Dissertations / Theses on the topic 'Q modulator'
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Unlu, Ozkaya Ayse. "Design And Implementation Of A Broadband I-q Vector Modulator And A Feedforward Linearizer For V/uhf Band." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611565/index.pdf.
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Considering the requirements of the commercial and military applications on amplitude and phase linearity, it is necessary to reduce nonlinearity of the amplifiers. There are several linearization techniques that are used to reduce nonlinearity effects. Feedforward linearization technique is known as one of the best linearization methods due to its superior linearization performance and broadband operation. Vector modulators which allows amplitude and phase modulation simultaneously, is the most important component of a feedforward system.
In this thesis, first of all a broadband V/UHF vector modulator designed and implemented. Then a feedforward system is investigated and implemented using the designed vector modulator for V/UHF band.
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Abdi, Abyaneh Mohammad. "Génération des signaux agrégés en fréquences dans le contexte de LTE-A." Electronic Thesis or Diss., Paris, ENST, 2016. https://pastel.hal.science/tel-03689710.
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Dans ce travail de thèse, on a proposé une structure de génération des signaux multi-porteuse afin de créer plusieurs oscillateurs locaux (OL ) tout en utilisant qu’un modulateur I/Q. Ces signaux peuvent être utilisés dans les récepteurs de LTE-A pour la transposition des signaux agrégé en fréquence vers la bande de base. On développe la structure afin de l’utiliser en émetteur répondant aux normes du standard LTE-A. La nouvelle structure nous permet de générer n signaux agrégés en fréquences, de manière simultanée, par une seule chaîne de transmission (c.a.d un modulateur I/Q, un OL). En utilisant cette structure on réduit le nombre de circuits utilisés, en comparaison du cas où n signaux agrégés en fréquences sont générés par n émetteurs. La fréquence d’échantillonnage est réduite dans notre cas par rapport au cas où les signaux sont générés directement de la bande de base à la bande RF avec des convertisseurs analogiques numériques adéquats. Dans la troisième partie, on se concentre sur les imperfections et les non linéarités du modulateur I/Q dans le cadre de notre structure multibande. On modélise le fonctionnement du modulateur multi-bande en utilisant les échantillons en entrée et en sortie. Notre modèle est dérivé de la série de Volterra qui prends en compte les effets non linéaires et les effets mémoires ainsi que les imperfections du modulateur I/Q. Puis, on obtient la fonction "inverse" du modèle et on l’applique à l’entrée du modulateur afin de corriger et linéariser la sortie du modulateur I/Q. La fonction "inverse" est appelée DPD (en anglais : Digital Pre-Distortion). Enfin, on a évalué le modèle et la DPD en simulations et en mesuresIn this dissertation, a signal generation structure is proposed using which a multitone Local Oscillator (LO) signal is created by a single I/Q modulator. These LOs can be used in the CA receivers to down-convert the transmitted component carriers simultaneously. The multi-tone LO signal structure is further developed to be used at the transmitter as a CA generation solution. Using the proposed structure n-component carriers can be generated in parallel. This structures requires lower sampling rates with respect to the case where RF signals are synthesized directly by digital-to- analog converters. Moreover, less circuitry is required, because one single I/Q modulator is used to generate n component carriers, instead of n I/Q modulators. This work follows on investigating the origin of impairments and mild nonlinearities in our I/Q modulator. To overcome these problems, we focus on the functionality of the overall system rather than each component of the I/Q modulator. This method is called behavioral modeling. Once the nonlinear model is obtained, if its inverse function is applied to the input, a linearized output is expected. The generation of the inverse function is called Digital Pre-Distortion (DPD). We propose a tri-band behavioral model for nonlinearities and impairments in tri-band CA using our I/Q modulator. Furthermore, the DPD of the model is evaluated in simulations and experiments
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Mayer, Sebastian. "Hilbert modular forms for the fields Q([square root]5), Q([square root]13) and Q([square root]17)." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=985767022.
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McCorkindale, Jane. "The 2-modular representation theory of PSUâ†3(q), q #ident to# 3(mod 4)." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279980.
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Kassaei, Payman L. 1973. "p-adic modular forms over Shimura curves over Q." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85304.
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Malmström, Mikael. "All-fiber modulators for laser applications." Doctoral thesis, KTH, Laserfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-105863.
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The objective of this thesis was to explore the usefulness of all-fiber modulators for laser applications. The modulators were all based on refractive index change achieved in the core of the studied fiber- components, exploiting either the elasto-optic effect or the electro-optic effect. This was realized with the aid of electrodes inside the fiber cladding close to the core that provided either thermal stress in the core, or an electric field across the core. The electrodes consisted of low melting-point alloys, such as BiSn and AuSn, which were pushed into the hole-fiber, in the liquid state, which then solidified to form solid electrodes filling the entire hole. Together with an analyzer such as a polarizer or an interferometer the achieved refractive index modulation in the core could then be translated into an amplitude modulation of the guided light, which was subsequently utilized for switching fiber-lasers to generate cavity dumped, Q-switched, or mode-locked pulses. The fast rise/fall-time of a few nanoseconds for the elasto-optic devices was due to the fast thermal expansion of the electrodes. The maximum repetition rate, however, was limited to a few tens of kHz, due to the slow thermal processes for dissipation of the applied energy. The electro-optic fiber components, which displayed similar rise/fall-times on the other hand, showed a much higher cut-off frequency of 16 MHz. The electro-optic, all-fiber switch was also employed to select single pulses at 1 MHz repetition rate out of a 7 MHz train of pulses. Additionally, simulations using the finite element method were performed in order to gain insight and to explain the underlying processes of the observed response of a long-period grating written in a 2-hole fiber with electrodes, when applying HV-pulses to one of these. The thesis shows that the studied fiber-components show great potential of becoming complementary devices with high damage threshold for all-fiber laser applications in the future.QC 20121129
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Sabra, Mostafa. "Développement de lasers à fibres thulium bi-fréquences à impulsions synchrones pour la réalisation de sources Térahertz." Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0118.
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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 nmAs 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
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Preece, Daryl. "Novel uses of spatial light modulators in optical tweezers." Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2619/.
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In recent years spatial light modulators (SLMs) have become an integral part of many optical trapping experiments. Yet their usefulness, which stems from their flexibility, is often under exploited. In this thesis I seek to demonstrate how it is possible to expand the range of optical trapping applications that may benefit from the use of spatial light modulators. From exploring the benefits of increased resolution to demonstrating novel applications like position clamping and polarization control, I show how SLMs are a resource which can benefit optical trapping in new and unconventional ways. The optical properties of liquid crystals have long been known however it is only recently that they have been applied to optical tweezers. The physics and operation of spatial light modulators are discussed in chapter 1, with specific attention paid to those aspects of operation which are of pertinent practical use to optical trapping. In chapter 2 it is shown how phase only modulation can be used to create effective holographic optical tweezers systems which are capable of manipulating micron scale particles and measuring pico-Newton forces. Chapter 3 charts the development and characterization of a 4 Mega-pixel spatial light modulator which was created as an improvement on current SLM technology. The role of SLMs in utilising lights angular momentum as a tool for creating rotational torque is discussed in chapter 4. In chapter 5 describes how SLMs can be used to create torques based the application of spin angular momentum to birefringent particles. We show, in chapter 6 how with suitable software engineering it is possible to both move optical traps and track particles in real time. Since the use of SLMs has been previously been limited by their bandwidth constraints we discuss in chapter 7 the use spatial light modulators in closed loop systems. We finish with a discussion of the use of SLMs in a new technique that may be applied to microrheology.
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Hart, Jaynee E. "Biochemical and genetic approaches to modulate phototropin photoreceptor sensitivity." Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/30991/.
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The necessity of light for plants to sustain their autotrophic lifestyle has made the optimization of growth to maximize light capture a crucial strategy for survival in light-limiting environments. Increases in light capture can be achieved through alterations in plant architecture, such as modifications to leaf position and stem length. Responses to the light environment are mediated by a network of photoreceptor proteins, which sense specific wavelengths of light and respond to light excitation by initiating signaling. Higher plants respond to red and far-red light through the phytochrome family, blue light through cryptochromes, the zeitlupe family, and phototropins, and UV-B light through the UV RESISTANCE LOCUS 8 photoreceptor. Of these photoreceptor proteins, the phototropins (phots) are perhaps the most closely tied to photosynthetic efficiency. Higher plant phots, phot1 and phot2, mediate leaf expansion to maximize the surface area available for light capture as well as control movement and positioning responses, such as petiole inclination, movement towards more favorable light conditions through phototropism, and, at a cellular level, chloroplast movement. Furthering the role of phots in optimizing responses upstream of photosynthesis, phot1 and phot2 also control stomatal opening in response to blue light, allowing the uptake of carbon dioxide into the leaf for fixation into sugars. In general, these responses are redundantly coordinated by both phot1 and phot2, with phot1 acting as the primary sensor due to its greater sensitivity. Because of the profound effect phots have on photosynthetic competence, the studies presented here examine phot1 with the goal of understanding the physiological role of phot1 sensitivity in plants and explore the possibility that enhancing phot1 sensitivity could increase plant growth. Phots consist of two N-terminal light sensing LOV (Light, Oxygen or Voltage) domains, LOV1 and LOV2, coupled to a serine/threonine kinase domain at the C-terminus. Each of the LOV domains bind a flavin mononucleotide (FMN) chromophore that allows these domains to perceive blue light. In darkness, FMN is non-covalently bound within each of the LOV domains, which repress the activity of the kinase domain. When FMN is excited by blue light, a covalent bond is formed between a conserved cysteine residue present within each LOV domain and FMN. LOV2 specifically is coupled to the kinase domain through two alpha helices, Jα and A’α, which become disordered following the formation of the covalent photoadduct. The unfolding of these alpha helices relieves repression of the kinase domain, initiating signaling. The onset of phot1 signaling is characterized by phot1 autophosphorylation and the dephosphorylation of the phot1 signaling partner NON-PHOTOTROPIC HYPOCOTYL 3 (NPH3). Over time, the covalent photoadduct decays and phot1 returns to its inactive dark state, completing the photocycle. The chemistry of the phot1 photocycle in vitro is understood in detail, but its downstream signaling following activation remains relatively elusive, with only a handful of signaling partners and phosphorylation substrates identified. For the sensitivity of phot1 to be thoroughly explored, how the phot1 photocycle affects plant growth as well as how phot1 activity is modulated by signaling partners needed to be addressed. Therefore, a biochemical approach was used to introduce mutations within LOV2 to slow its dark reversion to prolong signaling and investigate how this modulates phot1 sensitivity in vitro and in planta, and, secondly, a genetic strategy was employed to uncover whether any signaling processes can modulate phot1 sensitivity in plants. Compared to other photoreceptors that receive blue light through LOV domains, dark reversion of phot1 following a light stimulus is relatively fast, with the lit state lasting only approximately 15 minutes, while other LOV domains remain activated for many hours. To generate slow photocycle mutants of phot1, previous characterizations of slow photocycling LOV domains were exploited to engineer the phot1 photocycle to have a slower dark reversion by introducing mutations into LOV2. To study the photocycle in vitro, the phot1 light-sensing module consisting of the LOV1 and LOV2 domains (LOV1+LOV2) was heterologously expressed and purified from E. coli and the photocycle was measured spectrophotometrically. Using this approach, 13 LOV2 variants were generated and examined to identify slow photocycle mutants. Three mutations in LOV2, N476L, V478I, and L558I, were found to slow the LOV1+LOV2 photocycle in vitro. Following identification, these mutations were introduced into full-length phot1 expressed heterologously in insect cells to verify the autophosphorylation activity of each mutant. Following the characterization of the candidate slow photocycle mutants in vitro, each phot1 photocycle mutant was examined in planta in a phot1phot2 double mutant background to see whether possession of a slow photocycle increased phot1 sensitivity. Of the three candidate mutations, V478I and L558I were verified as possessing a slow dark reversion through the phosphorylation status of NPH3. NPH3 is dephosphorylated in a phot1-dependent manner following light treatment; it was found that in the presence of wild-type phot1, the phosphorylated form of NPH3 is recovered around one hour following a return to darkness after phot1 stimulation by blue light. By contrast, the dephosphorylated state of NPH3 was sustained in phot1-V478I and -L558I for a substantially longer period of time, consistent with a slow phot1 photocycle and prolonged phot1 activation in these mutants. Surprisingly, it was found that these mutants were less sensitive than wild-type phot1 for phototropism in response to low intensity light treatments. Furthermore, biomass accumulation was not increased in the phot1-L558I mutant under growth conditions consisting of very low light. While the photocycle mutants did not exhibit increased sensitivity or growth in response to continuous light treatments, evidence from collaborators indicated that phot1-L558I is more efficient than wild-type phot1 for the chloroplast accumulation response following brief pulses of blue light. While the role of the phot1 photocycle under continuous irradiation remained unclear, this enhanced chloroplast accumulation response implies that the phot1 photocycle is important for its sensitivity to brief irradiations. Unlike phot1, further work with phot2 later indicated that introducing a slow photocycle mutation to phot2 LOV2 can significantly increase growth in a phot1phot2 mutant background under continuous low light. To investigate other factors that may affect phot1 sensitivity, a genetic screen was undertaken in an attempt to identify suppressors of phot1 activity. The LOV2Kinase (L2K) transgenic line, which expresses a truncated version of phot1 in a phot1phot2 double mutant background, was previously found to be unable to respond to low-intensity blue light, though it can mediate phot1 responses when the light intensity is increased. Because L2K possesses this conditional phenotype, random mutations were introduced into the genome of L2K-expressing plants and a screen was established to identify mutants that were able to respond to low-intensity light with the hypothesis that those mutations could lie within suppressors of phot1 activity, allowing L2K to signal under circumstances where it ordinarily could not. Using this approach, three independent candidate suppressor mutants were identified that had increased sensitivity for the petiole positioning response under low light. One suppressor mutant was identified as a novel allele of the phytochrome B red light receptor, the second is likely to be a mutant of a transcription factor, and the identity of the third candidate suppressor is still not known, though it overexpressed the L2K protein. These candidate suppressors may represent novel modulators of phot1 activity and possible mechanisms for how these candidate suppressors may act on phot1 activity are discussed. In summary, both the biochemical and genetic approaches yielded mutants with increased sensitivity for phot1-mediated responses, enabling a more detailed understanding of how phot1 sensitivity influences its activity and plant growth.This lays the groundwork for extending the increased sensitivity observed in response to pulses in the photocycle mutants to responses other phot1-mediated responses, and for integrating new models of suppression of phot1 activity into our framework for phot1 activation and signaling.
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Dembélé, Lassina. "Explicit computations of Hilbert modular forms on Q(square root 5)." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38477.
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We compute the eigenvalues of the first few Hecke operators Tp (N( p ) ≤ 100) for all Hilbert modular forms on Q5 of parallel weight 2 and level of norm less than 500. This is done by exploiting the Jacquet-Langlands correspondence which allows us to transfer such computations to forms on the (totally definite) Hamilton quaternion algebra over Q5 . We use these computations to test numerically a conjecture of Oda on periods of Hilbert modular forms.
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Jennings, Derek. "An investigation into modular forms, Q-series, partitions and related applications." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239512.
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Mano, Toshiyuki. "Differential equations for Hilbert modular forms of Q([square root]{2})." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/150419.
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Gherman, Bogdan George. "Modular neural networks applied to pattern recognition tasks." Thesis, University of Kent, 2016. https://kar.kent.ac.uk/57814/.
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Pattern recognition has become an accessible tool in developing advanced adaptive products. The need for such products is not diminishing but on the contrary, requirements for systems that are more and more aware of their environmental circumstances are constantly growing. Feed-forward neural networks are used to learn patterns in their training data without the need to discover by hand the relationships present in the data. However, the problem of estimating the required size of the neural network is still not solved. If we choose a neural network that is too small for a particular given task, the network is unable to "comprehend" the intricacies of the data. On the other hand if we choose a network size that is too big for the given task, we will observe that there are too many parameters to be tuned for the network, or we can fall in the "Curse of dimensionality" or even worse, the training algorithm can easily be trapped in local minima of the error surface. Therefore, we choose to investigate possible ways to find the 'Goldilocks' size for a feed-forward neural network (which is just right in some sense), being given a training set. Furthermore, we used a common paradigm used by the Roman Empire and employed on a wide scale in computer programming, which is the "Divide-et-Impera" approach, to divide a given dataset in multiple sub-datasets, solve the problem for each of the sub-dataset and fuse the results of all the sub-problems to form the result for the initial problem as a whole. To this effect we investigated modular neural networks and their performance.
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Machado, de Oliveira Gisela Sofia Mendes. "Modulation of calcium signalling in human sperm by nitric oxide." Thesis, University of Birmingham, 2008. http://etheses.bham.ac.uk//id/eprint/197/.
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Nitric oxide (NO) generation by nitric oxide synthase (NOS) is implicated in gamete interaction and fertilization. In vitro studies were undertaken to assess the ability of human sperm and cumulus cells (surrounding the oocyte) to generate NO, investigate the mechanism of action of NO, the NO-mediated [Ca\(^{2+}\)]\(_i\) signalling pathways, the possible interaction of NO with progesterone (a product of cumulus) and its impact in the regulation of human sperm functions. Immunofluorescent staining revealed constitutive NOS in human cumulus. DAF-FM diacetate staining demonstrated NO production by cumulus cells. Human sperm exposure to NO donors caused mobilization of stored Ca\(^{2+}\) by a mechanism not requiring guanylate cyclase activation but mimicked by S-nitrosoglutathione (GSNO; an S-nitrosylating agent). Dithiothreitol application, to reduce protein –SNO groups, rapidly reversed the actions of NO and GSNO on [Ca\(^{2+}\)]\(_i\). The effects of NO, GSNO and dithiothreitol on protein S-nitrosylation, assessed using the biotin-switch assay, closely paralleled their actions on [Ca\(^{2+}\)]\(_i\). Progesterone mobilizes stored Ca\(^{2+}\) in human sperm, by a mechanism involving ryanodine receptor (RyR) activation. Pre-treatment with NO reduced the amplitude of the Ca\(^{2+}\) response to ryanodine (a RyR agonist), suggesting convergence of the actions of NO and ryanodine. Sperm pre-treatment with NO greatly enhanced the progesterone effect on [Ca\(^{2+}\)]\(_i\), causing a prolonged increase in flagellar excursion. We conclude that NO regulates mobilization of stored Ca\(^{2+}\) in human sperm by protein (possibly RyRs) S-nitrosylation, that this action is synergistic with that of progesterone and that this synergism is potentially highly significant in gamete interactions leading to fertilization.
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Bryant, Jack Alfred. "Position-dependent modulation of promoter activity in Escherichia coli." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4197/.
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Bacterial gene expression is primarily regulated at the initial step of transcription initiation. This regulation has traditionally been viewed as due to the DNA sequence of promoters and factors that bind to them. However, the bacterial chromosome is a highly compacted and ordered structure. To date, the effects of position within the chromosome on promoter activity have barely been investigated. Here, I report that activity of a single promoter, inserted at different loci in the Escherichia coli chromosome, is dependent upon position within the chromosome. Quantification of genomic DNA at a number of loci showed this was unrelated to gene dosage. Drastic changes in position-dependent hierarchies of promoter activity were observed on entry into stationary phase. However, no correlation between the orientation of a promoter, with respect to replication, and its activity was found. Several factors are involved in this variation, including local sequence context. Increased promoter activity at origin-proximal loci was shown to be due to DNA supercoiling, maintained by the action of DNA gyrase. Transcription was shown to have a negative influence on the activity of downstream promoters. Further to this, the position of a promoter, with respect to a repressor-encoding gene, had an effect on its repression, further suggesting a role for genome organisation in the regulation of transcription. Finally, extended protein occupancy domains were shown to repress activity of inserted promoters, indicating that these domains act to silence the genes they encode. The combined data show that the position of a promoter within the E. coli chromosome plays a significant part in transcriptional regulation, and that structure of the chromosome is also likely to play a role.
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Chang, Jia Kang. "Investigation on applying modular ontology to statistical language model for information retrieval." Thesis, University of Central Lancashire, 2015. http://clok.uclan.ac.uk/11803/.
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The objective of this research is to provide a novel approach to improving retrieval performance by exploiting Ontology with the statistical language model (SLM). The proposed methods consist of two major processes, namely ontology-based query expansion (OQE) and ontology-based document classification (ODC). Research experiments have required development of an independent search tool that can combine the OQE and ODC in a traditional SLM-based information retrieval (IR) process using a Web document collection. This research considers the ongoing challenges of modular ontology enhanced SLM-based search and addresses three contribution aspects. The first concerns how to apply modular ontology to query expansion, in a bespoke language model search tool (LMST). The second considers how to incorporate OQE with the language model to improve the search performance. The third examines how to manipulate such semantic-based document classification to improve the smoothing accuracy. The role of ontology in the research is to provide formally described domains of interest that serve as context, to enhance system query effectiveness.
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Ladd, Watson Bernard. "Algebraic Modular Forms on SO5(Q) and the Computation of Paramodular Forms." Thesis, University of California, Berkeley, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10817152.
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This dissertation describes a result that compares two level subgroups on different inner forms of GSp(4), and then uses this result and a conjecture of Ibukiyama’s to compute paramodular forms for all prime levels below 400. In the process 78 generic forms were computed, of which 47 had not been previously computed.
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Turko, Paul. "An investigation into the transport and modulation of synaptophysin positive vesicles." Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/3594/.
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Neuronal function, survival and architecture all critically depend on the precise transport of intracellular proteins to a vast array of synaptic connections. Disrupted intracellular transport leads to deficits in synaptic transmission, irregular cell morphology, misallocated organelles and cell death. In addition, axonal transport deficits have been noted in the early stages of several debilitating neurological conditions, thus, axonal transport deficits may contribute to disease progression. This makes it important that we understand the contribution of axonal transport to both physiological and pathophysiological cellular processes and to the transport of essential organelles. As such the aims of this project were as follows: to investigate the long-term transport properties of visualised synaptic vesicles, to investigate whether vesicle transport could be modulated by changes in neuronal activity, to examine whether vesicle transport deficits exist in certain disease models and to develop novel assays for focusing the study of vesicle transport to specific neuronal cell types. To investigate the transport properties of visualised synaptic vesicles we exploited a lentiviral vector to express a fluorescently tagged version of an abundant synaptic vesicle transmembrane protein, synaptophysin. Using synaptophysin-GFP (syp-GFP) as a synaptic vesicle marker we then tracked the movements of synaptic vesicles in the axons of dissociated hippocampal neurons. Synaptophysin-GFP expression revealed two fluorescent vesicle populations, one population that moved in a rapid and bi-directional manner and one population that accumulated into clusters of stationary vesicles at putative presynaptic sites. Each vesicle population was analysed independently. Moving vesicles were termed motile particles, whilst vesicle accumulations were termed vesicle clusters. To investigate potential activity-dependent changes in vesicle transport and vesicle cluster localisation we used acute or co-culture application of the GABAA receptor antagonists bicuculline (bic) (20µM) or Gabazine (gbz) (20µM), which can generate increased neuronal activity or epileptiform-like activity in vitro. As a result of bic treatment we observed a significant decrease in the size of stationary presynaptic vesicle clusters. Under control conditions the average size of vesicle clusters was 14.7±1.67µm2, reducing to 12.1±1.41µm2 following 10 hours of increased neuronal activity (p=0.0042, Wilcoxon-matched pairs test, n=80, 8 experiments). In addition, increased neuronal activity also led to a significant increase in vesicle cluster turnover, which increased from 28±6.89% under control conditions to 44±8.46% as a result of increased neuronal activity (p=0.0261, unpaired student t-test, n=25, 11 experiments). However, these changes were not accompanied by any alteration in vesicle transport, with the speed, the density and the proportion of motile particles remaining unaffected by increased neuronal activity (table 3.1). This suggests that each vesicle population may therefore be differentially modulated by increased neuronal activity. To probe deeper for potential activity-dependent vesicle transport changes we restricted our study of vesicle transport to a specific axonal subtype, the hippocampal mossy fiber. To visualise mossy fiber vesicle transport, lentivirus expressing syp-GFP was pressure injected directly into the cell body layer of the dentate gyrus (DG) in hippocampal organotypic slice cultures. This revealed syp-GFP positive vesicles occupying both small (2-15µm3) and large (˃15µm3) mossy fiber synaptic terminals, which were found in and along the stratum lucidum. By examining the distribution of vesicle clusters at different time points following gbz or bic treatment (0hrs, 4hrs, 12hrs, 24hrs and 48hrs) we were able to show that epileptiform activity caused a delayed (>12 hours) but significant decrease in the proportion of large vesicle clusters. By 24 and 48 hours there was a significant decrease in the proportion of large vesicle clusters following bic treatment, decreasing from 9.4±1.21% under control conditions (n=11, 5 experiments) to 4.84%±0.72% after 24hrs (n=10, 4 experiments) and to 3.3±0.73% after 48hrs (n=12, 5 experiments), P<0.001, one-way ANOVA. This decrease in the proportion of large vesicle clusters may represent an important pathophysiological change triggered by epileptiform activity. Importantly, we also observed the same decrease in the proportion of large vesicle clusters in a mouse model of Rett syndrome, which models a severe neurodevelopmental disorder caused by a mutation in the gene coding MeCP2. As a consequence of bic treatment we observed a significant decrease in the proportion of large vesicle clusters from 7.2% ±1.78% in control cultures (n=6, 2 experiments), down to 0.9% ±0.6% in 48hr bic treated cultures (n=8, 3 experiments) and recovering to 6.9%±1.5% following bic wash out (n=11, 3 experiments); p<0.0001, one way ANOVA. Interestingly, Mecp2Stop/y hippocampal organotypic slices showed a greater decrease in the proportion of large vesicle clusters following 48hrs of bic treatment. The proportion of large vesicle clusters in 48hr bic treated WT slices was 3.3%±0.73%, whilst in 48rs bic treated Mecp2Stop/y slices it was 0.9%±0.6%, p=0.01, two-way ANOVA. These observations suggest that Mecp2Stop/y hippocampal organotypic slices are more sensitive to epileptiform activity than WT slices and may possess deficits in the vesicle transport system. Primary dissociated hippocampal cell cultures benefit from being both optically and experimentally accessible but lack a defined cellular arrangement. This hampers both the identification and study of specific cell types and specific synaptic connections. To overcome this limitation we developed a modified dissociated cell culture assay for defining the arrangement of dissociated hippocampal neurons. We cultured purified DG and CA3 cell populations in close opposition using a magnetic barrier, but transduced only DG granule cells with lenti-synaptophysin-GFP in order to visualise vesicle transport specifically in mossy fibers. Immunocytochemistry and vital dyes were used to confirm that specific cell populations could be cultured in close proximity, to confirm that lentiviral transduction was highly selective to DG granule cells and to post-hoc identify that vesicle trafficking was occurring specifically in mossy fibers. Using this method it was possible to image vesicle transport specifically in mossy fibers and to investigate vesicle cluster dynamics at putative MF-CA3 synapses. We conclude that this method is a significant improvement to previous techniques because dissociated cells can be arranged to form physiologically relevant synaptic connections, whilst remaining highly accessible to both live imaging and experimental manipulation.
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Landassuri, Moreno Victor Manuel. "Evolution of modular neural networks." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3243/.
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It is well known that the human brain is highly modular, having a structural and functional organization that allows the different regions of the brain to be reused for different cognitive processes. So far, this has not been fully addressed by artificial systems, and a better understanding of when and how modules emerge is required, with a broad framework indicating how modules could be reused within neural networks. This thesis provides a deep investigation of module formation, module communication (interaction) and module reuse during evolution for a variety of classification and prediction tasks. The evolutionary algorithm EPNet is used to deliver the evolution of artificial neural networks. In the first stage of this study, the EPNet algorithm is carefully studied to understand its basis and to ensure confidence in its behaviour. Thereafter, its input feature selection (required for module evolution) is optimized, showing the robustness of the improved algorithm compared with the fixed input case and previous publications. Then module emergence, communication and reuse are investigated with the modular EPNet (M-EPNet) algorithm, which uses the information provided by a modularity measure to implement new mutation operators that favour the evolution of modules, allowing a new perspective for analyzing modularity, module formation and module reuse during evolution. The results obtained extend those of previous work, indicating that pure-modular architectures may emerge at low connectivity values, where similar tasks may share (reuse) common neural elements creating compact representations, and that the more different two tasks are, the bigger the modularity obtained during evolution. Other results indicate that some neural structures may be reused when similar tasks are evolved, leading to module interaction during evolution.
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Li, Zhiyuan. "Analysis of factors that modulate the toxicity of the yeast prion protein Rnq1." Thesis, University of Kent, 2016. https://kar.kent.ac.uk/55116/.
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Prions are infectious proteins that form transmissible, self-propagating amyloids that convert protein from its normal state into the prion state. The accumulation of amyloid is the causative agent of several neurodegenerative diseases, for instance, Huntington’s disease, which is caused by a polyglutamine expansion in the huntingtin (Htt) protein. In this study, a yeast-based Huntington’s disease model was created to investigate the mechanism of amyloid toxicity and how nuclear genes modulate this toxicity. The model amyloid used was Rnq1, a transferable epigenetic modifier which is able to form a prion known as [PIN+]. [PIN+] is known to enhance the formation of polyglutamine aggregates in yeast. In this study, a series of cellular assays were employed to determine the mechanism of Rnq1-mediated cytotoxicity and compared with polyglutamine-rich-protein-mediated cytotoxicity dependent upon the [PIN+] prion. In [PIN+] cells RNQ1 overexpression leads to a significant increase in the production of reactive oxygen species (ROS). Furthermore, overexpression of RNQ1 resulted in a nuclear migration defect in [PIN+] cells. Upf1 (Up-frameshift protein 1), a highly conserved protein that plays an important role in nonsense-mediated mRNA decay, was found to modify amyloid toxicity. In a upf1Δ deletion strain, both Rnq1 and polyglutamine-rich-protein-mediated cytotoxicity were suppressed in a [PIN+] background. To further study the novel role of Upf1 in amyloid toxicity, a combination of cell biological and genetic approaches were being employed.
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Dally, Jordanna. "Evaluation of novel epoxy-tigliane compounds as modulators of dermal fibroblast-myofibroblast differentiation, scar tissue resolution and fibrosis, and elucidation of their underlying mechanisms of action." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/120278/.
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EBC-46 and EBC-211 are novel epoxy-tiglianes found to occur naturally within seeds of the Fontain's Blushwood Tree, indigenous to the Queensland tropical rainforest in Australia. The Australian biotechnology company, QBiotics Group, has demonstrated that EBC-46 stimulates enhanced dermal wound healing responses in vivo, following cancer treatment and tumour destruction in domesticated animals. Consequently, QBiotics is developing EBC-46 as both a human and veterinary anti-cancer therapy. However, little is known on how the epoxy-tiglianes induce their exceptional healing effects; manifested as rapid wound re-epithelialisation, wound contraction/closure and minimal scarring. This study aimed to determine how EBC-46 and EBC-211 mediate these exceptional wound healing effects in vitro, via analysis of dermal fibroblast (DF)/myofibroblast genotypic and phenotypic responses; following epoxy-tigliane treatment (0.001 - 10 μg/mL). A number of wound healing responses were assessed, such as transforming growth factor-β1 (TGF-β1)-driven DF-myofibroblast differentiation, extracellular matrix (ECM) synthesis/turnover, global gene expression and underlying signalling pathways. Studies exhibited that EBC-46 and EBC-211 significantly inhibited α-smooth muscle actin (αSMA) expression, stress fibre formation and myofibroblast formation at 0.1 μg/mL and 10 μg/mL, respectively. Such concentrations were also shown to reduce type I/III collagen; and up-regulate matrix metalloproteinase-1 (MMP-1) gene and protein levels. The epoxy-tiglianes also increased elastin, hyaluronan and pericellular coat synthesis, via up-regulated hyaluronan synthase (HAS) expression. Microarray analysis and protein level validation identified numerous differentially expressed genes in epoxy-tigliane-treated DFs. Up-regulated genes included proteinases and other 'anti-fibrotic' genes; while down-regulated genes included protease inhibitors, myofibroblast- and cytoskeletal-related genes; as well as other 'pro-fibrotic' genes. Inhibitory effects upon TGF-β1-driven, DF-myofibroblast differentiation were shown to be protein kinase C (PKC)-dependent. This study has provided evidence to explain the reduced scarring responses observed in epoxy-tigliane-treated skin; highlighting the potential of epoxy-tiglianes as novel therapeutics for excessive scarring situations.
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Park, So Young [Verfasser]. "Context dependent modulation of value processing in the human brain / So Young Q. Park." Berlin : Freie Universität Berlin, 2012. http://d-nb.info/1026991625/34.
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Gehre, Dominic Steffen [Verfasser]. "Quaternionic modular forms of degree two over Q(-3,-1) / Dominic Steffen Gehre." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/1031115951/34.
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Brasil, Carlos Alexandre. "Tomografia de estados quânticos em sistemas de 3 q-bits: uma ferramenta da ressonância magnética nuclear para aplicações em computação quântica." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-01042008-145626/.
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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.
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Venzi, Marcello. "5-HT2A/2C receptor modulation of absence seizures and characterization of the GHB-model." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/70589/.
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Absence seizures (ASs) are non-convulsive epileptic events which are common in pediatric and juvenile epilepsies. They consist of EEG generalized spike-and-wave-discharges (SWDs) accompanied by an impairment of consciousness and are expressed within the thalamocortical network. This thesis initially focused on investigating the modulation of ASs by two serotonin receptors (5-HTRs), 5-HT2A and 5-HT2C, in a polygenic (i.e. Genetic Absence Epilepsy Rats from Strasbourg, GAERS) and a pharmacological (i.e. γ-hydroxybutyrate, GHB) model of ASs. It was found that, in GAERS, pharmacological activation of 5-HT2A/CRs blocked ASs, whereas 5-HT2AR antagonists increased seizure length. However, experiments on the GHB-model revealed that GHB induced not only ASs but also a period of sedation/hypnosis, a behavioural state that had been neglected in the literature. Thus, the rest of this thesis was devoted to further characterizing the GHB-model. The main result was that GHB-elicited ASs can be distinguished at the level of both EEG and behaviour. In vivo characterization of thalamic firing during GHB-elicited ASs and hypnosis via silicon probes in freely moving animals revealed that both states were accompanied by a decrease in firing rate. In particular, contrary to what was predicted by in vitro and in vivo experiments under neurolept anaesthesia, T-type Ca2+ channel-dependent burst firing in thalamic neurons was found in <10% of spike-and-wave complexes of SWDs. The prevalent activity of nucleus reticularis thalami neurons during ASs was either silence or tonic firing. Indeed, thalamic application of the potent T-type channel antagonist, TTAP-2, by reverse microdialysis did not affect GHB-elicited ASs. Finally, the development of an algorithm to classify GHB-elicited ASs demonstrated that the spectral properties of SWDs can be used to discriminate hypnosis and SWDs. Moreover, spectral coherence can be used in different experimental models of ASs to characterize SWDs according to their waveform regularity.
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Reid, Anne Marie. "Raf-1 kinase inhibitor protein modulation of the cellular response to chemotherapeutic drugs and PDE5 inhibitors." Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2497/.
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RKIP was initially discovered as an endogenous inhibitor of the ERK and NF-κB pathways,and was also shown to prolong the activation of GPCRs via inhibition of the GRK2 protein. Now increasing evidence has linked RKIP to a metastases suppressing and chemo-sensitising role in cancer cells.The chemo-sensitising effect of RKIP was investigated in a colon carcinoma cell line using a variety of chemotherapeutic agents from conventional agents to newer targeted therapies. Initial results suggested that role of RKIP in the modulation of chemotherapeutic drug response was at the level of apoptosis; there did not appear to be great observable effects in the cell proliferative response and the cell cycle distribution of the colon carcinoma cells after treatment with selected agents. Apoptosis modulation by RKIP occurred after treatment with doxorubicin, FasL, paclitaxel and TRAIL. TRAIL-treated colon carcinoma cells displayed increased cell death as the levels of RKIP within the cell were increased. In contrast, doxorubicin, FasL and paclitaxel-treated cells displayed a scaffold-like response as the levels of RKIP were increased in the cell; with WT RKIP-expressing cells being more sensitive to doxorubicin, FasL and paclitaxel-induced apoptosis than low or high RKIP-expressing colon carcinoma cells. There was no modulation of 5-FU, cisplatin and etoposide-induced apoptosis by RKIP. Indeed, these three agents did not appear to induce cell death in this colon carcinoma cell line. RKIP modulation of chemo-sensitivity has never been shown before in a colon carcinoma cell line and this is the first time that doxorubicin and FasL-induced apoptosis has been shown to be modulated by RKIP. Further, it is shown here, for the first time, that the modulation of chemotherapy-induced apoptosis by RKIP can change depending upon the cytotoxic drug employed as treatment. TRAIL and FasL, both members of the TNF super-family, were selected for further analysis due to the distinctive cell death responses observed as a consequence of the levels of RKIP within the cell. WT RKIP cells were sensitive to FasL treatment, and high RKIP cells were most sensitive to TRAIL administration. Increased sensitivity of high RKIP-expressing colon cells to TRAIL treatment appeared to involve up-regulation of the DR5 receptor; down-regulation of the anti-apoptotic molecule Bcl-xl; pIKK which activates the NF-κB pathway; and TRAF2 which has been shown to activate the NF-κB pathway. Whether RKIP directly interacts with these molecules is unknown however RKIP has been shown to bind upstream activators of the NF-κB pathway and another TRAF subtype TRAF6. YY1 expression was evident in the TRAIL-treated cells but the expression was unchanged as the levels of RKIP within the cell were altered. The FasL-treated cells also displayed decreased pIKK levels as the levels of RKIP were increased; it is possible that NF-κB was behaving as both pro- and anti-apoptotic within this cell line. Thus RKIP inhibition of the NF-κB pathway may have prevented FasL-induced apoptosis in the high RKIP-expressing colon carcinoma cells. The expression of TRAF6, which has been shown to bind RKIP, displayed a scaffold-like response with WT RKIP-expressing cells having the highest TRAF6 expression. This was also the case for the transcriptional regulator YY1, thus it is possible that both YY1 and TRAF6 were behaving in a pro-apoptotic-like manner in the WT RKIP-expressing cells. TRAF2 was also evident in the FasL-administered cells but the expression did not change regardless of the levels of RKIP within the cell. Overall, it appears that differential expression of TRAF adaptor proteins is responsible for the contrasting responses of TRAIL and FasL-treated cells with low, WT and high RKIP expression. Utilisation of particular TRAF adaptors or TRAF combinations by the TRAIL and Fas receptors may also account for the pro- and anti-apoptotic roles of the NF-κB pathway, and the recruitment or down-regulation of other proteins dependent upon the cell stimulus. How RKIP affects these proteins requires further investigation, however these results are exciting and novel, and strengthen evidence surrounding the role of RKIP in chemosensitivity. On another note, RKIP has been shown to bind the PDE5 inhibitor PF-3717842, therefore investigation of the effects of the PDE5 inhibitors sildenafil citrate and vardenafil citrate on RKIP inhibition of the ERK pathway in a colon carcinoma cell line were examined. The effects of the PDE5 inhibitors were compared to the cell migration inhibitor locostatin that has been shown to bind and inhibit RKIP, and prevent the RKIP-Raf-1 interaction. With TPA and EGF stimulation, locostatin appeared to act in a manner consistent with its known function as an RKIP inhibitor. The PDE5 inhibitors sildenafil citrate and vardenafil citrate displayed a similar trend to that of locostatin, although their effects on the ERK pathway were not as potent. It is possible that after EGF stimulation, the strong activation of B-Raf was over-shadowing the subtle effects of the drug treatments. Under growth conditions, the RKIP inhibitor locostatin did not appear to behave as an inhibitor of RKIP nor did the PDE5 inhibitors sildenafil citrate and vardenafil citrate. It is possible that the strong activation of various growth and proliferative cascades was impinging upon the ERK pathway, were overshadowing the drug effects, or resulting in off-target (RKIP-unrelated) effects of the drugs. In summary, the role of RKIP within the cell is becoming an increasingly exciting avenue of research and is consistently yielding new and interesting roles and interactions within the cell. Understanding and elucidating the roles of this intriguing protein within the cell will not only strengthen our knowledge of signal transduction regulation and modulation, but may also provide a new source of targeted therapy and means of manipulation in the treatment of cancer and chemotherapeutic drug resistance.
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George, David. "Examining the application of modular and contextualised ontology in query expansions for information retrieval." Thesis, University of Central Lancashire, 2010. http://clok.uclan.ac.uk/1865/.
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This research considers the ongoing challenge of semantics-based search from the perspective of how to exploit Semantic Web languages for search in the current Web environment. The purpose of the PhD was to use ontology-based query expansion (OQE) to improve search effectiveness by increasing search precision, i.e. retrieving relevant documents in the topmost ranked positions in a returned document list. Query experiments have required a novel search tool that can combine Semantic Web technologies in an otherwise traditional IR process using a Web document collection.
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Sutorý, Tomáš. "NOVÉ PRINCIPY CHARAKTERIZACE HRADLOVÝCH KAPACIT PRO SIGMA-DELTA MODULÁTORY." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-233499.
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This thesis deals with the utilization of new principles of characterization of gate capacitances for sigma-delta modulators. Sigma-delta modulators are the integral part of sigma-delta analog-to-digital converters. The proposed new method is characterized by high resolution and modest requirements for laboratory equipment. It allows characterizing capacitances whose values are within the range which is used in sigma-delta modulators. The thesis contains description of the new method, the analysis of measurement accuracy and experimental results.
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Dellacasagrande, Jérôme. "Infection de monocytes humains par Coxiella burnetii : modulation par cytokines." Aix-Marseille 2, 1999. http://theses.univ-amu.fr.lama.univ-amu.fr/1999AIX20672.pdf.
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Coxiella burnetii, l'agent pathogène responsable chez l'homme de la fièvre Q, est une bactérie intracellulaire stricte qui réside dans les monocytes/macrophages. Ces cellules sont douées de puissantes capacités microbicides qui leur confèrent un rôle essentiel dans la lutte anti-bactérienne. Ainsi, paradoxalement, C. Burnetii a pour cible les cellules destinées à la détruire. L'état d'activation des monocytes/macrophages, et par conséquent leur potentiel bactéricide, est contrôlé par les cytokines. Nous avons étudié l'effet des cytokines sur la survie de C. Burnetii dans les monocytes/macrophages humains. Nous avons identifié un déficit de bactéricidie des monocytes de patients atteints d'endocardite à C. Burnetii tandis que les monocytes de sujets sains éliminent rapidement la bactérie. Ce déficit n'est pas dû à un défaut général des fonctions microbicides des monocytes puisqu'il n'affecte que la réponse dirigée contre C. Bumetii. Il est lié à la surproduction de Tumor Necrosis Factor (TNF) par les monocytes des sujets atteints d'endocardite à C. Burnetii. Dans un modèle d'infection de monocytes de la lignée THP1, nous avons étudié les signaux nécessaires à la production de TNF. En réponse à C. Burnetii, l'ARN messager codant le TNF est détecté de façon précoce et transitoire. L'utilisation d'anticorps ou de peptides bloquant l'activité de l'intégrine αvβ3, le récepteur cellulaire de C. Burnetii, inhibe cette synthèse de TNF. Le lipopolysaccharide (LPS) bactérien stimule, lui, la production de TNF de la même manière que la bactérie. Notre hypothèse est que la production de TNF par les monocytes THP1 en réponse à C. Burnetii se déroule en deux étapes : la bactérie se fixe d'abord au monocyte via l'intégrine αvβ3, ce qui permet ensuite au LPS d'induire un fort signal de production de TNF. Le mode de vie intracellulaire à pH acide de C. Burnetii est vraisemblablement responsable de la faible efficacité de l'antibiothérapie dans le traitement de la fièvre Q chronique. L'activation des fonctions microbicides des monocytes/macrophages par les cytokines pourrait constituer un traitement complémentaire. L'interféron gamma (IFNγ) est connu pour être la principale cytokine activatrice des monocytes/macrophages. Dans le cas particulier de la fièvre Q, il a été montré que les lymphocytes· des malades présentent un déficit de production d'IFNγ en réponse à C. Burnetii. Nous avons évalué l'effet de l'IFNγ sur des monocytes THP1 préalablement infectés par C. Burnetii. L'IFNγ diminue la viabilité bactérienne et induit la mort par apoptose des cellules infectées. Le mécanisme. D'action de l'IFNγ est indépendant de la production des dérivés actifs de l'oxygène et de l'interleukine-1. Par contre, le TNF joue un rôle majeur dans l'apoptose induite par l'IFNγ. La mort par apoptose des cellules infectées par une bactérie intracellulaire stricte est probablement le·moyen le mieux approprié pour éliminer une telle bactérie. Enfin, nous avons montré que l'infection des monocytes par C. Burnetii diminue leur capacité de migration transendothéliale. Un tel résultat n'ayant jamais été décrit, les conséquences physiopathologiques qu'il implique restent à déterminer.
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Barroso, de Freitas Nuno Ricardo. "Some Generalized Fermat-type Equations via Q-Curves and Modularity." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/91288.
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The main purpose of this thesis is to apply the modular approach to Diophantine equations to study some Fermat-type equations of signature (r; r; p) with r >/= 5 a fixed prime and “p” varying. In particular, we will study equations of the form x(r) + y(r) = Cz(p), where C is an integer divisible only by primes “q” is non-identical to 1; 0 (mod “r”) and obtain explicit arithmetic results for “r” = 5, 7, 13.
We start with equations of the form x(5) + y(5) = Cz(p). Firstly, we attach two Frey curves E; F defined over Q(square root 5) to putative solutions of the equation.
Then by using the work of J. Quer on embedding problems and on abelian varieties attached to Q-curves we prove that the p-adic Galois representations attached to E, F can be extended to p-adic representations E), (F) of Gal(Q=Q). Finally, we apply Serre's conjecture to the residual representations (E), (F) and using Siksek's multi-Frey technique we conclude that the initial solution can not exist.
We also describe a general method for attacking infinitely many equations of the form x(r) + y(r) = Cz(p) for all r>/= 7. The method makes use of elliptic curves over totally real fields, modularity and irreducibility results for representations attached to elliptic curves and level lowering theorems for Hilbert modular forms. Indeed, for each fixed “r” we produce several Frey curves defined over K+, the maximal totally real subfield of Q(xi-r). Moreover, if “r” is of the form 6k + 1 we prove the existence of a Frey curve defined over K(0) the subfield of K(+) of degree k. We prove also an irreducibility result for the mod “p” representations attached to certain elliptic curves and a modularity statement for elliptic curves over totally real abelian number fields satisfying some local conditions at 3. Finally, for r = 7 and r = 13 we are able to compute the required spaces of (Hilbert) newforms and by applying our general methods we obtain explicit arithmetic results for equations of signature (7; 7; p) and (13; 13; p).
We end by providing two more Frey k-curves (a generalization of Q-curve), where “k” is a certain subfield of K(+), when “r” is a fixed prime of the form 4m+1.En esta tesis, utilizaremos el método modular para profundizar en el estudio de las ecuaciones de tipo (r; r; p) para r un primo fijado. Empezamos por utilizar la teoría de J. Quer sobre variedades abelianas asociadas con Q-curvas y embedding problems para producir dos curvas de Frey asociadas con hipotéticas soluciones de infinitas ecuaciones de tipo (5; 5; p). Después, utilizando la conjetura de Serre y el método multi-Frey de Siksek demostraremos que las hipotéticas soluciones no pueden existir. Describiremos también un método general que nos permite atacar un número infinito de ecuaciones de tipo (r; r; p) para cada primo “r” mayor o igual que 7. El método hace uso de curvas elípticas sobre cuerpos de números, teoremas de modularidad, teoremas de bajada de nivel y formas modulares de Hilbert. Además, para ecuaciones de tipo (7; 7; p) y (13; 13; p) calcularemos los espacios de formas modulares relevantes y demostraremos que una familia infinita de ecuaciones no admite cierto tipo de soluciones. Además, demostraremos un nuevo teorema de modularidad para curvas elípticas sobre cuerpos totalmente reales abelianos. Finalmente, para primos congruentes con 1 módulo 4 propondremos dos curvas de Frey más. Demostraremos que son “k-curves” (una generalización de Q-curva) y también que satisfacen las propiedades necesarias para que pueda ser útiles en la aplicación del método modular.
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Jarufe, Troncoso Claudio Felipe. "Development of modular components for radio astronomical receivers in the bands Q (30-50 GHZ) and W (80-110 GHZ)." Tesis, Universidad de Chile, 2018. http://repositorio.uchile.cl/handle/2250/164032.
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Doctor en Ingeniería EléctricaEste trabajo presenta el diseño, construcción y caracterización de dispositivos para receptores radioastronómicos en las bandas Q (30-50GHz) y W (80-110GHz). Por un lado, el dispositivo desarrollado para la banda Q es de interés para la banda 1 del telescopio argentino-brasileño LLAMA (Long Latin American Array). Por otro lado, los componentes de banda W pueden ser utilizados en la banda 3 de LLAMA o en posibles mejoras para el Telescopio Austral de Ondas Milimétricas (SMWT) que es mantenido por nuestro grupo. Para la banda Q, se diseñó y construyó un amplificador de bajo ruido utilizando un esquema hibrido de integración. Se integró un transistor de alta movilidad electrónica (HEMT) y un circuito integrado monolítico de microondas (MMIC) obtenido comercialmente. Con este diseño una temperatura de ruido inferior a 20 K y una ganancia superior a 30 dB pueden ser obtenidas. En la banda W se desarrollaron varios componentes. En primer lugar, se empaquetaron amplificadores comerciales MMIC de las compañías OMMIC y HRL. Al ser medidos a 15K estos amplificadores de bajo ruido alcanzaron temperaturas de ruido menores a 100K y ganancias superiores a 17 dB. Dada su disponibilidad comercial se determinó que son apropiados para ser utilizados como segundo amplificador en un receptor. Segundo, utilizando diodos Schottky comerciales, se fabricaron mezcladores sub-armónicos que cubren la banda W extendida. Las técnicas de desarrollo han variado desde el uso de componentes discretos hasta el diseño de MMICs para reducir el tamaño de los mezcladores. Los componentes mencionados previamente han sido ensamblados en un módulo compacto que puede ser utilizado en la etapa de mezcla de frecuencias. Este módulo posee una temperatura de ruido menor a 800 K y ganancia superior a 2dB a temperatura ambiente. Finalmente, se construyó una antena de ranura cuyo perfil ha sido optimizado para mejorar sus principales características (reflexiones, ancho de banda, polarización cruzada y simetría de haz). Entre las antenas de su tipo, esta es la única que posee un perfil optimizado lo que ha permitido obtener el mejor funcionamiento alcanzado hasta el momento.
Este trabajo ha sido parcialmente financiado por el Proyecto Gemini-Conicyt 32130023, Centro Basal de Astronomía y Tecnologías Afines (CATA), "Programa de Formación de Capital Humano Avanzado" de CONICYT y el Comité Mixto ESO-Chile
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Kyritsis, Georgios. "Theory and modelling of wavelength tunable laser transmitters with enhanced tuning range and their modulation performance." Thesis, University of Essex, 2015. http://repository.essex.ac.uk/15489/.
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The research that is described in detail in this thesis investigates key characteristics of the operation of Tunable Laser Diodes (TLDs), such as Continuous Wave (CW) operation, discontinuous, continuous and quasicontinuous wavelength tuning and direct Intensity Modulation (IM) (small-signal analysis). Two software simulation tools were used to model the TLDs and investigate their operation, Crosslight PICS3D and VPI (Virtual Photonics Incorporated). Two different Free-Carrier (FC) contributions to the refractive index change of the TLD during FC tuning were investigated, the FC plasma effect and the band-filling effect which uses the Kramers-Kronig (KK) relations (KK effect). It was found that the band-filling effect is heavily underestimated due to the lack of its investigation in published literature as it is the main contributor to the refractive index change instead of the plasma effect. Investigation on different types of wavelength tuning also took place. It was found that with careful design of the passive sections, such as the κL product, grating composition, section length and passive waveguide thickness the discontinuous, continuous and quasicontinuous tuning range can be enhanced greatly. The issue of output power decrease during discontinuous tuning in bulk and Multiple Quantum Well (MQW) TLDs was also addressed and it was found that the power drop can be delayed at latter stages of the tuning range by carefully selecting the Lorentzian lineshape of the gain spectrum. A power stabilisation was realised with continuous tuning. A small-signal analysis of directly intensity modulated TLDs during discontinuous tuning was also made and was found that the increase of the resonance frequency depends mainly on the increase of the differential gain with the wavelength change.
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Mabrouk, Kaïs. "Conception et réalisation d'un système de télécommunications MIMO avec formation numérique de faisceaux en réception : calibrage aveugle du démodulateur triphasé zéro-IF et comparaison au démodulateur classique à 2 voies I et Q." Paris, ENST, 2008. http://tel.archives-ouvertes.fr/tel-00409794.
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Dans le cadre de ce travail de recherche, nous nous somme intéressés à un système de télécommunication MIMO (Multiple Input Multiple Output) à multiplexage spatial utilisant des récepteurs Zero-IF et la technique de formation numérique de faisceaux (FF). Le domaine d'application de ces travaux de recherches peuvent être aussi bien les applications fixes (exp: WiFi, IEEE) que les applications mobiles (exp: LTE, 3GPP). La première partie de ce travail est consacrée à une étude comparative entre les différents types de démodulateurs cinq-port et triphasés. Cette étude a permis de mettre en évidence l'aspect tridimensionnel des démodulateurs cinq-port et triphasés, de gagner 20dB en termes de réjection des produits d'intermodulation des signaux adjacents et de trouver une nouvelle méthode de calibrage aveugle du récepteur. La seconde partie de la thèse se concentre sur le prototypage d'un système MIMO. Cette phase nous a permis d’exposer les difficultés de mise en place de ce genre de système et de souligner les nouvelles problématiques qui n’apparaissait pas auparavant dans les systèmes mono- transcepteur. Aussi, un algorithme de Formation de Faisceau a été développé dans cette partie. Ce FF numérique a permis non seulement d'accroître la capacité mais aussi la qualité de liaison en considérant le système MIMO comme N système SIMO en parallèle. Comparativement à la technique ZF(Zero Forcing), nous démontrons que le FF permet d'obtenir une meilleure qualité de signaux pour des faibles valeurs de rapport signal à bruitWithin the framework of this research work, we have interested to a MIMO (Multiple Input Multiple Output) telecommunication system using the spatial multiplexing, Zero-IF receptors and the digital beamforming technique. The first part in this work is consecrated to a comparative study between two different kinds of Zero-IF demodulators: the classical IQ demodulator and the five-port and three-phase one. This study has allowed to highlight the three dimensional aspect of five-port and three-phase demodulators, to win up to 20dB in terms of rejection of inter-modulation product. Also this three dimensional aspect discovery help us to find a new blind calibration method. The second part of this thesis focuses on the prototyping of a MIMO system. This phase has allowed us to set the difficulties of the implementation of this systems kind and to highlight new problematics that don’t appear beforehand in mono-transceiver system. Moreover, a beamforming algorithm was developed in this part. This digital beamfoming has permit to increase the capacity as well as the quality of link when considering the MIMO system as N parallel SIMO systems. Compared to the ZF (Zero Forcing technique), we have proved that the beamforming permit the achievement a better signal quality for lower values of the signal to noise ratio
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Xu, Changting. "Investigation of Modulation Methods to Synthesize High Performance Resonator-Based RF MEMS Components." Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1135.
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The growing demand for wireless communication systems is driving the integration of radio frequency (RF) front-ends on the same chip with multi-band functionality and higher spectral efficiency. Microelectromechanical systems (MEMS) have an overarching applicability to RF communications and are critical components in facilitating this integration process. Among a variety of RF MEMS devices, piezoelectric MEMS resonators have sparked significant research and commercial interest for use in oscillators, filters, and duplexers. Compared to their bulky quartz crystal and surface acoustic wave (SAW) counterparts, MEMS resonators exhibit impressive advantages of compact size, lower production cost, lower power consumption, and higher level of integration with CMOS fabrication processes. One of the promising piezoelectric MEMS resonator technologies is the aluminum nitride (AlN) contour mode resonator (CMR). On one hand, AlN is chemically stable and offers superior acoustic properties such as large stiffness and low loss. Furthermore, CMRs offer low motional resistance over a broad range of frequencies (few MHZ to GHz), which are lithographically-definable on the same silicon substrates. To date, RF MEMS resonators (include CMRs) have been extensively studied; however, one aspect that was not thoroughly investigated is how to modulate/tune their equivalent parameters to enhance their performance in oscillators and duplexers. The goal of this thesis is to investigate various modulation methods to improve the thermal stability of the resonator, its “effective” quality factor when used in an oscillator, and build completely novel non-reciprocal components. Broadly defined, modulation refers to the exertion of a modifying or controlling influence on something, herein specifically, the resonator admittance. In this thesis, three categories of modulation methods are investigated: thermal modulation, force modulation, and external electronic modulation. Firstly, the AlN CMR’s center frequency can be tunned by the applied thermal power to the resonator body. The resonator temperature is kept constant (for example, 90 °C) via a temperature sensor and feedback control such that the center frequency is stable over the whole operation temperature range of interest (e.g. –35 to 85 °C). The maximum power consumption to sustain the maximum temperature difference (120 ºC in this thesis) between resonator and ambient is reduced to a value as low as 353 μW – the lowest ever reported for any MEMS device. These results were attained while simultaneously maintaining a high quality factor (up to 4450 at 220 MHz device). The feedback control was implemented by either analog circuits or via a microprocessor. The analog feedback control, which innovatively utilized a dummy resistor to compensate for temperature gradients, resulted in a total power consumption of 3.8 mW and a frequency stability of 100 ppm over 120 ºC. As for the digital compensation, artificial neural network algorithm was employed to facilitate faster calibration of look-up tables for multiple frequencies. This method attained a frequency stability of 14 ppm over 120 ºC. The second modulation method explored in this thesis is based on the use of an effective external force to enhance the 3-dB quality factor of AlN CMRs and improve the phase noise performance of resonator-based oscillators. The force modulation method was embodied in a two-port device, where one of the two ports is used as a one-port resonator and the other is driven by an external signal to effectively apply an external force to the first port. Through this technique, the quality factor of the resonator was boosted by 140 times (up to 150,000) and the phase noise of the corresponding oscillator realized using the resonator was reduced by 10 dBc/Hz. Lastly, a novel magnetic-free electrical circulator topology that facilitates the development of in-band full duplexers (IBFD) for simultaneous transmit and receive (STAR) is proposed and modeled. Fundamentally, a linear time-invariant (LTI) filter network parametrically modulated via a switching matrix is used to break the reciprocity of the filter. The developed model accurately predicts the circulator behavior and shows very good agreement with the experimental results for a 21.4 MHz circulators built with MiniCircuit filter and switch components. Furthermore, a high frequency (1.1 GHz) circulator was synthesized based on AlN MEMS bandpass filters and CMOS RF switches, hence showing a compact approach that can be used in handheld devices. The modulation frequency and duty cycle are optimized so that the circulator can provide up to 15 dB of isolation over the filter bandwidth while good power transfer between the other two ports is maintained. The demonstrated device is expected to intrinsically offer low noise and high linearity. The combination of the first two modulation methods facilitates the implementation of monolithic, temperature-stable, ultra-low noise, multi-frequency oscillator banks. The third modulation technique that was investigated sets the path for the development of CMOS-compatible in-band full duplexers for simultaneous transmit and receive and thus facilitates the efficient utilization of the electromagnetic spectrum. With the aid of all these three modulation approaches, the author believes that a fully integrated, multi-frequency, spectrum-efficient transceiver is enabled for next-generation wireless communications.
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Ibanez, Elsa. "Idempotents de Jones-Wenzl évaluables aux racines de l'unité et représentation modulaire sur le centre de U¯_{q}sl(2)." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS233.
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Soit p∈ℕ*. On définit une famille d'idempotents (et de nilpotents) des algèbres de Temperley-Lieb aux racines 4p-ième de l'unité qui généralise les idempotents de Jones-Wenzl usuels. Ces nouveaux idempotents sont associés aux représentations simples et indécomposables projectives de dimension finie du groupe quantique restreint U¯_{q}sl(2), où q est une racine 2p-ième de l'unité. A l'instar de la théorie des champs quantique topologique (TQFT) de [BHMV95], ils fournissent une base canonique de classes d'écheveaux coloriés pour définir des représentations des groupes de difféotopie des surfaces. Dans le cas du tore, cette base nous permet d'obtenir une correspondance partielle entre les actions de la vrille négative et du bouclage, et la représentation de SL₂(ℤ) de [LM94] induite sur le centre de U¯_{q}sl(2), qui étend non trivialement de la représentation de SL₂(ℤ) obtenue par la TQFT de [RT91]Let p in N^*. We define a family of idempotents (and nilpotents) in the Temperley-Lieb algebras at 4p-th roots of unity which generalizes the usual Jones-Wenzl idempotents. These new idempotents correspond to finite dimentional simple and projective indecomposable representations of the restricted quantum group U¯_{q}sl(2), where q is a 2p-th root of unity. In the manner of the [BHMV95] topological quantum field theorie (TQFT), they provide a canonical basis in colored skein modules to define mapping class groups representations. In the torus case, this basis allows us to obtain a partial match between the negative twist and the buckling actions, and the [LM94] induced representation of SL₂(ℤ) on the center of U¯_{q}sl(2), which extends non trivially the [RT91] representation of SL₂(ℤ)
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Bolea, Alamañac Ana Isabel. "Conception et mise en œuvre de méthodes de compensation des effets du canal de propagation pour optimiser les ressources radio." Toulouse, ENSAE, 2004. http://www.theses.fr/2004ESAE0016.
Full textAbstract:
L'augmentation des besoins en bande passante et la saturation du spectre en bande Ku (12 GHz) pour les nouveaux systèmes de communications par satellite géostationnaires, poussent à l'utilisation de fréquences plus élevées (bande Ka et Q/V, 20 à 50 GHz) où de plus grandes largeurs de bandes sont disponibles, mais où les effets atmosphériques sont importants. Il faut alors définir des techniques adaptatives (FMT : fade mitigation techniques) qui permettent d’optimiser la couche physique du système en prenant en compte les conditions de propagation qui sont variables dans le temps. La définition optimisée de ces techniques adaptatives fait l'objet de cette thèse. Le rapport décrit tout d’abord les caractéristiques principales de la propagation dans ces bandes de fréquences. Les techniques adaptatives sont ensuite analysées. L'analyse s’appuie sur un système de référence multifaisceaux pour l’accès distribué à l’lnternet. Une méthode originale d’évaluation des performances système a été développée pour quantifier l’efficacité de ces techniques et choisir leur meilleure combinaison. L'analyse a révélé le besoin de nouvelles procédures d'optimisation des bilans de liaison qui ont été mises au point. Ainsi l'introduction de l'adaptation du schéma de modulation-codage (utilisant le standard DVB-SZ et une proposition d'extension du DVB-RCS) permet une nette amélioration des résultats en termes de capacité. Après avoir quantifié l’apport de ces techniques de compensation de façon théorique, la dernière partie des travaux de recherche est dédiée à l'implémentation des techniques étudiées. La principale difficulté réside, selon la technique FMT concernée, dans l'obtention de mesures fiables et rapides de la magnitude de l'affaiblissement ou du SNIR, rapport puissance porteuse à puissance du bruit (y compris brouillages). Plusieurs architectures d'implantation des techniques FMT ont été proposées. Les sources d’erreurs associées aux différentes fonctions mises en œuvre dans l'architecture FMT ont été identifiées et quantifiées. À partir de cette analyse, une méthode de définition des seuils et des marges de décision d’activation de chaque technique est proposée. La thèse se termine par les résultats obtenus à partir d’un simulateur de la boucle de contrôle FMT. Les simulations confirment l'amélioration des performances du système grâce à l'introduction des FMT, et mettent aussi en évidence l'intérêt de la proposition de répartition non-uniforme des seuils et des marges pour optimiser la boucle de contrôle FMT.
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Rafayelyan, Mushegh. "Singular beam shaping from spin-orbit flat optics." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0583/document.
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Dans ce travail nous avons résolu deux problèmes principaux de la mise en forme topologique de faisceau paraxial pour les composants plans : la modalité et le polychromatisme.Nous les résolvons en introduisant de nouveaux concepts d’éléments optiques à interaction spin orbite,à savoir la “q-plate modale” et la “q-plate Bragg-Berry”. D’un côté, la q-plate modale convertit un faisceau gaussien incident en un faisceau de Laguerre-Gauss pour un indice radial et un indice d’azimut donnés, ce qui par conséquent dépasse les capacités des q-plates conventionnelles qui ne modifient que le degré de liberté azimutal, c.à.d. le moment orbital angulaire de la lumière. À des fins expérimentales, deux approches ont été développées : une basée sur des lames de verres nanostructurées artificiellement, l’autre sur des défauts topologiques de cristaux liquides auto-organisés naturellement. D’un autre côté, la q-plate Bragg-Berry consiste en une fine couche inhomogène de cristaux liquides chiraux (cholestériques) devant un miroir, ce qui fournit une mise en forme de faisceau spin-orbite pleinement efficace sur une large bande spectrale du faisceau incident, contrairement au q-plates conventionnelles qui ne sont fabriqués que pour une longueur d’onde donnée. Par ailleurs, nous obtenons une mise en forme de faisceau spin-orbite ultra-large bande en induisant une modulation de la structure supramoléculaire torsadée des cristaux liquides cholestériques selon la direction de propagation de la lumière. Nous montrons également que la présence du miroir derrière permet un puissant contrôle spatio-temporel des propriétés vectorielles de la polarisation du champ lumineux générées par la q-plate Bragg-BerryIt is well-known that paraxial coherent electromagnetic fields can be completelycharacterized in terms of their radial and azimuthal spatial degrees of freedom in the transverse planethat add to the polarization degree of freedom and wavelength. In this work we address two mainissues of paraxial beam shaping that are the modality and the polychromaticity in the context of flatopticsthat we address by introducing novel concepts of spin-orbit optical elements. Namely, the‘modal q-plate’ and the ‘Bragg-Berry q-plate’. On the one hand, modal q-plate converts an incidentfundamental Gaussian beam into a Laguerre-Gaussian beam of given radial and azimuthal indices,hence going beyond the capabilities of conventional q-plates that only control the azimuthal degreeof freedom, i.e. the orbital angular momentum content of light. Towards experimental realization ofmodal q-plates, two approaches are developed: one based on artificially nanostructured glasses andanother based on naturally self-organized liquid crystal topological defects. On the other hand,Bragg-Berry q-plate consist of mirror-backed inhomogeneous thin film of chiral liquid crystal(cholesteric) that provides fully efficient spin-orbit beam shaping over broad spectral range of theincident beam, in contrast to the conventional q-plates that are designed for single wavelength.Furthermore, ultra-broadband spin-orbit beam shaping is achieved by inducing an extra modulationof the supramolecular twisted structure of the cholesteric liquid crystal along the propagationdirection. We also show that the presence of a back-mirror allows a powerful spatio-temporal controlof the polarization vectorial properties of the light fields generated by Bragg-Berry q-plate
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Rioual, Pascal. "Modélisation et commande d'un redresseur à MLI alimenté par un réseau déséquilibré." Cachan, Ecole normale supérieure, 1993. http://www.theses.fr/1993DENS0008.
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L'augmentation considérable ces dernières années du nombre de convertisseur sur le réseau d'alimentation se traduit par la nécessite de s'intéresser a la compatibilité entre les convertisseurs et le réseau. Le redresseur à mli est un convertisseur dont les caractéristiques lui permettent d'absorber des courants réseaux sinusoïdaux, et d'échanger de la puissance active et réactive avec le réseau. Le présent travail concerne l'étude de la modélisation et la commande de ce convertisseur ainsi que l'extension au cas d'un réseau déséquilibre. Le redresseur est contrôlé par une régulation cascade: des boucles internes régulent les courants réseaux, une boucle externe régule la tension de capacité. Les conséquences de l'apparition d'une perturbation de type creux de tension (distorsion harmonique sur les courants réseaux, oscillation a l'harmonique 2 des composantes continues) sont analysées puis simulées et vérifiées expérimentalement. Deux solutions sont étudiées: - une compensation s'appuyant sur une étude théorique du système. - la construction d'un régulateur robuste appliquant le principe du modèle interne de Wohnam et la méthode de placement de pôles par -stabilité. Les avantages obtenus permettent d'envisager une meilleure continuité de fonctionnement face aux creux de tension, un dimensionnement réduit du convertisseur, et la conservation des performances. Les domaines d'application concernes sont varies. Dans le domaine industriel, il s'agit des alimentations à bon facteur de puissance ou des procédés nécessitant le réglage du réactif
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Lavastre, Eric. "Déclenchement des microlasers solides émettant à 1,55 µm par un dispositif à semiconducteur." Université Joseph Fourier (Grenoble ; 1971-2015), 1998. http://www.theses.fr/1998GRE10173.
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Les microlasers emettant a 1,55 m sont des lasers solides de faible volume (<1 mm#3) a base de verre : er, yb dont les miroirs de la cavite sont directement deposes sur le milieu a gain. En introduisant un modulateur dans la cavite, il est possible de declencher le laser afin d'obtenir des impulsions de puissance crete elevee donc exploitables pour des applications telles que la telemetrie. L'objet de cette these est d'utiliser un dispositif a semiconducteur comme modulateur. De par leurs proprietes optiques et electriques, les semiconducteurs presentent un fort potentiel pour le declenchement passif et le declenchement actif. Les structures etudiees sont des couches epaisses et des structures a puits quantiques constituees d'in#xga#1##x##yal#yas epitaxiees sur un substrat d'inp. En declenchement passif dans une configuration microlaser, les meilleurs resultats ont ete obtenus avec une couche epaisse de 80 nm d'in#0#,#4#8ga#0#,#5#2as. Les energies et les puissances cretes par impulsion sont respectivement de 2 j et 2w avec un substrat d'inp semi-isolant et, 25 nj et 5w avec un substrat d'inp non dope. Ces differences dans les performances sont dues a des effets non-lineaires associes au substrat d'inp semi-isolant qui elargissent les impulsions. En declenchement actif, les premiers essais en cavite externe ont montre qu'il est possible de moduler l'emission laser en appliquant des creneaux de tension inferieurs a 20v pendant 1 s aux bornes d'une diode p. I. N dont la region intrinseque se compose de 10 puits quantiques d'in#0#,#5#3ga#0#,#4#7as dans des barrieres d'in#0#,#5#2al#0#,#4#8as. Afin d'optimiser l'effet du champ electrique, une structure mesa et une passivation ont ete realisees.
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Liaw, Yueh-Ru, and 廖嶽儒. "Design and implementation of I/Q modulator." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/86472847692886361767.
Full textAbstract:
碩士國立臺灣科技大學
工程技術研究所
83
In this paper, the design principles and implementation techniques of I/Q modulator are investigated. The I/Q modu- lator consists of DBMs(double-balanced mixers), phase shifter and power splitter/combiner, where each subcircuit has its distinct electric characteristics. To verify the theoretical results, we build the subcircuit by employing FR-4 boards, mixers and ferrite core. The measuremental results of each subcircuit and integrated I/Q modulator are discussed throu- ghly. We find that the characteristics of DBM dictate the per- formance of I/Q modulator.
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Huang, Chuan-Jung, and 黃絹容. "Design of Ka-band Up-Mixer and I/Q Modulator." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/37774964837132936799.
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Chung, Yi-Wei, and 鍾懿威. "Design of V-band Power Amplifier and I/Q Modulator." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/70578103754637080950.
Full textAbstract:
碩士國立臺灣師範大學
應用電子科技學系
101
The purpose of this dissertation is to develop a Power Amplifier and an I/Q Modulator in a V-band millimeter-wave transmitter system. They are fabricated on TSMC 90 nm 1P9M RF CMOS process. With the development of wireless communication technologies, radio frequency integrated circuit tends to higher frequency, higher data rate, wider bandwidth, and higher integration. For this subject, unlicensed multi-GHz bandwidth around V-band makes very high data rate transmission feasible. We adopt CMOS technology. It has the advantages of small size, low cost, low power consumption, and high level of integration, all of which are for MMW applications. To develop a Power Amplifier and an I/Q Modulator in a V-band millimeter-wave transmitter system. We are using Agilent ADS software and SONNET software to be the simulation tools. The first circuit is Power Amplifier, which utilizes three-stage common source configuration amplifier. The first and second stages are drive stages. The third stage is power stage. To purpose higher linearity, we combine a Pre-distortion Linearizer on the power stage. The circuit will have better linearity than without Linearizer. The second circuit is I/Q Modulator, which is using two Modified Gilbert-cell Mixer, one Coupler, and one Wilkinson Combiner.
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Ya-tingChan and 詹雅婷. "A study on Q-switched Ince-Gaussian laser generation with acousto-optic modulator." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/57199672130697982997.
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碩士國立成功大學
物理學系
103
The purpose of this study is to generate pulsed Ince-Gaussian(IG) lasers in end-pumped solid-state lasers and to reach different modes of selection and application of Q-switched pulsed lasers. The active Q-switch we adopting in this study is the acousto-optic (AO) modulator. However, we also adopt the chopper in this study. In the first part of the experiment, both of laser systems can be used to generate pulsed IG laser and observe the relaxation oscillation (RO). The second part of the experiment, we study on Q-switched Ince-Gaussian laser generation with AO modulator. Experimental result shows that, using AO Q-switched laser system, this study successfully generates pulsed IG lasers of several different modes. Besides, by classifying IGMs into even and odd groups, this study gives discussions on the relation between pulsed Ince-Gaussian lasers of different modes.
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Tsai, Yi-Chien, and 蔡宜蒨. "Design of Gilbert-cell Mixer, I-Q Modulator, and SPDT Switch in 60-GHz Applications." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/01544238454416459132.
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碩士國立臺灣大學
電信工程學研究所
97
This thesis discusses Gilbert-cell down-conversion mixer, broadband I-Q modulator with improved sideband suppression, and a distributed single-pole-double-throw switch. The main purpose is to explore the frequency conversion components such as mixer and I-Q modulator, and improve the performance of quadrature coupler used in I-Q modulator to combine two orthogonal signals, and develop a broadband switch for high-frequency application at 60 GHz. In this thesis, a 60-GHz down-conversion Gilbert-cell mixer is discussed and fabricated. Modulators are important components in transmitters, recently reported modulators around 60 or 70 GHz normally emphasize their broadband property. 90° couplers are needed to modulate baseband signals with QPSK modulation. However, it is not easy for conventional broadside coupler to provide balanced output amplitude and accurate 90° output phase split in a very broadband fasion. Therefore, these modulators normally achieve high sideband suppression only in norrowband ranges. Making use of the phase lead property of a composite left/right hand transmission line, broadband quadrature power splitter can be designed. It can improve the sideband suppression of conventional modulators. Finally, single-pole-double-throw switches are important switching components in transceivers. A distributed SPDT switch using mHEMT process is fabricated. The insertion loss at 60 GHz is only 2 dB, which reduces the noise introduced by the switches in transceivers. To obtain low insertion loss, the SPDT switch use only three transistors for each SPST switch branch. As a trade-off from low insertion loss, the isolation is moderate.
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Huang, Chi-Chung, and 黃啟創. "Q-switched and mode-locked pulses generation in a c-cut Nd:LuVO4 laser by simultaneous acousto-optic modulator and GaAs." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/946929.
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碩士國立臺北科技大學
光電工程系研究所
98
In this thesis, we investigate the characteristics of Q-switched and mode-locked (QML) pulses generation in c-cut Nd:LuVO4 laser by using an acousto-optic modulator (AOM) and GaAs wafer. In only using the AOM, the periodic QML envelope with relative high energy pulses has been experimentally demonstrate. However, the shape of generate Q-switched envelope is asymmetric that has longer falling time than rising time. This result is opposite to the Q-switching envelope generated by the GaAs wafer that has longer rising time. Besides, the period of the Q-switching envelope is un-regular and has relative large amplitude fluctuation. In order to generation periodic and symmetric Q-switched envelope, we combine AOM and GaAs wafer in laser cavity and demonstrate the more symmetric shape can be produced at lower pump power. However, the falling time of Q-switched envelope shrinkage seriously at relative higher pump power that is due to the two photon absorption of the GaAs
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Mayer, Sebastian [Verfasser]. "Hilbert modular forms for the fields Q(√5), Q(√13) and Q(√17) / vorgelegt von Sebastian Mayer." 2007. http://d-nb.info/985767022/34.
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Chen, Yao-Han, and 陳耀漢. "Cuspidal Q-rational Torsion Subgroups of Jacobians of Modular Curves." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/03286983872853541058.
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博士國立交通大學
應用數學系所
99
For p > 3 an odd prime and r > 0, let Γ be a congruence subgroup between Γ_1(p^r) and Γ_0(p^r). In this dissertation, we give an explicit basis for the group of modular units on X(Γ) that have divisors defined over Q. As an application, we determine the order of the cuspidal Q-rational torsion subgroup of J(Γ) generated by the divisor classes of cuspidal divisors of degree 0 defined over Q when Γ = Γ_0(p^r), Γ_1(p^r).
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Yen, Tzu-Hsiang, and 顏子翔. "Stable Q-switched mode-locked Yb-fiber laser by AO modulation." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/23551003944178131102.
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碩士國立交通大學
光電工程系所
97
In this thesis, reliable Q-switched mode-locking in an Yb-doped fiber laser is demonstrated by employing an acousto-optic modulator (AOM) and a linear fiber cavity. Within the Q-switched envelope, mode-locked pulses with the repetition rate of 40 MHz can be obviously seen and their repetition rate is equal to the RF driving frequency of the AOM. In our experimental observation, the width and the asymmetry ratio of the Q-switched envelopes depend on the modulation frequency of AOM. At lower modulation frequencies, satellite pulses can be seen with their number being also related to the modulation frequency of AOM. By alternation the optical focus spot size on the AO crystal, we demonstrate that the amplitude modulation of the AOM plays the dominant role for starting the harmonic mode-locking of the laser.
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Yang, Yi-Min, and 楊宜旻. "Dynamic OFDM Modulation with I/Q Compensation in 60 GHz RoF System." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/34157821059172078940.
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碩士國立交通大學
顯示科技研究所
100
As the development in technology and science, the requirements of multi-Gbps wireless transmission are more important. For increasing data transmission, we raise the carrier frequency to 60 GHz which can offers 7 GHz unlicensed band (57-64 GHz) according to Federal Communications Commission (FCC). However, because of the serious propagation loss of 60-GHz RF signal, the radio-over-fiber (RoF) system is proposed to reduce the overall cost of 60 GHz wireless access network. To receive the higher performance in 60 GHz RoF system, compensating I/Q imbalance is inevitable especially in 7 GHz band because there are not two components which have identical frequency response in practice. In this thesis, an adaptive equalizer in frequency domain is applied to compensate the influence of I/Q imbalance on OFDM signal. We successfully demonstrate a 32 Gb/s OFDM signal on 3m wireless distance at 60 GHz within 7-GHz license-free band. Transmission over 25-km standard single-mode fiber and 3m wireless distance were achieved with negligible penalty.
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Kun-GueiHong and 洪崑貴. "Dynamic behavior in the passive Q-switched Nd:YVO4 laser on pumping modulation." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/68080196281387953459.
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碩士國立成功大學
光電科學與工程學系
100
n this thesis, we study that the nonlinear dynamical behavior in passively Q-switched Nd:YVO4 laser. With increasing the modulation frequency of pumping source, the behavior of the pulse train in sequence will occur: period two, period three, period one and finally chaotic dynamics phenomena with some path of development. At the same time when the modulation frequency was closed to the pulse repetition frequency, the timing jitter of pulse train became very stable, and the pulse width compared with pulse train without modulation was compressed. In simulation, we modulated gain with sine wave. All the dynamic behavior of the pulse train of simulation corresponded with experiment. It’s easy to analyze that some pulses of the pulse train have stronger excitation and become the stronger peak intensity, and some pulses become weaker one because of small excitation. This phenomena lead to be period two signal. So does the period three, and so dose chaotic pulse train. The Q-switched pulse laser system can be controlled into special condition by gain-modulation with some special frequency.