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(2006) Doran, MichaelThesisThe transplantation of ex vivo expanded mobilized peripheral blood haematopoietic stem cells (PBSC), in place of unmanipulated cells following high dose chemotherapy, reduces the period of cytopenia associated with the therapy’s hemotoxicity. In this thesis the development and optimization of a preclinical prototype hollow fiber bioreactor (HFBR) for the ex vivo expansion of PBSC is described. Mass transport measurements and model of metabolite profiles demonstrate that Cuprophan and Polyflux are suitable membrane material for high-density cell expansion in a HFBR. Materials selected for the HFBR were found to be non-toxic following a 20-day saline extraction. Growth factor (GF) adsorption to the Polyflux membrane makes it unsuitable for expansion of GF dependent cells. However, the GF retention and minimal adsorption characteristics of the Cuprophan membrane are appropriate for this application. Cell-free medium degrades at 37ºC by an oxygen dependent process generating byproducts that inhibit cell growth. This process is relevant to perfusion bioreactors where the bulk of the medium is maintained at 37ºC and is cell-free. Albumin was shown to slow the degradation process but was itself degraded by shear damage inflicted during recirculation. Treating recirculating medium with dialysis against albumin was shown to be a more effective way to mitigate the effects of degradation and lengthen the functional life of albumin over conventional suspension of albumin in the recirculating medium. The preclinical prototype HFBR utilised dialysis against albumin to expand KG-1a cultures from densities as low as 3.5x10^5 cells/ml up to as high as 2x10^8 cells/ml with expansion rates equivalent to T-flask cultures. This process was then applied to PBSC where the targeted 100-fold expansion was achieved. Process optimization was continued using cord blood (CB) CD34+ cells. Growth factor loading sufficient for PBSC expansion in the HFBR was inadequate for CB expansions due to greater than anticipated CB uptake rates. The cell product from the HFBR contained significantly greater yields of CD34+ cells than attained using T-flask cultures. The HFBR platform is suitable for PBSC expansion and appears promising for CB expansion.
(2019) Zhang, WeizhengThesisWireless communication has been developed rapidly in recent years with the utilization of multiple-input multiple-output (MIMO) systems. One promising technique to support ultra-high data rate communication is massive MIMO, or large MIMO, where the number of antennas goes to tens or hundreds. Unmanned Aerial Vehicles (UAVs) have the advantages of high mobility and flexibility that can be used as aerial nodes to provide communication to ground users or base stations. In this thesis, the optimization of pilot based channel estimation with limited pilot length is studied for a massive MIMO system. The pilot length is optimized to maximize the system spectral efficiency. Then, the optimal pilot design is discussed under the constraint of finite pilot length. The performance of uplink signal-to-interference-plus-noise ratio (SINR) and the effect of feedback error are also analyzed in time division duplex (TDD) and frequency division duplex (FDD), respectively. Then, a large MIMO system is utilized for UAV communication. In order to provide directional beamforming, the channel estimation in UAV millimeter wave (mmWave) system is studied. A beam training and tracking method is proposed with user mobility. For beam training, a training codebook is designed based on user location distribution. For beam tracking, two tracking methods are proposed based on different types of user mobility to reduce the training overhead. The proposed beam training codebook provides larger average downlink capacity than the conventional codebook. The proposed beam tracking design is also shown to outperform the existing methods. Lastly, a multiple UAV system in mmWave band is considered and studied. Hybrid beamforming is designed for both fully connected antenna array and partially connected subarray structures. Furthermore, a simultaneous beam tracking scheme for multiple UAV users is proposed based on subarray structure, where both UAV mobility and instability effects are taken into consideration. Simulation results show that with the proposed method, the average downlink sum capacity is improved.
(2018) Khaled, MohammadThesisThe characteristic length of the thin film systems used nowadays in nanoscale thermoelectric and microelectric devices are comparable to the mean free path and wavelength of energy carriers. As a result, the application of classical theorise to characterise thermal transport at the nanoscale is questionable. However, it is essential to understand the underlying physics of heat propagation in thin film systems to control, manipulate, and manage thermal properties in micro and nanodevices. Understanding thermal properties by experiment are challenging, especially for materials with low thermal conductivity and small mean free path (MFP). On the other hand, molecular dynamics (MD) allows investigation of sophisticated crystalline, bulk, interface and surface effects of thermal conduction problem with accuracy, fidelity, and reliability. Nevertheless, the computational results of MD can suffer from the wrong choice of critical parameters, unfit empirical potentials for thermal application and provide unreliable thermal conductivity. Moreover, the dependence of the thermal boundary resistance (TBR) on temperature, thin film's dimension, and defects are not systematically assessed for the important thin films in the thermal application. To solve this problem, a systematic equilibrium molecular dynamics (EMD), addressing the critical issues in thermal conduction characterisation is proposed at the classical temperature range, where thermal conduction is dominated by phonons. The model has been validated by investigating the thermal conduction of Si and dielectrics used in thin film systems. The issue with empirical potential is addressed by critically assessing the performance of a potential on the basis of thermal conductivity, atomic energy and phonon density of state prediction. Later, thin film systems are studied to understand relative phonon propagation at the interface and quantify TBR's dependence on interface area, interfacial distance as well as temperature. Finally, the thermal resistance of thin film systems with defects is characterised to understand realistic phonon propagation scenario in the thermal application of thin film systems.