The process of sporulation in Bacillus subtilis serves as a paradigm for study of sporulation in all Bacillus and Clostridium species. During the process of sporulation there is a sequential and cell type specific activation of RNA polymerase sigma factors. The asymmetric sporulation septum forms, which divides the cell into the smaller prespore and the larger mother cell. Then, óF becomes active in the prespore and óE becomes active in the mother cell. Following completion of engulfment of the prespore by the mother cell, óG becomes active in the prespore and finally óK becomes active in the mother cell. At the time the sporulation septum forms only the 30% origin proximal portion of the chromosome is within the prespore. It is the responsibility of the SpoIIIE translocase to pump the remaining chromosome destined for the prespore into the prespore. We hypothesize that activation of óG does not occur until the complete chromosome has been translocated into the prespore, and the prespore has been engulfed by the mother cell. Our first method of investigation was to increase the time required to complete translocation of the chromosome into the prespore. Strains in which large inserts of foreign DNA have considerably increased the genome size were obtained and characterized. The strains have shown a delay in the completion of engulfment, which still occurred before the activation of óG. Activation was identified by visualization of GFP from a óG-directed promoter indicating translation of a product transcribed by óG. We have also shown that the terminus region of the chromosome entered the prespore shortly before the completion of engulfment. It was determined that the increased genome size did not result in a delay of the transcription of the structural gene for óG,spoIIIG. Using a strain in which the activity of the SpoIIIE translocase was reduced 2.5 fold we used a óG-directed GFP reporter to study óG activation under both time course and time lapse conditions. We again found that óG only became active following the completion of engulfment. Our second avenue of investigation was to change the site of replication termination. A strain was used in which several terminus associated genes have been relocated from their usual location near the terminus (172°) resulted in termination of replication occurring at 145° on the chromosome. In this strain, it has been found that, under both time course and time lapse microscopy conditions, óG activation still occurred only following completion of engulfment. The translocation of the chromosome in this strain was studied by time lapse microscopy using a óF- directed reporter and it was determined that the origin proximal region, the site of replication termination, and the traditional terminus region, were all translocated into the prespore prior to the completion of engulfment. The results support the hypothesis that there is a strong link requiring complete translocation of the chromosome, followed by engulfment of the prespore, before óG becomes active. / Microbiology and Immunology

The TOPEX/POSEIDON Project is a joint U.S. and French mission to develop and operate an Earth orbiting satellite capable of making accurate measurements of the mean sea level in a way that allows the study of ocean dynamics. The understanding of ocean dynamics is very important in order to study events such as El Nino. Soon after the launch of the TOPEX satellite, some unusually high, but localized, values of the ocean's radar cross section, sigma-0, were observed by scientists at the NASA Goddard Space Flight Center. These phenomena have been referred to as sigma-0 blooms, and are accompanied by an increase in noise in the significant wave height (SWH) and altitude measurements. Since approximately 5% of all data recorded by the satellite contains sigma-0 blooms, it is important to understand their causes so that corrective measures can be taken by NASA. This thesis investigates two possible origins of the sigma-0 blooms: a surface containing a step discontinuity in sigma-0, and a surface containing slick or calm areas. Models corresponding to the theoretical returns from these two types of surfaces are developed and studied. / Master of Science

The growing demand of “System on a Chip” applications necessitates integration of multiple devices on the same chip. Analog to Digital conversion is essential to interfacing digital systems to external devices such as sensors. This presents a difficulty since high precision analog devices do not mix well with high speed digital circuits. The digital environment constraints put demand on the analog portion to be resource efficient and noise tolerant at the same time. Even more demanding, Analog to Digital converters must consume a small amount of power since “System on a Chip” circuits often target portable applications. Analog to digital conversion based on Delta Sigma modulation offers an optimal solution to the above problems. It is based on digital signal processing theory and offers benefits such as small footprint, high precision, noise de-sensitivity, and low power consumption. This thesis presents a methodology for designing low power Delta Sigma modulators using a combination of modern circuit design techniques. The developed techniques have resulted in several modulators that satisfy the initial design parameters. We applied this method to design three different modulators in the 0.35um digital CMOS technology with a 3.3V supply voltage. A first order Self-Referenced modulator has a resolution of 8 bits and the lowest power consumption at 75 uW. The most successful design is the second order Self Referenced modulator that produces 12 bits of resolution with a power consumption of 87 uW. A second order Floating Gate modulator possesses features for high noise rejection, and produces 10 bits of resolution while consuming 276 uW. It is concluded that self-referenced modulators dissipate less power and offer higher performance as compared more complicated circuits such as the floating gate modulator. / Master of Science

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Complex magnetosphere-ionosphere coupling mechanisms result in high latitude irregularities that are difficult to characterize. Until recently, the polar and auroral irregularities remained largely unexplored. Inadequate infrastructures to deploy and maintain advanced dual frequency Global Navigation Satellite System (GNSS) receivers at high latitudes, especially in the Southern hemisphere, makes such an investigation a formidable task. Additionally, the complicated geometry of the magnetic field lines in these regions pose challenges in designing global scintillation models. This dissertation takes some steps towards bridging these gaps while advancing the state-of-the-art high latitude irregularity studies. In the first part of this dissertation, we briefly describe the Autonomous Adaptive Low-Power Instrument Platforms (AAL-PIP) experimental setup. These space science instrument platforms are being deployed in remote locations in Antarctica, improving the coverage of GNSS data availability. We explain in detail the method developed for analyzing high rate (typically 50 Hz) data from a novel dual-frequency Global Positioning System (GPS) receiver called Connected Autonomous Space Environment Sensor (CASES). We also report first observations from CASES at high latitudes. From this study, we established that CASES can be reliably used as a science grade GPS scintillation monitor. Following this, a novel three dimensional (3D) electromagnetic (EM) wave propagation model called "Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere" (SIGMA) was developed to simulate GNSS scintillations on ground. GPS scintillation simulations of significantly high fidelity are now possible with this model. While the model is global, it is the first such model which accounts for the complicated geometry of magnetic field lines at high latitudes. Using SIGMA, a sensitivity study is presented to understand the effect of geographical, propagation and irregularity parameters on the phase scintillations. This allows us to reduce the dimensionality of the design space while solving the inverse problem described next. In the final part, we utilize the tools developed for GPS measurement analysis and SIGMA to characterize the high latitude irregularities. We propose an inverse modeling technique to derive irregularity parameters by comparing the high rate (50 Hz) GNSS observations to the modeled outputs. We consider interhemispheric high latitude datasets for this investigation. We also implement SIGMA for analyzing a substorm event observed by AAL-PIP stations. One of the unique contributions of this research is to demonstrate that such an inverse modeling technique can form a basis in the investigation of the ionospheric irregularities. Moreover, availability of ample auxiliary data from multi-instrument observations can assist in this quest of understanding the physics of high latitude irregularities and their generation mechanisms. / Ph. D.

This thesis is devoted to a discussion of various aspects of supersymmetric quantum field theories in four and two dimensions. In four dimensions, 𝒩 = 1 supersymmetric quantum gauge theories on various four-manifolds are constructed. Many of their properties, some of which are distinct to the theories on flat spacetime, are analyzed. In two dimensions, general 𝒩 = (2, 2) nonlinear sigma models on S² are constructed, both for chiral multiplets and twisted chiral multiplets. The explicit curvature coupling terms and their effects are discussed. Finally, 𝒩 = (0, 2) gauged linear sigma models with nonabelian gauge groups are analyzed. In particular, various dualities between these nonabelian gauge theories are discussed in a geometric content, based on their Higgs branch structure. / Ph. D.

Wireless sensor nodes are emerging in a wide range of critical applications such as environmental monitoring, health applications, home automation and military surveillance and reconnaissance. The addition of low power wireless capability to such sensor nodes allows communication between a node and a base station or between nodes, resulting in the formation of wireless sensor networks. Sensor networks can use the information available from the distributed sensor nodes to determine the location and nature of a stimulus or environmental condition. The information collected by the base station can be used to determine the appropriate course of action for dealing with the stimulus. In chemical/biological defense or safety monitoring scenarios, wireless sensor networks can be used to identify and track harmful chemical or biological agents which might be present in a particular area. Due to the potentially remote areas that wireless sensor networks aim to cover, it is essential to minimize the power consumption of a sensor node so that it can operate over a long period of time without a connection to the power grid. Sensor nodes can contain multiple blocks, such as the readout circuit which interfaces with the sensor, an embedded processor, and the wireless transceiver circuits, all of which need to operate on a low power budget. This thesis specifically focuses on design of low power mixed signal readout circuits which interface with chemoresistive chemical sensors, i.e. sensors that demonstrate a variation of resistance (or impedance) in the presence of chemical agents. For this thesis, the sensor can be either a chemoresistive bead or a nanowire. By integrating multiple non-specific chemoresistive sensors together in arrays, a cross-reactive array can be realized, where the combined response of the arrayed sensors can be used to determine analytes present in a mixture even if their concentrations are low. In this thesis, a CMOS resistive readout circuit based on a sigma-delta ADC is presented. The design is used to measure the resistance of chemoresistive beads and nanowires with respect to time. The frequency of the ADC output varies as the resistance of a sensor changes and, based on the magnitude and duration of the variation, the type of chemical agent and its concentration can potentially be estimated. For future cross-reactive sensor applications, an array of 16x16 sites is also included in the readout circuit design. Individual sites in the sensor array can be accessed using addressing blocks which designed to select a particular row and column using an 8-bit addressing system. This thesis also covers the techniques used for integration of chemoresistive beads and nanowires into the array locations provided on the prefabricated CMOS IC. Measurement results that demonstrate the operation of the resistive readout circuitry are presented. Finally, a second readout circuit is proposed to measure complex impedance variations of a sensor device. Measurement of magnitude and phase changes of a sensor device can provide another degree of freedom in the analysis of chemical mixture. Simulation results demonstrating the functionality of the proposed impedance measurement system are also presented. / Master of Science

Welcome address for the 2024 Epsilon Sigma Conference.

Le fuseau de sommeil (FS) est un élément oscillatoire bref de l’électroencéphalogramme associé à la protection du sommeil. Il est plausible que les gens souffrant d’insomnie (INS), pour qui le sommeil est perturbé, puissent avoir une altération de leurs FS. De plus, par leur rôle dans l’inhibition du traitement sensoriel, les FS pourraient aussi intervenir dans la perception du sommeil et expliquer la mésestimation présente chez les INS. Par contre, une étude antérieure n’a pas démontré de différences quant au nombre ou à la densité des FS entre les INS et les bons dormeurs (BD). Le présent mémoire avait donc comme objectif de vérifier si les INS, comparativement aux BD, présentaient des différences quant aux caractéristiques des FS, en séparant deux types d’insomnie, paradoxale (IPA) et psychophysiologique (IPS). Les résultats indiquent une différence quant à la durée des FS, soit que les IPA ont des FS plus courts que les IPS et les BD. Ces résultats appuient en partie le rôle du FS dans la protection du sommeil. Pour ce qui est de la perception du sommeil, aucune des caractéristiques des FS de sommeil ne semble intervenir sur la sensation d’être endormi. / The sleep spindle is a brief oscillatory electroencephalographic event associated with sleep protection. It may be possible that insomnia sufferers (INS), who present less consolidated sleep, have sleep spindles alterations. Sleep spindle plays also a role in sensory inhibition, and thus, could be linked to sleep perception and explain misperception in INS. However, a prior study didn’t find any difference in number or density of sleep spindles between INS and good sleepers (GS). The objective of this project was to determine if differences may be found in sleep spindles characteristics between INS and GS, distinguishing for paradoxical insomnia (PARA-I) and psychophysiological insomnia (PSY-I). Results showed that the duration of sleep spindles in stage 2 is lower for PARA-I than for GS. These results partially support the protective function of sleep spindles. However, in regards of sleep misperception, sleep spindles characteristics do not seem to influence the sensation of being asleep.

Introduction: In recent years, there has been growing interest in regulation of gene expression by small non-coding RNA (sRNA). The first sRNA discovered in 1960s was 6S RNA from E. coli (length ~184 nt). It took ~ 30 years to obtain meaningful insights into its function. 6S RNA binds during stationary phase to RNA polymerase (RNAP) containing sigma factor 70 (primary sigma factor), thereby preventing transcription from σ70 - dependent promoters. In our laboratory we discovered a small RNA (length ~300 nt) in stationary phase of growht in Mycobacterium smegmatis. This sRNA was named Ms 1. The function of Ms 1 is uknown and preliminary experiments indicated that Ms 1may bind to RNAP that lacks σ factor (σA ). Goals: The aim of this Diploma project is to contribute to the characterization of Ms 1. Approaches: First, by molecular cloning, affinity chromatography and in vitro transcription I prepared the tools for subsequent experiments in vitro: RNAP, σA , Ms 1 and its mutated variants. Next, these tools were used for binding experiments on native gels and for transcription experiments. Results: RNAP, σA , Ms 1 and its variants were prepared. In vitro binding assays showed that wt Ms 1 but not a mutated variant of Ms 1 binds to RNAP. Using this assays were identified areas of Ms 1 that are important...