Lattice correspondence and fivefold twins of the orthorhombic (2/1, 1/1) and (1/0, 2/1) approximants in a Ga-Fe-Cu-Si alloy

In the rapidly solidified and annealed Ga₄₆Fe₂₃Cu₂₃Si₈ alloy, the base-centered orthorhombic (2/1, 1/1) and (1/0, 2/1) approximants of the decagonal quasicrystal, with lattice parameters of a=2.00 nm, b=1.25 nm, and c=1.40 nm and a=0.76 nm, b=1.25 nm, and c=2.40 nm, respectively, were found to coexist with a definite lattice correspondence relationship. At the interphase boundary, their {101} planes and the 〈101〉 directions in these planes coincide. There are four possible types of lattice correspondences which have been confirmed by electron diffraction patterns as well as by high-resolution electron microscopy (HREM) images. Moreover, such lattice correspondence relationships can be accounted for by the structural subunits with angles of n × 72 deg in these two orthorhombic approximants: flattened hexagons in the (1/0, 2/1) approximant, and octagons called “crown” subunits in the (2/1, 1/1) approximant. Various tilings of the crown subunits are discussed. In addition, fivefold rotational twins occur abundantly in both of these approximants and intergrowth between them is common. This can also be explained by their respective characteristic structural subunits.     

Cardiac contusion in a 2 1/2-year-old child

This case was unique in that we were seeing signs and symptoms of a cardiac contusion 11 hours after injury, when cellular edema was causing lethal bradyarrhythmias and hypotension. Keeping the possibility of a cardiac contusion in mind when caring for pediatric patients with trauma and including a 12-lead EKG more routinely for pediatric patients with chest trauma would increase identification of potential problems as early as possible. Although cardiac contusion is not common in children, it must not be overlooked.