Editors' Choice

Science  23 Jul 2010:
Vol. 329, Issue 5990, pp. 370
  1. Psychology

    Clarity of Writing

    1. Alexandra E. Levitt*

    Teacher evaluations of nonstandardized homework can be vulnerable to various sources of bias. Handwritten work in particular may be susceptible to the valuation that the teacher assigns to good penmanship. Greifeneder et al. describe a systematic bias induced by more pleasing script. When university students were tasked with grading physics essays, work of similar quality was rated more highly (on average, 0.5 grade points higher on a 6-point scale) when legible than when hard to read. The authors suggest that this is due to fluency—that is, information from legible essays can be extracted more easily than from illegible ones. Awareness of the bias was shown to negate its effects, and calling attention to this potential bias would therefore seem particularly important when grading handwritten essays. Those with indecipherable penmanship may be well advised to opt for the keyboard if given the choice.

    Soc. Psychol. Pers. Sci. 1, 230 (2010).

    • * Alexandra E. Levitt is an intern at Science.

  2. Biochemistry

    Inhibiting the Uninhibited

    1. Helen Pickersgill

    Combining genetic screens with small-compound libraries is an effective way of finding drug candidates, and identifying the chemical target can offer insight into the mechanisms by which these compounds exert their effects. Aghajan et al. have identified a specific inhibitor for an important and functionally diverse class of enzymes and used it to link amino acid biosynthesis to a disease-relevant signaling pathway. The target of rapamycin (TOR) protein kinase plays an important role in nutrient signaling in eukaryotes and regulates cell growth and proliferation; deregulation of the TOR pathway has been linked to human diseases, including cancer. The authors carried out a screen in yeast to identify small molecules that selectively enhanced the effects of rapamycin, which inhibits TOR. One of the compounds inhibited a member of the Skp1–Cullin–F-box (SCF) ubiquitin ligase family, SCFMet30, which regulates genes involved in methionine biosynthesis and has not previously been linked to the TOR pathway. Thus, this study has identified a potential therapeutic that could be useful in combination with rapamycin in the clinic.

    Nat. Biotechnol. 28, 738 (2010).

  3. Ecology

    Hawks Take Out Sparrows

    1. Sherman J. Suter

    Through its adaptability, deliberate and accidental introductions, and natural dispersal, the house sparrow (Passer domesticus) became the archetypical bird of human-modified habitats around the world. In recent decades, however, populations in many parts of its range have declined markedly. That trend has been attributed to changes in agricultural practices, but in Britain urban populations have suffered the steepest declines. Bell et al. therefore consider the role of predation, specifically by the Eurasian sparrowhawk (Accipiter nisus). Using occurrence data from winter garden feeding stations, the authors compare the eastward and southward recolonization of Britain by the sparrowhawk with spatial and temporal patterns in sparrow populations. A logistic model that incorporates predation successfully simulates the trajectories among sparrow populations in rural and urban sites in different regions. At sites, sparrow numbers were generally stable or increasing before the reestablishment of sparrowhawks; afterward, the numbers declined continuously. In addition, significantly greater declines in sparrow numbers were found where sparrowhawks were present. The authors also suggest that urban sparrows had long been free of pressure from avian predators, which left them especially vulnerable when sparrowhawks colonized urban areas.

    Auk 127, 411 (2010).

  4. Chemistry

    Gazing Up at a Cone

    1. Jake Yeston

    Chemical reaction trajectories tend to be largely confined to a single electronic potential energy surface. Occasionally, though, two surfaces intersect when vibrations on the lower surface become vigorous enough to match the energy level of the higher one. Such conical intersections (so termed because the surfaces taper to a cone in their vicinity) are often invoked to explain reaction dynamics but are rarely observed directly. Lim and Kim offer an unusually direct glimpse of a conical intersection in their study of the photolytic cleavage of the PhS-CH3 bond in thioanisole (Ph is phenyl). Specifically, they find that optically populating the first excited state leads predominantly to the production of an electronically excited PhS radical, yet in the narrow vicinity of a vibrational state 722 cm−1 above the excitation threshold, there is a sudden burst of ground-state PhS product. The presence in this energy regime of a conical intersection between the first and second excited states, associated with S-C stretching vibrations, appears to account for this behavior.

    Nat. Chem. 2, 10.1038/nchem.702 (2010).

  5. Astrophysics

    Flowing Farther

    1. Maria Cruz

    The meridional flow of solar plasma, from the sun's equator to its pole at the surface and then back to the equator at depth, carries magnetic flux in a circulation pattern analogous to a conveyor belt. Recent research has shown that in the last solar cycle (number 23), the meridional flow reached higher latitudes than in previous cycles—a phenomenon speculatively associated with the unexpected length of that cycle (12.5 years), which ended in 2009. Now, a flux-transport dynamo model by Dikpati et al. suggests that the combination of a long meridional flow, extending all the way to the pole, and a reduction in return flow speed may indeed have caused the unusually long duration of the last solar cycle and thereby delayed the onset of the current cycle. Long-term data from the Mount Wilson Observatory indicate that in previous cycles (such as number 22)—all with durations close to 10.5 years—the meridional flow only reached latitudes of 60° or 70°. The model predicts cycle durations consistent with those observed. Thus, it may be possible to determine the length of the solar cycle by measuring the latitudinal extent and speed of the meridional flow.

    Geophys. Res. Lett. 37, 10.1029/2010GL044143 (2010).

  6. Climate Science

    Untangling the Threads

    1. H. Jesse Smith

    During the last deglaciation, between approximately 18,000 and 10,000 years ago, the atmospheric concentration of CO2 rose from around 180 to more than 260 parts per million. Although several plausible explanations for this increase have been proposed, it has not yet been possible to assign one over the others definitively. Lourantou et al. provide an additional constraint for the competing scenarios: a record of the isotopic composition of the carbon in atmospheric CO2 over the time interval in question. Because different sources of atmospheric CO2 have distinct carbon isotopic compositions, the authors could determine where in the carbon system the CO2 was coming from by comparing their data with proxy records related to carbon cycle processes, and also by conducting simulations using carbon cycle box models. They conclude that most of the increase in atmospheric CO2 was caused by Southern Ocean ventilation and upwelling, with additional contributions at various times from a decline in marine productivity and a buildup of terrestrial carbon. More sophisticated Earth system models that incorporate carbon cycle–climate feedbacks could help to disentangle the contributions of the processes involved in the rise.

    Global Biogeochem. Cycles 24, GB2015 (2010).

  7. Cell Biology

    Where to Mate

    1. L. Bryan Ray

    When yeast cells detect mating pheromone, they undergo polarized growth or “shmoo” formation at the end of the cell facing the highest concentration of pheromone. Garrenton et al. report that this polarization relies on a localized accumulation of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] and consequent activation of the mitogen-activated protein kinase (MAPK) Fus3. The authors monitored the abundance and localization of PtdIns(4,5)P2 in pheromone-treated cells with fluorescent probes that contained the pleckstrin homology (PH) domain, which binds with high affinity and specificity to PtdIns(4,5)P2. The probe accumulated at the shmoo tip and was not seen in cells lacking the kinase that mediates the synthesis of PtdIns(4,5)P2. The MAPK scaffold protein Ste5 contains a PH domain that binds PtdIns(4,5)P2, and Ste5 was localized to the shmoo tip as long as PtdIns(4,5)P2 synthesis was sustained. The Ste5 scaffold brings together the kinase Fus3 and its activating kinases, and activation of Fus3 in response to pheromone was lost when synthesis of PtdIns(4,5)P2 at the shmoo tip was blocked.

    Proc. Natl. Acad. Sci. U.S.A. 107, 11805 (2010).

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