Examples of such thermodynamic properties include specific volume, specific enthalpy, or specific entropy. The adiabatic flash evaporation process is isenthalpic (occurs at constant enthalpy). However the standard enthalpy of combustion is readily measurable using bomb calorimetry. Such behavior is a result of an exothermic enthalpy of solution. Some heat must nevertheless be supplied to counter the heat lost to enthalpy of vaporization. They have high positive electron gain enthalpy and high ionization enthalpy. For an exothermic reaction, heat is released, making the net enthalpy change negative. Brandsma introduced standard entropy of activation and the standard enthalpy of activation. Gibbs free energy in protein folding is directly related to enthalpy and entropy. For an endothermic reaction, heat is absorbed, making the net enthalpy change positive. Olefin metathesis involves little change in enthalpy for unstrained alkenes. Disadvantages include low phase-change enthalpy, low thermal conductivity, and flammability. However, later studies suggested that both enthalpy and entropy factors were involved. The heat of fusion is significantly smaller than enthalpy of sublimation. The following is a selection of enthalpy changes commonly recognized in thermodynamics.