Regulators think that some high-frequency traders switched off their programs when prices began to spiral, fearful that their trades would be cancelled because of the severity of the declines.

ECONOMIST: America's stockmarket plunge

For example, the Controller respond to a frequency disturbance by turning off the heating element of a drying machine, but keep the tumbler turning.

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The SEC is also studying the effects of various trends that have shaped the U.S. stock markets over the course of the last decade, including the proliferation of high frequency trading and of off-exchange trading in so-called dark pools.

FORBES: SEC Sets 6-Month Test of Stock Circuit Breakers

The Acoustic Thermometry of Ocean Climate (ATOC) project is asking to extend its two-year permit to operate low-frequency sonar under the water off Kauai another five years.

CNN: waves

"Services between London and Swansea currently operate at a frequency of only one train an hour off-peak, " he added.

BBC: Swansea rail electrification plea from city leader

As The New York Times reported last year, profits from high-frequency trading have started to fall, off 74% in 2012 from the peak in 2009.

FORBES: Your Investing Hunch Is Internet Roadkill

The frequency, the depth of these engagements I think have really paid off.

WHITEHOUSE: Press Briefing

In addition to lean body mass, meal frequency plays a huge role in keeping your metabolism elevated, helping to keep extra pounds off while also stabilizing hormone and energy levels.

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It can use its High Frequency Instrument to look for the infrared emission from dust that is warmed by stars associated with far-off galaxies.

BBC: Science & Environment