Editors' Choice

Science  27 Jun 2014:
Vol. 344, Issue 6191, pp. 1477
  1. Materials Science

    Getting in shape to stay dry longer

    1. Ian S. Osborne

    A rose petal's textured surface effectively repels water.


    Many textured surfaces commonly found in the natural world, such as a rose petal, repel liquids extremely well. Taking a clue from Mother Nature, designers have begun to routinely incorporate surface textures into products ranging from waterproof outdoor clothing to self-cleaning windows. However, under high humidity or pressure, liquid can infiltrate some textured surfaces and reduce their super-hydrophobic properties. Checco et al. used x-rays to probe the interface region between liquid and a variety of textured silicon surfaces to show that the specific structure of a textured coating affects how the coating fails. This strategy could facilitate the rational design of better water-repellent coatings.

    Phys. Rev. Lett. 112, 216101 (2014).

  2. Cancer

    Long unwinding road to cancer treatment

    1. Paula A. Kiberstis

    Cancer chemotherapy is infamous for harming healthy cells. This collateral damage causes the side effects that range from unpleasant (such as hair loss) to life-threatening (such increased susceptibility to infection). They can be particularly devastating for elderly patients. Promising new data may one day lead to a safer treatment for a type of acute myeloid leukemia, which first strikes patients at age 66, on average. Mazurek et al. found that when they blocked mouse genes from expressing an enzyme called DDX5, the leukemia cells died, but healthy bone-marrow cells were unharmed. DDX5 made the cancer cells proliferate; inhibiting DDX5 made the cells accumulate toxic molecules called reactive oxygen species, which contributed to cancer cell death.

    Cell Rep. 7, 10.1016/j.celrep.2014.05.010 (2014).

  3. Aging

    Metformin's recipe for a long life

    1. L. Bryan Ray

    Metformin, a drug commonly prescribed to treat type 2 diabetes, has side effects, but some of these are beneficial, such as fighting certain cancers and increasing longevity. By studying the worm Caenorhabditis elegans, a model of aging, De Haes et al. discovered the molecular basis for how metformin may prolong lives. In treated worms, metformin promoted mitochondrial respiration, a process that converts nutrients into energy for the cell. Mitochondrial respiration also produces byproducts called reactive oxygen species (ROS), which can react with proteins, harming them. When the worms produced limited amounts of ROS, however, the life span of worms increased. The increase in life span required a protein called peroxiredoxin-2, which is oxidized by ROS and may then activate other enzymes to produce effects that promote longevity.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1321776111 (2014).

  4. Chemistry

    Knotty questions in molecular assembly

    1. Jake Yeston

    How would you tie a knot if you couldn't touch either end of the rope? In the past few years, chemists have solved that problem at the molecular scale by precisely designing strand fragments, then luring them into mutually overlapping arrangements around metal ions. Ayme et al. now have tested the limits of that approach, exploring how subtle changes to the strands affect the distribution of knots produced in the reaction. Specifically, the authors mixed two types of strands that differed only by the presence or absence of two oxygen atoms. They found that the types sorted themselves remarkably well in combination with iron ions: The longer strands assembled into cross-shaped groups of four, the shorter strands into star-shaped groups of five.

    Angew. Chem. Int. Ed. 53, 10.1002 anie.201404270 (2014).

  5. Cosmology

    Universe inflation or dust emissions?

    1. Adrian Cho

    Doubt enshrouds what was supposedly the biggest discovery in cosmology in a decade. In March, researchers working with BICEP2, a telescope at the South Pole, reported that the pinwheel swirls they saw in the polarization of the cosmic microwave background—the Big Bang's afterglow—came from gravitational waves rippling through the infant universe. That, they said, was the first direct evidence of an exponential growth spurt called inflation in the early universe. But others noted that the signal might emanate instead from dust in our galaxy. Now, in the published paper, Ade et al. write that their models of galactic dust “are not sufficiently constrained … to exclude the possibility of dust emission bright enough to explain the entire excess signal.”

    Phys. Rev. Lett. 112, 241101 (2014).

  6. Extinction

    Miss mammoths? Blame your ancestors

    1. Sacha Vignieri

    The now-extinct woolly mammoth.


    Imagine saber-toothed tigers, giant ground sloths, and car-sized glyptodonts—an armadillo relative—ranging across the entire planet. Only a few tens of thousands of years ago, such charismatic megafauna ruled the earth. What killed them—climate change or human activity? In the first global analysis of extinctions during the Pleistocene geological epoch, Sandom et al. found that the expansion of humans out of Africa most likely caused the extinctions over the past 100,000 years. The animals were easy targets: They lacked the fear of humans that comes with years and years of co-evolution.

    Proc. R. Soc. London Ser. B 281, 20133254 (2014).

  7. Animal Ecology

    The secrets of canopy dwellers revealed

    1. Andrew M. Sugden

    Many mammals in tropical forests spend much of their life in the canopy, which makes their behavior difficult to document. Treetop cameras can help, Gregory et al. report. The authors attached motion-triggered cameras high in the branches of a Peruvian tropical forest. In more than 1500 photographs taken over 6 months, they recorded 20 mammal species at crossing points between trees. The animals seemed unfazed by the cameras (though fluttering leaves did tend to trigger the cameras unnecessarily). Like the more familiar camera traps at ground level, arboreal camera traps may become an important tool for recording hitherto hidden behaviors.

    Methods Ecol. Evol. 5, 443 (2014).

    A two-toed sloth in the canopy.

  8. Materials Science

    Tubular friction at the nanoscale

    1. Marc S. Lavine

    When large-scale objects slide by each other, the amount of friction depends on their surface roughness and the contact area between them. At the nanoscale, though, different factors and forces can affect resistance to motion. Niguès et al. examine the response of multiwalled carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) as their concentric cylindrical layers are pulled past each other. Whereas the semiconducting CNTs show almost no resistance to sliding motion, the BNNTs show viscouslike dissipation that is proportional to the contact area. The authors attribute this difference to bond character: Boron nitride forms ionic bonds, whereas the bonds in CNTs are purely covalent. Because they slide so much less slickly when they touch, the BNNTs could make highly efficient nanoscale shock absorbers.

    Nat. Mater. 10.1038/nmat3985 (2014).

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