Editors' Choice

Science  17 May 2013:
Vol. 340, Issue 6134, pp. 788
  1. Geophysics

    Hawaii's Deep Plumbing System

    1. Nicholas S. Wigginton
    CREDIT: © DOUGLAS PEEBLES/CORBIS

    Hawaii's Deep Plumbing System Mauna Loa and Kilauea—separated by only ∼30 km on the island of Hawaii—are presently two of the most active volcanoes in the world. They are fueled by the magmatic activity associated with the Hawaiian hot spot, which provides a rich source of melted mantle materials. Does the activity at one influence the other? Shirzaei et al. show, using gas measurements and geophysical data, that the two volcanoes were linked during surges of uprising mantle material between 2006 and 2008. Satellite data of ground deformation and time-dependent inverse modeling suggest that the two volcanoes simultaneously inflated during a time of increased magma supply. A cluster of seismic events 20 km below Mauna Loa, near the deep magma source, immediately preceded activity at Kilauea—including increased CO2 emissions and a series of shallow "silent earthquakes." During times when the deep magma supply is not surging, there may be independent or anticorrelated volcanic activity at either volcano, related to older, shallower trapped magma.

    Geophys. Res. Lett. 40, 10.1002/grl.50470 (2013).

  2. Economics

    A Look at the Data

    1. Gilbert Chin

    A lot of people in the United States do not have health insurance, and one aim of the Patient Protection and Affordable Care Act is to expand the coverage of low-income individuals. In 2008, Oregon enrolled about 6000 new applicants, chosen via lottery, in its Medicaid plan. Baicker et al. now describe the 2-year outcomes for these individuals in comparison to a control group of 6000 people who had applied but were not chosen. In terms of finances, the enrollees had fared better: They had lower medical expenses and had incurred less debt. In terms of health care access, the enrollees had made more office visits and taken more advantage of preventive screenings. Neither of these outcomes is particularly surprising given the function of health insurance. What was surprising, and disappointing to some, was the lack of effect of coverage on the health of these individuals. This was assessed via many measures, but the most critical were three pre-specified indicators of high blood pressure (mm Hg), high cholesterol (mg/dl), and high blood sugar (glycated Hb); these parameters reflect underlying conditions that predict mortality due to chronic noncommunicable diseases. Changes in these measures might reasonably have been expected to be detectable within the time frame of 2 years, but none were seen. A final take-home message, much less actively debated in the blogosphere, is the importance of performing impact evaluations.

    N. Engl. J. Med. 368, 1713 (2013).

  3. Pathogens

    The End of Antiquity

    1. Caroline Ash

    The Justinian Plague, which resurfaced regularly between the 6th and 8th centuries, is thought to have assisted the decline of the Roman Empire, but it has, until now, only been speculatively diagnosed as bubonic plague caused by the bacterium Yersinia pestis. Using stringent ancient DNA anticontamination protocols, Harbeck et al. have genotyped new material from the early medieval graveyard at Aschheim, Bavaria, dating from the 6th century. This graveyard contained 438 individuals, often in multiple burials—a sign of crisis. The amount of bacterial material available was scant, but Y. pestis was identified from one individual using five key single-nucleotide polymorphisms identified in recent phylogenies. Genotyping confirmed this isolate as basal to isolates from the 14th-century Black Death and the modern (19th-century) third pandemic and that, like the other pandemics, it originated in China or Mongolia.

    CREDIT: JAMES LE PLAMER/WIKIMEDIA COMMONS

    PLoS Pathogens 9, 10.1371/journal.ppat.1003349 (2013).

  4. Chemistry

    UN Coaxed to Neutrality

    1. Jake Yeston

    The enormous quantity of energy released through fission of the uranium (U) nucleus has lent the element a widespread, intimidating reputation. At the lower energies prevailing in conventional chemistry, where electrons rather than neutrons are exchanged, U remains an intriguing target of study, chiefly on account of the involvement off orbitals in its bonding motifs. In this context, a long-sought coordination complex in which U formed a triple bond to nitrogen (N) was recently prepared (King et al., Reports, 10 August 2012, p. 717). The complex had a net negative charge (with U in the ÷5 oxidation state) that was compensated for by a sodium ion and relied for its stability on a protective chelating ligand. King et al. have now built on this prior work to oxidize the U(V) anion and thereby isolate, and structurally characterize, a neutral U(VI) nitride complex. Iodine proved the optimal outer sphere oxidant, and it was necessary that the sodium remain sequestered by a crown ether; attempts to oxidize a dimeric precursor with sodium bridging the terminal Ns led to competing halogenation in the coordination sphere. The U(VI)≡N linkage was prone to photoaccelerated C-H insertion chemistry, perhaps accounting for the failure of prior attempts to generate related motifs photolytically.

    Nat. Chem. 5, 10.1038/nchem.1642 (2013).

  5. Chemistry

    Shepherding Stem Cells

    1. Marc S. Lavine

    Stem cells, because of their ability to differentiate into multiple cell types, are of interest in aiding tissue repair and for treating diseases such as diabetes. However, their lack of specificity also makes it hard to guide them to the target tissue of concern. Leukocytes express transmembrane receptors that will bind with overexpressed proteins on damaged or pathologic tissues. Using this as their model, Jeong et al. synthesized a hyperbranched polyglycerol (HPG) that was covalently modified with octadecyl chains and vasculature binding peptides of sequence VHSPNKK, chosen for its binding affinity toward vascular endothelial adhesion molecules overexpressed by inflamed blood vessels. The modified HPG showed an affinity to bind to cell surfaces but without interfering with the metabolic activity of the cells. Two types of adiposederived mesenchymal stem cells (MSCs) were used in a flow cell across an endothelial cell sheet that had been exposed to tumor necrosis factor–α. The peptide-modified HPG decreased the rolling rate of the MSCs and increased the adhesion of the cells to the endothelium, although only by a factor of 2.

    CREDIT: © HYBRID MEDICAL ANIMATION/SCIENCE SOURCE

    J. Am. Chem. Soc. 135, 10.1021/ja400636d (2013).

  6. Physics

    Spin Thermometers

    1. Jelena Stajic

    Developing sensitive, noninvasive nanoscale thermometry is of great interdisciplinary interest, for example, as a tool for measuring tiny intracellular temperature gradients. Fluorescence-based thermometry provides probes of an appropriate size, but conventional techniques have limited temperature resolution. Toyli et al. use the temperature dependence of the energy levels of defect spins in diamond as a basis for sensitive fluorescence thermometry. The defects are of the type called the nitrogen vacancy (NV) center, previously used in magnetic and electric field sensing. To improve the sensitivity, the researchers extended the spin coherence time using dynamical decoupling; they also showed that the technique worked reliably at temperatures as high as 500 K, whereas a 0.1 K shift was easily resolved. It is expected that the temperature sensitivity can be further improved by extending the coherence times, for example, by using isotopically purified diamond to eliminate the main source of decoherence, 13C. In addition to cellular thermometry, potential thermal sensing applications for NV centers in nanostructured diamond include microfluidic thermometry and scanning thermal microscopy.

    Proc. Natl. Acad. Sci. U.S.A. 110, 10.1073/pnas.1306825110 (2013).

  7. Developmental Biology

    Putting on the Brakes

    1. Beverly A. Purnell

    Many mammals can delay embryo implantation in order to postpone pregnancy when conditions are unfavorable, or until later birthing seasons. Such embryonic diapause occurs when development is suspended in the blastocyst stage and implantation is prevented. Endocrine factors trigger diapause; however, the mechanism coordinating blastocyst dormancy and uterine quiescence remains unknown. Cha et al. show that the gene Msx1 is expressed when implantation is delayed, whether it occurs because of maternal lactation, ovariectomy, or the addition of antiestrogen. When implantation initiates, Msx1 expression is down-regulated. Further, genetic inactivation of Msx1 or Msx2 in the uterus results in the development of fewer blastocysts. In order for delayed implantation to occur, blastocyst dormancy must coincide with uterine quiescence. This work demonstrates a critical role of Msx1 in maternal regulation of embryonic diapause. The study finds that three distantly related mammalian orders—Rodentia (mouse), Carnivora (American mink), and Diprotodontia (Australian tammar wallaby)—display correlations between Msx expression and diapause, suggesting the presence of a conserved reproductive strategy across mammalian species.

    Open Biol. 3, 10.1098/rsob.130035 (2013).

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