Decrease In Fe Content Research Articles

Lithium Diffusion in Cation-Mixing-Free LiMn1-xFexPO4 Synthesized by Hydrothermal Process

Lithium diffusion properties of LiMn1-xFexPO4 synthesized by hydrothermal methods were characterized from electrochemical and structural analysis. Structural defects such as cation mixing in LiMn1-xFexPO4 impede the lithium-ion diffusion. Therefore, it is important to understand effects of cation mixing in LiMn1-xFexPO4 on lithium diffusivity of LiMn1-xFexPO4. The amount of cation mixing of lithium and Mn/Fe in LiMn1-xFexPO4 was obtained by means of neutron diffraction measurements. Rietveld refinements indicated that cation mixing in the prepared LiMn1-xFexPO4 was negligible. Apparent chemical diffusion coefficients (Dapp) of lithium of LiMn1-xFexPO4 dependent on the Mn/Fe ratio were obtained by potential-step chronoamperometry (PSCA) measurements of thin composite electrodes. Dapp of lithium insertion or extraction reaction of LiMn1-xFexPO4 for Mn2+/Mn3+ increased with Fe content. Dapp for Fe2+/Fe3+ slightly increased with decreasing Fe content. The difference of Dapp value was attributed to the activation energies (Ea) of lithium diffusion process of LiMn1-xFexPO4. The Ea of LiMn1-xFexPO4 for Mn2+/Mn3+ and Fe2+/Fe3+ was determined by the energy barrier of lithium hopping at the interphase between Li-rich and Li-poor phase under electrochemical kinetic conditions.

The isotopic signature and distribution of particulate iron in the North Atlantic Ocean

Iron (Fe) is a key micronutrient for life in the oceans. Particles play an important role in the marine biogeochemical cycling of Fe as a reservoir of marine Fe that may be directly accessible to phytoplankton, and as sources and sinks for seawater dissolved Fe. Here, we report the stable isotopic composition of Fe (δ56Fe) in suspended (0.8–51μm) particles from the US GEOTRACES GA03 North Atlantic zonal transect, in order to facilitate a better understanding of the marine biogeochemical cycling of Fe. Data are presented both for a total digestion of the particles, and for ‘ligand-leachable’ phases of Fe using a newly-developed pH 8 oxalate–EDTA leach. For total particle digests, the mean δ56Fe across the whole GA03 section was 0.08±0.09‰ (1 S.D.) which is equivalent to the isotope composition of known lithogenic Fe sources to the ocean. In contrast, ligand-leachable Fe was generally lighter than continental material with a mean δ56Fe of −0.30±0.17‰ (1 S.D.). Our data also provide valuable insight into Fe biogeochemical cycling in several key regions. In the deep ocean, but above the depths where near-sediment nephloid layers are present, ligand-leachable Fe is isotopically lighter in the deep Western Basin compared to the deep Central and Eastern Basins suggesting differences in particle surface chemistry between resuspended seafloor sediments, which may predominate in the west, and Saharan dust that predominates in the center and in the east. Within a nephloid layer above reduced continental margin sediments in the Eastern Basin, below the Mauritanian upwelling region, we report the lowest particulate δ56Fe values for both total and ligand-leachable Fe, suggesting a transfer of isotopically light dissolved porewater Fe2+ to the particulate phase. In contrast, δ56Fe values within a nephloid layer near Bermuda are similar to values higher in the water column. Within a hydrothermal plume sampled at the TAG hydrothermal field on the mid-Atlantic Ridge, decreasing Fe concentration and δ56Fe with distance from the vent indicate the water-column precipitation of Fe oxyhydroxides within the plume. Comparison between total and ligand-leachable particulate Fe concentrations throughout the transect also provides useful biogeochemical information. In the chlorophyll maximum, a high proportion of Fe in the labile phase demonstrates a relative lack of lithogenic material, while the high proportion of labile Fe observed between 2000 and 4000m depth to the west of the mid-Atlantic Ridge suggests that hydrothermal oxyhydroxide particles can be transported thousands of kilometers away from vent sites. Throughout the North Atlantic, measurements of total and ligand-leachable Fe concentration and δ56Fe are therefore useful tools for studying the biogeochemical cycling of particulate Fe.

Liquid phase oxidation of n-octane to C8 oxygenates over modified Fe-MOF-5 catalysts

The Metal Organic Framework materials Fe4-MOF-5, Fe2–Zn2-MOF-5 and Fe0.9–Zn3.1-MOF-5 were prepared. The XRD results showed the expected pattern of MOF-5 with a very sharp peak at a 2θ value below 10° which indicate that the material is highly crystalline. The SEM and TEM images showed that the catalysts are cubic in shape. The synthesised Fe4-MOF-5, Fe2–Zn2-MOF-5 and Fe0.9–Zn3.1-MOF-5 were tested in the oxidation of n-octane using H2O2 as an oxidant in acetonitrile as solvent. Conversions of 10.5, 4.2 and 3.6% were obtained for Fe4-MOF-5, Fe2–Zn2-MOF-5 and Fe0.9–Zn3.1-MOF-5 respectively. It was observed that primary carbon activation increased with decreasing Fe content, as C-1 selectivities of 9.5, 12.9 and 19.8% were achieved for Fe4-MOF-5, Fe2–Zn2-MOF-5 and Fe0.9–Zn3.1-MOF-5 respectively. Only C8 oxygenate products were observed, which include 1-octanol, 2-octanol, 3-octanol, 4-octanol, octanal, 2-octanone, 3-octanone, 4-octanone and octanoic acid. Furthermore, these catalysts were tested in the oxidation of cyclohexane using H2O2 in acetonitrile. Selectivities of 48.3% for cyclohexanol, 47.1% for cyclohexanone and 4.6% for hydroperoxycyclohexane were recorded at a conversion of 40% using Fe4-MOF-5 as a catalyst.

Dietary manganese supplementation influences the expression of transporters involved in iron metabolism in chickens.

To investigate the effects of dietary manganese (Mn) supplementation on iron (Fe) metabolism, a total of 480 50-week-old hens were fed the basal diet (control, 24.35 mg Mn/kg) without Mn supplementation for 6 weeks to reduce Mn storage in the body. Hens were then randomly assigned to one of three treatments, which included the control and control added with 60 or 300 mg Mn/kg diet (M-Mn or H-Mn). Duodenum, heart, liver, and tibia were collected in hens after 12-week feeding period. No significant differences were observed in egg production, feed/egg ratio, shell breaking strength, and shell thickness among different treatments. Compared with control or M-Mn, H-Mn decreased (P < 0.05) serum Fe concentration, while increased (P < 0.05) total Fe-binding capacity (TIBC). The Fe concentration decreased (P < 0.05) in duodenum, and tended to reduce (P < 0.10) in liver from control to M-Mn and to H-Mn; whereas, dietary Mn supplementation did not influence (P > 0.10) Fe concentration in the heart and tibia. In conjunction with reduced Fe retention, DMT1 mRNA expression decreased (P < 0.05) with dietary Mn concentration increasing in the duodenum and liver. Duodenal FPN1 mRNA level was higher (P < 0.05) in H-Mn group than that in control or M-Mn group, while hepatic FPN1 mRNA expression was lower (P < 0.05) in M-Mn or H-Mn group when compared with control. The results demonstrated that dietary Mn supplementation decreased Fe concentration in duodenum and liver of hens, which may be related to the alteration of DMT1 and FPN1 expression in these tissues.

Chromate alters root system architecture and activates expression of genes involved in iron homeostasis and signaling in Arabidopsis thaliana

Soil contamination by hexavalent chromium [Cr(VI) or chromate] due to anthropogenic activities has become an increasingly important environmental problem. To date few studies have been performed to elucidate the signaling networks involved on adaptive responses to (CrVI) toxicity in plants. In this work, we report that depending upon its concentration, Cr(VI) alters in different ways the architecture of the root system in Arabidopsis thaliana seedlings. Low concentrations of Cr (20-40µM) promoted primary root growth, while concentrations higher than 60µM Cr repressed growth and increased formation of root hairs, lateral root primordia and adventitious roots. We analyzed global gene expression changes in seedlings grown in media supplied with 20 or 140µM Cr. The level of 731 transcripts was significantly modified in response to Cr treatment with only five genes common to both Cr concentrations. Interestingly, 23 genes related to iron (Fe) acquisition were up-regulated including IRT1, YSL2, FRO5, BHLH100, BHLH101 and BHLH039 and the master controllers of Fe deficiency responses PYE and BTS were specifically activated in pericycle cells. It was also found that increasing concentration of Cr in the plant correlated with a decrease in Fe content, but increased both acidification of the rhizosphere and activity of the ferric chelate reductase. Supply of Fe to Cr-treated Arabidopsis allowed primary root to resume growth and alleviated toxicity symptoms, indicating that Fe nutrition is a major target of Cr stress in plants. Our results show that low Cr levels are beneficial to plants and that toxic Cr concentrations activate a low-Fe rescue system.

Magnetic Phase Diagrams of Tm&lt;sub&gt;2&lt;/sub&gt;Fe&lt;sub&gt;19-&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;Mn&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; and Tm&lt;sub&gt;2&lt;/sub&gt;Fe&lt;sub&gt;17+δ&lt;/sub&gt; Systems

The Tm2Fe19-xMnx (x = 0 - 1.5) and Tm2Fe16, Tm2Fe17, Tm2Fe18, Tm2Fe19 intermetallic compounds were synthesized and their magnetic and structural properties were studied. Magnetic measurements, X-ray and neutron diffraction investigations were used. The compounds crystallize in a disordered variant of the hexagonal Th2Ni17-type structure. The lattice parameters a, c increases in the Tm2Fe19-xMnx system, whereas c decreases and a increases in the Tm2Fe19 - Tm2Fe16 system as Fe content decreases. The temperatures of ferromagnetic ordering and spin-reorientation increase as Fe content decreases in these systems. Apparently, the decrease of occupation of defected dumbbell Fe (4e) site causes these regularities.

Dependence of Soft Magnetic Properties of &lt;inline-formula&gt; &lt;tex-math notation="TeX"&gt;${\rm Fe}_{81-85.5}{\rm Si}_{2}{\rm B}_{10}{\rm P}_{1.5-6}{\rm Cu}_{1}$ &lt;/tex-math&gt;&lt;/inline-formula&gt; Alloys on P Content

Effects of P content in amorphous and nanocrystalline FeSiBPCu soft magnetic alloys were investigated by comparing the corresponding change in the saturation magnetic flux density and coercivity. Ribbons were prepared using a high induction melting and melt spinning method. As-quenched Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">85.5</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.5</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> alloy consisted of minor crystalline phase. With an increase of P content, the glass forming ability was enhanced. The decrease in the saturation magnetic flux density associated with increased P content, was mainly ascribed to the decrease in Fe content. Nanocrystalline Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">87-x</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> alloys exhibited higher saturation magnetic flux density and lower coercivity, when x was >2 at%. The best soft magnetic performance was obtained at x = 2 at%, where the saturation magnetic flux density was 1.87 T. The coercivity was decreased with P content, indicating that the size of α-Fe grains became smaller with the increase of P content.

Temperature-dependent 57Fe Mössbauer spectroscopy and local structure of the mullite-type Bi2(FexGa1−x)4O9 (0.1≤x≤1) solid solution

The Bi2(FexGa1−x)4O9 oxide solid solution possessing a mullite-type structure has been investigated by 57Fe Mössbauer spectroscopy in dependence of composition (0.1≤x≤1) and temperature (293≤T/K≤1073). The spectra have been fitted with two doublets for tetrahedrally and octahedrally coordinated high-spin Fe3+ ions, respectively. The experimental areas of the subspectra were used to determine the distribution of iron on the two inequivalent structural sites. The fraction of iron cations occupying the octahedral site is found to increase with decreasing Fe content and the cation distribution is almost independent of temperature. The unusual temperature dependence of the quadrupolar splitting, QS, observed for the octahedral site with dQS/dT>0 is discussed in connexion with structural data for Bi2Fe4O9. The temperature dependence of Mössbauer isomer shifts and signal intensities is examined in the context of local vibrational properties of iron on the two inequivalent sites of the mullite-type lattice structure.

Enhancement of anomalous codeposition in the synthesis of Fe–Ni alloys in nanopores

In this paper we report an enhancement of anomalous codeposition in NiFe electrodeposition when using nanoporous templates. Depending on the deposition potential it is possible to obtain homogeneous nanowires of a high Fe concentration or of a concentration similar to the one of the electrolyte used. In addition, nanowires with a decreasing Fe concentration are found for intermediate overpotentials. Voltammetric studies relate this effect with a possible higher block of the cathode surface by adsorption of intermediated species in nanopores. A study of the effect of hydrogen bubbles shows a change in the composition in the areas surrounding the bubbles, and yields an increase in the deposition rate, which results in longer nanowires.

Synthesis, characterization and magnetic properties of nanocrystalline FexNi80−xCo20 ternary alloys

Fe–Ni–Co alloys of various compositions (FexNi80−xCo20,x=20–50) were synthesized by using a sodium borohydride reduction route. The phase purity and crystallite size was ascertained by using powder X-ray diffraction (XRD). The alloys crystallize in the face centered cubic (fcc) structure with lattice parameters, a=3.546–3.558Å. The XRD line broadening indicates the fine particle nature of the materials. The estimated crystallite sizes were found to be 27.5, 27, 24, and 22.8nm for x=20, 30, 40, and 50; alloys respectively. Scanning electron micrograph studies indicates particle sizes to be in the range of 83–60nm for Fe–Ni–Co alloys. The values of saturation magnetization for FexNi80−xCo20 are found to be in the range of 54.3–41.2emu/g and are significantly lower than the bulk values (175–180emu/g). The coercivity decreases from 170 to 122Oe with decrease in Fe content. The observed magnetic behavior has been explained on the basis of size, surface effects, spin canting and the presence of superparamagnetic fractions in the ultrafine materials.

Catalytic performance of sheet-like Fe/ZSM-5 zeolites for the selective oxidation of benzene with nitrous oxide

Hierarchical Fe/ZSM-5 zeolites were synthesized with a diquaternary ammonium surfactant containing a hydrophobic tail and extensively characterized by XRD, Ar porosimetry, TEM, DRUV–Vis, and UV-Raman spectroscopy. Their catalytic activities in catalytic decomposition of N2O and the oxidation of benzene to phenol with N2O as the oxidant were also determined. The hierarchical zeolites consist of thin sheets limited in growth in the b-direction (along the straight channels of the MFI network) and exhibit similar high hydrothermal stability as a reference Fe/ZSM-5 zeolite. Spectroscopic and catalytic investigations point to subtle differences in the extent of Fe agglomeration with the sheet-like zeolites having a higher proportion of isolated Fe centers than the reference zeolite. As a consequence, these zeolites have a somewhat lower activity in catalytic N2O decomposition (catalyzed by oligomeric Fe), but display higher activity in benzene oxidation (catalyzed by monomeric Fe). The sheet-like zeolites deactivate much slower than bulk Fe/ZSM-5, which is attributed to the much lower probability of secondary reactions of phenol in the short straight channels of the sheets. The deactivation rate decreases with decreasing Fe content of the Fe/ZSM-5 nanosheets. It is found that carbonaceous materials are mainly deposited in the mesopores between the nanosheets and much less so in the micropores. This contrasts the strong decrease in the micropore volume of bulk Fe/ZSM-5 due to rapid clogging of the continuous micropore network. The formation of coke deposits is limited in the nanosheet zeolites because of the short molecular trafficking distances. It is argued that at high Si/Fe content, coke deposits mainly form on the external surface of the nanosheets.

Depth profile investigation of the incorporated iron atoms during Kr+ ion beam sputtering on Si (001)

We investigate the incorporation of iron atoms during nano-patterning of Si surfaces induced by 2keV Kr+ ion beam erosion under an off-normal incidence angle of 15°. Considering the low penetration depth of the ions, we have used X-ray reflectivity (XRR) and X-ray absorption near edge spectroscopy (XANES) under grazing-incidence angles in order to determine the depth profile and phase composition of the incorporated iron atoms in the near surface region, complemented by secondary ion mass spectrometry and atomic force microscopy. XRR analysis shows the accumulation of metallic atoms within a near surface layer of a few nanometer thickness. We verify that surface pattern formation takes place only when the co-sputtered Fe concentration exceeds a certain limit. For high Fe concentration, the ripple formation is accompanied by the enhancement of Fe close to the surface, whereas no Fe enhancement is found for low Fe concentration at samples with smooth surfaces. Modeling of the measured XANES spectra reveals the appearance of different silicide phases with decreasing Fe content from the top towards the volume.

Rosette iron deficiency transcript and microRNA profiling reveals links between copper and iron homeostasis in Arabidopsis thaliana

Iron (Fe) is an essential plant micronutrient, and its deficiency limits plant growth and development on alkaline soils. Under Fe deficiency, plant responses include up-regulation of genes involved in Fe uptake from the soil. However, little is known about shoot responses to Fe deficiency. Using microarrays to probe gene expression in Kas-1 and Tsu-1 ecotypes of Arabidopsis thaliana, and comparison with existing Col-0 data, revealed conserved rosette gene expression responses to Fe deficiency. Fe-regulated genes included known metal homeostasis-related genes, and a number of genes of unknown function. Several genes responded to Fe deficiency in both roots and rosettes. Fe deficiency led to up-regulation of Cu,Zn superoxide dismutase (SOD) genes CSD1 and CSD2, and down-regulation of FeSOD genes FSD1 and FSD2. Eight microRNAs were found to respond to Fe deficiency. Three of these (miR397a, miR398a, and miR398b/c) are known to regulate transcripts of Cu-containing proteins, and were down-regulated by Fe deficiency, suggesting that they could be involved in plant adaptation to Fe limitation. Indeed, Fe deficiency led to accumulation of Cu in rosettes, prior to any detectable decrease in Fe concentration. ccs1 mutants that lack functional Cu,ZnSOD proteins were prone to greater oxidative stress under Fe deficiency, indicating that increased Cu concentration under Fe limitation has an important role in oxidative stress prevention. The present results show that Cu accumulation, microRNA regulation, and associated differential expression of Fe and CuSOD genes are coordinated responses to Fe limitation.

Synthesis and Characterization of Fe Doped TiO2 Nanoparticles by a Sol-Gel and Hydrothermal Process

Fe doped nanoparticles were prepared under high temperature and pressure conditions by mixture of metal nitrate solution and sol. Fe doped particles were reacted in the temperature range of 170 to for 6 h. The microstructure and phase of the synthesized Fe doped nanoparticles were studied by SEM (FE-SEM), TEM, and XRD. Thermal properties of the synthesized Fe doped nanoparticles were studied by TG-DTA analysis. TEM and X-ray diffraction pattern shows that the synthesized Fe doped nanoparticles were crystalline. The average size and distribution of the synthesized Fe doped nanoparticles were about 10 nm and narrow, respectively. The average size of the synthesized Fe doped nanoparticles increased as the reaction temperature increased. The overall reduction in weight of Fe doped nanoparticles was about 16% up to ; water of crystallization was dehydrated at . The transition of Fe doped nanoparticle phase from anatase to rutile occurred at almost . The amount of rutile phase of the synthesized Fe doped nanoparticles increased with decreasing Fe concentration. The effects of synthesis parameters, such as the concentration of the starting solution and the reaction temperature, are discussed.

Metal partitioning in sediments and mineralogical controls on the acid mine drainage in Ribeira da Água Forte (Aljustrel, Iberian Pyrite Belt, Southern Portugal)

► Organic-rich waste water drives the release of metals from acid drainage sediments. ► Precipitation/dissolution of Fe-hydroxides and sulfates controls water chemistry. ► Schwertmannite formation and transformation to Fe-hydroxides maintains low pH. ► Metals keep high concentration in solution with no effective attenuation mechanism. This work focuses on the geochemical processes taking place in the acid drainage in the Ribeira da Água Forte, located in the Aljustrel mining area in the Iberian Pyrite Belt. The approach involved water and stream sediment geochemical analyses, as well as other techniques such as sequential extraction, Mössbauer spectroscopy, and X-ray diffraction. Ribeira da Água Forte is a stream that drains the area of the old mine dumps of the Aljustrel mine, which have for decades been a source of acid waters. This stream flows to the north for a little over than 10 km, but mixes with a reduced, organic-rich, high pH waste water from the municipal waste water pools of the village. This water input produces two different results in the chemistry of the stream depending upon the season: (i) in the winter season, effective water mixing takes place, and the flux of acid water from the mine dumps is continuous, resulting in the immediate precipitation of the Fe from the acid waters; (ii) during the summer season, acid drainage is interrupted and only the waste water feeds the stream, resulting in the reductive dissolution of Fe hydroxides and hydroxysulfates in the stream sediments, releasing significant quantities of metals into solution. Throughout the year, water pH stays invariably within 4.0–4.5 for several meters downstream of this mixing zone even when the source waters come from the waste water pools, which have a pH around 8.4. The coupled interplay of dissolution and precipitation of the secondary minerals (hydroxides and sulfates), keeps the system pH between 3.9 and 4.5 all along the stream. In particular, evidence suggests that schwertmannite may be precipitating and later decomposing into Fe hydroxides to sustain the stream water pH at those levels. While Fe content decreases by 50% from solution, the most important trace metals are only slightly attenuated before the solution mixes with the Ribeira do Rôxo stream waters. Concentrations of As are the only ones effectively reduced along the flow path. Partitioning of Cu, Zn and Pb in the contaminated sediments also showed different behavior. Specific/non-specific adsorption is relevant for Cu and Zn in the upstream branch of Ribeira da Água Forte with acid drainage conditions, whereas the mixture with the waste water causes that the association of these metals with oxyhydroxide to be more important. Metals bound to oxyhydroxides are on the order of 60–70% for Pb, 50% for Cu and 30–60% for Zn. Organic matter is only marginally important around the waste water input area showing 2–8% Cu bound to this phase. These results also show that, although the mixing process of both acid and organic-rich waters can suppress and briefly mitigate some adverse effects of acid drainage, the continuing discharge of these waste waters into a dry stream promotes the remobilization of metals fixed in the secondary solid phases in the stream bed back into solution, a situation that can hardly be amended back to its original state.

Improvement of coercivity and thermal stability of anisotropic Nd13Fe79.4B7Nb0.3Ga0.3 powders by diffusion of Pr-Cu alloys

Highly anisotropic Nd13Fe79.4B7Nb0.3Ga0.3 powders from a self-organized rod-like disproportionation microstructure and room temperature magnetic properties of μ0Mr = 1.4 T, iHc = 13 kOe, and (BH)max = 41 MGOe are obtained by optimizing hydrogenation disproportionation desorption recombination (HDDR) process. Diffusion of Pr68Cu32 alloy into the HDDR powders further increases the coercivity of the powders to 18 kOe. This enhancement in coercivity is mainly attributed to the modification of grain boundaries including the decrease of Fe content and the increase of boundary thickness. The modified boundaries can work as effective pinning layers for domain walls. The thermal stability of magnetic properties of HDDR powders is also improved after the diffusion treatment.

Hydrothermal Dolomites in the Early Albian (Cretaceous) Platform Carbonates (NW Spain): Nature and Origin of Dolomites and Dolomitising Fluids

This study documents the temporal and lateral variation in petrographic and geochemical signatures of fault-related dolomite bodies in the Ranero and El-Moro areas (Karrantza valley, Cantabrian mountains; NW Spain). These dolomite bodies are hosted in Albian carbonates, which were deposited in the Basque-Cantabrian Basin as a result of an intense rift-related subsidence with associated faulting along various orientations. Fluid circulations generated replacive and cement dolomites, paragenetically followed by various calcite cements. Petrography, mineralogical and geochemical investigations (XRD, ICP, XRF, stable and Sr isotopes) helped in distinguishing hydrothermal stages. Two major dolomite facies were observed according to their Fe-content. Early dolomites are ferroan and replace limestone more significantly than the later, non ferroan dolomites. Dolomites are generally stoichiometric (49.76 to 51.59 M% CaCO<sub>3<sub/>) and exhibit a broad range of depleted δ<sup>18<sup/>O values (–18.7 to –10.5‰ V-PDB), which may indicate multiphase dolomitisation and/or different degrees of recrystallisation. Decreasing δ<sup>18<sup/>O values correlate with decreasing Fe content in dolomites. In the Ranero area, dolomites show less slightly depleted δ<sup>13<sup/>C values (–0.15 to +2.13‰ V-PDB) relative to the host limestone δ<sup>13<sup/>C signature, while these values are substantially more depleted in El-Moro area (down to –2.18‰ V-PDB). Hydrothermal calcites predating dolomitisation show less depleted δ<sup>18<sup/>O values (–14.15 to –12.1‰ V-PDB) than postdolomitisation calcite (–18.1‰ V-PDB). Sr isotope data suggest that the fluids interacted with siliciclastic lithologies (sandstone, shale). The dolomite fabric is variably altered through dedolomitisation and cataclastic deformation. Dolomitisation occurred in at least two main episodes. A first episode of pervasive ferroan dolomitisation probably resulted from compactional dewatering of basinal fluids from the nearby Basque trough and hydrodynamic fluid flow along the faults/fractures in the Albian carbonate platform. Subsequently, a second episode of very hot and localised dolomitisation may be related to igneous activity and convective flow.

Structural, electrical, optical and magnetic properties of chromium substituted Co–Zn nanoferrites Co0.6Zn0.4CrxFe2−xO4 (0⩽x⩽1.0) prepared via sol–gel auto-combustion method

Abstract Chromium substituted Co–Zn nanoferrites having the formula Co 0.6 Zn 0.4 Cr x Fe 2− x O 4 ( x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been synthesized using the sol–gel auto-combustion method. Characterized using FT-IR spectroscopy, powder X-ray diffraction, electrical and magnetic properties. XRD patterns indicated the formation of single-phased cubic spinel structure having space group Fd-3m for all the annealed samples. The lattice parameter has been observed to decrease with increasing substitution of Cr 3+ ions because of the smaller ionic radii of Cr 3+ (0.68 Ǻ) as compared to Fe 3+ (0.73 Ǻ). The electrical resistivity increases with increasing Cr 3+ concentration attributing to the reason that electrical conductivity decreases with decrease in Fe concentration because of the decrease in polaron hopping of Fe 2+ –Fe 3+ ions. The resistivity of all the annealed samples decreases with increasing temperature showing the semiconductor nature of the samples. The drift mobility also increases with increasing temperature because of the enhanced mobility of charge carriers due to thermal activation. The saturation magnetization ( M s ) decreases with increasing chromium content, due to the lower magnetic moment of Cr 3+ ion (3 μ B ) than that of Fe 3+ ion (5 μ B ).

Chemical state of Fe in LaNi1 − x Fe x O3 and its effect on electrical conduction property

Mossbauer absorption spectra of single phase LaNi1 − x Fe x O3 (0.2 ≤ x ≤ 1.0) have been measured. Increase of quadrupole splitting with increasing x from 0.2 to 0.6 suggested successful substitution of Fe ion for Ni. Variation of isomer shift with x suggested valence of Fe approched 4+, i.e., concentration of itinerant hole on Fe increased with decrease of Fe content, showing agreement with increase of electrical conductivity with decreasing x from 1.0 to 0.4. It can be prospected that higher electrical conductivity might be obtained if sintering property of the specimens with x less than 0.4 is improved.

Changes in biochemical and hematological parameters and metabolic hormones in Tsigai ewes blood in the first third of lactation

Abstract. The aim of this investigation is to determine changes in concentrations of biochemical and haematological parameters, as well as metabolic hormones in the blood of Tsigai ewes in the first third of lactation. The study included 10 ewes Tsigai breed monitored during three periods of lactation: 20 days, 40 and 60 days of lactation. Ewes were fed feed mixture (300 g/day) and meadow hay ad libitum. A significant decrease of concentrations of Ca and Na was recorded in the blood of sheep at the 40th day of lactation and later an increase at the 60th day of lactation. The opposite trend was determined for concentrations of P-inorganic. Also it was determined a significant decrease in Fe content and an increase in the concentrations of glucose, triglycerides and total protein in the first third of lactation. In the blood of ewes at 40th day of lactation it was found a significant decrease of the activity of AST and LDH in contrast to ewes at 20th day of lactation. Concentrations of T3 and T4 hormones were slightly increasing in the first third of lactation, but the differences were not significant. The blood insulin concentrations were significant increased in the first third of lactation. Haematological blood parameters in lactating ewes did not differ significantly and was within the reference values. Determining the concentration of biochemical and haematological parameters and concentrations of blood thyroid hormones and insulin in the first third of lactation are imposed as a precaution in order to better monitoring of Tsigai ewes during lactation.