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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Mathematical modelling of pulmonary arterial smooth muscle cell subtypes

Arshad, Haroon January 2016 (has links)
Alteration in the tone of pulmonary arteries may lead to disease such as pulmonary hypertension often associated with major cardiac complications. This dysfunction is partly in the pulmonary arterial smooth muscle cells (PASMCs) where the excitation-contraction coupling is modified by ion channel behaviour to increase the contractile force. Mathematical models of systemic smooth muscle cells (SMCs) that incorporate electrophysiological and chemomechanical mechanisms to understand the underlying cellular physiology have been successfully employed. Models of pulmonary arterial smooth muscle cells (PASMCs) are only beginning to emerge. Mathematical model prototyping with available experimental data and model investigation from different parameter values is a time-consuming and complex process. This thesis is concerned with the development and validation of mathematical models of excitation-contraction coupling in three types of PASMCs of the rat species, one homogeneous type originating from the distal pulmonary arteries and two from proximal pulmonary arteries. Some key novel additions from previous vascular SMC models include the distinct modelling of Ca2+ in the subplasmalemmal cytosolic region, incorporation of subunit-specific currents from the K+ channel family and a generic G-protein receptor model able to reproduce complex Ca2+ profiles. The main pulmonary and systemic arteries statistically differ in its response to phenylephrine in a wire myograph. The ionic currents of the models were validated against experimental data largely from rat species. The models replicate the recordings of Ca2+ and the resting potential (Em) profiles arising from agonist-induced cytosolic Ca2+ ([Ca2+]i) stimulation (G-protein activation), nifedipine, ryanodine, caffeine and niflumic acid. The distal PASMC model was sensitive to an increase in [Ca2+]i from G-protein activation although were less likely to reproduce Ca2+ oscillations than proximal PASMCs. The proximal models determined the likely proximal PASMC type in literature experiments recording [Ca2+]i and Em. I have developed software that enables other users to simulate Ca2+ and Em changes in SMC studies and the ability to parse a master file describing the mathematical model into different language formats to increase productivity. These models provide a foundation for further studies to better understand PASMC function in the context of normal physiology as well as pathological conditions.
52

Computational Model of Human Memory

Hempinstall, Susan January 2016 (has links)
Theories of Extended Mind have evolved in waves to reach the present state of disagreement with regard to whether or not external artefacts become part of the mind when used for memory purposes. A four-step approach has been used to address and resolve this disagreement. First, a new component for models of mind which provides a saliency function is provided. This saliency function corresponds to computational elements found necessary in large mainframe computer systems for handling rich data environments. Second, there is introduced a Computational Model of Memory containing the new component which models the operation of human memory. The Computational Model of Memory contains four interoperative elements including the new component, short-term memory, long-term memory, and a cross-reference associator. Third, the work of Marcin Milkowski is drawn upon to obtain a general method of assessing a computational model’s well-formedness, and the method is applied to prove the adequacy of the Computational Model of Memory. According to Milkowski’s schema, the model satisfies most criteria for a well-formed computational model, including in particular a separation between conceptual elements of the model, and constitutive elements of the model, which while explicitly related, are required to subsist at separate logical conceptual levels. Fourth, the Computational Model of Memory is applied to outstanding arguments in Extended Mind to clarify and resolve several of these arguments. The model serves to highlight where the nature of the disagreement depends upon a category error of reference, and further resolves a key disagreement by demonstrating that the mind may treat external artefacts as an alternative realizable constitutive element of short-term and long-term memory.
53

A computational model of human iron metabolism

Mitchell, Simon January 2013 (has links)
Iron is essential for virtually all organisms, yet it can be highly toxic if not properly regulated. Only the Lyme disease pathogen Borrelia burgdorferi has evolved to not require iron (Aguirre et al., 2013).Recent findings have characterised elements of the iron metabolism network, but understanding of systemic iron regulation remains poor. To improve understanding and provide a tool for in silico experimentation, a computational model of human iron metabolism has been constructed. COPASI was utilised to construct a model that included detailed modelling of iron metabolism in liver and intestinal cells. Inter-cellular interactions and dietary iron absorption were included to create a systemic computational model. Parameterisation was performed using a wide variety of literature data. Validation of the model was performed using published experimental and clinical findings, and the model was found to recreate quantitatively and accurately many results. Analysis of sensitivities in the model showed that, despite enterocytes being the only route of iron uptake, almost all control over the system is provided by reactions in the liver. Metabolic control analysis identified key regulatory factors and potential therapeutic targets. A virtual haemochromatosis patient was created and compared to a simulation of a healthy human. The redistribution of control in haemochromatosis was analysed in order to improve our understanding of the condition and identify promising therapeutic targets. Cellular prion protein (PrP) is an enigmatic protein, implicated in disease when misfolded, but its physiological role remains a mystery. PrP was recently found to have ferric-reductase capacity. Potential sites of ferric reduction were simulated and the findings compared to PrP knockout mice experiments. I propose that the physiological role of PrP is in the chemical reduction of endocytosed ferric iron to its ferrous form following transferrin receptor-mediated uptake.
54

Topological and Computational Models for Fuzzy Metric Spaces via Domain Theory

RICARTE MORENO, LUIS-ALBERTO 23 December 2013 (has links)
This doctoral thesis is devoted to investigate the problem of establishing connections between Domain Theory and the theory of fuzzy metric spaces, in the sense of Kramosil and Michalek, by means of the notion of a formal ball, and then constructing topological and computational models for (complete) fuzzy metric spaces. The antecedents of this research are mainly the well-known articles of A. Edalat and R. Heckmann [A computational model for metric spaces, Theoret- ical Computer Science 193 (1998), 53-73], and R. Heckmann [Approximation of metric spaces by partial metric spaces, Applied Categorical Structures 7 (1999), 71-83], where the authors obtained nice and direct links between Do- main Theory and the theory of metric spaces - two crucial tools in the study of denotational semantics - by using formal balls. Since every metric induces a fuzzy metric (the so-called standard fuzzy metric), the problem of extending Edalat and Heckmann's works to the fuzzy framework arises in a natural way. In our study we essentially propose two di erent approaches. For the rst one, valid for those fuzzy metric spaces whose continuous t-norm is the minimum, we introduce a new notion of fuzzy metric completeness (the so-called standard completeness) that allows us to construct a (topological) model that includes the classical theory as a special case. The second one, valid for those fuzzy metric spaces whose continuous t-norm is greater or equal than the Lukasiewicz t-norm, allows us to construct, among other satisfactory results, a fuzzy quasi-metric on the continuous domain of formal balls whose restriction to the set of maximal elements is isometric to the given fuzzy metric. Thus we obtain a computational model for complete fuzzy metric spaces. We also prove some new xed point theorems in complete fuzzy metric spaces with versions to the intuitionistic case and the ordered case, respec- tively. Finally, we discuss the problem of extending the obtained results to the asymmetric framework. / Ricarte Moreno, L. (2013). Topological and Computational Models for Fuzzy Metric Spaces via Domain Theory [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34670 / TESIS
55

Měření radiální tuhosti pneumatik / Tyre Radial Stiffness Measurement

Novodomský, Tomáš January 2020 (has links)
This thesis deals with the radial stiffness of a tyre. The first part of is devoted to a brief description of a tyre construction. The next part is devoted to measuring the radial stiffness of a tyre and the design of a new measuring device. The last part of the thesis deals with the influence of the radial stiffness of a tyre on the vertical dynamics of ta vehicle and simulations of this effect in the MATLAB / Simulink software.
56

Vliv vnitřního stínění na tepelnou stabilitu místnosti / The impact of inner shielding on the thermal stability of room

Kantor, Robert January 2013 (has links)
This thesis deals with internal shading devices and their influence on the thermal stability of the room. Furthermore, compares the differences in the behavior of different materials. Finally, compares the measured values with the computational models.
57

Vliv vnitřního stínění na tepelnou stabilitu místnosti / The impact of inner shielding on the thermal stability of room

Halva, Jiří January 2014 (has links)
This thesis deals the internal shielding elements and their influence on the thermal stability of the room and compares the differences in their characteristics.
58

Deformačně napěťová analýza prasečího femuru / Strain-Stress analysis of pig femur

Legerský, Radek January 2011 (has links)
This master’s thesis deals with the strain-stress analyses of the pig femoral bone in physiological and pathological condition. Pathological condition is determined by a significant defect in diaphysis of the bone fixed by using direct angular stable locking plate with screws. The thesis describes the creation of computational models with special focus on bone tissues models of material, which are based on analysis of digital images from computed tomography (CT). There are created and analyzed three types of computational models: the first one corresponds to physiological condition of femur, the second one to femur with significant defect and fixation plate and the third one to femur with significant defect, fixation plate and rod. Every model is loaded in three ways: the first of them simulating the experimental conditions of pressure testing of the femur, the second one bone stress in the sagittal plane and the third one stress by using load determined from probational release of the pig hind limb. Strain-stress states are determined by finite element method using Ansys computational system. Gained results of stress and strain are compared with experimental measurements. The thesis presents a basic idea of the mechanical behavior of porcine femur and porcine femur with significant bone defect.
59

Simulace přechodového režimu spalovacího motoru / Transition State Simulation of Combustion Engine

Forbelský, Antonín January 2011 (has links)
Master's thesis focuses on the simulation engine transients. The model of single-cylinder engine was constructed in simulation software Lotus Engine Simulation. Then was made simulation of transients. The thesis try to describe the influence of moment of inertia of the engine, the engine starting speed and process of throttle opening during the transients. For all modes also compare two methods of fuel control.
60

Výpočtový model kotle KWH / Computational Model of KWH Boiler

Koiš, Jiří January 2014 (has links)
The subject of this thesis is the computational model of existing KWH boiler. There is a short research in the introduction, which deals with combustion heat of considered boiler.  The stoichiometric and balance calculations of gasification chamber ZKG are performed first. The Balance calculations are based on the boiler thermal loss calculations, the losses were determined experimentally. The entire calculation is processed in a computational program for purposses of debugging and manipulation with partial calculations. The computational model that is proposed in this thesis provide better boiler proces understandig. The real boiler measurement is performed for evaluation. The next point is the result analyses, that shows potential boiler efficiency improvements.

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