A system and method for measuring the flow rate of a liquid in a tube non-invasively has a heating element that generates energy that is applied to the liquid to produce a heat marker that is detected by a temperature sensor located at a known distance from the heating element and the flow rate is calculated from measuring the travel time of the heat marker from the heating element to the sensor. Polypeptides having amino acid sequences of NRIF3 proteins are also provided. The apparatus includes a processor for receiving the output signal by the input keypad and associating an alphabetic character with the output signal.