9,111 research outputs found
Proprioceptive changes impair balance control in individuals with chronic obstructive pulmonary disease
Copyright @ 2013 Janssens et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Introduction: Balance deficits are identified as important risk factors for falling in individuals with chronic obstructive pulmonary disease (COPD). However, the specific use of proprioception, which is of primary importance during balance control, has not been studied in individuals with COPD. The objective was to determine the specific proprioceptive control strategy during postural balance in individuals with COPD and healthy controls, and to assess whether this was related to inspiratory muscle weakness. Methods: Center of pressure displacement was determined in 20 individuals with COPD and 20 age/gender-matched controls during upright stance on an unstable support surface without vision. Ankle and back muscle vibration were applied to evaluate the relative contribution of different proprioceptive signals used in postural control. Results: Individuals with COPD showed an increased anterior-posterior body sway during upright stance (p=0.037). Compared to controls, individuals with COPD showed an increased posterior body sway during ankle muscle vibration (p=0.047), decreased anterior body sway during back muscle vibration (p=0.025), and increased posterior body sway during simultaneous ankle-muscle vibration (p=0.002). Individuals with COPD with the weakest inspiratory muscles showed the greatest reliance on ankle muscle input when compared to the stronger individuals with COPD (p=0.037). Conclusions: Individuals with COPD, especially those with inspiratory muscle weakness, increased their reliance on ankle muscle proprioceptive signals and decreased their reliance on back muscle proprioceptive signals during balance control, resulting in a decreased postural stability compared to healthy controls. These proprioceptive changes may be due to an impaired postural contribution of the inspiratory muscles to trunk stability. Further research is required to determine whether interventions such as proprioceptive training and inspiratory muscle training improve postural balance and reduce the fall risk in individuals with COPD.This work was supported by the Research Foundation – Flanders (FWO) grants 1.5.104.03, G.0674.09, G.0598.09N and G.0871.13N
Impaired Postural Control Reduces Sit-to-Stand-to-Sit Performance in Individuals with Chronic Obstructive Pulmonary Disease
Abstract
Background: Functional activities, such as the sit-to-stand-to-sit (STSTS) task, are often impaired in individuals with chronic
obstructive pulmonary disease (COPD). The STSTS task places a high demand on the postural control system, which has
been shown to be impaired in individuals with COPD. It remains unknown whether postural control deficits contribute to
the decreased STSTS performance in individuals with COPD.
Methods: Center of pressure displacement was determined in 18 individuals with COPD and 18 age/gender-matched
controls during five consecutive STSTS movements with vision occluded. The total duration, as well as the duration of each
sit, sit-to-stand, stand and stand-to-sit phase was recorded.
Results: Individuals with COPD needed significantly more time to perform five consecutive STSTS movements compared to healthy controls (1966 vs. 1364 seconds, respectively; p = 0.001). The COPD group exhibited a significantly longer stand phase (p = 0.028) and stand-to-sit phase (p = 0.001) compared to the control group. In contrast, the duration of the sit phase (p = 0.766) and sit-to-stand phase (p = 0.999) was not different between groups.
Conclusions: Compared to healthy individuals, individuals with COPD needed significantly more time to complete those phases of the STSTS task that require the greatest postural control. These findings support the proposition that suboptimal postural control is an important contributor to the decreased STSTS performance in individuals with COPD
From a black to a multicultural school: how to move a system strategy?.
This study examines the way in which a school with exclusively minority children desegregates itself. Given the educational system in Belgium of competitive schools and parental choice, desegregation implies a system approach with differentiated content of education, a process of involving stakeholders and redefining the school's context.Strategy;
Magneto-exciton in planar type II quantum dots
We study an exciton in a type II quantum dot, where the electron is confined
in the dot, but the hole is located in the barrier material. The exciton
properties are studied as a function of a perpendicular magnetic field using a
Hartree-fock mesh calculation. Our model system consists of a planar quantum
disk. Angular momentum (l) transitions are predicted with increasing magnetic
field. We also study the transition from a type I to a type II quantum dot
which is induced by changing the confinement potential of the hole. For
sufficiently large magnetic fields a re-entrant behaviour is found from
to and back to , which results in a transition
from type II to type I.Comment: 6 pages, 12 figure
Information Transfer Implies State Collapse
We attempt to clarify certain puzzles concerning state collapse and
decoherence. In open quantum systems decoherence is shown to be a necessary
consequence of the transfer of information to the outside; we prove an upper
bound for the amount of coherence which can survive such a transfer. We claim
that in large closed systems decoherence has never been observed, but we will
show that it is usually harmless to assume its occurrence. An independent
postulate of state collapse over and above Schroedinger's equation and the
probability interpretation of quantum states, is shown to be redundant.Comment: 13 page
Switching to nonhyperbolic cycles from codimension two bifurcations of equilibria of delay differential equations
In this paper we perform the parameter-dependent center manifold reduction
near the generalized Hopf (Bautin), fold-Hopf, Hopf-Hopf and transcritical-Hopf
bifurcations in delay differential equations (DDEs). This allows us to
initialize the continuation of codimension one equilibria and cycle
bifurcations emanating from these codimension two bifurcation points. The
normal form coefficients are derived in the functional analytic perturbation
framework for dual semigroups (sun-star calculus) using a normalization
technique based on the Fredholm alternative. The obtained expressions give
explicit formulas which have been implemented in the freely available numerical
software package DDE-BifTool. While our theoretical results are proven to apply
more generally, the software implementation and examples focus on DDEs with
finitely many discrete delays. Together with the continuation capabilities of
DDE-BifTool, this provides a powerful tool to study the dynamics near
equilibria of such DDEs. The effectiveness is demonstrated on various models
Communicative patterns in organizational (healthcare) teams
As team processes are often consigned to a ‘black box’, this dissertation contributes to unpacking team-level communicative processes as drivers for organizational team functioning. Both conceptually and empirically, we aimed to untangle how communicative processes unfold during collaboration periods in organizational teams. In the first part of this dissertation, we contributed to a more process-oriented understanding of team-based collective intelligence. In addition, we developed a comprehensive framework to study communicative patterns from various aspects (i.e., content, structure, and temporality) and showed how patterned communication may relate to team and organizational-level outcomes. In our own empirical work, we found fine-grained evidence for more back-and-forth communicative patterns underlying the decision-making process in multidisciplinary healthcare team meetings, which seems to be rooted in insufficient orientation of the patients’ background problems. In addition, we observed that team members respond with emotionally laden communication after naturally occurring workflow interruptions, together with more conversational clarification. In sum, both scholars and practitioners benefit from understanding patterned communication because these insights offer sound foundations to reflect on improvements regarding organizational team functioning
Communicative patterns in organizational (healthcare) teams
As team processes are often consigned to a ‘black box’, this dissertation contributes to unpacking team-level communicative processes as drivers for organizational team functioning. Both conceptually and empirically, we aimed to untangle how communicative processes unfold during collaboration periods in organizational teams. In the first part of this dissertation, we contributed to a more process-oriented understanding of team-based collective intelligence. In addition, we developed a comprehensive framework to study communicative patterns from various aspects (i.e., content, structure, and temporality) and showed how patterned communication may relate to team and organizational-level outcomes. In our own empirical work, we found fine-grained evidence for more back-and-forth communicative patterns underlying the decision-making process in multidisciplinary healthcare team meetings, which seems to be rooted in insufficient orientation of the patients’ background problems. In addition, we observed that team members respond with emotionally laden communication after naturally occurring workflow interruptions, together with more conversational clarification. In sum, both scholars and practitioners benefit from understanding patterned communication because these insights offer sound foundations to reflect on improvements regarding organizational team functioning
Resonant backward scattering of light by a two-side-open subwavelength metallic slit
The backward scattering of TM-polarized light by a two-side-open
subwavelength slit in a metal film is analyzed. We show that the reflection
coefficient versus wavelength possesses a Fabry-Perot-like dependence that is
similar to the anomalous behavior of transmission reported in the study [Y.
Takakura, Phys. Rev. Lett. \textbf{86}, 5601 (2001)]. The open slit totally
reflects the light at the near-to-resonance wavelengths. In addition, we show
that the interference of incident and resonantly backward-scattered light
produces in the near-field diffraction zone a spatially localized wave whose
intensity is 10-10 times greater than the incident wave, but one order of
magnitude smaller than the intra-cavity intensity. The amplitude and phase of
the resonant wave at the slit entrance and exit are different from that of a
Fabry-Perot cavity.Comment: 5 figure
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