The statistical arrangement of oriented segments in natural scenes was recently proposed to be indicative of a cocircularity rule. In particular, the probability density function of the relative position of two oriented segments was found to be maximal along fixed angles on the plane, consistent with the two segments being tangent to two points of a circle. Does this observation point to a prev...

Circles are frequently used for modelling the growth of particle aggregates through the Voronoi diagram of circles, that is a special instance of the Johnson-Mehl tessellation. The Voronoi diagram of a set of sites is a decomposition of space into proximal regions. The proximal region of a site is the locus of points closer to that site than to any other one. Voronoi diagrams allow one to answe...

In this paper, we present a new method for camera calibration using concentric circles. We demonstrate that camera calibration is possible using two views of a concentric circle with known size. A new method to determine the position of the projected center of the circle is introduced. Based on the accurate estimation of the projected circle center of two sets of 3-D concentric circles, the pro...

It was about the end of my afternoon clinic, while I was examining a patient's fundus, that I became aware of some indistinctness of the view. When I failed to find the source of this opacity in the patient's ocular media, it was gradually borne in on me that the beam was in my own eye and not a mote in the patient's! At first the opacity was rather vague, but gradually over half an hour or so ...

Tangled DNA tightens chromosomes C ramming your vacation wardrobe into your luggage is a breeze compared with the packing job cells perform. Before they can divide, they have to scrunch long DNA molecules into tiny chromosomes. The tangles that form in DNA molecules help this chromosome compression, Kawamura et al. report. The team studies newt chromosomes—they are large and convenient to obser...

A generalization of Apollonian packing of circles Gerhard Guettler Colin Mallowsy Abstract Three circles touching one another at distinct points form two curvilinear triangles. Into one of these we can pack three new circles, touching each other, with each new circle touching two of the original circles. In such a sextuple of circles there are three pairs of circles, with each of the circles in...

Dolphins are known to show similarities to humans with respect to a range of visual perceptual tasks, but it is not well understood how dolphins perceive objects through vision. In this study, we tested the relative size discrimination of visual stimuli in a bottlenose dolphin (Tursiops truncatus) in order to examine whether dolphins could solve size discrimination problems using relative size ...

Two experiments studied the Ebbinghaus illusion as a function of four stimulus variables: the size of the context circles, the number of context circles, the distance between the context circles and the center circle, and the size of the center circle. The results provided a quantitative test of a judgmental model that considers the Ebbinghaus illusion to be comparative in nature. The context c...