Στην παρούσα Ειδική Ερευνητική Εργασία μελετόνται οι φωτοφυσικές ιδιότητες γνωστών χρωμοφόρων μορίων. Συγκεκριμένα μελετάται η Coumarin 30, η Fluorescein Isothiocyanate και η Dichlorofluorescein, τόσο με φασματοσκοπία σταθερής κατάστασης όσο και με φασματοσκοπία χρονικής ανάλυσης μέσω της τεχνικής Time Correlated Single Photon Counting. Η διερεύνηση γίνεται με τα μόρια αυτά να βρίσκονται σε μορφή διαλυμάτων με στόχο τον προσδιορισμό της συμπεριφοράς τους όταν αυτά βρισκονται σε διαφορετικά περιβάλλοντα (διαλύτες). Επιπλέον ερευνώνται οι αλληλεπιδράσεις των μορίων αυτών μέσω της φασματοσκοπίας σταθερής κατάστασης και χρονικής ανάλυσης όταν βρίσκονται σε μορφή μειγμάτων. / In this Master Thesis, the phophysical properties of chromophrores are investigated. Specifically, Coumarin 30, Fluorescein Isothiocyanate and Dichlorofluorescein are studied with steady – state spectroscopy as well as with time – resolved spectroscopy via the technique of Time Correlated Single Photon Counting. The study of these molecules focuses also on solvent – solute effects. Finally, interactions between them are also studied through steady – state spectroscopy and time resolved spectroscopy.

Les personnes non-voyantes montrent dans les différents aspects de leurs vies qu’elles sont capables de s’adapter à la privation visuelle en utilisant les capacités intactes comme l’ouï ou le toucher. Elles montrent qu’elles peuvent bien évoluer dans leur environnement en absence de vision et démontrent même des fois des habiletés supérieures à celles des personnes voyantes. La recherche de ces dernières décennies s’est beaucoup intéressée aux capacités adaptatives des non-voyants surtout avec l’avènement des nouvelles techniques d’imagerie qui ont permis d’investiguer des domaines qui ne l’étaient pas ou l’étaient difficilement avant. Les capacités supérieures des non voyants dans l’utilisation plus efficace des informations auditives et tactiles semblent avoir leur base neuronale dans le dans le cortex visuel désafférenté, qui continu à être fonctionnel après la privation sensorielle et s’en trouve recruté pour le traitement de stimulations dites intermodales : auditives, tactiles et même montre une implication dans des processus de plus haut niveau, comme la mémoire ou le langage. Cette implication fonctionnelle intermodale résulte de la plasticité du cortex visuel c'est-à-dire sa capacité à changer sa structure, sa fonction et d’adapter ses interactions avec les autres systèmes en l’absence de vision. La plasticité corticale n’est pas exclusive au cortex visuel mais est un état permanent de tout le cerveau. Pour mesurer l’activité du cortex visuel des non voyants, une mesure d’excitabilité de ses neurones consiste à mesurer le temps de recouvrement de l’onde N1 en potentiels évoqués, qui est plus rapide chez les non voyants dans la modalité auditive. En effet, les réponses en potentiels et champs évoqués ont été utilisés en EEG/MEG pour mettre en évidence des changements plastiques dans le cortex visuel des non-voyants pour le traitement de stimuli dans les modalités auditives et tactiles. Ces réponses étaient localisées dans les régions postérieures chez les non voyants contrairement aux contrôles voyants. Un autre type de réponse auditive a reçu moins d’intérêt dans la recherche concernant la réorganisation fonctionnelle en relation avec la privation sensorielle, il s’agit de la réponse auditive oscillatoire (Auditory Steady-State Response ASSR). C’est une réponse qui a l’avantage d’osciller au rythme de stimulation et d’être caractérisé par une réponse des aires auditives étiquetée à la fréquence de stimulation. Cette étiquette se présente sous la forme qu’un pic d’énergie spectrale important qui culmine aux fréquences présentes dans la stimulation. Elle a également l’avantage d’être localisée dans les régions auditives primaires, de là tout changement de localisation de cette réponse chez des non voyants en faveur des régions visuelles pourrait être considéré comme une évidence de la réorganisation fonctionnelle qui s’opère après une privation sensorielle précoce. Le but de cette thèse est donc d’utiliser la réponse oscillatoire à l’écoute des sons modulés en amplitude (MA) pour mettre en évidence les corrélats de la réorganisation fonctionnelle dans le cortex visuel des non-voyants précoces. La modulation de la réponse auditive dans les régions visuelles nous permettra de montrer qu’une réorganisation est possible chez les non-voyants pour ce traitement intermodal. La première étude est une validation du paradigme expérimental «frequency tagged sounds». Il s’agit de montrer qu’une tâche de détection de changement dans la stimulation, permet de moduler la réponse ASSR aux sons modulés en amplitude en vue de l’utiliser dans les études chez les non voyants et dans les conditions d’une privation visuelle transitoire (avec les yeux bandés). Un groupe de sujets voyants ont réalisé une tâche de détection de changement dans la stimulation les yeux ouverts dans deux conditions : écoute active qui consiste à détecter un changement dans la fréquence porteuse de la modulation en appuyant avec l’index droit sur un bouton de réponse et une condition d’écoute passive. Les sons étaient présentés en écoute monaurale et dichotique. Les résultats ont montré une différence significative à l’occurrence du changement dans la stimulation en écoute dichotique seulement. Les schémas de plus grande réponse controlatérale et de suppression binaurale décrit dans la littérature ont été confirmés. La deuxième étude avait pour but de mettre en évidence une réorganisation rapide de la réponse ASSR chez un groupe de sujets voyants dans les conditions de privation visuelle transitoire de courte durée, par bandage des yeux pendant six heures. Le même protocole expérimental que la première étude a été utilisé en écoute active seulement. Les résultats montrent que dans ces conditions une modulation de la réponse corticale en écoute dichotique dans les régions visuelles est possible. Ces sources d’activité occipitale adoptent une propriété du cortex auditif qui est le battement binaural, c'est-à-dire l’oscillation de la réponse ASSR à la différence des fréquences présentées dans chaque oreille. Cet effet est présent chez la moitié des sujets testés. La représentation corticale des sources occipitales évolue durant la période de privation et montre un déplacement des sources d’activité dans la direction antéropostérieure à la fin de la période de privation. La troisième étude a permis de comparer le traitement de la réponse ASSR dans un groupe de non-voyants congénitaux à un groupe de voyants contrôles, pour investiguer les corrélats de la réorganisation fonctionnelle de cette réponse après une privation sensorielle de longue durée c'est-à-dire chez des non voyants congénitaux. Les résultats montrent des différences significatives dans la représentation spectrale de la réponse entre les deux groupes avec néanmoins des activations temporales importantes aussi bien chez les non voyants que chez les contrôles voyants. Des sources distribuées ont été localisées dans les régions associatives auditives dans les deux groupes à la différence des non voyants où il y avait en plus l’implication des régions temporales inférieures, connues comme étant activées par la vision des objets chez les voyants et font partie de la voie visuelle du quoi. Les résultats présentés dans le cadre de cette thèse vont dans le sens d’une réorganisation rapide de la réponse auditive oscillatoire après une privation visuelle transitoire de courte durée par l’implication des régions visuelles dans le traitement de la réponse ASSR par l’intermédiaire du démasquage de connections existantes entre le cortex visuel et le cortex auditif. La privation visuelle de longue durée, elle conduit à des changements plastiques, d’une part intra modaux par l’extension de l’activité aux régions temporales supérieures et médianes. D’autre part, elle induit des changements inter modaux par l’implication fonctionnelle des régions temporales inférieures visuelles dans le traitement des sons modulés en amplitude comme objets auditifs alors qu’elles sont normalement dédiées au traitement des objets visuels. Cette réorganisation passe probablement par les connections cortico-corticales. / Blind persons show in their everyday life that they can efficiently adapt to visual deprivation by relying on their spared senses like touch or the sense of hearing. They also show they can challenge their environment without vision and sometimes even demonstrate superior abilities compared to sighted counterparts. In the last decades, research got more interested in adaptive capabilities of the blinds especially with the advent of new imaging techniques which made it possible to make giant steps investigating new avenues in the field of brain plasticity after sensory loss. The superior abilities of blind individuals take the form of a more efficient use of auditory and tactile information and find their neuronal correlates in the deafferented visual cortex. The visual cortex of the blind is still highly functional after visual deprivation and is recruited for the processing of cross modal auditory and tactile stimulations. It can even show implication in higher level memory or language processes. This functional involvement results from the plasticity of the visual cortex which is its ability to change its structure, its function and to adapt its interactions with the other systems in the absence of vision. Cortical plasticity is not exclusive to the visual cortex of the blind but is a permanent state of the brain. To appreciate cortical activity in the visual cortex of blind individuals, a measure of excitability of its neurons is used. This measure is represented by the recovery of the N1 component in ERPs to target detection, which is shorter in the auditory modality for the blind. Evoked potentials and evoked fields components in EEG and MEG have been shown to be reorganized in favour of the visual cortex of blind individuals compared to sighted ones for the auditory and tactile modalities. Posterior location for such components was found in the blind. The auditory steady-state response is another brain response that received less interest in the study of cortical reorganization after sensory loss. The ASSR has the advantage of oscillating at the stimulation rhythm and is characterized by a response in the auditory cortices tagged to the stimulation frequencies. The tag takes the form of an important spectral energy peak at the frequencies of stimulation in auditory areas. The ASSR is localized in left and right primary auditory areas, with this regard any posterior shift in the location of source activity in blind individuals also tagged to stimulation frequencies would be considered as an evidence of functional reorganization following sensory deprivation. The objectives of this work are to make use of the characteristics of the ASSR to amplitude modulated tones (AM) to investigate neural correlates of cross modal functional reorganization in the visual cortex of the blind for the processing of AM tones. The first study is a validation of the frequency tagging paradigm. A change detection auditory task can modulate the envelope amplitude of the ASSR response. The same paradigm is used to investigate cross modal reorganisation after long and short term visual deprivation. In this first study a group of healthy sighted individuals detected a change in the carrier frequency of AM tones, with eyes opened during monaural and dichotic listening. Two conditions were tested an active condition where they had to press a button each time they hear the change and a passive condition. Results show a significant increase in the envelope amplitude of the ASSR to the onset of the carrier frequency change, only for dichotic presentation. Patterns of activations of the ASSR were maintained, with larger responses in the hemisphere contralateral to the stimulated ear and binaural suppression for the ipsilateral inputs for the dichotic presentation. The second study was aimed to show that rapid changes in the ASSR to amplitude modulated tones (MA) are possible after short term sensory deprivation, by blindfolding sighted individuals for six hours. The same detection task was used but not the passive condition. Results show a modulation of the dichotic response in visual areas. The occipital source activity found, showed an auditory property as a binaural beat, which means an oscillating ASSR at a frequency equal to the difference of the frequencies presented to each ear. This effect was present in half of the participants and took place at the end of the blindfolding time. Cortical representation of the occipital sources showed a displacement of source activities in the antero-posterior direction at the end of transitory deprivation period. In the third study we compared the ASSR processing between early blind individuals (congenitally blind) group and healthy sighted controls group, to investigate the neural correlates of functional reorganization of this response after long term visual deprivation. Results show significant differences in the spectral representation of the response between the two groups. Important auditory temporal activations were found in the two groups. Distributed sources were localized in primary and secondary auditory areas for the two groups. A difference was found in blind individuals who showed additional activations of inferior temporal areas, known to be activated by objects vision in sighted individuals and being part of the what visual pathway. The results presented here are in line with a rapid reorganization of the ASSR after short term visual deprivation, and the implication of visual areas in the processing of AM tones for long term sensory deprivation in the congenitally blind. This was made possible by the unmasking of existing connections between auditory and visual cortices. Long term deprivation leads to plastic changes, in the auditory modality as a first step by the extension of activity to superior and middle temporal areas, then to cross modal changes with the functional involvement of inferior temporal areas in the processing of AM tones, considered as visual objects. This reorganization is likely to be mediated through lateral cortico-cortical connections.

Percevoir et synchroniser ses mouvements à une pulsation régulière en musique est une capacité largement répandue chez l’Homme, et fondamentale aux comportements musicaux. La pulsation et la métrique en musique désignent généralement une organisation temporelle périodique perçue à partir de stimuli acoustiques complexes, et cette organisation perceptuelle implique souvent une mise en mouvement périodique spontanée du corps. Cependant, les mécanismes neuraux sous-tendant cette perception sont à l’heure actuelle encore méconnus. Le présent travail a donc eu pour objectif de développer une nouvelle approche expérimentale, inspirée par l’approche électrophysiologique des potentiels évoqués stationnaires, afin d’explorer les corrélats neuraux à la base de notre perception de la pulsation et de la métrique induite à l’écoute de rythmes musicaux. L’activité neurale évoquée en relation avec la perception d’une pulsation a été enregistrée par électroencéphalographie (EEG) chez des individus sains, dans divers contextes : (1) dans un contexte d’imagerie mentale d’une métrique appliquée de manière endogène sur un stimulus auditif, (2) dans un contexte d’induction spontanée d’une pulsation à l’écoute de patterns rythmiques musicaux, (3) dans un contexte d’interaction multisensorielle, et (4) dans un contexte de synchronisation sensorimotrice. Pris dans leur ensemble, les résultats de ces études corroborent l’hypothèse selon laquelle la perception de la pulsation en musique est sous-tendue par des processus de synchronisation et de résonance de l’activité neurale dans le cerveau humain. De plus, ces résultats suggèrent que l’approche développée dans le présent travail pourrait apporter un éclairage significatif pour comprendre les mécanismes neuraux de la perception de la pulsation et des rythmes musicaux, et, dans une perspective plus générale, pour explorer les mécanismes de synchronisation neurale. / The ability to perceive a regular beat in music and synchronize to it is a widespread human skill. Fundamental to musical behavior, beat and meter refer to the perception of periodicities while listening to musical rhythms, and usually involve spontaneous entrainment to move on these periodicities. However, the neural mechanisms underlying entrainment to beat and meter in Humans remain unclear. The present work tests a novel experimental approach, inspired by the steady-state evoked potential method, to explore the neural dynamics supporting the perception of rhythmic inputs. Using human electroencephalography (EEG), neural responses to beat and meter were recorded in various contexts: (1) mental imagery of meter, (2) spontaneous induction of a beat from rhythmic patterns, (3) multisensory integration, and (4) sensorimotor synchronization. Our results support the view that entrainment and resonance phenomena subtend the processing of musical rhythms in the human brain. Furthermore, our results suggest that this novel approach could help investigating the link between the phenomenology of musical beat and meter and neurophysiological evidence of a bias towards periodicities arising under certain circumstances in the nervous system. Hence, entrainment to music provides an original framework to explore general entrainment phenomena occurring at various levels, from the inter-neural to the inter-individual level. / Thèse de doctorat réalisé en cotutelle avec l'Université catholique de Louvain, Belgique (Faculté de médecine, Institut de Neuroscience)

<p>The main hypothesis in this study is the development of a nanocomposite mediated amperometric biosensor for detection of hydrogen peroxide. The aim is to combine the electrochemical properties of both polyaniline and ferrocenium hexafluorophosphate into highly conductive nano composites capable of exhibiting electrochemistry in non acidic media / shuttling electrons between HRP and GCE for biosensor applications.</p>

The main objective of this work was to develop simple and sensitive electrochemical sensors for the detection of bisphenol A. To investigate the electrochemical behavior of BPA on a bare glassy carbon electrode. To apply the developed biosensor for the determination BPA by differential pulse voltammetry, electrochemical impedance spectrometry, square wave voltammetry and steady-state amperometry. To characterize the synthesized PDMA-PSS by cyclic voltammetry (CV), UV-Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM).

The technological changes and educational expansion have created the heterogeneity in the human species. Clearly, this heterogeneity generates a structure in the population dynamics, namely: citizen, permanent resident, visitor, and etc. Furthermore, as the heterogeneity in the population increases, the human mobility between meta-populations patches also increases. Depending on spatial scales, a meta-population patch can be decomposed into sub-patches, for examples: homes, neighborhoods, towns, etc. The dynamics of human mobility in a heterogeneous and scaled structured population is still its infancy level. We develop and investigate (1) an algorithmic two scale human mobility dynamic model for a meta-population. Moreover,the two scale human mobility dynamic model can be extended to multi-scales by applying the algorithm. The subregions and regions are interlinked via intra-and inter regional transport network systems. Under various types of growth order assumptions on the intra and interregional residence times of the residents of a sub region, different patterns of static behavior of the mobility process are studied. Furthermore, the human mobility dynamic model is applied to a two-scale population dynamic exhibiting a special real life human transportation network pattern. The static evolution of all categories of residents of a given site ( homesite, visiting sites within the region, and visiting sites in other regions) over continuous changes in the intra and inter-regional visiting times is also analyzed. The development of the two scale human mobility dynamic model provides a suitable approach to undertake the study of the non-uniform global spread of emergent infectious diseases of humans in a systematic and unified way. In view of this, we derive (2) a SIRS stochastic epidemic dynamic process in a two scale structured population. By defining a positively self invariant set for the dynamic model the stochastic asymptotic stability results of the disease free equilibrium are developed(2). Furthermore, the significance of the stability results are illustrated in a simple real life scenario that is under controlled quarantine disease strategy. In addition, the epidemic dynamic model (2) is applied to a SIR influenza epidemic in a two scale population that is under the influence of a special real life human mobility pattern. The simulated trajectories for the different states (susceptible, Infective, Removal) with respect to current location in the two-scale population structure are presented. The simulated findings reveal comparative evolution patterns for the different states and current locations over time. The SIRS stochastic epidemic dynamic model (2) is extended to a SIR delayed stochastic epidemic dynamic model(3). The delay effects in the dynamic model (3) is temporary and account for natural or infection acquired immunity conferred by the disease after disease recovery. Again, we justify the model validation as a prerequisite for the dynamic modeling. Moreover, we also exhibit the real life scenario under controlled quarantine disease strategy.In addition, the developed delayed SIR dynamic model is also applied to SIR influenza epidemic with temporary immunity to an influenza disease strain. The simulated results reveal an oscillatory effect in the trajectory of the naturally immune population. Moreover, the oscillations are more significant at the homesite. We further extended the stochastic temporary delayed epidemic dynamic model (3) into a stochastic delayed epidemic dynamic model with varying immunity period(4). The varying immunity period accounts for the varying time lengths of natural immunity against the infectious agent exhibited within the naturally immune population. Obviously, the stochastic dynamic model with varying immunity period generalizes the SIR temporary delayed dynamic.

The purpose of this study is to evaluate the effects and importance of different cross–section representations and energy group structures for steady state and transient analysis. More energy groups may be more accurate, but the calculation becomes much more expensive, hence a balance between accuracy and calculation effort must be find. This study is aimed at comparing a multi–group energy dynamics code, MGT (Multi–group TINTE) with TINTE (TIme Dependent Neutronics and TEmperatures). TINTE’s original version (version 204d) only distinguishes between two energy group structures, namely thermal and fast region with a polynomial reconstruction of cross–sections pre–calculated as a function of different conditions and temperatures. MGT is a TINTE derivative that has been developed, allowing a variable number of broad energy groups. The MGT code will be benchmarked against the OECD PBMR coupled neutronics/thermal hydraulics transient benchmark: the PBMR–400 core design. This comparative study reveals the variations in the results when using two different methods for cross–section generation and multi–group energy structure. Inputs and results received from PBMR (Pty) Ltd. were used to do the comparison. A comparison was done between two–group TINTE and the equivalent two energy groups in MGT as well as between 4, 6 and 8 energy groups in MGT with the different cross–section generation methods, namely inline spectrum– and tabulated cross–section method. The characteristics that are compared are reactor power, moderation– and maximum fuel temperatures and k–effective (only steady state case). This study revealed that a balance between accuracy and calculation effort can be met by using a 4–group energy group structure. A larger part of the available increase in accuracy can be obtained with 4–groups, at the cost of only a small increase in CPU time. The changing of the group structures in the steady state case from 2 to 8 groups has a greater influence on the variation in the results than the cross–section generation method that was used to obtain the results. In the case of a transient calculation, the cross–section generation method has a greater influence on the variation in the results than on the steady state case and has a similar effect to the number of energy groups. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

The purpose of this study is to evaluate the effects and importance of different cross–section representations and energy group structures for steady state and transient analysis. More energy groups may be more accurate, but the calculation becomes much more expensive, hence a balance between accuracy and calculation effort must be find. This study is aimed at comparing a multi–group energy dynamics code, MGT (Multi–group TINTE) with TINTE (TIme Dependent Neutronics and TEmperatures). TINTE’s original version (version 204d) only distinguishes between two energy group structures, namely thermal and fast region with a polynomial reconstruction of cross–sections pre–calculated as a function of different conditions and temperatures. MGT is a TINTE derivative that has been developed, allowing a variable number of broad energy groups. The MGT code will be benchmarked against the OECD PBMR coupled neutronics/thermal hydraulics transient benchmark: the PBMR–400 core design. This comparative study reveals the variations in the results when using two different methods for cross–section generation and multi–group energy structure. Inputs and results received from PBMR (Pty) Ltd. were used to do the comparison. A comparison was done between two–group TINTE and the equivalent two energy groups in MGT as well as between 4, 6 and 8 energy groups in MGT with the different cross–section generation methods, namely inline spectrum– and tabulated cross–section method. The characteristics that are compared are reactor power, moderation– and maximum fuel temperatures and k–effective (only steady state case). This study revealed that a balance between accuracy and calculation effort can be met by using a 4–group energy group structure. A larger part of the available increase in accuracy can be obtained with 4–groups, at the cost of only a small increase in CPU time. The changing of the group structures in the steady state case from 2 to 8 groups has a greater influence on the variation in the results than the cross–section generation method that was used to obtain the results. In the case of a transient calculation, the cross–section generation method has a greater influence on the variation in the results than on the steady state case and has a similar effect to the number of energy groups. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

In this thesis, we have analyzed the accuracy and stability aspects of weak boundary and interface conditions (WBCs) for high order finite difference methods on Summations-By-Parts (SBP) form. The numerical technique has been applied to wave propagation and flow problems. The advantage of WBCs over strong boundary conditions is that stability of the numerical scheme can be proven. The boundary procedures in the advection-diffusion equation for a boundary layer problem is analyzed. By performing Navier-Stokes calculations, it is shown that most of the conclusions from the model problem carries over to the fully nonlinear case. The work was complemented to include the new idea of using WBCs on multiple grid points in a region, where the data is known, instead of at a single point. It was shown that we can achieve high accuracy, an increased rate of convergence to steady-state and non-reflecting boundary conditions by using this approach. Using the SBP technique and WBCs, we have worked out how to construct conservative and energy stable hybrid schemes for shocks using two different approaches. In the first method, we combine a high order finite difference scheme with a second order MUSCL scheme. In the second method, a procedure to locally change the order of accuracy of the finite difference schemes is developed. The main purpose is to obtain a higher order accurate scheme in smooth regions and a low order non-oscillatory scheme in the vicinity of shocks. Furthermore, we have analyzed the energy stability of the MUSCL scheme, by reformulating the scheme in the framework of SBP and artificial dissipation operators. It was found that many of the standard slope limiters in the MUSCL scheme do not lead to a negative semi-definite dissipation matrix, as required to get pointwise stability. Finally, high order simulations of shock diffracting over a convex wall with two facets were performed. The numerical study is done for a range of Reynolds numbers. By monitoring the velocities at the solid wall, it was shown that the computations were resolved in the boundary layer. Schlieren images from the computational results were obtained which displayed new interesting flow features.

It has been observed that in certain cases the exposure of dyed fibres to aging techniques results in the strengthening of fibres. This thesis explores the hypothesis that the strengthening is due to radical cross-coupling reactions that could be initiated through metal ion mediated photodecarboxylation. The approaches taken in this research include kinetic experiments (using flash photolysis), examination of possible cross-coupling experiments (using species of opposite charge), and the design and examination of small molecule model systems. A flash photolysis system was developed and used in attempts to determine the rates of photochemical product formation for cobalt(III) amino acid complexes. Lower limits have been established for the rate of product formation in these systems. The lower limits are: 2 x 10⁷ s⁻¹ for [Co(bpy)2(gly)]²⁺; 2 x 10⁷ s⁻¹ for [Co(tpa)(gly)]²⁺; and 5 x 10⁶ s⁻¹ for [Co(tpa)(aib)]²⁺, where bpy is 2,2'-bipyridine; gly is glycinate; tpa is tris(2-pyridylmethyl)amine; and aib is aminoisobutyrate. In past studies, the rates of a series of cobalt(III) amino acid complexes were reported as being the same, and much slower. It is thought that in these cases it may not be the rate of the formation of product that was being measured, but rather the response time of the electronics that was being observed. In this thesis the results obtained for the rate for the aib complex were somewhat lower than those of the gly complexes. This may imply, for the aib complex at least, the rate of the formation of the metallocycle is being observed (and not the response times of the electronics or other limitations of the instrumentation), but the data is poor and there is considerable doubt about this. The steady state photolysis of opposite charged species [Co(bpy)2(gly)]²⁺ and [Co(EDTA)]⁻ is reported. The reactions were carried out on a small scale in deuterated solvent for NMR spectrometry analysis and also on a large scale for the possible isolation and characterisation of the products. Evidence was found for a different reaction occurring when both complexes were present. The exact nature of the product remains elusive. A model system was designed in which a dinuclear ligand would bind to two metal centres and a fibre mimic would be later added. Eight ligands are discussed that could potentially bind two octahedral metal centres. They all had a xylene spacing group linking the two polydentate sites together. Five of the ligands have two bidentate binding sites. The other three had two tridentate sites. The binding sites in three of the bis(bidentate) ligands were based on ethane-1,2- diamine (en). Two of these ligands produced hypodentate monocobalt and sundentate dicobalt complexes. The other two bidentate ligands were based on 2- aminomethylpyridine (ampy). Both of these ligands degraded in the complexation reaction conditions. The binding sites in the tridentate ligands were all based on tacn. Once again, the principal products isolated were hypodentate systems in which only one metal ion was coordinated by the ligands. There is a distinct pattern observed in the xylene spaced ligands to form hypodentate complexes with cobalt(III) metal centred complexes. There is evidence of the di-nuclear species from a reaction with a charcoal catalyst in the bis(bidentate) system. ¹H NMR spectrometry, ¹³C NMR spectrometry, elemental analysis, X-ray crystallography and UV-vis spectroscopy were used to study and characterise the complexes and ligands that were prepared in this project.