The mechanisms underlying the effect of alterations in Type I collagen on bone mechanical properties are not well defined. Clinical tools for evaluating fracture risk, such as dual energy x-ray absorptiometry (DXA) and quantitative ultrasound (QUS) focus on bone mineral and cannot detect changes in the collagen matrix. The mechanical response tissue analyzer (MRTA) is a potential tool for evaluating fracture risk. Thus, the focus of this work was to investigate the effects of collagen degradation on bone mechanical properties and examine whether clinical tools can detect these changes. Female and male emu tibiae were endocortically treated with 1 M potassium hydroxide (KOH) solution for 1-14 days and then either mechanically tested in three-point bending, fatigued to failure or fatigued to induce stiffness loss. Computed Tomography scans, DXA, QUS, MRTA and three-point bend testing in the elastic region were performed on emu tibiae before and after either KOH treatment or fatigue to induce stiffness loss. Fracture surfaces were examined to determine failure mechanisms. Bone mineral and bone collagen were characterized using appropriate techniques. Bone mineral-collagen interface was investigated using Raman spectroscopy and atomic force microscopy (AFM). Endocortical KOH treatment does not affect bone mineral however, it causes in situ collagen degradation, rather than removal and may be weakening the mineral-collagen interface. These changes result in significantly compromised mechanical properties. Emu tibiae show significant decreases in failure stress and increased failure strain and toughness, with increasing KOH treatment time. The significant increase in toughness of KOH treated bones is due to structural alterations that enhance the ability of the microstructure to dissipate energy during the failure process, thereby slowing crack propagation, as shown by fracture surface analysis. KOH treated samples exhibit a lower fatigue resistance compared to untreated samples at high stresses only for both sexes. Partial fatigue testing results in similar decreases in modulus for all groups and sexes. The MRTA detected these changes whereas DXA and QUS did not. MRTA detects changes in bone mechanical properties induced by changes in collagen quality and fatigue and could be a more effective tool for predicting fracture risk.

Carbon nanotubes (CNTs) and carbon nanofirbers (CNFs) have excellent properties (mechanical, electrical, magnetic, etc.), which can make them effective nanoreinforcements for improving the properties of materials. The incorporation of CNT/Fs in a wide variety of materials has been researched extensively in the past decade. However, the past study on the reinforcement of cementitious materials with these nanofilaments has been limited. The findings from those studies indicate that CNT/Fs did not significantly improve the mechanical properties of cementitious materials. Two major parameters influence the effectiveness of any discrete inclusion in composite material: The dispersion quality of the inclusions and the interfacial bond between the inclusions and matrix. The main focus of this dissertation is on the dispersion factor, and consists of three main tasks: First a novel thermodynamic-based method for dispersion quantification was developed. Second, a new method, incorporating the utilization of silica fume, was devised to improve and stabilize the dispersion of CNFs in cement paste. And third, the dispersion quantification method and mechanical testing were employed to measure, compare, and correlate the dispersion and mechanical properties of CNF-incorporated cement paste produced with the conventional and new methods. Finally, the main benefits, including the increase in strength and resistance to shrinkage cracking, obtained from the utilization of CNFs in cement paste will be presented. The investigations and the corresponding results show that the novel dispersion quantification method can be implemented easily to perform a wide variety of tasks ranging from measuring dispersion of nanofilaments in composites using their optical/SEM micrographs as input, to measuring the effect of cement particle/clump size on the dispersion of nano inclusions in cement paste. It was found that cement particles do not affect the dispersion of nano inclusions in cement paste significantly while the dispersion of nano inclusions can notably degenerates if the cement particles are agglomerated. The novel dispersion quantification method shows that, the dispersion of CNFs in cement paste significantly improves by utilizing silica fume. However, it was found that the dispersion of silica fume particles is an important parameter and poorly dispersed silica fume cannot enhance the overall dispersion of nano inclusions in cementitious materials. Finally, the mechanical testing and experimentations showed that CNFs, in absence of moist curing, even if poorly dispersed, can provide important benefits in terms of strength and crack resistance.

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 37-41). / viii, 52 leaves, bound ill. 29 cm

Aim: The aim of this research was to measure functional intraoral pressures using a newly developed method; specifically, three areas were examined. Firstly, this new approach to measurement allowed the equilibrium theory of tooth position to be re-addressed. Secondly, it allowed investigation the patterns of pressure change in the palatal midline during water swallowing. Lastly, this approach allowed a preliminary investigation of the affect of the viscosity of the food ingested on the pressures generated in the mouth. Methods: The participants were 6 healthy volunteers (4 males, 2 females) recruited from the post-graduate students at the University of Otago, School of Dentistry. The age range was 25 to 35 years. All had full permanent dentitions, Angle Class I occlusions (normal) with acceptable overbite and overjet relationship, and none of them had a history of previous orthodontic treatment. For each of the subjects a cast chrome-cobalt baseplate was constructed to house 8 miniature strain gauge pressure transducers (Precision Measurement Co. Michigan). The location of the sensors were standardised as follows: Three sensors were paired on the buccal and lingual surfaces of the central, canine and first molar. Two palatal vault sensors were placed in the midline of the palate, one at level of the distal of the first premolar, and the second slightly anterior to the junction of the hard and soft palate. Simultaneous recordings were taken during a set of tasks including water swallows, saliva swallows and food ingestion. Results: The results showed that swallowing was a highly complex wellcoordinated event, and that each individual had their own unique signature pattern of swallowing, characterised by pressure changes of high frequency, in excess of �1000 kPa/s. Conclusions: The analysis of the pressure acting on the teeth showed that although the pattern and magnitude of pressure generated varied among the group, the observation of waveforms would suggest a tendency for no inherent balance between the buccal and the palatal pressures on the teeth during swallowing for any of the individuals tested. This investigation of the pressure in the midline revealed an aspect previously not fully explored; these experiments showed that there were large and persistent negative pressures generated during swallowing, that preceded the positive pressures and which appear important in bolus propulsion The patterns of swallowing and the magnitudes of pressure generated, changed with the different consistency of the various substances ingested. There was a general trend for increased pressures during swallowing of substrates that are more viscous; water showed the lowest pressures, followed by saliva and finally jelly. Keywords: Tongue pressure, Intraoral pressures, Tongue dynamics, Swallowing.

The research work in this thesis involves an experimental and theoretical investigation for high speed machining of AISI 4140 medium carbon steels and AISI D2 tool steels which are classified as being difficult to machine materials. An experimental program was carried out to determine the cutting forces, chip formation, the secondary deformation zone thickness and surface roughness at different cutting speeds using a 0.4mm and 0.8mm nose radii ceramic tools and -7?? rake angle for annealed (virgin) AISI 4140 and heat treated AISI 4140 steel. Another series of experiments was carried out on the annealed (virgin) and heat treated AISI D2 with 0.4mm, 0.8mm and 1.2mm nose radii CBN (Cubic Boron Nitride) tools under various cutting conditions. A theoretical model is developed by taking into account the flow stress properties of the AISI 4140 (0.44% carbon content) to use with the Oxley Machining approach. To find the flow stress data for AISI D2 tool steel, the Johnson and Cook empirical constitutive equation is used as the constitutive model. In addition, the magnitude of tool radius should be also considered to determine the prediction of cutting performances. To account for the effect of nose radius edge in hard machining, a simplified geometrical method is used to model the parameters for application in the Oxley Model and works for the cutting conditions considered here. These extensions to the Oxley machining theory were verified by experimental results. These results show a good agreement between the Oxley machining theory and hard machining experiment at data. The research work described in this thesis provides useful data for hard machining conditions.

Passive knee motion is guided by the interaction of the articular surfaces and the restraining role of the soft-tissue structures. It is defined by characteristic kinematics within an envelope of motion. The main goal of this thesis was to simulate this characteristic motion by developing a subject-specific anatomically based finite element model. CT and MR image stacks were used to develop the geometry model and experimental (mechanical) test data was used as model input. Passive knee flexion was simulated and translational and rotational motion described using the Joint Coordinate System (JCS). The model was validated using clinical flexion and AP drawer tests. An ACL reconstruction model was also developed. Highest AP laxity was found at 30?? of flexion when the graft was positioned in the original native ACL insertion point. ACL tunnel positions were simulated according to surgical techniques. For this case, the highest AP laxity was displayed at 0?? of flexion. Four different graft materials were examined, with the quadriceps tendon graft exhibiting highest laxity, followed by the patellar tendon, braided hamstring and finally unbraided hamstring graft. The effect of malpositioning the graft's femoral attachment point from its central location was also investigated. The proximal femoral attachment point most closely mimicked the central attachment point in terms of AP laxity in the native ACL insertion group. In the ACL tunnel group, the posterior femoral attachment point most closely mimicked the intact knee. In this thesis it was found that changing the femoral insertion point of the graft can highly influence the AP laxity behaviour. Also using the surgical technique to create ACL tunnels may not necessarily produce the same kinematic behaviour as the intact knee. Lastly, this thesis has shown the importance of explicitly defining the local reference coordinate system when describing knee kinematics. Changing the coordinate system markedly alters the calculated kinematics. Ideally, a standardisation of local coordinate systems, similar to the JCS, would be proposed within the biomechanics community.

ix, 231, [123] leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Depts. of Chemical Engineering and Physical and Inorganic Chemistry, 1993

Typewritten copy / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physiology, 1954

The research work in this thesis involves an experimental and theoretical investigation for high speed machining of AISI 4140 medium carbon steels and AISI D2 tool steels which are classified as being difficult to machine materials. An experimental program was carried out to determine the cutting forces, chip formation, the secondary deformation zone thickness and surface roughness at different cutting speeds using a 0.4mm and 0.8mm nose radii ceramic tools and -7?? rake angle for annealed (virgin) AISI 4140 and heat treated AISI 4140 steel. Another series of experiments was carried out on the annealed (virgin) and heat treated AISI D2 with 0.4mm, 0.8mm and 1.2mm nose radii CBN (Cubic Boron Nitride) tools under various cutting conditions. A theoretical model is developed by taking into account the flow stress properties of the AISI 4140 (0.44% carbon content) to use with the Oxley Machining approach. To find the flow stress data for AISI D2 tool steel, the Johnson and Cook empirical constitutive equation is used as the constitutive model. In addition, the magnitude of tool radius should be also considered to determine the prediction of cutting performances. To account for the effect of nose radius edge in hard machining, a simplified geometrical method is used to model the parameters for application in the Oxley Model and works for the cutting conditions considered here. These extensions to the Oxley machining theory were verified by experimental results. These results show a good agreement between the Oxley machining theory and hard machining experiment at data. The research work described in this thesis provides useful data for hard machining conditions.

The research work in this thesis involves an experimental and theoretical investigation for high speed machining of AISI 4140 medium carbon steels and AISI D2 tool steels which are classified as being difficult to machine materials. An experimental program was carried out to determine the cutting forces, chip formation, the secondary deformation zone thickness and surface roughness at different cutting speeds using a 0.4mm and 0.8mm nose radii ceramic tools and -7?? rake angle for annealed (virgin) AISI 4140 and heat treated AISI 4140 steel. Another series of experiments was carried out on the annealed (virgin) and heat treated AISI D2 with 0.4mm, 0.8mm and 1.2mm nose radii CBN (Cubic Boron Nitride) tools under various cutting conditions. A theoretical model is developed by taking into account the flow stress properties of the AISI 4140 (0.44% carbon content) to use with the Oxley Machining approach. To find the flow stress data for AISI D2 tool steel, the Johnson and Cook empirical constitutive equation is used as the constitutive model. In addition, the magnitude of tool radius should be also considered to determine the prediction of cutting performances. To account for the effect of nose radius edge in hard machining, a simplified geometrical method is used to model the parameters for application in the Oxley Model and works for the cutting conditions considered here. These extensions to the Oxley machining theory were verified by experimental results. These results show a good agreement between the Oxley machining theory and hard machining experiment at data. The research work described in this thesis provides useful data for hard machining conditions.