A Star's Size. A star begins its life in a contracting nebula of gas and dust. As the density of the material increases under the influence of gravity, compression heats the material. If the material gets hot enough, hydrogen atoms begin fusing together to form helium atoms, and a star is born. A star will spend most of its life, called the main sequence phase, fusing hydrogen into helium. Click the image to see the animation. It's logical that a large nebula (one with a large amount of mass) will form a large star, and a small nebula will form a small star. However, in addition to a star's initial mass, a star's size also depends on the balance between the inward pull of gravity and the outward push of the energy produced by fusion. The entire sequence of a star's evolution can be described in terms of the changing balance between these two opposing forces.
Abbreviation for monoamine oxidase. MAO monoamine oxidase; see monoamine oxidase inhibitor, under inhibitor. MAO. abbr. monoamine oxidase. MAO. 1 abbreviation for monoamine oxidase. 2 abbreviation for maximal acid output. MAO Abbreviation for: maximum acid output (see there) medical assistance only monoamine oxidase (see there)
PCA: Commonly used abbreviation for patient-controlled analgesia. Analgesia simply means relief of pain. PCA is a method by which the patient controls the amount of pain medicine they receive. There are a number of different PCA systems. In the classic PCA system, the patient receives a preset dose of morphine by pressing a button on a computerized pump that is connected to an IV catheter. With PCA the patient may receive a small continuous flow of morphine and add more morphine as needed to provide a more constant level of comfort.