A luz na interpretação visual da obra de arte

A presente dissertação analisa e destaca a importância da iluminação na interpretação visual da obra de arte, em contexto museográfico. De facto, a luz detém potencialidades estéticas e semânticas que, devidamente estudadas e implementadas na iluminação expositiva, permitem revelar a autenticidade da obra de arte e facultar uma correcta literacia artística e uma boa interpretação visual. O estudo aprofundado desta temática, envolve uma abordagem interdisciplinar dos aspectos científicos mais significativos de aplicabilidade museográfica, fundamentais para a compreensão da complexa inter-relação entre a luz, a visão e o objecto. Neste âmbito, são analisadas as mais recentes investigações científicotecnológicas na área da neurofisiologia da visão e do respectivo processamento cerebral, novas teorias e modelos cognitivo-emocionais, importantes inovações luminotécnicas e uma nova área de especialização museográfica, o design de iluminação. Comprova-se que o conhecimento sobre estas matérias (descorado na maior parte dos museus portugueses) é imprescindível ao conservador e ao museólogo ou curador no desempenho das respectivas funções, em particular na investigação e no inventário da obra de arte e no acompanhamento das diferentes fases de concepção, montagem e manutenção da iluminação museográfica. A dissertação é amplamente documentada por elementos comprovativos - gráficos, estatísticas e fotografias - dela constando também a apreciação de três estudos de caso e a criação de dois instrumentos de trabalho inéditos: o quadro de classificação óptica dos principais materiais e técnicas artísticas e uma ficha técnica de iluminação. Numa época vincada pela cultura visual e pela globalização do conhecimento, as políticas museológicas têm procurado criar estratégias educativas, num propósito de crescente envolvimento de públicos. A iluminação museográfica revela-se, neste âmbito, uma das soluções basilares, enquanto instrumento eficaz de sublimação estético-artística da obra de arte e um poderoso meio de captar a atenção visual e desencadear a interpretação e a comunicação entre o público e o museu.This thesis analyzes and points out the importance of lighting in the visual interpretation of the work of art in the context of museology. In fact, light withholds an aesthetic and semantic potential that, when properly studied and applied in the exhibition’s lighting system, it reveals the art work authenticity and allows the viewer a good visual interpretation of the piece. An in-depth study of this topic involves an interdisciplinary approach, which brings together the scientific aspects of museography and its practical application, so needed for understanding the complex interrelation between the light, vision and the object. To this effect, an analysis was conducted of the latest research findings on the neurophysiology of the vision and related cerebral processes, as well as on the new theories and cognitive-emotional models, lighting innovations and, a new specialization area in the field of museology, that of the lighting design. Although traditionally neglected by the large majority of the Portuguese museums, knowledge in the above mentioned subjects is essential to the museum's staff in the performance of their duties, from the curator to the conservator, in particular when conducting the historical research of the art work, doing the inventory, or in the follow-up of the different stages of planning, installation, and maintenance of museographic lighting. This thesis is widely supported by evidence: graphical, statistical and photographic. In addition, it focuses on the analysis of three case studies and the generation of two instruments of work: the list for optical classification of main materials and artistic techniques and the technical lighting report. In current times, characterized by a visual culture and the globalization of knowledge, museums have followed policies that support new educational strategies that further engage the public. Museum lighting plays a fundamental role as an efficient instrument of aesthetic and artistic supremacy of the work of art, and a powerful tool to attract the visual attention and open the way for the interpretation and dialogue between the public and museum

Extraction of the Muon Signals Recorded with the Surface Detector of the Pierre Auger Observatory Using Recurrent Neural Networks

We present a method based on the use of Recurrent Neural Networks to extract the muon component from the time traces registered with water-Cherenkov detector (WCD) stations of the Surface Detector of the Pierre Auger Observatory. The design of the WCDs does not allow to separate the contribution of muons to the time traces obtained from the WCDs from those of photons, electrons and positrons for all events. Separating the muon and electromagnetic components is crucial for the determination of the nature of the primary cosmic rays and properties of the hadronic interactions at ultra-high energies. We trained a neural network to extract the muon and the electromagnetic components from the WCD traces using a large set of simulated air showers, with around 450 000 simulated events. For training and evaluating the performance of the neural network, simulated events with energies between 1018.5, eV and 1020 eV and zenith angles below 60 degrees were used. We also study the performance of this method on experimental data of the Pierre Auger Observatory and show that our predicted muon lateral distributions agree with the parameterizations obtained by the AGASA collaboration

A search for ultra-high-energy photons at the Pierre Auger Observatory exploiting air-shower universality

The Pierre Auger Observatory is the most sensitive detector to primary photons with energies above ∼0.2 EeV. It measures extensive air showers using a hybrid technique that combines a fluorescence detector (FD) with a ground array of particle detectors (SD). The signatures of a photon-induced air shower are a larger atmospheric depth at the shower maximum (X$_{max}$) and a steeper lateral distribution function, along with a lower number of muons with respect to the bulk of hadron-induced background. Using observables measured by the FD and SD, three photon searches in different energy bands are performed. In particular, between threshold energies of 1-10 EeV, a new analysis technique has been developed by combining the FD-based measurement of X$_{max}$ with the SD signal through a parameter related to its muon content, derived from the universality of the air showers. This technique has led to a better photon/hadron separation and, consequently, to a higher search sensitivity, resulting in a tighter upper limit than before. The outcome of this new analysis is presented here, along with previous results in the energy ranges below 1 EeV and above 10 EeV. From the data collected by the Pierre Auger Observatory in about 15 years of operation, the most stringent constraints on the fraction of photons in the cosmic flux are set over almost three decades in energy

Study on multi-ELVES in the Pierre Auger Observatory

Since 2013, the four sites of the Fluorescence Detector (FD) of the Pierre Auger Observatory record ELVES with a dedicated trigger. These UV light emissions are correlated to distant lightning strikes. The length of recorded traces has been increased from 100 μs (2013), to 300 μs (2014-16), to 900 μs (2017-present), to progressively extend the observation of the light emission towards the vertical of the causative lightning and beyond. A large fraction of the observed events shows double ELVES within the time window, and, in some cases, even more complex structures are observed. The nature of the multi-ELVES is not completely understood but may be related to the different types of lightning in which they are originated. For example, it is known that Narrow Bipolar Events can produce double ELVES, and Energetic In-cloud Pulses, occurring between the main negative and upper positive charge layer of clouds, can induce double and even quadruple ELVES in the ionosphere. This report shows the seasonal and daily dependence of the time gap, amplitude ratio, and correlation between the pulse widths of the peaks in a sample of 1000+ multi-ELVES events recorded during the period 2014-20. The events have been compared with data from other satellite and ground-based sensing devices to study the correlation of their properties with lightning observables such as altitude and polarity