Radiometric dating is done by comparing the ratio of a. two radioactive isotopes over time. b. a stable isotope to a decaying isotope. c. two nondecaying isotopes over time. d. the isotopes from two different elements over time.

According to social exchange theory, altruistic behaviors benefit the individual who performs them.

Atomic nuclei of almost all elements consist of

Air enters a gas turbine with two stages of compression and two stages of expansion at 100 kpa and 17°c. this system uses a regenerator as well as reheating and intercooling – the intercooler returns the air to the inlet temperature. the pressure ratio across each compressor is 4 ; 300 kj/kg of heat are added to the air in each combustion chamber; and the regenerator operates perfectly while increasing the temperature of the cold air by 20°c. determine the system’s thermal efficiency. assume isentropic operations for all compressor and the turbine stages and use constant specific heats at room temperature. (0.378)