This Week in Science

Science  05 Aug 2016:
Vol. 353, Issue 6299, pp. 553
  1. Social Sciences

    Asylum delay reduces employment

    1. NTK

    Delays in asylum processing harm employment prospects and subsequent integration.

    PHOTO:© XINHUA/ALAMY STOCK PHOTO

    The current refugee crisis calls for better understanding of how refugees integrate into life in a host country. A key element of integration is finding paid work. Hainmueller et al. found consistently that refugees across categories and origins who had to wait an additional year for the host government's asylum decision subsequently had difficulty finding employment. This finding is consistent with a pattern in which refugees whose asylum applications are slow become psychologically discouraged. Thus, speeding up asylum processing would appear to be a sensible policy for unlocking the economic potential of vulnerable people.

    Sci. Adv. 10.1126.sciadv.1600432 (2016).

  2. Shape-Memory Alloys

    Bend it, shape it, remember it

    1. Brent Grocholski

    Shape-memory alloys have the useful property of returning to their original shape after being greatly deformed. This process depends on the collective behavior of many small mineral grains in the metal. Using three-dimensional x-ray diffraction, Sedmák et al. tracked over 15,000 grains in a nickel-titanium shape-memory alloy as it moved through this transformation, thus linking microscopic changes to the bulk deformation.

    Science, this issue p. 559

  3. Archaeology

    Flood control initiates Chinese civilization

    1. Andrew M. Sugden

    Around four millennia ago, Emperor Yu the Great succeeded in controlling a huge flood in the Yellow River basin. This is considered to have led to the establishment of the Xia dynasty and the start of Chinese civilization. However, the dates of the events and the links between them have remained uncertain and controversial. Using stratigraphic data and radiocarbon dating, Wu et al. verify that the flood occurred and place the start of the Xia dynasty at about 1900 BC, thus reconciling the historical and archaeological chronologies (see the Perspective by Montgomery).

    Flood control marked the start of the Xia dynasty.

    PHOTO: © CLASSIC IMAGE/ALAMY STOCK PHOTO

    Science, this issue p. 579; see also p. 538

  4. Molecular Imaging

    Spatial organization inside the nucleus

    1. Valda Vinson

    In eukaryotic cells, DNA is packaged into a complex macromolecular structure called chromatin. Wang et al. have developed an imaging method to map the position of multiple regions on individual chromosomes, and the results confirm that chromatin is organized into large contact domains called TADS (topologically associating domains). Unexpectedly, though, folding deviates from the classical fractal-globule model at large length scales.

    Science, this issue p. 598

  5. Pregnancy

    A monofilament stitch in time

    1. Yevgeniya Nusinovich

    Cervical cerclage, a procedure that uses a suture to reinforce the cervical opening, is frequently used to reduce the risk of preterm delivery. A clinical study by Kindinger et al. shows that using a braided suture for cerclage is associated with a higher risk of preterm birth and intrauterine death than using a monofilament suture. The braided suture is more conducive to bacterial colonization, which results in vaginal dysbiosis and inflammation, helping to explain the clinical findings.

    Sci. Transl. Med. 8, 350ra102 (2016).

  6. Infectious Disease

    Setting the stage for HIV vaccines

    1. Angela Colmone

    Some HIV-infected individuals produce broadly neutralizing antibodies that can target multiple HIV strains. Moody et al. found that broadly neutralizing antibody production is associated with a higher frequently of autoantibodies, fewer regulatory T cells, and more circulating memory T follicular helper cells. Vaccine protocols that can mimic these immune perturbations may therefore promote better immune responses to HIV.

    Sci. Immunol. 10.1126/sciimmunol. aag0851 (2016).

  7. Biomineralization

    Recognition before nucleation

    1. Nicholas S. Wigginton

    Some algae have evolved a remarkable ability to grow ornate crystalline structures called coccoliths. These structures consist of an organic base plate and complex calcium carbonate minerals spreading outward. Gal et al. found that the algae control site-specific mineralization, not by interactions between the base plate and the growing mineral edge, but by directing large amounts of calcium to the base plate. Recognition between two organic constituents determines when and where crystal nucleation will take place.

    Science, this issue p. 590

  8. Axonal Degeneration

    Axonal pathology and necroptosis in ALS

    1. Stella M. Hurtley

    Necroptosis, a non–caspase-dependent form of cell death, can be reduced in disease states by inhibiting a kinase called RIPK1. Until now, no human mutations have been linked to necroptosis. Ito et al. show that loss of optineurin, which is encoded by a gene that has been implicated in the human neurodegenerative disorder ALS (amyotrophic lateral sclerosis), results in sensitivity to necroptosis and axonal degeneration. When RIPK1-kinase dependent signaling is disrupted in mice that lack optineurin, necroptosis is inhibited and axonal pathology is reversed.

    Science, this issue p. 603

  9. Graphene

    Teasing out chirality in graphene

    1. Jelena Stajic

    A chiral elementary particle has its spin pointing in either the same or the opposite direction as its momentum. In graphene, electrons have an analogous chirality, but observing it in electrical transport experiments is tricky. To do this, Wallbank et al. studied how electrons tunnel between two slightly misaligned graphene sheets separated by a layer of insulating hexagonal boron nitride. The chiral nature of the electrons imposed restrictions on the tunneling, which made it possible to discern the signatures of chirality in the data.

    Science, this issue p. 575

  10. Catalysis

    Membranes to make benzene from methane

    1. Phil Szuromi

    Methane gas is expensive to ship. It is usually converted into carbon monoxide and hydrogen and then liquefied. This is economically feasible only on very large scales. Hence, methane produced in small amounts at remote locations is either burned or not extracted. A promising alternative is conversion to benzene and hydrogen with molybdenumzeolite catalysts. Unfortunately, these catalysts deactivate because of carbon buildup; plus, hydrogen has to be removed to drive the reaction forward. Morejudo et al. address both of these problems with a solid-state BaZrO3 membrane reactor that electrochemically removes hydrogen and supplies oxygen to suppress carbon buildup.

    Science, this issue p. 563

  11. CRISPR Evolution

    The CRISPR-Cas evolutionary mix

    1. Guy Riddihough,
    2. Laura M. Zahn

    Prokaryotes are under a constant barrage of viruses and parasitic DNA. Many bacteria have adaptive immune systems called CRISPR-Cas that protect them from this onslaught. Although the underlying mechanism of CRISPR-Cas—based immunity is similar among prokaryote species, there are many variants. Mohanraju et al. review the common themes and the many differences in the basic structure and function of the CRISPR loci and associated effector Cas proteins. Abudayyeh et al. present an interesting version of a class 2 CRISPR-Cas single effector that appears to target single-stranded RNA viruses of bacteria and that could be valuably exploited for a range of biotechnological tools.

    Science, this issue p. 10.1126/science.aad5147, p. 10.1126/science.aad5573

  12. Analytical Methods

    Watching batteries fail

    1. Marc S. Lavine

    Rechargeable batteries lose capacity in part because of physical changes in the electrodes caused by electrochemical cycling. Lim et al. track the reaction dynamics of an electrode material, LiFePO4, by measuring the relative concentrations of Fe(II) and Fe(III) in it by means of high-resolution x-ray absorption spectrometry (see the Perspective by Schougaard). The exchange current density is then mapped for Li+ insertion and removal. At fast cycling rates, solid solutions form as Li+ is removed and inserted. However, at slow cycling rates, nanoscale phase separation occurs within battery particles, which eventually shortens battery life.

    Science, this issue p. 566; see also p. 543

  13. Nanomaterials

    Long-life excimer-like structures

    1. Marc S. Lavine

    Metal quantum clusters have ideal properties for medical applications such as imaging. The challenge is to prolong their transient properties for the fabrication of useful devices. Santiago-Gonzalez et al. arranged gold clusters in a supramolecular lattice held together by hydrogen bonding and showed that this material can be used for imaging of fibroblast cells. In the superstructure, the gold molecules can come together in the excited state as excimers and then dissociate to emit radiation. Because they are within a lattice, this behavior shows long-term stability. Furthermore, the lattice superstructure scavenges reactive oxygen species and reduces cell damage.

    Science, this issue p. 571

  14. Plant Science

    Searching for the Sun

    1. Pamela J. Hines

    The growth of immature sunflower plants tracks the Sun's movement. The young plants lean westward as the day progresses but reorient to the east each night. As the flowers mature and open, they settle into a stable east-facing orientation. Atamian et al. show how circadian rhythms regulate the east-west elongation of cells in the young plants' stems (see the Perspective by Briggs). They show that eastward-oriented flowers are warmer than westward-oriented flowers, and this warmth attracts pollinators. Auxin signaling pathways in the stem coordinate to fix the eastward orientation of the mature plant.

    Science, this issue p. 587; see also p. 541

  15. Bioengineering

    Xenobiotics to the rescue

    1. Nicholas S. Wigginton

    Contaminating microorganisms can be highly detrimental to the large-scale fermentation of complex low-cost feedstocks, such as sugarcane or dry-milled corn for biofuels or other industrial purposes. The challenge is that foreign organisms have to be inhibited without using antibiotics because of concerns about spreading antibiotic resistance. Shaw et al. engineered bacteria and yeast to use rare compounds as sources of nutrients (see the Perspective by Lennen). Engineering the common biocatalyst Escherichia coli, for example, to consume melamine as a nitrogen source allowed it to outcompete contaminating organisms. Similarly, engineering yeast to use cyanamide for nitrogen or phosphite for phosphorus also improved competitive fitness.

    Science, this issue p. 583; see also p. 542

  16. Neuroscience

    From channel mutation to neuropathy

    1. Nancy R. Gough

    A child with progressive early-onset motor neuropathy has revealed the molecular key to this profound disability. Kahle et al. discovered a point mutation in the gene encoding the K+-Cl transporter KCC3 in the patient's peripheral nervous system. The mutated transporter could not be inhibited by phosphorylation and remained constitutively active. Mice expressing KCC3 with the same mutation showed increased transporter activity and impaired locomotor function.

    Sci. Signal. 9, ra77 (2016).

  17. Topological Matter

    Classifying the cyrstalline fermionic zoo

    1. Jelena Stajic

    Elementary particles must obey the rules and symmetries of free space, unless, it turns out, they reside in a periodic crystal lattice. This periodicity can enhance variety among the resident fermionic species. Bradlyn et al. classify fermionic quasi-particles in a class of materials called semimetals and examine their topological properties (see the Perspective by Beenakker). In addition to the well-characterized Dirac, Majorana, and Weyl fermions, which can “live” in free space, crystal-space group symmetries allow other types of fermions to exist. Calculations indicate that these fermion types occur near the Fermi levels of known crystals, which bodes well for their experimental observation.

    Science, this issue p. 10.1126/science.aaf5037; see also p. 539

  18. Structural Biology

    Insights into proteasome inhibition

    1. Valda Vinson

    Proteasomes are large protein complexes that degrade and remove proteins to maintain proper cellular physiology and growth. Proteasomes are a validated target for anticancer therapy, but drug design has been hampered by poor understanding of how inhibitors interact with the active site. Schrader et al. succeeded in crystallizing various proteasome-inhibitor complexes. They subsequently obtained crystal structures for the native human proteasome and eight different inhibitor complexes at resolutions between 1.9 and 2.1 Å. The inhibitors sampled include drugs that are approved or in trial for cancer treatment.

    Science, this issue p. 594

Navigate This Article