Minimal Length Scale Scenarios for Quantum Gravity

We review the question of whether the fundamental laws of nature limit our ability to probe arbitrarily short distances. First, we examine what insights can be gained from thought experiments for probes of shortest distances, and summarize what can be learned from different approaches to a theory of quantum gravity. Then we discuss some models that have been developed to implement a minimal length scale in quantum mechanics and quantum field theory. These models have entered the literature as the generalized uncertainty principle or the modified dispersion relation, and have allowed the study of the effects of a minimal length scale in quantum mechanics, quantum electrodynamics, thermodynamics, black-hole physics and cosmology. Finally, we touch upon the question of ways to circumvent the manifestation of a minimal length scale in short-distance physics.Comment: Published version available at http://www.livingreviews.org/lrr-2013-

Effect of methylprednisolone on acute kidney injury in patients undergoing cardiac surgery with a cardiopulmonary bypass pump : a randomized controlled trial

BACKGROUND: Perioperative corticosteroid use may reduce acute kidney injury. We sought to test whether methylprednisolone reduces the risk of acute kidney injury after cardiac surgery. METHODS: We conducted a prespecified substudy of a randomized controlled trial involving patients undergoing cardiac surgery with cardiopulmonary bypass (2007-2014); patients were recruited from 79 centres in 18 countries. Eligibility criteria included a moderate-to-high risk of perioperative death based on a preoperative score of 6 or greater on the European System for Cardiac Operative Risk Evaluation I. Patients (n = 7286) were randomly assigned (1:1) to receive intravenous methylprednisolone (250 mg at anesthetic induction and 250 mg at initiation of cardiopulmonary bypass) or placebo. Patients, caregivers, data collectors and outcome adjudicators were unaware of the assigned intervention. The primary outcome was postoperative acute kidney injury, defined as an increase in the serum creatinine concentration (from the preoperative value) of 0.3 mg/dL or greater (>= 26.5 mu mol/L) or 50% or greater in the 14-day period after surgery, or use of dialysis within 30 days after surgery. RESULTS: Acute kidney injury occurred in 1479/3647 patients (40.6%) in the methylprednisolone group and in 1426/3639 patients (39.2%) in the placebo group (adjusted relative risk 1.04, 95% confidence interval 0.96 to 1.11). Results were consistent across several definitions of acute kidney injury and in patients with preoperative chronic kidney disease. INTERPRETATION: Intraoperative corticosteroid use did not reduce the risk of acute kidney injury in patients with a moderate-to-high risk of perioperative death who had cardiac surgery with cardiopulmonary bypass. Our results do not support the prophylactic use of steroids during cardiopulmonary bypass surgery