Editors' Choice

Science  20 Jul 2012:
Vol. 337, Issue 6092, pp. 270
  1. Sociology

    Intimidated by Equations?

    1. Barbara R. Jasny

    Although there is general agreement on the value of a strong tie between theory and data, forging links between theoretical and empirical approaches (and practitioners) is not as straightforward as it should be. New evidence of this disconnect comes from the work of Fawcett and Higginson, who examined the use of mathematical equations in 649 papers dealing with ecology and evolution that were published in 1998. They gathered citation data, excluding instances of self-citation. An increase in the number of equations per page of main text corresponded to a lower rate of citations. Overall, each additional equation in the main text of a paper was associated with a 28% decrease in the citation rate. Burying the equations in an appendix had a salutary effect on citation rate. When the citing papers were divided into theoretical and nontheoretical on the basis of their use of the word “model” in the abstract or title, the authors observed that the negative effect was due to the nontheoretical papers not citing papers with equations. There are caveats to the conclusions—examinations over longer periods of time, analysis of the relative content of the papers, and examination of the effect for online rather than print publication are all warranted. Although the authors conclude that better math education for biologists is the best long-term solution, they suggest that more immediate strategies could include the addition of explanatory text between equations.

    Proc. Natl. Acad. Sci. U.S.A. 109, 10.1073/pnas.1205259109 (2012).

  2. Ecology

    Half Truths

    1. Sacha Vignieri
    CREDIT: BROWN ET AL., BIOL. LETT. 8, 10.1098/RSBL.2012.0435 (2012)

    Deception is complicated because it requires the cognitive skills to both assess the potential for its efficacy and to carry it off. Cephalopods are known masters of deceptive behavior, often using camouflage as a way to rapidly mimic their environment, or even other organisms, in their attempts to avoid predation. Brown et al. now show that mourning cuttlefish (Sepia plangon) have taken this exceptional deceptive ability a step farther than mere run-of-the-mill camouflage. In most cuttlefish species, courting males assume a particular coloration when attempting to mate with females. This coloration attracts females but can also attract rival males, who may displace the courting male. In order to avoid attracting these potential competitors but still maintain the female's attention, males will often perform split coloration displays. They mimic female coloration on the side of their bodies facing a rival, while displaying male courtship coloration on the side facing the female. Males perform this split display only when they are approached by a single male, presumably because it is only under these circumstances that they are able to maintain an appropriately deceptive angle. These results confirm the idea that mimicry can be highly advantageous in many contexts and suggest that these types of social and deceptive interactions may have helped to shape the high cognitive functioning of cephalopods.

    Biol. Lett. 8, 10.1098/rsbl.2012.0435 (2012).

  3. Chemistry

    A Glimpse of Gold

    1. Julia Fahrenkamp-Uppenbrink

    Gold nanoparticles supported on titania have high catalytic activity; for example, in the oxidation of carbon monoxide at room temperature. What are the structural properties of the Au/TiO2 catalyst that enable this catalytic activity? Transmission electron microscopy has provided structural information, but the strong electron beam can damage the system, and it remains unclear whether the associated images represent the active structure of the catalyst. Kuwauchi et al. now report the use of environmental transmission electron microscopy, which allows the catalyst to be studied under reaction conditions. They find that the nanoparticle morphology varies systematically in differing environments, changing from faceted to round, depending on the gases present. In contrast, the support maintains its crystallinity throughout the experiments, and the interface between the particles and the support also remains stable. By systematically studying the effects of electron irradiation on the structure, the authors derive conditions under which no detectable structural damage occurs, thus making it possible to deduce the intrinsic structure of the catalyst under reaction conditions.

    Angew. Chem. Int. Ed. 51, 10.1002/anie.201201283 (2012).

  4. Materials Science

    Hot Templating

    1. Phil Szuromi
    CREDIT: SCHUSTER ET AL., J. AM. CHEM. SOC. 134, 10.1021/JA208941S (2012)

    One method for creating ordered mesoporous materials is to use the phase separation of block copolymers to create a mold for patterning a second material. Typically, the structure of the template is fixed after solvent evaporation. Schuster et al. applied small-angle x-ray scattering (SAXS) to follow the pyrolytic formation of mesoporous carbon films using commercial triblock polymers as templates and oligomeric resol as a carbon precursor. They spin-coated these solutions onto silicon substrates or spread them onto the surface of porous anodic alumina membranes, then monitored the thermal evolution of their structures with grazing incidence or in situ SAXS, respectively. Analysis showed that the self-assembly of the mesoporous phase (cylindrical holes in a face-centered orthorhombic or circular hexagonal structure, respectively) does not occur after solvent evaporation but during pyrolysis, and that changes in the heating rate can lead to changes in the unit-cell parameters.

    J. Am. Chem. Soc. 134, 10.1021/ja208941s (2012).

  5. Physics

    Intrinsic Origins

    1. Jelena Stajic

    Interfacing two unlike materials may give rise to unexpected properties resulting from the asymmetry of the structure. Such is the case in two-dimensional interfaces of perovskite oxide films; in the best-known example of the LaAlO3/SrTiO3 (LAO/STO) interface, ferromagnetism has been observed even though neither of the two materials is magnetic in the bulk. This and other interface effects are thought to originate from STO, but whether they are an intrinsic property of the electron liquid in STO is not known. Moetakef et al. study the magnetism in STO using two systems: GdTiO3/STO heterostructures and La-doped STO films; in both cases, STO is doped with carriers, from the interface or the La dopants, respectively. The authors observe ferromagnetism in both systems, and superconductivity coexisting with magnetism in the doped films. The ferromagnetic Curie temperature increases strongly with the carrier density measured through the Hall effect, and the data from the two systems fall onto the same curve, indicating universal dependence and an intrinsic mechanism.

    Phys. Rev. X 2, 021014 (2012).

  6. Chemistry

    Figure Nine

    1. Jake Yeston

    Nitrogen occurs naturally as a rather tightly bound neutral dimer, and anionic azide (N3) salts have long been accessible as well. A cation composed purely of nitrogen arrived only much more recently on the scene, with the preparation of an N5+ salt about a decade ago. The heavier congener phosphorus has followed a similar path: a variety of well-established neutral and negatively charged morphologies, but until now no tractable cation salts. Köchner et al. have filled the gap with the preparation of a P9+ salt. Key to its isolation was the use of an especially inert, aluminum-centered counterion adorned with trifluoromethyl groups. The synthesis entailed oxidation of neutral P4 by the nitrosonium salt of this counterion in dichloromethane solvent. Ultraviolet irradiation facilitated reaction of an apparent [P4NO]+ intermediate (and precipitation of excess neutral phosphorus) without damaging the ultimate product, which was isolable as a yellow-orange powder. Nuclear magnetic resonance spectroscopy in conjunction with theoretical calculations revealed a figure 8-type structure, of D2d symmetry, in which a central tetracoordinate P atom bridges two clusters of four P atoms each. The salt was also characterized by mass spectrometry and infrared and Raman spectroscopy, and persisted for weeks in room-temperature solution. The authors envision prospective applications of the salt in currentless deposition protocols.

    Angew. Chem. Int. Ed. 51, 6529 (2012).

  7. Ecology

    Diversity Persists

    1. Caroline Ash
    CREDIT: © BLICKWINKEL/ALAMY

    Marine ecosystems are characterized by high tropical and low polar biodiversity, and are correlated with water temperature. Fossil evidence hints at the persistence of such gradients for over 270 million years, but little is known about the details. Yasuhara et al. have chosen to examine the fossil record for North Atlantic zooplankton, because the fossils are abundant and the record is the most complete of any marine taxon. Times slices spanning the past 3 million years showed that tropical-high and polar-low diversity persisted throughout this period, with highest diversities during the mid-Pliocene. It seems that the species that have gone extinct since the Pliocene had narrower thermal tolerances than modern species and were selected out by the glaciation.

    Ecol. Lett. 15, 10.1111/j.1461-0248.2012.01828.x (2012).