Reproduction de : Thèse de doctorat : Chimie et physico-chimie des polymères : Le Mans : 2008. / Titre provenant de l'écran-titre.

A waterflood has been used as a secondary recovery process to maintain the reservoir pressure and displace the oil towards the producer. However, the existence of high-permeability zones (thief zones) can cause early water breakthrough and excessive water production, thus, leaving a significant amount of oil bypassed in heterogeneous reservoirs. In this work, thermally active (Bright Water®) and pH-sensitive polymers have been proposed as an in-depth conformance tool with detailed simulation studies. Thermally active polymers are triggered by temperature change, whereas pH-sensitive polymers are triggered by pH change. Upon activation, polymers provide high resistance to subsequent fluid flow and divert the flow into adjacent unswept zones. As a result, this leads to improved sweep efficiency, low oil-water-ratio, and incremental oil recovery. The modeling of a pH-sensitive polymer was based on the principles of the microgel modeling procedure developed by Huh et al. (2005). In addition, a modified model was developed to calculate equilibrium swelling ratio explicitly in terms of pH and ionic strength of solution instead of using a root-finding algorithm. Thermal active polymers were modeled in terms of gelation reaction, gel viscosity, gel adsorption, and permeability reduction factor. Thermally active and pH-sensitive polymers were coupled with UTGEL reservoir simulator in an attempt to assess applicability of these gels as a conformance tool. Sensitivity analysis studies were conducted through 3D synthetic models to investigate technical feasibility of thermally active and pH-sensitive polymers as an in-depth conformance tool. Results indicated that incremental oil recovery and conformance control depend on the polymer concentration, slug size, permeability contrast between matrix and thief zone, vertical to horizontal permeability ratio (kv/kh), treatment location, oil-to-water viscosity ratio, and adsorption level, among others. It is concluded in this study that the permeability contrast between matrix and thief zones appears to be one of the most important parameters that impacts treatment performance. Therefore, a high permeability contrast is a prerequisite to achieve technically and economically successful treatment. / text

Management of clubroot caused by the soil-borne biotrophic plant protist Plasmodiophora brassicae on canola and other Brassica crops is an important challenge to producers. Studies on the interaction of pH and temperature on root hair infection (RHI) and clubroot symptom development in canola roots revealed that high levels of clubroot can occur under optimum temperature, moisture and spore load, even at alkaline pH of 7.5. Clubroot was suppressed at all temperatures at pH 8.0, but not totally eliminated. The occurrence of maximum levels of root hair infection and clubroot development (RHI = 61%, Clubroot incidence (CI) & Disease severity index (DSI) = 100%) at temperatures of 20° and 25°C and pH of 5.0 to 6.5 was confirmed. The efficacy of biofungicides against P. brassicae was influenced by pathogen load, host, growth media and its properties. Drench application of Serenade and Prestop were moderately effective in reducing clubroot levels in canola (Brassica napus L. and B. rapa L.) and to a lesser extent in Shanghai pak choy (B. rapa L. ssp. Chinensis (Rupr.) var. communis Tsen and Lee). The mean clubroot incidence and severity caused by Pathotype 3 was found to be slightly higher than that of Pathotype 6. Clubroot level increased with increase in soil bulk density.

My MSc project aims at developing pH-responsive molecular tweezers for drug delivery applications. The project began with the synthesis of our 2nd generation tweezer, whose main objective was to improve our previous model, 1st generation tweezer, which contained a pH-responsive triad spacer and two naphthalene walls known to interact with hydrophobic drugs such as Mitoxantrone®. The naphthalene interaction sites were successfully modified to contain oligoethylene glycol chains to improve their water-solubility, in anticipation for more accurate measurements of pKa and binding constants in aqueous media. However, all attempts to convert such naphthalene derivatives into their corresponding boronic acid or ester through standard protocols (halogen-lithium exchange, palladium catalyzed borylation) failed. Without the required boronic acid/ester, the final Suzuki-Miyaura coupling with the di-bromo triad spacer was not achieved. Synthesis of the 3rd generation tweezer, which was modified to contain theophylline as the new interaction sites, was then attempted. The half-tweezer was successfully synthesized via copper (II) catalyzed coupling of theophylline with the 5-bromo-4-methoxyphenyl boronic acid. However, all attempts to convert it into the required boronic acid/ ester for the final Suzuki- Miyaura coupling reaction with 2,6-dibromopyridine failed. We then focused our attention on the conversion of the triad spacer into its corresponding diboronic acid. The synthesis of the triad diboronic acid was a success, however, the final copper (II) catalyzed reaction with theophylline to form the tweezer only yielded the mono-coupled product. Lastly, our 4th generation tweezer was engineered to avoid the synthetic difficulties encountered in the boronic acid/ ester synthesis stage. Using the commercially available 5-formyl-2-methoxyphenylboronic acid and o-phenylenediamine, we successfully synthesized a benzimidazole-derived “half tweezer” through ring condensation reaction. Alkylation of this half-tweezer was also successfully achieved, although purification of the alkylated product was not optimized. Using this crude product, we carried out the final tweezer reaction via Suzuki- Miyaura coupling with 2,6-dibromopyridine under microwave irradiation. 1H NMR results show formation of new species that is believed to be the 4th generation tweezer (although the presence of impurities made integration of the signals unreliable). Much work is needed in the purification of the alkylated half tweezer boronic acid in order to avoid complicated mixtures in the final tweezer reaction. / Thesis (Master, Chemistry) -- Queen's University, 2011-10-06 00:29:04.248

No description available.

No description available.

In the overlay Cognitive Radio (CR) networks, the low priority Secondary Users (SUs) must constantly monitor the occupied spectrum to detect the possible appearances of the high priority Primary Users (PUs) within the same spectrum portion. On detection, the SUs must vacate the occupied spectrum portion without interfering with the PUs beyond a certain threshold duration and must opportunistically access another idle spectrum portion to guarantee their seamless communication. This mechanism is known as the spectrum handoff process. In this thesis, we first introduce a novel approach to model the CR channel which is capable of capturing a more realistic behavior of the spectrum occupancy by both user types and that is more suitable for modeling the spectrum handoff process as opposed to the existing approaches. Then using that as a base we focus on building analytical models to capture the various aspects of the spectrum handoff process in a realistic manner.

Šiame magistro darbe tirta automobilių kelių infrastruktūros įtaka dirvožemio pH aplinkinėse teritorijose. Lietuvoje panašių tyrimų nėra atlikta. Pateiksiu pagrindinius tyrimo rezultatus: 1. Prie kelių, turinčių asfaltbetonio dangas, tiek paviršiniame, tiek gilesniame dirvožemio sluoksniuose, prie pat kelio sankasos, pastebėtas dirvožemio pH padidėjimas. Prie kelio su grunto danga dirvožemio pH padidėjimo nepastebėta. 2. Prie kelių su asfaltbetonio danga paviršinio dirvožemio sluoksnio mėginių rezultatai, paimti pirmaisiais mėnesiais, yra mažesni negu sekančių mėnesių. 3. Dirvožemio pH padidėjimą šalia kelių, padengtų asfaltbetonio danga, sieju su techninių druskų naudojimu. Jos gali spartinti kelio sankasos grunte esančių karbonatinių uolienų tirpimą. / My master project is devoted to influence of soil pH in the surrounding territories to road traffic transport. There are no comparable researching in Lithuania. I would like to introduce the main results of my project: 1. pH of soil increase are beholded in the soil of surface and in the deep of soil near the roads with blacktop. The soil pH is not behold near the unsurfaced road. 2. The soil of surface specimen’s results are taken from the previous month near the roads with blacktop. These results are less than during next month. 3. The soil pH increase near the roads with blacktop is related with technical soil using. Technical soil can be quickening by melting of carbonaceous rock in the priming of subgrade.

In this study the stability and nutrient removal performance of aerobic granules under variable operating pH and variable growth medium was investigated. The results indicated that alkaline pH (pH=9) inhibited nitrogen and phosphorus removal. Moreover, high pH induced granules breakage and resulted in an increased biomass concentration in the effluent. On the other hand, acidic pH (pH=6) did not have significant impacts on stability and nutrient removal efficiency of granules. Changing the growth medium from acetate-based wastewater to municipal wastewater resulted in loss of biological phosphorus removal while ammonium and COD removal stayed the same. The granules disintegrated during the first two weeks after changing the feed; re-granulation of the biomass was observed after the acclimation of bacteria to the new growth medium. However, the granules breakage did not exert significant impact on settling property of biomass.

A scalable method for the synthesis of polyethylene terephthalamide microcapsules grafted with polyacrylic acid to enable pH responsiveness has been developed. Microcapsules were produced by interfacial polymerisation of an oil-in-water emulsion in a 2 L batch reactor and subsequently circulated through an external loop reactor for UV irradiative surface grafting. Ungrafted microcapsule samples yielded 1.0 - 1.2 g desiccated capsules per experiment. Initial production trials were subject to severe agglomeration, observed during dialysis of the microcapsules with 30 % (v/v) ethanol solution. Lowering of the terephthaloyl dichloride monomer concentration, to 0.2 mol L⁻¹ in the chloroform / cyclohexane (3 : 1) organic solution, alleviated this unwanted agglomeration. Laser diffraction particle size analysis revealed microcapsules were produced with a 51 µm average diameter. A purpose built external loop irradiation reactor was used to facilitate graft polymerisation of acrylic acid on the microcapsules, using 254 nm UV light at 19 mW cm⁻². Characterisation of the external loop flow regime showed a mild deviation from ideal plug flow, with a vessel dispersion number of 0.014 and a Reynolds number of 1310. Confirmation of monomer polymerisation was ascertained by back titration and Fourier transform infrared spectroscopy. No distinction between homopolymer and grafted polyacrylic acid could be made by these characterisation methods. A Taguchi analysis on variables influencing grafting revealed high temperature to contribute most significantly to graft yield, followed by a long irradiation period. The development of a packed column pulse response method for testing pH response showed a high repeatability. However, release profile testing of a microcapsule slurry with an observed graft yield of 1.13 mmol g⁻¹ did not provide a definitive pH-based release of mPEG 5000 or PEGylated TAMRA dye. Determination of acrylic acid polymerisation kinetics following UV irradiation of the microcapsules is required for future optimisation of a functional graft yield.