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We have developed a numerical solution for the transfer of continuum radiation in axisymmetric geometry, based on a discrete ordinate lambda iteration method, with diffusion-synthetic acceleration. The method is applied to calculate temperature profiles in the infalling cloud surrounding a protostar. The shape of the cloud is modelled as a torroid. Frequency-dependence is treated in a two-group approximation, with separate opacities for the optical and infrared portions of the spectrum. Group opacities are derived from a database for the primitive solar nebula developed by Pollack et al. (1994 Ap. J. 421 p. 615). Since the opacities are temperature-dependent, the radiative transfer problem is nonlinear, and is shown to have multiple solutions, which depend on the initial state of the system. We determine the distance from the protostar at which various dust species undergo vaporization. Comparison is made to the known composition of Solar system bodies, providing constraints on the inheritance of material from the original molecular cloud.
