A DNA palindrome is a sequence of DNA followed by an exact inverted copy of itself. Palindromes are associated with gross chromosomal instability in mammalian cells. This may be related to their ability to extrude a double-stranded cruciform structure. In mammalian cells, palindromes have been shown to undergo centre-directed rearrangements resulting in a central region of asymmetry. This process occurs via a mechanism termed â centre break palindrome revisionâ . In this thesis, I have investigated palindrome revision in mammalian cells using two existing assays. In the first, performed by transfection of an extrachromosomal palindromic dimer, I have shown that joining of palindrome-mediated double-strand breaks does not depend solely on NHEJ and instead relies heavily on an alternate end-joining pathway. Using the second assay, the Line78 mouse model which contains a 15.4kb transgenic palindrome, I have shown that small modifications near the centre of the palindrome prevent these centre-directed rearrangements possibly by inhibiting cruciform formation.

A research program was conducted to investigate the application of composite materials in repairing corroded offshore risers, leading to the development of an optimized repair using a hybrid carbon/E-glass system. The objective of this research program was to investigate the feasibility of extending onshore composite repair techniques to offshore risers by developing integrated analytical and experimental methods. The study considered loads typical for offshore risers including internal pressure, tension, and bending. To fulfill this objective efforts included a state of the art assessment of current composite repair technology, designing a carbon-based composite repair system optimized by numerical simulation with prototype testing, and providing guidelines for industry in repairing and reinforcing offshore risers using composite materials. Research efforts integrated numerical modeling, as well as full-scale testing that included four composite repair manufacturers to assess the current state of the art on pipe samples with simulated corrosion reinforced with composite materials. Analysis and testing were also performed on the optimized carbon/E-glass system. The results of this program demonstrated that composite materials are a viable means for repairing corroded offshore steel risers as adequate reinforcement ensures that the steel risers are not loaded beyond acceptable design limits. For corroded risers, the results demonstrated through analysis and full-scale testing efforts that properly designed composite repair systems can provide adequate structural reinforcement to ensure that excessive strains are not induced in the steel when subjected to internal pressure, axial tension, and bending design loads. This was verified experimentally using strain gages placed beneath the composite repair. This program is the first of its kind and is thought to contribute significantly to the future of offshore riser repairs. It is likely that the findings of this program will foster future investigations involving operators by integrating their insights regarding the need for composite repair based on emerging technology. One of the most significant contributions to the existing body of work is the use of limit analysis in developing design limits for the repair of steel pipes using composite materials.

The deterioration of today's infrastructure particularly roadways and bridge decks has continued to increase over the years due to the larger axle loads, higher traffic volumes of densely populated cities. These highly congested areas have required the need to repair and rehabilitate the affected pavements in a timely manner with minimal traffic interruptions. Different rapid hardening binders were tested in this project to evaluate and characterize their performance when subjected to concrete distresses such as alkali-silica reaction, delayed ettringite formation, corrosion, freezing and thawing, salt scaling, sulfate attack, material incompatibility and volume changes. Among the cements tested were calcium aluminate cement, calcium sulfoaluminate cement, accelerated portland cement, alkali-activated fly ash, and three other proprietary blends available to the public. This thesis will summarize the preliminary findings of a comprehensive laboratory study focusing on rapid repair materials -- the final results of this study will be included in future publication (theses and final project report). / text

The ability to repair damaged mammalian axons to re-establish functional connections continues to be a goal for neuroscientists. Following axonal severance, proximal segments of mammalian axons seal themselves rapidly at the lesion site. Distal segments of severed mammalian axons undergo Wallerian degeneration within 24-72 hours. Prior to the onset of degeneration, distal axonal segments remain electrically excitable. The work described in this dissertation demonstrates that polyethylene glycol (PEG), a hydrophilic polymer, can rapidly repair severed axons by fusing the plasmalemmas of two closely apposed distal and proximal axonal segments. This plasmalemmal fusion restores morphological integrity of severed axons and their ability to conduct action potentials across the injury site. The ability to fuse proximal and distal severed axonal segments using PEG is improved when the axonal segments are exposed to antioxidants, such as melatonin and methylene blue, and also when microsutures provide additional support in transected sciatic nerves. The restoration of axonal continuity by PEG-fusion restores function, improving behavioral recovery in rats with crush-injured sciatic nerves, as well as those in which the sciatic is complete transected. / text

M. Tech. Electrical Engineering. / Discusses the appearance of partial discharge (PDs) is a problem of insulation failure in high voltage equipment used in power plants. As the insulation of equipment has a sensitive zone, therefore the quality of insulation plays an important role in such power equipment. PDs in power transformers are capable of leading to corrosion on solid insulating materials, thereby in the long term, causing a breakdown of the particular operating component. It follows that the real challenge is to identify the most appropriate method for the measurement and/or detection of PDs.

No description available.

No description available.

No description available.

The human Rad9A checkpoint protein is required for genomic stability and proper execution of the DNA damage checkpoint. Previous work has shown Rad9A to be the key member of a heterotrimeric toroidal structure known as the 911 complex, along with Hus1A and Rad1, which is similar in structure to PCNA. Recent literature suggests Rad9A is a novel oncogene, found to be upregulated in a number of cancers and high mRNA levels are thought to have a protective effect on tumour growth. This thesis describes two novel functions for the Rad9A protein. The first is as a facilitator for the nuclear translocation of the Claspin adaptor protein, required for successful Chk1-mediated checkpoint activation. The second is as part of a novel nuclear structure containing important members of the homologous recombination DNA repair pathway. Work described herein also confirms the existence of a Rad9A paralogue, Rad9B, that partially rescues defects associated with Rad9A-deficiency and is expressed in both tumour and undifferentiated embryonic stem cell lines. This work discusses these findings in the context of current literature and provides future experiments to continue investigations into the function of this vital checkpoint protein. / Thesis (Ph.D, Biochemistry) -- Queen's University, 2010-03-26 12:02:41.304

The shear horizontal wave propagation and vibration of piezoelectric coupled structures under an open circuit electrical boundary condition are studied. Following the studies on the dynamic response of piezoelectric coupled structures, the repair of both crack/notch and delaminated structures using piezoelectric materials are conducted. The main contribution was the proposed the active structural repair design using piezoelectric materials for different structures. An accurate model for the piezoelectric effect on the shear wave propagation is first proposed to guide the application of piezoelectric materials as sensors and actuators in the repair of engineering structures. A vibration analysis of a circular steel substrate surface bonded by a piezoelectric layer with open circuit is presented. The mechanical models and solutions for the wave propagation and vibration analysis of piezoelectric coupled structures are established based on the Kirchhoff plate model and Maxwell equation. Following the studies of the dynamic response of piezoelectric coupled structures, a close-loop feedback control repair methodology is proposed for a vibrating delaminated beam structure by using piezoelectric patches. The electromechanical characteristic of the piezoelectric material is employed to induce a local shear force above the delamination area via an external actuation voltage, which is designed as a feedback of the deflection of a vibrating beam and a delaminated plate, to reduce the stress singularity around the delamination tips. Furthermore, an experimental realization of an effective repair of a notched cantilever beam structure subjected to a dynamic loading by use of piezoelectric patches is reported. A small piezoelectric patch used as a sensor is placed on the notch position to monitor the severity of the stress singularity around the notch area by measuring the charge output on the sensor, and a patch used as an actuator is located around the notch area to generate a required bending moment by employing an actuation voltage to reduce the stress singularity at the notch position. The actuation voltage on the actuator is designed from a feedback circuit process. Through the analytical model, FEM simulation and experimental studies, the active structural repair method using piezoelectric materials is realized and proved to be feasible and practical.