The long-term effects of experienced macroeconomic shocks on wealth

This paper examines the long-term effects of experienced macro-economic shocks – defined as multi-year peak-to-trough GDP declines of at least 10 percent – on the wealth distribution, portfolio allocation, and risk attitudes of older individuals in Europe. We show that individuals who have experienced more economic depression episodes have lower wealth in absolute terms, a lower probability to invest in risky assets, and display higher risk aversion. When analysing early investment decisions, we find that individuals hit by a depression substitute risky investments with investment in housing, and that these early choices shape wealth in the long-term

Towards optimized suppression of dephasing in systems subject to pulse timing constraints

We investigate the effectiveness of different dynamical decoupling protocols for storage of a single qubit in the presence of a purely dephasing bosonic bath, with emphasis on comparing quantum coherence preservation under uniform vs. non-uniform delay times between pulses. In the limit of instantaneous bit-flip pulses, this is accomplished by establishing a new representation of the controlled qubit evolution, where the resulting decoherence behaviour is directly expressed in terms of the free evolution. Simple analytical expressions are given to approximate the long- and short- term coherence behaviour for both ohmic and supra-ohmic environments. We focus on systems with physical constraints on achievable time delays, with emphasis on pure dephasing of excitonic qubits in quantum dots. Our analysis shows that little advantage of high-level decoupling schemes based on concatenated or optimal design is to be expected if operational constraints prevent pulses to be applied sufficiently fast. In such constrained scenarios, we demonstrate how simple modifications of repeated periodic echo protocols can offer significantly improved coherence preservation in realistic parameter regimes.Comment: 13 figures,1 tabl

Fluid sources and stable isotope signatures in authigenic carbonates from the Northern Apennines, Italy

Funding was provided by the Italian PRIN 2009 Project (MIUR research grant to R. Capozzi) and by the Royal Society of Edinburgh (grant to D. Oppo). The authors wish to thank Joachim Reitner (Department of Geobiology, Centre for Geosciences, Georg-August-University of Göttingen, Germany), Stefano Bernasconi (Department of Earth Sciences, Geologisches Institut, ETH Zurich, CH) and Mario Mussi (CNR-Institute for Geosciences and Georesources, CNR-IGG, Pisa) for contributing in the stable isotopes analyses on carbonate samples; and to two anonymous reviewers.Peer reviewedPostprin

Mineralogia e geoquímica de carbonatos autigénicos do Golfo de Cádis

Mestrado em Ciências do Mar e das Zonas CosteirasEste trabalho apresenta a caracterização mineralógica e geoquímica de carbonatos autigénicos do Golfo de Cádis. Divide-se numa primeira parte introdutória onde se apresenta um resumo dos conceitos teóricos e o enquadramento geológico e estrutural da área em estudo, seguido da investigação realizada, incluindo a caracterização das amostras estudadas, a descrição dos métodos analíticos e apresentação e discussão dos resultados obtidos, que permitiram a sua caracterização mineralógica e geoquímica. As amostras estudadas provêm de vários vulcões de lama do Golfo de Cádis, localizados em diferentes enquadramentos tectónico - sedimentares. A caracterização mineralógica e geoquímica dos carbonatos autigénicos indicam uma formação em resultado da oxidação anaeróbica de metano na coluna sedimentar, a pouca profundidade, e reflectem características típicas de três processos de formação que deram origem aos três tipos litológicos presentes: chaminés, crostas e concreções carbonatadas.This work is focused on the mineralogy and geochemistry of authigenic carbonates from the Gulf of Cadiz. It is divided in an introductory part where the background concepts and the geological setting of the study area are presented, followed by the research work carried out in this master thesis project. The studied samples, the methods and the techniques applied are described, followed by the presentation of the main results and their discussion, concluding on their mineralogical and geochemical characterization and significance. The samples came from several mud volcanoes, on three different geological and tectonic settings of the Gulf of Cadiz. This mineralogical and geochemical characterization of the authigenic carbonates show the methane derived origin, especially the C and O isotopes, as resulting from anaerobic oxidation of methane in shallow sediments and permit to divide the samples in three main group based on mineralogy and morphology: chimneys, crusts and concretions. The data obtained compared with the literature model proposed, permit to prove the hypothesis about the formation processes of the three type. On the different type of carbonates is possible to recognize the influence of the MOW on the oxidation and bio-erosion of the chimneys and gas hydrates influence on two samples from the Michael Ivanov Mud Volcano. It is possible, due the isotopic data, move hypothesis on age of the three different type of carbonate, in particular has been possible to distinguish between the recent formation of the concretions and older formation of the chimneys

Compression and visual quality assessment for light field contents

Since its invention in the 19th century, photography has allowed to create durable images of the world around us by capturing the intensity of light that flows through a scene, first analogically by using light-sensitive material, and then, with the advent of electronic image sensors, digitally. However, one main limitation of both analog and digital photography lays in its inability to capture any information about the direction of light rays. Through traditional photography, each three-dimensional scene is projected onto a 2D plane; consequently, no information about the position of the 3D objects in space is retained. Light field photography aims at overcoming these limitations by recording the direction of light along with its intensity. In the past, several acquisition technologies have been presented to properly capture light field information, and portable devices have been commercialized to the general public. However, a considerably larger volume of data is generated when compared to traditional photography. Thus, new solutions must be designed to face the challenges light field photography poses in terms of storage, representation, and visualization of the acquired data. In particular, new and efficient compression algorithms are needed to sensibly reduce the amount of data that needs to be stored and transmitted, while maintaining an adequate level of perceptual quality. In designing new solutions to address the unique challenges posed by light field photography, one cannot forgo the importance of having reliable, reproducible means of evaluating their performance, especially in relation to the scenario in which they will be consumed. To that end, subjective assessment of visual quality is of paramount importance to evaluate the impact of compression, representation, and rendering models on user experience. Yet, the standardized methodologies that are commonly used to evaluate the visual quality of traditional media content, such as images and videos, are not equipped to tackle the challenges posed by light field photography. New subjective methodologies must be tailored for the new possibilities this new type of imaging offers in terms of rendering and visual experience. In this work, we address the aforementioned problems by both designing new methodologies for visual quality evaluation of light field contents, and outlining a new compression solution to efficiently reduce the amount of data that needs to be transmitted and stored. We first analyse how traditional methodologies for subjective evaluation of multimedia contents can be adapted to suit light field data, and, we propose new methodologies to reliably assess the visual quality while maintaining user engagement. Furthermore, we study how user behavior is affected by the visual quality of the data. We employ subjective quality assessment to compare several state-of-the-art solutions in light field coding, in order to find the most promising approaches to minimize the volume of data without compromising on the perceptual quality. To that means, we define and inspect several coding approaches for light field compression, and we investigate the impact of color subsampling on the final rendered content. Lastly, we propose a new coding approach to perform light field compression, showing significant improvement with respect to the state of the art

Extending 3-DoF Metrics to Model User Behaviour Similarity in 6-DoF Immersive Applications

Immersive reality technologies, such as Virtual and Augmented Reality, have ushered a new era of user-centric systems, in which every aspect of the coding-delivery-rendering chain is tailored to the interaction of the users. Understanding the actual interactivity and behaviour of the users is still an open challenge and a key step to enabling such a user-centric system. Our main goal is to extend the applicability of existing behavioural methodologies for studying user navigation in the case of 6 Degree-of-Freedom (DoF). Specifically, we first compare the navigation in 6-DoF with its 3-DoF counterpart highlighting the main differences and novelties. Then, we define new metrics aimed at better modelling behavioural similarities between users in a 6-DoF system. We validate and test our solutions on real navigation paths of users interacting with dynamic volumetric media in 6-DoF Virtual Reality conditions. Our results show that metrics that consider both user position and viewing direction better perform in detecting user similarity while navigating in a 6-DoF system. Having easy-to-use but robust metrics that underpin multiple tools and answer the question "how do we detect if two users look at the same content?" open the gate to new solutions for a user-centric syste