Background: Analyses of the individual-, social- and structural-level factors promoting the transmission of HIV and other blood-borne pathogens have consistently identified exposure to correctional environments, especially for individuals who use injection drugs (IDU), as a risk factor for infection. The objectives of this project were: to review the epidemiologic literature on incarceration and HIV infection among IDU, critically examining evidence presented supporting a causal linkage between imprisonment and infection; to investigate incarceration experiences in a cohort of active IDU; and to assess the possible effects of incarceration on the post-release risk environment of active IDU. Methods: Longitudinal datasets for quantitative analyses were derived from the Vancouver Injection Drug User Study (VIDUS) and the Scientific Evaluation of Supervised Injection (SEOSI), both prospective cohorts of IDU in Vancouver’s Downtown Eastside neighbourhood. In the first analysis, the prevalence and correlates of reporting incarceration in the the previous six months were identified in SEOSI using generalized estimating equations (GEE). In the second analysis, the possible effect of imprisonment on the prevalence of risk factors for HIV infection was estimated in VIDUS using linear growth curve analysis. Results: In the first analysis, 902 individuals interviewed at least once between 1 July 2004 and 30 June 2006 were included. Overall, 423 (46.9%) reported an incarceration event at some point during the study period. In a multivariate GEE model, recent incarceration was independently associated with a number of high-risk factors, including syringe sharing. In the second analysis, 1603 individuals were interviewed at least once between 1 May 1996 and 31 December 2005 and in cluded. Of these, 147 (9.2%) matched the study criteria and were included as cases; 742 (46.3%) were included as matched controls. In linear growth curve analyses adjusted for age, gender and ethnicity, syringe sharing was significantly more common in the incarcerated group (p = 0.03) after incarceration than in the control group. Conclusions: Our findings support the existence of a role for incarceration in continued viral transmission. In response, appropriate harm reduction measures should be expanded within correctional environments and social, political and legal reforms enacted to reduce the incidence of imprisonment for individuals who use illicit drugs.

Uno de los ámbitos de mayor interés en el campo de la química analítica es el análisis medioambiental, ya que hay que asegurar y mantener la calidad, ya sea del aire o del agua para que su composición no comporte ningún peligro para la salud de los seres vivos. Los diferentes procesos industriales han contribuido a mejorar la calidad de vida, pero pueden producir subproductos que si son introducidos directa o indirectamente en el agua causan serios problemas de contaminación. De este modo, es necesario el tratamiento de una gran cantidad de desechos industriales, los cuales requieren una continua minimización. Los avances en el campo del análisis medioambiental se han dirigido al desarrollo de nuevas técnicas que sean de fácil uso, que permitan minimizar la manipulación de la muestra, los costes y el tiempo de análisis, que no precisen del uso de disolventes orgánicos, que puedan ser fácilmente automatizadas y que sean rápidas. Entre las técnicas analíticas que presentan las características citadas se encuentran las técnicas de inyección de flujo.La instrumentación analítica actual permite generar datos de diferente dimensionalidad: los denominados datos de orden cero, cuando la señal obtenida por el detector para cada muestra es un escalar y este valor se relaciona con la concentración mediante un calibrado univariante; los datos de primer orden son aquellos que corresponden a un vector por muestra, y se relacionan con la concentración mediante una calibración multivariante o de primer orden; y datos de segundo orden, que son aquellos que corresponden a una matriz por muestra y aplican una calibración de segundo orden para relacionar la señal con la concentración de los analitos de interés. Los datos de orden cero son útiles en los casos en los que se tiene una respuesta única y específica para el analito de interés, mientras que los datos de primer orden permiten determinar la concentración de un analito en presencia de interferentes siempre que éstos estén contemplados en las muestras de calibrado. En el caso de tener interferentes no definidos o que éstos no se puedan reproducir en las muestras de calibrado, se emplean datos de segundo orden y calibraciones de segundo orden. Esta Tesis Doctoral se ha enmarcado en el desarrollo de nuevas metodologías analíticas para la determinación de subproductos de la industria de curtidos de pieles mediante un sistema de inyección de flujo, Análisis por inyección secuencial (SIA) y calibración de datos de segundo orden.SIA, Sequential Injection Analysis, es un sistema de inyección de flujo, introducido por el profesor Jaromir Ruzicka el 1990, en el que la muestra y los reactivos son aspirados de forma secuencial, se mezclan por difusión en el reactor y se transportan mediante un flujo hacia el detector. Un sistema SIA acoplado con un detector espectrofotométrico de diodos en fila (DAD) permite obtener datos de segundo orden, de forma que se recoge el espectro completo en un intervalo de longitudes de onda, a diferentes tiempos durante la elución del pico SIA. De esta forma se obtiene una matriz de datos (m x n), donde m son los diferentes tiempos y n las longitudes de onda de medida, para el análisis de cada una de las muestras.En este trabajo, se presentan diferentes aplicaciones mediante análisis por inyección secuencial y calibración de datos de segundo orden con resolución de curvas multivariante con mínimos cuadrados alternados (MCR-ALS) para la determinación y especiación de cromo y para la determinación de tres colorantes simultáneamente. También se presentan dos revisiones bibliográficas críticas acerca de la determinación de cromo y del análisis multicomponente en sistemas de flujo. Además se desarrolló una aplicación de Cromatografía por Inyección Secuencial (SIC) con resolución de curvas multivariante con mínimos cuadrados alternados para la determinación de fenoles.El cromo es un elemento ampliamente usado en esta industria. Su determinación tiene gran importancia medioambiental debido a la gran toxicidad de la especie de Cr(VI) como agente cancerígeno, mientras que el Cr(III) es un elemento esencial. En esta Tesis se presentan cuatro trabajos referidos a la determinación de cromo. En el primero, Use of multivariate curve resolution for determination of chromium in tanning samples using sequential injection analysis, Analytical and Bioanalytical Chemistry 382 (2005) 328-334 se basa en los fundamentos para permitir la determinación de cromo con el sistema SIA-MCR-ALS. Dependiendo de la capacidad de reacción del Cr(III) se puede diseñar una secuencia analítica en el sistema SIA de modo que se obtenga un sistema en evolución para obtener una matriz de datos como señal analítica. Cr(III) fue oxidado a Cr(VI) fuera del sistema SIA para aumentar la sensibilidad del Cr(III). De este modo, en el sistema SIA se produjo un gradiente de pH para provocar una conversión entre dos especies de Cr(VI), cromato y dicromato. El segundo artículo, Factorial design for optimizing chromium determination in tanning wastewater, Microchemical Journal 83 (2006) 98-104 consiste, tal y como el título sugiere, en la optimización del método desarrollado previamente para incorporar en una única etapa las dos etapas principales (oxidación de Cr(III) y evolución del Cr(VI)). El tercer trabajo, Chromium speciation using sequential injection analysis and multivariate curve resolution, Analytica Chimica Acta 571 (2006) 129-135 consiste en la determinación simultánea de Cr(III) y Cr(VI) debido a que la especiación de cromo es de gran interés, sobretodo en el campo medioambiental. Se llevó a cabo una derivatización previa de Cr(III), formando un complejo con ácido etilendiaminotetraacético (EDTA) para aumentar la sensibilidad del Cr(III). El sistema en evolución en el sistema SIA se generó mediante un gradiente de pH. El cuarto trabajo, Chromium determination and speciation since 2000, Trends in Analytical Chemistry, 25 (2006) 1006-1015 consiste en un trabajo bibliográfico que describe las posibilidades de determinación y especiación de cromo.Otros analitos de interés en este ámbito son los colorantes de los baños residuales, debido a su elevada toxicidad y a su baja biodegradabilidad. Por tanto, tiene gran relevancia el estudio de la proporción de colorantes en las muestras y su efecto al largo del tiempo. Tanto el cromo como los colorantes son compuestos de interés en otros ámbitos como por ejemplo, alimentos, artes gráficas, etc. Se presentan cuatro trabajos científicos en este ámbito con dos objetivos prácticos. Por un lado, controlar la cantidad de colorante que permanece en solución después del proceso de teñido, de modo que se puedan optimizar algunas de las etapas del proceso, y por otro lado, estudiar diferentes estrategias para reducir el porcentaje de colorantes en aguas residuales. El primer trabajo Sequential injection analysis with second-order treatment for the determination of dyes in the exhaustion process of tanning effluents, Talanta 71 (2007) 1393-1398 consiste en el desarrollo de un método analítico basado en SIA y calibración de datos de segundo orden (MCR-ALS) para determinar simultáneamente tres colorantes en muestras de deshecho de la industria de curtidos. Este método se aplicó a muestras curtidas con sales de cromo o con especies vegetales. El segundo trabajo Matrix effect in second-order data. Determination of dyes in a tanning process using vegetable tanning agents, Analytica Chimica Acta 600 (2007) 233-239 conlleva la aplicación del método a muestras curtidas con especies vegetales, ya que éstas son especies altamente absorbentes y provocan el conocido efecto matriz, por lo que se propusieron estrategias para tratar de corregir estos efectos. Para alcanzar el segundo objetivo se consideró la adsorción de colorantes en carbón activo como una estrategia atractiva para eliminar los colorantes. El tercer trabajo, Kinetic and adsorption study of acid dye removal using activated carbon, Chemosphere 69 (2007) 1151-1158 estudia la adsorción y los parámetros cinéticos, tanto para los colorantes individuales como para las mezclas. El cuarto trabajo, Experimental designs for optimizing and fitting the adsorption of dyes onto activated carbon, submitted, pretende obtener una superficie de respuesta de forma que, dependiendo de las concentraciones de colorantes, se puedan establecer las condiciones experimentales para obtener una predeterminada adsorción de colorantes en carbón activo.En la última etapa de la Tesis se exploraron diferentes posibilidades para aumentar la capacidad de los análisis simultáneos mediante sistemas de flujo y métodos de calibración de segundo orden. De este estudio se obtuvieron dos trabajos. El primero, Multicomponent analysis in flow systems, Trends in Analytical Chemistry, 26 (2007) 767-774 muestra una visión general de las determinaciones de múltiples analitos en sistemas de flujo. El segundo trabajo, Coupling of sequential injection chromatography with multivariate curve resolution alternating least squares for enhancement of peak capacity, Analytical Chemistry, 10.1021/ac071202h es el resultado de la combinación de dos estrategias propuestas para el análisis multicomponente, la cromatografía de inyección secuencial (SIC) y la calibración de datos de segundo orden con MCR-ALS. Este estudio se llevó a cabo en colaboración con el Grupo de Química Analítica, Automatización y Medioambiente de la Universidad de las Islas Baleares (UIB), en donde se realizó la parte experimental. / Environmental analysis is a field with high interest in the analytical chemistry community. It is very important to assure and maintain the quality, from air as well as from water, to avoid that its composition cause any risk for the living organisms. Different industrial processes have contributed to improve health quality, but they can produce intermediates that if are introduced direct or indirectly to the waters can cause important problems of pollution. In that way, it is necessary to treat a big amount of industrial wastes, which should be continuously minimized. Advances in the environmental field have been focusing on the development of new techniques of easy use, with low sample manipulation, low costs and short analysis times that could be easily automatised and fast. Flow analysis techniques can be found in this classification. The current analytical instruments can generate data with different dimensionality. The analytical signal can be a scalar (a single absorbance measure), a vector (single absorbance measurement along time), or a data matrix (spectrum recorded along time) per each analysed sample. These data have been classified, as zero-order data when the signal is a scalar, first-order data when is a vector, and second-order data when the signal is a matrix. Zero-order data are useful for cases in which we have a unique and specific response for the analyte of interest, meanwhile first-order data allow quantification of an analyte in the presence of interferents but they should be contained in the calibration samples. When the interferents are not known and they could not be present in the calibration samples, second-order data and second-order calibrations are used.This doctoral thesis has been carried out for developing new analytical methodologies for determining subproducts of the tanning industry using sequential injection analysis (SIA) and second-order calibration.SIA, Sequential Injection Analysis, is a flow injection system introduced in 1990 by Professor Jaromir Ruzicka, where the sample and reagents are introduced sequentially into the system, are mixed by diffusion process in the reactor and then they are pumped through the detector.A SIA system using a diode array spectrophotometer can generate second-order data, it means that the analytical signal is a data matrix for each sample on which we have absorbances in a wavelength interval in one axis and in a time interval in the other axis. In this project, we present different practical applications using sequential injection analysis and second-order calibration using multivariate curve resolution alternating least squares (MCR-ALS) for determining and speciating chromium and for determining three acid dyes simultaneously. Furthermore we present two bibliographic overviews about chromium determination and multicomponent analysis in flow systems. We also developed an application of sequential injection chromatography (SIC) using multivariate curve resolution alternating least squares (MCR-ALS) for determining phenolic derivatives. Chromium is an element widely used in the industry. Its determination presents high environmental interest because the toxicity of the Cr(VI) species as a carcinogenic agent, meanwhile Cr(III) is an essential element. In this Thesis we present four papers relative to chromium determination. The first paper Use of multivariate curve resolution for determination of chromium in tanning samples using sequential injection analysis, Analytical and Bioanalytical Chemistry 382 (2005) 328-334 is based on the basis to permit quantification of chromium with the system SIA-MCR-ALS. Depending on the capacity of reaction of Cr(III), different analytical sequences in the SIA system can be designed. Cr(III) was oxidized into Cr(VI) outside of the SIA system to increase Cr(III) sensibility. In that way, in the SIA system we induced a pH gradient to see the conversion of the two species of Cr(VI), chromate and dichromate. The second paper Factorial design for optimizing chromium determination in tanning wastewater, Microchemical Journal 83 (2006) 98-104 presents an automatic system for total chromium determination using different experimental designs to optimize the overall process. The third paper, Chromium speciation using sequential injection analysis and multivariate curve resolution, Analytica Chimica Acta 571 (2006) 129-135 is a paper in which the two main species of chromium, Cr(III) and Cr(VI), are determined simultaneously in a single analysis in the presence of interferents. The fourth paper, Chromium determinations and speciation since 2000, Trends in Analytical Chemistry, 25 (2006) 1006-1015 is a bibliographic study that describes the possibilities available for chromium determination and speciation.Other analytes of interest in this field are dyes from wastewater due to its high toxicity and its low biodegradability. That is why studying the proportion of dyes in samples and its effect through time presents high relevance. Chromium and dyes are compounds of high interest in other application fields, such as, foods, printing and graphic design, etc. We present four scientific papers in this field with two practical objectives. On the one hand, control the amount of dyes that remains in solution after the dyeing process has been done. On the other hand, study different strategies to reduce the percentage of dyes in wastewater. The first paper, Sequential injection analysis with second-order treatment for the determination of dyes in the exhaustion process of tanning effluents Talanta 71 (2007) 1393-1398, describes the developed method for determining three acid dyes in a single step. This method was applied to water samples of leathers tanned with chromium salts and with vegetal agents. The second paper Matrix effect in second-order data. Determination of dyes in a tanning process using vegetable tanning agents Analytica Chimica Acta 600 (2007) 233-239 presents strategies to use when a sample presents matrix effects using second-order data. To solve the second objective, we studied the behaviour of dyes on activated carbon and present the results in the third paper Kinetic and adsorption study of acid dye removal using activated carbon Chemosphere 69 (2007) 1151-1158 where we studied the adsorption and the kinetic parameters of dyes being alone in solution or in a mixture of them. The fourth paper, Experimental designs for optimizing and fitting the adsorption of dyes onto activated carbon Submitted, we described a sequential methodology to obtain a response surface and optimize the adsorption process as a way of eliminating dyes in wastewater samples from the tanning industry. In the last period of the Thesis, we explored different strategies to increase the capacity of simultaneous analysis using flow systems and second-order calibration. From this study, we obtained two papers. The first, Multicomponent analysis in flow systems, Trends in Analytical Chemistry, 26 (2007) 767-774, shows a general vision of multiple determinations in flow systems. The second paper, Coupling of sequential injection chromatography with multivariate curve resolution alternating least squares for enhancement of peak capacity, Analytical Chemistry 79 (2007) 7767-7774 shows a combination of two strategies proposed for multicomponent analysis, sequential injection chromatography (SIC) and second-order calibration with MCR-ALS. This study was carried out in collaboration with the Analytical Chemistry, Automation and Environment group of the University of the Balearic Islands.

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The present work is based on the need for understanding the in-cylinder flow and its subsequent effects on combustion in a valved-two-stroke spark ignition engine with fuel injection using Computational Fluid Dynamics (CFD) and experimental techniques. In this context, the CFD code KIVA-II has been modified to model the two-stroke engine gas exchange and combustion processes. A 3-D Cartesian grid generation program for complex engine geometry has been added to the KIVA code which has been modified to include intake and exhaust flow processes with valves. New and improved sub models for wall jet interaction, mixing controlled combustion and one dimensional wave action have also been incorporated. The modified version of the program has been used to simulate a fuel injected two-stroke spark ignition engine and parametric studies have been undertaken. The simulated flow, combustion and exhaust emission characteristics over a wide range of operating conditions show the expected trends in behaviour observed in actual engines. In the second phase of this study, the air-assisted-fuel-injection (AAFI) process into a cylinder has been simulated with a high resolution computational grid. The simulation results are presented and compared with experimental data obtained using the Schlieren optical technique. An approximate method based on the conservation of mass, momentum and energy of the spray jet and using a comparatively coarse grid has been suggested for simulating the AAFI process. The simulation study predicts a high degree of atomisation of fuel spray with Sauter mean diameter around 10 μm even with moderate air and fuel pressures. The penetration and width of spray are simulated within 15% of the experimental values. In the last phase of this study, the flow and combustion processes have been studied for a four-stroke spark ignition engine with the AAFI process. The simulation results obtained using this approximate method have been validated with experimental data generated for the same engine configuration.