Dissertations / Theses on the topic 'Q-bit'

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Study about contributions of the concept of quantum bit (q-bit) and analyze the possibilities in quantum computers processing and increase the data storage capacity for devices memory. From the analysis of the q-bit is possible to notice changing in mental and social structures beyond their direct interference in the process of memory as a way of preserving information in different formats. Observations in the contributions from Quantum Mechanics, by measuring process, for Information Science and theoretical-epistemic confluence between the two sciences complemented by some opinions around the issues that still needing answer. Insertion of terms entanglement and superposition that were identified as fundamental to understanding the concept of q-bit is the basis to accept the updates in the concepts, formulations and descriptions established in Information Science
Estudo das contribuições do conceito do bit quântico (q-bit) e suas possibilidades de processamento nos computadores quânticos e de aumento da capacidade de armazenamento dos dados em dispositivos de memória. A partir da análise do q-bit, é possível a percepção das alterações de estruturas mentais e sociais, além de sua interferência direta no processo de memória como meio de preservação de informações sob diversos formatos. Observações das contribuições a Mecânica Quântica para a Ciência da Informação e a confluência teórico epistêmica entre as duas ciências, complementadas por algumas ponderações em torno das questões que ainda necessitam de respostas. Inserção dos termos emaranhamento e superposição de estados identificados como fundamentais para o entendimento do conceito de q-bit. Tais termos são a base para dimensionar as alterações em conceitos, formulações e descrições consagrados na Ciência da Informação. Palavras-chave: Bit quântico

Measurements are made on superconducting Niobium on Sapphire and oxidized Silicon microwave coplanar resonators for quantum bit experiments. Device geometry and materials are investigated and quality factors in excess of a million have been observed. The resonant frequency as a function of temperature of a coplanar resonator is characterised in terms of the change in the number density of superconducting electrons. At lower temperatures, the resonant frequency no longer follows this function, and evidence is shown that this is associated with the resonant coupling of the resonant frequency with two level systems in the substrate. At T<2.2 K the resonant frequency scales logarithmically with the temperature, indicating that two level systems distributed in the volume of the Silicon Dioxide affect the electric permittivity. Applying higher input microwave power levels is shown to saturate these two level systems, essentially decoupling them from the CPR resonance. This is observed as an increase in resonant frequency and Q factor. The resonant frequency is also shown to have a high sensitivity to a magnetic field applied perpendicular to the plane of the coplanar resonator, with a quadratic dependence for the fundamental, second and third harmonics. Frequency shift of hundreds of linewidths are obtained. Coplanar resonator are fabricated and measured with current control lines built on chip, and these have shown to produce frequency shifts of tens of Kilohertz.

2010 - 2011
In this thesis I will discuss the theory of two level systems and the theory of the oscillating particles in quantum eld theory. In the rst chapter I will consider the time evolution of a two level system, a qubit, to show that it has inside a local in time gauge invariant evolution equation. I construct the covariant derivative operator and show that it is related to the free energy. The gauge invariance of the time evolution of the two level system is analogous to the phenomenon of birefringence.I also show that the two level systems present a Berry-like and an Anandan-Aharonov phase. Finally, I discuss entropy environment e ects and the distance in projective Hilbert space between two level states to show that the last one is properly related to the Aharonov - Anandan phase. In the second chapter I review the result obtained in QFT for particle mix- ing, analyzing the theoretical construction and the oscillation formula in the fermion case.I will emphasize the di erences between the quantum mechan- ics formulas and the QFT formulas.The unitary inequivalence between the avor and the mass eigenstates is also shown and the structure of the current for charged elds is nally discussed. I found a non - perturbative vacuum structure for the mixing particles that, among the other things, will lead to a non zero contribution to the value of the cosmological constant (chapter 3). Several links between rst and second chapter will arise from this thesis and will shed the light on the fact that it is possible to construct a generic two level quantum eld theory, that is an extension of the quantum mechanics bit theory in a quantum eld theory framework. [edited by author]
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Esta dissertação de mestrado aborda formulações computacionais e algoritmos para a busca e extração de padrões em cadeias biológicas. Em particular, o presente texto concentra-se nos dois problemas a seguir, considerando-os sob as distâncias de Hamming e Levenshtein: a) como determinar os locais nos quais um dado padrão ocorre de modo aproximado em uma cadeia fornecida; b) como extrair padrões que ocorram de modo aproximado em um número significativo de cadeias de um conjunto fornecido. O primeiro problema, para o qual já existem diversos algoritmos polinomiais, tem recebido muita atenção desde a década de 60, e ganhou novos ares com o advento da biologia computacional, nos idos dos anos 80, e com a popularização da Internet e seus mecanismos de busca: ambos os fenômenos trouxeram novos obstáculos a serem superados, em razão do grande volume de dados e das bastante justas restrições de tempo inerentes a essas aplicações. O segundo problema, de surgimento um pouco mais recente, é intrinsicamente desafiador, em razão de sua complexidade computacional, do tamanho das entradas tratadas nas aplicações mais comuns e de sua dificuldade de aproximação. Também é de chamar a atenção o seu grande potencial de aplicação. Neste trabalho são apresentadas formulações adequadas dos problemas abordados, assim como algoritmos e estruturas de dados essenciais ao seu estudo. Em especial, estudamos a extremamente versátil árvore dos sufixos, assim como uma de suas generalizações e sua estrutura irmã: o vetor dos sufixos. Grande parte do texto é dedicada aos filtros baseados em q-gramas para a busca aproximada de padrões e algumas de suas mais recentes variações. Estão cobertos os algoritmos bit-paralelos de Myers e Baeza-Yates-Gonnet para a busca de padrões; os algoritmos de Sagot para a extração de padrões; os algoritmos de filtragem de Ukkonen, Jokinen-Ukkonen, Burkhardt-Kärkkäinen, entre outros.
This thesis deals with computational formulations and algorithms for the extraction and search of patterns from biological strings. In particular, the present text focuses on the following problems, both considered under Hamming and Levenshtein distances: 1. How to find the positions where a given pattern approximatelly occurs in a given string; 2. How to extract patterns which approximatelly occurs in a certain number of strings from a given set. The first problem, for which there are many polinomial time algorithms, has been receiving a lot of attention since the 60s and entered a new era of discoveries with the advent of computational biology, in the 80s, and the widespread of the Internet and its search engines: both events brought new challenges to be faced by virtue of the large volume of data usually held by such applications and its time constraints. The second problem, much younger, is very challenging due to its computational complexity, approximation hardness and the size of the input data usually held by the most common applications. This problem is also very interesting due to its potential of application. In this work we show computational formulations, algorithms and data structures for those problems. We cover the bit-parallel algorithms of Myers, Baeza-Yates-Gonnet and the Sagots algorithms for patterns extraction. We also cover here the oustanding versatile suffix tree, its generalised version, and a similar data structure: the suffix array. A significant part of the present work focuses on q-gram based filters designed to solve the approximate pattern search problem. More precisely, we cover the filter algorithms of Ukkonen, Jokinen-Ukkonen and Burkhardt-Kärkkäinen, among others.

This thesis deals with the issue of the creation of a programme that would simulate the distortion that appears during the process of lossy audio coding. As the environment for the creation, the MATLAB programming language has been chosen. An encoder, which changes the subjective signal quality according to customer preferences for the bitrate, has been created as a practical part of this thesis. Its function is based on a dynamic bit allocation technique and includes an optional window switching algorithm. The theoretical background for the creation of the programme consists of an explanation of the main principles of lossy coding with emphasis on MPEG1 layer 3 operating principles. The practical chapter describes how the created programme and its parts work, and it includes results of the run quality testing. The testing was conducted using the objective assessment method PEMO-Q, and consisted of comparing the objective quality of the programme’s outputs to the quality of samples on which a regular MP3 encoder with identical settings was used.

This paper mainly deals with a special but highly-developing industry in China, net game industry. Due to the significant construction and improvement have been happening at China since 30 years ago, and the influence of traditional culture, population boom or demographic dividend and the invasion of western technologies and cultures, net game industry, which has been only existing for less than 15 years at China, has become one of most profitable industries and changed the living of millions of people. The goal of this essay is to explore the economic performance of networks during last dozen years in China and find the drivers and reasons. By picking up the data between 2001 and 2013, sufficient data and researches will be provided for the study for the network games in China.

I denna uppsats görs en fördjupning utbyggnaden av Stockholms tunnelbana till Nacka kommun. Syftet med uppsatsen har varit att undersöka huruvida det uppstår förändringar i fastigheters värde i nära och direkt anslutning till ny- eller utbyggd tunnelbana. Teorikapitlet behandlar olika teorier som beskriver varför vissa typer av fastigheter och verksamheter uppstår på vissa ställen. Teorin tar sats ur von Thünens sätt att förklara markanvändning. Uppsatsen går igenom hur betalningsviljan för mark dels skiljer sig mellan olika verksamheter och dels hur den avtar med avståndet från Central Business District (CBD). Kontor och handel har relativt sett högre betalningsvilja för fastigheter nära CBD än bostäder och bostäder har högre betalningsvilja än industrier. Med ökad tillgänglighet tack vare tunnelbana så uppstår fler unika områden (lokala CBD:s) där kontor och handel har större vilja att etablera sig. Tack vare ökad tillgänglighet och därmed ökat marknadsvärde så kan vi enligt Tobin’s Q förvänta oss ökad exploatering. Vidare analyseras 15 akademiska artiklar på ämnet. De artiklar som legat till grund för att bedöma värdeförändringen har studerat rapid transit system och genomfört analyser på försäljningsdata. Den genomsnittliga ökningen visar på att värdena för fastigheter går upp med 9,6 %. Artiklarna ger också en relevant input om eventuella yttre negativa omständigheter (som dock inte överstiger nyttorna) som uppstår med tunnelbana, till exempel ökad kriminalitet. Deltagarna i enkätundersökningen förväntar sig att alla typer av fastigheter värdemässigt kommer påverkas positivt inom en radie av 1 kilometer. De anser att det till en viss grad finns en marknad för privat medfinansiering samt att medelklassområden är de områden med högst betalningsvilja för tunnelbana.
This thesis delves deeply into the expansion of the Stockholm subway to Nacka municipality. The purpose has been to investigate whether there is a change in the valuation of properties in close proximity to new or expanded subway. The theory chapter covers different theories on land use and bid rent curves. The theories are based on von Thünen’s way of describing land use. The thesis goes through how the willingness to pay for land on one hand differs between different property types and on another hand decreases with distance to Central Business District (CBD). Offices and retail have a relatively higher willingness to pay for land in the proximity of CBD than residential and residential have a higher willingness to pay than industrial. With increased availability thanks to subway come numerous unique areas (local CBD’s) where office and retail have a higher willingness to establish. The increased availability also heightens the Tobin’s Q, which means we can expect a higher degree of exploitation. 15 academic papers that cover the issue are analyzed. The articles which are the basis for the reasoning on value change have studied rapid transit systems and conducted analysis on sales data. The average increase in property value of 9,6 %. The articles also gives good input on negative externalities (which however never exceeds the benefits), for example increased criminality. The participants in the survey are expecting that all types of properties will increase in value within a radius of 1 kilometer from the stations. They consider that there is a potential market for private co-financing and that middle-class areas are the ones with highest willingness to pay for subway.

Cette thèse a porté sur les principes de guidage, les propriétés linéaires et les outils de conception autour des fibres à cristal photonique à coeur creux (HC-PCF) à couplage inhibé (IC). Le guidage IC a été démontré comme une manifestation photonique de Q-BiC (état quasi lié dans un continuum) en étudiant des profils asymétriques et dépendants en polarisation dit Fano présentant une bande passante spectrale de 30 GHz. En utilisant le concept de IC, nous reportons la caractérisation linéaire de fibres IC HC-PCF supérieures à l’état de l’art. Par une optimisation de la forme du coeur, une fibre Kagome IC HC-PCF a démontré des pertes très faibles de 8,5 dB/km à 1030 nm associées à une bande passante à 3 dB de 225 nm. Une autre conception avec des entretoises de silice amincies à 300 nm a permis d’atteindre des pertes de 30 dB/km à 780 nm avec une bande de transmission fondamentale record décalée à 670 nm et capable de couvrir toutes les gammes spectrales du Ti:Sa, Yb et Er. Nous avons également travaillé sur la conception et la fabrication de IC HC-PCF présentant une gaine dont la structure est un réseau unique de tubes fins isolés. Une de ces fibres a permis de démontrer une transmission jusqu'à 220 nm avec des pertes records de 7,7 dB/km à ~ 750 nm, tandis qu’une seconde réalisation s’est traduit par une bande fondamentale de plus d’une octave allant de 600 à 1200 nm avec des pertes de 10-20 dB/km. Finalement, cette dernière fibre a été étudiée plus en détail pour déterminer les sources à l’origine des pertes due à la rugosité de surface présente à l’interface du contour du coeur
This thesis reported on guiding principles, linear properties and conceptual design tools of inhibited coupling (IC) guiding hollow-core photonic crystal fibers (HC-PCF). IC guidance was proved as photonic manifestation of Q-BiC (quasi bound-state-in-a-continuum) by investigating asymmetric and polarization dependent Fano profiles with bandwidth of 30 GHz in high resolution transmission spectra. By using IC design concept, we reported on linear characterization of state-of-the-art IC HC-PCFs. Based on core shaping optimization, a Kagome IC HC-PCF demonstrated ultra-low loss down to 8.5 km/km at 1030 nm associated with a 225 nm wide 3-dB bandwidth. Another Kagome design with thinner silica struts of 300 nm exhibited lowest loss of 30 dB/km at 780 nm along with record level fundamental bandwidth spreading down to 670 nm and able to cover the entire Ti:Sa, Yb and Er laser spectral ranges. We also reported on design and fabrication of single-ring tubular lattice IC HC-PCFs. One of these fibers demonstrated transmission down to 220 nm with a record transmission loss of 7.7 dB/km at ~750 nm, while the second one exhibited ultra-broad fundamental band with loss range of 10-20 dB/km over one octave spanning from 600 to 1200 nm. Finally, the second tubular fiber was further investigated for fundamental loss sources due to surface roughness around its core-contour

ALBUQUERQUE, R. M. Obtenção de portas lógicas quânticas em condensados de bose - Einstein. 2017. 77 f. Dissertação (Mestrado em Engenharia Elétrica e da Computação) - Campus de Sobral, Universidade Federal do Ceará, Sobral, 2017.
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Bose-Einstein condensate (BEC) coupled is a promising candidate to quantum computing. Being a macroscopic quantum phenomenon, Being a strong quantum system (BÖIH et al., 2009), its assembly and experimental control inside an atomic chip (HÄNSEL et al.,2001), further the optical networks (GREINER OLAF MANDEL, 2001), where it is found and manipulated in different network sites, assuring implementation conditions of Quantum Information Protocol. The definition of a Qubit in BECs was proposed considering the couple of two BEC’s in different hyperfine states throught a two-photon transition. We have identified each one of the condensates in their respective hyperfine levels like the states and the Qubit. Experimentally, it is possible both the identification of atoms that ate in each one of the hyperfine levels and the measurement of the condensate phase. With these information is possible to determine the superposition coefficients . In this coursework, we have studied the dynamics of two Bose-Einstein condensate (BEC) on its fundamental state, trapped and coupled by a quantum tunneling. Because of this coupling, there is population transference between two condensed modes. The coupling is adjusted in a way we have probability of occupation in two levels. We have shown that this system can be considerate viable to a Qubit. So, we have simulated the quantum gates NOT and Hadamard.
Condensados de Bose-Einstein (CBE) acoplados é candidato promissor à computação quântica. Por ser um fenômeno quântico macroscópico, por ser um sistema quântico robusto (BÖHI et al., 2009), por sua montagem e controle experimental dentro de um chip atômico (HÄNSEL et al., 2001), além das construções em redes ópticas (GREINER OLAF MANDEL, 2001), onde são localizados e manipulados em diferentes sítios da rede, garantindo condições de implementação de protocolos de Informação Quântica. A definição de um q-bit em CBEs foi proposta considerando o acoplamento de dois CBEs em diferentes estados hiperfinos através de uma transição de dois fótons. Identificamos cada um dos condensados nos seus respectivos níveis hiperfinos como os estados j0i e j1i do q-bit. Experimentalmente, é possível tanto a identificação dos átomos que estão em cada um dos níveis hiperfinos quanto a medição da fase dos condensados. Com estas informações é possível determinar os coeficientes de superposição a j0i+b j1i. No presente trabalho, estudamos a dinâmica de dois condensados de Bose - Eisntein (CBE) no estado fundamental, armadilhados e acoplados por tunelamento quântico. Devido a esse acoplamento, há transferência de população entre os dois modos condensados. O acoplamento é ajustado de maneira que tenhamos probabilidade de ocupação em dois níveis. Demonstramos que este sistema pode ser considerado viável a um q-bit. Então, simulamos as portas quânticas NOT e Hadamard.

Este trabalho consiste na análise de um método de reconstrução/tomografia de estado quântico em ressonância magnética nuclear utilizando pulsos de radiofreqüência não-seletivos, que possuem a propriedade de promover rotações globais do sistema de spins 7/2. Tal método foi aplicado para reconstruir estados relacionados à computação quântica. As operações lógicas e os estados iniciais envolvidos nas operações quânticas foram construídos através de pulsos modulados optimizados numericamente; o processo de optimização, em particular, não foi tratado nesse trabalho. Foram elaborados programas que simulam: a construção dos estados e portas lógicas utilizando os parâmetros dos pulsos modulados; a aplicação dos pulsos de tomografia e a geração dos dados necessários à reconstrução (amplitudes espectrais); construção de estados utilizando pulsos simples para testes das circunstâncias experimentais; o efeitos de possíveis problemas relacionados à amostra ou ao equipamento. Finalmente, foi elaborado um programa para reconstrução do estado a partir da leitura das amplitudes espectrais, que podem ser obtidas a partir dos programas relacionados no segundo item, ou experimentalmente. As implementações experimentais foram realizadas medindo sinais de RMN de núcleos de 133Cs, localizados em um cristal líquido, que, por possuírem spin 7/2, devido às interações Zeeman e quadrupolar elétrica, apresentam sete linhas espectrais distintas para transições entre níveis energéticos adjacentes; logo, é possível tratar esses núcleos como sistemas de 3 q-bits. Foram construídos estados pseudo-puros e aplicada uma das portas Toffoli. Além disso, uma discussão do algoritmo quântico de busca de Grover no contexto da Ressonância Magnética Nuclear é apresentada para uma futura implementação.
This work describes a quantum state tomography method in nuclear magnetic resonance using nonselective radiofrequency pulses that cause global rotations of spin 7/2 systems. This method was applied to tomograph states related to quantum computation. Numerically optimized modulated pulses allowed building the initial states and the logical operations involved in the quantum operations; particularly, the optimization process was not treated in this work. Several programs were constructed that simulate: o the construction of the quantum states and the logical operations by means of the modulated pulses parameters; o the application of the tomography pulses and the generation of the necessary data for tomography (spectral amplitudes); o the construction of the states using simple pulses for experimental condition tests; o the effects of possible problems related to the samples or equipments. Finally, a quantum state tomography program was elaborated to read the spectral amplitudes, which can be obtained from the programs related to the second item, or experimentally. The experimental implementations were performed measuring the NMR signals from spin 7/2 133Cs nuclei located in a liquid crystal under Zeeman and quadrupolar electric interactions. The NMR spectrum of these nuclei, under these interactions and located in an oriented sample, present 7 spectral lines for transitions between adjacent energetic levels; with this, it is possible to treat it like a 3 q-bits system. Pseudo-pure states were constructed and one Toffoli gate was applied. Furthermore, a discussion about the Grover\'s quantum search algorithm in the nuclear magnetic resonance context was presented for future implementation.

Syftet med studien är att undersöka om det nya personlighetsformuläret Pers Q fungerar på ungdomar samt studera eventuella könsskillnader i personlighet. Vidare undersöks om bakgrundsvariablerna årskurs, syskonplacering, sociokulturell bakgrund samt självuppskattad skolprestation har samband med personligheten. Studien är ett led i utprövningen av Pers Q som mäter verifierade personlighetsfaktorer med validitet för arbetskriterier. Respondenterna består av 138 killar och 233 tjejer från gymnasiet (n=371). En explorativ principalkomponentanalys verifierade en tidigare faktorstruktur med sju personlighetsfaktorer: Omtanke om andra (alfa ,87), Noggrannhet (,84), Social förmåga (,84), Kreativitet (,82), Humörinstabilitet (,77), Stresstålighet (,76) samt Självförtroende (,72). Resultatet visar signifikanta könsskillnader i fem av sju faktorindex. Slutresultatet visar att Pers Q är ett snabbt och lätthanterligt personlighetsformulär som fungerar väl på ungdomar.

Ostlänken är en planerad höghastighetsjärnväg mellan Järna och Linköping med stegvis byggstart från 2017, ett omfattande projekt som inkluderar totalt cirka 20 kilometer tunnel, varav en tunnel planeras att korsa Getåravinen. Undermarksbyggande är komplicerat och kontakt med svaghetszoner i berg innebär ökade risker för anläggning, miljö och omgivande fastigheter. För att åstadkomma en riskbedömning, dimensionering och ekonomisk kalkyl utförs undersökningar och ingenjörsgeologiska prognoser av bergkvalité och geologisk struktur. Studier har visat ett samband mellan naturliga lineament och svaghetszoner i berg. Därför var uppsatsens syfte att bedöma geologiska byggbarhetsfaktorer genom en strukturgeologisk karaktärisering av lineamentet Getåravinen. Arbetet fokuserade på ett avgränsat område inom Getåravinen där Sweco, på uppdrag av Trafikverket, har utfört ingenjörsgeologiska undersökningar inför den planerade anläggningen av Ostlänken.Arbetet utgick från en studie av lineament genom geologiska kartor, kärnborrprov och hällkarteringar kring Getåravinen, dessa analyserades sedan för att identifiera strukturgeologiska samband. Metoderna Inverse Distance Weighted och kriging användes för att prediktera berget i borrkärnornas omgivning utifrån kvalitéklassningarna Rock Mass Rating, Q-systemet och Rock Quality Designation. För att visa resultatet pedagogiskt och förbättra underlaget inför byggteknisk diskussion visualiserades resultatet i en Building Information Model i mjukvaruprogrammet AutoCAD Civil 3D. Resultatet visade cirka 20° avvikelse mellan lineamentet och huvudsprickriktningen i Getåravinen, det bekräftade ett sprickmönster som då generellt kan antas gälla för lineament vilket är användbar information vid undermarksbyggande. Prediktionerna visade en rumslig beskrivning av bergets klassificeringar och samband med lineamentet. Nyttan av prediktiva metoder var därmed god då även effektiv kvantifiering av bergklasserna möjliggjordes vilket kan implementeras vid undermarksbyggande.
The East Link is a planned high-speed rail link between Järna and Linköping with a gradual construction start in 2017, a comprehensive project covering a total of approximately 20 kilometers of tunnel, of which one tunnel is planned to cross the Getå ravine. Subsurface construction is complicated, and contact with weak zones in the rock implies increased risks for the tunnel construction, the environment and the surrounding real estates. In order to accomplish a risk assessment, dimensioning and economic calculation, geological engineering investigations of the rock’s quality and geological structure are carried out. Studies have shown a relationship between natural lineaments and weaknesses in the rock. Therefore, the purpose of this thesis was to assess geological constructability factors in the Getå ravine by using a characterization of structural geology. The focus was within a demarcated area where the consulting firm Sweco, on behalf of the Swedish Transport Administration, had performed engineering geological surveys for the planned construction of the East link.The thesis was based on a study of lineament in geological maps, core drill samples and bedrock mapping in the surroundings of the Getå ravine, which were later analysed to identify structural geological relations. The methods Inverse Distance Weighted and Kriging were used to predict the rock ambient to the core kernels based on the quality ratings Rock Mass Rating, Q System and Rock Quality Designation. In order to visualize the results pedagogically and enhance the basis for technical discussion regarding civil engineering, the results were visualized in a Building Information Model in the software AutoCAD Civil 3D. The result showed approximately 20° deviation between the lineament and the primary joint strike in the Getå ravine, it confirmed a joint pattern that can be generally assumed for natural lineaments which is useful information in subsurface construction. The predictions showed a spatial distribution of the rock's different quality ratings and relationship with the lineament. The utility of the predictive methods was therefore certain because of efficient quantification of the rock quality was made possible, which can be implemented when characterizing the rock into quality domains prior subsurface construction.

Il mare profondo rappresenta l’ambiente più grande del nostro pianeta, ma anche il meno esplorato. A causa dei cambiamenti climatici e dei crescenti impatti antropici, l’esistenza dei beni e servizi che questo ambiente fornisce è a rischio. Stime monetarie di tali benefici sono carenti. Elevata è la biodiversità che il mare profondo e, più in generale, gli oceani ospitano. Dalla letteratura emerge una grande variabilità della disponibilità a pagare (DAP) delle persone per la tutela della biodiversità marina. L’area geografica, le specie investigate e l’ammontare dei costi sono le variabili che maggiormente influenzano tale DAP. Molte delle relazioni tra la DAP e le variabili esplicative risultano non lineari. Una migliore comprensione della percezione che le persone hanno del mare profondo può facilitarne la valutazione economica. Utilizzando la metodologia Q, emergono punti di vista che differiscono per l’importanza attribuita a specie e habitat. L’uso di diverse condizioni di istruzione e le conoscenze scientifiche sono fattori importanti nel determinare la percezione che gli intervistati hanno del Mar Mediterraneo profondo, sebbene non sufficienti a spiegarne interamente la soggettività. Una grande eterogeneità nelle preferenze espresse da cittadini italiani, riguardo la loro DAP per la salvaguardia di tale ambiente, emerge da un esperimento di scelta discreta. Solamente alcuni dei soggetti intervistati, maggiormente sensibili verso la tutela delle risorse naturali, appaiono disponibili ad una donazione per la protezione del Mar Mediterraneo profondo, in particolar modo di ambienti a coralli. Persone con un elevato reddito, e che in passato hanno effettuato donazioni per la salvaguardia dell’ambiente, sono particolarmente disponibili a finanziare la ricerca scientifica sul Mar Mediterraneo profondo. Nessuna DAP emerge, invece, per ridurre il riscaldamento globale.
The deep sea represents the largest (but the least explored) biome on Earth. It is increasingly affected by anthropogenic stressors and climate changes, threatening the provision of crucial ecosystem services in the future. The monetary value of those benefits remains scarcely assessed. The deep sea and, more generally, oceans host a high biodiversity. A great variability in the people’s willingness to pay (WTP) for marine biodiversity emerges from the literature. Price vector, investigated species and location of studies represent the variables that most influence such WTP. Non-linear relationships between the WTP and most of the explaining variables are observed. A better understanding of people’s perception of deep sea may support its (non-market) valuation. Applying Q methodology, different perspectives on Mediterranean deep sea are revealed. The importance attributed to species and habitats vary between the points of view. The use of different conditions of instruction and the respondents’ expertise are important factors in determining the perception of Mediterranean deep sea, even if they cannot completely explain the participants’ subjectivity. A great heterogeneity in the preference of Italian citizens for preserving the Mediterranean deep sea emerges from a discrete choice experiment. Many respondents refuse to pay for supporting the protection of biodiversity and the scientific research on that remote and unfamiliar environment. By contrast, participants with a high awareness of the importance of natural resources are willing to pay for protecting, in particular, deep-water corals. High income and past donations for environmental protection positively influence the respondents’ willingness to fund further scientific researches on the Mediterranean deep sea. Overall, the global warming is of little concern for the participants, who are not willing to pay for limiting the temperature rise.

Migraine is a common and highly disabling neurological disorder that affect more than 10% of the general population; in 30% of the migraneours migraine headache is preceded by transient neurological symptoms referred as “migraine aura”. Familial Hemiplegic Migraine type 1 (FHM1) is a rare and very severe autosomal dominant subtype of migraine with aura (MA), that is considered a good model for studying migraine: FHM1 typical attacks resemble general MA attacks, but aura symptoms include also motor weakness or paralysis, often but not always unilateral. FHM1 is caused by mutations in the CACNA1A gene, with encodes the α1, pore-forming subunit of neuronal CaV2.1 voltage-gated Ca2+ channels, also referred as P/Q-type Ca2+ channels. FHM1 mutations produce gain-of-function of human recombinant CaV2.1 channels, mainly due to a shift of channel activation to more negative voltages and an increase of the open probability and single channel influx over a wide voltage range (Hans et al., 1999; Tottene et al., 2002, 2005; Pietrobon). Facilitation of experimentally induced cortical spreading depression (CSD) in knock-in (KI) mice carrying the human FHM1 mutation R192Q has been observed in vivo (van den Maagdenberg et al., 2004) and in vitro (Tottene et al., 2009). CSD, a wave of strong neuronal and glial depolarization that slowly progresses across the cerebral cortex, followed by long-lasting neural suppression, is the phenomenon underlying migraine aura and a likely primary cause of migraine headache. Tottene et al. (2009) recently demonstrated enhanced excitatory neurotransmission due to increased action potential-evoked Ca2+ influx through CaV2.1 channels and increased probability of glutamate release at cortical pyramidal cell synapses of R192Q KI mice. Using an in vitro model of CSD Tottene et al. also demonstrated a causative link between enhanced glutamate release and facilitation of CSD induced by brief pulses of high KCl in cortical slices of KI mice. These findings support a key role of CaV2.1 channels in CSD initiation and propagation. In the first part of my Ph. D project I further investigated the mechanisms of CSD induction and propagation and in particular the role of NMDA receptors and voltage-gated calcium channels. Results obtained were published in Tottene el al., 2011 (pdf attached in chapter 3). We adopted the in vitro model of CSD described in Tottene et al., 2009 and measured CSD threshold and velocity in acute cortical slices from WT mice before and after application of specific blockers. CSD was induced by pressure pulses of high KCl of increasing duration; the duration of the first pulse eliciting a CSD was taken as CSD threshold and the rate of horizontal spread of the change in intrinsic optical signal produced by CSD as CSD velocity. We investigated the role of NMDA using the general NMDA receptors inhibitor D-AP5 (50 μM). In the presence of D-AP5 stimuli up to 30-time the duration of the control threshold failed to induce a CSD. We investigated also the role of P/Q, N, R, and L-type voltage-gated calcium channels using the respective specific blockers: ω-agatoxin IVA (300 nM), ω-conotoxin GVIA (1 μM), SNX-482 (250 nM), and nimodipine (50 μM). Similarly to what observed after application of D-AP5, in the presence of ω-AgaIVA stimuli up to 30-time the duration of the control threshold failed to induce a CSD. Application of either ω-CgTxGVIA and SNX-482 only slightly increased CSD threshold (of about 10%) and slightly decreased CSD velocity (of about 15%) suggesting that N- and R-type voltage-gated Ca2+ channels may have a modulatory role in CSD induction and propagation. Application of nimodipine did not affect CSD induction nor propagation. The findings that application of D-AP5 or ω-AgaIVA inhibits CSD induction while ω-CgTxGVIA, SNX-482 and nimodipine have only a poor or null effect are consistent with and support a model of CSD initiation and propagation in which activation of presynaptic (and possibly postsynaptic) CaV2.1 channels and NMDA receptors plays a pivotal role (Tottene et al., 2011). The role of NMDA receptors was further investigated in FHM1 R192Q mice, which show an increased glutamate release from pyramidal neurons. In contrast to what happens in WT mice, application of D-AP5 in brain slices from KI mice did not prevent CSD induction, but significantly increased CSD threshold (90 ± 9%) and significantly decreased CSD velocity (47 ± 1%) relative to control. The different effect of D-AP5 in WT and KI mice suggests that other elements (beside NMDA receptors) could be involved in CSD initiation mechanisms. Current clamp recordings close to the KCl injection pipette (at fixed distance of 100 and 200 µm) allowed to observe different phases in voltage changes after the application of both sub-threshold and threshold KCl stimuli: it was possible, in fact, to distinguish three distinct peaks. While the first two peaks were present in both sub-threshold depolarizations and CSD, the third peak was specifically linked to CSD. Patch-clamp technique allowed to accurately describe different CSD phases but showed the obvious limitation to be restricted to only one cell. Ca2+ imaging of slices loaded with the Ca2+ sensitive indicator OGB1-AM allowed to observe several neurons at different distances from KCl-injecting pipette at the same time for each pulse. Simultaneous patch-clamp recordings and Ca2+ imaging showed a general correlation between voltage changes recorded in current-clamp and fluorescence peaks detected in Ca2+ traces. The physiological meaning of these different phases and their specific role in CSD induction and propagation are not clear and are currently object of study in our laboratory. Ca2+ imaging allowed to detect also intracellular calcium increases from astrocytes in response to KCl pulses. Astrocytes can support and amplify glutamatergic synaptic transmission by releasing glutamate that specifically act on NMDA receptors; astrocytic release of glutamate and other substances is induced by [Ca2+]int increases that are, in turn, stimulated by neuronal release of glutamate and other neurotransmitters. To test whether the neuron-astrocyte crosstalk is involved in CSD induction and propagation, threshold for CSD induction and velocity of CSD propagation were measured before and after inhibiting astrocytic [Ca2+]int increases by the application of cyclopiazonic acid (CPA, 50 µM), that emptied astrocytic Ca2+ internal stores without affecting neuronal response to KCl. CPA application did not affect CSD threshold or velocity in both WT and KI mice. These results show that neuron-astrocyte crosstalk seem not to be relevant in CSD induction and propagation. The combination of Ca2+ imaging and patch clamp recording permitted to observe, in the absence of external stimuli, spontaneous activity that occurs in the neocortical neural networks as slow oscillations between periods of synaptically-driven depolarizations with firing (up-states) followed by decreased synaptic inputs and ceasing of firing (down-states). At the same time spontaneous large Ca2+ oscillations were observed in astrocytes. To check whether neuron-astrocyte crosstalk could be involved in the generation or in the modulation of spontaneous neuronal network activity, astrocytic spontaneous oscillations were inhibited by application of CPA. In presence of CPA up-states were still present in both WT and KI mice; however CPA application led to a significant reduction of up-states frequency in WT (41 ± 3%, p = 0.0001), but not in KI mice (11 ± 6%, p = 0.12). These preliminary results are in agreement with a possible role of neuron-astrocyte crosstalk in spontaneous neuronal network activity.
L’emicrania è un disturbo neurologico comune ed altamente invalidante che colpisce più del 10% della popolazione in generale; nel 30% dei pazienti affetti da emicrania, la fase del dolore è preceduta da sintomi neurologici transienti definiti nel complesso “aura emicranica”. L’emicrania emiplegica familiare di tipo 1 (FHM1) è una forma autosomica dominante di emicrania con aura rara ma molto grave; l’FHM1 è considerata un buon modello per lo studio dell’emicrania: gli attacchi tipici di FHM1, infatti, ricapitolano molto quelli della normale emicrania con aura, tuttavia durante l’aura si presentano sintomi come debolezza motoria o paralisi, spesso ma non sempre unilaterale. L’FHM1 è dovuta a mutazioni nel gene CACNA1A che codifica la subunità α1 formante il poro dei canali Ca2+ neuronali voltaggio dipendenti CaV2.1, chiamati anche canali per il calcio di tipo P/Q. Le mutazioni FHM1 producono un guadagno di funzione dei canali ricombinanti umani CaV2.1; tale guadagno di funzione è principalmente dovuto allo spostamento della curva di attivazione del canale verso valori di potenziale più negativi e all’aumento della probabilità di apertura e dell’influsso di Ca2+ a livello di singolo canale in un ampio intervallo di potenziali vicini alla soglia di attivazione del canale (Hans et al., 1999; Tottene et al., 2002, 2005). Studi in vivo (van den Maagdenberg et al., 2004) ed in vitro (Tottene et al., 2009) hanno dimostrato come topi knock-in (KI) per la mutazione umana FHM1 R192Q presentino una facilitazione nell’induzione sperimentale della cortical spreading depression, il fenomeno neurologico alla base dell’aura emicranica e possibile evento innescante il tipico mal di testa caratterizzante l’emicrania. Dal punto di vista elettrico la CSD è un’onda di forte depolarizzazione neuronale e gliale, che si propaga lentamente attraverso la corteccia cerebrale ed è seguita da una lunga fase di soppressione neurale. Recentemente Tottene e colleghi (2009) hanno dimostrato un aumento nella trasmissione sinaptica eccitatatoria corticale dei topi FHM1 R192Q; tale aumento è dovuto all’aumentato influsso di Ca2+ evocato da potenziali d’azione attraverso i canali CaV2.1 ed al conseguente aumento nella probabilità di rilascio del neurotrasmettitore glutammato alle sinapsi piramidali di questi topi. Attraverso l’impiego di un modello in vitro, Tottene e colleghi hanno, inoltre, dimostrato il rapporto di causalità tra l’aumentato rilascio di glutammato dai neuroni piramidali e la facilitazione nell’induzione della CSD tramite brevi applicazioni pressorie di KCl a concentrazioni elevate in fettine di cervello da questi topi. Tali evidenze supportano l’ipotesi di un ruolo chiave dei canali CaV2.1 nei meccanismi di induzione e propagazione della CSD. La prima parte del mio progetto di dottorato ha avuto come scopo fondamentale l’approfondimento delle conoscenze riguardo i meccanismi che sottendono induzione e la propagazione della CSD; in particolare il mio interesse si è principalmente soffermato sul ruolo dei canali del calcio voltaggio-dipendenti e dei recettori NMDA. I risultati ottenuti sono stati pubblicati (Tottene et al., 2001, pdf allegato nel capitolo 3). Per conseguire gli scopi prefissi abbiamo impiegato il modello in vitro già in precedenza adottato da Tottene e colleghi (2009) ed abbiamo misurato la soglia di induzione della CSD e la velocità di propagazione della stessa in fettine corticali di topo wild-type (WT) prima e dopo l’applicazione di vari inibitori selettivi dei canali d’interesse. La durata del primo impulso in grado di indurre una CSD veniva considerata la soglia di induzione della stessa, mentre la velocità di propagazione della CSD coincideva con la velocità di propagazione dei cambiamenti nel segnale ottico intrinseco (IOS) associati ad essa. Il ruolo dei recettori NMDA è stato indagato mediante l’impiego di un inibitore selettivo in concentrazione saturante: D-AP5, 50 µM. In presenza di D-AP5 stimoli fino a 30 volte la soglia controllo non erano in grado di indurre una CSD. Abbiamo inoltre indagato il ruolo dei canali per il Ca2+ voltaggio-dipendenti di tipo P/Q, N, R ed L, usando i rispettivi inibitori specifici: ω-agatossina IVA (300 nM), ω-conotossina GVIA (1 μM), SNX-482 (250 nM) e nimodipina (50 μM). Similmente a quanto osservato in presenza di D-AP5, in presenza di ω-AgaIVA, stimoli fino a 30 volte la soglia controllo non erano in grado di indurre una CSD. Diversamente, l’applicazione di ω-CgTxGVIA o di SNX-482 provocava un lieve innalzamento della soglia (di circa il 10%) e una leggera diminuzione della velocità (di circa il 15%), suggerendo un ruolo modulatore dei canali per il calcio voltaggio-dipendenti di tipo N ed R nell’induzione e nella propagazione della CSD. Al contrario l’applicazione di nimodipina non aveva alcun effetto sulla soglia o sulla velocità della CSD. La dimostrazione che D-AP5 e ω-AgaIVA sono in grado di inibire totalmente l'induzione e la propagazione della CSD, mentre CgTxGVIA, SNX-482 e nimodipina presentano solo un lieve effetto, o nessun effetto, sono consistenti con ed avvalorano un modello di induzione e propagazione della CSD nel quale l’attivazione dei canali CaV2.1 presinaptici (e forse anche di quelli postsinaptici) e dei recettori NMDA ha un ruolo essenziale (Tottene et al., 2011). Il ruolo dei recettori NMDA è stato ulteriormente indagato, sfruttando i topi KI FKM1 R192Q, che presentano un incrementato rilascio di glutammato da parte dei neuroni piramidali. Contrariamente a quanto riscontrato nei WT, in questi topi l’applicazione di D-PA5 non era in grado di bloccare l’induzione della CSD, ma aumentava invece significativamente la soglia (90 ± 9%) e diminuiva significativamente la velocità (47 ± 1%) rispetto al controllo. Il diverso effetto del D-AP5 riscontrato nei topi WT ed in quelli KI potrebbe suggerire che altri elementi (oltre ai recettori NMDA) potrebbero essere coinvolti nell’induzione e nella propagazione della CSD. Registrazioni in current-clamp in prossimità del sito di eiezione del KCl, alle distanze fisse di 100 e 200 µm, hanno permesso di osservare e distinguere diverse fasi nei cambiamenti di voltaggio indotti dall’applicazione di stimoli di KCl sottosoglia e a soglia; è stato infatti possibile osservare la presenza di tre diversi picchi. Mentre i primi due picchi erano condivisi dalle depolarizzazioni sottosoglia e dalla CSD, la comparsa del terzo picco era specificamente legata all’induzione della CSD. La tecnica del patch-clamp ha permesso di descrivere nel dettaglio le diverse fasi di depolarizzazione, mostrando tuttavia l’ovvia restrizione di limitare l’osservazione ad una sola cellula per volta. Il Ca2+ imaging di fettine caricate con l’indicatore Ca2+ sensibile OGB1-AM ha invece permesso di monitorare allo stesso tempo diversi neuroni a diverse distanze dalla pipetta iniettante KCl dopo lo stesso stimolo. L’esecuzione simultanea di patch clamp e Ca2+ imaging nella stessa fettina ha dimostrato una generale correlazione tra le diverse fasi dei cambiamento di voltaggio registrate in current-clamp ed i picchi nelle tracce di fluorescenza. I possibili significati fisiologici e gli eventuali ruoli nell’induzione e nella propagazione della CSD di queste diverse fasi non sono ancora chiari e sono al momento attuale oggetto di studio nel laboratorio dove ho svolto la mia attività di ricerca. Gli esperimenti di Ca2+ imaging hanno permesso, oltre a quanto già descritto, di osservare incrementi nella concentrazione intracellulare di Ca2+ degli astrociti in risposta agli stimoli di KCl. Gli astrociti possono sostenere ed amplificare la trasmissione eccitatoria glutamatergica tramite rilascio di glutammato che agisce specificamente sui recettori NMDA; il rilascio di glutammato e di altre sostanze da parte degli astrociti è indotto da innalzamenti nella [Ca2+]int, causati a loro volta dal rilascio di diversi neurotrasmettitori (tra cui il glutammato) da parte dei neuroni. Per verificare se la comunicazione reciproca tra neuroni ed astrociti possa essere coinvolta nell’induzione e nella propagazione della CSD, la soglia e la velocità della CSD sono state misurate prima e dopo l’inibizione degli aumenti di Ca2+ intracellulare tramite applicazione di acido ciclopiazonico (CPA, 50 µM), in grado di svuotare gli stores di Ca2+ intracellulari senza influenzare la risposta dei neuroni al KCl. L’applicazione di CPA non influenzava né la soglia di induzione della CSD, né la velocità di propagazione sia nei topi WT che nei topi KI. Questi risultati suggeriscono che l’intercomunicazione tra neuroni ed astrociti non sia rilevante per l’induzione e la propagazione della CSD. La combinazione di Ca2+ imaging e patch clamp ha permesso l’osservazione, in assenza di stimolazione esterna, di attività spontanea che avviene normalmente nei networks neurali della neocorteccia; tale attività si presenta come oscillazioni lente tra periodi di depolarizzazioni indotte da attività sinaptica associate all’insorgenza di potenziali d’azione (up-states) e tra altri periodi in cui l’attività sinaptica diminuisce ed il firing scompare (down-states). Allo stesso tempo è stato possibile osservare la presenza di intense oscillazioni spontanee nella [Ca2+]int degli astrociti. Per verificare se la comunicazione reciproca tra neuroni ed astrociti potesse essere coinvolta nella generazione o nella modulazione dell’attività spontanea neuronale di network, tali oscillazioni spontanee degli astrociti sono state soppresse tramite l’applicazione di CPA. In presenza di CPA gli up-states neuronali erano ancora presenti sia nei topi WT, che nei KI, tuttavia nel primo caso si assisteva ad una riduzione significativa nella frequenza degli up-states (41 ± 3%, p = 0.0001), non riscontrabile nel caso dei topi KI (11 ± 6%, p = 0.12). Questi risultai preliminari sono in accordo con un possibile ruolo dell’intercomunicazione tra neuroni ed astrociti nell’attività spontanea dei network neuronali

The displacement operator is related to the displaced parity operator through a two dimensional Fourier transform. Both operators are important operators in phase space and the trace of both with respect to the density operator gives the Wigner functions (displaced parity operator) and Weyl functions (displacement operator). The generalisation of the parity-displacement operator relationship considered here is called the bi-fractional displacement operator, O(α, β; θα, θβ). Additionally, the bi-fractional displacement operators lead to the novel concept of bi-fractional coherent states. The generalisation from Fourier transform to fractional Fourier transform can be applied to other phase space functions. The case of the Wigner-Weyl function is considered and a generalisation is given, which is called the bi-fractional Wigner functions, H(α, β; θα, θβ). Furthermore, the Q−function and P−function are also generalised to give the bi-fractional Q−functions and bi-fractional P−functions respectively. The generalisation is likewise applied to the Moyal star product and Berezin formalism for products of non-commutating operators. These are called the bi-fractional Moyal star product and bi-fractional Berezin formalism. Finally, analysis, applications and implications of these bi-fractional transforms to the Heisenberg uncertainty principle, photon statistics and future applications are discussed.

The displacement operator is related to the displaced parity operator through a two dimensional Fourier transform. Both operators are important operators in phase space and the trace of both with respect to the density operator gives the Wigner functions (displaced parity operator) and Weyl functions (displacement operator). The generalisation of the parity-displacement operator relationship considered here is called the bi-fractional displacement operator, O(α, β; θα, θβ). Additionally, the bi-fractional displacement operators lead to the novel concept of bi-fractional coherent states. The generalisation from Fourier transform to fractional Fourier transform can be applied to other phase space functions. The case of the Wigner-Weyl function is considered and a generalisation is given, which is called the bi-fractional Wigner functions, H(α, β; θα, θβ). Furthermore, the Q−function and P−function are also generalised to give the bi-fractional Q−functions and bi-fractional P−functions respectively. The generalisation is likewise applied to the Moyal star product and Berezin formalism for products of non-commutating operators. These are called the bi-fractional Moyal star product and bi-fractional Berezin formalism. Finally, analysis, applications and implications of these bi-fractional transforms to the Heisenberg uncertainty principle, photon statistics and future applications are discussed.

Dans le cadre d’un projet collaboratif entre le laboratoire XLIM (UMR 7252 du CNRS et de l'Université de Limoges) et le laboratoire de recherche IPHT situé à Jena en Allemagne, mon projet de thèse consiste à développer un laser à fibre dopée thulium bi-fréquences largement accordable à impulsions synchrones pour la réalisation d’une source Térahertz puissante et accordable. Basé sur l’utilisation de deux réseaux de Bragg en volume (VBGs) et d’une fibre dopée thulium à double gaine et à maintien de polarisation (diamètre de coeur = 20 μm) fabriquée par la méthode REPUSIL, un laser mono-fréquence et bi-fréquences largement accordable a été réalisé et étudié en régime continu. Une accordabilité de 1nm à 144 nm a été obtenue avec une puissance supérieure à 4,5 W et un bon contraste signal sur bruit (~45 dB) et une largeur spectrale inférieure à 0,1 nm. En régime déclenché, un modulateur acousto-optique (AOM) a été utilisée en espace libre dans la cavité laser afin de générer les impulsions. La fibre à double gaine a été remplacée par une fibre dopée thulium à large coeur (40 μm) appelée FA-LPF pour repousser le seuil d’apparition des effets non-linéaires et travailler avec une fibre courte pour diminuer la durée d’impulsion et augmenter la puissance crête des impulsions obtenues. Une source déclenchée bi-fréquences largement accordable (de 3,8 nm jusqu’à 120nm) a été développée avec une puissance crête supérieure à 8 kW et une durée d’impulsion autour de 26 ns obtenues indépendamment de la valeur de Δλ pour une fréquence de répétition de 1 kHz. Un contraste supérieur à 20 dB a été obtenu limité par les pics parasites générés par le FWM pour les valeurs de Δλ inférieures à 45 nm. La largeur spectrale des raies lasers mesurée à 3 dB du maximum a été inférieure à 0,3 nm
As part of a collaborative project between the XLIM laboratory (UMR 7252 of the CNRS and the University of Limoges) and the IPHT research laboratory located in Jena, Germany, my thesis project consists in the development of a widely tunable dual-wavelength synchronous pulsed thulium doped fiber laser for the realization of an efficient and tunable terahertz source. Based on the use of two volume Bragg gratings (VBGs) and a double-clad, polarization-maintaining thulium doped fiber (core diameter = 20 μm) manufactured by the REPUSIL method, a widely tunable single-wavelength laser and dual-wavelength laser has been realized and studied in continuous regime. A tunability of 1 nm to 144 nm was obtained with a power more than 4.5 W and a good signal-to-noise contrast (~ 45 dB) and a spectral linewidth less than 0.1 nm. In pulse regime, an acousto-optic modulator (AOM) was used in free space in the laser cavity to generate the pulses. The double-clad fiber has been replaced by a large-core thulium doped fiber (40 μm) called FA-LPF to to fend off the threshold of non-linear effects and work with a short fiber to decrease the pulse duration and increase the peak power of the obtained pulses. A widely tunable (from 3.8 nm to 120 nm) Q-switched dual-wavelength synchronous-pulsed thulium-doped fiber laser was developed with a peak power more than 8 kW and a pulse duration around 26 ns obtained independently of the value of Δλ at 1 kHz of repetition rate. A contrast higher than 20 dB was obtained limited by the FWM peaks generated for Δλ values below 45 nm. The spectral linewidth of the laser measured at 3 dB of the maximum was less than 0.3 nm

碩士
國立中山大學
電機工程學系研究所
94
This thesis includes two topics. One is a low-power high-speed 8-bit pipelining CLA design using dual threshold voltage (dual- Vth) domino logic. The other is a low-cost digital I/Q separator for DVB-T receivers. A high speed and low power 8-bit CLA using dual- Vth domino logic blocks arranged in a PLA-like style with pipelining is presented. According to parallely precharge and sequentially evaluate in a cascaded set of domino logic blocks, transistors in the precharge part and the evaluation part of dual- Vth domino logic are, respectively, replaced by high Vth transistors to reduce subthreshold leakage current through OFF transistors, and low Vth transistors. Moreover, an nMOS transistor is inserted in the precharge phase of the output inverter such that the two-phase dual- Vth domino logic can be properly applied in a pipeline structure. Consequently, the proposed design keeps the advantage of high speed while attaining the effect of low power dissipation. A low-cost digital I/Q separator is presented in the second part of this thesis. Using digital I/Q separator in place of the traditional analog I/Q separator guarantees the design conquer gain and phase mismatch problems between the I and Q channels. The proposed design can berealized by inverters and shifters such that the goal of low cost can be achieved.

abstract: Built-in-Self-Test (BiST) for transmitters is a desirable choice since it eliminates the reliance on expensive instrumentation to do RF signal analysis. Existing on-chip resources, such as power or envelope detectors, or small additional circuitry can be used for BiST purposes. However, due to limited bandwidth, measurement of complex specifications, such as IQ imbalance, is challenging. In this work, a BiST technique to compute transmitter IQ imbalances using measurements out of a self-mixing envelope detector is proposed. Both the linear and non linear parameters of the RF transmitter path are extracted successfully. We first derive an analytical expression for the output signal. Using this expression, we devise test signals to isolate the effects of gain and phase imbalance, DC offsets, time skews and system nonlinearity from other parameters of the system. Once isolated, these parameters are calculated easily with a few mathematical operations. Simulations and hardware measurements show that the technique can provide accurate characterization of IQ imbalances. One of the glaring advantages of this method is that, the impairments are extracted from analyzing the response at baseband frequency and thereby eliminating the need of high frequency ATE (Automated Test Equipment).
Dissertation/Thesis
M.S. Electrical Engineering 2012