The effects of transients on photospheric and chromospheric power distributions

We have observed a quiet Sun region with the Swedish 1-meter Solar Telescope (SST) equipped with CRISP Imaging SpectroPolarimeter. High-resolution, high-cadence, H-alpha line scanning images were taken to observe different layers of the solar atmosphere from the photosphere to upper chromosphere. We study the distribution of power in different period-bands at different heights. Power maps of the upper photosphere and the lower chromosphere show suppressed power surrounding the magnetic-network elements, known as "magnetic shadows". These also show enhanced power close to the photosphere, traditionally referred to as"power halos". The interaction between acoustic waves and inclined magnetic fields is generally believed to be responsible for these two effects. In this study we explore if small-scale transients can influence the distribution of power at different heights. We show that the presence of transients, like mottles, Rapid Blueshifted Excursions (RBEs) and Rapid Redshifted Excursions (RREs), can strongly influence the power-maps. The short and finite lifetime of these events strongly affects all powermaps, potentially influencing the observed power distribution. We show that Doppler-shifted transients like RBEs and RREs that occur ubiquitously, can have a dominant effect on the formation ofthe power halos in the quiet Sun. For magnetic shadows, transients like mottles do not seem to have a significant effect in the power suppression around 3 minutes and wave interaction may play a key role here. Our high cadence observations reveal that flows, waves and shocks manifest in presence of magnetic fields to form a non-linear magnetohydrodynamic system.

The microphysics of collisionless shock waves

Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebulæ, active galactic nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless shock microphysics enters at different stages of shock formation, shock dynamics and particle energization and/or acceleration. It turns out that the shock phenomenon is a multi-scale non-linear problem in time and space. It is complexified by the impact due to high-energy cosmic rays in astrophysical environments. This review adresses the physics of shock formation, shock dynamics and particle acceleration based on a close examination of available multi-wavelength or in situ observations, analytical and numerical developments. A particular emphasis is made on the different instabilities triggered during the shock formation and in association with particle acceleration processes with regards to the properties of the background upstream medium. It appears that among the most important parameters the background magnetic field through the magnetization and its obliquity is the dominant one. The shock velocity that can reach relativistic speeds has also a strong impact over the development of the micro-instabilities and the fate of particle acceleration. Recent developments of laboratory shock experiments has started to bring some new insights in the physics of space plasma and astrophysical shock waves. A special section is dedicated to new laser plasma experiments probing shock physics.

No discrimination shock avoidance with sequential presentation of stimuli but shore crabs still reduce shock exposure

Insights into the potential for pain may be obtained from examination of behavioural responses to noxious stimuli. In particular, prolonged responses coupled with long-term motivational change and avoidance learning cannot be explained by nociceptive reflex but are consistent with the idea of pain. Here, we placed shore crabs alternately in two halves of a test area divided by an opaque partition. Each area had a dark shelter and in one repeated small electric shocks were delivered in an experimental but not in a control group. Crabs showed no specific avoidance of the shock shelter either during these trials or in a subsequent test in which both were offered simultaneously; however they often emerged from the shock shelter during a trial and thus avoided further shock. More crabs emerged in later trials and took less time to emerge than in early trials. Thus, despite the lack of discrimination learning between the two shelters they used other tactics to markedly reduce the amount of shock received. We note that a previous experiment using simultaneous presentation of two shelters demonstrated rapid discrimination and avoidance learning but the paradigm of sequential presentation appears to prevent this. Nevertheless, the data show clearly that the shock is aversive and tactics, other than discrimination learning, are used to avoid it. Thus, the behaviour is only partially consistent with the idea of pain.

On the Economics and Politics of Mobility

Exit, Voice and Political Change: Evidence from Swedish Mass Migration to the United States. During the Age of Mass Migration, 30 million Europeans immigrated to the United States. We study the long-term political effects of this large-scale migration episode on origin communities using detailed historical data from Sweden. To instrument for emigration, we exploit severe local frost shocks that sparked an initial wave of emigration, interacted with within-country travel costs. Because Swedish emigration was highly path dependent, the initial shocks strongly predict total emigration over 50 years. Our estimates show that emigration substantially increased membership in local labor organizations, the strongest political opposition groups at the time. Furthermore, emigration caused greater strike participation, and mobilized voter turnout and support for left-wing parties in national elections. Emigration also had formal political effects, as measured by welfare expenditures and adoption of inclusive political institutions. Together, our findings indicate that large-scale emigration can achieve long-lasting effects on the political equilibrium in origin communities. Mass Migration and Technological Innovation at the Origin. This essay studies the effects of migration on technological innovations in origin communities. Using historical data from Sweden, we find that large-scale emigration caused a long-run increase in patent innovations in origin municipalities. Our IV estimate shows that a ten percent increase in emigration entails a 7 percent increase in a muncipality’s number of patents. Weighting patents by a measure of their economic value, the positive effects are further increased. Discussing possible mechanisms, we suggest that low skilled labor scarcity may be an explanation for these results.  Richer (and Holier) Than Thou? The Impact of Relative Income Improvements on Demand for Redistribution. We use a tailor-made survey on a Swedish sample to investigate how individuals' relative income affects their demand for redistribution. We first document that a majority misperceive their position in the income distribution and believe that they are poorer, relative to others, than they actually are. We then inform a subsample about their true relative income, and find that individuals who are richer than they initially thought demand less redistribution. This result is driven by individuals with prior right-of-center political preferences who view taxes as distortive and believe that effort, rather than luck, drives individual economic success. Wealth, home ownership and mobility. Rent controls on housing have long been thought to reduce labor mobility and allocative efficiency. We study a policy that allowed renters to purchase their rent-controlled apartments at below market prices, and examine the effects of home ownership and wealth on mobility. Treated individuals have a substantially higher likelihood of moving to a new home in a given year. The effect corresponds to a 30 percent increase from the control group mean. The size of the wealth shock predicts lower mobility, while the positive average effect can be explained by tenants switching from the previous rent-controlled system to market-priced condominiums. By contrast, we do not find that the increase in residential mobility leads to a greater probability of moving to a new place of work.

Mesurer la résilience des ménages ruraux sénégalais : Une approche en termes de trajectoires et seuils de moyens d’existence

Full Text / Article complet

Mesurer la résilience des ménages ruraux sénégalais : Une approche en termes de trajectoires et seuils de moyens d’existence

Full Text / Article complet

Farmers' Resilience to Climate Change in the Welsh Marshes

Climate change will exacerbate challenges facing food security in the UK. Increasing frequency and intensity of extreme weather events will further impact upon farm systems. At the heart of the impending challenges to UK agricultural production, farmers’ resilience will be tested to new limits. Research into farmers’ resilience to climate change in the UK is distinctly underdeveloped when compared to research in developing and other developed nations. This research gap is addressed through exploration of farmers’ resilience in the Welsh Marches, establishing the role of risk perceptions, local knowledge and adaptive capacity in farmers’ decision-making to limit climate shocks. Further contributions to agricultural geography are made through experimentation of a ‘cultural-behavioural approach’, seeking to revisit the behavioural approach in view of the cultural-turn. The Welsh Marches, situated on the English-Welsh border, has been selected as a focal point due to its agricultural diversity, and known experiences of extreme weather events. A phased mixed methodological approach is adopted. Phase one explores recorded and reported experiences of past extreme weather events in local meteorological records and local newspaper articles. Phase two consists of 115 survey-questionnaires, 15 in-depth semi-structured interviews, and a scenario based focus group with selected farmers from the Welsh Marches. This allows farmers’ resilience to climate change in the past, present and future to be explored. Original contributions to knowledge are made through demonstrating the value of focusing upon the culture of a specific farm community, applying a ‘bottom-up’ approach. The priority given to the weather in farmers’ decision-making is identified to be determined by individual relationships that farmers’ develop with the weather. Yet, a consensus of farmers’ observations has established recognition of considerable changes in the weather over the last 30 years, acknowledging more extremes and seasonal variations. In contrast, perceptions of future climate change are largely varied. Farmers are found to be disengaged with the communication of climate change science, as the global impacts portrayed are distant in time and place from probable impacts that may be experienced locally. Current communication of climate change information has been identified to alienate farmers from the local reality of probable future impacts. Adaptation options and responses to extreme weather and climate change are identified from measures found to be already implemented and considered for the future. A greater need to explore local knowledge and risk perception in relation to farmers’ understanding of future climate challenges is clear. There is a need to conduct comparable research in different farm communities across the UK. Progression into establishing the role of farmers’ resilience in responding effectively to future climate challenges has only just begun.

Stochastic Modeling of Reversible Biochemical Reaction-Diffusion Systems and High-Resolution Shock-Capturing Methods for Fluid Interfaces

Thesis (Ph.D.)--University of Washington, 2016-08

Three essays in labor economics and applied econometrics

Méthodologie:Cadre conceptuel: Principal-agent

How game changers catalyzed, disrupted, and incentivized social innovation: three historical cases of nature conservation, assimilation, and women’s rights

We explore the impact of “game changers” on the dynamics of innovation over time in three problem domains, that of wilderness protection, women’s rights, and assimilation of indigenous children in Canada. Taking a specifically historical and cross-scale approach, we look at one social innovation in each problem domain. We explore the origins and history of the development of the National Parks in the USA, the legalization of contraception in the USA and Canada, and the residential school system in Canada. Based on a comparison of these cases, we identify three kinds of game changers, those that catalyze social innovation, which we define as “seminal,” those that disrupt the continuity of social innovation, which we label exogenous shocks, and those that provide opportunities for novel combinations and recombinations, which we label as endogamous game changers.

Prediction of Sudden Cardiac Arrest for Patients with Congestive Heart Failure

Thesis (Ph.D.)--University of Washington, 2016-07

Trois essais sur les banques et le pouvoir de marché

Cette thèse examine le rôle du pouvoir de marché dans le marché bancaire. L’emphase est mis sur la prise de risque, les économies d’échelle, l’efficacité économique du marché et la transmission des chocs. Le premier chapitre présente un modèle d’équilibre général dynamique stochastique en économie ouverte comprenant un marché bancaire en concurrence monopolistique. Suivant l’hypothèse de Krugman (1979, 1980) sur la relation entre les économies d’échelle et les exportations, les banques doivent défrayer un coût de transaction pour échanger à l’étranger qui diminue à mesure que le volume de leurs activités locales augmente. Cela incite les banques à réduire leur marge locale afin de profiter davantage du marché extérieur. Le modèle est solutionné et simulé pour divers degrés de concentration dans le marché bancaire. Les résultats obtenus indiquent que deux forces contraires, les économies d’échelle et le pouvoir de marché, s’affrontent lorsque le marché se concentre. La concentration permet aussi aux banques d’accroître leurs activités étrangères, ce qui les rend en contrepartie plus vulnérables aux chocs extérieurs. Le deuxième chapitre élabore un cadre de travail semblable, mais à l’intérieur duquel les banques font face à un risque de crédit. Celui-ci est partiellement assuré par un collatéral fourni par les entrepreneurs et peut être limité à l’aide d’un effort financier. Le modèle est solutionné et simulé pour divers degrés de concentration dans le marché bancaire. Les résultats montrent qu’un plus grand pouvoir de marché réduit la taille du marché financier et de la production à l’état stationnaire, mais incite les banques à prendre moins de risques. De plus, les économies dont le marché bancaire est fortement concentré sont moins sensibles à certains chocs puisque les marges plus élevés donnent initialement de la marge de manoeuvre aux banques en cas de chocs négatifs. Cet effet modérateur est éliminé lorsqu’il est possible pour les banques d’entrer et de sortir librement du marché. Une autre extension avec économies d’échelle montre que sous certaines conditions, un marché moyennement concentré est optimal pour l’économie. Le troisième chapitre utilise un modèle en analyse de portefeuille de type Moyenne-Variance afin de représenter une banque détenant du pouvoir de marché. Le rendement des dépôts et des actifs peut varier selon la quantité échangée, ce qui modifie le choix de portefeuille de la banque. Celle-ci tend à choisir un portefeuille dont la variance est plus faible lorsqu’elle est en mesure d’obtenir un rendement plus élevé sur un actif. Le pouvoir de marché sur les dépôts amène un résultat sembable pour un pouvoir de marché modéré, mais la variance finit par augmenter une fois un certain niveau atteint. Les résultats sont robustes pour différentes fonctions de demandes.

A assimetria na volatilidade das rendibilidades do preço do crude

Dissertação de Mestrado em Contabilidade e Análise Financeira

A NAIRU assessment: an applied case to Colombia’s labor markets

Given the discrepancy over the optimum levels of employment for Colombia, this research targets both, the national and urban, Non-Accelerating Inflation Rate of Unemployment (NAIRU) for the Colombian markets -- In doing so, there is a strong pertinence in estimating the constant NAIRU through raw and minimally altered data and providing the reader with a complete brief of the theory in which the model is founded -- The introduction of supply shocks is considered to attain improved estimations and a more reliable assessment of the NAIRU to those that have previously been attempted -- The backbone of the analysis is conducted through the relationship established by the Phillips curve from 2001 until 2015

El comportamiento de la inflación en Colombia durante el periodo 1955-2004

Este artículo corresponde a la investigación que se ha desarrollado para establecer el comportamiento de la inflación en Colombia durante el período 1955-2004, analizar los elementos que han incidido en su desempeño y establecer la teoría que soporta su análisis. El análisis se ha dividido en tres períodos que cubren los años 1955-2004, el primero, de 1955 a 1970 se relaciona con los años durante los cuales aún se tenía una tasa de cambio fija, tal como se había convenido en el tratado de Bretton Woods, y coincide con sucesivas crisis cambiarias que se reflejan en el comportamiento de la inflación