La lignine est l'un des biopolymères les plus importants sur Terre. Elle est extraite des plantes et représente la plus grande source de noyaux aromatiques dans la biomasse. De nombreux projets ayant pour but la dépolymérisation de la lignine en molécules de faibles poids moléculaires, valorisables par les industries chimiques, sont de plus en plus développés au vu du fort potentiel de cette bio-ressource. Le but de notre projet était de développer un nouveau système catalytique pour la dépolymérisation de la lignine. Nous nous sommes intéressés à la conception de nouveaux catalyseurs homogènes et hétérogènes, basés sur la structure connue du complexe Fe(TAML). Nous avons étudié leurs réactivité et stabilité en conditions de catalyse oxydante, et les avons comparés aux caractéristiques du Fe(TAML) existant. Pour ce faire, l'étude catalytique a été réalisée sur des molécules modèles de la lignine, dans le but d'éviter les problèmes analytiques liés à la structure du polymère. Dans un premier temps, nous présenterons la stratégie de fonctionnalisation du ligand TAML connu afin d'obtenir de nouveaux complexes qui puissent être greffés sur un support de silice. Dans un deuxième temps, nous parlerons des résultats de la catalyse oxydante en conditions homogènes et hétérogènes, et de l'influence du changement de la structure des ligands sur l'activité des catalyseurs / Lignin is one of the most abundant biopolymers on earth. It is issued from plants and represents the largest source of aromatics in biomass. Projects aiming at depolymerizing lignin to obtain value-added small molecules for the chemical industry are more and more developed due to the high potential of this bio-resource. The goal of our project was to develop a new catalytic system for the depolymerization of lignin. We have been interested in designing new homogeneous and heterogeneous catalysts based on the known structure of the Fe(TAML) complex. We have studied their reactivity and stability under oxidative catalysis conditions, and have compared them to the characteristics of the existing Fe(TAML). To do so, the catalysis study has been realized on lignin small model molecules to avoid the analytical problems related to a polymer backbone. In a first hand, we will present the strategy of functionalization of the known TAML ligand to design new complexes to be grafted on a silica support. In a second hand, we will talk about the results of oxidative catalysis in homogeneous and heterogeneous conditions, and the influence of the ligand structure change on the activity of the catalysts

Seventy-four methicillin-resistant Staphylococcus aureus (MRSA) from two Malaysian hospitals were characterised by both phenotypic and genotypic techniques. These isolates were collected over an 18 year time period in the years, 1982, 1989, 1994 and 2000. All of the Malaysian MRSA isolates were found to be multiresistant and resistant to at least five different antimicrobial agents. Over 30% of them were non-typable by the International Basic Set of bacteriophages. The majority of the typable isolates were susceptible to the group III phages, especially phage 85. The majority of the isolates carried one to six plasmids. Only two isolates were plasmid free. The plasmid profiles of these isolates, other than the 1982 isolates, were very similar to each other. Contour-clamped homogeneous electric field (CHEF) gel electrophoresis was used to examine the genetic relatedness of the isolates. Twenty-six CHEF patterns were found among the isolates. These CHEF patterns were closely related to each other. The predominant CHEF pattern A was found in the 1982, 1989 and 1994 isolates. The CHEF patterns of the year 2000 isolates were different to CHEF pattern A, but still closely related. All of the isolates were found to carry the Allotype III SCCmec and have coagulase-gene type 24. Multilocus sequence typing was preformed on the isolates with CHEF pattern A collected in different years. These isolates were found to have either sequence type 239 (ST239), or its single locus variant. The predominant Malaysian clone belongs to the pandemic clone ST239-MRSA-III that is pandemic in Asian countries. (Enright, 2003, Ko et al., 2005). / A 1.5 kb cryptic plasmid found in Malaysian isolates was indistinguishable from a cryptic plasmid found in an Australian isolate. A 3.0 kb cryptic plasmid found in Malaysian isolates was undistinguishable from a 3.0 kb plasmid found in Singaporean isolates. Class II multiresistance plasmids of 28, 30.5 and 35 kb were commonly found together in many Malaysian MRSA isolates. Both the 28 and 30.5 kb plasmids encode resistance to the heavy-metals and nucleic acid-binding (NAB) compounds. The 35 kb plasmid carries heavy-metal and NAB resistance but also encodes β-lactamase. Structurally these three plasmids are almost identical and probably have the same origin. The differences observed between these plasmids is probably due to excision or partial deletion of the β-lactamase transposon of the original plasmid. The 28 kb plasmid is identical to the 28 kb plasmid of Singaporean and some Australian isolates. A 20 kb plasmid in Indonesian isolates was found to be closely related to these three plasmids. A conjugative plasmid, pWBG707, conferring trimethoprim-resistance was found in Malaysian isolates. It did not carry either of the two staphylococcal trimethoprim-resistance genes, dfrA and dfrD. (Lyon and Skurray, 1987, Dale et al., 1995b) It either encodes a novel resistance gene or the recently discovered dfrG gene. (Sekiguchi et al., 2005) pWBG707 was also found to mobilise a small 3.0 kb kanamycin-resistance plasmid during conjugation. / The mecR1 and mecI genes regulating the transcription of the methicillin-resistance gene, mecA, were also examined in the isolates. The Malaysian isolate, WBG7422, with the predominant CHEF pattern A has a nonsense mutation in its mecI gene that disables it. However, its mecR1 gene is intact. The eastern Australia MRSA (EA MRSA), WBG525, has a CHEF pattern that is closely related to the Malaysian predominant CHEF pattern A and its mecI gene has a mutation identical to the Malaysian isolate. Unlike the Malaysian isolate however, its mecR1 gene has a 166 bp deletion. Both WBG7422 and WBG525 express Class III heterogeneous methicillin resistance. However, WBG525 has more highly resistant cell in its population than WBG7422. The loss of aminoglycoside resistance, together with c. 114 kb of chromosomal DNA, was observed in some Malaysian isolates. The deleted segment was found to carry the aacA-aphD gene that encodes a bifunctional aminoglycoside-modifying enzyme conferring resistance to many of the aminoglycosides. The Malaysian isolates were compared with MRSA from different countries. These MRSA included 18 epidemic MRSA (EMRSA) from the United Kingdom, 15 Australian nosocomial MRSA, five classical MRSA, 22 community-acquired MRSA (CMRSA) from Australia and New Zealand and 46 nosocomial MRSAs from eight Asian-Pacific countries and South Africa. These Asian-Pacific countries were Australia, PR China, Hong Kong, Indonesia, Japan, Philippines, Singapore and Taiwan. / The CHEF patterns of most of the Asian-Pacific and South African isolates were closely related to the Malaysian isolates. Isolates from Singapore, Indonesia and Philippines were found to have an identical CHEF pattern to the Malaysian CHEF patterns A5. The Asian-Pacific and South African isolates, including the Malaysian isolates, were found to be closely related to EMRSA-1, -4 and -7. These EMRSA belong to the ST239-MRSA-III clone and are coagulase-gene type 24. The isolates from Japan were the only Asian-Pacific isolates not related to the other Asian-Pacific isolates and EMRSAs. EMRSA-1 and EA MRSA have the same 166 bp deletion in their mecR1 gene. Both of these strains have closely related CHEF patterns, the same sequence type, coagulase-gene type and SCCmec. These results indicate that these two strains belongs to the same clone and confirms the international spread of this clone in the early 1980s. However, the Malaysian isolates have CHEF patterns that are more closely related to EMRSA-4 than to EMRSA-1. Similar to the Malaysian isolates EMRSA-4 has an intact mecR1 gene. The CMRSA isolates were not related to any of the nosocomial MRSA. They also have very diverse genetic backgrounds but carry less diverse SCCmec allotypes. Most of the CMRSA carry either Allotype IV or V SCCmec These results show that the spread of Malaysian MRSA is due to a single clonal expansion. Infection control measures would have to have been more efficient if this clone was to have been contained. The Malaysian epidemic clone is the Asian pandemic clone, ST239-MRSA-III. The Malaysian isolates and EMRSA-4 probably share the same ancestor. / The presence of the same MRSA strain in Malaysian hospitals and in the hospitals of neighbouring countries indicates that the inter-hospital spread of an epidemic MRSA has occurred. This observation also suggests that the infection control measures in Malaysian hospitals have not been totally effective. The ineffectiveness of infection control has left Malaysian hospitals vulnerable to the future importation of new pandemic clones and/or highly virulent or resistant clones.

Handoff is a call handling mechanism that is invoked when a mobile node moves from one cell to another. Such movement may lead to degradation in performance for wireless networks as a result of packet losses. A promising technique proposed in this thesis is to apply multicasting techniques aided by mobility prediction in order to improve handoff performance. In this thesis, we present a method that uses a Grey model for mobility prediction and a fuzzy logic controller that has been fine-tuned using evolutionary algorithms in order to improve prediction accuracy. We also compare the self-tuning algorithm with two evolutionary algorithms in terms of accuracy and their convergence times. Our proposed method takes into account signal strengths from the base stations and predicts the signal strength of the next candidate base station in order to provide improved handover performance. The primary decision for mobility prediction is the accurate prediction of signal strengths obtained from the base stations and remove any unwanted errors in the prediction using suitable optimisation techniques. Furthermore, the model includes the procedures of fine-tuning the predicted data using fuzzy parameters. We also propose suitable multicasting algorithms to minimise the reservation of overall network resource requirements during handoff with the mobility prediction information. To be able to efficiently solve the problem, the situation is modelled using a multicast tree that is defined to maintain connectivity with the mobile node, whilst ensuring bandwidth guarantees and a minimum hop-count. In this approach, we have tried to solve the problem by balancing two objectives through putting a weight on each of two costs. We provide a detailed description of an algorithm to implement join and prune mechanisms, which will help to build an optimal multicast tree with QoS requirements during handoff as well as incorporating dynamic changes in the positions of mobile nodes. An analysis of how mobility prediction helps in the selection of potential Access Routers (AR) with QoS requirements - which affects the multicast group size and bandwidth cost of the multicast tree -- is presented. The proposed technique tries to minimise the number of multicast tree join and prune operations. Our results show that the expected size of the multicast group increases linearly with an increase in the number of selected destination AR's for multicast during handoff. We observe that the expected number of joins and prunes from the multicast tree increases with group size. A special simulation model was developed to demonstrate both homogeneous and heterogeneous handoff which is an emerging requirement for fourth generation mobile networks. The model incorporates our mobility prediction model for heterogeneous handoff between the Wireless LAN and a cellular network. The results presented in this thesis for mobility prediction, multicasting techniques and heterogeneous handoff include proposed algorithms and models which aid in the understanding, analysing and reducing of overheads during handoff.

<p>This thesis describes mechanistic studies, rational ligand design, and synthesis of asymmetric transition metal catalysts. The topics addressed concerned [Papers I-VII]:</p><p>[I] The asymmetric addition of diethyl zinc to <i>N</i>-(diphenylphosphinoyl)benzalimine catalyzed by bicyclic 2-azanorbornyl-3-methanols was studied. An efficient route to both diastereomers of new bicyclic 2-azanorbornyl-3-methanols with an additional chiral center was developed, in the best case 97% ee was obtained with these ligands. The experimental results were rationalized by a computational DFT-study.</p><p>[II] An aza-Diels-Alder reaction of cyclopentadiene with chiral heterocyclic imines derived from (<i>S</i>)-1-phenylethylamine and different heteroaromatic aldehydes was developed. The cycloaddition proved to be highly diastereoselective and offers a very rapid access to possible biologically active compounds and interesting precursors for chiral (<i>P,N</i>)-ligands. </p><p>[III] A convenient and high-yielding method for the preparation of (<i>R</i>)-tolterodine, utilizing a catalytic asymmetric Me-CBS reduction was developed. Highly enantio-enriched (<i>R</i>)-6-methyl-4-phenyl-3,4-dihydrochromen-2-one (94% ee) was recrystallized to yield practically enantiopure material (ee >99%) and converted to (<i>R</i>)-tolterodine in a four-step procedure. </p><p>[IV] The reaction mechanism of the iridium-phosphanooxazoline-catalyzed hydrogenation of unfunctionalized olefins has been studied by means of DFT-calculations (B3LYP) and kinetic experiments. The calculations suggest that the reaction involves an unexpected IrIII-IrV catalytic cycle facilitated by coordination of a second equivalent of dihydrogen. On the basis of the proposed catalytic cycle, calculations were performed on a full system with 88 atoms. These calculations were also used to explain the enantioselectivity displayed by the catalyst.</p><p>[V and VI] A new class of chiral (<i>P,N</i>)-ligands for the Ir-catalyzed asymmetric hydrogenation of aryl alkenes was developed. These new ligands proved to be highly efficient and tolerate a broad range of substrates. The enantiomeric excesses are, so far, the best reported and can be rationalized using the proposed selectivity model.</p><p>[VII] The complex formed between the quincorine-amine, containing both a primary and a quinuclidine amino function, and [Cp*RuCl]₄ catalyzes the hydrogenation of aromatic and aliphatic ketones in up to 90% ee approx. 24-times faster than previously reported Ru-diamine complexes. The reason for the lower but opposite stereoselectivity seen with the quincoridine-amine, as compared to the quincorine-amine, was rationalized by a kinetic and computational study of the mechanism. The theoretical calculations also revealed a significantly lower activation barrier for the alcohol mediated split of dihydrogen, as compared to the non-alchol mediated process. A finding of importance also for the diphosphine/diamine mediated enantioselective hydrogenation of ketones.</p>

The theme of this thesis is the development of mononuclear Ru-based complexes that are capable of catalyzing the water oxidation (or O2-evolving) reaction, e.g. 2 H2O → O2 + 4 H+ + 4 e−. Several families of mononuclear Ru water oxidation catalysts were designed and prepared. They feature with anionic ancillary ligands that contain carboxylate or phenolate donors. The properties of the catalysts were investigated in various aspects including coordination geometry, electrochemical behavior, and ligand exchange. All catalysts showed outstanding catalytic activity towards water oxidation in the presence of cerium(IV) ammonium nitrate as a sacrificial oxidant. High-valent Ru intermediates involved in the reactions were characterized both experimentally and theoretically. The kinetics of catalytic water oxidation was examined based on one catalyst and a prevailing catalytic pathway was proposed. The catalytic cycle involved a sequence of oxidation steps from RuII−OH2 to RuV=O species and O−O bond formation via water-nucleophilic-attack to the RuV=O intermediate. By comparing properties and catalytic performance of Ru catalysts herein with that of previously reported examples, the effect of anionic ancillary ligands was clearly elucidated in the context of catalytic water oxidation. Aiming to further application in an envisaged artificial photosynthesis device, visible light-driven water oxidation was conducted and achieved primarily in a homogeneous three-component system containing catalyst, photosensitizer, and sacrificial electron acceptor. Moreover, one model Ru catalyst was successfully immobilized on ordinary glass carbon surface through a facile and widely applicable method. / <p>QC 20121112</p>

This thesis describes mechanistic studies, rational ligand design, and synthesis of asymmetric transition metal catalysts. The topics addressed concerned [Papers I-VII]: [I] The asymmetric addition of diethyl zinc to N-(diphenylphosphinoyl)benzalimine catalyzed by bicyclic 2-azanorbornyl-3-methanols was studied. An efficient route to both diastereomers of new bicyclic 2-azanorbornyl-3-methanols with an additional chiral center was developed, in the best case 97% ee was obtained with these ligands. The experimental results were rationalized by a computational DFT-study. [II] An aza-Diels-Alder reaction of cyclopentadiene with chiral heterocyclic imines derived from (S)-1-phenylethylamine and different heteroaromatic aldehydes was developed. The cycloaddition proved to be highly diastereoselective and offers a very rapid access to possible biologically active compounds and interesting precursors for chiral (P,N)-ligands. [III] A convenient and high-yielding method for the preparation of (R)-tolterodine, utilizing a catalytic asymmetric Me-CBS reduction was developed. Highly enantio-enriched (R)-6-methyl-4-phenyl-3,4-dihydrochromen-2-one (94% ee) was recrystallized to yield practically enantiopure material (ee &gt;99%) and converted to (R)-tolterodine in a four-step procedure. [IV] The reaction mechanism of the iridium-phosphanooxazoline-catalyzed hydrogenation of unfunctionalized olefins has been studied by means of DFT-calculations (B3LYP) and kinetic experiments. The calculations suggest that the reaction involves an unexpected IrIII-IrV catalytic cycle facilitated by coordination of a second equivalent of dihydrogen. On the basis of the proposed catalytic cycle, calculations were performed on a full system with 88 atoms. These calculations were also used to explain the enantioselectivity displayed by the catalyst. [V and VI] A new class of chiral (P,N)-ligands for the Ir-catalyzed asymmetric hydrogenation of aryl alkenes was developed. These new ligands proved to be highly efficient and tolerate a broad range of substrates. The enantiomeric excesses are, so far, the best reported and can be rationalized using the proposed selectivity model. [VII] The complex formed between the quincorine-amine, containing both a primary and a quinuclidine amino function, and [Cp*RuCl]4 catalyzes the hydrogenation of aromatic and aliphatic ketones in up to 90% ee approx. 24-times faster than previously reported Ru-diamine complexes. The reason for the lower but opposite stereoselectivity seen with the quincoridine-amine, as compared to the quincorine-amine, was rationalized by a kinetic and computational study of the mechanism. The theoretical calculations also revealed a significantly lower activation barrier for the alcohol mediated split of dihydrogen, as compared to the non-alchol mediated process. A finding of importance also for the diphosphine/diamine mediated enantioselective hydrogenation of ketones.

In this work the methods of mode decomposition and Fourier analysis of quantum fields on curved spacetimes previously available mainly for the scalar fields on Friedman-Robertson-Walker spacetimes are extended to arbitrary vector fields on general spatially homogeneous spacetimes. This is done by developing a rigorous unified framework which incorporates mode decomposition, harmonic analysis and Fourier analysis. Explicit constructions are performed for a variety of situations arising in homogeneous cosmology. A number of results concerning classical and quantum fields known for very restricted situations are generalized to cover almost all cosmological models.

The work in this thesis couples reactions with separations through the use of switchable and tunable solvents. Tunable solvents are mixed solvents which can be easily altered to afford conditions optimal for reaction or separation. Switchable solvents are solvents that can be switched when desired to alter their properties affording conditions suitable for separation. Other studies are of the reaction of CO2 with the amidine base DBU, and an NMR study of solvent-to-solute nuclear Overhauser effects. These examples constitute a marriage of reaction environment with separation environment, significantly, to the benefit of both.

I have structured my master's thesis in terms of an opposition between Kojeve's existentialist, Marxist philosophical formulation of Hegel's Phenomenology and Levinas's post-Heideggerian, anti-Hegelian phenomenology in Totality and Infinity. While Levinas's project is explicitly anti-totalitarian, Kojeve's reading of the Phenomenology emphasizes the End of History in Hegel's philosophy without shrinking from its totalizing aspects. While the philosophical project of each thinker is generally antithetical to the other, it is my contention that the universal and homogeneous state, conceived by Kojeve to be the rational realization of the end of history, is a legitimate moral project for Levinasian ethics. This thesis provides both an exegesis of Kojeve's reading of Hegel's master/slave dialectic in the Phenomenology and an interpretation of the tragedy of the slave understood in terms of Holderlin's theory of the tragic. It is through the master/slave dialectic that history consummates in the end of history. Later in the thesis, I outline Levinas's project as an ethics as first philosophy in opposition to the Eleatic traditions in Western philosophy. We can trace Levinas's project in his unconventional reading of the cogito and the idea of infinity. Whereas Descartes represents a philosophical return home for Hegel, Levinas's reading of Descartes represents a philosophical sojourn away from home in the second movement of the Meditations. With these notions, we have a formal basis in accounting for the conflict in Levinas's thought between the moral necessity of universal rights and the dangers of assimilation. Finally, I argue for why the universal and homogeneous state is an ethically worthy goal from a Levinasian perspective. On this question, I engage the thought of a number of thinkers of the left: Kojeve, Derrida, Horkheimer, Adorno and Zizek. I conclude that Levinas's thought on universalism and eschatology can serve as a moral basis for the left-Hegelian project of realizing a universal and homogeneous state. Because such a state is distinguishable from a totalizing End of History, the eschatological concern for one's singularity within history is compatible with the prophetic call to strive for political universality. Ultimately, it is the responsibility to this prophetic call that guarantees one's singularity.

Recent studies have shown that ruthenium(III) acetylacetonate is acting as homogeneous catalyst in the hydrolysis of sodium borohydride. Although trimethlyphosphite is found to be a poison for the catalytic hydrolysis of sodium borohydride, a longer observation of the reaction in the presence of ruthenium(III) acetylacetonate and 2 equivalent trimethylphosphite shows an unexpected enhancement in the catalytic activity after an induction period. The same rate enhancement is observed when 2 equivalent triphenylphosphine is added into the reaction solution. Addition of 1 equivalent 1,2-bis(diphenylphosphino)ethane, dppe, into the solution shows similarly a rate enhancement in the hydrolysis of sodium borohydride catalyzed by ruthenium(III) acetylacetonate. The effect of 1,2-bis(diphenylphosphino)ethane on the catalytic activity of ruthenium(III) acetylacetonate in the hydrolysis of sodium borohydride was studied by varying mole ratio of dppe / Ru(acac)3, ruthenium concentration, substrate concentration and temperature. The highest enhancement in the rate of hydrolysis was obtained when 1 equivalent dppe was used and therefore, this mole ratio of dppe / Ru(acac)3 was used in the further studies. The rate of the reaction was found to be first order in catalyst concentration and zero order in substrate concentration. From the evaluation of rate constant versus temperature data, the activation parameters for the hydrolysis of sodium borohydride catalyzed by ruthenium(III) acetylacetonate plus 1 equivalent dppe were found to be Ea= 59 &plusmn / 2 kJ/mol, &amp / #8710 / H&amp / #8800 / = 60 &plusmn / 1 kJ.mol-1 and &amp / #8710 / S&amp / #8800 / = -50 &plusmn / 3 J.(mol.K)-1. A series of control experiments were performed to characterize the active catalyst. However, the only useful information could be obtained by comparison of the UV-vis electronic absorption spectra taken from the solution during the catalytic reaction, is that, ruthenium(III) is reduced to ruthenium(II) in the course of reaction. It was concluded that a ruthenium(II) species is formed as a transient and may be the active catalyst in the reaction. After the reaction, the only ruthenium species isolated from the solution was the ruthenium(III) acetylacetonate.