Plasma medicine Plasma medicine Plasma medicine is an emerging field that combines plasma physics, life sciences and clinical medicine. It is being studied in disinfection, healing, and cancer. Most of the research is in vitro and in animal models. It uses ionized gas (physical plasma) for medical uses or dental applications . Plasma, often called the fourth state of matter, is an ionized gas containing positive ions and negative ions or electrons, but is approximately charge neutral on the whole. The plasma sources used for plasma medicine are generally low temperature plasmas, and they generate ions, chemically reactive atoms and molecules, and
Negative number 's together yields : The reasoning behind the second example is more complicated. The idea again is that losing a debt is the same thing as gaining a credit. In this case, losing two debts of three each is the same as gaining a credit of six: The convention that a product of two negative numbers is positive is also necessary for multiplication to follow the distributive law. In this case, we know that Since , the product must equal . These rules lead to another (equivalent) rule—the sign of any product "a" × "b" depends on the sign of