Transketolase is a TPP dependent enzyme that affects the availability of intermediates in both the Calvin cycle and non-oxidative pentose phosphate pathway. Previous studies have indicated that changes to the activity level of transketolase can limit growth and development as well as the production of isoprenoids, starch, amino acids and thiamine. The overall aim of this project was to further advance the understanding of the mechanism linking increased TK activity and thiamine metabolism. Nicotiana tabacum mutants with increased total transketolase activity ~ 2 to 2.5 fold higher than WT plants were shown to have a reduced growth and chlorotic phenotype. In seedlings, these phenotypes were attributed to a reduction in seed thiamine content. Imbibition of TKox seeds in a thiamine solution produced plants that were comparable to WT plants. However, the chlorotic but not growth phenotype was found to return unless the plants underwent irrigation with a thiamine solution indicating that TKox plants are unable to produce sufficient quantities of thiamine to meet demand. Furthermore, the application of deoxy-xylulose-5-phosphate was also found to be able to partially complement the phenotype suggesting that flux from the C3 cycle into the non-mevalonate pathway is being affected. Analysis of thiamine and TPP levels demonstrated that TKox plants were deficient in thiamine but not TPP in the majority of cases. In plants that had begun to flower, TKox lines had reduced thiamine and TPP levels in the 20th fully open leaf compared to the same leaf in WT plants. Furthermore, sampling of leaf tissue from both WT and TKox seedlings at the same developmental stage indicated that high levels of TK protein may lead to the accumulation of TPP in these areas causing a reduction in the levels of thiamine and TPP in the rest of the plant thereby limiting growth and development.

A change in environmental conditions often leads to changes of physiology and biochemical composition of microalgae. Temperature and light intensity are important environmental factors regulating the growth of microalgae. In this study, the elemental and biochemical composition were measured in 2 marine microalgae under different temperatures and light intensities in nutrient replete and deplete conditions. The effect of temperature was observed in the marine haptophyte Emiliania huxleyi (CCMP 1516) at nutrient replete semi-continuous cultures. Triplicate cultures were incubated different temperature from 14 to 22oC and under photon flux densities (PFD) 600 μmol photons m−2 s−1. The growth rate (GR) of E. huxleyi increased with temperature. Cell volume varied with temperature, being about 40% smaller at higher temperature (22oC). Cellular chlorophyll a (chl a), nitrogen, phosphorus, and carbon contents were also lower at 22oC than other temperatures. Protein, total amino acids from free and combined amino acid, and total pigments [mol accessory pigment (mol chl a)-1] were decreased with increasing temperature; however, the opposite response was observed in fatty acids. In addition to the effect of combined temperature and light intensity was investigated in the marine diatom Thalassiosira weissflogii (CCMP 1056) under nutrient-limited semi-continuous cultures. The cultures were incubated at 16 and 26°C and PFD of 50 ± 10 (low light; LL) and 500 ± 10 (high light; HL) μmol photons m−2 s−1. HL incubated-cultures were diluted at 50% day-1 and LL incubated-cultures were diluted at 25% day-1. The GR were largely set by dilution rate (nitrogen limitation), but not by temperature and irradiance. The GR were around 0.72 d-1 in HL placed-cultures and 0.32 d-1 in the LL placed-cultures. Temperature did not affect mean cell size, whereas mean cell size decreased with increased irradiance by 20 to 29 %. Both temperature and irradiance influenced cellular chl a, carbon and chl a specific light absorption. Cellular nitrogen and phosphorus varied with temperature and irradiance. Protein, total amino acid (free and combined amino acid) and total fatty acid increased with increased temperature and irradiance; however, the opposite response was found in carbohydrate. Overall, temperature and light affected elemental and biochemical composition in 2 marine microalgae. Both relationship of the chlorophyll (chl):carbon (C) and RNA:protein ratio and growth rate in E. huxleyi under variable temperature positively supported a bio-optical and growth rate hypothesis respectively. However, the opposite response was found in T. weissflogii. Instead the C:chl and RNA:protein ratio and growth rate in T. weissflogii under variable irradiance positively supported a bio-optical and growth rate hypothesis.

Aggregation of α-synuclein (α-syn) into toxic fibrils is a pathogenic hallmark of Parkinson’s disease (PD). This research aimed to develop peptides capable of inhibiting α-syn aggregation using a semi-rational design combined with a multiplexed intracellular Protein-fragment Complementation Assay (PCA) library screening system. Successfully selected peptides must bind to full length α-syn and lower its toxicity to confer bacterial growth. PCA selected peptides were characterized using several biophysical assays and a cell viability assay. The peptides were screened using library templates based on α-syn71-82 initially and later on the α-syn45-54 region in which many key mutations associated with early onset PD are found. In both cases we targeted the peptide libraries at the wild type protein or again by using mutated versions of α-syn. Results demonstrate that some of those selected peptides had the effect of delaying or even preventing the aggregation process, with others providing more subtle effects in reversing the fully formed amyloid fibrils. PCA peptides selected against 71-82 region of wild type α-syn showed a moderate level of efficacy whereas against mutants, it showed a low level of efficacy in inhibiting amyloid fibril formation. In the final part of the study, the peptide selected against 45-54 region of wild type α-syn was capable of preventing the aggregation and reducing the amyloid cytotoxicity at an equimolar ratio. We have thus demonstrated that the PCA strategy can be used as a generalised method for deriving peptide antagonists of α-syn aggregation, together with a new region; α-syn45-54 as an inhibitor target and produced a peptide inhibitor expected to provide a scaffold for future drug candidates to slow or even prevent the onset of PD.

The best characterised collagen IV disease is Alport syndrome, caused by α3.α4.α5(IV) mutations. Mutations affecting α1(IV)2α2(IV) can cause diseases, such as haemorrhagic stroke, aneurysm, haematuria, proteinuria, cataracts, vascular tortuosity and iris hypoplasia. Recent data has shown that α and COL4A2 mutations may be more common in the population than previously anticipated. However, the mechanisms of disease of all collagen IV mutations are poorly understood. The aim of this thesis was to investigate the disease mechanism in a selection of COL4A1, COL4A2 and COL4A5 mutations. Collagen IV is folded in the endoplasmic reticulum (ER) then secreted to provide the major structural component of the basement membrane (BM). As such, a combination of ex situ biopsies, in vitro cell cultures and an in vivo mouse model provided an excellent platform for investigating the intracellular and extracellular effects of mutant trimers. Primary dermal fibroblasts containing COL4A2 and COL4A5 mutations, and a Col4a1 mouse model were treated with the FDA approved chemical chaperone phenyl-4-butyric acid (PBA) to determine its effects on intracellular ER retention of trimers (which can activate ER stress), extracellular trimer incorporation into the BM, and disease phenotypes. In vitro and ex situ investigation of a COL4A2 mutation suggested that intracellular α1(IV)2α2(IV) accumulation and ER stress associated with severe BM defects and the disease. Intracellular accumulation and ER stress were reduced by PBA treatment, and treatment of a Col4a1 mouse model displayed elevated α1(IV)2α2(IV) incorporation onto the BM. In vivo PBA treatment did not exacerbate any defects, rescued some disease phenotypes, and had no effect on others. In addition, one of five COL4A5 mutations analysed in vitro displayed intracellular α3.α4.α5(IV) accumulation and ER stress that were ameliorated by PBA. Collectively these data suggest that ER stress and/or reduced α1(IV)2α2(IV) BM incorporation underlie some collagen IV pathologies, and provide novel evidence that they may be amenable to chemical chaperone therapy. More investigation is now needed to further dissect the relative contributions of ER stress and BM defects to collagen IV diseases.

A polymerase chain reaction (PCR) multiplex assay capable of amplifying 13 rapidly mutating Y chromosome short tandem repeats (RM Y-STRs) simultaneously was developed and optimised. This multiplex assay which was termed RM-Yplex is the first to include all 13 RM Y-STRs including DYF387S1, DYF399S1, DYF403S1a/b, DYF404S1, DYS449, DYS518, DYS526a/b DYS547, DYS570, DYS576, DYS612, DYS626 and DYS627. A developmental validation was performed following the Scientific Working Group for DNA Analysis Methods (SWGDAM) revised guidelines. Robustness and limitations of the assay were demonstrated through a range of studies including reproducibility, sensitivity, specificity, stability and mixture studies. Appropriate controls were used during the studies that included a number of male and female commercial controls including, 2800M, 9948 and Taqman male controls and 9947A female control. An allelic ladder was developed for the assignment of the alleles. This was done by choosing samples with different alleles, amplifying them and then adjusting the volumes of amplified products in a mixture. The developed mixtures were used to balance the composite ladder. Multiple alleles of the various loci included in the ladder were sequenced. Reference haplotypes were developed for the 5 male samples included in the Y chromosome Standard Reference Material 2395 (SRM2395) using RM-Yplex. The International Society of Forensic Genetics (ISFG) recommendations were followed for adopting allele nomenclature. As part of developmental validation, the assay was included in an external proficiency trial which was concluded successfully. An internal validation of RM-Yplex was carried out at the Department of Forensic Sciences and Criminology Laboratory, Dubai where apart from other studies; application of the assay was demonstrated using non-probative forensic casework samples. The value of RM-Yplex was demonstrated for differentiating close male relatives in a case where a previously used Y-STR multiplex assay had shown identical haplotypes for those individuals. 1160 male individual samples were analysed in this study including UAE, other Arabian Peninsula populations as well as two South Asian populations residing in United Arab Emirates. RM-Yplex haplotypes have extremely high power of discrimination. The haplotype diversity for RM-Yplex haplotype is much more than the existing commercial Y-STR assays. Population studies have been carried out for the Arab, Indian and Pakistani populations. AMOVA was conducted for determining the apportionment of diversity and pairwise FST’s were estimated between populations. These have shown a marked homogeneity within the UAE Arab sub-populations. MDS plots of pairwise FST’s indicated that populations were not grouped significantly in accordance with the geographical locations. A network analysis showed the extent of distribution of haplotypes of various populations and their relationships. A highly sensitive and reliable RM-Yplex multiplex assay has been thus developed, which is expected to help genetic populations studies and forensic casework.

The one-dimensional pyrolysis computational tool ThermaKin was used to predict the thermal decomposition behaviour of widely used synthetic polymers (polypropylene (PP) and polyethylene (PE)) with and without additives, in order to investigate the suitability of ThermaKin for novel fire retarded samples, under different thermal and fire conditions. The thermal decomposition of materials was investigated using simultaneous thermal analysis technique (STA) coupled with Fourier Transform Infrared Spectrometry (FTIR) at different heating rates and atmospheres. The results show that thermal decomposition of PP follows single mass-loss step, without formation of residue in nitrogen. It was also found that the pyrolysis shifted towards higher temperature with increase of heating rate at different atmospheres. ThermaKin fitted the TGA curves very well. The thermal decomposition behaviour of polypropylene grafted with 5wt% of maleic anhydride (MA), and reinforced with 5wt% of closite 20A as nanoclay (PP-gMA/NC) was also investigated. The main conclusions from this data are that during the thermal decomposition in different atmospheres, TGA curves showed a single step of decomposition process for all samples. The effect of clay is more pronounced during thermal oxidation. In N2 and air, a two-step reaction mechanism was fitted the experimental curves fairly well. The thermal decomposition of PE, pure and reinforced with different types of carbon fillers (single/multi wall carbon nanotubes, carbon fibres, carbon black and single/few layers of graphene nanosheets), at different loadings (0.1, 0.5 and 1 wt%) and atmospheres were investigated, to determine their suitability as potential fire retardant additives. Results showed that thermal decomposition of PE and its composites/nanocomposites followed a single mass-loss step at a range of temperatures, with no residue formation in N2. The DTG curve in air showed two mass loss rate peaks. The experimental results showed that all loadings of these different additives made no improvement to the thermal stability of PE/MA. In air, the compatibilising agent (MA) improved the thermal stability of pure PE, compared to these composites/nanocomposites at the selected loadings. Mechanisms of single or two-step reaction in N2, and three-step reaction in air for the thermal decomposition of PE with and without additives predicted fairly well the experimental curves. Finally, the work was extended to investigate the performance of ThermaKin to establish a model that is able to predict cone calorimetry results. ThermaKin predicted the burning rate of PE/MA, as a good agreement between the experimental and simulated curves was achieved. Sensitivity analysis was performed to investigate the influence of the variation of the material properties on the modelling results. It was found that the heat of decomposition is the most important parameter of those investigated and needs to be determined most accurately. Heat capacity and thermal conductivity are somewhat important. The absorption coefficient and the reflectivity are of lesser importance. In conclusion, this work shows that the combination of pyrolysis modelling, thermal and chemical analysis techniques provides a strong and powerful tool for generating a comprehensive understanding of the thermal decomposition of novel fire retardant materials. However, further work is needed to study the influence of the changes of the material properties in polymeric material while reinforced with different additives and how this will be reflected on the modelling parameters and mechanism.

No description available.

Section 1. A correlation technique is developed which enables the identification of systems belonging to a restricted class of non- linear systems. The method is applicable to a system which may be represented as a single-valued, instantaneous, time-invariant non-linearity followed by linear dynamics. The characteristic of the non-linearity and the impulse response of the linear element are found simultaneously in a single experiment. A class of pseudo-random test signals is studied, and results are derived for some situations in which the results are contaminated by noise. Further work is required to extend the applicability of the ·technique, to compare its performance with other methods of identification, and to investigate alternative test signals. Section 2. A simple eye-position transducer is described, which measures eyeball rotation about two axes.· Depending upon the characteristics of the subject's eye, and the operating conditions, an accuracy of as good as + 5% may be obtained over a range of 12º. The user wears a light-weight infra-red optical-electronic device on a spectacle frame. The transducer exploits the variation in infra-red reflectivity over the surface of the eyeball, and therefore varies in its performance from one subject to another. It may be used by some subjects in all lighting conditions except direct sunlight. Further work is needed to eliminatethe deficiencies of the device, but an investigation into television techniques, which are now feasible, should be made first. Section 3. The experimental determination of the region of asymptotic stability of a second order time invariant system may be considerably simplified by taking advantage of the nature of the trajectories wwhich form the boundary of the region. These trajectories are found easily by reverse time simulation. Further work is possible to investigate the extension of the method to higher order systems, but useful results seem unlikely.

In this work we study the properties of topological dynamical systems under a positive continuous change of velocity. In §l we define a flow obtained from a flow by a positive continuous change of velocity. We then prove that the time change flow is reversible so that we can recover the original flow. In §2 we define, following Kirillov, the first cohomology group of a dynamical system. A time change flow is then seen to be related to this first cohomology group. We now prove that there exists a group homomorphism between the first Čech cohomology group with integer coefficients and the first cohomology group of a compact dynamical system with coefficients in the reals. Winding numbers, due to Sol Schwartzman, are introduced and are shown to have an equivalent interpretation in terms of the first cohomology of a compact dynamical system. In §3 we show there is a natural invariant measure of a time change system in terms of the invariant measure of the original compact dynamical system. We now prove that ergodicity and unique ergodicity are preserved under a positive continuous change of velocity. Finally we relate the winding numbers of a time change system to the winding numbers of the original system, and show that under certain conditions they are invariant. In §4, we show that a compact dynamical system admits a Global Cross-Section if and only there exists an Eigen function, with non-zero eigenvalue, of a time change system. Lastly we show that, under certain conditions, a non-zero winding number is an eigenvalue associated to an eigen function of a time change dynamical system. In §5 we show that it is possible to eliminate eigen functions with non-zero eigenvalue under a positive continuous change of velocity of a compact dynamical system, if there exists at least one orbit homeomorphic to the real numbers : if, in addition, the original dynamical is ergodic we prove that weak-mixing is not invariant under a change velocity.

The perceptron and the hologram are two dissimilar devices which have been advanced as neurological models. It :is shown that there are other and perhaps more plausible models which have properties common to both of these devices. The performance of these intermediate models which are termed Associative Nets is described and analysed statistically. The main similarities and differences between perceptron theory and holography can also be demonstrated; it is possible to demonstrate formal links between the translation invariance in certain types of holography and group invariance in perception. theory. Some single proofs of certain theorems in the latter are also given and some other learning procedures are formulated. It is shown that the important difference between these various models resides in the method used to accomplish a modification. If this modification is an analogue of a neurological change a~ a synaptic level, then it should be possible to qualify the relevance of those models by determining what types of synaptic change can take place in different parts of the nervous system. -Although the evidence is far from complete, it suggests that the neocortex is limited to having one type of synaptic change. Finally, each model is discussed in respect of its neurological plausibility.