Some children's speech impairment resolves spontaneously. Others have persistent problems affecting academic and social development. Identifying early markers that reliably predict longterm outcome would allow better prioritization for preschool intervention. This article evaluates the significance of different types of speech errors, made by 93 four-year-olds in a longitudinal population cohort study, for performance at seven years. At four years, the non-age appropriate speech errors made on standardized assessments were categorized as: phonologically delayed

The shielding effects of a thin bubbly layer submerged in pure liquid on the propagation of acoustic waves are analyzed. By using the method of matched asymptotics, conditions across the bubbly layer are derived. They are: (1) that the pressure is continuous and (2) that the jump of normal velocity is related to the temporal derivative of pressure times a parameter representing the bulk property of the bubbly layer. This parameter is the product of a small number and a large number. The former is the wavenumber times the integral of the gas volume fraction β across the layer and the latter is the ratio of the density times the square of the speed of sound for the liquid phase to that for the gas phase. When the thin bubbly layer is adjacent to a rigid surface, their combined effect is described by an impedance boundary condition.

The BETA computer codes have been developed to study ideal magnetohydrodynamic equilibrium and stability of stellarators and to calculate neoclassical transport for electrons as well as ions by the Monte Carlo method. In this paper a numerical procedure is presented to select resonant terms in the electric potential so that the distribution functions and confinement times of the ions and electrons become indistinguishable.In the BETA codes the variational principle of ideal magnetohydrodynamics is implemented as a finite difference scheme to compute the equilibrium of a toroidal plasma in three dimensions without symmetry (1). The The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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