Editors' Choice

Science  23 Mar 2018:
Vol. 359, Issue 6382, pp. 1374
  1. Paleoecology

    Human impact on African forests

    1. Andrew M. Sugden

    Ancient forest fragmentation is a result of direct human impacts, not climate.

    PHOTO: MOKHAMAD EDLIADI/CIFOR

    About 2600 years ago, continuous forest in western central Africa was replaced by a mosaic of forest and savanna. It has been unclear, however, whether this was caused by climate change or expansion of the contemporary human population. Using a sedimentary record of vegetation and hydrological history from Cameroon, Garcin et al. confirm the key role of humans in this transition. Although the pollen record indicates an abrupt fragmentation of the forest, there is no signature of an accompanying hydrological change. Nor did the hydrology alter 500 years later when the landscape reverted once more to forest, indicating a negligible role for climate.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1715336115 (2018).

  2. Plant Science

    Natural variation in salt tolerance

    1. Pamela J. Hines

    Salt stress in agriculture is not just a matter of being near the ocean; as much as half of irrigated farmland is overly salty. Plants have strategies to adjust to saline conditions, such as reducing sodium uptake or altering the architecture of their root systems. Julkowska et al. analyzed a range of Arabidopsis thaliana genotypes to identify genetic loci that could drive changes in root architecture in response to salt. Natural variation across 347 A. thaliana accessions affected the angle of roots and the distribution of bulk between main and lateral roots, leading to identification of the genes responsible. For example, variation in gene expression in response to salt showed that the CYP79B2 (cytochrome P450 family 79 subfamily B2) gene serves to reduce lateral root growth in salt-stressed conditions.

    Plant Cell 29, 3198 (2017).

  3. Physics

    A circular solution for quantum simulation

    1. Jelena Stajic

    Quantum simulation can map challenging problems in complex materials onto better defined ones in simpler, easier-to-manipulate systems. Physical implementations range from trapped ions to superconducting qubits, each having distinct strengths and weaknesses. Nguyen et al. propose a quantum simulator that seems to combine many of the best features of the existing simulators in one system, while being within current experimental reach. The simulator is based on circular Rydberg atoms—with a highly excited electron orbiting the nucleus along a roughly circular path—where the atoms can be trapped by laser light, can be read out one by one, and have very long lifetimes. The interactions between such atoms would make it possible to simulate some of the most challenging problems in many-body physics.

    Phys. Rev. X 8, 011032 (2018).

  4. Optical Communication

    Faster, faster, faster

    1. Ian S. Osborne

    With consumer broadband speeds on the rise and the prospect of “fiber to the home” effectively providing access to unlimited bandwidth, actual end-user data rates will nevertheless be limited by the radio-frequency wireless routers. One solution (avoiding hardwiring) is optical wireless communication, whereby an optical system replaces the wireless link. The obvious issue is that gadgets in a room tend to move, and a direct line-of-sight connection between sender and receiver stations is required. Zhang et al. propose an optical beam-steering scheme that provides a sufficiently wide field of view and demonstrate a data rate of 40 gigabits per second. The ability to stream content in high definition on multiple devices without the “wheel of patience” would be a thing of the past.

    Opt. Lett. 43, 723 (2018).

  5. Climate Extremes

    The chill of a warming world

    1. H. Jesse Smith

    The blizzard Jonas of 2016, in the Bronx, New York, USA

    PHOTO: EDDTORO/SHUTTERSTOCK

    Why have some winters been so cold in some of the northern midlatitudes, even though global climate is getting hotter? Paradoxically, the answer may be that the Arctic itself is warming so quickly. Cohen et al. show that there is a clear relationship between Arctic temperatures and severe winter weather for the United States over the past two decades and that severe winter weather in the eastern United States has become more frequent as Arctic temperatures have risen. Although they were not included in the analysis, this relationship is likely valid for northern Europe and East Asia as well.

    Nat. Commun. 10.1038/s41467-018-02992-9 (2018).

  6. Neurogenesis

    Neurogenesis and the sleeping fly

    1. Beverly A. Purnell

    As we have all experienced, the body's alertness, cognitive abilities, and stress threshold depend on obtaining sufficient sleep. But why? Studies suggest that sleep is needed to set up the right brain connections. Szuperak et al. looked at the earliest stages of sleep by monitoring fruitfly larvae. To test for periods of rest, or sleep, they tried to arouse larvae by exposing them to a bright light. Fly larvae were indeed aroused from periods of rest, and as a result of this sleep disruption, they slept more at a later time, like other animals. Sleep-deprived larvae also showed decreased neurogenesis. This work suggests that flies may be a model for sleep, with possible implications for brain development.

    eLife 10.7554/eLife.33220.001 (2018).

  7. Biophysics

    Cell geometry regulates differentiation

    1. Gemma Alderton

    The size and shape (geometry) of cells regulate tension on the cytoskeleton and the contractility of the cell membrane. von Erlach et al. show that mesenchymal stem cells grown in different shapes have varying amounts of cell membrane microdomains known as lipid rafts. These are thought to be focal points for membrane-associated signaling, and the authors demonstrate that their occurrence was dependent on cytoskeletal contraction and cell geometry. Activation of signaling by the AKT kinase occurred at lipid rafts, and this was dependent on cell geometry and membrane contractility. Interestingly, AKT activation at lipid rafts was an important determinant of mesenchymal stem cell lineage, once differentiated.

    Nat. Mater. 17, 237 (2018).