The research investigates several critical design issues of continuous-time (CT) [Sigma Delta] modulators. The first is to investigate the sensitivity of CT [Sigma Delta] modulators to high-frequency clock spurs. These spurs down-convert the high-frequency quantization noise, degrading the dynamic range of the modulator. The second is to study the robustness of continuous-time loop filters under large RC product variations. Large RC variations in the CMOS process strongly degrade the performance of continuous-time [Sigma Delta] modulators, and reduce the production yield. The third is to model the harmonic distortion of one-bit continuous-time [Sigma Delta] modulators due to the interaction between the first integrator and the feedback digital-to-analog converter (DAC). A closed-form expression of the 3'rd-order harmonic distortion is derived and verified. Conventional CT [Sigma Delta] modulators employ all active integrators: each integrator needs an active amplifier. The research proposes a 5th-order continuous-time [Sigma Delta] modulator with a hybrid active-passive loop filter consisting of only three amplifiers. The passive integrators save power, and introduce no distortion. The active integrators provide gain and minimize internal noise contributions. A single-bit switched-capacitor DAC is employed as the main feedback DAC for high clock jitter immunity. An additional current steering DAC stabilizes the loop with the advantage of simplicity. To verify the proposed techniques, a prototype continuous-time [Sigma Delta] modulator with 2-MHz signal bandwidth is designed in a 0.25-¹m CMOS technology targeting for GPS or WCDMA applications. The experimental results show that the prototype modulator achieves 68-dB dynamic range over 2-MHz bandwidth with a 150-MHz clock, consuming 1.8 mA from a 1.5-V supply.

Συναπτική διέγερση και αναστολή βρίσκονται σε συνεχή δυναμική ισορροπία, απαραίτητη για την καλή λειτουργία του ΚΝΣ. Ένα από τα βασικά ανασταλτικά κυκλώματα του εγκεφάλου είναι αυτό της παλίνδρομης αναστολής. Το πιο χαρακτηριστικό, ίσως, παράδειγμα του κυκλώματος αυτού βρίσκεται στη CA1 περιοχή του ιππόκαμπου, η οποία προσφέρεται για ηλεκτροφυσιολογικές μελέτες in vitro, λόγω της στρωματοειδούς οργάνωσης των κυκλωμάτων ιππόκαμπου. Πρόσφατες έρευνες έχουν δείξει διαφορές στη δομή και λειτουργία των δύο πόλων του ιππόκαμπου, καθιστώντας αναγκαία τη συγκριτική τους μελέτη. Στην εργασία αυτή χρησιμοποιήθηκαν εξωκυττάριες καταγραφές από την πυραμιδική στοιβάδα σε συνδυασμό με το πρωτόκολλο διπλού ορθόδρομου ερεθισμού (περιορισμένα) και το πρωτόκολλο αντίδρομου-ορθόδρομου ερεθισμού (εκτενέστερα) για τη μελέτη του πλάτους και της διάρκειας της παλίνδρομης αναστολής σε τομές ραχιαίου και κοιλιακού ιππόκαμπου από αρσενικούς επίμυες, καθώς και της επίδρασης επί αυτής μιας σειράς καταπραϋντικών φαρμάκων που δρουν ως αλλοστερικοί ενισχυτές του GABAA υποδοχέα. Τα αποτελέσματα των πειραμάτων έδειξαν: Επαλήθευση της στρωματοειδούς οργάνωσης των κυκλωμάτων του ιππόκαμπου, με μεγαλύτερη κατευθυντικότητα των ανασταλτικών κυκλωμάτων στο ραχιαίο σε σχέση με τον κοιλιακό πόλο. Μεγαλύτερο πλάτος και διάρκεια και πιο αργή μείωση της παλίνδρομης αναστολής γενικά, και της GABAA συνιστώσας της ειδικότερα, στο ραχιαίο σε σχέση με τον κοιλιακό ιππόκαμπο. Ενίσχυση της παλίνδρομης αναστολής και στους δύο πόλους του ιππόκαμπου από διαζεπάμη, μιδαζολάμη, ζολπιδέμη, φαινοβαρβιτάλη, θειοπεντάλη, πεντοβαρβιτάλη, αλφαξαλόνη και προποφόλη. Συσχέτιση της αύξησης του πλάτους της αναστολής και της διάρκειας της ενίσχυσής της με την κλινική δράση της κάθε συγκέντρωσης φαρμάκου. Ενίσχυση της αποκλειστικά GABAA εξαρτώμενης αναστολής από υψηλές συγκεντρώσεις θειοπεντάλης και αλφαξαλόνης που δοκιμάστηκαν ενδεικτικά πολύ πέρα από τα φυσιολογικά χρονικά όριά της. Μεγαλύτερη διάρκεια ενίσχυσης της συναπτικής αναστολής από τις σχετικά υψηλότερες δόσεις φαρμάκων στο ραχιαίο σε σχέση με τον κοιλιακό πόλο. Έλλειψη δράσης του νευροστεροειδούς αλλοπρεγνανολόνη και των συνθετικών παραγώγων του στη συναπτική αναστολή. Περιορισμένος αριθμός in vivo πειραμάτων εκτίμησης της επίδρασης της αλλο-πρεγνανολόνης και των παραγώγων της στην αναστολή με το μοντέλο ελέγχου επιληπτικών κρίσεων που προκαλούνται από PTZ έδειξε πως, ενώ τα συνθετικά παράγωγα δεν είχαν καμία δράση, η αλλοπρεγνανολόνη είχε σημαντική θετική δράση / Synaptic excitation and inhibition are maintained in dynamic equilibrium, necessary for the proper function of the CNS. One of the basic inhibitory circuits of the brain is that of recurrent inhibition. The most distinctive example of recurrent inhibition occurs in the CA1 region of the hippocampus, a region particularly suited to in vitro electrophysiological investigations because of the unique lamellar organization of hippocampal circuits. Recent research has uncovered considerable differences in the structure and function of the two poles of the hippocampus necessitating a comparative study. In this study we used extracellular recordings from the pyramidal cell layer of dorsal and ventral rat hippocampal slices, in conjunction with limited use of the double orthodromic and more extensive use of the paired antidromic-orthodromic stimulation protocol in order to study the CA1 recurrent inhibition and the effects of a series of sedative drugs, with GABAA allosteric modulator properties, on it. The results of these experiments showed: A verification of the lamellar organization of hippocampal circuits. Dorsal pole inhibitory circuits showed a greater orientation specificity than ventral pole ones. A greater size and duration and a slower decay of recurrent inhibition in general, and of its GABAA-mediated component in particular, in dorsal compared to ventral hippocampus. An enhancement of recurrent inhibition in both hippocampal poles produced by diazepam, midazolam, zolpidem, phenobarbital, thiopental, pentobarbital, alfaxalone and propofol. A correlation between the enhancement of the size of recurrent inhibition or the duration of its enhancement and the clinical actions of every drug concentration tested. An enhancement of the exclusively GABAA-mediated recurrent inhibition by representative high concentrations of thiopental and alfaxalone well beyond its normal duration. A greater duration of recurrent inhibition enhancement by the relatively higher drug concentrations in dorsal compared to ventral hippocampus. A lack of action on synaptic inhibition by the neurosteroid allopregnanolone and its synthetic derivatives. A limited number of in vivo experiments assessing the effect of allopregnanolone and its derivatives on synaptic inhibition, measured as their ability to control epileptic seizures induced by acute injections of PTZ, showed that the synthetic derivatives had no effect whereas allopregnanolone had a significant positive effect.

[Truncated abstract] The principal aim of this thesis was to examine the response of the microbial community to the addition of small amounts (<50 μg C g-1 soil) of organic C substrates (‘trigger molecules’) to soil. This addition is comparative to indigenous soluble C concentrations for a range of soil types in Western Australia (typically measured between 20 and 55 μg C g-1 soil). Previously it has been reported that the application of trigger molecules to European soils has caused more CO2-C to be evolved (up to six fold) than was applied . . . Findings from this study indicated that there was an additional CO2 release (i.e. greater than the C added) on application of organic C substrates to some soil treatments. However, findings from this study indicate that the response of the microbial community to small additions of soluble C substrate is not consistent for all soil types and may vary due to greater availability of C, and supports the premise that microbial responses vary in a yet to be predicted manner between soil type and ecosystems. Differences in microbial response to the addition of soluble organic C are likely attributable to differences in soil attributes and environmental factors influencing both the diversity of microbes present and the frequency of food events. Theoretically, trigger molecules could also provide a possible control mechanism for microorganisms in arable farming systems. These mechanisms include stimulating either targeted pathogenic microorganisms that starve after depletion of a suitable substrate; or stimulating beneficial microorganisms to manipulate nutrient cycling, by targeting specific functional groups and altering mineralisation and immobilisation turnover rates.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Large close range environmental reflections or poor isolation between the transmit and receive paths of an FMCW radar can overload the receiver. The In phase and Quadrature phase (IQ) Reflected Power Canceller (RPC) provides a solution to the problem by cancelling any close range reflections. In this study a procedure to optimise the design of an RPC is developed and the performance limits of a practical RPC is investigated in depth. There are four focus areas in the evaluation and design of the IQ Reflected Power Canceller. First, an analysis was performed on a theoretical IQ Reflected Power Canceller, which provided insight into how the system functioned and made it possible to identify practical application issues that would arise during the design. The next focus area was the IQ Reflected Power Canceller’s dynamic range. Equations, based on the power and noise characteristics of each component in the canceller, were derived. From these equations, a system, with an optimised dynamic range, could be developed. Next, the IQ Reflected Power Canceller’s feedback loop stability was investigated. The canceller is an active negative feedback control system but, in order to obtain the negative feedback, the feedback signal has to be phase shifted by 180 degrees to the phase of the input signal. An analysis of the canceller’s RF phase contribution resulted in an equation that can be used to manage the nett RF phase in the feedback loop. The evaluation model of the IQ Reflected Power Canceller produced favourable results. The tests performed on the system included measuring the level of cancellation that can be achieved, whether the dynamic range corresponds to the predicted values and the amount of RF phase error that can be introduced in the feedback path while maintaining a stable system. The IQ Reflected Power Canceller was found to perform well in the evaluation. It provided a cancellation of more than 45 dB for close range reflections and the canceller remained stable across a wide range of RF centre frequencies (1 GHz). This means that the FMCW radar’s frequency modulation bandwidth will not be limited because of the IQ Reflected Power Canceller. The evaluation clearly showed that the modulator in the feedback loop is the critical element that determines the dynamic range of the radar with an RPC. / AFRIKAANSE OPSOMMING: Onvoldoende isolasie tussen die sender en ontvanger van ’n Frekwensie Gemoduleerde Kontinu Golf radar, sowel as groot weerkaatsings vanaf voorwerpe in die omgewing van die radar, veroorsaak dat die ontvanger versadig. Hierdie beperking veroorsaak dat die radar ’n verminderde dinamiese bereik het, en daarmee ook dat die radar se maksimum teiken-afstand verminder word. Die IQ Gereflekteerde Drywingskanselleerder kan as ’n oplossing gebruik word teen hierdie ongewenste refleksies. Hierdie navorsing poog om ’n kanselleerder te evalueer met die eind doel gestel daarop om ’n praktiese stelsel aanmekaar te sit. Die kanselleerder word geëvalueer deur na vier fokus areas te kyk. Eerstens word ’n ideale model opgestel, wat ’n beter begrip van die kanselleerder bewerkstellig. Uit hierdie ideale model, is daar praktiese oorwegings wat die kanselleerder affekteer, geïdentifiseer. Ten einde die dinamiese bereik van die radar ontvanger te verbeter, word ’n metode afgelei wat gebruik word om die kanselleerder se dinamiese bereik te optimeer. Hierdie metode neem die maksimum drywingsbeperkinge van die komponente in die kanselleerder in ag. Die kanselleerder is ’n aktiewe terugvoer beheerstelsel, en aangesien ’n sommeerder in die terugvoer lus gebruik word, moet die fase deur die lus met 180 grade geskuif word om sodoende ’n kansellerende sein by die ontvangde sein te tel. Die RF fase foute in die kanselleerder word geanaliseer deur ’n nie-ideale model van die kanselleerder op te stel. Hierdie nie-ideale model maak dit moontlik om die effek van ’n RF fase fout op die kanselleerder se stabiliteit te ondersoek. ’n Praktiese kanselleerder is ontwerp uit die inligting wat versamel is gedurende die evaluasie, en ’n werkende stelsel is aanmekaar gesit. Met hierdie praktiese kanselleerder is die hoeveelheid drywing-onderdrukking wat bereik kan word, gemeet. Die dinamiese bereik van die kanselleerder is ook bepaal en vergelyk met die teoreties berekende waardes. Die aannames oor die effek van die RF fase fout in die kanselleerder, is bevestig deur metings te neem. Goeie resultate is met die kanselleerder behaal. ’n Kansellasie van meer as 45 dB is gemeet vir naby-geleë refleksies. Die kanselleerder het ook stabiel gebly oor ’n wye band van senter-frekwensies (1 GHz). Dus sal die Frekwensie Gemoduleerde Kontinu Golf radar se modulasie bandwydte nie beperk word as gevolg van die kanselleerder nie. Uit die evaluasie is daar gevind dat die modulator die kritieke element in the kanselleerder se terugvoer lus is, dus bepaal die modulator die dinamiese bereik van die radar met ’n kanselleerder.

Traffic from wireless and mobile devices is predicted to increase 10-fold between 2014 and 2019, surpassing wired data traffic by 2016. Given the expected radio frequency (RF) capacity crunch, this growing wireless demand will have to be met using a variety of new technologies exploiting other parts of the electromagnetic spectrum. Promising research areas include the Millimetre Band as well as Optical Wireless Communications (OWC). Millimetre Band demonstrations have accomplished ultrafast multi-Gigabit links, making use of state-of-the-art fibre transmission systems. However, complex opto-electronic (OE) interfaces are required to convert the optical carrier into Millimetre wireless signals. To avoid these interfaces, an all-optical transparent network is proposed here, spanning over both the fibre and OWC domains, in order to deliver ultrahigh data rates to mobile end-users in indoor environments. This is supported by the recent deployment of fibre-to-the-home (FTTH) networks creating the potential for Terabit aggregate connections at the user's doorstep. Therefore, infrared fibre-wireless-fibre (FWF) links are studied to support data rates over 100 Gb/s in nomadic applications. The link coverage is achieved via narrow beam beamsteering over a wide field-of-view (FOV) using suitable localization and tracking techniques. The proposed model is inherently bidirectional and transparent, i.e. independent of the data rate and modulation format. In this thesis, the potential for ultrafast wide coverage OWCs using SMF-based transceivers and coherent transmission is demonstrated. A record data rate of 418 Gb/s and 209 Gb/s with a wide FOV of &theta;_FOV=±30° and &theta;_FOV=±20°, respectively, is shown at a free space range of 3 m. To the best of our knowledge, this is the fastest demonstration of an indoor wireless link that offers practical room-scale coverage. The automated alignment of this FWF link is also demonstrated with the design and implementation a mm-accurate localization and tracking system. Finally, architectures for point-to-multipoint communications are explored in order to adapt the system to multiple users.

Depuis plusieurs années, le volume de données échangé à travers le monde augmente sans cesse. Pour gérer cette large quantité d’information, des débits élevés de transmission de données sur de longues distances sont essentiels. Puisque les interconnections à base de cuivre ne peuvent pas suivre cette tendance, des systèmes de transmission optique rapides sont requis dans les centre de données. Dans ce contexte, la photonique sur silicium est considérée comme une solution pour obtenir des circuits photoniques intégrés à un coût réduit. Bien que cette technologie ait connu une croissance significative au cours de la dernière décennie, les transmetteurs actuels à haut débit de transmission sont principalement basés sur des sources laser externes. Par conséquent, l’objectif de ce travail de thèse était de concevoir et produire un transmetteur à haut débit de transmission de données pour la photonique sur silicium, doté d’une source laser intégrée.Ce transmetteur se compose d’un modulateur silicium de type Mach-Zehnder, co-intégré sur la même plaque avec un laser hybride III-V sur silicium à réseaux de Bragg distribués, dont la longueur d’onde d’émission peut être contrôlée électriquement autour de 1.3μm. La conception des différents éléments constituant à la fois le laser (coupleurs adiabatique entre le III-V et le silicium, miroirs de Bragg) et le modulateur (jonctions p-n, électrodes à ondes progressives) est détaillée, de même que leur fabrication. Pendant la caractérisation des transmetteurs, des taux de transmission de données jusqu’à 25Gb/s, pour des distances allant jusqu’à 10km ont été démontrés avec succès, avec la possibilité de contrôler la longueur d’onde jusqu’à 8.5nm. Par ailleurs, afin d’améliorer l’intégration de la source laser avec le circuit photonique sur silicium, une solution basée sur le dépôt à basse température (en-dessous de 400°C) d’une couche de silicium amorphe pendant la fabrication est aussi évaluée. Des tests sur une cavité laser à contre-réaction distribuée ont montré des performances au niveau de l’état de l’art (avec des puissances de sortie supérieures à 30mW), prouvant ainsi la viabilité de cette approche. / For several years, the volume of digital data exchanged across the world has increased relentlessly. To manage this large amount of information, high data transmission rates over long distances are essential. Since copper-based interconnections cannot follow this tendency, high-speed optical transmission systems are required in the data centers. In this context, silicon photonics is seen as a way to obtain fully integrated photonic circuits at an expected low cost. While this technology has experienced significant growth in the last decade, the high-speed transmitters demonstrated up to now are mostly based on external laser sources. Thus, the aim of this PhD thesis was to design and produce a high-speed silicon photonic transmitter with an integrated laser source.This transmitter is composed of a high-speed silicon Mach-Zehnder, co-integrated on the same wafer with a hybrid III-V on silicon distributed Bragg reflector laser, which emission wavelength can be electrically tuned in the 1.3μm wavelength region. The design of the various elements constituting both the laser (III-V to silicon adiabatic couplers, Bragg reflectors) and the modulator (p-n junctions, travelling-wave electrodes) is thoroughly detailed, as well as their fabrication. During the characterization of the transmitters, high-speed data transmission rates up to 25Gb/s, for distances up to 10km are successfully demonstrated, with the possibility to tune the operating wavelength up to 8.5nm. Additionally, in order to further improve the integration of the laser source with the silicon photonic circuit, a solution based on the low-temperature (below 400°C) deposition of an amorphous silicon layer during the fabrication process is also evaluated. Tests on a distributed feed-back laser structure have shown performances at the state-of-the-art level (with output powers above 30mW), thus establishing the viability of this approach.

Made available in DSpace on 2015-07-22T20:50:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-12-26. Added 1 bitstream(s) on 2015-08-11T03:25:54Z : No. of bitstreams: 1 Publico-11764a.pdf: 1760987 bytes, checksum: 26371946d909a5525c0bd6c7cc6d7c33 (MD5). Added 1 bitstream(s) on 2015-08-11T03:25:55Z : No. of bitstreams: 2 Publico-11764a.pdf: 1760987 bytes, checksum: 26371946d909a5525c0bd6c7cc6d7c33 (MD5) Publico-11764b.pdf: 969495 bytes, checksum: d87ae7194b036aaff67581e32d434f64 (MD5) / Objetivo: Verificar se indivíduos susceptíveis e não-susceptíveis às convulsões clônicas induzidas pelo DMCM, um agonista inverso benzodiazepínico, diferem: 1) na sensibilidade ao efeito hipnótico induzido pelo diazepam e por outros moduladores alostéricos positivos do receptor GABAA; 2) na marcação auto-radiográfica com o [3H]- flunitrazepam ao longo do encéfalo; 3) na marcação de [3H]-L-glutamato e do [3H]-MK 801 em membranas de regiões encefálicas; e 4) na atividade da enzima Na+/K+- ATPase, bem como na marcação da [3H]-ouabaína às isoenzimas Na+/K+- ATPase de alta e de baixa afinidade ao radioligante em membranas de regiões encefálicas. Métodos: Ratos Wistar, machos, adultos foram administrados intraperitonealmente duas vezes com uma DC50 de DMCM (com intervalo de uma semana entre as administrações), obtendo-se dois grupos distintos: o grupo susceptível às convulsões (SC), que apresentou convulsões clônicas em ambas as exposições à droga, e o grupo não-susceptível às convulsões (NSC), que não apresentou alterações motoras em ambas as exposições. Após cerca de 25 dias da segunda administração de DMCM, os grupos selecionados foram submetidos aos experimentos com os hipnóticos diazepam, pentobarbital e etanol, nos quais foram registrados o tempo e a latência de sono ou foram sacrificados e seus encéfalos retirados para os seguintes ensaios bioquímicos: 1) auto-radiografia com o [3H]-flunitrazepam; 2) marcação de [3H]-L-glutamato e de [3H]- MK 801 em membranas neuronais; e 3) atividade enzimática da Na+/K+- ATPase e marcação de [3H]-ouabaína em enzimas de alta e baixa afinidade em membranas neuronais. Resultados: O grupo SC apresentou menor tempo de sono induzido pelo diazepam com relação ao grupo NSC, embora não tenham se distinguindo no tempo de sono induzido pelo pentobarbital e pelo etanol. Com relação aos experimentos bioquímicos, observou-se uma menor marcação de [3H]-flunitrazepam na região CA2 ventral do hipocampo no grupo SC. Quanto à ligação de [3H]-L-glutamato foi menor no grupo SC nas regiões do córtex frontal, amígdala + córtex límbico e hipocampo, enquanto que a ligação de [3H]-MK 801 foi menor no córtex frontal, hipocampo e estriado. Embora os grupos não tenham se diferenciado na atividade enzimática da Na+/K+- ATPase, o grupo SC apresentou uma menor marcação da [3H]-ouabaína em isoenzimas de alta afinidade nas regiões do tronco encefálico, córtex frontal e hipocampo, bem como uma menor marcação de [3H]-ouabaína nas regiões do tronco encefálico e córtex frontal em isoenzimas de baixa afinidade. Conclusão: As diferenças entre os grupos quanto à sensibilidade ao efeito convulsivante do DMCM, à ansiedade observada em experimentos anteriores, bem como à sensibilidade ao efeito hipnótico do diazepam podem estar associadas a uma diferença nos sítios benzodiazepínicos da região CA2 ventral do hipocampo, na ix atividade glutamatérgica e em isoformas específicas da Na+/K+- ATPase em determinadas regiões encefálicas. / Objective: The aim of this work was to verify if rats susceptible and non-susceptible to clonic convulsions induced by DMCM, a benzodiazepine inverse agonist, differ: 1) in the sensitivity to the hypnotic effect induced by diazepam and by others positive allosteric modulators of GABAA receptors; 2) in auto-radiographical analysis of [3H]-flunitrazepam binding along the brain; 3) in the binding of [3H]-L-glutamate and of [3H]-MK 801 in membranes from discrete brain regions; and 4) in the Na+/K+-ATPase activity, as well as in the binding of [3H]-ouabain to Na+/K+-ATPase isoenzimes with high and low affinity to the radioligand in membranes from discrete brain regions. Methods: Adult, male, Wistar rats were administered with two intraperitoneal injections of a convulsant dose 50% (CD50) of DMCM (one-week interval between them), resulting in two distinct groups: the group susceptible to clonic convulsions (SC), which presented clonic convulsions in both the expositions to the drug, and the group nonsusceptible to clonic convulsions (NSC), which did not present any motor disturbance in both the expositions. After 25 days from the second exposition to DMCM, the selected groups were submitted to the experiments with the hypnotics diazepam, pentobarbital and ethanol, in which were registered the latency and the time of sleep or they were sacrified and their brains were removed to carry out the following assays: 1) autoradiography with [3H]-flunitrazepam; 2) binding with the [3H]-L-glutamate and with the [3H]-MK 801 in neuronal membranes; 3) enzymatic activity of Na+/K+-ATPase and binding of [3H]-ouabain to the isoenzimes with high and low affinity in neuronal membranes. Results: The SC group presented a lower sleeping time induced by diazepam compared to the NSC group, and did not differ in the sleeping time induced by pentobarbital and ethanol. Concearning the biochemical experiments, it was observed a lower binding of [3H]-flunitrazepam in the CA2 subregion of ventral hippocampus in the SC group. A lower binding of [3H]-L-glutamate was also observed in the SC group in the frontal cortex, amygdala plus limbic cortex and hippocampus, whereas the binding of [3H]-MK 801 was lower in the frontal cortex, hippocampus and striatum compared to the NSC group. Althougt the groups did not differ in the enzymatic activity of Na+/K+- ATPase, the SC group presented a lower binding of [3H]-ouabain to the high-affinity isoenzimes in the brainstem, frontal cortex and hippocampus, as well as a lower binding of [3H]-ouabain to the low-affinity isoenzimes in the brainstem and in the frontal cortex compared to the NSC group. Conclusion: The differences between the groups concerning the sensitivity to the convulsant effect of DMCM, the level of anxiety previously observed, as well as the sensitivity to the hypnotic effect of diazepam may be associated with the GABAA/benzodiazepine site in CA2 subregion of ventral hippocampus, with glutamatergic activity and with specific isoforms of Na+/K+-ATPase in rat brain regions. / TEDE / BV UNIFESP: Teses e dissertações

Orientador: Prof. Dr. Marcos Roberto da Rocha Gesualdi / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2016. / A holografia permite o registro e a reconstrução óptica de imagens 3D de objetos, pois um holograma carrega as informações de intensidade e fase da função da onda óptica espalhada pelo objeto. Com a evolução do armazenamento e da velocidade de processamento de dados em computadores, a viabilidade dos hologramas gerados por computador tem evoluído no decorrer dos anos. Na atualidade, a implementação experimental dos CGHs tem sido realizada por meio de novos dispositivos opto-eletrônicos, como os moduladores espaciais de luz, câmeras CMOS, e CCDs de alta resolução, além dos novos materiais fotossensíveis, permitindo o registro e reconstrução óptica de objetos tridimensionais e de feixes ópticos especiais. Por outro lado, as possibilidades do FPGA, um dispositivo lógico programável capaz de criar diferentes tipos de circuitos digitais, permite desenvolver um hardware capaz de melhorar os tempos de processamentos para a geração dos hologramas sintéticos. O objetivo deste trabalho é estudar a holografia gerada por computador a partir de algoritmos (software), a realização da reconstrução óptica destes hologramas usando dispositivos SLMs, bem como as possibilidades de implementação dos CGHs via FPGA (hardware) de cenas 3D virtuais. Desta forma, foram obtidos resultados de construção (gravação) numérica de CGHs de imagens estáticas e dinâmicas, 2D e 3D, via MATLAB e de reconstrução (reprodução) óptica usando dispositivos SLMs destas imagens estáticas e dinâmicas (cenas). / Holography allows three-dimensional recording and optical reconstruction of objects, as a hologram carries the information of the intensity and the optic wave¿s phase function spread over the object. With the evolution of data storage and processing speed in computers, the viability of creating holograms by computer has advance through the years. Today, the CGHs¿s experimental implementation has been performed by new optoelectronic devices, as special light modulators, CMOS cameras, e high resolution CCDs, besides new photosensitive materials, allowing recording and optical reconstruction of 3D objects and special optic beams. On the other hand, FPGA possibilities, a logic programmable device able to create different kind of digital circuits, enables the development of hardware to improve processing time when creating synthetic holograms. The main objective of this work is to study holography created by computer using algorithms (software), moreover the optical reconstruction of holograms utilizing SLMs devices, as the possibility of implementing CGHs by FPGA (hardware), of virtual 3D scenes. Therefore, results of numeric construction (recording) of CGHs of static and dynamic images were obtained, 2D and 3D, using MATLAB, and the optical reconstruction (reproduction) using SLMs devices of these images (scenes).

En premier lieu, des couches minces épitaxiales ont été obtenues sur des substrats de silicium grâce à l’utilisation de l’épitaxie par jets moléculaire et de couches tampons de titanate de strontium SrTiO3. Une technique de croissance par co-déposition a été développée de manière à obtenir un rapport Ba:Ti proche de la stoechiométrie, et ce afin d’éviter la formation de défauts cristallins dans la couche de BaTiO3. Le matériau déposé cristallise dans une structure de symétrie quadratique, ce qui est unpré-requis pour l’obtention de propriétés électro-optiques. De plus, selon les conditions de croissance, l’axe c de la maille élémentaire quadratique a pu être ajusté de manière à être aligné parallèlement ou perpendiculairement à la surface du substrat. L’utilisation d’une mince couche tampon de nucléation a également permis de croitre des films mincesBaTiO3 épitaxiées par pulvérisation, technique largement répandue en milieu industriel.Un coefficient de Pockels élevé a par la suite été obtenu sur de tellescouches épitaxiées. La valeur mesurée de 148pmV est clairement supérieure aux valeurs admises dans la littérature pour d’autres matériaux nonlinéairestels que le niobate de lithium, pour lequel un coefficient de31pmV est rapporté. La méthode de caractérisation électro-optique développée à cette occasion révèle également le caractère ferroélectrique des couches de BaTiO3, observé pour la première fois dans de tels matériaux épitaxiés sur silicium.Finalement, ces couches minces électro-optiquement actives ont été intégrées dans des dispositifs photoniques sur silicium. Dans cette optique,une structure de guide d’onde à fente a été utilisée en insérant 50nm deBaTiO3 entre deux couches de silicium. Dans ce type de structure, le confine mentoptique est 5 fois supérieur à celui obtenu pour des guides d’onde en silicium avec une gaine à base de BaTiO3. Des guides d’ondes rectilignesont tout d’abord été fabriqués, pour lesquels des pertes optiques del’ordre de 50−100 dB/cm ont été mesurées. Par la suite, des composants passifs fonctionnels ont été fabriqués, tels que des interféromètres typeMach-Zehnder, des résonateurs circulaires et des coupleurs. Finalement,la fonctionnalité de composants actifs a été démontrée pour la première fois, en se basant notamment sur des résonateurs ayant un facteur de qualité Q d’environ 5000, et pour lequel la résonance varie en fonction du champ électrique transverse. L’origine physique de cette variation n’a cependant pas pu être expliquée sur la seule base de l’effet Pockels. Cette thèse démontre que l’utilisation de nouveaux matériaux électro optiquement actifs au coeur de dispositifs photoniques sur silicium créede nouvelles opportunités pour la conception et l’ingénierie de circuitsphotoniques. L’intégration d’oxydes tels que barium titanate permet d’envisager de nouveaux concepts de dispositifs pour ajuster, moduler ou commuter la lumière au sein de circuits photoniques denses. De nouveaux défis et perspectives s’ouvrent également aux scientifiques pour modifier artificiellement les propriétés électro-optiques de ces matériaux, que ce soit par contrainte, dopage ou par l’ingénierie de multicouches. De telles avancées pourront sans aucun doute fortement améliorer les performances des dispositifs. / A novel concept of utilizing electro-optical active oxides in silicon photonic devices is developed and realized in the frame of this thesis. The integration of such oxides extends the silicon photonics platform by non-linear materials, which can be used for ultra-fast switching or low-power tuning applications. Barium titanate is used as active material as it shows one of the strongest Pockels coefficients among all oxides. Three major goals are achieved throughout this work: First, thin films of BaTiO3 are epitaxially grown on silicon substrates via molecular beam epitaxy (MBE) using thin SrTiO3 buffer layers. A shuttered co-deposition growth technique is developed in order to minimize the formation of defects in the BaTiO3 films by achieving a 1:1 stoichiometry between barium and titanium. The layers show a tetragonal symmetry and are therefore well-suited for electro-optical applications. The orientation of the long c -axis of the BaTiO3 crystal can be tuned to point perpendicular or parallel to the film surface, depending on the growth conditions. In addition, thin MBE-grown seed layers are combined with rf-sputter deposition. With this hybrid growth approach, rather thick ( > 100 nm), epitaxial BaTiO3 layers on silicon substrates are obtained with a commercially available, wide spread deposition technique. As a second goal, a strong Pockels coefficient of reff = 148 pm/V is determined in the epitaxial BaTiO3 films. This first experimental result on the electro-optical activity of BaTiO3 layers on silicon shows a clear enhancement compared to alternative non-linear materials such as lithium niobate with reff = 31 pm/V. By means of the electro-optical characterization method, also the presence of ferroelectricity in the films is demonstrated. Third, the electro-optical active BaTiO3 layers are embedded into silicon photonic devices. For this purpose, a horizontal slot-waveguide structure with a ~50 nm-thick BaTiO3 film sandwiched between two silicon layers is designed. With this design, the optical confinement in the active BaTiO3 layer is enhanced by a factor of 5 compared to Si-waveguide structures with a standard cross section and BaTiO3 as cladding. Straight BaTiO3 slot-waveguides with propagation losses of 50 − 100 dB/cm as well as functional passive devices such as Mach-Zehnder-interferometers, couplers, and ring resonators are experimentally realized. Additionally, first active ring resonators with Q-factors of Q~5000 are fabricated. The physical origin of the observed resonance shift as a function of the applied bias voltage, however, can not be conclusively clarified in the present work. The combination of high-quality, functional BaTiO3 layers with silicon photonic devices as demonstrated in this thesis offers new opportunities by extending the design palette for engineering photonic circuits with the class of electro-opticalactive materials. The integration of oxides such as BaTiO3 enables novel device concepts for tuning, switching, and modulating light in extremely dense photonic circuits. The integration also opens exciting challenges for material scientists to tailor the electro-optical properties of those oxides by strain engineering or fabrication of superlattice structures, which could ultimately lead to another boost of their electro-optical properties.

La glycoprotéine P ou Pgp est une protéine de transport transmembranaire qui a pour rôle principal d'évacuer hors des cellules les xénobiotiques et les toxines. Elle agit comme une pompe à efflux et est surexprimée par certaines cellules cancéreuses. Ainsi, via ce mécanisme, les cellules tumorales peuvent devenir résistantes aux antitumoraux et conduire à l'échec des traitements lors de la chimiothérapie anticancéreuse. Aussi, la modulation de l'activité de cette protéine peut être un des moyens permettant l'amélioration des traitements anticancéreux. La Pgp possède plusieurs sites de fixation de substrats dont deux sont relativement proches spatialement : un site à stéroïdes et un site à ATP permettant d'hydrolyser l'ATP, source d'énergie nécessaire au fonctionnement de la Pgp. Notre objectif a été de synthétiser des modulateurs bivalents stéroïdes/bras/nucléosides. Pour cela, nous avons dans un premier temps préparé des analogues de bases puriques et plus particulièrement des didéazapurines, les 5- et 6-azaindoles et les trioxopyrrolopyridines correspondant puis effectué la glycosylation de ces derniers. Dans un second temps, des modulateurs stéroïdiens ont été synthétisés : plusieurs ont montré une bonne activité modulatrice de la Pgp. Enfin, des bras polyéthylènes glycols de longueurs variables ont été reliés à l'adénine pour être ensuite fixés aux stéroïdes via une fonction amide / P-glycoprotein Pgp is a transmembrane transporter protein that protects cells from potentially toxic exogenous compounds. This protein acts as a molecular pump and is overexpressed in cancer cells. So via that mechanism, tumor cells exhibit intrinsic or acquired cross-resistance to diverse chemotherapeutic agents, resulting in the failure of chemotherapy for some cancers. The modulation of the efflux activity of that protein can be one of the mean that could increase anticancer treatments efficiency. Pgp has different substrates sites, two of which are spatially close : the steroid site and the ATP site, the latter is in charge of ATP hydrolysis which give the required energy for the Pgp efflux activity. Our goal was to synthesize bivalent modulators steroids/linker/nucleosides. First we have obtained purine bases analogues and particularly didéazapurines such as 5- and 6-azaindoles and the corresponding trioxopyrrolopyridines, then we have carried out the glycosylation of those compounds. Then, steroids modulators have been synthesized : some of them have shown a good modulation activity toward Pgp. Finally, polyethylene glycols chains with different length have been grafted on adenine so that they could be attached to the steroids via an amide function