FACTOID #53: If you thought Antarctica was inhospitable, think again - its land area is only ninety-eight percent ice. Reassuringly, the other 2% is categorised as "barren rock".
It was later used to require that all AM bandreceivers be able to pick up the new expanded band stations from 1620 to 1710 kilohertz.
It has most recently been used to begin requiring TV manufacturers to include tuners for digital television, although unlike the first two this will cause a large increase in the price of sets. This will be phased-in over several years, beginning with the larger sets. Some have objected to this mandate because it is mainly so the U.S. government can turn off analog stations and sell or auction the frequencies off, while it will cost consumers more for something which has so far gotten a lukewarm reception by the public.
By law, 85% of the households in an area must own at least one DTV tuner before the FCC can turn off analog stations. However, since most homes have more than one TV, a very small fraction of sets may actually continue working without the expense of a converter box when the threshold is reached.
Such protein-based channels or pores underlie much of physiology, from the firing of nerve cells in the brain to the regulation of water by the kidneys.
Ion channelsact like valves that regulate the flow of ions, such as potassium and sodium, across a cell's membrane.
MacKinnon later identified the structure of a channel that regulates the flow of chlorine ions.