Stars can be stretched and ripped apart by the super-massive black hole at the core of a galaxy. The remnant gaseous trail gradually circularizes in a ring of mass that spreads by the viscous forces into an accretion disc. In this thesis we have studied the spectral line profle time evolution of radiation refected by the accretion disc located around a super-massive black hole. We assume the central body to be a slowly rotating or non-rotating super-massive black hole with no charge, in the frst approximation represented by the Schwarzschild solution. In a sense of Shakura-Sunyaev standard accretion disc model with the kinematic viscosity parameter α ≈ 1 we allow the accretion disc evolution to be guided by the angular momentum transfer equation with the initial mass ring located at the tidal radius being the product of tidal disruption of a star passing by a super-massive black hole. During the simulations we keep varying the mass of the central body while we keep the mass and the radius of the star constant (M = 1M⊙ and R = 1R⊙), i.e. taking into account the solar-type stars only. We defer the prospects of the full analysis involving spin (and charge) of the central body for the future study as it will be necessary to use the equations for the redshift factor and the accretion disc evolution...

The behavior of fibers suspended in a flow between two counter-rotating discs has been studied experimentally. This is inspired by the refining process in the papermaking process where cellulose fibers are ground between discs in order to change performance in the papermaking process and/or qualities of the final paper product. To study the fiber behavior in a counter-rotating flow, an experimental set-up with two glass discs was built. A CCD-camera was used to capture images of the fibers in the flow. Image analysis based on the concept of steerable filters extracted the position and orientation of the fibers in the plane of the discs. Experiments were performed for gaps of 0.1-0.9 fiber lengths, and for equal absolute values of the angular velocities for the upper and lower disc. The aspect ratios of the fibers were 7, 14 and 28. Depending on the angular velocity of the discs and the gap between them, the fibers were found to organize themselves in fiber trains. A fiber train is a set of fibers positioned one after another in the tangential direction with a close to constant fiber-to-fiber distance. In the fiber trains, each individual fiber is aligned in the radial direction (i.e. normal to the main direction of the train). The experiments show that the number of fibers in a train increases as the gap between the discs decreases. Also, the distance between the fibers in a train decreases as the length of the train increases, and the results for short trains are in accordance with previous numerical results in two dimensions.Furthermore, the results of different aspect ratios imply that there are three-dimensional fiber end-effects that are important for the forming of fiber trains.

The methods used to store data on DVD-R discs have been proven to work over the last 15 years. However, there has been a growing concern that these discs will be outlasted by the paper records they were meant to replace. The data on a DVD-R is stored as optical contrasts which have the potential to be misread and even damaged. This damage may occur either on the surface or internally to the disc, especially on the recording layer itself. The literature is saturated with studies attempting to determine the time period in which discs may fail and what the general signs of the degradation are, but almost all fail to determine the fundamental causes of DVD degradation. In particular, the exact connection between the physical state of the disc and its digital errors is undetermined. This study undertook to develop a framework to study and understand this relationship. The study also consisted of a characterization validation experiment involving several brands of DVD-Rs. The framework constructed during the course of the research included several tools. Due to the lack of an existing tool able to aggregate the gathered data, a specialized software program, called SectorDraw, was developed. In the course of this study, this software tool was validated. Additionally, it was discovered that physical defects should be evaluated and characterized by using a process of visual inspection, microscope examination, and measurements. Although not all relationships between physical defects and digital errors were explored, the study established the fact that defects can directly cause bursts of digital errors. This indicated that there was a connection between physical defects and digital errors. It was also found that physical defects developed over time after treatments of artificial aging. The developed framework was established as viable for future research to study specific relationships between physical defects and digital errors.

Understanding chromosome structure and genome organization of Culicine mosquitoes can potentially contribute to the development of novel approaches to vector control. However, because of highly repetitive nature of the Aedes and Culex genomes, the structure of their polytene chromosomes is damaged by ectopic contacts that make the analysis difficult. Mitotic chromosomes from imaginal discs of 4th instar larvae of Aedes aegypti were tested as a source for the physical genome mapping for this mosquito. Chromosomes in imaginal discs are 10 times more abundant than chromosomes in nervous ganglia, and they do not accumulate chromosomal mutation as cell line chromosomes do. Prometaphase chromosomes in imaginal discs of Ae. aegypti are 4-5 times longer than metaphase chromosomes and can provide higher resolution for physical mapping. Cold temperature (+16°C) was proven to increase the number of the chromosomes. Hypotonic solution treatment of live larvae was proven to elongate chromosomes and improve banding patterns. We differentially stained these mitotic chromosomes with Giemsa and YOYO-1 to revile the banding pattern. We applied fluorescent in situ hybridization (FISH) procedure developed for human chromosomes to Ae. aegypti chromosomes. A strain from Culex pipiens, Cx. quinquefasciatus and their hybrids from the natural population in Virginia was successfully colonized in the laboratory. This strain can be used as a reliable source for cytogenetic studies. / Master of Science in Life Sciences

The goal of this research study was to create an artificial annulus fibrosus similar to that of the natural intervertebral disc, as well as find preliminary results for vertebral endplate connection and nucleus pulposus internal pressure, for the correction of disc degeneration in the spine. The three-part composite samples needed to demonstrate good shock absorption and load distribution while maintaining strength and flexibility, and removing the need for metal in the body, something of which no current total disc replacement or spinal fusion surgery can offer. For this study, the spinal disc was separated into its three different components, the annulus fibrosus, the nucleus pulposus, and the vertebral endplates, each playing a vital role in the function of the disc. Two low-cost materials were selected, a Covestro polyurethane and cellulose nanocrystals, for the purpose of creating a polymer composite spinal disc implant. A methodology was established for creating the cast composite material for use as an annulus fibrosus, while also investigating its mechanical properties. The same composite material was used to acquire preliminary results for vertebral endplate connection to the synthesized annulus, however no additional material was used to determine or mimic the mechanical properties of these endplates, due to time constraints. Also because of time constraints, the nucleus used in this study was only comprised of water with no other additives for preliminary testing since the natural nucleus is comprised of about 80-90% water. These properties were then compared to the mechanical properties of the natural disc, so that they could be finely tuned to emulate the natural disc. It is shown in this study that the composite material, when swelled in water, was able to mimic the annulus fibrosus in tensile strength and modulus, however showed higher compressive strength and modulus than ideal. The samples also did not undergo any permanent deformation within the realm of force actually introduced to the natural disc. The vertebral endplates showed decent adhesion to the synthesized annulus, however there were slight defects that became failure concentrators during compression testing. The nucleus showed promising results maintaining good internal pressure to the system causing better compressive load distribution, with barreling of the samples. / Master of Science / Spinal disc degeneration is a very prevalent problem in today’s society, effecting anywhere from 12% to 35% of a given population. It usually occurs in the lumbar section of the spine, and when severe enough, can cause bulging and herniation of the intervertebral disc itself. This can cause immense lower back pain in individual’s stricken with this disease, and in the US, medical costs associated with lower back pain to exceed $100 billion. Current solutions to this problem include multiple different treatment options of which, spinal fusion surgery and total disc replacement (TDR) are among the most common. Although these treatments cause pain relief for the majority of patients, there are multiple challenges that come with these options. For example, spinal fusion surgery severely limits the mobility of its patients by fusing two vertebrae together, disallowing any individual movement, and TDR can cause hypermobility in among the vertebrae and offer little to no shock absorption of loads. Therefore, a better treatment option is needed to relieve the pain of the patients, as well as maintain equal motion, shock absorption, and load cushioning to that of the normal intervertebral disc and remaining biocompatible. The goal of this research study was to create a three-component system, like that of the natural intervertebral disc, for the use of spinal disc replacement and to replace current options. The fabricated system was comprised of the three components found in the natural intervertebral disc; the annulus fibrosus, the nucleus pulposus, and the vertebral endplates. Because the system will need to go in-body, the materials used were all characterized as biocompatible materials; the polyurethane currently being used in medical devices and implants, and the cellulose nanocrystals (CNCs) coming from natural cellulose in sources such as wood and plants. The results determined that the mechanical properties of the system can be fine-tuned in order to mimic the natural strength and cushioning capabilities of the natural disc, based on CNC content added to the polyurethane, and when all three components of the system are added together, the compressive stress-strain is most similar to the natural disc in compression. However, the system did show failure in the connection between the annulus fibrosus and vertebral endplates, causing herniation of the nucleus similar to the initial problem attempting to be solved. For this, more ideal fabrication methods should be researched in the future including 3D printing techniques, injection molding, and roll milling. As well as alternate fabrication techniques, cell grow and viability should be determined to show that cells don’t die once the system in implanted.

It is possible that interruption of nociceptive input from intervertebral discs can be modulated through bilateral L1 and L2 dorsal root ganglia (DRG) blockade. In order to test this hypothesis, we prospectively collected data from patients with low-lumbar pain, accurately diagnosed as discogenic using provocation discography. Methods Twelve patients were recruited with a mean (SD) symptom duration of 13.7 (8.2) years. Bilateral DRG blocks of L1 and L2 were performed using methylprednisolone 80 mg, clonidine 75 µg and 0.5% bupivacaine 4 ml in each patient. Results Analysis of Brief Pain Inventories showed no significant change in pain scores. Conclusion We conclude that blocks of this nociceptive pathway in humans using bilateral DRG blocks has no therapeutic value.

This thesis focuses on the evolution of zonal flows in self-gravitating accretion discs and their resulting effect on disc stability; it also studies the process of disc gravito-turbulence, with particular emphasis given to the way the turbulent state is able to extract energy from the background flow and sustain itself by means of a feedback. Chapters 1 and 2 provide an overview of systems involving accretion discs and a theoretical introduction to the theory of accretion discs, along with potential methods of angular momentum transport to explain the observed accretion rates. To address the issue of the gravito-turbulence self-sustenance, a compressible non-linear spectral code (dubbed CASPER) was developed from scratch in C; its equations and specifications are laid out in Chapter 3. In Chapter 4 an ideal (no viscosities or cooling) linear stability analysis to non-axisymmetric perturbations is carried out when a zonal flow is present in the flow. This yields two instabilities: a Kelvin-Helmholtz instability (active only if the zonal flow wavelength is sufficiently small) and one driven by self-gravity. A stability analysis of the zonal flow itself is carried out in Chapter 5 by means of an axisymmetric linear analysis, using non-ideal conditions. This considers instability due to both density wave modes (which give rise to overstability) and slow modes (which result in thermal or viscous instability) and, thanks a different perturbation wavelength regime, represents an extension to the classical theory of thermal and viscous instabilities. The slow mode instability is found to be aided by high Prandtl numbers and adiabatic index γ values, while quenched by fast cooling. The overstability is likewise stabilised by fast cooling, and occurs in a non-self-gravitational regime only if γ ≲ 1.305. Lastly, Chapter 6 illustrates the results of the non-linear simulations carried out using the CASPER code. Here the system settles into a state of gravito-turbulence, which appears to be linked to a spontaneously-developing zonal flow. Results show that this zonal flow is driven by the slow mode instability discussed in Chapter 5, and that the presence of zonal flows triggers a non-axisymmetric instability, as seen in Chapter 4. The role of the latter is to constrain the zonal flow amplitude, with the resulting zonal flow disruption providing a generation of shearing waves which permits the self-sustenance of the turbulent state.

by Tsai Yee-Ah, Eva. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1997. / Incldues bibliographical references (leaves 108-112). / ABSTRACT --- p.iii / ACKNOWLEDGEMENTS --- p.vi / TABLE OF CONTENTS --- p.vii / LIST OF TABLES --- p.ix / LIST OF FIGURES --- p.x / CHAPTER / Chapter I. --- INTRODUCTION --- p.1 / Objectives --- p.2 / Chapter II. --- MARKET ANALYSIS --- p.4 / Overview of the Music Industry in Hong Kong --- p.4 / Hong Kong Classical Music Market and the Trends --- p.6 / Definition of Classical Music --- p.6 / Classical Music Becomes More Popular --- p.8 / More Record Stores in Hong Kong Selling Classical CDs --- p.10 / New Ways of Promoting Classical Music --- p.13 / New Classical Music Repertoires and the Trends --- p.15 / More Young Classical Performers --- p.16 / Major Classical Companies in Hong Kong --- p.17 / Bertelsmann Group --- p.17 / EMI --- p.19 / HNH Internationa] Ltd --- p.22 / PolyGram --- p.25 / Sony --- p.28 / Warner --- p.32 / Chapter III. --- RESEARCH METHODOLOGY --- p.37 / Secondary Data --- p.37 / Primary Data --- p.38 / Experience Survey --- p.38 / Sample Survey --- p.38 / Limitations of the Research --- p.42 / Research Design --- p.42 / Data Collection --- p.43 / Data Analysis --- p.44 / Chapter IV. --- RESEARCH FINDINGS AND DATA ANALYSIS --- p.48 / Response Rate --- p.48 / Outcome of Self-Administered Questionnaire Survey --- p.48 / Data Analysis --- p.49 / Editing --- p.49 / Coding --- p.50 / RESEARCH FINDINGS --- p.50 / Demographic Information of 200 Successful Respondents --- p.50 / Respondents' Opinions of HMV --- p.53 / Respondents' Usage Patterns of Classical CDs --- p.55 / Brand Name of the Record Company --- p.55 / Price --- p.60 / Selection Criteria in Buying Classical CDs --- p.61 / places for Buying Classical CDs --- p.72 / Reasons for Buying Classical CDs --- p.74 / Opinions of Sony's Classical CDs --- p.77 / Preferred Promotional Methods --- p.81 / Information Channels in Receiving Information about Classical CDs --- p.84 / Maximum Price Willing to Pay --- p.88 / Preferred Tangible Changes or Improvements --- p.89 / Conclusion --- p.91 / Competitive Profile --- p.91 / Market Profile --- p.92 / Customer Profile --- p.93 / Product Profile --- p.94 / Company Profile --- p.95 / Chapter V. --- "MARKETING PLAN FOR SONY'S CLASSICAL DIVISION, 1997-1998" --- p.97 / Target Markets --- p.97 / Marketing Objectives --- p.98 / Product Objectives --- p.98 / Pricing Objectives --- p.99 / Communication Objectives --- p.100 / Distribution Objectives --- p.105 / Monitoring System --- p.107 / Conclusion --- p.108 / APPENDIX --- p.110 / BIBLIOGRAPHY --- p.133

by Yau Ka Pui, Lea [and] Yeung Sze Man. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 108-112). / ABSTRACT --- p.II / TABLE OF CONTENTS --- p.IV / LIST OF ILLUSTRATIONS --- p.VI / LIST OF TABLES --- p.VII / ACKNOWLEDGEMENT --- p.IX / CHAPTER / Chapter I. --- INTRODUCTION --- p.1 / Global Trend --- p.2 / Music Industry in a Global Perspective --- p.2 / Growth of Mass Retailing IndusTRy in Hong Kong --- p.5 / Marketing Situation of the Small Music Retailers in Hong Kong --- p.7 / Product --- p.7 / Price --- p.8 / Place the Stores --- p.8 / Promotion --- p.9 / Emergence of CD Chain Stores in HK Music Retailing in Early 1990's --- p.10 / HMV CD Retailing Chain Stores --- p.10 / HMV as a Store Differentiator --- p.11 / HMV's unique Store Atmosphere: --- p.13 / Carefuliy Designed Entertainment Facilities in HMV --- p.14 / HMV's Role as an Information Provider --- p.15 / Market Reality --- p.19 / CHAPTER CONCLUSION --- p.20 / Chapter II. --- RESEARCH OBJECTIVES --- p.22 / Chapter III. --- METHODOLOGY --- p.24 / Data Collection --- p.25 / Sampling Plan --- p.25 / Terminology --- p.26 / Chapter IV. --- DATA ANALYSIS AND RESULTS --- p.29 / Causeway Bay Store --- p.29 / Profile of Existing Shoppers --- p.29 / "Profile of HMV Buyers and "" Mere Shoppers""" --- p.35 / Profile of Buyers with regard to their Purchase Volume --- p.39 / Shatin Store --- p.43 / Profile of Existing Shoppers --- p.43 / "Profile of HMV Buyers and “Mere Shoppers""" --- p.47 / Profile of Buyers with regard to their Purchase Volume --- p.49 / Summary of Analysis and Results --- p.51 / Chapter V. --- RECOMMENDATIONS --- p.54 / The Marketing Model --- p.55 / The Market Segmentation for HMV Customers --- p.56 / Target Group Analysis --- p.58 / Generic Marketing Objectives --- p.59 / Enlarge the Market --- p.60 / Increase Market Share --- p.60 / Improve Profitability --- p.60 / Specific Objectives for HMV --- p.61 / Analysis of Mere Shoppers --- p.62 / The Marketing Tactics for Mere Shoppers --- p.62 / Free CD Trial in Neighbouring Retail Stores --- p.63 / Coupons --- p.63 / Set a Time Slot for CD on Sales --- p.64 / Men's Day --- p.64 / Analysis of the Light Buyers --- p.66 / Feasible Marketing Tactics for the Light Buyers --- p.66 / HMV Club --- p.67 / Chance of Getting an Autographed CD --- p.68 / Chance of Getting an Autographed Poster or Photograph --- p.68 / Dedication Service --- p.69 / "Modification on the Current ""Members Card""" --- p.69 / Analysis of the Medium Buyers --- p.72 / Marketing Tactics for the Medium Buyers --- p.72 / Starting from the Existing Pool of Information --- p.72 / Store Image --- p.73 / The Real Meaning of Quality Service --- p.75 / A Private Listening Area --- p.76 / Analysis of the Heavy Buyers --- p.76 / Marketing Tactics for Heavy Buyers --- p.77 / Customer Retention Program --- p.77 / HMV Credit Card --- p.77 / Direct Mailing Service --- p.78 / Quality Service --- p.78 / A Private Listening Booth --- p.78 / Long-term Marketing Strategy --- p.79 / The Significance of a Customer Database --- p.80 / Blueprint for Customer Segmentation --- p.81 / Quality Data for precise Target Segments --- p.81 / Basis for Relationship Marketing --- p.82 / Customer Databases as a Survey Research Complement --- p.82 / Customer Survey as a Monitoring Means --- p.83 / Chapter Conclusion --- p.85 / Chapter VI. --- CONLUSION --- p.86 / Project Limitation --- p.86 / Objectives achieved in this HMV Project --- p.87 / Marketing Implications for Other Organisations --- p.88 / APPENDIX --- p.90 / BIBLOGRAPHY --- p.108

Alloys of titanium are highly preferred materials for their excellent strength to weight ratio but the tribological issues while using them has been posing challenging issues for the tribological analyst, which are still areas of active research. Ti-6Al-4V (Ti64) is the most popular alloy of titanium and our understanding of the fundamental mechanisms of wear and friction of this alloy is still not complete. Previous investigations related to the tribology of these alloys have suggested a synergistic effect of plastic deformation and tribo-oxidation. The present investigation described in this thesis explores the existence of one more mode, namely the formation of a Mechanically Mixed Layer (MML). The thesis examines the effect of these modes one by one and analyses the synergistic effect of these mechanisms, and also the effect of heat generation during sliding. The tribological condition existing have been varied by doing wear experiments using Ti64 pins sliding against alumina and SS316L (controls MML), diameter of pin (expected to control debris entrapment and thus MML formation), tribo-system (horizontal disc Vs vertical disc, which is also expected to control debris entrapment and thus MML formation), environment (ambient and vacuum, expected to control tribo-oxidation) and sliding speed (expected to control interface temperature and thus plastic deformation mechanism and tribo-oxidations). The division of the main chapters has been so made to present the findings spread over Chapters 5-8, with each chapter dealing with specific tribological test conditions. In each chapter, results from the tribological experimentations in the form of wear and friction are presented, together with the characterization methods which throw light into the tribological mechanisms. These characterization methods include Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDAX), X-Ray Diffraction (XRD) and Electron probe micro-analyzer (EPMA). Wherever possible, the debris collected from the experiments have been subjected to morphological and detailed chemical analysis, and a feature which has not been explored much in detail by tribological investigators, but having a promising potential. Experimental results from tribological testing when Ti64 pins slides against two different materials (Alumina and SS316L) in pin-on-disc tribometers under two different environmental conditions (ambient /vacuum) are analyzed. Each set of experiments looks at two different effects - (1) the effect of sliding speed on the tribological behavior while using a pin of a fixed diameter (all other parameters remaining the same) and (2) the effect of using pins of different diameters for a given set of parameters. Three different pin-sizes were employed (2.1 mm. 4.6 mm and 6.6 mm), the normal loads on these pins were changed according to the pin-size used so that all experiments were done at the same contact pressure (2.8 MPa). By performing the experiments against the ceramic disc (alumina) under vacuum conditions, the effect of this plastic deformation is studied in isolation because the possibility of the Tribo Chemical Reaction (TCR) due to oxidation is inhibited and no MML was found to be formed due to poor compatibility of mixing between the metallic pin and the ceramic disc. For the low speeds/strain rates experiments, the effect of plastic deformation as influenced by the adiabatic shear banding is seen to influence wear which progressively changes to temperature induced plastic deformation and wear. The situation is found to be different when we change the environmental conditions from vacuum to ambient for the same tribo-combination. The tests shows a reduction in wear rate with speed, and this is due to the oxide formations due to TCR as confirmed from the SEM/EDAX characterization. In contrast to previous experiments under vacuum, these permit the effect of TCR also to influence the tribological behavior. The scenario changes when the alumina disc is replaced by a metallic one (SS316L) and tests carried out in vacuum, as the MML was found to be formed with this tribo-pair. Because of the mutual affinity of the materials in the tribo-pair, the wear damage is severe in this case and the flash temperatures crossing the phase transition temperature (~880oC) for Ti64 at high speeds. The growth of the β phase with increase in the sliding (temperature) conditions is captured from the XRD spectra of the wear debris. Synergistic effect of all these mechanisms (plastic deformation, MML, and TCR) is permitted by conducting experiments with Ti64 pin against stainless steel and in ambient conditions. A comparison of the tribological response by presenting results when experiments are run over a range of speeds while using different sized pins under ambient conditions (and compared with similar results in vacuum) while using SS316L disc serve to demarcate the differences in the wear modes which are active/inactive depending on the tribological conditions. In addition a study incorporating the effect of frictional heating and its influence on the tribological phenomena is analyzed. Main conclusions from the thesis are: The wear resistance of Ti64 alloy when sliding against SS316L is found to be influenced by Strain Rate Response (SRR), Tribo Oxidation (TO), Mechanically Mixed Layer (MML) and the prevailing heat flux conditions at the contact. The wear rates were found to decrease marginally with sliding speeds (strain rates) up to a certain speed, which is ascribed to reduction in adiabatic shear band intensity with increase in strain rate. Adiabatic Shear Band (ASB), which allows easy crack propagation, intensity reduces as temperature of deformation of Ti64 is increased. From the results it can be confirmed that the propensity for formation of MML depends on compatibility of the disc and the pin material. The contribution due to of entrapment and retention of debris in the contact zone also would influence formation of the MML. The effect of frictional heating plays an influential role as it can affect the factors (TO, ASB, MML) governing the tribological response. The sensitivity to temperature, which is a marked feature of this alloy in undergoing softening, as confirmed by previous researchers, is reflected in the experimental results. Since the main factor that triggers the micro-structural instability is the energy dissipation that accompanies deformation more fundamental research which can improve the thermal transport properties of this alloy, would be the future scope of work of this thesis. Also, the unique composition of the MML which offers high wear resistance under specific operating conditions opens up the possibility of new such alloy formulations, production routes and techniques which should improve the tribological response of this alloy.