These ions, like the hydrogen ions that are the heart of every acid, have a single positive charge.

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When a voltage was applied at the ends of the yarns, these ions moved into the fibres, causing them to expand.

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If fired at high enough speed, these ions will come to rest a few thousandths of a millimetre below a wafer's surface.

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These ions are thought to help create new particles called aerosols and, when aerosols grow above a certain size, they become the seeds around which cloud droplets form.

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One of these involves shooting oxygen ions (electrically charged atoms) into the silicon wafers from which chips are subsequently cut.

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In the right circumstances these channels will allow the passage of sodium ions (the liquid to be investigated must have these added in the form of sodium chloride, or common salt, if they are not present naturally).

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The first of these to do so let sodium ions in.

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Like the oxygen ions in the traditional technique, these come to rest a few thousandths of a millimetre below the surface.

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When illuminated, these "opsin" proteins change the flow of electrically charged ions within the cell, to help the cell turn light into energy or as a sensory cue.

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As a result of these collisions, the atoms in the beams would lose electrons and become positively charged ions.

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