As detailed in the Supporting Information S1, our results show that in the high concentration region of the CCL19 and CCL21 gradients, cells exhibit repulsive migration away from the gradients; In contrast, in the low concentration region of the CCL19 and CCL21 gradients, cells chemotax to the gradients; in the middle region of the gradient fields, cells migrate randomly.
Wnt5a applied as a gradient from a pipette increased axon outgrowth rates (averaging 20 µm/h) and induced repulsive axon turning away from the Wnt5a source (average turning angle –23°, n = 25 axons) as previously described (Li et al., 2009).
Furthermore, an attractive EM pushing force on the active source directed toward the boundary or a repulsive pulling one pointing away from it can arise accordingly.
Mammalian Ryk is used by corticospinal axons to grow caudally within the spinal cord, away from repulsive sources of Wnt [4].
Previously, we found that bath applied Wnt5a increases cortical axon outgrowth and that Wnt5a gradients evoke repulsive growth cone turning away from the Wnt5a source simultaneous with increased outgrowth rates (Li et al., 2009).
They all combine this with quantitative measures of behavior and modeling to address the mechanisms that underlie how animals orient toward attractive stimuli (and away from repulsive stimuli), and show how the animals negotiate shifting stimulus landscapes.
Here we see a repulsive interaction which repels the spots away from each other if they approach too closely.
In order to refrain from the shortcoming of premature convergence, a two point reversal crossover operator is defined and in the repulsive process each particle is repelled away from some inferior solution in the current tabu list to fly towards some promising areas which can introduce some new information to guide the swarm searching process.
We show that two of these sites located at the twin boundary are more attractive to oxygen than bulk, while the sites away from the boundary are repulsive.
In explaining medium timescale adaptation phenomena we have focused on "repulsive" adaptation, where tuning curves are shifted away from an adapting stimulus.
