La représentation auditive motrice reflétée par la négativité de discordance chez l’enfant présentant un trouble du spectre de l’autisme

Il est maintenant bien établi que le cerveau humain est doté d’un système de neurones qui s’active tant à la perception qu’à l’exécution d’une action. Les neurones miroirs, ainsi que le système qu’ils forment avec des structures adjacentes appelées système neurones miroirs (SNM), ont été relié à la compréhension d’action et pourrait être impliqué dans les fonctions sociales de haut niveau tel que l’empathie et l’imitation. Dans la foulée spéculative reliant le SNM à la sphère sociale, le dysfonctionnement de ce système a rapidement gagné intérêt dans la genèse des anomalies du domaine social chez les personnes présentant le Trouble du spectre de l’autisme (TSA). Néanmoins, l’hypothèse voulant que le dysfonctionnement social des TSA repose sur une atteinte du SNM est controversée. En effet, les études soutenant cette hypothèse nécessitent des fonctions cognitives et sociales qui peuvent contribuer à l’obtention de résultats atypiques, telles que la compréhension des consignes, l’attention sur des stimuli sociaux ou la réalisation d’acte moteur. Récemment, un protocole auditif de négativité de discordance (MMN) utilisant des stimuli reliés à l’action humaine a été utilisé pour mesurer l’activité du SNM. Cette technique semble prometteuse dans la mesure où elle ne nécessite pas de capacités attentionnelles ou langagières, elle est brève et demande un montage minimal d’électrodes. Le premier article avait comme objectif principal de mesurer la validité de convergence du protocole MMN relié à l’action avec celui du rythme mu, le protocole le plus utilisé pour enregistrer l’activité miroir à l’aide de l’électroencéphalographie (EEG). Les modes de stimulation ont été délivrées en bloc successif à un groupe de 12 adultes en santé. Alors que les deux techniques ont modulé efficacement les régions fronto-centrales et centrales respectivement, mais ne sont pas corrélées, nous avons conclu qu’il est possible 2 qu’elles mesurent des aspects différents du SNM. Le deuxième article avait comme objectif principal de mesurer l’activité du SNM à l’aide du protocole MMN relié à l’action chez 10 enfants présentant un TSA ainsi que chez 12 enfants neurotypiques dans la même tranche d’âge (5-7ans). Chez les enfants TSA, nous avons montré un patron de latence inversée, comparativement aux enfants du groupe contrôle; ils traitaient plus rapidement les sons contrôles que les sons reliés à l’action humaine, alors que la tendance inverse était observée chez les contrôles. De plus, bien que les deux groupes différaient quant aux sons d’action, ils ne différaient pas quant aux sons contrôles. Quant à l’amplitude, les enfants TSA se distinguaient du groupe contrôle par une amplitude restreinte du son d’action provenant de la bouche. Par ailleurs, les mesures neurophysiologiques et neuropsychologiques n’étaient pas corrélées. En sommes, basé sur la prémisse que ce protocole MMN pourrait mesurer l’activité du SNM, cette thèse a comme but d’améliorer les connaissances quant à son utilisation chez l’adulte et l’enfant neurotypique ainsi que chez l’enfant TSA. Celui-ci pourrait ultimement être utilisé comme un biomarqueur potentiel du TSA.

Modélisation de l’activité électrique des oreillettes avant et après ablation par cathéter

- Réalisé au centre de recherche de l'hospital du Sacré-Coeur de Montréal. - Programme conjoint entre Université de Montréal et École Polytechnique de Montréal.

Traitement du cancer pulmonaire non à petites cellules par radiothérapie stéréotaxique d’ablation

Les néoplasies pulmonaires demeurent la première cause de décès par cancer au Québec représentant près de 6000 décès par année. Au cours des dernières années, la radiothérapie stéréotaxique d’ablation (SABR) s’est imposée comme un traitement alternatif à la résection anatomique pour les patients inopérables atteints d’un cancer pulmonaire non à petites cellules de stade précoce. Il s’agit d’une modalité de traitement qui permet d’administrer des doses élevées, typiquement 30-60 Gy en 1-8 fractions, dans le but de cibler précisément le volume de traitement tout en épargnant les tissus sains. Le Centre Hospitalier de l’Université de Montréal s’est muni en 2009 d’un appareil de SABR de fine pointe, le CyberKnife™ (CK), un accélérateur linéaire produisant un faisceau de photons de 6 MV dirigé par un bras robotisé, permettant d’administrer des traitements non-coplanaires avec une précision infra-millimétrique. Ce mémoire est dédié à la caractérisation de certains enjeux cliniques et physiques associés au traitement par CK. Il s’articule autour de deux articles scientifiques revus par les pairs. D’une part, une étude prospective clinique présentant les avantages de la SABR pulmonaire, une technique qui offre un excellent contrôle tumoral à long terme et aide au maintien de la qualité de vie et de la fonction pulmonaire. D’autre part, une étude de physique médicale illustrant les limites de l’acquisition d’images tomodensitométriques en auto-rétention respiratoire lors de la planification de traitement par CK.

Spray Pyrolysed Zinc Oxide Thin Films : Effects of Doping and Ion Beam Irradiation

In recent years scientists have made rapid and significant advances in the field of semiconductor physics. One of the most important fields of current interest in materials science is the fundamental aspects and applications of conducting transparent oxide thin films (TCO). The characteristic properties of such coatings are low electrical resistivity and high transparency in the visible region. The first semitransparent and electrically conducting CdO film was reported as early as in 1907 [1]. Though early work on these films was performed out of purely scientific interest, substantial technological advances in such films were made after 1940. The technological interest in the study of transparent semiconducting films was generated mainly due to the potential applications of these materials both in industry and research. Such films demonstrated their utility as transparent electrical heaters for windscreens in the aircraft industry. However, during the last decade, these conducting transparent films have been widely used in a variety of other applications such as gas sensors [2], solar cells [3], heat reflectors [4], light emitting devices [5] and laser damage resistant coatings in high power laser technology [6]. Just a few materials dominate the current TCO industry and the two dominant markets for TCO’s are in architectural applications and flat panel displays. The architectural use of TCO is for energy efficient windows. Fluorine doped tin oxide (FTO), deposited using a pyrolysis process is the TCO usually finds maximum application. SnO2 also finds application ad coatings for windows, which are efficient in preventing radiative heat loss, due to low emissivity (0.16). Pyrolitic tin oxide is used in PV modules, touch screens and plasma displays. However indium tin oxide (ITO) is mostly used in the majority of flat panel display (FPD) applications. In FPDs, the basic function of ITO is as transparent electrodes. The volume of FPD’s produced, and hence the volume of ITO coatings produced, continues to grow rapidly. But the current increase in the cost of indium and the scarcity of this material created the difficulty in obtaining low cost TCOs. Hence search for alternative TCO materials has been a topic of active research for the last few decades. This resulted in the development of binary materials like ZnO, SnO2, CdO and ternary materials like II Zn2SnO4, CdSb2O6:Y, ZnSO3, GaInO3 etc. The use of multicomponent oxide materials makes it possible to have TCO films suitable for specialized applications because by altering their chemical compositions, one can control the electrical, optical, chemical and physical properties. But the advantages of using binary materials are the easiness to control the chemical compositions and depositions conditions. Recently, there were reports claiming the deposition of CdO:In films with a resistivity of the order of 10-5 ohm cm for flat panel displays and solar cells. However they find limited use because of Cd-Toxicity. In this regard, ZnO films developed in 1980s, are very useful as these use Zn, an abundant, inexpensive and nontoxic material. Resistivity of this material is still not very low, but can be reduced through doping with group-III elements like In, Al or Ga or with F [6]. Hence there is a great interest in ZnO as an alternative of ITO. In the present study, we prepared and characterized transparent and conducting ZnO thin films, using a cost effective technique viz Chemical Spray Pyrolysis (CSP). This technique is also suitable for large area film deposition. It involves spraying a solution, (usually aqueous) containing soluble salts of the constituents of the desired compound, onto a heated substrate.

Characterisation of Transparent Conducting Thin Films Grown by Pulsed Laser Deposition and RF Magnetron Sputtering

Materials exhibiting transparency and electrical conductivity simultaneously, transparent conductors, Transparent conducting oxides (TCOs), which have high transparency through the visible spectrum and high electrical conductivity are already being used in numerous applications. Low-emission windows that allow visible light through while reflecting the infrared, this keeps the heat out in summer, or the heat in, in winter. A thin conducting layer on or in between the glass panes achieves this. Low-emission windows use mostly F-doped SnO2. Most of these TCO’s are n type semiconductors and are utilized in a variety of commercial applications, such as flat-panel displays, photovoltaic devices, and electrochromic windows, in which they serve as transparent electrodes. Novel functions may be integrated into the materials since oxides have a variety of elements and crystal structures, providing great potential for realizing a diverse range of active functions. However, the application of TCOs has been restricted to transparent electrodes, notwithstanding the fact that TCOs are n-type semiconductors. The primary reason is the lack of p-type TCOs, because many of the active functions in semiconductors originate from the nature of the pn-junction. In 1997, H. Kawazoe et al.[2] reported CuAlO2 thin films as a first p-type TCO along with a chemical design concept for the exploration of other p-type TCOs.

Growth and Characterization of ZnO based Heterojunction diodes and ZnO Nanostructuresby Pulsed Laser Ablation

Transparent conducting oxides (TCO’s) have been known and used for technologically important applications for more than 50 years. The oxide materials such as In2O3, SnO2 and impurity doped SnO2: Sb, SnO2: F and In2O3: Sn (indium tin oxide) were primarily used as TCO’s. Indium based oxides had been widely used as TCO’s for the past few decades. But the current increase in the cost of indium and scarcity of this material created the difficulty in obtaining low cost TCO’s. Hence the search for alternative TCO material has been a topic of active research for the last few decades. This resulted in the development of various binary and ternary compounds. But the advantages of using binary oxides are the easiness to control the composition and deposition parameters. ZnO has been identified as the one of the promising candidate for transparent electronic applications owing to its exciting optoelectronic properties. Some optoelectronics applications of ZnO overlap with that of GaN, another wide band gap semiconductor which is widely used for the production of green, blue-violet and white light emitting devices. However ZnO has some advantages over GaN among which are the availability of fairly high quality ZnO bulk single crystals and large excitonic binding energy. ZnO also has much simpler crystal-growth technology, resulting in a potentially lower cost for ZnO based devices. Most of the TCO’s are n-type semiconductors and are utilized as transparent electrodes in variety of commercial applications such as photovoltaics, electrochromic windows, flat panel displays. TCO’s provide a great potential for realizing diverse range of active functions, novel functions can be integrated into the materials according to the requirement. However the application of TCO’s has been restricted to transparent electrodes, ii notwithstanding the fact that TCO’s are n-type semiconductors. The basic reason is the lack of p-type TCO, many of the active functions in semiconductor originate from the nature of pn-junction. In 1997, H. Kawazoe et al reported the CuAlO2 as the first p-type TCO along with the chemical design concept for the exploration of other p-type TCO’s. This has led to the fabrication of all transparent diode and transistors. Fabrication of nanostructures of TCO has been a focus of an ever-increasing number of researchers world wide, mainly due to their unique optical and electronic properties which makes them ideal for a wide spectrum of applications ranging from flexible displays, quantum well lasers to in vivo biological imaging and therapeutic agents. ZnO is a highly multifunctional material system with highly promising application potential for UV light emitting diodes, diode lasers, sensors, etc. ZnO nanocrystals and nanorods doped with transition metal impurities have also attracted great interest, recently, for their spin-electronic applications This thesis summarizes the results on the growth and characterization of ZnO based diodes and nanostructures by pulsed laser ablation. Various ZnO based heterojunction diodes have been fabricated using pulsed laser deposition (PLD) and their electrical characteristics were interpreted using existing models. Pulsed laser ablation has been employed to fabricate ZnO quantum dots, ZnO nanorods and ZnMgO/ZnO multiple quantum well structures with the aim of studying the luminescent properties.

Rectangular Dielectric Resonator Antenna on a Conductor-backed Co-planar

In this paper, we present an effective excitation of a reelangular dielectric resonator antennas (DRA) with a conductor-hacked coplanar waveguide (CB-CPW). The radiation and resonance characteristics are found to van,, depending on the orientation of the DR on doe coplanar feed line. The effect of finite and infinite ground planes of CB-CPIV on the radiation characteristics of the rectangular DRA is studied. The orientation and position of the DR are optimized for maximum gain and bandwidth. The optimized antenna ,geometry offers --10.46 dBi gain and 7.5% bandwidth with low cross-polar radiation characteristics

Compact Wideband Antenna for 2.4 GHz WLAN Applications

A novel compact wideband antenna for wireless local area network (WLAN) applications in the 2.4 GHz band is presented. The proposed low profile antenna of dimensions 15 x 14.5 x 1.6 mm offers 18.6% bandwidth and an average gain of -5 dBi. The antenna can be excited directly using a 50 coaxial probe

BROADBAND WIDE COVERAGE UNIPLANAR ANTENNA

The Present thesis deals with the numerical as well as experimental investigations conducted on the resonance and radiation characteristics of Drum shaped monopole antenna, Funnel shaped monopole antenna and the shorted coplanar antenna.An introduction to the over view of antennas, state of the art planar antenna technologies, different feeding techniques and introduction of coplanar waveguides have been discussed.

Automation of Chemical Spray Pyrolysis Unit and Fabrication of Sprayed CuInS2/In2S3 Solar Cell

Aim of the present work was to automate CSP process, to deposit and characterize CuInS2/In2S3 layers using this system and to fabricate devices using these films.An automated spray system for the deposition of compound semiconductor thin films was designed and developed so as to eliminate the manual labour involved in spraying and facilitate standardization of the method. The system was designed such that parameters like spray rate, movement of spray head, duration of spray, temperature of substrate, pressure of carrier gas and height of the spray head from the substrate could be varied. Using this system, binary, ternary as well as quaternary films could be successfully deposited.The second part of the work deal with deposition and characterization of CuInS2 and In2S3 layers respectively.In the case of CuInS2 absorbers, the effects of different preparation conditions and post deposition treatments on the optoelectronic, morphological and structural properties were investigated. It was observed that preparation conditions and post deposition treatments played crucial role in controlling the properties of the films. The studies in this direction were useful in understanding how the variation in spray parameters tailored the properties of the absorber layer. These results were subsequently made use of in device fabrication process.Effects of copper incorporation in In2S3 films were investigated to find how the diffusion of Cu from CuInS2 to In2S3 will affect the properties at the junction. It was noticed that there was a regular variation in the opto-electronic properties with increase in copper concentration.Devices were fabricated on ITO coated glass using CuInS2 as absorber and In2S3 as buffer layer with silver as the top electrode. Stable devices could be deposited over an area of 0.25 cm2, even though the efficiency obtained was not high. Using manual spray system, we could achieve devices of area 0.01 cm2 only. Thus automation helped in obtaining repeatable results over larger areas than those obtained while using the manual unit. Silver diffusion on the cells before coating the electrodes resulted in better collection of carriers.From this work it was seen CuInS2/In2S3 junction deposited through automated spray process has potential to achieve high efficiencies.

PVC Supported Liquid Membrane and Carbon Paste Potentiometric Sensors Incorporating a Mn(III)-Porphyrin for the Direct Determination of Undissociated Paracetamol

PVC supported liquid membrane and carbon paste potentiometric sensors incorporating an Mn(III)-porphyrin complex as a neutral host molecule were developed for the determination of paracetamol. The measurements were carried out in solution at pH 5.5. Under such conditions paracetamol exists as a neutral molecule. The mechanism of molecular recognition between the Mn(III)-porphyrin and paracetamol, leading to potentiometric signal generation, is discussed.The sensitivity and selectivity toward paracetamol of carbon paste and polymeric liquid membrane electrodes incorporating an Mn(III)-porphyrin host were compared. The applicability of these sensors to the direct determination of paracetamol was checked by performing a recovery test in human plasma.

Fabrication of Potentiometric Sensors for the Selective Determination of Ketoconazole

The fabrication and analytical applications of two types of potentiometric sensors for the determination of ketoconazole (KET) are described. The sensors are based on the use of KET-molybdophosphoric acid (MPA) ion pair as electroactive material. The fabricated sensors include both polymer membrane and carbon paste electrodes. Both sensors showed a linear, stable and near Nernstian slope of 57.8mV=decade and 55.2mV=decade for PVC membrane and carbon paste sensors respectively over a relatively wide range of KET concentration (1×10-2-5×10-5 and 1×10-2-1×10-6). The sensors showed a fast response time of <30 sec and <45 sec. A useful pH range of 3–6 was obtained for both types of sensors. A detection limit of 2.96 10 5M was obtained for PVC membrane sensor and 6.91 10 6M was obtained for carbon paste sensor. The proposed sensors proved to have a good selectivity for KET with respect to a large number of ions. The proposed sensors were successfully applied for the determination of KET in pharmaceutical formulations. The results obtained are in good agreement with the values obtained by the standard method.

An Inter-digital Capacitive Electrode Modified as a Pressure Sensor

Inter-digital capacitive electrodes working as electric field sensors have been developed for touch panel applications. Evaluation circuits to convert variations in electric fields in such sensors into computer compatible data are commercially available. We report development of an Interdigital capacitive electrode working as a sensitive pressure sensor in the range 0-120 kPa. Essentially it is a touch/proximity sensor converted into a pressure sensor with a suitable elastomer buffer medium acting as the pressure transmitter. The performance of the sensor has been evaluated and reported. Such sensors can be made very economical in comparison to existing pressure sensors. Moreover, they are very convenient to be fabricated into sensor arrays involving a number of sensors for distributed pressure sensing applications such as in biomedical systems.

Photoconductivity studies on some semiconducting thin films for photovoltaic applications

Photoconductivity (PC) processes may be the most suitable technique for obtaining information about the states in the gap. It finds applications in photovoItaics, photo detection and radiation measurements. The main task in the area of photovoltaics, is to increase the efficiency of the device and also to develop new materials with good optoelectronic properties useful for energy conversion, keeping the idea of cost effectiveness. Photoconduction includes generation and recombination of carriers and their transport to the electrodes. So thermal relaxation process, charge carrier statistics, effects of electrodes and several mechanisms of recombination are involved in photoconductivity.A major effect of trapping is to make the experimentally observed decay time of photocurrent, longer than carrier lifetime. If no trapping centers are present, then observed photocurrent will decay in the same way as the density of free carriers and the observed decay time will be equal to carrier lifetime. If the density of free carriers is much less than density of trapped carriers, the entire decay of photocurrent is effectively dominated by the rate of trap emptying rather than by the rate of recombination.In the present study, the decay time of carriers was measured using photoconductive decay (PCD) technique. For the measurements, the film was loaded in a liquid Helium cryostat and the temperature was controlled using Lakshore Auto tuning temperature controller (Model 321). White light was used to illuminate the required area of the sample. Heat radiation from the light source was avoided by passing the light beam through a water filter. The decay current. after switching off the illumination. was measured using a Kiethely 2000 multi meter. Sets of PCD measurements were taken varying sample temperature, sample preparation temperature, thickness of the film, partial pressure of Oxygen and concentration of a particular element in a compound. Decay times were calculated using the rate window technique, which is a decay sampling technique particularly suited to computerized analysis. For PCD curves with two well-defined regions, two windows were chosen, one at the fast decay region and the other at the slow decay region. The curves in a particular window were exponentially fitted using Microsoft Excel 2000 programme. These decay times were plotted against sample temperature and sample preparation temperature to study the effect of various defects in the film. These studies were done in order to optimize conditions of preparation technique so as to get good photosensitive samples. useful for photovoltaic applications.Materials selected for the study were CdS, In2Se3, CuIn2Se3 and CuInS2• Photoconductivity studies done on these samples are organised in six chapters including introduction and conclusion.

Fabrication of Electrochemical Sensors for the Determination of Pharmaceuticals

Voltammetric sensors are an important class of electrochemical sensors in which the analytical information is obtained from the measurement of current obtained as a result of electrochemical oxidation/reduction.This current is proportional to the concentration of the analyte.Chemically modified electrodes(CMEs) have great significance as important analytical tools for the electrochemical determination of pharmaceuticals.The modification of electrode results in efficient determination of electro-active biomolecules at very lower potential without its major interferences.The operation mechanism of CMEs depends on the properties of the modifier materials that are used to promote selectivity towards the target analytes.Modified electrodes can be prepared by deposition of various compounds such as organic compounds ,conducting polymers,metal oxides,etc. on the various electrode surfaces.The thesis presents the development ,electrochemical characterization and analytical application studies of eight voltammetric sensors developed for six drugs viz.,Ambroxol,Sulfamethoxazole,PAM Chloride, Lamivudine,Metronidazole and Nimesulide.The modification techniques adopted as part of the present work include Multiwalled Carbon Nanotube(MWCNT) based modification.Electropolymerisation and Gold Nanoparticle (AuNP) based modifications.