1,267 research outputs found
Pulsar Prospects for the Cherenkov Telescope Array
In the last few years, the Fermi-LAT telescope has discovered over a 100
pulsars at energies above 100 MeV, increasing the number of known gamma-ray
pulsars by an order of magnitude. In parallel, imaging Cherenkov telescopes,
such as MAGIC and VERITAS, have detected for the first time VHE pulsed
gamma-rays from the Crab pulsar. Such detections have revealed that the Crab
VHE spectrum follows a power-law up to at least 400 GeV, challenging most
theoretical models, and opening wide possibilities of detecting more pulsars
from the ground with the future Cherenkov Telescope Array (CTA). In this
contribution, we study the capabilities of CTA for detecting Fermi pulsars. For
this, we extrapolate their spectra with "Crab-like" power-law tails in the VHE
range, as suggested by the latest MAGIC and VERITAS results.Comment: 4 pages, 3 figures. In Proceedings of the 2012 Heidelberg Symposium
on High Energy Gamma-Ray Astronomy. All CTA contributions at arXiv:1211.184
Lifestyle Influence on the Content of Copper, Zinc and Rubidium in Wild Mushrooms
The concentration of 18 trace elements in several species of fungi (arranged in three groups: ectomycorrhizae, saprobes, and epiphytes) has been determined. The measurements were made using the methodology of X-ray fluorescence. Higher contents of Cu and Rb (with statistical support) have been found in the ectomycorrhizal species. The Zn content reached higher concentrations in the saprophytic species. According to the normality test and the search for outliers, the species Clitocybe maxima and Suillus bellini accumulate large amounts of Cu and Rb, respectively, so that both can be named as “outliers.” The leftwards displacement of the density curves and their nonnormality are attributed to the presence of these two species, which exhibit hyperaccumulation skills for Cu and Rb, respectively. Regarding Zn absorption, no particular species were classified as outlier; therefore it can be assumed that the observed differences between the different groups of fungi are due to differences in their nutritional physiology
Procesos de instauración y consolidación democrática en el África de los '90
Abstract not available.Resumen no disponible
Grapevine leaf uptake of mineral elements influenced by sugar foam amendment of an acidic soil
The use of sugar foam (industrial waste from sugar beet extraction) as an acidic soil (raña) liming agent has been studied in a singular winegrowing region. The contents of the major elements (Al, Ca, Fe, K, Na, Mg, S, Si) and trace elements (As, Ba, Ce, Co, Cr, Cs, Cu, Ga, Hf, La, Mo, Nb, Nd, Ni, Pb, Rb, Sc, Sn, Sr, Ta, Th, U, V, W, Y, Zn, Zr) in the original soil, the amended soil and in grapevine leaves has been measured by X-ray fluorescence. The addition of sugar foam modified the agronomic properties of the original soil. The amendment caused a slight increase in major elements (Ca, 10.4 g·kg-1; Mg, 1.9 g·kg-1 and K, 12.9 g·kg-1) and decreased Al (from 62 to 57.8 g·kg-1) and Fe (from 41.2 to 26.5 g·kg-1) content. Regarding trace elements, there was an increase in levels of Ba, Rb and Sr in the amended soil in comparison to the original soil. The major elements that accumulated in the vine leaf were Ca, Mg and S (Biological Absorption Coefficient, BAC, greater than 1). As for trace elements in leaf, Ba and Sr had a "medium" BAC (0.27 and 0.8, respectively) whereas Rb had a "slight"value (0.08). It is worth noting that the bioaccumulation rate of Zn was greater than 1. The use of sugar foam as a liming agent did not have a negative effect on the absorption of major and trace elements in vine leaves and led to improved BAC values for essential elements in the grapevine. The treatment did not increase the amount of trace elements in the soil above the reference levels for the region.
Design of the Front End Electronics for the Infrared Camera of JEM-EUSO, and manufacturing and verification of the prototype model
The Japanese Experiment Module (JEM) Extreme Universe Space Observatory
(EUSO) will be launched and attached to the Japanese module of the
International Space Station (ISS). Its aim is to observe UV photon tracks
produced by ultra-high energy cosmic rays developing in the atmosphere and
producing extensive air showers.
The key element of the instrument is a very wide-field, very fast,
large-lense telescope that can detect extreme energy particles with energy
above eV. The Atmospheric Monitoring System (AMS), comprising, among
others, the Infrared Camera (IRCAM), which is the Spanish contribution, plays a
fundamental role in the understanding of the atmospheric conditions in the
Field of View (FoV) of the telescope. It is used to detect the temperature of
clouds and to obtain the cloud coverage and cloud top altitude during the
observation period of the JEM-EUSO main instrument. SENER is responsible for
the preliminary design of the Front End Electronics (FEE) of the Infrared
Camera, based on an uncooled microbolometer, and the manufacturing and
verification of the prototype model. This paper describes the flight design
drivers and key factors to achieve the target features, namely, detector
biasing with electrical noise better than V from Hz to MHz,
temperature control of the microbolometer, from C to C
with stability better than mK over hours, low noise high bandwidth
amplifier adaptation of the microbolometer output to differential input before
analog to digital conversion, housekeeping generation, microbolometer control,
and image accumulation for noise reduction
Spectroscopy and Orbital Analysis of Bright Bolides Observed over the Iberian Peninsula from 2010 to 2012
We present the analysis of the atmospheric trajectory and orbital data of
four bright bolides observed over Spain, one of which is a potential meteorite
dropping event. Their absolute magnitude ranges from -10 to -11. Two of these
are of sporadic origin, although a Geminid and a kappa-Cygnid fireball are also
considered. These events were recorded in the framework of the continuous
fireball monitoring and spectroscopy campaigns developed by the SPanish Meteor
Network (SPMN) between 2010 and 2012. The tensile strength of the parent
meteoroids is estimated and the abundances of the main rock-forming elements in
these particles are calculated from the emission spectrum obtained for three of
these events. This analysis revealed a chondritic nature for these meteoroids.Comment: Manuscript in press in Monthly Notices of the Royal Astronomical
Societ
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