First-principles studies of complex magnetism in Mn nanostructures on the Fe(001) surface

The magnetic properties of Mn nanostructures on the Fe(001) surface have been studied using the noncollinear first-principles real space-linear muffin-tin orbital-atomic sphere approximation method within density-functional theory. We have considered a variety of nanostructures such as adsorbed wires, pyramids, and flat and intermixed clusters of sizes varying from two to nine atoms. Our calculations of interatomic exchange interactions reveal the long-range nature of exchange interactions between Mn-Mn and Mn-Fe atoms. We have found that the strong dependence of these interactions on the local environment, the magnetic frustration, and the effect of spin-orbit coupling lead to the possibility of realizing complex noncollinear magnetic structures such as helical spin spiral and half-skyrmion.

Subdivision of Hysteresis Loss in Mn-Zn Ferrite Toroidal Cores

The hysteresis loss subdivision method proved to be a strong tool to help in the analysis of different energy dissipation mechanisms along the quasi-static hysteresis loop measured on electrical steels. This paper used the samemethod to discuss the mechanisms involving the energy loss dissipation in Mn-Zn ferrite toroidal cores. The samples, sintered under controlled atmosphere in industrial conditions, were measured under triangular waveform excitation at very low frequency (5 mHz) and peak flux densities varying from 0.05 T to 0.45 T. The results show a different behavior between the low inductions hysteresis loss (WLI) and the high induction hysteresis loss (WHI) which proves the existence of different energy dissipation mechanisms affecting these loss components.

Evaluation of Inductively Coupled Plasma Mass Spectrometry for Determining Ca, Cu, Fe, Mg, Mn, Se and Zn in Bovine Semen Samples using a Simple Sample Dilution Method

A simple and fast method for the determination of Ca, Cu, Fe, Mg, Mn, Se and Zn in bovine semen by quadrupole inductively coupled plasma spectrometry (q-ICP-MS) is described. Prior to analysis, samples (200 mu L) were diluted 1:50 in a solution containing 0.01% v/v Triton (R) X-100 and 0.5% v/v nitric acid and directly analyzed by ICP-MS. The limits of detection of the method are 0.3, 0.03, 0.2, 0.04, 0.04, 0.03 and 0.03 mu g L-1 for Ca-44, Cu-63, Fe-57, Mg-24, Zn-64, Se-82 and Mn-55, respectively. For purposes of comparison and method validation, four ordinary bovine semen samples were directly analyzed by ICP-MS and by flame atomic absorption spectrometry (FAAS) or graphite furnace atomic absorption spectrometry (GF AAS), with no statistical difference between the techniques at the 95% level when applying the t-test. Then, the proposed method was applied in the determinations of Ca, Cu, Fe, Mg, Mn, Se and Zn in collected samples of bovine semen from different breeds, which are used in reproduction programs and artificial insemination.

GaMnAs: Position of Mn-d levels and majority spin band gap predicted from GGA-1/2 calculations

Among all magnetic semiconductors, GaMnAs seems to be the most important one. In this work, we present accurate first-principles calculations of GaMnAs within the GGA-1/2 approach: We concentrate our efforts in obtaining the position of the peak of Mn-d levels in the valence band and also the majority spin band gap. For the position of the Mn-d peak, we find a value of 3.3 eV below the Fermi level, in good agreement with the most recent experimental results of 3.5 and 3.7 eV. An analytical expression that fits the calculated E-g(x) for majority spin is derived in order to provide ready access to the band gap for the composition range from 0 to 0.25. We found a value of 3.9 eV for the gap bowing parameter. The results agree well with the most recent experimental data. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4718602]

Evaluation of inductively coupled plasma mass spectrometry for determining Ca, Cu, Fe, Mg, Mn, Se and Zn in bovine semen samples using a simple sample dilution method

A simple and fast method for the determination of Ca, Cu, Fe, Mg, Mn, Se and Zn in bovine semen by quadrupole inductively coupled plasma spectrometry (q-ICP-MS) is described. Prior to analysis, samples (200 µL) were diluted 1:50 in a solution containing 0.01% v/v Triton® X-100 and 0.5% v/v nitric acid and directly analyzed by ICP-MS. The limits of detection of the method are 0.3, 0.03, 0.2, 0.04, 0.04, 0.03 and 0.03 µg L-1 for 44Ca, 63Cu, 57Fe, 24Mg, 64Zn, 82Se and 55Mn, respectively. For purposes of comparison and method validation, four ordinary bovine semen samples were directly analyzed by ICP-MS and by flame atomic absorption spectrometry (FAAS) or graphite furnace atomic absorption spectrometry (GF AAS), with no statistical difference between the techniques at the 95% level when applying the t-test. Then, the proposed method was applied in the determinations of Ca, Cu, Fe, Mg, Mn, Se and Zn in collected samples of bovine semen from different breeds, which are used in reproduction programs and artificial insemination.

Geochemistry of Fe-Mn crusts in sediments of the Central Indian Ridge

Layered Fe-Mn crusts from the off-axis region of the first segment of the Central Indian Ridge north of the Rodrigues Triple Junction were studied geochemically and mineralogically. Vernadite (delta-MnO2) is the main mineral oxide phase. 230Thxs and Co concentrations suggest high growth rates of up to 29 mm/Myr and a maximum age of the basal crust layer of 1 Ma. Whereas most of the major and minor elements show concentrations which are typical of hydrogenetic formation, Co, Pb, Ni and Ti concentrations are strikingly lower. Concentrations and distribution of the strictly trivalent rare-earths and yttrium (REY) are typical of hydrogenetic ferromanganese oxide precipitates, but in marked contrast, the crusts are characterized by negative CeSN (shale normalized) anomalies and (Ce/Pr)SN ratios less than unity. Profiles through the crusts reveal only minor variations of the REY distribution and (Ce/Pr)SN ratios range from 0.45 to 0.68 (compared to ratios of up to 2 for typical hydrogenetic crusts from the Central Indian Basin). The apparent bulk partition coefficients between the crusts and seawater suggest that for the strictly trivalent REY the adsorption-desorption equilibrium has been reached. Positive Ce anomalies in the partition coefficient patterns reveal preferential uptake of Ce, but to a lesser extent than in normal hydrogenetic crusts. A new parameter (excess Ce, Cexs) to quantify the degree of decoupling of Ce from REY(III) is established on the basis of partition coefficients. Cexs/Cebulk ratios suggest that the CIR crusts formed by precipitation of Fe-Mn oxides from a hydrothermal plume and that in hydrothermal plumes and normal seawater the enrichment of Ce results from the same oxidative sorption process. The growth rates, calculated with 230Thxs data as well as with the Co formula, are inversely related to Cexs.

Synthesis and characterization of some Mn(II) and Mn(III) complexes of N,N′-o-phenylenebis(salicylideneimine)(LH2) and N,N′-o-phenylenebis(5-bromosalicylideneimine)(L′H2). Crystal structures of [Mn(L)(H2O)(ClO4)], [Mn(L)(NCS)] and an infinite linear chain of [Mn(L)(OAc)]

A series of manganese(II) [Mn(L)] and manganese(III) [Mn(L)(X)] (X = ClO4, OAc, NCS, N3, Cl, Br and I) complexes have been synthesized from Schiff base ligands N,N′-o- phenylenebis(salicylideneimine)(LH2) and N,N′-o-phenylenebis(5- bromosalicylideneimine)(L′H2) obtained by condensation of salicylaldehyde or 5-Br salicylaldehyde with o-phenylene-diamine. The complexes have been characterized by the combination of IR, UV-Vis spectroscopy, magnetic measurements and electrochemical studies. Three manganese(III) complexes 3 [Mn(L)(ClO4)(H2O)], 5 [Mn(L)(OAc)] and 13 [Mn(L)(NCS)] have been characterized by X-ray crystallography. The X-ray structures show that the manganese(III) is hexa-coordinated in 3, it is penta-coordinated in 13, while in 5 there is an infinite chain where the MnL moieties are connected by acetate ions acting as bridging bidentate ligand. The cyclic voltammograms of all the manganese(III) complexes exhibit two reversible/quasi-reversible/ irreversible responses assignable to Mn(III)/Mn(II) and Mn(IV)/Mn(III) couples. It was observed that the ligand L′H2 containing the 5-bromosal moiety always stabilizes the lower oxidation states compared to the corresponding unsubstituted LH2. Cyclic voltammograms of the manganese(II) complexes (1 and 2) exhibit a quasi-reversible Mn(III)/Mn(II) couple at E1/2 -0.08 V for 1 and 0.054 V for 2. © 2005 Elsevier B.V. All rights reserved.

Modificação do eletrodo AWS E7018 com adição de filmes finos externos de PVC e Al, para soldagem de aço C-Mn

This paper suggests modifications in coating of electrodes providing an alternative for execution of welding with low hydrogen electrode AWS E7018 without having to dry it, reducing thus the cost and time of manufacturing of high resistance welds. The welds in this research were developed with basic coated electrodes (hygroscopic) – SMAW process – externally painted with aluminum spray paint for high temperatures or wrapped with thin plastic films (PVC) and aluminum foil films used commonly for food protection. The basic premise is that establishing a barrier between the atmosphere and the electrode coating could reduce the effects of high hygroscopicity presented by coatings of low hydrogen, minimizing this way the main source of supply of hydrogen to the fusion pool during welding. It is also expected that the addition of new materials from the electrode coating to the fusion pool would induce metallurgical changes in the deposited metal and, as a consequence, modifications in its mechanical properties. This research dealt with measuring the dissolved hydrogen in the deposited metal after welding with modified electrodes, evaluating the influence of these changes in the produced microstructures and in the mechanical properties of the resulting weld, and comparing the obtained results with the standard welding procedures and with the recently developed waterproof electrodes. The results obtained in most samples welded with modified electrodes showed increased mechanical resistance and increased tenacity due to the increased percentage of acicular ferrite in metal deposited without significant elevation of hardness, when compared with the traditional welding with AWS E7018 electrode and with ELBRÁS BRH4R waterproof electrode. The diffusing hydrogen measured in the modified electrodes was kept inside the parameters defined by international codes.

Modificação do eletrodo AWS E7018 com adição de filmes finos externos de PVC e Al, para soldagem de aço C-Mn

This paper suggests modifications in coating of electrodes providing an alternative for execution of welding with low hydrogen electrode AWS E7018 without having to dry it, reducing thus the cost and time of manufacturing of high resistance welds. The welds in this research were developed with basic coated electrodes (hygroscopic) – SMAW process – externally painted with aluminum spray paint for high temperatures or wrapped with thin plastic films (PVC) and aluminum foil films used commonly for food protection. The basic premise is that establishing a barrier between the atmosphere and the electrode coating could reduce the effects of high hygroscopicity presented by coatings of low hydrogen, minimizing this way the main source of supply of hydrogen to the fusion pool during welding. It is also expected that the addition of new materials from the electrode coating to the fusion pool would induce metallurgical changes in the deposited metal and, as a consequence, modifications in its mechanical properties. This research dealt with measuring the dissolved hydrogen in the deposited metal after welding with modified electrodes, evaluating the influence of these changes in the produced microstructures and in the mechanical properties of the resulting weld, and comparing the obtained results with the standard welding procedures and with the recently developed waterproof electrodes. The results obtained in most samples welded with modified electrodes showed increased mechanical resistance and increased tenacity due to the increased percentage of acicular ferrite in metal deposited without significant elevation of hardness, when compared with the traditional welding with AWS E7018 electrode and with ELBRÁS BRH4R waterproof electrode. The diffusing hydrogen measured in the modified electrodes was kept inside the parameters defined by international codes.

Effect of foliar application of Cu, Zn, and Mn on yield and quality indicators of winter wheat grain

Micronutrients are part of many crucial physiological plant processes. The combined application of N and micronutrients helps in obtaining grain yield with beneficial technological and consumer properties. The main micronutrients needed by cereals include Cu, Mn, and Zn. The subject of this study was to determine yield, quality indicators (protein content and composition, gluten content, grain bulk density, Zeleny sedimentation index, and grain hardness), as well as mineral content (Cu, Zn, Mn, Fe) in winter wheat grain ( Triticum aestivum L.) fertilized by foliar micronutrient application. A field experiment was carried out at the Educational and Experimental Station in Tomaszkowo, Poland. The application of mineral fertilizers (NPK) supplemented with Cu increased Cu content (13.0%) and ω, α/β, and γ (18.7%, 4.9%, and 3.4%, respectively) gliadins in wheat grain. Foliar Zn fertilization combined with NPK increased Cu content (14.9%) as well as high (HMW) and low molecular weight (LMW) glutenins (38.8% and 6.7%, respectively). Zinc fertilization significantly reduced monomeric gliadin content and increased polymeric glutenin content in grain, which contributed in reducing the gliadin:glutenin ratio (0.77). Mineral fertilizers supplemented with Mn increased Fe content in wheat grain (14.3%). It also significantly increased protein (3.8%) and gluten (4.4%) content, Zeleny sedimentation index (12.4%), and grain hardness (18.5%). Foliar Mn fertilization increased the content of ω, α/β, and γ gliadin fractions (19.9%, 9.5%, and 2.1%, respectively), as well as HMW and LMW glutenins (18.9% and 4.5%, respectively). Mineral NPK fertilization, combined with micronutrients (Cu + Zn + Mn), increased Cu and Zn content in grain (22.6% and 17.7%, respectively). The content of ω, α/β, and γ gliadins increased (20.3%, 10.5%, and 12.1%, respectively) as well as HMW glutenins (7.9%).

Estudo da labilidade de Cu(II), Cd(II), Mn(II) e Ni(II) em substâncias húmicas aquáticas utilizando-se membranas celulósicas organomodificadas

In this work commercial filters papers were organomodified with tetraethylorthosilicate (TEOS) and 3-aminopropyltriethoxysilane (3-APTS), aiming at the development of a new analytical procedure for in-situ speciation of labile and inert metal species in aquatic systems. Parameters that exert influence on the metal lability such as pH, chelating time, concentration and characteristics of the organic matter were studied in the laboratory using tests for metal recuperation. The results showed slower kinetics for Cu ion than for Ni, Mn and Cd in the absence of aquatic humic substances (AHS). The relative lability observed for complexed metals in aquatic humic substances using organomodified filter papers was Cu>>Cd>Ni>Mn. The pH values, structural characteristics and concentration of AHS exert strong influence on the lability of the metals. The results obtained showed that the utilization of organomodified filter papers can be an interesting and promising alternative for in situ characterization of metal lability in aquatic systems.

Extração de metais (K, Mg, Ba, Ca, Cr, Mn, Li, Fe) de água produzida utilizando sistema microemulsionado

The produced water is a byproduct formed due to production of petroleum and carries with it a high amount of contaminants such as oil particles in suspension, organic compounds and metals. Thus, these latter pollutants are very difficult to treat because of its high solubility in water. The objective of this work is to use and evaluate a microemulsioned system to remove metals ( K , Mg , Ba , Ca , Cr , Mn , Li , Fe ) of synthetic produced water. For the extraction of metals, it was used a pseudoternary diagram containing the following phases: synthetic produced water as the aqueous phase (AP), hexane as organic phase (OP), and a cosurfactant/surfactant ratio equal to four (C/S = 4) as the third phase, where the OCS (saponified coconut oil) was used as surfactant and n-butanol as cosurfactant. The synthetic produced water was prepared in a bench scale and the region of interest in the diagram for the removal of metals was determined by experimental design called. Ten points located in the phase Winsor II were selected in an area with a large amount of water and small amounts of reagents. The samples were analyzed in atomic absorption spectrometer, and the results were evaluated through a statistical assesment, allowing the efficiency analysis of the effects and their interactions. The results showed percentages of extraction above 90% for the metals manganese, iron, chromium, calcium, barium and magnesium, and around 45% for metals lithium and potassium. The optimal point for the simultaneous removal of metals was calculated using statistical artifact multiple response function (MR). This calculation showed that the point of greatest extraction of metals occurs was the J point, with the composition [72% AP, 9% OP, 19% C/S], obtaining a global extraction percentage about 80%. Considering the aspects analyzed, the microemulsioned system has shown itself to be an effective alternative in the extraction of metals on synthetic produced water remediation

Parametrage du modèle de culture STICS pour simuler la croissance des prairies de Brachiaria brizantha cv. BRS Piatã en conditions du Cerrado brésilien.

2015

Efeito da aplicação de lodo de esgoto na acumulação de Fe, Mn, Zn, Cu, Ni, PB e Cr em solo.

2008

Characterisation of soluble components and PAH in PM10 atmospheric particulate matter in Brisbane

Fours sets of PM10 samples were collected in three sites in SEQ from December 2002 to August 2004. Three of these sets of samples were collected by QLD EPA as a part of their regular air monitoring program at Woolloongabba, Rocklea and Eagle Farm. Half of the samples were used in this study for the analysis of water-soluble ions, which are Na+, K+, Mg2+, Ca2+, NH4 +, Cl-, NO3 -, SO4 2-, F-, Br-, NO2 -, PO4 -3 and the other half was retained by QLD EPA. The fourth set of samples was collected at Rocklea, specifically for this study. A quarter of the samples obtained from this set of samples were used to analyse water-soluble ions; a quarter of the sample was used to analyse Pb, Cu, Al, Fe, Mn and Zn; and the rests were used to analyse US EPA 16 priority PAHs. The water-soluble ions were extracted ultrasonically with water and the major watersoluble anions as well as NH4 + were analysed using IC. Na+, K+, Mg2+, Ca2+ Pb, Cu, Al, Fe, Mn and Zn were analysed using ICP-AES while PAHs were extracted by acetonitrile and analysed using HPLC. Of the analysed water-soluble ions, Cl-, NO3 -, SO4 2-, Na+, K+, Mg2+ and Ca2+ were high in concentration and determined in all the samples. F-, Br-, NO2 -, PO4 -3 and NH4 + ions were lower in concentration and determined only in some samples. Na+ and Cl- were high in all samples indicating the importance of a marine source. Principal Component Analysis (PCA) was used to examine the temporal variations of the water-soluble ions at the three sites. The results indicated that there was no major difference between the three sites. However, comparing the average concentrations of ions and Cl-/Na+ it was concluded that Woolloongabba had more marine influence than the other sites. Al, Fe and Zn were detected in all samples. Al and Fe were high in all samples indicating the significance of a source of crustal matter. Cu, Mn and Pb were in low concentrations and were determined only in some samples. The lower Pb concentrations observed in the study than in previous studies indicate that the phasing-out of leaded petrol had an appreciable impact on Pb levels in SEQ. This study reports for the first time, simultaneous data on the water-soluble, metal ion and PAH levels of PM10 aerosols in Brisbane, and provides information on the most likely sources of these chemical species. Such information can be used alongside those that already exist to formulate PM10 pollution reduction strategies for SEQ in order to protect the community from the adverse effects of PM pollution.