Science  12 Apr 2013:
Vol. 340, Issue 6129, pp. 128

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  1. On Twitter, #Antivaccination Goes Viral

    When fear goes viral on the Internet, it can help spread viruses in the real world. Antivaccination tweets, researchers find, spread much faster than those supportive of vaccines.

    Biologist and computer scientist Marcel Salathé and colleagues at Pennsylvania State University, University Park, collected almost half a million vaccine-related tweets during the 2009 influenza pandemic and categorized those relevant to flu as positive, negative, or neutral. (Undergrads rated the first 47,143 tweets; then an algorithm took over.) Negative tweets were often retweeted, while positive ones generally weren't, the team reported in a paper published online on 4 April in EPJ Data Science. Instead, too much positive sentiment appeared to backfire: Twitter users who received many provaccine tweets sent out more negative messages themselves. Perhaps some held antivaccination views that they didn't express "until they were bombarded with positive messages," Salathé says.

    "We are more compelled by fear than by rational thinking," says Paul Offit, director of the Vaccine Education Center at The Children's Hospital of Philadelphia in Pennsylvania. To reach the public, vaccine advocates may have to go negative themselves, he adds—for instance, by tapping into people's fear of losing a child.

  2. Tiny Bones, Giant Dinosaurs

    Nearly 200 million years ago, one species of sauropodomorph—those long-necked, herbivorous dinosaurs known to grow to great sizes—nested its eggs at a site near what has become southern China's Yunnan Province. Periodically, the nests were destroyed by floods, washing away all but some of the eggs and the tiny bones they contained.


    Today, this rare jumble of embryonic bones—some as thin as pencil lead—gives an unprecedented look at dinosaur embryos at various stages of development. Examining cross-sections of 24 different femurs from the species (probably of the genus Lufengosaurus), a team led by paleontologist Robert Reisz of the University of Toronto, Mississauga, in Canada observed a high proportion of vascular space inside the bones (pictured), indicating that these embryos grew extremely quickly—faster than any other known dinosaur and all living birds. This rapid embryonic development may have been the key to adult sauropodomorphs' towering physiques, the team reports online this week in Nature.

    The bone bed is a "spectacular find," because it offers a look at how the species grew over time, something no single embryo can do, says Luis Chiappe, a vertebrate paleontologist at the Natural History Museum of Los Angeles County in California.