Particle Competition and Cooperation in Networks for Semi-Supervised Learning

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of sedation on morbidity and mortality in the intensive care unit

CONTEXTO: Embora cerca de 30% a 50% dos pacientes hospitalizados em unidades de terapia intensiva (UTI) recebam algum tipo de sedativo, existe escassez de informações sobre efeitos adversos desta prática, especialmente no Brasil. Estes efeitos podem ser significantes e o uso de sedativos é associado a elevação de infecção e mortalidade, mesmo sendo difícil avaliar o impacto clínico deste procedimento. OBJETIVO: Avaliar o impacto da sedação sobre incidência de complicações e mortalidade em doentes graves durante internação em unidade de terapia intensiva. TIPO DE ESTUDO: Estudo prospectivo. LOCAL: Unidade de Terapia Intensiva Cirúrgica da Universidade Federal de São Paulo (UNIFESP) - Escola Paulista de Medicina. PARTICIPANTES: Após excluídos pacientes que permaneceram menos de 24 horas ou sem exames indispensáveis para o cálculo do índice de gravidade (APACHE II), restaram 307 pacientes. Estes foram divididos em dois grupos: Grupo Sedado e Grupo Não Sedado. Constatada heterogeneidade com relação ao APACHE II, foram pareados 97 sedados e 97 não sedados com idênticos índices de gravidade. VARIÁVEIS ESTUDADAS: Impacto da sedação e das técnicas sobre a mortalidade, tempo de internação, além da incidência de escara de decúbito ou pressão, trombose venosa profunda e infecção. RESULTADOS: Não houve diferença na incidência de trombose venosa profunda, entre os grupos Sedado e Não Sedado, enquanto que escara de decúbito foi significativamente maior nos sedados (p = 0,03). Infecção foi detectada em 45,4% dos pacientes com sedação e em 21,6% dos pacientes sem sedação (p = 0,006). A mortalidade para os pacientes que não receberam qualquer tipo de sedativo foi de 20,6% e, para aqueles que foram sedados durante a internação, foi de 52,6% (p < 0,0001). CONCLUSÕES: Conclui-se que a sedação está associada a maior duração da internação, morbidade e mortalidade significativas. Apesar da intensidade das associações encontradas, não é possível estabelecer relação causal entre sedação e mortalidade.

Particle Competition and Cooperation in Networks for Semi-Supervised Learning with Concept Drift

Concept drift is a problem of increasing importance in machine learning and data mining. Data sets under analysis are no longer only static databases, but also data streams in which concepts and data distributions may not be stable over time. However, most learning algorithms produced so far are based on the assumption that data comes from a fixed distribution, so they are not suitable to handle concept drifts. Moreover, some concept drifts applications requires fast response, which means an algorithm must always be (re) trained with the latest available data. But the process of labeling data is usually expensive and/or time consuming when compared to unlabeled data acquisition, thus only a small fraction of the incoming data may be effectively labeled. Semi-supervised learning methods may help in this scenario, as they use both labeled and unlabeled data in the training process. However, most of them are also based on the assumption that the data is static. Therefore, semi-supervised learning with concept drifts is still an open challenge in machine learning. Recently, a particle competition and cooperation approach was used to realize graph-based semi-supervised learning from static data. In this paper, we extend that approach to handle data streams and concept drift. The result is a passive algorithm using a single classifier, which naturally adapts to concept changes, without any explicit drift detection mechanism. Its built-in mechanisms provide a natural way of learning from new data, gradually forgetting older knowledge as older labeled data items became less influent on the classification of newer data items. Some computer simulation are presented, showing the effectiveness of the proposed method.

Mechanisms of follow-up to the Programme of Action on Population and Development in the countries of Latin America and the Caribbean

Includes bibliography

Proposal on indicators for follow-up to the goals of the International Conference on Population and Development in Latin America and the Caribbean

Includes bibliography

Does group size matter? Cheating and cooperation in Brazilian school children

Cooperation between individuals is an important requisite for the maintenance of social relationships. The purpose of this study was to investigate cooperation in children in the school environment, where individuals could cooperate or not with their classmates in a public goods game. We investigated which of the following variables influenced cooperation in children: sex, group size, and information on the number of sessions. Group size was the only factor to significantly affect cooperation, with small-group children cooperating significantly more than those in large groups. Both sex and information had no effect on cooperation. We suggest that these results reflect the fact that, in small groups, individuals were more efficient in controlling and retaliating theirs peers than in large groups. (C) 2008 Elsevier Inc. All rights reserved.

Particle Competition and Cooperation in Networks for Semi-Supervised Learning

Semi-supervised learning is one of the important topics in machine learning, concerning with pattern classification where only a small subset of data is labeled. In this paper, a new network-based (or graph-based) semi-supervised classification model is proposed. It employs a combined random-greedy walk of particles, with competition and cooperation mechanisms, to propagate class labels to the whole network. Due to the competition mechanism, the proposed model has a local label spreading fashion, i.e., each particle only visits a portion of nodes potentially belonging to it, while it is not allowed to visit those nodes definitely occupied by particles of other classes. In this way, a "divide-and-conquer" effect is naturally embedded in the model. As a result, the proposed model can achieve a good classification rate while exhibiting low computational complexity order in comparison to other network-based semi-supervised algorithms. Computer simulations carried out for synthetic and real-world data sets provide a numeric quantification of the performance of the method.

IMPULSE CONTROL AND COOPERATION IN CAPUCHIN MONKEYS (Cebus apella)

The benefits animals derive from living in social groups have produced the evolution of many forms of cooperative behavior. To cooperate, two or more individuals coordinate their actions to accomplish a common goal. One cognitive process that has the potential to influence cooperation is self control. Individuals delaying their impulsive choice for an immediate reward may potentially receive a larger reward later by cooperating with others. In this study, I measured whether brown capuchin monkeys (Cebus apella) were capable of impulse control and whether impulse control was related to cooperation. Impulse control and cooperation were measured using a lazy susan-like apparatus, on which animals could turn a wheel to receive food rewards. The capuchins went through two training phases that taught them how to turn the wheel efficiently to obtain rewards and how to turn the wheel to obtain the larger of two rewards. After training, I tested impulse control by giving the capuchins a choice between a smaller and a larger reward placed at shorter or more distant locations on the wheel. The capuchins demonstrated impulse control in that they tended to inhibit the impulse to select the smaller reward when it was closer and easier to reach and instead selected the larger reward when it was farther away. Cooperation was tested in all possible dyads of seven individuals, a total of 21 dyads, by allowing each dyad 10 trials to work together with effort on the lazy-susan so that each would obtain a reward. Seventeen out of 21 dyads cooperated by simultaneously moving the wheel in the same direction. The correlation between how often a particular dyad cooperated and their average impulse control score was not statistically significant, r(21) = -.125, p = .591. Capuchins demonstrated impulse control and cooperation using this novel apparatus but the two abilities were not related. Other factors such as the unique social relationship between two individuals may play a more prominent role in the motivation to cooperate rather than the cognitive capacity to inhibit behavior.