392 research outputs found
Effects of firn ice models on radio neutrino simulations using a RadioPropa ray tracer
No full textThe simulations for in-ice radio detectors rely on analytically solvable exponential ice models, allowing for computationally fast ray tracing. However, these models do not encompass the whole complexity of the ice which may result in systematic errors on the simulations and reconstructions. We incorporated a numerical ray tracer module in NuRadioMC based on RadioPropa with accept-able speed and accuracy that focuses on accommodating more complex ice models. Presented here are the ray tracer’s implementation, and a first simulation and reconstruction using this new module. This shows that changing the ice model from an exponential profile to a double-exponential profile (firn model) has non-trivial effects on the timing. As this is important for distance and direction reconstruction of neutrino events, we hope to investigate this influence further once other effects like in-ice reflections or birefringence are implemented in this ray tracer as well
Charakterisierung bimodaler Faziesverteilungen aus der Anisotropie der effektiven komplexen elektrischen Leitfähigkeit: Numerische 2D-Studie basierend auf Cole-Cole-Modellen
No full textCharacterization of bimodal facies distributions using effective anisotropic complex resistivity: A 2D numerical study based on Cole-Cole models
No full textTo determine the prevalence of conjunctivochalasis in patients with immune thyroid diseases, to determine whether there is any association between the 2 diseases, and to determine cytologic study of conjunctivochalasis through the cytology impression test.A clinical prospective cohort study carried out by the External Diseases Department in the Ophthalmology Sector and the Thyroid Department in the Endocrinology Sector at Federal University of Sao Paulo (UNIFESP). The patients included were divided into 2 groups following these inclusion criteria: a control group of 25 patients without thyroid diseases, confirmed after clinical and laboratory examinations (thyroid hormones), or any other ocular diseases. The study group consisted of 31 patients with thyroid diseases, the diagnosis of which was confirmed by the Endocrinology Sector. The thyroidopathies included were autoimmune diseases but excluded nonautoimmune diseases. A protocol endorsed by the UNIFESP was followed, using clinical and ophthalmological history, biomicroscopy, and impression cytology.Fifty-two percent of patients without thyroid diseases and 88% of patients with thyroid diseases presented with conjunctivochalasis. The risk ratio was 1.705 (Pr > chi(2) = 0.0038), indicating that there is an association between them. For the impression cytology in inferior bulbar conjunctiva, there was an association between the result of the impression cytology and conjunctivochalasis (Pearson chi(2) = 10.1190 Pr = 0.006).The prevalence of conjunctivochalasis in patients with autoimmune thyroid diseases was 88%. Patients with autoimmune thyroidopathy presented higher percentages of conjunctivochalasis than the control group, confirming the association between them. The cytologic study showed the highest prevalence of abnormal surface features in eyes with conjunctivochalasis
The effect of the atmospheric refractive index on the radio signal of extensive air showers using Global Data Assimilation System (GDAS)
No full textOne of the major systematic uncertainties in the measurement of Xmax from radio emission of EAS arises from variations of the refractive index in the atmosphere. The refractive index n varies with temperature, humidity and pressure, and the variations can be on the order of 10% for (n-1) at a given altitude. The effect of a varying refractive index on Xmax measurements is evaluated using CoREAS: a microscopic simulation of the radio emission from the individual particles in the cascade simulated with CORSIKA. We discuss the resulting offsets in Xmax for different frequency regimes, and compare them to a simple physical model. Under typical circumstances, the offsets in Xmax range from 4-11 g/cm2 for the 30-80 MHz frequency band. Therefore, for precise measurements it is required to include atmospheric data at the time and place of observation of the air shower into the simulations. The aim is to implement this in the next version of CoREAS/CORSIKA using the Global Data Assimilation System (GDAS), a global atmospheric model based on meteorological measurements and numerical weather predictions. This can then be used to re-evaluate the air shower measurements of the LOFAR radio telescope. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License (CC BY-NC-ND 4.0).</p
Cosmic ray mass composition with LOFAR
No full textThe LOFAR radio telescope measures the radio emission from extensive air showers with unprecedented precision. In the dense core individual air showers are detected by hundreds of dipole antennas. By fitting the complex radiation pattern to Monte Carlo radio simulation codes we obtain measurements of the atmospheric depth of the shower maximum X max with a precision of &lt; 20 g/cm 2 . This quantity is sensitive to the mass composition of cosmic rays. We discuss the first mass composition results of LOFAR and the improvements that are currently being made to enhance the accuracy of future analysis. Firstly, a more realistic treatment of the atmosphere will decrease the systematic uncertainties due to the atmosphere. Secondly, a series of upgrades to the LOFAR system will lead to increased effective area, duty cycle, and the possibility to extend the composition analysis down to the energy of 10 16.5 eV. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License (CC BY-NC-ND 4.0).</p
Study of the LOFAR radio self-trigger and single-station acquisition mode
No full textThe LOw Frequency ARay (LOFAR) observatory is a multipurpose radio antenna array aimed to detect radio signals in the frequency range 10-240 MHz. Radio antennas are clustered into over 50 stations, and are spread along Central and Northern Europe. The LOFAR core, where the density of stations is highest, is instrumented with the LOfar Radboud air shower Array (LORA), covering an area of about 300 m diameter centered at the LOFAR core position. Since 2011 the LOFAR core has been used for detecting radio-signals associated to cosmic-ray air showers in the energy range 1016 - 1018 eV. Data acquisition is triggered by the LORA scintillator array, which provides energy, arrival direction, and core position estimates of the detected air shower too. Thus only the core of the LOFAR array is currently used for cosmic-ray detection. In order to extend the energy range of the detected cosmic rays, it is necessary to expand the effective collecting area to the whole LOFAR array. On this purpose, a detailed study about the LOFAR potentialities of working in self-trigger mode, i.e. with the cosmic-ray data acquisition trigger provided by the radio-antenna only, is presented here. A new method based on the intensity and the frequency spectrum for determining the air shower position to be implemented on LOFAR remote stations is presented too. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License (CC BY-NC-ND 4.0).</p
CRPropa 3.2-an advanced framework for high-energy particle propagation in extragalactic and galactic spaces
No full textA Hybrid Monte Carlo Generator for Ultra-High Energy Cosmic Rays from their Sources to the Observer
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