Deep learning predicts path-dependent plasticity.

Plasticity theory aims at describing the yield loci and work hardening of a material under general deformation states. Most of its complexity arises from the nontrivial dependence of the yield loci on the complete strain history of a material and its microstructure. This motivated 3 ingenious simplifications that underpinned a century of developments in this field: 1) yield criteria describing yield loci location; 2) associative or nonassociative flow rules defining the direction of plastic flow; and 3) effective stress-strain laws consistent with the plastic work equivalence principle. However, 2 key complications arise from these simplifications. First, finding equations that describe these 3 assumptions for materials with complex microstructures is not trivial. Second, yield surface evolution needs to be traced iteratively, i.e., through a return mapping algorithm. Here, we show that these assumptions are not needed in the context of sequence learning when using recurrent neural networks, diverting the above-mentioned complications. This work offers an alternative to currently established plasticity formulations by providing the foundations for finding history- and microstructure-dependent constitutive models through deep learning.

Underreporting of cocaine and marijuana during the thrid trimester of gestation among pregnant adolescents

Objetive: The aim of this study is to check the validity of the self-report of drug use by pregnant adolescents, by comparing their responses to a structured interview about their use of cocaine and marijuana during the pregnancy with an analysis of their hair. Results: Hair analysis detected the use of cocaine and/or marijuana, 17 (1,7%) used only cocaine, and 3 (0,3%) used both drugs. None of the patients had reported the use of these substances in their interview with healthcare profissionals. Conclusion: Althougth the prevalence of the use of drugs during pregnancy is significant despite consistent evidence about the compromise of the neurobehavioral development of the newborns that are exposed to drugs during the prenatal period, drugs use is frequently not reported. Therefore, more sensitive methods of detection should be used so that appropriate medical and psychosocial interventions com be implemented for the mothers as well as for their children. (AU)