1,721,020 research outputs found
Computer assisted proof of branches of stationary and periodic solutions, and Hopf bifurcations, for dissipative PDEs
Full text linkWe discuss an approach to the computer assisted proof of the existence of branches of stationary and periodic solutions for dissipative PDEs, using the Brussellator system with diffusion and Dirichlet boundary conditions as an example, We also consider the case where the branch of periodic solutions emanates from a branch of stationary solutions through a Hopf bifurcation
Some Reversing Orbits for a Rattleback Model
Full text linkA physical rattleback is a toy that can exhibit counter-intuitive behavior when spun on a horizontal plate. Most notably, it can spontaneously reverse its direction of rotation. Using a standard mathematical model of the rattleback, we prove the existence of reversing motion, reversing motion combined with rolling, and orbits that exhibit such behavior repeatedly
Some Breathers and Multi-breathers for FPU-Type Chains
Full text linkWe consider several breather solutions for FPU-type chains that have been found numerically. Using computer-assisted techniques, we prove that there exist true solutions nearby, and in some cases, we determine whether or not the solution is spectrally stable. Symmetry properties are considered as well. In addition, we construct solutions that are close to (possibly infinite) sums of breather solutions
Branches and bifurcations of ejection-collision orbits in the planar circular restricted three body problem
Full text linkThe goal of this paper it to prove existence theorems for one parameter families (branches) of ejection-collision orbits in the planar circular restricted three body problem (CRTBP), and to study some of bifurcations of these branches. The CRTBP considers the dynamics of an infinitesimal particle moving in the gravitational field of two massive primary bodies. The motion of the primaries assumed to be circular, and we study ejection-collision orbits where the infinitesimal body is ejected from one primary and collides with the other (as opposed to more local ejections-collisions where the infinitesimal body collides with a single primary body in both forward and backward time). We consider branches of ejection-collision orbits which are (i) parameterized by the Jacobi integral (energy like quantity conserved by the CRTBP) with the masses of the primaries fixed, and (ii) parameterized by the mass ratio of the primary bodies with energy fixed. The method of proof is constructive and computer assisted, hence can be applied in non-perturbative settings and (potentially) to other conservative systems of differential equations. The main requirement is that the system should admit a change of coordinates which regularizes the collision singularities. In the planar CRTBP, the necessary regularization is provided by the classical Levi-Civita transformation
Effects of physical therapy for the management of patients with ankylosing spondylitis in the biological era.
No full textExercise is considered a fundamental tool for the management of ankylosing spondylitis (AS), in combination with pharmacological therapy that with the advent of biological therapy has improved dramatically the control of signs and symptoms of this challenging disease. Current evidence shows that a specific exercise protocol has not been validated yet. The purpose of this review is to update the most recent evidence (July 2010-November 2013) about physiotherapy in AS, analyzing the possible role and synergistic interactions between exercise and biological drugs. From 117 studies initially considered, only 15 were included in the review. The results support a multimodal approach, including educational sessions, conducted in a group setting, supervised by a physiotherapist and followed by a maintaining home-based regimen. Spa exercise and McKenzie, Heckscher, and Pilates methods seem promising in AS rehabilitation, but their effectiveness should be further investigated in future randomized controlled trials (RCTs). When performed in accordance with the American College of Sports Medicine guidelines, cardiovascular training has been proven safe and effective and should be included in AS rehabilitation protocols. Exercise training plays an important role in the biological era, being now applicable to stabilized patients, leading ultimately to a better management of AS by physiatrists and rheumatologists throughout the world. On the basis of the current evidence, further research should aim to determine which exercise protocols should be recommended
A Semilinear Fourth Order Elliptic Problem with Exponential Nonlinearity
No full textWe study a semilinear fourth order elliptic problem with exponential nonlinearity. Motivated by a question raised in [P.-L. Lions, SIAM Rev., 24 (1982), pp. 441–467], we partially extend results known for the corresponding second order problem. Several new difficulties arise and many problems still remain to be solved. We list those of particular interest in the final section
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
