Quasifission mass distributions in the synthesis of 274Hs with 26Mg and 36S projectiles

The potential energy landscape for the [Formula: see text] synthesis is evaluated in the framework of the macroscopic–microscopic model. The fragmentation potential calculated in a configuration space characterized by five degrees of freedom associated to elongation, mass asymmetry, necking, and left/right deformations reveals the existence of several minima and some pronounced valleys. The valleys correspond mainly to the [Formula: see text] and [Formula: see text] quasifission channels, but also for some paths in the formation of the compound nuclear system. In this context, two different paths are obtained for the [Formula: see text] and [Formula: see text] entrance channels. The [Formula: see text] path leads to the formation of an isomeric minimum that decays by fission. The [Formula: see text] path evidences a larger probability for the formation of the compound nucleus. Therefore, the two distributions obtained for the associated quasifission processes are very different.

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An energy landscape approach to locomotor transitions in complex 3D terrain

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1918297117 ◽

2020 ◽

Vol 117 (26) ◽

pp. 14987-14995 ◽

Cited By ~ 2

Author(s):

Ratan Othayoth ◽

George Thoms ◽

Chen Li

Keyword(s):

Potential Energy ◽

Complex Terrain ◽

Statistical Physics ◽

Energy Landscape ◽

Three Dimensional ◽

Single Mode ◽

Physical Interaction ◽

Landscape Approach ◽

3D Terrain ◽

Potential Energy Landscape

Effective locomotion in nature happens by transitioning across multiple modes (e.g., walk, run, climb). Despite this, far more mechanistic understanding of terrestrial locomotion has been on how to generate and stabilize around near–steady-state movement in a single mode. We still know little about how locomotor transitions emerge from physical interaction with complex terrain. Consequently, robots largely rely on geometric maps to avoid obstacles, not traverse them. Recent studies revealed that locomotor transitions in complex three-dimensional (3D) terrain occur probabilistically via multiple pathways. Here, we show that an energy landscape approach elucidates the underlying physical principles. We discovered that locomotor transitions of animals and robots self-propelled through complex 3D terrain correspond to barrier-crossing transitions on a potential energy landscape. Locomotor modes are attracted to landscape basins separated by potential energy barriers. Kinetic energy fluctuation from oscillatory self-propulsion helps the system stochastically escape from one basin and reach another to make transitions. Escape is more likely toward lower barrier direction. These principles are surprisingly similar to those of near-equilibrium, microscopic systems. Analogous to free-energy landscapes for multipathway protein folding transitions, our energy landscape approach from first principles is the beginning of a statistical physics theory of multipathway locomotor transitions in complex terrain. This will not only help understand how the organization of animal behavior emerges from multiscale interactions between their neural and mechanical systems and the physical environment, but also guide robot design, control, and planning over the large, intractable locomotor-terrain parameter space to generate robust locomotor transitions through the real world.

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