Current stoichiometric spark-ignited engine technologies require costly catalytic converters for reductions in tailpipe emissions. Load control is achieved by using a throttle, which is a leading contributor to reductions in efficiency. Spark-ignited lean burn natural gas engines have been proven to be more efficient and emit fewer pollutants than their stoichiometric counterparts. Load reduction in these engines can be achieved by regulating the air/fuel ratio of the intake charge thereby reducing the efficiency penalties inherent to throttling. Partially stratified charge (PSC) can provide further reductions in emissions and improvements in efficiency by extending the lean limit of operation. PSC is achieved by the ignition of a small quantity of natural gas in the vicinity of the spark plug. This creates an easily ignitable mixture at the spark plug electrodes, thereby providing a high energy ignition source for the ultra-lean bulk charge. Stratified charge engine operation using direct injection (DI) has been proposed as a method of bridging the throttleless load reduction gap between idle and ultra-lean conditions. A previous study was conducted to determine if PSC can provide a high-energy ignition source in a direct injected stratified charge engine. Difficulties with igniting the PSC injections in an air-only bulk charge were encountered. This study focuses on a fundamental Schlieren image-based analysis of PSC combustion. Natural gas was injected through a modified spark plug located in an optically accessible combustion bomb. The relationships between PSC injection timing, fuel supply pressure and spark timing were investigated. Spark timing is defined as the duration between commanded start of injection and the time of spark. As the fuel supply pressure was increased, the minimum spark timing that lead to successful combustion also increased. The largest spark timing window that led to successful combustion was determined to be 80 ms wide at an injection fuel supply pressure of 300 psi. The amount of unburned natural gas increased with increasing spark timing. A cold flow study of the PSC injection system was also conducted. The PSC injection solenoid was found to have a consistent average injection delay of 1.95 ms. The slope of the linear response region of observed injection duration to commanded injection duration was 8.4. Due to plenum effects, the average observed injection duration of the entire PSC system was an order of magnitude longer than the commanded injection duration and was found to vary significantly with fuel supply pressure. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

No description available.

Many methods exist in the literature for the prediction of pharmacokinetic parameters which describe drug distribution in rat and human, such as tissue-to-plasma partition coefficients (Kps) and volume of distribution (Vss). However, none of these methods make use of the in vivo information obtained at the early stages of the drug development process in the form of plasma concentration vs. time profiles. The overall aim of the presented study was to improve upon an existing Kp prediction method by making use of the distribution information contained within this experimental data. Chapter 2 shows that Kp values can be successfully obtained experimentally, but that this process is expensive and time-consuming. Chapter 3 compares six Kp prediction methods taken from the literature for their ability to predict the Kp values of 80 drugs. The Rodgers et al. model was found to be the most accurate, with over 77% of predictions within 3-fold of experimental values. This Chapter also discusses the Vss prediction ability of some of these methods, with the Poulin & Theil and Rodgers et al. models shown to be the most accurate predictors for rat Vss and human Vss respectively. Chapter 4 investigates the relationship between muscle Kp and the Kps of all other tissues, to show that experimental muscle Kp can be used as a surrogate from which all other non-adipose Kp values can be predicted. However, the predictions made using this method were shown to be less accurate than predictions made by the Rodgers et al. model for the same dataset of drugs. A relationship was identified between muscle Kp and tumour Kp in rat, suggesting a potential way to predict tumour Kp in the future. In Chapter 5, a novel method is developed whereby Kp predictions made by the Rodgers et al. model are updated using prior information obtained from the in vivo concentration-time profile. These updated values are then used within a physiologically-based pharmacokinetic (PBPK) model and are shown in Chapter 6 to generate improved predictions for other pharmacokinetic parameters such as Vss and clearance in both rat and human. 100% of human Vss predictions made by the most accurate of the novel methods presented here were within 3-fold of experimental values, compared to 68.8% of predictions made by the Rodgers et al. model. The work presented here has highlighted the need for a more accurate method for the prediction of Kp values, and has addressed this need by generating a model which improves upon the most accurate Kp prediction method currently found in the literature. This will lead to an increase in confidence in the use of predicted pharmacokinetic parameters within PBPK modelling.

In this thesis we are interested in the propagation of low-frequency linear elastic waves through composite materials. We use a variety of dynamic homogenization techniques to find the effective elastic properties of some composites. We consider composites with isotropic phases for ease of exposition but the theory could easily be extended to anisotropic inclusions or host.We use a Representative Volume Element approach with the Method of Asymptotic Homogenization to model a random fibre-reinforced composite. The fibres are all aligned in the same direction and are taken to be of infinite extent, so the composite is essentially two-dimensional. For a random composite we have considered the anti-plane case for SH wave propagation and the in-plane case for P and SV elastic wave propagation, extending the previous published work of Parnell and Abrahams (2006), (2008a), in which a periodic fibre-reinforced composite was studied. We also show, for a simple example, that it is possible to extend the Representative Volume Element method to a three-dimensional particulate composite.In this thesis an Integral Equation Method for homogenization is also studied, with application to periodic fibre-reinforced composites. We have extended the work of Parnell and Abrahams (2008b), which considered SH wave propagation only, to the case of P and SV wave propagation.

Positron emission tomography (PET) is a molecular imaging technique that provides a direct and accurate evaluation of tissue function in vivo. PET of the glucose analogue 18F-fluoro-deoxy-glucose, is increasingly in use to aid in gross target volume delineation in radiotherapy treatment planning (RTP) where it shows reduced inter-observer variability. The aim of this thesis was to develop and investigate a new technique for delineating PET-GTV with sufficient accuracy for RTP. A new technique, volume and contrast adjusted thresholding (VCAT), has been developed to automatically determine the optimum threshold value that measures the true volume on PET images. The accuracy was investigated in spherical and irregular lesions in phantoms using both iterative and filtered back-projection reconstructions and different image noise levels. The accuracy of delineation for the irregular lesions was assessed by comparison with CT using the Dice Similarity Coefficient and Euclidean Distance Transformation. A preliminarily investigation of implementing the newly developed technique in patients was carried out. VCAT proved to determine volumes and delineate tumour boundaries on PET/CT well within the acceptable errors for radiotherapy treatment planning irrespective of lesion contrast, image noise level and reconstruction technique.

The choroid plexuses are largely responsible for cerebrospinal fluid (CSF) secretion and therefore play a fundamental role in brain homeostasis. The membrane proteins involved in CSF secretion are not fully known. Several electroneutral transporters have been identified by molecular methods in choroid plexus epithelial cells but there is a lack of functional data to support their expression making it impossible to elucidate their role in CSF secretion fully. The activity of many of these transporters can be observed in cell volume regulation. Thus, the main aim of the present study was to determine the ability of mammalian choroid plexus epithelial cells to regulate their volume in response to anisosmotic challenge and to investigate the transporters involved.Experiments were performed on cells isolated from the mouse fourth ventricle choroid plexus. Cells were isolated using a combination of manual perturbation, the enzyme dispase and a Ca2+ free incubation to disrupt tight junctions. Cell volume was measured using a video-imaging method. Cells used in this study were all of a similar morphology and had a mean volume of 0.71 pL.Cells exhibited a HCO3- dependent regulatory volume increase (RVI) in response to hypertonic challenge. Strong evidence is presented that the Na+/H+ exchanger (NHE1) and the Cl-/HCO3- exchanger (AE2) contribute to the RVI but the Na+K+2Cl- cotransporter (NKCC1) and the epithelial Na+ channel (ENaC) do not. Choroid plexus cells exhibit a HCO3- dependent regulatory volume decrease (RVD) in response to hypotonic challenge. The RVD was unaffected by DIOA (an inhibitor of KCC activity), the K+ channel inhibitors TEA+, Ba2+ or 4AP or the Cl- channel inhibitors DIDS or NPPB. However removal of extracellular Ca2+ completely abolished cell swelling in response to hypotonic challenge. This sensitivity of volume change to Ca2+ was specific to cell swelling as cell shrinkage in hypertonic artificial CSF was unaffected by removal of extracellular Ca2+.Thus functional evidence is presented to further elucidate the role of several proteins in the choroid plexus cell volume regulatory response to anisosmotic challenge.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-01-10T11:46:03Z No. of bitstreams: 1 texto completo.pdf: 1907446 bytes, checksum: eb86838f2e24c52acf0b35eb5278859a (MD5) / Made available in DSpace on 2017-01-10T11:46:03Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1907446 bytes, checksum: eb86838f2e24c52acf0b35eb5278859a (MD5) Previous issue date: 2003-03-31 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / O presente estudo foi conduzido com o objetivo de elaborar tabelas de volume de povoamento para fragmentos florestais nativos do município de Viçosa, Minas Gerais, bem como de caracterizar as espécies florestais que ocorrem no município e os fragmentos florestais em termos de tamanho, forma e parâmetros qualitativos. A caracterização das espécies foi realizada mediante pesquisa bibliográfica, totalizando 10 trabalhos referentes a nove fragmentos florestais. Foram relacionadas 480 espécies pertencentes a 189 gêneros e 62 famílias. A família com maior número de espécies foi Leguminosae com 76 espécies. As espécies Apuleia leiocarpa, Dalbergia nigra, Piptadenia gonoacantha e Amaioua guianensis estiveram presentes em todos os trabalhos. A caracterização dos fragmentos florestais foi realizada utilizando uma base de dados digitais, disponibilizada pelo CEDEF (Centro de Estudos e Desenvolvimento Florestal), do Instituto Estadual de Florestas (IEF/MG), segundo a qual o município de Viçosa possui 289 fragmentos florestais, totalizando 6.836,58 ha, recobrindo cerca de 22,77% da área do município. Fragmentos de tamanho menor apresentaram tendência de maior valor de índice de circularidade. Apenas alguns fragmentos menores que 10 ha foram classificados como arredondados. Fragmentos acima de 20 ha foram classificados como muito alongados. Os dados para caracterizar os parâmetros qualitativos e quantitativos dos fragmentos e para o ajuste dos modelos de volume de povoamento foram obtidos através da amostragem por ponto horizontal (Bitterlich), utilizando-se fator de área basal (K) igual a 1 m2/ha. Os resultados das análises qualitativas mostraram que 42,14% das árvores apresentaram aproveitamento do fuste maior que 80%; 29,03% entre 50% e 79% e 28,83% menor que 50%. Quanto à infestação de cipós, 59,68% das árvores não apresentaram cipós; 18,14% apresentaram cipós somente no tronco; 4,64 % apresentaram cipós somente na copa; e 17,54% apresentaram cipós no tronco e na copa. O melhor modelo, tanto para estimar volume total com casca por hectare quanto para o volume do fuste com casca por hectare, foi aquele cujos volumes por hectare e as variáveis independentes área basal por hectare e altura do povoamento (altura total média e altura média dos fustes) estavam linearizadas. / The objective of the present work was to construct stand volume tables for native forest fragments of the municipality of Viçosa, Minas Gerais State, Brazil, as well as to characterize the forest species occurring in the region and the forest fragments by size, shape and qualitative parameters. The characterization of the species was made by means of 2 research in literature, totaling 10 different works related to nine forest fragments. A total of 480 species pertaining to 189 geners and 62 families were found. The family with the greatest number of species was Leguminosae with 76 species. In all works the species Apuleia leiocarpa, Dalbergia nigra, Piptadenia gonoacantha, and Amaioua guianensis were found. The characterization of the forest fragments was made using a digital database borrowed from CEDEF (Centro de Estudos e Desenvolvimento Florestal Forest Studies and Development Center) of the Instituto Estadual de Florestas (State Forest Institute IEF/MG), which states that the municipality of Viçosa has 289 forest fragments, totaling 6,836.58 ha, covering around 22.77% of the municipality area. Smaller fragments showed a tendency to have a greater value of the circularity index. Only some fragments smaller than 10 ha were classified as rounded. Fragments with more than 20 ha were classified as very elongated. Data to characterize the qualitative and quantitative parameters of the fragments and for the adjustment of the volume models of the stands were obtained through the horizontal point sampling (Bitterlich), using the basal area factor (K) equal to 1 m2/ha. The qualitative analyses results showed that 42.14% of the trees presented log yields of more than 80%; 29.03% presented log yields between 50 and 79%, and 28.83% presented log yields lower than 50%. In relation to vine infestations, 59.68% of the trees were free from them, 18.14% had vines only on the trunk, 4.64% had vines only at the crown, and 17.54% had vines on the trunk and crown. The best model both to estimate total volume with bark by hectare and to estimate log volume with bark by hectare were those the volumes per hectare of which, and the independent variables basal area per hectare and stand height (mean total height and mean height of logs) were linearized.

Submitted by Fernanda Rodrigues de Lima (fernanda.rlima@ufpe.br) on 2018-09-25T21:59:02Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Sostynis José de Albuquerque Silva.pdf: 2081022 bytes, checksum: feffc4559b38c5ac02f7373f7833972d (MD5) / Approved for entry into archive by Alice Araujo (alice.caraujo@ufpe.br) on 2018-09-27T22:42:25Z (GMT) No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Sostynis José de Albuquerque Silva.pdf: 2081022 bytes, checksum: feffc4559b38c5ac02f7373f7833972d (MD5) / Made available in DSpace on 2018-09-27T22:42:25Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Sostynis José de Albuquerque Silva.pdf: 2081022 bytes, checksum: feffc4559b38c5ac02f7373f7833972d (MD5) Previous issue date: 2016-09-27 / CAPES / A obesidade é uma doença multifatorial de prevalência crescente e vem adquirindo proporções epidêmicas em todo o mundo, sendo um dos principais problemas da saúde pública modernos. O sistema respiratório é particularmente acometido, desenvolvendo uma síndrome restritiva com a diminuição da expansibilidade pulmonar devido a resistência da parede torácica e elevação diafragmática, levando a redução nos volumes pulmonares, especialmente o VRE. Constitui-se consenso que a abordagem clínica geralmente é ineficaz e a cirurgia bariátrica se apresenta como melhor opção de tratamento. A cirurgia bariátrica é atualmente a única modalidade terapêutica a oferecer perda de peso maciça e mantida ao longo do tempo a pacientes obesos mórbidos. Esta dissertação apresenta dois artigos originais. O primeiro foi um estudo transversal que teve como objetivo avaliar o efeito da obesidade na função e ventilação pulmonar regional de mulheres obesas mórbidas avaliadas através tomografia de impedância elétrica, tivemos como resultado que indivíduos obesos apresentam espirometria e FMR próximas à de individuos eutróficos e que o ΔZ é reduzida nos obesos, sendo a distribuição do ventilação pulmonar semelhante ao indivíduo eutrófico com maior contribuição da região direita no indivíduo obeso. O segundo foi um estudo quase experimental que teve como objetivo avaliar o impacto da cirurgia bariátrica na função e ventilação pulmonar regional de obesos mórbidos através da espirometria e tomografia de impedância elétrica. Encontramos como resultados que a cirurgia bariátrica traz prejuízos à função pulmonar e à PIMax, e parece não exercer influência sobre a Ventilação pulmonar total e regional (ΔZ e VC) e a PEMáx de obesos mórbidos, e que a distribuição da ventilação pulmonar apresenta-se semelhante no período pré e pós operatório. Constituem-se como um dos primeiros trabalhos desenvolvidos buscando elucidar o comportamento da ventilação pulmonar do obeso, afim de guiar adequadamente a terapêutica no pré e pós operatório de cirurgia bariátrica a fim de melhorar a funcionalidade do sistema respiratório desses pacientes. / This study aimed to compare the function and regional lung ventilation with obese women and eutrophic individuals by spirometry and electrical impedance tomography and to evaluate the impact of bariatric surgery in the distribution of ventilation before and after surgery. METHODS: This is a cross-sectional study in which were included 10 morbidly obese women (BMI ≥ 40 kg/m²) and 11 eutrophic women (BMI between 18.5 -24.9 kg/m²) matched by age. This is an almost experimental study was to assess the forced spirometry and monitoring a quiet breathing with the Electrical Impedance Tomography (EIT) in the pre and 1 day after bariatric surgery. Another study was experimental study to assess the forced spirometry and monitoring a quiet breathing with the Electrical Impedance Tomography (EIT) in the pre and 1 day after bariatric surgery. Statistical analysis was performed using SigmaPlot software, and applied the Shapiro-Wilk test for normality, the t test for parametric data and the Mann-Whitney test for nonparametric, was adopted as statistically significant p-value < 0.05. RESULTS: We observed reductions in the total impedance variations (ΔZ total) and regional (ΔZ left and ΔZ lower) of the obese group compared to the eutrophic. Significant reductions were found between the groups for the contribution (%) of right and left (p<0,01) regions. Despite the right region further contribute to ventilation in both groups, it was observed that in obese this contribution is even greater when compared to eutrophic with consequent reduction in the left region contribution for these individuals. CONCLUSION: It was observed that the obese women do not show differences in spirometry and RMS compared to eutrophic ones and that the ventilation of obese women is reduced, being the distribution of ventilation more contributed by the right lung, as well as in eutrophic women. It follows that bariatric laparoscopic surgery causes significant reduction in pulmonary function but with maintenance of baseline ventilation and that the distribution of ventilation is greater in the right lung in relation to the left and greater in the posterior region compared to the anterior region preoperatively and postoperatively.

São analisados os efeitos da nitroglicerina (trinitrato de glicerol) sobre a circulação geral e fração de ejeção do ventrículo esquerdo, em pacientes protadores de comprometimento anátomo-funcional do mesmo. Utiliza-se o cateterismo cardíaco para obtenção de dados hemodinâmicos e cineangicardiográficos em 54 pacientes com uma média de idade de 45 anos.Consideram-se 4 grupos experimentais: G1 com SISTEMAS CARDIOVASCULAR NORMAL (7 casos), G2 com portadores de CARDIOPATIA OROVALVULAR ( 8 casos), G3 com portadores de ENDOMIOCARIOPATIA PRIMÁRIA DA FORMA CONGESTIVA (7 casos) e G4 com portadores de ALTERAÇÃO DA SINERGIA DE CONTRAÇÃO DO MIOCÁRDIO VENTRICULAR ESQUERDO POR ATEROSCLEROSE CORONÁRIA (28casos). Constituem parâmetro de estudo: frequencia cardíaca, pressão média no átrio direto, pressão média na artéria pulmonar, pressão diastólica cardíaco e fração de ejeção do ventrículo esquerdo, comparados antes e após administração de nitroglicerina por via sublingual. A fração de ejeção é calculada com base nos volumes diastólico final e sistólico final, de acordo com o modelo proposto por DODGE (24) e modificado por GREENE (43) e GAULT (37) A discussão dos resultados, bem como sua análise estatística, feita pelo teste de Student e Fischer para dados emparalhados, indica que a nitroglicerina, agindo sobre a circulação feral em paceitnes portadores de endomiocardiopatia primária da forma congestiva (G3), não reduz significativamente a pressão média no átrio direito, nem a pressõa diastólica final do ventrículo esquerdo, como ofez em pacientes com sistema cardiovascular normal (G1), em portadores de cardiopatia orovalvular (G2) e nos de alterações da sinergia de contração do miocárdio ventricular esquerdo por aterosclerose coronária (G4). A fração de ejeção do centrículo esquerdo, sob efeito da mesma substância, aumenta de modo significativo somente nos pacientes portadores de alteração da snergia de contração do miocárdio ventricular esquerdo por aterosclerose coronária (G4).

De nombreux descripteurs sont utilisés pour décrire les composites tissés. Cela est dû en partie aux différents usages que l’on peut en faire. Par exemple, le descripteur le plus approprié pour une simulation mécanique (par exemple, un maillage d’éléments finis), n’est pas nécessairement le même que pour un algorithme de contrôle non destructif (par exemple, des descripteurs statistiques issus d’images tomographiques). Cette recherche propose de reconnaître que, malgré les nombreuses formes que peuvent prendre ces descripteurs textiles, le composite tissé 3D qui nous intéresse est intrinsèquement structuré. En fait, il est principalement défini par son motif de tissage 3D (arrangement des torons). Cette caractéristique commune à tous les descripteurs peut être exploitée pour “construire des liens” entre les nombreuses analyses différentes. Ceux-ci peuvent être obtenus à travers de la Corrélation d’Images Volumiques (DVC), qui fournit le champ de déplacement reliant toute paire de descripteurs. Les avantages de la DVC sont démultipliés en permettant la “relaxation” de l’hypothèse fondamentale de la conservation des coefficients d’absorption (le contraste tomographique), et l’utilisation d’une technique de régularisation mécanique “complète”. Cela se traduit par un algorithme de recalage robuste et rapide. Il permet de mesurer les “différences métriques” (déformations et distorsions du toron) et d’identifier les “différences topologiques” possibles (par exemple, les anomalies de tissage) qu’un textile peut connaitre. En somme, ce nouvel “cadre de corrélation” permets l’unification des descripteurs textiles dans un seul descripteur topologique. Divers échantillons tissés observés à l’échelle méso ont été étudiés dans ce contexte. / Many descriptors are employed for describing the woven composites. This is, in part, due to the different uses one may give them. For example, the most appropriate descriptor for a mechanical simulation (e.g., a finite element mesh), may not necessarily be the same as for a nondestructive testing algorithm (e.g., statistical descriptors issued from tomographic images). This research proposes to acknowledge that, despite the many forms that these textile descriptors may take, the 3D woven composite tat interests us is intrinsically structured. In fact, it is mainly defined by its 3D weaving pattern (arrangement of yarns). This common characteristic to all descriptors can be exploited to “construct bridges” between the many different analyses. These can be obtained by means of Digital Volume Correlation (DVC), which provides the displacement field relating any pair of descriptors. It should be noted that the advantages of DVC are multiplied by allowing for the “relaxation” of the fundamental assumption of conservation of absorption coefficients (i.e., the tomographic contrast), and the use of a “complete” mechanical regularization technique. This results in a robust and fast registration algorithm. It allows measuring the “metric differences” (yarn deformations and distortions) as well as identifying the possible “topological differences” (e.g., weaving anomalies) that a textile may undergo. In short, this new “correlation framework” allows the unification of the textile descriptors into a single topological descriptor. Various woven samples observed at the meso-scale were studied in this context.