This Week in Science

Science  07 Oct 2005:
Vol. 310, Issue 5745, pp. 13
  1. The Blind Decision-Maker

    CREDITS: JOHANSSON ET AL.

    What is the relation between intention, choice, and introspection? Johansson et al. (p. 116) used a card trick in a simple decision task to identify a dissociation between awareness of the initial choice and the outcome when this has been surreptitiously altered. Participants were given a choice to make in the attractiveness of two female faces shown on two cards, and then asked to justify their choice as they examined the card with the alternative they had allegedly chosen. In some trials, the experimenters covertly switched the cards. In the majority of such trials, participants failed to recognize the switch, and proceeded to justify their choice of the card they were handed, although it was not the one they had selected.

  2. Chemically Switching Transistors

    Solution-based processing of inorganic semiconductors offers the potential of a high throughput and inexpensive fabrication alternative to conventional silicon-based technology. Talapin and Murray (p. 86) fabricated field-effect transistors with the conductive channels assembled from PbSe semiconductor nanocrystals via solution-phase processing. The nanocrystals form into ordered arrays and are initially insulating. Exposing the materials to hydrazine decreased the spacing between the nanocrystals, which increased their electronic coupling and resulted in n-type conduction. A mild heat treatment that desorbed the hydrazine switched the conduction back to p-type. The ability to readily switch reversibly between n- and p-transport will enable complementary metal oxide semiconductor circuitry to be fabricated with this technique.

  3. A Molecular Turnstile

    Progress in rational chemical synthesis has fostered the miniaturization of macroscopic engineering components, such as gears and ratchets, to the molecular scale. Fletcher et al. (p. 80; see the Perspective by Siegel et al.) have applied a sequence of reactions to a biaryl compound that effectively mimics the action of a turnstile. Through a succession of hydroxyl protection and deprotection steps, coupled with enantioselective lactone reductions, the authors achieve 360° rotation of one aryl ring about the other in a specific selected sense. The choice of reagents determines whether rotation about the carbon-carbon single bond axis is clockwise or counterclockwise.

  4. Sounding Out Subsurface Nanofeatures

    CREDITS: SHEKHAWAT AND DRAVID

    Nondestructive subsurface imaging in the size range from 10 to 100 nanometers is particularly challenging but would be valuable in applications ranging from device construction to cell biology. Shekhawat and Dravid (p. 89; see the Perspective by Diebold) have developed a technique, scanning near-field ultrasound holography, that takes advantage of both the phase and amplitude of scattered ultrasound waves to produce nanoscale-resolution images of internal substructure. Examples include images of voids in polymer coatings of SiN shallow trench structures and malaria parasites in red blood cells.

  5. A Bright Spot in the Distance

    Saturn's large moon Titan may have active exchange between its methane-rich lower atmosphere and surface. Cassini has recently studied one of the brightest surface features on Titan, which seems to have an unusual origin compared with other features that have been observed on the rest of the surface. Barnes et al. (p. 92) present analyses of data from several instruments on the spacecraft, as well as from the Keck Observatory, which show that this feature probably is produced by a methane-rich ground fog or veneer of methane rainfall.

  6. Tracking Marine Migrations

    Satellite tracking techniques have been used by Weng et al. (p. 104) and Bonfil et al. (p. 100) to reveal the habits and movements of salmon shark in the North Pacific and white shark in the southern Indian Ocean, respectively (see the news story by Pennisi). The endothermic salmon shark's niche extends from subtropical to subarctic waters. The white shark can rapidly cross distances in excess of 10,000 kilometers, from South Africa to Australia, in addition to regular migration along the southeastern South African coasts.

  7. Doing Double Duty

    A single gene in Arabidopsis, AVP1, encodes the pyrophosphatase that regulates acidity in the vacuole of the plant cell. Li et al. (p. 121; see the Perspective by Grebe) now report that this same enzyme also affects transport of the plant hormone auxin. Disruptions in auxin transport result in disruptions in shoot and root development. The effects of AVP1 on auxin function are mediated through distribution of the auxin efflux facilitator.

  8. Genes and Waves

    Slow electroencephalogram oscillations, or delta waves, represent one of the most important aspects of sleep and its regulation because they determine the depth of sleep, sleep consolidation, and sleep quality. Delta oscillations are also a direct measure of the need for sleep, and they are tightly regulated during development and aging. Maret et al. (p. 111) identified and functionally characterized a gene that codes for a vitamin A—activated ligand-dependent transcription factor, retinoic acid receptor beta (Rarb). This gene regulates slow-wave oscillations during sleep.

  9. Helping Neuronal Repair

    Regeneration of axons in the central nervous system after injury is limited in part because of inhibitory signals derived from myelin and glia. Koprivica et al. (p. 106; see the news story by Miller) screened a bank of small molecules to identify molecules that might alleviate the inhibition. The results implicate the epidermal growth factor receptor (EGFR) in the endogenous signaling that allows myelin to block neurite outgrowth. Of about 400 small molecules screened, tyrphostin variants seemed particularly effective. Because EGFR inhibitors are already in clinical use for cancer patients, it is possible that these findings could be exploited rapidly in the treatment of neuronal injury.

  10. Clues for the Origin of Killer Flu

    CREDIT: TUMPEY ET AL.

    The 1918 influenza pandemic killed more people than did the fighting in World War I, but the reasons for this virus's extraordinary virulence have remained enigmatic. Tumpey et al. (p. 77; see the news story by Kaiser) have used reverse genetics to generate an influenza virus bearing all eight gene segments of the pandemic virus. Subsequent pathogenicity studies in mice, chick embryos, and human lung cells show that the 1918 hemagglutinin and polymerase genes are responsible for the high virulence. The 1918 virus does not bear the molecular signatures of modern highly pathogenic strains, but it is lethal to chick embryos. The fully reconstructed virus kills mice rapidly and shows a high apical release from cultured human lung cells. The lung pathology in mice shows high viremia, destruction of the alveolar architecture, and distinct oedematous-hemorrhagic pathology. This work provides predictive insights for therapeutic options in case of a forthcoming influenza pandemic.

  11. Challenging Preconceptions

    Our knowledge of our own personalities comes from a long-standing familiarity with ourselves and, in a similar fashion, we often can gauge quite accurately the personalities of others whom we know well. In contrast, the stereotypes we hold may be based upon an amalgam of bits and pieces, gathered from public figures or celebrities and mixed with singular aspects of individuals whom we encounter casually or impersonally. Terracciano et al. (p. 96; see the Perspective by Robins) have compiled a well-established personality inventory to extract self-ratings, as well as observer ratings of specific people across roughly 50 nationalities, and a character survey to elicit the same sort of personality assessments of the mythic stereotypical native of these same nations. The first two sets of ratings based on specific ratings correlate well with each other when aggregated across the entire sample of each group; however, neither agrees with the common perception of the national character.

  12. Battles of the Sexes

    In mammals, the male gamete specifies male (XY) versus female (XX) offspring, but in birds, the female gamete determines male (ZZ) versus female (ZW) offspring. Albert and Otto (p. 119) develop a model that explores the evolution of display trait alleles that are expressed in both sexes, and considers how sexually antagonistic selection favors males or females depending on the mode of sex determination. Females evolve preferences to increase the fitness of daughters at the expense of sons in XY species, which results in less flashy male displays. In contrast, females are more likely to evolve preferences that increase the fitness of sons at the expense of daughters in ZW species, which leads directly to the evolution of exaggerated male displays. This model may explain why sexually selected characters are more commonly exaggerated in birds and butterflies, which both have ZW sex determination.

  13. Protons in Motion

    In aqueous solution, proton transfer from acidic to basic molecules is among the fastest and most common chemical reactions. Although the surrounding water clearly facilitates the process, the molecular details of its involvement remain fuzzy. Mohammed et al. (p. 83) have used infrared spectroscopy to observe an intermediate in the transfer of H+ from a photoexcited pyrene-derived acid to a chloroacetate base. The absorption of this transient complex, which persists for ~100 picoseconds, suggests an Eigen cation (H3O+) structure shuttling H+ from acid to base, consistent with the long-hypothesized von Grotthus transport mechanism. Spectra of the deuterated analog support this assignment.

  14. Astrocytes, Adenosine, and Synaptic Plasticity

    How do glial cells modulate or even control neurotransmission? Pascual et al. (p. 113) created transgenic mice in order to conditionally suppress release of transmitters from astrocytes. Basal synaptic transmission was increased, and long-term potentiation was decreased, in the hippocampus of the transgenic animals. Pharmacological studies further supported the hypothesis that adenosine, derived from adenosine triphosphate released by astrocytes, is a critical modulator of synaptic activity in these experiments.

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