Abstract Not Available.

Experiments employing molecular beams of atomic hydrogen and a hydrocarbon precursor were carried out in an attempt to deposit diamond films at the pressure of 10$\sp{-4}$ torr. No diamond films were deposited using methane, methyl iodide or di-tert-butyl peroxide as carbon sources. Only amorphous carbon films were deposited under some circumstances. By using a carbon-13 labeling technique, it was found that chloromethanes contribute to diamond growth via a new growth precursor(s) in the form of chlorocarbon radicals in addition to the methyl radical pathway in a hot filament reactor. On the other hand, fluoromethanes, bromomethane and iodomethane yield diamond through the methyl radical mechanism. It was argued that the drastically different behaviors among halocarbons in diamond CVD systems are attributable to the differences in their thermodynamic properties and kinetic parameters of the reactions of halocarbons with atomic hydrogen. It was demonstrated that low temperature deposition of diamond films can be achieved by either using chlorocarbons as carbon sources or adding HCl to a methane/hydrogen system. The major function of HCl under diamond CVD conditions is to generate chlorine atoms. These chlorine atoms in turn activate the hydrogenated diamond surface via a more efficient pathway, i.e., chlorine abstraction reaction of surface-adsorbed hydrogen atoms at low temperatures. As a result, diamond films were deposited by using methyl chloride at substrate temperatures as low as 300$\sp\circ$C. Studies of the dependence of the growth rate on the substrate temperature revealed the existence of two growth regions, i.e., the transport/diffusion-limited regime at high temperatures and the surface-controlled regime at low temperatures. The transition temperature was found to be around 730$\sp\circ$C and 570$\sp\circ$C for the $\rm CH\sb4/H\sb2$ and $\rm CCl\sb4/H\sb2$ systems respectively. It was also found that adding HCl to the $\rm CH\sb4/H\sb2$ deposition system yielded an increase in growth rates of diamond films at low temperatures. This phenomenon can be qualitatively explained by the Langmuir adsorption isotherm model with a modification by incorporating the Eley-Rideal mechanism for hydrogen abstraction.

The interaction between non-spherical nuclear charge distribution and the electric field gradient is described. Expressions for the energy levels (I = 1), the nuclear quadrupolar resonance, NQR, transition frequencies and line shape are derived. The general equations to obtain the inverse line width parameter, T$ sb2 sp star,$ from the self-quenched super-regenerative oscillator, SRO, NQR spectra are derived and tested. / The construction and operation of the $ sp{14}$N Sullivan and Dean SRO spectrometers are described. Limits in the sensitivity of the SRO to yield T$ sb2 sp star$ data are discussed. The operation and the constraints in obtaining line width data from a pulsed-FT spectrometer are given. The temperature dependence of $ sp{14}$N NQR frequencies, T$ sb2 sp star$ and line widths of series of anilines and hexamethylenetetramine are reported. / The NQR frequency and the contribution of static and dynamic effects to the line width are discussed as a function of temperature. The observed phase transitions are discussed.

No description available.

Anthropogenic volatile organic compounds (VOCs) and semi-volatile organic (SVOCs) compounds are atmospheric pollutants contributing to the photochemical formation of tropospheric ozone. We combined adsorption and UV photolysis techniques for the removal and degradation of selected VOCs and SVOCs. For adsorption, we synthesized magnetite nanoparticles, a naturally occurring material, to avoid unknown detrimental impacts associated with new materials, as was the case with chlorofluorcarbons. The removal efficiency with magnetite was up to 98 % for aromatics, and 30% for light alkanes. Magnetite nanoparticles were regenerated, characterized (TEM, XRD, BET), and reused with no decrease in reported removal efficiencies. Photolysis alone removed up to 30% of aromatics, and less than 20% of light alkanes. The combination of adsorption, and photolysis did not improve the removal efficiency. Adsorption was attributed to London dispersion interactions for light alkanes, and to acid-base properties for aromatics. Reductions by photolysis were attributed to reactive radicals. / Les composés volatiles et semi-volatiles organiques de sources anthropogéniques sont des polluants atmosphériques participant à la formation d'ozone troposphérique. Nous avons associé l'adsorption et la photolyse par rayons ultraviolets, pour enlever et détruire ces composés. Nous avons synthétisé des nanoparticules de magnétite, un matériel abondant dans la nature, afin d'éviter la création d'un autre problème de pollution comme il est parvenu avec l'utilisation des fluorocarbure chlorés. L'efficacité d'enlèvement par adsorption atteint un maximum de 98 % pour les composés aromatiques et un maximum de 30% pour les alcanes légers. Les particules ont été regénérées, caractérisées (MET, XRD, BET), et réutilisées; aucune baisse en efficacité d'enlèvement n'est notée. Les expériences de photolyse atteignent une réduction maximale de 30% pour les composés aromatiques et de 20% pour les alcanes légers. Sous nos conditions expérimentales, aucune amélioration n'est notée par l'association des deux processus (adsorption et photolyse). La réduction par adsorption est attribuée aux forces d'attraction London pour les alcanes et aux propriétés acides et basiques pour les aromatiques. La réduction par photolyse s'explique par la formation de radicaux réactifs.

Recently developed ultrasound contrast agents provide traditional ultrasound techniques with highly localized contrast within samples depending on contrast agent concentration. Contrast agents resonate at characteristic frequencies, allowing background signals in backscatter collected from samples to be easily removed through filtration, leaving only resonance from contrast agents remaining. The goal of this thesis was to develop analyte sensitive contrast agents based on molecularly imprinted poly(N-isopropylacrylamide) (pNIPA) nanogel polymers. Molecularly imprinted pNIPA was synthesized in presence of target analyte theophylline. Ultrasonic analysis of pNIPA behavior in the presence of varying theophylline concentration revealed amplitude changes at various frequencies. Analysis of chemically similar caffeine demonstrated ultrasonic changes at different frequencies.Solutions containing increasing amounts of theophylline in the 8.4 to 167 μM range with 1% by weight molecularly imprinted pNIPA in water were analysed ultrasonically. Concentration models displayed very high linearity (r2 coefficient exceeding 0.99). Additional concentration models were constructed in a matrix of solutions containing both the imprinted analyte theophylline, and interferant caffeine. Regression models for the two analytes demonstrated good linearity in the micromolar range (r2 of 0.98 for theophylline, 0.87 for caffeine) using different subsets of frequencies for each analyte.A tighter binding arrangement between analyte and pNIPA was achieved through synthesis of molecularly imprinted pNIPA in the collapsed phase. This increased analyte sensitivity and linear range to nanomolar concentrations. Quantification assays were carried out on a dopamine oxidation product, (5-6-dihydroxyindole, DHI), from 16.7 to 163 nM. High linearity was obtained (r2 correlation coefficient exceeding 0.99). The experiment was repeated in a presence of albumin, a biologically relevant interferant, with good agreement between actual and estimated concentration.Multi-analyte quantification was improved by combining two differently imprinted pNIPA nanogels to form multiplexed nanogels. Simultaneous quantification assays were carried out for theophylline (8.4 to 49 uM) and DHI (48.8 to 176 nM). Good linearity between estimated and actual concentrations were obtained (r2 of 0.99 for DHI, 0.96 for theophylline).Determination of a larger analyte, tobacco mosaic virus (TMV), was also carried out. Concentration models in the 9 to 140 ppb range showed excellent linearity (correlation coefficients exceeding 0.99). The process was repeated in presence of another virus, tomato bushy stunt virus (TBSV), acting as an interferant. Similar linearity was obtained.Critical points of the ultrasound quantification system based on molecularly imprinted nanogels are summarized in the Conclusion chapter. Improvements focusing on obtaining stronger ultrasonic signals in aforementioned analyses are discussed in the Future Works section. / Le développement des agents de contraste ultrasonique ont produit des agents qui fournissent du contraste très élevé et localisé dans l'échantillon, selon la concentration des agents. Ces agents résonnent avec des fréquences particulières, et facilitent la soustraction du bruit par filtration, qui laissent seulement le résonance des agents. Le but de cette thèse est de développer des agents de contraste capable de quantifier des analytes en utilisant des polymères poly(N-isopropylacrylamide) (pNIPA) imprimés avec des molécules cible comme point de départ. La synthèse des polymères pNIPA était faite en présence de la molécule théophylline. L'analyse ultrasonique de pNIPA en présence de differentes concentration de théophylline conduit à des changements d'amplitudes à plusieurs fréquences. L'analyse de pNIPA avec de la caféine a produit des changements à d'autres fréquences. Des solutions avec théophylline (8.4 à 167 μM) et 1% massique de pNIPA imprimé avec théophylline ont été analysées avec le système ultrasonique. Les modèles de concentration que cette analyse a produit ont un très haut niveau de linéarité (r2 plus que 0.99). Plusieurs modèles de concentration ont été construit avec une matrice de solution qui contenait théophylline et caféine. Les modèles de régression pour les deux analytes ont démontrés de la linéarité dans les concentrations micromolar (r2 de 0.98 pour théophylline, 0.87 pour caféine), utilisant différentes fréquences pour chaque analyte.Une affinité plus grande entre l'analyte et pNIPA a été gràce à la synthèse avec du pNIPA comprimé. Cela a élevé la sensibilité aux concentrations nanomolaires. Des quantifications d'un produit d'oxidation de la dopamine (5-6-dihydroxyindole, DHI) de 16.7 à 163 nM ont été faites. Les résultats ont démontrés une très bonne linéarité (r2 plus que 0.99). L'expérience a été reproduite avec de l'albumine dans chaque solution, encore avec des bons résultats.La quantification de plusieurs analytes simultanément a été améliorée avec la combinaison de deux nanogels pNIPA imprimés avec les différentes analytes. Les analyses de concentration ont été menées en parallèle pour la théophylline (8.4 à 49 uM) et le DHI (48.8 à 176 nM). Les concentrations estimées étaient en accord avec les concentrations actuelles (r2 de 0.99 pour DHI, 0.96 pour théophylline).Un analyte plus large, le virus tabac mosaïque (TMV), a été detecté avec le système ultrasonique. Des modèles de concentration de 9 à 140 ppb ont démontrés un très haut niveau de linéarité (r2 plus que 0.99). Le processus a été répeté avec un autre virus, tomate bushy stunt (TBSV), ajouté aux solutions de TMV avec des résultats semblables. Les aspects critiques du système de quantification ultrasonique sont récapitulés dans le chapitre de conclusion. Des améliorations pour obtenir des signaux plus fort dans les analyses ultrasoniques sont discutés dans la section futur.

A large tube microwave digestion system with capsule sample introduction has been developed. This is the first automatic pressurized microwave digestion system to use: (1) capsule sample introduction, (2) reagent addition, and (3) controlled venting, during a digestion. The digestion tube has built-in cooling, an infrared temperature sensor, an in-line pressure sensor, automatic venting, and a new type of valve, called the "Flange Valve". The flange valve was designed for loading capsules into the digestion tube and for easy cleaning of all valve and tube parts wetted by the sample. / The digestion tube is made of Teflon PFA$ sp circler,$ which is capable of operating at 200 psi and 200$ sp circ$C. Water, salt solutions, and concentrated nitric acid were used to characterize the system. / A process was developed to make capsules from ultra-clean polyacrylamide gel; it was used to make capsules for the analysis of soils, botanicals, and biological samples. A "Squeegee", a device equipped with a soft, gas-tight Teflon$ sp circler$ end pushed through the digestion tube with a flexible rod, was used to insert capsules into and remove digestate from the digestion tube. / Micro2, an interpretive language, written in-house, uses English-like instruction files to control the digestion. Micro2 uses pressure, temperature and time data to control venting, cooling, and heating during the digestion. Triggers and feedback loops in the instruction file allow Micro2 to adapt to changing conditions in the digestion tube to complete a digestion without loss of analyte. / Analysis of the digested samples revealed that, for the same digestion temperature, dissolution is identical to that performed in a conventional microwave bomb.

Novel approaches to thermal vaporization sample introduction for inductively coupled plasma (ICP) spectrometry using techniques with demountable sample supports are presented and compared. Developments and applications are presented for two sample introduction arrangements that use interchangeable sample probes in contact-free heating environments: direct sample insertion (DSI), and induction heating-electrothermal vaporization (IH-ETV). For the well-established technique of DSI, studies focused on the development and application of a pyrolytically coated graphite sample support, a feature common to conventional ETV systems. A process for coating sample probes in the ICP discharge was developed, and improvements were seen in both the reproducibility of the volatilization event and the appearance of the transient emission signals with ICP-optical emission spectrometry (OES) when a coated probe was used over an uncoated one. The pyrolytically coated sample probe was successfully used for the direct determination of several metals in wood pulps by ICP-OES, and was found not only to improve the appearance of the temporal signals, but also demonstrated a heightened resistance to chemical attack. For the prototypical IH-ETV system, a general study was first conducted to establish performance attributes and benchmarks such as heating characteristics, transport efficiency, and ICP-OES detection limits using several mixed carrier gases. The IH-ETV arrangement was found to be capable of rapid heating rates and precise, reproducible temperature control suitable for a thermal vaporization sample introduction technique. Of all the gas mixtures studied, the incorporation of 15% (v/v) SF6 into the Ar carrier flow resulted in the best overall conditions for the vaporization, transport and detection of analytes by ICP-OES. These conditions were successfully used for the determination of various metals in soil and sediment samples by ICP-OES using IH-ETV sample introduction. Addit

A sample introduction system was developed with the goal of improving the efficiency of introduction of slurries into an inductively coupled plasma for atomic emission spectrometry. The system consisted of a Legere nebulizer with a heated spray chamber followed by a condenser. A capillary injector tube of 1.0 mm i.d. was required to minimize the signal variations caused by fluctuations of the injection gas. Comparing with a conventional slurry system, the hot system increased the transport efficiency by 2 for liquid and solid samples while it decreased the water content of the aerosol by 38%: 9.3 mg/min compared to 14.8 mg/min. The heated chamber increased the signal intensities by a factor of 11 for liquid samples and by 3 for solid samples. The use of a hot nebulization gas did not contribute further to the signal enhancement of the system. The large difference in slopes of calibration curves for liquids and solids resulted in low accuracy for the analysis of marine sediments: less than 50% in general. Poor efficiency of decomposition of the solid particles is considered the cause of low accuracy.

Crystals of 34% exchanged Eu$ sp{3+} beta sp{ prime prime}$-alumina were studied using site-selective spectroscopic techniques. The Eu$ sp{3+}$ ions were found to exhibit spectra which could be categorized into three types of emitting centres. These emitting centres are related to the crystallographic sites available for Eu$ sp{3+}$ in $ beta sp{ prime prime}$-alumina, namely the mid-Oxygen and Beevers-Ross sites. The fluorescent lifetimes were measured and were found to be consistent with the site assignments, particularly in the variations possible in the Eu$ sp{3+}$ coordination in mid-Oxygen sites. Analysis of the emission intensities reveals that the calculated site populations are in agreement with previously published X-ray results. Crystal-field analysis of the spectra indicates that the different types of centres are subject to different crystal-field strengths and that effects such as J-mixing play an important role in the observed spectra. Point-charge lattice sum calculations on an idealized structure of the $ beta sp{ prime prime}$-alumina crystal are in qualitative agreement with the crystal-field analysis and also provide a model for the observed inhomogeneous linewidths based on the number of residual sodium atoms in the unit cell. In addition, several anomalous features of the Eu$ sp{3+}$ spectra are described and discussed in terms of the structure of the crystal and its influence on the Eu$ sp{3+}$ ion's energy levels.