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Dissertations / Theses on the topic 'Cell systems'
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1
Bradley, Thomas Heenan. "Modeling, design and energy management of fuel cell systems for aircraft." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26592.
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Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Parekh, David; Committee Member: Fuller, Thomas; Committee Member: Joshi, Yogendra; Committee Member: Mavris, Dimitri; Committee Member: Wepfer, William. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Shaffer, Christian Edward. "Flow system modeling with applications to fuel cell systems." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4198.
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Thesis (M.S.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains xii, 111 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 100-102).
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Holmes, David. "Advanced dielectrophoretic cell separation systems." Thesis, University of Glasgow, 2003. http://theses.gla.ac.uk/1160/.
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This thesis describes experimental and theoretical investigations into new particle handling and separation methods and techniques. It makes a major contribution to the rapidly expanding field of cell separation technology. A novel dielectrophoretic cell separation system has been developed, which is capable of processing large sample volumes (~50mL) in a flow through system. Previously reported dielectrophoretic cell separator systems typically process sample volumes in the 100mL range. The electrode configuration developed for this work allows the isolation and concentration of single particle types from large sample volumes; a method which could be further developed into a new rare-cell separation technology. In addition, a new technique of particle fractionation was developed termed ‘Dielectrophoretic Chromatography’. A cell separation chip was designed and built using standard micro-fabrication techniques. Experimental work was undertaken to demonstrate the function and limitations of the device. Numerical modelling of the particle motion in the device is presented and compared with experimental work for a number of different particle types, applied voltages and fluid flow rates. The dielectrophoretic separation system comprises a microfluidic channel, of cross-section 100mm x 10mm and length 50mm, with two sets of interdigitated microelectrode arrays. The first set of arrays, with characteristic electrode size 40mm, called a focussing device, has electrodes patterned onto the top and bottom surfaces of the flow channel. The second electrode array, which is part of the same device, has an electrode array patterned only on the bottom of the channel. Two sizes of secondary electrode array were used 20mm and 40mm. AC voltages (from 1V to 10V peak) are applied to the microelectrode, with a frequency between 10kHz to 180MHz. A dielectrophoretic force is exerted on the particles as they flow along the channel. The first electrode array uses negative dielectrophoresis to focus the stream of particles entering the device into a narrow sheet (one particle diameter thick) midway between the upper and lower channel surfaces. The second electrode array, down stream from the first is separately controllable.
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Spencer, Sabrina Leigh. "Origins of cell-to-cell variability in apoptosis." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55340.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Computational and Systems Biology Program, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 127-142).
Diversity within a population of organisms is typically ascribed to genetic differences. However, even members of a genetically identical group of cells or organisms in identical environments can exhibit variability in state and phenotype. One striking example of such heterogeneity is revealed when a genetically identical population of human cells is exposed to saturating doses of a death-inducing drug called TRAIL - many cells in the population will undergo apoptosis, a form of controlled cell death, but a fraction of cells always survives the treatment. The goal of this thesis was to understand the origins of variability in both the timing and the probability of death in TRAIL-induced apoptosis. To this end, both experimental and computational methods were implemented. Experiments examining the response of sister cells to TRAIL provided strong evidence that variability in initial conditions played a key role, and ruled out genetic, stochastic, and cell cycle effects as possible causes of heterogeneity in response. A detailed analysis of the relative contributions of three segments of the TRAIL pathway revealed that the majority of the variability in time-to-death arose upstream of mitochondrial outer membrane permeabilization (MOMP), with little contribution from downstream reactions. More specifically, the rate of cleavage of initiator caspase substrates was highly predictive of a cell's death time. However, to determine whether (as opposed to when) a cell will die, variation in the MOMP threshold became critical.
(cont.) This dependency was indicated by observation of the height of the MOMP threshold in surviving and dying cells and by modulation of this threshold via overexpression of anti-apoptotic regulators of MOMP. Simulations of cell-to-cell variability in TRAIL-induced apoptosis confirmed that the endogenous variability in apoptotic regulators was sufficient to produce the observed variability in death time. However, knowledge of the concentration of individual proteins did not allow prediction of death time because variation in other proteins masked the underlying trends. The ability to simulate heterogeneity in cellular response also led to the development of novel, biologically intuitive methods of sensitivity analysis, which revealed that sensitivities shift depending on whether knowledge of covariance in initial conditions is included. The ability to predict sensitivity and resistance of tumors to TRAIL would be clinically valuable, as TRAIL is currently in clinical trials as an anti-cancer therapy. The results described here represent progress toward understanding the "fractional killing" of tumor cells following exposure to chemotherapy, and for understanding variability in mammalian signaling pathways in general.
by Sabrina Leigh Spencer.
Ph.D.
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Swedenborg, Samuel. "Modeling and Simulation of Cooling System for Fuel Cell Vehicle." Thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326070.
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This report is the result of a master’s thesis project which covers the cooling system in Volvo Cars’ fuel cell test vehicle. The purpose is to investigate if the existing cooling system in the fuel cell test vehicle works with the current fuel cell system of the vehicle, in terms of sufficient heat rejection and thus sustaining acceptable temperature levels for the fuel cell system. The project also aims to investigate if it is possible to implement a more powerful fuel cell system in the vehicle and keep the existing cooling system, with only a few necessary modifications. If improvements in the cooling system are needed, the goal is to suggest improvements on how a suitable cooling system can be accomplished. This was carried out by modeling the cooling system in the simulation software GT-Suite. Then both steady state and transient simulations were performed. It was found that the cooling system is capable of providing sufficient heat rejection for the current fuel cell system, even at demanding driving conditions up to ambient temperatures of at least 45°C. Further, for the more powerful fuel cell system the cooling system can only sustain sufficient heat rejection for less demanding driving conditions, hence it was concluded that improvements were needed. The following improvements are suggested: Increase air mass flow rate through the radiator, increase pump performance and remove the heat exchanger in the cooling system. If these improvements were combined it was found that the cooling system could sustain sufficient heat rejection, for the more powerful fuel cell system, up to the ambient temperature of 32°C.
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Tesfahunegn, Samson Gebre. "Fuel Cell Assisted PhotoVoltaic Power Systems." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16942.
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Distributed generation (DG) systems as local power sources have great potential to contribute toward energy sustainability, energy efficiency and supply reliability. This thesis deals with DGs that use solar as primary energy input, hydrogen energy storage and conversion technologies (fuel cells and water electrolyzers) as long term backup and energy storage batteries and supercapacitors as short term backup. Standalone power systems isolated from the grid such as those used to power remote area off-grid loads and grid connected systems running in parallel with the main utility grid or a microgrid for local grid support are treated. As cost is the key challenge to the implementation of PV-hydrogen DGs, the main focus is developing sound control methods and operating strategies to help expedite their viability in the near future. The first part of the thesis deals with modeling of system components such as PV generator, fuel cell, lead acid/Li-ion storage batteries, electrolyzer, supercapacitor, power electronic converters and auxiliaries such as hydrogen storage tank and gas compressor. The subsystems are modeled as masked blocks with connectable terminals in Matlab®/Simulink® enabling easy interconnection with other subsystems. The models of main subsystems are fully/partially validated using measurement data or data obtained from data sheets and literature. The second part deals with control and operating strategies in PV hybrid standalone power systems. The models developed in the first part are used to simulate integrated systems. An attempt is made to provide some answers on how the different power sources and energy storages can be integrated and controlled using power electronics and feedback control to enhance improved performance, longer life time, increased supply reliability and minimize fuel use. To this end, new control methods and operating strategies are proposed to mediate near optimal intersubsystem power flows. The third part of the thesis concerns grid connected PV-Fuel cell power systems. Control schemes and operating strategies for integrating PV and fuel cell hybrids into the grid to serve both local demand and weak grids are investigated. How hydrogen energy storage and conversion technologies can be controlled to suppress PV fluctuations in future utility grids are also explored. A smoothing algorithm enhanced by a stepwise constant forecast is developed to enable more smooth and subhourly dispatchable power to be fed to the grid. The proposed methods were verified through longtime simulation based on realistic irradiance data over a number of typical days/weeks using suitably defined performance indices. It was learned that using power electronics and sound control methods, PV-hydrogen DGs can be flexibly controlled to solve lifetime and performance issues which are generally considered economic bottle necks. For example, conventionally in PV-hydrogen hybrids, to improve performance and life time, more battery capacity is added to operate fuel cell and electrolyzer under more stable power conditions in the face of highly fluctuating PV generation to prevent low state of charge (SOC) operation of the battery. Contrarily, in this thesis a sound control method is proposed to achieve the same objectives without oversizing the battery. It is shown that the proposed method can give up to 20% higher battery mean state of charge than conventional operation while PV fluctuation suppression rates up to 40% for the fuel cell and 85% for the electrolyzer are found for three typical days. It is also established that by predictively controlling battery SOC instead of conventional SOC setpoint control, substantial improvements can be obtained (up to 20-30% increase in PV energy utilization and ca. 25% reduction in fuel usage for considered days). Concerning use of hydrogen storage and conversion technologies in PV fluctuation suppression, results obtained from the developed smoothing mechanism and performance indices show that a trade-off should be made between smoothing performance and dispatchability. It was concluded that the right size of fuel cell and electrolyzer needs to be selected to optimize the dispatch interval and smoothing performance. Finally, a PV-hydrogen test facility which can act as show case for standalone, grid-connected and UPS applications was designed and built. The test facility was used to characterize key subsystems from which component models developed were experimentally validated. The facility also acted as a reference system for most of the investigations made in this thesis.
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Johnstone, Alex. "Microfluidic systems for neuronal cell culture." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/37822/.
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At a high level of abstraction, the brain is a system for analysing sensory information, and responding appropriately. That information is encoded and stored in the millions of neural circuits that comprise the brain. Deciphering this code is essential to understanding how memories are implemented in physiologically normal brain tissue, and to inferring the nature of some neurological disorders affecting memory such as Alzheimer’s disease, in which the neural encoding is aberrant or unsuccessful. One approach to this problem is to reduce the complexity of the brain functionality to three elements: stimuli, response, and reinforcement. The electrical activity of individual neurons can be recorded with electrodes, capturing the pathways of signal propagation in a network of cells. Individual neurons can be also induced to reliably respond to electrical or optical stimuli, so that they initiate, relay, or even block a signal. If the stimuli to a finite network of cells can be made heterogeneous so that only a sub-population of cells is targeted, then the network can be trained to react in a repeatable way to a given stimulus, testing the concept that the higher order functions of the brain can emerge from a simple set of underlying computational rules. Training however requires a mechanism for reinforcing only some of the possible pathways, in synchrony with stimuli and in response to the recorded network activity. In the intact brain, this mechanism is pharmacological: a neuromodulator such as dopamine is released throughout the brain, but as it only coincides with some but not all neuronal activity, the reinforcement is temporally selective. The key task of this project is to emulate this selective neuromodulator reinforcement in vitro in a finite neuronal network. The project must also provide capacity for heterogeneous stimulation and individual cell recording, which can be coordinated with the reinforcement under computer control. The strategy used was to develop microscale chambers to house a small network of cultured neurons. The chambers were integrated with existing cell recording and stimulating technologies, so that specific connections between neurons could be both monitored and induced. Neuronal cultures of a few hundred cells were successfully grown in microchannels, on substrates capable of recording their electrical activity. Thus it was possible to create a small cultured network in which complete network activity could be detected, subject to a sufficiently precise recording technique. Additionally, a fluid-handling system was developed in order to emulate the continual replenishment of nutrients and soluble gases that are essential to cell survival. The system is intended to deliver soluble chemicals that modulate neuronal activity, on a timescale that is consistent with neuromodulator delivery in the body. The fluid handling system comprises a set of pressure driven pumps under automated computer control. This system has the capacity to deliver neuromodulator in solution with high spatiotemporal precision. The ability to reliably deliver and wash off precise volumes of drugs in a matter of seconds, with no dilution of the intended concentration, will be of great benefit to researchers investigating the response of various cell types to different agonists.
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Faraday, David Brian Foster. "The mathematical modelling of the cell cycle of a hybridoma cell line." Thesis, University of Surrey, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341620.
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Ballester, Beltrán José. "Sandwich-like systems to engineer the cellular microenvironment." Doctoral thesis, Universitat Politècnica de València, 2015. http://hdl.handle.net/10251/48166.
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Abstract
While most of the in vitro cultures are carried out on bi-dimensional (2D)
substrates, most of the in vivo extracellular matrices are threedimensional
(3D). Consequently cells behave differently on 2D substrates
as a way to self-adaptation to a non-physiological environment. This fact
has encouraged the development of more relevant culture conditions
seeking to provide more representative models for biomedicine (e.g.
cancer, drug discovery and tissue engineering) and further insights into
any dimension-dependent biological mechanism. Different 3D culture
systems have been established though their variability and complexity
hinder their standardisation in common cell culture procedures. So, this
thesis deals with the dimensionality issue in cell/material interactions and
introduces sandwich-like microenvironments as a versatile tool to study
cell behaviour. Cells cultured within this system use both dorsal and
ventral receptors to adhere and spread, undergoing important changes
with respect to the 2D cultures and approaching to 3D conditions.
Stimulation of dorsal receptors has been previously addressed by
overlaying a protein gel on cells already attached on a 2D surface. Here we
propose a sandwich-like system that consists of two 2D surfaces so that
wider spectra of conditions can be investigated by changing the nature of
the substrate (material, topography…) and the protein coatings of both
ventral and dorsal sides.
Since sandwich culture provides an altered cellular adhesion
compared to the traditional 2D substrates by the excitation of the dorsal
receptors, changes in the intracellular signalling are expected, which
might alter important processes such as proliferation, morphology,
migration and differentiation. Hence this thesis evaluates the effect of
different sandwich culture parameters in cell behaviour.
First, cell fate upon adhesion was evaluated in terms of
morphology, proliferation and adhesion. Different conditions were studied
such as materials with different properties or protein coatings (dorsal and
ventral substrates), as well as the effect of sandwiching cells just after
seeding or after been allowed to adhere to the ventral substrate.
Interesting results were obtained such as the relationship between the
ability of cells to reorganise the ECM with cell morphology, proliferation
and adhesion, similarly as observed in 3D hydrogels (degradable vs nondegradable
systems).
Then, cell migration within sandwich culture was studied by live
imaging of a wound healing assay. Results revealed the key effect of both
ventral and dorsal substrates in determining the migration rate as well as
the migration mode used by cells. Moreover cells within the sandwich
culture migrating in the wound healing assay adopted an elongated cell
morphology that resembled cells migrating in other 3D systems. Beyond
differences in cell morphology and migration, dorsal stimulation
promoted cell remodelling of the extra-cellular matrix (ECM) over simple
ventral receptor activation in traditional 2D cultures.
Finally the effect of sandwich culture on cell differentiation was
evaluated. First we showed an increase in C2C12 myogenic differentiation
when cultured within the sandwich system. This enhancement was shown
to be dorsal stimulation dependent and related to an alteration of the
signalling pathway and the growth factor release. To determine if
sandwich culture leads only to myogenic differentiation or whether it
allows differentiation to other lineages, 4 different human mesenchymal
stem cells (hMSCs) lines were cultured under the same conditions. Results
showed the same sandwich environment triggered different cell
differentiation. This points out the importance of the microenvironment
cell niche in vivo, which highly influence cell fate, and thus the need of
mimicking it properly in vitro.
Overall, sandwich-like microenvironments switch cell behaviour
towards 3D-like patterns, demonstrating the importance of this versatile,
simple and robust approach to mimic cell microenvironments in vivo.Ballester Beltrán, J. (2014). Sandwich-like systems to engineer the cellular microenvironment [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48166
TESIS
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Avva, Jayant. "Complex Systems Biology of Mammalian Cell Cycle Signaling in Cancer." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1295625781.
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Babic, Julien. "New microfluidic systems for controlling the cell microenvironment during live-cell imaging." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1B047/document.
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Connaître en temps réel la réponse et le comportement des cellules et organismes modèles suite à des changements de leur environnement, ou à des modulations de leurs fonctions biologiques est devenu essentiel dans les sciences du vivant. Ces réponses nous permettent ensuite de comprendre les mécanismes qui régissent le fonctionnement des cellules vivantes, avec des implications en recherche fondamentale, appliquée et biomédicale. Un des plus gros défis technologiques reste le contrôle des paramètres environnementaux en microscopie haute résolution. De nos jours, aucun système ne permet de réguler un ensemble complexe de paramètres de manière précise, dynamique et simultanée tout en observant les cellules dans leur environnement. L’objectif de ma thèse est de mettre au point un tel dispositif permettant a minima une régulation fine de la température, de la composition du milieu, et notamment de la concentration de divers drogues. Ce système doit être compatible avec les applications les plus poussées en microscopie photonique. Mon approche au cours de ma thèse pour élaborer un tel système est l’utilisation de la microfluidique. En effet, c’est la seule technologie qui puisse de réaliser un tel multiplexage. Elle permet de manipuler des petites quantités de fluide à travers un système contenant des canaux de dimensions allant du micromètre au centimètre. Cet ordre de grandeur des canaux constitue un atout majeur (réduction de la consommation des réactifs, réduction des couts, cinétiques des réactions chimiques et biologiques élevées, temps de diffusion court, etc.) et permet d’allier les expériences biologiques à la microscopie. Mon objectif est de concevoir une puce microfluidique qui représentera un pas technologique majeur et ouvrira de nouvelles possibilités de rechercheMonitoring in real-time the response of cells and model organisms to the changes in their environment or to modulations of their biological functions has become essential in life sciences. One of the main technical challenges for biologists is the precise and dynamic control of various environmental parameters while doing high-resolution microscopy. My thesis consists of building a robust and versatile system, dedicated to live-cell imaging that will be compatible with adherent and non adherent models, that could provide a precise and simultaneous control of 1) the temperature, 2) the media exchanges and 3) the drug concentration while doing photonic microscopy. My approach is to use microfluidics, which is the best candidate in order to achieve this system and provides all the necessary controls of micro-scaled volumes for culturing, maintaining or analyzing cells. It produces miniaturized systems used as tools for biological experiments, in which channels of a micro-scaled dimension are used for the fluid circulation. The laminar flow in these chips allows fast molecule diffusion as well as fast temperature diffusion. Because of the high surface to volume ratio, the consumption of reagents is reduced, and media switches can be fast. This system will represent a major technical and beneficial step and will open new possibilities of research in biology
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Amer, Mahetab H. "Development of injectable cell delivery systems for high accuracy cell therapy applications." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/39839/.
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Cell-based therapeutic interventions are being developed for a variety of clinical indications, including irreversible retinal pathologies and stroke. Numerous cell therapy procedures use injection-based administration to deliver high density cell preparations, either systemically or directly. The mode of delivery of fragile cells can compromise treatment efficacy, which is dependent on cell viability and functionality post-injection. Reviewing current literature, there is a lack of comprehensive testing of the effects of injection-based cell delivery on the various parameters of cell function. This study investigated the effects of the administration process on a range of cell characteristics, and aimed to answer critical questions regarding possible reasons for failure to deliver a sufficient numbers of viable cells. Biomaterial-assisted cell delivery was also investigated to determine improvement of cell recovery and possible influence on cell fate. Primary human mesenchymal stem cells (hMSCs) and Swiss mouse embryonic fibroblast cell line (NIH 3T3) suspensions were drawn up into 100 μL Hamilton syringes with 30- and 34G needles. They were then ejected at rates ranging from 10-300 μL/min. A comprehensive toolset was employed to assess the effects of various injection parameters, including ejection rate and needle size. Cell dose recovery, viability, apoptosis, senescence and other parameters of cellular health were evaluated using various standard and multiplex assays. Trilineage differentiation potential of ejected hMSCs was also assessed. Moreover, various injectable cell carriers were explored in terms of improvement of cell recovery and potential influence on differentiation capacity. Ejections at slower flow rates resulted in a significantly lower percentage of dose delivered as viable cells, with ejections at 300 μL/min showing the maximum percentage of hMSCs dose delivered at 77.6 ± 11.7%. Lower cell numbers delivered at slower ejection rates were mainly attributed to cell retention within the delivery device. Normalised caspase-3/7 activity measurements ejected at 10 μL/min were also significantly higher than control. Quantification of differentiation of ejected hMSCs revealed that both ejection rate and cell carrier employed may exert an effect on differentiation capacity. The use of biomaterials as cell carriers significantly improved cell recovery. Ejection of hMSCs in gelatin solution resulted in 87.5 ± 14% of the cell dose being delivered as viable cells, in comparison with 32.2 ± 19% of the dose ejected in phosphate buffered saline (PBS) at 10 μL/min. This study shows that ejection rate, needle size and cell carrier have a significant impact on the percentage of cell dose delivered as viable cells, cellular health and differentiation potential post-ejection. Optimal delivery strategies for injectable cell-based therapeutics are required to enhance their efficacy and reproducibility. This study emphasises the importance of careful consideration of administration protocols, according to the nature of the administered cells and cellular responses post-ejection. The combination of the investigated factors, among others, may also influence the fate of stem cells injected, thereby affecting the success of cell-based therapies.
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Blanchard, Tina-Louise. "A Systems Engineering Reference Model for Fuel Cell Power Systems Development." Cleveland State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=csu1322713336.
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Lunn, Andrew Stuart. "A mini cell architecture for multimedia systems." Thesis, Lancaster University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337352.
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Monaghan, Paul Brendan. "Microfluidic systems for cell growth and assays." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271365.
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Colella, W. G. "Combined heat and power fuel cell systems." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411153.
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McBride, Claire Marie. "Characterisation of human cell cycle control systems." Thesis, University of Ulster, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274083.
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Varma, Sarvesh. "Cell-based sensors for quantifying cell health and disease progression in engineered systems." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112031.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 180-200).
Healthy cells create healthy beings, while dysfunctional cells cause disease. Studying disease requires an understanding of how cells become dysfunctional from physiological states. Gaining this insight in vitro involves subjecting cells to relevant microenvironments and utilizing methodologies for assaying cells. Critically, to obtain accurate and unbiased insight, it is important to ensure that the cellular microenvironment remains representative, and that the assay methodology itself does not adversely perturb cell state. This thesis presents an approach where cells 'report' upon their healthy or stressed states, which could be assessed to either learn disease mechanisms, or quantified to design 'cell-friendly' methodologies. We engineered cell-based sensors that emit stress-regulated fluorescence, and applied them to characterize how distinct microenvironments regulate cell health. Here, we describe two endeavors that highlight the utility of this approach. We first developed cell stress sensors for a diverse bioinstrumentation community to quantify the impact of engineered systems and methodologies upon cell health. Using NIH3T3 cells, we engineered sensors that report on stresses induced by DNA damage, heat shock, or fluid shear stresses. Each sensor provides sensitive and specific responses to stress-induced pathways (relevant to several cell types), and can be used for a multiplexed stress-readout. The sensors do not require additional reagents and can be conveniently quantified with flow cytometry and real-time imaging. Successful distribution and adoption of the sensors by external users enabled quantitative characterization of flow sorting systems in the context of cell health, which was not explored before. Hence, the cell-sensor methodology designed as an 'open source' tool, could potentially serve as a novel standard for quantifying cell stress, and broadly for designing 'cell-friendly' methodologies. We further utilized cell-based sensors to gain biological insight into stress-regulated diseases. We focused on atherosclerosis, a flow-regulated cardiovascular disease that remains a major cause of morbidity and mortality worldwide. We engineered a novel microfluidic platform to study atherogenesis in vitro that overcomes several limitations of existing models. This device emulates in vivo microenvironments by applying programmable spatiotemporal flow profiles observed from human patients directly upon cultured human cells. Utilizing an endothelial cell-based sensor (that reports on vascular health), device flows were validated with known biomarkers and endothelial signatures. Subsequently, these sensors were used to gain novel insight upon atherogenesis through the impact of hemodynamic flows upon endothelial function. Overall, this thesis presents a facile and quantitative approach to investigate complex cell-stress emergent from diverse bioinstrumentation or within a disease microenvironment, which can be utilized to discover how environmental conditions regulate cell physiology, and human health.
by Sarvesh Varma.
Ph. D.
19
Shevock, Bryan Wesley. "System Level Modeling of Thermal Transients in PEMFC Systems." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/31079.
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Fuel cell system models are key tools for automotive fuel cell system engineers to
properly size components to meet design parameters without compromising efficiency
by over-sizing parasitic components. A transient fuel cell system level model is being
developed that includes a simplified transient thermal and parasitics model. Model
validation is achieved using a small 1.2 kW fuel cell system, due to its availability. While
this is a relatively small stack compared to a full size automotive stack, the power,
general thermal behavior, and compressor parasitics portions of the model can be
scaled to any number of cells with any size membrane area. With flexibility in
membrane size and cell numbers, this model can be easily scaled to match full
automotive stacks of any size.
The electrical model employs a generalized polarization curve to approximate system
performance and efficiency parameters needed for the other components of the model.
General parameters of a stackâ s individual cells must be known to scale the stack
model. These parameters are usually known by the time system level design begins.
The thermal model relies on a lumped capacity approximation of an individual cell
system with convective cooling. From the thermal parameters calculated by the model,
a designer can effectively size thermal components to remove stack thermal loads.
The transient thermal model was found to match experimental data well. The steady
state and transient sections of the curve have good agreement during warm up and cool
down cycles.
In all, the model provides a useful tool for system level engineers in the early stages of
stack system development. The flexibility of this model will be critical for providing
engineers with the ability to look at possible solutions for their fuel cell power
requirements.Master of Science
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Ghazanfari, Amin. "Power Control for Multi-Cell Massive MIMO." Licentiate thesis, Linköpings universitet, Kommunikationssystem, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-160782.
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The cellular network operators have witnessed significant growth in data traffic in the past few decades. This growth occurs due to the increases in the number of connected mobile devices, and further, the emerging mobile applications developed for rendering video-based on-demand services. As the frequency bandwidth for cellular communication is limited, significant effort was dedicated to improve the utilization of the available spectrum and increase the system performance via new technologies. For example, 3G and 4G networks were designed to facilitate high data traffic in cellular networks in past decades. Nevertheless, there is a necessity for new cellular network technologies to accommodate the ever-growing data traffic demand. 5G is behind the corner to deal with the tremendous data traffic requirements that will appear in cellular networks in the next decade. Massive MIMO (multiple-input-multi-output) is one of the backbone technologies in 5G networks. Massive MIMO originated from the concept of multi-user MIMO. It consists of base stations (BSs) implemented with a large number of antennas to increase the signal strengths via adaptive beamforming and concurrently serving many users on the same time-frequency blocks. As an outcome of using Massive MIMO technology, there is a notable enhancement of both sum spectral efficiency (SE) and energy efficiency (EE) in comparison with conventional MIMO based cellular networks. Resource allocation is an imperative factor to exploit the specified gains of Massive MIMO. It corresponds to properly allocating resources in the time, frequency, space, and power domains for cellular communication. Power control is one of the resource allocation methods to deliver high spectral and energy efficiency of Massive MIMO networks. Power control refers to a scheme that allocates transmit powers to the data transmitters such that the system maximizes some desirable performance metric. In the first part of this thesis, we investigate reusing the resources of a Massive MIMO system, for direct communication of some specific user pairs known as device-to-device (D2D) underlay communication. D2D underlay can conceivably increase the SE of traditional Massive MIMO systems by enabling more simultaneous transmissions on the same frequencies. Nevertheless, it adds additional mutual interference to the network. Consequently, power control is even more essential in this scenario in comparison with conventional Massive MIMO systems to limit the interference that is caused between the cellular network and the D2D communication, thereby enabling their coexistence. In this part, we propose a novel pilot transmission scheme for D2D users to limit the interference to the channel estimation phase of cellular users in comparison with the case of sharing pilot sequences for cellular and D2D users. We also introduce a novel pilot and data power control scheme for D2D underlaid Massive MIMO systems. This method aims at assuring that D2D communication enhances the SE of the network in comparison with conventional Massive MIMO systems. In the second part of this thesis, we propose a novel power control approach for multi-cell Massive MIMO systems. The new power control approach solves the scalability issue of two well-known power control schemes frequently used in the Massive MIMO literature, which are based on the network-wide max-min and proportional fairness performance metrics. We first explain the scalability issue of these existing approaches. Additionally, we provide mathematical proof for the scalability of our proposed method. Our scheme aims at maximizing the geometric mean of the per-cell max-min SE. To solve this optimization problem, we prove that it can be rewritten in a convex form and then be solved using standard optimization solvers.
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樊智傑 and Chi-kit Fan. "An agent based infrastructure for manufacturing cell control." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31225950.
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Fan, Chi-kit. "An agent based infrastructure for manufacturing cell control /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B2359603x.
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Zhang, Sina. "Inter-cell Interference Coordination in Indoor LTE Systems." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91849.
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Inter-cell interference coordination in 3GPP Long Term Evolution system received much attention in recent years. However, most of the studies are based on ideal system with regular hexagon-shaped cell. The indoor environment has special characteristics that the building shape and BS locations are irregular; the traffic load has great variation compared to urban and rural area. So, conventional ICIC scheme may not be used in indoor situation directly. In this thesis, ICIC scheme is employed for indoor environment. Based on different quality of backhaul, static and dynamic schemes will be proposed. The performances of proposed schemes and the performance of system without ICIC will be simulated and compared. At last, how much the improvement of the system can acquire after applying ICIC schemes will be analyzed, and the question about whether it is good to apply ICIC scheme in indoor environment will be answered.
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Scheda, Riccardo. "Modeling cell differentiation using dynamical systems on graphs." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21721/.
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La cellula vivente è un sistema complesso governato da molti processi che non sono ancora stati compresi: il processo di differenziazione cellulare è uno di questi.
La differenziazione cellulare è il processo in cui le cellule di un tipo specifico si riproducono
e danno origine a diversi tipi di cellule. La differenziazione cellulare è regolata dai cosiddetti Gene Regulatory Networks (GRN). Un GRN è una raccolta di
regolatori molecolari che interagiscono tra loro e con altre sostanze nella cellula per governare i livelli di espressione genica di mRNA e proteine. Kauffman propose per
la prima volta nel 1969 di modellare GRN attraverso le cosiddette Random Boolean Networks (RBN). I RBN sono reti in cui ogni nodo può avere solo due possibili valori:
0 o 1, dove ogni nodo rappresenta un gene in GRN che può essere ”on” oppure ”off”.
Queste reti possono modellizzare i GRN perchè l’attività di un nodo rappresenta il livello di espressione di un gene nell’intera regolazione.
In questo lavoro di tesi ci avvaliamo di un modello matematico per sviluppare e riprodurre una possibile rete di regolazione genica per il processo di differenziazione
cellulare.
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Mosaffa, Payman. "Hybrid cell-centred/vertex model for multicellular systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/461678.
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This thesis presents a hybrid vertex/cell-centred approach to mechanically simulate planar cellular monolayers undergoing cell reorganisation. Cell centres are represented by a triangular nodal network, while the cell boundaries are formed by an associated vertex network. The two networks are coupled through a kinematic constraint which we allow to relax progressively. Cell-cell connectivity changes due to cell reorganisation or remodelling events, are accentuated. These situations are handled by using a variable resting length and applying an Equilibrium-Preserving Mapping (EPM) on the new connectivity, which computes a new set of resting lengths that preserve nodal and vertex equilibrium. As a by-product, the proposed technique enables to recover fully vertex or fully cell-centred models in a seamless manner by modifying a numerical parameter of the model. The properties of the model are illustrated by simulating monolayers subjected to imposed extension and during a wound healing process. The evolution of forces and the EPM are analysed during the remodelling events.Esta tesis presenta un modelo híbrido para la simulación mecánica de monocapas celulares. Este modelo combina métodos de vértices y centrados en la célula, y está orientado al análisis de deformaciones con reorganización celular. Los núcleos vienen representados por nodos que forman una malla triangular, mientras que las contornos (membranas y córtex) forman una malla poligonal de vértices. Las dos mallas se acoplan a través de una restricción cinemática que puede ser relajada de forma controlada. El estudio hace especial hincapié en los cambios de conectividad, tanto debidos a la reorganización celular como el remodelado del citoesqueleto. Estas situaciones se abordan a través de una longitud de referencia variable y aplicando un Mapeo con Conservación de Equilibrio (EPM) que minimiza el error en el equilibrio nodal y en los vértices. La técnica resultante puede ser adaptada progresivamente a través de un parámetro, dando lugar a un modelo exclusivamente de vértices o a uno de centros. Sus propiedades se ilustran en simulaciones de monocapas sujetas a una extensión impuesta y durante el proceso de cicatrizado de heridas. La evolución de las fuerzas y los efectos del EPM durante el remodelado se analizan en estos ejemplos.
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Eissing, Thomas. "A systems science view on cell death signalling." Düsseldorf VDI-Verl, 2008. http://d-nb.info/987858882/04.
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VERNEK, EDSON. "A CELL DYNAMICAL MODEL APPLIED TO GRANULAR SYSTEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=3628@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORNeste trabalho estudamos o comportamento dinâmico de um gás granular a baixa densidade do ponto de vista hidrodinâmico. Fizemos também uma análise de instabilidade linear das equações de Navier-Stockes para tais sistemas. Finalmente, construímos um modelo de sistema de celulas dinâmicas para simular computacionalmente esses sistema e o aplicamos a um gás granular, a fim de entender um pouco mais sobre seus comportamentos dinâmicos, sob diversas condições de contornos externos.
In this work we study the dynamic behavior of a granular gas at low density from the hydrodynamic point of view. We also perform a linear instability analysis of the Navier- Stockes for such systems. Finally we construct a cell dynamic systems model to simulate computationally these systems and apply it for a granular gas in order to understand a little more about its dynamic behavior, under several boundary conditions.
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VINHOZA, TIAGO TRAVASSOS VIEIRA. "RADIO RESEARCH MANAGEMENT TECHNIQUES FOR HIERARCHICAL CELL SYSTEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=4460@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORSistemas de celulares de múltiplas camadas (hierarquizados) são úteis para acomodar densidade alta de tráfego mantendo a qualidade de serviço. Estes sistemas procuram agregar as vantagens dos sistemas micro e macrocelulares que são respectivamente: o aumento da capacidade do sistema e a carga de sinalização da rede. Neste trabalho são analisados aspectos de projeto e desempenho de estruturas hierarquizadas como: compartilhamento do espectro entre as camadas de micro- células e macro-células bem como o desempenho de diferentes estratégias de handoff entre essas camadas. Um outro objetivo do trabalho foi o desenvolvimento de uma ferramenta simples de simulação capaz de testar as diversas estratégias de handoff e o desempenho do sistema para diferentes soluções para a distribuição dos recursos de rádio entre camadas.
Multilayer cell systems are useful to accommodate high traffic densities while still satisfying the QoS requirements. These systems combine the advantages of microcellular and macrocellular systems which are: the increase of system capacity and the reduction of the number of handoffs, hence decreasing the signaling load. This work address design aspects such as spectrum sharing between the macrocell and microcell layers and the performance of different handoff strategies considering both layers. Another goal of this work was the development of a simple, but realistic, simulation tool which will allow obtaining the radio resources management results here presented.
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McCall, Mark J. S. "Cell therapy manufacturing value systems and cost analysis." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/14935.
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Cell Therapies are promising clinical instruments with significant therapeutic potential and commercial promise. However, the industry engaged in their commercial and clinical development faces significant financial, technical, regulatory and market challenges. These challenges are compounded by an understanding gap in the cell therapy industry. Commercial failures and financial difficulties have forced the industry to address the need to provide value and estimate and control costs early in the development timeline. The problem is that this issue is not being systematically or thoroughly addressed in the academic community while they pursue potential future treatments. Articles that highlight the need to understand costs and value are appearing with increasing frequency highlighting a growing consensus that work needs to be carried out in this area. However examples of models and tools to predict or estimate or even calculate costs in developing and producing a product do not exist in the literature. This work consists of three parts. Part one entails a new model of the characteristics observed in cell therapy new product development. This model is an evolution of an activity based dependency structure matrix (DSM). Result from the model suggests that some favoured development strategies (such as applying for an orphan indication status) provide less financial benefit than is commonly expected. The ability to scale manufacturing levels between clinical trial phases is also a pressing problem. 3 Part two presents a model to predict the cost of manufacturing and delivering a cell therapy product. This cost of good supplied (COGS) model combines both rules and predictive activity based costing across multiple manufacturing platforms, cell types and supply chain configurations. This model highlights the significant cost burden of validating both single and, more markedly, multiple sites of manufacture. The model also examines the potential for economies of scale when using different production technology in the manufacture of human Mesenchymal Stem Cells. Based in part on the results and knowledge gleaned in parts one and two, part three outlines the development of a novel, scalable expansion system developed to enable lower cost, controlled manufacture of adherent cell populations. While still at an early stage of development the technology has demonstrated the ability to maintain cells in a high rate of growth for a longer period than traditional culture techniques. This allows for the creation of a manufacturing technology with a higher expansion ratio than manufacturing systems on the market today.
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Lakshminarayana, Subhash. "Cross Layer Design in MIMO Multi-cell Systems." Thesis, Supélec, 2012. http://www.theses.fr/2012SUPL0020/document.
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Les prévisions relatives trafic de données au sein des systèmes de communications sans-fil suggèrent une croissance exponentielle, principalement alimentée par l’essor de transferts vidéo mobiles. Etant donné la nature soudaine et fluctuante des demandes de transfert vidéo, il faut dès à présent réfléchir à de nouveaux algorithmes d’allocation de ressources performants. En effet, les algorithmes en couche physique traditionnels, qui réalisent de l’allocation de ressources sous l’hypothèse classique que les transmetteurs sont toujours saturés avec des bits d’information, risquent à l’avenir de s’avérer inefficients. Pour cette raison, les algorithmes de demain se doivent d’être dynamiques, dans le sens où ils seront capables de prendre en compte la nature stochastique des fluctuations du trafic de données et qu’ils intégreront des informations issus de processus de couches supérieures.L’idée centrale de cette thèse est de développer des algorithmes, travaillant avec des informations issues de la couche PHY et de la couche NET, dans un scénario Multi-cells et MIMO (Multiple Inputs, Multiple Outputs).Plus particulièrement, nous considérons un réseau de stations de base (BS) équipés avec plusieurs antennes, chargés de servir plusieurs terminaux mobiles équipés d’une seule antenne (UT) dans leurs cellules respectives. Ce qui nous différencie des travaux précédents, c’est que nous tenons compte de l’aléa avec lequel des demandes de transferts peuvent arriver et que, pour cette raison, nous modélisons la formation de queue de données au niveau des stations de base. Dans cette disposition, nous développons plusieurs algorithmes multicouches, réalisant de l’allocation de ressources décentralisée, et ce, dans une optique d’efficacité énergétique. En particulier, il s’agit ici de réaliser des algorithmes réalisant du beamforming de façon décentralisée et capables de contrôler des fluctuations de trafic, des algorithmes optimisant l’efficacité énergétique sous une contrainte de qualité de service moyenne, des algorithmes de planification décentralisés dans des scénarios multi-cellulaires. Dans cette perspective, nous choisissons de recourir non seulement à des outils d’optimisation de la théorie de Lyapunov, mais également à la théorie des matrices aléatoires et à la théorie du contrôle stochastiqueFuture wireless communication systems are expected to see an explosion in the wireless traffic which is mainly fueled by mobile video traffic. Due to the time varying and bursty nature of video traffic, wireless systems will see a widerrange of fluctuations in their traffic patterns. Therefore, traditional physical layer based algorithms which perform resource allocation under the assumption that the transmitters are always saturated with information bits, might no longer be efficient. It is, thus, important to design dynamic resource allocation algorithms which can incorporate higher layer processes and account for the stochastic nature of the wireless traffic.The central idea of this thesis is to develop cross-layer design algorithmsbetween the physical and the network layer in a multiple input multiple output (MIMO) multi-cell setup. Specifically, we consider base stations (BSs) equipped with multiple antennas serving multiple single antenna user terminals (UTs) in their respective cells. In contrast to the previous works, we consider the randomness in the arrival of information bits and hence account for the queuing at the BSs. With this setup, we develop various cross-layer based resource allocation algorithms. We incorporate two important design considerations namely decentralized design and energy efficiency. In particular, we focus on developing decentralized beamforming and traffic flow controller design, energy efficient design under time average QoS constraints and decentralized scheduling strategy in a multi-cell scenario. To this end, we use tools from Lyapunov optimization, random matrix theory and stochastic control theory
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Tarud, Sofy 1980. "Feasibility of fuel cell systems for building applications." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27135.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 109-110).
Worldwide electricity consumption will nearly double between 2001 and 2025 but the projects to increase electricity production and transport will not be enough to fulfill the demand. In the future, most of the power demand will be produced by Distributed Generation (DG) systems. DG refers to power generating technologies independent from the electrical grid, located at or near the location where electricity is consumed. Fuel Cells have become very attractive DG systems in recent years, however, Fuel Cells are still in their early stages of deployment and the advantages and disadvantages of such systems for commercial applications are unclear. A study to learn how Fuel Cells perform in commercial buildings was conducted. To compare the effectiveness of fuel cells to other prime movers the study looked at Phosphoric Acid and Molten Carbonate Fuel Cells, microturbines, and lean burning reciprocating engines. First, the hotel's natural gas and electricity load data was analyzed to understand the requirements and adequately size the DG systems. After, the economics and efficiency of the plant was looked at with and without opportunity for cogeneration. Finally, a sensibility analysis was conducted to assess the variability of the plant's savings if some of the assumed parameters changed PAFC and MCFC, in baseload operation, with and without an absorption chiller are both very attractive technologies for a DG installation at the hotel if initial capital costs are reduced. The initial capital investment of fuel cells can and should be reduced, either by government and/or utility incentives or decreases in costs due to economies of scale.
by Sofy Tarud.
S.M.
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Bruen, Thomas. "Control of active cell balancing systems : innovation report." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/108625/.
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Lithium-ion battery packs are increasingly being used for high power and energy applications such as electric vehicles and grid storage. These battery packs consist of many individual cells connected in series and/or parallel. Manufacturing tolerances and varied operating conditions mean that each cell will be different one from another, being able to store different amounts of energy and deliver different amounts of power. This also means some cells will finish charging or discharging before others, resulting in unutilised energy in the remaining cells. Passive balancing systems are often used in multi-cell battery packs to ensure that all of the cells can be fully charged. However, this does not account for differences in cell capacity, meaning that not all cells will be fully discharged. Active balancing systems have been developed to transfer energy between the cells, in theory allowing for stronger cells to compensate for weaker ones. However, their perceived cost and complexity have prevented them from being widely adopted in commercial applications. In this work, an innovative control strategy was developed to determine how and when to energy balance a set of battery cells, with the aim of maximising battery pack energy utilisation. A model-based control system was designed, using state of charge to evaluate the level of energy imbalance between cells. Real-time implementation using second-hand electric vehicle cells and commercial balancing hardware demonstrated that the control strategy can decrease the amount of unused charge in the battery pack from 8% with passive balancing to 1% with active balancing, which has significant impact for battery pack energy throughput, physical size, mass, and long-term health.
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Watts, Clare. "Electromagnetic sensing of cell suspensions in microfluidic systems." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/58859.
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Cancer is one of the leading causes of death worldwide, and cancers which metastasise, the process of cancer spreading from one organ to another within the body, have the highest fatality rates. Although the mechanism of metastasis is not well understood, the study of cells in the circulatory system which are known to seed tumours is of great importance in cancer research. Current methods for detection of such cells, although specific and sensitive, result in their destruction, and have drawbacks associated with a bias towards specific cell markers. This work seeks to assess the feasibility of using dielectric spectroscopy and the variation in dielectric properties of different cells at microwave frequencies to characterise and separate circulating tumour cells (CTCs) and other abnormal cells from peripheral circulating blood. This technique is non-destructive and label free, and opens the door to a flow-cytometer system based purely on the physical properties of different cells, capable of measuring them in their natural state. A novel coupled-resonator sensor is introduced in this work, and used to make dielectric measurements of polystyrene microspheres as well as single, flowing, viable cells of three different types at ~10 GHz. The results have been compared to Raman spectroscopy analysis of the cultured cells, showing potential correlation between the water content of the cell types investigated, and the response of the novel system. This is of diagnostic value, with cell hydration linked to carcinogenesis.
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Carvalho, Sofia Duarte Boia de Oliveira. "Establishing stem cell based systems to study neuropathologies." Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/10521.
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Mestrado em Biomedicina MolecularAs células estaminais distinguem-se dos outros tipos de células pela sua capacidade de auto-regeneraração e simultaneamente diferenciação em diferentes tipos celulares. Estas células dividem-se em duas categorias: células estaminais embrionárias e somáticas. As que se enquadram no primeiro grupo originam todos os tipos celulares de um determinado organismo (pluripotentes), enquanto as células estaminais somáticas originam apenas alguns tipos celulares (multipotentes). Atualmente, células diferenciadas podem no entanto ser geneticamente reprogramadas para um estado indiferenciado através da indução de expressão de genes específicos que estão altamente expressos em células estaminais embrionárias (células estaminais de pluripotência induzida). A possibilidade de estudar neuropatologias utilizando modelos baseados em células estaminais tem sido amplamente explorada nos últimos anos. Como tal, os principais objetivos desta dissertação foram o isolamento e proliferação de células estaminais da mucosa olfativa e a sua posterior diferenciação em células derivadas de neuroesferas olfativas (ONS) e células tipo neuronal (NLC). A caracterização do sistema modelo ONS foi igualmente realizada. Sequencialmente, foram utilizadas duas enzimas (Dispase e Colagenase) para isolar as células estaminais da mucosa olfativa. Células estaminais da lâmina própria e do epitélio da mucosa olfativa foram isoladas e proliferaram no meio DMEM/F12. Ambos os tecidos foram diferenciados em neuroesferas (utilizando meio DMEM/F12 suplementado com ITS-X, EGF e FGF2) e posteriormente em células derivadas de neuroesferas olfativas (utilizando meio DMEM/F12 suplementado com FBS) e em células tipo neuronal (usando meio neurobasal suplementado com B27, glutamina e glutamato). Os nossos resultados indicam que estabelecemos com sucesso culturas primárias de células estaminais olfativas a partir da mucosa olfativa de rato. A eficiência dos processos de isolamento e proliferação foi comprovada pela presença do marcador de estaminalidade nestina. A diferenciação das células estaminais em células derivadas de neuroesferas olfactivas (ONS) também for realizada com sucesso. A caracterização bioquímica dessas células revelou que, relativamente aos níveis de expressão da proteína precursora de amiloide de Alzheimer (PPA) e da proteína Tau, o sistema modelo em estudo apresenta resultados semelhantes aos obtidos com alguns sistemas modelo do tipo neuronal previamente caracterizados, nomeadamente as linhas celulares PC12 e SH-SY5Y. No entanto uma caracterização mais pormenorizada deve ser realizada. Os resultados obtidos fortalecem a hipótese de este modelo poder vir a ser utilizado para estudo dos mecanismos moleculares subjacentes a diversas neuropatologias, como a doença de Alzheimer.
Stem cells are distinguished from other cell types by their ability to both selfrenew and to differentiate into a diverse array of specialized cell types. Naturally occurring stem cells are divided into two categories: embryonic stem cells and somatic stem cells. While embryonic stem cells are able to generate all the differentiated cells of the developing soma (pluripotent stem cells), somatic stem cells assume increasing degrees of fate restriction as they specialize into specific tissue lineages (multipotent stem cells). Specialized cells can also be genetically reprogrammed to a stem cell-like state through the induced expression of key genes that are highly expressed in embryonic stem cells. The possibility to investigate neuropathologies using stem cells based systems has been widely explored in the last years. Therefore the main objectives of this dissertation were isolation and proliferation of olfactory mucosa stem cells that were further differentiated in olfactory neurospheres derived cells (ONS) and neuron-like cells (NLC). Characterization of the ONS model system was also performed. We sequentially used Dispase and Collagenase to isolate olfactory mucosa stem cells that further proliferate in DMEM/F12 medium. The stem cells of either lamina propria and epithelium of olfactory mucosa were isolated and proliferated. Both tissues were further differentiated in neurospheres (using DMEM/F12 supplemented with ITS-X, EGF and FGF2), and finally in olfactory neurospheres-derived cells (using DMEM/F12 medium) and neuron-like cells (using neurobasal medium supplemented with B27, glutamine and glutamate). Our results indicate that we successfully established primary cultures of olfactory stem cells from rat olfactory mucosa. The efficiency of the isolation/proliferation procedure was accomplished by positive immunostaining using the stemness marker nestin. The differentiation of the olfactory stem cells into olfactory neurospheres derived cells (ONS) was also effective. The preliminary morphological and biochemical characterization of the ONS models system was achieved and revealed that our ONS model system in term of APP and Tau expression levels behaves similarly to neuronal-like model systems previously characterized including PC12 and SHSY5Y cell lines. However, additional characterization should also be performed. Our results strength the hypothesis of using stem cells based model systems to study the cellular and molecular mechanisms underlying several neuropathologies, including Alzheimer’s disease.
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Chowdhury, S. M. Sifat Morshed. "Adaptive Cell Balancing for Modular Battery Management Systems." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1589392523754789.
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Kumar, Jothi Dinesh. "Novel stromal cell signalling systems in oesophageal cancer." Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/15257/.
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Myofibroblasts are recognised to play an important role in wound healing and the maintenance of tissue integrity. In addition, they are increasingly recognised to provide a supporting microenvironment for cancer cells. They secrete a variety of chemokines, cytokines, growth factors and proteases that collectively regulate cell proliferation, migration and invasion. Specific chemokines are known to recruit mesenchymal stromal cells (MSCs) to both tumours and normal tissue which may then give rise to myofibroblasts. Proteomic studies by Holmberg and Varro (unpublished observations) identified chemerin as an upregulated chemokine in conditioned media (CM) from oesophageal cancer associated myofibroblasts (CAMs) compared to adjacent tissue myofibroblasts (ATMs). Chemerin is potent chemo-attractant for immune and inflammatory cells. The objectives of this thesis were (a) to functionally characterise the oesophageal myofibroblasts,(b) validate the findings of previous proteomic studies and (c) determine the role of chemerin in MSC migration. Oesophageal CAMs from both squamous and adenocarcinoma tumours were shown to be more proliferative than their paired ATMs, or normal tissue myofibroblasts (NTMs). In addition, CAM conditioned media increased the proliferation and migration of two oesophageal cancer cell lines (OE21 and OE33) and stimulated MSC migration compared to ATM CM. The data suggest oesophageal CAMs promote an aggressive tumour microenvironment. Western blotting and ELISA confirmed increased chemerin secretion by squamous carcinoma CAMs. Chemerin and conditioned media from squamous carcinoma CAMs, stimulated MSC and OE21 cell migration; Chemerin neutralizing antibody reversed these effects and siRNA knockdown of chemerin in CAMs, or of its cognate receptor ChemR23 in MSCs, decreased migratory responses. Studies using pharmacological inhibitors or Western blot of cellular proteins indicated that chemerin stimulated MSCs via PKC, and p42/44, p38 MAP and JNK kinases. Macrophage Inhibitory Factor (MIF) was identified as a putative chemerin target in MSCs and validated by ELISA and Western blot of MSC media and cell extracts. MIF inhibited MSC migration in response to low or moderate concentrations of chemerin, indicating that it might restrain MSC migration in normal tissues but not in cancers where chemerin is elevated. Finally, confirmation of chemerin-chemR23 interactions was obtained using a chemR23 antagonist, CCX832. Chemerin induced MSC and OE21 cell migration was inhibited by CCX832. Moreover, transendothelial migration of MSCs in response to chemerin or CAM conditioned media was reversed by CCX832. Transendothelial migration was also shown to depend on chemerin-stimulated MMP-2 secretion. These findings indicate a molecular mechanism by which MSCs are recruited to tumours. Taken as a whole, this work indicates that myofibroblasts derived from oesophageal cancers differ from those in adjacent or normal tissue. The finding of increased chemerin in these cells is novel and may be relevant to MSC recruitment. Since it is possible to inhibit the effects of chemerin on MSCs using CCX832, there is the potential for a novel therapeutic approach to prevent cancer progression.
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Weinberger, Oskar. "Realisations of heteroclinic networks in coupled cell systems." Thesis, KTH, Matematik (Avd.), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-208179.
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In the theory of dynamical systems, heteroclinic networks are invariant objects in phase space with network structure, consisting of invariant sets (nodes) and connecting trajectories between them (edges). These are typically not robust dynamical phenomena, but can appear robustly for dynamical systems with network structure - so called coupled cell systems -due to the presence of certain synchrony related invariant subspaces. This link between networks in phase space and networks of dynamical systems is the topic of this thesis. Examples and results from the literature on the existence and construction of heteroclinic networks in coupled cell systems are presented and reviewed, focusing on heteroclinic realisation: how can coupled cell systems be constructed that support a given heteroclinic network? We seek to find explicit vector fields for such realisations, of which there are relatively few examples in the literature, and provide a polynomial vector field for a particular heteroclinic network and coupled system. Finally, we state and prove a theorem on the existence of additional equilibrium points for realisations of this heteroclinic network in such systems.Inom teorin för dynamiska system är heteroklina nätverk invariant objekt i tillståndsrummet som har nätverksstruktur i den mening att de består av invarianta mängder (noder) och förbindande banor mellan dem (kanter). Dessa objekt är typiskt inte robusta dynamiska fenomen, men kan förekomma robust för dynamiska system med nätverksstruktur - så kallade kopplade dynamiska system - tack vare särskilda invarianta underrum relaterade till synkroni. Det är denna koppling mellan nätverk i tillståndsrummet och nätverk av dynamiska system som är temat för detta examensarbete. En litteraturstudie kring exempel och resultat rörande existens och konstruktion av heteroklina nätverk i kopplade dynamiska system görs med fokus på heteroklin realisering: hur kan kopplade dynamiska system konstrueras att ha ett givet heteroklint nätverk? Vi söker explicita vektorfält för sådana realiseringar, av vilka det finns relativt få i litteraturen, och ger ett polynomt vektorfält för ett särskilt heteroklint nätverk och kopplat dynamiskt system. Slutligen formuleras och bevisas en ny sats rörande existensen av extra jämviktspunkter i realiseringar av detta heteroklina nätverk.
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Barria, Matus Marcelo Alejandro. "Modelling human prion replication in cell-free systems." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/10025.
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One of the key molecular events in the transmissible spongiform encephalopathies or prion diseases is the conformational conversion of the cellular prion protein PrPC into the misfolded and pathogenic isoform, PrPSc. Prion diseases are fatal neurodegenerative conditions affecting humans and other animal species, which present with diverse clinical and neuropathological phenotypes. In humans, prion diseases can occur as sporadic, familial or acquired forms. Sporadic Creutzfeldt–Jakob disease (sCJD) accounts for the majority of cases. The current classification system of human prion diseases recognizes several distinct clinico-pathological entities including sCJD, variant Creutzfeldt-Jakob disease (vCJD), Gerstmann–Straussler–Scheinker syndrome, fatal familial insomnia and variably protease-sensitive proteinopathy. Prion protein gene (PRNP) mutations and polymorphisms, and PrPSc types have a profound effect on these clinico-pathological phenotypes. Prion diseases of sheep and goats, cattle, and cervids are all actual animal health problems and present potential risks to human health. Thus far the only known zoonotic prion disease is bovine spongiform encephalopathy, which has resulted in vCJD in humans. The recognition of new forms of prion diseases in animal and humans has generated increased awareness of the animal and public health risks associated with prion disease. However the mechanisms involved in prion replication, transmission, and neurodegeneration remain poorly understood. This thesis uses in vitro PrP conversion assays (protein misfolding cyclic amplification and real time quaking-induced conversion) to model different aspects of human prion replication: Molecular susceptibility, genetic compatibility, spontaneous formation and the effect of molecules that might enhance or prevent conversion were each investigated in order to obtain a better understanding of the molecular mechanism of the prion replication. I have addressed the hypothesis that the major determinant factors in prion disease pathogenesis (PRNP genetics, PrPSc types and species barriers) are intrinsic to the prion protein conversion process and their effects can be faithfully recapitulated by in vitro conversion assays. The results shows that in vitro conversion assays used in this thesis can model the combined effects of different PrP type and genotypes, can replicate aspects of cross-species transmission potential and provide information about molecular barrier to zoonotic transmission, can model de novo PrPSc formation, and can assess the potential impact of chaperones on conversion of the human prion protein. In summary, this work provides evidence that the origin, propagation and transmission of prions can be meaningfully investigated in cell-free systems.
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Thorstensen, Anne Elisabeth. "Analysis of an Intermediate Band Solar Cell System : Based on Systems Engineering Principles." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-24227.
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The intermediate band solar cell (IBSC) is a so-called third generation solar cell, based on a new type of semiconductor materials; the intermediate band (IB) materials. In IB materials there is an additional intermediate energy band in the band gap of the semiconductor. Solar cells using such materials have an efficiency limit of 63 % in comparison to 41 % for solar cells made of conventional semiconductors. IBSCs have been attempted realized since 2001, based on toxic or non-abundant materials only. For sustainable development of IBSCs, it is important to identify materials and production routes that result in minimized environmental impacts.Two possible host materials for IBSCs were identified during a previous specialization project, and these were used as case materials to explore the challenges related to realization of sustainable IBSCs. This thesis describes the analysis of an IBSC system based on a ZnO/IB-Cu2O/Cu2O cell. The main objective was to analyze and optimize this intermediate band solar cell to determine if ZnO and Cu2O are promising IBSC materials. To get an overview of the functions and relationships of a complete IBSC system, a method combining the detailed materials technology field and holistic systems engineering process was utilized. This unusual combination and the fact that IBSCs are a relatively new and unexplored concept, resulted in a customized approach. Sustainable solutions for large-scale production of an IBSC system with focus on the cell structure and materials were found. Two cell cases were developed; an “advanced” cell with high quality materials and production, and one “simple” cell with a more conventional production route and less complex materials. The location of the desired IBSC system installation was set to a rooftop in Oslo, and a conventional photovoltaic (PV) system being planned there was used as an example. Desired and location-based performance parameters for an IBSC system located in Oslo were identified.A new approach that can solve combined materials technology and systems engineering assignments was developed. By utilizing this approach, challenges for ZnO and Cu2O as IBSC host materials were identified. These material challenges proved to be comprehensive, but might be overcome by customized growth of Cu2O single crystals to reduce resistivity, and tailoring the buffer layer and surface treatment at the ZnO/IB-Cu2O junction to reduce unwanted interface defects.
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Schlueter, Daniela K. "A multiscale systems biology study of in vitro cell migration and cancer cell invasion." Thesis, University of Dundee, 2013. https://discovery.dundee.ac.uk/en/studentTheses/9e7f0415-f565-4a3d-ade3-f3eb540bf088.
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Armiger, Travis J. "Force Propagation in Mammalian Cell Systems and the Relevance of the Mechanically Integrated Cell." Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1143.
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Mammalian cells are known to respond to both extra- and intra- cellular forces as well as the physical properties of the surrounding tissue. There is increasing evidence to support the fundamental role of force, applied to or generated within cells, in maintaining proper tissue function. The mechanical integration from the exterior of a cell to the interior of the nucleus is crucial for cellular sensing of, and response to, the physical environment. Further, misregulation of this mechanosensitive ability can lead to the development or propagation of many diseases such as cancers, cardiovascular diseases, and tissue fibrosis. In this thesis, we investigate the role of various proteins in regulating the mechanical properties of mammalian cells. We also develop techniques to examine the propagation of forces through cells and multicell systems with the aim of elucidating critical biophysical factors involved in regulating cell function. The idea that the genome can be regulated through changes in forces applied to cells or changes in the propagation of forces through a cell, (i.e. mechanotransduction) is becoming widely accepted. The complex interplay between biochemical and biophysical mechanisms that ultimately control mechanotransduction are beginning to be uncovered; however, a true understanding of this remarkable cellular process has not yet been achieved. By investigating multiple factors which impact mechanosensitivity (such as protein expression, cell-cell and cell-environment connections, cell generated contractions, and physical connections through the cellular interior), we aim to further the understanding of potential pathways of mechanotransduction. Through novel studies and technological advances, the field of cellular biomechanics will continue to grow as we hope to uncover the physical mechanisms that regulate cell function or lead to disease.
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May, Laurence George. "The effect of echinomycin upon DNA replication in cultured cells and cell-free systems." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624325.
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Ma, Teng. "Fibrer-based bioreactor systems in Mammalian cell culture and tissue engineering Human Trophoblast cells /." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488188894442926.
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Prince, Mark. "Smart microsystems for cell manipulations." Thesis, Aston University, 2006. http://publications.aston.ac.uk/12241/.
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This thesis documents the design, manufacture and testing of a passive and non-invasive micro-scale planar particle-from-fluid filter for segregating cell types from a homogeneous suspension. The microfluidics system can be used to separate spermatogenic cells from testis biopsy samples, providing a mechanism for filtrate retrieval for assisted reproduction therapy. The system can also be used for point-of-service diagnostics applications for hospitals, lab-on-a-chip pre-processing and field applications such as clinical testing in the third world. Various design concepts are developed and manufactured, and are assessed based on etched structure morphology, robustness to variations in the manufacturing process, and design impacts on fluid flow and particle separation characteristics. Segregation was measured using image processing algorithms that demonstrate efficiency is more than 55% for 1 µl volumes at populations exceeding 1 x 107. the technique supports a significant reduction in time over conventional processing, in the separation and identification of particle groups, offering a potential reduction in the associated cost of the targeted procedure. The thesis has developed a model of quasi-steady wetting flow within the micro channel and identifies the forces across the system during post-wetting equalisation. The model and its underlying assumptions are validated empirically in microfabricated test structures through a novel Micro-Particle Image Velocimetry technique. The prototype devices do not require ancillary equipment nor additional filtration media, and therefore offer fewer opportunities for sample contamination over conventional processing methods. The devices are disposable with minimal reagent volumes and process waste. Optimal processing parameters and production methods are identified with any improvements that could be made to enhance their performance in a number of identified potential applications.
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Goschorska, Maja. "Investigating the mechanisms of cell competition in mammals using in vitro systems." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/290214.
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Cell competition leads to elimination of a viable cell population, by fitter cells. Despite over forty years of research, the molecular mechanisms of competition in mammals are poorly understood. During my PhD I have investigated the mechanisms of competition by exploring an established mammalian cell culture system, in which wild-type MDCK cells eliminate scribble-deficient cells, and I have also developed a novel cell culture system to model mammalian competition. My work contributed to the discovery that scribble-deficient cells are eliminated not by biochemical exchange among cells, but by mechanical compaction. We termed this phenomenon mechanical competition. I employed transcriptional profiling to determine the molecular signature of mechanical losers, and identified activation of p53 signalling as their hallmark. My colleagues and I then demonstrated that elevation of p53 is both necessary and sufficient to trigger mechanical competition. In further investigating the mechanisms of mechanical competition, I found that compaction activates ROCK in scribble-deficient cells, and that this is required for their elimination. Inhibition of Src signalling in mechanical losers also protected them form out-competition, and integrin signalling is another pathway likely involved in mechanical competition. While investigating p53 competition, we observed that p53-high and p53-low cells engage in directional migration, with p53-high cells always at the migrating front. As a side-project, I investigated the role of p53 in directional migration, by exploring an established model with a single leader cell and multiple followers. We established a method to generate multinucleated leaders on demand. By creating leaders from p53-deficient cells, I established that p53 signalling is required for some, but not all multinucleated cells to trigger collective migration, thus implicating p53 signalling in a type of migration involved in wound healing. Finally, I successfully modelled p53-driven mechanical competition in a differentiated primary tracheal epithelial cell culture, thereby establishing a novel system to study mammalian competition, and also proving that p53 competition is conserved between different mammalian epithelia. Considering the involvement of p53, mechanical competition may play a major role in cancer.
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Sundararajan, Saravanan. "High-throughput measurement of gene expression in dynamic systems." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92237.
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Guck, Jochen Reinhold. "Optical deformability micromechanics from cell research to biomedicine /." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3037014.
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Duffy, Cairnan Robert Emmett. "New culture systems for mesenchymal stem cells." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/21044.
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Mesenchymal stem cells are the stem cells that replace the bone, fat and cartilage tissues of the human body. In addition, these cells can form muscles, ligaments and neurons. This wide multipotency has made mesenchymal stem cells of particular interest in the fields of tissue engineering and regenerative medicine. Furthermore, mesenchymal stem cells can modulate the immune system by reducing factors that increase inflammation and immune recognition. This immune recognition suppression has resulted in their application as part of bone marrow transplantation in the prevention of 'graft versus host‘ disease. There are hundreds of on-going clinical trials using these cells for the treatment of autoimmune diseases such as type I diabetes, arthritis and multiple sclerosis. The increasing importance of these cells has brought in to focus the culture methods used to for their expansion and manipulation. Currently, animal derived components are used as surfaces for their growth and as components in the culture media. This exposes these cells to animal pathogens and antigens that can be passed to the recipients of these cells. In the first part of this thesis, polymer microarrays were employed to identify alternatives to the biological surfaces currently used for mesenchymal stem cell culture. This platform allowed hundreds of polyacrylates/acrylamides and polyurethanes to be simultaneously scrutinised to identify surfaces that could support their growth and maintain their stem cell characteristics. Identified polymer surfaces were monitored in long-term culture (10 passages) and were shown to retain the cell phenotype and capacity to differentiate, thus providing chemically defined substrates for long-term mesenchymal stem cell culture. In the second part of this thesis, a 'smart‘ polymer microarray of hydrophilic cross-linked polymers (hydrogels) were used to remove another key biological component of culture, trypsin. These 'smart‘ hydrogels modulated their properties depending on the temperature. Hydrogels that could trigger mesenchymal stem cell release after a reduction in temperature were identified. A unique passaging system using a modest temperature reduction for 1h was developed as a passaging method. Cells were maintained and monitored for 10 passages using this novel enzyme free passaging method. Analysis of the mesenchymal stem cell phenotype and differentiation capacity revealed this method superior than conventional culturing methods. In the final part of this thesis, a 'knowledge-based‘ small molecule library was designed, which could potentially yield small molecules to manipulate/enhance the mesenchymal stem cell state without the use of biological components. The key protein pathways that control the stem cell state were examine with the bioinformatics tool GeneGo was used to identify compounds that affected these pathways, resulting in selection of 200 small molecules. The effect of the small molecules on the mesenchymal phenotype was examined and 5 small molecules were identified that enhanced the phenotype of these cells. The anti-inflammatory properties associated with the hit compounds led to the investigation of their effects on key surface proteins associated with the immune-modulatory state of the cells. In this preliminary study, two of the small molecules, estriol and spermine, increased the expression of a key mesenchymal stem cell marker STRO-1 and down regulated ICAM-1, a critical component of the immune modulation capacity of this cell type.
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Al-Obeidi, Arshed. "Single-cell reporters for inflammatory caspase activity." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93044.
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Thesis: S.M., Massachusetts Institute of Technology, Computational and Systems Biology Program, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (page 29).
Caspases are a 12-member family of human proteases that regulate apoptosis and inflammation. They serve as key effectors downstream of diverse signaling receptors and shape cell fate. Inflammatory caspases mediate the proteolytic processing of inflammatory cytokines and are essential in maintaining immune function, but also lead to disease when deregulated. In order to examine the activity of inflammatory caspases, we generated 2 inflammatory caspase reporters: a fluorescence resonance energy transfer (FRET) inflammatory caspase activity reporter as well as a fluorescent translocation inflammatory caspase reporter. These reporters were then used to study inflammatory caspase activity in vitro using recombinant caspases and in vivo using a simplified cell culture model. The inflammatory caspase activity reporters have the potential to capture inflammatory caspase activation under a variety of stimuli. They also have several advantages compared to existing methods: they are non-destructive and can be used for live single cell measurements; they do not require the addition of exogenous chemicals or cofactors; and they do not covalently modify the inflammatory caspases. Inflammatory caspase activation is a rapid, asynchronous process, and detecting the activity of the mature inflammatory caspase molecules is made difficult due to the short half-life of the enzyme. The reporters we have developed can fill this need.
by Arshed Al-Obeidi.
S.M.
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Chuan, Chen Max. "Fabrication and Characterizationof Low Temperature Annealed Silicon Bottom Cell for CELOGbased Tandem Solar Cell Systems." Thesis, KTH, Tillämpad fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231927.
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