L’imagerie par résonance magnétique (IRM) est un outil important pour l’investigation qualitative et quantitative de la physiologie du cerveau. L’investigation de l’activité neuronale à l’aide de cette modalité est possible grâce à la détection de changements hémodynamiques qui surviennent de manière concomitante aux activités de signalisation des neurones, tels l’augmentation régionale du débit sanguin cérébral (CBF) ou encore la variation de la concentration de désoxyhémoglobine dans les vaisseaux veineux. Pour étudier la formation de contrastes fonctionnels qui découlent de ces phénomènes, deux séquences de pulses ont été développées en vue d’expériences en IRM fonctionnelle (IRMf) visant l’imagerie du signal oxygéno-dépendant BOLD ainsi que de la perfusion. Le premier objectif de cette thèse fut le développement d’une séquence de type écho-planar (EPI) permettant l’acquisition entrelacée d’images en mode échos de gradient (GRE-EPI) ainsi qu’en mode échos de spins (SE-EPI) pour l’évaluation de la performance de ces deux méthodes d’imagerie au cours d’une expérience en IRMf BOLD impliquant l’utilisation d’un stimulus visuel chez 4 sujets adultes sains. Le deuxième objectif principal de cette thèse fut le développement d’une séquence de marquage de spins artériels employant un module de marquage fonctionnant en mode pseudo-continu (pCASL) pour la quantification du CBF au repos. Cette séquence fut testée chez 3 sujets adultes en bonne santé et sa performance fut comparée à celle d’une séquence similaire développée par un groupe de recherche extérieur. Les résultats de l’expérience portant sur le contraste BOLD indiquent une supériorité de la performance du mode GRE-EPI vis-à-vis celle du mode SE-EPI en termes des valeurs moyennes du pourcentage de l’ampleur d’effet et du score t associés à l’activité neuronale en réponse au stimulus. L’expérience visant la quantification du CBF démontra la capacité de la séquence pCASL développée au cours de ce projet de calculer des valeurs de la perfusion de la matière grise ainsi que du cerveau entier se retrouvant dans une plage de valeurs qui sont physiologiquement acceptables, mais qui demeurent inférieures à celles obtenues par la séquence pCASL développée par le groupe de recherche extérieur. Des expériences futures seront effectuées pour optimiser le fonctionnement des séquences présentées dans ce mémoire en plus de quantifier l’efficacité d’inversion de la séquence pCASL. / Magnetic resonance imaging (MRI) is an important tool for the qualitative and quantitative investigation of brain physiology. The investigation of neuronal activation using this modality is made possible by the detection of concomitantly-arising hemodynamic changes in the brain’s vasculature, such as localized increases of the cerebral blood flow (CBF) or the variation of the concentration of paramagnetic deoxyhemoglobin in venous vessels. To study the formation of functional contrasts that stem from these changes in MRI, two pulse sequences were developed in this thesis to carry out experiments in blood oxygenation level dependent (BOLD) and perfusion functional MRI (fMRI). The first objective laid out in this work was the development of an echo planar imaging (EPI) sequence permitting the interleaved acquisition of images using gradient-echo EPI and spin-echo EPI to assess the performances of these imaging techniques in a BOLD fMRI experiment involving a visual stimulation paradigm in 4 healthy adult subjects. The second main objective of this thesis was the development of a pseudo-continuous arterial spin labelling (pCASL) sequence for the quantification of cerebral blood flow (CBF) at rest. This sequence was tested on 3 healthy adult subjects and compared to an externally-developed pCASL sequence to assess its performance. The results of the BOLD fMRI experiment indicated that the performance of GRE-EPI was superior to that of SE-EPI in terms of the average percent effect size and t-score associated with stimulus-driven neuronal activation. The CBF quantification experiment demonstrated the ability of the in-house pCASL sequence to compute values of CBF that are within a range of physiologically-acceptable values while remaining inferior to those computed using the externally-developed pCASL sequence. Future experiments will focus on the optimization of the sequences presented in this thesis as well as on the quantification of the pCASL sequence’s labelling efficiency.

Dans la sémantique des cadres de Fillmore, les mots prennent leur sens par rapport au contexte événementiel ou situationnel dans lequel ils s’inscrivent. FrameNet, une ressource lexicale pour l’anglais, définit environ 1000 cadres conceptuels, couvrant l’essentiel des contextes possibles. Dans un cadre conceptuel, un prédicat appelle des arguments pour remplir les différents rôles sémantiques associés au cadre (par exemple : Victime, Manière, Receveur, Locuteur). Nous cherchons à annoter automatiquement ces rôles sémantiques, étant donné le cadre sémantique et le prédicat. Pour cela, nous entrainons un algorithme d’apprentissage machine sur des arguments dont le rôle est connu, pour généraliser aux arguments dont le rôle est inconnu. On utilisera notamment des propriétés lexicales de proximité sémantique des mots les plus représentatifs des arguments, en particulier en utilisant des représentations vectorielles des mots du lexique. / According to Frame Semantics (Fillmore 1976), word meanings are best understood considering the semantic frame they play a role in, for the frame is what gives them context. FrameNet is a lexical database that defines about 1000 semantic frames, along with the roles to be filled by arguments to the predicate calling the frame in a sentence. Our task is to automatically label argument roles, given their position, the frame, and the predicate (sometimes refered to as semantic role labelling). For this task, I make use of distributed word representations, in order to improve generalisation over the few training exemples available for each frame. A maximum entropy classifier using common features of the arguments is used as a strong baseline to be improved upon.

Collateral blood flow is the compensatory flow of blood to the tissue through secondary channels when the primary channel is compromised. It is of vital importance in cerebrovascular disease where collateral flow can maintain large regions of brain tissue which would otherwise have suffered ischaemic damage. Traditional x-ray based techniques for visualising collateral flow are invasive and carry risks to the patient. In this thesis novel magnetic resonance imaging techniques for performing vessel-selective labelling of brain feeding arteries are explored and developed to reveal the source and extent of collateral flow in the brain non-invasively and without the use of contrast agents. Vessel-encoded pseudo-continuous arterial spin labelling (VEPCASL) allows the selective labelling of blood water in different combinations of brain feeding arteries that can be combined in post-processing to yield vascular territory maps. The mechanism of VEPCASL was elucidated and optimised through simulations of the Bloch equations and phantom experiments, including its sensitivity to sequence parameters, blood velocity and off-resonance effects. An implementation of the VEPCASL pulse sequence using an echo-planar imaging (EPI) readout was applied in healthy volunteers to enable optimisation of the post-labelling delay and choice of labelling plane position. Improvements to the signal-to-noise ratio (SNR) and motion-sensitivity were made through the addition of background suppression pulses and a partial-Fourier scheme. Experiments using a three-dimensional gradient and spin echo (3D-GRASE) readout were somewhat compromised by significant blurring in the slice direction, but showed potential for future work with a high SNR and reduced dropout artefacts. The VEPCASL preparation was also applied to a dynamic 2D angiographic readout, allowing direct visualisation of collateral blood flow in the brain as well as a morphological and functional assessment of the major cerebral arteries. The application of a balanced steady-state free precession (bSSFP) readout significantly increased the acquisition efficiency, allowing the generation of dynamic 3D vessel-selective angiograms. A theoretical model of the dynamic angiographic signal was also derived, allowing quantification of blood flow through specified vessels, providing a significant advantage over qualitative x-ray based methods. Finally, these methods were applied to a number of patient groups, including those with vertebro-basilar disease, carotid stenosis and arteriovenous malformation. These preliminary studies demonstrate that useful clinical information regarding collateral blood flow can be obtained with these techniques.

1 Error! Unknown document property name. Abstract The presented master thesis deals with the topic of stereotypical presentations of disabled people in Czech newspapers and with its impact on the audience. This topic build on previous findings regarding repetitive stereotypical images and frames of disabled which were not only studied on newspapers. Simultaneously with those reoccurring frames and images we can also find positive of negative labels which are used in connection with disabled in newspapers. The work examines whether these phenomena occur also in Czech online and printed news. Using qualitative content analysis phenomena mentioned above were searched in randomly selected one hundred news. Requirement for choosing articles to selection was that the articles content need to be whole about handicapped people. Precisely, based on previous literature the text were analyzed and it was searched for narrative frames or models, stereotypical frames and labels that could be presented in texts. The purpose of this analysis was not only to demonstrate that those frames or labels are present in Czech newspaper articles but also make an attempt to fins new stereotypical frames or labels that those texts may contain. The second part of the analysis is to verify whether the public perceives these...

In dieser Arbeit sollte eine Derivatisierungsmethode entwickelt werden, die die duale Quantifizierung funktioneller Gruppen an Oberflächen mittels Röntgenphotoelektronenspektroskopie (XPS) und Fluoreszenz ermöglicht. Verschiedene Farbstoffe, die robuste Fluoreszenzeigenschaften mit hohen Fluorgehalten für XPS kombinieren, wurden auf ihre selektive Reaktion mit Aminogruppen getestet und der Prototyp einer tiefergehenden Analyse auf einer Oberfläche unterzogen. Durch Fluoreszenzlöschung konnten die Möglichkeiten der bimodalen Analyse nur begrenzt abgeschätzt werden, obwohl in XPS und Fluoreszenz intensive Signale gemessen wurden. Die Herstellung der Modelloberflächen mittels Gasphasenabscheidung von Silanen konnte durch Kontaktwinkelmessungen schrittweise optimiert werden. Die Kombination zweier Monoalkoxysilane ermöglichte die Herstellung von Oberflächen mit variabler Funktionalgruppendichte. Nach Reaktion mit dem dualen Marker ließen sich die Messungen aus XPS und Fluoreszenz mindestens über eine Größenordnung korrelieren. Durch Synchrotron-XPS (SR-XPS) und Röntgenfluoreszenz unter Totalreflektion (TXRF) konnte eine absolute und rückführbare Quantifizierung erzielt werden. Weitere Modelloberflächen auf Basis von Trialkoxysilanen zeigten, dass bei anwendungsnahen Proben Fluoreszenzlöschung auftritt. Diese konnte in einem gewissen Maße mittels Fluoreszenzlebensdauer berechnet werden. Darüberhinaus konnte mit der Photometrie eine unabhängige Methode gefunden werden, die die Quantifizierung des Farbstoffs an der Oberfläche in hoher Präzision ermöglicht und mit Hilfe der XPS auch der funtionellen Gruppen. Die Cavity Ring-Down Spektroskopie (CRDS) wurde als Laserbasierte Methode zur empfindlichen und ortsaufgelösten Messung der Absorption auf transparenten Substraten untersucht und erste vielversprechende Ergebnisse gewonnen. Weiterhin wurde ein modulares Farbstoffsystem entwickelt, das sowohl Variation der spektralen als auch der Bindungseigenschaften erlaubt. / This work aimed on the development of dual-mode labelling method that combines X-ray photoelectron spectroscopy (XPS) with fluorescence measurements for surface functional group quantification. Label dyes combining robust fluorescence properties with high fluorine contents were investigated towards their selective reaction with surface amino groups and the lead candidate subjected to detailed analysis on a surface. Fluorescence quenching precluded a detailed investigation of the capabilities of dual-mode labelling, despite providing sufficient signal in XPS and fluorescence scanning. The fabrication of surfaces using vapour deposition (VD) of silanes in toluene was optimized under aid of contact angle measurements. Binary mixtures of mono-alkoxy silanes were used to prepare surfaces with variable functional group density. Treatment with the label dye showed that XPS and fluorescence provide a linear overlap in signal generation over at least one order of magnitude. The combination of synchrotron radiation XPS (SR-XPS) and total reflection X-ray fluorescence spectroscopy (TXRF) provided an absolute and traceable quantification . Different model surfaces based on trialkoxy silanes showed strong fluorescence quenching. A fluorescence lifetime based correction was developed to account for such quenching effects. Additionally, the application of spectrophotometry provided a independent method of quantification for the surface bound dye and in combination with information obtained from XPS, to determine the surface functional group density. With cavity ring-down spectroscopy (CRDS), a laser based technique for highly sensitive and spatially resolved absorption measurements on transparent substrates could be developed and applied in a proof-of-concept. A modular system for the fabrication of label dyes with adjustable spectral properties and different binding sites was investigated using prototype candidates to prove the general applicability of such systems.

Le développement récent de l’endoscopie interventionnelle digestive nous a conduit à prendre en charge deux types de pathologies préoccupantes. Il s’agit d’une part des fistules digestives souvent responsables d’une morbi-mortalité élevée et d’autre part des sténoses œsophagiennes après résection tumorale endoscopique étendue. Dans ces deux situations, des phénomènes inflammatoires chroniques conduisent soit à l’absence de fermeture de la fistule soit à une fibrose importante responsable de sténose de l’œsophage. La thérapie cellulaire a déjà été utilisée pour diminuer ces phénomènes inflammatoires et entrainer une cicatrisation. La thérapie tissulaire par cellules souches organisées en construction 3D représente un avantage important en permettant de cibler le site d’action par dépôt direct du feuillet cellularisé. Notre objectif était d’évaluer l’effet thérapeutique de ces nouveaux outils pour fermer les fistules digestives et pour prévenir la survenue des sténoses œsophagiennes. La première étape a consisté a évaluer l’efficacité du traitement par des cellules souches mésenchymateuses provenant de moelle osseuse humaine, marquées puis organisées en doubles feuillets, dans un modèle de fistule entéro-cutanée post-chirurgicale chez la souris nude. L’évaluation clinique et en imagerie (IRM et microscopie confocale) a montré une meilleure cicatrisation avec une augmentation de la microvascularisation et une accélération de la fermeture de la fistule chez les souris greffées. Les effets observés semblent liés à une augmentation précoce de la synthèse des facteurs de réparation (EGF et le VEGF) et des cytokines anti-inflammatoires (TGF-ß2 et IL-10). Après avoir développé un modèle inédit de fistule oeso-cutanée chez le porc grâce à la mise en place par voie endoscopique et chirurgicale de prothèses plastiques entre la lumière œsophagienne et la peau, nous avons évalué l’efficacité thérapeutique d’un gel contenant des vésicules extracellulaires issues de cellules souches isolées du tissu adipeux de porc. Ce gel injecté dans la fistule par voie endoscopique a permis la fermeture des fistules. Enfin, la troisième partie de notre travail a consisté à évaluer l’efficacité de la greffe allogénique de doubles feuillets de cellules souches mésenchymateuses pour prévenir la survenue des sténoses œsophagiennes dans un modèle porcin après dissection sous muqueuse étendue. Il existait une réduction significative du taux de sténose œsophagienne cicatricielle dans le groupe greffé avec une fibrose moins importante. En conclusion, l’effet paracrine antifibrosant des cellules souches mésenchymateuses organisées en feuillets est efficace à la fois pour fermer les fistules entéro-cutanées chez la souris et pour prévenir les sténoses œsophagiennes chez le porc. Un gel avec des vésicules extracellulaires issues des cellules souches a de la même façon un effet cicatrisant anti-inflammatoire permettant la fermeture des fistules œsophagiennes chez le porc. Ces résultats sont très encourageants et posent la question d’une évaluation future chez l’homme. / Recent developments in digestive interventional endoscopy lead us to manage two types of digestive disease. First, it is digestive fistulas associated in many cases with high morbi-mortality; and second is oesophageal stenosis after extended superficial endoscopic resection. In both situations, chronic inflammatory process resulted in delayed or no fistula healing for the first case or oesophageal stenosis due to fibrosis. Cellular therapy has proved to be successful in reducing the inflammatory process and to promote tissue healing. Tissue therapy with 3D construct stem cells represents a major advantage by allowing a direct adaptation on the right place. Our objective was to evaluate the therapeutic effect of new strategy to close the digestive fistula and to prevent oesophageal stenosis. First step was to evaluate the effect of labelled human bone marrow derived mesenchymal stem cells engraftment in the form of double cellsheet in a post-surgical fistula model in nude mice. Clinical and radiological (MRI and probe based confocal microscopy) evaluation showed a better fistula healing with higher microvascularization and a faster fistula closing in grafted mice. These effects appear to be related to an increase production of factors involved in tissue repair (EGF et le VEGF) and anti-inflammatory cytokines (TGF-ß2 et IL-10). We developed an unpublished eso-cutaneous fistula in a porcine model after plastic catheters placement by surgical and endoscopic way between the oesophageal lumen and the skin. We evaluated the therapeutic effect of a hydrogel with extracellular vesicles extracted from porcine adipose derived stem cells. The hydrogel with vesicles was injected into the fistula by endoscopy. Radiological and histological evaluation 15 days after injection showed a fistula tract closure in treated group.The third part of this work was to evaluate the effect of allograft of adipose derived stem cells 3D construct to prevent the stenosis after extended endoscopic submucosal dissection in a porcine model. There was a significant reduction of number and degree of stenosis with decrease fibrosis infiltration in the grafted group.In summary, thanks to their paracrine and antifibrotic effect, the mesenchymal stem cells organised as 3D construct allowed fistula closure in an entero-cutaneous model in mice and prevention of stenosis after extended oesophageal submucosal dissection in a porcine model. Moreover, endoscopic hydrogel and extracellular vesicles injection allowed oesophageal fistula healing in a porcine model. These promising results pose the challenge of future clinical studies.

Die Entstehung von Tumoren und damit einhergehenden Veränderungen wurden insbesondere im letzten Jahrzehnt kontrovers diskutiert. Bisher standen nur wenige Datensätze mit ausreichender Datendichte zur Verfügung um eine umfassende Untersuchung der Regulation des Stoffwechsels durchzuführen. Die in dieser Arbeit zusammengefassten Projekte adressieren verschiedene Aspekte der Stoffwechselregulation und beschreiben die Verknüpfung von Zellkulturexperimenten mit innovativen Hochdurchsatz-Technologien, komplexer Datenanalyse und Computer-basierter Modellierung zur Bestimmung der Stoffwechselflüsse in eukaryotischen Zellen. Die Kombination von GC-MS und LC-MS basierten Technologien ermöglicht die quantitative Analyse des zentralen Kohlenstoffwechsels. Markierungsexperimente mit stabilen Isotopen (pSIRM) erlauben die dynamische Analyse der Stoffwechselaktivität. In verschiedenen Projekten wurden das Proteom und Metabolom von Krebszellen, humanen Stammzellen (hESCs), induzierten pluripotenten Stammzellen (iPS) und deren dazugehörigen differenzierten Vorläufer- oder Nachfolgerzellen bestimmt. Die multivariate, statistische Analyse der Daten ermöglichte die Differenzierung verschiedener Zelltypen basierend auf der Kombination aller quantitativ bestimmten Daten. Quantitative Bestimmungen der Poolgrössen, Isotopeninkorporationen, sowie der extrazellulären Raten in neuronalen, pluripotenten Vorläuferzellen (Luhmes d0) und Neuronen (Luhmes d6) ermöglichte die Bestimmung der Stoffwechselflusskarte beider Zelltypen unter Verwendung der instationären metabolischenen Flussanalyse (INST-MFA). Die Etablierung einer Qualitätskontrolle für GC-MS basierte Daten (MTXQC), sowie die Zuordnung der GC-MS Fragmente zur Molekülstruktur, ermöglichten den Ausbau des Netzwerkes des zentralen Kohlenstoffwechsels und die Implementierung der Daten für die metabolische Flussanalyse. / Metabolic reprogramming of the central carbon metabolism (CCM) is highly debated during the last decade. It describes the rearrangement of nutrient consumption for providing energy and building blocks for cellular proliferation and maintenance. So far, only sparse data are available for an in-depth analysis of metabolic reprogramming events. The herein summarised projects address metabolic programming from different perspectives and show the implementation of cell culture experiments, cutting-edge high-throughput technologies, bioinformatics, and computational modelling into one workflow providing the determination of metabolic flux maps of mammalian cells. The combination of GC-MS and LC-MS-based methodologies enable the quantitative analysis of proteins and metabolites of the CCM. Pulsed stable isotope-resolved metabolomics (pSIRM) experiments allow monitoring the fate of nutrients within the network of the CCM. The time-dependent and position-specific incorporation of carbon-13 leads to an indirect measurement of the metabolic flux, the only one functional readout of a cell. High-throughput technologies were applied in four projects to gain insights in metabolic reprogramming in cancer cell lines, human embryonic stem cells (hESCs), induced pluripotent stem (iPS) cells and their derived fibroblasts. A global principal component analysis demonstrated the discrimination of phenotypes by different classes of quantitative data. The comparison of metabolic and protein levels confirms the presence of the Warburg effect in both cell types. Though, the executing enzymes vary regarding their isoenzyme identity and expression levels. Methodological improvements provided the implementation of GC-MS derived data for INST-MFA. The mapping of GC-MS derived fragments to the molecule structure enables an extension of the CCM network. Robustness of the input data has been improved by the development of a R-scripting based quality control tool (MTXQC).

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Cette thèse aborde l'étude de la fonction cérébrale en Imagerie par Résonance Magnétique (IRM) à l'aide de deux séquences : l'IRM fonctionnelle (IRMf) BOLD et l'imagerie de perfusion par marquage de spins (ASL). Dans ce contexte, les analyses de groupe jouent un rôle important dans l'identification des dysfonctionnements globaux associés à une pathologie. D'autre part, les études individuelles, qui fournissent des conclusions au niveau d'un sujet unique, présentent un intérêt croissant. Dans ce travail, nous abordons à la fois les études de groupe et les analyses individuelles. Dans un premier temps, nous réalisons une analyse de groupe en IRMf BOLD en vue d'étudier la dysphasie chez l'enfant, une pathologie peu explorée en neuroimagerie. Nous mettons ainsi en évidence un fonctionnement et une latéralisation atypiques des aires langagières. Ensuite, nous nous concentrons sur les analyses individuelles. Nous proposons l'utilisation d'estimateurs robustes pour calculer les cartographies de débit sanguin cérébral en ASL. Ensuite, nous étudions la validité des hypothèses qui sous-tendent les analyses statistiques standard dans le contexte de l'ASL. Finalement, nous proposons une nouvelle méthode localement multivariée basée sur une approche a contrario. La validation de cette nouvelle approche est réalisée dans deux contextes applicatifs : la détection d'anomalies de perfusion en ASL et la détection de zones d'activation en IRMf BOLD. / This thesis deals with the analysis of brain function in Magnetic Resonance Imaging (MRI) using two sequences: BOLD functional MRI (fMRI) and Arterial Spin Labelling (ASL). In this context, group statistical analyses are of great importance in order to understand the general mechanisms underlying a pathology, but there is also an increasing interest towards patient-specific analyses that draw conclusions at the patient level. Both group and patient-specific analyses are studied in this thesis. We first introduce a group analysis in BOLD fMRI for the study of specific language impairment, a pathology that was very little investigated in neuroimaging. We outline atypical patterns of functional activity and lateralisation in language regions. Then, we move forward to patient-specific analysis. We propose the use of robust estimators to compute cerebral blood flow maps in ASL. Then, we analyse the validity of the assumptions underlying standard statistical analyses in the context of ASL. Finally, we propose a new locally multivariate statistical method based on an a contrario approach and apply it to the detection of atypical patterns of perfusion in ASL and to activation detection in BOLD functional MRI.

The β-acyloxyalkyl radical rearrangement has been known since 1967 but its mechanism is still not fully understood, despite considerable investigation. Since the migration of a β-trifluoroacetoxy group generally proceeds more rapidly and with more varied regiochemistry than its less electronegative counterparts, this reaction was studied in the hope of understanding more about the subtleties of the mechanism of the β- acyloxyalkyl radical rearrangement. The mechanism of the catalysed rearrangement of Nalkoxy- 2(1H)-pyridinethiones was also explored because preliminary studies indicated that the transition state (TS) for this process was isoelectronic with TSs postulated for the β-acyloxyalkyl radical and other novel rearrangements. ¶ A kinetic study of the rearrangement of the 2-methyl-2-trifluoroacetoxy-1-heptyl radical in solvents of different polarity was undertaken using a radical clock method. Arrhenius equations for the rearrangement in each solvent were: hexane, log10[kr (s-1)] = 11.8±0.3 – (48.9±0.7)/ θ; benzene, log10[kr (s-1)] = 12.0±0.2 – (43.7±0.8)/ θ; and propionitrile, log10[kr (s-1)] = 11.9±0.2 – (42.0±0.3)/ θ. Rate constants at 75˚C were: hexane, kr = 2.9 × 104; benzene, kr = 2.8 × 105; and propionitrile, kr = 4.0 × 105 s-1. The equilibrium constant for the reversible rearrangement at 80°C in benzene was 15.1 <K < 52.9. ¶ A regiochemical study with oxygen-labelled radicals revealed that trifluoroacetoxy group migration occurs with 66-83% label transposition (3,2 shift). The proportion of 3,2 shift is decreased by polar solvent, high temperature and low concentration of the reducing agent. Results of labelling experiments were consistent with cooperative 1,2 and 3,2 shifts, the former having Ea 9.5 kJmol-1 higher than the latter in benzene solution. ¶ An esr study of nine β-oxygenated radicals revealed that the temperaturedependent equilibrium conformation is controlled by a balance between steric and stereoelectronic effects. The influence of the latter is increased by electron-attracting β- substituents. Barriers to C α–C β rotation in β-oxyethyl radicals are approximately the same as for the propyl radical. Consequently, there is no significant through-space interaction between the β-substituent and the unpaired electron. ¶ Experimental results were consistent with a mechanism involving a combination of polarized 1,2 and 3,2 concerted shifts. The results may also be rationalised by the intermediacy of a contact ion pair, as well as combinations of the three options. ¶ The rearrangement of N-alkoxy-2(1H)-pyridinethiones is catalysed by oxidants, Lewis acids and protic acids. Pseudo first order kinetics are observed and there are moderate solvent effects. The migration of a 1,1-dideuteroallyl group occurs almost exclusively in a 1,4 sense. Migration of an enantiomerically enriched 1-phenylethyl group proceeds with predominant retention of configuration in chloroform, but with virtual racemisation in acetonitrile. Migrating groups do not become diffusively free during the rearrangement. Substituents which stablise positive charge at C1 migrate more rapidly. The bulk of evidence indicates that a catalyst activates the pyridinethione for rearrangement by promoting aromatisation. Mass-spectrometric analysis of an isolated intermediate and kinetic results are consistent with an intermolecular mechanism.