Master of Arts - Arts / During the Islamic period (8th to 15th centuries) glass beads are the most abundant evidence of international trade in southern Africa. Archaeologists, however, have underutilized them because they are small, monochrome and difficult to categorize. I show they can be divided into identifiable series that have temporal parameters. Once identified, the beads can help interpret site chronology as well as regional and international interaction. Glass beads are also useful in reconstructing trade patterns in the Indian Ocean. Present perceptions concerning Islamic period trade to eastern and southern Africa are based largely on Islamic ceramics and Arab documents. Thus, it is generally believed that trade to southern Africa was an extension of the East Coast monsoon-driven trade that was conducted mainly by local mariners familiar with the difficult conditions in the Mozambique Channel. Comparison of glass bead assemblages from eastern and southern Africa, however, shows that it is unlikely the beads reaching the south were traded through ports to the north. Based on distribution patterns and recent chemical analyses, I propose they were arriving directly from South and/or Southeast Asia.

A previous study, looking at the creep-rupture behaviour of mixed reinforcement GRP when immersed in water, had discovered that low loads, behaviour became temperature sensitive. Since the recorded time to failure of a sample was reduced at elevated temperatures, from that predicted by a linear extrapolation of the short term creep-rupture results, this deviation caused problems in the accurate prediction of long-term design stresses. In order to improve the accuracy of long term design predictions, it was decided to study the mechanisms of creep in GRP that initiates time dependent failure. From this, it was hoped that accurate design criteria suitable for predicting GRP response over a 30 year design life from short term creep tests, could be developed. This thesis reports the results obtained from such a study. A series of creep tests were performed on mixed reinforcement GRP samples at several stress levels, both in air, and in room temperature distilled water, using a microcomputer based data collection system. In conjunction with this work, damage development in samples, due to combinations of water uptake and creep loading, was followed, using both scanning electron, and optical, microscopy. Moisture uptake measurements were undertaken under a series of load/temperature regimes, and fibre/matrix debonding followed using photographic techniques. In this way, water absorption, both in terms of uptake rate, and location within a sample, could be characterised. Tensile tests were also performed to determine the standard mechanical properties of the mixed reinforcement GRP used. It was found that a critical damage state was created at loads in excess of 50% of ultimate, but not below. This took the form of between 2 and 8 neighbouring filament breaks in the longitudinal woven rovings at weave crossover points, producing microcracks in the reinforcement. The creation of this multifilament fracture damage during primary creep, was considered to be necessary for time dependent failure to occur in air. Secondary greep strain was found to increase in discrete steps, both in air and water. This was attributed to the formation of transverse grasks in the longitudinal woven rovings, propogating from the above critical damage. In water, diffusion was found to be non-Fickian. Moisture uptake increased with increases in applied load and temperature. Water was seen to accumulate at weave cross-over points when immersed under load. This led to stress-enhanced fibre corrosion in these regions, weakening the reinforcement, and reducing the failure time from that expected at the same load level in air. The localised nature of moisture degradation was thought to result in the formation of critical fibre damage at loads below 50% of ultimate, when immersed in water. Two design criteria based on the observed creep mechanisms, have been developed for GRP that predict response when loaded in either air, or water. Both predict the existence of creep-rupture limits at low loads.

Introduction: The survival of dental implants depends on osseointegration. Modifications to the implant surface are attractive for promoting the success of the implant. Abrading the surface of the implant with bioactive glass is an attractive option for improving the speed of osseointegration. Aims: To develop a bioactive glass that has the ability to enhance the surface roughness of the implant by embedding particles into the surface and to investigate the effect of grit blast parameters on the removal of the titanium from the surface. Methods: Three glasses based on SiO2-CaO-Na2O-P2O5-CaF2 were synthesized by a melt quench technique. The glasses were characterised and investigated for their bioactivity. Titanium discs were abraded with coarse glass particles by using a grit blast technique with different parameters, such as, distance, air pressure and speed. The depth, width of the abraded line and surface roughness (Ra) were measured by light profilometer. The distribution of the glasses on the titanium surface was measured by SEM-EDX. The biocompatibility of the abraded discs was tested in vitro using MC3T3-E1 cell line. Results: All glasses exhibited an amorphous structure with varied bioactivity. Changing the abrasion parameters influenced the amount of titanium removed and the surface coverage. The harder the glass the lower the amount of titanium removed and the wider the width of the abraded area. The Ra was significantly increased from 0.1μm to 1.6μm. The SEM-EDX analysis confirmed that the glasses were widely distributed and a higher coverage was seen with the harder glass. The abraded discs showed good biocompatibility in vitro. Conclusions: The designed compositions were successfully modifying the surface of the titanium. They are abrasive enough to significantly embed into the titanium surface by using the grit blast technique and increase their surface roughness. TheIntroduction: The survival of dental implants depends on osseointegration. Modifications to the implant surface are attractive for promoting the success of the implant. Abrading the surface of the implant with bioactive glass is an attractive option for improving the speed of osseointegration. Aims: To develop a bioactive glass that has the ability to enhance the surface roughness of the implant by embedding particles into the surface and to investigate the effect of grit blast parameters on the removal of the titanium from the surface. Methods: Three glasses based on SiO2-CaO-Na2O-P2O5-CaF2 were synthesized by a melt quench technique. The glasses were characterised and investigated for their bioactivity. Titanium discs were abraded with coarse glass particles by using a grit blast technique with different parameters, such as, distance, air pressure and speed. The depth, width of the abraded line and surface roughness (Ra) were measured by light profilometer. The distribution of the glasses on the titanium surface was measured by SEM-EDX. The biocompatibility of the abraded discs was tested in vitro using MC3T3-E1 cell line. Results: All glasses exhibited an amorphous structure with varied bioactivity. Changing the abrasion parameters influenced the amount of titanium removed and the surface coverage. The harder the glass the lower the amount of titanium removed and the wider the width of the abraded area. The Ra was significantly increased from 0.1μm to 1.6μm. The SEM-EDX analysis confirmed that the glasses were widely distributed and a higher coverage was seen with the harder glass. The abraded discs showed good biocompatibility in vitro. Conclusions: The designed compositions were successfully modifying the surface of the titanium. They are abrasive enough to significantly embed into the titanium surface by using the grit blast technique and increase their surface roughness. The glass abraded discs show both good bioactivity and biocompatibility in vitro.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Materials Science and Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / M.S.

This thesis examined the feasibility of fibre composite reinforcement in the furniture industry. The development of post war furniture design was reviewed, with particular emphasis on the main design movements and the use of new materials and technologies. The use of fibre composite materials in contemporary furniture was discussed in terms of technical development, environmental effects and psychological acceptance. Fibre reinforcements and adhesives were compared, as were fabrication techniques applicable to the existing British furniture industry. Particular emphasis has been placed on the fibre reinforcement of laminated timber sections as a method of overcoming many of the manufacturing problems of composites. Methods of analysing the behaviour under load of fibre reinforced laminated wood were reviewed. Resistance among the furniture buying public to modem, non-traditional furniture design was discussed, along with ways of making composite materials more aesthetically acceptable. Experimentation to determine the mechanical properties of fibre composite reinforced wood against wood control samples was undertaken, along with methods used to analyse the results for flat and curved samples. Modulus of elasticity, modulus of rupture and impact strength were measured, as was the level of distortion of the samples before and after testing. A full size chair form was produced to demonstrate the behaviour of the material on a larger scale. The development of the design was discussed in terms of ergonomic requirements, aesthetics, practicality and environmental concerns. The problem of predicting the behaviour of complex shapes was discussed and a finite element analysis of the form is carried out to gain an accurate picture of the composite's performance. Production of fibre reinforced materials was discussed, along with the furniture industry's reluctance to invest in new materials and technologies. The feasibility of adapting traditional furniture making skills and equipment to the production of fibre composite reinforced wood has been assessed.

Magmatism on Iceland is dominated by the eruption of tholeiitic lavas along two NE-SW trending rift zones that represent the loci of new crustal formation. Small volumes of transitional to alkaline magmas erupted along the ~120 km long Snæfellsnes Peninsula in western Iceland. The Snæfellsnes Peninsula is broken into three distinct volcanic systems; Ljósufjöll, Lýsuskard, and Snæfellsjökull. This study examines the geochemical compositions and depths of crystallization of alkaline basaltic glass to see if these features vary spatially along the peninsula. Glass MgO values range from 3.4 to 9.0 wt %, TiO2 ranges from 0.9 – 4.8 wt. % increasing westward along the peninsula. Estimations of crystallization pressures, based on the pressure dependence of ol±plag±cpx, average 4.6 ± 2.8 kbar, translating to depth a depth of 16.1 ± 10 km generally increasing with distance from the main rift zones. In some cases, cox-melt barometry was also used as a check on the glass cotectic pressures. Crustal thickness beneath Snæfellsnes has been estimated to be ~25 km, suggesting mid to lower crustal magma storage depths. Calculated depths in Snæfellsjökull and Lýsuskard are consistent and deep (22 ± 2.4 km) whereas the Ljósufjöll system is more varied. The Ljósufjöll system displays two groupings of depths, split lengthwise. The northern group exhibits depth between 15-26 km, like the rest of the peninsula, while the southern group has no discernable pattern. Previous data on post-glacial lavas reveals broad spatial trends in REEs across the peninsula. Basaltic glasses exhibit a wide range of La/Sm (1 – 5.6) suggesting a variation in melting percentage over a small area. Samples west of 22.33⁰W have higher Dy/Yb (>2.1) indicating a deeper melting depth due to residual garnet as well as a higher La/Sm (>10) indicative of a smaller degree of melting and/or an enriched source. These data have shown that melt storage occurs at near Moho depths along the peninsula but is highly variable in the eastern Ljósufjöll.

Cell attachment is vital for the integration of biomaterials in the body. Surface modification using cell adhesive peptides, such as Arginine-Glycine-Aspartic (RGD), has showed promise for enhancing cell adhesion. Cell adhesion on glass and polyethylene glycol (PEGylated) surfaces modified with active RGD and Proline- Histidine-Serine-Arginine-Asparagine (PHSRN) peptides as well as inactive RDG and HRPSN control peptides was investigated in serum free conditions using three cell lines; NIH3T3 fibroblasts, MC3T3 pre-osteoblasts and C2C12 pre-myoblasts. Peptide attachment to glass surfaces was confirmed by x-ray photoelectron spectroscopy and contact angle measurements. Cell attachment and spreading was equivalent on all peptide and fibronectin coated glass surfaces and was significantly higher than on unmodified glass after 3 hours. Cell attachment to the peptide modified glass was reduced in the presence of soluble RGD and RDG peptides, indicating that cell attachment to these surfaces may be integrin mediated, but not specific for RGD. Inhibition of protein synthesis with cycloheximide revealed that endogenous protein synthesis did not influence the specificity of cell attachment to the peptide modified glass surfaces in all cell types within a 3 hour period. However, cycloheximide treatment inhibited cell spreading on the peptide modified glass surfaces, suggesting that proteins synthesis was required for spreading. Long term adhesion studies, within a 24 hour period, showed that all cell lines were able to remain attached to the peptide modified glass surfaces, while C2C12 and MC3T3 cells were also able to form focal adhesions during this period. Cell attachment to peptide modified PEGylated surfaces over a 3 hour period showed that NIH3T3 and C2C12 cells experienced significantly higher levels of cell attachment on the RGD modified surface compared to the other peptides. MC3T3 cells attached to all the peptide modified PEGylated surfaces to the same extent, suggesting that cell attachment to peptide modified PEGlyated surfaces, can be cell type dependent. In conclusion all the peptides were able to promote cell adhesion on glass surfaces in the absence of a PEG linker. In the presence of a PEG linker cellular response to the peptide surfaces was both peptide and cell type dependent.

Bibliography: leaves 247-257. Electronic publication; Full text available in PDF format; abstract in HTML format. This thesis examines the flow of very viscous Newtonian fluids driven by gravity, with emphasis on the lumping of molten glass into a mould, as in the manufacture of optical components, which are in turn used to manufacture ophthalmic lenses. Electronic reproduction.[Australia] :Australian Digital Theses Program,2001.

The dynamics of thin polymer films display many differences from the bulk dynamics. Different modes of motions in polymers are affected by confinement in different ways. The enhancement in the dynamics of some modes of motion can cause anomalies in the glass transition temperature (Tg) of thin films, while other modes of motion such as diffusion can be substantially slowed down due to the confinement effects. In this thesis, different modes of dynamics are probed using different techniques. The interface healing of two identical polymer surfaces is used as a probe of segmental motion in the direction normal to the plane of the films and it is shown that this mode of motion is slowed down at temperatures above bulk glass transition, while the glass transition itself is decreased indicating that the type of motion responsible for the glass transition is enhanced. The glass transition measurements at different cooling rates indicate that this enhancement only happens at temperatures close to or below bulk glass transition temperature and it is not expected to be detected at higher temperatures where the system is in the melt state. It is shown that the sample preparation technique is not a factor in observing this enhanced dynamics, while the existence of the free surface can be important in observed reductions in the glass transition temperature. The dynamics near the free surface is further studied using a novel nano-deformation technique, and it is shown that the dynamics near the free surface is in fact enhanced compared to the bulk dynamics and this enhancement is increased as the temperature is decreased further below Tg. It is also shown that this mode of relaxation is much different from the bulk modes of relaxations, and a direct relationship between this enhanced motion and Tg reduction in thin films can be established. The results presented in this thesis can lead to a possib le universal picture that can resolve the behavior of different modes of motions in thin polymer films.

The dynamics of thin polymer films display many differences from the bulk dynamics. Different modes of motions in polymers are affected by confinement in different ways. The enhancement in the dynamics of some modes of motion can cause anomalies in the glass transition temperature (Tg) of thin films, while other modes of motion such as diffusion can be substantially slowed down due to the confinement effects. In this thesis, different modes of dynamics are probed using different techniques. The interface healing of two identical polymer surfaces is used as a probe of segmental motion in the direction normal to the plane of the films and it is shown that this mode of motion is slowed down at temperatures above bulk glass transition, while the glass transition itself is decreased indicating that the type of motion responsible for the glass transition is enhanced. The glass transition measurements at different cooling rates indicate that this enhancement only happens at temperatures close to or below bulk glass transition temperature and it is not expected to be detected at higher temperatures where the system is in the melt state. It is shown that the sample preparation technique is not a factor in observing this enhanced dynamics, while the existence of the free surface can be important in observed reductions in the glass transition temperature. The dynamics near the free surface is further studied using a novel nano-deformation technique, and it is shown that the dynamics near the free surface is in fact enhanced compared to the bulk dynamics and this enhancement is increased as the temperature is decreased further below Tg. It is also shown that this mode of relaxation is much different from the bulk modes of relaxations, and a direct relationship between this enhanced motion and Tg reduction in thin films can be established. The results presented in this thesis can lead to a possib le universal picture that can resolve the behavior of different modes of motions in thin polymer films.