Engineering nanocomposites for antimicrobial application

In this thesis, active and passive antimicrobial methods have been applied to fabricate antifouling surfaces. In the first study, we reported the synthesis and characterization of neat TiO2 and Ag-TiO2 composite nanofilms prepared on silicon wafer by sol-gel method. The synthesized Ag-TiO2 thin films showed enhanced bactericidal activities compared to the neat TiO2 nanofilm both in the dark and under UV illumination. The advantage of Ag-TiO2 nano-composites is to expand the nanomaterial’s antibacterial function to a broader range of working conditions. In the second study, we reported the synthesis, characterization and environmental application of nitrogen doped TiO2 photocatalyst in the form of powder and film. TiO2 photocatalysts were synthesized by hydrolysis of titanium tetra-isopropoxide in the presence of urea as nitrogen source. The visible light induced photocatalytic inactivation of bacteria (Escherichia coli) with the obtained nano-powders and nano-films was tested. In the following study, we reported the successful formation of a titanium dioxide (TiO2) layer on butyl rubber (BR) substrate, cotton sheet and silicon wafer surfaces by using modified liquid phase deposition (LPD) method at mild environmental conditions. Various synthetic conditions were studied to control the morphology and nanostructures of the deposited TiO2 coatings. Superoleophobic TiO2 coatings were prepared after surface fluorination. The formed TiO2 coatings showed excellent antibacterial adhesion ability. Superoleophobic surfaces, which are thought to limit bacterial contamination, were fabricated by an easy spray method. The surface of any polymers can be made superoleophobic using the following simple three-step process: (1) the spraying of polymer-nanoparticle mixtures; (2) cross-linking the coating to the substrate; and (3) chemical modification of the outer surface by perfluorosilane. Superoleophobicity is achieved by the combination of re-entrant and convex morphology of multiscale agglomerates produced by nano-particles embedded in polymer matrix and surface fluorination. Preparation parameters were optimized. Surface characterizations were extensively studied on the surface morphology, roughness and chemical compositions of the composite coatings with different nanofillers loading. The superoleophobic coatings presented excellent resistance to non-specific protein adsorption and show antibacterial adhesion. It is a promising material for biomedical and industrial applications

Ru-Sn oxide/C supported Pt anode catalysts for direct ethanol fuel cells

Direct alcohol fuel cells are promising power sources. Ethanol has recently attracted much attention since it is renewable, relatively safe and has a high energy density. In order to make best use of ethanol in fuel cells, many Pt-based catalysts have been studied. However, the low electrochemical activity of ethanol at the low potentials required for fuel cells has limited the development of direct ethanol fuel cells. This thesis describes the use of carbon black modified with Ru-Sn mixed oxides as supports for Pt nanoparticles. Since the Pt nanoparticles are on the surface of the Ru-Sn oxide, the promoting effect of Ru-Sn oxide is achieved, while the blockage of Pt active sites is minimized. Therefore, the high carbon dioxide selectivity of Pt can be retained and the performance at low potentials can be improved. The effects of reaction conditions, including Ru:Sn:C ratios, Pt loading, and heat treatment, have been investigated. Cyclic voltammetry allows rapid determination of the electrochemical performance of catalysts for preliminary screening. Product distribution results from an ethanol electrolysis cell provide the faradaic efficiency and mechanistic information. The best Pt-RuSnO₂/C catalyst showed better catalytic activity towards ethanol oxidation at low potentials than that of commercial Pt/C catalyst and retained relatively high faradaic efficiency

Leveraging TLA+ Specifications to Improve the Reliability of the ZooKeeper Coordination Service

ZooKeeper is a coordination service, widely used as a backbone of various distributed systems. Though its reliability is of critical importance, testing is insufficient for an industrial-strength system of the size and complexity of ZooKeeper, and deep bugs can still be found. To this end, we resort to formal TLA+ specifications to further improve the reliability of ZooKeeper. Our primary objective is usability and automation, rather than full verification. We incrementally develop three levels of specifications for ZooKeeper. We first obtain the protocol specification, which unambiguously specifies the Zab protocol behind ZooKeeper. We then proceed to a finer grain and obtain the system specification, which serves as the super-doc for system development. In order to further leverage the model-level specification to improve the reliability of the code-level implementation, we develop the test specification, which guides the explorative testing of the ZooKeeper implementation. The formal specifications help eliminate the ambiguities in the protocol design and provide comprehensive system documentation. They also help find critical deep bugs in system implementation, which are beyond the reach of state-of-the-art testing techniques. Our specifications have been merged into the official Apache ZooKeeper project

Estudo linguístico de palavras de origem chinesa no português

Neste trabalho, pretende-se estudar a presença, no universo da língua portuguesa, de palavras de origem chinesa. O enquadramento teórico partirá de uma panorâmica sobre o desenvolvimento e expansão da língua portuguesa e contemplará as condições históricas da incorporação de palavras de origem chinesa no português. A parte prática do estudo partirá de um levantamento sobre corpora online de usos e frequência destas palavras na língua. O estudo contempla aspetos léxico-semânticos e morfológicos.In this work, we intend to study the presence, in the universe of the Portuguese language, of words of Chinese origin. The theoretical framework will start from an overview of the development and expansion of the Portuguese language and will contemplate the historical conditions of the incorporation of words of Chinese origin in Portuguese. The practical part of the study will be based on a survey on online corpora of uses and frequency of these words in the language. The study includes lexical-semantic and morphological aspects.Mestrado em Português Língua Estrangeira/Língua Segund