This Week in Science

Science  12 Aug 2016:
Vol. 353, Issue 6300, pp. 660
  1. Hydrology

    Water dissolving and water removing

    1. Nicholas S. Wigginton

    Seepage of coastal groundwater rich in iron and other dissolved constituents

    PHOTO: MATTHIJS WETTERAUW/ALAMY STOCK PHOTO

    Not all groundwater ends up flowing into rivers. Some is discharged directly into the ocean along the coast. Although much lower in volume than water transported by rivers, such submarine groundwater discharge can be a hidden source of dissolved ions, nutrients, or contaminants from human activities. Sawyer et al. performed a high-resolution continental-scale analysis of fresh groundwater discharge along the coastline of the United States. In total, more than one-fifth of coastal waters are vulnerable to groundwater-borne contamination.

    Science, this issue p. 705

  2. Physics

    The deuteron is too small, too

    1. Jelena Stajic

    The radius of the proton has remained a point of debate ever since the spectroscopy of muonic hydrogen indicated a large discrepancy from the previously accepted value. Pohl et al. add an important clue for solving this so-called proton radius puzzle. They determined the charge radius of the deuteron, a nucleus consisting of a proton and a neutron, from the transition frequencies in muonic deuterium. Mirroring the proton radius puzzle, the radius of the deuteron was several standard deviations smaller than the value inferred from previous spectroscopic measurements of electronic deuterium. This independent discrepancy points to experimental or theoretical error or even to physics beyond the standard model.

    Science, this issue p. 669

  3. Life History

    Deep living for centuries

    1. Sacha Vignieri

    We tend to think of vertebrates as living about as long as we do, give or take 50 to 100 years. Marine species are likely to be very long-lived, but determining their age is particularly difficult. Nielsen et al. used the pulse of carbon-14 produced by nuclear tests in the 1950s—specifically, its incorporation into the eye during development—to determine the age of Greenland sharks. This species is large yet slow-growing. The oldest of the animals that they sampled had lived for nearly 400 years, and they conclude that the species reaches maturity at about 150 years of age.

    Science, this issue p. 702

  4. Brain Microcircuits

    Building new networks in the brain

    1. Peter Stern

    Donald Hebb's hypothesis that coactivation of neurons leads to the formation of ensembles of neurons has inspired neuroscientists for decades. The experimental creation of such ensembles has been technically challenging. Using two-photon optogenetic stimulation with single-cell resolution, Carrillo-Reid et al. discovered that recurrent activation of a group of neurons creates an ensemble that is imprinted in the brain circuitry. Activation of a single neuron can lead to recall of the entire ensemble in a phenomenon called pattern completion. The artificial ensemble persists over days and can be reactivated at later time points without interfering with endogenous circuitry.

    Science, this issue p. 691

  5. Atmospheric Chemistry

    Active fatty acid layers

    1. H. Jesse Smith

    Saturated fatty acids are considered to be inert, but they can be surprisingly reactive when present as a coating at an air-water interface. Rossignol et al. show that nonanoic acid is photochemically active when it is present as a monolayer on a water surface (see the Perspective by Vaida). Fatty acids are ubiquitous in the environment, and their photochemical processing could have a substantial impact on local ozone and particle formation.

    Science, this issue p. 699; see also p. 650

  6. Economic Policy

    Programs that buffer a financial shock work

    1. Gilbert Chin

    For people without a safety net of social and financial resources, a shock, such as medical expenses not covered by insurance, can be the first step in a downward spiral toward homelessness and morbidity. Evans et al. evaluate the effectiveness and cost of a program in Chicago that provides temporary financial assistance with the aim of enabling individuals to stay in their homes and out of homeless shelters. They find that one-time payments of up to $1500 greatly reduce the likelihood of homelessness. The estimated economic benefits exceed the estimated costs, with immeasurable psychic and physical benefits.

    Science, this issue p. 694

  7. Soft Electronics

    Soft and still responsive

    1. Marc S. Lavine

    Soft touch-conductive hydrogel

    PHOTO: KIM ET AL.

    Transparent touch screens, from large-panel interactive information maps to advanced cell phones, have become a part of daily life. However, such devices all use hard materials. Kim et al. have developed a soft touch panel based on polyacrylamide hydrogels (cross-linked polymers swollen with water) that are highly transparent and contain trapped LiCl to enhance conductivity. The hydrogels are soft and can be stretched extensively while still maintaining touch sensitivity.

    Science, this issue p. 682

  8. Bone Development

    Turning chondrocytes into bone killers

    1. Leslie K. Ferrarelli

    The skeletal defects caused by inhibitors of histone deacetylase (HDAC) enzymes limit the clinical value of these drugs. Carpio et al. found that a specific isoform, HDAC3, promotes bone growth by restricting the secretion of inflammatory factors from cartilage cells called chondrocytes. Mice that lacked Hdac3 in chondrocytes after birth had impaired long bone development. Chondrocytes from these mice had increased activation of a proinflammatory transcription factor. The findings help to explain why HDAC inhibitors are not a good option for children and pregnant women and for patients with bone fractures.

    Sci. Signal. 9, ra79 (2016).

  9. Transplantation

    Make way for stem cells

    1. Lindsey Pujanandez

    Current chemotherapy or radiation regimens to prepare the host bone marrow for transplantation of donor hematopoietic stem cells (HSCs) can be harmful. Chhabra et al. tested an alternative strategy in which the surface antigen CD47 is block-aded, which allows phagocytic myeloid cells to engulf host HSCs that are displaced by antibody targeting, effectively depleting HSCs from the bone marrow of immunocompetent mice and enabling engraftment of donor cells.

    Sci. Transl. Med. 8, 351ra105 (2016).

  10. Zika

    Global spread of Zika virus

    1. Caroline Ash

    Zika virus was identified in Uganda in 1947; since then, it has enveloped the tropics, causing disease of varying severity. Lessler et al. review the historical literature to remind us that Zika's neurotropism was observed in mice even before clinical case reports in Nigeria in 1953. What determines the clinical manifestations; how local conditions, vectors, genetics, and wild hosts affect transmission and geographical spread; what the best control strategy is; and how to develop effective drugs, vaccines, and diagnostics are all critical questions that are begging for data.

    Science, this issue p. 663

  11. Structural Biology

    A different gate design

    1. Valda Vinson

    The voltage-gated potassium channel Eag1 is overexpressed in tumor cells from a range of cancers, and inhibiting Eag1 reduces tumor growth. Whicher and Mackinnon determined the structure of a mammalian Eag1 bound to the inhibitor calmodulin at 3.78 Å resolution (see the Perspective by Toombes and Swartz). The organization of the voltage-sensing and pore domains differs from that of other potassium channels, indicating that the gating mechanism is distinct. The structure also shows how the channel can be closed by a ligand, independently of the position of the voltage sensor.

    Science, this issue p. 664; see also p. 646

  12. Extrasolar Planets

    Spying a planet in a triple-star system

    1. Keith T. Smith

    Thousands of extrasolar planets are now known, but only a handful have been detected in direct images. Wagner et al. used sophisticated adaptive optics to discover a planet in images of the triple-star system HD 131399 and to take a spectrum of its atmosphere (see the Perspective by Oppenheimer). The planet, about four times the mass of Jupiter, orbits around one star in the system while the other two stars move farther out. This unusual arrangement is puzzling: The planet's orbit may be stable, but it is unclear how it could have formed or migrated there. The results will be used to refine theories of planet formation.

    Science, this issue p. 673; see also p. 644

  13. Sleep Research

    Circadian rhythms and sleep deprivation

    1. Peter Stern

    Sleep deprivation, such as that experienced because of shift work, jet lag, sleep disorders, and aging, leads to deterioration of many aspects of health. Cognition deteriorates rapidly and substantially when we stay awake through the night. To investigate the time course of brain responses during sleep loss, Muto et al. scanned volunteers repeatedly during an extended period of wakefulness (see the Perspective by Czeisler) in which circadian and homeostatic drives differentially affected local brain regions.

    Science, this issue p. 687; see also p. 648

  14. Neurodegeneration

    Targeting three defects with one strategy

    1. Stella M. Hurtley

    The neurodegenerative diseases amyotrophic lateral sclerosis and frontotemporal dementia are most commonly caused by a mutation in the C9orf72 gene. The mutation is an expanded hexanucleotide repeat in a noncoding region. The expanded repeat produces sense and antisense RNA transcripts, which accumulate in patient cells and appear to sequester RNA-binding proteins. The sense and antisense transcripts are also translated into dipeptide repeat proteins, which are aggregation-prone and accumulate in the brain and spinal cord. Last, loss of function from reduced expression of C9orf72 in neurons and glia could contribute to the disease. Kramer et al. targeted both sense and antisense repeats by blocking a single gene called SPT4, which mitigated degeneration in human cells by reducing all three types of pathologies.

    Science, this issue p. 708

  15. Conservation

    For richer, for poorer

    1. Julia Fahrenkamp-Uppenbrink

    Human activities are increasingly causing ecosystem degradation. In a Perspective, Frank and Schlenker discuss some of the trade-offs between economic development and conservation. They argue that although it can be difficult to assign monetary value to ecosystems, not doing so risks giving them zero value. For effective conservation, governments must either send the right price signals or place ecosystems directly under protection. Between 1972 and 2012, richer countries have seen the largest increase in protected areas, showing that economic growth can be compatible with conservation.

    Science, this issue p. 651

  16. Alzheimer's Disease

    Mapping Alzheimer's disease

    1. Ali Shilatifard

    Alzheimer's disease (AD) is a chronic neurodegenerative disorder that progresses slowly into dementia and short-term memory loss. AD is thought to be caused by aggregation of Ab and tau proteins in plaques and tangles. Vendruscolo et al. investigated why aberrant protein aggregations are found in some tissues but not in others. It turns out that failure of protein homeostasis elevates expression of a specific subset of proteins that can be aggregated in AD. Thus, a tissue vulnerability map based on Ab and tau homeostasis in healthy tissue might be predictive for AD.

    Sci. Adv. 10.1126.sciadv.1600947 (2016).

  17. Organometallics

    Charging up the iron in ferrocene salts

    1. Jake Yeston

    Ferrocene is the archetype of the sandwich compounds, so called because a metal atom is inserted between two carbon rings. The elucidation of ferrocene's structure was pivotal to the development of organometallic chemistry during the mid-20th century. The ease with which the iron in the center of the molecule can toggle between the +2 and +3 oxidation states has made the compound a common electrochemical standard. Malischewski et al. report the synthesis and isolation of ferrocene salts with iron in the +4 state, which they characterize crystallographically and spectroscopically.

    Science, this issue p. 678

Navigate This Article