Dissertations / Theses on the topic 'Supported cluster'

Le reformage catalytique vise à transformer les naphtas en aromatiques à haut indice d'octane et à produire simultanément du dihydrogène. Le catalyseur utilisé est composé d’agrégats sub-nanométriques à base de platine hautement dispersées sur un support d’alumine-gamma dont le comportement en réaction pose de nombreuses questions. Nous étudions expérimentalement et théoriquement une réaction modèle qui sonde les sites métalliques, la déshydrogénation du methyl-cyclohexane en toluène. Une compréhension détaillée à l'échelle atomique des mécanismes impliqués et des paramètres cinétiques est nécessaire. Nous avons mise en œuvre des calculs DFT (PBE et PBE-dDsC) sur un modèle pertinent Pt13/alumine-gamma, afin de déterminer les intermédiaires, les états de transition et leurs enthalpies libres. Le mécanisme a été exploré via des étapes séquentielles de rupture des liaisons C-H. Une reconstruction des agrégats se produit le long du chemin réactionnel, mettant en évidence sa fluctionalité (confirmée par dynamique moléculaire). Les enthalpies libres d’activation de la rupture C-H, de migration d’hydrogène et de reconstruction de l’agrégat ont été systématiquement déterminées à T=625 K. L'enthalpie libre la plus élevée (ΔrG‡=95 kJ/mol) est trouvée pour la troisième rupture de liaison C-H sur le methyl-cyclohexène. L'intermédiaire le plus stable est le produit adsorbé {toluène+H2}. Cependant, d’autres étapes de rupture C-H ou de désorption du toluène sont compétitives. Les constantes de vitesse des étapes élémentaires obtenues par DFT sont introduites dans 8 modèles cinétiques différents de type Langmuir-Hinshelwood (LH). La nature de l'étape déterminante de la vitesse a été choisie en fonction des constantes de vitesse de chaque étape élémentaire individuelle, ou de la prise en compte de séquences d’étapes limitantes, grâce à une analyse de type « energetic span ». Nous avons finalement expérimentalement réalisé des tests catalytiques sur Pt/γ-alumine (0.3 wt% Pt) à différentes températures, temps de contact, pressions partielles d’hydrogène et de méthylcyclohexane, pour obtenir des données cinétiques expérimentales. L'enthalpie d'activation apparente de 196 kJ/mol calculée par l’un des meilleurs modèles LH (3ème rupture C-H limitante) est proche de l’expérience (195 kJ/mol). De plus, l’évolution des vitesses de réaction en fonction des pressions partielles d'hydrogène et de méthylcyclohexane est discutée au regard de l’expérience et des modèles. Même si les tendances sont recouvrées par les modèles, des écarts théorie-expérience sont mis au jour, ce qui ouvre des perspectives vers une modélisation microcinétique future<br>Catalytic reforming aims at transforming naphta into high octane aromatics and producing simultaneously dihydrogen. The catalyst used is composed of platinum-based sub-nanometric clusters highly dispersed on a gamma-alumina support which behavior under reaction conditions is the subject of numerous questions. We investigate experimentally and theoretically one model reaction probing the metal sites, the dehydrogenation of methyl-cyclohexane into toluene. A detailed atomic scale understanding of the mechanisms involved, and their related kinetic parameters, is required. We undertook DFT calculations with PBE and PBE-dDsC functionals on a relevant Pt13/γ-alumina model, in order to determine the intermediates, transition states and their free energies. The reaction mechanism was explored by assuming sequential C-H breaking steps. Reconstructions of the cluster and hydrogen migrations occur along the reaction pathway, highlighting its high fluctionality (also confirmed by molecular dynamics). Free energies of activation for C-H bond breaking, H migration and cluster’s reconstruction were systematically determined at T=625 K. The highest activation Gibbs free energy (ΔrG‡=95 kJ/mol) is found for the third C-H bond breaking on methyl-cyclohexene, while the most stable intermediate is the {toluene+H2} adsorbed product. However, other C-H bond breaking steps and eventually toluene desorption may compete. A comparison with the Pt (111) surface is also given. Rate constants of elementary steps estimated by DFT are introduced in 8 Langmuir-Hinshelwood (LH) kinetic models based on a single rate determining step (RDS) concept, or on a limiting steps sequence deduced from an energetic span analysis. We finally carried out experimental tests on Pt/γ-alumina catalysts (0.3 wt% Pt) at various temperatures, space times, hydrogen and methyl-cyclohexane partial pressures, to provide experimental kinetic data. The calculated apparent activation enthalpy is predicted to be 196 kJ/mol in close agreement with the experimental one (195 kJ/mol) for the best LH model (third C-H bond breaking as RDS). Moreover, the dependence of reaction rates on hydrogen and methyl-cyclohexane partial pressures are discussed with respect to experimental trends and models. Although the main trends are recovered by the kinetic model, some discrepancies are revealed. This work paves the way for a future microkinetic modeling

Record high CO2 emissions in the atmosphere and the need to find alternative energy sources to fossil fuels are major global challenges. Conversion of CO2 into useful fuels like methanol and methane can in principle tackle both these environment and energy concerns. One of the routes to convert CO2 into useful fuels is by using supported metal catalyst. Specifically, metal atoms or clusters (few atoms large in size) supported on oxide materials are promising catalysts. Experiments have successfully converted CO2 to products like methanol, using TiO2 supported Cu atoms or clusters. How this catalyst works and how CO2 conversion could be improved is an area of much research. We used a quantum mechanical tool called density functional theory (DFT) to obtain atomic and electronic level insights in the CO2 reduction processes on TiO2 supported metal atoms and clusters. We modeled small Cu clusters on TiO2 surface, which are experimentally synthesizable. Our results show that the interfacial sites in TiO2 supported Cu are able to activate CO2 into a bent configuration that can be further reduced. The Cu dimer was found to be the most reactive for CO2 activation but were unstable catalysts. Following Cu, we also identified other potential metal atoms that can activate CO2. Compared to expensive and rare elements like Pt, Au, and Ir, we found several early and mid transition metals to be potentially active catalysts for CO2 reduction. Because the supported metal atom or cluster is a reactive catalyst, under reaction conditions they tend to undergo aggregation and/or oxidation to form larger less active catalysts. We chose Co, Ni, and Cu group elements to study their catalyst stability under oxidizing reaction conditions. Based on the thermodynamics of Cu oxidation and kinetics of O2 dissociation, we found that TiO2 supported Cu atom or a larger Cu tetramer cluster were the likely species observed in experiments. Our work provides valuable atomic-level insights into improving the CO2 reduction activities and predicts potential catalysts for CO2 reduction to valuable fuels.

The graphene moiré superstructure formed on Ru(0001) (g/Ru(0001)) has shown the potential as a template to self-assemble super-lattices of metal nanoparticles as model catalysts. To explore the possibility of rational catalyst design on g/Ru(0001), detailed density functional theory (DFT) calculations have been performed to investigate the adsorption and diffusion of Rh and Au adatoms on g/Ru(0001). The consequences of different hopping rates for cluster nucleation have been explored by performing Monte Carlo-based statistical analysis, which suggests that diffusing species other than adatoms need to be taken into account to develop an accurate description of cluster nucleation and growth on this surface. DFT calculations have also been carried out to investigate the adsorption and diffusion of 18 4d (Y-Ag) and 5d (La-Au) transition metal adatoms on g/Ru(0001). Given the necessity to study larger diffusing species than adatoms, DFT calculations have been performed to study the adsorption and diffusion of Rh and Au dimers and trimers on g/Ru(0001). It was shown that the mobility of Rh clusters decreases with the increase of cluster size, while for Au, dimers diffuse faster than monomers and trimers on the moiré surface. We then used a genetic algorithm combined with DFT calculations to predict the lowest energy structure of a Au8 cluster on g/Ru(0001). Our prediction leads us to propose that Au clusters aggregates through Oswald ripening with Au dimer being the major diffusing species. Finally, we examined the morphology of a Cu19 cluster on g/Cu(111) using MD simulations with COMB3 potential. We also studied the mobility of Cu clusters on g/Cu(111) at elevated temperatures. The analysis suggests that g/Cu(111) may not be a suitable substrate for the formation and growth of isolated Cu clusters. All these calculation results have provided us a better understanding and useful insights into the nucleation and growth mechanism of metal clusters on graphene moiré.

This thesis describes a series of calix[n]arene polynuclear transition metal and lanthanide complexes. Calix[4]arenes possess lower-rim polyphenolic pockets that are ideal for the complexation of various transition metal and lanthanide centres. Surprisingly however, with only a few exceptions, the coordination chemistry of p-tBucalix[ 4]arene (TBC[4]), p-tBu-calix[8]arene (TBC[8]) and p-tBuhomotrioxacalix[ 3]arene (TBOC[3]) with paramagnetic transition metal ions for the purpose of making and studying magnetically interesting molecules is unknown. Chapter two describes the reaction of TBC[4] with manganese salts in the presence of an appropriate base (and in some cases co-ligand) resulting in the formation of a family of calixarene-supported [MnIII 2MnII 2] clusters (1-7) that behave as Single-Molecule Magnets (SMMs). These are: [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)6]·2MeOH (1), [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)4(H2O)2]·4MeOH·2DMF (2), [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)6]·2.8MeOH (3), [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)4(EtOH)(H2O)] (4), [MnIII 2MnII 2(OH)2(TBC[4])2(DMSO)6]·2MeOH·2DMSO (5) , [MnIII 2MnII 2(OH)2(TBC[4])2(DMSO)6] (6) and [MnIII 2MnII 2(OH)2(C[4])2(MeOH)6]·4MeOH (7). Variation in the alkyl groups present at the upper-rim of the cone allows for the expression of a degree of control over the self-assembly of these SMM building blocks, whilst retaining the general magnetic properties. The presence of various different ligands around the periphery of the magnetic core has some effect over the extended self-assembly of these SMMs. Chapter three describes how the combination of complementary cluster ligands; sodium phenylphosphinate and the N,O-chelate 2-(hydroxy-methyl)pyridine (hmpH) with TBC[4] results in the formation of two new calixarene-supported clusters. This being an unusual [MnIIIMnII]2 dimer of dimers [MnIIIMnII(O2P(H)Ph)(DMF)2(MeOH)2]2 (8) and a ferromagnetic [Mn5] cage that displays the characteristic bonding modes of each support [MnIII 3MnII 2(OH)2(TBC[4])2(hmp)2(DMF)6](TBC[4]-H)·xDMF ·xH2O (9). Chapter four details how using oxacalix[3]arenes can tune the nature of the metal binding site, by introduction of ≥ 1 ethereal bridge. This results in Mn(II) rather than Mn(III) bonding in the phenolic pocket, and that these components self-assemble with additional Mn(II) and Mn(III) ions to form a [Mn10] supertetrahedron with an unusual oxidation state distribution, [MnII 6MnIII 4O4(TBOC[3])4(Cl)4(DMF)3]∙3.3H2O ∙ 1.5DMF (10). Chapter five introduces a family of lanthanide complexes formed using TBC[8]. Variation in the experimental conditions employed in the reaction of TBC[8] with lanthanide salts (LnX3) provides access to Ln1, Ln2, Ln4, Ln5, Ln6, Ln7 and Ln8 complexes, [Gd(TBC[8]-2H)Cl(DMSO)4]·MeCN·H2O·(DMSO)2·hex (11), [CeIV 4(TBC[8]-6H)2(μ3- O)2(DMF)4]·(DMF)5·hex·MeCN (12), [TbIII 5(TBC[8]-5H)(μ4-O)(μ3- OH)4Cl(DMSO)8(H2O)3]Cl3·(DMSO)2(hex)2 (13), [CeIV 6(TBC[8]-6H)2(μ4-O)2(μ2-OMe)4(μ2- O)2(DMF)4]·(DMF)6·hex (14), [Dy7(TBC[8]-7H)(TBC[8]-6H)(μ4-O)2(μ3-OH)2(μ2- OH)2(DMF)9]·(DMF)3 (15) and [Gd8(TBC[8]-7H)2(μ4-CO3)2(μ5-CO3)2(μ2-HCO2)2(DMF)8] (16), with all polymetallic clusters containing the common bi-nuclear lanthanide fragment. Closer inspection of the structures of the polymetallic clusters reveals that all but one (Ln8) are in fact based on metal octahedra or the building blocks of octahedra.

First principles theoretical studies based on a gradient-corrected density functional approach have been carried out on the atomic and electronic properties and oxidation of Pdn (n=1-7) clusters supported on the TiO2(110) surface. The studies are aimed to address some of the fundamental issues related to the properties of supported Pdn clusters used as catalysts in oxidation reactions. Of those issues are the following: What are the atomic structures of Pdn clusters on the TiO2 surface? Upon oxidation, do O atoms from a dissociated O2 molecule spill over onto the underlying TiO2 sup- port? How strongly does spillover oxygen bind? What is the microscopic mechanism for the experimentally observed strong metal support interaction (SMSI) state where the Pd catalyst becomes encapsulated by the surface? Is this related to spillover oxygen? How do the properties of the Pdn clusters change when the TiO2 surface is marked with oxygen vacancies? As will be shown, the ground state geometries of supported Pdn clusters are driven by competing effects including intra-cluster interactions favoring compact structures and cluster support interactions favoring geometries that flatten out in the TiO2(110) surface channel. When exposed to O2, a single Pd atom only activates the O-O bond while all other clusters energetically favor a broken O-O bond. For PdnO2 (n=2-7), while one O is adsorbed on the Pdn cluster, the second O spills over to a lattice Ti site binding at the Pd-Ti interface. The binding strength of these spillover atoms is calculated to be surprisingly high, which is identified to be a result of long-range ionic interactions between Pd and spilled over oxygen. When oxygen spills onto lattice Ti sites, composite TiO motifs are formed that can exchange sites with Pd atoms with a minimal energy, opening the pathway for Ti migration and strong metal support interactions. For the TiO2 surface with oxygen vacancies, clusters bound at the vacancy site possess atomic and electronic properties that resemble bulk palladium. The theoretical findings are compared with recent experiments and are believed to provide insight toward developing a fundamental understanding of supported Pdn clusters as oxidation catalysts.

This dissertation describes experimental investigations of deposited atomic clusters and of films of metal particles produced by cluster deposition on graphite. It consists of three chapters presenting a review of the addressed subjects, the experimental techniques, and a summary of the results. The main body of results is described in full in afourth chapter as research papers. A systematic study of the impact of metal cluster trimers on highly oriented pyrolitic graphite (HOPG) is investigated. The creation of defects at the surface of graphite is found to be independento f the masso f the atoms in the two typeso f clusters considered The electron energy loss spectroscopy (EELS) of collective electronic excitations (plasmons) in a film of silver particles is presented A weak positive dispersion of the plasmon mode is measured and exhibits a higher ftequency of the mode with parallel momentum close to zero than in Ag surfaces. The adsorption of cinnamaldehydeis examined on nanostructured palladium surfaces. The EELS spectrum of cinnamaldehyde adsorbed on palladium is presented, as well as that of condensed layers of cinnamaldehyde on HOPG. Findings of this thesis involve different physical and chemical properties of the cluster surface system with a view in using cluster deposition for practical applications such as the investigation of model catalysts.

Nanoclusters offer unique physical and chemical behaviour, with the possibility of fine-tuning size and structures. Detailed theoretical studies can extend our understanding of these complicated systems. In this research, a good balance between accuracy and computational cost in describing electronic structure was sought via a combined Empirical Potential (EP) - Density Functional Theory (DFT) method. Global optimisation searches were performed using the Birmingham Cluster Genetic Algorithm and Basin-Hopping Monte Carlo algorithm coupled with the semi-empirical Gupta potentials. The sensitivity of the potentials was further studied for various potential parameterisations. Exploration of Pd-Au, Pd-Pt and Ni-Al clusters evidence the polyicosahedra – decahedra – face-centered cubic transitions, but below 50 atoms, these motifs are energetically very competitive, which led to a detailed structural study for the 34- and 38-atom clusters, as a function of composition. A qualitatively good agreement between EP and DFT was found, with a prevalence towards coreshell Dh\(_3\)\(_4\) and TO\(_3\)\(_8\) structure for Pd-Au and Pd-Pt clusters. The performance of empirical calculations varies with composition. On an MgO support, Pd-Au clusters showed significant size and composition effects. Consistent with the available experimental findings, Pd atoms preferentially bind to the oxygen sites at the interface and good cluster-substrate epitaxy was observed.

Les simulations numériques ont négligé jusqu’ici l’influence du support de silice amorphe sur la structure des nanoparticules métalliques déposées car l’interaction métal-silice amorphe est faible. Toutefois les études expérimentales montrent un effet de troncature sur la structure des nanoparticules. L’idée de ce travail a donc été d’étudier l’influence de ce support sur la structure et la morphologie des nanoparticules d’argent au moyen de la modélisation moléculaire (Monte Carlo et dynamique moléculaire). L’objectif de ce travail a été tout d'abord de déterminer le potentiel interatomique permettant de décrire l’interaction argent-silice. Ce potentiel a été obtenu sur la base des données expérimentales d'angles de mouillages en phase liquide et en phase solide. D’autre part, l'intensité d'interaction argent-silice a été déterminée par calculs DFT sur la cristobalite qui est un polymorphe de la silice cristalline présentant la même densité que la silice amorphe. Les énergies d'adhésions obtenues ont ainsi permis d'ajuster les paramètres du potentiel argent-silice de type Lennard-Jones. L’étude de la stabilité structurale des nanoparticules d'argent supportées à température nulle a été effectuée pour trois degrés d'approximation du support. (1) : un support parfaitement lisse décrit par un puits carré dont la profondeur est reliée à l’énergie d’adhésion, (2) : un support atomique de silice amorphe de surface plane et (3) : un support atomique de silice amorphe présentant une rugosité de surface. L’influence de la température sur la structure a été étudiée par fusion et recristallisation des nanoparticules d’argent sur les deux supports de silice amorphe. Afin d’étudier la stabilité structurale des nanoparticules en température, le calcul d’énergie libre des nanoparticules a été abordé<br>Numerical simulations have so far neglected the influence of amorphous silica substrate on the structure of metallic nanoparticles due to its relatively weak interaction with deposited nanoparticles. However, experimental studies have often shown a truncation effect on the structure of nanoparticles. The idea of this work was to study the influence of this substrate on the structure of silver nanoparticles using molecular modeling (Monte Carlo and molecular dynamics). The objective of this work was firstly to determine silver-silica interatomic potential. This was achieved using experimental data of wetting angles in solid and liquid phase. On the other hand, silver-silica interaction intensity was determined by DFT calculations on cristobalite which is a polymorph of crystalline silica having the same density as amorphous silica. The adhesions energies obtained were used to fit the Lennard-Jones parameters for the silver-silica interaction. The study of the structural stability of silver nanoparticles supported at zero temperature was performed for three levels of approximation of the support. (1): the smooth wall approximation where the support is described by a square-well whose depth is related to the adhesion energy of the nanoparticle, (2): an atomistic model of flat amorphous silica, (3): an atomistic model of rough amorphous silica. The influence of the temperature on the structure was investigated by melting and recrystallization of the silver nanoparticles deposited on the two silica supports. In order to study the temperature stability of the nanoparticles the free energy calculation of the nanoparticles was discussed

This thesis describes in a first part the synthesis of new mixed-metal clusters of ruthenium in association with palladium, platinum and tin. The use of monometallic dichloro complexes of Pd or Pt in reactions with negatively charged penta- or hexaruthenium clusters in the presence of a chlorine scavenger has been moderately successful in the case of Pd, but highly successful in the case of Pt. High yields were obtained in many instances. The mixed clusters [Ru<SUB>5</SUB>C(CO)<SUB>14</SUB>Pt(COD)], [Ru<SUB>6</SUB>C(CO)<SUB>16</SUB>Pt(COD)], [Ru<SUB>6</SUB>C(CO)<SUB>15</SUB>(Pt(COD))<SUB>2</SUB>] and [{Ru<SUB>6</SUB>C(CO)<SUB>16</SUB>}<SUB>2</SUB>Pt(MeCN)<SUB>2</SUB>] were characterised by X-ray crystallography. On the other hand, the use of [Pt(PPh<SUB>3</SUB>)<SUB>4</SUB>] allowed the isolation and structure determination of [Ru<SUB>6</SUB>C(CO)<SUB>16</SUB>PPh<SUB>3</SUB>] rather than mixed species. The reactivity of [Ru<SUB>5</SUB>C(CO)<SUB>14</SUB>Pt(COD)] and [Ru<SUB>6</SUB>C(CO)<SUB>16</SUB>Pt(COD)] with CO, PPh<SUB>3</SUB> and dppm was investigated, and led to the isolation of other mixed-metal and homometallic compounds. The crystal structures of the clusters [Ru<SUB>5</SUB>C(CO)<SUB>11</SUB>Pt(CO)(dppm)<SUB>2</SUB>], [Ru<SUB>6</SUB>C(CO)<SUB>13</SUB>(dppm)<SUB>2</SUB>] and [Ru<SUB>6</SUB>C(CO)<SUB>16</SUB>Pt<SUB>3</SUB>(dppm)<SUB>2</SUB>] were determined. Several Ru-Sn mixed clusters were also synthesised, and in particular reactions involving [PPN]<SUB>2</SUB>[Ru<SUB>6</SUB>C(CO)<SUB>16</SUB>] and SnCl<SUB>4</SUB> led to the isolation of [PPN][Ru<SUB>6</SUB>C(CO)<SUB>16</SUB>SnCl<SUB>3</SUB>] and [Ru<SUB>6</SUB>C(CO)<SUB>16</SUB>SnCl<SUB>2</SUB>], which were characterised crystallographically. In a second part, some of the new mixed-metal clusters were used as precursors for nanoparticle heterogeneous catalysts, using the mesoporous silica MCM-41 or carbon nanotubes as supports. A Ru-Pd/MCM-41 catalyst derived from a Pd<SUB>6</SUB>Ru<SUB>6</SUB> cluster was shown to be extremely active for the hydrogenation of alkenes to alkanes and of naphthalene to <I>cis-</I>decalin selectively. This material was characterised by STEM and <I>in situ</I> FTIR and EXAFS, which confirmed the bimetallic nature of the nanoparticles and their homogeneous small sizes and dispersion on the support. The shape of the nanoparticles was further assessed by theoretical calculations. A Ru-Sn/MCM-41 catalyst was prepared from [PPN][Ru<SUB>6</SUB>C(CO)<SUB>16</SUB>SnCl<SUB>3</SUB>] and shown to hydrogenate selectively cyclic poly-enes to their mono-enes, under solvent-free and low temperature conditions. This catalyst was also characterised by STEM and <I>in situ</I> FTIR and EXAFS, which indicated that the tin atom is the anchoring point for the bimetallic nanoparticles on the siliceous walls of MCM-41. Finally, the clusters [Ru<SUB>5</SUB>C(CO)<SUB>14</SUB>Pt(COD)], [Ru<SUB>6</SUB>C(CO)<SUB>16</SUB>Pt(COD)], [PPN][Ru<SUB>6</SUB>C(CO)<SUB>16</SUB>SnCl<SUB>3</SUB>] and [Ru<SUB>6</SUB>C(CO)<SUB>16</SUB>SnCl<SUB>2</SUB>] were used as ideal precursors for small-sized and evenly dispersed bimetallic nanoparticles supported on carbon nanotubes.

This thesis describes the preparation and study of a wide range of supported gold catalysts based on atomically-precise triphenyl phosphine stabilised gold clusters. This selected range of ligand-stabilised gold clusters were prepared in attempt to study the effect of increasing cluster nuclearity on the electronic and catalytic properties of these materials. A novel far-infrared study was conducted on the pure cluster materials in attempt to understand the metal-metal and the metal–ligand vibrations, which was also compared to the simulated spectra for each cluster. The design and activation of these novel catalysts based on gold clusters was discussed and the factors that influence activity were described. A comprehensive photoelectron study of the catalysts was conducted in an attempt to understand the electronic structure of the supported gold clusters and the effect of various activation conditions have on the electronic structure of the gold clusters. A selection of the prepared supported gold catalysts were tested for their catalytic activity for the partial oxidation of styrene and the influence of the several activation conditions on the reactivity of the catalyst is also examined. In collaboration, the application of a selection of ligand-stabilised gold clusters as hydrogen sensors and as catalysts for the photocatalytic generation of hydrogen from ethanol is also investigated.

There was an increase in a number of applications for a master degree program with the growth in time. It takes huge time to process all the application documents of each and every applicant manually and requires a high volume of the workforce. This can be reduced if automation is used for this process. In any case, before that, an analysis of the complete strides required in preparing was precisely the automation must be utilized to diminish the time and workforces must be finished. The application process for the applicant is actually participating in several steps. First, the applicant sends the complete scanned documents to the uni-assist; from there the applications are received by the student assistant team at the particular university to which the applicant had applied, and then they are sent to the individual departments. At the individual sections, the individual applications will be handled by leading an intensive study to know whether the applicant by their past capabilities scopes to satisfy the prerequisites of further study system to which they have applied. What's more, by considering the required points of interest of the applicant without investigating every single report, and to pack the information and diminish the preparing time for the specific division, by this postulation extend a solitary web apparatus is being produced that can procedure the application which is much dependable in the basic leadership procedure of application.

nÃo hÃ<br>This study includes an ex post evaluation of the project Local Productive Arrangement Limestone Cariri. The evaluation of public projects, especially those of a socio-economic focused on disadvantaged communities, closed conceptual difficulties, technical and methodological rides, generators, often, conflicts and frustrations that discourage its systematic implementation. The main objective of this study is to evaluate the project developed by the Federal and State of Cearà governments, whose main goal was to develop a comprehensive action in the production chain of stone Cariri acting on factors that affect their technological development and competitiveness of micro and small enterprises that constitute it. For this literature review was performed on the basis of theoretical frameworks relating to Local Production and Public Policy reviews and field research with the target audience of the project to support the APL Stone Cariri, in order to assess the achievements of implementation of the project and seek to understand the process by which the project achieved or not their goals. In the field research were applied questionnaires to the chain, addressing the 16 targets in the project to support the APL, to investigate the perception of the actors concerning the results presented in the final project report. The results of field research indicate weaknesses in project implementation, particularly regarding the need for greater interaction with the audience, as well as the excessive number of targets in various aspects of the APL, which ultimately undermine the effectiveness of the project. Finally, we present the conclusions and suggestions to be followed in future projects, aiming to achieve the effectiveness of public policies managed.<br>Este estudo contempla uma avaliaÃÃo ex post do projeto Arranjo Produtivo Local CalcÃrios do Cariri. A avaliaÃÃo de projetos pÃblicos, principalmente aqueles de cunho sÃcio-econÃmicos voltados para comunidades menos favorecidas, encerra dificuldades conceituais, tÃcnicas e metodolÃgicas de monta, geradoras, nÃo raro, de conflitos e frustraÃÃes que desestimulam a sua realizaÃÃo sistemÃtica. O objetivo maior desse trabalho à avaliar o projeto desenvolvido pelos governos Federal e Estadual atravÃs do Centro de Tecnologia Mineral e Secretaria de CiÃncia e Tecnologia do Estado do Cearà respectivamente, cujo principal objetivo era o de desenvolver uma ampla aÃÃo na cadeia produtiva da pedra Cariri, atuando sobre fatores que afetam seu desenvolvimento tecnolÃgico e a competitividade das micro e pequenas empresas que a constituem. Para tanto foi realizada pesquisa bibliogrÃfica com base nos referenciais teÃricos relativos a Arranjos Produtivos Locais e AvaliaÃÃes de PolÃticas PÃblicas, realizou-se ainda pesquisa de campo junto ao pÃblico alvo do projeto de apoio ao APL da Pedra Cariri, com a finalidade de aferir os resultados alcanÃados pela implementaÃÃo do projeto e compreender o processo pelo qual o projeto alcanÃou ou nÃo os seus objetivos. Na pesquisa de campo foram aplicados questionÃrios aos produtores da cadeia produtiva, abordando as 16 metas estabelecidas no projeto de apoio ao APL, no sentido de averiguar a percepÃÃo destes atores acerca dos resultados apontados no relatÃrio final do projeto. Os resultados da pesquisa de campo apontam fragilidades na execuÃÃo do projeto, notadamente, quanto à necessidade de uma maior interaÃÃo com o pÃblico alvo, bem como ao excessivo nÃmero de metas estabelecidas nos mais variados aspectos do APL, que acabaram por comprometer a efetividade do projeto. Por fim sÃo apresentadas as conclusÃes e sugestÃes a serem observadas em projetos futuros, visando alcanÃar a efetividade das polÃticas pÃblicas manejadas.

This dissertation is focused on understanding heterogeneous metal catalysts supported on oxides using a model catalyst system of SiO2 thin film supported metal nano-clusters. The primary technique applied to this study is scanning tunneling microscopy (STM). The most important constituent of this model catalyst system is the SiO2 thin film, as it must be thin and homogeneous enough to apply electron or ion based surface science techniques as well as STM. Ultra-thin SiO2 films were successfully synthesized on a Mo(112) single crystal. The electronic and geometric structure of the SiO2 thin film was investigated by STM combined with LEED, Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The relationship between defects on the SiO2 thin film and the nucleation and growth of metal nano-clusters was also investigated. By monitoring morphology changes during thermal annealing, it was found that the metal-support interaction is strongly dependent on the type of metal as well as on the defect density of the SiO2 thin film. Especially, it was found that oxygen vacancies and Si impurities play an important role in the formation of Pd-silicide. By substituting Ti atoms into the SiO2 thin film network, an atomically mixed TiO2-SiO2 thin film was synthesized. Furthermore, these Ti atoms play a role as heterogeneous defects, resulting in the creation of nucleation sites for Au nano-clusters. A marked increase in Au cluster density due to Ti defects was observed in STM. A TiO2-SiO2 thin film consisting of atomic Ti as well as TiOx islands was also synthesized by using higher amounts of Ti (17 %). More importantly, this oxide surface was found to have sinter resistant properties for Au nano-clusters, which are desirable in order to make highly active Au nano-clusters more stable under reaction conditions.

This diploma thesis will show how mutual cooperation of small and medium businesses in a tourism cluster can increase promotion and revenue in the tourism industry. Theoretical part of this study presents definitions, characteristics and typology of clusters. Later on, the theoretical part describes practices in the mapping of clusters and a cluster's lifecycle. The last chapters will summarize the benefits of clusters to its stakeholders and means of financing and program support via EU grants. Practical part is focused on the strategy of a tourism cluster in the Central Bohemian region of the Czech Republic. This strategy also includes useful examples of how the cluster members can actively and effectively participate in managing mutual activities and projects. Operations, organizational structure, finance and support are also topics that are going to be discussed in this study.

Modern applications are increasingly backed by large-scale data centres. Systems software in these data centre environments, however, faces substantial challenges: the lack of uniform resource abstractions makes sharing and resource management inefficient, infrastructure software lacks end-to-end access control mechanisms, and work placement ignores the effects of hardware heterogeneity and workload interference. In this dissertation, I argue that uniform, clean-slate operating system (OS) abstractions designed to support distributed systems can make data centres more efficient and secure. I present a novel distributed operating system for data centres, focusing on two OS components: the abstractions for resource naming, management and protection, and the scheduling of work to compute resources. First, I introduce a reference model for a decentralised, distributed data centre OS, based on pervasive distributed objects and inspired by concepts in classic 1980s distributed OSes. Translucent abstractions free users from having to understand implementation details, but enable introspection for performance optimisation. Fine-grained access control is supported by combining storable, communicable identifier capabilities, and context-dependent, ephemeral handle capabilities. Finally, multi-phase I/O requests implement optimistically concurrent access to objects while supporting diverse application-level consistency policies. Second, I present the DIOS operating system, an implementation of my model as an extension to Linux. The DIOS system call API is centred around distributed objects, globally resolvable names, and translucent references that carry context-sensitive object meta-data. I illustrate how these concepts support distributed applications, and evaluate the performance of DIOS in microbenchmarks and a data-intensive MapReduce application. I find that it offers improved, finegrained isolation of resources, while permitting flexible sharing. Third, I present the Firmament cluster scheduler, which generalises prior work on scheduling via minimum-cost flow optimisation. Firmament can flexibly express many scheduling policies using pluggable cost models; it makes high-quality placement decisions based on fine-grained information about tasks and resources; and it scales the flow-based scheduling approach to very large clusters. In two case studies, I show that Firmament supports policies that reduce colocation interference between tasks and that it successfully exploits flexibility in the workload to improve the energy efficiency of a heterogeneous cluster. Moreover, my evaluation shows that Firmament scales the minimum-cost flow optimisation to clusters of tens of thousands of machines while still making sub-second placement decisions.

Today, large public investments are being made with the aim of creating and developing cooperation between businesses in inter-organizational networks. Such initiatives are commonly denoted cluster initiatives and their underlying purpose are to spur innovation and regional growth. Much research has been conducted in this field, but relatively few studies have examined the process of cluster initiatives. By following the case of a regional cluster project within the tourism industry in the region of Dalarna, Sweden, the objective of this thesis is to deepen the understanding of the formation and development process of cluster initiatives. The investigation has been conducted by examining two main themes; the internal relationships within the cluster initiative and the relationships between the cluster initiative and its external stakeholders, such as funding agencies, regional government and local businesses. The analysis is based on a legitimacy perspective and indicates that the coordinating body of the cluster initiative, the hub, principally deals with a legitimation process. What occurs within the cluster initiative, between the members themselves and between the members and the hub, is legitimation. This also applies to external relationships, between the hub and its external stakeholders. A prerequisite for the realization of its mission is that the hub obtain and sustain legitimacy; legitimacy for itself, for the other members, for the idea, for the different activities and for the industry as such.

The use of asymmetric multi-core processors with on-chip computational accelerators is becoming common in a variety of environments ranging from scientific computing to enterprise applications. The focus of current research has been on making efficient use of individual systems, and porting applications to asymmetric processors. The use of these asymmetric processors, like the Cell processor, in a cluster setting is the inspiration for the Cell Connector framework presented in this thesis. Cell Connector adopts a streaming approach for providing data to compute nodes with high computing potential but limited memory resources. Instead of dividing very large data sets once among computation resources, Cell Connector slices, distributes, and collects work units off of a master data held by a single large memory machine. Using this methodology, Cell Connector is able to maximize the use of limited resources and produces results that are up to 63.3\% better compared to standard non-streaming approaches.<br>Master of Science

Durant les últimes tres dècades, les limitacions tecnològiques (com per exemple la capacitat dels dispositius d'emmagatzematge o l'ample de banda de les xarxes de comunicació) i les creixents demandes dels usuaris (estructures d'informació, volums de dades) han conduït l'evolució de les bases de dades distribuïdes. Des dels primers repositoris de dades per arxius plans que es van desenvolupar en la dècada dels vuitanta, s'han produït importants avenços en els algoritmes de control de concurrència, protocols de replicació i en la gestió de transaccions. No obstant això, els reptes moderns d'emmagatzematge de dades que plantegen el Big Data i el cloud computing—orientats a millorar la limitacions pel que fa a escalabilitat i elasticitat de les bases de dades estàtiques—estan empenyent als professionals a relaxar algunes propietats importants dels sistemes transaccionals clàssics, cosa que exclou a diverses aplicacions les quals no poden encaixar en aquesta estratègia degut a la seva alta dependència transaccional. El propòsit d'aquesta tesi és abordar dos reptes importants encara latents en el camp de les bases de dades distribuïdes: (1) les limitacions pel que fa a escalabilitat dels sistemes transaccionals i (2) el suport transaccional en repositoris d'emmagatzematge en el núvol. Analitzar les tècniques tradicionals de control de concurrència i de replicació, utilitzades per les bases de dades clàssiques per suportar transaccions, és fonamental per identificar les raons que fan que aquests sistemes degradin el seu rendiment quan el nombre de nodes i / o quantitat de dades creix. A més, aquest anàlisi està orientat a justificar el disseny dels repositoris en el núvol que deliberadament han deixat de banda el suport transaccional. Efectivament, apropar el paradigma de l'emmagatzematge en el núvol a les aplicacions que tenen una forta dependència en les transaccions és fonamental per a la seva adaptació als requeriments actuals pel que fa a volums de dades i models de negoci. Aquesta tesi comença amb la proposta d'un simulador de protocols per a bases de dades distribuïdes estàtiques, el qual serveix com a base per a la revisió i comparativa de rendiment dels protocols de control de concurrència i les tècniques de replicació existents. Pel que fa a la escalabilitat de les bases de dades i les transaccions, s'estudien els efectes que té executar diferents perfils de transacció sota diferents condicions. Aquesta anàlisi contínua amb una revisió dels repositoris d'emmagatzematge de dades en el núvol existents—que prometen encaixar en entorns dinàmics que requereixen alta escalabilitat i disponibilitat—, el qual permet avaluar els paràmetres i característiques que aquests sistemes han sacrificat per tal de complir les necessitats actuals pel que fa a emmagatzematge de dades a gran escala. Per explorar les possibilitats que ofereix el paradigma del cloud computing en un escenari real, es presenta el desenvolupament d'una arquitectura d'emmagatzematge de dades inspirada en el cloud computing la qual s’utilitza per emmagatzemar la informació generada en les Smart Grids. Concretament, es combinen les tècniques de replicació en bases de dades transaccionals i la propagació epidèmica amb els principis de disseny usats per construir els repositoris de dades en el núvol. Les lliçons recollides en l'estudi dels protocols de replicació i control de concurrència en el simulador de base de dades, juntament amb les experiències derivades del desenvolupament del repositori de dades per a les Smart Grids, desemboquen en el que hem batejat com Epidemia: una infraestructura d'emmagatzematge per Big Data concebuda per proporcionar suport transaccional en el núvol. A més d'heretar els beneficis dels repositoris en el núvol en quant a escalabilitat, Epidemia inclou una capa de gestió de transaccions que reenvia les transaccions dels clients a un conjunt jeràrquic de particions de dades, cosa que permet al sistema oferir diferents nivells de consistència i adaptar elàsticament la seva configuració a noves demandes de càrrega de treball. Finalment, els resultats experimentals posen de manifest la viabilitat de la nostra contribució i encoratgen als professionals a continuar treballant en aquesta àrea.<br>Durante las últimas tres décadas, las limitaciones tecnológicas (por ejemplo la capacidad de los dispositivos de almacenamiento o el ancho de banda de las redes de comunicación) y las crecientes demandas de los usuarios (estructuras de información, volúmenes de datos) han conducido la evolución de las bases de datos distribuidas. Desde los primeros repositorios de datos para archivos planos que se desarrollaron en la década de los ochenta, se han producido importantes avances en los algoritmos de control de concurrencia, protocolos de replicación y en la gestión de transacciones. Sin embargo, los retos modernos de almacenamiento de datos que plantean el Big Data y el cloud computing—orientados a mejorar la limitaciones en cuanto a escalabilidad y elasticidad de las bases de datos estáticas—están empujando a los profesionales a relajar algunas propiedades importantes de los sistemas transaccionales clásicos, lo que excluye a varias aplicaciones las cuales no pueden encajar en esta estrategia debido a su alta dependencia transaccional. El propósito de esta tesis es abordar dos retos importantes todavía latentes en el campo de las bases de datos distribuidas: (1) las limitaciones en cuanto a escalabilidad de los sistemas transaccionales y (2) el soporte transaccional en repositorios de almacenamiento en la nube. Analizar las técnicas tradicionales de control de concurrencia y de replicación, utilizadas por las bases de datos clásicas para soportar transacciones, es fundamental para identificar las razones que hacen que estos sistemas degraden su rendimiento cuando el número de nodos y/o cantidad de datos crece. Además, este análisis está orientado a justificar el diseño de los repositorios en la nube que deliberadamente han dejado de lado el soporte transaccional. Efectivamente, acercar el paradigma del almacenamiento en la nube a las aplicaciones que tienen una fuerte dependencia en las transacciones es crucial para su adaptación a los requerimientos actuales en cuanto a volúmenes de datos y modelos de negocio. Esta tesis empieza con la propuesta de un simulador de protocolos para bases de datos distribuidas estáticas, el cual sirve como base para la revisión y comparativa de rendimiento de los protocolos de control de concurrencia y las técnicas de replicación existentes. En cuanto a la escalabilidad de las bases de datos y las transacciones, se estudian los efectos que tiene ejecutar distintos perfiles de transacción bajo diferentes condiciones. Este análisis continua con una revisión de los repositorios de almacenamiento en la nube existentes—que prometen encajar en entornos dinámicos que requieren alta escalabilidad y disponibilidad—, el cual permite evaluar los parámetros y características que estos sistemas han sacrificado con el fin de cumplir las necesidades actuales en cuanto a almacenamiento de datos a gran escala. Para explorar las posibilidades que ofrece el paradigma del cloud computing en un escenario real, se presenta el desarrollo de una arquitectura de almacenamiento de datos inspirada en el cloud computing para almacenar la información generada en las Smart Grids. Concretamente, se combinan las técnicas de replicación en bases de datos transaccionales y la propagación epidémica con los principios de diseño usados para construir los repositorios de datos en la nube. Las lecciones recogidas en el estudio de los protocolos de replicación y control de concurrencia en el simulador de base de datos, junto con las experiencias derivadas del desarrollo del repositorio de datos para las Smart Grids, desembocan en lo que hemos acuñado como Epidemia: una infraestructura de almacenamiento para Big Data concebida para proporcionar soporte transaccional en la nube. Además de heredar los beneficios de los repositorios en la nube altamente en cuanto a escalabilidad, Epidemia incluye una capa de gestión de transacciones que reenvía las transacciones de los clientes a un conjunto jerárquico de particiones de datos, lo que permite al sistema ofrecer distintos niveles de consistencia y adaptar elásticamente su configuración a nuevas demandas cargas de trabajo. Por último, los resultados experimentales ponen de manifiesto la viabilidad de nuestra contribución y alientan a los profesionales a continuar trabajando en esta área.<br>Over the past three decades, technology constraints (e.g., capacity of storage devices, communication networks bandwidth) and an ever-increasing set of user demands (e.g., information structures, data volumes) have driven the evolution of distributed databases. Since flat-file data repositories developed in the early eighties, there have been important advances in concurrency control algorithms, replication protocols, and transactions management. However, modern concerns in data storage posed by Big Data and cloud computing—related to overcome the scalability and elasticity limitations of classic databases—are pushing practitioners to relax some important properties featured by transactions, which excludes several applications that are unable to fit in this strategy due to their intrinsic transactional nature. The purpose of this thesis is to address two important challenges still latent in distributed databases: (1) the scalability limitations of transactional databases and (2) providing transactional support on cloud-based storage repositories. Analyzing the traditional concurrency control and replication techniques, used by classic databases to support transactions, is critical to identify the reasons that make these systems degrade their throughput when the number of nodes and/or amount of data rockets. Besides, this analysis is devoted to justify the design rationale behind cloud repositories in which transactions have been generally neglected. Furthermore, enabling applications which are strongly dependent on transactions to take advantage of the cloud storage paradigm is crucial for their adaptation to current data demands and business models. This dissertation starts by proposing a custom protocol simulator for static distributed databases, which serves as a basis for revising and comparing the performance of existing concurrency control protocols and replication techniques. As this thesis is especially concerned with transactions, the effects on the database scalability of different transaction profiles under different conditions are studied. This analysis is followed by a review of existing cloud storage repositories—that claim to be highly dynamic, scalable, and available—, which leads to an evaluation of the parameters and features that these systems have sacrificed in order to meet current large-scale data storage demands. To further explore the possibilities of the cloud computing paradigm in a real-world scenario, a cloud-inspired approach to store data from Smart Grids is presented. More specifically, the proposed architecture combines classic database replication techniques and epidemic updates propagation with the design principles of cloud-based storage. The key insights collected when prototyping the replication and concurrency control protocols at the database simulator, together with the experiences derived from building a large-scale storage repository for Smart Grids, are wrapped up into what we have coined as Epidemia: a storage infrastructure conceived to provide transactional support on the cloud. In addition to inheriting the benefits of highly-scalable cloud repositories, Epidemia includes a transaction management layer that forwards client transactions to a hierarchical set of data partitions, which allows the system to offer different consistency levels and elastically adapt its configuration to incoming workloads. Finally, experimental results highlight the feasibility of our contribution and encourage practitioners to further research in this area.

PROCESSAMENTO DE DADOS DO ESTADO DO PARÁ<br>O objetivo deste trabalho é estudar a integração de mecanismos de reserva de recursos computacionais em infra-estruturas de software para aglomerados de computadores. Para realizar esse estudo, foi utilizado o framework CSBase, que é uma infra-estrutura de software concebida com o intuito de dar apoio à implementação e integração de aplicações científicas em ambientes distribuídos e heterogêneos. O CSBase oferece suporte à execução de aplicações em ambientes distribuídos e ao gerenciamento de usuários e de recursos computacionais, tais como computadores, arquivos de dados e aplicações. Entretanto, as primeiras aplicações desenvolvidas com o CSBase já demonstraram que são necessários mecanismos que permitam um melhor gerenciamento e controle dos recursos computacionais disponíveis em ambientes distribuídos, e especialmente em aglomerados de computadores dedicados à execução de aplicações de alto desempenho. Neste trabalho, apresentamos uma extensão ao framework CSBase que possibilita a reserva de processador para aplicações de usuários do sistema, e assim permitindo um gerenciamento mais eficiente dos recursos computacionais disponíveis. Essa extensão também garante que serão efetuadas as adaptações necessárias para acomodar eventuais variações no perfil de uso do processador por parte das aplicações. Como resultado dessa extensão, obteve-se a integração entre a monitoração de recursos distribuídos, a iniciação remota de aplicações, e um mecanismo de reserva de processador que proporcionou uma melhor utilização das máquinas disponíveis.<br>The goal of this work is to study the integration of resource reservation mechanisms with software infrastructures for cluster computing. To perform this study, we used the CSBase framework, which is a software infrastructure conceived to support the implementation and integration of scientific applications in heterogeneous and distributed environments. CSBase offers support for application execution in distributed environments, as well as support for management of users and computational resources, such as computers, data files and applications. However, the first applications developed with CSBase showed that it requires mechanisms to allow a better management of resources available in distributed environments, and especially in clusters of computers dedicated to execute high performance applications. In this work, we present an extension to CSBase that provides the reservation of processor time to user applications, thus allowing a more efficient resource management. This extension also guarantees that all required adaptations will be performed to accommodate variations in the applications´ processor usage profile. As a result of this extension, we achieved the integration of mechanisms for distributed resource monitoring, remote application execution, and processor reservation, providing a better utilization among the available machines.

The main purpose of object-oriented programming is to use encapsulation to reduce the amount of coupling within each object. However, object-oriented programming has some weaknesses in this area. To address this shortcoming, researchers have proposed an approach known as aspect-oriented programming (AOP). AOP is intended to reduce the amount of tangled code within an application by grouping similar functions into an aspect. To demonstrate the powerful aspects of AOP, it is necessary to extract aspect candidates from current object-oriented applications. Many different approaches have been proposed to accomplish this task. One of such approaches utilizes vector based clustering to identify the possible aspect candidates. In this study, two different types of vectors are applied to two different vector-based clustering techniques. In this approach, each method in a software system S is represented by a d-dimensional vector. These vectors take into account the Fan-in values of the methods as well as the number of calls made to individual methods within the classes in software system S. Then a semi-supervised clustering approach known as Support Vector Clustering is applied to the vectors. In addition, an improved K-means clustering approach which is based on Genetic Algorithms is also applied to these vectors. The results obtained from these two approaches are then evaluated using standard metrics for aspect mining. In addition to introducing two new clustering based approaches to aspect mining, this research investigates the effectiveness of the currently known metrics used in aspect mining to evaluate a given vector based approach. Many of the metrics currently used for aspect mining evaluations are singleton metrics. Such metrics evaluate a given approach by taking into account only one aspect of a clustering technique. This study, introduces two different sets of metrics by combining these singleton measures. The iDIV metric combines the Diversity of a partition (DIV), Intra-cluster distance of a partition (IntraD), and the percentage of the number of methods analyzed (PAM) values to measure the overall effectiveness of the diversity of the partitions. While the iDISP metric combines the Dispersion of crosscutting concerns (DISP) along with Inter-cluster distance of a partition (InterD) and the PAM values to measure the quality of the clusters formed by a given method. Lastly, the oDIV and oDISP metrics introduced, take into account the complexity of the algorithms in relation with the DIV and DISP values. By comparing the obtained values for each of the approaches, this study is able to identify the best performing method as it pertains to these metrics.

The paper examines the views, often associated with Porter, that clusters with deep collaborative networks and established local supply chains have good performance. The view that good cluster performance is not connected to the industrial sector is also assessed. Data from a Department of Trade and Industry (DTI) study on UK clusters are used to assess the impact on performance (employment growth and international competitiveness) of cluster depth, the stage of development of local supply chains, and industrial sector. The results of the analysis of the DTI data on clusters do not provide strong support for Porter-type views on cluster policy. Although established clusters are linked to employment growth, deep clusters are not associated with employment growth or international competitiveness, and clusters in the services, and media, computer-related and biotechnology sectors are more likely than manufacturing clusters to have good performance. Some of the major policy implications of the results are discussed in the light of the literature on the importance of regional, national, and international networks for the performance of clusters.

This thesis covers a number of different aspects of chemistry including molecular inorganic chemistry, nanochemistry and heterogeneous catalysis. The key aspect of our research is a bottom-up approach towards generating gold nano-particulate heterogeneous catalysts. Two phosphine-stabilised gold clusters containing Au9 and Au13 cores were prepared and used as molecular precursors to tailor specific size of gold nanoparticles. A number of techniques were employed to characterise the clusters as well as the catalysts in order to follow the nano-particulate creation. The conventional incipient wetness impregnation (WI) method was used to deposit clusters onto SiO2 nanosphere and Al2O3 supports followed by high temperature calcination (300°C and 500°C) for catalyst activation. A highlight of this thesis is the development of the tert-butyl hydroperoxide (TBHP) assisted deposition-precipitation method towards producing smaller size of gold nano-particulate catalysts. Catalyst activation at relatively low temperatures (95°C) via the TBHP method minimised gold agglomeration, gold nanoparticles obtained by this method being < 10 nm in diameter. The relationship between catalytic activity and the size of clusters used as well as the catalyst preparation method (WI vs TBHP) was studied by liquid phase oxidation of benzyl alcohol. Higher turnover frequencies (TOF) were observed employing catalysts prepared via the TBHP method and proved to be recyclable up to at least six times with only minimal decrease in catalytic performance. Attempts had also been made to synthesise heterobimetallic gold-metal catalysts containing palladium and tin. The synthesis, characterisation and catalytic activity of both heterobimetallic catalysts are also reported.

Summary Background Elevated blood lipids (particularly cholesterol and sub-fractions) contribute to the risk of developing cerebral, peripheral and cardiovascular disease and associated complications which are leading causes of morbidity and death. Statins reduce the risk of suffering vascular events, with or without decreasing cholesterol levels. Statin prescribing continues to increase but there is scope to improve prescribing and dosing, particularly in primary care. However, there is insufficient empirical evidence to inform approaches to quality improvement. Methods Following pilot work, we designed a new model of primary care based pharmacist-led intervention for General Practitioners (GPs) and nurses. The aim of the intervention (called Statin Outreach Support, SOS) was to improve statin prescribing by GPs, in line with recent evidence, targeting patients at highest risk of suffering a vascular event. Eleven trained pharmacists worked in SOS allocated practices one day per week for a year. During this period, the pharmacist met three times with all GPs, all nurses and other practice staff. Between meetings, pharmacists used patient level clinical and prescribing data to identify eligible patients and help practices initiate, up-titrate the dose or switch to simvastatin 40mg where indicated. The effectiveness of SOS was tested in a prospective single blind cluster randomised controlled trial. Usual care (UC) practices received no pharmacist support during the study. With a mean of 1.7 years follow up, the study had over 90% power (at 5% significance) to detect a difference of 12% in the proportion of patients with controlled cholesterol after practices had received the SOS intervention. Results Thirty one practices were recruited from the UK’s largest Health Board area. At randomisation, 16 practices were allocated to the SOS intervention and 15 to UC with 4,040 patients included at baseline. Recruited practices showed few differences compared with invited, non participating practices. Practices and patients randomised to each arm of the study had similar distributions with respect to age, complications, cholesterol levels and statin prescribing. The mean age was 68 years; 53% male, 45% ischaemic aetiology. Fifty nine percent had no statin prescribed at baseline; only 51% had cholesterol controlled. Follow up included 7586 patients in 29 practices (one practice had disbanded between recruitment and randomisation and another practice dropped out). Compared with UC, the SOS intervention achieved the primary endpoint of increasing the proportion of patients prescribed Simvastatin 40mg with controlled cholesterol (SOS 44.9% vs. UC 27.9%; odds ratio 1.79 (95% CI: 1.61, 1.98), p< 0.001). Secondary endpoints were also improved in the SOS arm practices. The intervention effect was strong and consistent across most subgroups including a positive impact on patients from practices in areas of greater socioeconomic deprivation. Conclusion A pragmatic, new, complex intervention was developed, tested and shown to be effective in a cluster randomised controlled trial with good internal and external validity. If implemented on a wider scale, in practices with comparable characteristics and baseline prescribing, the SOS intervention has the potential to reduce the burden of vascular events for patients with vascular disease. This work provides a convincing evidence base for the role of pharmacists collaborating with primary care practices, to improve statin prescribing and drug based cholesterol management, for patients at highest risk of suffering vascular events.

Density functional theory (DFT) calculations have been performed to gain insight into the role of defects present on the surface of graphene and TiO₂ based supports on supported metal clusters. The clusters considered are a Pt₃₈ cluster and a bimetallic Pt₃₂Pd₆ alloy. The defects considered on graphene based supports are monovacancy defective graphene, OH and COOH functionalised graphene. The defects considered on TiO₂ based supports are a partially reduced TiO₂(110) surface with a surface oxygen bridge vacancy and hydroxylated TiO₂(110) surface with surface OH groups. The defect free graphene and TiO₂ surfaces were also considered. For both the Pt₃₈ and Pt₃₂Pd₆ cluster, and on both defect containing graphene and TiO₂ (except on hydroxylated TiO₂(110) surface) the binding of the clusters is enhanced relative to binding on the defect free supports. Enhanced binding at the defects imply that the clusters are bound strongly to the support and thus less likely to detach from the support material relative to binding on the defect free supports. Therefore, the defects may improve the durability of the catalyst by limiting particle detachment. The electronic properties of the cluster are modified differently depending on the identity of the defect present on the support. On the graphene based supports, OH functionalisation is expected to result in weaker binding energy of adsorbate molecules, whereas COOH functionalisation is expected to result in stronger binding energy of adsorbates for the supported Pt₃₈ cluster. This is due to different shifts in d-band centre of the facets on the cluster supported on these supports. Therefore, it can be expected that the Pt₃₈ cluster supported on OH functionalised graphene will be more tolerant to poison molecules. This is due to reduced binding strength of adsorbates on OH functionalised graphene compared to adsorption on COOH functionalised graphene. For the Pt₃₂Pd₆ cluster the OH and COOH functional groups do not appreciably modify the d-band centre of the facets available to reactants, and thus is expected not to significantly modify the binding strength of adsorbate molecules relative to binding on the free unsupported Pt₃₂Pd₆ cluster. The binding energy of adsorbate molecules on the Pt₃₈ cluster supported on defect containing TiO₂ is expected to be stronger than on the Pt₃₈ cluster supported on defective graphene based supports, due to higher extent of upward shift of the d-band centre of the exposed facets. The enhanced binding energy of adsorbates on the Pt₃₈ cluster supported on TiO₂ supports may be detrimental to catalyst durability and activity. This can be due to strong binding of poison molecules and reaction intermediates which maybe too strongly bound on the surface such that they cannot participate in further reaction steps. Overall it might turn out that the functionalised graphene based supports are better support materials over the TiO₂ based materials for particular reactions. The Nb-doped partially reduced TiO₂(110) surface attaches the Pt₃₂Pd₆ cluster strongly to the support compared to the functionalised graphene supports. Furthermore, the binding energy of adsorbate molecules is expected to be weaker on the Pt₃₂Pd₆ cluster supported on the Nbdoped partially reduced TiO₂(110) surface compared to the functionalised graphene supports. This might be beneficial as poison molecules may be weakly bound to the cluster resulting in high resistance to poisoning which can also have a positive effect on catalyst activity. In addition to enhancing binding of the cluster to the support and affecting the binding energy of adsorbates on the supported clusters, some of the defects can also alter the ordering pattern of Pd and Pt atoms within the Pt₃₂Pd₆ cluster. OH functionalised graphene and Nbdoped partially reduced TiO₂(110) surface result in segregation of Pd towards the clustersupport interface, thereby exposing more Pt atoms at the surface facets of the cluster. The modified arrangement of Pt and Pd atoms may result in modification of the reactivity of the Pt₃₂Pd₆ cluster. The results of this study indicate that the defects can play a vital role in determining the activity and durability of the catalyst. By having the right combination of defects on the support material, the durability and catalytic activity of the catalyst can be fine-tuned simultaneously. This can lead to better design of catalysts.

Background Daily, companies generate enormous amounts of customer support tickets which are grouped and placed in specialised queues, based on some characteristics, from where they are resolved by the customer support personnel (CSP) on a first-in-first-out basis. Given that these tickets require different levels of urgency, a logical next step to improving the effectiveness of the CSPs is to prioritise the tickets based on business policies. Among the several heuristics that can be used in prioritising tickets is sentiment polarity. Objectives This study investigates how machine learning methods and natural language techniques can be leveraged to automatically predict the sentiment polarity of customer support tickets using. Methods Using a formal experiment, the study examines how well Support Vector Machine (SVM), Naive Bayes (NB) and Logistic Regression (LR) based sentiment polarity prediction models built for the product and movie reviews, can be used to make sentiment predictions on email support tickets. Due to the limited size of annotated email support tickets, Valence Aware Dictionary and sEntiment Reasoner (VADER) and cluster ensemble - using k-means, affinity propagation and spectral clustering, is investigated for making sentiment polarity prediction. Results Compared to NB and LR, SVM performs better, scoring an average f1-score of .71 whereas NB scores least with a .62 f1-score. SVM, combined with the presence vector, outperformed the frequency and TF-IDF vectors with an f1-score of .73 while NB records an f1-score of .63. Given an average f1-score of .23, the models transferred from the movie and product reviews performed inadequately even when compared with a dummy classifier with an f1-score average of .55. Finally, the cluster ensemble method outperformed VADER with an f1-score of .61 and .53 respectively. Conclusions Given the results, SVM, combined with a presence vector of bigrams and trigrams is a candidate solution for extracting sentiments from email support tickets. Additionally, transferring sentiment models from the movie and product reviews domain to the email support tickets is not possible. Finally, given that there exists a limited dataset for conducting sentiment analysis studies in the Swedish and the customer support context, a cluster ensemble is recommended as a sample selection method for generating annotated data.

Thesis (PhD)--Stellenbosch University, 2013.<br>ENGLISH ABSTRACT: This thesis focused on the provision of economic support to improve the outcomes of patients on TB treatment. Although the association between poverty and tuberculosis is generally acknowledged, there is little evidence to guide the use of economic interventions to improve tuberculosis control. In South Africa, a high burden country with extensive poverty, such evidence is particularly important. The first part of this thesis is a Cochrane systematic review of evidence from randomized controlled trials regarding the effectiveness of economic support among patients with tuberculosis. Eleven trials were included: ten conducted among marginalised groups in the United States on economic support for people on prophylactic treatment for latent TB; and one from Timor-Leste on economic support for patients with active TB. The review found that the use of economic interventions in patients with latent TB may increase the return rate for reading tuberculin skin test results, probably improves clinic re-attendance for initiation or continuation of prophylaxis and may improve completion of prophylaxis, compared to normal care. However, it is uncertain if economic support improves treatment completion in patients with active TB (low quality evidence). The second part of the thesis reports the findings of a pragmatic, cluster randomized controlled trial to evaluate the feasibility and effectiveness of delivering economic support to patients on treatment for active TB in South Africa. Patients with drug sensitive pulmonary TB were offered a monthly voucher valued at ZAR120 until completion of treatment or a maximum of eight months. Patients in control clinics received usual TB care. A parallel process evaluation provided contextual information to explain the trial findings. The qualitative component of this evaluation consisted of in-depth interviews with a sample of trial participants, including patients, nurses and health managers, to assess responses to the voucher and its administration. The quantitative component included a survey of patients’ household expenditure to assess patients’ levels of poverty and the effects of the voucher on these, and an analysis of the goods on which patients spent their vouchers. 4091 patients were included in the trial: 1984 in the control arm (10 clinics) and 2107 in the intervention arm (10 clinics). Intention to treat analysis showed a small but non-significant improvement in treatment success rates in intervention clinics (intervention 76.2%; control 70.7%; risk difference 5.6% (-1.2; 12.3%), p = 0.107). Fidelity to the intervention was low, partly because nurses preferred to issue vouchers based on perceived financial need, rather than on eligibility. Logistical difficulties in delivering vouchers to clinics also undermined fidelity. The vouchers did not significantly increase patients’ household expenditure, but were experienced by patients as helpful, especially in providing more food with which to take their tablets. Factors related to the administration of economic support may undermine its effectiveness in improving TB treatment outcomes. Further research is needed to explore how best to deliver such economic support to those eligible to receive it, particularly in low and middle income countries where the burden of tuberculosis is highest.<br>AFRIKAANSE OPSOMMING: Hierdie tesis was toegespits op die verlening van ekonomiese steun om die uitkomste van pasiënte op tuberkulose- (TB-) behandeling te verbeter. Hoewel die verband tussen armoede en TB in die algemeen erken word, is daar nie veel bewyse om die gebruik van ekonomiese intervensies ter verbetering van TB-beheer te staaf nie. In Suid-Afrika – ’n land met ’n hoë TB-las en wydverspreide armoede – is sulke bewyse veral belangrik. Die eerste deel van hierdie tesis behels ’n sistematiese Cochrane-oorweging van bewysmateriaal afkomstig van verewekansigde, gekontroleerde proewe oor die doeltreffendheid van ekonomiese steun aan pasiënte met tuberkulose. Altesame 11 proewe is ingesluit: Tien is gedoen onder gemarginaliseerde groepe in die Verenigde State met die fokus op ekonomiese ondersteuning aan mense wat profilaktiese behandeling vir latente TB ontvang het. Een, van Timor-Leste, was gefokus op ekonomiese ondersteuning aan pasiënte met aktiewe tuberkulose. Die ondersoek het aan die lig gebring dat, vergeleke met normale sorg, die gebruik van ekonomiese intervensies by pasiënte met latente tuberkulose tog die omdraaikoers vir die lees van tuberkulien-veltoetsresultate kan verhoog, waarskynlik hertoelating tot klinieke vir die inisiëring of voortsetting van profilakse verbeter, en die voltooiing van profilakse kan verbeter. Die tweede gedeelte van die tesis behels ’n verslag oor die bevindings van ’n pragmatiese, trosverewekansigde gekontroleerde proef, om te bepaal hoe doenlik en doeltreffend dit sou wees om ekonomiese steun te verleen aan pasiënte wat in Suid-Afrika vir aktiewe tuberkulose behandel word. Pasiënte met middelsensitiewe pulmonêre tuberkulose het tot en met die voltooiing van hul behandeling, of tot ’n maksimum van agt maande, ’n maandelikse koopbewys ter waarde van ZAR120 ontvang. Pasiënte in kontroleklinieke het die gewone TB-sorg ontvang. ’n Parallelle prosesevaluering het kontekstuele inligting voorsien ter verklaring van die bevindinge van die proef. Die kwalitatiewe komponent van hierdie evaluering het bestaan uit diepte-onderhoude met ’n steekproef van alle deelnemers aan die proefneming, insluitend pasiënte, verpleegpersoneel en gesondheidsbestuurders, om hul reaksies te bepaal op die koopbewys self sowel as op die administrasie daarvan. Die kwantitatiewe komponent het ’n opname oor pasiënte se huishoudelike besteding ingesluit, ter vasstelling van hul armoedevlak en die moontlike uitwerking van die koopbewys daarop, asook ’n ontleding van die goedere waarop pasiënte hul koopbewyse bestee het. Altesame 4 091 pasiënte is by die proef ingesluit – 1 984 in die kontrole-afdeling (10 klinieke) en 2 107 in die intervensie-afdeling (10 klinieke). ’n Voorneme-om-te-behandel- (ITT-) ontleding toon ’n klein dog nie-betekenisvolle verbetering in behandelingsuksessyfers in intervensieklinieke (intervensie 76,2%; kontrole 70,7%; risikoverskil 5,6% (-1,2; 12,3%), p = 0.107). Getrouheid aan die intervensie was laag – deels omdat verpleegkundiges verkies het om die koopbewyse op grond van veronderstelde finansiële behoeftigheid eerder as volgens die studiekriteria uit te deel. Die koopbewyse het nie pasiënte se huishoudelike besteding beduidend verhoog nie, maar pasiënte het dit wél as nuttig ervaar, veral omdat hulle daarmee meer kos kon koop om saam met hul pille in te neem. Faktore wat verband hou met die administrasie van ekonomiese ondersteuning kan die doeltreffendheid van sodanige steun in die verbetering van TB-behandelingsuitkomste ondermyn. Verdere navorsing word vereis om te verken wat die beste manier sou wees om sodanige ekonomiese steun te bied aan diegene wat daarvoor in aanmerking kom, veral in lae- en middel-inkomstelande, waar die TB-las die hoogste is.

During the last decades the specific manipulation of matter on the (sub-) nanometer scale, also known as nanoscience, became possible by technologies such as the scanning tunneling microscope. Nanocatalysts, i.e. catalytic active structures of up to a few nanometers in size, belong to this rather new class of materials. Unlike ordinary ’macroscopic’ catalytic materials, the performance of nanocatalysts does not simply scale, for instance, with the surface to volume ratio of the active material. In this Thesis model nanocatalysts are investigated by means of ab-initio density functional theory calculations. In paper I, we explain the experimentally observed catalytic characteristics of small gold clusters, Au1-4, on a regular magnesium oxide terrace towards the oxidation of carbon monoxide by thoroughly studying the adsorption of CO and O2 on these clusters. In the subsequent paper II, we study the feasibility of a catalytic water-mediated CO oxidation reaction on Au1-4/MgO and find that this reaction mechanism is not assessable for Au2,4/MgO and unlikely for Au1,3/MgO. Papers III and IV concentrate on the reactivity of clusters in the gas phase. Particularly, we focus on the relative stability of Au13 isomers and its potential for O2 dissociation (paper III). We find the lowest energy isomers, which contain a triangular prism at their center surrounded by a ring of the remaining seven atoms, to be generally stable upon O2 adsorption. The dissociation of O2 at certain sites of Au13 is found to be exothermic. In paper IV we performed scans of the Born-Oppenheimer potential energy surfaces of neutral and charged Cu3, Ag3, and Au3 to explore the thermally excited vibrations of these trimers. While the Born-Oppenheimer surface of Cu3 exhibits one fairly deep energy minimum, it is comparatively flat with two shallow minima in the case of Ag3. Hence for Ag3 there exist many thermally accessible geometries in a wide range of angles and bond lengths. For Au3, two distinct energy minima appear, being well-separated by a barrier of 180 meV. Already at room temperature, we find bond lengths changes of up to 5% for the studied trimers. Choosing Au3 as a case study for the changed reactivity of thermally excited modes, we find CO to bind up to 150 meV stronger to the excited cluster. Gold deposited on graphene and graphite was observed to form larger aggregates. In paper V, we study the electronic structures, high mobility, and substrate-mediated clustering processes of Au1-4 on graphene. Already in the 1970s is was speculated that dispersion forces, i.e. van der Waals forces, significantly contribute to the adsorption energies of gold atoms on graphite. We accounted for van der Waals interactions in our density functional theory calculations (paper VI) and investigated the influence of these dispersion forces on the binding of copper, silver, and gold adatoms on graphene. While copper and gold show a mixed adsorption mechanism, i.e. chemical binding plus attraction due to the van der Waals forces, silver is purely physisorbed on graphene.<br>Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 719

A variety of mass spectrometry experiments have been performed with the aim of further understanding of the ionisation processes involved and the gas-phase behaviour of various organic molecules within two ionisation techniques: Matrix-Assisted Laser Desorption Ionisation (MALDI) and Electrospray Ionisation (ESI). The majority of the studied compounds were C60 derivatised in various ways, either with addition of a ligand, or by the creation of an orifice within the cage structure with heteroatoms – Open-Cage Fullerenes (OCFs). The DCTB-MALDI investigations into the OCFs revealed a possible correlation between orifice size and the heteroatoms present in the orifice, to how the OCF behaved under elevated laser fluence. An extended investigation into the smallest hydrofullerene, C60H2, established for the first time decomposition-free conditions for its analysis, so that its oxidation over time, which has been controversial in the literature, could be studied. The use of pencil lead as a matrix was compared to the traditional matrix for fullerenes, DCTB. Pencil lead was found to be inferior as a matrix, however, proved an exceptionally easy way of creating sodium and potassium adducts, which was found to be useful in the differentiation of isomers of some of the OCFs. The formation of polyaromatic hydrocarbons adducts to C60 were synthesized and analysed with both MALDI and ESI-MS. These complexes are notoriously labile, yet a larger C60PAH:C60 peak intensity ratio was achieved than had been previously reported. The use of silver in ESI experiments was explored in depth. Initially, heterodimers of amino acids bound by silver (I) ions were created and fragmented in order to ascertain relative silver binding affinities, by use of the kinetic method. The same technique was applied to compounds that have been traditionally difficult to ionise with ESI-MS. These included pure fullerenes, fullerene derivatives, and various fullerene precursors. These compounds have been successfully arranged into order of their silver-ion affinities.

LGBTQ+ individuals report disproportionately high rates of depression and suicidal behaviors compared to the general populations, particularly among queer youth. Certain depressive symptoms and symptom clusters, namely hopelessness and self-blame, are predictive of suicidal behavior and outcomes. In contrast, perceived social support may act as a buffer against suicide ideation. The disparity in the rate of queer suicidality may be predicted by higher rates of hopelessness and self-blame, as well as lower rates of perceived social support among depressed queer youth in comparison to depressed non-queer youth. The current study will test this hypothesis using a sample of depressed queer and non-queer college students (n=145). Results indicate that queer students and non-queer students do not experience significantly different rates of hopelessness, self-blame, or perceived social support. Despite this finding, queer students report significantly higher rates of suicide and self-harm ideation. This suggests that differences in the suicide rate for queer individuals cannot be explained by differences in perceived social support or the manifestation of suicide-related depression symptom clusters. Additionally, depression severity was found to be a weaker predictor of suicide ideation for queer students than for non-queer students. This indicates that suicidality among queer populations may be less connected to experiences of depressive symptoms than it is for cisgender and heterosexual populations. Further research is needed to examine possible suicide predictors and risk factor differences that are unique to queer populations to explain the disparity in suicide rates.