Дисертації з теми "Bone bride"

Mestrado em Engenharia Mecânica
This thesis objective was to study the biomechanical aspects of the di erent repair techniques of bone loss in the proximal tibia, in the revision of total knee arthroplasty. We sought to speci cally evaluate how each of the di erent techniques changes the load transfer to the supporting bone, thus gauging the potential for bone resorption or fatigue failure of the supporting bone. Was also assessed, in a comparative way, the stability of each repair construction of the bone defects, relatively to the solutions without bone defects. We also sought, in this work, to evaluate the e ect of the use of intramedullary stems when associated to di erent techniques. For this purpose, as a rst step, we tried to perform a detailed analysis of the knee joint in its anatomical and biomechanical aspects, with special focus on arthroplasty and its revision process. We selected the knee prosthesis P.F.C. Sigma as an element for the realization of the comparative study. The prosthetic metal elements used in the di erent bone replacement constructions were also the same model, hemi-wedge, wedge and block total. As a complement two more bone repair techniques were also compared: using only bone cement in contrast with the use of a bovine bone graft. In the following phase experimental models were developed using the tibia in composite material, where the bone defects were created and the di erent techniques applied during "in vitro" surgeries. In order to assess the changes of load transfer and stability in the region annexed to the bone defect were placed gauges, allowing the evaluation of the models main surface deformations, as well as the use of video techniques for assessing the stability of the tibial plateau in the di erent techniques. These models were subjected to a severe case of load on the medial condyle where the defect is located, proceeding to evaluation and comparison of results of deformation and stability of the bone plate. At a later stage we proceeded to the development of nite element numerical models that seek to replicate the models evaluated experimentally. The models were subjected to two load cases, one case identical to the one applied in experimental models that allowed the validation of numerical models and another load case representing a physiological load condition during the walking cycle. The numerical models have allowed the assessment of biomechanical parameters, not eligible for evaluation before, using experimental models. Thereby the strains imposed on cortical and cancellous bone in the vicinity of the defect and in the interface with this have been analysed. These same models were compared with results obtained in experimental models in order to assess their correlation. The experimental and numerical results obtained allow us to show a good correlation between these numerical models demonstrating that they are able to faithfully replicate the behaviour of experimental models. The results obtained in both types of models show changes in load transfer and stability between the di erent types of techniques. The models with full wedge and block, on average, increased the strains on the medial side (the one with defect) of the cortical bone adjacent to the implant when compared with the bone and cement graft model and metallic hemi-wedge. However is during the construction with bovine bone graft that takes place the maximum increment of strain in cortical bone, on the medial side. These increases observed in the cortical bone for larger buildings is opposite to the behavior observed in the cancellous bone at the implant interface, in which case these constructions originate a reduction of deformation on the solution without defect. So the more invasive solutions potentiate the risk of fatigue damage in cortical bone and simultaneously increase the risk of bone resorption in the adjacent cancellous bone. In terms of stability only the metallic block implant proved to be signi cantly more stable than the other techniques. The additional stability provided by stems was felt only in less invasive constructions with the use of bone cement and hemi-wedge. The experimental and numerical results obtained allow us to show a good correlation between these numerical models demonstrating that they are able to faithfully replicate the behaviour of experimental models. The results obtained in both types of models show changes in load transfer and stability between the di erent types of techniques. The models with full wedge and block, on average, increased the strains on the medial side (the one with defect) of the cortical bone adjacent to the implant when compared with the bone and cement graft model and metallic hemi-wedge. However is during the construction with bovine bone graft that takes place the maximum increment of strain in cortical bone, on the medial side. These increases observed in the cortical bone for larger buildings is opposite to the behavior observed in the cancellous bone at the implant interface, in which case these constructions originate a reduction of deformation on the solution without defect. So the more invasive solutions potentiate the risk of fatigue damage in cortical bone and simultaneously increase the risk of bone resorption in the adjacent cancellous bone. In terms of stability only the metallic block implant proved to be signi cantly more stable than the other techniques. The additional stability provided by stems was felt only in less invasive constructions with the use of bone cement and hemi-wedge.
Nesta tese foi objectivo estudar os aspectos biomecânicos das diferentes técnicas de colmatação de perda óssea na tibia proximal aquando da revisão da artroplastia total do joelho. Procurou-se especi camente avaliar como cada uma das diferentes técnicas altera a transferência de carga ao osso de suporte, aferindo assim potenciais riscos de reabsorção óssea ou mesmo falha por fadiga do osso de suporte. Foi também avaliada de uma forma comparativa a estabilidade de cada construção de colmatação do defeito relativamente à solução sem defeito ósseo. Procurou-se também nesta tese avaliar o efeito da utilização da haste intramedular quando associada às diferentes técnicas. Para o efeito numa primeira fase procurou-se realizar uma analise detalhada à articulação do joelho na sua vertente anatómica e biomecânica com especial enfoque na artroplastia e no processo de revisão desta. Foi seleccionada a prótese do joelho P.F.C. Sigma como elemento para a realização do estudo comparativo, os elementos protésicos metálicos utilizados nas diferentes construções da substituição óssea foram também do mesmo modelo; hemi-cunha, cunha total e bloco. Em complemento foram também comparadas mais duas técnicas de colmatação óssea; uma com recurso apenas ao cimento ósseo e outra com a utilização de um enxerto de osso bovino. Na fase seguinte desenvolveram-se modelos experimentais com recurso à tibia em material compósito, onde os defeitos ósseos foram gerados e as diferentes técnicas de colmatação aplicadas através da realização de cirurgias "in-vitro". A m de aferir as alterações de transferência de carga e estabilidade foram colocados extensometros na região anexa ao defeito permitindo a avaliação das deformações principais na superfície dos modelos, assim como recorreu-se a utilização de técnicas de vídeo para avaliação da estabilidade do prato tibial nas diferentes técnicas. Estes modelos foram submetidos a um severo caso de carga no condilo medial onde se situa o defeito, tendo-se procedido à avaliação e comparação dos resultados das deforma ções no osso e estabilidade do prato. Numa fase posterior procedeu-se ao desenvolvimento de modelos numéricos de elementos nitos que procuram replicar os modelos avaliados experimentalmente. Este modelos foram submetidos a dois casos de carga, um idêntico ao aplicado nos modelos experimentais que permitiu a validação destes modelos numéricos e um outro caso de carga representativo de uma condição de carga mais siológica durante o ciclo de marcha. Este modelos numéricos permitiram a avaliação de parâmetros biomecânicos não passíveis de avaliação com recurso aos modelos experimentais anteriores. Foram assim analisadas as deformações impostas aos osso cortical e esponjoso na vizinhança do defeito e na interface com este. Estes mesmos modelos foram comparados com os resultados obtidos nos modelos experimentais de forma a avaliar a sua correlação. Os resultados experimentais e numéricos obtidos permitiram evidenciar boa correlação entre estes demonstrando que os modelos numéricos são capazes de replicar com delidade o comportamento dos modelos experimentais. Os resultados obtidos em ambos os tipos de modelos evidenciam alterações de transferência de carga e estabilidade entre os diferentes tipos de técnicas. Os modelos com cunha total e bloco aumentaram em média as deformações no lado medial (lado do defeito) do osso cortical adjacente ao implante quando comparados com o modelo de colmatação só com cimento ósseo e hemicunha. No entanto, os valores de máximos de incremento de deformação no osso cortical no lado medial ocorram para a construção com enxerto ósseo bovino. Estes incrementos observados no osso cortical para as construções de maior dimensão é oposto ao comportamento observado no osso esponjoso na interface com o implante, pois neste caso estas construções originam uma redução das deformações relativamente à solução sem defeito. Assim, temos que as soluções mais invasivas potenciam o risco de dano por fadiga óssea do osso cortical e simultaneamente potencializam o risco de reabsorção óssea no osso esponjoso adjacente. Em termos de estabilidade apenas a construção com bloco se revelou signi cativamente mais estável que as restantes técnicas. O efeito adicional de estabilidade das hastes apenas se fez sentir nas construções menos invasivas com recurso ao cimento ósseo e hemi-cunha.

Proteins are substances with great usage. For industrial usage, proteins are often taken from their natural enviroment. In foreign environment, it proteins can unfold and their function can be compromised. This is the reason for stabilization of proteins and one of ways to stabilization is using disulphide bonds. This work describes basic terms related to protein stabilization - proteins, their structure and interactions within them, basic terms from thermodynamics. Problem of protein stability is discussed and the factors which stabilize or destabilize protein are enumerated with the emphasis on disulphide bonds. Existing approaches to disulphide bonds design, dataset for testing own tool are described. Implementation of the tool using geometrical properties of the bonds and fl exibility of places in protein is described. The tool was tested on proteins with native disulfide bonds and compared to existing tools, also metrics FRO (fractional rank order) was used. Native disulfide bond was found in 64 % of cases, in 60 % of cases this native disulfi de bond was in the first quarter of ordered found disulfi de bonds.

Master of Science
Department of Civil Engineering
Robert J. Peterman
Epoxy polymer overlays have been used for decades on existing bridge decks to protect the deck and extend its service life. The polymer overlay’s ability to seal a bridge deck is now being specified for new construction. Questions exist about the amount of drying time needed to achieve an acceptable concrete moisture content to ensure an adequate bond to the polymer overlay. Current Kansas Department of Transportation (KDOT) specifications for new bridge decks call a 14 day wet curing period followed by 21 days of drying (Kansas DOT, 2007) If not enough drying is provided, the moisture within the concrete can form water vapor pressure at the overlay interface and induce delamination. If too much drying time is provided projects are delayed, which can increase the total project cost or even delay overlay placement until the next spring. A testing procedure was developed to simulate a bridge deck in order to test the concrete moisture content and bonding strength of the overlay. Concrete slabs were cast to test typical concrete and curing conditions for a new bridge deck. Three concrete mixtures were tested to see what effect the water –cement ratio and the addition of fly ash might have on the overlay bond strength. Wet curing occurred at 3 different temperatures (40°F, 73°F, and 100°F) to see if temperature played a part in the bond strength as well. The concrete was then allowed to dry for 3, 7, 14, or 21 days. Five epoxy-polymer overlay systems that had been preapproved by KDOT were each used in conjunction with the previously mentioned concrete and curing conditions. After, the slabs were setup to perform pull-off tests to test the tensile rupture strength. The concrete slabs with the different epoxy overlays were heated to 122-125°F to replicate summer bridge deck temperatures. Half of the pull-off tests were performed when the slabs were heated and half were performed once the slabs had cooled back down to 73°±5°F. Results from the pull-off tests as well as results from a moisture meter taken on the concrete prior to the overlay placement were compared and analyzed. Testing conditions were compared with each other to see which had a larger effect on the epoxy polymer overlay’s bond strength.

La thèse se compose de trois essais, abordant chacun la dichotomie entre la liaison et l'adhérence à partir d'un angle théorique différent. Dans le premier essai, je pose la question Comment Lier et Comment Adhérer et je propose un nouveau cadre théorique pour analyser le capital social, qui déconstruit sa principale fonction au-delà de la liaison ou de l'adhérence dans sa substance comme les relations sociales par rapport à la position dans la structure du réseau. Compte tenu de ces deux dimensions de l'analyse des réseaux sociaux, je propose quatre sources distinctes du capital social qui ont une valeur prédictive différente pour les réalisations individuelles - le réseau de liaison, les relations de liaison, le réseau d'adhérence et les relations d'adhérence - et j'examine leur valeur à la performance individuelle. La question du plomb dans le deuxième essai de ma thèse est Quand faut-il lier et Quand faut-il adhérer? Rejoignant la recherche sur la valeur éventuelle du capital social, je cherche comment l'organisation et les facteurs liés à l'emploi modèrent la relation entre chaque source de capital social à la performance et théorisent sur les stratégies que les individus devraient poursuivre afin d'obtenir de meilleures performances. Dans le troisième essai, je pose la question Sur Quelle Source devrais-je me fonder ? J'examine la puissance individuelle de chaque source de capital social et de la complémentarité entre les quatre d'entre eux. Je démontre que, bien que toutes les sources de capital social doivent avoir un impact positif sur la performance, certains d'entre eux pourraient supprimer le déploiement des autres formes
My dissertation expands the line of inquiry of the contingent value of social capital to individual performance by raising three novel questions. In the first essay of my dissertation I focus on “How to bridge and how to bond” and propose a new theoretical framework for analyzing social capital, which deconstructs its major function beyond bridging or bonding into its substance as social relations versus position in network structure. Considering these two dimensions of social network analysis I propose four distinct sources of social capital that have different predictive value for individual achievements: bridging network, bridging relations, bonding network and bonding relations. The lead question in the second chapter of my dissertation is “When to bridge and when to bond”. Joining the research on the contingent value of social capital, I look at organization and individual level factors to predict the value of each social capital source to performance and theorize about the strategies individuals should pursue in order to achieve better performance. In the third essay I ask “Should one start with bridging or with bonding?” Building on the categorization proposed in the first chapter I investigate the most successful social capital path to on-the-job performance

The primary objective of this research was to experimentally investigate material and bond properties of three different types of fiber reinforced polymer (FRP) bars, and determine their effect on the design of a bridge deck using FRP bars as the top mat of reinforcement. The properties evaluated include the tensile strength, modulus of elasticity, bond behavior, and maximum bond stress. The experimental program included 47 tensile tests and 42 beam end bond tests performed with FRP bars. Tensile strength of the bars from the tensile testing ranged from 529 MPa to 859 MPa. The average modulus, taken from all the testing, for each type of bar was found to range from 40 GPa to 43.7 GPa. The maximum bond stress from the beam end bond tests ranged from 9.17 MPa to 25 MPa. From the tests, design values were found in areas where the properties investigated were related. These design values include design tensile strength, design modulus of elasticity, bond coefficient for deflection calculations, bond coefficient for crack width calculations, and development length. The results and conclusions address design concerns of the different types of FRP bars as applied in the top mat of reinforcement of a bridge deck. A secondary objective was to evaluate the disparity in results between direct pullout tests, and beam end bond tests. Results from the experimentally performed beam end bond test were compared to previous literature involving the direct pullout tests. Results from the performed beam end bond tests were higher than all of the literature using direct pullout results. No recommendations were given on the disparity between the two test methods.
Master of Science

Calcium sulfoaluminate (CSA) cement was used to cast a prestressed voided deck slab bridge girder. The rapid-set properties of CSA cement allowed the initial concrete strength to reach the required 4300 psi needed in order to cut the prestressing strands 6.5 hours after casting. Prestress losses were monitored long-term using vibrating wire strain gages cast into the concrete at the level of the prestressing strands and the data was compared to the American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) predictions for prestress losses. AASHTO methods for prestress loss calculation were overestimated compared to the vibrating wire strain gage data. Material testing was performed to quantify material properties including compressive strength, tensile strength, static and dynamic elastic modulus, creep, and drying and autogenous shrinkage. The material testing results were compared to AASHTO predictions for creep and shrinkage losses. The bridge girder was tested at midspan and a distance 1.25 times the depth of the beam from the face of the support until failure. Midspan testing consisted of a crack reopening test to solve for the effective prestress in the girder and a test until failure. The crack reopen effective prestress was compared to the AASHTO prediction and AASHTO appeared to be effective in predicting losses based on the crack reopen data. The midspan failure was a shear failure, as accurately predicted by AASHTO. The 1.25d test resulted in a bond failure, which was accurately predicted by the AASHTO bond model for prestressed concrete. Funding for this project was provided by The Mountain Plains Consortium.

Two different asphalt concrete systems were examined in this research study. The existing system, consistent with current timber bridge construction practice, uses a preformed waterproofing membrane placed on a preservative treated wood deck overlaid with a bituminous concrete wearing surface. The second system consists of a treated wood deck overlaid with a base course of bituminous concrete, a waterproofing membrane, and a bituminous concrete wearing surface.

The testing regime used in this research to evaluate watertightness and bond performance incorporated three parameters: three waterproofing membranes, two wood preservative treatments, and two environmental degradation conditions induced by temperature cycling in a moisture saturated condition. Control groups were evaluated for each study parameter and duplicate specimens were prepared and tested for each of the study parameters. A total of 160 specimens were constructed and tested.

Watertightness of each system was determined by measuring the electrical impedance across a test specimen perpendicular to the direction of bond orientation in the pavement. The bond strength between each material of the paving systems was assessed using a shear test apparatus designed and built for this study.

In addition to the laboratory constructed specimens, three drilled cores were taken from a bridge located on Creekside Drive in East Pennsboro Township, Pennsylvania. The deck was constructed using the new design proposed in this research and each core was tested for watertightness and bond strength.

Results of watertightness testing indicated that low temperature environments appear to be most detrimental to system integrity in both the existing and proposed paving system configurations examined in this research. In general, each membrane appeared to perform equally well in the proposed paving system configuration as well as with all of the wood preservative treatments used in the existing pavement system.

Bond strength between asphalt and wood with no membrane was observed to be nonexistent whether or not any preservative treatment was present. The placement of a membrane between these two layers did, however, result in a significant increase in bond strength because each membrane tested was able to adhere to the wood base better than the asphalt overlay. This gain is strength was significantly offset when petroleum solvent based preservative treatments were present in the wood substrate. Protectowrap M400 membrane performed slightly better than the other membranes when used with untreated wood, but all of the membranes performed equally when preservative treatments were present. The highest interlayer bond strengths (asphalt/asphalt or asphalt/wood) observed in this research occurred when asphalt concrete surface material was placed directly on top of asphalt concrete base material, however the addition of a membrane between the asphalt lifts consistently reduced this strength. The results of bond testing indicate that the proposed system will perform better in terms of shoving in the pavement overlay. Based on bond test results of cores taken from the Creekside Drive bridge, it appears that a shear strength greater than 25 psi after 200 low temperature exposure cycles will provide acceptable paving system performance in a low temperature (0-40ºF) environment.

Master of Science

The objective of this study is to evaluate the bond durability of an epoxy-based polymer concrete wearing surface bonded to aluminum bridge decks. In the bridge design, an aluminum alloy bridge deck is used with a polymer concrete wearing surface. A modified mixed mode flexure fracture test was developed to assess the bond durability of specimens aged in the following environmental conditionings: 30°C [86°F], 98% RH; 45°C [113°F], 98% RH; 60°C [140°F], 98% RH; freezing and thawing; salt (NaCl) water soak; and 60°C [140°F], dry. The exposure times varied from none to twelve months. The critical strain energy release rate (Gc) of the bond was determined using a compliance technique. In spite of considerable scatter in the data, the results suggested that the interfacial bond toughness had been degraded by exposure conditions. The aging appeared to affect the polymer concrete overlay (silica aggregates/epoxy bond) as well. Fracture analysis and finite element modeling were completed for linear elastic behavior. Analytical and numerical solutions were in reasonably good agreement. Characterization of the bridge components and failure specimens were accomplished using analytical measurements including thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Techniques employed in the surface analysis included x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM).
Master of Science

Advanced composites have become one of the most popular methods of repairing and/or strengthening civil infrastructure in the past couple of decades. While the use of Fiber Reinforced Polymer laminates and sheets for the repair and strengthening of reinforced concrete structures is well established, research on the application of FRP composites to steel structures has been limited. The use of FRP material for the repair and rehabilitation of steel members has numerous benefits over the traditional methods of bolting or welding of steel plates. Carbon FRPs (CFRPs) have been preferred over other FRP material for strengthening of steel structures since CFRPs tend to posses higher stiffness. The emergence of high modulus CFRP plates, with an elastic modulus higher than that of steel, enables researchers to achieve substantial load transfer in steel beams before the steel yields. This research investigates both analytically and experimentally, the bond characteristics between ultra high modulus CFRP strengthened steel members and the flexural behavior of these members. A series of double strap joint tests with two different CFRP strip widths are carried out to evaluate the development length of the bond. Both ultra high modulus and normal modulus CFRP laminates are used to compare strengthened member performance. Steel plates reinforced with CFRP laminates on both sides are loaded in tension to evaluate the load transfer characteristics. Debonding under flexural loads is also studied for ultra high modulus CFRP strengthened steel girders. Flexural tests are carried out under 4-point bending on several small scale wide flange beams. This study also introduces the novel ultra high modulus CFRP plate strip panels for strengthening of steel bridge girders. The first field application of ultra high modulus CFRP laminates in strengthening steel bridge girders in the United States is also carried out as part of the research. Full scale load tests carried out before and after the strengthening are utilized to measure the degree of strengthening achieved and checked against the expected results. A finite element model is developed and calibrated using data obtained from the field testing of the bridge. The model is then used to evaluate the behavior of the bridge under different conditions before and after the strengthening process.

Skador och slitage på brokonstruktioner av betong beror på tösalter, armeringskorrosion och frostcykler i kombination med ökande trafiklaster. Den i särklass vanligaste reparationsåtgärden för dessa typer av skador är att göra en pågjutning. Metoden går ut på att först avlägsna det skadade eller dåliga betongskiktet innan en ny betong pågjuts. För att bedöma hur bra ett pågjutningsarbete är behöver vidhäftningen mellan den nya pågjutningen och gamla betongen fastställas. Den mest använda metoden för detta syfte är s.k. dragprovning som bestämmer draghållfastheten i vidhäftningen. I praktiken är dock vidhäftningens skjuvhållfasthet av större intresse och approximeras därför utifrån draghållfastheten, men med en vridprovning kan fogens skjuvhållfasthet direkt bestämmas. Syftet med examensarbetet är att undersöka vridprovningens reliabilitet för att i framtiden eventuellt kunna bestämma skjuvhållfastheten på ett mer direkt och korrekt sätt. I examensarbetet undersöks vridprovningens reliabilitet för att bestämma skjuvhållfastheten i fogen mellan pågjutning och gammal betong med dragprovningen som referens. Studien omfattar åtta parallellprovningar av drag- och vridprovningar där den lägst uppmätta skjuvhållfastheten jämförs med fogens dimensioneringsvärde enligt EK2. Examensarbetet görs i samband med Spårväg city-projektet vid Sergels torg, Stockholm, i uppdrag från Trafikkontoret i Stockholm och CBI Betonginstitutet. Resultaten från provningarna visade att fogbrott, som är av intresse, var vanligare för dragprovning än vridprovning. Den stora spridningen av mätvärdena var en konsekvens av det låga antalet fogbrott för vridprovningen. Medelvärdet för fogens draghållfasthet på 1,43 MPa tyder på god vidhäftning, men fogens skjuvhållfasthet bestämd med vridprovning visar ett medelvärde på endast 1,61 MPa och understiger det förväntade värdet på ca dubbla draghållfastheten d.v.s. 2,9 MPa. Intressant är att det lägst uppmätta värdet på skjuvhållfastheten på 0,83 MPa var ovanligt lågt, men fortfarande större än dimensioneringsvärdet enligt EK2 på 0,59 MPa. Studien har visat att vridprovningen är en svårtydlig metod för att bestämma skjuvhållfastheten i fogen mellan pågjutning och gammal betong. Anledningen till detta beror främst av tre faktorer, för få antal provningar, den stora spridningen av mätvärden samt de svårtolkade brottmoderna från vridprovningen. Trots detta tros vridprovningen vara en framtida metod för konstruktörer och beställare eftersom metoden är ett bra mätverktyg för att bestämma skjuvhållfastheten för pågjutna betongkonstruktioner som helhet och inte bara i fogen mellan pågjutning och befintlig betong.
Damages and wear on concrete bridges are due to de-icing salt or salt water, reinforcement corrosion and repeated freeze-thaw cycles in combination with increasing traffic loads. The most common repair operation for these types of damages is to remove the deteriorated concrete and replace it with a new concrete overlay. To evaluate how well a bonded concrete overlay is, the bond strength between the new and old concrete has to be determined. The most widely used method for this purpose is the so-called pull off test to determine the tensile bond strength. In practice however the shear bond strength is of greater interest and is therefore approximated on the basis of tensile bond strength, but with a torsion test the shear bond strength can be directly determined. The purpose of this study is to investigate the reliability of the torsion test to determine the shear bond strength in a more direct and accurate manner. The thesis examines the reliability of the torsion test to determine the shear bond strength with the pull off test as a reference. The study includes eight parallel tests of pull off and torsion tests where the lowest measured shear bond strength is compared with the calculated design value of shear bond strength according to EC2. The work is done in connection with the Spårväg city project at Sergels torg, Stockholm, in collaboration with the Traffic Administration Office in Stockholm and CBI, the Swedish Cement and Concrete Research Institute. The results of the tests showed that the failures in the interface between new and old concrete, which are of interest, were more common for pull off tests than torsion tests where only two of the eight test samples showed failure in the interface. The wide scatter of the measured values is a consequence of the low number of failures in the interface. The mean value of the tensile bond strength was 1,43 MPa, which indicates good bond strength. The shear bond strength however made with torsion tests show a mean value of only 1,61 MPa. Lower than the expected value of about twice the tensile bond strength of 2,86 MPa. Interestingly, the lowest measured value of the shear bond strength of 0,83 MPa was unusually low, but still higher than the calculated design value of shear bond strength of 0.59 MPa according to EC2. The study has shown that torsion test is a difficult method for determining the shear strength of the bond between the new and old concrete. The reason for this is mainly due to three factors, the low number of tests, the large scatter of values, and the difficulty to interpret failures of the test samples. Despite this the torsion test seems to be a future method for structural engineers and contractors as a tool to determine shear strength for repaired concrete structures in general and not only the shear bond strength.

L'avancée de la technologie des PRF a suscité l'intérêt de l'introduction de nouvelles fibres, comme la fibre de basalte, qui a un potentiel d'offrir une solution efficace, lorsqu’utilisée dans les structures en béton, soit sur la résistance à la corrosion, la durabilité et la rentabilité. En outre, les codes et les guides disponibles, ne fournissent pas de recommandations pour l'utilisation de barres en PRFB puisque les recherches passées dans ce domaine sont limitées. Donc, des travaux de recherche sont nécessaires pour caractériser et comprendre le comportement des barres de PRFB dans les éléments en béton armé. En conséquence, les objectifs principaux sont d'évaluer les caractéristiques à court et long terme des barres de PRFB nouvellement développées, ainsi que d'évaluer les performances structurales de ces nouvelles barres comme renforcement interne dans les poutres et les dalles de pont et d'introduire ce nouveau renforcement dans les codes et les guides de dimensionnement. Les tests expérimentaux ont été faits en trois parties. La première partie porte sur le développement de trois nouvelles barres et tendons en PRFB pour déterminer leurs propriétés physiques et mécaniques. Les performances à long terme et de durabilité ont été réalisées en conditionnant les barres de PRFB dans une solution alcaline simulant les conditions humides dans le béton pour déterminer la compatibilité comme renforcement interne dans les éléments en béton. Par la suite, les propriétés ont été déterminées et comparées avec des spécimens non conditionnés (référence). La seconde partie a porté sur sept dalles de pont en béton armé grandeur réelle avec les bords restreints, simulant les tabliers de pont les plus utilisés en Amérique du Nord, pour évaluer la performance des dalles renforcées de PRFB et d'acier. Les dalles mesurent 3000 mm de long × 2500 mm de large × 200 mm d'épaisseur. Les dalles ont été testées jusqu'à la rupture sous une charge concentrée au centre de celles-ci simulant l'empreinte d'une roue d'un camion. Les capacités en poinçonnement sont prédites en utilisant les exigences réglementaires disponibles, et sont comparées aux résultats expérimentaux. La troisième partie de cette étude portait sur les essais de 14 poutres en béton de 3100 mm de long × 200 mm de large × 300 mm de profond pour examiner le comportement en flexion et les performances en service des barres de PRFB avec deux états de surfaces: fini sablé et crénelé. Les poutres ont été testées en flexion en quatre points avec une portée libre de 2700 mm jusqu'à la rupture. Les résultats sont introduits et discutés en terme : du comportement de la fissuration, des flèches, de la capacité en flexion et des modes de ruptures. De plus, le coefficient d'adhérence (kb) des barres de PRFB est déterminé et comparé avec les recommandations des codes et guides actuels. Les résultats sont introduits et discutés en terme : du comportement de la fissuration, des flèches, de la capacité en flexion et des modes de ruptures. De plus, le coefficient d'adhérence des barres de PRFB est déterminé et comparé avec les recommandations des codes et guides actuels. Les résultats de l'étude concluent sur la viables pour la production des barres de PRFB pour respecter les exigences des codes actuelles. Également, les résultats d'essai indiquent que les barres de PRFB ont de bonnes propriétés mécaniques et peuvent être placées dans la même catégorie que les barres de PRFV, soit grade III. De plus, le comportement des poutres et des dalles de pont renforcées de PRFB est similaire que pour un renforcement en PRFV et PRFC et les exigences réglementaires sont applicables pour les barres de PRFB.
Abstract: The advances in fiber-reinforced-polymer (FRP) technology have spurred interest in introducing new fibers, such as basalt FRP (BFRP), which has the potential to offer an efficient solution when implemented in concrete structure, such as corrosion resistant, durable and cost-effective. Furthermore, the available design codes and guides do not provide any recommendations for the use of BFRP bars since fundamental studies and relevant applications are still limited. Therefore, investigations are needed to characterize and understand the behavior of BFRP bars in concrete members. Consequently, the main objectives of this experimental investigation are to evaluate the short- and long-term characteristics of newly developed BFRP bars, as well as evaluate the structural performance of these new bars as internal reinforcement for concrete beams and bridge-deck slabs to introduce these new reinforcing bars to the design codes and guides. The experimental tests were completed through three parts. The first part was conducted on three newly developed BFRP bars and tendons to investigate their physical and mechanical properties. Durability and long-term performance were assessed by conditioning the BFRP bars in an alkaline solution simulating the moist concrete environment to determine their suitability as internal reinforcement for concrete elements. Thereafter, the properties were assessed and compared with the unconditioned (reference) values. The second part of this study was conducted on seven full-scale edge-restrained concrete bridge-deck slabs simulating actual slab-on-girder bridge-deck that is commonly used in North America to evaluate the performance of concrete bridge-deck slabs reinforced with BFRP and steel bars. The deck slabs measured 3000 mm long × 2500 mm wide × 200 mm deep. The slabs were tested up to failure under single concentrated load acting on the center of each slab simulating the footprint of sustained truck wheel load. The punching shear capacities were predicted using the available provisions, and compared with the experimental results. The third part of this study included testing of fourteen concrete beams of 3100 mm long × 200 mm wide × 300 mm deep to investigate the flexural behavior and serviceability performance of sand-coated and ribbed BFRP bars in concrete beams. The beams were tested under four-point bending over a clear span of 2700 mm until failure. The results are introduced and discussed in terms of cracking behavior, deflection, flexure capacity, and failure modes. In addition, the bond-dependent coefficient (kb) of the BFRP bars was determined and compared with the recommendations of the current FRP design codes and guides. The findings of this study concluded the feasibility of producing BFRP bars meet the requirements of the current FRP standards. Also, the test results revealed that the BFRP bars had good mechanical behavior and could be placed in the same category as grade II and grade III GFRP bars. Moreover, the behavior of the concrete bridge-deck slabs and beams reinforced with BFRP bars was quite similar to the counterparts reinforced with glass- and carbon-FRP bars and the available FRP provisions are applicable for BFRP bars. The beam test results yielded an average bond-dependent coefficient (kb) of 0.76±0.03 and 0.83±0.03 for the sand-coated and ribbed BFRP bars, respectively.

The tricobalt cluster PhCCo3(CO)9 (1) reacts with the bidentate phosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) in the presence of added Me3NO to give the diphosphine-substituted cluster PhCCo3(CO)7(bma) (2). Cluster 2 is unstable in solution, readily losing CO to afford Co3(CO)6[(μ2-η2/η1-C(Ph)C=C(PPh2)C(O)OC(O)](μ2-PPh2) (3) as the sole observed product. VT-31P NMR measurements on cluster 2 indicate that the bma ligand functions as both a chelating and a bridging ligand. At -97 °C, 31P NMR analysis of 2 reveals a Keq of 5.7 in favor of the bridging isomer. The bridged bma cluster 2 is the only observed species above -50°C. The solid-state structure of 2 does not correspond to the major bridging isomer observed in solution but rather the minor chelating isomer. The conversion of 2 to 3 followed first-order kinetics, with the reaction rates being independent of the nature of the reaction solvent and strongly suppressed by added CO, supporting a dissociative loss of CO as the rate-determining step. The activation parameters for CO loss were determined to be ΔH≠ = 29.9 ± 2.2 kcal/mol and ΔS≠ = 21.6 ± 6 eu.

Orientador: Bruno Livani
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas
Made available in DSpace on 2018-08-25T22:20:14Z (GMT). No. of bitstreams: 1 Mongon_MauricioLealDias_D.pdf: 3191083 bytes, checksum: 7d82ec3811a7941ce0efb53f33c4ecea (MD5) Previous issue date: 2014
Resumo: Introdução: A amputação, especialmente dos membros inferiores, é um procedimento cirúrgico antigo que permite excelentes resultados quando realizada nas indicações apropriadas. Na década de 1940 , Ertl desenvolveu uma técnica reprodutível para amputação transtibial com o princípio de osteomioplastia , que restaurou a pressão intra-óssea por meio da obliteração do canal medular e ampliou a área de apoio terminal , formando uma ponte óssea entre a fíbula e a tíbia distais (sinostose). Objetivos: O objetivo deste estudo foi investigar a eficácia de uma modificação da técnica original Ertl, em que um retalho pediculado osteoperiosteal é usado para formar a ponte óssea na amputação transtibial em adultos . Resultados: Todos os nove pacientes apresentaram cotos indolores e capazes de apoio terminal total em 24 semanas pós-operatório. Conclusão: A construção de um retalho pediculado tibial osteoperiosteal cortical para alcançar uma ponte óssea durante a amputação transtibial é um procedimento seguro e eficaz que proporciona um coto estavel e indolor que permite apoio terminal. Trata-se de uma opção útil para pacientes jovens , atletas e pacientes com grande demanda física
Abstract: Background: Amputation, especially of the lower limbs, is an ancient surgical procedure that gives excellent results when conducted under the appropriate conditions. In the 1940s, Ertl developed a reproducible technique for transtibial osteomyoplastic amputation, which restored the intraosseous pressure through canal obliteration and expanded the area of terminal support by forming a bony bridge between the fibula and distal tibia. Objectives: The aim of this study was to investigate the effectiveness of a modification of the original Ertl technique, whereby a cortical tibial osteoperiosteal flap technique is used to achieve a bony bridge during transtibial amputation in adults. Results: All of the patients had stumps that were painless and able to bear the total terminal weight at 24th week post-surgery. Conclusion: The construction of a cortical tibial osteoperiosteal flap to achieve a bony bridge during transtibial amputation is a safe and effective procedure that provides a strong and painless stump that is terminal weight-bearing. This constitutes a useful option for young patients, athletes, and patients with high physical demands
Doutorado
Fisiopatologia Cirúrgica
Doutor em Ciências

Objetivo: Avaliar pacientes reabilitados com prótese tipo protocolo mandibular e analisar o impacto do diferente número de implantes utilizados na taxa de sobrevivência dos implantes, perda óssea marginal e sobrevivência das próteses. Material e métodos: Esta revisão sistemática foi conduzida segundo orientações do PRISMA e registrada sob número de registo CRD42016048523 (PROSPERO). A base de dados electrônica PubMed/MEDLINE foi pesquisada para artigos publicados até 17 de julho de 2016 sem restrições quanto ao ano de publicação e teve como objetivo responder a seguinte pergunta em formato PICO: "Em pacientes desdentados, protocolos mandibulares suportados por três implantes, comparados com diferente número de implantes, mostram taxa de sobrevivência de implantes, perda óssea marginal e sobrevivência da prótese satisfatórios?" Os estudos foram avaliados segundo os níveis de evidência OCEBM e a qualidade metodológica foi avaliada de acordo com a escala MINORS e ferramenta de risco de viés Cochrane. Foi realizada a estatística descritiva quando aplicável. Curvas de sobrevivência para os implantes foram construídas com o metódo de Kaplan Meyer e a perda óssea marginal foi analisada pelos testes de kruskal-Wallis, Dunn’s e Mann Whitney. Resultados: 21 estudos foram incluídos na síntese quantitativa. 4712 implantes e 1245 protocolos mandibulares foram examinados em 1245 pacientes. Os resultados foram agrupados em categorias com base no número de implantes instalados em cada paciente: grupo 1 (três implantes) mostrou uma taxa de sobrevivência do implante de 90%, grupo 2 (4 implantes) apresentou 95% e o grupo 3 (cinco implantes) atingiu a menor taxa de sobrevivência do implante (74%). Os grupos 1 e 3 apresentaram os menores valores de perda óssea no primeiro ano (0,73 e 0,70 mm respectivamente), com diferença estatisticamente significante do grupo 2 que registrou mediana = 1,31 mm (p = < 0,001). Conclusão: Apesar das limitações quanto à falta de estudos de elevado nível de evidência e da própria metodologia da pesquisa por termos MeSH, pôde-se concluir que protocolos mandibulares suportados por três implantes demonstraram sobrevivência de implantes e perda óssea marginal no primeiro ano satisfatórios. A sobrevivência de próteses, no entanto, foi inferior aos demais grupos e isto sugere um maior acompanhamento de tais reabilitações a fim de esclarecer dados e buscar soluções.
Purpose: To assess edentulous patients rehabilitated by implant-supported mandibular full-arch bridges and to analyze the impact of the different number of implants used on implant survival rate, bone loss around the fixtures and prosthesis survival rate. Material and methods: This systematic review followed PRISMA guidelines and was registered on PROSPERO (registration number CRD42016048523). PubMed/MEDLINE electronic database was searched for articles published up until July 17th, 2016 without restrictions about publication year and aimed to answer the following question in PICO format: “In edentulous patients, full arch-bridges supported by three implants, compared to those with different number of implants, show satisfactory implant survival rate, bone loss and prosthesis survival rate?” Evidence level of studies were evaluated according to OCEBM e the methodological quality by MINORS scale and Cochrane Risk of Bias Tool. Descriptive statistics was performed when applicable. Implant survival curves were constructed with Kaplan-meyer method and marginal bone loss was analyzed with kruskal-Wallis, Dunn’s and Mann Whitney tests. Results: 21 studies were enrolled. Overall, 4712 implants and 1245 implant-supported fullarch bridges were examined in 1245 patients. Results were grouped on categories based on the number of fixtures on each patient: Group 1 (three implants) showed an implant survival rate of 90%, Group 2 (four implants) presented 95% and the Group 3 (five implants) reached the lowest implant survival rate (74%). Group 1 and Group 3 showed the lowest values of first year bone loss (0.73 and 0.70 mm respectively), statistically significant different of Group 2 that registered median = 1,31mm (p = <0.001). Conclusion: Despite of the limitations regarding the lack of high level of evidence studies and the methodology of MeSH terms research itself, it was concluded that full archbridges supported by three implants show satisfactory implant survival rate and first year bone loss. The prosthesis survival rate, however, was inferior to the other groups and this suggests a bigger follow-up of these rehabilitations with the aim of clarifying data and search for solutions.
Dissertação (Mestrado)

The growth plate cartilage, which is located at the ends of children’s long bones, is responsible for longitudinal growth of the skeleton. However, due to its cartilaginous composition and its location, the growth plate is commonly injured, mostly through fractures. An undesirable outcome to growth plate fracture is the bony repair of the injured cartilage at the fractured area. Consequently, children often incur skeletal angular deformities and growth arrest. Current corrective surgical treatments for these outcomes are highly invasive, and therapeutic interventions are not possible as little is known about the mechanisms and pathways that lead to bone bridge formation. Using a rat model, previous studies have shown sequential inflammatory, fibrogenic, osteogenic and bone maturation responses involved in the bony repair of the injured growth plate. However, structural changes in the growth plate, at both the injury site and at the non-injured area, have not been closely examined previously, and little is known about the molecular mechanisms underlying the bony repair. Therefore, this PhD study, using a rat tibial growth plate injury model, aimed to examine the effects of growth plate injury on the structure and composition of the injured growth plate in a longitudinal study using micro-CT and histology. Microarray analysis of the injury site only, collected using laser capture microdissection was used to identify potential cellular and molecular mechanisms involved in bone bridge formation. In addition, Real Time RT-PCR on adjacent uninjured growth plate was used to examine potential cellular/molecular changes at the uninjured area and on whole growth plate scrapes to examine the potential involvement of Wnt signalling in bone bridge formation. Micro-CT analysis revealed a significant increase in bone material within the injury site (when compared to normal) at 14 and 60 days post-injury, where 12% and 40% of the injury site was replaced by bone, respectively. Interestingly, although there were no changes in growth plate thickness between injured and normal rats at either day 14 or 60, at day 60, many small bone tethers formed at the adjacent growth plate outside the injury site but none were found in normal aged-matched control rats. Histological studies revealed dereased proliferation but increased apoptosis of chondrocytes at the adjacent growth plate cartilage, and RT-PCR analysis revealed differential expression of apoptosis-regulatory genes Bcl-2 and FasL (compared to normal), confirming the increase in apoptosis in the adjacent uninjured growth plate. Down-regulation of Sox-9 and IGF-1 on days 7 and 14 suggests that growth plate injury may slow down the rate of longitudinal growth by decreasing chondrocyte proliferation and/or differentiaiton soon after injury. Lastly, bone matrix protein osteocalcin was increased on day 60, suggesting degeneration and bone formation at the adjacent uninjured area. Microarray analysis identified changes in several key BMP and Wnt signalling components across the time-course of bone bridge formation, including BMP-2, BMP-6, BMP-7, chordin, chordin-like 2, and Id-1, and β-catenin, Csnk2a1, SFRP-1 and SFRP-4, respectively, in early stages of bone bridge formation (day 4 and day 8). Osteocalcin expression was also prominent at day 8, supportive of osteoblast development and bone formation. During later stages (day 14), active bone formation and remodelling was prominent and was largely regulated by the BMP signalling pathway (increased BMP-1 and BMP-6 but decreased inhibitor chordin), as well as by Traf6, Fgfr1, osteopontin, Mmp9 and Wnt signalling, where several genes were up and down-regulated. Expression levels of Wnt signalling inhibitors (SFRP-1, SFRP-4 and Wisp1) were increased at days 8 and 14 and may be negatively regulating bone formation during the osteogenic phases of the repair of the growth plate injury site. Findings were also suggestive of an overall increase in the canonical Wnt signalling pathway at days 4 and14, supported by increased expression of β-catenin and drecreased expression of Wnt inhibitors, and decreased expression of Fzd1 and Fzd2 and increased Lef1 expression, respectively. Overall, this study found a complex balance between the canonical and non-canonical Wnt pathways as well as an association with BMP signalling over the time-course of bone bridge formation. Lastly, Real-Time PCR on Wnt signalling components revealed significant changes in gene expression of Wnt genes, receptors and inhibitors, but were inconclusive as the method of tissue isolation was not specific enough to represent true changes in gene expression.
Thesis (Ph.D.) -- University of Adelaide, School of Paediatrics and Reproductive Health, 2012

碩士
國立交通大學
多媒體工程研究所
98
A concept of strong-ties and weak-ties played an important role in complex network studies. However, different researcher would face following problem in defining strong or weak of links: (1) Ambiguous definition between strong and weak, and (2) Clear definition of limit between strong and weak but link is either strong-tie or weak tie (dichotomy method). We considered that characteristic of links varies in different network layers (hierarchy property). Some links have obvious influence on information transmission in local area, but have no effect on information transmission in global scale; and some link have significant influence on information transmission from local to global scale. To avoid ambiguous definition and dichotomy method when quantifying links, we applied characteristic of links to propose the concept of bridge link and bond link, and designed an algorism which can detect varies characteristic of links in the different network layers according to topology properties and statistically significant, then classify links into four types：Global bridge link, N degree bridge link, Bond link, and Sink bridge link. In this paper, we observed the characteristic of links in different layers under three real networks, and realized variation in properties of every links from local to global view, then classified links into different types according to the algorism. We can describe the topology structure and specific dynamic properties of networks by means of the proportion of different link types. Ultimately, we proposed three applications based on hierarchy property of links and the proportion of different link types: (1) find community structure in complex network; (2) complex network clustering; (3) analyzing the correlation between real-world network and theoretic network on topology structure. The results demonstrated that the concept we proposed not only led to decent results on these applications, but also resolved different problems with the consistent methodology. By analyzing and realizing hierarchy property of links, researchers in many fields of science will have a better understanding of design principle or evolution principle beyond complex network.

碩士
國立臺灣師範大學
化學研究所
92
The importance of hydrogen bonding has prompted us to investigate systems in which the strengths of hydrogen bonds can be modulated at will by external stimuli. Three-component systems consisting of a hydrogen-bonding site (electron donor), a bridge, and a reaction center (electron acceptor) have been designed to achieve this goal of hydrogen-bonding modulation. When the reaction center was protonated, a signal was sent out to the other end of the three-component molecule via intramolecular charge transfer (ICT) and thus affected the binding ability of the binding site. It has been found that the constituents of the bridge greatly influence the efficiency of remote signal communication between the reaction and binding centers. In the current theoretical study, we focused on the carbon-based conjugated bridges and studied the effects of bridge structure and substituents on signal transduction. It was found that the quinoidal bridges or bridges with cyano substitutions near the reaction center were more effective than the parent unsubstituted transoid (CH=CH)3 bridge. For bridges such as (CR1=CR2)n or (CR1=CR1-CR2=CR2)n, signal reduction due to longer bridge lengths could be minimized if R2 are substituted with electron-withdrawing substituents such as F and CN. Finally, the (C(CN)=C(CN))n bridges are signal amplifying, i.e., longer bridge lengths cause stronger binding change at the binding site.

Bridge expansion joints are directly subjected to traffic load, and thus prone to premature fatigue failure. Replacement of components such as modular bridge expansion joints is typically done in a staggered schedule to minimize traffic blockage. Field splices are used to connect the successively installed segments. These splices typically include a combination of field welding or bolting, and experience has shown that they often fail due to fatigue cracking. This thesis reports the investigation of hybrid FRP/steel splice details that avoid the use of field welding. Two configurations have been examined: A GFRP pultruded square tube section, adhesively bonded to the soffit of the spliced beam, consists the moment resisting component in one configuration, whereas the other takes advantage of two series of FRP plates for this purpose. Bolted steel plates splice the beam through web in both cases. The behaviour of these details has been studied extensively under vertical static loads. The effect of several parameters including bond length, FRP end shape, bond surface treatment, adhesive, etc. for each detail has been investigated. A three-dimensional, non-linear finite element model has been developed for each detail and validated using the experimental results. The bond strength of two adhesives was investigated experimentally using double shear lap splice tests. A new method is proposed to analyze the strength of the splice details. This method is based on the results obtained from shear lap splice tests and the verified finite element model developed for the splice detail. The finite element model could thus be used for further parametric studies. More experiments, however, are statistically required before using this model with confidence. The fatigue behaviour of one of the promising splice details has been investigated both experimentally and numerically. A special fatigue test set-up has been designed and used successfully for this purpose. Two fatigue tests to 1,000,000 cycles were run. One failed at 719, 347 cycles and the other survived 1,000,000 cycles. The predicted fatigue life as per the developed model was 871,840 cycles. More experiments are required to understand the fatigue behaviour of the splice detail under various stress ranges.
Thesis (Ph.D, Civil Engineering) -- Queen's University, 2011-11-30 16:53:07.385

University of Technology Sydney. Faculty of Arts and Social Sciences.
Although there has been a considerable amount of literature exploring the potential of social media for protest participation, only a few studies have explored this in less-established democracies such as the post-Soviet space. This study addresses this gap by examining the impact of Facebook use and online social capital on offline protest participation through the case of the post-Soviet Moldova: a hybrid state with a politically monopolised media, but a relatively uncensored internet. Specifically, it analyses the Moldovan protests against the governing political elites of 2015. The thesis aims to explore how the media and political contexts affect the relationship between social media, social capital and protest participation. In order to achieve this, a mixed methods research design was adopted in this thesis. This design combines both quantitative and qualitative data collection and analysis. The first quantitative phase consisted of a web survey that was administered through Facebook messenger and completed by protesters. The data were used to examine statistically the relationship between social media, online social capital and protest participation. The second qualitative phase consisted of semi-structured interviews with protesters and activists. Thematic analysis of data allowed to explain quantitative results in more depth. The findings of the two phases demonstrated that Facebook use had an impact on protesters’ participation; however, the contribution was small, and its significance lay in the dialogic relationship with other factors, such as television and offline social ties. First, the impact of Facebook on participation was mediated by online bridging social capital, the type of social capital that is missing or considered low in many post-Soviet countries. In a politically monopolised media context, the development of online bridging social capital allowed people to connect with a large and diverse network of actors; access novel and alternative information; find mobilising and political knowledge; form an opinion; and construct a collective identity, all significant antecedents of protest participation. However, the impact was small because it mainly described the post-Soviet young generation, the cohort that less engaged in the protests. The study also showed that the relationship between social media and protest resulted to be complex and its mobilising potential mainly rested on integrating and bridging online and offline, as well as other media channels. These elements were mutually constitutive and together emphasised the ways in which Facebook could support protest engagement. These results can inform broader theories about protest participation and digital activism in the post-Soviet space, which is vital when understanding non-Western contexts.

碩士
國立臺灣大學
化學研究所
93
Remote control of hydrogen bond strengths can be modulated in a three-component system consisting of a hydrogen bonding site (pyrrole), a conjugated bridge and a reaction center (imine). Protonation of the reaction center can trigger intramolecular charge transfer thus altering the binding ability of the remote hydrogen-bonding site. The signaltransduction from the reaction center to the hydrogen-bonding site can be easily observed. In the first part of the study, we investigated the effect of non-planarity in the π-conjugated system has on the binding strength in the three-component system. Computational study showed that the torsion angle between the binding site and the bridging unit could greatly influence the remote signal communication in our three-component system. Dihedral angle drive calculations on the hydrogen-bonding site were performed to show how the binding energies behaved as the torsion angle is varied. The results showed decay in the binding strength and transduction sensitivity as the torsion angle is increased. Small decrease in the binding energies is observed when the torsion angle is within 45°, so that intramolecular charge transfer is not seriously affected by small distortion in the torsion angle. When we compare the CH=CH bridge and N=N bridge, the N=N bridge, which displays more efficient charge-transfer ability than the CH=CH bridge in planar configuration, is less affected by the variation of the torsion angle, as long as the torsion angle is within 30°. In general, the decrease of binding energy in the α-systems is slightly more than the β-systems as the three-component systems become nonplanar. In the second part of the study, we observed the extent of charge transfer that was induced by metalation and compared it with protonation-induced charge transfer. We studied four three-component systems: system A (pure CH=CH-CH=CH bridge), system B (with two substituted CN groups in the CH=CH-CH=CH bridge), system C (with two substituted CN groups in the reaction center), and system D (with four substituted CN groups in the reaction center). The results showed that the abilities of charge transfer and sensitivity for metalation with M2+ ions are similar to protonation in all four systems. However, the abilities of charge transfer and sensitivity for metalation with M+ ions are very weak and are similar to the neutral state. The binding energies of different metals with the same oxidation state are similar (Ru2+ > Zn2+ = Mg2+ ; Li+ > Na+). The strengths of binding energies ordered from high to low observed in the four systems are system B > system D > system C > system A and sensitivities ordered from high to low in four systems are system D > system C > system B > system A. When we observed the bridge length effect on the four systems, the charge-transfer ability of system B is the least affected as the length of the bridge increase. Our studies have provided great insights in the understanding of remote hydrogen bond communication in our three-component systems and they could provide guidelines for the synthetic design of these materials.

碩士
國立中央大學
化學研究所
97
Remote control of hydrogen bond strengths can be modulated in a three-component system containing a hydrogen bonding site(pyrrole),a conjugated bridge and a reaction center (porphyrin). Metalation of the reaction center can trigger intramolecular charge transfer(ICT), thus altering the binding ability of the remote hydrogen-bonding site. In our computational study, we have investigated two topics. The first one is to study the effect of metalation in the porphyrin three-component systems with different bridge positions. In this case, we have found that the porphyrin ring does not induce ICT in the metalated states, so we changed the reaction center to heteroporphyrins. Remote control of hydrogen bond strengths was successfully achieved with heteroporphyrins. The second topic is to construct two different types of multiple-way control systems which have multiple binding sites controlled by one metalation center. One has the similar binding strengths at all binding sites and the other has different binding strengths. We also compare the effectiveness of metalation in terms of remote control in single-way and multiple-way systems.

The use of transition metal catalysts - either homogeneous (discrete well-defined metal complexes) or heterogeneous (more poorly-defined metal surfaces) - play an important role in the transformations of small substrates into larger, value-added compounds. Although heterogeneous catalysts have the greater industrial applicability, there has been enormous interest in homogeneous transition metal systems for effecting selective transformations of small substrate molecules. The bulk of these homogeneous systems are mononuclear. Perhaps surprisingly, very little research has focuses on systems with adjacent metal centres. Binuclear systems possess adjacent metals that may interact and possibly lead to transformations not observed in monometallic systems. It is this opportunity for adjacent metal involvement in substrate activation that is the focus of this dissertation. the goal of this research is to gain an increased understanding of metal-metal cooperativity and adjacent metal involvement in substrate transformations; how can adjacent metal involvement lead to substrate activation not seen in monometallic counterparts, and what role does each metal play in these interactions, particularly when the two metals are different. Throughout this dissertation examples of transformation unique to systems with at least two metals are presented and examined with a particular focus on the roles of the two metals and any associated binding modes in these transformations. In addition, by comparing the RhOs, RhRu and IrRu systems, the influence of metal substitution is also examined. For example, diazoalkane activation and C-c bond formation promoted by the Rh-based systems is investigated, the roles of the adjacent metals of the IrRu system in the conversion of methylene groups to oxygenates is examined, and the unusual geminal C-H bond activation of olefinic substrates is explored. Overall, the work presented within this thesis adds to the growing understanding of adjacent metal cooperativety, leading us toward a more rational approach to the design of homogeneous homo- and heterobimetallic catalysts, heterogeneous catalyst and nanoparticle catalysts for selective substrate transformations.