85 research outputs found
Growth Cone Pathfinding: a competition between deterministic and stochastic events
BACKGROUND: Growth cone migratory patterns show evidence of both deterministic and stochastic search modes. RESULTS: We quantitatively examine how these two different migration modes affect the growth cone's pathfinding response, by simulating growth cone contact with a repulsive cue and measuring the resultant turn angle. We develop a dimensionless number, we call the determinism ratio Ψ, to define the ratio of deterministic to stochastic influences driving the growth cone's migration in response to an external guidance cue. We find that the growth cone can exhibit three distinct types of turning behaviors depending on the magnitude of Ψ. CONCLUSIONS: We conclude, within the context of these in silico studies, that only when deterministic and stochastic migration factors are in balance (i.e. Ψ ~ 1) can the growth cone respond constructively to guidance cues
The Interplay between Branching and Pruning on Neuronal Target Search during Developmental Growth: Functional Role and Implications
Regenerative strategies that facilitate the regrowth and reconnection of neurons are some of the most promising methods in spinal cord injury research. An essential part of these strategies is an increased understanding of the mechanisms by which growing neurites seek out and synapse with viable targets. In this paper, we use computational and theoretical tools to examine the targeting efficiency of growing neurites subject to limited resources, such as maximum total neural tree length. We find that in order to efficiently reach a particular target, growing neurites must achieve balance between pruning and branching: rapidly growing neurites that do not prune will exhaust their resources, and frequently pruning neurites will fail to explore space effectively. We also find that the optimal branching/pruning balance must shift as the target distance changes: different strategies are called for to reach nearby vs. distant targets. This suggests the existence of a currently unidentified higher-level regulatory factor to control arborization dynamics. We propose that these findings may be useful in future therapies seeking to improve targeting rates through manipulation of arborization behaviors
Swimming in Granular Media
We study a simple model of periodic contraction and extension of large
intruders in a granular bed to understand the mechanism for swimming in an
otherwise solid media. Using an event-driven simulation, we find optimal
conditions that idealized swimmers must use to critically fluidize a sand bed
so that it is rigid enough to support a load when needed, but fluid enough to
permit motion with minimal resistance. Swimmers - or other intruders - that
agitate the bed too rapidly produce large voids that prevent traction from
being achieved, while swimmers that move too slowly cannot travel before the
bed re-solidifies around them i.e., the swimmers locally probe the fundamental
time-scale in a granular packing
Evaluation of Target Search Efficiency for Neurons During Developmental Growth
In this work we investigated how branching and pruning influence the probability of successfully connecting to neurons located at different locations away from the initiation point, under the assumption that the neuron has finite growth resources. We find out that balanced branching and pruning, and the distance to target are essential in determining the optimal growth parameters
Effects of reduced gravity on the granular fluid-solid transition: underexplored forces can dominate soft matter behaviors
Granular media are soft matter systems that exhibit some of the extreme
behavior of complex fluids. Understanding of the natural formation of planetary
bodies, landing on and exploring them, future engineering of structures beyond
Earth and planetary defense all hinge on the ability to predict the complex
mechanical behavior of granular matter. As we understand them, these behaviors
are linked to the granular fluid to solid transition. In this white paper, we
describe issues that emerge for granular systems under reduced gravity and
their implications for basic science and space exploration. (Topical White
Paper submitted to the NASA Biological and Physical Sciences in Space Decadal
Survey 2023-2032)Comment: arXiv admin note: text overlap with arXiv:1002.247
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