The most commonly used method of euthanasia of laboratory rodents is exposure to carbon dioxide (CO₂), but recent studies have shown that rodents find this gas aversive. The aim of my thesis was to evaluate rat aversion to inhalant agents that could be used as humane alternatives to CO₂. The first study used approach-avoidance testing to examine rat responses to argon-induced hypoxia when argon was introduced at flow rates of 40-239% of the test cage volume per min. Rats never remained in the test cage long enough to lose consciousness when tested with argon. They consumed fewer reward items, stopped eating sooner, and left the test cage more quickly than when tested with air. Rats stopped eating and left the test cage when the oxygen (O₂) concentration had dropped to about 7.7 and 6.8%, respectively, but these O₂ concentrations are too high to cause unconsciousness. Although humans exposed to hypoxia report only subtle symptoms that include cognitive impairments and light headedness, rats are burrowing rodents and could therefore be more sensitive to these effects. I conclude that argon is not a humane alternative to CO₂. The second study used approach-avoidance testing to evaluate rat responses to different concentrations of the inhalant anaesthetics halothane and isoflurane introduced with vaporizers or from soaked cotton balls. On the first day of exposure to anaesthetics, most rats remained in the test cage until they were ataxic and showing difficulty returning to the home cage. On subsequent days of testing most rats left the test cage within seconds, but if given the option, all promptly returned and stayed until they were ataxic, indicating that the learned aversion is transient. Rats were likely sedated by the time they chose to leave, suggesting that forced exposure from the onset of aversion until loss of consciousness is less of a welfare concern than forced exposure to non-sedating agents. I suggest that the use of inhalant anaesthetics for inducing unconsciousness prior to euthanasia is a more humane method than the commonly used CO₂. / Land and Food Systems, Faculty of / Graduate

No description available.

No description available.

Les jets de plasma sont largement utilisés dans l’industrie, dans les laboratoires pour des applications allant du traitement des déchets, à la découpe de pièces métalliques jusqu’aux dépôts de couches de protection. Dans la majorité de ces applications, les jets de plasma sont utilisés en régime turbulent. Ce régime est caractérisé par de fortes fluctuations panache, peu attractives dans le domaine du traitement des matériaux, car elles réduisent la répétabilité et le contrôle des processus. Des jets de plasma aux caractéristiques beaucoup plus stables peuvent être produits en réduisant le débit de gaz plasmagène. Ces jets de plasma sont appelés jets de plasma laminaire. Peu d’études ont été menées sur ce type de jet limitant le développement de ces torches. L’objectif du travail présenté dans ce mémoire est de réaliser l’étude d’un jet de plasma d’argon en régime laminaire à pression atmosphérique. Le diagnostic du jet a été réalisé par spectroscopie optique d’émission à partir de l’enregistrement des spectres atomique et moléculaire d’éléments présents dans le jet. Par ailleurs, ces résultats ont permis de montrer que le jet de plasma pompait l’air extérieur dans lequel fonctionnait la torche. En outre, les champs de vitesses du jet de plasma ont été mesurés par un tube de Pitot. Les distributions de températures et de vitesses déterminées expérimentalement ont été comparés aux résultats d’un modèle numérique. Pour finir, nous avons développé une méthode de mesure de la température du jet de plasma à partir des spectres d’émission des molécules de MgO et de CN produits respectivement à partir de la combustion de magnésium injecté dans le plasma et de la combustion de l’air. Ces molécules sont d’un grand intérêt dans les processus industriels mais aussi dans le domaine de l’aérospatial. / Plasma jets are widely employed both in industry and in laboratories for various applications such as wastetreatment, cutting or spraying protection coating. Usually, the plasma jets are employed in turbulent flowregime. This flow regime is characterised by large plasma jet fluctuations, undesirable in material processing, because they will reduce the process repeatability and controllability. A more stable plasma jet can be generated by reducing the flow rate of the plasma forming gas, and this is called a laminar plasma jet. Few studies have been published on the laminar plasma jet, which has limited the development of these torches. The aim of this thesis is to study a laminar argon plasma jet at atmospheric pressure. The plasma jet diagnostic was performed with an optical emission spectroscopy experiment. The atom and molecule spectra from the jet have been recorded. These results have shown that ambient air is entrained into the plasma jet. In addition, the plasma jet velocity fields were measured by a Pitot tube. The temperature and velocity distributions determined in the experiments were compared to the numeric model results. Finally, we have developed a method to measure the plasma jet temperature from the emission spectra of molecules of MgO and CN which are produced from the magnesium combustion injected into the plasma and the air combustion respectively. These molecules are of great interest in industrial processes but also in the field of aerospace.

Nanosatellites, such as Cubesats, are a rapidly growing sector of the space industry. Their popularity stems from their low development cost, short development cycle, and the widespread availability of COTS subsystems. Budget-conscious spacecraft designers are working to expand the range of missions that can be accomplished with nanosatellites, and a key area of development fueling this expansion is the creation of micropropulsion systems. One such system, originally developed at the Australian National University (ANU), is an electrothermal plasma thruster known as Pocket Rocket (PR). This device heats neutral propellant gas by exposing it to a Capacitively Coupled Plasma (CCP), then expels the heated gas to produce thrust. Significant work has gone towards understanding how PR creates and sustains a plasma and how this plasma heats the neutral gas. However, no research has been published on varying in the device's geometry. This thesis aims to observe how the size of the RF electrode affects PR operation, and to determine if it can be adjusted to improve performance. To this end, a thruster has been built which allows the geometry of the RF electrode to be easily varied. Measurements of the plasma density at the exit of this thruster with different sizes of electrode were then used to validate a Computational Fluid Dynamics (CFD) model capable of approximately reproducing experimental measurements from both this study and from the ANU team. From this CFD, the number of argon ions in the thruster was found for each geometry, since collisions between argon ions and neutrals are primarily responsible for the heating observed in the thruster. A geometry using a 10.5 mm electrode was observed to produce a 23% increase in the quantity of ions produced compared to the baseline 5 mm electrode size, and a 3.5 mm electrode appears to produce 88% more ions.

The anomalous Low Energy Excess (LEE) of electron neutrinos and antineutrinos in MiniBooNE has inspired both theories and entire experiments to probe the heart of its mystery. One such experiment is MicroBooNE. This dissertation presents an important facet of its LEE investigation: how a powerful systematic can be levied on this signal through parallel study of a highly correlated channel in muon neutrinos. This constraint serves to strengthen MicroBooNE's ability to confirm or validate the cause of the LEE and will lay the groundwork for future oscillation experiments in Liquid Argon Time Projection Chamber (LArTPC) detector experiments like SBN and DUNE. In addition, this muon channel can be used to test oscillations directly, demonstrated through the world's first muon neutrino disappearance search with LArTPC data.

BACKGROUND: Implants have been widely used in the medical field. It was adopted in dentistry, offering patients replacement of missing teeth. Researchers have been investigating techniques to improve implants’ survival. Among these techniques is plasma glow discharge. Radio-frequency Glow discharge (RGD) is a surface treatment and sterilization technique with the aim to improve the titanium oxide layer for better osseointegration. Previous studies have evaluated its effect on non-human cell lines with promising results. Up to date, there is no report on how RGD surface treatment of titanium affects normal human osteoblasts. MATERIAL AND METHODS: Human bone fragments were obtained from dental extraction sites and were processed to culture normal human osteoblasts. Cells were seeded on three different surfaces at a concentration of 1x105 cells per plate; Titanium discs with and without Argon RGD (ARGD), and tissue culture plates (TCP). Dishes were allocated to 3 timelines: 16 hours, 7 days and 14 days. The outcome measures were cell attachment, cell number, alkaline phosphatase and osteocalcin levels. RESULTS: Data was analyzed using a one-way ANOVA test. Mean cell proliferation percentage for the ARGD group at 7 days was the highest (167.966%). The difference in means among the three groups at 7 days was statistically significant (p=0.0022). At 14 days, the highest mean of cell proliferation percentage was highest for the ARGD group. When testing all pairs, at 7 days the differences in means were statistically significant between (ARGD vs. no ARGD, and ARGD vs. TCP) (p=0.0018, and p=0.0286), respectively. At 14 days, the differences in means were statistically significant between (ARGD vs. TCP, p= 0.0003) and (no ARGD vs. TCP, p=0.0007). There was a significant difference in means for alkaline phosphatase and osteocalcin at 7 and 14 days between TCP and ARGD, and TCP and no ARGD groups (p < 0.05). CONCLUSIONS: The results of this study on normal human osteoblasts indicated that ARGD significantly enhanced cell proliferation. There was no significant difference in osteogenic behavior between with and without ARGD treatment on titanium surfaces within the time studied. A prolonged phase of cell proliferation was observed in ARGD treated groups.

The effect of gas stirring in the ladle furnace on inclusion content in austenitic and duplex stainless steel has been investigated at Sandvik Materials Technology AB. The effect was mainly investigated by varying duration of stirring time and intensity of stirring. Any effect on inclusion content was determined by examining total oxygen content before and after the ladle treatment, along with mapping the chemical composition, size and size distribution of the inclusions. Any effect on slag composition was also determined. The effect of gas stirring was measured on a number of heats with continuous sampling during normal production. Data regarding oxygen content during the ladle refining process and the duration of the processes was used to determine a quantifiable relationship between stirring time, stirring intensity and resulting change in oxygen content. The result of the investigation was recommendations regarding the use of varied stirring intensities and duration of gas stirring for achieving negative net loss in oxygen content before and after ladle treatment.

A gamma scintillation spectrometer was assembled. and calibrated in a low background radiation area to analyze air samples. Air samples were taken from different locations in the physics building during reactor operation to determine the concentrations of A⁴¹ released to the surroundings of the building during reactor operation. The samples were collected in a one gallon polyethylene bottle with a 3 ¾” x 3 ¾” cylindrical well sealed in the bottom. The air samples were taken to the counting area and the sampling bottle placed on the detector, a 3” x 3" cylindrical NaI(TI) crystal which fitted into the well. The pulses from the detector were fed te a multi-channel analyzer. From the number of pulses per unit time under the photo-peak, the concentration of A⁴¹ for each location was determined. Samples were analyzed for 4, 7, and 10 kw from which a linear extrapolation was made to estimate the concentrations of A⁴¹ in these locations if higher power operation is authorized. / Master of Science

Cette thèse présente la dynamique ultrarapide de relaxation de molécules photochromes et des agrégats d'argon en phase gazeuse à l'échelle femtoseconde. Des expériences utilisant la technique « pompe-sonde » ont été menées sur un dispositif utilisant un faisceau moléculaire pulsé couplé à de l'imagerie de vitesse de photoélectron/photoion (VMI) et un spectromètre de masse à temps de vol (TOF-MS). Ces études nous ont permis de caractériser les changements de distribution électronique des différents systèmes en fonction du temps. Par ailleurs une étude théorie/expérience sur la caractérisation de la densité et de la distribution de vitesse au sein d'un faisceau moléculaire pulsé a aussi été réalisée. Dans le cas de la dynamique des dithienyléthènes, nous avons observé des mécanismes de relaxation électronique parallèles. Le paquet d'onde initial se sépare en deux parties distinctes. Une première partie se dirige vers l'état fondamental via une intersection conique, tandis que la deuxième partie reste quelques picosecondes dans l'état excité en oscillant avant de relaxer vers l'état fondamental. Cette étude nous a permis de comprendre la dynamique intrinsèque des différentes molécules étudiées, mais aussi d'étendre le mécanisme de relaxation à toute cette famille de molécules photochromes dans les trois phases dans lesquelles elles sont étudiées. Dans le cas des agrégats d'argon, deux phénomènes ont été observés à différentes échelles de temps. Le premier se produit dans les premières picosecondes et est la relaxation électronique d'un état excitonique à une vitesse d'environ 1 eV.ps⁻¹. Le deuxième phénomène résulte de la localisation de l'excitation sur une paire Ar₂* que nous avons pu observer à partir de 4-5 ps. L'éjection d'atomes d'argon excités a aussi été observée, nous permettant ainsi de connaitre la durée de vie maximale de l'état excitonique délocalisé. Ce travail a permis d'apporter des informations supplémentaires à celles fournies par les études réalisées en phase condensée. Il ouvre donc la voie vers l'étude de systèmes plus complexes tels que les nanoparticules en phase gazeuse. / This PhD thesis investigated the ultrafast dynamics of photochromic molecules and argon clusters in the gas phase at the femtosecond timescale. Pump-probe experiments are performed in a set-up which associates a versatile pulsed molecular beam coupled to a photoelectron/photoion velocity map imager (VMI) and a time-of-flight mass spectrometer (TOF-MS). Theses pump-probe experiments provides the temporal evolution of the electronic distribution for each system of interest. Besides, a modelization has been performed in order to characterize the density and the velocity distribution in the pulsed beam. Regarding the photochromic dithienylethene molecules, parallel electronic relaxation pathways were observed. This contrasts with the observation of sequential relaxation processes in most molecules studied so far. In the present case, the initial wavepacket splits in two parts. One part is driven to the ground state at the femtosecond time scale through a conical intersection, and the second part remains for ps in the excited state and experiences oscillations in a suspended well. This study has shed light into the intrinsic dynamics of the molecules under study and a general relaxation mechanism has been proposed, which applies to the whole family of dithienylethene molecules whatever the state of matter (gas phase or solution) in which they have been investigated. Concerning argon clusters excited at about 14 eV, two behaviors of different time scale have been observed at different time scales. The first one occurs in the first picoseconds of the dynamics. It corresponds to the electronic relaxation of an excitonic state at a rate of 1 eV.ps⁻¹. The second phenomenon corresponds to the localization of the exciton on the excimer Ar₂*. This phenomenon is observed 4-5 ps after the excitation. In this study, we also observed the ejection of excited argon atoms, addressing the lifetime of the delocalized excitonic state. This work provide additional informations compared to those contributed in condensed phase and it pave the way for new studies in gas phase on more complex system such as nanoparicles.