Diffusion-weighted magnetic resonance imaging can be used to estimate microstructural parameters of white matter in the brain. Two complementary techniques are investigated: the use of the temporal diffusion spectrum to explore small length scales and the STEAM technique to probe larger features. The diffusion spectrum has the potential to be more sensitive to small pores compared to conventional time-dependent diffusion. However, analytical expressions for the diffusion spectrum of particles only exist for simple geometries such as cylinders, which are often used as a model for intra-axonal diffusion. We propose a mathematical model for the extra-axonal space with parameters that are related to the microstructural properties of pore size, tortuosity, and surface-to-volume ratio. Measurements were made with an extra-axonal space phantom to validate the model. Fitted values for the phantom pore size match those from simulation. We extend the model to include the intra-axonal signal contribution. However, the parameters used to describe the intra- and extra-axonal spaces are related and it is important to remove redundant parameters to avoid overparameterization, which would make the model less robust. We propose analytical expressions to simplify the model. The model was then applied to measurements on fixed corpus callosum, which is a model system consisting of parallel axons. The estimated values of the axon volume fraction and mean and standard deviation of the axon radius distribution are comparable to those found in literature. Temporal diffusion spectra are useful for measuring the geometric properties of small spaces such as axon radii. However, longer diffusion times accessible using the STEAM sequence are necessary to probe structures with longer diffusion distances such as those parallel to the direction of axons. We used a model from the literature originally developed for use with animal magnetic resonance scanners and simplified it to quantify axial hindrance from data acquired on healthy volunteers in a clinical scanner. The interpretation of axial hindrance, which is a largely unexplored area of research, is discussed.

Récemment, une nouvelle classe d'ADN circulaire extrachromosomique (eccDNA) appelée microADN a été identifiée dans des tissus humains et murins. Ces microADNs ont une longueur de 100 à 400 pb, sont dérivés de régions génomiques non répétitives uniques et présentent un enrichissement au niveau des régions géniques et riches en GC. Bien qu'il ait été proposé qu'ils puissent provenir du métabolisme de l'ARN ou des défauts de réplication, leurs mécanismes de production et leur éventuelle fonctionnalité restent à déterminer. Grâce à l'analyse des microADNs extraits d'une série de 10 lignées cellulaires lymphoblastoïdes humaines (LCL), nous avons confirmé la distribution nonaléatoire des microADNs vers les régions actives du génome. Les microADNs identifiés présentaient des loci d'origine redondants et une périodicité de taille de 190 pb pouvant correspondre à la fragmentation de l'ADN lors de l'apoptose caspase-dépendante. L'apoptose induite de ces LCLs par des drogues chimiothérapeutiques (méthotrexate ou L-asparaginase) a entrainé la modulation de la diversité et de la taille des microADNs, suggérant qu'une partie de ces entités pourrait être des produits résiduels de la mort cellulaire apoptotique. Ainsi, bien que compatible avec l'observation initiale suggérant que les microADNs proviennent d'un processus physiologique normal, ces résultats impliquent une source de production alternative ou complémentaire. / Recently, a new class of extrachromosomal circular DNA (eccDNA) called microDNA was identified in mouse and human tissues. These microDNAs are 100 to 400 bp long, derive from unique nonrepetitive genomic regions and show an enrichment in GC rich and genic sequences. While it has been proposed that they could arise from RNA metabolism or replication defects, their production mechanisms and eventual functionality remain unclear. Through the analysis of microDNAs extracted from a series of 10 human lymphoblastoid cell lines (LCLs), we confirmed the non-random distribution of microDNA towards active regions of the genome. Identified microDNAs showed redundant loci of origin and a size periodicity of 190 bp that matched caspase-dependant DNA fragmentation of apoptotic cells. Strikingly, the chemotherapeutic drug-induced apoptosis (using methotrexate or Lasparaginase) of these LCLs modulated both diversity and size of microDNAs further suggesting that a part of microDNAs could represent circularized by-products of the programmed cell death. Thus, while compatible with the original observation that microDNAs originated from a normal physiological process, these results imply an alternative or complementary source of production.

Based upon two years of ethnographic fieldwork in London, England, which incorporated nearly 200 interviews with gang members, gang associates, and police officers, among others, this thesis addresses three questions presently unresolved in the street gangs literature: What is the business of gangs? How are gangs organised? And how do gangs recruit? With regard the business of gangs, this thesis illustrates how recreation, crime, enterprise, and extra-legal governance represent sequential stages in the evolutionary cycle of London’s street gangs. Gang member testimony emphasises how gangs typically begin life as neighbourhood-based peer groups, but also how, in response to external threats and financial commitments, gangs grow to incorporate street-level drugs distribution businesses that very much resemble the multi-level marketing structure of direct-sales companies. People join gangs to make money, achieve status, and obtain protection. Gangs engage in turf wars, acquire violent resources, and develop hierarchical structures in order to maintain provision of these desirable goods and services. Gang organisation, in turn, becomes a function of gang business. To better understand the nature and extent of gang organisation, this thesis moves on to discuss the presence of subgroups, hierarchy and leadership, pecuniary and non-pecuniary incentives, rules, responsibilities, and restrictions, and consequences for absconding within gangs. It further presents how, in order to convey reputation and achieve intimidation, gangs seek association with elements of popular culture that help promote their image. Finally, through the novel application of signalling theory to the gang recruitment process, this thesis demonstrates how gangs face a primary trust dilemma in their uncertainty over the quality of recruits. Given that none of the trust-warranting properties for gang membership can be readily discovered from observation, gangs look for observable signs correlated with these properties. Gangs face a secondary trust dilemma in their uncertainty over the reliability of signs because certain agents (e.g., police informants, rival gang members, and adventure-seekers) have incentives to mimic them. To overcome their informational asymmetry gangs thus screen for signs that are too costly for mimics to fake but affordable for the genuine article. The thesis concludes with a discussion of gang desistance and intervention in the context of escalating youth violence in London.

'Thieves-in-law' (vory-v-zakone in Russian or kanonieri qurdebi in Georgian) are career criminals belonging to a criminal fraternity that has existed at least since the 1930s in the Soviet Gulag. These actors still exist in one form or another in post-Soviet countries and have integrated into transnational organised criminal networks. For reasons yet to be explicated, thieves-in-law became exceptionally prevalent in the Soviet republic of Georgia. Here, by the 1990s, they formed a mafia network where this means criminal associations that attempt to monopolize protection in legal and illegal sectors of the economy. In 2005, Mikhail Saakashvili, the current president of Georgia claimed that 'in the past 15 years ... Georgia was not ruled by [former President] Shevardnadze, but by thieves-in-law.' Directly transferring anti-organised crime policy from Italy and America, Saakashvili's government made reform of the criminal justice system generally and an attack on the thieves-in-law specifically a cornerstone of the Rose Revolution. New legislation criminalises the possession of the status of ‘thief-in-law’ and of membership of criminal associations that constitute what is known as the ‘thieves’ world’ (qurduli samkaro). Along with a sweeping reform of the police and prisons and a ‘culture of lawfulness’ campaign, Georgian criminal justice reforms since 2003 may be seen as the first sustained anti-mafia policy to be implemented in a post-Soviet country. It also appears to have been very successful. The longevity and sudden decline of the thieves-in-law in Georgia provides the main questions that the following study addresses: How do we account for changes in the levels of resilience to state attack of actors carrying the elite criminal status of ‘thief-in-law’? How has this resilience been so effectively compromised since 2005? Utilising unique access to primary sources of data such as police files, court cases, archives and expert interviews this thesis studies the dynamics of changing mafia activities, recruitment practices, and structural forms of a criminal group as it relates to changes in the environment and, in particular, the recent anti-organised crime policy.

Distribués sous des licences permissives qui assurent des droits d'utilisation, de modification et de redistribution aux licenciés, l'élaboration des logiciels libres est fondée sur un modèle de développement décentralisé. Ces caractéristiques posent de nombreux défis au milieu juridique, particulièrement en ce qui a trait à la responsabilité civile. Ainsi, les développeurs se demandent dans quelles circonstances leur responsabilité civile peut être engagée suite à la défaillance de leur logiciel libre. De la même façon, ils questionnent la possibilité d'appliquer cette responsabilité à un nombre important de développeurs dispersés aux quatre coins du globe. L'analyse présentée montre que le droit, tel qu'il existe actuellement, est en mesure de résoudre la majorité des problèmes relatifs à la détermination et l'application de la responsabilité civile en matière de logiciels libres. Les règles de la responsabilité civile représentent donc un risque potentiel pour les développeurs de logiciels libres, même s'ils sont relativement bien protégés par les contextes juridiques et factuels. / Distributed under permissive licenses that guarantee the users use, modification and redistribution rights, the development of free software is decentralized. Numerous legal challenges flow from this, particularly respecting civil liability matthers. In consequence, developers are concerned regarding the circumstances in which they could be liable based on the faillure of their free software. They are equally questionning the possibility that numerous developers scattered around the world could be jointly liable. The analysis show that the law, in its actual form, is able to answer the majority of the issues resulting from the establishment and the application of civil liability regarding free software. In this way, civil liability rules are representing a potential risk to free software developers, even if they are relatively weil protected by the legal and factual contexts.

This study explored how course instructional format (i.e., online, face-to-face, or hybrid) is related to the frequency and duration of out-of-class communication (OCC) between college instructors and students, to student motives for communicating with teachers, and to perceived teacher approachability for conversation outside of class. Though differences in frequency of and student motives for engaging in OCC were not significant, students enrolled in face-to-face courses reported significantly more ongoing/durative OCC with their instructors compared to students enrolled other course types (i.e., online or hybrid). Students in fully online courses reported instructors to seem less receptive to but also less discouraging of OCC than students in face-to-face or hybrid courses. Overall, this study offers a sense of how students who seek informal interaction with instructors beyond the classroom are faring amid the increased reliance on web-based learning environments in higher education.

"This survey of extra-curricular activates in North Texas State Teachers College from 1919 to 1939 was made to determine when and how extra-curricular activates made their appearances and developed in this institution."--v.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

TITLE: Extra-curricular activities as a support to the School educational programmes SUMMARY: The diploma thesis deals with the theme of extra-curricular activities and their supporting the curricular documents. The objectives of this thesis are to describe how extra-curricular activities support the School Education Programmes and the acquisition of the cross-curricular subjects after class. To meet these objectives the author applies triangulation of qualitative methods with the grounded theory design. The benefits of this thesis lie in pointing out the fact that leisure time activities can support the acqusition of the cross curricular subjects in schools and the provision of further findings about the possibilities of extra-curricular activities within the frame of the School Education Programmes.

Le système d’activation du plasminogène (AP) comprenant les protéases uPA et tPA, et leur inhibiteur PAI-1, génère une activité protéolytique dans la matrice extracellulaire et contribue au remodelage tissulaire dans une grande variété de processus physiopathologiques, y compris la myogenèse squelettique, et la différenciation adipocytaire.Nous avons évalué son rôle spécifique dans la différenciation des cellules souches embryonnaires (ES) de souris. On a trouvé que les activités d’uPA et de tPA ainsi que les niveaux protéiques de PAI-1 sont maximaux dans les cellules différenciées, contrairement aux cellules ES indifférenciées où ils sont indétectables et augmentent progressivement dès le jour 3 de la différenciation. La différenciation adipocytaire dans le modèle des cellules ES est inhibée par le traitement par l’amiloride, un inhibiteur spécifique de l’uPA. Egalement, les cellules ES surexprimant une forme active du PAI-1 sous le contrôle d’un système d’expression inductible, montrent des capacités adipogéniques réduites après l’induction du gène. Nos résultats démontrent que le contrôle de l’adipogenèse des cellules ES par le système AP correspond à des étapes successives, différentes, depuis les cellules indifférenciées jusqu’aux cellules bien différenciées. De plus, les capacités de la différenciation adipogénique des cellules pluripotentes induites déficientes en PAI-1 sont augmentées par rapport aux cellules contrôles.Similairement, la myogenèse squelettique est réduite par l’inhibition de l’uPA par l’amiloride ou par la surexpression du PAI-1 durant l’étape terminale de la différenciation du jour 7 au jour 24. Cependant, l’interférence avec l’uPA durant les jours 0 à 3 de la différenciation, stimule la formation des myotubes. Les différenciations cardiomyocyotaire, neuronale, endothéliale et du du muscle lisse ne sont pas affectées par le traitement à l’amiloride ou la surexpression du PAI-1.Nos résultats montrent que le système AP est capable de moduler spécifiquement l’adipogenèse et la myogenèse squelettique des cellules ES par des mécanismes moléculaires successifs différents. / Regulation of the extracellular matrix (ECM) plays an important functional biological role either in physiological or pathological conditions. The plasminogen activation (PA) system, comprising the uPA and tPA proteases and their inhibitor PAI-1, is one of the main suppliers of extracellular proteolytic activity contributing to tissue remodeling. Although its function in development is well documented, its precise role in mouse embryonic stem cell (ESC) differentiationin vitro is unknown. We found that uPA and tPA activities and PAI-1 protein are very low in undifferentiated ESCs and increase strongly during the differentiation, reaching a maximum in well differentiated cells. Adipocyte formation by ESCs is inhibited by amiloride treatment, a specific uPA inhibitor. Likewise, ESCs expressing ectopic PAI-1 under the control of an inducible expression system, display reduced adipogenic capacities after induction of the gene. Our results demonstrate that the control of ESC adipogenesis by the PA system correspond to different successive steps from undifferentiated to well differentiated ESCs. Furthermore, the adipogenic differentiation capacities of PAI-1-/- induced pluripotent stem cells (iPSCs) are augmented as compared to wt iPSCs. Similarly, skeletal myogenesis is decreased by uPA inhibition or PAI-1 overexpression during the terminal step of differentiation. However, interfering with uPA during days 0 to 3 of the differentiation process augments ESC myotube formation. Neither neurogenesis, cardiomyogenesis, endothelial cell nor smooth muscle formation are affected by amiloride or PAI-1 induction. Our results show that the PA system is capable to specifically modulate adipogenesis and skeletal myogenesis of ESCs by successive different molecular mechanisms.