RED: Deep Recurrent Neural Networks for Sleep EEG Event Detection

The brain electrical activity presents several short events during sleep that can be observed as distinctive micro-structures in the electroencephalogram (EEG), such as sleep spindles and K-complexes. These events have been associated with biological processes and neurological disorders, making them a research topic in sleep medicine. However, manual detection limits their study because it is time-consuming and affected by significant inter-expert variability, motivating automatic approaches. We propose a deep learning approach based on convolutional and recurrent neural networks for sleep EEG event detection called Recurrent Event Detector (RED). RED uses one of two input representations: a) the time-domain EEG signal, or b) a complex spectrogram of the signal obtained with the Continuous Wavelet Transform (CWT). Unlike previous approaches, a fixed time window is avoided and temporal context is integrated to better emulate the visual criteria of experts. When evaluated on the MASS dataset, our detectors outperform the state of the art in both sleep spindle and K-complex detection with a mean F1-score of at least 80.9% and 82.6%, respectively. Although the CWT-domain model obtained a similar performance than its time-domain counterpart, the former allows in principle a more interpretable input representation due to the use of a spectrogram. The proposed approach is event-agnostic and can be used directly to detect other types of sleep events.Comment: 8 pages, 5 figures. In proceedings of the 2020 International Joint Conference on Neural Networks (IJCNN 2020

Classical Lie symmetries and reductions of a nonisospectral Lax pair

The classical Lie method is applied to a nonisospectral problem associated with a system of partial differential equations in 2+1 dimensions (Maccari A, J. Math. Phys. 39, (1998), 6547-6551). Identification of the classical Lie symmetries provides a set of reductions that give rise to different nontrivial spectral problems in 1+1 dimensions. The form in which the spectral parameter of the 1+1 Lax pair is introduced is carefully described.Comment: 11 pages (v2: A typo corrected in the authors' names

Estratigrafía y paleografia de las unidades alóctonas del Castell de Bac Grillera (Pirineo oriental, España)

En la presente nota se hace el estudio estratigráfico delenclave alóctono situado al E de Massanet de Cabrenys (Gerona).Estas unidades alóctonas, cuya mayor elevación corresponde al pico del Castell de Bac Grillera (1059 m.), reposan sobre los términos basales del Paleoceno como resultado final de una traslación gravitatoria procedente del NE. Las formaciones estudiadas son de aguas someras y presentan frecuentes cambios laterales de facies.Sobre el mecanismo de traslación y los rasgos estructurales aparecerá un nuevo artículo próximamente

Tectónica de las unidades alóctonas del Castell de Bac Grillera (Pirineo oriental, España)

Como previamente se anunció en anterior publicación sobreestas unidades alóctonas, en esta otra nota se completa el estudio de las mismas al referir los rasgos estructurales observados y el mecanismo de traslación que las originó. Esta traslación, de tipo gravitatorio, se efectuó sobre una superficie de erosión preexistente a partir del NE y se inició, al parecer, a principios del Biarritzense

Period Estimation in Astronomical Time Series Using Slotted Correntropy

In this letter, we propose a method for period estimation in light curves from periodic variable stars using correntropy. Light curves are astronomical time series of stellar brightness over time, and are characterized as being noisy and unevenly sampled. We propose to use slotted time lags in order to estimate correntropy directly from irregularly sampled time series. A new information theoretic metric is proposed for discriminating among the peaks of the correntropy spectral density. The slotted correntropy method outperformed slotted correlation, string length, VarTools (Lomb-Scargle periodogram and Analysis of Variance), and SigSpec applications on a set of light curves drawn from the MACHO survey