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<p>  </p> <p>As the pharmaceutical industry moves towards molecular obesity with the use of high throughput screening for identification of promising candidates, the low aqueous solubilities of new chemical entities pose significant challenges to achieving adequate oral absorption and bioavailability. Enabling formulations are often needed to address this issue. Amorphous solid dispersion (ASD), where an amorphous drug and a polymer are molecularly mixed, has gained popularity as a dissolution/solubility enhancing strategy over the years. Upon ASD dissolution, the release rate of drug is much higher than that of the neat amorphous form of the drug. More importantly, the apparent concentration of drug in the solution can exceed its amorphous solubility through the formation of a drug-rich colloidal phase in the solution, also called nanodroplets. The presence of nanodroplets has been shown to be beneficial for oral absorption and bioavailability and their formation during release is therefore desirable. However, such release profiles are only achieved at relatively low drug loadings (DLs) and release tends to drop with increasing DL. For ASDs based on polyvinylpyrrolidone/vinyl acetate (PVPVA), drug release drops drastically once the DL exceeds a certain value, called limit of congruency (LoC). The low DL at which the ASD demonstrates good release also presents additional challenges since it can create a pill burden for patients due to the large amount of polymer needed in the formulation. Therefore, to achieve optimal drug product performance, it is crucial to understand the mechanisms of drug release. Therefore, this thesis focuses on understanding the factors affecting, and the mechanisms of ASD drug release, as well as enhancing drug release through addition of surfactants. </p> <p>The glass transition temperature of a drug and its interaction with the polymer were identified as important factors affecting the drug release and LoC. Another phase transition occurring during ASD hydration/dissolution, amorphous-amorphous phase separation (AAPS), was shown to affect drug release from ASD significantly. During dissolution, water-induced AAPS occurs, and the initially miscible ASD separates into two phases, an insoluble drug-rich phase and a soluble water/polymer-rich phase. The formation of a continuous drug-rich phase at the ASD-solution interface was shown to be detrimental to drug release as it could act as barrier that blocked any further drug release. When the drug-rich phase formed adopted a discrete morphology or when phase separation occurred in the solution outside of the dissolving ASD matrix, good release could be achieved. Surfactants could interrupt the formation of the continuous drug-rich both kinetically and thermodynamically, improving drug release as a result. Other mechanisms of release enhancement by surfactants included increased polymer release rate, increased water ingress and plasticization. The findings in this thesis will provide insight into ASD release mechanisms, and facilitate rational excipient selection when designing ASD formulations.  </p>

As the Internet-of-everything continues diversifying, wireless nods sensors, wearables, and smart-objects will require mature technologies to harvest energy from the environment in which they are installed. Out of the many energy forms, solar and artificial light are constantly present and the utilization solar technologies including organic photovoltaics can provide advantages including flexibility, semitransparency, and lightweight. Additionally, the incredibly low environmental footprint and reduced manufacturing costs associated with solution processing can provide an edge for entry into the industrial and consumer markets. While the utilization of conjugated polymers and nonfullerenes elevated the efficiencies of organic photovoltaic for commercialization, increasing the technological readiness level requires the development of protocols to translate lab performance of state-the-art-materials to scalable manufacturing techniques that can be adapted for roll-to-roll processing. This dissertation demonstrates the full fabrication of high-performance OPV devices through techniques such as inkjet printing and slot-die coating. The development of ink formulation frameworks based on solvent engineering, rheological and interface properties, and solubility parameters sets the base for standardized high-yield processes with reduced environmental footprint in line with circular carbon initiatives. Moreover, the utilization of engineering strategies involving intrinsic properties of materials, device architectures, and integration enables the development of complex energy harvesting and sensing devices for potential utilization in agrivoltaics and biosensing.

The objective of this study is to elucidate as much as possible the theory and analysis of BOURDON tubes. Both thick-walled and thin-walled tubes are considered. Three papers, representative of the state-of-the-art of BOURDON tube analysis, are reviewed (References 1, 2, and 6): <p> 1. Wuest, W. "Theory of High-Pressure BOURDON Tubes". </p><p> 2. Andreeva, L. E>, "Elastic Elements of Instruments" </p> <p> 3. Dressler, R., "Elastic Shell-Theory Formulation for BOURDON Tubes" </p><p> Reanalysis of (3) above, with a different approach (Appendix A) checked and completed the general formulation by Dressler. The final forms of all necessary equations, boundary conditions, etc. to the solution of the three governing equations of the BOURDON tube with an elliptical cross-section are given. </p><p> Comparison of results of Andreeva's sensitivity equation with test data of Kardos, Mason and Exline (References 3, 4 and 5) using a qualitative approach as set out by Kardos (References 3 and 17) showed good correlation. </p><p> The study concludes with recommendations for the approach of future research and preliminary design procedures for BOURDON tubes. </p> / Thesis / Master of Engineering (ME)

<p> This dissertation examines the facility location problems in the presence of barrier regions and consists basically of four essays exploring new problems. Despite the fact that the facility location problems considering barriers to travel are more realistic than their unrestricted counterparts, research in the area is relatively limited. This is due to the computational complexity associated with them. </p> <p> The first essay analyzes the problem of locating a facility in a region in the presence of a probabilistic line barrier. The objective is to locate the facility such that the sum of the volume times distances between the facility and demand points is minimized. Some convexity results are presented and a solution algorithm is proposed. </p> <p> Another interrelated problem is locating a facility in a region where a fixed line barrier such as a borderline divides the region into two. The regions communicate with each other through a number of passage points located on the line barrier. A version of this problem with minisum objective has been studied in the literature where the locations of the passage points are known. The second essay considers a number of extensions to this problem and proposes an efficient solution methodology based on the Outer Approximation algorithm. </p> <p> The third essay discusses the problem of locating a rectangular barrier facility m an area where interactions among existing facilities are present. The problem has two objectives. The first objective is to minimize the interference of the barrier facility to the interactions among the existing facilities. The second objective is to find a center (minimax) location for the barrier facility. The problem is formulated as a bi-objective problem and a mixed integer program is proposed as a solution methodology. A Simulated Annealing algorithm is presented for an extension of the problem where expropriation of existing facilities is also possible. </p> <p> Finally, the last essay suggests a practical analog approach for facility location problems in the presence of barriers. The use of the analog for certain problems is justified through some analytical results and a number of problems that appeared in the literature are solved efficiently. </p> / Thesis / Doctor of Philosophy (PhD)

<p> It is known in the case of an electron gas that the Coulomb force between electrons is screened due to the density variation around the electrons. In a similar way the force acting between nucleons in nuclear matter may be appreciably different from the free nucleon-nucleon interactions. The main theme of this thesis is to examine the "Screening" effect of the nuclear force. To this end, first the dielectric formulation of the theory of an electron gas is reviewed. Relationship among the chain-diagram approximation, the random phase approximation and the dieledtric formulation is discussed in detail. These techniques are then applied to nuclear matter taking the one-pion exchange potential as an example. It is found that the screening effect on the nuclear force in nuclear matter is indeed quite appreciable. The validity of the approximations is discussed. </p> / Thesis / Master of Science (MSc)

An algorithm is presented for the solution of mechanical contact problems using the displacement based Finite Element Method. The corrections are applied as forces at the global level, together with any corrections for other nonlinearities, without having to nominate either body as target or contactor. The technique requires statically reducing the global stiffness matrices to each degree of freedom involved in contact. Nodal concentrated force are redistributed as continuous tractions. These tractions are re-integrated over the element domains of the opposing body. This creates a set of virtual elements which are assembled to provide a convenient mesh of the properties of the opposing body no matter what its actual discretizaton into elements. Virtual nodal quantities are used to calculate corrective forces that are optimal to first order. The work also presents a derivation of refereritial strain tensors. This sheds new light on the updated Lagrangian formulation, gives a complete and correct incremental form for the Lagrangian strain tensor and illustrates the role of the reference configuration and what occurs when it is changed. / Thesis / Doctor of Philosophy (PhD)

An algorithm is presented for the solution of mechanical contact problems using the displacement based Finite Element Method. The corrections are applied as forces at the global level, together with any corrections for other nonlinearities, without having to nominate either body as target or contactor. The technique requires statically reducing the global stiffness matrices to each degree of freedom involved in contact. Nodal concentrated force are redistributed as continuous tractions. These tractions are re-integrated over the element domains of the opposing body. This creates a set of virtual elements which are assembled to provide a convenient mesh of the properties of the opposing body no matter what its actual discretizaton into elements. Virtual nodal quantities are used to calculate corrective forces that are optimal to first order. The work also presents a derivation of refereritial strain tensors. This sheds new light on the updated Lagrangian formulation, gives a complete and correct incremental form for the Lagrangian strain tensor and illustrates the role of the reference configuration and what occurs when it is changed. / Thesis / Doctor of Philosophy (PhD)

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