Findings

Science  11 May 2012:
Vol. 336, Issue 6082, pp. 657
  1. Infants' Flexible Heads Go Back Millions of Years

    A human infant's skull changes shape as it squeezes through the birth canal because its cranial bones don't entirely fuse together for at least 2 years after birth. A study online this week in the Proceedings of the National Academy of Sciences (PNAS) shows that early humans who lived nearly 3 million years ago also experienced this delayed fusion. One possible explanation is that bipedalism, which constrains the shape of the human pelvis, created obstetrical challenges even for smaller-brained human ancestors.

    CREDIT: M. PONCE DE LEÓN AND CH. ZOLLIKOFER/UNIVERSITY OF ZURICH

    A team led by anthropologist Dean Falk of the School for Advanced Research in Santa Fe, New Mexico, looked at the metopic suture (MS), the joint between the cranium's two frontal bones, in a large number of fossil early humans, modern humans, chimpanzees, and bonobos. The MS of chimps and bonobos, they found, fuses very shortly after birth, whereas the MS of early and later hominins tends to fuse at 2 years of age or later.

    But Robert Martin, an anthropologist at the Field Museum in Chicago, Illinois, cautions that the age of MS closure is “notoriously variable” in modern humans. A more reliable indicator of overall skull fusion, he suggests, would be the closure of the anterior fontanelle “soft spot.” http://scim.ag/skullflex

  2. Late-Stage Grad Students Want Nonacademic Careers

    The further students progress through science graduate programs, the less likely they are to want a career in academic research, according to a survey of 4109 grad students from 39 top-tier research universities. Across all disciplines, the average number of students who rated academic jobs as “attractive” or “extremely attractive” dropped from 74% to 62% between the early and later stages of grad school. Careers in industry and startup companies either jumped up slightly or stayed about the same. Government jobs saw the biggest spike in relative attractiveness.

    Students in the life sciences in particular became disillusioned with academia: 78% of them rated faculty research positions as attractive early in grad school, and only 67% did so in later stages.

    The study, which appeared online 2 May in PLoS ONE, is among the first to look empirically at how students' career preferences change over time. The authors say it's difficult to tell what's discouraging students from faculty research jobs, but possibilities include the weak job market and seeing their advisers stress over tenure decisions and grants. http://scim.ag/PreferencesData

  3. The Fluid Mechanics of Walking With Coffee

    Fret no more, overburdened conference attendees. Scientists have learned how to avoid a common research pitfall: spilled coffee.

    CREDIT: H.C. MAYER AND R. KRECHETNIKOV

    Rouslan Krechetnikov, a mechanical engineer at the University of California, Santa Barbara, and graduate student Hans Mayer studied the problem, which involves the mechanics of walking as well as liquid sloshing, an interplay of accelerations, torques, and forces. They asked a person, filled mug in hand, to walk at different speeds, either focusing on the mug or looking straight ahead. A camera recorded the person's motion and the mug's trajectory while a tiny sensor on the mug recorded the instant of spillage.

    In their paper published last month in Physical Review E, Krechetnikov and Mayer show that everyday mug sizes produce natural frequencies that happen to match those of a person's leg movements during walking. So walking alone is tuned to drive coffee to oscillate in a mug. But small irregularities in walking can amplify oscillations, or sloshing.

    So how to avoid a spill? Walk more slowly, the researchers say, and leave a gap between the top of the coffee and the mug's rim. And watch what you're doing—so long as your mug isn't filled too high, a watched mug almost guarantees a clean run. http://scim.ag/spilledcoffee

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