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Transient Perturbation (transient + perturbation)
Selected AbstractsIndependent on-line control of the two hands during bimanual reachingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2004Jörn Diedrichsen Abstract Many studies on bimanual coordination have shown that people exhibit a preference for mirror-symmetric movements. We demonstrate that this constraint is absent when bimanual reaching movements are made to visual targets. We investigated the ability of humans to make on-line adjustments during such movements when one or both targets were displaced during the initial phase of the movements. Adjustments were as efficient during bimanual as unimanual movements, even when two adjustments had to be made simultaneously. When one target was displaced in the bimanual condition, the hand reaching to that target adjusted efficiently to the displacement. However, a small transient perturbation in the trajectory of the other hand was also observed. This perturbation was in the same direction as the displacement, rather than in mirror-symmetric direction. A control experiment demonstrated that these perturbations could be elicited by visual information alone, but that they were also influenced by whether an adjustment was required in the trajectory of the other hand. Our results demonstrate near independent control of the two arms during visually guided reaching. The subtle interference observed between the arms reflects interactions between target-related representations in visual coordinates rather than between movement-related representations in joint- or muscle-coordinates. [source] Effect of a transient perturbation on marine bacterial communities with contrasting historyJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2010O. Zemb Abstract Aims:, To evaluate the importance of the bacterial composition on the resilience of the organic matter assimilation in the sea. Methods and Results:, Chemostats were inoculated with coastal and offshore bacterial communities. Bacterial density and protein synthesis increased before stabilizing, and this response to confinement was more marked in the offshore chemostats. Before the toluene perturbation the community structure in the coastal chemostats remained complex whereas the offshore chemostats became dominated by Alteromonas sp. After the perturbation, bacterial protein synthesis was inhibited before peaking briefly at a level fivefold to that observed before the perturbation and then stabilizing at a level comparable to that before the perturbation. Alteromonas dominated both the coastal and the offshore communities immediately after the perturbation and the coastal communities did not recover their initial complexity. Conclusions:, Cell lysis induced by the toluene perturbation favoured the growth of Alteromonas which could initiate growth rapidly in response to the nutrient pulse. Despite their different community structure in situ, the resilience of protein synthesis of coastal and offshore bacterial communities was dependent on Alteromonas, which dominated in the chemostats. Significance and Impact of the Study:, Here we show that although Alteromonas sp. dominated in artificial offshore and coastal communities in chemostats, their response time to the shock was different. This suggests that future perturbation studies on resilience in the marine environment should take account of ecosystem history. [source] Self-organized regular surface patterning by pulsed laser ablationPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2009Juergen Reif Abstract The impact of intense ultra short laser pulses on solid surface - as in laser ablation - results in a transient perturbation of the material to a state far from equilibrium. Due to ultrafast relaxation of the transient disorder in a few picoseconds, self-organized surface patterns occur, with a typical feature size at the order of 100 nm or less, similar as observed in ion sputtering and explained by non-linear dynamics models. The feature size of these structures is determined by the deposited energy dose, their shape and orientation crucially depends on the state of polarization of the incident light. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Perturbation-independent community development in low-temperature anaerobic biological wastewater treatment bioreactorsBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010Pádhraig Madden Abstract The reproducibility and stability of low- temperature anaerobic wastewater treatment systems undergoing transient perturbations was investigated. Three identical anaerobic expanded granular sludge bed-based bioreactors were used to degrade a volatile fatty acid and glucose-based wastewater under sub-ambient (15°C) conditions. The effect of a variety of environmental perturbations on bioreactor performance was assessed by chemical oxygen demand removal. Temporal microbial community development was monitored by denaturation gradient gel electrophoresis (DGGE) of 16S rRNA genes extracted from sludge granules. Methanogenic activity was monitored using specific methanogenic activity assays. Bioreactor performance and microbial population dynamics were each well replicated between both experimental bioreactors and the control bioreactor prior to, and after the implementation of most of the applied perturbations. Gene fingerprinting data indicated that Methanosaeta sp. were the persistent, keystone members of the archaeal community, and likely were pivotal for the physical stability and maintenance of the granular biofilms. Cluster analyses of DGGE data suggested that temporal shifts in microbial community structure were predominantly independent of the applied perturbations. Biotechnol. Bioeng. 2010;105: 79,87. © 2009 Wiley Periodicals, Inc. [source] | ||||||||||