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  • Beyond plastic waste
    Science (IF 37.205) Pub Date : 2017-11-17
    Ellen MacArthur

    With more than 8 million tons of plastic entering the ocean each year, humanity must urgently rethink the way we make and use plastics, so that they do not become waste in the first place.

    更新日期:2017-11-19
  • News at a glance
    Science (IF 37.205) Pub Date : 2017-11-17
    American Association for the Advancement of Science

    In science news around the world, the Global Carbon Project predicts a 2% rise in carbon emissions this year, an obscure tick-borne malady called Kyasanur Forest disease spreads quickly through India, Republican lawmak­ers in the U.S. Senate are reviving a decadeslong push to open parts of Alaska’s Arctic National Wildlife Refuge to oil and gas drilling, and the Silicon Valley startup Planet Labs announces that its fleet of shoebox-sized space satellites now image Earth’s entire landmass every day. Also, President Donald Trump nominates Alex Azar, an attorney and former pharmaceutical executive, to head the U.S. Department of Health and Human Services, and Bill Gates announces a $100 mil­lion personal investment in Alzheimer’s disease research.

    更新日期:2017-11-19
  • ‘Biased’ opioids could yield safer pain relief
    Science (IF 37.205) Pub Date : 2017-11-17
    Meredith Wadman

    Nearly all of the roughly 64,000 Americans who died from opioid overdoses in 2016 succumbed because their breathing shut down, triggered by the effects of the drugs on important receptors in the brain stem. When they are activated, μ-opioid receptors potently relieve pain. They also control respiration. Now, for the first time, a drug that in binding these receptors causes powerful pain relief with less respiratory suppression is being evaluated for marketing approval by the Food and Drug Administration. Biotech company Trevana’s drug, oliceridine, acts as a μ-opioid receptor to activate a pain-relieving signaling pathway with less triggering of a separate path that leads to depressed breathing. Oliceridine is the first so-called “biased opioid” to emerge from human clinical trials. There will certainly be more: In a paper published inCellthis week, scientists at the Scripps Research Institute in Jupiter, Florida, have rigorously demonstrated for the first time in mice that the more biased a compound is toward activating the pain-relieving pathway, the less it suppresses breathing.

    更新日期:2017-11-19
  • ‘David and Goliath’ weather eyes set for launch
    Science (IF 37.205) Pub Date : 2017-11-17
    Eric Hand

    The polar weather satellite system will soon be safer. After years of rising costs and delays, the $1.6 billion Joint Polar Satellite System-1 (JPSS-1) was set to rocket into orbit this week. If successful, the launch will still fears that a failure of the JPSS-1’s aging predecessor would cripple the armada of polar satellites that provide 85% of the input data for weather forecast models. Hitchhiking on board the same rocket that is carrying the 4-meter-tall JPSS-1 is a strikingly smaller and cheaper probe that is a harbinger of a yet more resilient weather satellite system. The $3 million Microwave Radiometer Technology Acceleration—classed as a CubeSat because its components are stuffed into a stack of three 10-centimeter cubes—carries a cloud-penetrating microwave sensor that rivals one on the much bigger and costlier JPSS-1.

    更新日期:2017-11-19
  • Livestock drove ancient Old World inequality
    Science (IF 37.205) Pub Date : 2017-11-17
    Lizzie Wade

    Economic inequality has deep roots. A new study concludes that its ancient hotbed was the Old World: Societies there tended to be less equal than those in the New World, likely because of the use of draft animals. Researchers collected data on house size distribution from 62 archaeological sites in North America and Eurasia dating from before 8000 B.C.E. to about 1750 C.E. From there, they calculated each site’s Gini coefficient, a standard measure of inequality ranging from zero (perfect equality) to one (a single person has all the wealth). Inequality tended to gradually increase as societies transitioned from hunting and gathering to farming, supporting long-held hypotheses about how agriculture intensified social hierarchies. About 2500 years after the first appearance of domesticated plants in each region, average inequality in both the Old World and the New World hovered around a Gini coefficient of about 0.35. This figure stayed more or less steady in North America and Mesoamerica. But in the Middle East, China, Europe, and Egypt, where people had oxen to plow more land and horses to travel long distances, inequality kept climbing, topping out at an average Gini coefficient of about 0.6 about 6000 years after the start of agriculture. Still, those numbers are far below the wealth inequality seen today in the United States, which has a Gini coefficient of 0.8.

    更新日期:2017-11-19
  • After failed rescue effort, rare porpoise in extreme peril
    Science (IF 37.205) Pub Date : 2017-11-17
    Elizabeth Pennisi

    Last month, the Mexican government and an international team launched a last-resort plan to save the vaquita, one of the world’s smallest and most endangered cetaceans. With fewer than 30 vaquitas remaining, the group gathered on the shore of the Gulf of California in northern Mexico to try something unprecedented: Capture some of the porpoises, which grow to just 1.5 meters long, in a bid to breed them in captivity. At first, the $5 million effort—named VaquitaCPR—went better than expected, but then a female vaquita died while the researchers were trying to release her. VaquitaCPR leaders abandoned the rescue until an external review examines the circumstances of the death. But the risk of losing another may be too great for a second try. Instead, whether the vaquita, whose population has dropped 90% in the past several years because of illegal fishing net, survives another year now depends on clearing its waters of these nets.

    更新日期:2017-11-19
  • Autoimmune diseases surface after cancer treatment
    Science (IF 37.205) Pub Date : 2017-11-17
    Jennifer Couzin-Frankel

    A new class of cancer drugs is causing autoimmune diseases in some patients, as described last week at the Society for Immunotherapy of Cancer meeting in Oxon Hill, Maryland. Known as checkpoint inhibitors, these medicines rev up the immune system to fight cancer, with sometimes remarkable results. But physicians are now seeing a nasty, if treatable, side effect: the rapid onset of conditions including thyroid disease, colitis, and type 1 diabetes, which all result from an immune attack on the body’s own tissues. As cases mount, researchers across specialties are intensifying efforts to figure out whether certain cancer patients on checkpoint inhibitors are at higher risk—and to learn from this unusual side effect how other autoimmune attacks erupt.

    更新日期:2017-11-19
  • Ancient Australian goes home
    Science (IF 37.205) Pub Date : 2017-11-17
    John Pickrell

    In 1974, in the bone-dry Willandra Lakes Region World Heritage Site in Australia, scientists stumbled on a human skeleton in the dunes of long-vanished Lake Mungo. Dating revealed that “Mungo Man” was up to 42,000 years old, pushing back the first aboriginal habitation of Australia by tens of thousands of years. Now, the celebrated skeleton is going home. Capping a decadeslong custody battle, an aboriginal funeral service hearse set off on 14 November from the Australian National University in Canberra—where the remains were kept since their discovery—on a 700-kilometer drive across the outback to Willandra Lakes. There, they will be turned over to three tribes, which will decide whether to inter the remains or store them and allow research on the bones to continue.

    更新日期:2017-11-19
  • Oldest images of dogs show hunting, leashes
    Science (IF 37.205) Pub Date : 2017-11-17
    David Grimm

    Researchers have discovered what may be the world’s earliest images of dogs in northwestern Saudi Arabia. The depictions, carved into rocks at two sites in the Arabian Desert, appear to date to at least 8000 years ago and feature medium-sized canines—with pricked up ears, short snouts, and curled tails—in hunting scenes. The pictures also feature what appear to be leashes leading from the necks of several dogs to the waists of human hunters. If the dating holds up, this would be the earliest evidence for dog leashes in the archaeological record by thousands of years. Scientists speculate that these early dogs may have helped humans survive in this harsh landscape.

    更新日期:2017-11-19
  • A change of mind
    Science (IF 37.205) Pub Date : 2017-11-17
    Jennifer Couzin-Frankel

    Doctors routinely assess a patient’s risk of heart attack, various cancers, and diabetes, often intervening to slow or stop disease before it strikes. But preventing psychiatric conditions, from anxiety to depression to schizophrenia, has received scant attention. But in recent years, brain specialists have refined their ability to anticipate who’s at highest risk of psychosis—a defining feature of schizophrenia—identifying subtle signs in children and more vivid precursors in late adolescence. And increasingly, researchers feel they’d be derelict not to pursue prevention. A handful of prevention studies are up and running, ranging from cognitive therapies to pregnancy supplements for the fetal brain to psychiatric drugs. Last month, a German pharmaceutical company enrolled the first volunteer into what is intended to be a 300-person, randomized clinical trial, testing an experimental drug to prevent psychosis in those at extremely high risk. It’s believed to be the first time a company has poured millions of dollars into an effort like this one.

    更新日期:2017-11-19
  • Curtailing cascading failures
    Science (IF 37.205) Pub Date : 2017-11-17
    Raissa M. D'Souza

    Cascading behaviors are ubiquitous, from power-grid failures (1) to “flash crashes” in financial markets (2,3) to the spread of political movements such as the “Arab Spring” (4). The causes of these cascades are varied with many unknowns, which make them extremely difficult to predict or contain. Particularly challenging are cascading failures that arise from the reorganization of flows on a network, such as in electric power grids, supply chains, and transportation networks. Here, the network edges (or “links”) have some fixed capacity, and we see that some small disturbances easily dampen out, but other seemingly similar ones lead to massive failures. On page 886 of this issue, Yanget al.(5) establish that a small “vulnerable set” of components in the power grid is implicated in large-scale outages. Although the exact elements in this set vary with operating conditions, they reveal intriguing correlations with network structure.

    更新日期:2017-11-19
  • Feeding frenzy for cancer cells
    Science (IF 37.205) Pub Date : 2017-11-17
    Chi V. Dang

    Cancer cells are thought to undergo metabolic rewiring to scavenge waste products and recycle them as building blocks for growth. On page 941 of this issue, Spinelliet al.(1) report that ammonia could be recycled through glutamate dehydrogenase (GDH)–mediated reductive amination of α-ketoglutarate to produce the amino acid glutamate that, in turn, is converted to other amino acids such as aspartate and proline for biomass production (see the figure). This intriguing evidence of nitrogen fixation by breast cancer cells is reminiscent of nitrogen fixation in bacteria, yeast, and plants mediated by biochemical systems that evolved to harness nitrogen from the atmosphere for amino acid biosynthesis and biomass accumulation (2).

    更新日期:2017-11-19
  • Evolution of neurovirulent Zika virus
    Science (IF 37.205) Pub Date : 2017-11-17
    Gavin Screaton, Juthathip Mongkolsapaya

    In 2015, Zika virus (ZIKV) became headline news after its association with fetal microcephaly (severely reduced head circumference) in Brazil and was declared a public health emergency by the World Health Organization (WHO) (1). However, ZIKV was not new, it was first isolated from the Zika forest, Uganda in 1947 (2). ZIKV incited little interest compared to other flaviviruses, such as dengue virus (DENV), as it was not thought to cause severe disease. ZIKV infections were largely sporadic, and symptoms were usually mild and flu-like, with self-limiting fever, rash, and conjunctivitis. Around 80% of cases were asymptomatic, and epidemic activity had not been described (3). In 2007, large-scale explosive outbreaks of ZIKV infection were described in Micronesia, and the virus spread across the Pacific, reaching South America in 2015, where it rapidly spread through Brazil and neighboring countries (3–5). On page 933 of this issue, Yuanet al.(6) compared sequences of contemporary ZIKV strains with ancestral ZIKV isolates and describe a mutation that increases the neurovirulence of contemporary strains, which they propose underscores the increased pathogenicity of recent outbreaks.

    更新日期:2017-11-19
  • Advancing dengue vaccine development
    Science (IF 37.205) Pub Date : 2017-11-17
    Mark B. Feinberg, Rafi Ahmed

    Dengue virus (DENV) is a member of the viral genusFlavivirus, which also includes yellow fever virus (YFV) and Zika virus (ZIKV). DENV infection is a major and growing global health threat: There are ∼400 million cases of infection, ∼500,000 hospitalizations, and ∼12,500 deaths now estimated to occur each year (1). Dengue represents the most common mosquito-borne disease in humans (1). A remarkable 50% of the world's population now lives in regions where DENV transmission is manifest. Dengue is associated with a wide spectrum of clinical outcomes, ranging from mild febrile illnesses to dengue hemorrhagic fever to the most severe clinical presentation of dengue shock syndrome, which is characterized by profound systemic cytokine activation, vascular leakage, and shock—this carries a high risk of death. On page 929 of this issue, Katzelnicket al.(2) analyzed DENV infection outcome data gleaned from the long-term followup of a cohort of Nicaraguan children (2). They found that the risk of severe dengue disease upon subsequent DENV infection correlated with baseline DENV antibody concentrations (titers), which has implications for DENV vaccination approaches.

    更新日期:2017-11-19
  • Skin color variation in Africa
    Science (IF 37.205) Pub Date : 2017-11-17
    Hua Tang, Gregory S. Barsh

    The remarkable genetic diversity within African populations is both a signature and a storybook of human origins because descendants of the earliest humans who lived in Africa nearly 200,000 years ago have had the longest time to accumulate genetic variation. Although studying genetic diversity in African populations tells us a great deal about human history, there is even more to learn by juxtaposing the genetic diversity with the diversity of heritable traits (phenotypes). Yet, there is a paucity of such studies involving continental Africans (1). On page 887 of this issue, Crawfordet al.(2) demonstrate the potential insights that can come from ameliorating this disparity. They examined skin color variation in 2000 African individuals from different geographic locations and ethnic groups; the range, from light-skinned San hunter-gatherer populations in southern Africa to dark-skinned pastoralist populations in eastern Africa, far exceeds pigmentary diversity anywhere else on the planet (see the figure). Using a genome-wide association study (GWAS) that includes 1600 individuals living in Tanzania, Botswana, or Ethiopia, the authors identified regions of the genome that contribute to skin color variation and carried out a series of analyses to pinpoint the responsible genes.

    更新日期:2017-11-19
  • The promise of plastics from plants
    Science (IF 37.205) Pub Date : 2017-11-17
    Marc A. Hillmyer

    Polymers protect us from the elements, increase the fuel efficiency of cars, protect food from pathogens, help cure disease, and enable renewable-energy technologies. To promote, foster, and enable a sustainable society, we need polymers. Yet polymers can also create serious environmental challenges. Nearly all plastic packaging produced—more than 80 billion kg annually—originates from fossil resources and is disposed of after a relatively short period of use (1,2). An increasing fraction of plastic is recycled or incinerated to recover energy, but most ends up in landfills, littering cities or landscapes, and in the oceans (3). New recycling concepts (4), clean incineration, and the development of polymers that can rapidly degrade (5) will be key to addressing these problems. Shifting from petrochemical feedstocks to renewable resources—making plastics from plants—can also rectify some environmental challenges associated with petrochemical extraction and render plastics production sustainable (see the figure).

    更新日期:2017-11-19
  • The future of plastics recycling
    Science (IF 37.205) Pub Date : 2017-11-17
    Jeannette M. Garcia, Megan L. Robertson

    The environmental consequences of plastic solid waste are visible in the ever-increasing levels of global plastic pollution both on land and in the oceans. But although there are important economic and environmental incentives for plastics recycling, end-of-life treatment options for plastic solid waste are in practice quite limited. Presorting of plastics before recycling is costly and time-intensive, recycling requires large amounts of energy and often leads to low-quality polymers, and current technologies cannot be applied to many polymeric materials. Recent research points the way toward chemical recycling methods with lower energy requirements, compatibilization of mixed plastic wastes to avoid the need for sorting, and expanding recycling technologies to traditionally nonrecyclable polymers.

    更新日期:2017-11-19
  • Designed to degrade
    Science (IF 37.205) Pub Date : 2017-11-17
    Ann-Christine Albertsson, Minna Hakkarainen

    Around 50 years ago, interest arose in making plastics that can degrade in the environment (1). Since then, a stream of research efforts has chased the dream of environmentally friendly materials that disappear without leaving behind fragments or harmful products. Such environmentally degradable plastics are, however, difficult to produce in practice. Durability is one of the requirements for plastic in most technical applications, whereas degradability is necessary for recycling in nature. Although advances are being made in developing degradable materials with suitable properties for particular applications, it is crucial that they are seen as part of a range of approaches and that degradation will always require particular conditions that depend on the specific material and its chemical and physical structure and composition.

    更新日期:2017-11-19
  • Racing for academic glory and patents: Lessons from CRISPR
    Science (IF 37.205) Pub Date : 2017-11-17
    Arti K. Rai, Robert Cook-Deegan

    The much-publicized dispute over patent rights to CRISPR-Cas9 gene-editing technology highlights tensions that have been percolating for almost four decades, since the U.S. Bayh-Dole Act of 1980 invoked patents as a mechanism for promoting commercialization of federally funded research. With the encouragement provided by Bayh-Dole, academic scientists and their research institutions now race in dual competitive domains: the quest for glory in academic research and in the patent sphere. Yet, a robust economic literature (1,2) argues that races are often socially wasteful; the racing parties expend duplicative resources, in terms of both the research itself and the legal fees spent attempting to acquire patents, all in the pursuit of what may be a modest acceleration of invention. For CRISPR, and future races involving broadly useful technologies for which it may set a precedent, the relationship between these competitive domains needs to be parsed carefully. On the basis of legal maneuvers thus far, it appears that the litigants will try for broad rights; public benefit will depend on courts reining them in and, when broad patents slip through, on updating Bayh-Dole's pro-commercialization safeguards with underused features of the Act.

    更新日期:2017-11-19
  • Exploring exoplanets
    Science (IF 37.205) Pub Date : 2017-11-17
    Jennifer Carson

    In 1995, astronomers Michel Mayor and Didier Queloz announced they had detected the first "exoplanet" orbiting a main-sequence star, 51 light years away. Two months later, a team of astronomers led by Geoff Marcy confirmed Mayor's detection and found two more. Within a decade, hundreds of planets orbiting other stars had been detected. NASA's Kepler Telescope, launched into space in 2009, found a few thousand more.The Planet Factory, by Elizabeth Tasker, is the story of these 3000+ planets, "the travel log of how they came to form from dust particles to worlds so diverse that even Hollywood has failed to be weirder."

    更新日期:2017-11-19
  • The scapegoat
    Science (IF 37.205) Pub Date : 2017-11-17
    Jessica Eisner

    In his bookPatient Zero and the Making of the AIDS Epidemic, Richard McKay retraces the fits and starts of early AIDS research and how the evocative concept of a “patient zero” both captured the imagination of the general public and fed into the media hype that fueled speculation about the disease.

    更新日期:2017-11-19
  • The structural basis of flagellin detection by NAIP5: A strategy to limit pathogen immune evasion
    Science (IF 37.205) Pub Date : 2017-11-17
    Jeannette L. Tenthorey, Nicole Haloupek, José Ramón López-Blanco, Patricia Grob, Elise Adamson, Ella Hartenian, Nicholas A. Lind, Natasha M. Bourgeois, Pablo Chacón, Eva Nogales, Russell E. Vance

    Robust innate immune detection of rapidly evolving pathogens is critical for host defense. Nucleotide-binding domain leucine-rich repeat (NLR) proteins function as cytosolic innate immune sensors in plants and animals. However, the structural basis for ligand-induced NLR activation has so far remained unknown. NAIP5 (NLR family, apoptosis inhibitory protein 5) binds the bacterial protein flagellin and assembles with NLRC4 to form a multiprotein complex called an inflammasome. Here we report the cryo–electron microscopy structure of the assembled ~1.4-megadalton flagellin-NAIP5-NLRC4 inflammasome, revealing how a ligand activates an NLR. Six distinct NAIP5 domains contact multiple conserved regions of flagellin, prying NAIP5 into an open and active conformation. We show that innate immune recognition of multiple ligand surfaces is a generalizable strategy that limits pathogen evolution and immune escape.

    更新日期:2017-11-17
  • Photoionization in the time and frequency domain
    Science (IF 37.205) Pub Date : 2017-11-17
    M. Isinger, R. J. Squibb, D. Busto, S. Zhong, A. Harth, D. Kroon, S. Nandi, C. L. Arnold, M. Miranda, J. M. Dahlström, E. Lindroth, R. Feifel, M. Gisselbrecht, A. L’Huillier

    Ultrafast processes in matter, such as the electron emission after light absorption, can now be studied using ultrashort light pulses of attosecond duration (10−18seconds) in the extreme ultraviolet spectral range. The lack of spectral resolution due to the use of short light pulses has raised issues in the interpretation of the experimental results and the comparison with theoretical calculations. We determine photoionization time delays in neon atoms over a 40–electron volt energy range with an interferometric technique combining high temporal and spectral resolution. We spectrally disentangle direct ionization from ionization with shake-up, in which a second electron is left in an excited state, and obtain excellent agreement with theoretical calculations, thereby solving a puzzle raised by 7-year-old measurements.

    更新日期:2017-11-17
  • Arbitrary spin-to–orbital angular momentum conversion of light
    Science (IF 37.205) Pub Date : 2017-11-17
    Robert C. Devlin, Antonio Ambrosio, Noah A. Rubin, J. P. Balthasar Mueller, Federico Capasso

    Optical elements that convert the spin angular momentum (SAM) of light into vortex beams have found applications in classical and quantum optics. These elements—SAM-to–orbital angular momentum (OAM) converters—are based on the geometric phase and only permit the conversion of left- and right-circular polarizations (spin states) into states with opposite OAM. We present a method for converting arbitrary SAM states into total angular momentum states characterized by a superposition of independent OAM. We designed a metasurface that converts left- and right-circular polarizations into states with independent values of OAM and designed another device that performs this operation for elliptically polarized states. These results illustrate a general material-mediated connection between SAM and OAM of light and may find applications in producing complex structured light and in optical communication.

    更新日期:2017-11-17
  • Full momentum- and energy-resolved spectral function of a 2D electronic system
    Science (IF 37.205) Pub Date : 2017-11-17
    Joonho Jang, Heun Mo Yoo, L. N. Pfeiffer, K. W. West, K. W. Baldwin, Raymond C. Ashoori

    The single-particle spectral function measures the density of electronic states in a material as a function of both momentum and energy, providing central insights into strongly correlated electron phenomena. Here we demonstrate a high-resolution method for measuring the full momentum- and energy-resolved electronic spectral function of a two-dimensional (2D) electronic system embedded in a semiconductor. The technique remains operational in the presence of large externally applied magnetic fields and functions even for electronic systems with zero electrical conductivity or with zero electron density. Using the technique on a prototypical 2D system, a GaAs quantum well, we uncover signatures of many-body effects involving electron-phonon interactions, plasmons, polarons, and a phonon analog of the vacuum Rabi splitting in atomic systems.

    更新日期:2017-11-17
  • Tunable excitons in bilayer graphene
    Science (IF 37.205) Pub Date : 2017-11-17
    Long Ju, Lei Wang, Ting Cao, Takashi Taniguchi, Kenji Watanabe, Steven G. Louie, Farhan Rana, Jiwoong Park, James Hone, Feng Wang, Paul L. McEuen

    Excitons, the bound states of an electron and a hole in a solid material, play a key role in the optical properties of insulators and semiconductors. Here, we report the observation of excitons in bilayer graphene (BLG) using photocurrent spectroscopy of high-quality BLG encapsulated in hexagonal boron nitride. We observed two prominent excitonic resonances with narrow line widths that are tunable from the mid-infrared to the terahertz range. These excitons obey optical selection rules distinct from those in conventional semiconductors and feature an electron pseudospin winding number of 2. An external magnetic field induces a large splitting of the valley excitons, corresponding to ag-factor of about 20. These findings open up opportunities to explore exciton physics with pseudospin texture in electrically tunable graphene systems​.

    更新日期:2017-11-17
  • Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth
    Science (IF 37.205) Pub Date : 2017-11-17
    A. U. Abeysekara, A. Albert, R. Alfaro, C. Alvarez, J. D. Álvarez, R. Arceo, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, A. S. Barber, N. Bautista-Elivar, A. Becerril, E. Belmont-Moreno, S. Y. BenZvi, D. Berley, A. Bernal, J. Braun, C. Brisbois, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, M. Castillo, U. Cotti, J. Cotzomi, S. Coutiño de León, C. De León, E. De la Fuente, B. L. Dingus, M. A. DuVernois, J. C. Díaz-Vélez, R. W. Ellsworth, K. Engel, O. Enríquez-Rivera, D. W. Fiorino, N. Fraija, J. A. García-González, F. Garfias, M. Gerhardt, A. González Muñoz, M. M. González, J. A. Goodman, Z. Hampel-Arias, J. P. Harding, S. Hernández, A. Hernández-Almada, J. Hinton, B. Hona, C. M. Hui, P. Hüntemeyer, A. Iriarte, A. Jardin-Blicq, V. Joshi, S. Kaufmann, D. Kieda, A. Lara, R. J. Lauer, W. H. Lee, D. Lennarz, H. León Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis Raya, R. Luna-García, R. López-Coto, K. Malone, S. S. Marinelli, O. Martinez, I. Martinez-Castellanos, J. Martínez-Castro, H. Martínez-Huerta, J. A. Matthews, P. Miranda-Romagnoli, E. Moreno, M. Mostafá, L. Nellen, M. Newbold, M. U. Nisa, R. Noriega-Papaqui, R. Pelayo, J. Pretz, E. G. Pérez-Pérez, Z. Ren, C. D. Rho, C. Rivière, D. Rosa-González, M. Rosenberg, E. Ruiz-Velasco, H. Salazar, F. Salesa Greus, A. Sandoval, M. Schneider, H. Schoorlemmer, G. Sinnis, A. J. Smith, R. W. Springer, P. Surajbali, I. Taboada, O. Tibolla, K. Tollefson, I. Torres, T. N. Ukwatta, G. Vianello, T. Weisgarber, S. Westerhoff, I. G. Wisher, J. Wood, T. Yapici, G. Yodh, P. W. Younk, A. Zepeda, H. Zhou, F. Guo, J. Hahn, H. Li, H. Zhang

    The unexpectedly high flux of cosmic-ray positrons detected at Earth may originate from nearby astrophysical sources, dark matter, or unknown processes of cosmic-ray secondary production. We report the detection, using the High-Altitude Water Cherenkov Observatory (HAWC), of extended tera–electron volt gamma-ray emission coincident with the locations of two nearby middle-aged pulsars (Geminga and PSR B0656+14). The HAWC observations demonstrate that these pulsars are indeed local sources of accelerated leptons, but the measured tera–electron volt emission profile constrains the diffusion of particles away from these sources to be much slower than previously assumed. We demonstrate that the leptons emitted by these objects are therefore unlikely to be the origin of the excess positrons, which may have a more exotic origin.

    更新日期:2017-11-17
  • Compacted dimensions and singular plasmonic surfaces
    Science (IF 37.205) Pub Date : 2017-11-17
    J. B. Pendry, Paloma Arroyo Huidobro, Yu Luo, Emanuele Galiffi

    In advanced field theories, there can be more than four dimensions to space, the excess dimensions described as compacted and unobservable on everyday length scales. We report a simple model, unconnected to field theory, for a compacted dimension realized in a metallic metasurface periodically structured in the form of a grating comprising a series of singularities. An extra dimension of the grating is hidden, and the surface plasmon excitations, though localized at the surface, are characterized by three wave vectors rather than the two of typical two-dimensional metal grating. We propose an experimental realization in a doped graphene layer.

    更新日期:2017-11-17
  • Catalytic molten metals for the direct conversion of methane to hydrogen and separable carbon
    Science (IF 37.205) Pub Date : 2017-11-17
    D. Chester Upham, Vishal Agarwal, Alexander Khechfe, Zachary R. Snodgrass, Michael J. Gordon, Horia Metiu, Eric W. McFarland

    Metals that are active catalysts for methane (Ni, Pt, Pd), when dissolved in inactive low–melting temperature metals (In, Ga, Sn, Pb), produce stable molten metal alloy catalysts for pyrolysis of methane into hydrogen and carbon. All solid catalysts previously used for this reaction have been deactivated by carbon deposition. In the molten alloy system, the insoluble carbon floats to the surface where it can be skimmed off. A 27% Ni–73% Bi alloy achieved 95% methane conversion at 1065°C in a 1.1-meter bubble column and produced pure hydrogen without CO2or other by-products. Calculations show that the active metals in the molten alloys are atomically dispersed and negatively charged. There is a correlation between the amount of charge on the atoms and their catalytic activity.

    更新日期:2017-11-17
  • State-to-state chemistry for three-body recombination in an ultracold rubidium gas
    Science (IF 37.205) Pub Date : 2017-11-17
    Joschka Wolf, Markus Deiß, Artjom Krükow, Eberhard Tiemann, Brandon P. Ruzic, Yujun Wang, José P. D’Incao, Paul S. Julienne, Johannes Hecker Denschlag

    Experimental investigation of chemical reactions with full quantum state resolution for all reactants and products has been a long-term challenge. Here we prepare an ultracold few-body quantum state of reactants and demonstrate state-to-state chemistry for the recombination of three spin-polarized ultracold rubidium (Rb) atoms to form a weakly bound Rb2molecule. The measured product distribution covers about 90% of the final products, and we are able to discriminate between product states with a level splitting as small as 20 megahertz multiplied by Planck’s constant. Furthermore, we formulate propensity rules for the distribution of products, and we develop a theoretical model that predicts many of our experimental observations. The scheme can readily be adapted to other species and opens a door to detailed investigations of inelastic or reactive processes.

    更新日期:2017-11-17
  • Evolution of flower color pattern through selection on regulatory small RNAs
    Science (IF 37.205) Pub Date : 2017-11-17
    Desmond Bradley, Ping Xu, Irina-Ioana Mohorianu, Annabel Whibley, David Field, Hugo Tavares, Matthew Couchman, Lucy Copsey, Rosemary Carpenter, Miaomiao Li, Qun Li, Yongbiao Xue, Tamas Dalmay, Enrico Coen

    Small RNAs (sRNAs) regulate genes in plants and animals. Here, we show that population-wide differences in color patterns in snapdragon flowers are caused by an inverted duplication that generates sRNAs. The complexity and size of the transcripts indicate that the duplication represents an intermediate on the pathway to microRNA evolution. The sRNAs repress a pigment biosynthesis gene, creating a yellow highlight at the site of pollinator entry. The inverted duplication exhibits steep clines in allele frequency in a natural hybrid zone, showing that the allele is under selection. Thus, regulatory interactions of evolutionarily recent sRNAs can be acted upon by selection and contribute to the evolution of phenotypic diversity.

    更新日期:2017-11-17
  • Antibody-dependent enhancement of severe dengue disease in humans
    Science (IF 37.205) Pub Date : 2017-11-17
    Leah C. Katzelnick, Lionel Gresh, M. Elizabeth Halloran, Juan Carlos Mercado, Guillermina Kuan, Aubree Gordon, Angel Balmaseda, Eva Harris

    For dengue viruses 1 to 4 (DENV1-4), a specific range of antibody titer has been shown to enhance viral replication in vitro and severe disease in animal models. Although suspected, such antibody-dependent enhancement of severe disease has not been shown to occur in humans. Using multiple statistical approaches to study a long-term pediatric cohort in Nicaragua, we show that risk of severe dengue disease is highest within a narrow range of preexisting anti-DENV antibody titers. By contrast, we observe protection from all symptomatic dengue disease at high antibody titers. Thus, immune correlates of severe dengue must be evaluated separately from correlates of protection against symptomatic disease. These results have implications for studies of dengue pathogenesis and for vaccine development, because enhancement, not just lack of protection, is of concern.

    更新日期:2017-11-17
  • A single mutation in the prM protein of Zika virus contributes to fetal microcephaly
    Science (IF 37.205) Pub Date : 2017-11-17
    Ling Yuan, Xing-Yao Huang, Zhong-Yu Liu, Feng Zhang, Xing-Liang Zhu, Jiu-Yang Yu, Xue Ji, Yan-Peng Xu, Guanghui Li, Cui Li, Hong-Jiang Wang, Yong-Qiang Deng, Menghua Wu, Meng-Li Cheng, Qing Ye, Dong-Yang Xie, Xiao-Feng Li, Xiangxi Wang, Weifeng Shi, Baoyang Hu, Pei-Yong Shi, Zhiheng Xu, Cheng-Feng Qin

    Zika virus (ZIKV) has evolved into a global health threat because of its unexpected causal link to microcephaly. Phylogenetic analysis reveals that contemporary epidemic strains have accumulated multiple substitutions from their Asian ancestor. Here we show that a single serine-to-asparagine substitution [Ser139→Asn139(S139N)] in the viral polyprotein substantially increased ZIKV infectivity in both human and mouse neural progenitor cells (NPCs) and led to more severe microcephaly in the mouse fetus, as well as higher mortality rates in neonatal mice. Evolutionary analysis indicates that the S139N substitution arose before the 2013 outbreak in French Polynesia and has been stably maintained during subsequent spread to the Americas. This functional adaption makes ZIKV more virulent to human NPCs, thus contributing to the increased incidence of microcephaly in recent ZIKV epidemics.

    更新日期:2017-11-17
  • Atomic model for the dimeric FO region of mitochondrial ATP synthase
    Science (IF 37.205) Pub Date : 2017-11-17
    Hui Guo, Stephanie A. Bueler, John L. Rubinstein

    Mitochondrial adenosine triphosphate (ATP) synthase produces the majority of ATP in eukaryotic cells, and its dimerization is necessary to create the inner membrane folds, or cristae, characteristic of mitochondria. Proton translocation through the membrane-embedded FOregion turns the rotor that drives ATP synthesis in the soluble F1region. Although crystal structures of the F1region have illustrated how this rotation leads to ATP synthesis, understanding how proton translocation produces the rotation has been impeded by the lack of an experimental atomic model for the FOregion. Using cryo–electron microscopy, we determined the structure of the dimeric FOcomplex fromSaccharomyces cerevisiaeat a resolution of 3.6 angstroms. The structure clarifies how the protons travel through the complex, how the complex dimerizes, and how the dimers bend the membrane to produce cristae.

    更新日期:2017-11-17
  • Metabolic recycling of ammonia via glutamate dehydrogenase supports breast cancer biomass
    Science (IF 37.205) Pub Date : 2017-11-17
    Jessica B. Spinelli, Haejin Yoon, Alison E. Ringel, Sarah Jeanfavre, Clary B. Clish, Marcia C. Haigis

    Ammonia is a ubiquitous by-product of cellular metabolism; however, the biological consequences of ammonia production are not fully understood, especially in cancer. We found that ammonia is not merely a toxic waste product but is recycled into central amino acid metabolism to maximize nitrogen utilization. In our experiments, human breast cancer cells primarily assimilated ammonia through reductive amination catalyzed by glutamate dehydrogenase (GDH); secondary reactions enabled other amino acids, such as proline and aspartate, to directly acquire this nitrogen. Metabolic recycling of ammonia accelerated proliferation of breast cancer. In mice, ammonia accumulated in the tumor microenvironment and was used directly to generate amino acids through GDH activity. These data show that ammonia is not only a secreted waste product but also a fundamental nitrogen source that can support tumor biomass.

    更新日期:2017-11-17
  • Structural basis of bacterial transcription activation
    Science (IF 37.205) Pub Date : 2017-11-17
    Bin Liu, Chuan Hong, Rick K. Huang, Zhiheng Yu, Thomas A. Steitz

    In bacteria, the activation of gene transcription at many promoters is simple and only involves a single activator. The cyclic adenosine 3′,5′-monophosphate receptor protein (CAP), a classic activator, is able to activate transcription independently through two different mechanisms. Understanding the class I mechanism requires an intact transcription activation complex (TAC) structure at a high resolution. Here we report a high-resolution cryo–electron microscopy structure of an intactEscherichia coliclass I TAC containing a CAP dimer, a σ70–RNA polymerase (RNAP) holoenzyme, a complete class I CAP-dependent promoter DNA, and a de novo synthesized RNA oligonucleotide. The structure shows how CAP wraps the upstream DNA and how the interactions recruit RNAP. Our study provides a structural basis for understanding how activators activate transcription through the class I recruitment mechanism.

    更新日期:2017-11-17
  • Natural selection shaped the rise and fall of passenger pigeon genomic diversity
    Science (IF 37.205) Pub Date : 2017-11-17
    Gemma G. R. Murray, André E. R. Soares, Ben J. Novak, Nathan K. Schaefer, James A. Cahill, Allan J. Baker, John R. Demboski, Andrew Doll, Rute R. Da Fonseca, Tara L. Fulton, M. Thomas P. Gilbert, Peter D. Heintzman, Brandon Letts, George McIntosh, Brendan L. O’Connell, Mark Peck, Marie-Lorraine Pipes, Edward S. Rice, Kathryn M. Santos, A. Gregory Sohrweide, Samuel H. Vohr, Russell B. Corbett-Detig, Richard E. Green, Beth Shapiro

    The extinct passenger pigeon was once the most abundant bird in North America, and possibly the world. Although theory predicts that large populations will be more genetically diverse, passenger pigeon genetic diversity was surprisingly low. To investigate this disconnect, we analyzed 41 mitochondrial and 4 nuclear genomes from passenger pigeons and 2 genomes from band-tailed pigeons, which are passenger pigeons’ closest living relatives. Passenger pigeons’ large population size appears to have allowed for faster adaptive evolution and removal of harmful mutations, driving a huge loss in their neutral genetic diversity. These results demonstrate the effect that selection can have on a vertebrate genome and contradict results that suggested that population instability contributed to this species’s surprisingly rapid extinction.

    更新日期:2017-11-17
  • New Products
    Science (IF 37.205) Pub Date : 2017-11-17
    American Association for the Advancement of Science

    A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.

    更新日期:2017-11-17
  • Comment on “The extent of forest in dryland biomes”
    Science (IF 37.205) Pub Date : 2017-11-17
    Daniel M. Griffith, Caroline E. R. Lehmann, Caroline A. E. Strömberg, Catherine L. Parr, R. Toby Pennington, Mahesh Sankaran, Jayashree Ratnam, Christopher J. Still, Rebecca L. Powell, Niall P. Hanan, Jesse B. Nippert, Colin P. Osborne, Stephen P. Good, T. Michael Anderson, Ricardo M. Holdo, Joseph W. Veldman, Giselda Durigan, Kyle W. Tomlinson, William A. Hoffmann, Sally Archibald, William J. Bond

    Bastinet al. (Reports, 12 May 2017, p. 635) infer forest as more globally extensive than previously estimated using tree cover data. However, their forest definition does not reflect ecosystem function or biotic composition. These structural and climatic definitions inflate forest estimates across the tropics and undermine conservation goals, leading to inappropriate management policies and practices in tropical grassy ecosystems.

    更新日期:2017-11-17
  • Small vulnerable sets determine large network cascades in power grids
    Science (IF 37.205) Pub Date : 2017-11-17
    Yang Yang, Takashi Nishikawa, Adilson E. Motter

    The understanding of cascading failures in complex systems has been hindered by the lack of realistic large-scale modeling and analysis that can account for variable system conditions. Using the North American power grid, we identified, quantified, and analyzed the set of network components that are vulnerable to cascading failures under any out of multiple conditions. We show that the vulnerable set consists of a small but topologically central portion of the network and that large cascades are disproportionately more likely to be triggered by initial failures close to this set. These results elucidate aspects of the origins and causes of cascading failures relevant for grid design and operation and demonstrate vulnerability analysis methods that are applicable to a wider class of cascade-prone networks.

    更新日期:2017-11-17
  • Loci associated with skin pigmentation identified in African populations
    Science (IF 37.205) Pub Date : 2017-11-17
    Nicholas G. Crawford, Derek E. Kelly, Matthew E. B. Hansen, Marcia H. Beltrame, Shaohua Fan, Shanna L. Bowman, Ethan Jewett, Alessia Ranciaro, Simon Thompson, Yancy Lo, Susanne P. Pfeifer, Jeffrey D. Jensen, Michael C. Campbell, William Beggs, Farhad Hormozdiari, Sununguko Wata Mpoloka, Gaonyadiwe George Mokone, Thomas Nyambo, Dawit Wolde Meskel, Gurja Belay, Jake Haut, NISC Comparative Sequencing Program, Harriet Rothschild, Leonard Zon, Yi Zhou, Michael A. Kovacs, Mai Xu, Tongwu Zhang, Kevin Bishop, Jason Sinclair, Cecilia Rivas, Eugene Elliot, Jiyeon Choi, Shengchao A. Li, Belynda Hicks, Shawn Burgess, Christian Abnet, Dawn E. Watkins-Chow, Elena Oceana, Yun S. Song, Eleazar Eskin, Kevin M. Brown, Michael S. Marks, Stacie K. Loftus, William J. Pavan, Meredith Yeager, Stephen Chanock, Sarah A. Tishkoff

    Despite the wide range of skin pigmentation in humans, little is known about its genetic basis in global populations. Examining ethnically diverse African genomes, we identify variants in or nearSLC24A5,MFSD12,DDB1,TMEM138,OCA2, andHERC2that are significantly associated with skin pigmentation. Genetic evidence indicates that the light pigmentation variant atSLC24A5was introduced into East Africa by gene flow from non-Africans. At all other loci, variants associated with dark pigmentation in Africans are identical by descent in South Asian and Australo-Melanesian populations. Functional analyses indicate thatMFSD12encodes a lysosomal protein that affects melanogenesis in zebrafish and mice, and that mutations in melanocyte-specific regulatory regions nearDDB1/TMEM138correlate with expression of ultraviolet response genes under selection in Eurasians.

    更新日期:2017-11-17
  • Self-assembling peptide semiconductors
    Science (IF 37.205) Pub Date : 2017-11-17
    Kai Tao, Pandeeswar Makam, Ruth Aizen, Ehud Gazit

    Semiconductors are central to the modern electronics and optics industries. Conventional semiconductive materials bear inherent limitations, especially in emerging fields such as interfacing with biological systems and bottom-up fabrication. A promising candidate for bioinspired and durable nanoscale semiconductors is the family of self-assembled nanostructures comprising short peptides. The highly ordered and directional intermolecular π-π interactions and hydrogen-bonding network allow the formation of quantum confined structures within the peptide self-assemblies, thus decreasing the band gaps of the superstructures into semiconductor regions. As a result of the diverse architectures and ease of modification of peptide self-assemblies, their semiconductivity can be readily tuned, doped, and functionalized. Therefore, this family of electroactive supramolecular materials may bridge the gap between the inorganic semiconductor world and biological systems.

    更新日期:2017-11-17
  • Postcatalytic spliceosome structure reveals mechanism of 3′-splice site selection
    Science (IF 37.205) Pub Date : 2017-11-16
    Max E. Wilkinson, Sebastian M. Fica, Wojciech P. Galej, Christine M. Norman, Andrew J. Newman, Kiyoshi Nagai

    Introns are removed from eukaryotic mRNA precursors by the spliceosome in two transesterification reactions—branching and exon ligation. The mechanism of 3′-splice site recognition during exon ligation has remained unclear. Here we present the 3.7Å cryo-EM structure of the yeast P complex spliceosome immediately after exon ligation. The 3′-splice site AG dinucleotide is recognized through non-Watson-Crick pairing with the 5′-splice site and the branch point adenosine. After the branching reaction protein factors work together to remodel the spliceosome and stabilize a conformation competent for 3′-splice site docking, thereby promoting exon ligation. The structure accounts for the strict conservation of the GU and AG dinucleotides at the 5′ and 3′ ends of introns and provides insight into the catalytic mechanism of exon ligation.

    更新日期:2017-11-17
  • Structure of the yeast spliceosomal postcatalytic P complex
    Science (IF 37.205) Pub Date : 2017-11-16
    Shiheng Liu, Xueni Li, Lingdi Zhang, Jiansen Jiang, Ryan C. Hill, Yanxiang Cui, Kirk C. Hansen, Z. Hong Zhou, Rui Zhao

    The spliceosome undergoes dramatic changes in a splicing cycle. Structures of B, Bact, C, C*, and ILS complexes revealed mechanisms of 5′ splice site (ss) recognition, branching, and intron release, but lacked information on 3′ ss recognition, exon ligation and release. Here, we report a cryoEM structure of the postcatalytic P complex at 3.3Å resolution, revealing that 3′ ss is mainly recognized through non-Watson-Crick basepairing with the 5′ ss and branch point. Furthermore, an unidentified protein becomes stably associated with the P complex, securing the 3′ exon and potentially regulating Prp22 activity. Prp22 binds nucleotides 15-21 in the 3′ exon, enabling it to pull the intron-exon or ligated exon in a 3′ to 5′ direction to achieve 3′ ss proofreading or exon release, respectively.

    更新日期:2017-11-17
  • Vasohibins encode tubulin detyrosinating activity
    Science (IF 37.205) Pub Date : 2017-11-16
    Joppe Nieuwenhuis, Athanassios Adamopoulos, Onno B. Bleijerveld, Abdelghani Mazouzi, Elmer Stickel, Patrick Celie, Maarten Altelaar, Puck Knipscheer, Anastassis Perrakis, Vincent A. Blomen, Thijn R. Brummelkamp

    Tubulin is subjected to a number of posttranslational modifications to generate heterogeneous microtubules. The modifications include removal and ligation of the carboxy-terminal tyrosine of ⍺-tubulin. Whereas enzymes for most modifications have been assigned, the enzymes responsible for detyrosination, an activity observed forty years ago, have remained elusive. We applied a haploid genetic screen to find regulators of tubulin detyrosination. We identified SVBP, a peptide that regulates the abundance of Vasohibins (VASH1 and VASH2). Vasohibins, but not SVBP alone, increased detyrosination of ⍺-tubulin and purified Vasohibins removed the carboxy-terminal tyrosine of ⍺-tubulin. Vasohibins played a cell-type dependent role in detyrosination, but cells also contain an additional detyrosinating activity. Thus Vasohibins, hitherto studied as secreted angiogenesis regulators, constitute a long-sought missing link in the tubulin tyrosination cycle.

    更新日期:2017-11-17
  • Vasohibins/SVBP are tubulin carboxypeptidases (TCP) that regulate neuron differentiation
    Science (IF 37.205) Pub Date : 2017-11-16
    Chrystelle Aillaud, Christophe Bosc, Leticia Peris, Anouk Bosson, Pierre Heemeryck, Juliette Van Dijk, Julien Le Friec, Benoit Boulan, Frédérique Vossier, Laura E. Sanman, Salahuddin Syed, Neri Amara, Yohann Couté, Laurence Lafanechère, Eric Denarier, Christian Delphin, Laurent Pelletier, Sandrine Humbert, Matthew Bogyo, Annie Andrieux, Krzysztof Rogowski, Marie-Jo Moutin

    Reversible detyrosination of α-tubulin is crucial to microtubule dynamics and functions and defects have been implicated in cancer, brain disorganization, and cardiomyopathies. The identity of the tubulin tyrosine carboxypeptidase (TCP) responsible for detyrosination has remained unclear. We used chemical proteomics with a potent unique irreversible inhibitor to show that the major brain TCP is a complex of vasohibin-1 (VASH1) with the Small Vasohibin Binding Protein (SVBP). VASH1 and its homolog VASH2, when complexed with SVBP, exhibited robust and specific Tyr/Phe carboxypeptidase activity on microtubules. Knock down of vasohibins or SVBP and/or inhibitor addition in cultured neurons reduced detyrosinated α-tubulin levels and caused severe differentiation defects. Furthermore, knock down of vasohibins disrupted neuronal migration in developing mouse neocortex. Thus vasohibin/SVBP complexes represent long sought TCP enzymes.

    更新日期:2017-11-17
  • Comment on “The extent of forest in dryland biomes”
    Science (IF 37.205) Pub Date : 2017-11-10
    Marcelino de la Cruz, Pedro F. Quintana-Ascencio, Luis Cayuela, Carlos I. Espinosa, Adrián Escudero

    The study by Bastinet al. (Reports, 12 May 2017, p. 635) is based on an incomplete delimitation of dry forest distribution and on an old and incorrect definition of drylands. Its sampling design includes many plots located in humid ecosystems and ignores critical areas for the conservation of dry forests. Therefore, its results and conclusions may be unreliable.

    更新日期:2017-11-10
  • Science for global understanding
    Science (IF 37.205) Pub Date : 2017-11-10
    Flavia Schlegel

    Since its founding in 1945, the United Nations Educational, Scientific, and Cultural Organization (UNESCO) has been a leading convener and advocate for the natural and social sciences and the humanities. Every year since 2001, on 10 November, UNESCO's World Science Day reminds us of the importance of science for sustainable development and peace. This year's theme, “Science for Global Understanding,” also underpins the debates of scientists and policy-makers from around the world who are convening in Jordan this week at the UNESCO World Science Forum. One of their key concerns is the growing criticism of scientific integrity and denial of scientific findings. Building trust in science and fostering scientific excellence is central to all of UNESCO's work.

    更新日期:2017-11-10
  • News at a glance
    Science (IF 37.205) Pub Date : 2017-11-10
    American Association for the Advancement of Science

    In science news around the world, the U.S. Environmental Protection Agency rewrites the rules for its science advisory boards, researchers in China lose access to politically sensitive papers published by SpringerNature, the United Kingdom gets a new science adviser, and West African chimpanzees are set to get a new sanctuary in Guinea. Also, a Stanford University researcher sues the National Academy of Sciences for libel, the U.S. Postal Service releases a stamp to raise money for Alzheimer’s research, and the White House releases a climate change report that contradicts views voiced by some administration officials. Plus, mapping mosquitoes with mobile phones, constructing an entire epidermis with gene therapy, and giving diving elephant seals an oxygen boost—using carbon monoxide. We also announce the winner of this year’sScience/AAAS 10th annual “Dance Your Ph.D.” contest—aerial acrobatics that weave together braid theory, linear algebra, and murder.

    更新日期:2017-11-10
  • North Atlantic right whale faces extinction
    Science (IF 37.205) Pub Date : 2017-11-10
    Elizabeth Pennisi

    In a sad reversal of fortune, the North Atlantic right whale is in deep trouble again after rebounding in recent decades from centuries of hunting. Recent population trends are so dire that experts say the whale could vanish within 20 years. At a meeting of the Society for Marine Mammalogy in Halifax, Canada, experts reported that roughly 100 reproductively mature females remain. They are not surviving long enough or reproducing quickly enough for the species to survive. Ship strikes have long been a threat, and fatal entanglements in commercial fishing gear are taking an increasing toll. Even when an entangled female doesn’t die, the gear she drags can exhaust her, making her less likely to reproduce. The range of Eubalaena glacialis, the North Atlantic right whale—is one of the most “industrialized” stretches of ocean in the world, crowded with threats including ships, fishing operations, and energy infrastructure and governments are not keeping up with implementing protective policies as the whales shift northward in the summer.

    更新日期:2017-11-10
  • Giant radio telescope lends a hand in Puerto Rico relief
    Science (IF 37.205) Pub Date : 2017-11-10
    Daniel Clery

    More than a month on from Hurricane Maria, Arecibo Observatory, the gargantuan radio telescope built into a depression in Puerto Rico’s karst hills, is still waiting to resume normal operations. Despite have suffered little damage, the observatory, like the rest of the island, lacks enough fuel to run generators. Meanwhile, the telescope and its infrastructure have become the unlikely base for an ongoing relief effort for its roughly 110 staff and the communities around it. And in a painful irony, while the staff pull their own lives back together, they face the prospect that their professional careers in Puerto Rico may be about to end not because of a natural disaster, but because of shifting priorities. This week, the government advisers of the National Science Board will be discussing the observatory’s future.

    更新日期:2017-11-10
  • New tools offer clues to how the human brain takes shape
    Science (IF 37.205) Pub Date : 2017-11-10
    Ann Gibbons

    Our brains are bigger, relative to body size, than other animals’, but it’s not just size that matters. Elephants and whales have bigger brains, so comparing anatomy or even genomes of humans and other animals reveals little about the genetic and developmental changes that sent our brains down such a different path. Geneticists have identified a few key differences in the genes of humans and apes. But specifically how human variants of such genes shape our brain in development—and how they drove its evolution—have remained largely mysterious. Now, researchers are deploying new tools to understand the molecular mechanisms behind the unique features of our brain. At a symposium at The American Society of Human Genetics in Orlando, Florida, last month, they reported zooming in on the genes expressed in a single brain cell, as well as panning out to understand how genes foster connections among far-flung brain regions. Researchers are also experimenting with brain “organoids,” tiny structured blobs of lab-grown tissue, to detail the molecular mechanisms that govern the folding and growth of the embryonic human brain.

    更新日期:2017-11-10
  • Genomes rewrite cholera's global story
    Science (IF 37.205) Pub Date : 2017-11-10
    Kai Kupferschmidt

    By sequencing and comparing hundreds of bacterial genomes, researchers have shown that all of the explosive epidemics of cholera in Africa and the Americas in the past half-century arose after the arrival of new strains that had evolved in Asia. The work, published in two Science papers this week, could put to rest an old debate about the role of environmental factors in cholera’s global burden. It could also have a big impact on the fight against the disease, because it allows public health officials to concentrate their efforts on the imported strains that are likely to be the most dangerous.

    更新日期:2017-11-10
  • Polarizing head of House science panel to retire
    Science (IF 37.205) Pub Date : 2017-11-10
    Jeffrey Mervis

    Scientists are hoping that the retirement of Representative Lamar Smith (R–TX) is the first step toward a more civil science committee in the U.S. House of Representatives. On 2 November, Smith announced that he would not seek reelection next fall to a 17th term. Since becoming science committee chairman in January 2013, Smith has fought acrimonious battles with scientists over peer review, climate science, and the role of the federal government in supporting basic research. Many place him at the forefront of what some critics have dubbed a Republican “war on science.” Smith told constituents of his San Antonio, Texas–area district that “for several reasons, this seems like a good time” to step down. Representative Frank Lucas (R–OK) is seen as having the inside track to succeed Smith if the Republicans retain their House majority in the 2018 election. If the Democrats prevail, another Texan, Representative Eddie Bernice Johnson, is likely to take the gavel. In the meantime, Smith will serve one more year as chairman.

    更新日期:2017-11-10
  • Medical centers spearhead China's pharma push
    Science (IF 37.205) Pub Date : 2017-11-10
    Dennis Normile

    China’s pharma industry has limited R&D capabilities. Struggling under heavy patient loads, clinicians have little time for research and academics are under pressure to churn out peer-reviewed papers. As a result, universities have spun off few biotech ventures. Also hindering innovation are a slow regulatory review process and lax intellectual property protection. Now, China is endeavoring to raise its game in biomedicine. It’s launching five new translational medicine centers, each showered with $150 million in startup funds for buildings and instruments. And last month, China issued guidelines for overhauling the nation’s drug approval process by reforming clinical trial management, speeding reviews, allowing submission of foreign clinical trial data, and promoting innovation in drug and medical device development.

    更新日期:2017-11-10
  • Brain implant trials spur ethical discussions
    Science (IF 37.205) Pub Date : 2017-11-10
    Emily Underwood

    When a clinical trial of a pharmaceutical fails, participants usually move on by ceasing to take the drug. But it’s not that simple for some people who took part in a trial of a bold, experimental treatment for people with severe depression. The BROADEN trial, which implanted metal electrodes deep in the brain in a region called area 25, failed early on to show a statistically significant effect on depression and was halted after just 90 participants were treated. Yet 44 of those patients want to keep their implants. Last month, researchers at a meeting at the National Institutes of Health in Bethesda, Maryland, discussed the ethical issues that such scenarios raise, such as who is responsible for overseeing—and paying for—long-term care when participants want to keep their infants?

    更新日期:2017-11-10
  • The perfect wave
    Science (IF 37.205) Pub Date : 2017-11-10
    Jon Cohen

    A world champion surfer and a fluid mechanics specialist teamed up to create an artificial wave in a landlocked lake in central California that has astonished the surfing world. Kelly Slater, who has won the world surfing title an unprecedented 11 times, for more than a decade worked with Adam Fincham from the University of Southern California in Los Angeles to sculpt their vision of a rare natural phenomenon: a perfect wave. Fincham and his team used supercomputers to simulate the wave, which they then created in a laboratory wave tank. But small waves in a tank can be modeled with linear equations: What you put in comes out. When they moved to the artificial lake, which creates the wave by pulling a carefully crafted metal blade called a hydrofoil through the water, they had to adjust for a variety of nonlinear forces, like oscillations in the water body and turbulence. The end result, unveiled at a mock surf contest in September, is a wave that stands up to 2 meters high and alternates between a face that surfers can carve and a barrel that they can ride inside. The backers of “Kelly’s wave” hope to use it in professional contests and also to build resorts around it. If their plans come true, it will fundamentally alter where people can surf, the learning process, how professionals train, andThe Endless Summersearch for perfection.

    更新日期:2017-11-10
  • Killer clones
    Science (IF 37.205) Pub Date : 2017-11-10
    Mitch Leslie

    Mutations in our hematopoietic stem cells can allow one clone of blood cells to become abnormally abundant. Researchers have discovered that this imbalance, known as clonal hematopoiesis, is more common than they thought and becomes more prevalent as we get older. Fifty percent or more of people in their 80s may have the condition. Clonal hematopoiesis can have a profound effect on our health, boosting the risk of developing leukemia by more than 10 times and doubling the chances of developing heart disease or suffering a stroke. Researchers have uncovered one possible mechanism for its effects on the cardiovascular system, showing that the condition makes macrophages more pro-inflammatory.

    更新日期:2017-11-10
  • Cell cycle proteins moonlight in multiciliogenesis
    Science (IF 37.205) Pub Date : 2017-11-10
    Michelle Levine, Andrew Holland

    Multiciliated cells (MCCs) are a specialized population of postmitotic cells that are decorated with tens to hundreds of hairlike protrusions, termed motile cilia, that beat back and forth to direct fluid flow across an epithelium (1). MCCs line the respiratory tract, brain ventricles, and reproductive tracts of vertebrates and play a crucial role in tissue homeostasis; defects in the formation or movement of motile cilia can cause fertility defects, chronic respiratory infections, and/or a buildup of fluid in the brain. Despite their importance to human health, the pathways controlling the production of motile cilia in differentiating MCCs remain poorly understood. On page 803 of this issue, Al Jordet al.(2) shed light on this question by showing that multiciliated progenitor cells implement components of the mitotic cell cycle machinery to coordinate events that are required for motile ciliation and cellular differentiation, while avoiding cell division (mitosis).

    更新日期:2017-11-10
  • Linking smell to metabolism and aging
    Science (IF 37.205) Pub Date : 2017-11-10
    Jennifer L. Garrison, Zachary A. Knight

    The sense of smell, or olfaction, allows animals to survey the chemical landscape of the outside world and use this information to guide behavior. Olfactory cues are particularly important for the regulation of feeding, but how odor perception influences other aspects of energy homeostasis remains poorly understood. Recent work has begun to uncover some of these connections, revealing an unexpected role for olfaction in the control of metabolism and longevity.

    更新日期:2017-11-10
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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