given a blood flow velocity of 55cm/s, a Doppler angle of 52 degrees, and a transducer frequency of 7 MHz, calculate the Doppler shift frequency that would be found under the given conditions. if the pulse repetition frequency is 5.9 kHz, state the Nyquist limit frequency. Can spectral Doppler imaging be carried out without aliasing in the present case? Explain why or why not?