21. Surface tension has the dimension of force per unit length , or of energy per unit area. 22. Also, one picks a segment in the plane which is declared to be of unit length . 23. The " side centroid " comes from considering the sides to have constant mass per unit length . 24. The ribozyme acts to process the RNA transcripts to unit lengths in a self-cleavage reaction. 25. The physical model behind this method is the infinite line source with constant power per unit length . 26. As long as the rope has a non-zero mass per unit length this is needed. 27. The unit length for the grid was the kilometre; the British units were not even considered. 28. This can be found by a breadth-first search, as we let edges have unit length . 29. This vector is then normalized to unit length in order to enhance invariance to affine changes in illumination. 30. This may be more succinctly stated by realizing that directional data are in fact vectors of unit length .
