M.Com. (Economics) / The objective of this study was to obtain information that will enable the identification of the role, nature and magnitude of private road freight transport in the South African economy. The underlying rationale was the lack of information in this regard in South Africa. Information about private road freight transport was obtained on a sectoral basis by means of a literature analysis and an empirical investigation.

Thesis (Ph.D.)--University of the Witwatersrand, Faculty of Science, 1998. / This study was initiated in order to determine the identities and distribution patterns of the anopheline fauna, more especially the malaria vectors, in regions of Botswana prone to malaria epidemics. Field samples collected from Shakawe, Maun and Kasane over three consecutive years were subjected to morphological, cytogenetic, isoenzyme and PCR analyses. The results established that Anopheles arabiensis and Anopheles funestus were the predominant vector species.

Estudos recentes em materiais unidimensionais indicaram a necessidade de alterações na equação da dinâmica de captura de portadores por armadilhas. As experiências de Haarer e Möhwald em fenantreno PMDA mostraram que o tempo de captura das armadilhas decai linearmente com o campo elétrico, a partir de um campo crítico. Neste caso podemos admitir a substituição da fórmula clássica do tempo de captura pela razão entre a distância entre as armadilhas e a velocidade do portador sob ação do campo elétrico. A velocidade do portador devido ao campo é dada pelo produto da mobiliade do portador pelo campo elétrico. Assim, a equação de balanço de cargas nas armadilhas fica alterada pelo aparecimento explícito do campo elétrico, ocasionando mudanças no próprio processo de transporte. Neste trabalho, tentou-se encontrar o comportamento de materiais unidimensionais, na região de campo de ocorrência deste fenômeno e em suas proximidades, estudando-se a característica voltagem-corrente, bem como alguns processos transientes de tratamento analítico ameno. / Recent studies in one-dimensional systems show that the trapping equations must be changed. Haarer and Möhwald experiments on Phenanthrene PMDA showed that the trapping time decays linearly with the electric field, from a critical field on. Therefore we can assume that one should substitute the classical formula of the trapping time by the ratio between the intertrap distance and the drift velocity. The drift velocity is given by the product of the carrier mobility by the field. Thus the equation of carrier trapping becomes modified by the explicit dependence on the field that leads to changes in the transport itself. In this work we tried to find the response of a material in which such behavior is observed, by studying the current voltage characteristic, and also some transient processes amenable to analytical treatment.

by Chu Chi Yuen, Andrew. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 140-153). / Abstract also in Chinese. / ABSTRACT --- p.i / Chapter 1 --- INTRODUCTION --- p.3 / Chapter 1.1 --- Using Low density lipoprotein (LDL) as a drug carrier --- p.4 / Chapter 1.1.1 --- The structure of Low density lipoprotein (LDL) --- p.4 / Chapter 1.1.2 --- The metabolic pathway of LDL in human bodies --- p.4 / Chapter 1.1.3 --- The rationale for using LDL as a drug carrier --- p.7 / Chapter 1.1.4 --- Reconstitution of LDL with cytotoxic drugs --- p.9 / Chapter 1.1.5 --- Up and down regulation of LDL receptors --- p.11 / Chapter 1.2 --- Doxorubicin (DOX) --- p.12 / Chapter 1.2.1 --- Characteristics of DOX --- p.12 / Chapter 1.2.2 --- Drug actions of DOX --- p.14 / Chapter 1.2.3 --- The adverse side effects of DOX --- p.15 / Chapter 1.3 --- Multidrug resistance phenomenon in tumor cells --- p.17 / Chapter 1.3.1 --- The possible mechanisms of multidrug resistance --- p.19 / Chapter 1.3.2 --- The structure of P-glycoprotein --- p.20 / Chapter 1.3.3 --- The mechanisms of the P-glycoprotein --- p.22 / Chapter 1.3.4 --- Our aim in dealing with multidrug resistance --- p.22 / Chapter 2 --- MATERIALS AND METHODS --- p.23 / Chapter 2.1 --- Materials --- p.23 / Chapter 2.1.1 --- Animals --- p.23 / Chapter 2.1.2 --- Buffers --- p.24 / Chapter 2.1.3 --- Culture media --- p.25 / Chapter 2.1.4 --- Chemicals --- p.26 / Chapter 2.1.5 --- Culture of cells --- p.27 / Chapter 2.2 --- Methods --- p.29 / Chapter 2.2.1 --- In vitro studies --- p.29 / Chapter 2.2.2 --- In vivo studies --- p.44 / Chapter 3 --- RESULTS --- p.51 / Chapter 3.1 --- In vitro studies --- p.51 / Chapter 3.1.1 --- Preparation of LDL-DOX --- p.51 / Chapter 3.1.2 --- Comparison of the cytotoxicity of DOX and LDL-DOX on HepG2 cells --- p.59 / Chapter 3.1.3 --- Modulation of LDL receptors on HepG2 cells and ECV304 cells… --- p.63 / Chapter 3.1.4 --- The effect of combined treatment of LDL-DOX and hyperthermia on HepG2 cells --- p.84 / Chapter 3.1.5 --- The effect of LDL-DOX on resistant cell line R-HepG2 cells --- p.90 / Chapter 3.2 --- In vivo studies --- p.105 / Chapter 3.2.1 --- The comparison of organ distribution of LDL-DOX and DOXin BALB-c mice after administration --- p.105 / Chapter 3.2.2 --- The comparison of organ distribution of LDL-DOX and DOX in nude mice bearing HepG2 cells after adminstration --- p.108 / Chapter 3.2.3 --- Histological studies of heart of nude mice bearing HepG2 cells treated with DOX and LDL-DOX --- p.111 / Chapter 3.2.4 --- Myocardial injury measured by Lactate dehydrogenase (LDH) activity in nude mice bearing HepG2 treated with DOX and LDL- DOX --- p.117 / Chapter 3.2.5 --- The comparison of DOX and LDL-DOX on reducing the tumor sizes and weight in nude mice bearing HepG2 cells --- p.119 / Chapter 4 --- DISCUSSION --- p.122 / Chapter 4.1 --- In vitro studies --- p.122 / Chapter 4.1.1 --- Preparation of LDL-DOX complex --- p.122 / Chapter 4.1.2 --- The cytotoxicity ofLDL-DOX --- p.125 / Chapter 4.1.3 --- The combined treatment of hyperthermia and LDL-DOX --- p.129 / Chapter 4.1.4 --- The ability of LDL-DOX to circumvent muiltidrug resistance --- p.131 / Chapter 4.2 --- In vivo studies --- p.134 / Chapter 5 --- CONCLUSION --- p.136 / Chapter 5.1 --- Conclusion --- p.136 / Chapter 5.2 --- Future pospective --- p.139 / BIBLIOGRAPHY --- p.140

The field of nanomedicine has witnessed an incredible expansion, from a total market value in 2003 of $500 million expected to rise to $160 billion by 2015 (Global Industry Analysts, Inc.). The nanomedicine industry is forecasted to grow and have a significant impact on the economy, with sectors such as biomaterials, diagnostics and drug delivery expected to play a major role. This thesis gives a detailed account of the synthesis and characterisation of molecularly imprinted nanogels for drug delivery. Their toxicity and potential use as a targeted carrier to cancerous cells is evaluated. Initially an overview of nanomaterials and their uses in many areas such as agriculture, energy storage and technology are discussed. The impact of nanomaterials on the life sciences is examined; in particular their application in drug delivery is focussed upon. Chapters 2, 3 and 4 make up the results and discussion of this work. Chapter 2 focuses on developing the synthesis of the acrylamide based nanogels and, vitally, incorporating a suitable fluorescent tag in order to track the nanogels in vitro and in vivo. Fundamentally toxicity studies carried out on the nanogels, both in vitro and in vivo in Danio rerio (zebrafish) are reported in Chapter 3 to ensure the nanogels are biocompatible. Chapter 4 introduces an innovative approach, molecular imprinting, to incorporating a drug into the nanogels. The upload and release of Tamoxifen (a drug used to treat breast cancer) at reduced pH, was also analysed. Finally future development of the carrier is discussed and key issues that need to be addressed.

There is a growing interest in micro sized vehicles with the function of storing, targeting and controlled releasing of substances during the past few decades. However, delivering the desired drugs inside micro containers to living cells is a particular challenging topic of material science. Microcapsules made of polyelectrolyte multilayers exhibit low- or non-toxicity, appropriate mechanical stability, variable degradation and can incorporate remotely addressable release mechanisms in responding to stimuli and external triggering, making them well suitable for targeted drug delivery to live cells. This study investigates interactions between microcapsules made of synthetic (i.e. PSS/PAH) or natural (i.e. DS/PArg) polyelectrolyte and cells, with particular focus on the effect of the glycocalyx layer on the intake of microcapsules by human umbilical vein endothelial cells (HUVECs). Neuraminidase cleaves N-acetyl neuraminic acid residues of glycoproteins and targets the sialic acid component of the glycocalyx on the cell membrane. Three-dimensional CLSM images reveal that microcapsules functionalized with neuraminidase can be internalized by endothelial cells, whereas ones without neuraminidase are blocked by the glycocalyx layer. Uptake of the microcapsules is most significant in the first 2 hours. Following their internalization by endothelial cells, biodegradable DS/PArg capsules rupture by day 5, however, there is no obvious change in the shape and integrity of PSS/PAH capsules within the period of observation. Results from the study support our hypothesis that the glycocalyx functions as an endothelium barrier to cross membrane movement of microcapsules. Neuraminidase-loaded microcapsules can enter endothelial cells by cleaving the glycocalyx in their close proximity with minimum disruption of the glycocalyx layer, therefore they have high potential to act as drug delivery carriers to pass through the endothelium barrier of blood vessels into the surrounding tissue.

This dissertation considers the interconnections between trade and transportation. Through various theoretical and empirical analyses, I provide novel evidence of the simultaneity of trade and transportation, of spillover effects across integrated transport markets, and of the influence of the international transport sector on trade policy effectiveness and natural disaster induced trade disruptions. In the first substantive chapter, I develop a model of international trade and transportation. Accounting for the joint-production present in the international container shipping industry, I illustrate that freight rates adjust to differences in the international demands for transport and can result in balanced or imbalanced equilibrium trade in the presence of asymmetric freight rates. The empirical results exhibit the simultaneity of international trade and transportation costs and show that the dependence of transport costs on the trade imbalance can lead to spillover effects across bilateral export and import markets. In the second substantive chapter, I investigate the effects of maritime trade policy on bilateral trade in the presence of trade imbalances. Using the previously developed model, I show that the trade elasticities with respect to carrier costs vary systematically across transport markets, bilateral trade imbalances and differentiated products. Empirically, I estimate the varying effects of an EU environmental policy on U.S.-EU trade and provide strong evidence in support of the theoretical results. In the third substantive chapter, I analyze the dynamics and spatial distribution of the trade effects induced by natural disasters. I develop a spatial gravity model of international trade and apply the model to monthly US port level trade data. Empirically, I estimate the dynamic evolution of trade effects caused by Hurricane Katrina differentiating trade disruptions at the local port level. The estimates point to the static and dynamic resilience of international trade. While ports closest to Katrina's epicenter experience significant short-run reductions that can be of permanent nature, international trade handled by nearby ports rises in response to this disaster, both in the short- and in the long-run. Overall, the analysis underlines the significance of local infrastructure networks to reduce the devastation inflicted by natural disasters. This dissertation includes previously unpublished co-authored material.

Aim of thesis: Immuno-stimulating complexes (ISCOMs) are particulate vaccine delivery systems composed of Quillaja saponins, cholesterol and phospholipid. ISCOMs are typically spherical cage-like structures with a diameter of 40 nm and carry a negative charge. Incorporation of the respective vaccine antigen into the particles generates more potent vaccines than a simple mixture of both vaccine components. This requires the antigen to display either hydrophobic domains or positive charges, which allow interaction with the ISCOM particles. However, not all antigens fulfil this requirement and modification of these becomes necessary. Hence, the aim of this study was to design novel preparations of ISCOMs with a positive charge, suitable for adsorption of native hydrophilic antigens and poly-nucleotides, and test their potential as a novel vaccine carrier platform. Methods: Two cationic lipids, DC-cholesterol and DOTAP, were selected to prepare the cationic modifications of ISCOMs. DC-cholesterol substituted for cholesterol in classical ISCOMs, whereas DOTAP substituted for their phospholipid component. The phase behaviour of colloidal systems containing Quil-A, phosphatidylcholine (PC) and DC-cholesterol and of colloidal systems comprised of Quil-A, cholesterol and DOTAP was studied by transmission electron microscopy (TEM). Lipid-film hydration was utilised as the first method to prepare these colloidal systems. Selected compositions containing either DC-cholesterol or DOTAP were also prepared by dialysis as second method. A novel third method for preparing homogenous dispersions of classical ISCOMs was developed utilising ethanol injection. This method was also applied in an attempt to prepare cationic modifications of ISCOMs including DC-cholesterol and DOTAP. As in the colloidal systems comprising Quil-A, PC and DC-cholesterol transformations of structures were observed upon dilution with aqueous solutions, these transitions were also studied on classical ISCOMs using TEM and dynamic light scattering techniques. Loading of cationic colloidal structures composed of Quil-A, PC and DC-cholesterol was performed with the model protein antigen ovalbumin (OVA) and a model plasmid, and the resulting structures were analysed by fluorescence spectroscopy, TEM and gel electrophoresis. The immunological properties of non-loaded and OVA-loaded structures were studied in terms of their ability to activate murine bone marrow derived dendritic cells (mBMDC) as antigen presenting cells (APC) and OVA-specific CD8+ T cells in vitro. Results: Substitution of cholesterol in classical ISCOMs with DC-cholesterol resulted in the formation of cationic cage-like structures similar to the classical particles. These were observed in pseudo-ternary Quil-A:PC:DC-cholesterol systems and even in pseudo-binary Quil-A:DC-cholesterol systems prepared by lipid-film hydration. Compositions at which cage-like structures were observed included high weight proportions of DC-cholesterol (> 60%). However, samples were relatively heterogeneous, and aggregation of colloidal structures was observed at equimolar ratios of Quil-A and DC-cholesterol. The ionic strength, pH and composition of the hydration buffer were demonstrated to be important variables influencing the formation of cage-like structures. Morphological changes of pre-formed cationic cage-like structures were observed upon dilution. However, classical anionic ISCOMs showed a similar behaviour. The numbers of cationic cage-like structures appeared to increase upon prolonged storage of samples. Purification of structures and longitudinal analysis of their composition suggested an increased formation of stoichiometrically defined DC-cholesterol:Quil-A:PC complexes over time, rather than a change in composition. The substitution of phospholipid in classical ISCOMs with DOTAP also resulted in heterogeneous dispersions, and aggregation of colloidal structures was observed at equimolar ratios of Quil-A and DOTAP. Phase separation phenomena were proposed based on TEM observations. However, the formation of cage-like particles with a positive [zeta]-potential was not observed. Although ethanol injection was introduced as a novel method to prepare classical ISCOMs, its application did not result in more homogenous dispersions of cationic colloidal structures containing DC-cholesterol or DOTAP. Dialysis also failed to produce higher numbers of well-defined cationic particles, although using this method homogeneous, anionic ISCOM-like particles containing DOTAP were obtained. The efficient adsorption of OVA and plasmid DNA onto cationic structures containing Quil-A, PC and DC-cholesterol was demonstrated. The adsorption process was accompanied with a decrease in [zeta]-potential, aggregation of structures and changes in the ultra-structure, particularly at high protein:lipid ratios. The in vitro immunogenicity of dispersions containing Quil-A, PC and DC-cholesterol was equivalent to that of classical ISCOMs in terms of activation of mBMDC and OVA-specific CD8+ T cells, even though smaller amounts of Quillaja saponins and total lipid were co-delivered with OVA. Furthermore, the uptake of OVA by BMDC appeared to be more efficient in conjunction with the novel cationic dispersions. Conclusions: Cationic colloidal structures containing Quillaja saponins offer great potential as vaccine delivery systems. Their advantages thus far include simple and efficient adsorption of antigen, efficient uptake by APC and immunological activity in vitro. With further development, cationic carriers containing Quillaja saponins may constitute a very potent vaccine delivery platform suitable for a variety of subunit antigens, and suffice both pharmaceutical and immunological requirements.

Thesis (M.S.)--University of Delaware, 2006. / Principal faculty advisor: Tracy DeLiberty, Dept. of Geography. Includes bibliographical references.

The purpose of this work is to develop a new model for LDD n-MOSFET degradation in drain current under long-term AC use conditions for lifetime projection which includes a self-limiting effect in the hot-electron induced device degradation. Experimental results on LDD n-channel MOSFETs shows that the maximum drain current degradation is a function of the AC average substrate current under the various AC stress conditions but not a function of frequency or waveforms or different measurement configurations. An empirical model is constructed for circuit applications. It is verified that the self-limiting in drain current is due to the thermal re-emission of a trapped-hot-electron in the oxide. Results show that self-heating during AC stress releases trapped electrons, which in turn limits the maximum amount of drain current degradation. Moreover, tunneling to and from traps model is employed to visualize the internal mechanism of thermal recovery of electrons under different bias conditions. Although the LDD device structure can reduce the hot electron effect, various processing technologies can also affect the device reliability. A carbon doped LDD device with the first and the second level metal and passivation layer but without any final anneal shows that a significant reduction in the shifts of the threshold voltage of MOSFETs with time can be achieved. However, the long-term reliability projection of nMOSFETs based on DC stress tests alone is shown to be overly pessimistic. / Graduation date: 1992