Self-stabilizing uncoupled dynamics

Dynamics in a distributed system are self-stabilizing if they are guaranteed to reach a stable state regardless of how the system is initialized. Game dynamics are uncoupled if each player's behavior is independent of the other players' preferences. Recognizing an equilibrium in this setting is a distributed computational task. Self-stabilizing uncoupled dynamics, then, have both resilience to arbitrary initial states and distribution of knowledge. We study these dynamics by analyzing their behavior in a bounded-recall synchronous environment. We determine, for every "size" of game, the minimum number of periods of play that stochastic (randomized) players must recall in order for uncoupled dynamics to be self-stabilizing. We also do this for the special case when the game is guaranteed to have unique best replies. For deterministic players, we demonstrate two self-stabilizing uncoupled protocols. One applies to all games and uses three steps of recall. The other uses two steps of recall and applies to games where each player has at least four available actions. For uncoupled deterministic players, we prove that a single step of recall is insufficient to achieve self-stabilization, regardless of the number of available actions

Segmental stabilizing exercises and low back pain: What is the evidence?

Study design: A systematic review of randomized controlled trials. Objectives: To evaluate the effectiveness of segmental stabilizing exercises for acute, subacute and chronic low back pain with regard to pain, recurrence of pain, disability and return to work. Methods: MEDLINE, EMBASE, CINAHL, Cochrane Controlled Trials Register, PEDro and article reference lists were searched from 1988 onward. Randomized controlled trials with segmental stabilizing exercises for adult low back pain patients were included. Four comparisons were foreseen: (1) effectiveness of segmental stabilizing exercises versus treatment by general practitioner (GP); (2) effectiveness of segmental stabilizing exercises versus other physiotherapy treatment; (3) effectiveness of segmental stabilizing exercises combined with other physiotherapy treatment versus treatment by GP and (4) effectiveness of segmental stabilizing exercises combined with other physiotherapy treatment versus other physiotherapy treatment. Results: Seven trials were included. For acute low back pain, segmental stabilizing exercises are equally effective in reducing short-term disability and pain and more effective in reducing long-term recurrence of low back pain than treatment by GP. For chronic low back pain, segmental stabilizing exercises are, in the short and long term, more effective than GP treatment and may be as effective as other physiotherapy treatments in reducing disability and pain. There is limited evidence that segmental stabilizing exercises additional to other physiotherapy treatment are equally effective for pain and more effective concerning disability than other physiotherapy treatments alone. There is no evidence concerning subacute low back pain. Conclusion: For low back pain, segmental stabilizing exercises are more effective than treatment by GP but they are not more effective than other physiotherapy interventions

Stabilizing data-link over non-FIFO channels with optimal fault-resilience

Self-stabilizing systems have the ability to converge to a correct behavior when started in any configuration. Most of the work done so far in the self-stabilization area assumed either communication via shared memory or via FIFO channels. This paper is the first to lay the bases for the design of self-stabilizing message passing algorithms over unreliable non-FIFO channels. We propose a fault-send-deliver optimal stabilizing data-link layer that emulates a reliable FIFO communication channel over unreliable capacity bounded non-FIFO channels

A State-Space Approach to Parametrization of Stabilizing Controllers for Nonlinear Systems

A state-space approach to Youla-parametrization of stabilizing controllers for linear and nonlinear systems is suggested. The stabilizing controllers (or a class of stabilizing controllers for nonlinear systems) are characterized as (linear/nonlinear) fractional transformations of stable parameters. The main idea behind this approach is to decompose the output feedback stabilization problem into state feedback and state estimation problems. The parametrized output feedback controllers have separation structures. A separation principle follows from the construction. This machinery allows the parametrization of stabilizing controllers to be conducted directly in state space without using coprime-factorization

Physical demand but not dexterity is associated with motor flexibility during rapid reaching in healthy young adults

Healthy humans are able to place light and heavy objects in small and large target locations with remarkable accuracy. Here we examine how dexterity demand and physical demand affect flexibility in joint coordination and end-effector kinematics when healthy young adults perform an upper extremity reaching task. We manipulated dexterity demand by changing target size and physical demand by increasing external resistance to reaching. Uncontrolled manifold analysis was used to decompose variability in joint coordination patterns into variability stabilizing the end-effector and variability de-stabilizing the end-effector during reaching. Our results demonstrate a proportional increase in stabilizing and de-stabilizing variability without a change in the ratio of the two variability components as physical demands increase. We interpret this finding in the context of previous studies showing that sensorimotor noise increases with increasing physical demands. We propose that the larger de-stabilizing variability as a function of physical demand originated from larger sensorimotor noise in the neuromuscular system. The larger stabilizing variability with larger physical demands is a strategy employed by the neuromuscular system to counter the de-stabilizing variability so that performance stability is maintained. Our findings have practical implications for improving the effectiveness of movement therapy in a wide range of patient groups, maintaining upper extremity function in old adults, and for maximizing athletic performance

Stabilizing dilaton and baryogenesis

Entropy production by the dilaton decay is studied in the model where the dilaton acquires potential via gaugino condensation in the hidden gauge group. Its effect on the Affleck-Dine baryogenesis is investigated with and without non-renormalizable terms in the potential. It is shown that the baryon asymmetry produced by this mechanism with the higher-dimensional terms is diluted by the dilaton decay and can be regulated to the observed value.Comment: 20 pages, 3 figures, baryon asymmetry revised, errors corrected, references and comments adde