Each shell contains a small amount of explosive material, and some is used to produce whistles and other effects.

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In order to clone a human, scientists would remove the nucleus of an egg and extract its genetic material, leaving just its shell.

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In this research the scientists created a synthetic viral shell, but lacking its pathogenic RNA interior - the genetic material the virus uses to replicate itself.

BBC: Synchrotron yields 'safer' vaccine

With only the genetic material from the person to be cloned inside the shell of the egg, the cell would be jolted with electricity to activate cell division.

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As a recent inspection at the home of an Iraqi nuclear scientist demonstrated, and other sources confirm, material and documents are still being moved around in farcical shell games.

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Presses with the force of several tons are required to cut through the material before pieces are draped, molded and steamed to form the helmet shell.

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As with any vaccine, the aim is to prompt the immune system to recognise this outer shell and destroy the pathogen before it has time to lock onto cells and infect them with its genetic material.

BBC: Synchrotron yields 'safer' vaccine