156 research outputs found
Atmospheric monitoring and array calibration in CTA using the Cherenkov Transparency Coefficient
The Cherenkov Telescope Array (CTA) will be the next generation observatory
employing different types of Cherenkov telescopes for the detection of particle
showers initiated by very-high-energy gamma rays. A good knowledge of the
Earth's atmosphere, which acts as a calorimeter in the detection technique,
will be crucial for calibration in CTA. Variations of the atmosphere's
transparency to Cherenkov light and not correctly performed calibration of
individual telescopes in the array result in large systematic uncertainties on
the energy scale. The Cherenkov Transparency Coefficient (CTC), developed
within the H.E.S.S. experiment, quantifies the mean atmosphere transparency
ascertained from data taken by Cherenkov telescopes during scientific
observations. Provided that atmospheric conditions over the array are uniform,
transparency values obtained per telescope can be also used for the calibration
of individual telescope responses. The application of the CTC in CTA presents a
challenge due to the greater complexity of the observatory and the variety of
telescope cameras compared with currently operating experiments, such as
H.E.S.S. We present here the first results of a feasibility study for extension
of the CTC concept in CTA for purposes of the inter-calibration of the
telescopes in the array and monitoring of the atmosphere.Comment: All CTA contributions at arXiv:1709.0348
Competitividad de la oferta exportable de la uva de la Región Arequipa en el mercado de Estados Unidos. periodo 2010-2019
La presente investigación se enmarca en el tema “Competitividad de la oferta
exportable de la uva de la Región Arequipa en el mercado de Estados Unidos, periodo
2010 – 2019”. El propósito de la investigación es analizar la competitividad de la oferta
exportable de la uva en la región Arequipa en base al cálculo de indicadores de desempeño
comercial: Índice de Ventaja Comparativa Revelada (IVCR) y el Índice de Ventaja
Comparativa Revelada Normalizada (IVCRN).
Los resultados muestran una correlación fuerte; lo cual demuestra que el producto
en estudio presenta ventajas comparativas y competitivas en el mercado de Estados
Unidos, lo que contribuye en la posición del producto en las exportaciones del sector de
la región Arequipa. La región Arequipa aporta con el 4% de participación a nivel nacional
en los niveles de producción, y se encuentra dentro de las cinco principales regiones que
aportan al total de producción; muestra la segunda mayor tasa de crecimiento en
producción en el periodo con un 17%. En términos de rendimiento por hectárea, Arequipa
se encuentra en el primer lugar con una tasa de crecimiento en el orden del 7%. La oferta
exportable de Arequipa al 2019, es de US 637 mil.
Adicionalmente la uva de la región y del país ingresa a Estados Unidos cumpliendo el
protocolo sanitario coordinado entre SENASA y la oficina correspondiente del United
States Department of Agriculture (USDA). Por otro lado, se debe indicar sobre la
presencia de la Asociación de productores de Uva de mesa del Perú (PROVID) que da
soporte y representación a la producción y exportación de uva en el Perú ante instituciones
públicas y privadas nacionales e internacionale
Strategy Implementation for the CTA Atmospheric Monitoring Program
The Cherenkov Telescope Array (CTA) is the next generation facility of
Imaging Atmospheric Cherenkov Telescopes. It will reach unprecedented
sensitivity and energy resolution in very-high-energy gamma-ray astronomy. CTA
will detect Cherenkov light emitted within an atmospheric shower of particles
initiated by cosmic-gamma rays or cosmic rays entering the Earth's atmosphere.
From the combination of images the Cherenkov light produces in the telescopes,
one is able to infer the primary particle energy and direction. A correct
energy estimation can be thus performed only if the local atmosphere is well
characterized. The atmosphere not only affects the shower development itself,
but also the Cherenkov photon transmission from the emission point in the
particle shower, at about 10-20 km above the ground, to the detector. Cherenkov
light on the ground is peaked in the UV-blue region, and therefore molecular
and aerosol extinction phenomena are important. The goal of CTA is to control
systematics in energy reconstruction to better than 10%. For this reason, a
careful and continuous monitoring and characterization of the atmosphere is
required. In addition, CTA will be operated as an observatory, with data made
public along with appropriate analysis tools. High-level data quality can only
be ensured if the atmospheric properties are consistently and continuously
taken into account. In this contribution, we concentrate on discussing the
implementation strategy for the various atmospheric monitoring instruments
currently under discussion in CTA. These includes Raman lidars and ceilometers,
stellar photometers and others available both from commercial providers and
public research centres.Comment: (6 pages, 2 figures, Proceedings of the 2nd AtmoHEAD Conference,
Padova, Italy May 19-21, 2014
The EnMAP L2A Water Processor: Operational Performance And Application Of EnMAP Dedicated Water Reflectance Products
Launched in April 2022, EnMAP is an optical (VNIR/SWIR) remote sensing mission with high spatial (30m GSD) and spectral (FWHM ~6-12nm) resolution [1]. As ans unique feature of the mission, the L2A processor of the EnMAP ground segment processing chain has been designed and developed to provide dedicated water reflectance products to the users. It is based on the output of the Modular Inversion and Processing System (MIP) developed by EOMAP GmbH [2]. EnMAP water reflectance can be provided in two different flavours: subsurface irradiance reflectance and normalised water leaving reflectance [3]. The contribution will show the performance of the EnMAP L2A water processor in terms of a quality assessment of the dedicated water products, evaluating the accuracy of the estimated reflectance based on in-situ measurements from several AERONET-OC stations under different water and atmospheric conditions. Furthermore, the two products will be highlighted in terms of their use and advantages, in particular for the (hyperspectral) water community, and a number of applications using the EnMAP hyperspectral water reflectance data will be presented
Capilares cerebelosos y su microambiente : estudio ultraestructural e inmunocitoquímico
Tesis Universidad Complutense de Madrid, Facultad de Ciencias Biológicas, Departamento de Biología Celular (Morfología Microscópica), leída el 25-01-1993Los capilares cerebelosos constituyen la principal estructura constituyente de la barrera hematoencefalica en esta región cerebral, junto con el envoltorio glial perivascular. Las técnicas de microscopia electrónica convencional nos han permitido demostrar que la vaina glial no constituye una estructura continua, de forma que estas discontinuidades permiten el contacto entre elementos de naturaleza nerviosa y la pared de los vasos. En este sentido, todas las estirpes celulares de la corteza cerebelosa pueden entrar en contacto con la pared vascular. Las técnicas inmunohistoquimicas del pap nos han permitido demostrar la presencia de diversos neuromediadores (gaba, taurina, gilcina, serotonina, tiamina) y enzimas implicadas en su sintesis (gad, aat) en los capilares cerebelosos y su microambiente (glia perivascular y estructuras nerviosas asociadas a la pared vascular). Asi mismo, hemos puesto de manifiesto moleculas con una importante implicación funcional en los capilares y su microambiente (atpasa na+/k+, clatrina, alfa-actina). Estos hechos constituyen un importante reflejo morfológico del control glial y nervioso de la permeabilidad capilar y del flujo sanguíneo en los capilares de la corteza cerebelosa de la rataDepto. de Biología CelularFac. de Ciencias BiológicasTRUEpu
Tools and Procedures for the CTA Array Calibration
The Cherenkov Telescope Array (CTA) is an international initiative to build
the next generation ground-based very-high-energy gamma-ray observatory. Full
sky coverage will be assured by two arrays, one located on each of the northern
and southern hemispheres. Three different sizes of telescopes will cover a wide
energy range from tens of GeV up to hundreds of TeV. These telescopes, of which
prototypes are currently under construction or completion, will have different
mirror sizes and fields-of-view designed to access different energy regimes.
Additionally, there will be groups of telescopes with different optics system,
camera and electronics design. Given this diversity of instruments, an overall
coherent calibration of the full array is a challenging task. Moreover, the CTA
requirements on calibration accuracy are much more stringent than those
achieved with current Imaging Atmospheric Cherenkov Telescopes, like for
instance: the systematic errors in the energy scale must not exceed 10%.In this
contribution we present both the methods that, applied directly to the acquired
observational CTA data, will ensure that the calibration is correctly performed
to the stringent required precision, and the calibration equipment that,
external to the telescopes, is currently under development and testing.
Moreover, some notes about the operative procedure to be followed with both
methods and instruments, will be described. The methods applied to the
observational CTA data include the analysis of muon ring images, of carefully
selected cosmic-ray air shower images, of the reconstructed electron spectrum
and that of known gamma-ray sources and the possible use of stereo techniques
hardware-independent. These methods will be complemented with the use of
calibrated light sources located on ground or on board unmanned aerial
vehicles.Comment: All CTA contributions at arXiv:1709.0348
Quality Model for the Evaluation of Geospatial Web Services within the Spatial Data Infrastructure of Uruguay
Quality of Service (QoS), applied in particular to Web Services, is an area of increasing interest. One approach to deal with QoS issues is the identification of quality characteristics, usually documented in quality models. Geospatial Web Services are standardized service interfaces which facilitate the processing and exchange of distributed geographic information.
These services represent the technological backbone of Spatial Data Infrastructures (SDI), which are data-exchange frameworks geared towards promoting the availability and exploitation of geographic information. This paper proposes a quality model for the evaluation of Geospatial Web Services within IDEuy: the SDI of Uruguay. The development of this model was based on requirements pertaining to the Uruguayan context, leading international SDI initiatives and related work. The application of the model to evaluate services within IDEuy is also presented.Sociedad Argentina de Informática e Investigación Operativa (SADIO
A Newly Developed Algorithm for Cloud Shadow Detection - TIP Method
The masking of cloud shadows in optical satellite imagery is an important step in automated processing chains. A new method (the TIP method) for cloud shadow detection in multispectral satellite images is presented and compared to current methods. The TIP method is based on the evaluation of thresholds, indices and projections. Most state-of-the-art methods solemnly rely on one of these evaluation steps or on a complex working mechanism. Instead, the new method incorporates three basic evaluation steps into one algorithm for easy and accurate cloud shadow detection.
Furthermore the performance of the masking algorithms provided by the software packages ATCOR (“Atmospheric Correction”) and PACO (“Python-based Atmospheric Correction”) is compared with that of the newly implemented TIP method on a set of 20 Sentinel-2 scenes distributed over the globe, covering a wide variety of environments and climates. The algorithms incorporated in each piece of masking software use the class of cloud shadows, but they employ different rules and class-specific thresholds. Classification results are compared to the assessment of an expert human interpreter.
The class assignment of the human interpreter is considered as reference or “truth”. The overall accuracies for the class cloud shadows of ATCOR and PACO (including TIP) for difference areas of the selected scenes are 70.4% and 76.6% respectively. The difference area encompasses the parts of the classification image where the classification maps disagree. User and producer accuracies for the class cloud shadow are strongly scene-dependent, typically varying between 45% and 95%. The experimental results show that the proposed TIP method based on thresholds, indices and projections can obtain improved cloud shadow detection performance
- …