Ultrasonic wave propagation in cylindrical vessels and implications for ultrasonic reactor design

Reactors in which processes are enhanced by ultrasound are hampered by the lack of a theoretical framework on their design. Simulation results of ultrasonic wave propagation in a cylindrical geometry are presented in this work, which are then used to develop guidelines for the design of ultrasonic reactors. These guidelines are used to design a new type of reactor with a novel geometry, operating at a frequency of 27kHz, 39kHz and 82kHz. This reactor is characterized using Weissler's reaction dosimetr

Solid-state NMR studies of inclusion compounds

The work contained within this thesis is a study of inclusion compounds using solid-state NMR. Such compounds typically exhibit static and/or dynamic disorder, which precludes the use of diffraction-based techniques to obtain detailed structural information. Hence, due to its ability to probe local environments, solid- state NMR can be used to provide information which would otherwise be inaccessible. However, the dynamic nature of the guest molecules within inclusion compounds can yield unusual results for routinely applied experiments, such as cross polarisation, heteronuclear dipolar decoupling and dipolar dephasing. Therefore, some of the more fundamental aspects of solid-state NMR have first been explored. The inclusion compounds of particular interest are those which contain urea or thiourea as the host species. The ordering of guest molecules and host dynamics have been investigated via both one- and two-dimensional (^13)C and (^1)H NMR experiments for the 2-hydroxyalkane/urea inclusion compounds. For the 1-fluorotetradecane/urea inclusion compound, an approach involving a combination of (^1)H→(^13)C and (^19)F→(^13)C cross-polarisation experiments, with both single-channel (^H) and double-channel decoupling ((^1)H,(^19)F) has been devised to assign (^13)C resonances and hence deduce guest ordering. Steady-state and transient (^19)F MAS NOE experiments have been used to probe the dynamics of the 1-fluorotetradecane/urea inclusion compound. Using the considerable sensitivity advantage of (^19)F NMR, over that of (^13)C, a detailed study of the conformational dynamics exhibited by fluorocyclohexane molecules included within thiourea has been performed via bandshape analysis, selective polarisation inversion and 2D exchange experiments. Intermolecular distance measurements have been determined for adjacent fluoroalkane molecules within urea tunnels using a series of static (^19)F NMR experiments. From the results obtained, conclusions regarding the mutual orientations of adjacent end-groups in such compounds have been made

Women Beyond Tea: Fostering Tibetan Women Leaders of Tomorrow

Tibetan women leaders (TWLs) are a recent phenomenon within the Tibetan Exile Community. Before the 1950’s, Tibetans did not typically see women as leaders in public life (Thonsur, 2003). Women first entered public life as leaders after China invaded Tibet in the late 1950’s (Butler, 2003; Thonsur, 2003; McGranahan, 2010). The democratic reforms through the Central Tibetan Administration (CTA), the de facto government in exile for Tibetans, gave Tibetan women many rights and opportunities to develop their leadership capacity. However, women are still grossly underrepresented at the highest levels of leadership throughout the Tibetan Exile Community. To examine how the Tibetan Exile Community can cultivate leadership among the next generation of Tibetan women, this study conducted a survey of 42 young Tibetans and interviews with six established TWLs. The study found that TWLs possessed a particular set of skills that helped others identify them as leaders, faced immense challenges throughout their leadership journey, and implemented leadership strategies to help them persist as leaders. Day\u27s (2001) leadership development theory and Maparyan\u27s (2012) Womanist theory were used as theoretical frameworks to analyze and interpret the data

Validity of particle size analysis techniques for measurement of the attrition that occurs during vacuum agitated powder drying of needle-shaped particles

Analysis of needle-shaped particles of cellobiose octaacetate (COA) obtained from vacuum agitated drying experiments was performed using three particle size analysis techniques: laser diffraction (LD), focused beam reflectance measurements (FBRM) and dynamic image analysis. Comparative measurements were also made for various size fractions of granular particles of microcrystalline cellulose. The study demonstrated that the light scattering particle size methods (LD and FBRM) can be used qualitatively to study the attrition that occurs during drying of needle-shaped particles, however, for full quantitative analysis, image analysis is required. The algorithm used in analysis of LD data assumes the scattering particles are spherical regardless of the actual shape of the particles under evaluation. FBRM measures a chord length distribution (CLD) rather than the particle size distribution (PSD), which in the case of needles is weighted towards the needle width rather than their length. Dynamic image analysis allowed evaluation of the particles based on attributes of the needles such as length (e.g. the maximum Feret diameter) or width (e.g. the minimum Feret diameter) and as such, was the most informative of the techniques for the analysis of attrition that occurred during drying

Classifying green teas with near infrared hyperspectral imaging

Tea products analysis is currently limited to high-end analytical techniques such as high-performance liquid chromatography, gas chromatography and isotope analysis. However, these techniques are time-consuming, expensive, destructive and require trained experts to perform the experiments. In the present work, an application of near infrared hyperspectral imaging for the classification of similarly appearing green tea products is demonstrated. The tea products were classified based on their origin utilising a support vector machine classifier. Results showed good accuracy (96.36 ± 0.17%) for the classification of green tea products from seven different countries of origin

Comparison of the determination of a low-concentration active ingredient in pharmaceutical tablets by backscatter and transmission raman spectrometry

A total of 383 tablets of a pharmaceutical product were analyzed by backscatter and transmission Raman spectrometry to determine the concentration of an active pharmaceutical ingredient (API), chlorpheniramine maleate, at the 2% m/m (4 mg) level. As the exact composition of the tablets was unknown, external calibration samples were prepared from chlorpheniramine maleate and microcrystalline cellulose (Avicel) of different particle size. The API peak at 1594 cm(-1) in the second derivative Raman spectra was used to generate linear calibration models. The API concentration predicted using backscatter Raman measurements was relatively insensitive to the particle size of Avicel. With transmission, however, particle size effects were greater and accurate prediction of the API content was only possible when the photon propagation properties of the calibration and sample tablets were matched. Good agreement was obtained with HPLC analysis when matched calibration tablets were used for both modes. When the calibration and sample tablets are not chemically matched, spectral normalization based on calculation of relative intensities cannot be used to reduce the effects of differences in physical properties. The main conclusion is that although better for whole tablet analysis, transmission Raman is more sensitive to differences in the photon propagation properties of the calibration and sample tablets