Editors' Choice

Science  02 May 2014:
Vol. 344, Issue 6183, pp. 450
  1. Astronomy

    Solar Smoke Rings

    1. Margaret M. Moerchen

    The Sun's corona is over a hundred times hotter than the photospheric surface we are most used to seeing, but it is also a trillion times more diffuse. Comparatively faint features within the corona are therefore difficult to discern without blocking the photosphere, either with specialized cameras or during total eclipses. Druckmüller et al. took advantage of several eclipses from 2001 to 2010 to image the corona in white light with a range of exposure times that sampled its high dynamic range. By applying a new high-pass filter to these images, the authors extended the limit of visible features by three orders of magnitude. The observed complex and time-variant structures reflect the dynamic interaction of the coronal plasma with the turbulent magnetic flux over the solar surface. Familiar bright rays and looping arches dominate the corona on the largest scales, but more subtle vortex rings are newly revealed closer to the limb, with twisted helices and bubbles slightly farther out. The size range of structures in this turbulent medium may result from instabilities recorded in various evolutionary stages, and this hypothesis encourages future time-series observations that monitor these features continuously.

    Astrophys. J. 10.1088/0004-637X/785/1/14 (2014).

  2. Education

    Mentoring in All Its Varieties

    1. Melissa McCartney

    Mentoring is ubiquitous throughout the academic system, with mentors and mentees representing a diverse set of backgrounds, skill levels, and priorities. As the mentor culture expands to include both formal and informal peer connections between faculty members, as well as between students, the research community struggles to arrive at a single definition of what exactly mentoring is. Rather than add another definition to the mix, Dawson instead develops a framework for mentoring relationships that is capable of absorbing the current variety. Through an ongoing and nonsystematic survey of mentoring literature, an initial mentoring framework of 20 elements was created. Examples of these elements include selection: how mentors and mentees are chosen; matching: how mentoring relationships are created; and time: both length of relationship and the frequency of meetings during the relationship. Over a 5-year period, this framework was continually refined and reduced to 16 elements, on the basis of feedback from presentations of the framework at conferences and mentoring workshops and through consultations with researchers from education and human resources management. This work will be beneficial for anyone looking to institute a mentoring intervention, as this framework identifies important decision points around which proposals can be designed.

    Educ. Res. 43, 137 (2014).

  3. Parasitology

    Sometimes Schistosomiasis

    1. Caroline Ash

    Schistosomiasis-causing blood flukes infect hundreds of millions of people in tropical regions, but the occurrence of pathology is highly variable, with 5 to 10% of infections becoming severe. Likewise, schistosome infections take very different courses in different strains of mice; a phenomenon that relates to their relative ability to generate lymphocytes classified as CD4+ T helper 17 (TH17) cells. Sick children with blood flukes have also been found to have higher percentages of CD4+ TH17 cells. Ponichtera et al. have now discovered that the antigen-presenting dendritic cells of a mouse strain that develops severe hepatic granulomatous responses to schistosome eggs have a many times greater expression of a C-type lectin receptor called CD209a (a homolog of human ICAM-3–grabbing nonintegrin) on their cell surfaces as compared with a mouse strain that shows little pathology. CD209a is essential for the induction of the cytokines interleukin-1β and interleukin-23 that stimulate CD4+ TH17 cell development. Possibly the pathology of severe schistosomiasis is caused by elevated CD209a levels in some people sensitizing recognition of the fucose-rich glycans that coat the parasites' egg surface.

    J. Immunol. 10.4049/ jimmunol.1400121 (2014).

  4. Cell Signaling

    Finding Folliculin's Function

    1. L. Bryan Ray

    The tumor-suppressor protein folliculin (FLCN) is turning up as an important component of distinct cell signaling pathways that control cell growth and metabolism. FLCN's structure provides no recognizable clues to its function, but mutations in FLCN cause a cancer syndrome in humans. Exactly how it does so has remained unclear. Recent work showed that FLCN can act as a GAP (guanosine triphosphatase—activating protein) to control the kinase mTORC1, which regulates cell growth. Possik et al. report that FLCN binds to and inhibits another key regulatory kinase, AMPK (adenosine monophosphate–activated protein kinase), which helps maintain energy balance in the cell. Loss of FLCN acts through AMPK to help cells resist stresses such as starvation. This effect was mediated, at least in part, by increased autophagy. These results suggest that the loss of FLCN function in cancer cells may make them more tolerant of stress and thus more effective at invading tissues of the host organism.

    PLOS Genet. 10.1371/journal.pgen.1004273 (2014).

  5. Applied Physics

    Inducing a Single Vibration

    1. Ian S. Osborne

    Optomechanical systems typically consist of a mechanical oscillator or cantilever that can be driven by the optical radiation pressure of light. The light can either amplify the motion of the cantilever or be used to reduce the amount of vibration and effectively cool it. Recent work has demonstrated cooling to the extent that the number of vibrations, or phonons, in an oscillator can be quantized, even reaching the quantum-mechanical ground. Galland et al. introduce a method to introduce a single phonon into their mechanical oscillator. Starting off in the quantum-mechanical ground, they pump the system with a laser pulse that generates an entangled phonon-photon pair. Detection of the photon then heralds that a single-phonon state has been induced into the oscillator. The ability to deterministically control the number of vibrational quanta in such an optomechanical system has important implications for the likes of quantum information processing and quantum enhanced sensing applications.

    Phys. Rev. Lett. 112, 143602 (2014).

  6. Biomedicine

    Breaking Down a Barrier

    1. Paula A. Kiberstis

    Ischemic stroke, one of the most common causes of death and disability, occurs when a blood vessel supplying oxygen and nutrients to the brain becomes obstructed. Besides injuring brain cells, a stroke disrupts the function of endothelial cells in the blood-brain barrier (BBB), which exacerbates brain damage. The cellular mechanisms underlying BBB breakdown during a stroke are poorly understood. To study this, Knowland et al. created transgenic mice expressing a fluorescent reporter gene in endothelial cells and then, with the help of fluorescent dyes, used two-photon microscopy to image BBB function in the mice after an experimentally induced stroke. In contrast to a prevailing theory emphasizing the primary role played by a diffusion barrier called the tight junction, the imaging study revealed that the initial cause of BBB breakdown (occurring 6 hours after the stroke) was aberrant up-regulation of transcytosis, a process by which molecules are transported across the endothelial cell. It was not until 24 to 48 hours after the stroke that tight junctions showed structural defects. Understanding this sequence of events may lead to therapies that limit the brain damage caused by a stroke.

    Neuron 10.1016/j.neuron.2014.03.003 (2014)

  7. Paleontology

    Herbivores, After All

    1. Sacha Vignieri

    After the mass extinctions of the Cretaceous, many terrestrial ecosystems were dominated by large flightless birds. Although the bill anatomy of some of these species suggest a carnivorous diet, the diet of the largest of these, Gastornis, has been debated. Angst et al. conducted carbon isotope analysis on fossils of Gastornis and several contemporaneous herbivorous mammals across several European sites and compared these to isotope profiles from extant birds with known diets. The analysis revealed that Gastornis had an herbivorous diet. In fact, in order for a carnivore to have shown similar values it would have needed to prey almost entirely on species that fed on a type of plant that did not evolve until approximately 14 million years after the sampled individuals lived. Isotope evidence was corroborated with morphological comparison of Gastornis bill anatomy relative to that of extant birds, which suggested that the large muscle attachment area in Gastornis jaws is similar to that found in herbivorous species. This firm placement of Gastornis as an herbivore suggests that the community structure of Paleocene Europe was different from that found in North America at the time, and may in fact have been quite similar to the later systems seen on islands, such as Madagascar, where large flightless birds filled many different niches.

    Naturwissenschaften 10.1007/s00114-014-1158-2 (2014).