The nitrate radical (NO3·) was first identified as early as the 1881, but its role in atmospheric oxidation has only been identified within recent decades. Due to its high one-electron reduction potential and its reactivity toward a diverse set of substrates, it dominates nighttime atmospheric oxidation and has since been the subject of much work. Despite this, studies on NO3· hydrogen atom transfer reactions have been somewhat neglected in favor of its more reactive oxidative pathways. The first section of the dissertation will highlight the role of substrate structure, solvent effects, and the presence of a polar transition state on NO3· hydrogen abstractions from alcohols, alkanes, and ethers. In this work the acquisition of absolute rate constants from previously unexamined substrates was analyzed alongside a curated list of common organic pollutants degraded through hydrogen atom abstraction. It was found that NO3· reacts with low selectivity through an early polarized transition state with a modest degree of charge transfer. Compared to the gas-phase, condensed-phase reactions experience rate enhancement—consistent with Kirkwood theory—as a result of the polarized transition state. These insights are then applied to abstractions by NO3· from carboxylic acids in the next section. It was found that the rate constants for abstraction of α-carbons were diminished through induction by the adjacent carbonyl compared to the activation seen for the aforementioned substrates. The deactivation of abstraction by the carbonyl was found to be dramatically reduced as the substrate's alkyl chain was lengthened and/or branched. This apparent change in mechanism coincides with hydrogen abstraction of the alkyl chain for sufficiently large carboxylic acids and rules out the possibility of concerted bond breaking elsewhere in the molecule. Finally, the dissertation will cover some additional projects related to the overall nature of the work including examination of the kinetics of radical clock systems when complexed with metal ions and the examination of a highly oxidative biosourced monomer. / Doctor of Philosophy / The nitrate radical (NO3·) was first identified as early as the 1881, but its role in the breakdown of atmospheric pollutants has only been identified within recent decades. Operating primarily at night, NO3· serves as a major atmospheric oxidant—it breaks down pollutants by reactions that involve the removal of electrons from those substrates. This chemistry is particularly important in understanding the consequences of an increasingly industrialized world and the subsequent short-term health and environmental implications. Geographically, these reactions will occur in large concentrations near locations that contribute greatly to atmospheric pollution, such as above coal-powered plants, heavily industrialized areas, above the canopy of large forests, and immediately behind the engines of airplanes as they move through the sky. The proximity of these locations to large population centers has caused the pollutants to greatly impact human health. These contaminants have been linked to several of the leading global causes of death, such as ischemic heart disease, stroke, and respiratory illnesses. The first section of the dissertation will focus on the role of pollutant structure, the medium in which the reaction occurs, and the development of a charged complex when NO3· reacts with alcohols, alkanes, and ethers. These substrates are often found as the result of incomplete combustion when burning fuel or as products of even more sustainable biodiesels. In this work the exact rate constants were found for substrates that were previously unexamined and compared with similar known reaction rates. It was found that NO3· has a low preference for what it reacts with and passes through a modestly charged complex early in the reaction. Compared to gaseous reactions, reactions in a liquid environment proceed faster due to the formation of a charged complex. This was then applied to reactions with carboxylic acids in the next section. Carboxylic acids are often found in large concentrations above the canopy of large forests resulting from the oxidation of isoprenes that are naturally released from broad-leaf trees. It was found that these reactions were slower than reactions with alkanes as the development of the charged complex was inhibited due to the presence of an adjacent dipole. When the carboxylic acid was longer and/or more branched, the formation of the charged complex was no longer inhibited as the reaction site moved further from the dipole. A change in reaction pathway was observed when the acids were sufficiently large. This ruled out the possibility of the reaction occurring simultaneously with a fracturing and rearrangement elsewhere. Finally, the dissertation will cover some additional projects that share some overlap with the work already described including the study of the rates of radical clock systems in the presence of metal ions and the study of naturally sourced monomers that are prone to losing electrons.

Growing environmental concerns, coupled with increasing regulatory restrictions, are requiring industries to develop non-lead-based compositions of ferroelectric and piezoelectric materials. These materials—now widely used in sensors, actuators, and transducers—are for the most part lead-based compounds such as Pb(Zr,Ti)O₃ (PZT). Indeed, PZT represents the dominant market share for use in these technologies. Moreover, next generation compounds, which include Pb(Mg_1/3Nb_2/3)O₃-xat%PbTiO₃ (PMN-x%PT) crystals with ultrahigh piezo-/electromechanical properties, are also Pb-based systems and thus are problematic for meeting more restrictive environmental standards. As alternative, Pb-free ferroelectrics such as NBT-derived single crystals represent viable next-generation materials for use in ferro-/piezoelectric applications. Development of these types of NBT-based crystals has made important advancements in the last decade. In fact, the performances of NBT-based materials are beginning to approach the properties of the widely used commercial PZT ceramic material. Nonetheless, additional studies are needed before it being able to compete with PMN-x%PT and PZN-x%PT crystals in next-generation applications. As a new type of piezoelectric material, much remains to be learned about Pb-free piezoelectric crystals. For instance, in addition to enhancing our understanding the nature of the piezoelectric third-rank tensor coefficients such as d₃₃ and d₁₅, a thorough knowledge of the Curie temperature, leakage current, and electromechanical properties is also essential for increasing the applications potential of these crystals. As detailed herein, multiple dopants may have to be incorporated into NBT to modify its microstructure and properties to meet these specific requirements, which may further complicate its chemical structure-property relationships. This study, therefore, was designed to investigate the heterogeneous structure of NBT-based single crystals, using x-ray diffraction, transmission electron microscopy, and neutron inelastic scattering, with the goal of investigating the mechanism coupling of morphotropic phase boundary (MPB) and the maximum property responses in A-site disordered perovskite Pb-free piezoelectric systems. Using the framework of polar nanoregions and adaptive phase theory, I sought to determine how the nanostructure of these single crystals change with temperature and composition—and how these factors impact its properties. Diffuse scattering, domain morphology, and phonon dispersions were used to investigate both the static and dynamic properties of these heterogeneous structures. / Ph. D. / Growing environmental concerns, coupled with increasing regulatory restrictions, are requiring industries to develop non-lead-based compositions of ferroelectric and piezoelectric materials. These materials—now widely used in sensors, actuators, and transducers—are for the most part lead-based compounds such as Pb(Zr,Ti)O₃ (PZT). Indeed, PZT represents the dominant market share for use in these technologies. Moreover, next generation compounds, which include Pb(Mg_1/3Nb_2/3)O₃-xat%PbTiO₃ (PMN-x%PT) crystals with ultrahigh piezo- /electromechanical properties, are also Pb-based systems and thus are problematic for meeting more restrictive environmental standards. As alternative, Pb-free ferroelectrics such as (Na_1/2Bi_1/2)TiO₃ (NBT) -derived single crystals represent viable next-generation materials for use in ferro-/piezoelectric applications. Development of these types of NBT-based crystals has made important advancements in the last decade. In fact, the performances of NBT-based materials are beginning to approach the properties of the widely used commercial PZT ceramic material. Nonetheless, additional studies are needed before it being able to compete with PMN-x%PT and PZN-x%PT crystals in next-generation applications. As a new type of piezoelectric material, much remains to be learned about Pb-free piezoelectric single crystals. In addition to enhancing our understanding the nature of the piezoelectric properties, increasing the applications potential of these crystals is also essential. And these specific requirements from different applications further push the researchers to find a more effective model to lead the piezoelectric single crystals growth as well as developments. This study, therefore, was designed to investigate the unique microstructure of NBTbased single crystals, using x-ray diffraction, transmission electron microscopy, and neutron inelastic scattering, with the goal of investigating the mechanism coupling between the chemical compositions and the maximum property responses in these specific Pb-free piezoelectric systems. Using the framework of an advanced microstructure description model, I sought to determine how the nanostructure of these single crystals change with temperature and composition—and how these factors impact its properties. The results from different experiment methods also successfully supported each other and brought new perspectives to the Pb-free material researches.

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Efficient process design commonly relies on equation-of-state (EOS) models to provide reliable estimates of thermodynamic properties. The accuracy of EOS models, in turn, depends on the extent to which they account for intermolecular forces. The aim of this project was to improve the simplified Perturbed Chain - Statistical Associating Fluid Theory (sPC-SAFT), enabling it to account more accurately for complex molecular interactions. The more simple SAFT-based Cubic-Plus-Association (CPA) model was evaluated along similar lines for comparative purposes. A literature review showed that both sPC-SAFT and CPA have been widely applied in phase equilibria problems, but not extensively for the prediction of other thermodynamic properties. Consequently, an initial evaluation was performed on the ability of sPC-SAFT and CPA to predict first- and second-order thermodynamic properties. The properties of non-polar, polar and hydrogen bonding fluids were considered, showing that: a) sPC-SAFT and CPA generally predict first-order properties with the same accuracy, but sPC-SAFT provides improved predictions of second-order properties. Significant errors are, however, still observed with sPC-SAFT. b) A parameter regression study with sPC-SAFT, using model parameters obtained by including second-order properties in the regression function, results in poor predictions of the saturated vapour pressure and liquid density. c) Treating strong polar and dispersive forces together as Van der Waals forces results in many properties being poorly predicted by both sPC-SAFT and CPA. d) The major limitation of the association term in both CPA and sPC-SAFT is its inability to account for the influence of bond co-operativity, especially in alcohol/water mixtures. Based on these findings, the following improvements could be made: a) The development of a new association scheme for 1-alcohols, denoted the 2C association scheme. b) The extension of sPC-SAFT with the polar theories of Jog & Chapman (JC) and Gross & Vrabec (GV) to obtain sPC-SAFT-JC and sPC-SAFT-GV. c) The extension of CPA with modified versions of the aforementioned polar theories to obtain CPA-JC and CPA-GV. d) The development of a new ‘universal’ cross-association approach. The new 2C association scheme consists of one bipolar association site and one negative electron donor site and is a combination of the 1A and 2B/3B association schemes. Modelling 1-alcohols with the 2C scheme in sPC-SAFT results in improved VLE predictions of alcohol/water and alcohol/alcohol mixtures, but alcohol/alkane VLE is predicted less accurately compared to the 2B and 3B association schemes. sPC-SAFT-JC and sPC-SAFT-GV provide improved VLE predictions of mixtures with non-associating polar components compared to sPC-SAFT. VLE of polar/alkane and polar/polar systems can be represented accurately with no or only very small binary interaction parameters (BIPs). CPA-JC and CPA-GV also enable improved VLE predictions of the polar/alkane and polar/polar mixtures compared to CPA. sPC-SAFT-GV and sPC-SAFT-JC were also applied to several mixtures of associating components including alcohol/alkane, alcohol/alcohol and alcohol/water systems. New alcohol model parameters for both sPC-SAFT-GV and sPC-SAFT-JC based on the 2C, 2B and 3B association schemes were determined. The predictions of both sPC-SAFT-GV and sPC-SAFT-JC, based on any of the three association schemes, provide similar alcohol/alkane and alcohol/alcohol VLE representations, but the best phase equilibria predictions of water/alcohol systems are obtained when alcohols are modelled with the newly proposed 2C association scheme. The usefulness of a new ‘universal’ cross-association approach was demonstrated with both sPC-SAFT-GV and sPC-SAFT-JC. The philosophy behind the new approach is to set the association volume value of the solvating component equal to the cross-associating volume value of the 1-alcohol of the same molecular size and to determine an association energy value from binary VLE data. This approach aims to characterize the solvating behaviour of the cross-associating component. Preliminary results are demonstrated with systems containing acetone, propyl formate and ethyl acetate. Other thermodynamic properties, such as excess enthalpy and excess volume can be described with the new polar sPC-SAFT and CPA models. In the majority of cases, improvements are observed compared to the normal sPC-SAFT and CPA models, but BIPs are still required to obtain accurate correlations. However, these BIPs cannot be used in phase equilibria calculations and are generally property-specific. To summarise: Through the development of the 2C scheme, and the incorporation of polar terms into the sPC-SAFT model structure, notable improvement in the VLE predictions of polar (nonhydrogen bonding)/alkane, alcohol/alkane, alcohol/water and polar/alcohol systems could be obtained if compared to the original sPC-SAFT EOS. As such, the research pesented in this thesis encapsulates some significant novel contributions, viz.: a) A systematic evaluation of sPC-SAFT and CPA, providing better insight into their ability to predict thermodynamic properties. b) The development of the new 2C association scheme for 1-alcohols, as published in Ind. Eng. Chem. Res. 2011, 50, 8711–8725. c) The extension of sPC-SAFT with the polar theories of JC and GV, with application to non-associating components, as published in Fluid Phase Equilib. 2011, 305, 174–184. d) The extension of CPA with the JC and GV polar theories, as published in Fluid Phase Equilib. 2011, 312, 66–78. e) The application of sPC-SAFT-GV and sPC-SAFT-JC to associating components, including results with the new 2C association scheme. f) The development of the new ‘universal’ cross-association approach. / AFRIKAANSE OPSOMMING: Doeltreffende prosesontwerp steun grotendeels op toestandvergelykings (EOS) om goeie skattings van vloeistofeienskappe te voorspel. Die akkuraatheid van hierdie modelle word bepaal deur hoe goed hulle die invloed van molekulêre kragte kan naboots. Die doel van hierdie projek was dus om die ‘simplified Perturbed Chain-Statistical Associating Fluid Theory’ (sPC-SAFT) te verbeter, sodat dit komplekse molekulêre kragte beter kan beskryf. Die meer vereenvoudigte SAFT-gebaseerde ‘Cubic-Plus-Association’ (CPA) model was ook geëvalueer vir vergelykende doeleindes. 'n Literatuurstudie het getoon dat beide sPC-SAFT en CPA reeds wyd toegepas is in fase ewewig probleme, maar nie vir ander termodinamiese eienskappe nie. Gevolglik, is 'n aanvanklike ondersoek uitgevoer waarin die vermoë van sPC-SAFT en CPA om eerste- en tweede-orde termodinamiese eienskappe te voorspel, geëvalueer is. Die eienskappe van nie-polêre, polêre en waterstof-bindinde komponente is oorweeg en die hoof bevindinge uit hierdie ondersoek is: a) sPC-SAFT en CPA voorspel oor die algemeen eerste-orde eienskappe met dieselfde akkuraatheid, maar sPC-SAFT bied verbeterde voorspellings van tweede-orde eienskappe. Beduidende foute is egter steeds teenwoordig in die voorspellings van sPC-SAFT. b) 'n Model parameter regressie studie met sPC-SAFT het getoon dat deur tweede-orde eienskappe ook in die regressie-funksie in te sluit, swak skattings van die eienskappe wat nodig is vir 'n goeie fase-ewewig voorspellings, verkry word. c) Die gesamentlike behandeling van sterk polêre en dispersie kragte as Van der Waals kragte, lei tot swak voorspellings van baie eienskappe deur sPC-SAFT en CPA. d) Die hoof beperking van die assosiasie term wat gebruik word deur beide CPA en sPC-SAFT, is die term se onbekwaamheid om die invloed van verbinding-samewerkings te beskryf, veral in mengsels van alkohole met water. Hierdie bevindings het as basis gedien om die volgende verbeterings aan te bring: a) Die ontwikkeling van 'n nuwe assosiasie skema vir 1-alkohole: die 2C-assosiasie skema. b) Die uitbreiding van sPC-SAFT met die polêre teorieë van Jog & Chapman (JC) en Gross & Vrabec (GV) om sPC-SAFT-JC en sPC-SAFT-GV onderskeidelik te kry. c) Die uitbreiding van CPA met gewysigde weergawes van die polêre teorieë om CPA-JC en CPA-GV te kry. d) Die ontwikkeling van ʼn nuwe ‘universele’ kruis-assosiasie benadering. Die nuut-voorgestelde 2C assosiasie skema bestaan uit een bipolêre assosiasie sone en een negatiewe elektron skenker sone en is ʼn kombinasie van die 1A en 2B/3B assosiasie skemas. Die modellering van 1-alkohole met die 2C skema in sPC-SAFT lei tot 'n verbetering in damp-vloeistof ewewig (VLE) voorspellings van alkohol/water en alkohol/alkohol sisteme, maar vir alkohol/alkaan sisteme is minder akkurate voorspellings verkry in vergelyking met die 2B en 3B assosiasie skemas. sPC-SAFT-JC en sPC-SAFT-GV lewer beter VLE voorspellings van mengsels met nie-assosiërende polêre komponente in vergelyking met sPC-SAFT. Die VLE van polêre/alkaan en polêre/polêre stelsels kan akkuraat beskryf word deur beide modelle wanneer geen of baie klein binêre interaksie parameters (BIPs) gebruik word. CPA-JC en CPA-GV lewer ook verbeterde VLE voorspellings van polêre/alkaan en polêre/polêre mengsels in vergelyking met CPA. sPC-SAFT-GV en sPC-SAFT-JC is ook toegepas op verskeie assosiërende mengsels, insluitend: alkohol/alkaan, alkohol/alkohol en alkohol/water stelsels. Nuwe alkohol parameters is vir beide sPC-SAFT-GV en sPC-SAFT-JC bepaal gebaseer op die 2C, 2B en 3B assosiasie skemas. Die voorspellings van sPCSAFT- GV en sPC-SAFT-JC, gebaseer op enigeen van die drie assosiasie skemas, lewer soortgelyke alkohol/alkaan en alkohol/alkohol VLE voorspellings, maar die beste fase-ewewig voorspellings vir water/alkohol sisteme is verkry wanneer alkohole gemodelleer word met die 2C assosiasie skema. Die nuwe ‘universele’ kruis-assosiasie benadering is gedemonstreer met beide sPC-SAFT-GV en sPC-SAFT-JC. Die filosofie agter die nuwe benadering is om die assosiasie volume waarde van die solverende komponent gelyk te stel aan die kruis-assosiasie volume waarde van die 1-alkohol met dieselfde molekulêre massa. Die assosiasie energie waarde word dan bepaal vanaf binêre VLE data. Hierdie benadering poog om die solverende gedrag van die kruis-assosiërende komponent meer akkuraat te karakteriseer. Voorlopige resultate met mengsels van asetoon, propiel formaat en etiel asetaat dui aan dat merkwaardige verbeterings in VLE voorspellings gekry word. Ander termodinamiese eienskappe, soos oortollige entalpie en oortollige volume, is ook ondersoek met die nuwe polêre sPC-SAFT en CPA-modelle. In meeste gevalle word verbeterde resultate gekry in vergelyking met die oorspronklike sPC-SAFT en CPA modelle, maar groot BIPs word steeds benodig om aanvaarbare korrelasies te kry. Hierdie BIPs kan egter nie gebruik word vir fase-ewewig voorspellings nie en is eienskap-spesifiek. Om op te som: deur die ontwikkeling van die 2C skema, en insluiting van die polêre terme in die sPC-SAFT model struktuur, is merkwaardige verbeterings in die VLE voorspellings van polêre/alkaan, alkohol/alkaan, alkohol/water en polêre/alkohol sisteme gekry in vergelyking met die oorspronklike sPC-SAFT EOS. Die navorsing voorgelê in hierdie tesis het dus gelei tot die volgende nuwe bydraes: a) Die sistematiese evaluering van die vermoë van sPC-SAFT en CPA om termodinamiese eienskappe te voorspel. b) Die ontwikkeling van die nuwe 2C assosiasie skema vir 1-alkohole soos gepubliseer in Ind. Eng. Chem. Res. 2011, 50, 8711–8725. c) Die uitbreiding van sPC-SAFT met die polêre teorieë van JC en GV soos gepubliseer in Fluid Phase Equilib. 2011, 305, 174–184. d) Die uitbreiding van CPA met die polêre teorieë van JC en GV soos gepubliseer in Fluid Phase Equilib. 2011, 312, 66–78. e) Die toepassing van hierdie nuwe modelle op assosiërende komponente, insluitend resultate met die nuwe 2C skema. f) Die ontwikkeling van ʼn nuwe kruis-assosiasie benadering.

Après une période de rejet, la littérature est aujourd'hui revenue dans les classes de langue en tant que document authentique. Si cette position n'est plus contestée dans les discours théoriques, dans les faits, de nombreux enseignants mettent encore de coté ce support pédagogique qui véhicule presque malgré lui de nombreux sous-entendus. <br />Afin d'étendre le corpus dit " littéraire " et d'introduire dans la classe des documents motivants et présentant de nombreux avantages, nous proposons d'utiliser le terme " littérature " au pluriel, incluant les paralittératures, la littérature francophone ou la littérature dite " classique ". Cette ouverture peut notamment motiver les apprenants par l'utilisation de textes moins marqués, désacraliser l'exploitation des textes littéraires ou encore refléter davantage le marché actuel du livre. De plus, la diversité qualitative et thématique des littératures est un facteur qui permet d'adapter le support d'apprentissage au niveau de l'apprenant ou du groupe-classe.<br />Les littératures étant très vastes, nous avons porté notre attention sur un genre en particulier : le roman policier, qui est entré récemment dans les programmes scolaires français. Nous proposons une étude comparative d'un corpus constitué de descriptions urbaines issues d'une part de romans réalistes, et d'autre part de romans policiers du type polar urbain. Nous procédons ensuite à diverses expériences pour valider l'acquisition par les apprenants d'une compétence générique participant à la compétence lectoriale.

The interactions which occur between both polar and non-polar fluid phases and surfaces of various carbon materials: Activated Carbon (AC), non-porous Carbon Black (CB) and Multiwall Carbon Nanotubes (MWCNTs)with different surface chemistry have been studied. These are currently of great interest as they govern the interfacial behaviour of carbons in a wide range of applications; separation adn composite technologies being two prime examples. Consequently, techniques for chemical modification of carbon surfaces ar also of interest. Surface oxygen functional groups have been introduced, or modified, using the following oxidation techniques: liquid-phase oxidation (both AC and CB), Fenton and Birch reduction treatment (MWCNTs) and in a more controlled manner using gas-phase ozone treatment (CB). The chemistry of all the resulting carbon surfaces were characterised using X-ray Photoelectron Spectroscopy (XPS), which gives a quick and direct quantitative measure of the external surface composition. This technique, which has not yet been extensively employed in detailed adsorption studies, is a promising alternative to Temperature Programmed Desorption (TPD) and Boehm titration method in the determination of oxygen and other surface groups. Physical effects of the various surface modifications have been studied using a variety of techniques appropriate for the material in question. Scanning Electron Microscopy (SEM) images show some deteriorating effects of the liquid-phase oxidations on the structure of both activated carbon and carbon black materials. Conversely, surface areas from nitrogen adsorption at 77oK, coupled witj immersion calorimetry data for toluene, show thet the physical structure of the carbon blacks is not modified by ozone treatment. This has allowed a detailed study of the effects of surface oxygen level (i.e. polarity) on vapour adsorption. Regarding the MWCNT materials, detailed High-Resolution Electron Microscopy (HRTEM) photographs show that the multi-wall structure of the nanotubes in not significantly disrupted during the introduction of active functional groups by the Fenton or Birch treatment and therefore keeping intact their mechanical properties which augurs well for their use as reinforcement in composite structures whilst also improving their dispersion properties in polar fluids. A systematic shift to higher adsorption values, due to the increasing specific interactions between the alcohol -OH groups and the surface oxygen groups, is observed in all the isotherms of alcohols from the CB series as the total surface oxygen concentration ([O]T) increases. Moreover, this effect was observed to be most significant for methanol confirming that the mechanism of adsorption is dominated by hydrogen bonding and therefore dependant on the surface concentration of oxygen sites; whereas it becomes less marked in the case of ethanol and isopropanol respectively due to the increasing non-specific, dispersion, interactions of the alkyl chain with the non-polar carbon surface. Overall correlations were observed between the surface oxygen concentration [O]T, the resulting enthalpy of immersion -^Hi values and the characteristic energy E of the Dubinin-Radushkevich-Kaganer (DRK) equation obtained for toluene and these alcohols and the influence of the carbon surface chemistry on the character of the adsorption isotherms is also discussed. This behaviour is also observed and much more pronounced in the case of water adsorption on other oxidised carbon materials (AC, CB and MWCNT) due to the higher polarity of water molecules. The water adsorption data were analysed using in particular the Dubinin-Serpinsky (DS) equation and also some of its recent variations such as Barton and D'Arcy & Watt equations. The DS2 and various Barton equations were found to fit best the AC and CB materials modified by liquid-phase oxidations and also for the CB 03 series with increasing level of oxidation while both D'Arcy & Watt equations gave the best fittings for the MWCNTs materials. It was also shown that the resulting parameters ao (for the DS equation) describing the surface concentration of primary polar adsorption sites and as the limiting water adsorption value were both linked to the surface oxygen level [O]T. Regarding interfacial bonding, the oxidised CB and MWCNT materials are expected to show an improved physicochemical wetting of their surfaces by various resin compunds

Memoria (licenciado en ciencias jurídicas y sociales) / El presente trabajo tiene como objetivo el estudio del contrato de mandato, aplicado a un caso concreto de connotación nacional y de gran relevancia para los consumidores, como lo es el “Caso La Polar”, su estudio se centra en el aspecto jurídico del contrato de mandato inserto en el contrato de adhesión que la empresa ofreció a sus clientes, durante el período 2006-2011, denominado “Contrato de Línea de Crédito Tarjeta La Polar”. Para tal efecto, se analizará en detalle el contrato de mandato celebrado por la multitienda “La Polar”, desde una perspectiva normativa y práctica, se examina nuestro ordenamiento jurídico, desde la mirada del derecho común, el comercial y por cierto la Ley de protección de los Derechos de los Consumidores incluidas sus modificaciones, además se revisan las interpretaciones realizadas tanto por el Sernac en la demanda colectiva como por la empresa en cuestión, de manera que el lector pueda conocer y entender en detalle los términos de la cláusula que La Polar, utilizó como fundamento y justificativo para repactar de manera unilateral las deudas de sus clientes. Dicho estudio será realizado a través de dos capítulos: En el primero se estudiará el contrato de mandato y su regulación, para luego analizar las cláusulas que contiene el mandato de La Polar y determinar si nos encontramos frente a cláusulas abusivas o a una extralimitación del contrato. Mientras que en el segundo capítulo se dará a conocer el desarrollo mediático del caso, la línea argumentativa del Sernac y de la empresa, finalmente se expondrá la opinión crítica de la tesista frente al caso.

In this thesis, a critical analysis is proposed of the relationships between Inuit participation, science and policy in wildlife governance in the Nunavut Territory, Canada. This analysis situates the emergence of a participatory regime for the governance of wildlife in Nunavut, explores its performance and examines the relations between the ways in which wildlife governance arrangements are currently represented in policy and how they are played out in practice across the territory. To pursue these objectives, this research draws upon a number of theoretical perspectives and methodological strategies poised at a crossroads between environmental geography, science and technology studies, political ecology and ecological anthropology. It combines participant observation, semi-directed interviews and literature-based searches with approaches to the study of actor-networks, hybrid forums and scientific practices associated with Latour and Callon, as well as with Foucauldian and post-Foucauldian analyses of power, governmentality and subjectivity. This analysis suggests that the overall rationale within which wildlife governance operates in Nunavut remains largely based on a scientific and bureaucratic framework of resource management that poses significant barriers to the meaningful inclusion of Inuit views. In spite of their participation in wildlife governance through a range of institutional arrangements, consultation practices and research initiatives, the Inuit of Nunavut remain critical of the power relations embedded within existing schemes, where significant decision-making authority remains under the control of the territorial (or federal) government, and where asymmetries persist with regard to the capacity of various actors to produce and mediate their claims. In addition, while the use of Inuit knowledge, or Inuit Qaujimajatuqangit, in wildlife governance in Nunavut has produced some collaborative research and management endeavours, it has also crystallised a divide between ‘Inuit’ and ‘scientific’ knowledge, generated unresolved conflicts, fuelled mistrust among wildlife co-management partners and led to an overall limited inclusion of Inuit observations, values and beliefs in decision-making.

The discovery of the prokaryotic cytoskeleton has revolutionized our thinking about spatial organisation in prokaryotes. However, the roles different bacterial cytoskeletal proteins play in the localisations of diverse biomolecules are controversial. Bacterial chemotaxis depends on signalling through large protein clusters and each cell must inherit a cluster on cytokinesis. In Escherichia coli the membrane chemosensory clusters are polar and new static clusters form at pre-cytokinetic sites, ensuring positioning at new poles after cytokinesis and suggesting a role for the bacterial FtsZ and MreB cytoskeletons. Rhodobacter sphaeroides has both polar, membrane-associated and cytoplasmic, chromosome-associated chemosensory clusters. This study sought to investigate the roles of FtsZ and MreB in the partitioning of the two chemosensory clusters in R. sphaeroides. The relative positioning between the two chemosensory systems, FtsZ and MreB in R. sphaeroides cells during the cell cycle was monitored using fluorescence microscopy. FtsZ forms polar spots after cytokinesis, which redistribute to the midcell forming nodes from which gradients of FtsZ extend circumferentially to form the Z-ring. The proposed node-precursor model might represent a common mechanism for the formation of cytokinetic rings. The MreB cytoskeleton continuously reorganizes between patchy and filamentous structures, and colocalises with FtsZ at midcell. Membrane chemosensory proteins form individual dynamic unit-clusters with mature clusters containing about 1000 CheW₃ proteins. These unit-clusters diffuse randomly within the membrane but have a higher propensity for curved regions like cell poles. Membrane clusters do not colocalise with FtsZ and MreB and appear excluded from the Z-ring vicinity. The bipolar localisation of membrane clusters is established after cell division via random diffusion and polar trapping of clusters. The cytoplasmic chemosensory clusters colocalise with FtsZ at midcell in new-born cells. Before cytokinesis one cluster moves to a daughter cell, followed by the second moving to the other cell. FtsZ and MreB do not participate in the positioning of cytoplasmic clusters. Therefore the two homologous chemosensory clusters use different mechanisms to ensure partitioning, and neither system utilizes FtsZ or MreB for positioning.

Les changements climatiques amènent des transformations profondes de l’environnement arctique. La diminution de l’étendue de la couverture de glace permet un accès facilité aux ressources naturelles et aux communautés nordiques. Au Canada, la région arctique est caractérisée par une géographie archipélagique et un réseau de transport rudimentaire. Le transport maritime est le mode privilégié pour l’acheminement du fret aux communautés et aux sites industriels de l’Arctique. La littérature scientifique présente des lacunes importantes au sujet de la navigation commerciale dans l’Arctique canadien. Peu d’études portent sur le trafic de ravitaillement en raison de son volume peu élevé et de la faible diversité des types de produits transportés, bien qu’il s’agisse d’une activité grandement significative pour les populations et l’économie du Nord. Cette recherche vise à combler cette lacune en dressant un portrait du transport maritime et de la performance des opérations portuaires dans l’Arctique canadien. L’étude est structurée en quatre parties. Une analyse du trafic et des échanges maritimes est d’abord réalisée sous trois échelles : internationale, nationale et intra-arctique. Ensuite, l’étude de la flotte et des routes fait ressortir la distribution géographique des transporteurs. Puis, la performance des ports est mesurée grâce à des indicateurs et un système de cotation. Finalement, une évaluation des opérations maritimes arctiques est menée par l’entremise d’informations récoltées lors d’entrevues avec les membres de l’industrie maritime, de conférences et de travail de terrain. Les sujets abordés concernent l’évolution de la desserte, les défis posés par la navigation en milieu arctique et le développement des ports du Nord canadien. Les résultats de l’étude mènent à la conclusion que le transport maritime dans l’Arctique est caractérisé par une croissance positive du volume acheminé et une implication profonde des transporteurs dédiés à la desserte nordique, mais des infrastructures portuaires et maritimes sous-développées. / Climate change brings deep transformations in the Arctic environment. The reduction of the ice cover allows better access to northern communities and natural resources. In Canada, the Arctic region is characterized by an archipelagic geography and undeveloped transportation network. Marine transport is the favoured mode for supplying freight to local communities and industrial sites. The scientific literature shows important gaps on commercial navigation in the Canadian Arctic. Few studies have been conducted on marine traffic in the Arctic due to small tonnage and low product diversity, even though it is a significant activity for the northern people and the regional economy. This research aims to fill this gap by assessing maritime transportation and port operation efficiency in the Canadian Arctic. The structure of this study is four fold. First, a traffic and trade analysis is conducted under three scales: international, national and intra-arctic. Second, a fleet and routing assessment is done by means of carriers’ geographic distribution. Third, port performance is measured through specific indicators. Fourth, an evaluation is held on arctic marine operations through information collected during interviews with members of the maritime industry, workshops and field work. Problems addressed regard evolution of the sealift, challenges brought by Arctic navigation and development of northern Canadian ports. Results of this research lead to the conclusion that Arctic marine transportation displays positive traffic growth and serious involvement by carriers dedicated to Arctic sealift, but under-developed port and maritime infrastructures.

The topic of this master thesis is the international legal regulation of the protection of marine mammals. The thesis concentrates primarily on the analysis of the species based international law instruments for the protection of the individual marine mammal species. This thesis is divided into six chapters. The first chapter addresses the main principles of the international environmental law, which have the biggest influence on the protection of marine mammals (biodiversity protection, precautionary principle and sustainable development). The second chapter describes the regulation of fisheries, which is closely related to the protection of marine mammals. This part deals with the historical beginning of the international regulation of fisheries, the UN Convention on the Law of the Sea, the division of the sea areas, regulation of individual fish species and the regulation of fisheries after the UNCLOS. The particular instruments of protection of individual species of marine mammals except Cetaceans are described in the third chapter (i.e. polar bears, Pinnipeds and Sirenidae). The protection of Cetaceans is analyzed in detail in the fourth chapter. The protection of whales on the ground of International Whaling Commission is accented. This chapter describes also the standpoint of the whaling countries...