditions was judged by titrating APC with sodium hydroxide. The deoxidization of APC was tested with colorimetric analysis. APC showed the qualitatively identified reactions of iron (III). The content of iron (III) in APC ranged from 10% to 40%, and the water-solubility of APC was related to the content of iron (III). The complex was stable at physiological pH from 3 to 12, without precipitation and dissociation. At 37 degrees C, Fe (III) in the complex was completely reduced to Fe (III) by ascorbic acid in about 6 hours. APC can be qualitatively identified by using the qualitatively identified reactions of iron (III). When its iron (III) content is within 20%-25%, APC has a better ability to dissolve in water. And the complex is stable under physiological pH conditions.

Surface reactions of iron - enriched smectites: adsorption and transformation of hydroxy fatty acids and phenolic acids

NASA Astrophysics Data System (ADS)

Polubesova, Tamara; Olshansky, Yaniv; Eldad, Shay; Chefetz, Benny

2014-05-01

Iron-enriched smectites play an important role in adsorption and transformation of soil organic components. Soil organo-clay complexes, and in particular humin contain hydroxy fatty acids, which are derived from plant biopolymer cutin. Phenolic acids belong to another major group of organic acids detected in soil. They participate in various soil processes, and are of concern due to their allelopathic activity. We studied the reactivity of iron-enriched smectites (Fe(III)-montmorillonite and nontronite) toward both groups of acids. We used fatty acids- 9(10),16-dihydroxypalmitic acid (diHPA), isolated from curtin, and 9,10,16-trihydroxypalmitic acid (triHPA); the following phenolic acids were used: ferulic, p-coumaric, syringic, and vanillic. Adsorption of both groups of acids was measured. The FTIR spectra of fatty acid-mineral complexes indicated inner-sphere complexation of fatty acids with iron-enriched smectites (versus outer-sphere complexation with Ca(II)-montmorillonite). The LC-MS results demonstrated enhanced esterification of fatty acids on the iron-enriched smectite surfaces (as compared to Ca(II)-montmorillonite). This study suggests that fatty acids can be esterified on the iron-enriched smectite surfaces, which results in the formation of stable organo-mineral complexes. These complexes may serve as a model for the study of natural soil organo-clay complexes and humin. The reaction of phenolic acids with Fe(III)-montmorillonite demonstrated their oxidative transformation by the mineral surfaces, which was affected by molecular structure of acids. The following order of their transformation was obtained: ferulic >syringic >p-coumaric >vanillic. The LC-MS analysis demonstrated the presence of dimers, trimers, and tetramers of ferulic acid on the surface of Fe(III)-montmorillonite. Oxidation and transformation of ferulic acid were more intense on the surface of Fe(III)-montmorillonite as compared to Fe(III) in solution due to stronger complexation on

Polymersomes containing iron sulfide (FeS) as primordial cell model : for the investigation of energy providing redox reactions.

PubMed

Alpermann, Theodor; Rüdel, Kristin; Rüger, Ronny; Steiniger, Frank; Nietzsche, Sandor; Filiz, Volkan; Förster, Stephan; Fahr, Alfred; Weigand, Wolfgang

2011-04-01

According to Wächtershäuser's "Iron-Sulfur-World" one major requirement for the development of life on the prebiotic Earth is compartmentalization. Vesicles spontaneously formed from amphiphilic components containing a specific set of molecules including sulfide minerals may have lead to the first autotrophic prebiotic units. The iron sulfide minerals may have been formed by geological conversions in the environment of deep-sea volcanos (black smokers), which can be observed even today. Wächtershäuser postulated the evolution of chemical pathways as fundamentals of the origin of life on earth. In contrast to the classical Miller-Urey experiment, depending on external energy sources, the "Iron-Sulfur-World" is based on the catalytic and energy reproducing redox system FeS+H2S-->FeS2+H2. The energy release out of this redox reaction (∆RG°=-38 kJ/mol, pH 0) could be the cause for the subsequent synthesis of complex organic molecules and the precondition for the development of more complex units similar to cells known today. Here we show the possibility for precipitating iron sulfide inside vesicles composed of amphiphilic block-copolymers as a model system for a first prebiotic unit. Our findings could be an indication for a chemoautotrophic FeS based origin of life.

The role of sedimentology, oceanography, and alteration on the δ56Fe value of the Sokoman Iron Formation, Labrador Trough, Canada

NASA Astrophysics Data System (ADS)

Raye, Urmidola; Pufahl, Peir K.; Kyser, T. Kurtis; Ricard, Estelle; Hiatt, Eric E.

2015-09-01

The Sokoman Formation is a ca. 100-m-thick succession of interbedded iron formation and fine-grained siliciclastics deposited at 1.88 Ga. Accumulation occurred on a dynamic paleoshelf where oxygen stratification, coastal upwelling of hydrothermally derived Fe and Si, microbial processes, tide and storm currents, diagenesis, and low-grade prehnite-pumpellyite metamorphism controlled lithofacies character and produced complex associations of multigenerational chert, hematite, magnetite, greenalite, stilpnomelane and Fe carbonate. Hematite-rich facies were deposited along suboxic segments of the coastline where photosynthetic oxygen oases impinged on the seafloor. Hematitic, cross-stratified grainstones were formed by winnowing and reworking of freshly precipitated Fe-(oxyhydr)oxide and opal-A by waves and currents into subaqueous dunes. Magnetite-rich facies contain varying proportions of greenalite and stilpnomelane and record deposition in anoxic middle shelf environments beneath an oxygen chemocline. Minor negative Ce anomalies in hematitic facies, but prominent positive Ce and Eu anomalies and high LREE/HREE ratios in magnetite-rich facies imply the existence of a weakly oxygenated surface ocean above anoxic bottom waters. The Fe isotopic composition of 31 whole rock (-0.46 ⩽ δ56Fe ⩽ 0.47‰) and 21 magnetite samples (-0.29 ⩽ δ56Fe ⩽ 0.22‰) from suboxic and anoxic lithofacies was controlled primarily by the physical oceanography of the paleoshelf. Despite low-grade metamorphism recorded by the δ18O values of paragenetically related quartz and magnetite, the Sokoman Formation preserves a robust primary Fe isotopic signal. Coastal upwelling is interpreted to have affected the isotopic equilibria between Fe2+aq and Fe-(oxyhydr)oxide in open marine versus coastal environments, which controlled the Fe isotopic composition of lithofacies. Unlike previous work that focuses on microbial and abiotic fractionation processes with little regard for

Daily supplementation with iron increases lipid peroxidation in young women with low iron stores.

PubMed

King, Sarah M; Donangelo, Carmen M; Knutson, Mitchell D; Walter, Patrick B; Ames, Bruce N; Viteri, Fernando E; King, Janet C

2008-06-01

The aim of this study was to determine whether women with low iron stores (plasma ferritin iron supplement for 8 wks at a level commonly used to treat poor iron status develop increased lipid peroxidation as measured by ethane exhalation rates and plasma malondialdehyde. The women served as their own control as pre- and post-supplementation periods were compared. Twelve women participated in the study for a 70-day period and consumed daily iron supplements (98 mg of iron as ferrous sulfate) from day 14 to day 70. Baseline blood and expired air samples were obtained on days 1 and 14; measurements during supplementation were performed on days 56 and 70, that is at 6 and 8 weeks of supplementation. Iron status improved during the iron supplementation period; biochemical indicators of lipid peroxidation also increased. After 6 wks of iron supplementation, serum ferritin almost doubled and body iron more than doubled. Hemoglobin levels increased slightly and other indicators of iron status became normal. However, plasma malondialdehyde (MDA) and breath ethane exhalation rates (BEER) increased by more than 40% between baseline and 6 wks of supplementation; these increases correlated significantly with plasma iron and ferritin levels. MDA was positively correlated with BEER. BEER increased further after 8 wks of iron supplementation. The increased indicators of lipid peroxidation with duration of supplementation and as iron status improved suggest that providing daily nearly 100 mg iron may not be a totally innocuous regimen for correcting iron depletion in women.

Protective effect of mitochondrial-targeted antioxidant MitoQ against iron ion 56Fe radiation induced brain injury in mice.

PubMed

Gan, Lu; Wang, Zhenhua; Si, Jing; Zhou, Rong; Sun, Chao; Liu, Yang; Ye, Yancheng; Zhang, Yanshan; Liu, Zhiyuan; Zhang, Hong

2018-02-15

Exposure to iron ion 56 Fe radiation (IR) during space missions poses a significant risk to the central nervous system and radiation exposure is intimately linked to the production of reactive oxygen species (ROS). MitoQ is a mitochondria-targeted antioxidant that has been shown to decrease oxidative damage and lower mitochondrial ROS in a number of animal models. Therefore, the present study aimed to investigate role of the mitochondrial targeted antioxidant MitoQ against 56 Fe particle irradiation-induced oxidative damage and mitochondria dysfunction in the mouse brains. Increased ROS levels were observed in mouse brains after IR compared with the control group. Enhanced ROS production leads to disruption of cellular antioxidant defense systems, mitochondrial respiration dysfunction, altered mitochondria dynamics and increased release of cytochrome c (cyto c) from mitochondria into cytosol resulting in apoptotic cell death. MitoQ reduced IR-induced oxidative stress (decreased ROS production and increased SOD, CAT activities) with decreased lipid peroxidation as well as reduced protein and DNA oxidation. MitoQ also protected mitochondrial respiration after IR. In addition, MitoQ increased the expression of mitofusin2 (Mfn2) and optic atrophy gene1 (OPA1), and decreased the expression of dynamic-like protein (Drp1). MitoQ also suppressed mitochondrial DNA damage, cyto c release, and caspase-3 activity in IR-treated mice compared to the control group. These results demonstrate that MitoQ may protect against IR-induced brain injury. Copyright © 2018 Elsevier Inc. All rights reserved.

Low-lying level structure of 56Cu and its implications for the rp process

NASA Astrophysics Data System (ADS)

Ong, W.-J.; Langer, C.; Montes, F.; Aprahamian, A.; Bardayan, D. W.; Bazin, D.; Brown, B. A.; Browne, J.; Crawford, H.; Cyburt, R.; Deleeuw, E. B.; Domingo-Pardo, C.; Gade, A.; George, S.; Hosmer, P.; Keek, L.; Kontos, A.; Lee, I.-Y.; Lemasson, A.; Lunderberg, E.; Maeda, Y.; Matos, M.; Meisel, Z.; Noji, S.; Nunes, F. M.; Nystrom, A.; Perdikakis, G.; Pereira, J.; Quinn, S. J.; Recchia, F.; Schatz, H.; Scott, M.; Siegl, K.; Simon, A.; Smith, M.; Spyrou, A.; Stevens, J.; Stroberg, S. R.; Weisshaar, D.; Wheeler, J.; Wimmer, K.; Zegers, R. G. T.

2017-05-01

The low-lying energy levels of proton-rich 56Cu have been extracted using in-beam γ -ray spectroscopy with the state-of-the-art γ -ray tracking array GRETINA in conjunction with the S800 spectrograph at the National Superconducting Cyclotron Laboratory at Michigan State University. Excited states in 56Cu serve as resonances in the 55Ni(p ,γ )56Cu reaction, which is a part of the rp process in type-I x-ray bursts. To resolve existing ambiguities in the reaction Q value, a more localized isobaric multiplet mass equation (IMME) fit is used, resulting in Q =639 ±82 keV. We derive the first experimentally constrained thermonuclear reaction rate for 55Ni(p ,γ )56Cu . We find that, with this new rate, the rp process may bypass the 56Ni waiting point via the 55Ni(p ,γ ) reaction for typical x-ray burst conditions with a branching of up to ˜40 % . We also identify additional nuclear physics uncertainties that need to be addressed before drawing final conclusions about the rp -process reaction flow in the 56Ni region.

Iron vs. cobalt clathrochelate electrocatalysts of HER: the first example on a cage iron complex.

PubMed

Dolganov, Alexander V; Belov, Alexander S; Novikov, Valentin V; Vologzhanina, Anna V; Mokhir, Andriy; Bubnov, Yurii N; Voloshin, Yan Z

2013-04-07

New macrobicyclic 2-thiopheneboron-capped iron and cobalt(II) tris-dioximates showed high electrocatalytic activity for hydrogen production from H(+) ions. This is the first example of the hydrogen evolution reaction electrocatalyzed by a clathrochelate iron complex, which catalyzes the hydrogen production at low overpotential.

Pituitary iron and volume predict hypogonadism in transfusional iron overload.

PubMed

Noetzli, Leila J; Panigrahy, Ashok; Mittelman, Steven D; Hyderi, Aleya; Dongelyan, Ani; Coates, Thomas D; Wood, John C

2012-02-01

Hypogonadism is the most common morbidity in patients with transfusion-dependent anemias such as thalassemia major. We used magnetic resonance imaging (MRI) to measure pituitary R2 (iron) and volume to determine at what age these patients develop pituitary iron overload and volume loss. We recruited 56 patients (47 with thalassemia major, five with chronically transfused thalassemia intermedia and four with Blackfan-Diamond syndrome) to have pituitary MRIs to measure pituitary R2 and volume. Hypogonadism was defined clinically based on the timing of secondary sexual characteristics or the need for sex hormone replacement therapy. Patients with transfusional iron overload begin to develop pituitary iron overload in the first decade of life; however, clinically significant volume loss was not observed until the second decade of life. Severe pituitary iron deposition (Z > 5) and volume loss (Z < -2.5) were independently predictive of hypogonadism. Pituitary R2 correlated significantly with serum ferritin as well as liver, pancreatic, and cardiac iron deposition by MRI. Log pancreas R2* was the best single predictor for pituitary iron, with an area under the receiving operator characteristic curve of 0.88, but log cardiac R2* and ferritin were retained on multivariate regression with a combined r(2) of 0.71. Pituitary iron overload and volume loss were independently predictive of hypogonadism. Many patients with moderate-to-severe pituitary iron overload retained normal gland volume and function, representing a potential therapeutic window. The subset of hypogonadal patients having preserved gland volumes may also explain improvements in pituitary function observed following intensive chelation therapy. Copyright © 2011 Wiley Periodicals, Inc.

Catalytic Activity of μ-Carbido-Dimeric Iron(IV) Octapropylporphyrazinate in the 3,5,7,2',4'-Pentahydroxyflavone Oxidation Reaction with tert-Butyl Hydroperoxide

NASA Astrophysics Data System (ADS)

Tyurin, D. V.; Zaitseva, S. V.; Kudrik, E. V.

2018-05-01

It is found for the first time that μ-carbido-dimeric iron(IV) octapropylporphyrazinate displays catalytic activity in the oxidation reaction of natural flavonol morin with tert-butyl hydroperoxide, with the catalyst being stable under conditions of the reaction. The kinetics of this reaction are studied. It is shown the reaction proceeds via tentative formation of a complex between the catalyst and the oxidant, followed by O‒O bond homolytic cleavage. The kinetics of the reaction is described in the coordinates of the Michaelis-Menten equation. A linear dependence of the apparent reaction rate constant on the concentration of the catalyst is observed, testifying to its participation in the limiting reaction step. The equilibrium constants and rates of interaction are found. A mechanism is proposed for the reaction on the basis of the experimental data.

Iron-catalyzed cross-coupling of imidoyl chlorides with Grignard reagents.

PubMed

Ottesen, Lars K; Ek, Fredrik; Olsson, Roger

2006-04-27

[reaction: see text] A general, high yielding rapid iron-catalyzed cross-coupling reaction between Grignard reagents and imidoyl chlorides is described. These reactions are typically completed within 5 min, resulting in high yields of 71-96% using 5% iron catalyst in a THF-NMP solvent mixture. Functionalized imidoyl chlorides (e.g., R = CO(2)Me) gave excellent yields (89%).

Iron homeostasis and eye disease

PubMed Central

Loh, Allison; Hadziahmetovic, Majda; Dunaief, Joshua L.

2009-01-01

Summary Iron is necessary for life, but excess iron can be toxic to tissues. Iron is thought to damage tissues primarily by generating oxygen free radicals through the Fenton reaction. We present an overview of the evidence supporting iron's potential contribution to a broad range of eye disease using an anatomical approach. Firstly, iron can be visualized in the cornea as iron lines in the normal aging cornea as well as in diseases like keratoconus and pterygium. In the lens, we present the evidence for the role of oxidative damage in cataractogenesis. Also, we review the evidence that iron may play a role in the pathogenesis of the retinal disease age-related macular degeneration. Although currently there is no direct link between excess iron and development of optic neuropathies, ferrous iron's ability to form highly reactive oxygen species may play a role in optic nerve pathology. Lastly, we discuss recent advances in prevention and therapeutics for eye disease with antioxidants and iron chelators,. PMID:19059309

Formation of nickel and copper ferrites in ceramics: a potential reaction in the reuse of iron-rich sludge incineration ash.

PubMed

Shih, Kaimin

2012-12-01

This study investigates potential solid-state reactions for the stabilization of hazardous metals when reusing the incineration ash from chemically enhanced primary treatment (CEPT) sludge to fabricate ceramic products. Nickel and copper were used as examples of hazardous metals, and the iron content in the reaction system was found to play a major role in incorporating these hazardous metals into their ferrite phases (NiFe2O4 and CuFe2O4). The results from three-hour sintering experiments on NiO + Fe2O3 and CuO + Fe2O3 systems clearly demonstrate the potential for initiating metal incorporation mechanisms using an iron-containing precursor at attainable ceramic sintering temperatures (above 750 degrees C). Both ferrite phases were examined using a prolonged leaching experiment modified from the widely used toxicity characteristic leaching procedure (TCLP) to evaluate their long-term metal leachability. The leaching results indicate that both the NiFe2O4 and the CuFe2O4 products were significantly superior to their oxide forms in immobilizing hazardous metals.

Iron isotopic systematics of oceanic basalts

NASA Astrophysics Data System (ADS)

Teng, Fang-Zhen; Dauphas, Nicolas; Huang, Shichun; Marty, Bernard

2013-04-01

The iron isotopic compositions of 93 well-characterized basalts from geochemically and geologically diverse mid-ocean ridge segments, oceanic islands and back arc basins were measured. Forty-three MORBs have homogeneous Fe isotopic composition, with δ56Fe ranging from +0.07‰ to +0.14‰ and an average of +0.105 ± 0.006‰ (2SD/√n, n = 43, MSWD = 1.9). Three back arc basin basalts have similar δ56Fe to MORBs. By contrast, OIBs are slightly heterogeneous with δ56Fe ranging from +0.05‰ to +0.14‰ in samples from Koolau and Loihi, Hawaii, and from +0.09‰ to +0.18‰ in samples from the Society Islands and Cook-Austral chain, French Polynesia. Overall, oceanic basalts are isotopically heavier than mantle peridotite and pyroxenite xenoliths, reflecting Fe isotope fractionation during partial melting of the mantle. Iron isotopic variations in OIBs mainly reflect Fe isotope fractionation during fractional crystallization of olivine and pyroxene, enhanced by source heterogeneity in Koolau samples.

Iron isotope fingerprints of redox and biogeochemical cycling in the soil-water-rice plant system of a paddy field.

PubMed

Garnier, J; Garnier, J-M; Vieira, C L; Akerman, A; Chmeleff, J; Ruiz, R I; Poitrasson, F

2017-01-01

The iron isotope composition was used to investigate dissimilatory iron reduction (DIR) processes in an iron-rich waterlogged paddy soil, the iron uptake strategies of plants and its translocation in the different parts of the rice plant along its growth. Fe concentration and isotope composition (δ 56 Fe) in irrigation water, precipitates from irrigation water, soil, pore water solution at different depths under the surface water, iron plaque on rice roots, rice roots, stems, leaves and grains were measured. Over the 8.5-10cm of the vertical profiles investigated, the iron pore water concentration (0.01 to 24.3mg·l -1 ) and δ 56 Fe (-0.80 to -3.40‰) varied over a large range. The significant linear co-variation between Ln[Fe] and δ 56 Fe suggests an apparent Rayleigh-type behavior of the DIR processes. An average net fractionation factor between the pore water and the soil substrate of Δ 56 Fe≈-1.15‰ was obtained, taking the average of all the δ 56 Fe values weighted by the amount of Fe for each sample. These results provide a robust field study confirmation of the conceptual model of Crosby et al. (2005, 2007) for interpreting the iron isotope fractionation observed during DIR, established from a series of laboratories experiments. In addition, the strong enrichment of heavy Fe isotope measured in the root relative to the soil solution suggest that the iron uptake by roots is more likely supplied by iron from plaque and not from the plant-available iron in the pore water. Opposite to what was previously observed for plants following strategy II for iron uptake from soils, an iron isotope fractionation factor of -0.9‰ was found from the roots to the rice grains, pointing to isotope fractionation during rice plant growth. All these features highlight the insights iron isotope composition provides into the biogeochemical Fe cycling in the soil-water-rice plant systems studied in nature. Copyright © 2016 Elsevier B.V. All rights reserved.

Minocycline Attenuates Iron-Induced Brain Injury.

PubMed

Zhao, Fan; Xi, Guohua; Liu, Wenqaun; Keep, Richard F; Hua, Ya

2016-01-01

Iron plays an important role in brain injury after intracerebral hemorrhage (ICH). Our previous study found minocycline reduces iron overload after ICH. The present study examined the effects of minocycline on the subacute brain injury induced by iron. Rats had an intracaudate injection of 50 μl of saline, iron, or iron + minocycline. All the animals were euthanized at day 3. Rat brains were used for immunohistochemistry (n = 5-6 per each group) and Western blotting assay (n = 4). Brain swelling, blood-brain barrier (BBB) disruption, and iron-handling proteins were measured. We found that intracerebral injection of iron resulted in brain swelling, BBB disruption, and brain iron-handling protein upregulation (p < 0.05). The co-injection of minocycline with iron significantly reduced iron-induced brain swelling (n = 5, p < 0.01). Albumin, a marker of BBB disruption, was measured by Western blot analysis. Minocycline significantly decreased albumin protein levels in the ipsilateral basal ganglia (p < 0.01). Iron-handling protein levels in the brain, including ceruloplasmin and transferrin, were reduced in the minocycline co-injected animals. In conclusion, the present study suggests that minocycline attenuates brain swelling and BBB disruption via an iron-chelation mechanism.

Nitrate-dependent iron oxidation limits iron transport in anoxic ocean regions

NASA Astrophysics Data System (ADS)

Scholz, Florian; Löscher, Carolin R.; Fiskal, Annika; Sommer, Stefan; Hensen, Christian; Lomnitz, Ulrike; Wuttig, Kathrin; Göttlicher, Jörg; Kossel, Elke; Steininger, Ralph; Canfield, Donald E.

2016-11-01

Iron is an essential element for life on Earth and limits primary production in large parts of the ocean. Oxygen-free continental margin sediments represent an important source of bioavailable iron to the ocean, yet little of the iron released from the seabed reaches the productive sea surface. Even in the anoxic water of oxygen minimum zones, where iron solubility should be enhanced, most of the iron is rapidly re-precipitated. To constrain the mechanism(s) of iron removal in anoxic ocean regions we explored the sediment and water in the oxygen minimum zone off Peru. During our sampling campaign the water column featured two distinct redox boundaries separating oxic from nitrate-reducing (i.e., nitrogenous) water and nitrogenous from weakly sulfidic water. The sulfidic water mass in contact with the shelf sediment contained elevated iron concentrations >300 nM. At the boundary between sulfidic and nitrogenous conditions, iron concentrations dropped sharply to <20 nM coincident with a maximum in particulate iron concentration. Within the iron gradient, we found an increased expression of the key functional marker gene for nitrate reduction (narG). Part of this upregulation was related to the activity of known iron-oxidizing bacteria. Collectively, our data suggest that iron oxidation and removal is induced by nitrate-reducing microbes, either enzymatically through anaerobic iron oxidation or by providing nitrite for an abiotic reaction. Given the important role that iron plays in nitrogen fixation, photosynthesis and respiration, nitrate-dependent iron oxidation likely represents a key-link between the marine biogeochemical cycles of nitrogen, oxygen and carbon.

Iron metabolism and the role of the iron-regulating hormone hepcidin in health and disease.

PubMed

Daher, Raed; Manceau, Hana; Karim, Zoubida

2017-12-01

Although iron is vital, its free form is likely to be involved in oxidation-reduction reactions, leading to the formation of free radicals and oxidative stress. Living organisms have developed protein systems to transport free iron through the cell membranes and biological fluids and store it in a non-toxic and readily mobilizable form to avoid iron toxicity. Hepcidin plays a crucial role in maintaining iron homeostasis. Hepcidin expression is directly regulated by variations in iron intake and its repression leads to an increase in bioavailable serum iron level. However, in pathological situations, prolonged repression often leads to pathological iron overload. In this review, we describe the different molecular mechanisms responsible for the maintenance of iron metabolism and the consequences of iron overload. Indeed, genetic hemochromatosis and post-transfusional siderosis are the two main conditions responsible for iron overload. Long-term iron overload is deleterious, and treatment relies on venesection therapy for genetic hemochromatosis and chelation therapy for iron overload resulting from multiple transfusions. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Unveiling the high-activity origin of single-atom iron catalysts for oxygen reduction reaction.

PubMed

Yang, Liu; Cheng, Daojian; Xu, Haoxiang; Zeng, Xiaofei; Wan, Xin; Shui, Jianglan; Xiang, Zhonghua; Cao, Dapeng

2018-06-26

It is still a grand challenge to develop a highly efficient nonprecious-metal electrocatalyst to replace the Pt-based catalysts for oxygen reduction reaction (ORR). Here, we propose a surfactant-assisted method to synthesize single-atom iron catalysts (SA-Fe/NG). The half-wave potential of SA-Fe/NG is only 30 mV less than 20% Pt/C in acidic medium, while it is 30 mV superior to 20% Pt/C in alkaline medium. Moreover, SA-Fe/NG shows extremely high stability with only 12 mV and 15 mV negative shifts after 5,000 cycles in acidic and alkaline media, respectively. Impressively, the SA-Fe/NG-based acidic proton exchange membrane fuel cell (PEMFC) exhibits a high power density of 823 mW cm -2 Combining experimental results and density-functional theory (DFT) calculations, we further reveal that the origin of high-ORR activity of SA-Fe/NG is from the Fe-pyrrolic-N species, because such molecular incorporation is the key, leading to the active site increase in an order of magnitude which successfully clarifies the bottleneck puzzle of why a small amount of iron in the SA-Fe catalysts can exhibit extremely superior ORR activity.

Innovative Method for Separating Phosphorus and Iron from High-Phosphorus Oolitic Hematite by Iron Nugget Process

NASA Astrophysics Data System (ADS)

Han, Hongliang; Duan, Dongping; Wang, Xing; Chen, Siming

2014-10-01

This study puts forward a new method to separate phosphorus and iron from high-phosphorus oolitic hematite through iron nuggets process. Firstly, the physical, chemical, and microscopic characteristics of high-phosphorus oolitic hematite are investigated. Then, the reaction mechanisms of high-phosphorus hematite together with feasibility to separating phosphorus and iron by iron nugget process are discussed. Meanwhile, the experiments of high-phosphorus hematite used in rotary hearth furnace iron nugget processes are studied as well. The results indicate that the iron nugget process is a feasible and efficient method for iron and phosphorus separation of high-phosphorus oolitic hematite. The phosphorus content in iron nuggets is relatively low. Through the optimization of process parameters, the lowest of phosphorus in iron nuggets is 0.22 pct, the dephosphorization rate is above 86 pct, and the recovery of Fe is above 85 pct by the iron nugget process. This study aims to provide a theoretical and technical basis for economical and rational use of high-phosphorus oolitic hematite.

Iron doped fibrous-structured silica nanospheres as efficient catalyst for catalytic ozonation of sulfamethazine.

PubMed

Bai, Zhiyong; Wang, Jianlong; Yang, Qi

2018-04-01

Sulfonamide antibiotics are ubiquitous pollutants in aquatic environments due to their large production and extensive application. In this paper, the iron doped fibrous-structured silica (KCC-1) nanospheres (Fe-KCC-1) was prepared, characterized, and applied as a catalyst for catalytic ozonation of sulfamethazine (SMT). The effects of ozone dosage, catalyst dosage, and initial concentration of SMT were examined. The experimental results showed that Fe-KCC-1 had large surface area (464.56 m2 g -1 ) and iron particles were well dispersed on the catalyst. The catalyst had high catalytic performance especially for the mineralization of SMT, with mineralization ratio of about 40% in a wide pH range. With addition of Fe-KCC-1, the ozone utilization increased nearly two times than single ozonation. The enhancement of SMT degradation was mainly due to the surface reaction, and the increased mineralization of SMT was due to radical mechanism. Fe-KCC-1 was an efficient catalyst for SMT degradation in catalytic ozonation system.

Method for reducing iron losses in an iron smelting process

DOEpatents

Sarma, B.; Downing, K.B.

1999-03-23

A process of smelting iron that comprises the steps of: (a) introducing a source of iron oxide, oxygen, nitrogen, and a source of carbonaceous fuel to a smelting reactor, at least some of said oxygen being continuously introduced through an overhead lance; (b) maintaining conditions in said reactor to cause (1) at least some of the iron oxide to be chemically reduced, (2) a bath of molten iron to be created and stirred in the bottom of the reactor, surmounted by a layer of slag, and (3) carbon monoxide gas to rise through the slag; (c) causing at least some of said carbon monoxide to react in the reactor with the incoming oxygen, thereby generating heat for reactions taking place in the reactor; and (d) releasing from the reactor an offgas effluent, is run in a way that keeps iron losses in the offgas relatively low. After start-up of the process is complete, steps (a) and (b) are controlled so as to: (1) keep the temperature of the molten iron at or below about 1550 C and (2) keep the slag weight at or above about 0.8 ton per square meter. 13 figs.

Method for reducing iron losses in an iron smelting process

DOEpatents

Sarma, Balu; Downing, Kenneth B.

1999-01-01

A process of smelting iron that comprises the steps of: a) introducing a source of iron oxide, oxygen, nitrogen, and a source of carbonaceous fuel to a smelting reactor, at least some of said oxygen being continuously introduced through an overhead lance; b) maintaining conditions in said reactor to cause (i) at least some of the iron oxide to be chemically reduced, (ii) a bath of molten iron to be created and stirred in the bottom of the reactor, surmounted by a layer of slag, and (iii) carbon monoxide gas to rise through the slag; c) causing at least some of said carbon monoxide to react in the reactor with the incoming oxygen, thereby generating heat for reactions taking place in the reactor; and d) releasing from the reactor an offgas effluent, is run in a way that keeps iron losses in the offgas relatively low. After start-up of the process is complete, steps (a) and (b) are controlled so as to: e) keep the temperature of the molten iron at or below about 1550.degree. C. and f) keep the slag weight at or above about 0.8 tonne per square meter.

Involvement of cytosolic and mitochondrial iron in iron overload cardiomyopathy: an update.

PubMed

Gordan, Richard; Wongjaikam, Suwakon; Gwathmey, Judith K; Chattipakorn, Nipon; Chattipakorn, Siriporn C; Xie, Lai-Hua

2018-04-19

Iron overload cardiomyopathy (IOC) is a major cause of death in patients with diseases associated with chronic anemia such as thalassemia or sickle cell disease after chronic blood transfusions. Associated with iron overload conditions, there is excess free iron that enters cardiomyocytes through both L- and T-type calcium channels thereby resulting in increased reactive oxygen species being generated via Haber-Weiss and Fenton reactions. It is thought that an increase in reactive oxygen species contributes to high morbidity and mortality rates. Recent studies have, however, suggested that it is iron overload in mitochondria that contributes to cellular oxidative stress, mitochondrial damage, cardiac arrhythmias, as well as the development of cardiomyopathy. Iron chelators, antioxidants, and/or calcium channel blockers have been demonstrated to prevent and ameliorate cardiac dysfunction in animal models as well as in patients suffering from cardiac iron overload. Hence, either a mono-therapy or combination therapies with any of the aforementioned agents may serve as a novel treatment in iron-overload patients in the near future. In the present article, we review the mechanisms of cytosolic and/or mitochondrial iron load in the heart which may contribute synergistically or independently to the development of iron-associated cardiomyopathy. We also review available as well as potential future novel treatments.

Single-dose intravenous iron infusion or oral iron for treatment of fatigue after postpartum haemorrhage: a randomized controlled trial.

PubMed

Holm, C; Thomsen, L L; Norgaard, A; Langhoff-Roos, J

2017-04-01

To evaluate the clinical efficacy of a single-dose intravenous infusion of iron isomaltoside compared with current treatment practice with oral iron measured by physical fatigue in women after postpartum haemorrhage. Single-centre, open-label, randomized controlled trial. Participants received intravenous iron (n = 97) or oral iron (n = 99), and completed the Multidimensional Fatigue Inventory and Edinburgh Postnatal Depression Scale, and haematological and iron parameters were measured. Primary outcome was the aggregated change in physical fatigue score from baseline to 12 weeks postpartum. The difference in physical fatigue score was -0·97 (95% CI: -1·65; -0·28, P = 0·006) in favour of intravenous iron, but did not meet the predefined difference of 1·8. Across visits, we found statistically significant differences in fatigue and depression scores, as well as in haematological and iron parameters, all in favour of intravenous iron. There were no serious adverse reactions. A single dose of intravenous iron was associated with a statistically significant reduction in aggregated physical fatigue within 12 weeks after postpartum haemorrhage compared to standard medical care with oral iron below the prespecified criteria of clinical superiority. As patient-reported outcomes improved significantly and intravenous iron resulted in a fast hematopoietic response without serious adverse reactions, intravenous iron may be a useful alternative after postpartum haemorrhage if oral iron is not absorbed or tolerated. © 2017 The Authors. Vox Sanguinis published by John Wiley & Sons Ltd on behalf of International Society of Blood Transfusion.

Detailed characterization of the 1087 MeV/nucleon iron-56 beam used for radiobiology at the alternating gradient synchrotron

NASA Technical Reports Server (NTRS)

Zeitlin, C.; Heilbronn, L.; Miller, J.

1998-01-01

We report beam characterization and dosimetric measurements made using a 56Fe beam extracted from the Brookhaven National Laboratory Alternating Gradient Synchrotron (AGS) with a kinetic energy of 1087 MeV/nucleon. The measurements reveal that the depth-dose distribution of this beam differs significantly from that obtained with a 600 MeV/nucleon iron beam used in several earlier radiobiology experiments at the Lawrence Berkeley National Laboratory's BEVALAC. We present detailed measurements of beam parameters relevant for radiobiology, including track- and dose-averaged linear energy transfer (LET), fragment composition and LET spectra measured behind sample holders used in irradiations of biological samples. We also report measurements of fluence behind three depths (1.94, 4.68 and 9.35 g cm(-2)) of polyethylene targets with the 1087 MeV/nucleon beam, and behind 1.94 g cm(-2) of polyethylene with a 610 MeV/nucleon beam delivered by the AGS. These results are compared to earlier measurements with the 600 MeV/nucleon beam at the BEVALAC.

Nanoscale zero-valent iron (nZVI): aspects of the core-shell structure and reactions with inorganic species in water.

PubMed

Yan, Weile; Herzing, Andrew A; Kiely, Christopher J; Zhang, Wei-Xian

2010-11-25

Aspects of the core-shell model of nanoscale zero-valent iron (nZVI) and their environmental implications were examined in this work. The structure and elemental distribution of nZVI were characterized by X-ray energy-dispersive spectroscopy (XEDS) with nanometer-scale spatial resolution in an aberration-corrected scanning transmission electron microscope (STEM). The analysis provides unequivocal evidence of a layered structure of nZVI consisting of a metallic iron core encapsulated by a thin amorphous oxide shell. Three aqueous environmental contaminants, namely Hg(II), Zn(II) and hydrogen sulfide, were studied to probe the reactive properties and the surface chemistry of nZVI. High-resolution X-ray photoelectron spectroscopy (HR-XPS) analysis of the reacted particles indicated that Hg(II) was sequestrated via chemical reduction to elemental mercury. On the other hand, Zn(II) removal was achieved via sorption to the iron oxide shell followed by zinc hydroxide precipitation. Hydrogen sulfide was immobilized on the nZVI surface as disulfide (S(2)(2-)) and monosulfide (S(2-)) species. Their relative abundance in the final products suggests that the retention of hydrogen sulfide occurs via reactions with the oxide shell to form iron sulfide (FeS) and subsequent conversion to iron disulfide (FeS(2)). The results presented herein highlight the multiple reactive pathways permissible with nZVI owing to its two functional constituents. The core-shell structure imparts nZVI with manifold functional properties previously unexamined and grants the material with potentially new applications. Copyright © 2010 Elsevier B.V. All rights reserved.

Mitochondria and Iron: Current Questions

PubMed Central

Paul, Bibbin T.; Manz, David H.; Torti, Frank M.; Torti, Suzy V.

2017-01-01

Introduction Mitochondria are cellular organelles that perform numerous bioenergetic, biosynthetic, and regulatory functions and play a central role in iron metabolism. Extracellular iron is taken up by cells and transported to the mitochondria, where it is utilized for synthesis of cofactors essential to the function of enzymes involved in oxidation-reduction reactions, DNA synthesis and repair, and a variety of other cellular processes. Areas Covered This article reviews the trafficking of iron to the mitochondria and normal mitochondrial iron metabolism, including heme synthesis and iron-sulfur cluster biogenesis. Much of our understanding of mitochondrial iron metabolism has been revealed by pathologies that disrupt normal iron metabolism. These conditions affect not only iron metabolism but mitochondrial function and systemic health. Therefore, this article also discusses these pathologies, including conditions of systemic and mitochondrial iron dysregulation as well as cancer. Literature covering these areas was identified via PubMed searches using keywords: Iron, mitochondria, Heme Synthesis, Iron-sulfur Cluster, and Cancer. References cited by publications retrieved using this search strategy were also consulted. Expert Commentary While much has been learned about mitochondrial iron, key questions remain. Developing a better understanding of mitochondrial iron regulation will be paramount in developing therapies for syndromes that affect mitochondrial iron. PMID:27911100

IRON-TOLERANT CYANOBACTERIA: IMPLICATIONS FOR ASTROBIOLOGY

NASA Technical Reports Server (NTRS)

Brown, Igor I.; Allen, Carlton C.; Mummey, Daniel L.; Sarkisova, Svetlana A.; McKay, David S.

2006-01-01

The review is dedicated to the new group of extremophiles - iron tolerant cyanobacteria. The authors have analyzed earlier published articles about the ecology of iron tolerant cyanobacteria and their diversity. It was concluded that contemporary iron depositing hot springs might be considered as relative analogs of Precambrian environment. The authors have concluded that the diversity of iron-tolerant cyanobacteria is understudied. The authors also analyzed published data about the physiological peculiarities of iron tolerant cyanobacteria. They made the conclusion that iron tolerant cyanobacteria may oxidize reduced iron through the photosystem of cyanobacteria. The involvement of both Reaction Centers 1 and 2 is also discussed. The conclusion that iron tolerant protocyanobacteria could be involved in banded iron formations generation is also proposed. The possible mechanism of the transition from an oxygenic photosynthesis to an oxygenic one is also discussed. In the final part of the review the authors consider the possible implications of iron tolerant cyanobacteria for astrobiology.

Infant iron status affects iron absorption in Peruvian breastfed infants at 2 and 5 mo of age.

PubMed

Finkelstein, Julia L; O'Brien, Kimberly O; Abrams, Steven A; Zavaleta, Nelly

2013-12-01

Effects of prenatal iron supplementation on maternal postpartum iron status and early infant iron homeostasis remain largely unknown. We examined iron absorption and growth in exclusively breastfed infants in relation to fetal iron exposure and iron status during early infancy. Longitudinal, paired iron-absorption (⁵⁸Fe) studies were conducted in 59 exclusively breastfed Peruvian infants at 2-3 mo of age (2M) and 5-6 mo of age (5M). Infants were born to women who received ≥ 5100 or ≤ 1320 mg supplemental prenatal Fe. Iron status was assessed in mothers and infants at 2M and 5M. Infant iron absorption from breast milk averaged 7.1% and 13.9% at 2M and 5M. Maternal iron status (at 2M) predicted infant iron deficiency (ID) at 5M. Although no infants were iron deficient at 2M, 28.6% of infants had depleted iron stores (ferritin concentration <12 μg/L) by 5M. Infant serum ferritin decreased (P < 0.0001), serum transferrin receptor (sTfR) increased (P < 0.0001), and serum iron decreased from 2M to 5M (P < 0.01). Higher infant sTfR (P < 0.01) and breast-milk copper (P < 0.01) predicted increased iron absorption at 5M. Prenatal iron supplementation had no effects on infant iron status or breast-milk nutrient concentrations at 2M or 5M. However, fetal iron exposure predicted increased infant length at 2M (P < 0.01) and 5M (P < 0.05). Fetal iron exposure affected early infant growth but did not significantly improve iron status or absorption. Young, exclusively breastfed infants upregulated iron absorption when iron stores were depleted at both 2M and 5M.

Fabrication of Iron-Containing Carbon Materials From Graphite Fluoride

NASA Technical Reports Server (NTRS)

Hung, Ching-cheh

1996-01-01

Carbon materials containing iron alloy, iron metal, iron oxide or iron halide were fabricated. Typical samples of these metals were estimated to contain 1 iron atom per 3.5 to 5 carbon atoms. Those carbon materials containing iron alloy, iron metal, and/or Fe3O4 were magnetic. The kinetics of the fabrication process were studied by exposing graphite fluoride (CF(0.68)) to FeCl3 over a 280 to 420 C temperature range. Between 280 and 295 C, FeCl3 quickly entered the structure of CF(0.68), broke the carbon-fluorine bonds, and within 10 to 30 min, completely converted it to carbon made up of graphite planes between which particles of crystalline FeF3 and noncrystalline FeCl3 were located. Longer reaction times (e.g., 28 hr) or higher reaction temperatures (e.g., 420 C) produced materials containing graphite, a FeCl3-graphite intercalation compound, FeCl2(center dot)4H2O, and FeCl2(center dot)2H2O. These products were further heat treated to produce iron-containing carbon materials. When the heating temperature was kept in the 750 to 850 C range, and the oxygen supply was kept at the optimum level, the iron halides in the carbon structure were converted to iron oxides. Raising the heat to temperatures higher than 900 C reduced such iron oxides to iron metal. The kinetics of these reactions were used to suggest processes for fabricating carbon materials containing iron alloy. Such processes were then tested experimentally. In one of the successful trial runs, commercially purchased CF(0.7) powder was used as the reactant, and NiO was added during the final heating to 1200 C as a source of both nickel and oxygen. The product thus obtained was magnetic and was confirmed to be a nickel-iron alloy in carbon.

Further insights into the oxidation chemistry and biochemistry of the serotonergic neurotoxin 5,6-dihydroxytryptamine.

PubMed

Singh, S; Dryhurst, G

1990-11-01

The neurodegenerative properties of the serotonergic neurotoxin 5,6-dihydroxytryptamine (5,6-DHT) are widely believed to result from its autoxidation in the central nervous system. The autoxidation chemistry of 5,6-DHT has been studied in aqueous solution at pH 7.2. The reaction is initiated by direct oxidation of the indolamine by molecular oxygen with resultant formation of the corresponding o-quinone 1 and H2O2. A rapid nucleophilic attack by 5,6-DHT on 1 leads to 2,7'-bis(5,6-dihydroxytryptamine) (6) which is more rapidly autoxidized than 5,6-DHT to give the corresponding diquinone 7 along with 2 mol of H2O2. The accumulation of 6 in the reaction solution during the autoxidation of 5,6-DHT despite its more rapid autoxidation indicates that diquinone 7 chemically oxidizes 5,6-DHT (2 mol) to quinone 1 so that an autocatalytic cycle is established. The H2O2 formed as a byproduct of these autoxidation reactions can undergo Fenton chemistry catalyzed by trace transition metal ion contaminants with resultant formation of the hydroxyl radical, HO., which directly oxidizes 5,6-DHT to a radical intermediate (9a/9b). This radical is directly attacked by O2 to yield quinone 1 and superoxide radical anion, O2.-, which further facilitates Fenton chemistry by reducing, inter alia, Fe3+ to Fe2+. A minor side reaction of 1 with water leads to formation of at least two trihydroxytryptamines. Diquinone 7 ultimately reacts with 6, 5,6-DHT, and perhaps trihydroxytryptamines, leading via a sequence of coupling and oxidation reactions to a black indolic melanin polymer. Enzymes such as tyrosinase, ceruloplasmin, and peroxidase and rat brain mitochondria catalyze the oxidation of 5,6-DHT to form dimer 7 and, ultimately, indolic melanin. The role of the autoxidation and the enzyme-mediated and mitochondria-promoted oxidations of 5,6-DHT in expressing the neurodegenerative properties of the indolamine are discussed.

A General Map of Iron Metabolism and Tissue-specific Subnetworks

PubMed Central

Hower, Valerie; Mendes, Pedro; Torti, Frank M.; Laubenbacher, Reinhard; Akman, Steven; Shulaev, Vladmir; Torti, Suzy V.

2009-01-01

Iron is required for survival of mammalian cells. Recently, understanding of iron metabolism and trafficking has increased dramatically, revealing a complex, interacting network largely unknown just a few years ago. This provides an excellent model for systems biology development and analysis. The first step in such an analysis is the construction of a structural network of iron metabolism, which we present here. This network was created using CellDesigner version 3.5.2 and includes reactions occurring in mammalian cells of numerous tissue types. The iron metabolic network contains 151 chemical species and 107 reactions and transport steps. Starting from this general model, we construct iron networks for specific tissues and cells that are fundamental to maintaining body iron homeostasis. We include subnetworks for cells of the intestine and liver, tissues important in iron uptake and storage, respectively; as well as the reticulocyte and macrophage, key cells in iron utilization and recycling. The addition of kinetic information to our structural network will permit the simulation of iron metabolism in different tissues as well as in health and disease. PMID:19381358

Inorganic Reaction Mechanisms. Part I

ERIC Educational Resources Information Center

Cooke, D. O.

1976-01-01

Provides a collection of data on the mechanistic aspects of inorganic chemical reactions. Wherever possible includes procedures for classroom demonstration or student project work. The material covered includes gas phase reactions, reactions in solution, mechanisms of electron transfer, the reaction between iron III and iodine, and hydrolysis. (GS)

The Corrosion and Preservation of Iron Antiques.

ERIC Educational Resources Information Center

Walker, Robert

1982-01-01

Discusses general corrosion reactions (iron to rust), including corrosion of iron, sulfur dioxide, chlorides, immersed corrosion, and underground corrosion. Also discusses corrosion inhibition, including corrosion inhibitors (anodic, cathodic, mixed, organic); safe/dangerous inhibitors; and corrosion/inhibition in concrete/marble, showcases/boxes,…

Nanoscale and Microscale Iron Emulsions for Treating DNAPL

NASA Technical Reports Server (NTRS)

Geiger, Cherie L.

2002-01-01

This study demonstrated the feasibility of using emulsified nanoscale and microscale iron particles to enhance dehalogenation of (Dense Non-Aqueous Phase Liquid) DNAPL free-phase. The emulsified system consisted of a surfactant-stabilized, biodegradable oil-in-water emulsion with nanoscale or microscale iron particles contained within the emulsion droplets. It was demonstrated that DNAPLs, such as trichloroethene (TCE), diffuse through the oil membrane of the emulsion particle whereupon they reach an aqueous interior and the surface of an iron particle where dehalogenation takes place. The hydrocarbon reaction by-products of the dehalogenation reaction, primarily ethene (no chlorinated products detected), diffuse out of the emulsion droplet. This study also demonstrated that an iron-emulsion system could be delivered in-situ to the DNAPL pool in a soil matrix by using a simulated push well technique. Iron emulsions degraded pure TCE at a rate comparable to the degradation of dissolved phase TCE by iron particles, while pure iron had a very low degradation rate for free-phase TCE. The iron-emulsion systems can be injected into a sand matrix where they become immobilized and are not moved by flowing water. It has been documented that surfactant micelles possess the ability to pull pooled TCE into emulsion droplets where degradation of TCE takes place.

Decreased CD8-p56lck activity in peripheral blood T-lymphocytes from patients with hereditary haemochromatosis.

PubMed

Arosa, F A; da Silva, A J; Godinho, I M; ter Steege, J C; Porto, G; Rudd, C E; de Sousa, M

1994-05-01

Hereditary haemochromatosis (HH) is an autosomal recessive disease linked to certain MHC class-I specificities. The disease is characterized by increased iron absorption and, in some patients, abnormally low numbers of CD8+ T cells in the periphery. We were interested in whether CD4- and CD8-associated p56lck kinase activities were altered in patients with HH. In a study of 18 patients with HH (with and without low numbers of CD8+ cells), the level of autophosphorylation of the CD8-associated p56lck as well as its phosphotransferase activity, as determined by phosphorylation of an exogenous substrate, was significantly reduced by two- to three-fold relative to a control population of 23 healthy blood donors (P < 6 x 10(-7). CD8-p56lck activity was decreased in 16 out of 18 patients (ranging from 1.5- to 10-fold decrease). By contrast, the level of CD4-p56lck activity did not show an overall decrease relative to controls. In addition to an occasional decrease in the amount of CD8-associated lck, HH patient-derived T cells showed a consistent decrease in the relative CD8-p56lck specific activity. Immunofluorescence staining showed further that the difference could not be accounted by a discrepancy in the expression of CD8 alpha alpha or CD8 alpha beta complexes or MHC class I molecules. Decreased CD8-p56lck activity was seen both in patients undergoing intensive phlebotomy treatment and in patients in maintenance therapy (i.e. patients who had reached normal levels of iron stores), indicating that this abnormality does not appear to be corrected by iron depletion. To our knowledge, this is the first demonstration of an abnormality in a src-like receptor associated kinase in a human disease state linked to MHC class-I antigens.

Reduction of iron-bearing lunar minerals for the production of oxygen

NASA Technical Reports Server (NTRS)

Massieon, Charles; Cutler, Andrew; Shadman, Farhang

1992-01-01

The kinetics and mechanism of the reduction of simulants of the iron-bearing lunar minerals olivine ((Fe,Mg)2SiO4), pyroxene ((Fe,Mg,Ca)SiO3), and ilmenite (FeTiO3) are investigated, extending previous work with ilmenite. Fayalite is reduced by H2 at 1070 K to 1480 K. A layer of mixed silica glass and iron forms around an unreacted core. Reaction kinetics are influenced by permeation of hydrogen through this layer and a reaction step involving dissociated hydrogen. Reaction mechanisms are independent of Mg content. Augite, hypersthene, and hedenbergite are reduced in H2 at the same temperatures. The products are iron metal and lower iron silicates mixed throughout the mineral. Activation energy rises with calcium content. Ilmenite and fayalite are reduced with carbon deposited on partially reduced minerals via the CO disproportionation reaction. Reduction with carbon is rapid, showing the carbothermal reduction of lunar minerals is possible.

Beta decay of exotic TZ = -1, -2 nuclei: the interesting case of 56Zn

NASA Astrophysics Data System (ADS)

Orrigo, S. E. A.; Rubio, B.; Fujita, Y.; Blank, B.; Gelletly, W.; Agramunt, J.; Algora, A.; Ascher, P.; Bilgier, B.; Cáceres, L.; Cakirli, R. B.; Fujita, H.; Ganioğlu, E.; Gerbaux, M.; Giovinazzo, J.; Grévy, S.; Kamalou, O.; Kozer, H. C.; Kucuk, L.; Kurtukian-Nieto, T.; Molina, F.; Popescu, L.; Rogers, A. M.; Susoy, G.; Stodel, C.; Suzuki, T.; Tamii, A.; Thomas, J. C.

2014-03-01

The β decay properties of the Tz = -2, 56Zn isotope and other proton-rich nuclei in the fp-shell have been investigated in an experiment performed at GANIL. The ions were produced in fragmentation reactions and implanted in a double-sided silicon strip detector surrounded by Ge EXOGAM clovers. Preliminary results for 56Zn are presented .The 56Zn decay proceeds mainly by β delayed proton emission, but β delayed gamma rays were also detected. Moreover, the exotic β delayed gamma-proton decay was observed for the first time. The 56Zn half-life and the energy levels populated in the 56Cu daughter have been determined. Knowledge of the gamma de-excitation of the mirror states in 56Co and the comparison with the results of the mirror charge exchange process, the 56Fe(3He,t) reaction (where 56Fe has Tz = +2), were important in the interpretation of the 56Zn decay data. The absolute Fermi and Gamow-Teller strengths have been deduced.

Study of deuteron induced reactions on natural iron and copper and their use for monitoring beam parameters and for thin layer activation technique

NASA Astrophysics Data System (ADS)

Takács, S.; Tárkányi, F.; Sonck, M.; Hermanne, A.; Sudár, S.

1997-02-01

Excitation functions of deuteron induced nuclear reactions on natural iron and copper have been studied in the frame of a systematic investigation of charged particle induced nuclear reactions on metals for different applications. The excitation functions were measured up to 20 MeV deuteron energy by using stacked foil technique and activation method. The measured and the evaluated literature data showed that some reaction can be recommended for monitoring deuteron beams, and the excitation functions can be used to determine calibration curves for Thin Layer Activation Technique (TLA). Cross sections calculated by statistical model theory, STAPRE, taking into account preequilibrium effect are in reasonable agreement with the experimental results.

Electronic structure and reactivity of three-coordinate iron complexes.

PubMed

Holland, Patrick L

2008-08-01

[Reaction: see text]. The identity and oxidation state of the metal in a coordination compound are typically thought to be the most important determinants of its reactivity. However, the coordination number (the number of bonds to the metal) can be equally influential. This Account describes iron complexes with a coordination number of only three, which differ greatly from iron complexes with octahedral (six-coordinate) geometries with respect to their magnetism, electronic structure, preference for ligands, and reactivity. Three-coordinate complexes with a trigonal-planar geometry are accessible using bulky, anionic, bidentate ligands (beta-diketiminates) that steer a monodentate ligand into the plane of their two nitrogen donors. This strategy has led to a variety of three-coordinate iron complexes in which iron is in the +1, +2, and +3 oxidation states. Systematic studies on the electronic structures of these complexes have been useful in interpreting their properties. The iron ions are generally high spin, with singly occupied orbitals available for pi interactions with ligands. Trends in sigma-bonding show that iron(II) complexes favor electronegative ligands (O, N donors) over electropositive ligands (hydride). The combination of electrostatic sigma-bonding and the availability of pi-interactions stabilizes iron(II) fluoride and oxo complexes. The same factors destabilize iron(II) hydride complexes, which are reactive enough to add the hydrogen atom to unsaturated organic molecules and to take part in radical reactions. Iron(I) complexes use strong pi-backbonding to transfer charge from iron into coordinated alkynes and N 2, whereas iron(III) accepts charge from a pi-donating imido ligand. Though the imidoiron(III) complex is stabilized by pi-bonding in the trigonal-planar geometry, addition of pyridine as a fourth donor weakens the pi-bonding, which enables abstraction of H atoms from hydrocarbons. The unusual bonding and reactivity patterns of three

30 CFR 56.16012 - Storage of incompatible substances.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Storage and Handling § 56.16012 Storage of incompatible substances. Chemical substances, including... substances, where such contact could cause a violent reaction or the liberation of harmful fumes or gases. ...

Hypersensitivity reaction with deferasirox

PubMed Central

Sharma, Atul; Arora, Ekta; Singh, Harmanjit

2015-01-01

Thalassemias comprise a group of hereditary blood disorders. Thalassemia major presents with anemia within the first 2 years of life requiring frequent blood transfusions for sustaining life. Regular blood transfusions lead to iron overload-related complications. Prognosis of thalassemia has improved because of the availability of iron-chelating agents. Oral iron chelators are the mainstay of chelation therapy. Deferasirox is a new-generation oral iron chelator for once daily usage. We herein describe a patient of beta thalassemia major who developed an allergic manifestation in the form of erythematous pruritic skin rashes to the oral iron chelator deferasirox. This is a rare adverse reaction reported with deferasirox that led to a therapeutic dilemma in this particular case. PMID:25969661

IRON AND FREE RADICAL OXIDATIONS IN CELL MEMBRANES

PubMed Central

Schafer, Freya Q.; Yue Qian, Steven; Buettner, Garry R.

2013-01-01

Brain tissue being rich in polyunsaturated fatty acids, is very susceptible to lipid peroxidation. Iron is well known to be an important initiator of free radical oxidations. We propose that the principal route to iron-mediated lipid peroxidations is via iron-oxygen complexes rather than the reaction of iron with hydrogen peroxide, the Fenton reaction. To test this hypothesis, we enriched leukemia cells (K-562 and L1210 cells) with docosahexaenoic acid (DHA) as a model for brain tissue, increasing the amount of DHA from approximately 3 mole % to 32 mole %. These cells were then subjected to ferrous iron and dioxygen to initiate lipid peroxidation in the presence or absence of hydrogen peroxide. Lipid-derived radicals were detected using EPR spin trapping with α-(4-pyridyl-1-oxide)-N-t-butylnitrone (POBN). As expected, lipid-derived radical formation increases with increasing cellular lipid unsaturation. Experiments with Desferal demonstrate that iron is required for the formation of lipid radicals from these cells. Addition of iron to DHA-enriched L1210 cells resulted in significant amounts of radical formation; radical formation increased with increasing amount of iron. However, the exposure of cells to hydrogen peroxide before the addition of ferrous iron did not increase cellular radical formation, but actually decreased spin adduct formation. These data suggest that iron-oxygen complexes are the primary route to the initiation of biological free radical oxidations. This model proposes a mechanism to explain how catalytic iron in brain tissue can be so destructive. PMID:10872752

Iron chemistry at the service of life.

PubMed

Sánchez, Manu; Sabio, Laura; Gálvez, Natividad; Capdevila, Mercè; Dominguez-Vera, Jose M

2017-06-01

Iron is an essential element for almost all organisms on Earth. It is necessary for a number of crucial processes such as hemoglobin and myoglobin transport and storage of oxygen in mammals; electron transfer support in a variety of iron-sulfur protein or cytochrome reactions; and activation and catalysis of reactions of a wide range of substrate like alkanes, olefins, and alcohols. Living organisms adopted iron as the main metal to carry out all of these functions due to the rich coordination chemistry of its two main redox states, Fe 2+ and Fe 3+ , and because of its abundance in the Earth's crust and oceans. This paper presents an overview of the coordination chemistry of iron that makes it suitable for a large variety of functions within biological systems. Despite iron's chemical advantages, organisms were forced to manage with some drawbacks: Fe 3+ insolubility and the formation of toxic radicals, especially the hydroxyl radical. Iron chemistry within biology is an example of how organisms evolved by creating molecular machinery to overcome these difficulties and perform crucial processes with extraordinary elegance and efficiency. © 2017 IUBMB Life, 69(6):382-388, 2017. © 2017 International Union of Biochemistry and Molecular Biology.

Evidence of a reduction reaction of oxidized iron/cobalt by boron atoms diffused toward naturally oxidized surface of CoFeB layer during annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sato, Soshi, E-mail: sato.soshi@cies.tohoku.ac.jp; Honjo, Hiroaki; Niwa, Masaaki

2015-04-06

We have investigated the redox reaction on the surface of Ta/CoFeB/MgO/CoFeB magnetic tunnel junction stack samples after annealing at 300, 350, and 400 °C for 1 h using angle-resolved X-ray photoelectron spectroscopy for precise analysis of the chemical bonding states. At a capping tantalum layer thickness of 1 nm, both the capping tantalum layer and the surface of the underneath CoFeB layer in the as-deposited stack sample were naturally oxidized. By comparison of the Co 2p and Fe 2p spectra among the as-deposited and annealed samples, reduction of the naturally oxidized cobalt and iron atoms occurred on the surface of the CoFeB layer.more » The reduction reaction was more significant at higher annealing temperature. Oxidized cobalt and iron were reduced by boron atoms that diffused toward the surface of the top CoFeB layer. A single CoFeB layer was prepared on SiO{sub 2}, and a confirmatory evidence of the redox reaction with boron diffusion was obtained by angle-resolved X-ray photoelectron spectroscopy analysis of the naturally oxidized surface of the CoFeB single layer after annealing. The redox reaction is theoretically reasonable based on the Ellingham diagram.« less

Photoreduction and incorporation of iron into ferritins.

PubMed Central

Laulhère, J P; Labouré, A M; Briat, J F

1990-01-01

Pea seed ferritin is able to incorporate ferrous iron into the mineral core. Fe2+ may be formed by reduction of exogenous Fe3+ with ascorbate or by photoreduction by ferritin and by ferric citrate. In our experimental conditions the bulk of the photoreduction is carried out by ferritin, which is able to photoreduce its endogenous iron. Citrate does not enhance the photoreduction capacity of ferritin, and exogenous ferric citrate improves the yield of the reaction by about 30%. The mineral core of the ferritin is shown to photoreduce actively, and the protein shell does not participate directly in the photoreduction. Low light intensities and low concentration of reducing agents do not allow a release of iron from ferritins, but induce a 'redox mill' of photoreduction and simultaneous ferroxidase-mediated incorporation. High ascorbate concentrations induce the release of ferritin iron. These reactions are accompanied by the correlated occurrence of damage caused by radicals arising from Fenton reactions, leading to specific cleavages in the 28 kDa phytoferritin subunit. This damage caused by radicals occurs during the oxidative incorporation into the mineral core and is prevented by o-phenanthroline or by keeping the samples in the dark. Images Fig. 1. Fig. 2. Fig. 3. Fig. 5. PMID:2375759

Linkage of iron elution and dissolved oxygen consumption with removal of organic pollutants by nanoscale zero-valent iron: Effects of pH on iron dissolution and formation of iron oxide/hydroxide layer.

PubMed

Fujioka, Nanae; Suzuki, Moe; Kurosu, Shunji; Kawase, Yoshinori

2016-02-01

The iron elution and dissolved oxygen (DO) consumption in organic pollutant removal by nanoscale zero-valent iron (nZVI) was examined in the range of solution pH from 3.0 to 9.0. Their behaviors were linked with the removal of organic pollutant through the dissolution of iron and the formation of iron oxide/hydroxide layer affected strongly by solution pH and DO. As an example of organic pollutants, azo-dye Orange II was chosen in this study. The chemical composition analyses before and after reaction confirmed the corrosion of nZVI into ions, the formation of iron oxide/hydroxide layer on nZVI surface and the adsorption of the pollutant and its intermediates. The complete decolorization of Orange II with nZVI was accomplished very quickly. On the other hand, the total organic carbon (TOC) removal was considerably slow and the maximum TOC removal was around 40% obtained at pH 9.0. The reductive cleavage of azo-bond by emitted electrons more readily took place as compared with the cleavage of aromatic rings of Orange II leading to the degradation to smaller molecules and subsequently the mineralization. A reaction kinetic model based on the Langmuir-Hinshelwood/Eley-Rideal approach was developed to elucidate mechanisms for organic pollutant removal controlled by the formation of iron oxide/hydroxide layer, the progress of which could be characterized by considering the dynamic concentration changes in Fe(2+) and DO. The dynamic profiles of Orange II removal linked with Fe(2+) and DO could be reasonably simulated in the range of pH from 3.0 to 9.0. Copyright © 2015 Elsevier Ltd. All rights reserved.

Process to Produce Iron Nanoparticle Lunar Dust Simulant Composite

NASA Technical Reports Server (NTRS)

Hung, Ching-cheh; McNatt, Jeremiah

2010-01-01

A document discusses a method for producing nanophase iron lunar dust composite simulant by heating a mixture of carbon black and current lunar simulant types (mixed oxide including iron oxide) at a high temperature to reduce ionic iron into elemental iron. The product is a chemically modified lunar simulant that can be attracted by a magnet, and has a surface layer with an iron concentration that is increased during the reaction. The iron was found to be -iron and Fe3O4 nanoparticles. The simulant produced with this method contains iron nanoparticles not available previously, and they are stable in ambient air. These nanoparticles can be mass-produced simply.

Photochemical Reactions of (n(5)-Pentamethylcyclpentadienyl)-Dicarbonyliron-Alkyl and -Silyl Complexes: Reversible Ethylene Insertion into an Iron-Silicon Bond and Implications for the Mechanism of Transition Metal-Catalyzed Hydrosilation of Alkenes.

DTIC Science & Technology

1985-12-11

RD-R162 462 PHOTOCHEMICAL REACTIONS OF(N(S)-P NTANETNYLCVCLPENTADIENYL)-DICARRONVLIR.. (U) MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY...34 Photochemical Reactions of (n5-Pentamethylcyclpentadienyl)- Dicarbonyliron-Alkyl and -Silyl Complexes: Reversible Ethylene Insertion into an Iron-Silicon Bond...Chemical Society) PHOTOCHEMICAL REACTIONS OF (n5-PENTAMETHYLCYCLOPENTADIENYL)- DICARBONYLIRON-ALKYL AND -SILYL COMPLEXES: REVERSIBLE ETHYLENE INSERTION INTO

Arsenic Mobilization Influenced By Iron Reduction And Sulfidogenesis Under Dynamic Flow

NASA Astrophysics Data System (ADS)

Kocar, B. D.; Stewart, B. D.; Herbel, M.; Fendorf, S.

2004-12-01

Sulfidogenesis and iron reduction are ubiquitous processes that occur in a variety of anoxic subsurface and surface environments, which profoundly impact the cycling of arsenic. Of the iron (hydr)oxides, ferrihydrite possesses one of the highest capacities to retain arsenic, and is globally distributed within soils and sediments. Upon dissimilatory iron reduction, ferrihydrite may transform to lower surface area minerals, such as goethite and magnetite, which decreases arsenic retention, thus enhancing its transport. Here we examine how arsenic retained on ferrihydrite is mobilized under dynamic flow in the presence of Sulfurosprillum barnesii strain SES-3, a bacteria capable of reducing both As(V) and Fe(III). Ferrihydrite coated sands, loaded with 150 mg kg-1 As(V), were inoculated with S. barnesii, packed into a column and reacted with a synthetic groundwater solution. Within several days after initiation of flow, the concentration of arsenic in the column effluent increased dramatically coincident with the mineralogical transformation of ferrihydrite and As(V) reduction to As(III). Following the initial pulse of arsenic, effluent concentration then declined to less than 10 μ M. Thus, arsenic release into the aqueous phase is contingent upon the incongruent reduction of As(V) and Fe(III) as mediated by biological activity. Reaction of abiotically or biotically generated dissolved sulfide with iron (hydr)oxides may have a dramatic influence on the fate of arsenic within surface and subsurface environments. Accordingly, we examined the reaction of dissolved bisulfide and iron (hydr)oxide complexed with arsenic in both batch and column systems. Low ratios of sulfide to iron in batch reaction systems result in the formation of elemental sulfur and concomitant arsenic release from the iron (hydr)oxide surface. High sulfide to iron ratios, in contrast, appear to favor the formation of iron and arsenic sulfides. Our findings demonstrate that iron (hydr)oxides may

Investigation of Activation Cross Sections of the Proton Induced Nuclear Reactions on Natural Iron at Medium Energies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ditroi, F.; Tarkanyi, F.; Csikai, J.

2005-05-24

Iron is one of the most important structural materials in every field of science, technology, industry, etc. Its application in a radiating environment requires the knowledge of accurate excitation functions for the possible reactions in question. By using the Thin Layer Activation technique (TLA) the knowledge of such data is also extremely important even in the case of relative measurements to design the irradiation (irradiation energy, beam intensity, duration) and also for radioactive safety estimations. The cross sections are frequently measured at low energies but there are unsatisfactory and unreliable data in the energy range above 40 MeV.

Investigation of Activation Cross Sections of the Proton Induced Nuclear Reactions on Natural Iron at Medium Energies

NASA Astrophysics Data System (ADS)

Ditrói, F.; Tárkányi, F.; Csikai, J.; Uddin, M. S.; Hagiwara, M.; Baba, M.

2005-05-01

Iron is one of the most important structural materials in every field of science, technology, industry, etc. Its application in a radiating environment requires the knowledge of accurate excitation functions for the possible reactions in question. By using the Thin Layer Activation technique (TLA) the knowledge of such data is also extremely important even in the case of relative measurements to design the irradiation (irradiation energy, beam intensity, duration) and also for radioactive safety estimations. The cross sections are frequently measured at low energies but there are unsatisfactory and unreliable data in the energy range above 40 MeV.

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Q.; Muftikian, R.; Korte, N.

1998-06-02

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from effluents containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. The present invention also provides kits, devices, and other instruments that use the above-mentioned palladized iron bimetallic system for the dechlorination of chlorinated organic compounds. 10 figs.

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Q.; Muftikian, R.; Korte, N.

1997-03-18

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from effluents containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. The present invention also provides kits, devices, and other instruments that use the above-mentioned palladized iron bimetallic system for the dechlorination of chlorinated organic compounds. 10 figs.

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Quintus; Muftikian, Rosy; Korte, Nic

1997-01-01

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from effluents containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. The present invention also provides kits, devices, and other instruments that use the above-mentioned palladized iron bimetallic system for the dechlorination of chlorinated organic compounds.

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Quintus; Muftikian, Rosy; Korte, Nic

1998-01-01

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from effluents containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. The present invention also provides kits, devices, and other instruments that use the above-mentioned palladized iron bimetallic system for the dechlorination of chlorinated organic compounds.

Remeasurement and compilation of excitation function of proton induced reactions on iron for activation techniques

NASA Astrophysics Data System (ADS)

Takács, S.; Vasváry, L.; Tárkányi, F.

1994-05-01

Excitation functions of proton induced reactions on natFe(p, xn) 56Co have been remeasured in the energy region up to 18 MeV using stacked foil technique and standard high resolution gamma-ray spectrometry at the Debrecen MGC-20E cyclotron. Compilation of the available data measured between 1959 and 1993 has been made. The corresponding excitation functions have been reviewed, critical comparison of all the available data was done to obtain the most accurate data set. The feasibility of the evaluated data set was checked by reproducing experimental calibration curves for TLA by calculation.

Simultaneous iron and nickel isotopic analyses of presolar silicon carbide grains

DOE PAGES

Trappitsch, Reto; Stephan, Thomas; Savina, Michael R.; ...

2018-01-01

Aside from recording stellar nucleosynthesis, a few elements in presolar grains can also provide insights into the galactic chemical evolution (GCE) of nuclides. We have studied the carbon, silicon, iron, and nickel isotopic compositions of presolar silicon carbide (SiC) grains from asymptotic giant branch (AGB) stars to better understand GCE. Since only the neutron-rich nuclides in these grains have been heavily in uenced by the parent star, the neutron-poor nuclides serve as GCE proxies. Using CHILI, a new resonance ionization mass spectrometry (RIMS) instrument, we measured 74 presolar SiC grains for all iron and nickel isotopes. With the CHARISMA instrument,more » 13 presolar SiC grains were analyzed for iron isotopes. All grains were also measured by NanoSIMS for their carbon and silicon isotopic compositions. A comparison of the measured neutron-rich isotopes with models for AGB star nucleosynthesis shows that our measurements are consistent with AGB star predictions for low-mass stars between half-solar and solar metallicity. Furthermore, our measurements give an indication on the 22Ne( ,n) 25Mg reaction rate. In terms of GCE, we nd that the GCE-dominated iron and nickel isotope ratios, 54Fe/56Fe and 60Ni/ 58Ni, correlate with their GCE-dominated counterpart in silicon, 29Si/ 28Si. The measured GCE trends include the Solar System composition, showing that the Solar System is not a special case. However, as seen in silicon and titanium, many presolar SiC grains are more evolved for iron and nickel than the Solar System. This con rms prior ndings and agrees with observations of large stellar samples that a simple age-metallicity relationship for GCE cannot explain the composition of the solar neighborhood.« less

Simultaneous iron and nickel isotopic analyses of presolar silicon carbide grains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trappitsch, Reto; Stephan, Thomas; Savina, Michael R.

Aside from recording stellar nucleosynthesis, a few elements in presolar grains can also provide insights into the galactic chemical evolution (GCE) of nuclides. We have studied the carbon, silicon, iron, and nickel isotopic compositions of presolar silicon carbide (SiC) grains from asymptotic giant branch (AGB) stars to better understand GCE. Since only the neutron-rich nuclides in these grains have been heavily in uenced by the parent star, the neutron-poor nuclides serve as GCE proxies. Using CHILI, a new resonance ionization mass spectrometry (RIMS) instrument, we measured 74 presolar SiC grains for all iron and nickel isotopes. With the CHARISMA instrument,more » 13 presolar SiC grains were analyzed for iron isotopes. All grains were also measured by NanoSIMS for their carbon and silicon isotopic compositions. A comparison of the measured neutron-rich isotopes with models for AGB star nucleosynthesis shows that our measurements are consistent with AGB star predictions for low-mass stars between half-solar and solar metallicity. Furthermore, our measurements give an indication on the 22Ne( ,n) 25Mg reaction rate. In terms of GCE, we nd that the GCE-dominated iron and nickel isotope ratios, 54Fe/56Fe and 60Ni/ 58Ni, correlate with their GCE-dominated counterpart in silicon, 29Si/ 28Si. The measured GCE trends include the Solar System composition, showing that the Solar System is not a special case. However, as seen in silicon and titanium, many presolar SiC grains are more evolved for iron and nickel than the Solar System. This con rms prior ndings and agrees with observations of large stellar samples that a simple age-metallicity relationship for GCE cannot explain the composition of the solar neighborhood.« less

mRNA Regulation of Cardiac Iron Transporters and Ferritin Subunits in a Mouse Model of Iron Overload

PubMed Central

Brewer, Casey J.; Wood, Ruth I.; Wood, John C.

2014-01-01

Iron cardiomyopathy is the leading cause of death in iron overload. Men have twice the mortality rate of women, though the cause is unknown. In hemojuvelin-knockout mice, a model of the disease, males load more cardiac iron than females. We postulated that sex differences in cardiac iron import cause differences in cardiac iron concentration. RT-PCR was used to measure mRNA of cardiac iron transporters in hemojuvelin-knockout mice. No sex differences were discovered among putative importers of non-transferrin bound iron (L-type and T-type calcium channels, ZRT/IRT-like protein 14 zinc channels). Transferrin-bound iron transporters were also analyzed; these are controlled by the iron regulatory element/iron regulatory protein (IRE/IRP) system. There was a positive relationship between cardiac iron and ferroportin mRNA in both sexes, but it was significantly steeper in females (p<0.05). Transferrin receptor 1 and divalent metal transporter 1 were more highly expressed in females than males (p<0.01 and p<0.0001, respectively), consistent with their lower cardiac iron levels, as predicted by IRE/IRP regulatory pathways. Light-chain (L) ferritin showed a positive correlation with cardiac iron that was nearly identical in males and females (R2=0.41, p<0.01 and R2=0.56, p<0.05, respectively), while heavy-chain (H) ferritin was constitutively expressed in both sexes. This represents the first report of IRE/IRP regulatory pathways in the heart. Transcriptional regulation of ferroportin was suggested in both sexes, creating a potential mechanism for differential set points for iron export. Constitutive H-ferritin expression suggests a logical limit to cardiac iron buffering capacity at levels known to produce heart failure in humans. PMID:25220979

Characterization of Co and Fe-MCM-56 catalysts for NH3-SCR and N2O decomposition: An in situ FTIR study

NASA Astrophysics Data System (ADS)

Grzybek, Justyna; Gil, Barbara; Roth, Wieslaw J.; Skoczek, Monika; Kowalczyk, Andrzej; Chmielarz, Lucjan

2018-05-01

Two-step preparation of iron and cobalt-containing MCM-56 zeolites has been undertaken to evaluate the influence of their physicochemical properties in the selective catalytic reduction (NH3-SCR or DeNOx) of NO using NH3 as a reductant. Zeolites were prepared by the selective leaching of the framework cations by concentrated HNO3 solution and NH4F/HF mixture and consecutively, introduction of Co and Fe heteroatoms, in quantities below 1 wt%. Further calcination allowed to obtain highly dispersed active species. Their evaluation and speciation was realized by adsorption of pyridine and NO, followed by FTIR spectroscopy. Both Fe-MCM-56 zeolites showed excellent activities (maximum NO conversion 92%) with high selectivity to dinitrogen (above 99%) in the high temperature NH3-SCR process. High catalytic activity of Fe-MCM-56 zeolites was assigned to the formation of stable nitrates, delivering NO to react with NH3 at higher temperatures and suppressing the direct NO oxidation. It was found that more nitrates was formed in Fe-MCM-56 (HNO3) than in Fe-MCM-56 (HF/NH4F) and that could compensate for the lower Fe loading, resulting in very similar catalytic activity of both catalysts. At the same time both Co-and Fe-MCM-56 zeolites were moderately active in direct N2O decomposition, with maximum N2O conversion not higher than 80% and activity window starting at 500 °C. This phenomenon was expected since both types of catalysts contained well dispersed active centers, not beneficial for this reaction.

Iron crystallization in a fluidized-bed Fenton process.

PubMed

Boonrattanakij, Nonglak; Lu, Ming-Chun; Anotai, Jin

2011-05-01

The mechanisms of iron precipitation and crystallization in a fluidized-bed reactor were investigated. Within the typical Fenton's reagent dosage and pH range, ferric ions as a product from ferrous ion oxidation would be supersaturated and would subsequently precipitate out in the form of ferric hydroxide after the initiation of the Fenton reaction. These precipitates would simultaneously crystallize onto solid particles in a fluidized-bed Fenton reactor if the precipitation proceeded toward heterogeneous nucleation. The heterogeneous crystallization rate was controlled by the fluidized material type and the aging/ripening period of the crystallites. Iron crystallization onto the construction sand was faster than onto SiO(2), although the iron removal efficiencies at 180 min, which was principally controlled by iron hydroxide solubility, were comparable. To achieve a high iron removal rate, fluidized materials have to be present at the beginning of the Fenton reaction. Organic intermediates that can form ferro-complexes, particularly volatile fatty acids, can significantly increase ferric ion solubility, hence reducing the crystallization performance. Therefore, the fluidized-bed Fenton process will achieve exceptional performance with respect to both organic pollutant removal and iron removal if it is operated with the goal of complete mineralization. Crystallized iron on the fluidized media could slightly retard the successive crystallization rate; thus, it is necessary to continuously replace a portion of the iron-coated bed with fresh media to maintain iron removal performance. The iron-coated construction sand also had a catalytic property, though was less than those of commercial goethite. Copyright © 2011 Elsevier Ltd. All rights reserved.

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Quintus; Muftikian, Rosy; Korte, Nic

1997-01-01

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from various effluents or contaminated soil containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products.

Removal of selenite by zero-valent iron combined with ultrasound: Se(IV) concentration changes, Se(VI) generation, and reaction mechanism.

PubMed

Fu, Fenglian; Lu, Jianwei; Cheng, Zihang; Tang, Bing

2016-03-01

In this paper, the performance and application of zero-valent iron (ZVI) assisted by ultrasonic irradiation for the removal of selenite (Se(IV)) in wastewater was evaluated and reaction mechanism of Se(IV) with ZVI in such systems was investigated. A series of batch experiments were conducted to determine the effects of ultrasound power, pH, ZVI concentration, N2 and air on Se(IV) removal. ZVI before and after reaction with Se(IV) was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Results indicated that ultrasound can lead to a significant synergy in the removal of Se(IV) by ZVI because ultrasound can promote the generation of OH and accelerate the advanced Fenton process. The primary reaction products of ZVI and Se(IV) were Se(0), ferrihydrite, and Fe2O3. Copyright © 2015 Elsevier B.V. All rights reserved.

Assessment of Dextran Antigenicity of Intravenous Iron Preparations with Enzyme-Linked Immunosorbent Assay (ELISA)

PubMed Central

Neiser, Susann; Koskenkorva, Taija S.; Schwarz, Katrin; Wilhelm, Maria; Burckhardt, Susanna

2016-01-01

Intravenous iron preparations are typically classified as non-dextran-based or dextran/dextran-based complexes. The carbohydrate shell for each of these preparations is unique and is key in determining the various physicochemical properties, the metabolic pathway, and the immunogenicity of the iron-carbohydrate complex. As intravenous dextran can cause severe, antibody-mediated dextran-induced anaphylactic reactions (DIAR), the purpose of this study was to explore the potential of various intravenous iron preparations, non-dextran-based or dextran/dextran-based, to induce these reactions. An IgG-isotype mouse monoclonal anti-dextran antibody (5E7H3) and an enzyme-linked immunosorbent assay (ELISA) were developed to investigate the dextran antigenicity of low molecular weight iron dextran, ferumoxytol, iron isomaltoside 1000, ferric gluconate, iron sucrose and ferric carboxymaltose, as well as isomaltoside 1000, the isolated carbohydrate component of iron isomaltoside 1000. Low molecular weight iron dextran, as well as dextran-based ferumoxytol and iron isomaltoside 1000, reacted with 5E7H3, whereas ferric carboxymaltose, iron sucrose, sodium ferric gluconate, and isolated isomaltoside 1000 did not. Consistent results were obtained with reverse single radial immunodiffusion assay. The results strongly support the hypothesis that, while the carbohydrate alone (isomaltoside 1000) does not form immune complexes with anti-dextran antibodies, iron isomaltoside 1000 complex reacts with anti-dextran antibodies by forming multivalent immune complexes. Moreover, non-dextran based preparations, such as iron sucrose and ferric carboxymaltose, do not react with anti-dextran antibodies. This assay allows to assess the theoretical possibility of a substance to induce antibody-mediated DIARs. Nevertheless, as this is only one possible mechanism that may cause a hypersensitivity reaction, a broader set of assays will be required to get an understanding of the mechanisms that may

Assessment of Dextran Antigenicity of Intravenous Iron Preparations with Enzyme-Linked Immunosorbent Assay (ELISA).

PubMed

Neiser, Susann; Koskenkorva, Taija S; Schwarz, Katrin; Wilhelm, Maria; Burckhardt, Susanna

2016-07-21

Intravenous iron preparations are typically classified as non-dextran-based or dextran/dextran-based complexes. The carbohydrate shell for each of these preparations is unique and is key in determining the various physicochemical properties, the metabolic pathway, and the immunogenicity of the iron-carbohydrate complex. As intravenous dextran can cause severe, antibody-mediated dextran-induced anaphylactic reactions (DIAR), the purpose of this study was to explore the potential of various intravenous iron preparations, non-dextran-based or dextran/dextran-based, to induce these reactions. An IgG-isotype mouse monoclonal anti-dextran antibody (5E7H3) and an enzyme-linked immunosorbent assay (ELISA) were developed to investigate the dextran antigenicity of low molecular weight iron dextran, ferumoxytol, iron isomaltoside 1000, ferric gluconate, iron sucrose and ferric carboxymaltose, as well as isomaltoside 1000, the isolated carbohydrate component of iron isomaltoside 1000. Low molecular weight iron dextran, as well as dextran-based ferumoxytol and iron isomaltoside 1000, reacted with 5E7H3, whereas ferric carboxymaltose, iron sucrose, sodium ferric gluconate, and isolated isomaltoside 1000 did not. Consistent results were obtained with reverse single radial immunodiffusion assay. The results strongly support the hypothesis that, while the carbohydrate alone (isomaltoside 1000) does not form immune complexes with anti-dextran antibodies, iron isomaltoside 1000 complex reacts with anti-dextran antibodies by forming multivalent immune complexes. Moreover, non-dextran based preparations, such as iron sucrose and ferric carboxymaltose, do not react with anti-dextran antibodies. This assay allows to assess the theoretical possibility of a substance to induce antibody-mediated DIARs. Nevertheless, as this is only one possible mechanism that may cause a hypersensitivity reaction, a broader set of assays will be required to get an understanding of the mechanisms that may

Intravenous ferric carboxymaltose for the treatment of iron deficiency anemia

PubMed Central

Friedrisch, João Ricardo; Cançado, Rodolfo Delfini

2015-01-01

Nutritional iron deficiency anemia is the most common deficiency disorder, affecting more than two billion people worldwide. Oral iron supplementation is usually the first choice for the treatment of iron deficiency anemia, but in many conditions, oral iron is less than ideal mainly because of gastrointestinal adverse events and the long course needed to treat the disease and replenish body iron stores. Intravenous iron compounds consist of an iron oxyhydroxide core, which is surrounded by a carbohydrate shell made of polymers such as dextran, sucrose or gluconate. The first iron product for intravenous use was the high molecular weight iron dextran. However, dextran-containing intravenous iron preparations are associated with an elevated risk of anaphylactic reactions, which made physicians reluctant to use intravenous iron for the treatment of iron deficiency anemia over many years. Intravenous ferric carboxymaltose is a stable complex with the advantage of being non-dextran-containing and a very low immunogenic potential and therefore not predisposed to anaphylactic reactions. Its properties permit the administration of large doses (15 mg/kg; maximum of 1000 mg/infusion) in a single and rapid session (15-minute infusion) without the requirement of a test dose. The purpose of this review is to discuss some pertinent issues in relation to the history, pharmacology, administration, efficacy, and safety profile of ferric carboxymaltose in the treatment of patients with iron deficiency anemia. PMID:26670403

Kinetic studies on the oxidation of oxyhemoglobin by biologically active iron thiosemicarbazone complexes: relevance to iron-chelator-induced methemoglobinemia.

PubMed

Basha, Maram T; Rodríguez, Carlos; Richardson, Des R; Martínez, Manuel; Bernhardt, Paul V

2014-03-01

The oxidation of oxyhemoglobin to methemoglobin has been found to be facilitated by low molecular weight iron(III) thiosemicarbazone complexes. This deleterious reaction, which produces hemoglobin protein units unable to bind dioxygen and occurs during the administration of iron chelators such as the well-known 3-aminopyridine-2-pyridinecarbaldehyde thiosemicarbazone (3-AP; Triapine), has been observed in the reaction with Fe(III) complexes of some members of the 3-AP structurally-related thiosemicarbazone ligands derived from di-2-pyridyl ketone (HDpxxT series). We have studied the kinetics of this oxidation reaction in vitro using human hemoglobin and found that the reaction proceeds with two distinct time-resolved steps. These have been associated with sequential oxidation of the two different oxyheme cofactors in the α and β protein chains. Unexpected steric and hydrogen-bonding effects on the Fe(III) complexes appear to be the responsible for the observed differences in the reaction rate across the series of HDpxxT ligand complexes used in this study.

Iron-sulfur clusters as biological sensors: the chemistry of reactions with molecular oxygen and nitric oxide.

PubMed

Crack, Jason C; Green, Jeffrey; Thomson, Andrew J; Le Brun, Nick E

2014-10-21

recognized. This remarkable feature suggested that the original [4Fe-4S] cluster can be restored using persulfide as the source of sulfide ion. We have demonstrated that only iron and a source of electrons are required to promote efficient conversion back from the [2Fe-2S] to the [4Fe-4S] form. We propose this as a novel in vivo repair mechanism that does not require the intervention of an iron-sulfur cluster biogenesis pathway. A number of iron-sulfur regulators have evolved to function as sensors of NO. Although it has long been known that the iron-sulfur clusters of many phylogenetically unrelated proteins are vulnerable to attack by NO, our recent studies of Wbl proteins and FNR have provided new insights into the mechanism of cluster nitrosylation, which overturn the commonly accepted view that the product is solely a mononuclear iron dinitrosyl complex (known as a DNIC). The major reaction is a rapid, multiphase process involving stepwise addition of up to eight NO molecules per [4Fe-4S] cluster. The major iron nitrosyl product is EPR silent and has optical characteristics similar to Roussin's red ester, [Fe2(NO)4(RS)2] (RRE), although a species similar to Roussin's black salt, [Fe4(NO)7(S)3](-) (RBS) cannot be ruled out. A major future challenge will be to clarify the nature of these species.

A new analytical approach to understanding nanoscale lead-iron interactions in drinking water distribution systems.

PubMed

Trueman, Benjamin F; Gagnon, Graham A

2016-07-05

High levels of iron in distributed drinking water often accompany elevated lead release from lead service lines and other plumbing. Lead-iron interactions in drinking water distribution systems are hypothesized to be the result of adsorption and transport of lead by iron oxide particles. This mechanism was explored using point-of-use drinking water samples characterized by size exclusion chromatography with UV and multi-element (ICP-MS) detection. In separations on two different stationary phases, high apparent molecular weight (>669 kDa) elution profiles for (56)Fe and (208)Pb were strongly correlated (average R(2)=0.96, N=73 samples representing 23 single-unit residences). Moreover, (56)Fe and (208)Pb peak areas exhibited an apparent linear dependence (R(2)=0.82), consistent with mobilization of lead via adsorption to colloidal particles rich in iron. A UV254 absorbance peak, coincident with high molecular weight (56)Fe and (208)Pb, implied that natural organic matter was interacting with the hypothesized colloidal species. High molecular weight UV254 peak areas were correlated with both (56)Fe and (208)Pb peak areas (R(2)=0.87 and 0.58, respectively). On average, 45% (std. dev. 10%) of total lead occurred in the size range 0.05-0.45 μm. Copyright © 2016 Elsevier B.V. All rights reserved.

Influence of ascorbic acid on iron absorption from an iron-fortified, chocolate-flavored milk drink in Jamaican children.

PubMed

Davidsson, L; Walczyk, T; Morris, A; Hurrell, R F

1998-05-01

The influence of ascorbic acid on iron absorption from an iron-fortified, chocolate-flavored milk drink (6.3 mg total Fe per serving) was evaluated with a stable-isotope technique in 20 6-7-y-old Jamaican children. Each child received two test meals labeled with 5.6 mg 57Fe and 3.0 mg 58Fe as ferrous sulfate on 2 consecutive days. Three different doses of ascorbic acid (0, 25, and 50 mg per 25-g serving) were evaluated in two separate studies by using a crossover design. Iron isotope ratios were measured by negative thermal ionization mass spectrometry. In the first study, iron absorption was significantly greater (P < 0.0001) after the addition of 25 mg ascorbic acid: geometric mean iron absorption was 1.6% (range: 0.9-4.2%) and 5.1% (2.2-17.3%) for the test meals containing 0 and 25 mg ascorbic acid, respectively. In the second study, a significant difference (P < 0.05) in iron absorption was observed when the ascorbic acid content was increased from 25 to 50 mg: geometric mean iron absorption was 5.4% (range: 2.7-10.8%) compared with 7.7% (range: 4.7-16.5%), respectively. The chocolate drink contained relatively high amounts of polyphenolic compounds, phytic acid, and calcium, all well-known inhibitors of iron absorption. The low iron absorption without added ascorbic acid shows that chocolate milk is a poor vehicle for iron fortification unless sufficient amounts of an iron-absorption enhancer are added. Regular consumption of iron-fortified chocolate milk drinks containing added ascorbic acid could have a positive effect on iron nutrition in population groups vulnerable to iron deficiency.

Synthesis of kaolin supported nanoscale zero-valent iron and its degradation mechanism of Direct Fast Black G in aqueous solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Xiaoying; Chen, Zhengxian; Zhou, Rongbing

2015-01-15

Graphical abstract: UV–visible spectra of DFBG solution using K-nZVI (1:1) nanoparticles. (a) Before reaction; (b) during reaction; (c) after reaction. - Highlights: • Kaolin-supported Fe{sup 0} nanoparticle (K-nZVI) was synthesized. • Degradation of Direct Fast Black by K-nZVI was studied. • K-nZVI was characterized by SEM, XRD, UV and FIIR. • Degradation mechanism of Direct Fast Black was proposed. - Abstract: Calcinated kaolin supported nanoscale zero-valent iron (K-nZVI) was synthesized and used for the removal of tetrad azo-group dye-Direct Fast Black G (DFBG) from aqueous solution. The results demonstrated that after reacting for 10 min with an initial concentration ofmore » DFBG 100 mg L{sup −1} (pH 9.49), 78.60% of DFBG was removed using K-nZVI, while only 41.39% and 12.56% of DFBG were removed using nZVI and kaolin, respectively. K-nZVI with a mass ratio of nZVI nanoparticles versus kaolin at 1:1 was found to have a high degree of reactivity. Furthermore, scanning electron microscopy (SEM) confirmed that nZVI was better dispersed when kaolin was present. XRD patterns indicated that iron oxides were formed after reaction. Fourier transforms infrared spectra (FTIR) and UV–visible demonstrated that the peak in the visible light region of DFBG was degraded and new bands were observed. Kinetics studies showed that the degradation of DFBG fitted well to the pseudo first-order model. The degradation of DFBG by K-nZVI was based on its adsorption onto kaolin and iron oxides, and subsequently reduction using nZVI was proposed. A significant outcome emerged in that 99.84% of DFBG in wastewater was removed using K-nZVI after reacting for 60 min.« less

Biologically recycled continental iron is a major component in banded iron formations

PubMed Central

Li, Weiqiang; Beard, Brian L.; Johnson, Clark M.

2015-01-01

Banded iron formations (BIFs) record a time of extensive Fe deposition in the Precambrian oceans, but the sources and pathways for metals in BIFs remain controversial. Here, we present Fe- and Nd-isotope data that indicate two sources of Fe for the large BIF units deposited 2.5 billion y ago. High-εNd and -δ56Fe signatures in some BIF samples record a hydrothermal component, but correlated decreases in εNd- and δ56Fe values reflect contributions from a continental component. The continental Fe source is best explained by Fe mobilization on the continental margin by microbial dissimilatory iron reduction (DIR) and confirms for the first time, to our knowledge, a microbially driven Fe shuttle for the largest BIFs on Earth. Detailed sampling at various scales shows that the proportions of hydrothermal and continental Fe sources were invariant over periods of 100–103 y, indicating that there was no seasonal control, although Fe sources varied on longer timescales of 105–106 y, suggesting a control by marine basin circulation. These results show that Fe sources and pathways for BIFs reflect the interplay between abiologic (hydrothermal) and biologic processes, where the latter reflects DIR that operated on a basin-wide scale in the Archean. PMID:26109570

Biologically recycled continental iron is a major component in banded iron formations.

PubMed

Li, Weiqiang; Beard, Brian L; Johnson, Clark M

2015-07-07

Banded iron formations (BIFs) record a time of extensive Fe deposition in the Precambrian oceans, but the sources and pathways for metals in BIFs remain controversial. Here, we present Fe- and Nd-isotope data that indicate two sources of Fe for the large BIF units deposited 2.5 billion y ago. High-εNd and -δ(56)Fe signatures in some BIF samples record a hydrothermal component, but correlated decreases in εNd- and δ(56)Fe values reflect contributions from a continental component. The continental Fe source is best explained by Fe mobilization on the continental margin by microbial dissimilatory iron reduction (DIR) and confirms for the first time, to our knowledge, a microbially driven Fe shuttle for the largest BIFs on Earth. Detailed sampling at various scales shows that the proportions of hydrothermal and continental Fe sources were invariant over periods of 10(0)-10(3) y, indicating that there was no seasonal control, although Fe sources varied on longer timescales of 10(5)-10(6) y, suggesting a control by marine basin circulation. These results show that Fe sources and pathways for BIFs reflect the interplay between abiologic (hydrothermal) and biologic processes, where the latter reflects DIR that operated on a basin-wide scale in the Archean.

Monosodium glutamate for simple photometric iron analysis

NASA Astrophysics Data System (ADS)

Prasetyo, E.

2018-01-01

Simple photometric method for iron analysis using monosodium glutamate (MSG) was proposed. The method could be used as an alternative method, which was technically simple, economic, quantitative, readily available, scientifically sound and environmental friendly. Rapid reaction of iron (III) with glutamate in sodium chloride-hydrochloric acid buffer (pH 2) to form red-brown complex was served as a basis in the photometric determination, which obeyed the range of iron (III) concentration 1.6 - 80 µg/ml. This method could be applied to determine iron concentration in soil with satisfactory results (accuracy and precision) compared to other photometric and atomic absorption spectrometry results.

Reduction reactions and densification during in situ TEM heating of iron oxide nanochains

NASA Astrophysics Data System (ADS)

Bonifacio, Cecile S.; Das, Gautom; Kennedy, Ian M.; van Benthem, Klaus

2017-12-01

The reduction reactions and densification of nanochains assembled from γ-Fe2O3 nanoparticles were investigated using in situ transmission electron microscopy (TEM). Morphological changes and reduction of the metal oxide nanochains were observed during in situ TEM annealing through simultaneous imaging and quantitative analysis of the near-edge fine structures of Fe L2,3 absorption edges acquired by spatially resolved electron energy loss spectroscopy. A change in the oxidation states during annealing of the iron oxide nanochains was observed with phase transformations due to continuous reduction from Fe2O3 over Fe3O4, FeO to metallic Fe. Phase transitions during the in situ heating experiments were accompanied with morphological changes in the nanochains, specifically rough-to-smooth surface transitions below 500 °C, neck formation between adjacent particles around 500 °C, and subsequent neck growth. At higher temperatures, coalescence of FeO particles was observed, representing densification.

Opposing authigenic controls on the isotopic signature of dissolved iron in hydrothermal plumes

NASA Astrophysics Data System (ADS)

Lough, A. J. M.; Klar, J. K.; Homoky, W. B.; Comer-Warner, S. A.; Milton, J. A.; Connelly, D. P.; James, R. H.; Mills, R. A.

2017-04-01

Iron is a scarce but essential micronutrient in the oceans that limits primary productivity in many regions of the surface ocean. The mechanisms and rates of Fe supply to the ocean interior are still poorly understood and quantified. Iron isotope ratios of different Fe pools can potentially be used to trace sources and sinks of the global Fe biogeochemical cycle if these boundary fluxes have distinct signatures. Seafloor hydrothermal vents emit metal rich fluids from mid-ocean ridges into the deep ocean. Iron isotope ratios have the potential to be used to trace the input of hydrothermal dissolved iron to the oceans if the local controls on the fractionation of Fe isotopes during plume dispersal in the deep ocean are understood. In this study we assess the behaviour of Fe isotopes in a Southern Ocean hydrothermal plume using a sampling program of Total Dissolvable Fe (TDFe), and dissolved Fe (dFe). We demonstrate that δ56Fe values of dFe (δ56dFe) within the hydrothermal plume change dramatically during early plume dispersal, ranging from -2.39 ± 0.05‰ to -0.13 ± 0.06‰ (2 SD). The isotopic composition of TDFe (δ56TDFe) was consistently heavier than dFe values, ranging from -0.31 ± 0.03‰ to 0.78 ± 0.05‰, consistent with Fe oxyhydroxide precipitation as the plume samples age. The dFe present in the hydrothermal plume includes stabilised dFe species with potential to be transported to the deep ocean. We estimate that stable dFe exported from the plume will have a δ56Fe of -0.28 ± 0.17‰. Further, we show that the proportion of authigenic iron-sulfide and iron-oxyhydroxide minerals precipitating in the buoyant plume exert opposing controls on the resultant isotope composition of dissolved Fe passed into the neutrally buoyant plume. We show that such controls yield variable dissolved Fe isotope signatures under the authigenic conditions reported from modern vent sites elsewhere, and so ought to be considered during iron isotope reconstructions of past

Iron, growth, and the global epidemic of obesity.

EPA Science Inventory

Abstract: Iron is an essential nutrient utilized in almost every aspect of cell function and its availability has previously limited life. Those same properties which allow iron to function as a catalyst in the reactions of life also present a threat via generation of oxygen-ba...

Investigation of iron oxide reduction by TEM

NASA Astrophysics Data System (ADS)

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

1987-03-01

An “environmental cell” located in a high voltage transmission electron microscope has been used to study the reduction of single crystal iron oxides by hydrogen and hydrogen-argon mixtures. The cell enables a direct observation of the solid during reaction, thus permitting the nucleation and growth of solid reaction products to be observed. Hematite was reduced at temperatures in the range 387 to 610°C with gas pressures up to 5.3 kP. Reduction with pure hydrogen was considerably faster than when argon was present. Lath magnetite which rapidly transforms to porous magnetite and thence (more slowly) to porous iron was observed. The reduction of magnetite and of wustite single crystals was observed in the temperature range 300 to 514°C using both hydrogen and hydrogen-argon mixtures at gas pressures up to 6.6 kP. Incubation periods were found for magnetite reduction; during these periods faceted pits formed in the oxide. Iron formed in the early stages was epitaxial with the host magnetite; at later stages the epitaxy was lost and fissures frequently formed in the metal. The morphology of the iron differed between the gas mixtures. Disproportionation accompanied the reduction of wustite, producing intermediate polycrystalline magnetite despite reducing conditions. The disproportionation appeared to be promoted by the reduction reaction. For both oxides, reduction in the hydrogen-argon mixture was slower than in pure hydrogen.

Iron catalyzed coal liquefaction process

DOEpatents

Garg, Diwakar; Givens, Edwin N.

1983-01-01

A process is described for the solvent refining of coal into a gas product, a liquid product and a normally solid dissolved product. Particulate coal and a unique co-catalyst system are suspended in a coal solvent and processed in a coal liquefaction reactor, preferably an ebullated bed reactor. The co-catalyst system comprises a combination of a stoichiometric excess of iron oxide and pyrite which reduce predominantly to active iron sulfide catalysts in the reaction zone. This catalyst system results in increased catalytic activity with attendant improved coal conversion and enhanced oil product distribution as well as reduced sulfide effluent. Iron oxide is used in a stoichiometric excess of that required to react with sulfur indigenous to the feed coal and that produced during reduction of the pyrite catalyst to iron sulfide.

Iron-catalyzed intermolecular cycloaddition of diazo surrogates with hexahydro-1,3,5-triazines.

PubMed

Liu, Pei; Zhu, Chenghao; Xu, Guangyang; Sun, Jiangtao

2017-09-26

We report here an unprecedented iron-catalyzed cycloaddition reaction of diazo surrogates with hexahydro-1,3,5-triazines, providing five-membered heterocycles in moderate to high yields under mild reaction conditions. This cycloaddition features C-N and C-C bond formation using a cheap iron catalyst. Importantly, different to our former report on a gold-catalyzed system, both donor/donor and donor/acceptor diazo substrates are tolerated in this iron-catalyzed protocol.

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Q.; Muftikian, R.; Korte, N.

1997-04-01

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from various effluents or contaminated soil containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. 10 figs.

A balloon measurement of the isotopic composition of galactic cosmic ray iron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grove, J.E.

1989-01-01

The isotopic composition of galactic cosmic ray iron in the energy interval of approximately 1550 to 2200 MeV/nucleon was measured using a balloon-borne mass spectrometer. The instrument was flown from Palestine, Texas, in May 1984 for greater than 35 hours at an atmospheric depth of approximately 6 g/sq cm. Masses were derived by the Cerenkov-Energy technique. The Cerenkov counter employed a silica aerogel radiator with an index of refraction n = 1.1. Particle energies were measured in a stack of NaI(Tl) scintillators, which also provided particle trajectories. A detailed discussion of the sources of mass uncertainty is presented, including anmore » analytic model of the contribution from fluctuations in the Cerenkov yield from knock-on electrons. The achieved mass resolution is approximately 0.65 amu, which is consistent with the theoretical estimate. An Fe-54/Fe-56 abundance ratio of 0.14(sup +0.18)(sub -0.11) and an 84 percent confidence upper limit of Fe-58/Fe-56 is less than or = to 0.07 at the top of the atmosphere is reported. Combining the data with those of precious measurements of the composition of iron at lower energies, and using a model of the galactic propagation, cosmic-ray source abundance ratios of Fe-54/Fe-56 = 0.064(sup +0.032)(sub -0.027) and Fe-58/F3-56 is less than or = to 0.062 were derived. These values are consistent with the composition of solar system iron and place restrictions on the conditions under which cosmic-ray iron is synthesized.« less

Prenatal Iron Supplementation Reduces Maternal Anemia, Iron Deficiency, and Iron Deficiency Anemia in a Randomized Clinical Trial in Rural China, but Iron Deficiency Remains Widespread in Mothers and Neonates.

PubMed

Zhao, Gengli; Xu, Guobin; Zhou, Min; Jiang, Yaping; Richards, Blair; Clark, Katy M; Kaciroti, Niko; Georgieff, Michael K; Zhang, Zhixiang; Tardif, Twila; Li, Ming; Lozoff, Betsy

2015-08-01

Previous trials of prenatal iron supplementation had limited measures of maternal or neonatal iron status. The purpose was to assess effects of prenatal iron-folate supplementation on maternal and neonatal iron status. Enrollment occurred June 2009 through December 2011 in Hebei, China. Women with uncomplicated singleton pregnancies at ≤20 wk gestation, aged ≥18 y, and with hemoglobin ≥100 g/L were randomly assigned 1:1 to receive daily iron (300 mg ferrous sulfate) or placebo + 0.40 mg folate from enrollment to birth. Iron status was assessed in maternal venous blood (at enrollment and at or near term) and cord blood. Primary outcomes were as follows: 1) maternal iron deficiency (ID) defined in 2 ways as serum ferritin (SF) <15 μg/L and body iron (BI) <0 mg/kg; 2) maternal ID anemia [ID + anemia (IDA); hemoglobin <110 g/L]; and 3) neonatal ID (cord blood ferritin <75 μg/L or zinc protoporphyrin/heme >118 μmol/mol). A total of 2371 women were randomly assigned, with outcomes for 1632 women or neonates (809 placebo/folate, 823 iron/folate; 1579 mother-newborn pairs, 37 mothers, 16 neonates). Most infants (97%) were born at term. At or near term, maternal hemoglobin was significantly higher (+5.56 g/L) for iron vs. placebo groups. Anemia risk was reduced (RR: 0.53; 95% CI: 0.43, 0.66), as were risks of ID (RR: 0.74; 95% CI: 0.69, 0.79 by SF; RR: 0.65; 95% CI: 0.59, 0.71 by BI) and IDA (RR: 0.49; 95% CI: 0.38, 0.62 by SF; RR: 0.51; 95% CI: 0.40, 0.65 by BI). Most women still had ID (66.8% by SF, 54.7% by BI). Adverse effects, all minor, were similar by group. There were no differences in cord blood iron measures; >45% of neonates in each group had ID. However, dose-response analyses showed higher cord SF with more maternal iron capsules reported being consumed (β per 10 capsules = 2.60, P < 0.05). Prenatal iron supplementation reduced anemia, ID, and IDA in pregnant women in rural China, but most women and >45% of neonates had ID, regardless of

Matrix Infrared Spectra of Manganese and Iron Isocyanide Complexes.

PubMed

Chen, Xiuting; Li, Qingnuan; Andrews, Lester; Gong, Yu

2017-11-22

Mono and diisocyanide complexes of manganese and iron were prepared via the reactions of laser-ablated manganese and iron atoms with (CN) 2 in an argon matrix. Product identifications were performed based on the characteristic infrared absorptions from isotopically labeled (CN) 2 experiments as compared with computed values for both cyanides and isocyanides. Manganese atoms reacted with (CN) 2 to produce Mn(NC) 2 upon λ > 220 nm irradiation, during which MnNC was formed mainly as a result of the photoinduced decomposition of Mn(NC) 2 . Similar reaction products FeNC and Fe(NC) 2 were formed during the reactions of Fe and (CN) 2 . All the product molecules together with the unobserved cyanide isomers were predicted to have linear geometries at the B3LYP level of theory. The cyanide complexes of manganese and iron were computed to be more stable than the isocyanide isomers with energy differences between 0.4 and 4 kcal/mol at the CCSD(T) level. Although manganese and iron cyanide molecules are slightly more stable according to the theory, no absorption can be assigned to these isomers in the region above the isocyanides possibly due to their low infrared intensities.

Synthesis and characterization of a new Inonotus obliquus polysaccharide-iron(III) complex.

PubMed

Wang, Jia; Chen, Haixia; Wang, Yanwei; Xing, Lisha

2015-04-01

A new Inonotus obliquus polysaccharide-iron(III) complex (IOPS-iron) was synthesized and characterized. The preparation conditions of IOPS-iron(III) were optimized and the physicochemical properties were characterized by physicochemical methods, scanning electron microscopy (SEM), electron paramagnetic resonance (EPR) spectroscopy, fourier transform infrared (FTIR) spectroscopy, circular dichroism (CD) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy, respectively. The highest iron content of IOPS-iron(III) complex (19.40%) was obtained at the conditions: the ratio of IOPS and FeCl3 • 6H2O was 3:5 (w/w), the pH value of alkali solution was 10, the reaction temperature was 30 °C and the reaction time was 6h. The iron(III) was shown to be bound through the binding sites of the polysaccharide IOPS and it could form spatially separated iron centers on the polysaccharide backbone. IOPS-iron(III) complex was found to have good digestive availability and antioxidant activities in the in vitro assays, which suggested the IOPS-iron(III) complex might be used as a new iron supplement candidate. Copyright © 2015 Elsevier B.V. All rights reserved.

Iron Corrosion Observations: Pu(VI)-Fe Reduction Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reed, Donald T.; Swanson, Juliet S.; Richmann, Michael K.

Iron and Pu Reduction: (1) Very different appearances in iron reaction products were noted depending on pH, brine and initial iron phase; (2) Plutonium was associated with the Fe phases; (3) Green rust was often noted at the higher pH; (4) XANES established the green rust to be an Fe2/3 phase with a bromide center; and (5) This green rust phase was linked to Pu as Pu(IV).

Iron Deficiency and Iron-deficiency Anemia in Toddlers Ages 18 to 36 Months: A Prospective Study.

PubMed

Levin, Carina; Harpaz, Shira; Muklashi, Isam; Lumelsky, Nadia; Komisarchik, Ina; Katzap, Ilia; Abu Hanna, Manhal; Koren, Ariel

2016-04-01

In young children, iron deficiency (ID)-the most common cause of anemia-may adversely affect long-term neurodevelopment and behavior. We prospectively evaluated the prevalence of ID and iron deficiency anemia (IDA) in 256 healthy 18- to 36-month-old children in Northern Israel. Complete blood count and ferritin evaluation were performed, and risk factors were assessed. Hemoglobin (Hgb) was compared with first-year routine screening. Complete data were obtained from 208 children: 56.2% were boys; the mean age was 26.1±5.27 months. A prevalence of 5.8% IDA, 16.3% ID without anemia, 9.6% anemia with normal ferritin, and 68.3% normal Hgb and ferritin was found. In nonanemic infants at 1 year of age (n=156), ID/IDA was found in 19.9%, and 12.8% became anemic at study evaluation. Despite iron supplementation in the first year, and normal Hgb at first-year screening, ID and IDA were still prevalent, and might develop during the second year of life. Recognition of this child subset and consideration of iron supplementation are mandatory.

Iron silylamide-grafted periodic mesoporous silica.

PubMed

Deschner, Thomas; Törnroos, Karl W; Anwander, Reiner

2011-08-01

The surface chemistry of a series of well-defined metalorganic ferrous and ferric iron complexes on periodic mesoporous silica (PMS) was investigated. In addition to literature known Fe(II)[N(SiMe(3))(2)](2)(THF), Fe(II)[N(SiPh(2)Me(2))(2)](2), and Fe(III)[N(SiMe(3))(2)](2)Cl(THF), the new complexes [Fe(II){N(SiHMe(2))(2)}(2)](2) and Fe(III)[N(SiHMe(2))(2)](3)(μ-Cl)Li(THF)(3) were employed as grafting precursors. Selection criteria for the molecular precursors were the molecular size (monoiron versus diiron species), the oxidation state of the iron center (II versus III), and the functionality of the silylamido ligand (e.g., built-in spectroscopic probes). Hexagonal channel-like MCM-41 and cubic cage-like SBA-1 were chosen as two distinct PMS materials. The highest iron load (12.8 wt %) was obtained for hybrid material [Fe(II){N(SiHMe(2))(2)}(2)](2)@MCM-41 upon stirring the reaction mixture iron silylamide/PMS/n-hexane for 18 h at ambient temperature. Size-selective grafting and concomitantly extensive surface silylation were found to be prominent for cage-like SBA-1. Here, the surface metalation is governed by the type of iron precursor, the pore size, the reaction time, and the solvent. The formation of surface-attached iron-ligand species is discussed on the basis of diffuse reflectance infrared Fourier transform (DRIFT) and electron paramagnetic resonance (EPR) spectroscopy, nitrogen physisorption, and elemental analysis. © 2011 American Chemical Society

Weathering of iron sulfides under Mars surface ambient conditions

NASA Technical Reports Server (NTRS)

Blackburn, T. R.

1981-01-01

The study of iron sulfide surface alternation reactions under Mars' surface ambient conditions begun during 1980 was extended through improved irradiation design and experimental protocols. A wider range of humidities and more intense irradiation were incorporated in the study. X-ray photoelectron spectra of irradiated chips suggest formation of FeSO4, FeCO3, and an iron oxide on the iron sulfide substrates studied.

CO + H/sub 2/ reaction over nitrogen-modified iron catalysts. Quarterly technical progress report, October 1, 1983-December 30, 1983. [Denitriding of iron nitrides in both hydrogen and helium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delgass, W.N.

1984-02-01

The synthesis of epsilon-Fe/sub 2.7/N is confirmed by Moessbauer spectroscopy. Carburization of epsilon-iron nitride for 2.5 hours in 3H/sub 2//CO at 523 K starts the formation of a bulk structure similar to that seen during ..gamma..'-iron nitride carburization. Reaction of ..gamma..'-Fe/sub 4/N in 3CO/H/sub 2/ synthesis gas at 523 K shows a better bulk stability than reaction in 3H/sub 2//CO. Kinetic analysis of the product distribution at the higher CO ratio confirms greater activity and selectivity maintainance. The kinetics of denitriding in both He and H/sub 2/ was studied with a mass spectrometer. Extremely rapid nitrogen loss was observed frommore » both ..gamma..'-Fe/sub 4/N and epsilon-Fe/sub 2.7/N catalysts in H/sub 2/ at 523 K. In both cases a initial exposure to H/sub 2/ produced a significant amount of NH/sub 3/ which we ascribe to an active surface species. Hydrogenation of the bulk continued with a slow rise to a maximum about 90 seconds after the introduction of H/sub 2/. The denitriding activity of the epsilon-Fe/sub 2.7/N catalyst was significantly higher than that of the ..gamma..'-Fe/sub 4/N catalyst. In contrast, the denitriding rate of epsilon-Fe/sub 2.7/N in He was significantly slower than that in H/sub 2/ until high temperatures (773K) were reached. An overall activation energy of 41.5 kcal/mol was obtained for this process. Comparison of the denitriding rate of virgin epsilon-Fe/sub 2.7/N in H/sub 2/ with that of the same nitride after five minutes of carburization during the hydrocarbon synthesis reaction indicates large differences in the overall rate. The carburized nitride was some 300 times less active to bulk hydrogenation than the virgin catalyst, which is indicative of significant changes in the first few layers of the nitride during the initial minutes of the synthesis reaction. 17 references, 5 figures.« less

Iron-induced oligomerization of human FXN81-210 and bacterial CyaY frataxin and the effect of iron chelators

PubMed Central

Ahlgren, Eva-Christina; Fekry, Mostafa; Wiemann, Mathias; Söderberg, Christopher A.; Bernfur, Katja; Gakh, Olex; Rasmussen, Morten; Højrup, Peter; Emanuelsson, Cecilia; Isaya, Grazia

2017-01-01

Patients suffering from the progressive neurodegenerative disease Friedreich’s ataxia have reduced expression levels of the protein frataxin. Three major isoforms of human frataxin have been identified, FXN42-210, FXN56-210 and FXN81-210, of which FXN81-210 is considered to be the mature form. Both long forms, FXN42-210 and FXN56-210, have been shown to spontaneously form oligomeric particles stabilized by the extended N-terminal sequence. The short variant FXN81-210, on other hand, has only been observed in the monomeric state. However, a highly homologous E. coli frataxin CyaY, which also lacks an N-terminal extension, has been shown to oligomerize in the presence of iron. To explore the mechanisms of stabilization of short variant frataxin oligomers we compare here the effect of iron on the oligomerization of CyaY and FXN81-210. Using dynamic light scattering, small-angle X-ray scattering, electron microscopy (EM) and cross linking mass spectrometry (MS), we show that at aerobic conditions in the presence of iron both FXN81-210 and CyaY form oligomers. However, while CyaY oligomers are stable over time, FXN81-210 oligomers are unstable and dissociate into monomers after about 24 h. EM and MS studies suggest that within the oligomers FXN81-210 and CyaY monomers are packed in a head-to-tail fashion in ring-shaped structures with potential iron-binding sites located at the interface between monomers. The higher stability of CyaY oligomers can be explained by a higher number of acidic residues at the interface between monomers, which may result in a more stable iron binding. We also show that CyaY oligomers may be dissociated by ferric iron chelators deferiprone and DFO, as well as by the ferrous iron chelator BIPY. Surprisingly, deferiprone and DFO stimulate FXN81-210 oligomerization, while BIPY does not show any effect on oligomerization in this case. The results suggest that FXN81-210 oligomerization is primarily driven by ferric iron, while both ferric and

Atmospheric Processing and Iron Mobilization of Ilmenite: Iron-Containing Ternary Oxide in Mineral Dust Aerosol.

PubMed

Hettiarachchi, Eshani; Hurab, Omar; Rubasinghege, Gayan

2018-02-08

Over the last several decades, iron has been identified as a limiting nutrient in about half of the world's oceans. Its most significant source is identified as deposited iron-containing mineral dust that has been processed during atmospheric transportation. The current work focuses on chemical and photochemical processing of iron-containing mineral dust particles in the presence of nitric acid, and an organic pollutant dimethyl sulfide under atmospherically relevant conditions. More importantly, ilmenite (FeTiO 3 ) is evaluated as a proxy for the iron-containing mineral dust. The presence of titanium in its lattice structure provides higher complexity to mimic mineral dust, yet it is simple enough to study reaction pathways and mechanisms. Here, spectroscopic methods are combined with dissolution measurements to investigate atmospheric processing of iron in mineral dust, with specific focus on particle mineralogy, particle size, and their environmental conditions (i.e., pH and solar flux). Our results indicate that the presence of titanium elemental composition enhances iron dissolution from mineral dust, at least by 2-fold comparison with its nontitanium-containing counterparts. The extent of iron dissolution and speciation is further influenced by the above factors. Thus, our work highlights these important, yet unconsidered, factors in the atmospheric processing of iron-containing mineral dust aerosol.

Covariances for the 56Fe radiation damage cross sections

NASA Astrophysics Data System (ADS)

Simakov, Stanislav P.; Koning, Arjan; Konobeyev, Alexander Yu.

2017-09-01

The energy-energy and reaction-reaction covariance matrices were calculated for the n + 56Fe damage cross-sections by Total Monte Carlo method using the TENDL-2013 random files. They were represented in the ENDF-6 format and added to the unperturbed evaluation file. The uncertainties for the spectrum averaged radiation quantities in the representative fission, fusion and spallation facilities were first time assessed as 5-25%. Additional 5 to 20% have to be added to the atom displacement rate uncertainties to account for accuracy of the primary defects simulation in materials. The reaction-reaction correlation were shown to be 1% or less.

Prenatal Iron Supplementation Reduces Maternal Anemia, Iron Deficiency, and Iron Deficiency Anemia in a Randomized Clinical Trial in Rural China, but Iron Deficiency Remains Widespread in Mothers and Neonates123

PubMed Central

Zhao, Gengli; Xu, Guobin; Zhou, Min; Jiang, Yaping; Richards, Blair; Clark, Katy M; Kaciroti, Niko; Georgieff, Michael K; Zhang, Zhixiang; Tardif, Twila; Li, Ming; Lozoff, Betsy

2015-01-01

Background: Previous trials of prenatal iron supplementation had limited measures of maternal or neonatal iron status. Objective: The purpose was to assess effects of prenatal iron-folate supplementation on maternal and neonatal iron status. Methods: Enrollment occurred June 2009 through December 2011 in Hebei, China. Women with uncomplicated singleton pregnancies at ≤20 wk gestation, aged ≥18 y, and with hemoglobin ≥100 g/L were randomly assigned 1:1 to receive daily iron (300 mg ferrous sulfate) or placebo + 0.40 mg folate from enrollment to birth. Iron status was assessed in maternal venous blood (at enrollment and at or near term) and cord blood. Primary outcomes were as follows: 1) maternal iron deficiency (ID) defined in 2 ways as serum ferritin (SF) <15 μg/L and body iron (BI) <0 mg/kg; 2) maternal ID anemia [ID + anemia (IDA); hemoglobin <110 g/L]; and 3) neonatal ID (cord blood ferritin <75 μg/L or zinc protoporphyrin/heme >118 μmol/mol). Results: A total of 2371 women were randomly assigned, with outcomes for 1632 women or neonates (809 placebo/folate, 823 iron/folate; 1579 mother-newborn pairs, 37 mothers, 16 neonates). Most infants (97%) were born at term. At or near term, maternal hemoglobin was significantly higher (+5.56 g/L) for iron vs. placebo groups. Anemia risk was reduced (RR: 0.53; 95% CI: 0.43, 0.66), as were risks of ID (RR: 0.74; 95% CI: 0.69, 0.79 by SF; RR: 0.65; 95% CI: 0.59, 0.71 by BI) and IDA (RR: 0.49; 95% CI: 0.38, 0.62 by SF; RR: 0.51; 95% CI: 0.40, 0.65 by BI). Most women still had ID (66.8% by SF, 54.7% by BI). Adverse effects, all minor, were similar by group. There were no differences in cord blood iron measures; >45% of neonates in each group had ID. However, dose-response analyses showed higher cord SF with more maternal iron capsules reported being consumed (β per 10 capsules = 2.60, P < 0.05). Conclusions: Prenatal iron supplementation reduced anemia, ID, and IDA in pregnant women in rural China, but most women

[Changes of iron metabolism indices in children with various genotypes of thalassema].

PubMed

Huang, Yu-Jun; Wu, Shao-Guo; Ou, Xiao-Bing; Zhang, Li

2010-02-01

To study the value of iron metabolism indices, serum iron (SI), total iron blinding capacity (TIBC) and transferring (Tf), in thalassema. The serum samples from 9 children with silent alpha thalassema, 56 with standard alpha thalassema, 26 with HbH disease, 40 with beta+ thalassema, 56 with beta0 thalassema, 45 with iron deficiency anemia (IDA) and 70 healthy children were detected for SI, TIBC and Tf levels. The SI level increased (p<0.01), while the TIBC level decreased significantly in the beta0 thalassema group compared with those in the other groups (p<0.05 or 0.01), but the Tf level was not different. The Tf level of both the silent alpha thalassema and the standard alpha thalassema groups was statistically lower than that of the healthy group (p<0.01), but the levels of SI and TIBC were similar to the healthy group. Though the SI level of the HbH disease group was similar to the healthy group, the TIBC and Tf levels were statistically lower (p<0.01). Compared with Tf, SI and TIBC are better indices for monitoring iron loading in children with thalassema. The increased SI level and decreased TIBC level are two indices for the diagnosis of beta(0) thalassema in children with cellule anaemia.

A comparison of iron extraction methods for the determination of degree of pyritisation and the recognition of iron-limited pyrite formation

NASA Technical Reports Server (NTRS)

Raiswell, R.; Canfield, D. E.; Berner, R. A.

1994-01-01

Measurements of degree of pyritisation require an estimate of sediment iron which is capable of reaction with dissolved sulphide to form pyrite, either directly or indirectly via iron monosulphide precursors. Three dissolution techniques (buffered dithionite, cold 1 M HCl, boiling 12 M HCl) were examined for their capacity to extract iron from a variety of iron minerals, and iron-bearing sediments, as a function of different extraction times and different grain sizes. All the iron oxides studied are quantitatively extracted by dithionite and boiling HCl (but not by cold HCl). Both HCl techniques extract more iron from silicates than does dithionite but probably about the same amounts as are potentially capable of sulphidation. Modern sediment studies indicate that most sedimentary pyrite is formed rapidly from iron oxides, with smaller amounts formed more slowly from iron silicates (if sufficient geologic time is available). It is therefore recommended that the degree of pyritisation be defined with respect to the dithionite-extractable (mainly iron oxide) pool and/or the boiling HCl-extractable pool (which includes some silicate iron) for the recognition of iron-limited pyritisation.

Characterization of Co and Fe-MCM-56 catalysts for NH3-SCR and N2O decomposition: An in situ FTIR study.

PubMed

Grzybek, Justyna; Gil, Barbara; Roth, Wieslaw J; Skoczek, Monika; Kowalczyk, Andrzej; Chmielarz, Lucjan

2018-05-05

Two-step preparation of iron and cobalt-containing MCM-56 zeolites has been undertaken to evaluate the influence of their physicochemical properties in the selective catalytic reduction (NH 3 -SCR or DeNOx) of NO using NH 3 as a reductant. Zeolites were prepared by the selective leaching of the framework cations by concentrated HNO 3 solution and NH 4 F/HF mixture and consecutively, introduction of Co and Fe heteroatoms, in quantities below 1wt%. Further calcination allowed to obtain highly dispersed active species. Their evaluation and speciation was realized by adsorption of pyridine and NO, followed by FTIR spectroscopy. Both Fe-MCM-56 zeolites showed excellent activities (maximum NO conversion 92%) with high selectivity to dinitrogen (above 99%) in the high temperature NH 3 -SCR process. High catalytic activity of Fe-MCM-56 zeolites was assigned to the formation of stable nitrates, delivering NO to react with NH 3 at higher temperatures and suppressing the direct NO oxidation. It was found that more nitrates was formed in Fe-MCM-56 (HNO 3 ) than in Fe-MCM-56 (HF/NH 4 F) and that could compensate for the lower Fe loading, resulting in very similar catalytic activity of both catalysts. At the same time both Co-and Fe-MCM-56 zeolites were moderately active in direct N 2 O decomposition, with maximum N 2 O conversion not higher than 80% and activity window starting at 500°C. This phenomenon was expected since both types of catalysts contained well dispersed active centers, not beneficial for this reaction. Copyright © 2018 Elsevier B.V. All rights reserved.

Observed side feeding in incomplete fusion dynamics in 16O + 160Gd reaction at energy ∼5.6 MeV/A: Spin distribution measurements

NASA Astrophysics Data System (ADS)

Ali, Rahbar; Afzal Ansari, M.; Singh, D.; Kumar, Rakesh; Singh, D. P.; Sharma, M. K.; Gupta, Unnati; Singh, B. P.; Shidling, P. D.; Negi, Dinesh; Muralithar, S.; Singh, R. P.; Bhowmik, R. K.

2017-12-01

Spin distributions of various residues populated via complete fusion (CF) and incomplete fusion (ICF) reactions in the interaction of 16O with 160Gd at the projectile energy Eproj ∼ 5.6 MeV/A have been studied. The experimentally measured spin distributions of the residues associated with the ICF reactions are found to be distinctly different from those populated via the CF reactions. An attempt has been made to extract the side-feeding pattern from the spin distributions of CF and ICF reaction products. It has been observed that the CF products are strongly fed over a broad spin range. But, no side-feeding takes place in the low observed spins as low partial waves are strongly hindered in the fast α-emission channels (associated with ICF) in the forward direction. It has also been observed that the mean input angular momentum for direct α-emitting (ICF) channels is relatively higher than evaporation α-emitting (CF) channels, and it increases with direct α-multiplicity in forward direction.

Removal of As, Mn, Mo, Se, U, V and Zn from groundwater by zero-valent iron in a passive treatment cell: reaction progress modeling.

PubMed

Morrison, Stan J; Metzler, Donald R; Dwyer, Brian P

2002-05-01

Three treatment cells were operated at a site near Durango, CO. One treatment cell operated for more than 3 years. The treatment cells were used for passive removal of contamination from groundwater at a uranium mill tailings repository site. Zero-valent iron [Fe(0)] that had been powdered, bound with aluminosilicate and molded into plates was used as a reactive material in one treatment cell. The others used granular Fe(0) and steel wool. The treatment cells significantly reduced concentrations of As, Mn, Mo, Se, U, V and Zn in groundwater that flowed through it. Zero-valent iron [Fe(0)], magnetite (Fe3O4), calcite (CaCO3), goethite (FeOOH) and mixtures of contaminant-bearing phases were identified in the solid fraction of one treatment cell. A reaction progress approach was used to model chemical evolution of water chemistry as it reacted with the Fe(0). Precipitation of calcite, ferrous hydroxide [Fe(OH)2] and ferrous sulfide (FeS) were used to simulate observed changes in major-ion aqueous chemistry. The amount of reaction progress differed for each treatment cell. Changes in contaminant concentrations were consistent with precipitation of reduced oxides (UO2, V2O3), sulfides (As2S3, ZnS), iron minerals (FeSe2, FeMoO4) and carbonate (MnCO3). Formation of a free gas phase and precipitation of minerals contributed to loss of hydraulic conductivity in one treatment cell.

EGCG inhibit chemical reactivity of iron through forming an Ngal-EGCG-iron complex.

PubMed

Bao, Guan-Hu; Xu, Jie; Hu, Feng-Lin; Wan, Xiao-Chun; Deng, Shi-Xian; Barasch, Jonathan

2013-12-01

Accumulated evidence indicates that the interconversion of iron between ferric (Fe(3+)) and ferrous (Fe(2+)) can be realized through interaction with reactive oxygen species in the Fenton and Haber-Weiss reactions and thereby physiologically effects redox cycling. The imbalance of iron and ROS may eventually cause tissue damage such as renal proximal tubule injury and necrosis. Many approaches were exploited to ameliorate the oxidative stress caused by the imbalance. (-)-Epigallocatechin-3-gallate, the most active and most abundant catechin in tea, was found to be involved in the protection of a spectrum of renal injuries caused by oxidative stress. Most of studies suggested that EGCG works as an antioxidant. In this paper, Multivariate analysis of the LC-MS data of tea extracts and binding assays showed that the tea polyphenol EGCG can form stable complex with iron through the protein Ngal, a biomarker of acute kidney injury. UV-Vis and Luminescence spectrum methods showed that Ngal can inhibit the chemical reactivity of iron and EGCG through forming an Ngal-EGCG-iron complex. In thinking of the interaction of iron and ROS, we proposed that EGCG may work as both antioxidant and Ngal binding siderphore in protection of kidney from injuries.

Morphology and phase control of iron oxide polymorph nanoparticles

NASA Astrophysics Data System (ADS)

Cui, Hongtao; Wang, Li; Shi, Min; Li, Yanhong

2017-04-01

In this work, lepidocrocite (γ-FeOOH) nanobundles were prepared by a facile NH4F assisted epoxide precipitation route. The reactions between epoxide and [Fe(H2O)6]2+ promoted the hydrolysis and condensation of [Fe(H2O)6]2+, resulting in the formation of iron oxyhydroxide. After calcination of γ-FeOOH nanobundles at 400 °C, the produced α-Fe2O3 still kept the bundle morphology. Due to the unique chemistry of epoxide, the morphology and phase of iron oxide polymorph nanoparticles (goethite, akaganeite, lepidocrocite, magnetite) were well-controlled through controlling reaction conditions such as Fe2+ concentration, NH4F additive and reaction temperature. It is particularly interesting that NH4F working as phase controlling agent is able to control the phase development of iron oxyhydroxides. This phase control effect of NH4F is attributed to the promoted reaction rate of epoxide originating from the higher electronegativity of fluoride ions than chloride ions. Based on the results in this work and our other preliminary works, it is considered that this route can be used as a general strategy for controlling the morphology and phase of transition element compounds.

Decomposition of energetic chemicals contaminated with iron or stainless steel.

PubMed

Chervin, Sima; Bodman, Glenn T; Barnhart, Richard W

2006-03-17

Contamination of chemicals or reaction mixtures with iron or stainless steel is likely to take place during chemical processing. If energetic and thermally unstable chemicals are involved in a manufacturing process, contamination with iron or stainless steel can impact the decomposition characteristics of these chemicals and, subsequently, the safety of the processes, and should be investigated. The goal of this project was to undertake a systematic approach to study the impact of iron or stainless steel contamination on the decomposition characteristics of different chemical classes. Differential scanning calorimetry (DSC) was used to study the decomposition reaction by testing each chemical pure, and in mixtures with iron and stainless steel. The following classes of energetic chemicals were investigated: nitrobenzenes, tetrazoles, hydrazines, hydroxylamines and oximes, sulfonic acid derivatives and monomers. The following non-energetic groups were investigated for contributing effects: halogens, hydroxyls, amines, amides, nitriles, sulfonic acid esters, carbonyl halides and salts of hydrochloric acid. Based on the results obtained, conclusions were drawn regarding the sensitivity of the decomposition reaction to contamination with iron and stainless steel for the chemical classes listed above. It was demonstrated that the most sensitive classes are hydrazines and hydroxylamines/oximes. Contamination of these chemicals with iron or stainless steel not only destabilizes them, leading to decomposition at significantly lower temperatures, but also sometimes causes increased severity of the decomposition. The sensitivity of nitrobenzenes to contamination with iron or stainless steel depended upon the presence of other contributing groups: the presence of such groups as acid chlorides or chlorine/fluorine significantly increased the effect of contamination on decomposition characteristics of nitrobenzenes. The decomposition of sulfonic acid derivatives and tetrazoles

Iron binding to human heavy-chain ferritin.

PubMed

Pozzi, Cecilia; Di Pisa, Flavio; Bernacchioni, Caterina; Ciambellotti, Silvia; Turano, Paola; Mangani, Stefano

2015-09-01

Maxi-ferritins are ubiquitous iron-storage proteins with a common cage architecture made up of 24 identical subunits of five α-helices that drive iron biomineralization through catalytic iron(II) oxidation occurring at oxidoreductase sites (OS). Structures of iron-bound human H ferritin were solved at high resolution by freezing ferritin crystals at different time intervals after exposure to a ferrous salt. Multiple binding sites were identified that define the iron path from the entry ion channels to the oxidoreductase sites. Similar data are available for another vertebrate ferritin: the M protein from Rana catesbeiana. A comparative analysis of the iron sites in the two proteins identifies new reaction intermediates and underlines clear differences in the pattern of ligands that define the additional iron sites that precede the oxidoreductase binding sites along this path. Stopped-flow kinetics assays revealed that human H ferritin has different levels of activity compared with its R. catesbeiana counterpart. The role of the different pattern of transient iron-binding sites in the OS is discussed with respect to the observed differences in activity across the species.

Iron isotope fractionation during magmatic differentiation in Kilauea Iki lava lake.

PubMed

Teng, Fang-Zhen; Dauphas, Nicolas; Helz, Rosalind T

2008-06-20

Magmatic differentiation helps produce the chemical and petrographic diversity of terrestrial rocks. The extent to which magmatic differentiation fractionates nonradiogenic isotopes is uncertain for some elements. We report analyses of iron isotopes in basalts from Kilauea Iki lava lake, Hawaii. The iron isotopic compositions (56Fe/54Fe) of late-stagemeltveins are 0.2 permil (per thousand) greater than values for olivine cumulates. Olivine phenocrysts are up to 1.2 per thousand lighter than those of whole rocks. These results demonstrate that iron isotopes fractionate during magmatic differentiation at both whole-rock and crystal scales. This characteristic of iron relative to the characteristics of magnesium and lithium, for which no fractionation has been found, may be related to its complex redox chemistry in magmatic systems and makes iron a potential tool for studying planetary differentiation.

Iron isotope fractionation during magmatic differentiation in Kilauea Iki lava lake

USGS Publications Warehouse

Teng, F.-Z.; Dauphas, N.; Helz, R.T.

2008-01-01

Magmatic differentiation helps produce the chemical and petrographic diversity of terrestrial rocks. The extent to which magmatic differentiation fractionates nonradiogenic isotopes is uncertain for some elements. We report analyses of iron isotopes in basalts from Kilauea Iki lava lake, Hawaii. The iron isotopic compositions (56Fe/54Fe) of late-stage melt veins are 0.2 per mil (???) greater than values for olivine cumulates. Olivine phenocrysts are up to 1.2??? lighter than those of whole rocks. These results demonstrate that iron isotopes fractionate during magmatic differentiation at both whole-rock and crystal scales. This characteristic of iron relative to the characteristics of magnesium and lithium, for which no fractionation has been found, may be related to its complex redox chemistry in magmatic systems and makes iron a potential tool for studying planetary differentiation.

Effects of iron and iron chelation in vitro on mucosal oxidant activity in ulcerative colitis.

PubMed

Millar, A D; Rampton, D S; Blake, D R

2000-09-01

Reactive oxygen species may be pathogenic in ulcerative colitis. Oral iron supplements anecdotally exacerbate inflammatory bowel disease and iron levels are elevated in the inflamed mucosa. Mucosal iron may enhance hydroxyl ion production via Fenton chemistry. Conversely, the iron chelator, desferrioxamine, is reportedly beneficial in Crohn's disease. To assess the in vitro effects of exogenous iron and of iron chelators on the production of reactive oxygen species by colonic biopsies from normal control subjects and patients with ulcerative colitis. Luminol-amplified chemiluminescence was used to measure mucosal reactive oxygen species production both before and after addition in vitro of ferric citrate (100 microM), desferrioxamine (1 mM) and 1,10-phenanthroline (1 mM). Ferric citrate had no effect on the chemiluminescence produced by human colonic mucosa. However, desferrioxamine and phenanthroline reduced chemiluminescence by 47% (n=7, P=0.018) and by 26% (n=10, P=0.005), respectively, in inactive ulcerative colitis, and by 44% (n=9, P=0. 008) and 42% (n=11, P=0.006) in active disease. The lack of effect of ferric citrate suggests that sufficient free iron is already present in inflamed biopsies to drive the Fenton reaction maximally. The effects of desferrioxamine and 1,10-phenanthroline on the chemiluminescence of biopsies from patients with ulcerative colitis suggest that a clinical trial of topical iron chelation in active disease is indicated.

Iron Hydroxy Carbonate Formation in Zerovalent Iron Permeable Reactive Barriers: Characterization and Evaluation of Phase Stability

EPA Science Inventory

Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently obs...

Synthesis of phase-pure and monodisperse iron oxide nanoparticles by thermal decomposition

NASA Astrophysics Data System (ADS)

Hufschmid, Ryan; Arami, Hamed; Ferguson, R. Matthew; Gonzales, Marcela; Teeman, Eric; Brush, Lucien N.; Browning, Nigel D.; Krishnan, Kannan M.

2015-06-01

Superparamagnetic iron oxide nanoparticles (SPIONs) are used for a wide range of biomedical applications requiring precise control over their physical and magnetic properties, which are dependent on their size and crystallographic phase. Here we present a comprehensive template for the design and synthesis of iron oxide nanoparticles with control over size, size distribution, phase, and resulting magnetic properties. We investigate critical parameters for synthesis of monodisperse SPIONs by organic thermal decomposition. Three different, commonly used, iron containing precursors (iron oleate, iron pentacarbonyl, and iron oxyhydroxide) are evaluated under a variety of synthetic conditions. We compare the suitability of these three kinetically controlled synthesis protocols, which have in common the use of iron oleate as a starting precursor or reaction intermediate, for producing nanoparticles with specific size and magnetic properties. Monodisperse particles were produced over a tunable range of sizes from approximately 2-30 nm. Reaction parameters such as precursor concentration, addition of surfactant, temperature, ramp rate, and time were adjusted to kinetically control size and size-distribution, phase, and magnetic properties. In particular, large quantities of excess surfactant (up to 25 : 1 molar ratio) alter reaction kinetics and result in larger particles with uniform size; however, there is often a trade-off between large particles and a narrow size distribution. Iron oxide phase, in addition to nanoparticle size and shape, is critical for establishing magnetic properties such as differential susceptibility (dm/dH) and anisotropy. As an example, we show the importance of obtaining the required size and iron oxide phase for application to Magnetic Particle Imaging (MPI), and describe how phase purity can be controlled. These results provide much of the information necessary to determine which iron oxide synthesis protocol is best suited to a particular

Iron Isotope Systematics of the Bushveld Complex, South Africa: Initial Results

NASA Astrophysics Data System (ADS)

Stausberg, N.; Lesher, C. E.; Hoffmann-Barfod, G.; Glessner, J. J.; Tegner, C.

2014-12-01

Iron isotopes show systematic changes in igneous rocks that have been ascribed to fractional crystallization, partial melting, as well as, diffusion effects. Layered mafic intrusions, such as the Paleoproterozoic Bushveld Igneous Complex, are ideally suited to investigate stable isotope fractionation arising principally by fractional crystallization. The upper 2.1km of the Bushveld Complex (Upper and Upper Main Zone, UUMZ) crystallized from a basaltic magma produced by a major recharge event, building up a sequence of tholeiitic, Fe-rich, gabbroic cumulate rocks that display systematic variations in mineralogy and mineral compositions consistent with fractional crystallization. Within this sequence, magnetite joins the liquidus assemblage at ˜260m, followed by olivine at 460m and apatite at 1000m. Here, we present iron isotope measurements of bulk cumulate rocks from the Bierkraal drill core of UUMZ of the western limb. Iron was chemically separated from its matrix and analyzed for δ56Fe (relative to IRMM- 014) with a Nu plasma MC-ICPMS at the University of California, Davis, using (pseudo-) high resolution and sample-standard bracketing. The δ56Fe values for Bushveld cumulates span a range from 0.04‰ to 0.36‰, and systematically correlate with the relative abundance of pyroxene + olivine, magnetite and plagioclase. Notably, the highest δ56Fe values are found in plagioclase-rich cumulates that formed prior to magnetite crystallization. δ56Fe is also high in magnetite-rich cumulates at the onset of magnetite crystallization, while subsequent cumulates exhibit lower and variable δ56Fe principally reflecting fractionation of and modal variations in magnetite, pyroxene and fayalitic olivine. The overall relationships for δ56Fe are consistent with positive mineral - liquid Fe isotope fractionation factors for magnetite and plagioclase, and negative to near zero values for pyroxene and olivine. These initial results are being integrated into a forward model of

Enhanced Oxidative and Adsorptive Removal of Diclofenac in Heterogeneous Fenton-like Reaction with Sulfide Modified Nanoscale Zerovalent Iron.

PubMed

Su, Yiming; Jassby, David; Song, Shikun; Zhou, Xuefei; Zhao, Hongying; Filip, Jan; Petala, Eleni; Zhang, Yalei

2018-06-05

Sulfidation of nanoscale zerovalent iron (nZVI) has shown some fundamental improvements on reactivity and selectivity toward pollutants in dissolved-oxygen (DO)-stimulated Fenton-like reaction systems (DO/S-nZVI system). However, the pristine microstructure of sulfide-modified nanoscale zerovalent iron (S-nZVI) remains uncovered. In addition, the relationship between pollutant removal and the oxidation of the S-nZVI is largely unknown. The present study confirms that sulfidation not only imparts sulfide and sulfate groups onto the surface of the nanoparticle (both on the oxide shell and on flake-like structures) but also introduces sulfur into the Fe(0) core region. Sulfidation greatly inhibits the four-electron transfer pathway between Fe(0) and oxygen but facilitates the electron transfer from Fe(0) to surface-bound Fe(III) and consecutive single-electron transfer for the generation of H 2 O 2 and hydroxyl radical. In the DO/S-nZVI system, slight sulfidation (S/Fe molar ratio = 0.1) is able to nearly double the oxidative removal efficacy of diclofenac (DCF) (from 17.8 to 34.2%), whereas moderate degree of sulfidation (S/Fe molar ratio = 0.3) significantly enhances both oxidation and adsorption of DCF. Furthermore, on the basis of the oxidation model of S-nZVI, the DCF removal process can be divided into two steps, which are well modeled by parabolic and logarithmic law separately. This study bridges the knowledge gap between pollutant removal and the oxidation process of chemically modified iron-based nanomaterials.

Cardiac iron overload in sickle-cell disease.

PubMed

Meloni, Antonella; Puliyel, Mammen; Pepe, Alessia; Berdoukas, Vasili; Coates, Thomas D; Wood, John C

2014-07-01

Chronically transfused sickle cell disease (SCD) patients have lower risk of myocardial iron overload (MIO) than comparably transfused thalassemia major (TM) patients. However, cardioprotection is incomplete. We present the clinical characteristics of six patients who have prospectively developed MIO, to identify potential risk factors for cardiac iron accumulation. From 2002 to 2011, cardiac, hepatic, and pancreatic iron overload were assessed by R2 and R2 * magnetic resonance imaging techniques in 201 chronic transfused SCD patients as part of their clinical care. At the time, they developed MIO, five of six patients had been on chronic transfusion for more than 11 years; only one was on exchange transfusion. The time to MIO was correlated with reticulocyte and hemoglobin S percentages. All patients had qualitatively poor chelation compliance (<50%). All patients had serum ferritin levels >4600 ng/ml and liver iron concentration >22 mg/g. Pancreatic R2 * was >100 Hz in every patient studied (5/6). Cardiac iron rose proportionally to pancreas R2 *, with all patients having pancreas R2 *>100 Hz when cardiac iron was present. MIO had a threshold relationship with liver iron that was higher than observed in TM patients. In conclusion, MIO occurs in a small percentage of chronically transfused SCD patients and is only associated with exceptionally poor control of total body iron stores. Duration of chronic transfusion is clearly important but other factors, such as levels of effective erythropoiesis, appear to contribute to cardiac risk. Pancreas R2 * can serve as a valuable screening tool for cardiac iron in SCD patients. © 2014 Wiley Periodicals, Inc.

Numerical investigation of the effects of iron oxidation reactions on the fume formation mechanism in arc welding

NASA Astrophysics Data System (ADS)

Sanibondi, Paolo

2015-09-01

Fume formation during arc welding has been modelled using a stochastic approach taking into account iron oxidation reactions. The model includes the nucleation and condensation of Fe and FeO vapours, the reaction of gaseous O2 and O on the nanoparticle surface, the coagulation of the nanoparticles including a sintering time as a function of temperature and composition, assuming chemical equilibrium for species in the gaseous phase. Results suggest that fumes generated in gas metal arc welding with oxidizing shielding mixtures are composed of aggregates of primary particles that are nucleated from gas-phase FeO and further oxidized to Fe3O4 and Fe2O3 in the liquid and solid phase, respectively. The composition of the fumes at the end of the formation process depends on the relative initial concentration of Fe and O2 species in the gas mixture and on the diameter of the primary particles that compose the aggregates: as the oxidation reactions are driven by deposition of oxygen on nanoparticle surface, the oxidation of larger particles is slower than that of smaller particles because of their lower surface to volume ratio. Solid-state diffusion is limiting the oxidation process at temperatures lower than 1500 K, inducing the formation of not fully oxidized particles composed of Fe3O4.

7 CFR 56.56 - Issuance.

Code of Federal Regulations, 2011 CFR

2011-01-01

... MARKETING ACT OF 1946 AND THE EGG PRODUCTS INSPECTION ACT (CONTINUED) VOLUNTARY GRADING OF SHELL EGGS Grading of Shell Eggs Grading Certificates § 56.56 Issuance. (a) Resident grading basis. Certificates will...

Iron and nickel isotope compositions of presolar silicon carbide grains from supernovae

NASA Astrophysics Data System (ADS)

Kodolányi, János; Stephan, Thomas; Trappitsch, Reto; Hoppe, Peter; Pignatari, Marco; Davis, Andrew M.; Pellin, Michael J.

2018-01-01

We report the carbon, silicon, iron, and nickel isotope compositions of twenty-five presolar SiC grains of mostly supernova (SN) origin. The iron and nickel isotope compositions were measured with the new Chicago Instrument for Laser Ionization, CHILI, which allows the analysis of all iron and nickel isotopes without the isobaric interferences that plagued previous measurements with the NanoSIMS. Despite terrestrial iron and nickel contamination, significant isotopic anomalies in 54Fe/56Fe, 57Fe/56Fe, 60Ni/58Ni, 61Ni/58Ni, 62Ni/58Ni, and 64Ni/58Ni were detected in nine SN grains (of type X). Combined multi-isotope data of three grains with the largest nickel isotope anomalies (>100‰ or <-100‰ in at least one isotope ratio, when expressed as deviation from the solar value) are compared with the predictions of two SN models, one with and one without hydrogen ingestion in the He shell prior to SN explosion. One grain's carbon-silicon-iron-nickel isotope composition is consistent with the prediction of the model without hydrogen ingestion, whereas the other two grains' isotope anomalies could not be reproduced using either SN models. The discrepancies between the measured isotope compositions and model predictions may indicate element fractionation in the SN ejecta prior to or during grain condensation, and reiterate the need for three-dimensional SN models.

Dendritic core-shell nickel-iron-copper metal/metal oxide electrode for efficient electrocatalytic water oxidation.

PubMed

Zhang, Peili; Li, Lin; Nordlund, Dennis; Chen, Hong; Fan, Lizhou; Zhang, Biaobiao; Sheng, Xia; Daniel, Quentin; Sun, Licheng

2018-01-26

Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction. Here, we report a promisingly dendritic core-shell nickel-iron-copper metal/metal oxide electrode, prepared via dealloying with an electrodeposited nickel-iron-copper alloy as a precursor, as the catalyst for water oxidation. The as-prepared core-shell nickel-iron-copper electrode is characterized with porous oxide shells and metallic cores. This tri-metal-based core-shell nickel-iron-copper electrode exhibits a remarkable activity toward water oxidation in alkaline medium with an overpotential of only 180 mV at a current density of 10 mA cm -2 . The core-shell NiFeCu electrode exhibits pH-dependent oxygen evolution reaction activity on the reversible hydrogen electrode scale, suggesting that non-concerted proton-electron transfers participate in catalyzing the oxygen evolution reaction. To the best of our knowledge, the as-fabricated core-shell nickel-iron-copper is one of the most promising oxygen evolution catalysts.

Iron-Catalyzed C-O Bond Activation: Opportunity for Sustainable Catalysis.

PubMed

Bisz, Elwira; Szostak, Michal

2017-10-23

Oxygen-based electrophiles have emerged as some of the most valuable cross-coupling partners in organic synthesis due to several major strategic and environmental benefits, such as abundance and potential to avoid toxic halide waste. In this context, iron-catalyzed C-O activation/cross-coupling holds particular promise to achieve sustainable catalytic protocols due to its natural abundance, inherent low toxicity, and excellent economic and ecological profile. Recently, tremendous progress has been achieved in the development of new methods for functional-group-tolerant iron-catalyzed cross-coupling reactions by selective C-O cleavage. These methods establish highly attractive alternatives to traditional cross-coupling reactions by using halides as electrophilic partners. In particular, new easily accessible oxygen-based electrophiles have emerged as substrates in iron-catalyzed cross-coupling reactions, which significantly broaden the scope of this catalysis platform. New mechanistic manifolds involving iron catalysis have been established; thus opening up vistas for the development of a wide range of unprecedented reactions. The synthetic potential of this sustainable mode of reactivity has been highlighted by the development of new strategies in the construction of complex motifs, including in target synthesis. The most recent advances in sustainable iron-catalyzed cross-coupling of C-O-based electrophiles are reviewed, with a focus on both mechanistic aspects and synthetic utility. It should be noted that this catalytic manifold provides access to motifs that are often not easily available by other methods, such as the assembly of stereodefined dienes or C(sp 2 )-C(sp 3 ) cross-couplings, thus emphasizing the synthetic importance of this mode of reactivity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Treatments for iron-deficiency anaemia in pregnancy.

PubMed

Reveiz, Ludovic; Gyte, Gillian Ml; Cuervo, Luis Gabriel; Casasbuenas, Alexandra

2011-10-05

Iron deficiency, the most common cause of anaemia in pregnancy worldwide, can be mild, moderate or severe. Severe anaemia can have very serious consequences for mothers and babies, but there is controversy about whether treating mild or moderate anaemia provides more benefit than harm. To assess the effects of different treatments for anaemia in pregnancy attributed to iron deficiency (defined as haemoglobin less than 11 g/dL or other equivalent parameters) on maternal and neonatal morbidity and mortality. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (7 June 2011), CENTRAL (2011, Issue 5), PubMed (1966 to June 2011), the International Clinical Trials Registry Platform (ICTRP) (2 May 2011), Health Technology Assessment Program (HTA) (2 May 2011) and LATINREC (Colombia) (2 May 2011). Randomised controlled trials comparing treatments for anaemia in pregnancy attributed to iron deficiency. We identified 23 trials, involving 3.198 women. We assessed their risk of bias. Three further studies identified are awaiting classification. Many of the trials were from low-income countries; they were generally small and frequently methodologically poor. They covered a very wide range of differing drugs, doses and routes of administration, making it difficult to pool data. Oral iron in pregnancy showed a reduction in the incidence of anaemia (risk ratio 0.38, 95% confidence interval 0.26 to 0.55, one trial, 125 women) and better haematological indices than placebo (two trials). It was not possible to assess the effects of treatment by severity of anaemia. A trend was found between dose and reported adverse effects. Most trials reported no clinically relevant outcomes nor adverse effects. Although the intramuscular and intravenous routes produced better haematological indices in women than the oral route, no clinical outcomes were assessed and there were insufficient data on adverse effects, for example, on venous thrombosis and severe allergic reactions

Measurement of the cosmic-ray iron spectrum between 60 and 200 GeV per nucleon

NASA Technical Reports Server (NTRS)

Esposito, Joseph A.; Streitmatter, Robert E.; Balasubrahmanyan, V. K.; Ormes, Jonathan F.

1990-01-01

A measurement of the spectral index of Galactic cosmic-ray (GCR) iron has been made using a high-energy gas Cerenkov spectrometer. The spectral index of GCR iron is found to be 2.56 + or - 0.11 in the energy range 57-200 GeV/ nucleon. This result indicates that the source spectrum of GCR iron is similar to that of other primary GCR nuclei and is consistent with the simplest models of GCR propagation.

Iron oxides in human spleen.

PubMed

Kopáni, Martin; Miglierini, Marcel; Lančok, Adriana; Dekan, Július; Čaplovicová, Mária; Jakubovský, Ján; Boča, Roman; Mrazova, Hedviga

2015-10-01

Iron is an essential element for fundamental cell functions and a catalyst for chemical reactions. Three samples extracted from the human spleen were investigated by scanning (SEM) and transmission electron microscopy (TEM), Mössbauer spectrometry (MS), and SQUID magnetometry. The sample with diagnosis of hemosiderosis (H) differs from that referring to hereditary spherocytosis and the reference sample. SEM reveals iron-rich micrometer-sized aggregate of various structures-tiny fibrils in hereditary spherocytosis sample and no fibrils in hemochromatosis. Hematite and magnetite particles from 2 to 6 μm in TEM with diffraction in all samples were shown. The SQUID magnetometry shows different amount of diamagnetic, paramagnetic and ferrimagnetic structures in the tissues. The MS results indicate contribution of ferromagnetically split sextets for all investigated samples. Their occurrence indicates that at least part of the sample is magnetically ordered below the critical temperature. The iron accumulation process is different in hereditary spherocytosis and hemosiderosis. This fact may be the reason of different iron crystallization.

Iron therapy for pre-operative anaemia.

PubMed

Ng, Oliver; Keeler, Barrie D; Mishra, Amitabh; Simpson, Alastair; Neal, Keith; Brookes, Matthew J; Acheson, Austin G

2015-12-22

-treatment, pre-operatively but post-treatment, and post-operatively. Statistical analysis was performed using the Cochrane statistical software, Review Manager 2014. Outcome data were summarised in tables and a forest plot. Three prospective randomised controlled studies evaluated pre-operative iron therapy to correct anaemia (two in colorectal and one in gynaecological surgery) and included 114 patients in total. One compared oral iron versus standard care (Lidder 2007); one intravenous iron versus control (Edwards 2009); and one study compared oral versus intravenous iron (Kim 2009). Both colorectal trials reported the primary outcome (proportion of patients who received allogeneic blood transfusions) and meta-analysis showed a reduction in blood transfusions with the administration of iron therapy, but the reduction was not statistically significant (risk ratio (RR) 0.56, 95% confidence interval (CI) 0.27 to 1.18). All studies reported haemoglobin change but data for the anaemic patients were only available for two studies (Edwards 2009 and Kim 2009). Edwards 2009 showed no difference in haemoglobin at the end of treatment pre-operatively. The intravenous versus oral iron study showed an increase in haemoglobin with intravenous iron at the end of treatment pre-operatively (MD 1.90 g/dL, 95% CI 1.16 to 2.64; participants = 56), but the results are at high risk of bias because participants with less than 80% compliance with therapy were excluded from the analysis and compliance was lower in the oral iron group due to the side-effects of treatment (Kim 2009).None of the studies reported quality of life, short- or long-term mortality or post-operative morbidity. The use of iron therapy for pre-operative anaemia does not show a statistically significant reduction in the proportion of patients who received an allogeneic blood transfusion compared to no iron therapy. However, the 38 patients in our analysis falls far short of the 819 patients our information size calculation

The effects of iron deficiency on rat liver enzymes.

PubMed Central

Bailey-Wood, R.; Blayney, L. M.; Muir, J. R.; Jacobs, A.

1975-01-01

The effect of iron deficiency on a number or iron containing enzymes in rat liver has been examined. In addition, 6-phosphogluconate dehydrogenase and glucose 6-phosphate dehydrogenase have been assayed. Of the mitochondrial electron transport reactions only succinate-cytochrome C reductase activity was decreased in iron deficient animals. Microsomal reductase enzymes associated with the NADPH-oxidase system were also markedly decreased although cytochrome P450 concentrations were unaffected. Both 6-phosphogluconate dehydrogenase and glucose 6-phosphate dehydrogenase were reduced in young iron deficient rats but the former had returned to control levels at the age of 14 weeks. PMID:172099

Degradation of 4-Chloro-3,5-Dimethylphenol by a Heterogeneous Fenton-Like Reaction Using Nanoscale Zero-Valent Iron Catalysts

PubMed Central

Xu, Lejin; Wang, Jianlong

2013-01-01

Abstract Degradation of 4-chloro-3,5-dimethylphenol (PCMX) by a heterogeneous Fenton-like process using nanoparticulate zero-valent iron (nZVI) and hydrogen peroxide (H2O2) at pH 6.3 was investigated. Interactive effects of three factors—initial PCMX concentration, nZVI dosage, and H2O2 concentration—were investigated using the response surface method based on the Box–Behnken design. Experimental results showed that complete decomposition of PCMX and 65% of total organic carbon removal were observed after 30 min of reaction at neutral pH under recommended reaction conditions: nZVI, 1.0 g/L; H2O2, 18 mM; and initial PCMX concentration, 0.15 g/L. Based on the effects of scavengers n-butanol and KI, removal of PCMX was mainly attributed to the attack of •OH, especially the surface-bonded •OH. A possible degradation pathway of PCMX was proposed. PMID:23781127

Detection of iron-porphyrin proteins with a biochemiluminescent method in search of extraterrestrial life.

PubMed

Sotnikov, G G

1970-01-01

Iron-porphyrin proteins (catalase, peroxidase, hemoglobin, cytochrome C) represent an important group of redoxenzymes which have vitally important functions in micro-organisms. A biochemiluminescent method was employed for the detection of iron-porphyrin proteins. The reaction of luminol oxidation with H2O2 is accompanied by chemiluminescence. The rate of hydrogen peroxide decomposition increased 10(5)-10(7) -fold in the presence of the above enzymes as compared with ferrous (or ferric) ions. Possible application of this reaction for the detection of iron-porphyrin proteins of microbial origin was studied. Other authors have suggested this reaction for the detection of extraterrestrial life. Kinetics of the above reaction in the presence of iron-porphyrin proteins were shown to differ both in amplitude and duration of the signal from the pattern observed in the presence of non-hemin catalysts. The reaction pattern in the presence of mixed-soil populations is similar to those observed with pure bacterial cultures and individual iron-porphyrin proteins. Photometric tests revealed that among preparations studied the addition of 0.01% lysozyme was the most effective in destroying cell walls in microbial populations. However, removal of cell walls is not a necessary prerequisite for the detection of iron porphyrin since, for effective luminol oxidation with H2O2 the medium should be kept at pH 12.0. Pretreatment of microbial suspensions with ultrasound increased 2-fold the total signal due to iron porphyrins. The above method gives a reproducible signal indicating the presence of iron porphyrins when sterile nutrient media were innoculated with desert soil samples (Repeteck, Kara-Kum) and incubated for 13 hr. The device was able to detect the presence of no less than 10(5) - 10(6) cells per ml. The addition of limonite (Fe2O3 X nH2O) does not result in the appearance of an appreciable signal in the luminol + H2O2 system.

Tracing the secular evolution of the UCC using the iron isotope composition of ancient glacial diamictites

NASA Astrophysics Data System (ADS)

Liu, X. M.; Gaschnig, R. M.; Rudnick, R. L.; Hazen, R. M.; Shahar, A.

2014-12-01

Iron is the fourth most abundant element in the continental crust and influences global climate and biogeochemical cycles in the ocean1. Continental inputs, including river waters, sediments and atmospheric dust are dominant sources (>95%) of iron into the ocean2. Therefore, understanding how continental inputs may have changed through time is important in understanding the secular evolution of the marine Fe cycle. We analysed the Fe isotopic composition of twenty-four glacial diamictite composites, upper continental crust (UCC) proxies, with ages ranging from the Mesoarchean to the Paleozoic eras to characterize the secular evolution of the UCC. The diamictites all have elevated chemical index of alteration (CIA) and other characteristics of weathered regolith (e.g., strong depletion in soluble elements such as Sr), which they inherited from their upper crustal source region3. δ56Fe in the diamictite composites range from -0.59 to +0.23‰, however, most diamictites cluster with an average δ56Fe of 0.11± 0.20 (2s), overlapping juvenile continental material such as island arc basalts (IABs), which show a narrow range in δ56Fe from -0.04 to +0.14 ‰4. There is no obvious correlation between δ56Fe of the glacial diamictites and the CIA, except that the diamictite with the lowest δ56Fe at -0.59 ‰ also has the highest CIA = 89 (the Paleoproterozoic Makganyene Fm.). The data suggest that the Fe isotope compositions in the upper continental crust did not vary throughout Earth history. Interestingly, chemical weathering and sedimentary transport likely play only a minor role in producing Fe isotope variations in the upper continental crust. Anoxic weathering pre-GOE (Great Oxidation Event) does not seem to generate different Fe isotopic signatures from the post-GOE oxidative weathering environment in the upper continental crust. Therefore, large Fe isotopic fractionations observed in various marine sedimentary records are likely due to other processes occurring

Tracing the secular evolution of the UCC using the iron isotope composition of ancient glacial diamictites

NASA Astrophysics Data System (ADS)

Liu, X. M.; Gaschnig, R. M.; Rudnick, R. L.; Hazen, R. M.; Shahar, A.

2015-12-01

Iron is the fourth most abundant element in the continental crust and influences global climate and biogeochemical cycles in the ocean1. Continental inputs, including river waters, sediments and atmospheric dust are dominant sources (>95%) of iron into the ocean2. Therefore, understanding how continental inputs may have changed through time is important in understanding the secular evolution of the marine Fe cycle. We analysed the Fe isotopic composition of twenty-four glacial diamictite composites, upper continental crust (UCC) proxies, with ages ranging from the Mesoarchean to the Paleozoic eras to characterize the secular evolution of the UCC. The diamictites all have elevated chemical index of alteration (CIA) and other characteristics of weathered regolith (e.g., strong depletion in soluble elements such as Sr), which they inherited from their upper crustal source region3. δ56Fe in the diamictite composites range from -0.59 to +0.23‰, however, most diamictites cluster with an average δ56Fe of 0.11± 0.20 (2s), overlapping juvenile continental material such as island arc basalts (IABs), which show a narrow range in δ56Fe from -0.04 to +0.14 ‰4. There is no obvious correlation between δ56Fe of the glacial diamictites and the CIA, except that the diamictite with the lowest δ56Fe at -0.59 ‰ also has the highest CIA = 89 (the Paleoproterozoic Makganyene Fm.). The data suggest that the Fe isotope compositions in the upper continental crust did not vary throughout Earth history. Interestingly, chemical weathering and sedimentary transport likely play only a minor role in producing Fe isotope variations in the upper continental crust. Anoxic weathering pre-GOE (Great Oxidation Event) does not seem to generate different Fe isotopic signatures from the post-GOE oxidative weathering environment in the upper continental crust. Therefore, large Fe isotopic fractionations observed in various marine sedimentary records are likely due to other processes occurring

Oxygen Activation at Mononuclear Nonheme Iron Centers: A Superoxo Perspective

PubMed Central

Mukherjee, Anusree; Cranswick, Matthew A.; Chakraborti, Mrinmoy; Paine, Tapan K.; Fujisawa, Kiyoshi; Münck, Eckard; Que, Lawrence

2010-01-01

Dioxygen activation by iron enzymes is responsible for many metabolically important transformations in biology. Often a high-valent iron-oxo oxidant is proposed to form upon dioxygen activation at a mononuclear nonheme iron center, presumably via intervening iron-superoxo and iron-peroxo species. While iron(IV)-oxo intermediates have been trapped and characterized in enzymes and models, less is known of the putative iron(III)-superoxo species. Utilizing a synthetic model for the 2-oxoglutarate-dependent monoiron enzymes, [(TpiPr2)FeII(O2CC(O)CH3)], we have obtained indirect evidence for the formation of the putative iron(III)-superoxo species, which can undergo one-electron reduction, hydrogen-atom transfer, or conversion to an iron(IV)-oxo species, depending on the reaction conditions. These results demonstrate the various roles the iron(III)-superoxo species can play in the course of dioxygen activation at a nonheme iron center. PMID:20380464

Oxygen activation at mononuclear nonheme iron centers: a superoxo perspective.

PubMed

Mukherjee, Anusree; Cranswick, Matthew A; Chakrabarti, Mrinmoy; Paine, Tapan K; Fujisawa, Kiyoshi; Münck, Eckard; Que, Lawrence

2010-04-19

Dioxygen (O(2)) activation by iron enzymes is responsible for many metabolically important transformations in biology. Often a high-valent iron oxo oxidant is proposed to form upon O(2) activation at a mononuclear nonheme iron center, presumably via intervening iron superoxo and iron peroxo species. While iron(IV) oxo intermediates have been trapped and characterized in enzymes and models, less is known of the putative iron(III) superoxo species. Utilizing a synthetic model for the 2-oxoglutarate-dependent monoiron enzymes, [(Tp(iPr2))Fe(II)(O(2)CC(O)CH(3))], we have obtained indirect evidence for the formation of the putative iron(III) superoxo species, which can undergo one-electron reduction, hydrogen-atom transfer, or conversion to an iron(IV) oxo species, depending on the reaction conditions. These results demonstrate the various roles that the iron(III) superoxo species can play in the course of O(2) activation at a nonheme iron center.

Synthesis and Stability of Iron Nanoparticles for Lunar Environment Studies

NASA Technical Reports Server (NTRS)

Hung, Ching-cheh; McNatt, Jeremiah

2009-01-01

Simulant of lunar dust is needed when researching the lunar environment. However, unlike the true lunar dust, today s simulants do not contain nanophase iron. Two different processes have been developed to fabricate nanophase iron to be used as part of the lunar dust simulant: (1) Sequentially treating a mixture of ferric chloride, fluorinated carbon, and soda lime glass beads at about 300 C in nitrogen, at room temperature in air, and then at 1050 C in nitrogen. The product includes glass beads that are grey in color, can be attracted by a magnet, and contain alpha-iron nanoparticles (which seem to slowly lose their lattice structure in ambient air during a period of 12 months). This product may have some similarity to the lunar glassy regolith that contains Fe(sup 0). (2) Heating a mixture of carbon black and a lunar simulant (a mixed metal oxide that includes iron oxide) at 1050 C in nitrogen. This process simulates lunar dust reaction to the carbon in a micrometeorite at the time of impact. The product contains a chemically modified simulant that can be attracted by a magnet and has a surface layer whose iron concentration increased during the reaction. The iron was found to be alpha-iron and Fe3O4 nanoparticles, which appear to grow after the fabrication process, but stabilizes after 6 months of ambient air storage.

Mathematical model of the direct reduction of dust composite pellets containing zinc and iron

NASA Astrophysics Data System (ADS)

An, Xiu-wei; Wang, Jing-song; She, Xue-feng; Xue, Qing-guo

2013-07-01

Direct reduction of dust composite pellets containing zinc and iron was examined by simulating the conditions of actual production process of a rotary hearth furnace (RHF) in laboratory. A mathematical model was constructed to study the reduction kinetics of iron oxides and ZnO in the dust composite pellets. It was validated by comparing the calculated values with experimental results. The effects of furnace temperature, pellet radius, and pellet porosity on the reduction were investigated by the model. It is shown that furnace temperature has obvious influence on both of the reduction of iron oxides and ZnO, but the influence of pellet radius and porosity is much smaller. Model calculations suggest that both of the reduction of iron oxides and ZnO are under mixed control with interface reactions and Boudouard reaction in the early stage, but only with interface reactions in the later stage.

The Chemistry of Meteoric Iron

NASA Astrophysics Data System (ADS)

Self, D. E.; Plane, J. M. C.

About 120 tonnes of interplanetary dust enters the earth's atmosphere each day. Iron comprises a large fraction of this dust (12% by mass), and ablation of the particles gives rise to the layer of Fe atoms that occurs globally in the mesosphere around 85 km. Previous work in our laboratory has shown that Fe reacts rapidly with O3 to form FeO, which in turn reacts with O3, O2 and H2O to form FeO2, FeO3 and Fe(OH)2, respectively. The purpose of the present study was to determine which of these com- pounds provide stable reservoirs for iron below the atomic Fe layer, and hence form the "building blocks" of meteoric smoke particles which are implicated in phenomena lower in the atmosphere (e.g., noctilucent clouds and polar stratospheric ozone deple- tion). The reactions of these iron compounds were studied in a fast flow tube using the pulsed laser ablation of a rotating iron rod as the source of Fe atoms in the up- stream section of the tube. Iron compounds were produced by adding reactants further down the tube, and finally atomic O or H was added through a movable injector. At the downstream end of the tube, atomic Fe was detected by laser induced fluorescence at 248 nm. The following reactions were studied: FeO + O, FeO2 + O, FeO3 + O, FeO2 + O3, FeO3 + H2O, FeO3 + H, Fe(OH)2 + H, and FeOH + H. It is clear that the iron reservoir around 80 km is FeO3, which reacts very slowly with atomic O, in agreement with the requirements of a recent atmospheric model. However, Fe(OH)2 and FeO(OH), which are thermodynamically the most stable of these Fe species and eventually form from FeO3, are the likely building blocks of meteoric smoke.

Pathogenic implications of iron accumulation in multiple sclerosis

PubMed Central

Williams, Rachel; Buchheit, Cassandra L.; Berman, Nancy E. J.; LeVine, Steven M.

2011-01-01

Iron, an essential element used for a multitude of biochemical reactions, abnormally accumulates in the central nervous system of patients with multiple sclerosis (MS). The mechanisms of abnormal iron deposition in MS are not fully understood, nor do we know whether these deposits have adverse consequences, i.e., contribute to pathogenesis. With some exceptions, excess levels of iron are represented concomitantly in multiple deep gray matter structures often with bilateral representation, while in white matter pathological iron deposits are usually located at sites of inflammation that are associated with veins. These distinct spatial patterns suggest disparate mechanisms of iron accumulation between these regions. Iron has been postulated to promote disease activity in MS by various means: 1) iron can amplify the activated state of microglia resulting in the increased production of proinflammatory mediators; 2) excess intracellular iron deposits could promote mitochondria dysfunction; and 3) improperly managed iron could catalyze the production of damaging reactive oxygen species. The pathological consequences of abnormal iron deposits may be dependent on the affected brain region and/or accumulation process. Here we review putative mechanisms of enhanced iron uptake in MS and address the likely roles of iron in the pathogenesis of this disease. PMID:22004421

Cloud iron speciation: Experimental simulations

NASA Astrophysics Data System (ADS)

Sofikitis, A. M.; Colin, J. L.; Desboeufs, K. V.; Losno, R.

2003-04-01

The aim of our contribution is to identify major processes controlling iron speciation in the atmospheric aqueous phase. Fe is known to participate in a variety of redox reactions in cloud chemistry, as well as controlling free radical production in the troposphere. Iron cycling is slower than cycles with other catalytic transition metals (Cu, Mn). The residence time of each iron species is around ten minutes, this allows analytical separation and determination of each iron redox species and therefore its ratio. As the only source of trace metals in aqueous atmospheric phase is due to the solubilization of aerosols, we present here dissolution rate measurements obtained by laboratory experiments with an open flow reactor. This reactor enables us to reproduce the dissolution of a particle in aqueous atmospheric water. The dissolution rate and the speciation of iron are dependent on the mineralogy of the solid phase. Our experiments included Goethite, hematite and vermiculite, which are typical mineral constituents of dust particles. Comparisons were made with natural loess which is a blend of various crystalline and amorphous phases. We will present results of crustal origin particles dissolution experiments where kinetic parameters are determined, including iron speciation. Major functions of variation are pH and photochemistry in the aqueous weathering solution.

Iron isotopic fractionation between silicate mantle and metallic core at high pressure

PubMed Central

Liu, Jin; Dauphas, Nicolas; Roskosz, Mathieu; Hu, Michael Y.; Yang, Hong; Bi, Wenli; Zhao, Jiyong; Alp, Esen E.; Hu, Justin Y.; Lin, Jung-Fu

2017-01-01

The +0.1‰ elevated 56Fe/54Fe ratio of terrestrial basalts relative to chondrites was proposed to be a fingerprint of core-mantle segregation. However, the extent of iron isotopic fractionation between molten metal and silicate under high pressure–temperature conditions is poorly known. Here we show that iron forms chemical bonds of similar strengths in basaltic glasses and iron-rich alloys, even at high pressure. From the measured mean force constants of iron bonds, we calculate an equilibrium iron isotope fractionation between silicate and iron under core formation conditions in Earth of ∼0–0.02‰, which is small relative to the +0.1‰ shift of terrestrial basalts. This result is unaffected by small amounts of nickel and candidate core-forming light elements, as the isotopic shifts associated with such alloying are small. This study suggests that the variability in iron isotopic composition in planetary objects cannot be due to core formation. PMID:28216664

Colloidal synthesis of biocompatible iron disulphide nanocrystals.

PubMed

Santos-Cruz, J; Nuñez-Anita, R E; Mayén-Hernández, S A; Martínez-Alvarez, O; Acosta-Torres, L S; de la Fuente-Hernández, J; Campos-González, E; Vega-González, M; Arenas-Arrocena, M C

2018-08-01

The aim of this research was to synthesis biocompatible iron disulphide nanocrystals at different reaction temperatures using the colloidal synthesis methodology. Synthesis was conducted at the 220-240 °C range of reaction temperatures at intervals of 5 °C in an inert argon atmosphere. The toxicity of iron disulphide nanocrystals was evaluated in vitro using mouse fibroblast cell line. Two complementary assays were conducted: the first to evaluate cell viability of the fibroblast via an MTT assay and the second to determine the preservation of fibroblast nuclei integrity through DAPI staining, which labels nuclear DNA in fluorescence microscopes. Through TEM and HRTEM, we observed a cubic morphology of pyrite iron disulphide nanocrystals ranging in sizes 25-50 nm (225 °C), 50-70 nm (230 °C) and >70 nm (235 °C). Through X-ray diffraction, we observed a mixture of pyrite and pyrrohotite in the samples synthesized at 225 °C and 240 °C, showing the best photocatalytic activity at 80% and 65%, respectively, for the degradation of methylene blue after 120 minutes. In all experimental groups, iron disulphide nanocrystals were biocompatible, i.e. no statistically significant differences were observed between experimental groups as shown in a one-way ANOVA and Tukey's test. Based on all of these results, we recommend non-cytotoxic semiconductor iron sulphide nanocrystals for biomedical applications.

Role of the Δ Resonance in the Population of a Four-Nucleon State in the 56Fe → 54Fe Reaction at Relativistic Energies

NASA Astrophysics Data System (ADS)

Podolyák, Zs.; Shand, C. M.; Lalović, N.; Gerl, J.; Rudolph, D.; Alexander, T.; Boutachkov, P.; Cortés, M. L.; Górska, M.; Kojouharov, I.; Kurz, N.; Louchart, C.; Merchán, E.; Michelagnoli, C.; Pérez-Vidal, R. M.; Pietri, S.; Ralet, D.; Reese, M.; Schaffner, H.; Stahl, Ch.; Weick, H.; Ameil, F.; de Angelis, G.; Arici, T.; Carroll, R.; Dombrádi, Zs.; Gadea, A.; Golubev, P.; Lettmann, M.; Lizarazo, C.; Mahboub, D.; Pai, H.; Patel, Z.; Pietralla, N.; Regan, P. H.; Sarmiento, L. G.; Wieland, O.; Wilson, E.; Birkenbach, B.; Bruyneel, B.; Burrows, I.; Charles, L.; Clément, E.; Crespi, F. C. L.; Cullen, D. M.; Désesquelles, P.; Eberth, J.; González, V.; Habermann, T.; Harkness-Brennan, L.; Hess, H.; Judson, D. S.; Jungclaus, A.; Korten, W.; Labiche, M.; Maj, A.; Mengoni, D.; Napoli, D. R.; Pullia, A.; Quintana, B.; Rainovski, G.; Reiter, P.; Salsac, M. D.; Sanchis, E.; Valiente Dóbon, J. J.

2016-11-01

The 54Fe nucleus was populated from a 56Fe beam impinging on a Be target with an energy of E /A =500 MeV . The internal decay via γ -ray emission of the 10+ metastable state was observed. As the structure of this isomeric state has to involve at least four unpaired nucleons, it cannot be populated in a simple two-neutron removal reaction from the 56Fe ground state. The isomeric state was produced in the low-momentum (-energy) tail of the parallel momentum (energy) distribution of 54Fe, suggesting that it was populated via the decay of the Δ0 resonance into a proton. This process allows the population of four-nucleon states, such as the observed isomer. Therefore, it is concluded that the observation of this 10+ metastable state in 54Fe is a consequence of the quark structure of the nucleons.

The Study of HFE Genotypes and Its Expression Effect on Iron Status of Iranian Haemochromatosis, Iron Deficiency Anemia Patients, Iron-Taker and Non Iron-Taker Controls.

PubMed

Beiranvand, Elham; Abediankenari, Saeid; Rostamian, Mosayeb; Beiranvand, Behnoush; Naazeri, Saeed

2015-01-01

The role of HFE gene mutations or its expression in regulation of iron metabolism of hereditary haemochromatosis (HH) patients is remained controversial. Therefore here the correlation between two common HFE genotype (p.C282Y, p.H63D) and HFE gene expression with iron status in HH, iron deficiency anemia (IDA) and healthy Iranian participants was studied. For this purpose genotype determination was done by polymerase chain reaction--restriction fragment length polymorphism (PCR-RFLP). Real-Time PCR was applied for evaluation of HFE gene expression. Biochemical parameters and iron consumption were also assessed. Homozygote p.H63D mutation was seen in all HH patients and p.C282Y was not observed in any member of the population. A significant correlation was observed between serum ferritin (SF) level and gender or age of HH patients. p.H63D homozygote was seen to be able to significantly increase SF and transferrin saturation (TS) level without affecting on liver function. Our results also showed that iron consumption affects on TS level increasing. HFE gene expression level of IDA patients was significantly higher than other groups. Also the HFE gene expression was negatively correlated with TS. Finally, the main result of our study showed that loss of HFE function in HH is not derived from its gene expression inhibition and much higher HFE gene expression might lead to IDA. However we propose repeating of the study for more approval of our finding.

Oxidative Stress and the Homeodynamics of Iron Metabolism

PubMed Central

Bresgen, Nikolaus; Eckl, Peter M.

2015-01-01

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

Effects of microbial redox cycling of iron on cast iron pipe corrosion in drinking water distribution systems.

PubMed

Wang, Haibo; Hu, Chun; Zhang, Lili; Li, Xiaoxiao; Zhang, Yu; Yang, Min

2014-11-15

Bacterial characteristics in corrosion products and their effect on the formation of dense corrosion scales on cast iron coupons were studied in drinking water, with sterile water acting as a reference. The corrosion process and corrosion scales were characterized by electrochemical and physico-chemical measurements. The results indicated that the corrosion was more rapidly inhibited and iron release was lower due to formation of more dense protective corrosion scales in drinking water than in sterile water. The microbial community and denitrifying functional genes were analyzed by pyrosequencing and quantitative polymerase chain reactions (qPCR), respectively. Principal component analysis (PCA) showed that the bacteria in corrosion products played an important role in the corrosion process in drinking water. Nitrate-reducing bacteria (NRB) Acidovorax and Hydrogenophaga enhanced iron corrosion before 6 days. After 20 days, the dominant bacteria became NRB Dechloromonas (40.08%) with the protective corrosion layer formation. The Dechloromonas exhibited the stronger corrosion inhibition by inducing the redox cycling of iron, to enhance the precipitation of iron oxides and formation of Fe3O4. Subsequently, other minor bacteria appeared in the corrosion scales, including iron-respiring bacteria and Rhizobium which captured iron by the produced siderophores, having a weaker corrosion-inhibition effect. Therefore, the microbially-driven redox cycling of iron with associated microbial capture of iron caused more compact corrosion scales formation and lower iron release. Copyright © 2014 Elsevier Ltd. All rights reserved.

Mössbauer spectroscopy and the understanding of the role of iron in neurodegeneration

NASA Astrophysics Data System (ADS)

Friedman, A.; Galazka-Friedman, J.

2017-11-01

The possible role of iron in neurodegeneration may be related to the oxidative stress, triggered by Fenton reaction. In this reaction hydroxyl free radical production is generated by divalent iron. Motor symptoms of Parkinson's disease depend on the destruction of substantia nigra (SN). As the substantive questions were: 1/ what is the concentration of iron in the samples, 2/ what is the proportion of divalent vs. trivalent iron in the samples, and 3/ what is the iron-binding compound, it seemed appropriate to use Mössbauer spectroscopy to answer those questions. We found no difference in the concentration of total iron between PD and control, with the ratio of iron in PD vs. control being 1.00 ± 0.13. The divalent iron could not exceed 5% of the total iron. The main iron-binding compound in SN, both in PD and control is ferritin. Our further studies of ferritin in parkinsonian SN demonstrated a decrease, compared to control, of L-ferritin involved in the storage of iron within ferritin. This could allow an efflux of iron from the ferritin shell and an increase of non-ferritin iron in PD SN, which was confirmed by us. Mössbauer studies in Alzheimer showed slightly higher concentration of iron in hippocampal cortex with significantly higher concentrations of L and H ferritins compared to control. In atypical parkinsonism, progressive supranuclear palsy, higher concentration of iron was found in globus pallidus and SN compared to control. Mössbauer spectroscopy may play crucial role in further studies of human neurodegeneration.

Fabrication, characterization and applications of iron selenide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hussain, Raja Azadar, E-mail: hussainazadar@yahoo.com; Badshah, Amin; Lal, Bhajan

This review article presents fabrication of FeSe by solid state reactions, solution chemistry routes, chemical vapor deposition, spray pyrolysis and chemical vapor transport. Different properties and applications such as crystal structure and phase transition, band structure, spectroscopy, superconductivity, photocatalytic activity, electrochemical sensing, and fuel cell activity of FeSe have been discussed. - Graphical abstract: Iron selenide can be synthesized by solid state reactions, chemical vapor deposition, solution chemistry routes, chemical vapor transport and spray pyrolysis. - Highlights: • Different fabrication methods of iron selenide (FeSe) have been reviewed. • Crystal structure, band structure and spectroscopy of FeSe have been discussed.more » • Superconducting, catalytic and fuel cell application of FeSe have been presented.« less

Dominance of sulfur-fueled iron oxide reduction in low-sulfate freshwater sediments.

PubMed

Hansel, Colleen M; Lentini, Chris J; Tang, Yuanzhi; Johnston, David T; Wankel, Scott D; Jardine, Philip M

2015-11-01

A central tenant in microbial biogeochemistry is that microbial metabolisms follow a predictable sequence of terminal electron acceptors based on the energetic yield for the reaction. It is thereby oftentimes assumed that microbial respiration of ferric iron outcompetes sulfate in all but high-sulfate systems, and thus sulfide has little influence on freshwater or terrestrial iron cycling. Observations of sulfate reduction in low-sulfate environments have been attributed to the presumed presence of highly crystalline iron oxides allowing sulfate reduction to be more energetically favored. Here we identified the iron-reducing processes under low-sulfate conditions within columns containing freshwater sediments amended with structurally diverse iron oxides and fermentation products that fuel anaerobic respiration. We show that despite low sulfate concentrations and regardless of iron oxide substrate (ferrihydrite, Al-ferrihydrite, goethite, hematite), sulfidization was a dominant pathway in iron reduction. This process was mediated by (re)cycling of sulfur upon reaction of sulfide and iron oxides to support continued sulfur-based respiration--a cryptic sulfur cycle involving generation and consumption of sulfur intermediates. Although canonical iron respiration was not observed in the sediments amended with the more crystalline iron oxides, iron respiration did become dominant in the presence of ferrihydrite once sulfate was consumed. Thus, despite more favorable energetics, ferrihydrite reduction did not precede sulfate reduction and instead an inverse redox zonation was observed. These findings indicate that sulfur (re)cycling is a dominant force in iron cycling even in low-sulfate systems and in a manner difficult to predict using the classical thermodynamic ladder.

Dominance of sulfur-fueled iron oxide reduction in low-sulfate freshwater sediments

PubMed Central

Hansel, Colleen M; Lentini, Chris J; Tang, Yuanzhi; Johnston, David T; Wankel, Scott D; Jardine, Philip M

2015-01-01

A central tenant in microbial biogeochemistry is that microbial metabolisms follow a predictable sequence of terminal electron acceptors based on the energetic yield for the reaction. It is thereby oftentimes assumed that microbial respiration of ferric iron outcompetes sulfate in all but high-sulfate systems, and thus sulfide has little influence on freshwater or terrestrial iron cycling. Observations of sulfate reduction in low-sulfate environments have been attributed to the presumed presence of highly crystalline iron oxides allowing sulfate reduction to be more energetically favored. Here we identified the iron-reducing processes under low-sulfate conditions within columns containing freshwater sediments amended with structurally diverse iron oxides and fermentation products that fuel anaerobic respiration. We show that despite low sulfate concentrations and regardless of iron oxide substrate (ferrihydrite, Al-ferrihydrite, goethite, hematite), sulfidization was a dominant pathway in iron reduction. This process was mediated by (re)cycling of sulfur upon reaction of sulfide and iron oxides to support continued sulfur-based respiration—a cryptic sulfur cycle involving generation and consumption of sulfur intermediates. Although canonical iron respiration was not observed in the sediments amended with the more crystalline iron oxides, iron respiration did become dominant in the presence of ferrihydrite once sulfate was consumed. Thus, despite more favorable energetics, ferrihydrite reduction did not precede sulfate reduction and instead an inverse redox zonation was observed. These findings indicate that sulfur (re)cycling is a dominant force in iron cycling even in low-sulfate systems and in a manner difficult to predict using the classical thermodynamic ladder. PMID:25871933

Structure and reactivity of a mononuclear non-haem iron(III)–peroxo complex

PubMed Central

Cho, Jaeheung; Jeon, Sujin; Wilson, Samuel A.; Liu, Lei V.; Kang, Eun A; Braymer, Joseph J.; Lim, Mi Hee; Hedman, Britt; Hodgson, Keith O.; Valentine, Joan Selverstone; Solomon, Edward I.; Nam, Wonwoo

2012-01-01

Oxygen-containing mononuclear iron species—iron(III)–peroxo, iron(III)–hydroperoxo and iron(IV)–oxo—are key intermediates in the catalytic activation of dioxygen by iron-containing metalloenzymes1–7. It has been difficult to generate synthetic analogues of these three active iron–oxygen species in identical host complexes, which is necessary to elucidate changes to the structure of the iron centre during catalysis and the factors that control their chemical reactivities with substrates. Here we report the high-resolution crystal structure of a mononuclear non-haem side-on iron(III)–peroxo complex, [Fe(III)(TMC)(OO)]+. We also report a series of chemical reactions in which this iron(III)–peroxo complex is cleanly converted to the iron(III)–hydroperoxo complex, [Fe(III)(TMC)(OOH)]2+, via a short-lived intermediate on protonation. This iron(III)–hydroperoxo complex then cleanly converts to the ferryl complex, [Fe(IV)(TMC)(O)]2+, via homolytic O–O bond cleavage of the iron(III)–hydroperoxo species. All three of these iron species—the three most biologically relevant iron–oxygen intermediates—have been spectroscopically characterized; we note that they have been obtained using a simple macrocyclic ligand. We have performed relative reactivity studies on these three iron species which reveal that the iron(III)–hydroperoxo complex is the most reactive of the three in the deformylation of aldehydes and that it has a similar reactivity to the iron(IV)–oxo complex in C–H bond activation of alkylaromatics. These reactivity results demonstrate that iron(III)–hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes. PMID:22031443

Molecular imaging of labile iron(II) pools in living cells with a turn-on fluorescent probe.

PubMed

Au-Yeung, Ho Yu; Chan, Jefferson; Chantarojsiri, Teera; Chang, Christopher J

2013-10-09

Iron is an essential metal for living organisms, but misregulation of its homeostasis at the cellular level can trigger detrimental oxidative and/or nitrosative stress and damage events. Motivated to help study the physiological and pathological consequences of biological iron regulation, we now report a reaction-based strategy for monitoring labile Fe(2+) pools in aqueous solution and living cells. Iron Probe 1 (IP1) exploits a bioinspired, iron-mediated oxidative C-O bond cleavage reaction to achieve a selective turn-on response to Fe(2+) over a range of cellular metal ions in their bioavailable forms. We show that this first-generation chemical tool for fluorescence Fe(2+) detection can visualize changes in exchangeable iron stores in living cells upon iron supplementation or depletion, including labile iron pools at endogenous, basal levels. Moreover, IP1 can be used to identify reversible expansion of labile iron pools by stimulation with vitamin C or the iron regulatory hormone hepcidin, providing a starting point for further investigations of iron signaling and stress events in living systems as well as future probe development.

Impacts of dyebath auxiliaries on the reductive discoloration of Acid Orange 7 dye by high-carbon iron filings.

PubMed

Kumar, Raja; Sinha, Alok

This study proposed that the physicochemical effects of common dyebath auxiliaries on the bulk dye solution as well as on the iron surface can influence the reductive discoloration of effluent containing Acid Orange 7 (AO7) dye using high-carbon iron filings. Sodium chloride increased the discoloration rate because of the pitting corrosion on the iron surface, triggered by chloride anion. 'Salting out' effect of ammonium sulfate improved the reaction rate up to a certain concentration, beyond which it could compete with dye molecules for the reactive sites, as revealed by formed sulfite and sulfide. Urea drastically reduced the discoloration rates by its chaotropic effect on the bulk solution and by wrapping around the iron surface. Organic acids, namely acetic acid and citric acid, stimulated iron corrosion to improve the discoloration rates. The discoloration reaction was biphasic with an initial fast reaction phase, where in every case more than 70% discoloration was observed within 5 min of reaction, preceding a slow reaction phase. The experimental data could be well described using biphasic kinetics equation (R(2)> 0.997 in all cases) and a biphasic equation was developed considering the individual impact of co-existing auxiliaries on AO7 discoloration.

Liquid Phase Plasma Synthesis of Iron Oxide Nanoparticles on Nitrogen-Doped Activated Carbon Resulting in Nanocomposite for Supercapacitor Applications.

PubMed

Lee, Heon; Lee, Won-June; Park, Young-Kwon; Ki, Seo Jin; Kim, Byung-Joo; Jung, Sang-Chul

2018-03-25

Iron oxide nanoparticles supported on nitrogen-doped activated carbon powder were synthesized using an innovative plasma-in-liquid method, called the liquid phase plasma (LPP) method. Nitrogen-doped carbon (NC) was prepared by a primary LPP reaction using an ammonium chloride reactant solution, and an iron oxide/NC composite (IONCC) was prepared by a secondary LPP reaction using an iron chloride reactant solution. The nitrogen component at 3.77 at. % formed uniformly over the activated carbon (AC) surface after a 1 h LPP reaction. Iron oxide nanoparticles, 40~100 nm in size, were impregnated homogeneously over the NC surface after the LPP reaction, and were identified as Fe₃O₄ by X-ray photoelectron spectroscopy and X-ray diffraction. NC and IONCCs exhibited pseudo-capacitive characteristics, and their specific capacitance and cycling stability were superior to those of bare AC. The nitrogen content on the NC surface increased the compatibility and charge transfer rate, and the composites containing iron oxide exhibited a lower equivalent series resistance.

Ammonia from Iron(II) Reduction of Nitrite and the Strecker Synthesis: Do Iron(II) and Cyanide Interfere with Each Other?

NASA Technical Reports Server (NTRS)

Summers, David P.; Lerner, Narcinda; Chang, Sherwood (Technical Monitor)

1996-01-01

The question of whether the production of ammonia, from the reduction of nitrite by iron(II), is compatible with its use in the Strecker synthesis of amino acids, or whether the iron and the cyanide needed for the Strecker synthesis interfere with each other, is addressed. Results show that the presence of iron(II) appears to have little, or no, affect on the Strecker synthesis. The presence of cyanide does interfere with reduction of nitrite, but the reduction proceeds at cyanide/iron ratios of less than 4:1. At ratios of about 2:1 and less there is only a small effect. The two reactions can be combined to proceed in each other's presence, forming glycine from nitrite, Fe(+2), formaldehyde, and cyanide.

Association between renal iron accumulation and renal interstitial fibrosis in a rat model of chronic kidney disease.

PubMed

Naito, Yoshiro; Fujii, Aya; Sawada, Hisashi; Oboshi, Makiko; Iwasaku, Toshihiro; Okuhara, Yoshitaka; Morisawa, Daisuke; Eguchi, Akiyo; Hirotani, Shinichi; Masuyama, Tohru

2015-07-01

Iron accumulation is associated with the pathophysiology of chronic kidney disease (CKD). Renal fibrosis is a final common feature that contributes to the progression of CKD; however, little is known about the association between renal iron accumulation and renal interstitial fibrosis in CKD. Here we investigate the effects of iron chelation on renal interstitial fibrosis in a rat model of CKD. CKD was induced by 5/6 nephrectomy in Sprague-Dawley rats. At 8 weeks after operation, 5/6 nephrectomized rats were administered an oral iron chelator, deferasirox (DFX), in chow for 8 weeks. Other CKD rats were given a normal diet. Sham-operative rats given a normal diet served as a control. CKD rats exhibited hypertension, glomerulosclerosis and renal interstitial fibrosis. Iron chelation with DFX did not change hypertension and glomerulosclerosis; however, renal interstitial fibrosis was attenuated in CKD rats. Consistent with these findings, renal gene expression of collagen type III and transforming growth factor-β was increased in CKD rats compared with the controls, while iron chelation suppressed these increments. In addition, a decrease in vimentin along an increase in E-cadherin in renal gene expression was observed in CKD rats with iron chelation. CKD rats also showed increased CD68-positive cells in the kidney, whereas its increase was attenuated by iron deprivation. Similarly, increased renal gene expression of CD68, tumor necrosis factor-α and monocyte chemoattractant protein-1 was suppressed in CKD rats with iron chelation. Renal iron accumulation seems to be associated with renal interstitial fibrosis in a rat model of CKD.

Iron specificity of a biosensor based on fluorescent pyoverdin immobilized in sol-gel glass

PubMed Central

2011-01-01

Two current technologies used in biosensor development are very promising: 1. The sol-gel process of making microporous glass at room temperature, and 2. Using a fluorescent compound that undergoes fluorescence quenching in response to a specific analyte. These technologies have been combined to produce an iron biosensor. To optimize the iron (II or III) specificity of an iron biosensor, pyoverdin (a fluorescent siderophore produced by Pseudomonas spp.) was immobilized in 3 formulations of porous sol-gel glass. The formulations, A, B, and C, varied in the amount of water added, resulting in respective R values (molar ratio of water:silicon) of 5.6, 8.2, and 10.8. Pyoverdin-doped sol-gel pellets were placed in a flow cell in a fluorometer and the fluorescence quenching was measured as pellets were exposed to 0.28 - 0.56 mM iron (II or III). After 10 minutes of exposure to iron, ferrous ion caused a small fluorescence quenching (89 - 97% of the initial fluorescence, over the range of iron tested) while ferric ion caused much greater quenching (65 - 88%). The most specific and linear response was observed for pyoverdin immobilized in sol-gel C. In contrast, a solution of pyoverdin (3.0 μM) exposed to iron (II or III) for 10 minutes showed an increase in fluorescence (101 - 114%) at low ferrous concentrations (0.45 - 2.18 μM) while exposure to all ferric ion concentrations (0.45 - 3.03 μM) caused quenching. In summary, the iron specificity of pyoverdin was improved by immobilizing it in sol-gel glass C. PMID:21554740

Molecular dynamics simulation study of the early stages of nucleation of iron oxyhydroxide nanoparticles in aqueous solutions

DOE PAGES

Zhang, Hengzhong; Waychunas, Glenn A.; Banfield, Jillian F.

2015-07-29

Nucleation is a fundamental step in crystal growth. Of environmental and materials relevance are reactions that lead to nucleation of iron oxyhydroxides in aqueous solutions. These reactions are difficult to study experimentally due to their rapid kinetics. Here, we used classical molecular dynamics simulations to investigate nucleation of iron hydroxide/oxyhydroxide nanoparticles in aqueous solutions. Results show that in a solution containing ferric ions and hydroxyl groups, iron–hydroxyl molecular clusters form by merging ferric monomers, dimers, and other oligomers, driven by strong affinity of ferric ions to hydroxyls. When deprotonation reactions are not considered in the simulations, these clusters aggregate tomore » form small iron hydroxide nanocrystals with a six-membered ring-like layered structure allomeric to gibbsite. By comparison, in a solution containing iron chloride and sodium hydroxide, the presence of chlorine drives cluster assembly along a different direction to form long molecular chains (rather than rings) composed of Fe–O octahedra linked by edge sharing. Further, in chlorine-free solutions, when deprotonation reactions are considered, the simulations predict ultimate formation of amorphous iron oxyhydroxide nanoparticles with local atomic structure similar to that of ferrihydrite nanoparticles. Overall, our simulation results reveal that nucleation of iron oxyhydroxide nanoparticles proceeds via a cluster aggregation-based nonclassical pathway.« less

Dendritic core-shell nickel-iron-copper metal/metal oxide electrode for efficient electrocatalytic water oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Peili; Li, Lin; Nordlund, Dennis

Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction. Here in this paper, we report a promisingly dendritic core-shell nickel-iron-copper metal/metal oxide electrode, prepared via dealloying with an electrodeposited nickel-iron-copper alloy as a precursor, as the catalyst for water oxidation. The as-prepared core-shell nickel-iron-copper electrode is characterized with porous oxide shells and metallic cores. This tri-metal-based core-shell nickel-iron-copper electrode exhibits a remarkable activity toward water oxidation in alkaline medium with an overpotential of only 180 mV at a current density of 10 mA cm -2. The core-shell NiFeCu electrode exhibits pH-dependent oxygenmore » evolution reaction activity on the reversible hydrogen electrode scale, suggesting that non-concerted proton-electron transfers participate in catalyzing the oxygen evolution reaction. To the best of our knowledge, the as-fabricated core-shell nickel-iron-copper is one of the most promising oxygen evolution catalysts.« less

Dendritic core-shell nickel-iron-copper metal/metal oxide electrode for efficient electrocatalytic water oxidation

DOE PAGES

Zhang, Peili; Li, Lin; Nordlund, Dennis; ...

2018-01-26

Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction. Here in this paper, we report a promisingly dendritic core-shell nickel-iron-copper metal/metal oxide electrode, prepared via dealloying with an electrodeposited nickel-iron-copper alloy as a precursor, as the catalyst for water oxidation. The as-prepared core-shell nickel-iron-copper electrode is characterized with porous oxide shells and metallic cores. This tri-metal-based core-shell nickel-iron-copper electrode exhibits a remarkable activity toward water oxidation in alkaline medium with an overpotential of only 180 mV at a current density of 10 mA cm -2. The core-shell NiFeCu electrode exhibits pH-dependent oxygenmore » evolution reaction activity on the reversible hydrogen electrode scale, suggesting that non-concerted proton-electron transfers participate in catalyzing the oxygen evolution reaction. To the best of our knowledge, the as-fabricated core-shell nickel-iron-copper is one of the most promising oxygen evolution catalysts.« less

Oxidation-Induced Degradable Nanogels for Iron Chelation

NASA Astrophysics Data System (ADS)

Liu, Zhi; Wang, Yan; Purro, Max; Xiong, May P.

2016-02-01

Iron overload can increase cellular oxidative stress levels due to formation of reactive oxygen species (ROS); untreated, it can be extremely destructive to organs and fatal to patients. Since elevated oxidative stress levels are inherent to the condition in such patients, oxidation-induced degradable nanogels for iron chelation were rationally designed by simultaneously polymerizing oxidation-sensitive host-guest crosslinkers between β-cyclodextrin (β-CD) and ferrocene (Fc) and iron chelating moieties composed of deferoxamine (DFO) into the final gel scaffold in reverse emulsion reaction chambers. UV-Vis absorption and atomic absorption spectroscopy (AAS) was used to verify iron chelating capability of nanogels. These materials can degrade into smaller chelating fragments at rates proportional to the level of oxidative stress present. Conjugating DFO reduces the cytotoxicity of the chelator in the macrophage cells. Importantly, the nanogel can effectively reduce cellular ferritin expression in iron overloaded cells and regulate intracellular iron levels at the same time, which is important for maintaining a homeostatic level of this critical metal in cells.

Reductive dechlorination of trichloroethylene by iron bimetallics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orth, R.G.; Dauda, T.; McKenzie, D.E.

1998-07-01

Reductive dechlorination using a zero valence metal such as iron has seen an increase in interest with the extension of iron dechlorination to in-situ treatment of ground water. Studies to increase the rate of dechlorination and the long term stability have lead many to examine the use of bimetallic iron systems. Results are shown for bimetallic iron systems of Cu, Sn, Ni, Ag, Au, and Pd. All of these bimetallic couples form a galvanic couple which increase corrosion rates and the production of hydrogen. Increased rates of reaction normalized to surface area were observed for all the couples. The reactionmore » rates were found to depended on surface area and surface coverage of the iron. The results of studies in deuterium oxide indicate that the pathways changed as the bimetallic is changed and that the pathway in all cases could be a combination of dehydrohalgenation and sequential dechlorination. Degradation of DNAPL TCE by iron was found to be zero order and the type of product observed was different from that observed for TCE dissolved in water.« less

Oxidation-Induced Degradable Nanogels for Iron Chelation

PubMed Central

Liu, Zhi; Wang, Yan; Purro, Max; Xiong, May P.

2016-01-01

Iron overload can increase cellular oxidative stress levels due to formation of reactive oxygen species (ROS); untreated, it can be extremely destructive to organs and fatal to patients. Since elevated oxidative stress levels are inherent to the condition in such patients, oxidation-induced degradable nanogels for iron chelation were rationally designed by simultaneously polymerizing oxidation-sensitive host-guest crosslinkers between β-cyclodextrin (β-CD) and ferrocene (Fc) and iron chelating moieties composed of deferoxamine (DFO) into the final gel scaffold in reverse emulsion reaction chambers. UV-Vis absorption and atomic absorption spectroscopy (AAS) was used to verify iron chelating capability of nanogels. These materials can degrade into smaller chelating fragments at rates proportional to the level of oxidative stress present. Conjugating DFO reduces the cytotoxicity of the chelator in the macrophage cells. Importantly, the nanogel can effectively reduce cellular ferritin expression in iron overloaded cells and regulate intracellular iron levels at the same time, which is important for maintaining a homeostatic level of this critical metal in cells. PMID:26868174

When Density Functional Approximations Meet Iron Oxides.

PubMed

Meng, Yu; Liu, Xing-Wu; Huo, Chun-Fang; Guo, Wen-Ping; Cao, Dong-Bo; Peng, Qing; Dearden, Albert; Gonze, Xavier; Yang, Yong; Wang, Jianguo; Jiao, Haijun; Li, Yongwang; Wen, Xiao-Dong

2016-10-11

Three density functional approximations (DFAs), PBE, PBE+U, and Heyd-Scuseria-Ernzerhof screened hybrid functional (HSE), were employed to investigate the geometric, electronic, magnetic, and thermodynamic properties of four iron oxides, namely, α-FeOOH, α-Fe 2 O 3 , Fe 3 O 4 , and FeO. Comparing our calculated results with available experimental data, we found that HSE (a = 0.15) (containing 15% "screened" Hartree-Fock exchange) can provide reliable values of lattice constants, Fe magnetic moments, band gaps, and formation energies of all four iron oxides, while standard HSE (a = 0.25) seriously overestimates the band gaps and formation energies. For PBE+U, a suitable U value can give quite good results for the electronic properties of each iron oxide, but it is challenging to accurately get other properties of the four iron oxides using the same U value. Subsequently, we calculated the Gibbs free energies of transformation reactions among iron oxides using the HSE (a = 0.15) functional and plotted the equilibrium phase diagrams of the iron oxide system under various conditions, which provide reliable theoretical insight into the phase transformations of iron oxides.

Spectroscopic investigation and direct comparison of the reactivities of iron pyridyl oxidation catalysts

NASA Astrophysics Data System (ADS)

Song, Yang; Mayes, Howard G.; Queensen, Matthew J.; Bauer, Eike B.; Dupureur, Cynthia M.

2017-03-01

The growing interest in green chemistry has fueled attention to the development and characterization of effective iron complex oxidation catalysts. A number of iron complexes are known to catalyze the oxidation of organic substrates utilizing peroxides as the oxidant. Their development is complicated by a lack of direct comparison of the reactivities of the iron complexes. To begin to correlate reactivity with structural elements, we compare the reactivities of a series of iron pyridyl complexes toward a single dye substrate, malachite green (MG), for which colorless oxidation products are established. Complexes with tetradentate, nitrogen-based ligands with cis open coordination sites were found to be the most reactive. While some complexes reflect sensitivity to different peroxides, others are similarly reactive with either H2O2 or tBuOOH, which suggests some mechanistic distinctions. [Fe(S,S-PDP)(CH3CN)2](SbF6)2 and [Fe(OTf)2(tpa)] transition under the oxidative reaction conditions to a single intermediate at a rate that exceeds dye degradation (PDP = bis(pyridin-2-ylmethyl) bipyrrolidine; tpa = tris(2-pyridylmethyl)amine). For the less reactive [Fe(OTf)2(dpa)] (dpa = dipicolylamine), this reaction occurs on a timescale similar to that of MG oxidation. Thus, the spectroscopic method presented herein provides information about the efficiency and mechanism of iron catalyzed oxidation reactions as well as about potential oxidative catalyst decomposition and chemical changes of the catalyst before or during the oxidation reaction.

Electron Spectroscopy Studies of Iron, Iron Sulfides and Supported Iron Surfaces: Chemisorption of Simple Gases.

NASA Astrophysics Data System (ADS)

Lee, Yiu Chung

EELS was used to investigate the chemisorption of oxygen and carbon on iron. The EELS spectra of oxidized iron show characteristic features with strong enhancement of the interband transitions involving the Fe 3d band (4.6 and 7.5 eV) and moderate enhancement of the M(,2,3) transition doublet (54.4 and 58.2 eV). The changes in the electron energy loss structures with an overlayer of graphitic or carbidic carbon were investigated. The adsorption and growth of iron on Ni(100) has been studied using the combined techniques of LEED and EELS. Initially iron grows by a layer-by-layer mechanism for the first few layers. High iron coverages result in the observation of complex LEED patterns with satellites around the main (1 x 1) diffraction sports. This is due to the formation of b.c.c. Fe(110) crystallites arranged in domains with different orientations. EELS studies show the presence of three stages in the growth of iron on Ni(100): low-coverage, film-like and bulk-like. Auger and EELS were used to study the iron sulfide (FeS(,2), Fe(,7)S(,8) and FeS) surfaces. A characteristic M(,2,3) VV Auger doublet with a separation of 5.0 eV was observed on the sulfides. An assignment of the electron energy loss peaks was made based on the energy dependence of the loss peaks and previous photoemission results. The effect of argon ion bombardment was studied. Peaks with strong iron and sulfur character were observed. Heating the damaged sulfides results in reconstruction of the sulfide surfaces. The reactions of the sulfides with simple gases, such as H(,2), CO, CH(,4), C(,2)H(,4), NH(,3) and O(,2) were also studied. Using XPS, the chemisorption of SO(,2) on CaO(100) has been studied. The chemical state of sulfur has been identified as that of sulfate. The kinetics of SO(,2) chemisorption on CaO are discussed. The binding states of Fe and Na on CaO were determined to be Fe('2+) and Na('+) respectively. At low Fe or Na coverages (< 0.5 ML), there is a large increase in the rate of

JENDL-4.0/HE Benchmark Test with Concrete and Iron Shielding Experiments at JAEA/TIARA

NASA Astrophysics Data System (ADS)

Konno, Chikara; Matsuda, Norihiro; Kwon, Saerom; Ohta, Masayuki; Sato, Satoshi

2017-09-01

As a benchmark test of JENDL-4.0/HE released in 2015, we have analyzed the concrete and iron shielding experiments with the quasi mono-energetic 40 and 65 MeV neutron sources at TIARA in JAEA by using MCNP5 and ACE files processed from JENDL-4.0/HE with NJOY2012. As a result, it was found out that the calculation results with JENDL-4.0/HE agreed with the measured ones in the concrete experiment well, while they underestimated the measured ones in the iron experiment with 65 MeV neutrons more for the thicker assemblies. We examined the 56Fe data of JENDL-4.0/HE in detail and it was considered that the larger non-elastic scattering cross sections of 56Fe caused the underestimation in the calculation with JENDL-4.0/HE for the iron experiment with 65 MeV neutrons.

Direct Reduction of Iron Ore

NASA Astrophysics Data System (ADS)

Small, M.

1981-04-01

In the search for a pure, available iron source, steelmakers are focusing their attention on Directly Reduced Iron (DRI). This material is produced by the reaction of a low gangue iron ore with a hydrocarbonaceous substance. Commercially, DRI is generated in four different reactors: shaft (moving-bed), rotary kiln, fluidized bed, and retort (fixed-bed). Annual worldwide production capacity approaches 33 million metric tons. Detailed assessments have been made of the uses of DRI, especially as a substitute for scrap in electric furnace (EF) steelmaking. DRI is generally of a quality superior to current grades of scrap, with steels produced more efficiently in the EF and containing lower levels of impurities. However, present economics favor EF steel production with scrap. But this situation could change within this decade because of a developing scarcity of good quality scrap.

Iron and manganese oxide mineralization in the Pacific

USGS Publications Warehouse

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

1997-01-01

Iron, manganese, and iron-manganese deposits occur in nearly all geomorphologic and tectonic environments in the ocean basins and form by one or more of four processes: (1) hydrogenetic precipitation from cold ambient seawater, (2) precipitation from hydrothermal fluids, (3) precipitation from sediment pore waters that have been modified from bottom water compositions by diagenetic reactions in the sediment column and (4) replacement of rocks and sediment. These processes are discussed.

Highly selective biaryl cross-coupling reactions between aryl halides and aryl Grignard reagents: a new catalyst combination of N-heterocyclic carbenes and iron, cobalt, and nickel fluorides.

PubMed

Hatakeyama, Takuji; Hashimoto, Sigma; Ishizuka, Kentaro; Nakamura, Masaharu

2009-08-26

Combinations of N-heterocyclic carbenes (NHCs) and fluoride salts of the iron-group metals (Fe, Co, and Ni) have been shown to be excellent catalysts for the cross-coupling reactions of aryl Grignard reagents (Ar(1)MgBr) with aryl and heteroaryl halides (Ar(2)X) to give unsymmetrical biaryls (Ar(1)-Ar(2)). Iron fluorides in combination with SIPr, a saturated NHC ligand, catalyze the biaryl cross-coupling between various aryl chlorides and aryl Grignard reagents in high yield and high selectivity. On the other hand, cobalt and nickel fluorides in combination with IPr, an unsaturated NHC ligand, exhibit interesting complementary reactivity in the coupling of aryl bromides or iodides; in contrast, with these substrates the iron catalysts show a lower selectivity. The formation of homocoupling byproducts is suppressed markedly to less than 5% in most cases by choosing the appropriate metal fluoride/NHC combination. The present catalyst combinations offer several synthetic advantages over existing methods: practical synthesis of a broad range of unsymmetrical biaryls without the use of palladium catalysts and phosphine ligands. On the basis of stoichiometric control experiments and theoretical studies, the origin of the unique catalytic effect of the fluoride counterion can be ascribed to the formation of a higher-valent heteroleptic metalate [Ar(1)MF(2)]MgBr as the key intermediate in our proposed catalytic cycle. First, stoichiometric control experiments revealed the stark differences in chemical reactivity between the metal fluorides and metal chlorides. Second, DFT calculations indicate that the initial reduction of di- or trivalent metal fluoride in the wake of transmetalation with PhMgCl is energetically unfavorable and that formation of a divalent heteroleptic metalate complex, [PhMF(2)]MgCl (M = Fe, Co, Ni), is dominant in the metal fluoride system. The heteroleptic ate-complex serves as a key reactive intermediate, which undergoes oxidative addition with Ph

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

PubMed

Shanker, Uma; Singh, Gurinder; Kamaluddin

2013-06-01

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.

Iron [Fe(0)]-rich substrate based on iron-carbon micro-electrolysis for phosphorus adsorption in aqueous solutions.

PubMed

Deng, Shihai; Li, Desheng; Yang, Xue; Xing, Wei; Li, Jinlong; Zhang, Qi

2017-02-01

The phosphorus (P) adsorption properties of an iron [Fe(0)]-rich substrate (IRS) composed of iron scraps and activated carbon were investigated based on iron-carbon micro-electrolysis (IC-ME) and compared to the substrates commonly used in constructed wetlands (CWs) to provide an initial characterization of the [Fe(0)]-rich substrate. The results showed that P was precipitated by Fe(III) dissolved from the galvanic cell reactions in the IRS and the reaction was suppressed by the pH and stopped when the pH exceeded 8.90 ± 0.09. The adsorption capacity of the IRS decreased by only 4.6% in the second round of adsorption due to Fe(0) consumption in the first round. Substrates with high Ca- and Mg-oxide contents and high Fe- and Al-oxide contents had higher P adsorption capacities at high and low pH values, respectively. Substrates containing high Fe and Al concentrations and low Ca concentrations were more resistant to decreases in the P adsorption capacity resulting from organic matter (OM) accumulation. The IRS with an iron scrap to activated carbon volume ratio of 3:2 resulted in the highest P adsorption capacity (9.34 ± 0.14 g P kg -1 ), with minimal pH change and strong adaptability to OM accumulation. The Fe(0)-rich substrate has the considerable potential for being used as a CW substrate. Copyright © 2016 Elsevier Ltd. All rights reserved.

Cyanide Ligand Assembly by Carbon Atom Transfer to an Iron Nitride

DOE PAGES

Martinez, Jorge L.; Lin, Hsiu-Jung; Lee, Wei-Tsung; ...

2017-09-21

The new iron(IV) nitride complex PhB( iPr 2Im) 3Fe≡N reacts with two equivalents of bis(diisopropylamino)cyclopropenylidene (BAC) to provide PhB( iPr 2Im) 3Fe(CN)(N 2)(BAC). This unusual example of a four-electron reaction involves carbon atom transfer from BAC to create a cyanide ligand along with the alkyne iPr 2N-C≡C-N iPr 2. The iron complex is in equilibrium with an N 2- free species. Further reaction with CO leads to formation of a CO analogue, which can be independently prepared using NaCN as the cyanide source, while reaction with B(C 6F 5) 3 provides the cyanoborane derivative.

Mechanism and Influencing Factors of Iron Nuggets Forming in Rotary Hearth Furnace Process at Lower Temperature

NASA Astrophysics Data System (ADS)

Han, Hongliang; Duan, Dongping; Chen, Siming; Yuan, Peng

2015-10-01

In order to improve the efficiency of slag and iron separation, a new idea of "the separation of slag (solid state) and iron (molten state) in rotary hearth furnace process at lower temperature" is put forward. In this paper, the forming process of iron nuggets has been investigated. Based on those results, the forming mechanisms and influencing factors of iron nugget at low temperature are discussed experimentally using an electric resistance furnace simulating a rotary hearth furnace process. Results show that the reduction of iron ore, carburization of reduced iron, and the composition and quantity of slag are very important for producing iron nuggets at lower temperature. Reduction reaction of carbon-containing pellets is mainly at 1273 K and 1473 K (1000 °C and 1200 °C). When the temperature is above 1473 K (1200 °C), the metallization rate of carbon-containing pellets exceeds 93 pct, and the reduction reaction is substantially complete. Direct carburization is the main method for carburization of reduced iron. This reaction occurs above 1273 K (1000 °C), with carburization degree increasing greatly at 1473 K and 1573 K (1200 °C and 1300 °C) after particular holding times. Besides, to achieve the "slag (solid state) and iron (molten state) separation," the melting point of the slag phase should be increased. Slag (solid state) and iron (molten state) separation can be achieved below 1573 K (1300 °C), and when the holding time is 20 minutes, C/O is 0.7, basicity is less than 0.5 and a Na2CO3 level of 3 pct, the recovery rate of iron can reach 90 pct, with a proportion of iron nuggets more than 3.15 mm of nearly 90 pct. This study can provide theoretical and technical basis for iron nugget production.

Intermediates in the reaction of substrate-free cytochrome P450cam with peroxy acetic acid.

PubMed

Schünemann, V; Jung, C; Trautwein, A X; Mandon, D; Weiss, R

2000-08-18

Freeze-quenched intermediates of substrate-free cytochrome 57Fe-P450(cam) in reaction with peroxy acetic acid as oxidizing agent have been characterized by EPR and Mossbauer spectroscopy. After 8 ms of reaction time the reaction mixture consists of approximately 90% of ferric low-spin iron with g-factors and hyperfine parameters of the starting material; the remaining approximately 10% are identified as a free radical (S' = 1/2) by its EPR and as an iron(IV) (S= 1) species by its Mossbauer signature. After 5 min of reaction time the intermediates have disappeared and the Mossbauer and EPR-spectra exhibit 100% of the starting material. We note that the spin-Hamiltonian analysis of the spectra of the 8 ms reactant clearly reveals that the two paramagnetic species, e.g. the ferryl (iron(IV)) species and the radical, are not exchanged coupled. This led to the conclusion that under the conditions used, peroxy acetic acid oxidized a tyrosine residue (probably Tyr-96) into a tyrosine radical (Tyr*-96), and the iron(III) center of substrate-free P450(cam) to iron(IV).

Circulating non-transferrin-bound iron after oral administration of supplemental and fortification doses of iron to healthy women: a randomized study.

PubMed

Brittenham, Gary M; Andersson, Maria; Egli, Ines; Foman, Jasmin Tajeri; Zeder, Christophe; Westerman, Mark E; Hurrell, Richard F

2014-09-01

After the oral administration of iron, the production of circulating non-transferrin-bound iron may contribute to an increased risk of illness in malaria-endemic areas that lack effective medical services. In healthy women with a range of body iron stores, we aimed to determine effects on the production of circulating non-transferrin-bound iron resulting from the oral administration of 1) a supplemental dose of iron (60 mg) with water, 2) a supplemental dose of iron (60 mg) with a standard test meal, and 3) a fortification dose of iron (6 mg) with a standard test meal. With the use of serum ferritin as the indicator, healthy women with replete iron stores (ferritin concentration >25 μg/L; n = 16) and reduced iron stores (ferritin concentration ≤25 μg/L; n = 16) were enrolled in a prospective, randomized, crossover study. After the oral administration of aqueous solutions of ferrous sulfate isotopically labeled with ⁵⁴Fe, ⁵⁷Fe, or ⁵⁸Fe, blood samples were collected for 8 h, and iron absorption was estimated by erythrocyte incorporation at 14 d. At 4 h, serum non-transferrin-bound iron reached peaks with geometric mean (95% CI) concentrations of 0.81 μmol/L (0.56, 1.1 μmol/L) for 60 mg Fe with water and 0.26 μmol/L (0.15, 0.38 μmol/L) for 60 mg Fe with food but was at assay limits of detection (0.1 μmol Fe/L) for 6 mg Fe with food. For the 60 mg Fe without food, the area under the curve over 8 h for serum non-transferrin-bound iron was positively correlated with the amount of iron absorbed (R = 0.49, P < 0.01) and negatively correlated with serum ferritin (R = -0.39, P < 0.05). In healthy women, the production of circulating non-transferrin-bound iron is determined by the rate and amount of iron absorbed. The highest concentrations of non-transferrin-bound iron resulted from the administration of supplemental doses of iron without food. Little or no circulating non-transferrin-bound iron resulted from the consumption of a meal with a

Iron-binding antioxidant capacity is impaired in diabetes mellitus.

PubMed

Van Campenhout, Ann; Van Campenhout, Christel; Lagrou, Albert R; Moorkens, Greta; De Block, Christophe; Manuel-y-Keenoy, Begoña

2006-05-15

Increased lipid peroxidation contributes to diabetic complications and redox-active iron is known to play an important role in catalyzing peroxidation reactions. We aimed to investigate if diabetes affects the capacity of plasma to protect against iron-driven lipid peroxidation and to identify underlying factors. Glycemic control, serum iron, proteins involved in iron homeostasis, plasma iron-binding antioxidant capacity in a liposomal model, and non-transferrin-bound iron were measured in 40 type 1 and 67 type 2 diabetic patients compared to 100 nondiabetic healthy control subjects. Iron-binding antioxidant capacity was significantly lower in the plasma of diabetic subjects (83 +/- 6 and 84 +/- 5% in type 1 and type 2 diabetes versus 88 +/- 6% in control subjects, p < 0.0005). The contribution of transferrin, ceruloplasmin, and albumin concentrations to the iron-binding antioxidant capacity was lost in diabetes (explaining only 4.2 and 6.3% of the variance in type 1 and type 2 diabetes versus 13.9% in control subjects). This observation could not be explained by differences in Tf glycation, lipid, or inflammatory status and was not associated with higher non-transferrin-bound iron levels. Iron-binding antioxidant capacity is decreased in diabetes mellitus.

56Fe capture cross section experiments at the RPI LINAC Center

NASA Astrophysics Data System (ADS)

McDermott, Brian; Blain, Ezekiel; Thompson, Nicholas; Weltz, Adam; Youmans, Amanda; Danon, Yaron; Barry, Devin; Block, Robert; Daskalakis, Adam; Epping, Brian; Leinweber, Gregory; Rapp, Michael

2017-09-01

A new array of C6D6 detectors installed at the RPI LINAC Center has enabled the capability to measure neutron capture cross sections above the 847 keV inelastic scattering threshold of 56Fe through the use of digital post-processing filters and pulse-integral discriminators, without sacrificing the statistical quality of data at lower incident neutron energies where such filtering is unnecessary. The C6D6 detectors were used to perform time-of-flight capture cross section measurements on a sample 99.87% enriched iron-56. The total-energy method, combined with the pulse height weighting technique, were then applied to the raw data to determine the energy-dependent capture yield. Above the inelastic threshold, the data were analyzed with a pulse-integral filter to reveal the capture signal, extending the the full data set to 2 MeV.

On the mobility of iron particles embedded in elastomeric silicone matrix

NASA Astrophysics Data System (ADS)

Rabindranath, R.; Böse, H.

2013-02-01

In this contribution the rheological and magnetorheological properties of different polydimethylsiloxane (PDMS) based magnetorheological elastomers (MRE) are presented and discussed. In order to investigate the mobility of the iron particles with respect to the rheological characteristics, the iron particles were silanized with vinyltrimethoxysilane to enable a reaction between the modified particle and the cross-linking agent of the silicone elastomer. In addition, the vinyl-functionalized particles were further modified by the coupling of the superficial vinyl groups with a long-chain hydride terminated PDMS, which enables a reaction pathway with the vinyl terminated PDMS. On the other hand, the iron particles were treated with surfactants such as fatty acids, calcium and aluminum soaps, respectively, prior to vulcanization in order to increase the mobility of the iron particles in the elastomeric matrix. It was found, that both, the modification with the long-chain hydride terminated PDMS as well as the treatment with surfactants lead to an increase of the storage modulus G', the loss modulus G" and the loss factor tan δ in the magnetic field. It is concluded that both modifications, the coupling with long-chain hydride terminated PDMS as well as the treatment with surfactants, provide a greater mobility of the iron particles and hence a greater friction represented by the increase of the loss factor tan δ. Consequently it is assumed that untreated iron particles are less mobile in the rubber matrix due to covalent bonding with the silicone components, most likely due to the reaction of the hydroxyl groups on the metal surface with the silane groups of the cross-linking agent.

Preparation of Metalloporphyrin-Bound Superparamagnetic Silica Particles via "Click" Reaction.

PubMed

Hollingsworth, Javoris V; Bhupathiraju, N V S Dinesh K; Sun, Jirun; Lochner, Eric; Vicente, M Graça H; Russo, Paul S

2016-01-13

A facile approach using click chemistry is demonstrated for immobilization of metalloporphyrins onto the surface of silica-coated iron oxide particles. Oleic-acid stabilized iron oxide nanocrystals were prepared by thermal decomposition of iron(III) acetylacetonate. Their crystallinity, morphology, and superparamagnetism were determined using X-ray diffraction, transmission electron microscopy, and a superconducting quantum interference device. Monodisperse core-shell particles were produced in the silica-coating of iron oxide via microemulsion synthesis. Surface modification of these particles was performed in two steps, which included the reaction of silica-coated iron oxide particles with 3-bromopropyltrichlorosilane, followed by azido-functionalization with sodium azide. Monoalkylated porphyrins were prepared using the Williamson ether synthesis of commercially available tetra(4-hydroxyphenyl) porphyrin with propargyl bromide in the presence of a base. (1)H NMR and matrix-assisted laser desorption ionization confirmed the identity of the compounds. The prepared monoalkyne porphyrins were zinc-metalated prior to their introduction to azide-functionalized, silica-coated iron oxide particles in the click reaction. X-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy were used to characterize the surface chemistry after each step in the reaction. In addition, particle size was determined using dynamic light scattering and microscopy. The presented methodology is versatile and can be extended to other photoreactive systems, such as phthalocyanines and boron-dipyrromethane, which may lead to new materials for optical, photonic, and biological applications.

ZIP14 and DMT1 in the liver, pancreas, and heart are differentially regulated by iron deficiency and overload: implications for tissue iron uptake in iron-related disorders

PubMed Central

Nam, Hyeyoung; Wang, Chia-Yu; Zhang, Lin; Zhang, Wei; Hojyo, Shintaro; Fukada, Toshiyuki; Knutson, Mitchell D.

2013-01-01

The liver, pancreas, and heart are particularly susceptible to iron-related disorders. These tissues take up plasma iron from transferrin or non-transferrin-bound iron, which appears during iron overload. Here, we assessed the effect of iron status on the levels of the transmembrane transporters, ZRT/IRT-like protein 14 and divalent metal-ion transporter-1, which have both been implicated in transferrin- and non-transferrin-bound iron uptake. Weanling male rats (n=6/group) were fed an iron-deficient, iron-adequate, or iron-overloaded diet for 3 weeks. ZRT/IRT-like protein 14, divalent metal-ion transporter-1 protein and mRNA levels in liver, pancreas, and heart were determined by using immunoblotting and quantitative reverse transcriptase polymerase chain reaction analysis. Confocal immunofluorescence microscopy was used to localize ZRT/IRT-like protein 14 in the liver and pancreas. ZRT/IRT-like protein 14 and divalent metal-ion transporter-1 protein levels were also determined in hypotransferrinemic mice with genetic iron overload. Hepatic ZRT/IRT-like protein 14 levels were found to be 100% higher in iron-loaded rats than in iron-adequate controls. By contrast, hepatic divalent metal-ion transporter-1 protein levels were 70% lower in iron-overloaded animals and nearly 3-fold higher in iron-deficient ones. In the pancreas, ZRT/IRT-like protein 14 levels were 50% higher in iron-overloaded rats, and in the heart, divalent metal-ion transporter-1 protein levels were 4-fold higher in iron-deficient animals. At the mRNA level, ZRT/IRT-like protein 14 expression did not vary with iron status, whereas divalent metal-ion transporter-1 expression was found to be elevated in iron-deficient livers. Immunofluorescence staining localized ZRT/IRT-like protein 14 to the basolateral membrane of hepatocytes and to acinar cells of the pancreas. Hepatic ZRT/IRT-like protein 14, but not divalent metal-ion transporter-1, protein levels were elevated in iron-loaded hypotransferrinemic

Toward a Mechanistic Understanding of Anaerobic Nitrate-Dependent Iron Oxidation: Balancing Electron Uptake and Detoxification

PubMed Central

Carlson, Hans K.; Clark, Iain C.; Melnyk, Ryan A.; Coates, John D.

2011-01-01

The anaerobic oxidation of Fe(II) by subsurface microorganisms is an important part of biogeochemical cycling in the environment, but the biochemical mechanisms used to couple iron oxidation to nitrate respiration are not well understood. Based on our own work and the evidence available in the literature, we propose a mechanistic model for anaerobic nitrate-dependent iron oxidation. We suggest that anaerobic iron-oxidizing microorganisms likely exist along a continuum including: (1) bacteria that inadvertently 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 that efficiently accept electrons from Fe(II) to gain a growth advantage while preventing or mitigating the toxic reactions. Predictions of the proposed model are highlighted and experimental approaches are discussed. PMID:22363331

Matrix isolation infrared spectra, assignment and DFT investigation on reactions of iron and manganese monoxides with CH3Cl.

PubMed

Zhao, Yanying; Fan, Kexue; Huang, Yongfei; Zheng, Xuming

2013-12-01

The reactions of iron and manganese monoxide molecules (FeO, and MnO) with monochloromethane in solid argon have been studied by matrix isolation infrared spectroscopy and quantum chemistry calculations. When annealing, the reactions of FeO and MnO with CH3Cl first form the OM-(η(Cl)-CH3Cl) (MMn, Fe) complexes, which can isomerize to CH3MOCl (MMn, Fe) upon 300<λ<580 nm irradiation. The products were characterized by isotopic IR studies with CD3Cl and (13)CH3Cl and density functional calculations. Based on theoretical calculations, the OFe-(η(Cl)-CH3Cl) and OMn-(η(Cl)-CH3Cl) complexes have (5)A' and (6)A' ground state with Cs symmetry, respectively. The accurate CCSD(T) single point calculations illustrate the CH3MOCl isomerism are 13.8 and 3.1 kcal/mol lower in energy than the OM-(η(Cl)-CH3Cl) (MMn, Fe) complexes. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

Co-hydrothermal treatment of fallen leaves with iron sludge to prepare magnetic iron product and solid fuel.

PubMed

Gu, Lin; Li, Binglian; Wen, Haifeng; Zhang, Xin; Wang, Liang; Ye, Jianfeng

2018-06-01

The hydrothermal carbonization (HTC) was performed on Metasequoia Leaves (ML) in the presence of iron sludge, both of which were generated as solid residuals. The relations between sludge, char's properties and operating conditions were systemically investigated. Iron sludge primarily catalyzed the efficient formation of char with higher heating value (HHV) becoming 1.15-1.65 times of ML (18.21 MJ/kg) and was meanwhile reduced to magnetite. The hydrated Fe ions in octahedron crystals acted as nucleophiles facilitating the dehydration and decarboxylation reactions. The increased HHV is found strong temperature dependent while prolonging the residence time is more preferable for low organic acids generation. Thermogravimetric analysis confirmed the iron sludge enhanced conversion of volatile to fixed carbon. The as-prepared solid char showed better stability after catalytic HTC treatment, having ignition temperature increased from 253 to 426 °C as compared to the char prepared without iron sludge addition. Copyright © 2018 Elsevier Ltd. All rights reserved.

Pore- and micro-structural characterization of a novel structural binder based on iron carbonation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Sumanta, E-mail: Sumanta.Das@asu.edu; Stone, David, E-mail: dajstone@gmail.com; Convey, Diana, E-mail: Diana.Convey@asu.edu

2014-12-15

The pore- and micro-structural features of a novel binding material based on the carbonation of waste metallic iron powder are reported in this paper. The binder contains metallic iron powder as the major ingredient, followed by additives containing silica and alumina to facilitate favorable reaction product formation. Compressive strengths sufficient for a majority of concrete applications are attained. The material pore structure is investigated primarily through mercury intrusion porosimetry whereas electron microscopy is used for microstructural characterization. Reduction in the overall porosity and the average pore size with an increase in carbonation duration from 1 day to 4 days ismore » noticed. The pore structure features are used in predictive models for gas and moisture transport (water vapor diffusivity and moisture permeability) through the porous medium which dictates its long-term durability when used in structural applications. Comparisons of the pore structure with those of a Portland cement paste are also provided. The morphology of the reaction products in the iron-based binder, and the distribution of constituent elements in the microstructure are also reported. - Highlights: • Carbonation of iron produces a dense microstructure. • Pore volume in iron carbonate lower, critical size higher than those in OPC pastes • Reaction product contains iron, carbon, silicon, aluminum and calcium. • Power-law for porosity-moisture permeability relationship was established.« less

Iron-Mediated Oxidation of Methoxyhydroquinone under Dark Conditions: Kinetic and Mechanistic Insights.

PubMed

Yuan, Xiu; Davis, James A; Nico, Peter S

2016-02-16

Despite the biogeochemical significance of the interactions between natural organic matter (NOM) and iron species, considerable uncertainty still remains as to the exact processes contributing to the rates and extents of complexation and redox reactions between these important and complex environmental components. Investigations on the reactivity of low-molecular-weight quinones, which are believed to be key redox active compounds within NOM, toward iron species, could provide considerable insight into the kinetics and mechanisms of reactions involving NOM and iron. In this study, the oxidation of 2-methoxyhydroquinone (MH2Q) by ferric iron (Fe(III)) under dark conditions in the absence and presence of oxygen was investigated within a pH range of 4-6. Although Fe(III) was capable of stoichiometrically oxidizing MH2Q under anaerobic conditions, catalytic oxidation of MH2Q was observed in the presence of O2 due to further cycling between oxygen, semiquinone radicals, and iron species. A detailed kinetic model was developed to describe the predominant mechanisms, which indicated that both the undissociated and monodissociated anions of MH2Q were kinetically active species toward Fe(III) reduction, with the monodissociated anion being the key species accounting for the pH dependence of the oxidation. The generated radical intermediates, namely semiquinone and superoxide, are of great importance in reaction-chain propagation. The kinetic model may provide critical insight into the underlying mechanisms of the thermodynamic and kinetic characteristics of metal-organic interactions and assist in understanding and predicting the factors controlling iron and organic matter transformation and bioavailability in aquatic systems.

Iron supplementation prevents a decline in iron stores and enhances strength performance in elite female volleyball players during the competitive season.

PubMed

Mielgo-Ayuso, Juan; Zourdos, Michael C; Calleja-González, Julio; Urdampilleta, Aritz; Ostojic, Sergej

2015-06-01

The primary aim of this study was to examine the effects of 11 weeks of iron supplementation on hematological and strength markers in elite female volleyball players. Twenty-two volleyball players (aged 27.0 ± 5.6 years) from 2 Spanish First National League teams participated and were counterbalanced into 1 of 2 groups based upon iron status: (i) control group (CG, n = 11); or (ii) iron treatment group (ITG, n = 11), which received 325 mg/day of ferrous sulphate daily. Subjects performed their team's regimen of training or match play every day. Both groups were tested for hematological and strength levels at 2 points: (i) baseline (T0, before preseason) and (ii) 11 weeks later (T11, post-testing). Hematological parameters were serum iron (sFe), serum ferritin (FER), transferrin saturation index (TSI), and hemoglobin (Hb); strength assessments were bench press, military press, half-squat, power clean, clean and jerk, and pull-over. CG experienced a significant decrease (p < 0.05) for sFe (T0, 112.7 ± 31.5; T11, 69.0 ± 20.5 μg·dL(-1); -33.9%), FER (T0, 60.2 ± 28.6; T11, 38.2 ± 16.4 ng·mL(-1); -34.6%), TSI (T0, 29.4% ± 9.5%; T11, 17.4% ± 5.1%; -35.3%), and Hb (T0, 14.1 ± 1.0; T11, 13.0 ± 0.8 g·L(-1); -7.44%); however, ITG experienced no changes (p > 0.05). Consequently, in ITG all hematological parameters were significantly greater (p < 0.05) than CG at T11. There was greater (p < 0.05) percent increase in the clean and jerk (CG: +5.1% ± 20.9 vs. ITG: +29.0% ± 21.3%), power clean (CG: -5.8% ± 30.3% vs. ITG: +44.6% ± 56.6%), and total mean strength (CG: +10.9% ± 3.2% vs. ITG: +26.2% ± 3.6%) in ITG. Our findings suggest that oral iron supplementation prevents iron loss and enhances strength in female volleyball players during the competitive season.

Investigation of the kinetic mechanism of the demanganization reaction between carbon-saturated liquid iron and CaF2-CaO-SiO2-based slags

NASA Astrophysics Data System (ADS)

Duan, Sheng-chao; Li, Chuang; Guo, Han-jie; Guo, Jing; Han, Shao-wei; Yang, Wen-sheng

2018-04-01

The demanganization reaction kinetics of carbon-saturated liquid iron with an eight-component slag consisting of CaO-SiO2-MgO-FeO-MnO-Al2O3-TiO2-CaF2 was investigated at 1553, 1623, and 1673 K in this study. The rate-controlling step (RCS) for the demanganization reaction with regard to the hot metal pretreatment conditions was studied via kinetics analysis based on the fundamental equation of heterogeneous reaction kinetics. From the temperature dependence of the mass transfer coefficient of a transition-metal oxide (MnO), the apparent activation energy of the demanganization reaction was estimated to be 189.46 kJ·mol-1 in the current study, which indicated that the mass transfer of MnO in the molten slag controlled the overall rate of the demanganization reaction. The calculated apparent activation energy was slightly lower than the values reported in the literature for mass transfer in a slag phase. This difference was attributed to an increase in the "specific reaction interface" (SRI) value, either as a result of turbulence at the reaction interface or a decrease of the absolute amount of slag phase during sampling, and to the addition of calcium fluoride to the slag.

A Mononuclear Nonheme Iron(V)-Imido Complex

DOE PAGES

Hong, Seungwoo; Sutherlin, Kyle D.; Vardhaman, Anil Kumar; ...

2017-06-19

Mononuclear nonheme iron(V)-oxo complexes have been reported previously. Herein, we report the first example of a mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [(TAML)Fe V(NTs)] – . The spectroscopic characterization of 1 revealed an S = 1/2 Fe(V) oxidation state, an Fe—N bond length of 1.65(4) Å, and an Fe—N vibration at 817 cm –1. In conclusion, the reactivity of 1 was demonstrated in C—H bond functionalization and nitrene transfer reactions.

A Mononuclear Nonheme Iron(V)-Imido Complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Seungwoo; Sutherlin, Kyle D.; Vardhaman, Anil Kumar

Mononuclear nonheme iron(V)-oxo complexes have been reported previously. Herein, we report the first example of a mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [(TAML)Fe V(NTs)] – . The spectroscopic characterization of 1 revealed an S = 1/2 Fe(V) oxidation state, an Fe—N bond length of 1.65(4) Å, and an Fe—N vibration at 817 cm –1. In conclusion, the reactivity of 1 was demonstrated in C—H bond functionalization and nitrene transfer reactions.

RADIOACTIVE IRON ABSORPTION BY GASTRO-INTESTINAL TRACT

PubMed Central

Hahn, P. F.; Bale, W. F.; Ross, J. F.; Balfour, W. M.; Whipple, G. H.

1943-01-01

Iron absorption is a function of the gastro-intestinal mucosal epithelium. The normal non-anemic dog absorbs little iron but chronic anemia due to blood loss brings about considerable absorption—perhaps 5 to 15 times normal. In general the same differences are observed in man (1). Sudden change from normal to severe anemia within 24 hours does not significantly increase iron absorption. As the days pass new hemoglobin is formed. The body iron stores are depleted and within 7 days iron absorption is active, even when the red cell hematocrit is rising. Anoxemia of 50 per cent normal oxygen concentration for 48 hours does not significantly enhance iron absorption. In this respect it resembles acute anemia. Ordinary doses of iron given 1 to 6 hours before radio-iron will cause some "mucosa block"—that is an intake of radio-iron less than anticipated. Many variables which modify peristalsis come into this reaction. Iron given by vein some days before the dose of radio-iron does not appear to inhibit iron absorption. Plasma radio-iron absorption curves vary greatly. The curves may show sharp peaks in 1 to 2 hours when the iron is given in an empty stomach but after 6 hours when the radio-iron is given with food. Duration time of curves also varies widely, the plasma iron returning to normal in 6 to 12 hours. Gastric, duodenal, or jejunal pouches all show very active absorption of iron. The plasma concentration peak may reach a maximum before the solution of iron is removed from the gastric pouch—another example of "mucosa block." Absorption and distribution of radio-iron in the body of growing pups give very suggestive experimental data. The spleen, heart, upper gastro-intestinal tract, marrow, and pancreas show more radio-iron than was expected. The term "physiological saturation" with iron may be applied to the gastro-intestinal mucosal epithelium and explain one phase of acceptance or refusal of ingested iron. Desaturation is a matter of days not hours, whereas

Water oxidation: High five iron

NASA Astrophysics Data System (ADS)

Lloret-Fillol, Julio; Costas, Miquel

2016-03-01

The oxidation of water is essential to the sustainable production of fuels using sunlight or electricity, but designing active, stable and earth-abundant catalysts for the reaction is challenging. Now, a complex containing five iron atoms is shown to efficiently oxidize water by mimicking key features of the oxygen-evolving complex in green plants.

Determining Iron Content in Foods by Spectrophotometry.

ERIC Educational Resources Information Center

Adams, Paul E.

1995-01-01

Describes a laboratory experiment for secondary school chemistry students utilizing the classic reaction between the iron(III) ion and the thiocyanate ion. The experiment also works very well in other chemistry courses as an experience in spectrophotometric analysis. (PVD)

Iron Isotopic Fractionation in Earth's Lower Mantle

NASA Astrophysics Data System (ADS)

Yang, H.; Lin, J. F.; Hu, M. Y.; Bi, W.; Zhao, J.; Alp, E. E.; Roskosz, M.; Dauphas, N.; Okuchi, T.

2017-12-01

The Earth's bulk chemical composition is vital for deciphering the origin of this planet. Our estimation of the iron isotopic composition of the bulk Earth relies on the iron isotopic composition difference between the metallic core and silicate mantle. Previous studies1,2,3 on this fractionation scale have mostly focused on the alloying effects of light elements in the iron metal phases, while the pressure effects of the silicate mantle phases especially due to iron partitioning4 in the lower mantle minerals have not been fully addressed. For instance, Polyakov (2009) simply assumed equal iron distribution between ferropericlase and post-perovskite in his model. Shahar et al. (2016) only used bridgmanite as a proxy for the mantle while another lower mantle mineral ferropericlase was neglected. Here we have investigated the force constant of iron bonds in lower-mantle ferropericlase and bridgmanite crystals up to 104GPa using NRIXS(Nuclear Resonant Inelastic X-ray Scattering) and SMS(Synchrotron Mössbauer Spectroscopy) in a diamond anvil cell at sector-3 of the Advance Photon Source. These results are used to evaluate the pressure effects as well as the spin/valence states of iron5,6 on the force constant of iron bonds and the iron isotope distributions within the lower mantle and at the core-mantle boundary. We found that the liquid-solid iron isotopic fractionation during magma ocean crystallization was limited, however, the inter-mineral fractionation between ferropericlase and bridgmanite could be significant influenced by the spin/valence states at the lowermost mantle conditions. 1.Polyakov, V. B. Science 323, 912-914 (2009). 2.Shahar, A. et al. Science 352, 580-582 (2016). 3.Liu, J. et al. Nat. Commun. 8, 14377 (2017). 4.Irifune, T. et al. Science 327, 193-195 (2010). 5.Lin, J. F., Speziale, S., Mao, Z. & Marquardt, Rev. Geophys. 51, 244-275 (2013). 6.Mao, Z. et al. Am. Mineral. 102 (2017).

Attrition of precipitated iron Fischer-Tropsch catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datye, A.K.; Reardon, J.; Hanprasopwattana, A.

1996-12-31

Precipitated Iron catalysts used in slurry phase bubble column reactors are known to undergo attrition during use. The attrition reduces the lifetime of the catalyst as well as causing problems in separating the product liquids from the catalyst. In this study, the authors have investigated the underlying mechanisms that lead to attrition in precipitated iron catalysts. They have discovered that attrition takes place on two length scales. On the macro scale, attrition is caused by the break-up of the weak agglomerates that constitute this catalyst into individual crystallites. Addition of binders such as kaolin does not help significantly in strengtheningmore » the catalyst particles. In addition, there is a second process leading to nanoscale attrition that is caused by the break-up of individual iron oxide crystallites into nano particles of iron carbide as the catalyst is activated for reaction. Design of attrition resistant F-T catalysts must consider these two modes of catalyst attrition. Preliminary work in the laboratory directed at improving the attrition resistance of precipitated iron catalysts will also be described in this paper.« less

Relative effectiveness of HZE iron-56 particles for the induction of cytogenetic damage in vivo

NASA Technical Reports Server (NTRS)

Brooks, A.; Bao, S.; Rithidech, K.; Couch, L. A.; Braby, L. A.

2001-01-01

One of the risks of prolonged manned space flight is the exposure of astronauts to radiation from galactic cosmic rays, which contain heavy ions such as (56)Fe. To study the effects of such exposures, experiments were conducted at the Brookhaven National Laboratory by exposing Wistar rats to high-mass, high-Z, high-energy (HZE) particles using the Alternating Gradient Synchrotron (AGS). The biological effectiveness of (56)Fe ions (1000 MeV/nucleon) relative to low-LET gamma rays and high-LET alpha particles for the induction of chromosome damage and micronuclei was determined. The mitotic index and the frequency of chromosome aberrations were evaluated in bone marrow cells, and the frequency of micronuclei was measured in cells isolated from the trachea and the deep lung. A marked delay in the entry of cells into mitosis was induced in the bone marrow cells that decreased as a function of time after the exposure. The frequencies of chromatid aberrations and micronuclei increased as linear functions of dose. The frequency of chromosome aberrations induced by HZE particles was about 3.2 times higher than that observed after exposure to (60)Co gamma rays. The frequency of micronuclei in rat lung fibroblasts, lung epithelial cells, and tracheal epithelial cells increased linearly, with slopes of 7 x 10(-4), 12 x 10(-4), and 11 x 10(-4) micronuclei/binucleated cell cGy(-1), respectively. When genetic damage induced by radiation from (56)Fe ions was compared to that from exposure to (60)Co gamma rays, (56)Fe-ion radiation was between 0.9 and 3.3 times more effective than (60)Co gamma rays. However, the HZE-particle exposures were only 10-20% as effective as radon in producing micronuclei in either deep lung or tracheal epithelial cells. Using microdosimetric techniques, we estimated that 32 cells were hit by delta rays for each cell that was traversed by the primary HZE (56)Fe particle. These calculations and the observed low relative effectiveness of the exposure to HZE

Iron-catalysed fluoroaromatic coupling reactions under catalytic modulation with 1,2-bis(diphenylphosphino)benzene.

PubMed

Hatakeyama, Takuji; Kondo, Yoshiyuki; Fujiwara, Yu-Ichi; Takaya, Hikaru; Ito, Shingo; Nakamura, Eiichi; Nakamura, Masaharu

2009-03-14

A catalytic amount of 1,2-bis(diphenylphosphino)benzene (DPPBz) achieves selective cleavage of sp(3)-carbon-halogen bond in the iron-catalysed cross-coupling between polyfluorinated arylzinc reagents and alkyl halides, which was unachievable with a stoichiometric modifier such as TMEDA; the selective iron-catalysed fluoroaromatic coupling provides easy and practical access to polyfluorinated aromatic compounds.

Interactions between iron and organic matter may influence the fate of permafrost carbon in the Arctic

NASA Astrophysics Data System (ADS)

Cory, R. M.; Trusiak, A.; Ward, C.; Kling, G. W.; Tfaily, M.; Paša-Tolić, L.; Noel, V.; Bargar, J.

2017-12-01

The ongoing thawing of permafrost soils is the only environmental change that allows tremendous stores of organic carbon (C) to be converted into carbon dioxide (CO2) on decadal time scales, thus providing a positive and accelerating feedback to global warming. Evidence suggests that iron enhances abiotic reactions that convert dissolved organic matter (DOM) to CO2 in dark soils and in sunlit surface waters depending on its redox state and association with DOM (i.e., iron-DOM complexation). However, the complexation of iron in surface waters and soils remains too poorly understood to predict how iron influences the rates of oxidation of DOM to CO2. To address this knowledge gap, we characterized iron-DOM complexation in iron-rich soil and surface waters of the Arctic, in combination with measurements of DOM oxidation to CO2. These waters contain high concentrations of dissolved iron and DOM (up to 1 and 2 mM, respectively), and low concentrations of other potential ligands for iron such as sulfide, carbonate, chloride, or bromide. Ultra-high resolution mass spectrometry (FT-ICR MS) was used to identify ligands for iron within the DOM pool, and synchrotron based X-ray analysis (XAS and EXAFS) was used to assess iron's oxidation state, to detect iron complexation, and to constrain the chemical composition of the complexes. Across a natural gradient of dissolved iron and DOM concentrations, many potential ligands were identified within DOM that are expected to complex with iron (e.g., aromatic acids). EXAFS showed substantial complexation of reduced ferrous iron (Fe(II)) to DOM in arctic soil waters, on the basis of comparison to Fe(II)-DOM reference spectra. Identification of iron complexed to DOM in soil waters is consistent with strongly co-varying iron and DOM concentrations in arctic soil and surface waters, and supports our hypothesis that complexation of iron by DOM influences dark and light redox reactions that oxidize DOM to CO2. Understanding the molecular

Citric Acid-Modified Fenton's Reaction for the Oxidation of Chlorinated Ethylenes in Soil Solution Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seol, Yongkoo; Javandel, Iraj

Fenton's reagent, a solution of hydrogen peroxide and ferrous iron catalyst, is used for an in-situ chemical oxidation of organic contaminants. Sulfuric acid is commonly used to create an acidic condition needed for catalytic oxidation. Fenton's reaction often involves pressure buildup and precipitation of reaction products, which can cause safety hazards and diminish efficiency. We selected citric acid, a food-grade substance, as an acidifying agent to evaluate its efficiencies for organic contaminant removal in Fenton's reaction, and examined the impacts of using citric acid on the unwanted reaction products. A series of batch and column experiments were performed with varyingmore » H{sub 2}O{sub 2} concentrations to decompose selected chlorinated ethylenes. Either dissolved iron from soil or iron sulfate salt was added to provide the iron catalyst in the batch tests. Batch experiments revealed that both citric and sulfuric acid systems achieved over 90% contaminant removal rates, and the presence of iron catalyst was essential for effective decontamination. Batch tests with citric acid showed no signs of pressure accumulation and solid precipitations, however the results suggested that an excessive usage of H{sub 2}O{sub 2} relative to iron catalysts (Fe{sup 2+}/H{sub 2}O{sub 2} < 1/330) would result in lowering the efficiency of contaminant removal by iron chelations in the citric acid system. Column tests confirmed that citric acid could provide suitable acidic conditions to achieve higher than 55% contaminant removal rates.« less

Citric acid-modified Fenton's reaction for the oxidation of chlorinated ethylenes in soil solution systems.

PubMed

Seol, Yongkoo; Javandel, Iraj

2008-06-01

Fenton's reagent, a solution of hydrogen peroxide and ferrous iron catalyst, is used for an in situ chemical oxidation of organic contaminants. Sulfuric acid is commonly used to create an acidic condition needed for catalytic oxidation. Fenton's reaction often involves pressure buildup and precipitation of reaction products, which can cause safety hazards and diminish efficiency. We selected citric acid, a food-grade substance, as an acidifying agent to evaluate its efficiencies for organic contaminant removal in Fenton's reaction, and examined the impacts of using citric acid on the unwanted reaction products. A series of batch and column experiments were performed with varying H2O2 concentrations to decompose selected chlorinated ethylenes. Either dissolved iron from soil or iron sulfate salt was added to provide the iron catalyst in the batch tests. Batch experiments revealed that both citric and sulfuric acid systems achieved over 90% contaminant removal rates, and the presence of iron catalyst was essential for effective decontamination. Batch tests with citric acid showed no signs of pressure accumulation and solid precipitations, however the results suggested that an excessive usage of H2O2 relative to iron catalysts (Fe2+/H2O2<1/330) would result in lowering the efficiency of contaminant removal by iron chelation in the citric acid system. Column tests confirmed that citric acid could provide suitable acidic conditions to achieve higher than 55% contaminant removal rates.

Synthetic modeling chemistry of iron-sulfur clusters in nitric oxide signaling.

PubMed

Fitzpatrick, Jessica; Kim, Eunsuk

2015-08-18

Nitric oxide (NO) is an important signaling molecule that is involved in many physiological and pathological functions. Iron-sulfur proteins are one of the main reaction targets for NO, and the [Fe-S] clusters within these proteins are converted to various iron nitrosyl species upon reaction with NO, of which dinitrosyl iron complexes (DNICs) are the most prevalent. Much progress has been made in identifying the origin of cellular DNIC generation. However, it is not well-understood which other products besides DNICs may form during [Fe-S] cluster degradation nor what effects DNICs and other degradation products can have once they are generated in cells. Even more elusive is an understanding of the manner by which cells cope with unwanted [Fe-S] modifications by NO. This Account describes our synthetic modeling efforts to identify cluster degradation products derived from the [2Fe-2S]/NO reaction in order to establish their chemical reactivity and repair chemistry. Our intent is to use the chemical knowledge that we generate to provide insight into the unknown biological consequences of cluster modification. Our recent advances in three different areas are described. First, new reaction conditions that lead to the formation of previously unrecognized products during the reaction of [Fe-S] clusters with NO are identified. Hydrogen sulfide (H2S), a gaseous signaling molecule, can be generated from the reaction between [2Fe-2S] clusters and NO in the presence of acid or formal H• (e(-)/H(+)) donors. In the presence of acid, a mononitrosyl iron complex (MNIC) can be produced as the major iron-containing product. Second, cysteine analogues can efficiently convert MNICs back to [2Fe-2S] clusters without the need for any other reagents. This reaction is possible for cysteine analogues because of their ability to labilize NO from MNICs and their capacity to undergo C-S bond cleavage, providing the necessary sulfide for [2Fe-2S] cluster formation. Lastly, unique dioxygen

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

PubMed

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

2013-01-15

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 γ-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.

Evidence for the dipole nature of the low-energy γ enhancement in Fe 56

DOE PAGES

Larsen, A. C.; Blasi, N.; Bracco, A.; ...

2013-12-11

Here, the γ-ray strength function of 56Fe has been measured from proton-γ coincidences for excitation energies up to ≈11 MeV. The low-energy enhancement in the γ-ray strength function, which was first discovered in the ( 3He,αγ) 56Fe reaction, is confirmed with the (p,p'γ) 56Fe experiment reported here. Angular distributions of the γ rays give for the first time evidence that the enhancement is dominated by dipole transitions.

A comparative gene expression analysis of iron-limited cultures of Chaetoceros socialis and Pseudo-nitzschia arenysensis using newly developed iron assays

NASA Astrophysics Data System (ADS)

Abdala, Z. M.; Powell, K.; Cronin, D.; Chappell, D.

2016-02-01

A comparative gene expression analysis of iron-limited cultures of Chaetoceros socialis and Pseudo-nitzschia arenysensisusing newly developed iron assays Zuzanna M. Abdala, Kimberly Powell, Dylan P. Cronin, P. Dreux Chappell Diatoms, accounting for about 40% of the primary production in marine ecosystems, play a vital role in the dynamics of marine systems. Iron availability is understood to be a driving factor controlling productivity of many marine phytoplankton, including diatoms, as it functions as a cofactor for many proteins including several involved with photosynthetic processes. Previous work examining transcriptomes of diatoms of the Thalassiosira genus grown in controlled laboratory settings has identified genes whose expression can be used as sensitive markers of iron status. Data mining publically available diatom transcriptome data for these genes enables development of additional iron status assays for environmentally-relevant diatoms. For the present study, gene expression analysis of iron-limited laboratory cultures of Chaetoceros socialis and Pseudo-nitzschia arenysensis grown in continuous light was done using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). C. socialis and P. arenysensis serve as comparative models for analyzing gene expression in iron limitation in different ecological community assemblages. These data may ultimately assist to illuminate the function of iron in photosynthetic activity in diatoms.

Reactivity of Uranium and Ferrous Iron with Natural Iron Oxyhydroxides.

PubMed

Stewart, Brandy D; Cismasu, A Cristina; Williams, Kenneth H; Peyton, Brent M; Nico, Peter S

2015-09-01

Determining key reaction pathways involving uranium and iron oxyhydroxides under oxic and anoxic conditions is essential for understanding uranium mobility as well as other iron oxyhydroxide mediated processes, particularly near redox boundaries where redox conditions change rapidly in time and space. Here we examine the reactivity of a ferrihydrite-rich sediment from a surface seep adjacent to a redox boundary at the Rifle, Colorado field site. Iron(II)-sediment incubation experiments indicate that the natural ferrihydrite fraction of the sediment is not susceptible to reductive transformation under conditions that trigger significant mineralogical transformations of synthetic ferrihydrite. No measurable Fe(II)-promoted transformation was observed when the Rifle sediment was exposed to 30 mM Fe(II) for up to 2 weeks. Incubation of the Rifle sediment with 3 mM Fe(II) and 0.2 mM U(VI) for 15 days shows no measurable incorporation of U(VI) into the mineral structure or reduction of U(VI) to U(IV). Results indicate a significantly decreased reactivity of naturally occurring Fe oxyhydroxides as compared to synthetic minerals, likely due to the association of impurities (e.g., Si, organic matter), with implications for the mobility and bioavailability of uranium and other associated species in field environments.

7 CFR 56.42-56.43 - [Reserved

Code of Federal Regulations, 2010 CFR

2010-01-01

... AGRICULTURAL MARKETING ACT OF 1946 AND THE EGG PRODUCTS INSPECTION ACT (CONTINUED) VOLUNTARY GRADING OF SHELL EGGS Grading of Shell Eggs Prerequisites to Packaging Shell Eggs Identified with Grademarks §§ 56.42-56...

7 CFR 56.42-56.43 - [Reserved

Code of Federal Regulations, 2011 CFR

2011-01-01

... AGRICULTURAL MARKETING ACT OF 1946 AND THE EGG PRODUCTS INSPECTION ACT (CONTINUED) VOLUNTARY GRADING OF SHELL EGGS Grading of Shell Eggs Prerequisites to Packaging Shell Eggs Identified with Grademarks §§ 56.42-56...

The transformation of hexabromocyclododecane using zerovalent iron nanoparticle aggregates.

PubMed

Tso, Chih-ping; Shih, Yang-hsin

2014-07-30

Hexabromocyclododecane (HBCD), an emerging contaminant, is a brominated flame retardant that has been widely detected in the environment. In this study, nanoscale zerovalent iron (NZVI) aggregates are firstly used to treat HBCD and its removal under different geochemical conditions is evaluated. HBCD is almost removed from solutions by NZVI, with a kSA of 4.22×10(-3)Lm(-2)min(-1). An increase in the iron dosage and temperature increases the removal rate. The activation energy for the removal of HBCD by NZVI is 30.2kJmol(-1), which suggests that a surface-chemical reaction occurs on NZVI. HBCD is adsorbed on the NZVI surface, where electrons were transferred to HBCD, and consequently forms byproducts with less bromide. Three common groundwater anions decrease the reaction kinetics and efficiency of NZVI. The kobs of HBCD in the presence of anions is in the order: pure water >Cl(-)>NO3(-)≒HCO3(-). The inhibitory effect of these anions may be a result of the possible complexation of anions with the oxidized iron surface. The oxidized sites on NZVI and oxidized species of iron also contribute to the removal of HBCD by adsorption on NZVI from solutions. Copyright © 2014 Elsevier B.V. All rights reserved.

A randomized trial of iron isomaltoside 1000 versus oral iron in non-dialysis-dependent chronic kidney disease patients with anaemia.

PubMed

Kalra, Philip A; Bhandari, Sunil; Saxena, Sanjiv; Agarwal, Dhananjai; Wirtz, Georg; Kletzmayr, Josef; Thomsen, Lars L; Coyne, Daniel W

2016-04-01

Iron deficiency anaemia is common in patients with non-dialysis-dependent chronic kidney disease (NDD-CKD) and is often treated with oral or intravenous (IV) iron therapy. This trial compared the efficacy and safety of IV iron isomaltoside 1000 (Monofer®) and oral iron in NDD-CKD patients with renal-related anaemia. The trial was a Phase III open-label, comparative, multicentre, non-inferiority trial conducted in 351 iron-deficient NDD-CKD patients, randomized 2:1 to either iron isomaltoside 1000 (Group A) or iron sulphate administered as 100 mg elemental oral iron twice daily (200 mg daily) for 8 weeks (Group B). The patients in Group A were randomized into A1 (infusion of max. 1000 mg single doses over 15 min) and A2 (bolus injections of 500 mg over 2 min). A modified Ganzoni formula was used to calculate IV iron need. The primary end point was change in haemoglobin concentrations from baseline to Week 4. Iron isomaltoside 1000 was both non-inferior to oral iron at Week 4 (P < 0.001) and sustained a superior increase in haemoglobin from Week 3 until the end of the study at Week 8 (P = 0.009 at Week 3). The haemoglobin response was more pronounced with iron isomaltoside 1000 doses ≥1000 mg (P < 0.05). Serum-ferritin and transferrin saturation concentrations were also significantly increased with IV iron. Adverse drug reactions were observed in 10.5% in the iron isomaltoside 1000 group and 10.3% in the oral iron group. More patients treated with oral iron sulphate withdrew from the study due to adverse events (4.3 versus 0.9%, P = 0.2). Iron isomaltoside 1000 was more efficacious than oral iron for increase in haemoglobin and proved to be well tolerated at the tested dose levels in NDD-CKD patients. © The Author 2015. Published by Oxford University Press on behalf of ERA-EDTA.

Catalytic transformation of dinitrogen into ammonia and hydrazine by iron-dinitrogen complexes bearing pincer ligand

PubMed Central

Kuriyama, Shogo; Arashiba, Kazuya; Nakajima, Kazunari; Matsuo, Yuki; Tanaka, Hiromasa; Ishii, Kazuyuki; Yoshizawa, Kazunari; Nishibayashi, Yoshiaki

2016-01-01

Synthesis and reactivity of iron-dinitrogen complexes have been extensively studied, because the iron atom plays an important role in the industrial and biological nitrogen fixation. As a result, iron-catalyzed reduction of molecular dinitrogen into ammonia has recently been achieved. Here we show that an iron-dinitrogen complex bearing an anionic PNP-pincer ligand works as an effective catalyst towards the catalytic nitrogen fixation, where a mixture of ammonia and hydrazine is produced. In the present reaction system, molecular dinitrogen is catalytically and directly converted into hydrazine by using transition metal-dinitrogen complexes as catalysts. Because hydrazine is considered as a key intermediate in the nitrogen fixation in nitrogenase, the findings described in this paper provide an opportunity to elucidate the reaction mechanism in nitrogenase. PMID:27435503

Carbothermic Reduction Reactions at the Metal-Slag Interface in Ti-Bearing Slag from a Blast Furnace

NASA Astrophysics Data System (ADS)

Wang, Yao-Zu; Zhang, Jian-Liang; Liu, Zheng-Jian; Du, Cheng-Bo

2017-11-01

Carbothermic reduction reactions at the metal-slag interface and the mechanisms of iron loss during the smelting of vanadium-bearing titanomagnetite in a blast furnace are still not clear as a result of the limited ability to observe the high-temperature zone of a blast furnace. The chemical composition of a Ti-bearing slag was determined by x-ray fluorescence and x-ray diffraction. The interfaces were characterized by scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy. The interfacial chemical reactions were deduced based on the characterization results and on the thermodynamic calculations performed using Factsage 6.4. The results indicated that the forms of iron in the slag were iron droplets wetted by Ti(C x , N1- x ), mechanically separated by iron and iron oxide. The different forms possessed unique characteristics and were formed by different mechanisms. Iron droplets wetted by Ti(C x , N1- x ) were generated through a series of interfacial reactions between TiO2 in the slag and [C] and [N] in the metal. Iron droplets without attached Ti(C x , N1- x ) were mainly located on the edges of pores and were attributed to the reduction of Fe x O in the slag. Insufficient reduction of iron-bearing minerals made it difficult for iron droplets to aggregate and separate from the slag, which created an Fe x O-enriched zone.

Kinetic Studies of Iron Deposition in Horse Spleen Ferritin Using H2O2 and O2 as Oxidants

NASA Technical Reports Server (NTRS)

Lowery, Thomas J., Jr.; Bunker, Jared; Zhang, Bo; Costen, Robert; Watt, Gerald D.

2004-01-01

The reaction of horse spleen ferritin (HoSF) with Fe(2+) at pH 6.5 and 7.5 using O2, H2O2 and 1:1 a mixture of both showed that the iron deposition reaction using H2O2 is approx. 20- to 50-fold faster than the reaction with O2 alone. When H2O2 was added during the iron deposition reaction initiated with O2 as oxidant, Fe(2+) was preferentially oxidized by H2O2, consistent with the above kinetic measurements. Both the O2 and H202 reactions were well defined from 15 to 40 C from which activation parameters were determined. The iron deposition reaction was also studied using O2 as oxidant in the presence and absence of catalase using both stopped-flow and pumped-flow measurements. The presence of catalase decreased the rate of iron deposition by approx. 1.5-fold, and gave slightly smaller absorbance changes than in its absence. From the rate constants for the O2 (0.044 per second) and H2O2 (0.67 per second) iron-deposition reactions at pH 7.5, simulations of steady-state H2O2 concentrations were computed to be 0.45 micromolar. This low value and reported Fe2(+)/O2 values of 2.0-2.5 are consistent with H2O2 rapidly reacting by an alternate but unidentified pathway involving a system component such as the protein shell or the mineral core as previously postulated.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

PubMed Central

Kell, Douglas B

2009-01-01

Background The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. Review We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox

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

PubMed

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

2013-08-19

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

Hydrosilylation of aldehydes and ketones catalyzed by hydrido iron complexes bearing imine ligands.

PubMed

Zuo, Zhenyu; Sun, Hongjian; Wang, Lin; Li, Xiaoyan

2014-08-14

Two new hydrido iron complexes (2 and 4) were synthesized by the reactions of (4-methoxyphenyl)phenylketimine ((4-MeOPh)PhC=NH) with Fe(PMe3)4 or FeMe2(PMe3)4. The molecular structures of complexes 2 and 4 were confirmed by X-ray single crystal diffraction. Using hydrido iron complexes (1-4) as catalysts, the hydrosilylations of aldehydes and ketones were investigated. The four complexes were effective catalysts for this reduction reaction. Complex 1 among them is the best catalyst.

Complexation Key to a pH Locked Redox Reaction

ERIC Educational Resources Information Center

Rizvi, Masood Ahmad; Dangat, Yuvraj; Shams, Tahir; Khan, Khaliquz Zaman

2016-01-01

An unfavorable pH can block a feasible electron transfer for a pH dependent redox reaction. In this experiment, a series of potentiometric titrations demonstrate the sequential loss in feasibility of iron(II) dichromate redox reaction over a pH range of 0-4. The pH at which this reaction failed to occur was termed as a pH locked reaction. The…

Observation of universal strong orbital-dependent correlation effects in iron chalcogenides

DOE PAGES

Yi, M.; Liu, Z. -K.; Zhang, Y.; ...

2015-07-23

Establishing the appropriate theoretical framework for unconventional superconductivity in the iron-based materials requires correct understanding of both the electron correlation strength and the role of Fermi surfaces. This fundamental issue becomes especially relevant with the discovery of the iron chalcogenide superconductors. Here, we use angle-resolved photoemission spectroscopy to measure three representative iron chalcogenides, FeTe 0.56Se 0.44, monolayer FeSe grown on SrTiO 3 and K 0.76Fe 1.72Se 2. We show that these superconductors are all strongly correlated, with an orbital-selective strong renormalization in the dxy bands despite having drastically different Fermi surface topologies. Furthermore, raising temperature brings all three compounds frommore » a metallic state to a phase where the dxy orbital loses all spectral weight while other orbitals remain itinerant. As a result, these observations establish that iron chalcogenides display universal orbital-selective strong correlations that are insensitive to the Fermi surface topology, and are close to an orbital-selective Mott phase, hence placing strong constraints for theoretical understanding of iron-based superconductors.« less

Observation of universal strong orbital-dependent correlation effects in iron chalcogenides

PubMed Central

Yi, M.; Liu, Z-K; Zhang, Y.; Yu, R.; Zhu, J.-X.; Lee, J.J.; Moore, R.G.; Schmitt, F.T.; Li, W.; Riggs, S.C.; Chu, J.-H.; Lv, B.; Hu, J.; Hashimoto, M.; Mo, S.-K.; Hussain, Z.; Mao, Z.Q.; Chu, C.W.; Fisher, I.R.; Si, Q.; Shen, Z.-X.; Lu, D.H.

2015-01-01

Establishing the appropriate theoretical framework for unconventional superconductivity in the iron-based materials requires correct understanding of both the electron correlation strength and the role of Fermi surfaces. This fundamental issue becomes especially relevant with the discovery of the iron chalcogenide superconductors. Here, we use angle-resolved photoemission spectroscopy to measure three representative iron chalcogenides, FeTe0.56Se0.44, monolayer FeSe grown on SrTiO3 and K0.76Fe1.72Se2. We show that these superconductors are all strongly correlated, with an orbital-selective strong renormalization in the dxy bands despite having drastically different Fermi surface topologies. Furthermore, raising temperature brings all three compounds from a metallic state to a phase where the dxy orbital loses all spectral weight while other orbitals remain itinerant. These observations establish that iron chalcogenides display universal orbital-selective strong correlations that are insensitive to the Fermi surface topology, and are close to an orbital-selective Mott phase, hence placing strong constraints for theoretical understanding of iron-based superconductors. PMID:26204461

Diagnosis and treatment of iron-deficiency anaemia in pregnancy and postpartum.

PubMed

Breymann, C; Honegger, C; Hösli, I; Surbek, D

2017-12-01

Iron deficiency occurs frequently in pregnancy and can be diagnosed by serum ferritin-level measurement (threshold value < 30 μg/L). Screening for iron-deficiency anemia is recommended in every pregnant women, and should be done by serum ferritin-level screening in the first trimester and regular hemoglobin checks at least once per trimester. In the case of iron deficiency with or without anaemia in pregnancy, oral iron therapy should be given as first-line treatment. In the case of severe iron-deficiency anemia, intolerance of oral iron, lack of response to oral iron, or in the case of a clinical need for rapid and efficient treatment of anaemia (e.g., advanced pregnancy), intravenous iron therapy should be administered. In the postpartum period, oral iron therapy should be administered for mild iron-deficiency anemia (haemorrhagic anemia), and intravenous iron therapy for moderately severe-to-severe anemia (Hb < 95 g/L). If there is an indication for intravenous iron therapy in pregnancy or postpartum, iron-containing drugs which have been studied in well-controlled clinical trials in pregnancy and postpartum such as ferric carboxymaltose must be preferred for safety reasons. While anaphylactic reactions are extremely are with non-dextrane products, close surveillance during administration is recommended for all intravenous iron products.

Mechanistic Insight on the Activity and Substrate Selectivity of Nonheme Iron Dioxygenases.

PubMed

de Visser, Sam P

2018-06-07

Nonheme iron dioxygenases catalyze vital reactions for human health particularly related to aging processes. They are involved in the biosynthesis of amino acids, but also the biodegradation of toxic compounds. Typically they react with their substrate(s) through oxygen atom transfer, although often with the assistance of a co-substrate like α-ketoglutarate that is converted to succinate and CO 2 . Many reaction processes catalyzed by the nonheme iron dioxygenases are stereoselective or regiospecific and hence understanding the mechanism and protein involvement in the selectivity is important for the design of biotechnological applications of these enzymes. To this end, I will review recent work of our group on nonheme iron dioxygenases and include background information on their general structure and catalytic cycle. Examples of stereoselective and regiospecific reaction mechanisms we elucidated are for the AlkB repair enzyme, prolyl-4-hydroxylase and the ergothioneine biosynthesis enzyme. Finally, I cover an example where we bioengineered S-p-hydroxymandelate synthase into the R-p-hydroxymandelate synthase. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A specific role of the yeast mitochondrial carriers MRS3/4p in mitochondrial iron acquisition under iron-limiting conditions.

PubMed

Mühlenhoff, Ulrich; Stadler, Jochen A; Richhardt, Nadine; Seubert, Andreas; Eickhorst, Thomas; Schweyen, Rudolf J; Lill, Roland; Wiesenberger, Gerlinde

2003-10-17

The yeast genes MRS3 and MRS4 encode two members of the mitochondrial carrier family with high sequence similarity. To elucidate their function we utilized genome-wide expression profiling and found that both deletion and overexpression of MRS3/4 lead to up-regulation of several genes of the "iron regulon." We therefore analyzed the two major iron-utilizing processes, heme formation and Fe/S protein biosynthesis in vivo, in organello (intact mitochondria), and in vitro (mitochondrial extracts). Radiolabeling of yeast cells with 55Fe revealed a clear correlation between MRS3/4 expression levels and the efficiency of these biosynthetic reactions indicating a role of the carriers in utilization and/or transport of iron in vivo. Similar effects on both heme formation and Fe/S protein biosynthesis were seen in organello using mitochondria isolated from cells grown under iron-limiting conditions. The correlation between MRS3/4 expression levels and the efficiency of the two iron-utilizing processes was lost upon detergent lysis of mitochondria. As no significant changes in the mitochondrial membrane potential were observed upon overexpression or deletion of MRS3/4, our results suggest that Mrs3/4p carriers are directly involved in mitochondrial iron uptake. Mrs3/4p function in mitochondrial iron transport becomes evident under iron-limiting conditions only, indicating that the two carriers do not represent the sole system for mitochondrial iron acquisition.

The FIND-CKD study--a randomized controlled trial of intravenous iron versus oral iron in non-dialysis chronic kidney disease patients: background and rationale.

PubMed

Macdougall, Iain C; Bock, Andreas; Carrera, Fernando; Eckardt, Kai-Uwe; Gaillard, Carlo; Van Wyck, David; Roubert, Bernard; Cushway, Timothy; Roger, Simon D

2014-04-01

Rigorous data are sparse concerning the optimal route of administration and dosing strategy for iron therapy with or without concomitant erythropoiesis-stimulating agent (ESA) therapy for the management of iron deficiency anaemia in patients with non-dialysis dependent chronic kidney disease (ND-CKD). FIND-CKD was a 56-week, open-label, multicentre, prospective, randomized three-arm study (NCT00994318) of 626 patients with ND-CKD and iron deficiency anaemia randomized to (i) intravenous (IV) ferric carboxymaltose (FCM) at an initial dose of 1000 mg iron with subsequent dosing as necessary to target a serum ferritin level of 400-600 µg/L (ii) IV FCM at an initial dose of 200 mg with subsequent dosing as necessary to target serum ferritin 100-200 µg/L or (iii) oral ferrous sulphate 200 mg iron/day. The primary end point was time to initiation of other anaemia management (ESA therapy, iron therapy other than study drug or blood transfusion) or a haemoglobin (Hb) trigger (two consecutive Hb values <10 g/dL without an increase of ≥ 0.5 g/dL). The background, rationale and study design of the trial are presented here. The study has been completed and results are expected in late 2013. FIND-CKD was the longest randomized trial of IV iron therapy to date. Its findings will address several unanswered questions regarding iron therapy to treat iron deficiency anaemia in patients with ND-CKD. It was also the first randomized trial to utilize both a high and low serum ferritin target range to adjust IV iron dosing, and the first not to employ Hb response as its primary end point.

Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol over Nitrogen-Doped Carbon-Supported Iron Catalysts.

PubMed

Li, Jiang; Liu, Jun-Ling; Zhou, Hong-Jun; Fu, Yao

2016-06-08

Iron-based heterogeneous catalysts, which were generally prepared by pyrolysis of iron complexes on supports at elevated temperature, were found to be capable of catalyzing the transfer hydrogenation of furfural (FF) to furfuryl alcohol (FFA). The effects of metal precursor, nitrogen precursor, pyrolysis temperature, and support on catalytic performance were examined thoroughly, and a comprehensive study of the reaction parameters was also performed. The highest selectivity of FFA reached 83.0 % with a FF conversion of 91.6 % under the optimal reaction condition. Catalyst characterization suggested that iron cations coordinated by pyridinic nitrogen functionalities were responsible for the enhanced catalytic activity. The iron catalyst could be recycled without significant loss of catalytic activity for five runs, and the destruction of the nitrogen-iron species, the presence of crystallized Fe2 O3 phase, and the pore structure change were the main reasons for catalyst deactivation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Iron deficiency in ND-CKD: from diagnosis to treatment].

PubMed

Liberti, Maria Elena; Garofalo, Carlo; Sagliocca, Adelia; Borrelli, Silvio; Conte, Giuseppe; De Nicola, Luca; Minutolo, Roberto

2017-09-28

In non-dialysis-chronic kidney disease (CKD), iron deficiency is a frequent nutritional disorder due to either the greater tendency to occult gastrointestinal bleeding or to the chronic inflammatory state resulting in a reduced intestinal iron reabsorption through an increased synthesis of hepcidin. These phenomenon are responsible for a negative iron balance that compromises erythropoiesis and contributes to the pathogenesis of anemia in CKD. Several laboratory tests are now available to allow an adequate diagnosis of iron deficiency. Among the new parameters, the percentage of hypochromic red cells (% HYPO) and the reticulocyte hemoglobin content (CHr) are now considered as the most specific markers for diagnosing iron-deficiency erythropoiesis. Unfortunately, their implementation in clinical practice is limited by the scarce availability. In non-dialyzed CKD , subjects intolerant or non-responsive to oral iron therapy, can be effectively treated with novel intravenous iron preparations, such as iron carboxymaltose, that allow a complete and rapid correction of iron deficient anemia. Furthermore, this iron compound is associated with lower rate of adverse effects since the carbohydrate shell (carboxymaltose) is more stable than gluconate and saccarate thus reducing the release of free iron in the bloodstream. Of note, the possibility of administering this drug at high doses and reduced frequency decreases the risk of infusion reactions. Finally, a substantial economic saving mainly dependent on a reduction in indirect costs represents a further advantage in the use of iron carboxymaltose in this population. Copyright by Società Italiana di Nefrologia SIN, Rome, Italy.

Combining Textural Techniques to Explore Effects of Diagenesis and Low-grade Metamorphism on Iron Mineralogy and Iron Speciation

NASA Astrophysics Data System (ADS)

Slotznick, S. P.; Webb, S.; Eiler, J. M.; Kirschvink, J. L.; Fischer, W. W.

2016-12-01

Iron chemistry and mineralogy in the sedimentary rocks provide a valuable tool for studying paleoenvironmental conditions due to the fact that iron atoms can take on either the +II or +III valence state under geological redox conditions. One method utilizing this redox chemistry is `iron speciation', a bulk chemical sequential extraction technique that maps proportions of iron species to redox conditions empirically calibrated from modern sediments. However, all Precambrian and many Phanerozoic rocks have experienced post-depositional processes; it is vital to explore their effects on iron mineralogy and speciation. We combined light and electron microscopy, magnetic microscopy, (synchrotron-based) microprobe x-ray spectroscopy, and rock magnetic measurements in order to deconvolve secondary overprints from primary phases and provide quantitative measurement of iron minerals. These techniques were applied to excellently-preserved shale and siltstone samples of the 1.4 Ga lower Belt Supergroup, Montana and Idaho, USA, spanning a metamorphic gradient from sub-biotite to garnet zone. Previously measured Silurian-Devonian shales, sandstones, and carbonates in Maine and Vermont, USA spanning from the chlorite to kyanite zone provided additional well-constrained, quantitative data for comparison and to extend our analysis. In all of the studied samples, pyrrhotite formation occurred at the sub-biotite or sub-chlorite zone. Pyrrhotite was interpreted to form from pyrite and/or other iron phases based on lithology; these reactions can affect the paleoredox proxy. Iron carbonates can also severely influence iron speciation results since they often form in anoxic pore fluids during diagenesis; textural analyses of the Belt Supergroup samples highlighted that iron-bearing carbonates were early diagenetic cements or later diagenetic overprints. The inclusion of iron from diagenetic minerals during iron speciation analyses will skew results by providing a view of pore

Circulating non–transferrin-bound iron after oral administration of supplemental and fortification doses of iron to healthy women: a randomized study1234

PubMed Central

Andersson, Maria; Egli, Ines; Foman, Jasmin Tajeri; Zeder, Christophe; Westerman, Mark E; Hurrell, Richard F

2014-01-01

Background: After the oral administration of iron, the production of circulating non–transferrin-bound iron may contribute to an increased risk of illness in malaria-endemic areas that lack effective medical services. Objective: In healthy women with a range of body iron stores, we aimed to determine effects on the production of circulating non–transferrin-bound iron resulting from the oral administration of 1) a supplemental dose of iron (60 mg) with water, 2) a supplemental dose of iron (60 mg) with a standard test meal, and 3) a fortification dose of iron (6 mg) with a standard test meal. Design: With the use of serum ferritin as the indicator, healthy women with replete iron stores (ferritin concentration >25 μg/L; n = 16) and reduced iron stores (ferritin concentration ≤25 μg/L; n = 16) were enrolled in a prospective, randomized, crossover study. After the oral administration of aqueous solutions of ferrous sulfate isotopically labeled with 54Fe, 57Fe, or 58Fe, blood samples were collected for 8 h, and iron absorption was estimated by erythrocyte incorporation at 14 d. Results: At 4 h, serum non–transferrin-bound iron reached peaks with geometric mean (95% CI) concentrations of 0.81 μmol/L (0.56, 1.1 μmol/L) for 60 mg Fe with water and 0.26 μmol/L (0.15, 0.38 μmol/L) for 60 mg Fe with food but was at assay limits of detection (0.1 μmol Fe/L) for 6 mg Fe with food. For the 60 mg Fe without food, the area under the curve over 8 h for serum non–transferrin-bound iron was positively correlated with the amount of iron absorbed (R = 0.49, P < 0.01) and negatively correlated with serum ferritin (R = −0.39, P < 0.05). Conclusions: In healthy women, the production of circulating non–transferrin-bound iron is determined by the rate and amount of iron absorbed. The highest concentrations of non–transferrin-bound iron resulted from the administration of supplemental doses of iron without food. Little or no circulating non–transferrin-bound iron

A review of the antioxidant mechanisms of polyphenol compounds related to iron binding.

PubMed

Perron, Nathan R; Brumaghim, Julia L

2009-01-01

In this review, primary attention is given to the antioxidant (and prooxidant) activity of polyphenols arising from their interactions with iron both in vitro and in vivo. In addition, an overview of oxidative stress and the Fenton reaction is provided, as well as a discussion of the chemistry of iron binding by catecholate, gallate, and semiquinone ligands along with their stability constants, UV-vis spectra, stoichiometries in solution as a function of pH, rates of iron oxidation by O(2) upon polyphenol binding, and the published crystal structures for iron-polyphenol complexes. Radical scavenging mechanisms of polyphenols unrelated to iron binding, their interactions with copper, and the prooxidant activity of iron-polyphenol complexes are briefly discussed.

Influence of Atmospheric Processes on the Solubility and Composition of Iron in Saharan Dust.

PubMed

Longo, Amelia F; Feng, Yan; Lai, Barry; Landing, William M; Shelley, Rachel U; Nenes, Athanasios; Mihalopoulos, Nikolaos; Violaki, Kalliopi; Ingall, Ellery D

2016-07-05

Aerosol iron was examined in Saharan dust plumes using a combination of iron near-edge X-ray absorption spectroscopy and wet-chemical techniques. Aerosol samples were collected at three sites located in the Mediterranean, the Atlantic, and Bermuda to characterize iron at different atmospheric transport lengths and time scales. Iron(III) oxides were a component of aerosols at all sampling sites and dominated the aerosol iron in Mediterranean samples. In Atlantic samples, iron(II and III) sulfate, iron(III) phosphate, and iron(II) silicates were also contributors to aerosol composition. With increased atmospheric transport time, iron(II) sulfates are found to become more abundant, aerosol iron oxidation state became more reduced, and aerosol acidity increased. Atmospheric processing including acidic reactions and photoreduction likely influence the form of iron minerals and oxidation state in Saharan dust aerosols and contribute to increases in aerosol-iron solubility.

Anoxic photochemical oxidation of siderite generates molecular hydrogen and iron oxides

PubMed Central

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

2013-01-01

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

The role of T56 in controlling the flexibility of the distal histidine in dehaloperoxidase-hemoglobin from Amphitrite ornata.

PubMed

Jiang, Shu; Wright, Iain; Swartz, Paul; Franzen, Stefan

2013-10-01

The activation of dehaloperoxidase-hemoglobin (DHP) to form a ferryl intermediate requires the distal histidine, H55, to act as an acid base catalyst. The lack of ancillary amino acids in the distal pocket to assist in this process makes H55 even more important to the formation of active intermediates than in conventional peroxidases. Therefore, one can infer that the precise conformation H55 may greatly affect the enzymatic activity. Using site-direct mutagenesis at position T56, immediately adjacent to H55, we have confirmed that subtle changes in the conformation of H55 affect the catalytic efficiency of DHP. Mutating T56 to a smaller amino acid appears to permit H55 to rotate with relatively low barriers between conformations in the distal pocket, which may lead to an increase in catalytic activity. On the other hand, larger amino acids in the neighboring site appear to restrict the rotation of H55 due to the steric hindrance. In the case of T56V, which is an isosteric mutation, H55 appears less mobile, but forced to be closer to the heme iron than in wild type. Both proximity to the heme iron and flexibility of motion in some of the mutants can result in an increased catalytic rate, but can also lead to protein inactivation due to ligation of H55 to the heme iron, which is known as hemichrome formation. A balance of enzymatic rate and protein stability with respect to hemichrome formation appears to be optimum in wild type DHP (WT-DHP). Copyright © 2013 Elsevier B.V. All rights reserved.

Deferoxamine inhibition of malaria is independent of host iron status

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hershko, C.; Peto, T.E.

The mechanism whereby deferoxamine (DF) inhibits the growth of malaria parasites was studied in rats infected with Plasmodium berghei. Peak parasitemia was 32.6% (day 14) in untreated controls and 0.15% (day 7) in rats receiving 0.33 mg/g in 8 hourly DF injections, subcutaneously. DF inhibition of parasite growth was achieved without any reduction in transferrin saturation or hemoglobin synthesis and with only a partial (56%) depletion of hepatic iron stores. Dietary iron depletion resulted in anemia (hematocrit 25 vs. 46%), microcytosis (MCV 54 vs. 60 fl), and reduced transferrin saturation (17 vs. 96%) without any effect on infection (peak parasitemiamore » 30 vs. 36%). Similarly, parenteral iron loading with ferric citrate over 10 d (75 mg iron/kg) failed to aggravate infection. In a search for evidence of direct interaction between DF and parasitized erythrocytes, gel filtration and ultrafiltration was performed on hemolysates obtained from in vivo /sup 59/Fe-labeled parasitized erythrocytes. This showed that 1.1-1.9% of the intracellular radioiron was located in a chelatable, labile iron pool. Incubation of intact cells with 0-500 microM DF resulted in a proportional increase in intracellular iron chelation, and the chelation of all available labile intracellular iron was completed within 6 h. These observations indicate that the severity of P. berghei infection in rats and its in vivo suppression by DF are independent of host iron status and suggest that DF inhibition of malaria involves intracellular chelation of a labile iron pool in parasitized erythrocytes.« less

A Computational Model of Liver Iron Metabolism

PubMed Central

Mitchell, Simon; Mendes, Pedro

2013-01-01

Iron is essential for all known life due to its redox properties; however, these same properties can also lead to its toxicity in overload through the production of reactive oxygen species. Robust systemic and cellular control are required to maintain safe levels of iron, and the liver seems to be where this regulation is mainly located. Iron misregulation is implicated in many diseases, and as our understanding of iron metabolism improves, the list of iron-related disorders grows. Recent developments have resulted in greater knowledge of the fate of iron in the body and have led to a detailed map of its metabolism; however, a quantitative understanding at the systems level of how its components interact to produce tight regulation remains elusive. A mechanistic computational model of human liver iron metabolism, which includes the core regulatory components, is presented here. It was constructed based on known mechanisms of regulation and on their kinetic properties, obtained from several publications. The model was then quantitatively validated by comparing its results with previously published physiological data, and it is able to reproduce multiple experimental findings. A time course simulation following an oral dose of iron was compared to a clinical time course study and the simulation was found to recreate the dynamics and time scale of the systems response to iron challenge. A disease state simulation of haemochromatosis was created by altering a single reaction parameter that mimics a human haemochromatosis gene (HFE) mutation. The simulation provides a quantitative understanding of the liver iron overload that arises in this disease. This model supports and supplements understanding of the role of the liver as an iron sensor and provides a framework for further modelling, including simulations to identify valuable drug targets and design of experiments to improve further our knowledge of this system. PMID:24244122

Ba3Fe1.56Ir1.44O9: A Polar Semiconducting Triple Perovskite with Near Room Temperature Magnetic Ordering.

PubMed

Ferreira, Timothy; Carone, Darren; Huon, Amanda; Herklotz, Andreas; Stoian, Sebastian A; Heald, Steve M; Morrison, Gregory; Smith, Mark D; Loye, Hans-Conrad Zur

2018-05-29

The crystal chemistry and magnetic properties for two triple perovskites, Ba 3 Fe 1.56 Ir 1.44 O 9 and Ba 3 NiIr 2 O 9 , grown as large, highly faceted single crystals from a molten strontium carbonate flux, are reported. Unlike the idealized A 3 MM 2 'O 9 hexagonal symmetry characteristic of most triple perovskites, including Ba 3 NiIr 2 O 9, Ba 3 Fe 1.56 Ir 1.44 O 9 possesses significant site-disorder, resulting in a noncentrosymmetric polar structure with trigonal symmetry. The valence of iron and iridium in the heavily distorted Fe/Ir sites was determined to be Fe(III) and Ir(V) by X-ray absorption near edge spectroscopy (XANES). Density functional theory calculations were conducted to understand the effect of the trigonal distortion on the local Fe(III)O 6 electronic structure, and the spin state of iron was determined to be S = 5/2 by Mössbauer spectroscopy. Conductivity measurements indicate thermally activated semiconducting behavior in the trigonal perovskite. Magnetic properties were measured and near room temperature magnetic ordering (T N = 270 K) was observed for Ba 3 Fe 1.56 Ir 1.44 O 9 .

Detection of Remarkably Low Isotopic Ratio of Iron in Anthropogenic Aerosols and Evaluation of its Contribution to the Surface Ocean

NASA Astrophysics Data System (ADS)

Kurisu, M.; Iizuka, T.; Sakata, K.; Uematsu, M.; Takahashi, Y.

2015-12-01

It has been reported that phytoplankton growth in the High Nutrient-Low Chlorophyll (HNLC) regions is limited by dissolved iron (DFe) concentration (e.g., Martin and Fitzwater, 1988). Aerosol is known as one of the dominant sources of DFe to the ocean and classified into two origins such as anthropogenic and natural. A series of recent studies showed that Fe in anthropogenic aerosols is more soluble than that in natural aerosols (Takahashi et al., 2013) and has lower isotopic ratio (Mead et al., 2013). However, the difference between Fe isotopic ratio　(δ56Fe: [(56Fe/54Fe)sample/(56Fe/54Fe)IRMM-14]-1) of two origins reported in Mead et al. (2013) is not so large compared with the standard deviation. Therefore, the aim of this study is to determine Fe species and δ56Fe in anthropogenic aerosols more accurately and to evaluate its contribution to the ocean surface. Iron species were determined by X-ray absorption fine structure (XAFS) analysis, while δ56Fe in size-fractionated aerosols were measured by MC-ICP-MS (NEPTUNE Plus) after chemical separation using anion exchange resin. Dominant Fe species in the samples were, ferrihydrite, hematite, and biotite. It was also revealed that coarse particles contained a larger amount of biotite and that fine particles contained a larger amount of hematite, which suggested that anthropogenic aerosols were emitted during combustion processes. In addition, results of Fe isotopic ratio analysis suggested that δ56Fe of coarse particles were around +0.25‰, whereas that of fine particles were -0.5 ˜ -2‰, which was lower than the δ56Fe in anthropogenic aerosol by Mead et al. (2013). The size-fractionated sampling made it possible to determine the δ56Fe in anthropogenic aerosol. Soluble component in fine particles extracted by simulated rain water also showed much lower δ56Fe (δ56Fe = -3.9±0.12‰), suggesting that anthropogenic Fe has much lower isotopic ratio. The remarkably low δ56Fe may be caused by the

Synthetic and natural iron chelators: therapeutic potential and clinical use

PubMed Central

Hatcher, Heather C; Singh, Ravi N; Torti, Frank M; Torti, Suzy V

2013-01-01

Iron-chelation therapy has its origins in the treatment of iron-overload syndromes. For many years, the standard for this purpose has been deferoxamine. Recently, considerable progress has been made in identifying synthetic chelators with improved pharmacologic properties relative to deferoxamine. Most notable are deferasirox (Exjade®) and deferiprone (Ferriprox®), which are now available clinically. In addition to treatment of iron overload, there is an emerging role for iron chelators in the treatment of diseases characterized by oxidative stress, including cardiovascular disease, atherosclerosis, neurodegenerative diseases and cancer. While iron is not regarded as the underlying cause of these diseases, it does play an important role in disease progression, either through promotion of cellular growth and proliferation or through participation in redox reactions that catalyze the formation of reactive oxygen species and increase oxidative stress. Thus, iron chelators may be of therapeutic benefit in many of these conditions. Phytochemicals, many of which bind iron, may also owe some of their beneficial properties to iron chelation. This review will focus on the advances in iron-chelation therapy for the treatment of iron-overload disease and cancer, as well as neurodegenerative and chronic inflammatory diseases. Established and novel iron chelators will be discussed, as well as the emerging role of dietary plant polyphenols that effectively modulate iron biochemistry. PMID:21425984

Secreted Citrate Serves as Iron Carrier for the Marine Pathogen Photobacterium damselae subsp damselae

PubMed Central

Balado, Miguel; Puentes, Beatriz; Couceiro, Lucía; Fuentes-Monteverde, Juan C.; Rodríguez, Jaime; Osorio, Carlos R.; Jiménez, Carlos; Lemos, Manuel L.

2017-01-01

Photobacterium damselae subsp damselae (Pdd) is a Vibrionaceae that has a wide pathogenic potential against many marine animals and also against humans. Some strains of this bacterium acquire iron through the siderophore vibrioferrin. However, there are virulent strains that do not produce vibrioferrin, but they still give a strong positive reaction in the CAS test for siderophore production. In an in silico search on the genome sequences of this type of strains we could not find any ORF which could be related to a siderophore system. To identify genes that could encode a siderophore-mediated iron acquisition system we used a mini-Tn10 transposon random mutagenesis approach. From more than 1,400 mutants examined, we could isolate a mutant (BP53) that showed a strong CAS reaction independently of the iron levels of the medium. In this mutant the transposon was inserted into the idh gene, which encodes an isocitrate dehydrogenase that participates in the tricarboxylic acid cycle. The mutant did not show any growth impairment in rich or minimal media, but it accumulated a noticeable amount of citrate (around 7 mM) in the culture medium, irrespective of the iron levels. The parental strain accumulated citrate, but in an iron-regulated fashion, being citrate levels 5–6 times higher under iron restricted conditions. In addition, a null mutant deficient in citrate synthase showed an impairment for growth at high concentrations of iron chelators, and showed almost no reaction in the CAS test. Chemical analysis by liquid chromatography of the iron-restricted culture supernatants resulted in a CAS-positive fraction with biological activity as siderophore. HPLC purification of that fraction yielded a pure compound which was identified as citrate from its MS and NMR spectral data. Although the production of another citrate-based compound with siderophore activity cannot be ruled out, our results suggest that Pdd secretes endogenous citrate and use it for iron scavenging from

Disproportionation of hydroxylamine by water-soluble iron(III) porphyrinate compounds.

PubMed

Bari, Sara E; Amorebieta, Valentín T; Gutiérrez, María M; Olabe, José A; Doctorovich, Fabio

2010-01-01

The reactions of hydroxylamine (HA) with several water-soluble iron(III) porphyrinate compounds, namely iron(III) meso-tetrakis-(N-ethylpyridinium-2yl)-porphyrinate ([Fe(III)(TEPyP)](5+)), iron(III) meso-tetrakis-(4-sulphonatophenyl)-porphyrinate ([Fe(III)(TPPS)](3-)), and microperoxidase 11 ([Fe(III)(MP11)]) were studied for different [Fe(III)(Porph)]/[HA] ratios, under anaerobic conditions at neutral pH. Efficient catalytic processes leading to the disproportionation of HA by these iron(III) porphyrinates were evidenced for the first time. As a common feature, only N(2) and N(2)O were found as gaseous, nitrogen-containing oxidation products, while NH(3) was the unique reduced species detected. Different N(2)/N(2)O ratios obtained with these three porphyrinates strongly suggest distinctive mechanistic scenarios: while [Fe(III)(TEPyP)](5+) and [Fe(III)(MP11)] formed unknown steady-state porphyrinic intermediates in the presence of HA, [Fe(III)(TPPS)](3-) led to the well characterized soluble intermediate, [Fe(II)(TPPS)NO](4-). Free-radical formation was only evidenced for [Fe(III)(TEPyP)](5+), as a consequence of a metal centered reduction. We discuss the catalytic pathways of HA disproportionation on the basis of the distribution of gaseous products, free radicals formation, the nature of porphyrinic intermediates, the Fe(II)/Fe(III) redox potential, the coordinating capabilities of each complex, and the kinetic analysis. The absence of NO(2)(-) revealed either that no HAO-like activity was operative under our reaction conditions, or that NO(2)(-), if formed, was consumed in the reaction milieu.

Iron Homeostasis and Nutritional Iron Deficiency123

PubMed Central

Theil, Elizabeth C.

2011-01-01

Nonheme food ferritin (FTN) iron minerals, nonheme iron complexes, and heme iron contribute to the balance between food iron absorption and body iron homeostasis. Iron absorption depends on membrane transporter proteins DMT1, PCP/HCP1, ferroportin (FPN), TRF2, and matriptase 2. Mutations in DMT1 and matriptase-2 cause iron deficiency; mutations in FPN, HFE, and TRF2 cause iron excess. Intracellular iron homeostasis depends on coordinated regulation of iron trafficking and storage proteins encoded in iron responsive element (IRE)-mRNA. The noncoding IRE-mRNA structures bind protein repressors, IRP1 or 2, during iron deficiency. Integration of the IRE-RNA in translation regulators (near the cap) or turnover elements (after the coding region) increases iron uptake (DMT1/TRF1) or decreases iron storage/efflux (FTN/FPN) when IRP binds. An antioxidant response element in FTN DNA binds Bach1, a heme-sensitive transcription factor that coordinates expression among antioxidant response proteins like FTN, thioredoxin reductase, and quinone reductase. FTN, an antioxidant because Fe2+ and O2 (reactive oxygen species generators) are consumed to make iron mineral, is also a nutritional iron concentrate that is an efficiently absorbed, nonheme source of iron from whole legumes. FTN protein cages contain thousands of mineralized iron atoms and enter cells by receptor-mediated endocytosis, an absorption mechanism distinct from transport of nonheme iron salts (ferrous sulfate), iron chelators (ferric-EDTA), or heme. Recognition of 2 nutritional nonheme iron sources, small and large (FTN), will aid the solution of iron deficiency, a major public health problem, and the development of new policies on iron nutrition. PMID:21346101

Influence of atmospheric processes on the solubility and composition of iron in Saharan dust

DOE PAGES

Longo, Amelia F.; Feng, Yan; Lai, Barry; ...

2016-06-10

Aerosol iron was examined in Saharan dust plumes using a combination of iron near-edge X-ray absorption spectroscopy and wet-chemical techniques. Aerosol samples were collected at three sites located in the Mediterranean, the Atlantic, and Bermuda to characterize iron at different atmospheric transport lengths and time scales. Iron(III) oxides were a component of aerosols at all sampling sites and dominated the aerosol iron in Mediterranean samples. In Atlantic samples, iron(II and III) sulfate, iron(III) phosphate, and iron(II) silicates were also contributors to aerosol composition. With increased atmospheric transport time, iron(II) sulfates are found to become more abundant, aerosol iron oxidation statemore » became more reduced, and aerosol acidity increased. As a result, atmospheric processing including acidic reactions and photoreduction likely influence the form of iron minerals and oxidation state in Saharan dust aerosols and contribute to increases in aerosol-iron solubility.« less

Oncoidal granular iron formation in the Mesoarchaean Pongola Supergroup, southern Africa: Textural and geochemical evidence for biological activity during iron deposition.

PubMed

Smith, A J B; Beukes, N J; Gutzmer, J; Czaja, A D; Johnson, C M; Nhleko, N

2017-11-01

We document the discovery of the first granular iron formation (GIF) of Archaean age and present textural and geochemical results that suggest these formed through microbial iron oxidation. The GIF occurs in the Nconga Formation of the ca. 3.0-2.8 Ga Pongola Supergroup in South Africa and Swaziland. It is interbedded with oxide and silicate facies micritic iron formation (MIF). There is a strong textural control on iron mineralization in the GIF not observed in the associated MIF. The GIF is marked by oncoids with chert cores surrounded by magnetite and calcite rims. These rims show laminated domal textures, similar in appearance to microstromatolites. The GIF is enriched in silica and depleted in Fe relative to the interbedded MIF. Very low Al and trace element contents in the GIF indicate that chemically precipitated chert was reworked above wave base into granules in an environment devoid of siliciclastic input. Microbially mediated iron precipitation resulted in the formation of irregular, domal rims around the chert granules. During storm surges, oncoids were transported and deposited in deeper water environments. Textural features, along with positive δ 56 Fe values in magnetite, suggest that iron precipitation occurred through incomplete oxidation of hydrothermal Fe 2+ by iron-oxidizing bacteria. The initial Fe 3+ -oxyhydroxide precipitates were then post-depositionally transformed to magnetite. Comparison of the Fe isotope compositions of the oncoidal GIF with those reported for the interbedded deeper water iron formation (IF) illustrates that the Fe 2+ pathways and sources for these units were distinct. It is suggested that the deeper water IF was deposited from the evolved margin of a buoyant Fe 2+ aq -rich hydrothermal plume distal to its source. In contrast, oncolitic magnetite rims of chert granules were sourced from ambient Fe 2+ aq -depleted shallow ocean water beyond the plume. © 2017 John Wiley & Sons Ltd.

Non-invasive detection of iron deficiency by fluorescence measurement of erythrocyte zinc protoporphyrin in the lip

PubMed Central

Hennig, Georg; Homann, Christian; Teksan, Ilknur; Hasbargen, Uwe; Hasmüller, Stephan; Holdt, Lesca M.; Khaled, Nadia; Sroka, Ronald; Stauch, Thomas; Stepp, Herbert; Vogeser, Michael; Brittenham, Gary M.

2016-01-01

Worldwide, more individuals have iron deficiency than any other health problem. Most of those affected are unaware of their lack of iron, in part because detection of iron deficiency has required a blood sample. Here we report a non-invasive method to optically measure an established indicator of iron status, red blood cell zinc protoporphyrin, in the microcirculation of the lower lip. An optical fibre probe is used to illuminate the lip and acquire fluorescence emission spectra in ∼1 min. Dual-wavelength excitation with spectral fitting is used to distinguish the faint zinc protoporphyrin fluorescence from the much greater tissue background fluorescence, providing immediate results. In 56 women, 35 of whom were iron-deficient, the sensitivity and specificity of optical non-invasive detection of iron deficiency were 97% and 90%, respectively. This fluorescence method potentially provides a rapid, easy to use means for point-of-care screening for iron deficiency in resource-limited settings lacking laboratory infrastructure. PMID:26883939

Pivotal Role of Iron in the Regulation of Cyanobacterial Electron Transport.

PubMed

González, A; Sevilla, E; Bes, M T; Peleato, M L; Fillat, M F

2016-01-01

Iron-containing metalloproteins are the main cornerstones for efficient electron transport in biological systems. The abundance and diversity of iron-dependent proteins in cyanobacteria makes those organisms highly dependent of this micronutrient. To cope with iron imbalance, cyanobacteria have developed a survey of adaptation strategies that are strongly related to the regulation of photosynthesis, nitrogen metabolism and other central electron transfer pathways. Furthermore, either in its ferrous form or as a component of the haem group, iron plays a crucial role as regulatory signalling molecule that directly or indirectly modulates the composition and efficiency of cyanobacterial redox reactions. We present here the major mechanism used by cyanobacteria to couple iron homeostasis to the regulation of electron transport, making special emphasis in processes specific in those organisms. © 2016 Elsevier Ltd. All rights reserved.

Graphene oxide nanoplatforms to enhance catalytic performance of iron phthalocyanine for oxygen reduction reaction in bioelectrochemical systems

NASA Astrophysics Data System (ADS)

Costa de Oliveira, Maida Aysla; Mecheri, Barbara; D'Epifanio, Alessandra; Placidi, Ernesto; Arciprete, Fabrizio; Valentini, Federica; Perandini, Alessando; Valentini, Veronica; Licoccia, Silvia

2017-07-01

We report the development of electrocatalysts based on iron phthalocyanine (FePc) supported on graphene oxide (GO), obtained by electrochemical oxidation of graphite in aqueous solution of LiCl, LiClO4, and NaClO4. Structure, surface chemistry, morphology, and thermal stability of the prepared materials were investigated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, atomic force microscopy (AFM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The catalytic activity toward oxygen reduction reaction (ORR) at neutral pH was evaluated by cyclic voltammetry. The experimental results demonstrate that the oxidation degree of GO supports affects the overall catalytic activity of FePc/GO, due to a modulation effect of the interaction between FePc and the basal plane of GO. On the basis of electrochemical, spectroscopic, and morphological investigations, FePc/GO_LiCl was selected to be assembled at the cathode side of a microbial fuel cell prototype, demonstrating a good electrochemical performance in terms of voltage and power generation.

Alginate Inhibits Iron Absorption from Ferrous Gluconate in a Randomized Controlled Trial and Reduces Iron Uptake into Caco-2 Cells

PubMed Central

Wawer, Anna A.; Harvey, Linda J.; Dainty, Jack R.; Perez-Moral, Natalia; Sharp, Paul; Fairweather-Tait, Susan J.

2014-01-01

Previous in vitro results indicated that alginate beads might be a useful vehicle for food iron fortification. A human study was undertaken to test the hypothesis that alginate enhances iron absorption. A randomised, single blinded, cross-over trial was carried out in which iron absorption was measured from serum iron appearance after a test meal. Overnight-fasted volunteers (n = 15) were given a test meal of 200 g cola-flavoured jelly plus 21 mg iron as ferrous gluconate, either in alginate beads mixed into the jelly or in a capsule. Iron absorption was lower from the alginate beads than from ferrous gluconate (8.5% and 12.6% respectively, p = 0.003). Sub-group B (n = 9) consumed the test meals together with 600 mg calcium to determine whether alginate modified the inhibitory effect of calcium. Calcium reduced iron absorption from ferrous gluconate by 51%, from 11.5% to 5.6% (p = 0.014), and from alginate beads by 37%, from 8.3% to 5.2% (p = 0.009). In vitro studies using Caco-2 cells were designed to explore the reasons for the difference between the previous in vitro findings and the human study; confirmed the inhibitory effect of alginate. Beads similar to those used in the human study were subjected to simulated gastrointestinal digestion, with and without cola jelly, and the digestate applied to Caco-2 cells. Both alginate and cola jelly significantly reduced iron uptake into the cells, by 34% (p = 0.009) and 35% (p = 0.003) respectively. The combination of cola jelly and calcium produced a very low ferritin response, 16.5% (p<0.001) of that observed with ferrous gluconate alone. The results of these studies demonstrate that alginate beads are not a useful delivery system for soluble salts of iron for the purpose of food fortification. Trial Registration ClinicalTrials.gov NCT01528644 PMID:25391138

The variability in iron speciation in size fractionated residual oil fly ash particulate matter (ROFA PM).

PubMed

Pattanaik, Sidhartha; Huggins, Frank E; Huffman, Gerald P

2016-08-15

Ambient particulate matter (PM) containing iron can catalyze Fenton reaction leading to the production of reactive oxygen species in cells. It can also catalyze atmospheric redox reaction. These reactions are governed by the physicochemical characteristics of iron in ambient PM. As a surrogate for ambient PM, we prepared residual oil fly ash PM (ROFA PM) in a practical fire tube boiler firing residual oils with varying sulfur and ash contents. The ROFA particles were resolved into fine PM or PM2.5 (aerodynamic diameter (AD)<2.5μm) and coarse PM or PM2.5+ (AD between 2.5μm and 50μm). The iron speciation in PM2.5+ was ascertained using X-ray absorption spectroscopy and leaching method while that in PM2.5 was reported earlier. The results of both studies are compared to get an insight into the variability in the iron speciation in different size fractions. The results show the predominance of ferric sulfate, with a minor spinal ferrite in both PM (i.e. ZnxNi1-xFe2O4 in PM2.5, ZnFe2O4 in PM2.5+). The iron solubility in ROFA PM depends on its speciation, mode of incorporation of iron into particle's carbonaceous matrix, the grade and composition of oils, and pH of the medium. The soluble fraction of iron in PM is critical in assessing its interaction with the biological systems and its toxic potential. Copyright © 2016 Elsevier B.V. All rights reserved.

Evaluation of pain and inflammation associated with hot iron branding and microchip transponder injection in horses.

PubMed

Lindegaard, Casper; Vaabengaard, Dorte; Christophersen, Mogens T; Ekstøm, Claus T; Fjeldborg, Julie

2009-07-01

To compare effects of hot iron branding and microchip transponder injection regarding aversive behavioral reactions indicative of pain and inflammation in horses. 7 adult horses. In a randomized controlled clinical crossover study, behavioral reactions to hot iron branding and microchip transponder injection were scored by 4 observers. Local and systemic inflammation including allodynia were assessed and compared by use of physiologic and biochemical responses obtained repeatedly for the 168-hour study period. Serum cortisol concentration was measured repeatedly throughout the first 24 hours of the study. Sham treatments were performed 1 day before and 7 days after treatments. Hot iron branding elicited a significantly stronger aversive reaction indicative of pain than did microchip transponder injection (odds ratio [OR], 12.83). Allodynia quantified by means of skin sensitivity to von Frey monofilaments was significantly greater after hot iron branding than after microchip transponder injection (OR, 2.59). Neither treatment induced signs of spontaneously occurring pain that were observed during the remaining study period, and neither treatment induced increased serum cortisol concentrations. Comparison with sham treatments indicated no memory of an unpleasant event. The hot iron branding areas had significantly increased skin temperature and swelling (OR, 14.6). Systemic inflammation as measured via serum amyloid A concentration was not detected after any of the treatments. Microchip transponder injection induced less signs of pain and inflammation and did not seem to pose a higher long-term risk than hot iron branding. Consequently, results indicated that hot iron branding does inflict more pain and should be abandoned where possible.

Electrochemical behavior of meso-substituted iron porphyrins in alkaline aqueous media

NASA Astrophysics Data System (ADS)

Berezina, N. M.; Bazanov, M. I.; Maksimova, A. A.; Semeikin, A. S.

2017-12-01

The effect meso-substitution in iron porphyrin complexes has on their redox behavior in alkaline aqueous solutions is studied via cyclic voltammetry. The voltammetric features of the reduction of iron pyridylporphyrins suggest that the sites of electron transfer lie at the ligand, the metal ion, and the pyridyl moieties. The electron transfer reactions between the different forms of these compounds, including the oxygen reduction reaction they mediate, are outlined to show the sequence and potential ranges in which they occur in alkaline aqueous media. Under our experimental conditions, the iron porphyrins exist as μ-oxo dimmers whose activity for the electrocatalytic reduction of oxygen displays a considerable dependence on the nature of the substitutents and nitrogen isomerization (for pyridylporphyrins) and grows in the order (Fe( ms-Ph)4P)2O, (Fe[ ms-(Py-3)Ph3]P)2O, (Fe[ ms-(Py-4)4]P)2O, and (Fe[ ms-(Py-3)4]P)2O.

Hydrogen-bearing iron peroxide and the origin of ultralow-velocity zones

NASA Astrophysics Data System (ADS)

Liu, Jin; Hu, Qingyang; Young Kim, Duck; Wu, Zhongqing; Wang, Wenzhong; Xiao, Yuming; Chow, Paul; Meng, Yue; Prakapenka, Vitali B.; Mao, Ho-Kwang; Mao, Wendy L.

2017-11-01

Ultralow-velocity zones (ULVZs) at Earth’s core-mantle boundary region have important implications for the chemical composition and thermal structure of our planet, but their origin has long been debated. Hydrogen-bearing iron peroxide (FeO2Hx) in the pyrite-type crystal structure was recently found to be stable under the conditions of the lowermost mantle. Using high-pressure experiments and theoretical calculations, we find that iron peroxide with a varying amount of hydrogen has a high density and high Poisson ratio as well as extremely low sound velocities consistent with ULVZs. Here we also report a reaction between iron and water at 86 gigapascals and 2,200 kelvin that produces FeO2Hx. This would provide a mechanism for generating the observed volume occupied by ULVZs through the reaction of about one-tenth the mass of Earth’s ocean water in subducted hydrous minerals with the effectively unlimited reservoir of iron in Earth’s core. Unlike other candidates for the composition of ULVZs, FeO2Hx synthesized from the superoxidation of iron by water would not require an extra transportation mechanism to migrate to the core-mantle boundary. These dense FeO2Hx-rich domains would be expected to form directly in the core-mantle boundary region and their properties would provide an explanation for the many enigmatic seismic features that are observed in ULVZs.

Oxidation of dissolved iron under warmer, wetter conditions on Mars: Transitions to present-day arid environments

NASA Technical Reports Server (NTRS)

Burns, R. G.

1993-01-01

The copious deposits of ferric-iron assemblages littering the surface of bright regions of Mars indicate that efficient oxidative weathering reactions have taken place during the evolution of the planet. Because the kinetics of atmosphere-surface (gas-solid) reactions are considerably slower than chemical weathering reactions involving an aqueous medium, most of the oxidation products now present in the martian regolith probably formed when groundwater flowed near the surface. This paper examines how chemical weathering reactions were effected by climatic variations when warm, wet environments became arid on Mars. Analogies are drawn with hydrogeochemical and weathering environments on the Australian continent where present-day oxidation of iron is occurring in acidic ground water under arid conditions.

Tungsten carbide encapsulated in nitrogen-doped carbon with iron/cobalt carbides electrocatalyst for oxygen reduction reaction

NASA Astrophysics Data System (ADS)

Zhang, Jie; Chen, Jinwei; Jiang, Yiwu; Zhou, Feilong; Wang, Gang; Wang, Ruilin

2016-12-01

This work presents a type of hybrid catalyst prepared through an environmental and simple method, combining a pyrolysis of transition metal precursors, a nitrogen-containing material, and a tungsten source to achieve a one-pot synthesis of N-doping carbon, tungsten carbides, and iron/cobalt carbides (Fe/Co/WC@NC). The obtained Fe/Co/WC@NC consists of uniform Fe3C and Co3C nanoparticles encapsulated in graphitized carbon with surface nitrogen doping, closely wrapped around a plate-like tungsten carbide (WC) that functions as an efficient oxygen reduction reaction (ORR) catalyst. The introduction of WC is found to promote the ORR activity of Fe/Co-based carbide electrocatalysts, which is attributed to the synergistic catalysts of WC, Fe3C, and Co3C. Results suggest that the composite exhibits comparable electrocatalytic activity, higher durability, and ability for methanol tolerance compared with commercial Pt/C for ORR in alkaline electrolyte. These advantages make Fe/Co/WC@NC a promising ORR electrocatalyst and a cost-effective alternative to Pt/C for practical application as fuel cell.

Hydrogen Plasma Processing of Iron Ore

NASA Astrophysics Data System (ADS)

Sabat, Kali Charan; Murphy, Anthony B.

2017-06-01

Iron is currently produced by carbothermic reduction of oxide ores. This is a multiple-stage process that requires large-scale equipment and high capital investment, and produces large amounts of CO2. An alternative to carbothermic reduction is reduction using a hydrogen plasma, which comprises vibrationally excited molecular, atomic, and ionic states of hydrogen, all of which can reduce iron oxides, even at low temperatures. Besides the thermodynamic and kinetic advantages of a hydrogen plasma, the byproduct of the reaction is water, which does not pose any environmental problems. A review of the theory and practice of iron ore reduction using a hydrogen plasma is presented. The thermodynamic and kinetic aspects are considered, with molecular, atomic and ionic hydrogen considered separately. The importance of vibrationally excited hydrogen molecules in overcoming the activation energy barriers, and in transferring energy to the iron oxide, is emphasized. Both thermal and nonthermal plasmas are considered. The thermophysical properties of hydrogen and argon-hydrogen plasmas are discussed, and their influence on the constriction and flow in the of arc plasmas is considered. The published R&D on hydrogen plasma reduction of iron oxide is reviewed, with both the reduction of molten iron ore and in-flight reduction of iron ore particles being considered. Finally, the technical and economic feasibility of the process are discussed. It is shown that hydrogen plasma processing requires less energy than carbothermic reduction, mainly because pelletization, sintering, and cokemaking are not required. Moreover, the formation of the greenhouse gas CO2 as a byproduct is avoided. In-flight reduction has the potential for a throughput at least equivalent to the blast furnace process. It is concluded that hydrogen plasma reduction of iron ore is a potentially attractive alternative to standard methods.

Protocol to determine accurate absorption coefficients for iron containing transferrins

PubMed Central

James, Nicholas G.; Mason, Anne B.

2008-01-01

An accurate protein concentration is an essential component of most biochemical experiments. The simplest method to determine a protein concentration is by measuring the A280, using an absorption coefficient (ε), and applying the Beer-Lambert law. For some metalloproteins (including all transferrin family members) difficulties arise because metal binding contributes to the A280 in a non-linear manner. The Edelhoch method is based on the assumption that the ε of a denatured protein in 6 M guanidine-HCl can be calculated from the number of the tryptophan, tyrosine, and cystine residues. We extend this method to derive ε values for both apo- and iron-bound transferrins. The absorbance of an identical amount of iron containing protein is measured in: 1) 6 M guanidine-HCl (denatured, no iron); 2) pH 7.4 buffer (non-denatured with iron); and 3) pH 5.6 (or lower) buffer with a chelator (non-denatured without iron). Since the iron free apo-protein has an identical A280 under non-denaturing conditions, the difference between the reading at pH 7.4 and the lower pH directly reports the contribution of the iron. The method is fast and consumes ~1 mg of sample. The ability to determine accurate ε values for transferrin mutants that bind iron with a wide range of affinities has proven very useful; furthermore a similar approach could easily be followed to determine ε values for other metalloproteins in which metal binding contributes to the A280. PMID:18471984

Safety Profile of Oral Iron Chelator Deferiprone in Chinese Children with Transfusion-Dependent Thalassaemia.

PubMed

Botzenhardt, Sebastian; Sing, Chor W; Wong, Ian C K; Chan, Godfrey Chi-Fung; Wong, Lisa Y L; Felisi, Mariagrazia; Rascher, Wolfgang; Ceci, Adriana; Neubert, Antje

2016-01-01

There is a lack of knowledge regarding the incidence of serious adverse drug reactions (ADR) to the oral iron chelator deferiprone in Chinese children with transfusion-dependent thalassaemia. In this retrospective population-based cohort study, paediatric thalassaemia patients in Hong Kong were screened for serious and medically important adverse events related to deferiprone therapy using diagnosis codes, laboratory data and hospital admissions. Potential ADRs were assessed by reviewing concomitant medications, diagnoses and laboratory data and evaluated using standardised causality assessment. Eighty-seven patients contributing 169.8 person-years were included. Thirty ADRs were identified in 21 patients. Most ADRs (56.0%) occurred in the first three months of therapy. Neutropenia occurred in 11 patients (12.6%; incidence rate 6.5 per 100 patient-years) and severe neutropenia (agranulocytosis) was observed in 5 patients (5.7%, incidence rate 2.9 per 100 patient-years). Other identified ADRs involve severe arthropathy, elevated liver enzymes and mild thrombocytopenia. In conclusion, the safety profile of DFP therapy in Chinese children suffering from transfusion-dependent thalassaemia is in line with previous studies of non-Chinese children. However, unlike previous studies, we observed a relatively high incidence of agranulocytosis and neutropenia in patients with simultaneous combined therapy. Hence close monitoring for white blood cell counts is advised in Chinese children under combined iron chelation therapy. Further prospective clinical and pharmacogenetic studies are required to better evaluate this important safety signal. • Half of the identified ADRs related to deferiprone therapy occurred during the first three months of treatment. • A relatively high incidence of agranulocytosis and neutropenia. Hence close monitoring for white blood cell counts is advised in Chinese children under combined iron chelation therapy.

Regulation of reaction forces during the golf swing.

PubMed

McNitt-Gray, J L; Munaretto, J; Zaferiou, A; Requejo, P S; Flashner, H

2013-06-01

During the golf swing, the reaction forces applied at the feet control translation and rotation of the body-club system. In this study, we hypothesized that skilled players using a 6-iron would regulate shot distance by scaling the magnitude of the resultant horizontal reaction force applied to the each foot with minimal modifications in force direction. Skilled players (n = 12) hit golf balls using a 6-iron. Shot distance was varied by hitting the ball as they would normally and when reducing shot distance using the same club. During each swing, reaction forces were measured using dual force plates (1200 Hz) and three-dimensional kinematics were simultaneously captured (110 Hz). The results indicate that, on average, the peak resultant horizontal reaction forces of the target leg were significantly less than normal (5%, p < 0.05) when reducing shot distance. No significant differences in the orientation of the peak resultant horizontal reaction forces were observed. Resultant horizontal reaction force-angle relationships within leg and temporal relationships between target and rear legs during the swing were consistent within player across shot conditions. Regulation of force magnitude with minimal modification in force direction is expected to provide advantages from muscle activation, coordination, and performance points of view.

Effect of thiamine hydrochloride on the redox reactions of iron at pyrite surface. [Fourth quarterly techical progress report, September 1990--November 1990

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pesic, B.; Oliver, D.J.

1990-12-31

The present investigation is a part of our studies on the electro chemical aspects of pyrite bioleaching involving Thiobacillus ferrooxidans. Previously (1,2) we have examined the effect of T. ferrooxidans and their metabolic products on the redox reactions of Fe{sup 2+}/Fe{sup 3+} couple at the pyrite surface. Results obtained suggest that beyond 1. 5 days during their growth in a batch fermenter, the bacteria and their metabolic products completely cover the pyrite surface and shut down all electron transfer across the electrode-solution interface. In addition, it has been observed that the bacteria serve as the nucleation site for jarosite formation,more » which is found detrimental to bioleaching. In the present work we have focussed on the effect of the presence of vitamins on the redox chemistry of iron. Our examination of the effect of the presence of thiamine hydrochloride in the redox behavior of Fe{sup 2+}/Fe{sup 3+} at the pyrite surface has revealed that thiamine hydrochloride does not undergo chemical interaction with ferrous or ferric iron. However, it may adsorb onto the pyrite surface causing polarization of the pyrite electrode.« less

Viable cold-tolerant iron-reducing microorganisms in geographically diverse subglacial environments

NASA Astrophysics Data System (ADS)

Nixon, Sophie L.; Telling, Jon P.; Wadham, Jemma L.; Cockell, Charles S.

2017-03-01

Subglacial environments are known to harbour metabolically diverse microbial communities. These microbial communities drive chemical weathering of underlying bedrock and influence the geochemistry of glacial meltwater. Despite its importance in weathering reactions, the microbial cycling of iron in subglacial environments, in particular the role of microbial iron reduction, is poorly understood. In this study we address the prevalence of viable iron-reducing microorganisms in subglacial sediments from five geographically isolated glaciers. Iron-reducing enrichment cultures were established with sediment from beneath Engabreen (Norway), Finsterwalderbreen (Svalbard), Leverett and Russell glaciers (Greenland), and Lower Wright Glacier (Antarctica). Rates of iron reduction were higher at 4 °C compared with 15 °C in all but one duplicated second-generation enrichment culture, indicative of cold-tolerant and perhaps cold-adapted iron reducers. Analysis of bacterial 16S rRNA genes indicates Desulfosporosinus were the dominant iron-reducing microorganisms in low-temperature Engabreen, Finsterwalderbreen and Lower Wright Glacier enrichments, and Geobacter dominated in Russell and Leverett enrichments. Results from this study suggest microbial iron reduction is widespread in subglacial environments and may have important implications for global biogeochemical iron cycling and export to marine ecosystems.

Synthesis, characterization and performance of high energy ball milled meso-scale zero valent iron in Fenton reaction.

PubMed

Ambika, Selvaraj; Devasena, M; Nambi, Indumathi Manivannan

2016-10-01

Understanding contaminant degradation by different sized zero valent iron (ZVI) particles is one important aspect in addressing the long-term stability of these particles in field studies. In this study, meso zero valent iron (mZVI) particles were synthesised in a milling time of 10 h using ball milling technique. The efficacy of mZVI particles for removal of phenol was quantitatively evaluated in comparison with coarse zero valent iron (cZVI) and nano zero valent iron (nZVI) particles. Phenol degradation experiments were carried out in sacrificial batch mode at room temperature independently with cZVI, nZVI and mZVI under varied pH conditions of 3, 4, 6, 7, 8 and 10. Batch experiments substantiating the reactivity of mZVI under unbuffered pH system were also carried out and compared with buffered and poorly buffered pH systems. mZVI particles showed consistent phenol degradation at circum-neutral pH with efficiency of 44%, 67%, and 89% in a span of 5, 10 and 20 min respectively. The dissolved iron species and residual iron formation were also measured as a function of pH. Unbuffered systems at circum-neutral pH produced less residual iron when compared to buffered and poorly buffered systems. At this pH, oxidation of Fe(2+) produced a different oxidant Ferryl ion, which was found to effectively participate in phenol degradation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Spatial Modeling of Iron Transformations Within Artificial Soil Aggregates

NASA Astrophysics Data System (ADS)

Kausch, M.; Meile, C.; Pallud, C.

2008-12-01

Structured soils exhibit significant variations in transport characteristics at the aggregate scale. Preferential flow occurs through macropores while predominantly diffusive exchange takes place in intra-aggregate micropores. Such environments characterized by mass transfer limitations are conducive to the formation of small-scale chemical gradients and promote strong spatial variation in processes controlling the fate of redox-sensitive elements such as Fe. In this study, we present a reactive transport model used to spatially resolve iron bioreductive processes occurring within a spherical aggregate at the interface between advective and diffusive domains. The model is derived from current conceptual models of iron(hydr)oxide (HFO) transformations and constrained by literature and experimental data. Data were obtained from flow-through experiments on artificial soil aggregates inoculated with Shewanella putrefaciens strain CN32, and include the temporal evolution of the bulk solution composition, as well as spatial information on the final solid phase distribution within aggregates. With all iron initially in the form of ferrihydrite, spatially heterogeneous formation of goethite/lepidocrocite, magnetite and siderite was observed during the course of the experiments. These transformations were reproduced by the model, which ascribes a central role to divalent iron as a driver of HFO transformations and master variable in the rate laws of the considered reaction network. The predicted dissolved iron breakthrough curves also match the experimental ones closely. Thus, the computed chemical concentration fields help identify factors governing the observed trends in the solid phase distribution patterns inside the aggregate. Building on a mechanistic description of transformation reactions, fluid flow and solute transport, the model was able to describe the observations and hence illustrates the importance of small-scale gradients and dynamics of bioreductive

Iron Isotopes in Meteorites

NASA Astrophysics Data System (ADS)

Kehm, K.; Alexander, C. M.; Hauri, E. H.

2001-12-01

The recent identification of naturally occurring isotopic mass fractionation of the transition met-als on the Earth has prompted a search for similar variability in meteorites. Studies of Cu, Zn, and Fe, for example, have revealed per-mil level and larger mass fractionations between different bulk meteorites. Such variations can result from temperature-sensitive isotope exchange reactions and kinetic processes, and therefore may reflect conditions in the solar nebula and on meteorite parent bodies. Recent advances in ICP-MS have permitted isotope studies of transition metals and other elements with similarly small isotopic mass dispersions. Among the transition metals, Fe is perhaps the most difficult to analyze by ICP-MS because plasma sources are copious producers of argide molecules that interfere with the measurement of iron isotopes. However, the stable isotope behavior of Fe is of special interest because it is a non-refractory major element in meteorites, present in a variety of mineral associations and redox states. Considerable effort has gone into overcoming the inherent analytical difficulties of measuring Fe using ICP-MS. We recently reported on a technique that achieves argide reduction by operating the plasma source in so-called 'cold' mode. In this presentation, we report results from this ongoing work. To date, analyses of nine different meteorites, and eight individual Tieschitz (H3) chondrules have been completed, along with a number of measurements of the Hawaiian basalt sample Kil1919. All of the bulk meteorite compositions, which include both chondrites and irons, have identical 56Fe/54Fe to within ~ 0.14 per mil (2 sigma), and are indistinguishable from the composition of the terrestrial basalt. The Tieschitz chondrules, on the other hand, tend to have isotopically light compositions. This could reflect formation from fractionated starting material. Alternatively, Fe condensation, under non-equilibrium conditions can enrich light isotopes

Reaction Gradients Viewed Inside Single Photoactive Particles

NASA Astrophysics Data System (ADS)

Alpert, P.; Corral Arroyo, P.; Dou, J.; Kreiger, U.; Luo, B.; Peter, T.; Ammann, M.

2017-12-01

In terms of chemical selectivity and spatial resolution, a technique known as scanning transmission X-ray microscopy coupled to near-edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS) is unmatched and will remain so for years into the future. We present a recent development coupling STXM/NEXAFS to a custom-built photochemical environmental reactor in which aerosol particles reside allowing for in situ chemical imaging. A laboratory investigation of metal-organic complex photochemistry was conducted. Transition metals are of great importance to atmospheric chemistry and aerosol photochemical aging due to their ability to catalyze oxidation reactions. Aerosol particles composed of mixtures of citric acid and iron citrate were probed for their organic carbon composition and iron oxidation state under atmospherically relevant conditions. At 40% relative humidity, oxygen diffusion and reaction was severely limited. Fe was reoxidized in the first 200 nm of the particle surface leaving reduced iron in the core. Similar gradients were observed at 60% RH, however waiting approximately 2 hours in the dark resulted in a recovery of the initial Fe(III) concentration. We draw two main conclusions from our findings. Frist, the oxidation gradients must have been the result of anoxic conditions at the interior of aerosol particles. This was predicted using a newly developed model for molecular diffusion through multiple layers with a reaction framework describing the photochemical processing of the metal organic matrix. Second, the lifetime of organic radicals in an anoxic diffusion limited organic matrix must be considerably long ( hours) to completely reoxidize iron as they wait for molecular oxygen. Long radical lifetimes in viscous organic aerosol in turn, could create high radical concentrations or favor radical-radical reactions in particles typically not considered when oxygen is plentiful. Our results impact predictions of aerosol physiochemical properties, e

Dehalogenation of Polybrominated Diphenyl Ethers and Polychlorinated Biphenyl by Bimetallic, Impregnated, and Nanoscale Zerovalent Iron

PubMed Central

Zhuang, Yuan; Ahn, Sungwoo; Seyfferth, Angelia L.; Masue-Slowey, Yoko; Fendorf, Scott; Luthy, Richard G.

2011-01-01

Nanoscale zerovalent iron particles (nZVI), bimetallic nanoparticles (nZVI/Pd), and nZVI/Pd impregnated activated carbon (nZVI/Pd-AC) composite particles were synthesized and investigated for their effectiveness to remove polybrominated diphenyl ethers (PBDEs) and/or polychlorinated biphenyls (PCBs). Palladization of nZVI promoted the dehalogenation kinetics for mono- to tri-BDEs and 2,3,4-trichlorobiphenyl (PCB 21). Compared to nZVI, the iron-normalized rate constants for nZVI/Pd were about 2-, 3-, and 4-orders of magnitude greater for tri-, di-, and mono-BDEs, respectively, with diphenyl ether as a main reaction product. The reaction kinetics and pathways suggest an H-atom transfer mechanism. The reaction pathways with nZVI/Pd favor preferential removal of para-halogens on PBDEs and PCBs. X-ray fluorescence mapping of nZVI/Pd-AC showed that Pd mainly deposits on the outer part of particles, while Fe was present throughout the activated carbon particles. While BDE 21 was sorbed onto activated carbon composites quickly, debromination was slower compared to reaction with freely dispersed nZVI/Pd. Our XPS and chemical data suggest about 7% of the total iron within the activated carbon was zero-valent, which shows the difficulty with in-situ synthesis of a significant fraction of zero-valent iron in the micro-porous material. Related factors that likely hinder the reaction with nZVI/Pd-AC are the heterogenous distribution of nZVI and Pd on activated carbon and/or immobilization of hydrophobic organic contaminants at the adsorption sites thereby inhibiting contact with nZVI. PMID:21557574

Ellagic acid inhibits iron-mediated free radical formation

NASA Astrophysics Data System (ADS)

Dalvi, Luana T.; Moreira, Daniel C.; Andrade, Roberto; Ginani, Janini; Alonso, Antonio; Hermes-Lima, Marcelo

2017-02-01

Polyphenols are reported to have some health benefits, which are link to their antioxidant properties. In the case of ellagic acid (EA), there is evidence that it has free radical scavenger properties and that it is able to form complexes with metal ions. However, information on a possible link between the formation of iron-EA complexes and their interference in Haber-Weiss/Fenton reactions was not yet determined. Thus, the present study investigated the in vitro antioxidant mechanism of EA in a system containing ascorbate, Fe(III) and different iron ligands (EDTA, citrate and NTA). Iron-mediated oxidative degradation of 2-deoxyribose was poorly inhibited (by 12%) in the presence of EA (50 μM) and EDTA. When citrate or NTA - which form weak iron complexes - were used, the 2-deoxyribose protection increased to 89-97% and 45%, respectively. EA also presented equivalent inhibitory effects on iron-mediated oxygen uptake and ascorbyl radical formation. Spectral analyses of iron-EA complexes show that EA removes Fe(III) from EDTA within hours, and from citrate within 1 min. This difference in the rate of iron-EA complex formation may explain the antioxidant effects of EA. Furthermore, the EA antioxidant effectiveness was inversely proportional to the Fe(III) concentration, suggesting a competition with EDTA. In conclusion, the results indicate that EA may prevent in vitro free radical formation when it forms a complex with iron ions.

FIND-CKD: a randomized trial of intravenous ferric carboxymaltose versus oral iron in patients with chronic kidney disease and iron deficiency anaemia.

PubMed

Macdougall, Iain C; Bock, Andreas H; Carrera, Fernando; Eckardt, Kai-Uwe; Gaillard, Carlo; Van Wyck, David; Roubert, Bernard; Nolen, Jacqueline G; Roger, Simon D

2014-11-01

The optimal iron therapy regimen in patients with non-dialysis-dependent chronic kidney disease (CKD) is unknown. Ferinject® assessment in patients with Iron deficiency anaemia and Non-Dialysis-dependent Chronic Kidney Disease (FIND-CKD) was a 56-week, open-label, multicentre, prospective and randomized study of 626 patients with non-dialysis-dependent CKD, anaemia and iron deficiency not receiving erythropoiesis-stimulating agents (ESAs). Patients were randomized (1:1:2) to intravenous (IV) ferric carboxymaltose (FCM), targeting a higher (400-600 µg/L) or lower (100-200 µg/L) ferritin or oral iron therapy. The primary end point was time to initiation of other anaemia management (ESA, other iron therapy or blood transfusion) or haemoglobin (Hb) trigger of two consecutive values <10 g/dL during Weeks 8-52. The primary end point occurred in 36 patients (23.5%), 49 patients (32.2%) and 98 patients (31.8%) in the high-ferritin FCM, low-ferritin FCM and oral iron groups, respectively [hazard ratio (HR): 0.65; 95% confidence interval (CI): 0.44-0.95; P = 0.026 for high-ferritin FCM versus oral iron]. The increase in Hb was greater with high-ferritin FCM versus oral iron (P = 0.014) and a greater proportion of patients achieved an Hb increase ≥1 g/dL with high-ferritin FCM versus oral iron (HR: 2.04; 95% CI: 1.52-2.72; P < 0.001). Rates of adverse events and serious adverse events were similar in all groups. Compared with oral iron, IV FCM targeting a ferritin of 400-600 µg/L quickly reached and maintained Hb level, and delayed and/or reduced the need for other anaemia management including ESAs. Within the limitations of this trial, no renal toxicity was observed, with no difference in cardiovascular or infectious events. NCT00994318. © The Author 2014. Published by Oxford University Press on behalf of ERA-EDTA.

Influence of welding fume on systemic iron status.

PubMed

Casjens, Swaantje; Henry, Jana; Rihs, Hans-Peter; Lehnert, Martin; Raulf-Heimsoth, Monika; Welge, Peter; Lotz, Anne; Gelder, Rainer Van; Hahn, Jens-Uwe; Stiegler, Hugo; Eisele, Lewin; Weiss, Tobias; Hartwig, Andrea; Brüning, Thomas; Pesch, Beate

2014-11-01

Iron is the major metal found in welding fumes, and although it is an essential trace element, its overload causes toxicity due to Fenton reactions. To avoid oxidative damage, excess iron is bound to ferritin, and as a result, serum ferritin (SF) is a recognized biomarker for iron stores, with high concentrations linked to inflammation and potentially also cancer. However, little is known about iron overload in welders. Within this study, we assessed the iron status and quantitative associations between airborne iron, body iron stores, and iron homeostasis in 192 welders not wearing dust masks. Welders were equipped with personal samplers in order to determine the levels of respirable iron in the breathing zone during a working shift. SF, prohepcidin and other markers of iron status were determined in blood samples collected after shift. The impact of iron exposure and other factors on SF and prohepcidin were estimated using multiple regression models. Our results indicate that respirable iron is a significant predictor of SF and prohepcidin. Concentrations of SF varied according to the welding technique and respiratory protection used, with a median of 103 μg l(-1) in tungsten inert gas welders, 125 μg l(-1) in those wearing air-purifying respirators, and 161 μg l(-1) in other welders. Compared to welders with low iron stores (SF < 25 μg l(-1)), those with excess body iron (SF ≥ 400 μg l(-1)) worked under a higher median concentration of airborne iron (60 μg m(-3) versus 148 μg m(-3)). Even though air concentrations of respirable iron and manganese were highly correlated, and low iron stores have been reported to increase manganese uptake in the gastrointestinal tract, no correlation was seen between SF and manganese in blood. In conclusion, monitoring SF may be a reasonable method for health surveillance of welders. Respiratory protection with air-purifying respirators can decrease iron exposure and avoid chronically higher SF in welders working with

Autocatalytic formation of an iron(IV)-oxo complex via scandium ion-promoted radical chain autoxidation of an iron(II) complex with dioxygen and tetraphenylborate.

PubMed

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

2014-06-04

A non-heme iron(IV)-oxo complex, [(TMC)Fe(IV)(O)](2+) (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), was formed by oxidation of an iron(II) complex ([(TMC)Fe(II)](2+)) with dioxygen (O2) and tetraphenylborate (BPh4(-)) in the presence of scandium triflate (Sc(OTf)3) in acetonitrile at 298 K via autocatalytic radical chain reactions rather than by a direct O2 activation pathway. The autocatalytic radical chain reaction is initiated by scandium ion-promoted electron transfer from BPh4(-) to [(TMC)Fe(IV)(O)](2+) to produce phenyl radical (Ph(•)). The chain propagation step is composed of the addition of O2 to Ph(•) and the reduction of the resulting phenylperoxyl radical (PhOO(•)) by scandium ion-promoted electron transfer from BPh4(-) to PhOO(•) to produce phenyl hydroperoxide (PhOOH), accompanied by regeneration of phenyl radical. PhOOH reacts with [(TMC)Fe(II)](2+) to yield phenol (PhOH) and [(TMC)Fe(IV)(O)](2+). Biphenyl (Ph-Ph) was formed via the radical chain autoxidation of BPh3 by O2. The induction period of the autocatalytic radical chain reactions was shortened by addition of a catalytic amount of [(TMC)Fe(IV)(O)](2+), whereas addition of a catalytic amount of ferrocene that can reduce [(TMC)Fe(IV)(O)](2+) resulted in elongation of the induction period. Radical chain autoxidation of BPh4(-) by O2 also occurred in the presence of Sc(OTf)3 without [(TMC)Fe(IV)(O)](2+), initiating the autocatalytic oxidation of [(TMC)Fe(II)](2+) with O2 and BPh4(-) to yield [(TMC)Fe(IV)(O)](2+). Thus, the general view for formation of non-heme iron(IV)-oxo complexes via O2-binding iron species (e.g., Fe(III)(O2(•-))) without contribution of autocatalytic radical chain reactions should be viewed with caution.

Antarctic iron meteorites: An unexpectedly high proportion of falls of unusual interest

NASA Technical Reports Server (NTRS)

Clarke, R. S., Jr.

1986-01-01

The inhabited and explored areas of Earth have contributed 725 iron meteorites, accounting for 28% of the 2611 authenticated meteorites known of all types. Observed fall statistics give a much different view of relative abundance. The 42 historic iron meteorite falls spanning 230 years suggests a frequency of one fall per 5.6 years and represents only 4.9% of the total 853 known falls. Antarctic iron meteorite recoveries offer promise of providing a new perspective on the influx problem. At least 42 iron meteorite specimens were found during the last 25 years by various field teams working in Antarctica. Most of these specimens were not described in detail, but the available data indicates that 21 separate falls are represented, 50% of the number of recovered specimens. Twelve of the 21 falls were both structurally classified and placed into chemical groups. They are listed in order of increasing structural complexity and/or Ni content.

Auxiliary iron-sulfur cofactors in radical SAM enzymes.

PubMed

Lanz, Nicholas D; Booker, Squire J

2015-06-01

A vast number of enzymes are now known to belong to a superfamily known as radical SAM, which all contain a [4Fe-4S] cluster ligated by three cysteine residues. The remaining, unligated, iron ion of the cluster binds in contact with the α-amino and α-carboxylate groups of S-adenosyl-l-methionine (SAM). This binding mode facilitates inner-sphere electron transfer from the reduced form of the cluster into the sulfur atom of SAM, resulting in a reductive cleavage of SAM to methionine and a 5'-deoxyadenosyl radical. The 5'-deoxyadenosyl radical then abstracts a target substrate hydrogen atom, initiating a wide variety of radical-based transformations. A subset of radical SAM enzymes contains one or more additional iron-sulfur clusters that are required for the reactions they catalyze. However, outside of a subset of sulfur insertion reactions, very little is known about the roles of these additional clusters. This review will highlight the most recent advances in the identification and characterization of radical SAM enzymes that harbor auxiliary iron-sulfur clusters. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases. Copyright © 2015 Elsevier B.V. All rights reserved.

A Global Atmospheric Model of Meteoric Iron

NASA Technical Reports Server (NTRS)

Feng, Wuhu; Marsh, Daniel R.; Chipperfield, Martyn P.; Janches, Diego; Hoffner, Josef; Yi, Fan; Plane, John M. C.

2013-01-01

The first global model of meteoric iron in the atmosphere (WACCM-Fe) has been developed by combining three components: the Whole Atmosphere Community Climate Model (WACCM), a description of the neutral and ion-molecule chemistry of iron in the mesosphere and lower thermosphere (MLT), and a treatment of the injection of meteoric constituents into the atmosphere. The iron chemistry treats seven neutral and four ionized iron containing species with 30 neutral and ion-molecule reactions. The meteoric input function (MIF), which describes the injection of Fe as a function of height, latitude, and day, is precalculated from an astronomical model coupled to a chemical meteoric ablation model (CABMOD). This newly developed WACCM-Fe model has been evaluated against a number of available ground-based lidar observations and performs well in simulating the mesospheric atomic Fe layer. The model reproduces the strong positive correlation of temperature and Fe density around the Fe layer peak and the large anticorrelation around 100 km. The diurnal tide has a significant effect in the middle of the layer, and the model also captures well the observed seasonal variations. However, the model overestimates the peak Fe+ concentration compared with the limited rocket-borne mass spectrometer data available, although good agreement on the ion layer underside can be obtained by adjusting the rate coefficients for dissociative recombination of Fe-molecular ions with electrons. Sensitivity experiments with the same chemistry in a 1-D model are used to highlight significant remaining uncertainties in reaction rate coefficients, and to explore the dependence of the total Fe abundance on the MIF and rate of vertical transport.

Selective Removal of Iron from Low-Grade Ti Ore by Reacting with Calcium Chloride

NASA Astrophysics Data System (ADS)

Kang, Jungshin; Okabe, Toru H.

2017-02-01

Recently, titanium metal production by molten salt electrolysis using CaCl2 as molten salt and TiO2 or rutile (94 to 96 pct TiO2) as feedstock has been drawing attention. However, when a low-grade Ti ore (mainly FeTiO3) is used as feedstock, removal of iron (Fe) from the ore is indispensable. In this study, the influence of reaction temperature, reaction time, particle size of the ore, and source country for the ore on the removal of iron by selective chlorination using CaCl2 was assessed. Experimental results showed that the mass percent of iron in the ore decreased from 49.7 to 1.79 pct under certain conditions by selective removal of iron as FeCl2. As a result, high-grade CaTiO3 was produced when the ore particles smaller than 74 µm reacted with CaCl2 at 1240 K (967 °C) for 8 to 10 hours. Therefore, this study demonstrates that the removal of iron from the ore is feasible through the selective chlorination process using CaCl2 by optimizing the variables.

Cosmogenic effects on Cu isotopes in IVB iron meteorites

NASA Astrophysics Data System (ADS)

Chen, Heng; Moynier, Frédéric; Humayun, Munir; Bishop, M. Cole; Williams, Jeffrey T.

2016-06-01

We measured Cu isotope compositions of 12 out of the 14 known IVB iron meteorites. Our results show that IVB iron meteorites display a very large range of δ65Cu values (-5.84‰ < δ65Cu < -0.24‰; defined as per mil deviation of the 65Cu/63Cu ratio from the NIST-976 standard). These Cu isotopic data display clear correlations with W, Pt, and Os isotope ratios, which are very sensitive to secondary neutron capture due to galactic cosmic ray (GCR) irradiation. This demonstrates that δ65Cu in IVB irons is majorly modified by neutron capture by the reaction 62Ni(n,γ)63Ni followed by beta decay to 63Cu. Using correlations with Pt and Os neutron dosimeters, we calculated a pre-exposure δ65Cu of -0.3 ± 0.8‰ (95% conf.) of IVB irons that agrees well with the Cu isotopic compositions of other iron meteorite groups and falls within the range of chondrites. This shows that the volatile depletion of the IVB parent body is not due to evaporation that should have enriched IVB irons in the heavy Cu isotopes.

Reaction Mechanisms of Metals with Hydrogen Sulfide and Thiols in Model Wine. Part 2: Iron- and Copper-Catalyzed Oxidation.

PubMed

Kreitman, Gal Y; Danilewicz, John C; Jeffery, David W; Elias, Ryan J

2016-05-25

Sulfidic off-odors arising during wine production are frequently removed by Cu(II) fining. In part 1 of this study ( 10.1021/acs.jafc.6b00641 ), the reaction of H2S and thiols with Cu(II) was examined; however, the interaction of iron and copper is also known to play an important synergistic role in mediating non-enzymatic wine oxidation. The interaction of these two metals in the oxidation of H2S and thiols (cysteine, 3-sulfanylhexan-1-ol, and 6-sulfanylhexan-1-ol) was therefore examined under wine-like conditions. H2S and thiols (300 μM) were reacted with Fe(III) (100 or 200 μM) alone and in combination with Cu(II) (25 or 50 μM), and concentrations of H2S and thiols, oxygen, and acetaldehyde were monitored over time. H2S and thiols were shown to be slowly oxidized in the presence of Fe(III) alone and were not bound to Fe(III) under model wine conditions. However, Cu(II) added to model wine containing Fe(III) was quickly reduced by H2S and thiols to form Cu(I) complexes, which then rapidly reduced Fe(III) to Fe(II). Oxidation of Fe(II) in the presence of oxygen regenerated Fe(III) and completed the iron redox cycle. In addition, sulfur-derived oxidation products were observed, and the formation of organic polysulfanes was demonstrated.

Carbon nanotube synthesis via the catalytic chemical vapor deposition of methane in the presence of iron, molybdenum, and iron-molybdenum alloy thin layer catalysts

NASA Astrophysics Data System (ADS)

Yahyazadeh, Arash; Khoshandam, Behnam

In this study, we documented the catalytic chemical vapor deposition synthesis of carbon nanotubes (CNTs) using ferrocene and molybdenum hexacarbonyl as catalyst nanoparticle precursors and methane as a nontoxic and economical carbon source for the first time. Field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, wavelength dispersive X-ray spectrometry and transmission electron microscopy of the thin layer catalyst as a simple and cost effective catalyst preparation after methane decomposition reaction, along with Fourier transform infrared spectroscopy and Raman spectroscopy confirmed the growth of CNTs, from bimetallic nanoparticles, which are converted into iron-molybdenum alloy nanoparticles at 700 °C for pretreatment by hydrogen after chemical vapor deposition of thin layers. An investigation of the weight percentages of the chemical elements present in the CNTs synthesized from iron-molybdenum catalyst using quartz sheet substrate at 750 °C, confirmed a significant carbon yield of 75.4% which represents high catalyst activity. Additionally, multi-walled carbon nanotubes (∼16-55 nm in diameter and 1.2 μm in length) were observed in the iron-molybdenum alloy sample after methane decomposition reaction at 750 °C for 35 min. To show the role of iron and molybdenum coated on silicon substrate as two thin layer catalysts, samples were considered for CNTs growth (diameter ∼47-69 nm) at 800 °C and 830 °C, respectively. Moreover, the effect of hydrogen pretreatment was evaluated in terms of active metal coating properly. The best graphitic structure due to Raman spectroscopy outcomes (ID/IG ratio) was obtained for iron coated on a quartz sheet, which was estimated at 0.8505. Thermogravimetric analysis proved the thermal stability of the synthesized CNTs using iron thin-layer catalyst up to 350 °C.

Invar alloys: information from the study of iron meteorites.

NASA Astrophysics Data System (ADS)

Goldstein, J. I.; Williams, D. B.; Zhang, J.; Clarke, R.

The iron meteorites were slow cooled (<108years) in their asteroidal bodies and are useful as indicators of the phase transformations which occur in Fe-Ni alloys. In the invar composition range, the iron meteorites contain a cloudy zone structure composed of an ordered tetrataenite phase and a surrounding honeycomb phase either of gamma or alpha phase. This structure is the result of a spinodal reaction below 350°C. The Santa Catharina iron meteorite has the typical invar composition of 36 wt% Ni and its structure is entirely cloudy zone although some of the honeycomb phase has been oxidized by terrestrial corrosion. Invar alloys would contain such a cloudy zone structure if more time was available for cooling. A higher temperature spinodal in the Fe-Ni phase diagram may be operative in invar alloys but has not been observed in the structure of the iron meteorites.

Using Iron to Treat Chlorohydrocarbon-Contaminated Soil

NASA Technical Reports Server (NTRS)

Hitchens, G. Duncan; Hodko, Dalibor; Kim, Heekyung; Rogers, Tom; Singh, Waheguru Pal; Giletto, Anthony; Cisar, Alan

2004-01-01

A method of in situ remediation of soil contaminated with chlorinated hydrocarbon solvents involves injection of nanometer-size iron particles. The present method exploits a combination of prompt chemical remediation followed by longer-term enhanced bioremediation and, optionally, is practiced in conjunction with the method of bioremediation described earlier. Newly injected iron particles chemically reduce chlorinated hydrocarbons upon contact. Thereafter, in the presence of groundwater, the particles slowly corrode via chemical reactions that effect sustained release of dissolved hydrogen. The hydrogen serves as an electron donor, increasing the metabolic activity of the anaerobic bacteria and thereby sustaining bioremediation at a rate higher than the natural rate.

The fragmentation of 510 MeV/nucleon iron-56 in polyethylene. I. Fragment fluence spectra

NASA Technical Reports Server (NTRS)

Zeitlin, C.; Miller, J.; Heilbronn, L.; Frankel, K.; Gong, W.; Schimmerling, W.

1996-01-01

The fragmentation of 510 MeV/nucleon iron ions in several thicknesses of polyethylene has been measured. Non-interacting primary beam particles and fragments have been identified and their LETs calculated by measuring ionization energy loss in a stack of silicon detectors. Fluences, normalized to the incident beam intensity and corrected for detector effects, are presented for each fragment charge and target. Histograms of fluence as a function of LET are also presented. Some implications of these data for measurements of the biological effects of heavy ions are discussed.

The Oxidation of Iron: Experiment, Simulation, and Analysis in Introductory Chemistry

ERIC Educational Resources Information Center

Schubert, Frederic E.

2015-01-01

In this exercise, an actual chemical reaction, oxidation of iron in air, is studied along with a related analogue simulation of that reaction. The rusting of steel wool is carried out as a class effort. The parallel simulation is performed by students working in small groups. The analogue for the reacting gas is a countable set of discrete marble…

Remediation of Ni(2+)-contaminated water using iron powder and steel manufacturing byproducts.

PubMed

Jin, Jian; Zhao, Wei-Rong; Xu, Xin-Hua; Hao, Zhi-Wei; Liu, Yong; He, Ping; Zhou, Mi

2006-01-01

Steel manufacturing byproducts and commercial iron powders were tested in the treatment of Ni(2+)-contaminated water. Ni2+ is a priority pollutant of some soils and groundwater. The use of zero-valent iron, which can reduce Ni2+ to its neural form appears to be an alternative approach for the remediation of Ni(2+)-contaminated sites. Our experimental data show that the removal efficiencies of Ni2+ were 95.15% and 94.68% at a metal to solution ratio of 20 g/L for commercial iron powders and the steel manufacturing byproducts in 60 min at room temperature, respectively. The removal efficiency reached 98.20% when the metal to solution ratio was 40 g/L for commercial iron powders. Furthermore, we found that the removal efficiency was also largely affected by other factors such as the pHs of the treated water, the length of time for the metal to be in contact with the Ni(2+)-contaminated water, initial concentrations of metal solutions, particle sizes and the amount of iron powders. Surprisingly, the reaction temperature appeared to have little effect on the removal efficiency. Our study opens the way to further optimize the reaction conditions of in situ remediation of Ni2+ or other heavy metals on contaminated sites.

Enhanced Fenton-like removal of nitrobenzene via internal microelectrolysis in nano zerovalent iron/activated carbon composite.

PubMed

Hu, Sihai; Wu, Yaoguo; Yao, Hairui; Lu, Cong; Zhang, Chengjun

2016-01-01

The efficiency of Fenton-like catalysis using nano zerovalent iron (nZVI) is limited by nZVI aggregation and activity loss due to inactive ferric oxide forming on the nZVI surface, which hinders electron transfer. A novel iron-carbon composite catalyst consisting of nZVI and granular activated carbon (GAC), which can undergo internal iron-carbon microelectrolysis spontaneously, was successfully fabricated by the adsorption-reduction method. The catalyst efficiency was evaluated in nitrobenzene (NB) removal via the Fenton-like process (H2O2-nZVI/GAC). The results showed that nZVI/GAC composite was good for dispersing nZVI on the surface of GAC, which permitted much better removal efficiency (93.0%) than nZVI (31.0%) or GAC (20.0%) alone. Moreover, iron leaching decreased from 1.28 to 0.58 mg/L after reaction of 240 min and the oxidation kinetic of the Fenton-like reaction can be described well by the second-order reaction kinetic model (R2=0.988). The composite catalyst showed sustainable catalytic ability and GAC performed as a medium for electron transfer in internal iron-carbon microelectrolysis to promote Fe2+ regeneration and Fe3+/Fe2+ cycles. Therefore, this study represents an important method to design a low cost and high efficiency Fenton-like catalyst in practical application.

Effects of spin crossover on iron isotope fractionation in Earth's mantle

NASA Astrophysics Data System (ADS)

Qin, T.; Shukla, G.; Wu, Z.; Wentzcovitch, R.

2017-12-01

Recent studies have revealed that the iron isotope composition of mid-ocean ridge basalts (MORBs) is +0.1‰ richer in heavy Fe (56Fe) relative to chondrites, while basalts from Mars and Vesta have similar Fe isotopic composition as chondrites. Several hypotheses could explain these observations. For instance, iron isotope fractionation may have occurred during core formation or Earth may have lost some light Fe isotope during the high temperature event in the early Earth. To better understand what drove these isotopic observations, it is important to obtain accurate Fe isotope fractionation factors among mantle and core phases at the relevant P-T conditions. In bridgmanite, the most voluminous mineral in the lower mantle, Fe can occupy more than one crystalline site, be in ferrous and/or ferric states, and may undergo a spin crossover in the lower mantle. Iron isotopic fractionation properties under spin crossover are poorly constrained, while this may be relevant to differentiation of Earth's magma ocean. In this study we address the effect of these multiple states on the iron isotope fractionation factors between mantle and core phases.

GROUND WATER REMEDIATION OF CHROMIUM USING ZERO-VALENT IRON IN A PERMEABLE REACTIVE BARRIER

EPA Science Inventory

A series of laboratory experiments were performed to elucidate the chromium transformation and precipitation reactions caused by the corrosion of zero-valent iron in water-based systems. Reaction rates were determined for chromate reduction in the presence of different types of ...

Iron

MedlinePlus

... too little iron, you may develop iron deficiency anemia. Causes of low iron levels include blood loss, poor diet, or an inability to absorb enough iron from foods. People at higher risk of having too little iron are young children and women who are pregnant or have periods. ...