Dissertations / Theses on the topic 'News Polarization'

This thesis revolves around the subject of fake news, a phenomenon that has been highly discussed with the advent of the internet-based media. It aims to shed light on the problem of fake news and its implications in the Turkish mainstream media by mainly departing from the discourse theory, as well as by using additional theoretical approaches over fake news and media in polarized settings. In that sense, five research questions were developed to understand how fake news items disseminate in the Turkish media ecosystem, and what this could mean for the Turkish mainstream media specifically from the contexts of political partisanship and polarization. In order to answer the research questions, a total number of 687 fake news items have been analyzed in three different data sets. After providing an overall picture of the problem of fake news in the Turkish media ecosystem, the thesis specifically focuses on fake news items that circulate within the Turkish mainstream media. Overall, 77 fake news items are further subjected to an analysis of discourse activity schema in order to find out the narratives that the fake news items are connected to the Turkish political and social context. The research shows that the use of fake news items in the Turkish mainstream media indicates divergent and conflicting epistemologies over certain social and political themes, which are government- opposition divide, secular religious divide, economy, and education. Moreover, the research also indicates that certain social and political themes are under the discursive hegemony of certain groups within the Turkish mainstream media organizations. These themes are found to be anti-immigration, anti-US, anti-Israel, and FETO. Eventually, two main points are discussed in relation to the given theoretical background. First, the problem of fake news in the Turkish mainstream media indicates a damaged understanding of journalism in the country, which requires a reorientation and reexamination. Second, media in polarized settings may increase partisan alignments and divergent epistemologies, which can lead to the use of fake news items in order to empower certain agendas.

Political Science
Ph.D.
This dissertation extends the media effects literature into the realm of social media. Scholars have long known that partisan news contributes to political polarization, but claim that such effects are often limited to those who tune into politics. Social media, however, can filter political information to those typically uninterested in politics. Because social media feature entertainment and political news in the same space, entertainment-seekers may inadvertently see political news that they normally avoid in traditional media contexts. Through a combination of observational research, survey experiments, and field experiments, I demonstrate that social media facilitate personal influence, drawing new audiences to political news. This increased exposure to partisan media contributes to political polarization, regardless of the ideological congruence between source and receiver, or of news- or entertainment-seeking habits of the audience. But the most important contributions of this dissertation are how it demonstrates the need for scholars to use innovative methods that incorporate personal influence into social media studies, and that it draws scholarly attention to inadvertent media effects for entertainment-seeking audiences. Social media bring political news to new audiences numbering in the millions. Political communication scholars would be remiss not to investigate their influence.
Temple University--Theses

This thesis examines the effects of discourses by journalists from six major media outlets in the United States covering the Atlanta massage parlor shootings. Through conducting critical discourse analysis, this research investigates the journalist's use of language, content selection, and positioning to understand journalistic reporting's role in influencing and promoting xenophobia towards Asian Americans and furthering the polarization of political ideologies. This research sampled news articles from various news outlets along a political spectrum, including the New York Times, The Washington Post, Fox News, CNN, NPR, and The Wall Street Journal. This analysis is conducted through analyzing observations and patterns found in 42 news articles by the selected news outlets, alongside a framework of communication theories including gatekeeping, framing, agenda-setting, and the representation of Asian Americans in media. This thesis is relevant to current events because there is an increase in anti-Asian sentiments due to the COVID- 19 pandemic.  Overall, this study found that most journalists reporting the Atlanta massage parlor shootings utilized forms of framing and gatekeeping in the sampled articles. Observations found that the journalists practiced framing and gatekeeping, which displayed patterns of biases in their journalistic reporting. Additionally, this study found that the news media tended to use language that potentially dictates public discourse through agenda-setting practices. This thesis found that these biases attract specific audiences, which ultimately promote xenophobia and polarization. Journalists debated if a racial motive influenced the shooting. This debate between journalists was a crucial observation in identifying how framing and agenda-setting influenced furthered polarization of political ideologies. This thesis found patterns of language supporting a white racial frame that ultimately perpetuate a white hegemony.  Moreover, patterns of journalistic reporting showed how representation, or lack of it, can contribute to xenophobic tendencies and increased anti-Asian sentiments. The results of this thesis signify the importance of language selection by journalists in reporting racially sensitive issues. This thesis displays the necessity for further research on how to promote journalistic language that minimizes biases.

Le premier chapitre de cette thèse considère une entreprise de médias financée par la publicité qui choisit l'emplacement idéologique de ses nouvelles et cible les consommateurs qui peuvent partager les nouvelles avec leurs abonnés sur les médias sociaux. Après avoir étudié comment l'incitation de chaque consommateur ciblé à partager les nouvelles est façonnée par l'emplacement des nouvelles et la distribution des emplacements idéologiques de ses abonnés, nous étudions la stratégie de l'entreprise pour maximiser l'étendue du partage des nouvelles et constatons que lorsque la moyenne (respectivement, la variance) des localisations idéologiques des suiveurs est une fonction convexe (respectivement concave) de la localisation d'un consommateur ciblé, l'entreprise est susceptible de produire des informations polarisées.Dans le deuxième chapitre, nous considérons une plate-forme monopolistique fournissant un continuum de contenus différenciés verticalement et étudions la conception des contrats de filtrage optimaux lorsque les consommateurs ont des types binaires. Un contrat précise un ensemble de contenus, un prix et si la consommation de contenus fait ou non l'objet d'une publicité. Nous distinguons les allocations de contenu descendantes des allocations ascendantes et permettons le regroupement d'informations d'un ensemble de contenus. Nous constatons que la publicité peut inciter la plate-forme à utiliser une allocation ascendante pour les consommateurs de type faible, tandis que les contrats basés sur un abonnement utilisent toujours des allocations descendantes. La publicité a tendance à inciter la plateforme à augmenter la quantité de contenu consommée en recourant au regroupement d'informations, ce qui augmente le surplus du consommateur. Lorsque la consommation de contenu ne peut pas être subventionnée par un prix négatif, la plateforme peut trouver optimal de proposer un contrat freemium, qui étend (réduit) l'ensemble de consommation, par rapport au cas de la subvention à la consommation, pour des allocations ascendantes (allocations descendantes ) et augmente (réduit) ainsi le surplus du consommateur. Enfin, lorsque les types élevés subissent une nuisance publicitaire plus importante que les types faibles, la plate-forme peut avoir une incitation socialement excessive à montrer de la publicité aux types faibles afin d'extraire la rente d'information des types élevés.Dans le troisième chapitre, nous étudions les réseaux de licences de brevets à l'équilibre qui surgissent entre des entreprises concurrentes symétriques. Nous envisageons des accords de licence qui ne peuvent pas spécifier de redevances mais qui peuvent utiliser des frais fixes et se concentrer sur des réseaux efficaces sur le plan bilatéral. Nous constatons que le réseau complet, qui génère le résultat le plus compétitif, est toujours efficace bilatéralement. Lorsqu'il y a trois firmes symétriques, nous fournissons une caractérisation complète de tous les réseaux de licences bilatéralement efficaces. Lorsque les brevets sont indépendants, nous constatons que le réseau en étoile menant au monopole n'est jamais bilatéralement efficace. En particulier, lorsque la réduction des coûts du brevet est suffisamment importante, il y a un grand contraste : bien qu'un accord de licence multilatéral permette aux entreprises de mettre en œuvre le résultat du monopole, le réseau complet est l'unique réseau bilatéralement efficace. Nous fournissons une condition générale dans laquelle le réseau complet est à la fois le résultat unique efficace sur le plan bilatéral et le résultat unique de maximisation des profits de l'industrie pour un nombre donné d'entreprises. Nos résultats offrent des implications politiques claires en faveur des licences à prix fixe par rapport aux licences à tarif en deux parties, y compris les redevances
The first chapter of this thesis considers an ad-financed media firm that chooses the ideological location of its news and targets consumers who can share the news with their followers on social media. After studying how each targeted consumer's incentive to share the news is shaped by the location of the news and the distribution of her followers’ ideological locations, we study the firm's strategy to maximize the breadth of news sharing and find that when the mean (respectively, the variance) of the followers' ideological locations is a convex (respectively, concave) function of a targeted consumer's location, the firm is likely to produce polarized news.In the second chapter, we consider a monopoly platform providing a continuum of vertically differentiated content and study the design of the optimal screening contracts when consumers have binary types. A contract specifies a set of content, a price and whether or not the content consumption is subject to advertising. We distinguish top-down content allocations from bottom-up allocations and allow for informational bundling of a content set. We find that advertising can induce the platform to use bottom-up allocation for low-type consumers while subscription-based contracts always use top-down allocations. Advertising tends to induce the platform to expand the amount of content consumed by resorting to informational bundling, which increases consumer surplus. When content consumption cannot be subsidized by a negative price, the platform may find it optimal to offer a freemium contract, which expands (reduces) the consumption set, relative to the case of consumption subsidy, for bottom-up allocations (top-down allocations) and thereby increases (reduces) consumer surplus. Finally, when high types experience larger ad nuisance than low types, the platform may have a socially excessive incentive to show advertising to low types in order to extract the information rent of high types.In the third chapter, we study equilibrium patent licensing networks that arise among symmetric competing firms. We consider licensing agreements that cannot specify royalties but can use fixed fees and focus on bilaterally-efficient networks. We find that the complete network, which generates the most competitive outcome is always bilaterally efficient. When there are three symmetric firms, we provide a complete characterization of all bilaterally-efficient licensing networks. When patents are independent, we find that the star network leading to monopoly is never bilaterally efficient. In particular, when the cost reduction from patent is large enough, there is a big contrast: although a multilateral licensing agreement allows the firms to implement the monopoly outcome, the complete network is the unique bilaterally-efficient network. We provide a general condition under which the complete network is both the unique bilaterally-efficient outcome and the unique industry-profit-maximizing outcome for any given number of firms. Our results offer clear-cut policy implications in favor of fixed-fee licensing relative to two-part tariff licensing including royalties

Vår studie undersöker fenomenet ekokammare och hur den manifesterar sig på svenska nyhetsmediers Facebooksidor. Vårt material består av fem opinionsartiklar från fem olika dagstidningar, samt kommentarsfält tillhörande dessa opinionsartiklar. Studiens teoretiska ramverk består av två huvudteorier: selektiv exponering och Faircloughs kritisk diskursanalytiska teori. Faircloughs kritiska diskursanalys utgör också vår huvudmetod, som vi använder för att analysera den diskursiva praktiken som sker i opinionsartiklarna och dess tillhörande kommentarsfält. Resultatet visar att en ekokammare går att tyda på nästan alla kommentarsfält, vilket kan tyda på en politisk polarisering i hur läsare konsumerar svenska nyhetsmedier.
Our study examines the phenomenon echo chamber and how it manifests itself on Facebook pages of Swedish news media. Our material consists of five opinion articles from five different Swedish newspapers, as well as the comments section connected to the opinion articles. The study’s theoretical framework consists of two main theories: selective exposure and Fairclough’s theory of critical discourse analysis. Fairclough’s critical discourse analysis also constitute as our main method, which we use to analyse the discursive practice used in opinion articles and comments sections connected to them. The result shows that an echo chamber is observable in almost all of the comment sections, which indicates a political polarization in how readers consume Swedish news media.

The main purpose of this study has been to explore and determine how the journalistic work was used by internet users to start and keep a discussion on the internet going. We started in the aftermath of a local arson in a town of Sweden, where a discussion on the internet forum Flashback and the local newspapers commentary fields was raised. We have used these discussions to study what part the journalistic work play in these events. To do that we used a critical discourse analysis and a rhetoric analysis to investigate how these discussions use news articles to make their point. We divided the comments into four different categories, which are comments about understandings of the event, comments that talked about the matters of fact, criticism pointed at the newspaper and comments that identify the offenders. The result of the analysis shows that both forums use journalistic work as facts in their discussions. Both also use earlier articles that were written before the arson, to make their point in the discussion.

This thesis analyses the processes undergone by mainstream media during the independence debate in Catalonia, focusing on the relationship among media, their audiences and governments through different empirical perspectives. It is made up of three articles. The first examines the evolution of media audiences in Catalonia based on an unpublished compilation of data and evaluates changes in their consumption patterns coinciding with periods of greater political intensity since this debate reached the political arena. It defines and proves the existence of two stable media systems, the Catalan and the Spanish systems. The second article presents the results of a content analysis of the top twelve outlets with highest consumption in Catalonia in the period 2012-15 from a framing approach, and highlights the main differences between the two systems in the tone applied to the political actors and the predominance of two specific frames designed for the analysis from the political discourse (“right to decide” and “rule of law”). Finally, the third article analyses the polarization of media audiences coinciding with the independence debate and confirms the homogenization of media audiences towards the issue.
Aquesta tesi analitza els processos que han experimentat els mitjans de comunicació de masses durant el debat sobre la independència a Catalunya, centrant-se en la relació entre els mitjans de comunicació, els seus públics i els governs a través de diferents enfocaments empírics. Està format per tres articles. El primer examina l’evolució de les audiències dels mitjans de comunicació a Catalunya a partir d’una recopilació inèdita de dades i avalua els canvis en els seus patrons de consum coincidint amb períodes de major intensitat política des que aquest debat va arribar a l’àmbit polític. Defineix i demostra l’existència de dos sistemes de mitjans estables, el català i l’espanyol. El segon article presenta els resultats de l’anàlisi del contingut dels dotze mitjans amb més consum a Catalunya en el període 2012-15 des de la perspectiva del framing i destaca les principals diferències entre els dos sistemes en el to aplicat als actors polítics i en el predomini d’un dels dos marcs específics dissenyats a partir de l’anàlisi del discurs polític (“dret a decidir” i “estat de dret”). Finalment, el tercer article analitza la polarització de les audiències dels mitjans coincidint amb el debat sobre la independència i confirma l’homogeneïtzació de les audiències dels mitjans de comunicació sobre el tema.

Chemotaxis, the ability of a cell to migrate towards a directional stimulus, is a basic property of virtually all cells at some stage in their development. Chemotaxis is preceded by the development of a polarized cellular morphology. The region of the cell closest to the attractant forms a broad lamellipod. The contents of the cell flow forward into this lamellipod and the rear of the cell becomes constricted into a narrow uropod. These local differences in cell structure and function presumably reflect local differences in cell chemistry, but the chemical processes involved are poorly understood. Ca+2 is known to play a ubiquitous role as an essential second messenger in many cellular processes, but its role in chemotaxis is unclear. While many chemotactic stimuli cause Ca+2 to rise intracellularly, the relationship between this rise in Ca+2 and local changes in cell behavior has been difficult to understand. In my dissertation work, I directly tested the role of cellular Ca+2 changes in polarization and chemotaxis by simultaneously imaging intracellular Ca+2 and cell morphology. This work was carried out on single eosinophils isolated from the newt, Taricha granulosa, because of their large size (~100 um, when polarized) and rapid responsiveness (~20 um/min) to chemotactic stimuli present in newt serum. An imaging system was developed to simultaneously image cell behavior, and intracellular Ca+2 following microinjection of the Ca+2 sensitive fluorescent probe, Fura-2. Cell behavior was quantified from time lapse video images captured by a SIT video camera, stored on a video optical disk recorder, and later digitized for analysis. Quantitation was accomplished by interactively tracing the cell's outline and determining the position of the geometric centroid. Variation in the radius of the outline from the centroid was used to calculate a "polarization index", which could be monitored over time. Cell speed was calculated from the movement of the centroid over time. Agents which are known to interfere with Ca+2 signalling significantly inhibited both the polarization and the movement of cells in response to 10% newt serum. These treatments included: chelation of extracellular Ca+2 with EGTA, the organic Ca+2 channel antagonist, verapamil, the inorganic Ca+2 channel blocker, cobalt, the Ca+2 ionophore, ionomycin, and caffeine, an agent known to release Ca+2 from internal stores. In contrast, the K+ ionophore, valinomycin, and treatment of cells with dibutryl cAMP had no effect on cell behavior. The development of a polarized, motile morphology following stimulation of newt eosinophils with 10% serum was accompanied by a rise in intracellular Ca+2. In addition, Ca+2 in a polarized, moving cell was non-uniformly distributed and periodic elevations in intracellular Ca+2 were seen during changes in cell behavior. In turning cells, Ca+2 was significantly higher than in cells moving in a straight line and there was a clearly detectable gradient of Ca+2 within the cell. The region closest to the new direction of movement had the lowest Ca+2 and the rear of the cell was significantly higher. This gradient persisted following a turn, even though Ca+2 was much lower overall in cells moving in a straight line. A gradient of Ca+2 along the long axis of the cell might be important for the differential regulation of different regions of the moving cell. Loading cells with the cell-permeant, esterified form of Fura-2 revealed a region of high Ca+2 associated with the microtubule organizing center (MTOC). This region was surrounded by a membrane system labeled by the lipid soluble, membrane potential sensitive dye, DiOC6(3). This region of Ca+2 was depleted by caffeine treatment. These observations, coupled with the effects of caffeine on cell behavior, suggest that a Ca+2 storage site associated with the MTOC may play a role in regulating cell polarization and chemotaxis. The effects of releasing "caged calcium" on cell behavior and [Ca2+]i were examined as a means of directly testing the ability of changes in [Ca2+]i to regulate cell behavior. Although photolysis of the compound inhibited cell polarization and movement, technical problems made it difficult to attribute these effects entirely to the release of Ca2+. The results presented here, particularly the gradients of [Ca2+]i which were observed, suggest that local regulation of the cytoplasmic components involved in cell movement by local differences in [Ca2+]i could, in part, explain the regional specialization seen during this process. This form of regulation will be discussed in detail, as will potential mechanisms to test for its function during cell polarization and chemotaxis.

Depuis sa découverte, la spectroscopie de Résonance Magnétique Nucléaire (RMN) a permis de grandes avancées scientifiques dans de nombreux domaines allant de la physique à la médecine. L'inconvénient majeur de la RMN est sa faible sensibilité intrinsèque, due à la très faible polarisation des spins nucléaires. Au cours de ces 20 dernières années, la Polarisation Dynamique Nucléaire (PDN) s'est développée comme technique très prometteuse permettant d'augmenter la polarisation de spin nucléaire, et l'intensité des signaux en RMN liquide ou solide de plusieurs ordres de grandeur. Dans les mêmes conditions expérimentales, la polarisation de spin de l'électron est beaucoup plus grande que la polarisation de spin nucléaire et la PDN permet le transfert de cette forte polarisation à partir d'un agent de polarisation paramagnétique (habituellement un radical libre organique) vers les noyaux avoisinants. L'augmentation de l'intensité du signal RMN (I) est caractérisé par un facteur d'exaltation ε=I(μw ON)/I(μw OFF).L'objectif principal de cette thèse est la synthèse d'agents de polarisation, de type dinitroxyde, solubles dans l'eau et très efficaces pour des expériences de MAS ssNMR/PDN. Nous avons préparé une large série de dérivés du bTurea solubles dans l'eau et leurs performances PDN ont été évaluées à différent champs magnétiques. En remplaçant les groupements méthyl des fonctions TEMPO par des cycles pyranyl, ainsi qu'en introduisant des chaînes PEG sur le linker urée, AMUPol (ε=247) et PyPolPEG2OH (ε=303) ont entre autres été obtenus. Ce sont actuellement les agents de polarisation les plus efficaces pour des expériences de MAS ssNMR/PDN en milieux aqueux
Nowadays, Nuclear Magnetic Resonance (NMR) spectroscopy has become a very powerful technique that can be used to address a wide range of problems, ranging from physics to medicine. The major limitation of NMR is its intrinsic low sensitivity, resulting from the very small nuclear spin polarizations observed even at high magnetic fields. During the last two decades, Dynamic Nuclear Polarization (DNP) has emerged as a very promising approach to enhance NMR signal intensities of solids and liquids by several orders of magnitude. All things being equal, electron spin polarization is much higher than nuclear spin polarization and DNP exploits the microwave-driven transfer of polarization from a paramagnetic polarizing agent (usually an added exogenous organic free radical) to the surrounding nuclei. The enhancement of NMR signal intensities (I) is characterized by the enhancement factor ε=I(μw ON)/I(μw OFF). The main objective of this PhD thesis was the development of new water-soluble dinitroxides, highly efficient polarizing agents for MAS solid-state NMR/DNP applications. We have designed and prepared a large series of water-soluble bTurea (TEMPO-N(H)-C(O)-(H)N-TEMPO), derivatives, and their DNP performance was tested at different magnetic fields (mainly 9.4 T). Replacing the methyl groups of TEMPO moieties with pyranyl rings, and introducing PEG chains on the urea linker we obtained, among others, two derivatives, AMUPol (ε = 247) and PyPolPEG2OH (ε = 303) which are currently the most efficient water-soluble polarizing agents for MAS ssNMR/DNP experiments for aqueous media

Broadband wireless communications require wideband antennas to support large number of users and higher data rates. Desirable features of a wideband antenna are low-profile, dual-polarization and wide bandwidth in a compact size. Many existing wideband antennas are large in size and some have only circular polarization. On the other hand low-profile, dual-polarized antennas frequently have limited bandwidth. This dissertation reports on results from original research into several new wideband antennas. All are compact and planar, and many are low-profile and dual-polarized. Since 1994, Virginia Tech Antenna Group (VTAG) has performed research on the wideband, low-profile and dual-polarized antennas of compact size. This research resulted in the following antenna innovations: the Fourpoint, Fourtear, PICA (Planar Inverted Cone Antenna), diPICA (dipole PICA) and LPdiPICA (Low-Profile diPICA) antennas. They are all planar in geometry so one can easily construct them in a compact size. The antennas were characterized and investigated with extensive simulations and measurements. The computed and measured data demonstrates that some of the antennas appear to have the characteristics of the self-complementary antenna and most of the proposed antennas provide more than a 10:1 impedance bandwidth for a VSWR < 2. Patterns, however, are degraded at the high end of the frequency. Several tapered ground planes were proposed to improve the radiation pattern characteristics without degrading the impedance performance. A simulation result proposed a possibility of another antenna inventions providing 10:1 pattern bandwidth with the 10:1 impedance bandwidth. Research into wideband antennas demonstrated that the newly invented antennas are closely related each other and are evolved from a primitive element, PICA. Not only the comprehensive investigation but also a practical antenna design has been done for commercial base-station array antennas and to phased array antennas for government applications. This dissertation presents results of comprehensive investigation of new planar wideband antennas and its usefulness to the broadband wireless communications.
Ph. D.

Nowadays, silicon photonics is a widely studied research topic. Its high-index-contrast and compatibility with the complementary metal-oxide-semiconductor technology make it a promising platform for low cost high density integration. Several general problems have been brought up, including the lack of silicon active devices, the difficulty of light coupling, the polarization dependence, etc. This thesis aims to give new attempts to novel solutions for some of these problems. Both theoretical modeling and experimental work have been done. Several numerical methods are reviewed first. The semi-vectorial finite-difference mode solver in cylindrical coordinate system is developed and it is mainly used for calculating the eigenmodes of the waveguide structures employed in this thesis. The finite-difference time-domain method and beam propagation method are also used to analyze the light propagation in complex structures. The fabrication and characterization technologies are studied. The fabrication is mainly based on clean room facilities, including plasma assisted film deposition, electron beam lithography and dry etching. The vertical coupling system is mainly used for characterization in this thesis. Compared with conventional butt-coupling system, it can provide much higher coupling efficiency and larger alignment tolerance. Two novel couplers related to silicon photonic wires are studied. In order to improve the coupling efficiency of a grating coupler, a nonuniform grating is theoretically designed to maximize the overlap between the radiated light profile and the optical fiber mode. Over 60% coupling efficiency is obtained experimentally. Another coupler facilitating the light coupling between silicon photonic wires and slot waveguides is demonstrated, both theoretically and experimentally. Almost lossless coupling is achieved in experiments. Two approaches are studied to realize polarization insensitive devices based on silicon photonic wires. The first one is the use of a sandwich waveguide structure to eliminate the polarization dependent wavelength of a microring resonator. By optimizing the multilayer structure, we successfully eliminate the large birefringence in an ultrasmall ring resonator. Another approach is to use polarization diversity scheme. Two key components of the scheme are studied. An efficient polarization beam splitter based on a one-dimensional grating coupler is theoretically designed and experimentally demonstrated. This polarization beam splitter can also serve as an efficient light coupler between silicon-on-insulator waveguides and optical fibers. Over 50% coupling efficiency for both polarizations and -20dB extinction ratio between them are experimentally obtained. A compact polarization rotator based on silicon photonic wire is theoretically analyzed. 100% polarization conversion is achievable and the fabrication tolerance is relatively large by using a compensation method. A novel integration platform based on nano-epitaxial lateral overgrowth technology is investigated to realize monolithic integration of III-V materials on silicon. A silica mask is used to block the threading dislocations from the InP seed layer on silicon. Technologies such as hydride vapor phase epitaxy and chemical-mechanical polishing are developed. A thin dislocation free InP layer on silicon is obtained experimentally.
QC20100705

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Dynamic nuclear polarization (DNP) is now established as a powerful technique for improving the sensitivity of NMR signals by several orders of magnitude, enabling otherwise impossible experiments. Unfortunately, the enhancements obtained at high magnetic fields (> 9 T) are only a small fraction of the theoretical limit due to the fact that current DNP mechanisms, including the cross effect and solid effect, utilize continuous wave (CW) microwave irradiation, and scale unfavorably with B0. This has motivated us to develop new DNP methods that do not suffer from the same field dependences. Our first attempt resulted in the observation of the Overhauser effect in insulating solids doped with 1,3-bisdiphenylene-2-phenylallyl (BDPA) or sulfonated-BDPA (SA-BDPA) radical. As opposed to all other CW DNP mechanisms, the enhancement of the OE in insulating solids scales favorably with B0, increasing in magnitude in going from 5 T, to 9.4 T, to 14.1 T, and to 18.8 T. This finding sheds a new light on the seemingly well-understood Overhauser effect. Our second approach is to perform time domain or pulsed DNP, which differs fundamentally from CW DNP, and like CP and INEPT transfers, is in principle independent of B0. In particular, we have investigated the performance of two related pulse sequences including the nuclear orientation via electron spin locking (NOVEL) and integrated solid effect (ISE) at magnetic fields ranging from 0.35 T to 3.35 T. The NOVEL pulse sequence relies on a matching condition between the nuclear Larmor frequency and the electron Rabi frequency, resulting in a fast polarization transfer from electron to protons (hundreds of ns time scale). Furthermore, we showed that adding amplitude modulation to the microwave field, analogous to a ramped CP experiment, led to longer mixing time (ps time scale) but improved the enhancement by a factor of 1.4 to 2. Finally, we implemented a new version of the integrated solid effect (ISE) by modulating the microwave frequency instead of sweeping the B0 which is technically challenging in high field superconducting magnets. In comparison to NOVEL, ISE gives similar DNP enhancement even far below the NOVEL condition. Our study sets the foundation for further development of time domain DNP at high fields.
by Thach V. Can.
Ph. D.

This essay examines how the conflict in Libya in 2011 was reported by the Swedish newspaper Dagens Nyheter and the American newspaper The New York Times. The purpose is to examine how the conflict is portrayed and what similarities and differences that exist between the two newspapers. We have used a quantitative content analysis and critical discourse analysis to get our results. In conclusion, both newspapers polarize the conflict to a large extent, resulting in a one-sided and biased account. However The New York Times is more objective and neutral in its portrayal of the conflict.

This dissertation includes two parts. In the first part the study is focused on the fabrication of multifunctional thin films for photovoltaic applications. There is no doubt about the importance of transforming world reliance from traditional energy resources, mainly fossil fuel, into renewable energies. Photovoltaic section still owns very small portion of the production, despite its fast growth and vast research investments. New methods and concepts are proposed in order to improve the efficiency of traditional solar cells or introduce new platforms. Recently, ferroelectric photovoltaics have gained interest among researchers. First objective in application of ferroelectric material is to utilize its large electric field as a replacement for or improvement of built-in electric field in semiconductor p-n junctions which is responsible for the separation of generated electron-hole pairs. Increase in built in electric field will increase open-circuit voltage of the solar cell. In this regard, thin films of ferroelectric hafnium dioxide doped with silicon have been fabricated using physical vapor deposition techniques. Scanning probe microscopy techniques (PFM and KPFM) have been employed to analyze ferroelectric response and surface potential of the sample. The effects of poling direction of the ferroelectric film on the surface potential and current-voltage characteristics of the cell have been investigated. The results showed that the direction of poling affects photoresponse of the cell and based on the direction it can either improved or diminished. In the second part of this work, epitaxial thin films have been synthesized with physical vapor deposition techniques such as sputtering and electron beam evaporation for the ultimate goal of producing multifunctional three-dimensional structures. Three-dimensional structures have been used for applications such as magnetic sensors, filters, micro-robots and can be used for modification of the surface of solar cells in order to improve light absorption and efficiency. One of the important techniques for producing 3-D structures is using origami techniques. The effectiveness of this technique depends on the control of parameters which define direction of bending and rolling of the film or curvature of the structure based on the residual stress in the structure after film’s release and on the quality and uniformity of the film. In epitaxially grown films, the magnitude and direction of the stress are optimized, so the control over direction of rolling or bending of the film can be controlled more accurately. For this purpose, deposition conditions for epitaxy of Zn, Fe, Ru, Ti, NaCl and Cr on Si, Al2O3 or MgO substrates have been investigated and optimized. Crystallinity, composition and morphology of the films were characterized using reflective high energy diffraction (RHEED), Auger electron spectroscopy (AES), energy dispersive X-ray (EDX), and scanning electron microscopy (SEM).

In this thesis a new three–dimensional (3D) vector radiative transfer model, the Solver for Polarized Atmospheric Radiative Transfer Applications (SPARTA) is introduced, validated against benchmark results, and applied to scientific problems. SPARTA employs the statistical forward Monte Carlo technique for efficient column–response pixel–based radiance calculations comprising polarization for 3D inhomogeneous cloudless and cloudy atmospheres. By means of SPARTA, two scientific issues in the field of radiative transfer are investigated. A sensitivity study has been conducted to illustrate the errors introduced by neglecting the effects of polarization in radiation simulations. Two atmospheric scenarios have been considered: a pure one–dimensional (1D) Rayleigh atmosphere and two–dimensional (2D) realistic inhomogeneous dust fields. In case of a purely molecular atmosphere, these errors strongly depend on molecular anisotropy, isotropic reflection, and more importantly, on single scattering albedo and optical thickness (saturation occurs for τ close to 1). Overall errors in the reflected field range up to about 10.5%. On the other hand, for rather high optical thickness, the bias induced by ignoring polarization for realistic inhomogeneous atmospheres is negligible (less than 1%). In addition, solar radiative transfer simulations for LIDAR–measured fields of optical properties of Saharan dust have been performed in order to quantify the effects induced by neglecting the horizontal photon transport and internal inhomogeneities (3D radiative effects) in radiance simulations including polarization. Results are presented for two exemplary mineral dust fields constructed from LIDAR observations. For each case, three radiative calculations are investigated: a 1D calculation according to the plane–parallel (1D mode); an Independent Pixel Approximation (IPA mode); and the 2D mode. The differences in domain–averaged normalized radiances of reflection and transmission are insignificant between the 1D or IPA and 2D calculation modes. However, local differences were observed since extinction is hinge on horizontal spatial variability. In the areas with large spatial variability in optical thickness, the radiance fields of the 2D mode differ about ±20% for the first and second Stokes elements (I, Q) from the fields of the 1D mode. This work points to a brand–new field: the quantification of the sensitivity of polarization to 3D radiative effects.

In this thesis different materials have been developed to use them in electrochemical cells. The electrochemical cells studied can be divided into two material big groups: solids oxides and acid salts materials. In the first group, materials to use them in electrodes for fuel cells an electrolyzer based on oxygen ion conductor electrolytes were optimized. Pertaining to this group, the influence of doping the Ba0.5Sr0.5Co0.8Fe0.2O3-d perovskite with 3% of Y, Zr and Sc in B position (ABO3-d) was checked. That optimization could reduce the polarization resistance of electrodes and improve the stability with time. Additionally, the limiting mechanisms in the oxygen reduction reaction were determined, and the influence of CO2 containing atmospheres was checked. La2NiO4+d;, pertaining to the Ruddlesden-Popper serie, is a mixed conductor of electron and oxygen ions. This compound was doped in La position (with Nd and Pr) and in Ni position (with Co). The dopants introduced were able to produce structural change and improve the cell performance, reducing in more than one order of magnitude the La1.5Pr0.5Ni0.8Co0.2O4+d; polarization resistance respect to the reference material (La2NiO4+d). In addition, the properties of an electrode based on the pure electronic conductor, La0.8Sr0.2MnO3-d; (LSM), were optimized. The triple phase boundary was enlarged by the addition of a second phase with ionic conductivity. That strategy made possible to reduce the electrode polarization resistance. In order to improve the oxygen reduction reaction, the addition of different catalysts by infiltration was studied. The different infiltrated oxides changed the electrochemistry properties, being the praseodymium oxide the catalyst which made possible a reduction in two orders of magnitude the electrode polarization resistance respects to the composite without infiltration. Furthermore, the efficiency of the cell working in fuel cell and electrolyzer mode was improved. Concerning the materials selected to use as electrodes on proton conductor electrolytes, the efficiency of electrodes based on LSM was optimized by using a second phase with protonic conductivity (La5.5WO12-d) and varying the sintering temperature of the electrode. Finally, the catalytic activity of the cell was boosted by infiltrating samaria doped ceria nanoparticles, achieving higher power densities for the fuel cell. The materials pertaining to the Ruddlesden-Popper series and studied for ionic conductor electrolytes were also used for cathodes in proton conductor fuel cells. After checking the compatibility with the electrolyte material, the influence of different electrode sintering temperatures and air containing atmospheres (dry, H2O y D2O) on the cathode performance was studied. Finally, the electrochemical cells based on acid salts (CsH2PO4) were designed and optimized. In that way, different cell configurations were studied, enabling to obtain thin and dense electrolytes and active electrodes for the hydrogen reduction/oxidation reactions. The thickness of the electrolyte was reduced by using steel and nickel porous supports. Furthermore, an epoxy resin type was added to the electrolyte material to enhance the mechanical properties. The electrodes configuration was modified from pure electronic conductors to composite electrodes. Moreover, copper was selected as an alternative of the expensive platinum working at high operation pressures. The cells developed were able to work with high pressures and with high content of water steam in fuel cell and electrolyzer modes.
En la presente tesis doctoral se han desarrollado materiales para su uso en celdas electroquímicas. Las celdas electroquímicas estudiadas, se podrían separar en dos grandes grupos: materiales de óxido sólido y sales ácidas. En el primer grupo, se optimizaron materiales para su uso como electrodos en pilas de combustible y electrolizadores, basados en electrolitos con conducción puramente iónica. Dentro de este grupo, se comprobó la influencia de dopar la perovskita Ba0.5Sr0.5Co0.8Fe0.2O3-d, con un 3% de Y, Zr y Sc en la posición B (ABO3-d). Esta optimización llevó a la reducción de la resistencia de polarización así como a una mejora de la estabilidad con el tiempo. Así mismo, se determinaron los mecanismos limitantes en la reacción de reducción de oxígeno, y se comprobó la influencia de la presencia de CO2 en condiciones de operación. El La2NiO4+d perteneciente a la serie de Ruddlesden-Popper, es un conductor mixto de iones oxígeno y electrones. Éste, fue dopado tanto en la posición del La (con Nd y Pr) como en la posición del Ni (con Co). Los dopantes introducidos además de producir cambios estructurales, provocaron mejoras en el rendimiento de la celda, reduciendo para alguno de ellos, como el La1.5Pr0.5Ni0.8Co0.2O4+d, en casi un orden de magnitud la resistencia de polarización del electrodo de referencia (La2NiO4+d). De la misma manera, se optimizaron las propiedades del electrodo basado en el conductor electrónico puro La0.8Sr0.2MnO3-d (LSM). La adición de una segunda fase, con conductividad iónica, permitió aumentar los puntos triples (TPB) en los que la reacción de reducción de oxígeno tiene lugar y reducir la resistencia de polarización. Con el fin de mejorar la reacción de reducción de oxígeno, se estudió la adición de nanocatalizadores mediante la técnica de infiltración. Los diferentes óxidos infiltrados produjeron el cambio de las propiedades electroquímicas del electrodo, siendo el óxido de praseodimio el catalizador que consiguió disminuir en dos órdenes de magnitud la resistencia de polarización del composite no infiltrado. De la misma manera, la mejora de la eficiencia del electrodo infiltrado con Pr, mejoró los resultados de la celda electroquímica trabajando como pila (mayores densidades de potencia) y como electrolizador (menores voltajes). En lo que respecta a los materiales seleccionados para su uso como electrodos en electrolitos con conductividad protónica, se optimizó la eficiencia del cátodo basado en LSM, mediante el uso de una segunda fase conductora protónica (La5.5WO12-d) y variando la temperatura de sinterización del electrodo. Finalmente, se mejoró la actividad catalítica mediante la infiltración de nanopartículas de ceria dopada con samario, produciendo mayores densidades de corriente de la pila de combustible. Los materiales pertenecientes a la serie de Ruddlesden-Popper y usados para cátodos en pilas iónicas, fueron empleados también para cátodos en pilas protónicas. Después de comprobar que el material electrolítico (LWO) era compatible con los compuestos de la serie de Ruddlesden-Popper, se estudió la influencia de la temperatura de sinterización de los electrodos en el rendimiento, así como de la composición de la atmosfera de aire (seca, H2O y D2O). Finalmente, se diseñó y optimizó las celdas electroquímicas basadas en sales ácidas (CsH2PO4). En este sentido, se estudiaron diferentes configuraciones de celda, que permitieran obtener un electrolito denso con el menor espesor posible y unos electrodos activos a la reacción de reducción/oxidación de hidrógeno. Se consiguió reducir el espesor del electrolito soportando la celda en discos de acero y níquel porosos. Se añadió una resina tipo epoxi al material electrolítico para aumentar sus propiedades mecánicas. De la misma manera, se cambió la configuración de los electrodos pasando por conductores electrónicos puros a electrodos compuestos por conductores
En la present tesis doctoral es van desenvolupar materials per al seu ús en cel·les electroquímiques. Les cel·les electroquímiques estudiades poden ser dividides en dos grans grups: materials d'òxid sòlid i sals àcides. En el primer grup, es van optimitzar materials per al seu ús com a elèctrodes en piles de combustible i electrolitzadors, basats en electròlits amb conducció purament iònica. Dins d'este grup, es va comprovar la influència de dopar la perovskita Ba0.5Sr0.5Co0.8Fe0.2O3-d amb un 3% de Y, Zr i Sc en la posició B (ABO3-d;). Esta optimització va portar a la reducció de la resistència de polarització així com a una millora de l'estabilitat amb el temps. Així mateix, es van determinar els mecanismes limitants en la reacció de reducció d'oxigen, i es va comprovar la influència de la presència de CO2 en condicions d'operació. El La2NiO4+d pertanyent a la sèrie de Ruddlesden-Popper, és un conductor mixt d'ions oxigen i electrons. Este, va ser dopat tant en la posició del La (amb Nd i Pr) com en la posició del Ni (amb Co). Els dopants introduïts a més de produir canvis estructurals, van provocar millores en el rendiment de la cel·la, reduint per a algun d'ells, com el La1.5Pr0.5Ni0.8Co0.2O4+d, en quasi un ordre de magnitud la resistència de polarització de l'elèctrode de referència (La2NiO4+d). De la mateixa manera, es van optimitzar les propietats de l'elèctrode basat en el conductor electrònic pur La0.8Sr0.2MnO3-d (LSM). L'addició d'una segona fase, amb conductivitat iònica, va permetre augmentar els punts triples (TPB), en els que la reacció de reducció d'oxigen té lloc, i reduir la resistència de polarització. A fi de millorar la reacció de reducció d'oxigen, es va estudiar l'adició de nanocatalitzadors per mitjà de la tècnica d'infiltració. Els diferents òxids infiltrats van produir el canvi de les propietats electroquímiques de l'elèctrode, sent l'òxid de praseodimi el catalitzador que va aconseguir disminuir en dos ordres de magnitud la resistència de polarització del composite no infiltrat. De la mateixa manera, la millora de l'eficiència de l'elèctrode infiltrat amb Pr, va millorar els resultats de la cel·la electroquímica treballant com a pila (majors densitats de potència) i com a electrolitzador (menors voltatges). Pel que fa als materials seleccionats per al seu ús com a elèctrodes en electròlits amb conductivitat protònica, es va optimitzar l'eficiència del càtode basat en LSM, per mitjà de l'ús d'una segona fase conductora protònica (La5.5WO12-d;) i variant la temperatura de sinterització de l'elèctrode. Finalment, es va millorar l'activitat catalítica mitjançant la infiltració de nanopartícules de ceria dopada amb samari, produint majors densitats de corrent de la pila de combustible. Els materials pertanyents a la sèrie de Ruddlesden-Popper i usats per a càtodes en piles iòniques, van ser empleats també per a càtodes en piles protòniques. Després de comprovar que el material electrolític (LWO) era compatible amb els compostos de la sèrie de Ruddlesden-Popper, es va estudiar la influència de la temperatura de sinterització dels elèctrodes en el rendiment, així com de la composició de l'atmosfera d'aire (seca, H2O i D2O). Finalment, es van dissenyar i optimitzar les cel·les electroquímiques basades en sals àcides (CsH2PO4). En este sentit, es van estudiar diferents configuracions de cel·la, que permeteren obtindre un electròlit dens amb el menor espessor possible i uns elèctrodes actius a la reacció de reducció/oxidació d'hidrogen. Es va aconseguir reduir l'espessor de l'electròlit suportant la cel·la en discos d'acer i níquel porosos. Es va afegir una resina tipus epoxi al material electrolític per a augmentar les seues propietats mecàniques. De la mateixa manera, es va canviar la configuració dels elèctrodes passant per conductors electrònics purs a elèctrodes compostos per conductors protònics
Navarrete Algaba, L. (2017). New electrochemical cells for energy conversion and storage [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/78458
TESIS

Les macrophages sont fonctionnellement polarisés en macrophages inflammatoires et microbicides (M1) ou immunorégulateurs (M2). Que les monocytes circulants soient polarisables n’est pas démontré. Nous avons étudié la signature transcriptionnelle par microarray et RT-PCR en temps réel de monocytes humains stimulés par l’IFN-γ, un inducteur des macrophages M1 et l’IL-4, un inducteur des macrophages M2. Leur profil de réponse précoce est dépendent de l’agoniste alors que la réponse tardive des monocytes est similaire qu’ils soient stimulés par l’IFN-γ ou l’IL-4. Cette approche dynamique de la réponse monocytaire permet probablement une étude bien plus pertinente des patients atteints d’une fièvre Q que le modèle de polarisation macrophagique. Par ailleurs, la prévalence de la fièvre Q est plus importante chez l’homme que chez la femme. Comme il a été montré que des gènes associés au cycle circadien sont modulés chez les souris infectées par Coxiella burnetii, la bactérie responsable de la fièvre Q, nous avons étudié ces gènes au cours de la fièvre Q. C’est ainsi que le gène Per2 est fortement exprimé chez les hommes atteints d’une fièvre Q aiguë. Ces résultats suggèrent donc que la modulation de gènes circadiens est associée à une maladie infectieuse chez l’homme. L’expression des gènes LNX1 and LNX2, qui codent deux enzymes impliquées dans le catabolisme des protéines, est accrue dans l’endocardite de la fièvre Q mais pas dans la fièvre Q aiguë
Macrophages are functionally polarized into inflammatory and microbicidal (M1) and immunoregulatory (M2) cells. If circulating monocytes may be polarized is not known. We determined the transcriptional signatures of human monocytes stimulated with IFN-γ and IL-4, known to induce the polarization of macrophages into M1 and M2 cells, respectively, using microarrays and real-time RT-PCR. We found that monocytes exhibited an early pattern of activation specific to IFN-γ or IL-4 and a late pattern of activation common to both agonists. The selected biomarkers of early and late responses were tested in patients with Q fever. We showed that the kinetic model of monocyte activation enables a dynamic approach for the evaluation of patients with acute Q fever or Q fever endocarditis. On the other hand, it is known that the prevalence of Q fever is related to sex and is higher in men than in women. Based on previous studies on an experimental model of infection by Coxiella burnetii, the agent of Q fever, we hypothesized that circadian genes are differently modulated in men and women with Q fever. We showed that the expression of the Per2 gene was significantly increased in males with acute Q fever compared with healthy volunteers but did not differ in females with Q fever and healthy females. These results suggest that that the modulation of circadian genes is associated with a human infectious disease. We also found that the expression of LNX1 and LNX2 genes that encode two enzymes involved in protein degradation is increased in Q fever endocarditis but not in acute Q fever

Did the new Bolivian Constitution of 2009 influence a change on its democratic model? The thesis of the article claims that as a result of how the Constitution elaboration process was carried out on a frame of certain historical conditions, the product elaborated –The Constitution- by the Constituent Assembly had little substantial change in contrast to former Constitutions. Historical constrains of the Bolivian economy and the polarization of the actors involved on the elaboration process of the new Constitution had a great influence to prevent a substantially different new one. Progressive’s elements were introduced as a matter of result of the Bolivian revolution as Human Rights, Plurinationality, and Regional Autonomies, but certain constitutional prerogatives remained unchanged to preserve the status quo. The presence of corporatists, rentist and statist actors has been a trend along Bolivian history, which does allow the reproduction of the internal political relationships of the Bolivian model and inhibits the possibility of a substantial change or re-foundation. Furthermore, the pos-contitutional situation will consolidate a democracy that hardly would break the historical constrains thatrules its hybrid character.
¿La nueva Constitución Boliviana del 2009 motivó un cambio sustancial en su modelo democrático? La tesis del artículo argumenta que la poca variación sustancial en el producto elaborado –la Constitución- por la Asamblea Constituyente, en comparación a Constituciones anteriores, fue fruto de cómo se llevó a cabo el proceso de elaboración de la misma aunque se debe resaltar algunas consideraciones históricas. Las constricciones históricas de la economía boliviana así como la polarización de actores en la elaboración de la nueva Constitución tuvieron una gran influencia al impedir una refundación de la misma. Si bien hubo un gran recojo de elementos progresistas fruto de la revolución boliviana como Derechos Humanos, Plurinacionalidad y Autonomías Regionales, aún se mantuvieron ciertas prerrogativas constitucionales a actores que protegían el status quo. La presencia de actores corporativistas, rentistas y estatistas se ha mantenido a lo largo del tiempo, por lo que se permite la reproducción de las relaciones políticas internas del modelo boliviano y se inhibe la posibilidad de su reemplazo o refundación. Esto derivó en una situación posconstitucional que consolidará una democracia que dificultosamente podrá quebrar las ataduras de un pasado que condiciona su carácter híbrido.

La résonance magnétique nucléaire (RMN) fournit des informations structurelles et dynamiques précieuses à l'échelle atomique, cependant, la faible sensibilité et résolution des signaux empêchent l’étude d'objets moléculaires plus importants. Nous présentons 3 stratégies de marquage isotopique pour différentes expériences RMN des protéines en solution et démontrons leur potentiel pour l'étude structurale des biomolécules. Parmi les stratégies envisagées, 2 utilisent l'expression in vitro pour obtenir des protéines marquées sélectivement sur un groupe chimique et/ou acide aminé dans un environnement perdeutéré. Avec l’utilisation de séquences d'impulsions TROSY, ces échantillons ont permis des gains spectraux importants lorsque ils étaient spécifiquement marqués sur des groupes amide ou sur le méthylène des glycines tout en maintenant un taux de deutération élevé sur les autres fonctions chimiques des protéines. La troisième stratégie de marquage protéique utilise des protocoles in vivo pour des applications RMN innovantes: l'hyperpolarisation de noyaux en solution qui augmente leur sensibilité de plusieurs ordres de grandeur. La durée de vie de cette hyperpolarisation est régie par le temps de relaxation longitudinale des noyaux, qui est réduit pour les protéines à température ambiante. En isolant les noyaux d'intérêt dans un environnement perdeutéré, les interactions dipolaires créées par les protons voisins sont éliminées et les noyaux hyperpolarisés relaxent beaucoup plus lentement. L'hyperpolarisation d'un petit domaine protéique a été entreprise avec succès mais les conditions de dissolution doivent encore être améliorées pour conserver une phase aqueuse homogène
Nuclear Magnetic Resonance (NMR) provides valuable structural and dynamic information at the atomic scale, however, the low sensitivity and resolution of signals rapidly preclude investigations of larger molecular objects. We present three isotopic labeling strategies for different protein-solution NMR experiments and demonstrate their potential for the structural study of biomolecules in solution. Among the strategies considered, two are based on the use of in vitro protein expression to obtain selectively labeled proteins of a certain chemical group and/or amino acid in a perdeuterated environment. Perdeuteration is essential for the optimal use of Transverse Relaxation Optimized Spectroscopy pulse sequences. They allowed significant spectral gains when samples were specifically labeled on amide groups or on the methylene of glycines while maintaining a very high rate of deuteration on the other chemical functions of the proteins. The third protein labeling strategy employed is based on in vivo protocols but used in innovative NMR applications: a technique of hyperpolarization of nuclei in solution which increases their sensitivity by several orders of magnitude. The lifetime of this hyperpolarization is governed by the longitudinal relaxation time of nuclei, which are reduced for proteins at room temperature. By isolating the nuclei of interest in a perdeuterated environment, dipolar interactions created by neighboring protons were eliminated and hyperpolarized nuclei relaxed much more slowly. Hyperpolarization of a small protein domain was successfully undertaken at 1K but the dissolution conditions need to be improved in order to preserve a homogeneous aqueous phase

Le Congrès des Etats-Unis est une institution méconnue, mal comprise et souvent dénigrée, y compris par ses propres membres. On le dit en crise, inadapté aux exigences du monde moderne. L’objectif est donc d’évaluer les forces et les faiblesses objectives du Congrès contemporain pour le réinsérer dans la dynamique des freins et contre-pouvoirs au coeur du système politique américain. La période retenue s’étale de la victoire des Républicains menés par Newt Gingrich en 1994 jusqu’aux élections de mi-mandat de 2006 et au retour des Démocrates. De la présidence Clinton à Bush, ces douze années offrent un contexte institutionnel varié. Elles forment une trajectoire historique fascinante de la rhétorique révolutionnaire qui accompagne les victoires de 1994 à la résignation d’une défaite marquée par une certaine corruption institutionnelle, partisane et idéologique. Le cœur de notre étude vise à étudier les conséquences institutionnelles du retour à un équilibre partisan dans les deux chambres du Congrès. La compétition entre les deux partis a été accompagnée par la polarisation du système politique. Notre étude retrace les débuts de l’entrée dans une nouvelle ère sur la colline du Capitole. On cherchera à combiner une approche politique et institutionnelle en analysant plus particulièrement trois domaines de l’action politique particulièrement révélateurs: les finances via la procédure budgétaire, la réforme de l’Etat providence, et les relations avec le judiciaire via les nominations des Juges d’Appel fédéraux, lieu privilégié de frictions entre la Maison-Blanche et le Sénat. À cette perspective institutionnelle, il s’agira d’ajouter une étude sociologique de cohorte des membres du Congrès, nécessaire pour comprendre les ressorts de l’action institutionnelle. Au-delà des membres de la chambre, l’étude d’une période dominée par le parti de l’éléphant nous permettra de plonger au cœur du mouvement conservateur. Après avoir présenté les racines historiques de l'idéologie conservatrice qui domine au sein du Parti républicain, il s'agira de révéler comment un mouvement contestataire a transformé l’institution du Congrès mais aussi comment l’institution a transformé le mouvement conservateur et le Parti républicain. Dans un contexte international de renforcement du pouvoir exécutif, l’étude du Congrès doit permettre de redécouvrir certaines leçons sur les modalités de fonctionnement d’un système démocratique. Il s’agit de montrer qu'au-delà des questions techniques, des jeux de procédures obscures, dans la tension qui anime le Congrès, se joue l’avenir du concept de démocratie représentative ; de rétablir un certain équilibre dans la perception du système américain : système plus complexe qu’il n’apparaît dans les médias et même parfois la littérature. On ne peut se contenter d’étudier la présidence impériale sans prêter attention au vortex qui siège, toujours, au coeur de la constitution. Ainsi, sans faire un panégyrique du pouvoir législatif, il s’agira de remettre en cause la tentation d’un Césarisme plus ou moins démocratique qui chercherait à faire du Congrès une chambre d’enregistrement des volontés de l’exécutif
The United States Congress is often disparaged including by its own members. The critics of the institution decry the gridlock on Capitol Hill and Congress's alleged inability to deal with the challenges of the modern world. The unpopularity of today's Congress calls into question its ability to represent the American people. In that context it is necessary to try to assess whether or not Congress is truly dysfunctional. To that end, this study proposes to study a period of twelve years from 1994 to 2006 during which the Republican party dominated the institution. In 1994, under the leadership of Newt Gingrich, the Republicans returned to the majority in the House of Representatives for the first time in forty years. In 2006, after another midterm election, the Republican majorities in the House and the Senate were soundly defeated. Drawing on the long and tortuous history of the relationship between the Republican party and conservatism, the new majorities proposed large-scale change that amounted to a conservative revolution. They had initially laid out a clearly conservative agenda that insisted on balancing the budget and reducing the size of government. A detailed study of their fiscal policy and their attempts at entitlement reform over the period actually leads us to conclude that they eventually governed over ever larger deficits and a growing federal government whose policies were adjusted to favor different portions of the population. It is therefore necessary to try to account for the discrepancy between the initial goals and the eventual results. This entails studying first the evolution of the Republican members of Congress themselves to see whether the policy changes can be explained by the members becoming more moderate. Another explanation centers on the relationship between the members of the Congress and their constituents. The Republican majorities could have been forced to moderate their positions by the voters themselves in the elections of 1996, 1998, 2000, 2002 and 2004. Here the complex interplay that implies the interpretation of election results comes into play. Over the past decades, the American political system has been polarizing clearly. The growing ideological gap between the two parties and their bases calls into question the institutional stability of an institution built on the necessity to compromise. Especially since both parties have polarized while the margins of the majorities have grown more narrow. It is thus essential to look at the constraints set up by the institutional system. The arcane nuances of the legislative process directly impinges on the content of legislation. Indeed, if the majority rules decisively over the House of Representatives, in the Senate, the minority can very easily block most initiatives. The growing recourse to procedural shortcuts offered by the budget process is a testament to that fact.Finally, the relationship with the president of the United States is very much a factor in the equation. The twelve years of Republican domination in Congress covers two very different periods. Until January 2001, they had to battle with President Clinton in a context of divided government. Following George W. Bush's election in 2000, they started working under the command of the White House. The stark contrast in the way Senate republicans dealt with the two presidents when it came to their judicial nominees for the Federal Courts of Appeal offers an excellent opportunity to evaluate the continuing yet variable strength of the system of checks and balances set up by the U.S. Constitution. A deeper understanding of the workings of the contemporary Congress might allow for a more nuanced vision of the institution as much more than a roadblock on the road of presidential leadership and, perhaps, lead to a better appreciation of the way its members are trying or failing to fulfill their constitutional duty

Thesis (Ph.D.)--Kent State University, 2009.
Title from PDF t.p. (viewed Feb 25, 2010). Advisor: Oleg Lavrentovich. Keywords: electro-optical applications of liquid crystals, beam steering devices, polarization rotator, negative refraction, electrically tunable lens, colloidal dynamics, bidirectional motion of colloidal particles in liquid crystals controlled by backflow. Includes bibliographical references.

This master’s thesis conducts a discourse analysis on a political organization within the New Christian Right (NCR), the American Family Association (AFA). The purpose of the study is to analyze the conditions of possibility for a politics that aims to prevent progress for LGBT rights and does so by analyzing the political terrain where operations of power produce particular and meaningful political practices. As analytical tools the study relies on a theory of the political by Ernesto Laclau and Chantal Mouffe, who together with Michel Foucault also provide an elaborate theory of power. Theoretical work by Wendy Brown provides insights into how politics can be expressed when social antagonisms are prevented from engaging in political contestation. Results of the discourse analysis trace social antagonisms in AFA discourse to a dislocation of the social where new articulatory practices have established new relationships between elements of discourse and thereby also changed the nature of social intelligibility and interaction. AFA discourse articulates family values based on the privileged signifiers of freedom, democracy and rights, which is utilized both for a separatist politics of discrimination and an inclusive politics of social assimilation. AFA discourse shows many points of antagonism and organizes an enemy in postmodernism. Freedom as a mode of governmentality conditions the political demands that are and can be made which can be traced to a hegemonic neoliberal articulation. AFA discourse challenges neoliberal hegemony through the process of separatism, yet is intimately bound to the hegemonic way of making political demands in order to gain discursive strength and legitimacy.

Cette thèse étudie les relations entre l’innovation et la qualité de l’emploi. L’innovation est considérée comme le moteur principal de la croissance économique, mais les changements technologiques induisent des mutations importantes de l’emploi et du travail. L’innovation est donc au cœur de nombreuses préoccupations, elle est au centre des recommandations formulées par les pouvoirs publics et les organisations internationales. Ses multiples effets suscitent de plus en plus d’interrogations puisque la période récente est marquée par une intensification des dynamiques d’innovation avec notamment l’émergence de nouveaux cycles technologiques ; elle est vectrice de transformations pour l’emploi qu’il est nécessaire de qualifier. Cette thèse adopte une perspective principalement empirique, tout en se fondant sur une approche théorique institutionnaliste et évolutionniste. La qualité de l’emploi est envisagée dans une perspective multidimensionnelle, incluant notamment les conditions de travail, les horaires et la durée du travail, la qualité contractuelle et les rémunérations. De même l’innovation est analysée dans sa complexité afin de faire ressortir des effets hétérogènes selon les formes considérées (stratégie, type d’innovation, degré de rupture et degré de nouveauté). Les résultats de cette étude justifient l’intérêt d’un champ d’étude spécifique en économie sur les liens entre innovation et qualité de l’emploi. Tout en confirmant que certaines innovations ont des effets directs positifs sur la qualité de l’emploi, cette thèse montre que des effets indirects ainsi que certaines formes de diffusion d’innovation détériorent la qualité contractuelle des emplois et les conditions de travail. Par ailleurs, si l’innovation (quelle que soit sa forme) est souvent associée à de meilleures conditions contractuelles (salaire, stabilité, etc.), elle induit néanmoins une intensification du rythme et des exigences en emploi. Ce travail formule une principale recommandation dans le contexte de l’intensification des dynamiques d’innovation et des modèles économiques fondés sur la connaissance – tout en appelant à de futurs travaux et à une amélioration des données disponibles. Afin d’éviter une polarisation des conditions de travail et une montée des inégalités, il est nécessaire d’adapter les systèmes de redistribution et de régulation pour faire face aux effets indirects négatifs de la diffusion des innovations
This thesis investigates the relationships between innovation and job quality. Innovation is considered to be the main driver of economic growth, but technological change leads to significant mutations of employment and labor. As such, innovation represents a key concern for recommendations made by public authorities and international organizations. The multiple effects of innovation have raised new questions, since the recent period has been characterized by an intensification of innovation dynamics –specifically, the emergence of new technological cycles. This thesis adopts an empirical perspective, while relying on a theoretical framework inspired by the institutionalist and evolutionary approach. Job quality is considered from a multidimensional perspective, including working conditions, working hours and working duration, contractual quality, and wages. Similarly, innovation is analyzed in its complexity, in order to highlight the heterogeneous effects of innovation depending on the considered forms (strategy, type of innovation, degree of disruption, degree of novelty, etc.). This work provides additional support to a specialized and specific scholarship (within economics) that focuses on the relationship between innovation and job quality. While ascertaining that some innovations have direct positive effects on job quality, this thesis shows that indirect effects –as well as some forms of diffusion of innovation–deteriorate the contractual quality of jobs and working conditions. Moreover, innovation – whatever its form might be – is often associated with better contractual conditions (wage, stability), but also leads to an increase in working intensity and demands for employees.This thesis makes a key recommendation, in the context of intensified innovation dynamics and knowledge – based economic model – however, we also call for further work and improved data availability. In order to avoid the polarization of working conditions and the rise of inequalities, it is necessary to adapt redistribution and regulatory systems so that they would cope with the negative indirect effects of the diffusion of innovations, which cannot be fully addressed by current institutions

This dissertation explores how journalists in the United States and Germany have been addressing declining levels of trust and attacks on their credibility. I comparatively examine how journalists interpret the trust crisis, and consequently, the strategies they have developed for addressing it. This study is based on multi-site ethnography: I interviewed 87 journalists, conducted observations in 15 local and national newsrooms, and examined metajournalism from the United States and Germany. Findings show that U.S. and German journalists interpret declining trust and anti-media sentiments differently: U.S. journalists believe they stem from information gaps and lacking media literacy, while German journalists believe they reflect a sense of alienation. And so, in their efforts to gain credibility, U.S. journalists focus on increasing transparency and showcasing their professionalism, while German journalists focus on increasing reciprocity and showing that they listen to criticism from outside the profession. As this dissertation shows, both U.S. and German news media are thoroughly professionalized, but their different relationships to their audiences and communities shape different perceptions on — and strategies for — trust building.

Doctor of Philosophy
Department of Economics
William F. Blankenau
This dissertation investigates two essential features of the US economy. First, it explores how news about future productivity changes business cycle fluctuations. Using the a representative agent model, it shows that implementation labor in workplace organization could be an important channel through which news about the fundamentals can realistically generate US business cycle fluctuations. Further this idea is extended using the perspective of sunspot fluctuations. In particular, the model can lead to multiple equilibria under specific parameterizations. Second, a general equilibrium model has been developed with heterogeneous agents to explain the wage polarization feature of the US labor market, particularly how the price of an important technology is connected to lifetime earnings of agents and affects their college decisions. The following summarizes the three chapters of my dissertation. The first chapter which I co-authored with Dr. Blankenau, argues that purchasing investment goods does not directly increase the productive capacity of a business. Changes in the business through the installation of capital, worker training, and workplace reorganization are often required. These changes themselves are not easily automated. Change requires workers. We build a model where investment requires a complementary labor input. This mechanism is embedded in a representative agent model with capacity utilization, adjustment costs, and separable preferences. We show that this environment can yield positive co-movement between consumption, investment, and labor hours when the economy experiences a news shock about future productivity, thus providing an additional channel through which news shocks can generate key business cycle features. The second chapter is an extension of the first chapter. I investigate the indeterminacy in a representative agent model with implementation labor and increasing returns in production. First, my analysis shows that a representative agent with implementation labor can exhibit increasing returns to scale. Then I show that self-fulfilling beliefs of agents lead to business cycle fluctuations in which multiple equilibria can arise under specific parameterizations. Specifically, implementation labor in the production of capital is the highly important, necessary condition for the self-fulling equilibrium outcome. The third chapter, which is also a joint work with Dr. Blankenau, discusses the wage polarization feature of the US labor market. We build a general equilibrium model with heterogeneous agents, showing how wage polarization can emerge when the price of computer capital falls. Consequently, we find the share of the population with a college degree decreases. Our findings are consistent with recent empirical data that show a U-shaped wage growth pattern in the US as well as a slower growth rate of college-educated workers despite the high returns of investing in education. In the model, we assume that each agent is born with a portfolio of skills. Specifically, each agent can provide manual labor, routine labor, and abstract labor and must decide how much of each to provide. An agent can increase efficiency in all types of labor by attending college. All three types of labor are valued in the labor market at an endogenously determined wage rate. Computer capital is a substitute for routine labor. As its price falls and its quantity increases, agents with a relative aptitude for routine labor no longer find it advantageous to attend college. Since routinization of tasks harms middle-income agents, the model has government policy implications for observed wage polarization.

abstract: The development of the internet provided new means for people to communicate effectively and share their ideas. There has been a decline in the consumption of newspapers and traditional broadcasting media toward online social mediums in recent years. Social media has been introduced as a new way of increasing democratic discussions on political and social matters. Among social media, Twitter is widely used by politicians, government officials, communities, and parties to make announcements and reach their voice to their followers. This greatly increases the acceptance domain of the medium. The usage of social media during social and political campaigns has been the subject of a lot of social science studies including the Occupy Wall Street movement, The Arab Spring, the United States (US) election, more recently The Brexit campaign. The wide spread usage of social media in this space and the active participation of people in the discussions on social media made this communication channel a suitable place for spreading propaganda to alter public opinion. An interesting feature of twitter is the feasibility of which bots can be programmed to operate on this platform. Social media bots are automated agents engineered to emulate the activity of a human being by tweeting some specific content, replying to users, magnifying certain topics by retweeting them. Network on these bots is called botnets and describing the collaboration of connected computers with programs that communicates across multiple devices to perform some task. In this thesis, I will study how bots can influence the opinion, finding which parameters are playing a role in shrinking or coalescing the communities, and finally logically proving the effectiveness of each of the hypotheses.
Dissertation/Thesis
Masters Thesis Computer Science 2020

Dissertação de mestrado em Ciências da Comunicação (área de especialização em Investigacao)
O progressivo avanço do discurso de ódio e da incivilidade nas relações sociais que ocorrem no ciberespaço se apresenta como um dos grandes desafios da atualidade que emergiram com o desenvolvimento das tecnologias. No contexto da discussão política no Brasil, a relevância desse tipo de discurso depreciativo mudou substancialmente a partir de 2013, quando a polarização começou a ganhar contornos profundos. Nas eleições presidenciais de 2018, a situação chegou a um nível vultuoso e o período da campanha ainda ficou marcado pelo uso intenso das mídias sociais como ferramentas estratégicas para propagação de um discurso conservador, contra as minorias e os direitos humanos. Com o objetivo de identificar os padrões de comportamento nas redes sociais após as eleições, esta pesquisa está focada na produção de discurso de ódio e incivilidade nos comentários em notícias publicadas por 16 veículos de comunicação no Twitter. O corpus do estudo reúne 13.074 notícias e 394.115 comentários. Os dados foram submetidos à análise de conteúdo quantitativa e qualitativa, de forma automatizada e manual. Sucintamente, o estudo apontou que, após a eleição, o discurso de ódio permaneceu significativo em notícias relacionadas às ações e/ou pronunciamentos do atual presidente da República do Brasil, Jair Bolsonaro, e outros membros do governo. Além disso, temas que figuraram como slogans de campanha e fazem parte do discurso político do presidente atraíram um volume maior de comentários odiosos. Por fim, a pesquisa identificou que o grau de incivilidade presente na interação dos utilizadores é elevado, contribuindo para um abismo cada vez mais profundo nas redes sociais.
One of the major challenges emerging from the development of communication and information technologies is the progressive advancement of hate speech and incivility in social relations that occurs in cyberspace. In the context of political discussion in Brazil, increased polarization from 2013 onward increased the relevance of this kind of derogatory discourse. The 2018 presidential election was, in that sense, a landmark with the intensive usage of social networks in political campaigns to reinforce a discourse against minorities and human rights. Aiming to identify behavioral patterns in social networks after the elections, this research focuses on the production of hate speech and incivility in commentary on news published by 16 media outlets on Twitter. The study corpus brings together 13,074 news and 394,115 comments. Data were subjected to quantitative and qualitative content analysis, both automatically and manually. Briefly, the study pointed out that after the election, hate speech remained significant in news related to the actions and/or pronouncements of the current President of the Republic of Brazil, Jair Bolsonaro, and other members of the government. In addition, themes that appeared as campaign slogans and are part of the president's political speech attracted a greater volume of hateful comments. Finally, research has identified that the degree of incivility present in user interaction is high, contributing to an everwidening gulf in social networks.

Yes
This paper presented a new circular polarization reconfigurable antenna for 5G wireless communications. The antenna, containing a semicircular slot, was compact in size and had a good axial ratio and frequency response. Two PIN diode switches controlled the reconfiguration for both the right-hand and left-hand circular polarization. Reconfigurable orthogonal polarizations were achieved by changing the states of the two PIN diode switches, and the reflection coefficient |S11| was maintained, which is a strong benefit of this design. The proposed polarization-reconfigurable antenna was modeled using the Computer Simulation Technology (CST) software. It had a 3.4 GHz resonance frequency in both states of reconfiguration, with a good axial ratio below 1.8 dB, and good gain of 4.8 dBic for both modes of operation. The proposed microstrip antenna was fabricated on an FR-4 substrate with a loss tangent of 0.02, and relative dielectric constant of 4.3. The radiating layer had a maximum size of 18.3 18.3 mm2, with 50 W coaxial probe feeding.
European Union’s Horizon 2020 research and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424.

Yes
This paper presents a circular polarization reconfigurable antenna for 5G applications, which is compact in size and has good axial ratio and frequency response. The proposed microstrip antenna is designed on a FR-4 substrate with a relative dielectric constant of 4.3 and has a maximum size of 30×30 mm2 with 50 Ω coaxial probe feeding. This design has two PIN diode switches controlling reconfiguration between right hand circular polarization (RHCP) and left hand circular polarization (LHCP). To achieve reconfigurability, a C-slot rectangular patch antenna with truncated corner techniques is employed by cutting off two corners on the radiating patch. The proposed antenna has been simulated using CST microwave studio software: it has 3.35-3.77 GHz and 3.4-3.72 GHz bands for both states of reconfiguration, and each is suitable for 5G applications with a good axial ratio of less than 1.8 dB and good gain of 4.8 dB for both modes of operation.
Innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424, UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.

碩士
國立成功大學
機械工程學系碩博士班
101
A dynamic polarization scanning ellipsometry based on the Mueller matrix formulation and Stokes polarimetry is proposed for dynamically extracting the effective ellipsometric parameters of anisotropic material. The effective ellipsometric parameters (Ѱp’p’, Ѱp’s’, Ѱs’p’, Δp’p’, Δp’s’, and Δs’p’) describe the amplitude ratio and phase difference of two orthogonal waves in any arbitrary coordinate system with a scanning angle θ relative to the X-Y coordinate frame. The dynamic polarization scanning ellipsometry is composed of a linear polarization scanner and a polarization state analyzer. In a linear polarization scanner, an EO modulator is modulated to scan the linear polarization states of incident light with orientations in the range of 0˚ ~ 180˚. In a polarization state analyzer, two EO modulators are implemented for dynamically extracting the Stokes vectors. As a result, characteristic of a twisted nematic liquid crystal cell modulated by an AC voltage is verified by a dynamic polarization scanning ellipsometry. The dynamic variations in twist angle and tilt angle of a twisted nematic liquid crystal cell are successfully extracted by a genetic algorithm (GA) in curve fitting. Thus, without dynamically scanning the mechanical stage in the incident angle or the sample in a traditional ellipsometry or dynamically scanning spectrum in a spectroscopic ellipsometry, the frequency response in the new dynamic polarization scanning ellipsometry can be easily improved. Besides, this new system can also extract the Mueller matrix of the sample as long as the scattering effect of the sample is small enough to be ignored. It is noted that 200000 groups of Stokes parameters per second can be extracted by using the new polarization state analyzer if 200MS/s DAQ card is used. As compared to the commercial PSA from a famous company (Hinds Instruments) with only extracting 100 groups of Stokes parameters per second, the performance of number groups of Stokes parameters per second is greatly improved. Importantly, the use of EO modulators will not only improve the angular resolution, but will also eliminate mechanical vibration from a rotation mechanical stage; thereby improving the accuracy of the measurement results. In addition, this new dynamic polarization scanning ellipsometry can also provide high-speed measurement to characterize the physical properties of the anisotropic sample. For example, if 200MS/s DAQ card is used, 1000 groups of physical parameters per second can be extracted by using this new dynamic polarization scanning ellipsometry. Finally, the applications of the new dynamic polarization scanning ellipsometry in semiconductor/LCD industries can be explored in an in-line monitoring on thin-film growth on substrate and optical properties on LCD panel.

碩士
國立臺灣科技大學
電機工程系
95
In this thesis, two quasi-Yagi antennas are designed for applications in UHF RFID band and the 5 GHz-WLAN band, respectively. The antenna geometry, design concept, simulated and measured results are carefully discussed in Chapter 2 and Chapter 3. The experimental results demonstrate that the proposed antennas feature a compact size, wide impedance bandwidth, moderate gain, and excellent front-to-back ratio. In Chapter 4, a reconfigurable patch antenna for RFID system applications is proposed. By utilizing four PIN diodes on a microstrip patch, the proposed antenna can be operated in two linear polarized states as well as left and right hand circular polarized states. The antenna demonstrates a wide impedance bandwidth, excellent front-to-back ratio and acceptable axial ratio as operated in circular polarization. The analysis and design in this thesis is based on the full-wave electromagnetic solver Ansoft HFSS and the experimental equipment in the Communication and Electromagnetic Technology Center in NTUST are used to verify the performance of the proposed antennas.

碩士
國立成功大學
機械工程學系碩博士班
92
Optical activity which is a character of some substances can be applied to many domains, such as the measurement of glucose concentration. In this report, we firstly developed a new liquid-crystal (LC) polarization modulator consisting of one LC variable retarder and two quarter wave plates. This modulator could be used to replace the Faraday modulator in modulating the polarization angle of light. We passed a linearly polarizing light through the LC modulator and an analyzer to obtain a modulated signal. After demodulating the signal by using the new demodulation system, the rotation angle caused by optical activity would be derived. This polarimeter has simpler structure, less optical elements, and a cheaper modulator than traditional one. To be integrated and non-invasive glucose sensor will be the purpose of this system.

Observations of sea ice from space are routinely used to monitor sea ice extent, concentration and type to support human marine activity and climate change studies. In this study, eight dual-polarization (dual-pol) (HH/HV) RADARSAT-2 ScanSAR images acquired over the Gulf of St. Lawrence during the winter of 2009 are analysed to determine what new or improved sea ice information is provided by dual-pol C-band synthetic aperture radar (SAR) data at wide swath widths, relative to single co-pol data. The objective of this study is to assess how dual-pol RADARSAT-2 ScanSAR data might improve operational ice charts and derived sea ice climate data records. In order to evaluate the dual-pol data, ice thickness and surface roughness measurements and optical remote sensing data were compared to backscatter signatures observed in the SAR data. The study found that: i) dual-pol data provide improved separation of ice and open water, particularly at steep incidence angles and high wind speeds; ii) the contrast between new, young and first-year (FY) ice types is reduced in the cross-pol channel; and iii) large areas of heavily deformed ice can reliably be separated from level ice in the dual-pol data, but areas of light and moderately ridged ice cannot be resolved and the thickness of heavily deformed ice cannot be determined. These results are limited to observations of new, young and FY ice types in winter conditions. From an operational perspective, the improved separation of ice and open water will increase the accuracy of ice edge and total ice concentration estimates while reducing the time required to produce image analysis charts. Further work is needed to determine if areas of heavily ridged ice can be separated from areas of heavily rafted ice based on knowledge of ice conditions in the days preceding the formation of high backscatter deformed ice. If rafted and ridged ice can be separated, tactical ridged ice information should be included on image analysis charts. The dual-pol data can also provide small improvements to ice extent and concentration data in derived climate data records. Further analysis of dual-pol RADARSAT-2 ScanSAR data over additional ice regimes and seasons is required.

abstract: Scattering from random rough surface has been of interest for decades. Several methods were proposed to solve this problem, and Kirchho approximation (KA) and small perturbation method (SMP) are among the most popular. Both methods provide accurate results on rst order scattering, and the range of validity is limited and cross-polarization scattering coecient is zero for these two methods unless these two methods are carried out for higher orders. Furthermore, it is complicated for higher order formulation and multiple scattering and shadowing are neglected in these classic methods. Extension of these two methods has been made in order to x these problems. However, it is usually complicated and problem specic. While small slope approximation is one of the most widely used methods to bridge KA and SMP, it is not easy to implement in a general form. Two scale model can be employed to solve scattering problems for a tilted perturbation plane, the range of validity is limited. A new model is proposed in this thesis to deal with cross-polarization scattering phenomenon on perfect electric conducting random surfaces. Integral equation is adopted in this model. While integral equation method is often combined with numerical method to solve the scattering coecient, the proposed model solves the integral equation iteratively by analytic approximation. We utilize some approximations on the randomness of the surface, and obtain an explicit expression. It is shown that this expression achieves agreement with SMP method in second order.
Dissertation/Thesis
Masters Thesis Electrical Engineering 2017

碩士
國立成功大學
機械工程學系碩博士班
95
Optical coherence tomography (OCT) based on the low coherence interferometry (LCI) is a powerful technique for performing in-depth cross-sectional imaging in scattering media for the resolution of micrometer without invasion. In earlier research, there have been report of the measurement of refractive index (n) and thickness (t) by use of OCT, and subsequently, the polarization-sensitive OCT (PSOCT) combining the properties of the low coherence interferometry and polarimetry has the ability to detect the birefringence induced by the structural change between any reflected layers. A polarization-sensitive OCT without necessary high-precision scanning stage and stage controller for measurements in the thickness, mean　refractive index, apparent phase retardation, and optical axis orientation has been established. In the research, the stretched derivation based on conventional PSOCT for the actual apparent phase retardation, the order and the birefringence are developed is present. The extraordinary and ordinary refractive indices of the sample can be extracted from the measured parameters once appropriate values of the order and apparent phase retardation of the multiple-order birefringent material have been specified. Furthermore, a method to directly extracting precise values for the extraordinary and ordinary refractive indices of a birefringent sample is developed by measuring the optical path difference induced by the two refractive indices, which requires the use of a thermal light source and careful dispersion compensation in order to improve the axial resolution. As a result, the novel PSOCT system would have the capabilities in measuring the extraordinary and ordinary refractive indices, thickness, phase retardation and optical axis orientation of a single-layer birefringent sample. As the knowledge from author, this is the first instrument that could measure all the optical parameters of the linear birefringence materials from only one system. It is believed that this novel measuring system could be applied in the opto-electronics industries for highly precise measurements in various optical parameters.

The Standard Model of particle physics which attempts to describe all matter and all forces in the universe (except gravity),has been in agreement with most of the experiments till date. However theoretically and phenomenologically many questions remain unanswered in the SM. The present and future colliders will help the physicists learn more about the nature of matter and all forces in the universe. In this thesis work we have mainly focused on the physics case of the future linear collider which will be a succession of the presently running Large Hadron Collider in CERN Geneva. As an introduction to the thesis work in Chapter 1 we have discussed in detail about the most planned future collider the International Linear Collider. This collider apart from being a high luminosity machine will have the advantage of beam polarization. Chapter 2 discusses about the basis structure of the Standard Model, along with its many unanswered questions. Some of the theories proposed to take care of these deficiencies are also discussed. These theories apart from explaining the shortcomings of the SM, also predicts many new particles and are thus phenomenologically rich. Exploration of these new physics scenarios can be done many ways. A detailed investigation of the direct production of particles which are not present in the SM spectrum, is one of the techniques provided the particles are within the collider reach. The other is an indirect way, where deviations from SM is studied by a through scrutinization of the SM processes. Provided new physics is observed in either of the way, in the present or future colliders it becomes necessary to pin point them. The main objective of this thesis work has been to look for various scenarios, both in a direct and indirect way and identify them. The different cases of beam polarization is also explored. Overall we find that the full potential of the linear collider can be realized only with the availability of the electron and positron beam polarization, both transverse and longitudinal. We give an overview of the importance of beam polarization and its inclusion in the calculation of e+e- collisions in Chapter 3. In Chapter 4 we have considered the possibility of finger printing the presence of heavy additional Z′bosons that arise naturally in extensions of the Standard Model such as E6 models and left-right symmetric models, through their mixing with the standard model Z boson. They are probed using W pair production and leptonic decay of one of the W’s. The Littlest Higgs Model which addresses the hierarchy problem and where the Z′arises naturally is also considered. By considering a class of observables including total cross sections, energy distributions and angular distributions of decay leptons we find significant deviation from the Standard Model predictions for these quantities with right-handed electrons and left-handed positrons at √s=800 GeV. This process complements the study of fermion pair production processes that have been considered before for discrimination between these models. We have then studied the possibility of identifying a strongly interacting Wboson sector inChapter5 which is consistent with present day Large Hadron Collider searches, at the International Linear Collider with longitudinal as well as transversely polarized electron and positron beams. We account for the final state interaction using a suitable Omnes formalism in terms of a plausible resonance description, and carry out thorough analyses of cross sections, asymmetries and angular distributions of the Ws. In order to have a fully comprehensive study we also carry out a comparison with other extensions of the Standard Model, where an s channel resonance like heavy additional Z′bosons arise naturally. We also consider the effect of the strong final state interaction on a correlation that depends on(φ- - φ+), where the φ∓are the azimuthal angles of decay leptons, and find that it is a useful discriminant. The importance of top polarization in the process e+e−→ tt with transverse beam polarization to probe interactions of the scalar and tensor type beyond the Standard Model and the way to disentangle their individual contributions is discussed in Chapter 6. 90% confidence level limits on the interactions with realistic integrated luminosity are presented and are found to improve by an order of magnitude compared to the case when the spin of the top quark is not measured. Sensitivities of the order of a few times 10−3 TeV−2 for real and imaginary parts of both scalar and tensor couplings at √s=500 and 800 GeV with an integrated luminosity of 500 fb−1 and completely polarized beams is shown to be possible. We next consider the process e+e- → γ Z with transverse beam polarization in the presence of anomalous CP-violating γZZ coupling λ1 and γγZ coupling λ2 in Chapter 7. We point out that similar to the approach in Chapter 6 if the final-state spins are resolved, then it becomes possible to fingerprint the anomalous coupling Reλ1. 90% confidence level limit on Reλ1 achievable with center-of-mass energy of 500 GeV or 800 GeV with realistic initial beam polarization and integrated luminosity is of the order of few times of 10−2 when the helicity of Zis used and 10−3 when the helicity of γis used. The resulting corrections at quadratic order to the cross section and its influence on these limits are also evaluated and are shown to be small. In Chapter 8 the production of the lightest neutralinos in the radiative process e+e−→ χ˜10χ˜10γ in supersymmetric models with grand unification is considered. We consider models wherein the standard model gauge group SU(3)c x SU(2)L x U(1)Y is unified in to the grand unified gauge groups SU(5),or SO(10). We compare and contrast the dependence of the signal cross section on the grand unified gauge group, and different representations of the grand unified gauge group, into which the standard model gauge group is unified. We carry out a comprehensive study of the radiative production process which includes higher order QED corrections in our calculations. In addition we carry out a detailed study of the background to the signal process coming from the Standard Model radiative neutrino production e+e−→ νv*γ, as well as from the radiative production of the scalar partners of the neutrinos (sneutrinos) e+e ν˜ν˜γ. The latter can be a major supersymmetric background to the radiative production of neutralinos when the sneutrinos decay invisibly. Finally in Chapter 9, we conclude and present the summary of the thesis.

碩士
國立臺灣科技大學
電子工程系
89
This thesis describes the analysis and simulation results of a new IP over dense wavelength division multiplexing (DWDM) architecture. This architecture is based on a novel ransmission approach that uses two orthogonal linear polarizations to carry the header and payload signals, respectively. Routing is based on optical burst switching (OBS) and multiprotocol label switching (MPLS) technologies. Optical routers split the header and payload signals by polarizers in the optic domain. This approach overcomes the problems that a optical packet is split into header and payload by complication optical architecture or transmitting separately on different wavelengths/channels. A simulation result for the case that an optical packet is transported through 50 km polarization-maintaining fiber link is presented. A comparison of the bit error ratio (BER) uses DWDM transmission technology with different optical switching methods is also made. Simulations are also conducted to evaluate the quality of service (QoS) performance in terms of wavelength utilization, burst loss probability, queuing delay, and throughput. We show the new architecture that uses polarization-maintaining fiber to transmit optical bursts, can improve the loss probability and decrease the optical buffer size.

碩士
國立虎尾科技大學
光電工程系光電與材料科技碩士班
106
In this thesis, we proposed a new method for small polarization rotation measurement. The method is based on the use of a half-wave plate and a high-stability common-path heterodyne interferometry. When the azimuth angle at 22.5 degree of a half-wave plate, the phase has a distinct change caused by the small polarization rotation of the incident light. The optical rotation properties of a material, such as glucose solution, can be introduced in the phase with the concentration of the solution. Finally, the phase can be measured using a Lock-in amplifier, and the relevant formula between them can also be found with a recording table.

The static dipole polarizabilities and ionization potentials of the first and second main group elements, including the charged ions, are obtained from all-electron relativistic coupled-cluster theory using a scalar relativistic Douglas-Kroll Hamiltonian. Spin-orbit coupling effects are investigated using a fully relativistic four-component Dirac-Coulomb-Hartree-Fock scheme followed by a second-order many-body perturbation treatment to account for electron correlation. Periodic trends in the dipole polarizabilities and the ionization potentials are discussed. In each case, a detailed discussion on electron correlation and relativistic effects are given. A relationship for relativistic and electron correlation effects between the dipole polarizability and the ionization potential is established. Particular attention is paid to the evaluation of a near basis set limit quality of the dipole polarizabilities. This is accomplished by the evaluation of all-electron basis sets used, followed by an extensive study on the convergence behavior of the dipole polarizabilities with respect to a finite basis set expansion. The present all-electron dipole polarizabilities are believed to be very precise, especially for charged ions where the availability of experimental values are limited. Scalar relativistic small-core pseudopotentials are fitted and their performance is tested in terms of static dipole polarizabilities and ionization potentials. It is demonstrated that the small core definition of the pseudopotential (nine-valence electron for the main group 1 and ten-valence electron for the main group 2 elements) enables us to safely omit core-valence correlation without scarifying accuracy. Following atomic dipole polarizabilities, applications are made to molecules starting with alkali dimers and their singly charged ions. The scalar relativistic pseudopotentials of this study are used to calculate equilibrium bond lengths, dissociation energies, vibrational frequencies and the dipole polarizabilities of these dimers. The change in the molecular dipole polarizabilities from the corresponding atomic dipole polarizabilities are discussed in terms of molecular bonding models. Simple ammonia complexes of the alkali-metals and their singly charged ions are studied. The equilibrium geometries, dissociation energies, harmonic vibrational frequencies as well as the dipole polarizabilities of these complexes are given.

Dipolar couplings are one of the major source of structural information. Due to their dependence on the distance between the nuclei and the angle of orientation of the dipolar vector with respect to the magnetic field, they provide significant insight into the geometry and topology of molecules. As the dipolar interactions are in general present in the solid phase of the compounds, solid state NMR experiments have gained significant popularity and is widely used. Separated Local Field NMR spectroscopy based on cross-polarization technique has been used to measure the heteronuclear dipolar couplings in solid state. However, the technique undergoes many experimental challenges and requires further development. This thesis is concerned mainly with the development of techniques to measure the dipolar couplings accurately in oriented molecules. In this regard, a method for fast data acquisition is also proposed. The first chapter briefly introduces the basics of NMR spectroscopy, methodologies applied for obtaining a high resolution NMR spectrum in the solid state. An introduction to liquid crystals is presented and the nature of NMR interaction in the liquid crystalline phases is described. In chapter-2, a new pulse scheme has been proposed that includes the X-nucleus polarization in the SLF experiments and is shown to provide better sensitivity and resolution. A quantitative analysis with simulation and experimental results are also presented. In chapter-3, the performance of various homonuclear decoupling pulse schemes incorporated into SLF experiments tested on oriented systems are compared. The proposed pulse schemes are shown to provide high resolution spectrum with accurate dipolar coupling measurement for natural abundant samples and for uniformly labeled compounds as well. Theoretical description with simulation and experimental results shown here are found to provide optimum results under several technical complications seen with respect to the conventional methods used for SLF experiments. Chapter-4, an attempt is made to reconstruct 2D J-resolved and 2D- SLF spectra from several 1D experimental data. This is achieved with the help of projection reconstruction method and is shown to provide high resolution 2D spectrum with saving of experimental time by an order of two. Chapter-5, high resolution spectra from SLF experiments under phase alternating pulses and using amplitude and time averaged nutation techniques are shown for accurate dipolar coupling measurement with a dramatic reduction in rf power. This is important as the use of low rf power leads to low sample heating and can be applied suitably for the study of liquid crystals and salty biomolecules. Chapter-6, attempts are made to characterize two novel thiophene based liquid crystals using both solution and solid state NMR spectroscopy. C-H dipolar couplings measured from SLF experiments are mainly used to find the order parameters and geometry of the molecules.