Tetrachromacy class eventually lose two of their four cones. The normal explanation of tetrachromacy is that the organism's retina contains four types of higher-intensity light receptor (called cone cells in vertebrates as opposed to rod cells, which are lower intensity light receptors) with different absorption spectra. This means that the animal may see wavelengths beyond those of a typical human being's eyesight, and may be able to distinguish between colors that, to a normal human, appear to be identical. Species with tetrachromatic color vision may have an unknown physiological advantage over rival species. The goldfish ("Carassius auratus auratus") and zebrafish ("Danio
Optical stretcher stretcher, it was also shown that cancerous cells differ significantly in their mechanical properties from their healthy counterparts. The authors claim that the 'optical deformability' can be used as a biomechanical marker to distinguish cancerous from healthy cells, and even that higher stages of malignancy can be detected. A typical optical stretcher setup consists of the following main parts: Objects trapped in the optical stretcher usually have diameters on the scale of 10 micrometer, which is very large compared to the laser wavelengths used (often 1064 nm). It is thus sufficient to consider the interaction with the laser light in