How do they get the stripes in the toothpaste?

Are cellphones safe? Why should cornflour make irradiated skin more comfortable? Why do dogs turn in circles before they lie down or defaecate? Are there any materials transparent to the eye but opaque to a camera? Is the Sun orbiting anything? How do they get the stripes in the toothpaste? Is blood donation an alternative to dieting? What do cows actually eat - grass, or bacteria? And why are birds so clever yet we rule the world? Join Dr Chris and the 702 crew for the first episode of Ask the Naked Scientists, 2012...