plasma, biological: see blood.

plasma, in physics, fully ionized gas of low density, containing approximately equal numbers of positive and negative ions (see electron and ion). It is electrically conductive and is affected by magnetic fields. The study of plasma, called plasma physics, is especially important in research efforts to produce a controlled thermonuclear reaction (see nuclear energy). Such a reaction requires extremely high temperatures; it has been computed that a temperature of about 10 million degrees Celsius would be needed to initiate the reaction between deuterium and tritium. By passing a very high electric current through plasma great heat is produced and, simultaneously, an electromagnetic field is created, causing the plasma to withdraw from the walls of its container. The contraction of the plasma, called the pinch effect, prevents the container from being destroyed, but the effect may become unstable too quickly for the fusion reaction. The properties of plasma are distinct from those of the ordinary states of matter, and for this reason many scientists consider plasma a fourth state of matter. Interstellar gases, as well as the matter inside stars, are thought to be in the form of plasma, thus making plasma a common form of matter in the universe. See also condensate.

Any of a major class of proteins insoluble in pure water and soluble in dilute saline (salt) solutions. In their natural state, the protein chain is folded into a globular form. Globulins are found in many plants, especially cereals. Globulins in animal fluids include enzymes, antibodies (the gamma globulins), lipoproteins, complement components, transport proteins, and various types of fibrous and contractile proteins.

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Subgroup of the globulins. In humans and many other mammals, most antibodies are in the gamma globulin fraction of blood. A human gamma globulin preparation may be administered (by injection) to persons lacking immunity, either generally or to a particular disease, after exposure or before expected exposure.

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A malignant proliferation of abnormal plasma cells that populate the marrow-containing bones of the body. The affected plasma cells produce myeloma protein, a monoclonal antibody that replaces normal antibodies in the blood, thereby increasing susceptibility to infection and renal failure. Symptoms include pain, anemia, weakness, infection, a tendency to hemorrhage, shortness of breath, kidney insufficiency, bone fractures, and neurological symptoms. It is considered a progressive and incurable disease; treatments with thalidomide, bone-marrow transplantation, and high-dose chemotherapy may extend life span, although success rates are variable.

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Electrically conducting medium in which there are roughly equal numbers of positively and negatively charged particles, produced when the atoms in a gas become ionized (see ionization). Plasma is sometimes called the fourth state of matter (the first three being solid, liquid, and gas). A plasma is unique in the way it interacts with itself, with electric and magnetic fields, and with its environment. It can be thought of as a collection of ions, electrons, neutral atoms and molecules, and photons in which some atoms are being ionized at the same time as electrons are recombining with other ions to form neutral particles, while photons are continuously being produced and absorbed. It is estimated that more than 99percnt of the matter in the universe exists in the plasma state.

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