Onset of the Kelvin-Helmholtz instability in partially ionized magnetic flux tubes

Context. Recent observations of solar prominences show the presence of turbulent flows that may be caused by Kelvin-Helmholtz instabilites (KHI). However, the observed flow velocities are below the classical threshold for the onset of KHI in fully ionized plasmas. Aims. We investigate the effect of partial ionization on the onset of KHI in dense and cool cylindrical magnetic flux tubes surrounded by a hotter and lighter environment. Methods. The linearized governing equations of a partially ionized two-fluid plasma are used to describe the behavior of small-amplitude perturbations superimposed on a magnetic tube with longitudinal mass flow. A normal mode analysis is performed to obtain the dispersion relation for linear incompressible waves. We focus on the appearance of unstable solutions and study the dependence of their growth rates on various physical parameters. An analytical approximation of the KHI linear growth rate for slow flows and strong ion-neutral coupling is obtained. An application to solar prominence threads is given. Results. The presence of a neutral component in a plasma may contribute to the onset of the KHI even for sub-Alfv\'enic longitudinal shear flows. Collisions between ions and neutrals reduce the growth rates of the unstable perturbations but cannot completely suppress the instability. Conclusions. Turbulent flows in solar prominences with sub-Alfv\'enic flow velocities may be interpreted as consequences of KHI in partially ionized plasmas.Comment: 8 pages, 4 figures. Accepted for publication in A&

El despido colectivo: una aproximación jurisprudencial del procedimiento

El despido colectivo es la decisión empresarial que mayor impacto tiene en el entorno social, por ello, concierne al Estado su intervención para evitar desajustes en el mercado de trabajo y, por consiguiente, en la economía del país. Esto ha llevado a establecer un complejo procedimiento que deben cumplir con rigor los empleadores, con el fin de evitar que se produzca el fraude. El presente trabajo trata de analizar la figura de esta modalidad de extinción contractual masiva desde todos sus ámbitos, tanto desde el procedimiento sustantivo, como desde el procesal, complementándolo en cada fase, con las interpretaciones y los criterios con los que los órganos jurisdiccionales han ido moldeando la legislación, protegiendo en la medida de lo posible al trabajador, la parte más débil de la relación laboral, de los abusos del empresario y su afán por maximizar el beneficio.Grado en Relaciones Laborales y Recursos Humano

Radioresistance in lung cancer: a molecular approach

Lung cancer represents one-quarter of the deaths caused by cancer. Despite the advances in treatments, chemo and radiotherapy remain the foundation of treatment for this disease, and the survival rate is still at 10%, mainly due to the recurrences after treatment. Tumors that re-emerge after a radiation treatment are usually radioresistant and challenging to treat. This research shows that lung cancer cells that have survived treatment with radiation therapy show characteristics of cancer stem cells and epithelial to mesenchymal transition. Moreover, radioresistant non-small cell lung cancer exhibited alterations of critical prosurvival signaling pathways, higher expression and activation of DNA repair genes, and altered expression of cytokines and receptors

Selfies of imperial cormorants (Phalacrocorax atriceps): What is happening underwater?

During the last few years, the development of animal-borne still cameras and video recorders has enabled researchers to observe what a wild animal sees in the field. In the present study, we deployed miniaturized video recorders to investigate the underwater foraging behavior of Imperial cormorants (Phalacrocorax atriceps). Video footage was obtained from 12 animals and 49 dives comprising a total of 8.1 h of foraging data. Video information revealed that Imperial cormorants are almost exclusively benthic feeders. While foraging along the seafloor, animals did not necessarily keep their body horizontal but inclined it downwards. The head of the instrumented animal was always visible in the videos and in the majority of the dives it was moved constantly forward and backward by extending and contracting the neck while travelling on the seafloor. Animals detected prey at very short distances, performed quick capture attempts and spent the majority of their time on the seafloor searching for prey. Cormorants foraged at three different sea bottom habitats and the way in which they searched for food differed between habitats. Dives were frequently performed under low luminosity levels suggesting that cormorants would locate prey with other sensory systems in addition to sight. Our video data support the idea that Imperial cormorants' efficient hunting involves the use of specialized foraging techniques to compensate for their poor underwater vision.Fil: Gómez Laich, Agustina Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; ArgentinaFil: Yoda, Ken. Nagoya University; JapónFil: Zavalaga, Carlos. Universidad Científica del Sur; Perú. Nagoya University; JapónFil: Quintana, Flavio Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina. Wildlife Conservation Society; Estados Unido

Analyzing {\gamma}-rays of the Galactic Center with Deep Learning

We present a new method to interpret the $\gamma$-ray data of our inner Galaxy as measured by the Fermi Large Area Telescope (Fermi LAT). We train and test convolutional neural networks with simulated Fermi-LAT images based on models tuned to real data. We use this method to investigate the origin of an excess emission of GeV $\gamma$-rays seen in previous studies. Interpretations of this excess include $\gamma$ rays created by the annihilation of dark matter particles and $\gamma$ rays originating from a collection of unresolved point sources, such as millisecond pulsars. Our new method allows precise measurements of the contribution and properties of an unresolved population of $\gamma$-ray point sources in the interstellar diffuse emission model.Comment: 24 pages, 11 figure

Iron and cobalt hydroxides: Describing the oxygen evolution reaction activity trend with the amount of electrocatalyst

Although the amount of oxygen evolution electrocatalyst is a factor determining its efficiency, its fundamental correlation with activity remains unclear. To address this issue, we take advantage of a urea-based chemical bath deposition method (CBD) that enables to control the amount of electrocatalyst (Fe(OH)2 and α-Co(OH)2) deposited on conducting glass. The thickness of the resulting films, whose use in electrocatalysis is unprecedented, is tuned by controlling the deposition time. The turnover frequency (TOF) for O2 generation decreases drastically as the electrocatalyst amount increases from equivalent coverages of 3.5 monolayers (ML) for Fe(OH)2 and of 0.06 ML for α-Co(OH)2 electrodes. The contrasting behavior of both hydroxides comes from the different structure of the incipient deposits, formed by small acicular nanoparticles in the case of Fe(OH)2 and larger flat microparticles in the case of α-Co(OH)2. The former structure allows a large fraction of the Fe sites to be in direct contact with solution, while such a fraction rapidly diminishes with loading for α-Co(OH)2. In addition, the resulting Co(OH)2 electrodes show TOFs similar or higher than those of electrodes prepared by more complex routes. The optimum ultrathin films are remarkably stable in alkaline media, showing that the preparation of efficient electrocatalysts for oxygen evolution with an extremely small amount of metal through a novel, facile and scalable CBD is possible.Financial support of the Spanish Ministry of Economy and Competitiveness through project MAT2015-71727-R (FONDOS FEDER) is gratefully acknowledged. J. Q. thanks to the Spanish Ministry of Education, Culture, and Sport (MECD) for the award of an FPU predoctoral grant (FPU15/02005)