Achilles tendinopathy is a prevalent, highly debilitating condition. It is believed to result from repetitive overuse, which creates micro-damage tendon, and initiates a catabolic cell response. The aetiology of tendinopathy remains poorly understood, therefore appropriate treatment remains unclear. Current data support the use of shock wave therapy and eccentric exercise as some of the more effective treatment options for tendinopathy. Studies have shown that these treatments generate perturbations within tendon at a frequency of approximately 8-12Hz. Consequently, it is hypothesised that 10Hz loading initiates increased anabolic tenocyte behaviour promoting tendon repair. The primary aim of this thesis is to investigate the effects of 10Hz perturbations on tenocyte metabolism, comparing tenocyte gene expression in response to a 10Hz and 1Hz loading profile. A variety of in vitro models for mechanically stimulating cells were explored, comparing tissue explants with isolated cells on a 2D or within a 3D collagen gel. The mechanical environment of each model was investigated, in addition to cell viability and gene stabilisation following strain, as needed for future cell studies. 3D collagen gels arose as the most suitable model. Human tenocytes from healthy semitendinosus and tendinopathic Achilles tendons were seeded into 3D collagen gels and subjected to cyclic strain at 10Hz and 1Hz to establish cell response. Tenocyte gene expression was characterised using qRT-PCR. Healthy tenocytes showed increased expression of all analysed genes in response to loading. Furthermore, the increase was significantly larger in the 10Hz loading group. Tendinopathic tenocytes showed a more varied response, possibly indicative of an early healing response. Nevertheless, the response to 10Hz loading was consistently greater than seen with 1Hz loading. Analysis of the signalling pathways involved suggested that the IL1 signalling pathway may be involved in the strain response reported. This study has demonstrated for the first time that loading at a frequency of 10Hz may enhance metabolic response in healthy tenocytes.

Tendons transfer forces from muscle to bone and allow the locomotion of the body. However, tendons, especially for tendons in the hand, get lacerated commonly in different injuries and the healing of tendon within the narrow channel in the hand will normally lead to tendon adhesion and sacrificed tendon mechanics. Researches have been focused on addressing tendon adhesion prevention but neglecting healed tendon mechanics. This thesis discusses the principles and challenges in the design of biomaterials regarding flexor tendon repair with advanced polymer chemistry and materials science. A rational platform, not only focusing on the prevention of tendon adhesion, but devoting more efforts on final healed properties of tendons via implementing glycopolymer-based materials to guide tendon cells attachment, was designed, fabricated and characterized. Controlled ring opening polymerizations and atom transfer radical polymerizations were combined for the synthesis of miktoarm well-defined block copolymers. Para-fluorine click reactions were then implemented to afford glycopolymers with glucose units. Obtained copolymers were transformed into 3D membranes constituting a porous fibrous structure utilizing electrospinning. The aligned structure was then fabricated to optimize the mechanics of these materials for practical application as well as reconstruct normal tendon physiological structure. Lastly, the toxicity, cell affinity and cell activity of obtained materials were evaluated in vitro employing tendon cells as a cell line to confirm the suitability of obtained platforms for flexor tendon repair.

Concrete repair materials are being widely used to restore and extend the service life of structures. While most cement-based repair materials are compatible with concrete structures, their durability properties do not attract much attention which it deserves from researchers. Since repair materials can deteriorate like conventional concrete, the search for reliable, long-lasting concrete repair materials is becoming more intensive. Amongst other factors, concrete permeability and chloride diffusivity within concrete are believed to play a major role in determining the durability and success of the repair. These two parameters determine the penetration rate of aggressive substances into concrete and how fast degradation could take place. A number of test methods have been proposed to study these two factors, and the commonly used test methods are water penetration, surface/bulk electrical resistivity, rapid chloride permeability (RCP), and half-cell potential. However, the relationship between each durability test method and their correlation with compressive strength measurement have not been fully understood. So, in this study, we aim for using multiple testing techniques, destructive and non-destructive, to evaluate the durability of concrete repair materials as well as correlating different test methods. Three types of commercially available cement-based materials are tested and evaluated, and results have indicated that cementitious concrete mortar (termed as Mix M) amongst others has the best durability performance which means low water permeability, high resistivity, and compressive strength. Whereas, the flexural performance of Mix M still needs some improvement in terms of flexural strength and flexural toughness. For various durability testing methods, surface resistivity is found to have a strong linear relation and a polynomial relation to bulk resistivity and water permeability respectively. No relationship is established between concrete resistivity and compressive strength, though high-strength concrete tends to have a high resistivity in our study. RCP test results do not correlate well with resistivity measurements, which requires further study to overcome its heating and binding effect when measurements are being taken. Half-cell potential method is used for validating test results but it reveals no difference for materials with different permeability and resistivity. A model is proposed to counteract temperature’s effect while calculating the coefficient of diffusion, which indicates the concrete to resist chloride diffusion. It is found that this model can shift the RCP measurement slightly closer to its theoretical prediction but the difference between them is still large. Therefore, further research is required for acquiring more raw data from RCP measurements as the regression analysis input. In addition, a more comprehensive model that involves more correction factors for binding effects, etc., is also needed. / Graduate / 2020-04-30

Thesis (M.Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Bibliography: p. 259-263. / Architectural preservation in America has led to an increase in imitative architecture in many sectors of the profession and, as one architectural historian has pointed out, there is no historical precedent for imitative architecture. Fortunately, buildings can only rarely be preserved in a static form: they grow, evolve, and change in response to many circumstances. Too often the form of an addition or extension is determined by aligning cornice lines, using the same building materials, the same window and doors, and a similar roof structure. Essential formal issues are often not addressed. Four case studies are made, each being either an addition, an extension, or a transformation. Differing sizes and scales are explored. Accesses and circulation options are studied, as well as room sizes design decisions. Mostly drawings comprise the work, and they are additive form studies. / by Robert Peabody Brown, Jr. / M.Arch.

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The present study has developed poly ε-caprolactone (PCL)/ poly lactic acid (PLA) films with specific internal structure suitable to prepare nerve guide conduit for peripheral nerve repair. The film preparation method has been carried out using an environmental chamber to prepare the solvent cast films with the specific surface structure. Different cellular behaviour of neuronal cell cultures was seen on the pitted films with different pits configurations (size and distribution). The consistent surface morphology provided a reliable surface structure for further in vitro and in vivo studies. The effect of a medical grade sterilisation process using gamma radiation at eight doses (0-45kGy) on PCL/PLA films was explored. It has been shown that material properties, including mechanical strength, were significantly affected, while cellular behaviour and responses (NG108-15) were improved. Grooved films with three groove shapes (Sloped, Square, and V shape) were prepared using patterned silicon substrates, photolithography and wet/dry etching. The groove patterns were successfully transferred and good mechanical strength was observed for grooved PCL/ PLA. Oriented growth of NG108-15 cells was observed on the patterned films with an improved alignment and organisation on SL and V shape grooved films. UV-ozone treatment was used to increase hydrophilicity of PCL/PLA films to improve Schwann cells behaviour. No negative effect was observed on cell growth and proliferation on the treated films however the mechanical properties were reduced. Schwann cells expressed typical long spindle-shape morphology with cell-to-cell interaction in longitudinal direction on the treated grooved films. Consistent to in vitro experiment with NG108-15, Schwann cells alignment was also improved on SL and V shape grooves. A three-week in vivo study was carried out to test grooved and non-grooved conduits in a rat sciatic nerve model. The grooved conduits showed better regeneration, with SL-grooved film showing a significant improvement of nerve regeneration. A separate in vivo study evaluated the effect of wall-thickness on nerve regeneration. However, it was shown that the wall thickness had no positive effect, and the conduit with improved mechanical strength adversely affected the nerve regeneration. In conclusion, a nerve guide conduit was developed with the optimised surface structure to support nerve regeneration. The promising in vitro and in vivo studies together with the suitable biomechanical properties and specific surface structure and morphology indicate that the grooved PCL/PLA conduit is a viable treatment for peripheral nerve repair.

DNA interstrand cross-links are a form of genomic damage that cause a block to replication and transcription of DNA in cells and cause lethality if unrepaired. Chemical agents that induce cross-links are particularly effective at inactivating rapidly dividing cells and, because of this, have been used to treat hyperproliferative skin disorders such as psoriasis as well as a variety of cancers. However, evidence for the removal of cross-links from DNA as well as resistance to cross-link-based chemotherapy suggests the existence of a cellular repair mechanism. Characterizing the pathways involved in DNA interstrand cross-link repair has been challenging due to the inherent structure of the damage as it precludes the use of an undamaged, complementary strand of DNA as a template for repair. A number of models of cross-link repair have been proposed based on the identification of hypersensitive repair mutants as well as biochemical evidence that specific repair enzymes are capable of incising cross-linked structures from DNA. Together, these models have suggested the involvement of multiple repair pathways--such as nucleotide exicision repair, translesion synthesis, recombination of double-strand breaks, and base excision repair--operating in sequential steps to correct the damage. Most of the studies from which these models arose are complicated by the fact that cross-linking agents induce multiple forms of damage or they lack in vivo confirmation of how the repair phenomenon occurs in organisms. In this study, I use Escherichia coli as a model organism to examine the involvement of the aforementioned pathways in DNA interstrand cross-link repair in vivo. This organism was useful in early cross-link studies and, with its highly conserved repair processes, maintains the potential for delineating how cross-links are removed in higher organisms. In Chapter I, I introduce background information on different cross-linking agents, the complications of studying cross-link repair, and the candidate repair pathways that have been implicated to date. In Chapter II I demonstrate that there is a limited involvement of the nucleotide excision repair helicase, translesion polymerases, and double-strand break repair enzymes through survival analysis of cells defective in these proteins. For this analysis, I use 8-methoxypsoralen plus UVA as a cross-linking agent and angelicin plus UVA as a monofunctional comparator. The observation that uvrD mutants-- defective in helicase II of nucleotide excision repair--were nearly as resistant to 8-methoxypsoralen-induced damage as wild type cells led me to examine the incision rate of cross-links from endogenous plasmid DNA. Surprisingly, cross-links were not efficiently removed from DNA in uvrD mutants relative to wild type cells. These seemingly contradictory results were rectified when I quantified cross-link formation in cell cultures and revealed that as few as one cross-link per chromosome can inactive wild type cells, a lethal quantity that is lower than what has been previously reported. Taken together, these observations suggest that although cross-links are incised in wild type cells, repair is still not a highly productive event in E. coli. In Chapter III I examine the involvement of the base excision repair pathway in cross-link repair and demonstrate that Nth and Fpg Glycosylases, Xth and Nfo AP-Endonucleases sensitize Escherichia coli to psoralen-induced DNA damage. This is shown by comparative survival analysis in angelicin plus UVA and 8-methoxypsoralen plus UVA treatment whereby nth-, fpg-, and xth-mutants are each more resistant than wild type cells to either treatment. This suggests that when these gene products are present they impact the production or removal of monoadducts. nfo-mutants were different in that the cells were only hyperresistant to 8-methoxypsoralen monoadducts and cross-links, either implying that the Nfo enzyme interacts specifically with psoralen monoadducts rather than angelicin monoadducts or that the enzyme impedes cross-link removal. Finally, in Chapter IV a summary of the results is provided as well as future directions that may be explored following this study.

BRCA1 is a caretaker of genome integrity with various molecular functions, which are required for development and tumor suppression. These include the homology-directed repair (HDR) of DNA double strand breaks, stalled replication fork protection (SFP), transcription, chromatin remodeling and cell cycle checkpoint control. Recent studies reported that BRCA1 is required for reprogramming to pluripotency, but its specific role remains unknown. In this work, we use separation of function mutants for the roles of BRCA1 in HDR and SFP to show that BRCA1 is required to repair replication-associated DNA double strand breaks by homologous recombination during reprogramming. Deficiency in SFP proved inconsequential to induced pluripotent stem (iPS) cell generation and cells with this phenotype did not experience reduced reprogramming. Thus, the primary limiting factor for the transition to pluripotency is a specific class of DNA damage: double strand breaks, likely occurring in late replicating regions which require repair by homologous recombination. These findings identify an important role of DNA damage, linked to the progression of DNA replication, in limiting cell type transitions during reprogramming. Most studies on iPS cell generation have focused on gene expression as a limiting step, in part due to the wide availability of tools to analyze transcription. Since the progression of DNA replication and DNA damage during S-phase are cell type specific, we have started the development of a sequencing platform to map various aspects of replication progression, such as origin usage, polymerase direction,pausing and stalling. In this work, we demonstrate that nucleotide analogs, incorporated during DNA synthesis in mammalian cells, can be detected by Nanopore sequencing.

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During the turbulent times facing contemporary organisations, managers and employees need a precise understanding of the nature of team dynamics that develops quality service to customers. Extensive literature searches reveal few research studies focused on the nature of teamwork, which develops value to customers. The purpose of this study is to examine the value of teamwork for providing quality service within the Hong Kong shiprepair industry, outline the insight gleaned and recommend future research. This study aims to link empirically the Western developed Deutsch's (1949a, 19496, 1973, 1980, 1985, 1990) Theory of Cooperation and Competition with the innovation of teamwork and to assist in understanding the variance in the performance of these teams. Literature suggests that the relationships and interaction within the work teams can very much impact the overall performance of these work teams. The extent that these work teams are able to develop cooperative goals can promote productive and constructive communication and problem solving (constructive controversy) in their interactions. A constructive interaction leads to team members' perception of high team confidence. With trust, strong work relationship, team morale and perceived confidence, team effectiveness is enhanced on quality customer service (Alper, Tjosvold and Law, 1998; Tjosvold, Hui and Law, 1998; Tjosvold, Moy and Sasaki, 1996, 1999; Wong et al., 1999). The research also tests the extent of impact of traditional Chinese values of power distance and collectivism as contributing to cooperative goals and encourages an openminded discussion of opposing views (constructive controversy). It proposes that by adopting cooperative goals, shiprepair yard management in Hong Kong may meet the twin challenges of involving employees fully into the organisation and providing quality service to customers. / The result suggests that the Western derived Theory of Cooperation and Competition, if appropriately and skillfully expressed, might have the potential as one alternative to understand the goal interdependence dynamics as experienced by the Hong Kong Chinese in the shiprepair industry. Nevertheless, the result is not confirmatory to the main hypothesis of the study that team confidence is significantly related to quality customer service. Findings of this study question whether a Western theory or research instrument derived is appropriate for application to a Chinese work setting (Bond and Wang, 1983). Although it is useful to test concepts developed in one culture to another, yet theories from the West cannot be assumed to apply in the East (Hofstede, 1993; Triandis, 1983). An important finding of this research is, however, that this Western derived theory might not be suitable to be applied in a work group of very low levels of education and/or low exposure to the modern workplace practice and Western influences.