4,378 research outputs found
Cosmic-ray measurements by reconstructing longitudinal profiles for the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) will be the next generation gamma-ray observatory in the energy range from 20 GeV to 300 TeV, offering 5-10 times better flux sensitivity than the current generation of imaging atmospheric Cherenkov telescopes. Each telescope will capture an image of the Cherenkov light produced when air showers created by gamma rays or cosmic rays pass through the atmosphere. The longitudinal development of the shower in the atmosphere can be studied by measuring the number of charged particles produced as a function of depth. The reconstruction of the longitudinal shower profile provides the depth of the shower maximum Xmax which is a mass-sensitive parameter useful for cosmic ray composition. In this work, we reconstruct the longitudinal profile and the Xmax of air showers initiated by two kinds of cosmic ray species, proton, and iron, with energies between 10 TeV and 300 TeV. This reconstruction is different from other methods that have been used in the past as template-based fit techniques that require a detailed and computing-intensive simulation chain. In contrast, we use for the first time a parameterized function for the angular distribution of Cherenkov light around the shower axis.</p
Drivers for spatial modelling of a critically endangered seabird on a dynamic ocean area: Balearic shearwaters are non-vegetarian
1. Spatial modelling is an important research tool to improve our knowledge about
the distribution of wildlife in the ocean. Using different modelling techniques
(MaxEnt and a generalized linear mixed model), a predictive habitat suitability
model was developed for one of the most threatened seabirds in the world: the
Balearic shearwater, Puffinus mauretanicus.
2. Models were developed using a 10-year dataset from the Gulf of CĂĄdiz (on the
south-western Iberian Peninsula), a key foraging area for Balearic shearwaters
during migration and the non-breeding season.
3. Predictive habitat maps strongly matched the observed distribution patterns,
pointing to bathymetric features as the main modelling drivers. The species was
concentrated on shallow areas (up to approximately 100 m in depth) of the continental
shelf, very close to the mouth of the Guadalquivir River. In contrast with
previous studies, Balearic shearwater distribution in the highly dynamic Gulf of
CĂĄdiz was not correlated with areas of high chlorophyll a concentration.
4. This lack of spatial correlation probably arises from the delay between the
phytoplankton bloom and the response of the zooplankton and small fish that are
preyed upon by Balearic shearwaters, which may result in important displacements
of this trophic chain across the Gulf of CĂĄdiz.
5. The analysis presented contributes to a better understanding of the spatial
distribution and ecology of the critically endangered top predator in the Gulf of
CĂĄdiz and offers important information to improve management plans.VersiĂłn del editor1,92
A MegaCam Survey of Outer Halo Satellites. VI: The Spatially Resolved Star Formation History of the Carina Dwarf Spheroidal Galaxy
We present the spatially resolved star formation history (SFH) of the Carina
dwarf spheroidal galaxy, obtained from deep, wide-field g,r imaging and a
metallicity distribution from the literature. Our photometry covers
deg, reaching up to times the half-light radius of Carina with a
completeness higher than at , more than one magnitude fainter
than the oldest turnoff. This is the first time a combination of depth and
coverage of this quality has been used to derive the SFH of Carina, enabling us
to trace its different populations with unprecedented accuracy. We find that
Carina's SFH consists of two episodes well separated by a star formation
temporal gap. These episodes occurred at old ( Gyr) and intermediate
(- Gyr) ages. Our measurements show that the old episode comprises the
majority of the population, accounting for of the stellar mass
within times the King tidal radius, while the total stellar mass derived
for Carina is , and the stellar
mass-to-light ratio . The SFH derived is consistent with no recent
star formation which hints that the observed blue plume is due to blue
stragglers. We conclude that the SFH of Carina evolved independently of the
tidal field of the Milky Way, since the frequency and duration of its star
formation events do not correlate with its orbital parameters. This result is
supported by the age/metallicity relation observed in Carina, and the gradients
calculated indicating that outer regions are older and more metal poor.Comment: Accepted in ApJ (22 pages, 13 figures
Methodology proposal for the location of microsatellites in the equine genome
We present a relatively simple methodology for the detection of microsatellite sequences in partial genetic libraries in plasmids, consisting mainly in a new DNA extraction protocol and the use of a probe (TG)7T to locate different types of microsatellites.Se presenta una metodologĂa relativamente sencilla para la detecciĂłn de secuencias microsatĂ©lites a partir de genotecas parciales en plĂĄsmidos, que consiste fundamentalmente en un nuevo protocolo de extracciĂłn de DNA y el empleo de una sonda (TG)7T para localizar diferentes tipos de microsatĂ©lites
A branch-point approximant for the equation of state of hard spheres
Using the first seven known virial coefficients and forcing it to possess two
branch-point singularities, a new equation of state for the hard-sphere fluid
is proposed. This equation of state predicts accurate values of the higher
virial coefficients, a radius of convergence smaller than the close-packing
value, and it is as accurate as the rescaled virial expansion and better than
the Pad\'e [3/3] equations of state. Consequences regarding the convergence
properties of the virial series and the use of similar equations of state for
hard-core fluids in dimensions are also pointed out.Comment: 6 pages, 4 tables, 3 figures; v2: enlarged version, extension to
other dimensionalities; v3: typos in references correcte
Conformational dissection of a viral intrinsically disordered domain involved in cellular transformation
Intrinsic disorder is abundant in viral genomes and provides conformational plasticity to its protein products. In order to gain insight into its structure-function relationships, we carried out a comprehensive analysis of structural propensities within the intrinsically disordered N-terminal domain from the human papillomavirus type-16 E7 oncoprotein (E7N). Two E7N segments located within the conserved CR1 and CR2 regions present transient α-helix structure. The helix in the CR1 region spans residues L8 to L13 and overlaps with the E2F mimic linear motif. The second helix, located within the highly acidic CR2 region, presents a pH-dependent structural transition. At neutral pH the helix spans residues P17 to N29, which include the retinoblastoma tumor suppressor LxCxE binding motif (residues 21-29), while the acidic CKII-PEST region spanning residues E33 to I38 populates polyproline type II (PII) structure. At pH 5.0, the CR2 helix propagates up to residue I38 at the expense of loss of PII due to charge neutralization of acidic residues. Using truncated forms of HPV-16 E7, we confirmed that pH-induced changes in α-helix content are governed by the intrinsically disordered E7N domain. Interestingly, while at both pH the region encompassing the LxCxE motif adopts α-helical structure, the isolated 21-29 fragment including this stretch is unable to populate an α-helix even at high TFE concentrations. Thus, the E7N domain can populate dynamic but discrete structural ensembles by sampling α-helix-coil-PII-Ă-sheet structures. This high plasticity may modulate the exposure of linear binding motifs responsible for its multi-target binding properties, leading to interference with key cell signaling pathways and eventually to cellular transformation by the virus.Instituto de FĂsica de LĂquidos y Sistemas BiolĂłgico
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