This Week in Science

Science  19 Aug 2011:
Vol. 333, Issue 6045, pp. 918
  1. Propagating Pictures of Malaria

    Malaria infection may originate from just one infective mosquito, and so to be able to out-run the host's defenses, the parasite has to ramp up its numbers rapidly. The range of checks and balances acting during infection cannot be measured by simply taking blood samples. Metcalf et al. (p. 984; see the Perspective by Day and Fowkes) used several large data sets to mathematically model the ecology of mouse malaria and developed an important measure of the infection, the effective propagation number (Pe). Pe varies through time, depending on the strength of the host's immune responses and the depletion of mature red blood cells.

  2. Aneuploidy and Cancer


    Cancer cells often show aneuploidy—a state in which cells have an abnormal number of chromosomes (see the Perspective by Kolodner et al.). Sheltzer et al. (p. 1026) constructed yeast strains containing extra copies of a single chromosome to analyze the effects of aneuploidy in cells. Aneuploidy led to other genetic abnormalities in the cells similar to the sort of “genomic instability” that is a hallmark of cancer cells. Cancer genome analysis by Solomon et al. (p. 1039) revealed how aneuploidy may arise in a subset of tumors. A broad range of human tumors harbor inactivating mutations in STAG2, an X-linked gene that encodes a subunit of cohesin, a protein complex that controls the separation of sister chromatids during cell division. In cultured tumor cells, targeted replacement of the defective copy of STAG2 with the wild-type gene partially reversed the cells' chromosomal instability, which supports the hypothesis that STAG2 is a tumor suppressor gene that helps to prevent mishaps in chromatid separation.

  3. Sunspot Forecasting

    Sunspots are manifestations of solar magnetism on the surface of the Sun, associated with major eruptive events that can cause power outages on Earth and damage satellites and spacecraft. Ilonidis et al. (p. 993) developed a technique that allows sunspots to be detected 1 to 2 days before they appear at the surface, promising to improve space weather forecasts. Application of this technique to four emerging sunspot regions shows that the magnetic fields that form sunspots in the deep solar interior are stronger than previously predicted and are generated at least 65,000 kilometers below the surface.

  4. Cold-Atom Frustration

    The interaction between the charge- and spin-degrees of freedom of condensed-matter systems can often give rise to a vast suite of complex electronic and magnetic phases. Struck et al. (p. 996, published online 21 July) show that the ability to tune the sign and strength of the interaction between atoms of a Bose-Einstein condensate trapped in a triangular optical lattice can be used to study magnetic ordering and the complex phases associated with magnetic frustration. The cold-atom approach offers the possibility of experimentally tunable system that can be used to simulate the complex interactions that occur in condensed matter systems.

  5. Circle of Five

    Lithium ion batteries operate by storing negative charge in a layered carbon lattice and compensating it with lithium ions (Li+) inserted between the layers. Zabula et al. (p. 1008) performed careful crystallographic and spectroscopic characterization of the polycyclic aromatic hydrocarbon corannulene (C20H20). Reduction with four charge equivalents produced a dimeric sandwich motif, in which two carbon sheets encase a ring of five Li+ ions, with several external ions compensating the rest of the charge. The findings revise a widely accepted proposed structure positing a less dense arrangement of four internal Li+ ions.

  6. Equal Opportunity?

    Workforce diversity has been considered central to the U.S. NIH objective of improving the nation's health through research. Ginther et al. (p. 1015; see the Policy Forum by Tabak and Collins) estimate the association between the self-identified race or ethnicity of an applicant for an NIH R01 research grant and the probability of receiving an award from 2000 to 2006. After controlling for demographics, educational background, training, prior research, and employer the authors found that black applicants were significantly less likely to receive research funding than white applicants.

  7. Making a Move

    The distributions of many terrestrial organisms are shifting in latitude and/or elevation in response to changing climate. In a meta-analysis of data from studies in both hemispheres, Chen et al. (p. 1024) show that distributions of a wide range of plant and animal species are shifting faster than previously realized. A clear association was identified between magnitude of distribution change and magnitude of warming. These estimates of rate of change may now be used with greater confidence to parameterize models of the impact of climate change on biodiversity.

  8. Do Teaching and Research Mix?

    Graduate students in the sciences put a lot of focus on research. Feldon et al. (p. 1037) analyzed whether time that graduate students spent teaching helped their research programs. An analysis of the quality of research proposals submitted by graduate students suggested that students involved in teaching developed greater skills than those who spent their time only on research.

  9. Wires on Sapphire


    Long, aligned semiconductor nanowires are needed for their eventual incorporation into electronic devices. Tsivion et al. (p. 1003) show a route to grow GaN nanowires with specific growth directions on different planes of sapphire and show how the different sapphire planes affect the wire quality and growth. The wires produced were successfully incorporated into a functional electroluminescent device.

  10. Forests as Carbon Sink

    The forests of the world are absorbing a substantial fraction of the CO2 released to the atmosphere by anthropogenic activities. Pan et al. (p. 988, published online 14 July) provide an updated and improved estimate of the role of the world's forests in the global carbon budget. Using the latest inventory data and analyses allowed an estimate of the average global annual uptake of atmospheric CO2 by forests from 1990 to 2007 at 2.4 petagrams of carbon, an amount comparable to earlier estimates of the entire terrestrial carbon sink.

  11. Portrait of a Graphene Dopant

    The properties of electronic materials can be modified by the addition of dopants, which are usually elements with a different valence shell configuration that can add or take away an electron from the material's conduction band. Zhao et al. (p. 999) studied nitrogen-doped graphene grown on copper with scanning tunneling microscopy, as well as with a variety of spectroscopic methods. The nitrogen atom was observed to substitute for carbon in the graphene lattice, and strong modification of the electronic properties was localized to a few lattice spacings around the dopant atom.

  12. All Whirling at Once

    Rotational spectroscopy is a powerful probe of gas-phase molecular structure, of particular use in characterizing distant interstellar compounds that are inaccessible to most other techniques. Interpreting the spectra can be challenging, however, as they often resemble a dense forest of signals arising from molecules with a range of different isotopic compositions. Schröter et al. (p. 1011, published online 7 July; see the Perspective by Pate) devised a technique that combines rotational spectroscopy with mass spectrometry, facilitating the assignment of overlapping signals to their respective sources in an isotopically complex mixture. They demonstrate the technique on a carbon disulfide sample (comprising multiple combinations of 12C, 13C, and four sulfur isotopes) and further describe its applicability to probing rotational correlations with varying electronic structures, as well as masses.

  13. Vertebrate Gene Regulation Evolution

    A large amount of DNA in vertebrate genomes shows evolutionary conservation, but does not appear to be part of a mature transcript. Lowe et al. (p. 1019; see the Perspective by Wray) observed shifts during the evolution of vertebrate gene regulation by estimating the emergence of conserved noncoding elements in vertebrate genomes and inferring the target genes that they likely control. Early evolutionary innovations involved transcription factors and other developmental genes; then came a period of changes to genes involved in extracellular signaling, and, most recently, there has been a period in which these changes occurred most frequently. These shifts occurred simultaneously and independently in five vertebrate lineages.

  14. Making Better Antibodies Through Inhibition

    Immunotherapies that promote anti-tumor immunity—including cancer vaccines, adoptive cellular therapies, and monoclonal antibodies—are increasingly being pursued in the clinic to treat a variety of cancers. One monoclonal antibody that is of particular interest is an agonist antibody specific for CD40, a member of the tumor necrosis family of receptors, which has shown modest efficacy in small clinical trials. Antibody ligation of CD40 promotes maturation of antigen-presenting cells which in turn can drive enhanced T cell- and macrophage-mediated tumor toxicity. Li and Ravetch (p. 1030; see the Perspective by Smyth and Kershaw) now show that optimal anti-tumor immunity in a variety of mouse models required that the Fc portion of the CD40 antibody engaged the Fcγ receptor, FcγRIIB. This was unexpected because FcγRIIB typically transduces inhibitory signals to immune cells. Engineering of antibodies that preferentially bind activating Fcγ receptors showed that only the inhibitory Fcγ receptor was able to mediate an anti-tumor effect. Thus, careful engineering of the Fc region should be considered when designing monoclonal antibody therapeutics.

  15. Inspirational Teaching

    High-school students bring their personalities and opinions into the classroom, making it sometimes difficult for teachers to get their subject matter across. Allen et al. (p. 1034) now show that a year-long coaching program aimed at the social interactions between teachers and students can help the teachers produce better classroom outcomes, including measurable improvement in student learning. Thus, as important as it is for teachers to convey their subject matter well, it seems also important for them to manage the social dynamic with their students effectively.