A 467.8 ng sample of unknown radioactive substance was placed in storage and its mass measured periodically after 47 days the amount of radioactive substance had decreased 58.48 ng how many half-lives of the non-radioactive substance have occurred

Consider a culture medium on which only gram-positive organisms such as staphylococcus aureus colonies can grow due to an elevated nacl level. a yellow halo surrounds the growth, indicating the bacterium fermented a sugar in the medium, decreasing the ph as a result and changing the color of a ph indicator chemical. this type of medium would be referred to as a differential and enrichment culture.