This Week in Science

Science  20 Mar 2015:
Vol. 347, Issue 6228, pp. 1325
  1. Solar Physics

    Sunspot cycle driven by linked fields

    1. Margaret M. Moerchen

    A sunspot emerges at the solar surface

    PHOTO: JOHN CHUMACK / SCIENCE SOURCE

    Sunspots indicate magnetic flux emerging at the Sun's surface. Sunspots change over an 11-year time scale, which depends on the behavior of the probable magnetic dynamo within. Cameron et al. suggest that the flux revealed by sunspot activity is effectively driven by the magnetic field strength at the Sun's poles. Their mathematical reasoning explains why the polar field activity can predict the sunspot cycle.

    Science, this issue p. 1333

  2. Micelle Assembly

    Cylindrical polymer micelles pack in 3D

    1. Marc S. Lavine

    When you control chemistry, solvents, temperature, and concentration, surfactants and block copolymers will readily assemble into micelles, rods, and other structures. Qiu et al. take this to new lengths through precise selection of longer polymer blocks that self-assemble through a crystallization process (see the Perspective by Lee et al.). They chose polymer blocks that were either hydrophobic or polar and used miscible solvents that were each ideal for only one of the blocks. Their triblock comicelles generated a wide variety of stable three-dimensional superstructures through side-by-side stacking and end-to-end intermicellar association.

    Science, this issue p. 1329; see also p. 1310

  3. Stem Cell Aging

    Keeping stem cells in tip top condition

    1. Stella M. Hurtley

    Stem cells are important in the maintenance and growth of tissues. For the health of the organism as a whole, it is important that only healthy stem cells be used. Mohrin et al. elucidated a regulatory branch of the mitochondrial unfolded protein response that is coupled to cellular energy metabolism and proliferation in stem cells (see the Perspective by Ocampo and Belmonte). Mitochondrial protein folding stress triggered a metabolic checkpoint that regulates the cell cycle. Deregulation of this pathway interfered with stem cell quiescence and compromised regenerative function.

    Science, this issue p. 1374; see also p. 1319

  4. Epilepsy Treatment

    Targeting metabolism to tackle seizures

    1. Peter Stern

    About 1% of us suffer from epilepsy. Unfortunately, presently available drugs do not work for a third of epileptic patients. Sada et al. wanted to develop compounds to treat drug-resistant epilepsy (see the Perspective by Scharfman). They focused on a metabolic pathway in the brain, the astrocyte-neuron lactate shuttle. They found that lactate dehydrogenase, a key molecule in nerve cell metabolism, controls brain excitability. Searching for a substance that selectively targets this molecule, they found a potential anti-epileptic drug that strongly suppressed drug-resistant epilepsy in an animal model.

    Science, this issue p. 1362; see also p. 1312

  5. Crystal Growth

    From iron clusters to iron mineral

    1. Nicholas S. Wigginton

    Growing a mineral out of solution, either in the lab or in nature, requires the assembly of atoms or clusters of ions. The structure of some common iron oxides hints that tiny iron-oxygen clusters may serve as mineral building blocks, but isolating these often unstable clusters is challenging. Sadeghi et al. not only isolated but were able to control the growth and dissolution of an iron-oxygen cluster that is a likely precursor to the most common iron oxide mineral, ferrihydrite.

    Science, this issue p. 1359

  6. Conservation Ecology

    Habitat fragmentation reduces biodiversity

    1. Barry Pogson

    Ongoing deforestation in the Brazilian rainforest

    PHOTO: © PHOTOSHOT HOLDINGS LTD / ALAMY

    The destruction of natural habits and encroachment by human activities lead to a loss of biodiversity and fragmented ecosystems. However, ecologists have long argued about the contribution of fragmentation to the loss of biodiversity. Haddad et al. synthesized a diverse set of studies of the impacts of habitat fragmentation that together covered multiple biomes over five continents and nearly four decades. Habitat fragmentation did indeed lower biodiversity of diverse species by around 50% within a few decades. Furthermore, 70% of the world's forested areas are close enough to human activity for biodiversity to be threatened by fragmentation.

    Sci. Adv. 10.1126/sciadv.1500052 (2015).

  7. Paleoanthropology

    Finding Homo nearly 3 million years ago

    1. Andrew M. Sugden

    The fossil record of humans is notoriously patchy and incomplete. Even so, skeletal remains and artifacts unearthed in Africa in recent decades have done much to illuminate human evolution. But what is the origin of the genus Homo? Villmoare et al. found a fossil mandible and teeth from the Afar region in Ethiopia. The find extends the record of recognizable Homo by at least half a million years, to almost 2.8 million years ago. The morphological traits of the fossil align more closely with Homo than with any other hominid genus. DiMaggio et al. confirm the ancient date of the site and suggest that these early humans lived in a setting that was more open and arid than previously thought.

    Science, this issue p. 1352, p. 1355

  8. Immunology

    Limiting allergic responses with B cells

    1. John F. Foley

    Although most immunological B cells promote immune responses, some B cells secrete the anti-inflammatory cytokine interleukin-10 (IL-10) and have immunosuppressive properties. Kim et al. found that these B cells inhibited the activation of mast cells, immune cells that are critical regulators of allergic reactions. Mice lacking these special B cells had more severe symptoms of anaphylaxis. Mast cell inhibition required physical contact with the B cells, which stimulated the B cells to produce more IL-10. Thus, IL-10–producing B cells might provide a therapeutic target for treating allergic diseases.

    Sci. Signal. 8, ra28 (2015).

  9. Applied Optics

    Color correcting planar optics

    1. Ian S. Osborne

    The functionality of many bulk optical elements can now be replaced by specially designed structures fabricated in thin films. This planar optics approach, however, has generally been applicable to only a narrow band of wavelengths. Aieta et al. show that chromatic dispersion, or color dependence, can be compensated for by the judicious design of the surface. The results demonstrate a general approach for the fabrication of broadband and lightweight optical elements that can be engineered into planar thin films.

    Science, this issue p. 1342

  10. Materials Science

    Adding autonomy to materials science

    1. Marc S. Lavine

    Shape-memory alloys can alter their shape in response to a change in temperature. This can be thought of as a simple autonomous response, albeit one that is fully programmed at the time of fabrication. It is now possible to build materials or combinations of materials that can sense and respond to their local environment, in ways that might also include simple computations and communication. McEvoy and Correll review recent developments in the creation of autonomous materials. They look at how individual abilities are added to a material and the current limitations in the further development of “robotic materials.”

    Science, this issue 10.1126/science.1261689

  11. Translation

    Measuring translation in space and time

    1. Beverly A. Purnell

    The ribosome translates the information contained within messenger RNAs (mRNAs) into proteins. When and where ribosomes encounter mRNAs can regulate gene expression. Halstead et al. developed an RNA biosensor that allows single molecules of mRNAs that have never been translated to be distinguished from ones that have undergone translation by the ribosome in living cells (see the Perspective by Popp and Maquat). The authors demonstrated the utility of their technique by examining the spatial and temporal regulation of translation in single cells and in Drosophila oocytes during development.

    Science, this issue p. 1367; see also p. 1316

  12. Additive Manufacturing

    Fast, continuous, 3D printing

    1. Marc S. Lavine

    Although three-dimensional (3D) printing is now possible using relatively small and low-cost machines, it is still a fairly slow process. This is because 3D printers require a series of steps to cure, replenish, and reposition themselves for each additive cycle. Tumbleston et al. devised a process to effectively grow solid structures out of a liquid bath. The key to the process is the creation of an oxygen-containing “dead zone” between the solid part and the liquid precursor where solidification cannot occur. The precursor liquid is then renewed by the upward movement of the growing solid part. This approach made structures tens of centimeters in size that could contain features with a resolution below 100 µm.

    Science, this issue p. 1349

  13. RNA Biochemistry

    RNA kinetics may define regulatory hierarchy

    1. Guy Riddihough

    The double-helical structure of DNA suggests immediately how nucleic acid polymers can recognize and bind to homologous sequences. Target recognition by RNA is vital in many biological processes. Fei et al. used super-resolution microscopy of tagged RNAs and computer modeling to understand how RNA-RNA base-pairing reactions occur in vivo. They studied a small RNA (sRNA) that targets a messenger RNA (mRNA) for degradation in bacteria. They observed a slow rate of association as the sRNA searched for its mRNA target, but thereafter a fast rate of dissociation. This explains the need for high concentrations of sRNA to cause mRNA degradation. The sRNA found different target mRNAs at different rates, allowing the generation of a regulatory hierarchy.

    Science, this issue p. 1371

  14. Regenerative Medicine

    Healing heart borrows from development

    1. Megan Frisk

    With a limited ability to repair itself after injury, the mature heart may need to look to development for some lessons. By reactivating pathways that are present during mammalian development, it may be possible to encourage cardiac regeneration. In mice, Tian et al. found that the microRNA cluster mir302-367 stimulates cardiomyocyte proliferation during early heart development by inhibiting the Hippo signaling pathway. Transient treatment with mimics of miR302-367 promoted cardiac regeneration in mice after myocardial infarction, suggesting that such small RNAs can be harnessed therapeutically to repair the adult heart.

    Sci. Transl. Med. 7, 279ra38 (2015).

  15. Heavy Fermions

    Uncovering the symmetry of a hidden order

    1. Jelena Stajic

    Cooling matter generally makes it more ordered and may induce dramatic transitions: Think of water becoming ice. With increased order comes loss of symmetry; water in its liquid form will look the same however you rotate it, whereas ice will not. Kung et al. studied the symmetry properties of a mysteriously ordered phase of the material URu2Si2 that appears at 17.5 K. They shone laser light on the crystal and studied the shifts in the frequency of the light. The electron orbitals of the uranium had a handedness to them that alternated between the atomic layers.

    Science, this issue p. 1339

  16. Superconductivity

    Picking out the elusive stripes

    1. Jelena Stajic

    Copper-oxide superconductors have periodic modulations of charge density. Typically, the modulation is not the same for the whole crystal, but breaks up into small nanosized domains. Bulk experiments show that the density is modulated along both axes in the copper-oxide plane, but it is not clear whether this is true only on the scale of the whole crystal or also locally, for each domain. Comin et al. analyzed the charge order in the compound YBa2Cu3O6+y, using resonant x-ray scattering, and found that it was consistent with a local unidirectional, so-called stripy, ordering.

    Science, this issue p. 1335

  17. Statistics

    Are you asking the right questions of your data?

    1. Julia Fahrenkamp-Uppenbrink

    Data analyses are central to scientific inquiry. But not all data analyses are the same, and confusing one kind of analysis with another can lead to wrong interpretations. In a Perspective, Leek and Peng argue that data analyses can be grouped into six types, ranging from comparatively simple descriptive analyses to much more challenging predictive, causal, and mechanistic analyses. In studies that involve multiple analyses of different types, it is crucial to be aware of the analysis type at each step.

    Science, this issue p. 1314

  18. Vibrational Dynamics

    Getting a handle on the CH5+ spectrum

    1. Jake Yeston

    Protonated methane, CH5+, fascinates chemists because it seems to break the rules. There's no obvious place for the fifth hydrogen to bind, and so what happens is that all five hydrogens shuffle about like participants in an endless round of a musical chairs game. And yet the molecule has a vibrational spectrum that suggests some semblance of tighter ordering. Asvany et al. have now measured high-resolution vibrational spectra at two low temperatures (10 and 4 K). (See the Perspective by Oka). Their accompanying analysis makes headway on assigning the peaks and enhancing understanding of the molecule's dynamic structure.

    Science, this issue p. 1346; see also p. 1313

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