The following dissertation is divided into two parts. Part I deals with the modeling of helium trapping at oxide-iron interfaces in nanostructured ferritic alloys (NFAs) using density functional theory (DFT). The modelling that has been performed serves to increase the knowledge and understanding of the theory underlying the prevention of helium embrittlement in materials. Although the focus is for nuclear reactor materials, the theory can be applied to any material that may be in an environment where helium embrittlement is of concern. In addition to an improved theoretical understanding of helium embrittlement, the following DFT models will provide valuable thermodynamic and kinetic information. This information can be utilized in the development of large-scale models (such as kinetic Monte Carlo simulations) of the microstructural evolution of reactor components. Accurate modelling is an essential tool for the development of new reactor materials, as experiments for components can span decades for the lifetime of the reactor. Part II of this dissertation deals with the development, and use of, kinetic Monte Carlo (KMC) simulations for improved efficiency in investigating catalytic chemical reactions on surfaces. An essential technique for the predictive development and discovery of catalysts relies on modelling of large-scale chemical reactions. This requires multi-scale modelling where a common sequence of techniques would require parameterization obtained from DFT, simulation of the chemical reactions for millions of conditions using KMC (requiring millions of separate simulations), and finally simulation of the large scale reactor environment using computational fluid dynamics. The tools that have been developed will aid in the predictive discovery, development and modelling of catalysts through the use of KMC simulations. The algorithms that have been developed are versatile and thus, they can be applied to nearly any KMC simulation that would seek to overcome similar challenges as those posed by investigating catalysis (such as the need for millions of simulations, long simulation time and large discrepancies in transition probabilities). / Ph. D.

Abstract provided by Publisher Complex performance diagnostics in sports medicine should contain maximal aerobic and maximal anaerobic performance. The requirements on appropriate stress protocols are high. To validate a test protocol quality criteria like objectivity and reliability are necessary. Therefore, the present study was performed in intention to analyze the reliability of maximal lactate production rate (VLamax) by using a sprint test, maximum oxygen consumption (VO2max) by using a ramp test and, based on these data, resulting power in calculated maximum lactate-steady-state (PMLSS) especially for amateur cyclists. All subjects (n=23, age 26 ± 4 years) were leisure cyclists. At three different days they completed first a sprint test to approximate VLamax. After 60 min of recreation time a ramp test to assess VO2max was performed. The results of VLamax-test and VO2max-test and the body weight were used to calculate PMLSS for all subjects. The intra class correlation (ICC) for VLamax and VO2max was 0.904 and 0.987, respectively, coefficient of variation (CV) was 6.3 % and 2.1 %, respectively. Between the measurements the reliable change index of 0.11 mmol∙l-1∙s-1 for VLamax and 3.3 ml∙kg-1∙min-1 for VO2max achieved significance. The mean of the calculated PMLSS was 237 ± 72 W with an RCI of 9 W and reached with ICC = 0.985 a very high reliability. Both metabolic performance tests and the calculated PMLSS are reliable for leisure cyclists.

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.

Le traitement de l’épilepsie chez le jeune enfant représente un enjeu majeur pour le développement de ce dernier. Chez la grande majorité des enfants atteints de spasmes infantiles et chez plusieurs atteints de crises partielles complexes réfractaires, le vigabatrin (VGB) représente un traitement incontournable. Cette médication, ayant démontré un haut taux d’efficacité chez cette population, semble toutefois mener à une atteinte du champ visuel périphérique souvent asymptomatique. L’évaluation clinique des champs visuels avec la périmétrie chez les patients de moins de neuf ans d’âge développemental est toutefois très difficile, voire impossible. Les études électrophysiologiques classiques menées auprès de la population épileptique pédiatrique suggèrent l’atteinte des structures liées aux cônes de la rétine. Les protocoles standards ne sont toutefois pas spécifiques aux champs visuels et les déficits soulignés ne concordent pas avec l’atteinte périphérique observée. Cette thèse vise donc à élaborer une tâche adaptée à l’évaluation des champs visuels chez les enfants en utilisant un protocole objectif, rapide et spécifique aux champs visuels à partir des potentiels évoqués visuels (PEVs) et à évaluer, à l’aide de cette méthode, les effets neurotoxiques à long terme du VGB chez des enfants épileptiques exposés en bas âge. La validation de la méthode est présentée dans le premier article. La stimulation est constituée de deux cercles concentriques faits de damiers à renversement de phase alternant à différentes fréquences temporelles. La passation de la tâche chez l’adulte permet de constater qu’une seule électrode corticale (Oz) est nécessaire à l’enregistrement simultané des réponses du champ visuel central et périphérique et qu’il est possible de recueillir les réponses électrophysiologiques très rapidement grâces l’utilisation de l’état-stationnaire (steady-state). La comparaison des données d’enfants et d’adultes normaux permet de constater que les réponses recueillies au sein des deux régions visuelles ne dépendent ni de l’âge ni du sexe. Les réponses centrales sont aussi corrélées à l’acuité visuelle. De plus, la validité de cette méthode est corroborée auprès d’adolescents ayant reçu un diagnostic clinique d’un déficit visuel central ou périphérique. En somme, la méthode validée permet d’évaluer adéquatement les champs visuels corticaux central et périphérique simultanément et rapidement, tant chez les adultes que chez les enfants. Le second article de cette thèse porte sur l’évaluation des champs visuels, grâce à la méthode préalablement validée, d’enfants épileptiques exposés au VGB en jeune âge en comparaison avec des enfants épileptiques exposés à d’autres antiépileptiques et à des enfants neurologiquement sains. La méthode a été bonifiée grâce à la variation du contraste et à l’enregistrement simultané de la réponse rétinienne. On trouve que la réponse corticale centrale est diminuée à haut et à moyen contrastes chez les enfants exposés au VGB et à haut contraste chez les enfants exposés à d’autres antiépileptiques. Le gain de contraste est altéré au sein des deux groupes d’enfants épileptiques. Par contre, l’absence de différences entre les deux groupes neurologiquement atteints ne permet pas de faire la distinction entre l’effet de la médication et celui de la maladie. De plus, la réponse rétinienne périphérique est atteinte chez les enfants épileptiques exposés au Sabril® en comparaison avec les enfants neurologiquement sains. La réponse rétinienne périphérique semble liée à la durée d’exposition à la médication. Ces résultats corroborent ceux rapportés dans la littérature. En somme, les résultats de cette thèse offrent une méthode complémentaire, rapide, fiable, objective à celles connues pour l’évaluation des champs visuels chez les enfants. Ils apportent aussi un éclairage nouveau sur les impacts à long terme possibles chez les enfants exposés au VGB dans la petite enfance. / Epilepsy control is a major issue for the normal development in children. For the vast majority of children with infantile spasms and for some with refractory complex partial seizures, vigabatrin (VGB) represents the main treatment. VGB, which have shown high efficiency rate in this population, may, however, induce a peripheral visual field deficit, often asymptomatic. Clinical visual field assessment with perimetry is practically impossible in patients less than nine years of developmental age. Electrophysiological studies in epileptic children suggest an impact on the retinal structures related to the cones. However, standard protocols are not field-specific and the deficits reported in the literature are not coherent with the peripheral deficit observed. Thus, this thesis aims to develop a fast and efficient electrophysiological protocol to examine the visual field’s integrity, which would be useful in pediatric testing and to assess the visual field long-term effects of the VGB in school-aged epileptic children exposed early in life. The first article concerns the method’s validation. The stimulation is made of two high-contrast radial checks reversing at two different temporal frequencies. Adult testing reveals that only one electrode (Oz) is needed to record simultaneously both central and peripheral visual fields and that steady-state use allows fast gathering of both electrophysiological responses. No effect of age or sex was found in the comparison of adult and child’ responses. Moreover, the visual acuity, as calculated by the binocular visual acuity index, was related to the central signal when comparing healthy participants with central visual impaired adolescents. Our method presents several advantages in evaluating visual fields integrity, as it is fast, reliable and efficient, and applicable in children. The aim of the second article of the thesis is the assessment of the long term visual effect on the visual field in children exposed to VGB in infancy in comparison to epileptic children exposed to other antiepileptics and with healthy children using the previously validated electrophysiology method with the addition of contrast variation and simultaneous recording of electroretinograms. Results reveal a cortical central deficit at high and mid-range contrast in VGB exposed-children and at high contrast in other antiepileptic exposed group. The contrast gain is also affected in both epileptic groups. The absence of difference between both epileptic groups does not allow distinguishing the impact of medication and/or seizure disorder. The peripheral retinal response is also altered in the VGB-exposed group in comparison to the healthy group. The peripheral retinal response is related to the exposition duration. This result concurs with previous studies in the literature. Finally, the results of the thesis offer an objective, fast, efficient and alternative method to assess visual fields in children. They also bring a new point of view on the likely long term impacts of the VGB in children exposed in infancy.

Background: The purpose of this study was the comparison of the calculated (MLSSC) and experimental power (MLSSE) in maximal lactate steady-state (MLSS) during cycling. Methods: 13 male subjects (24.2 ± 4.76 years, 72.9 ± 6.9 kg, 178.5 ± 5.9 cm, V_O2max: 60.4 ± 8.6 ml min−1 kg−1, V_ Lamax: 0.9 ± 0.19 mmol l-1 s-1) performed a ramp-test for determining the V_O2max and a 15 s sprint-test for measuring the maximal glycolytic rate (V_ Lamax). All tests were performed on a Lode-Cycle-Ergometer. V_O2max and V_ Lamax were used to calculate MLSSC. For the determination of MLSSE several 30 min constant load tests were performed. MLSSE was defined as the highest workload that can be maintained without an increase of blood-lactate-concentration (BLC) of more than 0.05 mmol l−1 min−1 during the last 20 min. Power in following constant-load test was set higher or lower depending on BLC. Results: MLSSE and MLSSC were measured respectively at 217 ± 51 W and 229 ± 47 W, while mean difference was −12 ± 20 W. Orthogonal regression was calculated with r = 0.92 (p < 0.001). Conclusions: The difference of 12 W can be explained by the biological variability of V_O2max and V_ Lamax. The knowledge of both parameters, as well as their individual influence on MLSS, could be important for establishing training recommendations, which could lead to either an improvement in V_O2max or V_ Lamax by performing high intensity or low intensity exercise training, respectively. Furthermore the validity of V_ Lamax -test should be focused in further studies.

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.

Thèse de doctorat réalisé en cotutelle avec l'Université catholique de Louvain, Belgique (Faculté de médecine, Institut de Neuroscience) / 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.

In everyday situations individuals make decisions. For example, a tourist usually chooses a crowded or recommended restaurant to have dinner. Perhaps it is an individual decision, but the observed pattern of decision-making is a collective phenomenon. Collective behaviour emerges from the local interactions that give rise to a complex pattern at the group level. In our example, the recommendations or simple copying the choices of others make a crowded restaurant even more crowded. The rules of interaction between individuals are important to study. Such studies should be complemented by biological experiments. Recent studies of collective phenomena in animal groups help us to understand these rules and develop mathematical models of collective behaviour. The most important communication mechanism is positive feedback between group members, which we observe in our example. In this thesis, we use a generic experimentally validated model of positive feedback to study collective decision-making. The first part of the thesis is based on the modelling of decision-making associated to the selection of feeding sites. This has been extensively studied for ants and slime moulds. The main contribution of our research is to demonstrate how such aspects as "irrationality", speed and quality of decisions can be modelled using differential equations. We study bifurcation phenomena and describe collective patterns above critical values of a bifurcation points in mathematical and biological terms. In the second part, we demonstrate how the primitive unicellular slime mould Physarum Polycephalum provides an easy test-bed for theoretical assumptions and model predictions about decision-making. We study its searching strategies and model decision-making associated to the selection of food options. We also consider the aggregation model to investigate the fractal structure of Physarum Polycephalum plasmodia. / <p>Fel serie i tryckt bok /Wrong series in the printed book</p>

The content of this Master´s Thesis is creating of dynamic models of distributed energy sources in PSCAD and their validation in chosen operation regimes. In the introduction of this thesis is summarized theoretical knowledge about methods for power systems analysis and there is a comparison of static and dynamic methods for power systems analysis. Static methods are used to calculate electric variables in grid nodes. In compare with them, dynamic methods are used to study instantaneous electrical and mechanical variables not only in grid nodes, but also at components of power system. Secondly, we individually designed distributed energy sources in according to requirements, we made a topology of distribution grid and we integrated these energy sources to the distribution grid. Finally, we chose some operation regimes, and studied a behavior of energy sources during these operation regimes.

The content of this Master´s Thesis is creating of dynamic models of distributed energy sources in PSCAD and their validation in chosen operation regimes. In the introduction of this thesis is summarized theoretical knowledge about methods for power systems analysis and there is a comparison of static and dynamic methods for power systems analysis. Static methods are used to calculate electric variables in grid nodes. In compare with them, dynamic methods are used to study instantaneous electrical and mechanical variables not only in grid nodes, but also at components of power system. Secondly, we individually designed distributed energy sources in according to requirements, we made a topology of distribution grid and we integrated these energy sources to the distribution grid. Finally, we chose some operation regimes, and studied a behavior of energy sources during these operation regimes.