Time-Slotted Spreading Factor Hopping for Mitigating Blind Spots in LoRa-Based Networks.

It has been demonstrated that LoRa-based wide area networks (WANs) can cover extended areas under harsh propagation conditions. Traditional LoRaWAN solutions based on single-hop access face important drawbacks related to the presence of blind spots. This paper aims to tackle blind spots and performance issues by using a relaying approach. Many researchers investigating multi-hop solutions consider a fixed spreading factor (SF). This simplifies synchronization and association processes, but does not take advantage of the orthogonality between the virtual channels (i.e., frequency, SF) that help to mitigate blind spots. This paper proposes a time-slotted spreading factor hopping (TSSFH) mechanism that combines virtual channels and time slots into a frame structure. Pseudo-random scheduling is used inside blind spots, which simplifies the end-devices' communication process and network organization. The results show how collisions decrease inside blind spots when more communication opportunities become available as more relaying nodes can be listening in different cells (i.e., frequency, SF-offset, time-offset). This has a direct impact on the collision-free packet delivery ratio (PDR) metric, which improves when more listening windows are opened, at the expense of faster battery depletion.

Colitis por derivación fecal / Colitis fecal derivation

Las colostomías e ileostomías siguen siendo parte del armamentario del cirujano moderno en el tratamiento de las enfermedades congénitas, inflamatorias,neoplásicas y traumáticas; aunque sus indicaciones se reservan para situaciones específicas, su morbilidad continúa siendo tópico de actualidad. Con el propósito de investigar la frecuencia, presentación clínica, endoscópica e histológica de la colitis por derivación en segmentos del colon desfuncionalizado, se realizó un estudio prospectivo de pacientes con colostomías o ileostomías que consultaron para cierre del estoma, los cuáles se evaluaron clínica, histologicamente y por endoscopía antes y después del cierre. De un total de 27 pacientes seguidos durante un año, 20 presentaron hallazgos endoscópicos con confirmación histológica de colitis por derivación (74.1/100). Se define el comportamiento de esta entidad y su tratamiento, resaltando que el cirujano debe reconocerla para no retrasar innecesariamente el cierre del estoma pensando que se trata de una enfermedad inflamatoria intestinal o infecciosa