Editors' Choice

Science  02 Jul 2010:
Vol. 329, Issue 5987, pp. 14
  1. Economics

    Educating the Consumers

    1. Brad Wible

    Many efforts to improve education aim to increase the supplies of teachers and schools; in some cases, supply may outstrip demand, which is thought to be driven in part by long-term earnings that accrue with increasing education. However, many families, especially those in developing countries, may lack complete information about long-term returns, and misperception of the economic benefits could influence demand. In the Dominican Republic, for example, large declines in enrollment are seen after the eighth grade, which marks the final year of compulsory education. Jensen asked 2250 of those eighth-grade boys to estimate the earnings of adult men who had completed primary school only, and also of men who had spent 4 more years to complete secondary school. The estimated benefit for completing secondary school was only one-fourth as large as the actual benefit. A randomly chosen subset of boys was then given accurate information about the enhanced earnings. Four years after the initial survey, those boys had completed roughly 0.2 more years of schooling as compared to boys who were not given earnings information. Although some educational interventions offer near-term financial rewards directly to students, for example in return for high test scores or reading lots of books, a supply of earnings information may be an inexpensive way to promote more years of schooling.

    Quart. J. Econ. 125, 515 (2010).

  2. Neuroscience

    Self-Assembled Circuits

    1. Pamela J. Hines

    The mammalian brain develops as growth factors and transcription factors define fields of morphogenesis, with some types of neurons migrating outward from deep generative zones and other types of neurons migrating along the surface from distant generative zones. The result might be compared to a geopolitical map supported by an infrastructure of shipping, communication, and regulatory networks. Zhou et al. used a mouse mutant in which the neocortex had been disconnected from the rest of the brain in order to analyze the development of the surface map. In normal mice, a few weeks of postnatal development complete the brain's organization; the mutant mice survive during this phase but die at about 3 weeks of age. During these weeks, the mutant mice, despite having disconnected brains, display a variety of behaviors: eating, drinking, walking, and swimming. Some aspects, such as circadian rhythms of activity, are noticeably disrupted. Interneurons are present at normal densities, although reduced numbers reflect the generalized atrophy of their brains. Projection neurons seem particularly susceptible to attrition, and layer 4 of the cortex seems particularly dependent on its connections. Otherwise, the disconnected mouse brain shows a considerable ability to organize itself.

    J. Neurosci. 30, 7928 (2010).

  3. Cell Biology

    Exploiting an Exploiter

    1. Helen Pickersgill

    Viruses have evolved diverse mechanisms to take control of the host cells in which they replicate. All plus-stranded RNA viruses, such as hepatitis A and poliovirus, use host cell membranes for replication in the cytoplasm. Coronaviruses such as SARS and mouse hepatitis virus (MHV), which infect the mammalian gastrointestinal and respiratory tracts, induce the formation of double membrane vesicles; the cellular origin of these membranes has been unclear. Reggiori et al. find that MHV accumulates cellular membranes by hijacking part of a protein degradation pathway known as ERAD, which is associated with the endoplasmic reticulum. As a quality-control step in protein degradation, the chaperone protein EDEM1 is sequestered in small vesicles away from the endoplasmic reticulum to distinct cellular compartments. MHV exploits this event to obtain endoplasmic reticulum–derived membranes for its own use. Both EDEM1 and the autophagy-associated protein LC3 associated with virus-induced double membrane vesicles, and down-regulation of LC3 protected cells from MHV infection. By identifying the mechanism whereby this coronavirus recruits host membranes for replication, the authors have identified potential therapeutic targets, which may also be applicable to other viruses in this family.

    Cell Host Microbe 7, 500 (2010).

  4. Neuroscience

    No Slacking Off

    1. Lisa D. Chong

    Characteristics of the inherited mental disorder fragile X syndrome are deficiencies in learning, memory, and cognition. The condition results from the lack of fragile X mental retardation protein (FMRP), which binds to RNA and to cytosolic proteins involved in protein synthesis. Brown et al. have found that FMRP binds to a third type of target: a membrane protein called Slack, which is a sodium-activated potassium channel. FMRP increased Slack channel activity in a Xenopus oocyte expression system and altered the pattern of electrical conductance, and sodium-dependent potassium channel conductance was reduced in cells isolated from the brain of mice lacking FMRP. These channels are known to maintain neuronal activity during high-frequency stimulation, and these findings point to a role for FMRP in sustaining a level and pattern of channel activity during repetitive neuronal stimulation.

    Nat. Neurosci. 13, 10.1038/nn.2563 (2010).

  5. Geology

    Slow Slip in Depth

    1. Brooks Hanson

    The largest earthquakes occur at subduction zones, which accommodate the convergence of two tectonic plates. Thanks to dense GPS and seismic networks along these zones, we have a more detailed, and now complicated, view of how this convergence occurs: Many subduction zones exhibit a phenomenon termed “slow slip.” Gomberg et al. provide an overview of this process in the Cascadia Subduction Zone, where it has been heavily studied. Here, the GPS data show that the westward motion of the North American plate reverses regularly over periods ranging from days to several weeks. Unusual small earthquake tremors at depths of 40 to 50 km along the subduction zone, a bit deeper than the area expected for major quakes, increase dramatically at this time and explain the lag in plate motion. Nearly 40 such events have been studied in the Cascadia subduction zone, and they also vary from north to south. The current model posits that the slow slip is related to fluid release by metamorphic reactions in the subduction zone, but implies that the plate interface at depth is weak and critically stressed. Thus understanding and monitoring slow slip may be critical for hazard assessment here and elsewhere.

    Geol. Soc. Am. Bull. 122, 963 (2010).

  6. Chemistry

    Stacked Platinum

    1. Marc S. Lavine

    Platinum is a remarkably versatile chemical catalyst. Recently, chemists have also begun to direct its coordination properties toward the assembly of complex supramolecular structures. Frischmann et al. constructed a family of tunable Schiff base proligands that were designed to self-assemble in head-to-tail fashion when coordinated to Pt2+. The proligands—substituted salicylaldimines—could be generated in situ or before metalation. Puckered Pt4 macrocycles formed that would then stack in either single or alternating configurations, depending on the bulkiness of the peripheral R group, with the latter dominant as the R group increased in size. The authors were surprised to find that when R was 2-hexyldecyl, the columnar macrocycles formed lyotropic liquid crystalline phases when concentrated in nonpolar organic solvents. The complexes showed poor solubility in cyclohexanone, but when cast from a solution using this solvent, they formed parallel columns that were spaced 4 nm apart and extended for hundreds of nanometers. These arrays thus offer a method to access nanotubes with stacked columns of Pt2+ ions.

    J. Am. Chem. Soc. 132, 7668 (2010).

  7. Chemistry

    Oxidative Flow

    1. Jake Yeston

    Alcohol oxidation is a common step in the synthesis of pharmaceutical intermediates, and oxygen is in many ways the ideal reagent to induce it. The gas is plentiful and nontoxic, and so is the by-product, water, that it's shuffled into as the reaction ensues. Unfortunately, oxygen also has several serious drawbacks that have largely precluded its use in this context. In too pure a form, it can react violently with solvents and other peripheral organic fragments. At the same time, it is a competing challenge to keep enough of the gas mixed with the liquid reaction medium to inhibit catalyst decomposition. As a result, oxidations still often rely on expensive reagents and generate associated toxic by-products. Ye et al. now present a reactor design that makes substantial progress in surmounting these obstacles. They employ a dilute stream of 8% oxygen in nitrogen, so as to avoid combustion hazards, and they implement a continuously flowing reaction process to optimize mixing. Using several previously reported palladium-based catalysts, they demonstrate high alcohol oxidation yields across a diverse substrate pool on scales ranging from tens of grams to a kilogram.

    Green Chem. 12, 10.1039/c0gc00106f (2010).