This Week in Science

Science  09 Dec 2016:
Vol. 354, Issue 6317, pp. 1245
  1. Development Economics

    Substituting minutes for money

    1. Gilbert Chin

    Two African women complete a mobile money transaction.

    CREDITS: (TOP TO BOTTOM) AMINIAN ET AL.; DAVID DOREY-KENYA COLLECTION/ALAMY STOCK PHOTO

    In developing countries, bank branches and fixed-line telecommunications are scarce, whereas mobile phones are plentiful. These factors have led to the use of mobile money, whereby money can be deposited to an account linked to a phone, transferred to other users, and converted back into cash. Suri and Jack show that increased access to mobile money has increased long-term consumption in Kenya and reduced the number of households in extreme poverty.

    Science, this issue p. 1288

  2. Neuroscience

    Birds of a feather sing together

    1. Peter Stern

    How do birds know that a song that they hear is from a member of their own species, and how do they learn their songs in the first place? Araki et al. identified two types of brain cells involved in how finches learn their songs (see the Perspective by Tchernichovski and Lipkind). When zebra finches were raised by Bengalese finch foster parents, they learned a song whose morphology resembled that of their foster father. However, the temporal structure remained zebra finch–specific, suggesting that it is innate. Gadagkar et al. recorded activity in specific dopamine neurons in singing zebra finches while controlling perceived song quality with distorted auditory feedback. This distorted feedback represented worse performance than predicted and resulted in negative prediction errors. These findings suggest again that finches have an innate internal goal for their learned songs.

    Science, this issue p. 1282, p. 1234; see also p. 1278

  3. Organic Chemistry

    Catching a break in polyphenol synthesis

    1. Jake Yeston

    Chemical synthesis is usually rather different from playing with a modeling kit. If two large fragments of a molecule are not properly oriented, it is not typically possible to break them apart, rotate one, and then paste them back together. Yet that is precisely the trick that Keylor et al. used to synthesize two plant-derived polyphenols. Resveratrol forms a variety of dimers, trimers, and tetramers. When one central carbon-carbon bond links the fragments, it is weak enough to break spontaneously and reversibly at room temperature. The authors leveraged this equilibrium to generate an efficient route to two of the tetramers, nepalensinol B and vateriaphenol C.

    Science, this issue p. 1260

  4. Topological Matter

    An edge that is hard to get rid of

    1. Jelena Stajic

    A distinguishing characteristic of topological insulators (TIs) is that they have conducting states on their boundary—a surface for a three-dimensional (3D) TI or a line edge for a 2D TI. Sessi et al. used scanning tunneling spectroscopy to discover unusual 1D states in a 3D crystalline TI. The states appeared on the edge of a particular kind of step in the crystal and survived large magnetic fields and increased temperatures. This robustness bodes well for the potential use of these states in practical applications.

    Science, this issue p. 1269

  5. Ecological Genomics

    Mapping genetic adaptations to pollution

    1. Laura M. Zahn

    Many organisms have evolved tolerance to natural and human-generated toxins. Reid et al. performed a genomic analysis of killifish, geographically separate and independent populations of which have adapted recently to severe pollution (see the Perspective by Tobler and Culumber). Sequencing multiple sensitive and resistant populations revealed signals of selective sweeps for variants that may confer tolerance to toxins, some of which were shared between resistant populations. Thus, high genetic diversity in killifish seems to allow selection to act on existing variation, driving rapid adaptation to selective forces such as pollution.

    Science, this issue p. 1305; see also p. 1232

  6. Synthetic Biology

    Engineering cells to regulate glucose

    1. Valda Vinson

    Diabetes mellitus affects hundreds of millions of people worldwide. Blood glucose levels are chronically deregulated in diabetics, and this can lead to many serious disorders, including cardiovascular disease and renal failure. Xie et al. engineered a synthetic circuit into human cells that can sense the glucose concentration and respond to correct deregulation. Implants containing designer cells improved glucose regulation in diabetic mice.

    Science, this issue p. 1296

  7. Composites

    Super sensitive, not so silly, putty

    1. Marc S. Lavine

    Many composites blend stiff materials, such as glass or carbon fibers, into a softer elastic polymer matrix to generate a material with better overall mechanical toughness. Boland et al. added graphene to a lightly cross-linked silicone polymer (also known as Silly Putty). The resulting composite has unusual mechanical properties, allowing the manufacture of strain sensors that can detect respiration and the footsteps of spiders.

    Mixing graphene into Silly Putty

    PHOTO: AMBER/TRINITY COLLEGE DUBLIN

    Science, this issue p. 1257

  8. Parkinson's Disease

    A mitochondrial target for slowing PD

    1. Orla M. Smith

    At present, there are no disease-modifying treatments to stall the progression of Parkinson's disease (PD). A drug in development to treat diabetes might provide a way to slow it down. The drug, MSDC-0160, targets a recently identified carrier of pyruvate (a major substrate for energy production) into mitochondria. Ghosh et al. successfully used the drug to block neurodegeneration in several different cellular and animal models of PD. Furthermore, in two mouse models of PD, cellular autophagy was restored and neuroinflammation was reduced.

    Sci. Transl. Med. 8, 368ra174 (2016).

  9. Infectious Disease

    Diseases emerge when forests degrade

    1. Shahid Naeem

    Why emerging infectious diseases originate in tropical habitats remains a mystery, but habitat degradation may play a role. Mycobacterium ulcerans causes the tropical skin disease Buruli ulcer. Morris et al. looked for the presence of M. ulcerans in invertebrates and fish that they collected from 17 aquatic sites in French Guiana. They used molecular probes to quantify the mycobacterium and stable isotopes to quantify food web structure. Their findings linked habitat degradation to increases in the abundance of species lower down on the food chain—species more likely to carry the mycobacterium.

    Sci. Adv. 10.1126.sciadv.1600387 (2016).

  10. Chemistry

    Cooperation between frustrated partners

    1. Jake Yeston

    What might you do with a hat that had so many decorations dangling from the brim that you couldn't put it on? Lewis acids and bases are the molecular versions of hats and heads. Stephan reviews the surprising chemistry of so-called frustrated Lewis pairs (FLPs), which cannot form their natural complex together. Over the past decade, such systems (most often comprising a borane with a nitrogen or phosphorus partner) have been used to catalyze hydrogenation reactions, activate a number of other small molecules, and generally promote a wide range of cooperative chemical reactivity.

    Science, this issue p. 10.1126/science.aaf7229

  11. Microfluidics

    Aspects of the design

    1. Marc S. Lavine

    In microfluidics systems, the small size of the channels ensures that the flow profiles are laminar, so solute mixing is largely governed by diffusion in the absence of active mixing. Aminian et al. revisited the classic phenomenon of Taylor diffusion to investigate the effects that the aspect ratio of the conduit has on the longtime axial distribution of solutes. They show both numerically and experimentally that the aspect ratio controls the skewness of this distribution, and thus pipe design alone is enough to control mixing profiles.

    Science, this issue p. 1252

  12. Asymmetric Catalysis

    Crafting chiral boron building blocks

    1. Jake Yeston

    Carbon-boron bonds are easily transformed into a wide variety of C–C, C–N, and C–O bonds. With that flexibility in mind, Schmidt et al. show that nickel complexes can catalyze asymmetric alkylation of carbon centers adjacent to boron. This protocol creates chiral alkylboronates that function as stable precursors to numerous complex molecules. The reaction proceeds in stereo-convergent fashion—forming a single product from either mirror image of the α-haloboronate reagent. Successive reactions can also create chains of adjacent chiral alkyl centers with stereochemistry set by the configuration of the ligand bound to nickel.

    Science, this issue p. 1265

  13. Radio Astronomy

    Probing the intergalactic magnetic field

    1. Keith T. Smith

    Fast radio bursts (FRBs) are powerful flashes of astronomical radio waves that last just milliseconds and whose origins are a matter of debate. Ravi et al. discovered a FRB that is exceptionally bright (see the Perspective by Kaspi). This allowed them to measure how the polarization of the signal varies with wavelength (Faraday rotation). Combining this with the time delay of the flash at different wavelengths revealed the mean magnetic field along the line of sight. Assuming that the FRB originates from a colocated galaxy, the results constrain the intergalactic magnetic field and will inform models of galaxy formation and cosmology.

    Science, this issue p. 1249; see also p. 1230

  14. Origin of Life

    Beating the curse of the parasite

    1. Guy Riddihough

    The evolution of molecular replicators was a critical step in the origin of life. Such replicators would have suffered from faster-replicating “molecular parasites” outcompeting the parental replicator. Compartmentalization of replicators inside protocells would have helped ameliorate the effect of parasites. Matsumura et al. show that transient compartmentalization in nonbiological materials is sufficient to tame the problem of parasite takeover. They analyzed viral replication in a droplet-based microfluidic system, which revealed that as long as there is selection for a functional replicator, the population is not overwhelmed by the faster-replicating parasite genomes.

    Science, this issue p. 1293

  15. Viral Evolution

    A laboratory model of viral speciation

    1. Laura M. Zahn

    New species arise through the evolution of barriers to reproduction. This process is well understood where the emerging species are spatially isolated from one another. But the process of sympatric speciation—where the diverging species co-occur—is more enigmatic. Bacterial viruses make good models for addressing such questions because of their rapid generation times. Meyer et al. took bacteriophage λ and grew it on a mix of two strains of Escherichia coli. The virus duly split its host preferences into lineages with differing affinity for their respective E. coli hosts. In some experiments, the phages diverged to the extent that they became reproductively restricted to one strain of E. coli, even when the other was present.

    Science, this issue p. 1301

  16. Brain Research

    Time is a subjective experience

    1. Peter Stern

    Time, like space, is one of the fundamental dimensions of all our experiences. However, organisms do not work like clocks, and our judgment about the passage of time is variable, depending on circumstances. Soares et al. systematically investigated midbrain dopaminergic neurons during timing behavior in mice (see the Perspective by Simen and Matell). When measuring and manipulating mouse activity, the authors observed that dopaminergic neurons controlled temporal judgments on a time scale of seconds.

    Science, this issue p. 1273; see also p. 1231

  17. Climate

    Pacemaker of the ice ages, 40 years on

    1. Julia Fahrenkamp-Uppenbrink

    In a Science paper published 40 years ago, geoscientists Hays, Imbrie, and Shackleton provided evidence that small changes in Earth's orbit around the Sun are behind the ice age cycles of the past ∼2.5 million years. They thus provided observational support for the Milankovitch theory that until then had been difficult to verify. In a Perspective, Hodell explores the history of this influential discovery and the continuing challenges in understanding the underlying mechanisms. Focusing on ice growth phases rather than deglaciations and exploring the period before 0.8 million years ago may be particularly helpful for understanding these mechanisms.

    Science, this issue p. 1235

  18. Calcium Signaling

    Inhibiting calcium uptake ubiquitously

    1. Wei Wong

    The membrane transporter SERCA keeps cytoplasmic calcium levels low. Micropeptides that inhibit SERCA in muscle have been characterized. Anderson et al. sought to identify micropeptides that could perform this inhibitory function in nonmuscle tissues. Like their muscle-specific counterparts, ELN (endoregulin) and ALN (another-regulin) inhibited the activity of SERCA isoforms that are abundant in nonmuscle tissues. Thus, micropeptides may regulate other membrane transporters that are structurally related to SERCA.

    Sci. Signal. 9, ra119 (2016).