Although it is well documented how introduced species can negatively affect native species, we only poorly understand how they may alter ecosystem functions. We investigated how an invasive fish affected the flux of aquatic insects to terrestrial food webs using mesocosms in a desert spring ecosystem. We compared aquatic insect emergence between alternative community states with monocultures and polycultures of two native species of fish, least chub (Iotichthys phlegethontis) and Utah chub (Gila atraria) plus, introduced western mosquitofish (Gambusia affinis). We tested three hypotheses: (1) aquatic insect biomass will be greater than terrestrial insect biomass and thus, constitute a vital source of energy for terrestrial consumers (2) invasive mosquitofish will negatively impact the biomass of emerging aquatic insects, and (3) terrestrial consumers will negatively respond to decreased emerging aquatic insect biomass. Aquatic insects represented 79% of the flying insect community, and treatments with mosquitofish significantly reduced emergent aquatic insect biomass by 60% relative to the control without mosquitofish. Behavioral traits of invasive species are important, because mosquitofish most heavily affected insects that emerged during the day. Also, spiders that build horizontal webs were negatively correlated with decreasing aquatic insect biomass. Invasive mosquitofish can achieve very dense populations because of their high intrinsic rate of population increase, which can significantly disrupt the flow of energy between aquatic and terrestrial ecosystems, thereby reducing the energy available for terrestrial consumers.

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Silicones elastomers are widely used all over the world due to their unusual properties when compared to their carbon-based counterparts. Synthetic methods for their synthesis are still quite limited and the traditional silicone products are not able to completely meet the requirement for modern materials. Silicone elastomers with customized structures and with higher levels of sustainability will be the research focus for the development of next generation materials. The element sulfur and its functional groups are growing players in modern polymer and materials science, since sulfur reactions are exceptionally versatile. The incorporation of sulfur reactions into the design and preparation of silicone materials can lead to silicones with unique properties for various research interests. Initial exploration was focused on the creation of general and simple methods for 3D printing silicone elastomers using thiol-ene chemistry. However, silicone inks suitable for 3D printing are still quite limited. Photo-initiated thiol-ene chemistry was proposed to design a rapid cure silicone ink for extrusion 3D printing. Unlike other radical reactions, the relatively oxygen insensitive thiol-ene was able to provide the necessary rapid reaction rate and build up the necessary viscosity for practical printing in less than 2 seconds in the presence of air. Various customized silicone structures with different moduli were obtained with a relative fast printing speed. The use of thiol oxidation reactions in the synthesis of silicone elastomers is also demonstrated in this thesis. Reductive cleavage of the resulting disulfide bridge was successfully performed with the presence of hydrosilane and B(C6F5)3 catalyst. Herein, a synthetic method to reversible silicone elastomers based on the disulfide linkage is described. This method could be extended to cleave the disulfide and polysulfide linkage in used automotive rubber materials. Various kinds of sulfur-cured rubbers were successfully devulcanized to polymeric oil. This simple and efficient method could potentially offer a solution for the huge amount of tire waste produced every year. Finally, a new method for preparing thermoplastic silicone elastomers with ionic linkages is reported. A novel dicarboxylic acid-modified silicone was synthesized though thiol-Michael additions. The resulting ionic crosslinked networks were built though the neutralization between carboxylic and amino silicone. Thermoplastic silicone elastomers with unique viscoelastic behavior can be obtained. In summary, the thesis demonstrates that sulfur chemistry is an exceptional synthetic tool for the silicone chemist. / Thesis / Doctor of Philosophy (PhD)

This thesis is a study in the application of kinematics coupled with elastic body mechanics. Most studies in kinematics assume all mechanism links to be inelastic. Furthermore, the methods of kinematic synthesis have generally been developed to meet requirements of displacement, velocity and acceleration. The work presented in this thesis differs in two important aspects. First, one grounded link of a four-bar linkage is replaced by a cantilevered beam in flexure to produce a force generating mechanism. Second, the synthesis method presented here allows the generation of these mechanisms in closed form for prescribed force generation. A compound archery bow that incorporates four-bar linkages has been developed as an example. This design relies on the non-linear mechanical advantage of the four-bar linkage and the bow mechanics to provide a resistance curve that is more compatible with the human strength curve. In addition, by modifying the bow kinematics, more potential energy can be stored, and thus potentially more kinetic energy can be transferred to the arrow than with previous bows. / Master of Science

Integrated Pest Management (IPM) technologies have proven to be effective at increasing agricultural productivity and have been credited for providing economic, health, and environmental benefits in many developing countries. In South Asia, population growth and the increasing demand for nutritious foods have put pressure on farmers to produce more food with a relatively inelastic supply of land. Productivity enhancing practices, like IPM, have helped some farmers to meet this demand; however, with over 50 million farmers in Bangladesh and Nepal it is difficult to reach them with information about new agricultural technologies. This study evaluates the current IPM dissemination strategy being implemented by the Bangladesh Department of Agricultural Extension (DAE) and uses a linear programming (LP) model to propose alternative strategies that may extend the total benefits from IPM technologies. Additionally, using data from a household survey, a bivariate probit model and a two-step endogenous participation model are used to identify factors that may influence both knowledge and adoption of IPM practices in three regions of Nepal. The results from the LP model suggest that more farmers could be effectively reached by reallocating funding that is currently used for interpersonal communications (i.e. extension agent visits and farmer field schools) to more widespread methods such as mass media and field days. The model also suggests that a dynamic dissemination strategy is necessary to encourage adoption of IPM technologies with differing characteristics and levels of complexity. The econometric analysis suggests that farmers with "network linkages" to agricultural information and inputs, such as membership in a farmer organization, are more likely to be aware of IPM and to adopt IPM practices. The survey data also suggest that farmers who are members of Marketing Planning Committees (MPC) may be more likely to adopt more IPM practices when compared to non-members. Overall, the study suggests that strategically disseminating IPM information is vital to promote the adoption of these technologies in South Asia. / Master of Science

No / A significant potential beneficial impact of foreign direct investment arises from a foreign affiliate's propensity to purchase inputs from suppliers in the host economy. This issue is of particular interest where the host is a developing country and the linkage is likely to contribute to the development of local suppliers. We compare variations in local input linkages across four countries: Cambodia, Malaysia, Thailand and Viet Nam, all member countries of the Association of South-East Asian Nations (ASEAN). Using multiple linear regressions, our findings indicate that the degree of local input linkages is highest when foreign affiliates perform a strategic role in the transnational corporation network and are embedded in the host economy. Non-firm factors are also important determinants, especially the industry of investing firms and the existence of a supply base. Building on the findings, a series of policies to enhance supplier-foreign affiliate linkages are proposed.

No / This paper examines the linkage effects of foreign direct investment (FDI) on firm-level productivity in Chinese manufacturing. It is found that FDI generates positive vertical linkage effects in Chinese manufacturing at both the national and regional levels, and limited positive horizontal spillovers at the regional level. While OECD firms gain from both vertical and (probably) horizontal linkages, Hong Kong, Macao and Taiwanese firms benefit only from backward linkage effects. In the domestic sector, in which we are most interested, both state-owned enterprises (SOEs) and non-SOEs are hurt by competition from foreign firms in the same industries. While SOEs gain from vertical linkages with foreign firms, non-SOEs are unable to do so. The patterns of productivity spillovers from FDI in Chinese manufacturing seem to be determined by one key factor ¿ the technological capabilities of the firms involved. Important data limitations and policy implications of this research are discussed.

Yes / This paper examines the impact of state intervention in French-German inter-firm linkages and discusses the implications of conflicting national interests for the furthering of single market integration. It demonstrates that despite initial success in launching large-scale cross-border alliances in strategic sectors, France and Germany have remained divided by their own industrial nationalism. It argues that their respective attitudes towards industrial policy are less contradictory than would appear at first sight, but that transcending industrial nationalism by Europeanising the notion of economic patriotism would be an essential pre-condition for a more efficient EU-wide industrial policy within a better integrated internal market.