41 research outputs found
DĂ©tection et suivi des singularitĂ©s de phase par le suivi des fronts de dĂ©polarisation dans un modĂšle informatique de ïŹbrillation auriculaire
La ïŹbrillation auriculaire aïŹecte un nombre grandissant dâindividus chaque annĂ©e et peut mener Ă de graves complications telles quâun accident vasculaire cĂ©rĂ©bral. Une approche thĂ©rapeutique est la thermo- ou cryoablation par cathĂ©ter de zones tissulaires essentielles au maintien des Ă©pisodes de ïŹbrillation. Une des cibles proposĂ©es pour lâablation est le centre des rotors qui maintiennent lâarythmie en crĂ©ant des rĂ©entrĂ©es stables. Ces rotors sont dĂ©tectĂ©s Ă partir de signaux de cartographie Ă©lectrique ou optique ou dans des simulations Ă lâaide du concept de singularitĂ© de phase (SP). Lâanalyse de ces SP donne une description de la dynamique de la ïŹbrillation. Le suivi dans le temps (tracking) des SP a une importance critique pour calculer la durĂ©e de vie des rotors et leur stabilitĂ©. Lâobjectif du projet est donc dâamĂ©liorer les algorithmes de dĂ©tection et de suivi des SP. Nous avons dĂ©veloppĂ© des modĂšles de tissus cardiaques 2D avec des hĂ©tĂ©rogĂ©nĂ©itĂ©s dynamiques (variations battement Ă battement), ionique (conductance des canaux potassiques), et structurelles (ïŹbrose). Des Ă©pisodes de ïŹbrillation ont Ă©tĂ© simulĂ©s dans ces modĂšles. Le script dĂ©veloppĂ© permet de suivre avec prĂ©cision les SP de lâensemble de simulations. La performance de cet algorithme varie en fonction de la complexitĂ© de la dynamique Ă©tudiĂ©e et du pas de temps utilisĂ© pour faire le suivi. Une correction a posteriori et une simpliïŹcation Ă partir dâun facteur de seuillage (Ïps = 15ms) permettent de mettre en Ă©vidence les rotors permanents avec une longue durĂ©e de vie. Cet algorithme permettra donc de faciliter les analyses de dynamique de ïŹbrillation auriculaire en contexte de simulation sous la forme de feuillet tissulaire 2D. La mĂ©thode utilisĂ©e est aussi gĂ©nĂ©ralisable aux modĂšles 3-dimensionnels.Atrial fibrillation affects a growing number of individuals each year. These patients are subject
to severe complication such as AVCs if a treatment is not applied to their condition.
One possible therapeutic approach is catheter ablation of the problematic tissue with heat or
cold. This method targets fibrillation sources known as rotors. To allow for a more efficient
and personalizable treatment, detection of such rotors is done through electrical or optical
signal cartography. The resulting map of membrane potentials can then be used to find
the center of the target rotors: phase singularities (PS). PS analysis allows a deeper understanding
of AF dynamics. Moreover, tracking these reentries is essential for the evaluation
of PS lifespan. The sources with longer the lifespans can be identified as stable and kept as
possible candidates for ablative therapy.
The projects objective is to improve PS detection and tracking algorithms
We have developed 2D atrium models with dynamic (beat-to-beat variation), ionic (potassium
channel conductance) and structural (fibrosis) heterogeneities. Episodes of atrial fibrillation
were simulated for each model.
The developed method allows for precise PS tracking for the simulated cases of AF. The
error rate of the method is dependent of the temporal resolution and the complexity of the
fibrillation dynamics. By applying a post-processing correction method and a threshold to
the lower lifespan values ( ps = 15ms) it is possible to highlight longer lasting rotors that
could be considered permanent when the temporal resolution is sufficiently low (dt = 0.1ms).
The result of the following project allows for easier AF dynamics analysis for simulated
2D sheet cases. The method is theoretically applicable to 3D cases if the algorithm is adapted
to such models
Stratégie de sélection de la bande de fréquences avec écoute spectrale en temps réel pour une radio tactique à étalement de spectre par saut de fréquence
La radio cognitive permet un usage opportuniste des bandes du spectre des radiofrĂ©quences. LâidĂ©e dâune utilisation plus efficace et opportuniste du spectre des radiofrĂ©quences est Ă©galement intĂ©ressante pour les militaires et les services dâurgence compte tenu de la congestion grandissante des ondes radio, et ce dans toutes les bandes de frĂ©quences Ă cause de lâaccroissement de lâutilisation de dispositifs sans fil.
Dans ce mĂ©moire, on se permet dâadapter aux rĂ©alitĂ©s et aux exigences dâune radio tactique les concepts clĂ©s des travaux rĂ©alisĂ©s sur lâĂ©coute spectrale et du modĂšle commercial de la radio cognitive. On prĂ©sente les exigences requises et les algorithmes les plus populaires pour effectuer une Ă©coute spectrale efficace et faire de la dĂ©tection de signaux. On prĂ©sente une stratĂ©gie de sĂ©lection de bandes de frĂ©quences avec une Ă©coute spectrale basĂ©e sur un dĂ©tecteur dâĂ©nergie pour une radio tactique utilisant la technique dâĂ©talement de spectre par saut de frĂ©quence et un duplexage par rĂ©partition dans le temps. La stratĂ©gie repose sur deux prĂ©misses ; la premiĂšre, la bande de frĂ©quences avec le moins dâĂ©nergie reprĂ©sente le meilleur choix de bande de frĂ©quences ; la seconde, la radio qui reçoit est la mieux placĂ©e pour faire lâĂ©coute spectrale afin de dĂ©terminer la meilleure bande de frĂ©quences Ă utiliser.
Les simulations de la stratĂ©gie dĂ©veloppĂ©e, lorsquâelle est mise en prĂ©sence dâinterfĂ©rences, donnent des rĂ©sultats pouvant atteindre des gains de plus de 65% si lâenvironnement Ă©lectromagnĂ©tique des radios varie lentement par rapport Ă la durĂ©e des sauts de frĂ©quence. Les simulations ont Ă©galement permis de dĂ©terminer les paramĂštres clĂ©s et leurs valeurs optimales pour la stratĂ©gie proposĂ©e en fonction des caractĂ©ristiques du canal
La vierge, la mÚre et la putain : persistance des archétypes féminins judéo-chrétiens dans quatre romans québécois contemporains
Ce mémoire propose d'examiner les figures archétypales féminines dans quatre romans récents afin d'en vérifier la prégnance dans des oeuvres issues d'écrivaines québécoises. Plus précisément, il s'agit de vérifier si la pureté de la triade archétypale "vierge-mÚre-putain" a toujours cours sur l'horizon actuel, que l'on dit marqué par l'hétérogénéité. Mobilisant un cadre théorique posant l'identité comme étant construite -- notamment par la culture, à travers le processus de socialisation --, l'étude se déploie en trois temps principaux. Le premier chapitre consiste en une analyse des profils sémantiques des personnages féminins en tenant compte des caractéristiques attribuées à chacun des personnages, à leurs discours et à leurs actions. Le second chapitre relÚve les éléments relatifs à la socialisation des protagonistes en lien avec les différentes stratégies narratives déployées par les auteures. La place occupée par la religion dans les récits est également étudiée. Enfin, le troisiÚme chapitre explore les lieux : à travers ceux-ci, c'est la "fonction" du personnage qui est surtout questionnée
Contribution Of Cover Crop Roots To Soil Fertility And Crop Nutrition In Organic Spring Wheat In Quebec, Canada.
Assessing the contribution of cover crops (i.e. crops that are planted to improve soil health â not for harvest) to soil fertility is particularly complex. Little is known about how much N and how N from decomposing cover crop roots will become available to subsequent crops. The objective of the project was to determine the respective N contribution of shoots and roots of annual cover crop species to crop N uptake in organic spring wheat. A 2-year field experiment was conducted twice (2016-2017, 2017-2018) in Quebec, Canada. Cover crops were grown and terminated in Year 1, and a cash crop of spring wheat was grown the subsequent year (Year 2). Four annual cover crop species (common vetch, field pea, forage radish, and cereal rye) and four cover crop biomass input levels (shoot only, root only, and shoot plus root) were tested. Forage radishes and peas produced the highest total biomass (shoot and root) while radishes produced the highest root biomass. Common vetch had higher shoot N concentration than other species whereas its root N concentration was similar to radishes and peas. At spring wheat seeding, soil mineral N content (0-45 cm) was significantly higher in whole CC treatments (39 kg N ha-1) compared to treatments of shoot or root only (33 and 29 kg N ha-1, respectively). In 2017, spring wheat yields were higher following the whole CC than following the shoot or root parts only. Improving our understanding on soil N budget may help to reduce N losses from cover crop-based cropping systems such as organic farming systems. On a broader scale, this research aims to reduce the impact of organic farming on the environment by increasing its N use efficiency
TESS Hunt for Young and Maturing Exoplanets (THYME) IX: a 27 Myr extended population of Lower-Centaurus Crux with a transiting two-planet system
We report the discovery and characterization of a nearby (~ 85 pc), older (27
+/- 3 Myr), distributed stellar population near Lower-Centaurus-Crux (LCC),
initially identified by searching for stars co-moving with a candidate
transiting planet from TESS (HD 109833; TOI 1097). We determine the association
membership using Gaia kinematics, color-magnitude information, and rotation
periods of candidate members. We measure it's age using isochrones,
gyrochronology, and Li depletion. While the association is near known
populations of LCC, we find that it is older than any previously found LCC
sub-group (10-16 Myr), and distinct in both position and velocity. In addition
to the candidate planets around HD 109833 the association contains four
directly-imaged planetary-mass companions around 3 stars, YSES-1, YSES-2, and
HD 95086, all of which were previously assigned membership in the younger LCC.
Using the Notch pipeline, we identify a second candidate transiting planet
around HD 109833. We use a suite of ground-based follow-up observations to
validate the two transit signals as planetary in nature. HD 109833 b and c join
the small but growing population of <100 Myr transiting planets from TESS. HD
109833 has a rotation period and Li abundance indicative of a young age (< 100
Myr), but a position and velocity on the outskirts of the new population, lower
Li levels than similar members, and a CMD position below model predictions for
27 Myr. So, we cannot reject the possibility that HD 109833 is a young field
star coincidentally nearby the population.Comment: 23 pages, 15 figures, Accepted for publication in A
CaractĂ©risation des parties aĂ©riennes et racinaires des cultures de couverture en dĂ©robĂ©e et leur contribution au rendement du blĂ© lâannĂ©e subsĂ©quente
Ce projet avait pour but dâĂ©tudier la contribution respective des parties racinaires et aĂ©riennes de quatre espĂšces de cultures de couverture (CC) (seigle dâautomne (Secale cereale L.), radis fourrager (Raphanus sativus L.), vesce commune (Vicia sativa L.) et pois fourrager (Pisum sativum L.)) implantĂ©es en dĂ©robĂ©e durant lâautomne sur la productivitĂ© dâun blĂ© de printemps (Triticum aestivum L.) lâannĂ©e subsĂ©quente. Durant les deux annĂ©es de lâexpĂ©rience, rĂ©pĂ©tĂ©es sur deux sites adjacents (2016-2017 et 2017-2018) Ă la Station agronomique de lâUniversitĂ© Laval, situĂ©e Ă Saint-Augustin-de-Desmaures (Qc), le contenu en azote (N) minĂ©ral du sol, la biomasse sĂšche et la concentration en N et en carbone (C) des parties racinaires et aĂ©riennes des CC ainsi que les rendements et le contenu en N du blĂ© ont Ă©tĂ© dĂ©terminĂ©s. Parmi les CC Ă©tudiĂ©es, le radis et le pois sont les deux espĂšces qui ont produit la plus forte biomasse sĂšche totale (aĂ©rienne et racinaire) alors que câest le radis qui a produit la biomasse racinaire la plus Ă©levĂ©e. La vesce commune avait une concentration en N plus Ă©levĂ©e que les autres espĂšces dans ses parties aĂ©riennes alors quâelle avait une concentration en N similaire au radis et au pois dans ses racines. Au moment de la destruction du pois et de la vesce, le contenu en N minĂ©ral dans les 15 premiers cm du sol de ces espĂšces Ă©tait plus Ă©levĂ© que celui du radis et du seigle. Le contenu en N minĂ©ral dans les 45 premiers cm du sol Ă©tait significativement plus Ă©levĂ© au semis du blĂ© dans les traitements dâincorporation des CC entiĂšres par rapport aux traitements dâincorporation des parties aĂ©riennes ou racinaires seules. En 2017, les rendements du blĂ© Ă©taient plus Ă©levĂ©s suite Ă lâincorporation des CC entiĂšres que suite Ă lâincorporation des parties aĂ©riennes ou racinaires seules
Spatio-Temporal Variation of Elemental Contamination and Health of Mya arenaria Clam in the Saguenay–St. Lawrence Marine Park
The impacts of pollution and long-term effects of local clam populations are misunderstood in estuaries. The purpose of this study was to follow inorganic contamination in tissues, changes of physiological health indicators, such as condition factor (CF), growth index (GI), resistance in air emersion and dehydration rate, for 5 years in Mya arenaria clams. The sampling scheme comprised one reference site, two sites impacted by human activity (thereafter polluted) and one site recognized as a Saint-Lawrence Estuary (SLE) beluga whale feeding area without known pollution source (Baie Sainte-Marguerite (BSM)). This study revealed that the elemental contamination profiles in clams were increased but differed between the polluted and BSM compared to the reference site. At polluted sites, clams were contaminated by Ag (2.4-fold of reference site), Mn (2.5-fold) and V (6.3-fold). With respect to BSM, clams were mainly contaminated by Ce (2.5-fold), Co (2-fold), Ga (2-fold), La (2.8-fold), Hg (2.5-fold), Ni (2.2-fold), Sm (2-fold) and V (20-fold). This contamination profile suggests sources of pollution from particulate combustion products of gasoline/diesel, crude oil and urban inputs of pollution. The CF, GI and air survival time were all reduced in clams at the polluted sites, while only the CF and dehydration rates were decreased and increased, respectively, at BSM. Long-term analysis revealed that CF and GI tended to decrease over time with episodes of strong amplitude changes and became more resilient to air survival time. In conclusion, the long-term contamination of clams towards metals and elements could compromise the health status of local clam populations. The increased contamination of clams at BSM could represent a risk to the endangered SLE beluga whale population
Organic No-Till Systems in Eastern Canada: A Review
For more than a decade, studies have aimed to adapt the agronomy of organic no-till systems for the environmental conditions of Eastern Canada. Most research on organic no-till practices in Eastern Canada has been conducted in the province of QuĂ©bec, where 4% of farms are certified organic, and results from these trials have been published in technical reports available in French. The objective of this review was to revisit previous research work on organic farming in Eastern Canadaâthe majority of which has been published as technical reports in the French languageâin order to highlight important findings and to identify information gaps. Cover crop-based rotational no-till systems for organic grain and horticultural cropping systems will be the main focus of this review. Overall, a few trials have demonstrated that organic rotational no-till can be successful and profitable in warmer and more productive regions of Eastern Canada, but its success can vary over years. The variability in the success of organic rotational no-till systems is the reason for the slow adoption of the system by organic farmers. On-going research focuses on breeding early-maturing fall rye, and terminating cover crops and weeds with the use of bioherbicides
Validation of the Pain Beliefs and Perceptions Inventory
OBJECTIVE: To examine the test-retest reliability, construct validity and factor structure of the Pain Beliefs and Perceptions Inventory (PBPI)