There are different polarization fields on the Zn face and O face along the c-axis of the ZnO single crystal due to the influence of the spontaneous polarization. In this work we will determine the internal field directions of both faces of the 0.5mm thick ZnO single crystal by photoreflectance and contactless electroreflectance techniques. We found that Zn face has inversion phase line shape, which means its internal field directs outward; O face has same phase line shape, which means its internal field directs inward.

No description available.

No description available.

No description available.

Cilia are microtubule-based organelles that project into the extracellular space and have various functions including transducing sensory information, regulating developmental signalling pathways, and generating directed fluid flow, making them important regulators of vertebrate development and homeostasis. Despite their importance, there are many aspects of cilia formation and function that remain poorly understood. The planar cell polarity (PCP) pathway is a branch of Wnt signalling that provides positional information to cells and is required for polarized morphogenic cell movements. Previous studies of PCP effector proteins suggested that PCP signalling was required for cilia formation. However, these proteins are not specific to the PCP pathway and are shared with other branches of Wnt signalling. To determine the role of a core and specific PCP regulator on ciliogenesis, I examined maternal-zygotic (MZ) vangl2 zebrafish mutants using an in vivo marker of cilia, Arl13b-GFP. Analysis of MZvangl2 mutants revealed that PCP is not required for cilia formation but is required for the posterior tilting and posterior positioning of motile cilia, essential for directed fluid flow. A parallel branch of studies suggested that cilia are actually required to regulate PCP signalling because defects in PCP-mediated morphogenic movements were observed with the knockdown of certain proteins that localize at or near cilia or basal bodies. To determine whether cilia were required to establish PCP, I generated MZ-intraflagellar transport-88 (IFT88) mutants, where ciliogenesis is completely abolished. Analysis of MZift88 mutants revealed that cilia are not directly required for PCP-mediated morphogenic movements. However, I observed that MZift88 mutants had defects in oriented cell divisions (OCD) occurring during gastrulation. Remarkably, these divisions occur prior to cilia formation, suggesting a cilia-independent role for IFT proteins in cell divisions, which may have important consequences on the interpretation of the role of cilia in disease.

Polarized cell movements are essential to the cell rearrangements that occur during morphogenesis. In Xenopus, cell polarity is reflected in the directional cell intercalations that drive the morphogenetic movements characterizing gastrulation. While these cell behaviours are well described, the molecular mechanism underlying this cell polarity is unknown. PAR-3 is a multi-domain scaffolding protein and a key regulator of cell polarity. I have isolated a cDNA encoding Xenopus PAR-3 and generated several mutant constructs, each lacking a conserved domain. Initial characterization of GFP-tagged PAR-3 in A6 cells demonstrates localization to points of cell-cell contact in epithelial sheets, as well as at the leading edge of migrating cells. PAR-3 constructs lacking the CR1 or PDZ1 domain fail to compartmentalize properly and are found in the cytoplasm. Eliminating the PDZ3 domain resulted in a loss of contact inhibition. Mutation of the aPKC phosphorylation site created a membrane hyper-accumulation phenotype. Together these data suggest that the CR1 and PDZ1 domains mediate membrane compartmentalization that is modulated through aPKC phosphorylation, while the PDZ3 domain is required for contact inhibition. In embryos, PAR-3 is expressed throughout gastrulation and over-expression of PAR-3 inhibits blastopore closure indicating a requirement during gastrulation. Inhibition is relieved when the construct lacking the CR1 domain is over-expressed. PAR-3 was localized to the cell periphery in axial mesoderm. Localization was abolished with deletion of the CR1 domain indicating that membrane targeting of PAR-3 is required for gastrulation and this targeting is dependent on oligomerization of PAR-3. This investigation also suggests PAR-3 functions independent of the PAR complex in Xenopus embryos indicating involvement of a different PAR-3 signaling pathway.

Cilia are microtubule-based organelles that project into the extracellular space and have various functions including transducing sensory information, regulating developmental signalling pathways, and generating directed fluid flow, making them important regulators of vertebrate development and homeostasis. Despite their importance, there are many aspects of cilia formation and function that remain poorly understood. The planar cell polarity (PCP) pathway is a branch of Wnt signalling that provides positional information to cells and is required for polarized morphogenic cell movements. Previous studies of PCP effector proteins suggested that PCP signalling was required for cilia formation. However, these proteins are not specific to the PCP pathway and are shared with other branches of Wnt signalling. To determine the role of a core and specific PCP regulator on ciliogenesis, I examined maternal-zygotic (MZ) vangl2 zebrafish mutants using an in vivo marker of cilia, Arl13b-GFP. Analysis of MZvangl2 mutants revealed that PCP is not required for cilia formation but is required for the posterior tilting and posterior positioning of motile cilia, essential for directed fluid flow. A parallel branch of studies suggested that cilia are actually required to regulate PCP signalling because defects in PCP-mediated morphogenic movements were observed with the knockdown of certain proteins that localize at or near cilia or basal bodies. To determine whether cilia were required to establish PCP, I generated MZ-intraflagellar transport-88 (IFT88) mutants, where ciliogenesis is completely abolished. Analysis of MZift88 mutants revealed that cilia are not directly required for PCP-mediated morphogenic movements. However, I observed that MZift88 mutants had defects in oriented cell divisions (OCD) occurring during gastrulation. Remarkably, these divisions occur prior to cilia formation, suggesting a cilia-independent role for IFT proteins in cell divisions, which may have important consequences on the interpretation of the role of cilia in disease.

Thesis (Ph.D.)--University of Toronto, 2006. / Source: Dissertation Abstracts International, Volume: 67-06, Section: A, page: 2340. Includes bibliographical references (p. 322-341).

Thesis (B.A. (Hons.)) -- University of Adelaide, Dept. of Psychology, 1979.

Thesis (Ph. D.)--University of Virginia, 1998. / Spine title: Effects of substrates on polarity. Includes bibliographical references (p. 143-153). Also available online through Digital Dissertations.