Editors' Choice

Science  03 Jun 2011:
Vol. 332, Issue 6034, pp. 1128
  1. Astrophysics

    The Big Bulge

    1. Maria Cruz

    A classical spiral galaxy has three stellar components: a central, roughly spherical bulge; a thin disk around this bulge; and a halo. Typically, the bulge resembles an elliptical galaxy. However, not all bulges follow this classical picture; some, which astronomers call pseudobulges, are disk-like. Fisher and Drory made an inventory of galaxy bulge types within 11 million parsecs from Earth (1 parsec corresponds to ∼3.26 light-years). They counted the number of elliptical galaxies (pure bulges) and spiral galaxies with classical bulges, with no bulges, or with pseudobulges by star formation rate and stellar mass. Galaxies without a bulge (pure disk galaxies) or with a pseudobulge are the most common type in the local region analyzed. In this region, two-thirds of new stars are formed in galaxies with pseudobulges and three-quarters of the stellar mass is in disks. It is not clear how pseudobulges form—whether by merging of galaxies or by slow, steady evolution of the disk. The frequency of enhanced star formation in the central regions of galaxies with bulges indicates that long-term, non-episodic processes are at play in bulge growth. If pseudobulges are not the result of mergers, then it is difficult to reconcile the numbers found in this study with those predicted by models of galaxy evolution.

    Astrophys. J. 733, L47 (2011).

  2. Education

    One Size Does Not Fit All

    1. Pamela J. Hines

    Some children, particularly those with a more fearful temperament, are more sensitive than others to the influence of parents, teachers, and environment. Studying preschoolers, Kegel et al. attempt to link this with a particular genetic polymorphism. Children played a literacy-geared computer game that delivered instruction and assignments to all participants, but differed in whether it delivered feedback about the children's choices. A feature that distinguished the groups of children was whether they carried the long variant of the dopamine D4 receptor gene, which is associated with lower dopamine reception efficiency. Children who carried this polymorphism were more susceptible to the effects of feedback from the computer program. They outperformed the control group when feedback guided their learning, and they did worse than the control group when feedback was absent. In contrast, children with the short variant of the gene seemed to be unruffled by the presence or absence of feedback. For education, just as for shoes, a good fit to the individual produces the best result.

    Mind Brain Educ. 5, 71 (2011).

  3. Climate Science

    Wind Winding Down

    1. H. Jesse Smith

    Increasing concentrations of greenhouse gases in the atmosphere, emitted by human activities, have caused Earth's climate to warm. Climate warming has been linked to a host of other environmental changes, one of the most evident being an increase in the amount of water present as vapor in the atmosphere, a simple change entirely predictable by the Clausius-Clapeyron equation. Other possible changes to the climate system are not so simple or predictable. Gastineau and Soden evaluate the potential impact of warming on windiness, combining daily satellite observations and climate model simulations in order to determine how tropical surface wind extremes may have responded over the past two decades. They report that both observations and models show a reduction in the strongest wind events, in response to higher tropical sea surface temperatures, and that light wind event frequencies have increased over the same period. These findings help to confirm what has up to now only been suggested by models. The authors suggest that the well-documented increase in the frequency and intensity of extreme precipitation events, which at first may seem inconsistent with a weakening of the large-scale circulation, is therefore mainly a result of increasing atmospheric water vapor.

    Geophys. Res. Lett. 38, L09706 (2011).

  4. Microbiology

    Multiple Metabolic Cooperations

    1. Caroline Ash

    The toxic liquids that ooze out of old mine workings have been fruitful hunting grounds for microbial ecologists, primarily because the range of organisms that can tolerate such extreme conditions is limited and makes for tractable wild ecosystems to study. Bertin et al. undertook a metagenomic investigation of the microflora in a stream biofilm exiting the former mine of Carnoulès in France. They found a community dominated by seven organisms with complementary and apparently intertwined metabolisms. Three strains allied to Thiomonas, Acidithiobacillus, and Gallionella are inorganic nitrogen and carbon dioxide fixers. These primary producers supply other members of the consortium with organic nutrients, in an apparently coordinated way: For example, an Acidobacteria clade possesses transporters for simple carbohydrates, whereas a Thiobacillus-like organism is equipped to handle complex carbohydrates. A candidate new species of Fodinabacter appears to make important contributions to recycling organic compounds released by other organisms, and in turn provides them with essential cofactors, such as cobalamin, which then activates iron oxidation in Acidiothiobacillus. The seven also seem to be represented by other genotypes, which indicates an ability to shift the metabolic emphasis when conditions change.

    ISME J. 5, 10.1038/ismej.2011.51 (2011).

  5. Cell Biology

    Not Death-Defying

    1. Stella M. Hurtley

    Caveolae are membrane invaginations found at the surface of mammalian cells that are enriched in cholesterol. Cholesterol-binding proteins known as caveolins play a key role in caveolar formation and are also involved in intracellular cholesterol transport. Mutation or disruption of caveolin genes have been linked to a variety of pathologies, including lipodystrophy, cardiovascular disease, diabetes, and cancer. Bosch et al. examined the cellular pathology associated with caveolin disruption in embryonic fibroblast cells from caveolin 1 (CAV1)–deficient mice. The cells exhibited reduced proliferation and survival when subjected to glucose restriction—a phenotype associated with compromised mitochondria. Indeed, mitochondrial membranes from the CAV1-deficient cells contained elevated levels of free cholesterol, which was associated with reduced resistance to antioxidants. The mitochondria thus accumulated reactive oxygen species, which promoted cell death. Thus, mitochondrial dysfunction appears to be the underlying cause of the variety of pathologies observed in CAV1-deficient animals.

    Curr. Biol. 21, 681 (2011).

  6. Policy

    Measuring Subsidy Success

    1. Barbara R. Jasny

    After devastating mudslides and floods in 1998 killed thousands of people and displaced millions, the Chinese government undertook a massive effort to fight erosion, called the Sloping Land Conversion Program (SLCP). Under the SLCP, farmers on steep slopes in the Yangtze and Yellow River basins have been given cash subsidies and rice in exchange for allowing their farmland to be restored to forest or grassland and finding jobs other than farming. Part of the goal was to promote a change in the work activities of the people living in these areas to something that would be more sustainable for the ecosystem. Li et al. surveyed 20 villages containing participants and nonparticipants in 2008 to determine the effects of this program on the economics of people in a rural area of western China. Participation in the program increased household income, especially for low- and medium-income households. Income inequality was less among households participating in the SLCP than among those that did not; however, it did not change the traditional employment of the participants in the way that had been anticipated—many were still involved in forestry-related activities or animal husbandry.

    Proc. Natl. Acad. Sci. U.S.A. 108, 7721 (2011).

  7. Physics

    Scattered Enhancement

    1. Ian S. Osborne

    One route to enhance the operation of solar cells is to mop up as much of the incident light as possible for subsequent conversion into useful electric current. However, there tends to be a tradeoff between the cost associated with fabricating a complex structure, as well as the amount of material used, and the overall payoff in terms of improved performance. A simple approach is to use a randomly textured back surface reflector to increase the chance of absorption. The optical properties of metal nanoparticles, particularly their ability to strongly scatter light, have made them targets for exploration. Moreover, nanoparticles can couple the scattered light into a nearby dielectric. Spinelli et al. use simulations to systematically study how the shape and size of silver nanoparticles influence the scattering of light into a dielectric substrate. Their results provide a method to better understand the scattering and incoupling processes involved and the possibility of optimizing optoelectronic sensors and photovoltaics at the design stage.

    Opt. Express 19, 303 (2011).

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