Kuwait is undergoing rapid economic growth involving substantial developments along its coastal shores and the marine environment. Many of the activities in the region are associated with oil industry, which can pollute the shores leading to contamination from oil residues, tar balls and trace metals. About 2 million barrels of oil are spilled annually from routine discharges into the Gulf, which derives mainly from dirty ballast waters and tank washing. The comprehensive literature review of hazardous substances in Kuwait’s marine environment has concluded that for the majority of these pollutants, contamination is localized around industrialised areas, and elsewhere is generally below the permitted international standards. These finding have been supported by a fieldwork. This has been conducted to assess the use of biomarkers (bile metabolites and EROD activities) for 60 fish consisting of two native species Giant sea catfish (Arius thalassinus) and (Pelates quadrilineatus) to demonstrate the potential for the concentrations of oil based contaminants present to induce detectable levels of biological effects in fish species living in Kuwait’s marine environment. Therefore, the focus of this research has shifted its attention to another anthropogenic source that chronically pollute Kuwait’s marine environment. One of the main sources of contaminants is the continuous discharge of sewage, which impacts many locations around Kuwait. Sewage is known to contain wide array of substances that could pose an ecotoxicological impact at different levels of the ecosystem. One such threat is posed by antimicrobial agents that contribute to the growing global concern surrounding the prevalence of antimicrobial resistant (AMR) bacteria. Therefore, a major theme of this research project was to conduct a novel survey of the prevalence of AMR bacteria isolated from Kuwait’s marine environment. The AMR screening, including 598 E.coli isolated from seawater and bivalves samples during summer and winter seasons against 23 frontline antibiotics, revealed that resistance was observed from a number of locations (particularly associated with sewage outlets) for the majority of antibiotics (seawater: summer 89 - 64%; winter 90 - 57% and bivalves: summer 77%; winter 88%). A baseline screening for the class 1 integron which is known to be implicated in disseminating the antimicrobial resistance among bacteria was conducted for the isolated 598 E.coli. The findings highlighted the prevalence of such molecular genetic elements especially around the sewage outlets (36% of tested E.coli). The whole genome sequencing was conducted for a representative E.coli (26 E.coli) and it showed that E.coli derived from Kuwait’s marine environment possessed a variety of genes implicated in antimicrobial resistance potential against wide spectrum of antibiotics and suggesting that genes are exchanged via the horizontal gene transfer. These observations and recording of antimicrobial resistance phenomenon support the notion that marine environment could act not only as a reservoir for antimicrobial resistance but could also play a significant role in driving it. The AMR bacteria is considered as an effective tool for monitoring the impacts of sewage pollution. Furthermore, it highlights one of the key human health risks sewage pollution poses and its assessments allows a fully integrated health assessment of Kuwait’s marine environment to be undertaken. This will ultimately lead to recommendations outlining the future monitoring and remediation requirements required by Kuwait to tackle this issue including rational antibiotics consumption and stewardship; developing effective wastewater treatment processes to improve removal efficiency of these pollutants in sewage treatment plants; more researches on this area will provide scientific information for responsible authorities to make up regulatory standards and guidelines to control environmental dissemination of these emerging contaminants.

Reproduction de : Thèse de doctorat : Linguistique et Sémiologie de l'arabe : Lyon 2 : 2003. Reproduction de : Thèse de doctorat : Langue et Lettres arabes : Tunis 1 : 2003. / Thèse soutenue en co-tutelle. Thèse rédigée en arabe, le vol. 2 est un résumé en français. Titre provenant de l'écran-titre. Bibliogr. 221 réf.

I present a detailed study of the magnetic propertie of electron-beam evaporated Pdo.4Nio.6 alloy thin films by means of ferromagnetic resonance measurements on extended films of varying thickness and anisotropic magnetoresistance measurements lithographically patterned high aspect-ratio ferromagnetic electrodes, respectively. The results reveal that the direction of the magnetization with respect to the film plane strongly depends on the electrode lateral dimensions, transitioning from in-plane magnetization for extended films to out of the plane magnetization for electrode width below 2-3 microns, reaching ~58 degrees for electrode widths of about 100nm (nanowires). This behavior arises from a competition between the film demagnetizing vector, which leads to in-plane magnetization for extended films , and an intrinsic uniaxial anisotropy, which overcomes the magnetostatic energy for laterally constrained films, pulling the magnetization off plane.

Ongoing antibiotic drug discovery is vital as antimicrobial resistance continues to be a significant issue faced in the clinic. Natural products have long been a highly productive source to mine for new antimicrobials. While it has been challenging to discover new and unique antimicrobial natural products, numerous drugs have been derived from studying how natural products function as secondary metabolites. Previous studies suggested that screening natural product extract fraction libraries for antimicrobials can be more productive than screening crude extracts alone. These studies from large industrial enterprises are generally not directly portable to an academic setting due to significant infrastructure costs. We developed a screening platform consisting of low pressure reversed-phase chromatographic separation of methanolic extracts of bacteria and fungi to generate a prefractionated natural product library. This platform is suitable for academic labs to screen for antimicrobial compounds. A large growth inhibitor screen against multiple pathogens and lab strains of microbes was conducted to assess the validity of the advantages of screening fraction libraries versus crude extract libraries and to search for potential new drug-like compounds. Hits were investigated for reproducibility, isolated, and purified. One compound was discovered in an antifungal screen which may be a novel lipopeptide. / Thesis / Master of Science (MSc) / To combat the growing antibiotic resistance crisis, new strategies for drug discovery must be investigated and implemented. Natural products from bacteria and fungi have long been a source of critically important drugs. Prior research suggests that looking for vital natural products in fraction libraries can be more productive than screening crude extracts. Here the development and assessment of a fractionation library suitable for an academic lab's ingrained limitations are described. Assessing the library indicates an increased hit rate on screening fractions compared to crude extract. Furthermore, pursuing these hits may have revealed a novel antifungal lipopeptide.

I denna uppsats presenteras resultatet av ett examensarbete i maskinkonstruktion på KTH. Arbetet har utförts på uppdrag av Poki Robotics via konsultbolaget Omecon.Poki Robotics vill automatisera uppsamlingen av golfbollar på så kallade driving ranges, genom att nyttja en hjuldriven autonom robot med ett tillhörande uppsamlingssläp. Enligt Poki Robotics samlas 5000 golfbollar upp under en intensiv dag, vilket innebär att en total massa av ca 230 kg måste uppsamlas och förflyttas. Detta ställer höga krav på dragkraften som drivlinan måste förse roboten med.Rapporten beskriver konceptframtagningen av drivlinan till den hjuldrivna autonoma roboten. Konceptet genererades genom att först utvärdera framdrivning inom robotik i en förstudie. Olika styrsystem utvärderades utifrån ställda krav på mjukvarubaserad styrning, mekanisk komplexitet, effektivitet och mobilitet. Styrsystemen utvärderades i en Pugh-matris som mynnade ut i två styrningar som visades mest lovande. Styrningarna utvärderades med en terrängmekanisk beräkningsmodell för att utvärdera framdrivande egenskaper, och därmed bedöma vilken som var mest lämpad för syftet utifrån ställda krav.För den lämpade styrningen genererades och utvärderades koncept för drivlinan med avseende på underhåll, montage, tillverkning, robusthet och förmåga att uppta laster. Det slutgiltiga konceptet bestod av en borstlös likströmsmotor, försedd med ett planetväxelhuvud och en parallell hjulaxel med en kuggremsutväxling.Konceptframtagningen resulterade i en CAD-modell som visade att drivlinan uppfyllde dimensionella krav.Den terrängmekaniska beräkningsmodellen nyttjades enbart som ett verktyg för att ge en indikation på prestanda och som indata för konstruktionen. Beräkningsmodellen har begränsningar i form av att den inte är lämpad för små hjuldiametrar, att den inte tar hänsyn till rotförstärkt mark samt att den utesluter de pneumatiska däckens elastiska egenskaper. / This thesis presents the result of a master thesis in machine design at KTH. The task was performed for Poki Robotics via the consulting firm Omecon.Poki Robotics wants to generate an autonomous solution for the collecting of golf balls on driving ranges, by utilizing a wheeled autonomous mobile robot coupled with a towed collecting unit. According to Poki Robotics, 5000 golf balls are collected on a busy day, yielding a total mass of approximately 230 kg that must be collected and towed. This sets high demands on the towing force that needs to be provided by the powertrain.The report describes the concept generation of the powertrain for a wheeled autonomous robot. A prestudy was done to evaluate wheeled locomotion in mobile robotics. Different steering systems were evaluated by different metrics including mechanical complexity, efficiency, mobility and demand for software-based control. The steering systems were evaluated using Pugh matrices, yielding two steering systems that showed to be promising. A terramechanical analytical model was used to further evaluate tractive performance of the two steering systems, to conclude which steering system was most suitable for the purpose with respect to the set requirements.Concepts were generated and evaluated for the powertrain of the chosen steering system, with respect to maintenance, assembly, manufacturing, robustness and load carrying capacity. The final concept yielded an EC-motor with a planetary gearhead, with a parallel wheel shaft and a timing belt gearing.The concept generation resulted in a CAD-model showing that the powertrain met the targeted dimensional constraints.The terramechanical analytical modelling was used solely as a tool for indication of performance and as input data for design. The model has limitations due to it not being suitable for small wheel diameters, not taking root reinforcement of the soil into account and excluding the pneumatic tire’s elastic properties.

The present rapid increase in the number of space missions demands a decrease in the cost of satellite equipment, but also requires the development of instruments that have low power consumption, low weight, and small size.Anisotropic magnetoresistance (AMR) sensors can answer these needs on account of their small size, weight, and power consumption. AMR sensors also produce lower noise than either giant magnetoresistance (GMR) or tunnel magnetoresistance (TMR) devices and are thus more suitable for space applications.The type of AMR sensor developed in this study was a Planar Hall EffectBridge (PHEB) sensor. The FM layer was also coupled with an AFM layer in order to fix the internal magnetization of the FM layer.One technique that was employed in order to meet the low-noise requirement was to make the FM layer thicker than has previously been attempted.In doing so, the exchange bias field between the AFM layer and the FMlayer is no longer high enough to bias the thicker FM layer, so in order to correct this unwanted effect, the material stack was upgraded to two AFM–FM interfaces. With this configuration, it became possible to increase the exchange field by up to 60%. Stronger exchange bias leads to a thicker FMlayer and so to lower noise in the device performance. Another strategy that was used to lower the resistance of the device was to implement an NiFeX alloy instead of the standard NiFe. NiFeX consists of an alloy of NiFe andCu, Ag, or Au; the last of these is known to have very low resistivity.This solution leads to a significant lowering of the device’s resistance. A recent technological advance used to fabricate devices with lower resistance is to deposit a multilayer of AFM–FM.

Coherent injection, detection and manipulation of spins in semiconductor nansotructures can herald a new genre of information processing devices that are extremely energy-efficient and non-volatile. For them to work reliably, spin coherence must be maintained across the device by suppressing spin relaxation. Suppression can be accomplished by structural engineering, such as by confining spin carriers to the lowest subband in a semiconductor quantum wire. Accordingly, we have fabricated 50-nm diameter InSb nanowire spin valves capped with Co and Ni nanocontacts in which a single conduction subband is occupied by electrons at room temperature. This extreme quantum confinement has led to a 10-fold increase in the spin relaxation time due to dramatic suppression of the D’yakonov -Perel’ (DP) spin relaxation mechanism. We have observed the spin-valve and Hanle effects at room temperature in these systems. Observing both effects allowed us to estimate the carrier mobility and the spin relaxation length/time and we found that the latter is ~10 times larger than the value reported in bulk InSb despite a four orders of magnitude decrease in the carrier mobility due to surface roughness scattering. We ascribe this dramatic increase in spin relaxation time to the suppression of the DP relaxation mode due to single subband occupancy. Modulation of spin relaxation rate by an external agent can open new possibilities for spintronic devices. Any agent that can excite electrons from the lowest subband to higher subbands will dramatically increase the DP spin relaxation rate. We have shown that the spin relaxation rate in InSb nanowires can be modulated with infrared light. In the dark, almost all the electrons in the nanowires are in the lowest conduction subband, resulting in near-complete absence of DP relaxation and long spin coherence length. This results in a high resistance state in a spin valve whose ferromagnetic contacts have anti-parallel spin polarizations. Under infrared illumination, higher subbands get populated and the DP spin relaxation mechanism is revived, leading to a three-fold decrease in the spin relaxation length. As a result, injected spins flip in the spacer layer of the spin valve and this causes the spin valve resistance to drop. Therefore, this effect can be exploited to implement an infrared detector. We also studied the transport behavior of a single nanowire (~50 nm diameter) captured between two non-magnetic contact pads. The wire was attached between the pads using dielectrophoresis. A giant (∼10,000,000%) negative magnetoresistance at 39 mT field was observed at room temperature in Cu nanowires contacted with Au contact pads. In these nanowires, potential barriers form at the two Cu/Au interfaces because of Cu oxidation that results in an ultrathin copper oxide layer forming between Cu and Au. Current flows when electrons tunnel through, and/or thermionically emit over these barriers. A magnetic field applied transverse to the direction of current flow along the wire deflects electrons toward one edge of the wire because of the Lorentz force, causing electron accumulation at that edge and depletion at the other. This makes the potential barrier at the accumulated edge shorter and at the depleted edge taller. The modulation of the potential barrier height with a magnetic field dramatically alters the tunneling and/or thermionic emission rate causing a giant magnetoresistance. Currently, effort is underway to demonstrate strain sensitive anisotropic magnetoresistance (AMR) in a single Co-Cu-Co nanowire spin valve. AMR is caused by spin-orbit coupling effects which makes the resistance of a ferromagnet depend on the angle between the direction of current flow and the magnetization. The resistance maximizes when the angle is 00 or 1800 and minimizes when the angle is 900. When an external magnetic field is applied in a direction opposite to a ferromagnet’s magnetization, the latter begins to rotate in the direction of the field and hence its resistance continuously changes. This results in a trough in the magnetoresistance of a spin valve structure between the two fields when the magnetization starts to rotate and when the magnetization completes the rotation. We have observed a magnetoresistance peak (instead of trough) in the Co-Cu-Co spin valve, which is due to the normal spin valve effect that overshadows AMR. However, when an intense infrared light source is brought close to the sample, the peak gets overshadowed by a trough, showing that the AMR effect becomes dominant. We attribute this intriguing feature to the fact that the AMR effect is strongly influenced by strain. Heating by the light source generates strain in the Co contacts owing to unequal thermal expansion of Co and the underlying substrate. We also observed that the AMR effect becomes more pronounced as the light source is brought closer to the sample, resulting in increased heating and hence increased strain generation.

An alternative cycle proposed for refrigeration and gas liquefaction is active magnetic regenerator (AMR) refrigeration. This technology relies on solid materials exhibiting the magnetocaloric effect, a nearly reversible temperature change induced by a magnetic field change. AMR refrigeration devices have the potential to be more efficient than those using conventional refrigeration techniques but, for this to be realized, optimum materials, regenerator design, and cycle parameters must be determined. This work focuses on the development and validation of a transient one-dimensional finite element model of an AMR test apparatus. The results of the model are validated by comparison to room temperature experiments for varying hot heat sink temperature, system pressure, and applied heat load. To demonstrate its applicability, the model is then used to predict the performance of AMRs in situations that are either time-consuming to test experimentally or not physically possible with the current test apparatus.

In the past decade, active magnetic regenerative (AMR) refrigeration technology has progressed towards commercial application. The number of prototype systems and test apparatuses has steadily increased thanks to the worldwide research efforts. Due to the extensive variety of possible implementations of AMR, design methods are not well established. This thesis proposes a framework for approaching AMR device design. The University of Victoria now has three functional AMR Refrigerators. The newest system constructed in 2012 operates near-room-temperature and is intended primarily as a modular test apparatus with a broad range of control parameters and operating conditions. The design objectives, considerations and analysis are presented. Extensive data has been collected using the machines at the University of Victoria. Performance metrics are used to compare the devices. A semi-analytical relationship is developed that can be used as an effective modelling tool during the design process. / Graduate / 0548

An alternative cycle proposed for refrigeration and gas liquefaction is active magnetic regenerator (AMR) refrigeration. This technology relies on solid materials exhibiting the magnetocaloric effect, a nearly reversible temperature change induced by a magnetic field change. AMR refrigeration devices have the potential to be more efficient than those using conventional refrigeration techniques but, for this to be realized, optimum materials, regenerator design, and cycle parameters must be determined. This work focuses on the development and validation of a transient one-dimensional finite element model of an AMR test apparatus. The results of the model are validated by comparison to room temperature experiments for varying hot heat sink temperature, system pressure, and applied heat load. To demonstrate its applicability, the model is then used to predict the performance of AMRs in situations that are either time-consuming to test experimentally or not physically possible with the current test apparatus.