Observation of Pulsed γ-Rays Above 25 GeV from the Crab Pulsar with MAGIC

One fundamental question about pulsars concerns the mechanism of their pulsed electromagnetic emission. Measuring the high-end region of a pulsar's spectrum would shed light on this question. By developing a new electronic trigger, we lowered the threshold of the Major Atmospheric γ-ray Imaging Cherenkov (MAGIC) telescope to 25 giga-electron volts. In this configuration, we detected pulsed γ-rays from the Crab pulsar that were greater than 25 giga-electron volts, revealing a relatively high cutoff energy in the phase-averaged spectrum. This indicates that the emission occurs far out in the magnetosphere, hence excluding the polar-cap scenario as a possible explanation of our measurement. The high cutoff energy also challenges the slot-gap scenario.

Improving the performance of the single-dish Cherenkov telescope MAGIC through the use of signal timing

The Cherenkov light flashes produced by Extensive Air Showers are very short in time. A high bandwidth and fast digitizing readout, therefore, can minimize the influence of the background from the light of the night sky, and improve the performance in Cherenkov telescopes. The time structure of the Cherenkov image can further be used in single-dish Cherenkov telescopes as an additional parameter to reduce the background from unwanted hadronic showers. A description of an analysis method which makes use of the time information and the subsequent improvement on the performance of the MAGIC telescope (especially after the upgrade with an ultra fast 2 GSamples/s digitization system in February 2007) will be presented. The use of timing information in the analysis of the new MAGIC data reduces the background by a factor two, which in turn results in an enhancement of about a factor 1.4 of the flux sensitivity to point-like sources, as tested on observations of the Crab Nebula.

Optimized dark matter searches in deep observations of Segue 1 with MAGIC

We present the results of stereoscopic observations of the satellite galaxy Segue 1 with the MAGIC Telescopes, carried out between 2011 and 2013. With almost 160 hours of good-quality data, this is the deepest observational campaign on any dwarf galaxy performed so far in the very high energy range of the electromagnetic spectrum. We search this large data sample for signals of dark matter particles in the mass range between 100 GeV and 20 TeV. For this we use the full likelihood analysis method, which provides optimal sensitivity to characteristic gamma-ray spectral features, like those expected from dark matter annihilation or decay. In particular, we focus our search on gamma-rays produced from different final state Standard Model particles, annihilation with internal bremsstrahlung, monochromatic lines and box-shaped signals. Our results represent the most stringent constraints to the annihilation cross-section or decay lifetime obtained from observations of satellite galaxies, for masses above few hundred GeV. In particular, our strongest limit (95% confidence level) corresponds to a ~ 500 GeV dark matter particle annihilating into τ+τ−, and is of order langleσannvrangle simeq 1.2 × 10−24 cm3 s−1 a factor ~ 40 above the langleσannvrangle simeq thermal value.

Persistent random walk model for transport trough thin slabs

We present a model for transport in multiply scattering media based on a three-dimensional generalization of the persistent random walk. The model assumes that photons move along directions that are parallel to the axes. Although this hypothesis is not realistic, it allows us to solve exactly the problem of multiple scattering propagation in a thin slab. Among other quantities, the transmission probability and the mean transmission time can be calculated exactly. Besides being completely solvable, the model could be used as a benchmark for approximation schemes to multiple light scattering.

Epidermal growth factor secreted from submandibular salivary glands interferes with the lipolytic effect of adrenaline in mice

We had described that epidermal growth factor (EGF) interfered with the lipolytic effect of catecholamines in isolated adipocytes. Since catecholamines stimulate the release of EGF from submandibular salivary glands to blood plasma in male mice, we studied whether EGF affected also the lipolytic response to adrenaline in whole animals. We studied the effect of adrenaline in sialoadenectomized and sham-operated mice receiving or not a high dose of EGF following adrenaline injection. There was no difference in plasma EGF concentration between sham-operated and sialoadenectomized animals receiving saline. After adrenaline administration plasma EGF increased by 20-fold in sham-operated but did not increase in sialoadenectomized mice. Indeed, the increase was much higher (more than 100-fold) in mice receiving exogenous EGF. The effect of adrenaline on plasma concentration of both glycerol and nonesterified fatty acids was higher as lower was plasma EGF concentration. Isolated adipocytes obtained from sham-operated or sialoadenectomized mice had identical lipolytic response to adrenaline. The lipolytic response of adipocytes to isoproterenol was decreased by addition of EGF. To study whether the interference with the in vivo lipolytic effect of adrenaline had further metabolic consequences, we measured plasma b-hydroxybutyrate concentration in plasma. There was no difference in the response to adrenaline between sham-operated and sialoadenectomized mice in spite of the difference in plasma nonsterified fatty acid concentration. Studies in isolated hepatocytes indicated that ketogenesis run at near maximal rate in this range of substrate concentration. These results suggest that EGF in the physiological range decreases the lipolytic effect of adrenaline but does not compromise further metabolic events like the enhancement of ketogenesis.

The Coordinated Radio and Infrared Survey for High-mass Star Formation. II. Source Catalog

The CORNISH project is the highest resolution radio continuum survey of the Galactic plane to date. It is the 5 GHz radio continuum part of a series of multi-wavelength surveys that focus on the northern GLIMPSE region (10° < l < 65°), observed by the Spitzer satellite in the mid-infrared. Observations with the Very Large Array in B and BnA configurations have yielded a 1.''5 resolution Stokes I map with a root mean square noise level better than 0.4 mJy beam 1. Here we describe the data-processing methods and data characteristics, and present a new, uniform catalog of compact radio emission. This includes an implementation of automatic deconvolution that provides much more reliable imaging than standard CLEANing. A rigorous investigation of the noise characteristics and reliability of source detection has been carried out. We show that the survey is optimized to detect emission on size scales up to 14'' and for unresolved sources the catalog is more than 90% complete at a flux density of 3.9 mJy. We have detected 3062 sources above a 7σ detection limit and present their ensemble properties. The catalog is highly reliable away from regions containing poorly sampled extended emission, which comprise less than 2% of the survey area. Imaging problems have been mitigated by down-weighting the shortest spacings and potential artifacts flagged via a rigorous manual inspection with reference to the Spitzer infrared data. We present images of the most common source types found: H II regions, planetary nebulae, and radio galaxies. The CORNISH data and catalog are available online at http://cornish.leeds.ac.uk.

Landscape Systems and Human Land-Use Interactions in Mediterranean Highlands and Littoral Plains during the Late Holocene: Integrated Analysis from the InterAmbAr Project (North-Eastern Catalonia).

The main goal of the InterAmbAr reseach project is to analyze the relationships between landscape systems and human land-use strategies on mountains and littoral plains from a long-term perspective. The study adopts a high resolution analysis of small-scale study areas located in the Mediterranean region of north-eastern Catalonia. The study areas are distributed along an altitudinal transect from the high mountain (above 2000m a.s.l.) to the littoral plain of Empordà (Fig. 1). High resolution interdisciplinary research has been carried out from 2010, based on the integration of palaeoenvironmental and archaeological data. The micro-scale approach is used to understand human-environmental relationships. It allows better understanding of the local-regional nature of environmental changes and the synergies between catchment-based systems, hydro-sedimentary regimes, human mobility, land-uses, human environments, demography, etc.

Massive protostars as gamma-ray sources.

Massive protostars have associated bipolar outflows with velocities of hundreds of km s-1. Such outflows can produce strong shocks when they interact with the ambient medium leading to regions of nonthermal radio emission. Aims. We aim at exploring under which conditions relativistic particles are accelerated at the terminal shocks of the protostellar jets and whether they can produce significant gamma-ray emission. Methods. We estimate the conditions necessary for particle acceleration up to very high energies and gamma-ray production in the nonthermal hot spots of jets associated with massive protostars embedded in dense molecular clouds. Results. We show that relativistic bremsstrahlung and proton-proton collisions can make molecular clouds with massive young stellar objects detectable by the Fermi satellite at MeV-GeV energies and by Cherenkov telescope arrays in the GeV-TeV range. Conclusions. Gamma-ray astronomy can be used to probe the physical conditions in star-forming regions and particle acceleration processes in the complex environment of massive molecular clouds.

Capçal extrusor per a un sistema de tecnologia additiva

El departament de GREP de la UdG disposa d’un sistema de tecnologia additiva, laFab@home model 1, una impressora 3D o també anomenada de prototipat ràpid. Ésuna màquina de dimensions reduïdes, versàtil i de cost reduït, que a partir d’un modelgenerat a CAD, es capaç de fabricar objectes sòlids tridimensionals mitjançant lasuperposició de capes horitzontals.Les impressores 3D neixen de la necessitat de realitzar, en un temps relativament curt,proves de geometries complexes, que executades en un procés de manofacturaciónormal pot ser llarg i d’elevat cost.Gran part de les màquines de característiques similars a la Fab@home, tenen modelspreparats fabricar / extrudir peces a partir de silicones, aliments o polímers. Ara bé, laconformació per extrusió de plàstic és a partir de polímer verge en forma de fil.El present projecte té l’objectiu de dissenyar un sistema de conformació que permetimanufacturar polímer en forma de gra i s’adapti al funcionament de la Fab@home, amb l’argot corresponent, es tracta d’adaptar la Fab@home al fused depositionmodeling (FDM)

Noves funcionalitats per desenvolupar el treball en grup a dins de l'ACME

La plataforma ACME (Avaluació Continuada i Millora de l’Ensenyament) va ser creada l’any 1998 per un grup de professors del departament d’Informàtica i Matemàtica Aplicada. L’ACME es va concebre com una plataforma d’e-learning, és a dir, un sistema que mitjançant l’ús d’Internet afavorís l’aprenentatge, permeten la interactivitat entre l’alumne i el professor. La creació de la plataforma ACME tenia com a objectiu reduir el fracàs dels alumnes en les assignatures de matemàtiques, però degut a l’èxit que va suposar en aquestes, es va decidir incorporar la metodologia de treball ACME a altres disciplines com la programació, les bases de dades, la química, l’economia, etc. de manera que actualment es poden desenvolupar activitats ACME en moltes disciplines. Actualment l’ACME s’utilitza com a complement a les classes presencials, on el professor exposa de manera magistral els conceptes i resol algun exercici a mode d’exemple, per a que després l’alumne, utilitzant la plataforma ACME, intenti resoldre els exercicis proposats pel professor.L’objectiu d’aquest projecte és desenvolupar l’anàlisi, disseny i implementació de les modificacions necessàries a incorporar a la plataforma ACME per tal de millorar el gestor de grups, els exercicis Excel i finalment permetre el treball en grup. El projecte consta de tres parts: millorar les interfícies del professor i de l’alumne, la millora del exercicis Excel i la resolució d’exercicis en grup

L'Ajuntament de Vic durant la guerra civil (1936-1939)

Amb l’avinentesa que l’any 2006 coincideix amb el setantè aniversari de l’inici de la Guerra Civil espanyola, aquest article analitza l’Ajuntament de Vic en el període bèl·lic a partir de les actes municipals. Tenint en compte les limitacions de la documentació oficial, l’article tracta sobre el context polític de la ciutat i la seva evolució, l’actuació municipal i, finalment, les conseqüències personals que va tenir per als tres alcaldes que va tenir Vic en aquells anys.

L’impuls de l'educació durant la Segona República: l'ensenyament públic a Osona (1931-1936)

L’educació en general va rebre un fort impuls durant la Segona República, a través de dotar de millors condicions materials i humanes l’ensenyament públic. La comarca d’Osona no va quedar al marge d’aquesta onada de transformacions, la graduació d’escoles nacionals a moltes poblacions i la construcció de nous edificis escolars van acabar amb la precarietat amb què subsistia l’ensenyament públic a la comarca. Paral·lelament es van produir altres canvis a l’entorn de l’educació, entre els quals l’article tracta el de l’oficialitat de l’ensenyament laic.