In particular, we study the influence of an upper mixed layer (UML) in this system and show that it leads to a variety of dynamic effects: (i) Our model predicts alternative density profiles with a maximum of biomass either within or below the UML, there by the system may be bistable or the relaxation from an unstable state may require a long-lasting transition. (ii) Reduced mixing in

the deep layer can induce oscillations of the biomass; we show that a UML can sustain these oscillations even if the diffusivity is less than the critical mixing for a sinking phytoplankton population. (iii) A UML can strongly modify the outcome of competition between different phytoplankton species, yielding bistability both in the spatial distribution and in the species composition. (iv) A light limited selleck chemicals llc species can obtain a competitive advantage AZD5363 price if the diffusivity in the deep layers is reduced

below a critical value. This yields a subtle competitive exclusion effect, where the oscillatory states in the deep layers are displaced by steady solutions in the UML. Finally, we present a novel graphical approach for deducing the competition outcome and for the analysis of the role of a UML in aquatic systems. (C) 2009 Elsevier Ltd. All rights reserved.”
“Gait initiation (GI) is the transient period between posture and movement. Its central programming takes into account the environmental constraints as well as the constraints induced by the body itself. Patients with peripheral sensory neuropathies display a severe proprioceptive deficit leading to balance and gait impairments and rely on a variety of compensatory mechanisms

and are known to be dependent on vision. Cl was studied on eight healthy subjects and five patients in order to assess the effect of somatosensory loss on the different phases of GI, combined with a manipulation of the visual inputs. Our main hypothesis PD173074 molecular weight is that the proprioceptive deficit would induce an adaptation of the Cl process, especially when modifying the lower part of peripheral vision. The results show that the pathology induces some adaptations of the Cl process, characterized by a decrease of the motor performance (assessed by the maximal anteroposterior velocity of the center of gravity at the end of the first step), a decrease in the spatial parameters (assessed by the peak amplitude of the backward shift of the center of foot pressure during the anticipation phase and the length of the first step), and a non-modification of the temporal parameters (assessed by the duration of the anticipation phase and of the first step). The suppression of the lower part of peripheral vision has no effect on the Cl process. The role of the lower part of peripheral vision seems therefore to be less critical for GI, than for balance and locomotion. (C) 2010 Elsevier Ireland Ltd. All rights reserved.