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34 Topic Pages Found in Science and starting with the letter V
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Open Vaccination

means of producing immunity against pathogens, such as viruses and bacteria, by the introduction of live, killed, or altered antigens that stimulate

Open Vacuum

theoretically, space without matter in it. A perfect vacuum has never been obtained; the best man-made vacuums contain less than 100,000 gas molecules

Open Vampire bats
Vampire bats

name for the blood-drinking bats of the family Desmodontidae, found in the New World tropics. Vampire bats feed exclusively on the blood of living


( vӘnā'dēӘm ), metallic chemical element; symbol V; at. no. 23; at. wt. 50.9415; m.p. about 1,890degrees Celsius; b.p. 3,380degrees Celsius; sp. gr.


change of a liquid or solid substance to a gas or vapor. There is fundamentally no difference between the terms gas and vapor, but gas is used

Vapor pressure

pressure exerted by a vapor that is in equilibrium with its liquid. A liquid standing in a sealed beaker is actually a dynamic system: some molecules

Open Variable stars
Variable stars

star that varies, either periodically or irregularly, in the intensity of the light it emits. Other physical changes are usually correlated with the

Varnish and varnishing

homogeneous solution of gum or of natural or synthetic resins in oil (oil varnish) or in a volatile solvent (spirit varnish), which dries on exposure

Vascular plant

Fossil evidence indicates that the first vascular plants ( tracheophytes ) were simple, dichotomously branched organisms about 5–10 cm in height. In

Vegetable oils

Vegetable oils are purified fats of plant origin that are either liquid or solid at room temperature. Vegetable oils are used for cooking, frying, and