Ionic medium effects on equilibrium constants .1. Proton, copper(II), cadmium(II), lead(II) and acetate activity coefficients in aqueous solution

The molar single ion activity coefficients associated with hydrogen, copper(II), cadmium(II) and lead(II) ions were determined at 25 degrees C and ionic strengths between 0.100 and 3.00 M (NaClO4), whereas for acetate the ionic strengths were fixed between 0.300 and 2.00 M, held with the same inert electrolyte. The investigation was carried out potentiometrically by using proton-sensitive glass, copper, cadmium and lead ion-selective electrodes and a second-class Hg\Hg-2(CH3COO)(2) electrode. It was found that the activity coefficients of these ions (y(i)) can be assessed through the following empirical equations:log y(H) = -0.542I(0.5) + 0.451I; log y(Cu) = -1.249I(0.5) + 0.912I; log y(Cd) = -0.829I(0.5) + 0.448I(1.5);log y(Pb) = -0.404I(0.5) + 0.117I(2); and log y(Ac) = 0.0370I .

Electrostatic force microscopy as a tool to estimate the number of active potential barriers in dense non-Ohmic polycrystalline SnO2 devices

In the present work, electroactive grain boundaries of highly dense metal oxide SnO2-based polycrystalline varistors were determined by electrostatic force microscopy (EFM). The EFM technique was applied to identify electroactive grain boundaries and thus estimate the amount of active grain boundary, which, in the metal oxide SnO2-based varistor, was calculated at around 85%, i.e., much higher than that found in traditional metal oxide ZnO-based varistors. The mean potential barrier height value obtained from the EFM analysis was in complete agreement with the values calculated from the C-V measurements, together with a complex capacitance plane analysis that validates the methodology proposed here. (c) 2006 American Institute of Physics.

Characterization of dense lead lanthanum titanate ceramics prepared from powders synthesized by the oxidant peroxo method

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

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.

Prevention of experimental venous thrombosis induced by contrast medium in the rat

In order to assess experimentally the usefulness of some procedures employed in man to prevent venous thrombosis following phlebography, thrombosis was induced in rats using sodium diatrizoate in a temporarily isolated segment of a jugular vein. The prevention of thrombosis was attempted by washing out the vein with physiologic saline or saline plus heparin or by injecting saline plus heparin in the opposite jugular vein. Thrombosis occurred in all animals in the control group and in the group treated with saline alone. Both treatment schemes with heparin significantly reduced the incidence of thrombosis, the wash out with heparin being more effective than systemic heparin.