Synthesis and electrochemical behavior of single-crystal magnetite nanoparticles

Water-dispersed magnetite nanoparticle synthesis from iron(II) chloride in dimethyl sulfoxide (DMSO)-water solution at different DMSO-water ratios in alkaline medium was reported. TEM and XRD results suggest a single-crystal formation with mean particle size in the range 4-27 nm. Magnetic nanoparticles are formed by the oxidative hydrolysis reaction from green rust species that leads to FeOOH formation, followed by autocatalysis of the adsorbed available Fe(II) on the FeOOH surfaces. The available hydroxyl groups seem to be dependent on the DMSO-water ratio due to strong molecular interactions presented by the solvent mixture. Goethite phase on the magnetite surface was observed by XRD data only for sample synthesized in the absence of DMSO. In addition, cyclic voltammetry with carbon paste electroactive electrode (CV-CPEE) results reveal two reduction peaks near 0 and +400 mV associated with the presence of iron(III) in different chemical environments related to the surface composition of magnetite nanoparticles. The peak near +400 mV is related to a passivate thin layer surface such as goethite on the magnetite nanoparticle, assigned to the intensive hydrolysis reaction due to strong interactions between DMSO-water molecules in the initial solvent mixture that result in a hydroxyl group excess in the medium. Pure magnetite phase was only observed in the samples prepared at 30% (30W) and 80% (80W) water in DMSO in agreement with the structured molecular solvent cluster formation. The goethite phase present on the, magnetite nanoparticle surface like a thin passivate layer only was detectable using CV-CPEE, which is a very efficient, cheap, and powerful tool for surface characterization, and it is able to determine the passivate oxyhydroxide or oxide thin layer presence on the nanoparticle surface.

Investigation of the corrosion behaviour of AA 2024-T3 in low concentrated chloride media

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electrochemical Behavior of Cu-9% Al-5% Ni-2% Mn Alloy in Chloride Media

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Pauli blocking and medium effects in nucleon knockout reactions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synergistic action of both Aspergillus niger and Burkholderia cepacea in co-culture increases phosphate solubilization in growth medium

Co-inoculation of the fungus Aspergillus niger and the bacterium Burkholderia cepacia was undertaken to understand the interaction between different species of phosphate-solubilizing microorganisms (PSM). PSM were inoculated in a single or mixed (A. nigerB.similar to cepacia) culture. During 9 similar to days of incubation, microbial biomass was enhanced, accompanied with increases in the levels of soluble phosphate and titratable acidity, as well as increased acid phosphatase activity. Production of acids and levels of phosphate solubilization were greater in the co-culture of A.similar to nigerB.similar to cepacia than in the single culture. The quantity of phosphate solubilized by the co-culture ranged from 40.51 +/- 0.60 to 1103.64 +/- 1.21 similar to mu g similar to PO4 3-similar to mL-1 and was 922% higher than single cultures. pH of the medium dropped from 7.0 to 3.0 in the A.similar to niger culture, 3.1 in the co-culture, and 4.2 in the B.similar to cepacia culture. on the third day of postinoculation, acid production by the co-culture (mean 5.40 +/- 0.31 similar to mg NaOH mL-1) was 1990% greater than single cultures. Glucose concentration decreased almost completely (9799% of the starting concentration) by the ninth day of the incubation. These results show remarkable synergism by the co-culture in comparison with single cultures in the solubility of CaHPO4 under in vitro conditions. This synergy between microorganisms can be used in poor available phosphate soils to enhance phosphate solubilization.

Protein synthesis studies in skeletal muscle of aging rats. II. In vitro studies with 0.5M potassium chloride washed polyribosomes

To investigate further the age-related reduction in muscle protein synthesis activity found previously using a crude polyribosome/pH 5 system (Pluskal et al., 1984), a 0.5M KCl washing procedure was utilized to remove the nonribosomal factors from polyribosomes isolated from male Sprague-Dawley rats in the following age groups: young (1 to 2 months), mature (12 months), and aged (22 to 24 months). Using a common source of enriched elongation factor fraction from young animals, it was not possible to demonstrate any significant difference (p > .05) in protein synthesis between the 0.5M KCl-washed polyribosomes isolated from the various age groups. Using a cell-free system containing young salt washed polyribosomes stimulated by the addition of 0.5M KCl-wash fractions, however, it was shown that the mature and aged salt-wash fractions were less (p < .05) active than material from young animals. Thus, the observed decline in protein synthesis efficiency during aging may be attributed to a reduced capacity to promote initiation/elongation by the nonribosomal salt wash fractions of muscle polyribosomes.

Pancreas damage and intratracheal NiCl2 administration. Effects of nickel chloride.

Changes in activities of Cu-Zn superoxide dismutase (SOD- E.C.1.15.1.1.) and lactate dehydrogenase (LDH- E.C.1.1.1.27.) and levels of copper, total protein, triglycerides, phospholipids and total lipids were investigated in pancreas of rats after intratracheal administration of NiCl2 (8.4 mumol/kg). Nickel chloride induced increased SOD activity in pancreas and erythrocytes. This elevation was related to increased copper and decreased phospholipid content in pancreas of these animals. In conclusion, the ability of an animal to tolerate nickel chloride induced damage was governed by a delicate balance between the generation of cytotoxic agents and the various pancreas defense capabilities.

Transient non-Darcy forced convective heat transfer from a flat plate embedded in a fluid-saturated porous medium

Transient non-Darcy forced convection on a flat plate embedded in a porous medium is investigated using the Forchheimer-extended Darcy law. A sudden uniform pressure gradient is applied along the flat plate, and at the same time, its wall temperature is suddenly raised to a high temperature. Both the momentum and energy equations are solved by retaining the unsteady terms. An exact velocity solution is obtained and substituted into the energy equation, which then is solved by means of a quasi-similarity transformation. The temperature field can be divided into the one-dimensional transient (downstream) region and the quasi-steady-state (upstream) region. Thus the transient local heat transfer coefficient can be described by connecting the quasi-steady-state solution and the one-dimensional transient solution. The non-Darcy porous inertia works to decrease the velocity level and the time required for reaching the steady-state velocity level. The porous-medium inertia delays covering of the plate by the steady-state thermal boundary layer. © 1990.

Fluorapatite solubilization by Aspergillus niger in vinasse medium

Fluorapatite solubilization by Aspergillus niger using diluted vinasse at a relative density of 45° Brix may be an alternative to the usual processes for obtaining soluble phosphate. After 13 days of culture, a production of 1.2g l-1 soluble phosphate was obtained for 5g l-1 fluorapatite added to the vinasse, as well as production of 11 gl-1 dry mycelial mass and a substantial reduction of the polluting components of the medium, i.e. a 78 and 94% reduction of total and reducing sugars, respectively, and a 48 and 80% reduction of total and soluble solids, respectively. In less diluted medium, increased sugar content led to a greater production of dry mass but also to a reduction of soluble phosphate content. When fluorapatite concentration in vinasse was increased from 5.0 to 7.5 or 10.0 g l-1, soluble phosphate accumulation increased by 0.28 and 0.15 g l-1, respectively. Addition of ammonium nitrate or rotary shaking of the culture mixture did not lead to the production of larger amounts of soluble phosphate than obtained in the absence of these factors. © 1990.

Nickel chloride: potential accumulation from the airway. Toxicokinetics in rats.

The rate removal of nickel from the airway was measured in vivo. Removal in vivo was studied by intratracheal injection of nickel chloride solutions. Regardless of time after injection, the lungs and heart retained the greatest concentration of nickel and 40 days after 1.68 mumol administration they were the organs where nickel was still significantly measurable. The slow removal of nickel may indicate the presence of high affinity binding sites in the lung. Nickel can interact with others metals, such as copper and zinc, so that nickel exposure may have public health implications.

Protective effect of nickel chloride on superoxide damage: enhancement of CuZn superoxide dismutase affinity to the oxygen free radical.

The effect of nickel from soluble NiCl2 on Cu-Zn superoxide dismutase (SOD) activity, as well as on rate of nitro blue tetrazolium reduction, was studied in vitro since lipid peroxidation has been implicated in cell damage by nickel insoluble compounds, whose toxicity and carcinogenicity are well established. The physical and chemical nature of nickel compounds is one of the key determinations of its toxicity. Soluble nickel freely enter cells, but is just as readily excreted reducing the opportunity for production of lipid damage. Nickel from NiCl2 strongly activated SOD activity. In vitro addition of nickel chloride to a crude lung preparation altered the KM for SOD without changing the Vmax. Nickel chloride produced increased enzyme affinity to the substrate, because decreased (O2-) concentration that yields half-maximal velocity. The combination of nickel and SOD may contribute to stabilization of the particular conformation of SOD responsible for maximal catalytically activity.

Effect of nicotinic stimulation of the amygdaloid complex on water and sodium chloride intake

We studied the nicotine stimulation of the amygdaloid complex (AMG) on sodium and water intake in satiated and water-deprived rats. Nicotine produced no change in sodium or water intake in satiated animals when injected directly into the AMG. In water-deprived animals, nicotine injected into the AMG (basolateral nuclei) only blocked sodium chloride intake. We have previously demontrated that carbachol inhibits water and sodium intake in both satiated and water-deprived animals injected into the AMG. Injection of hexamethonium into the AMG totally blocked water intake in satiated and water-deprived animals. Hexamethonium injected into the AMG prior to nicotine produced no change in sodium intake. Thus, the present data suggest that sodium and water intake are mediated by a specific population of cholinoceptive neurons in the amygdaloid complex.

Approximate solution for non-Darcy transient film condensation in a porous medium

The problem of non-darcian transient film condensation adjacent to a vertical flat plate embedded in a porous medium has been considered. The governing equation for the boundary layer thickness was obtained by an integral method and solved approximately by the method of integral relations. It is shown that the results are in good agreement with those obtained exactly by the method of characteristics.

Interaction in culture medium of acttnomycetes and native fungi wtth rhizobia that form nodules in Neonotonia wighth lackley (perennial soybean)

The relationship between soil fungi and actinomycetes, with rhizobia that produce nodulation in Neonotonia wightii (perennial soybean) was studied in culture medium in order to obtain material to be used in mixed inoculations of this legume. A field experiment was designed to provide soil samples and isolate microorganisms belonging to these groups that are capable of interfering in the development of two selected rhizobium strains. Results show that the Bradyrhizobium strains used in the experiment, which are efficient in nodulation of Neonotonia wightii, are highly sensitive to substances produced in the culture medium by actinomycetes and fungi.