With highly demanding requirement in current emerging cloud storage and personal computers, hard disk drive recording with high stability and high volume has attached much attention in industry and academy. Recording media and recording head feasible for future high-density recording are both crucial to utilize magnetic recording with 1T bit/in2 recording density. Recoding media with FePt for high density and high stability was investigated in this thesis using FePt polymers with imprinting methods and FePt thin films with ion-beam bombardment technologies. The FePt polymers can be patterned using imprint at micro-and nano-scales. The micro-and nano-patterns could be retained on substrates after sintering at high temperatures. The high magnetic coercivity was proved with line and dot patterns at different scales. Recording heads with Al2O3based magnetic tunneling junction sensors were also studied in thesis. The magnetic tunneling junction sensors were proved to work stable at different temperatures varying from -30oC to 100oC. The long time running test up to 100 hours also proved the stability of the magnetic tunneling junction sensors working in extreme temperatures. Withstate-of-art patterning and depositing technologies, new ideas about using FePt polymer to work as magnetic recording media and using ion beam bombardments to tune the FePt magnetic properties were verified. The feasibility of using Al2O3 based magnetic tunneling junction sensors as recording head was also discussed. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Low back pain (LBP) is associated with intervertebral disc (IVD) degeneration and exerts enormous socioeconomic burdens on the society. The nucleus pulposus (NP) is the structural and functional core of the IVD, and plays vital roles in its homeostasis. Although the etiology of IVD degeneration is not fully understood, the cellular changes of the NP have been proposed to be associated with degeneration. Conventional management for IVD degeneration primarily targets to relieve LBP and other symptoms without restoring or preserving disc function. Novel therapeutic strategies have emerged with an aim to retard or even reverse disc degeneration. In particular, the use of growth factors, such as the bone morphogenetic proteins (BMP), has received considerable attention due to their anabolic effects on extracellular matrix (ECM) synthesis by NP cells. BMP-2 and BMP-7 are of great interest for their involvement in osteogenesis, chondrogenesis, and development and maintenance of the IVD. To date, the benefits of BMP-2 on disc degeneration are controversial, given the inconsistent findings from animal model studies. The effectiveness of BMP-7 in disc repair, however, has been well demonstrated both in vitro and in vivo. A better understanding of the differences between BMP-2 and BMP-7 regulatory action on NP cells may facilitate future applications of BMP in disc repair/regeneration. This study hypothesized that BMP-2 and BMP-7 act differentially on human NP cells via different signal transduction processes. The differential effect of BMP-2 and BMP-7 was first tested in bovine NP cells using a three-dimensional culture system (alginate beads). Both BMP-2 and BMP-7 enhanced ECM production and phenotypic characteristics of bovine NP cells. Notably, BMP-7 was significantly more potent than BMP-2 in this regard. The effects of BMPs were further tested on non-degenerated (ND-NP) and degenerated (D-NP) human NP cells. The DMMB assay revealed that BMP-7 exerted a superior up-regulatory action on GAG production of D-NP cells compared to BMP-2. Furthermore, the overall response of D-NP cells to BMP-2 and BMP-7 was significantly lower than ND-NP cells. Immunohistochemical staining and quantitative RT-PCR assays demonstrated that D-NP cells possess a more fibroblastic and less chondrocyte-like phenotype than ND-NP cells. At the mRNA level, the BMP receptor BMPR1A was not expressed in D-NP cells. BMP-7, but not BMP-2, induced expression of BMPR1A in D-NP cells. On the other hand, gene expression of selected TGF-β pathway components and hypoxia pathway components were significantly up-regulated by BMP-2 but down-regulated by BMP-7. These findings suggest that D-NP cells can activate differential molecular cascades in response to BMP-2 and BMP-7. In conclusion, this study showed a superior effect of BMP7 in up-regulation of classical BMP signaling components including BMP receptor BMPR1A. The reduced responsiveness of D-NP cells to BMP-2 and BMP-7 stimulation may be related to a different expression pattern of BMP receptors. This study provides insights into the differential regulatory actions of BMP-2 and BMP-7 on human NP cells and facilitates the future application of BMPs in managing disc degeneration. / published_or_final_version / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

No description available.

Thesis (M.D.)--University of Adelaide, 1989. / Includes bibliographical references (leaves 107-109).

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 154-162). Also available in print.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 96-103).

Thesis (Ph.D.)--Drexel University, 2009. / Includes abstract and vita. Includes bibliographical references (leaves 145-161).

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 99-101).

Thesis (Ph. D.)--University of Washington, 2008. / Vita. Includes bibliographical references (leaves 98-100).

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 67-68). Also available in electronic version.