Velocity and attenuation of scalar and elastic waves in random media: a spectral function approach.

This paper investigates the scattering of scalar and elastic waves in two-phase materials and single-mineral-cubic, hexagonal, orthorhombic-polycrystalline aggregates with randomly oriented grains. Based on the Dyson equation for the mean field, explicit expressions for the imaginary part of Green's function in the frequency-wavenumber domain (ω, p), also known as the spectral function, are derived. This approach allows the identification of propagating modes with their relative contribution, and the computation of both attenuation and phase velocity for each mode.

Lopsided growth of Earth's inner core.

Hemispherical asymmetry is a prominent feature of Earth's inner core, but how this asymmetry relates to core growth is unknown. Based on multiple-scattering modeling of seismic velocity and attenuation measurements sampling the whole uppermost inner core, we propose that the growth of the solid core implies an eastward drift of the material, driven by crystallization in the Western Hemisphere and melting in the Eastern Hemisphere. This self-sustained translational motion generates an asymmetric distribution of sizes of iron crystals, which grow during their translation.

Risk factors for early and late onset of respiratory symptoms in babies born through meconium.

We sought (1) to identify risk factors for meconium aspiration syndrome (MAS) among infants born to women whose labors were complicated by thick-consistency meconium-stained amniotic fluid (MSAF), and (2) to determine whether risk factors and infant prognosis differ according to the time of onset of respiratory distress. We performed a secondary analysis of a multicenter randomized trial of amnioinfusion (AI) for the prevention of MAS among women with thick-consistency MSAF. MAS was defined as onset of respiratory distress requiring oxygen supplementation within the first 4 hours of life.