Transition Metals Iron Research Articles

Characterization of organic‐coated solids isolated from different oil sands

AbstractSolids isolated from weathered oil sands ores and those having low‐ and high‐fine solids content were studied. The organic matter (OM) adsorbed on the solids was found insoluble in most common solvents, contributing significantly to the change of solid surface properties. The surface properties of these solids were found to affect the entire process cycle of obtaining synthetic crude oil from surface‐mined oil sands using a water‐based extraction process, and managing the existing tailings ponds. In this study, the low‐fine solids ore possessed the lowest amount of organic‐coated solids and highest bitumen recovery. Siderite and pyrite, which tend to concentrate in the hydrocarbon phase were observed in the isolated solids from the weathered and high‐fine ores but were absent in the low‐fine ores. In all the ores studied, the solids from the bitumen froth possess less quartz, and more carbonates compared with solids from the tailings. Elemental analysis by energy dispersive X‐ray spectroscopy (EDX) and elemental analyser revealed the presence of more transition metals (iron and titanium), and carbon in the solids obtained from the bitumen froth when compared with those from the tailings. Infrared (IR) spectroscopy study substantiated the results obtained by X‐ray diffraction and elemental analysis. IR spectra showed a likely association between OM and carbonates in the organic‐coated solids isolated from bitumen froth. More organic‐coated solids were found in weathered oil sands than in other types of ores and observed to reduce bitumen recovery from oil sands.

Structural, acidic and catalytic features of transition metal-containing molecular sieves in the transformation of C 4 hydrocarbon

MCM-41 mesoporous materials and silicoaluminophosphates (SAPO-5) were prepared by gel hydrothermal crystallization. Both series of materials were modified by transition metals (chromium or iron close to 1 wt%). The synthesized solids were characterized by chemical analysis, XRD, nitrogen adsorption–desorption isotherms, SEM, EPR, XPS, IR of ammonia or pyridine adsorption studies, and 29Si, 27Al and 31P NMR. The catalysts were evaluated in the n-butane isomerization in order to assess their properties with regard to alkane transformations. The properties of the solids were modified by adding metals that altered the morphology, structural features and acidic character of the solids and result in an efficient performance in the transformation of n-butane in comparison with the pure counterparts. The introduction of Cr or Fe enhanced the catalytic ability of silicoaluminophosphates to produce isobutane. Fe and Cr modified silicoaluminophosphates were shown to be more efficient in the transformation of n-butane in comparison with the MCM-41 analogues. However, the activity of these iron-containing molecular sieves was considered too low in comparison with performances of iron-modified modernite. This was ascribed to an initial redox C 4 activation step occurring in synergy with Brønsted sites with sufficient acid strength which is indeed higher than that provided by MCM-41 and SAPO molecular sieves.

A thioredoxin reductase-like protein from the thermophile, Thermus scotoductus SA-01, displaying iron reductase activity

The transition metal iron is an important element for the sustenance of life--it can function either as an electron acceptor or as a donor and serves as a cofactor in many enzymes activities. The cytoplasmic NAD(P)H-dependent ferric reductase in Thermus scotoductus SA-01 shares high sequence and structural similarity to prokaryotic thioredoxin reductases. Here we report the sequence of the ferric reductase (which is typically annotated as a thioredoxin reductase-like protein) and a comparative kinetic study with the thioredoxin reductase from SA-01. Structurally, the most noteworthy difference, immediately apparent from the protein sequence, is the absence of the disulphide redox centre in the ferric reductase. This is the first report relating the attributes of such a redox protein to its ability to reduce a ferric substrate.

Oxidative properties of ambient PM 2.5 and elemental composition: Heterogeneous associations in 19 European cities

We assessed the extent to which constituents of PM 2.5 (transition metals, sodium, chloride) contribute to the ability to generate hydroxyl radicals ( OH) in vitro in PM 2.5 sampled at 20 locations in 19 European centres participating in the European Community Respiratory Health Survey. PM 2.5 samples ( n = 716) were collected on filters over one year and the oxidative activity of particle suspensions obtained from these filters was then assessed by measuring their ability to generate OH in the presence of hydrogen peroxide. Associations between OH formation and the studied PM constituents were heterogeneous. The total explained variance ranged from 85% in Norwich to only 6% in Albacete. Among the 20 centres, 15 showed positive correlations between one or more of the measured transition metals (copper, iron, manganese, lead, vanadium and titanium) and OH formation. In 9 of 20 centres OH formation was negatively associated with chloride, and in 3 centres with sodium. Across 19 European cities, elements which explained the largest variations in OH formation were chloride, iron and sodium.

Essential transition metal homeostasis in plants

The homeostasis of the essential transition metals copper, iron, manganese and zinc requires balanced activities of transporters that mediate import into the cell, distribution to organelles and export from the cell. Transcriptional control is important for the regulation of cellular homeostasis. In the case of Fe and Cu much progress has been made in uncovering the regulatory networks that mediate homeostasis, and key transcription factors have now been described. A master regulator of Cu homeostasis in Arabidopsis thaliana, AtSPL7, is related to the Chlamydomonas master regulator CCR1, suggesting that the key switch is conserved between the two systems even though different sets of targets are regulated in the two systems.

Preparation and Characterization of Polyesterurethane Metallopolymers Containing Transition Metal Ions

AbstractSeveral series of metallopolymers (MP) were synthesized from a MDI‐based polyesterurethane and various transition metal ion species, namely, copper(II), manganese(II), cobalt(II), iron(III) and chromium(III). Each series of MP were prepared by using different initial molar ratios urethane groups/metal ions (U/M). MP were characterized in comparison with the parent polyurethane (PU) by atomic absorption spectrometry (AAS), UV‐vis absorption spectroscopy, FT‐IR spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA) and tensile testing. The transition metal ions form coordination complexes with polyurethane functional groups, the intermolecular complexation resulting in the crosslinking of polymer chains. As a consequence, modifications take place in the original structure of PU, e.g. hydrogen bonding and crystallinity of the hard‐segment domains. MP compared with PU present differences in viscoelastic and mechanical behaviors, which generally indicate the reinforcing effect of metal ions on the polyurethane matrix, as well in thermal stability. It was revealed that each transition metal ion has specific effects on the structure and properties of PU. The implications and mechanisms behind these observations are discussed.

Survey of the K-shell emission from heliumlike ions with an X-ray microcalorimeter

The Electron Beam Ion Trap Microcalorimeter Spectrometer (ECS) routinely surveys the K-shell x-ray spectra that fall into the energy range between 200 eV and 14,000 eV. The spectra serve as in situ energy references and include the K-shell emission from ions between boron at the low-energy end and krypton at the high end. Example spectra are presented of the n = 2 → n = 1 emission from heliumlike noble gas ions neon, argon, and krypton, from the heliumlike transition metals iron and nickel, as well as the heliumlike ions of boron, silicon, sulfur, and germanium.

Multiple protective activities of neuroglobin in cultured neuronal cells exposed to hypoxia re‐oxygenation injury

Oxidative stress is associated with the pathology of acute and chronic neurodegenerative disease. We have cloned a human neuroglobin (Nb) construct and over-expressed this protein in cultured human neuronal cells to assess whether Nb ameliorates the cellular response to experimental hypoxia-reoxygenation (H/R) injury. Parental cells transfected with a blank (pDEST40) vector responded to H/R injury with a significant decrease in cellular ATP at 5 and 24 h after insult. This was coupled with increases in the cytosolic Ca(2+), and the transition metals iron (Fe), copper (Cu), and zinc (Zn) within the cell body, as monitored simultaneously using X-ray fluorescence microprobe imaging. Parental cell viability decreased over the same time period with a approximately 4 to 5-fold increase in cell death (maximum approximately 25%) matched by an increase in caspase 3/7 activation (peaking at a 15-fold increase after 24 h) and condensation of beta-actin along axonal processes. Over-expression of Nb inhibited ATP loss and except for significant decreases in the sulfur (S), chlorine (Cl), potassium (K) and Ca(2+) contents, maintained cellular ion homeostasis after H/R insult. This resulted in increased cell viability, significantly diminished caspase activation and maintenance of the beta-actin cytoskeletal structure and receptor-mediated endocytosis. These data indicate that bolstering the cellular content of Nb inhibits neuronal cell dysfunction promoted by H/R insult through multiple protective actions including: (i) maintenance of cellular bioenergetics; (ii) inhibition of Ca(2+) influx; (iii) a reduction in cellular uptake of Fe, Cu and Zn at the expense of S, Cl and K; and (iv) an enhancement of cell viability through inhibiting necrosis and apoptosis.

IscR Controls Iron-Dependent Biofilm Formation in Escherichia coli by Regulating Type I Fimbria Expression

Biofilm formation is a complex developmental process regulated by multiple environmental signals. In addition to other nutrients, the transition metal iron can also regulate biofilm formation. Iron-dependent regulation of biofilm formation varies by bacterial species, and the exact regulatory pathways that control iron-dependent biofilm formation are often unknown or only partially characterized. To address this gap in our knowledge, we examined the role of iron availability in regulating biofilm formation in Escherichia coli. The results indicate that biofilm formation is repressed under low-iron conditions in E. coli. Furthermore, a key iron regulator, IscR, controls biofilm formation in response to changes in cellular Fe-S homeostasis. IscR regulates the FimE recombinase to control expression of type I fimbriae in E. coli. We propose that iron-dependent regulation of FimE via IscR leads to decreased surface attachment and biofilm dispersal under iron-limiting conditions.

Energy-loss magnetic chiral dichroism (EMCD): Magnetic chiral dichroism in the electron microscope

A new technique called energy-loss magnetic chiral dichroism (EMCD) has recently been developed [P. Schattschneider, et al.Nature441,486 (2006)] to measure magnetic circular dichroism in the transmission electron microscope (TEM) with a spatial resolution of 10 nm. This novel technique is the TEM counterpart of x-ray magnetic circular dichroism, which is widely used for the characterization of magnetic materials with synchrotron radiation. In this paper we describe several experimental methods that can be used to measure the EMCD signal [P. Schattschneider, et al.Nature441,486 (2006); C. Hébert, et al.Ultramicroscopy108(3), 277 (2008); B. Warot-Fonrose, et al.Ultramicroscopy108(5), 393 (2008); L. Calmels, et al.Phys. Rev. B76,060409 (2007); P. van Aken, et al.Microsc. Microanal.13(3), 426 (2007)] and give a review of the recent improvements of this new investigation tool. The dependence of the EMCD on several experimental conditions (such as thickness, relative orientation of beam and sample, collection and convergence angle) is investigated in the transition metals iron, cobalt, and nickel. Different scattering geometries are illustrated; their advantages and disadvantages are detailed, together with current limitations. The next realistic perspectives of this technique consist of measuring atomic specific magnetic moments, using suitable spin and orbital sum rules, [L. Calmels, et al.Phys. Rev. B76,060409 (2007); J. Rusz, et al.Phys. Rev. B76,060408 (2007)] with a resolution down to 2 to 3 nm.

198 POSTER Genetic polymorphisms associated with adverse events in childhood acute lymphoblastic leukaemia treated with SHOP-2005 protocol

Transition metals in fine particulate matter generated by combustion induce oxidative DNA damage and inflammation. However, there is remarkable inter-individual variability in susceptibility to these damages.To assess this variability, an ex vivo study was performed using lymphocytes of 47 Caucasian healthy subjects. Cell samples were exposed to a water solution of oil fly ash (OFA). This was formed by the distinctive transition metals vanadium, iron, and nickel. Oxidative DNA damage was evaluated by testing cell viability, intracellular ROS production and 8-oxo-dG. DNA fragmentation and DNA repair capacity were assessed by using the Alkaline-Halo assay. GSTM1, GSTT1, hOGG1, and C677T and A1298C MTHFR gene polymorphisms were tested. Demographic and behavioral factors, collected by questionnaire, were also considered.OFA induced damages showed: (a) a 20-fold variation in range among different subjects in ROS production, (b) a 7-fold variation in range of 8-oxo-dG, and (c) a 25-fold variation in range in DNA repair capacity.A significant increase in DNA damage was detected in GSTT1-deficent subjects compared with wild type genotype carriers. Increases in cytoplasmic ROS and decreases in DNA repair capacity (P < 0.05) were observed in C677T and A1298C variants of MTHFR. A remarkable protective effect of high fruits and vegetable intake was observed for ROS production and DNA damage. Conversely, an adverse effect of meat intake was observed on ROS increase, DNA damage and repair capacity, probably due to the increased intake of bioavailable iron. Smoking decreased DNA repair capacity, while age increased OFA-induced DNA damage.The wide comparative analysis of the complex interactions network, between genetic and behavioral factors provides evidence of the remarkable role of several lifestyle factors. In comparison to genetic polymorphisms they seem to have a higher weight in determining individual susceptibility to the adverse effects of airborne pollutants as transition metals.

Electronic Structure of Ternary Ruthenium-Based Hydrides

We have investigated the electronic structure and bonding characteristics of a series of ternary hydrides composed of transition metals (iron, ruthenium, osmium) and different alkaline-earth elements. Using first-principle methods to compute the electronic structure, the systematic investigation of this isostructural series of compounds allows us to establish chemical trends on different properties. We extend our investigation to the case of low-symmetry, low-hydrogen-coordination ruthenium-based hydrides. We were able to systematize the computed properties in terms of transition-metal−hydrogen and interlattice interactions. We found that the charge state of the transition metal correlates with the hydrogen site energy, indicating the importance of the charge redistribution in the molecular anions. The H site energy exhibits an interesting correlation with the hydride formation enthalpy. The formation enthalpy, from the elements, shows a correlation with the interlattice interaction energy, indicating the importance of the alkaline-earth sublattice.

Interaction of Iron Atoms with Pristine and Defective (8, 0) Boron Nitride Nanotubes

Interaction of transition metal Fe atoms with pristine and defective (8, 0) boron nitride nanotubes have been investigated using density functional theory calculation. Our results indicate that a single Fe atom can adsorb on the outer wall of a perfect BN tube exothermically, and it can migrate along the tube surface easily, forming a stable Fe−Fe dimer for the double Fe atom adsorption. The presence of intrinsic defects, including single vacancy, divacancies, and Stone−Wales defects, can enhance the reactivity of BN tubes toward Fe. Special focus has been paid to the modulation on magnetic moment and spin configuration of atomic Fe adsorbed on the defect. Stable Fe−Fe dimer adsorption states exist on all intrinsic defects, characterized by distortion of local defect structures. Our findings propose a possible way for experiment to functionalize the BN tubes with transition metal iron.

IRON’S STAR RISING

PRECIOUS METALS currently are the basis of catalysts that are well understood by chemists and widely used in labs, industrial processes, and automobile catalytic converters. But the metals—such as platinum, palladium, and rhodium—are rare and expensive, and they can be toxic and difficult to recycle. Catalysts enable some 90% of chemical processes, and chemists are always on the lookout for new ones. As they consider how to foster a more sustainable future, they are seeking alternatives that not only are greener and less expensive than current catalysts but also as effective or better. Matthias Beller and coworkers Stephan Enthaler and Kathrin Junge at the Leibniz Institute for Catalysis at the University of Rostock, in Germany, make up one team of chemists that has been giving serious thought to possible alternatives. They have investigated the first-row transition metals iron, copper, zinc, and manganese as potential homogeneous catalysts that can contribute to a more sustainable chemical enterprise. ...

Growth and magnetization study of transition metal doped GaN nanostructures

AbstractThis work presents the MOCVD growth and characterization of optically active GaN nanostructures which have been doped with the transition metals manganese and iron for potential spintronic applications. Introduction of both these transition metals in GaN nanostructures enhanced the nucleation of the nanostructures resulting in reduced lateral dimensions and increased nanostructure density. Both Ga1–xMnxN and Ga1–xFexN nanostructures showed hysteresis behaviour at 5 K. Further VSM measurements on Ga1–xFexN nanostructures at 300 K showed a hysteresis curve with a reduced coercive filed and displayed superparamagnetic behaviour. These magnetically active nanostructures are promising and provide an incentive to further study them with the aim of eventually utilizing them in spintronic applications and improving device efficiency. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Hydrothermal syntheses and crystal structures of hybrid materials based on Keggin cluster modified by iron complexes

Three new organic-inorganic hybrid complexes based on the Keggin polyoxometalates (POMs) modified by transition metal iron and N-ligand organic moiety: [Fe(phen)3]2 (1) [Fe(phen)2(H2O)]2 · 2H2O (2) and [Fe(phen)3]2 · 0.5H2O (3) (phen = 1,10-phenanthroline) have been hydrothermally synthesized and structurally characterized. Crystal data for complex 1: C72H48Fe2M12N12O41PV, triclinic, , a = 11.6618(2) Å, b = 13.8523(2) Å, c = 14.9168(2) Å, α = 105.87(3)°, β = 93.103(2)°, γ = 96.609(2)°, V = 2293.2(5) Å3, Z = 1; for complex 2: C48H32Fe2PMo12N8O44, triclinic, , b = 13.357(3) Å, c = 13.701(3) Å, α = 69.09(3)°, β = 71.37(3)°, γ = 78.21(3)°, V = 1766.4(6) Å3, Z = 1; for complex 3: C72H50Fe2Mo12N12O41Ge, triclinic, , b = 13.676(3) Å, c = 14.627(3) Å, α = 105.05(3)°, β = 109.64(3)°, γ = 93.07(3) °, V = 2185.6(7) Å3, Z = 1. Other characterizations by element analysis, IR, XPS and TGA analysis are also described. Their electrochemical properties have been studied in the paper.

Thioredoxin in coronary culprit lesions: Possible relationship to oxidative stress and intraplaque hemorrhage

The present study investigated the expression of thioredoxin (TRX), an important anti-oxidative protein, and its relationship to plaque instability in atherectomy specimens from 43 and 42 patients with stable (SAP) and unstable (UAP) angina pectoris, respectively. We histologically assessed thrombus formation, cellular elements, localization of TRX and of oxidized low density lipoprotein (ox-LDL), intraplaque hemorrhage, and transition metal iron (Fe 2+, Fe 3+) deposition in these specimens. The clinical characteristics of the two groups did not differ except for aspirin administration. The incidence of thrombus formation was more frequent ( P = 0.005) and immunopositive areas of macrophage, TRX and ox-LDL were significantly larger in patients with UAP than SAP ( P < 0.001, each). Macrophages were mainly immunoreactive for TRX and ox-LDL. Intraplaque hemorrhage evaluated by glycophorin A immunoreactivity and Fe 2+/Fe 3+ deposition was also more obvious in lesions from patients with UAP than SAP ( P < 0.001, each). Additionally, immunopositive areas of TRX and ox-LDL positively correlated with Fe 2+/Fe 3+ deposition and were also associated with thrombus formation. Although the underlying mechanisms remain unknown, TRX was up-regulated in response to increased oxidative stress and associated with intraplaque hemorrhage of coronary culprit lesions, and thus might be a potent marker of plaque instability.

The Kubo–Greenwood calculation of conductivity of the simple and non-simple liquid metals in a wide temperature range

We calculated the temperature dependences of electroconductivity for the different metals, such as alkalis (caesium), transition metals (iron), and mercury by Kubo–Greenwood formula. Atomic models of 1000–4000 atoms were obtained by Shommers method using the data of diffractional experiments for the wide temperature range. The electronic structure and interaction parameters for supercells of 30–50 atoms were got by LMTO method. The recursion method was used for the calculation of DOS and diffusivity quotients. The lowering of the DOS at the Fermi level was carefully examined.The results obtained are in good agreement with other authors' in views on the nature of the metal-nonmetal transition in different liquid metals. The calculated DOS and conductivity for all metals match the experimental data well.

Oxidation of Sulfur Components in Diesel Fuel with Tert-Butyl Hydroperoxide Using Chromium Containing Catalysts

Transition metal (iron, cobalt, and chromium) substituted Hexagonal Mesoporous Aluminophosphate (HMA), and AlPO4-5 were studied for the oxidative desulfurization (ODS) reaction of refractory sulfur compounds such as DBT (dibenzothiophene) and 4,6-DMDBT (4,6- dimethyldibenzothiophene). Selective oxidation activity varies with the kind of transition metal employed. The ODS activity of HMA substituted catalyst follows the order: CrHMA &gt;&gt; CoHMA ≥ FeHMA. Comparison between HMA and AlPO-5, CrHMA catalyst shows better performance than Cr-AlPO4-5 catalyst when tert-butyl hydroperoxide is used as oxidizing agent.

H2 Adsorption on 3d Transition Metal Clusters: A Combined Infrared Spectroscopy and Density Functional Study

The adsorption of H2 on a series of gas-phase transition metal (scandium, vanadium, iron, cobalt, and nickel) clusters containing up to 20 metal atoms is studied using IR-multiple photon dissociation spectroscopy complemented with density functional theory based calculations. Comparison of the experimental and calculated spectra gives information on hydrogen-bonding geometries. The adsorption of H2 is found to be exclusively dissociative on Sc(n)O+, V(n)+, Fe(n)+, and Co(n)+, and both atomic and molecularly chemisorbed hydrogen is present in Ni(n)H(m)+ complexes. It is shown that hydrogen adsorption geometries depend on the elemental composition as well as on the cluster size and that the adsorption sites are different for clusters and extended surfaces. In contrast to what is observed for extended metal surfaces, where hydrogen has a preference for high coordination sites, hydrogen can be both 2- or 3-fold coordinated to cationic metal clusters.