Evolution of interstellar grains: observations, theory, laboratory experiments

The principal aim is to derive the properties of interstellar grains as a probe of local physical condition and as a basis for predicting such properties as related to infrared emissivity and radiative transfer, which can affect the evolution of dense clouds. First the criteria for grain models based directly on observations of gas and dust are developed. A summary of the chemical evolution of grains and gas in diffuse and dense clouds follows. Finally, a brief excursion is made into the relation between dust in dense clouds and objects in the solar system. These objects may provide us with a source of evidence for the presolar environment and, by inference, regions of star formation. (Auth.)