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Biomaterial surface properties such as microtopography and energy can change cellular responses at the cell-implant interface. Phospholipase D (PLD) is required for differentiation of osteoblast-like MG63 cells on machined and grit-blasted titanium surfaces. Here, we determined if PLD is also required on microstructured/high-energy substrates and the mechanism involved. shRNAs for human PLD1 and PLD2 were used to silence MG63 cells. Wild-type and PLD1 or PLD1/2 silenced cells were cultured on smooth-pretreatment surfaces (PT); grit-blasted, acid-etched surfaces (SLA); and SLA surfaces modified to have higher surface energy (modSLA). PLD was inhibited with ethanol or activated with 24,25-dihydroxyvitamin-D₃ [24R,25(OH)₂D₃]. As surface roughness/energy increased, PLD mRNA and activity increased, cell number decreased, osteocalcin and osteoprotegerin increased, and protein kinase C (PKC) and alkaline phosphatase specific activities increased. Ethanol inhibited PLD and reduced surface effects on these parameters. There was no effect on these parameters after knockdown of PLD1, but PLD1/2 double knockdown had effects comparable to PLD inhibition. 24R,25(OH)₂D₃increased PLD activity and production of osteocalcin and osteoprotegerin, but decreased cell number on the rough/high-energy surfaces. These results confirm that surface roughness/energy-induced PLD activity is required for osteoblast differentiation and that PLD2 is the main isoform involved in this pathway. Here we showed that PLD is activated by 24R,25(OH)₂D₃ in a surface-dependent manner and inhibition of PLD reduced the effects of surface microstructure/energy on PKC, suggesting that PLD mediates the stimulatory effect of microstructured/high-energy surfaces via PKC-dependent signaling.

Additive friction stir deposition (AFSD) of AZ31B magnesium alloy was conducted to examine evolution of grain structure, phases, and crystallographic texture. AFSD was carried out using a hollow tool made from tool steel at a constant rotational velocity of 400 rpm on the AZ31B base plate. Bar stock of AZ31B was utilized as a feed material. The linear velocity of the tool was varied in the range of 4.2-6.3 mm/s. The feed rate of the material had to be maintained at a half value compared to the corresponding linear velocity for the successful deposition. The layer thickness and length of the deposits were kept constant at 1 mm and 50 mm respectively. The tool torque and actuator force values were recorded during the process and for calculation of the average input energy for each processing condition. Temperature during the AFSD experiments was monitored using a type k thermocouple located 4 mm beneath the deposition surface at the center of the deposition track. The average input energy values showed a decreasing trend with increasing tool linear velocity. The temperature values during deposition were ∼0.7 times the liquidus of the alloy. The deposited material then was examined by laser microscope and profilometer, X-ray diffraction, scanning electron microscopy, electron back scatter diffraction (EBSC), contact angle measurement and micro hardness tests. The AFSD AZ31B samples showed reduction in areal surface roughness with an increase in the tool linear velocity. The X-ray spectra revealed increase in the intensity of prismatic planes of α-Mg phase with increase in tool linear velocity. AFSD of AZ31B Mg alloy resulted in shifting of the grain size from a broader and courser distribution within the feed material to a tighter distribution. Moreover, EBSD observations confirmed the refinement in grain size distribution as well as the presence of predominantly prismatic texture for the AFSD samples when compared to the feed material. There was a marginal improvement in the hardness for the AFSD samples compared to the feed material. However, there was no significant change in the contact angle measurements in simulated body fluid for the AFSD samples compared to the feed material. The current work demonstrated ability of AFSD technique for the additive fabrication of magnesium-based alloys and provided a methodology for examining various process attributes influencing the processing-structure-property relationship.

To survive in today's manufacturing environments companies must push the standards of accuracy and speed to the highest levels possible. Electro Discharge Machining (EDM) has been used for over 50 years and recent developments have seen the use of EDM become much more viable. The goal of this research is to produce and evaluate electrodes produced by different manufacturing methods. The use of electroforming and spray-metal deposition has only recently become viable methods of producing usable rapid tooling components. The speed and accuracy as well as the cost of manufacture play a vital role in the tool and mould manufacturing process. Electroforming and spray-metal deposition offer an alternate option to traditional machining of electrodes. Electroforming is one method of producing electrodes for EDM. The fact that electroforming can be used to produce multiple electrodes simultaneously gives it the advantage of saving on costs when multiple electrodes are needed. Spray-metal deposition offers another alternative that is much cheaper and relatively faster to manufacture. The used of these non-traditional manufacturing methods in this research are compared to the performance of traditional solid electrodes in terms of machining time, material removal rate, tool wear rates and surface roughness at several standard machining settings. The results of this research are presented in this thesis along with conclusions and comments on the performance of the different methods of electrode manufacture. The major findings of the research include the solid electrodes performed better than the electroformed electrodes in Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (Ra) at all machine settings. However it was found that the production cost of the solid electrodes was six times that of the electroformed electrodes. The production of spray metal electrodes was unsuccessful. The electrode shell walls were not an even thickness and the backing material broke through the shell making them unusable. It is concluded that with further refinements and research, electroforming and spray metal processes will become an extremely competitive method in electrode manufacture and other rapid tooling processes.

Thesis (M.S.)--Ohio University, March, 2004. / Title from PDF t.p. Includes bibliographical references (leaves 61-62).

Thesis (Ph.D.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 252-266.

Thesis (M. App. Sc.)--Carleton University, 2005. / Includes bibliographical references. Also available in electronic format on the Internet.

Thesis (M.S.)--University of Michigan, 1966.

Thesis (M.S.)--University of Michigan, 1983.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 189-198).