Why would scientists use a control sample that has no dna from bighead carp in edna surveillance? a. to amplify the dna in small samples b. to serve as a positive control against samples c. to cut sample dna into fragments d. to verify that no dna has contaminated the gel

Air is contained in a variable-load piston-cylinder device equipped with a paddle wheel. initially, air is at 400 kpa and 17°c. the paddle wheel is now turned by an external electric motor until 75 kj/kg of work has been transferred to air. during this process, heat is transferred to maintain a constant air temperature while allowing the gas volume to triple. calculate the required amount of heat transfer in kj/kg.