Bike lanes are identified with health—a way to make a city greener and encourage people to exercise. New research from the Harvard School of Public Health, though, throws some cold water on that notion: When you arrive at an intersection on your bike, panting hard, you’re getting in shape, but you’re also sucking down undue amounts of car exhaust.
The researchers, led by master’s degree student Piers MacNaughton, measured pollution along five bike routes in Boston. They included bike lanes, which run directly adjacent to traffic; bike paths, which are at a distance from the road; and lanes shared by buses and cyclists. The researchers pedaled these routes with a device to measure pollution, specifically two exhaust elements known to increase cardiovascular and lung cancer risks—black carbon and nitrogen dioxide.
The researchers found that concentrations of the two pollutants were about one-third higher on bike lanes compared to bike paths. Air quality was especially bad at intersections, where cars idle and accelerate, and which bike paths often bypass. Distance really did make a difference: The Paul Dudley White Bike Path, which runs near crowded Storrow Drive, has lower levels of pollution than bike lanes on quieter streets, thanks to up to 150 feet of separation from the road and a line of trees to block exhaust. This led the researchers to conclude, “urban planners should push for the development of bike paths instead of bike lanes whenever possible and should design bike paths with vegetation between the cyclists and the vehicle traffic.”
Over the past 40 or so years, MIT has developed arguably the most influential economics department in the world. Its graduates and faculty members collect the field’s most prestigious awards by the armload and sit in positions of power around the world. Former chairman of the Federal Reserve Ben Bernanke is an MIT graduate, as is Stanley Fischer, former governor of the Bank of Israel. Lawrence Summers was an MIT undergrad major. How did an economics department that got a relatively late start—it didn’t open until the 1940s—develop so much clout?
A new study, “MIT’s Rise to Prominence,” by economic historian Andrej Svorencik of the University of Mannheim in Germany, looks at how MIT’s tight, illustrious alumni network has helped its graduates catch and surpass other powerhouse economics departments. In the paper, which will be published in a forthcoming issue of History of Political Economy, Svorencik creates “academic family trees” to analyze the relationships between the 1,316 graduate students MIT has produced since 1970, when MIT first started churning out PhDs on par with the other big schools like Harvard and Berkeley, and the 165 faculty members who served as their research advisers.
He finds there’s a powerfully insular quality to the way those relationships have played out—“a fairly large community of economists who are to a large extent trained by a few key advisers who were mostly trained at MIT as well”—and graduates are more likely to stay in academia than graduates of other top universities, amplifying their research and policy importance.
At universities, insularity is regarded as a bad thing, because you catch better faculty members when you cast a wider net. MIT’s hiring practices are surely as competitive as they come, but Svorencik’s analysis suggests that academic dynasties work like other kinds of dynasties—there’s benefit in keeping things close and pressing an advantage once you gain it.
Roast your coffee by ear
Coffee fans CAN get obsessive, weighing their grounds and carefully measuring the temperature of the water. But how often do they really listen to their coffee beans?
They might want to start. Justin Wilson, a mechanical engineer at the University of Texas, Austin and avowed coffee fanatic, has found that coffee beans emit a pattern of cracking during the roasting process that may be key to knowing when a batch is done.
Coffee beans start out green and need to be roasted at high temperatures before grinding and brewing. In an article published online in the Journal of the Acoustical Society of America, Wilson, who mainly studies underwater sounds, explained that there are a number of ways human roasters and automated machines know when to stop—they can judge by time, color, aroma, temperature, even the gas content in the roasting chamber.
But a simpler technique, Wilson argues, might be just to listen to the sounds of the beans, which are remarkably consistent from one batch to another. At around 200 degrees Celsius, beans emit a “first crack,” releasing the expanding gas and steam that have built up inside. At around 230 degrees they emit a second crack, softer and more rapid, after which the beans start to burn. Wilson writes, “The sounds of first crack are qualitatively similar to the sound of popcorn popping while second crack sounds more like the breakfast cereal Rice Krispies in milk.” Wilson thinks sensitivity to bean cracks could be programmed into a new generation of roasting machines, which would turn off when the beans sound just right.
Kevin Hartnett is a writer in South Carolina. He can be reached at firstname.lastname@example.org.