The rich club phenomenon in the classroom.

We analyse the evolution of the online interactions held by college students and report on novel relationships between social structure and performance. Our results indicate that more frequent and intense social interactions generally imply better score for students engaging in them. We find that these interactions are hosted within a "rich-club", mediated by persistent interactions among high performing students, which is created during the first weeks of the course.

Heterogeneous atrial wall thickness and stretch promote scroll waves anchoring during atrial fibrillation.

Aims: Atrial dilatation and myocardial stretch are strongly associated with atrial fibrillation (AF). However, the mechanisms by which the three-dimensional (3D) atrial architecture and heterogeneous stretch contribute to AF perpetuation are incompletely understood. We compared AF dynamics during stretch-related AF (pressure: 12 cmH(2)O) in normal sheep hearts (n = 5) and in persistent AF (PtAF, n = 8)-remodelled hearts subjected to prolonged atrial tachypacing.

[Gastrointestinal manifestations in patients with primary immunodeficiencies causing antibody deficiency].

Introduction: Primary immunodeficiencies can lead to gastrointestinal manifestations that are still not well defined.

Objective: To analyze gastrointestinal manifestations associated with primary immunodeficiencies.

Material And Methods: We performed a retrospective study that included patients diagnosed with primary antibody deficiencies in a third-level hospital.

Oxygen-sensitive potassium channels in chemoreceptor cell physiology: making a virtue of necessity.

The characterization of the molecular mechanisms involved in low-oxygen chemotransduction has been an active field of research since the first description of an oxygen-sensitive K(+) channel in rabbit carotid body (CB) chemoreceptor cells. As a result, a large number of components of the transduction cascade, from O(2) sensors to O(2)-sensitive ion channels, have been found. Although the endpoints of the process are analogous, the heterogeneity of the elements involved in the different chemoreceptor tissues precludes a unifying theory of hypoxic signaling, and it has been a source of controversy.

Mechanisms of stretch-induced atrial fibrillation in the presence and the absence of adrenocholinergic stimulation: interplay between rotors and focal discharges.

Background: Both atrial stretch and combined adrenocholinergic stimulation (ACS) have been shown to favor initiation and maintenance of atrial fibrillation (AF). Their respective contributions to the electrophysiological mechanism remains, however, incompletely understood.

Objective: This study endeavored to determine the mechanism of maintenance of stretch-related AF (SRAF) in the presence and absence of ACS and to assess how focal discharges interact with rotors to modify the level of complexity in the activation patterns to perpetuate AF.