1,152 research outputs found
Long-term denudation rates from the Central Andes (Chile) estimated from a digital elevation model using the black top hat function and inverse distance weighting : implications for the neogene climate of the Atacama Desert
A methodology for determining long-term denudation rates from morphologic markers in a Digital Elevation Model (DEM) is checked by a comparative study of two drainage basins in the Precordillera of the Central Andes. In both cases the initial configuration of an incised pediment surface has been restored by using two different methods: the Black Top Hat (BTH) function and the Inverse Distance Weighting (IDW) interpolation. Where vertical incision and hillslope erosion are recorded, the 1DW appears to be the most adequate to reconstitute the pediment surfaces. Conversely, where only vertical incision is observed, the BTH describes more precisely the former pediment surfaces and it is easier to solve. By subtracting the DEM from the reconstructed marker we calculated an eroded volume, and estimated its uncertainty by considering Root Mean Square Error (RMSE) and DEM grid error. For the last similar to 10 Myr we obtained long-term denudation rates of 7.33 +/- 1.6 m/Myr in the San Andres drainage basin and 13.59 +/- 1.9 m/Myr in the El Salado drainage basin. These estimations are largely in agreement with other reported estimates of long-term denudation rates in the Atacama Desert. Comparison with long-term denudation rates reported in a wide range of climatic regimes suggests that our estimates cannot be explained by the current rainfall in the Precordillera. However they could be explained by a rainfall similar to that reported 40 km to the east in the Puna. This suggests that during the time span concerned the geomorphologic evolution of the study area, this evolution is dominated by an orographically controlled rainfall pattern. The preserved pediment surface and the small long term denudation rates determined in this study also indicate that the Precordillera was never reached by humid tropical air masses and precipitation as currently observed in the Altiplano during the summer months
Fractura-luxación posterior de hombro tratada mediante la técnica de McLaughlin
Se presenta un caso de luxación posterior de hombro, con fractura por impactación
de la cabeza humeral, ocasionada por crisis convulsivas. Estas lesiones no son fáciles de reconocer
en los primeros momentos, y en nuestro caso se precisó de un estudio radiográfico en distintas
proyecciones y una TAC. Se realizó tratamiento quirúrgico mediante la técnica original de
McLaughlin. A los 7 meses de la intervención el paciente ha recuperado casi totalmente la movilidad
en dicho hombro y está libre de dolor.A case of posterior dislocation of the shoulder with locked fracture of the humeral
head after a convulsive seizure is reported. At first stages, this type is very difficult to recognize.
In our case, a radiographic study in different views and a CT-scan were needed. Surgical
treatment were carried out according to McLauglin's original technique. Seven months after surgery
the patient had regained almost complete range of shoulder motion and was pain-free
On the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars
The F-GAMMA program is a coordinated effort to investigate the physics of
Active Galactic Nuclei (AGNs) via multi-frequency monitoring of {\em Fermi}
blazars. The current study is concerned with the broad-band radio spectra
composed of measurement at ten frequencies between 2.64 and 142 GHz. It is
shown that any of the 78 sources studied can be classified in terms of their
variability characteristics in merely 5 types of variability. The first four
types are dominated by spectral evolution and can be reproduced by a simple
two-component system made of the quiescent spectrum of a large scale jet
populated with a flaring event evolving according to Marscher & Gear (1985).
The last type is characterized by an achromatic change of the broad-band
spectrum which must be attributed to a completely different mechanism. Here are
presented, the classification, the assumed physical system and the results of
simulations that have been conducted.Comment: 2011 Fermi Symposium proceedings - eConf C11050
Nonthermal properties of supernova remnant G1.9+0.3
The properties of the - presumably - youngest Galactic supernova remnant
(SNR) G1.9+0.3 are investigated within the framework of nonlinear kinetic
theory of cosmic ray acceleration in SNRs. The observed angular size and
expansion speed as well as the radio and X-ray emission measurements are used
to determine relevant physical parameters of this SNR. Under the assumption
that SNR G1.9+0.3 is the result of a Type Ia supernova near the Galactic center
(at the distance d=8.5 kpc) the nonthermal properties are calculated. In
particular, the expected TeV gamma-ray spectral energy density is predicted to
be as low as erg
cm s, strongly dependent () upon the
source distance d.Comment: 7 pages, 5 figures, accepted for publication in Ap
F-GAMMA: On the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars
The F-GAMMA program is a coordinated effort to investigate the physics of
Active Galactic Nuclei (AGNs) via multi-frequency monitoring of Fermi blazars.
In the current study we show and discuss the evolution of broad-band radio
spectra, which are measured at ten frequencies between 2.64 and 142 GHz using
the Effelsberg 100-m and the IRAM 30-m telescopes. It is shown that any of the
78 sources studied can be classified in terms of their variability
characteristics in merely 5 types of variability. It is argued that these can
be attributed to only two classes of variability mechanisms. The first four
types are dominated by spectral evolution and can be described by a simple
two-component system composed of: (a) a steep quiescent spectral component from
a large scale jet and (b) a time evolving flare component following the
"Shock-in-Jet" evolutionary path. The fifth type is characterised by an
achromatic change of the broad band spectrum, which could be attributed to a
different mechanism, likely involving differential Doppler boosting caused by
geometrical effects. Here we present the classification, the assumed physical
scenario and the results of calculations that have been performed for the
spectral evolution of flares.Comment: Proceedings of the conference: "The Central Kiloparsec in Galactic
Nucleic: Astronomy at High Angular Resolution 2011", August 29 - September 2,
2011, Bad Honnef, German
The costs of preventing and treating chagas disease in Colombia
Background: The objective of this study is to report the costs of Chagas disease in Colombia, in terms of vector disease control programmes and the costs of providing care to chronic Chagas disease patients with cardiomyopathy.
Methods: Data were collected from Colombia in 2004. A retrospective review of costs for vector control programmes carried out in rural areas included 3,084 houses surveyed for infestation with triatomine bugs and 3,305 houses sprayed with insecticide. A total of 63 patient records from 3 different hospitals were selected for a retrospective review of resource use. Consensus methodology with local experts was used to estimate care seeking behaviour and to complement observed data on utilisation. Findings: The mean cost per house per entomological survey was of 2004), whereas the mean cost of spraying a house with insecticide was 46.4 and 1,028, whereas lifetime costs averaged $11,619 per patient. Chronic Chagas disease patients have limited access to healthcare, with an estimated 22% of patients never seeking care. Conclusion: Chagas disease is a preventable condition that affects mostly poor populations living in rural areas. The mean costs of surveying houses for infestation and spraying infested houses were low in comparison to other studies and in line with treatment costs. Care seeking behaviour and the type of insurance affiliation seem to play a role in the facilities and type of care that patients use, thus raising concerns about equitable access to care. Preventing Chagas disease in Colombia would be cost-effective and could contribute to prevent inequalities in health and healthcare.Wellcome Trus
Cosmic-ray acceleration in supernova remnants: non-linear theory revised
A rapidly growing amount of evidences, mostly coming from the recent
gamma-ray observations of Galactic supernova remnants (SNRs), is seriously
challenging our understanding of how particles are accelerated at fast shocks.
The cosmic-ray (CR) spectra required to account for the observed phenomenology
are in fact as steep as , i.e., steeper than the
test-particle prediction of first-order Fermi acceleration, and significantly
steeper than what expected in a more refined non-linear theory of diffusive
shock acceleration. By accounting for the dynamical back-reaction of the
non-thermal particles, such a theory in fact predicts that the more efficient
the particle acceleration, the flatter the CR spectrum. In this work we put
forward a self-consistent scenario in which the account for the magnetic field
amplification induced by CR streaming produces the conditions for reversing
such a trend, allowing --- at the same time --- for rather steep spectra and CR
acceleration efficiencies (about 20%) consistent with the hypothesis that SNRs
are the sources of Galactic CRs. In particular, we quantitatively work out the
details of instantaneous and cumulative CR spectra during the evolution of a
typical SNR, also stressing the implications of the observed levels of
magnetization on both the expected maximum energy and the predicted CR
acceleration efficiency. The latter naturally turns out to saturate around
10-30%, almost independently of the fraction of particles injected into the
acceleration process as long as this fraction is larger than about .Comment: 24 pages, 5 figures, accepted for publication in JCA
Efecto de los grados día de ayuno y del hacinamiento previos al sacrificio sobre el contenido estomacal y respuesta de estrés en trucha arcoíris (Oncorhynchus mykiss)
El ayuno pre-sacrificio es una práctica rutinaria en acuicultura que se lleva a cabo para vaciar el aparato digestivo disminuyendo la cantidad de heces y previniendo una
contaminación de la canal (Robb, 2008). Sin embargo, el ayuno puede también incrementar los niveles de estrés de los peces y si estos son lo suficientemente altos afectan a la calidad
de la canal (Poli et al., 2005)
Radio and gamma-ray follow-up of the exceptionally high activity state of PKS 1510-089 in 2011
We investigate the radio and gamma-ray variability of the flat spectrum radio
quasar PKS 1510-089 in the time range between 2010 November and 2012 January.
In this period the source showed an intense activity, with two major gamma-ray
flares detected in 2011 July and October. During the latter episode both the
gamma-ray and the radio flux density reached their historical peak.
Multiwavelength analysis shows a rotation of about 380 deg of the optical
polarization angle close in time with the rapid and strong gamma-ray flare in
2011 July. An enhancement of the optical emission and an increase of the
fractional polarization both in the optical and in radio bands is observed
about three weeks later, close in time with another gamma-ray outburst. On the
other hand, after 2011 September a huge radio outburst has been detected, first
in the millimeter regime followed with some time delay at centimeter down to
decimeter wavelengths. This radio flare is characterized by a rising and a
decaying stage, in agreement with the formation of a shock and its evolution,
as a consequence of expansion and radiative cooling. If the gamma-ray flare
observed in 2011 October is related to this radio outburst, then this strongly
indicates that the region responsible for the gamma-ray variability is not
within the broad line, but a few parsecs downstream along the jet.Comment: 14 pages, 12 figures, accepted for publication in MNRA
- …