Search

In this thesis, the effect of formulation on liposomes prepared by spray-drying, freeze- drying and spray-freeze-drying has been investigated. In related work the effect of freeze- drying on the transfection efficiency of a peptide/pDNA complex following freeze-drying- rehydration was also achieved. The effect of disaccharide and anti-adherent concentration on the stability of spray- dried liposomes was investigated. The optimum formulations contained a combination of 10% sucrose or 15% trehalose together with 0.5% (w/w) leucine. However, a marked increase in size of the rehydrated liposomes was obtained with further addition of 1% (w/w) leucine. Liposomes prepared by both the ethanol injection and proliposome method retained similar characteristics. Liposome powder containing 15% trehalose/0.5% leucine displayed the best aerodynamic characteristics probably because of the higher Tg value for trehalose. Next liposomes were prepared by the alcohol-based proliposome method to investigate the effects of sucrose or trehalose concentration on stability to freeze-drying. Tg' values of these dispersions were much lower than the Tg' of the pure sugar solutions leading to product collapse, while drug leakage and increased liposome size was seen for those formulated with 10% trehalose. Inclusion of an ethanol expulsion step increased Tg' and enabled preservation of structural stability and drug encapsulation following freeze-drying- rehydration. A spray-freeze-drying study demonstrated that inclusion of 30% (w/w) sucrose or trehalose prevented drug leakage but could not prevent size increase. The powders obtained exhibited a more compact structure with particle sizes of around 10 urn instead of the typical porous structure seen for spray freeze-dried powders. Addition of 5% PVP into liposome suspensions containing 10% disaccharide demonstrated some Iyoprotective effect in terms of entrapment efficiency was not as protective as the formulation containing 30% trehalose. An attempt to develop spray-dried polymer-coated liposomes suitable for nasal delivery was made. A combination of 10% (w/w) trehalose dihydrate and 0.2% (w/w) L-Leucine could effectively protect liposomes constituted of soya lecithin, DMPG and cholesterol against spray-drying damage albeit with a slight liposomal size increase. The addition of polymer coatings reduced the protective effect of sugars to a differing extent, while the size of chitosan- and TMC-coated liposomes was substantially greater than those with alginate coating. TMC-coated liposomes retained the highest BSA encapsulation and also still exhibited the ability to penetrate bovine nasal mucosa. The mucoadhesive strength of the powders was TMC-coated ~ chitosan-coated > alginate-coated liposome ~ uncoated liposomes. The peptide:pDNA (RALA-pEGFP-N1) complexes at various N/P ratios were freeze-dried. The N/P ratio of 1:10 exhibited the highest transfection efficiency, that was unexpectedly slightly increased after freeze-drying. Surprisingly, it was found that transfection efficiency of pEGFP-N1 complexed with RALA tended to gradually decrease with increasing concentration of trehalose and could unexpectedly be slightly improved by freeze-drying. CD spectra demonstrated that the a-helix structure of RALA became predominant upon association with pDNA and was not affected by trehalose. However, as added amount of trehalose at 50:1 or over 600:1 (w/w) of Iyoprotectant to pDNA, the secondary structure conversion of a-helix to partly random coil of RALA in the peptide/pDNA complexes was observed following freeze-drying although this was not correlated with transfection efficiency.

Recently, electrically conductive adhesives (ECA) materials have evolved into an important technological area with the continual development of solar cell packaging technology along with other areas, which typically incorporate electrically conductive fillers into a polymeric matrix to render the composite conductive.1 Standard application of ECA seeks to replace solder alloy for die attachment and electrical interconnect due to its toxicity. In order to make the insulate polymeric material achieve conductive property, the inside fillers should form a channel between the two-physical surface where electrons can transfer through, which is supported by threshold percolation theory.2,3 However, to achieve the desired conductivity, the ECAs material usually relies on metal fillers with high loading, which obviously increasing the cost of material and limit its mechanism properties. Therefore, to overcome this challenge, low-dimensional carbon materials was investigated in this work (such as graphene, carbon nanotube). Low-dimensional carbon material possesses high aspect ratio and high mobility, which can employ with traditional mental fillers (silver) to enhance the conductivity at reduced filler loading.4 In this work, we produced functionalized exfoliated graphene sheets, mixing the functionalized graphene(EFG) and multi-wall carbon nanotube (MWCNT) with silver flakes into Polydimethylsiloxane (PDMS) matrix to produce ECA material. Electrical conductivities of 83.3 S/cm are reachable at a loading of 12 vol% silver with only 7 wt% CNT filler. In the edge-functionalized graphene system, 89.3 S/cm conductivity is reached at 15 vol% loading of silver with only 8 wt% added edge-functionalized graphene.

I study the stability and doctor-optimality of doctors' proposing cumulative offer process in the many-to-one matching with contracts. First, I explore some conventional hospital-by-hospital conditions on each hospital's choice function, and show that unilateral substitutability is equivalent to observable substitutability across doctors combined with cumulative offer achievability, each of which is a necessary condition for cumulative offer process to be doctor-optimally stable in a sense that if a hospital does not satisfy the condition, then we could construct some choice functions for other hospitals such that cumulative offer process is not doctor-optimally stable for some doctors' preference profile. Then, I focus on the joint properties of the choice functions for the entire group of hospitals and introduce two joint conditions---independence of proposing order and group cumulative offer achievability---and show that when these conditions are satisfied, cumulative offer process is always doctor-optimally stable. And it is by far the weakest sufficient condition. Moreover, these two conditions are necessary in a sense that if not, then there exists a doctors' preference profile and a proposing order such that cumulative offer process is not doctor-optimally stable. At last, I also introduce doctor's preference monotonicity and show that when cumulative offer process is doctor-optimally stable, this condition guarantees its strategy-proofness.

In this work, a generalized methodology, combining thermodynamic assessment of various etching chemistries and kinetic verification of etching efficacy, is proposed. To screen various chemistries, reactions between the dominant vapor phase/condensed species at various partial pressures of reactants are first considered. The volatility of etch product is determined to aid the selection of viable etch chemistry. Magnetic tunnel junction (MTJ) based magnetic random access memory (MRAM) was chosen as a case study to address the challenge of patterning various metals. Ar ion beam milling was a traditional method in patterning MRAM devices; however, sidewall re-deposition became severe as the features size decreased while aspect ratio increased. Selected metals (Fe, Co, Pt) and their alloys within the MRAM were studied by the generalized approach. To validate the thermodynamic calculation, films were patterned using a modified reactive ion etch process of halogen discharge with subsequent H2 plasma exposure. The etch rate of Fe, Co, and Pt were enhanced 40%, 25%, and 20% respectively with secondary H2 chemistry. X-ray photoelectron spectroscopy (XPS) suggested chemical removal of non-volatile metal chlorides by H2 plasma. Moreover, characterization through superconducting quantum interference device (SQUID) proved that coercive field strength of magnetic alloy after Cl2 plasma can be recovered by additional H2 plasma exposure from 63.6 to 20.9 Oe. To further improve selectivity to mask materials, the chemical organic etch of generating highly volatile etching product was investigated. The metal etch by organic chemical was first analyzed by thermodynamic calculation, and selectivities of Co to Fe etched by acac and hfac solutions were predicted. A series of etching experiment was verified the theoretical calculation through etch rate measurement and identification of etch products through inductively coupled plasma - mass spectroscopy (ICP-MS). Ar ion beam assisted chemical etch (IBACE) was then investigated to develop a vacuum-compatible and highly effective process in patterning magnetic metal stacks. The etching of Co by alternating Ar ion beam and acac vapor showed an enhancement of the etch rate by approximately 180% compared to that of Ar ion beam only. The etch rate of Co by alternating Ar ion beam and acac vapor was much greater than the sum of the two, suggesting a synergistic effect of chemical etching along with physical sputtering was developed. The final validation of this generalized approach was to assess the highly chemical etch in order to avoid the sputtering effect. A sequential etch with new surface modification of 500 W O2 plasma at 5 mtorr and organic vapor etch of formic acid was developed to pattern Fe, Cu, Co, Pd, and Pt, and the etch rate were 4.2, 3.7, 2.8, 1.2, 0.5 nm/cycle, respectively. A high selectivity of metal oxide to metal by formic acid vapor was achieved, suggesting one of the most important requirement in atomic layer etch, self-limiting reaction, was fulfilled. By controlling the thickness of oxides with O2 plasma oxidation, the etch rate of metals could be controlled in atomic scale level. The patterned samples of Co and MTJ stack were investigated in the optimized condition, and an isotropic etching profile, high selectivity of mask to metals, and retaining of magnetic characteristic were observed, suggesting a process with solely chemical etch was carried out. An anisotropic etching profile of Co was demonstrated by biasing sample with 200 V in O2 plasma, and an etch rate of 7.5 nm/cyc was achieved with sequential etch.

This dissertation is on mergers and acquisitions (M&A). Two studies are proposed to examine what factors impact performance and partner selection in the context of M&A. Event study methodology is used to capture the capital market effects of announcements of M&A in both studies. Four hundred and eighty two announcements are identified from 1980 to 2011 from the SDC M&A database. Other data sources include CRSP and COMPUSTAT. The Wall Street Journal and PR Newswire are used to specify the announcement dates.Previous research examines the impact of corporate strategy on performance. Study one extends previous research by introducing the notion of alignment between corporate strategy and strategic objective. Corporate strategy is of two types – value creation (emphasis on R&D) or value appropriation (emphasis on marketing). Strategic objectives are operationalized as either enhancement or diversification. The study proposes that firms whose corporate strategies are aligned with strategic objectives are better performers than those that are not aligned. Empirical findings based on capital market reactions strongly support this proposition.Study two accesses the effect of capability alignment between acquiring and acquired firms. Capability alignment between strategic partners is operationalized along marketing and R&D. Empirical results show that the capital market favors acquiring firms that have strong R&D capability. Although technological innovation is a motivating factor in a firm’s acquisition, capital market actually favors acquiring firms that have weak R&D capability but strong marketing capability and acquired firms that have weak R&D but strong marketing capability for their enhancement objective.

China is rapidly transforming into one of the world's most powerful economies, and the state encourages technological innovation to ensure that this trend continues. In particular, the state entices its citizens to receive education abroad and then return home to apply particular experience and expertise to their homeland's continued development. Yet despite these apparent advantages, Chinese technological products are generally not competitive with Western ones in the global market. Why does this paradox exist? This dissertation explores this puzzle, focusing on how technological innovation is being re-defined and produced by the Chinese government as well as by transnational Chinese professionals within the context of the global economy.Through archival research, discourse analysis, and 12 months of participant observation and interviews in Beijing, China, I arrive at the following conclusions. First, innovation development in China is constructed by the state as a political imagination driven by nationalistic entrepreneurialism. I call this mode of innovation development "imagined innovation." Moreover, through governing specific people and constructing nationalistic discourses, the state aims at consolidating capital, expertise, and other resources at the transnational level to reinforce state sovereignty. While this nationalistic strategy is successful in attracting foreign-trained Chinese to return to China in order to develop indigenous innovation, these professionals, labeled as "Haigui," also face various cultural obstacles in their everyday operations, which at times impede original innovation from taking place, due to the utilitarian nature of imagined innovation that favors political agendas and economic profits over cultivating original creativity.Nationalistic entrepreneurialism creates conditions in which Haigui can mainly rely on the efficient imitation and modification of Western technologies to gain competitive advantages in the Chinese market. However, driven by professional entrepreneurialism, Haigui also find themselves uniquely situated to identify innovative markets as well as develop socially creative practices to manage Chinese employees and promote their products. They do so in part through objectifying themselves by drawing on their cross-cultural experience, thus enabling them to flexibly develop technological and entrepreneurial practices. I call this form of subject-making "reflexive subjectivity" to illustrate how Haigui engage in reflexive thinking as they negotiate the difficult terrain of state power, market variations, and cultural differences.Therefore, I use the term "innovative entrepreneurship" to articulate the dynamic and multiple ways in which innovation is understood and produced in China under global influences. It is a constellation of political strategies, cultural practices, and business ethics that aims to build technological innovation in heterogeneous socio-cultural contexts. Ultimately, the rise of China in the global economy poses new questions about how to conceptualize innovation, as well as its relationship to international and Chinese markets. This research offers a new perspective on contemporary Chinese culture and politics with respect to innovation, and its arguments offer theoretical contributions as well as insights for policymakers and prospective Haigui entrepreneurs.