Équations différentielles à retard et leur application en hématopoïèse, avec étude du cas de la neutropénie cyclique

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Analyse des bifurcations dans un modèle du flutter auriculaire

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

Ion-acoustic envelope modes in a degenerate relativistic electron-ion plasma

A self-consistent relativistic two-fluid model is proposed for one-dimensional electron-ion plasma dynamics. A multiple scales perturbation technique is employed, leading to an evolution equation for the wave envelope, in the form of a nonlinear Schrödinger type equation (NLSE). The inclusion of relativistic effects is shown to introduce density-dependent factors, not present in the non-relativistic case - in the conditions for modulational instability. The role of relativistic effects on the linear dispersion laws and on envelope soliton solutions of the NLSE is discussed.

Wulf Hopf: Freiheit – Leistung – Ungleichheit, Bildung und soziale Herkunft in Deutschland. Weinheim und München: Juventa 2010 [Rezension]

Rezension von: Wulf Hopf: Freiheit – Leistung – Ungleichheit, Bildung und soziale Herkunft in Deutschland Weinheim und München: Juventa 2010 (268 S.; ISBN 978-3-7799-2174-5)

Degenerate mixtures of rubidium and ytterbium for engineering open quantum systems

In the last two decades, experimental progress in controlling cold atoms and ions now allows us to manipulate fragile quantum systems with an unprecedented degree of precision. This has been made possible by the ability to isolate small ensembles of atoms and ions from noisy environments, creating truly closed quantum systems which decouple from dissipative channels. However in recent years, several proposals have considered the possibility of harnessing dissipation in open systems, not only to cool degenerate gases to currently unattainable temperatures, but also to engineer a variety of interesting many-body states. This thesis will describe progress made towards building a degenerate gas apparatus that will soon be capable of realizing these proposals. An ultracold gas of ytterbium atoms, trapped by a species-selective lattice will be immersed into a Bose-Einstein condensate (BEC) of rubidium atoms which will act as a bath. Here we describe the challenges encountered in making a degenerate mixture of rubidium and ytterbium atoms and present two experiments performed on the path to creating a controllable open quantum system. The first experiment will describe the measurement of a tune-out wavelength where the light shift of $\Rb{87}$ vanishes. This wavelength was used to create a species-selective trap for ytterbium atoms. Furthermore, the measurement of this wavelength allowed us to extract the dipole matrix element of the $5s \rightarrow 6p$ transition in $\Rb{87}$ with an extraordinary degree of precision. Our method to extract matrix elements has found use in atomic clocks where precise knowledge of transition strengths is necessary to account for minute blackbody radiation shifts. The second experiment will present the first realization of a degenerate Bose-Fermi mixture of rubidium and ytterbium atoms. Using a three-color optical dipole trap (ODT), we were able to create a highly-tunable, species-selective potential for rubidium and ytterbium atoms which allowed us to use $\Rb{87}$ to sympathetically cool $\Yb{171}$ to degeneracy with minimal loss. This mixture is the first milestone creating the lattice-bath system and will soon be used to implement novel cooling schemes and explore the rich physics of dissipation.

Analysis of the "Sonar Hopf" Cochlea

The "Sonar Hopf" cochlea is a recently much advertised engineering design of an auditory sensor. We analyze this approach based on a recent description by its inventors Hamilton, Tapson, Rapson, Jin, and van Schaik, in which they exhibit the "Sonar Hopf" model, its analysis and the corresponding hardware in detail. We identify problems in the theoretical formulation of the model and critically examine the claimed coherence between the described model, the measurements from the implemented hardware, and biological data.

Invertibility characterization of Wiener-Hopf plus Hankel operators on variable exponent Lebesgue spaces via even asymmetric factorization

We obtain invertibility and Fredholm criteria for the Wiener-Hopf plus Hankel operators acting between variable exponent Lebesgue spaces on the real line. Such characterizations are obtained via the so-called even asymmetric factorization which is applied to the Fourier symbols of the operators under study.

Degenerate Gases of Strontium for Studies of Quantum Magnetism

We describe the construction and characterization of a new apparatus that can produce degenerate quantum gases of strontium. The realization of degenerate gases is an important first step toward future studies of quantum magnetism. Three of the four stable isotopes of strontium have been cooled into the degenerate regime. The experiment can make nearly pure Bose-Einstein condensates containing approximately 1x10^4 atoms, for strontium-86, and approximately 4x10^5 atoms, for strontium-84. We have also created degenerate Fermi gases of strontium-87 with a reduced temperature, T/T_F of approximately 0.2. The apparatus will be able to produce Bose-Einstein condensates of strontium-88 with straightforward modifications. We also report the first experimental and theoretical results from the strontium project. We have developed a technique to accelerate the continuous loading of strontium atoms into a magnetic trap. By applying a laser addressing the 3P1 to 3S1 transition in our magneto-optical trap, the rate at which atoms populate the magnetically-trapped 3P2 state can be increased by up to 65%. Quantum degenerate gases of atoms in the metastable 3P0 and 3P2 states are a promising platform for quantum simulation of systems with long-range interactions. We have performed an initial numerical study of a method to transfer the ground state degenerate gases that we can currently produce into one of the metastable states via a three-photon transition. Numerical simulations of the Optical Bloch equations governing the three-photon transition indicate that >90% of a ground state degenerate gas can be transferred into a metastable state.

Análise estequiométrica da dinâmica não-linear de redes de reações químicas

Dissertação (mestrado)—Universidade de Brasília, Instituto de Química, Programa de Pós-Graduação em Química, 2016.

Adaptivity and a posteriori error control for bifurcation problems I: the Bratu problem

This article is concerned with the numerical detection of bifurcation points of nonlinear partial differential equations as some parameter of interest is varied. In particular, we study in detail the numerical approximation of the Bratu problem, based on exploiting the symmetric version of the interior penalty discontinuous Galerkin finite element method. A framework for a posteriori control of the discretization error in the computed critical parameter value is developed based upon the application of the dual weighted residual (DWR) approach. Numerical experiments are presented to highlight the practical performance of the proposed a posteriori error estimator.

Connected Hopf algebras of finite Gelfand-Kirillov dimension

Following the seminal work of Zhuang, connected Hopf algebras of finite GK-dimension over algebraically closed fields of characteristic zero have been the subject of several recent papers. This thesis is concerned with continuing this line of research and promoting connected Hopf algebras as a natural, intricate and interesting class of algebras. We begin by discussing the theory of connected Hopf algebras which are either commutative or cocommutative, and then proceed to review the modern theory of arbitrary connected Hopf algebras of finite GK-dimension initiated by Zhuang. We next focus on the (left) coideal subalgebras of connected Hopf algebras of finite GK-dimension. They are shown to be deformations of commutative polynomial algebras. A number of homological properties follow immediately from this fact. Further properties are described, examples are considered and invariants are constructed. A connected Hopf algebra is said to be "primitively thick" if the difference between its GK-dimension and the vector-space dimension of its primitive space is precisely one . Building on the results of Wang, Zhang and Zhuang,, we describe a method of constructing such a Hopf algebra, and as a result obtain a host of new examples of such objects. Moreover, we prove that such a Hopf algebra can never be isomorphic to the enveloping algebra of a semisimple Lie algebra, nor can a semisimple Lie algebra appear as its primitive space. It has been asked in the literature whether connected Hopf algebras of finite GK-dimension are always isomorphic as algebras to enveloping algebras of Lie algebras. We provide a negative answer to this question by constructing a counterexample of GK-dimension 5. Substantial progress was made in determining the order of the antipode of a finite dimensional pointed Hopf algebra by Taft and Wilson in the 1970s. Our final main result is to show that the proof of their result can be generalised to give an analogous result for arbitrary pointed Hopf algebras.

Kissing stenting of aortic bifurcation for aorto-iliac obstructive disease: a comparison between bare metal stents and covered stents

INTRODUCTION Aim of this multicentric study:to compare the short-and mid-term results of bare metal stents(BMS)and covered stents(CS)in the Kissing Stent(KS)technique. METHODS Patients undertaking a KS with BMS or CS between January 2017-August 2021 included. Morphological features of plaques were classified as per the extension of calcifications and thrombosis. Every endpoint and outcome was compared in relation to BMS or CS. All patients included received dual anti-platelets DAPT)for at least one month. RESULTS Thirty-four patients enrolled,17 treated with BMS and 17 with CS. Average age 66 years. The 80% of patients were part of TASC C-D categories. DAPT was administered to 82.4%(28/34)of patients with a mean duration of 4.4±1.6 months. Mean follow-up 32.1±17.8 months. Technical Success was 100%. Immediate Clinical Success was reached in 29 cases(85.3%). Immediate and 30-day Clinical Success was higher in CS(64.7% vs 100%, p=.01). Overall Clinical Success at 1-year follow-up was 91.2%,and resulted significantly higher in CS(82.4% vs 100%,p .04). Overall Primary Patency,Assisted Patency,and Secondary Patency at 30 days were 97.1%,97.1%,and 100%,without differences between BMS and CS(94.1% vs 100%,94.1% vs 100%,and 100% vs 100%;p =.7). Two cases(5.9%)of thrombosis were registered,and both occurred within 3 months after the procedure and both in the BMS,without statistical differences with the CS group(11.8% vs 0%,p .48). Both cases of thrombosis occurred in patients who were not treated with dual antiplatelet therapy(33.3% vs 0%,p .027). Survival statistically differed only at the mean follow-up in favour of CS(70.6% and 100%,p .04). CONCLUSIONS The endovascular approach is currently safe and effective in the treatment of AIOD,and KS offers excellent results in particular if performed with CS; however,no statistically significant differences emerged between the two types of stents in terms of patency,reintervention,and complications. DAPT seems to warrant the best results in terms of patency,although there is still no consensus about the ideal duration of administration.

A structural theorem for co-commutative Hopf algebras

Lo scopo di questa tesi è studiare alcune proprietà di base delle algebre di Hopf, strutture algebriche emerse intorno agli anni ’50 dalla topologica algebrica e dalla teoria dei gruppi algebrici, e mostrare un collegamento tra esse e le algebre di Lie. Il primo capitolo è un’introduzione basilare al concetto di prodotto tensoriale di spazi vettoriali, che verrà utilizzato nel secondo capitolo per definire le strutture di algebra, co-algebra e bi-algebra. Il terzo capitolo introduce le definizioni e alcune proprietà di base delle algebre di Hopf e di Lie, con particolare attenzione al legame tra le prime e l’algebra universale inviluppante di un’algebra di Lie. Questo legame sarà approfondito nel quarto capitolo, dedicato allo studio di una particolare classe di algebre di Hopf, quelle graduate e connesse, che terminerà con il teorema di Cartier-Quillen-Milnor-Moore, un teorema strutturale che fornisce condizioni sufficienti affinché un’algebra di Hopf sia isomorfa all’algebra universale inviluppante dei suoi elementi primitivi.

Contribuições da escola para a (de)formação dos sujeitos surdos

O artigo discute, a partir do diálogo entre materialismo histórico dialético e a psicanálise winnicottiana, as contribuições da escola para a constituição da identidade de sujeitos surdos. A análise de bibliografia pertinente apontou para a escassez de trabalhos que consideram a relação entre a escola e os processos de subjetivação dessas pessoas. Para compreender as discussões desse campo, foram realizadas reflexões sobre os fenômenos escolares contemporâneos à luz da Psicologia para uma Educação Formativa - e não deformadora - para todas e todos. Quanto à população surda, apesar de não haver consenso a respeito dos efeitos da escolarização em instituições inclusivas ou especializadas, concluiu-se que os profissionais da Educação precisam de liberdade e condições objetivas para criar/recriar espaços e estratégias de aprendizagem, com a finalidade de proporcionar aos educandos - e a si mesmos - experiências de relações mais horizontais com o outro, esteja ele marcado pela diferença linguística, sensorial, orgânica, etária, cognitiva ou étnica.

Rotation curve bifurcations as indicators of close recent galaxy encounters

Context. Rotation curves of interacting galaxies often show that velocities are either rising or falling in the direction of the companion galaxy. Aims. We seek to reproduce and analyse these features in the rotation curves of simulated equal-mass galaxies suffering a one-to-one encounter as possible indicators of close encounters. Methods. Using simulations of major mergers in 3D, we study the time evolution of these asymmetries in a pair of galaxies during the first passage. Results. Our main results are: (a) the rotation curve asymmetries appear right at pericentre of the first passage, (b) the significant disturbed rotation velocities occur within a small time interval, of similar to 0.5 Gyr h(-1), and, therefore, the presence of bifurcation in the velocity curve could be used as an indicator of the pericentre occurrence. These results are in qualitative agreement with previous findings for minor mergers and flybys.