An automatic correction tool for relational database schemas

A Web-based tool developed to automatically correct relational database schemas is presented. This tool has been integrated into a more general e-learning platform and is used to reinforce teaching and learning on database courses. This platform assigns to each student a set of database problems selected from a common repository. The student has to design a relational database schema and enter it into the system through a user friendly interface specifically designed for it. The correction tool corrects the design and shows detected errors. The student has the chance to correct them and send a new solution. These steps can be repeated as many times as required until a correct solution is obtained. Currently, this system is being used in different introductory database courses at the University of Girona with very promising results

View-dependent information theory quality measures for pixel sampling and scene discretization in flatland

In this paper, we present view-dependent information theory quality measures for pixel sampling and scene discretization in flatland. The measures are based on a definition for the mutual information of a line, and have a purely geometrical basis. Several algorithms exploiting them are presented and compare well with an existing one based on depth differences

Informational Aesthetics Measures

The Birkhoff aesthetic measure of an object is the ratio between order and complexity. Informational aesthetics describes the interpretation of this measure from an information-theoretic perspective. From these ideas, the authors define a set of ratios based on information theory and Kolmogorov complexity that can help to quantify the aesthetic experience

Shape complexity based on mutual information

Shape complexity has recently received attention from different fields, such as computer vision and psychology. In this paper, integral geometry and information theory tools are applied to quantify the shape complexity from two different perspectives: from the inside of the object, we evaluate its degree of structure or correlation between its surfaces (inner complexity), and from the outside, we compute its degree of interaction with the circumscribing sphere (outer complexity). Our shape complexity measures are based on the following two facts: uniformly distributed global lines crossing an object define a continuous information channel and the continuous mutual information of this channel is independent of the object discretisation and invariant to translations, rotations, and changes of scale. The measures introduced in this paper can be potentially used as shape descriptors for object recognition, image retrieval, object localisation, tumour analysis, and protein docking, among others

An information theoretic framework for image segmentation

In this paper, an information theoretic framework for image segmentation is presented. This approach is based on the information channel that goes from the image intensity histogram to the regions of the partitioned image. It allows us to define a new family of segmentation methods which maximize the mutual information of the channel. Firstly, a greedy top-down algorithm which partitions an image into homogeneous regions is introduced. Secondly, a histogram quantization algorithm which clusters color bins in a greedy bottom-up way is defined. Finally, the resulting regions in the partitioning algorithm can optionally be merged using the quantized histogram

Point sampling with uniformly distributed lines

In this paper we address the problem of extracting representative point samples from polygonal models. The goal of such a sampling algorithm is to find points that are evenly distributed. We propose star-discrepancy as a measure for sampling quality and propose new sampling methods based on global line distributions. We investigate several line generation algorithms including an efficient hardware-based sampling method. Our method contributes to the area of point-based graphics by extracting points that are more evenly distributed than by sampling with current algorithms

Random walk radiosity with generalized absorption probabilities

The author studies random walk estimators for radiosity with generalized absorption probabilities. That is, a path will either die or survive on a patch according to an arbitrary probability. The estimators studied so far, the infinite path length estimator and finite path length one, can be considered as particular cases. Practical applications of the random walks with generalized probabilities are given. A necessary and sufficient condition for the existence of the variance is given, together with heuristics to be used in practical cases. The optimal probabilities are also found for the case when one is interested in the whole scene, and are equal to the reflectivities

Error and complexity of random walk Monte Carlo radiosity

The author studies the error and complexity of the discrete random walk Monte Carlo technique for radiosity, using both the shooting and gathering methods. The author shows that the shooting method exhibits a lower complexity than the gathering one, and under some constraints, it has a linear complexity. This is an improvement over a previous result that pointed to an O(n log n) complexity. The author gives and compares three unbiased estimators for each method, and obtains closed forms and bounds for their variances. The author also bounds the expected value of the mean square error (MSE). Some of the results obtained are also shown

Reuse of paths in light source animation

In this paper we extend the reuse of paths to the shot from a moving light source. In the classical algorithm new paths have to be cast from each new position of a light source. We show that we can reuse all paths for all positions, obtaining in this way a theoretical maximum speed-up equal to the average length of the shooting path

The use of pulse amplitude modulated fluorescence techniques for metal toxicity assessment in fluvial biofilms

Metal pollution in rivers is in great concern with human activities in the fluvial watershed. This thesis aims to investigate the potential use of chl-a fluorescence parameters as biomarkers of metal toxicity, and to find cause-effect relationships between metal exposures, other environmental factor (i.e. light), and functional and structural biofilm responses. This thesis demonstrates that the use of chl-a fluorescence parameters allows detect early effects on biofilms caused by zinc toxicity, both in the laboratory as in polluted rivers. In microcosm experiments, the use of chl-a fluorescence parameters allows evaluates structural changes on photosynthetic apparatus and in algal groups’ composition of biofilms long-term exposed to zinc. In order to evaluate the effects of chronic metal pollution in rivers, it is recommended the use of biofilm translocation experiments and the use of a multi-biomarker approach.

Uso de metilprednisolona como tratamento adjuvante do choque hipovolémico, distributivo e séptico

Hoje em dia, o uso abusivo de corticosteroide nos vários tipos de choque(hipovolémico,distributivo e séptico) tem levado a debates polémicos. Ao comparar, os resultados dos inúmeros autores que abordaram este tema, não é possível tirar uma conclusão unânime. A opinião de cada um diverge, havendo autores que apoiam e outros que refutam a sua utilização no choque. O objetivo deste estudo consiste em verificar se o uso metilprednisolona vai surtir algum benefício na reversão e sobrevivência do choque, nos animais, em que a terapêutica inicial de abordagem ao choque não tenha surtido efeito. O presente estudo foi realizado no Hospital Veterinário da Arrábida (HVA), em Azeitão, ao longo de um período de 7 meses, decorrido entre 1 de Setembro de 2011 até 31 Março de 2012. Durante esse tempo, procedeu-se ao acompanhamento de 57 animais em choque hipovolémico, distributivo ou séptico. Nas primeiras horas após ser instituído a fluidoterapia de choque e vasopressores, existiram animais em estudo que não conseguiu estabilizar a pressão arterial média (PAM) dentro dos valores normais de referência. Nestes casos foi administrado um tratamento adjuvante com metilprednisolona. Através da análise descritiva da população em estudo verificou-se que a taxa de mortalidade foi menor no grupo de canídeos e felídeos em que não se efetuou o tratamento adjuvante com metilprednisolona.

Biopolítica y gran relato nacional: presencia espectral del mundo aborigen en tres novelas de la selva (Estudios)

Escritas durante la primera mitad del siglo XX, Canaima, La vorágine, y Sangama son tres novelas de la selva en las cuales aparece una representación del mundo indígena del Amazonas o del Orinoco. Se ha repetido que se trataba de novelas progresistas, que encerraban una crítica del sistema social de la época, y más particularmente del genocidio acarreado por la explotación del caucho durante el “ciclo da borracha”. Sin embargo estas ficciones nos proporcionan un enfoque ambiguo de la realidad indígena. Una visión impregnada por las mismas concepciones del siglo XIX que favorecieron los excesos, maltratos y masacres que dichas novelas pretenden denunciar. Este ensayo se propone analizar la matriz científica de estas representaciones, insistiendo en el paradigma racialista decimónico, derivado de la teoría evolucionista y de la ideología del progreso. Los indios de las ficciones se desplazan como fantasmas en un universo mágico, embrujado, o infernal que carece de realidad. Este “flor” romántico es la proyección literaria de una estrategia biopolítica que se da en las sociedades de la época: la cuestión gira en torno a la construcción del pueblo nacional. Los “aparecidos” del espacio novelesco son un momento de unas estrategias discursivas más globales: se trata de construir una homegeneidad nacional a partir de una etnicidad ficticia que requiere el rechazo del “otro atrasado”. El espectro es la huella o el testigo de esta violencia fundadora.