Hemodialysis is a renal replacement therapy that removes waste solutes from the blood stream using concentration gradients across a membrane. In order to overcome several shortcomings and increase the waste removal rate, a new dialyzer (filter) design is proposed in this study. In the new dialyzer design, the blood concurrently flows with a sheath fluid in a micro-fluidic channel. Because the blood stream directly contacts the sheath stream, it is important to prevent blood cell migration from the blood stream to the sheath stream while providing enough time for the waste solutes to diffuse into the sheath stream. This research was intended to understand the migration behavior of red blood cells (RBC) and platelets in non-uniform suspension flow, where the blood and sheath flows in direct contact, and apply the results to identify the feasible design space of the proposed dialyzer. The effect of different flow conditions and channel geometry on the blood cell extraction ratios (ER), the ratio of cells lost into the sheath stream, in non-uniform suspension flows was parametrically studied using Lattice Boltzmann and Spectrin Link (LB-SL) method based direct numerical simulation (DNS). Analyzing ER over the flow distance showed that the channel size and the area ratio of sheath to channel are the main variables that affect the ER. Based on the relationship found, a meta-model of RBC ER was created, although platelet ERs showed only a general trend. Based on the study, feasible conditions that will retain blood cells in the blood stream were identified. Then, the DNS results of blood cell ER were used with a molecule diffusion model and a hemodialysis system model to study the feasibility of the proposed dialyzer design that maximizes middle molecule filtration with limited blood cell and protein loss. No feasible design was found in the studied range suggesting that relying purely on the diffusion based on the direct contact for the removal of middle molecules is not a feasible solution with the small channel size (~700 µm) due to the loss of protein. It suggested that in order to increase the middle molecule removal while maintain the protein level, clearance ratio of middle molecule to protein should be increased using large channel size, small sheath stream thickness, long tubule length, and slow blood flow velocity. The intellectual merit of this research lies in understanding the migration behavior of blood cells in a non-uniform suspension. This knowledge helped to establish the feasibility of the proposed dialyzer design and can be applied in a variety of applications for the manipulation of cells in a micro-fluidic channel.

Over the past years, levee failures during floods have caused significant losses of lives and properties in the nation. Majority of these failures were induced by seepage through granular foundation soils underneath the top soil on which the levees were built. One of methods to mitigate this phenomenon includes the treatment of the granular soil deposits with an engineered fluid delivered by permeation (permeation grouting), resulting in a less pervious deposit. Since the conventional cement-based suspensions and chemical solutions may cause groundwater contamination due to long term reaction with groundwater, clay suspension such as bentonite suspension can be an alternative in terms of environmental friendliness and long-term safety. Moreover, the suspensions, after being permeated, are expected to be stable in the pore space due to the thixotropic nature of bentonite. The main challenge in this approach is being able to permeate a concentrated suspension through the pores of a granular material. To achieve a significant reduction in the hydraulic conductivity, concentrated bentonite suspensions should be used; however, concentrated suspensions can have low mobility, resulting in a low penetration depth and little practical application. The main objective of this study is to investigate the permeation of concentrated bentonite suspensions by controlling their rheological properties. The first portion of this research focuses on measuring the rheological properties of the various engineered bentonite suspensions over time. The second point of focus of this research is the parameters affecting the flow of the bentonite suspensions through granular soils, and the final focal area is determining the hydraulic performance of the grouted granular soils. In order to achieve these objectives, an experimental program was developed in this research. First, rheological tests were performed with the bentonite suspensions with and without various concentrations of sodium pyrophosphate (SPP); SPP is an ionic additive that is used to reduce the initial yield stress and viscosity of bentonite suspensions. A stress controlled test with the vane geometry produced rheological parameters with a minimal disturbance. Suspensions were stored in sealed cups and tested at various times to measure the long term thixotropic changes in yield stress and viscosity. Second, the various concentrations of the bentonite suspensions were injected at a constant pressure through clean sands which were prepared at various conditions (relative density, fine contents, and grain size) in order to investigate soil and suspension parameters affecting the flow of the bentonite suspensions. The results from these experimental tests were utilized to develop a groutability criterion of bentonite suspensions for practical purposes. Finally, the saturated hydraulic conductivity of the treated soils was measured using falling and rising head method. The traditional concept of “clay void ratio” was re-examined. The results from this study showed that the modified bentonite suspensions could be used as an alternative grout in permeation grouting to improve hydraulic performance of the permeable granular soils. / text

A recently mandated change in the use of pharmaceutical propellants spurred the development and reevaluation of aerosolized pharmaceuticals. Chlorofluorocarbon (CFC) propellants were commonly used in pressurized metered dose inhalers (MDIs), but were unfortunately linked to the depletion of the ozone layer. As such, a search for new propellants was initiated and ultimately resulted in the implementation of hydrofluoroalkane (HFA) propellants in MDIs. These HFA propellants however demonstrated significantly different properties than CFCs and necessitated a considerable amount of reformulation efforts. Not only did HFAs demonstrate different physiochemical properties, but in some cases these differences necessitated reengineering of the delivery device. Unfortunately HFA propellants are considered greenhouse gasses, albeit to a lesser degree than CFCs, so the development of alternate delivery methods has been ongoing. One delivery method that has received significant attention and resources is dry powder inhalers (DPIs). DPIs are a propellant-free alternative to aerosolized drug delivery, and demonstrate some advantages and disadvantages compared to the use of MDIs and nebulizers.In addition to the modernization of pharmaceutical agents, excipients, and delivery devices, technological advances have allowed for different and/or improved characterization of pharmaceutical aerosols. Particle size characteristics of aerosols are the primary physical measure examined and are relevant to ensure proper and reproducible drug delivery to the lung. Likewise, chemical analysis of the pharmaceutical agent is extremely important for pharmaceutical development and monitoring, including solubility determination, stability monitoring, and ultimately, dose emitted. Because many limitations exist in characterization however, and because experimental means can be costly with regard to labor and materials, prediction of aerosol performance characteristics based on formulation and device variables are valuable.Previous work predicting the performance of solution based MDIs has opened the door for improved prediction of suspension based MDI systems. Suspension aerosol prediction has been examined in the past, but additional information is now available to more appropriately model suspension MDI systems that include polydisperse drug material and emit polydisperse droplets.

I examined the suspension feeding of four freshwater unionid mussels, Elliptio complanata, Elliptio dilatata, Fusconaia flava and Strophitus undulatus to help explain how more than 30 species can coexist in a single river, as well as to contribute new insights into their basic biology. I examined whether the flux of algae affected the suspension feeding (clearance rate, CR) of unionids in a flow chamber. CR varied with seston flux (J = UC, where U is the velocity and C is the algal concentration) for the 4 species examined. The lotic species (E. dilatata) cleared up to four times more water than lentic species (E. complanata). Differences in CRs were found among E. dilatata, F. flava, and S. undulatus from the same hydrodynamic habitat at the highest flux tested; the CR of E. dilatata varied with the hydrodynamics of its native river. These results provide new insight into how seston flux influences unionid suspension feeding, which may help to explain niche breadth in this group.

No description available.

This work describes the development of a microfluidic platform that can be used to study suspension stability and crystallization with in droplets as a function of time and concentration. Techniques for monodisperse droplet formation, droplet trapping and storage, and droplet dehydration are developed and used to design a microfluidic platform that can be adapted for the applications of interest. A geometric model is developed to predict the droplet shape and emulsion structure generated by microfluidic nozzles. However, droplet volume and structure spacing cannot be independently controlled using microfluidic nozzles, and a design consisting of an array of traps is considered to achieve the desired structure for stable, extended droplet observation. The dehydration of aqueous droplets stored in the array is characterized as a function of relative humidity, and is shown to be reasonably estimated as a species diffusing from a sphere into an infinite medium. The microfluidic platform for droplet dehydration is combined with particle tracking to show that the stability of particle suspensions can be probed as a function of salt concentration. The flocculation behavior observed in the trapped droplets agrees well with corresponding macroscale measurements as well as with previously published studies. The platform is also used to generate substantial sample sizes to measure nucleation statistics and crystal growth rates of glycine as a function of initial concentration, environmental conditions, and the presence of additives. These applications show proof of concept that the microfluidic platform is a useful tool for the analysis of the behavior observed during particle aggregation and crystallization.

Current physical supports used in cryogenic storage vessels, in which liquid hydrogen is stored, conduct heat from the environment to the liquid hydrogen which causes the hydrogen temperature to rise and ultimately leads to hydrogen losses due to boil-off. The focus of this study is to investigate magnetic levitation as a possible suspension mechanism, eliminating the use of current physical supports and so doing reducing hydrogen losses due to boil-off. A conceptual design of a container which makes use of magnetic suspension is presented in this study. The concept is validated on the basis of the forces obtainable between a paramagnetic aluminium plate and an electromagnet, as well as the forces obtainable between a neodymium magnet and a bulk Yttrium-Barium-Copper-Oxide superconductor. The forces between the paramagnetic aluminium plate and electromagnet were determined mathematically and tested experimentally. The forces between the magnet and superconductor were determined mathematically and by finite element modelling and simulations using ANSYS Multiphysics. The results obtained in the mathematical- and finite element studies were then validated experimentally. It was found that the forces obtained experimentally between the aluminium plate and electromagnets are inadequate for magnetic suspension of the inner vessel given in the conceptual design. It was also found that the forces obtained experimentally and in the simulation studies for the magnet and superconductor of this study were inadequate due to shortcomings in the magnet and superconductor obtained for experimental tests. The conclusion of this study is that electromagnetic levitation should not be used as a magnetic suspension mechanism for storage of liquid hydrogen. It is also concluded that superconducting levitation can not be used as a suspension mechanism for the concept presented in this study, unless the methods suggested to increase the levitation forces between the neodymium magnet and superconductor are executed. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

Current physical supports used in cryogenic storage vessels, in which liquid hydrogen is stored, conduct heat from the environment to the liquid hydrogen which causes the hydrogen temperature to rise and ultimately leads to hydrogen losses due to boil-off. The focus of this study is to investigate magnetic levitation as a possible suspension mechanism, eliminating the use of current physical supports and so doing reducing hydrogen losses due to boil-off. A conceptual design of a container which makes use of magnetic suspension is presented in this study. The concept is validated on the basis of the forces obtainable between a paramagnetic aluminium plate and an electromagnet, as well as the forces obtainable between a neodymium magnet and a bulk Yttrium-Barium-Copper-Oxide superconductor. The forces between the paramagnetic aluminium plate and electromagnet were determined mathematically and tested experimentally. The forces between the magnet and superconductor were determined mathematically and by finite element modelling and simulations using ANSYS Multiphysics. The results obtained in the mathematical- and finite element studies were then validated experimentally. It was found that the forces obtained experimentally between the aluminium plate and electromagnets are inadequate for magnetic suspension of the inner vessel given in the conceptual design. It was also found that the forces obtained experimentally and in the simulation studies for the magnet and superconductor of this study were inadequate due to shortcomings in the magnet and superconductor obtained for experimental tests. The conclusion of this study is that electromagnetic levitation should not be used as a magnetic suspension mechanism for storage of liquid hydrogen. It is also concluded that superconducting levitation can not be used as a suspension mechanism for the concept presented in this study, unless the methods suggested to increase the levitation forces between the neodymium magnet and superconductor are executed. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

Optical nephelometry is the measurement of the angular distribution of light scattered from a particle suspension. Experimental nephelometers confirm the predictions of optical models and their readings are inverted to determine properties of unknown suspensions. Single scattering models, which assume a single particle interaction prior to detection, are used to model tenuous suspensions in the nephelometer. Multiple scattering models can be used to obtain higher-order solutions, but lack generality. Any given method addresses some subset of possible problems, e.g. tenuous or dense suspensions, small or large particles. This thesis explores the feasibility of using empirical models to extrapolate the single scattering approach in a non-linear manner, improving the generality of a multiple-scattering description. Initially, single scattering (Mie) theory for spherical particles is presented and extended to polydispersions of particles and to spectral scattering. The principle of integrating the single scattering result over a finite scattering volume is examined as a precursor to modelling the actual nephelometer. A low-cost, PC controlled scanning nephelometer is developed with a 0.9° resolution and ±150° range and a small (-25ml) volume sample cell. The photodiode detector has a numerical aperture of 0.079, providing, for most angles, a scattering volume with length 10mm and cross-section determined by the HeNe laser source ('-1mrn 2). The optics of the air/glass/water interfaces and of single and first-order multiple scattering over the scattering volume are modelled. These models are found to predict the scattering footprints observed in tenuous suspensions of spherical latex particles. Experimental data are obtained from tenuous to relatively dense (5% by volume) suspensions of latex spheres over a size range of 54nm to 14tm. These data are compared with single and first-order multiple scattering and their form and dependencies are considered. They are used to train an empirical neural (multi-layer perceptron) model of the multiple scattering based on particle characteristics and on the scattering footprint of the individual particles. This non-linear extrapolation of the single scattering model is applied to the nephelometer, improving the generality over a purely theoretical multiple scattering approach. The trained neural model is used, initially, to investigate some of the empirical characteristics of the multiple scattering process.

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