PVC are extensively applied in many fields, such as cables, pipes, vehicles, shoes, toys and infusion bags. Generally, plasticizers are blended with PVC to improve the ability of process in industrial production; however, the toxic plasticizers will gradually migrate to the surface of products and such a leakage results in brittleness of plasticized PVC and environmental pollution. In other words, humans are frequently exposed to the potential risks. According to previous researches, cross-linked PVC was proved that it was able to hinder the migration of plasticizer. Thus, in this research, we selected some commercially used cross-linking agents and employed six different tests based on mechanical, tribological and microscopy analysis in order to seek the best solution against plasticizer migration. Thus, we expected to develop a cross-linked flexible PVC which performed improved long-term performance and extended lifetime.

Chapas de poli(metacrilato de metila) podem ser modificadas por meio da adição de um agente promotor de ligações cruzadas e um plastificante objetivando incrementar seu desempenho durante a termoformagem. A interação intermolecular, modificada com a adição de diferentes quantidades de um agente promotor de ligações cruzadas (TEGDMA) e pela presença de um plastificante (DOP) faz com que as macromoléculas sejam ancoradas e afastadas respectivamente. O desenvolvimento deste trabalho objetivou, avaliar as propriedades físicas, mecânicas, térmicas e o processamento via termoformagem para duas diferentes temperaturas de termoformagem em um molde cilíndrico, a uma mesma taxa de deformação e determinado a influência da formulação, para cinco chapas que se diferenciaram nas quantidades de TEGDMA e uma quantidade fixada de DOP para duas das formulações. Os resultados mostraram que há incremento na deformação com as modificações introduzidas quando comparado a uma chapa sem adição de TEGDMA ou DOP e as propriedades destas chapas como dureza superficial, módulo de rigidez e temperatura de transição vítrea apresentaram mudanças sensíveis, que caracterizam vantagens no uso dos dois componentes. / Poly(methyl methacrylate) sheets can be modified adding a cross-linking agent and a plasticizer, to increase performance during thermoforming. The intermolecular interaction modification can be achieved adding different amount of cross-linking agent (TEGDMA) and a plasticizer (DOP). They have an effect on the network polymer system improving the intermolecular interaction and increasing the macromolecular distances, respectively. The aim of this study was to prepare acrylic sheets formulations with differents amounts of TEGDMA and a fixed amount of DOP, and thermoformed using at differents process temperatures and a mould cylinder at the same strain rate. Samples were carried out and their properties physical, mechanical, thermal and thermoformability was characterized. The results have shown strain increases, changes in surface hardness, Young moduli and glass transition temperature, compared to a reference acrylic sheet.

Submitted by Luciane Willcox (luwillcox@gmail.com) on 2016-09-12T17:18:24Z No. of bitstreams: 1 Tese_Doutorado_ICC.pdf: 40560568 bytes, checksum: 1e1c7efcf21605b84ddacb307516a772 (MD5) / Approved for entry into archive by Luciane Willcox (luwillcox@gmail.com) on 2016-09-12T18:02:31Z (GMT) No. of bitstreams: 1 Tese_Doutorado_ICC.pdf: 40560568 bytes, checksum: 1e1c7efcf21605b84ddacb307516a772 (MD5) / Made available in DSpace on 2016-09-12T18:02:31Z (GMT). No. of bitstreams: 1 Tese_Doutorado_ICC.pdf: 40560568 bytes, checksum: 1e1c7efcf21605b84ddacb307516a772 (MD5) Previous issue date: 2016-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Programa de Apoio à Pesquisa Estratégica em Saúde (Papes) da Fiocruz, Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Microsoft Research. / Instituto Carlos Chagas, Fiocruz-PR, Curitiba, PR, Brasil / O estudo de estruturas e interações proteicas é uma importante área de pesquisa para se entender as funções das proteínas. No entanto, essa é também uma das áreas de grandes desafios experimentais, devido à inerente complexidade atômica de proteínas e peptídeos. Os métodos de elucidação estrutural de alta resolução (e.g. difração de raios-X e RMN) são hoje os considerados “padrões-ouro” para esses tipos de estudos. No entanto, uma grande parte das proteínas e seus respectivos complexos não são passíveis de serem resolvidos por esses métodos, motivando o desenvolvimento de novas técnicas para a caracterização estrutural de proteínas e seus complexos. Neste sentido, a espectrometria de massas acoplada à técnica de crosslinking (XL-MS) é uma grande promessa, devido às suas características intrínsecas, tais como alta sensibilidade e ampla aplicabilidade. Neste trabalho, desenvolveu-se um software com aplicações pioneiras, denominado SIM-XL, capaz de identificar peptídeos covalentemente ligados e analisados por espectrometria de massas, a fim de caracterizar estruturas de proteínas, bem como de complexos proteínas-proteínas e proteína-peptídeo. Esse software faz uso de técnicas de reconhecimento de padrões para resolver um gargalo na modelagem proteica e interação proteína-proteína. Portanto, o algoritmo aqui apresentado, traz benefícios imediatos nas áreas de biologia e biotecnologia e indiretamente, em diversas outras áreas, como por exemplo, no desenvolvimento de novos fármacos. / The study of protein structures and interactions is an important area of development for understanding the function of proteins. However, this is also an area of great experimental challenge, due to the inherent atomic complexity of proteins and peptides. The methods of structural elucidation of high-resolution (e.g. X-ray diffraction and NMR) are currently considered the “gold standard” for these types of studies. However, many proteins are not amendable to being solved by these methods; thus motivating the development of new techniques for structural characterization of proteins and their complexes. In this regard, mass spectrometry coupled by crosslinking technique (XL-MS) poses as a promise to overcome these limitations as it provides a high sensitivity and wide applicability. Here we present SIM-XL, a software pioneer in many ways, capable of identifying cross-linked peptides analyzed by mass spectrometry and thus ultimately aiding in structural characterization and in determining protein-protein interactions. Our software uses pattern recognition strategies to address a bottleneck in protein modeling and protein-protein interaction. As such, various fields related to biology and biotechnology suffer an immediate benefit from this work, and other areas, say, the development of new drugs, are indirectly benefited as well.

Chapas de poli(metacrilato de metila) podem ser modificadas por meio da adição de um agente promotor de ligações cruzadas e um plastificante objetivando incrementar seu desempenho durante a termoformagem. A interação intermolecular, modificada com a adição de diferentes quantidades de um agente promotor de ligações cruzadas (TEGDMA) e pela presença de um plastificante (DOP) faz com que as macromoléculas sejam ancoradas e afastadas respectivamente. O desenvolvimento deste trabalho objetivou, avaliar as propriedades físicas, mecânicas, térmicas e o processamento via termoformagem para duas diferentes temperaturas de termoformagem em um molde cilíndrico, a uma mesma taxa de deformação e determinado a influência da formulação, para cinco chapas que se diferenciaram nas quantidades de TEGDMA e uma quantidade fixada de DOP para duas das formulações. Os resultados mostraram que há incremento na deformação com as modificações introduzidas quando comparado a uma chapa sem adição de TEGDMA ou DOP e as propriedades destas chapas como dureza superficial, módulo de rigidez e temperatura de transição vítrea apresentaram mudanças sensíveis, que caracterizam vantagens no uso dos dois componentes. / Poly(methyl methacrylate) sheets can be modified adding a cross-linking agent and a plasticizer, to increase performance during thermoforming. The intermolecular interaction modification can be achieved adding different amount of cross-linking agent (TEGDMA) and a plasticizer (DOP). They have an effect on the network polymer system improving the intermolecular interaction and increasing the macromolecular distances, respectively. The aim of this study was to prepare acrylic sheets formulations with differents amounts of TEGDMA and a fixed amount of DOP, and thermoformed using at differents process temperatures and a mould cylinder at the same strain rate. Samples were carried out and their properties physical, mechanical, thermal and thermoformability was characterized. The results have shown strain increases, changes in surface hardness, Young moduli and glass transition temperature, compared to a reference acrylic sheet.

No description available.

<p>DNA interstrand cross-links (ICLs) occur when various chemical agents bind to chromosomal DNA and form a covalent bond between adjacent strands, preventing unwinding of the DNA double helix. The formation of an ICL is therefore extremely toxic to cells and necessitates quick removal and subsequent repair. Human SNM1A is a 5’-phosphate-dependent exonuclease that has been shown to be selectively involved in ICL repair; however the mechanism by which it processes ICL substrates remains unclear. To address this, our research is focused on the structural and functional characterization of SNM1A to determine this mechanism of substrate processing. In this thesis, we report the purification of human SNM1A_698-1040 as a His₆-NusA tagged protein from 4 L of <em>E. Coli</em> cell culture. This protein was found to possess 5’-phosphate-dependent exonuclease activity, and demonstrated a preference for ssDNA. Additionally, electrophoretic mobility shift assays performed with a D736A/H737A mutant suggest that the binding of SNM1A to DNA is independent of the presence of a 5’ phosphate. Collectively, these results provide insight into the mechanism of SNM1A substrate processing in ICL repair, and establish a platform for future studies of this protein.</p> / Master of Science (MSc)

Collagen type I is an extracellular matrix (ECM) protein that affords tensile strength and biological scaffolding to numerous vertebrate and invertebrate tissues. This strength has been attributed to the triple-helical structure of the collagen type I molecules, their organization into fibrils, and the presence of inter-molecular, covalent, enzymatic crosslinks. There are several different types of these crosslinks; their composition is tissue-specific and dependent upon factors such as age and health. Furthermore, these enzymatic crosslinks tend to form specifically at amino/N- and carboxy/C-terminal crosslinking sites. The mechanical behavior of collagen type I has been investigated, via experiment and theory, at the level of the molecule, microfibril, fibril, and fiber. However, the influence of different enzymatic crosslinks and their location (e.g., N- vs. C-site) on the mechanics of collagen type I has not been investigated in the literature. We employed molecular dynamics to model the mechanical behavior of uncrosslinked and crosslinked ~23-nm-long molecular segments and ~65-nm-long microfibril units of collagen type I. We then used these molecular simulations to construct a model of a single collagen type I fibril by considering the ~65-nm-long microfibril units arranged in series and then in parallel. When a uniaxial deformation was applied along the long axis of the molecular models, N-crosslinks aligned rapidly at lower strains followed by C-crosslinks more gradually at higher strains, leading to a two-stage crosslink recruitment. Then when comparing the influence of different enzymatic crosslinks, significant differences were observed for the high-strain elastic moduli of our microfibril unit models, namely and in increasing order, uncrosslinked, immature crosslinked (HLKNL and deH-HLNL), mature HHL-crosslinked, and mature PYD-crosslinked. At the fibril level, our low- and high-strain elastic moduli were in good agreement with some literature data, but in over-estimation of several other literature reports. Future work will seek to address simplifications and limitations in our modeling approach. A model such as this, accounting for different enzymatic crosslink types, may allow for the prediction of the mechanics of collagen fibrils and collagenous tissues, in representation of healthy and diseased states. / Ph. D.

No description available.

New polymer cure chemistry is described, wherein the onset of free radical cross-linking is delayed without compromising cure yields. The addition of an acrylate-functionalized nitroxyl, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl (AOTEMPO), to a peroxide-cure formulation quenches free radical activity during the initial stages of the cross-linking process, trapping alkyl radicals as alkoxyamines that bear acrylate functionality. Polymer cross-linking by macro-radical combination is suppressed until all nitroxyl is consumed, at which point radical oligomerization of polymer-bound acrylate groups generates the desired covalent network. As a result, cross-link density losses incurred during radical trapping are recovered during the oligomerization phase of the process. The effectiveness of this approach is demonstrated for a range of polymers, peroxide initiators, reaction temperatures and reagent loadings. Furthermore, AOTEMPO formulations are compared directly to other delayed-onset additives that are used in commercial practice. / Thesis (Master, Chemical Engineering) -- Queen's University, 2012-06-11 10:09:20.848

abstract: Current treatment methods for cerebral aneurysms are providing life-saving measures for patients suffering from these blood vessel wall protrusions; however, the drawbacks present unfortunate circumstances in the invasive procedure or with efficient occlusion of the aneurysms. With the advancement of medical devices, liquid-to-solid gelling materials that could be delivered endovascularly have gained interest. The development of these systems stems from the need to circumvent surgical methods and the requirement for improved occlusion of aneurysms to prevent recanalization and potential complications. The work presented herein reports on a liquid-to-solid gelling material, which undergoes gelation via dual mechanisms. Using a temperature-responsive polymer, poly(N-isopropylacrylamide) (poly(NIPAAm), the gelling system can transition from a solution at low temperatures to a gel at body temperature (physical gelation). Additionally, by conjugating reactive functional groups onto the polymers, covalent cross-links can be formed via chemical reaction between the two moieties (chemical gelation). The advantage of this gelling system comprises of its water-based properties as well as the ability of the physical and chemical gelation to occur within physiological conditions. By developing the polymer gelling system in a ground-up approach via synthesis, its added benefit is the capability of modifying the properties of the system as needed for particular applications, in this case for embolization of cerebral aneurysms. The studies provided in this doctoral work highlight the synthesis, characterization and testing of these polymer gelling systems for occlusion of aneurysms. Conducted experiments include thermal, mechanical, structural and chemical characterization, as well as analysis of swelling, degradation, kinetics, cytotoxicity, in vitro glass models and in vivo swine study. Data on thermoresponsive poly(NIPAAm) indicated that the phase transition it undertakes comes as a result of the polymer chains associating as temperature is increased. Poly(NIPAAm) was functionalized with thiols and vinyls to provide for added chemical cross-linking. By combining both modes of gelation, physical and chemical, a gel with reduced creep flow and increased strength was developed. Being waterborne, the gels demonstrated excellent biocompatibility and were easily delivered via catheters and injected within aneurysms, without undergoing degradation. The dual gelling polymer systems demonstrated potential in use as embolic agents for cerebral aneurysm embolization. / Dissertation/Thesis / Ph.D. Bioengineering 2012