A framework for Thinking about Distributed Cognition

As is often the case when scientific or engineering fields emerge, new concepts are forged or old ones are adapted. When this happens, various arguments rage over what ultimately turns out to be conceptual misunderstandings. At that critical time, there is a need for an explicit reflection on the meaning of the concepts that define the field. In this position paper, we aim to provide a reasoned framework in which to think about various issues in the field of distributed cognition. We argue that both relevant concepts, distribution and cognition, must be understood as continuous. As it is used in the context of distributed cognition, the concept of distribution is essentially fuzzy, and we will link it to the notion of emergence of system-level properties. The concept of cognition must also be seen as fuzzy, but for different a reason: due its origin as an anthropocentric concept, no one has a clear handle on its meaning in a distributed setting. As the proposed framework forms a space, we then explore its geography and (re)visit famous landmarks

Phase Space Engineering in Optical Microcavities I: Preserving near-field uniformity while inducing far-field directionality

Optical microcavities have received much attention over the last decade from different research fields ranging from fundamental issues of cavity QED to specific applications such as microlasers and bio-sensors. A major issue in the latter applications is the difficulty to obtain directional emission of light in the far-field while keeping high energy densities inside the cavity (i.e. high quality factor). To improve our understanding of these systems, we have studied the annular cavity (a dielectric disk with a circular hole), where the distance cavity-hole centers, d, is used as a parameter to alter the properties of cavity resonances. We present results showing how one can affect the directionality of the far-field while preserving the uniformity (hence the quality factor) of the near-field simply by increasing the value of d. Interestingly, the transition between a uniform near- and far-field to a uniform near- and directional far-field is rather abrupt. We can explain this behavior quite nicely with a simple model, supported by full numerical calculations, and we predict that the effect will also be found in a large class of eigenmodes of the cavity.Comment: 12th International Conference on Transparent Optical Network

Étude des éléments impliqués dans le transport et la régulation traductionnelle de l'ARNm ASH1 chez la levure Saccharomyces cerevisiae

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Human Skin Modelling and Rendering

Creating realistic-looking skin is one of the holy grails of computer graphics and is still an active area of research. The problem is challenging due to the inherent complexity of skin and its variations, not only across individuals but also spatially and temporally among one. Skin appearance and reflectance vary spatially in one individual depending on its location on the human body, but also vary temporally with the aging process and the body state. Emotions, health, physical activity, and cosmetics for example can all affect the appearance of skin. The spatially varying reflectance of skin is due to many parameters, such as skin micro- and meso-geometry, thickness, oiliness, and pigmentation. It is therefore a daunting task to derive a model that will include all these parameters to produce realistic-looking skin. The problem is also compounded by the fact that we are very well accustomed to the appearance of skin and especially sensitive to facial appearances and expressions. Skin modelling and rendering is crucial for many applications such as games, virtual reality, films, and the beauty industry, to name a few. Realistic-looking skin improves the believability and realism of applications. The complexity of skin makes the topic of skin modelling and rendering for computer graphics a very difficult, but highly stimulating one. Skin deformations and biomechanics is a vast topic that we will not address in this dissertation. We rather focus our attention on skin optics and present a simple model for the reflectance of human skin along with a system to support skin modelling and rendering

Complex microwave conductivity of Pr1.85_{1.85}Ce0.15_{0.15}CuO4−δ_{4-\delta} thin films using a cavity perturbation method

We report a study of the microwave conductivity of electron-doped Pr$_{1.85}$Ce$_{0.15}$CuO$_{4-\delta}$ superconducting thin films using a cavity perturbation technique. The relative frequency shifts obtained for the samples placed at a maximum electric field location in the cavity are treated using the high conductivity limit presented recently by Peligrad $\textit{et}$ $\textit{al.}$ Using two resonance modes, TE$_{102}$ (16.5 GHz) and TE$_{101}$ (13 GHz) of the same cavity, only one adjustable parameter $\Gamma$ is needed to link the frequency shifts of an empty cavity to the ones of a cavity loaded with a perfect conductor. Moreover, by studying different sample configurations, we can relate the substrate effects on the frequency shifts to a scaling factor. These procedures allow us to extract the temperature dependence of the complex penetration depth and the complex microwave conductivity of two films with different quality. Our data confirm that all the physical properties of the superconducting state are consistent with an order parameter with lines of nodes. Moreover, we demonstrate the high sensitivity of these properties on the quality of the films

Sensitivity of the retrosplenial cortex to distal damage in a network associated with spatial memory: Evidence from lesion and gene expression studies in the rat

This thesis explores the influence of brain regions in the extended hippocampal system on the activity of the retrosplenial cortex in the rat. The primary motivation of the experiments presented in this thesis is to improve the understanding of the vulnerability of the retrosplenial cortex, especially in the context of diencephalic amnesia and Alzheimer's disease. Using molecular imaging, it is shown that discernible networks of brain regions are active even at different training levels of the same spatial memory task, not just between different tasks. I provide evidence that multiple brain regions exhibit a relationship with memory. Importantly, these regions display associations with different memory components, which change according to the experience and the performance level of the subjects. The lesion studies provide information about the vulnerability of granular b retrosplenial cortex to distal damage in certain regions. The pattern of the terminations of the projections from each region to the retrosplenial cortex does not appear to be predictive of the impact that damage to each will have on immediate-early gene activity in the latter. In addition to the anterior thalamic nuclei, the retrosplenial cortex is vulnerable to damage in the entorhinal cortex and in the hippocampus, but not in the laterodorsal thalamic nucleus. I show that retrosplenial cortex dysfunction can occur as early as one week after anterior thalamic nuclei lesions. Evidence is also shown to suggest that both granular and dysgranular subregions of the retrosplenial cortex are affected as a result of anterior thalamic nuclei lesions. Finally, the presence of hormonal alterations in dysfunctional retrosplenial cortex tissue and evidence from a microarray analysis suggest that this region exhibits widespread alterations in cellular function after anterior thalamic nuclei lesions. The effects presented and the mechanisms that are proposed contribute to our understanding of the vulnerability of the retrosplenial cortex to neurological insults

Performativité, pouvoir et subjectivité : la généalogie foucaldienne comme pratique de liberté

Que l’on parle de la folie, de la délinquance ou de la sexualité, la performativité traverse toujours l’analyse de Foucault : les discours constituent des objets de savoir en introduisant des effets normatifs propres à des pratiques de pouvoir. C’est pourquoi la généalogie foucaldienne se refuse toujours de prendre l’Homme comme une donnée apriorique, mais se penche plutôt sur le phénomène historique de sa constitution. En reconnaissant les diverses technologies de fabrication de soi, la généalogie ouvre donc un espace possible de transformation de la subjectivité qui « cherche à relancer aussi loin et aussi largement que possible le travail indéfini de la liberté »

Modélisation des réseaux de régulation de l’expression des gènes par les microARN

Les microARN sont de petits ARN non codants d'environ 22 nucléotides impliqués dans la régulation de l'expression des gènes. Ils ciblent les régions complémentaires des molécules d'ARN messagers que ces gènes codent et ajustent leurs niveaux de traduction en protéines en fonction des besoins de la cellule. En s'attachant à leurs cibles par complémentarité partielle de leurs séquences, ces deux groupes de molécules d'ARN compétitionnent activement pour former des interactions régulatrices. Par conséquent, prédire quantitativement les concentrations d'équilibres des duplexes formés est une tâche qui doit prendre un compte plusieurs facteurs dont l'affinité pour l'hybridation, la capacité à catalyser la cible, la coopérativité et l'accessibilité de l'ARN cible. Dans le modèle que nous proposons, miRBooking 2.0, chaque interaction possible entre un microARN et un site sur un ARN cible pour former un duplexe est caractérisée par une réaction enzymatique. Une réaction de ce type opère en deux phases : une formation réversible d'un complexe enzyme-substrat, le duplexe microARN-ARN, suivie d'une conversion irréversible du substrat en produit, un ARN cible dégradé, et de la restitution l'enzyme qui pourra participer à une nouvelle réaction. Nous montrons que l'état stationnaire de ce système, qui peut comporter jusqu'à 10 millions d'équations en pratique, est unique et son jacobien possède un très petit nombre de valeurs non-nulles, permettant sa résolution efficace à l'aide d'un solveur linéaire épars. Cette solution nous permet de caractériser précisément ce mécanisme de régulation et d'étudier le rôle des microARN dans un contexte cellulaire donné. Les prédictions obtenues sur un modèle de cellule HeLa corrèlent significativement avec un ensemble de données obtenu expérimentalement et permettent d'expliquer remarquablement les effets de seuil d'expression des gènes. En utilisant ces prédictions comme condition initiale et une méthode d'intégration numérique, nous simulons en temps réel la réponse du système aux changements de conditions expérimentales. Nous appliquons ce modèle pour cibler des éléments impliqués dans la transition épithélio-mésenchymateuse (EMT), un mécanisme biologique permettant aux cellules d'acquérir une mobilité essentielle pour proliférer. En identifiant des éléments transcrits différentiellement entre les conditions épithéliale et mésenchymateuse, nous concevons des microARN synthétiques spécifiques pour interférer avec cette transition. Pour ce faire, nous proposons une méthode basée sur une recherche gloutonne parallèle pour rechercher efficacement l'espace de la séquence du microARN et présentons des résultats préliminaires sur des marqueurs connus de l'EMT.MicroRNAs are small non-coding RNAs of approximately 22 nucleotide long involved in the regulation of gene expression. They target complementary regions to the RNA transcripts molecules that these genes encode and adjust the concentration according to the needs of the cell. As microRNAs and their RNA targets binds each other with imperfect complementarity, these two groups actively compete to form regulatory interactions. Consequently, attempting to quantitatively predict their equilibrium concentrations is a task that must take several factors into account, including the affinity for hybridization, the ability to catalyze the target, cooperation, and RNA accessibility. In the model we propose, miRBooking 2.0, each possible interaction between a microRNA and a binding site on a target RNA is characterized by an enzymatic reaction. A reaction of this type operates in two phases: a reversible formation of an enzyme-substrate complex, the microRNA-RNA duplex, and an irreversible conversion of the substrate in an RNA degradation product that restores the enzyme which can subsequently participate to other reactions. We show that the stationary state of this system, which can include up to 10 million equations in practice, has a very shallow Jacobian, allowing its efficient resolution using a sparse linear solver. This solution allows us to characterize precisely the mechanism of regulation and to study the role of microRNAs in a given cellular context. Predictions obtained on a HeLa S3 cell model correlate significantly with a set of experimental data obtained experimentally and can remarkably explain the expression threshold effects of genes. Using this solution as an initial condition and an explicit method of numerical integration, we simulate in real time the response of the system to changes of experimental conditions. We apply this model to target elements involved in the Epithelio-Mesenchymal Transition (EMT), an important mechanism of tumours proliferation. By identifying differentially expressed elements between the two conditions, we design synthetic microRNAs to interfere with the transition. To do so, we propose a method based on a parallel greedy best-first search to efficiently crawl the sequence space of the microRNA and present preliminary results on known EMT markers

Le rôle de la performativité dans la méthode de Michel Foucault

Partant des rapports problématiques de Foucault à la performativité austinienne, ce mémoire investigue les évolutions méthodologiques de l’archéologie et de la généalogie en soulignant les éléments qu’elles extraient de la théorie des actes de langage. Si les savoirs que nous restituent les premiers travaux de Foucault produisent une série d’effet dans le réel, c’est parce que l’analyse du discours découvre une performativité d’un niveau inédit par rapport aux énoncés performatifs d’Austin : les discours aux énoncés anonymes tirent des effets de pouvoir au travers même de leurs prétentions descriptives. De façon analogue, les analyses plus tardives des processus de subjectivation dévoilent comment dans cette articulation entre savoir et pouvoir le rapport du sujet à lui-même se donne comme la pierre de touche du discours : le sujet doit tenir sur lui-même une série précise de propos dont la récitation et l’adhésion apparaissent nécessaire pour fonder, voire produire sa subjectivité. Pareille fondation se veut corrélative d’un troisième niveau de performativité, soit celle d’un discours du sujet par lui-même et sur lui-même, en somme, une performativité de la subjectivation.Starting from the problematic relationship of Foucault towards Austin’s performativity, this research investigates the methodological evolutions of the archeology and genealogy while looking at the elements imported from the speech act theory. If the knowledges that depict Foucault’s early works are producing a series of effects into reality, it is because the analysis of discourse discovers a new level of performativity in comparison to Austin’s performative utterances: the anonymous discourses generate effects of power through their own descriptive functions. In a similar way, the later analysis of subjectivation procedures shows how inside the articulation of knowledge and power the relationship to the self is a key element of discourse: the subject must recite and adhere to precise types of utterances to produce and establish his subjectivity. Such foundation is the correlate of a third level of performativity where the discourse of the self must be held by the subject and on himself, in other words a performativity of subjectivation