Possible thermistor identification found in thermal conductivity cell
Those are most likely diodes or transistors. Thermistors are typically two terminals devices and are almost never connected in series (it makes it near impossible to use the stein-hart equation to find the actual temperature). On digikey there are zero thermistors available in an SOT package such as these.
Looking up the code 151 brings up a 15V zener diode PZM15NB1.
Measure across the terminals with a DMM in diode mode to get a better idea, it may be difficult but one could still probe the cutoff tips of the SOT packages.