Meta-learning and Enforcing Useful Conservation Laws in Sequential Prediction Problems

In recent years, deep learning techniques have enjoyed storied success in a wide array of problem domains, including computer vision, natural language processing, and robotics. While much of this success can be attributed to increasing availability of both data and computing resources, the inductive biases induced by various training methods, model components, and architectures has helped enable efficient generalization as well. Useful biases often exploit symmetries in the prediction problem, such as convolutional neural networks relying on translation equivariance. Automatically discovering such useful symmetries is a promising path to greatly improving the performance of ML systems, but it still remains a challenge. In this work, we focus on sequential prediction problems in real and simulated physical domains and take inspiration from Noether’s theorem to reduce the problem of finding inductive biases to that of meta-learning useful conserved quantities. We propose Noether Networks: a class of models where an unsupervised, meta-learned conservation loss is optimized inside the prediction function. This adapts the model weights to the particular input and imposes the approximate meta-learned conservation law in the predictions. We show, theoretically and experimentally, that Noether Networks improve prediction quality, providing a general framework for discovering inductive biases in sequential prediction problems.M.Eng

Transtracheal jet ventilation: a life-threatening or life-saving device

Jet ventilation through the trachea can cause airway injury and death due to high airway pressure and tension pneumothorax. Intratracheal and intrapulmonary pressures developed in a lung/trachea simulator were measured using a commercial transtracheal jet ventilator coupled with a commercial 12-gauge IV catheter. Intrapleural pressures ranged from 0 to 55 cmH2O as the jet driving pressure was varied from 10 to 54 psi. Simultaneous intratracheal pressures ranged from 4 to 328 cm H2O over the same range of driving pressures. Driving pressure was a linear function of nozzle pressure over a range from 15 to 54 psi. Extreme caution must be exercised when selecting an untested catheter for use with the jet ventilator to minimize the risk of barotrauma. Testing should be performed before placing catheter-jet systems into use

Nontraumatic spinal epidural hematoma during pregnancy: diagnosis and management concerns.

OBJECTIVE: Nontraumatic spinal epidural hematoma (SEH) during pregnancy is rare. Therefore, appropriate management of this occurrence is not well defined. The aim of this study was to extensively review the literature on this subject, to propose some novel treatment guidelines. METHODS: Electronic databases, manual reviews and conference proceedings up to December 2011 were systematically reviewed. Articles were deemed eligible for inclusion in this study if they dealt with nontraumatic SEH during pregnancy. Search protocols and data were independently assessed by two authors. RESULTS: In all, 23 case reports were found to be appropriate for review. The mean patient age was 28 years and gestational age was 33.2 weeks. Thirteen cases presented with acute interscapular pain. The clinical picture consisted of paraplegia, which occurred approximately 63 h after pain onset. Spinal cord decompression was performed within an average time of 20 h after neurological deficit onset. Fifteen patients had cesarean deliveries, even when the gestational age was less than 36 weeks. CONCLUSION: This review failed to identify articles, other than case reports, which could assist in the formation of new guidelines to treat SEH in pregnancy. However, we believe that SEH may be managed neurosurgically, without requiring prior, premature, cesarean section

Post-yield and failure properties of cortical bone

Ageing and associated skeletal diseases pose a significant challenge for health care systems worldwide. Age-related fractures have a serious impact on personal, social and economic wellbeing. A significant proportion of physiological loading is carried by the cortical shell. Its role in the fracture resistance and strength of whole bones in the ageing skeleton is of utmost importance. Even though a large body of knowledge has been accumulated on this topic on the macroscale, the underlying micromechanical material behaviour and the scale transition of bone's mechanical properties are yet to be uncovered. Therefore, this review aims at providing an overview of the state-of-the-art of the post-yield and failure properties of cortical bone at the extracellular matrix and the tissue level