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 .

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.

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.