Editors' Choice

Science  15 Jul 2016:
Vol. 353, Issue 6296, pp. 259
  1. Planetary Science

    Smashing bits to show asteroid strength

    1. Keith T. Smith

    Optical image showing chondrules in a meteorite fragment.

    PHOTO: YVES MARROCCHI

    How strong is an asteroid? Earth rocks are poor analogs because of differences in composition, gravity during formation, and geologic processing. Cotto-Figueroa et al. tested samples from two large meteorites (pieces of asteroid that have fallen to Earth) by crushing them in a vice to measure the bulk material properties. By comparing cubes of different sizes, they extrapolated the strength of meter-sized asteroids, finding values that are consistent with the observed break-up of meteors as they enter Earth's atmosphere. The results will be useful for planning sample return or asteroid mining missions or for deflecting potentially hazardous asteroids away from Earth.

    Icarus 277, 73 (2016).

  2. Health Economics

    Why pay more for medicine in some places?

    1. Brad Wible

    The cost of health care varies widely with geography in the United States, but the role of place-specific supply versus demand has been unclear. Finkelstein et al. studied the migration of elderly Medicare recipients to show that supply features, such as physician preference for aggressive care and the proportion of for-profit hospitals in a region, accounted for 50 to 60% of the variation. Roughly a quarter of the variability was probably due to observable differences in patients' health, with the rest due to patients' preferences and unmeasured health issues. The findings suggest that policies aimed at changing doctors' behaviors by altering incentives could be more promising than those aimed at changing patients' preferences.

    Quart. J. Econ. http://economics.mit.edu/files/11482 (2016).

  3. Tumor Immunology

    A less personal cancer therapy?

    1. Paula A. Kiberstis

    Many new cancer therapies are built around the concept of personalized medicine. This includes an emerging class of therapeutic cancer vaccines that induce the immune system to destroy tumor cells expressing patient-specific neoantigens. Such vaccines may not work well for breast cancer, a tumor type that expresses few neoantigens. Conceivably, a therapeutic vaccine could be designed to target tumor-associated antigens that are shared among breast cancer patients, assuming such shared antigens exist. Munson et al. provide evidence that they do. They analyzed T cell receptor (TCR) sequences of tumor-infiltrating lymphocytes in 20 breast cancer patients and found a panel of TCRs shared among patients' tumors and peripheral blood that were not present in peripheral blood of healthy controls.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1606994113 (2016).

  4. Paleogenomics

    Immigration and admixture in Europe

    1. Andrew M. Sugden

    Early Neolithic farmers moved through the Aegean region as they traveled from Asia to Europe.

    PHOTO ©ROBERTHARDING/ALAMY STOCK PHOTO

    The Neolithic transition in Europe marked the shift from hunting-gathering societies to sedentary farming societies. Evidence has been accumulating from DNA recovered from human remains that the transition was the result of migration and admixture of farmers from western Asia, rather than cultural transmission. The route of this migration (or migrations) has been less certain. Hofmanova et al. analyzed paleogenomic data from Neolithic individuals from Greek and Turkish sites to provide evidence of genetic links between early farmers in the Aegean region and those in Central Europe. Their data indicate the importance of the Aegean region as the direct migration route of early Neolithic famers from southwest Asia into Europe.

    Proc. Natl. Acad. Sci. U.S.A. 113, 6886 (2016).

  5. Physics

    Shaping the interaction potential

    1. Jelena Stajic

    Alkali atoms have been the workhorse of cold-atom research thanks to their favorable spectral properties. Over the past decade, however, some of the alkaline earth elements, such as Sr, have proven their worth and expanded the capabilities of cold atoms as quantum simulators and optical clocks. Gaul et al. add another piece to the toolbox of alkaline earth elements. Using a three-state system, they optically excited some of the atoms in a Sr gas to a highly excited Rydberg state. The procedure resulted in a strong effective interaction that, for some parameters, had a pronounced peak at a finite distance. This unusually shaped potential may enable the exploration of exotic phases.

    Phys. Rev. Lett. 116, 243001 (2016).

  6. Anthropology

    Poor predictors

    1. Sacha Vignieri

    Muscle attachment sites on fossils or bones may not accurately indicate hand activities such as tool use.

    PHOTO: CARLOS ANDRE SANTOS/SHUTTERSTOCK

    Although it poses a challenge, we have a great interest in understanding the behavior of extinct species. One approach that is commonly used to infer past behavior, especially of hominids, is the reconstruction of muscle anatomy from regions of muscle-to-bone attachment, or entheses, that remain on fossils or bones. Williams-Hatala et al. looked at hands from human cadavers to determine how accurate entheses are for predicting muscle morphology and therefore function. Looking across the measures most often used to infer hand function and tool use in hominids, they found very little correlation between the characteristics of entheses and attached muscle morphology. Because we know little about how entheses are shaped by stress and strain, they argue, caution should be used when extrapolating complex behaviors from these remnants.

    Sci. Rep. 10.1038/srep28353 (2016)

  7. Organ Development

    Modeling pancreas development with CRISPR

    1. Beverly A. Purnell

    Reprogramming cells from one fate to another enables researchers to generate and study rare cell types. Combining this approach with TALEN (transcription activator-like effector nuclease) and CRISPR/Cas genome-editing technologies opens the way to understanding transcriptional control of organ development. Zhu et al. used these methods to study pancreatic development and disease. With a direct differentiation protocol, 50- to 80%-definitive endoderm cells were generated, and transcription factors that are key to pancreatic development (PDX1, RFX6, PTF1A, GLIS3, MNX1, NGN3, HES1, and ARX) were systematically knocked out using CRISPR/Cas to generate mutant hESC lines. This work confirmed prior findings but also revealed that RFX6 regulates pancreatic progenitor number, that PDX1 is dosage-sensitive for pancreatic endocrine development, and that NGN3 has a divergent role in mice and humans.

    Cell Stem Cell 18, 755 (2016).