Fully Vaccinated Can Unmask Often, CDC Says As the number of vaccinated Americans continues to rise and evidence mounts that the vaccines may reduce viral transmission in addition to lessening disease severity, the CDC announced Thursday that fully-vaccinated people may be able to go mask-free except in specific crowded indoor situations. The announcement caused celebration in some circles and anxiety in others, with people wondering how the new guidelines fit into their personal risk assessments. Sarah Zhang, staff writer at The Atlantic, joins Ira to talk about the latest news in the pandemic and beyond, including a WHO committee report discussing the early days of the outbreak, the latest on the Colonial gas pipeline shutdown, research into cats’ love of sitting in boxes, and more.   Can An Algorithm Explain Your Knee Pain? In an ideal world, every visit to the doctor would go something like this: You’d explain what brought you in that day, like some unexplained knee pain. Your physician would listen carefully, run some tests, and voila—the cause of the issue would be revealed, and appropriate treatment prescribed. Unfortunately, that’s not always the result. Maybe a doctor doesn’t listen closely to your concerns, or you don’t quite know how to describe your pain. Or, despite feeling certain that something is wrong with your knee, tests turn up nothing. A new algorithm shows promise in reducing these types of frustrating interactions. In a new paper published in Nature, researchers trained an algorithm to identify factors often missed by x-ray technicians and doctors. They suggest it could lead to more satisfying diagnoses for patients of color. Dr. Ziad Obermeyer, associate professor of Health Policy and Management at the University of California, Berkley joins Ira to describe how the algorithm works, and to explain the research being done at the intersection of machine learning and healthcare.   Ever Wonder Why Big Cereal Chunks Are Always On Top? You may not have heard of it, but you’ve probably seen the “brazil nut effect” in action—it’s the name for the phenomenon that brings larger nuts or cereal chunks to the top of a container, leaving tinier portions at the bottom of the mix. But the process by which granular materials mix is weirdly hard to study, because it’s difficult to see what’s going on away from the visible surfaces of a container. In recent work published in the journal Scientific Reports, researchers turn the power of three-dimensional time-lapse x-ray computer tomography onto the problem. By using a series of CT scans on a mixed box of nuts as it sorted itself by size, the researchers were able to capture a movie of the process—finally showing how the large Brazil nuts turn as they are forced up to the top of the mix by smaller peanuts percolating downwards. Parmesh Gajjar, a research associate in the Henry Moseley X-ray Imaging Facility at the University of Manchester, talks with SciFri’s Charles Bergquist about the imaging study, and the importance of size segregation in mixing of materials—with applications from the formation of avalanches to designing drug delivery systems.   This Alaskan Glacier Is Moving 100 Times Faster Than Usual One of the glaciers on Alaska’s Denali mountain has started to “surge.” The Muldrow Glacier is moving 10-100 times faster than usual, which is about three feet per hour. About 1% of glaciers “surge,” which are short periods where glaciers advance quickly. Geologist Chad Hults has been on the glacier to study it during this surge period. He talks about how the glacier’s geometry and hydrology contribute to this surge period.