155 research outputs found
On negative flows of the AKNS hierarchy and a class of deformations of bihamiltonian structure of hydrodynamic type
A deformation parameter of a bihamiltonian structure of hydrodynamic type is
shown to parameterize different extensions of the AKNS hierarchy to include
negative flows. This construction establishes a purely algebraic link between,
on the one hand, two realizations of the first negative flow of the AKNS model
and, on the other, two-component generalizations of Camassa-Holm and Dym type
equations.
The two-component generalizations of Camassa-Holm and Dym type equations can
be obtained from the negative order Hamiltonians constructed from the Lenard
relations recursively applied on the Casimir of the first Poisson bracket of
hydrodynamic type. The positive order Hamiltonians, which follow from Lenard
scheme applied on the Casimir of the second Poisson bracket of hydrodynamic
type, are shown to coincide with the Hamiltonians of the AKNS model. The AKNS
Hamiltonians give rise to charges conserved with respect to equations of motion
of two-component Camassa-Holm and two-component Dym type equations.Comment: 20 pages, Late
Vertex Operators and Soliton Solutions of Affine Toda Model with U(2) Symmetry
The symmetry structure of non-abelian affine Toda model based on the coset
is studied. It is shown that the model possess
non-abelian Noether symmetry closing into a q-deformed
algebra. Specific two vertex soliton solutions are constructed.Comment: 17 pages, latex, misprints corrected, version to appear in J.Phys
Exact static soliton solutions of 3+1 dimensional integrable theory with nonzero Hopf numbers
In this paper we construct explicitly an infinite number of Hopfions (static,
soliton solutions with non-zero Hopf topological charges) within the recently
proposed 3+1-dimensional, integrable and relativistically invariant field
theory. Two integers label the family of Hopfions we have found. Their product
is equal to the Hopf charge which provides a lower bound to the soliton's
finite energy. The Hopfions are constructed explicitly in terms of the toroidal
coordinates and shown to have a form of linked closed vortices.Comment: LaTeX, 7 pg
The complex Sine-Gordon equation as a symmetry flow of the AKNS Hierarchy
It is shown how the complex sine-Gordon equation arises as a symmetry flow of
the AKNS hierarchy. The AKNS hierarchy is extended by the ``negative'' symmetry
flows forming the Borel loop algebra. The complex sine-Gordon and the vector
Nonlinear Schrodinger equations appear as lowest negative and second positive
flows within the extended hierarchy. This is fully analogous to the well-known
connection between the sine-Gordon and mKdV equations within the extended mKdV
hierarchy.
A general formalism for a Toda-like symmetry occupying the ``negative''
sector of sl(N) constrained KP hierarchy and giving rise to the negative Borel
sl(N) loop algebra is indicated.Comment: 8 pages, LaTeX, typos corrected, references update
Sala de espera como estratégia de educação em saúde no campo da atenção às doenças sexualmente transmissíveis
Este artigo apresenta e discute uma experiência de sala de espera no âmbito da atenção às doenças sexualmente transmissíveis - DST, desenvolvida em um serviço especializado na atenção às DST, localizado em Porto Alegre-RS. O objetivo da sala de espera foi oferecer uma possibilidade de prevenção e educação em saúde, tendo por base uma abordagem participativa e problematizadora, buscando diferenciar-se da lógica prescritiva, centrada na transmissão de informação, hegemonicamente presente nos serviços de saúde. A atividade ocorreu diariamente, antecedendo a consulta médica de homens que procuravam o serviço para atendimento relacionado às DST. Entendida como uma atividade relativa ao campo de competências profissionais (Campos, 2002), foi coordenada por duplas de residentes multiprofissionais (Psicólogos, Nutricionistas, Enfermeiros e Assistentes Sociais). A abordagem da sala de espera utilizou-se das contribuições da prática do aconselhamento em HIV/Aids, buscando trabalhar com aspectos afetivos/emocionais, informativos e avaliação de riscos. Através de uma perspectiva problematizadora, buscou-se interrogar e colocar em análise as relações que as pessoas estabelecem com a sexualidade, as DST e o uso do preservativo. Esta intervenção propiciou maior acesso a informações (sobre as DST, insumos de prevenção, tratamento e testagem anti-HIV) e discussão sobre aspectos relacionados às repercussões das DST na vida afetiva e sexual, reconfigurando o momento de espera em um momento de prevenção e educação em saúde
Transcranial direct current stimulation over multiple days improves learning and maintenance of a novel vocabulary
Introduction: Recently, growing interest emerged in the enhancement of human potential by means of non-invasive brain stimulation. In particular, anodal transcranial direct current stimulation (atDCS) has been shown to exert beneficial effects on motor and higher cognitive functions. However, the majority of transcranial direct current stimulation (tDCS) studies have assessed effects of single stimulation sessions that are mediated by transient neural modulation. Studies assessing the impact of multiple stimulation sessions on learning that may induce long-lasting behavioural and neural changes are scarce and have not yet been accomplished in the language domain in healthy individuals
Myosin II activity regulates vinculin recruitment to focal adhesions through FAK-mediated paxillin phosphorylation
© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License. The definitive version was published in Journal of Cell Biology 188 (2010): 877-890, doi:10.1083/jcb.200906012.Focal adhesions (FAs) are mechanosensitive adhesion and signaling complexes that grow and change composition in response to myosin II–mediated cytoskeletal tension in a process known as FA maturation. To understand tension-mediated FA maturation, we sought to identify proteins that are recruited to FAs in a myosin II–dependent manner and to examine the mechanism for their myosin II–sensitive FA association. We find that FA recruitment of both the cytoskeletal adapter protein vinculin and the tyrosine kinase FA kinase (FAK) are myosin II and extracellular matrix (ECM) stiffness dependent. Myosin II activity promotes FAK/Src-mediated phosphorylation of paxillin on tyrosines 31 and 118 and vinculin association with paxillin. We show that phosphomimic mutations of paxillin can specifically induce the recruitment of vinculin to adhesions independent of myosin II activity. These results reveal an important role for paxillin in adhesion mechanosensing via myosin II–mediated FAK phosphorylation of paxillin that promotes vinculin FA recruitment to reinforce the cytoskeletal ECM linkage and drive FA maturation.This work was supported by NHLBI (C.M. Waterman and A.M.
Pasapera; and grant HL093156 to D.D. Schlaepfer) and the Burroughs
Wellcome Fund (E. Rericha)
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