Small diatomic and triatomic 3d transition metal species are excellent model systems for understanding metal-ligand interactions important to larger complexes. Because of the unpaired 3d electrons, these radicals often occur in states with high angular momentum (electron spin, orbital, or nuclear spin). Three questions are particularly relevant to studying monosubstituted 3d metal compounds. What are the fundamental geometric, bonding, and electronic properties? How accurately does currentquantum mechanical theory describe the interactions in high spin states? Assuming these molecules may be present in the interstellar medium, what are the precise transition frequencies that can be used for radioastronomy?To answer these questions, pure rotational spectroscopy has been applied to eleven simple molecules containing 3d transition metals. The small radicals were synthesized in the gas phase and examined in situ. Both direct absorption, submillimeter spectroscopy and Fourier transform microwave spectroscopy were used to cover thefrequency range 8-660 GHz. New synthetic techniques, including oven-insulating methods, use of a longitudinal AC discharge, and emphasis on organometallic precursors, were developed to improve reaction yields.Spectra were recorded for four categories of 3d metal compounds: vanadium molecules, cobalt radicals, zinc species, and several monocyanides. Frequently, the data exhibited signs of perturbations either from low-lying excited electronic states, a common feature with 3d electrons, or from avoided crossings of hyperfine levels. The data were analyzed using effective Hamiltonians, and spectroscopic constants have been determined for rotational, fine structure, and hyperfine interactions. The measurements haveprovided transition frequencies as references for astronomical studies; these values are accurate to within 50 kHz for direct measurements and usually within 100 kHz for frequencies calculated from determined molecular constants.Rotational constants have been used to establish precise molecular geometries. Fine structure and hyperfine data provided insight into 3d metal bonding properties (molecular orbital composition and electron distribution) and structure of electronic state manifolds. In some cases, it was necessary to develop new terms for the Hamiltonian expressions to accurately describe the interactions observed in the spectra. These terms include deperturbation parameters and the first complete description of lambda-doubling for Phi states.

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The demand for posterior aesthetic restorations has dramatically increased in recent years. Several new materials have been developed with improved aesthetic, adhesive and mechanical properties. However, microleakage elimination, especially if the margins are on dentine or cementum, and attainment of optimum mechanical properties for posterior use, are still questionable. The aim of this study was to investigate microleakage and surface microhardness of a nanofilled, a nanohybrid and an ormocer based nano-ceramic composite restorative material.

<p>Amalgam bonding agents have been shown to enhance retention of amalgam restorations by mechanical means. However, recent studies showed that the use o glass ionomer cements and resin cements as lining and bonding materials to amalgam restorations will increase the retentive strength of the amalgam restorations, hence reducing the micro leakage and secondary caries. The purpose of this study was to compare the relative retentive strength of conventional amalgam restorations and bonded amalgam restorations using resin adhesive, glass ionomer cements and resin cements.</p>

Tannins and humic substances commonly referred to as natural organic matter (NOM), constitute an important component of natural water and soil systems. These species contain numerous phenol and carboxyl functional groups whose reactivity is strongly dependent on both the quantity and location of these moieties on the aromatic ring. In the realistic environmental conditions, both phenolic and carboxylic functional groups are adsorbed on a variety of colloidal metal oxide surfaces. Unfortunately, due to the complexity of humic-based substances, experimental data involving mineral-humate interactions are difficult to interpret. Here, we aim to develop a more detailed understanding of mineral-NOM interactions in aquatic systems, using self-assembled monolayers (SAMs) of simple organic acids having functional groups similar to those found in humic substances. SAMs of 4-(12-mercaptododecyl)benzene-1,2-diol (o-hydroxyphenol-terminated), 5-(12-mercaptododecyl)benzene-1,3-diol (m-hydroxyphenol-terminated), bis(11-thioundecyl) hydrogen phosphate (monoprotic phosphate) and 11-thioundecyl dihydrogen phosphate (diprotic phosphate) were prepared and deposited on a Au(111) surface. The composition of elements present on the surface were determined by X-ray Photoelectron Spectroscopy (XPS) and the orientation of monolayers on the Au(111) surface was explored by Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) Chemical force spectrometry has been used to determine the surface pKa of the monolayers and further used to explore the role of phenolic groups in the surface complexation of NOM by monitoring adhesion forces between iron and aluminum oxide sample and hydroxyphenol-terminated Atomic Force Microscopy (AFM) modified tip. The results are discussed in the context of hydrogen bonding between corresponding species. The system in which there are multiple hydroxyl groups ortho to the carboxylic groups or adjacent to one another on the benzene ring results in significantly different force-distance profiles when interacting with the hydroxyphenol tip. / Thesis (Ph.D, Chemistry) -- Queen's University, 2013-06-18 00:22:06.646