This Week in Science

Science  14 Aug 2015:
Vol. 349, Issue 6249, pp. 701
  1. Quantum Optics

    Complex quantum optical circuitry

    1. Ian S. Osborne

    This versatile universal linear optics chip is reprogrammable


    Encoding and manipulating information in the states of single photons provides a potential platform for quantum computing and communication. Carolan et al. developed a reconfigurable integrated waveguide device fabricated in a glass chip (see the Perspective by Rohde and Dowling). The device allowed for universal linear optics transformations on six wave-guides using 15 integrated Mach-Zehnder interferometers, each of which was individually programmable. Functional performance in a number of applications in optics and quantum optics demonstrates the versatility of the device's reprogrammable architecture.

    Science, this issue p. 711; see also p. 696

  2. Ebola Vaccine

    Shortening the time to protection

    1. Caroline Ash

    Although Ebola vaccine candidates have entered clinical trials in West Africa, there is little information available on the mechanism of protection. A single dose of the recombinant vesicular stomatitis virus–Ebola vaccine protects nonhuman primates, acting primarily through antibody responses. Marzi et al. found that this vaccine generates a robust immune response in macaques to a West African strain of Ebola virus within days of immunization (see the Perspective by Klenk and Becker). Innate immune responses developed in as little as 3 days and increased the chances of survival, with complete antibody protection acquired 7 days after immunization.

    Science, this issue p. 739; see also p. 693

  3. Microtechnology

    CRISPR-Cas9 delivery by microfluidics

    1. Philip Yeagle

    Delivering plasmids to difficult-to-transfect cells just got a bit easier. Han et al. report a microfluidic approach to deliver plasmids encoding single-guide RNA and Cas9 with high efficiency and high cell viability to mammalian cells. Rapid mechanical deformation of cell membranes generated temporary holes, permitting the transfer of plasmids without the use of viruses. The approach allowed for successful genome editing and gene loss-of-function in different cell lines across humans and mice. Editing mutations in this way could become an important tool for developing gene therapies.

    Sci. Adv. 10.1126.sciadv.00454 (2015).

  4. Evolution

    Helping the next generation diversify

    1. Laura M. Zahn

    Parasitism, including infections, can negatively affect fitness. Parents can help the next generation by increasing genetic diversity so that offspring can avoid or fight off these deleterious interactions more easily. For fruit flies, Singh et al. observed that in response to bacterial infection or predation by a parasitic wasp, the next generation showed increased recombination. However, this increase in genetic diversity was not due to increased recombination rates, but rather an unequal allocation of gametes that have undergone recombination. Infection therefore drives plasticity in the parental gametes, resulting in more diverse offspring.

    Science, this issue p. 747

  5. Geophysics

    Lower crustal deformation takes a turn

    1. Brent Grocholski

    Collisions creating mountain belts frequently involve a tectonic plate plunging into the mantle. Huang et al. connect the deformation of rock from the subducting plate to the surface topography in Taiwan (see the Perspective by Long). Subsurface deformation mapping required interpreting certain seismic wave velocities as they travel through the crust. The subsequent images of Taiwan's deep crust show two distinct layers of deformation. The bottom layer comprises the subducting slab, which is being pulled into the mantle. This mechanically couples with the upper layer of crust, compressing it into a mountain range.

    Science, this issue p. 720; see also p. 687

  6. 2D Materials

    Tuning the band gap of black phosphorus

    1. Jelena Stajic

    Most materials used in electronics are semiconductors. The sizable energy gap in their electronic structure makes it easy to turn the conduction of electricity on and off. Graphene naturally lacks this band gap unless it undergoes certain modifications. Kim et al. studied the electronic structure of black phosphorus—a related two-dimensional material. By sprinkling potassium atoms on top of single layers of black phosphorus, the material changed from being a semiconductor to having a gapless linear dispersion similar to that of graphene.

    Science, this issue p. 723

  7. Language Development

    Marmosets learn to talk baby-talk

    1. Sacha Vignieri

    As human infants grow, their vocalizations change from cries, to babbles, to words. This pattern has been presumed to be absent from other primates. Indeed, the development of bird song is often regarded as a closer approximation of human language development. Takahashi et al., however, observed that marmoset cries and calls in the first 2 months after birth mature in much the same way as they do in humans (see the Perspective by Margoliash and Tchernichovski). Calls changed as the infants' vocal structures grew and were influenced by feedback from their parents.

    Science, this issue p. 734; see also p. 688

  8. DNA Repair

    How to repair broken replication forks

    1. Guy Riddihough

    Double-strand breaks in DNA are extremely dangerous to the integrity of our genomes. Most arise from problems encountered by replication forks during duplication of genomic DNA. Break-induced replication is known to use an error-prone DNA polymerase to repair such damage. Mayle et al. show that cells limit error-prone DNA synthesis by preventing the DNA polymerase from inadvertently switching to a related sequence with an incorrect template. The repair of the break is achieved by using a structure-specific nuclease to prevent formation of a long single-stranded region.

    Science, this issue p. 742

  9. Drug Delivery

    Hydrogels cozy up to inflamed tissues

    1. Megan Frisk

    Inflammation drives many chronic conditions. Directing potent drugs to the site of inflammation is highly desirable for improving treatment. Zhang et al. designed a hydrogel that self-assembles and delivers hydrophobic anti-inflammatory drugs directly to inflamed colon cells. Dexamethasone-loaded hydrogel enemas administered to a genetic mouse model of ulcerative colitis—a type of inflammatory bowel disease—relieved inflammation more effectively than free dexamethasone. In tissue samples from these patients, as well as in a chemically induced mouse model of colitis, hydrogel microfibers preferentially attached to inflamed tissue.

    Sci. Transl. Med. 7, 300ra128 (2015)

  10. Glial Cell Signaling

    Cell type–specific glial networks

    1. Peter Stern

    Glial cells respond to neurotransmitters when nerve cells communicate with each other. Glial cells themselves release gliotransmitters that regulate neural synaptic transmission. Martín et al. studied this reciprocal relationship in a brain region called the dorsal striatum, which has two types of experimentally identifiable neurons and two types of synapses (see the Perspective by Gittis and Brasier). Subpopulations of glial cells selectively responded to the activity of one specific type of neuron. In turn, these specifically activated glial cells signaled only to the same type of neurons but not the other, indicating that glial-nerve signaling is largely cell-type specific.

    Science, this issue p. 730; see also p. 690

  11. Device Technology

    Improving transistors with nanomaterials

    1. Phil Szuromi

    High-performance silicon transistors and thin-film transistors used in display technologies are fundamentally limited to miniaturization. Incorporating nanomaterials—such as carbon nanotubes, graphene, and related two-dimensional materials like molybdenum disulfide—into these devices as gate materials may circumvent some of these limitations. Franklin reviews the opportunities and challenges for incorporating nanomaterials into transistors to improve performance. Because high-performance transistors are distinct from thin-film transistors, incorporating them into flexible or transparent platforms raises new challenges.

    Science, this issue 10.1126/science.aab2750

  12. HIV-1 Vaccines

    Microbiota can mislead antibodies

    1. Kristen L. Mueller

    Unlike the response to many viral infections, most people do not produce antibodies capable of clearing HIV-1. Non-neutralizing antibodies that target HIV-1's envelope glycoprotein (Env) typically dominate the response, which is generated by B cells that cross-react with Env and the intestinal microbiota. Williams et al. analyzed samples from individuals who had received a vaccine containing the Env protein, including the gp41 subunit. Most of the antibodies were non-neutralizing and targeted gp41. The antibodies also reacted to intestinal microbiota, suggesting that preexisting immunity to microbial communities skews vaccineinduced immune responses toward an unproductive target.

    Science, this issue 10.1126/science.aab1253

  13. Paleoceanography

    Slow circulation in the cold Arctic

    1. H. Jesse Smith

    The Arctic Ocean and Nordic Seas together supply dense, sinking water to the Atlantic Meridional Overturning Circulation (AMOC). The redistribution of heat by the AMOC, in turn, exerts a major influence on climate in the Northern Hemisphere. Thornalley et al. report that during the last glacial period, those regions were nearly stagnant and supplied almost none of the water that they presently contribute to the AMOC. This low rate of flow into the Atlantic was probably due to an absence of vigorous deep-water formation in the Arctic Mediterranean as a consequence of the extensive ice cover there at that time.

    Science, this issue p. 706

  14. Applied Optics

    Chirality from achiral structures

    1. Ian S. Osborne

    The most common materials used in electronics produce only a simple optical response. Dhara et al. observed a complex circular photogalvanic effect in silicon nanowires, with the magnitude and direction of the induced photocurrent dependent on the polarization of the light. The specifics of the structure and geometry of the component materials are responsible for the effect. It should therefore be possible to engineer the same effect in other achiral materials and thus expand the box of enhanced functional materials for optical applications.

    Science, this issue p. 726

  15. Magnetism

    Control of magnetism in heterostructures

    1. Jelena Stajic

    The interface between two different materials in a heterostructure can exhibit properties unique to either of the two materials alone. A well-known example is a conducting gas that forms when LaAlO3 is grown on SrTiO3, but only if the LaAlO3 layer is at least four unit cells thick. Wang et al. report a similarly abrupt magnetic transition in a heterostructure formed by another oxide (LaMnO3) on the same SrTiO3 substrate. Even though bulk LaMnO3 is an antiferromagnet, when six or more unit-cell layers of it were deposited on SrTiO3, it behaved like a ferromagnet.

    Science, this issue p. 716

  16. Climate Change

    Has there been a global warming hiatus?

    1. Julia Fahrenkamp-Uppenbrink

    Between 1999 and 2013, average temperatures at Earth's surface rose more slowly than in the preceding decades, despite fast rises in greenhouse gas emissions. This “hiatus” has led some to question the accuracy of climate model projections. In a Perspective, Trenberth explains how natural climate variability is likely to be larger on decadal time scales than commonly appreciated. Interannual and decadal processes in the Pacific Ocean strongly influence how fast temperatures rise. Although the underlying climate warming trend continues, natural climate variability can overwhelm it for short periods of time, as during the recent “hiatus.”

    Science, this issue p. 691

  17. Vascular Biology

    Maintaining vascular health with HDL

    1. Wei Wong

    Flow through blood vessels subjects endothelial cells to abnormal shear forces at specific locations. This triggers inflammation, which contributes to atherosclerotic plaque formation. Galvani et al. found that the endothelial cell receptor S1P1, which is activated by a lipid mediator abundant in blood, suppresses vascular inflammation and atherosclerosis in mice. This mediator, S1P, binds to different chaperone proteins and suppresses inflammation in cultured endothelial cells only when bound to the lipoprotein ApoM+HDL. Thus, S1P may contribute to the protective effect of HDL—commonly called “good cholesterol”—in atherosclerosis.

    Sci. Signal. 8, ra79 (2015).