What all of these channels have is what's called a selectivity filter, so this filter filters out the type of ion that's going to be allowed through.

这些离子通道都有的一部分,就是所谓的选择性过滤器，这个过滤器,会滤过允许穿过的离子。

麻省理工公开课 - 化学原理课程节选

And there's two parts of the filter.

这个过滤器由两部分组成。

麻省理工公开课 - 化学原理课程节选

Eclipse glasses, dark welder's goggles or an astronomer's filter made for sun viewing are recommended if people want to look skyward.

CNN: Upcoming solar eclipse to project 'ring of fire'

And more concretely, Google's filter won't erase the alleged copyright infringement that's already occurred on the site for more than a year.

FORBES: Magazine Article

In case you don't have your smartphone app handy, the taps are equipped with LED lights to show the water's filter status as well -- blue means clean, yellow means not so much and red means you should probably get a new filter, pronto.

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