Site unnoccupied by an atom or ion in a crystal lattice.
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Immunization against an infectious disease by exposure to the appropriate
Software which is used to detect, eradicate and repair the effects of computer
Synonym for the virus used in vaccine procedures to produce immunity to smallpox. Differs from cowpox and smallpox virus in minor antigens only and was probably derived originally from cowpox virus. The virus has proved very stable ie not liable to mutation and safe to use in humans, and produces long-lasting cell mediated immunity. Genes for other viral antigens have been introduced into vaccinia virus by recombinant DNA techniques with the intention that immunization with the recombinant strain shall produce protective immunity against other viruses also,
A cavity, containing sap and separated from the cytoplasm by a membrane, the tonoplast.
Literally, a space totally devoid of any matter. In practice this is impossible, but is approached in interstellar regions. On Earth, the best vacuums produced have a pressure of about 10~8 N m ~2. Used loosely for any pressure lower than atmospheric, eg in train braking systems and 'vacuum' cleaners,
Behaviour manifested in the apparent absence of the external stimuli that normally elicit the activity, presumably because of internal factors governing the motivation to perform the behaviour,