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APS March Meeting 2012: February 2012: Monthly Archives

APS March Meeting 2012: February 2012 Archives

Crowd outside the session on Majorana fermions

An over-capacity crowd greeted Leo Kouwenhoven’s talk on Majorana fermions

By Margaret Harris

The hottest talk of the APS March Meeting so far took place yesterday, when Leo Kouwenhoven revealed that his group at TU Delft in the Netherlands may have observed Majorana fermions in one-dimensional nanowires.

Majorana fermions have a curious property – they are their own antiparticles – and particle physicists have been looking for fundamental Majorana fermions for decades. A few years ago, condensed-matter physicists got in on the act too, seeking evidence of Majorana-like behaviour in fermionic quasiparticles such as those formed by electrons in superconductors. But so far, no-one has ever found conclusive evidence that such particles exist – so if this nanowire result holds up, it would be quite the coup for Kouwenhoven and his group.

Unfortunately, Kouwenhoven’s talk was so popular that the crowd overflowed into the hallway outside, and with conference centre staff talking anxiously about fire regulations, it proved impossible for me to squeeze in (Eugenie Reich of Nature was luckier – you can read her summary here). So instead, I headed to the room next door, where Krastan Blagoev of the US National Science Foundation was delivering an inspiring talk on the kinetics of metastatic cancer.

Map of obesity rates in the US in 2004 and 2008

Obesity rates in the US in 2004 and 2008. (Courtesy: Lazaros Gallos)

By Margaret Harris at the APS March Meeting

The data on obesity are pretty unequivocal: we’re fat, and we’re getting fatter. Explanations for this trend, however, vary widely, with the blame alternately pinned on individual behaviour, genetics and the environment. In other words, it’s a race between “we eat too much”, “we’re born that way” and “it’s society’s fault”.

Now, research by Lazaros Gallos has come down strongly in favour of the third option. Gallos and his colleagues at City College of New York treated the obesity rates in some 3000 US counties as “particles” in a physical system, and calculated the correlation between pairs of “particles” as a function of the distance between them. This calculation allowed them to find out whether the obesity rate among, say, citizens of downtown Boston was correlated in any way to the rates in suburban Boston and more distant communities.

It wouldn’t have been particularly surprising if Gallos’ team had found such correlations on a small scale. The economies of Boston and its suburbs are tightly coupled, for one thing, and their demographics are also not so terribly different. But the data indicated that the size of the “obesity cities” – geographic regions with correlated obesity rates – was huge, up to 1000 km. In other words, the obesity rate of downtown Boston was strongly correlated not only with the rates in the city’s suburban hinterland, but also with rates in far-off New York City and hamlets in northern Maine.

This correlation was independent of the obesity rate itself – there are “thin cities” as well as obese ones – and also far stronger than correlations in other factors, such as the economy or population distribution, would suggest. The exception, intriguingly enough, was the food industry, which also showed tight correlations between geographically distant counties.

Gallos isn’t claiming that the food industry is causing obesity. He also doesn’t discount the importance of food choices and genetic factors: what you eat and who you are will clearly play a big role in determining whether or not you, as an individual, will become obese. However, he points out that our genes haven’t changed that much since the US obesity epidemic began in the 1980s, and neither, presumably, has our willpower. The difference, he says, is that on a societal level, increasingly large numbers of us are living in an “obese-o-genic” environment, and “the consensus is that the system makes you eat more”.

Gallos says he’ll post this research on arXiv sometime in the next few days [UPDATE 29/2/12: here’s the link to the paper]. In the meantime, I’ll be testing his hypothesis personally in the obese-o-genic environment of a major scientific conference, complete with multiple breakfasts, receptions and lunches. Pass the pastries, please!

Photo of Boston Common sign

Boston Common and the Park Street Church, part of the city’s “Freedom Trail”.

By Margaret Harris at the APS March Meeting in Boston

The American Physical Society’s March Meeting doesn’t really kick off until tomorrow morning, but with many of the 6000+ delegates arriving a day early, we’re rapidly heading towards a critical mass of physicists here in Boston. Even the good citizens of New England’s largest city are starting to notice the influx; as I was walking along the “Freedom Trail” of historic landmarks earlier today, I met a park ranger who estimated that I was 10th physicist he’d spoken to that afternoon.

Anyway, from tomorrow until Thursday I’ll be swapping sight-seeing trips for talks on a wide range of physics topics. Many of the sessions are devoted to superconductivity, which remains a popular field a quarter of a century after the famous “Woodstock of Physics” March Meeting when the first high-temperature superconductors took centre stage.

Physicists with a keen interest in graphene will face some particularly tough decisions on which talks to attend, with 39 separate sessions devoted to carbon’s newest and sexiest (well, unless you prefer diamonds or buckyballs) allotrope.

There’s also some intriguing-sounding interdisciplinary sessions on the physics of cancer and the aftermath of the Fukushima nuclear incident. And finally, I’m hoping to learn more about the latest nifty experiments in my PhD field of atomic and molecular physics.

First, though, I need to go eat some of Boston’s famous seafood…

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