Plant viruses have developed a number of strategies that enable them to become obligate intracellular parasites of many agricultural crops. Potato virus X (PVX) belongs to a group of positive-sense, single-stranded plant RNA viruses that replicate on host membranes and form elaborate structures known as viral replication complexes (VRCs) that contain viral RNA (vRNA), proteins and host cellular components. VRCs are the principal sites of viral genome replication, virion assembly and packaging of vRNA for export into neighbouring cells. For many animal viruses, host membrane association is crucial for RNA export. For plant viruses, it is not yet known how vRNA is transported to and through plant plasmodesmata. PVX encodes genetic information required for its movement between cells; three viral triple gene block (TGB) movement proteins and a viral coat protein are essential for viral trafficking. This research project studies the relationship between PVX and its host plants, Nicotiana benthamina and Nicotiana tabacum. A particular focus of this project is exploration of the structural and functional significance of the PVX VRC and how the virus recruits cell host components for its replication and movement between cells. The role of specific viral proteins in establishing the VRC, and the ways in which these interact with host organelles, was investigated. A combination of different approaches was used, including RNA-binding dyes and a Pumilio-based bimolecular fluorescence complementation assay for detection of the vRNA, fluorescent reporters for virusencoded proteins, fluorescent reporters for host organelles involved in viral replication, and also transgenic tobacco plants expressing reporters for specific plant components (endoplasmic reticulum, Golgi, actin, microtubules and plasmodesmata). In addition, mutagenesis was used to study the functions of individual viral proteins in replication and movement. All of these approaches were combined to achieve live-cell imaging of the PVX infection process. The PVX VRC was shown to be a highly compartmentalised structure; (+)-stranded vRNA was concentrated around the viral TGB1 protein, which was localised in discrete circular compartments within the VRC while coat protein was localised to the external edges of the VRC. The vRNA was closely associated with host components (endoplasmic reticulum and actin) shown to be involved in the formation of the VRC. The TGB2/TGB3 viral proteins were shown to colocalise with the host endomembranes (ER) and to exit these compartments in the form of motile granules. vRNA, TGB1, TGB2 and CP localised to plasmodesmata of the infected cells. TGB1 was shown to move cell-to-cell and recruit ER, Golgi and actin in the absence of viral infection. In the presence of virus, TGB1 targeted the VRCs in several neighbouring cells. A model of PVX replication and movement is proposed in which TGB1 functions as a key component for recruitment of host components into the VRC to enable viral replication and spread.

The largest class of cell surface receptors in mammalian genomes is the superfamily of G protein-coupled receptors (GPCRs) which are activated by a wide range of extracellular responses such as hormones, pheromones, odorants, and neurotransmitters. Drugs which have therapeutic effects on a wide range of diseases are act on GPCRs. In contrast to traditional idea, it is recently getting accepted that G-protein coupled receptors can form homo- and hetero-dimers and this interaction could have important role on maturation, internalization, function or/and pharmacology. Bimolecular fluorescence complementation technique (BiFC) / is an innovative approach based on the reassembly of protein fragments which directly report interactions. In our study we implemented this technique for detecting and visualizing the GPCR interactions in yeast cells. The enhanced green fluorescent protein (EGFP) fractionated into two fragments at genetic level which does not possess fluorescent function. The target proteins which are going to be tested in terms of interaction are modified with the non-functional fragments, to produce the fusion proteins. The interaction between two target proteins, in this study Ste2p receptors which are alpha pheromone receptors from Saccharomyces cerevisiae, enable the fragments to come in a close proximity and reassemble. After reassembly, EGFP regains its fluorescent function which provides a direct read-out for the detection of interaction. Further studies are required to determine subcellular localization of the interaction. Moreover, by using the fusion protein partners constructed in this study, effects of agonist/antagonist binding and post-translational modifications such as glycosylation and phosphorylation can be examined. Apart from all, optimized conditions for BiFC technique will guide for revealing new protein-protein interactions.

This theses investigates the carrier dynamics in Indium Nitride thin films grown on Si(111) substrates by means of ultrafast time-resolved photoluminescence (TRPL) apparatus. The study of energy relaxation shows hot phonon effective is prominent at photogenerated carrier concentration above 4¡Ñ10^18cm^-3 and become insignificant at carrier concentration below 7¡Ñ10^17cm^-3. Effective phonon emission times in the range of 116 to 23 femtoseoncds are obtained from the time evolution of carrier temperature assuming that the carrier-LO-phonon interaction is the dominant energy relaxation process. In the study of carrier recombination, the TRPL¡¦s are studied at the peak energies of the time-integrated PL at various lattice temperatures and are converted to decay rates with a rate equation, which includes the nonradiative and radiative coefficients, and a nonlinear dependence of PL intensity on the photogenerated carrier concentration. The increase with temperatures of the Shockley-Read-Hall rates implies that, in addition to the mid-gap defect states, a thermally activated trapping may become prominent at high lattice temperatures due to the increased kinetic energy gained by the carriers. The radiative recombination is the dominated recombination mechanism at low temperature but become trivial at high temperature. The fitted radiative coefficient at a temperature of 35K is consistent to the theoretical prediction. The Auger recombination exhibits a quadratic dependence on carrier concentration and becomes effective at high carrier concentration and at high temperature. The fitted Auger recombination coefficients are comparable to those of InGaAs and InGaAsP materials with band gap energies in the range of 0.6-0.8eV.

An understanding of the atomic-scale features of chemical and physical processes taking place behind the shockwave front will help in addressing some of the major challenges in energetic materials research. The high pressure shockwave environment can be simulated using computational techniques to predict mechanical and chemical properties of a shocked material. Density functional theory calculations were performed to investigate uniaxial compressions of diamond and both hydrostatic and uniaxial compressions of TATB and NEST-1. For diamond, we calculated shear stresses for uniaxial compressions in the , , and directions and discovered the anomalous elastic regime which is responsible for the significant delay of plastic deformation behind a shockwave. For TATB, the hydrostatic equation of state, bulk modulus, and equilibrium structure were calculated using an empirical van der Waals correction. The principal stresses, shear stresses, and energy change per atom calculated for uniaxial compressions in the directions normal to the {001}, {010}, {011}, {100}, {101}, {110}, and {111} planes show highly anisotropic behavior. A similar study was performed for the newly synthesized energetic material NEST-1 in order to predict mechanical properties under uniaxial compression. From the similarities in the calculated principal stresses for each compression direction we conclude that NEST-1 is likely to exhibit relatively isotropic behavior as compared to other energetic materials. Finally, reactive molecular dynamics of shock-induced initiation chemistry in detonating PETN was investigated, using first-principles density functional theory, in order to identify the reaction mechanisms responsible for shock sensitivities in energetic materials. The threshold collision velocity of initiation for each orientation was determined and correlated with available experimental data on shock sensitivity. The production of NO2 was found to be the dominant reaction pathway in every reactive case. The simulations show that the reactive chemistry of initiation occurs at very short time scales ~10E?¹³ s at highly non-equilibrium conditions, and is driven by dynamics rather than temperature.

Free-radical polymerisation (FRP) has been one of the most important techniques for producing materials used in a very wide variety of applications and has enhanced the lives of millions of people around the world. However, for many years a number of fundamental questions regarding the key kinetic processes involved in FRP have remained unresolved. In particular, an accurate description of the mechanism for diffusion-controlled bimolecular termination has proven elusive. As a result, conventional modelling tools for FRP have often proven unreliable. The aim of this thesis, therefore, was to accurately study the evolution of the bimolecular termination rate coefficient during free radical polymerisation using a new and more accurate methodology based on ‘controlled/living’ reversible addition-fragmentation chain transfer (RAFT) polymerisation. This was undertaken in order to develop a more precise understanding of bimolecular termination and thereby develop a more reliable modeling approach capable of predicting the rates of reaction and evolution of molecular weight distributions for a wide range of experimental conditions and a wide range of functional monomers. The RAFT-CLD-T (RAFT Chain-Length-Dependent Termination) Method was used to determine accurate values for the conversion and chain-length-dependent termination rate coefficient, kti,i(x), as a function of various parameters. These parameters included the chain size, i, polymer concentration (or conversion, x), chain length size distribution and chain architecture/structure. The accuracy of the RAFT-CLD-T Method was crucial to this work, therefore, an important part of this thesis was devoted to evaluating the reliability of this technique. Below 5 % conversion and above 80 % conversion the method was found to be unreliable due to the effects of chain-length-dependent propagation, high PDI’s and short-long termination. However, between 5 % and 80 % conversion it was found that the method is extremely robust and a series of easy-to-use experimental guidelines were determined for accurately applying the RAFT-CLD-T Method. The effects of chain size, chain size distribution, solution polymer concentration, and matrix architecture were examined for the RAFT-mediated polymerisations of methyl methacrylate (MMA), styrene (STY) and methyl acrylate (MA). It was found that four distinct scaling regimes of termination are observed: (1) a ‘short’ chain dilute solution regime, (2) a ‘long’ chain dilute solution regime, (3) a semi-dilute solution regime and (4) a concentrated solution regime. In dilute polymer solutions, chain-length-dependent power law exponents, ’s, determined during the polymerisation of MMA, STY and MA (where kti,i(x)  i-) indicated that termination follows two major scaling regimes with exponents of approximately ~0.5 to 0.6 for ‘short’ chains and and ~0.12 to 0.16 for ‘long’ chains. Importantly, these exponents are in excellent agreement with theoretical predictions for translational and segmental diffusion-controlled termination, respectively. At increasing polymer concentrations, kti,i(x) falls rapidly coinciding with the onset of the gel effect. By comparing results from the RAFT-mediated polymerisations of MMA, STY, MA, and vinyl acetate (VAc) with theoretical models, we found that the onset of the gel effect coincided closely with the theoretical onset of chain overlap. Considerable uncertainty has plagued the evaluation of this phenomenon, but using a difunctional RAFT agent we showed this uncertainty arises from the influence of broad MWD’s on chain overlap and short-long termination. Finally, critical tests of this theory involving the bimolecular termination of linear radicals in solutions of star polymer confirmed that the gel effect coincided with chain overlap. Beyond the gel effect termination slows enormously, passing through the ‘semi-dilute solution’ regime and into the ‘concentrated solution’. In semi-dilute solution, theoretical predictions based on scaling theory (i.e. the ‘blob’ model) were in excellent agreement with results for the polymerisation of PSTY in linear and star polymer solutions, indicating that the solvent quality diminished both with increasing chain length and through the addition of a star polymer matrix. In concentrated solutions, the chain-length-dependent power law exponent increased linearly with conversion. For example, for MMA the chain length dependence of kt in the gel regime scaled as gel = 1.8x + 0.056, suggesting that reptation alone does not describe termination in the concentrated solution. Values of gel for PSTY, MA, and VAc were in similar agreement, indicating that a mechanism intermediate between unentangled and entangled semi-dilute scaling laws applies in the concentrated solution regime. Interestingly, gel values for these monomers were found to decrease with increasing chain flexibility in the order gel(MMA)> gel(STY)> gel(VAc)> gel(MA), suggesting matrix mobility is rate determining in concentrated solutions. Similarly, gel values were also larger in star polymer solutions, coinciding with decreasing matrix mobility. Thus, although it has been commonly believed that polymer chains diffuse via reptation above the gel effect, these results show that this only occurs for solutions containing rigid and/or highly immobile macromolecules and in very high concentrations. To describe these behaviours, a semi-empirical ‘composite kt model’ was also developed to describe kti,i(x) as a function of i and x up to high conversions. We showed that the model is very simple to implement and accurate for modelling a wide range of functional monomers and experimental conditions. In particular, we showed the method was accurate for modelling RAFT-mediated polymerisations of a very wide range of monomers (MA, MMA, and PSTY) and was even accurate for modelling conventional FRP’s. Thus, the model provides a simple, flexible and accurate method for predicting the rate of reaction and evolution of molecular weight distributions across a range of experimental conditions based on accurate kti,i(x) values.

Free-radical polymerisation (FRP) has been one of the most important techniques for producing materials used in a very wide variety of applications and has enhanced the lives of millions of people around the world. However, for many years a number of fundamental questions regarding the key kinetic processes involved in FRP have remained unresolved. In particular, an accurate description of the mechanism for diffusion-controlled bimolecular termination has proven elusive. As a result, conventional modelling tools for FRP have often proven unreliable. The aim of this thesis, therefore, was to accurately study the evolution of the bimolecular termination rate coefficient during free radical polymerisation using a new and more accurate methodology based on ‘controlled/living’ reversible addition-fragmentation chain transfer (RAFT) polymerisation. This was undertaken in order to develop a more precise understanding of bimolecular termination and thereby develop a more reliable modeling approach capable of predicting the rates of reaction and evolution of molecular weight distributions for a wide range of experimental conditions and a wide range of functional monomers. The RAFT-CLD-T (RAFT Chain-Length-Dependent Termination) Method was used to determine accurate values for the conversion and chain-length-dependent termination rate coefficient, kti,i(x), as a function of various parameters. These parameters included the chain size, i, polymer concentration (or conversion, x), chain length size distribution and chain architecture/structure. The accuracy of the RAFT-CLD-T Method was crucial to this work, therefore, an important part of this thesis was devoted to evaluating the reliability of this technique. Below 5 % conversion and above 80 % conversion the method was found to be unreliable due to the effects of chain-length-dependent propagation, high PDI’s and short-long termination. However, between 5 % and 80 % conversion it was found that the method is extremely robust and a series of easy-to-use experimental guidelines were determined for accurately applying the RAFT-CLD-T Method. The effects of chain size, chain size distribution, solution polymer concentration, and matrix architecture were examined for the RAFT-mediated polymerisations of methyl methacrylate (MMA), styrene (STY) and methyl acrylate (MA). It was found that four distinct scaling regimes of termination are observed: (1) a ‘short’ chain dilute solution regime, (2) a ‘long’ chain dilute solution regime, (3) a semi-dilute solution regime and (4) a concentrated solution regime. In dilute polymer solutions, chain-length-dependent power law exponents, ’s, determined during the polymerisation of MMA, STY and MA (where kti,i(x)  i-) indicated that termination follows two major scaling regimes with exponents of approximately ~0.5 to 0.6 for ‘short’ chains and and ~0.12 to 0.16 for ‘long’ chains. Importantly, these exponents are in excellent agreement with theoretical predictions for translational and segmental diffusion-controlled termination, respectively. At increasing polymer concentrations, kti,i(x) falls rapidly coinciding with the onset of the gel effect. By comparing results from the RAFT-mediated polymerisations of MMA, STY, MA, and vinyl acetate (VAc) with theoretical models, we found that the onset of the gel effect coincided closely with the theoretical onset of chain overlap. Considerable uncertainty has plagued the evaluation of this phenomenon, but using a difunctional RAFT agent we showed this uncertainty arises from the influence of broad MWD’s on chain overlap and short-long termination. Finally, critical tests of this theory involving the bimolecular termination of linear radicals in solutions of star polymer confirmed that the gel effect coincided with chain overlap. Beyond the gel effect termination slows enormously, passing through the ‘semi-dilute solution’ regime and into the ‘concentrated solution’. In semi-dilute solution, theoretical predictions based on scaling theory (i.e. the ‘blob’ model) were in excellent agreement with results for the polymerisation of PSTY in linear and star polymer solutions, indicating that the solvent quality diminished both with increasing chain length and through the addition of a star polymer matrix. In concentrated solutions, the chain-length-dependent power law exponent increased linearly with conversion. For example, for MMA the chain length dependence of kt in the gel regime scaled as gel = 1.8x + 0.056, suggesting that reptation alone does not describe termination in the concentrated solution. Values of gel for PSTY, MA, and VAc were in similar agreement, indicating that a mechanism intermediate between unentangled and entangled semi-dilute scaling laws applies in the concentrated solution regime. Interestingly, gel values for these monomers were found to decrease with increasing chain flexibility in the order gel(MMA)> gel(STY)> gel(VAc)> gel(MA), suggesting matrix mobility is rate determining in concentrated solutions. Similarly, gel values were also larger in star polymer solutions, coinciding with decreasing matrix mobility. Thus, although it has been commonly believed that polymer chains diffuse via reptation above the gel effect, these results show that this only occurs for solutions containing rigid and/or highly immobile macromolecules and in very high concentrations. To describe these behaviours, a semi-empirical ‘composite kt model’ was also developed to describe kti,i(x) as a function of i and x up to high conversions. We showed that the model is very simple to implement and accurate for modelling a wide range of functional monomers and experimental conditions. In particular, we showed the method was accurate for modelling RAFT-mediated polymerisations of a very wide range of monomers (MA, MMA, and PSTY) and was even accurate for modelling conventional FRP’s. Thus, the model provides a simple, flexible and accurate method for predicting the rate of reaction and evolution of molecular weight distributions across a range of experimental conditions based on accurate kti,i(x) values.

Free-radical polymerisation (FRP) has been one of the most important techniques for producing materials used in a very wide variety of applications and has enhanced the lives of millions of people around the world. However, for many years a number of fundamental questions regarding the key kinetic processes involved in FRP have remained unresolved. In particular, an accurate description of the mechanism for diffusion-controlled bimolecular termination has proven elusive. As a result, conventional modelling tools for FRP have often proven unreliable. The aim of this thesis, therefore, was to accurately study the evolution of the bimolecular termination rate coefficient during free radical polymerisation using a new and more accurate methodology based on ‘controlled/living’ reversible addition-fragmentation chain transfer (RAFT) polymerisation. This was undertaken in order to develop a more precise understanding of bimolecular termination and thereby develop a more reliable modeling approach capable of predicting the rates of reaction and evolution of molecular weight distributions for a wide range of experimental conditions and a wide range of functional monomers. The RAFT-CLD-T (RAFT Chain-Length-Dependent Termination) Method was used to determine accurate values for the conversion and chain-length-dependent termination rate coefficient, kti,i(x), as a function of various parameters. These parameters included the chain size, i, polymer concentration (or conversion, x), chain length size distribution and chain architecture/structure. The accuracy of the RAFT-CLD-T Method was crucial to this work, therefore, an important part of this thesis was devoted to evaluating the reliability of this technique. Below 5 % conversion and above 80 % conversion the method was found to be unreliable due to the effects of chain-length-dependent propagation, high PDI’s and short-long termination. However, between 5 % and 80 % conversion it was found that the method is extremely robust and a series of easy-to-use experimental guidelines were determined for accurately applying the RAFT-CLD-T Method. The effects of chain size, chain size distribution, solution polymer concentration, and matrix architecture were examined for the RAFT-mediated polymerisations of methyl methacrylate (MMA), styrene (STY) and methyl acrylate (MA). It was found that four distinct scaling regimes of termination are observed: (1) a ‘short’ chain dilute solution regime, (2) a ‘long’ chain dilute solution regime, (3) a semi-dilute solution regime and (4) a concentrated solution regime. In dilute polymer solutions, chain-length-dependent power law exponents, ’s, determined during the polymerisation of MMA, STY and MA (where kti,i(x)  i-) indicated that termination follows two major scaling regimes with exponents of approximately ~0.5 to 0.6 for ‘short’ chains and and ~0.12 to 0.16 for ‘long’ chains. Importantly, these exponents are in excellent agreement with theoretical predictions for translational and segmental diffusion-controlled termination, respectively. At increasing polymer concentrations, kti,i(x) falls rapidly coinciding with the onset of the gel effect. By comparing results from the RAFT-mediated polymerisations of MMA, STY, MA, and vinyl acetate (VAc) with theoretical models, we found that the onset of the gel effect coincided closely with the theoretical onset of chain overlap. Considerable uncertainty has plagued the evaluation of this phenomenon, but using a difunctional RAFT agent we showed this uncertainty arises from the influence of broad MWD’s on chain overlap and short-long termination. Finally, critical tests of this theory involving the bimolecular termination of linear radicals in solutions of star polymer confirmed that the gel effect coincided with chain overlap. Beyond the gel effect termination slows enormously, passing through the ‘semi-dilute solution’ regime and into the ‘concentrated solution’. In semi-dilute solution, theoretical predictions based on scaling theory (i.e. the ‘blob’ model) were in excellent agreement with results for the polymerisation of PSTY in linear and star polymer solutions, indicating that the solvent quality diminished both with increasing chain length and through the addition of a star polymer matrix. In concentrated solutions, the chain-length-dependent power law exponent increased linearly with conversion. For example, for MMA the chain length dependence of kt in the gel regime scaled as gel = 1.8x + 0.056, suggesting that reptation alone does not describe termination in the concentrated solution. Values of gel for PSTY, MA, and VAc were in similar agreement, indicating that a mechanism intermediate between unentangled and entangled semi-dilute scaling laws applies in the concentrated solution regime. Interestingly, gel values for these monomers were found to decrease with increasing chain flexibility in the order gel(MMA)> gel(STY)> gel(VAc)> gel(MA), suggesting matrix mobility is rate determining in concentrated solutions. Similarly, gel values were also larger in star polymer solutions, coinciding with decreasing matrix mobility. Thus, although it has been commonly believed that polymer chains diffuse via reptation above the gel effect, these results show that this only occurs for solutions containing rigid and/or highly immobile macromolecules and in very high concentrations. To describe these behaviours, a semi-empirical ‘composite kt model’ was also developed to describe kti,i(x) as a function of i and x up to high conversions. We showed that the model is very simple to implement and accurate for modelling a wide range of functional monomers and experimental conditions. In particular, we showed the method was accurate for modelling RAFT-mediated polymerisations of a very wide range of monomers (MA, MMA, and PSTY) and was even accurate for modelling conventional FRP’s. Thus, the model provides a simple, flexible and accurate method for predicting the rate of reaction and evolution of molecular weight distributions across a range of experimental conditions based on accurate kti,i(x) values.

Free-radical polymerisation (FRP) has been one of the most important techniques for producing materials used in a very wide variety of applications and has enhanced the lives of millions of people around the world. However, for many years a number of fundamental questions regarding the key kinetic processes involved in FRP have remained unresolved. In particular, an accurate description of the mechanism for diffusion-controlled bimolecular termination has proven elusive. As a result, conventional modelling tools for FRP have often proven unreliable. The aim of this thesis, therefore, was to accurately study the evolution of the bimolecular termination rate coefficient during free radical polymerisation using a new and more accurate methodology based on ‘controlled/living’ reversible addition-fragmentation chain transfer (RAFT) polymerisation. This was undertaken in order to develop a more precise understanding of bimolecular termination and thereby develop a more reliable modeling approach capable of predicting the rates of reaction and evolution of molecular weight distributions for a wide range of experimental conditions and a wide range of functional monomers. The RAFT-CLD-T (RAFT Chain-Length-Dependent Termination) Method was used to determine accurate values for the conversion and chain-length-dependent termination rate coefficient, kti,i(x), as a function of various parameters. These parameters included the chain size, i, polymer concentration (or conversion, x), chain length size distribution and chain architecture/structure. The accuracy of the RAFT-CLD-T Method was crucial to this work, therefore, an important part of this thesis was devoted to evaluating the reliability of this technique. Below 5 % conversion and above 80 % conversion the method was found to be unreliable due to the effects of chain-length-dependent propagation, high PDI’s and short-long termination. However, between 5 % and 80 % conversion it was found that the method is extremely robust and a series of easy-to-use experimental guidelines were determined for accurately applying the RAFT-CLD-T Method. The effects of chain size, chain size distribution, solution polymer concentration, and matrix architecture were examined for the RAFT-mediated polymerisations of methyl methacrylate (MMA), styrene (STY) and methyl acrylate (MA). It was found that four distinct scaling regimes of termination are observed: (1) a ‘short’ chain dilute solution regime, (2) a ‘long’ chain dilute solution regime, (3) a semi-dilute solution regime and (4) a concentrated solution regime. In dilute polymer solutions, chain-length-dependent power law exponents, ’s, determined during the polymerisation of MMA, STY and MA (where kti,i(x)  i-) indicated that termination follows two major scaling regimes with exponents of approximately ~0.5 to 0.6 for ‘short’ chains and and ~0.12 to 0.16 for ‘long’ chains. Importantly, these exponents are in excellent agreement with theoretical predictions for translational and segmental diffusion-controlled termination, respectively. At increasing polymer concentrations, kti,i(x) falls rapidly coinciding with the onset of the gel effect. By comparing results from the RAFT-mediated polymerisations of MMA, STY, MA, and vinyl acetate (VAc) with theoretical models, we found that the onset of the gel effect coincided closely with the theoretical onset of chain overlap. Considerable uncertainty has plagued the evaluation of this phenomenon, but using a difunctional RAFT agent we showed this uncertainty arises from the influence of broad MWD’s on chain overlap and short-long termination. Finally, critical tests of this theory involving the bimolecular termination of linear radicals in solutions of star polymer confirmed that the gel effect coincided with chain overlap. Beyond the gel effect termination slows enormously, passing through the ‘semi-dilute solution’ regime and into the ‘concentrated solution’. In semi-dilute solution, theoretical predictions based on scaling theory (i.e. the ‘blob’ model) were in excellent agreement with results for the polymerisation of PSTY in linear and star polymer solutions, indicating that the solvent quality diminished both with increasing chain length and through the addition of a star polymer matrix. In concentrated solutions, the chain-length-dependent power law exponent increased linearly with conversion. For example, for MMA the chain length dependence of kt in the gel regime scaled as gel = 1.8x + 0.056, suggesting that reptation alone does not describe termination in the concentrated solution. Values of gel for PSTY, MA, and VAc were in similar agreement, indicating that a mechanism intermediate between unentangled and entangled semi-dilute scaling laws applies in the concentrated solution regime. Interestingly, gel values for these monomers were found to decrease with increasing chain flexibility in the order gel(MMA)> gel(STY)> gel(VAc)> gel(MA), suggesting matrix mobility is rate determining in concentrated solutions. Similarly, gel values were also larger in star polymer solutions, coinciding with decreasing matrix mobility. Thus, although it has been commonly believed that polymer chains diffuse via reptation above the gel effect, these results show that this only occurs for solutions containing rigid and/or highly immobile macromolecules and in very high concentrations. To describe these behaviours, a semi-empirical ‘composite kt model’ was also developed to describe kti,i(x) as a function of i and x up to high conversions. We showed that the model is very simple to implement and accurate for modelling a wide range of functional monomers and experimental conditions. In particular, we showed the method was accurate for modelling RAFT-mediated polymerisations of a very wide range of monomers (MA, MMA, and PSTY) and was even accurate for modelling conventional FRP’s. Thus, the model provides a simple, flexible and accurate method for predicting the rate of reaction and evolution of molecular weight distributions across a range of experimental conditions based on accurate kti,i(x) values.

The problem with which this investigation is concerned is that of measuring the rate coefficients for termolecular charge transfer reactions of He2+ in atmospheric pressure afterglows with the minority reacting species. Of particular interest was the discovery that the presence of a third body can change an improbable charge transfer reaction involving He+2 into a very probable one, as in the case of the reaction with argon. For example, in Tables II and II it was shown that less than a 300 torr pressure of helium was required to double the effective rate of reaction of argon with He2+ while over 3000 torr was required for CH4. The sensitivity of the method has been sufficient to detect termolecular components as small as 2 x 10-30 cm /sec and values were found to range widely from 2 x 10 for Ne to 67 x 10-30 cm6/sec for CO2. The size of these termolecular rates not only served to explain specific anomalous efficiencies of the charge transfer process observed in atmospheric pressure lasers but also suggested the general importance of three-body ion-molecule reactions in higher pressure plasmas.

Parkinson’s disease is an incurable neurodegenerative disease characterized by motor deficits, owing to dopaminergic denervation in the nigrostriatal pathway. The abnormal formation of hallmark Lewy bodies underlies the disease process. The pre-synaptic protein alpha- synuclein (⍺-syn) has prion-like properties arising from its propensity to propagate, seed misfolding, and self-aggregate. Pathogenesis is postulated to arise in olfactory and enteric regions, exploiting connected neuronal pathways to ultimately propagate to the substantia nigra pars compacta. There is little known about the earliest stages of ⍺-syn aggregation and its prion-like propagation mechanisms. Bimolecular fluorescence complementation of ⍺-syn aggregates has allowed us to directly visualize aggregation in transgenic mice and mice transduced with an adeno-associated virus vector. Although our transgenic mice expressed BiSyn in a mosaic fashion that limited utility, we were successful in transducing neurons in the mouse striatum. This work has validated the AAV2/9-CMV-BiSyn approach as groundwork for future systematic studies.