When shoes slide across a floor, wave-like deformations of the sole can generate squeaking. The pitch of the squeak depends on the rate at which deformations are generated.
Wright's visit came shortly after Venezuela's National Assembly passed a law to allow both private and foreign investment in its oil industry, following two decades of tight state control.
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The Dutch have quietly adopted working just a four-day week. But what has been its impact, and can it last?