Planar cell polarity (PCP) is the organization of cellular characteristics within the plane of a tissue. PCP manifests both structurally, as in the directionality of insect bristles or mammalian skin hair, or dynamically, as in vertebrate neurulation, gastrulation, and oriented cell division in the kidney. Two well-conserved pathways are known to regulate PCP in invertebrates and in vertebrates: the Frizzled/PCP pathway and the Fat-Dachsous (Ft-Ds) pathway. The latter consists of the cadherins Ft and Ds, along with the Golgi kinase Four-jointed (Fj) and the transcriptional co-repressor Atrophin (Atro). Ft and Ds can bind each other, suggesting a mechanism for signal transduction. Fj phosphorylates Ft and Ds, modulating their binding affinities for each other. Atro is proposed to link Ft-Ds signaling with downstream events in the nucleus during eye development. The details of Ft-Ds binding, and the consequences of their interactions with other members of the pathway are poorly understood. In this work, I quantitatively analyzed Ft-Ds pathway mutant clones for their effects on ommatidial polarity in the Drosophila eye. My findings suggest that the Ft-Ds pathway regulates PCP independently of asymmetric cellular accumulation of Ft or Ds. I found that Atro has a position-specific role in regulating polarity in the eye, that Fj dampens clonal polarity signals, and that asymmetric accumulation of the atypical myosin Dachs is not essential for production and propagation of a long-range PCP signal. My observations suggest that Ft and Ds interact to modulate a secondary signal that regulates long-range polarity, that signaling by the Ds intracellular domain is dependent on Ft, and that ommatidial fate specification is genetically separable from long-range signaling.

En aquesta tesi, proposem la fabricació y la caracterització d’un microconcentrador de gasos, per ser acoblat amb un microsistema de detecció, per millorar el seu límit de detecció davant els gasos tòxics. Aquest estudi s’aplica especialment al benzè, que es un compost d’alta cancerigenitat. El preconcentrador proposat esta basat en estructura plana, que, es una opció de fabricació més simple y permet una millor aïllament tèrmic amb el resta d’unitats del microsistema, qu’els estructures 3D proposats a la literatura. No obstant, els factors de concentració obtinguts amb l’estructura plana queden generalment més baixos, per causa de la menor quantitat de material absorbent que pot acollir. En aquesta tesis, es va superar aquest problema mitjançant l’utilització del carboní actiu, un adsorbent d’alta capacitat d’adsorció, així com l’optimització de les condicions de funcionament del dispositiu. Finalment, acoblant el microconcentrador amb un micro-cromatògraf, vam aconseguir una detecció sensible y selectiva del benzè en barreja amb altres volàtils a l’aire. / The present thesis focuses on the fabrication and characterization of a gas microconcentrator for to be coupled with a detection microsystem, in order to lower its detection limit towards toxic gases and vapours in contaminated areas. This study was more especially applied to the preconcentration of benzene, a cancerigenic compound at low ppb level. A preconcentrator based on a planar structure was proposed regarding its simpler fabrication, better thermal insulation and lower power consumption, compared to the 3D structures proposed conventionally in literature. In order to obtain higher concentration factors with such structure, its small size was compensated by using a high adsorption capacity adsorbent such as activated carbon as well as the optimization of the preconcentration conditions of the device. Finally, the microconcentrator was validated as injection unit when coupled with a microchromatographic system, where a sensitive and selective analysis of benzene in mixture with other VOCs was achieved.

L'objet de ce travail a consisté dans l'optimisation et réalisation d'une périphérie Planar haute tension, permettant d'obtenir une tenue en tension dépassant 2000V. Parmi des protections périphériques existantes la protection par l'implantation latérale appelée "poche" semblait être une solution très performante pour obtenir une tenue en tension très élevé. Dans un premier temps, nous avons optimisé la structure de cette protection en utilisant des simulateurs bidimensionnels (ATHENA, ATLAS). Les résultats de simulation confirment que la dose active de cette périphérie est l'un des paramètres important à contrôler. La profondeur et la longueur de poche sont les deux autres paramètres à prendre en compte pour l'optimisation de cette périphérie. La variation de la tenue en tension est présentée en fonction de l'évolution de chacun de ces paramètres. Les résultats de l'étude de la sensibilité de la tenue en tension vis-à-vis de la dose active de la poche ont permis d'établir une méthodologie de conception d'une périphérie monopoche optimale et de développer une périphérie bipoche permettant de bien dominer la dose active de poche donc d'améliorer la tenue en tension. Ensuite, pour valider les résultats de simulation en raison de simplification nous avons choisi la diode de type PIN comme élément de test. Nous avons réalisé et caractérisé les diodes avec différentes géométries des périphéries monopoche et bipoche. Les résultats expérimentaux obtenus sur la tenue en tension confirment que la périphérie bipoche optimale permet d'atteindre des valeurs de claquage en volume. Ces résultats montrent à la fois la faisabilité des dispositifs et leurs bonnes performances. Enfin, pour compléter notre étude de conception de périphérie Planar haute tension à poche nous avons étudié le courant de fuite des diodes réalisés. Nous avons mis en évidence que les charges dans l'oxyde et à l'interface ont une influence importante sur la tenue en tension et le courant de fuite.

Planar cell polarity (PCP) is the organization of cellular characteristics within the plane of a tissue. PCP manifests both structurally, as in the directionality of insect bristles or mammalian skin hair, or dynamically, as in vertebrate neurulation, gastrulation, and oriented cell division in the kidney. Two well-conserved pathways are known to regulate PCP in invertebrates and in vertebrates: the Frizzled/PCP pathway and the Fat-Dachsous (Ft-Ds) pathway. The latter consists of the cadherins Ft and Ds, along with the Golgi kinase Four-jointed (Fj) and the transcriptional co-repressor Atrophin (Atro). Ft and Ds can bind each other, suggesting a mechanism for signal transduction. Fj phosphorylates Ft and Ds, modulating their binding affinities for each other. Atro is proposed to link Ft-Ds signaling with downstream events in the nucleus during eye development. The details of Ft-Ds binding, and the consequences of their interactions with other members of the pathway are poorly understood. In this work, I quantitatively analyzed Ft-Ds pathway mutant clones for their effects on ommatidial polarity in the Drosophila eye. My findings suggest that the Ft-Ds pathway regulates PCP independently of asymmetric cellular accumulation of Ft or Ds. I found that Atro has a position-specific role in regulating polarity in the eye, that Fj dampens clonal polarity signals, and that asymmetric accumulation of the atypical myosin Dachs is not essential for production and propagation of a long-range PCP signal. My observations suggest that Ft and Ds interact to modulate a secondary signal that regulates long-range polarity, that signaling by the Ds intracellular domain is dependent on Ft, and that ommatidial fate specification is genetically separable from long-range signaling.

In this thesis, miniaturized wavelength interrogators based on planar lightwave circuits (PLCs) are investigated and developed for the optical fiber sensing applications in the aircraft structural health monitoring (SHM) and optofluidic analysis. Two interrogation systems based on an arrayed waveguide grating (AWG) and an Echelle diffractive grating (EDG) are developed and used to convert the optical sensing signals into strain, temperature, vibration, damage, and humidity information for the aircraft SHM. A fiber Bragg grating (FBG) sensing system using developed interrogators is then demonstrated in a field test for aircraft SHM applications. For optofluidic analysis, a PLCs based optofluidic device consisting of two on-chip lens sets is built to enhance the optical manipulation capability of particles. Then, a solution to a multi-functional Lab-on-a-Chip platform for optofluidic analysis is proposed, which integrates the developed particle maneuvering device, grating-structured sensors, and miniaturized interrogators.

iv ABSTRACT DESIGN AND CONSTRUCTION OF REDUCED SIZE PLANAR SPIRAL ANTENNA IN THE 0.5-18 GHz FREQUENCY RANGE YILDIZ, 5nan&ccedil / M.S., Department of Electrical and Electronics Engineering Supervisor: Prof. Dr. Altunkan HIZAL October 2004, 106 pages In this thesis, theoretical and practical evaluation of usual spiral antenna is revised. Working principles of both types of planar spiral antennas as Equiangular and Archimedean are introduced. A predesigned microstrip tapered balun used for feeding section of a spiral antenna is simulated on Ansoft HFSS software. Successful simulation results are obtained and measurements of implemented balun structure are made by using an HP 8722 D vector network analyzer. Antenna measurement techniques used in this study are introduced. Measurement set-ups are defined and some preliminary knowledge is given on these. As the main matter of thesis, reduced size planar spiral antennas are designed and implemented. Return loss, gain / radiation and polarization patterns of antennas are measured. Datasets of measurements are compared with each other and with reference spiral antenna. Quite promising results are obtained and size reduction of spiral antenna is achieved in many aspects.

In recent years, the interest for miniaturization of spaceborne instruments and subsystems has increased steadily, as this enables development of small and lightweight satellite classes as well as more versatile payloads on traditional spacecraft. In essence, this thesis work is an investigation of the applicability of magnetoresistive technology to a magnetometer intended for space. Two types of magnetoresistive sensors, promising with respect to performance competiveness also after considerable miniaturization, were developed and evaluated, namely magnetic tunnel junctions and planar Hall effect bridge sensors. In the case of the magnetic tunnel junctions, much effort was put on the micromanufacturing process. Two schemes were developed and evaluated for sensor contouring: one employing focused ion beam processes for rapid prototyping, and the other combining sputtering and x-ray photoelectron spectroscopy for precise etch depth monitoring during ion etching. For the former, the resulting implantation damages were investigated with chemical analysis and correlated to the sensor properties. In the latter, the depth of the etching was monitored live with a resolution sufficient to stop the etching in the 1 nm thick tunneling barrier. The effect and extent of redeposition were investigated by transmission electron microscopy and micromagnetic analysis. With the knowledge so gained, the tunneling magnetoresistance of the manufactured junctions could be improved significantly and their inherent noise could be reduced. As a step in space flight qualification, the magnetic tunnel junctions were subjected to both g and particle radiation, leaving them unaffected by the first, but rendering them a reduced tunneling magnetoresistance ratio and an increased coercivity by the latter. In the case of the planar Hall effect bridge sensors, their inherent noise was thoroughly investigated, revealing both electric and magnetic 1/f noise at low frequencies along with thermal noise at higher frequencies. In addition, an analytical model of the magnetic properties of the planar Hall effect bridges was developed, and a design process, based on the model, was established to optimize the bridges for a particular application. In conclusion, both types of sensors show great promises for use in space. Of the two, the planar Hall effect bridge sensors had a better detection limit at low frequencies, whereas the magnetic tunnel junctions were more precise at higher frequencies. However, both sensors had a bandwidth greatly exceeding that of traditional spaceborne magnetometers. A magnetometer employing the magnetic tunnel junctions from this work is currently included as payload onboard the Vietnamese satellite F-1 scheduled for launch this year. A magnetometer using magnetoresistive sensors – planar Hall effect sensors, magnetic tunnel junctions, or both – enables a mass reduction of more than two orders of magnitudes compared with traditional systems.

The purpose of this thesis is to introduce and demonstrate several biological processes or phenomena using posterior lateral line system of zebrafish as a model. The first part of this work focuses on the highly dynamic tissue remodeling under the control of morphogenetic territories. In particular, eya1 gene is studied to add a susbtantial mechanism during migration of lateral line primordium. I propose that combinatorial Wnt/β-catenin and Fgf signaling control the spatialtemporal profile of Dkk expression to dynamically confine Wnt/β-catenin to the mesenchyme. The second part of this thesis mainly discusses about the existence of tissue compartment whereby Notch signaling involves in governing the regeneration anisotropy. I also discuss the importance of centrifugal movement of hair cell progenitors to propagate and maintain bilateral symmetry in the neuromasts. The last part of this thesis emphasizes on the epigenetic study in order to validate the involvement of macroH2A during development of zebrafish embryos. / La intención de ésta tesis es introducir y demostrar diversos procesos biológicos o fenómenos, usando como modelo el sistema de la línea lateral posterior del pez cebra. La primera parte de éste trabajo se enfoca en el proceso dinámico de remodelación de los tejidos bajo el control de territorios morfogénicos. En particular, se estudia el gen Eya1, como mecanismo sustancial en la migración del primordio de la linea lateral. Propongo que la señalización combinatorial de Wnt/B-catenin y FGF controla el patrón de expresión de Dkk, para confinar dinámicamente Wnt/B-catenin al tejido mesenquimal. La segunda parte de ésta tesis, principalmente discute acerca de la existencia de una compartimentalización de los tejidos, en dónde la señalización via Noch está involucrada en el control de la anisotropía en la regeneración. También se discute la importancia de los movimientos centrífugos de los progenitores de las células ciliadas para propagar y mantener la simetria bilateral en los neuromastos. La última parte de la Tesis emfatiza en el estudio epigenético, para validar la implicación de macroH2A en el desarrolllo de los embriones del pez cebra.

Au cours de ce projet de thèse, j’ai étudié le lien fonctionnel entre la morphogénèse épithéliale et la signalisation Delta-Notch, dans le cadre de la formation du tube neural chez le poisson-zèbre. La signalisation Delta-Notch est primordiale pour le développement embryonnaire et le maintien de l’homéostasie des tissus adultes. De façon inattendue, j’ai observé suite à la perte-de-fonction de Mib une perte de la polarité apico-basale dans le neuro-épithélium de la moelle épinière embryonnaire. L’analyse plus poussée de ce phénotype m’a ensuite permis de montrer que l’activité de l’intégralité de la signalisation Notch est requise pour l’établissement de la polarité apico-basale dans le tube neural de poisson-zèbre. En effet, l’inhibition des ligands de Notch et des activateurs transcriptionnels situés en aval, Rbpja et Rbpjb, résulte en l’interruption de la polarité apico-basale. De plus, l’activation ectopique de Notch entraîne un sauvetage complet de la polarité apico-basale dans les embryons déplétés pour Mib. Finalement, le mutant Mib échoue à activer la transcription de protéines de polarité apicale Crumbs1 et Crumbs2a au cours de la formation du tube neural, ce qui suggèrerait que la signalisation Notch agit en amont des complexes de polarité. De façon surprenante, nous avons également montré que le composant de la signalisation Notch, Mib, affecte les mouvements de convergence-extension et la division cellulaire orientée, appelée C-divisions, durant la neurulation et la gastrulation à travers la signalisation PCP. Cet effet de Mib sur la PCP est indépendant de son rôle sur la signalisation Notch. Généralement, cette étude révèle un double-rôle de Mib. / In this Ph.D. project, I study the functional link between epithelial polarity and Delta-Notch signaling in the context of zebrafish neural tube morphogenesis. Notch signaling, one of the major signaling pathways and of prime importance in neurogenesis, has been widely studied for its function in cell fate specifications. Surprisingly, I found that the Notch signaling component Mindbomb (Mib) loss-of-function led to a loss of apico-basal polarity in the neuroepithelium of the embryonic spinal cord. I further explored that the activity of the entire Notch signaling pathway is actually required for the earliest steps of establishment of apico-basal polarity in the zebrafish neural tube. Indeed, inhibition of Notch ligands and downstream transcriptional activators Rbpja and Rbpjb resulted in a disruption of apico-basal polarity. Moreover, ectopic activation of Notch ensued to a complete rescue of apico-basal polarity in Mib loss of function embryos. Furthermore, Mib mutant embryos fail to upregulate the transcription of the apical polarity proteins Crumbs1 and Crumbs2a in the course of neural tube formation, suggesting that Notch signalling might act upstream of polarity complexes. Moreover, I found that Mib affects convergent-extension movements and oriented cell divisions during neurulation and gastrulation through an effect on planar cell polarity. Remarkably, this effect of Mib on PCP is independent of its role in Notch signaling. These results indicate a novel role of Mib in the regulation of PCP signaling. Altogether, this study revealed a dual role of Mib in the epithelial morphogenesis of the zebrafish neural tube.

Orientador: Paulo Ricardo da Silva / Banca: Weber Flavio Pereira / Banca: Marcelo Messias / Resumo: Consideramos dois casos principais de bifurcação de órbitas periódicas não hiperbólicas que dão origem a ciclos limite. Nosso estudo é feito para sistemas lineares por partes com três zonas em sua fórmula mais geral, que inclui situações sem simetria. Obtemos estimativas tanto para a amplitude como para o período do ciclo limite e apresentamos uma aplicação de interesse em engenharia: sistemas de controle. / Abstract: We consider two main cases of bifurcation of non hyperbolic periodic orbits that give rise to limit cycles. Our study is done concerning piecewise linear systems with three zones in the more general formula that includes situations without symmetry. We obtain estimates for both the amplitude and the period of limit cycles and we present a applications of interest in engineering: control systems. / Mestre