Colloidal suspensions of disk-like particles have been of interest in both colloidal and liquid crystal studies because they exhibit unique liquid crystalline phases different from those of rod-like molecules. Disk-like particles, such as asphaltenes in heavy oil industry, clay particles in agriculture, and red blood cells in biology, are of great interest in a variety of industries and scientific areas. However, to fabricate monodisperse microdisks, uniform in structure or composition with precise control of particle size and shape has not yet succeeded. In this thesis, we show an experimental strategy of using microfluidic technique to fabricate homogeneous α-eicosene microemulsions with chloroform in an aqueous solution of sodium dedecyl sulfate (SDS). The monodisperse chloroform emulsions, generated by the glass-based microfluidic devices, ensure the precise control on microdisk particle size and shape. A systematic investigation was performed to study the relation between the resulted microdisk size and the initial concentration of α-eicosene in chloroform before evaporation. The smectic liquid crystalline phase inside the wax particles controls the coin-like disk shape below the melting temperature of wax’s rotator phase. The kinetics of the disk formation is observed using a polarized light microscope. Dynamic light scattering is used to characterize the Brownian motion of the microdisks, and the rotational diffusion is estimated from the image sequences taken by the charge-coupled device (CCD) camera. Effort has been put into collecting a large quantity of microdisks to investigate the discotic liquid crystalline phases, which can be readily probed by light scattering and microscope. In comparison, X-ray and neutron have to be used for the atomic liquid crystalline phase investigation.

Multimedia im Wohnzimmer - Dank Linux kann man sich zurücklehnen! Welche Funktionen können Wohnzimmerrechner übernehmen? Welche Anforderungen stellen sie an die Umgebung? Und welche Rolle spielt Linux dabei?

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: multimedia; disk scheduling; admission control. Includes bibliographical references (p. 135-138).

Thesis (Ph. D.)--Drexel University, 2004. / Includes abstract and vita. Includes bibliographical references (leaves 168-182).

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 72-74).

The calculation of the physical conditions near the inner rim of a protoplanetary disk using the new computational model Pisco is described. Diagnostic plots illustrate solutions for disk structure, radiation field, chemical composition, and heating and cooling of the disk in a steady-state approximation for both disks with unsettled dust and with settled dust. Disks with unsettled dust are found to have hotter gas temperatures above the disk photosphere and a more pronounced temperature inversion at the disk photosphere. Recommendations are made for the development of Pisco. Pisco has the potential to explore what observed molecular emission can imply about disk structure. / text

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

Background: An association between cartilaginous endplate (CEP) defects and intervertebral disc (IVD) degeneration has been previously suggested in animal and cadaveric studies. CEP defects may also be involved in Schmorl’s nodes (SN). There have been no previous reports in the literature that describe the use of ultrashort time-to-echo (UTE) MRI to assess the CEP in humans in vivo. In chapter 5 of this thesis, a retrospective study of paediatric spines and the neurocentral synchondrosis (NCS) was singled out to report the incidence of NCS and to raise the hypothesis of NCS as a precursor of SN. Purpose: To assess the feasibility of detecting CEP defects in live humans using UTE MRI, and to assess their relationship with IVD degeneration and SN. Subjects and Methods: A total number of 22 subjects underwent T2-weighted (T2W) and UTE MRI to assess for the presence and severity of IVD degeneration, the presence of SN and for the presence of CEP defects. SN and IVD degeneration were confirmed by assessing T2W images and IVD degeneration was graded according to the Schneiderman classification. CEP defects were defined as discontinuity of high signal over 4 consecutive images and were independently assessed by two raters. Results: Analyses of CEP defects between IVD degeneration and SN were performed separately. For the study of CEP defects and IVD degeneration, subjects with SN were excluded. 37 out of 108 (34.3%) CEPs had defects, which mainly occurred at T12/L1, L1/L2 and L4/L5 (p=0.008). Inter-rater reliability was substantial (Kappa statistic= 0.67, p<0.001). Multivariate logistic regression revealed that lower BMI (p=0.009) and younger (p=0.034) individuals had a decreased likelihood of having CEP defects. A statistically significant association was found to exist between the presence of cartilaginous endplate defects and intervertebral disc degeneration (p=0.036). Degenerated discs with CEP defects were found in L4/5 and L5/S1, while degenerated discs with no CEP defects were found throughout the whole lumbar region. Mean degeneration scores of L4/5 and L5/S1 levels with CEP defects were higher than that of L4/5 and L5/S1 levels without. For the study of CEP defects and SN, with all 22 subjects assessed, 125 out of 264 (47.3%) CEPs had defects. 40 SN were found, and among those, 35 SN had CEP defects (87.5%). 125 CEPs had the presence of CEP defects; among them, a large number of CEP defects did not have SN underneath (92 out of 125, 73.2%). Conclusion: The studies demonstrate the feasibility of using UTE MRI in live humans to assess the integrity of the CEP. Longitudinal studies may reveal the diagnosis of CEP defects to be clinically beneficial for assessment of IVD degeneration and SN. / published_or_final_version / Diagnostic Radiology / Master / Master of Philosophy

Introduction: Intervertebral disc (IVD) degeneration is suggested to begin from the nucleus pulposus (NP). Evidence from various studies highlights mesenchymal stem cells (MSC), in most cases using bone marrow derived MSC, as a potential stem cell source for NP regeneration. However MSC can be isolated from many sources with various characteristics. There are indications that fetal or close to fetal tissue sources contain MSC with relatively undifferentiated phenotype with respect to MSC from adult sources. Moreover, umbilical cord (C)-MSC may have better chondrogenic differentiation potential than bone marrow (B)-MSC. We hypothesize CMSC are different from BMSC, and more efficient than BMSC in stimulating NP regeneration. Methods: MSC were isolated from human bone marrow and umbilical cord with corresponding ethical approval. BMSC and CMSC were characterized for cell surface marker expression profile and differentiation potential.. RT-PCR of interest genes in NP cells isolated from scoliosis and degenerate discs was performed to search for NP degeneration indicators. Conditioned media (CM) was collected from confluent MSC monolayer, and used for stimulation of four batches of degenerated NP cells isolated from human degenerative intervertebral discs. Cell proliferation and cytotoxicity were assessed by MTT assay. Proteoglycan content were measured by DMMB assay. Gene expression of a series of degeneration related molecules including ACAN, SOX9, CDH2, CD55, KRT19, KRT18, FBLN1 and MGP, and fibrosis related molecules, including MMP12, HSP47, COL1A1, COL3A1 and FN1, of NP cells in MSC-CM were determined by real- time RT-PCR. All results were normalized to the control cells in basal medium. The expression of discogenic, chondrogenic and osteogenic markers on BMSC and CMSC were compared by RT-PCR. Results and Conclusion: CMSC were similar to BMSC and fulfilled the minimum criteria of MSC, however the expression of CD146, CD106 and Stro-1 was different, and BMSC had a spontaneous osteogenesis tendency while CMSC expressed chondrogenic marker even without TGF-beta stimulation. BMSC demonstrated a paracrine effect on modulating human degenerated NP cells towards a non-degenerative phenotype in stimulating cell proliferation, slightly enhancing proteoglycan production, upregulating KRT19 while downregulating MMP12. Compared with BMSC, a higher paracrine effect of CMSC was disclosed in modulating the phenotype of NP cells in all aspects tested, and an intrinsic higher expression on CMSC of ‘potential NP markers’, including KRT19, KRT18 and CD55, but lower expression of osteogenic markers, including RUNX2 and ALPL, was revealed, which indicate a higher potential of CMSC for future clinical application to treat IVD degeneration diseases. KRT19 and MMP12 were also confirmed to be the highest differentially expressed candidate genes between cultured scoliosis and degenerated human NP cells, indicating a high indicator potential of NP degeneration. Furthermore, a subpopulation was detected in the degenerated NP cells that possessed macrophage-like phenotype and activities, which may play a role in the pathogenesis of IVD degeneration. In conclusion, studies in this thesis highlighted CMSC as a superior source than BMSC for IVD repair. Further investigations into the active agents in the conditioned media and the signalling pathway may help to elucidate the mechanism of the effect. / published_or_final_version / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

Intervertebral disc tissue engineering is challenging because it involves the integration of multiple tissues with distinct structures and compositions such as lamellar annulus fibrosus, gel?like nucleus pulposus and cartilage endplate. Each of them has different compositions and different structures. It is hypothesized that integration of tissues can be enhanced with appropriate mechanical and biological stimuli. Meanwhile, effect of torsional stimulus on cell re?orientation in mesenchymal stem cell?collagen tubular constructs is investigated in this study. Furthermore, it is proposed that these findings can be used to fabricate a multicomponent unit for intervertebral disc tissue engineering. It has been demonstrated that mechanical and biological stimuli can stabilize the interface between osteogenic and chondrogenic differentiated constructs with enhanced ultimate tensile stress while the phenotype of osteogenic and chondrogenic differentiated constructs were maintained. Scanning electronic microscopic images have shown aligned collagen fibrils and presence of calcium at the interface, indicating the possibility of the formation of a calcified zone. In addition, it is proven that torsional stimulus triggered re?orientation of mesenchymal stem cells in collagen lamellae towards a preferred angle. Cell alignments were confirmed by using a MatLab?based program to analyze the actin filament and the cell alignment via Phalloidin and Hematoxylin staining, respectively. Cells and actin filaments were inclined around 30o from the vertical axis, while cells and filaments in the control group (static loading) aligned along the vertical axis. Furthermore, a double?layers bioengineered unit was fabricated, with intact osteogenic differentiated parts at both ends. Comparatively higher cell density was observed at the interface between layers, demonstrating the interactions between layers, while the phenotype of each part was maintained in 14 days culture. This study concludes that a multi?components bioengineered unit with preferred cell alignments can be fabricated. This provides new insights to future development of bioengineered spinal motion segment for treating late stage disc degeneration. / published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy