University of Córdoba (Spain)

About: University of Córdoba (Spain) is a education organization based out in Cordova, Spain. It is known for research contribution in the topics: Population & Catalysis. The organization has 12006 authors who have published 22998 publications receiving 537842 citations. The organization is also known as: University of Córdoba (Spain) & Universidad de Córdoba.

The effects of grape must fermentation conditions on volatile alcohols and esters formed by Saccharomyces cerevisiae

Abstract: Changes in aroma compounds synthesised from grape must during fermentation carried out by Saccharomyces cerevisiae, in semi-aerobic, anaerobic, short aeration conditions and after adding ergosterol and oleic acid to the must were studied. The biosynthesis of these aroma compounds was strongly dependent on the fermentation conditions and on the growth of the yeast. Ethanol, isoamyl alcohols, isobutyl alcohol, phenethyl alcohol and isoamyl, butyl and hexyl acetates were produced in greater concentrations in semiaerobic conditions, mainly during cellular growth. 1-Butanol and 1-pentanol were produced in greater levels in anaerobic conditions, when cellular growth was lower. Ergosterol and oleic acid added to the musts generally increased the levels of the aroma compounds in wine compared to those obtained in anaerobic conditions. © 1997 SCI.

Constructing Ensembles of Classifiers by Means of Weighted Instance Selection

Abstract: In this paper, we approach the problem of constructing ensembles of classifiers from the point of view of instance selection. Instance selection is aimed at obtaining a subset of the instances available for training capable of achieving, at least, the same performance as the whole training set. In this way, instance selection algorithms try to keep the performance of the classifiers while reducing the number of instances in the training set. Meanwhile, boosting methods construct an ensemble of classifiers iteratively focusing each new member on the most difficult instances by means of a biased distribution of the training instances. In this work, we show how these two methodologies can be combined advantageously. We can use instance selection algorithms for boosting using as objective to optimize the training error weighted by the biased distribution of the instances given by the boosting method. Our method can be considered as boosting by instance selection. Instance selection has mostly been developed and used for k -nearest neighbor (k -NN) classifiers. So, as a first step, our methodology is suited to construct ensembles of k -NN classifiers. Constructing ensembles of classifiers by means of instance selection has the important feature of reducing the space complexity of the final ensemble as only a subset of the instances is selected for each classifier. However, the methodology is not restricted to k-NN classifier. Other classifiers, such as decision trees and support vector machines (SVMs), may also benefit from a smaller training set, as they produce simpler classifiers if an instance selection algorithm is performed before training. In the experimental section, we show that the proposed approach is able to produce better and simpler ensembles than random subspace method (RSM) method for k-NN and standard ensemble methods for C4.5 and SVMs.

The Long-Term Effects of Coping Strategy Use in Victims of Bullying.

Abstract: The ways in which children appraise and cope with school bullying are likely to influence the long-term outcomes experienced. To examine this possibility, 219 Spanish undergraduate students (73 male, 146 female) aged between 18 and 40, completed an adapted version of the Retrospective Bullying Questionnaire (RBQ; Schafer et al., 2004) and a distress scale (Rivers, 1999). Results indicated that neither coping strategies reported by victims of bullying nor the match between control appraisal and coping strategy influenced levels of distress experienced as adults. Control, threat and challenge appraisals did, however, influence long-term distress. Explanations for these effects are discussed, and include the possibility that appraisals may directly influence levels of distress and the quality of emotions experienced by victims during the actual bullying episode. Active strategies were perceived by students to be effective in dealing with bullying, whereas those centered on avoiding the conflict, or which involved aggression, were considered ineffective.