La croissance rapide du marché des télécommunications a conduit à une augmentation significative du nombre de bandes de fréquences allouées et à un besoin toujours plus grand en terminaux offrant un accès à un maximum de standards tout en proposant un maximum de services. La miniaturisation de ces appareils, combinée à la mise en place de fonctions supplémentaires, devient un vrai challenge pour les industriels. Une solution consiste à utiliser des fonctions hyperfréquences accordables (filtres, commutateurs, amplificateurs,...). A ce jour, trois technologies d'accord sont principalement utilisées : capacités variables, matériaux agiles ou encore MEMS RF. Dans le cadre de cette thèse, nous avons travaillé sur l'optimisation de dispositifs hyperfréquences reconfigurables en utilisant des couches minces ferroélectriques KTN et des diodes varactor. Nos premiers travaux étaient relatifs à l'optimisation des dispositifs hyperfréquences accordables à base de couche minces KTN. Dans ce sens, nous avons tout d'abord caractérisé le matériau KTN en basse et haute fréquence afin de déterminer ses caractéristiques diélectriques et ses caractéristiques en température. Nous avons ensuite réalisé des dispositifs hyperfréquence élémentaires tels des capacités interdigitées et des déphaseurs à base de KTN. Leurs performances ont alors été comparées aux mêmes dispositifs réalisés cette fois à base de la solution la plus utilisée BST. Bien qu'un léger avantage soit acquis à la solution BST, il n'en reste pas moins vrai que les résultats avec le matériau KTN sont très proches indiquant que cette voie peut également, après optimisation, apporter une alternative au BST. La seconde partie de nos travaux concerne la réalisation de filtres planaires accordables en fréquence à base de matériaux KTN et de diodes varactor. Nous avons ainsi réalisé deux filtres passe-bande accordables. Un premier filtre passe-bande de type " open loop " possédant deux pôles agiles en fréquence centrale et un second filtre passe-bande de type SIR rendant possible l'accord de sa fréquence centrale ainsi que de sa bande passante à partir de diodes varactor. Lors de la conclusion sur nos travaux, nous évoquons les suites à donner à ce travail et les perspectives.

Cooper, Heron and Heward define maintenance as the extent to which a learner continues to perform a target behavior after the intervention has been terminated. Testing for maintenance allows the trainer to see if gains were sustained following the termination of a treatment program. In addition, once it is shown that a learner's skills have remained in the repertoire, assessment of generalization is possible. Previous literature in behavior skills training have assessed maintenance in a variety of settings for a variety of skills. Following maintenance assessments, booster sessions are commonly used to re-train skills that did not maintain at criterion levels. The current project assessed the maintenance of caregivers' skills following a training package used to teach three behavior management techniques (use reinforcement, pivot, protect-redirect) at a large, residential care facility. Procedures were developed to assess caregivers' maintenance of the three behavior management techniques using a pre-test- post-test design. If needed, skills were re-established using 5-20 minute booster sessions. The results showed that time between post-test and maintenance did not seem to have a strong effect on maintenance scores. In general, post-test scores were somewhat indicative of maintenance scores, and patterns were most apparent across tools.

No description available.

The advances in modern communication systems have brought about devices with more functionality, better performance, smaller size, lighter weight and lower cost. Meanwhile, the requirement for newer devices has become more demanding than ever. Tunability and flexibility are both long-desired features. Tunable devices are ‘smart’ in the sense that they can adapt to the dynamic environment or varying user demand as well as correct the minor deviations due to manufacturing fluctuations, therefore making it possible to reduce system complexity and overall cost. It is also desired that electronics be flexible to provide conformability and portability. Previously, tunable devices on flexible substrates have been realized mainly by dicing and assembling. This approach is straightforward and easy to carry out. However, it will become a “mission impossible” when it comes to assembling a large amount of rigid devices on a flexible substrate. Moreover, the operating frequency is often limited by the parasitic effect of the interconnection between the diced device and the rest of the circuit on the flexible substrate. A recent effort utilized a strain-sharing Si/SiGe/Si nanomembrane to transfer a device onto a flexible substrate. This approach works very well for silicon based devices with small dimensions, such as transistors and varactor diodes. Large-scale fabrication capability is still under investigation. A new transfer technique is proposed and studied in this research. Tunable BST (Barium Strontium Titanate) IDCs (inter-digital capacitors) are first fabricated on a silicon substrate. The devices are then transferred onto a flexible LCP (liquid crystalline polymer) substrate using iv wafer bonding of the silicon substrate to the LCP substrate, followed by silicon etching. This approach allows for monolithic fabrication so that the transferred devices can operate in millimeter wave frequency. The tunability, capacitance, Q factor and equivalent circuit are studied. The simulated and measured performances are compared. BST capacitors on LCP substrates are also compared with those on sapphire substrates to prove that this transfer process does not impair the performance. A primary study of a reflectarray antenna unit cell is also conducted for loss and phase swing performance. The BST thin film layout and bias line positions are studied in order to reduce the total loss. Transferring a full-size BST-based reflectarray antenna onto an LCP substrate is the ultimate goal, and this work is ongoing at the University of Central Florida (UCF). HFSS is used to simulate the devices and to prove the concept. All of the devices are fabricated in the clean room at UCF. Probe station measurements and waveguide measurements are performed on the capacitors and reflectarray antenna unit cells respectively. This work is the first comprehensive demonstration of this novel transfer technique.

En l'absence d'un vaccin efficace et avec des thérapies antirétrovirales incapables d'éradiquer le virus, le VIH-1 reste un problème de santé publique mondial. Des immunothérapies à base d'anticorps sont à l'étude pour éliminer les réservoirs cellulaires, qui représentent un obstacle incontournable à la guérison du VIH-1. Les glycoprotéines d'enveloppe du VIH-1 (Env) représentent le seul antigène du virus exposé à la surface des cellules infectées et constituent donc la principale cible des anticorps. L’Env non-liée adopte sa conformation « fermée », reconnue préférentiellement par les anticorps neutralisants. L'interaction avec CD4 fait passer Env dans sa conformation « ouverte », exposant des épitopes conservés reconnus par les anticorps non-neutralisants (nnAbs) présents dans le sérum d’individus infectés par le VIH-1 (sérums VIH+). Les nnAbs peuvent éliminer les cellules infectées par la cytotoxicité cellulaire dépendante des anticorps (ADCC). Cependant, les protéines accessoires Nef et Vpu diminuent l’expression de surface de CD4 et BST-2 afin d’évader à la reconnaissance et l'élimination des cellules infectées par les nnAbs. Dans cette thèse, nous caractérisons en détail la contribution d’Env, Nef et Vpu pour échapper aux réponses humorales et explorons de nouvelles stratégies pour sensibiliser les cellules infectées à l’ADCC. Pour quantifier plus adéquatement la réponse ADCC, nous avons identifié des biais dans les tests largement utilisés, notamment pour évaluer les corrélats de protection vaccinale. Il s'agit de l'incapacité à faire la distinction entre l'élimination des cellules infectées et des cellules non-infectées, et l'utilisation de constructions virales comportant un gène rapporteur empêchant l’expression de Nef. En utilisant un nouveau marquage intracellulaire, nous avons confirmé l’effet protecteur de Nef et Vpu contre l’ADCC. Ensuite, nous avons étudié les déterminants d’Env et Vpu modulant la susceptibilité des cellules infectées à l’ADCC médiée par les nnAbs. Certaines caractéristiques structurelles d'Env modulent ses transitions conformationnelles, incluant le domaine d'association du trimère, le site de clivage de la furine et la cavité Phe43. L’altération de ces composantes augmente la sensibilité des cellules infectées à l'ADCC par les sérums VIH+. Outre l’inhibition de CD4 et BST-2, Vpu cible également NTB-A et PVR, des ligands de récepteurs activateurs des cellules NK. Cependant, la polyfonctionnalité de Vpu est compromise par l’augmentation de BST-2 par les interférons de type I (IFN-I), sensibilisant ainsi les cellules infectées aux réponses NK. En utilisant un modèle de souris humanisée, nous validons l'importance de Vpu pour échapper à la pression immunitaire des nnAbs in vivo. Enfin, nous avons exploré de nouvelles stratégies pour sensibiliser les cellules infectées à l'ADCC en modulant la conformation d’Env avec des mimétiques moléculaires de CD4 (CD4mc). Nous avons identifié des résidus bordant la cavité Phe43 modulant la sensibilité au CD4mc. L’accumulation d’Env induite par les IFN-I augmente la capacité du CD4mc à sensibiliser les cellules infectées à l'ADCC par les sérums VIH+. Globalement, cette thèse dévoile une caractérisation approfondie des déterminants viraux et cellulaires modulant la susceptibilité des cellules infectées par le VIH-1 aux réponses humorales. Une meilleure compréhension de ces mécanismes est nécessaire pour développer des nouvelles stratégies capables d’éradiquer les réservoirs viraux. / In the absence of an effective vaccine and with antiretroviral therapies unable to eradicate the virus, HIV-1 remains a global public health problem. Antibody-based immunotherapies are currently being investigated to eliminate cellular reservoirs, which represent a major obstacle towards an HIV-1 cure. HIV-1 envelope glycoproteins (Env) represent the only virus-specific antigen exposed at the surface of infected cells and therefore is the main target for antibodies. In its unliganded form, Env samples a ‘closed’ conformation, preferentially recognized by neutralizing antibodies. Interaction with CD4 drives Env into its ‘open’ conformation, exposing conserved epitopes recognized by non-neutralizing antibodies (nnAbs) present in sera from HIV-1 infected individuals (HIV+ sera). NnAbs can eliminate infected cells by antibody-dependent cellular cytotoxicity (ADCC). However, HIV-1 encodes for the accessory proteins Nef and Vpu which decrease cell surface levels of CD4 and BST-2, thus avoiding recognition and elimination of infected cells by nnAbs. In this thesis, we characterize in detail the contribution of Env, Nef, and Vpu to evade humoral responses and explore new strategies for sensitizing infected cells to ADCC. In an effort to develop a more adequate quantification of ADCC responses, we identified major biases in widely used assays, including the ones used to assess correlates of vaccine protection. These include the inability to distinguish between the elimination of infected and uninfected cells and the use of viral constructs coding for a reporter gene that prevents Nef expression. Using a novel intracellular staining, we confirmed the protective effect of Nef and Vpu against ADCC responses. Next, we studied the different Env and Vpu determinants modulating the susceptibility of infected cells to nnAbs-mediated ADCC responses. Certain Env structural features modulate its conformational transitions, including the trimer association domain, the furin cleavage site and the Phe43 cavity. Alterations of these components increase the susceptibility of HIV-1-infected cells to ADCC mediated by HIV+ sera. In addition to inhibiting CD4 and BST-2, Vpu also targets NTB-A and PVR, which act as ligands for NK cell activating receptors. However, we found that the polyfunctionality of Vpu can be compromised by the upregulation of BST-2 by type I interferons (IFN-I), thereby sensitizing infected cells to NK cell responses. Using a humanized mouse model, we validate the importance of Vpu to escape the immune pressure of nnAbs in vivo. Finally, we explored new strategies to bypass the protective effect of Vpu and Nef and sensitize HIV-1-infected cells to ADCC by modulating Env conformation using small CD4-mimetic compounds (CD4mc). We identified a network of residue lining the Phe43 cavity that modulates Env sensitivity to CD4mc. The enhanced surface expression of Env by type I IFNs boosts the ability of CD4mc to sensitize HIV-1-infected cells to ADCC by HIV+ sera. Overall, this thesis sheds light on a thorough characterization of viral and cellular determinants modulating the susceptibility of HIV-1-infected cells to humoral responses. A better understanding of these mechanisms is needed to develop new strategies able to eradicate viral reservoirs.

No description available.

Patch antennas are fundamental elements in many microwave communications systems. However, patch antennas receive/transmit signals over a very narrow bandwidth (typically a maximum of 3% bandwidth). Design modifications directed toward bandwidth expansion generally yield 10% to 40% bandwidth. The series varactor tuned patch antenna configuration was the bandwidth enhancement method explored in this research; this configuration is implemented by dividing a patch antenna into multiple sections and placing varactors across the resultant gaps. In addition to yielding a large bandwidth, the configuration has a number of ancillary benefits, including straightforward integration and design flexibility. Through the research represented by this work, the properties of the series varactor tuned patch antenna, herein referred to as the Fragmented Patch Antenna (or FPA), were explored and optimized. As a result, an innovative patch antenna was produced that yielded 63.4% frequency tuning bandwidth and covered a frequency range between 2.8 and 5.4 GHz. The wide bandwidth was achieved through a detailed parametric study. The products of this study were the discovery of multiple tuning resonances that were used to expand the tuning bandwidth and the understanding/documentation of the significance of specific antenna dimensions. Measurement results were obtained through the fabrication of a prototype antenna using semiconductor varactors. In the second research phase, the construction of capacitors using the tunable permittivity material Barium Strontium Titanate (BST) was investigated. Using this material in conjunction with nano-fabrication techniques, varactors were developed that had good estimated performance characteristics and were considered appropriate for integration into adaptive microwave circuitry, such as the tunable antenna system. The varactors were constructed by using Focused Ion Beam (FIB) milling to create a nano-scale capacitive gap in a transmission line. A combination of end-point current detection (EPD) and cross-section scanning electron (SEM) and ion beam (FIB) microscope images were used to optimize the milling procedure. The future extensions of this work include the integration of the BST varactors with the antenna design; the configuration of the developed BST varactors lends itself to a straightforward integration with the FPA antenna.