This thesis aims at investigating women’s force in development through engagement in informal, small-scale entrepreneurship. During fieldwork in Babati, Tanzania, network analyses and semi-structured interviews have been conducted, capturing responsibilities, challenges and opportunities of informal women entrepreneurs. The theoretical framework centres socio-economic analyses, through development and feminist economics. Two theories, about development through capital accumulation and cumulative processes, are compared and supplemented with a gender and empowerment perspective. The results are presented through narratives, complemented with a general picture. It is concluded that informal female entrepreneurs are important in development of Babati. They face challenges due to economic, social and gender-related conditions such as lack of capital, high interest rates, poverty, lack of education, malfunctioning government, discouraging men, and increased workload from domestic responsibilities. Their complex, informal networks, based on cooperation and solidarity, are seen as a driver in development. Top-down policies that fight gender norms, empower women, and identify informal workers can improve their situation, but for these to trickle down, a bottom-up approach is required. This thesis pushes for recognising that people living in poverty contribute to economic growth and development, and that empowerment of informal women entrepreneurs is essential for a profound, pro-poor development that trickles up.

The prewetting of a trickle-bed reactor has important implications in the design and operation of these reactors. This is because the prewetting changes the flow morphology (shape and texture) of the liquid flowing through the bed and leads to the existence of multiple hydrodynamic states. The extent of this change in flow morphology can be seen in the effect the prewetting of the reactor has on the pressure drop, liquid holdup and gas-liquid mass transfer. The following prewetting procedures were used: -- Levec-wetted: the bed is flooded and drained and after residual holdup stabilisation the gas and liquid flow is reintroduced -- Kan-wetted: the bed is operated in the pulse flow regime and liquid and gas flow rates are reduced to the desired set point -- Super-wetted: the bed is flooded and gas and liquid flow are introduced once draining commences For the pressure drop: -- The different prewetting procedures resulted in two distinct regions (Upper region Kan and Super-wetted, Lower region Dry and Levec-wetted) -- There was no significant difference between the Dry and Levec-wetted beds -- The pressure drop in the Kan and Super-wetted beds can be as much as seven times greater than the pressure drop in the Dry and Levec-wetted beds For the liquid holdup: -- The different prewetting procedures resulted in four distinct regions (Kan-wetted, Super-wetted, Levec-wetted, Dry bed) -- The liquid holdup in the Kan-wetted bed can be as much as four times greater than the liquid holdup in the Dry bed -- The liquid holdup in the Levec-wetted can be as much as thirty percent lower than the liquid holdup in the Kan-wetted bed For the gas-liquid mass transfer: -- The different prewetting procedures resulted in three distinct regions (Kan and Super-wetted, Levec-wetted, Dry bed) -- The volumetric gas-liquid mass transfer coefficient in the Kan and Super-wetted beds can be as much as six times greater than the mass transfer coefficient in the Dry bed -- The volumetric gas-liquid mass transfer coefficient in the Kan and Super-wetted beds can be as much as two and a half times greater than the mass transfer coefficient in the Levec-wetted bed While an increase in the liquid flow rate results in an increase in the pressure drop, liquid holdup and gas-liquid mass transfer for all of the experiments, the effect of increasing gas flow on the measured variables were more pronounced for the prewetted beds. In a prewetted bed (Kan, Super and Levec-wetted) an increase in the gas flow rate causes an increase in the volumetric gas-liquid mass transfer coefficient and a decrease in the liquid holdup. The decrease in the liquid holdup is due to the fact that the increased gas flow rate causes the films around the particles to thin and spread out. In the dry bed the flow is predominantly in the form of rivulets and the increase in gas flow rate does not affect the liquid holdup. In the case of the volumetric gas-liquid mass transfer coefficient the increased gas flow rate causes an increase in the mass transfer coefficient regardless of the prewetting procedure. This increase is due to the effect that the gas flow rate has on the liquid holdup as well as the increase in the gas-liquid interfacial area due to the increased gas-liquid interaction. If the pulsing in the Kan-wetted bed is induced by increasing the gas flow rate and keeping the liquid flow rate constant the results are significantly different. The pressure drop in the gas-pulsing experiments was lower than the pressure drop in the recorded in the Kan and Super-wetted beds, but higher than the pressure drop in the dry and Levec-wetted beds. However, the liquid holdup in the gas-pulsing experiments was higher than the liquid holdup in any of the other beds. The volumetric gas-liquid mass transfer coefficient in the gas-pulsing experiments was lower than the mass transfer coefficients of the Kan and Super-wetted beds, but higher than the mass transfer coefficients in the dry and Levec-wetted beds. The multiple operating points obtained from the different prewetting procedures are by no means the only possible operating points. By simply decreasing the draining time in the Levec-wetted bed steady state operating points can be found between those of the Super and Levec-wetted beds. This alludes to the fact that the operating conditions determined from the different prewetting modes are only boundaries and that the actual operating point can lie anywhere between these boundaries. The existence of these multiple hydrodynamic states complicates things further when a correlation is developed to determine the pressure drop, liquid holdup or the volumetric gas-liquid mass transfer coefficient. No correlation tested was able to accurately predict the pressure drop, liquid holdup or volumetric gas-liquid mass transfer coefficient in the dry or prewetted beds. / Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2007. / Chemical Engineering / unrestricted

The existence of multiple hydrodynamic states (MHS) in trickle bed operation has been proved by hysteresis observed in flow loops, as well as variation between different prewetting modes. The most common theory presented as explanation for the existence of MHS, is the film vs. rivulet concept. Based on this concept, it was suspected that in-situ upsets might promote the formations of films, thereby providing a method through which the hydrodynamic states of the Dry and Levec modes can be manipulated to perform like the Kan Liquid and Super modes. Large performance enhancements can be obtained by altering the prewetting procedure, even for systems with a low surface tension. For the water system, the gas liquid mass transfer coefficient of the Kan Liquid and Super modes could be as much as 6 times greater than that of the Dry mode. For the low surface tension system, the gas liquid mass transfer of the Kan Liquid and Super modes could be up to 8 times greater than that of the Dry mode. Through a thorough investigation of various types of transient upsets and manipulation strategies, it was confirmed that prewetting is indeed the only way by which drastic variation in hydrodynamic states may be obtained. None of the investigated upsets (hysteresis, periodic operation or surface tension doping) resulted in changes in the liquid morphology that could compare to the significant variation that was observed by varying the prewetting mode. Two methods were identified by which the hydrodynamic gaps between the less uniform (Dry and Levec) modes and the more uniform modes (Kan Liquid and Super) could be bridged. The first is to reduce the Levec draining time, while the second method may be seen as an in-situ type of Kan Liquid prewetting. This type of prewetting was obtained during doping with a low surface tension liquid, at a flow rate associated with the high interaction regime for the low surface tension system. Though the hysteresis cycles did not drastically alter the predominant flow type, interesting trends were observed, some of which raised doubt about the application of the films vs. rivulet concept. One mode in particular displayed behaviour which contributed to this doubt, namely the Kan Gas mode; • Gas liquid mass transfer on this mode decreased with an increase in liquid flow rate • Relatively low pressure drops on this mode corresponded to relatively high liquid holdup • It was the only mode that exhibited no hysteresis with gas flow variation, on any of the hydrodynamic parameters The various trends and variations observed with the different types of upsets, leads to the conclusion that the concept of films vs. rivulets simply does not provide adequate explanation of the observed results. In general, two flow types may be distinguished. That which is caused by an initial increase in liquid flow rate as opposed to that which is caused by an initial increase in gas flow rate An investigation to determine the behaviour of each of the investigated parameters near the transition boundaries on all the modes, as well as a repetition of this study with non-intrusive visual techniques is recommended. / Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2008. / Chemical Engineering / unrestricted

Trickle flow is encountered in a variety of process engineering applications where gas and liquid flow through a packed bed of stationary solid. Owing to the complexities of three interacting phases, a fundamentally exhaustive description of trickle flow hydrodynamics has not been achieved. A complicating factor in describing the hydrodynamics is the fact that the hydrodynamic state is dependent not only on the present operating conditions but also on their entire history, including fluid flow rate changes and pre-wetting procedures. This phenomenon is termed hydrodynamic multiplicity and is the subject of this work. Hydrodynamic multiplicity greatly complicates both the experimental investigation into the behaviour of a trickle flow column and the theoretical modelling of the observed behaviour. Broadly speaking, this study addresses hydrodynamic multiplicity on three levels. First, a conceptual framework is proposed that can be used to study hydrodynamic multiplicity with limited resources. It is based on the absolute limiting values that the hydrodynamic parameters can adopt for a certain set of conditions, and encompasses both flow rate hysteresis loops and pre-wetting procedures. There are 5 such hydrodynamic modes. When the existing literature is critically evaluated in light of this framework, it is established that the reported experimental studies have not addressed all the issues. Previous modelling attempts are also shown to be unable to qualitative explain all the existing data. Moreover, authors have suggested different (and often contradictory) physical mechanisms responsible for hydrodynamic multiplicity. Secondly, an experimental investigation intended to supplement the existing literature and illustrate the utility of the proposed framework is launched. This includes bed-scale measurements of liquid holdup, pressure drop and gas-liquid mass transfer for a variety of conditions including different flow rates, pressures, particle shapes, particle porosity and surface tension. The second part of the experimental effort uses radiography and tomography in new ways to visualise the temporal and spatial characteristics of the different hydrodynamic modes. The tomographic investigation incorporates advanced image processing techniques in order to culminate in a pore-level evaluation of the hydrodynamic modes that reveals additional features of hydrodynamic multiplicity. Thirdly, the experimental insights are condensed into a set of characteristic trends that highlight the features of hydrodynamic multiplicity. A pore-level capillary mechanism is then introduced to qualitatively explain the observed behaviour. The mechanism shows how the differences in advancing and receding contact angles and the characteristics of the packed structure (or pore geometries) are ultimately responsible for the observed hydrodynamic multiplicity behaviour. Lastly, the effect of hydrodynamic multiplicity on trickle bed reactor performance is discussed. It is established experimentally that depending on the reaction conditions, different modes yield optimal performance. The idea of optimizing the performance by manipulating the hydrodynamic state is introduced. In totality, this work advances the understanding of trickle flow hydrodynamics in general and hydrodynamic multiplicity in particular. / Thesis (PhD (Chemical Engineering))--University of Pretoria, 2008. / Chemical Engineering / unrestricted

Please read the abstract in the dissertation. Copyright / Dissertation (MEng)--University of Pretoria, 2011. / Chemical Engineering / unrestricted

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Enteral nutrition (EN) is often delayed in critically ill patients despite strong evidence to support that early enteral nutrition feeding is beneficial in this population. Adverse outcomes in critically ill patients in which nutrition is delayed include a longer length of stay and time on the ventilator, and a higher incidence of pneumonia and hospital mortality. The purpose of this literature review was to evaluate the current evidence regarding trophic enteral feeds in mechanically ventilated adult patients with acute respiratory distress syndrome (ARDS)/acute lung injury (ALI) and associated clinical outcomes. A retrospective literature review was performed to identify articles published on the topic of trophic feeds in mechanically ventilated adult patients with ALI/ARDS, with a focus on associated clinical outcomes. The studies included in this literature review indicated that the dose and timing of enteral nutrition in critically ill patients with ARDS/ALI had an effect on clinical outcomes. It is possible that additional variables such as the level of organ dysfunction and varying definitions for trophic enteral nutrition also influenced clinical outcomes. The United States (U.S.) and Canadian guidelines for nutrition supportrecommend either trophic or full EN for patients with ARDS/ALI on the basis that these two feeding strategies have similar patient outcomes over the first week of hospitalization. After reviewing the literature, we conclude that caution is warranted when following this recommendation. Regressions suggest full calorie enteral nutrition administered early in the course of critical illness significantly increased the odds of mortality, whereas full calorie enteral nutrition administered later reduced the odds of mortality.

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