Magnesium alloys are being increasing considered for many automotive applications due their low density and high strength to weight ratio. However, joining of these materials by welding and especially to dissimilar materials such as aluminum or steel or mechanically by riveting at room temperature have faced many challenges. Research presented in thesis explores a new hot joining process referred to as Upset Protrusion Joining (or UPJ) as a means of mechanically joining cast magnesium alloy to other similar or dissimilar sheet materials. UPJ is being developed as a rapid and reliable joining method to be implemented in the automotive industry for weight and manufacturing cost reduction. It involves a cylindrical protrusion emanating perpendicular to the flat surface of a cast plate-like magnesium component that is fitted through a hole in another plate or sheet material. The two components are then clamped together, electrically heated and compressed perpendicular to the axis of the protrusion. During this process, the protrusion expands circumferentially to fill the hole as well as the region above the hole thus entrapping the sheet metal between the mushroomed head and the casting. The effect of different UPJ process parameters such as applied current, current duration, compression loading rate and compression distance were studied through experimentation that involved a newly developed computer-controlled experimental UPJ setup. The studies involved two cast magnesium alloys of interest to automotive industry, AM60 and AZ91, with protrusions of 11 mm diameter and 14 mm height on a 2 mm thick plate. Studies of the material properties and UPJ process parameters were performed to find optimal process parameters to achieve satisfactory quality of the joint in terms of post-UPJ joint strength with appearance. Also, microstructural studies, temperature measurements in the protrusion region, and electrical resistivity measurements were performed for the two alloys to fundamentally understand their roles in promoting temperature dependent material flow, strain localization, and fracture in the UPJ process. Lastly, materials specific process window for UPJ process was identified based on the experimental work for creation of robust UPJ joints with acceptable joint strengths in tensile shear mode of failure. This new hot joining method was shown as an industrially viable joining method for cast magnesium component. UPJ is a rapid joining method and provides good joint-strength depending upon joint specifications. This method can be implemented in automotive and other industrial manufacturing environment for joining cast component to a similar or dissimilar wrought sheet component. / Thesis / Master of Applied Science (MASc)

Indispensable to all modes of migration used during single cell metastasis, cytoplasmic protrusions are pivotal in surveying cells local surroundings which ultimately initiates migration of the cell body. Cancer cell migration is fairly well studied with the traditional focus on protrusion driven cell body displacement, while less is known on the role of protrusions in sensing cellular microenvironments. Here, we present a suspended and aligned fiber platform capable of high spatio-temporal imaging of protrusions capable of sensing fiber curvature contrasts independent of cell migration. By varying the diameter of suspended fibers, we are able to maintain cell migration along low curvature-large diameter (2μm) fibers, while solely allowing cells to sense, initiate, and mature protrusions on orthogonally deposited high curvature-low diameter (~100, 200 and 600 nm) fibers. Using highly aggressive breast MDA-MB-231 and brain glioblastoma DBTRG-05MG model systems, we find that MDA-MB-231 protrusion maturation dynamics are more sensitive to changes in fiber curvature and fibronectin ligand coating concentration compared to DBTRG-05MG. Furthermore, we find that vimentin intermediate filaments localize within 70% of mature protrusions, which normally form on larger diameter fibers. Additionally, protrusion lengths fluctuate continuously until the protrusion is either terminated or stabilized, and occasionally protrusions are observed to shed cytoplasmic fragments. Through manipulation of curvature contrasts, we demonstrate single protrusive hierarchical decomposition and coordination in zeroth (main), first and second order branches. The fiber curvature platform presented here uniquely allows cancer cells to sense nanofiber curvature contrasts, thus providing new mechanistic insights in protrusion initiation, maturation, and hierarchical coordination. / Master of Science

In a targeted proteomic screen to identify polarity protein complexes, a number of Scribble (Scrib) -associating proteins were identified; of particular interest was the Nitric Oxide Synthase 1 Adaptor Protein (NOS1AP). NOS1AP contains an N-terminal phosphotyrosine binding (PTB) domain and a C-terminal PSD-95/Dlg homology/ZO-1 (PDZ) binding motif that associates with neuronal NOS (NOS1). We show that the PTB domain of NOS1AP associates with the fourth PDZ domain of Scrib. We identified NOS1AP binding partners including three key regulators of dendritic spine formation, beta-Pix, Git1, and PAK, which require Scrib to associate with NOS1AP. Overexpression of NOS1AP in cultured hippocampal neurons increases dendritic protrusions, a process dependent on the PTB domain. The increase in dendritic protrusions can be blocked by the co-expression of a dominant negative Rac construct. NOS1AP, and the PTB domain of NOS1AP influence Rac activity. Together these data suggest that Scrib and NOS1AP function as important scaffolding proteins in the mammalian synapse and that NOS1AP functions in the dendritic spine by influencing Rho GTPase activity.

Lors de l’élaboration des aciers plats inoxydables, un recuit haute température de courte durée (60 s environ), sous atmosphère oxydante (O2/H2O/CO2/N2) est mis en place après laminage à froid. Ce recuit entraîne la formation d’une couche d’oxyde de faible épaisseur qui est éliminée par un décapage. Ces étapes de recuit et décapage peuvent entraîner une perte de qualité du produit fini, se traduisant par une perte de brillance. L’acier bistabilisé Ti, Nb (AISI 441) est sensible à la dégradation de surface. L’objectif de la thèse est d’identifier les phénomènes à l’origine de la perte de brillance. Les travaux menés consistent à étudier les couches d’oxyde et le comportement de l’acier lors du décapage. Une morphologie originale de l’interface interne avec la présence de protrusions métalliques a été observée. L’étude des protrusions par la microscopie électronique à balayage couplée à une sonde ionique focalisée : MEB-FEG/FIB, a permis de proposer un mécanisme décrivant leur formation. Ce mécanisme s’appuie sur la précipitation de la silice qui semble également être un élément clé pour comprendre la dégradation de surface. Un lien entre perte de brillance et teneur en chrome dans le substrat a été établi. La déchromisation de l’acier liée au recuit est susceptible d’être facilitée par les protrusions. / During the industrial processing line of stainless steel flat products, a short annealing (60 s) at high temperature in a gas furnace-oxidizing atmosphere (O2/H2O/CO2/N2) takes place after cold rolling. This annealing leads to the formation of a thin oxide film which is then removed by a pickling step at the end of the process. The annealing and pickling stages may cause a loss of gloss, resulting in a loss of product quality. The steel bistabilizied Ti, Nb (AISI 441) is sensitive to this surface degradation. The aim of this thesis is to identify the phenomena leading to the loss of gloss. Our work consists in studying the oxide layers and the behavior of steel during pickling. A peculiar morphology of the internal interface with the presence of metallic protrusions was observed. The protrusions investigation using a scanning electron microscopy coupled with a focused ion beam: MEB-FEG/FIB, allowed us to propose a mechanism of their formation. This mechanism is based on the precipitation of silica which also appears to be a key point to understand the surface degradation. A link between the loss of gloss and the chromium content in the substrate was established and the chromium depletion related to the annealing is likely to be facilitated by protrusions.

Morton’s syndrome is a foot condition where the 1st metatarsal does not protrude as far distally as the 2nd metatarsal. Clinicians believe that short 1st metatarsal protrusion affects foot mechanics and leads to painful conditions of the foot. Normal protrusion ratio of the 1st and 2nd metatarsal has not been delineated in scientific literature, and little is known about the mechanics of feet with short 1st metatarsal protrusion beyond anecdotal clinical evidence. In the first part of this two-part study, a novel tool was developed to guide metatarsal measurement and reduce measurement error so values for normal metatarsal protrusion ratios could be established. In the second part, subjects were divided into those with shorter and longer than average 1st metatarsal protrusion ratio and we measured if there were any differences in the foot-floor forces between the two groups. In Part 1, the feet of 65 healthy subjects were measured with a novel measurement tool and it was determined that the average ratio (1st metatarsal/2nd metatarsal) was 0.902, suggesting a 1st metatarsal that does not protrude as far distally as the 2nd metatarsal. For Part 2, participants were divided into two groups: the short 1st metatarsal group had a ratio of more than one standard deviation below the mean (0.866 or lower) while the control group had a metatarsal ratio of more than one standard deviation above the mean (0.938 or higher). We hypothesized that short 1st metatarsal protrusion would cause an imbalance across the forefoot because the 1st metatarsal would not be able to carry the required load on the medial side of the foot; however, the results of the gait study did not show this as only forces in the walking direction near toe-off correlated with metatarsal protrusion ratio. We can only speculate as to the relationship between the metatarsal protrusion ratio and increased shear force in the walking direction, but it is possible that to compensate for the diminished stabilizing capacity of the shorter 1st metatarsal, the foot must push off with more force to propel the body forward. / Thesis (Master, Rehabilitation Science) -- Queen's University, 2013-01-14 14:38:55.255

Magister Scientiae Dentium - MSc(Dent) / Aim: The aim of this study was to assess the effect of retraction of anterior teeth on pharyngeal airway dimensions, after orthodontic treatment of bimaxillary protrusion cases by means of the extraction of four premolars. Method: A total of 88 lateral cephalometric radiograph pairs, consisting of a pre-treatment and post-treatment radiograph taken for orthodontic treatment of bimaxillary protrusion by means of extraction of four premolars, was used. The pharyngeal airway space, measured across three different levels, as well as the length of the maxilla and mandible were assessed for changes from pre-treatment to post-treatment. Pearson’s correlation coefficient was used to determine the degree to which the change in pharyngeal airway space was associated with the change in maxilla or mandible length. Results: The pre-treatment average pharyngeal airway space measurements were recorded as 15.23mm for the Superior Pharyngeal Airway Space, 11.63mm for the Middle Pharyngeal Airway Space and 13.56mm for the Inferior Pharyngeal Airway Space. The average reduction in the pharyngeal airway space was noted as 1.21mm, 1.64mm and 2.23mm respectively. All with statistically significant P values of <0.001.

No description available.

En algorithmique et en complexité, la plus grande part de la recherche se base sur l’hypothèse que P ≠ NP (Polynomial time et Non deterministic Polynomial time), c'est-à-dire qu'il existe des problèmes dont la solution peut être vérifiée mais non construite en temps polynomial. Si cette hypothèse est admise, de nombreux problèmes naturels ne sont pas dans P (c'est-à-dire, n'admettent pas d'algorithme efficace), ce qui a conduit au développement de nombreuses branches de l'algorithmique. L'une d'elles est la complexité paramétrée. Elle propose des algorithmes exacts, dont l'analyse est faite en fonction de la taille de l'instance et d'un paramètre. Ce paramètre permet une granularité plus fine dans l'analyse de la complexité.Un algorithme sera alors considéré comme efficace s'il est à paramètre fixé, c'est-à-dire, lorsque sa complexité est exponentielle en fonction du paramètre et polynomiale en fonction de la taille de l'instance. Ces algorithmes résolvent les problèmes de la classe FPT (Fixed Parameter Tractable).L'extraction de noyaux est une technique qui permet, entre autre, d’élaborer des algorithmes à paramètre fixé. Elle peut être vue comme un pré-calcul de l'instance, avec une garantie sur la compression des données. Plus formellement, une extraction de noyau est une réduction polynomiale depuis un problème vers lui même, avec la contrainte supplémentaire que la taille du noyau (l'instance réduite) est bornée en fonction du paramètre. Pour obtenir l’algorithme à paramètre fixé, il suffit de résoudre le problème dans le noyau, par exemple par une recherche exhaustive (de complexité exponentielle, en fonction du paramètre). L’existence d'un noyau implique donc l'existence d'un algorithme à paramètre fixé, la réciproque est également vraie. Cependant, l’existence d'un algorithme à paramètre fixé efficace ne garantit pas un petit noyau, c'est a dire un noyau dont la taille est linéaire ou polynomiale. Sous certaines hypothèses, il existe des problèmes n’admettant pas de noyau (c'est-à-dire hors de FPT) et il existe des problèmes de FPT n’admettant pas de noyaux polynomiaux.Un résultat majeur dans le domaine des noyaux est la construction d'un noyau linéaire pour le problème Domination dans les graphes planaires, par Alber, Fellows et Niedermeier.Tout d'abord, la méthode de décomposition en régions proposée par Alber, Fellows et Niedermeier, a permis de construire de nombreux noyaux pour des variantes de Domination dans les graphes planaires. Cependant cette méthode comportait un certain nombre d’imprécisions, ce qui rendait les preuves invalides. Dans la première partie de notre thèse, nous présentons cette méthode sous une forme plus rigoureuse et nous l’illustrons par deux problèmes : Domination Rouge Bleue et Domination Totale.Ensuite, la méthode a été généralisée, d'une part, sur des classes de graphes plus larges (de genre borné, sans-mineur, sans-mineur-topologique), d'autre part, pour une plus grande variété de problèmes. Ces méta-résultats prouvent l’existence de noyaux linéaires ou polynomiaux pour tout problème vérifiant certaines conditions génériques, sur une classe de graphes peu denses. Cependant, pour atteindre une telle généralité, il a fallu sacrifier la constructivité des preuves : les preuves ne fournissent pas d'algorithme d'extraction constructif et la borne sur le noyau n'est pas explicite. Dans la seconde partie de notre thèse nous effectuons un premier pas vers des méta-résultats constructifs ; nous proposons un cadre général pour construire des noyaux linéaires en nous inspirant des principes de la programmation dynamique et d'un méta-résultat de Bodlaender, Fomin, Lokshtanov, Penninkx, Saurabh et Thilikos. / In the fields of Algorithmic and Complexity, a large area of research is based on the assumption that P ≠ NP(Polynomial time and Non deterministic Polynomial time), which means that there are problems for which a solution can be verified but not constructed in polynomial time. Many natural problems are not in P, which means, that they have no efficient algorithm. In order to tackle such problems, many different branches of Algorithmic have been developed. One of them is called Parametric Complexity. It consists in developing exact algorithms whose complexity is measured as a function of the size of the instance and of a parameter. Such a parameter allows a more precise analysis of the complexity. In this context, an algorithm will be considered to be efficient if it is fixed parameter tractable (fpt), that is, if it has a complexity which is exponential in the parameter and polynomial in the size of the instance. Problems that can be solved by such an algorithm form the FPT class.Kernelisation is a technical that produces fpt algorithms, among others. It can be viewed as a preprocessing of the instance, with a guarantee on the compression of the data. More formally, a kernelisation is a polynomial reduction from a problem to itself, with the additional constraint that the size of the kernel, the reduced instance, is bounded by a function of the parameter. In order to obtain an fpt algorithm, it is sufficient to solve the problem in the reduced instance, by brute-force for example (which has exponential complexity, in the parameter). Hence, the existence of a kernelisiation implies the existence of an fpt algorithm. It holds that the converse is true also. Nevertheless, the existence of an efficient fpt algorithm does not imply a small kernel, meaning a kernel with a linear or polynomial size. Under certain hypotheses, it can be proved that some problems can not have a kernel (that is, are not in FPT) and that some problems in FPT do not have a polynomial kernel.One of the main results in the field of Kernelisation is the construction of a linear kernel for the Dominating Set problem on planar graphs, by Alber, Fellows and Niedermeier.To begin with, the region decomposition method proposed by Alber, Fellows and Niedermeier has been reused many times to develop kernels for variants of Dominating Set on planar graphs. Nevertheless, this method had quite a few inaccuracies, which has invalidated the proofs. In the first part of our thesis, we present a more thorough version of this method and we illustrate it with two examples: Red Blue Dominating Set and Total Dominating Set.Next, the method has been generalised to larger classes of graphs (bounded genus, minor-free, topological-minor-free), and to larger families of problems. These meta-results prove the existence of a linear or polynomial kernel for all problems verifying some generic conditions, on a class of sparse graphs. As a price of generality, the proofs do not provide constructive algorithms and the bound on the size of the kernel is not explicit. In the second part of our thesis, we make a first step to constructive meta-results. We propose a framework to build linear kernels based on principles of dynamic programming and a meta-result of Bodlaender, Fomin, Lokshtanov, Penninkx, Saurabh and Thilikos.

acase@tulane.edu

La polymérisation d'actine fournit la force qui produit directement la motilité dans un grand nombre de cas, mais certaines observations suggèrent que la motilité amiboïde fasse appel à d'autres mécanismes. En utilisant le modèle d'Entamoeba histolytica, il avait été précédemment observé que ces cellules produisent des protrusions transitoires, nécessaires au mouvement. Des mutations affectant l'activité de la myosine et des molécules d'adhésion inhibent l'activité protrusive et la motilité [Coudrier et al., 2005]. En nous appuyant sur ces observations, nous avons fait l'hypothèse que les mouvements amiboïdes d'Entamoeba histolytica sont contrôlés par une instabilité dynamique cyclique du cortex cellulaire : la membrane plasmique produit un bleb par détachement du cytosquelette cortical, sous l'action d'une pression interne due à la contraction acto-myosine, puis le cortex se reforme sous la surface du bleb. L'expansion initiale rapide (plus rapide que les vitesses maximales de polymérisation d'actine) et l'analogie avec des blebs apoptotiques produits par rupture protéolytique des liens cytosquelette-membrane, étaient des indications fortes que Entamoeba histolytica se déplace en émettant des blebs initialement dépourvus de cortex, ce que nous avons pu confirmer par microscopie de fluorescence sur des amibes dont l'actine-F était marquée. Expérimentalement, la formation des protrusions a été analysée en détails par vidéo-microscopie. Les protrusions se développent tout d'abord durant quelques centaines de millisecondes à de très hautes vitesses (jusqu'à quelques dizaines de μm/sec). Ensuite, leur expansion se poursuit avec une membrane ayant une forme localement sphérique et en l'absence d'organites intracellulaires dans la protrusion. A un stade ultérieur, le cortex d'actine basal disparaît et l'expansion qui s'ensuit s'ac- compagne d'un large flot d'organites intracellulaires. Les protrusions peuvent soit être rétractées, soit stabilisées. Le cycle de blebbing / stabilisation conduit à des mou- vements cellulaires sans direction persistante, qui se poursuivent des heures durant. Nous présentons ici un modèle physique décrivant les paramètres de contrôle de cette instabilité dynamique. En utilisant la pression d'aspiration d'une micropipette, nous pouvons produire des protrusions, et la géométrie contrôlée de l'expérience donne lieu à des événements protrusifs reproductibles, qui peuvent être décrits en détail par une modélisation quantitative appropriée. De telles instabilités corticales pourraient donc représenter une façon distincte de générer de la motilité cellulaire, pertinente entre autres dans un contexte d'invasion pathogène ou dans le cadre des mouvements de cellules immunitaires.