Understanding the formation and evolution of planetary systems is one of the most fundamental challenges in astronomy. To directly image and study young exoplanets and the circumstellar disks they... Show moreUnderstanding the formation and evolution of planetary systems is one of the most fundamental challenges in astronomy. To directly image and study young exoplanets and the circumstellar disks they form from, dedicated high-contrast imaging instruments are built. Several of these instruments have polarimetric modes that are particularly powerful to reach the large contrasts required to directly image these objects as well as to characterize them. This thesis aims to improve the polarimetric sensitivity, accuracy, and capabilities of high-contrast imaging polarimeters for the detection and characterization of exoplanets and circumstellar disks. In addition, this thesis presents the first direct detections of linear polarization from self-luminous planetary mass companions. The focus of this thesis is mostly on ground-based high-contrast imaging, in particular with the instrument SPHERE-IRDIS at the Very Large Telescope. This thesis covers many aspects of high-contrast imaging polarimetry, ranging from theoretical work, calibrations, and the development of new observing techniques to actual scientific polarimetric measurements and astrophysical interpretation. Show less
Computer simulations have been used to model psychological and sociological phenomena in order to provide insight into how they affect human behavior and population-wide systems. In this study,... Show moreComputer simulations have been used to model psychological and sociological phenomena in order to provide insight into how they affect human behavior and population-wide systems. In this study, three agent-based simulations (ABSs) were developed to model opinion dynamics in an online social media context. The main focus was to test the effects of ‘social identity’ and ‘certainty’ on social influence. When humans interact, they influence each other’s opinions and behavior. It was hypothesized that the influence of other agents based on ingroup/outgroup perceptions can lead to extremism and polarization under conditions of uncertainty. The first two simulations isolated social identity and certainty respectively to see how social influence would shape the attitude formation of the agents, and the opinion distribution by extension. Problems with previous models were remedied to some extent, but not fully resolved. The third combined the two to see if the limitations of both designs would be ameliorated with added complexity. The combination proved to be moderating, and while stable opinion clusters form, extremism and polarization do not develop in the system without added forces. Show less
This study goes beyond the analysis of the causes of the emergence of populist actors in the party system, focusing instead on those cases in which populism and its counterpart anti-populism,... Show moreThis study goes beyond the analysis of the causes of the emergence of populist actors in the party system, focusing instead on those cases in which populism and its counterpart anti-populism, translate into an ideological and discursive divide that contributes to structuring a certain party system. When populism/anti-populism emerges as a political cleavage, the factors behind parties’ political choices in general, and electoral coalition preferences in particular, can be affected. For this new cleavage to start to polarize, a change in the political opportunity structure is needed. In fact, when the political opportunity structure opens as a consequence of events external to the party system new actors may enter the system, producing a change in the dynamic of competition. Moreover, considering also the organizational density of the parties in the system, defined as the power of penetration of a given party, both in terms of intensity and reach, this dissertation can shed light on the likely duration not only of the parties but also of the cleavage. Show less
Taking a series of popular jokes about fictitious “anti-societies” as its point of departure, this article explores the responses to the transformation of reform in the decade between 1825 and 1835... Show moreTaking a series of popular jokes about fictitious “anti-societies” as its point of departure, this article explores the responses to the transformation of reform in the decade between 1825 and 1835 and places them in the context of social and political change brought about by Jacksonian democracy. Rooted in the tradition of the moral reform society, through specialization of its aims, the anti-society seemed to become a democratic pendant of older reform societies and was thought to play a more divisive role in local communities. Critics denounced the new societies for their prescriptive character, the prominent role women played, and the “spirit of opposition” they triggered. Contemporaries increasingly understood the evolution of reform culture from the relatively harmonious religious and moral reform societies of the Benevolent Empire of the first quarter of the 19th century to the oppositional and highly contested organizations of radical antislavery and temperance of the 1830s as a serious threat to the social order and the future of the United States. Using the Benign Violation Theory of Humor, this article argues that the American reaction to anti-societies suggests that while they were broadly perceived as a threat to the social order from the late 1820s on, this threat was at first understood to be benign, and thus could be laughed off, while from 1833 on, anti-societies were increasingly regarded as a destructive force, and provoked substantial fears that could justify violent responses as an alternative way to reinforce the “normal” order of things. Show less
