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| We study regularity criteria for the nonstationary solutions of the Navier-Stokes equations in the whole three-dimensional space or with periodic boundary conditions based on the velocity gradient. We pay a special attention to the criteria based on an additional regularity of 1) one directional derivative of the velocity field, 2) the gradient of one velocity component, 3) only one of the nine entries of the velocity gradient and 4) two or more entries of the velocity gradient possibly combined with an additional information on the regularity of one velocity component. |
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