The Fermi Gamma-ray Space Telescope (Fermi) has focused the intensive multi-wavelength and international observational effort on blazars since it was launched in 2008. Part of this effort involves systematic monitoring of the highly variable polarization of the continuum emission from these objects. These observations are valuable in that they provide direct information on the degree of ordering and orientation on the sky of the magnetic field within the non-thermal emission region(s). Unfortunately, it is not yet possible to measure the polarization of the inverse-Compton continuum, only that of the lower-energy synchrotron emission. The inability to directly compare the polarization of the two dominant continuum sources in blazars is a drawback and leads to more ambiguities in determining their relative locations. There are many compelling examples of strong connections between -ray, X-ray, UV/optical/IR, and radio behavior in blazars that suggest the same region produces much of the observed emission at all wavelengths at least some of the time. However, the wealth of polarization behavior seen relative to flux changes invariably results in a complex situation that is difficult to interpret and model. The long-term blazar monitoring program undertaken at Steward Observatory is designed to primarily obtain accurate optical polarimetry of -ray-bright blazars during the Fermi mission with the goal of gaining important insights into the jet structure and physics of these objects. Data from this program are available to all researchers as soon as reductions are completed. I briefly detail the current status and progress of the program and the data products available. Although the wide variety of polarization behavior in blazars adds another layer of complexity to an already difficult problem, I summarize several important conclusions that can be drawn from the polarization information gathered during the Fermi era.

O objetivo deste trabalho foi implementar um sistema para a determinação do coeficiente piroelétrico em materiais poliméricos. O método consiste em variar a temperatura da amostra de forma senoidal e medir a corrente em função do tempo. Através do sinal da corrente elétrica e da sua diferença de fase com a temperatura, separa-se a corrente elétrica de origem piroelétrica, a partir da qual se determina o coeficiente piroelétrico. Apresenta-se a caracterização do sistema abrangendo aspectos como o intervalo de temperatura das medidas e amplitude e freqüência da oscilação da temperatura. O método foi empregado para realizar medidas exploratórias com o polímero ferroelétrico poli(fluoreto de vinilideno), PVDF, polarizado pela aplicação de uma rampa de tensão, e com o polímero poli(metacrilato de metila), PMMA, com corante polar, polarizado com o triodo de corona. Nas medidas foram variados os parâmetros do processo de polarização elétrica tais como o campo elétrico máximo e a temperatura / An experimental setup to measure the pyroelectric coefficient of polymers was implemented. The method is based on the measurement of the electric current generated by the sample when its temperature was set to oscillate sinusoidally. Using the measured current and its phase difference related with the temperature thepyroelectric current was obtained, from that the pyroelectric coefficient was determined. It is shown the characterization of the experimental system such as the temperature amplitude and frequency interval of operation. The method was applied in exploratory measurements employing the ferroelectric polymer poly(vynilidene fIuoride), PVDF, poled by a ramp voltage, and the poly(methyl metacrylate), PMMA, having a polar dye, poled with the carona triode. Measurements were performed far different poling conditions such as the maximum applied field and temperature

Alpha matting is one of the key techniques in image processing and is used to extract accurate foreground from a still image or video sequences. Chroma keying is a special case of alpha matting with a solid background color. Color spill is one of the difficulties in chroma keying, and it has not been effectively solved by current methods. Sometimes, an image contains both reflected regions and transparent regions. When the foreground in such images is chroma keyed, reflection on the foreground is often falsely treated as transparency and causes unreal foreground extraction and composition. This problem is called color spill. Color spill suppression aims to extract the opaque foreground with the correct transparency descriptor (i.e. alpha value) and remove the reflected background color on it. When the background color presented on the foreground is simultaneously caused by reflection and transparency, color spill suppression becomes extremely challenging. It is because that the reflection removal and the actual transparency estimation is a dilemma. Our proposed method for color spill suppression is to separate reflected regions from transparent regions, and process reflected regions as foreground while keeping transparency unchanged at the same time. In this thesis, we propose a novel method for color spill suppression for chroma keying. The quality of the estimated alpha matte could be significantly improved. In our approach, we suppress color spill by using the polarization and the optical flow algorithm based on disparity estimation. Specifically, we make the assumption that reflection changes more than transparency when the scene is captured by a binocular camera with a polaroid filter. Based on this assumption, we took stereo images with polarization filter, registered stereo images by optical flow and conducted the variance analysis on histograms of input images to separate transparency and reflection. Our experiments show that the opaque foreground with background color spill can be reliably extracted while the real transparency can be kept.

My dissertation, titled “From the machine mind to the human mind: using machine learning to understand (ir)rationality, bias and polarization in human beings,” investigates ways in which human minds operate and seeks to uncover the causes of biasedness, limited rationality, and polarization of human minds, to eventually devise tools to compensate for such human limitations. Chapter 2 of the thesis focuses on the evaluation of information and decision making under enormous information asymmetry, in the setting of patients evaluating doctors’ medical advice. Patients were found to be poor evaluators who were unable to distinguish good from bad due to their lack of medical expertise, and unable to overcome their own irrationality and bias. I emphasize the ramification of such limited rationality, which might lead to the adoption of suboptimal or bad medical opinions, and propose ways to improve this situation by redesigning some features of the platform, and/or implementing new policies to help good doctors on the platform. Chapter 3 focuses on developing a new metric that reliably measures the ideology of the US elites. This metric was developed based on congressional reports which made it unique and relatively independent from established metrics based on roll call votes, such as DW-NOMINATE. First, I leveraged a neural network-based approach to decompose the speech documents into frames and topics components, with all ideological information funneled into the frames component. Eventually, two different ideology metrics were obtained and validated: an embedding vector and an ideological slant score. Later I showed that our new metrics can predict party switchers and trespassers with high recall. In chapter 4, I applied the newly obtained metric (mainly slant scores) to investigate various aspects of the congress, such as the heterogeneity of ideology among the members, the temporal evolution of partisan division, the bill passing, and the re-election strategy of the senators.

Currently, the most utilized desalination technology is reverse osmosis (RO), where a membrane is used as a physical barrier to separate the salts from the seawater, using high hydraulic pressure as driving force. A major problem in RO systems is biofouling, caused by severe growth of bacterial biofilms. Both, the need of an external energy input, as well as biofouling, impose a high cost on RO operation. Forward osmosis (FO) is an alternative membrane process that uses an osmotic pressure difference as driving force. FO uses a concentrated draw solution to generate high osmotic pressure, which extracts water across a semi permeable membrane from a feed solution. One of the main advantages of FO is the limited amount of external energy required to extract water from the feed solution. The objective of this research is the assessment of the impact of spacers, separating the membrane sheets, and biofouling on the FO system performance. This type of studies allow the optimization of membrane devices and operational conditions. For this, a two dimensional numerical model for FO systems was developed using computational fluid dynamics (CFD). This model allowed the evaluation of the impact of (i) spacers and (ii) biofilm, and (iii) the combined impact of spacers and biofilm on the performance of FO systems. The results obtained showed that the presence of spacers improved the performance of FO systems. Cavity configuration spacer gave the higher water flux across the membrane in clean systems; whereas for biofouled systems, the submerged configuration showed a better performance. In absence of spacers, the thickness or amount of biofilm is inversely proportional with the water flux. Furthermore, membrane surface coverage of the biofilm is more important than the amount of biofilm in terms of the impact on the performance. The numerical model can be adapted with other parameters (e.g. membrane and spacer thickness, feed and draw solution, solution concentration, etc.) to predict the impact of biofilm on FO systems under different experimental conditions. The use of numerical modeling may contribute to faster development of economic viable FO based desalination systems.

With over 550,000 American lives claimed by COVID-19, over 30 million confirmed infections, and historic job losses across the nation, evaluations of the pandemic response from the Trump Administration have been polarizing. In the eyes of many Americans, President Trump’s Coronavirus response has been lacking in swiftness and efficacy, while many others see the governmental response as competent or having exceeded expectations. In light of previous research, to expect these evaluations to be politically polarized would be reasonable, but at what point do these partisan biases fall away? This survey study will test how partisan biases influence Americans’ evaluations of President Donald Trump’s – and President Biden’s – handling of the Coronavirus pandemic response – factoring in how respondents have been personally affected by the pandemic or personally know someone who has been. These experiences with COVID-19 will be quantified by proximity to loss of life due to, and infection of, COVID-19, as well as job loss as a result of the effects of the virus. As devastating as these experiences may be, I expect the influence of partisan biases to be overwhelmingly correlated with respondents’ evaluations of both President Trump’s and President Biden’s COVID-19 response when compared to the correlation of personal experience. As the findings will suggest, these expectations prove to be accurate; Republicans indicate substantially higher levels of satisfaction with President Trump’s pandemic response when compared to Democrats, with the reverse relationship observed for evaluations of President Biden, and this holds true at all levels of proximity. Further, partisan identity yields a considerably larger magnitude of correlation with these evaluations when compared to personal experience. Unfortunately, Americans do not seem to hold their presidents accountable for their actions (or inaction) by learning from even the most traumatic experiences; party overpowers all else. The findings of this study will greatly enrich the current literature on the extent to which partisan biases influence evaluations of government, and will provide insight into the reliability of democratic accountability, and, resultantly, the very functioning of American democracy.

The consequences and aftermaths of the 2008 Great Recession have played an important role in stirring people fear and agony to 'some' other people. The phenomenon is defined as the root of affective polarization. Research has claimed that affective polarization derives from partisan identity and the theory of social identity, and those affects are developed and reached beyond the classic concept of ideological polarization. During the post-economic crisis, a number of successful new radical right parties has surged across the continent. In addition, Western European politics has severely been polarized and increasingly characterized by growing hostility and incivility across partisan lines. Simultaneously, the trend of deinstitutionalization of party system goes upward across Europe. This article seeks to investigate a puzzle of whether and how increasing levels of party system deinstitutionalization are associated with increasing polarization. Assessing the association between party system deinstitutionalization and the two dimensions of polarization between 1997 and 2017 (82 elections in 15 countries), the empirical result shows such an unexpected result and strongly implies the underestimated effects of political structures on party system deinstitutionalization and polarization while...

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / This research addresses the dynamics that developed on the official Twitter account of Peru’s former president, Martín Vizcarra, before and during the Covid-19 pandemic. In the analysis, four trends crucial to political activity via Twitter are explored. These are the predominance of the emotional and affective component, the growing influence of fake news, deepening polarization that prevents dialogue, and the use of the platform as an information window. Results show that the pandemic effected a change in the account’s dynamics and audience participation: posting frequency on the @MartinVizcarraC account decreased, but Twitter users’ engagement more than doubled compared with the pre-pandemic period. In addition, the account strongly tended toward predominance of the emotional and affective component and informative value was the second most relevant topic for Vizcarra’s account. The communication of @MartinVizcarraC was unidirectional, focusing on the dissemination of content and avoiding conversation.

The diploma thesis deals with the influence of magnetic and electromagnetic fields on signals transmitted by optical fibers. Subsequently, the results of individual measured values are evaluated and analyzed, which were measured using an interferometer and a polarimeter. The first part deals with the theoretical analysis of the principles of interference and polarization of light. It further explains the basic operation of the above-mentioned devices as well as the immunity of the optical fiber to EMI. The second part of the work presents selected devices and technologies that were used as a source of electromagnetic or magnetic radiation. Subsequently, individual phenomena are plotted both in the course of time and with the help of a spectrogram or Poincaré sphere. From the measured results we can conclude that the commonly available technologies, which were selected for the diploma thesis, will not cause greater negative problems to the signal on measured frequencies in optical fibre, that could degrade the transmitted signal.

Phospholipid bilayers are the principal component of the cell membrane. Membranes ensure the maintenance of processes required for cells’ survival by regulating the inflow and outflow of nutrients and other molecules using membrane proteins. However, studying the cell membrane is challenging because of its complexity and small size. In-vitro membrane models made of phospholipids are important tools for studying membranes. In this work, we aim to study the fluidity of phospholipid bilayers of different lipids using general polarization (GP) of the fluorescent probe Laurdan as a measure. We will focus on the relative importance of head groups and fatty acids in the phospholipid. For this purpose, we are synthesizing chimeric lipids with the common human head group phosphocholine paired with bacterial fatty acids. We will compare the response of the human and chimeric lipids to temperature and biofuels to ascertain whether improved stress tolerance can be obtained with the chimeras.