Variabilidad temporal de algunas propiedades químicas en un suelo sometido a distintas sucesiones de cultivo Temporal variability of chemical properties in a soil with three cultivation systems

El presente trabajo ha sido realizado en la Finca Experimental "La Poveda" en Arganda del Rey (Madrid), con las siguientes coordenadas geográficas: latitud 40º19' N; longitud 3º19' W Gr; y altitud 550 m. El objetivo principal consiste en el estudio de la variabilidad temporal de algunas propiedades químicas en un suelo sometido a distintas sucesiones de cultivo. Para el estudio de la variabilidad temporal de las características químicas el muestreo se realizó en los meses de febrero y septiembre de 1993 y febrero y septiembre de 1994. La materia orgánica del sistema Prado/Veza-Avena presenta el menor coeficiente de variación con respecto a los sistemas monocultivo de Cebada y Veza-Avena/Girasol. El menor contenido de materia orgánica a lo largo del tiempo lo presenta el sistema Cebada/Cebada. Los sistemas Prado/Veza-Avena y Veza-Avena/Girasol presentaron contenidos de materia orgánica 42,86% y 40,54% superiores al del sistema Cebada/Cebada.<br>This study has been carried out at the Experimental Station "La Poveda" in Arganda del Rey (Madrid), with the following geographical coordinates: latitude 40&ordm;19' N; longitude 3&ordm;19' W Gr; and altitude 550 m. The main objective was to study the temporal variability of chemical properties in a soil with three cultivation systems. In order to study variation with time of chemical characteristics, samples were taken in February and September 1993 and February and September 1994. Organic matter content in the prairie/vetch-oat system had the smallest variation coefficient with respect to barley and vetch-oat/sunflower systems. Along with the time the barley/barley system presented a lower organic matter content. The crop systems pasture/vetch-oat and vetch-oat/sunflower presented an organic matter content 42.86 and 40.54% higher than that presented by barley/barley system, respectively

Very high-energy gamma-ray follow-up program using neutrino triggers from IceCube

We describe and report the status of a neutrino-triggered program in IceCube that generates real-time alerts for gamma-ray follow-up observations by atmospheric-Cherenkov telescopes (MAGIC and VERITAS). While IceCube is capable of monitoring the whole sky continuously, high-energy gamma-ray telescopes have restricted fields of view and in general are unlikely to be observing a potential neutrino-flaring source at the time such neutrinos are recorded. The use of neutrino-triggered alerts thus aims at increasing the availability of simultaneous multi-messenger data during potential neutrino flaring activity, which can increase the discovery potential and constrain the phenomenological interpretation of the high-energy emission of selected source classes (e.g. blazars). The requirements of a fast and stable online analysis of potential neutrino signals and its operation are presented, along with first results of the program operating between 14 March 2012 and 31 December 2015

Multi-messenger Observations of a Binary Neutron Star Merger

International audienceOn 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim 1.7\,{\rm{s}}$ with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg(2) at a luminosity distance of ${40}_{-8}^{+8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 $\,{M}_{\odot }$. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim 40\,{\rm{Mpc}}$) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position $\sim 9$ and $\sim 16$ days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta