This Week in Science

Science  27 Jun 2014:
Vol. 344, Issue 6191, pp. 1476
  1. Nonhuman Genetics

    Only one way to make an electric organ?

    1. Laura M. Zahn

    Electric fish have independently evolved electric organs that help them to communicate, navigate, hunt, and defend themselves. Gallant et al. analyzed the genome of the electric eel and the genes expressed in two other distantly related electric fish. The same genes were recruited within the different species to make evolutionarily new structures that function similarly.

    Science, this issue p. 1522

  2. Sensory Biology

    How hawkmoths sniff out a flower

    1. Sacha Vignieri

    Pollinators such as butterflies and bees are the true targets of the flower odors we love so much. Though we might imagine insects “following their noses,” the wealth of odors in the real world can drown out the smell of a flower, making it hard to find. Riffel et al. found that hawkmoths find angel's trumpets by creating a neuronal picture within their antennal lobe, the part of the moth brain that receives olfactory signals from the antennae (see the Perspective by Szyszka). The picture represents both the flower and the background odors. Finding a flower involves a complex reading of both background and target odors, and changes in the background odors—including human pollutants—can hinder the process.

    Science, this issue p. 1515; see also p. 1454

  3. Early Animals

    Building coral reefs in ancient times

    1. Nicholas S. Wigginton

    540 million years ago, in the dawn before the Cambrian explosion, evolution was setting the stage for the global rise of animals. Before they took over the seas, the earliest animals developed strategies to defend themselves against predators. These strategies, which remain common today, include forming skeletons and building reefs. Penny et al. discovered a massive fossil reef deposit in Namibia made up of tiny coneshaped early animals known as Cloudina. The reef, which is 20 million years older than other ancient reefs, was probably formed as the Cloudina adapted to benefit from reefs, which protect the animals and allow them to feed more efficiently.

    Science, this issue p. 1504

  4. Quantum Metrology

    Measuring tiny forces with atomic clouds

    1. Jelena Stajic

    For projects such as detecting gravity waves, physicists need to measure tiny forces precisely. Schreppler et al. developed an extremely sensitive method for force measurement. They applied a known force on a cloud of ultracold rubidium atoms in an optical cavity. The force caused the atoms to oscillate, and the researchers used optical measurements to monitor the motion. Under optimal conditions, the authors could measure forces with a level of sensitivity only four times worse than the fundamental limit imposed by the Heisenberg uncertainty principle.

    Science, this issue p. 1486

  5. Virus Entry

    How Lassa virus breaks and enters

    1. Stella M. Hurtley

    Lassa virus, which spreads from rodents to humans, infecting about half a million people every year, can lead to deadly hemorrhagic fever. Like many viruses, Lassa virus binds to cell surface receptors. Jae et al. now show that to enter a cell, the virus requires a second receptor, this one inside the infected cell. This requirement sheds light on the “enigmatic resistance” of bird cells to Lassa virus observed three decades ago. Although bird cells have the cell surface receptor, the intracellular receptor cannot bind the virus, stopping it in its tracks.

    Science, this issue p. 1506

  6. Human Cognition

    Selecting the most successful strategy

    1. Peter Stern

    The brain's prefrontal cortex helps us to make decisions in an uncertain and constantly changing environment. Donoso et al. present a model of human reasoning as an algorithm implemented in the prefrontal cortex (see the Perspective by Hare). Brain-imaging experiments supported this model. Depending on the prevailing circumstances, human reasoning can either adapt ongoing behavioral strategies or switch to previously learned strategies. Only when neither approach is appropriate will the brain create new strategies.

    Science, this issue p. 1481, see also p. 1446

  7. Cancer

    Old drug learns new anticancer trick

    1. Yevgeniya Nusinovich

    Cancer researchers have been trying to develop drugs that inhibit angiogenesis, the formation of new blood vessels that nourish a tumor and allow it to grow. A few drugs that fight angiogenesis are now used for some cancers, but they are not always effective. Xu et al. report a potential addition to the antiangiogenic armamentarium: nonsteroidal anti-inflammatory agents such as celecoxib, familiar remedies for arthritis. In mice, celecoxib inhibits blood vessel growth by a different mechanism than existing angiogenesis inhibitors. A combination of the two types of drugs was particularly effective in reducing tumor growth and spread.

    Sci. Transl. Med. 6, 242ra84 (2014).

  8. Nanofluidics

    Watching lead flow at the nanoscale

    1. Jake Yeston

    Microfluidic devices have recently become useful in commercial chemical synthesis. But what about fluid dynamics at the nanometer scale? Lorenz and Zewail used an electron microscope with nanosecond time resolution to capture images of molten lead flowing through a nanotube. They flash-melted the metal with a laser pulse to begin their flow measurements at a precise time point. The experiments offered insights into viscous friction as well as heat-transfer dynamics in a channel one-thousandth as wide as a strand of hair.

    Science, this issue p. 1496

    Conceptual view of molten lead flowing through zinc oxide nanotubes.

  9. Batteries

    Watching battery materials in action

    1. Marc S. Lavine

    When batteries get rapidly charged and discharged repeatedly, they will often stop working. This is especially true when the cycling changes the crystal structure of the battery components. Liu et al. examined the structural changes in components of a type of lithium battery (see the Perspective by Owen and Hector). Their findings explain why LiFePO4 delivers unexpectedly good electrochemical performances, particularly during rapid cycling.

    Science, this issue p. 10.1126/science.1252817; see also p. 1451

  10. Valleytronics

    Using the valleys in monolayer MoS2

    1. Jelena Stajic

    The electronic structure of the two-dimensional material MoS2 has two distinct “valleys” of energy that may help to carry information in future electronic devices. Mak et al. observed the so-called valley Hall effect in a monolayer of MoS2. The electrons from different valleys moved in opposite directions across the sample, with one valley being overrepresented with respect to the other. The scientists achieved this by shining circularly polarized light on the material, which created an imbalance in the population of the two valleys. The findings may enable practical applications in the newly formed field of valleytronics.

    Science, this issue p. 1489

  11. Machine Learning

    Discerning clusters of data points

    1. Jelena Stajic

    Cluster analysis is used in many disciplines to group objects according to a defined measure of distance. Numerous algorithms exist, some based on the analysis of the local density of data points, and others on predefined probability distributions. Rodriguez and Laio devised a method in which the cluster centers are recognized as local density maxima that are far away from any points of higher density. The algorithm depends only on the relative densities rather than their absolute values. The authors tested the method on a series of data sets, and its performance compared favorably to that of established techniques.

    Science, this issue p. 1492

  12. Gas Formation

    Making of methane deep underground

    1. Nicholas S. Wigginton

    Technologies such as hydraulic fracturing, or “fracking,” can now extract natural gas from underground reservoirs. Within the gas, the ratio of certain isotopes holds clues to its origins. Stolper et al. analyzed a wide range of natural gas, including samples from some of the most active fracking sites in the United States. Using a “clumped isotope” technique, the authors could estimate the high temperatures at which methane formed deep underground, as well as the lower temperatures at which ancient microbes produced methane. The approach can help to distinguish the degree of mixing of gas from both sources.

    Science, this issue p. 1500

  13. Membrane Trafficking

    Supplying power: Right time, right place

    1. Stella M. Hurtley

    Cell membranes are very flexible and easily molded to shape; however, to physically pinch off a membrane vesicle from a membrane tube still requires power. A type of molecular machine known as dynamin is involved in this sort of membrane remodeling. Dynamins use guanosine triphosphate (GTP) rather than the more commonly used cellular energy source adenosine triphosphate to work. Boissan et al. now show that two separate dynamins found in the cytoplasm or the mitochondria both use the same sort of enzyme—nucleoside diphosphate kinases—to provide GTP at just the right time and the right place to power membrane fission.

    Science, this issue p. 1510

  14. Microbial Evolution

    Clouding evolution's crystal ball

    1. Laura M. Zahn

    Because of a sort of mutation buffering process, different starting mutations can tend to end up with similar overall affects on an organism's fitness. Kryazhimskiy et al. evolved lines of yeast, each originating from distinct single genotypes, under the same selective regimen. A subset of clones from these adapted populations was subjected to fitness assays and sequenced. Populations with lower initial fitness, adapted more rapidly than populations with higher initial fitness, so that in the end the fitness levels were similar.

    Science, this issue p. 1519

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