noun, Biology. 1. an orientation of an organism to an external stimulus, as light, especially by growth rather than by movement. Origin of tropism. 1895-1900. First recorded in 1895-1900; independent use of -tropism. Related forms. tropismatic.
Friction on as-grown graphene (Fig. 1c) is ultra-low and rather uniform with its magnitude close to the previous reports4. In contrast, friction on graphene after ï¬uorination becomes
Friction can be reduced by adding a lubricant or by smoothing and polishing surfaces, according to the HyperPhysics program at Georgia State University. For some substances, smoothing only reduces friction to a point, after which friction increases with further smoothing.