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Pain is a complex, ubiquitous phenomenon that can be debilitating and costly. Although it is well known that some individuals can easily tolerate pain while others are more intolerant to pain, little is known of the neurophysiological bases of these differences. Because differences in sensory information processing may underlie variability in tolerance to pain and because measures of sensory gating are used to explore differences in sensory information processing, sensory gating among college students (N = 14) who are tolerant or intolerant to pain was investigated. This investigation explored the hypothesis that those who were more tolerant to pain would evidence greater sensory gating. Pain tolerance was first determined using a cold pressor task. Sensory gating was then determined by the amount of attenuation of the amplitude of a second painful, electrical, somatosensory stimulus (S2) in relation to the amplitude of an identical first stimulus (S1) in a paired-stimulus evoked potential (EP ) paradigm. The results obtained showed the intolerant group exhibiting greater physiological reactivity than the tolerant group, indicating that the tolerant group attained greater sensory gating than the intolerant group. / Ph. D.

Smoking is one of the leading causes of death in the world. About 80% of smokers start smoking before the age of 18. In the Appalachian area and the South in the United States, smoking percentages among adults and adolescents are higher than in other regions. Female smoking shows a variety of different trends from male smoking, and smoking brings particular health problems related to production to female smokers. These findings highlighted the importance of studying female teenage smokers in southwest Virginia. The initial project aimed to identify risk factors that might prevent smoking in an early stage. Dr. Helen Crawford led the Cognitive Neuroscience Lab at Virginia Tech in discovering the psychophysiological vulnerabilities of female teenage smokers. Toward this end, event-related potential (ERP), personality, and behavioral data were collected in teenage female smokers and non-smokers. These data were analyzed to examine possible psychophysiological vulnerabilities in female teenage smokers such as deficits in brain and cognitive function, personality traits, and environment influences. The purpose of this dissertation is to further analyze these data to elaborate and clarify the relationships among these vulnerabilities toward understanding teenage smoking behavior. Participants were 49 teenage girls (smokers and non-smokers) with age from 14 to 18. The measures included sensory gating, platelet MAO-B activity, attention, memory, temperament, schizotypal personality, recognition of facial expressions, taste and smell. The initial set of analyses compared smokers and non-smokers, including those classified as high and low dependent, on all dependent measures. The results suggested some psychophysiological vulnerabilities in female teenage smokers, which have been used as support for the self-medication and the orbito-frontal dysfunction models of why teenagers smoke (Crawford et al., 2004). Further examination of these factors may help teenagers to reduce the smoking dependency and possibly improve cognitive function. Specifically, this dissertation focused on the role of the variable of monoamine oxidase-B (MAO-B) in the correlations among sensory gating, MAO and other cognitive and personality measures. All smokers were divided into high and low MAO groups first. Comparison analyses were conducted between them. The high MAO group showed better sensory gating function than the low MAO group. Correlation analyses were conducted among all of the measures. The significant linear relationships between MAO and sensory gating, MAO and CO level and MAO and temperament were demonstrated. MAO activity positively correlated with the sensory gating function and negatively correlated with CO level and temperament characteristics. Finally, to explore the mechanisms of the relationship between MAO and sensory gating, the neurotransmitter systems related to MAO and sensory gating were discussed. / Ph. D.

Modern devices such as smartphones and smartwatches spend a large amount of their life idle, waiting for external events. During this time, they are expending energy, using up battery life. Increasing power consumption is a rising concern to users and researchers alike. Power gating, turning off a blocks of hardware when idle, reduces static power consumption. The Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) currently employed in processors leak current. Even in power gated circuits, MOSFET power gating may only save between 60-80% of power. A different type of switch, a Nanoelectromechanical Systems (NEMS) switch, presents an air gap between the source and drain while in the off state, eliminating subthreshold leakage current. The NEMS switch is slower to operate and only has a finite number of switching before breaking. They should be switched with caution. Proposed in this thesis is a hybrid power gating model wherein a MOSFET is placed in series with a NEMS switch. Power gating the Floating Point Unit (FPU) of a processor is studied through the use of modern open source computer architecture simulators. Each switch type is used to model power gating to observe energy savings and performance costs. The hybrid power gating model is more flexible across a variety of applications. Energy savings are comparable to single NEMS switch power gating for applications with low FPU activity. Any performance loss remains low, matching that of MOSFETs. Processor electrical costs are heavily reduced while devices remain operating at a near-optimal speed. / Master of Science

Yes / X-ray crystallography has provided tremendous insight into the different structural states of membrane proteins and, in particular, of ion channels. However, the molecular forces that determine the thermodynamic stability of a particular state are poorly understood. Here we analyze the different X-ray structures of an inwardly rectifying potassium channel (Kir1.1) in relation to functional data we obtained for over 190 mutants in Kir1.1. This mutagenic perturbation analysis uncovered an extensive, state-dependent network of physically interacting residues that stabilizes the pre-open and open states of the channel, but fragments upon channel closure. We demonstrate that this gating network is an important structural determinant of the thermodynamic stability of these different gating states and determines the impact of individual mutations on channel function. These results have important implications for our understanding of not only K+ channel gating but also the more general nature of conformational transitions that occur in other allosteric proteins. / Wellcome Trust

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Le sujet de cette thèse est la réduction de consommation dans les circuits digitaux, et plus particulièrement dans ce cadre les méthodes basées sur la réduction de la fréquence de commutation moyenne, au niveau transistor. Ces méthodes sont structurelles, au sens où elles ne sont pas liées à l’optimisation des caractéristiques physique du circuit mais sur la structure de l’implémentation logique, et de ce fait parfaitement indépendantes de la technologie considérée. Nous avons développé dans ce cadre deux méthodes nouvelles. La première est basée sur l’optimisation de la structure de la partie combinatoire d’un circuit pendant la synthèse logique. La seconde est centrée sur la partie séquentielle du circuit. Elle consiste en la recherche de conditions permettant de détecter qu’un sous-circuit devient inactif, de sorte à pouvoir désactiver ce sous-circuit en coupant la branche correspondante de l’arbre d’horloge, et utilise des méthodes formelles pour prouver que la fonctionnalité du circuit n’en serait pas affectée. / The topic of this thesis are methods for power reduction in digital circuits by reducing average switching on the transistor level. These methods are structural in the sense that they are not related to tuning physical properties of the circuitry but to the internal structure of the implemented logic an d therefore independent on the particular technology. We developed two novel methods. One is based on optimizing the structure of the combinatorial part of a circuit during synthesis. The second method is focused on sequential part of the circuit. It looks for clock gating conditions that can be used to disable idle parts of a circuit and uses formal methods to prove that the function of the circuit will not be altered.

L’imagerie de filtrage en polarisation est une technique populaire largement utilisée en optique pour le biomédical pour le sondage des tissus superficiels, pour le sondage de volumes plus profonds, mais aussi pour l’examen sélectif de volumes sub-surfaciques. Du fait de l’effet de ’mémoire de polarisation’ de la lumière polarisée, l’imagerie de filtrage en polarisation elliptique est sensible á des épaisseurs de tissus différentes, depuis la surface, accessible avec la polarisation linéaire, jusqu’á une épaisseur critique accessible par la polarisation circulaire. Nous nous concentrons sur des méthodes utilisant des combinaisons de polarisations elliptiques afin de sélectionner la portion de lumière ayant maintenu son état de polarisation et éliminer le fond pour un meilleur contraste avec de plus une information sur la profondeur. Avec ce type de filtrage, il est possible d’accéder á des profondeurs de tissus biologiques bien définies selon l’ellipticité de polarisation. De plus, ces travaux ont permis d’étendre la méthode á la spectroscopie pour quantifier la concentration en chromophores á une profondeur spécifique. Les méthodes développées ont été validées in vivo á l’aide d’expériences réalisées sur des anomalies de la peau et aussi sur le cortex exposé d’un rat anesthésié. Enfin, une étude préliminaire a été réalisée pour examiner la possibilité d’étendre la méthode á l’imagerie de 'speckle'. Des tests préliminaires réalises sur fantômes montrent l’influence de l’ellipticité de polarisation sur la formation et le comportement du speckle, ce qui offre la possibilité d’accéder á des informations sur le flux sanguin á des profondeurs spécifiques dans les tissus. / Polarization gating imaging is a popular and widely used imaging technique in biomedical optics to sense tissues, deeper volumes, and also selectively probe sub-superficial volumes. Due to the ‘polarization memory’ effect of polarized light, elliptical polarization gating allows access to tissue layers between those of accessible by linear or circular polarizations. As opposed to the conventional linearly polarized illumination, we focus on polarization gating methods that combine the use of elliptically polarized light to select polarization-maintaining photons and eliminate the background while providing superior contrast and depth information. With gating, it has also become possible to access user-defined depths (dependent on optical properties) in biological tissues with the use of images at different ellipticities. Furthermore, this investigation allowed the application of polarization gating in spectroscopy to selectively quantify the concentration of tissue chromophores at user-desired depths. Polarization gating methods have been validated and demonstrated with in vivo experiments on abnormalities of human skin (nevus, burn scar) and also on the exposed cortex of an anaesthetized rat. Finally, as a first step towards the use of coherent illumination, adding the concept of polarimetry to laser-speckle imaging was demonstrated. Preliminary tests on phantoms (solid and liquid) suggested evidence of the influence of polarization ellipticity on the formation and behaviour of speckles, which could pave the way for more insight in the study of blood flow in tissues.

In this work, power supply noise contribution, at a particular node on the power grid, from clock/power gated blocks is maximized at particular time and the synthetic gating patterns of the blocks that result in the maximum noise is obtained for the interval 0 to target time. We utilize wavelet based analysis as wavelets are a natural way of characterizing the time-frequency behavior of the power grid. The gating patterns for the blocks and the maximum supply noise at the Point of Interest at the specified target time obtained via a Linear Programming (LP) formulation (clock gating) and Genetic Algorithm based problem formulation (Power Gating).