It is for this reason that is referred to as a complementary DNA or cDNA. Though there are numerous processes for synthesizing cDNA, the best way of doing so is by using mature or fully spliced mRNA. This is usually done by using the enzyme reverse transcriptase.
Ammonia is used as refrigerant prominently in the refrigeration systems of food industry like dairies, ice creams plants, frozen food production plants, cold storage warehouses, processors of fish, poultry and meat and number of other applications.
This type of refrigeration system takes advantage of the fact that the solubility of ammonia in water changes as the temperature of the system changes. This type of refrigeration is beyond the scope of Thermo-CD, but you should be aware of its existence.