Orientador: Paulo Fernando de Arruda Mancera / Banca: Cláudia Pio Ferreira / Banca: Norberto Anibal Maidana / Resumo: O caranguejo-uçá, Ucides cordatus, tem fundamental importância para os manguezais, seu ambiente natural, realizando a decomposição de matéria orgânica, e também sendo um importante biomonitor de áreas críticas. Sua comercialização é considerada a atividade econômica mais importante relacionada a manguezais, e essencial para o sustento das comunidades ribeirinhas. Desde 1997, têm sido observados eventos de mortandade das populações dessa espécie, com redução de até 85% das coletas. Em tais eventos, os caranguejos doentes apresentavam sintomas comuns, entre eles, uma considerável dificuldade de locomoção, e consequentemente, dificuldade de retornar às suas tocas. Por essa razão, esta enfermidade foi chamada de Doença a do Caranguejo Letárgico (DCL). Em 2005, comprovou-se que o agente causador da DCL é o fungo patogênico Exophiala cf psycrophila, um fungo do Filo Ascomycota... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The mangrove crab, Ucides cordatus, plays a crucial role in a variety of ecosystem processes in its environment, such as nutrient cycling, and it is a biomonitor of critical areas. Moreover, it is an important component in the economy of several underprivileged communities that depend on it for their subsistence. Beginning in 1997, massive mortalities of U. cordatus have been report by crabcollectors, such as 85% reduction in collection rates in some regions. Crabs in areas of high mortality share several common symptoms, such as lethargy, poor motor control and inability to return to the upright position when turned upside down. Hence, this pathology is called Lethargic Crab Disease (LCD). Finally, in 2005, there were several evidences showing that LCD is caused by a fungus of Phylum Ascomycota, Exophiala cf psycrophila. The DCL fungus is not easily found among the periods in which the mortalities occur, been detected only into the mangrove crab U. cordatus, all asymptomatic. There is also no evidence of the presence of this fungus in the soil or plant samples of the mangrove. As a result, the initial hypothesis is that the disease spreads among the estuaries through dispersal of the fungus by the sea. Based on the epidemiology of the LCDdisease,we construct amathematical model using a system of partial differential equations, considering diffusion and advection processes, to describe the dispersion of the disease through the mangrove complexes. The aim of this work is to find travelling waves solutions for the developed model, that connect two equilibrium points. For this, we analyse the characteristic polynomial fromthe jacobianmatrix evaluated at one of equilibrium points, the disease-free equilibrium, and present results about the necessary conditions for the existence of travelling wave solution, numerical simulations and finally, estimate the minimum value... (Complete abstract click electronic access below) / Mestre

The objective of this study is to introduce a more refined methodological approach for signalling corporate collapse. The proposed methodological approach provides informed stakeholders in a corporation with a tool that would help them signal impending collapse with a higher degree of accuracy than the existing mainstream methodology. By doing so, the proposed methodological approach helps stakeholders take appropriate measures, if possible, to save their company from collapse. The motivation behind this study emanates from a need in the literature in relation to coming up with a new methodological approach that is superior to what is available. For example, Jones and Hensher (2004), one of the most recent studies in the field, stated that over the past three decades there has been a conspicuous absence of modelling innovation in the literature on financial distress prediction, as well as a failure to keep abreast of important methodological developments emerging in other fields of the social sciences. Specifically, this study introduces a new ratio-based multivariate methodological approach for signalling corporate collapse, called Multi-Level Modelling (MLM). Moreover, this study demonstrated that MLM provides informed stakeholders in a corporation with a tool that would help them signal impending collapse with a higher degree of accuracy than Multiple Discriminant Analysis (MDA), which is the mainstream benchmark methodological approach. By doing so, MLM helps stakeholders take appropriate measures, if possible, to save their company from collapse. The empirical results depicted the superiority of MLM over MDA. MLM generated better overall predictive power and dramatically reduced the occurrence of Type I error (classifying a collapsed company as non-collapsed). Moreover, MLM achieved those results while at the same time capturing variations in industry sectors among the data sample of companies. This is something that MDA was not capable of.

Experimental studies were undertaken to improve the radiation dose response and ease of manufacture of polymer gel dosimeters that use N-isopropyl acrylamide (NIPAM) as the monomer. An alternative carageenan gelling agent was tested in place of gelatin. Although the carageenan did reduce the gelling time for the dosimeter solution, the dose response of the dosimeters was unsatisfactory. An alternative antioxidant system, ascorbic acid and Cu2+, was investigated with the aim of reducing the toxicity of dosimeter materials and providing opportunities for commercial production of prepackaged dosimeter kits. Unfortunately, the new antioxidant was ineffective for the NIPAM-based dosimeters that were studied. Three cosolvents, glycerol, N-propanol and isopropanol, were used to increase the solubility of N,N’-methylene-bisacrylamide (Bis) crosslinker in polymer gel dosimeter recipes that use NIPAM. These cosolvents enabled the manufacture of polymer gel dosimeters with higher levels of dissolved crosslinker than was previously possible. Preliminary results using x-ray computed tomography to read the resulting gels are very promising, due to enhancements in dose sensitivity. Dosimeters with high N,N’-methylene-bisacrylamide content that used isopropanol or glycerol as cosolvents had good optical clarity prior to irradiation, but did not produce reliable optical CT results for non-uniformly-irradiated gels. Further experiments and recipe optimization are required to determine whether gels with cosolvents and high levels of N,N’-methylene bisacrylamide can be used effectively for verifying spatially non-uniform dose distributions using x-ray computed tomography. A mathematical model that includes inhibition of NIPAM-Bis polymerization was developed and the inhibition effects of MEHQ and oxygen in polymer gel dosimeters were simulated. Kinetic parameters were obtained from the literature and were estimated using experimental data obtained by our research group. Good agreement was obtained between model predictions and experimental data with and without oxygen contamination. Simulation results indicate that MEHQ has little influence on the duration of the inhibition period and the rate of polymerization when no oxygen contamination is present, so that removal of MEHQ from dosimeter recipes is not required. Effective oxygen removal is very important to achieve reliable dosimeter results. / Thesis (Master, Chemical Engineering) -- Queen's University, 2008-12-16 15:59:14.034

This thesis is devoted to mathematical modelling, including numerical simulation, in nonlinear laser physics. We study the concrete problem of finding optimal parameters for soliton lasers which is important for many applications. The basic mathematical tool used in our studies is the theory of nonlinear differential equations and numerical methods of their investigations.

The harvesting of immature mammalian oocytes (eggs) and their maturation in a laboratory environment, known as in-vitro maturation (IVM), provides an alternative to the harvesting of mature oocytes for in-vitro fertilisation (IVF) programs. The nutrient environment of an oocyte matured in vitro is known to have a significant effect on its potential to successfully mature, and it is desirable for the in-vitro nutrient environment to mimic the natural environment in vivo. This thesis describes an interaction between mathematical modelling and experimental investigation designed to build upon understanding of the nutrient environment of the oocyte in vivo, which is difficult to determine via experiment alone. A general mathematical model of nutrient transport to the oocyte, through its surrounding cumulus cells is developed. This model is applicable in-vivo and in-vitro across several species and to a number of important nutrients. Nutrient transport in this system - the cumulus-oocyte complex (COC) - is of particular importance, as it is this system that is normally removed for IVM treatments, and its solution under in-vivo conditions allows the nutrient concentration reaching the oocyte to be determined, given a known concentration immediately surrounding the COC. To successfully apply this model, parameters representing the rate of nutrient transport into cells within the COC must be accurately determined. These parameters are determined by a combination of experimental procedures and mathematical modelling in the case of an important nutrient to oocyte development, glucose. This work gives insight into the concentration dependence of glucose uptake into cell types that are important in regulating oocyte development, and to the behaviour of the oocyte itself with regard to glucose uptake. Finally models to describe the transport of two key nutrients, oxygen and glucose, from the vascular system in the ovary, through the ovarian follicle to the oocyte are developed. These make use of experimental results found in the study of glucose transport in the COC, and show that the geometry of the follicle has a significant impact on the nutrient environment of the COC, and hence by inference the nutrient environment of the oocyte. Work discussed in this thesis has been published [31, 156] and submitted for publication [30]. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1374636 / Thesis (Ph.D.) -- University of Adelaide, School of Mathematical Science, 2009

Thesis (Ph.D.)--University of Wollongong, 2004. / Typescript. Includes bibliographical references: p. 521-546.

Two important factors in cancer progression are: metastatic ability, cancer spreading and disrupting healthy function of bodily processes; and heterogeneity, the variation in different cancers caused by genetics, the microenvironment, and stochasticity. In this thesis, we investigate two scenarios of interest using models and techniques inspired by interacting particle systems. First, we model osteocyte network formation. Within bone, dendritic osteocytes form a spatial network allowing communication between osteocytes and osteoblasts located on the bone surface. This communication network facilitates coordinated bone formation. In the presence of a cancer, osteocytes manifest with either over- or under-developed phenotypes. Preliminary studies measuring the number of osteocytes per unit area show that the number density of osteocytes changes between healthy and pathological bone. We develop a mathematical framework to describe spatial networks, and present a stochastic agent-based model for bone formation. Our approach allows us to probe both network structure and number density of osteocytes in bone. Analysis of our model is possible via mean-field equations. We consider variations of our model to predict how changing measurable biological parameters relating to osteoblast differentiation can allow for different morphologies. We use our model to hypothesise reasons for the limited efficacy of zoledronate therapy on metastatic breast cancer. Second, we model the diffusive microenvironment between cells to aid with pathology slide analysis. Intra-tumor phenotypic heterogeneity limits accuracy of clinical diagnostics and hampers the efficiency of anti-cancer therapies. Dealing with this cellular heterogeneity requires adequate understanding of its sources; phenotypes of tumour cells integrate hardwired (epi-)mutational differences with responses to microenvironmental cues. The latter come in the form of both direct physical interactions, and gradients of secreted signalling molecules. Here, we develop a partial differential equation based model that allows the separation of phenotypic responses to signalling gradients within tumour microenvironments from the combined influence of responses mediated by direct physical contact and hardwired (epi-)genetic differences. We apply our model for the analyses of breast cancer histological specimens. Our approach allows partial deconvolution of the complex inputs that shape phenotypic heterogeneity of tumour cells, and identifies cells that significantly impact gradients of signalling molecules.

Fallopia japonica (Houtt. Ronse Decraene) (syn. Reynoutria japonica syn. Polygonum cuspidatum, Japanese knotweed) is an aggressively invasive alien weed in the United Kingdom (UK) and throughout its introduced range. Its presence can herald considerable costs, both in terms of its ecological impact as a threat to biodiversity and economically due to the physical damage caused to property and the associated costs of treatment and disposal of the plant. There is therefore increasing interest in eradicating this alien species and as a result many different management techniques have been applied to try and control its spread. It is important to ascertain which of these are most appropriate in any given situation and so tools that can test the impact and efficiency of these techniques both quickly and cheaply would be extremely useful. In this thesis mathematical models are developed for the spatial spread of F. japonica on a local scale in the UK.

Background: Despite the so-called "generalised" nature of many epileptic seizures, patient specific spatio-temporal properties have been shown using imaging data at the macroscopic level of the cortex. Previous computational models have failed to account for spatial heterogeneities at the scale of the entire cortex. Furthermore, one of they key benefits of developing a model is the ability to easily test stimulation protocols. Previous studies of generalised spike-wave (the hallmark of absence epilepsy) have abstracted away from this.METHODSIn this work we develop a set of models of epileptic activity, one of which is at the scale of the entire cortex and incorporates anatomically relevant connectivity from human subjects. A similar model incorporating physiologically relevant thalamocortical circuitry is developed in order to test hypotheses regarding stimulation protocols.RESULTSWe show that the model can account for large-scale spatio-temporal dynamics similar to those seen in epileptic patients. We demonstrate, using the model of thalamocortical interaction, that such a modelling approach can be used for the evaluation of stimulation protocols which are shown to successfully abort the seizure prematurely.CONCLUSIONThis work highlights the importance of computational modelling to support existing data and to make specific predictions regarding testable hypotheses. For example, a stimulus given at the correct time with the correct amplitude will stop the seizure.

In laser percussion drilling, a series of laser pulses with specified energies and durations irradiate the workpiece surface to gradually heat, melt, and vaporise material until a hole with-required depth-and-diameter-is-achieved. Despite being the quickest technique for producing small diameter holes, laser percussion drilling regularly suffers from difficulties in controlling the hole quality such as hole circularity, hole taper and recast layer. Therefore, in order to produce holes to a specific requirement at minimum cost and time, it is crucial to fully understand the effects of each parameter on hole quality. In this research, a new mathematical model for multiple pulsed laser drilling is developed to predict the hole depth, hole taper, and recast layer thickness, and to investigate the effects of key laser parameters on hole dimensions. The new model accounts for recoil pressure, melt ejection, O2 assist gas effects, as well as solidification of the melt. The development of-the new model is divided into two stages; pulse on stage where interaction between laser beam-material takes place, and pulse off stage where solidification of the melt is modelled. Governing equations are established from heat conduction, energy, and mass equations at the solid-liquid and liquid-vapour interfaces with appropriate boundary and initial conditions. Analytical solutions are derived by using Mathematica 7 software as a tool to solve the system of non-linear equations. To validate the model, experimental work has been conducted and the measured results are compared to those calculated from the model. It is shown that the new model gives a good prediction of the hole depth and acceptable prediction of the recast layer thickness. Laser peak power and pulse width are shown to have a significant influence over the drilled hole quality whereas the changes due to pulse frequency are less pronounced.