Background. Operative stabilisation of paediatric supracondylar elbow fractures is most commonly achieved through the use of percutaneous Kirschner wires. These implants are inert, cheap and simple to use. However, the requirement for removal and the possibility of pin site infection provides opportunity for the development of new techniques that eliminate these drawbacks. Bioabsorbable pins that remain in situ and allow definitive closure of skin at the time of surgery could provide such advantages. However, their ability to maintain fracture reduction and their effect on the growth plate has not been adequately evaluated. Hypotheses. The Acumed® Biotrak Helical Nail (a bioabsorbable fixation implant) has comparable strength to Kirschner wires and does not result in significant disruption of the growth plate or subsequent growth. Studies. Three complementary studies were performed. (1) A retrospective cohort analysis was performed to establish the prevalence of complications related to Kirschner wire fixation of paediatric supracondylar elbow fractures. (2) A saw-bone model was designed to compare the mechanical performance of the Helical Nail and Kirschner wires. (3) An ovine model was designed to assess the in vivo effects of the Helical Nail on limb growth and physeal morphology. The surgical practicalities of the device and its potential for use in the paediatric setting were evaluated. The primary outcome was femoral length six months after Helical Nail insertion. Micro-CT evaluation of growth plate thickness, percentage disruption and bony infiltration was undertaken – the first time this technique has been used in a large animal study. Traditional histopathological techniques complimented the Micro-CT analysis and offered comment on the microscopic appearance of the growth plate immediately adjacent to the bioabsorbable nails. Results. The infection rate within a large tertiary referral centre was 9.6%, which was marginally higher than previous cohort studies. Mechanical testing demonstrated that the Helical Nail had comparable strength in rotation, but inferior resistance to posterior translation, when compared to Kirschner wires. In the ovine model, the Helical Nail disrupted 3.4% of the physis. The nails had no effect on femoral growth during the six month study period. Micro-CT analysis of both the helical nail and Kirschner wire groups demonstrated multiple bony bridges, with two cases of physeal tethering in the Helical Nail group. There was no difference in physeal thickness or bony infiltration of the physis. Histopathology did not reveal any significant inflammatory or foreign body reaction adjacent to the nails. Conclusion. The Helical Nail demonstrated a number of encouraging attributes which indicate its potential. However, in its current state the device is not suitable for use in the stabilisation of paediatric supracondylar elbow fractures.

Dissertation (MSc)--University of Pretoria, 2012. / Companion Animal Clinical Studies / MSc / Unrestricted

Magister Scientiae - MSc / Characterisation of fractured rock aquifers is important when dealing with groundwater protection and management. Fractures are often good conduits for water and contaminants, leading to high flow velocities and the fast spread of contaminants in these aquifers. A cost effective methodology is required for the characterisation of the role of individual fractures contributing to flow to boreholes in fractured rock aquifers. Literature shows that some of the conventional methods used to characterise hydraulic properties in fractured rock aquifers are expensive, complicated, time consuming and are associated with some disadvantages such as over-or under- estimations of flow rates. This thesis evaluates the use of Fluid Electrical Conductivity (FEC) logging in fractured rock aquifers. This FEC data are compared to various traditional methods used to determine aquifer hydraulic properties applied at the Franschhoek and Rawsonville research sites. Both these sites were drilled into the fractured rock Table Mountain Group (TMG) Aquifer, forming one of the major aquifers in South Africa. / South Africa

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Sun, Minghui. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 125-159). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Diss. (sammanfattning) Linköping : Linköpings universitet, 2007. / Härtill 4 uppsatser.

Diss. (sammanfattning) Linköping : Linköpings universitet, 2007. / Härtill 4 uppsatser.

Le but de ce travail est de comprendre les relations entre la déformation et la diagenèse dans les carbonates. Pour cela, l’échelle du m au dam est adéquate car elle permet de séparer les effets matriciels, des fractures et des failles. Celle-ci est sous la résolution de la sismique, donc peu de données géophysiques et diagénétiques spatiale et quantitatives sont disponibles, le plus souvent limitées aux données 1D de puit.Nous avons choisi 4 affleurements présentant des hétérogénéités et des intensités de déformation et de diagenèse diverses. Un protocole multi-échelle et multidisciplinaire a été développé, comprenant de la géophysique à l’échelle du cm au dam, de la diagenèse structurale et de la géochimie sur les ciments de fracture. Nous montrons un fort effet d’échelle entre les Vp en laboratoire et à l’affleurement dû à des hétérogénéités sédimentaire, d’enfouissement et structurale, qui conduisent à différents motifs géostatistiques.Les fractures ont l’effet le plus fort sur les Vp, modulé par leur cimentation, et qui peut entièrement effacer la signature initiale du faciès. La réactivation des fractures induit une anisotropie directionnelle de 10% due à des changements dans le remplissage des fractures, caractérisés par de multiples phases de cimentation, broyage et dissolution.Dans les zones de faille, l’anisotropie sismique est amplifiée, conduisant à un fort affaiblissement de la roche au cisaillement et à une diminution de Vp autour de la faille. Les données géochimiques tracent plusieurs flux de fluides diagénétiques et soulignent les fortes interactions entre l’évolution de la perméabilité, la diagenèse structurale et la signature géophysique des carbonates. / The aim of this work was to understand the relationships between deformations and diagenesis in carbonates. The relevant scale to study it may be the m to dkm scale which allows individualizing fracture, fault and matrix effects. This scale is under the seismic resolution, so few quantitative diagenetic and geophysical spatial data are available, mainly constrained to 1D borehole.Therefore, we selected 4 dkm scale outcrops displaying various heterogeneities and intensities of deformation and diagenesis. We developed a multidisciplinary/multiscale protocol including geophysics from cm to dkm scale along with structural diagenesis study and geochemical measurements on fractures cements. We found a strong scale effect between laboratory and outcrop Vp due to sedimentary, burial and structural heterogeneities that lead to different geostatistical patterns. Fractures have the strongest effect on Vp, being modulated by their cementation and can erase the initial facies acoustic signature. The fracture reactivation induce a 10% Vp directional anisotropy due to microscale changes in the fractures infillings characterized by multiple cementation, crushing and dissolution phases. In fault-zones the seismic anisotropy magnitude is amplified, leading to a strong directional rock shear weakening and a Vp decrease around the fault, caused by higher discontinuities aperture and brecciation. Geochemical data indicate that the Vp signature evolution is linked to different diagenetic fluids flow origins occurring during each deformation phase. This underlines the strong interplay between permeability evolution, structural diagenesis and geophysical signature in carbonates.