SALVAGING THE SPIRIT OF THE METER-MODELS TRADITION: A MODEL OF BELIEF REVISION BY WAY OF AN ABSTRACT IDEALIZATION OF RESPONSE TO INCOMING EVIDENCE DELIVERY DURING THE CONSTRUCTION OF PROOF IN COURT

Conversations occurring in a society of communicating systems can be studied according to a model where the main concept is a theory and exchanges are governed by syntactic, semantic, and pragmatic devices. In the present paper we discuss these issues, focusing on the role played by situations where context marks are meaningful for governing dialogues. We take the case of intelligent tutors, in particular one for logic programming under development, as the application example behind this research. Finally, we stress that the flexibility of interactions depends to a great extent on the ability of knowledge-based systems to face open situations.     

MICROBIOLOGICAL QUALITY OF CEBRERO CHEESE FROM NORTHWEST SPAIN

Cebrero cheese is traditionally manufactured from raw cow's milk in the Cebrero mountains of Galicia (NW Spain). We report determinations of pH and a_w, and counts of total aerobic bacteria, psychrotrophs, Enterobacteriaceae, Escherichia coli, coagulase-positive Staphylococcus aureus, Listeria, molds and yeasts, in 49 samples. E. coli count exceeded the level permitted by Spanish legislation in 51% of samples. S. aureus count exceeded the level permitted in 20% of the samples. In one sample, with pH 5.06, two species of Listeria (L. monocytogenes and L. seeligeri) were detected. Although the pH of this cheese is fairly low, it does not appear to be sufficient to prevent the occurrence of certain pathogenic microorganisms.     

PURIFICATION AND PARTIAL CHARACTERIZATION OF TWO PROTEINACEOUS α-AMYLASE INHIBITORS FROM TRITICALE

A total of six α-amylase inhibitory proteins (isoinhibitors) were extracted from triticale (Triticum X Secale) seeds and two of them were purified to homogeneity. The isoinhibitors were extracted by 70% ethanol and produced, by Sephadex G-100 chromatography, two peaks that exhibited α-amylase inhibitory activity. Further purification of the most active peak by DEAE-cellulose chromatography resulted in six active fractions. Two of them designated as TAI-5 and TAI-6, considered to be homogeneous by both acidic and alkaline electrophoresis, were partially characterized. The isoelectric points were 4.80 and 4.70, and the molecular weights 39, 200 and 29, 200, respectively. Under dissociating conditions the molecular weights were 13, 500 and 13, 000, suggesting that the isoinhibitors are composed of three and two subunits, respectively. Both isoinhibitors were stable at different pHs, relatively stable at 98C, and resistant to proteolysis by trypsin, chymotrypsin and pepsin. The optimum interaction pH for both isoinhibitors with human salivary amylase was 7.9. They exhibited specificity to human salivary and porcine pancreatic α-amylases, but had no inhibitory activity on Bacillus subtillis, Aspergillus oryzae and endogenous triticale α-amylases.     

Biochemical changes during the ripening of homemade 'San Simón da Costa' raw milk cheese

'San Simón da Costa' cheese is a traditional smoked variety produced in the northwest of Spain from cow's milk. Biochemical changes were determined during its ripening. Its high calcium and phosphorus content and its low NaCl and sodium content stand out. This cheese undergoes moderate proteolysis. The most abundant free amino acid at the end of the ripening was glutamic acid, followed by tryptophan, leucine, arginine and phenylalanine. The lipolysis throughout ripening is slight; the most abundant free fatty acid being oleic, followed by palmitic and butyric acid.     

STARCH MOBILIZATION AND SUCROSE ACCUMULATION IN THE PULP OF KEITT MANGOES DURING POSTHARVEST RIPENING

Sugar is a determinant for the quality of mangoes, but information about its accumulation is scarce. Although starch can contribute to sugar production during ripening, not much is known about the enzymes involved. This work presents the changes in carbohydrate and enzymes during the development and ripening of Keitt mangoes. Starch disappearance was concomitant to a fivefold increase of sucrose, the most abundant sugar of the ripe fruits. The activities of α-amylase, β-amylase, phosphorylase and isoamylase were detected in the pulp, and while α-amylase increased parallel to the starch content, β-amylase presented a 20-fold increase during ripening. On the other hand, high phosphorylase activity was observed when fruits were still accumulating starch, and lowered during ripening. Isoamylase was detected during development and increased slightly during ripening, which would be in agreement to the expected role for isoamylases as acting on both subproduct of starch synthesis and degradation.

PRACTICAL APPLICATIONS

The present work reinforces our previous works that Keitt mangoes do not ripen when attached to the tree. This fact allowed us to study all the starch degradation after mango harvesting which does not occur with the other cultivars. Data obtained in this work reinforce the role of α-amylase, β-amylase and isoamylase rather than the starch phosphorylases on starch granule degradation in mangoes, and the subsequent soluble sugar accumulation.     

EFFECT OF PROTEIN SYNTHESIS INHIBITORS ON THE CLIMACTERIC OF BANANA (Musa acuminata)

Protein synthesis inhibitors (Actinomycin D and cycloheximide) were infiltrated into banana slices by contact or under vacuum. Drastic reduction of the climacteric period was observed in both types of infiltration when cycloheximide was infiltrated into slices, compared to the Actinomycin D group and to a control group infiltrated with water. Ethylene production was stimulated when both protein synthesis inhibitors were used, in comparison to the water control group irrespective of the type of infiltration adopted. Ethylene production was higher in the vacuum infiltrated groups. It is suggested that cycloheximide and Actinomycin D affect the equilibrium of ripening differently, giving rise to the distinct responses observed.     

DESIGN SENSITIVITY ANALYSIS AND OPTIMAL DESIGN OF COMPOSITE STRUCTURES USING HIGHER ORDER DISCRETE MODELS

This paper deals with the structural optimization of multilaminated composite plate structures of arbitrary geometry and layup, using single layer higher order shear deformation theory discrete models. The structural and sensitivity analysis formulation is developed for a family of C° Lagrangian elements. The design sensitivities of static response for objective and/or constraint functions, such as maximum displacements, stress failure criterion and elastic strain energy, with respect to ply angles and ply thickness are presented. The objectives of the design are the minimization of the structural elastic strain energy, minimization of maximum deflection and/or the minimization of the structure volume. The accuracy and relative performance of the proposed discrete models are compared and discussed among developed elements and alternative models. Several test designs are optimized to show the applicability of the proposed refined discrete models.     

Computation of the transfer function for singular systems

A method for the computation of the transfer function for linear time-invariant singular SISO systems is presented. The system must be reduced to the Hessen-berg/triangular form, then the transfer function denominator and numerator are obtained by two simple formulae derived from the expression of the determinant of a Hessenberg matrix. The problem of computing a minimal representation by removing the input and output decoupling zeros via Hessenberg/triangular form is also considered. Unitary transformations are used and so the numerical stability is preserved. An extension to multivariable systems is proposed.