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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Micro- and nanoscale investigations of interfacial physicochemical processes

Rudd, Nicola Clare January 2007 (has links)
No description available.

Low temperature equilibria in binary systems, including the solid phase

Moran, David William January 1959 (has links)
No description available.

Ultrasonic and photonic stimulation of solid/liquid interfacial processes

Macfie, Gavin January 2001 (has links)
No description available.

Multiphase flow in deforming porous media : a finite element approach

Li, Xi-Kui January 1991 (has links)
No description available.

The role of the pentose phosphate pathway in TMPyP4 resistance and the telomere uncapping response

Andrew, Elizabeth Joan January 2012 (has links)
G-quadruplex stabilising ligands are of interest as potential anti-cancer drugs. Gquadruplexes are folded DNA structures which can form in guanine-rich regions of DNA or RNA, and stabilisation of these structures at telomeres can result in the inhibition of telomerase activity. In this thesis, Saccharomyces cerevisiae was used as a model to examine the in vivo cellular response to treatment with the G-quadruplex stabilising ligand TMPyP4. The findings indicate that the pentose phosphate pathway (PPP) is key for resistance to TMPyP4, since the absence of PPP genes resulted in increased sensitivity to treatment with the ligand. However, the TMPyP4-sensitivity exhibited by pppΔ strains is most likely due to oxidative stress caused by the photosensitivity of the porphyrin. There are also potential links between PPP activity, the response to uncapped telomeres and the DNA damage response (DDR). The cdc13- 1 mutant strain, in which the telomere binding protein Cdc13 is defective, was used to explore these connections. Here, I demonstrate that deletion of key PPP genes results in suppression of the temperature-sensitive growth phenotype of cdc13-1. In addition, the activity of the enzyme which catalyses the initial step of the oxidative phase of the PPP, Zwf1, increases in cdc13-1 strains. Studies of Zwf1 activity in strains arrested in late anaphase and G1, however, suggest that the increase in Zwf1 activity is due to the phase of the cell cycle in which the strains are arrested, rather than the DDR. The work described here demonstrates that the PPP is intrinsically linked to the response to a variety of cellular stresses. Due to its role in the Warburg effect, a metabolic shift observed in tumour cells, examination of PPP function is important not only for the study of normal tissues but also immortal cancer cells, and lessons in budding yeast can lead to important insights.

Reaction and separation process integration

Linke, P. January 2001 (has links)
No description available.

Thermodynamics of biomacromolecular interactions in aqueous solutions

Roberts, Dorota January 2011 (has links)
An understanding of the interactions between polyelectrolytes and proteins is vital to determine structure and functionality of materials constructed of these two components. Possible applications for the protein-polyelectrolyte composites are ranging from materials used to deliver drugs to the methods of protein stabilisation for storage of therapeutics, biosemsors, and encapsulation of medicines for triggered release. The binding of globular proteins to the polyelectrolyte chains can prevent undesired protein aggregation and may help to extend the shelf-life of the protein-containing food. The aim of this project is to study the mechanism of non-covalent binding between proteins and polyelectrolytes, responsiveness of the proteinpolyelectrolyte composites to external stimuli such as changing pH, presence of salt of different types and concentrations or influence of enzyme on the integrity of protein-polyelectrolyte multilayer film. Our study was focused on the effects of different mono- and multivalent salts on binding affinitybetween a negatively charged polyelectrolyte - poly(styrene sulfonate) PSS and bovine serumalbumin BSA or myoglobin. The complex formation between these polymers was examinedusing the static light scattering (SLS), turbidimetric and potentiometric titrations, differentialscanning calorimetry (DSC) and theoretical studies based on molecular dynamics simulations. We established that the inter- and intramolecular interactions between proteins and polyelectrolytes are primarily driven by the electrostatic forces at the conditions when thepolymers are in low ionic strength solutions and attractive or repulsive relations are based upon the charge density and its distribution. When proteins are interacting with polyelectrolytes in solutions of high ionic strength the electrostatic interactions are screened by the salt originated co-ions. In these conditions there is a competition between salting-out effect on proteins leading to protein aggregation or protein-polyelectrolyte complex formation, which can prevent undesired protein-protein association. The forces driving the attractive interactions at high ionic strength are of non-electrostatic origin, these are mainly hydrophobic forces. The computer simulation study shows that more flexible polyanionic chains are stronger binders to the positive patches on protein surface than these of a more rigid backbone. Also a total energy of binding depends on a sum of electrostatic and non-electrostatic energies. The formation of multilayers composed of a protein and a polyelectrolyte, where componentswere: poly-L-lysine – a positively charged homopolypeptide and polygalacturonic acid - apolysaccharide was examined using a quartz crystal microbalance with dissipation monitoring. A 10 and 11 layer film, deposited on the charged surface, exhibited the linear growth pattern for first 5 layers and exponential growth for a flowing 5 (or 6) layers. The influence of pectinase enzyme on digesting the polygalacturonic acid component of the multilayer was most effective for 1 AU/mL concentration of pectinase. After the enzyme was applied the multilayer film was fully disintegrated within the period of 20 minutes for pectinase at 1 AU/mL and the time of disintegration was extended to 120 minutes for pectinase at 0.1 AU/mL.Silk fibroin aqueous solutions were tested rheologically for their structural properties involvingthe existence of fibroin aggregates. We examined the process of ageing of fibroin solutions and solid-liquid transformations taking place within the fluid. The transitions between viscous and elastic behaviour of the fibroin’s semi-dilute solutions were initiated by strain, shear frequency and temperature. We highlighted that the irreversible change in secondary structure of the silk fibroin in aqueous solutions are taking place after the 48 hour period of time since the preparation of protein fluids. We recommend that further processing of silk fibroin such aselectrospinning should be completed within the 48 hour after dissolution.

Aspects of relations between metastable and stable phases in the iron-sulphur system

Lennie, A. R. January 2009 (has links)
No description available.

Surface freezing in surfactant/alkane/water systems

Ash, Philip Andrew January 2011 (has links)
Surface freezing transitions in mixed monolayers of a homologous series of cationic surfactants, the alkyltrimethyl ammonium bromides (CnTAB where n = 12, 14, 16, 18), as well as a range of non-ionic, zwitterionic and biological surfactants, have been investigated ellipsometrically with a range of n-alkanes (Cm where m = 12 – 20, 28). Two distinct solid phases are observed depending upon the chain length difference between surfactant and n-alkane. Type I solid phases consist of a surface frozen mixed monolayer and are formed when this difference is small. Type II solid phases are bilayer structures with a frozen layer of neat n-alkane above a liquid-like mixed monolayer. Type II freezing was thought to occur via wetting of surface frozen n-alkane, as previously reported type II transitions took place in the presence of surface frozen n-alkanes. Thermodynamically stable type II solid phases have now been found in the presence of n-alkanes that do not show surface freezing at the air/alkane interface, however, and so this picture is incomplete. In the presence of pentadecane, for example, the biological surfactant lyso-OPC forms a stable type II solid phase 6.5 °C above the n-alkane bulk melting point. Such a large surface freezing range is unprecedented for a type II system. Studies using external reflection FTIR (ER-FTIRS) and vibrational sum-frequency spectroscopies (VSFS) have been used to probe these novel behaviours. Results were fully consistent with the proposed structures of both type I and type II surface frozen layers. 2D correlation analysis of ER-FTIR spectra as a function of temperature showed that type II frozen layer formation does not proceed via a simple wetting transition, with the formation of a transient intermediate implied. Evidence for such an intermediate was provided by dynamic ellipsometry measurements on the type II C18TAB/n-eicosane system.

Electrochemical methods for the dechlorination and detection of chlorinated ethenes

Wylie, Lisa Anne January 2003 (has links)
Chlorinated ethenes in the environment are dechlorinated by accepting electrons from electron donors found in nature. Such reductive dechlorination forms the basis of this research into remediation and detection of these compounds in the environment. The reducing abilities of one of the strongest electron donors known, tetraki s(dimethylamino)ethylene (TDAE), were used to abiotically simulate reductive dechlorination. TDAE was found to form an electron donor-acceptor complex with tetrachloroethene, and to very rapidly reduce trichloroethene and cis-dichloroethene via removal of the most positive chlorine. Microbiological studies of bacteria utilising chlorinated ethenes in their metabolic systems established that Vitamin B,2 (cyanocobalamm) is of great importance to the dechlorination process, acting as a cofactor for the organism's dehalogenase enzyme. The dechlorination mechanism involves cobalt (I) as the active transition metal in extremely reducing conditions. A series of analytical experiments were undertaken to establish the reductive capability of cobalt (I), both in a simple cobalt salt and in vitamin 812, under reducing conditions. Molasses was used as a hydrogen source and an electron donor in simulation of the biotic process. Results indicate that Vitamin B12 is more successful at dechlorination than simple cobalt salts, but neither system presents an ideal method for commercial dechlorination based on current experimental process. Remediation of environmental tetra- and trichloroethene contamination would be improved by the development of on-line sensors. Glutathione, an intracellular sulfhydryl tripeptide comprising glutamyl, cysteinyl, and glycinyl, bonds with alkyl halides via the thiol group in its cysteine moeity, and displays characteristic redox behaviour, presenting an ideal prospective system for development of a relevant biosensor. Potentiometric and amperometric studies have been carried out to determine the efficacy of the proposed system; results indicate that response to and selectivity for alkyl halides at environmental concentrations can be achieved.

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