Machine Learning in Automated Text Categorization

The automated categorization (or classification) of texts into predefined categories has witnessed a booming interest in the last ten years, due to the increased availability of documents in digital form and the ensuing need to organize them. In the research community the dominant approach to this problem is based on machine learning techniques: a general inductive process automatically builds a classifier by learning, from a set of preclassified documents, the characteristics of the categories. The advantages of this approach over the knowledge engineering approach (consisting in the manual definition of a classifier by domain experts) are a very good effectiveness, considerable savings in terms of expert manpower, and straightforward portability to different domains. This survey discusses the main approaches to text categorization that fall within the machine learning paradigm. We will discuss in detail issues pertaining to three different problems, namely document representation, classifier construction, and classifier evaluation.Comment: Accepted for publication on ACM Computing Survey

From sleep spindles of natural sleep to spike and wave discharges of typical absence seizures: is the hypothesis still valid?

The temporal coincidence of sleep spindles and spike-and-wave discharges (SWDs) in patients with idiopathic generalized epilepsies, together with the transformation of spindles into SWDs following intramuscular injection of the weak GABAA receptor (GABAAR) antagonist, penicillin, in an experimental model, brought about the view that SWDs may represent ‘perverted’ sleep spindles. Over the last 20 years, this hypothesis has received considerable support, in particular by in vitro studies of thalamic oscillations following pharmacological/genetic manipulations of GABAARs. However, from a critical appraisal of the evidence in absence epilepsy patients and well-established models of absence epilepsy it emerges that SWDs can occur as frequently during wakefulness as during sleep, with their preferential occurrence in either one of these behavioural states often being patient dependent. Moreover, whereas the EEG expression of both SWDs and sleep spindles requires the integrity of the entire cortico-thalamo-cortical network, SWDs initiates in cortex while sleep spindles in thalamus. Furthermore, the hypothesis of a reduction in GABAAR function across the entire cortico-thalamo-cortical network as the basis for the transformation of sleep spindles into SWDs is no longer tenable. In fact, while a decreased GABAAR function may be present in some cortical layers and in the reticular thalamic nucleus, both phasic and tonic GABAAR inhibitions of thalamo-cortical neurons are either unchanged or increased in this epileptic phenotype. In summary, these differences between SWDs and sleep spindles question the view that the EEG hallmark of absence seizures results from a transformation of this EEG oscillation of natural sleep

Le diagnostic des ulcérations gastriques à l'ère de l'endoscopie

Des biopsies dirigées ont été réalisées au cours de 404 gastroscopies pour ulcérations gastriques. Après contrôle ultérieur du diagnostic, les lésions peuvent être réparties en 347 ulcères bénins et 57 cancers ulcériformes. Un diagnostic exact de cancer a été apporté plus fréquemment par l'endoscopie (66 % des cas) que par l'examen radiologique (20 % des cas). Dans les meilleures conditions, la biopsie dirigée permet ce diagnostic dans 83 % des cas. La biopsie dirigée multiple des ulcérations gastriques apparaît donc comme la méthode diagnostique la plus sûre

Contribution of proximal endoscopy in chronic diarrhea associated with immuno-deficiency

a L'apport de l'entèroscopie dans la mise en évidence de l'étiologie des diarrhées chroniques par déficit immunitaire été précisé par une étude rétrospective portant sur 225 malades. Un délicit de l'immunité humorale, global ou sélectif, a été constaté chez 8 malades. L'étude indique que l'observation d'une atrophie villositaire et/ou d'une hyperplasie nodulaire lymphoïde constituent des signes d'appels. La découverte grâce à l'entéroscopie d'une lambliase méconnue apporte des arguments identiques. La connaissance de l'existence d'un déficit sérique en IgA ne dispense pas de l'entéroseopie et de la numération des plasmocytes muqueux compte tent d'une possible absence de concordance entre immunité locale et immunité systémique