This Week in Science

Science  08 May 2015:
Vol. 348, Issue 6235, pp. 644
  1. Physics

    A circular route to confine electrons

    1. Ian S. Osborne

    The whispering gallery at St. Paul's

    CREDITS: (TOP TO BOTTOM) GAO ET AL.; © ANGELO HORNAK/ALAMY

    Physical barriers are used to confine waves. Whether it is harbor walls for sea waves, a glass disk for light, or the “whispering gallery” circular chamber walls in St. Paul's Cathedral for sound, the principle of confinement—reflection—is the same. Zhao et al. used that same principle to confine electrons in a nanoscale circular cavity in graphene. Periodic patterns within the cavity were associated with an electronic wave version of whispering gallery modes. The tunability of the cavity size may provide a route for the manipulation of electrons in graphene and similar materials.

    Science, this issue p. 672

  2. Human Genomics

    Expression, genetic variation, and tissues

    1. Laura M. Zahn

    Human genomes show extensive genetic variation across individuals, but we have only just started documenting the effects of this variation on the regulation of gene expression. Furthermore, only a few tissues have been examined per genetic variant. In order to examine how genetic expression varies among tissues within individuals, the Genotype-Tissue Expression (GTEx) Consortium collected 1641 postmortem samples covering 54 body sites from 175 individuals. They identified quantitative genetic traits that affect gene expression and determined which of these exhibit tissue-specific expression patterns. Melé et al. measured how transcription varies among tissues, and Rivas et al. looked at how truncated protein variants affect expression across tissues.

    Science, this issue p. 648, p. 660, p. 666; see also p. 640

  3. Geophysics

    Silent slip events get shallow

    1. Brent Grocholski

    Clues to help better predict the likelihood of devastating earthquakes and tsunamis may be embedded in a more gentle type of rumbling. Using oceanbottom seismometers, Yamashita et al. report rare observations of migrating tremors in the shallow part of a subduction zone off southern Kyushu, Japan. The tremors appear to be linked to a very low-frequency earthquake and seem to migrate to the region where big earthquakes are generated. The tremors may be tracing how and where stress gets concentrated onto the earthquake-producing portion of the fault.

    Science, this issue p. 676

  4. Surface Science

    Using friction to guide fabrication

    1. Brent Grocholski

    Ultralow friction found in certain layered materials such as graphite is important in the construction of nanomechanical devices. Koren et al. combined measurements and modeling to characterize the interaction of sliding graphite planes (see the Perspective by Liechti). This helped them to make small graphite devices that featured rotational pivots and multiple locking positions.

    Science, this issue p. 679

  5. Bioengineering

    Keeping tabs on tiny worms

    1. Megan Frisk

    Filarial nematodes—tiny parasitic worms that can enter the bloodstream—are common in some parts of Africa. One of these worms, Loa loa, causes loiasis but is not compatible with current ivermectin-based mass drug administration (MDA) programs. These programs aim to eliminate other worms that cause onchocerciasis and lymphatic filariasis. To pinpoint people to exclude from MDA, D'Ambrosio et al. devised a mobile phone–based strategy for quantifying Loa microfilariae in whole blood. A mobile phone video camera and a custom algorithm tracked the worm's “wriggling” motion. The device was packaged for point-of-care use—including its own smartphone “app”—and successfully diagnosed Loa-infected people in Cameroon, Africa.

    Sci. Transl. Med. 7, 286re4 (2015).

  6. Optogenetics

    An optogenetic tool to silence neurons

    1. Valda Vinson

    Potassium channels in the cell membrane open and close in response to molecular signals to alter the local membrane potential. Cosentino et al. linked a light-responsive module to the pore of a potassium channel to build a genetically encoded channel called BLINK1 that is closed in the dark and opens in response to low doses of blue light. Zebrafish embryos expressing BLINK1 in their neurons changed their behavior in response to blue light.

    Science, this issue p. 707

  7. Vaccines

    Extra dividends from measles vaccine

    1. Caroline Ash

    Vaccination against measles has many benefits, not only lifelong protection against this potentially serious virus. Mina et al. analyzed data collected since mass vaccination began in high-income countries when measles was common. Measles vaccination is associated with less mortality from other childhood infections. Measles is known to cause transient immunosuppression, but close inspection of the mortality data suggests that it disables immune memory for 2 to 3 years. Vaccination thus does more than safeguard children against measles; it also stops other infections taking advantage of measles-induced immune damage.

    Measles vaccination

    PHOTO: TEK IMAGE/SCIENCE SOURCE

    Science, this issue p. 694

  8. Tissue Regeneration

    Inhibiting Hippo to mend broken hearts

    1. Wei Wong

    Activation of the Hippo signaling pathway prevents organ overgrowth. The pathway inhibits the activity of the transcriptional coactivator Yap, which is important during development. However, this same activity limits the ability of some organs to regenerate after injury. Morikawa et al. found that Yap target genes not only included cell cycle genes but also genes encoding cytoskeletal remodeling proteins or proteins that link the cytoskeleton to the extracellular matrix. Cardiomyocytes from Hippo signaling–deficient mice formed cellular protrusions typical of migrating cells and more readily moved toward scar sites after cardiac injury. Thus, inhibiting the Hippo pathway could help with heart regeneration.

    Sci. Signal. 8, ra41 (2015).

  9. Malaria

    A way to dissect malaria's secrets

    1. Stella M. Hurtley

    Malaria has exerted a strong selective force on the human genome. However, efforts to identify host susceptibility factors have been hindered by the absence of a nucleus in red blood cells. Egan et al. developed an approach involving blood stem cells to discover host factors critical for Plasmodium falciparum infection of red blood cells. The authors identified an essential host receptor for parasite invasion that could provide a target for malaria therapeutics.

    Science, this issue p. 711

  10. Soil Science

    Global soil resources under stress

    1. Nicholas S. Wigginton

    The future of humanity is intertwined with the future of Earth's soil resources. Soil provides for agriculture, improves water quality, and buffers greenhouse gases in the atmosphere. Yet human activities, including agricultural soil erosion, are rapidly degrading soil faster than it is naturally replenished. At this rate, human security over the next century will be severely threatened by unsustainable soil management practices. Amundson et al. review recent advances in understanding global soil resources, including how carbon stored in soil responds to anthropogenic warming. Translating this knowledge into practice is the biggest challenge remaining.

    Science, this issue 10.1126/science.1261071

  11. Supernovae

    Stellar metals shine toward our eyes only

    1. Margaret M. Moerchen

    Taking a different look at a familiar star may still yield surprises. Boggs et al. trained the x-ray vision of the NuSTAR observatory on the well-studied supernova 1987A. Core-collapse explosions such as SN 1987A produce a titanium isotope, 44Ti, whose radioactive decay yields hard x-ray emission lines. All the emission associated with 44Ti appears to be from material moving toward us, with none moving away. This implies that the explosion was not symmetric. These findings help to explain the mechanics of SN 1987A and of core-collapse supernovae in general.

    Science, this issue p. 670

  12. Solar Cells

    Going toward the grains

    1. Phil Szuromi

    Great strides have been made in improving the efficiency of organic-inorganic perovskite solar cells. Further improvements are likely to depend on understanding the role of film morphology on charge-carrier dynamics. de Quilettes et al. correlated confocal fluorescence microscopy images with those from scanning electron microscopy to spatially resolve the photoluminescence and carrier decay dynamics from films of organic-inorganic perovskites. Carrier lifetimes varied widely even between grains, and chemical treatments could improve lifetimes

    Science, this issue p. 683

  13. Catalysis

    Waste not, want not

    1. Phil Szuromi

    Natural gas often escapes or is deliberately burned at remote exploration sites because there is no economical way to transport it to markets. One route proposed for converting its main component, methane, into a more readily transported liquid is conversion to benzene over zeolites containing molybdenum (Mo). However, this method suffers from low conversion efficiency. Gao et al. identified the active Mo nanostructures as well as deactivated carbide species that form during this reaction. They were also able to recover and even enhance the zeolite catalytic activity after oxygen treatments.

    Science, this issue p. 686

  14. Inorganic Chemistry

    Mimicking the oxygen evolution center

    1. Nicholas S. Wigginton

    Making a synthetic analog of plant photosynthesis is a key goal for exploiting solar energy and replacing fossil fuels. Zhang et al. synthesized a manganese-calcium cluster that looks and acts like the oxygen evolution center in photosystem II (see the Perspective by Sun). The mimic structurally resembles the biological complex, with the notable exception of bridging protein ligands and water-binding sites on a dangling Mn atom. Functionally, however, the cluster's metal center readily undergoes four redox transitions, which contribute to splitting water into oxygen. This and other synthetic mimics will pave the way for developing more efficient catalysts for artificial photosynthesis.

    Science, this issue p. 690; see also p. 635

  15. Chromosomes

    Building stable centromeres

    1. Guy Riddihough

    Each of our chromosomes has a single centromere, seen as a constriction during cell division, which is required for accurate chromosome segregation to daughter cells. Falk et al. show that the special histone protein known as CENP-A, which forms part of the nucleosomes at centromeres, makes the chromatin at these constrictions very stable and long-lived. This stability is conferred by a protein-binding partner, CENP-C, recruited to the centromere by the CENP-A histone. Binding of CENP-C to CENP-A–containing nucleosomes alters the behavior of the macromolecular centromere complex to help it maintain its identity

    Science, this issue p. 699

  16. Structural Virology

    Measles virus capsid at high resolution

    1. Kristen L. Mueller

    Viruses rely on their capsid proteins to package and protect their genome. For measles virus and other Mononegavirales family members, multiple capsid proteins together form a helical shell around the viral RNA (collectively called the nucleocapsid). Gutsche et al. now report a high-resolution cryoelectron microscopy structure of the measles virus nucleocapsid. The structure reveals how the nucleocapsid assembles and how the nucleo-protein and viral RNA interact, both of which may inform drug design

    Science, this issue p. 704

  17. Infectious Diseases

    Lung imaging for better TB treatments

    1. Julia Fahrenkamp-Uppenbrink

    Tuberculosis treatments typically take 6 months to complete. Although the success rate is high for full treatment, many patients do not complete the treatment course. Attempts to develop drugs with shorter treatment times have not been successful. In a Perspective, Barry highlights the role that recent imaging advances can play in assessing the success of drug candidates. For example, serial computed tomography imaging can be used to map the lung at millimeter resolution and monitor changes in particular lung regions in response to treatment. This and other imaging methods have the potential to improve the quality of clinical trials by defining quantitative target outcomes.

    Science, this issue p. 633

  18. Semiconductors

    Oriented mesostructure for energy conversion

    1. Zakya H. Kafafi

    The orientation-controlled growth of mesoporous channels in single-crystal semiconductors is extremely difficult but highly desirable in optical devices. Zhao et al. used a simple evaporation process to synthesize three-dimensional open mesoporous titanium dioxide microspheres with uniform size (~800 nm), well-controlled radially oriented mesoporous channels, and “single-crystal”–like walls. Dye-sensitized solar cells using such microspheres showed good power conversion efficiency up to 12%. This evaporation-driven approach may provide a path for tailoring the orientation and self-assembly of other mesoporous metallic oxides and open the door for their potential use in optoelectronic devices.

    Sci. Adv. 10.1126/sciadv.1500166 (2015).

Navigate This Article