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M.Sc. / Dense non-aqueous phase liquids (DNAPLs) are groups of chemicals often found beneath the water surface when chemical contamination of water occurs and they are called groundwater contaminants. Their improper storage and extensive use in industries as well as their slow degradation provide a long term source for of low level contamination of ground- and river water. Evidence from both human and animal studies suggests that volatile organic and organochlorinated compounds (specific types of DNAPLs), may increase host susceptibility to microbial infection, induce alterations in the maturation of effector immune cells and compromise immune surveillance mechanisms. These effects of DNAPLs hold special relevance for people living with HIV/AIDS. In light of this, the present study investigated the in vitro immunological effects of the two most common DNAPLs contaminants, Trichloroethylene (TCE) and Aroclor-1254 (ARO) in peripheral blood mononuclear cells (PBMCs) of immunocompromised and healthy donors. TCE and ARO were successfully dissolved in cell culture medium and added to freshly isolated PBMCs in a 1:1 ratio. Following incubation, cell functionality and cytotoxicity (or immunotoxicity) were assessed using MTT and LDH. Viability was confirmed and/or cell death analyzed by flow cytometry. Culture supernatants were used to assess NO and cytokine production as well as for quantification of viral replication. TCE and ARO induced a significant (p<0.05) decrease in cell viability/functionality in a dose-dependent manner. Flow cytometric analysis of cell death pathways indicated that TCE and ARO induced apoptosis. These chemicals also induced the secretion of both NO and proinflammatory cytokines suggesting that they may induce apoptosis via an inflammatory pathway, which may explain the mitochondrial dysfunction as determined by the MTT assay. ARO effects were more prominent than those of TCE, and both were more detrimental to HIV positive PBMCs compared to uninfected cells. The viral p24 levels increased in a dose-dependent fashion suggesting an effect for TCE and ARO on viral replication. This research concludes that DNAPL-contamination is detrimental to especially immuno-compromised systems.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2015. / Recently there has been signi cant interest in new types of metals called non-Fermi liquids, which cannot be described by Landau Fermi liquid theory. Landau Fermi liquid theory is a theoretical model used to describe low energy interacting fermions or quasiparticles. There is a growing interest in constructing an e ective eld theory for these types of metals. One of the paradigms to understand these metals is by the use of Wilsonian renormalization group (RG) to study a theoretical toy model consisting of fermions coupled to a gapless order parameter eld. Here we will study fermions coupled to gapless bosons (order parameter) below the upper critical dimension (d = 3). We will treat both fermions and bosons on equal footing and construct an e ective eld theory which only integrates out high momentum modes. Then we compute the one-loop RG ows for the Yukawa coupling and four-Fermi interaction. We will discuss log2 and log3 subleties associated with the one loop RG ows for the four-Fermi interaction and how they can be circumvented.

Silver nanoparticles (sub 10 nm), supported on, or in, cellulose, have been demonstrated to be well stabilised and immobilised during application in a model continuous reaction: the reduction of 4-nitrophenol (4-NP) to 4-aminophenol with sodium borohydride. The production of these silver nanoparticles (NP), within the cellulose supports, was carried out by either in situ reduction of silver precursors absorbed into the preformed cellulose supports, or, by inclusion of ex situ synthesised NPs (prepared in DMSO solutions) in the dissolution of cellulose and trapping upon subsequent coagulation of cellulose. The effects of NP synthesis method (affecting particle size and agglomeration) and the cellulose morphology and porous structure were examined with respect to the catalytic activity of the materials. The in situ reduction of a silver salt with aqueous NaBH4 solutions (0.03 to 1.0 wt. %) led to tuneable Ag NP sizes with mean diameters of 5 to 11 nm (TEM) and metal loadings of 0.5-1.0 wt. %. The catalytic activity of these samples in the 4-NP reduction reaction (0.05 mM, 0.167 M NaBH4, 30 °C) was demonstrated to increase upon decreasing NP size: TOF values of 22–356 h-1, consistent with a Langmuir-Hinshelwood mechanism. The porous structure of these Ag-cellulose materials (0.2 to 294 m2 g-1) was demonstrated to be variable and dependent on drying treatments of the regenerated cellulose hydrogel. Thermal drying, freeze-drying and critical point drying resulted in materials with different bulk structure and porosity. In turn the different porosities resulted in extremely different catalyst activities, e.g. Ag-cellulose catalyst (0.3 mm disks) thin film, hydrogel and cryogel phases exhibited TOF values of 2, 12 and 178 h-1, respectively. In addition, the NP synthesis could be carried out in either the cellulose hydrogel or cryogel, which led to different extents of Ag NP catalyst stabilisation against agglomeration during the 4-NP reaction and catalyst recovery and recycling. The Ag NPs synthesised in the cryogel cellulose disks were observed to undergo agglomeration (TEM) after use in 4 repeat batch reductions, whilst those NPs synthesised in the hydrogel cellulose, prior to freeze-drying to the final cryogel catalyst material, did not exhibit any agglomeration upon 4 repeat reduction reactions. The ex situ reduction of Ag and Au NPs was carried out by the reduction of AgOAc and Au(OAc)3 by DMSO and variation of the NP synthesis parameters, such as time (10 min – 1h) and temperature (50 – 80 °C), allowed for control of the NP sizes (3 to 6 nm Ag NPs and 4 to 11 nm Au NPs, TEM). It was demonstrated that the addition of the polysaccharide starch (0.42 wt. % in DMSO) allowed for consistent Ag NP size (ca. 4 nm) to be achieved throughout the 8 h synthesis, the starch acting as both the reducing and capping agent, maintaining the small sizes and narrow particle size distributions of the NPs upon aging (72 h). A kinetic model with a bimolecular nucleation step was developed to describe this reduction of the silver acetate by the starch/DMSO system. However, contact of the NPs with solutions of imidazolium ILs, 1-Ethyl-3-methylimidazolium acetate (EmimOAc) and 1-Butyl-3-methylimidazolium chloride (BmimCl) in DMSO, used in the dissolution of cellulose, led to the oxidation of the Ag(0) and Au(0) NPs. Thus, when these NP solutions were mixed in cellulose solutions regeneration by phase inversion with the aim of preparing cellulose/NP composites led to materials with negligible metal loadings (AAS). This oxidation, of the metal NPS, was partially overcome by stabilisation of the starch capped Ag NPs by pre-treatment with cellulose (1:1 mixture of α and MC cellulose). However, the activity of the resulting Ag-cellulose catalyst (0.5 wt. % AAS, 6.7 nm TEM) was much lower than the Ag-cellulose catalysts prepared by in situ reduction of silver in the cellulose hydrogel, despite the comparable NP sizes. This was presumed to be a result of encapsulation of the Ag NPs by the cellulose, leading to a decrease in the accessible surface of the NPs. Finally, the use of Ag NP / cellulose composites, prepared by in situ reduction of silver in cellulose hydrogel beads (0.19 wt. %, 6.4 nm), were demonstrated in the continuous reduction of 4-NP in a packed bed reactor (τ’ 100 g s dm-3). The activation energies of the reactions of 4-NP catalysed by the Ag-cellulose catalyst materials were determined (3.2 to 9.4 kJ mol-1) from Arrhenius plots, which demonstrated that above 20 °C the reaction was likely subject to diffusion limitations in the cellulose beads. The high degree of stabilisation of the Ag NPs against agglomeration imparted by the cellulose support was demonstrated: the rate of reaction was observed to be constant over 120 h, treating 45 L of 4-NP solution, with the catalyst material after use demonstrating no significant leaching of silver, or agglomeration, of NPs (AAS, TEM).

Typescript (photocopy). / Digitized by Kansas Correctional Industries

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Systems known as complex materials have key attributes that contribute to their designation as "complex''. For example, evolving dynamical properties add complexity, as is observed in supercooled liquids. Polymers and proteins are structurally complex as they can fold in different conformations, with these different conformations affecting different biological functions or physical properties. Complex materials generally have interesting macroscopic properties that are difficult to predict from their microscopic (molecular) constituents. The connection between microscopic features and macroscopic properties in these materials has been a subject of study for decades, yet the ability to wield strong predictive power in these materials remains elusive. Imaging can provide information in both space and time necessary to understand how the microscopic details in these materials yield the observed macroscopic properties. Moreover, time-sequenced imaging allows one to understand how these properties might evolve. To image these details however, requires high resolution in both time and space. Unfortunately, obtaining images and extracting information from these images becomes quite difficult as the length scales of interest become small, especially when signal-to-background ratios are low. My dissertation work addresses the challenge of extracting such information by developing quantitative methods to circumvent obstacles related to obfuscation from low signal as well as the diffraction limit, with high-throughput and high-resolution. I apply these techniques towards the study of the following complex materials via imaging: (1) single molecules rotating in a supercooled liquid (2) conjugated polymers containing multiple emitters within the diffraction limit (3) solvent vapor annealing mediated conjugated polymer aggregation and (4) collagen gels during their formation and perturbation. The first chapter describes how the local dynamics in a supercooled liquid may be assessed by the rotations of single-molecule probes. To resolve rotations however, requires splitting the fluorescence signal from single-molecules into orthogonal polarizations thereby reducing the already low signal-to-background ratio (SBR) expected from single-molecule experiments. The data is further complicated by instances of photoblinking and out-of-plane rotation, when only background signal is present. A convenient method for excluding background signal was developed via a Monte Carlo simulation for discriminating points in the trajectory composed only of background signal that is robust to SBR. These simulations also showed an SBR dependance for the accuracy of the values extracted from rotational autocorrelation functions. This method was used experimentally to directly demonstrate ergodicity in supercooled liquids. The next chapter focuses on conjugated polymers, which display a complex relationship between chain conformation and photophysics. This conformational complexity exists even at the single-chain level, obscuring the understanding of how excitons behave in the bulk, such as in a device. Understanding this relationship however, is difficult as conformation and photophysics are hard to access in operando not only because a single conjugated polymer chain is smaller than the diffraction limit, but also because a fluorescing conjugated polymer emits light from many locations. The overall conformation is typically assessed using polarization modulation measurements, which only provide mesoscale information about a chain's conformation. A super-resolution method was developed to map the distribution of emitters and trace out single-chain conformation. The extracted radii of gyration for these single-chains matched well with polymer theory. Chapter three describes the development of experimental and image analytical tools to bridge single-chain studies of photophysics in conjugated polymer, to the photophysics that might be observed in a conjugated polymer device where chain-chain contacts and high levels of local ordering may be present. It has been shown previously that solvent vapor annealing can be used to prepare conjugated polymer aggregates of various levels of internal ordering. However, solvent vapor annealing is a process that is difficult to control and difficult to evaluate. Therefore, a first-of-its-kind apparatus was constructed that can generate and deliver solvent vapor in a controlled fashion to swell polymer films while monitoring both film dynamics by fluorescence imaging as well as swelling extent via a quartz crystal microbalance. Fluorescent images acquired during aggregation showed heterogeneous diffusion among aggregates, possibly indicating heterogeneous sizing. Fluorescent characterization of presumably differently sized aggregates indicates a possible emergent quenching phenomenon in a bulk conjugated polymer material. The final chapter of this dissertation describes an effort to characterize dynamics in collagen gels. Collagen gels form through a complex sol-gel process precipitated by nucleation and growth fibrillogenesis. To probe the long length scales of interest here, single-molecule methods were not practical. Instead, an optical flow algorithm was explored to detect key physical events in the evolving system. One effort aims to characterize the dynamics of the early gelation process. In particular, the optical flow measurements provide a high-resolution measure for the moment at which the sol-gel transition occurs. Another application involves the use of optical flow to observe distortions in the collagen network while it is undergoing strain stiffening. Preliminary studies show that at critical strain, local breaks in the gel propagate throughout the gel until the gel completely loses its ability to sustain stress. In general, the ability to quantify details about complex materials from imaging data can be quite a complex endeavor itself, requiring awareness of the physical phenomena of interest, how said phenomena manifests optically, and the use and development of appropriate algorithms. As described in this dissertation, the proper use and/or development of the proper image analysis methods allow for extraction of key information from dense data.

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In spite of their importance in many systems, liquid surfaces have been explored at the microscopic level to a much lesser extent than solids. Most surface analysis must take place in vacuum, a major drawback for liquids. The technique of time-of-flight scattering and recoil spectrometry (TOF-SARS) has been applied to molecular liquid surfaces for the first time. The apparatus borrows key elements from previous TOF-SARS experiments on solids and from molecular beam scattering (MBS) and features excellent surface specificity and the ability to detect all elements. A high-vacuum time-of-flight spectrometer was developed for the purpose of measuring the surface atomic concentration of atoms in low-vapor pressure liquid samples, and hence to infer preferred surface orientations. The TOF-SARS experiment involves surface bombardment with inert gas ions in the 1-3 keV energy range. During the interaction surface atoms may either (a) induce scattering of primary ions or (b) recoil from the surface. A binary collision model describes the kinematics and dynamics of the interactions well, allowing prediction of velocities and probabilities of particles leaving the surface. Particles that reach a detector along a ~1.1 m flight path are separated by velocity, and signals are collected as a histogram, revealing relative measured intensities that are converted to ratios of accessible surface atoms. Comparing the measured atomic ratios with computer-simulated accessible atomic ratios for various possible orientations gives insight into preferred surface orientation. A number of systems were explored m this work: liquids including a complementary pair of molecules having distinct 'head-tails' structures; glycerol as a highly H-bonded system, and a room-temperature molten salt. Preliminary results reveal that surface molecules appear in most cases to adopt some preferred orientation at the interface. The TOF-SARS technique was able to distinguish 'head' from 'tail' in molecules exhibiting that structure, suggesting only part of the head was accessible. In glycerol, all but two possible orientations were ruled out but the symmetrical nature of the molecule prohibits definitive assignment. The ionic liquid was found to have the cation and anion sharing the surface population roughly equally, and a preferred orientation for the substituted aromatic anion was discovered. / Graduation date: 2000