This thesis presents an independent analysis of the data from 3-He-filled proportional counters from the third phase of the Sudbury Neutrino Observatory (SNO) data. These counters were deployed in SNO's heavy water to independently detect neutrons produced by the neutral current interaction of 8-B solar neutrinos with deuterium. Previously published results from this phase were based on a spectral analysis of the energy deposited in the proportional counters. The work in this thesis introduces a new observable based on the time-profile of the ionization in the counters. The inclusion of this observable in a maximum-likelihood fit increases the potential to distinguish neutrons from backgrounds which are primarily due to alpha-decays. The combination of this new observable with the energy deposited in the counters results in a more accurate determination of the number of neutrons. The analysis presented in this thesis was limited to one third of the data from the proportional counters, uniformly distributed in time. This limitation was imposed to reconcile different time-lines between the submission of this thesis, a thorough review of this work by the SNO Collaboration and results from an independent analysis that is still underway. Analysis of this reduced data set determined that 398 +/- 29 (stat.) +/- 9 (sys.) neutrons were detected in this reduced data-set. The number compares well to the previous analysis of the data, based only on a spectral analysis of the deposited energy, which determined that 410 +/- 44 (stat.) +/- 9 (sys.) were detected in the same time period. The analysis presented here has led to a substantial increase in the statistical accuracy. Assuming that the statistical accuracy will increase when the full data set is analyzed, the results from this thesis would bring the uncertainty in the 8-B solar neutrino flux to down 6.8% from 8.5% in the previously published results. The work from the thesis is intended to be included in a future analysis of the SNO data and will result in a more accurate measurement of the total flux of solar neutrinos from 8-B as well as reduce the uncertainty in the $\theta_{12}$ neutrino oscillation mixing angle. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2009-09-16 15:56:28.195

No description available.

The SNO+ experiment is a kilo-tonne scale liquid scintillator detector located at SNOLAB in Sudbury, Ontario, Canada. As the successor to the Sudbury Neutrino Observatory, SNO+ will use linear alkylbenzene (LAB) as the scintillator to study neutrinos. During the solar phase, ux measurements will be made of low energy neutrinos originating in the Sun. In another phase, 800 kg of tellurium will loaded into the scintillator to search for neutrinoless double beta decay. Measurements will also be made of neutrinos coming from nearby nuclear reactors and from inside Earth's mantle and crust. To enable these multiple physics goals, a sensitive calibration procedure must be carried out in order to fully understand the detector. The optical and energy responses of the detector will be measured with calibration sources deployed throughout the acrylic vessel. These sources must be connected to the observatory deck above the vessel by gas capillaries, optical bres, and signal wires housed in specially designed submersible umbilical cables. The design and fabrication of these umbilical cables is presented. Development work on a deployed radon calibration source will also be described. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2014-05-30 15:56:19.906

L'influence de la nature des électrodes sur les performances des capteurs de gaz à base d'oxyde métallique semiconducteur sont reconnu et prouvé expérimentalement. Ici, pour la première fois nous fournissons une mise en évidence par spectroscopie infrarouge (DRIFTS) de l'influence de la nature d'électrodes (Pt et Au) sur la chimie de surface lors de la détection de CO aux sur couche épaisse de SnO₂. Nos résultats montrent que la nature et la concentration des intermédiaires de réaction de CO (les carbonates et carboxylates) dépendent de la présence et de la nature des électrodes. De plus, les mesures en thermodésorption prouvent que l'influence de la nature des électrodes joue un rôle clé sur l'adsorption d'oxygène à la surface SnO₂. Ces résultats sont discutés au sein d'un modèle empirique.

Devido à elevada razão superfície/volume dos nanomateriais, estes apresentam propriedades únicas que são consequência das propriedades de suas superfícies. Para estabilizar as nanopartículas, as quais tendem ao crescimento para reduzir o excesso de energia, uma estratégia é a introdução de aditivos que segreguem na superfície e reduzam a energia de superfície. Neste trabalho, o sistema de importância tecnológica SnO2-TiO2 foi estudado. Nanopartículas de Sn1-xTixO2 (0,00 x 1,00) foram sintetizadas pelo método dos precursores poliméricos. Difratogramas de raios X mostram que uma solução sólida com estrutura do tipo rutilo é obtida para x 0,90. A evolução dos parâmetros de rede, os espectros obtidos por perda de energia de elétrons (EELS) e os espectros no infravermelho coletados no modo de refletância difusa (DRIFT) sugerem a segregação do Ti4+ na superfície, que justifica a elevada solubilidade do Ti4+ no SnO2. Os espectros Raman são coerentes com a segregação, mostrando que, mesmo sem a formação de segunda fase, ocorrem regiões ricas em Ti. A segregação está relacionada também à redução do tamanho de cristalito e ao aumento da área de superfície específica devido à redução da energia de superfície (de 1,40 Jm-2 em x = 0,00 até 1,08 Jm-2 em x = 0,50) determinada por calorimetria de adsorção de água e coerente com os dados da calorimetria de dissolução. Para x 0,90, ocorre a formação da fase anatásio além do rutilo e os fenômenos de estabilização dos polimorfos podem ser explicados pela modificação da energia de superfície. Com base na caracterização feita, as atividades fotocatalíticas das nanopartículas foram avaliadas e foi verificado um aumento da eficiência devido à superior área de superfície das amostras aditivadas em relação às amostras puras. / Due to the high surface/volume ratio, nanomaterials have unique properties as a consequence of their surface properties. In order to stabilize the nanoparticles, which tend to grow to reduce their excess energy, one can introduce additives that are prone to segregate at the surfaces and reduce the surface energy. In this work, the technologically relevant SnO2-TiO2 system was studied. Sn1-xTixO2 (0.00 x 1.00) nanoparticles were synthesized by polymeric precursors method. X-ray diffraction patterns show that a rutile-structured solid solution is formed for x 0.90. Lattice parameters evolution, electron energy loss spectra (EELS) and diffuse reflectance infrared spectra (DRIFT) suggest a Ti4+ surface segregation, which explains the high Ti4+ solubility in SnO2. Raman spectra are in accord with the segregation, showing Ti-rich sites in the absence of a second crystalline phase. The segregation is also related to a decrease in the crystallite size and an increase in the surface area due to a decrease in the surface energy (from 1.40 Jm-2 for x = 0.00 to 1.08 Jm-2 for x = 0.50) determined by water adsorption calorimetry and consistent with drop solution calorimetry data. For x 0.90, the formation of anatase occurs in addition to rutile, and the polymorphic stability can be explained according to the surface energy modification. Based on these results, photocatalytic activity of the samples were evaluated, and an increase in the efficiency due to a higher surface area was observed for the samples containing additive compared to pure samples.

La conductivité électrique du dioxyde d'étain varie en fonction de la température du matériau, de la nature et de la concentration de gaz environnant. Ce travail de thèse montre que le traitement par les méthodes d'analyse multivariables des signaux de conductance électrique d'un seul capteur, obtenus en descente de température, permet la détermination de concentrations de mélanges binaires ou ternaires d'éthanol (0-80ppm), de monoxyde de carbone (0-300ppm) et de méthane (0-1000ppm). Une partie de cette étude a été consacrée à la conception et à la réalisation d'un banc automatique de tests permettant l'acquisition des conductances électriques de quatre capteurs en cycle thermique et sous cycles gazeux. Elle a aussi mis en évidence des effets (humidité,) pouvant perturber la mesure. Deux technologies de fabrication de capteur ont été utilisées en vue d'obtenir des signatures, conductance fonction de la température, distinctes pour chaque gaz, assez reproductibles d'un capteur a l'autre et suffisamment stables Dans le temps pour permettre l'exploitation des signaux par les méthodes d'analyse multivariables : Dioxyde d'étain sous forme de couches minces obtenues par évaporation réactive, ou sous forme de barreaux de poudre frittée. Dans une dernière partie, il a été montré que la détermination quantitative de gaz par l'application des méthodes de chimiométrie était possible bien que la relation entre les conductances électriques d'une part, les températures et les concentrations d'autre part était non linéaire. D'ailleurs, la modélisation avec la méthode partial least square et un prétraitement permet d'obtenir des performances comparables a celles obtenues avec les réseaux de neurones. Enfin, un système autonome de démonstration a été réalisé en utilisant l'ensemble des optimisations mis en évidence dans cette dernière partie. Des prédictions en conditions réelles ont montré de bonnes corrélations avec les mesures effectuées par des analyseurs classiques de gaz.

Ce travail concerne la modification de la sélectivité de couches minces de dioxyde d'étain par l'ajout de couches superficielles en vue de la réalisation de microcapteurs de gaz. Une partie de cette étude a été consacrée à la caractérisation des différentes couches, essentiellement par la diffraction des rayons X sous incidence rasante en raison des faibles épaisseurs étudiées. Les couches minces de dioxyde d'étain sont élaborées soit par évaporation réactive soit par un procédé de dépôt chimique en phase vapeur (CVD). Quant aux couches superficielles, elles ont été choisies soit pour leur action catalytique vis-à-vis de certains gaz (cas des couches de platine, de palladium ou de rhodium) soit pour leur pouvoir de filtration comme les couches de silice. Dans une seconde partie, les performances électriques des couches de dioxyde d'étain modifiées par les couches superficielles ont été évaluées sur un banc de test. Il s'agit de suivre les variations de conductance sous gaz (éthanol, monoxyde de carbone, méthane, oxydes d'azotes) en fonction de la température. Il a été ainsi mis en évidence le rôle catalytique de certains matériaux, ce qui a permis d'obtenir des couches plus sélectives pour un gaz donné. Enfin, cette étude a abouti à la réalisation de microcapteurs de gaz dans lequel l'élèment sensible se trouve sous forme de couche mince.

Nanobelts are a new class of semiconducting metal oxide nanowires with great potential for nanoscale devices. The present research focuses on the manipulation of SnO₂ nanobelts suspended in ethanol using microfluidics and electric fields. Dielectrophoresis (DEP) was demonstrated for the first time on semiconducting metal oxide nanobelts, which also resulted in the fabrication of a multiple nanobelt device. Detailed and direct real-time observations of the wide variety of nanobelt motions induced by DEP forces were conducted using an innovative setup and an inverted optical microscope. High AC electric fields were generated on a gold microelectrode (~ 20 µm gap) array, patterned on glass substrate, and covered by a ~ 10 µm tall PDMS (polydimethylsiloxane) channel, into which the nanobelt suspension was introduced for performing the DEP experiments. Negative DEP (repulsion) of the nanobelts was observed in the low frequency range (< 100 kHz) of the applied voltage, which caused rigid body motion as well as deformation of the nanobelts. In the high frequency range (~ 1 MHz - 10 MHz), positive DEP (attraction) of the nanobelts was observed. Using a parallel plate electrode arrangement, evidence of electrophoresis was also found for DC and low frequency (Hz) voltages. The existence of negative DEP effect is unusual considering the fact that if bulk SnO₂ conductivity and permittivity values are used in combination with ethanol properties to calculate the Clausius Mossotti factor using the simple dipole approximation theory; it predicts positive DEP for most of the frequency range experimentally studied. A fluidic nanobelt alignment technique was studied and used in the fabrication of single nanobelt devices with small electrode gaps. These devices were primarily used for conducting impedance spectroscopy measurements to obtain an estimate of the nanobelt electrical conductivity. Parametric numerical studies were conducted using COMSOL Multiphysics software package to understand the different aspects of the DEP phenomenon in nanobelts. The DEP induced forces and torques were computed using the Maxwell Stress Tensor (MST) approach. The DEP force on the nanobelt was calculated for a range of nanobelt conductivity values. The simulation results indicate that the experimentally observed behavior can be explained if the nanobelt is modeled as having two components: an electrically conductive interior and a nonconductive outer layer surrounding it. This forms the basis for an explanation of the negative DEP observed in SnO₂ nanobelts suspended in ethanol. It is thought that the nonconductive layer is due to depletion of the charge carriers from the nanobelt surface regions. This is consistent with the fact that surface depletion is a commonly observed phenomenon in SnO₂ and other semiconducting metal oxide materials. The major research contribution of this work is that, since nanostructures have large surface areas, surface dominant properties are important. Considering only bulk electrical properties can predict misleading DEP characteristics.

Genome sequencing has yielded unparalleled insights into fundamental biological processes and the genetics that guide them. In contrast to expectations that protein-coding genes would be the primary output of eukaryotic genomes, however, it is now clear that the vast majority of transcription is devoted to noncoding RNAs (ncRNAs). Although originally regarded as 'transcriptional noise', it is now clear that these transcripts are essential regulators of genetic activity. In this thesis I build upon the hypothesis that the genomes of eukaryotes encode a regulatory 'RNA machine' dominated by ncRNAs. In the Introduction (Chapter 1) I discuss how prior gene models may have inadvertently prevented a full understanding of ncRNAs, review the transcriptional landscape of eukaryotes, and examine the biogenesis and function of small regulatory RNAs. In support of a role for ncRNAs in complex metazoa, Chapter 2 presents data showing a positive correlation between the proportion of non-protein-coding DNA and biological complexity, suggesting that the evolutionary trajectory of intricate developmental phenotypes may have been facilitated by ncRNAs. In the following chapters two more 'gears' are added to the RNA machine. Chapter 3 details the discovery of snoRNA-derived RNAs - an evolutionarily ancient class of Argonaute-assocaited RNA whose biogenesis overlaps with microRNAs (miRNAs) and silencing RNAs (siRNAs). Likewise, Chapter 4 reports a new class of ~18 nt transcription initiation RNAs (tiRNAs) derived from regions proximal to transcription start sites. tiRNAs are enriched at GC-rich promoters and regions of active transcription, implicating them in transcriptional regulation. Chapter 5 presents evidence that tiRNAs are restricted to metazoa, and describes a model of RNA Polymerase II dependent tiRNA biogenesis. This thesis concludes with a general discussion of the implications of these findings, and the potential development of RNA therapeutics. Gathering evidence suggests that eukaryotic genomes are driven by a complex and interwoven network of RNA regulatory feedback loops. This thesis takes a small step towards developing a complete picture of this system.

Genome sequencing has yielded unparalleled insights into fundamental biological processes and the genetics that guide them. In contrast to expectations that protein-coding genes would be the primary output of eukaryotic genomes, however, it is now clear that the vast majority of transcription is devoted to noncoding RNAs (ncRNAs). Although originally regarded as 'transcriptional noise', it is now clear that these transcripts are essential regulators of genetic activity. In this thesis I build upon the hypothesis that the genomes of eukaryotes encode a regulatory 'RNA machine' dominated by ncRNAs. In the Introduction (Chapter 1) I discuss how prior gene models may have inadvertently prevented a full understanding of ncRNAs, review the transcriptional landscape of eukaryotes, and examine the biogenesis and function of small regulatory RNAs. In support of a role for ncRNAs in complex metazoa, Chapter 2 presents data showing a positive correlation between the proportion of non-protein-coding DNA and biological complexity, suggesting that the evolutionary trajectory of intricate developmental phenotypes may have been facilitated by ncRNAs. In the following chapters two more 'gears' are added to the RNA machine. Chapter 3 details the discovery of snoRNA-derived RNAs - an evolutionarily ancient class of Argonaute-assocaited RNA whose biogenesis overlaps with microRNAs (miRNAs) and silencing RNAs (siRNAs). Likewise, Chapter 4 reports a new class of ~18 nt transcription initiation RNAs (tiRNAs) derived from regions proximal to transcription start sites. tiRNAs are enriched at GC-rich promoters and regions of active transcription, implicating them in transcriptional regulation. Chapter 5 presents evidence that tiRNAs are restricted to metazoa, and describes a model of RNA Polymerase II dependent tiRNA biogenesis. This thesis concludes with a general discussion of the implications of these findings, and the potential development of RNA therapeutics. Gathering evidence suggests that eukaryotic genomes are driven by a complex and interwoven network of RNA regulatory feedback loops. This thesis takes a small step towards developing a complete picture of this system.