Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Linear tuning the frequency of an erbium-doped fiber ring laser using both a Fabry-Perot filter and an electro-optic tunable filter has been experimentally demonstrated. The rate of frequency change is determined by monitoring the fringes produced by laser light transmitted through a fiber Fabry-Perot interferometer. The fiber ring laser has been tuned over a 50 nm spectral range when using the Fabry-Perot filter and a tuning rate of 16480 nm/s has been achieved. The spectral width of the laser is 0.049 nm and the nearest sidelobe to the main peak is more than 30 dB below the central lobe. When the electro-optic tunable filter is used, a spectral range of 11 nm is reached. The spectral width is 2.33 nm and is in close agreement with the filter theoretical results. The sidelobe to main peak difference is around 13 dB.

Synthesis of novel amphiphilic copolymers based on sugar moieties: development of new architectures and biomedical applications As early as in the 50’s, amphiphilic copolymers started to attract much interest in the frame of polymer science thanks to their self-assemblies as organized nano-structures in a selective solvent. The resulting micelles or vesicles have emerged as potentially useful materials in the biomedical field such as drug delivery systems when matching the specific conditions of size, coating nature and functionalization,… Moreover, active cell-targeting increases the therapeutic effect by selectively delivering the drug to the required cells. Accordingly, carbohydrates have drawn much attention due to the cell recognition processes they can mediate. Carbohydrates are thus incorporated in polymer backbones to mimic the naturally occurring substrate for the adapted cell receptors. The originality of this thesis is based on the use of sugar moieties as potential multi-hydroxylated initiators for the polymerization of various lactones. This leads to well-defined amphiphilic polymer architectures along with the development of a more facile route for the incorporation of carbohydrates in polymer chains to promote active cell-targeting of the as-obtained nano-structures. The first part of the thesis aims at describing the synthesis of novel amphiphilic brush-like polymers via two pathways. A first approach relies upon the synthesis of polyester arms initiated from the alcohol groups of pending sugars distributed along a preformed hydrophilic polymethacrylate backbone obtained by controlled radical polymerization (via ATRP). Various metal-based and organic catalysts/activators have been studied to lead to the desired architectures using this “grafting from” technique. In another synthetic strategy, the lactone polymerization using a carbohydrate initiator has been carried out, followed by end-chain derivatization reactions yielding brush-like copolymers via a “grafting through” technique. Slight modifications of the end-chain functionalities have also afforded the possibility to synthesize amphiphilic mikto-arm copolymers which self-assemble in aqueous medium in micelles characterized by interesting size features affording promising applications as new drug delivery systems. On the other hand this thesis also focuses on the use of carbohydrate moieties in amphiphilic diblock copolymers such as poly(ε-caprolactone)-b-poly(methacrylate-graft-poly(ethylene oxide)-co-6-O-methacryloyl-D-galactopyranose) or poly(ε-caprolactone)-b-poly(methacrylate-graft-poly(ethylene oxide)-co-1-O-methacryloyl-D-mannofuranose), using the combination of lactone ring-opening polymerization with ATRP of the respective functionalized comonomers, followed by selective post-polymerization sugar deprotection. Next to these copolymers based on polylactones and polymethacrylates, fully degradable amphiphilic block copolymers composed of a polycarbonate backbone have been originally designed. To that end, a multi-step procedure involving the synthesis of sugar-substituted cyclic carbonates, block copolymerization reactions and ultimate selective sugar deprotection, has been investigated. The self-organization of the resulting copolymers, e.g., poly(trimethylene carbonate)-b-poly(3-O-(5’-methyl,5’-carboxy-1’,3’-dioxan-2’-one)-D-glucopyranose), has been studied in aqueous medium. Interestingly, the so-formed polymeric micelles proved to display remarkable living cell-targeting properties. Fabian Suriano

The aim of this research was to prepare high performance and fully biodegradable polymer nanocomposites. The most representative polymers classified as biodegradable are poly(!-caprolactone) (PCL) (issued from petrochemistry) and polylactide (PLA) (issued from renewable bio-resources). Biodegradable nanoparticles purposely extracted from biomass were selected, namely Cellulose NanoWhiskers (CNW) and Starch NanoCrystals (SNC). CNW are rod-like nanoparticles with 2 nanometric dimensions while SNC consists in nanosheets, thus with 1 nanometric dimension. A 3 nanometric-dimension particle often considered as “silica- type nanocage” was selected to complete this study, namely Polyhedral Oligomeric Silsesquioxane (POSS). The addition of such nanoparticles was expected to enhance several properties of the filled polymer matrix, especially thermo-mechanical performances and extent of crystallinity. In this field, the quality of the nanoparticle dispersion throughout the matrix is an essential parameter to produce nanocomposite materials with largely improved properties. One of the most cited techniques to overcome nanofiller aggregation and even agglomeration relies upon the creation of strong chemical bonds between the nanoparticle and the polymer matrix, leading to the preparation of so-called nanohybrids. For that purpose, the surface of the nanoparticles was first modified by chemical grafting and polymerization reactions. The ring-opening polymerization (ROP) of e-caprolactone and L,L-lactide catalyzed by tin(II) 2- ethylhexanoate (tin octoate, Sn(Oct)2) was initiated from functional groups available on the nanoparticle surface. The grafting efficiency was demonstrated for the three investigated nanofiller/polyester systems. Different characterization techniques were approached depending on the nanofiller nature. In a second step, the so-formed nanohybrids were used as “masterbatches” and dispersed in their corresponding commercial polyester matrices, i.e. PCL and PLA, by melt-compounding using a mini-lab twin screw extruder. The nanocomposite materials were fully characterized, correlating morphological observations with thermal, mechanical and rheological properties. To highlight the beneficial effect of the surface covalent grafting, simple melt-blends, i.e., containing unmodified nanofillers and polyester matrices (PCL or PLA) were prepared. The level of property improvement was most of the time directly related to the degree of nanofiller dispersion, and proved systematically better in case of masterbatch-based materials. Keeping in mind the effect of the nanoparticle geometry, as well as its mechanical modulus, crystallinity or extent of dispersion within the polyester matrix, the rod-like 2D-nanofiller, namely cellulose nanowhiskers extracted from ramie, appeared as the most efficient candidate for polyester reinforcement. The incorporation of PCL chains surface-grafted onto CNW contributed to substantially increasing the overall thermo- mechanical properties, most likely due to the formation of a strong physical chain network between surface- grafted chains and chains composing the matrix. Additionally, CNW-based nanohybrids revealed their potential as both nucleating sites dramatically increasing the crystallization rate of PLA matrix and compatibilizing PCL/PLA immiscible blends.

Since oil-in-water emulsions combine good cooling and lubricating capabilities, they have been commonly used in cold rolling nowadays. In order to understand the tribology characteristics of the emulsion during the cold rolling process, the effects of load, sliding speed, material of specimen, surface roughness and type of emulsion on the tribology characteristics of cold rolling are investigated by using the multi-purpose friction and wear tester.The P (load) ¡VV (sliding speed) curve was investigated under the conditions of load (below 2.4GPa), sliding speed (below 2.2m/s) at lower specimen roughness. Results show that QK-N36 emulsion can differentiate between boundary lubrication regime and initial seizure according to their friction coefficient, but RL-61 emulsion cannot differentiate them. Therefore, the load carrying capacity of RL-61 emulsion is better than that of QK-N36 emulsion, and its friction coefficient is also lower than that of QK-N36 emulsion. However, this tendency of experimental results is different from the cold-rolling practice.Under the lower load and higher surface roughness conditions with different hardness of specimen, the friction coefficient of RL-61 emulsion is higher than that of QK-N36 emulsion. This tendency of experimental results is the same as the rolling practice. Under the lower load condition with SDK-11 specimen, the friction coefficient of RL-61 emulsion varies gradually in the range of 0.07 ~ 0.09 located in the boundary lubrication regime, but the friction coefficient of QK-N36 emulsion reduces to 0.02~0.04 located in the mixed lubrication regime.

In this thesis we describe a coupled model of Earth's magnetosphere that consists of the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamics (MHD) simulation, the MIX ionosphere solver and the Rice Convection Model (RCM). We report some results of the coupled model using idealized inputs and model parameters. The algorithmic and physical components of the model are described, including the transfer of magnetic field information and plasma boundary conditions to the RCM and the return of ring current plasma properties to the LFM. Crucial aspects of the coupling include the restriction of RCM to regions where field-line averaged plasma-beta <=1, the use of a plasmasphere model, and the MIX ionosphere model. Compared to stand-alone MHD, the coupled model produces a substantial increase in ring current pressure and reduction of the magnetic field near the Earth. In the ionosphere, stronger region-1 and region-2 Birkeland currents are seen in the coupled model but with no significant change in the cross polar cap potential drop, while the region-2 currents shielded the low-latitude convection potential. In addition, oscillations in the magnetic field are produced at geosynchronous orbit with the coupled code. The diagnostics of entropy and mass content indicate that these oscillations are associated with low-entropy flow channels moving in from the tail and may be related to bursty bulk flows and bubbles seen in observations. As with most complex numerical models, there is the ongoing challenge of untangling numerical artifacts and physics, and we find that while there is still much room for improvement, the results presented here are encouraging. Finally, we introduce several new methods for magnetospheric visualization and analysis, including a fluid-spatial volume for RCM and a field-aligned analysis mesh for the LFM. The latter allows us to construct novel visualizations of flux tubes, drift surfaces, topological boundaries, and bursty-bulk flows.

Integrated ring resonators have attracted a considerable interest in optical communications because of their small size and wide range of applicability. Here we consider several aspects of these devices, beginning with a tunable hybrid ring resonators consisting of a silicon over insulator (SOI) ring covered with a polymer layer in a variable electric field. Varying the field changes the polymer refractive index and consequently the resonance condition of the cavity. This device offers a large degree of optical confinement together with a high modulation speed. Subsequently, we design and present fabrication results for a Wavelength Division Multiplexing (WDM) multiplexer/demultiplexer formed from a series of ring resonators with two channels separated by 50 GHz each that is predicted to exhibit a free spectral range (FSR) of 100 GHz , signal dispersion less than 30 ps/nm and a signal cross-talk less than -23 dB. Finally, we analyze the application of the coupled ring waveguide circuit to rotation sensors based on the Sagnac phase shift. Here, however our analysis indicates that a single ring, of the same area exhibits a higher degree of sensitivity to rotational motion than a multiple ring circuit.

Syftet med denna uppsats är att utforska hur resocialiserings- och uppfostrans-ideal av sinnesslöa fungerade vid Västmanlands sinnesslöanstalt å Sofielund. Studien är en fallstudie med individfokus, som följer 18 intagna skolhemsele-ver vid sinnesslöanstalten i Sofielund. Det material som har använts är bland annat intagningslistor, journaler och personliga akter för de 18 undersöknings-personerna, som finns tillgängliga hos Landstingsarkivet Västmanland. Av denna undersökning framkommer bland annat att de 18 undersökningsperso-nerna kom från relativt normala familjer och hemförhållanden, som i de flesta fallen tillhörde arbetarklassen. Samtliga undersökningspersoner ansågs vara bildbara vid intagningen till Sofielund och den största delen av dem ansågs före intagningen lida av lättare sinnesslöhet (idioti). Dessutom ansågs inte någon av dem vara farlig för sin omgivning. Skolpersonalens beskrivningar stödjer inte heller uppfattningen om att de skulle ha ansetts vara farliga. Om de 18 undersökningspersonerna framkommer att de i vissa fall inte ansågs vara bildbara av skolledningen, tidigare utlåtanden till trots. Följaktligen visar resultatet på att en stor del av undersökningspersonerna blev hemskickade efter utskrivning från skolhemmet, möjligen för att de ansågs vara bildbara och därmed inte var lämpliga i skolhemmet. Denna studies resultat pekar också på att uppföljningen av undersökningspersonerna var relativt systema-tisk. En sammanfattande slutsats i denna studie är också att det inte var ovanligt att undersökningspersonerna skickades hem, trots att de flesta gjorde ganska små framsteg i skolan.