RESUMO
When deformed beyond their elastic limits, crystalline solids flow plastically via particle rearrangements localized around structural defects. Disordered solids also flow, but without obvious structural defects. We link structure to plasticity in disordered solids via a microscopic structural quantity, "softness," designed by machine learning to be maximally predictive of rearrangements. Experimental results and computations enabled us to measure the spatial correlations and strain response of softness, as well as two measures of plasticity: the size of rearrangements and the yield strain. All four quantities maintained remarkable commonality in their values for disordered packings of objects ranging from atoms to grains, spanning seven orders of magnitude in diameter and 13 orders of magnitude in elastic modulus. These commonalities link the spatial correlations and strain response of softness to rearrangement size and yield strain, respectively.
RESUMO
Growth, development, and neurologic status were assessed at 1 year of age in 38 infants of birth weight less than 1,000 gm who were born in 1976 through 1978. Twenty had received mechanical ventilation as newborns, and this group had a significantly higher incidence of respiratory distress syndrome, seizures, cardiac arrest, bronchopulmonary dysplasia, and retrolental fibroplasia than those not ventilated. The ventilated infants had a high incidence (70%) of bronchopulmonary dysplasia and of retrolental fibroplasia (20% grade III or IV). Seven of eight infants with severe developmental delay (greater than 2 SD), six of nine with moderate delay (greater than 1 SD), and seven of eight with neurologic disability had received ventilation. There was no difference in growth between the ventilated and nonventilated children. Of the total group, 53% showed no problems.
