It is required precipitate a protein contained in $20$ liters of aqueous solution at $10\backslash$deg C in a tank at a concentration of $0\mathrm{.}5$ g$/$liter$.$ The protein is a globular protein with a molecular weight of $900,000$ and a diffusion coefficient of $1\mathrm{.}5\backslash$times $107$ cm$2/$s at $10$C$.$ The precipitate particles have a density of $2\mathrm{.}3$ g$/$cm$3.$ The solution is stirred with a $25$ W$(0\mathrm{.}1$ hp$)$ motor. Calculate the concentration of nuclei at the end of the $$initial mixing$$ period.