Editors' Choice

Science  24 Mar 2017:
Vol. 355, Issue 6331, pp. 1278
  1. Stream Geometry

    A new angle on streams

    1. H. Jesse Smith

    Stream branching angles vary with aridity.

    CREDIT: PLANET

    Climate has clear effects on streams. Theory and observations both show that channel incision rates increase with precipitation, and chemical erosion rates scale with temperature, but how does the surface geometry of rivers depend on those factors? Seybold et al. analyzed nearly 1 million river junctions across the contiguous United States and found that branching angles vary systematically with climatic aridity. Branching angles are smaller in arid regions than in humid ones, where groundwater seepage is more important, and are stronger functions of aridity than of other commonly invoked controls such as topographic gradient or downstream concavity. These findings may aid in characterizing channelization processes in landscapes where relict streams are found, such as on Mars.

    Geophys. Res. Lett. 10.1002/2016GL072089 (2017).

  2. Medical Diagnostics

    Turning toys into tools

    1. Megan Eldred

    Getting medical diagnostic tools to areas in developing countries with few resources has always been a considerable challenge. Bhamla et al. have created a centrifuge mostly made of paper, which they call the “paperfuge.” It is cheap to make, lightweight, and easy to operate, without any need for electricity. Based on the mechanical theory of an old whirligig toy, this device can spin blood samples at speeds of 125,000 rpm and achieve centrifugal forces of 30,000g. Researchers are thus able to separate plasma from blood in less than 1.5 min. This time is adequate for initial anemia diagnosis, but isolation of malaria parasites needs around 15 min. The device is customizable and opens up many opportunities for easy-to-access blood diagnostics.

    Nat. Biomed. Eng. 1, 0009 (2017).

  3. Physiology

    Stronger pancreas through starvation

    1. L. Bryan Ray

    Starvation stresses an animal and can cause tissue loss. Regeneration after refeeding seems to mimic developmental activation of cells and replenishes depleted tissues. Cheng et al. tested the effects on mice of a low-calorie (low in carbohydrates and protein) but high-fat diet that resembles the metabolic effects of fasting but is easier for humans to tolerate. In models of type 1 and type 2 diabetes, mice on this diet showed improved insulin secretion and glucose homeostasis. The diet promoted signaling and transcriptional changes reminiscent of those that occur during the development of pancreatic endocrine cells. The findings raise the possibility of reprogramming endogenous cells in the pancreas to restore function lost in diabetes.

    Cell 10.1016/j.cell.2017.01.040 (2017).

  4. RNA Editing

    The evolution of edited RNA transcripts

    1. Laura M. Zahn

    Drosophila species have evolved many RNA editing sites to fine-tune neurological function.

    PHOTO: COURTESY NICOLAS GOMPEL AND BENJAMIN PRUD'HOMME

    Differences occur between nucleotides encoded within DNA and the RNAs transcribed from these sequences. Such RNA editing can lead to changes in the amino acid composition of resulting proteins, and the removal of editing can have pathological consequences. Examining the occurrence of A-to-I editing in coding and noncoding RNA transcripts in 13 Drosophila species, Zhang et al. recorded the origin, loss, and maintenance of edited sites across the species. They found that editing can affect gene expression and that sites in both coding and noncoding sequences could be under evolutionary selection to maintain editing. In addition, RNA editing in the 3′ untranslated region of genes may contribute to mRNA degradation and may be a mechanism by which transcript levels are regulated.

    PLOS Genet. 13, e1006563 (2017).

  5. Galaxies

    Recovering galaxy images from noisy data

    1. Keith T. Smith

    The information that can be extracted from an image of a galaxy is fundamentally limited by the resolution and noise in the data. Schawinski et al. have applied a machine learning method to galaxy images, which is trained by comparing artificially degraded images with the originals. The algorithm is then used to recover features from previously unseen degraded images, which it performs more successfully than traditional deconvolution techniques. The method requires assuming that the target galaxies look similar to those in the training set, and individual details can be lost or misidentified, but it should be useful for studying statistical properties of galaxies in large surveys.

    Mon. Not. R. Astron. Soc.467, L110 (2017).

  6. Cancer

    Notch1 promotes cancer spread

    1. Priscilla N. Kelly

    Mutations that activate Notch have been identified in several cancers. Weiland et al. find that Notch1 signaling within endothelial cells (ECs) promotes the invasion of distant organs by tumors. Abnormally high levels of active Notch1 are found in blood vessels associated with advanced human cancers. Similarly, in mice, when Notch1 is activated in the ECs, circulating tumor cells increase in the bloodstream. Mobilization of tumor cells leads to the recruitment of white blood cells called neutrophils into the tumors and the production of VCAM1, which is used by cancer cells to adhere to new sites. Therapies in mice targeting either VCAM1 or Notch1 are effective in reducing neutrophil influx and tumor progression.

    Cancer Cell 10.1016/j.ccell.2017.01.007 (2017).

  7. 2D Materials

    Dirac cones in a boron monolayer

    1. Jelena Stajic

    When pure boron is evaporated onto a silver substrate, a structure made up of a single layer of boron atoms can form. Several different structures have been predicted and fabricated, but it is unclear whether the electronic properties of this so-called borophene can rival those of its better known cousin graphene. Feng et al. made a sheet of boron atoms on a silver substrate that had a characteristic striped and flat structure. Although the atoms were not arranged in a hexagonal lattice, like carbon atoms are in graphene, the electronic structure of borophene showed similar linearly dispersing electronic states, called Dirac cones. The discovery may lead to applications of monolayer boron in electronic devices.

    Phys. Rev. Lett. 118, 096401 (2017).

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