On proof- and model-based techniques for reasoning with uncertainty

In this article we compare two well-known techniques for reasoning with uncertainty—namely, Incidence Calculus and Fagin-Halpern's version of the Theory of Evidence—from a viewpoint not so frequently explored for such techniques. We argue that, despite the equivalence relations that these techniques have been proved to hold, they have intrinsically different rǒles as representations of uncertainty for automated reasoning, in the sense that the former represents approximations to uncertainty values due to impossibility to achieve exact results by proof-theoretic means, and the latter represents model-theoretic limits of definability of uncertainty values. © 1995 John Wiley & Sons, Inc.     

Photosynthetic production of Dunaliella biomass from natural salt water and carbon dioxide

A Dunaliella strain has been isolated and grown in a medium containing saline lake water. Using 40% saline water and mixture of CO₂-air (4% CO₂) the algae grew with a specific growth rate of 0.073 h⁻¹. The maximum cell concentration was 5.6 × 10⁷ cells cm⁻³ which corresponded to 3.63 g dm⁻³ of dry biomass. Using 80% saline water, a glycerol concentration of 1.47 g glycerol g⁻¹ of, protein was obtained which amounted to 44.3% of Dunaliella dry weight. Fermentor CO₂ from a continuous yeast culture was also used as carbon source for photosynthetic growth. At 2.5% CO₂ in the exit gas a decrease of the specific growth rate was observed but the final concentration attained was comparable to that obtained with CO₂-air mixtures.     

Curved composite boundary elements for second-order two-dimensional problems

Finite elements with a curved edge often require relatively large numerical effort to form.^1–4 Relatively simple triangular elements with a single curved edge are developed in this paper for second-order, two-dimensional problems. A convex boundary element is formed as a composite of two straight-edged triangles and a circular sector. Application of the convex composite boundary element results in less numerical effort for a comparable error in circular and elliptical domain test problems than the application of straight-edged elements in all cases shown, and in most cases when compared to the curved isoparametric elements. For domains with concave boundaries, the application of straight-edged, concave composite boundary and curved isoparametric elements give comparable accuracies and numerical efforts because of a fortuitous cancellation of error that occurs with straight-edged elements in this case.     

Isolation of Vibrio cholerae O1 from aquatic environments and foods in Pernambuco State, Brazil

Gastrointestinal symptoms and fecal frequency following ingestion of yogurt containing 15 g of galacto-oligosaccharides (GOS) per d were observed in 12 healthy volunteers. The effect of GOS on intestinal microflora was also studied in six volunteers. Defecation frequency increased during the administration period, but gastrointestinal symptoms, especially flatulence, also increased. The level of fecal bifidobacteria did not increase by the yogurt intake, but a significant increase was observed in the fecal bacteria growing on MRS media. The results indicate that dietary GOS increase gastrointestinal symptoms and fecal frequency in normal adults and have an effect on intestinal microecosystem.     

Smoothing of signals with bounded error

Samples of a signal are observed with bounded errors. In this correspondence a simple and direct solution to the problem of constructing a smooth curve based on these observations is given. The smoothness of a curve is considered proportional to the energy in the second derivative of the signal.     

Leaching behaviour of a galvanic sludge in sulphuric acid and ammoniacal media

Leaching studies of a sludge produced by the physico-chemical treatment of wastewaters generated by a Ni/Cr plating plant were carried out in both sulphuric acid and ammoniacal media aiming to decide which of them would be the best treatment for this kind of waste material. The dissolution behaviour of some metals (Cu, Ni, Cr and Zn) was studied in order to assure the best metal recovery conditions in subsequent processes by the use of some separation methods such as solvent extraction and precipitation techniques. Therefore, the study here presented deals with the first chemical stage of an integrated treatment process. For the sulphuric acid leaching, maximal conversions obtained were 88.6% Cu, 98.0% Ni and 99.2% Zn for the following experimental conditions: a 100 g L(-1) acid concentration, a 5:1 liquid-to-solid ratio (L/S), a particle size less than 1 mm, a digestion time of 1h, a stirring speed of 700 rpm (all at room temperature and under atmospheric pressure). As expected, no selectivity was achieved for the sulphuric acid leaching, despite this option yielding much higher metal ion dissolution when compared with that reached by ammoniacal leaching. The use of this latter medium allowed the extraction of Cu and Ni without Cr species, but rates of conversion were only about 70% for Cu and 50% for Ni, much lower than those obtained for sulphuric acid leaching.