Estimation of Symmetric Channels for Discrete Cosine Transform Type-I Multicarrier Systems: A Compressed Sensing Approach

The problem of channel estimation for multicarrier communications is addressed. We focus on systems employing the Discrete Cosine Transform Type-I (DCT1) even at both the transmitter and the receiver, presenting an algorithm which achieves an accurate estimation of symmetric channel filters using only a small number of training symbols. The solution is obtained by using either matrix inversion or compressed sensing algorithms. We provide the theoretical results which guarantee the validity of the proposed technique for the DCT1. Numerical simulations illustrate the good behaviour of the proposed algorithm.

Outward Rectification of Voltage-Gated K+ Channels Evolved at Least Twice in Life History

Voltage-gated potassium (K+) channels are present in all living systems. Despite high structural similarities in the transmembrane domains (TMD), this K+ channel type segregates into at least two main functional categories—hyperpolarization-activated, inward-rectifying (Kin) and depolarization-activated, outward-rectifying (Kout) channels. Voltage-gated K+ channels sense the membrane voltage via a voltage-sensing domain that is connected to the conduction pathway of the channel. It has been shown that the voltage-sensing mechanism is the same in Kin and Kout channels, but its performance results in opposite pore conformations. It is not known how the different coupling of voltage-sensor and pore is implemented. Here, we studied sequence and structural data of voltage-gated K+ channels from animals and plants with emphasis on the property of opposite rectification. We identified structural hotspots that alone allow already the distinction between Kin and Kout channels. Among them is a loop between TMD S5 and the pore that is very short in animal Kout, longer in plant and animal Kin and the longest in plant Kout channels. In combination with further structural and phylogenetic analyses this finding suggests that outward-rectification evolved twice and independently in the animal and plant kingdom.

Segmentación automática de la red fluvial con base geomorfológica: una herramienta útil en la restauración de ríos (río Porma, León)

La segmentación automática del sistema fluvial con base geomorfológica puede ser una herramienta útil en la restauración de ríos. Tradicionalmente el criterio experto permitía identificar tramos fluviales homogéneos; sin embargo, existen métodos automáticos más objetivos y fiables favorecidos por avances en las técnicas de computación, en las tecnologías de sistemas de información geográfica y en la calidad de la información espacial. Se han aplicado métodos de segmentación automática a respuestas univariantes y multivariantes, basados en técnicas permutacionales y de randomnización multi-respuesta sobre variables geomorfológicas sistemáticamente extraídas con la ayuda de sistemas de información geográfica. Se muestra la utilidad de esta herramienta en distintas fases de un proyecto de restauración, como son: la caracterización del contexto geomorfológico, la diagnosis del efecto de presiones sobre el sistema y la identificación de tramos preferentes para su conservación. Las técnicas descritas se han aplicado al río Porma (Cuenca del Duero, León) regulado desde 1968.