Physics Today Daily Edition
BBC: A supercomputer simulation presented at the American Physical Society meeting in Baltimore, Maryland, this week, models the human circulatory system in three dimensions. The simulated network, which tracks blood flow through all arteries larger than 1 mm across, is based on images captured by full-body CT and MRI scans of the circulatory system of a single person. Flow measurements in the simulation closely matched those of a 3D printed version of the circulatory system, both when the blood was free-flowing and when it was pulsed in a way that mimicked a heartbeat. Amanda Randles of Duke University and her team attempted the project primarily as a proof-of-concept because most previous simulations have focused on smaller sections of the circulatory system. The goal is to model how medical interventions, such as stents or other surgical modifications, might affect the system as a whole.
Science: The Neutron Landscape Group (NLG) was commissioned to determine the effect of the upcoming closures of a variety of neutron beam sources in Europe. According to the NLG, two-thirds of Europe's current neutron sources were built in the 1960s and 1970s and are scheduled to be shut down. The group's report, released last week, says that if all the aging facilities that are scheduled to close over the next 15 years do so, then the supply of neutrons for research will be reduced by 40–50%. That reduction accounts for the addition of the European Spallation Source (ESS) in Lund, Sweden, which will be the world's largest neutron source when it begins operating around 2019. However, due to limited funding, the ESS will have only 16 instruments running in the first 10 years of operation. That would not be close to offsetting the 40 instruments present at the Institut Laue–Langevin (ILL) in Grenoble, France, which is expected to close in 2023. The NLG suggests that maintaining the ILL, which would cost around €200 million ($222 million), would help reduce the loss of neutron production to just 20%.
IEEE Spectrum: In 1961 Rolf Landauer of IBM theorized that there is a minimum amount of energy required by computational systems to reset or erase a bit of information. His calculations showed that at room temperature, that limit is 3 × 10−21 J (3 zJ). In 2012 a team of researchers demonstrated that the limit could be reached in a nonmagnetic physical system. Now Jeffrey Bokor of the University of California, Berkeley, and his colleagues have shown that Landauer's principle does apply to a magnetic system more representative of actual computer storage. Bokor's team created an array of nano-sized magnetic dots that were magnetically aligned. Using an external magnetic field, the scientists could flip the dots between binary states and effectively erase the data that the dots stored. The team found that the dots consumed around 6 zJ of energy at room temperature—twice the Landauer limit but within the level of uncertainty of the experiment. The researchers suggest that slight variations in the orientations of the magnets were enough to account for the higher value.