AN INVESTIGATION OF VARIABLE VALVE TIMING EFFECTS ON HCCI ENGINE PERFORMANCE

The Homogeneous Charge Compression Ignition (HCCI) engine is a promising combustion concept for reducing NOx and particulate matter (PM) emissions and providing a high thermal efficiency in internal combustion engines. This concept though has limitations in the areas of combustion control and achieving stable combustion at high loads. For HCCI to be a viable option for on-road vehicles, further understanding of its combustion phenomenon and its control are essential. Thus, this thesis has a focus on both the experimental setup of an HCCI engine at Michigan Technological University (MTU) and also developing a physical numerical simulation model called the Sequential Model for Residual Affected HCCI (SMRH) to investigate performance of HCCI engines. The primary focus is on understanding the effects of intake and exhaust valve timings on HCCI combustion. For the experimental studies, this thesis provided the contributions for development of HCCI setup at MTU. In particular, this thesis made contributions in the areas of measurement of valve profiles, measurement of piston to valve contact clearance for procuring new pistons for further studies of high geometric compression ratio HCCI engines. It also consists of developing and testing a supercharging station and the setup of an electrical air heater to extend the HCCI operating region. The HCCI engine setup is based on a GM 2.0 L LHU Gen 1 engine which is a direct injected engine with variable valve timing (VVT) capabilities. For the simulation studies, a computationally efficient modeling platform has been developed and validated against experimental data from a single cylinder HCCI engine. In-cylinder pressure trace, combustion phasing (CA10, CA50, BD) and performance metrics IMEP, thermal efficiency, and CO emission are found to be in good agreement with experimental data for different operating conditions. Effects of phasing intake and exhaust valves are analyzed using SMRH. In addition, a novel index called Fuel Efficiency and Emissions (FEE) index is defined and is used to determine the optimal valve timings for engine operation through the use of FEE contour maps.

Analisi delle problematiche ambientali dello stabilimento siderurgico ILVA e parziale valutazione dell’impatto delle sue emissioni in atmosfera attraverso il modello CALPUFF

Il presente lavoro di tesi riguarda lo studio di un modello di stima delle emissioni per la previsione della contaminazione ambientale in aria. Il lavoro è stato svolto all’interno del DICAM dell’Università di Bologna attraverso il supporto del relatore Giacomo Antonioni e dei correlatori Ada Saracino e Gigliola Spadoni. L’applicazione modellistica, attraverso l’uso del software CALPUFF, ha trattato le emissioni del camino E312 della sezione Agglomerazione dello stabilimento siderurgico ILVA di Taranto nell’anno 2015. Gli inquinanti simulati sono quelli per i quali lo SME fornisce il flusso di massa: SO2, NOx, PM. Le polveri sono state considerate completamente costituite da polveri PM10 e per esse si è calcolata la concentrazione al suolo e la deposizione. A partire dai risultati per le polveri, ipotizzando che siano in parte veicolati da esse, sono state valutate anche le concentrazioni e le deposizioni di Diossine. Della configurazione modellistica “ottimale” sono stati presentati: ▪ Per i macroinquinanti le medie annue di concentrazione al suolo, e quindi, la dispersione degli inquinanti. ▪ Per i microinquinanti i valori massimi di concentrazione annua e di deposizione ottenuti nell’area di studio. Nel caso in esame, lo studio è stato riferito alla rete deposimetrica di gestione ILVA (per mancanza di dati deposimetrici della rete di gestione ARPA). In particolare è stato preso in considerazione il deposimetro del quartiere Tamburi a fronte delle criticità rilevate nei mesi di Novembre 2014 e Febbraio 2015, tale per cui, visti gli elevatissimi valori di deposizione, vista la notevole importanza che i dati deposimetrici hanno rispetto al rischio sanitario per ingestione, è stata aperta un’indagine della procura che ha affidato l’analisi a ARPA PUGLIA congiunta con l’ISPRA (che ne ha mandato ministeriale) e la Regione Puglia. A fronte di tali episodi, il seguente studio ha voluto fornire un resoconto deposimetrico per l’anno 2015.

Evaluation of isoprene degradation in the detailed tropospheric chemical mechanism, MCM v3, using environmental chamber data

The isoprene degradation mechanism included in version 3 of the Master Chemical Mechanism (MCM v3) has been evaluated and refined, using the Statewide Air Pollution Research Center (SAPRC) environmental chamber datasets on the photo-oxidation of isoprene and its degradation products, methacrolein (MACR) and methylvinyl ketone (MVK). Prior to this, the MCM v3 butane degradation chemistry was also evaluated using chamber data on the photo-oxidation of butane, and its degradation products, methylethyl ketone (MEK), acetaldehyde (CH3CHO) and formaldehyde (HCHO), in conjunction with an initial evaluation of the chamber-dependent auxiliary mechanisms for the series of relevant chambers. The MCM v3 mechanisms for both isoprene and butane generally performed well and were found to provide an acceptable reaction framework for describing the NOx-photo-oxidation experiments on the above systems, although a number of parameter modifications and refinements were identified which resulted in an improved performance. All these relate to the magnitude of sources of free radicals from organic chemical process, such as carbonyl photolysis rates and the yields of radicals from the reactions of O3 with unsaturated oxygenates, and specific recommendations are made for refinements. In addition to this, it was necessary to include a representation of the reactions of O(3P) with isoprene, MACR and MVK (which were not previously treated in MCM v3), and conclusions are drawn concerning the required extent of free radical formation from these reactions. Throughout the study, the performance of MCM v3 was also compared with that of the SAPRC-99 mechanism, which was developed and optimized in conjunction with the chamber datasets.

Evaluation of alkene degradation in the detailed tropospheric chemistry mechanism, MCM v3, using environmental chamber data

The representation of alkene degradation in version 3 of the Master Chemical Mechanism (MCM v3) has been evaluated, using environmental chamber data on the photo-oxidation of ethene, propene, 1-butene and 1-hexene in the presence of NOx, from up to five chambers at the Statewide Air Pollution Research Center (SAPRC) at the University of California. As part of this evaluation, it was necessary to include a representation of the reactions of the alkenes with O(3P), which are significant under chamber conditions but generally insignificant under atmospheric conditions. The simulations for the ethene and propene systems, in particular, were found to be sensitive to the branching ratios assigned to molecular and free radical forming pathways of the O(3P) reactions, with the extent of radical formation required for proper fitting of the model to the chamber data being substantially lower than the reported consensus. With this constraint, the MCM v3 mechanisms for ethene and propene generally performed well. The sensitivity of the simulations to the parameters applied to a series of other radical sources and sink reactions (radical formation from the alkene ozonolysis reactions and product carbonyl photolysis; radical removal from the reaction of OH with NO2 and β-hydroxynitrate formation) were also considered, and the implications of these results are discussed. Evaluation of the MCM v3 1-butene and 1-hexene degradation mechanisms, using a more limited dataset from only one chamber, was found to be inconclusive. The results of sensitivity studies demonstrate that it is impossible to reconcile the simulated and observed formation of ozone in these systems for ranges of parameter values which can currently be justified on the basis of the literature. As a result of this work, gaps and uncertainties in the kinetic, mechanistic and chamber database are identified and discussed, in relation to both tropospheric chemistry and chemistry important under chamber conditions which may compromise the evaluation procedure, and recommendations are made for future experimental studies. Throughout the study, the performance of the MCM v3 chemistry was also simultaneously compared with that of the corresponding chemistry in the SAPRC-99 mechanism, which was developed and optimized in conjunction with the chamber datasets.

Chronic intermittent hypoxia increases rat sternohyoid muscle NADPH oxidase expression with attendant modest oxidative stress

Chronic intermittent hypoxia (CIH) causes upper airway muscle dysfunction. We hypothesized that the superoxide generating NADPH oxidase (NOX) is upregulated in CIH-exposed muscle causing oxidative stress. Adult male Wistar rats were exposed to intermittent hypoxia (5% O2 at the nadir for 90 s followed by 210 s of normoxia), for 8 h per day for 14 days. The effect of CIH exposure on the expression of NOX subunits, total myosin and 4-hydroxynonenal (4-HNE) protein adducts in sternohyoid muscle was determined by western blotting and densitometry. Sternohyoid protein free thiol and carbonyl group contents were determined by 1D electrophoresis using specific fluorophore probes. Aconitase and glutathione reductase activities were measured as indices of oxidative stress. HIF-1α content and key oxidative and glycolytic enzyme activities were determined. Contractile properties of sternohyoid muscle were determined ex vivo in the absence and presence of apocynin (putative NOX inhibitor). We observed an increase in NOX 2 and p47 phox expression in CIH-exposed sternohyoid muscle with decreased aconitase and glutathione reductase activities. There was no evidence, however, of increased lipid peroxidation or protein oxidation in CIH-exposed muscle. CIH exposure did not affect sternohyoid HIF-1α content or aldolase, lactate dehydrogenase, or glyceraldehyde-3-phosphate dehydrogenase activities. Citrate synthase activity was also unaffected by CIH exposure. Apocynin significantly increased sternohyoid force and power. We conclude that CIH exposure upregulates NOX expression in rat sternohyoid muscle with concomitant modest oxidative stress but it does not result in a HIF-1α-dependent increase in glycolytic enzyme activity. Constitutive NOX activity decreases sternohyoid force and power. Our results implicate NOX-dependent reactive oxygen species in CIH-induced upper airway muscle dysfunction which likely relates to redox modulation of key regulatory proteins in excitation-contraction coupling.

Reciclagem seletiva de canais radiculares

Introdução: O presente trabalho introduz um novo tema na área da Endodontia: Reciclagem Seletiva de Canais Radiculares. Tem os mesmos princípios de desinfecção, conformação e obturação que o retratamento endodôntico não cirúrgico convencional, no entanto é menos invasivo. Está indicado em casos de insucesso prévio no tratamento endodôntico e na presença de próteses. Objetivos: Esta dissertação tem como objectivo principal apresentar um possível novo tratamento na área da Endodontia. Procedeu-se a uma revisão bibliográfica, analisando a literatura que versa o tema, de modo a introduzi-lo dentro da área do retratamento endodôntico não cirúrgico nos seus diferentes procedimentos: Desobturação e materiais utilizados, instrumental utilizado, irrigantes e a sua utilidade e aplicabilidade na prática clínica. Materiais e Métodos: Para a elaboração da presente dissertação, foi realizada uma pesquisa bibliográfica, no presente ano, recorrendo-se aos motores de pesquisa on-line: b-On, Pubmed, Scielo e Google Académico, realizando a pesquisa através das palavras-chave: “endodontic retreatment”, ”root canal system”, “endodontic irrigation”, “endodontic solvent”, “pro-taper”, “reciproc”, “clorohexidine”, “sodium hipoclorite”, “obturation” que foram então combinadas entre si de múltiplas e sucessivas formas. Foram utilizados 50 artigos dos 87 seleccionados, um livro e uma revista. Discussão: Na literatura científica, são comparados vários materiais para a realização do retratamento endodôntico não cirúrgico, como solvente o que melhores resultados apresenta na dissolução da Gutta-Percha é o Xilitol seguido do clorofórmio. Como solução irrigante a Clorohexidina tem um grande potencial nos casos de retratamento por ser mais eficaz em bactérias Gram+ e pela sua substantividade que permite que a sua actividade bacteriana seja contínua. O sistema Reciproc® pela sua forma em S no corte transversal e possuir dois bordos cortantes, aliados à sua composição pela nova liga M-Wire, mais resistente à torção e fadiga cíclica parece ser a melhor opção tanto para desobturação do SCR como re-instrumentação. Com a imagiologia tridimensional, a Reciclagem Selectiva de Canais Radiculares pode ser explorada e tornar-se uma técnica mais conservadora em casos de retratamento ao conseguir-se determinar qual a raiz com lesão apical. Conclusão: Perante este novo método mais conservador de realizar o retratamento endodôntico não cirúrgico, o exame radiológico por CBCT é o grande responsável pela sua realização. Com ele podemos ter acesso à tridimensionalidade de todas as estruturas orais e consequentemente atingir um diagnóstico correcto, com mais informação disponível. Este novo método, aliado aos melhores materiais utilizados no RTENC convencional poderão permitir ao clínico a realização de um retratamento não cirúrgico seguro, mais conservador para a estrutura dentária e para potenciais próteses que possam estar presentes. São necessários mais estudos com um follow-up mais prolongado para determinar a real efetividade deste tratamento.

Highly specific changes in antioxidant levels and lipid peroxidation in Parkinson's disease and its progression : disease and staging biomarkers and new drug targets.

There is evidence that immune-inflammatory, stress of reactive oxygen and nitrogen species (IO&NS) processes play a role in the neurodegenerative processes observed in Parkinson's disease (PD). The aim of the present study was to investigate peripheral IO&NS biomarkers in PD. We included 56 healthy individuals and 56 PD patients divided in two groups: early PD stage and late PD stage. Plasma lipid hydroperoxides (LOOH), malondialdehyde (MDA), nitric oxide metabolites (NOx), sulfhydryl (SH) groups, catalase (CAT) activity, superoxide dismutase (SOD) activity, paraoxonase (PON)1 activity, total radical trapping antioxidant parameter (TRAP) and C-reactive protein (CRP) were measured. PD is characterized by increased LOOH, MDA and SOD activity and lowered CAT activity. A combination of five O&NS biomarkers highly significantly predicts PD with a sensitivity of 94.5% and a specificity of 86.8% (i.e., MDA, SOD activity, TRAP, SH-groups and CAT activity). The single best biomarker of PD is MDA, while LOOH and SOD activity are significantly associated with late PD stage, but not early PD stage. Antiparkinson drugs did not affect O&NS biomarkers, but levodopa+carbidopa significantly increased CRP. It is suggested that MDA may serve as a disease biomarker, while LOOH and SOD activity are associated with late PD stage characteristic. New treatments for PD should not only target dopamine but also lipid peroxidation.

The magnitude of the snow-sourced reactive nitrogen flux to the boundary layer in the Uintah Basin, Utah, USA

Reactive nitrogen (Nr=NO, NO2, HONO) and volatile organic carbon emissions from oil and gas extraction activities play a major role in wintertime ground-level ozone exceedance events of up to 140 ppb in the Uintah Basin in eastern Utah. Such events occur only when the ground is snow covered, due to the impacts of snow on the stability and depth of the boundary layer and ultraviolet actinic flux at the surface. Recycling of reactive nitrogen from the photolysis of snow nitrate has been observed in polar and mid-latitude snow, but snow-sourced reactive nitrogen fluxes in mid-latitude regions have not yet been quantified in the field. Here we present vertical profiles of snow nitrate concentration and nitrogen isotopes (δ15N) collected during the Uintah Basin Winter Ozone Study 2014 (UBWOS 2014), along with observations of insoluble light-absorbing impurities, radiation equivalent mean ice grain radii, and snow density that determine snow optical properties. We use the snow optical properties and nitrate concentrations to calculate ultraviolet actinic flux in snow and the production of Nr from the photolysis of snow nitrate. The observed δ15N(NO3-) is used to constrain modeled fractional loss of snow nitrate in a snow chemistry column model, and thus the source of Nr to the overlying boundary layer. Snow-surface δ15N(NO3-) measurements range from -5‰ to 10‰ and suggest that the local nitrate burden in the Uintah Basin is dominated by primary emissions from anthropogenic sources, except during fresh snowfall events, where remote NOx sources from beyond the basin are dominant. Modeled daily-averaged snow-sourced Nr fluxes range from 5.6-71x107 molec cm-2 s-1 over the course of the field campaign, with a maximum noon-time value of 3.1x109 molec cm-2 s-1. The top-down emission estimate of primary, anthropogenic NOx in the Uintah and Duchesne counties is at least 300 times higher than the estimated snow NOx emissions presented in this study. Our results suggest that snow-sourced reactive nitrogen fluxes are minor contributors to the Nr boundary layer budget in the highly-polluted Uintah Basin boundary layer during winter 2014.

Cálculo de constantes ópticas de películas delgadas de Cu3BiS3 a través del método de Wolfe

Se calculó la obtención de las constantes ópticas usando el método de Wolfe. Dichas contantes: coeficiente de absorción (α), índice de refracción (n) y espesor de una película delgada (d ), son de importancia en el proceso de caracterización óptica del material. Se realizó una comparación del método del Wolfe con el método empleado por R. Swanepoel. Se desarrolló un modelo de programación no lineal con restricciones, de manera que fue posible estimar las constantes ópticas de películas delgadas semiconductoras, a partir únicamente, de datos de transmisión conocidos. Se presentó una solución al modelo de programación no lineal para programación cuadrática. Se demostró la confiabilidad del método propuesto, obteniendo valores de α = 10378.34 cm−1, n = 2.4595, d =989.71 nm y Eg = 1.39 Ev, a través de experimentos numéricos con datos de medidas de transmitancia espectral en películas delgadas de Cu3BiS3.

Las reformas emprendidas en Túnez de la mano del FMI y el BM ¿Precedente para la revolución de los Jazmines?”(1987-2010)

El estallido de la “Revolución de los Jazmines” cuestionó el éxito de un país que por más de dos décadas fue exaltado por el Banco Mundial (BM) y el Fondo Monetario Internacional (FMI) por los logros alcanzados gracias a un programa de restructuración económica. Las exigencias e inconformidades de los manifestantes, que iban más allá de la falta de garantías democráticas, permitieron ver que el país sufría de problemas estructurales relacionados a los altos niveles de desempleo, la precariedad de la situación laboral y la desigualdad. Esta monografía pretende evaluar el papel que tuvieron las reformas económicas y en general el modelo de desarrollo que siguió Túnez de la mano del FMI y el BM, en el surgimiento y consolidación de las condiciones que dieron lugar a la Revolución de los Jazmines a finales del año 2010.