12,890 research outputs found
Functional Electrical Stimulation mediated by Iterative Learning Control and 3D robotics reduces motor impairment in chronic stroke
Background: Novel stroke rehabilitation techniques that employ electrical stimulation (ES) and robotic technologies are effective in reducing upper limb impairments. ES is most effective when it is applied to support the patients’ voluntary effort; however, current systems fail to fully exploit this connection. This study builds on previous work using advanced ES controllers, and aims to investigate the feasibility of Stimulation Assistance through Iterative Learning (SAIL), a novel upper limb stroke rehabilitation system which utilises robotic support, ES, and voluntary effort. Methods: Five hemiparetic, chronic stroke participants with impaired upper limb function attended 18, 1 hour intervention sessions. Participants completed virtual reality tracking tasks whereby they moved their impaired arm to follow a slowly moving sphere along a specified trajectory. To do this, the participants’ arm was supported by a robot. ES, mediated by advanced iterative learning control (ILC) algorithms, was applied to the triceps and anterior deltoid muscles. Each movement was repeated 6 times and ILC adjusted the amount of stimulation applied on each trial to improve accuracy and maximise voluntary effort. Participants completed clinical assessments (Fugl-Meyer, Action Research Arm Test) at baseline and post-intervention, as well as unassisted tracking tasks at the beginning and end of each intervention session. Data were analysed using t-tests and linear regression. Results: From baseline to post-intervention, Fugl-Meyer scores improved, assisted and unassisted tracking performance improved, and the amount of ES required to assist tracking reduced. Conclusions: The concept of minimising support from ES using ILC algorithms was demonstrated. The positive results are promising with respect to reducing upper limb impairments following stroke, however, a larger study is required to confirm this
Sufficiency Criterion for the Validity of the Adiabatic Approximation
We examine the quantitative condition which has been widely used as a
criterion for the adiabatic approximation but was recently found insufficient.
Our results indicate that the usual quantitative condition is sufficient for a
special class of quantum mechanical systems. For general systems, it may not be
sufficient, but it along with additional conditions is sufficient. The usual
quantitative condition and the additional conditions constitute a general
criterion for the validity of the adiabatic approximation, which is applicable
to all dimensional quantum systems. Moreover, we illustrate the use of the
general quantitative criterion in some physical models.Comment: 9 pages, no figure,appearing in PRL98(2007)15040
O assistente social como mediador cultural em escolas públicas dos bairros de Guamá e Terra firme
I Congresso Internacional América Latina e Interculturalidade: América Latina e Caribe: cenários linguístico-culturais contemporâneos, 07, 08 e 09 de novembro de 2013 - UNILAA intervenção do Assistente Social nas atividades de arte e cultura nas instituições de ensino
fundamental e médio nos bairros do Guamá e da Terra Firme. Estudos anteriores constatam que estes
não são apenas espaços de violência, como registra a mídia. São espaços multiculturais e agregadores de
cultura antiviolência, onde os sujeitos artistas utilizam a arte como meio de transformação social,
através do método fenomenológico busco contribuir para a sistematização da intervenção do assistente
social na área da educação e cultura, identificando as atividades de arte e cultura nas instituições de
ensino fundamental e médio, importância nas instituições em que são desenvolvidas e habilidades
requeridas ao profissional de Serviço Social. A metodologia conduziu a investigação nos respectivos
bairros com os alunos que estudam nas instituições de ensino fundamental e médio nos bairros, por
meio de aplicação de questionários sócioeconômicocultural que ao definir cultura identificaram as
manifestações culturais que estavam ocorrendo no mês (junho/2013) em que o questionário foi aplicado,
quanto ao fazer profissional do Serviço Social, a maioria dos alunos da escola pública estadual
relacionam o trabalho do assistente social com a prestação de ajuda e auxílio. Os alunos da escola
pública federal demonstraram maior efetividade e segurança na resposta, em consonância com o Código
de Ética do Assistente Social, também foi realizada entrevista semiestruturada com a Assistente Social
das instituições de ensino. Segundo a pesquisa identificase a sobrecarga do profissional do serviço social
com as demandas postas pelos alunos no processo de ensino e aprendizagem, de tal modo que não
possa acompanhar atividades de arte e cultura desenvolvidas nas instituições de ensino, e por meio de
levantamentos bibliográficos e visitas de observação ao local de pesquisa foi possível identificar as
atividades, projetos de extensão de arte e cultura nas instituições de ensino
Spiral Evolution in a Confined Geometry
Supported nanoscale lead crystallites with a step emerging from a
non-centered screw dislocation on the circular top facet were prepared by rapid
cooling from just above the melting temperature. STM observations of the top
facet show a nonuniform rotation rate and shape of the spiral step as the
crystallite relaxes. These features can be accurately modeled using curvature
driven dynamics, as in classical models of spiral growth, with boundary
conditions fixing the dislocation core and regions of the step lying along the
outer facet edge.Comment: 4 pages, 3 figures, to be published in Physical Review Letter
Kraus representation for density operator of arbitrary open qubit system
We show that the time evolution of density operator of open qubit system can
always be described in terms of the Kraus representation. A general scheme on
how to construct the Kraus operators for an open qubit system is proposed,
which can be generalized to open higher dimensional quantum systems.Comment: 5 pages, no figures. Some words are rephrase
Correlation dynamics between electrons and ions in the fragmentation of D molecules by short laser pulses
We studied the recollision dynamics between the electrons and D ions
following the tunneling ionization of D molecules in an intense short pulse
laser field. The returning electron collisionally excites the D ion to
excited electronic states from there D can dissociate or be further
ionized by the laser field, resulting in D + D or D + D,
respectively. We modeled the fragmentation dynamics and calculated the
resulting kinetic energy spectrum of D to compare with recent experiments.
Since the recollision time is locked to the tunneling ionization time which
occurs only within fraction of an optical cycle, the peaks in the D kinetic
energy spectra provides a measure of the time when the recollision occurs. This
collision dynamics forms the basis of the molecular clock where the clock can
be read with attosecond precision, as first proposed by Corkum and coworkers.
By analyzing each of the elementary processes leading to the fragmentation
quantitatively, we identified how the molecular clock is to be read from the
measured kinetic energy spectra of D and what laser parameters be used in
order to measure the clock more accurately.Comment: 13 pages with 14 figure
Operator-sum representation of time-dependent density operators and its applications
We show that any arbitrary time-dependent density operator of an open system
can always be described in terms of an operator-sum representation regardless
of its initial condition and the path of its evolution in the state space, and
we provide a general expression of Kraus operators for arbitrary time-dependent
density operator of an -dimensional system. Moreover, applications of our
result are illustrated through several examples.Comment: 4 pages, no figure, brief repor
Quantitative conditions do not guarantee the validity of the adiabatic approximation
In this letter, we point out that the widely used quantitative conditions in
the adiabatic theorem are insufficient in that they do not guarantee the
validity of the adiabatic approximation. We also reexamine the inconsistency
issue raised by Marzlin and Sanders (Phys. Rev. Lett. 93, 160408, 2004) and
elucidate the underlying cause.Comment: corrected typos. Eq. (32) is corrected. No other change
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