Made available in DSpace on 2014-10-09T12:27:16Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:06Z (GMT). No. of bitstreams: 0 / Tratamentos de superfície são técnicas amplamente utilizadas com a finalidade de aumentar a resistência à corrosão de materiais metálicos. No caso específico do alumínio e ligas de alumínio, o tratamento com cromo hexavalente é um dos processos mais utilizados. Isso, em razão da eficiência e da facilidade de aplicação desse processo. Entretanto, em virtude de restrições ambientais e do elevado custo de tratamento de resíduos gerados neste processo, métodos alternativos para sua substituição vêm sendo avaliados. Neste contexto, o presente estudo investigou o processo de formação e proteção à corrosão fornecida por filmes de moléculas autoorganizáveis de compostos à base de fosfonatos sobre a liga de alumínio 1050. Para definir as condições do tratamento foram utilizadas medidas de condutividade e de ângulo de contato, juntamente com ensaios eletroquímicos. Técnicas eletroquímicas, especificamente: medidas de variação do potencial a circuito aberto (PCA), espectroscopia de impedância eletroquímica (EIE) e polarização potenciodinâmica foram utilizadas para avaliar a proteção à corrosão. Os diagramas experimentais de impedância foram interpretados utilizando circuitos elétricos equivalentes que simulam modelos do filme de óxido que se forma na superfície da liga. Os resultados fornecidos com a liga tratada com moléculas auto-organizáveis foram comparados com resultados obtidos em iguais condições com amostras da liga sem qualquer tratamento ou cromatizada com Cr(VI) e mostraram que o tratamento com moléculas auto-organizáveis aumenta significativamente a resistência à corrosão da liga e apresenta, em determinadas condições, desempenho próximo ao fornecido pelo processo de cromatização. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Orientador: Carlile Campos Lavor / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-08-25T18:42:28Z (GMT). No. of bitstreams: 1 Rezende_GermanoAbudde_D.pdf: 1418033 bytes, checksum: 61d29b02274278ede5ffca797e26371a (MD5) Previous issue date: 2014 / Resumo: A geometria de distâncias é o estudo da geometria baseado no conceito de distância. Ela é útil em várias aplicações, onde os dados de entrada consistem de um conjunto incompleto de distâncias, e a saída é um conjunto de pontos no espaço euclidiano, que realiza as distâncias dadas. No Problema de Geometria de Distâncias (DGP), é dado um inteiro K > 0 e um grafo simples, não direcionado, G = (V,E,d), cujas arestas são ponderadas por uma função não negativa d. Queremos determinar se existe uma função (realização) que leva os vértices de V em coordenadas no espaço euclidiano K-dimensional, satisfazendo todas as restrições de distâncias dadas por d. Um DGPk (com K fixado) está fortemente relacionado a um outro tipo de problema, que trata dos possíveis completamentos de uma certa matriz de distâncias euclidianas. Este último pode ser visto, em um certo sentido, como o "dual do primeiro problema". Neste trabalho, exploramos essa dualidade com a finalidade de propor melhorias no método Branch-and-Prune aplicado a uma versão discreta do DGPk / Abstract: Distance Geometry is the study of geometry based on the concept of distance. It is useful in many applications where the input data consists of an incomplete set of distances, and the output is a set of points in some Euclidean space which realizes the given distances. In the Distance Geometry Problem (DGP), it is given an integer K > 0 and a simple undirected weighted graph G = (V,E,d), whose edges are weighted by a non-negative function d. We want to determine if there is a (realization) function that associates the vertices of V with coordinates of the K-dimensional Euclidean space satisfying all distance constraints given by d. A DGPk (with K fixed) is closely related to another type of problem, which treats the possible completions of a certain Euclidean distance matrix. In some sense, this is the "dual" of the first problem. We explore this duality in order to improve the Branch-and-Prune method applied to a discrete version of the DGPk / Doutorado / Matematica Aplicada / Doutor em Matemática Aplicada

This work describes an investigation into the solution-phase binding of anionic guests by bimacrocyclic lanthanide complexes. It outlines the preparation of different classes of complexes bearing two metallic domains, and the effects of association on both the complex and the guest. Chapter one provides a cursory introduction to the fundamental properties of the lanthanides with a focus on luminescence. A brief literature review is given on the use of emissive lanthanide probes for the sensing of analytes. Chapter two concerns the preparation and properties of a series of binuclear complexes in which the two centres are linked with a short spacer group, with the aim of selectively sequestering small anions such as the halides in solution. The concept of luminescence titration will be introduced and then used to assess the binding parameters of a selection of guests. Chapter three describes a related class of ditopic lanthanide complexes in which the two metal centres are separated by a semi-rigid butyne linking group. Luminescence studies are again used to evaluate the binding constants of homologous series of dianions to ascertain how the size, geometry and functionalization of the anionic guest impacts on binding. Chapter four explores the coordination of phosphate species and assesses the ability to bind biologically significant phosphates of some of the complexes from Chapter 3. Chapter five details an investigation into the effects on guest-selectivity of further lengthening the linking unit which separates the two macrocyclic binding domains. Chapter six summarises the work done throughout the thesis and draws some overarching conclusions, as well as highlighting areas for further study. Chapter seven describes the experimental procedures.

The thesis entitled “Exploring Intermolecular Space by Charge Density Analysis in Molecular Crystals” consists of five chapters. A short introductory note highlights the importance of intermolecular interactions and presents the current status of charge density analysis to obtain insights into such interactions. Charge density analysis of crystalline materials by using high resolution X-ray diffraction data has become routine and enables derivation of reliable one electron properties associated with the electron density. The results obtained from single crystal X-ray diffraction data at low temperature have been compared with periodic theoretical calculations using B3LYP/6-31G** methods to unequivocally establish the nature of weak interactions. Chapter 1 describes the quantitative analysis of Cl∙∙∙Cl intermolecular interactions in compounds 2-chloro-3-quinolinyl methanol, 2-chloro-3-hydroxypyridine and 2-chloro-3-chloromethyl-8-methylquinoline, which are corresponding to type I (trans and cis) and type II (L) geometries of Cl∙∙∙Cl interactions respectively. The 3D static deformation density plots from charge density analysis unequivocally suggest that both ‘cis’ and ‘trans’ type I geometries show decreased repulsion whereas type II geometry is attractive based on the nature of “polar flattening” of the electron density around the Cl atom. The topological features derived at bond critical point (BCP) of Cl∙∙∙Cl interactions also support the observed results. Chapter 2 discusses hetero-halogen (Cl∙∙∙F) and homo-halogen (F∙∙∙F) intermolecular interactions involving “organic fluorine” in compounds 2-chloro-4-fluorobenzoic acid and 4-flurobenzamide respectively. Charge density distributions show polar flattening effects at both atoms Cl and F, however the extent of polarization is small on F in comparison with that of the Cl atom. 3D static deformation density plots depict δ+ ∙∙∙δ− interactions for Cl∙∙∙F intermolecular interactions while F∙∙∙F interactions show small decreased repulsion features. The topological properties of F∙∙∙F interactions bring out the similarity between F∙∙∙F and Cl∙∙∙Cl interactions. Chapter 3 describes the nature of C−Cl∙∙∙O=C halogen bond in 2, 5-dichloro-1, 4-benzoquinone, a molecule specifically chosen to depict this interaction dominantly. The topological values at bond critical point, three dimensional static deformation density features and electrostatic potential isosurfaces unequivocally establish the attractive nature of C−Cl∙∙∙O=C halogen bond in the crystalline lattice. Chapter 4 discusses the generation of multi-component systems (for example cocrystals and salts) of active pharmaceutical ingredients (API). Two systems associated with nicotinamide, one with salicylic acid and the other with oxalic acid as coformers resulting in 1:1 molecular complexes have been analyzed. The charge density analysis, particularly at the proton transfer region clearly bring out the differences between cocrystal and salt thus providing insights into the continuum in the proton transfer pathways in molecular crystals. Chapter 5 describes a new methodology [supramolecular synthon based fragment approach (SBFA)] concerning transferability of experimental charge density multipole parameters and building a database using well defined supramolecular synthons. The modularity and robustness of supramolecular synthons are used to transfer experimental charge density multipole parameters of synthons derived from a high resolution X-ray diffraction study to target molecules possessing these synthons as fragments in the crystalline lattice. The synthesized charge density and derived topological properties on target molecules using routine single crystal diffraction data are comparable with both experimental and theoretical charge density results. SBFA thus is expected to provide an additional database which can be applied to include intermolecular interactions space in the modeling directly unlike the available ones such as ELMAM, INVARIOM and UBDB. Further, SBFA approach can be extended to the determination and synthesis of charge density properties in macromolecules such as polypeptides, nucleic acids and proteins. APPENDIX contains reprints of the articles published which comprises of the work carried out in addition to the above five chapters.

Orientador: Carlile Campos Lavor / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-08-26T22:04:46Z (GMT). No. of bitstreams: 1 Fidalgo_FelipeDelfiniCaetano_D.pdf: 5383479 bytes, checksum: 8f7bf5142b44fa99ea2742f6183ee1c6 (MD5) Previous issue date: 2015 / Resumo: Motivado por estudos em estruturas 3D de proteínas, biomoléculas imprescindíveis no estudo da vida, surgiu um problema chamado Discretizable Molecular Distance Geometry Problem (DMDGP) que provou ser NP-Difícil. Para resolvê-lo, existe um algoritmo da literatura, Branch & Prune (BP), que utiliza uma estratégia combinatória de exploração de uma árvore binária de soluções associada ao problema. Além disso, foram descobertas relações de simetria que permitem obter uma solução, a partir de outra, através de reflexões nos chamados vértices de simetria. Alguns pesquisadores passaram a realizar este trabalho em paralelo (ParallelBP), dividindo uma instância em sub-instâncias, resolvendo localmente com o BP (o que pode ser feito em duas direções) e unindo as sub-soluções com movimentos rígidos, com o intuito de determinar as soluções em menor tempo. Nossa proposta é fornecer uma estratégia Dividir-e-Conquistar para resolver o DMDGP, de modo a melhorar a abordagem em paralelo. Ela possui três estágios. Inicialmente, dividimos uma instância em sub-instâncias duas-a-duas sobrepostas através dos vértices de simetria. Depois, utiliza-se os chamados gaps para decidir a direção em que o BP deve fornecer a solução local. Por fim, utilizamos rotações baseadas na Álgebra de Quatérnios para combinar as sub-soluções em soluções factíveis / Abstract: Motived by studies in 3D structures of proteins, essential biomolecules for Life, arised a problem called Discretizable Molecular Distance Geometry Problem (DMDGP) which proved to be NP-Hard. Aiming to solve it, there is an algorithm in the literature, Branch & Prune (BP), which uses a combinatorial strategy of exploring a binary tree of solutions that is associated to the problem. Moreover, some symmetry relations have been discovered which allows the obtainance of one solution from the other one by means of reflections in the so-called symmetry vertices. Some researchers started to do this work using parallel computing (ParallelBP), dividing one instance into sub-instances, solving the problem locally with the BP (what can be done in two directions) and joining the sub-solutions with rigid movements, with the objective of determining the solutions in a smaller time. Our purpose, thus, is to provide a Divide-and-Conquer strategy to solve the DMDGP in order to improve the parallel version. It has three stages. Initially, the instance is divided into sub-instances two-by-two overlapping by means of the symmetry vertices. After, the so-called gaps are used to decide the direction that the BP ought to provide the local solution. Finally, we propose to use Quaternion Rotations to combine sub-solutions into feasible solutions / Doutorado / Matematica Aplicada / Doutor em Matemática Aplicada

Computational chemistry lies at the intersection of chemistry, physics, mathematics, and computer science, and can be used to explain the behavior of atoms and molecules, as well as to augment experiment. In this work, computational chemistry methods are used to predict structural and energetic properties of small molecules, i.e. molecules with less than 60 atoms. Different aspects of computational chemistry are examined in this work. The importance of examining the converged orbitals obtained in an electronic structure calculation is explained. The ability to more completely describe the orbital space through the extrapolation of energies obtained at increasing quality of basis set is investigated with the use of the Sapporo-nZP-2012 family of basis set. The correlation consistent Composite Approach (ccCA) is utilized to compute the enthalpies of formation of a set of molecules and the accuracy is compared with the target method, CCSD(T,FC1)/aug-cc-pCV∞Z-DK. Both methodologies are able to produce computed enthalpies of formation that are typically within 1 kcal mol-1 of reliable experiment. This demonstrates that ccCA can be used instead of much more computationally intensive methods (in terms of memory, processors, and time required for a calculation) with the expectation of similar accuracy yet at a reduced computational cost. The enthalpies of formation for systems containing s-block elements have been computed using the multireference variant of ccCA (MR-ccCA), which is designed specifically for systems that require an explicit treatment of nondynamical correlation. Density functional theory (DFT) has been used for the prediction of the structural properties of a set of lanthanide trihalide molecules as well as the reaction energetics for the rearrangement of diphosphine ligands around a triosmium cluster.

No description available.

No / We describe a series of experiments designed to investigate the conformational transition that highly-branched polymers with ligands undergo when interacting with bacteria, a process that may provide a new sensing mechanism for bacterial detection. Fluorescent highly-branched poly(N-isopropyl acrylamide)s (HB-PNIPAM) were prepared by sequential self-condensing radical copolymerizations, using anthrylmethyl methacrylate (AMMA) and fluorescein-O-acrylate (FA) as fluorescent comonomers and 4-vinylbenzyl pyrrole carbodithioate as a branch forming monomer. Differences in reactivity necessitated to first copolymerize AMMA then react with FA in a separate sequential monomer feed step. Modifications of the chain ends produced vancomycin-functional derivatives (HB-PNIPAM-Van). The AMMA and FA labels allow probing of the conformational behaviour of the polymers in solution via Forster resonance energy transfer experiments. It was shown that interaction of this polymer's end groups with Staphylococcus aureus induced a macromolecular collapse. The data thus provide conclusive evidence for a conformational transition that is driven by binding to a bacterium.