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<p> The integration of silicon germanium (SiGe) in the base of heterojunction bipolar transistors (HBTs) has recently put the alloy into prominence to produce fast-switching transistors. However, the thin highly doped SiGe base makes the transistor susceptible to base dopant outdiffusion during device processing, which results in device performance degradation. Adding carbon to the base was shown to significantly suppress boron outdiffusion and help retain the narrow as-grown profile. Dopant behavior in the presence of various species needs to be well understood and modeled for two reasons: (1) to have accurate and predictive process simulators; and (2) to obtain insight into process development. </p> <p> Modeling carbon diffusion and its role in suppressing boron diffusion in silicon and SiGe has been studied by several groups. While boron diffusion is well-established, different modeling regimes have been developed for carbon diffusion. Each of the existing studies has focused on subsets of the available experimental data. We present a consistent and complete model that accounts for carbon and boron diffusion in silicon and SiGe, under equilibrium and non-equilibrium conditions. In our regime, carbon diffusion is modeled according to the kick-out and Frank-Tumbull mechanisms for diffusion; in addition, we incorporate the carbon clustering phenomenon. To completely model boron diffusion, we account for the boron-interstitial clustering (BICs) effect and the { 311} defects that are associated with boron transient enhanced diffusion (TED). In the developed model we make use of the well-established literature data for carbon diffusion, as well as boron diffusion and Si self-diffusion. The model was verified by simulating experiments that involve boron and/or carbon diffusion in silicon and SiGe and cover the complete temperature range of 750 - 1070 °C. The test structures include published experiments in addition to recent experimental results obtained through collaboration, and feature diffusion in inert and oxidizing ambients, under rapid thermal annealing (RTA) conditions, as well as in the presence of implant damage. We also investigated the validation of the model without the inclusion of either the clustering or the Frank-Turnbull reactions. </p> / Thesis / Master of Applied Science (MASc)

The binding of the elements lithium and boron to human plasma proteins is investigated through the techniques of thermal neutron activation and helium isotope mass spectrometry. Since normal physiological levels of lithium and boron in blood and plasma are in the ultratrace (ppb) range, lithium in particular is frequently below the detection limit of many instruments. The success of the detection method used in this work is due to the extremely large cross section of ⁶Li for the thermal neutron reaction ⁶Li(n,³H)⁴He, and of ¹⁰B for the thermal neutron reaction ¹⁰B(n,α)⁷Li. The high sensitivity of the mass spectrometer, originally designed for oceanographic studies of helium isotopes and tritium, allows measurement of as little as 2x10⁴ atoms of ³He from the decay of tritium, and 2x10¹⁰ atoms of ⁴He from alpha-particles. It has frequently been stated that lithium does not bind to plasma proteins. However, our results clearly show that lithium does bind to a number of these proteins, at least 𝘪𝘯 𝘷𝘪𝘵𝘳𝘰. Boron is also shown to bind to proteins, with a pattern similar to that of lithium . Although a clear identification of the specific plasma proteins which bind lithium and boron must await further investigation, a number of possibilities are suggested here, based on the data obtained. / Thesis / Master of Science (MSc)

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Organoboron compounds are ubiquitous in organic chemistry. Fundamental transformations utilizing organoboron compounds are a necessary addition to any organic chemist's synthetic toolbox. In addition to their extensive use as synthetic intermediates, organoboron compounds are being increasingly studied for their material and medicinal properties. Excitingly, significant advances have been made over the years towards the synthesis of a wide variety of organoboron substrates. In the case of vinylboronic acids, synthesis primarily occurs through cis addition of boron reagents across triple bonds. However, methods affording trans addition products are scarce. Furthermore, many current methods rely on the use of expensive and toxic transition-metal catalysts. Herein, we describe the development of trans addition of boron reagents across polarized triple bonds to afford novel vinylboronic acids. Emphasis is placed on the transition metal-free nature of the reactions as well as the regio- and stereoselectivity observed in the products. In addition, the synthetic utility of the resulting trans addition products is demonstrated in the synthesis of biologically relevant molecules. We first describe the Brønsted base-mediated trans silaboration of propiolamides in which two functional groups with orthogonal reactivity are simultaneously installed. We then go on to describe an organocatalyzed trans hydroboration of propiolate esters as well as a complementary Brønsted base-mediated trans hydroboration reaction of propiolamides. To conclude this portion, we demonstrate how the products from the previous methods can be used to synthesize difluoroborylacrylamides which possess unique and versatile reactivity. Herein we disclose the first small-molecule inhibitors of the sphingosine-1-phosphate (S1P) transporter spinster homolog 2 (SPNS2). While little is known in regard to the structure and function of SPNS2, previous studies have demonstrated the vital role SPNS2 plays in S1P mediated processes and have identified SPNS2 as a potential clinical target. For example, SPNS2 is critical to S1P-mediated lymphocyte egress from primary lymphoid tissues. Thus, small molecule inhibition of SPNS2 represents a novel therapeutic strategy for the treatment of autoimmune disorders such as multiple sclerosis. In this study, we report the discovery of small molecule inhibitors that display low micromolar activity using a novel yeast-based SPNS2 assay. Inhibitor structure-activity-relationship studies led to the discovery of the imidazole-based amine inhibitor 7.54. Furthermore, administration of 7.54 to mice recapitulates the lymphopenic phenotype observed in previous SPNS2 knockout studies. / Doctor of Philosophy / Boron-containing compounds are important in organic chemistry and are involved in the synthesis of a variety of materials and medicines used in everyday life. As such, the ability to efficiently and sustainably prepare boron-containing compounds has far reaching consequences. Access to an important class of boron-containing compounds known as vinylboronic acids has previously been established; however, product selectivity is often limited to what is referred to as cis addition products. Furthermore, access to the corresponding trans addition products is often limited to processes involving expensive transition metal catalysts that produce environmentally toxic waste. Herein, novel transition metal-free trans addition processes are described for preparing vinylboronic acids. In addition, the application of the resulting products is demonstrated through the synthesis of biologically relevant compounds. Sphingosine-1-phosphate (S1P) is an important signaling lipid that is involved in a variety of physiological processes. Improper balance in the amount of S1P in the body is associated with a variety of disease states such as autoimmunity and cancer. Two drugs that inhibit S1P-mediated processes have been approved by the FDA, fingolimod (Gilenya®) and siponimod (Mayzent®). However, there are drawbacks to targeting the S1P receptor directly, including dose-limiting side effects that are associated with these drugs. Consequently, recent efforts have focused on developing new ways to control the effects of S1P. Herein, we describe the discovery and development of the first reported inhibitors of the S1P transporter, spinster homolog 2 (SPNS2). A library of compounds was synthesized and tested for SPNS2 inhibition. The resulting structure-activity-relationship studies led to the discovery of the imidazole-based propanamine derivative 7.54. Furthermore, we demonstrate the potential of SPNS2 inhibition to control the effects of S1P in mice. These studies provide a foundation for future SPNS2-based drug discovery that will hopefully lead to the development of improved therapies for the treatment of autoimmune disease and cancer.

No / Reverse Osmosis (RO) process is widely used for seawater desalination. In this work, we considered a small scale SWRO (Spiral Wound Reverse Osmosis) desalination unit which is enough to cover the need of a medium size hotel complex at Limassol city in Cyprus. The pH of the seawater in the region is 7.95 and the temperature varies from 17 to 27 °C. The aim of this study is to identify the configuration of the RO process and the optimum operating parameters such as pH and pressure that can minimise the total annualised cost of the process subject to acceptable quality of freshwater in terms of boron concentrations throughout the year. For this purpose, the mathematical model for boron rejection developed earlier by the authors is used but incorporates cost functions. The model is based on solution-diffusion model which can describe solvent and solute transport mechanism through the membranes. With the variation of seasonal seawater temperature, the key finding of this study was that by choosing the right combination of pH and pressure, substantial economical savings up to 16 % could be achieved.